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The Advantages of Canvas Tarps

Descripción:     The Advantages of Canvas Tarps     Tarpaulins (tarps) made of canvas are some of the most versatile tarps on the market today. These tarps can be flame retardant, water resistant, and mildew resistant. Canvas tarps come in several fabric gauges, from 10-ounce to 17-ounce and up. (The higher the number, the heavier and more durable the fabric.) Prices range from around $10 for small, untreated canvas tarps, to hundreds of dollars for large waterproof and fire-retardant models. The tarps come in countless sizes and can be used for a multitude of purposes from painting to landscaping to camping.     One of the most common uses of tarps and canvas is to protect furniture, carpets and other items while painting inside or outside. While canvas tarps are more expensive than disposable plastic tarps, they can be used over and over again. Canvas tarps are heavy and will stay in place without a lot of complicated taping and securing, and fit well over curved surfaces. They are usually less slippery than disposable plastic tarps, so they are also safer as there is less chance of injury due to falls.     Canvas tarps can be used when landscaping as well. Lightweight waterproof tarps are perfect for protecting grass or plants during snowstorms. Tarps have been used for decades to cover baseball diamonds and football fields during inclement weather; the tarp can be removed as soon as the rain has stopped and play can usually resume immediately.     Many of the finest tents are made of canvas. Adventurous and inventive campers can make their own camping accommodations with canvas tarps, straps and a few poles. These structures will provide shade, will be water and wind resistant, and are a fraction of the cost of a regular tent.     Canvas tarps are versatile and cost effective. They can be used in many diverse situations and are sturdy and dependable.     Tonneau Covers Info provides detailed information on truck, hard, fiberglass, folding, retractable, vinyl, and discount tonneau covers.     There are various types of tarps such as Steel tarp, Hay tarp, Canvas tarp, Poly tarp, etc. Tarps are large strong sheets that are flexible and water-resistant. Different tarps are made up of different materials like canvas, polyester, polyethylene, etc. Tarps are multi-functional and are used for various purposes. They are used at a construction site to cover the debris or in a flatbed truck or trailer to protect the load that they are carrying. Canvas tarps are one such type of tarp that is used for covering the load carried on a flatbed trailer. They are used for certain kinds of the load because they are breathable and less abrasive. Normally every trucker keeps few canvas traps with them all the time just in case of emergencies. Canvas tarps are lightweight, affordable, and long-lasting. According to me, mytee products is a one-stop destination to buy the best quality canvas tarps. At here you will get the best quality tarps to satisfy all your flatbed needs.     Home  Automotive Tips  5 Major Benefits of Canvas Tarps with Features     AUTOMOTIVE TIPS     5 Major Benefits Of Canvas Tarps With Features     FAISAL- JUL 29, 2020001080     Share On Facebook     Tweet It     There are various types of tarps such as Steel tarp, Hay tarp, Canvas tarp, Poly tarp, etc. Tarps are large strong sheets that are flexible and water-resistant. Different tarps are made up of different materials like canvas, polyester, polyethylene, etc. Tarps are multi-functional and are used for various purposes. They are used at a construction site to cover the debris or in a flatbed truck or trailer to protect the load that they are carrying. Canvas tarps are one such type of tarp that is used for covering the load carried on a flatbed trailer. They are used for certain kinds of the load because they are breathable and less abrasive. Normally every trucker keeps few lumber tarps with them all the time just in case of emergencies. Canvas tarps are lightweight, affordable, and long-lasting. According to me, mytee products is a one-stop destination to buy the best quality canvas tarps. At here you will get the best quality tarps to satisfy all your flatbed needs.     Canvas-Tarps     Canvas tarps are multi-functional and have various benefits. Some of the benefits of canvas tarps are given below,     1) Environment friendly:     Environment-friendly     Canvas tarps are made from cotton; this makes canvas tarps eco-friendly in nature. If canvas tarps are properly taken care of then they last longer than poly tarps. You can easily dispose of canvas tarps when they deteriorate and after a certain time they get completely decompose. Canvas tarps are versatile and you can use them over and over again. Once the canvas tarps wear out then you can use it for some other purpose that is not more important like covering your bike or anything else. All these features make canvas tarps environment friendly.     2) Breathable:     Canvas tarps are made up of natural materials so it allows air to flow between the individual fibers. This is an important feature because it doesn’t allow the load to rust. Breathable tarps prevent moisture from building on the load. Hence, these tarps are mostly considered for moisture-sensitive loads. The breathable property of canvas tarps makes it a perfect option to cover load in a flatbed truck during warmer weather.     Canvas tarps are ideal for securing various equipment like construction, industrial, farming, etc. These tarps are flame retardant and that is why they can be used in places where combustible materials are present. Because of their amazing features and property, they are considered an excellent choice for equipment loads.     Canvas tarps can be used in different atmospheric conditions like heat, rain, or snow because they are breathable and water-resistant. They are mostly used in outdoor conditions to cover any kind of equipment or outdoor furniture. You can use these tarps at construction sites to cover and secure construction materials. Canvas tarps are also used to cover farming equipment because they can provide protection against rust. This eventually increases the life span of the logistics equipment. While you are transporting any product that needs to be fresh throughout the journey then canvas tarps are preferred over any other tarps. Canvas tarps are a good option if you want to protect any stationery load. However, canvas tarps should not be used for covering trailers or canopies because they have low tear strength at the seams. These tarps should also be avoided in high UV areas.     Canvas tarps will get dirty over a certain period of time. Hence, it becomes important to keep them clean. Canvas tarps are not machine washable. To clean the canvas tarps just wipe the spots with the help of soap or detergent that are specifically designed for cleaning canvas tarps. This way you can easily clean the canvas tarps. The reason why canvas tarps should not be cleaned using laundry washer and dryer is that these tarps are coated with wax and that can stain the laundry washer and dryer.     Tarpaulins (tarps) made of canvas are some of the most versatile tarps on the market today.  These tarps can be flame retardant, water resistant, and mildew resistant.  Canvas tarps come in several fabric gauges, from 10-ounce to 17-ounce and up.  (The higher the number, the heavier and more durable the fabric.)  Prices range from around $10 for small, untreated canvas tarps, to hundreds of dollars for large waterproof and fire-retardant models.  The tarps come in countless sizes and can be used for a multitude of purposes from painting to landscaping to camping.      One of the most common uses of canvas tarps is to protect furniture, carpets and other items while painting inside or outside.  While canvas tarps are more expensive than disposable plastic tarps, they can be used over and over again.  Canvas tarps are heavy and will stay in place without a lot of complicated taping and securing, and fit well over curved surfaces.  They are usually less slippery than disposable plastic tarps, so they are also safer as there is less chance of injury due to falls.       Canvas tarps can be used when landscaping as well.  Lightweight waterproof tarps are perfect for protecting grass or plants during snowstorms.  Tarps have been used for decades to cover baseball diamonds and football fields during inclement weather; the tarp can be removed as soon as the rain has stopped and play can usually resume immediately.      Many of the finest tents are made of canvas.  Adventurous and inventive campers can make their own camping accommodations with canvas tarps, straps and a few poles.  These structures will provide shade, will be water and wind resistant, and are a fraction of the cost of a regular tent.      Canvas tarps are versatile and cost effective.  They can be used in many diverse situations and are sturdy and dependable.     Tarps have been around for hundreds of years. The original use for a tarp was on the high seas. Sailors used to cover sheets of canvas in tar to protect goods from salt spray and water damage during transit. Over the years, the tarp has had several various uses, but usually remained as a way to keep dirt, water, and other contaminates off something, whether it was furniture, people, dirt, or any other number of things.     Over the years, different materials have been used to make the tarp. Tarps have been made from nylon, canvas, cotton, plastic, polyester, and even metal. Throughout history, the tarp has had its ups and downs. Here are some highlights from the tarp’s history from its earliest days until now.     1400-1600     The tarp was used mainly at sea as a way to protect sailors and the items they transported across the seas. The original name for the tarp was the “tarpaulin.” This name came from combining the two words “tar” and “pall.” The pall was the fabric used by the sailors as a trailer cover.     1600-1900     The tarp moved inland. Many people used tarps for protecting items during travel, such as for covering wagons during moves. During the 1700s, the tarp became used for land travel as a tent covering. The waterproof surface of the tarp helped keep travelers and soldiers warm.     1900-Present     During the industrial revolution, the tarp received major changes. The tarp was made from a variety of materials, such as plastics, polyester, rubber, and a variety of other materials. People now used the tarp for nearly anything, from covering the floor to prevent paint splatters to keeping leaks off a roof until the rain stopped. Today, people use the tarp for a variety of uses, including camping, construction, transportation, and protection.

