• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2009년도 Korea Superconductivity Society Meeting 2009
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• pp.74-74
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• 2009

• 동력기계공학회지
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• 제16권3호
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• pp.5-9
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• 2012

Novel mechanisms for Energy Recovery Devices are proposed to diminish the pressure loss in the high-pressure reverse-osmosis system. In the beginning, the state-of-the-art in the design of Energy Recovery Devices is reviewed and the features of each model are investigated. The direct-coupled axial piston pump(APP) and axial piston motor(APM) showed 39% energy recovery at operating pressure of reverse osmosis desalination systems, 60 bar. Meanwhile, the developed PM2D model, in which APM pistons are arranged parallel to those of APP, is more compact and showed higher efficiency in a preliminary test. Loss-reduction mechanisms employing rod piston and double raw valve port are additionally proposed to enhance the efficiency and durability of the device.

• 비파괴검사학회지
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• 제21권6호
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• pp.630-633
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• 2001

본 연구에서는 국내에서 생산되는 에어콘용 팬의 진동해석을 위해 ESPI를 이용하였다. 기존의 진동해석 실험으로 많이 사용되는 가속도계를 에어콘용 팬에 직접 적용하는 데에는 형상의 제약 등으로 적용이 어려워 비접촉 진동해석기술을 요구하였다. 실험은 가진 장치를 이용하여 팬에 가진을 하고 ESPI를 이용하여 진동모드 및 고유주파수, 고유주파수의 범위를 검사하였다. 또한, 실험결과는 유한요소 해석과 비교되었으며, 실험결과로부터 실제 팬의 사용 회전수에서 제품의 신뢰성을 평가하였다 본 연구에서 사용된 ESPI는 품질개선을 위한 재질변화 또는 형상변화 시 설계측면에서 효과적인 설계정보를 제공할 수 있으며, 기존의 진동해석 기술의 단점을 보완할 수 있으리라 사료된다.

• 한국기계가공학회지
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• 제15권3호
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• pp.79-85
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• 2016

Truing process is a very important process for recovering the shape of wheels worn by continuous grinding operation. In this study, the devices, controller, and spindle for electro-discharge truing were developed, and the electro-discharge truing method was applied to metal-bonded grinding wheels and compared with the conventional truing method. The shapes of the grinding wheels were measured by a surface profile measurement device. The protrusion of abrasives on the surface of the wheels was compared with the conventional truing method using an optic microscope measurement device. The experimental results showed that the performance of the electro-discharge truing method, in terms of the protrusion of abrasives on the surface of the wheels and the recovery of the shape of the worn wheels, was similar to that of the conventional truing method.

• 한국생산제조학회지
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• 제23권3호
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• pp.218-222
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• 2014

A 3D printer was used to fabricate a micro-TAS system for biomedical applications. A polymeric medical device fabrication based on a 3D printer can be performed at atmospheric conditions. A CAD- and CAM-based system is a flexible method to design medical components, and a 3D printer is a suitable device to perform this task. In this research, a 100-micron-wide fluidic channel was fabricated with a high-aspect ratio. A cross-sectional SEM image confirmed its possible usage in a micro-reactor using 3D printers. CNC-machined samples were compared to 3D printer-fabricated samples, and the advantages and disadvantages were discussed. Based on the SEM images, the surface roughness of the 3D printed reactor was not affected by wet or dry conditions due to its manufacturing principle. An aspect ratio of 5 to 1 was achievable with 100-${\mu}$ m-wide fluid channels. No melting was found, and the shape of channels was straight enough to be used for micro reactors.

