自主推进俯仰震荡翼型的数值模拟研究

运用自适应多重网格法和内置边条法研究了俯仰震荡翼型的运动.通过研究翼型的原地摆动与自由游动,提出了一种确定自主推进俯仰震荡翼型推力的方法,得到了推力系数、功率系数和推进效率与Strouhal数的关系.与以往研究不同的是,我们还得到了Strouhal数随雷诺数的变化规律.此外,从自由游动翼型诱导出的涡量场中可以清楚的观察到旋涡的合并,这与实验研究非常吻合.     

双气圈动力学模型的建立与求解

在建立自由气圈的动力学模型的基础上,进一步提出了双气圈的动力学模型。该模型整体化求解双气圈纱线的形态和张力的方法,既改进了以往忽略控制环的解析方法,又避免了求解中由边界条件的不确定性带来的计算上的繁琐和近似。因微分方程中加入了切向空气阻力、纱线的卷取速度及重力等微影响因素,使模型更为严密、可靠,同时拓宽了模型的使用范围。     

The temperature fields around the tip of a fast running crack

When a crack is running, the temperature rise is a quite important actual problem, which not only depends on some material constants, but also the propagation velocity and the distribution of the heat resource density. In this paper, the shape of plastic zone around the crack tip and the density of heat resource have been discussed and the model of the temperature fields has been proposed. The numerical results with PMMA are given and compared with other theories and experimental results     

Effect of end‐tethered polymers on surface adhesion of glassy polymers

The adhesion between a glassy polymer melt and substrate is studied in the presence of end‐grafted chains chemically attached to the substrate surface. Extensive molecular dynamics simulations have been carried out to study the effect of the areal density ∑ of tethered chains and tensile pull velocity v on the adhesive failure mechanisms. The initial configurations are generated using a double‐bridging algorithm in which new bonds are formed across a pair of monomers equidistant from their respective free ends. This generates new chain configurations that are substantially different than the original two chains such that the systems can be equilibrated in a reasonable amount of cpu time. At the slowest tensile pull velocity studied, a crossover from chain scission to crazing is observed as the coverage increases, while for very large pull velocity, only chain scission is observed. As the coverage increases, the sections of the tethered chains pulled out from the interface form the fibrils of a craze that are strong enough to suppress chain scission, resulting in cohesive rather than adhesive failure. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 199–208, 2004     

系留无人机系统振动特性分析

为了对系留无人机系统的振动特性进行分析,本文将无人机的运动作为系留缆绳的边界条件,得到了系留无人机系统的面内运动方程.通过平衡分析得到了系留缆绳在风场中的平衡张力和平衡曲率的近似表达式,然后对系留无人机系统的运动方程进行线性化处理,最终求得了系留缆绳法向的频率方程和振型.在此基础上,数值分析了无人机驱动力和无人机倾角对...     

热球子宫内膜去除术治疗功血的临床分析

目的:探讨热球子宫内膜治疗仪治疗功能失调性子宫出血的疗效。方法:对58例功血患者进行病例对照研究,分别采用热球型子宫内膜治疗仪和宫腔镜子宫内膜电切术进行治疗,观察疗效、并发症。结果:热球子宫内膜去除术和宫腔镜子宫内膜电切术治疗功血的总有效率无明显差异,但热球法无月经及点滴量月经率高,且手术时间短,并发症少。结论:热球子宫内膜去除术治疗功血疗效确切,是—种安全、简便、微创的方法。     

系留气球载雷达系统目标探测技术

气球载雷达由于升到空中观测目标,目标回波与杂波共存,使目标检测的难度加大,因此强杂波背景下的目标检测技术是气球载雷达系统的关键。提出使用高增益低副瓣天线、强杂波信号处理和滤波技术来使目标观测画面清晰、目标跟踪稳定,并分析了未来系留气球载雷达系统目标检测技术需求。     

球载雷达与红外联合探测系统研究

针对球载预警探测装备的应用需求,探讨了在系留气球平台实现雷达与红外联合探测系统的意义;研究了雷达与红外联合探测信息融合的处理流程,包括搜索与跟踪和联合目标分类与识别的处理流程,提供了基于点迹、航迹的搜索与跟踪融合处理算法;构建了外场试验系统,开展了搜索与跟踪融合处理算法的系统检验,验证了雷达与红外联合探测系统对目标探测精度和跟踪稳定性提高的有效性。试验结果表明,雷达与红外联合探测系统可提高球载预警探测系统的作战效能。     

气球载雷达云雨杂波建模与仿真

气球载雷达升空工作,面临强大的地海杂波和云雨杂波,尤其当目标处于云雨杂波区时,雷达的探测性能将受到严重影响。该文主要研究分析气球载雷达的云雨杂波特性。首先建立了气球载雷达云雨杂波的几何模型,然后在分析影响云雨杂波特性的各种因素的基础上,导出了气球载雷达在指定距离门内云雨杂波模型的表达式,最后通过仿真给出了气球载雷达云雨杂波的距离方位维杂噪比和距离-多普勒谱特性,其结果可以为气球载雷达杂波抑制和信号处理方法的研究提供参考。     

主动脉内球囊反搏的研究

研究了主动脉内球囊反搏的原理、应用指标、方法、有效指征及护理,强调应重视反博效果,做好生命体征及血液动力学的监测.