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A line source is a source of air, noise, water contamination or electromagnetic radiation that emanates from a linear (one-dimensional) geometry. The most prominent linear sources are roadway air pollution, aircraft air emissions, roadway noise, certain types of water pollution sources that emanate over a range of river extent rather than from a discrete point, elongated light tubes, certain dose models in medical physics and electromagnetic antennas. While point sources of pollution were studied since the late nineteenth century, linear sources did not receive much attention from scientists until the late 1960s, when environmental regulations for highways and airports began to emerge. At the same time, computers with the processing power to accommodate the data processing needs of the computer models required to tackle these one-dimensional sources became more available. In addition, this era of the 1960s saw the first emergence of environmental scientists who spanned the disciplines required to accomplish these studies. For example, meteorologists, chemists, and computer scientists in the air pollution field were required to build complex models to address roadway air dispersion modeling. Prior to the 1960s, these specialities tended to work within their own disciplines, but with the advent of NEPA, the Clean Air Act, the Noise Control Act in the USA, and other seminal legislation, the era of multidisciplinary environmental science had begun. For electromagnetic linear sources, the principal early advances in computer modeling arose in the Soviet Union and USA when the end of World War II and the Cold War were fought partially by progress in electronic warfare, including the technologies of active antenna arrays. ==Linear air pollution source== (詳細はarterials are in violation of U.S. National Ambient Air Quality Standards where millions of Americans live or work. Even the interior of a building does not really protect inhabitants from adverse exterior air quality, since the exterior air is the intake supply, and it is well known that indoor air quality is typically worse than exterior air. A roadway travelled by motor vehicles can be idealized by a line source emitting air pollutants. This mathematical problem was first solved in 1970 by a collaboration of physics, mathematics and computer science.〔Michael Hogan, ''Theoretical basis for atmospheric diffusion from a linear source'', ESL Inc., Environmental Systems Laboratory, Publication IR-29, Sunnyvale, Ca., May 4, 1970〕〔Richard J. Venti, ''Atmospheric diffusion models for roadway sources'', ESL Inc., Environmental Systems Laboratory, Publication ET-22, Sunnyvale, Ca., October 5, 1970.〕 The original theory assumed steady-state traffic conditions and meteorology on a perfectly straight roadway. Currently the models have evolved to treat variable meteorology, time-variant traffic operations and complex roadbed geometries. Current technology allows highway designers and city planners to analyze alternative roadway development plans and assess air quality impacts. The same basic model theory can be applied to airport operations, since the linear source is merely an inclined line. In the early 1970s these ESL models were refined into area source models to account for the finite width of the roadway. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「line source」の詳細全文を読む スポンサード リンク
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