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    A fuzzy fully distributed trust management system in wireless sensor networks

    , Article AEU - International Journal of Electronics and Communications ; Volume 70, Issue 1 , 2016 , Pages 40-49 ; 14348411 (ISSN) Jadidoleslamy, H ; Aref, M.R ; Bahramgiri, H ; Sharif University of Technology
    Elsevier GmbH  2016
    Wireless sensor networks (WSNs) usually consist of many tiny sensor nodes and a Sink. Problems like nodes' misbehavior due to malicious, compromised or selfishness intentions, and WSNs' security vulnerabilities against different attacks due to free and unprotected communications, untrusted and broadcasted transmissions, hostile environments and limited resources, degrade the security and overall performance of WSNs. In another direction, most of the traditional security mechanisms are unsuitable for WSNs. One significant security solution against these problems is Trust Management System (TMS); TMS enhances the security by detecting the nodes' abnormal behaviors; it improves the cooperation... 

    New reactive power calculation method for electric arc furnaces

    , Article Measurement: Journal of the International Measurement Confederation ; Volume 81 , 2016 , Pages 251-263 ; 02632241 (ISSN) Samet, H ; Masoudipour, I ; Parniani, M ; Sharif University of Technology
    Elsevier B.V  2016
    In this study main reactive power calculation methods are evaluated and compared. Furthermore, a novel simple method that can be used for calculation of reactive power in electric arc furnace (EAF) plants is proposed. The focus here is on their application in the control system of static VAr compensators (SVCs). SVC can compensate only the fundamental harmonic component. So the reactive power signal used in the control system should be sensitive only to the main harmonic component. In addition, the reactive power calculation should be fast enough that SVC can follow the quick changes of the load to mitigate the flicker efficiently. To compare various reactive power calculation methods and to... 

    Elastic moduli tensors, ideal strength, and morphology of stanene based on an enhanced continuum model and first principles

    , Article Mechanics of Materials ; Volume 110 , 2017 , Pages 1-15 ; 01676636 (ISSN) Shodja, H. M ; Ojaghnezhad, F ; Etehadieh, A ; Tabatabaei, M ; Sharif University of Technology
    Elsevier B.V  2017
    The present work aims to provide an accurate description of the tensile behavior of the planar as well as low-buckled stanene and to capture their ideal strength in armchair (AC)- and zigzag (ZZ)-directions. For an accurate description of anisotropic response of such hyperelastic materials as stanene, consideration of a highly nonlinear constitutive model in which up to the fourth power of strains is incorporated is inevitable. By utilizing first principles calculations based on density functional theory (DFT), the second, third, fourth, and fifth order elastic moduli tensors corresponding to both planar and low-buckled states are obtained. Moreover, the morphology of the free-standing... 

    Microscopic structure and solubility predictions of multifunctional solids in supercritical carbon dioxide: a molecular simulation study

    , Article Journal of Physical Chemistry B ; Volume 121, Issue 7 , 2017 , Pages 1660-1674 ; 15206106 (ISSN) Noroozi, J ; Paluch, A. S ; Sharif University of Technology
    Molecular dynamics simulations were employed to both estimate the solubility of nonelectrolyte solids, such as acetanilide, acetaminophen, phenacetin, methylparaben, and lidocaine, in supercritical carbon dioxide and understand the underlying molecular-level driving forces. The solubility calculations involve the estimation of the solute's limiting activity coefficient, which may be computed using conventional staged free-energy calculations. For the case of lidocaine, wherein the infinite dilution approximation is not appropriate, we demonstrate how the activity coefficient at finite concentrations may be estimated without additional effort using the dilute solution approximation and how... 

    Molecular dynamics study of two dimensional silicon dioxides with in-plane negative poisson's ratio

    , Article Computational Materials Science ; Volume 153 , 2018 , Pages 258-267 ; 09270256 (ISSN) Safaei, S ; Tavakoli, R ; Jafary Zadeh, M ; Sharif University of Technology
    In the present work, the mechanical properties, in particular, the Poisson's ratio of four two-dimensional silica structures, called here α,β,γ and δ are studied by means of molecular dynamics simulations. The α structure has been synthesized experimentally and the others have been reported as the most stable low-energy structures that reveal in-plane negative Poisson's ratio based on the first principles calculations. Among these structures, β-silica exhibits the largest in-plane negative Poisson's ratio which is 2–4 times higher than penta-graphene. Our results illustrate that the classical molecular dynamics simulation reproduces results in agreement with those of the first principles... 

