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sharif-ahmadian--alireza
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Reducing the Energy Consumption of Fault-Tolerant Embedded Systems Using Feedback Control Approaches
, M.Sc. Thesis Sharif University of Technology ; Ejlali, Alireza (Supervisor)
Abstract
Recently, the tradeoff between low energy consumption and high fault-tolerance has attracted a lot of attention as a key issue in the design of real-time embedded systems. Dynamic Voltage Scaling (DVS) is known as one of the most effective low energy techniques for real-time systems. Control-theoretic DVS techniques, which have been exploited recently for DVS-enabled systems, are able to adapt well to dynamic workload. In this thesis, we have combined the above two important issues i.e., the control-theoretic DVS and fault-tolerance, and investigated reducing the energy consumption of fault-tolerant hard real-time systems using feedback control theory. Our proposed feedback-based DVS method...
Development of an Energy Management Technique for Automata-Based Embedded Systems
, M.Sc. Thesis Sharif University of Technology ; Ejlali, Alireza (Supervisor)
Abstract
Event-based embedded systems are usually energy-constrained and also have to be highly reliable. This thesis presents a novel energy-efficient standby-sparing technique for eventbased embedded systems. It speculatively pre-executes reaction tasks prior to events, resulting in a high available slack time for energy management. Although the prediction might be wrong, we will show that in average the proposed speculative standby-sparing technique (SSS) consumes less energy compared to non-speculative techniques. We present some real-life examples of event-based embedded systems to justify practical use for the proposed technique. To evaluate SSS extensive experiments were conducted on a variety...
Simulation of Drug Delivery to Knee Cartilage using High Intensity Focused Ultrasound and Providing Solutions to Improve Drug Delivery
, M.Sc. Thesis Sharif University of Technology ; Ahmadian, Mohamad Taghi (Supervisor)
Abstract
According to statistics published by the World Health Organization, 9.6% of men and 18% of women over the age of 60 exhibit symptoms of osteoarthritis(OA). Cur- rently, there is no cure for OA, but there are medications that have shown promising results. Drug delivery methods to the cartilage include oral and injectable adminis- tration, neither of which deliver sufficient amounts of the drug to the cartilage unless administered in high doses, which can cause toxicity. High-Intensity Focused Ultra- sound (HIFU) can play a role in drug delivery to the cartilage by creating a pressure field. HIFU application to the body is non-invasive as it is applied externally. Ad- ditionally, HIFU can...
Effect of temper rolling and subsequent annealing on texture development and magnetic permeability of semi-processed electrical steel with 2.3 wt.% Si
, Article International Journal of Materials Research ; Volume 109, Issue 10 , 2018 , Pages 930-937 ; 18625282 (ISSN) ; Akbarzadeh, A ; Sharif University of Technology
Carl Hanser Verlag
2018
Abstract
The effect of temper rolling and subsequent annealing on texture development and magnetic properties of semi-processed non grain oriented electrical steel has been investigated. The result shows that 5 % temper rolling and final annealing at 850 8C resulted in strong a-fiber component. The etch-pit technique shows that strain induced boundary migration is responsible for new texture component augmentation. Vibrating sample magnetometery reveals that maximum and minimum magnetic permeability are related to rolling and transverse directions, respectively. Average magnetic permeability is improved to some extent as a result of temper rolling and subsequent annealing. © Carl Hanser Verlag GmbH &...
The influence of vertical deflection of the supports in modeling squeeze film damping in torsional micromirrors
, Article Microelectronics Journal ; Volume 43, Issue 8 , 2012 , Pages 530-536 ; 00262692 (ISSN) ; Taghi Ahmadian, M ; Sharif University of Technology
Elsevier
2012
Abstract
The objective of this work is to create an analytical framework to study the problem of squeezed film damping in micromirrors considering the bending of the supporting torsion microbeams. Using mathematical and physical justifications, nonlinear Reynolds equation governing the behavior of the squeezed gas underneath the mirror is linearized. The resulting linearized equation is then nondimensionalized and analytically solved for two cases of the infinitesimal and finite tilting angle of the mirror. The obtained pressure distribution from the solution of the Reynolds equation is then utilized for finding the squeezed film damping force and torque applied to the mirror. The results show that...
