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Cooling+Heating flows in galaxy clusters: Turbulent heating, spectral modeling, and cooling efficiency
, Article Astrophysical Journal ; Volume 884, Issue 1 , 2019 ; 0004637X (ISSN) ; Afshordi, N ; Khosroshahi, H. G ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
The discrepancy between expected and observed cooling rates of X-ray emitting gas has led to the cooling-flow problem at the cores of clusters of galaxies. A variety of models have been proposed to model the observed X-ray spectra and resolve the cooling-flow problem, which involves heating the cold gas through different mechanisms. As a result, realistic models of X-ray spectra of galaxy clusters need to involve both heating and cooling mechanisms. In this paper, we argue that the heating timescale is set by the magnetohydrodynamic (MHD) turbulent viscous heating for the Intracluster plasma, parameterized by the Shakura-Sunyaev viscosity parameter, α. Using a cooling+heating flow model, we...
Phase transition in modified newtonian dynamics (Mondian) self-gravitating systems
, Article Entropy ; Volume 23, Issue 9 , 2021 ; 10994300 (ISSN) ; Rahvar, S ; Rahimi Tabar, M. R ; Sharif University of Technology
MDPI
2021
Abstract
We study the statistical mechanics of binary systems under the gravitational interaction of the Modified Newtonian Dynamics (MOND) in three-dimensional space. Considering the binary systems in the microcanonical and canonical ensembles, we show that in the microcanonical systems, unlike the Newtonian gravity, there is a sharp phase transition, with a high-temperature homogeneous phase and a low-temperature clumped binary one. Defining an order parameter in the canonical systems, we find a smoother phase transition and identify the corresponding critical temperature in terms of the physical parameters of the binary system. © 2021 by the authors. Licensee MDPI, Basel, Switzerland
Solution of the Measurement Problem in Some Formulation of Quantum Mechanics and Bohm's Theory
, M.Sc. Thesis Sharif University of Technology ; Golshani, Mehdi (Supervisor)
Abstract
In spite of succesfull achievements of standard quantum mechanics in describing variety of physical phenomenons, this theory has some conceptual problems in some areas. One of the important problems is the behavior of macroscopic objects and their interaction with microscopic systems, which is called “measurement problem”. Actually because the standard quantum mechanic is linear, it anticipates the occurrence of superposition of macroscopic states which is in contrast with our understanding of macroscopic objects. The standard theory answers this problem by using the wave function reduction principle.
There has been various proposals about the mechanism of wave function reduction,...
There has been various proposals about the mechanism of wave function reduction,...
Observational Tests of MOdified Gravity (MOG)and Non-Local Gravity with Galaxies’ Dynamic
, Ph.D. Dissertation Sharif University of Technology ; Rahvar, Sohrab (Supervisor) ; Moffat, John (Co-Advisor)
Abstract
Dark matter is one of the biggest unsolved problems in physics and cosmology. Almost 85 percent of the gravitational matter is not luminous and it’s properties is unknown. In recent decades variety of investigations regarding dark matter has been done which we will mention in the beginning part of this thesis. We continue testing MOdified gravity (MOG), Non-Local-Gravity (NLG) and MOdified Newtonian Dynamics (MOND) in a different scale by using the rotation curves of dwarf galaxies. In addition we compare MOG, MOND and NLG together to see which one better fit observed data. In another investigation that is reported in this thesis, we fit the observed acceleration data of galaxy cluster Abell...
Towards energy optimization of transparent watermarks using entropy masking
, Article IASTED International Conference on Internet and Multimedia Systems and Applications, EuroIMSA 2005, Grindelwald, 21 February 2005 through 23 February 2005 ; 2005 , Pages 259-264 ; 0889864861 (ISBN) ; Ghaemmaghami, S ; Hamza M. H ; Sharif University of Technology
2005
Abstract
An invisible image watermarking scheme tends to insert the mark in a transparent manner, with the highest possible energy. Several watermarking algorithms use human visual models as perceptual masks to maximize the power of watermark. We take advantage of inhibitory and excitatory characteristics of eye receptors which yield an extra capacity, for amplifying watermark power, while still satisfying imperceptibility constraint. Spatial-domain image entropy is used as a measure of strength of inhibitory effect. The principle of our idea is based on the decomposition of mark sequence into two parts, corresponding to two complementary sets of pixels in spatial-domain. These sets are determined...
