Any sufficiently advanced technology is indistinguishable from magic, the science fiction writer Arthur C. Clarke once wrote. If that is true, then a new generation of smart prosthetics—systems that combine mechanical devices with electronic intelligence to replace body parts—have begun to edge into the realm of the magical

This appeared to be the case when Michael Callahan cast a spell over National Instruments Corp.'s annual users meeting in Austin, Texas, this past August. The 25-year-old president of a startup, Ambient Corp. of Champaign, Ill., joined National Instruments' senior vice president of research, Tim Dehne, on the stage. o

Before more than 4,000 people, Callahan attached a black collar around Dehne's neck. He then told Dehne to think of some words. On two huge screens behind them, a laptop attached to the collar registered activity. A second or two later, the computer voiced Dehne's thoughts: "This is really neat stuff." o

Callahan then pointed to Ambient's cofounder, Thomas Coleman, seated in a wheelchair at the back of the stage. Using thought alone—while holding his hands in the air—Coleman maneuvered his wheelchair to the front of the stage, spun it around, and rode back to his previous position. o

Callahan and Coleman call their speech-capturing technology the Audeo. They hope it will let the mute speak and that application of the same principles will give people who cannot move their hands or legs the ability to wheel from room to room, move a computer cursor, turn on the lights, and switch television channels at home. o

A new bionic hand enables users to move the thumb and index finger independently of the remaining three fingers, a significant advance in dexterity over prior claw-like mechanisms

The Audeo works by intercepting nerve signals as they move through the neck to the vocal cords. "The brain is sending a signal to the proper place, even if those muscles are not working," Callahan explained. o

The collar around Dehne's neck contained transducers that pick up those signals. "It's like I'm talking in a conference room and you press your ear to the glass," Callahan said. "It's muffled, but you can still hear what I'm saying. We try to do that with the electrical signal made by your nerves. We capture it, then process and condition it to turn it into something useful." o

This is similar to how an electrocardiogram works, but with one very significant difference: An EKG measures the electrical impulses created by a contracting muscle. These are relatively strong signals. The Audeo measures nerve pulses that are orders of magnitude smaller. o

"The challenge," Callahan said, "is getting a clean, reliable signal and then filtering out the noise from the body's other nerves, and then doing something with it in a robust way." o

(Ambient in Illinois, by the way, is totally unrelated to the Ambient Corp. in Newton, Mass., which is involved in technology for broadband communication over power lines.) o

traffic accidents occur with mind-numbing regularity

According to the U.S. Department of Transportation, more than 10 million vehicles were involved in 6.2 million accidents in 2005. Of that, 1.8 million collisions injured nearly 2.7 million people. Another 39,189 crashes left 43,443 dead . o

It sounds like wholesale carnage. Yet the number of fatalities and injuries per mile has fallen by half over the past 20 years. o

The reason is that passenger vehicles protect their occupants better. Active safety systems, such as traction control and antilock brakes, provide more control during emergency maneuvers. Passive safety systems, such as seat belts, air bags, and energy-absorbing crumple zones, lessen the severity of injuries in a crash. According to the Department of Transportation, seat belts saved 16,000 lives and air bags 3,000 lives in 2005. o

This past April, the U.S. Department of Transportation announced that it would go beyond active and passive safety systems to mandate the first use of a truly intelligent safety system. The new standard requires automakers to equip all vehicles with electronic stability control, which automatically brakes individual wheels during skids, by Sept. 1, 2011. o

The agency estimates that electronic stability control will save between 5,300 and 9,600 lives and prevent as many as 238,000 injuries each year. o

ESC is more than a safety breakthrough. It opens the door to entirely new types of intelligent safety systems that use sensors and computers to anticipate and respond to threats— independently of the driver. o

The Department of Transportation safety estimates are based on experience. The number of ESC-enabled cars on the road has been growing steadily since Germany's Robert Bosch GmbH and Daimler AG introduced the technology in 1995. Today, most European cars and about one-third of U.S. vehicles use ESC. U.S. automakers make it standard on nearly all sport utility vehicles and vans, and plan to increase the number of cars with ESC well in advance of the 2011 deadline. o

