multi-objective model
در نشریات گروه صنایع-
حمل و نقل بخش قابل توجهی از تولید ناخالص ملی و مصرف محصولات نفتی هر کشوری را به خود اختصاص می دهد. در کشور ما با توجه به تحریم های سال های اخیر و عدم توسعه ی سامانه های حمل و نقل ریلی، هوایی و دریایی، استفاده از حمل و نقل جاده ای بیشتر شده است. حمل و نقل جاده ای بیشترین نقش را در تولید گازهای گلخانه ای نظیر کربن دی اکسید دارد. بااین حال حمل و نقل یکی از عناصر اصلی لجستیک بوده و مسیله ی مسیریابی وسایل نقلیه با در نظر گرفتن آلودگی از جمله مهم ترین مسایل در این حوزه است. بنابراین در این مقاله با درنظر گرفتن عواملی چون بار وسیله نقلیه، سرعت وسیله نقلیه، پارامترهای آلایندگی وسیله نقلیه نظیر ضریب بهره وری سوخت و موتور، شیب مسیر، تراکم رفت وآمد، سرعت و جهت باد، دمای هوا و جنس آسفالت به بهینه سازی هزینه های ناشی از مصرف سوخت و دستمزد راننده پرداخته شده است. همچنین با درنظر گرفتن تقاضا به صورت احتمالی و سامانه توزیع با جمع آوری و تحویل کالا، یک مدل ریاضی احتمالی عددصحیح آمیخته خطی به منظور کمینه سازی مجموع هزینه های ذکر شده ارایه گردیده است. استفاده از این مدل موجب تخمین دقیق تر هزینه های سامانه شده و منجر به تحلیل و برنامه ریزی بهتر برای سازمان ها می شود. باتوجه به اینکه مسیله ی مطرح شده از نوع مسایل با درجه سختی بالا می باشد، مسیله در ابعاد بزرگ با ترکیب دو الگوریتم فراابتکاری یادگیری ماشین حداکثری و برنامه ریزی ژنتیک حل شده است. با توجه به نتایج حاصل شده از محاسبات، الگوریتم ترکیبی توسعه یافته قابلیت تخمین جواب با دقت مناسبی را دارد و از سرعت عمل بالایی نسبت به الگوریتم های مشابه برخوردار است.کلید واژگان: مسیریابی وسایل نقلیه، مدل چند هدفه، جمع آوری و تحویل، تقاضای احتمالی، یادگیری ماشین حداکثریTransportation plays a significant role in the gross domestic product and oil consumption of every nation. In our country, a combination of recent sanctions and underdeveloped rail, air, and sea transportation systems has led to an increased reliance on road transport. Unfortunately, road transport contributes significantly to the emission of greenhouse gases, particularly carbon dioxide. Nevertheless, transportation is a vital aspect of logistics, and addressing pollution in vehicle routing stands as a paramount concern within this realm.This paper introduces a model aimed at optimizing fuel consumption costs, considering various factors such as vehicle load, speed, pollution, as well as parameters like fuel and engine efficiency, incline, traffic density, wind speed and direction, air temperature, asphalt quality, and driver remuneration. Additionally, this mathematical linear mixed-integer model incorporates probabilistic demand and a distribution system involving both delivery and pickup processes, all geared towards cost minimization.By employing this model, organizations can achieve more precise cost estimates, enhanced analysis, and improved planning. Given the NP-hard nature of the problem, its resolution involves the amalgamation of two meta-heuristic algorithms: Extreme Learning Machine (ELM) and Genetic Programming (GP). Experimental results indicate that the developed hybrid algorithm offers highly accurate estimations in a remarkably short time span when compared with similar algorithms.Keywords: Vehicle Routing Problem, Multi-Objective Model, Delivery, Pickup, Probabilistic demand, Extreme Learning Machine, Genetic Programming
