Sharif Digital Repository

Recent widespread blackouts around the world have highlighted the fact that power grids must not only ensure reliability against high-probability, low-impact events (HPLI), but also against low-probability, high-impact events (HILP) such as earthquakes, hurricanes, and hurricanes and resist against unnatural events such as cyber attacks. On the other hand, transformation of traditional electricity distribution systems into smart networks that have the ability to automatically perform switching and fault locating can enable utilities to minimize operational costs in case of HILP events occurences. Although the use of distribution automation has been suggested as one of the smart grid... 

Recognizing people mentioned in the text of narrations, is of the main importance in validating narrations in narration analysis. The problem naturally reduces to two sub-problems: Firstly, named entities related to narrators in the text should be determined. Secondly, if they are ambigous, the purpose of each should be clearified. In this resaerch, it is tried to apply pre-trained language models in soultion of the first sub-problem. For the purpose of entity linking with entities in a KB, graph-based model is suggested  

Polymer composites, due to its exclusive properties, has a special place in industry. Epoxy resin with high adhesion property, low density, thermal stability and high chemical resistance has a special place as matrix in fabrication of high technology hybrid composites. Hybrid composites, due to its high strength and long fatigue life, used to reinforcing building structures and manufacturing fuselage. Layer and reactive structure near the firm core and wear-resistant of NDs, used to improvement of epoxy reisn and hybrid NanoComposite interphase properties. In this study, for improvement of the properties of hybrid NanoComposites, used the NDs in 0.25, 0.5 and 1 %wt with amine and carboxyl... 

Flow characteristics analysis over a wing, is one of the pioneer challenges in super and sub-sonic flow near flying objects. Taking into account of growing rate of low aspect ratio utilization, usually called Delta wings, investigation of vortex behavior over this wings is highly noticeable. In addition, the lack of research in this branch of Aerodynamics inside the country, considering it’s critical application, has doubled the importance of doing research in this filled. Experimental researches on super-sonic flow over a Delta wing is limited and there are not much accurate researches about vortexes in this category of wings. In this work, the main effort is to investigate the phenomena in... 

In recent years, a series of deep connections have been found between the ideas that used to be in the Algebraic Theory of Quantum Fields and the important problems of High Energy and Fundamental Physics. In the 1960s and later, some people who were mostly closer to mathematicians were trying to formulate the basics and principles of Quantum Field Theory in mathematically precise way. Many and various efforts have been made in this direction. One of these important efforts has been the Algebraic Theory of Quantum Fields. The main motivation in the Algebraic Theory of Quantum Fields is to focus on the operators and observables of the theory and study the algebraic structure between them instead... 

Morphology and alignment of endothelial cells (ECs) have great influence on plaque formation. These alignments are based on the cyclic strains and wall shear stress (WSS) on the arterial wall. In the present study, cyclic strains and WSS are investigated to predict the secondary plaque locations downstream of the primary stenosis. Therefore, left coronary artery (LCA) with its branches to left anterior descending (LAD) and left circumflex (LCX) are 3D located on a virtual sphere to consider the cardiac motion. Stenoses are placed at the beginning of the bifurcation with varying degrees from 40% to 70% based on diameter reduction. Healthy coronary is also constructed to compare with those of... 

The thesis opens with a discussion of the distinction between some of the classical and the constructive notions in mathematical analysis. There then follows a description of the three main varieties of modern constructive mathematics: Bishop’s constructive mathematics, the recursive constructive mathematics of the Russian School, and Brouwer’s intuitionistic mathematics. The main purpose of the thesis is to prove the independence, relative to Bishop’s constructive mathematics, of each of the following statements:There exists a bounded, point-wise continuous map of [0, 1] into R that is not Lebesgue measurable.If µis a positive measure on a locally compact space, then every real-valued map... 

In this study، a novel frequency multiplier chain for wideband millimeter-wave applications at 28 GHz is presented. Millimeter-wave imaging systems require high frequency and wide bandwidth to accurately detect hidden objects. Various methods have been proposed to increase the frequency of generated signals, but in the meantime، frequency multiplier structures exhibit better performance in terms of bandwidth، power consumption and, harmonic rejection. These circuits are widely used in High-frequency telecommunication systems such as 5th generation mobile services. To design a frequency quadrupler، two multiplier stages based on the improved quadrature Gilbert structure were used. Generating... 

Breast cancer is one of the most common cancer types and is the leading cause of cancerrelated death among females according to American Cancer Society statistics. Breast screening and early detection is the most effective method of management and treatment of this disease. Currently, several imaging systems for breast cancer detection are being used among which microwave imaging has caught the attention of many as a promising tool for early breast cancer detection. Microwave imaging is considered as a non-invasive, relatively low-cost, Fast, convenient, and safe method for breast cancer screening. this research aims to implement a 3D imaging system that operates based on the microwave... 

In this thesis, a low-power low-phase-noise 28 GHz voltage-controlled oscillator for 5G applications is presented. At first, to select the best structure in terms of FoM, various types of inductors and transformers have been designed and EM simulated. The class-C structure which leads to the highest FoM is chosen eventually. In order to increase oscillation amplitude and reduce phase noise while preserving FoM, a high-frequency noise filter is presented. This filter which is based on a λ/8 microstrip transmission line has solved the conventional filter problems e.g. narrow bandwidth, coupling with oscillator inductor and practical implementation issues.The oscillator is designed, EM... 

