The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
Margaritis Kostoglou - One of the best experts on this subject based on the ideXlab platform.
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the equal size binary Breakage Problem evolution toward a steady shape or periodic behavior
Journal of Colloid and Interface Science, 2006Co-Authors: Margaritis KostoglouAbstract:Abstract During the last few years, the self-similar particle size distribution for a particle population undergoing Breakage in equal size fragments has been derived using approximating, numerical, and analytical means. But very recently it was shown [N.V. Mantzaris, J. Phys. A Math. Gen. 38 (2005) 5111] through transient simulation of the Breakage process that the particle size distribution in case of Breakage in two equal fragments, never attains a steady shape, i.e., a self-similar form. The new results give rise to questions about the real meaning and utility of the previously derived self-similar distributions for these systems. The scope of the present work is to answer these questions and it is attempted using only analytical (exact) means for the solution of the transient Breakage Problem. In doing so, the very interesting and rich underlying structure and properties of the solutions of the equal size Breakage Problem (seemingly, very simple) are revealed. It appears that the utility of the known self-similar distributions for this particular Problem has to be redefined but yet not entirely abandoned.
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On the self-similar solution of fragmentation equation: Numerical evaluation with implications for the inverse Problem.
Journal of Colloid and Interface Science, 2005Co-Authors: Margaritis Kostoglou, Anastasios J. KarabelasAbstract:It is well known that the fragmentation equation admits self-similar solutions for evolving particle-size distributions (PSD); i.e., if the shape of PSD is independent of time after an initial transient period. Although an analytical derivations of the self-similar PSD cases have been studied extensively, results for cases requiring numerical solutions are rare. The aim of the present work is to fill this gap for the case of homogeneous Breakage functions. The known analytical and approximate solutions for the self-similar PSD are reviewed and a general algorithm for the numerical solution is proposed. Results for a broad range of Breakage functions (kernel and rate) are presented. Further, the work is focused on the sensitivity of the relation between self-similar PSD and Breakage kernel and its influence on the inverse Breakage Problem, i.e., that of estimating the Breakage kernel from experimental self-similar PSDs. Useful suggestions are made for tackling the inverse Problem.
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on the Breakage Problem with a homogeneous erosion type kernel
Journal of Physics A, 2001Co-Authors: Margaritis Kostoglou, A J KarabelasAbstract:The Breakage equation with a homogeneous erosion type kernel is studied herein. This type of kernel renders the handling of the Breakage equation by conventional techniques very difficult, necessitating alternative Problem solving approaches. Exploiting the structure of the erosion-Breakage kernel, a new particle erosion equation is derived as the first-order term of a formal perturbation expansion with respect to kernel parameters. However, even this new equation is very difficult to treat because of the multimodality of its solution associated with the developing generations of fragments. In order to overcome this difficulty, the Problem is decomposed into a system of equations for the size distribution of the generations of fragments which admits unimodal solutions. The properties and the methods of solution (analytical, method of moments, etc) are studied extensively. Using solution techniques developed in this paper, results are reported for some simple cases, revealing a very interesting and rather unusual structure of the solutions of the erosion-Breakage equation. PACS number: 0590
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Theoretical analysis of the steady state particle size distribution in limited Breakage processes
Journal of Physics A, 1998Co-Authors: Margaritis Kostoglou, Anastasios J. KarabelasAbstract:The steady state particle size distribution is examined, resulting from a Breakage process with a maximum stable size and a homogeneous continuous kernel. The dynamic Breakage Problem is transformed into one that allows direct solutions for the steady state distribution. The latter depends on the Breakage kernel and on the ratio of critical to initial size. As this ratio goes to zero the steady state distribution approaches its limiting form obtained by the authors previously [7]. A general theoretical analysis concerning the steady state distribution is presented herein. The asymptotic behaviour is determined with regard to various limits. Perturbation analysis for nearly uniform kernels reveals several interesting features of the Problem. For the general continuous kernel, the Problem can be cast in a matrix form amenable to a conventional theoretical treatment. Finally, comparisons of the new results with existing solutions of the dynamic Problem, for large times, confirm their validity.
P. M. Khilar - One of the best experts on this subject based on the ideXlab platform.
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VehiHealth: An Emergency Routing Protocol for Vehicular Ad Hoc Network to Support Healthcare System
Journal of Medical Systems, 2015Co-Authors: S. K. Bhoi, P. M. KhilarAbstract:Survival of a patient depends on effective data communication in healthcare system. In this paper, an emergency routing protocol for Vehicular Ad hoc Network (VANET) is proposed to quickly forward the current patient status information from the ambulance to the hospital to provide pre-medical treatment. As the ambulance takes time to reach the hospital, ambulance doctor can provide sudden treatment to the patient in emergency by sending patient status information to the hospital through the vehicles using vehicular communication. Secondly, the experienced doctors respond to the information by quickly sending a treatment information to the ambulance. In this protocol, data is forwarded through that path which has less link Breakage Problem between the vehicles. This is done by calculating an intersection value I _ v a l u e for the neighboring intersections by using the current traffic information. Then the data is forwarded through that intersection which has minimum I _ v a l u e . Simulation results show VehiHealth performs better than P-GEDIR, GyTAR, A-STAR and GSR routing protocols in terms of average end-to-end delay, number of link Breakage, path length, and average response time.
