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Kinematic Analysis and Experimental Verification on the Locomotion of Gecko

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Journal of Bionic Engineering 2009年第3期6卷 246-254页

作者： Woochul Nam TaeWon Seo Byungwook kim DongsuJeon Kyu-Jin Cho jongwon kim School of Mechanical and Aerospace Engineering Seoul National University Mechanical Engineering Carnegie Mellon University

This paper presents a kinematic analysis of the locomotion of a gecko,and experimental verification of the kinematic *** analysis is important for parameter design,dynamic analysis,and optimization in biomimetic robot research. The proposed kinematic analysis can simulate,without iteration,the locomotion of gecko satisfying the constraint conditions that maintain the position of the contacted feet on the *** the method has an advantage for analyzing the climbing motion of the quadruped mechanism in a real time *** kinematic model of a gecko consists of four legs based on 7-degrees of freedom spherical-revolute-spherical joints and two revolute joints in the *** motion of the kinematic model is simulated based on measurement data of each *** motion of the kinematic model simulates the investigated real gecko's motion by using the experimental *** analysis solves the forward kinematics by considering the model as a combination of closed and open serial mechanisms under the condition that maintains the contact positions of the attached feet on the ground. The motions of each joint are validated by comparing with the experimental *** addition to the measured gait,three other gaits are simulated based on the kinematic *** maximum strides of each gait are calculated by workspace *** result can be used in biomimetic robot design and motion planning.

关键词： kinematic analysis locomotlon of gecko lizard gait simulation various gaits workspace analysis

Multi-Agent Deep Reinforcement Learning-Based Resource Allocation in HPC/AI Converged Cluster

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Computers, Materials & Continua 2022年第9期72卷 4375-4395页

作者： Jargalsaikhan Narantuya Jun-Sik Shin Sun Park jongwon kim Department of Cloud Kakao Enterprise CorpSeongnam13494Korea AI Graduate School Gwangju Institute of Science and Technology(GIST)Gwangju61005Korea

As the complexity of deep learning(DL)networks and training data grows enormously,methods that scale with computation are becoming the future of artificial intelligence(AI)*** this regard,the interplay between machine learning(ML)and high-performance computing(HPC)is an innovative paradigm to speed up the efficiency of AI research and ***,building and operating an HPC/AI converged system require broad knowledge to leverage the latest computing,networking,and storage ***,an HPC-based AI computing environment needs an appropriate resource allocation and monitoring strategy to efficiently utilize the system *** this regard,we introduce a technique for building and operating a high-performance AI-computing environment with the latest ***,an HPC/AI converged system is configured inside Gwangju Institute of Science and Technology(GIST),called GIST AI-X computing cluster,which is built by leveraging the latest Nvidia DGX servers,high-performance storage and networking devices,and various open source ***,it can be a good reference for building a small or middlesized HPC/AI converged system for research and educational *** addition,we propose a resource allocation method for DL jobs to efficiently utilize the computing resources with multi-agent deep reinforcement learning(mDRL).Through extensive simulations and experiments,we validate that the proposed mDRL algorithm can help the HPC/AI converged cluster to achieve both system utilization and power consumption *** deploying the proposed resource allocation method to the system,total job completion time is reduced by around 20%and inefficient power consumption is reduced by around 40%.

关键词： Deep learning HPC/AI converged cluster reinforcement learning

Microtubule Biomechanical Properties under Deformation and Vibration

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Journal of Biomedical Science and Engineering 2022年第1期15卷 36-43页

作者： Ramana Pidaparti jongwon kim College of Engineering University of Georgia Athens USA Department of Radiation Oncology University of Arizona Tucson USA

Microtubules (MT) are of great engineering importance due to their potential applications as sensors, actuators, drug delivery, and others. The MT properties/mechanics are greatly affected by their biomechanical environment and it is important to understand their biological function. Although microtubule mechanics has been extensively studied statically, very limited studies are devoted to the biomechanical properties of microtubule undergoing deformation and vibration. In this study, we investigate the biomechanical properties of the microtubule under bending deformation and free vibration using 3D finite element analysis. Results of force-deformation and vibration frequencies and mode shapes obtained from the finite element analysis are presented. The results indicate that the force-deformation characteristics vary with time/phases and become non-linear at higher time intervals. The modes of MT vibration and frequencies are in the GHz range and higher modes will involve combined bending, torsion and axial deformations. These higher modes and shapes change their deformation which might have implications for physiological and biological behavior, especially for sensing and actuation and communication to cells. The bending force-deformation characteristics and vibration modes and frequencies should help further understand the biomechanical properties of self-assembled microtubules.

