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mathematical-approaches
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Conflict resolution maneuvers based on genetic algorithm modified webs
, Article 2009 IEEE Aerospace Conference, Big Sky, MT, 7 March 2009 through 14 March 2009 ; 2009 ; 1095323X (ISSN); 9781424426225 (ISBN) ; Alaeddini, A ; Sharif University of Technology
2009
Abstract
In this paper, the problem of designing optimal conflict-free maneuvers for planar multiple aircraft encounters is studied. The maneuvers propose suitable heading changes for aircraft in a cooperative manner. The new mathematical approach provides optimal trajectories to resolve a wide variety of conflicts, especially in the presence of high-altitude Clear Air Turbulence (CAT). The proposed approach effectively uses Genetic Algorithms (GA), together with modified webs, to quickly find conflict-resolving maneuvers. Different case studies show the method is fast enough to be used for real-time applications when resolving conflicts involving two aircraft. It is also efficient enough to resolve...
Novel mathematical approaches for analyzing time dependent creep deformations in reinforced metals
, Article Journal of Mechanical Science and Technology ; Volume 27, Issue 11 , 2013 , Pages 3277-3285 ; 1738494X (ISSN) ; Mondali, M ; Abedian, A ; Sharif University of Technology
2013
Abstract
The objective of this paper is to present some novel insights for solving a second stage creep problem in metal matrix composites. First, a new analytical approach is developed for obtaining some unknowns in second stage creep of short fiber composites under an applied axial load. The unknowns are the radial, circumferential, axial, shear and equivalent stresses, which are determined by approximation of creep constitutive equations and using proper assumed displacement rates. A nonlinear differential equation is solved employing suitable and correct approximate assumptions. Then, the difference of the stress components utilizing creep constitutive equations and assumed displacement rates is...
Analysis of imperfections in N-phase high-Q band-pass filters
, Article IEEE International Symposium on Circuits and Systems, ISCAS 2015, 24 May 2015 through 27 May 2015 ; Volume 2015-July , May , 2015 , Pages 273-276 ; 02714310 (ISSN) ; 9781479983919 (ISBN) ; Kananian, S ; Behmanesh, B ; Atarodi, S. M ; Fotowat Ahmady, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
The effect of clock skew and duty-cycle on the performance of high-Q N-phase band-pass filters (BPFs) have been examined in this paper. Following a mathematical approach and using the analytical derivations carried out, the effects of such non-idealities as clock skew and duty-cycle error are determined in an N-path filter. It is analytically proved that image signals from all integer multiples of the clock signal, rather than just those at (1 ± kN) multiples of the clock signal, land atop the wanted RF spectrum. In a real world clock generator, with non-idealities in effect, filtering property and proper behavior of the filter is adversely affected. Finally, system level simulation along...
Application of a mathematical method in calculation of the skin variation during a real field acidizing operation
, Article Chemical Engineering Science ; Volume 192 , 2018 , Pages 829-839 ; 00092509 (ISSN) ; Jamshidi, S ; Jahangiri, H. R ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The efficiency of an acidizing operation is usually assessed through ordinary well testing methods. These methods are performed only after the acidizing operation, and it is difficult to monitor and evaluate real-time efficiency of acidizing operation. Understanding the performance of the acidizing during the service, by analysis of the acidizing data is a viable approach to this costly and challenging process. The estimation of the skin changes needs an appropriate mathematical method that can handle the main aspects of an acidizing operation. It is tedious to model a real acidizing operation due to the heterogeneity of the reservoir, an unknown reaction rate of acid in reservoir condition,...
On the introduction of a qualitative variable to the neural network for reactor modeling: Feed type
, Article Industrial and Engineering Chemistry Research ; Volume 48, Issue 8 , 2009 , Pages 3820-3824 ; 08885885 (ISSN) ; Mehdizadeh, H ; Bozorgmehry Boozarjomehry, R ; Towfighi Darian, J ; Sharif University of Technology
2009
Abstract
Thermal cracking of hydrocarbons converts them into valuable materials in the petrochemical industries. Multiplicity of the reaction routes and complexity of the mathematical approach has led us use a kind of black-box modelingsartificial neural networks. Reactor feed type plays an essential role on the product qualities. Feed type is a qualitative character. In this paper, a method is presented to introduce a range of petroleum fractions to the neural network. To introduce petroleum cuts with final boiling points of 865 °F maximum to the neural network, a real component substitute mixture is made from the original mixture. Such substitute mixture is fully defined, it has a chemical...
On the free vibration response of rectangular plates, partially supported on elastic foundation
, Article Applied Mathematical Modelling ; Volume 36, Issue 9 , September , 2012 , Pages 4473-4482 ; 0307904X (ISSN) ; Mofid, M ; Akin, J. E ; Sharif University of Technology
2012
Abstract
Rectangular plates on distributed elastic foundations are widely employed in footings and raft foundations of variety of structures. In particular, mounted columns and single footings may partially occupy the rectangular plate of any kind. This study deals with free vibration problem of thin rectangular plates on Winkler and Pasternak elastic foundation model which is distributed over a particular arbitrary area of the plate. Closed form solutions are developed through solving the governing differential equations of plates. Moreover, a novel mathematical approach is proposed to find the exact analytical solution of free vibration of plates with mixed or fully-clamped boundary conditions....
