Sharif Digital Repository

Forward scatter radar is a special kind of bistatic radar. It is designed to detect targets near the transmitter-receiver line which is called baseline. It has a number of promising features such as larger target radar cross-section (RCS) than that of traditional radars, applicability of shadow inverse SAR (SISAR) algorithms, high performance in automatic target recognition and identification, and robustness to stealth technology. On the other hand, it also has some inherent limitations, including the absence of range resolution (potentially leading to a high Doppler clutter level) and operation within narrow angles relative to the transmitter-receiver baseline. Target detection in forward... 

Numerous structures which are involved in seismic soil-pile-structure interaction have been damaged، failure in piles or even collapsed that can’t predict. Because of difficult modeling in soil، pile، structure interaction prediction the response of structure is impossible. In this study with using the finite element Abaqus software tries to understand the effect of soil pile structure interaction in structure response. By using the time history of Elcentro، structure with different boundary conditions were analyzed and the response of them were compared. Models have different boundary condition such as fixed base، pile groups and pile raft. Also in this study the effect of mat in... 

Over the last years, research about writable virtual machine introspection has been started. This approach has the benefits of readonly virtual machine introspection. Additionally, it has more applications, such as automated defense against malware programs, than the read-only approach. In the read-only VMI, data is gathered from virtual machine hardware states and then analysis in virtual machine monitor. In writable one, hypervisor can modify virtual machine kernel state. Consistency issue is an essential challenge for out-vm writable VMI. In the best of our knowledge, only one implementation try to solve this consistency issue. However it cannot resolve this issue completely. Other VMI... 

The purpose of this study is to investigate the efficiency of a flamelet method along with the LES1 approach in the modeling of a turbulent premixed flame behind the bluff-body. In this flame ,because of the high turbulence intensity and fuel dilution, there is a significant interaction between the turbulence and chemical kinetics. In this study, first, the cold flow is modeled using LES and RANS2 approaches. Then, using the Flame-Generated Manifold (FGM) model and a presumed PDF model, the turbulent reacting flow is simulated.Comparison of the results of the LES and RANS showed that the accuracy of the LES method in simulating the physics of turbulent flow is much higher than RANS, but its... 

In this study, an alkaline bath for co-deposition of Fe and Pd was selected. In order to investigate the mechanism of deposition, each of the metals iron and palladium electrodeposited from selected bath separately; and the kinetics of electrodeposition by electrochemical techniques such as linear voltammetry, cyclic voltammetry, chronoamperometry and chronopotentiometry were evaluated. Electrodeposition processes of Fe, Pd and their alloy were irreversible and under diffusion of reducing agents are controlled. Moreover the electroreduction of palladium from utilized bath was performed in two steps. At following, the mechanism of iron– palladium alloy electrocrystallization was discussed and... 

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... 

With development of power electronic science and with the existence of different power electronic converters in this field, the need for improving their operation and the fault detection methods of these converters, the need for simulation and test of them is strong felt. However, experimental constrain such as damage risks, reliability, costs, and so on obviate the need for making the converter and the need for testing it and its controller. Accordingly, we do the testing on a special platform for Real-Time simulation.Control/protection platform needs to be tested and its functionality should be verified prior to installation and commissioning.Testing in theReal-Time simulator environment... 

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... 

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... 

Online advertisements have captured a major part of websites and mobile applications nowadays. In this kind of advertisements, as soon as a user interacts with a website or a mobile application, we have to decide which ad to show in a fraction of a second. In online advertising systems, revenue increases only when a user clicks on an ad banner or when they interact with the ad. So in order to select the best (most profitable) ad banner, the probability of clicking on or interacting with the ad banner must be estimated and then the most profitable ad will be selected.So one of the most essential problems in online display advertising, is estimating the probability of the click on a certain... 