A G Callagy - One of the best experts on this subject based on the ideXlab platform.
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MALFUNCTIONS OF A STEAM TURBINE MECHANICAL CONTROL SYSTEM
Failure Analysis Case Studies II, 2020Co-Authors: J.h. Bulloch, A G CallagyAbstract:This paper is aimed at elucidating the cause of a series of malfunctions involving the bending or breaking of main steam turbine throttle valve spindles which occurred at service times ranging from hundreds to several thousand hours in a number of 270 MW steam raising units. It was clearly established, by two distinct approaches (one engineering, one micromechanistic) that the stresses which produced these malfunctions were bending in nature and were the result of out-of-alignment deflections. In the case of the bent spindles the stresses were very high and approached flow strength levels of around 8000 MPa while the broken spindles were the results of fatigue initiation and subsequent growth from a thread root (stress concentration) location on the spindle. Using relevant fatigue crack propagation data for the valve spindle material at 300°C it was demonstrated that fatigue failures occurred at spindle deflections of between 0.9 and 1.6 mm. Finally, it was demonstrated that the fatigue Breakage Problem could be significantly reduced, especially at the lower end of the valve spindle deflection range, by a combination of re-profiling the thread root and shot peening. © 1998 Published by Elsevier Science Ltd. All rights reserved.
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Malfunctions of a steam turbine mechanical control system
Engineering Failure Analysis, 1998Co-Authors: J.h. Bulloch, A G CallagyAbstract:This paper is aimed at elucidating the cause of a series of malfunctions involving the bending or breaking of main steam turbine throttle valve spindles which occurred at service times ranging from hundreds to several thousand hours in a number of 270 MW steam raising units. It was clearly established, by two distinct approaches (one engineering, one micromechanistic) that the stresses which produced these malfunctions were bending in nature and were the result of out-of-alignment deflections. In the case of the bent spindles the stresses were very high and approached flow strength levels of around 8000 MPa while the broken spindles were the results of fatigue initiation and subsequent growth from a thread root (stress concentration) location on the spindle. Using relevant fatigue crack propagation data for the valve spindle material at 300°C it was demonstrated that fatigue failures occurred at spindle deflections of between 0.9 and 1.6 mm. Finally, it was demonstrated that the fatigue Breakage Problem could be significantly reduced, especially at the lower end of the valve spindle deflection range, by a combination of re-profiling the thread root and shot peening.
Nikos V Mantzaris - One of the best experts on this subject based on the ideXlab platform.
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transient and asymptotic behaviour of the binary Breakage Problem
Journal of Physics A, 2005Co-Authors: Nikos V MantzarisAbstract:The general binary Breakage Problem with power-law Breakage functions and two families of symmetric and asymmetric Breakage kernels is studied in this work. A useful transformation leads to an equation that predicts self-similar solutions in its asymptotic limit and offers explicit knowledge of the mean size and particle density at each point in dimensionless time. A novel moving boundary algorithm in the transformed coordinate system is developed, allowing the accurate prediction of the full transient behaviour of the system from the initial condition up to the point where self-similarity is achieved, and beyond if necessary. The numerical algorithm is very rapid and its results are in excellent agreement with known analytical solutions. In the case of the symmetric Breakage kernels only unimodal, self-similar number density functions are obtained asymptotically for all parameter values and independent of the initial conditions, while in the case of asymmetric Breakage kernels, bimodality appears for high degrees of asymmetry and sharp Breakage functions. For symmetric and discrete Breakage kernels, self-similarity is not achieved. The solution exhibits sustained oscillations with amplitude that depends on the initial condition and the sharpness of the Breakage mechanism, while the period is always fixed and equal to ln 2 with respect to dimensionless time.
S. K. Bhoi - One of the best experts on this subject based on the ideXlab platform.
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VehiHealth: An Emergency Routing Protocol for Vehicular Ad Hoc Network to Support Healthcare System
Journal of Medical Systems, 2015Co-Authors: S. K. Bhoi, P. M. KhilarAbstract:Survival of a patient depends on effective data communication in healthcare system. In this paper, an emergency routing protocol for Vehicular Ad hoc Network (VANET) is proposed to quickly forward the current patient status information from the ambulance to the hospital to provide pre-medical treatment. As the ambulance takes time to reach the hospital, ambulance doctor can provide sudden treatment to the patient in emergency by sending patient status information to the hospital through the vehicles using vehicular communication. Secondly, the experienced doctors respond to the information by quickly sending a treatment information to the ambulance. In this protocol, data is forwarded through that path which has less link Breakage Problem between the vehicles. This is done by calculating an intersection value I _ v a l u e for the neighboring intersections by using the current traffic information. Then the data is forwarded through that intersection which has minimum I _ v a l u e . Simulation results show VehiHealth performs better than P-GEDIR, GyTAR, A-STAR and GSR routing protocols in terms of average end-to-end delay, number of link Breakage, path length, and average response time.
