Sharif Digital Repository

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... 

This study investigates the effect of commodity price shock, including oil and base metals prices, on Tehran exchange and industries stock returns. These industries have the largest market share in Tehran exchange and may heavily depend on global prices. Using weekly data from 1387 to 1396, Multifactor and VAR models are performed to analyze the variance decomposition and impulse response function of each industry to 1% price shock. In addition to global prices, some macroeconomic factors that are likely to affect stock returns are considered. The results show that commodities price shocks have dynamic and significant effects on stock returns  

With the rise of the concept of “Big Data”, both data volumes and data processing time increased, imposing the need for new methods of processing and computation of said data.Analytical and computational methods in Machine Learning are some of the most important applications of Big Data processing. There exist many methods of data analysis in the Machine Learning field, each requiring extensive processing on Big Data. One of the methods for working with Big Data is Distributed Systems. MapReduce is one of the most popular methods distributed computation by increasing the ease and speed of distributed processing of big data. But a number of bottlenecks have been discovered in MapReduce which... 

In this thesis, we first explain how we can construct three-point amplitudes for both massive and massless particles by solely knowing the Lorentz invariance and spin or helicity of particles. Then, using BCFW recursion relation, we determine the tree-level amplitudes. To calculate the loop amplitude, we apply the unitarity of Smatrix.The unitarity relates the tree-level amplitudes to loop level. Finally, I discuss some exciting topics in this field, including color-kinematics duality, some relevant applications of contemporary S-matrix theory in effective field theories  

During years, supersymmetry has been a candidate for resolution of Higgs mass fine-tuning problem that is quadratic dependence of scalar mass radiative correction to UV-physics. So, supersymmetry phenomenology is of great importance. As accelerators have reached energy of 13 TeV in recent years and sparticles have not yet been observed, it is important to have a theory in hand, describing SUSY breaking dynamics with scale of SUSY breaking above the energies currently accessible to accelerators. As a result of mass-sum-rule constraint which holds in theories with spontaneous SUSY breaking at tree level and leads to light sparticles and even tachyonic directions, there are currently no... 

Although electronic banking service has been introduced in Iran for more than a decade، today half of the people who go to the physical bank branches are the ones can do their affairs via e-banking. The banks’ managers attribute the main reason for these unnecessary travels to insufficient trust towards e-banking systems. One of the important tools in this regard is mobile banking which is prevailing around the world، however it has not prevailed enough in Iran. This research has tried to investigate the cognitive and non-cognitive dimensions of trust to mobile banking. The data for this research has been collected from users of mobile bank service who have filled the online research... 

Shia theology has gone through different transformations throughout history. In the contemprorary age diverse studies have been carried out in order to discribe it’s preceding changes and future transformations. This tesis tends to show at first that “MacIntyre’s method of historical-philosophical study” is an overally justified model for such studeis, in comparison with the two other models of “Kuhn’s model of scientific revolutions” & “Lakatos’s research programs.” Afterwards, this model has been used for the study of shia theology and a brief narration of the rationality traditions of shia theology through the Iranian tradition has been given. The focus of this section has been on the... 

Massive MIMO is a key enabling technology in the fifth generation (5G) wireless communication systems. In this technology, the base station is equipped with a large number of antennas (e.g. 100-200) and communicates with a relatively smaller number of user terminals. The large number of antennas at the base station, on one hand, has enabled unprecedented improvements in data rate and energy-efficiency, while on the other hand has posed challenges on the practical deployment of this technology.One of these challenges, is the high computational complexity of the baseband processing algorithms, such as precoding, due to the large number of antennas. In this research, we propose a novel ZF... 

One of the open questions in particle physics and cosmology is matter-antimatter asymmetry in the Universe. Observations at different scales in the early universe indicates that the number of baryons and leptons are greater than the number of anti-baryons and anti-leptons. Various mechanisms in the last 50 years, have been proposed to generate this asymmetry from a symmetric Universe. They can be classified into two groups: models which add new particles and interactions and models which consider gravity and time dependent background fields. The basic difference is that if they respect CPT symmetry or not. In this thesis we take the second approach. We study the neutrino sector of the... 

Energy storage is a pivotal technology to dealing with increasing demand for reliability and challenges of renewable energy integration. This thesis provides a benders decomposition framework for expansion studies of energy storage systems (ESSs) in high wind penetrated power system and uncertainties of wind farms expansion and wind speed. This work proposes probabilistic and robust approaches to determine the optimal location and size of storage devices to reduse wind curtailment. The proposed methodologies are implemented on the modified IEEE 73-bus test system and their anticipated applicability are compared to each other and well verified  

One function of futures markets is to signal about future spot prices. This role is accommodated by creating a way for future tradings. In futures markets, different types of investors, including speculators, arbitrators, and hedgers, trade based on their expectations of the future. The better the agents are in pricing, the more significant this role of financial markets. Therefore, it is possible that futures prices contain information that helps to predict maturity spot prices. This study examines the performance of using gold coin futures prices in forecasting with the help of data from December 2008 to July 2016. Studying the cointegration relationships between futures and maturity... 

The dRGT theory of massive gravity is a consistent theory of interacting massive spin 2 particles. As an effective field theory compared to observational data, its UV cutoff is rather low. Namely, unitarity is violated at low energies in scattering of longitudinal modes. In this dissertation, we give a brief review of the dRGT theory and its challenges. Of particular interest is the question of its UV completion in a more consistent model. Then, we show that this theory can be obtained from a topological gauge theory in one higher dimension. After dimensional reduction and symmetry breaking via boundary conditions, we obtained four dimensional effective field theories including the dRGT plus... 

The turbulent waves of the sea and their impact have always been one of the challenges of marine activities. Recently, with the world economic development and the boom of maritime tourism, providing comfort for the occupants of ships and boats has become one of the issues of engineering concern. Therefore, different methods are used to address this challenge. In this article, we first review these methods and then try to choose the optimal method and design a system for a relatively small boat that can compete with other methods. The method of choice is "damping mass", which has never been used to reduce the movement of boats. In this paper, by obtaining the equations governing the physics... 

Jetsurf is a recreation vessel at sea. It is a surfboard that is equipped with a motor propulsion system and provides surfing, which is an exciting and popular sport, in calm seas, lakes, dams, rivers and natural and artificial canals. This project is divided into four steps. In the first step, the appropriate dimensions for the design of this device are specified. In the second step, to calculate the resistance of jetsurf, at first a model with similar dimensions including experimental results in Star CCM+ software was validated by computational fluid dynamics method and Overset dynamic mesh technique and then jetsurf resistance with dimensions of 1.8x0.6x0.225 meters was calculated. In the... 

The growing requirements for renewable energy production lead to the development of a new series of systems, including wave and tidal energy conversion systems. Due to their sensitivity and the impact of the aggressive marine environment, the selection of the most adequate location for these systems is a major and very important task. Several factors, such as technological limitations, environmental conditions, administrative and logistic conditions, have to be taken into account in order to support the decision for best location. The aim of the present study is to provide an Atlas of IRAN Offshore Renewable Energy Resources (hereafter called ‘the Atlas’) to map out wave and tidal resources...