Loading...
Search for:
taherian-fard--hossein
0.183 seconds
Total 1600 records
Vortex Dynamics in Magnetic Phase Diagram of High Tc Cuprate Oxides
, M.Sc. Thesis Sharif University of Technology ; Khosroabadi, Hossein (Supervisor) ; Akhavan, Mohammad (Supervisor)
Abstract
In the 1950s, Abrikosov predicted the mixed state in superconductors (type II superconductors) which lead to a Noble Prize in 2003 with the experimental verification by shubnikov. Mixed-state is a network of magnetic flux lines with quantized flux (vortices) in superconductors. High-temperature superconductors are of Type II which the existense of vortices in a significant part of the temperature-field phase diagram of them, is an obvious phenomenon. These superconductors provided a proper context for understanding physical phenomena related to vortices and access to experimental data to compare with those provided by statistical mechanics. Vortices can move inside the superconductor by the...
3D asymmetric carbozole hole transporting materials for perovskite solar cells
, Article Solar Energy ; Volume 189 , 2019 , Pages 404-411 ; 0038092X (ISSN) ; Heydari, M ; Ahangar, H ; Mohammadi, H ; Taherian Fard, H ; Taghavinia, N ; Samadpour, M ; Tajabadi, F ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Carbazole compounds are p-type hole-transporting materials (HTMs) useful for perovskite solar cells (PSCs). In this work, we developed a new class of carbazol based HTMs; non-fused 3-D asymmetric structures (S14 and S12) as HTM of PSCs. To the best of our knowledge, there is no report on non-fused HTMs with a high glass transition temperature (Tg = 165 °C), which reduces crystallization and suppresses grain boundaries in glassy film, resulting in long-term durability. Experimental results show that tuning the carbazole moiety in S14 structure has a constructive influence on geometrical alignment, hole mobility, hydrophobicity, stability as well as efficiency. The resultant power conversion...
FPGA-Based Implementation of Deep Learning Accelerator with Concentration on Intrusion Detection Systems
, M.Sc. Thesis Sharif University of Technology ; Jahangir, Amir Hossein (Supervisor)
Abstract
Intrusion Detection System (IDS) is an equipment destined to provide computer networks security. In recent years, Machine Learning and Deep Neural Network (DNN) methods have been considered as a way to detect new network attacks. Due to the huge amounts of calculations needed for these methods, there is a need for high performance and parallel or specific processors, such as Application Specific Integrated Circuit (ASIC), Graphical Processor Unit (GPU) and Field-Programmable Gate Array (FPGA). The latter seems more suitable than others due to its higher configurability and lesser power consumption. The goal of this study is the acceleration of a DNN-based IDS on FPGA. In this study, which is...
Effect of Reduction in Behavior Factor on Steel Structures and their Dimensions
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
As you know, the behavior factor is one of the important parameters and values for calculating earthquake force and base cutting in the building. In this research, the effect of coefficient of behavior (R) on metal structures has been investigated. For this purpose, we selected a metal structure with an average bending frame and dual system with shear wall and examined it. To determining the effect of this coefficient on different structures, we modeled the structures with regular and irregular plans. Considering the structure height effect and also the type of soil on the site of the proposed structure to the factor and refractive coefficient (B) and its direct impact on the magnitude of...
The Effect of Relationship Lending on the Contract terms of the Loans
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor)
Abstract
This study examin the effect of relationship lending on the contract terms of the loans consist of loan rate, avalibility of the loan and collateral reqierements. For this purpose, we use 4850 data of loan granted by GHavamin bank in three months Farvardin, Ordibehesht and KHordad in 1395. The results of this study indicate relationship lending has a negative significant effect on the loan rate, a positive significant effect on the availability of the loan and positive insignificant effect on the collateral requirements. Thus, relationship lending as a solution for information asymmetry, leading to cost advantage for the banks. Banks transfer this advantage to client by lowering the loan...
