جستجوی مقالات مرتبط با کلیدواژه "mathematical modeling" در نشریات گروه "صنایع"
تکرار جستجوی کلیدواژه «mathematical modeling» در نشریات گروه «فنی و مهندسی»-
One of the constant problems that people with mental health conditions are faced with now is that they cannot establish a good relationship with their therapist, or the client's disease type is not in the therapist's specialty. These clients may not receive adequate treatment and stop the therapy before feeling well. Therefore, the classification of mental patients based on their disorder types and allocating a therapist with the same expertise to them could lead to better treatment and improve the quality of the therapy sessions. This paper will compare several machine learning (ML) algorithms to classify patients with mental conditions. Moreover, benefiting from the best ML algorithm, patients will be categorized into different classes based on their disorder types. Finally, a mathematical model will be developed to determine the allocation policy of therapists to each group of patients to maximize the summation of the utilization between therapists and patients. To explore the implementation of the proposed method, we have conducted a real-life case study to assess the validation of the model.Keywords: Mental Health, Data-Driven Decision-Making, Scheduling, Mathematical Modeling, Machine Learning, Patient Allocation
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Journal of Quality Engineering and Production Optimization, Volume:8 Issue: 2, Summer-Autumn 2023, PP 1 -20In this paper, the Risk-constrained Cash-In-Transit Vehicle Routing Problem (RCITVRP) is addressed with time windows, pickups, and deliveries. It is crucial for Cash-In-Transit (CIT) companies involved in transporting valuable or hazardous goods to identify risks. Therefore, owing to the high level of risk in CIT operations (e.g., armed robbery or attack), a bi-objective mixed-integer non-linear programming (MINLP) model is used to minimize travel costs and the risks associated with transporting valuables. For risk minimization, a new risk measure is developed, which includes: (i) the level of vulnerability for each vehicle, and (ii) the threat probability on each route. In addition, multiple vehicles are considered with capacity limitations. The epsilon-constraint method, a multi-objective exact solution approach, is implemented to solve the proposed model. Furthermore, several numerical examples are generated to evaluate the model and the solution method, which clearly show the best route with minimum cost and minimum risk (cost value = 112, risk value = 64,600). Eventually, a case study is provided to investigate the applicability of the proposed model.Keywords: Cash-In-Transit Problem, Mathematical Modeling, Multi-Objective, RCITVRP, Risk Assessment, Robbery
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هدف
این مقاله به مطالعه مساله برنامه ریزی پرورش ماهی در زنجیره های مختلف و مدیریت فروش در یک مزرعه پرورش ماهی در طول یک افق زمانی مشخص می پردازد و هدف آن تعیین بهینه زمان شروع و میزان تخم ریزی در زنجیره های مختلف، زمان صید و مدیریت سفارشات موجود در دوره های مختلف می باشد.
روش شناسی پژوهش:
در این مطالعه، یک فرمول بندی جدید در قالب یک مدل برنامه ریزی خطی عدد صحیح آمیخته ارایه شده است که می تواند جواب بهینه مساله را در مدت زمان کوتاهی پیدا کند. در مدل پیشنهادی جدید، برخی از مراحل میانی زنجیره پرورش ماهی که هیچ تاثیری بر تصمیمات کلیدی ندارند، نادیده گرفته می شوند و درنتیجه اندازه و پیچیدگی مدل پیشنهادی بدون نادیده گرفتن فرضیات حاکم بر مساله و از دست رفتن بهینگی جواب ها کاهش می یابد.
یافته هاپس از پیاده سازی مدل پیشنهادی، با استفاده از نمونه داده های مختلف، مشاهده می شود که اندازه مدل، تعداد متغیرها و زمان اجرای آن در مقایسه با مدل مشابه کم تر است و با وجود اضافه کردن فرضیات واقعی جدیدی به مساله، این مدل قادر است در زمان کوتاهی جواب مساله شامل حجم و زمان تخم ریزی در هر زنجیره پرورش، زمان صید و نیز پذیرش یا رد تقاضاهای عمده را در دوره های مختلف به صورت بهینه تعیین کند.
اصالت/ارزش افزوده علمی:
در این مطالعه برای مساله زمان بندی زنجیره های پرورش ماهی و مدیریت فروش که تاکنون مطالعات اندکی در این زمینه صورت گرفته است، یک مدل جدید برنامه ریزی خطی عدد صحیح آمیخته ارایه شده است که در مقایسه با مدل موجود قبلی هم فرضیات واقعی بیشتری در آن لحاظ شده است و هم زمان اجرای کم تری دارد.