    Development of a novel analytical method for calculating the dose equivalent rate as a case study of fields which obey the inverse square law

    , Article Journal of Instrumentation ; Volume 14, Issue 9 , 2019 ; 17480221 (ISSN) Moshkbar Bakhshayesh, K ; Sharif University of Technology
    Institute of Physics Publishing  2019
    The field of any point source which is broadened equally in all directions without any limitation to its range is within category of the inverse square law (ISL). As a case study, the dose equivalent (DE) rate is calculated. For calculating the DE rate, the radiation source can be divided into multiple layers and each layer is fractionated to multiple rectangular surfaces. Each rectangular surface can be replaced with three types of sectors. The DE rate of a source on a target is then sum of DE rates of sectors. The developed method is independent of the target position relative to the source and is used for the dose calculation of any arbitrary arrangement of source and target. As an... 

    Analytical calculation for input impedance of a circularly-polarized ferrite disk antenna including higher order modes

    , Article International Journal of RF and Microwave Computer-Aided Engineering ; Volume 29, Issue 8 , 2019 ; 10964290 (ISSN) Ahmadvand, A ; Heydari, M. B ; Rejaei, B ; Ghalibafan, J ; Sharif University of Technology
    John Wiley and Sons Inc  2019
    We propose an accurate analytical model for a circularly polarized antenna comprising a normally magnetized, grounded ferrite disk with a metalized top surface. The antenna is assumed to be excited by a conventional current probe. In the case of a thin ferrite disk, the electromagnetic fields of the dominant mode of the antenna do not vary in the direction normal to the disk. However, with increasing thickness of the ferrite disk, higher order modes start to affect antenna characteristics such as resonance frequency. This work presents an analysis of the structure that takes into account all higher modes of the antenna. To validate the theoretical calculations, HFSS simulations are... 

    Two-dimensional porous graphitic carbon nitride C6N7 monolayer: first-principles calculations

    , Article Applied Physics Letters ; Volume 119, Issue 14 , 2021 ; 00036951 (ISSN) Bafekry, A ; Faraji, M ; Fadlallah, M. M ; Abdolhosseini Sarsari, I ; Jappor, H. R ; Fazeli, S ; Ghergherehchi, M ; Sharif University of Technology
    American Institute of Physics Inc  2021
    The fabrication of the C6N7 monolayer [Zhao et al., Sci. Bull. 66, 1764 (2021)] motivated us to discover the optical, structural, mechanical, and electronic properties of the C6N7 monolayer by employing the density functional theory (DFT) method. We find that the shear modulus and Young's modulus of the C6N7 monolayer are smaller than the relevant values of graphene. However, Poisson's ratio is more significant than that of graphene. Applying the PBE (HSE06) functional bandgap of the C6N7 monolayer is 1.2 (1.97) eV, and the electronic dispersion is almost isotropic around the Γ point. C6N7 is more active in the ultraviolet region as compared to the visible light region. This study provides... 

    Extended gibbs free energy and laplace pressure of ordered hexagonal close-packed spherical particles: A wettability study

    , Article Langmuir ; Volume 37, Issue 28 , 2021 , Pages 8382-8392 ; 07437463 (ISSN) Bayat, A ; Ebrahimi, M ; Rahemi Ardekani, S ; Saievar Iranizad, E ; Zaker Moshfegh, A ; Sharif University of Technology
    American Chemical Society  2021
    The wetting property of spherical particles in a hexagonal close-packed (HCP) ordering from extended Gibbs free energy (GFE) and Laplace pressure view points is studied. A formalism is proposed to predict the contact angle (θ) of a droplet on the HCP films and penetration angle (α) of the liquid on the spherical particles. Then, the extended Laplace pressure for the layered HCP ordering is calculated and a correlation between the wetting angle, sign of pressure, and pressure gradient is achieved. Our results show that the sign and the slope of pressure are important criteria for determining the wettability state and it is found that the contact angle is independent of the particle radius, as... 

    Design and Fabrication of Microfluidic System to Produce Microgel for Drug Delivery Application

    , M.Sc. Thesis Sharif University of Technology Shieh, Hamed (Author) ; Bastani, Dariush (Supervisor) ; Saadatmand, Maryam (Supervisor) ; Eskandari, Mahnaz (Supervisor)
    Due to the increasing need of use of drugs and insufficient efficiency of conventional methods, drug delivery systems has gathered a lot of interests. There are different systems existing for controlled drug delivery, among which is implementation of hydrogel microparticles (microgels) as carriers with high potential. The most important factor in these systems is size distribution of drug-carrying microgels and a narrow size distribution leads to a controlled and suitable release. Due to unique characteristics of microfluidic systems, significant focus has been placed on them nowadays for production of microgels with suitable morphology and narrow size distribution. Therefore, in this study... 

