• 한국정밀공학회지
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• 제33권12호
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• pp.1007-1013
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• 2016

This paper presents the development of a magneto-optical encoder for higher precision and smaller size. In general, optical encoders can have very high precision based on the position information of the slate, while their sizes tend to be larger due to the presence of complex and large components, such as an optical module. In contrast, magnetic encoders have exactly the opposite characteristics, i.e., small size and low precision. In order to achieve encoder features encompassing the advantages of both optical and magnetic encoders, i.e., high precision and small size, we designed a magneto-optical encoder and developed a method to detect absolute position, by compensating for the error of the hall sensor using the linear table compensation method. The performance of the magneto-optical encoder was evaluated through an experimental testbed.

• Smart Structures and Systems
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• 제24권5호
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• pp.641-648
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• 2019

The authors investigate the feasibility of applying a vision-based displacement-measurement technique in the characterization of a SMA damper recently introduced in the literature. The experimental campaign tests a steel frame on a uni-axial shaking table driven by sinusoidal signals in the frequency range from 1Hz to 5Hz. Three different cameras are used to collect the images, namely an industrial camera and two commercial smartphones. The achieved results are compared. The camera showing the better performance is then used to test the same frame after its base isolation. U-shaped, shape-memory-alloy (SMA) elements are installed as dampers at the isolation level. The accelerations of the shaking table and those of the frame basement are measured by accelerometers. A system of markers is glued on these system components, as well as along the U-shaped elements serving as dampers. The different phases of the test are discussed, in the attempt to obtain as much possible information on the behavior of the SMA elements. Several tests were carried out until the thinner U-shaped element went to failure.

• The Journal of Korean Physical Therapy
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• 제35권1호
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• pp.19-23
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• 2023

Purpose: The purpose of this study is to analyze the brain waves and develop various exercise programs to improve the physical and mental aspects of stroke patients when neurological physical therapy and sitting table tennis exercise are applied to stroke patients. Methods: In this study, an experiment was conducted on 15 patients diagnosed with stroke, and training was performed after changing the ping-pong table to a sitting position to apply ping-pong exercise to stroke patients. After training was conducted for 40 minutes twice a week for 4 weeks, brain waves were measured before and after. EEG was measured using Laxtha's DSI-24 equipment as a measurement tool, and data values were extracted through the Telescan program. Results: Most of the relative beta waves showed a significant difference before and after the intervention. As for the characteristics of beta waves, this result can be seen as being highly activated during exercise or other activities. Conclusion: Ping-pong exercise in a sitting position is a good intervention method for stroke patients, and it can help to use it as basic data in clinical practice by showing brain activity.

• 한국정밀공학회지
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• 제12권2호
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• pp.48-58
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• 1995

A micro positioning system using piezoelectric actuators have very wide application region such as ultra-precision machine tool, optical device, measurement systen. In order ro keep a high precision displacement resolution, they use a position sensor and feedback the error. From the practical point of view, a high-resolution displacement sensor system are very expensive and difficult to guarantee such sensitive sensors work properly in the hard opera- tion environment of industry. In this study, a micro-positioning grinding table which does not require position sensor but uses piezoelectric voltage feedback, has been developed. It is driven by hystersis-considering reference input voltage which calculated from computer and then uses actuator/sensor characteristics of piezoelectric materials. From the result of experiments we proved a fast and stable response of micro-positioning system and suggested efficient technique to control the piezoelectric actuator. And through grinding experiments, it is revealed that a characteristics of ground surfaces transient to plastic deformation as extremely small depth of grinding.

