Tan Nguyen - Academia.edu (original) (raw)

Papers by Tan Nguyen

Journal of Mechanical Science and Technology, 2001

This paper deals with dynamic analysis of Pipeline Inspection Gauge (PIG) flow control in natural... more This paper deals with dynamic analysis of Pipeline Inspection Gauge (PIG) flow control in natural gas pipelines. The dynamic behaviour of PIG depends on the pressure differential generated by injected gas flow behind the tail of the PIG and expelled gas flow in front of its nose. To analyze dynamic behaviour characteristics (e.g. gas flow, the PIG position and velocity) mathematical models are derived. Two types of nonlinear hyperbolic partial differential equations are developed for unsteady flow analysis of the PIG driving and expelled gas. Also, a non-homogeneous differential equation for dynamic analysis of the PIG is given. The nonlinear equations are solved by method of characteristics (MaC) with a regular rectangular grid under appropriate initial and boundary conditions. Runge-Kutta method is used for solving the steady flow equations to get the initial flow values and for solving the dynamic equation of the PIG. The upstream and downstream regions are divided into a number of elements of equal length. The sampling time and distance are chosen under Courant -Friedrich-Lewy (CFL) restriction. Simulation is performed with a pipeline segment in the Korea gas corporation (KOGAS) low pressure system, Ueijungboo-Sangye line. The simulation results show that the derived mathematical models and the proposed computational scheme are effective for estimating the position and velocity of the PIG with a given operational condition of pipeline.

J Mech Sci Technol, 2002

This paper presents hybrid control of an active suspension system with a full-car model by using ... more This paper presents hybrid control of an active suspension system with a full-car model by using H∞, and nonlinear adaptive control methods. The full-car model has seven degrees of freedom including heaving, pitching and rolling motions. In the active suspension system, the controller shows good

Journal of Mechanical Science and Technology, Jan 8, 2003

This paper deals with verification of the theoretical model for dynamic behavior of Pipeline Insp... more This paper deals with verification of the theoretical model for dynamic behavior of Pipeline Inspection Gauge (PIG) traveling through high pressure natural gas pipeline. The dynamic behavior of the PIG depends on the differential pressure across its body. This differential pressure is generated by injected gas flow behind the tail of the PIG and expelled gas flow in front of its nose. To analyze the dynamic behavior characteristics such as gas flow in pipeline, and the PIG position and velocity, not only the mathematical models are derived, but also the theoretical models must be certified by actual pigging experiment. But there is not any found results of research on the experimental certification for dynamic behavior of the PIG. The reason is why the fabrication of the PIG as well as, a field application are very difficult. In this research, the effectiveness of the introduced solution using the method of characteristics (MOC) was certified through field application. In-line inspection tool, 30" geometry PIG, was fabricated and actual pigging was carried out at the pipeline segment in Korea Gas Corporation (KOGAS) high pressure system, Incheon LT(LNG Terminal)-Namdong GS(Governor Station) line. Pigging is fulfilled successfully. Comparison of simulation results with experimental results show that the derived mathematical models and the proposed computational schemes are effective for predicting the position and velocity of the PIG with a given operational conditions of pipeline.

Journal of Mechanical Science and Technology, 2001

This paper introduces modeling and simulation results for pipeline inspection gauge (PIG) with by... more This paper introduces modeling and simulation results for pipeline inspection gauge (PIG) with bypass flow control in natural gas pipeline. The dynamic behaviour of the PIG depends on the different pressure across its body and the bypass flow through it. The system dynamics includes: dynamics of driving gas flow behind the PIG, dynamics of expelled gas in front of the PIG, dynamics of bypass flow, and dynamics of the PIG. The bypass flow across the PIG is treated as incompressible flow with the assumption of its Mach number smaller than 0.45. The governing nonlinear hyperbolic partial differential equations for unsteady gas flows are solved by method of characteristics (MOC) with the regular rectangular grid under appropriate initial and boundary conditions. The Runge-Kuta method is used for solving the steady flow equations to get initial flow values and the dynamic equation of the PIG. The sampling time and distance are chosen under Courant-Friedrich-Lewy (CFL) restriction. The simulation is performed with a pipeline segment in the Korea Gas Corporation (KOGAS) low pressure system, Ueijungboo -Sangye line. Simulation results show us that the derived mathematical model and the proposed computational scheme are effective for estimating the position and velocity of the PIG with bypass flow under given operational conditions of pipeline.

