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A．Use the formal manner of address.B．Use the informal manner of address.C．Address peop
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We can use timber as the most crucial material to promote design and crafts.
Noise enters our ears as powerful waves of mechanical energy. Scientists measure sound intensity in decibels (db), with each doubling of energy adding ten decibels. Ordinary conversation measures about 60 db; a child's scream hits around 90 db. On this logarithmic scale, the scream is potentially 1,000 times more powerful.
Each day, over five million Americans are exposed on the job to at least 90 db, the maximum safe level for an eight-hour period according to the federal Occupational Safety and Health Administration. "This standard isn't ideal, because noise affects individuals differently," says William Clark of Washington University's Central Institute for the Deaf in St. Louis. "In theory, the standard should protect the lifetime hearing ofg0 percent of workers. However, it assumes that a worker's ears will have 16 hours of quiet each day during which to recover -- an unlikely assumption for most people."
Sound causes thousands of tiny hairs in the inner ear to vibrate. These vibrations trigger nerve impulses to the brain, which are perceived as sound. Prolonged exposure to 85 db or more, or far shorter exposure to very intense levels -- such as the 140-db shock waves from a shotgun blast -- can irrevocably damage some of these delicate inner-ear hairs. Ronald Reagan suffered permanent injury during his acting days when a 38-caliber pistol loaded with blanks was fired near his right ear. As a result, he now wears a hearing aid. Audiologists predict that by the year 2000, as many people could be wearing hearing aids as now wear contact lenses.
Many people believe that weaker hearing is an inevitable part of aging. But studies show that those who live in low-noise environments tend to have very little hearing loss in old age.
In noisy industrial nations, however, even young people suffer damaged hearing. David Lipscomb, a former professor of audiology at the University of Tennessee at Knoxville, tested over a thousand incoming freshmen and discovered that six of every ten had heating loss typical of the elderly. Rock music is one cause. The noise in a reek-concert hall can easily exceed 120 db, roughly the level of an air-raid siren. High-tech gadgets such as powerful portable stereos also threaten to put our hearing into a downward spiral.
Based on the logarithmic scale discussed in the first paragraph, how many times can a shotgun blast be more powerful than rock music？
A．Your heat rate is lowered.B．It becomes harder to relax.C．You become too tired to sle
Architecture
Architecture, the practice of building design and its resulting products; customary usage refers only to those designs and structures that are culturally significant. Architecture is to building as literature is to the printed word. One would say today that architecture must satisfy its intended uses, must be technically sound, and must convey aesthetic meaning. But the best buildings are often so well constructed that they go beyond their original use. They then survive not only as beautiful objects, but as documents of the history of cultures, achievements in architecture that testify to the nature of the society that produced them. These achievements are never wholly the work of individuals. Architecture is a social art.
Architectural form. is inevitably influenced by the technologies applied, but building technology is conservative and knowledge about it is cumulative (积累的). Precast (预制的) concrete, for instance, has not made brick out of date. Although design and construction have become highly sophisticated and are often computer directed, this complex apparatus (器械) rests on preindustrial traditions inherited from thousands of years during which most structures were lived in by the people who erected them. The technical demands on building remain the elemental ones-to exclude enemies, and to avoid discomforts caused by an excess of heat or cold or by the intrusion of rain, wind, or pests. This is no trivial assignment even with the best modem technology.
The availability of suitable materials fostered the crafts to exploit them and influenced the shapes of buildings. Large areas of the world were once forested, and their inhabitants developed carpentry (木工工作). Although it has become relatively scarce, timber remains an important building material.
Many kinds of stone lend themselves to building. Stone and marble were chosen for important monuments because they are fireproof and can be expected to endure. Stone is also a sculptural material; stone architecture was often integral with stone sculpture. The use of stone has declined, however, because a number of other materials are more adaptive to industrial use and assembly.
Some regions lack both timber and stone; their peoples used the earth itself, stuffing certain mixtures into walls or forming them into bricks to be dried in the sun. Later they baked those substances in kilns, producing a range of bricks and files with greater durability. Thus, early cultures used substances occurring in their environment and invented the tools, skills, and technologies to exploit a variety of materials, creating a legacy that continues to inform. more industrialized methods.
Building with stones or bricks is called masonry (石建筑或砖建筑). The elements join together through sheer gravity or the use of bonding materials, first composed of lime and sand. The Romans found natural cement that, combined with inert substances, and produced concrete. They usually faced this with materials that would give a better finish. In the early 19th century truly waterproof cement was developed, the key ingredient of modem concrete.
In the 19th century also, steel suddenly became abundant; rolling mills turned out shapes that could make structural frames stronger than the traditional wooden frames. Moreover, steel rods could be positioned in wet concrete so as to greatly improve the flexibility of that material, giving impetus early in the 20th century to new forms facilitated by reinforced concrete construction. The subsequent large quantity of aluminum provided cladding (surfacing) material that was lightweight and virtually maintenance free. In recent decades, elaborate systems for vertical transportation, the control of temperature and humidity, forced ventilation, artificial lighting, sanitation, control of fire, and the distribution of electricity and other services have been deve
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