کلید واژگان: پذیرش سفارشات, تعیین اندازه انباشته, صنعت پرورش ماهی, مدل سازی ریاضیPurposeThis article studies an issue in the fish farming industry in which the goal is to find the best multi-period planning for handling various chains, including ordering, breeding, and selling of trout over a time horizon.
MethodologyIn this study, a new formulation is presented as a mixed integer linear programming model that could find the optimum solution quickly. In the new proposed formulation, some intermediate stages of the breeding chain that do not affect decisions are ignored, and therefore, the size and complexity of the proposed model reduce without compromising the optimality of the answers.
FindingsAfter implementing the proposed model, using different data samples, it can be seen that this model achieves the optimal solution in a short time, including volume and time of spawning in each breeding chain and different periods, harvesting time, and accepting or rejecting the main demands.
Originality/Value:
In this paper, the issue of scheduling of fish farming chains and sales management, which there are a few studies in this field, has been studied and a new mixed integer linear programming model is presented. Compared to the previous model, this model has more realistic assumptions and less complexity and execution time.
Keywords: order acceptance, Lot sizing, Fishing industry, Mathematical Modeling -
اخیرا زنجیره های تامین و شبکه های تامین در حال توسعه به سمت شبکه های تامین درهم آمیخته اند. این ساختارهای جدید، پویا و درحال تکامل، متفاوت از زنجیره تامین های خطی با ساختارهای ایستا هستند و نیاز به بازنگری در برخی از مفاهیم سنتی دارند. هدف این پژوهش، مدل سازی ریاضی شبکه تامین درهم آمیخته سه سطحی (شامل تامین کننده، تولیدکننده، مشتریان) با محوریت تاب آوری است. روش این پژوهش، از نوع بنیادی کاربردی است. رویکرد آن از نوع کمی و از نوع مدل سازی ریاضی است. در این تحقیق، ابتدا مساله مدل سازی می شود و با استفاده از داده های واقعی، در نرم افزار GAMS حل شده و پس از تعیین مقادیر بهینه متغیرهای تصمیم، نتایج آن تحلیل گردیده است. همچنین، روی پارامتر موثر (ظرفیت تولید) تحلیل حساسیت انجام شده است. نتایج نشان داد افزایش پارامتر ظرفیت به دلیل ثابت بودن تقاضا و کمتر بودن تقاضا از ظرفیت تولید تاثیری بر اهداف شبکه نداشت. مدل پیشنهادی ضمن بهینه سازی شبکه های تامین درهم آمیخته ، قادر است تاب آوری شبکه را نیز در مقابل اختلال تقویت کند. از سوی دیگر، کارایی رویکرد پیشنهادی از طریق به کارگیری آن در مطالعه موردی شبکه تامین درهم آمیخته کاشی و سرامیک نشان داده شده است.
کلید واژگان: شبکه تامین درهم آمیخته, پویایی زنجیره تامین, مدل سازی ریاضی, تاب آوری, بهینه سازی چندهدفهJournal of Industrial Engineering Research in Production Systems, Volume:10 Issue: 20, 2023, PP 77 -89Recently, supply chains and supply networks are developing towards intertwined supply networks. These new, dynamic structures are different from linear supply chains with static structures and require a revision of some traditional concepts. The aim of this research is mathematical modeling of the three-level supply network (including suppliers, firms, customers) based on resilience. Its approach is quantitative and mathematical modeling. In this research, first the problem is modeled and solved using real data in GAMS software, and after determining the optimal values of the decision variables, the results are analyzed. Also, a sensitivity analysis has been performed on the effective parameter (production capacity). The analysis of the results showed that increase of the capacity parameter did not affect the total cost of the network due to the constant demand. The proposed model, while optimizing the intertwined supply networks, is able to strengthen the resilience of the network in the face of disruption. On the other hand, the effectiveness of the proposed approach has been shown by using it in a case study of the intertwined supply network of tiles and ceramics.
