Sharif Digital Repository

The Reliability of substation structures with consideration of earthquake uncertainties is one of the most important subjects in structural analysis in recent years. In this project we first introduce IEEE-693-2005, which is the most effective and comprehensive seismic design code for electronic substations. Also in second chapter the rudimentary aspects of Reliability Theory and methods for evaluating the reliability of substation structures is introduced. Then with modeling the most common and most important electronic substation devices in Iran, with consideration of all seismic parameters and their uncertainties, the reliability of these structures evaluated. In this project for... 

There are several applications of wireless sensor networks wherein the data collected by the sensors in the network are critical and hence have to be reliably transported to the sink, example of such applications are fire detection in a forest or controlling vibration on body of dam. Reliable communication in wireless sensor networks is hard to achieve efficiently using methods in conventional systems like Internet. End-to-end retransmission is inefficient, or in some cases impossible. It is well-known that Reed-Solomon codes may be used to provide error correction for multiple failures in RAID-like systems. To the coding theorists, this technique is a straight forward extension to a basic... 

Considerable attention has been given in recent years to renewable energy sources due to concerns about dwindling fuel reserves and the potential impact of conventional energy systems on the environment. Wind power is one form of renewable energy resources and also considered as Dispersed Generation (DG). Widespread utilization of wind power imposes many effects on planning and operation of power system. In other side, reliability evaluation and enhancement is an important factor in modern power system planning and operation. So, reliability assessment of wind turbines is of great importance and will receive more attention in the future according to increase of WT utilization. The... 

Adiabatic logic families are a group of logic circuits which operate based on adiabatic principles to tremendously reduce power consumption. These families have basic difference with common logic families in transistor level structure and there signals are not quadrangular but trapezoidal. Also, in these systems the source lines and clock pulse are the same. Research on Adiabatic families needs theoretical information in reversible computing. So we will start this project with explaining fundamental information in this field. After that some of these logic families are introduced and three important and widely used of them (SCRL-RERL-2LAL) are chosen to simulate. In each of these families... 

Growth in the number of transistors on a single die has made Network-on-Chips more vulnerable to transient faults such as Crosstalks, SEUs and MBUs. The aim of this thesis is to evaluate the effects of virtual channel structures on the performance and the power consumptions of NoCs in the presence of transient faults. Evaluations have been carried out by different switch architectures and experimental conditions, i.e., different traffic and fault injection rates. In this regard, we have measured the power and latency of the switch both in different buffer allocation mechanisms and different switching methods. The evaluated switching methods in this work vary from Virtual Cut through (VCT) to... 

Knowing the shape and type of the breakdown of a system or the system components, for a maintenance manager or maintenance engineer is significantly important. It is also important that the existing information concerning the system performance predict and prevent a sudden failure to be probably taken place. Maintenance has gained in importance as a support function for ensuring equipment availability, quality products, on-time deliveries, and plant safety. Cost effectiveness and accuracy are two basic criteria for good maintenance. Many studies in the area of equipment maintenance, replacement, and reliability require that the failure characteristic of a component to be estimated from... 

Natural disasters claim major losses in human lives and belongings, as well as national infrastructures. Taking major earthquake as an example, the study has considered two sides of the problem, both before and after the incident. The former side is formulated as a multipartite optimization problem, in which each party’s activities are directed toward the long-term solution of the original problem. A heuristic method to solve the multipartite problem, and solve three example problems to show the applicability of the method was proposed. The solutions of example problems show that a directed problem solution reaches a better solution (in terms of the objective function value) than the... 

The development of communication infrastructure in power systems has provided the grid with the availability of accurate information and has increased the reliability of the grid and its responsibility to disturbances. However, there have been some concerns about the negative impacts of the reliance on the information infrastructure. Inadequacies in the control and communication systems have been reported to be the contributing factors to situations that led to major blackouts. The functionality and reliability of the power grid is undoubtedly influenced by its communication infrastructure. In this thesis we are trying to model and analyze the failures that may occur in a power system and... 

Smart grid brings miscellaneous concepts and advantages; increasing power quality, decreasing outages, motivating the consumers to participate in power system plans, and accommodating distributed generations (DG) are the most important purposes of smart grid implementation. Appearance of modern technologies makes operators devise better operation function. The effect of these technologies on the power system should be probed by sufficient criterions. In addition, preventing undesirable consequences of new technologies operation in the grid is the requirement of having smarter grid. In this thesis, based on the smart home concept two issues are discussed. In the first issue, a new algorithm... 

Nowadays power electronic devices have a wide usage in the industries for power conditioning. As a point of view, reliability is one of the most important figure of merits that should be considered to have long life time and also have more probability to do exactly the proposed mission. One of the widely used converter topologies is DC-DC step down converter which is used in different applications such as battery charger and voltage regulator. In this project, a step down DC-DC converter with Buck topology is designed with reliability consideration. Failure rate of power components are predicted based on MIL-HDBK-217. In addition, failure rate of auxiliary components of power devices are... 

