Sharif Digital Repository

In this research, an Index of Iran informal economy in response to the government interventions in credit, labor and product markets is stimated by EMIMIC model. To do this, first these interventions are measured using principal components analysis. In the model, the variables GDP and employment are used as indicators and taxation rates, government distortions in credit, labor and product markets, government expenditure, per capita income, unemployment and inflation as causes of the informal economy. We conclude these government interventions have affected Iran informal economy and their influence is more than indirect interventions influence such as taxation. The estimated index of Iran... 

Network coding generalizes conventional routing algorithms. It considers data streams as mathematical entities which can be processed in the nodes of networks. In this work, after a concise introduction to network coding, we focus on security issues in network coding form an information theoretic point of view. First we introduce fundamental concepts of network coding such as linear network coding and random network coding. Then, we accentuate the advantages and disadvantages of network coding. To investigate security in network coding, we introduce perfect security and weak security as two different levels of security against wire tapper. Then we scrutinize the prerequisite for reaching... 

In this study we investigate the performance of amplify-and-forward (AF) and beamforming schemes in wireless networks. In our study we consider a general cooperative network consisting one transmit-receive pair and an arbitrary number of relays in which each relay has a separate power constraint. A two-step master-slave protocol is deployed in which at the first stage, relays listen to the transmitter and at the second stage, relays forward the recently received signal coherently. Main contributions of this dissertation are providing the exact closed-form of bit error rate analysis in the case of general AF networks, providing an integral-form upper bound of error probability of network... 

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... 

One of the obvious features of financial markets is the spread of crisis across the markets, which is called contagion and realized in forms of return and volatility spillover. Using the daily data on the stock price from December 2006 through June 2010, this study aims to examine the presence and significance of these spillovers between Tehran and Dubai Stock Exchange, by a FIVECM technique. The FIVECM provides long-run equilibrium relationships between the returns in the markets and short-run dynamics of involved endogenous variables. Furthermore, it takes into account presence of fractionality in the time series’ integration. Our analytical framework, models the spillover effects in... 

Due to fast growth of wireless mobile networks, video transmission over wireless media has been widely studied. As wireless networks are error prone, there is a high possibility of loss in sent packets. Since time limitations in real-time video applications should be met, the delay- related to resending packets -is not acceptable and the error should to be concealed at receiver side. In this thesis, with respect to different concealment methods, two new methods for temporal error concealment are proposed. In the first method, an optimized set of motion vectors is formed using motion vectors in surrounding blocks of the lost macro block, and then this set is searched for the best motion... 

Streaming video over the Internet has become popular in recent years. There are also popular solutions for data delivery, but these approaches are very inflexible and unpleasant because no appropriate error recovery technique isprovided in the application level of these systems for multimedia contents. In the past few years numerous error resilience Peer-to-Peer (P2P) systems have been introduced but still there is no fully dynamic error recovery technique. In this thesisthe researcher proposed a frame-based hybrid FEC-ARQ (Forward Error Correction – Automatic Repeat request) error recovery in Variable Bit Rate (VBR) video streams based on the network situation in a way that before... 

Error concealment is one of the effective ways to alleviate the effect of packet loss in video communication over error-prone environments. In order to estimate lost macro-blocks, we have employed Bayesian estimation as an efficient and robust framework. Gaussian process regression has been used as the modeling approach through this framework. Considering luminance component as Gaussian process,a minimum mean squared error estimation of the lost macro-block is obtained. This estimator, as a function of the existing data, is only determined by the covariance matrix defined over them. Therefore,the main step in Gaussian process regression, is construction of the convenient covariance matrix... 

In this thesis, we intend to propose low cost SED-tolerant techniques for different compo­ nents of embedded processors core including data path components such as register file and ALU as well as control path components such as control unit. Since the reliability es­ timation is the essential step in design of a fault-tolerant system, we propose fast and accu­ rate analytical soft error rate (SER) estimation techniques in Section 4. The proposed techniques have the ability to measure: 1) the SER of a design; 2) the SER of each indi­ vidual gate and FF, and 3) the SER of a specific path in the design. Using such infor­ mation, designers can selectively protect the vulnerable parts... 

The aggressive device scaling and exponential increase in transistor counts on a chip have increasingly made the modern integrated circuits more susceptible to soft errors. Soft errors are caused by strikes from energetic particles such as neutrons and alpha particles. These errors are making a significant impact in the microelectronics industry. An essential step to design a highly reliable digital system with minimal performance and power penalty is Soft Error Rate (SER) estimation of system components.We propose a very fast and accurate analytical approach to estimate the overall SER and to identify the most vulnerable gates, flip-flops, and paths of a circuit. Our proposed approach fully... 

The wide range of embedded processors and their reliance on nano-scale technologyhave brought them serious concerns on reliability, power consumption, timeliness and cost. Therefore, theseconcernsmust be addressed at the design process withemploying minimum facilities.This thesis proposes a low-cost concurrent error detection method based on control flow checking suitable for embedded processors. Most of the previous control flow checking methods either do not consider the embedded processors concerns, or they are not applicable to processors with on-chip cache memories.The key idea behind the proposed control flow checking method is to embed specific hardware components in the IP core of an... 

