GCr15钢球／Cr7C3涂层盘摩擦副在大气与真空中摩擦学性能的比较

本文比较了Cr_7C_3硬质涂层盘与钢球组成的滑动摩擦副在真空和大气中的干摩擦磨损特性,发现在真空中的平均滑动摩擦系数μ和钢球体积磨损率△W都比在大气中的低;对于动态滑动摩擦系数μ,存在一个临界滑动距离Sc,当滑动距离S小于这一距离时,μ_(真空)>μ_(大气),而当S超过这一距离时,则μ_(真空)<μ_(大气)。通过磨痕形貌扫描电子显微镜观测和微区X-射线能谱成分分析,发现由于真空中的粘着作用和摩擦热效应都明显增强,涂层中的Cr原子更容易向钢磨损表面转移并形成(Fe,Cr)碳化物膜,因而使μ和△W均下降。文章还讨论了转移膜的形成速率与载荷及滑动速度的关系,以及转移膜与摩擦振动的关系等。     

关于等离子体诊断

Ⅰ.引言等离子体在一宽广的条件范围内工作。压力接近真空到几十巴;电流从几安到约10万安;流速从零到几千米/秒(流动可以呈现层流或湍流特性,可以强加速(象在收缩-扩张喷管中)或强减速(通过激波时))。由于这些多变的情况,温度可以是零点几电子伏到10电子伏量级,粒子密度和等离子体成分也在相应范围改变。非平衡效应在用作开关和加工方面都可起重要作用。对某一个领域(如开关)中给定的宽广应用范围,使用几种诊断方法是重      

直排式真空预压法加固软土地基的试验与研究

目前常规真空预压法加固软土是通过设置真空管网、水平向排水砂垫层和竖向排水体共同完成。为节省砂源和经费,设计了直排式真空预压法,它是对常规真空预压法的技术改进和创新。本文通过对直排式真空预压与常规真空预压现场试验区的监测与检测数据对比分析得出：直排式真空预压大幅度提高了真空预压的能效,即直排式真空预压在排水板不同深度内的真空压力比常规真空预压高出10％～50％,且深度越深效果越显著; 直排式真空预压的沉降速率比常规真空预压提高约30%,直排式真空预压比常规真空预压平均总沉降量提高493%,缩短了预压时间; 同时直排式真空预压法所加固的土体,其各项物理力学指标均好于常规的真空预压法,且不需中粗砂垫层,节省了材料,降低了工程造价。     

动静法与动力学普遍定理的比较

动静法与动力学普遍定理都是动力学的普遍规律,它们对任何动力学向题都是正确的.但是另一方面,任何规律都不包括现象中的一切联系,而只是在一定的范围和条件下才起作用.我们需要将有关的规律加以比较,弄清它们的联系与区别,更好地掌握它们的应用范围和应用方法.1.在用动静法分析质点系动力学问题时,如取固定点为力矩中心得力系平衡方程:...     

真空低温环境下超声马达驱动特性研究― 空载特性

利用自制的一套真空低温超声马达摩擦驱动特性测试系统,选取了4种工程塑料作为超声马达转子摩擦材料,测试出超声马达在真空低温环境下的空载转速,研究了真空度、环境温度和摩擦材料等因素对行波超声马达空载特性的影响.结果表明,随着真空度的增加,马达的空载转速下降;随着环境温度的降低,马达的空载转速下降.比较了所选4种工程塑料的驱动特性,筛选出一种在真空低温环境下空载特性较好的超声马达转子摩擦材料.     

第2届中国真空学会代表大会和学术会议

出席和列席代表共300余人。江苏省和南京市的领导,上级科协领导,航天工业部领导以及国际真空科学技术与应用协会司库、原日本真空学会会长井街仁等应邀参加了开幕式。会议期间交流了自1979年10月中国真空学会成立以来四年间真空科学与技术的进展。大会共收到学术论文250余篇,内容包括真空物理、真空冶金、真空获得技术、真空测量与校准、真空质谱分析与检漏、真空在电子器件中应用以及薄膜技术等。      

Co+C离子注入层的摩擦磨损行为研究

采用金属蒸气真空弧放电离子源在奥氏体不锈钢上进行Co C离子的双注入与同时注入,研究了Co C双注入层和同时注入层元素的成分深度分布及其摩擦磨损行为.结果表明:双注入和同时注入方式均能够在不锈钢表面产生1个Co与C共存区域,注入离子浓度范围宽化,强化范围增加;双注入和同时注入均能够提高不锈钢的表面硬度,降低其表面的摩擦系数,提高其耐磨性;采用大剂量同时注入方式改善摩擦磨损性能的效果优于双注入方式.     

