Sharif Digital Repository

The purpose of this thesis is sliding mode control of a roll-pitch seeker by considering the zenith pass problem. This problem takes place when the target appears in front of the seeker’s head. First, the mathematical model of the roll and pitch frames is obtained by the Newton-Euler equations of motion. Then, a MIMO sliding mode controller is designed. The performance of the controller is investigated in the presence of model uncertainties and seeker disturbances. The results indicate that the designed controller is robust enough and provides a suitable performance in the stabilization, tracking and guidance loops.
 

Nowadays, Gas turbines are developing more than before and one of the most important components of these turbines improving continuously is their combustor. In the recent years strict standards for controlling the amount of pollutants releasing from aero engines have been established and these standards are moving towards limiting these pollutants. Hence one of the most important criteria of combustor design is keeping its emissions at a lowest possible amount. In this study, at first an algorithm for combustor design has been calculated and then by means of this algorithm the combustor of CF6-80E1A4 engine is designed again. The amount of the produced emissions of the designed combustor has... 

Taking into account the impact of advertising on the reference price, we propose an optimal pricing strategy for supply chains in competitive industries subject to reference price effect. Most of researches do not consider the competition among supply chains. An industry with two competing supply chains is considered. Each supply chain includes a manufacturer who sells his/her product via a retailer. There are two types of structures: integrated and decentralized (it is assumed that the relation in a chain is Manufacturer– Stackelberg). Each manufacturer offers wholesale price to his/her retailer anticipating the retailer’s order quantity. In addition, the retailers choose their retail... 

A concern in the production sour oil and gas is the corrosion caused by the acid gas H2S. Even though corrosion resistant alloys (CRA) have long been available as a material selection option that mitigates H2S corrosion, the carbon steel is in general more cost-effective for oil and gas facilities. The aim of this study is to investigate the mechanical properties of 410NiMo cladding on a low alloy steel substrate. In this investigation, two successive layers of ER410NiMo were clad on low alloy steel substrates. To reduce the likelihood of Hydrogen Induced Cracking (HIC) and producing stable hydrogen traps, Post Weld Heat Treatment (PWHT) was used. To characterize the mechanical properties of... 

In this study, industrial steel (DIN 17135) underwent a new purification process with the aim of removing non-metallic inclusions and producing clean steel. Samples of steel were levitated in synthetic slag from the CaO-CaF2-Al2O3 system by an electromagnetic field. The effect of time, temperature and slag composition factors on the inclusions content of sample has been investigated. The images of the optical microscope were evaluated according to the ASTM E 45 standard, which according to the extracted results, the removal process was done to the desired extent. On the other hand, as the time and temperature of the process and the weight percentage of CaF2 increase, the number and size of... 

Content-Based Image Retrieval has been an active research area in recent years, due to the vast amount of digital media available via the Internet. In this work we formulate contentbased image retrieval as machine learning problem using the relevance feedback technique and propose a learning algorithm adapted to specific properties of image retrieval. After studying specific properties of image retrieval as a machine learning problem, we propose a Bayesian framework for image retrieval based on one-class learning and test it on different image datasets. The proposed method is a kernel based approach and can also utilize domain knowledge in the form of prior knowledge in constructing a model... 

The most important task of a power system is generating and transmitting electricity for consumers, according to electricity quality standards. One of these quality criteria is preservation of grid frequency close to nominal value with continuity of energy delivery to consumers. Electricity is a specific commodity that its generation and consumption should be equal continually; otherwise the network frequency will change and may become unstable, causing severe damage to the network equipment. There for different control and protective actions are deployed to maintain balance between generation and consumption, and thus to keep grid frequency close to nominal value. Characteristics of... 

With development of nanotechnology in medicine, nanoparticles are used for detection of tumor and cancer biomarkers. Magnetic nanoparticles are widely used for therapeutic and diagnostic objectives, because of their biocompatibility, ease of preparation and strong magnetic properties. Genistein (C15H10O5) is a soy isoflavone which is used for its anti-cancer activities. It is used for inhibition of cell proliferation, cell growth, and tumor invasion. The aim of this study is to assess the impact of nano-conjugation of geinstein as chemotherapeutic agent against cancer. For preparation of typical iron oxide Nanoparticles, Magnetite nanoparticles were synthesized by coprecipitating iron (II)... 

Global growth of electrical energy consumption and various limitations on the use of fossil fuels, such as environmental problems, rising prices and their limited available resources, have resulted in growing interest and investment in the usage of renewable energy generation, especially photovoltaic (PV) systems. Although the off-grid operation of PV systems was its dominant operation form in the past, proliferation of these systems has made the grid-connected operating mode widespread in recent years. However, their grid connection causes technical problems which need to be resolved. This thesis studies and analyses the steady state and dynamic operation of PV systems in grid-connected... 

