Sharif Digital Repository

Employing array of antennas in amny signal processing application has received considerable attention in recent years due to major advances in design and implementation of large dimentional antennas. In many applications we deal with such large dimentional antennas which challenge the traditional signal processing algorithms. Since most of traditional signal processing algorithms assume that the number of samples is much more than the number of array elements while it is not possible to collect so many samples due to hardware and time constraints.
In this thesis we exploit new results in random matrix theory to charachterize and describe the properties of Sample Covariance Matrices... 

During the last six decades, there were remarkable developments in the field of gas turbines. In the early 1950’s, the effciency of gas turbines was 20% and it is improved up to more than 40% for modern gas turbines. In addition, due to the implementation of the combined power cycles, the thermal effciency have been reached to 60%. According to the recent developments, further improvements in this field seem to be more costly and diffcult to obtain. Rotating detonation combustor (RDC) is a new generation of detonation combustors which has simpler design and several advantages compared to jet engine combustors, but it has its intrinsic problems which seem resolvable. Given that the RDC... 

Adaptive beamforming performance is very sensitive to any mismatch between actual and presumed steering vectors of desired signal. In addition to this sensitivity, presence of desired signal in training snapshots dramatically reduces the convergence rate, as compared to the case that signal-free training snapshots are available.
The present work is aimed at proposing a new adaptive beamformer that is robust against direction-of-arrival (DOA) mismatch and has high convergence rate. This method is based on desired signal elimination from training snapshots and sub-array beamforming technique. To this end, a Blocking matrix that converts primary data to desired signal free data is... 

One of the most important equipment in a power station is desuperheater which its operation has effect on power station performance and efficiency.It is necessary to identify and evaluate the most important factors that have effect on its performance. Using desuperheater cause that the temperature of exhausting superheat steam of boiler decreases to the desired quantity. If the temperature of superheat steam is very high, it will cause burning of superheater pipes that is very dangerous.Steam is used for two purpose of power generating and operational process. Unfortunately these applications have different requirement. In power generating for maximizing efficiency, turbine needs high... 

A Synthetic Aperture Radar (SAR) is a system which collects the received signal from a ground target area along linear motion of a flying vehicle carrying it, in order to provide a very high resolution 2D image of it. In Inverse SAR (ISAR), the radar is fixed on the ground and the data collection is performed along the linear motion of the aerial target. Using a second receiver antenna close to the main transceiver antenna of ISAR, it is possible to make a three-dimensional (3D) image of the target, or equivalently find the 3D coordinates of the target scattering points. Such system is called bistatic, monopulse or interferometric ISAR (InISAR). In the conventional model of ISAR, the flying... 

Numerical investigation of flow field and determination of velocity components in swirl flow are novel and important subjects in combustion chamber of swirl flow. The exact understanding of vortex phenomena and flow structures in vortex engine results in better design and control in terms of stability, geometry, cooling, and combustion efficiency. Although, numerical approaches are computationally complex, they are worthwhile and efficient. The aim of this work is to study the velocity field in a bidirectional swirl flow within the combustion chamber using numerical approaches. The investigation of flow field has been performed in the cold chamber. Four different models (RSM and LES) have... 

A significant large amount of modern SOCs is occupied by SRAMs. Nowadays more than 70% of the Microprocessor area is occupied by SRAMs. The fast growth of battery-operated portable applications has compelled the SRAM designers to consider subthreshold operation as a viable choice to reduce the power consumption. In most such applications, the speed of the SRAM is not the challenging parameter therefore the thrust toward low power design influence the design choices in various parts of the SRAM architecture. With technology scaling to the nanometer, Bitline leakage current and offset voltage deteriorate SRAM reading performance since SRAM cell current is close to the Bitline leakage current.... 

Considering the undeniable role of technology in modern era, we investigate both the concept of technology as well as its relation as a tool with human beings. Modern technologies have had both positive and negative impact on human individual and social lives. In particular, the labor problems, environmental problems, distortion of the classic human perception of the world, and many other problems provide a very disparate perspective compare with the notion of techno-utopianism. Therefore, many contemporary philosophers such as Andrew Feinberg have made serious criticisms of technology and its consequences. Feinberg states that there is a possibility in reforming the currently derailed role... 

The air distribution is the main factor of contaminant transportation in cleanrooms. The experimental method is the most reliable one for investigation of flow field, which the difficulties associated with it, has limited not only the examination of the flow field in cleanrooms, but also the improvement of their qualities. Most of the experimental researches in indoor air quality concern conventional rooms and do not take into account specific supply-exhaust diffuser configurations, which are used in cleanrooms. Using small-scale models can reduce the complexity and the cost of measurements. In this research, the 3D velocity field of a small-scale cleanroom is measured in three different... 

There are a wide variety of radar systems that one of them is MIMO Radars. After a spark in communication in 1998 that developed MIMO communication, recently there has been a great attention towards MIMO radar systems. MIMO radars divided into co-located and widely separated branch. In this thesis, the spatial diversity and multiplexing gain and the tradeoff between them in MIMO communication and MIMO radar systems investigated. Diversity and multiplexing gains in communication defined analytically, so diversity and multiplexing gain presented as detection probability improvement and throughput or capacity improvement respectively. Also tradeoff between these two gains investigated... 

