Sharif Digital Repository

Electricity distribution companies always strive to operate the power network efficiently and reliably so that their network be able to satisfy the growing needs for electricity. To achieve these goals in a power network, a comprehensive asset management plan with a sound policy for inspection, periodic maintenance, replacement, and disposal of depreciated equipment is required. One of the high-risk sectors of the electricity grid is the insulation section of distribution and transmission lines. In recent years, composite insulators have been used more widely because of their desirable characteristics such as: hydrophobicity, lower price, and lower weight if compared with the another... 

Magnetic bearings have been introduced in recent decades to overcome the problem of energy loses due to friction in bearings of rotating machinery. In magnetic bearings, the rotor is suspended by magnetic forces without any friction. These bearings are of the two types of passive and active. In Passive Magnetic Bearings (PMB), magnetic forces are generated by permanent magnets and have the ability to tolerate a small distribution. In Active Magnetic Bearings (AMB) magnetic forces are generated by electromagnets and have the ability to tolerate larger distributions than the PMB can. Since AMB is inherently unstable, it is necessary to use controllers to stabilize it. Due to the nonlinear... 

In this study different kinds of solid phase microextraction fibers based on sol-gel technology were employed for extraction and pre-concentration of phenol in occupational air and oxadiargyl in plant and environmental samples. In the first work, a SPME method followed by on-fiber derivatization and gas chromatography-mass spectrometry detection (GC-MS) was developed for the analysis of phenol in the air. The application and feasibility of three different sol-gel based SPME fibers with different polarities, polar and non-polar poly (dimethylsiloxane) (PDMS) and polyethylene glycol (PEG), have been studied. Influential parameters such as fiber coating type, type of derivatization reagent,... 

Alzheimer's disease is the most common type of dementia, which has been recognized as the seventh most common fatal disease in the elderly over 65 years of age. Despite all the research done to recognize and treat this disease, so far there is no cure for this disease, and even most of the chemical treatments that are prescribed for Alzheimer's patients are only effective towards reducing the symptoms of this disease and lose their effectiveness as it progresses. Therefore, in the last two decades, in order to find a way to better understand and even treat AD, scientists have reached a concept called brain frequency stimulation, which can improve people's cognitive performance without the... 

Thiomersal is an organomercury compound. This compound is a well established antiseptic and antifungal agent. It has been used as a preservative in vaccines, immuno-globulin preparations, skin test antigens, antivenins, ophthalmic and nasal products, and tattoo inks. Thiomersal is very toxic by inhalation, ingestion, and in contact with skin, with a danger of cumulative effects. It is also very toxic to aquatic organisms and may cause long-term adverse effects in aquatic environments.
Thiomersal's main use is as an antiseptic and antifungal agent in vaccines. In multidose injectable drug delivery systems, it prevents serious adverse effects such as the Staphylococcus infection that,... 

Novel high-throughput device and their applications as the microextraction systems for pesticide multiresidue determination is the centre of this research. 96 extracting unit based on solid phase microextraction and micro-Solid phase extraction were constructed and applied for high-throughput extraction.
In the first work, a high-throughput SPME on 96-well plate together with gas chromatography-mass spectrometry was developed for the determination of pesticide residues in cucumber samples. A home-made Teflon block consisting ninety-six holes was constructed to 96 SPME fibers being positioned in. SPME fibers consisted of stainless steel rods with a 1.0 cm polydimethylsiloxane tubing... 

During the recent years, manufactures and industries have paid attention to occupational health and safety of their employees. Formaldehyde is known as a probable carcinogenic agent and its large consumption made industries to consider it as a risk factor for occupational health. At vaccine production industries, Formaldehyde is used as disinfectant and stabilizer. In this study, a solid-phase microextraction (SPME) method based on kinetic and equilibrium calibration strategies was developed for monitoring of formaldehyde in the biologics production areas. The application and feasibility of three different sol-gel based SPME fibers with different polarities have been investigated. Two... 