Fecha de Publicación: 28-09-21

How battery chargers work

Descripción:     How battery chargers work     If you've read our main article on batteries, you'll know all about these portable power plants. An example of what scientists refer to as electrochemistry, they use the power of chemistry to release stored electricity very gradually.     What happens inside a typical battery—like the one in a flashlight? When you click the power switch, you're giving the green light to chemical reactions inside the battery. As the current starts flowing, the cells (power-generating compartments) inside the battery begin to transform themselves in startling but entirely invisible ways. The chemicals from which their components are made begin to rearrange themselves. Inside each cell, chemical reactions take place involving the two electrical terminals (or electrodes) and a chemical known as the electrolyte that separate them. These chemical reactions cause electrons (the tiny particles inside atoms that carry electricity) to pump around the circuit the battery is connected to, providing power to the flashlight. But the cells inside a battery contain only limited supplies of chemicals so the reactions cannot continue indefinitely. Once the chemicals are depleted, the reactions stop, the electrons cease flowing through the outer circuit, the battery is effectively flat—and your lamp goes out.     That's the bad news. The good news is that if you're using a rechargeable battery, you can make the chemical reactions run in reverse using a battery charger. Charging up a battery is the exact opposite of discharging it: where discharging gives out energy, charging takes energy in and stores it by resetting the battery chemicals to how they were originally. In theory, you can charge and discharge a rechargeable battery any number of times; in practice, even rechargeable batteries degrade over time and there eventually comes a point where they're no longer willing to store charge. At that point, you have to recycle them or throw them away.     All battery chargers have one thing in common: they work by feeding an electric current through batteries for a period of time in the hope that the cells inside will hold on to some of the energy passing through them. That's roughly where the similarity between chargers begins and ends!     The cheapest, crudest chargers use either a constant voltage or constant current and apply that to the batteries until you switch them off. Forget, and you'll overcharge the batteries; take the waterproof battery charger off too soon and you won't charge them enough, so they'll run flat more quickly. Better chargers use a much lower, gentler "trickle" charge (maybe 3–5 percent of the battery's maximum rated current) for a much longer period of time.     Batteries are a bit like suitcases: the more you pack in, the harder it is to pack in any more—and the longer it takes. That's easy to understand if you remember that charging a battery essentially involves reversing the chemical reactions that take place when it discharges. In a laptop battery, for example, charging and discharging involve shunting lithium ions (atoms missing electrons) back and forth, from one electrode (where there are many of them) to another electrode (where there are few). Since the ions all carry a positive charge, it's easier to move them to the "empty" electrode at the start. As they start to build up there, it gets harder to pack more of them in, making the later stages of charging harder work than the earlier ones.     Overcharging is generally worse than undercharging. If batteries are fully charged and you don't switch off the charger, they'll have to get rid of the extra energy you're feeding in to them. They do that by heating up and building up pressure inside, which can make them rupture, leak chemicals or gas, and even explode. (Think of overcharging as overcooking a battery and you might just remember not to do it!)     Slightly more sophisticated timer chargers switch themselves off after a set period, though that doesn't necessarily prevent overcharging or undercharging because the ideal charging time varies for all sorts of reasons (how much charge the battery held to begin with, how hot it is, how old it is, whether one cell is performing better than others, and so on). The best chargers work intelligently, using microchip-based electronic circuits to sense how much charge is stored in the batteries, figuring out from such things as changes in the battery voltage (technically called delta V or ΔV) and cell temperature (delta T or ΔT) when the charging is likely to be "done," and then switching off the current or changing to a low trickle charge at the appropriate time; in theory, it's impossible to overcharge with an intelligent waterproof car charger.     Nickel cadmium (also called "nicad" or NiCd), the oldest and perhaps still best known type of rechargeable batteries, respond best either to fairly rapid charging (providing it doesn't make them hot) or slow trickle charging.     Nickel metal hydride (NiMH) batteries use newer technology and look exactly the same as nicads, but they're generally more expensive because they can store more charge (shown on the battery packaging as a higher rating in mAH or milliampere-hours). NiMH batteries can be fast charged (on high current for several hours, at the risk of overheating), slow charged (for about 12–16 hours using a lower current), or trickle charged (with a much lower current than nicad), but they should really be charged only with an NiMH charger: a rapid nicad charger may overcharge NiMH batteries.     Expert opinions seem to differ on whether nickel batteries experience what's widely known as the memory effect. This is the well-reported phenomenon where failure to discharge a nickel-based battery before charging (when you're "topping up" a partly discharged battery with a quick recharge) reputedly causes permanent chemical changes that reduce how much charge the battery will accept in future. Some people swear the memory effort is real; others are equally insistent that it's a myth. The real explanation for an apparent memory effect is voltage depression, where a battery that hasn't been fully discharged before charging temporarily "thinks" it has a lower voltage and charge-storing capacity than it should have. Battery experts insist you can cure this problem by charging and discharging a battery fully a few times more.     It's generally agreed that nickel-based batteries need to be "primed" (charged fully before they're used for the first time), so be sure to follow exactly what the manufacturers say when you take your new batteries out of the packet.     There are two simple reasons why there are so many different sizes and types of batteries: a bigger battery has more chemicals inside it so it can store more energy and release it for longer; bigger batteries also tend to have more cells inside them so they can produce a higher voltage and current to power bigger things (brighter flashlight bulbs or higher-powered motors). By the same token, bigger rechargeable batteries need charging for longer. The more energy you expect to get out of a rechargeable battery (the longer you expect it to last), the longer you'll need to charge it (or the higher the charging current you'll need to use). A basic law of physics called the conservation of energy tells us you can't get more energy out of a battery than you put into it.     Most people tend to put things on to charge "overnight" without paying too much attention to exactly what that means—but your batteries will work better and last longer if you charge them for the right number of hours. How long is that? It can be very confusing, especially if you use batteries that didn't come supplied with your waterproof marine charger. Never fear! All you have to do is read what it says on your batteries and you should find (often in tiny writing) the recommended charging current and charge times. If you have a basic charger, simply check its current rating and adjust the charge time accordingly. Bear in mind what we've said elsewhere about matching your charger to your batteries, however.     Lithium-ion rechargeable batteries are usually built into gadgets such as cellphones, MP3 players, digital cameras, and laptops. Typically they come with their own chargers, which automatically sense when charging is complete and cut off the power supply at the right time. Lithium-ion batteries can become dangerously unstable when the battery voltage is either too high or too low, so they're designed never to operate under those conditions. If the voltage gets too low (if the battery discharges too much during use), the appliance should cut out automatically; if the voltage gets too high (during charging), the electric transportation battery charger will cut out instead. Although lithium-ion batteries don't show a memory effect, they do degrade as they get older. A typical symptom of aging is gradual discharge for a period of time (maybe an hour or so) followed by a sudden, dramatic, and completely unexpected cut-out of the appliance after that. Read more about how lithium ion batteries work.     Lead-acid batteries are popular because they're simple, cheap, reliable, and use well-proven technology that dates back to the middle of the 19th century. Generally they last for several years, though that depends entirely on how well they are maintained—in other words, charged and discharged. They do take quite a long time to charge (typically up to 16 hours—several times longer than they take to fully discharge), and that can lead to a tendency both to undercharge (if you don't have time to charge them properly before you next use them) or overcharge (if you put them on charge and forget all about them). Undercharging, charging with the wrong voltage, or leaving batteries unused causes a problem known as sulfation (the formation of hard lead sulfate crystals), while overcharging causes corrosion (permanent degradation of the positive lead plate through oxidation, analogous to rusting in iron and steel). Both will affect the performance and life of a lead-acid battery. Overcharging also tends to degrade the electrolyte, decomposing water (by electrolysis) into hydrogen and oxygen, which are given off as gases and therefore lost to the battery. That makes the acid stronger and more likely to attack the plates, which will reduce the battery's performance. It also means there's less electrolyte available to interact with the plates, also reducing the performance. From time to time, batteries like this have to be topped up with distilled water (not ordinary water) to keep the acid at the optimum strength and at a high enough level to cover the plates.

Fecha de Publicación: 28-09-21

Cars that watch you watch them steer

Descripción:     Cars that watch you watch them steer     The automobile, in American life, has long been a hallmark of freedom. A teenager’s first driver’s license offers freedom from Mom and Dad. A new car and the open road bring the freedom to chase the American dream. But as more technology creeps in to help drivers, so, too, will systems that eavesdrop on and monitor them, necessitated not by convenience but by new safety concerns.     Cameras that recognize facial expressions, sensors that detect heart rates and software that assesses a driver’s state of awareness may seem like superfluous flights of fancy, but they are increasingly viewed as part of an inevitable driving future.     At upstarts like the electric car company Byton and mainstream mainstays like Volvo, car designers are working on facial recognition, drowsy-driver alert systems and other features for keeping track of the people behind the wheel.     The most immediate impetus: concerns about the safe use of driver-assistance options like automatic lane-keeping that still require drivers to pay attention. And when truly autonomous vehicles finally arrive, the consensus among automakers and their suppliers is that new ways will be needed to check on drivers and passengers to make sure they are safe inside.     “It’s really taken off from no car monitor to tactile monitoring to taking a look at your eyes,” said Grant Courville, a vice president at BlackBerry QNX, which creates in-dash software systems. “I definitely see more of that coming as you get to Level 3 cars,” he added, referring to vehicles that can perform some self-driving functions in limited situations.The feature is part of the car’s Super Cruise system, the first hands-free driving tool to operate on select United States highways. The camera tracks a driver’s head position and eye movements to ensure that the person is attentive and able to retake control of the car when needed.     Similar concerns about BMW’s semi-autonomous systems prompted the German carmaker to add a driver monitoring camera in its 2019 X5 sport utility vehicle. The video camera is mounted in the instrument cluster as part of BMW’s Extended Traffic Jam Assistant system, part of a $1,700 package, that allows the car to go autonomous — with driver monitoring — in stop-and-go traffic under 37 miles per hour.     “It looks at the head pose and the eyes of the driver,” said Dirk Wisselmann of BMW’s automated driving program. “We have to, because by doing so it empowers us to add more functionality.”     Automakers understand that tracking technology raises privacy issues, so BMW does not record or store the ahd car monitor information, Mr. Wisselmann said.     Perhaps still smarting from lessons learned in the past, G.M. also does not record what transpires inside the car’s cabin, the company said. In 2011, G.M. tried to change the user agreement in its OnStar service to allow it to share driver information with third-party companies. The backlash from owners was so swift and severe that the Supreme Court cited the episode as proof that people had an expectation of privacy in their cars.     “But it’s not just about distraction management,” said Jada Smith, a vice president in the advanced engineering department at the auto supplier Aptiv. During an autonomous driving demonstration, she pointed out that such driver monitoring systems can assess a driver’s cognitive load levels — how many tasks the person is trying to juggle — and then adjust other car functions.     “If the driver is not fully aware,” Ms. Smith said, “we might brake faster.” Other ideas include putting radar inside the car for interior sensing like detecting that a child has been left behind. (Every nine days a child left in a car dies from vehicular heatstroke in the United States, according to KidsAndCars.org, an advocacy group.)     It was infants’ being left in cars that first prompted Guardian Optical Technologies, based in Tel Aviv, to develop in-cabin monitoring technology, said Tal Recanati, the company’s chief business officer. The company has now expanded its 3-D vision and “micro vibration” sensing system to recognize faces, check seatbelt use, even adjust elements like airbag deployment velocity based on a passenger’s approximate weight. Eventually Guardian’s technology could be able to judge the emotional state of people in the car.     Affectiva, a Boston company developing technology for measuring emotions, has been conducting such research for several years to assess driver behavior. On a closed test track peppered with distractions — people dressed as construction workers, a security vehicle with flashing lights, pedestrians, fake storefronts — Affectiva demonstrated how the company’s program works in tandem with a “collaborative driving” system made by the Swedish auto supplier Veoneer. Veoneer’s technology can control steering and braking on its own, with the occasional intervention of a human driver.     Affectiva collected a variety of driver information during the test, measuring elements like the amount of grip on the wheel, throttle action, vehicle dome camera, facial and head movements. It then compared that information with what was happening around the car to determine how much trust the driver had in the semi-autonomous system and the perceived level of cognitive load.     “We want them to trust the car — but not too much,” said Ola Bostrom, a vice president of research at Veoneer. “The driver still has to be engaged” in order to take over the controls when a car encounters a situation it can’t handle.     To deliver other advanced services, like augmented reality information about nearby businesses and locations, it will also be necessary to monitor what drivers are paying attention to, said Andrew Poliak, a vice president at Panasonic Automotive Systems. And companies as diverse as Mercedes-Benz and the voice-recognition company Nuance want to add Alexa-like services, meaning that your sedan or S.U.V. may always be listening.     “So these systems are going to become standard in all cars,” said Nakul Duggal, who leads the automotive products group at Qualcomm.     Will privacy concerns then recede in the rearview mirror of advancing technologies?     When fully autonomous vehicles begin circulating on public roads, designers note, they will have to be able to detect when people enter or exit a vehicle, who the person is, whether they have left anything behind in the car, and especially if a person has become disabled (because of intoxication or a medical emergency). And that information will inevitably be shared online, although there may be ways that some people can still preserve their sense of independence in the car.     “In the future, it may be different for people who own their own cars, where there’s more privacy,” said Mr. Wisselmann at BMW, “and for people who use robo taxis, where there will be less.”     It’s 2025 and you’re cruising down the highway late at night. It’s been a long day and your eyelids feel heavy. All of a sudden, you hear three beeps, lights flash, your car slows down, and it pulls itself safely to the side of the road.     This scenario is closer to becoming reality than you may think, and although vehicle camra get all the headlines, most drivers will experience something like it long before they can buy a car that drives itself.     Full self-driving cars are taking longer to arrive than techno-optimists predicted a few years ago. In fact, in a financial filing Wednesday, Tesla acknowledged it may never be able to deliver a full self-driving car at all.     But with features such as automated cruise control, steering assist and automatic highway lane changing, new cars come loaded with driver-assist options. As they proliferate, the task of a human driver is beginning to shift from operating the vehicle to supervising the systems that do so.     That development carries promise and peril. Decades of research make clear that humans aren’t good at paying attention in that way. The auto industry’s answer: systems that monitor us to make sure we’re monitoring the car.     Such systems, usually relying on a driver-facing camera that car rear view monitor and head movements, already have been deployed in tens of thousands of long-haul trucks, mining trucks and heavy construction vehicles, mainly to recognize drowsiness, alcohol or drug use, and general distraction.     Some new automobile models can already be purchased with option packages that include monitoring systems, usually as part of driver-assist features such as lane keeping and automated cruise control. They include cars from General Motors, Ford, Toyota, Tesla, Subaru, Nissan and Volvo.     One reason for the sudden rush: European regulators plan to require such systems be installed on every new car sold there by mid-decade.     The top U.S. car industry lobby, recently renamed the Alliance for Automotive Innovation, told a Senate panel Tuesday that it welcomes regulation that would require driver-monitoring systems in all new cars sold with driver-assist technologies. The National Transportation Safety Board, after several fatal Tesla Autopilot crashes, has recommended that safety regulators require more robust systems than the one Tesla uses to keep drivers engaged.     So-called advanced driver-assist systems serve as a bridge as companies work to develop safe, fully self-driving cars, which are beginning to appear in very limited locations. Most driverless car developers put tight restrictions on how they can be used and where they can go.     “We’re in an in-between phase at the moment,” said Colin Barnden, a market analyst at Semicast Research.     On the plus side, such technologies can reduce driving stress and, if deployed responsibly, improve safety. At the same time, the less input a car needs from a human driver, the harder it is for that driver to remain vigilant. Humans aren’t good at “monitoring things, waiting for something to go wrong. We just aren’t wired to do that,” Barnden said.     Driver-monitoring systems come in two basic types: eye trackers and steering wheel sensors. In either case, if a driver is detected not paying attention, warnings are sounded through lights or sounds or both; if the driver doesn’t reengage, the car pulls itself to the roadside and stops.     Tesla uses the steering sensor. Practically everybody else uses eye trackers.    