In this thesis, the design of a fully-integrated Millimeter-wave Broadband power amplifier in TSMC 0.18 µm CMOS technology is studied. The Darlington cell with cascode topology was adopted as the power cell to improve the maximum available gain of transistors in standard 0.18 µm CMOS technology to make it eligible of operating at Ka band. Furthermore, by proposing a new topology as an improved Darlington-cascode with intermediate inductor in the Darlington pair, the improvement in flat power gain at Ka band and more importantly, in available power gain of active element at high frequencies of the Ka band is achieved. The proposed power amplifier is a two stage structure with the driver stage... 

The blood pressure (BP) is one of the most vital signs to monitor human health. Hypertension is a major public health problem that is associated with morbidity and mortality. In the past decades, the number of people with hypertension disease has been increased. According to Ministry of Health, 54 percent of hypertensive patients are unaware of this health threat. Therefore, accurate and continuous measurement of BP is essential for its prevention and treatment. Traditional non-invasive methods of BP monitoring use an inflatable cuff, which causes discomfort due to occlusion of the artery and can not be used continuously. Numerous studies have attempted to present methods without using a... 

In this study, we present the front end of receiving end of an ultra-wideband imaging system designed for mobile users, operating within the 10 to 20 GHz frequency range with a 10 GHz bandwidth. The choice of this specific frequency and bandwidth aims to achieve the requisite range and lateral resolution for desired imaging outcomes. Additionally, the selection of this frequency band is motivated by its favorable performance in various weather conditions and its non-ionizing nature within the microwave spectrum, prioritizing human health in the research endeavor.Despite the advantageous characteristics associated with this frequency band, designing within such a broad bandwidth and frequency... 

Automatic classification of different sleep stages is an important and challenging research topic in the field of biomedical signal processing. The methods proposed so far for this purpose have been based on multi-channel physiological signals such as electroencephalogram , electrooculogram, and electromyogram . These signals can provide valuable information about the individual's sleep pattern and stages, but their use in a home environment is limited due to the need for complex equipment and specialized skills. Therefore, the development of a sleep stage classification method based on a single-channel signal that can achieve this goal with high accuracy without the need for complex... 

Design of a 28GHz phased array receiver front-end for 5G applications in CMOS 0.18um technology in the frequency band from 27.5 to 28.3 GHz is presented in this thesis. We use an RF phase shifting structure which consists of a low-noise amplifier, a phase shifter and a power combiner. The low-noise amplifier is designed using common-source cascode topology with a transformer-based gm-boosting technique in order to enhance the power gain and reduce the noise figure. A vector sum phase shifter is then designed to further enhance the gain. A Wilkinson power combiner with lumped elements is designed as the power combiner. The results of simulating a single RX chain shows a maximum of 15 dB... 

Power harvesters are used to generate energy for electronic devices. These electrical energy generators consist of three main parts: energy source, power electronic converter and energy storage. In order to minimize some of the weaknesses of these devices, including low power density and low reliability, the hybrid power harvesting method can be utilized. In this thesis, we design and build a hybrid energy harvester considering the advantages of simultaneous usage of solar and thermal energies for a wearable sensor, focusing on "efficiency enhancement" and "availability improvement". In the designed device, both solar and thermal energy harvesting units operate independently. In the solar... 

On the demand of higher directivity, higher throughput and less interference, phased array systems and MIMO have become attractive to reach these goals. The advantages of phased array systems include the ability to perform electronic beam steering and arbitrary pattern synthesis. Phase shifters and variable gain amplifiers are used to reach these advantages. In this thesis, a ‘’ C‘’ band (4.8 GHz-6.2 GHz) vector-sum phase shifter using HMIC technology for realizing a phased array receiver is designed. This phase shifter can change the signal phase and amplitude. The main blocks of this phase shifter are low-insertion phase and low-noise variable gain amplifier, which consists of current... 

Reliability in today's world plays a pivotal role. As technology makes progress in various industries such as aviation and defense, the need for high reliability of systems is felt more and more. In this regard, reliability is directly related to the lives of people, and its high level can play a significant role in the profitability of organizations. Selective Maintenance, as one of the research areas in the field of reliability optimization, strives to enhance the reliability of the system and minimize the costs of the system by finding optimal maintenance policy. In the models that have been presented to optimize the selective maintenance policy, the assumption that the repair cost of... 

The main purpose of this research was functionalizing graphene, in order to achieve higher hydrophobicity, and producing nanocomposite of functionalized graphene and titanium dioxide by hydrothermal method, and sequently invastigation on photocatalytic properties of the powders and corrosion properties of EPD coated samples. Graphene oxide was synthesized by improved Hummers method and reduced and sequently was functionalized through the chemical process with hydrazine and octadecylamine respectively. Then the nanocomposite of functionalized graphene-titania was synthesized by use of titanium isopropoxide precursor and its photocatalytic properties were measured. The analysis of the...