液浮惯性元件的真空检漏和真空充液

本文叙述了真空检漏和真空充液对液浮惯性元件的重要作用；分析了惯性元件出现漏油和气泡的诸多原因及其对惯性元件性能的影响；介绍并讨论了提高真空检漏和真空充液质量必须解决的工艺关键问题。通过实践指出了在液浮惯性元件真空充液过程中易入的一般误区，提出了一种行之有效的新的改进真空充液工艺的途径。     

神龙一号真空系统研制

加速器真空系统的主要作用是减小电子束在传输过程中的束流损失以及满足加速器部件的真空绝缘要求。神龙一号真空系统研制是在理论分析和实验结果的基础上,就真空系统如何配置、真空梯度和漏率选择等方面的问题进行研究,并在满足加速器物理需求的前提下,选择最有效的真空系统设计方案。神龙一号真空系统采用1台抽速为1200L/s的罗茨-滑阀泵机组作为前级,采用43台抽速为400～500L/s的涡轮分子泵作为主泵,涡轮分子泵沿束线均匀分布。目前,神龙一号在开机1h以内,系统真空度达到5×10-4Pa,真空系统运行稳定可靠,满足设计要求。     

SS-4干膜的真空摩擦磨损性能

本文报导了SS-4干膜在真空中的摩擦磨损性能,并与SS-2干膜的性能作了比较。其耐磨性是SS—2干膜的2.2倍,但摩擦系数较高,该干膜的摩擦系数和耐磨性随着试验负荷、速度的增加而下降;干膜厚度、环境气氛、对摩偶件材料及涂膜底材等均对该干膜的真空摩擦磨损性能有着不同程度的影响。     

Piezomagnetic and piezoelectric poling effects on mode I and II crack initiation behavior of magnetoelectroelastic materials

The ferrite and ferroelectric phase of magnetoelectroelastic (MEE) material can be selected and processed to control the macroscopic behavior of electron devices using continuum mechanics models. Once macro- and/or microdefects appear, the highly intensified magnetic and electric energy localization could alter the response significantly to change the design performance. Alignment of poling directions of piezomagnetic and piezoelectric materials can add to the complexity of the MEE material behavior to which this study will be concerned with.Appropriate balance of distortional and dilatational energy density is no longer obvious when a material possesses anisotropy and/or nonhomogeneity. An excess of the former could result in unwanted geometric change while the latter may lead to unexpected fracture initiation. Such information can be evaluated quantitatively from the stationary values of the energy density function dW/dV. The maxima and minima have been known to coincide, respectively, with possible locations of permanent shape change and crack initiation regardless of material and loading type. The direction of poling with respect to a line crack and the material microstructure described by the constitutive coefficients will be specified explicitly with reference to the applied magnetic field, electric field and mechanical stress, both normal and shear. The crack initiation load and direction could be predicted by finding the direction for which the volume change is the largest. In contrast to intuition, change in poling directions can influence the cracking behavior of MEE dramatically. This will be demonstrated by the numerical results for the BaTiO₃–CoFe₂O₄ composite having different volume fractions where BaTiO₃ and CoFe₂O₄ are, respectively, the inclusion and matrix.To be emphasized is that mode I and II crack behavior will not have the same definition as that in classical fracture mechanics where load and crack extension symmetry would coincide. A striking result is found for a mode II crack. By keeping the magnetic poling fixed, a reversal of electric poling changed the crack initiation angle from θ₀=+80° to θ₀=−80° using the line extending ahead of the crack as the reference. This effect is also sensitive to the distance from the crack tip. Displayed and discussed are results for r/a=10⁻⁴ and 10⁻¹. Because the theory of magnetoelectroelasticity used in the analysis is based on the assumption of equilibrium where the influence of material microstructure is homogenized, the local space and temporal effects must be interpreted accordingly. Among them are the maximum values of (dW/dV)_max and (dW/dV)_min which refer to as possible sites of yielding and fracture. Since time and size are homogenized, it is implicitly understood that there is more time for yielding as compared to fracture being a more sudden process. This renders a higher dW/dV in contrast to that for fracture. Put it differently, a lower dW/dV with a shorter time for release could be more detrimental.     

Numerical and geometrical analysis of bifurcation and chaos for an asymmetric elastic nonlinear oscillator

An asymmetric nonlinear oscillator representative of the finite forced dynamics of a structural system with initial curvature is used as a model system to show how the combined use of numerical and geometrical analysis allows deep insight into bifurcation phenomena and chaotic behaviour in the light of the system global dynamics.Numerical techniques are used to calculate fixed points of the response and bifurcation diagrams, to identify chaotic attractors, and to obtain basins of attraction of coexisting solutions. Geometrical analysis in control-phase portraits of the invariant manifolds of the direct and inverse saddles corresponding to unstable periodic motions is performed systematically in order to understand the global attractor structure and the attractor and basin bifurcations.     

