汽车空调用旋叶压缩机型线的动力特性分析

气缸型线是影响汽车空调用旋叶式压缩机性能的重要因素之一。以带密封圆弧的气缸型线为研究对象，分析了几种典型型线对压缩机的容积变化、滑片运动特性以及转子合力及力矩的影响。研究结果表明，三角函数曲线具有较好的速度和加速度特性；对连接密封圆弧和主曲线的过渡曲线进行优化，能有效的减少滑片的冲击、振动和噪声；型线的构成对压缩机轴功率的影响可以忽略。     

Integral formulations and bounds for two phase Stefan problems initially not at their fusion temperature

Summary The classical two phase Stefan problems for spheres, cylinders and slabs do not, in general, admit exact solutions. For a number of genuine two phase moving boundary problems involving these geometries integral formulation are obtained which generalize known results for idealized one phase Stefan problems and can be utilized to obtain upper and lower bounds on the motion of the moving boundary, even though the analysis is complicated considerably by the presence of a nontrivial second phase. The problems considered are the inward thawing of an initially subcooled solid contained within a finite sphere, cylinder or slab, or within a region bounded by concentric spheres, cylinders or planes, as well as the outward thawing of an initially subcooled solid in the finite region surrounding a sphere, cylinder or plane. The relation of the integral for the boundary motion to the enthalpy is noted, and the bounds obtained for the cases of inward thawing of spheres, cylinders and slabs are compared with exact numerical solutions, generated by the enthalpy method. From these comparisons it becomes apparent that the bounds are adequate when the latent heat is the dominant thermal factor, that is, when more heat is required to produce the change of phase than to warm the substance. However, when this is not the case, that is, when the sensible heat is the dominant thermal factor, further analysis is needed.With 5 Figures     

Efficient global optimization applied to wind tunnel evaluation-based optimization for improvement of flow control by plasma actuators

A kriging-based genetic algorithm called efficient global optimization (EGO) was employed to optimize the parameters for the operating conditions of plasma actuators. The aerodynamic performance was evaluated by wind tunnel testing to overcome the disadvantages of time-consuming numerical simulations. The proposed system was used on two design problems to design the power supply for a plasma actuator. The first case was the drag minimization problem around a semicircular cylinder. In this case, the inhibitory effect of flow separation was also observed. The second case was the lift maximization problem around a circular cylinder. This case was similar to the aerofoil design, because the circular cylinder has potential to work as an aerofoil owing to the control of the flow circulation by the plasma actuators with four design parameters. In this case, applicability to the multi-variant design problem was also investigated. Based on these results, optimum designs and global design information were obtained while drastically reducing the number of experiments required compared to a full factorial experiment.     

Modeling of measured target pressure profiles in three hypervelocity impact experiments

A 24 g aluminum sphere was shot at a sparse array of cylinders with nominal initial projectile velocity of 4 and 5 km/s. Pressure profiles were measured with cased carbon resistor gages at two locations in a projectile impacted water filled cylinder and two of its neighbors on three shots. The pressure maxima were in the 1–13 kbars range. The experiments are modeled with the ALE3D code and several techniques are used to concentrate zoning at places of interest. There is excellent agreement between the measured and calculated pressure profiles for two shots and good agreement for the third. Comparison of the calculated pressure profiles with those from more refined calculations for two shots suggest that we are near convergence with respect to zone size.     

Quasi-diffraction-free beams.

A diffraction-free beam is obtained by the superposing of plane waves whose wave vectors make an angle with the propagation axis. These plane waves are realized with point sources that are distributed uniformly around a circle and an infinitely large aperture lens. After the field passes through the lens it has nondiffracting properties and is described by the zero-order Bessel function. Relaxing these conditions makes the beam diffraction free within only a limited region. The beam generated from such a geometry is referred to as a quasi-diffraction-free beam. The effects of the width of the annular source on the beam spread are discussed and compared with those for a Gaussian beam. Approximate expressions for quasi-diffraction-free beams are also obtained.     

Finite element analysis of multilevel acoustic Fresnel lenses

Fresnel lenses have recently emerged as viable alternatives to conventional spherical lenses for focusing ultrasonic waves in acoustic microscopy systems. Although these lenses are relatively straightforward to manufacture, their bulk represents a major handicap. A remedy to this problem is to use multilevel acoustic Fresnel lenses. Multilevel lenses are surface relief structures that can be fabricated very precisely using existing VLSI semiconductor technology. However, accurate tools for designing lenses to achieve the desired efficiency and power specifications are not available. This paper presents a finite element study of multilevel acoustic Fresnel lenses. Results showing ultrasonic wave propagation through such surface relief structures together with the resulting diffraction profiles are presented. The high efficiency and focusing power of these lenses are also demonstrated. Simulation results together with a discussion on various multilevel lens design issues are presented. These results confirm the advantages of such lenses, and suggest that the finite element model can serve as a valuable tool for designing, simulating, and studying lens profiles prior to their fabrication     

