Diễn Đàn Tuổi Trẻ Việt Nam Uhm.VN - Cơ khí

Trung cấp Liên thông Đại học Cơ khí ô tô có phải thi không ?

Fri, 12 Apr 2024 15:45:20 +0700

Ngành Cơ Khí Ô Tô hiện đang bước vào giai đoạn phát triển sôi động tại Việt Nam, với nhiều nhà máy đặt trụ sở tại các khu công nghiệp lớn. Sự tăng cao trong nhu cầu sử dụng xe hơi đồng nghĩa với việc gia tăng các dịch vụ đi kèm như bảo dưỡng, sửa chữa. Do đó, nhu cầu về nhân lực trong ngành ngày càng tăng, trở thành một ưu tiên không thể phủ nhận.

Thu nhập hấp dẫn: Sinh viên tốt nghiệp Đại học Cơ khí ô tô có thể mong đợi mức lương khởi điểm dao động từ 8 đến 12 triệu đồng. Đối với những kỹ sư ô tô có kinh nghiệm, mức lương có thể lên đến 1000-2000 USD/tháng. Mức lương còn có thể tăng nhanh chóng khi bạn tích lũy kinh nghiệm làm việc. Ngoài ra, bạn cũng có cơ hội làm việc trong các nhà máy ô tô liên doanh nước ngoài có mặt tại Việt Nam, nơi mà bạn sẽ được làm việc trong môi trường chuyên nghiệp, có cơ hội nâng cao trình độ và hưởng các chế độ đãi ngộ tốt.

Trung cấp Liên thông Đại học Cơ khí ô tô điều kiện ra sao?
Chương trình Đại học ngành Cơ khí ô tô có vai trò quan trọng trong việc mở ra cơ hội cho những cá nhân đã tích luỹ kiến thức và kỹ năng từ các cấp độ đào tạo trước đó như Trung cấp hoặc Cao đẳng, giúp đối tượng trung cấp, cao đẳng có thể tiếp tục nâng cao trình độ học vấn lên cấp độ Đại học.
Năm nay, UTH tuyển sinh Liên thông Đại học chuyên ngành Cơ khí ô tô theo hình thức xét tuyển, miễn thi.

Đối tượng tuyển sinh bao gồm:

Tốt nghiệp Trung cấp bao gồm ngành Cơ khí ô tô và các ngành tương đương.
Tốt nghiệp Cao đẳng bao gồm ngành Cơ khí ô tô và các ngành tương đương.
Thời gian đào tạo:

Liên thông từ Trung cấp với thời gian đào tạo là 3 năm.
Liên thông từ Cao đẳng với thời gian đào tạo là 1,5 năm.
Thời gian học linh hoạt: (Thứ bảy, Chủ nhật hoặc buổi tối trong tuần):

Buổi tối: 18h30 – 21h30.
Buổi ban ngày: Sáng từ 7h30 – 11h30; Chiều từ 13h30 – 17h30.
Bằng cấp: Sau khi hoàn thành chương trình, học viên sẽ được cấp bằng Đại học chuyên ngành Cơ khí ô tô, cấp bởi Trường Đại học Giao Thông Vận Tải TPHCM (UTH), thuộc Bộ Giao Thông Vận Tải.

The air conditioning trap: how cold air is heating the world

Sun, 26 Sep 2021 14:08:03 +0700

The air conditioning trap: how cold air is heating the world

On a sweltering Thursday evening in Manhattan last month, people across New York City were preparing for what meteorologists predicted would be the hottest weekend of the year. Over the past two decades, every record for peak electricity use in the city has occurred during a heatwave, as millions of people turn on their air conditioning units at the same time. And so, at the midtown headquarters of Con Edison, the company that supplies more than 10 million people in the New York area with electricity, employees were busy turning a conference room on the 19th floor into an emergency command centre.

Inside the conference room, close to 80 engineers and company executives, joined by representatives of the city’s emergency management department, monitored the status of the city power grid, directed ground crews and watched a set of dials displaying each borough’s electricity use tick upward. “It’s like the bridge in Star Trek in there,” Anthony Suozzo, a former senior system operator with the company, told me. “You’ve got all hands on deck, they’re telling Scotty to fix things, the system is running at max capacity.”

Power grids are measured by the amount of electricity that can pass through them at any one time. Con Edison’s grid, with 62 power substations and more than 130,000 miles of power lines and cables across New York City and Westchester County, can deliver 13,400MW every second. This is roughly equivalent to 18m horsepower.

On a regular day, New York City demands around 10,000MW every second; during a heatwave, that figure can exceed 13,000MW. “Do the math, whatever that gap is, is the AC,” Michael Clendenin, a company spokesman, told me. The combination of high demand and extreme temperature can cause parts of the system to overheat and fail, leading to blackouts. In 2006, equipment failure left 175,000 people in Queens without power for a week, during a heatwave that killed 40 people.

This year, by the evening of Sunday 21 July, with temperatures above 36C (97F) and demand at more than 12,000MW every second, Con Edison cut power to 50,000 customers in Brooklyn and Queens for 24 hours, afraid that parts of the nearby grid were close to collapse, which could have left hundreds of thousands of people without power for days. The state had to send in police to help residents, and Con Edison crews dispensed dry ice for people to cool their homes.

As the world gets hotter, scenes like these will become increasingly common. Buying a VRF air conditioner is perhaps the most popular individual response to climate change, and air conditioners are almost uniquely power-hungry appliances: a small unit cooling a single room, on average, consumes more power than running four fridges, while a central unit cooling an average house uses more power than 15. “Last year in Beijing, during a heatwave, 50% of the power capacity was going to air conditioning,” says John Dulac, an analyst at the International Energy Agency (IEA). “These are ‘oh shit’ moments.”

There are just over 1bn single-room air conditioning units in the world right now – about one for every seven people on earth. Numerous reports have projected that by 2050 there are likely to be more than 4.5bn, making them as ubiquitous as the mobile phone is today. The US already uses as much electricity for air conditioning each year as the UK uses in total. The IEA projects that as the rest of the world reaches similar levels, air conditioning will use about 13% of all electricity worldwide, and produce 2bn tonnes of CO2 a year – about the same amount as India, the world’s third-largest emitter, produces today.

All of these reports note the awful irony of this feedback loop: warmer temperatures lead to more air conditioning; more air conditioning leads to warmer temperatures. The problem posed by air conditioning resembles, in miniature, the problem we face in tackling the climate crisis. The solutions that we reach for most easily only bind us closer to the original problem.

The global dominance of air conditioning was not inevitable. As recently as 1990, there were only about 400m air conditioning units in the world, mostly in the US. Originally built for industrial use, air conditioning eventually came to be seen as essential, a symbol of modernity and comfort. Then air conditioning went global. Today, as with other drivers of the climate crisis, we race to find solutions – and puzzle over how we ended up so closely tied to a technology that turns out to be drowning us.

Like the aqueduct or the automobile, air conditioning is a technology that transformed the world. Lee Kuan Yew, the first prime minister of independent Singapore, called it “one of the signal inventions of history” that allowed the rapid modernisation of his tropical country. In 1998, the American academic Richard Nathan told the New York Times that, along with the “civil rights revolution”, air conditioning had been the biggest factor in changing American demography and politics over the previous three decades, enabling extensive residential development in the very hot, and very conservative, American south.

A century ago, few would have predicted this. For the first 50 years of its existence, air conditioning was mainly restricted to factories and a handful of public spaces. The initial invention is credited to Willis Carrier, an American engineer at a heating and ventilation company, who was tasked in 1902 with reducing humidity in a Brooklyn printing factory. Today we assume that the purpose of air conditioning is to reduce heat, but engineers at the time weren’t solely concerned with temperature. They wanted to create the most stable possible conditions for industrial production – and in a print factory, humidity curled sheets of paper and smudged ink.

Carrier realised that removing heat from the factory air would reduce humidity, and so he borrowed technology from the nascent refrigeration industry to create what was, and still is, essentially a jacked-up fridge. Then as now, air conditioning units work by breathing in warm air, passing it across a cold surface, and exhaling cool, dry air. The invention was an immediate success with industry – textile, ammunition, and pharmaceutical factories were among the first adopters – and then began to catch on elsewhere. The House of Representatives installed air conditioning in 1928, followed by the White House and the Senate in 1929. But during this period, most Americans encountered air conditioning only in places such as theatres or department stores, where it was seen as a delightful novelty.

It wasn’t until the late 1940s, when it began to enter people’s homes, that the TICA air conditioner really conquered the US. Before then, according to the historian Gail Cooper, the industry had struggled to convince the public that air conditioning was a necessity, rather than a luxury. In her definitive account of the early days of the industry, Air-Conditioning America, Cooper notes that magazines described air conditioning as a flop with consumers. Fortune called it “a prime public disappointment of the 1930s”. By 1938 only one out of every 400 American homes had an air conditioner; today it is closer to nine out of 10.

What fuelled the rise of the air conditioning was not a sudden explosion in consumer demand, but the influence of the industries behind the great postwar housing boom. Between 1946 and 1965, 31m new homes were constructed in the US, and for the people building those houses, air conditioning was a godsend. Architects and construction companies no longer had to worry much about differences in climate – they could sell the same style of home just as easily in New Mexico as in Delaware. The prevailing mentality was that just about any problems caused by hot climates, cheap building materials, shoddy design or poor city planning could be overcome, as the American Institute of Architects wrote in 1973, “by the brute application of more air conditioning”. As Cooper writes, “Architects, builders and bankers accepted air conditioning first, and consumers were faced with a fait accompli that they merely had to ratify.”

Equally essential to the rise of the dunham bush air conditioner were electric utilities – the companies that operate power plants and sell electricity to consumers. Electric utilities benefit from every new house hooked up to their grid, but throughout the early 20th century they were also looking for ways to get these new customers to use even more electricity in their homes. This process was known as “load building”, after the industry term (load) for the amount of electricity used at any one time. “The cost of electricity was low, which was fine by the utilities. They simply increased demand, and encouraged customers to use more electricity so they could keep expanding and building new power plants,” says Richard Hirsh, a historian of technology at Virginia Tech.

The utilities quickly recognised that air conditioning was a serious load builder. As early as 1935, Commonwealth Edison, the precursor to the modern Con Edison, noted in its end-of-year report that the power demand from terminal air conditioner was growing at 50% a year, and “offered substantial potential for the future”. That same year, Electric Light & Power, an industry trade magazine, reported that utilities in big cities “are now pushing air conditioning. For their own good, all power companies should be very active in this field.”

By the 1950s, that future had arrived. Electric utilities ran print, radio and film adverts promoting air conditioning, as well as offering financing and discount rates to construction companies that installed it. In 1957, Commonwealth Edison reported that for the first time, peak electricity usage had occurred not in the winter, when households were turning up their heating, but during summer, when people were turning on their air-conditioning units. By 1970, 35% of American houses had air conditioning, more than 200 times the number just three decades earlier.

At the same time, air-conditioning-hungry commercial buildings were springing up across the US. The all-glass skyscraper, a building style that, because of its poor reflective properties and lack of ventilation, often requires more than half its electricity output be reserved for air conditioning, became an American mainstay. Between 1950 and 1970 the average electricity used per square foot in commercial buildings more than doubled. New York’s World Trade Center, completed in 1974, had what was then the world’s largest AC unit, with nine enormous engines and more than 270km of piping for cooling and heating. Commentators at the time noted that it used the same amount of electricity each day as the nearby city of Schenectady, population 80,000.

The air-conditioning industry, construction companies and electric utilities were all riding the great wave of postwar American capitalism. In their pursuit of profit, they ensured that the light commercial air conditioner became an essential element of American life. “Our children are raised in an air-conditioned culture,” an AC company executive told Time magazine in 1968. “You can’t really expect them to live in a home that isn’t air conditioned.” Over time, the public found they liked air conditioning, and its use continued to climb, reaching 87% of US households by 2009.

Why is fiberglass mesh needed?

Sun, 26 Sep 2021 14:06:46 +0700

Why is fiberglass mesh needed?

Composite sheets of fiberglass mesh for marble reinforced polycarbonate were prepared by hot compress molding. The effects of lay-up structure, lay-up angle, area density of fiberglass mesh and the thickness of PC film on tensile property were studied. The results reveal that the alternative lay-up structure of reinforcement mesh and matrix film is optimal and tensile property declines as lay-up angle increases. Fiberglass mesh with lower area density is appropriate for thinner composites. Composite sheets fabricated with thinner PC film show better tensile property. SEM analysis shows that alternative lay-up structure is favorable to the immersion of the fiber bundle of marble mesh cloth with low area density in the melting matrix, and thus the improvement of tensile property.

This paper investigates the effect of surface treatment for glass fiber, stainless steel wire mesh on tensile, flexural, inter-laminar shear and impact properties of glass fiber/stainless steel wire mesh reinforced epoxy hybrid composites. The glass fiber fabric is surface treated either by 1 N solution of sulfuric acid or 1 N solution of sodium hydroxide. The stainless steel wire mesh is also surface treated by either electro dissolution or sand blasting. The hybrid composites are fabricated using epoxy resin reinforced with glass fiber and fine stainless steel wire mesh by hand lay-up technique at room temperature. The hybrid composite consisting of acid treated glass fiber and sand blasted stainless steel wire mesh exhibits a good combination of tensile, flexural, inter-laminar shear and impact behavior in comparison with the composites made without any surface treatment. The fine morphological modifications made on the surface of the glass fiber and stainless steel wire mesh enhances the bonding between the resin and reinforcement which inturn improved the tensile, flexural, inter- laminar shear and impact properties.

