Research Interest
Therapeutic Ultrasound, Treatment Planning, Computational Mechanics, Finite Element Method, Structural Analysis
Therapeutic Ultrasound, Treatment Planning, Computational Mechanics, Finite Element Method, Structural Analysis
Therapeutic Ultrasound
I am interested in developing neuro-therapeutic methods using transcranial focused ultrasound (tFUS). My current researches include non-invasive blood-brain barrier disruption for drug delivery and functional neuromodulation for altering abnormal neuronal activity.
I am interested in developing neuro-therapeutic methods using transcranial focused ultrasound (tFUS). My current researches include non-invasive blood-brain barrier disruption for drug delivery and functional neuromodulation for altering abnormal neuronal activity.
1. Localized Blood-Brain Barrier Opening
The blood-brain barrier (BBB) limits the delivery of drugs to the central nervous system. Transcranial application of focused ultrasound combined with vascular introduction of microbubbles has emerged as a technique that can temporarily open the BBB in a non-invasive fashion, thus providing new opportunities to deliver therapeutic agents to a specific region of the brain. Most studies on this topic have been carried out in small animals, with inclusion of a limited number of studies on non-human primate and humans. Further investigation on large animals has been warranted to bridge the gap between these models. We showed that focal delivery of ultrasound pressure waves, in conjunction with intravascular administration of microbubbles, regionally opened the BBB of the sheep, as demonstrated from dynamic contrast-enhanced magnetic resonance imaging data that characterized the extravasated gadolinium-based MR contrast agents. Based on the monitoring of the animal behavior during the post-FUS survival periods up to two months, as well as histological analysis, the method can be safely applied to sheep.
The blood-brain barrier (BBB) limits the delivery of drugs to the central nervous system. Transcranial application of focused ultrasound combined with vascular introduction of microbubbles has emerged as a technique that can temporarily open the BBB in a non-invasive fashion, thus providing new opportunities to deliver therapeutic agents to a specific region of the brain. Most studies on this topic have been carried out in small animals, with inclusion of a limited number of studies on non-human primate and humans. Further investigation on large animals has been warranted to bridge the gap between these models. We showed that focal delivery of ultrasound pressure waves, in conjunction with intravascular administration of microbubbles, regionally opened the BBB of the sheep, as demonstrated from dynamic contrast-enhanced magnetic resonance imaging data that characterized the extravasated gadolinium-based MR contrast agents. Based on the monitoring of the animal behavior during the post-FUS survival periods up to two months, as well as histological analysis, the method can be safely applied to sheep.
KYoon, W Lee, E Chen, JE Lee, P Croce, A Cammalleri, L Foley, AL Tsao, SS Yoo. Localized blood-brain barrier opening in ovine model using image-guided transcranial focused ultrasound, under review.
A Cammalleri, P Croce, W Lee, K Yoon, SS Yoo. Therapeutic potentials of localized blood-brain barrier disruption by non-invasive transcranial focused ultrasound: A technical Review, in press.
A Cammalleri, P Croce, W Lee, K Yoon, SS Yoo. Therapeutic potentials of localized blood-brain barrier disruption by non-invasive transcranial focused ultrasound: A technical Review, in press.
2. Neuromodulation
Transcranial focused ultrasound (FUS) has emerged as a new brain stimulation modality. Technology modulating neural activity offers newnon-pharmacological treatments for neurologic and psychiatric disorders as well as new tools for functional brain mapping.FUS-mediated neuromodulation technique has distinct advantages over other methods as an ability to deliver acoustic energy to a few millimeter-scale area with deep penetration depth under non-invasive fashion.
Transcranial focused ultrasound (FUS) has emerged as a new brain stimulation modality. Technology modulating neural activity offers newnon-pharmacological treatments for neurologic and psychiatric disorders as well as new tools for functional brain mapping.FUS-mediated neuromodulation technique has distinct advantages over other methods as an ability to deliver acoustic energy to a few millimeter-scale area with deep penetration depth under non-invasive fashion.
K Yoon, W Lee, E Chen, JE Lee, P Croce, A Cammalleri, L Foley, SS Yoo, Effects of sonication parameter on transcranial focused ultrasound-mediated neuromodulation in ovine model, in preparation.
