نشریه صنعت لاستیک ایران
پیاپی 90 (تابستان 1397)

In present complicated business environment, uncertainties have a great role. In the meantime, for business continuity, the organizations must have more accuracy about their requirements. Uncertainty in lead times is a usual issue in supply chains. This issue comes from some constraints in financial and logistic systems. For this reason, using of inventory control models with deterministic parameters can create various mistakes. To overcome these issues the stochastic inventory models are used. Since the bladder rings are considered as production tools in tire manufacturing process then optimal inventory management of these items can due to more productivity. In this study, we propose a new mathematical model for an inventory control systems with uncertainty in demand and lead times. The results demonstrate that using of proposed model can lead to reducing the shortage costs and increasing of service level of warehouse. Furthermore, existence of coordination between reorder point and safety stock with demand level and lead times shows that the proposed mathematical model has a good potential to use in real-life problems.

The process of mixing is one of the most important steps in which raw materials must pass through to become the elastomeric products. The quality of after mixing processes depends mainly on the uniformity and quality of the mixed blend. The economical production of Rubber products is also directly affected by mixing process. The main purpose of mixing is to provide mixtures that are more uniforms with the finest properties and baking characteristics. In all processes, mixing and distributing the materials are essential. A good mix is in high quality in terms of both distribution and the degree of separation. In order to achieve the desired properties in a mixture, it is necessary to mix all the components completely together. Considering the special importance of mixing, in the production of a mixture and determining the role of fill factor in an optimal dispersion in relation to determining the proper batch weight, in this paper, we try to find the optimum fill coefficient from the finger-print graph using the power and t-ram curves.

the main objective of this research is the future scenario of the country's rubber industry based on soft systems methodology. In this study, using two methods of futures studies, structural analysis and scenario analysis, firstly, identifying the key factors affecting the future of the rubber industry of the country and then developing future scenarios. Became subsequently, using one of the research tools that includes soft systems methodology, these scenarios will become Better. The preliminary data of the research were collected using interviews with the managers and experts of the country's rubber industry and reviewing the literature. The questionnaire was analyzed using MIC- MAC software. Among the 24 key factors extracted, by reviewing the literature and interviewing experts, key factors entered the checklist questionnaire and the 13 key factors according to their assumptions related to them at 0.05, were selected according to experts' opinion. Based on the results of the research, two factors of production technology and performance the value chain of petrochemical industries were considered as the affecting variables in the future of country's rubber industry. Finally, four scenarios were presented.

The purpose of this research is to provide a model and model for selecting a sustainable supplier. The researcher, through library studies, interviews with experts and experts in tire producing companies, and preparing a questionnaire to identify the factors that affect this relationship. Indicators that influence the selection of sustainable supplier selection in this research are financial position and market share, proposed price, timely delivery of goods, recycling rates, the use of clean technologies, contamination, the number of trained staff and employee satisfaction, and Customers In this research, weighing these indices was determined by comparing the fuzzy pair between these indices and using the fuzzy hierarchical process analysis method. In order to accurately determine the weight of the indices, Shannon Entropy method was used. Finally, the weights obtained from these two methods were combined and the final weight was obtained. These weights were used in the Interval TOPSIS method. Then the companies were ranked according to the coefficient of closeness obtained by the distance tops method, and the top company was selected.

The fact that factors caused success previously, today, may lead to failure due to changes in business environments. To improve engineers’ efficiency, it is necessary to adjust industrial organizations to changes in environment and maintain competitive situation in business markets. Therefore, this issue that minimize the risk of fallibility, is considered as an inevitable necessity. Not only is it required that engineers achieve expected competency and eligibility to encounter environment changes efficiently, but also these competencies promote their capability for presenting appropriate methodology in critical situations, innovative and novel plans as well as implementing appropriate projects. To this end, some criteria should be determined to assess the aforementioned competencies, which lead to make decision about the role of engineers in project management. In this study, the writer tried to discuss required competencies for engineers in addition considered the role of competency and efficiency in successful management of organizational projects based on PMBOK standard. This article is based on clarify and analytical methods, using writer’s experiences, library and internet searches.