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    A hybrid root transformation and decision on belief approach to monitor multiattribute Poisson processes

    , Article International Journal of Advanced Manufacturing Technology ; Volume 75, Issue 9-12 , December , 2014 , Pages 1651-1660 ; ISSN: 02683768 Niaki, S. T. A ; Javadi, S ; Fallahnezhad, M. S ; Sharif University of Technology
    Abstract
    Most of industrial applications of statistical process control involve more than one quality characteristics to be monitored. These characteristics are usually correlated, causing challenges for the monitoring methods. These challenges are resolved using multivariate quality control charts that have been widely developed in recent years. Nonetheless, multivariate process monitoring methods encounter a problem when the quality characteristics are of the attribute type and follow nonnormal distributions such as multivariate binomial or multivariate Poisson. Since the data analysis in the latter case is not as easy as the normal case, more complexities are involved to monitor multiattribute... 

    Estimating the change point of the parameter vector of multivariate Poisson processes monitored by a multi-attribute T 2 control chart

    , Article International Journal of Advanced Manufacturing Technology ; Volume 64, Issue 9-12 , February , 2013 , Pages 1625-1642 ; 02683768 (ISSN) Niaki, S. T. A ; Khedmati, M ; Sharif University of Technology
    2013
    Abstract
    When a control chart signals an out-of-control condition, knowing when the process has really changed (the change point) accelerates the identification of the source of special causes and makes the corrective measures to be taken sooner. In this paper, a new multi-attribute T 2 control chart based on two transformation methods is initially proposed to monitor the parameter vector of multi-attribute Poisson processes. Then, the maximum likelihood estimators (MLE) of the process change point designed for both linear trend and step change disturbances are derived. Next, using Monte Carlo simulation, we show the performances of the proposed estimators are satisfactory. Finally, through... 

    How compressible are innovation processes?

    , Article IEEE Transactions on Information Theory ; Volume 64, Issue 7 , 2018 , Pages 4843-4871 ; 00189448 (ISSN) Ghourchian, H ; Amini, A ; Gohari, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    The sparsity and compressibility of finite-dimensional signals are of great interest in fields, such as compressed sensing. The notion of compressibility is also extended to infinite sequences of independent identically distributed or ergodic random variables based on the observed error in their nonlinear $k$ -term approximation. In this paper, we use the entropy measure to study the compressibility of continuous-domain innovation processes (alternatively known as white noise). Specifically, we define such a measure as the entropy limit of the doubly quantized (time and amplitude) process. This provides a tool to compare the compressibility of various innovation processes. It also allows us... 

    Random Interlacements and Amenability

    , M.Sc. Thesis Sharif University of Technology Imani, Sahar (Author) ; Haji Mir Sadeghi, Miromid (Supervisor)
    Abstract
    In this thesis, we consider the model of random interlacement on transient graghs, which was first introduced by Sznitman for the special case of Zd(d > 3) in 2010’s. in Sznitman’s case, it was shown that on Zd: for any intensity u > 0, the interlacement set is almost surely connected. The main result of this thesis says that for transient, transitive graphs, the above property holds if and only if the graph is amenable. In paticular, we show that in nonamenable transitive graphs, for small values of the intensity u the interlacement set has infinitely many infinite clusters. We also provide examples of nonamenable transitive graphs, for which the interlacement set becomes connected for... 

    Which Factors Determine Demand for Children Among the Iranian Urban Households?

    , M.Sc. Thesis Sharif University of Technology Kabiri Renani, Mahboubeh (Author) ; Keshavarz Haddad, Gholamreza (Supervisor)
    Abstract
    This research intends to investigate demand for children among Iranian Urban Households in an intra-household bargaining decision process. Using, Household’s Expenditures Survey of Iran(2008), a count regression technique which takes into acount the over-dispersion and under-dispersion of Poisson scheme is specified as function of intra-household bargaining factors, and family’s characteristics. Our findings confirm the significance and a priory expected directions of distribution factors (intra-household bargaining power) and household’s characteristic, effects. Robustness checks verify the accuracy and appropriateness of the generalized Poisson. To examine the exogeneity explanatory... 

