Sharif Digital Repository

Assembly line is the most well-known mass production system which was first used by Henry Ford in automobile industries. Malfunction of a station will have an impact on the whole assembly line. Having a great impact on the performance of the whole assembly line, Interaction of the stations on each other should be considered precisely. In this paper we will use discrete event simulation to improve performance of a station and the whole assembly line by smoothing the exit rate, which is the entrance rate to the next station. At the end of this article, the results for a case problem are illustrated and several conclusions are driven. © 2007 IEEE  

The classical economic production quantity (EPQ) model is a well-known and commonly used inventory control technique. A common assumption in the EPQ model is that all units produced are of perfect quality, since in practice non-conforming product or scrap items are possible, this assumption will underestimate the actual required quantity. The objective of this paper is to provide a framework to integrate product of imperfect quality items, inspection errors, rework and scrap items into a single EPQ model. To achieve this objective a suitable mathematical model is defined and the optimal production lot size which minimizes the total cost is obtained  

This paper considers an imperfect production system in which defective items are produced in. each cycle of production. We assume that the defectives produced within each cycle will be reworked immediately after each production run is completed. We also assume some scrap is produced and detected during the rework period. Further, we assume that the number of scrapped items produced during the rework period is a random variable. For this system, using some theorem from the renewal theory, the expected total cost function per unit time is derived and the optimal batch quantity is obtained  

Systematic management of enterprise knowledge, e.g. new ideas, innovations and patents, has a great impact on business sustainability and growth. Without comprehensive assessment of knowledge assets, agile companies can not design and run knowledge promotion programs required for survival in competitive environments in modern economy. A comprehensive framework for the assessment of as-is situation and development of knowledge promotion plans includes (a) assessing the as-is situation- the quantity and quality of organizational knowledge; (b) developing a situational program based on assessment results, business strategy and knowledge maturity indicators; (c) and working out an action plan in... 

The inventory system under consideration consists of one central warehouse and many identical retailers controlled by continuous review inventory policy ( R, Q). We assume independent Poisson demands with constant transportation times for the retailers and a constant lead time for replenishing orders from an external supplier for the warehouse. Unsatisfied demands are assumed to be lost in the retailers and unsatisfied retailer orders are backordered in the warehouse. We develop an approximate cost function to find optimal reorder points for given batch sizes in all installations and the related accuracy is assessed through simulation. © 2005 Elsevier B.V. All rights reserved  

Stock return is usually considered to be affected by firm's financial ratios as well as economic variables. Fundamental method assume that stock returns is not solely related to the stock market. Most result come from the company condition, industry situation and whole economy. In this paper, this relationship between stock return and fundamentals is studied using the data for 22 pharmaceutical companies in Tehran Stock Exchange over a 7 year period, and effective factors on stock return are investigated. Because of our data natural we used panel data model from econometric methods. The results show that 80 pecent of change in stock return can be explained with 9 fundamental variables... 

In this paper, a bi-objective multi-products economic production quantity (EPQ) model is developed, in which the number of orders is limited and imperfect items that are re-workable are produced. The objectives of the problem are minimization of the total inventory costs as well as minimizing the required warehouse space. The model is shown to be of a bi-objective nonlinear programming type, and in order to solve it two meta-heuristic algorithms namely, the non-dominated sorting genetic algorithm (NSGA-II) and multi-objective particle swarm optimization (MOPSO) algorithm, are proposed. To verify the solution obtained and to evaluate the performance of proposed algorithms, two-sample t-tests... 

In the restructured power systems, generating companies (Genco) are responsible for selling their product in the energy market. In this condition, the question is how much and for what price must each Genco generate to maximize its profit. Therefore, this paper intends to propose a rational method to answer this question. In the proposed methodology, the hourly forecasted market clearing price (FMCP) is used as a reference to model the possible and probable price strategies of Gencos. The forecasted price is the basis of the bidding strategies of each Genco, which can be achieved by solving a bi-level optimization problem using GAMS (general algebraic modeling system) language. The first... 

This paper presents a new method to analyze the bidding strategies of Generating Companies (GENCOs) with regard to demand elasticity. It is assumed that the available information of each GENCO about its opponents is incomplete and only the minimum and maximum generation levels of their opponents, as well as their fuel type, are known. In the proposed methodology, GENCOs prepare their strategic bids according to a Supply Function Equilibrium (SFE) model. GENCOs will change their bidding strategies until Nash equilibrium points are obtained. The general Algebraic Modeling System (GAMS) has been used to solve the maximization modules using the MINOS optimization software with non Linear... 

This paper describes a new method for analyzing the bidding strategies of Generating Companies (GENCOs) in the Independent System Operator (ISO) point of view. ISO uses these results to detect the participants that have the potential for market power or actual exercise of market power. ISO models all GENCOs with perfect information. The proposed methodology uses the marginal cost of GENCOs as an initial point for bidding strategies of GENCOs and improves bidding strategies based on the objective function of GENCOs, the state of them in each hour of the day and with regard to ISO's market clearing problem. ISO tries to maximize the social welfare or minimize consumer's payments. The model... 

