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    Detection of thermal infrared (TIR) anomalies related to the M s=5.1 earthquake on Oct. 14, 2004 near Ravar (SE Iran)

    , Article Journal of the Earth and Space Physics ; Volume 35, Issue 4 , 2010 ; 03781046 (ISSN) Askari, Gh ; Hafezi, N ; Rahimi Tabar, M. R ; Ansari, A. R ; Sharif University of Technology
    2010
    Abstract
    Over the last two decades there have been numerous reports from different seismically active regions of the world that thermal infrared (TIR) anomalies can be identified around the epicentral areas before major earthquakes [e.g. (Tronin et al., 2002)]. The TIR anomalies reportedly appear as early as 14 to 7 days before the seismic events and affect areas as large as 1000s to 100,000s km2 in size. Our case study for detection of TIRs using NOAA-AVHRR data(Band 4) is an Ms = 5.1 earthquake that occurred on 14th October 2004 near Ravar in Kerman province located in Loot and Tabas deserts, southeast-central Iran. The area is part of the Golbaf-Sirj seismogenic zone. It includes major faults... 

    Simulation of optical interstellar scintillation

    , Article Astronomy and Astrophysics ; Volume 552, Article No. A93 , 2013 ; 00046361 (ISSN) Habibi, F ; Moniez, M ; Ansari, R ; Rahvar, S ; Sharif University of Technology
    2013
    Abstract
    Aims. Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected on a longer time scale when the light of remote stars crosses an interstellar turbulent molecular cloud, but it has never been observed at optical wavelengths. The aim of the study described in this paper is to fully simulate the scintillation process, starting from the molecular cloud description as a fractal object, ending with the simulations of fluctuating stellar light curves. Methods. Fast Fourier transforms are first used to simulate fractal clouds. Then, the illumination pattern resulting from the crossing of background star light through these refractive clouds is calculated... 

    Searching for galactic hidden gas through interstellar scintillation: Results from a test with the NTT-SOFI detector

    , Article Astronomy and Astrophysics ; Volume 525, Issue 6 , 2010 ; 00046361 (ISSN) Habibi, F ; Moniez, M ; Ansari, R ; Rahvar, S ; Sharif University of Technology
    2010
    Abstract
    Aims. Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected at a longer time scale when the light of remote stars crosses an interstellar molecular cloud, but it has never been observed at optical wavelength. In a favorable case, the light of a background star can be subject to stochastic fluctuations on the order of a few percent at a characteristic time scale of a few minutes. Our ultimate aim is to discover or exclude these scintillation effects to estimate the contribution of molecular hydrogen to the Galactic baryonic hidden mass. This feasibility study is a pathfinder toward an observational strategy to search for scintillation, probing... 

    Study of a strategy for parallax microlensing detection towards the Magellanic Clouds

    , Article Astronomy and Astrophysics ; Volume 412, Issue 1 , 2003 , Pages 81-90 ; 00046361 (ISSN) Rahvar, S ; Moniez, M ; Ansari, R ; Perdereau, O ; Sharif University of Technology
    EDP Sciences  2003
    Abstract
    In this article, we have investigated the possibility to distinguish between different galactic models through microlensing parallax studies. We show that a systematic search for parallax effects can be done using the currently running alert systems and complementary photometric telescopes, to distinguish between different lens distance distributions. We have considered two galactic dark compact object distributions, with total optical depths corresponding to the EROS current upper limits. These models correspond to two extreme hypotheses on a three component galactic structure made of a thin disk, a thick disk, and a spherically symmetric halo. Our study shows that for sub-solar mass... 

    Two phase modal analysis of nonlinear sloshing in a rectangular container

    , Article Ocean Engineering ; Volume 38, Issue 11-12 , August , 2011 , Pages 1277-1282 ; 00298018 (ISSN) Ansari, M. R ; Firouz Abadi, R. D ; Ghasemi, M ; Sharif University of Technology
    2011
    Abstract
    Sloshing, or liquid free surface oscillation, in containers has many important applications in a variety of engineering fields. The modal method can be used to solve linear sloshing problems and is the most efficient reduced order method that has been used during the previous decade. In the present article, the modal method is used to solve a nonlinear sloshing problem. The method is based on a potential flow solution that implements a two-phase analysis on sloshing in a rectangular container. According to this method, the solution to the mass conservation equation, with a nonpenetration condition at the tank walls, results in velocity potential expansion; this is similar to the mode shapes... 