Fecha de Publicación: 28-09-21

Control Valve

Descripción:     Control Valve     This valve controls the expulsion of oil from the spring side of the second gear band servo piston at speeds in the region of 60 km/h. The time period for oil to exhaust then depends upon the governor pressure varying the effective exhaust port restriction. Line pressure oil from the spring side of the second gear band servo piston passes through a passage leading to the 3–2 kickdown valve annular groove and from there to the 2–3 shift valve annular groove. Here some oil exhausts out from a fixed restriction while the remainder passes via a passage to the 3–2 control valve. As the vehicle speed approaches 60 km/h the governor pressure rises sufficiently to force back the 3–2 control valve piston, thus causing the wasted (reduced diameter) part of the control valve to complete the exhaustion of oil.     Valves control the gas flowing into and out of the engine cylinder. The camshaft and valve spring make up the mechanism that lifts and closes the valves. The valve train determines the performance characteristics of four-stroke-cycle engines.     There are two types of valve, inlet and exhaust. Figure 6.1 shows an exhaust valve. An inlet valve has a similar form. The commonly used poppet valve1 is mushroom-shaped. Figure 6.2 illustrates the parts of the valve. A cotter (not shown in Fig. 6.2) which fixes the valve spring retainer to the valve, is inserted into the cotter groove.Alumina valves and seats     corrosion resistant control valve come in many forms: butterfly valve, ball and seat valve, disk-valve, piston-sleeve metering valve, and dart valve, to name but a few. Alumina has been used in many industrial valves. Water faucet valves of the standard disk-on-disk configuration are very common and are discussed in Section 12.2.8. Since they share almost all the same features of pump rotary valves.     Dart valve plugs and seats are a fluid-flow-control component. When used in the mineral processing industry, or in other industries where slurries, or corrosive liquids, or corrosive slurries are flowing, these valve/plug systems need to be highly wear resistant, especially the plug which can be particularly exposed to the flow of the erosive/corrosive fluids. An example of a dart valve and plug is shown in Fig. 12.17. Alumina valves are an increasingly common technology in general.     One revolution of the camshaft gives the amount of valve lift shown in Fig. 6.3. The valve stem moves in the valve guide and also revolves slowly around the stem. The revolving torque is generated by the expansion and contraction of the valve spring.     An engine basically needs one inlet valve and one exhaust valve per cylinder but most modern engines use four valves per cylinder. This multi-valve configuration raises power output, because the increased inlet area gives a higher volume of gas flow. Contemporary five-valve engines use three inlet valves and two exhaust valves to increase trapping efficiency at medium revolutions.     Figure 6.4 summarizes the functions of the valve. The shape of the neck, from the crown to the valve stem, ensures that the gas runs smoothly. The valve typically receives an acceleration of 2000 m/s2 under high temperatures. Valves must be of light weight to allow the rapid reciprocating motion.     With the single seated control valve lowered, the hydraulic pump is applied to bring the bottom plate of the mould to the lower limit. The separator is then lowered into the mould and fed with the shell and the inner core materials. The vibrator is switched on for 5 s to consolidate the content. The space created by consolidation is topped up. The vibrator is switched on again while the separator is extracted from the moulds. The top of the content of mould is flattened, and the mould lid closed and clamped. With the single seated balanced control valve raised, the hydraulic pump is engaged to stress the content to the desired compaction pressure, which was readable on the gauge. The mould lid is opened and with the control valve raised, the block is ejected from the mould.     Typical specimens of hollow SCEB produced with the mechanical kit are shown in Fig. 13.8. The two holes reduced the overall weight of block by 24%. It is also anticipated that the hollowed nature of the block will accommodate any expansion of the inner core material.     Active or passive valves control the flow of samples and reagent through the different steps. Passive valves are able to control fluid movement in a limited way, for example, by allowing flow in one direction through a channel but not in the other one as described above On the other hand, active valves need to be actuated externally using a smart control strategy that typically makes use of sensors to have feedback (Schumacher et al., 2012). Actuation of these valves is very often performed by electrical means, for example, by having a current flow through a copper line and then heating a chamber filled with air that expands and deflects a flexible membrane, which closes a microfluidic channel. Sometimes the deformation of such a membrane is directly performed by using pressurized air coming from an external source, making the valve actuation purely pneumatic instead of electrothermal.     The open tank and multi hole single seated control valve arrangement (Fig. 4) used here together with the 3% cavitation criterion in Fig. 2 is considered to be an industry-based and reliable method for determination of NPSHR in the pump best efficiency region, ISO . More elaborate closed vacuum tank arrangements are used by pump manufacturers to establish NPSHR-curves for water. The measured NPSHR-values obtained here for water (Fig. 5) were about 10% larger than values from the GIW-pump curves. This means that the slurry NPSHR-results in Fig. 5 were about 1.5 times the water values from the pump curves. The scatter may represent the increased cavitation intensity of flow disturbances in an open tank system when compared to a closed tank arrangement.     Experimental closed tank results for sands with average particle sizes of 0.18 and 0.5 mm in pumps with impeller diameters of 0.35 and 0.6 m, respectively, were reported by Herbich . Slurry densities were up to about 1400 kg/m3. It was found that the NPSHR-values (expressed in m of slurry) were similar to the water values, independent of the slurry density. Similar results were also reported by Herbich and Ladouani et al. for non-settling clay-silt slurries with densities of up to 1300 kg/m3 in pumps with impeller diametres less than 0.275 m. Ladouani et al. used an open-tank loop arrangement. Detailed inspection of their data indicates that the independence of the slurry density on NPSHR was limited to flow rates smaller than about 70% of the best efficiency point (BEP). With larger flow rates, NPSHR increased with increasing slurry densities, giving values from 1 to about 2 times the water values in the BEP-region.     The results obtained here were for flow rates close to BEP. Field NPSHR results agreed reasonably well with the laboratory data for the same type of pump pumping phosphate (Fig. 1) at about 500 rpm for flow rates of about 75% of BEP, Addie et al. . In practice, it is therefore reasonable to assume that the laboratory NPSHR-results obtained here are applicable for the flow rate region where most slurry pumps operate today (0.75 to 1.0 of BEP).     Balancing (Fig. 12.15(a and b)) With the compressed air passing to the brake actuator chambers, air pressure is built up beneath the upper and lower pistons. Eventually the upthrust created by this air pressure equals the downward spring force; the pistons and valve carrier lift and the inlet valves close, thus interrupting the compressed air supply to the brake actuators. At the same time, the exhaust valves remain closed. The valves are then in a balanced condition with equal force above an below the upper piston and with equal air pressure being held in both halves of the brake line circuits.     Pushing the treadle down still further applies an additional force on top of the graduating spring. There will be a corresponding increase in the air pressure delivered and a new point of balance will be reached.     Removing some of the effort on the foot treadle reduces the force on top of the graduating spring. The pistons and valve carrier will then lift due to the air pressure and piston return springs. When this occurs the inlet valves remain closed and the exhaust valves open to exhausting air pressure from the brake actuators until a state of balance is obtained at lower pressure.     Releasing brakes (Fig. 12.15(b)) Removing the driver's force from the treadle allows the upper and lower piston and the valve carrier to rise to the highest position. This initially causes the inlet/exhaust valves to close their inlet seats, but with further upward movement of the pistons and valve assembly both exhaust valves open. Air from both brake circuits will therefore quickly escape to the atmosphere thus fully releasing the brakes.     It’s difficult to obtain the flow of sequential valves due to lack of measurement data. The main steam is separated through the four valves and then enter into corresponding group of nozzles. The only flow data we can get from measurement is the main steam. Although there are various formulas to calculate the theoretical flow of valves, flow characteristics of valves are required to obtain the actual flow. However, the flow characteristics of sequential valves are not available through experiment. So a calculation method rely on operation data is necessary.