关键词： Microtubule Vibration Deformation Finite Element Method Biomechanical Properties

Effect of Laryngopharyngeal Anatomy on Expiratory Airflow and Submicrometer Particle Deposition in Human Extrathoracic Airways

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Open Journal of Fluid Dynamics 2013年第4期3卷 286-301页

作者： Xiuhua Si Jinxiang Xi jongwon kim Department of Engineering Calvin College Grand Rapids USA Department of Mechanical and Biomedical Engineering Central Michigan University Mount Pleasant USA

The objective of this study is to systematically assess the influences of the larynopharyneal anatomical details on airflow and particle behaviors during exhalation by means of image-based modeling. A physiologically realistic nose-throat airway was developed with medical images. Individual airway anatomy such as uvula, pharynx, and larynx were then isolated for examination by progressively simplifying this image-based model geometry. Low Reynolds number (LRN) k-w model and Langrangian tracking model were used to simulate the dynamics of airflow and particle transport for a wide range of exhalation conditions (4-45 L/min) and particle sizes (1 nm-1 μm). Results showed that pharyngeal anatomical details exerted a significant impact on breathing resistance and particle profiles. Abrupt pressure drop resulting from the uvula-related airway obstruction was observed. Even though the total deposition rate in the nasal airway is largely unaffected by the upstream effect, the local deposition patterns vary notably. Results of this study also indicate that the pressure drop appears to be an appropriate parameter to characterize the geometric variations for diffusive depositions. Inclusion of pressure drop (D0.5Q-0.62dp0.07) gives an improved correlation than using the conventional diffusion factor (D0.5Q﹣0.28).

关键词： Medical Image-Based Modeling Nasal Airflow Uvula Breathing Resistance Nanoparticle Deposition

Design of 3D Space Following Positioning System Based on ZigBee

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Journal of Applied Mathematics and Physics 2015年第1期3卷 25-31页

作者： Liang Zhang Xinnian Li Honghuan Zhu jongwon kim School of Mechanical Electrical & Information Engineering Shandong University Weihai China School of Electrical Electronics & Communication Engineering Korea University of Technology and Education Chonan Korea

The research on positioning system and spatial alignment is a big topic. In this paper, we proposed a design (that) studies two issues. One is the study of range positioning algorithm based on ZigBee communication system. The other one is spatial alignment platform which is controlled with two servos. Hardware and software control system was realized, which also consists of two parts, ZigBee network positioning system and automatic orientation platform.

关键词： ZigBee Wireless Sensor Network 3D Space Positioning Spatial Alignment

The Role of Relative Spinal Motion during Feline Galloping for Speed Performance

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Journal of Bionic Engineering 2014年第4期11卷 517-528页

作者： Young Kook kim jongwon Park Byungho Yoon Kyung-Soo kim Soohyun kim Robotics Program Korea Advanced Institute of Science and Technology (KAIST) Daejeon 305-701 Republic of Korea Department of Mechanical Engineering Korea Advanced Institute of Science and Technology (KAIST) Daejeon 305-701 Republic of Korea

Felines use their spinal column to increase their running speed at rapid locomotion performance. However, its motion profile behavior during fast gait locomotion has little attention. The goal of this study is to examine the relative spinal motion profile during two different galloping gait speeds. To understand this dynamic behavior trend, a dynamic motion of the feline animal （Felis catus domestica） was measured and analyzed by motion capture devices. Based on the experiments at two different galloping gaits, we observed a significant increase in speed （from 3.2 m.s-1 to 4.33 m.s-1） during the relative motion profile synchronization between the spinal （range： 118.86~ to 168.00~） and pelvic segments （range： 46.35~ to 91.13~） during the hindlimb stance phase （time interval： 0.495 s to 0.600 s）. Based on this discovery, the relative angular speed profile was applied to understand the possibility that the role of the relative motion match during high speed locomotion generates bigger ground reaction force.