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با توجه به تهدیدات جهانی مانند بیماریهای همهگیر و جنگ برای زنجیرههای تامین، طراحی مجدد شبکه تامینکنندگان با معیارهای چرخهای، کاهش هزینه و پشتیبان گیری مناسب برای کاهش ریسک عرضه، یک نیاز حیاتی در جامعه صنعتی امروز است. لذا این مقاله برای پاسخگویی به این مسیله، یک مدل چندهدفه با اهداف متناقض برای طراحی شبکه تامینکنندگان قابلاعتماد چرخهای با لحاظ قابلیت اشتراک دانش، پشتیبان، مهارت، شبکههای همکاری قابلاعتماد، هزینه، ظرفیت، تخصیص سفارش و معیارهای چرخهای برای محصول ماژولار توسعه داد. مدل پیشنهادی برای طراحی شبکه بهطور همزمان عوامل کلیدی: 1) معیارهای چرخهای، 2) شبکه همکاری و سوابق قبلی بین تامینکنندگان، 3) مهارت، 4) قابلیت اشتراک دانش و تجربه، و 5) هزینه و تامینکنندگان پشتیبان را در نظر گرفت. مدل بامطالعه عددی داده شبیهسازیشده و نیز با داده واقعی دوربین الکترواپتیکی، ارزیابی شد و با روش دقیق محدودیت اپسیلون تقویتشده و الپیمتریک و حل دقیق مسایل در مقیاس کوچک اعتبارسنجی گردید و تحلیل حساسیت نیز انجام گردید؛ لذا ابتدا یک محصول ماژولار انتخاب گردید و تعداد ماژولها با خوشهبندی مشخص شد. پسازآن معیارها، پارامترها و متغیرها تعیین گردید و پس از فرمولبندی و حل مدل، مدل اعتبار سنجی گردید و نتایج، تیمها و تخصیص بهینه سفارش تعیین گردید. از نتایج حاصل از حل مدل با داده ساختگی، تیم اصلی (1، 2، 3، 4 و 15) و تیم پشتیبان (4، 8 و 9) به دست آمد. همچنین از نتایج حاصل از حل مدل با داده واقعی، تیم اصلی (1، 2، 3، 8، 9 و 10) و تیم پشتیبان (4) به دست آمد. نتایج نشان داد که این رویکرد بر اساس تمامی مفروضات، شبکه تامینکنندگان قابلاطمینان چرخهای بهینه را در دو مجموعه اصلی و پشتیبان با کمترین هزینه، بیشترین اشتراک دانش و قابلیت اعتماد و معیارهای چرخهای پیشنهاد مینماید. نتایج منطبق با نیاز جامعه صنعتی مدرن میباشد. در پایان پیشنهادهایی برای تحقیقات آینده ارایه گردید.
کلید واژگان: معیارهای چرخه ای (دایرهای یا مدور)، انتخاب تامین کنندگان چرخه ای قابل اطمینان و تخصیص سفارش، ماتریس ساختار طراحی، معماری محصول ماژولار، مدل چندهدفهDue to global threats such as pandemics and wars affecting supply chains, redesigning the supplier network with circular criteria, cost reduction and proper supplier backup to reduce supply risk is a an importtant need in today's industrial society. To address this issue, this paper developed a multi-objective model with conflicting objectives to design a circular reliable supplier network considering knowledge sharing capability, backup, skills, reliable cooperation networks, cost, capacity, order allocation, and circular criteria for a modular product. The proposed model for network design simultaneously considers the following key factors: 1) circular criteria, 2) cooperation network and historical records between suppliers, 3) skills, 4) ability to share knowledge and experience, and 5) cost and backup suppliers. The model was evaluated with the numerical study of the simulated data as well as with the real data of the electro-optical camera, and it was validated with the precise method of augmented epsilon constraint method and LPmetric and the exact solution of small-scale problems, and the sensitivity analysis was also performed.; Therefore, first a modular product was selected and the number of modules was determined by clustering. Then, the parameters and variables were determined and after formulating and solving the model, the model was validated and the results, teams and optimal order allocation were determined. From the results of solving the model with artificial data, the main team (1, 2, 3, 4 and 15) and the support team (4, 8 and 9) were obtained. Also, according to the results of solving the model with real data, the main team (1, 2, 3, 8, 9 and 10) and the support team (4) were obtained. The results showed that, based on all the assumptionsو this approach, suggests the network of optimal circular reliable suppliers in two main and supporting groups with the lowest cost, the most knowledge sharing and reliability and circular criteria. The results are in line with the needs of modern industrial society. At the end, suggestions for future research were presented.