Fecha de Publicación: 28-09-21

How Cement Mixers Work

Descripción:     How Cement Mixers Work     In addition to the mixing energy applied to the fresh concrete (i.e. shearing during mixing), the shear history after mixing is also important. This applies especially to binder rich concretes like the different types of high performance concrete (HPC). With this in mind, the shear rate is analyzed inside a drum of a concrete tank truck. The objective is to better understand the effect of transport of fresh concrete, from the ready mix plant to the building site. The analysis reveals the effect of different drum charge volume and drum rotational speed. Also, the effect of yield stress and plastic viscosity is investigated. The work shows that the shear rate decreases in an exponential manner with increasing drum charge volume. It is also shown that for a given drum speed, the shear rate decreases both with increasing plastic viscosity and yield stress.     Since civilizations first started to build, the human race has sought materials that bind stones into solid formed mass. After the discovery of Portland cement in 1824 (year of patent), concrete has become the most commonly used structural material in modern civilizations. The quality of the concrete structure is of course dependent on the quality of each constituent used in the concrete mix. However, this is not the only controlling factor. The quality also depends very much on the rheological properties of the fresh concrete during placement into the formwork . That is, the concrete must be able to properly flow into all corners of the mold or formwork to fill it completely, with or without external consolidation depending on workability class. Tragic events may sometimes be traced back to concrete of unsuitable consistency resulting in, for example, coldjoint and honeycombing. Therefore, one of the primary criteria for a good concrete structure is that the fresh concrete exhibits satisfactory rheological properties during casting . The use of simulation of flow to analyze such behavior is something that has been increasing in popularity for the last decade , , , , , , , . In 2014, a RILEM state-of-the art report (TC 222-SCF) was made specifically on this subject . Here, such method is used to analyze the shear rate inside a concrete truck mixer for a wide range of cases. Previously in , such simulation was reported for the case of yield stress 50 Pa and plastic viscosity 50 Pa ?s, in which the aim was to verify a special truck mixer simulator.     In addition to the energy applied during mixing (i.e. shearing during mixing) , , , the shear history after mixing is also important , , . This applies especially for binder rich concretes like the (rich) high performance concrete (HPC). This is due to the influence that the binder exerts on the concrete as a whole in terms of thixotropic- and structural breakdown behavior (these two terms are well explained in ). The rheological state of the binder depends heavily on the shear rate and especially on its history , , . That is, in a highly agitated system (high shear rate), the cement particles will disperse, making the overall fresh concrete more flowable. While in a slowly agitated system, the cement particles will coagulate and thus thicken the overall fresh concrete.     The rheological properties of the fresh concrete depends on the proportions of each constituent as well as on their quality. However, as is apparent from the above paragraph, conditions like the shear rate during transport can play a major role on final workability. That is, a concrete batch with seemingly target rheological behavior at the ready mix plant can become unsuitable at the building site due to thixotropic thickening, caused by insufficient agitation during transport (i.e. low shear rate). The decrease in the slump during transport in truck mixer can be up to 90 mm, which corresponds to a deviation of one and a half consistency class . Such could lead to the refusal of acceptance, or in the case of acceptance, make successful casting in awkward sections or through congested reinforcement difficult, resulting for example in honeycombing , .     In this work, the shear rate is analyzed inside the drum of a concrete fuel tank truck. This is done to better understand the potential effect of transport, from the ready mix plant to the building site, in terms of the concrete final rheological state. From Section 1.2, a higher shear rate will imply increased dispersion of the cement particles and thus more flowable concrete during the casting phase. Likewise, a lower shear rate will imply insufficient agitation, increased thixotropic rebuild and thus stiffer concrete during casting.     Because the shear rate within the drum is highly non-uniform and time dependent, meaning , a two step integration is most necessary to generate quantifiable values for analysis and comparison, which is shown later. The final outcome is given by  and is simply referred to as “shear rate”. Here, this shear rate is analyzed as a function of drum rotational speed f = 0.03, 0.07, 0.11, 015, 019 and 0.23 rps (revolutions per second) and drum charge volume V = 2.6 m3, 5.4 m3 and 8.2 m3. In addition to this, the effect of yield stress τ0 = 0, 150 and 300 Pa and plastic viscosity μ = 25, 75 and 125 Pa ?s, is analyzed.     The simulation software used in this work is the OpenFOAM. It is licensed under the GNU General Public License (GNU GPL) and available at http://openfoam.org, without charge or annual fee of any kind. The benefits of using a GNU GPL licensed code rather than a closed commercial code, is that the user has always a full access to the source code, without any restriction, either to understand, correct, modify or enhance the software. Here, this is a highly desirable feature since a custom made solver is used for the current analysis. The software OpenFOAM is written in C++. As such, an object-oriented programming approach is used in the creation of data types (fields) that closely mimics those of mathematical field theory . For the code parallelization and communication between processors, the domain decomposition method is used with the Message Passing Interface, or MPI . In OpenFOAM, the collocated mesh system (in Cartesian coordinates) is applied in conjunction with the finite volume method (FVM).     The mesh in Fig. 1 is generated with a native OpenFOAM mesh utility called blockMesh. To investigate the mesh dependency of the numerical result, two different mesh densities (or mesh resolutions) are used, namely 58,888 and 372,568 cells, which are shown in the left and right illustrations of Fig. 1, respectively. For the former case, 88% of the cells are hexahedra, while it is 99% for the latter case. In either case, the remaining cells consist of prisms, tetrahedra and polyhedra. In the end of the mesh generation, its quality is checked with another native OpenFOAM utility, named checkMesh.     The internal dimensions shown to the left and right in Fig. 1 are identical and were directly measured at the local concrete premixing plant: the internals consists of two helix shaped blades, in which the blade thickness is roughly 8 mm, while the height is about 430 mm. The space between two adjacent blades is 620 mm on the average. As shown in Fig. 1, all these numbers vary as a function of the location within the drum. These number also change as a function of time, depending on drum usage. That is, the concrete wears and tears the internals of the drum with time.     Decrease of availability of fossil fuels and environment issues, push research towards the development of high efficiency power trains for vehicles that transport people, goods and mobile operating machines, like the concrete 5cbm mixer truck considered in this paper. Conventional concrete 3cbm mixer truck use diesel engine to move the truck and a hydraulic system which keep spinning the concrete drum. A hybrid powertrain based on battery-powered electrical drives can replace the conventional hydraulic system assuring an efficiency improvement. Furthermore, thanks to the reversibility of the electrical drives, it is possible to recover kinetic energy during the braking phases of the truck. Aim of this paper is to study and develop a hybrid powertrain for the concrete mixer drum. The study is based on a full energetic model of the vehicle developed for sizing the components and designing the control strategies. A model of the conventional hydraulic 8cbm mixer truck has also been proposed in order to evaluate the benefit introduced by the proposed hybrid system. Simulation models have been validated comparing experimental data collected on a conventional mixer truck in different operating conditions.     Most construction equipment is easy to understand. Cranes move things up and down. Dump trucks load up, move out and unload. Bulldozers push and graders grade. The one exception to this is the humble cement mixer, beloved by children, hated by in-a-hurry drivers, and misunderstood by most people outside the cab of the 30,000-pound (13,608-kilogram) behemoths.     While concrete has been around in one form or another since before the Romans built the Appian Way, the transit mixer is a child of the 20th century. But recent invention or not, the mixer is here to stay.     The misunderstanding begins with the name. What people refer to as a cement mixer is known in the construction industry as a concrete mixer and comes in a large number of types, sizes and configurations to handle the many tasks set before it each day. That need to fill so many roles means the machine is dynamic, changing shape and form as the needs of the people using concrete change as well.     In this article we'll examine some of the major types of mixers, from the traditional drum-shaped ready-mix transit mixer to the less-common but growing in popularity volumetric mixer, essentially a concrete plant on wheels. How cement mixers work and why they work the way they do is a fascinating combination of old and new technology. You'll never see a cement mixer the same way again.     But before we begin, let's clarify the difference between cement and concrete. In baking terms, the difference between concrete and cement is the difference between flour and a loaf of bread. Concrete is a generic term for a mix of aggregate -- usually stone or gravel, water and cement. Modern cement is a complex blend of finely ground minerals, and goes by the generic name of "portland." Concrete is made by combining the three ingredients in a mixer, whether that mixer is stationary or driving down the road, and the water is absorbed by the cement, which then binds the aggregate together, creating concrete.    

