Loading...
Search for: mechanism
0.014 seconds
Total 3505 records

    Engineering mechanics 2

    , Book ; Gross, D. (Dietmar)
    Springer  2018

    Quantum ergodicity for a class of non-generic systems

    , Article Journal of Physics A: Mathematical and Theoretical ; Volume 49, Issue 5 , 2015 ; 17518113 (ISSN) Asadi, P ; Bakhshinezhad, F ; Rezakhani, A. T ; Sharif University of Technology
    2015
    Abstract
    We examine quantum normal typicality and ergodicity properties for quantum systems whose dynamics are generated by Hamiltonians which have residual degeneracy in their spectrum and resonance in their energy gaps. Such systems can be considered atypical in the sense that degeneracy, which is usually a sign of symmetry, is naturally broken in typical systems due to stochastic perturbations. In particular, we prove a version of von Neumann's quantum ergodic theorem, where a modified condition needs to hold in order to have normal typicality and ergodicity. As a result, we show that degeneracy of spectrum does not considerably modify the condition of the theorem, whereas the existence of... 

    Simulation of elasto-plastic deformations in composites by flow rules

    , Article Indian Journal of Science and Technology ; Vol. 7, issue. 2 , 2014 , pp. 180-184 ; ISSN: 09746846 Monfared, V ; Fazaeli, D ; Daneshmand, S ; Shafaghatian, N ; Sharif University of Technology
    Abstract
    In this paper, a novel model is proposed to predict stress behavior in the fibrous polymer composites under an applied tensile axial loading. Tangential stress is obtained by simulating between polymeric matrix flow (polyester) and fluid flow. In the other words, creep behavior of the petrochemical material or polymeric resin (matrix) is modeled using fluid flow theory. Furthermore, behavior of the shear stress is predicted by suitable mathematical functions. Finally, important relation is extracted by combining the solid and fluid mechanics formulations  

    Effect of ECAP temperature on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy

    , Article Progress in Natural Science: Materials International ; Volume 26, Issue 2 , 2016 , Pages 182-191 ; 10020071 (ISSN) Shaeri, M. H ; Shaeri, M ; Ebrahimi, M ; Salehi, M. T ; Seyyedein, S. H ; Sharif University of Technology
    Elsevier B.V  2016
    Abstract
    The effect of equal channel angular pressing (ECAP) at different temperatures (room temperature, 120, 150 and 180 °C) on microstructure and mechanical properties of Al-7075 solid solution alloy was investigated. Microstructure of the specimens was examined using orientation imaging microscopy, transmission electron microscopy as well as X-ray diffractometer, and mechanical properties were measured by Vickers microhardness and tensile tests. Microstructural investigations showed that after 3 or 4 passes of ECAP, fine grains with average grain sizes in range of 300-1000 nm could be obtained at different ECAP temperatures. Increasing ECAP temperature from 120 to 180 °C caused a decrease in... 

    Time operator in relativistic quantum mechanics

    , Article Communications in Theoretical Physics ; Volume 68, Issue 1 , 2017 , Pages 35-38 ; 02536102 (ISSN) Khorasani, S ; Sharif University of Technology
    Abstract
    It is first shown that the Dirac's equation in a relativistic frame could be modified to allow discrete time, in agreement to a recently published upper bound. Next, an exact self-adjoint 4 × 4 relativistic time operator for spin-1/2 particles is found and the time eigenstates for the non-relativistic case are obtained and discussed. Results confirm the quantum mechanical speculation that particles can indeed occupy negative energy levels with vanishingly small but non-zero probablity, contrary to the general expectation from classical physics. Hence, Wolfgang Pauli's objection regarding the existence of a self-adjoint time operator is fully resolved. It is shown that using the time... 