Keywords: Intertwined Supply Network, Supply Chain Dynamics, Mathematical Modeling, Resilience, Multi-Objective Programing -
Journal of Advances in Industrial Engineering, Volume:57 Issue: 1, Winter and Spring 2023, PP 75 -95Airlines try to reduce costs by improving the quality of their operational schedules. However, numerous uncontrollable factors make disruptions inevitable. A flight delay or cancellation caused by disruption may spread throughout the network and increase the operational costs by affecting the schedule of other flights, including aircraft, crew, and passengers’ itineraries. While previous researchers have focused on one of these aspects or sequential approaches, the resulted solutions cannot lead to a reliable operational solution due to the complex relationships between these factors in practice. Therefore, integrated recovery approaches are highly essential. The main objective of this research is to provide a fully integrated recovery model that contains various recovery scenarios to tackle the disruption and delay propagation with more flexibility and acceptable solution time. So, an integrated model for crew, aircraft, and passenger recovery problem is proposed in this paper. The proposed model is formulated as MILP, based on individual flight legs to achieve a more accurate schedule with better recovery solution. Options such as aircraft reassignment, crew swapping, reassignment of passengers, and ticket refunds are considered as alternatives to face disruption. Moreover, the considerations related to crew rest-time and maintenance requirements are also included in the model. Due to the NP-Hard nature of the problem, the Genetic algorithm is used as the solution approach successfully for the real-world data to limit delay propagation on various random flights.Keywords: Integrated Airline Recovery Problem, Mathematical Modeling, Delay Propagation, Genetic Algorithm
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Journal of Quality Engineering and Production Optimization, Volume:7 Issue: 2, Summer-Autumn 2022, PP 34 -59In this paper, we offer an analysis and model of a manufacturing line that uses a priority mechanism to process various types of parts in faulty machinery. The manufacturing line comprises machines separated in a set order by storage rooms where components are fluxed. When it is possible, a machine works on the most important part first and only switches to less important parts if it is unable to produce the most important ones. Only one sort of function is required for each section. Because it is expected that the processing line machinery can handle a range of part types, switching from one kind of component to another will not result in any setup penalty. Only when unable to process higher priority parts owing to obstruction or hunger can the machines work on the lower priority parts. The machines function according to a fixed priority rule. The purpose of this study is to develop mathematical formulations and procedures for each kind of component in a flexible production line. In a variety of supply and demand scenarios, the multipart line's qualitative behavior is described.. To better understand the line, we devise decomposition equations and a solution technique to put them to use. With suitable line parameters, the method converges consistently. The findings of the decomposition were verified using simulations. The line's fascinating behavior may be seen in the system's study of many parameters.Keywords: Flexible manufacturing systems (FMS), Mathematical modeling, Production lines
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در این مقاله، نوع خاصی از مسیله مکان یابی-تخصیص هاب برای یک مطالعه موردی واقعی معرفی شده است. با توجه به اینکه معمولا تسهیلات هاب ظرفیت محدودی دارند، مسیله در حالت ظرفیت دار بررسی می-شود. همچنین، از آنجایی که معمولا خدمات به روش های مختلفی به مشتریان ارایه می شود و مطالعه این موضوع به حل مسیله در دنیای واقعی کمک می کند، مدل مسیله براساس نوع خدمت طراحی شده است. براساس مطالعات انجام شده، این موضوع در مطالعات پیشین مورد بررسی قرار نگرفته است. این مسیله بر اساس یک مطالعه موردی در سیستم هاب پستی شرکت ملی پست جمهوری اسلامی ایران بررسی شده است. در این مطالعه یک مدل ریاضی با توجه به ویژگی های این سیستم پیشنهاد شده است. همچنین برای حل مدل ارایه شده از روش حل دقیق با استفاده از حل کننده CPLEX استفاده شده است. بر اساس محاسبات انجام شده و مقایسه با شرایط موجود، مدل ریاضی ارایه شده در برخورد با مسایل طراحی شبکه هاب شرکت پست ج.ا.ا. موثر است و منجر به کاهش هزینه ها نسبت به سیستم فعلی می شود.
کلید واژگان: مسئله مکان یابی-تخصیص هاب, مدل سازی ریاضی, مکان یابی ظرفیت دار, مکان یابی مبتنی بر نوع خدمتIn this paper, a special type of hub location-allocation problem is introduced for a real case study. Considering that the hub facilities usually have a limited capacity, the problem is investigated in the capacitated mode. Also, since services are usually provided to customers in different ways, and studying this helps to solve real-world problems, the problem model is designed based on the type of service. To our knowledge, this issue has not been investigated in previous studies. This issue has been investigated based on a case study in the postal hub system of the National Post Company of the Islamic Republic of Iran. This problem can be generalized in various other applications such as online stores, airports and telecommunication systems, and modeling based on the conditions in these systems and providing a suitable solution method can be used as an applied research. In this study, a mathematical model is proposed according to the characteristics of this system. Also, the exact solution method using the CPLEX solver has been used to solve the presented model. Based on the calculations and comparison with the existing conditions, the mathematical model presented in dealing with the design issues of the hub network of J.A. Post Company. It is effective and leads to cost reduction compared to the current system. Based on the results obtained from the implementation of the mathematical model, the provinces of Tehran, Tabriz, Mashhad, Ahvaz, Shiraz, Isfahan and Kerman were determined as postal hub centers. This is while in the current situation, the provinces of Tehran, Tabriz, Mashhad, Ahvaz, Shiraz, Isfahan and Hamadan are used as land postal hubs.
