风机叶片噪声的有源消声研究

建立了风机转动时产生的动叶气动噪声和静叶干涉噪声的声学模型，推导了声功率的表达式，根据最小辐射声功率准则导出了有源消声控制方程，并探讨了次级声源的配置参数对消声效果的影响。     

I型裂纹虚拟裂纹闭合法的误差分析及修正

对虚拟裂纹闭合法的误差来源进行了分析。依据Griffith的椭圆裂纹近似理论,针对虚拟裂纹闭合法的位移相等假设,提出了一种修正方法。用有限元程序计算了二维I型裂纹的扩展问题,并与理论近似解做了比较。计算结果表明,修正以后可以得到更好的精度,在裂纹长度较短时,修正效果更好。     

Exact slip-buckling analysis of two-layer composite columns

A mathematical model for slip-buckling has been proposed and its analytical solution has been found for the analysis of layered and geometrically perfect composite columns with inter-layer slip between the layers. The analytical study has been carried out to evaluate exact critical forces and to compare them to those in the literature. Particular emphasis has been placed on the influence of interface compliance on decreasing the bifurcation loads. For this purpose, a preliminary parametric study has been performed by which the influence of various material and geometric parameters on buckling forces have been investigated.     

The study of sabot-discarding mechanism of gas-propelled APDS

I.IntroductionDifferentfromthetraditionaIarmor-piercingprojectilewithdiscardingsabot(abbreviatedtoAPDS),thegas-propeIIedAPDSautomatical1ydiscardsitssabotbasedonaerodynamicsprinciples.Simpleinstructure,itis1nadeupofarod-likeshellandacylindricalhollowsabot(…     

The flow of incompressible immiscible fluids between two plates

Summary The flow of layers of different heights of n incompressible immiscible fluids between two plates has been considered and it has been shown that whatever be the number of fluids and whatever be their heights, a unique velocity maximum always exists and a formula for finding the layer in which this maximum occurs has been given. For the particular case of two layers it has been shown that the curve of total flux against the ratio of the heights of the fluids has always a point of inflexion. Further this ratio has been determined so that the fluxes of the two fluids are equal.     

Interface end stress field of antiplane of orthotropic bimaterials

The orthotropic bimaterial antiplane interface end of a flat lap is studied by constructing new stress functions and using the composite complex function method of material fracture. The expressions of stress fields, displacements fields and the stress intensity factor around the flat lap interface end are derived by solving a class of generalized bi-harmonic equations. The result shows that this type of problem has one singularity, the stress field has no singularity when two materials have constant ratio F 〉 0, the stress field has power singularity, and the singularity index has a trend to -1/2 as F increases. The derived equation is verified with FEM analysis.     

Nonlinear Effects of the Stress Driven Rearrangement Instability of Solid Free Surfaces

The roughness of the free surface of a non-hydrostatically stressed solid has been expanded in Fourier series and the influence of the first three harmonics of this development has been investigated by means of a static variational calculation of the elastic and surface energies. The deformation of the bumps and grooves of the roughness has been determined and the optimal shape of the free surface has been characterized. Mathematics Subject Classifications (2000) 82B24, 73C05, 73C02, 73V25, 73B30, 73S10.     

框架结构缺损识别的交错迭代法

对具有局部缺损刚度框架结构识别的逆分析问题进行了研究,在采用有限元最小二乘法的基础上,提出了非线性最小化过程的交错迭代方法。算例及分析表明,本文方法是一种精度高、收敛迅速、应用方便的逆分析方法。     

Removability of singular sets of harmonic maps

It is proved that a harmonic map with small energy and the monotonicity property is smooth if its singular set is rectifiable and has a finite uniform density; moreover, the monotonicity property holds if the singular set has a lower dimension or its gradient has higher integrability. This work generalizes the results in [CL, DF, LG12], which were proved under the assumption that the singular sets are isolated points or smooth submanifolds.     

Rotary motion of the parametric and planar pendulum under stochastic wave excitation

In this paper a rotary motion of a pendulum subjected to a parametric and planar excitation of its pivot mimicking random nature of sea waves has been studied. The vertical motion of the sea surface has been modelled and simulated as a stochastic process, based on the Shinozuka approach and using the spectral representation of the sea state proposed by Pierson–Moskowitz model. It has been investigated how the number of wave frequency components used in the simulation can be reduced without the loss of accuracy and how the model relates to the real data. The generated stochastic wave has been used as an excitation to the pendulum system in numerical and experimental studies. For the first time, the rotary response of a pendulum under stochastic wave excitation has been studied. The rotational number has been used for statistical analysis of the results in the numerical and experimental studies. It has been demonstrated how the forcing arrangement affects the probability of rotation of the parametric pendulum.     

