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Valence bond phases in S = 1/2 Kane-Mele-Heisenberg model
, Article Journal of Physics Condensed Matter ; Vol. 26, issue. 45 , 2014 ; ISSN: 09538984 ; Mosadeq, H ; Shahbazi, F ; Jafari, S. A ; Sharif University of Technology
2014
Abstract
The phase diagram of the Kane-Mele-Heisenberg model in a classical limit [47] contains disordered regions in the coupling space, as the result of competition between different terms in the Hamiltonian, leading to frustration in finding a unique ground state. In this work we explore the nature of these phases in the quantum limit, for a S = 1/2. Employing exact diagonalization in Sz and nearest neighbour valence bond bases, and bond and plaquette valence bond mean field theories, we show that the disordered regions are divided into ordered quantum states in the form of plaquette valence bond crystals and staggered dimerized phases
Mixed-Halide CH3NH3PbI3−xXx (X=Cl, Br, I) perovskites: vapor-assisted solution deposition and application as solar cell absorbers
, Article ChemPhysChem ; 2016 , Pages 2382-2388 ; 14394235 (ISSN) ; Tajabadi, F ; Shahbazi, S ; Gholipour, S ; Taghavinia, N ; Sharif University of Technology
Wiley-VCH Verlag
2016
Abstract
There have been recent reports on the formation of single-halide perovskites, CH3NH3PbX3 (X=Cl, Br, I), by means of vapor-assisted solution processing. Herein, the successful formation of mixed-halide perovskites (CH3NH3PbI3−xXx) by means of a vapor-assisted solution method at ambient atmosphere is reported. The perovskite films are synthesized by exposing PbI2 film to CH3NH3X (X=I, Br, or Cl) vapor. The prepared perovskite films have uniform surfaces with good coverage, as confirmed by SEM images. The inclusion of chlorine and bromine into the structure leads to a lower temperature and shorter reaction time for optimum perovskite film formation. In the case of CH3NH3PbI3−xClx, the optimum...
A three-step method for the deposition of large cuboids of organic–inorganic perovskite and application in solar cells
, Article ChemPhysChem ; 2016 , Pages 2389-2394 ; 14394235 (ISSN) ; Malekshahi Byranvand, M ; Tajabadi, F ; Afshar, Sh ; Taghavinia, N ; Sharif University of Technology
Wiley-VCH Verlag
2016
Abstract
A three-step method for the deposition of CH3NH3PbI3 perovskite films with a high crystalline structure and large cuboid overlayer morphology is reported. The method includes PbI2 deposition, which is followed by dipping into a solution of C4H9NH3I (BAI) and (BA)2PbI4 perovskite formation. In the final step, the poorly thermodynamically stable (BA)2PbI4 phase converts into the more stable CH3NH3PbI3 perovskite by dipping into a solution of CH3NH3I. The final product is characterized by XRD, SEM, UV/Vis, and photoluminescence analysis methods. The experimental results indicate that the prepared perovskite has cuboids with high crystallinity and large sizes (up to 1 μm), as confirmed by XRD...
Fast detection of open-switch fault in cascaded H-Bridge multilevel converter
, Article 6th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2015, 3 February 2015 through 4 February 2015 ; February , 2015 , Pages 538-543 ; 9781479976539 (ISBN) ; Zolghadri, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
Cascaded H-Bridge converter has recently been utilized in different high-power applications due to its modular and simple structure. In order to have a balanced operation after a fault occurrence in this converter, it is necessary to detect the switch fault and its location. In this paper, a fast power switch fault detection method is presented to identify the fault and its location. Only one voltage measurement per phase is required by this method, and the fault detection is faster compared to the existing methods. Moreover, it is easy for implementation on an FPGA device, due to the use of simple math, relational and state machine blocks. The proposed method is verified by computer...
