Sharif Digital Repository

Design of superconducting material based wide band radiation detectors has recently been attractive. Interesting features of detectors, which are based on Josephson Junctions such as high sensitivity in a wide range of frequencies and low power consumption, potentially have many advantages over other semiconductor-based photo-detectors. According to variety of applications of high-Tc superconductors, particularly YBCO, and significant progress in manufacturing of thin films and Josephson junctions, this thesis mainly focuses on investigation of radiation effects on I-V characteristics of high-Tc step-edge Josephson junctions experimentally. The current-voltage characteristics of fabricated... 

The centralized and decentralized control approaches are the most effective control approaches to be applied in micro grids. However, practically to rerduce the cost and improve the reliability, decentralized control is usually employed. Initially, this thesis discusses the components and dynamic model of the micro grid in order to evaluate the stability. Then, it introduces the decentralized control methods which can be used in a micro grid. In the next step, a sample micro gird is studied (with high ratio of lines R/X). This microgrid has three DG plants having DC voltage sources, inverter, and LCL filter. The performance of AVR controls is evaluated by combining the PQ and droop control... 

Microfluidic technology is a field of science that deals with the design, fabrication, and experimental tests of small-scale fluid systems and has made great strides over the past decade. As an interdisciplinary field, this growing field of technology has many applications in medicine, diagnostics, chemical analysis, electronics industry, etc. One of the primary applications of the microfluidic devices is the development of " laboratory on-chip (LOC)" tools as point-of-care (POC) diagnostic tools, such as, rapid detection during surgery. A LOC device includes various application modules, sample transfer and preparation modules, separation modules, and detection and analysis modules. The... 

Microfluidics is an emerging technology that has attracted lots of attention in recent years due to its remarkable capabilities. This technology that operates fluids in micron dimensions, has led to the emergence of lab-on-a-chip platforms that have the ability to perform one or more laboratory operations on a small scale. One of the most important applications of lab-on-a-chip devices is cell sorting which is done in various methods. In this study, we intend to provide a simple and practical solution for cell sorting by designing a comprehensive and optimized system. In this regard, we design a new generation of microfluidic devices, known as digital microfluidics, which has the ability to... 

The removal of ethylene glycol, one of the most widely used antifreez, with moving bed biofilm reactor (MBBR) was studied. Beside of ethylene glycol, the synthetic wastewater contained molasses and other salts as nutrient source. The packings were composed of polyethylene and shaped like small cylinders with a surface area of 500 m2 per m3 bulk volume of carriers(KMT). The COD of the feed was adjusted by varying the ratio of ethylene glycol to molasses. The total COD was 1252.5, 1345 and 1500 mg/L. The resulted showed that when the biofilm grows on the packings and its thickness is good enough, the removal efficiency increased. The increase was attributed to higher concentration of biomass... 

The hydrogenation of carbon dioxide to methanol represents a promising route for the efficient use of an anthropogenic greenhouse gas, in which catalysts play a key role in carbon dioxide conversion and methanol selectivity. In this study, firstly, CuO-ZnO-Al2O3, CuO-ZnO-ZrO2, CuO-ZnO-ZrO2-Al2O3, CuO-ZnO-Al2O3-CeO2 and CuO-ZnO-ZrO2-CeO2 catalysts were made using co-precipitation method, then these catalysts were characterized by inductively coupled plasma optical emission spectrometry, specific surface area and pore size distribution, X-ray diffraction, Field Emission Scanning Electron Microscopy, temperature programmed reduction. Finally, in order to compare the performance of the catalysts... 

Wear is the most important cause of surface damage occurs by direct contact of surfaces. Increasing the quality and strength of surface against different kinds of destructive phenomena is significant in manufacturing of mechanical parts. Surface nanocrystallisation can improve the surface protection against wear and can be done by lazer beam and shot peening. In this investigation by sever shot peening process the surface of A356 Aluminium alloy transforms to nanocrystal structure. The dry sliding wear and friction behaviors of A356 Aluminum were evaluated using a pin-on-disk apparatus at ambient conditions. The stationary diameter of 5mm stainless steel pin produced a wear track (scar) on... 