Membrane bioreactors (MBRs) which are commonly understood as the combination of membrane filtration and biological treatment using activated sludge have several advantages, but membrane fouling reduces the membrane efficiency, permeability and lifetime. An alternative is replacing a moving bed biofilm reactor (MBBR) with the activated sludge system which may reduce the effect of membrane fouling. The sludge produced in MBBRs has poor settling characteristics, therefore, their efficiency is limited by the sedimentation tank performance and they require a larger settling surface. The combination of moving bed biofilm reactors and membrane bioreactors can compensate for the drawbacks of both of... 

In this text to find the answer of the question “ what is it to be physical” in a definition form or a scheme of the term physical, firstly we sought for a possible consensus among recent physicists and philosophers. But from their answers not only we did not find any clear consensus but also most of them confess that the term is ambiguous and unclear. In a general aspect, we can categorize the answers to two theoretical and realistic perspective. The theoretical perspective, beside circularity and Hempel’s triviality, seems not to present any criteria for being physical. In realistic perspective, it seems that there is no ontologic constraint for being physical, that is from “being... 

The application of membranes for separate of particles in mainly microbial flacs , are fast growing in biological treatment systems. Membrane bioreactors are now considered as one of the major new processes in wastewater treatment. However , membranes are expensive and costly. This study is carried out to test an innovative , locally made filters for separation of flocs in an MBBR reactor. This innovative filter is replacing a traditional settling tank. This type of filters is made very cheaply and has important advantages in installing and operation. Experiments were carried out in a laboratory scale MBBR unit. A filter unit consisting of 3 innovative filter tubes were placed and the... 

This thesis addresses the problem of dynamic security assessment in power sys-tems with an emphasis on its application in restructured power systems and issues arising in its applications. The new electric utility environment has an immedi-ate consequence of emphasis on reliability and secure operation of power systems. This requires faster and more precise methods to assess the dynamic aspect of se-curity. On the other hand, this issue is becoming challenging when the determined dispatch might not be accommodated due to violation of the limits.This thesis addresses the problem of dynamic security assessment in power sys-tems with an emphasis on its application in restructured power systems... 

Are the returns of the mineral companies in Tehran Stock Exchange affected by the changes in the commodity price at the Iran Mercantile Exchange? By implementing a Multi-Factor Model we will calculate the firms’ value elasticity to the commodity price changes. We try to explain the estimated elasticities on the basis of the firm’s fundamental variables using a discounted cash flow valuation model. An unbalanced panel data estimation is employed for this purpose. Afterwards, we will suggest a novel model on the ground of the assumption that the commodity prices and firm values follow the Geometric Brownian Motion. The result of the model is that the elasticity can be explained by commodity... 

Rotor contact with a stationary element of a rotating machine and the subsequent rubbing at the contact area is a serious malfunction that may lead to the machine’s catastrophic failure. In the past decades, many studies have been done on the rubbing phenomena, its different regimes and its various consequences on the machine performance and safety. However, most of them have used a simple model to investigate the rubbing interaction between the rotor and the stator. This simple model consists of the Jeffcott rotor, as a model for the real rotors, and a rigid annular block surrounding the rotor, as a model for the real stators. The objective of this thesis is to build an algorithm to... 

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... 

Value at risk of an asset, is the asset’s expected maximum loss for a certain period of time and at a specified confidence level. Value-at-Risk can be calculated in the bank with its inter-nal method or standardized method. when a method have more violation number then bank need to keep more daily capital requirements. under the Basel 2 agreement if the violation of method more than 10 times in year, the Bank uses the standardized method.
There are trade off Between daily capital charge and violations. Therefore, existing methods for calculating the value at risk, usually lead to much daily capital charge or many violations. Studies show with combination of different methods to calculate... 

The purpose of introducing this thesis is to review the difference between Standard Quantum mechanics and Bohmian Quantum mechanics. The aim of this dissertation is not only to contrast these theories with respect to formulation, but also to briefly review their historical, philosophical and sociological aspects. This dissertation consists of two main sections. The first section is about reviewing the emergence profile of these theories and the formation of each theory along its historical path. In addition some beliefs about the founders of these theories and the impact of their beliefs on the evolution of their theories are put forward. As a complement to the above, the prevailing social...