A generalizable model for seizure prediction based on deep learning using CNN-LSTM architecture
, Article 2018 IEEE Global Conference on Signal and Information Processing, GlobalSIP 2018, 26 November 2018 through 29 November 2018 ; 2019 , Pages 469-473 ; 9781728112954 (ISBN) ; Aghajan, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
This work proposes a novel deep learning-based model for prediction of epileptic seizures using multichannel EEG signals. Multichannel images are first constructed by applying short-time Fourier transform (STFT) to Electroencephalography (EEG) signals. After a preprocessing step, a CNN-LSTM neural network is trained on the STFTs in order to capture the spectral, spatial and temporal features within and between the EEG segments and classify them as preictal or interictal stage. The proposed method achieves a sensitivity of 98.21%, a false prediction rate (FPR) of 0.13/h and a mean prediction time of 44.74 minutes on the CHB-MIT dataset. As the main contribution of this work, by using a...
Impact of mobile source emission inventory adjustment on air pollution photochemical model performance
, Article Urban Climate ; Volume 32 , 2020 ; Hosseini, V ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Coupled weather forecasting and chemical transport models are useful tools to evaluate air pollution episodes in big cities for the purpose of forecasting and air pollution abatement measures' evaluation. However, large set of accurate data of various sources and modeling calibrations are needed for such complex modeling system to be reliable. The problem becomes more obvious when the model is operated over a domain in which there is a general lack of accurate input data such as emission inventory data. The current study investigates the possibility of model tuning for more accurate prediction of air pollutant concentrations in the city of Tehran in an air pollution episode as a case study....
Simultaneous Hypothesis Testing and False Discovery Rate
, M.Sc. Thesis Sharif University of Technology ; Alishahi, Kasra (Supervisor)
Abstract
The purpose of this thesis is to introduce and review a recent methods in simultaneous hypothesis testing. False discovery rates, Benjamini and Hochberg’s FDR Control Algorithm, is the great success story of the new methodology. Much of what follows is an attempt to explain that success in empirical Bayes terms.The later chapters are at pains to show the limitations of current largescale statistical practice: Which cases should be combined in a single analysis? How do we account for notions of relevance between cases? What is the correct null hypothesis? How do we handle correlations? Some helpful theory is provided in answer, but much of the argumentation is by example, with graphs and...
Effect of Carrier Gas Pressure on the Size of Cu Nanoparticles Prepared by ELM Method
, M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad (Supervisor)
Abstract
In this report the important factors affecting the levitation melting of copper are discussed. Pure copper nanoparticles were synthesized by utilizing an Electromagnetic Levitation Melting Gas Condensation (ELM-GC) method. Pure bulk copper samples were melted and evaporated by electromagnetic levitation technique in an inert gas atmosphere in a silica tube. Copper nanoparticles were formed from ascending vapor by employing high purity argon and helium as carrier gases and cooling agents. The pressure of inert gas was changed in both helium and argon atmospheres to investigate on pressure’s effect. Particle size and morphology of the produced nanoparticles were studied by Field Emission...
Assessing and Comparing Risk indices in BOT and DBB Delivery Methods in Freeway and Highway Construction Projects
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
The present survey study aims at investigating and comparing risk indices in highway and freeway projects implemented through Build-Operate-Transfer (BOT) and Design-Bid-Build (DBB) delivery methods. In this regard, two distinct questionnaires were developed (one for BOT and one for DBB delivery method) and interviews were conducted, too. The questionnaires were, then, sent to the target population, i.e. all the experts and agents involved in highway and freeway construction projects implemented through either BOT or DBB method. The collected data were then submitted to Statistical Package for Social Sciences (SPSS), version 22.00, to be analyzed. The results showed that risks had generally...
Condition Monitoring of CNG Electrocompressors
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mahdi (Supervisor)
Abstract
In order to increase the service life and prevent the breakdown of apparatuses, instalations and equipments, we are in a position to maintain them. In this regard, there are three methods for maintenance of machineries, which are called reaction maintenance, preventive maintenance and predictive maintenance. By carrying out a predictive method or monitoring the situation, it is possible to know the health of the machine and take the necessary measures before the damages occurs. Vibration analysis, temperature analysis, oil analysis and flow analysis can be used for monitoring the situation. Reciprocating compressors are one of the most costly repair equipment that needs to be monitored...