Data Revues 14439506 V20ss2 S1443950611004185, 2011

Methods: Microvascular resistance was measured utilising the index of microcirculatory resistance... more Methods: Microvascular resistance was measured utilising the index of microcirculatory resistance (IMR) in 24 patients undergoing elective PCI for stable angina. A coronary PressureWire was used to measure IMR prior to PCI using the equation Pa Tmn(Pd − Pw/Pa − Pw), where Pa and Pd refer to hyperaemic aortic and distal coronary pressure respectively, Tmn the mean transit time of 3 ml of saline injected into the culprit artery and Pw the coronary wedge pressure. Body mass index, age, fasting LDL, HDL and blood sugar, blood pressure and smoking status (pack-years) were recorded in each patient prior to PCI. Associations were assessed using Pearson's correlation coefficients. Linear regression analysis was used to assess correlates of IMR.

Journal of Mechanical Science and Technology, Jul 31, 2004

Wall-following control problem for a mobile robot is to move it along a wall at a constant speed ... more Wall-following control problem for a mobile robot is to move it along a wall at a constant speed and keep a specified distance to the wall. This paper proposes wall-following controllers based on Lyapunov function candidate for a two-wheeled mobile robot (MR) to follow an unknown wall. The mobile robot is considered in terms of kinematic model in Cartesian coordinate system. Two wall-following feedback controllers are designed : full state feedback controller and observer-based controller. To design the former controller, the errors of distance and orientation of the mobile robot to the wall are defined, and the feedback controller based on Lyapunov function candidate is designed to guarantee that the errors converge to zero asymptotically. The latter controller is designed based on Busawon's observer as only the distance error is measured. Additionally, the simulation and experimental results are included to illustrate the effectiveness of the proposed controllers. Straight velocity of mobile robot at its center point [m/s] Angular velocity of mobile robot at its center point [rad/s] Angular velocities of the right and left wheels [rad/s] Velocity of point W[m/s] Time rate of the change of t--t direction [rad/sJ Distance and angular errors [m] Constant speed [m/s3 Desired distance value [m] Known function Class C 1 that the first derivatives are continuous with respect to their arguments An observability matrix A symmetric positive definite matrix Positive number Radius of the roller [m~ Length of the sensor [m]

Optics Letters, 2015

We investigate the uniqueness of the plane-wave decomposition of temporally deterministic, spatia... more We investigate the uniqueness of the plane-wave decomposition of temporally deterministic, spatially random fields. Specifically, we consider the decomposition of spatially ergodic and, thus, statistically homogeneous fields. We show that when the spatial power spectrum is injective, the plane waves are the only possible coherent modes. Furthermore, the randomness of such fields originates in the spatial spectral phase, i.e., the phase associated with the coefficients of each plane wave in the expansion. By contrast, the spectral amplitude is deterministic and is specified by the spatial power spectrum. We end with a discussion showing how the results can be translated in full to the time domain.

ISIE 2001. 2001 IEEE International Symposium on Industrial Electronics Proceedings (Cat. No.01TH8570), 2001

This paper introduces a simple nonlinear control method for pipeline inspection gauge (PIG) flow ... more This paper introduces a simple nonlinear control method for pipeline inspection gauge (PIG) flow in a natural gas pipeline. The PIG is controlled using the amount of bypass flow across its body. The dynamic behavior of the PIG depends on the different pressure across its body and the bypass flow through it. The system dynamics includes: dynamics of driving gas

Quantitative Phase Imaging, 2015

ABSTRACT

Quantitative Phase Imaging, 2015

Biomechanics in Ergonomics, Second Edition, 2007

... have been evaluated both in vitro and in vivo on their effect of ligament healing with variab... more ... have been evaluated both in vitro and in vivo on their effect of ligament healing with variable results (Batten et al, 1996; Letson and Dahners, 1994 ... KA and Frank, CB, 1997, The normal structure and function of the ligaments and their responses to injury and repair, in Dee, RM et ...

