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A device has been produced which can detect the contamination of the test gas by the driver gas in a reflected shock tunnel. This device monitors the static pressure in a converging duct. The duct is designed to choke at a predetermined contamination level due to the change in the specific heat ratio produced by the contaminants. Experimental results are given for a freestream enthalpy of nominally 6 MJ/kg. 相似文献
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Xiaoping Zhou Qinghong Hou Qihu Qian Yongxing Zhang 《Acta Mechanica Solida Sinica》2013,26(4):373-387
A new non-Euclidean continuum damage model is proposed to investigate the zonal disintegration phenomenon of the surrounding rocks around deep spherical tunnels under hydrostatic pressure condition as well as the total elastic stress field distributions.The elastic stress fields of the surrounding rocks around deep spherical tunnels under hydrostatic pressure condition are obtained.If the elastic stresses of the surrounding rocks satisfy the strength criterion of the deep rock masses,the number,size and location of fractured and nonfractured zones are determined.The efect of physico-mechanical parameters of the surrounding rocks on the zonal disintegration phenomenon is studied and numerical computation is carried out.It is found from numerical results that the number,size and location of fractured and non-fractured zones are sensitive to the physico-mechanical parameters of the surrounding rocks. 相似文献
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Single crystals of the new Bi(III) phosphates, Rb6Bi4(PO4)2(P2O7)3, have been isolated and their structure has been determined by X-ray diffraction techniques. This compound crystallizes in the monoclinic space group P21/c with a=9.077(1)Å, b=9.268(2)Å, c=36.418(6)Å, β=95.75(1)° and Z=8. The crystal structure is made up of BiO5 and BiO6 polyhedra sharing the corners with PO4 tetrahedra and P2O7 diphosphate groups. The structure can be described as infinite anionic layers with composition [Bi4(PO4)2(P2O7)3]∞6− parallel to the [301] plane, connected via P-O-Bi bridges to form a three-dimensional open framework. This framework delimits tunnels running along [100] and [010] directions, where the rubidium ions reside. This compound exhibits a rubidium ion conduction but with rather low conductivity value at 640 K. 相似文献
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Elaborating the discrete hydrocarbon molecule bicyclo[2.2.2]-2,5,7-octatriene in three-dimensions, a unique, hypothetical allotrope of carbon is produced. Such a structure possesses a principal 6-fold axis; along this axis are hexagonal, organic tunnels with about a 5.70 Å outside tunnel diameter across opposite vertices, and an actual, inside diameter of 4.16 Å when taking into account the covalent radius of tetrahedral carbon. Across opposite edges, the outside hexagonal tunnel diameter is 4.94 Å, and the inside tunnel diameter is 3.61 Å. These tunnels are lined alternately with hexagonally disposed ethane-like functions and hexagonally disposed ethene-like functions that stack along the tunnel axis. The lattice lies in space group P6/mmm, and it has the Schläfli symbol given by (6, 32/5), it is therefore topologically related to the graphite–diamond hybrids. Because of the hexagonal symmetry of the unit cell, and also due to the fact that its polygonality is six, the structure has been given the name hexagonite. There are 10 carbon atoms in the unit of pattern, and the density is 2.50 g/cm3; bordered by the densities of graphite at 2.27 g/cm3 and diamond at 3.56 g/cm3. Its large organic channels, lined with π organic functions, may make it particularly useful as an organic zeolite material, or alternatively as a host lattice for ionic conduction. The electronic band structure of the empty, hexagonal host lattice is described. 相似文献
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TbCu(TeO3)2Cl was obtained in high yield from high temperature solid-state reac-ion of Tb4O7,CuO,CuCl2 and TeO2 in a 1:2:2:8 molar ratio at 710 ℃ in an evacuated quartz tube. Its structure was established by single-crystal X-ray diffraction. The title compound crystal-lizes in monoclinic,space group P21/c,with a=5.409(2),b=14.994(6),c=9.183(4),β= 98.884(5)°,V=735.8(5) ?3 and Z=4. TbCu(TeO3)2Cl is isostructural with LnCu(TeO3)2X (Ln= Dy,X= Cl; Ln=Er,X=Cl,Br). Its structure features a three-dimensional (3D) network built from Tb(Ⅲ) and Cu(II) ions interconnected by tellurite and chloride anions; the chloride anion and the lone-pair electrons of the tellurium(IV) ions are oriented toward the cavities of the tunnels in the network. Solid-state luminescent spectrum of TbCu(TeO3)2Cl shows a strong emission band at 545 nm with a luminescent life time of 291 μs. 相似文献
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To simulate the pressure wave generated by a train travelling through a tunnel, we implement a discontinuous Galerkin (DG) method for the solution of the one‐dimensional equations of variable area flow. This formulation uses a spatial discretisation via Legendre polynomials of arbitrary degree, and the resulting semi‐discrete system is integrated using an explicit Runge–Kutta scheme. A simulation of subsonic steady flow in a nozzle shows that the scheme produces stable solutions, without the need for artificial dissipation, and that its performance is optimal for polynomial degrees between 5 and 7. However, when dealing with an unsteady area, we report the presence of numerical oscillations that are not due to the steep pressure fronts in the flow but rather to the projection of a moving area, with piecewise continuous derivatives onto a fixed grid. We propose a reformulation of the DG method to eliminate these oscillations that, put in simple terms, amount to splitting the integrals where the derivatives of the cross‐sectional area are discontinuous into subintegrals where they are continuous. The resulting method does not exhibit oscillations, and it is applied here to two practical cases involving train‐induced pressure waves in a tunnel. The first application is a validation of the DG method through comparison of its computational results with pressure data measured during transit at the Patchway tunnel near Bristol (UK). The second application is a study of the influence of the nose shape and length on the pressure wave gradients responsible for sonic boom at tunnel exit portals to show that the proposed modification is able to deal with realistic train shapes. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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盾构法隧道模型试验中的相似关系 总被引:4,自引:1,他引:3
盾构法是在软土中建造隧道常用的施工法.讨论其模型试验和实物之间的转换问题.根据Goodier理论建立相似关系,考虑了土体的黏弹塑性性质和大变形问题,包括推进压、推进速度、出土量、土体损失率、以及注浆量等施工参数对地层移动的影响.给出的公式可用于盾构法隧道的实验设计和数据分析. 相似文献
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In this paper, a semi-analytical elastic plane strain solution was provided for stress field around a lined non-circular tunnel subjected to uniform ground load. Concrete lining and the surrounding rock mass were assumed as linearly elastic materials. Due to complexity of the problem for non-circular geometric configurations, complex variable method introduced by Muskhelishvili and conformal mapping functions were used to determine stress components within concrete lining and the surrounding rock mass. Finally, the solution was validated by ABAQUS finite element software through an example. Very good agreement was demonstrated between semi-analytical and numerical solution although some discrepancies were found at tunnel corners where large curvature existed. It was demonstrated that the solution predicted stress components more accurately around the tunnels, especially the corners with large stress concentration. Practical significance of the solution was placed in the fact that it could be used as a quick-solver with high accuracy. 相似文献