    Erratum: Multifractal detrended fluctuation analysis of sunspot time series (Journal of statistical mechanics: Theory and experiment)

    , Article Journal of Statistical Mechanics: Theory and Experiment ; Volume 2011, Issue 9 , 2011 ; 17425468 (ISSN) Sadegh Movahed, M ; Jafari, G. R ; Ghasemi, F ; Rahvar, S ; Reza Rahimi Tabar, M ; Sharif University of Technology

    Characteristic angular scales in cosmic microwave background radiation

    , Article Journal of Statistical Mechanics: Theory and Experiment ; Issue 11 , 2006 ; 17425468 (ISSN) Ghasemi, F ; Bahraminasab, A ; Movahed, S. M. S ; Rahvar, S ; Sreenivasan, K. R ; Rahimi Tabar, M. R ; Sharif University of Technology
    2006
    Abstract
    We investigate the stochasticity in temperature fluctuations in the cosmic microwave background (CMB) radiation data from the Wilkinson Microwave Anisotropy Probe. We show that the angular fluctuation of the temperature is a Markov process with a Markov angular scale, ΘMarkov = 1.01 -0.07+0.09. We characterize the complexity of the CMB fluctuations by means of a Fokker-Planck or Langevin equation and measure the associated Kramers-Moyal coefficients for the fluctuating temperature field T (n̂)and its increment, ∇ T = T(n̂2). Through this method we show that temperature fluctuations in the CMB have fat tails compared to a Gaussian distribution. © 2006 IOP Publishing Ltd and SISSA  

    Multifractal detrended fluctuation analysis of sunspot time series

    , Article Journal of Statistical Mechanics: Theory and Experiment ; Issue 2 , 2006 ; 17425468 (ISSN) Movahed, M. S ; Jafari, G. R ; Ghasemi, F ; Rahvar, S ; Rahimi Tabar, M. R ; Sharif University of Technology
    2006
    Abstract
    We use multifractal detrended fluctuation analysis (MF-DFA), to study sunspot number fluctuations. The result of the MF-DFA shows that there are three crossover timescales in the fluctuation function. We discuss how the existence of the crossover timescales is related to a sinusoidal trend. Using Fourier detrended fluctuation analysis, the sinusoidal trend is eliminated. The Hurst exponent of the time series without the sinusoidal trend is 0.12 ± 0.01. Also we find that these fluctuations have multifractal nature. Comparing the MF-DFA results for the remaining data set to those for shuffled and surrogate series, we conclude that its multifractal nature is almost entirely due to long range... 

    Technical English for mechanical engineers

    , Book Alemi, Minoo ; Meghdari,Ali
    Sharif University Press  2014
    Abstract
    Local educational institutions produce in-house English for Specific Purpose (ESP) materials according to the curriculum policies designated and developed by the Ministry of Higher Education In Iran. To this end, this book aims to be used in the Iranian setting at the tertiary level for undergraduate students majoring in Mechanical Engineering. Moreover, the style of English usage in this ESP textbook is American.
    Regarding the content of the textbook, it has both thematic organizations in which the topics are relevant and includes sufficient treatment of the target language areas necessary for the students. The principle organizing approach of this textbook is theme-based. In addition,... 

    “It from Bit” and quantum mechanics

    , Article Foundations of Science ; Volume 25, Issue 2 , 2020 , Pages 375-384 Barzegar, A ; Shafiee, A ; Taqavi, M ; Sharif University of Technology
    Springer  2020
    Abstract
    John Archibald Wheeler is one of the staunchest advocates of the idea that information is more fundamental than anything else in physics. In this paper, we examine the status of this idea summarized in Wheeler’s slogan ‘it from bit’ in the context of Bohmian Mechanics and spontaneous collapse models. We will argue that any question about the status of ‘it from bit’ crucially depends on the particular interpretation of these theories one favors. © 2019, Springer Nature B.V  

    Geometrically nonlinear rectangular simply supported plates subjected to a moving mass

    , Article Acta Mechanica ; Vol. 225, issue. 2 , February , 2014 , pp. 595-608 ; ISSN: 00015970 Enshaeian, A ; Rofooei, F. R ; Sharif University of Technology
    Abstract
    The dynamic deformation of a geometrically nonlinear rectangular simply supported plate under a moving lumped mass is evaluated using mode expansion method. The governing differential equations of motion for a largely deformable rectangular plate are derived using Lagrange method based on appropriate in and out-of-plane spatial functions which satisfy the proposed boundary conditions. Although the proposed procedure is applicable for any arbitrary edge boundary conditions, only the simply supported plates are addressed in the present work. On the other hand, all inertial components of the moving mass are included in the derivation of the equations of motion. A numerical example is used to... 