The Open Clinical Chemistry Journal, 2010

2011 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, 2011

In this paper, we proposed a novel method to improve colonic polyp detection in computed tomograp... more In this paper, we proposed a novel method to improve colonic polyp detection in computed tomographic colonography. Utilizing the human knowledge workers via the Amazon Mechanical Turk (MTurk) webservice, we distributed polyp detections from a computer-aided detection system (CAD) to anonymous online knowledge workers and asked them to distinguish true and false polyp candidates. We combined decisions from the CAD

Biomedical optics express, 2013

We report the use of a twisted nematic liquid-crystal spatial light modulator (TNLC-SLM) for quan... more We report the use of a twisted nematic liquid-crystal spatial light modulator (TNLC-SLM) for quantitative phase imaging. The experimental setup is a new implementation of the SLIM principle, which is a phase shifting, white light method for quantitative phase imaging. The approach is based on switching between the phase and amplitude modulation modes of the SLM. Our system is able to deliver a 0.99 nm spatial and 1.33 nm temporal pathlength sensitivity while retaining the optical transverse resolution. The system is implemented as an additional module mounted to a conventional microscope, which makes the system very easy to deploy and integrate with other imaging modalities.

Medical Imaging 2012: Computer-Aided Diagnosis, 2012

ABSTRACT

Frontiers in Optics 2014, 2014

ISIE 2001. 2001 IEEE International Symposium on Industrial Electronics Proceedings (Cat. No.01TH8570), 2001

Currently, adaptive educational hypermedia systems (AEHS) are described with nonuniform methods, ... more Currently, adaptive educational hypermedia systems (AEHS) are described with nonuniform methods, depending on the specific view on the system, the application, or other parameters. There is no common language for expressing functionality of AEHS, hence these systems are difficult to compare and analyze. In this paper we investigate how a logical description can be employed to characterize adaptive educational hypermedia. We propose a definition of AEHS based on first-order logic, characterize some AEHS due to this formalism, and discuss the applicability of this approach.

In this paper a robust control is applied to a two-wheeled mobile manipulator (WMM) to follow a s... more In this paper a robust control is applied to a two-wheeled mobile manipulator (WMM) to follow a smooth curved trajectory and pick an object in the 3D workplace. The dynamic motion equation of the mobile manipulator is derived taking into account parametric uncertainties, external disturbances, and the dynamic interactions between the mobile platform and the manipulator; then, a robust controller is derived based on the bounded conditions of the parameters of the total system. In addition, an USB camera is used to detect the object's coordinates in 3D space, and a practical method of camera calibration is introduced for detecting the relative position between the object and the camera which is needed for the manipulator to pick it. Also, a combined system which composed of a computer and a multi-dropped PIC-based controller is developed using USB-CAN communication to meet the performance of demand of the whole system. What's more, the simulation results are included to illu...

Tissue Engineering Part A, 2008

Previous studies have shown that cultured cells align with the local topography of their substrat... more Previous studies have shown that cultured cells align with the local topography of their substrate following a concept called "contact guidance." Additionally, if the topography is highly aligned, the cells produce newly synthesized matrix that is also aligned. The objective of this study was to elucidate the positive effect of cell seeding on an elongated porcine small intestinal submucosa (SIS), which has been shown to improve ligament and tendon healing, by measuring the cellular response as a result of the changes in alignment. Because elongation is known to align the fibers of SIS through recruitment along the direction of elongation, we hypothesized that rabbit bone marrow-derived cells (BMDCs) seeded on SIS with improved fiber alignment would increase the expression and production of collagen following the concept of contact guidance. Using the small-angle light-scattering technique, it was found that a 15% elongation together with BMDC seeding on SIS (elongated, seeded group) improved its alignment of collagen fibers up to 16 times more than no elongation and no BMDC seeding (non-elongated, non-seeded group). Furthermore, BMDCs were also aligned along the direction of elongation and showed 200% greater collagen type I gene expression in the elongated, seeded group than in Petri dish controls. More importantly, the production of collagen was also 24% greater. The results of this study demonstrate that alignment of a bioscaffold can result in positive changes in cellular response, making the bioscaffold more attractive for functional tissue engineering to potentially enhance healing of ligaments and tendons.