Regarding the increasing trend of network costumers and services, requirement of high-speed and high quality seems to be inevitable. Therefor much effort has been put to issue the problem properly in recent years. Optical fiber networks are attending more attention and optical fiber channels are dominating the world of networking and data. Applying new methods such as CDMA and OFDM raise the issue of maximum achievable rate and quality of these systems.These include the main concentration of this project. First, optical channels are modeled.Then, applying OFDM and CDMA methods, lower and upper bound of channel capacity will be determined  

Critical sets and defining sets in combinatorics have been attended by mathematics fans. These subjects have been debated since 1997 and a lot of researches have been done about them and a lot of articles have been published. But number of unsolved questions might be more than answered questions. In these years critical sets for Latin square and defining sets for vertex coloring have been attended and also enough researches about issues related to defining sets for edge coloring and total coloring have not been done. For these reasons we focus on these issues in this thesis. Issues like defining sets for edge coloring and total coloring in complete graphs, generalized Petersen graphs and also... 

In this dissertation, Data analysis and information retrieval from incomplete observations are investigated in different applications. Incomplete observations may be induced by lack of observations or part of data affected by specific noise (quantization noise). Data-driven algorithms are among important hot topics. Our goal is to process the lost information inducing certain assumption on big data structures. Then, the approach is to mathematically model the problem of interest as an optimization problem. Next, the designed algorithms for the optimization problems are proposed trying to cut down on the computational complexity of as well as enhancing recovery accuracy for big data... 

The Internet of Things (IoT) is one of the fields witnessing a significant growth in recent years and is expected to make the lives of so many people go under substantial changes. IoT will exploit large numbers of smart objects in people’s everyday life to bring smartness into reality and this necessitates correct and seamless connection and integration between smart entities. One of the key tasks of the IoT platform is providing such a connection, which is assigned to the resource discovery framework.A resource discovery framework should consider requirements and challenges present in the IoT environment. Heeding the literature, one finds deficiencies in this field. These shortcomings are... 

One of the best ways to overcome the weaknesses of technology services in different industries is right technology transfer with feasibility in the country. 3D painters have been recently widely used industrially in different countries. The 3D printer is one of the new emerging technologies, enabling the production of every 3D objects with any complexity. 3D printing has provided the possibility of producing, in fastest, more economics and regardless of those complexities. By transfer of this kind of technology and proper management, a huge transformation can created in all industries and factories. To do this, there are several technologies of 3D printing, that each of them used in various... 

The most important challenge in microgrids is the coordination of distributed energy resources (DERs), due to the existence of several DERs with fugacious characteristics. Also, energy management in the microgrid is very important because there may be conflicting needs or poor communication between different elements of the microgrid. In this work, a robust frame associated with a quantum version of the Teaching-Learning-Based Optimization (quantum TLBO) algorithm is proposed for the first time to the microgrid optimal energy management problem. Uncertainties in the load and in the output power of renewable energy sources are modeled using robust optimization (RO). The operation cost of the... 

Nowadays electricity power has a key role in developing various aspects of the world. The great importance of fossil fuel power plants come from their large contribution in electricity power generation. Among the different fossil fuel power generation technologies, supercritical power plants have great advantages. They are an advanced power generation technology with high plant efficiency, high coal utilization and low emission. Their complexity and existing many unavoidable uncertainty sources in their dynamic such as changes of ambient temperature, climate condition and wear of components make their control challenging. To overcome mentioned problems and achieving a good performance, a... 

The relationship between art and philosophy has been disputed for a long time and its history goes back to the ancient Greece. The dominant literary form at that time was poetry or tragedy, which are the first side of this relationship. On the other side was philosophical ethics. Plato and Aristotle are the main protagonists in this quarrel, which is known as the "Ancient Quarrel". I will first examine this quarrel and follow its different forms in the modern era, in which Hegel plays a prominent role by proposing the "end of art" thesis. By examining the criticisms made to this thesis, I will make clear the context in which the contemporary defenses that I explained in the following... 

Expert finding is an important task in community question answering (CQA) websites, enabling the routing of new questions towards users who have the highest level of expertise in the relevant topic. This method helps question raisers receive satisfactory responses in a shorter time and makes it easier for answerers to find questions they are interested in and have enough expertise to answer. . The primary goal in expert finding is to learn the representation of questions and expert candidates based on the history of answered questions. Many existing approaches generate a unique representation for users without considering the specific question asked. Additionally, many of these approaches...