岩石细观损伤破坏的观测研究

利用扫描电镜（ Ｓ Ｅ Ｍ ）,对香港白岗岩等岩样在单轴压缩状态下,进行细观结构（μｍ 尺度）观察,研究其微损伤的萌生、扩展、连接直至破坏的行为,分析了白岗岩等岩石的细观破坏机制及其与宏观力学行为的关系,得到了一些重要的感性认识和若干观察记录．为认识岩爆发生的机理及复杂应力状态下岩石损伤破坏的理论分析提供了实验依据     

Speculative Behavior and Asset Price Dynamics

This paper deals with speculative trading. Guided by empirical observations, a nonlinear deterministic asset pricing model is developed in which traders repeatedly choose between technical and fundamental analysis to determine their orders. The interaction between the trading rules produces complex dynamics. The model endogenously replicates the stylized facts of excess volatility, high trading volumes, shifts in the level of asset prices, and volatility clustering.     

An analytical solution for the model of drug distribution and absorption in small intestine

According to the physiological and anatomical characteristics of small intestine, neglecting the effect of its motility on the distribution and absorption of drug and nutrient, Y. Miyamoto et al.^[1] proposed a model of two-dimensional laminar flow in a circular porous tube with permeable wall and calculated the concentration profile of drug by numerical analysis. In this paper, we give a steady state analytical solution of the above model including deactivation term. The obtained results are in agreement with the results of their numerical analysis. Moreover the analytical solution presented in this paper reveals the relation among the physiological parameters of the model and describes the basic absorption rule of drug and nutrient through the intestinal wall and hence provides a theoretical basis for determining the permeability and reflection coefficient through in situ experiments. The project supported by NSF of Shandong Province     

SPR误差评估在动静力数值分析中的验证与应用

有限元方法是一种便捷、强大的分析方法,常用于解决工程设计和研究中的各种复杂问题,但作为一种逼近的数值分析方法,其计算结果存在一定的误差,需要利用合理的误差评估方法评价有限元解并为进一步的改进提供依据.因此,将SPR误差评估嵌入弹塑性有限元静力数值分析中,验证在该计算中SPR误差评估的可靠性,并应用于相应的流弹塑性的动力分析中,为进一步优化网格、改进有限元计算结果提供依据.     

智能结构有限元动力模型的建立及主动振动控制和抑制

采用一种新的压电板单元，建立了含有分布压电传感元件和执行元件结构（智能结构）的有限元动力模型。利用两种反馈控制律，研究了智能结构振动控制与抑制的问题，并提出了智能结构主动振动控制和抑制的一种方法。最后，提供了数值示例，说明本文提出方法的应用。     

钢摩擦磨损的概率统计模型

本文根据对钢磨陨表面系统的扫描电子显微镜与俄歇电子能谱仪分析提出了摩擦磨损的概率统计模型,其要点在于将真实接触面积内的接触形式区分为3种,即氧化膜-氧化膜、金属-金属和金属-氧化膜,并且指出每一种接触形式的比率都是随机的,因而都服从概率分布。本文应用概率统计方法推导出了摩擦系数与磨损率的数学表达式。在推导过程中使用了一个“新鲜暴露金属发面”的新概念。理论计算结果与实测值相吻合。     

Analytical solutions to the 2D elasticity and thermoelasticity problems for inhomogeneous planes and half-planes

This paper presents a method for analytical solving the plane elasticity and thermoelasticity problems for planes and half-planes which exhibit inhomogeneous material properties in one of the planar directions (in the case of half-plane, the inhomogeneity direction is assumed to be perpendicular to the boundary.) With the aid of direct integration of equilibrium equations, the original problems are reduced to the set of governing, harmonic equations with corresponding conditions. In the transform domain of the integral Fourier-transform, the governing equations are reduced to an integral equation which is solved by simple iteration technique. The rapid convergence of the iterative procedure is established to perform the numerical calculation. The authors gratefully acknowledge the financial support of this research by the National Science Council (Republic of China) under Grant NSC 95-2221-E-002-048-MY2. The co-author, Yu Tokovyy, gratefully acknowledges the particular financial support of this research by the grant of the President of Ukraine for young scientists (No GP/F13/0094).     

Hall and ion slip effects on peristaltic flow and heat transfer analysis with Ohmic heating

The peristaltic transport of a magnetohydrodynamic （MHD） fluid is exam- ined for both symmetric and asymmetric channels. Hall and ion slip effects are taken into account. The heat transfer is analyzed by considering the effects of viscous and Ohmic dissipations. The relevant flow problems are first modeled, and then the closed form solutions are constructed under the assumptions of long wavelength and low Reynolds number. The solutions are analyzed through graphical illustration. It is noted that the velocity increases but the temperature decreases with the increases in the Hall and ion slip parameters. The axial pressure gradient is less in magnitude in the presence of Hall and ion slip currents. The Hall and ion slip effects are to decrease the maximum pres- sure against which peristalsis works as a pump. The free pumping flux decreases with the increases in the Hall and ion slip parameters. The increases in the Hall and ion slip parameters result in an increase in the size of the trapped bolus.