5.1 This standard does not purport to address the mean spectral irradiance incident on tilted or vertical fenestration or building-integrated systems over a day, a season, or a year. The spectral irradiance distributions have been chosen to represent a reasonable near-upper limit for solar radiation when these systems are exposed to clear-sky conditions similar to those used to calculate solar heat loads of buildings. The diffuse spectral irradiance distributions can also be used to represent conditions when these systems are shaded from the direct sun.
5.2 Absorptance, reflectance, and transmittance of solar radiation are important factors in studies of light transmission through semi-transparent plates. These properties are normally functions of wavelength, which require that the spectral distribution of the solar flux be known before the solar-weighted property can be calculated.
5.3 To compare the relative performance of competitive products by computerized simulations, or to compare the performance of products subjected to experimental tests in laboratory conditions, a reference standard solar spectral distribution for both direct and diffuse irradiance is desirable.
5.4 The table provides appropriate standard spectral irradiance distributions for determining the relative optical performance of semi-transparent materials and other systems. The table may be used to evaluate components and materials for the purpose of solar simulation where the direct and the diffuse spectral solar irradiances are needed separately.
该光谱仪在户外主要利用太阳辐射作为照明光源,利用响应度定标数据,可测量并获得地物目标的光谱辐亮度;利用漫反射参考板对比测量,可获得目标的反射率光谱信息;通过对经过标定的漫反射参考板的测量,可获得地面的总照度以及直射、漫射照度光谱信息;利用特定的辅助测量装置,可获得地面目标的BRDF(方向反射因子)光谱信息参数。...
K冕由日冕中自由电子散射太阳光球层的直射光而形成,K冕的亮度能够反映日冕中自由电子和离子密度的分布。太阳爆发活动中的日冕物质抛射,是日冕物质在较短时间内被大规模抛出太阳表面的现象,是太阳大气中最剧烈的爆发活动,也是来自太阳最大规模和最具破坏性的爆炸。日冕物质抛射携带了大量日冕等离子体,其密度的动态变化与K冕形成机制极为相关,K冕的观测具有重要科学研究价值。...
假定地球是一个球体,那么同一个时间在地球上不同的地方,太阳线与地平面的夹角是不一样的。只要测出这个夹角的差以及两地之间的距离,地球周长就可以计算出来。他听说在埃及的塞恩即今天的阿斯旺,夏至这天中午的阳光悬在头顶,物体没有影子,光线可以直射到井底,表明这时的太阳正好垂直塞恩的地面,埃拉托色尼意识到这可以帮助他测量地球的圆周。关注材料科学与工程微信公众号,了解更多科学之美。...
明视野:即是用物镜孔径遮挡绕射电子束,仅让直射电子束通过成像。暗视野:则是用物镜孔径遮挡直射电子束,仅让绕射电子束通过成像。透射电镜基本结构透射电子显微镜是把经加速和聚集的电子束投射到非常薄的样品上,电子与样品中的原子碰撞而改变方向,从而产生立体角散射。散射角的大小与样品的密度、厚度相关,因此可以形成明暗不同的影像,影像将在放大、聚焦后在成像器件(如荧光屏、胶片、以及感光耦合组件)上显示出来。...
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