Contact deformation of a cylinder under its compression by two flat plates

It is shown that the known formula for the computation of the rapprochement of axes of cylinders does not account for their contact deformation. It is shown that the known computational procedure of the rapprochement of plates compressing a roller placed between them takes incompletely into account the contact deformation. Because of the consideration of the contact deformation of cylinders, a refined formula was obtained to compute of the rapprochement deformation of flat surfaces of plates compressing one or two cylinders and the rapprochement deformation of axes of cylinders. The computations are compared with experimental data.     

Teaching conceptual design using axiomatic design to engineering students and practitioners

As the demand for new designs increases in the engineering community, the importance of conceptual design increases. Students practice discussion type methodologies such as brainstorming; however, they usually do not learn conceptual design methods. To meet the demand for new designs, a logical method should be taught in a conceptual design class. This class will provide students with hands-on experience from a design project using the logical method. Axiomatic design is selected for the conceptual design method and taught to undergraduate students, graduate students and practitioners. In this paper, the author reports on the teaching experience with different levels of students. The axiomatic design framework is taught and design projects are given. The syllabus has been developed for each group, and teaching methods are discussed as well as the pedagogical aspects. While undergraduate students easily agree with the instructor’s viewpoint, many of them have difficulties in designing a real product. Some graduate students doubt the usefulness of axiomatic design. However, they can successfully apply the method to projects, whereas experienced practitioners have difficulties in attacking a new method. Once they understand the method, they can solve the problems they face in the workplace. The educational outcome does not manifest immediately and should be evaluated in a long-term study.     

圆薄片零件精密研磨实验研究

通过对钨合金圆薄片零件的精密研磨实验，确立了钨合金圆薄片零件精密加工工艺路线；分析了弱刚性零件研磨常用装夹方式对研磨精度的影响；设计了专用研磨工装，使零件在研磨过程中几乎处于自由状态，有助于降低零件研磨后的形位公差；叙述了手工研磨操作和研磨过程中应注意的事项，分析了研磨过程中出现的问题和采取的措施。     

考虑效率时蜗杆传动作用力的新算法

蜗杆传动因效率低,在力的大小计算时应计效率;而在考虑效率时,蜗杆副力的计算式不统一,这里推导出考虑效率时力的大小计算的两套公式。     

多向安装隔振器的研究与应用

由于受所处载体空间的限制,电子设备在不同载体中需要以不同方向进行安装。因此必须解决电子设备在不同方向安装时隔振系统的固有频率变化问题,才能保证设备的性能稳定。文中介绍了采用活动铰支承加轴向与径向弹性元件的典型结构来设计多向安装隔振器的方法。在隔振器力学模型分析的基础上,利用能量法推导出其固有频率的计算公式。通过对侧装安装方式典型实例的试验,验证其计算公式的正确性。另外,试验输入与输出的对比表明,该多向安装隔振器在三坐标方向实现了解耦设计,解决了多向安装隔振器的隔振缓冲难题。该多向安装隔振器的设计分析计算方法为类似隔振器的设计计算提供了理论指导。     

Constrained minimization utilizing GA based pattern recognition of immune system

The immune system has pattern recognition capabilities based on reinforced learning, memory and affinity maturation interacting between antigens and antibodies. The paper deals with the adaptation of artificial immune system into genetic algorithm based design optimization. The present study utilizes the pattern recognition from the immune system and the evolution from genetic algorithm. The basic idea is derived from the fact that designs should be distinguished whether they are usable/feasible or infeasible and should be improved towards the optimal solution. For the expression of design solutions, binary coded strings are used to represent antigens and antibodies in artificial immune system and chromosomes in genetic algorithm. The paper discusses the procedure of constrained optimization that does not rely on any detailed mathematical formulation for constraint handling. A number of mathematical function minimization problems are examined for verification, and practical engineering optimization problems including inequality constraints are explored to support the proposed strategy.     

