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Entropy generation analysis of thermally developing forced convection in fluid-saturated porous medium
, Article Applied Mathematics and Mechanics (English Edition) ; Volume 29, Issue 2 , 2008 , Pages 229-237 ; 02534827 (ISSN) ; Ejlali, A ; Hooman, F ; Sharif University of Technology
2008
Abstract
Entropy generation for thermally developing forced convection in a porous medium bounded by two isothermal parallel plates is investigated analytically on the basis of the Darcy flow model where the viscous dissipation effects had also been taken into account. A parametric study showed that decreasing the group parameter and the Péclet number increases the entropy generation while for the Brinkman number the converse is true. Heatline visualization technique is applied with an emphasis on the Br < 0 case where there is somewhere that heat transfer changes direction at some streamwise location to the wall instead of its original direction, i.e., from the wall. © 2008 Editorial Committee of...
Entropy generation for forced convection in a porous channel with isoflux or isothermal walls
, Article International Journal of Exergy ; Volume 5, Issue 1 , 2008 , Pages 78-96 ; 17428297 (ISSN) ; Hooman, F ; Mohebpour, S. R ; Sharif University of Technology
Inderscience Publishers
2008
Abstract
A numerical study is reported to investigate the entropy generation due to forced convection in a parallel plate channel filled by a saturated porous medium. Two different thermal boundary conditions are considered being isoflux and isothermal walls. Effects of the Poclet number, the porous medium shape factor, the dimensionless temperature difference for isothermal walls, the dimensionless heat flux for isoflux walls, and the Brinkman number on the Bejan number as well as the local and average dimensionless entropy generation rate are examined. Copyright © 2008 Inderscience Enterprises Ltd
Reliability-based Evaluation and Calibration of Load Combinations for the Design of Steel Building Structures of Iran
, M.Sc. Thesis Sharif University of Technology ; Mahsuli, Mojtaba (Supervisor) ; Ghasemi, Hooman ($item.subfieldsMap.e)
Abstract
The objective of this thesis is to evaluate and calibrate design load combinations of steel building structures of Iran based on the reliability theory. The importance of this research stems from recognition that the design load combinations for steel structures in Section 6 of the National Building Code of Iran have been completely adopted from the ASCE/SEI 7-10 standard, whereas the factors that affect these load combinations differ in Iran from those of the United States. Examples are the difference in the construction industry economy, lower quality of here and the differences in probability distributions for the specifications of steel. Hence, the load combinations need to be calibrated...
A resistive ram-based FPGA architecture equipped with efficient programming circuitry
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 65, Issue 7 , 2018 , Pages 2196-2209 ; 15498328 (ISSN) ; Asadi, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Despite the considerable effort has been put on the application of Non-Volatile Memories (NVMs) in Field-Programmable Gate Arrays FPGAs, previously suggested designs are not mature enough to substitute the state of-the-art SRAM-based counterparts mainly due to the inefficient building blocks and/or the overhead of programming structure which can impair their potential benefits. In this paper, we present a Resistive Random Access Memory RRAM-based FPGA architecture employing efficient Switch Box (SB) and Look-Up Table (LUT) designs with programming circuitry integrated in both SB and LUT designs that creates area and power efficient programmable components while precluding performance...
A study of Quasars at Optical Wavelengths as a Means of Detecting Gravitational Grating
, M.Sc. Thesis Sharif University of Technology ; Rahvar, Sohrab (Supervisor)
Abstract
After Supernovae and gamma-ray bursts, Quasars are the brightest in the Universe. They are powered by supermassive black holes which lie at the center of the galaxies. Perturbations in space-time metrics by massive galaxies near the line of sight of the quasar can lead to strong lensing and create multiple pictures. Gravitationally lensed quasar systems yield abundant data sets for astrophysical and cosmological experimentation. In this thesis survey results of the multiply lensed SDSS J1206+4332 is studied. Candidate phenomenons are microlensing and gravitational grating. Gravitational grating studies the interaction of electromagnetic wave and gavitational wave in both geometric and wave...
