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Papers by Boo Cheong Khoo

Research paper thumbnail of Physical methods of reducing the transmission of nosocomial infections via ultrasound and probe

Research paper thumbnail of The generalized singular value decomposition and the general (A-λB)-problem

Research paper thumbnail of The Cellular Structure and Its Tracks of a H2/O2/Ar Detonation Waves

Research paper thumbnail of Mathematical modeling and simulation of a distillation column

ISBN 978-967-5760-03-7 Abstract Distillation column processing is the most vital separation techn... more ISBN 978-967-5760-03-7 Abstract Distillation column processing is the most vital separation technology for today’s industry. An inclination to controlling distillation columns in a manner that is economically efficient depends much on the selection of reliable systems. This paper presents a detailed methodology to derive a mathematic modeling and simulation analysis for a distillation column based on continuous and non-linear model of the mass and energy balance. The mathematical modeling is then used as the reference model system to examine the ability of the developed distillate column tower dealing with the model-plant mismatch and feed disturbances inputs.

Research paper thumbnail of Effect of Column Inlet and Outlet Geometry on Large-scale HPLC

Research paper thumbnail of Mathematical modeling, control and simulation of petroleum distillation column

Research paper thumbnail of Effect of High-Intensity Focused Ultrasound on Enterococcus Faecalis Planktonic Suspensions and Biofilms

Ultrasound in Medicine & Biology, 2013

In this study, the effect of high-intensity focused ultrasound (HIFU) on Enterococcus faecalis on... more In this study, the effect of high-intensity focused ultrasound (HIFU) on Enterococcus faecalis on both planktonic suspensions and biofilms was investigated. E. faecalis persist in secondary dental infections as biofilms. Glass-bottom Petri dishes with biofilms were centered at the focal point of the HIFU wave generated by a 250-kHz transducer. Specimens were subjected to HIFU exposure at different periods of 30, 60 and 120 s. The viable bacteria, removal effect and bacterial viability of biofilms attached to the Petri dish surface were studied by colony-forming units (CFUs), scanning electron microscopy and confocal microscopy, respectively. The removal and bactericidal effects of HIFU are dependent on the exposure time. A significant reduction in biofilm thickness and CFU was found with the increase in HIFU exposure. The removal or bactericidal effect of HIFU was more significant starting from 60 s of exposure. This study highlighted the potential application of HIFU as a novel method for root canal disinfection.

Research paper thumbnail of Concentration Dependence of Yield Stress and Dynamic Moduli of Kaolinite Suspensions

Langmuir : the ACS journal of surfaces and colloids, Jan 16, 2015

The concentration dependence of yield stress and dynamic moduli of kaolinite suspensions is studi... more The concentration dependence of yield stress and dynamic moduli of kaolinite suspensions is studied. Complex electrostatic interactions between kaolinite platelets promote a more liquid-like behavior, with clay particles changing from attractive interactions to a face-face repulsive interaction as the mass fraction of clay particles increases. A yield stress model is developed based on the repulsive interaction between disk-shaped particles, which yields a good prediction of experimental observations when repulsive face-face interaction is dominant. The critical concentration when attractive interaction changes completely to face-face repulsive interaction is estimated from the theory. Four regions are identified in the variation of yield stress as a function of the concentration.

Research paper thumbnail of Integrating legacy instruments in an LXI based test and measurement system

2008 IEEE AUTOTESTCON, 2008

LAN Extension for Instrumentation (LXI) is a new standard for test and measurement industries. Th... more LAN Extension for Instrumentation (LXI) is a new standard for test and measurement industries. The idea promotes time based measurement capability with the aid of IEEE1588 Precision Time Protocol (PTP) running over the Ethernet network among test and measurement systems. However, legacy instruments do not have the sense of absolute time within the instrument to be synchronized with LXI units.

Research paper thumbnail of Study of cell seeding on porous poly(d,l-lactic-co-glycolic acid) sponge and growth in a Couette–Taylor bioreactor

Chemical Engineering Science, 2010

Research paper thumbnail of Spatial Simulation of 2D Tollmien-Schlichting Wave Over Volume Based Viscoelastic Layer

Recent Advances in Computational Science and Engineering

Research paper thumbnail of Turbulent Transition in Plane Couette Flows

New Trends in Fluid Mechanics Research

Research paper thumbnail of Numerical simulation of fully nonlinear sloshing waves in three-dimensional tank under random excitation

Ocean Systems Engineering

ABSTRACT

Research paper thumbnail of Fast centroidal Voronoi Delaunay triangulation for unstructured mesh generation

Journal of Computational and Applied Mathematics

ABSTRACT

Research paper thumbnail of The Modified Ghost Fluid Method Applied to Fluid-Elastic Structure Interaction