Fecha de Publicación: 28-09-21

Bus HVAC energy consumption test method based on HVAC unit

Descripción:     Bus HVAC energy consumption test method based on HVAC unit     In this study, passenger comfort and the air pollution status of the micro-environmental conditions in an air-conditioned bus were investigated through questionnaires, field measurements, and a numerical simulation. As a subjective analysis, passengers' perceptions of indoor environmental quality and comfort levels were determined from questionnaires. As an objective analysis, a numerical simulation was conducted using a discrete phase model to determine the diffusion and distribution of pollutants, including particulate matter with a diameter air quality and dissatisfactory thermal comfort conditions in Jinan's air-conditioned bus system. To solve these problems, three scenarios (schemes A, B, C) were designed to alter the ventilation parameters. According to the results of an improved simulation of these scenarios, reducing or adding air outputs would shorten the time taken to reach steady-state conditions and weaken the airflow or lower the temperature in the cabin. The airflow pathway was closely related to the layout of the air conditioning. Scheme B lowered the temperature by 0.4? K and reduced the airflow by 0.01? m/s, while scheme C reduced the volume concentration of PM 10 to 150? ??g/m 3 . Changing the air supply angle could further improve the airflow and reduce the concentration of PM 10 . With regard to the perception of airflow and thermal coA system of air-conditioning using Lithium Bromide absorption system is used as an alternative refrigerant that will not pollute the atmosphere. Lithium Bromide is a chemical salt soluble in water.      There is a big difference between vapour compression system and LiBr 2 absorption system. The absorption air conditioning system is made of a generator, a condenser, an evaporator and an absorber with necessary pumps and piping. When LiBr 2 solution is heated under low pressure, water will evaporate first, while LiBr 2 will remain in the solution and will become more concentrated. The water is the refrigerant in this system. The generator, where the water is vapourised, is heated using an electric heater or solar energy. The LiBr 2 weak solution under low pressure in the generator is heated and the water evaporate into vapour. The vapour produced is then cooled in the condenser and then expanded into the evaporator. The refrigerant (water) in evaporator change phase from liquid to vapour by absorbing heat from cooling water, which flow in the coil in the evaporator. The chilled water obtained is then pumped into the fan coil, which will be used in conditioning the passenger area of the bus. The water vapour from the evaporator is absorbed into LiBr 2 solution in the absorber, forming a weak solution of LiBr 2 . the weak solution from the absorber is then pumped back to the generator to regenerate. The absorption system does not use compressor, but requires pumps that need lower input power compared to that of a compressor. The system is considered as a new application for the bus. This will have great potential and will be environmentally friendly. The model in this study will be used for calculation of the cooling load for the bus.     Comfortable journey with commercial buses is an essential goal of transportation companies. An air-conditioning system can play an important role for this comfortable journey but it can put extra load on the engine and extra cost in the fuel consumption. The purpose of this work is to increase the performance of air-conditioning system of the buses by reducing the load on the engine and fuel consumption. Using a two-phase ejector as an expansion valve can increase the coefficient of performance (COP) of the air-conditioning system. An improvement in the COP can reduce the empty vehicle weight and fuel consumption of buses. Two-phase ejector dimensions can be determined using the empirical methods available in the literature. In this paper, the two-phase ejector dimensions of air conditioning system for a bus are calculated using the analytical and numerical methods. First of all, the thermodynamic analysis of the vapor-compression refrigeration cycle with a two-phase ejector is performed, and then the ejector dimensions are subsequently determined. The cooling loads of the midibus and bus with R134a as a refrigerant are assumed to be 14? kW and 32? kW, respectively. The total length of the two-phase ejector for the midibuses and buses due to these cooling loads, are computed to be 480.8? mm and 793.1? mm, respectively. Also, an experimental setup is installed on a truck air conditioner to turn it into the ejector air conditioning system to validate theoretical results with the experimental study. - Highlights: a€￠ Determination of two-phase ejector dimensions of a bus air-conditioning system. a€￠ Thermodynamic analysis of the two-phase ejector cooling system. a€￠ Experimental study on a midibus air conditioner using two-phase ejector.     A novel control strategy to improve energy efficiency and to enhance passengers' thermal comfort of a new roof top bus multiple circuit air conditioning (AC) system operating on partial load conditions is presented. A novel strategy for automatic control of the AC system was developed based on numerous experimental test runs at various operating conditions, taking into account energy saving and thermal comfort without sacrificing the proper cycling rate of the system compressor. For this task, more than 50 test runs were conducted at different set point temperatures of 21, 22 and 23 C. Fanger's method was used to evaluate passenger thermal comfort, and the system energy consumption was also calculated. A performance comparison between that of the conventional AC system and that of the newly developed one has been conducted. The comparison revealed that the adopted control strategy introduces significant improvements in terms of thermal comfort and energy saving on various partial load conditions. Potential energy saving of up to 31.6% could be achieved. This results in a short payback period of 17 months. It was found from the economic analysis that the new system is able to save approximately 20.0% of the life cycle cost. A novel control strategy to improve energy efficiency and to enhance passengers' thermal comfort of a new roof top bus multiple circuit air conditioning (AC) system operating on partial load conditions is presented.      A novel strategy for automatic control of the bus ac parts was developed based on numerous experimental test runs at various operating conditions, taking into account energy saving and thermal comfort without sacrificing the proper cycling rate of the system compressor. For this task, more than 50 test runs were conducted at different set point temperatures of 21, 22 and 23 deg. C. Fanger's method was used to evaluate passenger thermal comfort, and the system energy consumption was also calculated. A performance comparison between that of the conventional AC system and that of the newly developed one has been conducted. The comparison revealed that the adopted control strategy introduces significant improvements in terms of thermal comfort and energy saving on various partial load conditions. Potential energy saving of up to 31.6% could be achieved. This results in a short payback period of 17 months. It was found from the economic analysis that the new system is able to save approximately 20.0% of the life cycle cost.     Air-conditioners (AC) usually consume the most electricity among all of the auxiliary components in an electric bus, over 30% of the battery power at maximum. On-board passengers carried by the electric bus are important but random heat sources, which are obsessional disturbances for the cabin temperature control and energy management of the AC system. This paper aims to improve the AC energy efficiency via passenger amount variation analysis and forecast in a model predictive control (MPC) framework. Three forecasting approaches are proposed to realize the passenger amount variation prediction in real-time, namely, stochastic prediction based on Monte Carlo, radial basis function neural network (RBF-NN) prediction, and Markov-chain prediction. A sample passenger number database along a typical bus line in Beijing is built for passenger variation pattern analysis and forecast. A comparative study of the above three prediction approaches with different prediction lengths (bus stops in this case) is conducted, from both the energy consumption and temperature control perspectives. A predictive AC controller is developed, and evaluated by comparing with Dynamic Programming (DP) and a commonly used rule-based control strategy.      Simulation results show that all the three forecasting methods integrated within the MPC framework are able to achieve more stable temperature performance. The energy consumptions of MPC with Markov-chain prediction, RBF-NN forecast and Monte Carlo prediction are 6.01%, 5.88% and 5.81% lower than rule-based control, respectively, on the Beijing bus route studied in this paper.     This paper presents a test method for determination of energy consumption of bus HVAC units. The energy consumption corresponds to a bus engine fuel consumption increase during the bus hvac parts operation period. The HVAC unit energy consumption is determined from the unit input power, which is measured under several levels of bus engine speeds and at different levels of testing heat load in the laboratory environment. Since the bus engine fuel consumption is incrementally induced by powering an HVAC unit, the results are subsequently recalculated to the unit fuel consumption under the defined road cycles in terms of standardized diesel engine. The method is likewise applicable either for classic or electric HVAC units with a main consumer (compressor or high voltage alternator) mechanically driven directly from the bus engine and also for electric HVAC units supplied from an alternative electric energy source in case of hybrid or fully electric buses.    

Fecha de Publicación: 28-09-21

Introduction to Injection Mold Verification

Descripción:     Introduction to Injection Mold Verification     Injection molding is one of the most commonly used production processes for plastics. This is rightly so as it offers a viable solution for the mass production of high-quality injection automotive parts from a broad range of polymers. In the automotive industry, where consistency, safety, and quality are of utmost importance, automotive plastic injection molding is an important manufacturing process.     This article will be discussing automotive plastic injection molding from various aspects, including its history, advantages, applications, alternative solutions, and materials. Swipe down and read on!     In the early days of the automotive industry, cars were made almost entirely of metal, which meant they were clunky and extremely heavy. However, the industry became advanced and the plastics market erupted in the 1940s and 50s. Therefore, automotive manufacturers began to experiment with plastic car parts in their production.     In the 1970s, manufacturers rolled out the first cars with plastic decorative elements. Later in the 80s, they also introduced more functional parts like plastic headlights, bumpers, and fenders.     In the early 2000s, automotive manufacturers unveiled the first plastic structural components for cars, which had the advantage of being more lightweight than their metal counterparts, unlocking improved fuel efficiency and cheaper production. Today, injection molding is now a dominant production method for manufacturing plastic car parts in the automotive industry.     Injection molding is an established production process in which automotive mould manufacturers inject molten plastic materials into a mold cavity. The melted plastic then cools and hardens, and the manufacturers extract the finished part. Though the mold design process is critical and challenging (a poorly designed mold can result in defects), injection molding itself is a reliable method for producing solid plastic parts with a high-quality finish.     Here are a few reasons why the process is beneficial for automotive plastic parts production:     1. Repeatability     In the automotive industry, repeatability—or the ability to consistently produce identical parts—is crucial. Because automotive plastic injection molding typically relies on robust metal molds, the final molded automotive parts produced using the mold are practically identical. Some factors come into play with injection molding, but injection molding is a highly repeatable process if the mold has a good design and finishing.     2. Scale and Cost     The injection mold-making process can be an expensive process due to the cost of the mold. However, it remains a highly scalable process whose overall cost decreases as the manufacturer makes more parts. For mass production applications, injection molding is thus beneficial to the manufacturer. For anything less than mass production, however, injection molding tooling costs may curb the cost efficiency of the process.     3. Material Availability     A significant benefit of using injection molding for automotive production is the wide range of rigid, flexible, and rubber plastics the process is compatible with. Manufacturers use a wide range of different polymers for various applications in the automotive industry, including ABS, polypropylene, acrylic, acetal, nylon, polycarbonate, and more.     4. High Precision and Surface Finish     Injection molding is ideal for producing plastic parts with relatively simple geometries and results in high surface finish quality. Manufacturers have many finish options when producing parts, including various surface textures—such as glossy, rough, or matte—which they apply directly to the automotive exterior mould rather than the molded part. However, different plastic materials also influence the final surface finish.     5. Color Options     In automotive plastic injection molding, it is easy to modify the colors of molded automotive parts to fit the vehicle’s color scheme. Unlike other processes, injection molding allows you to mix dyes with the raw material pellets before manufacturing begins. This produces solid, consistent coloration without the need for painting or tinting after the molding is complete.     6. Fast Prototypes with Rapid Tooling     Although automotive manufacturers widely use injection molding for mass production of auto parts, they also use it as a prototyping tool. By creating fast, low-cost aluminum molds with rapid tooling — usually by additive manufacturing or CNC machining — automotive mold manufacturers can turn around short runs of prototype molded car components much faster than traditional (steel) tooling.     For the past two decades or so, many under-the-hood components that manufacturers formerly made from metal have been transitioned to plastic. For these applications, robust polymers such as ABS, Nylon, and PET are common. However, manufacturers now make parts such as cylinder head covers and oil pans using injection molding. This method offers lower weights and costs compared to metal parts.     Injection molding is an established process for many exterior automotive components, including fenders, grilles, bumpers, door panels, floor rails, light housings, and more. Splash guards are a fine example for demonstrating the durability of injection molded parts. In addition, the components, which protect the car from road debris and minimize splashing, are often made from rubber or other durable and flexible materials.     In many cases, molded plastics serve as an alternative to metals. Formerly, manufacturers make items like brackets, trunk lids, seatbelt modules, and air-bag containers exclusively from metal. Nowadays, injection molding is the preferred production method for these plastics.     On the other hand, manufacturers can sometimes replace molded plastic parts with 3D-printed plastic car parts. This happens especially in prototyping, where there is less need for extreme durability or a smooth surface finish. Many moldable plastics can serve as FDM 3D printer filaments or as SLS 3D printer powders for nylons. Some specialist and high-temp 3D printers can also print reinforced composites for high-strength parts.     At RapidDirect, we offer professional injection molding services, delivering mass-produced plastic car parts to clients in the automotive and other industries. Our services include thermoplastic injection molding, over-molding, insert molding, and mold making. In the latter case, our experts work with clients to produce high-quality molds for prototyping or large production runs.     We also work with a wide range of plastic injection materials, including strong, heat resistant, and rigid thermoplastics; flexible, fast curing thermoplastics; and durable, high-temperature rubber plastics. Our professional automotive plastic injection molding services enable our automotive clients to obtain high-quality molded automotive parts that meet their application requirements.     Rapid Tooling processes are developing and proving to be a reliable method to compete with subtractive techniques for tool making. This paper investigates large volume production of components produced from Selective Laser Melting (SLM) fabricated injection moulding tool inserts. To date, other researchers have focused primarily on investigating the use of additive manufacturing technology for injection moulding for low-volume component production rather than high volume production. In this study, SLM technology has been used to fabricate four Stainless Steel 316L tool inserts of a similar geometry for an after-market automotive spare part. The SLM tool inserts have been evaluated to analyse the maximum number of successful injections and quality of performance. Microstructure inspection and chemical composition analysis have been investigated. Performance tests were conducted for the four tool inserts before and after injection moulding in the context of hardness testing and dimensional accuracy. For the first reported time, 150,000 injected products were successfully produced from the four SLM tool inserts. Tool inserts performance was monitored under actual operating conditions considering high-level demands. In the scope of this research, SLM proved to be a dependable manufacturing technique for most part geometries and an effective alternative to subtractive manufacturing for high-volume injection moulding tools for the aftermarket automotive sector.     At this point of the process, we’ve released our designs to our vendor and molds build has started. The time we have now could vary from 3–4 weeks to 20 weeks or more, depending on the household mould and part. During this time, there are two things we should do:     Time control. It is quite common that the container mould maker will send a bi-weekly report with detailed progress regarding the mold manufacturing. You may want to look only that the first trial, T1, is as promised, but you may also want to monitor the progress to predict delays. For that, you may need a professional who has a deep understanding of the steps of mold manufacturing.     Regroup and start preparing for T1. We have the time to look back into our plans and check if we covered all bases, if we defined all we wanted to, and if we covered operation issues such as raw materials for the testing, as well as double checking that the mold maker has the latest part drawings, etc.     I’ll explain how I see the difference between T0 and T1.     The first stage before injection of the plastic that will form into parts is to see that the mold works. This is what I call T0. This is the first time the mold maker mounts the mold on the injection machine and sees that the moving elements move well, that the plastic melt flows well, that the cooling performs, and more. Just like every car manufacturer will have a “dry run” of the car before it is driven out of the assembly hanger, the mold maker should ensure this machine performs its basic functions before handing samples for examining.     If the mold performs well in T0, then this test can be called T1 because we have samples. However, T1 samples might not (or, in some predefined cases, should not) be within the final dimensions; the surface finish is not final; and we may have visual marks, flashes, and mismatches. That being said, the samples are a milestone with two main aspects: one is that the mold maker delivered a mold — a tool, a machine — that can produce the parts we had up until now only as a CAD file, 2D drawings, and models. The other is that the developer gets the queue to initiate the final stage of the product development, what we call the “T1 to T-final” (the well-known Tf) phase, which is the “money time” of our project.     To clarify, this stage is not a chair mould process validation (installation qualification, operational qualification, performance qualification). This is the stage in which we aim to achieve a verified, stable part that will qualify our definitions. Once we get that, we may initiate mold performance validation.

