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A Finite Element Study on Seismic Behavior of Various Concrete Column Retrofitting Methods
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
In recent years, in order to investigate the structural performance in seismic zones, concrete column reinforcement and observing their behavior under cyclic loading have attracted considerable attentions. The ductility and energy absorption capability of structure play an important role in structural performance against earthquake and consequently its failure patterns. A new chapter of these investigations has begun by the reinforcement of the concrete members, a major part of which is concerned with the confinement of concrete members in order to increase their ductility and energy absorption against the forces induced by earthquake. In this study, three prominent methods of concrete...
Synthesis and Characterization of a Metal-Organic Molecular Cage with Anthracene Derivative Linkers and the Study of its Host-Guest Chemistry
, M.Sc. Thesis Sharif University of Technology ; Jamali, Sirous (Supervisor)
Abstract
Through the bromination reaction of anthracene, the compound 9,10-dibromoanthracene (1) was synthesized. Subsequently, using a Suzuki coupling mechanism and the pinacol ester of 4-pyridineboronic acid, the ligand 9,10-bis(4-pyridyl)anthracene (2) was obtained. A cubic molecular cage [(PtMe3)8(9,10-bis(4-pyridyl)anthracene)12][OTf]8 (5) with trimethylplatinum(IV) (PtMe3) vertices and anthracene-based linkers was synthesized from the reaction of [PtMe3I]4 (3) with 9,10-bis (4-pyridyl)anthracene(2) linker in the presence of AgOTF (OTf = trifluoromethanesulfonate) in a 1:6 molar ratio. The structure of 5 was characterized by NMR spectroscopy in solution state. The ratio of aromatic to aliphatic...
Constructing the Bayesian network for components reliability importance ranking in composite power systems
, Article International Journal of Electrical Power and Energy Systems ; Volume 43, Issue 1 , 2012 , Pages 474-480 ; 01420615 (ISSN) ; Ebrahimi, A ; Fotuhi Firuzabad, M ; Sharif University of Technology
2012
Abstract
In this paper, Bayesian Network (BN) is used for reliability assessment of composite power systems with emphasis on the importance of system components. A simple approach is presented to construct the BN associated with a given power system. The approach is based on the capability of the BN to learn from data which makes it possible to be applied to large power systems. The required training data is provided by state sampling using the Monte Carlo simulation. The constructed BN is then used to perform different probabilistic assessments such as ranking the criticality and importance of system components from reliability perspective. The BN is also used to compute the frequency and...
Study of acoustic bubble cluster dynamics using a lattice Boltzmann model
, Article Chinese Physics B ; Volume 24, Issue 2 , 2015 ; 16741056 (ISSN) ; Taeibi-Rahni, M ; Massah, H ; Sharif University of Technology
Institute of Physics Publishing
2015
Abstract
The search for the development of a reliable mathematical model for understanding bubble dynamics behavior is an ongoing endeavor. A long list of complex phenomena underlies the physics of this problem. In the past decades, the lattice Boltzmann method has emerged as a promising tool to address such complexities. In this regard, we have applied a 121-velocity multiphase lattice Boltzmann model to an asymmetric cluster of bubbles in an acoustic field. A problem as a benchmark is studied to check the consistency and applicability of the model. The problem of interest is to study the deformation and coalescence phenomena in bubble cluster dynamics, as well as the screening effect on an acoustic...
Energy Efficient Software Defined Networks
, M.Sc. Thesis Sharif University of Technology ; Hemmatyar, Ali Mohammad Afshin (Supervisor)
Abstract
With a growing concern on the considerable energy consumed by data centers, research efforts are targeting toward green data centers with higher energy efficiency. Networks are essential to today’s highly instrumented and connected society. Currently responsible for a fraction of the energy the IT sector consumes, networks rely on equipments that often use a constant amount of power regardless of their utilization; a worsening scenario as traffic is expected to increase by a factor of three in the next few years. Datacenter networks, for instance, employ devices that consume several kilowatts of power even when idle. This work aims to improve the energy efficiency of datacenter networks by...
