Sharif Digital Repository

This paper studies a simultaneous weekly assignment and scheduling decisionmaking problem in operating theaters with elective patients. Because of limited recourses in hospitals, considering assignment and scheduling decisions simultaneously can help mangers exploit the available resources more efficiently and make the work-load uniformly distributed during the planning horizon. This procedure can significantly reduce hospital costs and increase satisfaction of patients and personnel. This paper formulates the mentioned problem as a Mixed Integer Linear Program (MILP) considering applicable assumptions like finite recovery beds and limitation of equipment. Since the problem is NP-hard, in... 

Next generation wireless networks will consist of different types of radio access technologies. Emerging diverse applications have attracted a lot of users. Therefore, having the best connectivity anytime anywhere has become an important issue. Users would like to have continuous high quality network connection even when they handover from one network type to the other. Each access technology has its own features and service quality. In this regard, when there is a handover, it is important to choose the most suitable network based on user needs. Different algorithms have been proposed for network selection. Multi Attribute Decision Making (MADM) methods are widely used due to their... 

Subcontractor (SC) selection is a critical part of SC management, and a major challenge is the existence of multiple criteria that the project management team needs to evaluate in the selection process. To overcome this challenge, the Kano model is applied to classify the selection criteria into five categories including must-be, reverse, one-dimensional, attractive, and indifferent. Data were obtained via a questionnaire based on Kano model concepts to categorize the identified selection criteria. The obtained results show that the selection criteria can be categorized into three categories; must-be, one-dimensional, and attractive. According to this categorization, the weight of criteria... 

In process robustness studies, it is desirable to minimize the influence of noise factors on the system and simultaneously determine the levels of controllable factors optimizing the overall response or outcome. In the cases when a random effects model is applicable and a fixed effects model is assumed instead, an increase in the variance of the coefficient vector should be expected. In this paper, the impacts of this assumption on the results of the experiment in the context of robust parameter design are investigated. Furthermore, two criteria are considered to determine the optimum settings for the control factors. In order to better understand the proposed method and to evaluate its... 

The environmental targets set by power sectors throughout the world are the main drivers toward increasing the share of variable renewable energy sources (VRESs). Growth of VRESs will lead to a higher demand for operational flexibility due to their stochastic nature. Traditionally, conventional generation units provide the major share of additional required flexibility that may result in a higher depreciation. Motivated by this challenge, this paper investigates the potential of Demand Response (DR) as an emerging alternative in systems with significant amounts of wind power. To this end, a comprehensive set of DR programs including tariff-based, incentive-based and combinational DR programs... 

The desired milling process with high material removal rate (MRR) and low surface roughness of the product can be achieved only if machining chatter is absent. Incorporating chatter into the optimal selection of the machining parameters leads to a complex problem. Therefore, the approach of selecting conservative intervals for the machining parameters is usually employed instead. In this paper, a practical approach is proposed to specify the optimal machining parameters (depth of cut and spindle speed) in order to maximize MRR and minimize forced vibrations by considering machining chatter. Firstly, the worst-case scenario-based optimization problem in terms of the surface quality is solved... 

Blood availability in hospitals is of high humanitarian importance, thus blood shortage is not desired at all. High wastage rate of blood in hospitals is an important issue, which becomes more important as the standards of health care services becomes higher. In order to address blood shortage and wastage issues in a hospital, this paper develops a new inventory management model as a decision making tool to help making tactical and operational level decisions for a Hospital Blood Bank (HBB) inventory management. These decisions include issuance and ordering policy and the aim of the model is to reduce blood wastage and shortage. For this purpose, a multi period, multi-product inventory... 

With the rapid proliferation of residential rooftop photovoltaic (PV) systems, current and voltage unbalance issues have become a matter of great concern in low voltage (LV) distribution feeders. To overcome the issues, this study proposes a model to optimally rephase customers and PVs among the three phases via static transfer switches (STSs). The optimal STS placement is also considered in the model to achieve a cost effective solution with optimum number and location of STSs. The objective is to minimise total energy losses caused by current unbalance, minimise the number of STSs, and keep voltage unbalance along the feeder within the acceptable range. The model is solved via a... 

Geothermal energy is a type of renewable energy with high availability and independence from climatic and atmospheric conditions. It has been shown that geothermal energy is technically, economically and environmentally more suitable for hydrogen production than other renewable sources. Hydrogen has wide applications in many fields including cooling, oil, gas, petrochemical, nuclear, and energy industries. Afghanistan has significant potential in geothermal power generation and also several hydrogen-consuming industries that provide opportunities for geothermal-based hydrogen production. This study attempted to find suitable locations for the construction of geothermal power plant for... 

The objective of this paper is to apply computational fluid dynamic (CFD) as a complementary tool for clinical tests to not only predict the present and future status of left coronary artery stenosis but also to evaluate some clinical hypotheses. In order to assess the present status of the coronary artery stenosis severity, and thereby selecting the most appropriate type of treatment for each patient, fractional flow reserve (FFR), instantaneous wave free-ratio (iFR), and coronary flow reserve (CFR) are calculated. To examine FFR, iFR, and CFR results, the effect of geometric features of stenoses, including diameter reduction (%), lesion length (LL), and minimum lumen diameter (MLD), is... 

