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A more accurate prediction of liquid evaporation flux
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 23, Issue 2 , 2004 , Pages 45-53 ; 10219986 (ISSN) ; Sabzyan, H ; Zeini Isfahani, A ; Parsafar, G ; Sharif University of Technology
Iranian Journal of Chemistry and Chemical Engineering
2004
Abstract
In this work, a more accurate prediction of liquid evaporation flux has been achieved. The statistical rate theory approach, which is recently introduced by Ward and Fang and exact estimation of vapor pressure in the layer adjacent to the liquid-vapor interface have been used for prediction of this flux. Firstly, the existence of an equilibrium layer adjacent to the liquid-vapor interface is considered and the vapor pressure in this layer and its thickness calculated. Subsequently, by using the Fick's second law, an appropriate vapor pressure expression for the pressure of equilibrium layer is derived and by this expression and the statistical rate theory approach, evaporation flux is...
Comparison of the Maximum Likelihood Ratio Detectors with the Hough Detectors in RADAR Detection Applications
, M.Sc. Thesis Sharif University of Technology ; Nayebi, Mohammd Mahdi (Supervisor)
Abstract
In this work, Hough detector has been compared with optimum detectors. We consider 2-D range-time data space, which is constructed by storing the radar returns from different range cells during several successive scans. In this space, target trajectory can be modeled as a straight line for short time intervals, and can be extracted by applying Hough transform transcendentally. In this work, a new detection method based on the likelihood ratio in the data space with Gaussian noise is introduced. ALR and GLR processors have been designed. Then formulas for probability of detection and false alarm rate is calculated, and verified via simulations. A new criterion for estimation quality is...
An optimum pre-filter for ICA based multi-input multi-output OFDM system
, Article International Journal of Innovative Computing, Information and Control ; Volume 7, Issue 6 , June , 2011 , Pages 3499-3508 ; 13494198 (ISSN) ; Asharif, M. R ; Khosravi, M ; Yamashita, K ; Sharif University of Technology
2011
Abstract
This paper presents an optimum pre-filter for ICA based multi-input multi-output OFDM system. In our former work, we presented a pre-filter solution for multiuser reconstruction in ICA based MIMO-OFDM systems [1,2]. Here, based on the structure of the system and former pre-filter solution, an optimization problem has been designed to give us the optimum pre-filter. The designed problem is based on minimization of the estimation error of ambiguities inherent to ICA in reconstruction of the data after separation. The optimization problem is mathematically solved and a set of optimized coefficients are obtained. Among the obtained set as optimum coefficients, optimum coefficients are acquired...
An optimum pre-filter for ICA based mulit-input multi-output OFDM system
, Article ICETC 2010 - 2nd International Conference on Education Technology and Computer, 22 June 2010 through 24 June 2010 ; Volume 5 , 2010 , Pages V5129-V5133 ; 9781424463688 (ISBN) ; Alsharif, M. R ; Khosravi, M ; Yamashita, K ; Sharif University of Technology
2010
Abstract
This paper presents an Optimum pre-filter for ICA based mulit-input multi-output OFDM System. In our former work, we presented a pre-filter solution for multiuser reconstruction in ICA based MIMO-OFDM systems [1], [2]. Here, based on the structure of the system and former prefilter solution, an optimization problem has been designed to give us the optimum pre-filter. The designed problem is based on minimization of the estimation error of ambiguities inherent to ICA in reconstruction of the data after separation. The optimization problem is mathematically solved and a set of optimized coefficients are obtained. Among the obtained set as optimum coefficients, optimum coefficients are acquired...
Effect of the shear loading direction on shear behavior of rock and finding new empirical method for determining JRC by fractal dimension
, Article Annual Conference of the Canadian Society for Civil Engineering 2007: Where the Road Ends, Ingenuity Begins, Yellowknife, NT, 6 June 2007 through 9 June 2007 ; Volume 1 , 2007 , Pages 259-267 ; Sadaghiani, M. H ; Askari, M ; Khosravi, M ; Sharif University of Technology
2007
Abstract
Effect of different conditions on shear behaviour of rock has been investigated by various researchers. As known, in larger scale the continuity of the rock material is interrupted by separated planes such as bedding planes, faults, shear zones, closure and the behaviour converts to be inelastic and anisotropic. Generally, discontinuities appear repeatedly in more than one preferential direction, creating a three dimensional structure, reducing its stiffness and shear strength as mechanical effects and increasing its transport velocity associated with discontinuity flow as hydraulic effects. They also make rock behavior more complex and different compared to the behavior of soil. According...
Experimental Studies and Finite Element Analysis of Polymer Nanocomposites Reinforced with Graphene Sheets under Impact Loading
, M.Sc. Thesis Sharif University of Technology ; Naghdabadi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor)
Abstract
In the experimental approach, graphene and Graphene Oxide (GO) were synthesized through a chemical method. In order to study the quality of GO, characterization tests were performed. Then, reinforced polymer with GO and graphene was made. Moreover, tension, compression and Split- Hopkinson pressure bar tests were performed on standard samples of reinforced polymer nanocomposite. The experimental data show that nanoparticles have a destructive effect in very low and high percentages for extension test as well as in high percentages for compression test. On the other hand, graphene is more effective than GO on improving material properties. Furthermore, comparison of compression results in...