Design and analysis of a 3-link micro-manipulator actuated by piezoelectric layers
, Article Mechanism and Machine Theory ; Volume 112 , 2017 , Pages 43-60 ; 0094114X (ISSN) ; Jafarishad, H ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
The purpose of this paper is to design and analyze a 3-link micro-device proposed as a micro-manipulator. This micro-manipulator includes 3 micro-beams as links connected to one another with no conventional or flexural joints. While the structure of the micro-manipulator is monolithic, end-effector workspace is achieved through deflection of links which is actuated by piezoelectric layers. By combining static analysis of the links through a multilayer piezoelectric beam model and kinematic analysis of the micro-manipulator, inverse kinematic has been solved utilizing the Taylor series expansion technique and the perturbation method. The obtained results through the present model reveal that...
A new model for dynamic analysis of side mounted diffuser valve micropumps
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Mehrabian, A ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
Valveless micropumps are widely used due to simple structure, durability and low maintenance. Understanding the fluid-membrane interaction and performance criteria is still a challenging problem for the scientists. In this work, a new model for side mounted valve micropumps is developed to obtain dynamic response of micropump with respect to piezoelectric actuation. The parameters of this model are obtained in terms of actuation frequency and geometrical dimensions of the micropump. Balancing elastic, inertial and damping forces result in the governing equation of the micropump system model. Analytical studies for the bottom mounted valve micropump indicate pump flux is independent of the...
Piecewise affine large signal modeling of PFC rectifiers
, Article 2007 IEEE International Symposium on Industrial Electronics, ISIE 2007, Caixanova - Vigo, 4 June 2007 through 7 June 2007 ; 2007 , Pages 3362-3366 ; 1424407559 (ISBN); 9781424407552 (ISBN) ; Molla Ahmadian, H ; Sharif University of Technology
2007
Abstract
A problem associated with modeling and control of the power factor correction rectifiers is that the ac variations in duty cycle, as well as in the ac input voltage and current are not small, and hence the traditional small signal analysis is not justified. Nonetheless, the low-frequency components of the converter can be modeled via the circuit averaging technique, but the resulting equivalent circuits are, in general, time varying and highly nonlinear. Nonlinear stability analysis methods are not appropriate for analysis and control design of such complicated circuits. In this paper a piecewise affine approximation is introduced for modeling of switching circuits. This approach makes the...
A new cylindrical element formulation and its application to structural analysis of laminated hollow cylinders
, Article Finite Elements in Analysis and Design ; Volume 44, Issue 9-10 , 2008 , Pages 617-630 ; 0168874X (ISSN) ; Bonakdar, M ; Sharif University of Technology
2008
Abstract
Design and application of superelements in efficient prediction of the structural behavior in a short time has been one of the research interests in the last decade. Superelements are those elements which are capable of producing the same accurate result instead of several combined simple elements. In this paper a new 16-node cylindrical superelement is presented. Static and modal analyses of laminated hollow cylinders subjected to various kinds of loadings and boundary conditions are performed using this element. Some numerical examples are given to illustrate and validate the developed method. The accuracy of the results is evident from comparison of the findings with exact solution method...
Design optimization by numerical characterization of fluid flow through the valveless diffuser micropumps
, Article Journal of Physics: Conference Series ; Volume 34, Issue 1 , 2006 , Pages 379-384 ; 17426588 (ISSN) ; Mehrabian, A ; Sharif University of Technology
Institute of Physics Publishing
2006
Abstract
Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. In this paper, an extended numerical study on fluid flow through micropump chamber and diffuser valves is conducted to find out the optimum working conditions of micropump. In order to obtain maximum generality of the reported results, an analytical study along with a dimensional analysis is presented primarily, to investigate the main dimensionless groups of parameters affecting the micropump net flux. Consequently, the parameters appeared in the main dimensionless groups have been changed in order to understand how the pump rectification...
