An enhanced Gauss-Newton inversion algorithm using a dual-optimal grid approach

We developed two algorithms for solving the nonlinear electromagnetic inversion problem in the Earth. To achieve a balance between efficiency and robustness, both algorithms employ the Gauss-Newton inversion method. Moreover, to speed up the inversion's computational time, the so-called optimal grid technique is utilized. The first algorithm uses a forward solver with a very coarse optimal grid to calculate the Jacobian matrix. Hence, in this scheme we employ two different sets of optimal grids. One set is used to compute the data mismatch to be minimized and the other set is used to construct the Jacobian matrix. In the second approach we use a fixed-point iteration process where the inverse kernel is approximated on a coarse optimal grid that does not significantly compromise accuracy. The advantage of these optimal grids is that they considerably reduce the computation time without compromising accuracy. Numerical examples for two-dimensional axially symmetric and three-dimensional anisotropic configurations are used to demonstrate the advantage of using both algorithms over the standard Gauss-Newton inversion method.     

On computer communication network reliability under programexecution constraints

The authors propose a technique to compute software system reliability (SSR). The method, called FARE (fast algorithm for reliability evaluation), does not require a priori knowledge of multiterminal connections (MCs) for computing the reliability expression. An effort is made to sole the problem of N-version programming by using the FARE approach. Owing to its short execution time and low memory requirement, FARE can be used to calculate the SSR of fairly large distributed systems     

ESCAF?A New and Cheap System for Complex Reliability Analysis and Computation

ESCAF stands for ``Ensemble de Simulation et de Calcul de Fiabilité' - (``Electronic Simulator to Compute and Analyze Failures'). This paper describes the apparatus and illustrates, with examples, the multiple possibilities afforded to system design engineers, reliability engineers, and researchers: 1. Simulating and analyzing, directly or through fault trees, complex systems with as many as 416 components. 2. Simulating and analyzing networks with 2-way information flow. 3. Studying sequential circuits and flow networks. An exceptionally simple, cheap, and easy-to-use apparatus, ESCAF is employed typically to determine and list cut sets and (for s-coherent systems) minimal cut sets, or path sets and minimal path sets; to gauge the importance of each component or event by constructing histograms; to compute system failure probability or unavailability, for both s-coherent and non-coherent systems; and to detect potential weak-points in design. An optional diode plug programming matrix allows common-cause failures to be studied. To analyze a system with ESCAF, it is simulated very simply by standard integrated circuits mounted on one or more special cards. When inserted in the 440 × 226 × 470 mm basic ESCAF unit, these cards are automatically connected to a failure combination generator. This circuit generates all combinations of component failures (or fault tree basic events), first one-by-one, then two-by-two, and so on. The ESCAF processing unit analyzes the resulting system output states and derives the wanted information. The basic ESCAF unit is connected to one or two standard peripherals (visual display unit, printer, punched tape or diskette, etc.     

网络端端可靠度的上下界计算研究

考虑精确计算较大规模网络的端端可靠度属于NP—hard问题,提出一种计算网络端端可靠度的近似方法,算法分别基于最小路集和不交最短路集来计算网络端端可靠度的上下界,并在此基础上给出了示例来阐明算法的有效性,该计算方法的算法实现简单,能快速计算出网络的端端相对可靠度。     

Efficient algorithms for k-out-of-n andconsecutive-weighted-k-out-of-n:F system

A new reliability model, consecutive-weighted-k-out-of-n:F system, is proposed and an O(n) algorithm is provided to evaluate its reliability. An O(n·min(n,k)) algorithm is also presented for the circular case of this model. The authors design an O(n) parallel algorithm using k processors to compute the reliability of k-out-of-n systems, that achieves linear speedup     

Reliability Analysis of Phased-Mission System With Independent Component Repairs

This paper proposes a hierarchical modeling approach for the reliability analysis of phased-mission systems with repairable components. The components at the lower level are described by continuous time Markov chains which allow complex component failure/repair behaviors to be modeled. At the upper level, there is a combinatorial model whose structure function is represented by a binary decision diagram (BDD). Two BDD ordering strategies, and consequently two evaluation algorithms, are proposed to compute the phased-mission system (PMS) reliability based on Markov models for components, and a BDD representation of system structure function. The performance of the two evaluation algorithms is compared. One algorithm generates a smaller BDD, while the other has shorter execution time. Several examples, and experiments are presented in the paper to illustrate the application, and the advantages of our approach.     

