A two-dimensional contraction channel with a theoretically designed concave-oblique-convex wall profile is proposed to obtain a smooth planar-to-planar shock transition with shock intensity amplification that can easily overcome the limitations of a conventional shock tube. The concave segment of the wall profile, which is carefully determined based on shock dynamics theory, transforms the shock shape from an initial plane into a cylindrical arc. Then the level of shock enhancement is mainly contributed by the cylindrical shock convergence within the following oblique segment, after which the cylindrical shock is again "bent" back into a planar shape through the third section of the shock dynamically designed convex segment. A typical example is presented with a combination of experimental and numerical methods, where the shape of transmitted shock is almost planar and the post-shock flow has no obvious reflected waves. A quantitative investigation shows that the difference between the designed and experimental transmitted shock intensities is merely 1.4%. Thanks to its advantage that the wall profile design is insensitive to initial shock strength variations and high-temperature gas effects, this method exhibits attractive potential as an efficient approach to a certain, controllable, extreme condition of a strong shock wave with relatively uniform flow behind.

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Abstract. The changes of leaves elevation are mainly influenced by sunlight. This paper makes the ASD (Area exposed to the Sunlight per Day) exposure model of leaves, which is analysis respectively from the tree only a leaf and two leaves, further proving more pieces of the leaves. We get the conclusion that the half of the sun's rays effective angle is the best elevation for any leaves. It provides the general model of leaves elevation changes with theoretical guidance and technical support. IntroductionIf we observe the trees around us carefully, we can find the elevations of leaves are different. What is the reason of making them grow in that way? The main function of the leaves is to absorb the sunlight for photosynthesis [1], so the change of the leaf elevation also is mainly for effective absorption of sunlight.At present, a few scholars do research on the best elevation, because there are many factors in trees environment which cause the leaf elevation to vary, such as tree gene, geographic position, temperature, influence by surrounding animals which make it difficult to work out a general mathematics model of the best elevation. This paper simplified model, starting with the leaves of the 2d independent tree (the 2d independent tree refers to a tree of which the leaves can not be influenced by other trees).in the leaves only by the influence of elevation light as assume, make the leaves of ASD exposure model, and get rules of the elevation changes.

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