    Change Point Detection and Analysis in Poisson Processes

    , M.Sc. Thesis Sharif University of Technology Kamali, Mahsa (Author) ; Akhavan Niaki, Taghi (Supervisor)
    Abstract
    Control charts are one of the most important tools in statistical process control to detect assignable causes. The goal of a control chart is to detect an out-of-control state quickly so that process engineers can initiate their search for the special cause sooner. Once the special cause has been identified, the appropriate action can then be taken to improve the process.A new method to estimate the change point of Poisson rate parameter when the step change occurs is proposed in this thesis. That is, the rate parameter is assumed to suddenly shift from its in-control value to an out-of control value at a single unknown point in the process.To do this, a belief that the process is in-control... 

    A novel technique to control the traffic of wireless ad-hoc network by fuzzy systems and prediction with neural network

    , Article Proceedings - CIMSim 2011: 3rd International Conference on Computational Intelligence, Modelling and Simulation, 20 September 2011 through 22 September 2011, Langkawi ; 2011 , Pages 18-21 ; 9780769545622 (ISBN) Afshar, M. T ; Manzuri, M.T ; Sharif University of Technology
    Abstract
    Wireless Ad-hoc Networks have been proposed for variety of applications. In this paper our goal is to find crisis points in the roads, such as accident locations, and asphalt-destruction points, which may cause traffics along the roads. The applied method for traffic prediction is based on back propagation algorithm. In this paper the length of packets are assumed to be constant. Along the road the traffic is modeled by a Poisson Process. With this model we can produce packets. The number of packets which are sending from a typical node to the other nodes is controlled by a fuzzy system. By appropriate training of a neural network, we have shown that, having the traffic packets at time (t)... 

    A model for traffic prediction in wireless ad-hoc networks

    , Article Communications in Computer and Information Science ; Volume 241 CCIS , 2011 , Pages 328-335 ; 18650929 (ISSN) ; 9783642273360 (ISBN) Afshar, M. T ; Manzuri, M. T ; Latifi, N ; Sharif University of Technology
    Abstract
    In recent years, Wireless Ad-hoc networks have been considered as one of the most important technologies. The application domains of Wireless Ad-hoc Networks gain more and more importance in many areas. One of them is controlling and management the packet traffic. In this paper our goal is controlling the performance of every sections of pipeline of the factory by checking network periodically. Along the factory the traffic is modeled with a Poisson process. We present, with obtaining traffic packets at time (t) for each node in Wireless Ad-hoc Network, we can completely train a Neural Network and successfully predict the traffic at time (t+1) for each node. By this way we can recognize the... 

    Importance analysis considering time-varying parameters and different perturbation occurrence times

    , Article Quality and Reliability Engineering International ; Volume 35, Issue 8 , 2019 , Pages 2558-2578 ; 07488017 (ISSN) Noroozian, A ; Baradaran Kazemzadeh, R ; Zio, E ; Akhavan Niaki, S. T ; Sharif University of Technology
    John Wiley and Sons Ltd  2019
    Abstract
    Importance measures are integral parts of risk assessment for risk-informed decision making. Because the parameters of a risk model, such as the component failure rates, are functions of time and a perturbation (change) in their values can occur during the mission time, time dependence must be considered in the evaluation of the importance measures. In this paper, it is shown that the change in system performance at time t, and consequently the importance of the parameters at time t, depends on the parameters perturbation time and their value functions during the system mission time. We consider a nonhomogeneous continuous time Markov model of a series-parallel system to propose the... 

    Recurrent poisson factorization for temporal recommendation

    , Article IEEE Transactions on Knowledge and Data Engineering ; Volume 32, Issue 1 , 2020 , Pages 121-134 Hosseini, S. A ; Khodadadi, A ; Alizadeh, K ; Arabzadeh, A ; Farajtabar, M ; Zha, H ; Rabiee, H. R ; Sharif University of Technology
    IEEE Computer Society  2020
    Abstract
    Poisson Factorization (PF) is the gold standard framework for recommendation systems with implicit feedback whose variants show state-of-the-art performance on real-world recommendation tasks. However, they do not explicitly take into account the temporal behavior of users which is essential to recommend the right item to the right user at the right time. In this paper, we introduce Recurrent Poisson Factorization (RPF) framework that generalizes the classical PF methods by utilizing a Poisson process for modeling the implicit feedback. RPF treats time as a natural constituent of the model, and takes important factors for recommendation into consideration to provide a rich family of... 