An optimal SVD-based watermarking framework through linear programming
, Article IASTED International Conference on Internet and Multimedia Systems and Applications, EuroIMSA 2005, Grindelwald, 21 February 2005 through 23 February 2005 ; 2005 , Pages 271-274 ; 0889864861 (ISBN) ; Ghaemmaghami, S ; Hamza M. H ; Sharif University of Technology
2005
Abstract
Transparent, robust watermarking schemes tend to insert invisible watermarks with the highest possible energy. Singular values, in singular value decomposition (SVD), are shown to be robust to intentional and unintentional attacks. However, none of the algorithms proposed in the literature considered the visual imperceptibility constraint imposed by the human visual models. In this paper, we introduce an optimal SVD-based embedding framework, based on the well-known linear programming concept. Given a binary sequence of the mark, we show how to insert the message with the highest possible magnitude, without outlawing the just noticeable thresholds driven by the human visual system models in...
Modified gravity (MOG) and the abell 1689 cluster acceleration data
, Article European Physical Journal Plus ; Volume 132, Issue 10 , 2017 ; 21905444 (ISSN) ; Zhoolideh Haghighi, M. H ; Sharif University of Technology
2017
Abstract
The galaxy cluster system Abell 1689 has been well studied and yields good lensing and X-ray gas data. Modified gravity (MOG) is applied to the Abell 1689 cluster and the acceleration data is well fitted without assuming dark matter. Newtonian dynamics and modified Newtonian dynamics (MOND) are shown not to fit the acceleration data, while a dark matter model based on the Navarro-Frenk-White (NFW) mass profile is shown to fit the acceleration data for the radial range r> 200 kpc. © 2017, Società Italiana di Fisica and Springer-Verlag GmbH Germany
An investigation on the torsional sensitivity and resonant frequency of an AFM with sidewall and top-surface probes
, Article ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC/CIE2010, Montreal, QC, 15 August 2010 through 18 August 2010 ; Volume 4 , 2010 , Pages 589-599 ; 9780791844120 (ISBN) ; Ahmadian, M. T ; Haghighi, P ; Haghighi, A ; Sharif University of Technology
2010
Abstract
The resonant frequencies and torsional sensitivities of an atomic force microscope (AFM) with assembled cantilever probe (ACP) are studied. This ACP comprises a horizontal cantilever, a vertical extension and two tips located at the free ends of the cantilever and the extension which makes the AFM capable of simultaneous topography at top-surface and sidewalls of microstructures especially microgears which consequently leads to a time-saving swift scanning process. In this work, the effects of the sample surface contact stiffness and the geometrical parameters such as the ratio of the vertical extension length to the horizontal cantilever length and the distance of the vertical extension...
An investigation on the flexural sensitivity and resonant frequency of an AFM with sidewall and top-surface probes
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 12 November 2010 through 18 November 2010, Vancouver, BC ; Volume 10 , 2010 , Pages 419-427 ; 9780791844472 (ISBN) ; Ahmadian, M. T ; Haghighi, P ; Haghighi, A ; Sharif University of Technology
2010
Abstract
The resonant frequencies and flexural sensitivities of an atomic force microscope (AFM) assembled cantilever probe which comprises a horizontal cantilever, a vertical extension and two tips located at the free ends of the cantilever and the extension are studied. This probe makes the AFM capable of simultaneous topography at top-surface and sidewalls of microstructures especially microgears which leads to a time-saving swift scanning process. In this work, the effects of the sample surface contact stiffness and the geometrical parameters such as the ratio of the vertical extension length to the horizontal cantilever length and the distance of the vertical extension from clamped end of the...
Sensitivity and resonant frequency of an AFM with sidewall and top-surface probes for both flexural and torsional modes
, Article International Journal of Mechanical Sciences ; Volume 52, Issue 10 , October , 2010 , Pages 1357-1365 ; 00207403 (ISSN) ; Ahmadian, M. T ; Haghighi, P ; Haghighi, A ; Sharif University of Technology
2010
Abstract
The resonant frequencies and flexural sensitivities of an atomic force microscope (AFM) with assembled cantilever probe (ACP) are studied. This ACP comprises a horizontal cantilever, a vertical extension and two tips located at the free ends of the cantilever and the extension, which makes the AFM capable of simultaneous topography at top surface and sidewalls of microstructures especially microgears, which consequently leads to a time-saving swift scanning process. In this work, the effects of the sample surface contact stiffness and the geometrical parameters such as the ratio of the vertical extension length to the horizontal cantilever length and the distance of the vertical extension...
