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Spread-time/time-hopping UWB CDMA communication
, Article IEEE International Symposium on Communications and Information Technologies: Smart Info-Media Systems, ISCIT 2004, Sapporo, 26 October 2004 through 29 October 2004 ; Volume 2 , 2004 , Pages 1047-1050 ; 0780385934 (ISBN) ; Salehi, J. A ; Sharif University of Technology
2004
Abstract
The use of Spread-Time CDMA for ultrawideband (UWB) wireless communication is proposed and its capability for supporting many high data rate users is investigated. Furthermore we will study a hybrid technique, namely, Spread-Time/Time-Hopping to increase the capacity of the above mentioned technique and simultaneously minimizing the effect of near-far in a typical CDMA system
Design and implementation of a predictive controller for reducing the torque ripple in direct torque control based high frequency induction motor drives
, Article 2004 IEEE 35th Annual Power Electronics Specialists Conference, PESC04, Aachen, 20 June 2004 through 25 June 2004 ; Volume 2 , 2004 , Pages 1169-1174 ; 02759306 (ISSN) ; Zolghadri, M. R ; Roye, D ; Guiraud, J ; Schanen, J. L ; Sharif University of Technology
2004
Abstract
In Direct Torque Control, selection of each voltage vector is based on the measured parameters in the beginning of the sampling period. Due to the fast dynamic of torque, this delay causes an extra torque ripple. In this paper, a new predictive controller is proposed for compensating this delay and reducing the torque ripple. The stator current is measured in the beginning of each sampling period and its expected value in the end of period is predicted according to an extrapolation algorithm. This algorithm is performed by calculating the slope of stator current variation according to the stator flux variation. Thus, there is no need to solve the high order equations of machine. The...
Design and implementation of a predictive controller for reducing the torque ripple in direct torque control based induction motor drives
, Article 2004 IEEE 35th Annual Power Electronics Specialists Conference, PESC04, Aachen, 20 June 2004 through 25 June 2004 ; Volume 1 , 2004 , Pages 476-481 ; 02759306 (ISSN) ; Zolghadri, M. R ; Roye, D ; Guiraud, J ; Crebier, J. C ; Sharif University of Technology
2004
Abstract
In Direct Torque Control, selection of each voltage vector is based on the measured parameters in the beginning of the sampling period. Due to the fast dynamic of torque, this delay causes an extra torque ripple. In this paper, a new predictive controller is proposed for compensating this delay and reducing the torque ripple. The stator current is measured two times at the beginning of each sampling period and its expected value at the end of period is predicted according to an extrapolation algorithm. Thus, there is no need to machine parameters and the algorithm is quite robust against machine parameters variations. The calculation of the electromagnetic torque is performed using the...
The fractal array and the fibonnaci sierpinski gasket
, Article IEEE Antennas and Propagation Society Symposium 2004 Digest held in Conjunction with: USNC/URSI National Radio Science Meeting, Monterey, CA, 20 June 2004 through 25 June 2004 ; Volume 2 , 2004 , Pages 1291-1294 ; 02724693 (ISSN) ; Toghraee, R ; Salimi, K ; Sharif University of Technology
2004
Abstract
We have constructed the Koch array factor using decomposition of the array factor and solving it with matrix methods, rather than regular inverse Fourier transform method. With the aid of non-uniform sampling we have made some improvements in the main beam while the array elements are reduced significantly. We have also consider the Fibonnaci Sierpinski gasket
A novel demodulation technique for recovering PPM signals in the presence of additive noise
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) ; Volume 3124 , 2004 , Pages 541-547 ; 03029743 (ISSN); 3540225714 (ISBN); 9783540225713 (ISBN) ; Marvasti, F ; Sharif University of Technology
Springer Verlag
2004
Abstract
In this paper, we propose a novel method for demodulating Pulse Position Modulation (PPM) signals based on Reed-Solomon decoding algorithm. It is shown that the proposed technique outperforms the conventional demodulating method base on Reed-Solomon algorithm in case that the PPM signals are corrupted by Additive White Gaussian Noise (AWGN). © Springer-Verlag 2004
Normal state conduction in Gd(Ba2-xPrx)Cu 3O7+δ
