• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.508-511
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• 2011

Dust released from the rotating timber cutting process causes various kinds of diseases as well as safety issues. Although there were lots of efforts to reduce the amount of dust by installing large-sized dust collectors or by using expensive high-quality cutters, they proved to be not so effective. In this study we want to modify and improve the design of the rotary cutter system to prevent dust from being released to the environment as possible by using computational fluid dynamics (CFD) analysis. We have developed CFD models of the conventional cutter and several design modifications. Through the CFD analysis the characteristics of the air flow was predicted, and then the behavior of dust produced during the cutting process was analyzed for different designs. The most efficient design feature to capture dust inside the cutter as much as possible was chosen based on the CFD analysis results. Finally the prototype of the ratary saw machine was constructed and tested to check the dust capturing efficiency, which result is reasonably consistent with the predicted performance through the CFD analysis.

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.257-262
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• 2001

A Littman type tunable external-cavity diode laser system was developed. The laser output which is the Oth-order diffracted beam from a diffraction grating in an external cavity is a single longitudinal mode. Its FWHM was measured as less than 9 MHz. With the diode driving current of 140 mA and operating temperature of $25^{\circ}C$, the coarse tuning range of 3.475 urn was measured. A fine tuning experiment in which an external mirror was rotated by a PZT driven by a sawtooth wave was performed, and its tuning range of 0.042 urn was measured. sured.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.29-32
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• 1996

기존의 안과 진단 및 치료 기기의 안구 고정장치는 진단 및 치료에 있어서 피검사자와 검사자에 사이에 충분한 협조가 되지 않을 경우 진단의 비효율성과 치료의 안정성등의 문제가 발생하고있다. 따라서 이러한 문제를 보완하기 위하여 SLO의 전면 세극등을 소형의 반사경으로 대치하고 표시등을 후면의 먼거리에 수직으로 배열시켜서 피검사자에게 적당한 높이의 고정등을 선택하게하여 수직방향의 안구 위치를 고정시키고 SLO(Scanning Laser Ophthalmoscope)의 좌우 회전기능으로 표적의 수평방향을 근절시킨 후에 검사자의 조작으로 원격조정되는 서보장치를 이용하여 다시 반사경을 전방향으로 미세하게 회전되게하여 정확한 위치로 안구를 이동시키게 하는 원격조정 표적 추적장치를 개발하였다. 이에 따라 피검사자는 거울에 비친 먼거리의 허상을 보게 되어 세극등을 이용한 근접주사방식의 단점인 안구의 축동, 폭주등으로 인한 환자의 눈의 피로를 최소화하면서 피검사자의 안구를 검사자가 원하는 위치로 고정시킬 수 있게 함으로써 임상실험에서 안과 진단의 정확성과 관리도를 높이고 치료의 효율성과 안전성을 증가시킬 수 있는 원격조정 추적장치로써의 성능을 확인하였다.

• The Journal of the Acoustical Society of Korea
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• v.42 no.1
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• pp.7-15
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• 2023

Recently, as interest in air quality in vehicles increases, the use of fine dust detection sensors for air quality measurement is becoming common. An axial-flow fan is inserted in the fine dust sensor installed in the air conditioning system in the vehicle to prevent dust from sinking directly on the sensor. When the sensor operates, the flow noise caused by the rotation of the axial-flow fan acts as a major noise source of the fine dust sensor. flow noise is recognized as one of the product competitiveness of fine dust sensors. In this study, the noise was gradually reduced at the same flow rate by improving the flow performance of the small axial flow fan. First, a virtual fan performance tester consisting of about 20 million grids was developed to analyze the aerodynamic performance of the target small axial-flow fan. In addition, the flow field was simulated by using compressible Large Eddy Simulation for direct computation of flow noise as well as high-accurate prediction of flow rate. The validity of numerical method are confirmed through the comparison of predicted results with experimental ones. After the effects of pitch angle on flow performance were analyzed using the verified numerical method, the pitch angle was determined to maximize the flow rate. It was found that the flow rate was increased by 8.1 % and noise was reduced by 0.8 dBA when the axial-flow fan with the optimum pitch angle was used.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.2
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• pp.43-48
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• 2011

The maximum current density of copper electrorefining is 350 A/$m^2$ and the higher current density is required to promote the copper productivity. The 1000 A/$m^2$ high current density is possible when rotating disc electrode is employed to reduce diffusion thickness. The copper electroplating with 1000 A/$m^2$ is possible at 400 rpm. Thiourea and glue were used to improve the electrodeposition behaviors during copper electrorefining process. Potentiodynamic polarization tests were conducted to investigate the effects of additives on copper electrodeposition. Galvanostatic tests were also conducted at 1000 A/$m^2$. Copper were electroplated on cylindrical rotating electrodes to give the uniform flow on the electrode surface. The lowest surface roughness was obtained when 16 ppm thiourea was added to the electrolytes. The surface roughness was increased with glue concentration. The surface hardness was not influenced by addition of glue. The copper nuclei were getting smaller with thiourea concentration, however there is no glue effects on copper nucleation.

