• Journal of Biomedical Engineering Research
• /
• v.36 no.2
• /
• pp.37-42
• /
• 2015

In this paper, we propose a wrist rehabilitation training device using pneumatic inflation and deflation of air cells. By alternating inflation and deflation of upper and lower air cells, the device makes the flexional and extensional movement for wrist rehabilitation. With the angular displacement sensor, it measures the flexion-extension angle of the wrist during the training and the bending angle is used for the automatic control of the device. Using the sensor output, the regression equation was obtained to measure the bending angle of the wrist from a wrist rehabilitation training device. The measurement error of the device was evaluated by comparing the measurement output with the angle from the photograph. The measurement error of wrist bending angle between the sensor and photo was $3.2^{\circ}$ in average. With additional test and improvement, the pneumatic wrist rehabilitation training device might be used for rehabilitation training.

• Journal of the Korean earth science society
• /
• v.34 no.3
• /
• pp.249-256
• /
• 2013

For the purpose of recording polarization of the earth's atmosphere, the entire sky was photographed using the all-sky camera when the Sun was just above the horizon. The ratio and width of polarization were defined using the photograph, and a method to measure them was developed. Time-series photography of the polarization ratio and its width enabled us to qualitatively analyze the polarization phenomena which changes depending on the weather conditions. Findings indicated that polarization was co-related with air pollutants in a meaningful way. The polarization phenomena of the Earth's atmosphere are influenced by air pollutants. The more air pollutants exist in the air, the lower polarization ratio and the bigger polarization width it has. It is suggested that air pollutants disperses more photons, which makes it possible to observe the polarization phenomena in the vast area of the sky.

• The Journal of Korean Academy of Prosthodontics
• /
• v.25 no.1
• /
• pp.303-316
• /
• 1987

The purpose f this study was to evaluate the effect of resin film thickness on the tensile bond strength and to compare the tensile bond strengths of 4 differently treated metal surfaces. For the experiment, seventy metal specimens were cast with Verabond and divided into I, II, III, groups. The metal specimens in group I were electrolytically etched and cemented with Panavia under finger pressure. Cement film thickness was regulated with metal spacers. The metal specimens in Group II were treated by 4 methods, such as electrolytic etching method, salt-roughened method, EZ-oxisor method , chemical etching method and cemented with Panavia. In group III, electrolytically etched metal specimens were cemented with Hy-Bond. The etched surface of metal specimens and the cement film thickness were examined under the scanning electron microscope. Results were as follows; 1. The tensile bond strength showed no significant difference between $30{\mu}m,\;80{\mu}m,\;130{\mu}m$ film thicknessspecimens. 2. There was no significant difference in the tensile bond strength between the 4 differently treated metal specimens. 3. The tensile bond strength showed significant difference between Panavia and Hy-Bond. 4. Scanning electron microscope photograph revealed that tile interdendritic eutectic was removed in electrolytically etched metal surfaces hilt even dendritic arm was removed in Chemically etched metal surfaces. 5. The metal surfaces which were air-abraded with $50{\mu}m$ aluminum oxide showed roughness and small crack on scanning electron microscope photograph.

• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.1
• /
• pp.7-13
• /
• 2015

Unmanned air vehicles (UAVs) are getting popular not only as a private usage for the aerial photograph but military usage for the surveillance, reconnaissance and supply missions. For an UAV to successfully achieve these kind of missions, geolocation (localization) must be implied to track an interested target or fly by reference. In this research, we adopted multi-sensor fusion (MSF) algorithm to increase the accuracy of the geolocation and verified the algorithm using two multicopter UAVs. One UAV is equipped with an optical camera, and another UAV is equipped with an optical camera and a laser range finder. Throughout the experiment, we have obtained measurements about a fixed ground target and estimated the target position by a series of coordinate transformations and sequential Kalman filter. The result showed that the MSF has better performance in estimating target location than the case of using single sensor. Moreover, the experimental result implied that multi-sensor geolocation algorithm is able to have further improvements in localization accuracy and feasibility of other complicated applications such as moving target tracking and multiple target tracking.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.1
• /
• pp.55-63
• /
• 1997

A numerical investigation has been made for flows in an axisymmetric circular cylinder with an impulsively rotating cone located at the bottom of the container. The axisymmetric container is completely filled with a viscous fluid. Major parameter for the present research is only the vertex angle of the cone, otherwise Reynolds number and aspect ratio of the vessel are fixed. Main interest concerns on the vortex breakdown of meridional circulation by impulsive rotation of the cone with respect to the longitudinal axis of the cylinder. Numerical method has been used to integrate momentum and continuity equations on a generalized body-fitted grid system. The pattern of vortex breakdown is quite different from that in a right circular cylinder with flat endwall disks. The flow visualization photograph of the preceeding work by Escudier is compared with the present numerical results and the two results are in good agreements. Also flow data are plotted to gain a deep understanding for the present phenomena of the vortex breakdown. The conclusions of this work are clearly explained by the classical theory of the vortex flows in a finite geometry.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.85-92
• /
• 2004