Quality of service provisioning in optical CDMA packet networks
, Article Journal of Optical Communications and Networking ; Volume 2, Issue 5 , 2010 , Pages 283-292 ; 19430620 (ISSN) ; Pakravan, M. R ; Sharif University of Technology
2010
Abstract
An enhanced media access control (MAC) layer protocol that uses the signaling method benefits of the physical layer in order to provide different levels of quality to different users in optical code-division multiple-access (OCDMA) packet networks is presented. In the proposed network architecture the users are categorized into two classes of service, one having a higher quality level and the other having a lower quality level. Users of each class transmit at the same power level and different from the other classes users. Also, the MAC of each user estimates the amount of interference on the channel and adjusts the packet transmissions time to improve network performance. Through simulation...
Discrimination between gamma and proton-induced showers using the parabolic shape of the air shower front
, Article Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment ; Volume 1042 , 2022 ; 01689002 (ISSN) ; Bahmanabadi, M ; Sharif University of Technology
Elsevier B.V
2022
Abstract
It was used CORSIKA simulations to investigate the characteristics of showers with energies comprised between 1014–1016eV. All simulations were performed for an altitude of 1200 m above sea level (altitude of Alborz Observatory at Tehran). By fitting the parabolic curve on the air shower front, its focal length can be obtained. The results of this study show that the focal length of the air shower front of gamma rays is separable from cosmic protons and this can be used as a hybrid for other methods of separating the two kind particles from each other. © 2022
Numerical Simulation of Compressible Flow with Nonequilibrium Chemistry Effects by Solving Boltzmann Equation using High-Order Accurate Finite-Difference Method
, M.Sc. Thesis Sharif University of Technology ; Hejranfar, Kazem (Supervisor)
Abstract
In this study, a gas kinetic model is presented and applied to investigate the compressible rarefied gas flows with nonequilibrium chemical reactions effects. The formulation of the Boltzmann equation is extended to incorporate these chemical reactions, and the resulting equations are numerically solved using the fifth-order WENO finite difference method to achieve high accuracy. The present research focuses on solving one-dimensional flows. After developing the WENO-based Boltzmann solver, its validation is performed through numerical simulations of different one-dimensional shock tube problems under different conditions. The results show good agreement with existing results, confirming the...
Intelligent classification of web pages using contextual and visual features
, Article Applied Soft Computing Journal ; Volume 11, Issue 2 , 2011 , Pages 1638-1647 ; 15684946 (ISSN) ; Fotouhi, M ; Khaleghi, M ; Sharif University of Technology
2011
Abstract
In this paper we address classification of Web content and in particular its application in the detection of pornographic Web pages. Filtering of undesirable Web content is mainly achieved based on blocking a specific Web address via searching it in a reference list of black URLs or doing a plain contextual analysis on the page by searching special keywords in the text. The main problem with current filtering methods is the requirement for instantly update of the URL list and also the high rate of over-blocking the usual pages. In this paper, we propose an intelligent approach which is based on using textual, profile, and visual features in a hierarchical structure classifier. Textual...
A scalable dependability scheme for routing fabric of SRAM-based reconfigurable devices
, Article IEEE Transactions on Very Large Scale Integration (VLSI) Systems ; Volume 23, Issue 9 , August , 2015 , Pages 1868-1878 ; 10638210 (ISSN) ; Asadi, H ; Khaleghi, B ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
With the continual scaling of feature size, system failure due to soft errors is getting more frequent in CMOS technology. Soft errors have particularly severe effects in static random-access memory (SRAM)-based reconfigurable devices (SRDs) since an error in SRD configuration bits can permanently change the functionality of the system. Since interconnect resources are the dominant contributor to the overall configuration memory upsets in SRD-based designs, the system failure rate can be significantly reduced by mitigating soft errors in routing fabric. This paper first presents a comprehensive analysis of SRD switch box susceptibility to short and open faults. Based on this analysis, we...
