Modeling a shared-load k-out-of-n:G system

A Markov model for analyzing the reliability and availability of an n-unit shared-load repairable k-out-of-n:G system with imperfect switching is presented. The equations for both time-dependent and steady-state system availability are given. An inverse Laplace transform is used to solve the simultaneous differential equations for the nonrepairable case. A generalized analytic function for system reliability is obtained. Examples are provided to demonstrate the model and the impact of a load-sharing strategy on the reliability. The load-sharing strategy can improve system reliability and availability, if the controller and switching parameters are adequate. The proposed approach and solution are helpful to system engineers and reliability analysts     

A hybrid model for weekday replacements with infant mortality failures

A hybrid availability model of a repairable system with infant mortality failures is proposed. The hybrid model can efficiently represent different types of state transitions by the use of a hierarchy of models: (1) a time-discretized component submodel, which provides a piecewise-linear failure rate during an operating interval; (2) a phased-mission model, which transforms the state probability vector according to repair activity; and (3) a combinatorial model, which is used to predict the number of working units among a collection of identical components. The modeling approach is illustrated by predicting the expected number of working components for a multiple-component system where replacement components are ordered at the end of business hours each weekday end. Replacement occurs on the next weekday morning.     

Simple S-parameter model for receiving antenna array

A simple S-parameter model is described for a receiving antenna array. The model is useful in studying the effect of system imperfections such as mutual coupling between antenna elements and mismatch of circuit components on the performance of an adaptive array     

A global model for rapid thermal processors

A simple model for the components that make up a rapid thermal processing system is given. These components are the furnace, the pyrometer used to measure temperature, and the control system that utilizes the pyrometer measurement to control the power to the lamps. The models for each of the components are integrated in a numerical code to give a computer simulation of the complete furnace operation. The simulation can be used to investigate the interaction of the furnace, temperature-sensing technique, and the control system. Therefore, the interplay of heat transfer (furnace) properties, optical (pyrometer) parameters, and control gains can be studied. The objective is to define variability in wafer temperature as process parameters change. The following three applications of the model are included: (1) a simulation of open-loop operation; (2) a simulation of the ramp up and subsequent operation with a step change in wafer optical properties; and (3) a simulation of the rapid thermal chemical vapor deposition of polysilicon on silicon oxide which demonstrates the applicability model for actual processes. A technique for correction of pyrometer output to improve temperature control is also presented     

A model for system reliability with common-cause failures

A model for the analysis of systems subject to common-cause failures is proposed. The system consists of a finite number of components that are subject to: (1) statistically independent failures, and (2) external failure causes (they need not be mutually statistically independent) for groups of components. Applications to fault-tree analysis and network reliability problems are discussed     

Automatic digital correction of measurement data based onM-point autocalibration and inverse polynomial approximation

A microprocessor-controlled measurement system model comprising m-point autocalibration and inverse polynomial approximation of the measurement-system transfer characteristics is described. A voltage-to-frequency converter is used for an analog-to-digital conversion of an input quantity. The model is restricted to measurements of slow-varying analog input quantities, and it is suitable for application in severe temperature conditions, common to a variety of industrial environments. By utilizing the computing power of microprocessors, a higher accuracy of measurements can be achieved with low-performance electronic components     

A reliability model of a system with dependent components

A model of a multi-component system with dependent components in the time stationary case is presented. A procedure fits the parameters of the model with respect to given data such as the correlation coefficients. The system reliability of the fitted model is evaluated     

Applications of SPICE for modeling miniaturized biomedical sensor systems

This paper proposes a model for a miniaturized signal conditioning system for biopotential and ion-selective electrode arrays. The system consists of three main components: sensors, interconnections, and signal conditioning chip. The model for this system is based on SPICE. Transmission-line based equivalent circuits are used to represent the sensors, lumped resistance-capacitance circuits describe the interconnections, and a model for the signal conditioning chip is extracted from its layout. A system for measurements of biopotentials and ionic activities can be miniaturized and optimized for cardiovascular applications based on the development of an integrated SPICE system model of its electrochemical, interconnection, and electronic components.     

