Sharif Digital Repository

The price elasticity of gasoline demand is a key parameter in evaluation of various policy options. However, most of the literature uses aggregate data to identify this elasticity. Temporal and spatial aggregation make elasticity estimates unreliable. We employ a unique dataset of all gasoline transactions in Iran during a four-month period around an unexpected exogenous price change to identify price elasticity. After controlling for date and individual fixed effects we estimate a robust significant price elasticity of -0.127. Aggregation of the same data by week, month, and city yields an estimate of -0.3 indicating a significant bias in earlier studies. We also identify a significant... 

The growth of user traffic and appearance of new services, has changed architecture of mobile networks. Data flows have different requirments based on their services. Mobile platform should be able to recognize services and slice network resources based on them. Different approaches have been investigated using relevant standards and numerous articles. The focus of this thesis is on implement a platform based on fourth generation mobile networks that can differentiate between data flows according to their respective required QoS.We have implemented an IMS network and connected it to a mobile core network But IMS network just supports session-based services. We introduced a solution for non... 

Production of semi solid slurry and creating the globular alloy structure is possible in the ways of Electromagnetic stirring and Gas induced semi solid, which are used widely in industrial scale. Because of the weak magnetic field in the middle part of stirrer, this part is being emptied of melt. As a result, The porous graphite cone is used in this part in order to inject the gas bubbles.In this research, the semi solid A356 Aluminum alloy, is produced under different durations and stirring flux using a three phase Electromagnetic stirrer and injection of the Argon gas. Consequently the slurry was transferred to a mold and compacted by a drop weight. By investigating and analyzing the... 

As the Business environment becomes more and more competitive, companies are forced to push themselves to use their capabilities in order to gain success. The success of the companies depends on their business knowledge and the strategies they use to compete in global market. The purpose of this study is to examine the attitude of consumers towards Beem products in Iran and the potential customers’ attitude toward home appliance product in Arab State of Persian Gulf (ASPG) in order to define the most proper strategy of adaptation to enter into an international market and increase the market share in a new environment. Quantitative methods have been chosen for gathering data. Two sets of... 

Microrobots have the potential to access small spaces for manipulation or for acting as a sensor. Magnetic microrobots are the most common types of microrobots. Magnetic microrobots have gained particular traction for medical applications due to safety of tissues. For instance, disease diagnosis, minimally invasive surgery and cell manipulation are potential applications of magnetic microrobots. The performance of a single microrobot could be improved by using multiple robots. For example each microrobot could carry a small payload to a goal inside a microfluidic channel, or could assemble fast and in parallel. In order to employ multiple robots, it is necessary to control each microrobot... 

Magnetic steering of continuum robots is a promising technology that uses a magnetic field to control the robot without contact and can improve the accessibility, safety, and accuracy of the robot. On the other hand, magnetic localization can also be used as a positioning method without direct line of sight in various applications. Common magnetic localization methods face the challenge of dependence on initial guess, divergence, and high computational cost. In this research, by eliminating the unknowns related to the orientation and rewriting the equations, a new method for magnetic localization has been presented. The advantage of the new method in convergence and increasing the speed of... 

Today Ethernet is the predominant technology for implementing Local Area Networks. Its privileges encourage service providers to extend Ethernet from Local Area Networks to Metropolitan Area Networks or even Wide Area Networks. Ethernet benefits such as low operational costs, well interoperability, plug-n-paly characteristic and rapid provisioning on demand make Ethernet ideal for Metropolitan Area Networks.But Ethernet by itself has some weakness like flat structure that makes it unfit for use in Metropolitan Area Networks. A suitable solution for taking advantages of Ethernet benefits in service provider network is using Ethernet in access network and applying multi-point to multi-point... 

Recent advancement in wireless communications, electronics, low power design and also tendency to use high performance low cost products have led to emergence of Wireless Sensor Networks (WSNs). As the main purpose of a WSN is information gathering and it’s transmission to the sink node, the main problem is to deliver information correctly with minimum energy consumption. Besides, whereas the majority of developed applications for WSNs are event-critical applications, achieving reliable data transfer as the main factor of dependability and quality of service seems vital. However, data transmission is unreliable over multi-hop WSN due to the unreliability of wireless links and node failures. ... 

Recent success of Deep Learning models, resulted in their evergrowing application in many fields. However these models usually require huge datasets, which can sometimes be hard to collect. One of the challenges related to medical data, is the Batch Effect; Medical data is usually gathered through multiple experiments. Each experiment might have a slightly different conditions than the other, resulting a shift in the data related to that batch. Batch effects can have more severe impact during testing time, as the shift in the data distribution could be bigger. Many methods have been proposed to reduce or remove the effect of external conditions on data distribution.Deep Learning models have... 

For several years, self-organizing networks have been introduced by 3GPP to reduce the costs of mobile operators. Self-organizing networks, by introducing a kind of intelligence to the mobile network, will cause optimal performance and, as a result, reduce the operating costs of operators. Improving network coverage and increasing user data rates are always among the priorities of operators to increase profits and customer satisfaction. Coverage and capacity optimization is one of the most important functions introduced in self-organized networks. In this study, in addition to the coverage and capacity optimization function, the load balance optimization and the contradictory interaction of... 