Keywords: Circular Criteria, Selection of Reliable Circular Suppliers, Order Allocation, Design Structure Matrix, Modular Product Architecture, Multi-Objective Model -
Journal of Quality Engineering and Production Optimization, Volume:7 Issue: 2, Summer-Autumn 2022, PP 93 -106In this study, we combine an interval type-2 fuzzy best-worst method (IT2FBWM) with the interval VIKOR method for the first time to evaluate and prioritize sustainable suppliers in circular supply chains. To weigh the criteria, an interval type-2 best worst approach is employed, and the interval VIKOR methodology is utilized to assess the suppliers in the presence of uncertainty. Risk is presented in all supply chain activities, and its occurrence affects all dimensions of the supply chain and can cause damage to them and, therefore, must be appropriately managed. A new mixed-integer linear programming model is then formulated to identify each risk's optimal strategy or response. The multi-objective model minimizes total costs and response time and maximizes risk responses to secondary and primary risks. An improved version of augmented ε-constraint method (AUGMECON2) is also employed to produce separate Pareto-optimal solutions. Finally, the suggested strategy is applied to four main suppliers in the food company. The findings of the proposed integrated approach demonstrate the applicability and efficiency in the food industry.Keywords: Supply Chain, Sustainable supplier selection, Interval type-2 fuzzy sets, Best-Worst method, Interval VIKOR, Multi-objective model
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هدف
بهینه سازی تراز منفی پرتفوی مالی شعب با رعایت محدودیت های تعریف شده در نظام بانکی ایران.
روش شناسی پژوهشدر سال های اخیر مدل های متعددی برای سبد سرمایه گذاری پیشنهاد شده است. در بانک ها، عملیات سرمایه پذیری به موازات سرمایه گذاری انجام می شود. جذب سپرده و پرداخت وام ارکان اصلی سرمایه پذیری و سرمایه گذاری هستند و اساس پرتفوی منابع و مصارف در بانک را شکل می دهند. در این پژوهش یک مدل برنامه ریزی چند هدفه طراحی شده است، که اهداف آن ماکزیمم سازی بازدهی و مینیم سازی ریسک هستند.
یافته هارویکرد مسیله بگونه ای است که با اخذ هزینه های اداری و پرسنلی و نرخ های سود سپرده و تسهیلات و نرخ مبادلات بازار داخلی بتواند پرتفوهای متنوع پیشنهاد دهد. شعب متناسب با اقتضایات خود پرتفوی مناسب را به عنوان هدف و برنامه کاری انتخاب می کنند.
اصالت/ارزش افزوده علمیبه دلیل ماهیت مسیله، که غیرخطی سخت می باشد، مدل با استفاده از الگوریتم تکاملی NSGA-II حل شده است. خروجی حل مسیله، مجموعه ای از جواب های بهینه، روی مرز پاراتو می باشد. هر یک از پرتفوها، متناسب با میزان بازدهی و ریسک، یک انتخاب استراتژیک برای تصمیم گیرنده است.
کلید واژگان: پرتفوی، موسسات مالی و اعتباری، بازدهی و ریسک، الگوریتم NSGA-II، مدل چند هدفهPurposeOptimizing the negative balance of the financial portfolio of branches by observing the limits defined in the banking system of Iran.
MethodologyIn recent years, several models have been proposed for the investment portfolio. In banks, Fundraising operations are carried out in parallel with investments. Attracting deposits and repaying loans are the main pillars of investment and form the basis of the resource and expenditure portfolio in the bank. In this research, a multi-objective planning model is designed to maximize returns and minimize risk.
FindingsThe approach of the problem is such that by taking administrative and personnel costs and interest rates on deposits and facilities and exchange rates of the domestic market can offer a variety of portfolios. The branches select the appropriate portfolio as the goal and work plan according to their requirements.
Originality/ValueDue to the nature of the problem, which is hard nonlinear, the model is solved using NSGA-II evolutionary algorithm. The output of solving the problem is a set of optimal solutions on the Pareto frontier. Each of the portfolios is a strategic choice for the decision-maker, according to the level of return and risk.
Keywords: Portfolio, Financial, Credit Institutions, Return, risk, NSGA-II algorithm, multi-objective model -
Journal of Industrial Engineering and Management Studies, Volume:9 Issue: 1, Winter-Spring 2022, PP 95 -108
Scheduling is a vital part of daily life that has been the focus of attention since the 1950s. Knowledge of scheduling is a very important and applicable category in industrial engineering and planning of human life. In the field of education, scheduling, and timetabling for best results in classroom teaching is one of the most challenging issues in university programming. As each university has its own rules, policies, resources, and restrictions a unique model of scheduling and timetabling cannot implement. This can cause more complexity and challenging point which needs to be considered scientifically. This study presents a sound scientific model of timetabling and classroom scheduling to improve faculties’ desirability based on days, times, and contents preferences. A sample in Parand branch of Islamic Azad university chooses using the Bat metaheuristic algorithm. By considering the limitations, some unchangeable constraints regarding the specific rules and minimal linear delimitation of the soft constraints of the model, using the appropriate meta-heuristic algorithm to reduce the model run time to a minimum. The results show that the algorithm achieves better results in many test data compared to other algorithms due to meeting many limitations in the problem coding structure. The Bat algorithm is compared with four other algorithms while comparing the results of solving the proposed mathematical model with five metaheuristic algorithms to evaluate the performance. In this research, a multi-objective model is presented to maximize the desirability of professors and to solve the model using Bat, Cuckoo Search, Artificial bee colony, firefly, and Genetic algorithms. In this research 40 different runs of each algorithm were compared, and conclusions were drawn. Modeling has been solved with GAMS and MATLAB software and using the bat meta-heuristic algorithm. It is concluded that in this model, the bat algorithm is the most appropriate algorithm with the shortest time, which has caused the satisfaction of the professors of the educational departments of this academy.
