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exponential-distributions
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Reliability assessment of the standby system with dependent components by bivariate exponential distributions
, Article Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability ; Volume 236, Issue 5 , 2022 , Pages 761-769 ; 1748006X (ISSN) ; Gholami, P ; Sharif University of Technology
SAGE Publications Ltd
2022
Abstract
In the reliability analysis of systems, all system components are often assumed independent and failure of any component does not depend on any other component. One of the reasons for doing so is that considerations of calculation and elegance typically pull in simplicity. But in real-world applications, there are very complex systems with lots of subsystems and a choice of multiple components that may interact with each other. Therefore, components of the system can be affected by the occurrence of a failure in any of the components. The purpose of this paper is to give an explicit formula for the computation of the reliability of a system with two parallel active components and one spare...
Modeling an Inventory-queueing System for a Producer-retailer System with a Special (r,Q) Inventory Control Policy and Exponential Leadtime
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
This thesis covers the problem of a 2-echolen inventory system including a producer and retailer. Producer makes each part and stores it in its own warehouse which is capable of holding as many as S parts. Time that takes for the producer to produce each part is described by an exponential distribution with a fixed rate. Retailer which has its own warehouse with capacity R sees customers arriving with a Poisson distribution. If either of retailer or producer is out of inventory, system does not accept new customers and it is a lost sale, otherwise the customer is served. Whenever retailer runs out of stock, it places an order of size R. producer then looks at its own inventory, if possible a...
Distributed binary majority voting via exponential distribution
, Article IET Signal Processing ; Volume 10, Issue 5 , 2016 , Pages 532-542 ; 17519675 (ISSN) ; Golestani, S. J ; Sharif University of Technology
Institution of Engineering and Technology
Abstract
In the binary majority voting problem, each node initially chooses between two alternative choices. The goal is to design a distributed algorithm that informs nodes which choice is in majority. In this study, the authors formulate this problem as a hypothesis testing problem and propose fixed-size and sequential solutions using classical and Bayesian approaches. In the sequential version, the proposed mechanism enables nodes to test which choice is in majority, successively in time. Hence, termination of the algorithm is embedded within it, contrary to the existing approaches which require a monitoring algorithm to indicate the termination. This property makes the algorithm more efficient in...
Decision rule of repetitive acceptance sampling plans assuring percentile life
, Article Scientia Iranica ; Volume 19, Issue 3 , June , 2012 , Pages 879-884 ; 10263098 (ISSN) ; Niaki, S. T. A ; Rasool, M ; Fallahnezhad, M. S ; Sharif University of Technology
2012
Abstract
In this research, Repetitive Group Sampling (RGS) plans are developed for the Weibull and generalized exponential distributions. To design the proposed plans, the median of a life-time is first used as the quality parameter. Then, a decision-making framework is developed, based on first and second type errors. Next, based on acceptable and limiting quality level criteria, tables are obtained to select the parameters of the proposed decision-making framework. The advantages of the proposed method over single sampling plans are discussed at the end
Predictive-reactive rescheduling for new order arrivals with optimal dynamic pegging
, Article 16th IEEE International Conference on Automation Science and Engineering, CASE 2020, 20 August 2020 through 21 August 2020 ; Volume 2020-August , 8 October , 2020 , Pages 710-715 ; Saitou, K ; Sharif University of Technology
IEEE Computer Society
2020
Abstract
This paper presents a new predictive-reactive rescheduling method for adjusting production schedules in response to the unplanned arrival of new orders in multi-level production. It is based on the concept of dynamic pegging, which enables the reassignment of the Work-In-Progress (WIP) to the existing or newly arrived orders at the time of rescheduling. Extending our previous work on reactive rescheduling with dynamic pegging, the new approach incorporates a probabilistic predictive model of new order arrival in the initial scheduling at the begging of the scheduling horizon. A Mixed Integer Programming (MIP) model is developed for two-phase, predictive-reactive scheduling before and after...