Model-based topography estimation in trolling mode atomic force microscopy
, Article Applied Mathematical Modelling ; Volume 77 , 2020 , Pages 1025-1040 ; Sajjadi, M ; Nejat Pishkenari, H ; Sharif University of Technology
Elsevier Inc
2020
Abstract
In this study, a novel approach based on a modified Kalman filter algorithm is presented to directly estimate and measure the surface topography of samples by trolling mode atomic force microscopy. Trolling mode atomic force microscopy was introduced as an atomic force microscopy alternative to overcome imaging problems in liquid environments by reducing the liquid-resonator interaction forces. In conventional imaging techniques, the time to reach the steady state periodic motion of the oscillating probe restricts scanning speed. To overcome this limitation, we propose a novel imaging technique for trolling mode atomic force microscopy based on the system dynamics model and using the...
Torsional sensitivity and resonant frequency of an AFM with parallel sidewall probes
, Article Proceedings of the ASME Design Engineering Technical Conference, 15 August 2010 through 18 August 2010, Montreal, QC ; Volume 5 , 2010 , Pages 987-996 ; 9780791844137 (ISBN) ; Kahrobaiyan, M. H ; Haghighi, P ; Yousefi, A ; Sharif University of Technology
2010
Abstract
The resonant frequencies and torsional sensitivities of an atomic force microscope (AFM) assembled cantilever probe which comprises a horizontal cantilever, two vertical extensions and two tips located at their free ends are studied. This probe makes the AFM capable of measuring, for instance, the outer/inner diameter, roundness and roughness of microstructures like micro-holes and micro nozzles which leads to a time-saving swift scanning process. In this work, the effects of the sample surface contact stiffness and the geometrical parameters such as the ratio of the vertical extension length to the horizontal cantilever length and the distance of the first vertical extension from the...
Real-time topography and hamaker constant estimation in atomic force microscopy based on adaptive fading extended kalman filter
, Article International Journal of Control, Automation and Systems ; Volume 19, Issue 7 , 2021 , Pages 2455-2467 ; 15986446 (ISSN) ; Nejat Pishkenari, H ; Sharif University of Technology
Institute of Control, Robotics and Systems
2021
Abstract
In this study, a novel technique based on adaptive fading extended Kalman filter for atomic force microscopy is proposed to directly estimate the topography of a sample surface without needing any control system. While in conventional imaging techniques, the scanning speed or the bandwidth is limited due to a relatively large settling time, the method proposed in this research is able to address this issue and estimate the topography throughout transient oscillation of the microcantilever. With this aim, an estimation process using an adaptive fading extended Kalman filter (augmented with forgetting factor) as the system observer is designed and coupled with the system dynamics to obtain...
Towards a calculus for nondeterministic schemas in Z
, Article International Journal of Software Engineering and Knowledge Engineering ; Volume 22, Issue 6 , September , 2012 , Pages 839-865 ; 02181940 (ISSN) ; Mirian Hosseinabadi, S. H ; Sharif University of Technology
World Scientific
2012
Abstract
In our previous work, we presented a Z-based formalism, called NZ, by which one can explicitly specify bounded, unbounded, erratic, angelic, demonic, loose, strict, singular, and plural nondeterminism. The NZ notation is mainly based on a new notion of operation schemas, called multi-schema. Since the operations of the Z schema calculus do not work on multi-schemas anymore, in this paper we augment NZ with a new set of schema calculus operations that can be applied on multi-schemas as well as ordinary operation schemas. To demonstrate the usability of the resulting formalism, we show how this formalism can assist to model game-like situations and concurrent systems as two well-known classes...
A safe stopping protocol to enable reliable reconfiguration for component-based distributed systems
, Article 6th International Conference on Fundamentals of Software Engineering, FSEN 2015, 22 April 2015 through 24 April 2015 ; Volume 9392 , November , 2015 , Pages 100-109 ; 03029743 (ISSN) ; 9783319246437 (ISBN) ; Heydarnoori, A ; Haghighi, H ; Sharif University of Technology
Springer Verlag
2015
Abstract
Despite the need for change, highly available software systems cannot be stopped to perform changes because disruption in their services may consequent irrecoverable losses. Current work on runtime evolution are either too disruptive, e.g., "blackouts" in unnecessary components in the quiescence criterion approach or presume restrictive assumptions such as the "black-box design" in the tranquility approach. In this paper, an architecture-based approach, called SAFER, is proposed which provides a better timeliness by relaxing any precondition required to start reconfiguration. We demonstrate the validity of the SAFER through model checking and a realization of the approach on a component...