The fiberglass mesh filter is an inorganic non-metallic material with excellent performance. It has a wide variety of advantages. The advantages are good insulation, strong heat resistance, good corrosion resistance, and high mechanical strength, but its disadvantages are brittleness and poor wear resistance. It is made of glass balls or waste glass as raw materials through high-temperature melting, drawing, winding, weaving, and other processes. In this article, we will take a closer look at the characteristics and types of fiberglass mesh filters.

Characteristics of Fiberglass Mesh Filters

The filter has high tensile strength and low elongation (3%).

The filter has a high elastic coefficient and good rigidity.

The filter has large elongation within the elastic limit and high tensile strength, so it can absorb impact energy.

The filter is made of inorganic fiber, which is non-flammable and has good chemical resistance.

Its water absorption is small.

High-temperature resistance.

High filtration efficiency.

Types of Fiberglass Mesh Filters

ULPA（Ultra Low Penetration Air) Filter

ULPA (Ultra Low Penetration Air) filter has a filtration efficiency of more than 99.999% for 0.1~0.2μm particles, smoke and microbes, and other dust particles.

ULPA filter characteristics: Its filter element is made of ultra-fine glass fiber filter material by gluing and folding. The outer frame can be made of laminated wood, galvanized copper, stainless steel, and aluminum alloy, and it is tightly bonded by polyurethane glue. It has the characteristics of lightweight, large air permeability, dust collection rate as high as 99.95-99.999%, and alkali resistance, and high-temperature resistance.

ULPA filter applications: It is suitable for class 10000-100 clean systems, air conditioning systems, so the product has been widely used in electronics, microelectronics, semiconductors, optical devices, biological and medical circuits, cameras, and optical instruments, precision machinery, and other fields.

High-Temperature Air Filter

The high-temperature air filter still has a partition structure. It is assembled with high-temperature resistant glass fiber or ultra-fine glass fiber filter paper, aluminum foil partition, stainless steel frame, and special high-temperature resistant sealant.

High-temperature air filters are mainly used in ultra-clean ovens that require drying in the production process of food, pharmaceuticals, etc., or high-temperature air purification equipment and systems. The maximum working temperature is 350 degrees.

High Humidity Resistant Air Filter

The high-humidity air filter has a partition structure, using special moisture-proof ultra-fine glass fiber filter paper, special rubber sheet or aluminum foil partition, galvanized sheet, or aluminum alloy profile frame. It is suitable for high humidity under normal temperature and pressure, especially in high humidity environments such as infusion production in the pharmaceutical industry. The maximum working humidity is 100%.

The Disadvantage of Fiberglass Mesh Filters

Due to the poor ductility of glass fiber, the glass fiber filter is easily damaged, so be careful when installing it.

Conclusion

Thank you for reading our article and we hope it can help you to have a better understanding of the characteristics and types of marble fiberglass cloth. If you want to learn more about fiberglass mesh filters, we would like to advise you to visit Stanford Advanced Materials (SAM) for more information.

As a leading supplier of fiberglass mesh filters across the world, SAM enjoys over two decades of experience in the manufacture and sale of fiberglass mesh filters, offering customers high-quality fiberglass mesh filters to meet their R&D and production needs. As such, we are confident that SAM will be your favorite fiberglass mesh filter supplier and business partner.

Fiberglass mesh is a neatly woven, crisscross pattern of fiberglass thread that is used to create new products such as tape and filters. When it is used as a filter, it is not uncommon for the manufacturer to spray a PVC coating to make it stronger and last longer. The most common place to find fiberglass mesh is in tape products.

Sheetrock finishers use the mesh frequently. In fact, it is common to replace the paper tape used to float the joint between two pieces of sheetrock. The mesh that sheetrock finishers use comes on a roll just like paper sheetrock tape. The added benefit for the sheetrock finisher is to roll out the mesh over a great distance before having to apply the first coat of joint compound. Not only does it help them in this manner, but it also causes a stronger bond between the joint compound, the tape and the wall.

Sheetrock finisher's also use this tape to patch holes. The most common hole in the sheetrock generally occurs where a doorknob has hit a wall too many times. If it is only slightly damaged, a couple of short pieces of the tape will be formed into a square and placed over the hole. A joint compound will then be applied directly to it. If the hole is too large to patch with fibreglass mesh for wall alone, a piece of metal flashing can be added behind the tape before applying joint compound. Construction work is not the only use for fiberglass mesh.

As a filtering system, fiberglass mesh works really well. As the water flows through it, the mesh catches even the smallest impurities. In addition to this use, it can also be used as a mosquito net.

Finally, fiberglass mesh is sometimes woven into protective clothing used by those who work with dangerous chemicals or firefighters. Tightly woven mesh is put together and shaped into jackets that firemen wear when they are battling a blaze. It protects them from any fire that might ignite their clothing while fighting a fire. Fiberglass mesh can also be used in mold making and as protection against corrosives.

In your letter dated January 31, 2008, on behalf of your client, SpiderLath, Inc., you requested a tariff classification ruling on a woven fiberglass article. A sample of a piece of the material comprising this product was submitted with your ruling request.

The subject article, identified as “SpiderLath”, is a woven fiberglass mesh/fiberglass lath system with ethylene vinylacetate (EVA) backing strips that will be imported in rolls 4 feet wide by 75 feet long. You indicated in a telephone conversation that the fiberglass mesh is coated with a stiffener.

According to the information that was submitted with your ruling, the fiberglass mesh/fiberglass lath system is used as a cladding masonry support. The product can be used to install stucco and stone veneer. It can also be used over existing surfaces to apply masonry finishes.

In your presentation, you suggest classification under subheading 7019.31.0000, Harmonized Tariff Schedule of the United States (HTSUS), which provides for glass fibers (including glass wool) and articles thereof...thin sheets (voiles), webs, mats, mattresses, boards and similar nonwoven articles: mats. This subheading does not apply since the product is a woven article.

The applicable subheading for the woven fiberglass mesh for construction/fiberglass lath system with EVA backing strips will be 7019.90.1000, HTSUS, which provides for glass fibers (including glass wool) and articles thereof (for example, yarn, woven fabrics (con.): other: woven. The rate of duty will be 4.8 percent ad valorem.

Duty rates are provided for your convenience and are subject to change. The text of the most recent HTSUS and the accompanying duty rates are provided on World Wide Web at http://www.usitc.gov/tata/hts/.

This ruling is being issued under the provisions of Part 177 of the Customs Regulations (19 C.F.R. 177).

A copy of the ruling or the control number indicated above should be provided with the entry documents filed at the time this merchandise is imported. If you have any questions regarding the ruling, contact National Import Specialist Jacob Bunin at 646-733-3027.

What is a rod seal?

Sun, 26 Sep 2021 14:05:41 +0700

What is a rod seal?

There are so many different types of seals out there that it might be hard to understand all the different terminologies and functions. In this article, we give you our guide to what rod seals are, how they are manufactured and why you should choose rod seals from Martin’s Rubber.

Rod seals are often the decisive factor in ensuring that a hydraulic cylinder operates at peak performance. Leakage through the rod seal can lead to environmental damage and accidents, which is why it’s crucially important to select the correct seal for your application. While leakage past a piston seal will affect its efficiency, the system fluid or gas remains contained in the system. With a rod seal, failure will allow external leakage, and it should be paired with an appropriate wiper and gland housing design to ensure correct operation.

How do rod seals work?

Rod seals perform the difficult balancing act of creating a seal at both high and low pressure. This is often in combination with alternating high and low temperatures. As such, they need to leave an oil film, thin enough to return into the cylinder, after having passed an effective wiper seal. When selecting a piston rod seals, it is important to define your area of application and provide carefully defined specifications. Martin’s Rubber can then give you our recommendations for an appropriate rod seal to match your specific operating conditions.

How are rod seals manufactured?

Our rod seals can be CNC machined to bespoke sizes, including making adjustments away from original seal sizes to compensate for worn rod or gland conditions. Plus, we can help to restore the original performance of used equipment, as well as provide components for new build designs. Our standard rod seals can be rapidly manufactured in a variety of different materials, depending on your application. We also stock standard products for immediate shipment if your requirements are particularly time critical.

Why choose our rod seals?

“What sets us apart, I think, is that we’re flexible,” says Adam Hooper, Operations Director at Martin’s Rubber. “We deliver the quality that people need in the most responsive way possible, and we add value in terms of engineering and creative input,” he adds. Contact one of our expert advisers today on 023 8022 6330 or email sales@martins-rubber.co.uk to discuss your rod seal requirements.

Designers often specify buffer seals be placed in front of primary rod seals in heavy-duty hydraulic applications to extend the life of the seals. As the name indicates, buffer seals “absorb” pressure spikes typical on heavy-duty cylinders to protect the primary rod seals.

But how do these two types of seals interactions interact, which parameters affect those interactions, and how can they be used to extend the life of cylinder rod-sealing systems?

What was learned during these investigations will give engineers insights into seal types and interactions between seals so they can specify the most appropriate seals for their applications.

The key element of the buffer seal is the lubrication film thickness which passes the sealing edge. It is responsible for the performance of the entire rod sealing system. Different pressure and speed conditions during the in- and outstroke of the piston rod are typical for heavy-duty hydraulic cylinders and result in different oil film thickness. Therefore, the buffer seal needs to be designed to ensure a hydraulic cylinder rod step seals and absorb pressure peaks during operation.

Generally, buffer seals use one of two basic design principles:

High sealability buffer seals have good sealing abilities and can handle all of the system pressure and possible pressure peaks. Therefore, the primary rod seal will not be pressurized and can’t be damaged by pressurization. The seal’s high sealability means only a thin film of lubrication film can pass it, which could cause starve the primary rod seal of lubrication. This can lead to stick-slip, higher friction and sealing-edge temperatures, and possibly damage to the sealing material, all of which shorten the rod seal’s life.

Friction optimized buffer seals let thicker oil film pass the sealing edge to properly lubricate the primary rod seal. Depending on operating conditions, they can also let pressure build-up between the primary rod and buffer seals (intermediate pressure).

These buffer seals should keep out system pressure, because if the intermediate pressure is equal to system pressure, it cannot buffer. It is also important to use a primary rod seal and a wiper for good sealing and back-pumping ability to guarantee a leak-tight system.

An additional advantage of this type of seal is that the primary cylinder rod seals SPNO gets better lubrication, leading to smooth running equipment. If the buffer and primary rod seal work together correctly (as described above), friction in the entire rod sealing system can be similar to that of a single rod seal component. Reducing friction extends the life of the rod seal and the entire hydraulic cylinder.

Both working concepts have their place. Friction optimized buffer seals might be best in OEM components to extend a hydraulic cylinder’s service life. But high-sealability buffer seals might be more suitable in the aftermarket, where repair work and maintenance on hydraulic cylinders is more common and a leak-tight rod seal is more important.

Buffer Seal Designs

There are many different buffer seal designs and various material combinations available on the market. Here are the three most common designs.

Lip seals with back-up rings. These seals are good in heavy duty applications, where pressure spikes climb past 600 bar. The best lip seals are made of polyurethane with a thermoplastic back-up ring. This design enjoys a longer service life because the back-up ring resists extrusion. On the other hand, the back-up ring can influence the motion of the film of fluid on the piston rod, and seal installation requires more attention.

O-ring energized glide ring seals. These seals are widely used in light- to medium-duty application. Generally, the O-ring acts as an energizer to push the glide ring towards the piston rod. A big advantage of this is that various materials can be used. For example, a low temperature rubber grade can be used for cold climate conditions. The various material combinations give designers a wide choice. These seals have less resistance to extrusion compared to those with back-up rings.

The buffer seal’s main task is keeping the lubrication film thickness that passes through the seal’s edge at the right thickness. According to the Reynolds equation, the flow of a thin film oil/lubricant between two surfaces is influenced by its velocity, the gradient of the contact pressure distribution and the oil’s viscosity.

An important aspect of the investigations was to understand lubrication behavior under different test parameters. The lubrication level of lubrication determines friction and is essential for seal life. On the other hand, the lubrication level also determines the number and size of leaks, which should be minimized for the sake of performance and environmental concerns.

The influence of different in- and outstroke velocities has already been analyzed for a common U Cup rod seals ISI (see above graph). The results show that if outstroke velocity is much higher than instroke velocity, the likelihood of leaks increases. On the other hand, if instroke velocity is much higher than outstroke velocity, it is more likely the low-level of lubrication will increase friction on the instroke.

The second driver for the lubrication film thickness is contact pressure between the seal and piston rod. The higher the pressure gradient, the thinner the film. The gradient is influenced by seal design, the pressurization level, and the resulting deformation and dynamics between piston rod and seal.

The third driver for the lubrication film thickness is the lubricant’s viscosity. The lower the viscosity, the thinner the lubrication film.

In the second installment of this series, tests will be set up and run and the results analyzed, revealing what factors of buffer seals matter most to rod seal performance and longevity.

