Sharif Digital Repository

The frequency divider is one of the components of a frequency synthesizer. Regenerative frequency divider is one of the frequency division methods and is used in narrow band applications. In this thesis, the process of designing & fabricating Ka band and Ku band regenerative frequency dividers is reported. A bandwidth of 550MHz for the Ka band divider and 400MHz for the Ku band divider have been achieved. Multiple passive structures such as microstrip filters, Wilkinson power dividers and a waveguide-to-microstrip transition have been designed during the fabrication of the mentioned frequency dividers. According to the results of the simulations, the bandwidth of the waveguide-to-microstrip... 

The use of polyaniline as an electrochromic conductive polymer was highly regarded. However, due to problems such as poor solubility, the researchers decided to use aniline oligomer as an alternative. Meanwhile, aniline pentamer received more attention due to its good solubility in organic solvents and acceptable conductivity. On the other hand, it is possible to increase the conductivity and also to respond more to stimuli to groups that have certain characteristics. In this study, aniline pentamer and carbazole-derived were used. First, nitro and bromoethanol groups are added to carbazole. Due to its fluorescence properties, carbazole can, in addition to increasing the conductivity, which... 

Usually the structures are designed based on the fixed-base assumption; however this assumption is not always correct and the bed flexibility should be considered. This effect which is called soil-structure interaction, change the response of structure on both elastic and inelastic behavior. In the regulations for the design of structures on flexible base, generallysoil-structure system is replaced with an equivalent fixed base structure; in the way that the design force of soil-structure system with reasonable accuracy can be estimated by equivalent fixed-base structure. In some regulations, dynamic characteristics of equivalent structure have been determined on elastic state and the... 

In this thesis, the problem of placing a minimum number of phasor measurement units (PMUs) in a transmission system is considered so that faults on all lines of the network can be diagnosed and located irrespective of their locations. For this purpose, a PMU placement algorithm is proposed to calculate the required data for impedance-based fault-location of any fault line in the network, achieving the full potential of the circuit laws throughout the system. Another algorithm is then proposed to compute the voltage and current values of the fault line for fault-location purposes. Moreover, as many networks are already equipped with PMUs, the proposed algorithm makes it possible to locate... 

In the last few decades Seismic Regulations attitude’s has been undergone significant changes from various aspects. One of these aspects is entering new topics based on the latest scientific achievements. Soil-Structure Interaction terms was from such issues which had found their ways into Seismic codes as an optional effective factor. In recent years, Based on this new attitude and Scientific achievements, Soil-Structure Interaction terms entrance into Iranian seismic code (2800 Standard), is also has been studied. Naturally, applying these criteria will impact on the design and performance of structures, because of reducing effect of soil structure interaction on decreasing base shear... 

Intercultural Communicative Competence has been the focus of much academic inquiries in the field of second/foreign language learning in the last decades since learners’ ability to communicate authentically in the target language has been recognized among the scholars. This study aimed to address this issue in the Iranian academic environment where there was almost a gap in not touching the cultural issues of target language in a focused and organized manner in language classes at universities. For that purpose, an intercultural syllabus was designed for a 14-week course of English short story in the Minor Program at Sharif University of Technology. The syllabus was an integration of various... 

The Vehicular Ad hoc Network (VANET) have been presented to enhance the safety and comfort of driver and passengers. Thus, the functionality of VANET is related to the accuracy of disseminated messages about surrounding environment. Therefore, it is critical to detect the true reports among false reports which they have been reported by malicious nodes. However, in this research, the proposed scheme presents a centralized trust management assessment scheme named Detection of Best Report (DBR) in vehicular ad hoc environments. Each received message is evaluated individually according to its reporter interactions during event reporting. Based on this evaluation in RSU, the most reliable nodes... 

The main purpose of the study was to introduce and utilize e-Readers in teaching and testing and compare the participants’ reading performance with those of the participants using paper books. To explore the learners’ perspectives and attitudes toward the use of electronic publications, 60 upper intermediate and advanced English language learners’ experience was examined via the data which were collected through interviews on their motivation and engagement. The two phases of this study were conducted in two separate sessions with a time interval of twenty days. In order to create a description of the details of the participants’ experiences using e-Readers, a descriptive analysis of their... 

Separation of particles and cells is one of the most important and practical methods in fields such as biomedicine, medicine and industry. In microfluidics There are various methods for particles and cells separation According to the source of them, they can be categorised as active and passive techniques. Active techniques rely on an external force field. The most important advantage of this method is controlling the force on the particles during the experiment. However, the flow speed is always limited because particles must be exposed to the outer force field for sufficient duration to achieve effective functionality. passive techniques depend entirely on the channel geometry or intrinsic... 

Cognitive Radio (CR) technology enables dynamic spectrum access (DSA) to overcome the problems of unlicensed bands which is becoming overcrowded. However, providing an acceptable quality of service (QoS) for cognitive users requiresmore sophisticated approachesdut to the existence of primary users (PU) with their high priority over licensed bands. Additionally, reducing interference with primary users so that they can communicate without interruption is of extreme importance. In order to meet cognitive user’s quality of service as much as possible and reduce interference with PUs, a new class-based multipath on-demand routing protocol for cognitive radio networks (CMORC) is proposed. CMORC... 

