Sharif Digital Repository

The alloy steel plant was exploited in1999; and the maintenance department starts its function and its activities according to the written PM software by Austria’s BOHLER Company. The PM program was written for the entire factory. Having worked with the PM for eight years, now it is possible to evaluate its performance. There are two main problems in the maintenance system; firstly, the existing PM System is incomplete, some important feature of the PM program is incomplete. Secondly there are lacks of a good auditing system to evaluate the PM orders. To evaluate the weakness of the current PM system and to study application of TPM, a section of the factory was... 

The aim of this project is design and implementation of the “gradiometer RF SQUID base Vibrating Sample Magnetometer (VSM)”. Different sections of the system have been designed such as pick up coils, vibration system and electronic circuits. The piezoelectric crystal has been concerned for vibration system. At the first step, we have implemented the basic VSM system. In the basic system, voltage induces in two series opposite pick up coils and its output is recognizable via electronic circuits. At the second phase of the project, the electronic circuits of basic VSM system have been replaced with the RF SQUID gradiometer and its electronic circuits. Afterwards, the sensitivity and the gain... 

Suspension system is one of the most influential components of vehicle in the area of stability and comfort. The suspension system is designed based on the use of the vehicle and stable characteristics. Obviously, being distant from the designed spots and applying various gates, its optimized performance is lost. Semi-active suspensions by changing their features get floating designed spots to be created and suspension system is always in optimum conditions through a suitable control. This research covers the efficacy of using damper Magneto Rheological which is called damper (MR) on the performance of vehicle suspension system in reducing vibrations. This damper is considered as a device in... 

Activated Carbon as a highly efficient and low price absorbent has manifold functions in separation and absorption processes in liquid or gas phases. These applications in liquid phase include bleaching in sugar syrup, water and wastewater treatment and in gas phase utilizing them in gas masks and solvent recycling process. Wide variety of base materials could be used to produce activated carbon. For instance rare cellulose materials -wood, coconut shell, Pyrenees and agricultural wastes-, carbon materials-coal, petroleum coke, tar- and polymer materials- tires and plastics wastes- could be mentioned. In this thesis, feasibility of producing activated carbon based on using walnut, almond... 

Jean-Pierre Serre in 1955, in his famous article “Faisceaux Algébriques Cohérents” asked if there is any finitely generated projective module on polynomial rings which is not free. Or equivalently: is there any non-trivial algebraic vector bundle over an affine space? The negative answer to this question is known as Serre’s conjecture and it was an open problem in algebra and affine algebraic geometry until 1976, when it was proved independently by Quillen and Suslin. The challenge of solving this question and its consequences led to a vast amount of research in commutative algebra, homological algebra and algebraic K-theory and inspired generalizations and similar questions. In this thesis... 

The purpose of this research is the aerodynamic design of a 100 kW transonic ducted fan. Today, the aviation industry is moving towards the design of electric driven aircraft propulsion. Transonic ducted fans are one of the viable options that have been used in medium and heavy aircrafts due to their high specific power. In this research, the meanline model has been used for the initial design. By applying the design constraints, design limitations, design and functional parameters, the initial design point is found and then a sensitivity analysis is performed with respect to the effective design parameters to obtain the optimal design point. For the initial design of the transonic ducted... 

Since direct measurement of neutron energy, unlike measuring the energy of ionizing radiation, is difficult, and the use of indirect methods for detecting and measuring neutron energy with high resolution and acceptable efficiency are not possible, the neutron time of flight method is the only direct neutron energy spectroscopy method. This issue is considered and evaluated in two methods: direct and scattering neutron time of flight. For this purpose, we have considered the 241Am-9Be source. In this method, neutron velocity can be determined by measuring time. is the time for the neutron that travels at distance of . The next method is the dispersed neutron time of flight method, in... 

The Pulse Laser Deposition (PLD), Sputtering, Evaporation and Metal-Organic Chemical Vapor Deposition are the common methods for thin film fabrication. The mentioned methods are very costly for commercials application. Due to the importance of cost in large thin film fabrication, scientist tried to find a low-cost method. The low-cost non-hazardious Metal Organic Deposition (MOD), method which is based on chemical manufacturing method was developed. The type of the solvent and removal the destructive residual materials are the main challenge in this method. In this project, by utilizing acetyl acetone method, high quality MOD YBCO superconducting thin film has been fabricated and will be... 

The short-term expansion planning of the private utilities, as well as the emerging technologies such as photovoltaic panels (PVs), plug-in hybrid electric vehicles (PHEVs), cryptocurrency mining, and storage elements spread, make the long-term load estimation of distribution transformers (DTs) noticeably imprecise. In response, the number of overload and underload transformers is growing in recent years. The utilities normally analyze the loading of their DTs annually to determine the DTs, which should be replaced. The simplest, but expensive way is to substitute them with the newly purchased DTs. However, financial profit motivates the utilities to relocate in-service undersized and... 

The electrical conductivity of the solution has been one of the important physical quantities in many application. In this respect many probes and devices such as conductive sensors have been devised. In this study electrical properties of different water samples at frequency step range of 100-100000 Hz are measured by using the long cylindrical capacitive sensor and a measuring module (LCR-703). Operation of the capacitance measurement module for such probes is based on the auto balancing bridge method. Comparison of the measured capacitances and measured resistances for different water samples shows a decrease by increasing the measurement frequency. In another study the dielectric... 

Because of the inability of conventional methods to regenerate the infarcted part of the heart, regenerative medicine based on using scaffolds and hydrogels incorporation with cells and biological factors emerges as a promising approach. Micro-structures, especially hollow microcapsules created by the microfluidic system, has received a great deal of attention due to their inspired biomimetic structures, providing complete coverage cells, and preventing an immune response, consequently. This study aimed to use a microfluidic system to fabricate hollow microcapsules and investigate the behavior of rat cardiomyoblast cells (H9C2) along with exosomes within these structures. These structures'... 

The continuous rise in electricity demand and the ever growing power generation in different power networks over the world have caused the short circuit level in the power systems to exceed the operational rating of the installed power devices (including cables, circuit breakers and buses). Replacing these devices with new higher rating devices is an expensive solution. From this point of view, utilizing fault current limiters is an economical solution. Superconducting fault current limiters form an efficient category of current limiters. This type is expected to be studied and used widely in future due to their advantages. In this thesis, the first chapter reviews the superconductivity... 

Terahertz waves which includes frequencies between 100 GHz to 10 THz of electromagnetic spectrum have found many applications in science, medical treatments and industry. One of the recent methods to produce these waves is using nonlinear properties of superconductors based on Josephson junctions which inherently appear in some superconductors called BSCCO. Stack of intrinsic junctions of these superconducting materials can radiate terahertz waves by only applying a DC voltage across them. This Thesis investigates some of these structures based on Josephson junctions to produce coherent radiation of terahertz waves. For the optimization of the radiation power, this study also investigates...