A semantic-aware ontology-based trust model for pervasive computing environments
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 23 June 2008 through 25 June 2008, Oslo ; Volume 5060 LNCS , 2008 , Pages 47-59 ; 03029743 (ISSN) ; 3540692940 (ISBN); 9783540692942 (ISBN) ; Jalili, R ; Amini, M ; Sharif University of Technology
2008
Abstract
Traditionally, to handle security for stand-alone computers and small networks, user authentication and access control mechanisms would be almost enough. However, considering distributed networks such as the Internet and pervasive environments, these kinds of approaches are confronted with flexibility challenges and scalability problems. This is mainly because open environments lack a central control, and users in them are not predetermined. In such ubiquitous computing environments, issues concerning security and trust become crucial. Adding trust to the existing security infrastructures would enhance the security of these environments. Although many trust models are proposed to deal with...
Trust inference in web-based social networks using resistive networks
, Article Proceedings- 3rd International Conference on Internet and Web Applications and Services, ICIW 2008, Athens, 8 June 2008 through 13 June 2008 ; 2008 , Pages 233-238 ; 9780769531632 (ISBN) ; Amini, M ; Jalili, R ; Sharif University of Technology
2008
Abstract
By the immense growth of the Web-Based Social Networks (WBSNs), the role of trust in connecting people together through WBSNs is getting more important than ever. In other words, since the probability of malicious behavior in WBSNs is increasing, it is necessary to evaluate the reliability of a person before trying to communicate with. Hence, it is desirable to find out how much a person should trust another one in a network. The approach to answer this question is usually called trust inference. In this paper, we propose a new trust inference algorithm (Called RN-Trust) based on the resistive networks concept. The algorithm, in addition to being simple, resolves some problems of previously...
PTO: A trust ontology for pervasive environments
, Article 22nd International Conference on Advanced Information Networking and Applications Workshops/Symposia, AINA 2008, Gino-wan, Okinawa, 25 March 2008 through 28 March 2008 ; 2008 , Pages 301-306 ; 1550445X (ISSN) ; 0769530966 (ISBN); 9780769530963 (ISBN) ; Jaili, R ; Amini, M ; Sharif University of Technology
2008
Abstract
Traditionally, to handle security for stand-alone computers and small networks, user authentication and access control mechanisms would be almost enough. However, considering distributed networks such as the Internet and pervasive environments, these kinds of approaches confront with flexibility challenges and scalability problems. This is mainly because of that open environments lack a central control, and users in them are not predetermined, in such ubiquitous computing environments, issues concerning security and trust become crucial. Adding trust to the existing security infrastructures would enhance the security of these environments. Although many trust models have been proposed to...
A new insight to the assessment of asphaltene characterization by using fortier transformed infrared spectroscopy
, Article Journal of Petroleum Science and Engineering ; Volume 205 , 2021 ; 09204105 (ISSN) ; Saeedi Dehaghani, A ; Ayatollahi, S ; Kharrat, R ; Sharif University of Technology
Elsevier B.V
2021
Abstract
This research aims to present asphaltene fraction of oil by FTIR spectrum technique. For this purpose, three different oil samples with various SARA contents and almost identical API degrees were utilized in this research. Two asphaltenic oil samples were referred to as ‘A’ and ‘B’, and the aliphatic oil sample was named as ‘C’. First of all, the asphaltene fraction was extracted through the IP-143 test. The possible chemical bonds and functional groups were identified through NMR tests. Then, the FTIR spectrums of the oil samples and the extracted corresponding asphaltene fractions were taken. The interpretations were used to find the functional groups in the FTIR of the oil samples that...
The mechanistic investigation on the effect of the crude oil /brine interaction on the interface properties: A study on asphaltene structure
, Article Journal of Molecular Liquids ; Volume 360 , 2022 ; 01677322 (ISSN) ; Saeedi Dehaghani, A ; Ayatollahi, S ; Kharrat, R ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Despite many attempts to study the interaction of fluids in low-salinity flooding, they do not examine the principles of interphasic transition phenomena. This study aims to provide a new understanding of liquid–liquid interactions during the low-salinity water interaction through a series of experiments on the oil, emulsion, and aqueous phase. Three samples of crude oils with different asphaltene concentrations and structures with known physical properties are in contact with different solutions. The brine pH, conductivity, and crude oil viscosity experiments before and after contacting the oil with brine showed that the heteroatom concentration and compaction of crude oil asphaltene...
