疲劳设计方法的进展

本文对早期疲劳设计方法,包括无限寿命设计、安全寿命设计、破损-安全寿命设计、损伤容限设计作了简单的回顾,对可靠性设计新方法作了详尽描述,同时还对疲劳寿命估算中的名义应力法与局部应力应变法进行了比较,最后对今后这课题的研究提出了一些建议。

气体激光器中光强迭加原则的物理基础

本文就气体激光器的普遍情况证明,当扩散之快足以几乎完全消除空间烧孔时,在输运方程的受激发射和受激吸收项中可以应用Rigrod光强迭加原则,从而明确了光强迭加原则的物理基础。通过对CO_2-N_2-H_2O系统进行的具体分析指出,在通常的连续波气体激光器中,计算场分布和功率输出时往往可应用光强迭加原则.

自由分子流中镜面反射模型是否自相矛盾?——Krzywoblocki“论自由分子流的基础观点”一文的错误

本文指出了美国力学工作者Krzywoblocki在他的文章[1]中所犯的两个推理上的錯誤,即:(1)在計算反射分子的动量流时,搞乱了反射方向;(2)把分子的动量流量和物体所受的压力錯誤地等同起来,事实上在反射时,它們具有相反的符号。由于这些錯誤,他得到了鏡面反射模型自相矛盾的結論,即:要么P_r(?)P_i,t_r(?)-t_i;要么如令P_r=P_i,t_r=-t_i,則将导致物理上荒謬的条件。我們利用他的計算証明了P_r=P_i,t_r=-t_i是完全正确的。在[1]中还列举了鏡面反射中三种理論上可能的法向速度变化情况:a)ξ_r~(a)=-ξ′+e_1U,b)ξ_r~(b)=ξ′+e_1U,c)ξ_r~(c)=-ξ′-e_iU;并証明了c)是应該拋弃掉的,伹认为似乎不能分辨其余哪一种是唯一可能的。我們証明了仅第一种,即錢学森所建議的那一种是可能的。

On the topological bifurcation of flows around a rotating circular cylinder

Flow fields around a rotating circular cylinder in a uniform stream are computed using a low dimensional Galerkin method. Results show that the formation of a Fopple vortex pair behind a stationary circular cylinder is caused by the structural instability in the vicinity of the saddle located at the rear of the cylinder. For rotating cylinder a bifurcation diagram with the consideration of two parameters, Reynolds number Re and rotation parameter a, is built by a kinematic analysis of the steady flow fields.

Three-dimensional finite element analysis of composites with coated spherical inclusions

A three-dimensional finite element analysis has been used to determine the internal stresses in a three-phase composite. The stresses have been determined for a variety of interphase properties, the thicknesses of the interphase and the volume fractions of particles. Young's modulus has been calculated from a knowledge of these stresses and the applied deformation. The calculations show that stress distributions in the matrix and the mechanical properties are sensitive to the interphase property in the three-phase composites. The interfacial stresses in the three-dimensional analysis are in agreement with results obtained by an axisymmetric analysis. The predicted bulk modulus in three-dimensional analysis agrees well with the theoretical solution obtained by Qui and Weng, but it presents a great divergence from that in axisymmetric analyses. An investigation indicates that this divergence may be caused by the difference in the unit cell structure between two models. A comparison of the numerically predicted bulk and shear modulus for two-phase composites with the theoretical results indicates that the three-dimensional analysis gives quite satisfactory results.

Fusion energy-production from a deuterium-tritium plasma in the jet tokamak

Describes a series of experiments in the Joint European Torus (JET), culminating in the first tokamak discharges in deuterium-tritium fuelled mixture. The experiments were undertaken within limits imposed by restrictions on vessel activation and tritium usage. The objectives were: (i) to produce more than one megawatt of fusion power in a controlled way; (ii) to validate transport codes and provide a basis for accurately predicting the performance of deuterium-tritium plasmas from measurements made in deuterium plasmas; (iii) to determine tritium retention in the torus systems and to establish the effectiveness of discharge cleaning techniques for tritium removal; (iv) to demonstrate the technology related to tritium usage; and (v) to establish safe procedures for handling tritium in compliance with the regulatory requirements. A single-null X-point magnetic configuration, diverted onto the upper carbon target, with reversed toroidal magnetic field was chosen. Deuterium plasmas were heated by high power, long duration deuterium neutral beams from fourteen sources and fuelled also by up to two neutral beam sources injecting tritium. The results from three of these high performance hot ion H-mode discharges are described: a high performance pure deuterium discharge; a deuterium-tritium discharge with a 1% mixture of tritium fed to one neutral beam source; and a deuterium-tritium discharge with 100% tritium fed to two neutral beam sources. The TRANSP code was used to check the internal consistency of the measured data and to determine the origin of the measured neutron fluxes. In the best deuterium-tritium discharge, the tritium concentration was about 11% at the time of peak performance, when the total neutron emission rate was 6.0 × 10¹⁷ neutrons/s. The integrated total neutron yield over the high power phase, which lasted about 2 s, was 7.2 × 10¹⁷ neutrons, with an accuracy of ±7%. The actual fusion amplification factor, Q_DT was about 0.15