Keywords: Location-allocation hub problem, Mathematical modeling, capacitated location, location based on service type -
The aim of this paper is to propose a mathematical model for two dental centers in a competitive market of dental tourism. Dental tourists are looking for cheaper treatment with proper quality, and dental centers are looking to maximize their profits by providing services to tourists. Government also monitors dental centers by setting tariffs (subsidies or taxes). This problem is modeled and solved in the form of Stackelberg (or Leader-Follower) game. The government as the leader determines the amount of tariffs and then the dental centers as the followers simultaneously determine the price and quality level of their services. To solve the game, first the equilibrium values related to the price and quality level of the services of the dental centers have been calculated by Nash equilibrium. Then, according to the equilibrium values obtained for dental centers, the optimal amount of tariffs are calculated. Finally, to clarify the proposed model a numerical example is provided and sensitivity analysis is performed on some parameters. In this paper, for the first time a mathematical model is developed for pricing and determining the quality of services in a competitive market of dental tourism. The obtained results indicate that increasing the amount of subsidy will lead to a decrease in the prices of service provided by the dental centers. Moreover, by increasing the amount of subsidies allocated to the dental centers, the government can expand the dental tourism industry.Keywords: Mathematical Modeling, Stackelberg game, Leader-Follower Strategy, pricing
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متوازن بودن خط تولید به لحاظ زمان بندی و توزیع بار برروی ماشین ها می تواند سبب ارتقاء شاخص های حایز اهمیت تحویل و تولید به موقع گردد که رضایت مشتری و مزیت رقابتی را برای تولید ایجاد می کند. توازن خط تولید موجب کاهش هزینه های ظرفیت ازدست رفته و نامتوازن بودن در خطوط می گردد. الگوریتم رابین هود از روش های بالانس تولید است که مهم ترین مزیت آن برنامه ریزی آنلاین تولید و توزیع متناسب بار برروی ماشین ها می باشد؛ اما وقتی تعداد سفارشات کار زیاد است؛ این روش پاسخ گو نیست. در این مقاله، تمرکز بر بهینه سازی و توسعه مدل ریاضی الگوریتم رابین هود است؛ به طوری که این مدل بتواند برنامه ریزی تعداد زیاد سفارشات کار را انجام دهد. توسعه مدل با دو هدف کمینه کردن بیشینه ی بار روی سیستم تولید، و کمینه کردن زمان اتمام سفارش ها برروی ماشین ها صورت می پذیرد. مساله ی بالانس تولید جزو مسایل NP-hard می باشد و با توجه به این که برای این گونه از مسایل راه حل سریع و قابل انجام در زمان معقول پیدا نشده است؛ برای یافتن جواب های نزدیک به بهینه ی مدل ریاضی چندهدفه ارایه شده، از الگوریتم NSGA-II استفاده گردیده است. نتایج حاصل از توسعه مدل ریاضی در الگوریتم رابین هود نشان می دهد که بالانس خط تولید در تعداد سفارشات زیاد و تغییرات لحظه ای در برنامه تولید، با استفاده ازاین روش می تواند برنامه ریزی تولید را ارتقاء دهد.
کلید واژگان: بالانس به هنگام خط تولید, الگوریتم رابین هود, مدل سازی ریاضی, الگوریتم ژنتیک نامغلوب مرتب شدهJournal of Industrial Engineering Research in Production Systems, Volume:8 Issue: 17, 2021, PP 437 -451Balanced production line in terms of timing and load distribution on machines can improve the important indicators of timely delivery and production, which creates customer satisfaction and competitive advantage for production.Production line balance reduces lost capacity costs and unbalanced lines.Robin Hood algorithm is one of the production balance methods, the most important advantage of which is online production planning and proportional distribution of load on machines, but when the number of work orders is large, this method is not responsive.This paper focuses on optimizing and developing the mathematical model of Robin Hood algorithm so that this model can plan a large number of work orders.Development of the model with two objectives minimizing the maximum load on the production system and minimizing the order completion time Takes place on machines.The problem of production balance is one of the NP-hard problems, and since no Iuick and feasible solution to such problems has been found in a reasonable time, the NSGA algorithm can be found to find close to optimal solutions to the proposed multi-objective mathematical model.-II has been used.The results of the development of the mathematical model in Robin Hood algorithm show that the balance of the production line in the large number of orders and momentary changes in the production plan, using this method can improve production planning.
