基于小波包变换的爆破地震波时频特征提取及分析

为了研究爆破地震波振动分量的传播规律，在微风化花岗岩石场地进行了孔径为76ram，孔深为5mm的单孔和单段多孔爆破试验，获得该场地爆破地震波加速度衰减规律，加速度衰减系数为k=3698，a=2．046，并研究出该场地基频范围为48Hz～74Hz。采用小波包技术对爆破地震波测试信号进行时频特征量提取，分析试验所测得爆破地震波不同频带下小波包系数的衰减规律。在此基础上通过研究场地介质对爆破振动分量的动态响应衰减作用，分析形成爆破地震波多频带特征的机理。     

Liquid 4He: Contributions to First Principles Theory. I. Quantized Vortices and Thermohydrodynamic Properties

Quantized vortices in liquid ⁴ He are treated quantum mechanically with realistic many-body model wave functions in variational calculations for energy and core structure at T = 0 K. A rectilinear vortex and both small and large vortex rings are studied. Calculated results indicate that rotons are not just small-quantized vortex rings. We compare our results for quantized vortices with experimental data and with theoretical results calculated by others. Correlated basis functions and standard statistical mechanics are used in treating thermohydrodynamic properties of flowing liquid ⁴ He. The Helmholtz potential is evaluated for a model of the flowing liquid that includes phonons and interacting rotons. Characteristics of this potential are discussed. The physical nature of negative superfluid density is explained. Superfluid density, entropy, and specific heat for liquid He-II are evaluated using our theory and the results are compared with experimental data. Very good agreement is found, except in a small temperature range near the λ transition. We indicate that results obtained here can be used in extending the theory to include thermally excited vortices and to investigate the possible role of vortices in accounting for the λ transition in liquid ⁴ He.      

A Novel Primal-mixed Finite Element Approach for Heat Transfer in Solids

A new reliable primal–mixed finite element approach for the heat transfer analysis in solids, is examined in detail. The essential contribution is that both variables of interest, temperature and heat flux, are calculated simultaneously from the same system of finite element equations. In addition, as a novelty, continuity of the trial and test heat flux functions is enforced, to avoid the need for some a posteriori heat flux smoothing technique. In order to minimize the accuracy error and enable introduction of the flux constraints, tensorial character of the present finite element equations is fully respected. The proposed finite element is subjected to low and high order convergence and efficiency tests in steady state and transient heat transfer analysis, which enlighten its solvability, stability, accuracy and effectiveness, i.e. its reliability.     

舰船静置爆炸气泡时总纵强度计算方法研究

新型“大气泡能”概念武器在水下爆炸能产生大气泡，对船体总纵强度造成很大影响，有可能使舰体发生纵向折断或倾覆。为研究这种作用，建立了舰船静置爆炸气泡时总纵弯曲强度的理论计算方法。采用静置爆炸气泡的假设，将气泡产生的浮力损失和压力差转化为等效载荷，计算气泡作用后船体的总纵弯矩和剪力并进行强度校核。以某舰艇为例进行计算，结果表明，爆炸气泡作用下船体的剪力和弯矩比静浮状态增大很多，船体发生纵向折断破坏的危险性也随之增大。     

太赫兹辐射产生技术进展

分别就光学技术和电子学技术产生太赫兹波的方法,介绍其产生原理、研发现状和最新进展,重点介绍了光电导、光整流、参量振荡器和太赫兹量子级联激光器.     

耦合双原子与单模光场相互作用系统中量子信息的传递

利用全量子理论,研究了耦合双原子与单模光场的相互作用过程.结果表明:在不同条件下,量子纠缠信息在腔场与原子之间可相互传递、交换以及保持;原子间的耦合作用主要影响量子信息的交换过程.     

Molecular simulation on structure–property relationship of polyimides with methylene spacing groups in biphenyl side chain

In our early research, the experiment of three synthesized polyimides (PP0DA-PI, PP2DA-PI and PP6DA-PI) with different methylene spacing groups in biphenyl side chain but with the same backbone reveals that the PP6DA-PI with six methylene flexible spacing groups in biphenyl side chain has lower intrinsic viscosity, density and glass transition temperature than those of the PP0DA-PI without methylene spacing group and PP2DA-PI with two methylene spacing groups in biphenyl side chains but keeps the mechanical property to that of the PP0DA-PI and PP2DA-PI. The aim of this paper is to explain the addition of the methylene spacing groups leading to the diversity of polyimide’s properties; molecular mechanics and molecular dynamics techniques were adapted to generate reasonable molecular models to establish the structure–property relationship of polyimide. Lots of interesting results have been obtained as follows. The modeling of chain conformation shows that the biphenyl side groups in PP0DA-PI are almost vertical to the backbone, whereas the biphenyl side groups in PP6DA-PI are almost parallel to the backbone indicating that PP6DA-PI exhibits a strong intra-chain interaction leading to in situ reinforcement interaction between the main chain and the side chain validated by the charge density, dipole moment and force current property of the two phenyls in biphenyl side chains. For this reinforcement in PP6DA-PI, the original modulus has been enhanced to some extent. Meanwhile, though the PP6DA would be more reactive due to higher charge density on N atom of the diamine monomer, the bulk structure of the side chain hindering the polymerization approach of the monomers leads to lower intrinsic viscosity of PP6DA-PAA. The density of PP6DA-PI does not decrease excessively with respect to the increase in chain length because of the bended side chain in this system. Furthermore, using conformational grid scan, potential energy contour map illuminates that the addition of the methylene spacing group in biphenyl side chain decreases the energy barrier in synchronous rotational bonds of the backbone resulting in lower glass transition temperature of PP6DA-PI.     

Au/锗/氧化硅纳米多层膜/p-Si结构的电致发光机制研究

用射频磁控溅射法制备了锗/氧化硅纳米多层膜,在室温下测量了Au/锗/氧化硅纳米多层膜/pSi结构的电致发光.利用位形坐标模型分析了锗/氧化硅纳米多层膜的发光中心,并用量子限制-发光中心模型对该纳米结构的电致发光过程作了研究,研究表明锗/氧化硅纳米多层膜的电致发光主要来自SiO2层的发光中心.     

考虑位移要求的大型三维连续体结构拓扑优化数值技术研究

大型复杂三维结构拓扑优化设计既具有理论意义,又具有重要的应用价值。基于等效转换的非奇异的结构优化模型,研究结构位移要求的最小结构重量设计问题。首先,介绍了位移约束的三维结构优化准则和公式。而后,为了提高拥有数万个单元以上的三维结构的计算效率,结合结构位移计算的迭代方法,在分析用于结构特性参数计算模型的基础上,建立了一套三维结构拓扑优化的求解策略和算法。最后,给出了几个典型和复杂的三维结构的拓扑优化设计算例。算例表明求解策略和算法是正确和有效的,且具有广泛的工程应用前景。     

反向挤压过程无网格伽辽金热力耦合分析

针对反向热挤压过程变形剧烈,摩擦接触边界随变形的累积而逐渐增大,相应的摩擦力边界上的节点密度逐渐变小的问题,采用自适应边界节点布置方法施加摩擦力边界条件。同时,采用集中热容法解决初始时温度场震荡的问题。并推导给出了刚粘塑性无网格伽辽金方法热力耦合分析公式,实现了轴对称反向挤压过程的无网格伽辽金热力耦合分析。通过对典型工件的无网格数值模拟分析以及与刚粘塑性有限元分析结果的对比,验证了所建立模型和相应处理技术的准确性。