    Expectation-maximization algorithm to develop a normal distribution NHPP reliability growth model

    , Article Engineering Failure Analysis ; Volume 140 , 2022 ; 13506307 (ISSN) Nadjafi, M ; Gholami, P ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    One of the most important goals of any organization for a product that goes into the design or manufacturing process is to improve its reliability. Reliability growth is defined as improving a product's criteria (input parameters) during operation using changes in design or production. This paper presents a hardware-centric approach for the reliability growth of systems following normal distribution based on the Non-Homogeneous Poisson Process (NHPP). To reach this goal, the reliability growth modeling equations for the NHPP with the assumption of the normal distribution for failure data are extracted and obtained. Then, the maximum likelihood estimation technique based on the... 

    Inventory Management in Two-Echelon Chain with Shortage

    , M.Sc. Thesis Sharif University of Technology Sodachi, Majid (Author) ; Haji, Alireza (Supervisor)
    Abstract
    The thesis has considered a two-echelon supply chain which consists of one central warehouse and multiple retailers. Assume all retailers and the warehouse follow a continuous review inventory model. The costumer’s demand comes to retailers in a Poisson process. The retailers replenish their stocks from the warehouse in an (S-1, S) inventory control policy and the warehouse replenishes its stocks in an (r, Q) inventory control policy from an external supplier with an infinite capacity. It may be more representative to model stockouts as lost sales when the retailers are in a competitive market or in monopoly markets all demand will be backorder. Therefore, if the market situation goes... 

    Deriving the Cost Function and Optimal Boundaries for a Two-level Inventory System with Information Sharing and Identical Retailers

    , M.Sc. Thesis Sharif University of Technology Afshar Sedigh, Amir Hosein (Author) ; Haji, Rasoul (Supervisor)
    Abstract
    In this study we consider a two-level supply chain, with a supplier and a number of identical retailers, demand process is Poisson with random rate. All retailers apply (R,Q) policy with backorder case for their inventory control supplier fulfills the orders of retailers according to FIFO discipline. At any point of time the supplier has online information about inventory position of all retailers.
    Whenever the inventory position of a retailer reaches to a fixed value (s) above its reorder point, the supplier orders a batch of size Q to an outside source with infinite capacity. Lead-time of each retailer is equal to the sum of a constant transportation time and a delay time which is... 

    Optimizing capacity, pricing and location decisions on a congested network with balking

    , Article Mathematical Methods of Operations Research ; Volume 74, Issue 2 , October , 2011 , Pages 233-255 ; 14322994 (ISSN) Abouee Mehrizi, H ; Babri, S ; Berman, O ; Shavandi, H ; Sharif University of Technology
    2011
    Abstract
    In this paper, we consider the problem of making simultaneous decisions on the location, service rate (capacity) and the price of providing service for facilities on a network. We assume that the demand for service from each node of the network follows a Poisson process. The demand is assumed to depend on both price and distance. All facilities are assumed to charge the same price and customers wishing to obtain service choose a facility according to a Multinomial Logit function. Upon arrival to a facility, customers may join the system after observing the number of people in the queue. Service time at each facility is assumed to be exponentially distributed. We first present several... 

    Analytical performance modeling of elastic optical links with aligned spectrum allocation

    , Article Computer Networks ; Volume 88 , September , 2015 , Pages 40-50 ; 13891286 (ISSN) Vaezi, K ; Akar, N ; Sharif University of Technology
    Elsevier  2015
    Abstract
    Abstract Elastic optical networking has recently been proposed for use in optical transport networks to cope with increasingly heterogeneous and dynamic demand patterns. In this paper, we study the blocking performance of a multi-class elastic optical link for which a demand needs to be allocated a contiguous subset of the entire spectrum. This problem is different than the well-known blocking problem in multi-class multi-server loss systems due to the contiguous allocation constraint. We first propose a non-work-conserving aligned spectrum allocation policy which is shown to outperform the conventional first fit-based work-conserving allocation policy without alignment. Subsequently, for... 