Effects of liquid second viscosity in high-amplitude sonoluminescence
, Article Chinese Physics Letters ; Volume 21, Issue 2 , 2004 , Pages 356-359 ; 0256307X (ISSN) ; Sadighi Bonabi, R ; Taeibi Rahni, M ; Daemi, M ; Sharif University of Technology
Allerton Press Inc
2004
Abstract
The well-known Rayleigh-Plesset (RP) equation is the base of nearly all hydrodynamical descriptions of the sonoluminescence phenomenon. A major deficiency of this equation is that it accounts for viscosity of an incompressible liquid and compressibility, separately. By removing this approximation, we have modified the RP equation, considering effects of liquid second viscosity. This modification exhibits its importance at the end of an intense collapse, so that the new model predicts the appearance of a new picosecond bouncing during high-amplitude sonoluminescence radiation. This new bouncing produces very sharp (sub-picosecond) peaks on the top of the sonoluminescence pulse. These new...
Numerical Simulation of Bubble Cluster Dynamics, Using Lattice Boltzmann Method
, Ph.D. Dissertation Sharif University of Technology ; Tayyebi Rahni, Mohammad (Supervisor) ; Massah, Hamid Reza (Co-Advisor)
Abstract
Bubble cluster has attracted the interests of many researches since the early twentieth century. Despite its easy generation and numerous occurrences, its study is extremely complex. Describing the dynamical behavior of bubble clusters is possible when quite a few simplifying assumptions are utilized. In other words, one can observe that with current approaches, the relevant theoretical researches are not very valuable. In this research, however, lattice Boltzmann method, a rather recent mesoscopic approach, was used to study the behavior of bubbles in a bubble cluster. Of course, this is only the beginning and there is a long way before getting close to experimental results. However, there...
Silica-supported DABCO-tribromide: A recoverable reagent for oxidation of alcohols to the corresponding carbonyl compounds
, Article Scientia Iranica ; Volume 20, Issue 3 , 2013 , Pages 598-602 ; 10263098 (ISSN) ; Masoud, N ; Foroushani, B. K ; Saryazdi, S ; Ghonouei, N ; Daemi, E ; Sharif University of Technology
2013
Abstract
In this study, 1,4-diazabicy lo[2.2.2] octane (DABCO) tribromide was immobilized on silica support by using 3-chloro propyl trimethoxy silane to obtain a silica-supported DABCO tribromide reagent. The synthesized reagent was characterized with elemental analysis, FT-IR spectroscopy, and thermo-gravimetric analysis (TGA). This reagent has been applied in the conversion of alcohol to corresponding carbonyl compounds. Alcohol oxidation reactions yield in 52-95%, and the reagent may be recycled five times with further bromine treatment
Planning screw insertion trajectory in lumbar spinal fusion using pre-operative CT images
, Article Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS, 25 August 2015 through 29 August 2015 ; Volume 2015-November , 2015 , Pages 3639-3642 ; 1557170X (ISSN) ; 9781424492718 (ISBN) ; Ahmadian, A ; Mirbagheri, A ; Ahmadian, A. H ; Saberi, H ; Amidi, F ; Alirezaie, J ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
Spinal fusion permanently connects two or more vertebrae in spine to improve stability, correct a deformity or reduce pain by immobilizing the vertebrae through pedicle screw fixation. Pedicle screws should be inserted very carefully to prevent possible irrecoverable damages to the spinal cord. Surgeons use CT/fluoroscopic images to find how to insert the screws safely. However, there is still human error, as determining precise trajectory in 3D space is difficult because of asymmetric structure of pedicle. In this study we attempt to propose a shape based method to help the surgeons to find the more accurate and safe path for screw insertion that minimizes the risk or invasiveness of the...
Grid Homology and the Existence of Exotic Structures on R4
, M.Sc. Thesis Sharif University of Technology ; Moghaddasi, Reza (Supervisor) ; Eftekhari, Eaman (Supervisor) ; Daemi, Ali Akbar (Co-Advisor)
Abstract
Knot theory is the study of ambient isotopy classes of compact 1–manifolds in a 3-manifold. In classical knot theory this 3-manifold is R3 or S3. This field has experienced a great transformative advances in recent years because of its strong connections with and a number of other mathematical disciplines including topology of 3-manifolds and 4-manifolds, gauge theory, representation theory, categorification, morse theory, symplectic geometry and the theory of pseudo-holomorphic curves. In this thesis we start with classical knot theory, introducing some of its (classical) invariants like unknotting number, Seifert genus and slice genus of a knot, knot group and finally Alexander Polynomial...
