The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
B.j. Jarosz - One of the best experts on this subject based on the ideXlab platform.
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Interstitial instrumentation for therapeutic ultrasonic heating: modeling the discrete blood vessels
IEEE Transactions on Instrumentation and Measurement, 2000Co-Authors: B.j. JaroszAbstract:Instrumentation for interstitial ultrasound (US) heating is an important emerging technology in thermotherapy of deep seated tumors or those hard to reach by external devices. The instrumentation has special significance in case of radio-and/or chemotherapy resistant lesions. Its efficacy strongly depends on local tissue properties, especially local blood vessels. We evaluate effects of the vessels on Temperature distribution elevated from basal by deposition of ultrasound energy. In the proposed model, we take into account several micron diameter vessels in proximity to the US four-applicator array. At large distances from the array, the volume is assigned a modified effective thermal conductivity. Our Finite Element Analysis of the so-defined problem shows that modelling under the assumption of constant, basal Temperature across the vessels' lumen leads to erroneous results. The simulations agree best with experiments if fixed Nodal Temperature is applied at 60% of the lumen. We specify requirements on the array to avoid local underheating that could lead to performance failure of the instrumentation.
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Interstitial instrumentation for therapeutic ultrasonic heating: modeling the discrete blood vessels
IMTC 99. Proceedings of the 16th IEEE Instrumentation and Measurement Technology Conference (Cat. No.99CH36309), 1999Co-Authors: B.j. JaroszAbstract:Interstitial ultrasound instrumentation became an important technology in thermotherapy of deep seated or hard to reach by external devices tumors. The instrumentation efficacy strongly depends on focal tissue properties, especially local blood vessels. We evaluate effects of the vessels on Temperature distribution elevated from basal by deposition of ultrasound energy. In the proposed model, we take into account several micron diameter blood vessels in proximity to ultrasound four-applicator array. The tissue at large distances from the array is modeled as a volume of modified effective conductivity. Our Finite Element Analysis of so defined problem indicates best agreement between simulation and experiment with the choice of fixed Nodal Temperature not across the vessel nor the vessel lumen but at 60% of the lumen. We evaluate requirements on the array to avoid local underheating that could lead to performance a failure of the instrumentation.
Bing Ye Xu - One of the best experts on this subject based on the ideXlab platform.
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Limit and Shakedown Analysis of Circular Tube Containing External Pit
The Open Mechanical Engineering Journal, 2012Co-Authors: Xian Feng Wang, Feng Xing, Bing Ye XuAbstract:The circular tubes containing external pit defects are analyzed in a lower-bound finite element computational form based on the static shakedown theorem. The shakedown analysis has not been commonly used in the engineering due to the large amount of computations. To overcome the numerical difficulties, a Temperature parameter method is used, in which a pseudo-Temperature field is applied to the structure and the resulting self-equilibrium thermoelastic stress is treated as the residual stress field which is used in the analysis. The pseudo Temperature is assumed as a harmonic function satisfying the uniqueness theorem, therefore the Nodal Temperature matrix of the whole structure can be expressed by the boundary Nodal Temperature matrix. The nonlinear yield condition is piece-wise linearized so that the shakedown analysis is transformed into a linear programming problem in which the strategic variable is boundary Nodal Temperature and objective variable is the loading multiplier. The relations of limit and shakedown pressures to geometric parameters of various defects are presented.
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Shakedown Analysis of Cylindrical Shells Containing Part-Through External Pit
Advanced Materials Research, 2010Co-Authors: Xian Feng Wang, Feng Xing, Bing Ye XuAbstract:A lower-bound shakedown analysis for cylindrical shells containing defects is performed based on the static shakedown theorem in a finite element computational form. To overcome the numerical difficulties, the pseudo-Temperature field is applied to a structure and the resulting thermo-elastic stress is considered as the self-equilibrium residual-stress field. The pseudo Temperature is assumed as a harmonic function satisfying the uniqueness theorem, therefore the Nodal Temperature matrix of the whole structure can be expressed by the boundary Nodal Temperature matrix. The nonlinear yield condition is piece-wise linearized so that the shakedown analysis is transformed into a linear programming problem in which the strategic variable is boundary Nodal Temperature and objective variable is the loading multiplier. The relations of limit and shakedown pressures to geometric parameters of various defects are presented.
A T Souflaris - One of the best experts on this subject based on the ideXlab platform.
