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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  

This paper considers scheduling tasks while minimizing the power consumption of one or more processors, each of which can go to sleep at a fixed cost α. There are two natural versions of this problem, both considered extensively in recent work: minimize the total power consumption (including computation time), or minimize the number of "gaps" in execution. For both versions in a multiprocessor system, we develop a polynomial-time algorithm based on sophisticated dynamic programming. In a generalization of the power-saving problem, where each task can execute in any of a specified set of time intervals, we develop a (1+23α) -approximation, and show that dependence on α is necessary. In... 

We reduce the problem of minimum interval cost flow problem (MICFP) introduced by Hashemi et al. (2006) to the well-known minimum cost flow problem (MCFP)  

Cutting a cake is a metaphor for the problem of dividing a resource (cake) among several agents. The problem becomes non-trivial when the agents have different valuations for different parts of the cake (i.e., one agent may like chocolate, while the other may like cream). A fair division of the cake is one that takes into account the individual valuations of agents and partitions of the cake based on some fairness criterion. Fair division may be accomplished in a distributed or centralized way. Due to its natural and practical appeal, it has been a subject of study in economics. To the best of our knowledge, the role of partial information in fair division has not been studied so far from an... 

Over-the-air (OTA) software download is a key enabling technology for terminal reconfigurations. With increasing the number of network protocols, variety of software products with different software providers and new software threats, it becomes important to download and install assured software on the mobile terminals. Most of the related research works on downloading assured software, focus on software validation after download, and mainly on the terminal. In this paper, a model is proposed in which an Assurance Agency is exploited. This agency is responsible for performing software examination and validations. Unlike related work, examination and validation operations are centrally... 

We use multifractal detrended fluctuation analysis (MF-DFA) to numerically investigate correlation, persistence, multifractal properties and scaling behavior of the hourly spot prices for the Spain electricity exchange-Compania O Peradora del Mercado de Electricidad (OMEL). Through multifractal analysis, fluctuations behavior, the scaling exponents and generalized Hurst exponents are studied. Moreover, contribution of fat-tailed probability distributions and nonlinear temporal correlations to multifractality is studied. © 2007 Elsevier B.V. All rights reserved  

The inventory system under consideration consists of one central warehouse and an arbitrary number of retailers controlled by a continuous review inventory policy (R,Q). Independent Poisson demands are assumed with constant transportation times for all 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. An approximate cost function is developed to find optimal reorder points for given batch sizes in all installations and the related accuracy is assessed through simulation. © Sharif University of Technology, January... 

Due to increase of per capita water usage, water supply costs and population growth rate; optimal usages of available resources are vital. This is especially important in developing countries. If we add water resource deficits to the above problems, its importance duplicates. One of the ways of using resources optimally is utilizing transferred water in distribution systems properly and preventing its loss. Unaccounted for water (UFW) is an indicator of water loss in most cities. A big part of UFW is due to leakage of pipeline in distribution systems. Researchers have found direct relation between leakage and pressure in distribution systems. Earlier works have shown a series of laboratory... 

Microbubbles are broadly used as ultrasound contrast agents. In this paper we use a low-cost flow focusing microchannel fabrication method for preparing microbubble contrast agents by using some surface active agents and a viscosity enhancing material to obtain appropriate microbubbles with desired lifetime and stability for any in vitro infusion for velocity measurement. All the five parameters that govern the bubble size extract and some efforts are done to achieve the smallest bubbles by adding suitable surfactant concentrations. By using these microbubbles for the echo-particle image velocimetry method, we experimentally determine the velocity field of steady state and pulsatile pipe... 

Wireless Sensor Networks are composed of small, low cost, resource-constrained computing nodes equipped with low power wireless transceivers. In this paper, we study and model the time and energy cost of Kerberos protocol by using timed automata in WSN. We model check the protocol using UPPAAL. We show that considering time in the analysis of security protocols yield more confident results  

In spite of the recent steady increase of the volume of the second-hand markets, often customers remain in doubt regarding the quality and durability of the secondhand products. Aiming to reduce and share this uncertainty, dealers offer warranty on their products. Offering warranty for second-hand products is a relatively new marketing strategy employed by dealers of used electronic equipment, furniture, automobiles, etc. Usually, for used products, the dealer's expected warranty cost is a function of product reliability, past age and usage, servicing strategy and conditions and terms of the warranty policy/contract. Sometimes the offered policy is limited by two parameters, typically the... 