Density currents, caused by the intrusion of dense fluids under lighter ambient fluids, frequently occur in both natural and industrial situations. As a result of the density differences, the driving force can arise from soluble substances, temperature differences, etc. If the driving force comes from suspended particles including silt and mud, the currents are called turbidity currents. Due to the variation in concentration and the consequent driving force along the flow path, turbidity currents are significantly more complicated than saline currents. These currents play the most important role in sedimentation in lakes, seas and oceans. In addition, turbidity currents are the main factor... 

Music information reterival systems have a lot of applications in music filtering and broadcast monitoring due to the huge amount of multimedia data these days. In these systems the feature extraction method is called audio fingerprinting. Small size of fingerprints allows the systems to search efficiently in thousands or millions numbers of audio songs. The input signal is usually just a couple of seconds long and degraded in several ways. The goal is to design a system which is robust to signal degradations and efficient to search. In this thesis one of the basic systems is reviewed and improved in several ways. This system uses spectrogram of signals to extract features and build an... 

The abstract is the most important section of the thesis because many readers limit most of their reading to abstracts, saving in-depth reading for specific theses. It should give the reader a "preview" of what's to come. The abstract should emphasize new and important aspects of the study or observations. The purpose of the abstract is to allow researchers to decide whether or not to read the whole thesis. The abstract is what researchers read first to decide if the thesis is important, interesting, and it allows them to assess the relevance of a thesis to their own research, without having to read the entire thesis. Thus, it is crucial that the abstract both summarize succinctly the key... 

The impact of opening of the metro station in the city, given the advantages and disadvantages faced by residents adjacent to the station, could have different effects on housing prices. Various studies have been conducted to reveal the impact of urban transport on the value of property, each with different results. In the investigation of this issue, there has been positive, negative or even insignificant effect on the construction of a transport corridor on the value of the property. In this research, the effect of the opening of the metro station as a type of transportation corridor has been investigated on the value of residential properties around the station. Different parts of Tehran,... 

Reconfigurable devices are a popular platform for fast prototyping of digital system due to having high performance of hardware implementation along with flexibility of software. However, reconfigurable devices suffer from area, performance and dependability gaps in comparison with their Application Specific Integrated Circuit (ASIC) counterparts, which greatly limits their application.
The dependability gap originates from the sensitivty of configuration memory to soft errors. When a reconfigurable device configuration memory is affected by soft errors, their configuration will be invalid until reconfigured. Since the routing fabric is the origion of over 80% of soft errors in... 

In this thesis, performance of share stocks after Initial Public Offering has been investigated. According to the findings, underpricing and long-term underperformance phenomena have been witnessed in Tehran Stock Exchange and this conforms with the findings of researches in other markets. This study also showed that there is no meaningful difference between private and state-owned offerings in terms of short-term and long-term performance and, in disagreement with the results of similar studies in other stock markets, long-term return of state-owned offerings is less than market return in the same period. Furthermore, this study revealed that amongst various characteristics of offerings,... 

Offshore structures are valuable structures used in the offshore petroleum and gas fields for the purpose of hydrocarbon production operation. These structures are influenced by wave loads. Sea waves are inherently alternative and for this reason fatigue failure is considered as one of the most important modes of failure in these structures. Joints in these structures are made by tubes and they are called tubular joints. The joining process in manufacturing of these joints is welding. Welding process induces residual stresses, mostly tensional, in the substructure of materials. This tensional residual stress has a destructive effect on fatigue life of the joint and increases probability of... 

With the growing development of the aviation industry, the emitted jet noise from civil and military aircraft has become a challenging issue in the development of this industry. Despite recent advances in simulation methods using for fluid phenomena, understanding the nature and physics of noise generated by jet flows has been a complex puzzle for the last decades. Although numerical methods are currently able to predict the jet noise, it is still not possible to fully understand the physics of this phenomenon and subsequently use it to control the emitted sound. In this research, with the purpose of studying the pressure fluctuation caused by large-scale coherent turbulence structures in... 

Quadcopters are a bunch of vertical takeoff and landing UAVs and generally consist of four symmetric arms, each possessing a rotor-blade at the end. Quadcopters are able to retain their state and position by performing static maneuverability. Conventional quadcopters have less actuators (four engines) than their DOF (six degrees of freedom in the space). Thus, it is impossible to control all DOF of the system independently. Nevertheless, one can make a solution to this problem by increasing the number of actuators, so that each rotor-blade can also rotate about the corresponding arm. Such a quadcopter is so called a “tilt-rotor quadcopter”. The aim of this work is to model a tilt-rotor... 

Fractured reservoirs have allocated a significant portion of Iran's and the world's oil and gas reserves, underscoring the importance of predicting the performance of these reservoir types in the oil and gas industry. Predicting the performance of fractured reservoirs by professional reservoir simulators, especially in enhanced recovery conditions, requires precise information on fracture flow functions, which is often limited. These functions vary for each reservoir based on the distinct characteristics of the rock and fluid, and the only way to determine them is through appropriate laboratory experimentation and modeling of the results. Currently, in simulation models, the relative...