This has given researchers plenty of data to analyze. In 2004, the National Highway and Traffic Safety Administration looked at 1997-2002 crash data from the first cars with ESC. It found that the system reduced single-vehicle crashes by 35 percent in passenger cars and by a remarkable 67 percent in SUVs. It also reduced fatalities by similar percentages. o

In 2006, the Insurance Institute for Highway Safety concluded that electronic stability control could prevent nearly one-third of all fatal crashes and reduce rollovers by as much as 80 percent. Automakers apparently knew this well before the study because ESC comes as standard equipment on most top-heavy SUVs. o

A 2006 study by the University of Michigan's Transportation Research Institute found that electronic stability control reduced non-fatal, loss-of-control crashes by 53 percent for SUVs and 40 percent for passenger cars. On wet, snowy, or icy roads, those percentages climb to 88 percent for SUVs and 75 percent for cars. o

"Electronic stability control is probably the most significant automotive safety technology since the seat belt," said John Woodrooffe, who heads the institute's safety analysis division. o

Over and Under

ESC helps maintain control of a vehicle by keeping it headed in the direction the driver wants it to go. o

Spinning out, or oversteering, occurs when a car turns too quickly. Imagine, for example, that an object falls off the back of a truck. The driver swerves sharply to the left to avoid it and then tries to straighten the car. Turning the front wheels back to the right orients the car in the right direction, but the momentum from the turn keeps the rear of the car sliding to the left. The car fishtails, starts to spin, and can go off the road. o

Drivers can maintain control by working the brakes and countersteering, momentarily turning away from their intended direction. Even a driver who learns how to do this may fail to execute during the few seconds that a crisis lasts. o

ESC works in the background, constantly comparing the direction of the vehicle's front wheels—its intended direction—with its actual direction. It can tell when the car's direction changes too quickly, and apply the brakes selectively to individual wheels (some ESC systems also reduce engine torque) to keep the vehicle from fishtailing and spinning out. o

The system also works when drivers understeer. This often happens when they misjudge a curve. They enter too fast, and then try to execute a sharp turn at high speeds. Electronic stability control senses that the vehicle's direction is not changing fast enough for the steering wheel position, and when the front of the car starts to drift, it applies brakes selectively to keep the vehicle on the road. Electronic stability control builds on two earlier advances, antilock brakes and traction control, according to Phil Headley, chief engineer for advanced technology in Continental AG's Continental automotive systems division, a major ESC supplier. "It has been an evolution," Headley said. o

Antilock brakes, he noted, can only reduce, not increase, brake pressure. They generally use induction or magnetic sensors to monitor the speed of each wheel as it rotates. When the driver brakes and the system senses some wheels moving slower than the others, it releases brake pressure on the slow wheels to keep them from locking. This results in faster, more accurate braking. o

Electronic stability control gathers information about wheel speed, steering wheel direction, lateral acceleration, and yaw rate. It compares the data with a computer algorithm to determine if the vehicle has begun to skid. o

Traction control keeps the car from losing traction when the driver applies too much throttle or steering. Both traction control and antilock brakes measure wheel spin. But whereas antilock brakes release pressure on wheels that are slowing down, traction control increases brake pressure on wheels that are rotating too fast. o

"This system adds more valves and more logic to antilock brakes," Headley said. "It can brake the drive wheels and use the engine controller to reduce torque. The most important difference is that traction control can apply the brakes without the driver touching them." o

Electronic stability control combines sophisticated sensors and high-octane computing to take intelligent brake control to an entirely new level. o

A typical ESC system starts with some of the same basic elements as antilock brakes and traction control. These elements include wheel speed sensors and a hydraulic modulator unit that senses and controls brake pressure for each individual wheel. o

ESC takes over operation of the hydraulic modulator when engaged. ESC uses three types of sensors not found on other active safety systems. The first measures the angle of the steering wheel to determine where the driver wants to go. One variation uses an LED to shine a light through a perforated disc on the steering column that turns with the wheel, but it takes a few moments of driving to fully enable the system. A second variant uses a calibrated microprocessor that retains the position of the steering wheel in memory, even if the car battery has been removed. o