    Passive primary/backup-based scheduling for simultaneous power and reliability management on heterogeneous embedded systems

    , Article IEEE Transactions on Sustainable Computing ; 2022 , Pages 1-12 ; 23773782 (ISSN) Yari-Karin, S ; Siyadatzadeh, R ; Ansari, M ; Ejlali, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2022
    Abstract
    In addition to meeting the real-time constraint, power/energy efficiency and high reliability are two vital objectives for real-time embedded systems. Recently, heterogeneous multicore systems have been considered an appropriate solution for achieving joint power/energy efficiency and high reliability. However, power/energy and reliability are two conflict requirements due to the inherent redundancy of fault-tolerance techniques. Also, because of the heterogeneity of the system, the execution of the tasks, especially real-time tasks, in the heterogeneous system is more complicated than the homogeneous system. The proposed method in this paper employs a passive primary/backup technique to... 

    3D modeling of a superconducting transition edge detector

    , Article 29th Iranian Conference on Electrical Engineering, ICEE 2021, 18 May 2021 through 20 May 2021 ; 2021 , Pages 56-60 ; 9781665433655 (ISBN) Ansari, S ; Nazifi, R ; Yaghoubi Arzefouni, M ; Mohajeri, R ; Mirzaei, I ; Fardmanesh, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    Improving the sensitivity and the time response of the superconducting transition edge detectors as one of the most promising technologies for millimeter and sub-millimeter wavelength radiation power detection is essential. Having an accurate 3D model for these detectors enables us to design faster detectors with higher sensitivity and detectivity. In this paper, we report on a 3-dimensional finite element model of a current biased superconducting YBa2Cu3O7-x (YBCO) transition-edge detector fabricated by a low-cost Metal-Organic deposition method. The obtained simulation results are in good agreement with the measured response of the detectors. Also, as the simulation results suggest,... 

    Understanding EROS2 observations toward the spiral arms within a classical Galactic model framework

    , Article Astronomy and Astrophysics ; Volume 604 , 2017 ; 00046361 (ISSN) Moniez, M ; Sajadian, S ; Karami, M ; Rahvar, S ; Ansari, R ; Sharif University of Technology
    EDP Sciences  2017
    Abstract
    Aims. EROS (Expérience de Recherche d'Objets Sombres) has searched for microlensing toward four directions in the Galactic plane away from the Galactic center. The interpretation of the catalog optical depth is complicated by the spread of the source distance distribution. We compare the EROS microlensing observations with Galactic models (including the Besançon model), tuned to fit the EROS source catalogs, and take into account all observational data such as the microlensing optical depth, the Einstein crossing durations, and the color and magnitude distributions of the catalogued stars. Methods. We simulated EROS-like source catalogs using the HIgh-Precision PARallax COllecting Satellite... 

    Peak power management to meet thermal design power in fault-tolerant embedded systems

    , Article IEEE Transactions on Parallel and Distributed Systems ; Volume 30, Issue 1 , 2019 , Pages 161-173 ; 10459219 (ISSN) Ansari, M ; Safari, S ; Yeganeh Khaksar, A ; Salehi, M ; Ejlali, A. R ; Sharif University of Technology
    IEEE Computer Society  2019
    Abstract
    Multicore platforms provide a great opportunity for implementation of fault-tolerance techniques to achieve high reliability in real-time embedded systems. Passive redundancy is well-suited for multicore platforms and a well-established technique to tolerate transient and permanent faults. However, it incurs significant power overheads, which go wasted in fault-free execution scenarios. Meanwhile, due to the Thermal Design Power (TDP) constraint, in some cases, it is not feasible to simultaneously power on all cores on a multicore platform. Since TDP is the maximum sustainable power that a chip can consume, violating TDP makes some cores automatically restart or significantly reduce their... 