Evaluation of some exponential random number generators implemented by FPGA
, Article IASTED International Conference on Parallel and Distributed Computing and Networks, as part of the 23rd IASTED International Multi-Conference on Applied Informatics, Innsbruck, 15 February 2005 through 17 February 2005 ; 2005 , Pages 578-583 ; 10272666 (ISSN) ; Miremadi, S. G ; Ejlali, A. R ; Fahringer T ; Hamza M. H ; Sharif University of Technology
2005
Abstract
Normally, random number generators produce uniformly distributed values. In some cases, such as Monte Carlo simulation, non-uniform distributed values (e.g. exponential distribution and weibull distribution) are required. One way of producing non-uniformly distributed random values, is to add an extra hardware to a uniformly distributed random number generator. In this paper, three different methods are studied to generate exponential random values. These methods are based oft three algorithm of logarithm evaluating namely: CORDIC, Interpolation and Piecewise lookup table. The study is based on an experimental evaluation of the above methods, using FPGA chips, to compare the speed, hardware...
Scheduling tasks with exponential duration on unrelated parallel machines
, Article Discrete Applied Mathematics ; Volume 160, Issue 16-17 , November , 2012 , Pages 2462-2473 ; 0166218X (ISSN) ; Ghodsi, M ; Sharif University of Technology
2012
Abstract
This paper introduces a stochastic scheduling problem. In this problem a directed acyclic graphs (DAG) represents the precedence relations among m tasks that n workers are scheduled to execute. The question is to find a schedule Σ such that if tasks are assigned to workers according to Σ, the expected time needed to execute all the tasks is minimized. The time needed to execute task t by worker w is a random variable expressed by a negative exponential distribution with parameter λ wt and each task can be executed by more than one worker at a time. In this paper, we will prove that the problem in its general form is NP-hard, but when the DAG width is constant, we will show that the optimum...
State estimation of nonlinear dynamic systems using weighted variance-based adaptive particle swarm optimization
, Article Applied Soft Computing Journal ; Volume 34 , September , 2015 , Pages 1-17 ; 15684946 (ISSN) ; Pourtakdoust, S. H ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
New heuristic filters are proposed for state estimation of nonlinear dynamic systems based on particle swarm optimization (PSO) and differential evolution (DE). The methodology converts state estimation problem into dynamic optimization to find the best estimate recursively. In the proposed strategy the particle number is adaptively set based on the weighted variance of the particles. To have a filter with minimal parameter settings, PSO with exponential distribution (PSO-E) is selected in conjunction with jDE to self-adapt the other control parameters. The performance of the proposed adaptive evolutionary algorithms i.e. adaptive PSO-E, adaptive DE and adaptive jDE is studied through a...
Exact electroelastic field of a functionally graded piezoelectric cantilever beam subjected to pure body force loading
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010 ; Volume 2 , 2010 , Pages 45-52 ; 9780791849163 (ISBN) ; Hashemi, R ; Kargarnovin, M. H ; Naghdabadi, R ; Sharif University of Technology
Abstract
The electroelastic response of functionally graded piezoelectric cantilever beams which includes the effect of body force is presented in this paper. The material properties such as elastic compliance, piezoelectric and dielectric impermeability are assumed to be graded with different indices in the thickness direction according to exponential distributions. Systems of fourth order inhomogeneous partial differential equations (PDEs) which are satisfied by the stress and induction functions and involve the body force terms are derived. Spectral forms for electrical and mechanical variables in the x-axis are employed to convert the partial differential governing equations and the associated...
