Sharif Digital Repository

A two-dimensional, two-phase, nonisothermal model was developed in this work to investigate the water transport characteristic and water distribution in a direct methanol fuel cell (DMFC). Emphasis is placed on exploring the water distribution in different layers of DMF. The water and methanol crossover through the membrane were considered with the effect of diffusion, electro-osmotic drag, and convection. Governing equations including the prton and electron transport, continuity, momentum, species transport for methanol, water, and gases species, and the auxiliary equations are coupled to determine the output parameters. These parameters are the concentration distribution of the species,... 

In the proton exchange membrane fuel cells (PEM, the produced water would be divided into two phases of vapor and liquid. distribution of both liquid and vapor phases in different cell layers affects the performance, the efficiency and the life of a fuel cell significantly. Moreover, Nano pores of the cathode catalyst layer are involved with some phenomena such as electrochemical reaction kinetics, heat and mass transfer and interface phase change. One of the most important problems in the performance of fuel cells is distribution of liquid water in the porous areas. Water flooding in fuel cells causes to delay in oxygen transport to active sites in the catalyst layer because the pores of... 

Fuel Cell with Polymer membrane uses a reaction with Hydrogen and Oxygen as reactants to produce electricity. As the product of this reaction is water, this fuel cell produce clean energy. But if the produced water accumulates it can cause problems for fuel cell which can lead to complete failed of fuel cell. On the other hand water shortage in PEM fuel cell also can cause problems. So we need to have continues water management inside of PEM fuel cell. For this sake having knowledge about water inside of PEM fuel cell and specially the Gas Diffusion Layer which is the layer with responsibly to help the fuel cell to manage the water, is necessary. One of the ways for gaining that knowledge... 

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... 

Power distribution systems are experiencing restructuring owning to the increasing trend of integrating renewable energy sources as well as privatization in the network. In this regard, the dependence of power generation by renewable energy sources on meteorological characteristics would challenge the conventional procedures of operating the system. Respectively, while the expansion of renewable energy sources would facilitate supplying the demand loads locally; the issues associated with the uncertainty and variability of power generation by these units should be addressed in future operational schemes of distribution systems. This condition has resulted in the development of the... 

The usage of plugin hybrid electric vehicles has environmental benefits. However, the penetration of these components raises important concerns for grid planning. Thus, it is necessary to model the load change due to their charge to investigate the impact of these vehicles on distribution networks. For this reason, it is necessary to determine the specifications of these vehicles, such as battery charge and energy consumption on daily trips. In addition, the study of some behavioral patterns of these vehicles and some experts are necessary to complete the model.In this thesis, an active distribution network is planned using dynamic programming formulation. In this model, some buses are added... 

Issues related to the environmental pollution, greenhouse gas emissions, as well as the limited supply of fossil fuels and their rising prices have led to the deployment of distributed energy technologies in power systems. With the increasing penetration of distributed energy sources in distribution systems, smart grids, and in particular, microgrids have emerged as a suitable and widely accepted solution for controlling and utilizing these resources. Microgrids can enhance energy efficiency in a sustainable power grid as well as the reliability of the distribution system, through supporting high penetration of renewable energy sources and providing island performance.In view of growing... 

Electric energy distribution system (DS) reliability has a great impact on the quality of service provided to customers. On the other hand, improving the reliability performance in a DS is an expensive task. So, determining an efficient and economical target for the reliability of DSs is imperative. This thesis aims to determine efficient and economical reliability targets for reliability indices of DS based on data envelopment analysis (DEA) considering distribution feeders as the decision-making units (DMUs). For this sake, using the fuzzy c-mean (FCM) method, feeders are clustered and the membership degrees are determined so that the target associated with each feeder gets greater impact... 

In recent years, due to the increase in distributed generation, the use of renewable energy sources and the emergence of restructuring and energy markets, traditional distribution networks transform to complex and active distribution networks. These issues, along with requirements such as increasing power quality and reliability, have increased the need to provide active distribution management systems and the use of effective network monitoring, control and protection systems. Due to the complexity and expanse of distribution networks, as well as the development of the use of metering elements and remotely controllable elements, one of the important issues in these systems is the... 

The development of smart meters enables gathering and analysis of a large amount of data about electrical energy consumption in electric power distribution systems. This data and the obtained behavioral patterns of customers have a wide variety of applications. To name a few, classification of customers based on their consumption patterns, damaged smart meter identification, non-technical loss identification and measuring participation rate of customers in demand response programs are among the applications. So far, many studies have been done for consumption pattern identification. However, abnormality detection in electric energy consumption has captured growing attention due to the... 