Advances in Applied Mathematics and Mechanics

In this work, the modified ghost fluid method is developed to deal with 2D compressible fluid int... more In this work, the modified ghost fluid method is developed to deal with 2D compressible fluid interacting with elastic solid in an Euler-Lagrange coupled system. In applying the modified Ghost Fluid Method to treat the fluid-elastic solid coupling, the Navier equations for elastic solid are cast into a system similar to the Euler equations but in Lagrangian coordinates. Furthermore, to take into account the influence of material deformation and nonlinear wave interaction at the interface, an Euler-Lagrange Riemann problem is constructed and solved approximately along the normal direction of the interface to predict the interfacial status and then define the ghost fluid and ghost solid states. Numerical tests are presented to verify the resultant method.

Research paper thumbnail of Investigation of Turbulent Transition in Plane Couette Flows Using Energy Gradient Method

Advances in Applied Mathematics and Mechanics

The energy gradient method has been proposed with the aim of better understanding the mechanism o... more The energy gradient method has been proposed with the aim of better understanding the mechanism of flow transition from laminar flow to turbulent flow. In this method, it is demonstrated that the transition to turbulence depends on the relative magnitudes of the transverse gradient of the total mechanical energy which amplifies the disturbance and the energy loss from viscous friction which damps the disturbance, for given imposed disturbance. For a given flow geometry and fluid properties, when the maximum of the functionK(a function standing for the ratio of the gradient of total mechanical energy in the transverse direction to the rate of energy loss due to viscous friction in the streamwise direction) in the flow field is larger than a certain critical value, it is expected that instability would occur for some initial disturbances. In this paper, using the energy gradient analysis, the equation for calculating the energy gradient functionKfor plane Couette flow is derived. The ...

Research paper thumbnail of Transient response of stiffened composite submersible hull to underwater explosion bubble

Research paper thumbnail of Wave Propagation in a Three-Dimensional, Fully-Nonlinear Numerical Wave Tank Based on Multi-transmitting Formula Coupled Damping Zone Method

Qatar Foundation Annual Research Forum Proceedings

Research paper thumbnail of On the numerical technique for the simulation of hypervelocity test flows

Research paper thumbnail of Theory and Prediction of Turbulent Transition

International Journal of Fluid Machinery and Systems

Research paper thumbnail of Physical methods of reducing the transmission of nosocomial infections via ultrasound and probe

Research paper thumbnail of The generalized singular value decomposition and the general (A-λB)-problem

Research paper thumbnail of The Cellular Structure and Its Tracks of a H2/O2/Ar Detonation Waves

Research paper thumbnail of Mathematical modeling and simulation of a distillation column

ISBN 978-967-5760-03-7 Abstract Distillation column processing is the most vital separation techn... more ISBN 978-967-5760-03-7 Abstract Distillation column processing is the most vital separation technology for today’s industry. An inclination to controlling distillation columns in a manner that is economically efficient depends much on the selection of reliable systems. This paper presents a detailed methodology to derive a mathematic modeling and simulation analysis for a distillation column based on continuous and non-linear model of the mass and energy balance. The mathematical modeling is then used as the reference model system to examine the ability of the developed distillate column tower dealing with the model-plant mismatch and feed disturbances inputs.

Research paper thumbnail of Effect of Column Inlet and Outlet Geometry on Large-scale HPLC

Research paper thumbnail of Mathematical modeling, control and simulation of petroleum distillation column

Research paper thumbnail of Effect of High-Intensity Focused Ultrasound on Enterococcus Faecalis Planktonic Suspensions and Biofilms

Ultrasound in Medicine & Biology, 2013

In this study, the effect of high-intensity focused ultrasound (HIFU) on Enterococcus faecalis on... more In this study, the effect of high-intensity focused ultrasound (HIFU) on Enterococcus faecalis on both planktonic suspensions and biofilms was investigated. E. faecalis persist in secondary dental infections as biofilms. Glass-bottom Petri dishes with biofilms were centered at the focal point of the HIFU wave generated by a 250-kHz transducer. Specimens were subjected to HIFU exposure at different periods of 30, 60 and 120 s. The viable bacteria, removal effect and bacterial viability of biofilms attached to the Petri dish surface were studied by colony-forming units (CFUs), scanning electron microscopy and confocal microscopy, respectively. The removal and bactericidal effects of HIFU are dependent on the exposure time. A significant reduction in biofilm thickness and CFU was found with the increase in HIFU exposure. The removal or bactericidal effect of HIFU was more significant starting from 60 s of exposure. This study highlighted the potential application of HIFU as a novel method for root canal disinfection.