SS Yoo, K Yoon, P Croce, A Cammalleri, R Margolin, W Lee. Focused ultrasound brain stimulation to anesthetized rats induces long-term changes in somatosensory evoked potentials, International Journal of Imaging System and Technology, 2018.
W Lee, P Croce, R Margolin, A Cammalleri, K Yoon, SS Yoo. Transcranial focused ultrasound stimulation of moter cortical area in freely-moving awake rats, BMC Neuroscience, 2018.
SS Yoo, K Yoon, P Croce, A Cammalleri, R Margolin, W Lee. Focused ultrasound brain stimulation to anesthetized rats induces long-term changes in somatosensory evoked potentials, International Journal of Imaging System and Technology, 2018.
W Lee, P Croce, R Margolin, A Cammalleri, K Yoon, SS Yoo. Transcranial focused ultrasound stimulation of moter cortical area in freely-moving awake rats, BMC Neuroscience, 2018.
3. Ultrasound Simulation
Numerical simulation to predict intracranial acoustic propagation from focused ultrasound (FUS) sources typically demands sophisticated computations. We developed a multi-resolution simulation method based on the finite-difference time-domain formulation to expedite the computation by providing flexibility of the spatial resolution. The simulation was also accelerated by parallelized computation through the graphic processing unit. The accuracy in modeling the transcranial FUS propagation from a singe-element transducer was assessed by comparing the simulation results to actual hydrophone measurements using ex vivo sheep skulls. The method can provide semi-real time feedback for users guiding the acoustic focus to the region-of-interest.
Numerical simulation to predict intracranial acoustic propagation from focused ultrasound (FUS) sources typically demands sophisticated computations. We developed a multi-resolution simulation method based on the finite-difference time-domain formulation to expedite the computation by providing flexibility of the spatial resolution. The simulation was also accelerated by parallelized computation through the graphic processing unit. The accuracy in modeling the transcranial FUS propagation from a singe-element transducer was assessed by comparing the simulation results to actual hydrophone measurements using ex vivo sheep skulls. The method can provide semi-real time feedback for users guiding the acoustic focus to the region-of-interest.
K Yoon, W Lee, P Croce, A Cammalleri, SS Yoo. Multi-resolution simulation of focused ultrasound propagation through ovine skull from a single-element transducer, Physics in medicine & Biology, 2018.
Computational Mechanics
My interest lies in understanding the physics and mechanics of solids and developing advanced numerical techniques. I developed numerous mathematical formulation and simulation programs which can more efficiently analyze mechanical problems.
My interest lies in understanding the physics and mechanics of solids and developing advanced numerical techniques. I developed numerous mathematical formulation and simulation programs which can more efficiently analyze mechanical problems.
1. Development of Beam Finite Elements
The developed continuum mechanics based beam elements can accurately and efficiently describe the complex mechanical behavior under various loading and boundary conditions. The most outstanding feature is that the beam elements can implicitly consider nonlinear strain terms such as Wagner and Von Karman strains and its local couplings. They can encompass various analysis which not possible within the existing beam model.
The developed continuum mechanics based beam elements can accurately and efficiently describe the complex mechanical behavior under various loading and boundary conditions. The most outstanding feature is that the beam elements can implicitly consider nonlinear strain terms such as Wagner and Von Karman strains and its local couplings. They can encompass various analysis which not possible within the existing beam model.
*K Yoon, Y Lee, PS Lee. A continuum mechanics based 3-D beam finite element with warping displacements and its modeling capabilities, Structural Engineering and Mechanics, 2012.
*K Yoon, PS Lee. Modeling the warping displacements for discontinuously varying arbitrary cross-section beams, Computers & Structures, 2014.
*K Yoon, PS Lee. Nonlinear performance of continuum mechanics based beam elements focusing on large twisting behaviors, Computer Methods in Applied Mechanics and Engineering, 2014.
*K Yoon, PS Lee. Modeling the warping displacements for discontinuously varying arbitrary cross-section beams, Computers & Structures, 2014.
*K Yoon, PS Lee. Nonlinear performance of continuum mechanics based beam elements focusing on large twisting behaviors, Computer Methods in Applied Mechanics and Engineering, 2014.