Nowadays, with the increasing number of polyethylene terephthalate wastes, the issue of its recycling has become very important. Among the problems of polyethylene terephthalate recycling are its loss of crystallinity and mechanical properties. Recycled polyethylene terephthalate does not have the properties of new polyethylene terephthalate and using its mixture with other materials is an effective way to remove its waste from nature and return it to the production cycle. The aim of this study is to produce a mixture of recycled polyethylene terephthalate with polycarbonate and glass fibers with mechanical properties such as good impact strength, which ultimately leads to the production of... 

In this thesis, we investigate the statistical performance of the array processing algorithms. Theoretical performance analysis leads to better methods that outperform the existing algorithms. Besides, analytical performance analysis, results in a more profound understanding of the nature of the considered problem. First of all, problem of covariance matrix estimation, in the non-Gaussian signal case will be investigated. We will focus on a nonparametric estimator which relies on the sign of the data to estimate the covariance matrix on an element-by-element basis. It was known that, sign estimator may give invalid covariance estimates in higher dimensions of the data. We prove this fact in... 

Transmit waveform plays a significant role in active sensing systems. High speed and off-the-shelf processors, digital arbitrary waveform generators, and solid state transmitters have paved the way for an increased capability to adapt the transmit signal and the receive fil-ters with respect to (w.r.t.) the illuminated environment. In this thesis, we have considered the waveform design problem for different scenarios, in two parts. Firstly, we have con-sidered the problem for the extended target model in single-input single-output (SISO) radars. There, we have assumed known target impulse response (TIR) with an unknown reflection factor and found the waveform corresponding to the optimal... 

Superconducting SQUID sensors are one of the most sensitive magnetic sensors that have been ever produced. Due to their high sensitivity, these sensors have many applications in different fields. Magnetic Imaging and far away targets detections are of these applications. In this project, a magnetic imaging system based on Superconducting SQUID sensors have been designed and implemented. In SQUID applications one of the most important problems is the cancelation of the unwanted fields including background low frequency and high frequency fields. In residential and urban areas the interference of Electricity network is considered as one of the major noise sources. While the high frequency... 

Anti-lock brakes car as one of the most fundamental and vehicle stability control system is considered. Solenoid valves, one-way valves, Accumulator, damper orifices and other components is a crucial role in the anti-lock system performance, so that the performance of the system and thus affect the dynamic performance of the vehicle. This is the most important part of the anti-lock brake System and These components are all new brake system.In this study a complete modeling of hydraulic control unit and obtain sufficient data to model the dynamic behavior of the hydraulic control unit to be seen. operators working in higher frequencies are weak and virtually reached saturation and efficient... 

Investigating the behavior of piled-raft foundations is a three-dimensional problem. The shape and location of the piles in the raft as well as the complex interaction of the soil-structure in these foundations should be analyzed in a three-dimensional fashion to indicate the real behavior of this type of foundations. The soil must also be analyzed in a nonlinear state to achieve the correct bearing capacity of these foundations. In this research, a nonlinear 3D analysis was performed using FLAC3D to investigate the behavior of piled-raft foundations, and the effect of various factors such as the length, arrangement and number of the piles, the loading level and the thickness of the raft, on... 

Ever increasing demand for higher data rate in wireless communication in the face of limited or underutilized spectral resources has motivated the introduction of cognitive radio for dynamic access to spectrum. In dynamic spectrum access a new type of users called secondary users measure the spectrum to see if it is occupied by licensed users (primary users or PU). When channel is empty secondary users can use it to transmit signal. This approach is called spectrum sensing. Hidden PU problem can severely defect detection ability of non-cooperativ spectrum sensing systems. Cooperative spectrum sensing (CSS) uses spatial diversity of spectrum sensors to tackle this problem. There are two kinds... 

The repair, maintenance and cleaning of marine equipment and ships, as well as the optimization of these operations to reduce their costs have always been of interest to researchers. After a few hours of floating in seawater, an inanimate organic layer forms on the surface of marine structures. After a few months, the thickness of this layer increases. This will increase the drag by 30 to 40 percent. Hull cleaning operation increases efficiency, saves time and money, prolongs equipment life and reduces maintenance and repair costs.In this project, the types of marine fouling according to environmental conditions were identified, next a type of fouling (Barnacle) was selected, which has more...