, Article European Physical Journal B ; Volume 33, Issue 4 , 2003 , Pages 381-390 ; 14346028 (ISSN) ; Akhavan, M ; Sharif University of Technology
2003
Abstract
The normal state resistivity of single phase polycrystalline Gd(Ba 2-x Pr x )Cu3O7+δ samples with 0.0 ≤ x ≤ 0.50 have been investigated. There is a distinct metal-insulator transition at xMITc = 0.2 and a superconductor-insulator transition at xSITc = 0.35 with the increase of x. The two-dimensional variable range hopping is dominant in the normal state resistivity of the samples. The localization length, hopping range, and hopping energy of carriers show that Pr doping strongly localizes the carriers in normal state, and finally causes the suppression of superconductivity. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003
Compressive strength of concrete cylindrical columns confined with fabric-reinforced cementitious matrix composites under monotonic loading: Application of machine learning techniques
, Article Structures ; Volume 42 , 2022 , Pages 205-220 ; 23520124 (ISSN) ; Zhang, D ; Shadabfar, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The reinforcement of concrete columns with fabric reinforced cementitious matrix (FRCM) is one of the most challenging issues in the construction of concrete structures, as there is still an absence of a promising model to assess their performance. This is because the behavior of such elements is complex and accompanied by a high margin of uncertainty. To address this issue, this study compiles a large dataset of the performance of FRCM-reinforced concrete columns under monotonic load. The obtained dataset is then used to train an artificial neural network (ANN) as a promising method for predicting the compressive strength of concrete columns with acceptable accuracy. Afterward, using a...
Self-Aware data processing for power saving in resource-constrained iot cyber-physical systems
, Article IEEE Sensors Journal ; Volume 22, Issue 4 , 2022 , Pages 3648-3659 ; 1530437X (ISSN) ; Taherinejad, N ; Rabbani, R ; Azizi, Z ; Mohin, S ; Fotowat Ahmady, A ; Mirabbasi, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
Given the emergence of the Internet of Things (IoT) Cyber-Physical Systems (CPSs) and their omnipresence, reducing their power consumption is among the major design priorities. To reduce the power consumption of such systems, we propose the use of a signal-dependent sampling method in a bottom-up fashion, which can lead to up to a 94% reduction in the overall system power with negligible or no loss in performance. Moreover, the proposed technique provides further flexibility for self-aware CPSs to dynamically adjust the number of data samples that are needed for processing (and consequently reduce the power consumption) based on the application at hand and the desired trade-off between...
Source Localization by Analysis the Response of Detectors Using Inverse Methods
,
M.Sc. Thesis
Sharif University of Technology
;
Vosoughi, Naser
(Supervisor)
Abstract
Localization of a neutron point source using a designed computer program namely “MCMC-MATURE” is performed. The computer program analyses several detector responses in some certain media by Markov Chain Monte Carlo (MCMC) method and a new iteration algorithm. Identification of the possible regions of source position would be found by analyzing the initial fluxes generated by mesh tally of MCNPX computer code. The designed computer program is capable to generate the flux between detectors. “Regular-Sequential”, “Irregular-Sequential” and “Non-Sequential” are three methods used for sampling the generated random number in two dimensions. Each sample multiplied by a sampling function and lead to...
Design of a Portable Dilution Sampling System for Measuring Fine Particle and Vocs Emissions from Vehicles and Stack in Iran
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Vahid (Supervisor)
Abstract
Combustion sources such as diesel vehicles are the most of the particular matter sources in ambient air. Near the tailpipe, exhaust is very hot, condense and have high velocity. This properties cause to need special methods and instrument to collect them. Numerously of combustion sources will emitted the VOCs, IVOCs, and SVOCs. This component mixed with ambient air and changing to particle phase from gas phase. Reaction between nitrogen oxides with sunlight cause to damage ozone layer and tissue in long time. Furthermore, breathe of VOCs gases cause to eye irritation, gastrointestinal effects, Damage to the nervous system, headache, dizziness, fatigue, vibration and loss of organ...
