Sharif Digital Repository

This research attempts to develop the optimal solution for an inventory problem consisting of a single machine which produces items some of which may be defective. We assume that no shortages are allowed and all defective items are to be reworked. Setup cost for rework and waiting time of defectives are considered. This research consists of two different parts. In the first part we consider two different policies where in the first policy in each cycle after the regular production the machine is setup for the rework of defectives of the same cycle. In the second policy several cycles constitute a period. All the defectives produced in the period are reworked in the last cycle of that period.... 

Currently, using biocompatible and injectable polymeric microcarriers as one of the efficient methods to transfer cells and active agents has gained much attention for bone regenerative medicine. However, they have some drawbacks such as weak mechanical stability and lack of mineral materials, which are the major ingredients of the bone tissues. Accordingly, it is expected that mimicking the chemical and physical structure of bone tissues could be valuable in their medical applications. Herein, a new porous biodegradable microcarriers (MCs) made of silk fibroin-oxidized alginate-bioactive glass was fabricated by electrospraying method. Response surface methodology (RSM) was used to study the... 

One of the encouraging technologies for resolving the lack of clean water in the world is forward osmosis process (FO). Reaching to a optimized development of FO membranes is essential to make fo process commercially viable.
This study’s aim is to develop a thin film composites (TFC) membrane with high FO performance (good water flux and high salt rejection) in order to seawater desalination.
Polyacrylonitrile (PAN), a hydrophilic polymer, is a less considered polymer in fabricating support layer for TFC FO membranes .TFC membranes consist of a selective polyamide active layer formed by interfacial polymerization on top of a support layer fabricated by non-solvent induced phase... 

Immensity and profundity of mathematical logic have provided an opportunity for its interconnection with other branches of science, one of which is computer science where theory of dependent types and lambda calculus lounges amongst the area of their overlap. The former has been engendered for the sake of deepening the connection between mathematical logic and programming. On the other side, lambda calculus which is a formal system in mathematical logic and computer science, developed as a tool for formal computations, could also be counted as a programming discipline. It is the objective of this thsis to study the two aforementioned fields with emphasis on unification of higher-order... 

In today’s world, social networks have become one of the primary sources for the creation and propagation of news. Social news aggregators are one of the main actors in this area in which users create news items and use positive or negative votes to indicate their preference
toward a news item. This approach suffers from several problems raging from being prone to the dominance of a united adversary to difficulty in decerning between correct and fake new news and lack of incentive for honest behaviors. In this paper, we propose a graphbased news aggregator in which instead of voting on new items, users submit their votes on the relations between news items. This method of voting... 

We study the problem of preclustering a set $B$ of imprecise points in~$\Reals^d$: we wish to cluster the regions specifying the potential locations of the points such that, no matter where the points are located within their regions, the resulting clustering approximates the optimal clustering for those locations. We consider $k$-center, $k$-median, and $k$-means clustering, and obtain the various results. Then we study the higher order Voronoi Tessellations as an important concept in clustering area. Generalizing Lee’s inductive argument for counting the cells of higher order Voronoi tessellations in $\Reals^2$ to $\Reals^3$, we get precise relations in terms of Morse theoretic quantities... 

In the current century, an energy storage is one of the critical and important factors affecting on human life. Rechargeable batteries, specially Lithium ion batteries (LIBs), can be considered as ideal energy storage devices including various advantages e.g. high energy and power densities. In this work, Tin IV sulfide (SnS2) and its composites, making by conductive materials e.g. Reduced Graphene Oxide (SnS2@rGO), are prepared during two different synthesis methods consisting of Hydrothermal and Hot-bath, and their properties are investigated as anode material in LIB. The structural and electrochemical analyses demonstrated that the composite sample prepared by hot-bath method exhibited... 

One of the crucial matters in the area of Supply Chain Management is the ability of a supply chain to act and react under different circumstances. A helpful tool to understand the supply chain is simulation modeling. With the help of simulation modeling, we can provide the opportunity for the agents in a model to perform based on the defined environment.In the current research, a complete literature review is performed on the topics of supply chain planning and various distribution models and algorithms. With the focus on the vaccine as a critical item, we propose a model to distribute vaccines based on the degree of agents, and we realize that vaccine distribution, while facing huge demand... 

Due to the data centers rapid growth and introduction of a new basic type of massive data processing platforms which requires accelerators to speedup computation and enhance the efficiency and reduce power consumption, using accelerators is inevitable. Communication and data transfer time between software and hardware is the most of time spent on the use of accelerators. By optimizing this part of the hardware / software platform, we have achieved substantial results in this area. The aim of our study is to organize a survey of real accelerator characteristics. To figure out its defects and main drawbacks, in addition to improving the overall efficiency of system. The implementation of... 