Optimization for rising or falling ridge systems in non-spherical designs

The response surface (RS) methodology is a well-known tool employed for product and process optimization. In some engineering optimization problems the fitted response has a rising or falling ridge system, namely the stationary point of response is remote from the design region. For such a case, usually the classical method, called ridge analysis (RA), is employed to specify the optimum operating conditions for an optimization problem. In this paper, it is proven that the RA does not guarantee the global maximum or minimum point of response in the experimental region for non-spherical designs such as face-centered designs, Box-Behnken designs, and two-level factorial designs. The current study proposes an approximation based on the use of desirability function technique to solve this ridge optimization problem, and demonstrates that the desirability function technique is more effective than the RA technique described by Myers and Montgomery (2002) for non-spherical designs which are frequently applied for engineering problems. To show the effectiveness and advantages of the proposed technique, a case study is presented to optimize the forming parameters of a tube hydroforming (THF) process where a Box-Behnken design is employed.     

Buckling limit evaluations for reactor vessel of ABTR

We evaluated the buckling limit of a conceptually designed reactor vessel of the Advanced Burner Test Reactor (ABTR) for a horizontal safe shutdown earthquake (SSE) seismic load. In this evaluation, both seismic isolation and non-isolation designs were considered for thin reactor vessels subjected to elevated temperature services. For calculating the buckling load, two kinds of methods, a numerical simulation method using finite element analysis and an evaluation formula driven from a theoretical basis, were used. To consider the material aging effect caused by a 60-year design lifetime and 510°C normal operating temperature, an isochronous stress-strain curve corresponding to these conditions was used for the nonlinear elastic-plastic buckling analysis method. From the evaluation results of the buckling load, it was found that plasticity behavior significantly affects the buckling strength, but that the initial geometrical imperfections have little effect. Also, the non-seismic isolation design does not satisfy the buckling limit rules of the ASME BPV Section III, Subsection NH, but the seismic isolation design does satisfy it with sufficient margins.     

基于均匀设计条件下的混料设计在油品配方中的应用

介绍了有约束条件的混料设计和无约束条件的混料设计的算法，并运用基于均匀设计条件下推导出的混料设计表进行了组织试验。试验结果表明：无约束条件的混料设计可以很好地满足油品配方设计要求。该算法简单易行，易于推广，尽管精确度稍差，但从评价油品配方的角度来衡量是完全可行的。     

离轴三反航天测绘相机焦距的计算

为了精确计算离轴三反相机的焦距以保证其测绘精度,对经典测绘模型和相关公式进行了必要的修正。首先,重新定义了离轴三反测绘相机的交会角,并对经典焦距计算公式做了修正;其次,分析了地球曲率对离轴三反测绘相机焦距计算的影响,进一步修正了焦距计算公式。实例计算表明:当要求地面像元分辨率为2m,在CCD像元尺寸为8μm,轨道高度为700km,离轴角为7°条件下,应用经典计算公式得出的斜视相机焦距与应用修正后的计算公式所得出的斜视相机焦距相对偏差达到2.6%,说明对测绘精度影响很大。因此,在采用离轴三反相机进行摄影测量时,斜视相机焦距的计算应考虑离轴角后对经典公式进行必要的修正,而正视相机的焦距计算可以沿用经典计算公式。     

锥形件拉深成形中的弯曲与反弯曲变形分析及拉深力的计算

针对帽形弯曲成形,建立了弯曲与反弯曲的几何模型,分析了板坯多角弯曲时的弯曲和反弯曲现象,给出了产生反弯曲变形的判定条件。在此基础上,进一步研究了锥形件拉深成形中的弯曲与反弯曲问题,指出了在拉深初期并不产生反弯曲变形。计算拉深力时,应首先判断是否产生了反弯曲变形,然后再考虑反弯曲变形对成形过程的影响。     

Ultrastructure of the frog retina after high-pressure freezing and freeze substitution

