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Activated porous carbon derived from black tea waste for supercapacitor electrode
Hojong Eom,Joo Young Kim,Sunyoung Bae,Inho Nam 한국분석과학회 2021 학술대회논문집 Vol.2021 No.11
As the amount of used black tea waste is increasing, it demands economically and environmentally efficient recycling method. Herein, we reacted black tea waste under various conditions to use as an active material for supercapacitors. Among value-added products generated by recycling method, supercapacitors have received a great attention. In our study, black tea waste was converted to the activated hydrochar after hydrothermal carbonization process followed by activation process with KOH. It provided a large surface area and porous structure that is suitable for an active material for supercapacitor. In order for the black tea waste to have high surface area and specific capacitance, the reaction temperature and the ratio of KOH were optimized. As a result, activated hydrochar of black tea waste has a large surface area of 1,062 m² and specific capacitance up to 200 F·g<SUP>-1</SUP> at 1 mV·s<SUP>-1</SUP>. In addition, it remained 98.8% charge-discharge capacitance after 2000 cycles at the current density of 5 A·g<SUP>−1</SUP>. In conclusion, black tea waste might be abundant source of porous carbon for supercapacitor after hydrothermal carbonization followed by KOH activation.
Novel Telecentric Collimator Design for Mobile Optical Inspection Instruments
Hojong Choi,Seongil Cho,Jaemyung Ryu Optical Society of Korea 2023 Current Optics and Photonics Vol.7 No.3
A collimator refers to an optical system that images a collimated beam at a desired point. A resolution target located at a near distance can be converted into a virtual image located at a long distance. To test the resolution for mobile cameras, a large target is placed at a long distance. If a collimator system is used, the target can be placed at a near distance. The space required for a resolution inspection can thus be drastically reduced. However, to inspect a mobile camera, the exit pupil of the collimator system and the entrance pupil of the mobile camera must match, and the stop of the collimator system must be located on the last surface. Because a collimator system cannot be symmetrical with respect to the stop, the distortion becomes extremely large, which can be corrected by combining the collimator symmetrically with respect to the object plane. A novel system was designed to inspect an optical lens on a mobile phone. After arranging the refractive power, lenses were added using the equivalent lens design method. The distortion was reduced to less than 1%. This optical system satisfies a half-field angle of 45° and an optical performance sufficient for inspection.
Hojong Gil,Sihyun Ryu,Sang-Kyoon Park,Jiseon Ryu 대한인간공학회 2018 大韓人間工學會誌 Vol.37 No.6
Objective: The purpose of this study was to determine the difference of motions using the new calculation method of COP area and to investigate the correlation with the change of the foot eversion. Background: The quantitative analysis process on the data of COP revealed in the process of repetitive gait and running cycle is essentially required and through COP trajectories, the correlations between ground and feet can be effectively examined. Method: Thirty young males participated in this study. They were asked to run on an instrumented treadmill (Bertec, USA) at speeds of 3.5m/s and 4.5m/s for running. A system of motion analysis cameras (Oqus 300, Qualisys, and Sweden) and pedar-X system (Novel GmbH, Germany) were used to collect joint angles and COP trajectories, and Shoelace Formula was used to calculate the area of multiple COP lines from running. The analysis variables were the area of COP, the COP range, the COP velocity, and the ankle joint eversion angle. The Pearson"s correlation coefficient was calculated to investigate the relations between variables. Results: The running at 4.5m/s showed the smaller area of COP and the range of COP, but the greater velocity of COP (p <0.05) in comparison with the running at 3.5m/s. There was a positive correlation between the area of COP and the anteriorposterior range of COP (r =.350). Additionally, there was a negative correlation between the area of COP and the maximum eversion angle of ankle joint (r =-.418). Conclusion: The findings indicate that the method using the Shoelace Formula to calculate the area of COP was able to determine the difference between running speeds and predict the maximum eversion angle of the ankle joint. Application: Based the results, the area of COP trajectories newly presented in this study is judged to be used as a variable to predict running speed and the eversion angle of the ankle joint.
