用工业工程思想发现、解决和预防问题

在工厂现场问题研究的基础上,联系生活实际,对问题科学进行了研究.定义了什么叫问题;探讨了问题的本质;对工作生活中问题进行了分类;阐明了问题和风险以及问题和矛盾之间的关系.利用工业工程(IE)的思想,分析了普遍的如何发现问题及解决问题的思维过程;阐明了在工作和生活中如何利用问题的实质去发现问题,并最终解决和预防问题.报告了解决问题的三个原则、注意事项和步骤.     

Pre‐college Electrical Engineering Instruction: The Impact of Abstract vs. Contextualized Representation and Practice on Learning

Background While engineering instructional materials and practice problems for pre‐college students are often presented in the context of real‐life situations, college‐level texts are typically written in abstract form. Purpose (Hypothesis ) The goal of this study was to jointly examine the impact of contextualizing engineering instruction and varying the number of practice opportunities on pre‐college students' learning and learning perceptions. Design/ Method Using a 3 × 2 factorial design, students were randomly assigned to learn about electrical circuit analysis with an instructional program that represented problems in abstract, contextualized, or both forms, either with two practice problems or four practice problems. The abstract problems were devoid of any real‐life context and represented with standard abstract electrical circuit diagrams. The contextualized problems were anchored around real‐life scenarios and represented with life‐like images. The combined contextualized‐abstract condition added abstract circuit diagrams to the contextualized representation. To measure learning, students were given a problem‐solving near‐transfer post‐test. Learning perceptions were measured using a program‐rating survey where students had to rate the instructional program's diagrams, helpfulness, and difficulty. Results Students in the combined contextualized‐abstract condition scored higher on the post‐test, produced better problem representations, and rated the program's diagrams and helpfulness higher than their counterparts. Students who were given two practice problems gave higher program diagram and helpfulness ratings than those given four practice problems. Conclusions These findings suggest that pre‐college engineering instruction should consider anchoring learning in real‐life contexts and providing students with abstract problem representations that can be transferred to a variety of problems.     

Airline planning and scheduling: Models and solution methodologies

The airline industry is a representative industry with high cost and low profitability. Therefore, airlines should carefully plan their schedules to ensure that overall profit is maximized. We review the literature on airline planning and scheduling and focus on mathematical formulations and solution methodologies. Our research framework is anchored on three major problems in the airline scheduling, namely, fleet assignment, aircraft routing, and crew scheduling. General formulation, widely used solution approaches, and important extensions are presented for each problem and integrated problems. We conclude the review by identifying promising areas for further research.     

Inverse problem of controlling the interface velocity in Stefan problems by conjugate gradient method

Abstract

The conjugate gradient method of minimization with adjoint equation is used successfully to solve the inverse problem in estimating an appropriate boundary control function such that the phase front moves at a desired velocity in the Stefan problem.

It is assumed that no prior information is available on the functional form of the unknown control function, therefore, it is classified as the function estimation in inverse calculation. The stability and accuracy of the inverse analysis using present algorithm are examined by comparing the results of the previous work by Voller [12].

Results show that the estimated control function by using conjugate gradient method did not exhibit oscillatory behavior in the inverse calculations for a broad range of front velocity while in [12] the inverse solutions are very sensitive to phase front velocity, therefore the application of future time stepping [2] is necessary in [12].

The advantage of applying this algorithm in inverse analysis lies in its stability as compared to the conventional minimization process [12]. Artificial future time stepping is unnecessary during the inverse calculation, since it is still an uncertainty in the inverse analysis. Furthermore, the inverse solutions obtained by the present method are found to be more accurate than the solutions obtained by the conventional minimization process.     

Thermal deformation in a thin circular plate due to a partially distributed heat supply

In this paper, we develop an integral transform to determine temperature distribution in a thin circular plate, subjected to a partially distributed and axisymmetric heat supply on the curved surface, and study the thermal deformation. The results, obtained in series form in terms of Bessel’s functions, are illustrated numerically.     