2. Development of Shell Finite Elements
The objective of this work is to improve performance of 3-node triangular shell element based on the concept of the MITC3 shell element. In these works, the locking problems are successfully alleviated by applying numerical techniques such as new tying scheme, Hellinger-Reissner functional, and the partition of unity method.
The objective of this work is to improve performance of 3-node triangular shell element based on the concept of the MITC3 shell element. In these works, the locking problems are successfully alleviated by applying numerical techniques such as new tying scheme, Hellinger-Reissner functional, and the partition of unity method.
* Y Lee, K Yoon, PS Lee. Improving the MITC3 shell finite element by using the Hellinger-reissner principle, Computers & Structures, 2012.
* HM Jun, K Yoon, PS Lee, KJ Bathe. The MITC3+ shell element enriched in membrane displacements by interpolation covers, Computer Methods in Applied Mechanics and Engineering, 2018.
* HM Jun, K Yoon, PS Lee, KJ Bathe. The MITC3+ shell element enriched in membrane displacements by interpolation covers, Computer Methods in Applied Mechanics and Engineering, 2018.
3. Composite Material Model
A nonlinear 3D finite element formulation for functionally graded beams is developed. This work is the world first investigation into FG beam finite elements in 3D with consideration for the warping effect. An efficient method to represent the intricate warping effect for elastoplastic torsional analysis of composite beams is also developed. A major challenge in this work is how to account for the evolution of warping functions efficiently as materials yield at various locations at different rates. The proposed method shows an excellent performance in various numerical examples despite its simplicity.
A nonlinear 3D finite element formulation for functionally graded beams is developed. This work is the world first investigation into FG beam finite elements in 3D with consideration for the warping effect. An efficient method to represent the intricate warping effect for elastoplastic torsional analysis of composite beams is also developed. A major challenge in this work is how to account for the evolution of warping functions efficiently as materials yield at various locations at different rates. The proposed method shows an excellent performance in various numerical examples despite its simplicity.
* K Yoon, PS Lee, DN Kim. Geometrically nonlinear finite element analysis of functionally graded 3D beams considering warping effects, Composite Structures, 2015.
* K Yoon, DN Kim, PS Lee. Nonlinear torsional analysis of 3D composite beams using the extended St. Venant solution, Structural Engineering and Mechanics, 2017..
* K Yoon, PS Lee, DN Kim. An efficient warping model for elastoplastic torsional analysis of composite beams, Composite Structures, 2017.
* K Yoon, DN Kim, PS Lee. Nonlinear torsional analysis of 3D composite beams using the extended St. Venant solution, Structural Engineering and Mechanics, 2017..
* K Yoon, PS Lee, DN Kim. An efficient warping model for elastoplastic torsional analysis of composite beams, Composite Structures, 2017.
4. Force Identification for Nonlinear Dynamic System
A robust and accurate force identification method for nonlinear dynamic system is developed. Since the proposed method precisely calculate and update sensitivities in respective time step by using nonlinear Newmark time integration method, superb performance is available even in the highly nonlinear condition including large displacement and large rotation condition. The developed technique is applied to operation of UAV (unmanned aerial vehicle).
A robust and accurate force identification method for nonlinear dynamic system is developed. Since the proposed method precisely calculate and update sensitivities in respective time step by using nonlinear Newmark time integration method, superb performance is available even in the highly nonlinear condition including large displacement and large rotation condition. The developed technique is applied to operation of UAV (unmanned aerial vehicle).
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5. EDISON Project
EDISON (EDucation-research Integration through Simulation On the Net) is an open simulation platform bridging to computational science for higher education and advanced research. It aims to provide on the web high-performance computing environment, simulation software for problems in various science and engineering fields, and educational contents. Through this project, I developed and distributed diverse source codes for finite element analysis. The source codes are also shared and can be downloaded in "ARCHIVE" tap.
EDISON (EDucation-research Integration through Simulation On the Net) is an open simulation platform bridging to computational science for higher education and advanced research. It aims to provide on the web high-performance computing environment, simulation software for problems in various science and engineering fields, and educational contents. Through this project, I developed and distributed diverse source codes for finite element analysis. The source codes are also shared and can be downloaded in "ARCHIVE" tap.
