The cycle time distribution

Cycle time is the total elapsed time to move a unit of work from the beginning to the end of a physical process. It is a variable that is used to reduce the costs and increase the output of the physical process. In this note, the exact probability distribution of the cycle time variable is derived. Exact expressions are provided for its probability density function and moments. It is shown how these results could be used for cycle time reduction. Finally, a computer program and tabulations are provided for the associated percentage points.     

比较法真空标准漏孔校准方法研究

比较法校准真空标准漏孔是通过四极质谱计比较气体流量计提供的标准气体流量与被校真空标准漏孔产生的离子流获得校准值。主要介绍了比较法真空标准漏孔的校准方法、装置原理、校准过程及校准结果的处理等,并提出了减小测量不确定度的影响因素。     

Comparison of annular wavefront interpretation with Zernike circle polynomials and annular polynomials

A general wavefront fitting procedure with Zernike annular polynomials for circular and annular pupils is proposed. For interferometric data of typical annular wavefronts with smaller and larger obscuration ratios, the results fitted with Zernike annular polynomials are compared with those of Zernike circle polynomials. Data are provided demonstrating that the annular wavefront expressed with Zernike annular polynomials is more accurate and meaningful for the decomposition of aberrations, the calculation of Seidel aberrations, and the removal of misalignments in interferometry. The primary limitations of current interferogram reduction software with Zernike circle polynomials in analyzing wavefronts of annular pupils are further illustrated, and some reasonable explanations are provided. It is suggested that the use of orthogonal basis functions on the pupils of the wavefronts analyzed is more appropriate.     

Adaptive One-Factor-at-a-Time Experimentation and Expected Value of Improvement

This article concerns adaptive experimentation as a means for making improvements in design of engineering systems. A simple method for experimentation, called “adaptive one-factor-at-a-time,” is described. A mathematical model is proposed and theorems are proven concerning the expected value of the improvement provided and the probability that factor effects will be exploited. It is shown that adaptive one-factor-at-a-time provides a large fraction of the potential improvements if experimental error is not large compared with the main effects and that this degree of improvement is more than that provided by resolution III fractional factorial designs if interactions are not small compared with main effects. The theorems also establish that the method exploits two-factor interactions when they are large and exploits main effects if interactions are small. A case study on design of electric-powered aircraft supports these results.     

The Construction of a 217–19 Resolution V Plan in Eight Blocks of 32

The problem of discriminating among several chemical routes is treated with the use of experimental design. The process variables for each route are related to the cost of that route through regression equations. The variable settings which promise the minimum cost are determined and a probability distribution about that cost is constructSed. For each point in the design, estimates of the most likely results along with the lower and upper bounds are provided before any of the experimentation is carried out. As the experimentation proceeds, the estimates for the unrun portion of the design are constantly improved. A weighted regression analysis is carried out and always includes the information generated from the experiments as well ss that provided by the estimates. An example is included where few experiments are necessary to achieve the desired discrimination.     

Low cycle fatigue and mechanical properties of magnesium alloy Mg–6Zn–1Y–0.6Ce–0.6Zr at different temperatures

The paper deals with low cycle fatigue (LCF) and mechanical properties of Mg–6Zn–1Y–0.6Ce–0.6Zr alloy at both room and elevated temperatures. Fractural microstructures of the test specimens were also analyzed. Based on the experimental results some guidelines about the application of the Mg alloy are provided. A detailed review of existing literature on LCF of other Mg alloys is provided and comparison with appropriate results of other authors was made. Due to scarcity of results, special attention is given to the low cycle fatigue properties at elevated temperatures. LCF results are assessed relative to the loading defined as a fraction of the ultimate tensile stress. With such criterion, it can be said that increase in temperature leads to the more favorable environment for low cycle fatigue of Mg alloy at hand.     

A Modified Formula for Calculating Customer Service Under Continuous Inventory Review

This article shows that a formula commonly used for establishing safety stocks can lead to erroneous results, particularly when the magnitude of forecast errors over a replenishment lead time is large in comparison with the replenishment quantity. A correct procedure involving only slightly more computational effort is developed. Numerical results are provided for the case of normally distributed forecast errors.     

带约束拉杆矩形钢管混凝土的本构关系

对带约束拉杆矩形钢管混凝土在轴压下的受力机理进行分析,在带约束拉杆方形钢管混凝土本构关系的基础上,针对矩形钢管截面长边、短边对混凝土约束作用大小不同及约束拉杆沿长边、短边布置数量不同等特点,应用基于混凝土真三轴试验的破坏准则确定核心混凝土的峰值强度,从而提出适合带约束拉杆矩形钢管混凝土柱数值计算的本构关系,并根据相关试验结果对本构关系的参数进行确定。应用该本构关系对有关试件进行荷载-应变关系的全过程计算,并与试验结果比较,两者吻合良好。     

Analytic treatment of field diffusion into hysteretic magnetic materials

This paper reapproaches the very classic problem of the analytic study of nonlinear diffusion of electromagnetic fields in conducting media. Significant contributions that appeared in the literature on this topic are cited in order to highlight the interest and the efforts provided by the scientific community on this topic as well as the aim and the main results of this work. The capabilities of two analytic procedures for estimating the energy losses in magnetic materials with hysteresis are shown and discussed. One formulation reduces the full nonlinear diffusion problem to a linear problem through an optimization procedure and is suited for thick cores. A second formulation approximates the magnetic field behavior by means of polynomials and provides good results for thin laminations. Energy losses are evaluated for magnetic materials with different B-H relations operating in wide frequency intervals. A scalar Preisach model, numerically treated, is used as a benchmark and, finally, calculations are compared with experimental data provided by other authors.     

