利用皮秒脉冲激光驱动瞬态X射线激光

报道了利用皮秒激光驱动产生瞬态类镍银X射线激光的实验结果.采用一路脉冲宽度为数百皮秒的激光作为预脉冲，配合另一路皮秒激光作为主脉冲联合驱动平面靶，获得了一定强度的类镍银X射线激光输出，输出能量约为5—10nJ. 关键词： 瞬态X射线激光 长短脉冲联合驱动 皮秒脉冲激光     

Numerical investigation of hydroplaning characteristics of three-dimensional patterned tire

Hydroplaning characteristics of patterned tire on wet road are investigated by making use of finite volume and finite element methods. A detailed 3-D patterned tire model is constructed by our in-house modeling program and the rainwater flow is considered as incompressible and inviscid. Meanwhile, the fluid–structure interaction between the highly complicated tire tread and the rainwater flow is effectively treated by the general coupling method. Through the numerical experiments, the rainwater flow drained through tire grooves, hydrodynamic pressure and contact force are investigated and compared with those of the three-grooved tire model.     

Numerical simulation of a fluid-saturated soil under a dynamically loaded pile

The behaviour of the soil under a dynamically loaded pile toe is studied. The soil is modelled as a fluid saturated porous continuum. The constitutive behaviour of the solid skeleton is described by the elasto-plastic model of Drücker-Prager. The wave propagation is simulated with a dynamical finite-element program.A two-phase model of soil gives useful information about effective stress and pore pressure in the soil. In saturated soil the main wave under the pile toe propagates more downards than in dry soil, due to the higher compressional stiffness in saturated soil. The plastic zone under the pile toe propagates with the velocity of the fast compressional wave. The pore fluid influences the plasticity strongly and can be expected to affect pile driving too.The distribution of effective stress and pore pressure under the pile toe depends on the permeability of the soil and cannot be calculated uniquely from a single-phase calculation. Therefore, a nonlinear soil cannot be modelled correctly as a conventional single-phase material.     

A consideration of curved interfaces in stress-assisted martensite formation

A purely mechanical, sharp interface model is developed to consider curved interfaces that have been observed between martensite phase variants. The approach is based on a theory of small strains as distinct from small displacement gradients. It admits a realistic characterization of each phase with standard elasticity tensors and allows for inhomogeneous states of strain within each phase including inhomogeneous, finite rotations. The model indicates that any signficant interface curvature must be due to material rotation because interfaces cannot be finitely curved with respect to the material lattice. It is also found that the interface driving traction is not influenced by local lattice rotations unless inertia affects the reaction.     

波长校准用低压石英汞灯驱动电源的研制

研制波长校准用低压石英汞灯电源,用于驱动汞灯起辉并维持稳态发光。电路由EMI滤波电路、桥式整流电路、LCC半桥谐振逆变电路、控制电路和保护电路5部分组成。采用系统建模与仿真验证电路的可行性并计算电路参数理论值,利用示波器和功率表验证电源输出参数,功率输出稳定性不大于0.03 W。根据紫外可见近红外分光光度计国防最高计量标准对研制的电源驱动汞灯的工作效果进行评价。结果表明,汞灯能够输出系列特征谱线,谱线相对强度稳定性不大于5.16%;汞灯工作3 h后,灯管外壳表面温度为43℃。该驱动电源的性能参数满足JJG112–2015《低压石英汞灯波长标准器检定规程》的要求。     

沉桩问题的光弹性模拟研究

实现了桩身直接贯入的沉桩光弹性模拟方法。应用这一方法研究了沉桩过程中桩周土体中的弹性应力场及其影响区域，指出Ｖｅｓｉｃ土体扩孔理论的适用范围     

MB2镁等四种金属材料的本构关系和动态断裂研究

采用炸药爆轰－分离飞片加载装置与电容传感技术相结合，由高速示波器连续记录靶板自由面速度剖面，通过波剖面的时间分辨测量，研究了ＭＢ＿２镁、ＬＹ－１２铝、钨合金、２１６９钢四种金属材料的动力学响应特性，给出了这几种材料在弹性－理想塑性模型假设下的本构关系，还给出了它们的动态断裂强度，并对标准化层裂强度与破坏比功、屈服强度之间的相关性进行了分析和讨论。     

Non-isothermal kinetics of a moving phase boundary

In this paper we derive an explicit formula for a kinetic relation governing the motion of a phase boundary in a bilinear thermoelastic material capable of undergoing solid-solid phase transitions. To obtain the relation, we study traveling wave solutions of a regularized problem that includes viscosity, heat conduction and convective heat exchange with an ambient medium. Both inertia and latent heat of transformation are taken into account. We investigate the effect of material parameters on the kinetic relation and show that in a certain range of parameters the driving force becomes a non-monotone function of the interface velocity. The model also predicts a nonzero resistance to phase boundary motion, part of which is caused by the thermal trapping. Received: November 15, 2001 / Published online September 4, 2002 RID="*" ID="*" e-mail: annav@math.pitt.edu Communicated by Lev Truskinovsky, Minneapolis     

驾驶员可靠性筛选数学模型分析

利用随机分组测试理论和算法,建立了汽车驾驶员安全可靠性筛选的定量分析数学模型,在统计分析观察时间段的基础上,可以筛选出安全可靠的驾驶员,驾驶员年龄段,为选拔汽车驾驶员,提高驾驶员素质,防止人为差错导致交通事故,提供理论依据.     

网络品牌忠诚驱动因素分类研究

将网络品牌分为传统品牌的网络延伸和网络新品牌两种形式,通过分析网络品牌忠诚的动态形成过程,构建了网络品牌忠诚驱动要素研究模型。实证研究发现,网络品牌的符号因素、属性因素、精神因素、价值观因素、传播因素、体验因素都与网络品牌忠诚正相关,但两类网络品牌忠诚的关键驱动因素存在差别。体验因素、价值观因素和属性因素是网络新品牌忠诚的关键驱动因素,而属性因素、体验因素和传播因素对网络化的传统品牌忠诚度有重要影响。