After introducing “Prosopect Theory” by Kahneman and Tversky in 1979, it is mostly used as an alternative to expected utility theory in order to study human decision making under risky situatutions. Loss aversion has been considered as an important aspect of this theory. In this study, we review loss aversion and the effects of education and gender on it. Finally, we study the effect of repeating a gamble on its participants’ loss aversions. The results show that education and gender have direct effects on loss aversion and repeating a gamble can decrease loss aversion of participants.

 

Spam filtering is one of the large scale applications of machine learning. Much research has been carried out in the machine learning field with regards to spam filtering. Most of this work falls in the areas of batch learning or offline incremental learning. In batch learning, the learning process is carried out once on all the learning data. In applications such as spam filtering, in which the learning data is large in comparison to memory resources and data is generated in a stream, using incremental learning is required, in which the learning phase is repeated periodically. In each learning iteration of an offline incremental learning algorithm, a new set of data is learnt by the... 

The spherical ensemble is a well-studied determinantal process with a fixed number of points on the sphere. The points of this process correspond to the generalized eigenvalues of two appropriately chosen random matrices, mapped to the surface of the sphere by stereographic projection. This model can be considered as a spherical analogue for other random matrix models on the unit circle and complex plane such as the circular unitary ensemble or the Ginibre ensemble, and is one of the most natural constructions of a (statistically) rotation invariant point process with repelling property on the sphere. In this dissertation we study the spherical ensemble and its local repelling property by... 

This study investigates investment strategies in the cryptocurrency domain by adapting the robust framework of factor investing _traditionally applied in equity markets_ to the specific characteristics of crypto-assets. In this regard, 111 major cryptocurrencies were analyzed over the period from January 2021 to December 2024. To determine the number of relevant factors, the Principal Component Analysis (PCA) method was employed, which suggested a single-factor model for the tested asset portfolio. To evaluate the predictive power of factors such as market, size, value, momentum, trading volume, as well as a derivative-based benchmark factor, statistical techniques including the t-test and... 

Various application of polyethylene material in different industries caused to modern techniques for controlling and measuring specifications of micro-particle suspension. Many industries try to increase stability of suspensions in front of their phase separation.
Because of the consequences of suspension homogeneity, at first, we measured this property. Then, the stability was tested by three different methods. In the first method, the transmitted laser light was measured to assay the suspensions stability. In the second, number of sediments of particles was counted. Sedimentation velocity of particles was measured directly by using a horizontal microscope as the third method. The... 

Knock is an abnormal phenomena in combustion engines and one the main limiter elements in increasing engine efficiency. From years ago, recognition and elimination of this phenomenon had studied by investigators and various approaches to anticipation had presented. One of the newest methods is using of property variety in air and fuel mixture with using technologies like Variable Valve Timing (VVT) system.
The purpose of this work is development a simple model in basis physics of 3 zone, homogeneous, ignition combustion with a partial kinetics model that this model can predict the knock phenomenon onset with good precision for various qualities of mixture. This study survey effect of... 

The study of nonlinear systems estimation techniques is necessary due to radar measurement equations which commonly contain range and angle, nonlinearly related to motion state variables.Hence in this thesis we make a through study of various nonlinear estimation techniques and important dynamic modelsfor airborne maneuvering and ballistic targets. Then we represent a novel method based on nonlinear vector transformation which tries to improve common nonlinear estimation techniques.Two Algorithms, DBF and MBF, baesd on data fusion is proposed to fuse a model data and also various models abilities in a separate chapter.Finally several estimator filters are simulated and analysed for two... 

Passive radars using illuminators of opportunity have attracted much attention in recent years. The worldwide inter-operability for microwave access (WiMAX) signal is a new illumination source for passive radar. This paper presents a study to understand and to demonstrate the feasibility of using WiMAX signals for passive radar. The study includes WiMAX signal analysis, the design and implementation of a WiMAX-based passive radar demonstrator, the associated radar signal processing scheme, and some approaches to yield an effective removal of the undesired peaks in WiMAX ACF  

Designers consider formation of slug flow in pressurized pipes because of hazardous effects of this flow pattern. Therefore, researchers, using different methods, attempt to study formation of slug flow and its effects. For numerical simulation of this phenomenon, In spite of existence of commercial 2D or 3D two-phase models, numerical models used for the slug flow modeling are 1D. In this thesis, a 2D model has been developed to simulate the initiation and formation of slug flow and estimation of the effects in pressurized pipes. Most important assumptions used in this model are existence of turbulence, surface tension and air compressibility. Isothermal condition has been supposed for... 

One of the key issues in the operations of on orbit servicing to unmanned satellites is to provide a safe and reliable docking process. In this thesis, the dynamic behavior of a flexible probe in the central docking mechanism of unmanned satellites is investigated. For this purpose, first a dynamic analysis software has been applied to build a three dimensional model with the assumption of flexible clamped beam as a shock absorber, finally, the impact phenomone is simulated. therefore, in addition to solving a three-dimensional problem and studying the impact phenomenon between chaser and target satellite, it is possible to consider the parameters such as the type of connection between the...