Sharif Digital Repository

In this thesis, we introduce limited-sharing multi-party computation; in which there is a network of workers (processors) and a set of sources, each having access to a massive matrix as a private input. These sources aim to offload the task of computing a polynomial function of the matrices to the workers, while preserving the privacy of data. We also assume that the load of the link between each source and each worker is upper bounded by a fraction of each input. The objective is to minimize the number of workers needed to perform the computation, such that even if an arbitrary subset of t 1 workers, for some t 2 N, collude, they cannot gain any information about the input matrices. This... 

In the present study, the buckling of generally laminated truncated conical shells having thickness variation expressed by a linear function, subjected to axial compression with simply or clamped supports has been considered. To begin with, the fundamental relations for a conical shell with variable thickness have been derived applying thin-walled shallow shell theory of Donnell-type and theorem of minimum potential energy; non-linear terms of Donnell equations by the help of adjacent-equilibrium criterion are linearized. Governing equations are solved using power series method and are applicable for all combinations of classical boundary conditions. The results are validated with Galerkin... 

One of usual criterion which detrimines how much two polynomials are close to each other is smallness of the norm of vector that is formed from subtraction of their corresponding coefficients. Using this criterion, in this dissertation we become involved in investigation of two similar problems. First one is determination of the closest non-Hurwitz polynomial to a Hurwitz one. During this activity, the robustness margin of Hurwitz polynomial whose coefficients are subject to uncertainty is determined. The second problem is determination of the closest Hurwitz polynomial to another polynomial which is not Hurwitz. Unlike to the first problem, this problem is extremely hard. The solution of... 

Observed performance of nonstructural components and building contents during recent earthquakes demonstrated their significance to control economic seismic losses and downtime. Since a large portion of nonstructural equipments installed in buildings are acceleration sensitive devices, reasonable estimation of the acceleration they undergo during an earthquake has an important role in rational design of secondary systems and subsequently in reducing the earthquake damages. Although a comprehensive amount of research studies have been conducted to date to approximate the floor acceleration demands of a multistory building subjected to the earthquake ground motion, in most work, the soil... 

Nowadays with development of applications that stream video over internet, compression efficiency of video has become very important. On the other hand, Watermarking and video coding are two conflicting technologies. One adds redundancy and other tries to remove it. We have proposed a H.264 watermarking method that does not increases the bit rate. Unlike most of watermarking schemes, this methods embeds the watermark in inter coded frames. Abundance of these frames in video is impressively more than intra frames, so a lot of capacityis eventuated. But these frames are highly compressed using motion compensation, and are very sparse. To avoid from bit rate increment, this method only embeds... 

Islanding detection methods are divided into three main groups as remote, active and passive. Although passive schemes have larger Non Detection Zones (NDZ) relative to other schemes, they are more used in utilities due to their low costs and less PQ problems than in other schemes. Passive Schemes are based on the measurements of passive system parameters. These parameters are measured at the point of common coupling (PCC). A new approach in passive techniques is the use of data-mining to classify the system parameters which affect the islanding detection. Therefore, by finding an efficient and robust data-mining algorithm, the inherent problem of passive schemes, which is their relatively... 

The wide-area damping controller (WADC) has been proposed to enhance the damping of inter-area oscillations. The most challenging deficiencies to make this controller practical are the power system operating condition changes and the inherent time delay of remote signals. They can deteriorate the controller performance and the whole system stability if not properly accounted for in the design procedure. This thesis presents an adaptive delay compensator (ADC) on the basis of the latest development in the wide-area measurement system (WAMS) to cater to varying latencies. The proposed compensator can effectively reciprocate the phase deviation resulting from varying delays to improve the... 

In this work, we consider the problem of secure multi-party computation (MPC). This system includes Γ sources, N processing nodes or workers and one data collector or master. Each node has a constraint on its storage,such that it can store 1/m fraction of size of each input matrices from each node. In addition, up to t of these workers are adversary and may collude to gain information about the private inputs or can do malicious actions to make the final result incorrect. The objective is to calculate an arbitrary polynomial of some massive private matrices as inputs while the privacy is preserved. The main concern in these kind of systems is to reduce the minimum number of workers needed... 

After the heart-rending earthquake in Bam and its severe losses, the engineering community forced to pay special attention to the seismic vulnerability of traditional structures. Therefore, with the aim of reducing of such devastations to minimum, a multi-phase research project was defined at Sharif University of Technology to study the vulnerability and retrofitting of these structures which the current study is the eighth phase of that series research. In the third and fourth phases of this project, a typical adobe building with dome roof was chosen for study making use of shaking table facilities. The tests included both un-retrofitted and retrofitted states and considerable seismic... 