    The Effect of GPU for Radiation Transport of Photons and Electrons for dose Calculation

    , M.Sc. Thesis Sharif University of Technology Osat, Saeed (Author) ; Sohrabpour, Mostafa (Supervisor) ; Vosoughi, Naser (Co-Advisor)
    In radiotherapy, dose calculation is one of the most important stages that should be carefully done for patient treatment planning. Dose calculation methods have been developed from early dose algorithms that used analytical methods to relatively recent high precision monte carlo methods.Monte carlo methods while very accurate in dose estimations usually suffer from long computation time. In the recent time the emphasis for reduction of the computation time has been focused on software techniques as well as on hardware technology development. One example of hardware development has been graphic processing unit (GPU) which was introduced in 2006 by the Nvidia to accelerate the processing and... 

    Design and Fabrication of a Balance Training Apparatus

    , M.Sc. Thesis Sharif University of Technology Behjat, Amir (Author) ; Behzadipour, Saeed (Supervisor) ; Farahmand, Farzam (Co-Advisor)
    One of the main reasons of being unable in doing routine jobs is the disability to attain and keep balance. This ability can be restored using rehabilitation techniques. A physiotherapist can be very helpful. This approach, however, apart from being very time consuming and expensive, needs quite a few physiotherapists. The physiotherapist will be prone to physical damages as well. This leads to improving therapy methods which do not require a physiotherapist. Using the rehabilitation balance devices can help solve the problem to some extents. If good device with reliable value system be developed, this device can be used without physiotherapist.
    This project has been carried out to... 

    Analytical investigation on fundamental electrical characteristics of large air-gap superconducting synchronous machine

    , Article Journal of Magnetics ; Volume 18, Issue 3 , 2013 , Pages 260-267 ; 12261750 (ISSN) Yazdanian, M ; Elhaminia, P ; Zolghadri, M. R ; Fardmanesh, M ; Sharif University of Technology
    In this paper a general 2-D model of a large air-gap synchronous machine either with non-magnetic or magnetic core rotor is investigated and electrical characteristics of the machine are analytically calculated. Considering the general model, analytical equations for magnetic field density in different regions of the large air-gap machine are calculated. In addition, self and mutual inductances in the proposed model of the machine have been developed, which are the most important parameters in the electromagnetic design and transient analysis of synchronous machines. Finite element simulation has also been performed to verify the obtained results from the equations. Analytical results show... 

    Mapping dispersion fluctuations along optical fibers using brillouin probing and a fast analytic calculation

    , Article 2013 Conference on Lasers and Electro-Optics, CLEO ; 2013 ; 9781557529725 (ISBN) Alishahi, F ; Vedadi, A ; Denisov, A ; Soto, M. A ; Mehrany, K ; Bres, C. S ; Thevenaz, L
    A simple analytic formula is derived to extract tiny dispersion fluctuations along highly nonlinear fibers from distributed measurements of parametric gain. A refined BOTDA scheme, suitable to track Kerr processes, enables low noise measurements  

    Influence of the hydrogen bonding on the basicity of selected macrocyclic amines

    , Article Journal of Physical Organic Chemistry ; Volume 25, Issue 9 , 2012 , Pages 803-810 ; 08943230 (ISSN) Nasiri, M ; Shakourian Fard, M ; Fattahi, A ; Sharif University of Technology
    The optimized minimum-energy geometries of different macrocyclic amines and their protonated structures were determined by using ab initio and density functional theory (DFT) calculations. All the gas phase optimizations and energy calculations were performed at the DFT/B3LYP/6-311++G(d,p) level of theory. The HF/6-31 + G(d,p) level was used for all single point calculations in the solution phase. Geometry optimizations indicate that the most stable structures are stabilized by intramolecular hydrogen bonds. The proton affinity (PA) of macrocyclic amines is controlled by the strength of intramolecular hydrogen bonds of macrocyclic amines. These hydrogen bonds strongly influence the basicity... 