Majorana zero-energy mode and fractal structure in fibonacci-kitaev chain
, Article Journal of the Physical Society of Japan ; Volume 86, Issue 11 , 2017 ; 00319015 (ISSN) ; Sugimoto, T ; Tohyama, T ; Sharif University of Technology
2017
Abstract
We theoretically study a Kitaev chain with a quasiperiodic potential, where the quasiperiodicity is introduced by a Fibonacci sequence. Based on an analysis of the Majorana zero-energy mode, we find the critical p-wave superconducting pairing potential separating a topological phase and a non-topological phase. The topological phase diagram with respect to Fibonacci potentials follow a self-similar fractal structure characterized by the box-counting dimension, which is an example of the interplay of fractal and topology like the Hofstadter's butterfly in quantum Hall insulators. © 2017 The Physical Society of Japan
Accelerating federated edge learning
, Article IEEE Communications Letters ; Volume 25, Issue 10 , 2021 , Pages 3282-3286 ; 10897798 (ISSN) ; Balef, A. R ; Dinh, C. T ; Tran, N. H ; Ngo, D. T ; Anh Le, T ; Vo, P. L ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
Transferring large models in federated learning (FL) networks is often hindered by clients' limited bandwidth. We propose $ extsf {FedAA}$ , an FL algorithm which achieves fast convergence by exploiting the regularized Anderson acceleration (AA) on the global level. First, we demonstrate that FL can benefit from acceleration methods in numerical analysis. Second, $ extsf {FedAA}$ improves the convergence rate for quadratic losses and improves the empirical performance for smooth and strongly convex objectives, compared to FedAvg, an FL algorithm using gradient descent (GD) local updates. Experimental results demonstrate that employing AA can significantly improve the performance of FedAvg,...
Study of the effect of thermal dispersion on internal natural convection in porous media using fourier series
, Article Transport in Porous Media ; Volume 131, Issue 2 , 2020 , Pages 537-568 ; Graf, T ; Tran, T. V ; Ataie Ashtiani, B ; Simmons, C. T ; Younes, A ; Sharif University of Technology
Springer
2020
Abstract
Natural convection in a porous enclosure in the presence of thermal dispersion is investigated. The Fourier–Galerkin (FG) spectral element method is adapted to solve the coupled equations of Darcy’s flow and heat transfer with a full velocity-dependent dispersion tensor, employing the stream function formulation. A sound implementation of the FG method is developed to obtain accurate solutions within affordable computational costs. In the spectral space, the stream function is expressed analytically in terms of temperature, and the spectral system is solved using temperature as the primary unknown. The FG method is compared to finite element solutions obtained using an in-house code...
A probabilistic artificial neural network-based procedure for variance change point estimation
, Article Soft Computing ; Vol. 19, issue. 3 , May , 2014 , pp. 691-700 ; ISSN: 14327643 ; Niaki, S. T. A ; Moghadam, A. T ; Sharif University of Technology
2014
Abstract
Control charts are useful tools of monitoring quality characteristics. One of the problems of employing a control chart is that the time it alarms is not synchronic with the time when assignable cause manifests itself in the process. This makes difficult to search and find assignable causes. Knowing the real time of manifestation of assignable cause (change point) helps to find assignable cause(s) sooner and eases corrective actions to be taken. In this paper, a probabilistic neural network (PNN)-based procedure was developed to estimate the variance change point of a normally distributed quality characteristic. The PNN was selected based on trial and error among different types of...
Two studies of framework-usage templates extracted from dynamic traces
, Article IEEE Transactions on Software Engineering ; Volume 38, Issue 6 , 2012 , Pages 1464-1487 ; 00985589 (ISSN) ; Czarnecki, K ; Binder, W ; Bartolomei, T. T ; Sharif University of Technology
2012
Abstract
Object-oriented frameworks are widely used to develop new applications. They provide reusable concepts that are instantiated in application code through potentially complex implementation steps such as subclassing, implementing interfaces, and calling framework operations. Unfortunately, many modern frameworks are difficult to use because of their large and complex APIs and frequently incomplete user documentation. To cope with these problems, developers often use existing framework applications as a guide. However, locating concept implementations in those sample applications is typically challenging due to code tangling and scattering. To address this challenge, we introduce the notion of...