Dynamic analysis of orthotropic laminated composite plates under axial load on elastic foundation
, Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 10716947 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) ; Pirbodaghi, T ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2006
Abstract
In this paper, free vibration analysis of laminated composite plates is carried out using first shear deformation theory and finite element method. Effect of axial tension and compression forces on the natural frequencies of the structure is investigated. Applying elastic foundation under the laminated composite plates has enabled us to achieve desired frequencies. The displacements are based C0 - nine plate bending element and each node has three degree of freedom. The equations of motion are derived using Hamilton's principle. Results indicate the tension forces will increase the natural frequency while the compression force reduces the natural frequency. The buckling force of plate is...
Online prediction of plate deformations under external forces using neural networks
, Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 10716947 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) ; Mobini, A ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2006
Abstract
Recently online prediction of plate deformations in modern systems have been considered by many researchers, common standard methods are highly time consuming and powerful processors are needed for online computation of deformations. Artificial neural networks have capability to develop complex, nonlinear functional relationships between input and output patterns based on limited data. A good trained network could predict output data very fast with acceptable accuracy. This paper describes the application of an artificial neural network to identify deformation pattern of a four-side clamped plate under external loads. In this paper the distributed loads are approximated by a set of...
A control-theoretic energy management for fault-tolerant hard real-time systems
, Article Proceedings - IEEE International Conference on Computer Design: VLSI in Computers and Processors, 3 October 2010 through 6 October 2010 ; 2010 , Pages 173-178 ; 10636404 (ISSN) ; 9781424489350 (ISBN) ; Hosseingholi, M ; Ejlali, A ; Sharif University of Technology
2010
Abstract
Recently, the tradeoff between low energy consumption and high fault-tolerance has attracted a lot of attention as a key issue in the design of real-time embedded systems. Dynamic Voltage Scaling (DVS) is known as one of the most effective low energy techniques for real-time systems. It has been observed that the use of control-theoretic methods can improve the effectiveness of DVS-enabled systems. In this paper, we have investigated reducing the energy consumption of fault-tolerant hard real-time systems using feedback control theory. Our proposed feedback-based DVS method makes the system capable of selecting the proper frequency and voltage settings in order to reduce the energy...
Passive position finding of stationary targets: Based on circulation and the least square concept
, Article ISPACS 2012 - IEEE International Symposium on Intelligent Signal Processing and Communications Systems ; 2012 , Pages 390-394 ; 9781467350815 (ISBN) ; Mahdavi, A ; Jamshidi, Z ; Sharif University of Technology
2012
Abstract
A method for two dimensional position finding of stationary targets whose bearing measurements suffers from indeterminable bias and random noise has been proposed. The algorithm uses convex optimization to minimize an error function which has been calculated based on circular as well as linear loci of error. Taking into account a number of observations, certain modifications have been applied to the initial crude method so as to arrive at a faster, more accurate method. Simulation results of the method illustrate up to 30% increase in accuracy compared with the well-known least square filter
Fault injection in mixed-signal environment using behavioral fault modeling in Verilog-A
, Article Proceedings of the IEEE International Workshop on Behavioral Modeling and Simulation, BMAS, 23 September 2010 through 24 September 2010, San Jose, CA ; September , 2010 , Pages 69-74 ; 21603804 (ISSN) ; 9781424489954 (ISBN) ; Miremadi, S. G ; Sharif University of Technology
2010
Abstract
Fault injection methods have been used for analyzing dependability characteristics of systems for years. In this paper we propose a practical mixed-signal fault injection flow that is fast as well as accurate. We described three classes of most common faults: i) Single event transients, ii) Electro-Magnetic interference and iii) Power disturbance faults. Fault models are implemented directly into circuit's devices using behavioral fault description in Verilog-A language. As an example for dependability evaluation, some test circuits have been prepared and the results of fault injection on their designs have been reported
Distributed and decentralized state estimation in gas networks as distributed parameter systems
, Article ISA Transactions ; Volume 58 , September , 2015 , Pages 552-566 ; 00190578 (ISSN) ; Bozorgmehry Boozarjomehry, R ; Sharif University of Technology
ISA - Instrumentation, Systems, and Automation Society
2015
Abstract
In this paper, a framework for distributed and decentralized state estimation in high-pressure and long-distance gas transmission networks (GTNs) is proposed. The non-isothermal model of the plant including mass, momentum and energy balance equations are used to simulate the dynamic behavior. Due to several disadvantages of implementing a centralized Kalman filter for large-scale systems, the continuous/discrete form of extended Kalman filter for distributed and decentralized estimation (DDE) has been extended for these systems. Accordingly, the global model is decomposed into several subsystems, called local models. Some heuristic rules are suggested for system decomposition in gas pipeline...