压电材料变分原理逆问题的研究——动力学中的逆问题

研究了压电材料耦合动态场中Hamilton 型和Gurtin 型变分原理的逆问题。采用变积方法, 建立了各级变分原理和广义变分原理, 为建立横观各向同性压电材料的动力学有限元分析模型提供了依据。      

The Conjugacy Search Problem in Public Key Cryptography: Unnecessary and Insufficient

The conjugacy search problem in a group G is the problem of recovering an from given and h = x ⁻¹ gx. This problem is in the core of several recently suggested public key exchange protocols, most notably the one due to Anshel, Anshel, and Goldfeld, and the one due to Ko, Lee et al. In this note, we make two observations that seem to have eluded most people’s attention. The first observation is that solving the conjugacy search problem is not necessary for an adversary to get the common secret key in the Ko–Lee protocol. It is sufficient to solve an apparently easier problem of finding such that h = ygx for given . Another observation is that solving the conjugacy search problem is not sufficient for an adversary to get the common secret key in the Anshel–Anshel–Goldfeld protocol.     

Selecting and assessing challenge problems

Abstract

Organisations conducting research programs often focus the work of their scientists and technologists on challenge problems (CPs). These challenges are designed to ensure that progress is measurable and relevant to the goals of the program sponsor. Generating and selecting pertinent CPs is difficult, as is assessing their value. We describe a method of generating and selecting CPs and its application in a highly collaborative, multi-organisation research program. Thirty-eight biologists, chemists, mathematicians and computer scientists across academic, commercial and government organisations generated and ranked their top choices from among 12 richly described candidate challenge problems. A ranked-choice voting formula was applied. Five CPs were highly scored; the remaining seven were distributed across a lower range of scores. The program sponsor subsequently directed researchers to address six CPs, including the elected five. Analysis of the rationales that participants offered for their CP rankings revealed four domain-independent dimensions of value: capability, speed, impact and synergy. These dimensions of value can help managers of interdisciplinary research programs systematically select a portfolio of CPs that will efficiently apply utilise resources towards program goals and facilitate measurement of scientific progress.     

特殊圈上的逆1-maxian问题

逆1-maxian问题主要研究如何在一定的预算下修改网络中边的长度,使得其他所有顶点到预先给定顶点的距离之和尽可能的大.研究了特殊4-圈上的逆1-maxian问题,得到了该问题在任意预算下的最优解.然后,将问题推广到特殊n-圈的情形.最后,得到Hamming距离下特殊n-圈情形的一个最优解.     

非拉梅问题的过盈配合结构装配应力的研究

对于经过盈装配而结成一体的构件,在装配过程中所产生的“装配应力”,往往与“工作应力”是同一数量级甚至在某些情况下大于“工作应力”。故而在对这类结构进行强度计算和结构设计中,装配应力是不容忽视的因素。因此,探究和获得装配应力可靠的计算方法具有重要的理论意义和实用价值。对于不同等长度的包容件,被包容件结成一体的过盈配合结构,其装配应力的可靠计算方法,一直未获得解决。作者对此进行了研究探讨、做了大量计算并经试验验证,满意地解决了对任意形状的轴对称过盈配合结构的装配应力计算问题。     

A multi-population genetic algorithm approach for solving ill-posed problems

In this paper we develop a multi-population genetic algorithm (GA) for regularizing nonlinear ill-posed problems. Real coded genetic algorithms are used for calculating the minimizers of the Tikhonov functional. The algorithm is based on evolving separate populations for various values of the regularization parameter. The rate of convergence of the algorithm is substantially increased by exchanging information between neighbouring populations by the process of migration.     

AN INVERSE PROBLEM IN PREDICTING TEMPERATURE DEPENDENT HEAT CAPACITY PER UNIT VOLUME WITHOUT INTERNAL MEASUREMENTS

An inverse analysis utilizing the conjugate gradient method and the minimization of adjoint equation is used successfully to estimate the temperature dependent heat capacity per unit volume in a homogeneous medium. No prior information is available on the functional form of the unknown heat capacity in the present study, thus, it is classified as the function estimation in inverse calculation. The accuracy of the inverse analysis is examined by using simulated exact and inexact measurements obtained within the medium. Results show that an excellent estimation on the heat capacity per unit volume can be obtained by using just boundary measurements (i.e. internal measurements are unnecessary) and the CPU time used in VAX-9420 computer is less than one second. The advantages of applying this algorithm in inverse analysis can greatly simplify the experimental set-up, diminish the sensitivity to the measurement errors and reduce the CPU time in inverse calculation, while the reliable predictions can still be achieved.     