In this thesis we study the structure of locally solvable, solvable, locally nilpotent, and nilpotent maximal subgroups of skew linear groups. In [5] it has been conjectured that if D is a division ring and M a nilpotent maximal subgroup of , then D is commutative. In connection with this conjecture we show that if M a nilpotent maximal subgroup of , then M is an abelian group. Also we show that is a solvable maximal subgroup of real quaternions and so give a counterexample to Conjecture 3 of [5], which states that if D is a division ring and M a solvable maximal subgroup of , then D is commutative. Also we completely determine the structure of division rings with a non-abelian... 

Given a finite dimensional F-centeral simple algebra A = Mn(D), denote by A′ the derived group of its unit group A*. In this thesis, the Frattini subgroup Φ(A*) of A*for various fields F is investigated. Setting G = F* ∩ Φ(A*), when F is a local or global field the group G is completely determined. For global fields it is proved that when F is a real global field, then Φ(A*) = Φ(F*)Z(A′) otherwise Φ(A*) = ∩F*p where the intersection is taken over primes p not dividing the degree of A. Using the connection between Φ(A*) and Φ(F*) via Z(A′), Φ(A*) is also calculated for some particular division rings D.

 

The low female labor force participation rate in the Iranian labor market relative to the global average and even to countries that do not differ significantly from the socio-economic characteristics of our country is one of the important questions of the Iranian labor market. In this study, we seek to answer the question of whether the economic participation rate of married women will increase if the gender gaps in wages, job findings and job losses among women and men are eliminated in the Iranian labor market. To answer this question using household expenditure and income data and labor force data, we show that between the two categories of occupations, in terms of the share of women's... 

In the first part of this research, we reported a liquid sensor array for detection and classification of biological thiols, based on aggregation of gold nanoparticles (AuNPs) with different coatings as sensor elements. Thiol mediated aggregation of AuNPs was visualized via UV–vis spectra. The spectral changes, as a consequence of aggregation of AuNPs, made a unique pattern of spectra for each analyte and allowed for the selective detection and discrimination of the biological molecules. HCA and PCA analysis demonstrated the discrimination of various thiols of different concentrations (i.e. 10–800 mmol L-1 for cysteine, 200–700 mmol L-1 for both glutathione and glutathione disulfide).... 

Acidizing operation is performed in oil and gas reservoirs with the aim of overcoming formation damages, increasing permeability and reducing skin factor. In carbonate reservoir, the hydrochloric acid increases the permeability of the areas around the well to a more than its initial value by dissolving part of the formation minerals. Considering that most of Iran's oil and gas reservoirs are in the category of carbonate reservoirs, it is important to study the reaction kinetics of carbonate minerals and acids used in acidizing operation. The complex and multifactorial nature of the acidizing operation in the reservoirs has made it very difficult to design a successful and optimal operation.... 

Fatigue crack growth can have harmful effects on the reliability rotary machine. While an early warning to crack, can be used to extend the life of these expensive machines and increase reliability.Structural Vibration Condition Monitoring as a primary fault detection method, achieved to a lot amazing result and for this reason studies vibration behavior of cracked rotational shaft is a big issue for engineers of dynamic machine.In this research, first check the fault detection methods based on structural vibration condition monitoring, mode shape methods were extracted. Then by modeling rotational shaft in computer and creation of crack on it, fault detection quality of these methods have... 

It is important to provide an appropriate and economically method with technical and engineering considerations to stabilize excavated underground spaces. The necessity of this, especially for the construction of underground metro stations located in the cities which faces many problems, is more evident. In this research, it has been tried to introduce an optimal method according to the type of area for the construction of the underground station. In order to obtain stress and strain condition in structural elements and surface deformations due to different stages of excavating, numerical modeling in FLAC3D has been used. By examining the parameters that affect the sustainability of this... 

In the present study, the effects of increasing the value of shale gas production, either due to increased production or price increases, have been studied on economic variables such as employment, wage, property value and the number of births. In this regard, the data for each of these variables was used at the county level in the United States of America between 2000 and 2011. In order to estimate the desired effects, counties are divided into two types of boom and non-boom counties. The findings indicate that increasing natural gas production will lead to more employment and wage growth in boom counties than non-boom counties. Also, during the period of increasing production, the value of... 

Co-movement between inflation and nominal interest in response to an interest rate shock, dubbed neo-fisherianism, has been the subject of contentious debate since the advent of non-inflationary ZLB environment. We design an economic model rich with banking features to understand the economic responses to permanent and long-term interest rate shocks. We find that responses to a permanent positive interest rate shock depend on the monetary authorities’ speculation of the new long-term inflation rate, with the most probable outcome being a permanent increase in inflation. Responses to a long-term positive interest rate shock depict an increase and then decrease in inflation. We also discover... 

In this study, we aim to learn representations from microscopic cell images that effectively capture the features of drugs affecting the cells, allowing us to identify effective drugs for treating a disease. We employ two parallel learning paths using predictive and generative models. Specifically, we have achieved a predictive model on the RxRx19a dataset that, unlike previous models, is interpretable, optimized, and robust to dras- tic changes in drug properties. Additionally, we have developed the first generative model on this dataset, which not only generates high-quality images but also discovers a meaningful latent space. This latent space divides the representation into relevant...