Fecha de Publicación: 28-09-21

Beauty & Style

Descripción:     Beauty & Style     Earrings, ornaments decorating the ears, have been one of the principal forms of jewelry throughout recorded history. The term usually refers to ornaments worn attached to the earlobes, though in the late twentieth century it expanded somewhat to include ornaments worn on other parts of the ear, such as ear cuffs, and is used to describe pieces of jewelry in earring form, even when they are worn through piercings in other parts of the body (for example, in the nose). The most common means of fashion earrings to the earlobes has been to pierce holes in the lobes, through which a loop or post may be passed. But a variety of other devices have also been used, including spring clips, tensioning devices such as screw backs, and, for particularly heavy earrings, loops passing over the top of the ear or attaching to the hair or headdress.     In many cultures and contexts, earrings have traditionally been worn as symbols of cultural or tribal identity, as markers of age, marital status, or rank, or because they are believed to have protective or medicinal powers. Even when they have served other purposes, however, the primary function of earrings has been a decorative one. As earrings are so prominently placed near the face, and at the juncture between costume and coiffure, they, perhaps more than any other element of jewelry, have been particularly responsive to changes in fashion; as hairstyles, hats, collars, and necklines have risen and fallen, earrings have correspondingly increased and decreased in size and prominence, and during many periods they have been instrumental in balancing and tying together the desired fashionable appearance.     In antiquity, earrings were one of the most popular forms of jewelry. The crescent-shaped gold hoops worn by Sumerian women around 2500 B.C.E. are the earliest earrings for which there is archaeological evidence. By 1000 B.C.E., tapered hoop (also known as boat-shaped) earrings, most commonly of gold but also of silver and bronze, had spread throughout the Aegean world and Western Asia. In Crete and Cyprus, earrings were embellished with twisted gold wire, clusters of beads, and pendants stamped out of thin sheet gold.     In Egypt, earrings were introduced about 1500 B.C.E. and were later worn by both men and women. Many Egyptian earrings took the form of thick, mushroom-shaped studs or plugs, which required an enlarged hole to be stretched in the earlobe; these could be of gold, with a decorated front surface, or of humbler materials such as colored glass or carved jasper. Ear studs consisting of two capped tubes that screwed together could be worn alone, but some also had elaborate pendants of gold cornflowers, or falcons with flexible tail feathers inlaid with glass.     In the first millennium B.C.E., Etruscan and Greek goldsmiths brought new refinement and artistry to earrings, which were valued as both an adornment and a sign of wealth. Variations on the hoop were the so-called leech earring, a thick tube secured by a hidden wire, and the Etruscan box-type earring, which encased the earlobe in a wide horizontal cylinder. Disk earrings, with pendants in the form of amphorae (ancient Greek jars), figures of Eros, and decorative beads and chains, were another popular form, joined about 330 B.C.E. by twisted gold hoops with animal-head finials. All of these forms were stamped out of thin sheets of gold and decorated with fine palmettes, scrolls, and flowers in twisted wire and granulation; such earrings were fairly light in weight, but gave an extremely rich effect.     Roman earrings were similar to Etruscan styles until the first century C.E., when new styles with disks and pendants mounted on s-shaped ear hooks appeared. Colored stones and pearls were favored, and earring styles proliferated to satisfy the Roman taste for ostentatious display. At its height, the Roman Empire had the effect of standardizing styles of jewelry over much of the known world; after the center of influence shifted to Byzantium (Constantinople) in C.E. 330, and Roman influence began to decline, local variations once more emerged. Characteristic Byzantine earrings were plain gold hoops with multiple pearl pendants hung on chains, and crescent-shaped 925 silver open hoop earrings.     In Europe, earrings virtually disappeared between the eleventh and sixteenth centuries, as hairstyles and headdresses that completely covered the ears, and later high ruff collars, made them impractical. Earrings finally began to revive in the late sixteenth century, as ruffs gave way to standing collars. At first, complex enameled designs were popular, but improved techniques of gem cutting soon shifted the emphasis to faceted diamonds. In the seventeenth century, large, pear-shaped pearl pendants were a favorite earring style, and those who could afford to do so wore two in each ear. It was also fashionable to wear pendant earrings on strings or ribbons threaded through the earlobes and tied in bows, and to tie ribbon bows at the tops of earrings to achieve the same effect. Similar earring styles were also worn by fashionable gentlemen, but usually in one ear only.     By the late seventeenth century, earrings had become an essential element of dress, and larger and more elaborate forms began to develop. Two of these became the dominant styles of the eighteenth century: the girandole, in which a single top cluster branches out like a chandelier to support three pear-shaped drops, and the pendeloque, a top cluster with a long single pendant. New sources of diamonds, along with new methods of cutting them, developed early in the eighteenth century, made them the material of choice for jewelry, and high-quality paste imitations were also available. Glittering girandoles and pendeloques, visually tied to the ears by stylized ribbon bows of diamonds set in silver, effectively balanced the high, powdered hairstyles of the period. Despite their refined and delicate appearance, such large earrings were quite heavy; some had additional rings soldered to the tops, permitting the wearer to take some of the weight off of her ears by tying the earrings to her hair.     When the neoclassical style of dress and simpler hairstyles came into fashion at the end of the eighteenth century, earrings became lighter and simpler. Jewelry of cut steel, seed pearls, Berlin iron, and strongly colored materials such as coral and jet, harmonized well with neoclassical fashions, and classically inspired cameos and intaglios were set in all kinds of jewelry. Heavy girandoles gave way to pendant earrings composed of flat, geometric elements connected by light chains. "Top-and-drop" earrings, composed of a small top element attached to the ear wire, from which a larger, often teardrop-shaped element is suspended, also came to the fore around 1800, and remained the most popular earring style throughout the nineteenth century. Matched sets of jewelry, known as parures, assumed new importance in the nineteenth century, and they were available even to women of modest means. These sets usually included at least a matching necklace or brooch and earrings, but could also include bracelets, buckles, and a tiara or tiara-comb.     In the 1810s and 1820s, the trend toward lighter and more delicate jewelry continued, and settings of gold filigree or elaborate wirework (known as cannetille) were very popular. In the 1820s, a romantic interest in the past also inspired jewelry designers to revive historical styles from the ancient world to the eighteenth century, and a modified version of the girandole earring returned, along with elaborate gothic tracery and rococo-revival scroll-work. As hairstyles became more elaborate in the 1830s, earrings became more prominent, with small tops and long drops reaching nearly to the shoulders. In spite of their size, these s925 silver earrings were fairly light in weight, owing to lightweight settings of gold cannetille or of repoussé (embossed relief raised from behind with a hammer), which had largely replaced cannetille by the 1840s. Earrings with long, torpedo-shaped drops of carved gemstones with applied gold filigree were also popular, many with detachable drops to allow the tops to be worn alone.     In the late 1840s and through the 1850s, a new hair-style, with hair parted in the middle and gathered to the back of the head in loops that covered the ears, caused a virtual disappearance of earrings. Around 1860, once again owing to a return to upswept hairstyles, long pendant earrings made a comeback, and through the 1860s and 1870s they were produced in an astonishing variety of styles. One major theme was historical revival, with Egyptian and Classical styles particularly popular. Some revival earrings, such as those produced by the Castellani family in Rome, were fairly faithful reproductions of recent archaeological discoveries; others were fanciful pastiches of classical earring forms, architectural elements, and other motifs such as amphorae. Earrings with carved classical reliefs of coral or lava, or Roman glass micro-mosaics, were very fashionable, and were often brought back as souvenirs by travelers to Italy. Other popular styles were naturalistic renditions of leaves, flowers, insects, and birds' nests in gold, enamel, and semiprecious stones; enameled renaissance-revival styles; and, for more precious gems, floral sprays and cascades. A new style in the 1870s was the fringe or tassel earring, with a graduated fringe of pointed drops suspended from a large oval pendant.     In the last two decades of the nineteenth century, large pendant earrings went out of fashion, in part because they were incompatible with the newly fashionable high dress and blouse collars, and with the elaborate "dog collar" necklaces worn for evening, which almost completely covered the neck. Small single-stone and 925 sterling silver cuba earrings, either firmly mounted to the ear wire or mounted as pendants to move and catch the light, were the most commonly worn style through the early twentieth century. The most fashionable earrings of all were diamond solitaires, which became more available after the opening of the South African diamond fields in the late 1860s. New cutting machines and open-claw settings, both of which increased the amount of light reflected by diamonds and made solitaire earrings more appealing, were developed in the 1870s. To prevent valuable diamond earrings from being lost, catches were added to secure the bottoms of the ear wires. Another innovation, first patented in 1878, was the earring cover, a small hinged sphere of gold, sometimes finished in black enamel, which could be snapped over a diamond earring to protect it from loss or theft. By the end of the century diamond ear studs (also called screws), with a threaded post passing through the ear, and held securely in back by a nut screwed onto the post, were also popular.     By 1900, as earrings declined in size and importance, many women stopped wearing them altogether. Some commentators denounced ear-piercing as barbaric, and women who pierced their ears were considered "fast," or not quite respectable. (In the United States, some of the reaction against pierced ears may be credited to the desire of "native" Americans to distinguish themselves from the large numbers of immigrant women, almost all with pierced ears, who were arriving from Europe at the time.) In spite of piercing's negative image, small screw earrings continued to be worn, and new screw-back fittings, which could be tightened onto unpierced earlobes, were available for those who did not wish to pierce their ears. Around 1908, pendant earrings were revived, but with light, articulated drops of smaller stones rather than single-stone drops; diamonds, pearls, and stones matching the color of the costume were the most popular materials.     The earring revival continued into the 1910s, aided considerably by a growing acceptance of costume jewelry. Jewelry could now be selected for its decorative value rather than its intrinsic value, and women could afford to own many pairs of earrings to match particular costumes; the rise of costume jewelry also made ear piercing less necessary, as women were less concerned about losing inexpensive earrings. (Many women, as was still true in the early 2000s, also had adverse reactions to the cheaper metals used in costume jewelry, which made pierced earrings seem less practical.) The fashion for the Oriental and exotic inspired by Paul Poiret and the Ballets Russes was reflected in bead necklaces and long drop earrings of Chinese amber, jade, black and red jet (glass), and carved tortoiseshell. Empire-revival fashions also inspired a revival of nineteenth-century jewelry styles and materials, including cut steel and cameos.     By the early 1920s, earrings were again almost universally worn, and the range of exotic styles had expanded to include hoop and pendant earrings of Spanish or Gypsy inspiration, Egyptian styles inspired by the discovery of King Tutankhamen's tomb in 1922, nineteenth-century antiques, and picturesque "peasant" styles from around the world. As reported by the New York Times in 1922, in the 1920s earrings could "no longer … be considered as an article of jewelry; they are the article of jewelry." With dress styles now comparatively simple, and many women bobbing their hair, earrings were considered an essential finishing touch-a means both of filling in the area between the ear and shoulder and of expressing the wearer's personality. Bold geometric pendant 925 stud earrings, made of diamonds and platinum contrasted with strongly colored materials such as onyx and lapis lazuli, were displayed at the Exposition International des Arts Décoratifs in 1925, and this style, which became known as Art Deco, remained popular for both precious and costume earrings for the remainder of the decade.    