关键词： feline galloping galloping gait pattern relative spinal motion speed performance phase match

Modeling asymmetric fracture mechanics of Mg alloy wire in drawing process

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Journal of Magnesium and Alloys 2024年第5期12卷 2057-2069页

作者： Sunghoon Choi jongwon Shin Joung Sik Suh Dongchoul kim Department of Mechanical Engineering Sogang UniversitySeoul04107Republic of Korea Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea

In this study,a numerical analysis was conducted on the ductile fracture of a 2-mm diameter Mg-1Zn-0.5Mn-0.5Sr-0.1Ca alloy wire during *** hexagonally close-packed crystal structure of Mg alloys causes asymmetric fracture behavior,especially in the compression *** aim of this study is to develop a comprehensive damage model for Mg alloy wire that accurately predicts ductile fracture,with a focus on the compression region.A novel experimental method was introduced to measure the ductile fracture of Mg alloy wires under different stress *** wire drawing process was simulated using the Generalized Incremental Stress-State dependent damage(GISSMO)Model and the Semi-Analytical Model for Polymers(SAMP)*** damage model's prediction and the experimental results were found to be in excellent agreement,especially in determining crack *** analysis established a safe zone diagram for die angle and reduction ratio,and experimental validation confirmed the feasibility of this *** proposed damage model can provide a practical and reliable analysis for optimizing the drawing process of Mg alloy wire.

关键词： Mg alloy Wire drawing Finite element method Damage model Safe zone diagram

Significant enhancement of photoresponsive characteristics and mobility of MoS2-based transistors through hybridization with perovskite CsPbBr3 quantum dots

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Nano Research 2019年第2期12卷 405-412页

作者： Taeho Noh Heung Seob Shin Changwon Seo Jun Young kim jongwon Youn Jeongyong kim Kwang-Sup Lee Jinsoo Joo Department of Physics Korea University Seoul 02841 Republic of Korea Department of Advanced Materials and Chemical Engineering Hannatn University Daejeon 34430 Republic of Korea Department of Energy Science Sungkyunkwan University Suwon 16419 Republic of Korea

Inorganic perovskite CsPbBr3 quantum dots (QDs) are potential nanoscale photosensitizers;moreover,two-dimensional (2-D) molybdenum disulfide (MoS2) has been intensively studied for application in the active layers of optoelectronic *** this study,heterostructures of 2D-monolayered MoS2 with zero-dimensional functionalized CsPbBr3 QDs were prepared,and their nanoscale optical characteristics were *** effect of n-type doping on the MoS2 monolayer after hybridization with perovskite CsPbBr3 QDs was observed using laser confocal microscope photoluminescenca (PL) and Raman ***-effect transistors (FETs) using MoS2 and the MoS2-CsPbBr3 QDs hybrid were also fabricated,and their electrical and photoresponsive characteristics were investigated in terms of the charge transfer *** the MoS2-CsPbBr3 QDs-based FETs,the field effect mobility and photoresponsivity upon light irradiation were enhanced by ~ 4 times and a dramatic ~ 17 times,respectively,compared to the FET prepared without the parovskite QDs and without light *** is noteworthy that the photoresponsivity of the MoS-2-CsPbBr3 QDs-based FETs significantly increased with increasing light power,which is completely contrary to the behavior observed in previous studies of MoS2-based *** increased mobility and significant enhancement of the photoresponsivity can be attributed to the n-type doping effect and efficient energy transfer from CsPbBr3 QDs to *** results indicate that the optoelectronic characteristics of MoS2-based FETs can be significantly improved through hybridization with photosensitive parovskite CsPbBr3 QDs.

关键词： MoS2 perovskite quantum dot transistor photoresponsivity mobility charge transfer