The aim of this paper is to investigate the vendor managed inventory (VMI) problem of a single-vendor single-buyer supply chain system, in which the vendor is responsible to manage the buyer's inventory. To include an extended applicability in real-world environments, the multiproduct economic production quantity model with backordering under three constraints of storage capacity, number of orders, and available budget is considered. The nonlinear programming model of the problem is first developed to determine the near optimal order quantities along with the maximum backorder levels of the products in a cycle such that the total VMI inventory cost of the system is minimized. Then, a genetic... 

The economic viability of industrial processes strongly depends on their safe and reliable operation. The method of inherent safe process design enables systematic consideration of safety measures in order to ensure process safe operation at the early stages of process design. The challenge is that the economic measures that are often considered for the design of industrial processes are often incommensurable with the safety measures. In the present research, a novel framework is proposed in which the safety criteria are quantified based on consequence modeling and aggregated with the economic performance using multi-objective optimization programming. The developed methodology was applied... 

One of the major problems in liberalized power markets is loss allocation. In this paper, a new method for allocating transmission losses to pool market participants is proposed. The proposed method is fundamentally based on Bialek's "Tracing the flow of electricity" method. The losses is allocated to market participants using the loss weight factors (LWFs) which are obtained from the square current magnitude and Z-bus matrix. The LWF method is based on a solved load flow and strongly emphasizes on current magnitude while considers network topology. The method has been implemented and tested on several networks and one sample summarized in the paper. The results show that the method has an... 

This paper considers a two-level supply chain consisting of one warehouse and one retailer. In this model we determine the optimal ordering policy according to inventory and transportation costs. We assume that the demand rate by the retailer is known. Shortages are allowed neither at the retailer nor at the warehouse. We study this model in two cases; decentralized and centralized. In the decentralized case the retailer and the warehouse independently minimize their own costs; while in the centralized case the warehouse and the retailer are considered as a whole firm. We propose an algorithm to find economic order quantities for both the retailer and the warehouse which minimize the total... 

This paper proposes a new method for recognizing the price maker firms in the Independent System Operator (ISO)'s point of view. In the proposed methodology, at the first, all firms are supposed to be as price takers. Then the state of each firm will be changed from price taker to price maker and the obtained profit in either of cases is compared. In the proposed methodology the Supply Function Equilibrium (SFE) model is used for modeling a price maker firm's bidding strategy. If a price maker firm changes the market clearing price (MCP) noticeably, that firm is realized as a price maker. GAMS (General Algebraic Modeling System) language has been used to solve the market simulation model... 

Nowadays automation in distribution systems is growing largely. Automated and remote controlled switches play prominent rules in automated distribution systems. By opening and closing these remote controlled switches in emergency states when a fault has been occurred we can manage fault and restoration process in order to minimize interruption time and costs. In the normal states feeder load management and power loss minimization can be controlled by these remote controlled switches. Finding optimum numbers and optimum locations for installing these switches is the main concern in this between. Up to now a number of algorithms have been developed for optimum switch placement. In this paper a... 

Considerable attention has been devoted to demonstrate reliability enhancement of power systems with power wheeling transactions. The impacts of power wheeling on power systems depends on various factors such as direction, amount of power/energy wheeled, system topology and sink or source nodes of power system. The effects on Iran Composite Power System (ICPS) reliability of wheeling energy from Azerbaijan to Turkmenistan are presented in this paper. This transaction is done through the transmission facilities on north part of ICPS. The sensitivity of ICPS to the direction and amount of power wheeling is attended. Finally, the optimum value for power wheeling is determined and the associated... 

The economic production quantity (EPQ) model is often used in manufacturing environments to assist firms in determining the optimal production lot size that minimizes the overall production-inventory costs. While there are some unrealistic assumptions in the EPQ model that limit its real-world applications, in this research, some of these assumptions such as (1) infinite availability of warehouse space, (2) all of the produced items being perfect, and (3) the existence of one product type are relaxed. In other words, we develop a multi-product EPQ model in which there are some imperfect items of different product types being produced such that reworks are allowed and that there is a... 

Construction and demolition (C&D) waste dreadful impacts increasingly cause public concerns. Aiming to boost resource exploitation efficiency, circular economy is contemplated a pertinent C&D waste management practice. However, transitioning to circular economy in C&D waste management is hindered by barriers which are to be found and overcome to adeptly handle this kind of waste. In this paper 22 potential crisp barriers are identified through reviewing the seminal literature which could be categorized under three dimensions of behavioral, technical, and legal. Six experts in behavioral, technical, and legal sciences working in sustainable C&D projects were asked to rate the dimensions and... 

This paper reports on the application of low-grade sensible waste heat (liquid phase) driven multi-effect distillation (MED) technology to exploit waste heat sources that are generally abundant in the petrochemical industries especially, those located close to the Persian Gulf's coastline. For this purpose, a techno-economic feasibility study by considering local capital and operating costs for a selected petrochemical plant has been conducted. In this study, a sensible waste heat stream (practically at 80 °C in the liquid phase), which is actively cooled by the cooling process of the plant, is considered as the heat source for the proposed desalination process. This process can recover...