Journal of Mechanical Science and Technology, 2001

This paper deals with dynamic analysis of Pipeline Inspection Gauge (PIG) flow control in natural... more This paper deals with dynamic analysis of Pipeline Inspection Gauge (PIG) flow control in natural gas pipelines. The dynamic behaviour of PIG depends on the pressure differential generated by injected gas flow behind the tail of the PIG and expelled gas flow in front of its nose. To analyze dynamic behaviour characteristics (e.g. gas flow, the PIG position and velocity) mathematical models are derived. Two types of nonlinear hyperbolic partial differential equations are developed for unsteady flow analysis of the PIG driving and expelled gas. Also, a non-homogeneous differential equation for dynamic analysis of the PIG is given. The nonlinear equations are solved by method of characteristics (MaC) with a regular rectangular grid under appropriate initial and boundary conditions. Runge-Kutta method is used for solving the steady flow equations to get the initial flow values and for solving the dynamic equation of the PIG. The upstream and downstream regions are divided into a number of elements of equal length. The sampling time and distance are chosen under Courant -Friedrich-Lewy (CFL) restriction. Simulation is performed with a pipeline segment in the Korea gas corporation (KOGAS) low pressure system, Ueijungboo-Sangye line. The simulation results show that the derived mathematical models and the proposed computational scheme are effective for estimating the position and velocity of the PIG with a given operational condition of pipeline.

J Mech Sci Technol, 2002

This paper presents hybrid control of an active suspension system with a full-car model by using ... more This paper presents hybrid control of an active suspension system with a full-car model by using H∞, and nonlinear adaptive control methods. The full-car model has seven degrees of freedom including heaving, pitching and rolling motions. In the active suspension system, the controller shows good

Journal of Mechanical Science and Technology, Jan 8, 2003

This paper deals with verification of the theoretical model for dynamic behavior of Pipeline Insp... more This paper deals with verification of the theoretical model for dynamic behavior of Pipeline Inspection Gauge (PIG) traveling through high pressure natural gas pipeline. The dynamic behavior of the PIG depends on the differential pressure across its body. This differential pressure is generated by injected gas flow behind the tail of the PIG and expelled gas flow in front of its nose. To analyze the dynamic behavior characteristics such as gas flow in pipeline, and the PIG position and velocity, not only the mathematical models are derived, but also the theoretical models must be certified by actual pigging experiment. But there is not any found results of research on the experimental certification for dynamic behavior of the PIG. The reason is why the fabrication of the PIG as well as, a field application are very difficult. In this research, the effectiveness of the introduced solution using the method of characteristics (MOC) was certified through field application. In-line inspection tool, 30" geometry PIG, was fabricated and actual pigging was carried out at the pipeline segment in Korea Gas Corporation (KOGAS) high pressure system, Incheon LT(LNG Terminal)-Namdong GS(Governor Station) line. Pigging is fulfilled successfully. Comparison of simulation results with experimental results show that the derived mathematical models and the proposed computational schemes are effective for predicting the position and velocity of the PIG with a given operational conditions of pipeline.

Journal of Mechanical Science and Technology, 2001

This paper introduces modeling and simulation results for pipeline inspection gauge (PIG) with by... more This paper introduces modeling and simulation results for pipeline inspection gauge (PIG) with bypass flow control in natural gas pipeline. The dynamic behaviour of the PIG depends on the different pressure across its body and the bypass flow through it. The system dynamics includes: dynamics of driving gas flow behind the PIG, dynamics of expelled gas in front of the PIG, dynamics of bypass flow, and dynamics of the PIG. The bypass flow across the PIG is treated as incompressible flow with the assumption of its Mach number smaller than 0.45. The governing nonlinear hyperbolic partial differential equations for unsteady gas flows are solved by method of characteristics (MOC) with the regular rectangular grid under appropriate initial and boundary conditions. The Runge-Kuta method is used for solving the steady flow equations to get initial flow values and the dynamic equation of the PIG. The sampling time and distance are chosen under Courant-Friedrich-Lewy (CFL) restriction. The simulation is performed with a pipeline segment in the Korea Gas Corporation (KOGAS) low pressure system, Ueijungboo -Sangye line. Simulation results show us that the derived mathematical model and the proposed computational scheme are effective for estimating the position and velocity of the PIG with bypass flow under given operational conditions of pipeline.

