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.
該光譜儀在戶外主要利用太陽輻射作為照明光源,利用響應度定標數據,可測量并獲得地物目標的光譜輻亮度;利用漫反射參考板對比測量,可獲得目標的反射率光譜信息;通過對經過標定的漫反射參考板的測量,可獲得地面的總照度以及直射、漫射照度光譜信息;利用特定的輔助測量裝置,可獲得地面目標的BRDF(方向反射因子)光譜信息參數。...
K冕由日冕中自由電子散射太陽光球層的直射光而形成,K冕的亮度能夠反映日冕中自由電子和離子密度的分布。太陽爆發活動中的日冕物質拋射,是日冕物質在較短時間內被大規模拋出太陽表面的現象,是太陽大氣中最劇烈的爆發活動,也是來自太陽最大規模和最具破壞性的爆炸。日冕物質拋射攜帶了大量日冕等離子體,其密度的動態變化與K冕形成機制極為相關,K冕的觀測具有重要科學研究價值。...
假定地球是一個球體,那么同一個時間在地球上不同的地方,太陽線與地平面的夾角是不一樣的。只要測出這個夾角的差以及兩地之間的距離,地球周長就可以計算出來。他聽說在埃及的塞恩即今天的阿斯旺,夏至這天中午的陽光懸在頭頂,物體沒有影子,光線可以直射到井底,表明這時的太陽正好垂直塞恩的地面,埃拉托色尼意識到這可以幫助他測量地球的圓周。關注材料科學與工程微信公眾號,了解更多科學之美。...
明視野:即是用物鏡孔徑遮擋繞射電子束,僅讓直射電子束通過成像。暗視野:則是用物鏡孔徑遮擋直射電子束,僅讓繞射電子束通過成像。透射電鏡基本結構透射電子顯微鏡是把經加速和聚集的電子束投射到非常薄的樣品上,電子與樣品中的原子碰撞而改變方向,從而產生立體角散射。散射角的大小與樣品的密度、厚度相關,因此可以形成明暗不同的影像,影像將在放大、聚焦后在成像器件(如熒光屏、膠片、以及感光耦合組件)上顯示出來。...
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