Cognitive Radio (CR), as a new concept to efficiently utilize a licensed spectrum, and this has received intensive attension in recent years. By applying the cognitive technique, an unlicensed user (the secondary user (SU)) is allowed to transmit at the Primary User’s (PU) spectrum band under some conditions. Different approaches have been introduced to be utilized by the SU in order to be able to efficiently transmit at the PR’s spectrum without any sustainsial destructive effects on PR transmission and reception, which one of them is using multiple antenna in the cognitive transmitter. Hereby, CR is able to increase its throughput without substansial harmfull effect on PR’ transmission by... 

Nowadays, wireless communications for multimedia purposes is widely spreaded especially due to video communication demands. One of important considerations in this area is to receive video stream with less effect of errors related to transition channel as well as optimal utilization of bandwidth. The H.264 is exploited as the most efficient video compression standard and because of its predictive nature of encoder and decoder, it is very sensitive to error propagation, so error resilient technics should be applied along with the video compression to reduce the visual impacts of error occurrence and propagation. In this thesis existing methods of video error resilience, video quality measures... 

Complex networks serve as generic models for many social, technological and biological systems that have been shown to share a number of common structural properties such as power-law degree distribution and small-worldness. These networks determine interactions and influence the spread of diseases, behaviours and ideas. Epidemics and failures like new behaviours ideas and innovations can spread throughout a network and prevent it from doing its functionalities. In this work, we investigate error and attack tolerance of epidemic spreading in complex networks. The main content of this thesis is arranged in three sections as follows: Firstly, the effect of random and systematic failures is... 

Recently, cooperative communications have gained much interest due to its ability to mitigate fading in wireless networks through achieving spatial diversity while resolving the difficulties of installing multiple antennas on small communication terminals. There have been considerable research efforts on the performance analysis of cooperative diversity. This is while most of the current works assume that perfect knowledge of the channel information is available at the destination and/or relay terminals. However, in many practical scenarios, due to the errors caused by Doppler shift or noise on the pilot signals the perfect estimation of channel coefficients is not possible. In this thesis,... 

After years of disputes on one of the most important challenges in our national economy, finally in Dey 1388 (January 5, 2010) the “Targeted Subsidies Law” was passed by the Iranian parliament. Based on this law, all fiscal (explicit) and quasi-fiscal (implicit) subsidies for goods and services will be removed from the government’s general budget and redistributed among public with a different system. Implementation of the Targeted Subsidies Plan legislation as one of the important decisions in Iran’s economy has widely gotten the attention of economists, scientists and policymakers at industries, universities and other governmental sectors. Firms and other economic actors such as producers... 

Brain computer interfaces (BCI) are systems designed to understand the brain function from activation patterns and dynamics recorded from the brain activity and use this knowledge to give disabled people the ability to communicate with their surroundings. Features are extracted from recorded signals from the brain while occupied in a mental task and classified into categories related to the task given. These classifiers are then used for the estimation of user anticipation. Usually, the tasks defined are meant to evoke or induce a potential in the pattern of the brain. Awareness of error responses is one of the cognitive functions of the brain which occurs when a response is in conflict with... 

An analytical method is developed for description of the assembly process and dimensional error propagation in planar truss structures using two core concepts of “triangular unit cell” and “redundant member”.In order to clarify backbone of the developed method, its connections with other studies in the fields of tolerance analysis, robust design and structural optimization are discussed.Subsequently, triangular unit cell is defined as the basic element of internally determinate trusses and a suitable formulation is derived for calculating its dimensional error propagations characteristics.It is shown that having such a model for a single unit cell is sufficient for tolerance analysis of the... 

Sampling is the process of selecting and analyzing part of population and generalizing the results to estimate characteristics of the population. Time and cost considerations or the destructive nature of experiments are the main reasons why we study a sample instead of the whole population. In typical applications, sampling units are well-defined which means these units can be defined, selected and analyzed separately. This is the case in taking samples from a human population or products that consist of distinct units. If sampling units are not well-defined, as in the case of a bulk material (e.g., a pile of dust or other particulate materials, a tankful of liquid, the air or other gases)... 

Volatility is the most important components in numerous finance applications. So, the methods of volatility forecast with reasonable accuracy require a deep attention.In this thesis with considering several distributions for error term, GARCH forecasting performance is evaluated on the intra- day data of "Foolad" stock returns by two loss functions of "MAE" and "HMAE". This evaluation is done in three forecast horizons, 1 day, 5 days and 20 days. Finally, the result of this study is as follows. GARCH (1, 1) forecast model with skewed t- student error distribution has the minimum value in the both loss functions for 1 day and 5 day forecast horizons. Also GARCH (1, 1) forecast model with t-...