• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.183-188
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• 2003

The present work was conducted to build a propulsion system for an airship. For this purpose, free shaft gas-turbine was modified to produce electrical power. he experiments were carried out to analyze the driving rotor condition at various power shaft loads. From this analysis, an appropriate damping device was required, and the changeable inertial moment from the fly-wheel was applied. Without the appropriate damping device, instability was found, and it was resulted as power loss. Also the amount of inertial moment was certified by the performance of dynamic transient effects from the engine test results. Knowledge gained from this research could benefit the propulsion and power conversion community by increasing the better understanding of shaft loads and inertial effects.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.659-666
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• 2019

Proton exchange membrane fuel cells (PEMFCs) generate electricity by electrochemical reactions of hydrogen and oxygen. PEMFCs are expected to alternate electric power generator using fossil fuels with various advantages of high power density, low operating temperature, and environmental-friendly products. PEMFCs have widely been used in a number of applications such as fuel cell vehicles (FCVs) and stationary fuel cell systems. However, there are remaining technical issues, particularly the long-term durability of each part of fuel cells. Degradation of a carbon supported-platinum catalyst in the anode and cathode follows various mechanistic origins in different fuel cell operating conditions, and thus accelerated stress test (AST) is suggested to evaluate the durability of electrocatalyst. In this article, comparable protocols of the AST durability test are intensively explained.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.39.4-40
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• 2018

KMTNet 광시야 망원경의 성능 개선을 위해 2017년에 이루어진 주요 작업으로 주경 배플(baffle) 설치, 주경 코팅, 돔 플랫(dome flat) 장치 설치에 대해 발표한다. 망원경 주경의 가장자리(turn down edge)는 경면 가공이나 코팅 상태가 균질하지 않을 수 있으며, 이로 인한 난반사는 밝은 별 주위에 넓은 wing profile과 여러 갈래의 방사상 빛줄기를 만든다. 이런 난반사를 제거하기 위해 주경면 바로 앞에 배플을 설치하였다. 주경의 광학 성능과 집광력이 최적이 되도록 배플 내부 직경 값을 1,580 mm로 조정하여 설치한 결과, 관측 영상에서 별의 영상이 크게 개선되었다. 호주 관측소는 상대적으로 습기가 높아서 망원경 주경의 반사율이 빨리 낮아졌으며, 이를 개선하기 위해 기존의 코팅(protected silver)을 제거하고 알루미늄으로 새로 코팅하였다. KMTNet 3개 관측소는 주경의 반사율과 코팅 면의 확대 영상을 정기적으로 모니터링하여 광학 성능의 변화를 추적하고 있다. 밤하늘 플랫(twilight sky flat) 영상을 보완하기 위해, 돔 인클로져에 플랫 스크린과 광원을 설치하여 돔 플랫 영상을 획득하였다. 마지막으로 KMNet 관측시스템을 운영하며 발생한 돔 회전 및 돔 셔터 구동부 문제 등에 대해 소개하고, 문제 발생 원인과 주기, 문제 해결 방안을 발표한다.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.2
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• pp.381-389
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• 2012

This paper proposes a method which corrects location data of GPS for navigation of outdoor mobile robot. The method uses a Bayesian filter approach called the particle filter(PF). The method iterates two procedures: prediction and correction. The prediction procedure calculates robot location based on translational and rotational velocity data given by the robot command. It incorporates uncertainty into the predicted robot location by adding uncertainty to translational and rotational velocity command. Using the sensor characteristics of the GPS, the belief that a particle assumes true location of the robot is calculated. The resampling from the particles based on the belief constitutes the correction procedure. Since usual GPS data includes abrupt and random noise, the robot motion command based on the GPS data suffers from sudden and unexpected change, resulting in jerky robot motion. The PF reduces corruption on the GPS data and prevents unexpected location error. The proposed method is used for navigation of a mobile robot in the 2011 Robot Outdoor Navigation Competition, which was held at Gwangju on the 16-th August 2011. The method restricted the robot location error below 0.5m along the navigation of 300m length.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.2 no.2
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• pp.157-174
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• 2007