A Combined Method of Context-based and Social-based Routing Protocols for Opportunistic Networks
, M.Sc. Thesis Sharif University of Technology ; Hemmatyar, Ali Mohammad Afshin (Supervisor)
Abstract
Opportunistic networks are special ad-hoc networks in which nodes exploit any opportunisty of pairwise contact to forward packets, without requiring any fixed infrastructures. Routing in Opportunistic Networks due to intermittently connected, non-existence an end to end path between source and destination and with a dynamic topology is a challenging issue. There are several different routing approaches in deliver packets from source to destinations. This approaches can be divided into four categories: awareness approaches, Non-Awareness, direct Delivery and coding based. Use of awareness approaches can be more improved routing process. This category consists of two parts: Context-Aware and...
The Simulation of Ice Formation and Growth in Three Phase Flow of Airstream with Supercooled Liquid Water Droplet
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
In this study, a new finite-element-volume (FEV) arbitrary Lagrangian-Eulerian (ALE) method is suitably extended to simulate the three-phases flows air, liquid water droplets and ice in ice accretion, i.e., over flying object surfaces. This methods benefit from the advantages of both finite-volume and finite-element methods. This method is developed for the first time to simulate three phases turbulent flows. Since the ice formation and growth needs grid movement consistant with ice boundary movement, we have used ALE approach to fulfill this requirment. In this regard, we use the linear spring analogy approach to move the hybrid triangular-rectangular mesh suitably. Facing with a chaotic...
Theoretical investigation on the structural and electronic properties of complexes formed by thymine and 2'-deoxythymidine with different anions
, Article Structural Chemistry ; Volume 23, Issue 1 , July , 2012 , Pages 17-28 ; 10400400 (ISSN) ; Fattahi, A ; Sharif University of Technology
2012
Abstract
Hydrogen bonding interactions between thymine nucleobase and 2'-deoxythymidine nucleoside (dT) with some biological anions such as F - (fluoride), Cl - (chloride), OH - (hydroxide), and NO 3 - (nitrate) have been explored theoretically. In this study, complexes have been studied by density functional theory (B3LYP method and 6-311++G (d,p) basis set). The relevant geometries, energies, and characteristics of hydrogen bonds (H-bonds) have been systematically investigated. There is a correlation between interaction energy and proton affinity for complexes of thymine nucleobase. The nature of all the interactions has been analyzed by means of the natural bonding orbital (NBO) and quantum theory...
Influence of cation-heteroatom (Li+, Na+, and K +) interaction on the structural and thermochemical properties of 2′-deoxythymidine nucleoside: Qtaim and NBO analyzes
, Article Journal of Theoretical and Computational Chemistry ; Volume 12, Issue 2 , December , 2013 ; 02196336 (ISSN) ; Fattahi, A ; Sharif University of Technology
2013
Abstract
Density functional theory (DFT) method and B3LYP/6-311++G(d,p) basis set were used to determine coordination geometries, binding strength, and metal ion affinity (MIA) for interaction of 2′-deoxythymidine (dT) with alkali metal cations including Li+, Na+, and K+. Calculations demonstrated that the interaction of dT with these cations is tri-coordinated η (O2, O4′, O5′). Among these cations, Li + cation exhibited the most tendency for interaction with dT. Cations via their interaction with dT can affect the N-glycosidic bond length, the values of pseudorotation of the sugar ring, the orientation of base unit with respect to sugar ring and the acidity of O5′H, O3′H, and N3H groups in 2′-dT...
Effect of electrical parameters on morphology, chemical composition, and photoactivity of the nano-porous titania layers synthesized by pulse-microarc oxidation
, Article Electrochimica Acta ; Volume 55, Issue 8 , 2010 , Pages 2760-2766 ; 00134686 (ISSN) ; Moshfegh, A. Z ; Golestani Fard, F
2010
Abstract
TiO2 layers were grown via pulse type microarc oxidation process under different applied voltages, frequencies, and duty cycles. Surface chemical composition and phase structure of the synthesized layers were studied utilizing X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Furthermore, scanning electron microscope (SEM) and atomic force microscope (AFM) were employed to investigate surface morphology and topography of the layers. It was revealed that the layers had a porous structure with both anatase and rutile phases. The anatase relative content in the layers increased with the applied frequency; meanwhile, it decreased with duty cycle at low applied voltages, but...