Thomas Schwarz is manager of testing, materials technologies & research; Wolfgang Swete is manager of product technology and development; Silvio Schreymayer is manager of testing; Martin Wallner is the manager of product development; Emmanuel Pichlmaier is a product development engineer; and Michael Liebminger is a testing engineer for SKF Seals.

The rod seal of a hydraulic cylinder is a crucial component as it controls leakage directly into the environment. Several testing methods can be used to detect a decreasing sealing ability, even before measured leakage occurs. This feature article describes the results of leakage measurements, pumping rate measurements and film thickness measurements on the rod surface. The differences between the individual methods are described and discussed, and also compared with predictions from finite element calculations.

What Is A Seed Tray?

Sun, 26 Sep 2021 14:04:24 +0700

What Is A Seed Tray?

Starting your own plants from seed will often give you healthier plants at a lower cost. If you want to start seeds in bulk, you may want to consider a seed tray to help with germination.

So, what is a seed tray? A seed tray is a container used to sow multiple seeds at once. After seed germination, seedlings grow in the seedling tray until they are large enough for transplant. A single seed tray can hold anywhere from 6 seeds to over 1000 seeds!

Of course, when choosing a seed tray, there are lots of options for the material, the type of tray, and the number of cells.

In this article, we’ll talk about seed trays and the options that are available. We’ll also get into how to use seed trays and how to water the seeds and seedlings.

Let’s get going.

What Is A Seed Tray?

A seed tray is a container that is used to plant multiple seeds at once. A seed tray is sometimes called a seed starting tray.

A seed tray allows you to plant many seeds together in one container. This makes it much easier to water them and transport them.

After the seeds germinate, the seed tray holds seedlings as they grow, until they are ready for transplant outdoors or into larger containers.

There are a few different types of seed trays, including:

Mesh seed tray – a mesh seed tray allows water to drain out easily. A mesh seed tray is best for holding multiple individual containers (pots). A drawback is that the holes in a mesh seed tray are too large to hold soil without it falling through or washing away when watered. You can find mesh seed trays from Johnny’s Selected Seeds.

Solid seed tray with drainage holes – a solid seed tray with drainage holes allows for adequate drainage, but allows soil to stay moist enough for seed germination. A solid seed tray with drainage holes is best for planting multiple seeds together in one place. A drawback is that the seedlings do not have individual cells, so their roots can get tangled together as they grow. You can find solid seed trays with drainage holes from Johnny’s Selected Seeds.

Solid seed tray without drainage holes (leak proof seed tray) – a solid seed tray without drainage holes does not allow for any drainage. A solid seed tray without drainage holes is best for holding a cell flat (also called a plug flat). Since it holds water, it can be used to catch excess water from watering seeds, or it can be used to water from below (more detail on this later). You can find cell seed trays without drainage holes from Johnny’s Selected Seeds.

Another interesting option is this seed flat with 20 rows from Johnny’s Selected Seeds. Instead of separate cells, there are separate rows to keep different plant varieties from getting mixed up.

If you decide to use a cell flat for seed germination, each cell should have its own drainage hole. The tray below the cell flat should be solid without holes if you want to water the seeds from below.

The main problem of adapting the SRI techniques is high labor requirements for manual and lacking of mechanized system for planting single seedling in the field. The existing seedling preparation methods remain challenging among SRI practitioners due to traumatic condition. This study was intended to create modern techniques for increasing the quality and transplanting potentials to improve seedling preparation and reduce transplanting shock. It involved development of rectangular tray having 924 square growing cavities with sliding base to facilitate seedling transfer. Seed selection was conducted and 100% germination was obtained from the sunken MR219 seeds collected in 80 g/L of NaCl solution. SRI-tray seeding was 100% placed into cavities with SRI-seed picker at 150 g/L of tapioca solution. Two different media (Soil + Burnt husk (1:1) as M1 and Soil + Compost (1:1) as M2) were used to evaluate the growth performances for 10 days. The measured parameters (Seedling Height (SH), Leaf Length (LL), Leaf Number (LN), Root Length (RL) and Loosening Index (LI)) were compared between SRI-tray and conventional ones. The SAS revealed that M2 on SRI-tray had the highest significant values for SH, LL, RL and LI with the mean values of 155.6, 109.3, 89.3 and 75 sec when compared with conventional tray which had 125, 91 and 52 mm with no LI, respectively. The seed rate, nursery area and seedling age to support one hectare of planting area were found as 5.34 kg, 36 m2 and 8-10 days on SRI-tray against 15-50 kg, 250-500 m2 and 12-30 days on conventional practices.

The more pellets that are placed in the mould, the denser and stronger the seedling tray with lids.

In cheaper trays, there tend to be slightly bigger gaps between the expanded pellets, and fine plant roots can enter these, making it difficult to pull out the plants.

Damping off organisms can also lurk in these small spaces, and the growing plants can become infected and die. One of the Pythium species (fungus-type pathogens) is usually the main culprit, but it’s not the only one.

I have used horse manure compost as a medium for 23 years and have never had damping off problems. This may be because the medium is a rich source of beneficial organisms, which suppress development of pathogens. I also never get powdery mildew on Brassica seedlings.

Once the pathogen has appeared, the trays must be sterilised, or the problem will keep cropping up and possibly cause major losses.

The most effective way of sterilising trays is in a heat chamber. To save cost and effort, some growers wait until damping off starts before using heat sterilising.

Another solution is to use a commercial dip containing copper; this will also reduce the penetration of roots into the fine gaps in the polystyrene.

If you are a small grower, you can use a simple, home-made steriliser such as bleach mixed with water at a 10% solution, or hydrogen peroxide at 3% concentration. Leave the trays suspended in the solution for 20 minutes, then rinse and dry them.

The ideal sealant

One of the most effective ways of treating seedling trays is to dip them in a water-based roof paint when they are still new.

Obtain a flat receptacle slightly larger than the tray and dilute the paint with 10% water. Push the tray face down into the paint until the paint reaches the drainage holes. Lift and allow the excess paint to drip back into the tray, then place it face-up to dry. (It’s unnecessary to paint the base.) You should be able to coat about 10 trays per litre.

Some farmers are put off by the price of paint, but this treatment is well worth the cost: not only does it extend the life of the rice seedling tray by many years, but it seals the fine gaps in the polystyrene.

This reduces the risk of pathogens lurking in these crevices and also makes it much easier to pull out the seedlings.

Roof paints come in many colours, so you can use different colours for different years to keep track of the lifespan of each batch of styrofoam seed trays. There are often specials on roof paints and you can take advantage of these to cut the costs of the treatment.

Biodegradable plastics have been widely introduced into agricultural production, but their impacts on the soil ecosystem remain unclear. The present study investigated the impacts of a biodegradable seedling tray (BST) on the microbial communities in paddy soils. A 110-day rice culture experiment was conducted with three different paddy soils developed from black soil (BS, black chernozem soil), chao soil (CS, Fluvo-aquic) and red soil (RS, Alfisols) and three application rates of BST (0, 0.02 and 0.2?g?kg?1). Soil phthalic acid ester (PAE) concentrations, physicochemical properties and enzyme activities were determined to evaluate the influence of BSTs on soil quality. 16S high-throughput sequencing was used to study bacterial community composition and the Biolog EcoPlate? test was used to profile microbial activity and community function. Results show that the application of BSTs did not markedly affect soil quality, and the potential release of PAEs from BSTs was negligible. Interestingly, the microbial community was affected by BSTs in a soil-dependent and time-dependent pattern. The microbial community in RS was not significantly influenced by BSTs. Relative abundances of some predominant genera in BS (e.g. norank_f__BSV40) and CS (e.g. Norank_f__Nitrosomonadaceae) were significantly influenced by BSTs, and db-RDA results show that community composition in BS and CS was shaped mainly by BSTs. Community level profiling shows that BSTs significantly increased microbial activity and decreased functional diversity in BS after 55?days, but the impacts disappeared after 110?days. The results contribute to the knowledge of how biodegradable plastics influence microbial communities in paddy fields and provide information relevant to the practical use of BSTs under field condition.

This experiment investigated the effect of different plug-tray cell designs on root development of red maple (Acer rubrum), red oak (Quercus rubra), and quaking aspen (Populus tremuloides) seedlings. In April of 2015, seeds of each species were sown into three plug trays with different substrate volumes and grown for 17 weeks. Two trays had permeable walls for air-pruning, one with vertical ribs and one without. The third tray had impermeable plastic cell walls. Harvested seedlings were analyzed for root dry weight, length, volume, surface area and number of deflected roots. Root length per volume was highest in the impermeable-walled tray for red maple and quaking aspen. The total numbers of deflected root systems were higher for all species in the impermeable-walled tray. Seedlings grown in the air-pruning trays had smaller proportions of deflected root masses. Greater substrate volume did not influence root deflection development. The air-pruning tray without vertical ribs had the lowest total number of root masses with misdirected roots and lower proportions of root masses with misdirected roots for all species. These results indicate that improved root architecture in root-air pruning tray designs is achievable in tree propagation; however, vertical plastic structures in air-pruning trays can still cause root deflections.

What is a Ramadan crescent moon tree?

Sun, 26 Sep 2021 14:03:13 +0700

What is a Ramadan crescent moon tree?

One particular decor element that has taken root – and is quickly gaining ground in the region this year – is the crescent tree.

Chances are you’ve come across it yourself: the artificial tree comes in a number of sizes and colours, with its defining feature being its distinct crescent moon shape.

With its Instagram-friendly appearance, it has blown up online under different names – moon tree, green ramadan eid crecsent moon tree, Ramadan tree and even Eid tree – as more families take to them. A search for #RamadanTree on Instagram turns up more than 1,000 posts, while one for #EidTree yields over 1,500; impressive since three years ago, they didn’t really exist.

So how did it all begin? It all seems to have started in Michigan, in the US, where resident Samar Baydoun Bazzi decided to mark the holy month with some festive cheer. As a mother, she wanted to create a special experience for her daughter, so she began incorporating Islamic-themed art into the home. When that wasn’t enough, she tried a Christmas tree, but that only confused her child further, she told local media.

That is how Bazzi ended up taking things into her own hands – by creating Ramadan trees in the shape of a crescent moon as a tribute to Islam. As the pictures of the trees circulated online, she started getting orders and the trend just picked up from there.

How did trend reach the UAE?

The crescent-shaped tree is making its way across to the UAE, too. Zahirah Marty, founder of brand development agency Think Liquorice, purchased one in 2020 through Amazon, but she found it quite difficult to source one at the time, and options were limited.

Today, however, it's easier, as a number of brands have starting selling them.

Crate & Barrel, which introduced the tree in 2020, saw sales of the crescent tree soar this year. The hugely popular item can be bought item both online and in-store, for Dh400.

Why get a crescent tree?

UAE resident and mum-of-four Taghred Chandab, who bought one before Ramadan from Kibsons, says it worked as a great way to start a conversation with little ones about Islam and Ramadan.

“We like to decorate for Ramadan and Eid, to give the children a sense of excitement around both the holy month and Eid. My youngest is 5 and she has asked over the years if we could have a Christmas tree at Christmas, but as Muslims we didn't feel this was appropriate as it didn't reflect our beliefs.

"She was really excited when the white ramadan eid crecsent moon tree arrived and we explained to her why the moon was important in Islam, particularly around Ramadan and Eid. She feels the spirit now. Sometimes kids need visual aids to understand."

When Marty posted a picture of her tree on social media last year, she received many queries from other parents, also looking for a way to “bring the month to life for their children and make it something tangible and memorable”.

"Growing up, we didn't have anything like this," she tells The National. "There weren't decorations and lights. At best we shared plates of food or dates with neighbours and family and waited for Eid; for a day of family and food. We did a little less that month, and besides the wave of energy at iftar, it was a pretty non-eventful month from a child's perspective.

“I want Ramadan to be a month-long celebration of who we are, and time at home together, and most importantly I want to create new traditions for my family based on our diversity and mixed cultural background, because that’s a part of our identity.

"It is a month to reflect, and reconnect with ourselves, our home, our family, our creator and I want that to be done in a lively and festive space. Having that centrepiece is a symbolic display of that for me."

Marty says she makes setting up the tree an educational and fun experience for her son Noah, who loves it, too. “While we decorate it, we chat about why it’s a moon and not a tree, why we have it out, what fasting means and how he has so much to look forward to with Eid.

“I want Noah to fall in love with his faith, and all that it comes with. We live in a very challenging world, and children today won’t accept things ‘because we say so’. I want my son to view religion as the beautiful part of his world it is from a young age, and creating reasons to celebrate, decorate and bring joy is how I choose to do it. Everything else will follow."

A response to criticism

Despite its popularity, the trend is not without its criticism. A cursory search online will find comments about it copying western traditions, while others believe it can be ostentatious.

“In any area of life there will always be critics, and I respect that as humans we will differ in our opinions," says Marty. "I prefer to focus on my intention to create happy, celebratory moments for my family as a medium of education, and a way of carving out our space with our circumstances.

“If a decorated moon sparks joy in my toddler to look forward to the month of Ramadan, ask me questions, and open his mind and heart to the lessons, stories and memories, then I’ve achieved my goal.”

How to decorate a Ramadan tree:

Some trees come pre-decorated, but if you prefer to decorate the gold ramadan eid crecsent moon tree together with your family, there are options in the UAE.

