微型网状结构支架的力学性能研究

冠状动脉支架为圆柱形微型网状结构，直径1mm，厚度0．1mm，长度10～16mm。在经皮冠状动脉介入PCI治疗中由球囊充气撑开到直径为2．5～3．5mm的支架，在血管内承受血管壁回弹压力。为了保持血液流通支架必须保持其几何圆形。这是一个结构弹塑性稳定性问题。但是目前国际上对于支架的力学性能质量指标主要以强度性能评定而不涉及支架屈曲性能是不妥的。本文对于支架的强度和屈曲性能进行了全面的理论分析和实验研究，自行研制了智能式电子检测仪成功地对微型网状结构支架的强度和屈曲性能实现了实测实验研究。由于微型支架的离散型网状结构的特点，在实验中出现一些特殊的屈曲现象。本文研究结果对于支架的形状与性能设计的改进和力学性能质量标准规范的制订具有重要意义。     

旋转带电体磁矩计算的若干法则与算例

本文在文献 [1]、[2 ]等的基础上给出关于旋转带电体的磁矩计算的若干法则 ,均以定理形式表达 ,并列表枚举其相关算例     

Efficient discretization of pressure‐correction equations on non‐orthogonal grids

An alternative discretization of pressure‐correction equations within pressure‐correction schemes for the solution of the incompressible Navier–Stokes equations is introduced, which improves the convergence and robustness properties of such schemes for non‐orthogonal grids. As against standard approaches, where the non‐orthogonal terms usually are just neglected, the approach allows for a simplification of the pressure‐correction equation to correspond to 5‐point or 7‐point computational molecules in two or three dimensions, respectively, but still incorporates the effects of non‐orthogonality. As a result a wide range (including rather high values) of underrelaxation factors can be used, resulting in an increased overall performance of the underlying pressure‐correction schemes. Within this context, a second issue of the paper is the investigation of the accuracy to which the pressure‐correction equation should be solved in each pressure‐correction iteration. The scheme is investigated for standard test cases and, in order to show its applicability to practical flow problems, for a more complex configuration of a micro heat exchanger. Copyright © 2003 John Wiley & Sons, Ltd.     

Lax Pairs for Equations Describing Compatible Nonlocal Poisson Brackets of Hydrodynamic Type and Integrable Reductions of the Lamé Equations

We solve the problem of describing compatible nonlocal Poisson brackets of hydrodynamic type. We prove that for nonsingular pairs of compatible nonlocal Poisson brackets of hydrodynamic type, there exist special local coordinates such that the metrics and the Weingarten operators of both brackets are diagonal. The nonlinear evolution equations describing all nonsingular pairs of compatible nonlocal Poisson brackets of hydrodynamic type are derived in these special coordinates, and the integrability of these equations is proved using the inverse scattering transform. The Lax pairs with a spectral parameter for these equations are found. We construct various classes of integrable reductions of the derived equations. These classes of reductions are of an independent differential-geometric and applied interest. In particular, if one of the compatible Poisson brackets is local, we obtain integrable reductions of the classical Lamé equations describing all orthogonal curvilinear coordinate systems in a flat space; if one of the compatible brackets is generated by a constant-curvature metric, the corresponding equations describe integrable reductions of the equations for orthogonal curvilinear coordinate systems in a space of constant curvature.     

Interpolatory integration rules and orthogonal polynomials with varying weights

We investigate which types of asymptotic distributions can be generated by the knots of convergent sequences of interpolatory integration rules. It will turn out that the class of all possible distributions can be described exactly, and it will be shown that the zeros of polynomials that are orthogonal with respect to varying weight functions are good candidates for knots of integration rules with a prescribed asymptotic distribution.Research supported by the Deutsche Forschungsgemeinschaft (AZ: Sta 299/4-2).     

Evaluating the financial performance of bank branches

We evaluate the financial performance of most of the branch offices of a large European savings bank for a recent accounting period. We employ a complementary pair of nonparametric techniques to evaluate their financial performance, in terms of their ability to conserve on the expenses they incur in building their customer bases and providing customer services. We find variation in the ability of branch offices to perform this task, and agreement on the identity of the laggard branches. We then employ parametric techniques to determine that the list of indicators on which their financial performance is evaluated can be reduced without statistically significant loss of information to bank management. Both findings suggest ways in which the bank can increase the profitability of its branch network. A previous version of this paper was presented at CORE, Université Catholique de Louvain, Louvain-la-Neuve, Belgium, where we received many helpful comments from the audience. We are grateful to three referees for their helpful comments as well.     

Vicious random walkers in the limit of a large number of walkers

The vicious random walker problem on a line is studied in the limit of a large number of walkers. The multidimensional integral representing the probability that thep walkers will survive a timet (denotedP _t ^(p) ) is shown to be analogous to the partition function of a particular one-component Coulomb gas. By assuming the existence of the thermodynamic limit for the Coulomb gas, one can deduce asymptotic formulas forP _t ^(p) in the large-p, large-t limit. A straightforward analysis gives rigorous asymptotic formulas for the probability that after a timet the walkers are in their initial configuration (this event is termed a reunion). Consequently, asymptotic formulas for the conditional probability of a reunion, given that all walkers survive, are derived. Also, an asymptotic formula for the conditional probability density that any walker will arrive at a particular point in timet, given that allp walkers survive, is calculated in the limittp.     

超细Sr2CeO4 粉体微乳液-高温法制备条件的正交试验及其发光性能研究

本文首先利用正交试验确定了微乳液-高温法合成蓝色发光Sr₂CeO₄超细粉体的最佳制备条件。接着研究了最佳条件下制备的Sr₂CeO₄超细粉体的性能。场发射扫描电镜(FE-SEM)显示，在850 ℃、900 ℃、1 000 ℃或者更高温度下退火4 h制备的粉体的形状分别呈球状、梭状和球状，平均粒径分别在100 nm左右和1 μm以内。X射线粉末衍射数据分析表明，该超细粉体属于正交晶系。室温下的光致发光光谱显示，该粉体的激发光谱有3个激发峰，主峰分别位于262 nm、281 nm和341 nm，而其发射光谱只呈现出1个发射峰，主峰位于约470 nm。与高温固相制备方法相比，微乳液-高温法可以在较低温度下制备出超细的粉体，而且它不但在262 nm处出现了一个新的激发峰，主激发峰和发射峰的位置也分别蓝移了大约30 nm和12 nm。     

正交试验法优化CS汽化吸附条件

通过正交试验设计,优化了影响西埃斯(CS)标准样品管制备的参数:汽化温度、采样流速、采样时间。结果表明,CS标准样品管的最佳吸附条件为汽化吸附温度:260℃,采样N2流速:330mL/min,采样时间:15min。在15~1500ng范围内,色谱峰面积与进样量有良好的线性关系,线性相关系数为0.9995,检出限为6.0ng。     

辣根过氧化物酶反应的化学动力学分析

用辣根过氧化物酶来处理废水中的苯酚和氯酚为许多人所关注。采用停流快速混合技术，利用快速扫描紫外可见分光光度计得到辣根过氧化物酶催化过氧化氢氧化苯酚聚合过程的瞬态光谱数据。对此测量数据矩阵用正交投影及遗传算法解析后，确定体系中产生紫外吸收的物种数，及辣根过氧化物酶中间体形式的纯光谱信息，进而解出反应过程中各组分的动力学曲线。