Late time sky as a probe of steps and oscillations in primordial Universe
, Article Journal of Cosmology and Astroparticle Physics ; Volume 2018, Issue 1 , 2018 ; 14757516 (ISSN) ; Baghram, S ; Sharif University of Technology
2018
Abstract
The standard model of cosmology with nearly Gaussian, isotropic, scale invariant and adiabatic initial conditions describes the cosmological observations well. However, the study of any deviation from the mentioned conditions will open up a new horizon to the physics of early universe. In this work, we study the effect of the oscillatory and step-like features in potentials of inflationary models in late time large scale structure observations. Mainly we study the matter power spectrum, number density of the structures, dark matter halo bias and specifically CMB lensing. We show that the oscillatory models can introduce some degeneracy with late time effects on BAO scale. We also conclude...
A numerical study of dust deposition effects on photovoltaic modules and photovoltaic-thermal systems
, Article Renewable Energy ; Volume 135 , 2019 , Pages 437-449 ; 09601481 (ISSN) ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Dust deposition on the surface of solar systems is one of the main parameters that significantly affects the performance of such systems. In this study, the effect of dust deposition density on the performance of photovoltaic modules (PV) and photovoltaic-thermal systems (PVT) is numerically investigated. Accordingly, all layers of a monocrystalline silicon PV module for both systems are simulated. Moreover, the effect of various system parameters on the performance of both clean and dusty PV module and PVT system are studied. The studied parameters included: solar radiation intensity, ambient temperature, coolant inlet temperature, and coolant inlet velocity. The obtained results indicate...
Effect of electropulsing on microstructure and hardness of cold-rolled low carbon steel
, Article Journal of Materials Research and Technology ; Volume 8, Issue 3 , 2019 , Pages 3114-3125 ; 22387854 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
Elsevier Editora Ltda
2019
Abstract
The application of electropulsing treatment (EPT) is studied on the microstructure and hardness of cold-rolled low carbon steel. The effects of electrical pulses on the grain refinement, precipitate size evolution and hardness are investigated. It is found that applying electrical pulse decreases the grain and precipitate size and increases the hardness in the early stages of electropulsing, but the grain and precipitate size is increased and the hardness is decreased by continuing electropulsing. Also, the effect of electropulsing treatment variables as well as treated time and number of periods are discussed. It is demonstrated that increasing treated time can accelerate achieving maximum...
Long-term energy and exergy analysis of heat pumps with different types of ground and air heat exchangers
, Article International Journal of Refrigeration ; Volume 100 , 2019 , Pages 414-433 ; 01407007 (ISSN) ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Heat pumps as the only end-use cooling/heating technology with a Coefficient of Performance (COP) greater than one, have attracted a great deal of attention over the past decade. In this study, the long-term energy and exergy analysis of four different types of heat pump systems: a common Air Source Heat Pump (ASHP), an ASHP with Ground Air Heat Exchanger (GAHE), a Ground Source Heat Pump (GSHP) with Horizontal Ground Water Heat Exchanger (HGWHE), and a GSHP with Vertical Ground Water Heat Exchanger (VGWHE) is performed. It is considered that all systems are used for space cooling and heating of a residential building. A mathematical model that takes into account the variations of building...
A novel methodology for designing a multi-ejector refrigeration system
, Article Applied Thermal Engineering ; Volume 151 , 2019 , Pages 26-37 ; 13594311 (ISSN) ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Ejector refrigeration system has many advantages over traditional compressor-based systems, including: simplicity, low installation and operating costs and the ability to operate with low-grade thermal energy sources. However, its main drawbacks are low Coefficient of Performance (COP) and failure at high ambient temperatures. To overcome these problems, a novel methodology for designing a multi-ejector refrigeration system is proposed. This system utilizes a parallel array of ejectors instead of one ejector. Therefore, the system can continuously operate at its optimum efficiency. Each ejector works within a specific range of condensing pressures. The condenser pressure governs the...