A refinement approach for developing probabilistic programs
, Article 2009 14th International CSI Computer Conference, CSICC 2009, 20 October 2009 through 21 October 2009 ; 2009 , Pages 140-145 ; 9781424442621 (ISBN) ; Mirian Hosseinabadi, S. H ; Sharif University of Technology
2009
Abstract
In this paper, we introduce a refinement approach to develop probabilistic programs formally. To achieve this goal, we first present a way to specify probabilistic programs in a Z-based notation. We then use an existing method of translating Z into a refinement calculus to transform our Z-style specifications of probabilistic programs into specification statements of the refinement calculus. We finally add new laws to the refinement calculus helping us to refine the resulting specification statements into probabilistic choice constructs of a probabilistic imperative language. In this way, we will provide a completely formal way for developing probabilistic programs. ©2009 IEEE
Nondeterminism in constructive Z
, Article Fundamenta Informaticae ; Volume 88, Issue 1-2 , 2008 , Pages 109-134 ; 01692968 (ISSN) ; Mirian Hosseinabadi, S. H ; Sharif University of Technology
2008
Abstract
The abstraction inherent in most specifications and the need to specify nondeterministic programs are two well-known sources of nondeterminism in formal specifications. In this paper, we present a Z-based formalism by which one can specify bounded, unbounded, erratic, angelic, demonic, loose, strict, singular, and plural nondeterminism. To interpret our specifications, we use a constructive set theory, called CZ set theory, instead of the classical set theory Z. We have chosen CZ since it allows us to investigate the notion of nondeterminism from the formal program development point of view. In this way, we formally construct functional programs from Z specifications and then probe the...
An approach to nondeterminism in translation of CZ set theory into martin-Löf 's theory of types
, Article Electronic Notes in Theoretical Computer Science ; Volume 159, Issue 1 , 2006 , Pages 117-137 ; 15710661 (ISSN) ; Mirian Hosseinabadi, S. H ; Sharif University of Technology
2006
Abstract
Due to the high level of abstraction involved in formal specification of software systems, nondeterminism comes as an inevitable part of formal specifications. Therefore, support for nondeterminism should be provisioned in developing programs from their formal specifications. In this paper, an existing translation of CZ set theory into Martin-Löf's theory of types is extended to consider nondeterministic specifications in CZ language. © 2006 Elsevier B.V. All rights reserved
A one-DOF passive glove for thumb rehabilitation
, Article Scientia Iranica ; Volume 29, Issue 4 B , 2022 , Pages 1806-1816 ; 10263098 (ISSN) ; Zohoor, H ; Haghighi, S. E ; Soleimanimehr, H ; Sharif University of Technology
Sharif University of Technology
2022
Abstract
Wearable robots are becoming increasingly practical to use to rehabilitate wounded parts of the body as the number of injuries to the hand, particularly fingers, has increased. Wearable robots are designed to help people save time and money. This exoskeleton is intended to rehabilitate the thumb such that it may do an opposing movement with one Degree Of Freedom (DOF) and a cable system. Two drums, one on the thumb and the other on the tip of the assistive finger place the cables, which feature a cable adjusting screw that can be adjusted for fingers of various lengths. To choose the assistive finger from 4 intact fingers, the two perspectives of the cable length changes and finger forces...
Polyelectrolyte nanocomposite membranes using imidazole-functionalized nanosilica for fuel cell applications
, Article Journal of Macromolecular Science, Part B: Physics ; Volume 54, Issue 1 , Nov , 2015 , Pages 17-31 ; 00222348 (ISSN) ; Ghaffarian, S. R ; Nouri, M ; Jaafarnia, E ; Haghighi, A. H ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
The preparation and characterization of a new type of nanocomposite polyelectrolyte membrane, based on DuPont Nafion/imidazole-modified nanosilica (Im-Si), for direct methanol fuel cell applications is described. Related to the interactions between the protonated imidazole groups, grafted on the surface of nanosilica, and negatively charged sulfonic acid groups of Nafion, new electrostatic interactions can be formed in the interface of Nafion and Im-Si which result in both lower methanol permeability and also higher proton conductivity. Physical characteristics of these manufactured nanocomposite membranes were investigated by scanning electron microscopy, thermogravimetry analysis,...