Sharif Digital Repository

Nowadays functionally graded materials have many applications in various industries. One of these applications can be the manufacturing of thick-walled vessels. Thick-walled vessels under internal pressure and high temperatures gradient require materials with higher strength, like Functionally Graded Materials (FGM) and can be reinforced by some mechanical processes like autofrettage. In this process under certain loading some part of vessels enters into plastic zone and upon unloading some residual stresses will be generated. Moreover it is very important to find out the depth of this plastic zone, In addition, minimizing the stress distribution vs. depth of plastic zone under applied... 

To provide a stable foundation for human knowledge Descartes presumed that human being is composed of two distinct substances, the mind and the body. But, the solution through which he wanted to explain the correlation between these substances, was not accepted by other philosophers, and thereafter this problem was known as mind-body problem. This problem arises some other philosophical problems including solipsism and the problem of other minds. In this thesis, considering the grammar of such words like memory, understanding, and thinking I will show that having an exact description of these concepts we would be able to escape from these inclination to seek something behind these words, and... 

In Radiation Detection Systems applied in Spectroscopy and Imaging, if the rate of particle incidence with detector is high, the output pulses being stacked up on each other will be expected, which is known as “Pulse Pile-up”. Pulse pile-up might result in a serious disorder of energy and timing data expected from the pulses. In recent decades and after successful implementation of pile-up rejection methods on analog circuits, considering development and progression in the field of digital, different algorithms based on pileup correction methods have been developed to obtain all spectrum information, whether energy, rise time and recorded pulses. Such methods can be compared in different... 

The subject of this study is design of a linear quadratic Gaussian controller based on identification of dynamic behavior of unmanned model helicopter “Raptor” in its hover flight. To achieve this end, first, the helicopter linear transfer functions are identified with frequency response method by applying specific inputs to the model of Raptor in the X-Plane software and receiving system outputs via Simulink. Next, using the identified dynamic model of the helicopter, an optimum linear controller is designed for hover flight. As an optimum linear controller needs all the state variables, a Kalman filter is utilized to estimate them, using outputs of various sonsors such as GPS and gyro.... 

The problem of separation of audio sources is one of the oldest issues raised in the field of audio processing, which has been studied for more than half a century. The main focus of recent research in this field has been on improving the sound quality resulting from the separation of sound sources with the help of deep neural networks. This is despite the fact that in most applications of audio source separation, such as the application of meeting transcription, we do not need the separated audio of people. Rather, we need a pipeline of converting overlapping speech to text, which, by receiving the audio in which several people have spoken, outputs the text spoken by the people present in... 

Radio Frequency IDentification (RFID) is an increasingly important area in automatic identification. Low cost RFID tags (labels) are considered as the next generation of barcodes and their purpose is to compensate for shortcomings in computer recognition of objects using cameras. Supply chain management, access control, animal identification,e-passports along with the possibility of having e-health, e-agriculture and smart homes are few examples of RFID application developments. Despite its low cost, ubiquity, and widespread usage, RFID tags suffer from several major drawbacks, particularly information leakage and traceability. In RFID authentication protocols, both information leakage and... 

Convolutional Neural Networks are a kind of neural network applicable in machine vision and image processing. The accuracy of these networks is dependent on different features such as network size network and input size. Today, researchers are improving the accuracy of neural networks by increasing their size. As a result, networks' computation will increase as well. The bigger the size of the neural network, the harder its hardware implementation. One of the proposed solutions to overcome this issue is to change the number representation while preserving the network accuracy. It's challenging to implement floating-point computation on hardware as it consumes a high amount of power and... 

Hot deformation behavior of Al-SiC nanocomposites was investigated in this study. Aluminum powders with mean size of 60 micron and SiC nanopowders (mean size of 45nm) in amounts of 1 and 2 volume percents, as reinforced part, were mixed and milled for 40 hours by planetary ball mill. After degassing at 450 oC for 1 hour, milled powders were pressed into Aluminum cans (in Argon atmosphere) and then hot extruded. Extrusion ratio was 1:14. High density billets (with 98% of theoretical density) were produced because of that high extrusion ratio. TEM microstructure studies showed that fine distribution of reinforcements and Aluminum Oxides obtained via this procedure. Hardness and Uniaxial... 

Electrical substations and its vital components such as switchgears, have experienced severe damage during recent earthquakes, followed by widespread blackouts around the world. To improve the seismic resiliency of power grids and use probabilistic decision-making frameworks, comprehensive fragility data for the different equipment is needed. The purpose of this study is to assess the vulnerability of equipment in substations and to develop fragility curves for this equipment. For this purpose, four main equipment of switchgear, namely circuit breaker, disconnect switch, current transformer and surge arrester, have been modeled in three dimensions and verified. After examining the different...