The second critical ESC sensor is the microelectromechanical accelerometer, which measures lateral acceleration. The accelerometers usually use a cantilever or comb that deforms during acceleration or deceleration (much like the antenna on a car whipping back and forth). The deformation changes the cantilever's electrical properties in proportion to the degree of acceleration. Micro accelerometers have been used on vehicles to activate air bags since the mid-1990s. o

The yaw rate sensor, which measures the degree of rotation around a vehicle's vertical axis, was new when Bosch and Mercedes introduced it in 1995. At its heart is a MEMS gyroscope that takes advantage of the tendency of vibrating objects to keep vibrating in the same plane. When the gyro rotates out of that plane, it creates a bending strain that electronics sense and transmit to the ESC computer. o

The sensors work together, measuring, calculating, and comparing to determine when the control system should intervene. ESC monitors the yaw rate sensor and accelerometers to gauge the position of the car and how fast it is changing. It compares that information with the direction of the steering wheel. It must be finely tuned, so it can tell the difference between a driver shooting around a slower car on a two-lane country road and a driver who loses control to avoid an unexpected obstacle. o

Fahrenheit 3,600

Everywhere you look, the gas turbine industry is running hot

One of the basic rules of gas turbines is that the hotter the gas that enters the work-producing turbine from the combustor, the greater the thermal efficiency and output. Still, there are limits. Turbine inlet temperatures in the gas path of modern high-performance jet engines usually don't exceed 3,000°F, while non-aviation gas turbines operate at 2,700°F or lower

But 3,600°F? That temperature exceeds the melting point of iron and the boiling point of molten silver. And yet the turbine airfoils in the new F135 jet engine that powers the Joint Strike Fighter Lightning II are capable of operating at these extreme temperatures. The F135 gas turbine is the first production jet engine in this new 3,600°F class, designed to withstand these highest, record-breaking turbine inlet temperatures

There have been, in fact, quite a few accomplishments in the gas turbine industry over the last year. GE put into operation a simple-cycle 100 MW turbine that runs at 46 percent efficiency. Pratt & Whitney ramped up production of engines for a new class of aircraft, the very light jet. And construction of the first pebble bed nuclear reactor, set to be built in South Africa, was placed on the schedule

But 3,600°F? That's hot. The JSF engine represents a bold—and necessary—step forward. This 40,000-pound thrust engine will power all three variants of the JSF: an Air Force fighter that takes off conventionally, a carrier-based Navy jet, and a short takeoff/vertical landing aircraft for the Marines. The STOVL version is the first aircraft to be able to do the "Hat Trick"—take off in a short distance, go into supersonic flight, then hover and land vertically. These varied missions require a very high thrust-to-weight ratio, and thus high turbine inlet temperatures

Last December, at Pratt & Whitney's Middletown, Conn., plant, Ed Crow, retired senior vice president and head of engineering at Pratt, took a few of us from the University of Connecticut Mechanical Engineering Department to view a F135 engine disassembled after 600 to 800 hours of operation. The blades and vanes of the high turbine, clad with ceramic thermal barrier coatings, are made of single crystal superalloys, which soften and melt at temperatures between 2,200 and 2,600°F. (Single crystal alloys were the subject of an article, "Crown Jewels," in ME magazine in February 2006.) Turbine airfoils closest to the combustor operate in a gas stream that can exceed their superalloy melting point by 1,000°F

  So how do turbine airfoils survive running conditions in this 3,600°F class engine? The vanes and blades are cooled to maintain acceptable service temperatures, some eight-tenths to nine-tenths of their melting temperature. Each high-temperature turbine airfoil is formed from an elaborate investment casting to accommodate the intricate internal passages and surface hole patterns necessary to channel and direct cooling air (bled from the compressor) within and over external surfaces of the airfoil structure. An error in airfoil cooling hole location or in cooling air pressure ratios could cause airfoil gas path inhalation rather than film cooling exhalation, which at the JSF's high turbine gas path temperatures would induce airfoil expiration. The JSF turbine film cooling design is based on some 30 years of gas turbine industry film cooling research and development, and unequivocally pushes forward the state-of-the-art of turbine performance and durability

