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Biomimetic Quadruped Robot with a Spinal Joint and Optimal Spinal Motion via Reinforcement Learning

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Journal of Bionic Engineering 2021年第6期18卷 1280-1290页

作者： young Kook kim Woojin Seol Jihyuk Park LV R&D Team Electro-technology R&D CenterLS Electric Co.LtdCheongju28437Republic of Korea Digital Innovation Unit Korea Hydro&Nuclear Power Co.Ltd1312-gil YuseongdaeroYusung-guDaejeon34101Republic of Korea Department of Automotive Engineering College of Mechanical and IT EngineeringYeungnam University280 Daehak-roGyeongsanGyeongbuk38541Republic of Korea

Feline animals can run quickly using spinal joints as well as the joints that make up their four *** paper describes the development of a quadruped robot including a spinal joint that biomimics feline *** developed robot platform consists of four legs with a double 4-bar linkage type and one simplified rotary *** addition,Q-learning,a type of machine learning,was used to find the optimal motion profile of the spinal *** bounding gait was implemented on the robot system using the motion profile of the spinal joint,and it was confirmed that using the spinal joint can achieve a faster Center of Mass(CoM)forward speed than not using the spinal *** the motion profile obtained through Q-learning did not exactly match the spinal angle of a feline animal,which is more multiarticular than that of the developed robot,the tendency of the actual feline animal spinal motion profile,which is sinusoidal,was similar.

关键词： Quadruped robot system Bioinspired methods Legged robots Machine learning Q-learning

A unified formulation of optimal guidance-to-collision law for accelerating and decelerating targets

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Chinese Journal of Aeronautics 2022年第7期35卷 40-54页

作者： young-Won kim Boseok kim chang-Hun LEE Shaoming HE Department of Aerospace Engineering Korea Advanced Institute of Science and TechnologyDaejeon 34141Republic of Korea School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

This paper provides a unified formulation of optimal guidance-to-collision law for a target with an arbitrary acceleration or *** collision course for general target acceleration or deceleration is first determined from the engagement geometry in conjunction with the nonlinear engagement kinematics in the proposed *** heading error defined in the collision course is then adopted as a variable to be nullified for accomplishing the intercept *** proposed guidance law is derived based on the heading error dynamics and the optimal error dynamics to ensure optimality and finite-time *** illustrative examples,the proposed guidance command for a constant target acceleration and a target deceleration in the form of a quadratic function of speed are ***,the time-to-go prediction method is suggested for implementing the proposed *** characteristics of the proposed guidance command are analytically investigated to provide insight into the proposed *** key benefits of the proposed method lie in not producing unnecessary guidance commands near a target compared to other methods and ensuring optimality in guidance command even in the nonlinear engagement ***,numerical simulations are performed to validate the proposed method and to show our findings.

关键词： Guidance-to-collision law Optimal guidance Optimal error dynamics Target acceleration or deceleration Unified formulation

LiTFSI salt concentration effect to digest lithium polysulﬁdes for high-loading sulfur electrodes

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Journal of Energy Chemistry 2023年第3期78卷 574-581,I0015页

作者： Jin-Kwang Song Moonsoo kim Seongbae Park young-Jun kim SKKU Advanced Institute of Nano Technology(SAINT) Sungkyunkwan UniversitySuwon 16419Republic of Korea Department of Nano Engineering Sungkyunkwan UniversitySuwon 16419Republic of Korea

Sulfur utilization improvement and control of dissolved lithium polysulﬁde(LiPS;Li_(2)S x,2 详细信息

Sulfur utilization improvement and control of dissolved lithium polysulﬁde(LiPS;Li_(2)S x,2

关键词： Lithium-sulfur battery Electrolyte concentration Li2S deposition High-loading sulfur electrode

Tribological properties of multilayer tetrahedral amorphous carbon coatings deposited by filtered cathodic vacuum arc deposition

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Friction 2021年第5期9卷 1292-1302页