Research paper thumbnail of Concentration Dependence of Yield Stress and Dynamic Moduli of Kaolinite Suspensions

Langmuir : the ACS journal of surfaces and colloids, Jan 16, 2015

The concentration dependence of yield stress and dynamic moduli of kaolinite suspensions is studi... more The concentration dependence of yield stress and dynamic moduli of kaolinite suspensions is studied. Complex electrostatic interactions between kaolinite platelets promote a more liquid-like behavior, with clay particles changing from attractive interactions to a face-face repulsive interaction as the mass fraction of clay particles increases. A yield stress model is developed based on the repulsive interaction between disk-shaped particles, which yields a good prediction of experimental observations when repulsive face-face interaction is dominant. The critical concentration when attractive interaction changes completely to face-face repulsive interaction is estimated from the theory. Four regions are identified in the variation of yield stress as a function of the concentration.

Research paper thumbnail of Integrating legacy instruments in an LXI based test and measurement system

2008 IEEE AUTOTESTCON, 2008

LAN Extension for Instrumentation (LXI) is a new standard for test and measurement industries. Th... more LAN Extension for Instrumentation (LXI) is a new standard for test and measurement industries. The idea promotes time based measurement capability with the aid of IEEE1588 Precision Time Protocol (PTP) running over the Ethernet network among test and measurement systems. However, legacy instruments do not have the sense of absolute time within the instrument to be synchronized with LXI units.

Research paper thumbnail of Study of cell seeding on porous poly(d,l-lactic-co-glycolic acid) sponge and growth in a Couette–Taylor bioreactor

Chemical Engineering Science, 2010

Research paper thumbnail of Spatial Simulation of 2D Tollmien-Schlichting Wave Over Volume Based Viscoelastic Layer

Recent Advances in Computational Science and Engineering

Research paper thumbnail of Turbulent Transition in Plane Couette Flows

New Trends in Fluid Mechanics Research

Research paper thumbnail of Numerical simulation of fully nonlinear sloshing waves in three-dimensional tank under random excitation

Ocean Systems Engineering

ABSTRACT

Research paper thumbnail of Fast centroidal Voronoi Delaunay triangulation for unstructured mesh generation

Journal of Computational and Applied Mathematics

ABSTRACT

Research paper thumbnail of The Modified Ghost Fluid Method Applied to Fluid-Elastic Structure Interaction

Advances in Applied Mathematics and Mechanics

In this work, the modified ghost fluid method is developed to deal with 2D compressible fluid int... more In this work, the modified ghost fluid method is developed to deal with 2D compressible fluid interacting with elastic solid in an Euler-Lagrange coupled system. In applying the modified Ghost Fluid Method to treat the fluid-elastic solid coupling, the Navier equations for elastic solid are cast into a system similar to the Euler equations but in Lagrangian coordinates. Furthermore, to take into account the influence of material deformation and nonlinear wave interaction at the interface, an Euler-Lagrange Riemann problem is constructed and solved approximately along the normal direction of the interface to predict the interfacial status and then define the ghost fluid and ghost solid states. Numerical tests are presented to verify the resultant method.

Research paper thumbnail of Investigation of Turbulent Transition in Plane Couette Flows Using Energy Gradient Method

Advances in Applied Mathematics and Mechanics

The energy gradient method has been proposed with the aim of better understanding the mechanism o... more The energy gradient method has been proposed with the aim of better understanding the mechanism of flow transition from laminar flow to turbulent flow. In this method, it is demonstrated that the transition to turbulence depends on the relative magnitudes of the transverse gradient of the total mechanical energy which amplifies the disturbance and the energy loss from viscous friction which damps the disturbance, for given imposed disturbance. For a given flow geometry and fluid properties, when the maximum of the functionK(a function standing for the ratio of the gradient of total mechanical energy in the transverse direction to the rate of energy loss due to viscous friction in the streamwise direction) in the flow field is larger than a certain critical value, it is expected that instability would occur for some initial disturbances. In this paper, using the energy gradient analysis, the equation for calculating the energy gradient functionKfor plane Couette flow is derived. The ...

Research paper thumbnail of Transient response of stiffened composite submersible hull to underwater explosion bubble

Research paper thumbnail of Wave Propagation in a Three-Dimensional, Fully-Nonlinear Numerical Wave Tank Based on Multi-transmitting Formula Coupled Damping Zone Method

Qatar Foundation Annual Research Forum Proceedings

Research paper thumbnail of On the numerical technique for the simulation of hypervelocity test flows

Research paper thumbnail of Theory and Prediction of Turbulent Transition

International Journal of Fluid Machinery and Systems