Sampling and Distortion Tradeoffs for Band-limited Periodic Signals
, Ph.D. Dissertation Sharif University of Technology ; Marvasti, Farokh (Supervisor)
Abstract
One of the funadmental problems in signal processing is finding the best sampling strategy of a continuous time signal, and then finding the best strategy for compressing the obtained signal samples. The sampling and compression steps are designed with the aim of minimizing the distortion of the reconstructed signal. The problem of finding the best sampling strategy has been widely studied in the signal processing literature. In particular, the Nyquist–Shannon sampling theorem gives a sufficient condition for perfect reconstruction of a continuous-time signal of finite bandwidth. Most of the signal processing literature deals with deterministic signals, with relatively less attention paid to...
Improvement of Level Crossing Sampling’s Performance in Sample Reconstruction, Data Compression and Sampler Stages
, M.Sc. Thesis Sharif University of Technology ; Marvasti, Farokh (Supervisor)
Abstract
Level crossing sampling is a sampling method in which a sample is taken whenever signal crosses predefined and specific levels. In this dissertation, some recommendations are made in order to increase the sampler’s performance in the sampling, data compression, and reconstruction stages.The IMATMirror algorithm is introduced in the sample reconstruction stage. This algorithm is derived from the IMAT reconstruction method. However, additional data processing is done in each iteration, causing the reconstructed signal to satisfy some properties of the Level-Crossing samples.In order to solve the problem of level crossing sampling of extremely bursty signals (ECG signals for example), a sampler...
Investigation of asphaltene adsorption in sandstone core sample during CO2 injection: Experimental and modified modeling
, Article Fuel ; Vol. 133 , 2014 , Pages 63-72 ; ISSN: 00162361 ; Ghotbi, C ; Taghikhani, V ; Shahrabadi, A ; Sharif University of Technology
Abstract
In this work, asphaltene adsorption in a sandstone core sample under dynamic conditions and during miscible CO2 injection was studied using live oil sample which is close to real conditions in petroleum reservoirs. In order to investigate of damage in sandstone core sample by the deposited material such as asphaltene, the morphology analysis of sandstone core sample using scanning electron microscopic method was studied. Also analyses of the adsorbed material in sandstone core sample by Soxhlet extraction using an azeotrope mixture and with SARA method were performed. The experimental results show that by increasing the flow rate of injected CO2, the amount of asphaltene in retained material...
EEG-based functional brain networks: does the network size matter?
, Article PloS one ; Volume 7, Issue 4 , 2012 ; 19326203 (ISSN) ; Salehi, N ; Jalili, M ; Knyazeva, M. G ; Sharif University of Technology
PLOS
2012
Abstract
Functional connectivity in human brain can be represented as a network using electroencephalography (EEG) signals. These networks--whose nodes can vary from tens to hundreds--are characterized by neurobiologically meaningful graph theory metrics. This study investigates the degree to which various graph metrics depend upon the network size. To this end, EEGs from 32 normal subjects were recorded and functional networks of three different sizes were extracted. A state-space based method was used to calculate cross-correlation matrices between different brain regions. These correlation matrices were used to construct binary adjacency connectomes, which were assessed with regards to a number of...
A predictive loss minimisation direct torque control of permanent magnet synchronous motors
, Article Australian Journal of Electrical and Electronics Engineering ; Volume 9, Issue 1 , 2012 , Pages 89-98 ; 1448837X (ISSN) ; Vaez Zadeh, S ; Tahami, F ; Sharif University of Technology
2012
Abstract
Although permanent magnet synchronous motors (PMSMs) are inherently of high efficiency, their efficiency is enormously dependent on their control strategy. The purpose of this paper is to improve the efficiency of PMSMs under a direct torque control (DTC) method. The main idea behind the proposed method is to predict a required small change of the statorflux amplitude at each sampling period to reduce the machine electrical loss before the change is applied. Accordingly, at every sampling time, a voltage vector is predicted and applied to the machine to change the flux amplitude in a xvay that the electrical loss decreases. The results of simulation show significant improvement in the...
