Sharif Digital Repository

In order to increase the life-cycle of membrane filtration systems, energy efficient membranes are being developed in membrane bioreactor systems. Technology has been introduced which allows the power required to aerate the membrane for cleaning to be reduced whilst still maintaining a high flux level. Mechanical cleaning processes have also been adopted using granulates as an alternative to conventional forms of cleaning; this reduces energy consumption and also reduces the area required for filtration tanks.Membrane properties have also been enhanced to reduce fouling tendencies by modifying surface properties. This can be noted in the biotechnology industry where membrane surfaces have... 

To understand the impact of predation by different types of predators on the vole population dynamics,we formulate a three differential equation model describing the population dynamics of voles, the “specialist predator”and the “generalist predator.” First we perform a local stability study of the different steady states of the basic model and deduce that the predation rates of the “specialist” as well as the “generalist” predator are the main parameters controlling the existence/extinction criteria of the concerned populations. Next we analyze the model from a thermodynamic perspective and study the thermodynamic stability of the different equilibria. The analysis revealsthat when the... 

In this study biological denitrification method by moving bed biofilm reactor is investigated. The main advantage of MBBR reactor is due to their capacity for high removal rates and low operational problems such as clogging. Two MBBRs in series with 3 liter volume each, were designed in experimental set up and used in this research. Nitrification reactor worked under aerobic conditions and denitrification reactor operated under anaerobic conditions. Methanol was used as carbon source in the reactors throughout the study. Fifty percent of each reactor volume was occupied with KMT1 packing. To finding the optimum nitrate loading rate, the concentration of ammonium and nitrate were changed from... 

Bridges are among the crucial elements of transportation networks, and play an important role in facilitating emergency relief efforts following earthquakes. For this reason, it is emparative to monitor their damages to ensure about their performace in earthquakes. The structure of a bridge is divided into two parts, namely the superstructure and substructure. Due to the relatively high rigidity and strength of superstructures, most of structural damage is usually concentrated in substructures, which may ultimately affect the overall stability of the bridge. Therefore, assessing the level of damage in the substructure is of utmost concern. This research attempts to evaluate the damage in the... 

The variety of 2D materials and their wide range of properties, as well as numerous methods to manipulate them, have made this class of materials among prominent candidates for the future of the energy industry. Among the means available to tailor nanomaterials performance for such applications, introducing dopants and the creation of heteroatom-doped structures are of great interest. In this study, mixtures of urea, boric acid, and graphene oxide, as cheap and available precursors, were used to synthesize C-doped h-BN nanosheets. After the implementation of TGA/DSC to select a suitable calcination temperature of 950 C°, the samples were successfully synthesized with relatively precise... 

Increasing demand in power systems necessitates the Generation Expansion Planning (GEP) which is to determine the type, size, and location of new generating units in a planning horizon. The final solution of GEP is based on the minimum cost and/or optimum reliability taking into account various constraints such as capacity of units and lines, operating constraints, and budget restrictions. This paper presents a model based on scenarios for generation expansion planning and units retirement decision. The proposed model could be used by vertically integrated utilities as well as the ISOs in electricity markets to obtain generation expansion schemes. In this approach, uncertainty of units are... 

The current restructuring trend in power industry emplaces the owners and managers under a great pressure to not only reduce the associated investment costs, but also reasonably cut the operation and maintenance expenses as much as possible, while keeping both the power quality and reliability requirements met. Reliability-Centered Maintenance (RCM) has been proved to be in response to this dilemma in power systems since it has been yet successfully applied in various engineering contexts worldwide. This process is more challenging when it comes to the power transmission systems because of its bulkiness and complex structure. On the other hand, market involvement and its intricate behavior... 

Current trend of energy consumption and aging infrastructure of electricity grids mandates high amounts of investment in transmission and distribution networks. On the other hand, with increased awareness about environmental issues, share of renewable energy resources in power generation portfolio has risen in recent years. Microgrids, as one of the most promising solutions to tackle these issues, are able to accommodate high penetration levels of renewable energy sources and distributed generation in distribution systems. However, microgrids sizes are limited due to some operational considerations and as a result, efficient management of distribution systems with high penetration of... 

The main concern of power system planners and operators is to serve electric energy services economically and in an acceptable reliability level. Nowadays, in developing integrated large-scale power networks, reliability evaluation becomes a very tough and time-consuming process. The complexity of this assessment is mainly because of the large number of components, their possible operating states, different faults that can happen, and environmental and other affecting parameters. In power systems, in order to address the complexity, reliability evaluation can be conducted in three different levels. The most complicated study among these three levels is HLII that is so-called composite... 

In the past several decades, with the increasing evolution of electricity markets, maintenance philosophy has gradually changed, and maintenance process plays a crucial role on the profitability and effectiveness of companies. Therefore, this leads managers to use modern strategies that their performance has been proved in various industries and therefore, traditional strategies have lost their effectiveness. Reliability-Centered Maintenance (RCM) is one of the most successful strategies wherein the maintenance process of system components is linked to improvements in the system reliability and profit of companies. RCM has not been thoroughly furnished in generation system yet. This thesis... 

Railroads should be well maintained for safe and efficient operation. The most important reason for the failure of railways is overload and asymmetric load on them. Also, the proper interval for repairs should be adjusted to fit the load crossed over. In order to carry out all these tasks, a constant observation of the weight on the rails must take place. Current dynamic weighing systems are costly. In addition, the installation of these systems is time-consuming and causes permanent damage to the rails. On the other hand, some of the cheaper models of weighing systems require full stop and static weighing, which practically does not work at all, especially on busy rails due to delays. The... 

Virtual power plant (VPP) aggregates the capacity of many diverse distributed energy resources (DERs); it creates a single operating profile from a composite of the parameters characterizing each DER and can incorporate the impact of the network on aggregated DER output. In modern power systems, technical virtual power plants (TVPPs) play an important role enabling presence of DERs in electricity markets. This thesis addresses the optimal bidding strategy problem of a TVPP that participates in the day-ahead (DA) electricity market. TVPP schedules its energy resources in a manner that maximize its profit in DA market. Hence, the optimal schedule of its resources is achieved. In a proposed... 

In recent years, the development of demand response programs with the aim of activating the demand side in order to achieve a wide range of economic and technical benefits in the development of the power system structure has been considered. With the implementation of incentive-based demand response plans, customers receive financial rewards based on changing their load pattern in the favor of electricity companies. However, mid-term and long-term planning to take advantage of this potential requires accurate estimation of the demand response potential in the power system. Also, the value of the baseline load curve of the customers (an estimate of the energy consumption of the customers if... 

According to uncertainty of retailer's customers electricity load and energy price in day-ahead and real-time markets, different scenarios are faced to an electricity retailer. As a result, due to possibility of different scenarios accurance, profit and financial loss of retailer has uncertainty and significant financial risk is imposed to retailer. Electricity retailers for earning the expected profit, reduction ofpossibility of scenarios with little profit (or much loss) and reduction of their risks, use different sources. bilateral contracts, like forward and call option,local wind turbines, distributed generaion, demand response, like load shift and curtailment can be named. This... 

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... 

Implementing distribution automation system (DAS) in distribution networks needs a huge investment which usually cannot be funded entirely in a short period of time. So distribution companies (DISCOs) should develop long term plans to equip their network with automation technologies as far as economically justifiable. Similarly, DISCOs have network capacity expansion (NCX) plans which specify the scheme of construction of feeders and substations. Since considering DAS may lead to more efficient NCX plans, the planner should revise the NCX plan through the DAS planning. On the other hand, for DAS planning it is necessary to consider a NCX plan as a platform to determine the time and location...