Today, in large projects such as constructing oil, gas and petrochemical refineries, it is inevitable to use modern management methods and project timing. On the other hand, in classic scheduling case, the focus is on balance between time and cost of carrying out projects, which in such a situation, one of possible solutions to shorten time of implementing project is to accelerate activities. This acceleration can affect the quality of conducting projects and environmental impacts, in addition to impose more costs. Hence, in such studies, environmental impacts and quality of activities were also considered as new indicators in case of project time-cost balance. There has been proposed a new mathematical model with four indicators: cost, time, quali-ty and environmental impacts. The provided model is a multi-objective mathematical model of zero-and-one programming type that despite traditional models, in which there is only considered an implementation mode for carrying out activities and a pre-conditional relationship between activities, modes of implementing activities are as multi-form and the dependence relationship between the activities is a generalized pre-requisite. Including the relationships brings the problem closer to the real world. Because of NP-hard of the problem in large dimensions and the necessity of using meta-heuristic Algorithms, we used MOBEE algorithm to solve the model. Manuscript profile

In the current world, the debate on the reinstatement and reuse of consumer prod-ucts has become particularly important. Since the supply chain of the closed loop is not only a forward flow but also a reverse one; therefore, companies creating integ-rity between direct and reverse supply chain are successful. The purpose of this study is to develop a new mathematical model for closed loop supply chain net-work. In the real world the demand and the maximum capacity offered by the sup-plier are uncertain which in this model; the fuzzy theory discussion was used to cover the uncertainty of the mentioned variables. The objective functions of the model include minimizing costs, increasing revenues of recycling products, increas-ing cost saving from recycling and environmental impacts. According to the NP-hard, an efficient algorithm was suggested based on the genetic Meta heuristic algo-rithm to solve it. Twelve numerical problems were defined and solved using the NSGA-II algorithm to validate the model Manuscript profile

امروزه دغدغه های مدیران در پروژه های نفت،گاز و پتروشیمی،تکمیل پروژه ها در موعد مقرر با بالاترین سطح کیفیت اجرای فعالیت ها، صرف کمترین هزینه های مالی و کمترین اثرات مخرب زیست محیطی می باشد. از این رو برقراری موازنه بین چهار هدف متضاد زمان، هزینه،کیفیت و اثرات زیست محیطی از اهمیت ویژه ای برای مدیران برخوردار است. با نگاهی عمیق تر به اهداف مذکور مشخص می شود تمرکز بر روی هر کدام از اهداف چهارگانه منجر به ایجاد تغییراتی بر روی سایر اهداف خواهد شد به عبارتی دیگر بین اهداف مذکور تناقض وجود دارد. به همین منظور در این مطالعه سعی شده است مدلی ریاضی برای موازنه اهداف چهارگانه ارائه گردد که خواسته ها و نیازهای مدیران پروژه را برآورد سازد و به مسائل دنیای واقعی نزدیکتر باشد. مدل ارائه شده از نوع مدل ریاضی چند هدفه صفر و یک است که در این مدل فعالیت های پروژه دارای ماهیتی چند حالته و غیرقابل انقطاع هستند و ظرفیت منابع محدود و مشخص و روابط پیش‌نیازی فعالیت ها از نوع روابط پیش‌نیازی کلی در نظر گرفته شده است. جهت اعتبارسنجی، مدل پیشنهادی با استفاده از نرم افزار GAMS و حل کننده CPLEX توسط روش محدودیت اپسیلون توسعه یافته بر روی داده های واقعی یک پروژه نفتی حل شده و جواب بهینه آن به دست آمده است و نتایج حاصل از تحلیل حساسیت های مختلف گزارش شده است. Manuscript profile

In this research, the production of multi-products using one machine is investigated in continuous time. The machine has limited capacity and can produce only one product at any time. To change the product, the machine should be set up. Due to the difference in demand for products, there is no need to equate the number of machine start-ups for these products, by removing this constraint, a nonlinear mathematical model is presented that gives the optimal production lot size for each product. To solve the single-constraint nonlinear model, the Lagrange method is used. For a numerical example, the obtained solution is compared with the method of rotating a constant cycle. Due to the total cost, the solution was better than the solution of the rotation cycle method. Also, contrary to the rotation cycle method, the total holding cost is equal to the total setup costs, which is similar to the Wilson inventory basic formula. Manuscript profile