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Yunsuk Choi(Yunsuk Choi),Hyunseok Jee(Hyunseok Jee) 대한운동학회 2023 아시아 운동학 학술지 Vol.25 No.1
BACKGROUND Various factors-based properties of the skeletal muscle are determined by mechanical stress, chemical stimuli, neuromuscular stimuli, different protein isoforms etc. The properties of the muscle are formed in the process of the balance between anabolism and catabolism. Especially, the anabolism on the way of the cell proliferation to its differentiation is accompanied by various controlling signal pathways. OBJECTIVE The purpose of this study focused on the mTOR/S6K system, Myosin, and Myocilin among these signaling pathways, especially on previously reported studies on the contribution of Myocilin to the skeletal muscle fiber type transformation. METHODS To identify the molecular pathways related to muscle development, the KEGG Mapper was used to present the mTOR-related signaling system that has not been identified so far. RESULTS Consequently, it suggests that it affects the myogenic process, through the path of PI3K->AKT- >MEF2->MyoC->mTOR->p70S6K->S6. CONCLUSIONS It also suggests that Myocilin serves as a potential effector to control skeletal muscle cell type. Furthermore, more detailed study on the potential target-oriented (to the fast or slow fiber type change) role of Myocilin for enhancing the health state by adjusted exercise programs developed by its optimal type, intensity, frequency, and time is awaited.
A Triple-Power-Mode Digital Polar CMOS RF Power Amplifier With LO Duty Cycle Control
Choi, Hyunseok,Lee, Dong-Ho,Hong, Songcheol IEEE 2016 IEEE microwave and wireless components letters Vol.26 No.9
<P>A triple-power-mode digital polar CMOS power amplifier (DPA) with a high dynamic range is presented. The triple-power-mode to enhance the efficiency when operating under back-off power is facilitated by the combination of a switched output transformer to change the load impedance and a reduced duty cycle of the LO input signal of the DPA for additional back-off power. This static power-mode method for the low-power region can be used with a DPA which has a high dynamic range in conjunction with a digitally controlled bias generator. An improvement in the PAE from 14.5% to 28.7% is achieved at a back-off power of 6.5 dB from a peak output power of 21.54 dBm at 1.7 GHz. A digital transmit power control (TPC) range of 68.2 dB for WCDMA is realized without any external components.</P>
Hyunseok Choi,Yumi Lee,Songcheol Hong Professional Technical Group on Microwace Theory a 2014 IEEE Transactions on Microwave Theory and Techniqu Vol. No.
<P>A digitally modulated CMOS power amplifier (DPA) for a polar transmitter with a high dynamic range is presented. To improve local oscillator (LO) leakage, which limits the minimum output power of the DPA, the unit amplifier cell of the DPA employs a balanced mixer-type LO canceller at the power stage and a virtual ground is introduced in the layout of the output-power combining networks. A high dynamic range of the output power is simply achieved by adjusting gate-bias voltage of a cascode transistor in each power amplifier (PA) cell using a digitally controlled bias generator. This architecture allows a few-mA drain current at a low Tx power level without degrading the linearity. An array of unit PA cells is segmented to have a 10-bit amplitude resolution, and the bias generator is designed to have 8-bit control of the average output power. The peak output power is 24.4 dBm with an overall efficiency of 43% at 800 MHz. The total output dynamic range is 102.8 dB. A simple static pre-distortion helps the DPA achieve an average efficiency of 35% with a root mean square error vector magnitude of 3.59% while delivering linear output power of 22 dBm for WCDMA. The range of the digital transmit-power control for the WCDMA signal is 49.7 dB. This chip is fabricated in a 65-nm RF CMOS process.</P>
Dynamic driveline torque estimation during whole gear shift for an automatic transmission
Choi, Hyunseok,Hwang, Jaewoong,Choi, Seibum Elsevier 2018 Mechanism and machine theory Vol.130 No.-