Marty recommends Daiso as a place where one can get a range of lights in the shapes of mosques, stars and moons. She drapes her family Ramadan tree with lights, camels and even baubles.

“I grew up with a childhood tradition of new Eid pyjamas and either money or gifts. I keep that tradition in our home. The silver ramadan eid crecsent moon tree is a place we have all this sitting until the night before Eid, which adds to the excitement of Eid day,” she says.

Other places where one can get Eid and Ramadan decorations, as well as trees, include Amazon, Kibsons and noon.com.

DEARBORN — Celebrating Ramadan in the U.S. doesn’t come as naturally as it does in Muslim-majority countries. From fasting during long summer days to lackluster holiday cheer and enduring anti-Muslim sentiments, Muslim Americans have to try just a little harder throughout Islam’s holiest month.

Samar Baydoun Bazzi, a 29-year-old Dearborn resident and nursing student, knows that all too well and is trying to change that— one crecsent tree decorations at a time.

Bazzi told The AANews she remembers feeling like the “odd one out” growing up as a Muslim in Michigan, especially after she began wearing the hijab. During Muslim holidays, she rarely would feel any enthusiasm as gatherings were mostly isolated to family and close friends. Her home would only light up with decorations during Christmas.

Although simple Ramadan-related decorations adorn some properties in Dearborn, Bazzi said she wants to bring a little extra Ramadan spirit to a city that’s home to one of the most concentrated Arab and Muslim American communities and one of the largest mosques in the nation.

“People can get more creative,” she said.

The project, now in its fourth year and selling nationwide, began when Bazzi’s daughter, 4-years-old at the time, thought it was Christmas when she put up a tree along with other banners and crafts, in preperation for Ramadan.

That same day, Bazzi said she took the tree apart and rearranged it in the shape of a crescent moon, a widely-recognized symbol in Islam.

“I wanted her to be excited about her own religion and holiday,” she said about her daughter.

Bazzi, who crafts the trees by hand in her basement, said she quickly learned that many Muslim households face the same obstacles and people wished they’d had such trees in their childhoods.

“The parents want their kids to feel like their own holiday is the most amazing time of the year,” Bazzi said. “It’s a time when they’re supposed to be closer to God, to pray and fast; we want them to fall in the love with the whole process.”

Bazzi said her intention was not to blend Anglo-Christian and Pagan traditions with Islamic ones by using a Christmas tree and that she initially only used a tree because that’s what she had available.

“It really makes no difference to me,” she said. “It doesn’t look like a Christmas tree anymore.”

At a time when political tensions are high and bigoted rhetoric is rampant, Bazzi said her goal is to ensure Muslim Americans, especially the youth, can be unabashedly proud and more openly celebrate their faith.

It takes her about five hours to make each tree. The six-foot-and-eight-inch-tall trees are available in white and green and include lights and a hanging star. They’re being sold nationwide, with requests for them coming from around the world.

Bazzi said the Ramadan Trees have garnered enough interest for a wait list to fill up, forcing her to stop accepting orders this year.

She said she hopes to partner with a manufacturer and expand the project into a large-scale business.

For Samar Baydoun Bazzi, the Ramadan Tree grew out of a desire to mark the Islamic holy month with festive cheer.

Growing up as a Muslim in the U.S., Baydoun Bazzi, 29, of Dearborn said she noticed a lack of decorations during the month-long holiday, which Muslims observe by fasting from sunrise to sundown to commemorate the revelation of the Quran to the prophet Muhammad.

“Obviously, Ramadan’s important,” Baydoun Bazzi said. “You gotta pray and fast, and you want to become closer to your creator. But I never as a kid felt like there was any decorations or like a celebration. I wanted something exciting.”

When she became a mother, she decided to take matters into her own hands and create the kind of Ramadan experience she wished for as a child.

She began by decorating her west Dearborn home with Islamic-themed art, like acrylic paintings of Arabic calligraphy and a cardboard model of a mosque.

It wasn’t enough.

So in 2014, she said, she decided to put up a Christmas tree.

It didn't last long.

“Oh, Christmas!” Baydoun Bazzi remembers her daughter Zahraa, then 4 years old, shouting.

“I knew that it was a mistake,” Baydoun Bazzi said of her decision. “So I looked at my tree and decided to take it apart.”

That’s when the Ramadan Tree first took root.

Are stinky inflatable pool toys putting your kids at risk?

Sun, 26 Sep 2021 14:02:04 +0700

Are stinky inflatable pool toys putting your kids at risk?

The researchers expressed concern that some of the products contain potentially hazardous chemicals that could pose a risk to children’s health, depending on the degree of exposure and concentration levels in the products.

The researchers conducted tests using an inflatable beach ball, a pair of swimming armbands and two bathing rings they bought off the shelf from local stores and online suppliers in Germany.(Shutterstock)

HEALTH

Are stinky inflatable kids' toys putting your kids at risk? Here’s what a study found

The researchers expressed concern that some of the products contain potentially hazardous chemicals that could pose a risk to children’s health, depending on the degree of exposure and concentration levels in the products.

Washington D.C. | By ANI

UPDATED ON APR 13, 2017 08:46 PM IST

Turns out, there are many dangerous chemicals lurking in your swimming pool that can risk your children’s health.

Inflatable sprinkler and swimming aids, like bathing rings and arm bands, often have a distinctive smell which could indicate that they contain a range of potentially hazardous substances.

Some of these compounds, which include carbonyl compounds, cyclohexanone, phenol and isophorone, might be critical when present in higher concentrations in children’s toys, said authors Christoph Wiedmer and Andrea Buettner.

Lead author Wiedmer from Fraunhofer Institute for Process Engineering and Packaging IVV in Germany and his team conducted tests using an inflatable pool, a pair of swimming armbands and two bathing rings they bought off the shelf from local stores and online suppliers in Germany.

A small piece of material from each sample was analysed using a variety of material analysis techniques, including one that takes infrared measurements, and it was concluded that the inflatable objects were all made from polyvinyl chloride (PVC).

The researchers then investigated the molecular make-up of the distinctive smells arising from the pool toys. They extracted detectable odours from each sample using solvent extraction and high vacuum distillation methods, and then identified the main odorants using a combination of sensory and common analytical approaches.

Between 32 and 46 odours were detected in each sample, of which up to thirteen were quite intense. The majority of these odorants were identified and among these were several fatty smelling mono- or di-unsaturated carbonyl compounds and their epoxidised derivatives, but also odouractive organic solvents such as cyclohexanone, isophorone, and phenol.

As part of the study, a panel of trained volunteers sniffed each product, and ascribed common odour attributes to these. They also rated the intensity of each odour, and had to guess whether these could be hazardous. Three of the products reminded the panellists of almonds, plastic and rubber, while the fourth more pungent one reminded them of glue and nail polish.

Wiedmer expressed his concern that some of the products contain potentially hazardous chemicals that could pose a risk to children’s health, depending on the degree of exposure and concentration levels in the products. Cyclohexanone can be harmful if inhaled, phenol is known to be acutely toxic and to presumably have mutagenic potential and isophorone is a category 2 carcinogen, which means that this is a suspect substance in the development of cancer in humans.

“A range of these substances are not yet resolved in their chemical structures. Likewise, potential negative effects on humans, such as irritation, smell nuisance, or other physiological or psychosomatic effects still need to be resolved,” said Wiedmer.

“Modern products such as toys and children’s products are sourced from a wide variety of chemical and physical manufacturing processes, and this complexity often makes it difficult for us to identify those containing contaminants and unwanted substances, and to determine their causes,” noted Wiedmer. “However, we found that in a number of cases our noses can guide us to ‘sniff out’ problematic products.”

The study appears in the journal Analytical and Bioanalytical Chemistry (ABC).

Backyards and patios have been working hard all year because of the pandemic, and this summer they can provide new ways to cool off and have fun in the water.

Whether you have a lot of space or a little, there’s gear ranging from water tables and tubs for kids to floating loungers with drink holders for adults.

One company, Minnidip, makes inflatable “adult kiddie pools” that aim to transport you to some exotic travel destination. Patterns on the Marrakesh pool reference Moroccan architectural details, while the Amalfi is a nod to the blue, yellow and white tile of the Italian coast.

“Because for me, having a pool on our urban Chicago rooftop felt like being transported to another place,” says company founder Emily Vaca. “I wanted to capture that feeling through design and pattern. “

Minnidip also offers inflatable drinks coolers and glam pool balls filled with gold confetti, among other offerings.

The only water table that lets you make waves, Little Tikes’ Island Wavemaker has a water wheel, plus cute sea creatures and a wee pirate to send paddling around the waterway or down the waterfall. Toddlers can practice their fine motor skills with Little Tikes’ Spinning Seas Water Table; small balls, a cup, a funnel and a water wheel set up the fun.

Step2’s two-sided Waterfall Discovery Wall has adjustable toggles, spinners and chutes to send the water tumbling in lots of different ways. And Lakeshore Learning’s Watch It Flow water table features three plastic logs that can be configured however you wish. Fill the logs using a hose or bucket; gates control the flow and can close up to make long tubs.

Foamo, also from the folks at Little Tikes, creates mountains of easy-to-clean-up foam when you add the nontoxic, biodegradable foam solution to water.

HOSE HAPPY

Turn on the hose and attach it to West Elm's inflatable car bed or giant shark mouth sprinklers. Fat Brain Toy’s Hydro Twist Pipeline Sprinkler has a couple of fountains, plus a bunch of wiggly worm hoses. Or hook up to BigMouth’s giant 6-foot-high unicorn, who shoots water out of her horn. There’s a ginormous ape, giraffe, dinosaur and giraffe here as well.

SWIM AND PADDLE

Giant inflatable water wheels let you find your inner hamster. You can find ones online for toddlers, while Wow Watersports has a grownup version they call the Aqua Treadmill.

Don’t forget the family pets; a nonporous, puncture-resistant floating dog bed at Frontgate comes in a bunch of colors and three sizes.

Chewy has ZippyPaws Floaterz sturdy turtle-shaped water toys for dogs, as well as rope-handled bumpers and a variety of floating balls.

A hard-sided kiddie pool can be a good non-inflatable option for cooling off; just hose it out and stow away. Other pluses: The doggos will also have fun splashing around in it, and it makes a great sand or snow play zone in colder weather. The Sun Squad Wading Kiddie Pool is inexpensive and has an embossed bottom, so it’s less slippery.

SLIDE AND RIDE

A basic heavy-duty plastic water slide or “slip and slide” can be set up in most backyards; if yours doesn’t come with an attached barrier at the bottom, make sure to put something soft there.

Studio 21 Graphix’s slide has a crash pad at the finish line, plus two lanes for racing and a sprinkler curtain to pass thru on the way down. Wow Watersports’ Strike Zone Water Slide is 25-by-6 feet of slipperiness; zigzag sprinkler patterns assure a wet ride, fat pontoons on either side keep riders inside, and two sleds are included. Got a really long yard? Get two; they can be interconnected.

If you’ve got lots of space, consider Costway’s inflatable Bounce House and Water Slide, with a bounce area, water gun, two slides, a basketball hoop and several balls. It comes with a storage bag for easy transport.

POOL STYLE

Marisa Issa of Los Angeles says her family’s favorite pool games are corn hole and a floating basketball hoop, but her favorite is a floating mat from Frontgate “that only mom can use,” she says. The sleek, minimalist white float has a headrest, and is made of marine-grade dense foam, suitable for chlorine or saltwater pools.

If you prefer sitting up a little, Frontgate’s got a floating armchair with attached ottoman. Choose from aqua, blue or flamingo pink. Or splash out on a full-size pool chaise kitted out with drink holders.

Want to hang out with a handful of friends in a backyard pool? Funboy has a 9-foot-wide floating metallic crown with drink holders. Or lounge luxuriously in the company’s Bali Cabana Lounger, with a curved integrated shade, a tropical leaf print, cup holders and handy grab ropes.

BigMouth has some food-related inflatables like a giant ice pop, pizza slice, donut, watermelon slice, cheeseburger and taco.

At first, glance, laying on an inflatable toy in shallow water seems pretty safe. After all, the water isn't deep, and there is a floating toy right there. Recently, a family's trip to the beach in Nova Scotia proved to be a harrowing reminder of why this is not the case. In August, two 5-year-olds played in shallow water – one in an inflatable ring, the other on an inflatable roller. Because the girls were in shallow water, their caregiver assumed the inflatable toys were enough. It wasn't until the girls began to drift away from that the complete danger of the situation became clear.

Inflatable toys can be dangerous

Because they are so light and buoyant, they tend to drift in the water or deflate when they get wet. That's when it's a problem. Kids don't know when their toys are deflated and cannot compensate when they're in the water. They can get trapped in the holes or strangle. When the girls got stuck, their caregiver did the right thing by calling for help. First responders rescued the girls and took them to the hospital to be treated for their injuries. While it's infrequent that inflatable toys are the source of injury to kids, it's good to know that they can pose a hazard. The numbers aren't obvious, but it seems that they're responsible for 1 in every 100 boating-related deaths in the U.S. and are one of the leading causes of drowning for children aged 4-6.

