The Analysis of a Production Line with Unreliable Machines and Random Processing Times

This paper develops an efficient analytical method for the analysis of an n-machine production line with unreliable machines and random processing times. The behavior of the n-machine line is approximated by the behaviors of the (n — l) two-machine lines based on the decomposition. Simulation and numerical experiment show that the analytical method works well and is very efficient.     

带有止步和状态相依的M／Hk／1排队系统——矩阵几何解法

本文研究了带有止步和状态相依的M/Hk/1排队系统,建立了排队模型的拟生灭过程并获得了系统的平衡条件.利用拟生灭过程理论得到系统稳态概率的矩阵几何解.通过求解分块矩阵方程组,给出了系统边界状态概率的迭代计算公式.在此基础上,得到了系统的平均队长,平均等待队长和平均止步率等一些性能指标.     

Automatic Petri Net Simulation Model Generation for a Continuous Flow Transfer Line with Unreliable Machines

A production line is studied with several machines in series. The machines are separated with finite buffers. They can break down and have to be repaired. Production is assumed to be continuous, i.e. no individual products can be identified. Analytical models for the performance evaluation of such a system are scarce. Analytical results for the throughput can be obtained only under very restrictive assumptions. The performance study of longer transfer lines requires either approximation or simulation. A Petri net model is developed for an n‐machine ‐buffer system. The rules to design the Petri net transitions are given. The automatic generation of a discrete‐event simulation model from the Petri net model is explained. Finally, some potential applications of the Petri net are illustrated. These applications include the simulation of transfer lines with complex stochastic behaviour, the optimization of buffer size and allocation and the evaluation of approximation models for long transfer lines. Using the simulation model described in this paper, quality and reliability engineers can simulate the performance of a given continuous flow transfer line and evaluate the effect of performance‐increasing measures such as the insertion of extra buffer space or the use of more reliable machines. Copyright © 2004 John Wiley & Sons, Ltd.     

滑动回归最小二乘算法在某电动振动台模型辨识中的应用

在分析电动振动台数学模型的基础上,利用先进的滑动回归最小二乘辨识算法,有效地开展了电动振动台这一复杂电力学系统阶数和时延的确认、参数估计,并建立了系统的ARMA模型.给出了某型电动台空台面和另一型振动台带滑台的模型辨识结果,并通过正弦扫频试验实例给出了模型验证.结果表明,该算法辨识精度高,收敛速度快,鲁棒性强,抗噪声能力强,在电动振动台系统辨识上能取得良好的效果.     

An Efficient Algorithm for Analysis of Transfer Lines With Unreliable Machines and Finite Buffers

In a recent paper [3], Gershwin proposed a decomposition method for the approximate analysis of transfer lines with unreliable machines and finite buffers. The method is based on a decomposition of the line into a set of two-machine lines. It leads to a set of equations which are solved using an iterative algorithm. Experimental results have shown that this technique is very accurate. However, it may happen that the algorithm fails to converge. In this paper, we propose to replace the original set of equations by an equivalent one, which is again solved using an iterative procedure. This new algorithm is simpler than the previous one, and its computational complexity is lower. Moreover, on all examples we tested, the algorithm always converged.     

A Simple Recursive Algorithm for Simultaneous Magnitude and Frequency Estimation

A new approach in the design of digital algorithms for simultaneous local system magnitude and frequency estimation of a signal with time-varying frequency is presented. The algorithm is derived using the maximum likelihood method. The pure sinusoidal voltage model was assumed. The investigation has been simplified because the total similarity to the state of the problem of dc offset and frequency estimation has been noticed. Finite impulse response (FIR) digital filters are used to minimize the noise effect and to eliminate the presence of harmonic effects. The algorithm showed a very high level of robustness, as well as high measurement accuracy over a wide range of frequency changes. The algorithm convergence provided fast response and adaptability. This technique provides accurate estimates in about 25 ms and requires modest computations. The theoretical bases of the technique are described. To demonstrate the performance of the developed algorithm, computer-simulated data records are processed. The proposed algorithm has been tested in a laboratory to establish its feasibility in a real-time environment.     

Numerical Solution of the Dielectric Equation for a Coaxial Line

Dielectric measurements using a coaxial transmission line terminated by a shielded open circuit give rise to the transcendental equation z tan z = c, where c = a + jb is a measured quantity. Since a ? 0, Newton's method will rapidly converge to one of the roots unless it gets trapped in an attractive cycle. Regions containing the lowest and second-lowest roots are sketched. Moreover, starting values are given in terms of the quantity c so that the method will converge to the desired root among the first four roots and also avoid attractive cycles. Using high-precision arithmetic, the error in z may be estimated numerically in terms of the error in c.     

Parametric Wave-Aberration Retrieval from Point-Spread Function Data by use of a Pyramidal Recursive Algorithm

A new, to my knowledge, procedure for retrieving the wave aberration from the point-spread function is presented. It uses the Levenberg-Marquardt optimization algorithm in a mutiresolution pyramidal scheme. The method, tested with simulated large aberrations without initial estimates, accelerates convergence and avoids stagnation in local minima.     