• Korean Journal of Materials Research
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• v.6 no.1
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• pp.67-78
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• 1996

제 3원소가 첨가된 금속간 화합물 TiAI 금속간 화합물 분말을 PREP법(플라즈마 회전전극법)으로 제조하여, 통.방전 강압소결법에 의해 치밀한 소결체를 만들었다. 이에 대해 첨가 원소의 종류와 열처리에 따른 고온 및 상온 압축 특성의 변화를 조사하였다. 소결체의 미세조직은 ${\gamma}$/$\alpha$2 lamella로 이루어진 완전 변태구조였고, 결정립의 크기는 140-150$\mu\textrm{m}$였으며 계단형 결정립계를 나타내었다. 소결체를 ($\alpha$+${\gamma}$)구역인 130$0^{\circ}C$에서 2시간 동안 열처리한 결과, 모든 조성의 시편이 등축점 ${\gamma}$와 lamella로 이루어진 전형적인 duplexrn조로 변태하였다. 상온 압축 시험에서 시편은 파괴될 때까지 가공경화 현상이 나타났으며, Cr을 첨가한 시편이 가장 큰 파괴응력과 변형률을 나타내었다. 한편, 고온 압축 시험의 경우 온도상승 때문에 가공경화의 속도가 감소되었고, 80$0^{\circ}C$에서는 가공경화와 회복이 균형을 이루는 소위 정상 상태의 변형을 보였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.5
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• pp.1176-1181
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• 1995

Microdrilling is one of the most difficult operations because of the poor chip discharge and the weakness of tool. This study is concerned about the development of a microdrilling monitoring system that is useful for minimizing the tool breakage and enhancing the machinability in the air spindle based microdrilling. The system is composed of a drilling state detection unit and an adaptive step-feed control unit that controls the micro-stepping motor driven spindle axis. Drilling states such as overload, tood breakage are recognized by the change of the air spindle speed which is measured via the reflective photo sensor. Based on the monitoring results, the adaptive step-feed control algorithm adjusts the step increment to keep the decrease of spindle speed within a specified range. The results of evaluation tests have shown that the developed system is very effective to prevent the breakage of microdrill and improves the productivity in comparison with the conventional microdrilling.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.81-87
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• 2020

A stable rotational-to-linear motion transformation structure using a driving mechanism with 2 degrees of freedom was developed for an orthogonal mechanism to prevent the interference of each axis in 2D motion. In this mechanism, a step motor was used for precise position control. This structure was developed to maneuver workparts in micro particle blast machining experiments. To determine the real-time performance of micro particle blast machining, the control, input, and output were operated simultaneously and precise position control was implemented, using a timer interrupt with multiple execution codes. The two step motors obtained precise position control by removing backlash with a ball-screw mechanism. The device has menu-type control codes for user-friendliness, and real-time sequence control was simultaneously adopted for user control input.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.103.1-103.1
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• 2012

본 연구는 차량경량화를 위하여 높은 인장강도와 우수한 인성을 가지는 590MPa급 이상조직강(Dual phase steel)을 이용하여 1991년 TWI(The Welding Institute)에서 개발된 마찰교반접합을 적용하여 접합을 실시하였다. 접합의 공정조건으로 툴의 회전속도는 250~350 RPM, 접합속도로는 50~350 mm/min로 겹치기접합을 실시하였다. 접합에서 사용된 툴은 Megastir에서 제작한 고융점마찰교반접합용 툴인 PCBN(Q-60)을 이용하였고 연구에 사용된 DP590은 포스코(POSCO)에서 제작된 1.4t(mm) 두께인 AHSS(advanced high strength steels)을 사용하였다. 모재인 DP590과 접합체의 미세조직은 광학현미경과 주사전자현미경을 이용하여 관찰하였으며 기계적 특성은 경도시험과 인장시험을 실시하여 조사하였다. 경도의 분포는 모재에서 약 220~230Hv이며 TMAZ부분에서 상승하기 시작하여 접합부에서 약 320Hv까지 상승하는 경향을 보였으며 인장시험 결과 접합속도 100~200 mm/min에서는 모든 시편이 모재에서 파단되어지는 것을 확인할 수 있었다. 위와 같은 결과 300~350 RPM, 100~200 mm/min의 공정조건에서는 접합이 성공적으로 이루어졌으며 차량경량화에 적용이 가능하다고 판단되어진다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.3
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• pp.334-339
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• 2010

The development of high-speed spindle have been studied extensively for micro machining in advanced industrial countries. The research of miniaturized high-speed air spindle is important part which needs for the micro machining process of high quality. So, This study was to carry out results about design characteristics of miniaturized high-speed air spindle. We had designed 4type turbines and shaft. They were simulated in use the computer simulation programs. We made them as products. They measured RPM (revolutions per minute). As a result of experiments, there was a contrast among 4type Turbines. it reached 384,000rpm in 4.5bar of air pressure. And, We tried to compare the results of measurement whit the results of computer simulation.