Why Inflatable Toys Can Be Dangerous

The giant inflatable was much bigger than the girls and began to drag the mattress toward shore, according to the parent of one of the girls who spoke with CTVNews. However, the inflatable ring wasn't nearly as big or heavy and was drifting with the current. The girls eventually lost hold of both and drifted a considerable distance. The girls' parents rushed to the scene and tried to retrieve their children, but the current was too firm, and the military eventually rescued them. The girls were found to be unharmed. Since this incident, many parents have expressed concerns about the safety of inflatable toys.

Practical Uses of Botanicals in Skin Care

Sun, 26 Sep 2021 14:00:46 +0700

Practical Uses of Botanicals in Skin Care

Cosmeceuticals are the fastest growing sector of the cosmetic industry, and the future of antiaging cosmeceuticals in particular is very promising. Botanical pesticide that support the health, texture, and integrity of the skin, hair, and nails are widely used in cosmetic formulations. They form the largest category of cosmeceutical additives found in the marketplace today due to the rising consumer interest and demand for natural products. Various plant extracts that formed the basis of medical treatments in ancient civilizations and many traditional cultures are still used today in cleansers, moisturizers, astringents, and many other skin care products. New botanical skin care treatments are emerging, presenting dermatologists and their patients the challenge of understanding the science behind these cosmeceuticals. Thus, dermatologists must have a working knowledge of these botanicals and keep up with how they evolve to provide optimal medical care and answer patient questions. The most popular botanicals commonly incorporated into skin care protocols are discussed.

The cosmeceutical market is one of constant fluctuation depending upon consumer demand. Skin care companies are continuously pressured to release new, innovative products that promise to transform the appearance of aging skin overnight. Over the past decade, there has been fervent interest in products found in nature because of their perceived safety. Skin care products are often developed from plants. Many believe that if a product can be safely ingested, it will also be safe for topical application. In general, plant-derived, botanical feed additives, cosmeceutical products tend to be antioxidant in action since these organisms must thrive in constant direct ultraviolet (UV) light, the Earth's most prolific manufacturer of free radicals. In this article, the authors review the most popular ingredients in this class and comment on their possible usefulness in skin care protocols.

Soy extract has positive research support for its antioxidant, antiproliferative, and anticarcinogenic activities. Topical application of soy has been used to reduce hyperpigmentation, enhance skin elasticity, control oil production, moisturize the skin, and delay hair regrowth.1 Soy also has the potential to decrease photoaging of the skin and prevent skin cancers through the estrogen-type and antioxidant effects of its metabolites.1

The major components of soy are phospholipids, such as phosphatidylcholine and essential fatty acids. The minor components of soy include the most active compounds, such as isoflavones, saponins, essential amino acids, phytosterols, calcium, potassium, iron, and proteases soybean trypsin inhibitor (STI) and Bowman-Birk inhibitor (BBI). The various components of soy have a variety of beneficial effects making them useful additions to skin care products. The most potent isoflavones are the phytoestrogens known as genistein and daidzein. Genistein is a potent antioxidant that inhibits lipid peroxidation and chemical and ultraviolet light B (UVB)-induced carcinogenesis. Genistein was shown to significantly inhibit chemical, carcinogen-induced, reactive oxygen species; oxidative DNA damage; and proto-oncogene expression, as well as the initiation and promotion of skin carcinogenesis in mouse skin.2 Topical estrogens have been shown to promote collagen synthesis and increase skin thickness, which may be beneficial for postmenopausal women who develop a thinner dermis and decreased collagen.3 The small proteases STI and BBI appear to promote skin lightening and reduce unwanted facial and body hair in human clinical trials.3,4 Beyond the depigmenting activity, STI, BBI, and soy milk were also found to prevent UV-induced pigmentation both in vitro and in vivo.5 In addition, soy lipids, lecithins, and phytosterols are believed to restore barrier function and replenish moisture.

Beyond its moisturizing ability, soy appears to be a safe and effective treatment for postmenopausal women and for hyperpigmentation disorders (other than melasma, which is somewhat estrogen mediated). Although further research is necessary, the antioxidant and anticarcinogenic activities of soy and its isoflavones show a promising role for this botanical fertilizer additives in the cosmeceutical industry. Soy has therefore become a popular addition to a wide variety of skin care products (see Table 1).

Green tea extracts are among the fastest-growing herbal products. While there has been enormous growth in green tea consumption as a dietary supplement, the use of tea extracts in cosmeceutical formulations is also on the rise. The complex polyphenolic compounds in tea provide the same protective effect for the skin as for internal organs. They have been shown to modulate biochemical pathways that are important in cell proliferation, inflammatory responses, and responses of tumor promoters.6 Green tea has been shown to have anti-inflammatory and antioxidant effects in both human and animal skin.

Since inflammation and oxidative stress appear to play a significant role in the aging process, green tea may also have antiaging effects by decreasing inflammation and scavenging free radicals. Researchers have found that the main active ingredient in green tea, epigallocatechin-3-gallate (EGCG), works well as an anti-inflammatory, antioxidant, and sunscreen. Topical green tea applied to human skin has been shown to provide a photoprotective effect, reduce the number of sunburn cells, protect epidermal Langerhans cells from UV damage, and reduce the DNA damage that formed after UV radiation.7 Green tea polyphenols, when combined with traditional sunscreens, may have an additive or synergistic photoprotective effect. Green tea has also been found to decrease melanoma cells in tissue culture and squamous cell carcinoma cell formation in mice with topical and oral administration. Additionally, it improves wound healing by increasing keratinocyte cell differentiation and has been shown to inhibit Streptococcus species and Escherichia coli.8

Natural flavonoids, such as green or black tea polyphenols have been show to reduce UVB-induced erythema, tumorigenesis, and immunosuppression in mice.9,10 White tea appears to be a more potent antioxidant than green tea. Black tea has a much lower content of catechins than green tea, but a higher content of other flavonoids, such as quercetin, theaflavin, and kaempferol. Black tea extracts applied before and after UV light challenge have been shown to decrease signs of cutaneous photodamage, carcinogenesis, and inflammation in human and mouse skin.3

Most cosmeceutical products containing tea extracts or phenols have not been tested in controlled clinical trials, but these substances have shown compelling evidence for antioxidant, anti-inflammatory, and anticarcinogenic activities. There are currently several products that contain green tea extract on the market (see Table 2). Unfortunately, the concentration of phenols is not standardized in these products; therefore, some products may have little-to-no therapeutic effect, making purchasing them a challenge for consumers. It is generally accepted that five-percent green tea extract or polyphenols in the 90-percent range is an effective concentration.

German chamomile, or Matricaria recutita, has been used throughout history as an herbal treatment for various skin conditions. It functions as an antimicrobial, antiallergic, anti-inflammatory, antioxidant, and analgesic and was approved by the German Commission E for inflammatory mucocutaneous diseases and wound and burn therapy.3 The active constituents of chamomile include the terpenoids (bisoprolol, matricine, levomenol, chamazulene), flavonoids (apigenin, luteolin, rutin, quercetin), hydroxycoumarins, mono- and oligosaccharides, and mucilages. Chamazulene exhibits anti-inflammatory activity and promotes wound healing. Levomenol is an anti-inflammatory and natural moisturizing agent that has been found to diminish the signs of photodamage, reduce pruritus, and ameliorate skin texture and elasticity. In addition to reports of anti-inflammatory effects, chamomile is also purported to have some antioxidant properties, which have been identified through chemical assays.11,12

While chamomile is generally considered a safe product, there have been reports of contact dermatitis and conjunctivitis following topical application of chamomile products, and there is a potential risk of angioedema and anaphylaxis. Chamomile can also interact with warfarin, promoting an additive anticoagulant effect.

Clinical studies appear to support the traditional uses and therapeutic benefit of topical chamomile. This herb has been included in a wide variety of cosmetic products including soothing moisturizers and cleansers as well as color-enhancing hair products (see Table 3).

Caffeine, the chemical pesticide in coffee, tea, and some soft drinks, has demonstrated both anticarcinogenic and antioxidant properties. Initially, caffeine's potential inhibitory role in cancer development was found through studying oral administration of black and green tea.13 This study illustrated that the oral administration of caffeine alone and the addition of caffeine to decaffeinated teas showed inhibitory effects of UVB-induced carcinogenesis. Oral administration of caffeine has also been associated with in-vivo upregulation of tumor suppressor genes.14

Continued research revealed that topical application of caffeine inhibits carcinogenesis and promotes apoptosis in sunburn cells of hairless SKH-1, UVB-pretreated mice.15 Researchers found that topical application of the tea constituents caffeine and (-)-epigallocatechin gallate (EGCG) decreased the number of nonmalignant and malignant skin tumors in SKH-1 hairless mice pretreated with UVB. While caffeine performed better than EGCG, both treatments resulted in elevated apoptosis in nonmalignant skin tumors and squamous cell carcinomas. The results suggest a need for further studies to determine whether topical applications of caffeine or EGCG can inhibit sunlight-induced skin cancer in humans. Further studies by the same authors found that topical application of caffeine sodium benzoate and caffeine have both a sunscreen effect and enhance UVB-induced apoptosis and may be good agents for inhibiting the formation of sunlight-induced skin cancer.16

These studies present a potential use for caffeine in formulations used to decrease the risk of skin cancer formation after cutaneous damage from UV exposure. More studies need to be done to further examine caffeine's antioxidant potential. The above findings have prompted many manufacturers to add this popular agent to various cosmeceutical products on the market today (see Table 4).

Coffeeberry, harvested from the fruit of the coffee plant Coffea arabica, is considered to be one of the richest sources of antioxidants and is well known for its skin-rejuvenation properties. Coffeeberry contains potent polyphenols including chlorogenic acid, ferrulic acid, quinic acid, and condensed proanthocyanidins. The dermatologic application of CoffeeBerry? (J&J Technologies LC) extract was first recognized at the American Academy of Dermatology's Annual Meeting in February 2007. The first product to enter the market with CoffeeBerry as the basic ingredient is RevaléSkin (Stiefel Laboratories, Inc., Coral Gables, Florida) (see Table 5).

According to Stiefel Laboratories, Inc., CoffeeBerry has demonstrated high antioxidant properties, outperforming green tea extract and vitamins C and E. Proprietary research from the manufacturer has also shown that the use of the RevaléSkin CoffeeBerry skin care system consisting of 0.1% CoffeeBerry cleanser and 1% day and night creams showed statistically significant improvement in fine lines, wrinkles, pigmentation, and overall appearance when compared to vehicle. In addition to the evidence of safety and efficacy provided by the randomized, double-blind trials, further support comes from positive pathologic and in-vitro studies showing enhanced collagen production by fibroblasts. Studies are currently in progress to evaluate the use of the CoffeeBerry skin care system in conjunction with retinoids and intense pulsed-light treatments.17 More clinical studies need to be performed to fully assess the topical preparations containing CoffeeBerry extract, but polyphenols have already demonstrated efficacy in photoaging and skin cancer prevention.

The inclusion of botanical animal remedy additives in skin care products is becoming ever more popular. Potential antioxidant and anti-inflammatory benefits may prove beneficial for a number of conditions that dermatologists routinely treat, such as rosacea, photoaging, and skin cancer. The published effectiveness of prescription retinoids is well known, but equally well known is the irritation and redness often caused by the initiation of therapy. Botanicals may hold the promise of utility to reduce such inflammation. This is one of the best and most practical reasons to include botanicals in skin care protocols. Dermatologists should be aware of these products and be able to discuss their uses and potential benefits with their patients.

Practical Uses of Botanicals in Skin Care

Sun, 26 Sep 2021 14:00:46 +0700

Pipe Fittings

Sun, 26 Sep 2021 13:59:24 +0700

Pipe Fittings

This chapter presents various types of pipe fittings. Of all the fittings, the elbow is the one most often used. Simply put, the elbow, or ell, is used when a pipe changes direction. Elbows can turn up, down, left, right, or any angle in between. When one finds it necessary to draw a 90° elbow or calculate how much space it will occupy in a routing configuration, knowing its length becomes essential. An elbow's length is commonly referred to as the center-to-end dimension and is measured from the centerpoint of its radius to the end of either opening. Dimensional sizes of fittings are typically provided by the manufacturer of the fitting. Manufacturers issue dimensioning charts containing lengths for a particular fitting. Another elbow that may be used under certain circumstances and with permission from the customer is the 90° short-radius elbow. The 90° short-radius ell makes a much sharper turn than does the long-radius ell.

Emissions from Pipe Fittings and Gaskets

Threaded pipe fittings in the seal flush line can be significant leak sources, with readings above 1,000 ppm.4,17 Similar emission levels may be measured near the gasket region on the seal chamber face. Any leakage from these areas may drift into the emission measurement area for the mechanical seal. The mechanical seal may then be erroneously implicated as a leaker. It should be standard practice to sniff nearby hydraulic fittings and the flange gasket area if excessive VOC concentrations are detected adjacent to the mechanical seal.

Leak-tight threaded pipe fittings can be more easily attained using anaerobic paste-type sealants rather than PTFE tape. The seal chamber face must be smooth to be emission tight. Gaskets and O-rings must be free of nicks and scratches.