    MANA: Microarchitecting a temporal instruction prefetcher

    , Article IEEE Transactions on Computers ; 2022 , Pages 1-1 ; 00189340 (ISSN) Ansari, A ; Golshan, F ; Barati, R ; Lotfi Kamran, P ; Sarbazi Azad, H ; Sharif University of Technology
    IEEE Computer Society  2022
    Abstract
    L1 instruction(L1-l) cache misses are a source of performance bottleneck. While many instruction prefetchers have been proposed, most of them leave a considerable potential uncovered. In 2011, Proactive Instruction Fetch (PIF) showed that a hardware prefetcher could effectively eliminate all instruction-cache misses. However, its enormous storage cost makes it impractical. Consequently, reducing the storage cost was the main research focus in instruction prefetching in the past decade. Several instruction prefetchers, including RDIP and Shotgun, were proposed to offer PIF-level performance with significantly lower storage overhead. However, our findings show that there is a considerable... 

    An optimal Liouville-Type Theorem for Radial Entire Solutions of the Porous Medium Equation with Source

    , M.Sc. Thesis Sharif University of Technology Ansari, Hajar (Author) ; Hesaraki, Mahmoud (Supervisor)
    Abstract
    In this thesis , we consider nonnegative (continuous) weak solutions of the porous medium equation with source , u_t-∆u^m=u^p, and p>m>1 .
    Assume that, m>1 and 1< p/m u_t-∆u^m=u^p,xϵR^n ,tϵR
    has no nontrivial, bounded radial solutions u≥0 .
    In one space-dimensional, the conclusion of the result mentioned above remains true without the assumption of the radial symmetry. The proof is based on the intersection-comparison arguments , zero number argum- ents and a key step is to show the... 

    Feasibility Study of Manufacturing of Disposable Plant Containers

    , M.Sc. Thesis Sharif University of Technology Ansari, Mahmood (Author) ; Mostafavi, Mostafa (Supervisor)
    Abstract
    Although laws vary in the competitive business world of today and the changing supply and demand parameters show that the process of delivering new products to market is very important.Most organizations today have found that spending more than ever on trusting in traditional competitive levers such as quality, cost reduction and differentiation in selling more products and services are not enough to be successful in market, instead notions such as speed, flexibility andagility can have a significant trend toward offering new products and services. There aresome good reasons for knew that organizations need new ways to develop their new products to survival, compete with its competitors and... 

    Finite Element Analysis of Buckling and Snaking Vibration for Drill String in the Horizental Well

    , M.Sc. Thesis Sharif University of Technology Ansari, Amir (Author) ; Behzad, Mehdi (Supervisor)
    Abstract
    Snaking Vibration and buckling of drill string in the horizontal well was investigated in this research. Sinusoidal and helical critical buckling load are obtained for a specific drill string.
    Drill string is modeled both analytically and numerically (finite element method). Drill pipes are considered as a clamped-clamped beam with constant cross section and the well is considered as a hollow cylinder. The thickness of cylinder was large enough to model the surrounding soil of the well. Buckling is a complex deformation and is somehow a random phenomenon. In addition, the length and the continuous contact between drill pipes and the well make the finite element model very huge and the... 

    Development of Seismic Fragility Curves for Reinforced Concrete Tall Buildings

    , M.Sc. Thesis Sharif University of Technology Ansari, Mojtaba (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    This study focuses on the risk assessment of reinforced concrete tall buildings subjected to ground motion excitation. In order to assess the vulnerability of tall buildings, twelve-, and twenty-four-story four-bay reinforced concrete moment resisting frames are studied. This evaluation is done through developing fragility curves. These fragility curves provide the probability of exceeding the multiple damage states for a given intensity (e.g. CAV) of ground motion excitation. To develop the fragility curves, a great number of nonlinear dynamic analyses were conducted in the open-source platform OpenSees. Since the PEER Guidelines for Performance-Based Seismic Design of tall buildings (PEER,... 

    Optimization of supercritical carbon dioxide extraction of essential oil from spearmint (Mentha spicata L.) leaves by using Taguchi methodology

    , Article Journal of Supercritical Fluids ; Volume 67 , July , 2012 , Pages 123-130 ; 08968446 (ISSN) Ansari, K ; Goodarznia, I ; Sharif University of Technology
    2012
    Abstract
    In this study, the essential oil of aerial parts species of a plant called Spearmint was extracted by CO 2 to optimize the results of the supercritical extraction process. In order to achieve maximum total yield extraction and SF-CO 2 concentration, tests were done in a laboratorial pilot considering the Taguchi method under following condition: pressure. 90,100,140,170 bar, temperature. of 35, 40, 45, 50 °C, mean particles size: 250,500,710,1000 μm, flow rate 1,3,5,8 ml/s and dynamic time 30,50,90,120 min. The optimizing conditions for SCE and SF-CO 2 concentration are: 90 bar, 45 °C, 500 μm, 5 ml/s, 120 min and 90 bar, 35 °C, 250 μm, 1 ml/s, 30 min. SCE total yield and CO 2 concentration... 

