Sharif Digital Repository

World population growth, depletion of fossil fuels resources depletion and increased air pollution resulting from their consumption, human society has had to replace fossil fuels with renewable sources. In this context, the production of hydrogen using solar energy is feasible candidate to replace fossil fuels, which can be produced by water splitting in a photoelectrochemical (PEC) cell using an appropriate photocatalyst. This clean production method has been attended by many researchers in recent years. The most common photocatalyst for the conversion of sunlight to hydrogen by splitting water is Titanium dioxide (TiO2). But high energy gap and fast electron-hole recombination rate in TiO2... 

For several years, self-organizing networks have been introduced by 3GPP to reduce the costs of mobile operators. Self-organizing networks, by introducing a kind of intelligence to the mobile network, will cause optimal performance and, as a result, reduce the operating costs of operators. Improving network coverage and increasing user data rates are always among the priorities of operators to increase profits and customer satisfaction. Coverage and capacity optimization is one of the most important functions introduced in self-organized networks. In this study, in addition to the coverage and capacity optimization function, the load balance optimization and the contradictory interaction of... 

Steel shear wall is a lateral load resistance system, which has been taken into consideration in recent decades for designing and reinforcing high-rise buildings. This system is comprised of steel filler panel surrounded by frame members including beams and columns. Steel shear walls are presently fabricated in two types, stiffened and unstiffened. According to numerous conducted research, it can be stated that the stiffened type has better seismic performance. The use of stiffeners with a great number of executive details is required to spend more time and costs on the construction sector. In order to solve these problems, some experimental and numerical studies have been conducted on... 

The problem of restoring power systems after a complete or partial blackout is as old as the power industry itself. In recent years, due to economic competition and deregulation, power systems are operated closer and closer to their limits. At the same time, power systems have increased in size and complexity. Both factors increase the risk of major power outages. After a blackout, power needs to be restored as quickly and reliably as possible, and consequently, detailed restoration plants are necessary. This thesis concentrates on the initial stages of restoration where load pickup and frequency control problem is identified. The best sequence of load pickup for power plants during power... 

Due to unusual response of structures of buildings with irregularity in their architecture to dynamic excitations, to have a comprehensive knowledge of their behavior during earthquakes is of utmost importance. Building irregularities are in general divided into two major categories, namely Irregularity in Plane and Irregularity in Elevation, and one of the forms of the latter is where there is a split in the levels of the building. In this work, through a series of case studies, the effects of P- phenomenon on the behavior of steel split-level building structures were studied. 5, 10 and 15 story buildings with 5 and 6 bays, and level splitting of 30, 60, 90, 120 and 150 cm were studied. All... 

The earthquake engineering is the meeting of knowledge and techniques in studying, designing, implementing, controlling and strengthening various structures against seismic loads. The assessment of the performance of structures through previous earthquakes has shown that one of the major causes of damage to the existing buildings is the excessive displacements caused by the asymmetric load distribution, stiffness or resistance. Such irregularities, lead to severe dynamic reactions, especially torsion ones. Today, many structures can be considered as irregularity in plan and height. For this reason, it is expected that these structures will be highly vulnerable to seismic loads as compared to... 

The power control of horizontal axis wind turbines can affect significantly the vibration loads and fatigue life of the tower and the blades. In this thesis, we are going to consider both the power control and vibration load mitigation of the tower fore-aft vibration. For this purpose, at first, we developed a fully coupled model of the NREL 5MW turbine. This model considers the full aeroelastic behavior of the blades and tower and is validated by experiment results, comparing the time history data with the FAST (Fatigue, Aerodynamics, Structures, and Turbulence ) code which is developed by NREL (National Renewable Energy Lab in the United States). In the next, to estimate EWV, a novel... 

The demand for independent power generation has been increased in recent years due to the growing demand in distributed networks, losses and power qaulity in power systems. These losses occur in transmission to distribution networks from the generation sites to the end-user loads which have harmonic losses besides fundamental losses.. The non-linear load makes the harmonics flow in the line and create the harmonic losses. However, in a distributed network with several DGs of different types and with all kinds of variable nature loads, an optimal power balance in the system has to be achieved. This optimal objective, which results in minimal energy losses over a specific period of time,... 

A tsunami is a series of tides most commonly caused by the deformation of the sea floor during a submarine earthquake. They are extremely long waves with the distance between successive peaks or troughs on the order of 10’s to 100’s of miles. They are also generated by landslides, volcanic eruptions or more rarely by asteroid impact. These causes change in location on the surface of the water which in turn creates numerous waves that spread out from the zone of turbulence. Few current design codes for coastal structures include tsunami. Even those that do, the bases for taking the hydrodynamic loads into the design are often grossly simplified and may be overly conservation and/or... 

Needs for construction of rock structures and underground ones such as underground tunnels, dam foundations, trenches for roads and railways, power plants and caverns built to keep oil, gas and nuclear waste has increased dramatically. In order to design, construct and excavate these underground structures safely and economically, full understanding of rock mass properties, suitable tools and practical techniques of drilling are necessary. Because of existing discontinuities, including joints and layered rock masses and their effects on mechanical behavior of rock mass, it is necessary for the geo-mechanical profile, shear strength and failure mechanism of rock mass to be accurately... 