作者： young-Jun JANG Jae-Il kim Wooyoung LEE Jongkuk kim Department of Extreme Environmental Coatings Surface Technology DivisionKorea Institute of Materials Science(KIMS)Gyeongnam-do 51508Republic of Korea Department of Mechanical Science and Engineering Graduate School of EngineeringNagoya UniversityNagoya 464-8603Japan

Tetrahedral amorphous carbon(ta‐C)has emerged as an excellent coating material for improving the reliability of application components under high normal ***,we present the results of our investigations regarding the mechanical and tribological properties of a 2‐μm‐thick multilayer ta‐C coating on high‐speed steel *** composed of alternating soft and hard layers are fabricated using filtered a cathodic vacuum arc with alternating substrate bias voltages(0 and 100 V or 0 and 150 V).The thickness ratio is discovered to be 1:3 for the sp2‐rich and sp3‐rich *** results show that the hardness and elastic modulus of the multilayer ta‐C coatings increase with the sp3 content of the hard *** hardness reached approximately 37 GPa,whereas an improved toughness and a higher adhesion strength(>29 N)are *** friction performance(μ=0.07)of the multilayer coating is similar to that of the single layer ta‐C thick coating,but the wear rate(0.13×10^(–6) mm^(3)/(N∙m))improved under a high load of 30 *** further demonstrate the importance of the multilayer structure in suppressing crack propagation and increasing the resistance to plastic deformation(H3/E2)ratio.

关键词： tetrahedral amorphous carbon(ta‐C) filtered cathodic vacuum arc deposition multilayer coatings alternating substrate bias voltage wear resistance plastic deformation resistance

Effect of nanoclay on properties of porous PVdF membranes

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 141-147页

作者： Hae-young HWANG Deuk-Ju kim Hyung-Jun kim young-Taik HONG Sang-Yong NAM School of Materials Science and Engineering Engineering Research Institute i-Cube Center Gyeongsang National University Fuel Cell Research Center Korea Institute of Science and Technology Seoul 136-791 Korea Energy Material Research Center Korea Research Institute of Chemical Technology Daejeon 305-600 Korea

The main requirements for battery separators are high porosity which can serve pathways of lithium ion and space for gel electrolytes to impregnate in a membrane and mechanical strength to allow easy handling for battery assembly. Generally, it appears the trade-off relationship between the porosity and mechanical strength of the membrane. PVdF composite membranes containing nano-size clays were used to improve the mechanical strength of the membrane without affecting the membrane porosity. The composite membranes were prepared by phase inversion method controlling the membrane preparation conditions such as retention time. The resultant membranes show increased mechanical properties with similar membrane porosity around 80 % compared to the pristine PVdF membrane. Incorporation of nonoclay can be considered as an effective method to improve the mechanica! strength in porous membrane supports, especially in a separator.

关键词： Li-ion battery separator poly(vinylidene fluoride) nanocomposite

Transmural penetration of sigmoid colon and rectum by retained surgical sponge after hysterectomy

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World Journal of Gastroenterology 2016年第10期22卷 3052-3055页

作者： Woo young Shin chan Hyuk Im Sun Keun Choi Yun-Mee Choe Kyung Rae kim Department of Surgery Inha University HospitalInha University College of Medicine

Gossypiboma is a surgical sponge that is retained in the body after the operation. A 39-year-old female presented with vague lower abdominal pain, fever, and rectal discharge 15 mo after hysterectomy. The sponge remaining in the abdomen had no radiopaque marker. Therefore a series of radiographic evaluations was fruitless. The surgical sponge was found in the rectosigmoid colon on colonoscopy. The sponge penetrated the sigmoid colon and rectum transmurally, forming an opening on both sides. The patient underwent low anterior resection and was discharged without postoperative complications.