    Peak Power Management in Fault-tolerant Embedded Systems

    , M.Sc. Thesis Sharif University of Technology Ansari, Mohsen (Author) ; Ejlali, Alireza (Supervisor)
    Abstract
    Technology scaling allows integrating multiple cores onto a single chip to make the mainstream for advanced embedded systems. However, technology scaling is envisaged to aggravate the reliability of on-chip systems due to increasing transient fault rate due to lower voltages and shrinking transistor dimensions that lead to smaller critical charges. Transient faults are typically resulted due to high-energy particle strikes in hardware and manifest as bit flips. Multi-core systems provide a great opportunity to implement reliability mechanisms such as redundant multithreading (RMT) and process level redundancy. Task replication (e.g. RMT) is a well-established technique to achieve high... 

    The effects of geometrical parameters on force distributions and mechanics of carbon nanotubes: A critical study

    , Article Communications in Nonlinear Science and Numerical Simulation ; Volume 14, Issue 12 , 2009 , Pages 4246-4263 ; 10075704 (ISSN) Ansari, R ; Motevalli, B ; Sharif University of Technology
    2009
    Abstract
    In this paper, using the continuum approximation together with Lennard-Jones potential, a new semi-analytical expression is given to evaluate the van der Waals interaction between two single-walled carbon nanotubes. Based on this expression, two new formulations are also proposed to model multi-walled carbon nanotubes. In the first one, the interactions between each pair of shells from the inner and outer tubes are summed up over all of the pairs, whereas in the second formulation, a set of correction factors are applied to convert the results of double-walled carbon nanotubes to the correlated multi-walled ones. With respect to the present formulations, extensive studies on the variations... 

    Modelling and economic evaluation of pressure-retarded osmosis power plant case study: Iran

    , Article International Journal of Ambient Energy ; 2017 , Pages 1-13 ; 01430750 (ISSN) Ansari, A ; Abbaspour, M ; Sharif University of Technology
    2017
    Abstract
    In recent years, a growing interest in investigation of new energies has been observed. Pressure-retarded osmosis (PRO) could be a feasible source of renewable energy. This study aims to present a model based on the present technology of PRO power plant components for design and economic evaluation of a PRO power plant, and to investigate case studies in order to demonstrate how each main component of a PRO power plant affects the economic evaluation. Therefore, all the mechanisms including intake and outfall systems, pre-treatment system, membrane system, and transportation and generation systems are explicated and meant to present the capability of the model to design the PRO power plant.... 

    Seismic Assessment of Bridges with Spill-through Abutments

    , M.Sc. Thesis Sharif University of Technology Ansari, Saeed (Author) ; Maleki, Shervin (Supervisor)
    Abstract
    This research is studying seismic behavior of bridges with spill-through abutments. There is a lot of studies in the literature about the behavior of piers and different types of them in the field of seismic assessment of bridges. But seismic behavior of abutments has paid less attention. In addition, most researches in this field are about common types of abutments like wall-type or integral abutments and also there are few standards and design guidelines about spill-through abutments.However spill-through abutments had been used by designers, especially they are common in Iran.In this research, a bridge with a spill-through abutment is designed as a benchmark. The benchmark bridge is... 

    Modelling and economic evaluation of pressure-retarded osmosis power plant case study: Iran

    , Article International Journal of Ambient Energy ; Volume 40, Issue 1 , 2019 , Pages 69-81 ; 01430750 (ISSN) Ansari, A ; Abbaspour, M ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    In recent years, a growing interest in investigation of new energies has been observed. Pressure-retarded osmosis (PRO) could be a feasible source of renewable energy. This study aims to present a model based on the present technology of PRO power plant components for design and economic evaluation of a PRO power plant, and to investigate case studies in order to demonstrate how each main component of a PRO power plant affects the economic evaluation. Therefore, all the mechanisms including intake and outfall systems, pre-treatment system, membrane system, and transportation and generation systems are explicated and meant to present the capability of the model to design the PRO power plant....