A neural network applied to estimate Burr XII distribution parameters
, Article Reliability Engineering and System Safety ; Volume 95, Issue 6 , June , 2010 , Pages 647-654 ; 09518320 (ISSN) ; Hosseinifard, S. Z ; Coit, D. W ; Sharif University of Technology
2010
Abstract
The Burr XII distribution can closely approximate many other well-known probability density functions such as the normal, gamma, lognormal, exponential distributions as well as Pearson type I, II, V, VII, IX, X, XII families of distributions. Considering a wide range of shape and scale parameters of the Burr XII distribution, it can have an important role in reliability modeling, risk analysis and process capability estimation. However, estimating parameters of the Burr XII distribution can be a complicated task and the use of conventional methods such as maximum likelihood estimation (MLE) and moment method (MM) is not straightforward. Some tables to estimate Burr XII parameters have been...
Multi-objective optimization of job shops with automated guided vehicles: A non-dominated sorting cuckoo search algorithm
, Article Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability ; 2020 ; Akhavan Niaki, S. T ; Niknamfar, A. H ; Hassanlu, M. G ; Sharif University of Technology
SAGE Publications Ltd
2020
Abstract
The reliability of machinery and automated guided vehicle has been one of the most important challenges to enhance production efficiency in several manufacturing systems. Reliability improvement would result in a simultaneous reduction of both production times and transportation costs of the materials, especially in automated guided vehicles. This article aims to conduct a practical multi-objective reliability optimization model for both automated guided vehicles and the machinery involved in a job-shop manufacturing system, where different machines and the storage area through some parallel automated guided vehicles handle materials, parts, and other production needs. While similar machines...
An economic-statistical design of simple linear profiles with multiple assignable causes using a combination of MOPSO and RSM
, Article Soft Computing ; Volume 25, Issue 16 , 2021 , Pages 11087-11100 ; 14327643 (ISSN) ; Ershadi, M. M ; Haghighi Naeini, S ; Akhavan Niaki, S. T ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
An economic-statistical design with multiple assignable causes following exponential distribution is presented in this paper for linear profiles. For this purpose, a tri-objective optimization model is proposed to minimize the cost with desired statistical performances. Average Run Length (ARL) as the primary statistical measure is employed for the appraisal of the designed linear profiles. The first objective to be minimized is a cost function that models the implementation cost in different states. The second objective is to maximize ARL or the in-control average run-length of the monitoring scheme. The third objective to be minimized is ARL 1 or the out-of-control average run-length of...
Multi-objective optimization of job shops with automated guided vehicles: A non-dominated sorting cuckoo search algorithm
, Article Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability ; Volume 235, Issue 2 , 2021 , Pages 306-328 ; 1748006X (ISSN) ; Akhavan Niaki, S. T ; Niknamfar, A. H ; Hassanlu, M. G ; Sharif University of Technology
SAGE Publications Ltd
2021
Abstract
The reliability of machinery and automated guided vehicle has been one of the most important challenges to enhance production efficiency in several manufacturing systems. Reliability improvement would result in a simultaneous reduction of both production times and transportation costs of the materials, especially in automated guided vehicles. This article aims to conduct a practical multi-objective reliability optimization model for both automated guided vehicles and the machinery involved in a job-shop manufacturing system, where different machines and the storage area through some parallel automated guided vehicles handle materials, parts, and other production needs. While similar machines...
Estimating the four parameters of the Burr III distribution using a hybrid method of variable neighborhood search and iterated local search algorithms
, Article Applied Mathematics and Computation ; Volume 218, Issue 19 , 2012 , Pages 9664-9675 ; 00963003 (ISSN) ; Abbasi, B ; Niaki, S. T. A ; Abdi, M ; Sharif University of Technology
2012
Abstract
The Burr III distribution properly approximates many familiar distributions such as Normal, Lognormal, Gamma, Weibull, and Exponential distributions. It plays an important role in reliability engineering, statistical quality control, and risk analysis models. The Burr III distribution has four parameters known as location, scale, and two shape parameters. The estimation process of these parameters is controversial. Although the maximum likelihood estimation (MLE) is understood as a straightforward method in parameters estimation, using MLE to estimate the Burr III parameters leads to maximize a complicated function with four unknown variables, where using a conventional optimization such as...