Analysis of throughput and delay in a spectrally phase-encoded optical CDMA packet network
, Article 4th IEEE and IFIP International Conference on Wireless and Optical Communications Networks, WOCN 2007, Singapore, 2 July 2007 through 4 July 2007 ; 2007 ; 1424410045 (ISBN); 9781424410040 (ISBN) ; Khaleghi, S ; Jamshidi, K ; Sharif University of Technology
2007
Abstract
In this paper, analysis of the throughput and delay in a spectrally phase-encoded optical code-division multiple-access (OCDMA) system, using a simplified slotted packet network protocol is conducted. Steady-state throughput and average packet delay of the system are derived. In evaluating the performance of the system, only multiple access interference is considered and other sources of noise are neglected. Comparing different systems with the fixed bit rate and chip duration leads us to conclude that increasing the code length will improve the performance of networks with small average activity; but in highly active networks, decreasing the code length will result in a significant...
Investigation on the Effect of Earthquake loads on Segmental Lining in Tunnel
, M.Sc. Thesis Sharif University of Technology ; Sadaghiani, Mohammad Hossein (Supervisor)
Abstract
Recently, considerable efforts have been devoted to evaluation of seismic dynamic response of a circular tunnel. Conventional approaches have considered integral liners embedded in an elastic medium. In this study, we model a circular tunnel driven by TMB in homogeneous soil. Tunnel lining with 6 pieces of segments is analyzed by software in three dimensions. The results demonstrate that the stiffness difference between the segment and joints can enhance the internal forces of the segment significantly, which is crucial for the design of segments. The design of tunnel segment joints and joints between tunnels and portal structures are investigated by comparing with different parameters of...
Investigation of the Characteristics of High Energy Cosmic Rays Using the Corsika Code
, M.Sc. Thesis Sharif University of Technology ; Bahmanabadi, Mahmoud (Supervisor)
Abstract
This thesis discusses cosmic particles. Cosmic particles are originated by stars and black holes that could live in the Milky Way or other galaxies. These energetic particles can be protons, carbon, iron, gamma, electrons and positrons, and so on. After reaching the earth, these particles collide with atmospheric atoms to make the first interaction, which leads to the production of secondary particles. The number of secondary particles produced also increases steadily due to successive collisions with atmospheric atoms. The set of secondary particles that originate from the cosmic primary particle is called the extensive air shower. The aim of this paper is to investigate the properties of...
Numerical and Laboratory Modeling of the Movement of Stems of Aquatic Plants under the Effect of Waves
, M.Sc. Thesis Sharif University of Technology ; Jamali, Mirmosadegh (Supervisor)
Abstract
Studying the dynamics of submerged and semi-submerged plant stems in shallow waters is important because it affects environmental processes and the stability of coastal ecosystems. The stems play a key role in ecosystem management by influencing wave energy dissipation. One of the effective parameters in stem dynamics is structural damping, which hasn't really been included in numerical models describing stem behavior before. In this research, two numerical models were developed to study the stem motion under waves; one model was for small deformations and the other one for large deformations. The results showed that both models predicted the stem dynamic behavior with quite good accuracy....
Providing multiclass of services in optical CDMA packet networks
, Article 4th IEEE/IFIP International Conference in Central Asia on Internet, ICI 2008, Tashkent, 23 September 2008 through 25 September 2008 ; 2008 ; 9781424422838 (ISBN) ; Pakravan, M. R ; Goudarzi, H ; Sharif University of Technology
2008
Abstract
In this paper we discuss and analyze an enhanced media access control (MAC) layer protocol which uses the signaling method benefits of physical layer in order to provide different quality of service (QoS) levels in optical code-division multiple-access (OCDMA) packet networks. In the proposed network architecture the users are categorized into the high and low classes of service. Users of each class transmit at the same power level and different from the other classes' users. Also, the MAC of each user estimates the amount of interference on the channel and adjusts the packet transmission's time to improve network performance. Through simulation it is shown that the combination of...
