计算机辅助激光合作目标的研制

简要介绍了激光合作目标的研制过程及其取得的成果.对用户和后续的设计者们有参考价值.     

Extremal Synthesis for Generic Planar Systems

For a generic single-input planar control system we analyze the structure of the set of extremals for the time-optimal problem. Generically all extremals are finite concatenations of regular arcs that are bang or correspond to a smooth feedback. Moreover, the support of extremals is a Whitney stratified set. We collect these information in the definition of extremal synthesis. In the cotangent bundle, we give a topological classification of the singularities of the extremal synthesis and study the projections of the support of extremals (regarded as a two-dimensional object, after normalization) from ² × S ¹ to the plane. With respect to the Whitney classical singularities here we deal with a stratified set with edges and corners, and along with cusps and folds, we find other stable singularities.     

Passive cathodic water/air management device for micro-direct methanol fuel cells

A high efficient passive water/air management device (WAMD) is proposed and successfully demonstrated in this paper. The apparatus consists of cornered micro-channels and air-breathing windows with hydrophobicity arrangement to regulate liquids and gases to flow on their predetermined pathways. A high performance water/air separation with water removal rate of about 5.1 μl s⁻¹ cm⁻² is demonstrated. The performance of the proposed WAMD is sufficient to manage a cathode-generated water flux of 0.26 μl s⁻¹ cm⁻² in the micro-direct methanol fuel cells (μDMFCs) which are operated at 100 mW cm⁻² or 400 mA cm⁻². Furthermore, the condensed vapors can also be collected and recirculated with the existing micro-channels which act as a passive water recycling system for μDMFCs. The durability testing shows that the fuel cells equipped with WAMD exhibit improved stability and higher current density.     

Chebyshev pseudospectral method of viscous flows with corner singularities

Chebyshev pseudospectral solutions of the biharmonic equation governing two-dimensional Stokes flow within a driven cavity converge poorly in the presence of corner singularities. Subtracting the strongest corner singularity greatly improves the rate of convergence. Compared to the usual stream function/ vorticity formulation, the single fourth-order equation for stream function used here has half the number of coefficients for equivalent spatial resolution and uses a simpler treatment of the boundary conditions. We extend these techniques to small and moderate Reynolds numbers.     

Comparative experimental study of hot-rolled and cold-formed rectangular hollow sections

Square and rectangular hollow sections are generally produced either by hot-rolling or cold-forming. Cross-sections of nominally similar geometries, but from the two different production routes may vary significantly in terms of their general material properties, geometric imperfections, residual stresses, corner geometry and material response and general structural behaviour and load-carrying capacity. In this paper, an experimental programme comprising tensile coupon tests on flat and corner material, measurements of geometric imperfections and residual stresses, stub column tests and simple and continuous beam tests is described. The results of the tests have been combined with other available test data on square and rectangular hollow sections and analysed. Enhancements in yield and ultimate strengths, beyond those quoted in the respective mill certificates, were observed in the corner regions of the cold-formed sections—these are caused by cold-working of the material during production, and predictive models have been proposed. Initial geometric imperfections were generally low in both the hot-rolled and cold-formed sections, with larger imperfections emerging towards the ends of the cold-formed members—these were attributed largely to the release of through thickness residual stresses, which were themselves quantified. The results of the stub column and simple bending tests were used to assess the current slenderness limits given in Eurocode 3, including the possible dependency on production route, whilst the results of the continuous beam tests were evaluated with reference to the assumptions typically made in plastic analysis and design. Current slenderness limits, assessed on the basis of bending tests, appear appropriate, though the Class 3 slenderness limit, assessed on the basis of compression tests, seems optimistic. Of the features investigated, strain hardening characteristics of the material were identified as being primarily responsible for the differences in structural behaviour between hot-rolled and cold-formed sections.     

矿山非对中导线测量方法研究

针对矿山测量等地下工程平面控制测量传统方法中存在的对中和照准点上悬持线不稳定性问题，基于偏心观测理论和自由设站方法，对地下导线测量的设点、观测、计算、精度分析及可行性进行分析探讨，并通过部分实验证明该方法的可行性。     

再谈地基应力系数的配套问题

指出了应力系数表“不配套”现象的严重问题，讨论了应力系数的两类组合和应力系数公式的统一系列等问题。     

砼双向楼板在均布荷载作用下板角抗裂承载力探究

推导出现浇双向板在均布荷载作用下，板角不先出现裂缝的抗弯、抗剪承载力计算公式。     

A wind turbine blade profile analysis code based on the singularities method

The aerodynamic characteristics of wind turbines are closely related to the geometry of their blade profiles. The innovation and the technological development of wind turbine blade profiles can be centred on two tendencies. The first is to improve the shape of the existing airfoils and the second is to design new shapes of airfoils in order to get some more ambitious aerodynamic characteristics and enhanced performance.The aim of this paper is to develop an accurate airfoil analysis lower order code, based on the singularities method, for wind turbine applications. The 2D incompressible potential flow model has been used. In the implementation of the singularities method, source–vortex distributions over the airfoil contour are used to compute the flow characteristics. The accuracy and the validity of the results have been tested using experimental data obtained from Wind Turbine Airfoil Catalogue “Risø National Laboratory, Roskilde, Denmark, August 2001” and have shown considerable agreement.     

Variable thermal singularity boundary elements in the study of neighbouring singularities

Two new boundary elements are presented for the simulation of variable order thermal singularities in two dimensions. The first can model the variable order temperature derivative and heat flux singularities at one end of the element. The second element can simulate the temperature derivative and heat flux singularities at both the ends of the element simultaneously. These elements are useful for studying the interaction of variable order thermal neighbouring singularities. They are employed here for the computation of stress intensity factors in the crack–crack interaction problems under thermal load. To improve the accuracy of such computations a modified crack closure integral based method is adapted. Examples of mode I and mode II centre crack, two collinear neighbouring cracks, kinked crack in a plate, and tee joint with a kinked edge crack under thermal or thermal and mechanical loading are studied to illustrate the usefulness of these elements in the study of neighbouring thermal singularities. Copyright © 2001 John Wiley & Sons, Ltd.