Sharif Digital Repository

In the current digital era, the large number of mobile developers and android applications has led to intense competition. Users can easily access many android applications to meet their needs. This abundance of available software makes it difficult for developers to attract and retain users, as they can easily switch from one application to another. This switch can happen if the current application does not meet the user’s needs, has issues, or if a better alternative is available. Therefore, developers must focus on keeping their users satisfied. To ensure user satisfaction, developers need to address user needs effectively. This includes fixing reported issues, adding new features, and... 

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... 

Arising from the intersection of two modern ideas in logic and mathematics, namely Type Theory - specifically Martin-Löf’s intuitionistic type theory, and Homotopy Theory, Homotopy Type Theory has introduced a novel formalism that formalizes every mathematical object - including constructions, definitions, and proofs - in a specific and fundamentally different way from other interpretive frameworks (such as set theory), bringing forth new results - both philosophically and mathematically. The first goal of this research is to understand the meaning of Homotopy Type Theory as a foundation for mathematics through exploring this new formalism. The second goal of this research is to understand... 

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... 

For validation of simulation, plasma actuator was modelled on a flat plate in quiescent flow, which is result in low-speed jet near the wall. The results were compared with similar model and were showed good agreement with them. After that, blade was modelled in three-dimensional manner with MRF technique and periodic method and the results were validated in clean situation (absence of plasma). In the following, turbine was analysed with a code, which was written in MATLAB software based on BEM method and the results were compared with present CFD simulation. Then, plasma actuator was used in chordwise in parts of the blade to improve wind turbine performance. Also it was used in spanwise... 

In recent years, most of the programmer’s problems are solved using Q&A websites, e.g. Stack Overflow. Since the number of users, questions and answers in these websites are rapidly increasing, manually moderating and enhancing the quality of the posts (specially the answers) seems to be impossible. Despite the various studies on issues with Q&A websites and facilitating their use, there has been no studies on the field of improving the quality of answers. In this study, we intend to provide an appropriate solution to enhance the problem of low-quality answers. In order to demonstrate the proposed approach, we recommend a tool called StImp, which is a plugin for Eclipse. Using this plugin,... 

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. ... 

In this research, aluminium sandwich structure was manufactured by accumulative roll bonding (ARB). In this method, aluminum AA5083 strip was used as the matrix and titanium hydride was selected as the foaming agent powder. Due to the use of particle foaming agent in the first pass, reduction, preheat temperature, rolling speed and the percentage of powder particles parameters were examined. Finally, the 66% reduction, 400 °C preheat temperature and 25 rpm rolling speed, were considered as the optimal values. At the next stage of this process 50% reduction was applied at each pass and this process was repeated up to five passes. After ward, in order to create a sandwich structure, aluminum...