Sharif Digital Repository

The following thesis is concerned with the effect of channel feedback in tracking and stability of linear Gaussian systems over Additive White Gaussian Noise (AWGN) channel when the decoder is the Kalman filter and encoder is the innovation encoder. When the feedback channel is described by a noisy link or a random switch, it is shown that stability is not possible for unstable systems. But for stable systems, an innovation encoder, Kalman filter decoder and a certainly equivalent controller for tracking and stability are presented. When the feedback channel is described by a deterministic switch, for both stable and unstable systems, an innovation encoder, Kalman filter decoder and a... 

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... 

Inlet air cooling is a simple and economical method to increase the power output of gas turbines. High-pressure fogging systems and mechanical chillers are two common methods. High water consumption, damage to compressor blades by water droplets, and inefficiency in humid climates are disadvantages of high-pressure fogging systems. Mechanical chillers have high electricity consumption and initial costs. In this research, an earth-to-air heat exchanger (EAHE) is introduced as a new method for inlet air cooling of gas turbines and is technically and economically compared with the two common methods in the long term in the climate of Tehran city. Temperature distribution in the ground is... 

Carbon dioxide is one of the main geenhouse gases emitted from factories as well as transportation vehicles that adversely affect the atmosphere and cause global warming. Among the proposed solutions to reduce carbon dioxide in the atmosphere, carbon dioxide separation would be the most viable medium-term approach. However, the high cost of carbon dioxide separation prevents the development of carbon dioxide absorption technologies. Therefore, it seems that integrating separation and production processes is the most efficient way to save energy and reduce carbon emissions. This method decrease a high proportion of the energy consumption in upstream operations (carbon dioxide removal,... 

In this thesis, we study and analyze the performance of matched and partially-matched re-ceivers for a typical Ultra Wide-band Spectrally-Encoded Spread-Time (SE/ST) CDMA in the presence of multiple tone jammers and a coexisting OFDM system. We investigate a scenario in which there is not any information about the jammer and OFDM subcarrier frequencies in the transmitter side and we try to cancel jammers and interferences at the receiver. For this case, we demonstrate that by using a partially-matched filter at the receiver in an environment with multiple tone jammers and some coexisting systems the performance of the SE/ST system can be improved. We also assume K asynchronous users and... 

Increasing need to high rates of transmission through radio channels is a challenging problem in wireless communications. Simple implementation and high spectral efficiency of OFDM system turned it into a suitable choice to meet this need. Accurate estimation of the communication channel has a significant impact on performance of Orthogonal Frequency Division Multiplexing (OFDM) systems. Conventional methods of channel estimation are not able to exploit the inherent sparsity of the channel that is due to sparse distribution of scaterrers. On the other hand, Compressed Sensing (CS) is getting attention in variety of aspects such as communications, recently.CS-based channel estimation exploits... 

By direct and alternating electric field applied to thin film of liquid suspended in the air we can spin out and control it. Rotation pattern depends on the geometry of the electrodes and the applied magnetic field. This is called a rotating liquid film (Liquid Film Motor). To determine the cause of rotation, different models have been proposed. In this project we have tried to check the accuracy of any of the models. Using particle velocimetry using the photo, we calculate the velocity pattern. Then, using the Navier-Stokes equation calculate the acceleration and viscosity from the velocity. Then, for a special arrangement using a finite diffrent method, electric potential and the electric... 

Synthetic Aperture Radar (SAR) is a coherent imaging technique capable of generating fine resolution images from long term standoff ranges, either day or night. The use of multiple antennas for SAR is referred to as multichannel SAR or Multiple-Input Multiple-Output(MIMO) SAR and offers the additional abilities to perform height estimation of the ground, improve the resolution and suppress undesired interferences. Ground moving target indication (GMTI) is the one that we explored in this research. Since the pattern of moving target in imaging zone is sparse, we can use compressed sensing for reducing computational complexity caused by additional channels. In our thesis, after modelling the... 

Achieving various data rates over a wide range of applications and in a multiple-access scenario should be done under certain power and bandwidth constraints. Emerging UWB communications has opened a novel perspective against different wireless network challenges, especially overwhelming data rates. In the research field, we begin our thesis with exposition of UWB, narrowband interference and spread time codes. We elaborate on the properties of spread time codes through frequency domain analysis of a reusable multiple-access scheme. Evaluating the variance of ISI, MAI and RUI, we demonstrate the spread time codes behave in an optimum manner, i.e., the most RUI resistibility, along with all... 

The present study, which is about practical methods of improving productivity in Mashhad ring factory, is presented in five chapters. In the foreword, the need for an attitude to improve productivity at the national level as well as in industry has been mentioned and has laid the groundwork for starting a discussion of productivity and practical solutions to improve it. In the first chapter, by defining productivity, considers the different perceptions of societies about productivity and finally deals with misconceptions about the concept of productivity. In the second chapter, based on committed articles from the American Society of Industrial Engineering, discusses the role of industrial... 

The present study was an endeavor to investigate the effectiveness of English full and keyword captions in comparison to Farsi full and keyword subtitles and no caption with regard to English language learners’ listening comprehension and incidental vocabulary acquisition. For this purpose, 76 English as a foreign language (EFL) learners at Sharif University of Technology from five intact classes were assigned to each condition. Preliminary English test was administered to measure learners’ listening performance before and after the treatment. Researcher-made vocabulary tests based on the difficult words that were captioned in the videos were included in vocabulary tests. The treatment...