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In large-space building, the distribution of vertical temperature has obvious difference. According to this feature, the energy consumption in air-conditioning would be greatly reduced if the designs of airflow are preferable in these buildings. The low sidewall air supply system is widely installed in the large-space buildings since it can directly sent the handled air to the personnel activity area, thereby has lower energy consumption than other systems. In this paper, a Gebhart-Block synchronous solving model is built to solve the vertical temperature distribution of an actual large-space building with low sidewall air supply system. The simulative physical model is divided into eight blocks in the vertical direction. According to the mechanism of heat transfer, unsteady-state heat balance equation is established for indoor air and wall in each block. The unsteady and synchronous solving model is established with integrating these balance equations. Furthermore, to predict the temperature distribution of indoor air and inner wall surface, the theoretical values of this model are calculated with programming by Visual Basic.

In order to detect the crack width of the concrete surface, we propose an algorithm of local rotation of images. Firstly, we calculate the normal direction of the given point in the crack to get the rotation angel. Secondly, we take a sub-image centering in the point, and rotate the sub-image around the point to make the crack in the sub-image changing to be vertical. Finally, the crack width is defined by the number of pixels on the line where the point is. By this algorithm, we can calculate the width of every cross-section on the entire crack, and the automation of the crack width detection will be come true. Based on this, we can also derive the crack length through the number of pixels on the crack (area) and the crack width. Theoretical analysis and numerical experiments show that this algorithm has high precision and good stability.