高压驱动研究方法的改进及其对质点运动的研究

从分析二维运动的测试原理入手 ,利用高速狭缝扫描摄影技术建立了测试系统 ,该系统能获得二维运动的轨迹和速度 ,从而把高速狭缝扫描摄影的研究领域由一维拓展到了二维 ,并对不同种测试系统进行了比较。利用新的测试系统获得了物体运动的照片 ,研究了质点高压下的运动 ,同时 ,获得了变形速度和变形角。     

The study of chamber rockburst by the CUSP model of catastrophe theory

ＴＨＥＳＴＵＤＹＯＦＣＨＡＭＢＥＲＲＯＣＫＢＵＲＳＴＢＹＴＨＥＣＵＳＰＭＯＤＥＬＯＦＣＡＴＡＳＴＲＯＰＨＥＴＨＥＯＲＹＰａｎＹｉ－ｓｈａｎ（潘一山）,ＺｈａｎｇＭｅｎｇ－ｔａｏ（章梦涛）,ＬｉＧｕｏ－ｚｈｅｎｇ（李国臻）（ＦｕｘｉｎＭｉｎｉｎｑＩｎｓ...     

Bending,damping and fatigue of metals

It has been shown that the plastic strain at the outside fiber of a rectangular beam subjected to uniform bending is significantly greater than the measured permanent set. Damping tests have been evaluated in terms of known strain distribution and it has been shown that the results are compatible with experimental data. The elastic limit, which corresponds to the fatigue limit, has been estimated using the results of damping tests. An excellent correlation between the predicted values of the fatigue limit and some conventionally determined fatigue data has been obtained.     

A numerical study of the behaviour of a gas–liquid interface subjected to periodic vertical motion

A numerical study has been undertaken to examine the behaviour of a gas liquid interface in a vertical cylindrical vessel subjected to a sinusoidal vertical motion. The computational method used is based on the simplified marker‐and‐cell method and includes a continuum surface model for the incorporation of surface tension. The numerical results indicate that the surface tension has very little effect on the period and amplitude of oscillations of the interfacial waves. The stability of the interfacial waves has been found to depend on the initial pressure pulse disturbance, and exponential growth of the interfacial wave has been observed in some cases. The influence of the amplitude and frequency of the forcing oscillations has also been investigated. The results are in good agreement with available experimental and analytical solutions. Copyright © 2002 John Wiley & Sons, Ltd.     

Investigation of Entry Region Turbulent Flows of Non-Gray Gases

The entrance region turbulent flow between parallel planes has been investigated numerically. Variation of fluid properties with temperature has been considered. Monte Carlo simulation has been used with a narrow band non-gray model to investigate radiative transfer. The effects of radiative transfer and variable properties have been separately and systematically considered. Representative results are included for carbon monoxide and carbon dioxide. For the conditions considered, the results show that the variable properties exert a stronger influence compared to radiative transfer alone.     

The criterion algorithm of relation of implication between periodic orbits (I)

In recent years, there is a wide interest in Sarkovskii’s theorem ami the related study. According to Sarkovskii’s theoren if the continuous self-mapf of the closed interval has a 3-pcriodic orbit, then fmust has an n-pcriodic orbit for any positive integer n. But f can not has all n-periodic orbits for some n.For example, let Evidently, f has only one kind of 3-periodic orbit in the two kinds of 3-periodic orbits. This explains that it isn’t far enough to uncover the relation between periodic orbits by information which Sarkovskii’s theorem has offered. In this paper, we raise the concept of type of periodic orbits, and give a feasible algorithm which decides the relation of implication between two periodic orbits.     

Possibility of a master plot for material functions of high-polymer solutions

A new systematic method has been developed for estimating rheological properties (such as relaxation time, viscosity, primary normal stress difference) for various polymer solutions form the zero-shear-rate specific viscosity and a dimensionless shear rate.A linear relation has been found between the relaxation time and the zero-shear-rate specific viscosity on a double-logarithmic plot, and a new master plot for the primary normal stress difference has been established. In addition the applicability of the FENE-P dumbbell model to high-polymer solutions is discussed.     

Effect of loosely bonded undulated boundary surfaces of doubly layered half-space on the propagation of torsional wave

This paper investigates the propagation of torsional wave in an initially stressed poroelastic layer with corrugated as well as loosely bonded boundary surfaces, sandwiched between a corrugated fiber-reinforced layer and a viscoelastic half-space under initial stress. The velocity equation has been obtained in closed form analytically and the substantial effect of affecting parameters on the phase velocity of torsional surface wave has been demonstrated numerically and graphically. Comparative study has been made to observe the effect of flatness parameter, reinforcement, viscoelasticity and porosity on the phase velocity, meticulously. Some particular cases have also been discussed and it is found that velocity equation is in well-agreement to the classical Love wave equation. Moreover, some remarkable observation has been made through numerical computation and graphical demonstration for fiber-reinforced layer of carbon fiber-epoxy resin, poroelastic layer of sandstone and a viscoelastic half-space.     

Transformation of the bridge during drop separation

The geometry of flows during separation of pendant drops of liquids with significantly different physical properties (alcohol, water, glycerin, oil) has been studied by high-speed video recording. The dynamics of the processes involving the formation of bridges of two characteristic shapes—slightly nonuniform in thickness and with thinning of the upper and lower ends—has been investigated. It has been shown that the shape change of the separated bridge has a number of stages determined by the properties of the liquid. As a result, the bridge is transformed into a small drop—a satellite drop.