Fecha de Publicación: 28-09-21

Can Liquid Nails Bond Wood To Metal?

Descripción:     Can Liquid Nails Bond Wood To Metal?     It’s a common household problem. However, you have another problem. You have a wooden bathroom door and a metal knob. What’s the quickest way to reattach the two surfaces? Can you trust your tube of liquid nails to do the job?     Liquid Nails can bond wood to metal. You can use some variations of liquid nails in construction projects and home improvement projects to bond wood and metal. They have a potent formula that performs in all weather conditions.      Adhesives are a fast and easy solution to most household and construction projects. Most times, you need to bond similar items such as wood on wood or plastics. In other cases, you are faced with the task of joining different surfaces together.      We look at whether liquid nails, a polyurethane adhesive, sticks to their word in a market awash with adhesives. Let’s find out if liquid nails heavy duty can bond wood to metal.      "Liquid Nails" (Liquid Nails) - construction adhesive, which is suitable for connecting all sorts of things by gluing. It is so called because when it is used, parts and surfaces are very firmly glued to each other, as if nails are connected. "Liquid nails" are a mixture of polymers and rubber. They are supplied to the market in the form of tubes of various capacities from 200 to 900 ml. For ease of application and uniform dosing, experts recommend using a construction pistol. How to choose it correctly, and what to look for, will be discussed in the article.     Rechargeable devices are good for their autonomy. They function with a Li-Ion battery. Thanks to the handle, the output of the adhesive is provided, and its speed can also be adjusted - the harder you press, the more glue comes out. The only negative is that you often need to charge the battery or change batteries.     Electric gun It differs from the wireless analogue only in the absence of a battery. The rest of the functionality is the same. Apply them an adhesive substance is obtained quickly and economically. Usually such devices are used by specialists. There is a lot of such a unit, so for use in the home, when there is no large scope of work, the purchase is inappropriate. Insert the composition into the gun is also quite difficult.     If Liquid Nails has bonded to your drywall and you want to remove it, apply heat or a solvent before scraping. This process will make removal easier and reduce damage to the drywall surface. Use a heat gun to soften the Liquid Nails or apply mineral spirits, petroleum jelly, or a similar compound to the dried adhesive. Once the Liquid Nail Glue has softened, scrape it off your drywall. If there is any damage after removal, patch your drywall with joint compound before painting.     Liquid Nails and other construction adhesives won’t irreparably ruin drywall. Construction adhesives bond to the drywall’s paper surface but will not penetrate any deeper than the surface. This means that if you use the right methods to remove Liquid Nails, the damage will be minimal.     Liquid Nails won’t ruin drywall because it only bonds to the paper surface of drywall.     If you’ve removed paneling or a wall fixture that was secured to drywall with Liquid Nails, you’ll probably be left with a bumpy residue of adhesive that won’t budge. Don’t panic. You can get rid of the adhesive and make your walls beautiful again. Just try these techniques.     Heat Gun or Blow Dryer     In many cases, heat will return hardened Liquid Nails to a softer consistency. Use a construction-grade heat gun or a blow dryer to heat the Liquid Nails. Once it begins to change to a putty-like consistency, use a scraper or putty knife to peel the Liquid Nails from your drywall slowly.     Use this heat gun or a blow dryer to heat up the dried Liquid Nails.     As the Liquid Nails changes to a putty-like consistency, use a scraper to remove it from your drywall.     These heat tools are safe to use with drywall and will not cause damage to your walls.     This method is safe to use because drywall is very heat-resistant. The water in gypsum remains in an unevaporated state until temperatures reach 176°F (80°C). Only at temperatures above this point will the water begin to evaporate, increasing the chance of damage to the drywall. You can thus use a heat gun or blow dryer to heat residual construction adhesive without posing a threat to your drywall.     Changing your stair treads is a small but powerful way to update your home. With all the construction adhesives on the market, the household name of liquid nails for flooring comes to mind first, but is it suitable for stair treads? We’ve taken a look into the inner workings of adhesives to find out for you!     Liquid Nails’ brand name is not the first recommended adhesive for stair treads due to its high water content. The higher the moisture levels, the more chances of warping as it dries. A polyurethane glue, such as Loctite PL Premium, is a highly recommended adhesive.     Since the stair treads, or the surface of your stairs, receives a lot of foot traffic, you’ll want to make sure it’s properly installed. We have insider tips and tricks on installing the strongest tread and looking at how to finish them with stains. Keep reading to learn these processes and more!     In particular, Liquid Nails have low VOC but are solvent-based and can cause warping to wood. VOC, or volatile organic compound, is the odor often associated with strong adhesives. The higher the VOC, the more intense the smell, which will require more airflow to reduce breathing it in.     There is also a long curing time to Liquid Nails that can extend your project longer than desired. Liquid Nails can be a good choice for smaller woodworking projects that require a strong bond, but it is better to use a poly construction glue for home improvement. If you only have Liquid Nails available near you, make sure it has low VOC and is not water-based. Then do a test with two pieces of wood to see how it interacts.     To begin, there are four main parts of stairs. The first is the base, known as the stinger. This is the full wooden cut-out board that acts as a ground to lay the treads on. Next are the stairs risers. These are the vertical faces of the stairs that meet the back and then the front of each tread.     Of course, then we have the tread itself, which is the actual stepping surface. Finally, there are the stairs nosing. The nosing is the extra bit of stair tread that over hands above the riser. You can also add a cove molding, which goes over the joint of the riser and tread. It looks similar to adding crown molding to your walls. There are a few extra teams for their build, but these are the main components.     Start by ensuring that the stair tread and sub-tread surfaces, if applicable, are clean of any dust or debris. When working without a stair sub-tread, put globs of glue about 3-4 inches apart on the top of the risers. If there is any glue spillage, you can add a cove molding underneath the treads nosing to hide it, and dress up the stairs. A cove molding is like a skirt underneath the nosing to mask the contact point of the wood.     Subtreads are typically seen on fully closed-in stairs, such as new construction and homes with no basements. They are often made of plywood and are the unfinished version of your staircase. When you have these to work with, you’ll place two rows of quarter-sized globs of adhesive 5-6 inches apart. You’ll want one row in the front and the second towards the back.     Nails are absolutely recommended to use alongside adhesives. While adhesives alone have a strong grip, nails act as a clamping feature to hold the wood to the glue. The pressure from the nails helps reduce the chance of the treads shifting.     Safety is a huge concern when constructing stairs. There is an extra wooden piece that you can add to help strengthen the treads. Known as a glue block, these are 3-4 inch triangular or square parts that go underneath the stairs. You’ll want to install these at any instance wood touches wood.     Glue blocks can be installed with just glue, and often 2 or 3 are placed on the underside where the riser meets the tread. The blocks, along with the staircases skirtboard, should be sealed with a fill caulk. After you put a line down, smooth it out and make sure no small holes appear. Sealing both will help keep moisture out and give the stairs a clean, finished look.     Should I Stain Stair Treads Before Installation?     Yes! Staining your treads before installing them means you’ll be able to see how the stain looks once it drys. You’ll save yourself the headache of trying to restain or remove your new stairs. Also, if you’ve never stained wood before, a good practice run will help you determine how much stain is needed and the best technique to use.     The wood should be totally dry and away from moisture before staining. One of the biggest causes of warping is when the wood planks have different moisture levels throughout. Drier parts of the wood will dry faster after the stain is applied and will tighten at a different rate than the slightly more wet areas.     Along with seeing how the stain will look, for any odd reason, if there is warping, you’ll be able to fit your cut treads again into the stingers to make sure it still fits. Staining is a great way to seal your treads and give them a protective coat against heavy usage.     While liquid nails mirror may not be the first recommendation for installing stair treads, you have other options. Polyurethane adhesives with low VOC will give your stair joints the strength they need. You should use finishing nails alongside an adhesive to act as a pressure hold while the glue dries. Taking time to revamp your staircase will make a huge impact on the quality of your home.