Keywords: University Course Timetabling, multi-objective model, bat meta-heuristic algorithm -
Volatility in competitive businesses has increased the uncertainty and ambiguity of decision-makings. Uncertainties are known as risks in the literature reviews. The present study developed the model proposed by Kirilmaz and Erol to mitigate risks and ambiguity in decision makings in the green supply chain. An initial multi-objective procurement plan was developed using a robust planning model considering costs, purchase discounts, carbon emissions and uncertainty as the first priority. The paper applies a scenario-based approach to consider an uncertain customer demand in different scenarios. The scenario-based model ensured that regret whereas scenarios are not probability. Moving toward the green supply chain decreases the costs that exert negative and devastating effects on the environment. As the second priority, risk was ultimately incorporated into this plan. A hypothetical data-set was examined and a cost analysis performed to evaluate the quality of the obtained solutions and the performance of the proposed model.
Keywords: Supply chain risk management, robust optimization, Uncertainty, multi-objective model -
فصلنامه مهندسی تصمیم، پیاپی 9 (پاییز 1398)، صص 139 -159
مساله زمانبندی کلاسهای دانشگاهی از جمله مسایلی است که اخیرا به صورت قابل ملاحظهای مورد توجه دانشگاهها و گروههای آموزشی قرار گرفته است. در این مقاله، مدلی دو هدفه برای یک مساله زمانبندی کلاسهای درسی ارایه شده است که از یک طرف به دنبال کمینهسازی هزینه تخصیص دروس به اساتید در کلاسهای موجود و در دورههای زمانی از روزهای مختلف هفته است و از طرف دیگر سعی دارد با کیمنهسازی مجموع زمان بیکاری اساتید در محیط دانشگاه، رضایتمندی اساتید را که همواره مورد توجه بوده است، افزایش دهد. همچنین در این مقاله، به منظور در نظر گرفتن هزینههای تخصیص دروس برخلاف مطالعات گذشته که مقادیری از پیش تعیین شده برای این ضرایب در نظر میگرفتند از رویکرد تحلیل سلسلهمراتبی استفاده شده است که گروههای آموزشی تصمیمگیرنده را قادر میسازد تا معیارهای مختلفی را برای اندازهگیری ضریب هزینههای تخصیص در نظر بگیرند. در نهایت به منظور بررسی کارایی مدل پیشنهادی یک مطالعه موردی بر روی دپارتمان مهندسی صنایع دانشگاه بوعلی سینا همدان مورد انجام شده است. رویکرد مذکور امکان ایجاد اولویت میان روزهای هفته، دورههای زمانی در طول روز، کلاسهای درس و حتی اساتید ارایه دهنده را فراهم میآورد. بعلاوه با استفاده از این رویکرد میتوان فاصله خالی بین ارایه کلاسهای درس را کاهش داد و جابجایی دانشجویان میان کلاسها را نیز به حداقل مقدار خود میرسد.
کلید واژگان: مساله زمانبندی درس های دانشگاهی، مدل چند هدفه، رویکرد تحلیل سلسله مراتبی (AHP)، رضایتمندی اساتیدRecently, university courses time tabling problem has been attended as a main issue by most universities and educational departments. In this paper, a bi-objective model is proposed to formulate a university courses time tabling problem which aims to minimize the cost of assigning courses to professors and classes during time horizon and maximize professorschr('39') satisfaction through minimizing their total idle time, simultaneously. Furthermore, despite of previous similar works in this area in which predefined values are considered as the assignmentchr('39') cost coefficients, in this paper, for the first time, an analytical hierarchy process (AHP) approach is used to calculate these coefficients which enables educational departments to attend various criteria in considering assignment cost coefficients. Finally, to evaluate the efficiency of the proposed model, a real case study in industrial engineering faculty of Bu-Ali Sina University is done.