Multi-item production routing problem with backordering: a MILP approach

The aim of this paper is to present mixed integer linear programming formulations for the production routing problem with backordering (PRP-B) and a new hybrid heuristic to solve the problem. The PRP-B is considered in the context of a supply chain consisting of a production facility with limited production and storage capacities and geographically dispersed points of sale with limited storage capacities. The PRP-B integrates multiple item lot sizing decisions and vehicle routing decisions to the points of sale, where backordering of end customer demands is allowed at a penalty. Two integrated mixed integer programming models are formulated and a solution procedure consisting of a relax-and-fix heuristic combined with a local search algorithm is proposed. The numerical results show that this hybrid heuristic outperforms a state-of-the-art MIP commercial solver, in terms of solution quality and CPU times.     

Multiple-choice knapsack-based heuristic algorithm for the two-stage two-dimensional cutting stock problem in the paper industry

This study examines a two-stage two-dimensional cutting stock problem encountered by a paper mill company. The problem includes various machine-related and operational constraints based on real-world situations. Paper products are manufactured using two major cutting processes. Each cutting machine has a specific minimum and maximum width for input and output rolls and is limited by the maximum number of rolls it can cut at the same time. A mathematical model is presented to formally address the problem and an efficient multiple-choice knapsack-based heuristic algorithm is proposed to solve the problem. To demonstrate the efficiency of the proposed heuristic algorithm, computational experiments are conducted on test data-set generated from real-world data provided by a large paper mill company in the Republic of Korea.     

Inverse analysis for evaluation of the shear modulus of inhomogeneous media by torsion experiments

The present paper addresses the problem on torsion of a circular indentor with a flat base on a half-space covered by an inhomogeneous coating with shear modulus arbitrarily varying in-depth. Approximate analytical solution of this problem is developed. The obtained formulas allow one to determine the distribution of contact stresses under indentor, as well as the dependence of the torsion moment applied to the indentor from the twisting. It is shown that the approximate formulas are asymptotically exact both at large and small values of characteristic dimensionless geometrical parameter of the problem.Based on the analysis of the derived solution, we suggest evaluation technique for the shear modulus of a functionally-graded coating in the case when it depends on one parameter only. The technique uses the data received in the course of torsion experiments by a series of indentors of various radii.     

广义欧几里德Steiner问题的研究与进展

广义欧几里德Steiner问题足指确定连接平面上一组给定点的满足特定连通性要求的最短网络的问题。本文主要介绍了比问题的研究与进展,在建立了求给定平面点集的最矩U-连通(或边连通)生成网络的整数规划模型的基础上,证明了文献[13]中所给的一个例子是错误的,并提出了一些关于广义Steiner问题的进一步研究的问题。     

两种解振动反问题算法的同一性及应用

根据矩阵最佳逼近与加权残值理论，把求解振动反问题时所使用的矩阵逼近法和极值化算法统一为不同范数定义下的最小二乘问题，这对部分振频和／或振型给定情况下振动反问题的求解提供了一个有效工具。结合某大型飞机机翼颤振吹风模型的动力设计，本文给出了工程应用的具体数值例子。大量的算例结果表明：与矩阵逼近法具有同一性的极值化方法计算精度和计算效率很高，可直接用于工程实际。     

Improved Identification Schemes Based on Error-Correcting Codes

As it is often the case in public-key cryptography, the first practical identification schemes were based on hard problems from number theory (factoring, discrete logarithms). The security of the proposed scheme depends on an NP-complete problem from the theory of error correcting codes:the syndrome decoding problem which relies on the hardness of decoding a binary word of given weight and given syndrome. Starting from Stern’s scheme [18], we define a dual version which, unlike the other schemes based on the SD problem, uses a generator matrix of a random linear binary code. This allows, among other things, an improvement of the transmission rate with regards to the other schemes. Finally, by using techniques of computation in a finite field, we show how it is possible to considerably reduce: — the complexity of the computations done by the prover (which is usually a portable device with a limited computing power), — the size of the data stored by the latter. Received March 10, 1995; revised version December 1, 1995