    A cable-driven grasping mechanism with lock/unlock constraints

    , Article Proceedings of the ASME Design Engineering Technical Conference ; Volume 6 A , 2013 ; 9780791855935 (ISBN) Abyaneh, S ; Saber, O ; Zohoor, H ; Sharif University of Technology
    American Society of Mechanical Engineers  2013
    Abstract
    The application of manipulators is becoming more and more popular in object handling especially when it is desired to have access to remote areas in destructive or hazardous taskspaces. For this purpose, a hand-like mechanism must be designed to be used as an end-effector, which can grasp objects. In this paper a cable driven grasping mechanism has been presented. In the proposed mechanism each finger consists of three phalanxes which are actuated by a single motor. Locking and unlocking constraints are used in the mechanism in order to generate an anthropomorphic motion, in which, the order of reaching phalanxes to the object is sequential. In this way, each phalanx starts moving toward the... 

    DFT investigations for "Fischer" esterification mechanism over silica-propyl-SO3H catalyst: Is the reaction reversible?

    , Article Computational and Theoretical Chemistry ; Volume 1071 , 2015 , Pages 27-32 ; 2210271X (ISSN) Vafaeezadeh, M ; Fattahi, A ; Sharif University of Technology
    Elsevier  2015
    Abstract
    For the first time, the mechanism of Fischer esterification between acetic acid and ethanol over silica-functionalized propylsulfonic acid (silica-propyl-SO3H) catalyst was explored by means of computational modeling techniques. For this purpose, 6-edge-atom cage-like cluster comprising Si-O-Si sequences has been selected to represent the surface of the catalyst. The results indicate that the reaction goes through concerted transition states. In all optimized structures no proton (H+) transfer occurs from catalyst to the substrates and the role of the catalyst is via the activation of the substrates through the formation of strong hydrogen bonds (H-bonds). Furthermore, the energetic diagram... 

    Study on electrowinning of cobalt by cyclic voltammetry technique

    , Article Iranian Journal of Materials Science and Engineering ; Volume 7, Issue 2 , 2010 , Pages 45-48 ; 17350808 (ISSN) Nusheh, M ; Yoozbashizadeh, H ; Sharif University of Technology
    2010
    Abstract
    Nowadays cobalt is mostly produced through the electrowinning process of sulfate solutions. Regarding to the competition between the precipitation of cobalt ions and evolution of hydrogen gas on the cathode surface during the reduction process in a sulfate bath, investigation on the mechanism of metal precipitation is of great importance. In the present work, study on the kinetics of cobalt electrowinning and the mechanism of the involved reactions have been carried out. The obtained results, confirm the mechanism of cobalt precipitation by depletion of hydroxides. The effects of temperature and scan rate parameters were studied on electrowinning of cobalt by cyclic voltammetry technique.... 

    Electrochemical Redox Behaviour of Temozolomide Using a Glassy Carbon Electrode

    , Article Electroanalysis ; Volume 22, Issue 22 , September , 2010 , Pages 2633-2640 ; 10400397 (ISSN) Ghalkhani, M ; Fernandes, I. P. G ; Oliveira , S. C. B ; Shahrokhian, S ; Oliveira Brett, A. M ; Sharif University of Technology
    2010
    Abstract
    The electrochemical behaviour of temozolomide on a glassy carbon electrode has been investigated. The reduction of temozolomide is an irreversible process, pH dependent, and the mechanism involves the addition of one electron and one proton to C5 to form an anion radical, causing the irreversible breakdown of the tetrazinone ring. The oxidation mechanism of temozolomide is an irreversible, adsorption-controlled process, pH dependent up to value close to the pKa and occurs in two consecutive charge transfer reactions, with the formation of the hydroxylated product. The electroanalytical determination of TMZ led to a detection limit of 1.1 μM  