On the throughput and outage probability of multi-relay networks with imperfect power amplifiers
, Article IEEE Transactions on Wireless Communications ; Volume 14, Issue 9 , May , 2015 , Pages 4994-5008 ; 15361276 (ISSN) ; Svensson, T ; Eriksson, T ; Nasiri Kenari, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
This paper studies the energy-limited performance of multi-relay networks. Taking the properties of the power amplifiers (PAs) into account, we derive closed-form expressions for the optimal power allocation, the outage probability and the throughput in the cases with a sum consumed energy constraint. Moreover, we analyze the diversity and the multiplexing gains of the PA-aware systems. Finally, we investigate the performance of large-scale multi-relay networks and develop efficient multi-relay systems with low cooperation overhead. The numerical and the analytical results show that the inefficiency of the PAs affects the outage probability and the throughput of the multi-relay systems...
Online jointly estimation of hysteretic structures using the combination of central difference Kalman filter and Robbins–Monro technique
, Article JVC/Journal of Vibration and Control ; 2020 ; Bakhshi, A ; Yang, T. T. Y ; Sharif University of Technology
SAGE Publications Inc
2020
Abstract
Rapid assessment of structural safety and performance right after the occurrence of significant earthquake shaking is crucial for building owners and decision-makers to make informed risk management decisions. Hence, it is vital to develop online and pseudo-online health monitoring methods to quantify the health of the building right after significant earthquake shaking. Many Bayesian inference–based methods have been developed in the past which allow the users to estimate the unknown states and parameters. However, one of the most challenging part of the Bayesian inference–based methods is the determination of the parameter noise covariance matrix. It is especially difficult when the number...
Online probabilistic model class selection and joint estimation of structures for post-disaster monitoring
, Article JVC/Journal of Vibration and Control ; 2020 ; Bakhshi, A ; Yang, T. T. Y ; Sharif University of Technology
SAGE Publications Inc
2020
Abstract
Online selection of the appropriate model and identifying its parameters based on measured vibrational data are among the challenging issues in dynamic system identification. After a severe earthquake, quick monitoring and assessment of structural health status play a crucial role in effective critical risk management for the building owners and decision-makers. The Bayesian multiple modeling approach is a suitable tool for optimal model class selection, which is used in this article mainly for improving data fitting precision, decreasing dimensions of structural unknown vector through removing unnecessary parameters, detecting the occurrence and type of predominant phenomenon related to...
Online probabilistic model class selection and joint estimation of structures for post-disaster monitoring
, Article JVC/Journal of Vibration and Control ; Volume 27, Issue 15-16 , 2021 , Pages 1860-1878 ; 10775463 (ISSN) ; Bakhshi, A ; Yang, T. T .Y ; Sharif University of Technology
SAGE Publications Inc
2021
Abstract
Online selection of the appropriate model and identifying its parameters based on measured vibrational data are among the challenging issues in dynamic system identification. After a severe earthquake, quick monitoring and assessment of structural health status play a crucial role in effective critical risk management for the building owners and decision-makers. The Bayesian multiple modeling approach is a suitable tool for optimal model class selection, which is used in this article mainly for improving data fitting precision, decreasing dimensions of structural unknown vector through removing unnecessary parameters, detecting the occurrence and type of predominant phenomenon related to...
Online jointly estimation of hysteretic structures using the combination of central difference kalman filter and robbins–monro technique
, Article JVC/Journal of Vibration and Control ; Volume 27, Issue 1-2 , 2021 , Pages 234-247 ; 10775463 (ISSN) ; Bakhshi, A ; Yang, T. T. Y ; Sharif University of Technology
SAGE Publications Inc
2021
Abstract
Rapid assessment of structural safety and performance right after the occurrence of significant earthquake shaking is crucial for building owners and decision-makers to make informed risk management decisions. Hence, it is vital to develop online and pseudo-online health monitoring methods to quantify the health of the building right after significant earthquake shaking. Many Bayesian inference–based methods have been developed in the past which allow the users to estimate the unknown states and parameters. However, one of the most challenging part of the Bayesian inference–based methods is the determination of the parameter noise covariance matrix. It is especially difficult when the number...