A generalized algorithm for evaluating distributed-programreliability

A one-step algorithm, GEAR (generalized evaluation algorithm for reliability), is introduced that computes the reliability of a distributed computing system (DCS), which usually consists of processing element, memory unit, input/output devices, data-files, and programs as its shared resources. The probability that a task or an application can be computed successfully by sharing the required resources on the DCS is termed the system reliability. Some of the important reliabilities defined using the above concept are discussed, including terminal-pair, computer-network, distributed-program, and distributed-system. GEAR is general enough to compute all four of these parameters, and does not require any prior knowledge about multiterminal connections for computing reliability expression. Many examples are included to illustrate the usefulness of GEAR for computing reliability measures of a DCS     

Computing support-minimal subfunctions during functionaldecomposition

The growing popularity of look-up table (LUT)-based field programmable gate arrays (FPGA's) has renewed the interest in functional or Roth-Karp decomposition techniques. Functional decomposition is a powerful decomposition method that breaks a Boolean function into a set of subfunctions and a composition function. Little attention has so far been given to the problem of selecting good subfunctions after partitioning the input variables into the disjoint bound and free sets. Therefore, the extracted subfunctions usually depend on all bound variables. In this paper, we present a novel decomposition algorithm that computes subfunctions with a minimal number of inputs. This reduces the number of LUT's and improves the usage of multiple-output SRAM cells. The algorithm iteratively computes subfunctions; in each iteration step it implicitly computes a set of possible subfunctions and finds a subfunction with minimal support. Moreover, our technique finds nondisjoint decompositions, and thus unifies disjoint and nondisjoint decomposition. The algorithm is very fast and yields substantial reductions of the number of LUT's and SRAM cells     

Computing multivalued input-output Characteristics in the circuits containing bipolar transistors

The paper deals with dc circuits including bipolar transistors represented by the Ebers-Moll model. An important question how to efficiently compute multivalued input-output characteristics of these circuits is considered. A switching variables approach for tracing a multivalued single-branched characteristic, which can be considered as some kind of continuation method, is developed. A new strategy of switching variables is proposed and the generalized implicit function theorem is used as the mathematical background. Unfortunately, this approach suffers from major shortcomings when it is directly applied to bipolar transistor circuits, due to specific nonlinearities of the transistor model, causing the sharp-turning-point problem. To overcome this problem, a variable transformation is proposed, which leads to smooth solution curves. An efficient algorithm combining the developed variant of switching variable method with the proposed transformation is described. A generalized version of the algorithm enables us to compute multivalued characteristics composed of disconnected branches, under the assumption that at least one point on each branch can be found. It is illustrated via four examples of realistic transistor circuits including a voltage regulator, the Schmitt trigger, a line receiver, and their combination.     

A computation method for evaluating importance-measures of gates ina fault tree

This paper extends the Birnbaum importance measure for a basic-event level to a gate-event level. In a fault tree when statistical dependency between gate events exists. An explicit formula is given for gate reliability importance (GR-Imp), and shows how it can compute GR-Imp by using a conventional fault-tree algorithm. The computational algorithm for GR-Imp is given along with numerical results for illustrative examples     

Analysis of multiple FSS screens of unequal periodicity using an efficient cascading technique

In this paper, we present an efficient cascading procedure for analyzing frequency selective surface (FSS) systems consisting of multiple FSS screens of unequal periodicity embedded in multiple dielectric layers. In this procedure, we first find a global period for the FSS system by studying the composite in its entirety. Next, we compute the scattering matrix [S] of each of the FSS subsystems for the global Floquet harmonics by applying a relationship we establish that maps the [S] matrix of the subsystem for the individual Floquet harmonics to that for the global harmonics. This mapping-cum-filling process substantially reduces the effort needed to compute the [S] matrix of a subsystem. Finally, we compute the [S] of the entire system by applying a modified cascading formulation, in which one matrix inversion step is eliminated, resulting in a reduction in the total computing resource requirement as well as time. Two numerical examples are given to illustrate the efficiency and effectiveness of the technique.     

Classification of unilateral vocal fold paralysis by endoscopic digital high-speed recordings and inversion of a biomechanical model

Hoarseness in unilateral vocal fold paralysis is mainly due to irregular vocal fold vibrations caused by asymmetries within the larynx physiology. By means of a digital high-speed camera vocal fold oscillations can be observed in real-time. It is possible to extract the irregular vocal fold oscillations from the high-speed recordings using appropriate image processing techniques. An inversion procedure is developed which adjusts the parameters of a biomechanical model of the vocal folds to reproduce the irregular vocal fold oscillations. Within the inversion procedure a first parameter approximation is achieved through a knowledge-based algorithm. The final parameter optimization is performed using a genetic algorithm. The performance of the inversion procedure is evaluated using 430 synthetically generated data sets. The evaluation results comprise an error estimation of the inversion procedure and show the reliability of the algorithm. The inversion procedure is applied to 15 healthy voice subjects and 15 subjects suffering from unilateral vocal fold paralysis. The optimized parameter sets allow a classification of pathologic and healthy vocal fold oscillations. The classification may serve as a basis for therapy selection and quantification of therapy outcome in case of unilateral vocal fold paralysis.     