Keywords: University Course Time Tabling Problem, Multi-objective Model, Analytical Hierarchy Process (AHP), Professors Satisfaction -
In this paper, an integrated mathematical model of the dynamic cell formation and production planning, considering the pricing and advertising decision is proposed. This paper puts emphasis on the effect of demand aspects (e.g., pricing and advertising decisions) along with the supply aspects (e.g., reconfiguration, inventory, backorder and outsourcing decisions) in developed model. Due to imprecise and fuzzy nature of input data such as unit costs, capacities and processing times in practice, a fuzzy multi-objective programming model is proposed to determine the optimal demand and supply variables simultaneously. For this purpose, a fuzzy goal programming method is used to solve the equivalent defuzzified multi-objective model. The objective functions are to maximize the total profit for firm and maximize the utilization rate of machine capacity. The proposed model and solution method is verified by a numerical example.
Keywords: Dynamic cell formation, production planning, fuzzy goal programming, pricing, advertising, multi-objective model -
یکی از عوامل مهم برای شرکت های قدرتمند تولیدی به منظور بقا در محیط رقابتی امروزی، کاهش هزینه های تولید محصول است. مواد و تجهیزات تامین شده از تامین کنندگان نقش مهمی را در مدیریت زنجیره تامین ایفا کرده و در تصمیمات لجستیکی یک شرکت و مکان یابی تسهیلات تولیدی، تاثیر زیادی در طراحی زنجیره تامین از منظر برنامه ریزی حمل و نقل و توزیع دارد. هدف از انجام این پژوهش، ارائه یک مدل یکپارچه برای مسائل انتخاب تامین کنندگان، تخصیص سهم به تامین کنندگان و مکان یابی تسهیلات تولیدی در یک زنجیره تامین چند دوره ای و چند محصولی با در نظرگیری اهداف اقتصادی، قابلیت اطمینان شبکه و ارزشیابی تامین کنندگان منتخب می باشد. در این راستا یک مدل برنامه ریزی عدد صحیح مختلط توسعه داده شده و برای مسائل با اندازه کوچک توسط روش دقیق حل شده است. از آنجایی که مسئله پیشنهادی زنده می باشد، برای حل مسائل با اندازه بزرگ، الگوریتم فراابتکاری بهینه سازی چند هدفه میرایی ارتعاشات (MOVDO) با معرفی معیارهایی در جهت بررسی نتایج ارائه می شود. نتایج عددی نشان می دهد که الگوریتم MOVDO زمان حل مسئله را کاهش و جواب هایی نزدیک به بهینه و با درصد اختلاف کمی نسبت به روش دقیق را ارائه می دهد که در معیار کیفیت جواب نیز وضعیت خوبی دارد.
کلید واژگان: الگوریتم چندهدفه میرایی ارتعاشات، انتخاب تامین کنندگان، زنجیره تامین، مدل چندهدفهFor powerful manufacturing firms, one of the important factors for survival in today's competitive environment is decreasing production costs. Materials and equipment supplied play an important role in supply chain management and production facilities location, have a significant impact on supply chain design from the perspective of transportation and distribution planning in logistics decisions of the company. The purpose of this study is to provide an integrated model for supplier selection, quota allocation and production facility location problems in a multi - period and multi - product supply chain by considering economic goals, network reliability and evaluation of selected suppliers. In this regard, a mixed integer programming model has been developed and solved for small size problems by an exact method. Since the proposed problem is NP-hard, a Multi-Objective Vibration Damping Optimization (MOVDO) algorithm is proposed by introducing criteria for examining the results to solve large-scale problems. Numerical results show that the MOVDO algorithm reduces the problem solving time and provides near-optimal solutions with a small percentage difference compared to the exact method, which is also good in the quality of the response criterion.