• 한국콘텐츠학회논문지
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• 제11권10호
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• pp.349-354
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• 2011

투시검사실내 공간산란선 분포에 대한 정확한 정보와 환자, 검사 자 등에 대한 피폭을 줄이고자 투시용방사선 발생장치를 이용한 실험결과는 다음과 같았다. 테이블과 동일한 높이의 경우 산란선은 50 cm지점과 250 cm 지점에서 0.78 mGy/min ~ 0.04 mGy/min (95 %), 테이블 하 방향 50 cm의 경우 0.17 mGy/min ~ 0.02 mGy/min (86 %), 테이블 상 방향 50 cm 의 경우 1.37 mGy/min ~ 0.05 mGy/min (96 %) 로 감소하였고 상 방향 50 cm 보다 수평지점에서 50 ~ 60% 선량 감소를 나타냈고 하 방향 50 cm 지점에서는 90 ~ 95%정도의 감소율을 나타냈다. 조사야 조절장치의 경우 25%로 줄였을 때 50 cm 지점에서 0.78 mGy/min 에서 0.16 mGy/min 으로, 250 cm 지점에서 0.04 mGy/min 에서 0.01 mGy/min으로 평균 80% 정도 감소하였다. 피사체의 유무의 경우 피사체가 없는 경우 모든 측정지점에서 평균 96.7% 공간 산란선량이 감소하였다.

• 한국기계가공학회지
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• 제6권3호
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• pp.112-118
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• 2007

Recently, the machine tools called multi-task machines, which mounted rotary axes on the table or spindle are used increasingly. Accordingly, multi-task machine tool takes a growing interest on the motion accuracy of feed drive system. In this study, measurement and diagnosis of motion errors ware attempted from circular pattern obtained by using DBB (Double ball bar) device. Those were obtained at both clockwise and counter clockwise motions in mutually perpendicularly intersecting three planes. The reliability of error measurement system for multi-task machine tool was verified by the direct test cutting.

• 한국기계가공학회지
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• 제6권3호
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• pp.31-37
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• 2007

Recently, the machine tools called multi-task machines, which mounted rotary axes on the table or spindle are used increasingly. Accordingly, multi-task machine tool takes a growing interest on the motion accuracy of feed drive system. In this study, measurement and diagnosis of motion errors ware attempted from circular pattern obtained by using DBB (Double ball bar) device. Those were obtained at both clockwise and counter clockwise motions in mutually perpendicularly intersecting three planes. The reliability of error measurement system for multi-task machine tool was verified by the direct test cutting.

• 한국정밀공학회지
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• 제8권4호
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• pp.41-54
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• 1991

Laser speckle photography-one of the Laser speckle measurement methods which, recently, are used widely in various science, and engineering applications are succesfully used in the non-contact measurement of In-plaane displacement. In this study, automated measurement and analysis are tried in the laser speckle photo- graphy method using a video camera, computer control and processing, and a X-Y positioning table driven by computer controlled stepping motor. The experiment was compared with the theorecial strain and stress data from finite element method. The result showed that displacement, strain and stress can be measured more accurately and conveniently by using this approach.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1195-1198
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• 2003

Micro former has been known as a useful tool for machining micro parts. It makes micro holes automatically with punches, a hole-shape die and material by rotation of crank shaft synchronously. Micro displacement in micro forming affects on the performance of machining because micro forming size is similar with its mechanical displacement. Therefore, the measurement of this micro displacement is essential to be guaranteed to obtain high forming precision in the whole machine as well as its devices. This paper addresses the development of a laser interferometer to measure micro displacement for a micro former. The laser interferometer is able to measure micro displacement during a few micro seconds with non-contact. For the experiment, a laser probe is installed on the optical table with optical devices and a micro displacement generating device. The velocity decoding board is also added to calculate doppler shift frequency directly. Finally simple experiments are conducted to confirm its functional operation.

• 한국정밀공학회지
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• 제27권1호
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• pp.58-63
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• 2010

A new contact force estimation technique is proposed. Keeping the contact force at a certain level between finishing tool and the object is essential since the quality of the finished surface is very sensitive to the contact force during the finishing process. However, the contact force measurement cannot be obtained by simply installing load cells under machine table or in the middle of tool linkage. The reason is that the weight of the machine table and the tool linkage are much heavier than the force to be measured. To that end, a method for estimating disturbance is proposed for a system that is similar to the mechanism of the finishing machine, and the same method is applied to estimate the contact force of the brush-type finishing machine. To verify the effectiveness of the proposed method, a small scale test set-up has been built and the method has been tested.