Sharif Digital Repository

Team and organizational leadership, has always been noted by researchers as an important factor in team effectiveness and organizational success. In past, leadership was considered a top down process in which one person (leader) played all the leadership roles. Recently, new models have been suggested by researchers, considering the increased demand due to changes in business world, how organizations work and how they interact with their environment. One of these models that have attracted a lot of attention from scholars and organizations is distributed leadership. This new model of leadership is considered to be a complement to vertical (Conventional model of) leadership. In this model... 

In this work, mathematical models are employed to predict transient temperature field, fluid flow within the melt zone and distribution of thermal and residual stresses during and after GTAW process. At the first step, fluid flow in the weld pool and transient temperature field within the metal being welded are determined by simultaneously solving the equations of conservation of mass, energy and momentum. To do so, a commercial finite volume base-program, FLUENT, is utilized. In the next step, temperature distribution during cooling as well as resulting thermal and residual stresses are predicted by means of a commercial finite element base program, ABAQUS. The employed models are capable... 

In this thesis, we consider multiple-antenna K-user interference channels with backhaul collaboration in one side (among the transmitters or among the receivers) and investigate the trade-off between the rate in the channel versus the communication load in the backhaul. In this investigation, we focus on a first order approximation result, where the rate of the wireless channel is measured by the degrees of freedom (DoF) per user, and the load of the backhaul is measured by the entropy of backhaul messages per user normalized by log of transmit power, at high power regimes. This trade-off is fully characterized for the case of even values of K, and approximately characterized for the case of... 

In the recent years, there has been an increasing attention toward usage of ultrasonic for enhanced oil recovery practices. But, thorough knowledge of active mechanisms and spreading and characterization of developed fingers during this practice is not available. From the other hand, due to limited amount of light oil fields, more attentions towards recovery from heavy oils is the need of the hour. Documents show that the big issues during the enhanced oil recovery from heavy crudes are high density of reservoir oil as well as poor development of fingers during injection due to high mobility ratios. In this study, results of ultrasound effect on the heavy oil recovery and its effect on the... 

In this project, a system designed for balancing a flexible rotor, without any need for shutting down the rotor. Then, functionality of this system, studied with experimental assessments. The method used in this plan, is classified into active online balancing methods of rotors which can change the mass distribution of the rotor, to improve the balancing condition, during operation. In order to reach this goal, a balancer plane is designed that by angular displacement of two nonconcentric masses, each driven with an electrical actuator, sets a desired unbalancy vector. Then, a rotor designed, which after mounting balancer plane, could be classified into the flexible rotors according to... 

One of the most significant aerial vehicles which has been subject of study of so many engineers and students is quadrotor or quadcopter, which is a cross sectional configuration of motors and propellers. This aerial robot is controlled through slight differences between the angular velocities of the four motors, and robot dynamics is completely nonlinear, thus sophisticated control algorithms are needed. The aim of this project consists of design, fabrication and control of a quadrotor capable of stable hovering. First, some preliminary decisions about general charachteristics of the robot were made. According to these decisions, other mechanical parts were designed and fabricated. Then,... 

Nowadays, apatite mineral is one of the most sought for the recovery of rare earth elements. This mineral is also the main source of phosphoric acid production. To achieve this end, apatite has to react with sulfuric acid to give phosphoric acid. This process is called the wet process. During the wet process, more rare elements enter the remaining solids called phosphogypsum (PG). For the dissolution of rare elements, PG, which is the same as chalk, can be leach with an acidic solution. In this project, the phosphate concentrate from Chadormalu iron ore waste after characteristics diagnosis is digested in concentrated sulfuric acid at temperatures below 100 ° C, and then hydration is... 

In this thesis, we investigate speaker verification as a biometric technology to verify a person based on his/her claim. Text-dependent speaker verification systems are preferred in commercial and security applications and these systems have better performance in limited data condition based on a prior knowledge about speakers that are assumed to be cooperative. Limited amount of enrollment data is a major concern in this thesis. Speaker dependent model construction and channel variability issues on telephone-based text-dependent speaker verification applications are surveyed. Due to the lack of an appropriate database for the task, we collected a database which is referred to as text-prompt... 

Naïve hardware implementation of encryption modules can cause leakage about the secret information. Attackers can use this information to extract the secret key. This approach is known as side channel attack (SCA). An example of such attacks is differential power analysis (DPA), which uses a number of traces of power consumption of the encryption device. One of the proposed methods to deal with such attack is using dual rail logic. In previous implementations based on a dual rail logic, symmetric complementary mapping with the cross coupling and pre-charging is being used. This method has relatively high delay and cost; however, significant increase in the level of security can be achieved.... 

This work concerns with experimental and modeling investigation of the asphaltene damage removal using ultrasonic wave irradiation. A specific core holder apparatus was designed and utilized for in situ ultrasonic exposure to damaged core plug at different conditions of exposure time, ultrasound power and distances between sound source and plug. Injection of many pore volumes of an asphaltenic crude oil was used for creating asphaltene induced damaged in porous media through permeability measurements. The deposited asphaltene during oil injection as well as asphaltene removal due to ultrasonic exposure was evaluated using IP-143 analysis. The results revealed that ultrasound application... 