Feature-based design: Four hypotheses for future CAD systems

Features are meaningful abstractions of geometry that engineers use to reason about components, products, and processes. For design activity, features are design primitives, serve as the basis for product representations, and can incorporate information relevant to life-cycle activities such as manufacturing. Research on feature-based design has matured to the point that results are being incorporated into commercial CAD systems. The intent of this paper is to look forward. Hence, this paper does not play the role of a standard survey, which necessarily only reviews the past. Nevertheless, an appropriate historical context is provided as a basis for these particular futuristic projections. Applications of feature-based design and technologies of feature representations are reviewed, then open research issues are identified and put in the context of past and current work. Features are prominent as catalysts for computer-based design tools, but the vision presented expands upon this basis, delving beyond features. For that future design environment, four hypotheses are proposed as research challenges: two on the existence of fundamental subfeature elements and relationships for features, one that presents a new definition of design features, and one that argues for the successful development of concurrent engineering languages. Evidence for these hypotheses is provided from recent research results and from speculation about the future of feature-based design.     

Boundary element formulation of axisymmetric problems for an elastic halfspace

Axisymmetric problems for an elastic halfspace are commonly analyzed by the boundary element (BE) method by employing the axisymmetric fundamental solution for the fullspace. In such cases, the discretization of the free surface is required, with its truncation at an appropriate location from the axis of symmetry. This paper presents the BE implementation of the axisymmetric fundamental solution for an elastic halfspace, given in terms of integrals of the Lipschitz–Hankel type, that satisfies in advance the boundary condition of zero traction on the free surface and the decay of displacements in the far field. Explicit equations for post-processing the results at internal points are provided, as well as adequate numerical schemes to evaluate the boundary integrals arising in the method. This formulation can be easily implemented in existing BE computational codes for axisymmetric fullspace problems, requiring only a few modifications. Numerical results are provided to validate the proposed formulation.     

舰船辐射噪声模拟技术研究

本文对舰船辐射噪声的模拟技术进行了研究,给出了线谱,连续谱噪声,噪声调制的模拟方法,进行了计算机模拟,研制了可编程模拟器。通过对模拟器输出信号的处理和分析,结果表明该模拟器能很好地再现舰船辐射噪声的典型声学特征。     

Approach to analyse and design nearly sinusoidal oscillators

A method to analytically evaluate the linearity performance of harmonic oscillators is proposed. The approach is based on the phasor method and provides closed-form equations that extend our knowledge on harmonics generation and are particularly useful for the designer. Three design examples (tunnel diode, Colpitts and Hartley oscillators) are provided and simulations are found in close agreement with expected results.     

超声波散射式颗粒测量及其测量结果单值性的分析

提出了一种超声波散射式颗粒测量方法,论述了该技术应用的理论基础,并在详细分析其测量原理基础上,指出了在单频率换能器和单散射角下进行颗粒测量时存在着测量结果多值性的可能。给出了解决这一关键技术问题所采取的可能方案和措施。     

小周期结构Helmholtz方程的多尺度计算

本文研究小周期结构Helmholtz方程的多尺度计算。我们用各向异性多尺度方法(HMM)求解小周期结构Helmholtz问题。借助于渐近分析技术,在对HMM方法深入分析的基础上,我们给出了精确与HMM方法近似解之间的误差估计,并讨论和分析了利用微结构信息校正HMM逼近解的技巧。最后,我们用数值例了验证了理论结果的正确性。     

A theoretical approach for evaluating the plane strain fracture toughness of ductile metals

Fracture Mechanics of Ductile Metals (FMDM) theory is used to obtain the plane strain fracture toughness, K_lc, for different materials. The traditional approach for obtaining the K_lc value is to conduct several standard tests on cracked plates that are costly and time consuming. The fracture toughness value provided by the FMDM theory depends on the stress-strain curve for the material in question, and this is readily available in MIL-HDBK-5 and other reliable sources. The results of the plane strain fracture toughness (K_lc) values provided by the FMDM theory were compared with the experimental data and it was concluded that the two are in excellent agreement. It is proposed that, in the interest of economy and convenience, K_lc testing could be replaced by the FMDM theory.     

An integer linear programming model to support customer-driven material planning in synchronised,multi-tier supply chains

This paper describes an integer linear programming model conceived as an alternative to a traditional material requirements planning (MRP) system for extending the concept of supply chain synchronisation upstream in a multi-tier supply chain. In this model, we assume there is an incumbent application for transmitting original equipment manufacturer (OEM) requirements to first-, second- and third-tier suppliers. The proposed model is regarded as being embedded within a web-enabled, multi-tier, supply chain information system that provides the application for transmitting the production requirements. The principal motivation for having second- and third-tier suppliers that are synchronised with OEM and first-tier activity is the significant inventory, lead time and responsiveness gains that can potentially be achieved. Here, inventory is considered as a whole across a supply chain, and stock-outs are prohibited for the first-tier supplier. For illustration purposes, an example based on a real, automotive case study is provided. The model results proved better in terms of inventory and bullwhip reduction than those found in a previous simulation-based approach. Also, a comparison of the proposed case results with those of a conventional MRP application is provided.     

Binary nonlinear joint transform correlator performance with different thresholding methods under unknown illumination conditions

The correlation performance of binary joint transform correlators with unknown input-image light illumination is investigated for different thresholding methods used in the Fourier plane. It is shown that a binary joint transform correlator that uses a spatial frequency dependent threshold function for binarization of the joint power spectrum is invariant to uniform input-image illumination. Computer simulations and optical experimental results are provided.