    Phase diagram of the XXZ ferrimagnetic spin-(1/2, 1) chain in the presence of transverse magnetic field

    , Article Journal of Statistical Mechanics: Theory and Experiment ; Volume 2011, Issue 8 , August , 2011 ; 17425468 (ISSN) Langari, A ; Abouie, J ; Asadzadeh, M. Z ; Rezai, M ; Sharif University of Technology
    We investigate the phase diagram of an anisotropic ferrimagnetic spin-(1/2, 1) in the presence of a non-commuting (transverse) magnetic field. We find a magnetization plateau for the isotropic case while there is no plateau for the anisotropic ferrimagnet. The magnetization plateau can appear only when the Hamiltonian has the U(1) symmetry in the presence of the magnetic field. The anisotropic model is driven by the magnetic field from the Néel phase for low fields to the spin-flop phase for intermediate fields and then to the paramagnetic phase for high fields. We find the quantum critical points and their dependence on the anisotropy of the aforementioned field-induced quantum phase... 

    Comparative modeling of stochastic versus regular arrangement of TRISO particles in HTTR

    , Article Progress in Nuclear Energy ; Volume 78 , January , 2015 , Pages 291-296 ; 01491970 (ISSN) Torabi Ardakani, A ; Ghofrani, M. B ; Ezzati, A. O ; Sharif University of Technology
    Elsevier Ltd  2015
    TRISO particles are the specific features of HTTR and generally HTGR reactors. Their heterogeneity and random arrangement in graphite matrix of these reactors create a significant modeling challenge. In this study, an algorithm is proposed for modeling random arrangement of TRISO particles in the fuel compacts of HTTR. The effect of this arrangement on criticality calculations, i.e. effective multiplication factor and critical position of control rods, is then compared with regular arrangement. Regular arrangement was modeled by positioning each TRISO as a fixed sphere in the center of a cubic lattice and subsequently, each fuel compact was filled with around 13,000 (approximate number of... 

    Improving network's performability using parallel processing

    , Article 6th International Conference on Networking, ICN'07, Sainte-Luce, Martinique, 22 April 2007 through 28 April 2007 ; 2007 , Pages 40-45 ; 0769528058 (ISBN); 9780769528052 (ISBN) Shaad Zolpirani, M ; Bidmeshki, M. M ; Miremadi, S. G ; Sharif University of Technology
    IEEE Computer Society  2007
    By occurring failures in computer networks, routing protocols are triggered to update routing and forwarding tables. Because of invalid tables during update-time, transient loop may occur and packet-drop rate and end-to-end delay increase which means that the quality of service decreases. This paper proposes a parallel architecture for a router to recalculate and update routing table. Simulation results show that with dual-processor architecture, this update time could be up to 40% improved, depending on the network topology and the size of tables. This paper also studies the effect of this speed-up on networks' performability, i.e. the ability to deliver services at predefined level. A... 

    DFT calculations on the retro-ene reactions, part II: Allyl n-propyl sulfide pyrolysis in the gas phase

    , Article Journal of Molecular Structure: THEOCHEM ; Volume 686, Issue 1-3 , 2004 , Pages 37-42 ; 01661280 (ISSN) Izadyar, M ; Gholami, M. R ; Haghgu, M ; Sharif University of Technology
    The mechanism and kinetic aspects of the retro-ene reaction of the Allyl n-propyl sulfide and its deuterated derivative were studied using four different types of density functional theory methods with eight different levels of the basis sets. The activation energies were determined at 550.65 K. As a consequence of our calculations, a transition state is concluded that consists of a polar six-center cyclic structure. We found that the combination B3PW91/6-311++G** produces activation energy values closer to the experimental ones, but the simpler combination B3LYP/6-31G* produces excellent values too in less time. Our calculations show that the activation parameters obtained from the B3... 

    Iterative interference cancellation and decoding for a coded UWB-TH-CDMA system in multipath channels using MMSE filters

    , Article 14th IEEE 2003 International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC2003, Beijing, 7 September 2003 through 10 September 2003 ; Volume 2 , 2003 , Pages 1555-1559 ; 0780378229 (ISBN); 9780780378223 (ISBN) Bayesteh, A ; Nasiri Kenari, M ; Sharif University of Technology
    In this paper, we consider a low-complexity iterative receiver for decoding multi-user information data for the bandwidth efficient convolutionally coded UWB-TH-CDMA system, in a multipath channel. The proposed receiver structure consists of a bank of soft interference cancellers (SIC), followed by a block of MMSE filters. The outputs of these filters, are feeded to a bank of likelihood calculators (LC), each followed by a soft-input soft-output (SISO) convolutional decoder. Information is fed back from SISO decoders to SICs for interference cancellation. This receiver requires the knowledge of the attenuation and delay of the strongest path of each active user. We evaluate the performance...