Nonlinear Filters Applied to Tightly Coupled Integration of INS/GPS/PL for Precise Navigation in Automatic Landing of UAVs
, M.Sc. Thesis Sharif University of Technology ; Nobahari, Hadi (Supervisor) ; Ghanbarpour Asl, Habib (Supervisor)
Abstract
One of the most dangerous phases of the flight is landing. Newly automatic landing is noticed. The vital element in an automatic landing system is navigation system. In this document, a PL/INS/DGPS auto landing system is introduced.In a PL based navigation system, accuracy is highly under the influence of relative geometry between PLs position and flight path. Therefore, it is necessary to locate PLs on the best position. An optimization is used to find PLs best configuration that increases the navigation performance. Tightly coupling of INS and GPS/PL is preferred, because some problems lead to GPS satellite signal unavailability
Including Facilities in an Embedded Processor for External Watchdog Processors
, M.Sc. Thesis Sharif University of Technology ; Miremadi, Ghassem (Supervisor)
Abstract
The wide range of embedded processors and their reliance on nano-scale technologyhave brought them serious concerns on reliability, power consumption, timeliness and cost. Therefore, theseconcernsmust be addressed at the design process withemploying minimum facilities.This thesis proposes a low-cost concurrent error detection method based on control flow checking suitable for embedded processors. Most of the previous control flow checking methods either do not consider the embedded processors concerns, or they are not applicable to processors with on-chip cache memories.The key idea behind the proposed control flow checking method is to embed specific hardware components in the IP core of an...
Performance Evaluation of MANET’s IDSs Using Stochastic Activity Networks (SANs)
, M.Sc. Thesis Sharif University of Technology ; Movaghar, Ali (Supervisor)
Abstract
Blackhole and grayhole attacks have been become two of the major security concerns in mobile ad hoc networks (MANET). To achieve security in MANETs, a lot of mechanisms had been proposed by now. Using intrusion detection systems(IDSs) is one of the important mechanism to reach this goal. Thus, a well-known IDS was chosen and analyzed in this thesis. Furthermore, a collaborative bayesian filter approach for this intrusion detection system was proposed to enhance its performance. Then the performance of this approach was considered. This intrusion detection system was analyzed using stochastic modeling like continuous time markov chain(CTMC), stochastic reward net(SRN) and stochastic...
Joint Pilot Power & Pattern Design for Compressive OFDM Channel Estimation
, M.Sc. Thesis Sharif University of Technology ; Mashhadi, Saeed (Supervisor)
Abstract
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...
Modelling and Prediction Air Polutants Level in Tehran Using Dynamic Neural Networks
, M.Sc. Thesis Sharif University of Technology ; Erhami, Mohammad (Supervisor)
Abstract
In parallel to the growing of population in Tehran metropolitan, air pollution in this city has become to a major problem. From which high concentration of pollutants have adverse effects on public health, accurate estimating and forecasting of concentrations for several days ahead, can provide the possibility to implement the management measures to reduce hazard and risks. Among the air pollution models, application of statistic models based on neural network in comparison to the traditional deterministic models are easier and less costly. In most studies, static models use a classical single MLP to predict one step ahead. For this purpose ANN models are required to estimate next value of...
Impact of Hydraulic Hysteresis on Hydro-mechanical Behaviour of Infilled Fractured Rocks in Unsaturated Condition
, M.Sc. Thesis Sharif University of Technology ; Khosravi, Ali (Supervisor)
Abstract
Recent studies have shown that comprehensive characterization of the behavior of infilled rock fractures under saturated and unsaturated conditions requires knowledge of morphological details of fracture surface, as well as state of stress of infill materials and their initial innate conditions (e.g., void ratio, water content, degree of saturation and dry density). This study presents the details and typical results from a new testing approach to study the hydro-mechanical behavior of the infilled rock fractures under different stress states and saturation conditions. The new testing approach incorporates the axis translation technique for suction control, a flow pump for the measurement of...
A Semi-Emperical Model for Small Starin Shear Modulus of Unsaturated Low Plasticity Soils
, M.Sc. Thesis Sharif University of Technology ; Khosravi, Ali (Supervisor)
Abstract
The shear modulus of soils is a key material quantity which is frequently used in the evaluation of wave propagation through soil layers in dynamic response analyses for many geotechnical systems. The shear modulus, G, is defined as the slope of the shear stress-strain hysteresis loop and is significantly influenced by the shear strain amplitude induced in a soil specimen. Of particular interest in geotechnical engineering, the value of shear modulus for strains less than 10-6 defined as the small strain shear modulus, Gmax. The early experimental studies on the shear modulus of water-saturated or dry soil showed that shear modulus is highly dependent on mean effective sress, p´, and void...