Structural Engineering
I am also interested in understanding the mechanical properties of complex structural system. I proposed new structural designs and their optimal operation.
1. Offshore Floating Dock
In this work, a novel accuracy control system for an Offshore Floating Dock(OFD) using ballast planning is developed. The proposed system can estimate the deformation of OFD according to its local loadings and ballast plans; further, it searches for the optimal ballast plan to satisfy the prescribed target deformation shape of the platform, which is deduced from the accuracy requirements of the block erection. The system is implemented to an OFD in Samsung Heavy Industries (SHI) and used for the accuracy control during the construction of Jack & Saint Malo (JSM) offshore structure project.
In this work, a novel accuracy control system for an Offshore Floating Dock(OFD) using ballast planning is developed. The proposed system can estimate the deformation of OFD according to its local loadings and ballast plans; further, it searches for the optimal ballast plan to satisfy the prescribed target deformation shape of the platform, which is deduced from the accuracy requirements of the block erection. The system is implemented to an OFD in Samsung Heavy Industries (SHI) and used for the accuracy control during the construction of Jack & Saint Malo (JSM) offshore structure project.
* Silver prize in samsung tech. award (very first time in history of Samsung Heavy Industry).
* S Yeo, K Yoon, PS Lee, Y Hong, J Cha, H Chung. Ballast planning for accuracy control on offshore floating dock, submitted.
* S Yeo, K Yoon, PS Lee, Y Hong, J Cha, H Chung. Ballast planning for accuracy control on offshore floating dock, submitted.
2. Concentric-tube Continuum Robot
Concentric-tube continuum robots have formed an active field of research in robotics because of their manipulative exquisiteness essential to facilitate delicate surgical procedures. Here we present a finite element modeling approach to investigating the dynamics of concentric-tube continuum robots. In this model, each tube is discretized using MITC shell elements and its transient responses are computed implicitly using the Bathe time integration method. Inter-tube contacts, the key actuation mechanism of this robot, are modeled using the constraint function method with contact damping to capture the hysteresis in robot trajectories.
Concentric-tube continuum robots have formed an active field of research in robotics because of their manipulative exquisiteness essential to facilitate delicate surgical procedures. Here we present a finite element modeling approach to investigating the dynamics of concentric-tube continuum robots. In this model, each tube is discretized using MITC shell elements and its transient responses are computed implicitly using the Bathe time integration method. Inter-tube contacts, the key actuation mechanism of this robot, are modeled using the constraint function method with contact damping to capture the hysteresis in robot trajectories.
* C Baek, K Yoon, DN Kim. Finite element modeling of concentric-tube continuum robots, Structural Engineering and Mechanics, 2016.
3. Blast Hardened Bulkhead
A new concept of blast hardened bulkheads (BHBs) effectively used for vulnerability hardening in naval ships is presented. The major advantage of the new concept is that it can be easily adopted for operating naval ships. The effectiveness of the new concept is verified by experimental tests and numerical simulations.
A new concept of blast hardened bulkheads (BHBs) effectively used for vulnerability hardening in naval ships is presented. The major advantage of the new concept is that it can be easily adopted for operating naval ships. The effectiveness of the new concept is verified by experimental tests and numerical simulations.
* SH Kim, H Woo, GG Choi, K Yoon. A new concept of blast hardened bulkheads with attached aluminum foam, Structural Engineering and Mechanics, 2018.
4. Material Cutting Simulation
The objective of this work is to understand mechanics of cutting process and to investigate the relation between various process conditions and surface defections.
The objective of this work is to understand mechanics of cutting process and to investigate the relation between various process conditions and surface defections.
5. Turbine Blade
In this work, the integrated design-analysis software for turbine blades is developed. In recent version, the air foil can be designed by using spline curves. The blades can be modeled and analyzed by using the MITC4 shell and the continuum mechanics based beam element. Static, free vibration and nonlinear dynamics analysis are available.
In this work, the integrated design-analysis software for turbine blades is developed. In recent version, the air foil can be designed by using spline curves. The blades can be modeled and analyzed by using the MITC4 shell and the continuum mechanics based beam element. Static, free vibration and nonlinear dynamics analysis are available.