Context-Aware ontology-based security measurement model
, Article Journal of Information Security and Applications ; Volume 67 , 2022 ; 22142134 (ISSN) ; Aref, M. R ; Rasti, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Security measurement models (SMMs) and quantitative security metrics (QSMs) are crucial pillars of systematic security measurement. How to design the enhanced SMMs and effective QSMs has been seriously considered in recent years. However, to the best of our knowledge, a desirable SMM has not yet been provided to measure the security effectiveness of a national-level network (NLN) due to its specific attributes. NLN has three main attributes, including plurality and diversity of network components, continuous changes, and simultaneous functionalities. These attributes cause three major challenges to designing a desirable SMM for NLN, including complexity, dynamic measurement, and...
Comprehensive comparison of security measurement models
, Article Journal of Applied Security Research ; 2022 ; 19361610 (ISSN) ; Aref, M. R ; Rasti, M ; Sharif University of Technology
Routledge
2022
Abstract
Security measurement models (SMMs) and their corresponding derived metrics form the main pillars of a systematic security measurement. Providing a desirable SMM is very challenging and has been investigated over the past two decades, so that numerous SMMs have been proposed and several surveys on SMMs have been performed. However, to the best of our knowledge, neither a systematic taxonomy nor a comprehensive comparison has yet been proposed for SMMs. This paper focuses on the comprehensive comparison of SMMs relying on a feature-based approach. The plurality and diversity of the compared SMMs enable us to deduce all the open issues. © 2021 Taylor & Francis Group, LLC
Comprehensive Comparison of Security Measurement Models
, Article Journal of Applied Security Research ; Volume 18, Issue 3 , 2023 , Pages 333-401 ; 19361610 (ISSN) ; Aref, M. R ; Rasti, M ; Sharif University of Technology
Routledge
2023
Abstract
Security measurement models (SMMs) and their corresponding derived metrics form the main pillars of a systematic security measurement. Providing a desirable SMM is very challenging and has been investigated over the past two decades, so that numerous SMMs have been proposed and several surveys on SMMs have been performed. However, to the best of our knowledge, neither a systematic taxonomy nor a comprehensive comparison has yet been proposed for SMMs. This paper focuses on the comprehensive comparison of SMMs relying on a feature-based approach. The plurality and diversity of the compared SMMs enable us to deduce all the open issues. © 2021 Taylor & Francis Group, LLC
TooT: An efficient and scalable power-gating method for NoC routers
, Article 10th IEEE/ACM International Symposium on Networks-on-Chip, NOCS 2016, 31 August 2016 through 2 September 2016 ; 2016 ; 9781467390309 (ISBN) ; Taram, M ; Khaleghi, B ; Hessabi, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
With the advent in technology and shrinking the transistor size down to nano scale, static power may become the dominant power component in Networks-on-Chip (NoCs). Powergating is an efficient technique to reduce the static power of under-utilized resources in different types of circuits. For NoC, routers are promising candidates for power gating, since they present high idle time. However, routers in a NoC are not usually idle for long consecutive cycles due to distribution of resources in NoC and its communication-based nature, even in low network utilizations. Therefore, power-gating loses its efficiency due to performance and power overhead of the packets that encounter powered-off...
Introduction to emerging SRAM-Based FPGA architectures in dark silicon Era
, Article Advances in Computers ; Volume 110 , 2018 , Pages 259-294 ; 00652458 (ISSN); 9780128153581 (ISBN) ; Ebrahimi, Z ; Khaleghi, B ; Asadi, H ; Sharif University of Technology
Academic Press Inc
2018
Abstract
The increased leakage power of deep-nano technologies in the one hand, and exponential growth in the number of transistors in a given die particularly in Field-Programmable Gate Arrays (FPGAs) have resulted in an intensified rate of static power dissipation as well as power density. This ever-increasing static power consumption acts as a power wall to further integration of transistors and has caused the breakdown of Dennard scaling. To meet the available power budget and preclude reliability challenges associated with high power density, designers are obligated to restrict the active percentage of the chip by powering off a selective fraction of silicon die, referred to as Dark Silicon....