As a research to develop a SCRAM jet engine is actively conducted, a necessity to produce a high-enthalpy flow in a laboratory is increasing. In order to develop the SCRAM-jet engine, stabilized combustion in a supersonic flow-field should be attained, in which a duration time of flow is extremely short. Therefore, a mixing process of breathed air and fuel, which is injected into supersonic flow-fields is one of the most important problem. Since, the flow inside SCRAM jet engine has high-enthalpy, an experimental facility is required to produce such high-enthalpy flow-field. In this study, a detonation-driven shock tunnel was built and was used to produce high-enthalpy flow. Further-more, SCRAM jet engine model equipped backward-facing step was installed at test section and flow-fields were visualized using color-schlieren technique and high speed video camera. The fuel was injected perpendicular to the flow of Mach number three behind backward-facing step. The height of the step, distance of injection and injection pressure were changed to investigate the effects of step on a mixing characteristic between air and fuel. The schlieren photograph and pressure histories show that the fuel was ignited behind the step.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.1 no.1
• /
• pp.66-79
• /
• 1993

To construct the design back data for a lean-burn gas engine, we have designed a constant volume combustion chamber with sub-chamber. With constant volume ratio of main-sub combustion chamber and constant equivalence ratio of methane-air mixture, the influence of geometric configurations(diameter, injection angle, number, length) of passagehole upon combustion characteristics were studied. It was found that combustion characteristics in the main combustion chamber were greatly influenced by the injection angle and length of passagehole.

• Proceedings of the KSRS Conference
• /
• 2007.03a
• /
• pp.88-91
• /
• 2007

국립산림과학원 산림조사과에서는 지식정보화사업의 지원 하에 남한 전체 낱장/정사항공 사진 영상 DB툴 구축하고， 항공사진검색시스텀 (aerophoto.kfri.go. kr)을 개발하여 대국민 인터넷 서비스를 제공하고 있다. 본 논문에서는 5TB 대용량 항공사진 원본 영상과 메타자료를 웹 지리정보 서비스에 적합하도록 자료의 변환 방식，소프트웨어와 하드웨어의 최적 구성안, 그리고 응용 검색 시스템의 개발 기능을 소개 한다. 또한，항공사진 웹 검색 시스템은 벡터 지리정보와 항공사진 영상을 각각 전송하여 융합하고 분석하는 기능을 담당하는 클라이언트 모듈을 한정된 네트워크 환경에서 대용량 자료의 검색 속도 향상을 위하여 비동기식 처리 방식으로 개선하였다. 그리고 국가 지리정보 인프라인 정사항공사진 자료를 타 시스템과 연계 활용하기 위한 방안으로 ESRI ArcGIS 의 Plug-in 적용 사례를 제시한다.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.6
• /
• pp.1582-1589
• /
• 1994

The characteristics Prandt1-Meyer expansion of supersonic flow with condensation through a wavy wall in a channel are investigated by experiment and numerical direct marching method of characteristics. In the present study, for the case of moist air flow in the type of indraft supersonic wind tunnel, the dependency of location of formation and reflection of the oblique shock wave generated by the wavy wall and the distribution of flow properties, on the specific humidity and temperature at the entrance of wavy wall and the attack angle of the wavy wall to the main stream is clarified by schlieren photograph, distribution of static pressure and Mach number, and plots of numerical results. Also, we confirm that the wavy wall plays an important key role in the formation of oblique shock wave, and that the effect of condensation on the flow field appears apparently.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.8
• /
• pp.589-595
• /
• 2009

The instability wave formed near nozzle region grows to vortex with large scale in downstream region of spray. It plays an important role in the fuel-air mixing, combustion process and engine exhaust emissions in direct injection diesel engine. The objective of this study is to analyze effect of variant parameters (injection pressure, ambient gas density, etc.) and fuel properties on spray instability near nozzle region. Spray structure near nozzle region was investigated using a magnification photograph. A pulsed Nd-YAG laser was used as a light source, and image was taken by CCD camera. The following conclusions are drawn from this experimental analysis. In low ambient density, the effect of fuel properties on spray instability near nozzle region is dominant. In high ambient density, the effect of ambient gas on spray instability near nozzle region is dominant. High jet velocity has strong influence on spray instability.