Deterministic and Predictable behaviors are two important constraints in real-time embedded systems. Using cache memories alongside of CPUs may lead to nondeterministic and unpredictable behaviors in embedded systems. To avoid these behaviors, embedded system designers use Scratchpad Memories (SPMs). In addition, using embedded systems in safty-critical applications need to include reliability and fault tolerance. The first challenge to using SPM is the management of its contents,called SPM Mapping. SPM Mappingconsists of three important parts:1) Determining the most frequent parts of programs, 2) Efficient assignment of SPM area to those parts, and 3) Controlling the transitions of those... 

The present study aimed to investigate the effects of old and young oxide films on the mechanical properties and reliability of Cast Al A356.2 alloy. The results indicate that the presence of oxides within the microstructure of the alloy decreased the tensile properties of the alloy and increased their scattering. Beside this, the presence of the oxides decreased the reliability of the alloy. The results showed that the presence of double oxide films (especially old oxides) decreased the Weibull modulus of tensile properties and resulted in bi-Weibull distribution in tensile properties of the alloy. The results also indicate that using of a clean melt (with high quality), is vital for... 

Reliability analysis in engineering systems is one of important parts in design stage. Stress-Strength method is a method for reliability analysis in engineering systems. To obtain reliability, stress and strength distribution functions should be known, but these functions depend on design parameters and mostly these parameters are unknown. Usually obtaining exact stress and strength distributions is difficult and there is some uncertainty in distribution functions and their parameters. Also, weakness and uncertainty in data makes it difficult to calculate exact stress and strength distributions. In the case, when data is weak, results in point estimation methods (for example Maximum... 

Power Amplifiers are key components in new modern communication systems such as space and airborne applications, point to point networks and phase array modules. There are miscellaneous challenges in designing power amplifiers based on application and type of the system; high power, gain, bandwidth, linearity, efficiency, reliability, cost and size. Compromising among existence trade-offs is the state of the art for designing PAs. Meanwhile, technology improvements pay the way toward developing appropriate process in the realm of cost, cut-off frequency, voltage breakdown, thermal and reliance features. Throughout this thesis, challenges in designing high power amplifiers in the pHEMT GaAs... 

Nowadays, using of microwave integrated circuits in military and industry applications has been became popular, especially with the advent of monolithic microwave integrated circuits which provide possibility of fabrication of amplifiers in large volume with high precision and appropriate cost. Power amplifiers as the last block of transmitters, are such circuits that are too attractive in this area. Since high power amplifiers consume a lot of power in transistors, large amount of heat will be in the surface of chip. Loss of some of consumed power in amplifiers results increasing transistor’s channel and chip surface temperature. Increase in channel temperature results degradation in... 

Today, with the development of power electronics and the emergence of various multilevel converters, possibility of operation at the voltage and powers higher than the rated value of components is provided. The reliability of these converters due to their high power is important. In this project, design of multilevel inverter with cascaded H-bridge structure have been studied for a medium voltage and high power 3.3 KV, 1MVA application, due to its advantages over other structures. This converter is composed of several cascaded low voltage full-bridge cells. Therefore, the converter is composed of many semiconductor elements that the reliability of them depends on the physical stresses such... 

Today, global on-chip communications become a critical power bottle-neck in high-performance many-core architectures. The importance of power dissipation in NoCs along with power reduction capability of on-chip optical interconnects offers optical network-onchip (ONoC) as a novel technology solution which can introduce on-chip interconnection architecture with high transmission capacity and low power consumption. However, the basic elements that are used in ONoCs are very temperature-sensitive. This may lead to changes in their physical characteristics which will cause incorrectness in network’s functionality. In this thesis, we propose an approach that even the elements change physically... 

Maintenance management of power system components has been always one of the main challenges among the power system operation concerns. Experiencing the fast developments in power industries, and the power networks rapid expansions (as a consequence of power system energy consumpsion growth) while utilities have limitations on their annual investment budgets and the operational costs. Therefore, a more cost-effective maintenance plan is searched for. Various types of maintenance have been nowadays implemented in power systems, all over the world. Among them, reliability-centered maintenance and condition-based maintenance (CBM) can be addressed. Circuit breakers (CBs) from long ago are... 

Memories are one of the main component in the embedded systems, and owing to their vulnerability to error, this part of system must be fault tolerant. Single error correction (SEC) codes are one of the most commonly used methods against sot errors. However, on the other hands as the technology scales, multiple bit upsets (MBUs) are becoming more likely to occur in the memories and the SEC codes have lost their effectiveness in fault coverage. Therefore a greater attention is devoted to the codes with the higher fault coverage such as single error correction/double error detection (SEC/DED) codes. These codes increase the delay, area and power consumption overhead. These parameters are the... 

Application of special technologies is necessary for design and implementation of smart distribution systems. These technologies offer different facilities for users of distribution systems. One of the important goals of smart distribution systems is the improvement of reliability of local electricity services. This process requires information and data exchange between the smart devices and control center which applicable through communication infrastructure. If the communication infrastructure specified for automatic distribution faces to some problems, it is not possible to control the error because of absence of effective connection between the smart devices of network and control...