非线性系统非平稳随机响应矩计算的Newmark递推算法

利用Ｎｅｗｍａｒｋ离散化格式，结合时变等价线性化步骤，导出了计算非线性系统受白噪声和非白噪声随机激励作用下非平稳响应协方差矩阵的递推算法。该算法计算步骤简单，易于在计算机上实现，计算效率高。算例表明，其所得计算结果和ＭｏｎｔｅＣａｒｌｏ模拟结果符合较好。     

一种有效的机场安检X光手提行李图像两级增强方法

针对低对比度X光手提行李图像在机场安检中容易产生高虚警或高漏警的问题,提出了一种两级X光图像增强方法.首先,应用离散小波变换和独立分量分析方法对低能和高能X光图像去噪并融合,实现一级增强.然后,利用本文提出的自适应正弦灰度变换实现二级增强.实验结果表明,本文方法能够有效地改善图像质量,优于文中给出的其它增强方法,更有利...     

Approximating Performance Measures for a Network of Unreliable Machines

Manufacturing facilities have machines that are subject to random breakdowns. The machines, which are located at different geographical locations, have to be repaired by a service unit who operates from a service center. Therefore, the travel time becomes an important part of the total service time. This paper contains approximate models to evaluate the system performance when the service unit does not have to return to the service center after every service, i.e., it can go directly from one machine to the next waiting in the queue. For most cases of practical interest, this problem is too complex to be solved exactly. Therefore, approximate models to calculate the performance measures of interest, for example system uptime or mean downtime, are important.     

连接不相交线段成简单多边形(链)的算法

提出一个实际问题，即如何连接平面上h条线段成一简单多边形或者简单多边形链，并证明了连接平面上线段集S成一简单多边形链的一个充分条件，S中有一条线段连接凸壳CH（S）中不相邻顶点，另外还提出了连接平面上线段集S成一简单多边形或者简单多边形链的算法，其基本思想是首先逐层计算线段集S的凸壳，并将这些凸壳改变多边形；然后计算各多边形之间的交点，进而删去这些交点。最后合并若干个简单多边形为一个简单多边形，当S中线段数目n较大时，用分治思想可以设计分治算法，较好地求解了这个问题，利用计算机求解这个问题上有实际应用价值。     

图象序列中检测运动小目标的递归算法

分析了一种基于卡尔曼滤波理论的时域递归低通滤波算法。这种算法根据运动小目标,背景干扰和噪声在图象序列中的差异,能够抑制背景,增强小目标并将其从相对静止的背景中有效地分离出来。在恒虚警概率条件下,该算法可以在低信噪比的情况下,减小背景干扰和随机噪声的影响,提高信噪比,选取适当的阈值,能够得到清晰的小目标轮廓,通过仿真验证了这种算法的有效性     

TIDSS问题处理器的研究与实现

本文阐述了TIDSS(Test Intelligent Decision Support System-TIDSS)系统中核心部件问题处理器(PPS)的设计方法,提出了具有广义的智能问题处理器(IPPS的系统结构和一种问题求解的方法,并且经过实践检验,证明是正确的。     

基于2D-WLDH和最大类间方差的图像阈值分割及其快速递推算法

本文提出了一个新的二维直方图(2D-WLDH),同时提出了基于2D-WLDH和最大类间方差的图像阈值选取方法,并导出相应快速递推算法。新提出的2D-WLDH在区域划分时可以避免传统直方图区域划分时面临的不合理的假设,通过计算比较小的归一化的WLD值来准确估计目标和背景的概率。本文实验结果表明:与现有的有关算法相比,本文提出的阈值选取快速递推算法不仅使分割后的图像区域内部更均匀、边界形状更准确、抵抗噪声稳健,而且同时其运行时间还减少了约84.93%。     

三维场量的等值线生成算法

提出了一种八节点六面体单元的三维场量等值线生成方法.经实例验证,该三维场量等值线生成方法是合理、有效的.     

求平面点集独立线段的一个联机算法

令Ｓ为一个有限平面点集合，线段Ｌ（ｐ，ｑ），ｐ，ｑ∈Ｓ称为Ｓ的一个独立线段当且仅当不存在两个端点在Ｓ中的线段与Ｌ（ｐ，ｑ）相交。本文给出了时间复杂度为Ｏ（ｎ＾２ｌｏｇｎ）和修正时间复杂度为Ｏ（ｎｌｏｇｎ）的联机算法。这一算法与已知的脱算法具有相同的时间复杂度。     

Recursive Computation of Free Resolutions and a Generalized Koszul Complex

This article describes a new algorithm to compute a free resolution of an ideal of (or module over) a commutative ring R combining the Koszul complex with Groebner basis methods. The algorithm computes the resolution of an ideal I via the resolutions of a sequence of subideals differing by one generator each time. The article discusses special orderings and criteria applicable to this algorithm and gives some timings based on an implementation within the computer algebra system Singular. Keywords:Free resolution, Koszul complex, Syzygies, Groebner basis algorithm.     

不规则三角网递归生长算法过程的动态实时可视化

可视化技术目前常常用于科学计算的结果展示.针对不规则三角网(TIN:Triangulated Irregular Network)递归生长算法,提出将可视化技术从应用于TIN生成结果扩展到应用于TIN生成过程的思想,探讨了面向过程动态实时可视化的内容,将图元可视化内容归纳为颜色、尺寸、位置和文本4种状态.结合Delaunay三角网的递归生长算法,深入研究了活动图元的位置状态问题,利用OpenGL验证了动态实时可视化的可行性.这一思想可有效支持TIN相关算法的研究与设计.