With the advent of semantic technology' access control cannot be done in a safe way unless the access decision takes into account the semantic relationships among the entities in a semantic-aware environment. The SBAC model (Semantic Based Access Control model) considers this issue in its decision making process. However' time plays a crucial role in new computing environments'which is not supported in SBAC. In this paper' we propose the Temporal Semantic Based Access Control (TSBAC) model' as an extension of SBAC' which enhances the specification of user-defined authorization rules by constraining time interval and temporal expression over users' history of accesses. TSBAC uses logical... 

Web-based E-Leaning Systems (WELSs) have emerged as new means of skill training and knowledge acquisition, encouraging both academia and industry to invest resources in the adoption of these systems. Traditionally, most pre- and post-adoption tasks related to evaluation are carried out from the viewpoints of technology. Since users have been widely recognized as being a key group of stakeholders in influencing the adoption of information systems, their attitudes about these systems are considered as pivotal. Therefore, based on the theory of multi-criteria decision making and the research results concerning user satisfaction in the fields of human-computer interaction and information... 

All realistic Multi-Criteria Decision Making (MCDM) problems face various kinds of uncertainty. Since the evaluations of alternatives with respect to the criteria are uncertain they will be assumed to have stochastic nature. To obtain the uncertain optimism degree of the decision maker fuzzy linguistic quantifiers will be used. Then a new approach for fuzzy-stochastic modeling of MCDM problems will be introduced by merging the stochastic and fuzzy approaches into the OWA operator. The results of the new approach, entitled FSOWA, give the expected value and the variance of the combined goodness measure for each alternative. Robust decision depends on the combined goodness measures of... 

In order to achieve a hydrogen economy, developing widespread hydrogen supply systems are vitally important. A large number of technological options exist and are still in development for hydrogen production, storage, distribution., which cause various pathways for supplying hydrogen. Besides the technical factors, there are other effective parameters such as cost, operability, reliability, environmental impacts, safety and social implications that should be considered when assessing the different pathways as optimal and viable long-term alternatives. To aid this decision-making process, we have developed a generic optimization-based model for the long-range energy planning and design of... 

This paper introduces how to incorporate fuzzy set theory with discrete-event simulation in order to model uncertain activity duration in simulating a real-world system, especially when insufficient or no sample data are available. A case study is developed to apply this method to select a scenario to implement the maintenance program in a constant work in process (CONWIP) system. The maintenance activities directly or indirectly affect on production system performance such as response time production costs and etc. so we used the fuzzy simulation to determine the maintenance affects on the system performance. Finally we used the fuzzy simulation result to develop a fuzzy multi attribute... 

In order to design a decision-making framework in production environments, in this study, we use both the stochastic dynamic programming and Bayesian inference concepts. Using the posterior probability of the production process to be in state λ (the hazard rate of defective products), first we formulate the problem into a stochastic dynamic programming model. Next, we derive some properties for the optimal value of the objective function. Then, we propose a solution algorithm. At the end, the applications and the performances of the proposed methodology are demonstrated by two numerical examples. © 2007 Asian Network for Scientific Information  

This article proposes a new three-stage stochastic framework for dealing with predictable two-phase natural disasters in distribution systems. This framework is a multiobjective optimization, in which the amount of curtailed energy, the number of switching actions, and the vulnerability of operational components are selected as the main criteria for decision-making process. The optimization problem is formulated in the form of a stochastic mixed-integer linear programming (MILP) problem. In this article, a windstorm event followed by flooding is analyzed as a two-phase natural disaster. In this regard, the uncertainties associated with gust-wind speed, floodwater depths, and load demands are... 

Industrial loads play an important role in the success of demand response programs (DRPs). However, these programs may compromise the consumers' convenience, which can overshadow their real-world practicality. In response, this article provides a two-level decision-making tree approach to effectively determine the participation abilities of different industrial processes in DRPs considering various features and abilities of these customers. The level I of this framework introduces several classifying variables by which a basic criterion is extracted to classify different industrial processes applying the analytic hierarchy process (AHP). A participation factor is then introduced in level II... 

Choosing the right place to set up temporary hospitals is one of the most important and urgent measures for pandemic response. To solve this problem, we propose a new hybrid approach based on two steps. Firstly, since human health is highly sensitive to the impact of decisions about temporary hospital locations and a mistake may pose severe threat to human lives, we propose a new risk-averse multi-criteria decision-making (MCDM) approach. To choose the alternatives with the fewest possible weaknesses, a comprehensive hierarchal structure of relevant criteria categorized into environmental, social, economic, and infrastructural, along with a new risk-averse best-worst method (BWM), are... 

Storing information from incoming stimuli in working memory (WM) is essential for decision-making. The prefrontal cortex (PFC) plays a key role to support this process. Previous studies have characterized different neuronal populations in the PFC for working memory judgements based on whether an originally presented stimulus matches a subsequently presented one (matching-rule decision-making). However, much remains to be understood about this mechanism at the population level of PFC neurons. Here, we hypothesized differences in processing of feature vs. spatial WM within the PFC during a matching-rule decision-making task. To test this hypothesis, the modulation of neural activity within the...