Fecha de Publicación: 28-09-21

Basic electrical quantities: current, voltage, power

Descripción:     Basic electrical quantities: current, voltage, power     Voltage and current are the cornerstone concepts in electricity. We will create our first mental models for these basic electrical quantities. We will also talk about power, which is what happens when voltage and current act together.     The concept of electricity arises from an observation of nature. We observe a force between objects, that, like gravity, acts at a distance. The source of this force has been given the name charge. A very noticeable thing about electric force is that it is large, far greater than the force of gravity. Unlike gravity, however, there are two types of electric charge. Opposite types of charge attract, and like types of charge repel. Gravity has only one type: it only attracts, never repels.     Conductors are made of atoms whose outer, or valence, electrons have relatively weak bonds to their nuclei, as shown in this fanciful image of a copper atom. When a bunch of metal atoms are together, they gladly share their outer electrons with each other, creating a "swarm" of electrons not associated with a particular nucleus. A very small electric force can make the electron swarm move. Copper, gold, silver, and aluminum are good conductors. So is saltwater.     There are also poor conductors. Tungsten—a metal used for light bulb filaments—and carbon—in diamond form—are relatively poor conductors because their electrons are less prone to move.     Insulators are materials whose outer electrons are tightly bound to their nuclei. Modest electric forces are not able to pull these electrons free. When an electric force is applied, the electron clouds around the atom stretch and deform in response to the force, but the electrons do not depart. Glass, plastic, stone, and air are insulators. Even for insulators, though, electric force can always be turned up high enough to rip electrons away—this is called breakdown. That's what is happening to air molecules when you see a spark.     Semiconductor materials fall between insulators and conductors. They usually act like insulators, but we can make them act like conductors under certain circumstances. The most well-known semiconductor material is Silicon (atomic number 141414). Our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones. The atomic-level details of how semiconductor devices work are governed by the theories of quantum mechanics.     The online monitoring equipment installed on the high-voltage power bus is supported by reliable and stable DC power, which cannot be obtained from industrial low-voltage AC power or chemical battery. This paper presents a circuit based on the principle of electromagnetic induction to obtain low-voltage low-power DC power supply from high voltage power supply bus. The circuit consists of energy-acquired coil, the rectifier and regulator circuit, and the shunt coils. This power supply can work with small current in the bus, also it can output stable DC voltage in the case of large current in the bus by starting shunt coil. The experimental data indicates that the output voltage of the power supply are 3.3 V and 5 V, the output power is greater than 120 mW and the bus starting current is less than 5A, all these can suffice for the online monitoring equipment.     With the rapid development of the world’s aerospace technologies, a high-power and high-reliability space high-voltage power supply is significantly required by new generation of applications, including high-power electric propulsion, space welding, deep space exploration, and space solar power stations. However, it is quite difficult for space power supplies to directly achieve high-voltage output from the bus, because of the harshness of the space environment and the performance limitations of existing aerospace-grade electronic components. This paper proposes a high-voltage power supply module design for space welding applications, which outputs 1 kV and 200 W when the input is 100 V. This paper also improves the efficiency of the high-voltage converter with a phase-shifted full-bridge series resonant circuit, then simulates the optimized power module and the electric field distribution of the high-voltage circuit board.     The flexible combination of power supply modules for different space high-voltage applications is a well approach to solve the design problems of space high voltage rectifier block. Power supply modules can solve the problems in performance limitations of aerospace-grade devices in space high-voltage applications, and make it easier to carry out insulation protection. Therefore, space power module is very important in space high-voltage systems.     This paper proposes a space high-voltage power module with high boost ratio and a new improvement module to improve the efficiency.     China is the global test bed for ultra-high voltage (UHV) transmission lines, a technology that can carry electricity across vast distances with much greater efficiency than the high voltage lines that you’re probably used to seeing.     Since 2006, it’s built 19 of these multi-billion-dollar lines, stretching almost 30,000 kilometres and supplying 4% of national electricity demand. For comparison, no other country has a single UHV line in full commercial operation.     But China’s enthusiasm for UHV is waning. The technology is beset by conflicts of interest between grid companies and central and local governments. The lines themselves are underperforming, and more recent projects are coming online amid a period of electricity generation overcapacity.     This means that approvals for new lines have slowed, and grid companies are unlikely to meet their targets for new ones.     Chinese grid companies have pursued Ultra High Voltage projects to solve a logistical dilemma: coal, hydro, wind, and solar resources are concentrated in the interior, but the heaviest energy demand is along the urbanised east coast.     In normal high voltage rectifier assembly, a lot of the power is lost as it’s moved across China’s enormous terrain. The benefit of UHV lines is that they have dramatically reduced losses.     China has deployed two types of UHV line. Direct current (UHVDC) lines suit transmission from A to B over distances of more than 1,000 kilometres; whereas alternating current (UHVAC) lines work better over slightly shorter distances but permit branching links along the way.     Grid companies have been keen adopters, with State Grid, which covers 88% of China’s territory, especially interested. Its 2013-2020 construction plan envisioned six AC and 13 DC lines by 2013, and 10 AC and 27 DC lines by 2020. In Inner Mongolia alone, company officials spoke of 11 lines running from the province’s coal and renewable hotspots by 2020.     But rollouts have slowed, and few analysts expect State Grid will deliver on its 2020 target. In fact, its national UHV backbone scheme, which is the centrepiece of its UHVAC ambitions, looks unlikely to happen anytime soon.     Sparks fly     State Grid’s UHV plans suggested remarkable ambition, but did not always align with those of central and provincial policymakers.     Central officials have clashed with State Grid planners on its backbone scheme, which envisions a lattice of six UHVAC lines to synchronise grids that are currently in State Grid’s territory. But officials worry about nationwide blackouts cascading across these interconnected grids. Analysts suggest that State Grid has shelved the backbone plan for now and is focusing on UHVAC lines within individual grids instead.     Meanwhile, the economic case for new UHVDC lines from the interior has weakened amidst slowing growth in electricity demand.     National demand growth averaged 11.7% from 2003-12 but fell to 4.5% in 2012-17, bottoming out at 0.5% in 2015. This drop has deepened overcapacity in China’s power sector, which according to Bloomberg New Energy Finance was 35% in 2016.     Pervasive overcapacity means less need for new transmission projects.     China’s “Priority Transmission Lines for Air Pollution Prevention”, a scheme announced in 2014 that included the construction of nine UHV lines, is set for completion this year. National Energy Administration (NEA) officials said in December 2017 that this scheme “can satisfy electricity demand for the country’s main power consumption regions before 2020”.     Unsurprisingly, then, approvals for new UHV projects – which take 3-4 years to construct – have been slow, with just one project approved in 2016, and two in 2017.     Local tensions     Certain regional governments targeted for UHV projects have also been sceptical.     Provinces get larger boosts to gross domestic product (GDP), employment, and revenue from building their own power plants rather than importing power from other provinces. Even new lines with central government backing have sometimes failed to get provincial acceptance.     For example, the UHVDC Sichuan Number Four line would take Sichuan hydropower to Jiangxi province, and was singled out for construction in the 13th Five-Year Plan (2016-2020). But as NEA officials noted last autumn, Jiangxi does not want this power. The province is bringing more coal-fired power plants online in 2018 so wants to delay the new line until after 2025. Hubei province is also reluctant to accept long-debated new lines from north-west China.     Disappointing gains     Grid companies have their own reasons for being cautious about new Ultra High Voltage lines. Revenues from these mega-projects depend on the amount of power they can transmit. But utilisation of existing lines has been lower than expected, with non-hydro lines performing particularly badly.     What’s more, the impact of UHV on renewable energy “curtailment” in inland China has also been disappointing, undermining the case for investment. Curtailment refers to energy that never reaches the grid and is wasted, for reasons including a lack of transmission capacity or quotas for coal-power consumption.     China’s UHV lines transmit wind and solar power in combination with coal power, which remains the major electricity source. Nonetheless, even a minority share of UHV transmission capacity can still take sizeable loads of renewables from China’s interior to coastal markets. Backers of UHV lines have jumped on this point when championing the technology.     Yet after a decade of UHV development, renewable curtailment levels remain high, especially in north-western regions. National curtailment rates in 2017 were 12% for wind and 6% for solar, several percentage points below their 2016 peaks. Still, China has room for improvement; in Europe, curtailment rates in countries with high levels of wind-power production have been consistently below 5%.     Analysis by environmental researcher Darrin Magee and geographer Thomas Hennig suggests that in 2015, curtailment in Yunnan reached 95 terawatt hours (TWh) – more than six times the reported rate, and enough to power Portugal and Singapore combined for one year.     Lagging wind and solar     Ultra high voltage multiplier lines successfully transported 172.5 TWh of renewable energy in 2016, or 3.2% of national power consumption. However, 93% of that power came from five lines used for hydropower only.     Some of China’s non-hydro lines have relied less on renewables than supporters had hoped. Caixin Energy reports that, according to experts at State Grid, renewable shares in lines planned to take a coal-renewable mix should target 30%. Three such lines were in operation for at least part of 2016. Their performance was uneven. Ningdong-Zhejiang carried 29% renewables, and the Southern Hami-Zhengzhou line’s share was at 23%, but Ximeng-Jinan took none at all.     The Zhebei-Fuzhou line was framed initially as a vehicle for nuclear and wind consumption but did not take any wind in 2016. Reports are unclear on whether it has since added wind to its power mix – though it has added coal.     It is hoped that these shortfalls will be temporary. One non-hydro UHV line that launched in 2017 has been relying on coal because the renewable projects planned to accompany it faced construction delays. Overall transmission volumes increased significantly for China’s first UHV lines in their initial five years. Several new UHV lines that take renewables have also come online since mid-2016.     But the shrinking space for new UHVDC projects is a persistent concern for Western provinces, where rapid capacity additions in renewable energy has left long-distance transmission infrastructure struggling to keep pace.     Power sector reforms     UHV is certainly not solely to blame for renewable curtailment problems in the interior. They point to a wider set of challenges facing China’s power sector, which are the focus of reform initiatives launched in 2015. These reforms have included some UHV-specific measures. But many hindrances to the development of UHV lines are best addressed through more comprehensive power sector reforms.     These include power trade markets to make it easier for coastal provinces to buy power from the interior (and locally) at short-notice; measures to strengthen the competitive position of long-distance clean energy against local coal plants; and reforms to reduce disputes around grid planning between central government and provinces.     These reforms are at an early stage. But while enthusiasm for UHV in China is fizzling, the technology will still have a role in the country’s renewable transition. How successful the reforms are will determine what kind of a role that is.    

Fecha de Publicación: 28-09-21

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