There are many innovations turning up in the latest experimental and production electric cars, affecting everything from batteries to motors to control systems. The need to make them all work together is prompting a complete rethink about the way cars should be designed and manufactured, and it is unclear which technologies will dominate as the constraints imposed by internal combustion engines give way to the new limits and possibilities associated with electric propulsion. (46) But one group of engineers have stuck their necks out and declared that a particular technology, the electric hub motor, is likely to become the most widely used drive system.At this week’s Deutsche Messe technology show in Hanover, researchers at the Fraunhofer Institute displayed an electric vehicle which they are using as a test platform to investigate new vehicle systems. (47) It includes electric hub motors, which they have developed to be markedly more powerful than any such motors currently available. The motors have all the necessary power and control systems integrated into the wheel hub, greatly reducing the number of connections between the hub motors and the rest of the vehicle.(48) Because hub motors can deliver power independently to each wheel, tricks like four-wheel-drive are possible, and with software monitoring each wheel, stability and traction control can also be built-in. Besides dispensing with the traditional engine bay on a car, hub motors save space and weight because there is no need for a mechanical transmission, with its driveshafts and differential units.(49) Some critics of the technology think having heavy electric motors in the wheels of cars will have a negative effect on vehicle handling. But Hermann Pleteit, a project manager with one of the 33 Fraunhofer research centres that have teamed up to work on the experimental car, says the chassis and many other parts of the vehicle can be configured in such a way to compensate for this.Several carmakers and component suppliers are interested in hub motors. Michelin, for one, is developing a system it calls the Active Wheel. (50) As well as an electric motor to drive the wheel, it contains a second electric motor to operate an active suspension system that is also built into the wheel hub. Michelin reckons this arrangement, which is now being tested in cars, could make other conventional parts, like shock absorbers, unnecessary. Because hub motors can deliver power independently to each wheel, tricks like four-wheel-drive are possible, and with software monitoring each wheel, stability and traction control can also be built-in.
It has been almost half a decade since Norman Mailer described leas Vegas in his novel The American Dream. But it (1) to be one of the most (2) and exhilarating (使人愉快的) holiday destinations in the world. An end-less (3) of colorful sights and activities are surrounded by skyscrapers and the magnificent Nevada desert. With (4) shopping, luxury spas, five-star dining and some of the most extravagant entertainment, you will (5) see, this is a city (6) offers an experience like no other. Perhaps the enduring appeal of this " (7) capital of the world", though, is that it always has something (8) to offer. Recently the Hard Rock Café has been (9) up its act, completing with a new 42 000 sq ft venue, 1 000-seater cinema and an "interactive rock wall"-allowing customers the chance to (10) images of Hard Rock’s collection. City Center is an $ 8.5 billion (£5.3 billion) complex on the Strip; a place that, in a city already (11) with extraordinary casinos (娱乐场) and hotels, stands out from the (12) It was the largest privately (13) construction project in the US and has three stand-alone hotels, a sprawling shopping and entertainment district and two 37-storey glass towers of (14) flats, designed by the likes of Norman Foster. Another Las Vegas (15) , Planet Hollywood, has (16) with luxury developers to create Westgate Towers--where you could own a piece of the action and a chance to come back to Las Vegas every year. (17) , the only thing you’ll (18) of in Vegas is not knowing which club, restaurant or spa to choose from. But then you can always ask a(n) (19) or the concierge--the fantastic thing about this city is that its residents (20) it as much as you will.
A. polishing
B. laying
C. handing
D. standing