Nowadays, power systems are facing significant changes in traditional network operation and planning approaches with the introduction of distributed generation energy sources and increasing concerns about environmental issues. On the other hand, the Distribution Management System (DMS) in the current situation with low levels of observability and automation, controls and monitors the distribution network, which will not meet the challenges of the Active Distribution Network (ADN). For this purpose, in the first part of this dissertation, considering that the supply of network loads is important from the operator and distribution network management point of view and the voltage range and... 

With the increase of renewable energy generation in power systems, the flexibility of power systems has been challenged and the high potential of resources in active distribution systems for providing flexibility has been noticed by system operators and planners to help system flexibility. In this regard, these resources can participate in the Flexible Ramp Product market which is a new product that is defined for this purpose. In this work, the management of these resources has been modeled in an active distribution system for participating in this market by considering the network constraints, the uncertainty of renewable generation and forecasted prices of products in DA and RT markets,... 

Nowadays, with the expansion of restructuring and privatization in power systems, energy markets are growing rapidly, within distribution networks. In order for such markets to be implemented in practice, the technical constraints and issues of the distribution network, which are mainly the power loss and congestion of lines and also the bus voltage violations, must also be considered within the framework provided for them. Hence, this dissertation presents some new structures for Peer-to-peer (P2P) energy markets, in which the technical issues of the distribution network could be considered. Moreover, a model predictive control method is used in the proposed structures of this dissertation... 

In the problem of Distributed Multi¬User Secret Sharing (DMUSS), in which K users are connected through some error¬free links to N distinct storage nodes with the same size M information unit, the users desire to retrieve their corresponding secret message through an arbitrary set of accessible storage nodes. A trusted master node, which knows all of the secret messages transmits correctly and privately, the messages with a means of coding. The capacity of Distributed Multi¬User Secret Sharing is the supremum of all achievable schemes satisfying privacy and correctness conditions. In this thesis we have investigated two notions of privacy namely, individual and joint privacy. Individual... 

Electricity distribution systems are dynamically expanded in anticipation of new demands. Cost and reliability are the most important factors in finding the optimal plans for network expansion. Recently, implementation of incentive reliability regulations has accentuated the role of reliability considerations in distribution systems studies. This is because such incentive schemes create a direct link between distribution companies' revenues and their service reliability. Thus, these schemes have changed the role of reliability from a technical constraint to an economic factor. In this occasion, distribution companies require new techniques to incorporate the effects of incentive reliability... 

Nowadays, concerns about the reduction of fossil fuels and environmental issues, have made renewable resources more important. Among these resources, photovoltaic (PV) systems are more popular than others, due to their environmental compatibility and unlimited availability of sunlight. Increasing the penetration level of PV systems in electricity networks presents various technical and control challenges such as voltage and frequency variations; and protection and harmonics issues. In this thesis, voltage rise problem due to reverse power flow in distribution feeders is discussed. This is one of the main obstacles to the expansion of these resources in distribution networks.Various solutions... 

Proliferation of distributed energy resources and the developing of smart grid concepts are of a great importance. This, however, influences the future of power systems and necessitates more studies in order to cope with the changes. In this regard, uncontrollability issues are arised by introducing the renewable energy resources in the power systems. To address this issue, energy storage systems are used to mitigate negative consequences of using renewable energy resources. Accordingly, in this thesis, a new framework for determining the capacity and location of the energy storage systems is proposed. In addition, reconfiguration of distribution network is also concerned in order to... 

Sensor Networks are set of devices which are distributed throughout an environment and are connected to each other, usually wirelessly, to collect environmental information including temperature, aire pressure, moist, pollution and physiological functions of the human body. Each device consists of a microprocessor, converter and power supply, transmitter and a receiver. In this study we intend to investigate such setup and the measured signals assuming they are sparse. A sparse signal is a discrete time signal most of indices of which are equal to zero. With this assumption at hand, we will be able to reduce the sampling rate and take advantage of sparse signal processing techniques. This... 

In this thesis, we argue that in many basic algorithms for machine learning, including support vector machine (SVM) for classification, principal component analysis (PCA) for dimensionality reduction, and regression for dependency estimation, we need the inner products of the data samples, rather than the data samples themselves. Motivated by the above observation, we introduce the problem of private inner product retrieval for distributed machine learning, where we have a system including a database of some files, duplicated across some non-colluding servers. A user intends to retrieve a subset of specific size of the inner products of the data files with minimum communication load, without... 

Distribution power systems are undergoing a fundamental transition with the introduction of microgrids (MGs) and proliferation of renewable energy sources inspired mainly by privacy and environmental concerns. In this regard, energy management methods employed by utilities should take into account the intermittent nature of RESs power production while coping with the independent operation of MGs. Transactive energy (TE) is an emerging concept which utilizes economic-based mechanisms to facilitate the dynamic and decentralized management of active agents of the system. However, the energy transactions between transactive agents could have adverse impacts on the technical aspect of the system...