Adobe buildings on one hand are very heavy and hence generate great amounts of inertia loads during earthquakes. Their response is also amplified in the high-frequency earthquake waves due to great stiffness. On the other hand, these structures proved vulnerable during past earthquakes because of low strength and ductility. Considering the fact that there are too many structures of this kind throughout the country and a majority of their residents are the poor, seismic retrofitting of these building should be taken as a priority rather than reconstruction. It is obvious that the proposed retrofitting technique should be simple, feasible and economical, as well. Among possible retrofitting... 

The present study deals with the development of development of fragility curves for confined masonry buildings with the emphasis on masonry school buildings by means of numerical simulation. In doing so and based on the results of several previously-performed tests in Iran, simple analytical models for confined masonry walls capable of predicting various failure modes and also simulating different behavioral characteristics of these walls in the form of cyclic force-displacement curves were presented. In order to endure the ability of the proposed analytical models in simulation of seismic response of existing confined masonry buildings, a static-cyclic in-situ test on a real typical... 

In communications systems, coding is used to combat channel errors. The redundancy introduced by coding enables the detection and/or correction of errors occurring in the channel. In addition to communications systems, coding is also beneficial in various other systems such as distributed storage systems and blockchain systems to cope with node failures, data erasures, and adversarial behaviors attempting to modify information. In existing applications of coding, it is generally assumed that the encoding operation is performed correctly and without errors, and errors are applied to the encoded data. In recent years, applications have emerged where the assumption of error-free encoding is not... 

In response to pressing energy crises and environmental concerns, enhancing the performance of existing energy conversion systems, such as gas turbines, and tapping into renewable resources have become critical imperatives. Escalating ambient temperatures poses a notable challenge, hampering the efficiency of gas turbines. This study rigorously explores the feasibility of Earth to Air Heat Exchangers (EAHEs) as a pragmatic solution to cool gas turbine inlet air. This study has two main parts. In the first part, this study puts forward a novel hybrid analytical-numerical model for predicting the performance of HGHEs and in the second part, an exhaustive techno-economic analysis is employed to... 

Medical images contain human body pictures and are widely used for diag-nosis and surgical purposes. Compression is needed for medical images for some applications such as profiling a patient's data or transmission systems. Due to the importance of the information of medical images, lossless or visually lossless compression is preferred. Lossless compression mainly consists of transformation and encoding steps. On the other hand, hardware implementation of lossless compression algorithm accelerates real time tasks such as online diagnosis and telemedicine. Lossless JPEG, JPEG-LS and lossless version of JPEG2000 are few well known methods for lossless compression. In this thesis, we introduce... 

Pitch or fundamental frequency is one of the components of speech production. Pitch detection is the process of determining the period of the vocal cords closure or in other words, the time duration of one glottal closing, opening and returning phase. There are different algorithms for pitch detection purposes, each of which has some advantages and disadvantages. Pitch detection algorithms can be classified into event pitch detection and non-event pitch detection. Dyadic wavelets transform is an example of event pitch detection. Modified higher order moment, which is based on the Autocorrelation function, is non-event pitch detection. Dyadic wavelets transform is a fast and simple pitch... 

Structural Health Monitoring (SHM) means to give a diagnosis of the “state” of the subjects. Small leaks along the entire lengths of oil pipelines are detected and located by monitoring.Nowadays health monitoring of pipeline in water, gas, oil and chemical industry has been the focus of researchers. This is due to the fact that leak accidents may cause great economic problems to human resources as well as extreme environmental pollution. This project focuses on a visual and photographic observation system as leakage detection to monitor long range pipelines. In this system, several cameras with overlapping views are located along the entire lengths of pipelines. We are using digital cameras... 

One of the ultimate goals in robotics is to design autonomous robots. Among other things, this means a robot has to be able to plan its own motion. To be able to plan a motion, a robot must have some knowledge about the environment in which it is moving. Some of this information can be provided by a floor plan. For other information the robot will have to rely on its sensors. In this thesis, we consider that the environment is unknown for the robot. So, the robot uses weak sensor to planning its motion. The sensor can distinguish between colors. The robot can follow the colors. Therefore, we need to specify the umber of colors in which the robot can navigate by them. We propose an efficient... 

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)...