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2001年，我国城镇居民家庭人均可支配收入达6860元，比1996年增长()%，年平均增长7．23%。
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Ways to Create Colors in a Photograph
There are two ways to create colors in a photograph. One method called additive, starts with three basic colors and adds them together to produce some other color. The second method called subtractive, starts with white light(a mixture of all colors in the spectrum(光谱))and by taking away some or all other colors, leaves the one desired.
In the additive method, separate colored lights combine to produce various other colors. The three additive primary colors are green, red and blue (each providing about one-third of the wavelengths in the total spectrum). Mixed in varying proportions, they can produce all colors. Green and red light mix to produce yellow, red and blue light mix to produce magenta (a purplish pink) ; green and blue mix to produce cyan (a bluish green). When equal parts of all three of these primary-colored beams of light overlap(重叠), the mixture appears white to the eye.
In the subtractive process colors are produced when dye(染料) absorbs some wavelengths and so passes on only part of the spectrum. The subtractive primaries are cyan, magenta and yellow; these primaries or dyes absorb red, green and blue wavelengths respectively, thus subtracting them from white light. These dye colors are the complementary colors to the three additive primaries of red, green and blue. Properly combined, the subtractive primaries can absorb all colors of light, producing black. But, mixed in varying proportions, they also can produce any color in the spectrum.
Whether 3 particular colors is obtained by adding colored lights together or by subtracting some light from the total spectrum, the result looks the same to the eye. The additive process was employed for early color photography. But the subtractive method, while requiring complex chemical techniques, has turned out to be more practical and is the basis of all modern color films.
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According to experts' opinion, online promotion should he replaced by new ways.
从城市交通和城市建设的经济性出发，城市干道网密度以()为宜。
The First Navigational Lights
In the New World the first navigational lights were probably lanterns hung at harbor entrances. The first lighthouse was put up by the Massachusetts Bay Colony in 1716 on little Brewster Island at the entrance to Boston Harbor. Paid for and maintained by "light dues" levied on ships, the original beacon was blown up in 1776. By then there were only a dozen of so true lighthouses in the colonies. Little over a century later, there were 700 lighthouses.
The first eight lighthouses erected on the west coast in the 1850's featured the same basic new England design: a Cape Cod dwelling with the tower rising from the center or standing close by. In New England and elsewhere, though, lighthouses reflected a variety of architectural styles. Since most stations in the Northeast were built on rocky eminences, enormous towers were not the rule. Some were made of stone and brick, others of wood or metal. Some stood on pilings or stilts; Some were fastened to rock with iron rods. Farther south, from Maryland through the Florida Keys, the coast was low and sandy, it was often necessary to build tall towers there, massive structures like the majestic Cape Hatteras, North Carolina lighthouse, which was lit in 1870. At 190 feet, is the tallest brick lighthouse in the country.
Notwithstanding differences in appearance and construction, most American lighthouses shared several features: a light, living quarters and sometimes a bell (later, a foghorn). They also had something else in common, a keeper and usually, the keeper's family. The keeper's essential task was trimming the lantern wick in order to maintain a steady, bright flame. The earliest keepers came from every walk of life ; they were seamen, farmers, mechanics, rough mill hands and appointments were often handed out by local customs commissioners as political plums. After the administration of lighthouses was taken over in 1852 by the United States Lighthouse Board, an agency of the Treasury Department, the keeper gradually became highly professional.
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