Fabrication and Electrical Properties Evaluation of PA/CNT Conductive Nanocomposite with Low Percolation Threshold
, M.Sc. Thesis Sharif University of Technology ; Bagheri, Reza (Supervisor)
Abstract
Polyamide-6 is a thermoplastic polymer that is classified as electrically non-conductive materials. One way of adding conductivity to the polymer matrices is by utilizing them in a nanocomposite form. Superior mechanical and electrical properties of Carbon Nanotubes make them worthy of being chosen as reinforcement in nanocomposites to extend their operation to a broader range of applications, like conductive nanocomposites, mainly polymer-based matrices. The Nanotubes have chemical affinity and tend to entangle and aggregate. Because of this, to achieve a uniform and remarkable electrical conductivity is hard-to-reach. state of entanglement effects correctly melt methods of polymer blend...
Three-dimensional forced Burgers turbulence supplemented with a continuity equation
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 63, Issue 5 II , 2001 , Pages 563081-5630813 ; 15393755 (ISSN) ; Masoudi, A. A ; Rahimi Tabar, M. R ; Rastegar, A. R ; Shahbazi, F ; Sharif University of Technology
2001
Abstract
The turbulent limit of three dimensional Burger equation was studied. An adjusting parameter emerged through the calculations, based on mean field analysis, that was the scaling exponent of conditional density-density correlations. Two kinds of solutions were also shown for velocity-increment probability density function (PDF)
Roughness of undoped graphene and its short-range induced gauge field
, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 76, Issue 19 , 2007 ; 10980121 (ISSN) ; Neek Amal, M ; Asgari, R ; Shahbazi, F ; Nafari, N ; Rahimi Tabar, M. R ; Sharif University of Technology
2007
Abstract
We present both numerical and analytical studies of graphene roughness with a crystal structure including 500×500 atoms. The roughness can effectively result in a random gauge field and has important consequences for its electronic structure. Our results show that its height fluctuations in small scales have a scaling behavior with a temperature dependent roughness exponent in the interval of 0.6<χ<0.7. The correlation function of height fluctuations depends on temperature with a characteristic length scale of ≈90 Å (at room temperature). We show that the correlation function of the induced gauge field has a short-range nature with a correlation length of about 2-3 Å. We also treat the...
Zero tension Kardar-Parisi-Zhang equation in (d + 1)-dimensions
, Article Journal of Statistical Physics ; Volume 116, Issue 5-6 , 2004 , Pages 1521-1544 ; 00224715 (ISSN) ; Tabei, S. M. A ; Masoudi, A. A ; Shahbazi, F ; Rahimi Tabar, M. R ; Sharif University of Technology
2004
Abstract
The joint probability distribution function (PDF) of the height and its gradients is derived for a zero tension d + 1-dimensional Kardar-Parisi-Zliang (KPZ) equation. It is proved that the height's PDF of zero tension KPZ equation shows lack of positivity after a finite time tc. The properties of zero tension KPZ equation and its differences with the case that it possess an infinitesimal surface tension is discussed. Also potential relation between the time scale tc and the singularity time scale tc,v→0 of the KPZ equation with an infinitesimal surface tension is investigated. © 2004 Springer Science+Business Media, Inc
Accelerating 3-D capacitance extraction in deep sub-micron VLSI design using vector/parallel computing
, Article 13th International Conference on Parallel and Distributed Systems, ICPADS, Hsinchu, 5 December 2007 through 7 December 2007 ; Volume 2 , December , 2007 ; 15219097 (ISSN); 9781424418909 (ISBN) ; Sarbazi Azad, H ; Sharif University of Technology
2007
Abstract
The widespread application of deep sub-micron and multilayer routing techniques makes the interconnection parasitic influence become the main factor to limit the performance of VLSI circuits. Therefore, fast and accurate 3D capacitance extraction is essential for ultra deep sub-micron design (UDSM) of integrated circuits. Parallel processing provides an approach to reducing the simulation turn-around time. In this paper, we present parallel formulations for 3D capacitance extraction based on P-FFT algorithm, on a personal computer (PC) or on a network of PCs. We implement both vector and parallel versions of 3D capacitance extraction algorithm simultaneously and evaluate our implementation...