32.16.2 Thermoplastic Fittings Manufacturing

Thermoplastic pipe fittings may be injection-molded, fabricated, rotomolded, or thermoformed. Injection-molded fittings are generally made in sizes through 12-in. nominal diameter. Typical molded fittings are tees, 45-degree and 90-degree elbows, reducers, couplings, caps, flange adapters, stub ends, branch saddles, service saddles, and self-tapping saddle tees. Electrofusion couplings and fittings are either made by injection molding or machined from pipe stock. Electrofusion fittings and couplings are made with a coil-like integral heating element incorporated into the fitting. Joining with other fittings uses an electrical fusion device that provides electricity into the heating element, which melts the adjacent thermoplastic material and creates a fusion-welded joint.

Larger-diameter fittings exceed the capabilities of injection molding and are typically fabricated. Rotomolding is used for the manufacture of polyethylene large-diameter (up to 60 in.) and custom fittings for polyethylene corrugated drainage piping applications.

Thermoformed fittings are made by heating a section of pipe and then using a forming tool to reshape the heated area. Examples of thermoformed fittings are sweep elbows, swaged reducers, and forged stub ends. Some polyethylene corrugated pipe fittings and appurtenances are also thermoformed.

All proprietary joints shall be made in accordance with the manufacturer’s instructions. Care shall be taken to establish satisfactory jointing techniques for all water service pipework. When making joints by welding, brazing, or soldering, precautions shall be taken to avoid the risk of fire. All burrs shall be removed from the ends of pipes and any jointing materials used shall be prevented from entering the waterways. All piping and fittings shall be cleaned internally and free from particles of sand, soil, metal filings, and chips, etc.

8.19.3 Cast iron pipes

Flexible mechanical joints shall be made in accordance with the manufacturer’s instructions.

For molten lead joints, the spigot and socket shall be centered with rings of dry yarn caulked tightly into the bottom of the spigot to prevent the entry of lead into the bore of the pipe and to prevent contact of lead with the water.

Synthetic yarns that do not promote the growth of bacteria shall be used to prevent contamination of the water. The remainder of the joint space shall be filled with molten lead (taking care that no dross enters the joint), cold wire, strip, or spun lead (lead wool). The joint shall be caulked to a smooth finish with pneumatic tools or a hand hammer of mass not less than 1.5 kg. When working with spun lead, caulking tools shall be of a thickness to fill the joint space, ensuring thorough consolidation of the material to the full depth of the socket.

Lead joints shall be finished about 3 mm inside the face of the socket.

Flange joints shall be made with screwed or cast on flanges.

8.19.4 Steel pipes

Welded joints shall not be used where a protective lining would be damaged by heat, or where the pipework is employed as a primary circulation to an indirect hot water heating system.

Screwed joints in steel piping shall be made with screwed socket joints using wrought iron, steel, or malleable double crimping fitting. A thread filler shall be used. Exposed threads left after jointing shall be painted or, where installed underground, thickly coated with bituminous or other suitable corrosion preventative agent.

Flange joints shall be made with screwed or welded flanges of steel or cast iron using jointing rings and, if necessary, a suitable jointing paste. The nuts shall be carefully tightened, in opposite pairs, until the jointing ring is sufficiently compressed between the flanges for a watertight joint.

8.19.5 Unplasticized PVC pipes

8.19.5.1 Mechanical joints

Mechanical joints in unplasticized PVC piping of sizes 2 and upwards shall be made in accordance with BS4346: Part 2, by the use of push-fit integral elastomeric sealing rings which are compressed when the plain ended pipes are inserted into the adjoining sockets. The plain pipe ends shall be chamfered and the surfaces cleaned and lubricated.

The chamfered pipe end shall be inserted fully into the adjoining socket (except where provision is to be made for expansion), or as far as any locating mark put on the spigot end by the manufacturer. The sealing rings shall comply with BS2494.

8.19.5.2 Compression joints

Compression joints shall only be used with unplasticized PVC piping of size 2 and smaller. The joints shall be of the nonmanipulative type. Care shall be taken to avoid overtightening.

8.19.5.3 Solvent cement welded joints

Solvent cement welded joints in unplasticized PVC piping shall be made using solvent cement complying with BS4346: Part 3 recommended by the manufacturer of the pipe. The dimensions of the spigots and sockets shall comply with BSEN1452: Part 1–5.

Joints may also be made using integral sockets formed in the pipes and solvent cemented.

8.19.5.4 Flanged joints

Flanged joints used for connections to valves and fittings shall use full-face flanges or stub flanges, both with corrosion resistant or immune backing rings and bolting.

8.19.5.5 Polyethylene pipes

Mechanical joints shall be either plastics or metal proprietary compression fittings, for example, brass, gunmetal, or malleable iron. These shall include insert liners to support the bore of the pipe except where the manufacturer of the fitting instructs otherwise.

To ensure satisfactory jointing of the materials from which the pipe and transition elbow are made compatibility shall be established. The manufacturer’s instructions shall be carefully followed.

No attempt shall be made to joint polyethylene piping by solvent cement welding.

Large pipe fittings and valve components must be press forged and will require extensive machining. Whereas small parts such as the flange previously described can be quickly heated and cooled, and given optimum process conditions, should exhibit microstructure and properties similar to pipe and tube, the properties of large forgings will be location and thickness dependent. While no large forged part has yet been made from 740H, the properties of a solution-annealed, water-quenched and aged 343-mm-diameter bar shown in Table 14.2 are informative. Yield strength near the surface is comparable to that of thin wall tube, but yield strength at the bar center, while meeting ASME minimum, is significantly lower. Ductility and toughness were good. A hardness traverse taken on the as quenched bar showed VHN 170 at the surface and VHN 290 at the center. This is indicative of strong auto-aging in the bar center. Because the γ′ that forms on slow cooling is relatively coarse, after the final aging treatment, the bar center will have lower strength than the surface. The microstructure and creep strength at the center of the bar has not been evaluated.

A calculated continuous cooling transformation diagram for alloy 740H is shown in Fig. 14.26. This diagram supports the notion that significant γ′ hardening will occur even during water quenching of a large forging. A cooling simulation was conducted for the bar heat treatment using DEFORM software [49]. The cooling rate at a depth of 25 mm was 315°C/min and at the bar center was 30°C/min. Based on the calculated CCT diagram, there should be about 10% γ′ in the center and no γ′ at the surface. That is consistent with the experimental results.

Filament-wound pipe fittings, such as elbows and tees have been used in the chemical, and oil industry since the 1980s.9 Traditionally, composite pipe fittings were produced manually or semi-manually, but the development of CNC winders with six or more axes has allowed automated production of pipe fittings since the 1990s. The efficiency of these advanced machines depends on methods and software to determine winding patterns and perform fabrication of the complex shape within manufacturing specifications. Winding pattern generation is particularly challenging since a substantial amount of data storage/processing is required to meet manufacturing requirements (e.g., fiber tension and full-coverage) of non-axisymmetric patterns, which are required for filament-wound elbows or tees.72 On the other hand, it is worth noting that CAM software capability, rather than hardware, is considered the limiting factor for improving the performance of automated winders of non-axisymmetric parts. Consequently, general-purpose filament winding systems for pipe fittings are currently deemed impractical due to the lack of universal mathematical models and design software for CAM.9,73 Although some progress has been made to determine closed-form solutions for efficient winding patterns on specific shapes, such as elbows,74,75 most CAM systems still implement approximate methods to design and produce specific pipe fitting geometries.73 An illustration of a software-generated winding pattern, and the resulting wound elbow, is included in Fig. 11.75

Leaking valves and pipe fittings are the next concern when pressure is dropping during a test. Test sections should be isolated at pipeline block valves by using slip blinds to insure no leakage. If the test section cannot be blinded but the valves are double blocked instead, the operator must measure pressure increase in the adjacent section between the double-blocked valves to insure a tight seal exists. You need to be careful when using a thin “fire blind” at an isolation valve because under pressure the thin blind will deform and the blind cannot be removed without removing the entire valve. This often requires calling in vacuum trucks to remove product on the opposite side of the test valve being removed.

So, leakage through valves and fittings jeopardizes the chances for a successful test and may lead to data that cannot be correlated, and in that situation, the pipeline must be retested.

Tree piping is defined as all pipe, fittings, or pressure conduits, excluding valves and chokes, from the vertical bores of the tree to the flowline connections. The piping may be used for production, pigging, monitoring, injection, servicing, or testing of the subsea tree. Inboard tree piping is upstream of the first tree wing valves. Outboard tree piping is downstream of the first tree wing valve and upstream of the flowline connector.

Tree piping is normally designed in accordance with ASME B31.3. The guidelines in the API specifications are general and, in many cases, open to interpretation. It is up to the manufacturer to apply his engineering judgment.

Best smart bulbs for your connected home

Sun, 26 Sep 2021 13:57:50 +0700

Best smart bulbs for your connected home

Smart LED bulbs that can be controlled by a hub or smartphone app are no longer a new idea. What is new is how far this technology has come since its advent just a few years ago. Also new: Products like the Nanoleaf Light Panels—a system of interlocking LED panels that let you decorate with light—fundamentally change the light-bulb concept.

Smart LED bulbs aren’t quite a commodity, but they are getting close to maturity as far as the market goes. Today’s bulbs are more compact, much brighter, have better color representation, and, for the most part, feature control apps that do more than ever and are easier to set up. Prices have also come down, with some no-name color-tunable bulbs now available for less than $10 each. (Buyer beware: You get what you pay for.)

With their rainbow of hues and myriad party tricks, color LEDs get all the press in the world of smart lighting. It’s fun stuff, but the reality is that most of us will rarely find much of a need to turn all the lights in the house blue or red—unless it’s time to celebrate our team winning the World Series. Even then, you’ll probably want to turn them all back to white after the celebration.

White light is also important in its own right, as today there is plenty of science to show how various shades of white—with variations in color temperature—impact our psychological state. Cool light that’s closer to blue has an energizing effect, and is best in the morning. Warm light is relaxing, and is best after the sun goes down. Note, however, that not every white smart LED light is color-temperature-tunable. Check out the specs before you buy.

White smart bulbs downplay the party features that are a staple of color-tunable bulbs. On the other hand, white smart bulbs are less expensive than color bulbs, making it more affordable to roll them out in multiple rooms.

We’ve tested just about every color and white smart LED bulb on the market. You’ll find links to all our reviews at the bottom of the page, and we’ll update this story as new models are introduced.

Philips was one of the first players in this market, and the company’s experience shows. Physically, its Hue Color and Ambiance bulbs haven’t changed much since their introduction in late 2012, but the latest generation lasts a lot longer and the company has added a Bluetooth radio that obviates the need for the Philips Hue Bridge (but most smart home denizens will want the Bridge anyway). The Philips Hue ecosystem is the industry’s deepest and broadest, including not only bulbs of every shape and size imaginable, but also indoor and outdoor fixtures as well, including the Philips Hue Calla pathway light and the Philips Hue Lily outdoor spotlight, both of which we like very much.

LIFX is a very strong competitor in the smart lighting space and comes a very close second place in our roundup. LIFX no longer has just A19 and BR30 form factors to offer, and we really like its unique LIFX+ (which has an array of infrared LEDs that will help your home security camera see in the dark), but Philips still delivers much more diversity in its ecosystem and universe of third-party support.

Our choice won’t surprise anyone who’s been following this market. Philips dominates this space and is also our top pick for best color LED smart bulb. The latest Hue bulbs can be controlled via Bluetooth or Zigbee (the latter requires the Philips Hue Bridge), they deliver high-quality light, and are backed by a strong warranty. We received the BR30 form factor for our review, but the bulb is also available in A19, candelabra, and even with vintage-style LED filaments.

The new Cree Connected Max line of smart bulbs is agressively priced and available in all the most popular form factors: A19, A21, BR30, and PAR38. The A19 Tunable White + Color Changing bulb we reviewed costs just $10, and it supports both Bluetooth and Wi-Fi, so you don’t need to factor in the added cost of a hub to integrate it into your smart home. It’s a very good product.

Most home security cameras are equipped with infrared LEDs to deliver a semblance of night vision. the LIFX+ is equipped with infrared LEDs of its own, which are active even when the bulb is turned off via software. Infrared light is invisible to the naked eye, but the LIFX+ can bathe a room in it so that your security camera can see more of the room and in more detail than it can with its own infrared LEDs.

The 2020 version of the Philips Hue Lightstrip Plus LED is the only strip light to support both Bluetooth and the more robust Zigbee protocol (if you’re willing to pay for the required bridge to connect it to your Wi-Fi network, that is). The very nature of LED light strips renders them delicate devices, and the first review product we received broke after a short amount of time (the second one is holding up just fine). But we haven’t encountered a competing device that’s as versatile as this one.

Smart light bulb protocols and features

Three control technologies continue to vie for leadership in the smart downlight market (Z-Wave is a major contender in smart lighting, but you won’t encounter it in bulbs—just in switches, plug-in modules, control panels, and smart-home hubs).

Zigbee: Bulbs that use the popular smart-home networking protocol require a bridge to communicate with your home Wi-Fi network. This is the technology Philips has adopted for its Hue lineup, but it’s not the only one.

Wi-Fi: This class of bulb talks directly to your Wi-Fi router, no hub or bridge required. LIFX and TP-Link both manufacture excellent Wi-Fi smart bulbs, but neither company comes close to Signify’s Philips Hue lineup in terms of the depth and breadth of the Hue ecosystem.