The commercial breakthrough of micro-tubular solid oxide fuel cells (MT-SOFCs) is still facing so many challenges because of the complexity of their manufacturing process and the high cost associated with them. By deploying electrophoretic deposition as a simple and cost-effective method, the different components of the fuel cells (the anode, electrolyte, and cathode) can deposit on the graphite rod as a sacrificial substrate. The next step is eliminating the sacrificial substrate which will make hollow rods of cell components. The results of this study show that the use of a particular type of pencil lead will have a minimal negative impact on the overall fuel cell performance, leading to a... 

In this research, aluminum matrix composites (AMCs) reinforced by different contents of zirconium dioxide nanoparticles, graphite microparticles, and a mixture of both with various hybrid ratios, into a cold-rolled Aluminum1050 as base metal, fabricated by 4-passes friction stir processing. Observations show that the processing of composites reinforced by Gr particles is significantly hard due to the low friction coefficient of graphite resulting in the decline in the maximum temperature during the process and the type of base metal. The mixtures of graphite and zirconia resulted in more homogenous dispersion of particles in the matrix due to deterring a drastic drop in friction coefficient... 

In this research, aeroelastic model of an elastic flapping wing has been derived in order to be integrated with the flight dynamic model. The model developed in this research well describes the coupled and nonlinear behavior of the passive torsional deformations of the wing during flapping motion. Based on this obtained equations, a precise propulsion model proper for flapping wing vehicles has been introduced. The effect of geometric and mechanical properties of the wing is being accounted. In order to validation of the analytical model several FMAVs as well as an instrumented test stand for online measurements of forces, flapping angle and power consumption have been designed and built... 

Using camera in localization its pose and connected things, with using camera images has been inspected in this thesis which categorized in passive localization. Although using these methods seems to be rather difficult, human can passively perceive its position in space. This is a preface for new positioning systems.
In this thesis assume that some cameras are ready for Image sharing then we introduce algorithms for cameras relative locations and rotation matrices. This method gives local information and can uses range scaners as inputs. Other works in last decade tryed on 3D reconstruction and graphic section and rarely explored multi-camera localization and reduction of its... 

Deriving the shape, area, volume, and orientation of a defect from the ultrasonic nondestructive testing images of the oil pipelines, paves the way for the estimation of its severity. This paper describes the design and implementation of an automatic structure which can move an ultrasonic probe over the surface of a test sample, while preserving the distance, i.e. stand-off, between them, whatever the shape of the surface might be. The fixed stand-off is implemented, closing a feedback loop with a distance meter sensor. Also an integrated software environment is developed for the control of the table, data acquisition, data processing and displaying the results. After acquiring the... 

Large data sources labeled by experts at cost are essential for deep learning success in various domains. But, when labeling is expensive and labeled data is scarce, deep learning generally does not perform well. The goal of semi-supervised learning is to leverage abundant unlabeled data that one can easily collect. New semi-supervised algorithms based on data augmentation techniques have reached new advances in this field. In this work, by studying different textual augmentation techniques, a new approach is proposed that can obtain effective information signals from unlabeled data. The method encourages the model to generate the same representation vectors for different augmented versions... 

One of the most crucial methods to Ensure correct software performance is testing. On this ground, one of the most critical discussions regarding software testing is the effectiveness of a test suite. Program state coverage is a criterion for determining the effectiveness of a test suite. This criterion indicates the number of program states that are executed for the lines. Since the total number of program states cannot be calculated to measure coverage, this criterion proposes a fixed number of 10 to measure program state coverage. Also, according to calculations for the program state in the execution of each line, the time complexity of this criterion is high. In this thesis, providing... 

The current thesis argues about employee Performance Appraisal System (PAS) of damavand project which is one of the MAPNA Combined Cycle Power Plant Construction and Development Co (MD-2) projects.A few studies have been done in the field of human resource management in project structure and project-based organizations in comparison with classic organizations structure. the PAS might have a different role in project structure as a function in human resource management.In this research the required data has collected via interview with employees and some top managers of MD-2 Company.and Theme analysis has been used to analyzing the data. this study has described the effect of organizational,... 

In line with advances in science and technology in the areas of robotics, artificial intelligence, computer and control, unmanned vehicles are being more utilized and focused. On the other hand, development and further advances of these vehicles is highly dependent on the level of their autonomy. Motion planning is one of the most important issues in this regard. Due to high levels of autonomy required for unmanned air vehicles (UAV), the subject of motion planning is of valuable interest in aerospace applications. The goal of the motion planning problem, that is the subject of this research, is to extract an optimal trajectory for the UAV from an initial location toward its target point... 

In recent years, there has been an increasing concern about harmonic distortion and the effects of harmonics on power systems. Nonlinear loads such as electronic power supplies, battery chargers, motor drives, UPS systems and … are the primary source of harmonic currents. Harmonic currents generated by nonlinear loads flow from the load into the power system due to the network low path of impedance Harmonic currents cause additional heat and losses in power system components and results in voltage distortion as well.To deal with the problems associated with harmonics and to reduce their effects on power networks, study of the effects of non-linear loads on distribution networks is essential....