Keywords: Online balancing, Robin Hood Algorithm, Mathematical Modeling, NSGA-II -
در این مقاله یک مدل یکپارچهی تولید موجودی برای زنجیرهی تامین دو سطحی شامل یک تولیدکننده و چند خردهفروش با در نظر گرفتن کیفیت مواد اولیه و محصول نهایی، قیمت محصول نهایی بر اساس طول عمر باقیمانده و تخفیفهای مقداری برای مواد اولیه ارایه میشود. هدف اصلی در این پژوهش به دست آوردن تعداد محموله مواد خام وارد شده، تعداد محمولهی محصول نهایی تحویل داده شده به خردهفروشان در یک چرخهی تولید و زمان چرخهی تولید است به طوری که سود کل سیستم بیشینه شود. در مدل ریاضی NLMIP پیشنهادی نرخ تولید و تقاضا ثابت فرض شده و کمبود مجاز نیست. برای نمایش عملکرد مدل و الگوریتم، به حل یک مثال و تحلیل حساسیت پرداخته میشود. نتایج نشان میدهد که بسته به میزان نرخ زوال، تعداد و حجم سفارشات تغییر میکنند به صورتی که با افزایش این نرخ تعداد سفارشات افزایش و میزان آنها کاهش مییابد.
کلید واژگان: کنترل موجودی, زنجیره ی تامین, کالای فاسد شدنی, تخفیف مقداری, مدل سازی ریاضیEffective coordination in a supply chain plays a vital role in improving its efficiency. This becomes more critical when it comes to deteriorating materials and products in order to reduce a huge amount of waste or demand fluctuations. Integrated management can effectively reduce the total cost including waste costs, holding costs, shipping, and delivering costs and increase the income, especially when the price or even the demand is affected by the freshness. In this article, an integrated production-inventory system for a perishable product in a two-echelon supply chain, including a producer and multi-retailers, is considered. The quality of raw material and finished product varies at the holding interval and the price is an age-dependent function. Volume discounts are available. The shortage is not allowed. The rates of production and demand are considered determined and fixed. The numbers of deliveries to retailers are not essentially equal. The objective is to determine the number of raw material deliveries to the producer and the number of deliveries from the producer to each retailer in a production cycle in a way that total profit is maximized. This combination of assumptions has not been considered in the literature yet. A nonlinear mixed-integer programming model is developed for the problem. Because of the complexity of the problem, a metaheuristic algorithm is employed to solve the numerical examples. An example is solved and sensitivity analysis is done using a genetic algorithm. The results show that the optimal number of orders and also the economic order sizes change corresponding to the rate of deterioration such that the higher the rate of deterioration, the larger the number of orders and the lower the size of each order. The profit almost increases significantly in the presence of volume discounts in all cases and also increases when a different number of delivers per each cycle for different retailers is possible.
Keywords: Inventory control, Supply chain, deteriorating product, quantity discount, mathematical modeling -
International Journal of Research in Industrial Engineering, Volume:9 Issue: 4, Autumn 2020, PP 304 -312
Operating rooms (ORs) are among the most influential departments of a hospital that a major portion of its expenditures and revenues originate from it. Due to the limited resources and the presence of different stockholders, effective management, and the optimal planning of this department are challenging. This paper develops a mathematical model to address the integrated problem of the operating room and surgical member scheduling with the objective of makespan minimization. In the proposed model, several aspects, including the availability and necessity of surgical members and equipment, and lunch break consideration, are incorporated. Finally, a case study related to an OR department in a general hospital is provided to assess the applicability and performance of the proposed model.
