分子模拟技术对润滑脂滴点的初步预测

制备了不同类型的单皂和复皂润滑脂，测定了其理化性能。采用分子模拟技术对润滑脂滴点进行了初步预测，并计算了润滑脂中各种金属皂分子间氢键键长和分子体积模量。结果表明，复合钙皂和复合锂皂的分子体积模量分别大于钙皂和锂皂的分子体积模量。金属皂分子体积模量与其所形成的润滑脂的滴点呈对应关系，即分子体积模量大的，其形成的润滑脂滴点也高，反之则反。采用分子模拟技术可以从分子的层次指导润滑脂的研究。     

Stress Concentration Factors for a Circular Hole in Curved Beams Under Bending Loads

Abstract: As a contribution to the field of stress concentration studies, the case of circular hole in curved bar elements under bending is hereby studied. Trend values of stress concentration factors (SCF) are presented based on selected variables of the problem for two critical hole locations. The results will help to identify an SCF law for practical use by applying the statistical method of regression analysis. Two approximations obtained by means of computational methods are compared with those obtained by photoelastic experimental method.     

Application of the dynamical flexural resonance technique to industrial materials characterisation

The determination of the Young’s modulus and damping coefficient Q⁻¹ by means of non-destructive vibrating techniques has been applied to bulk and coated industrial materials. Extensions of a previous analytic model of composite beam allow to determine accurately the macroscopic modulus of each component of multilayered structural materials as coated superalloys or nitride-hardened steels. Furthermore, the study of glasses and polymers has been investigated. An attempt of normalisation of the modulus versus temperature curves allows to establish master curves depending on the specific structure, from metallic glasses to polymeric glasses. Finally a comparison of dynamical modulus and Q⁻¹ values measured between resonant (>1 kHz) and subresonant techniques (10⁻³ to 10 Hz) in relation to the loading frequencies applied in real conditions has been under folder. For metallic materials such as forged or rolled titanium alloys, the brittle-to-fragile transition occurs abruptly or smoothly with a shift of 300 K following the range of excitation frequencies.     

Implicit integration and consistent tangent modulus of a time‐dependent non‐unified constitutive model

This paper describes the implicit integration and consistent tangent modulus of an inelastic constitutive model with transient and steady strain rates, both of which are time‐ and temperature‐dependent; the transient rate is influenced by the evolution of back stress decomposed into parts, while the steady rate depends only on applied stress and temperature. Such a non‐unified model is useful for high‐temperature structural analysis and is practical owing to the ease in determining material constants. The implicit integration is shown to result in two scalar‐valued coupled equations, and the consistent tangent modulus is derived in a quite versatile form by introducing a set of fourth‐rank constitutive parameters into the discretized evolution rule of back stress. The constitutive model is, then, implemented in a finite element program and applied to a lead‐free solder joint analysis. It is demonstrated that the implicit integration is very accurate if the multilinear kinematic hardening model of Ohno and Wang is employed, and that the consistent tangent modulus certainly affords quadratic convergence to the Newton–Raphson iteration in solving nodal force equilibrium equations. Copyright © 2003 John Wiley & Sons, Ltd.     

宽带智能天线系统中的频率补偿技术

在无线通信中,智能天线系统在抑制窄带多径干扰方面具有得天独厚的优势,但是用于宽带无线通信系统中时,就需要采用频率补偿方法.重点介绍基于频谱分解、聚焦和插值算法的补偿技术,并对这3种频率补偿技术的性能进行比较,结果表明在应用补偿技术的系统中,系统性能有显著的改善,其中插值算法具有最优的性能.     

Strain waves in colliding bars having nonparallel faces

The paper reports the experimental investigation data for the effect that nonparallel faces of bars under impact exert on the parameters of longitudinal and bending strain waves generated in the bars. The changes in stress magnitudes in the bar under impact with growing angle of the impact faces offset are described. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 6, pp. 73–78, November–December, 2006.     

混凝土大坝导温系数反演及其随时间变化的规律

随着时间的推移,混凝土的导温系数将发生变化,为了了解参数随时间的变化规律,利用原型观测资料对导温系数进行分段反演,从而拟合出大坝混凝土导温系数随时间的变化规律.     

Swelling behavior induced by alteration in granite and its implications on underground excavation

Granite is commonly recognized as an ideal medium for underground construction. However, in the site investigation for Heimifeng Pumped Storage Power Station project, it was found that there are swelling behaviors induced by alteration in granite and eventually causing slaking and disintegration of rock blocks. The study shows that hydrothermal alteration in granite is primarily due to the intrusion of multi-phase igneous magma. The clay minerals, such as montmorillonite, chlorite, kaolinite, are the main causes for the swelling behavior of granite. In the exploratory adits, alteration was observed to occur mainly along faults or fractures in the rock masses and resulted in roof caving if water is present. Some of the highly altered borehole cores swell and crack within 24 h in water and eventually disintegrate completely. From the testing results on the samples, the maximum axial free swelling strain is about 1.2%, while the maximum axial confined swelling strain is around 0.1% with swelling stress less than 25 kPa. Under free swelling tests, 80% of swelling is completed within 24 hours. Under confined swelling condition, swelling process is completed within 1 h for some samples, with 80% of maximum swelling strain finished within around 22 h for most of the samples. Contraction of samples occurs after swelling completed. The strength of granite, reflected by deformation and elastic moduli, shear strength, decreases due to alteration. The deformation and elastic moduli are even lower compared to highly weathered rock. The shear strength is between that for highly weathered and slightly weathered rocks. The swelling characteristics of the altered rock present great challenges for support or lining during construction and operation stages. Support or lining shall be in place immediately after excavation. Since the rock may swell when encountering water, the shotcrete shall be designed accordingly. During the construction of access tunnel and caverns, water shall be drained in time. Drainage directly from surface shall be avoided so as to prevent floor heave.     

Equivalent Control of Constrained Multibody Systems

This paper investigates the title problem from the perspective ofdetermining which forcesystems, although different, will have the same dynamic effectwhen applied to a mechanical system.A procedure is presented for determining how differences incontrol force/moment input are nullifiedby constraints on the system. This in turn provides a basis foroptimal control. The theoreticaldevelopment is illustrated by a series of examples with a model ofa redundant manipulator – a constrained/controlled triple pendulum.     

Influence of polymer modulus on the percolation threshold of latex-based composites

Monodispersed copolymer emulsions with different glass transition temperatures were synthesized to investigate the effect of room temperature polymer matrix modulus on the electrical properties of carbon black (CB) filled segregated network composites. The emulsion with the highest modulus at room temperature produced composites with the lowest percolation threshold. The threshold for a composite made from a copolymer latex containing an equal ratio of butyl acrylate and methyl methacrylate (BA5) is 1.5 vol%, while the percolation threshold for the much lower modulus BA7 (7:3 BA/MMA ratio) is 4.93 vol%. The microstructure of each composite shows significant differences in the level of CB dispersion within the polymer matrix. Higher modulus polymer particles push the CB more efficiently into the interstitial space between them, resulting in a lower percolation threshold. This modulus effect was confirmed by increasing the drying temperature, where the moduli of latexes (BA5, BA5.5, and BA6) were more similar and the percolation thresholds for three composites also become closer to one another.