Reply to "comment on 'renormalization group analysis and numerical simulation of propagation and localization of acoustic waves in heterogeneous media'"
, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 77, Issue 21 , 2008 ; 10980121 (ISSN) ; Esmailpour, A ; Vaez Allaei, S. M ; Shahbazi, F ; Sahimi, M ; Rahimi Tabar, M. R ; Sharif University of Technology
2008
Abstract
Based on extensive new numerical simulations, we show that Chu's arguments and objections against our previous results are invalid. In addition, we explain the origin of the differences between our results and the previous ones, obtained based on a simple model of one-dimensional disordered materials. © 2008 The American Physical Society
Evaluation of tehran clean air action plan using emission inventory approach
, Article Urban Climate ; Volume 27 , 2019 , Pages 446-456 ; 22120955 (ISSN) ; Hassani, A ; Hosseini, V ; Sharif University of Technology
Elsevier B.V
2019
Abstract
The city of Tehran, the capital of Iran, has been facing severe air quality problems. The air quality of Tehran has been stated as unhealthy over one-third of year during the last two decades. According to the last emission inventory of Tehran for the base year of 2013 mobile sources contribute by about 6, 46, 98, 87, and 70% of total primary SOx, NOx, CO, VOC and PM emission. A number of policies have been implemented in Tehran during the last two decades to tackle the air quality issue. Concentrated mostly on transportation sector, these policies aimed to improve fuel quality and emission performance of vehicles. Nevertheless, there is no quantified evaluation regarding the effectiveness...
Autonomous road pavement inspection and defect analysis for smart city maintenance
, Article 5th International Conference on Pattern Recognition and Image Analysis, IPRIA 2021, 28 April 2021 through 29 April 2021 ; 2021 ; 9781665426596 (ISBN) ; Majidi, B ; Movaghar, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
The detection and repair of the cracks in the road pavement is a very time consuming task which should be performed periodically in order to maintain the safety and quality of the road network. There are various types of road pavement cracks and each type requires different management and repair method and also each type indicates a different problem in that section of the road. In this paper, an autonomous machine learning based visual inspection system for detection and classification of the road pavement cracks is proposed. The proposed framework uses deep neural networks in order to detect and classify longitudinal, alligator and asphalt cracks. A dataset of images from different road...
A Novel Approach for Seizure Prediction using EEG Signals
, M.Sc. Thesis Sharif University of Technology ; Karbalaei Aghajan, Hamid (Supervisor)
Abstract
As the fourth most common neurological disorder, epilepsy affects lots of people all around the world, some of whom have to live with unpredictable seizures uncontrollable by surgery or medication. Hence, Developing systems for detection and prediction of the epileptic seizures will help the patients to avoid the possible damages caused by sudden seizures. This study addresses the task of epileptic seizure prediction, using three different novel approaches. The first approach, which is based on anomaly detection, contains three steps: feature extraction from EEG signals, training a one-class SVM classifier, and a post-processing step. The second method exploits a recurrent neural network to...
Design Hybrid Renewable Energy Systems by A Multi-objective Robust Optimization Model
, M.Sc. Thesis Sharif University of Technology ; Eshghi, Kourosh (Supervisor)
Abstract
Nowadays the popularity of renewable energy is increasing due to its clean and inexhaustible nature. Also, if the local potential of each area is used, there is no cost to connect to electricity network. But these energies have low reliability due to their oscillating nature. To solve this problem, it is proposed to use systems based on several sources of energy called hybrid systems. In this research, a mathematical model is proposed to design a renewable hybrid system that minimizes the present value of costs while maximizing system’s reliability. To consider the uncertainty in the solar radiation data and energy demand, Bertsimas’s robust model is applied to our model. In which variables...