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991.
Little EE Calfee RD Fabacher DL Carey C Blazer VS Middleton EM 《Environmental science and pollution research international》2003,10(3):167-172
Background Exposure to harmful levels of ultraviolet-B radiation (UVB), a component of solar radiation, has been suggested as a potential
cause of amphibian declines.
Methods We measured solar radiation (UVB, ultraviolet-A, and visible) wavebands in breeding ponds of Bufo boreas (boreal toad, a montane species that has undergone severe population declines) and Bufo woodhousii (Woodhouse’s toad, a plains toad that has not experienced declines) and examined tolerances of these species to simulated
solar UVB exposures in the laboratory.
Results We found larvae of both species to be tolerant of simulated solar UVB in excess of solar UVB levels observed in their breeding
ponds. B. boreas tadpoles were more tolerant of simulated solar UVB exposure than B. woodhousii tadpoles, possibly because of greater amounts of photoprotective melanin in B. boreas skin.
Conclusions UVB levels observed in B. boreas habitats do not currently appear to constitute a threat to the survival of these animals; however, long-term (>1 month) exposure
to UVB levels comparable to levels associated with the water interface appears to reduce survival in B. woodhousii tadpoles. Therefore, future increases in surface and water column UVB radiation in bufonid habitats might pose significant
survival risks to B. boreas or B. woodhousii populations. 相似文献
992.
993.
家用电器工频电磁辐射水平分析 总被引:2,自引:0,他引:2
对电磁波的产生机理以及对人体的危害进行了分析阐述,对人们日常生活中的家用电器电磁辐射水平进行了调查测量,分析了不同家用电器的电磁辐射水平,并有针对性提出了一些科学有效的防护措施。 相似文献
994.
滨医附院ECT室周围的电离辐射污染监测与调查分析表明:现役ECT工作场所γ空气吸收剂量率基本处于天然放射性本底水平,ECT室的辐射防护设施设计是合理的,具有重要的现实意义,该辐射防护设施具有推广价值. 相似文献
995.
Lauren E. Hay George H. Leavesley Martyn P. Clark Steve L. Markstrom Roland J. Viger Makiko Umemoto 《Journal of the American Water Resources Association》2006,42(4):877-890
ABSTRACT: The ability to apply a hydrologic model to large numbers of basins for forecasting purposes requires a quick and effective calibration strategy. This paper presents a step wise, multiple objective, automated procedure for hydrologic model calibration. This procedure includes the sequential calibration of a model's simulation of solar radiation (SR), potential evapotranspiration (PET), water balance, and daily runoff. The procedure uses the Shuffled Complex Evolution global search algorithm to calibrate the U.S. Geological Survey's Precipitation Runoff Modeling System in the Yampa River basin of Colorado. This process assures that intermediate states of the model (SR and PET on a monthly mean basis), as well as the water balance and components of the daily hydrograph are simulated consistently with measured values. 相似文献
996.
Summary Since IARC classified ELF magnetic field as Possibly Carcinogenic to Human the fear from 50/60 Hz magnetic field exposure
had been increased to the state of public “panic”. Subsequently, environment quality preservation organizations increased
their pressure on their government to adopt the “precautionary principle” and to reduce the allowable ELF Magnetic Field exposure
to much lower values than are recommended by ICNIRP-1998. As an example the present Environmental Ministry in Israel recommendation
is to lower the ELF Field exposure to 10 mG averaged over 24 h.
As a result of this stringent exposure guideline imposed by the government, electrical engineers who are involved in the deployment
and installation of large and medium electrical utilities, such as overhead power lines, transformers, UPS systems, electrical
public transportation, switching stations, etc., are much more aware to the need to employ special measures and methods for
reducing the magnetic fields that might be emitted from such utilities.
There are few computer codes that are capable of analyzing with great accuracy magnetic and electric fields surrounding single
phase and three phase electrical utilities in a 3-D system. The best presentations of the analysis results are by equi-value
contours depicting electric and magnetic fields. This graphical presentation is a powerful design tool that enables better
deployment and installation design aided to reduce the magnetic field emissions from high-power electrical utilities.
This paper describes the various types of graphical presentations available for ELF field contours, the dependent and independent
variants and parameters, magnetic field animation for optimization of power line installation and routing, and finally an
example that demonstrates the usefulness of the graphical presentation tools. 相似文献
997.
N. M. Salem 《The Environmentalist》2005,25(2-4):241-246
Summary The thermal effect due to electromagnetic absorption by human tissues is investigated at different frequencies ranging from
101–1016 Hz. Special emphasis is being considered in the microwave band used in wireless communications of the mobile industry. The
present work examines basically the thermal effect that arises as the duration of exposure to the electromagnetic radiation
and its dosage is increased. Using a computer simulation, a semi-classical model is adopted, were the photon-phonon interaction
is mediated by a homogenous sample of identical elements, which are naturally in harmonic modes of vibration. The phonon lifetime
is also included in this work. These thermal effects decrease with frequency in conformity with experimental results. This
model is then extrapolated to the individual cells of a human tissue and the possible rise in temperature is estimated. 相似文献
998.
以地震波广义散射(包括透射、折射、反射、绕射等)为背景,以求解其反演问题为主线,在回顾反演理论发展的同时,着重对地震波逆散射问题研究过程中各种数学、物理的基本理论和基本假设如何被应用以及非线性偏微分方程的求解过程及其作用做理论分析,同时对地震波逆散射问题中相应数学方法的发展过程及在使用中尚存在的问题做简单介绍。在文末,指出了现在地球物理界在地质结构异常较强烈所造成的非弱散射的反演问题上所遇到的问题。进而就今后如何处理这类问题的数学研究方法和假设中应注重的问题提出了一些想法和展望。 相似文献
999.
高速公路丙烷罐车爆炸事故的后果分析 总被引:4,自引:1,他引:4
本文针对公路丙烷罐车爆炸事故的实例,对事故发生的原因进行了分析.分析结果认为,事故属于沸腾液体扩展蒸汽爆炸(BLEVE),事故对人员和财产危害包括3个方面:火球热辐射、爆炸冲击波超压和抛射碎片.本文介绍了这3种危害的数学模型和方法,并针对事故实例进行了分析和计算.结果表明,在事故发生现场100m范围内的热辐射可致人死亡或造成三度烧伤;冲击波超压在80m范围外会使玻璃破碎,但无人员伤亡;抛射碎片在334 m的范围内都可能对人体造成伤害.由此,可以得出火球热辐射是事故中最主要危害的结论. 相似文献
1000.
通过外墙窗口喷出火焰问题的研究 总被引:3,自引:2,他引:1
用传热学,流体力学等的有关知识,从理论上分析了通过外墙窗口喷出火焰的有关问题,并对这些问题进行了实验研究。结果表明:喷了火焰具有较强的传热的能力,它可能成为建筑火灾由低层向高层蔓延的重要原因。 相似文献