This paper suggests a zenith luminance converting factor. By means of multiplying outdoor horizontal sky illuminance by this factor, the value of zenith luminance of the sky can be obtained.

本文建议了一种天顶亮度转换系数，它与室外无遮挡水平面上的天空散射光照度相乘，就能获得该天空类型的天顶亮度值。

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Cloud storage services with two-factor include Dropbox, Google Drive and Microsoft's Sky Drive.

CNN: Six tech resolutions for 2013

When you factor in some of the other common expenses like expensive commercial office space, perhaps sky-high midtown Manhattan office space, along with expensive travel, and the costs quickly add up.

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