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一般情况下，指定分包人的款项由业主直接支付。 ()
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几个月前，来自一些地方的研究人员演示了使光以每秒17米的缓慢速度通过一堆冰冷的钠原子的过程。但是把原子冷却到接近绝对零度是非常困难的，要使以慢光为基础的应用能够变为现实，需要采用简单一些的方法。
德克萨斯州农业机械大学的韦尔奇博士意识到，在冰冷的钠原子中使光速降低的基本原理在热的铷原子中也同样适用。用热的铷原子做实验要简单得多，它包括把一个装有固体铷金属的特殊透明容器(称为“小室”)加热到大约100摄氏度，然后把两束经过细微调节、波长略微不同的激光射入小室。
即使穿过普通的透明材料，比如玻璃或水，光速也会略微降低，因为光会与组成材料的原子相互作用。但是在这种情况下，影响是微弱的，并且任何加强这种影响的试图都会导致光的吸收。因此，重要的是使光的速度降低，而且不至于被吸收。韦尔奇博士通过小室做到了这一点。这种方法把铷原子置于一种非常微妙的量子状态中，在这种状态下铷原子不能吸收光。同时，两束光的相互作用产生了另外一束波长很长的光，这束光的传播速度比原先两束光的速度要慢得多。
降低光速能获得诸如非线性等其他一些效应。在大多数情况下，光的行为是线性的：把入射到玻璃上的光的强度增加一倍，穿过玻璃的光的强度也会增加一倍。但是，非线性意味着入射光的微小变化会导致透射光的巨大改变。正是这种性质使光学开关的设计者们兴奋不已。
加利福尼亚大学的工程师阿塔奇认为，人们在通过光缆传送光脉冲时，常常需要把某个用来与其他信号作对比的信号延迟一段时间。目前的做法是把其中一个脉冲沿着为此目的而专门建造的很多光纤发送出去，而采用一个大小为1升、装满高温铷气的小室能够达到同样的目的并且更加有效。
韦尔奇小组的成员卡什说，装满铷气的小室在改变激光束以产生难以获得的波长方面极其有效。他们已在考虑运用这．个原理制造一个廉价、高效的紫外线源，由于紫外线波长短，因此可以用来读取刻录在光盘等媒介上的形状更小、排列更紧密的数据。
文中画线处“影响”一词的意思是()
3000户业主的年收入分组资料如下表，则年收入众数为()元。
In the eighteenth century, Japan's feudal overlords, from the shogun to the humblest samurai, found themselves under financial stress. In part, this stress can be attributed to the overlords' failure to adjust tog rapidly expanding economy, but the stress was also due to factors beyond the overlords' control. Concentration of the samurai in castle towns had acted as a stimulus to trade. Commercial efficiency, in turn, had put temptations in the way of buyers. Since most samuri had been reduced to idleness by years of peace, encouraged to engage in scholarship and martial exercises or to perform. administrative tasks that took little time, it is not surprising that their tastes and habits grew expensive. Overlords' income, despite the increase in rice production among their tenant farmers, failed to keep pace with their expenses. Although shortfalls in over- lords' income resulted almost as much from laxity among their tax collectors (the nearly invitable outcome of hereditary office holding) as from their higher standards of living, a misfortune like a fire or flood, bringing an increase in expenses or a drop in revenue, could put a domain in debt to the city rice-brokers who handled its finances. Once in debt, neither the individual samurai nor the shogun himself found it easy to recover.
It was difficult for individual samurai overloads to increase their income because the amount of rice that farmers could be made to pay in taxes was not unlimited, and since the income of Japan's central government consisted in part of taxes collected by the shogun from his huge domain, the government too was con- strained. Therefore, the Tokugawa shoguns began to look to other sources for revenue. Cash profits from government -owned mines were already on the decline because the most easily worked deposits of salver and gold had been exhausted, although debasement of the coinage had compensated for the loss. Opening up new farmland was a possibility, but most of what was suitable had already been exploited and further reclamation was technically unfeasible. Direct taxation of the samurai themselves would be politically dangerous. This left the shoguns only commerce as a potential source of government income.
Most of the country's wealth, or so it seemed, was finding its way into the hands of city merchants. It appeared reasonable that they should contribute part of that revenue to ease the shogun's burden of financing the state. A means of obtaining such revenue was soon found by levying forced loans, known as goyokin; although these were not taxes in the strict sense, since they were irregular in timing and arbitrary in a- mount, they were high in yield. Unfortunately, they pushed up prices. Thus, regrettably, the Tokugawa shoguns' search for solvency for the Government made it increasingly difficult for individual Japanese who lived on fixed stipends to make ends meet.
The passage is most probably taken from ______.
Although the distribution of recorded music went digital with the introduction of the compact disc in the early 1980s, technology has had a large impact on the way music is made and recorded as well. At the most basic level, the invention of MIDI (Musical Instrument Digital Interface), a language enabling computers and sound synthesizers to talk to each other, has given individual musicians powerful tools with which to make music.
“The MIDI interface enabled basement musicians to gain power which had been available only in expensive recording studios,” One expert observed. “It enables synthesis of sounds that have never existed before, and storage and subsequent simultaneous replay and mixing of multiple sound tracks. Using a moderately powerful desktop computer running a music composition program and a 500 synthesizer, any musically literate person can write -- and play! -- a string quartet in an afternoon."
Whereas many musicians use computers as a tool in composing or producing music, Tod Machover uses computers to design the instruments and environments that produce his music. As a professor of music and media at the MIT Media Lab, Machover has pioneered hyper - instruments: hybrids of computers and musical instruments that allow users to create sounds simply by raising their hands, pointing with a "virtual baton," or moving their entire body in a "sensor chair."
Similar work on a "virtual orchestra" is being done by Geoffrey Wright, head of the computer music program at John Hopkins University's Peabody Conservatory of Music in Baltimore, Maryland. Wright uses conductors' batons that emit infrared light beams to generate data about the speed and direction of the batons, data that can then be translated by computers into instructions for a synthesizer to produce music.
In Machover's best -known musical work, Brain Opera (1996), 125 people interact with each other and a group of hyper - instruments to produce sounds that can be blended into a musical performance. The final opera is assembled from these sound fragments, material contributed by people on the Web, and Machover's own music. Machover says he is motivated to give people "an active, directly participatory relationship with music."
More recently, Machover helped design the Meteorite Museum, a remarkable underground museum that opened in June 1998 in Essen, Germany. Visitors approach the museum through a glass atrium, open an enormous door, enter a cave, and then descend by ramps into various multimedia rooms. Machover com- posed the music and designed many of the interactions for these rooms. In the Transflow Room, the undulating walls are covered with 100 rubber pads shaped like diamonds. "By hitting the pads you can make and shape a sound and images in the room. Brain Opera was an ensemble of individual instruments, while the Transflow Room is a single instrument played by 40 people. The room blends the reactions and images of the group."
Machover's projects at MIT include Music Toys and Toys of Tomorrow, which are creating devices that he hopes will eventually make a Toy Symphony possible, Machover describes one of the toys as an embroidered ball the size of a small pumpkin with ridges on the outside and miniature speakers inside. “We've recently figured out how to send digital information through fabric or thread,” he said. “So the basic idea is to squeeze the ball and where you squeeze and where you place your fingers will affect the sound produced. You can also change the pitch to high or low, or harmonize with other balls.”
Computer music has a long way to go before it wins mass acceptance, however. Martin Goldsmith, host of National Public Radio' s Performance Today, explains why: "I think that a reason a great moving piece of computer music hash' t been written yet is that -- in this instance -- the technology stands between the creator and the receptor and prevents a real human connect
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