Tolerance analysis of assemblies with asymmetric tolerances by unified uncertainty-accumulation model based on fuzzy logic
, Article International Journal of Advanced Manufacturing Technology ; Volume 53, Issue 5-8 , 2011 , Pages 777-788 ; 02683768 (ISSN) ; Movahhedy, M. R ; Sharif University of Technology
Abstract
In mechanical assemblies, individual components are placed together to deliver a certain function. The performance, quality, and cost of the mechanical assembly are significantly affected by its tolerances. Toleranced dimensions inherently generate an uncertain environment in a mechanical assembly. This paper presents a proper method for tolerance analysis of mechanical assemblies with asymmetric tolerances based on an uncertainty model. This mathematical approach is based on fuzzy logic and tolerance accumulation models such as worst-case and root-sum-square methods. A fuzzy-based tolerance representation is developed to model uncertainty of tolerance components in the mechanical...
Replacement-repair policy based on a simulation model for multi-state deteriorating products under warranty
, Article Scientia Iranica ; Volume 16, Issue 1 E , 2009 , Pages 26-35 ; 10263098 (ISSN) ; Vahdani, H ; Sharif University of Technology
2009
Abstract
In this paper, a replacement-repair model is developed to study a warranty servicing policy for a class of multi-state deteriorating and repairable products, based on a computer simulation analysis. In each working state there is a determined probability for transition to each of the subsequent states, given that it has made a transition out of that state. There are two parameters that determine the manufacturer's decision to repair or replace a failed item, assuming that the buyer's claim is valid; the deterioration degree of the item and the length of the residual warranty period. Beside these two parameters, other inputs to the model are: the number of working and failure states, the...
Rigorous silica solubility estimation in superheated steam: Smart modeling and comparative study
, Article Environmental Progress and Sustainable Energy ; Volume 38, Issue 4 , 2019 ; 19447442 (ISSN) ; Shokrollahi, A ; Esmaeili Jaghdan, Z ; Ghazanfari, M. H ; Sharif University of Technology
John Wiley and Sons Inc
2019
Abstract
One of the main issues of wastewater treatment is the silica deposition in steam turbines. Evaporation of silica with the steam in adequate concentration is one of the main sources of scale formation in steam turbines. In this study, the authors introduce the utilization of a genetic-based approach—gene expression programming (GEP)—for solubility prognostication of the silica in superheated steam of boilers with respect to water silica content and pressure. The result of GEP mathematical approach is a new algebraic formula to achieve our goals. Developed model predicts the silica solubility in the range of 0.8–22.1 MPa and 1–500 mg/kg for pressure and boiler water silica content,...
An integrated process configuration of solid oxide fuel/electrolyzer cells (SOFC-SOEC) and solar organic Rankine cycle (ORC) for cogeneration applications
, Article International Journal of Energy Research ; Volume 45, Issue 7 , 2021 , Pages 11018-11040 ; 0363907X (ISSN) ; Karimian Bahnamiri, F ; Mehrpooya, M ; Sharif University of Technology
John Wiley and Sons Ltd
2021
Abstract
This research work presents a novel integrated structure for the cogeneration of electricity and renewable syngas. The base structure of the process is developed by solid oxide cells in which electricity is generated by the natural gas-fueled fuel cell unit, and renewable syngas is produced by the electrolyzer cell unit. Direct integration between fuel cell and electrolyzer cell units is established for optimal use of fuel cell off-gases. To improve system's sustainability, a solar power cycle, including solar collectors coupled with an organic Rankine cycle (ORC), is designed to provide renewable electricity for steam and CO2 co-electrolysis operation. 1D mathematical approaches are...
A new mathematical approach for detection of active area in human brain fMRI using nonlinear model
, Article Biomedical Engineering - Applications, Basis and Communications ; Volume 22, Issue 5 , 2010 , Pages 409-418 ; 10162372 (ISSN) ; Fatemizadeh, E ; Sharif University of Technology
Abstract
Functional magnetic resonance imaging (fMRI) is widely-used for detection of the brain's neural activity. The signals and images acquired through this imaging technique demonstrate the human brain's response to pre-scheduled tasks. Several studies on blood oxygenation level-dependent (BOLD) signal responses demonstrate nonlinear behavior in response to a stimulus. In this paper we propose a new mathematical approach for modeling BOLD signal activity, which is able to model nonlinear and time variant behaviors of this physiological system. We employ the Nonlinear Auto Regressive Moving Average (NARMA) model to describe the mathematical relationship between output signals and predesigned...