椭圆柱透镜组准直半导体激光束的优化设计

采用光线矢量法设计了两个相互垂直的椭圆截面柱透镜组来准直半导体激光束。利用多目标优化中的加权和法进行优化计算，并提出自适应加权系数优化法。此方法能根据计算结果自动调整加权系数，从而达到最佳的优化结果。计算结果表明，该准直系统可达到45μrad左右的发散角，远远优于其它截面柱透镜组（毫弧度数量级）的准直效果。同时两柱透镜间距取适当值，还可在远场形成圆形光宽。     

诊断内燃机各缸作功均匀性的曲轴简谐扭振反算法

简要介绍了各种诊断内燃机各缸作功均匀性的方法及其局限性；依据内燃机动力学的基本理论，提出了一种利用轴系一个惯量的扭振信号多谐次分量反算内燃机各缸作功均匀性的新方法；详细推导和说明了该方法的基本原理；以某6L240柴油机为对象，进行了选用3个谐次的扭振简谐分量准确反算出各缸作功均匀性的仿真研究。理论分析和仿真研究表明．新方法只需以各缸停缸实验得到的扭振幅频特性参数为基础，利用一个惯量的扭振信号多谐次分量就可反算出内燃机各缸平均有效压力。方法简便准确，既不依靠轴系结构参数等较难获得的先验知识，又适用于内燃机轴系存在扭振的情况。     

Optical characterization of ophthalmic lenses by means of modulation transfer function determination from a laser speckle pattern

A method is presented for measuring the modulation transfer function of ophthalmic lenses by use of the generation of laser speckle with an integrating sphere. The measurements are performed with a rectangular double-slit aperture positioned at the output port of the integrating sphere. The distance between the lens and the detector determines the spatial frequency being tested; therefore high frequencies are tested close to the lens and low frequencies are tested far away from the lens. We can conclude that the double-slit method can be a versatile technique for comparing the optical quality of ophthalmic lenses from different makers.     

The simultaneous use of 4×4 and 2×2 bilinear stress elements for viscoelastic flows

Mixed finite elements for viscoelastic flows based on a 4×4 sub-linear interpolation for the extra stress components satisfy the Babuska-Brezzi condition and are highly stable. They have been proved to be quite satisfactory in solving problems with strong stress boundary layers. In this work, we examine the simultaneous use of 4×4 and 2×2 bilinear stress elements in an attempt to reduce the computational cost without sacrificing the accuracy. The 4×4 bilinear elements are employed in regions where the stress field is anticipated to be steep while the 2×2 elements carry the burden elsewhere with a much smaller number of stress nodes. Additional constraints along the sides shared by different elements are necessary in order to preserve conformity. The method is applied to the creeping flow of a Maxwell fluid around a sphere falling along the axis of a cylindrical tube. Results are given for three mixed finite element formulations: the Galerkin method, the consistent streamline-upwind/Petrov-Galerkin method (SUPG) and the non-consistent streamline-upwind method (SU). Particular emphasis is given on the calculated drag correction factors. The effect of the sphere/cylinder diameter ratio is also examined.     

圆柱与圆锥轴线相交时左侧相贯线上最右点的解析证明与图解

轴线相交的圆柱、圆锥两曲面立体相贯时,产生左右两条空间相贯线曲线。该文以左侧相贯线为研究对象,用数学方法证明圆柱立体的半径在一定范围内变化时,左侧相贯线上最右点的变化规律,由此提出了准确绘制左侧相贯线上最右点的图解方法。左侧相贯线上的最右点在两条特殊相贯线上,分别在锥和与锥相切的球的相贯线上及在柱和与锥相切的球的相贯线上。     

用于坐标测量机上测量与评定形位误差的软件包

为强化坐标测量机的功能，本文建立了评定直线、平面、圆、圆柱、圆锥、球等六项基本要素形状误差的、符合国家标准的数学模型，并用ＴＵＲＢＯＣ语言编制了计算程序．它不仅可直接用于评定位置时确定基准的理想要素，而且稍加扩展又可用来评定位置误差．本软件包可ＣＡＤ／ＣＡＭ系统联网，从而也极大地提高了ＣＡＤ／ＣＡＭ系统的效率．     

Transient natural convection flow over vertical cylinder with variable surface temperatures

An analysis is made for transient natural connective flow over a vertical cylinder with surface temperature of the cylinder varying as x ⁿ , a power function of distance from the leading edge. A Crank-Nicolson type of implicit finite difference method is used to solve the governing non-linear set of equations. Numerical results are obtained and presented for air and water with various n. The transient velocity and temperature profiles, local and average skin-friction and Nusselt numbers are shown graphically. The effects of exponent n on velocity and temperature profiles, skin-friction and rate of heat transfer have been analysed. The velocity and temperature profiles are compared with the available results in the literature and it is found to be in good agreement.     