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power transformer thermal analysis by using an advanced coupled 3d heat transfer and fluid flow fem model
International Journal of Thermal Sciences, 2012Co-Authors: Marina A Tsili, Eleftherios I Amoiralis, A G Kladas, A T SouflarisAbstract:Abstract Thermal performance in oil-immersed power transformers is governed by the flow of oil, acting both as an electrical insulator and a medium for the transfer of heat generated in the core and windings toward the tank and the surrounding air. This paper presents the development of an advanced three-dimensional (3D) finite element model for the coupled solution of heat transfer and fluid flow equations governing transformer thermal performance. The main advantages of the proposed method are: (i) no need to predefine the convection coefficients at the interfaces between the active part/tank walls and the circulating oil, (ii) detailed representation of specific transformer parts that play an important role in the accurate representation of oil flow and heat dissipation (such as winding cooling ducts and corrugated tank panels) through an automated design process, enhancing the model accuracy with the least possible computational effort and (iii) accurate definition of the transformer heat sources (core and windings loss). The proposed methodology provides an integrated tool for thermal simulation, able to predict detailed thermal distribution in a specific transformer, without requiring prior knowledge of Nodal Temperature or Temperature gradient values.
Bhupendra Singh Chauhan - One of the best experts on this subject based on the ideXlab platform.
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Temperature transients of piston of a Camless S.I Engine using Temperature transients of piston of a Camless S.I Engine using Temperature transients of piston of a Camless S.I Engine using Temperature transients of piston of a Camless S.I Engine usin
2020Co-Authors: Kanwarjabar Singh Gill, Khushpreet Singh, Bhupendra Singh ChauhanAbstract:Abstract Simplified finite element model of spark ignition (SI) engine to analyse combustion heat transfer is presented. The model was discredited with 3D thermal elements of global length 5 mm. The fuel type is petrol. Internal Nodal Temperature of cylinder body is defined as 21000C to represent occurrence of gasoline combustion. Material information and isotropic material properties are taken from published report. The heat transfer analysis is done for the instant of combustion. The model is validated by comparing the computed maximum Temperature at the piston surface with the published result. The computed Temperature gradient at the crucial parts are plotted and discussed. It has been found that the critical top surface suffered from thermal and the materials used to construct the engine parts strongly influenced the Temperature distribution in the engine. The model is capable to analyze heat transfer in the engine reasonably and efficiently. Key words : Piston, Boundary conditions, Thermal analysis, NASTRAN etc.
Xian Feng Wang - One of the best experts on this subject based on the ideXlab platform.
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Limit and Shakedown Analysis of Circular Tube Containing External Pit
The Open Mechanical Engineering Journal, 2012Co-Authors: Xian Feng Wang, Feng Xing, Bing Ye XuAbstract:The circular tubes containing external pit defects are analyzed in a lower-bound finite element computational form based on the static shakedown theorem. The shakedown analysis has not been commonly used in the engineering due to the large amount of computations. To overcome the numerical difficulties, a Temperature parameter method is used, in which a pseudo-Temperature field is applied to the structure and the resulting self-equilibrium thermoelastic stress is treated as the residual stress field which is used in the analysis. The pseudo Temperature is assumed as a harmonic function satisfying the uniqueness theorem, therefore the Nodal Temperature matrix of the whole structure can be expressed by the boundary Nodal Temperature matrix. The nonlinear yield condition is piece-wise linearized so that the shakedown analysis is transformed into a linear programming problem in which the strategic variable is boundary Nodal Temperature and objective variable is the loading multiplier. The relations of limit and shakedown pressures to geometric parameters of various defects are presented.
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Shakedown Analysis of Cylindrical Shells Containing Part-Through External Pit
Advanced Materials Research, 2010Co-Authors: Xian Feng Wang, Feng Xing, Bing Ye XuAbstract:A lower-bound shakedown analysis for cylindrical shells containing defects is performed based on the static shakedown theorem in a finite element computational form. To overcome the numerical difficulties, the pseudo-Temperature field is applied to a structure and the resulting thermo-elastic stress is considered as the self-equilibrium residual-stress field. The pseudo Temperature is assumed as a harmonic function satisfying the uniqueness theorem, therefore the Nodal Temperature matrix of the whole structure can be expressed by the boundary Nodal Temperature matrix. The nonlinear yield condition is piece-wise linearized so that the shakedown analysis is transformed into a linear programming problem in which the strategic variable is boundary Nodal Temperature and objective variable is the loading multiplier. The relations of limit and shakedown pressures to geometric parameters of various defects are presented.