The JSF engine is just one product in the $3.7 billion military gas turbine market, which includes jet engine production for the world's fighter aircraft—such as the F15, F16, F22, F35, and Typhoon—military cargo, transport, refueling, and special-purpose aircraft. And that's just a fraction of the total worldwide gas turbine market

   ابزاری شامل جرم، یک فنر ، و یک (TMD) یک میراگر جرمی تنظیم شده میراگر است که به سازه ای جهت کاهش پاسخ دینامیکی آن متصل میگردد . فرکانس میراگر به فرکانس سازه به گونه ای تنظیم میگردد که در آن فرکانس تحریک میگردد، میراگر در فاز مخالف شروع به ارتعاش نماید که بدین نحو انرژی بوسیله نیروی اینرسی میراگر که به سازه اعمال میگردد، کاهش می یابد . فرضیه میراگر جرمی تنظیم شده در سال 1909 برای کاهش حرکات سالن Frahm برای اولین بار توسط (TMD) و Ormondroyd بوسیله TMD کشتی مورد استفاده قرار گرفت . بعدها تئوری در مقاله ای در سال 1928 ارائه گردید. که بوسیله بحثهای مفصلتری Den Hartog راجع به تنظیمات و پارامترهای میرائی بهینه در کتاب "ارتعاشات دینا میکی" آقای هارتوق پیگیری گردید ( 1940 ). تئوری اولیه برای یک سیستم یک درجه آزادی نامیرا تحت اثر بارهای سینوسی مورد استفاده قرار گرفت . تحقیقات مربوط به سیستم های Randall et al یک درجه آزادی داری میرائی نیز بوسیله محققان زیادی از جمله انجام Tasi & Lin ( و ( 1993 Warburton (1980،1981،1982) ، (1981) پذیرفته است.

    الیاف کربن نسل جدیدی از الیاف پر استحکام است . این مواد از پرولیز کنترل شده گونه هایی از الیاف مناسب تهیه می شود ؛ به صورتی که بعد از پرولیز حداقل 90 درصد کربن باقی بماند . الیاف کربن نخستین بار درسال 1879 میلادی زمانی که توماس ادیسون از این ماده به عنوان رشته پرمقاومت در ایجاد روشنایی الکتریکی استفاده کرد ، پای به عرصه علم و فن آوری گذاشت . با این حال درآغاز دهه 1960 بود که تولید موفق تجاری الیاف کربن ، با اهداف نظامی و به ویژه برای کابرد در هواپیمای جنگی ، آغاز شد . دردهه های اخیر ، الیاف کربن در موارد غیر نظامی بسیاری ، همچون هواپیماهای مسافربری و باربری ، خودروسازی ، ساخت قطعات صنعتی ، صنایع پزشکی ، صنایع تفریحی – ورزشی و بسیاری موارد دیگر کاربردهای روزافزونی یافته است . الیاف کربن در کامپوزیت های با زمینه سبک مانند انواع رزین ها به کار می رود . کامپوزیت های الیاف کربن در مواردی که استحکام و سختی بالا به همراه وزن کم و ویژگی های استثنایی مقاومت به خوردگی مدنظر باشند ، یگانه گزینه پیش روست . همچنین هنگامی که مقاومت مکانیکی در دمای بالا ، خنثی بودن از لحاظ شیمیایی و ویژگی ضربه پذیری بالا نیز انتظار برود ، بازهم کامپوزیت های کربنی بهترین گزینه هستند . با توجه به این ویژگی ها ، پهنۀ گسترده موارد کاربرد این ماده در گستره های گوناگون فن آوری به سادگی قابل تصور است .

Motor Magazine

Motor is an Australian motoring magazine published monthly by ACP Magazines. Motor magazine was originally Modern Motor, the former word connecting it with its first publishing company. However, colloquially it was called Motor, and it formally adopted this title in the late 1990s

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