PZT-4紧凑拉伸试样的断裂分析

基于线性压电材料的复势理论,通过解析分析,导出了一种分析有限压电板裂纹问题的解析数值方法.首先,计算了含中心裂纹有限板的断裂参数,与Woo和Wang的解析数值法(Int J Fract,1993,62:203～218)相比较,表明该方法具有很高的精度和很好的计算效率.随后,采用该方法和有限元法计算了PZT-4紧凑拉伸试样在绝缘裂纹面边界条件下断裂时的断裂参数,发现各断裂参数的临界值分散性很大,不能作为压电材料的单参数断裂准则.进而,针对试样真实的裂隙形状,采用有限元法计算了裂隙尖端的应力、电位移场,比较了裂隙内介质的介电性能对裂隙尖端场的影响,计算了带微裂纹的真实裂隙模型的断裂参数并进行了理论分析.

高超声速乘波飞行器气动特性研究(英文)

用计算流体力学和风洞试验的方法对以锥导乘波体为基础生成的高超声速乘波飞行器的气动性能进行了研究。结果表明,以马赫数6,攻角4度为设计状态的乘波体,在马赫数5~7,攻角4~6度的范围内,都具有良好的气动特性,升阻比接近4。最后,提出了一个简单的以参考温度方法为基础的粘性阻力分析方法。该方法配合使用风洞试验和计算流体的结果,可以用来验证计算流体中难以计算准确的粘性阻力,也可以用来分析在风洞试验难以直接得到的粘性阻力。对于工程上的粘性阻力分析是一个有用的办法。

量纲分析

量纲分析是一门非常值得研究和学习的知识，它是探讨科学规律，解决科学和工程的一个有效的工具。熟练掌握量纲分析应当是科学和技术工作者应有的基本训练。
本书内容包括：量纲分析的基本概念；量纲分析在熟知的力学现象中的应用；量纲分析在某些经典的力学问题中的应用以及郑哲敏先生的研究集体近三四十年中在爆炸力学诸多的应用实例等几个部分。 

水动力学讲义手稿

水动力学讲义手稿》是1958年钱学森先生在清华大学给第一届力学研究班学员讲授《水动力学》课程用的备课笔记。钱先生选材简赅精切，遴的内容具有基础性、经典性，整个手稿清晰耐读，详略得体，推演细腻，覆盖全面。
《水动力学讲义手稿》可供科技人员、教研人员及广大师生研究和学习之用。

燃烧物理学基础

On The Thermally Induced Cracking Of A Segmented Coating Deposited On The Outer Surface Of A Hollow Cylinder

In this work, the thermally induced cracking behavior of a segmented coating has been investigated. The geometry under consideration is a hollow cylinder with a segmented coating deposited onto its outer surface. The segmentation cracks are modeled as a periodic array of axial edge cracks. The finite element method is utilized to obtain the solution of the multiple crack problem and the Thermal Stress Intensity Factors (TSIFs) are calculated. Based on dimensional analysis, the main parameters affecting TSIFs are identified. It has been found that the TSIF is a monotonically increasing function of segmentation crack spacing. This result confirms that a segmented coating exhibits much higher thermal shock resistance than an intact counterpart, if only the segmentation crack spacing is narrow enough. The dependence of TSIF on some other parameters, such as normalized time, segmentation crack depth, convection severity as well as material constants, has also been discussed. (C) 2008 Elsevier B.V. All rights reserved.

Color centers in Yb : YAG crystals grown by temperature-gradient techniques

Yb: YAG (Yb: Y3Al5O12) crystals have been grown by temperature-gradient techniques (TGT) and their color centers and impurity defects were investigated by means of gamma irradiations and thermal treatment. Two color centers located at 255 and 290 nm were observed in the as-grown TGT-Yb: YAG. Analysis shows that the 255 nm band may be associated with Fe3+ ions. Absorption intensity changes of the 290 nm band after gamma irradiation and thermal treatment indicate that this band may be associated with oxygen-vacancy defects. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

平板偏振膜的角度特性研究

当入射光倾斜入射到平板偏振膜上时，在两种偏振光的反射带边缘处出现P偏振光高透而S偏振光高反的情况．利用F-P结构的膜系设计了偏振膜．随着入射角的增大，S光的带宽、消光比及参考波长线性增大。而膜层中电场强度的最大值和界面处的电场强度均减小，只有P偏振光的变化特性跟布儒斯特角有关．分析膜层的界面特性和膜层中的缺陷分布情况，可得偏振膜P偏振光的阈值随入射角的增大而增大．结果表明。在P光透过率可使用的范围内，入射角越大，消光比越大，场强在膜层中的分布越低，但P偏振光的透过率有所降低．