Keywords: Operating room, Nurse scheduling, Mathematical Modeling, Lunch break -
International Journal of Research in Industrial Engineering, Volume:9 Issue: 4, Autumn 2020, PP 318 -327In this research, we present a mathematical model for allocating people to different jobs and shifting employees between related jobs. This action will reduce the repetitive activities workload and ergonomic risks at the planned time horizon, and finally increases the organization's efficiency. In this proposed model, the devices are semi-automatic and it is possible to allocated more than one task to one person. Regarding the modeling and the case study of the constraints, it is shown that the complexity of this problem type is NP-Hard, and the result of accurate methods for solving the problem is not possible in a reasonable time. Due to this Simulated Annealing (SA) algorithm is used to study the proposed model and comparison of the results of SA algorithm with the results of precise optimization methods shows the better performance of the Simulated Annealing algorithm in terms of the time and answer quality.Keywords: Job Rotation, Mathematical Modeling, physical injuries, Simulated Annealing Algorithm
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During the last three decades, the concept of integrated decision making in the supply chain becomes one of the essential aspects of supply chain management (SCM). This concept explores the interdependence between facility location, flow allocation between facilities, transportation system structure, and inventory control system. This study presents a new form of the location-routing problem of facilities under uncertainty in a supply chain network for deteriorating items through taking environmental considerations, cost, and procurement time and customer satisfaction into account, to simultaneously minimize total system costs, maximal delivery time and emissions across the entire network and maximize customer satisfaction. The research problem is formulated in a mixed-integer nonlinear multi-objective programming. In order to solve the model, the combination of the two Benders decomposition algorithm and Lagrange multiplier liberalization, as well as the combination of red deer algorithm and annealing simulation, was proposed. For validation, the results of the proposed algorithm in different size examples are compared with the results of the exact method solution by MATLAB software. The mean error of the proposed algorithm for the objective function is less than 4% compared to the exact method in solving the sample problems. Besides, the results of the algorithm performance are investigated based on standard indices. The computational results show the efficiency of the algorithm for a wide range of problems with different sizes. The location decisions are interdependent, and the process of determining the optimal values of these variables interact together, which can lead to an optimal system.Keywords: Location-routing, Multi-level Supply Chain, Multiproduct deteriorating items, Multiproduct, Mathematical Modeling
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Today, with the advancement of sciences in various fields, mathematics is being optimally used in all sciences, mathematics is therefore widely used in other sciences, and Islamic and military sciences are no exception, and mathematics can be used to design various offensive and defensive operations in battlefields and solve battlefield equations in order to gain absolute or relative superiority over the enemy as in the game theory of war, the application of mathematics can be clearly seen. This practical research, conducted through a library method, has modeled the challenges between the two armies of Imam ʿAlī ibn Abī Ṭālib (AS) and a group called the Māriqīn or Khawārij in the battle of Nahrawān using Game Theory and analyzed each army’s strategies against each other, and finally explore the war utility to find the strategic equilibrium point between them. Therefore, we calculate the utility function for the set of strategies of each of the two armies including the army of Amir al-Mu’minin, ʿAlī ibn Abī Ṭālib (AS) and the Khawārij of Nahrawān and analyze it.Keywords: Strategies, Mathematical Modeling, game theory, Battle of Nahrawān
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Sustainability in the supply chain means pushing the supply chain to focus on social, economic and environmental aspects, and addressing the existing problems in the traditional supply chain. Considering the importance of evaluating supply chain networks, especially in the field of perishable commodities, this paper aimed to design a mathematical model for the reverse supply chain of perishable goods, taking into account the sustainable production system. In this research, four objective functions were considered to maximize profitability and the level of satisfaction with the use of technology, minimize costs and measure environmental impacts. The results of the implementation of the proposed model for a manufacturing company show that objective functions are sensitive to demand, so the change in demand changes the objective functions, in particular the profitability function.
Keywords: Reverse logistics chain network, Sustainable production system, Perishable products, Mathematical modeling -
Right now employment of polices and tools to decrease the carbon emission through electricity generation from renewable resources is one of the most important problem in energy policy. Tradable Green Certificate (TGC) is an economics mechanism to support green power generation. Any country has the challenge to choose an appropriate policy and mechanism for design and implementation of TGC. The purpose of this study is to help policy makers to design and choose the best scenario of TGC by evaluating six scenarios, based on game theory approach. This study will be useful for increasing the effectiveness of TGC system in interaction with electricity market. Particularly, the competition between thermal and renewable power plants is modeled by mathematical modeling tools such as cooperative games like Nash and Stackelberg. Each game is modeled by taking into account of the two following policies. The results of the six scenarios and the sensitivity analysis of some key parameters have been evaluated by numerical studies. Finally, in order to evaluate the scenarios we calculated the level of social welfare in the all scenarios. The results of all models demonstrate that when the green electricity share (minimum requirement) increases the TGC price decreases. Moreover, in all scenarios when the minimum requirement is 100% then the maximum level of social welfare is not met. Also when the minimum requirement is less than 50%, the scenarios with the market TGC price policy have more social welfare in comparison with the scenarios with fixed TGC price policy.
