Sharif Digital Repository

Journals and conferences in computer science are the major venue for publishing new achievement in the field. It is an expert opinion that a number of top conferences in computer science are even more important than journals. In this work we aim at studying this in terms of citation analysis. To this end, we took 100 top journals and 63 top conferences and extracted their citation graph through Scopus dataset. We then constructed the citation graph in which the nodes were the journals and conferences and the links corresponded to the citations of the papers. We used various measures to rank the nodes in the graph. The ranking methods included Prestige, PageRank, Eigenfactor, HITS and SALSA.... 

Regarding the analysis of real-world networks, the ability to detect regions of high density or “community” is of great importance in network science. The motivation behind this endeavor comes from many publications confirming that the agglomeration of relations is meaningful on its own. At the same time, there have been some attempts, although less than the unsigned route, toward the detection of community in groups of positive relations (similar to unsigned mode) that have, internally, as few negative ties as possible. As an example, signed Modularity is one of the few algorithms in this route.In this thesis, we first tried to analyze the structure of real networks to find out about the... 

In this research, we examine the profitability of momentum investing strategy in Middle East stock markets in 2005- 2014. We find that momentum strategy is not profitable in this period, since market was negative in many months of studying period. However, we find that the momentum strategy generate positive return following up market, and negative return following down market, which is similar to its performance in other stock markets. Our results show that pastmarket return determines winner and looser portfolio. Following up markets, high beta stocks constitute looser portfolio and low beta stocks constitute winner portfolio. Conversely, following down markets, high beta stocks constitute... 

Removing nitrogen, as one the most surface and ground water contaminant is very important and in order to achieve this aim,nitrification and denitrification are effective and economical methods. In this work, moving bed biofilm reactor (MBBR) with initial denitrification structure, adapted from modified LUDZACK-ETTINGER (MLE) method used in order to industrial wastewater treatment with COD value in range of 900-2100 mg/lit and ammonium in range of 150-430 mg/lit in 3 hydrolic retention time of 18 , 12 and 8 hours.Aerobic reactor volume is 14.4 liter and anoxic reactor volume is 7.2 liter and reflux flow amount from aerobic reactor to anoxic reactor has considered being 3 times of anoxic... 

Mankind with it’s finite resources (Time, Energy, …) cannot make use of every accessible option in daily activities (such as buying items, listening to music and reading news), and is restricted to decide on a handful of them. Available options are increasing on a daily basis and these surplus of available options had an adverse effect; Thus, leading us to more baffling situations. As a result, need for external assistance appeared in decision situations. Considering exceptional computation power available to computers, a framework named Recommender Systems were developed. Recommender systems try to use their accessible data in order to make fitting suggestions to users. Personalization and... 

All rotating machines (such as internal combustion engines, reciprocating compressors, propulsion systems, etc.) experience torsional vibration during Start up, continuous working conditions and blackout. Torsional vibrationis due to pressure rhythms, engine dynamic torques, etc. All components of a rotating system must convey dynamic torque in addition to the static torque.Excessive Torsional vibrations cause wear and damage such as gears, gear teeth damage and failure to the main shaft.Online monitoring of torsional vibrations of the machine can be displayed machine condition at any moment and consider the risk in early diagnosis. Shaft torsional vibration monitoring can detect cracks in... 

Long Term Evolution (LTE) aims the peak data rates in excess of 300 Mb/s, which may appear to be challenging to achieve due to the existence of some blocks such as the turbo decoder. One efficient approach to achieve this throughput is by parallelizing the Log Maximum a Posteriori (MAP) algorithm in the turbo decoder. In fact, the interleaver is known to be a major challenging part of the turbo decoder due to its need to the parallel interleaved memory access. LTE uses Quadratic Permutation Polynomial (QPP) interleaver, which makes it suitable for the parallel decoding. In this thesis, first, we propose an efficient architecture for the QPP interleaver, called the Add-Compare-Select (ACS)... 

Nitrogen compounds are becoming increasingly important in wastewater management, because of the many effects that nitrogenous material can have on the environment that need nitrogen removal. In this study, the performance of a submerged fixed bed reactor in nitrogen removal, constructed two anoxic and aerobic sections under Modified Ludzack-Ettinger process was investigated. Laboratory experiments were conducted at a constant COD concentration of 350 mg/lit, hydraulic retention times of 8, 12 and 18 hours and influent ammonia loading rate between 0.128 and 0.955 g NH3/m2.day. Nitrogen removal efficiency was obtained between 80.4 and 97.3%, and COD removal efficiency was achieved between 88.9... 

The rapid growth in the health care technology, has made the Body Area Network (BAN) as an attracting topic for research and design development. BAN devices have restrictions on their size and power consumption. Monitoring the respiratory signal is crucial in many medical applications and is normally part of a BAN system. Traditional methods for the respiration measurement are normally based on measuring the volume of air inhaled and exhaled by lungs (like a spirometer) or oxygen saturation in blood. However, these methods have numerous drawbacks including their high cost and limited accessibility. In this thesis, a novel scheme is proposed to derive the respiratory signal from the... 

Recommender systems are in the center of network science and becoming increasingly important in individual businesses for providing efficient personalized services and products to users. The focus of previous research in the field of recommendation systems was on improving the precision of the system through designing more accurate recommendation lists. Recently, the community has been paying attention to diversity and novelty of recommendation list as key characteristics of modern recommender systems. In many cases, novelty and precision do not go in the same direction and the accuracy-novelty dilemma is one of the challenging problems in recommender systems, which needs efforts in making a... 