Adaptive motion planning with artificial potential fields using a prior path
, Article International Conference on Robotics and Mechatronics, ICROM 2015, 7 October 2015 through 9 October 2015 ; 2015 , Pages 731-736 ; 9781467372343 (ISBN) ; Jamzad, M ; Sharif University of Technology
2015
Abstract
Motion planning in an autonomous agent is responsible for providing smooth, safe and efficient navigation. Many solutions for dealing this problem have been offered, one of which is, Artificial Potential Fields (APF). APF is a simple and computationally low cost method which keeps the robot away from the obstacles in environment. However, this approach suffers from trapping in local minima of potential function and then fails to produce motion plans. Furthermore, Oscillation in presence of obstacles or in narrow passages is another disadvantage of the method which makes it unqualified for many planning problems. In this paper we aim to resolve these deficiencies by a novel approach which...
Adaptive square-root cubature-quadrature Kalman particle filter via KLD-sampling for orbit determination
, Article Aerospace Science and Technology ; Volume 46 , October–November , 2015 , Pages 159-167 ; 12709638 (ISSN) ; Pourtakdoust, S. H ; Sharif University of Technology
Elsevier Masson SAS
2015
Abstract
Orbit determination (OD) problem utilizing onboard sensors is a key requirement for many current and future space missions. Though there exists ample research and work on this subject, a novel algorithm is presented in this paper for the nonlinear problem of OD. In this regard, initially a new cubature-quadrature particle filter (CQPF) that uses the square-root cubature-quadrature Kalman filter (SR-CQKF) to generate the importance proposal distribution is developed. The developed CQPF scheme avoids the limitation of the standard particle filter (PF) concerning new measurements. Subsequently, CQPF is enhanced to take advantage of the relative entropy (Kullback-Leibler Distance) criterion to...
Study of Biomolecules Imaging Using Molecular Dynamics Simulations
, Article Nano ; Volume 10, Issue 7 , October , 2015 ; 17932920 (ISSN) ; Nejat Pishkenari, H ; Moosavi, A ; Meghdari, A ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2015
Abstract
The process of imaging a biomolecule by atomic force microscope (AFM) is modeled using molecular dynamics (MD) simulations. Since the large normal force exerted by the tip on the biosample in contact and tapping modes may damage the sample structure and produce irreversible deformation, the noncontact mode of AFM (NC-AFM) is employed as the operating mode. The biosample is scanned using a carbon nanotube (CNT) as the AFM probe. CNTs because of their small diameter, high aspect ratio and high mechanical resistance attract many attentions for imaging purposes. The tip-sample interaction is simulated by the MD method. The protein, which has been considered as the biomolecule, is ubiquitin and a...
Face recognition using boosted regularized linear discriminant analysis
, Article ICCMS 2010 - 2010 International Conference on Computer Modeling and Simulation, 22 January 2010 through 24 January 2010, Sanya ; Volume 2 , 2010 , Pages 89-93 ; 9780769539416 (ISBN) ; Kasaei, S ; Alizadeh, S ; Sharif University of Technology
2010
Abstract
Boosting is a general method for improving the accuracy of any given learning algorithm. In this paper, we have proposed the boosting method for face recognition (FR) that improves the linear discriminant analysis (LDA)-based technique. The improvement is achieved by incorporating the regularized LDA (R-LDA) technique into the boosting framework. R-LDA is based on a new regularized Fisher's discriminant criterion, which is particularly robust against the small sample size problem compared to the traditional one used in LDA. The AdaBoost technique is utilized within this framework to generalize a set of simple FR subproblems and their corresponding LDA solutions and combines the results from...
Hall anomaly in CNT-doped Y-123 high temperature superconductor
, Article Physica C: Superconductivity and its Applications ; Volume 470, Issue 5-6 , 2010 , Pages 309-312 ; 09214534 (ISSN) ; Manivannan, N ; Kim, K. H ; Daadmehr, V ; Akhavan, M ; Sharif University of Technology
2010
Abstract
In order to study the Hall effect in pure and CNT-doped Y-123 polycrystalline samples, we have measured the longitudinal and transverse voltages at different magnetic field (0 - 9 T) in the normal and vortex states. In the normal state, the Hall coefficient is positive and decreases with increasing temperature, and can be approximately fitted to RH = a + bT-1. We have found a sign reversal in the pure sample for the magnetic field of about 3 T, and double sign reversal of the Hall coefficient in the 0.7 wt% CNT-doped sample at about 3 and 5 T. The Hall resistivity in our samples depends on the pinning