Keywords: Green electricity, Tradable Green Certificate, Game theory, Mathematical modeling -
In this paper, we introduce a two stages model for allocation of injuries and medical supplies to medical centers. In the first stage a multi objective mathematical model allocates injured people from the affected neighborhood to medical centers. In the second stage a single objective linear model allocates medical supplies from the supply points to medical centers. The first stage’s objective is simultaneously minimizing the total relief time and costs and maximizing the level of matching the type of injury with the specialized field of the medical centers those injuries are sent. The second stage’s objective is to minimize the costs of allocating medical supplies to medical centers. An integrated model that combines the two previous models is presented and comparing the results with the two stages model. Proposed models are applied to one of the districts of Tehran to demonstrate their effectiveness. The case study includes two affected neighborhood and four medical centers and three supply points. ϵ-constraint method is used to produce the Pareto optimal solutions in a MOMP.
Keywords: Emergency condition, Mathematical Modeling, assignment, Multi-objective Programming, ϵ-constraint method -
توانایی هر سازمان در هماهنگ کردن تصمیمات با مشتری نهایی، باعث افزایش رضایت مشتری و ایجاد مزیت رقابتی و سودآوری بیشتر سازمان می شود. با توجه به اهمیت عملیات تولید، انتقال و تحویل محصول در سازمان هایی که مشتریان در گستره ی وسیع جغرافیایی پراکنده اند، در این مقاله شبکه ی بهینه یی برای اتخاذ تصمیمات بهینه ی یکپارچه ی تولید، انتقال و توزیع محصولات نهایی معرفی شده و مدل ریاضی شبکه ی پیشنهادی در فضای تولیدی جریان کارگاهی ارائه شده است. در این تحقیق به کمک مفهوم محدوده ی مشتریان، در شبکه ی پیشنهادی انتقال محصول به مراکزمحدوده ی مشتریان به روش ارسال مستقیم و همچنین تحویل در داخل محدوده ی مشتریان به روش مسیریابی انجام شده است. به منظور سنجش عملکرد مدل، مسائل عددی استاندارد تصادفی در اندازه های مختلف تولید شده و پس از حل، کارایی مدل پیشنهادی ارزیابی شده است. در انتها نیز بخش تحلیل حساسیت به بررسی تاثیر عوامل مختلف بر روی شبکه پرداخته است.
کلید واژگان: شبکه ی بهینه ی تولید و انتقال و توزیع, رویکرد یکپارچه, سیستم تولیدی جریان کارگاهی, مدل سازی ریاضی, تحلیل حساسیتDue to the market globalization, implementation of the integrated approaches among various operations in a supply chain network has become one of the fundamental decisions for the manufacturers to gain more bene- ts and competitive advantages for their production systems. Most of the production scheduling studies assumes job sequencing without attention to the delivery concept or by assuming delivery after production hieratically and separately. Also, the ability of the organization to coordinate their operational decisions with nal customers, increase customer satisfaction, followed by competitive advantage and ultimately more protable for the organization. Given the importance of production, transportation and delivery of products to nal customers in organizations that are customers are in wide geographical locations, in this study, the optimized network is developed for integrated decisions of production, transportation and delivery of nished products to the customer. Thus, the joint scheduling of production and delivery operations as both pivotal and important operations in the manufacturing system is studied with an integrated vision in this paper. A mixed integer programing (MIP) model is developed to formulate the proposed network in ow shop system. In proposed network, transportation of orders to the center of customer areas is done via direct delivery method and delivery within the customer area is done by routing. The models objective function is to minimize total cost for the integrated model, which includes sum of the production cost and delivery cost. In order to assess model performance and in the absence of standard numerical example, some numerical examples are randomly generated in dierent sizes and then solved to show the eciency of the proposed model. As well as to evaluate the impact of various decisions on the objective function of the proposed network, the detailed sensitivity analysis was conducted to evaluate the impact of various factors on the network.