关键词： Gossypiboma Textiloma Retained foreign object Surgical sponge Radiopaque marker

Effect of an extraction solvent on the antioxidant quality of Pinus densiflora needle extract

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Journal of Pharmaceutical Analysis 2019年第3期9卷 193-200页

作者： Thamizhiniyan Venkatesan young-Woong Choi young-Kyoon kim Department of Forest Products and Biotechnology College of Science and TechnologyKookmin University

Pinus densiflora needle extract (PDNE) is widely reported to have many pharmacological activities including antioxidant potential. However, the solvent system used for extraction greatly affects its antioxidant quality. Hence, in the present study, we investigated the effect of a different ratio (vol/vol) of ethanol to water (0-100%) in the extraction of PDNE with potent antioxidant capacity. The chemical assays, 2,2-diphenyl-1 picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), were conducted to assess the antioxidant potential of PDNE. Subsequently, the cytoprotective effect of PDNE was determined using tert-butyl hydroperoxide (TBHP)-challenged HepG2 cellular model. The needle extracts from 40% ethanol (PDNE-40) showed greater radical scavenging activity followed by 60%, 20%, 80%, 0% and 100% ethanol extracts. EC50 value of the most active extract, PDNE-40, was 8.56 ± 0.51 μg/mL, relative to 1.34 ± 0.28 μg/mL of the standard trolox (for ABTS radical), and 75.96 ± 11.60 μg/mL, relative to 4.83 ± 0.26 μg/mL of the standard trolox (for DPPH radical). Either PDNE-20 or PDNE-40 pretreatment remarkably decreased the levels of reactive oxygen species (ROS), lipid peroxides and protein carbonyls in TBHP-challenged HepG2 cells. In addition, both PDNE-20 and PDNE-40 significantly reversed the decreased ratio of reduced (GSH) to oxidized (GSSG) glutathione. Moreover, these two extracts showed a significant inhibitory effect on TBHP-induced nuclear damage and loss of cell viability. In summary, the inclusion of 40% ethanol in water for extraction of Pinus densiflora needle greatly increases the antioxidant quality of the extract.

关键词： Pinus densiflora needle extract Oxidative stress Cytoprotective Natural antioxidant

Optimal operation of microgrid using hybrid differential evolution and harmony search algorithm

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Frontiers in Energy 2016年第3期10卷 355-362页

作者： S. SURENDER REDDY Jae young PARK chan Mook JUNG Department of Railroad and Electrical Engineering Woosong University Republic of Korea Department of Railroad and Civil Engineering Woosong UniversityRepublic of Korea

This paper proposes the generation scheduling approach for a microgrid comprised of conventional generators, wind energy generators, solar photovoltaie （PV） systems, battery storage, and electric vehicles. The electrical vehicles （EVs） play two different roles： as load demands during charging, and as storage units to supply energy to remaining load demands in the MG when they are plugged into the microgrid （MG）. Wind and solar PV powers are intermittent in nature; hence by including the battery storage and EVs, the MG becomes more stable. Here, the total cost objective is minimized considering the cost of conventional generators, wind generators, solar PV systems and EVs. The proposed optimal scheduling problem is solved using the hybrid differential evolution and harmony search （hybrid DE-HS） algorithm including the wind energy generators and solar PV system along with the battery storage and EVs. Moreover, it requires the least investment.

关键词： battery storage electric vehicles (EVs),microgrid (MG) optimal scheduling solar photovoltaic(PV) system wind energy conversion system

Positive solutions for a Lotka-Volterra prey-predator model with cross-diffusion and Holling type-Ⅱ functional response

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Science China Mathematics 2014年第5期57卷 991-1010页

作者： ZHOU Jun kim chan-Gyun School of Mathematics and Statistics Southwest University Department of Mathematics College of William and Mary

We consider a Lotka-Volterra prey-predator model with cross-diffusion and Holling type-II functional *** main concern is the existence of positive solutions under the combined effect of cross-diffusion and Holling type-II functional ***,a positive solution corresponds to a coexistence state of the ***,we study the sufficient conditions to ensure the existence of positive solutions by using degree theory and analyze the coexistence region in parameter *** addition,we present the uniqueness of positive solutions in one dimension ***,we study the stability of the trivial and semi-trivial solutions by analyzing the principal eigenvalue of the corresponding linearized system,and then we characterize the stable/unstable regions of semi-trivial solutions in parameter plane.

关键词： Lotka-Volterra prey-predator model Holling type-II functional response cross-diffusion positive solutions coexistence uniqueness degree theory