    Recurrent poisson factorization for temporal recommendation

    , Article Proceedings of the ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, 13 August 2017 through 17 August 2017 ; Volume Part F129685 , 2017 , Pages 847-855 ; 9781450348874 (ISBN) Hosseini, S. A ; Alizadeh, K ; Khodadadi, A ; Arabzadeh, A ; Farajtabar, M ; Zha, H ; Rabiee, H. R ; Sharif University of Technology
    Abstract
    Poisson factorization is a probabilistic model of users and items for recommendation systems, where the so-called implicit consumer data is modeled by a factorized Poisson distribution. There are many variants of Poisson factorization methods who show state-of-the-art performance on real-world recommendation tasks. However, most of them do not explicitly take into account the temporal behavior and the recurrent activities of users which is essential to recommend the right item to the right user at the right time. In this paper, we introduce Recurrent Poisson Factorization (RPF) framework that generalizes the classical PF methods by utilizing a Poisson process for modeling the implicit... 

    Evaluating the Rate of Compressibility of Sparse Stochastic Processes

    , M.Sc. Thesis Sharif University of Technology Ghourchian, Hamid (Author) ; Amini, Arash (Supervisor) ; Aminzadeh Gohari, Amin (Supervisor)
    Abstract
    In most stochastic models with uncountable cardinality of sample space with non-trivial probability measures, the inherent information is infinite. The continuous-valued random variables and continuous-domain random processes are among such objects. Therefore, a fidelity criterion must be defined between the stochastic subject and its estimated version. Although there are some criteria for of stochastic continuous signals, based on quantizing the signal in both time and amplitude domains, we are going to define a criterion which is for stochastic processes in bounded time domain. Next, the criterion will be expressed in general sources perspective and the optimum rate of coding will be... 

    An exact analysis of a joint production-inventory problem in two-echelon inventory systems

    , Article Naval Research Logistics ; Volume 58, Issue 8 , 2011 , Pages 713-730 ; 0894069X (ISSN) Abouee Mehrizi, H ; Berman, O ; Shavandi, H ; Zare, A. G ; Sharif University of Technology
    Abstract
    We consider a two-echelon inventory system with a manufacturer operating from a warehouse supplying multiple distribution centers (DCs) that satisfy the demand originating from multiple sources. The manufacturer has a finite production capacity and production times are stochastic. Demand from each source follows an independent Poisson process. We assume that the transportation times between the warehouse and DCs may be positive which may require keeping inventory at both the warehouse and DCs. Inventory in both echelons is managed using the base-stock policy. Each demand source can procure the product from one or more DCs, each incurring a different fulfilment cost. The objective is to... 

    A model for admission control of returned products in a remanufacturing facility using queuing theory

    , Article International Journal of Advanced Manufacturing Technology ; Volume 54, Issue 1-4 , April , 2011 , Pages 403-412 ; 02683768 (ISSN) Karamouzian, A ; Teimoury, E ; Modarres, M ; Sharif University of Technology
    2011
    Abstract
    This paper deals with decision making in a remanufacturing facility where returned products arrive according to a Poisson process. Arrivals have different routings among the facility stations since they have different defects and need different operations. A returned product is either accepted for remanufacturing or sold at a salvage value without working on it in order to reduce congestion. The authors provide an analytical model using a queuing network theory to obtain the best policy for accepting returned products. Furthermore, a continuous genetic algorithm is implemented to solve the model, which happens to be a mixed integer nonlinear programming problem. Several examples are solved... 

    Recurrent poisson factorization for temporal recommendation

    , Article IEEE Transactions on Knowledge and Data Engineering ; 2018 ; 10414347 (ISSN) Hosseini, S ; Khodadadi, A ; Alizadeh, K ; Arabzadeh, A ; Farajtabar, M ; Zha, H ; Rabiee, H. R. R ; Sharif University of Technology
    IEEE Computer Society  2018
    Abstract
    Poisson Factorization (PF) is the gold standard framework for recommendation systems with implicit feedback whose variants show state-of-the-art performance on real-world recommendation tasks. However, most of the previous work do not explicitly take into account the temporal behavior of users which is essential to recommend the right item to the right user at the right time. In this paper, we introduce a Recurrent Poisson Factorization (RPF) framework that generalizes the classical PF methods by utilizing a Poisson process for modeling the implicit feedback. RPF treats time as a natural constituent of the model, and takes important factors for recommendation into consideration to provide a...