Performability of the hypercube [reliability]

The authors address the problem of modeling and evaluating the composite performance and reliability measures (performability) of a hypercube architecture running a specific application. A generalized stochastic Petri net (GSPN) is used to model the component failures and repairs in the hypercube. The GSPN model defines the dimension and number of subcubes available for the application. This model generalizes previously proposed models for hypercube reliability and automatically generates the underlying Markov chain needed for performability analysis. A novel performability analysis algorithm is presented that computes both the moments and the distribution of performability in O( N³). The algorithm is conceptually simpler than those previously reported. An example is given to illustrate the modeling process and demonstrate the importance of performability analysis for mission-critical systems     

A generalized SSI reliability model considering stochastic loading and strength aging degradation

A generalized stress-strength interference (SSI) reliability model to consider stochastic loading and strength aging degradation is presented in this paper. This model conforms to previous models for special cases, but also demonstrates the weakness of those models when multiple stochastic elements exist. It can be used for any nonhomogeneous Poisson loading process, and any kind of strength aging degradation model. To solve the SSI reliability equation, a numerical recurrence formula is presented based on the Gauss-Legendre quadrature formula to calculate multiple integrations of a random variable vector. Numerical analysis of three examples shows this SSI reliability model provides accurate results for both homogeneous & nonhomogeneous Poisson loading processes.     

An Improved Moment-Matching Algorithm for Evaluating Top-Event Probability Bounds

This paper proposes improvements in the momentmatching algorithm developed by Apostolakis & Lee (A&L algorithm). The moment-matching method in the A&L algorithm evaluates reliability uncertainty by: 1) assuming that system reliability is governed by the Johnson SB distribution; and 2) calculating reliability bounds by using the moment-matching method, given the reliability mean value and variance. The proposed (T.S.S.) algorithm deletes the singular points and the strict peak in the numerical integration by variable transformation in step 2 above, and uses Newton's method in the convergence calculation. As a result, an increase in calculation accuracy and reduction of computation time are realized. Some numerical examples demonstrate the effect of the T.S.S. algorithm.     

Preprocessing minpaths for sum of disjoint products

Network reliability algorithms which produce sums of disjoint products (SDP) are sensitive to the order in which the minimal pathsets are analyzed. The minpaths are preprocessed by choosing this order in the hope that an SDP algorithm will then provide a relatively efficient analysis. The most commonly used preprocessing strategy is to list the minpaths in order of increasing size. This paper gives examples for which this strategy is not optimal. A new preprocessing strategy which works well for SDP algorithms with single-variable inversion (SVI) is introduced. It is also observed that optimal preprocessing for SVI-SDP can be different from optimal preprocessing for SDP algorithms which use multiple-variable inversion; one reason for this is that MVI-SDP algorithms handle disjoint minpaths much more effectively than SVI-SDP algorithms do. Both kinds of SDP algorithms profit from prior reduction of elements and of subsystems which are in parallel or in series.     

The Influence of Initial-Phases of a PN Code Set on the Performance of an Asynchronous DS-CDMA System

The authors point out the need forfixed PN code sets for test purposes from thestandpoint of numerical analysis and simulation of anasynchronous DS–CDMA system and its sub-system units.An agreement on test sequence sets and their initialphases for fixing the probability distributionfunction of the multiple-access interference (MAI)random variable is necessary in order to make thenumerical performance results of different researchgroups and authors commensurable in large systemdesign projects and in the CDMA literature. Theconclusions are drawn from numerical examples ofinitial-phase optimization with the AO/LSE, LSE/AO,MSE/AO, CO/MSQCC and MSQCC/CO criteria, and byreviewing the literature. Optimization criteria arecompared from the standpoint of minimum MAI.Conclusions are drawn from their order of quality andthe conditions under which the optimization ispracticable. Finally, some binary and quadri-phase PNcode sets for fixing the MAI signal component for testpurposes are reviewed.     

计算无圈有向网络ST可靠性的一个新方法

本文考虑计算无圈有向网络的ＳＴ可靠性问题（至少存在一条从源点ｓ到汇点ｔ的正常运行道路的概率）。文章引进了深度优先搜索（Ｄｅｐｔｈ－ＦｉｒｓｔＳｅａｒｃｈ）有序根树的概念并提出一个新的计算无圈有向网络ＳＴ可靠性的拓扑公式。以该公式为基础,我们利用ＤＦＳ方法提出一个新的计算无圈有向网络ＳＴ可靠性算法,它能生成简洁的可靠性表达式,进而有效地计算无圈有向网络的ＳＴ可靠性。两个例子例证了我们的结论     

多观测样本联合信息加权稀疏表示分类算法

多观测样本分类问题中,同一对象的多观测样本均看作一个整体进行识别,其同等看待各个观测样本。考虑到其每个观测样本包含判别信息量不同,针对如何有效利用其可信度问题,提出基于观测样本联合加权稀疏表示多观测样本分类算法。首先将多多观测样本分解成单样本,分别对各个样本进行稀疏求解得到其各自的稀疏度和残差,进而联合二者确定其相应可信度。然后给各观测样本进行可信度加权,重构出加权多观测样本。最后,再采用整体稀疏表示对其进行分类。在ETH-80物体数据库、CMU-PIE人脸数据库和BANCA数据库上进行大量对比实验,实验结果证明该算法的有效性,提高识别精度的同时使算法的鲁棒性得到保证。