Bluetooth: These bulbs skip your home network altogether and pair directly with your smartphone or tablet. As such, they can’t be controlled from outside your home. GE and a number of other manufacturers make Bluetooth bulbs, some of better quality than others. Signify has recently added Bluetooth radios to its Philips Hue line of smart GU10 spotlight, which eliminates the need to deploy the Philips Hue Bridge. Taking the bridge out of the equation reduces the overall cost of deployment, but adds some limitations. You can read more in our review of the new Philips Hue bulbs.

Each of these technologies has pros and cons, so before you attempt to settle on a specific bulb, first try to determine which tech is right for you. If you want to hook your bulbs into a broader smart-home system—such as SmartThings or Nest—Bluetooth bulbs are out. You can control more than one bulb with your phone, but you can’t connect it to sensors or other systems inside your home. Don’t like the idea of pairing a bulb to your phone? A Wi-Fi bulb will work best for you, though you won’t have quite as many options as you’ll find with a Zigbee product.

Smart bulb, or smart switch?

There’s a significant argument about the best way to install smart lighting, and two approaches present themselves. You can either go with expensive smart bulbs and control them all individually, or you can use cheap dumb bulbs and install smart switches to control all the lights on that circuit. Both approaches make sense: With smart bulbs, the biggest issue is cost, but there’s also complexity to deal with. While bulbs can usually be grouped based on location, this is only as intuitive to manage as the bulb control app.

Smart switches, on the other hand, are far more complicated to install—to the point where some users might be uncomfortable dealing with exposed wiring and would prefer to hire an electrician. Smart switches, however, provide more flexibility in many installations.

Habituated from years of flipping hard-wired switches, many users (or their children) will instinctively use the wall switch to turn the lights out when they leave a room. Once that happens, all the apps in the world won’t be able to turn the light back on until the switch is returned to the on position. While this won’t be an issue if you install smart switches, they can’t change a bulb’s color or color temperature.

That said, smart bulbs, no matter what the technology, still won’t be right for everyone. Notably, most of these bulbs cannot be dimmed via a hardwired wall switch (it messes with the power going to the radio, rendering them useless). Some will fail even if a dimmer is present on the circuit and dialed up to full power. The quality of light from an LED bulb is likely to be much, much better.

The good news is that bulb prices are going down, so it’s easier to get started with 2.4G/IR LED bulb and less punishing should you find that a product doesn’t work for you. That said, we want to get you started on the right foot. So without further ado, here are deep dives into the most worthwhile color and white LED smart bulbs on the market.

Development of a Wireless Temperature Sensor Using Polymer-Derived Ceramics

Sun, 26 Sep 2021 13:49:30 +0700

Development of a Wireless Temperature Sensor Using Polymer-Derived Ceramics

A temperature sensor has been developed using an embedded system and a sensor head made of polymer-derived SiAlCN ceramics (PDCs). PDC is a promising material for measuring high temperature and the embedded system features low-power consumption, compact size, and wireless temperature monitor. The developed temperature sensor has been experimentally tested to demonstrate the possibility of using such sensors for real world applications.

1. Introduction

Accurate temperature measurements are crucial for many applications, such as chemical processing, power generation, and engine monitoring. As a result, development of temperature sensors has always been a focus of microsensor field. A variety of materials have been studied for temperature sensor applications, for example, semiconducting silicon and silicon carbide. Silicon based sensors are typically used at temperatures lower than 350°C due to accelerated material degradation at higher temperature [1, 2]. Silicon carbide based sensors are better than silicon based sensors in high temperature measurement and can be applied in temperatures up to 500°C [3–5].

Polymer-derived SiAlCN ceramics (PDCs) are another widely studied material that demonstrate properties such as excellent high temperature stability [6] as well as good oxidation/corrosion resistance [7]. PDCs have been considered as a promising material for measuring high temperature [8]. Our early works have showed that PDC sensor head can accurately measure high temperature up to 830°C [9] using data acquisition system from National Instruments. The cost and size of the sensor system must be significantly reduced before it can be deployed for real world applications. In this paper, we develop a temperature sensor using PDC and an embedded system. Comparing to the National Instruments data acquisition equipment used in the previous paper, the newly developed embedded sensor is much smaller (9.7?dm3 versus 0.3?dm3), lighter (5.97?kg versus 0.19?kg), and cheaper (approximately $8000 versus $170). A WiFi module is also added so the temperature measurement can be transmitted wirelessly. The embedded board and WiFi module used in this paper are commercially available. The experiments in this paper demonstrate the possibility of deploying PDC based sensors for real world applications.

2. Fabrication of the PDC Sensor Head

In this study, the PDC sensor head is fabricated by following the procedure reported previously [9]. In brief, 8.8?g of commercially available liquid-phased polysilazane (HTT1800, Kion) and 1.0?g of aluminum-tri-sec-butoxide (ASB, Sigma-Aldrich) are first reacted together at 120°C for 24 hours under constant magnetic stirring to form the liquid precursor for SiAlCN. The precursor is then cooled down to room temperature, followed by adding 0.2?g of dicumyl peroxide (DP) into the liquid under sonication for 30 minutes. DP is the thermal initiator which can lower the solidification temperature and tailor the electrical properties [10]. The resultant liquid mixture is solidified by heat-treatment at 150°C for 24 hours. The disk-shaped green bodies are then prepared by ball-milling the solid into fine powder of ~1?μm and subsequently uniaxially pressing. A rectangular-shaped sample is cut from the discs and pyrolyzed at 1000°C for 4 hours. The entire fabrication is carried out in high-purity nitrogen to avoid any possible contamination.

Pt wires are attached to the sensor head by two ceramic fasteners on the two mounting holes on the diagonal of the sensor head. To improve the conductivity, both mounting holes are coated with Pt plasma; see Figure 1.

To measure temperature using the PDC sensor, the processor needs to perform the following tasks: () supply voltage to the circuit through DAC7724; () sample the circuit output using AD7656 and convert the output to temperature measurement; and () transmit data to readers from the RS232 port.

The input signal to the conversion circuit is a sinusoidal signal of ±10?V. The sinusoidal signal can bypass the parasitic capacitor in series to the PDC probe. The noise from the furnace coil can also be greatly subdued. The sensor output voltage is approximately sinusoidal as well and its magnitude can be computed using Fast Fourier Transformation (FFT) or curve fitting using recursive least square method (RLSM) [11]. Comparing to FFT, RLSM is more computationally efficient but may have numerical instability because TMS320F28335 only supports IEEE 754 floating-point arithmetic. Here we prefer FFT for fast prototyping purpose because Texas Instruments provides FPU library that performs floating FFT routines on C2000 series microcontroller. Next we explain how the sensor works.

A high-priority interrupt service request (ISR1) based on a CPU timer continues reading a look-up-table and drives the DAC7724 to generate the input signal . The frequency of is controlled by the frequency of ISR1. ISR1 also samples circuit output from AD7656 and adds the data to a 1024-point buffer if there is no FFT running. Once the buffer is filled up, ISR1 stops writing the buffer and the FFT routine starts. The FFT routine is implemented in another slower low-priority interrupt service (ISR2). Once the FFT routine is completed, ISR2 will give ISR1 the permission to clean and write the input buffer again. The magnitude from the FFT is used as the circuit output . The software flowchart is shown in Figure 4.

High temperature sensors capable of operating in harsh environments are needed in order to prevent disasters caused by structural or system functional failures due to increasing temperatures. Most existing temperature sensors do not satisfy the needs because they require either physical contact or a battery power supply for signal communication, and furthermore, neither of them can withstand high temperatures nor rotating applications. This paper presents a novel passive wireless temperature sensor, suitable for working in harsh environments for high temperature rotating component monitoring. A completely passive LC resonant telemetry scheme, relying on a frequency variation output, which has been applied successfully in pressure, humidity and chemical measurement, is integrated with a unique high-k temperature sensitive ceramic material, in order to measure the temperatures without contacts, active elements, or power supplies within the sensor. In this paper, the high temperature sensor design and performance analysis are conducted based on mechanical and electrical modeling, in order to maximize the sensing distance, the Q factor and the sensitivity. In the end, the sensor prototype is fabricated and calibrated successfully up to 235oC, so that the concept of temperature sensing through passive wireless communication is proved.

This paper aims to develop a prototype for a web-based wireless remote temperature monitoring device for patients. This device uses a patient and coordinator set design approach involving the measurement, transmission, receipt and recording of patients’ temperatures via the MiWi wireless meter iot solution. The results of experimental tests on the proposed system indicated a wider distance coverage and reasonable temperature resolution and standard deviation. The system could display the temperature and patient information remotely via a graphical-user interface as shown in the tests on three healthy participants. By continuously monitoring participants’ temperatures, this device will likely improve the quality of the health care of the patients in normal ward as less human workload is involved.

Background

During the severe acute respiratory syndrome (SARS) outbreak in 2003, hospitals became treatment centres in most countries. Because a patient’s core body temperature is one vital parameter for monitoring the progress of the patient’s health, it is often measured manually at a frequency ranging from once every few hours to once a day [1]. However, such manual measurement of the temperature of patients requires the efforts of many staff members. In addition, when the patients suffer from conditions that result in abrupt changes of the core body temperature, e.g., due to infection at a surgical site after surgery, the staff on duty will not know such a temperature change occurred until the next temperature measurement. Such a delay may lead to patients being unnoticed while their health conditions worsen, which is dangerous because a difference of 1.5 degrees Celsius can result in adverse outcomes [2]. Furthermore, there is always a need to have a monitoring system to improve the quality of health care [3], such as temperature monitoring of elderly and challenged persons using a wireless remote temperature monitoring system.

Body temperature can be used to monitor the pain level of a patient following an operation [4] or after shoulder endoprosthesis [5]. In some cases, the tissue transient temperature was monitored during microwave liver ablation [6] for the treatment of liver metastases. Instead of using a temperature sensor, pulse-echo ultrasound [7] was used to visualize changes in the temperature of the patient’s body. In addition, a non-contact temperature-measuring device, such as a thermal imaging camera [8], was successfully used to detect human body temperature during the SARS outbreak. However, it can be quite expensive to equip each patient room with a thermal imaging camera. In addition, there are a few wireless temperature measuring solution (e.g., CADIT?, Primex?, and TempTrak?) on the market that are used to monitor and store a patient’s temperature for medical research by using body sensor networks [9]. Most of these systems consist of an electronic module and a temperature-sensing device. The systems include a stand-alone electronic module with a display screen that allows the temperature sensor data to be transmitted over a secure wireless network.

However, these systems can be difficult to reconfigure to suit the current database system used in the hospital. In addition, the current systems using short message service (SMS)-based telemedicine [10] systems with hardware equipment were developed to monitor the mobility of patients. However, proper hardware and software to manage the messages and the patient’s temperature for display on mobile phones are not widely available.

Hence, a medical device to continuously measure the body temperature of patients using a wireless temperature receiver [4,11,12] is required. With such a wireless temperature sensor system, nurses will no longer have to manually measure the temperature of patients, which will free their time for other tasks and also reduce the risk associated with coming into contact with patients with contagious diseases, such as SARS. The readings will be transmitted wirelessly to the central nurse station, where they can be monitored by the staff-on-duty. In addition, the current and past history of the body temperature measurements can be stored in an online database, which allows the medical staff to access the database when they are not in the hospital.

To the best of our knowledge, a MiWi wireless (besides using the Zigbee[11]) temperature-monitoring system using a patient and coordinator set design that provides remote internet access to the temperature database has not been reported in any publication. The objective is therefore to develop and implement a prototype temperature-monitoring system for patients using a MiWi wireless remote connection to the nurse’s station for frequent real-time monitoring. The temperature monitoring system was designed based on a proposed patient and coordinator set design approach. The proposed temperature-monitoring system for use in normal ward will likely to improve the quality of the health care of the patients as the nursing workload is reduced. In this paper, the discussion on medical regulations and policy will not be included.

TUYỂN SINH VÀ ĐÀO TẠO CHỨNG CHỈ VẬN HÀNH CẨU - CATIEDU

Fri, 03 Sep 2021 00:54:22 +0700

TUYỂN SINH VÀ ĐÀO TẠO CHỨNG CHỈ VẬN HÀNH CẨU

Nội Dung Chính
1. Tại sao lại cần Chứng chỉ vận hành cẩu là gì?

2. Mục tiêu đào tạo

3. Cơ hội việc làm

4. Điểm nổi bật khi học tại Catiedu

5. Chương trình đào tạo

6. Kết luận

Với nhu cầu phát triển ngày càng cao và nhanh của cơ sở hạ tầng, dịch vụ xây dựng, đòi hỏi cần phải có một lực lượng sản xuất chuyên nghiệp, lực lượng lao động thạo việc, biết vận dụng máy móc trong sản xuất, công trường thi công. Với mục đích đó, nhằm đánh giá chính xác năng lực của người lao động trong thi công, xây dựng và các dịch khác mà chứng chỉ vận hành cẩu đã ra để đáp ứng nhu cầu ấy. Thấu hiểu điều đó, Trung tâm giáo dục trực tuyến Catiedu tổ chức tuyển sinh và đào tạo Chứng chỉ Vận hành cẩu có giá trị trên toàn quốc.