In many types of tissue, high-pressure freezing (HPF), followed by freeze substitution, can produce excellent ultrastructural preservation at depths over 10 times that obtained by other cryofixation techniques. However, in the case of neural tissue, the benefits of HPF have not been realized. In the present study, isolated frog ( Rana pipiens) retina was sliced at a thickness of 150 or 350 μm, rapidly frozen in a Balzers HPM 010 high-pressure freezer, and freeze substituted with 1% OsO₄ and 0.1% tannic acid in acetone. Specially designed HPF chambers and specific freezing media (35% high-MW dextran for 150-μm slices or 15% low-MW dextran for 350-μm slices) were required for adequate freezing.
The quality of preservation after HPF was excellent throughout the retina in both the 150- and 350-μm slices, compared with chemically fixed slices. Specifically, HPF resulted in better preserved cellular, mitochondrial and nuclear membranes in all retinal layers.
This is the first study to successfully cryofix all of the layers of the retina. The increased depths of adequate freezing achieved by HPF should facilitate various ultrastructural studies of retina, as well as of other CNS tissues, where preservation approaching that of the 'native' state is required.     

基于实际齿形的塑料齿轮强度修正系数计算

为了提高塑料齿轮齿根强度计算解析法的精度,建立了寻找塑料齿轮齿根危险截面位置的目标函数。基于笔者所开发的软件平台上设计的实际齿形,采用寻找目标函数最大值的方法计算出与齿形有关的强度修正系数,即对应于齿根危险截面的齿形系数和应力集中系数。该计算方法的特点是综合考虑了模数、齿数、压力角、变位系数、齿厚偏差、齿根圆角半径等多因素对强度修正系数的影响。     

A fracture movement monitoring system to aid in the assessment of fracture healing in humans

This paper presents a new design for a device to monitor the motion of fracture fragments in diaphyseal tibial fractures. The device measures the motion that occurs at the fracture site when loaded by gait or by manipulation. It has undergone rigorous calibration and acceptance trials. The device has been used in ethically approved research clinics held at the North Staffordshire Hospital (40 patients). The paper presents a selection of results obtained using the new device. The results demonstrate several new ways of assessing fracture healing by examining fracture site motion. The following conclusions were drawn: 1. If fracture monitoring devices are to be attached to bone screws, it is essential to minimize bone screw errors. To do this, each patient must have similar bone screw lengths, orientations, alignment and siting. This is only achievable using a peroperative reduction device. 2. If fracture stiffness is to be used as a measure of fracture healing, load rate should be controlled; at the very least strain rate should be controlled. 3. It is imperative that fracture stiffness be measured in more than one plane by a biplanar device so that asymmetry may be accommodated. 4. Fracture stiffness, on its own, is probably not a sufficiently rigorous measure of healing end-point. The quantifiably viscoelastic properties of healing callus should be taken into account.     

环形油垫静压推力轴承考虑油流惯性的承载能力计算公式

本文在假定间隙中油流为不可压缩、稳定、轴对称的层流,且轴向分速度V z=0等条件下,利用纳维-斯托克斯方程,导出了考虑油流惯性的环形油垫静压推力轴承承载能力的计算公式,并利用该式直接给出了圆形油垫静压推力轴承承载能力的计算公式。这些公式既能在工程上实用,又是分析静压推力轴承工作特性的理论基础。     