Information cascade or affection in a broad social network is introduced as a dynamic epidemic phenomenon in the society. As people notify a new innovation, technology, or hobby, they try to share it with their friends, colleges or neighbors. Till now most of the cascade models are presented for unsigned network, in which all links have the same sign (such as friends and trusted networks). In these networks cascade is independent of the edge sign. But in reality signed networks are as common as simple networks. Thus, in this thesis, we study information cascade in networks with positive and negative edges. We link the cascade size to community structure of signed networks; communities are... 

Trust prediction, the ability to identify how much to trust to allocate an unknown user, is an important prerequisite toward the development of scalable on-line e-commerce communities. We are more likely to purchase an item from a seller on an e-commerce websites such as eBay or Amazon, if our trusted acquaintances have reported positive experiences with that seller in the past. Reviews from trusted users will carry more weight towards the purchasing decision than reviews from anonymous or unknown customers. Thus, these platforms must support computational mechanisms for propagating trust between users. One of the significant challenges in the trust prediction problem is the unprecedented... 

The World Wide Web has been experiencing a massive growth regarding its content and users in recent years; therefore the need for effective means of accessing and processing available items has attracted a wide range of researchers and industries. Recommender systems has emerged to help both users to find what they may be interested in and the producers to sell their products more efficiently. As the number of these techniques grow, the need to evaluate them properly increases as well. However the proposed evaluation metrics are very diverse and often inconsistent with each other. Although there had been immense research in this field, there is no united and proper approach for evaluation of... 

Eutrophication and algae growth is one of the consequences of high concentration of nutrients in surface water bodies; therefore, both phosphorus and nitrogen existing in wastewater or at least one of them should be decreased to a standard amount before entering water to rivers. This can prevent eutrophication and detriment to the ecosystem of rivers. An investigation on both biological and chemical phosphorus and carbon removal in low loading rate influent ( below 100) has been carried out in this research. Investigated topics includes aerobic COD removal in IFAS reactor, comparison of biological nutrient removal to the combination of chemical and biological method, effect of the order of... 

With the over-increasing growth of the information provided for the web users, from content providing systems and web stores to social networks, the exictence of recommender systems is strongly needed. Recommender systems personalize web for the users and help them with finding relevent information in the huge era of World Wide Web. Collaborative filtering methods are known as the most successful and vastly used recommendation systems. Although they generally outperform content-based algorithms, in cold-start situation and especially in the presence of the new items, they fail to predict ratings for the new items or make good recommendations. This problem is not negligible in the systems... 

Natural gas power plant installed in power system as rapid start unit. In the recent decades, with increasing in the number of gas generating units in the world, consideration of natural gas transmission network in optimal solution of security-constrained unit commitment (SCUC) become a non-negligible problem. The gas transmission grid constraints integrated into the scheduling of thermal units in the proposed model for minimizes power system operating cost. In a power plant transmission of natural gas to power plant is very important because congestion in natural gas pipeline increases. This model could consider natural gas storage tank in gas transmission network as decision variable.... 

Recommender systems are in the center of network science and are becoming increasingly important in individual business for providing efficient personalized services and products to users. The focus of previous research in the field of recommendation systems were on improving the accuracy of the system through designing more accurate recommendation lists. Recently, the community has been paying attention to diversity and novelty of recommendation list as key characteristics of modern recommender systems. In many cases, novelty and precision do not go in the same direction and the accuracy-novelty dilemma is one of the challenging problems in recommender systems, which needs efforts in... 

Ultra-sensitive magnetometers based on Radio Frequency Superconducting Quantum Interference Device (rf SQUID), have wide applications in Non-destructive Evaluation (NDE), geophysical measurements and biomagnetic measurements, especially in magnetocardiography (MCG) systems. A superconducting module coupled to rf SQUID is designed to provide a resonance frequency in GHz range (according to the electronic system frequency), as well as concentrating the magnetic flux in the effective area of SQUID. The signal can be measured through a port pumping AC power to the module. The resonator has been also implemented by lumped element tank circuits, but the quality factor of these circuits are usually... 

Given the great importance and urgency of preventive operation against illegal drug trafficking as a social scourge, it is necessary to schedule and optimize the police decision in order to interdict further distribution of this harmful product. In this thesis, we study interdiction of drug distribution as multi-period maximum flow profit network interdiction on a multi-commodity flow and multi-source-sink network. The drug distribution network consists of criminal who are dynamically connected and seek to maximize the total flow profit from sources to sinks while the police aim to reduce aim to reduce total flow profit over long period of time by monitoring and interdicting criminals due to... 

In order to increase the service life and prevent the breakdown of apparatuses, instalations and equipments, we are in a position to maintain them. In this regard, there are three methods for maintenance of machineries, which are called reaction maintenance, preventive maintenance and predictive maintenance. By carrying out a predictive method or monitoring the situation, it is possible to know the health of the machine and take the necessary measures before the damages occurs. Vibration analysis, temperature analysis, oil analysis and flow analysis can be used for monitoring the situation. Reciprocating compressors are one of the most costly repair equipment that needs to be monitored...