    A combined approach based on K-means and modified electromagnetism-like mechanism for data clustering

    , Article International Journal of Information Technology and Decision Making ; Volume 16, Issue 5 , 2017 , Pages 1279-1307 ; 02196220 (ISSN) Mehdizadeh, E ; Teimouri, M ; Zaretalab, A ; Akhavan Niaki, S. T ; Sharif University of Technology
    Abstract
    Clustering is one of the useful methods in many scientific fields. It is a classification process to group data in specific clusters based on their similarities. Many heuristic and meta-heuristic algorithms have been successfully applied in the literature to solve clustering problems. Among them, the K-means is one of the best due to its simplicity and computational efficiency. However, it suffers from several drawbacks, the most significant of which is its dependency on the initial state that leads to trapping in local optima. In this paper, the K-means method is combined with a modified electromagnetism-like mechanism (MEM) algorithm to develop a new algorithm called K-MEM in order to... 

    Payment minimisation auction with security constraints

    , Article IET Generation, Transmission and Distribution ; Volume 11, Issue 6 , 2017 , Pages 1370-1380 ; 17518687 (ISSN) Nouri, A ; Hosseini, S. H ; Sharif University of Technology
    Institution of Engineering and Technology  2017
    Abstract
    Among the different options available for market clearing mechanisms, offer cost minimisation mechanism is being used in most electric power markets. The payments are then calculated based on locational marginal prices (LMPs). The payments can be significantly higher due to the inconsistency of the clearing and pricing mechanisms. Payment cost minimisation (PCM) mechanism which directly minimises the total payment has been recently proposed to solve this issue. In this study, an auction mechanism is proposed for payment to suppliers minimisation (PSM) based on the LMPs instead of consumers payment minimisation (CPM). Using a proper formulation for the supply side reserve LMPs, the complete... 

    Novel experimental methods for the determination of the boundaries between conventional, severe and over shot peening processes

    , Article Surfaces and Interfaces ; Volume 13 , 2018 , Pages 233-254 ; 24680230 (ISSN) Maleki, E ; Unal, O ; Amanov, A ; Sharif University of Technology
    Elsevier B. V  2018
    Abstract
    Shot peening process is one of the severe plastic deformation methods which is well-recognized for the surface layer integrity of the components. This process, according to its energy level, can be categorized into three different cases of conventional, severe, and over shot peening. The aforementioned types of shot peening have positive and/or negative effects on their related performing conditions. In this study, the boundaries between these processes were determined for the first time by presenting novel approaches. The foundations of the presented approaches are microstructural investigations. The microstructures were characterized using optical microscopy, scanning electron microscopy,... 

    Effect of copper content on tensile mechanical properties of ternary NiTiCu alloy nanowire: molecular dynamics simulation

    , Article Materials Today: Proceedings ; Volume 5, Issue 1 , 2018 , Pages 1552-1555 ; 22147853 (ISSN) Fazeli, S ; Vahedpour, M ; Sadrnezhaad, K ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    Molecular dynamics (MD) simulation was used to study of mechanical properties of NiTiCu with different content of copper. It was shown that the percent composition of copper are significantly affects the stress-strain curves curve. The results showed that as the Cu content increased, the Yield Strength and Young's modulus decreased. © 2017 Elsevier Ltd  

    QBism is not so simply dismissed

    , Article Foundations of Physics ; Volume 50, Issue 7 , 2020 , Pages 693-707 Barzegar, A ; Sharif University of Technology
    Springer  2020
    Abstract
    QBism is one of the main candidates for an epistemic interpretation of quantum mechanics. According to QBism, the quantum state or the wavefunction represents the subjective degrees of belief of the agent assigning the state. But, although the quantum state is not part of the furniture of the world, quantum mechanics grasps the real via the Born rule which is a consistency condition for the probability assignments of the agent. In this paper, we evaluate the plausibility of recent criticism of QBism. We focus on the consequences of the subjective character of the quantum state, the issue of realism and the problem of the evolution of the quantum state in QBism. In particular, drawing upon...