Loading...
Search for:
yavari-darani--amir-arsalan
0.11 seconds
Total 1268 records
Joint Computation Offloading and Service Caching in Edge Computing Environments
, M.Sc. Thesis Sharif University of Technology ; Hessabi, Shaahin (Supervisor) ; Movaghar, Ali (Supervisor)
Abstract
With the expansion of the Internet of Things (IoT) and the growing need for real-time data processing, cloud computing has been adopted as a solution for convenient access to large-scale computational resources. However, transmitting massive volumes of distributed data to the cloud can lead to increased network congestion, latency, and reduced efficiency. In response to this challenge, edge computing has emerged with the aim of performing computation and storage closer to data-generation sources, attracting the attention of both researchers and industry practitioners. The proximity of edge nodes to IoT devices reduces latency and improves the utilization of data; nevertheless, the limited...
Comparison of the Maximum Likelihood Ratio Detectors with the Hough Detectors in RADAR Detection Applications
, M.Sc. Thesis Sharif University of Technology ; Nayebi, Mohammd Mahdi (Supervisor)
Abstract
In this work, Hough detector has been compared with optimum detectors. We consider 2-D range-time data space, which is constructed by storing the radar returns from different range cells during several successive scans. In this space, target trajectory can be modeled as a straight line for short time intervals, and can be extracted by applying Hough transform transcendentally. In this work, a new detection method based on the likelihood ratio in the data space with Gaussian noise is introduced. ALR and GLR processors have been designed. Then formulas for probability of detection and false alarm rate is calculated, and verified via simulations. A new criterion for estimation quality is...
Optimal Multicriteria Design of HTS Transformer and Construction of a Laboratory Scale Sample
, Ph.D. Dissertation Sharif University of Technology ; Vakilian, Mehdi (Supervisor) ; Fardmanesh, Mehdi (Co-Supervisor) ; Hekmati, Arsalan (Co-Supervisor)
Abstract
Employing high-temperature superconducting (HTS) tapes, instead of copper or aluminum wires for winding in a superconducting transformer, results in a series of significant advantages; such as: smaller volume, lighter weight, higher efficieny, greatly extended overload capability, better voltage regulation, lower life cycle cost, fault current limiting capability, lower environmental pollution and lower risk potential against fire hazards.In this thesis, optimal design of flux diverter using genetic algorithm for axial short circuit force reduction in HTS transformers has been performed. Then, multilayered flux diverters have been proposed for reduction of weight and losses. The impact of...
Model enrichment: Concept, measurement, and application
, Article Journal of Simulation ; Volume 6, Issue 2 , 2012 , Pages 125-140 ; 17477778 (ISSN) ; Roeder, T ; Sharif University of Technology
2012
Abstract
Simplicity and validity are recognized as important attributes of an effective simulation model. However, some disagreement exists both on the definitions of these concepts and on quantitative measures for them. This paper introduces Enrichment Level (EL) for (simulation) models. The EL is a quantitative measure to compare the effectiveness of alternative models when used in a particular project. While there is no conceptual restriction on expanding the EL, it currently captures the bias, speed, variance, and scope of a model as the main contributing enrichment factors. This paper explores these factors and suggests a utility-based method to combine them according to the relative importance...
Estimating terminal velocity of rough cracks in the framework of discrete fractal fracture mechanics
, Article Engineering Fracture Mechanics ; Volume 77, Issue 10 , 2010 , Pages 1516-1526 ; 00137944 (ISSN) ; Khezrzadeh, H ; Sharif University of Technology
2010
Abstract
In this paper we first obtain the order of stress singularity for a dynamically propagating self-affine fractal crack. We then show that there is always an upper bound to roughness, i.e. a propagating fractal crack reaches a terminal roughness. We then study the phenomenon of reaching a terminal velocity. Assuming that propagation of a fractal crack is discrete, we predict its terminal velocity using an asymptotic energy balance argument. In particular, we show that the limiting crack speed is a material-dependent fraction of the corresponding Rayleigh wave speed
Experimental Study on Two-Phase Flow Characteristics in Micro-Channels
, M.Sc. Thesis Sharif University of Technology ; Nouri, Ali (Supervisor)
Abstract
The present study provids an experimental investigation on two-pase flow characteristics in microchannels. Experiment were conducted with a mixture of air and water in horizontal circular pyrex channel with 400µm inner diameter. The pressure drop and flow rates of the liquid and gas were measured using new method and images of the flow patterns recorded by high shutter speed camera. The gas and liquid superficial velocity ranges were 0.025-12.5m/s and 0.016-3.6m/s, respectively. The flow pattern map is developed from the observed flow patterns based on phases superficial velocity as wel as We numbers of liquid and gas phases. The flow pattern map is compared with those of larger channels....