Maintenance costs in airlines change as time passes. As airplane ages, it needs more often and more expensive checks. Due to these growing expenses, airlines are getting more interested in cost analysis. Under financial pressure, they avoid buying new airplanes and try to maintain the old ones, but sometimes try to cut the maintenance costs by ignoring or delaying some checks. In other words, they are more disposed to spend small amount of money frequently through time, than to spend a great deal on a new airplane with low maintenance costs. Therefore, in such situations, the following questions raise that what solution is more efficient as we look dynamically to the system? For answering... 

As a high proportion of the total generated electricity energy and the power system costs is due to the power losses in lines, allocating the loss and associated cost to the system loads and generating units is a substantial issue in deregulated power systems. The procedure to accomplish this cost allocation is designated as 'loss cost allocation' (LCA). So far, a number of LCA methods have been proposed for transmission networks. A few papers have compared different loss allocation methods, which are the methods which calculate the loss (and not necessarily the loss cost) allocated to the loads and generating units. However, this paper presents a comparative study of LCA methods. In this... 

In this paper, the interaction between various window specifications and different climate conditions is investigated. For this purpose, simultaneous effects of several aspects including glazing system, glass type, filling gas, glass thickness, window frame fraction, and interior shading are considered under three different climatic conditions. To evaluate the energy performance of various considered alternatives, the energy simulation of a base case building is evaluated in a computer environment. Using the validated model, the energy analysis is quantitatively performed, and cost-benefit analyses from the viewpoints of both residents and government are carried out based on the domestic and... 

This study considers a two-level supply chain system consisting of one warehouse and a number of identical retailers. In this system, we incorporate transportation costs into inventory replenishment decisions. The transportation cost contains a fixed cost and a variable cost. We assume that the demand rate at each retailer is known and the demand is confined to a single item. First, we derive the total cost which is the sum of the holding mid ordering cost at the warehouse and retailers as well as the transportation cost from the warehouse to retailers. Then, we propose a search algorithm to find the economic order quantities for the warehouse and retailers which minimize the total cost. ©... 

This paper considers a two-level supply chain consisting of one warehouse and a number of identical retailers. Unlike the common practice which determines the optimal ordering policy according to inventory costs only, in this model we consider the transportation cost as well. We suppose that the delivery of each order from the warehouse to any retailer is made by a single vehicle without splitting. We also assume that there are three types of vehicles which are defined as small, medium and large. Each type has its own fixed cost, variable cost, and the capacity size. We assume that the demand rate at each retailer is known and the demand is confined to a single item. Shortages are allowed... 

This manuscript presents a framework to develop vector error correction (VEC) models applicable to forecasting the short- and long-run movements of the average hourly earnings of construction labor, which is an essential predictor of the construction labor costs. These models characterize the relationship between average hourly earnings and a set of explanatory variables. The framework is applied to develop VEC forecasting models for the average hourly earnings of construction labor in the USA based on the identified variables that govern its movements, such as Global Energy Price Index, Gross Domestic Product, and Personal Consumption Expenditures. More than 150 candidate VEC models were... 

Open access to transmission networks as well as designing an efficient cost allocation method are the key points that provide free competition for participants in power market. Restructuring in power systems has created new challenges which emphasize the development and fairness of economical criteria such as pricing of different services in market environment. Besides, the charge of network usage is a controversial subject, itself. To address this problem, many methods for transmission line cost allocation have been proposed. Amongst them, MW-Mile methods are based on the extent of use concept. Inability to take various fixed together with variable imposed costs into account can be... 

In this research, application of the Endurance Time (ET) method in performance-based design of structures with and without consideration of uncertainties is investigated and a practical optimum design procedure is proposed. The ET method is used as an analytical assessment tool because of its capabilities in response estimation with an affordable computational demand. In the first step of the proposed method, ET analysis is implemented in a multi-objective optimum design procedure in order to achieve a set of Pareto optimal designs. Optimization is conducted with respect to initial cost and expected life cycle cost using a deterministic approach. For each design alternative the median... 

Gasification of black liquor is an alternative recovery technology. Pulp and paper industries are turning their attention to black liquor gasification as a replacement for recovery boilers. Gasification-combined cycle exergoeconomic analyses have been used to study the economical and exergetical performance of black liquor. Both conventional iterative exergoeconomic optimization and multi objective evolutionary optimization have been applied. The iterative optimization results have been compared with evolutionary programming results in order to evaluate the accuracy. The strength of proposed optimization methods are elucidated in a case study applied to Mazandaran Wood and Paper Industries...