Dependability analysis of systems with on-demand and active failuremodes, using dynamic fault trees

Safety systems and protection systems can experience two phases of operation (standby and active); an accurate dependability analysis must combine an analysis of both phases. The standby mode can last for a long time, during which the safety system is periodically tested and maintained. Once a demand occurs, the safety system must operate successfully for the length of demand. The failure characteristics of the system are different in the two phases, and the system can fail in two ways: (1) it can fail to start (fail on-demand), or (2) it can fail while in active mode. Failure on demand requires an availability analysis of components (typically electromechanical components) which are required to start or support the safety system. These support components are usually maintained periodically while not in active use. Active failure refers to the failure while running (once started) of the active components of the safety system. These active components can be fault tolerant and use spares or other forms of redundancy, but are not maintainable while in use. The approach, in this paper, automatically combines the "availability analysis of the system in standby mode" with the "reliability analysis of the system in its active mode." The general approach uses an availability analysis of the standby phase to determine the initial state probabilities for a Markov model of the demand phase. A detailed method is presented in terms of a dynamic fault-tree model. A new "dynamic fault-tree construct" captures the dependency of the demand-components on the support systems, which are required to detect the demand or to start the demand system. The method is discussed using a single example sprinkler system and then applied to a more complete system taken from the off-shore industry     

基于DEVS的分布式仿真构件形式描述

构件理论在分布式仿真领域正扮演着越来越重要的角色.为了规范化地描述和设计仿真构件,基于离散事件系统规范对构件进行了研究.通过扩展经典离散事件系统规范,形式化地定义了仿真原子构件模型和耦合模型,并对构件的组合过程和机制进行了研究.通过定理证明,该仿真耦合构件具有耦合封闭性,使得可以通过仿真原子构件和耦合构件不断地进行层次式迭代组合,构造出一个更加复杂的构件或系统,为基于DEVS的形式化组合仿真研究进行了前期理论探讨.     

The Simulation of Repolarization Events of the Cardiac Purkinje Fiber Action Potential

A mathematical model based on the formalism of the Hodgkin-Huxley equations was implemented on a microcomputer system and used to simulate the membrane action potential of cardiac Purkinje fibers. The complete model is a modification of the representation used by McAllister et al. [1], mainly with respect to the outward current components during the late plateau, the repolarization phase, and the slow repolarization phase of the action potential. A new formulation of the potassium conductance was used, involving two distinct types of ionic channels corresponding, respectively, to the experimentally observed inward-going and outward-going rectification properties of the Purkinje fiber membrane. A unified representation of the Purkinje fiber current components was thus obtained which provides a more satisfactory interpretation of experimental results than was possible with the original model of McAllister et al. [1]. The membrane channel for the potassium pacemaker current is characterized by a set of first-order activation?inactivation variables and a constant fully activated conductance. The other channel carries the potassium current involved in the late plateau and repolarization phase of the action potential.     

Reliability of A Tree Network

This paper presents a mathematical model for computing the reliability of a system with redundant components in a tree configuration. This model is quite general and can be applied to any system representable by the appropriate tree. A typical example is cited. A computer program that computes reliability of a system with a tree configuration up to n stages is also presented in the Appendix.     