Data Revues 14439506 V20ss2 S1443950611004185, 2011

Methods: Microvascular resistance was measured utilising the index of microcirculatory resistance... more Methods: Microvascular resistance was measured utilising the index of microcirculatory resistance (IMR) in 24 patients undergoing elective PCI for stable angina. A coronary PressureWire was used to measure IMR prior to PCI using the equation Pa Tmn(Pd − Pw/Pa − Pw), where Pa and Pd refer to hyperaemic aortic and distal coronary pressure respectively, Tmn the mean transit time of 3 ml of saline injected into the culprit artery and Pw the coronary wedge pressure. Body mass index, age, fasting LDL, HDL and blood sugar, blood pressure and smoking status (pack-years) were recorded in each patient prior to PCI. Associations were assessed using Pearson's correlation coefficients. Linear regression analysis was used to assess correlates of IMR.

Journal of Mechanical Science and Technology, Jul 31, 2004

Wall-following control problem for a mobile robot is to move it along a wall at a constant speed ... more Wall-following control problem for a mobile robot is to move it along a wall at a constant speed and keep a specified distance to the wall. This paper proposes wall-following controllers based on Lyapunov function candidate for a two-wheeled mobile robot (MR) to follow an unknown wall. The mobile robot is considered in terms of kinematic model in Cartesian coordinate system. Two wall-following feedback controllers are designed : full state feedback controller and observer-based controller. To design the former controller, the errors of distance and orientation of the mobile robot to the wall are defined, and the feedback controller based on Lyapunov function candidate is designed to guarantee that the errors converge to zero asymptotically. The latter controller is designed based on Busawon's observer as only the distance error is measured. Additionally, the simulation and experimental results are included to illustrate the effectiveness of the proposed controllers. Straight velocity of mobile robot at its center point [m/s] Angular velocity of mobile robot at its center point [rad/s] Angular velocities of the right and left wheels [rad/s] Velocity of point W[m/s] Time rate of the change of t--t direction [rad/sJ Distance and angular errors [m] Constant speed [m/s3 Desired distance value [m] Known function Class C 1 that the first derivatives are continuous with respect to their arguments An observability matrix A symmetric positive definite matrix Positive number Radius of the roller [m~ Length of the sensor [m]

Optics Letters, 2015

We investigate the uniqueness of the plane-wave decomposition of temporally deterministic, spatia... more We investigate the uniqueness of the plane-wave decomposition of temporally deterministic, spatially random fields. Specifically, we consider the decomposition of spatially ergodic and, thus, statistically homogeneous fields. We show that when the spatial power spectrum is injective, the plane waves are the only possible coherent modes. Furthermore, the randomness of such fields originates in the spatial spectral phase, i.e., the phase associated with the coefficients of each plane wave in the expansion. By contrast, the spectral amplitude is deterministic and is specified by the spatial power spectrum. We end with a discussion showing how the results can be translated in full to the time domain.

ISIE 2001. 2001 IEEE International Symposium on Industrial Electronics Proceedings (Cat. No.01TH8570), 2001

This paper introduces a simple nonlinear control method for pipeline inspection gauge (PIG) flow ... more This paper introduces a simple nonlinear control method for pipeline inspection gauge (PIG) flow in a natural gas pipeline. The PIG is controlled using the amount of bypass flow across its body. The dynamic behavior of the PIG depends on the different pressure across its body and the bypass flow through it. The system dynamics includes: dynamics of driving gas

Quantitative Phase Imaging, 2015

ABSTRACT

Quantitative Phase Imaging, 2015

Biomechanics in Ergonomics, Second Edition, 2007

... have been evaluated both in vitro and in vivo on their effect of ligament healing with variab... more ... have been evaluated both in vitro and in vivo on their effect of ligament healing with variable results (Batten et al, 1996; Letson and Dahners, 1994 ... KA and Frank, CB, 1997, The normal structure and function of the ligaments and their responses to injury and repair, in Dee, RM et ...

