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Enhanced generalized modeling method for compliant mechanisms: Multi-Compliant-Body matrix method
Hyunho Lim,Young-Man Choi 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.4
The multi-rigid-body matrix method (MRBMM) is a generalized modeling method for obtaining the displacements, forces, and dynamic characteristics of a compliant mechanism without performing inner-force analysis. The method discretizes a compliant mechanism of any type into flexure hinges and rigid bodies by implementing a multi-body mass-spring model using coordinate transformations in a matrix form. However, in this method, the deformations of bodies that are assumed to be rigid are inherently omitted. Consequently, it may yield erroneous results in certain mechanisms. In this paper, we present a multicompliant- body matrix-method (MCBMM) that considers a rigid body as a compliant element, while retaining the generalized framework of the MRBMM. In the MCBMM, a rigid body in the MRBMM is segmented into a certain number of body nodes and flexure hinges. The proposed method was verified using two examples: the first (an XY positioning stage) demonstrated that the MCBMM outperforms the MRBMM in estimating the static deformation and dynamic mode. In the second example (a bridge-type displacement amplification mechanism), the MCBMM estimated the displacement amplification ratio more accurately than several previously proposed modeling methods.
압축공기를 이용한 초공동 수중주행체용 환기공동 발생기 개발
임설(Seol Lim),박현호(Hyunho Park),임재혁(Jaehyock Lim),유영준(Youngjoon Yu),윤현걸(Hyungull Yoon) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.5
초공동 수중주행체를 위한 환기공동 발생기를 개발하였다. 초공동 현상을 발생시키기 위한 장치는 자연공동 발생기와 환기공동 발생기가 있다. 이 중에서 환기공동 발생기는 자연공동 발생기로부터 발생한 공동을 확장시키고 유지시키는 역할을 한다. 개발된 환기공동 발생기는 시뮬레이션과 실험적 방법으로 성능 및 안전성을 검증하였다. A gas ventilation system for a supercavitating projectile has been developed. Usually, Natural cavity and ventilated cavity methods are used for the supercavitation generator. The role of gas ventilation system is to expansion and keep the cavity created by natural cavity generator(cavitator). Developed gas ventilation system is verified and validated by simulation and experimental methods.
Development of Modular Control System Based on Closed-Loop Control for Wind Farms
( Hyunho Ji ),( Taehyoung Kim ),( Jeongtaek Lim ),( Kyung Sun Ham ) 한국인터넷정보학회 2021 인터넷정보학회논문지 Vol.22 No.6
The use of renewable energy sources for power generation has been steadily increasing. Power generation using renewable energy has the advantage of not generating carbon but has the disadvantage of high volatility depending on the weather. This volatility makes stable power supply difficult. Curtailment is occurring to address volatility. Various facilities are operated together to solve the loss caused by the curtailment. The existing SCADA must be modified for turbine control reflecting the conditions of various facilities. However, since it is difficult to modify SCADA, a modular control system is required. In this study, we propose Modular Control System Based on Closed-Loop Control for Wind Farms. Since the control logic can be changed without modifying SCADA, it is easy to respond to changes. The developed modular control system was evaluated as a lab test and confirmed to operate smoothly. Through future research, the experiment will be conducted by applying a modular control system to the actual wind farm.
Development of PLA/PBSeT blend films for sustainable food packaging applications
Hyunho Jang,Sun Jong Kim,Sangwoo Kwon,Yongsan Kim,Daegyu Lim,Su-Il Park 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10
Poly (lactic acid) (PLA) is the most representative commercial biodegradable polymer for food packaging applications. However, due to the brittleness of PLA, several strategies such as blending with Poly (butylene adipate-co-terephthalate) (PBAT) have been implemented for use in the food flexible packaging field. In this study, poly (butylene sebacate-co-terephthalate) (PBSeT), new synthesized bio-degradable high-ductile polymer, was blended with PLA and their properties were investigated. The flexibility of PLA/PBSeT blend films significantly increased with adequate tensile strength as increase PBSeT content up to 25%. In contrast, mechanical properties of the high PBSeT content blend film, 60% of PLA with 40% of PBSeT, dramatically decreased cause by limited miscibility. The PLA film became translucent by blending with PBSeT, but showed a screening effect of UV-A and UV-B (280-400 nm). The oxygen transfer rate of PLA/PBSeT blend films exhibited no significant differences with the neat PLA and PBSeT film. The PLA/PBSeT blend film can be considered as an alternative candidate for the PLA/PBAT blend film, which is widely used as a biodegradable food flexible packaging material.
Analog front-end measuring biopotential signal with effective offset rejection loop.
Lim, Seunghyun,Kim, Hyunho,Song, Haryong,Cho, Dong-Il Dan,Ko, Hyoungho Pergamon Press 2015 Bio-medical materials and engineering Vol.26 No.1
<P>This paper presents an analog front-end (AFE) IC design for recording biopotential signals. The AFE employs a capacitively coupled instrumentation amplifier to achieve a low-noise and high-common mode rejection ratio (CMRR) system. A ripple reduction loop is proposed to reduce the ripple generated by the up-modulating chopper. The low frequency noise is attenuated by an input AC coupling capacitor, and is attenuated again by a DC servo loop. The proposed AFE features a differential gain of 71 dB, and a CMRR of 89 dB, at 50 Hz. Furthermore, the proposed AFE can robustly acquire biopotential signals even in the presence of an input offset and ripples.</P>
Lim, DaeGyu,Kim, Youngsan,Kwon, Sangwoo,Jang, Hyunho,Park, Su-il Korea Society of Packaging Science and Technology 2021 한국포장학회지 Vol.27 No.2
The gamma irradiation was on to Poly(butylene sebacate-co-terephthalate) (PBSeT), Poly(butylene adipate-co-terephthalate) (PBAT), Poly(lactic acid) (PLA) and casting polypropylene (CPP) at dose levels from 0 to 50 kGy. The properties of gamma irradiated samples were analyzed using DSC, TGA, UTM and FT-IR spectra. The mechanical and thermal properties of PBSeT and PBAT after gamma irradiation were less affected than CPP. The tensile strength and elongation of PBSeT was not affected by gamma irradiation, while these of PBAT, PLA and CPP were significantly decreased at 50 kGy gamma-ray dose. The thermal stability of PBSeT, PBAT, PLA and CPP showed a similar tendency to tensile strength. The glass transition temperature(T<sub>g</sub>) and melting temperature(T<sub>m</sub>) of PBSeT and PBAT were not altered by increasing gamma-ray dose, while these of PLA and CPP decreased. The chemical composition of all samples was not modified by gamma irradiation, and it was confirmed by FT-IR spectra. Based on mechanical and thermal stability studies of gamma irradiation on bioplastics, tested biodegradable packaging materials showed a potential to be used in sterilization process up to 35 kGy.