Preservation of partial orderings under the formation ofk-out-of-n:G systems of i.i.d. components

The authors discuss the preservation of certain partial orderings by a k-out-of-n:G system of i.i.d. components. If the lifetime of a component A is larger than that of a component B in the likelihood ratio, failure rate, or stochastic ordering, then a k-out-of-n:G system formed by n i.i.d. components of type A has a larger lifetime, in that ordering, than that of a similar system consisting of n i.i.d. components of type B. However, if the lifetime of a component A is larger than that of a component B in mean residual life, harmonic-average mean residual life, or variable orderings, it is not necessary that a k-out-of-n:G system formed by n i.i.d. components of type A has a larger lifetime, in that ordering, than that of a similar system consisting of n i.i.d. components of type B     

An adaptive technique for determining a reduced model for a system

A reduced or sparse system model is discussed that will contain only the most significant components, as opposed to a complete finite impulse response (FIR) model which may not be very accurate with the requirement of only a few components. The technique presented uses an adaptive delay filter to provide the sparse model and compares it to the model obtained with the standard adaptive filter     

Reliability theory for large linear systems with helping neighbors

Ways to model large systems, whose redundancy consists of the ability of neighbors to help (replace faulty units), at least for a degraded mode of operation, are shown. A general approach of determining and evaluating a fault-tree for such systems is given. One-dimensional (linear) arrays of components are emphasized, and linear consecutive quasi-3-out-of-n:F systems and circular consecutive 3-out-of- n:F systems are discussed. In all cases, explicit formulas-most of them recursive-are given for system unavailability and for mean system-failure frequency for nonidentical s-independent components. As to methodology, the good adaptation of the Shannon decomposition to finding recursive results is amply demonstrated     

自校正解耦融合Kalman预报器及其收敛性

对于带有未知模型参数和噪声方差的多传感器系统,通过系统辨识方法,得到模型参数和噪声方差的信息融合估计,将其代入到最优分量按标量加权融合Kalman预报器中,得到自校正信息融合Kalman预报器,实现了状态分量的解耦。通过动态误差系统分析（DESA）方法严格证明了提出的自校正Kalman预报器按一个实现收敛于最优融合Kalman预报器,因此它有渐近最优性。应用信号处理的仿真例子验证了其有效性。     

Recursive estimation of time-dependent reliability

This paper considers the recursive estimation of time-dependent reliability of p(≥1) components of a system using the multivariate state-space model, given the failure rates of components of the system. The estimated model can also be used for forecasting. An illustrative example is discussed.     

Near-field qualification methodology

A methodology that is a combination of analysis, computer simulation, component certification, self-tests, and comparison tests is presented for the accuracy qualification of near-field antenna measurement ranges. The analysis uses closed-form equations to establish upper-bound far-field determination errors due to near-field measurement errors. Computer simulation is used to model the specific near-field measurement errors associated with the near-field measurement system components. The closed-form equations and computer simulations are used to form a near-field error budget for each of the near-field measurement system components. A near-field system component certification is undertaken to measure the near-field measurement system component error and establish that they are within the error budget     

Understanding convolutional neural networks with a mathematical model

This work attempts to address two fundamental questions about the structure of the convolutional neural networks (CNN): (1) why a nonlinear activation function is essential at the filter output of all intermediate layers? (2) what is the advantage of the two-layer cascade system over the one-layer system? A mathematical model called the “REctified-COrrelations on a Sphere” (RECOS) is proposed to answer these two questions. After the CNN training process, the converged filter weights define a set of anchor vectors in the RECOS model. Anchor vectors represent the frequently occurring patterns (or the spectral components). The necessity of rectification is explained using the RECOS model. Then, the behavior of a two-layer RECOS system is analyzed and compared with its one-layer counterpart. The LeNet-5 and the MNIST dataset are used to illustrate discussion points. Finally, the RECOS model is generalized to a multilayer system with the AlexNet as an example.     

便携式防空导弹武器系统可靠性分析与设计

可靠性是衡量武器系统性能的一项重要指标,也是影响系统效能的重要因素.在阐述可靠性及可靠性模型等基本概念的基础上,建立便携式防空导弹武器系统的可靠性模型,从可靠性设计的具体要求出发,结合便携式防空导弹武器系统组成及使用特点,提出了系统可靠性的量化评估模型和提高系统可靠性的设计方法,对提高便携式防空导弹武器系统可靠性和系统...