A Cost-effective Light Emitting Diode-acoustic System for Preclinical Ocular Applications
Hojong Choi,Jaemyung Ryu,Jung-Yeol Yeom 한국광학회 2018 Current Optics and Photonics Vol.2 No.1
Opto-acoustic systems provide structural and functional information regarding biological tissues. Conventional opto-acoustic systems typically employ continuous or pulsed lasers as transmission sources. Compared to lasers, light emitting diodes (LEDs) are cost-effective and relatively portable excitation sources but are non, coherent. Therefore, in this study, a relatively low cost lens - a type of Ramsden eyepiece - was specially designed to theoretically calculate the illumination and achieve a constant brightness across the pupil of an eye. In order to verify the capability of the developed light-emitting diode-acoustic (LEDA) systems, we carried out experiments on bovine and bigeye tuna eyeball samples, which are of similar size to the human eye, using low frequency (10 MHz) and high frequency (25 MHz) ultrasound transducers. High frequency ultrasound transducers are able to provide higher spatial resolution compared to low frequency ultrasound transducers at the expense of penetration depth. Using the 10 MHz and 25 MHz ultrasound transducers, acceptable echo signals (3.82, 3.94, and 5.84 mV at 10 MHz and 282, 1557, 2356 mV at 25 MHz) from depth greater than 3 cm and 6 cm from the anterior surface of the eye were obtained. We thereby confirmed that the LEDA system using a pulsed LED with the designed Ramsden eyepiece lens, used in conjunction with low and high frequency ultrasound transducers, has the potential to be a cost-effective alternative method, while providing adequate acoustic signals from bovine and bigeye tuna ocular areas.
Effects of an 8-week Pilates Core Training on the Stability and Symmetry of the L-sit on Rings
( Hojong Gil ),( Sihyun Yoo ),( Sukhoon Yoon ) 한국운동역학회 2016 한국운동역학회지 Vol.26 No.4
Objective: Gymnastics on rings needs a high level of muscle strength with balance ability for controlling the body. A study on a new balance training program is necessary for elite gymnasts. Therefore, the purpose of this study was to investigate the effects of an 8-week pilates core-muscle training on balance ability and asymmetry index of the L-sit on the rings in male elite gymnasts. Method: Ten elite gymnasts (age: 20.6±0.7 years, height: 169.9±4.9 cm, weight: 65.4±5.6 kg, career duration: 20.6±0.7 years), who are students at K-university, participated in this study. Results: First, the range of the COM tended to decrease in the anterior-posterior direction. Second, the left hip joint angle and knee extension and ankle dorsiflexion angles significantly increased after the pilates training. Third, the ROM also increased. Fourth, the symmetry value increased in the hip angle, while the symmetry index in all joints of the ROM decreased. As a result, the pilates core-muscle training influenced the static balance ability during the L-sit on the rings. Conclusion: Accordingly, the pilates core-muscle training is suitable in enhancing the basic balance ability in gymnastics on rings.
생활환경 맞춤형 건강증진·추적관리 스마트 헬스 시스템을 활용한 1인가구 건강 모니터링 구축에 관한 연구
장호종(Hojong Chang),김영이(Youngyi Kim),이우근(Woo-geun Lee),이채석(Chae-Seok Lee),이지혜(Ji Hye Lee),한병훈(Byunghun Han),김아령(A-Ryoung Kim),송은채(Eunchae Song),남승범(Seung Bum Nam) 대한전자공학회 2023 대한전자공학회 학술대회 Vol.2023 No.6
Since COVID-19, it has become necessary to establish a health care system for health promotion and tracking management as a government response to the medically vulnerable class (single-person households, etc.). In the global healthcare market, not only traditional medical companies but also IT companies such as Apple and Amazon are leading the market, and countermeasures are needed. In this paper, we discuss the establishment of single-person household health monitoring using a smart health system for health promotion and tracking management tailored to the living environment.