Keywords: MOVDO, Suppliers Selection, Supply Chain, Multi- Objective Model -
In today's world, natural disasters such as earthquakes, floods, crises such as terrorist attacks and protests threaten the lives of many people. Hence, in this research we present a mathematical modeling that provide efficient and effective model to locate temporary depot, equitable distribution of resources and movement of injured people to health centers, with the aim of developing the multi-objective model and considering multiple central depot, multiple temporary depot and several type of relief items in the model . This paper is considered certainty state and uncertainty of influencing parameters of the models in robust optimization for three different levels uncertainty and in different size with consideration of traditional goals function and humanitarian purposes functions simultaneously. The model has been solved with multi-objective Particle Swarm optimization algorithm (MOPSO) and GAMS software to validate the model. Some numerical examples are presented. In Addition, we present sensitivity analyzes of model and study the relationship of the number of temporary depot location and the number of injured people to move to health centers and the number of uncovered damaged points.Keywords: Humanitarian crisis management, multi- objective model, temporary depot location, robust optimization, multi-objective Particle Swarm optimization (MOPSO)
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The efficient management of nursing personnel is of vital importance in a hospital’s environment comprising a vast share of the hospital’s operational costs. In the nurse scheduling problem (NSP), the target is to allocate shifts to the nurses in order to satisfy the hospital’s demand during the planning horizon by considering different objective functions. This paper presents a multi-objective mathematical model with the aims of reducing the costs that the hospital is supposed to pay, maximizing nurses’ satisfaction, and balancing the workload of nurses. Nurses’ preferences for working in particular shifts and weekend off are considered in this model. In order to solve the model, a two-step procedure is used. In the first step, to show the applicability of the proposed model, a real case study is provided and is solved using augmented ε-constraint method. Then, the best solution is selected among Pareto solutions using data analysis envelopment (DEA). Finally, several analyses are performed to develop managerial implications.Keywords: Nurse scheduling problem, multi-objective model, augmented ?-constraint method, Data Envelopment Analysis (DEA)
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Surgical theater is one of the most expensive hospital sources that a high percentage of hospital admissions are related to it. Therefore, efficient planning and scheduling of the operating rooms (ORs) is necessary to improve the efficiency of any healthcare system. Therefore, in this paper, the weekly OR planning and scheduling problem is addressed to minimize the waiting time of elective patients, overutilization and underutilization costs of ORs and the total completion time of surgeries. We take into account the available hours of ORs and the surgeons, legal constraints and job qualification of surgeons, and priority of patients in the model. A real-life example is provided to demonstrate the effectiveness and applicability of the model and is solved using ε-constraint method in GAMS software. Then, data envelopment analysis (DEA) is employed to obtain the best solution among the Pareto solutions obtained by ε-constraint method. Finally, the best Pareto solution is compared to the schedule used in the hospitals. The results indicate the best Pareto solution outperforms the schedule offered by the OR director.Keywords: Multi objective model, OR planning, scheduling, ?, constraint method, Data envelopment analysis
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Industrial hazardous materials (hazmat) are byproduct of industrial production and include hazardous goods, such as flammable, toxic and corrosive materials that pose a risk to the environment.Hazardous waste management includes collection, transportation, treatment, recycling and disposal of industrial hazardous material in an organized manner. With the increasing industrialization of countries, the issue of waste management is more important than before. Therefore, the main purpose of this research is to optimize locations of recycling centers and routing hazardous. The methods used to solve the mathematical model include the ε-constraint method and the NSGA II algorithm.First, we examine the validation of proposed model. Then, the optimal values of the parameters of multi-objective meta-heuristic algorithm are determined by Taguchi approach and the proposed algorithms are used to solve the given problem for 19 examples with different sizes. Finally, two algorithms are compared based on the fiveidentified criteria. In addition, the run time for both methods was calculated and large-scale results were presented based on the multi-objective genetic algorithm. The results show the efficiencyofmulti-objective genetic algorithm in solving given problem, and in particular for problems with larger sizes.Keywords: Multi-objective location-routing, hazardous waste management, multi-objective model
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This paper presents a multi-objective mixed-integer nonlinear programming model to design a group layout of a cellular manufacturing system in a dynamic environment, in which the number of cells to be formed is variable. Cell formation (CF) and group layout (GL) are concurrently made in a dynamic environment by the integrated model, which incorporates with an extensive coverage of important manufacturing features used in the design of CMSs. Additionally, there are some features that make the presented model different from the previous studies. These features include the following: (1) the variable number of cells, (2) the integrated CF and GL decisions in a dynamic environment by a multi-objective mathematical model, and (3) two conflicting objectives that minimize the total costs (i.e., costs of intra and inter-cell material handling, machine relocation, purchasing new machines, machine overhead, machine processing, and forming cells) and minimize the imbalance of workload among cells. Furthermore, the presented model considers some limitations, such as machine capability, machine capacity, part demands satisfaction, cell size, material flow conservation, and location assignment. Four numerical examples are solved by the GAMS software to illustrate the promising results obtained by the incorporated features.
Keywords: dynamic cellular manufacturing systems, Multi-objective model, Cell formation, group layout
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