Keywords: Optimized network production, transmissionand delivery, integrated approach, Flow shop productionsystem, mathematical modeling, sensitivity analysis -
اخیرا در صنایع تولیدی، مسائل مرتبط با مصرف انرژی اهمیت یافته است. در مسایل کلاسیک زمان بندی، تلاش ها عمدتا در جهت بهینه سازی معیارهای عملکرد مرتبط با زمان بوده است و کمتر به بررسی معیارهای مربوط به مصرف انرژی پرداخته شده است. در این تحقیق، ما به دنبال جبران این نقص می باشیم که با ارائه یک مدل سه هدفه عدد صحیح مختلط در محیط جریان کارگاهی به بررسی کاهش مصرف انرژی، زمان اتمام و زمان دیرکرد کارها پرداخته ایم. بعد از اعتبارسنجی مدل با حل مثال عددی در مقیاس کوچک به روش مجموع وزنی و روش دقیق اپسیلون-محدودیت در نرم افزار گمز، مدل را در مقیاس بزرگ و متوسط توسط الگوریتم های فراابتکاری NSGA-II و SPEA-II حل می نماییم. نتایج مقایسات میان روش دقیق و روش های فراابتکاری نشان می دهد که این الگوریتم ها کارایی لازم برای حل مدل را دارا هستند. از این میان، الگوریتم NSGA-II عملکرد بهتری را از لحاظ دو معیار کیفیت و نظم نقاط پارتو ارائه داده است.کلید واژگان: مدل سازی ریاضی, زمان بندی جریان کارگاهی, مصرف انرژی, زمان اتمام, زمان دیرکرد, الگوریتم های فراابتکاریEnergy consumption considerations in production systems have recently attracted the attention of researchers. In conventional production scheduling models the importance has more often been given to time-related rather than to energy-related performance measures. In this paper we simultaneously consider energy consumption, completion time and tardiness in the presented Multi-Objective Mixed Integer Programming flow shop scheduling model. After validating the model by solving small-scale numerical examples with Weighted Sum and Epsilon-constraint method in GAMS, the large and medium-scale examples are solved via NSGA-II and SPEA-II metaheuristic-algorithms. The results proves the efficiency of the proposed algorithms.Keywords: Energy consumption, mathematical modeling, completion time, tardiness, metaheuristic algorithms
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افزایش هزینه ها و پایین بودن رضایت شغلی کادر پرستاری بیمارستان ها متاثر از بهره گیری از روش های سنتی و غیرعلمی در تخصیص پرستاران به شیفت ها می باشد. بخش مراقبت های اورژانس از واحدهای ویژه بیمارستانی که مطالعه و بررسی جریان بیمار از حساسیت بالایی برخوردار است. در این پژوهش ابتدا وضعیت فعلی بخش اورژانس بیمارستان امام رضا (ع) تبریز توسط نرم افزار Arena 14 طراحی شده است. سپس در ادامه سه سناریو با تعداد پرستاران متفاوت، حالت فعلی این بخش را با سناریو های مطرح شده مقایسه می کند. برای بررسی هزینه ها و رضایت شغلی پرستاران در هر سناریو، یک مدل ریاضی برنامه ریزی غیر خطی عدد صحیح ارائه شده است. در این مدل، علاوه بر بهینه کردن هزینه و رضایت شغلی پرستاران، تخصیص مناسبی نیز از شیفت بندی پرستاران مدنظر قرار گرفته است. در بخش پایانی با تحلیل خروجی های هر دو مدل شبیه سازی و برنامه ریزی غیر خطی، مشخص شده است که تعداد پرستاران موجود برای این بخش کافی نبوده و باید 6 پرستار به این بخش اضافه شوند.کلید واژگان: بهینه سازی زمان فرآیند ارائه خدمات, شبیه سازی, مدل سازی ریاضی, روش معیار جامع (GCM)Patient waiting time, the costs, and nurses job satisfaction level are important criteria in providing services in hospital. One of the main causes of long patient waiting times is the lack of sufficient expert staff in the hospital. Increased costs and low job satisfaction of nursing staff in hospitals are the result of applying traditional and nonscientific methods in assigning nurses to shifts. The emergency department is one of the special units in the hospital, in which studying the patient flow is highly important. In this study, the current status of Imam Reza Hospital emergency department in Tabriz, Iran is simulated using ARENA 14 software, in order to assess the costs and size of the waiting line. Then, the current status of this department is compared with three scenarios with different number of nurses. In order to evaluate the costs and nurse job satisfaction in each scenario, a nonlinear integer programming mathematical model is proposed. In this model, nurses are properly assigned to shifts and weekdays in order to minimize the costs and to increase nurse job satisfaction. Finally, analyzing both nonlinear programming and simulation model, the results show that the number of nurses in this department is not sufficient and that six nurses should be added to the staff.Keywords: Generalized Center Method, Mathematical Modeling, Multi-Objective Allocation Problem, Optimization of Service Provision Time, Simulation
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