Modeling and state estimation for gas transmission networks
, Article Journal of Natural Gas Science and Engineering ; Volume 22 , 2015 , Pages 551-570 ; 18755100 (ISSN) ; Bozorgmehry Boozarjomehry, R ; Sharif University of Technology
Elsevier
2015
Abstract
In this paper, a non-isothermal model of natural gas in pipelines including mass, momentum and energy balance equations are used as model equations for modeling and state estimation in gas pipeline systems. It is shown that differential equations describing the dynamic behavior of a high-pressure and long-distance gas transmission network (GTN) can be solved efficiently using the orthogonal collocation method. The issues corresponding to the presence of discontinuities in the dynamic model is substantially discussed and studied. The non-isothermal model of a GTN can experience discontinuities during transient operations, which causes challenges in simulation and state estimation in this...
New attacks on UMTS network access
, Article 2009 Wireless Telecommunications Symposium, WTS 2009, 22 April 2009 through 24 April 2009 ; 2009 ; 9781424425884 (ISBN) ; Salimi, S ; Salahi, A ; Sharif University of Technology
2009
Abstract
In this paper we propose two new attacks on UMTS network. Both attacks exploit the UMTS-GSM interworking and are possible in the GSM access area of UMTS network. The first attack allows the attacker to eavesdrop on the entire traffic of the victim UMTS subscriber in the GERAN coverage of the UMTS network. The second attack is an impersonation attack i.e. the attacker impersonates a genuine UMTS subscriber to a UMTS network and fools the network to provide services at the expense of the victim subscriber in its GERAN coverage. © 2009 IEEE
Dynamic optimization of natural gas networks under customer demand uncertainties
, Article Energy ; Volume 134 , 2017 , Pages 968-983 ; 03605442 (ISSN) ; Bozorgmehry Boozarjomehry, R ; Sharif University of Technology
2017
Abstract
In natural gas transmission networks, the efficiency of daily operation is strongly dependent on our knowledge about the customer future demands. Unavailability of accurate demand forecasts makes it more important to be able to characterize the loads and quantify the corresponding uncertainty. A planning strategy for natural gas transmission networks under future demand uncertainty is addressed, which involves coupling of a gas transmission network dynamic simulator with the stochastic optimization framework. Loads from a gas-fired power plant are studied where the loads are characterized by a number of uncertain parameters, and unscented transform is utilized for uncertainty propagation....
ECI-cache: a high-endurance and cost-efficient I/O caching scheme for virtualized platforms
, Article SIGMETRICS 2018 - Abstracts of the 2018 ACM International Conference on Measurement and Modeling of Computer Systems ; 12 June , 2018 , Pages 73- ; 9781450358460 (ISBN) ; Mutlu, O ; Asadi, H ; Sharif University of Technology
Association for Computing Machinery, Inc
2018
Abstract
In recent years, high interest in using Virtual Machines (VMs) in data centers and cloud computing has significantly increased the demand for high-performance data storage systems. A straightforward approach to providing a high-performance storage system is using Solid-State Drives (SSDs). Inclusion of SSDs in storage systems, however, imposes significantly higher cost compared to Hard Disk Drives (HDDs). Recent studies suggest using SSDs as a caching layer for HDD-based storage subsystems in virtualized platforms. Such studies neglect to address the endurance and cost of SSDs, which can significantly affect the efficiency of I/O caching. Moreover, previous studies only configure the cache...