The Open Clinical Chemistry Journal, 2010

2011 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, 2011

In this paper, we proposed a novel method to improve colonic polyp detection in computed tomograp... more In this paper, we proposed a novel method to improve colonic polyp detection in computed tomographic colonography. Utilizing the human knowledge workers via the Amazon Mechanical Turk (MTurk) webservice, we distributed polyp detections from a computer-aided detection system (CAD) to anonymous online knowledge workers and asked them to distinguish true and false polyp candidates. We combined decisions from the CAD

Biomedical optics express, 2013

We report the use of a twisted nematic liquid-crystal spatial light modulator (TNLC-SLM) for quan... more We report the use of a twisted nematic liquid-crystal spatial light modulator (TNLC-SLM) for quantitative phase imaging. The experimental setup is a new implementation of the SLIM principle, which is a phase shifting, white light method for quantitative phase imaging. The approach is based on switching between the phase and amplitude modulation modes of the SLM. Our system is able to deliver a 0.99 nm spatial and 1.33 nm temporal pathlength sensitivity while retaining the optical transverse resolution. The system is implemented as an additional module mounted to a conventional microscope, which makes the system very easy to deploy and integrate with other imaging modalities.

Medical Imaging 2012: Computer-Aided Diagnosis, 2012

ABSTRACT

Frontiers in Optics 2014, 2014

ISIE 2001. 2001 IEEE International Symposium on Industrial Electronics Proceedings (Cat. No.01TH8570), 2001

Currently, adaptive educational hypermedia systems (AEHS) are described with nonuniform methods, ... more Currently, adaptive educational hypermedia systems (AEHS) are described with nonuniform methods, depending on the specific view on the system, the application, or other parameters. There is no common language for expressing functionality of AEHS, hence these systems are difficult to compare and analyze. In this paper we investigate how a logical description can be employed to characterize adaptive educational hypermedia. We propose a definition of AEHS based on first-order logic, characterize some AEHS due to this formalism, and discuss the applicability of this approach.

In this paper a robust control is applied to a two-wheeled mobile manipulator (WMM) to follow a s... more In this paper a robust control is applied to a two-wheeled mobile manipulator (WMM) to follow a smooth curved trajectory and pick an object in the 3D workplace. The dynamic motion equation of the mobile manipulator is derived taking into account parametric uncertainties, external disturbances, and the dynamic interactions between the mobile platform and the manipulator; then, a robust controller is derived based on the bounded conditions of the parameters of the total system. In addition, an USB camera is used to detect the object's coordinates in 3D space, and a practical method of camera calibration is introduced for detecting the relative position between the object and the camera which is needed for the manipulator to pick it. Also, a combined system which composed of a computer and a multi-dropped PIC-based controller is developed using USB-CAN communication to meet the performance of demand of the whole system. What's more, the simulation results are included to illu...

Tissue Engineering Part A, 2008

Previous studies have shown that cultured cells align with the local topography of their substrat... more Previous studies have shown that cultured cells align with the local topography of their substrate following a concept called "contact guidance." Additionally, if the topography is highly aligned, the cells produce newly synthesized matrix that is also aligned. The objective of this study was to elucidate the positive effect of cell seeding on an elongated porcine small intestinal submucosa (SIS), which has been shown to improve ligament and tendon healing, by measuring the cellular response as a result of the changes in alignment. Because elongation is known to align the fibers of SIS through recruitment along the direction of elongation, we hypothesized that rabbit bone marrow-derived cells (BMDCs) seeded on SIS with improved fiber alignment would increase the expression and production of collagen following the concept of contact guidance. Using the small-angle light-scattering technique, it was found that a 15% elongation together with BMDC seeding on SIS (elongated, seeded group) improved its alignment of collagen fibers up to 16 times more than no elongation and no BMDC seeding (non-elongated, non-seeded group). Furthermore, BMDCs were also aligned along the direction of elongation and showed 200% greater collagen type I gene expression in the elongated, seeded group than in Petri dish controls. More importantly, the production of collagen was also 24% greater. The results of this study demonstrate that alignment of a bioscaffold can result in positive changes in cellular response, making the bioscaffold more attractive for functional tissue engineering to potentially enhance healing of ligaments and tendons.