In this paper, we introduce a novel decision making strategy on how to assign markets to a multi-item newsvendor’s problem. We present a new formulation method based on the integration of news-vendor problem and dynamic programming approach alongside an efficient solution method. Suppose there are n distinct products and corresponding time intervals for selling them in different markets. These products will be worthless (perishable) at the end of each interval. Our proposed framework represents a trade-off between costs associated with staying in a market for further periods and costs of relocating the business in a new market. The objective is to maximize the total profit of our decisions... 

Due to the negative effects of conventional plastics on the enviroment, especially in the packaging sector, extensive efforts have been put to replace these polymers with biodegradable polymers. Starch is one of the biodegradable polymers which has attracted a lot of attentions because of low cost and good processability. Native starch has the form of granule and can be processed to a continuous phase after gelatinization in the presence of a plasticizer. The resulting material is a biodegradable plastic-like material called thermoplastic starch (TPS) which is processed using conventional technologies, but suffers from low mechanical properties and high hydrophilicity. Addition of natural... 

In this study, utilizing the so-called “flow forming”, a cold-bonding process is developed to produce multi-layered thin-walled tubes and cylinders. In this process, which is entitled as “spin-bonding”, two layers of tubes are bonded by thickness reduction. Al/Al and Cu/Al tubes were bonded at various temperatures, thickness reductions, feed rates and roller attack angles. The bonding quality was examined by peel test, metallography and SEM fractography. Moreover, spin-bonding was accumulatively applied to aluminum tubes up to 4 cycles as a severe plastic deformation (SPD) for thin-walled tubes and cylinders entitled as “Accumulative Spin-Bonding” (ASB). Beside of experimental works,... 

According to current trend of energy production and consumption in the world, economic problems in various countries and too many eco-system disorders in which created by an unsustainable trend in development, recently, the concept of “sustainability” and in the following “sustainable development” has been featured by scientists, researchers and policy makers in different scientific disciplines specially energy system engineering. Therefore exact recognition of unsustainability of local and global energy supply and demand system is very essential. In this research after selection of five energy indicators for sustainable development by Delphi and MCDM methods, future perspective of Iranian... 

Amount of strain has been always considered as the primary parameter affecting the microstructural and strength evolutions during Severe Plastic Deformation (SPD). However, these evolutions unavoidably saturate in large strains under deformation with constant conditions, i.e. constant deformation temperature, strain rate and strain path. In this study, effects of these factors on the microstructural and flow behavior of Ultra-Fine Grain (UFG) aluminum (AA 1050 and AA 5052) processed by Accumulative Roll-Bonding (ARB) are investigated. The flow behavior and its time-dependent aspect are evaluated up to large strains by Plane Strain Compression (PSC) and Stress Relaxation (SR) tests. ... 

Increasing global final energy demand and the use of fossil fuels to meet this amount of energy demand have raised concerns about environmental impacts of fossil fuel consumption and the reduction of fossil energy reserves. Among the energy consumer sectors including industry, transport activities, agriculture, and households, the household sector is one of the most important sectors, regarding its share of total final energy consumption. Heating and cooling systems, which mainly use fossil fuels, are the biggest energy consumers in the household sector. Hence, optimal management of the heating and cooling systems can play an effective role in reducing energy costs in buildings. In this... 

The transportation sector is the largest oil consumer sector in the world. Iran is no exception to this, and the transportation sector, especially road transport, has a large share of oil and energy consumption in Iran. Diesel supply security in The road transport system has been implemented but it has not been properly managed for gasoline, as the country has been an importer of gasoline for many years and large cities suffering the pollution caused by light duty vehicles. Analyze the transportion of light duty vehicle by the game theory method can detect the barriers to reducing fuel consumption. For this purpose, the main Actors affecting the transport of light duty vehicles - people,... 

The purpose of this research is to design and construct a test stand for the study of the kinematic and flow pattern of bluff bodies oscillating motion due to the induction of wake vortices. An experimental investigation was conducted to explore the effect of bluff bodies cross section to optimize the amount of electrical energy withdraw by electromagnetic harvester. The tests are carried out on cylinders with square section and rectangular sections with a length to width ratio of 1/2 and 2/1 and height of 50 cm, at speeds of 5 to 35 m/s in eiffel type wind tunnel. The effect of cylinder cross-section on the amount of energy harvested showed that the amplitude of oscillation in square-shaped... 

Sanctions are one of the most important variables influencing Iran's domestic and international decision-making and have had many effects on Iran's economy and politics in recent years. Iran's ability to influence the oil market and harm the interests of the sanctioning countries in this market raises the question of whether such a capability could affect the outcome of sanctions and lead to the withdrawal of those sanctioning countries. A theoretical examination of the issue of sanctions using game theory shows that if the sanctioned country is not able to retaliate in areas other than the disputed issue, the sanctions game may not reach an equilibrium in which the sanctions are lifted but...