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Fracture initiation is a key factor of hydraulic fracturing, as lack of research on fracture initiation position.The perforation geostress mechanical model of low permeability reservoir is built according to the rock mechanics, seepage mechanics, elastic-plastic mechanics, considering solid-fluid coupling and rock material nonlinearity. Adopting the transient analysis, low-permeability reservoir geostress distribution of different stages is obtained using the finite element, such as drilling - cementing - perforation –fracturing. Determine the fracture initiation position and fracture pressure combining with the rock failure criterion. Calculated on well Ao332-32, the error rate of initiation pressure between test and calculation is 3.5 percent. It is proved that the model is reasonable.

An anisotropic damage model for concrete subjected to compressive fatigue loading is developed based on continuum damage mechanics with the concept of bounding surface. The damage and stress-strain relationships for concrete between monotonic and fatigue loading are obtained by means of the assumption of uniqueness deformation. The related parameters of the model are regressed by the test results of monotonic, single stage fatigue and the combination of multi-stage fatigue and monotonic of the paper. The comparison indicates a good agreement between the theory and the experiment results.

Based on the material properties of AlGaInP LED, this paper proposes an approach for predicting the junction temperature. The junction temperature of AlGaInP LED predicted from this study agrees with the available experimental data. The junction temperature increases with increasing the injection current and substrate thickness of LED.

This paper proposes a theoretical expression for the ultimate relationship between the crack gauge monitoring data and steel stress gauge ones in dam concrete, based on the equation for crack width of reinforced concrete member, when the cracks expanded to the crack-control steel. In addition, a practical method is developed for analyzing and determining the crack stability of dam concrete, which predicts whether a crack elongated to the crack-control steel or not by comparing the observed values to the theoretical ultimate value. The provided method is proven to be proper to evaluate the crack stability of dam, which is simple and practical.