A novel colour model for colour detection

Colour detection plays an important role for many computer vision-based applications. However, most existing colour detection methods tend to be environment dependent since slight changes of environmental factors such as illumination or shadowing effects could greatly reduce their performances. In this paper, a new colour model is introduced to allow enhanced colour detection from images, even with significantly different lighting conditions and image qualities. The proposed colour model is called the HPBr colour model. It is converted from the RGB colour model and it consists of three colour components, namely, hue (H), purity (P) and brightness (Br). This colour model can be represented in three different geometric shapes: diamond, sphere and cylinder. To assess the effectiveness of the model, two different colour detection methods have been applied onto benchmark images. Experimental results from both methods confirmed that the proposed colour model produced the best colour detection results among existing models.     

Lens design using group indices of refraction

Abstract

An approach to lens design is described in which the ratio of the group velocity to the speed of light (the group index) in glass is used, in conjunction with the more familiar phase index of refraction, to control certain chromatic properties of a system of thin lenses in contact. It is shown that, at the wavelength of a maximum or minimum (where the phase power of a lens is locally independent of wavelength), the group power is equal to the phase power. It is further shown that, in a lens consisting of three or more elements, the phase and group powers can be constrained to be both equal and independent of wavelength (achromatic) at one or more wavelengths. In the neighbourhood of such wavelengths, both the first and the second derivatives of phase power with respect to wavelength are zero, giving this type of lens (in principle) an exceptionally high degree of achromatism not previously described, herein called group achromatism. The first-order design of thin-lens systems is illustrated by examples with the help of a computer program incorporating the methods described.     

Fracture resistant properties of AerMet steels

The purpose of this study is to report well-controlled experiments conducted to determine the fracture resistant properties of AerMet® 100 steels. One of the objectives of this study is to determine the influence of fracture toughness properties on the fracture and fragmentation process. Both sphere impact tests and cylinder expansion test geometry were used to determine the dynamic fracture resistant coefficients. These experiments were conducted at strain rates of 14 × 10³ /s for the cylinder expansion tests; the strain rates for the sphere impact tests varied over 50 to 100 × 10³/s. Fracture resistant coefficients of 60 MPa √m and 20 MPa √m are obtained from the cylinder test and the sphere impact test, respectively. These measurements do not agree with the static fracture toughness values reported in the literature.     

A quadrature of the two-dimensional equations of the hydrodynamics of an incompressible ideal liquid and a model of the flow around convex symmetric bodies with suction or injection

A class of solutions of the steady-state hydrodynamic equations of an incompressible liquid has been considered in the Euler approximation when the pressure field is described by an additive function of the form P(x; y)=F(x)+G(y). It turns out that this class of solutions includes potential flows such as wave motion of a liquid with a finite depth, a flow inside a right angle, and a hypersonic gas flow around a sphere in the approximation of constant density near the stagnation point. Among nonpotential flows, this class includes, in particular, a hypersonic flow around a cylinder. The results obtained are used to construct a model of a flow around convex symmetric bodies with suction or injection. This model can be of interest in solving some problems of physicochemical technology, for example, separation of gas mixtures and isotopes.V. E. Firsov Saratov State Pedagogical Institute, Saratov, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 1–2, pp. 59–65, July–August, 1994.     

Axisymmetric contact of an elastic layer underlain by rigid base

Axisymmetric contact problems of an elastic layer are studied in this paper. The lower surface of the layer is either bonded to or in smooth contact with a rigid base. The upper surface is in tensionless smooth contact with a rigid flat cylinder, a rigid sphere, an elastic sphere or a circular plate, respectively. A general method is developed so that all these related problems are treated in a straightforward and like manner. In comparison to the other methods used in previous papers, the simplicity and high numerical accuracy are the major advantages of this method. The convergence is proved by comparing the numerical values to some available analytical solutions. Extensive numerical results for contact radii, displacements and contact pressures are provided.     

Comparing the lens displacement profile data by using the sequential approach for selecting alternative suppliers

The lens module is a critical part of the camera module. The quality of the lens module significantly influences the auto-focus and image stability functions of the camera module. A new approach that uses sequential tests is proposed to select the alternative suppliers that provide the qualified parts as the current supplier under the linear profile data. Having several qualified alternative suppliers can reduce the dependency on one supplier, improve bargaining power, and reduce capacity risk. The lens displacement that has a linear relationship with current is the quality characteristic for evaluating the lens module suppliers. To select the qualified alternative suppliers, the proposed sequential approach tests the profile difference between the current supplier and the investigated suppliers. The simulation results show that the power of the sequential approach is higher than the simultaneous confidence bands method in differentiating profiles. Last, the proposed approach is effectively applied to select the qualified alternative lens module suppliers for the camera module manufacturer. Procuring the lens module from the selected suppliers can maintain production quality and flexibility for the camera module manufacturer in practice.