Result that study to serve to apply epitaxy style magnet nerve curer in nerve human nature disease treatment is as following. Designed probe actually with special quality research about coil probe of magnet curer firstly. Impose and revealed all drives about treatment probe embodying power device using MOSFET that is electric power element secondly. Could receive energy value that is proportional in number to close with actuality coil value by manufacture about treatment coil probe by third and come out. This could embody treatment pulse by disease, and saved pulse third and so on by damping pulse form through a special quality experiment variously specially. High amplitude treatment pulse(great strong) maximizes curative effect at short time and will be bought that demand is magnified greatly at the future in this research.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.677-680
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• 2008

Miniaturization of equipments which have wireless network function and sensor have changed utilization method of computer in daily life, and have contributed to development for ubiquitous computing environment. In this paper, we design camera control system based wireless mobile and web-environmental through which nurse, doctor and family of patient can share and observe the information on condition of patient in hospital. Besides, this camera control system makes it possible to integrate diverse equipments of hospital into one system, and to conduct remote control function which can be applied to the patient control system. It is impossible to control shooting direction of camera apparatus in a remote area for observing patient in a hospital room through general web camera. So in this paper, we showed new design; we attached step motor which can rotate 360 degrees to web camera, and the step motor can operate through control board. Besides, we developed application for two environments, mobile and web-based environment, which enables us to offer proper efficiency in accordance with condition of observer through observation of control and collected image data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.5
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• pp.391-403
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• 2013

Propeller aircraft propelled by an electric propulsion system is gaining a renewed interest because of ever-increasing environmental concern on harmful emissions emitted from conventional jet engines and national energy security. Traditional aircraft sizing methods are not readily applicable to electric propulsion aircraft that utilize a variety of alternative energy sources and power generation systems. This study showcases an electric propulsion aircraft sizing exercise based on a generalized, power based sizing method. A general aviation aircraft is propelled by an electric propulsion system that comprises of a propeller, a high temperature super conducting motor, a Proton Exchange Membrance(PEM) fuel cell system fuelled with hydrogen, and power conditioning equipment. In order to assess the impact of technology progression, aircraft sizing was conducted for two different sets of technology assumptions for electric components, and the results were compared with conventional baseline aircraft.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.10
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• pp.833-839
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• 2013

Thermal vacuum test should be performed prior to launch to verify satellites' functionality in a harsh space environment which is represented by extremely cold temperatures and vacuum conditions. A thermal vacuum chamber which consists of a vacuum vessel, a pumping system, and a thermal control system are used to perform thermal vacuum tests of a satellite system and its components. A cryogenic blower is a core component of the closed loop thermal control system for thermal vacuum chambers. This paper describes the fan design of the cryogenic blower, the design of the thermal protection interface between the driving part and the fluid part, which were verified by thermal and structural analyses. The performance of the cryogenic blower is confirmed by similarity test on the test bench.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.3
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• pp.189-196
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• 2018

Propeller performance measurement system for high altitude UAV was designed and applied to the wind tunnel test for 2 propeller models with a diameter around 1 m. Mechanical power of the propeller was directly measured by using the torque sensor installed on the rotating axis. The thrust of whole operation body including the propeller was measured by thrust road cell. The guide rail system was suggested to reduce the weight influence of operation body on the thrust road cell. The influence of each measured variables on the aerodynamic coefficients was studied with the repeatability and uncertainty analysis. This analysis result shows that the accuracies of the road cell and the wind velocity were major factors for the thrust coefficient. Propeller performance with typical RPM was measured with various wind speeds and the test results was summarized by performance coefficients for 5 different RPM.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6453-6457
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• 2015

In this paper, the theoretical analysis for a solenoid with a finite length was verified by the finite element simulation. The solenoids are widely being used in the field of mechanical, industrial, medical industry due to their simple structure and fast responses. Solenoid actuators use an electromagnetic force. A magnetic field is formed around the solenoid coil when a current is applied. The magnetic force generated by the magnetic field enables an inside plunger to move linearly. The axial and radial magnetic fields (magnetic flux density, B) at a certain point were calculated from the Biot-Savart's law and compared with the simulation analysis from the ANSYS-Magnetostatic S/W. Comparison result, an error exists in the error range, and could therefore verify the accuracy.