• 한국정밀공학회지
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• 제17권10호
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• pp.56-62
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• 2000

A fast and precise technique to make 3-dimensional object which is called direct metal shaping process is processed. It is very useful technique in design and inspection. Using this developed system, a solid object is made. In experiment, test parts are built by varying three factors, laser power, scan path, scan speed. This process used device, which is different from the widely used in rapid prototyping in that powder feeding device is used. Spraying powder directly at the focused laser beam and then three dimensional object is made by the deposit of melted metal powder. The optimum scanning path is found to be zigzag path, which had little thermal affection on base metal. As a result of these experiments, it was found that optimum scanning speed is 15mm/sec laser power is 50W. This constructed 3-dimensional object could be used in mold manufacturing directly.

• 한국전기전자재료학회논문지
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• 제30권5호
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• pp.270-275
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• 2017

Current progress in the development of semiconductor technology in applications involving high electron mobility transistors (HEMT) and power devices is hindered by the lack of adequate ways todissipate heat generated during device operation. Concurrently, electronic devices that use gallium nitride (GaN) substrates do not perform well, because of the poor heat dissipation of the substrate. Suggested alternatives for overcoming these limitations include integration of high thermal conductivity material like diamond near the active device areas. This study will address a critical development in the art of GaN on diamond (GOD) structure by designing for ideal heat dissipation, in order to create apathway with the least thermal resistance and to improve the overall ease of integrating diamond heat spreaders into future electronic devices. This research has been carried out by means of heat transfer simulation, which has been successfully demonstrated by a finite-element method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2175-2178
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• 2005

Selective Laser Sintering(SLS) method is one of Rapid Prototyping(RP) technologies. It has been used to fabricate desirable part to sinter powder and stack the fabricated layer. Since the sintering process occurs using infrared laser having high thermal energy, shrinkage and curling of the fabricated part occurs according to thermal distribution. Therefore, the fast scanning path generation is necessary to eliminate the factors of quality deterioration. In case of fabricating larger size parts, the unique scanning device and scanning path generation should be considered. In this paper, the development of SLS machines being capable of large size fabrication(800${\times}$1000${\times}$800 mm, W${\times}$D${\times}$H) will be addressed. The dual laser system and the unique scanning device have been designed and built, which employ CO2 lasers and dynamic 3-axis scanners. The developed system allows scanning a larger planar surface with the desired laser spot size. Also, to generate the fast scanning paths, adaptive path generation is needed with respect to the shape of each layer, and not simply x, y scanning, but the scanning of arbitrary direction should be enabled. To evaluate the suggested method, the complex part will be used for the experiment fabrication.

• 한국정밀공학회지
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• 제30권3호
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• pp.260-265
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• 2013

To increase the machine accuracy by improving the stiffness of spindle bearings, preload was applied to the spindle bearings. The methods of fixed position preload, convertible preload, constant pressure preload, and variable preload are used to apply the preload to the spindle bearing. The previous studies performed by the author of this study were variable preload methods using rubber pressure and centrifugal force based on mechanical systems. This study proposed a toggle joint mechanism that could be applied to variable preload method using centrifugal force and rubber pressure to increase the preload. Also, a finite element analysis was conducted to predict the deformation of the rubber and change of the preload. And the analysis results showed that the preload by the device using rubber pressure only was increased by the toggle joint mechanism using rubber pressure.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.248-251
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• 1995

Nowadays, the internal images of a human body can be easily provided by the ultrasound imaging, the X-ray CT, or the MRI device, among which the ultrasound imaging device has good resolution for soft tissues of a human body compared with the other devices. Furthermore, the use of ultrasound imaging devices will increase in future especially in the obstetrics, territory, since it does not give harm to the human body. Although several techniques have been investigated until now in order to extract organs from ultrasound images, very few of them have achieved satisfactory results because of low contrast and high noise nature of images. This paper proposes a technique for automatic extraction of the gall bladder area from ultrasound images. The proposed technique first extracts a small reliable area of a gall bladder from an ultrasound image employing smoothing, binarization, expanding and shrinking, and labeling, and then expands the area referring to the binarized version of the original image. The technique is examined its performance by real ultrasound images of a gall bladder and satisfactory results are obtained. Some problems to be solved are discussed finally.