Characterizing the Impact of Void Ratio and Stress Path on the Small Strain Shear Modulus of Unsaturated Silt
, M.Sc. Thesis Sharif University of Technology ; Khosravi, Ali (Supervisor)
Abstract
Early efforts in soil dynamics have shown that the analysis of soil behavior under cyclic or random loading conditions is highly dependent on some representative material properties, the dynamic shear modulus, the Poisson’s ratio, and the damping ratio. Of particular interest is the value of dynamic shear modulus for strains less than 10-6 defined as the maximum or small strain shear modulus Gmax. Improvements in experimental unsaturated soil mechanics have led to the definition of trends between Gmax with different parameters most notably unsaturated stress state, degree of saturation and void ratio. However, the tests in these studies were mostly conducted on specimens experiencing...
Analysis of Dimensions, Objective and Implementation of Knowledge Management in Production Institutes
, M.Sc. Thesis Sharif University of Technology ; Mostafavi, Mostafa (Supervisor)
Abstract
The increasing significance and deployment of knowledge management(KM) is the main reason for selecting the topic of this research. This research tries to analyse the dimensions and KM implementation methods in press section of maintenance department in Saipa company. This study has a qualitative approach and the method is based on a case study. Data has been collected by questionnaires. Two questionnares have been provided in this research and distributed among different staff of press section in maintenance department. The concept of knowledge management maturity is applied and the goal of first questionnaire is based on this concept. The level of KM maturity is assessed via this...
Joint pilot power and pattern design for compressive OFDM channel estimation
, Article IEEE Communications Letters ; Volume 19, Issue 1 , November , 2015 , Pages 50-53 ; 10897798 (ISSN) ; Mashhadi, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
This letter investigates the deterministic design of pilot power and pattern for sparse channel estimation in OFDM systems based on minimizing the coherence of the DFT sub-matrix. It has been suggested that the pilot pattern forming a cyclic difference set (CDS) or almost difference set (ADS) is optimal. So, we proposed a deterministic procedure that jointly optimized for pattern and power of pilots as a solution. First, pilot patterns forming CDS/ADS were gathered through a search. Then, the power was numerically allocated to the different pilots from all the patterns. Finally, the pilot pattern and power pair leading to minimum coherence was selected from the available pairs. Simulation...
Soil-structure Interaction in Geothermal Foundations
, M.Sc. Thesis Sharif University of Technology ; Khosravi, Ali (Supervisor)
Abstract
Regarding the issue that significant amount of energy consumption in the world is dedicated to heating and cooling of the buildings, by using traditional methods of heating and cooling, the environment is facing serious problems like green house gases. There were various techniques for decreasing the amount of contaminants stem from this process. Heat-exchanger energy piles are one of the most common methods that will result in economic usage of energy resources. Assessing the long-term behavior of the energy piles requires comprehensive understanding of the complex interaction between soil and pile subjected to mechanical and thermal loadings. Several numerical and analytical methods have...
Impact of Net Stress on Stress State of an Unsaturated Sand
, M.Sc. Thesis Sharif University of Technology ; Khosravi, Ali (Supervisor)
Abstract
Results of an advanced suction controlled triaxial test device in an attempt to define the constitutive relationship between suction stress and matric suction (Suction Stress Characteristic Curve, SSCC) for unsaturated sand was presented. The suction stress is a macroscopic stress that incorporates the effects of capillary van der Waals forces cementation, and electrical double-layer repulsion into the definition of effective stress for unsaturated soils. Results of previous studies on silt and clay indicated that variations in the suction stress, during drying path had a non-linear increasing trend with matric suction with greater values upon wetting. However, due to different material...
The Physical Modeling and Analysis of Seismic Soil-Pile Interaction in Unsaturated Sand Using Geotechincal Centrifuge
, M.Sc. Thesis Sharif University of Technology ; Khosravi, Ali (Supervisor)
Abstract
The seismic behavior of pile-supported systems has been an active area of research over the past decades. However, focus has mostly been on evaluating the seismic response of structures embedded in either dry or fully saturated, especially liquefying soil conditions. In this study, a series of dynamic centrifuge tests have been conducted to investigate the effects of soil’s degree of saturation on the seismic behavior of pile-supported superstructures. The scaled physical model tests were carried out on two distinct pile-mass systems embedded in uniform sand layers. A steady state infiltration technique was used to control matric suction profiles in the sand layer prior to shaking. The...
Quantum Cryptanalysis of SPN Block ciphers
, M.Sc. Thesis Sharif University of Technology ; Eghlidos, Taraneh (Supervisor)
Abstract
Quantum computers can be used to process complex computations much more efficient than their classical counterparts. Cryptanalysis of classical ciphers is no exception to this rule. Most quantum cryptanalysis of symmetric ciphers is based on finding the periodicity, linear structure, and confidential information of the target algorithm. In this thesis, assuming that the attacker has access to the quantum computer, we propose a quantum method for deriving the appropriate differential characteristic of block ciphers, using Simon's quantum algorithm. It is worth noting that, unlike classical methods, where increasing the number of rounds of the target block cipher increases the complexity of...