<P><B>Abstract</B></P> <P>This study proposes a novel method for estimation of driveline torque of wet type AT (Automatic transmission). The previous methods of torque estimation in the clutch-to-clutch shift mechanism is mainly applicable to the single gear shift. Thus, they require specific definitions of each gear shift and signal processing corresponding to the multi-gear shift. This study distinctly develops driveline torque estimator based on the whole transmission model, which is capable in applying on any conditional gear shift. This paper, also, incomparably investigates brake/clutch model including centrifugal force, describing physical behavior of real parts. In addition, the development of the method includes adaptive brake and clutch torque estimator in order to compensate variation factor during the shift. The estimation performance of the proposed estimator is evaluated both in simulations and experiments. The results demonstrate that the proposed methods can estimate the driveline torques effectively during the whole gear shift and well describes the typical clutch-to-clutch phenomena such as inter-locking.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A whole gear shift model without signal processing for a vehicle with an AT is developed with practical aspects. </LI> <LI> Wet typed brake and clutch are modeled describing physical behavior of real parts. </LI> <LI> A torque estimator with adaptation is designed to estimate torque through both brakes or clutches and the output shaft in an AT. </LI> <LI> The effectiveness of the developed torque estimator is demonstrated by simulations and experiments. </LI> <LI> The proposed methods well describe the typical clutch-to-clutch phenomena such as inter-locking. </LI> </UL> </P>
Hyunseok Choi(최현석),Tao Jiang(강타오),Hong Seok Kim(김홍석) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
Titanium alloys are widely used in orthopedic devices because of their low density, high tensile strength, good corrosion resistance, and biocompatibility. However, since titanium and its alloys have inferior surface properties in terms of friction and wear resistance, there are still limitations in their application to the parts where sliding contact occurs. In this study, SiC nanoparticles were laser clad on the Ti-6Al-4V surface to simultaneously improve the friction and wear properties of the titanium alloys. Laser cladding was performed by changing the ambient conditions and laser parameters. The effect of process variables on the microstructure, hardness, and friction coefficient of the coating layer was analyzed. SiC nanoparticles reacted with the Ti element in the molten pool to create the reinforcement phases such as TiC and Ti<sub>5</sub>Si<sub>3</sub>. Oxygen supplied in the laser cladding process contributed to significantly reducing the coefficient of friction of the Ti-6Al-4V surface by creating the oxide phases such as TiO<SUB>2</SUB> and SiO<SUB>2</SUB>. Consequently, after the laser surface treatment of SiC nanoparticles in an oxygen environment, the hardness of Ti-6Al-4V improved by about three times and the coefficient of friction was reduced by more than 80%.
Non - Java 장치를 지원하기 위한 Jini 서로게이트 시스템의 설계 및 구현
최현석(Hyunseok Choi),모상덕(Sangdok Mo),정광수(Kwangsue Chung),오승준(Seoungjun Oh) 한국정보과학회 2002 정보과학회논문지 : 정보통신 Vol.29 No.6
최근 내장형 장치를 인터넷과 연결하고자 하는 요구가 늘어나고 있다. 이러한 정보기기들 간의 동적인 분산 네트워크를 구성하는 기술로서 Jini 기술이 주목을 받고 있다. 그러나, 소형 장치에 Jini 기술을 적용하여 서비스를 제공하기 위해서는 높은 하드웨어 사양을 요구하는 문제점이 지적되고 있다. 본 논문에서는 이러한 non-Java 장치를 Jini 네트워크에 접속하여 Jini 서비스를 제공하기 위한 Jini 서로게이트 시스템(Surrogate System)과 non-Java 장치간의 서로게이트 프로토콜(Surrogate Protocol)을 설계하고 자바 언어로 구현하였다. 서로게이트 시스템은 장치가 Jini 네트워크에 연결되어 Jini 서비스를 제공하기 위해 필요한 Discovery와 Join 과정을 대리해주는 역할을 수행한다. Jini 클라이언트는 서로게이트 시스템을 통해 장치가 제공하는 서비스를 이용할 수 있다. 구현한 서로게이트 시스템이 정상적으로 동작하는지 검증하기 위해 Jini 예제 프로그램을 만들어 시험하였다. 시험결과, 구현한 서로게이트 시스템을 이용해 Jini 클라이언트가 non - Java 장치의 서비스를 이용할 수 있음을 확인하였다. Recently, there has been increasingly demand for connecting a embedded device to the Internet. Jini technology is interested in automatically composing a distributed network with devices. But, there are some problems that the device needs high hardware requirements to adopt Jini technology for supporting Jini-enabled services. In this paper, we focused on design and implementation of surrogate system that supports non-Java devices in Jini networks. This system and protocol are implemented in Java language. The surrogate system delegates Discovery and Join processing to support a Jini service in connected networks. A Jini client can use service of the device through the surrogate system. We tested a Jini sample program to verify the implemented surrogate system. In the test result, we showed that the Jini client can use functionalities and operations of the non-Java device through the surrogate system.