Mobile big data contains vast statistical features in various dimensions, including spatial, temporal, and the underlying social domain. Understanding and exploiting the features of mobile data from a social network perspective will be extremely beneficial to the wireless networks, e.g., operation and maintenance (O&M), planning, optimization, and marketing. In this paper, we categorize and analyze the big data collected from real wireless cellular networks. Then, we study the social characteristics of mobile big data and highlight several research directions for mobile big data in the social computing areas.

Thickness and order number are important parameters for a wave plate in optical experiments. However, the encapsulation of the wave plate makes its thickness difficult to measure directly. In this paper, we propose an indirect measurement method to obtain the thickness and order number of a uniaxial crystal wave plate. With this method only the maximum and minimum values of the optical power of the transmitted light through the wave plate are measured in the experiment by rotating the wave plate around its optical axis. This simple method is easy to realize in the college physics laboratory, and it is also of importance for students to further understand the underlying physics of the wave plates.

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