Steel structures are one of the most common structures in the world. One of the main parts of these structures is the connections, which are divided into three main categories of fixed, semi-rigid and joints, according to
the different criteria provided in the guidelines and codes. Perhaps the main challenge facing civil engineers has been designing efficient connections against lateral loads (seismic loads, wind loads). This issue has received more and more attention from designers due to the poor performance of the fasteners against lateral loads. Investigating and evaluating semi-rigid connections as one of the main part of steel structures against various loads, especially lateral... 

Bones adapt their form and structure to make an efficient use of their mass against the applied mechanical loads. So, it is not surprising to assume that the geometry and density distribution of a bone contains information about its loading history. The objective of this work was to develop a framework to simulate the bone remodeling procedure as a topology optimization process and then use this framework to develop a simple technique for estimating the dominant joint loads based on the bone’s density distribution.
At first, the remodeling equation was derived from the structural optimization task of minimizing the strain energy in each time step, using the level set method. Employment... 

The goal of this research is to study the effect of local microcracking due to step by step pressure loading on the durability properties of geopolymer concrete. To better understand the behavior of GGBS-based GPC under different pressure stress levels, some experiments such as water permeability and water absorption conducted on the samples at each state of damage. Also, non-destructive tests such as ultrasonic waveform and pulse velocity (UPV) was used to quantify the extent of damage at each step. GGBFS and a blend of sodium silicate solution and 10 molar sodium hydroxide solution with SSSH⁄ ratio of 2 were used for production of GPC samples. GPC, OGPC and OPC samples with water to binder... 

Existing design methods for steel frames has been improved over the last three decades in order to incorporate the behavior of semi-rigid steel connections in furtherance of frame design and since the analysis and design of structures is often done based on the assumption of completely rigid or pinned behavior,therefore, the actual behavior of connections and their modeling can help to understand the actual behavior of structures.Knowledge of the initial rotational stiffness of the connection is important for elastic analysis of structures. Investigations show that structures with semi-rigid connections have many features which are the causes to prefer these kinds of connections to the... 

In recent years,because of increasing problems that result from water shortage ,using of wastewater treated by high quality and entering them to water cycle is considered more than past.Large amount of waste waterare produced through cooling towers in industries per a day .Therefore ,cooling tower’s blow down is a most important source for reclamation and reuse of water .The purpose of this project was investigation ofefficiency of submerged aerated filter for treating low organic simulated blowdown water as a feed . The experimental unit consisted of 8/5 L filled with 70 percent of propylene media . After obtaining steady –state condition ,The SAF reactor was tested under... 

In this thesis, two types of smart switch & driver chips are designed in 0.18 um HV BCD technology; low side driver and high side driver. These drivers are smart, because of having various types of protection and detection circuits, which protect switch, driver and connected load, versus errors that can be occurred by the user or other environmental effects. The protection circuits are battery over & under voltage shutdown, current limit, inductive load clamper and thermal shutdown. Load status is checked by status detection circuit and reported to user by one bit flag. Battery voltage can vary from 7 V to 40 V and output current is limited to 2 A. Designed high side and low side drivers are... 

Piles are usually used in groups. The complicated interaction between piles on the one hand and between piles and their surrounding soil on the other hand, have made it difficult to recognize mechanisms that influence the pile group behavior and analyze it accurately. In this research, three dimensional models in ABAQUS software were used to investigate response of single piles and pile groups under lateral loading in clayey soils. Configuration of piles in a group, connection of piles to the pile cap, pile spacings, and pile cross section were taken into consideration as some important factors affecting response of pile groups. All the modeled piles were categorized as long piles. In order... 

The aim of this thesis was to find the optimum retention time for treatment of synthetic petroleum wastewater by a wastewater treatment system made with a bucket, mineral material and earthworms residing in a vermibed. In order to make the desired flow happen, height difference was utilized. The polluting substance used for making wastewater was BTEX. As the wastewater was synthetic, the concentration was also a variable. The ultimate soluble concentration was 3200 mg/l and more concentrations were not tested. Parameters such as number of worms, worm’s growth rate and their distribution pattern, humidity amount and distribution and worm’s acclimatization time during organic loading shock... 

Nonlinear transmission line (NLTL) a guiding structure contains nonlinear elements. For discrete NLTLs, this structure is periodically loaded with nonlinear elements. In the structure of this line nonlinear elements such as ceramic capacitors, nonlinear magnetic elements, vector diodes, Mos transistors, etc can be used. With the rapid development of semiconductor devices and microwave band systems, the demand for implementation of NLTLs has increased. These lines provide wide band-width, cut-off frequencies over the hundreds of GHz and picosecond rise time for various systems.Among the applications of NLTL, the generation of high power RF pulses has attracted the most attention. In this... 

In order to reduce investment and operation costs of the power systems, transmission expansion planning is inevitable. In fact, transmission expansion planning is to determine when, where and how many lines need to be added to power system with a minimum of investment and operating costs. In this thesis, transmission expansion planning has been performed at uncertainty in generation and N-1 criterion condition where uncertainty in generation means uncertainty in the moment of adding power plant to power system. In previous studies, transmission expansion planning was performed with DC-load flow in which, the power loss and voltage profiles were ignored due to the approximation in the...