Dynamic NMR Study of Ethyle-4-Morpholine-Carbotiate
, M.Sc. Thesis Sharif University of Technology ; Tafazzoli, Mohsen (Supervisor)
Abstract
In this project rotational barrier around the C-N bond in 4-ethyle-morpholine- carboxylate has been studied using DNMR spectroscopy. Spectra were taken at variable temperature, and then with simulation of bandshape broadening pattern at coalescence region, rate constants of exchange were obtained for all temperatures. For simulation of line-shape broadening Spinworks software was used, that with two interfaces made possible simulation with two bandshape simulator programs, DNMR and MEXICO. The rate constants obtained from simulations, were used for calculation of thermodynamic activation parameters (∆G#, ∆H#, ∆S# and Ea). ∆G# 298 value of 13.66 Kcal/mol for 4-ethyle-morpholine- carboxylate...
A more accurate prediction of liquid evaporation flux
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 23, Issue 2 , 2004 , Pages 45-53 ; 10219986 (ISSN) ; Sabzyan, H ; Zeini Isfahani, A ; Parsafar, G ; Sharif University of Technology
Iranian Journal of Chemistry and Chemical Engineering
2004
Abstract
In this work, a more accurate prediction of liquid evaporation flux has been achieved. The statistical rate theory approach, which is recently introduced by Ward and Fang and exact estimation of vapor pressure in the layer adjacent to the liquid-vapor interface have been used for prediction of this flux. Firstly, the existence of an equilibrium layer adjacent to the liquid-vapor interface is considered and the vapor pressure in this layer and its thickness calculated. Subsequently, by using the Fick's second law, an appropriate vapor pressure expression for the pressure of equilibrium layer is derived and by this expression and the statistical rate theory approach, evaporation flux is...
The Zerodivisor Graph of a Qoset
, M.Sc. Thesis Sharif University of Technology ; Pournaki, Mohammad Reza (Supervisor)
Abstract
We study colorings of quasiordered sets (qosets) with a least element 0. To any qoset Q with 0 we assign a graph (called a zerodivisor graph) whose vertices are labelled by the elements of Q with two vertices x; y adjacent if the only elements lying below x and y are those lying below 0. We prove that for such graphs, the chromatic number and the clique number coincide
Experimental Studies and Finite Element Analysis of Polymer Nanocomposites Reinforced with Graphene Sheets under Impact Loading
, M.Sc. Thesis Sharif University of Technology ; Naghdabadi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor)
Abstract
In the experimental approach, graphene and Graphene Oxide (GO) were synthesized through a chemical method. In order to study the quality of GO, characterization tests were performed. Then, reinforced polymer with GO and graphene was made. Moreover, tension, compression and Split- Hopkinson pressure bar tests were performed on standard samples of reinforced polymer nanocomposite. The experimental data show that nanoparticles have a destructive effect in very low and high percentages for extension test as well as in high percentages for compression test. On the other hand, graphene is more effective than GO on improving material properties. Furthermore, comparison of compression results in...
