Loading...
Search for:
transition-curves
0.008 seconds
Fractional delayed damped Mathieu equation
, Article International Journal of Control ; Volume 88, Issue 3 , 2015 , Pages 622-630 ; 00207179 (ISSN) ; Haeri, M ; Nazari, M ; Butcher, E. A ; Sharif University of Technology
Taylor and Francis Ltd
2015
Abstract
This paper investigates the dynamical behaviour of the fractional delayed damped Mathieu equation. This system includes three different phenomena (fractional order, time delay, parametric resonance). The method of harmonic balance is employed to achieve approximate expressions for the transition curves in the parameter plane. The n = 0 and n = 1 transition curves (both lower and higher order approximations) are obtained. The dependencies of these curves on the system parameters and fractional orders are determined. Previous results for the transition curves reported for the damped Mathieu equation, delayed second-order oscillator, and fractional Mathieu equation are confirmed as special...
A Model for optimizing railway alignment considering bridge costs, tunnel costs, and transition curves
, Article Urban Rail Transit ; Volume 5, Issue 4 , 2019 , Pages 207-224 ; 21996687 (ISSN) ; Shafahi, Y ; Hashemian, S. E ; Sharif University of Technology
Springer
2019
Abstract
Owing to wide-ranging searches (there are various alignments between two points) as well as complex and nonlinear cost functions and a variety of geometric constraints, the problem of optimal railway alignment is classified as a complex problem. Thus, choosing an alignment between two points is usually done based on a limited number of alignments designed by experts. In recent years, the study of railway alignment optimization has shown the importance of optimization and the introduction of various algorithms and their usefulness in solving different problems. It is expected that applying meta-heuristic optimization algorithms such as methods based on swarm intelligence can lead to better...
A Model for Optimizing Railway Alignment Problem Considering Bridge and Tunnel Cost and Using Transional Curves
, M.Sc. Thesis Sharif University of Technology ; Shafahi, Yusof (Supervisor)
Abstract
Due to large range searches (there are various alignments between two points) as well as the complex and non-linear cost functions and a variety of geometric constraints, the problem of optimal railway alignment is known as a difficult problem. For this reason, choosing an alignment between two points is usually done based on a limited number of alignments put forward by experts. In recent years, the study of the railway alignment optimization raised again due to the importance of optimization and introduction of various algorithms and their progress in solving various problems. It is expected that applying metaheuristic optimization algorithms, such as methods based on Swarm intelligence...
Sample complexity of total variation minimization
, Article IEEE Signal Processing Letters ; Volume 25, Issue 8 , 2018 , Pages 1151-1155 ; 10709908 (ISSN) ; Haddadi, F ; Amini, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
This letter considers the use of total variation (TV) minimization in the recovery of a given gradient sparse vector from Gaussian linear measurements. It has been shown in recent studies that there exists a sharp phase transition behavior in TV minimization for the number of measurements necessary to recover the signal in asymptotic regimes. The phase-transition curve specifies the boundary of success and failure of TV minimization for large number of measurements. It is a challenging task to obtain a theoretical bound that reflects this curve. In this letter, we present a novel upper bound that suitably approximates this curve and is asymptotically sharp. Numerical results show that our...
Evaluation of Microstructure and Wear Behaviour of Nicrbsi Composite Coating Deposited by Atmospheric Plasma Spray and Plasma Transferred Arc on Steel Substrate
, M.Sc. Thesis Sharif University of Technology ; Movahedi, Mojtaba (Supervisor) ; Kokabi, Amir Hossein (Supervisor)
Abstract
Nowadays, in many industrial applications, protecting surfaces has become necessary. This research attempted to create a coating resistant to the wear of NiCrBSi with the help of the atmospheric plasma spray and the process of plasma Transferred Arc on the substrate of the simple carbon steel. Also, in order to study the effect of compositing on hardness and abrasive properties of the APS coatings, NiCrBSi powder was strengthened with 25 weight percent of Titanium Carbide particles so that the NiCrBSi-25TiC composite coating could also be created. According to the nature of the APS process, the substructure of this coating always has some porosity and layered structure, and the connection of...