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- 저자 : 황성일 ( Seongill Hwang ) (검색결과 4 건)
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스파크점화직분식 CNG의 점화성 및 연소화염 특성에 대한 연구
황성일 ( Seongill Hwang ),정성식 ( Sungsik Chung ),염정국 ( Jeongkuk Yeom ),전병열 ( Byongyeul Jeon ),이진현 ( Jinhyun Lee ) 한국분무공학회 2016 한국액체미립화학회지 Vol.21 No.1
For the SI engines, at only full load, the pumping loss has a negligible effect, while at part load conditions, the pumping loss increases. To avoid the pumping loss, the spark-ignited engines are designed to inject gasoline directly into the combustion chamber. In the spark-ignited direct-injection engines, ignition probability is important for successful combustion and the flame propagation characteristics are also different from that of pre-mixed combustion. In this paper, a visualization experiment system is designed to study the ignition probability and combustion flame characteristics of spark-ignited directinjection CNG fuel. The visualization system is composed of a combustion chamber, fuel supply system, air supply system, electronic control system and data acquisition system. It is found that ambient pressure, ambient temperature and ambient air flow velocity are important parameters which affect the ignition probability of CNG-air mixture and flame propagation characteristics and the injected CNG fuel can be ignited directly by a spark-plug under proper ambient conditions. For all cases of successful ignition, the flame propagation images were digitally recorded with an intensified CCD camera and the flame propagation characteristics were analyzed.
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Seongil Hwang(황성일),Hyunah Kang(강현아),Sang Hoon Kang(강상훈) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
The mechanical impedance of the human arm is a physical entity that corresponds to the clinical assessment of muscle tone, a muscle’s resistance to passive stretching. Quantification of the human arm mechanical impedance may provide us with a deeper understanding of the changes in upper limb post-stroke. A previous study using a low friction robot (i.e., MIT-MANUS) showed low reliability(< 0.8) of the estimation for frequency below ~5Hz. However, recent studies elucidated that the low reliability could be due to nonlinearities in the robot (e.g., joint friction), not in the human arm. In this study, to clarify the reason for the low reliability, the experiment was conducted using a direct-drive robot almost identical to the MIT-MANUS, and the spring arrays, the second-order linear system. The result showed high reliability under a robust impedance control compensating nonlinearity of robots, but low reliability under a simple PD control. This is indirect yet strong evidence that the low reliability was caused by the nonlinearity of the robots, not the human arm.
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Seongil Hwang(황성일),Hyunah Kang(강현아),Sang Hoon Kang(강상훈) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.6
The mechanical impedance of the upper limb corresponds to the muscle tone, a muscle’s resistance to passive stretching. Quantifying the impedance provides a deeper understanding of the changes in the upper limb post-stroke. A previous study with MIT MANUS, known for its low joint frictions, showed low reliability(< 0.8) in low-frequencies ( (<5Hz). A conjecture for low reliability was the nonlinear properties of upper limb muscles. However, recent studies elucidated that the low reliability could be due to nonlinear frictions in robot joints instead of the muscle nonlinearities. An experiment was conducted using a direct drive robot almost identical to the MIT MANUS and a spring array with known mechanical impedance to clarify the reason. The result showed, in the low frequencies, reliability was high when using the robot a robust impedance control compensating the nonlinear frictions in robot joints. In contrast, low reliability was obtained in the low frequencies when using the same robot under a proportional-derivative (PD) control that does not compensate for the friction. These results indicate that the low reliability was caused by the nonlinear frictions in robot joints, not by the nonlinearities in the human arm.
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이제훈(Jehoon Lee),황성일(Seongill Hwang),장동현(Donghyun Jang) 한국자동차공학회 2018 한국자동차공학회 부문종합 학술대회 Vol.2018 No.6
Electric vehicles were developed based on the principle in which electrical energy is supplied from a high voltage battery to an electric motor for generation of driving force. Unlike the conventional vehicles, electric vehicles are operated only using a battery and motor without an engine. Since high voltage parts such as the electric motor use body insulation, they require a different failure diagnosis process compared to the conventional vehicles and it is extremely difficult to find the cause of failure. In this paper, changes in insulation resistance value were analyzed using an exclusive diagnostic equipment and high voltage measuring device to define insulation resistance value of each part in a vehicle that showed warning light and unintentional stopping due to insulation breakdown. The cause of warning light and unintentional stopping was found to be high voltage insulation breakdown occurring inside HPCU.
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