Numerical Analysis and Experimental Study of the Piezoresistivity of the Flexible Polymer Nanocomposites
, Ph.D. Dissertation Sharif University of Technology ; Naghdabadi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor)
Abstract
This research investigates the piezoresistivity of MWCNT/thermoplastic polyurethane (MWCNT-TPU) nanocomposite through both experimental and numerical modeling approaches. Piezoresistive materials are those whose electrical conductivity changes with deformation. Key challenges in the experimental phase included the potential for non-uniform nanoparticle dispersion and agglomeration, as well as the method of measuring electrical resistance under strain, given the inherently high electrical resistance of polymeric materials. In the modeling phase, challenges comprised the high computational cost due to the microstructure's geometry and properties, and the necessity of accounting for the...
A rigorous finite volume model to simulate subaerial and submarine landslide-generated waves
, Article Landslides ; 2015 , Pages 1-19 ; 1612510X (ISSN) ; Ataie Ashtiani, B ; Sharif University of Technology
Springer Verlag
2015
Abstract
This paper presents a new landslide-generated wave (LGW) model based on incompressible Euler equations with Savage-Hutter assumptions. A two-layer model is developed including a layer of granular-type flow beneath a layer of an inviscid fluid. Landslide is modeled as a two-phase Coulomb mixture. A well-balanced second-order finite volume formulation is applied to solve the model equations. Wet/dry transitions are treated properly using a modified non-linear method. The numerical model is validated using two sets of experimental data on subaerial and submarine LGWs. Impulsive wave characteristics and landslide deformations are estimated with a computational error less than 5 %. Then, the...
Numerical modeling of subaerial and submarine landslide-generated tsunami waves—recent advances and future challenges
, Article Landslides ; Volume 13, Issue 6 , 2016 , Pages 1325-1368 ; 1612510X (ISSN) ; Ataie Ashtiani, B ; Sharif University of University
Springer Verlag
2016
Abstract
Landslide-generated waves (LGWs) are among natural hazards that have stimulated attentions and concerns of engineers and researchers during the past decades. At the same period, the application of numerical modeling has been progressively increased to assess, control, and manage the risks of such hazards. This paper represents an overview of numerical studies on LGWs to explore associated recent advances and future challenges. In this review, the main landslide events followed by an LGW hazard are scrutinized. The uncertainty regarding landslide characteristics and the lack of data concerning generated tsunami properties highlights the necessity of probabilistic analysis and numerical...
Simulation of wave generated by landslides in Maku dam reservoir
, Article Prediction and Simulation Methods for Geohazard Mitigation - Proceedings of the International Symposium on Prediction and Simulation Methods for Geohazard Mitigation, IS-KYOTO 2009, 25 May 2009 through 27 May 2009 ; 2009 , Pages 91-96 ; 9780415804820 (ISBN) ; Ataie Ashtiani, B ; Sharif University of Technology
2009
Abstract
In this work, impulsive wave generation and propagation generated by landslides are studied numerically for a real case. Maku dam reservoir, in the northwestern of Iran is considered as the case study. Generated wave heights, wave run-up, maximum wave height above the dam crest and the probable overtopping volume have been evaluated, using a two-dimensional numerical model (LS3D). This model is validated using available three-dimensional experimental data for simulating impulsive wave caused by sub-aerial landslides. Based on the results, the generated wave height for first and second scenarios are 12 m and 18 m respectively. The wave height of 8 m is observed close to dam body. Because of...
On the effects of landslide deformability and initial submergence on landslide-generated waves
, Article Landslides ; 2018 ; 1612510X (ISSN) ; Ataie Ashtiani, B ; Sharif University of Technology
Springer Verlag
2018
Abstract
This paper represents a numerical study on the effects of landslide initial submergence and its geotechnical and rheological properties on the characteristics of landslide-generated waves (LGWs) and landslide deformation. A number of 117 numerical experiments are performed using a two-layer Coulomb Mixture Flow (2LCMFlow) model on a real-sized numerical flume as a simplified cross section of the Maku dam reservoir, located in the Northwest of Iran. Three different initial locations are considered for landslide representing a subaerial (SAL), a semi-submerged (SSL), and a submarine (SML) landslide. Based on the numerical results, the majority of SMLs and in some cases SSLs generate tsunami...
