نشریه نخبگان علوم و مهندسی
سال پنجم شماره 4 (مهر 1399)

Sustainable supply chain has become an accurate part of the corporate strategy. In this research, a real case study of the natural gas supply chain has been investigated. Using concepts related to natural gas industry and the relations among the components of gas and oil wells, refineries, storage tanks, dispatching, transmission and distribution network, a seven-echelon supply chain has been offered and presented schematically. The aim of this paper is to optimize a case study using a multi-objective and multi-period model. A small-sized model was verified and solved using an improved augmented εconstraint algorithm to generate Pareto optimal solutions and assessed trade-offs among objectives in order to help decision makers make an optimal decision. Sensitivity analysis was conducted on its parameters. To the best of our knowledge, this is the first study that presents a multi-objective optimization model for the sustainable natural gas supply chain.

In recent decades, manufacturing of tires have been rocketed. The main cause of this process is development of automobile industry in worldwide, so the high volume of scrap tires has been created massive stockpiles zones. Furthermore, environmental threat related to waste tires, and disposing them properly has come to a world crisis, due to the requirement more spacious storage than other wastes and the massive volume and their fixed shape. Therefore, there is immediate and effective need of recovering and reusing waste tires. Waste tires have efficient applications in engineering, especially mortars and concrete. The results of various investigations have demonstrated that rubberized self-compacting concretes show lower compressive strength, modulus of elasticity, stiffness, rheological properties, fracture energy, durability, flexural strength, ultrasonic pulse velocity etc. and higher deformability before failure, saving in cement and aggregate usage, dynamic properties, strain capacity, fatigue strength etc. Therefore, adding waste rubber into self-compacting concretes leaves a numerous positive and negative impacts on its properties. In this paper, authors present an overview of literature investigating of waste rubber used as an additive or fine and/or coarse aggregate replacement in self-compacting concrete with special attention on positive and negative influences on fresh and hardened self-compacting concrete properties.

Nowadays, Supply chains can be explored through two concepts of resilience and sustainability. This paper attempted to conduct a meta-analysis of a resilient and sustainable supply chain while proposing a new conceptual model. Meta-analysis is a type of quantitative meta-study conducted only on the results of previous studies. With a focus on a decade of studies from 2011 to February 2020, this paper intended to explore the literature on resilient-sustainable supply chains. To that end, a total of 39 relevant papers were selected and reviewed. The statistical population comprised 15 papers dealing with both resilience and sustainability. Moreover, the dimensions and indicators of analyses were identified based on the opinions of 10 supply chain experts and the Delphi method. Based on the collected data, a new conceptual model was presented with initial information and conceptual models not reflected in previous independent research. In the newly proposed conceptual model, the supply chain resilience and sustainability were contributed by several components including structure (34%), resources (31%), capabilities (13%), innovation and production (7%), and transportation and environmental assessment (4%). Furthermore, information sharing plays a key role in facilitation and integration of supply chain resilience and sustainability. Since findings indicate the growing importance of global energy consumption and a large research gap in this area, it is highly recommended that future studies focus on supply chain sustainability and resilience in the energy sector. In this research, for the first time, the meta-analysis approach was applied in a resilient and sustainable supply chain, and based on the received information, a conceptual model was proposed that the initial information and conceptual models in previous independent studies did not show.

Nanoclay- supported Preyssler heteropolyacid as a new and effective nanocomposite was used to improve the compressive strength of concrete. The cement pastes used in this study were a mix of water, ordinary Portland cement and nanoclay- supported Preyssler heteropolyacid. The nanoclaysupported Preyssler were added into the concrete with different concentrations of 1, 2, 3, 4 and 5% by the weight of cement amount. Water/cement ratio was 0.35 and the dimension of the cubic samples was 15 ×15 ×15 Cm. Compressive strength tests were done on hardened specimens. The obtained results revealed that the addition of nanoclay- supported Preyssler heteropolyacid into the concrete samples led to increase in compressive strength of concrete specimens equal to 23.2% at 28 days for dosage of 3%.

Familiarity in the computer game industry can attract young people to with the most important jobs and incomes in this industry. Today is one of the most profitable industries are the video games and relatively new industry during these years it has grown in various fields. The purpose of this research is to review the history of making computer games in Iran and the world and to introduce job opportunities and various strategic dimensions of the production of such games in the game industry and to introduce strategic business evaluation models. The research method of this article is library and descriptive. Researchers have introduced various components of business models in the field of gaming industry according to the review of books, articles and authoritative scientific sites about the gaming industry. The results of this research can provide a comprehensive view to researchers and industrialists in the field and the design and production of computer games in moving towards the promotion of this business.

Resilience and sustainable supply chain has become an integral part of the corporate strategy. In this paper, a real case study of the natural gas supply chain has been investigated. Using concepts related to natural gas industry and the relations among the components of gas and oil wells, refineries, storage tanks, dispatching, transmission and distribution network, a seven-level supply chain has been introduced and presented schematically. The aim of this paper is to optimize a case study using a fuzzy goal programming multi-period and multi-product model considering recovery, environmental and economic costs, total revenue and service level as fuzzy goals and maximize the total degree of satisfaction of goals as objective function. A small-sized problem was solved using GAMS 23.2.1 software and sensitivity analysis was conducted on its parameters. To the best of our knowledge, this is the first study that presents a fuzzy goal-programming model for the optimization of resilience and sustainable natural gas supply chain by trade-offs among recovery, environmental and economic costs, total revenue and service level approach in order to help decision makers make an optimal decision.

Due to the heterogeneity of the molecules in the biological hull environment, it is not possible to apply Maxwell’s equations analytically, so approximate methods and radiation transfer theory should be used. In this paper, an approximate solution for the propagation of electromagnetic waves in biological tissues has been presented by a mathematical modeling based on Kubelka-Munk theory, which is one of the most commonly used methods to test the optical properties of biological tissues in medical physics and also the physical and optical properties of electromagnetic waves have been studied by calculating the absorption and scattering coefficients of light in the tissue.

The municipality is one of the institutions of civil society in the constitution within the framework of governance in social, local and urban areas it is considered as part of the development and participatory structure of the country. which necessarily appears with a structure that is possible only through the intervention of the people municipality is one of the necessities of the social system. The quality level determines the level of satisfaction public service is one of the dimensions of citizens' lives. In the urban environment, the quality of services and ease of access to services are the determinants of satisfaction. This is possible by measuring the level of citizens' satisfaction and appropriate and real knowledge of themselves and the existing challenges and strengths and weaknesses, threats and potential opportunities. The purpose of this article is to design a model for measuring citizens' satisfaction with the performance of development projects in District 5 of Tehran. For this purpose after a thorough review of the theoretical foundations and research background, the dimensions and indicators of measuring citizens' satisfaction with the performance of municipalities were identified and reviewed and approved by experts in District 5. The questionnaire was then distributed among 150 citizens of District 5. The results indicate the impact of the dimensions of development, urban services, supervision and socio-cultural on the level of citizens' satisfaction with the performance of development projects.