Along with the huge applications of wireless networks and creation of advanced wireless technologies, such as Bluetooth, WiFi, 3G and 4G, an evolution of Mobile Ad Hoc Networks emerged called opportunistic networks. In these networks, network topology is unpredictable; therefore, to send the message to the destination, moving nodes were used opportunistically. So one of the main challenges in this type of network is the routing problem. Amongst existing methods, methods that apply context information can help greatly to choose the right path. In this thesis a method was presented to gather information applying cell network classification and learning cellular automata, from the location of... 

St52 was heated at 745°C for 70 minutes and then quenched into a salt bath at 400°C. To obtain different volume fraction of bainite and martensite with constant volume fraction of ferrite (67%), samples were quenched into water after different times. Presence of three phases of ferrite, bainite and martensite was proved by optical microscope and hardness test. Different volume fractions were measured by image analysis. Optical microscope results showed that with increasing of martensite up to 9.4%, morphology of martensite is a uniform distribution of small and sphere particles. These samples then were cold worked at various degrees. Tensile test and hardness test show that increasing the... 

In this thesis, we consider the problem of online conflict-free coloring for regions. First, we analyze online variant of the conflict-free coloring of intervals on the line, where each newly inserted interval must be assigned a color upon insertion such that the coloring remains conflict-free, i.e. for every point p in the union of the current intervals, there must be an interval I with a unique color among all intervals covering p. we present deterministic algorithm for achieving this goal which uses O(log^3⁡n) color. Next, we consider the online conflict-free coloring of nearly-equal axis-parallel rectangles in the plane and present a deterministic algorithms which uses O(log^12⁡n)... 

A grid simulator is a system for testing various types of grid-connected devices, such as inverters of renewable energy sources, chargers, power supplies, etc. In this project, the design and implementation of a 3 KVA three-phase regenerative programmable AC current source is presented. In the future, this structure can be used as a grid simulator. The topology used for the current source is a two-level three-phase AC to DC converter. The current source can operate in constant current (CC), constant power (CP), constant impedance (CI), and constant voltage (CV) modes. In the constant current operating mode, the user sets the amplitude and phase of the 1st, 5th, 7th, 11th, and 13th harmonics... 

In this work we intend toeconomically recovery of residual from terephthalic acid production unit in the Tondgooyan petrochemical company. Major component of this residual is catalysts, benzoic acid and amount of terephthalic acid product. Catalysts contains of cobalt, manganese and bromide which recycled by water extraction. Effective variable on extraction process is dilution ratio of water to residue, extraction temperature and time. Optimum condition of catalystsrecovery consist of dilution ratio of water to residue 6:1, extraction temperature and time is 45 C° and 40 minrespectively. Recovery yield of cobalt, manganese and bromide in this optimum condition is 91.21, 91.89 and 92.53... 

Detection and classification of arrhythmia is important especially for patients in Emergency care units. Early diagnosis of cardiac arrhythmia makes it possible to choose appropriate anti arrhythmic drugs, and is thus very important for improving arrhythmia therapy. Computer-Assisted Diagnostic (CAD) Systems are used in recent decades in which extracted features and classifiers are the most important factor. In this project, we try to focus on both of these two major factors in heart arrhythmia classification using HRV signal. Therefore, in this project, we try to classify different groups of arrhythmia using HRV signal processing especially the nonlinear processing. Our main aim is to... 

This thesis represents the obstacle avoidance of a fixed-wing small aircraft using optical flow information of cameras mounted on the aircraft. The thesis consists of two main sections. In section one, the ideal optical flow has been simulated based on the camera model, complete six DOF of flight equations, and the geometry of the environment. An analytical formula has been derived to relate the obstacle detection distance to the maneuverability of the aircraft. Having the obstacle detection distance, the control and navigation algorithms have been developed to achieve a collision-free flight for the aircraft in urban canyons and junctions. The effect of some parameters such as approach... 

Capacitor setting and reconfiguration are of main means of loss reduction and voltage profile improvement in distribution system operation. Cooperation between these two strategies can effectively minimize power losses in distribution system automation. Also, from the medium and long term viewpoint, capacitor placement and reconfiguration can be used for loss reduction and reliability enhancement. In this section, the sum of losses cost, capacitor investment cost and reliability cost should be minimized. Regarding the need to solve two non-linear combinatorial optimization problems simultaneously, metaheuristic algorithms are used in this thesis. Specifically, Elitist Genetic Algorithm,... 

Nowadays, one of the most important challenges in the design of digital circuits is their susceptibility to the strike of high energy particles which leads to the Single Event Transient (SET) and Multiple Event Transients (MET). In fact, technology scaling which results in lower supply voltage, higher operating frequency, and lower nodal capacitance, makes today’s digital circuits more susceptible not only to high energy particles but also to low energy particles. Moreover emerging deep sub-micron technologies and the integration of more cells in today’s chips have caused higher probability of MET occurrences. A lot of research has tried to reduce the soft error rate due to high energy...