A rigorous finite volume model to simulate subaerial and submarine landslide-generated waves
, Article Landslides ; Volume 14, Issue 1 , 2017 , Pages 203-221 ; 1612510X (ISSN) ; Ataie Ashtiani, B ; Sharif University of Technology
Springer Verlag
2017
Abstract
This paper presents a new landslide-generated wave (LGW) model based on incompressible Euler equations with Savage-Hutter assumptions. A two-layer model is developed including a layer of granular-type flow beneath a layer of an inviscid fluid. Landslide is modeled as a two-phase Coulomb mixture. A well-balanced second-order finite volume formulation is applied to solve the model equations. Wet/dry transitions are treated properly using a modified non-linear method. The numerical model is validated using two sets of experimental data on subaerial and submarine LGWs. Impulsive wave characteristics and landslide deformations are estimated with a computational error less than 5 %. Then, the...
On the effects of landslide deformability and initial submergence on landslide-generated waves
, Article Landslides ; Volume 16, Issue 1 , 2019 , Pages 37-53 ; 1612510X (ISSN) ; Ataie Ashtiani, B ; Sharif University of Technology
Springer Verlag
2019
Abstract
This paper represents a numerical study on the effects of landslide initial submergence and its geotechnical and rheological properties on the characteristics of landslide-generated waves (LGWs) and landslide deformation. A number of 117 numerical experiments are performed using a two-layer Coulomb Mixture Flow (2LCMFlow) model on a real-sized numerical flume as a simplified cross section of the Maku dam reservoir, located in the Northwest of Iran. Three different initial locations are considered for landslide representing a subaerial (SAL), a semi-submerged (SSL), and a submarine (SML) landslide. Based on the numerical results, the majority of SMLs and in some cases SSLs generate tsunami...
Ambient Vibrations Effect on Sensitive Equipment Using Passive and Active Control Method
, M.Sc. Thesis Sharif University of Technology ; Bakhshi, Ali (Supervisor)
Abstract
Today, with improvements in industries such as the sensitive equipment’ industries and the optics industries which need great precision for their optimum performance, the need for a vibration-free environment is felt more than ever. The main objective in this thesis is the effective reduction of the effects of ambient vibrations on points on an optical concrete table using active control. In this research, other than separating the table with the passive method, the reduction of vibrations with active control and the LQR algorithm is investigated. In order to study the dynamic characteristics of the table and to observe the active control process better and more carefully, finite element...
Impact of Practical Beam Shapes on the Performance of Free Space Optical
, M.Sc. Thesis Sharif University of Technology ; Marvasti, Farokh (Supervisor)
Abstract
Free-Space Optical (FSO) communication has received an increasing attention in recent years with its ability to achieve ultra-high data rates (at the order of multiple gigabits per second) over unlicensed optical spectrum. A major degrading factor, particulary in long links is the stmospheric turbulence induced fading. In this thesis, we use spatial diversity and use and make several contributions to the performance analysis of MIMO (Mutli Input-Multi Output) FSO systems. We use MRC(Maximum Ratio Combining),EGC(Equal Gain Combinig),SC(Selection Combinig) and yield significant performance improvments. Finally we import the charectristic of different beamshapes and yields performance...
Nonlinear Filters Applied to Tightly Coupled Integration of INS/GPS/PL for Precise Navigation in Automatic Landing of UAVs
, M.Sc. Thesis Sharif University of Technology ; Nobahari, Hadi (Supervisor) ; Ghanbarpour Asl, Habib (Supervisor)
Abstract
One of the most dangerous phases of the flight is landing. Newly automatic landing is noticed. The vital element in an automatic landing system is navigation system. In this document, a PL/INS/DGPS auto landing system is introduced.In a PL based navigation system, accuracy is highly under the influence of relative geometry between PLs position and flight path. Therefore, it is necessary to locate PLs on the best position. An optimization is used to find PLs best configuration that increases the navigation performance. Tightly coupling of INS and GPS/PL is preferred, because some problems lead to GPS satellite signal unavailability