Wear characteristics of metals

Although there are still many gaps in our knowledge of the factors involved in tribological interactions, there is sufficient information available to characterise the commonly encountered wear mechanisms. Many techniques are currently available to modify surfaces to improve their wear characteristics, but these are usually applied after a problem has become apparent in service. These techniques are not usually included in the original design because most engineers do not appreciate the effect of operating conditions on the life of components. The precise role of physical and mechanical properties of metals in wear is little understood. Much effort has been expended in our understanding of bulk properties. Considerably more effort is now required to understand surface properties. Halling has stated that the major growth area for the next decade lies in the role of surface treatments for improving tribological characteristics²⁴. These, however, are already becoming available faster than our rate of understanding of their precise tribological properties.Design guides for widely used engineering metals in different conditions of treatment are required under specific wear conditions. Few materials combinations have been examined in the metallurgical detail demonstrated by Lea. This approach should be further extended to produce wear maps with their associated atlas of surface and sub-surface microstructure showing both satisfactory and unsatisfactory wear behaviour.An appreciation of the cost wear would bring about a greater awareness of the problems involved and greater effort would be applied to producing long term solutions instead of the concentration on short term expediencyThe major problem, however, is the lack of communication between those with the knowledge and those who should be using it in their designs. The tribologist should produce more information related to the behaviour of materials in service. He should be encouraged to publish more case studies and solutions related to specific engineering components or systems.     

Estimating the total number of lymphatic valves in infant lungs with the fractionator

The fractionator is illustrated by means of a biomedical example involving the estimation of the number of lymphatic valves in lungs of infants who had died from sudden infant death syndrome (SIDS) and other known causes. The method is unbiased irrespective of tissue deformations and it does not require external information such as section thickness. An upper bound of the coefficient of error of the estimate of the number of valves within one lung was 6.5%, despite the fact that the number of valves counted per lung at the last stage ranged between 11 and 37 only. The upper bound includes the biological variation of the number of valves among infant lungs. Some theoretical remarks are also made on the efficiency of the fractionator. It is suggested, for instance, that the initial sampling stages cause more impact on the precision of the final estimator than the subsequent stages, and that an optimal arrangement of fragments submitted to systematic sampling should have the smallest fragments at the ends, with fragment contents increasing smoothly toward the middle of the series.     

Fully automated intensity compensation for confocal microscopic images

One well-recognized problem in three-dimensional (3D) confocal microscopic images is that the intensities in deeper slices are generally weaker than those in shallower slices. The loss of intensity with depth hampers both qualitative observation and quantitative measurement of specimens. Two major types of methods exist to compensate for this intensity loss: the first is based on the geometrical optics inside the specimen, and the second applies an empirical parametric intensity decay function (IDF) of depth. A common feature shared by both methods is that they are parameter-dependent. However, for the optics-based method there are as yet no fully automated parameter-setting approaches; and for the IDF method the traditional profile-fitting approach cannot provide proper parameters if the presumed IDF model does not match the experimental intensity–depth profile of the 3D image. In this paper, we propose a novel maximum-entropy (ME) approach to fully automated parameter-setting. In principle the ME approach is suitable for any compensation method as long as it is parameter-dependent. The basic assumption is that without intensity loss an ideal 3D image should be generally homogeneous with respect to depth and this axial homogeneity can be represented by the entropy of a normalized intensity–depth profile. Experiments on real confocal images showed that such a profile was consistent with visual evaluation of axial intensity homogeneity and that the ME approach could provide proper parameters for both compensation methods mentioned above. Moreover, for the IDF method, experiments on both real and simulated data showed that the ME approach could provide more precise parameters than with traditional profile-fitting. The Appendix provides a proof that under certain conditions the global maximization of the profile-entropy is guaranteed.     

基于模糊PID的工程车辆远程控制系统

为满足工程车辆控制系统的信息化和智能化发展需求,设计了基于无线局域网的工程车辆远程控制系统,并提出了一种基于模糊PID的网络化远程控制算法.该方法不依赖具体的网络参数和数学模型,易于工程实现.最后通过计算机仿真和实验验证了设计方案的可行性和有效性.     

A signal decomposition or lowpass filtering with Hilbert transform?

Recently, Chen and Wang discovered an explicit formula that makes use of the Hilbert transform for accurate decomposition of a lower harmonic from a signal composition. This letter presents another proof with a new interpretation for the formula using the Bedrosian identity for overlapping signals. This new and simpler proof is based only on the Hilbert transform and does not involve presentation of the Fourier transform. As a result the discovered formula is introduced as a lowpass filter suitable for non-stationary signals.