Sharif Digital Repository

We develop an integrated vendor-buyer model for a two-stage supply chain. The vendor manufactures the product and delivers it in a number of equal-sized batches to the buyer. The items delivered are presented to the end customers in a display area. Demand is assumed to be positively dependent on the amount of items displayed. The objective is to maximize total supply chain profit. The numerical analysis shows that buyer-vendor coordination is more profitable in situations when demand is more stock dependent. It also shows that the effect of double marginalization provides a link between the non-coordinated and the coordinated case  

In this paper, a multiproduct single-machine production system under economic production quantity (EPQ) model is studied in which the existence of only one machine causes a limited production capacity for the common cycle length of all products, the production defective rates are random variables, shortages are allowed and take a combination of backorder and lost sale, and there is a service rate constraint for the company. The aim of this research is to determine the optimal production quantity, the allowable shortage level, and the period length of each product such that the expected total cost, including holding, shortage, production, setup and defective items costs, is minimized. The... 

Chlorella vulgaris was cultivated in a hybrid (two-stage) system. The effect of the transferring time from nutrient-replete phase with a low light intensity (photobioreactor) to the nutrient deprivation phase (open pond) with a higher light intensity, as well as the effect of initial cell concentration in the deprivation phase, on the growth rate and lipid content of the microalgae was investigated. The microalgae were transferred to the nutrient deprived medium at different intervals with various initial cell concentrations. Transferring the cultivated medium of the 4th day with the initial cell concentration of 66 mg L−1 into the deprivation phase resulted in a highest lipid productivity... 

Complex product systems (CoPS) industries largely contribute to industrial development, economic growth and creation of national wealth in both developed and developing economies. CoPS also show a number of specific characteristics as a distinctive category of industrial products in comparison with mass-produced consumer goods. These aspects have attracted the attention of scholars to study CoPS over the last two decades, resulting in a fairly extensive body of literature on the subject. However, there is a further need to connect research findings in this area, to illustrate a macro view of the development in the field, explore common themes, and identify possible paths into the future.... 

In this note, we study the behavior of independent sets of maximum probability measure in tensor graph powers. To do this, we introduce an upper bound using measure preserving homomorphisms. This work extends some previous results concerning independence ratios of tensor graph powers. © 2008 Elsevier B.V. All rights reserved  

The economic production quantity (EPQ) is one of the most applicable model in production and inventory control environments. Like other classical production and inventory control models, it is derived based upon assumptions that cause limited real-world applications. Continuous and constant-rate delivery of orders, infinite availability of warehouse spaces, and applicability on a single product are some of these assumptions. In order to make the EPQ model more applicable to real-world production and inventory control problems, in this paper, we expand this model by assuming that the orders may be delivered discretely in the form multiple pallets. In addition, we may have more than one... 

Construction industry is one of the most important fractions of economy in developing countries. This industry consumes enormous amounts of raw materials and produces considerable waste. The optimization of construction material usage not only saves costs but also can significantly contribute towards Sustainable Development. This article addresses Construction Waste Management as an approach to improve construction productivity, with a focus on its application in developing countries. The status of construction waste production and management in Tehran metropolitan, Iran-as a developing country-is investigated and compared with the status of developed countries. Subsequently, barriers to... 

Pichia pastoris is used extensively as a production platform for many recombinant proteins. The dissolved oxygen (DO) is one of the most important factors influencing protein production. The influence of the DO on productivity has not been studied independent from the feed rate. In this work, various DO levels were investigated independent from the feed rate. The model system was recombinant P. pastoris under the control of methanol-induced alcohol oxidase promoter, which expressed HRP as the target protein. No significant effect was observed in terms of titer and specific productivity, which is a confirmation of the fact that the DO in a one-compartment system cannot boost productivity for... 

Nowadays companies strive to survive in a competitive global environment. To speed up product development/modifications, it is suggested to adopt a collaborative product development approach. However, despite the advantages of new IT improvements still many CAx systems work separately and locally. Collaborative design and manufacture requires a product information model that supports related CAx product data models. To solve this problem many solutions are proposed, which the most successful one is adopting the STEP standard as a product data model to develop a collaborative CAx platform. However, the improvement of the STEP's Application Protocols (APs) over the time, huge number of STEP... 

The economic production quantity (EPQ) model is often used in manufacturing environments to assist firms in determining the optimal production lot size that minimizes the overall production-inventory costs. While there are some unrealistic assumptions in the EPQ model that limit its real-world applications, in this research, some of these assumptions such as (1) infinite availability of warehouse space, (2) all of the produced items being perfect, and (3) the existence of one product type are relaxed. In other words, we develop a multi-product EPQ model in which there are some imperfect items of different product types being produced such that reworks are allowed and that there is a... 

Economic production and on-time ordering are among the most important topics related to production and inventory control issues. An economical production needs a comprehensive and precise planning to be implemented in all production stages. To have a controlled and comprehensive planning system, economic order quantity (EOQ) or economic production quantity (EPQ) models are usually used in various production-inventory environments to minimize costs, avoid delays in orders, and achieve high performance. To meet the demands, sometimes a multiperiod production-inventory planning that involves several products requires outsourcing. In this paper, a production-procurement plan that integrates EOQ... 

In this paper a web based production system is proposed. This system consists of a web services agent to manage the receipt the order from the customer, a price agent to predict the price of the product for the customer, a decision agent to build up a virtual enterprise to manufacture and deliver of the product to the customer and make essential decisions of the system and a design and control agent to do the engineering tasks related to the production process of the product. This structure provides the production system with a high level of agility and flexibility. © 2019 IEEE  

Microalgae's biomass productivity and oil content depend heavily on the method of its cultivation. In this study, nutrient removal from municipal wastewater by Chlorella vulgaris in batch culture was investigated. Carbon dioxide was supplied from sodium hydrogen carbonate. Effect of parameters including light intensity, sodium hydrogen carbonate concentration, and daily illumination time on the productivity of biomass and lipid was investigated. Lipid and biomass production of C.vulgaris increased at higher concentration of sodium hydrogen carbonate concentration and higher light intensity until a certain value and then decreased, but longer daily illumination time, increased both biomass... 

In this paper, an Economic Production Quantity (EPQ) model is studied, in which the production defective-rate follows either a uniform or a normal probability distribution. Shortages are allowed and take a backorder state, and the existence of only one machine causes a limited production capacity for the common cycle length of all products. The aim of this research is to determine the optimal production quantity of each product, such that the expected total cost including holding, shortage, production, setup and defective items cost is minimized. The mathematical model of the problem is derived, for which the objective function is proved to be convex. Then, a derivative approach is utilized... 

This study aims to construct a quantitative framework to assess biological production of hydrogen from agricultural residues in a country or region. The presented model is able to determine proper crops for biohydrogen production, its possible applications and use as well as environmental aspects. A multiplicative decomposition method was designed to forecast future production and Monte Carlo simulation was employed in the model to evaluate the risk of estimations. From 2013 to 2050, the hydrogen production capacity could increase from 53.59 to 164.41 kilotonnes (kt) in Iran. The highest contribution to biohydrogen production (52.1% in 2013 and 73.3% in 2050) belongs to cereal crops...