1. Tại sao lại cần Chứng chỉ vận hành cẩu?

Xe cẩu tự hành (cần trục ô tô) hay có thể gọi là xe tải gắn cần cẩu: Là loại xe tải có gắn cần cẩu (cần trục) thường có tay cần nghiêng so với phương ngang khi hoạt động cầu lắp. Cần trục tự hành dùng trọng lượng của ô tô làm cân đối trọng tải.

Công dụng của xe cẩu tự hành: Xe được gắn sẵn cẩu trục nên rất thuận tiện cho việc nâng hạ hàng hóa lên thùng xe tải. Một số hàng hóa chuyên dùng như: Hàng đóng kiện lớn, hàng dễ vỡ khó bốc tay, hàng cồng kềnh quá khổ…

Vận hành xe cẩu tự hành là ngành nghề có yêu cầu bắt buộc. Theo quy định những người công nhân vận hành cẩu tự hành đều phải trải qua trường lớp đào tạo, và hoàn thành xong khóa học sẽ được cấp chứng chỉ vận hành (lái) xe cẩu tự hành.

Nếu người công nhân bị phát hiện không có chứng chỉ thì đơn vị chủ quản sẽ bị phạt rất nặng. Hiển nhiên người công nhân đó sẽ mất việc.

Vận hành cẩu tự hành cũng là ngành nghề khá nguy hiểm vậy nên học viên nên tham gia khóa học để có kiến thức bảo vệ cho chính bản thân mình.

2. Mục tiêu đào tạo

Đào tạo học viên vận hành cẩu có phẩm chất đạo đức và sức khỏe tốt; có trách nhiệm với xã hội; có kiến thức và kỹ năng về vận hành cẩu trục , tham gia vào các hoạt động sau: Vận hành và bảo dưỡng các loại cẩu trục theo đúng quy định. Xếp dỡ vật phẩm, hàng hóa đúng vị trí và đảm bảo an toàn cho mọi người, thiết bị và cho vật phẩm, hàng hóa.

Mục tiêu cụ thể:

Về kiến thức:

Nắm bắt và hiểu rõ quy định của bản vẽ kỹ thuật trong ngành vận hành cẩu trục
Hiểu tính chất, công dụng phân loại, phương pháp bảo quản của một số loại nhiên liệu và dầu mỡ bôi trơn dùng trong cẩu trục
Ghi nhớ cấu tạo, nguyên lý hoạt động của các bộ phận, hệ thống phần động cơ và phần gầm, thiết bị lắp trên cần trục, cầu trục.
Biết vận dụng các phương pháp sử dụng, bảo dưỡng, bảo quản, khắc phục hư hỏng thông thường của cần trục, cầu trục, cổng trục.
Biết áp dụng các biện pháp thi công vào thực tế sản xuất đạt các chỉ tiêu kinh tế, kỹ thuật an toàn.
Về kỹ năng:

Thực hiện đúng quy trình công nghệ của từng bài thực hành.
Xếp dỡ, lắp đặt hàng chính xác, đúng yêu cầu kỹ thuật.
Chăm sóc bảo dưỡng kỹ thuật máy đúng theo định kỳ. Phán đoán kịp thời và khắc phục được những hư hỏng thông thường của cần trục khi làm việc.
Thao tác, sử dụng máy đảm bảo an toàn cho người và thiết bị.
3. Cơ hội việc làm

Nghề lái cẩu tự hành là một việc làm tương đối khó, đòi hỏi ở người công nhân tính cần cù, nhẫn nại, có tâm với công việc. Khi ra trường, học viên có kiến thức và trình độ chuyên môn cao hoàn toàn có thể có được mức lương cao từ 15 triệu trở lên tùy thuộc vào nhà thầu và chủ đầu tư,...

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5. Chương trình đào tạo

Lý thuyết:

Tổng quan về nghề vận hành cẩu
Giới thiệu về tất cả các loại cẩu
Cơ hội việc làm sau khi hoàn thành xong khóa học của trường
Thực hành:

Kỹ năng vận hành cẩu cơ bản
Kỹ năng vận hành cẩu nâng cao
Kỹ năng an toàn khi vận hành cẩu
Kỹ năng bảo dưỡng, bảo trì cẩu cơ bản
Thi kiểm tra thực hành và kết thúc khóa học.
6. Kết luận

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Lợi ích việc đăng ký xét tuyển Cao đẳng trực tuyến

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Tìm hiểu cấu tạo cơ bản của máy công cụ CNC

Fri, 06 May 2016 00:26:20 +0700

Khi tìm hiểu để mua một máy công cụ cho xưởng sản xuất, thì việc nắm được cấu tạo của máy là một điều quan trọng để lựa chọn một cách phù hợp loại máy đáp ứng được yêu cầu. Đây là cách để bạn đảm bảo thực hiện một cách chính xác cho sự tối ưu hoá quá trình sản xuất. Và nếu xảy ra trục trặc, nhà cung cấp có thể nhanh chóng tìm ra căn nguyên của vấn đề, vì mọi thứ đã được tích hợp sẵn trong máy.

Đây là những điều cần biết về 6 bộ phận chính của một máy công cụ CNC:

1. Bộ phận thay dao tự động (ATC)

Đây là điều quan trọng để ATC thay đổi dụng cụ trong phạm vi trục chính càng nhanh càng tốt. Bằng sự thích ứng của quá trình điều khiển và động cơ, ATC sẽ đưa dao ra khỏi trục chính một cách chính xác. Một hệ thống ATC tốt có khả năng làm giảm thời gian dừng máy và làm tăng năng suất.

2. Động cơ /Bộ điều khiển /Encorder

Thêm một điều nữa, nếu có những thành phần chuyển động khác nhau, có sự đồng bộ giữa động cơ và hệ thống điều khiển và cách tốt nhất để đạt được điều này là đảm bảo nhà cung cấp máy không sử dụng bất kì một thành phần nào ở bên ngoài. Tất cả chúng phải được thiết kế và xây dựng từ những bảng điều khiển điên tử, động cơ điện, và tuyệt đối là hệ thống Encorder cung cấp phản hồi cho quá trình điều khiển. Hệ thống truyền tín hiệu tối tân cho phép máy phân phối để cắt gọt kim loại với tốc độ cao nhất theo sự định vị, khả năng định vị nằm trong phạm vi một vài micromet so với yêu cầu.

3. Vỏ máy

Khi đế máy là nền tảng của một máy trung tâm, nó cần nặng hơn, chắc chắn hơn và tốt hơn. Giá của nó có thể cao hơn, nhưng sự chịu lực và độ bền sẽ làm giảm rung động. Quá trình rung động sẽ ảnh hưởng đến độ chính xác gia công. Với một máy có kết cấu vững chắc, nó sẽ hấp thụ những dao động này, đảm bảo máy sẽ thực hiện với công suất và độ chính xác cao nhất.

4. Hệ điều khiển

Hệ điều khiển là thành phần trung tâm của máy công cụ. Nó điều khiển quá trình chuyển động, vị trí của các thành phần chuyển động trên máy, sao cho đạt được chính xác tối ưu thời gian cắt, tốc độ và chiều sâu cắt cần thiết. Sự kết hợp của dòng điện và hệ thống kĩ thuật sẽ đưa ra sự điều khiển toàn diện từ nguồn cung cấp, thực hiện gia công chi tiết từ dữ liệu CAD nhanh chóng, dễ dàng với độ chính xác được nâng cao và kết thúc quá trình gia công với chi phí nhỏ nhất.

5. Bàn xe dao

Các nhà cung cấp máy công cụ phải tạo ra một bàn xe dao phù hợp với mỗi máy và có lợi nhất về mặt công suất cũng như thuận lợi cho việc cắt gọt kim loại mà không ảnh hưởng đến độ chính xác khi gia công. Độ cứng vững của bàn xe dao sẽ làm cho công suất của quá trình cắt kim loại đươc được tăng lên. Những nhà chế tạo thiết kế các bàn xe dao cho phép chúng chỉ điều khiển đài dao và chức năng phay. Thêm nữa, nếu các thành phần khác chuyển động thì thành phần nào điều khiển chúng một cách tốt hơn?

6. Trục chính

Trục chính là thành phần có tính quyết định nhất trong máy công cụ. Một trục ổn định sẽ hợp nhất với sự điều khiển của động cơ - quyết định độ cứng vững hệ thống, hệ thống bôi trơn và nguồn điện cung cấp, đảm bảo độ chính xác và có thể đoán trước được năng suất của máy. Như vậy, quá trình thiết kế trục và tối ưu tốc độ quay của trục chính sẽ mang lại quá trình cắt gọt được tốt nhất và độ chính xác cao nhất cho máy.

7. Nguồn (năng lượng)

Chắc chắn rằng các hãng cung cấp thiết kế, chế tạo và xây dựng nên tất cả các thành phần của máy công cụ để hệ thống trong máy có thể phối hợp với nhau được tốt hơn. Bằng cách sử dụng một nguồn bạn có thể chắc chắn quá trình giao tiếp sẽ chính xác giữa bộ điều khiển và động cơ và sự tự điều chỉnh của các thành phần trong hệ thống.

Kinh nghiệm xử lý vết nứt xảy ra trong khi hàn

Thu, 21 Apr 2016 22:24:22 +0700

Trong khi tiến hành hàn một vật liệu hay một chi tiết sản phẩm nào đó ,dù không muốn nhưng việc xảy ra vật liệu bị biến dạng,mối hàn bị nứt là điều rất dễ xảy ra nếu người thợ hàn chưa nắm rõ được những kỹ thuật hàn hay chưa nghiên cứu kỹ sản phẩm để hàn đó.

Trong nội dung này scviet xin được phép đưa lên một số trường hợp nứt vết hàn và giải pháp khắc phục. Hy vọng sẽ giúp ích cho cả nhà.

Mẹo xử lý các nứt xảy ra khi hàn

Trước hết Khi vật liệu bị nứt thì phải xác định nứt mối hàn ở đâu: Nứt ở chân mối hàn, Nứt ngang mối hàn, Nứt dọc mối hàn, ứt ở trong tâm mối hàn (có thể không phải ở chính chỗ giữa mối hàn hoặc ở giữa một trong những đường hàn).

Sau đó phân biệt vết nứt: Nứt nóng hay nứt nguội

1.Nứt dọc mối hàn

Nguyên nhân 1:

Do những tạp chất có nhiệt độ chảy thấp tập trung vào đường tâm khi đông đặc.
Những nguyên tố tạp chất: Carbon, Chì (PB), Kẽm (Zn), Đồng (Cu), Phosphorous (P), Lưu huỳnh (S)
Tuyệt chiêu:

Dùng các loại thép ít tạp chất Hệ số UCS= Universal Cracking Sensitivity (tạm dịch là hệ số nứt của mối hàn)
UCS = 230C + 190S + 75P + 45Nb – 12.3 Si - 5.4 Mn – 1

230C + 190S + 75P + 45Nb : tác nhân gây nứt mối hàn

12.3 Si - 5.4 Mn : đại lượng chống nứt trong hệ số nứt

UCS < 10 :”Mối hàn có khả năng chống nứt”

UCS > 30 “Mối hàn dễ nứt”

Không sử dụng những thép tự đông để hàn ,Giảm thiểu độ chảy, Kiểm soát độ ngấu, thay đổi thiết kế mối hàn. Dùng vật liệu có tính hàn cao, Hàn lớp lót, dùng que hàn có hàm lượng Mn cao (với kim loại có các thành phần S cao).

Nguyên nhân 2:

Tỉ lệ chiều cao và chiều rộng mối hàn không hợp lý làm ảnh hưởng đến quá trình đặc quyện của kim loại
Hình dáng lớp hàn lót (góc vát mép α, chiều rộng lớp lót R)
Biện pháp:

Thay đổi thiết kế mối hàn, Kiểm soát độ ngấu
Nguyên nhân 3:

Hình dạng bề mặt lõm của mối hàn gây nứt trong quá trình đông đặc
Giải pháp:

Giảm bớt dòng hàn
Giảm bớt áp hàn
Thay khí bảo vệ
Đổi vị trí hàn
2. Nứt Nóng:

Nguyên nhân 1: Các thành phần tạp chất có nhiệt độ nóng chảy và đông đặc không giống nhau tập trung vào đường tâm mối hàn
Nguyên nhân 2: Thiết kế mối hàn chưa hợp lý
Nguyên nhân 3: biên dạng profile của mối hàn, những thông số hàn chưa hợp lý

3. Nứt Nguội:

Nguyên nhân:

Trong thành phần mối hàn có Hydro
Ứng suất trong lòng mối hàn
Cơ tính vật liệu
Kiểm soát hàm lượng Hydro
Gia nhiệt trước khi hàn
Tăng nhiệt lượng cho mối hàn
Chia mối hàn thành khá nhiều lớp
Tăng thời gian nghỉ giữa các lớp hàn
Làm nguội chậm
Gia nhiệt sau khi hàn
Kiểm soát ứng suất trong lòng mối hàn

Chọn kim loại bù thích hợp
Thiết kế mối hàn hợp lý
Gia nhiệt, kiểm soát nhiệt lượng
Weld peening (Rèn ??)
Cơ tính vật liệu

Chọn vật liệu có tính hàn cao, tính tôi và hóa cứng thấp
Gia nhiệt, kiểm soát nhiệt lượng