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3차원 실시간 디지털 스페클 토모그래피를 이용한 부탄 밀도 분포 분석
고한서(H.S.Ko),박광희(-H.Park),김용재(Y.-J.Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Transient and asymmetric density distributions have been investigated by digital speckle tomography. Multiple CCD images captured movements of speckles in three angles of view simultaneously because the flow were asymmetric and transient. The speckle movements between no flow and downward butane flow from a circular half opening have been calculated by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. The three-dimensional density fields have been reconstructed from the fringe shift by a real-time multiplicative algebraic reconstruction technique(MAPT).
고한서(H. S. Ko),박광희(K. H. Park),서형렬(H. -R. Seo),하종수(J. -S. Ha) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
Thermal error compensation has been developed for CNC (Computer Numerical Control) machining center with moving heat sources. The thermal error in CNC machining center has an effect on machining accuracy more than the geometric error does. Thus, temperature distributions of a spindle unit have been analyzed numerically by a Finite Differential Method and experimentally by an infrared (IR) camera in this study. A multiple variable method has been derived to estimate the thermal deformation of the machine origin stably and effectively after measuring deformation and temperature data. The experimental results for a vertical machining center have shown that the thermal errors of the machine origins were reduced more than 30% by the developed method.
정전기력 방식의 Drop-on Demand 토출을 위한 MEMS 잉크젯헤드 제작
孫尙郁(S. U. Son),金永珉(Y. M. Kim),崔在鎔(J. Y. Choi),李錫漢(S. H. Lee),高漢瑞(H. S. Ko),金容載(Y. J. Kim),邊渡泳(D. Y. Byun) 대한전기학회 2007 전기학회논문지 Vol.56 No.8
This paper presents a novel electrostatic drop-an-demand ejector with a conductive pole inside nozzle. The MEMS fabricated pole-type nozzle shows a significant improvement in the performance and reliability of forming meniscus and generating a micro dripping mode of droplet out of the meniscus. It is verified experimentally that the use of the pole-type nozzle. The liquid is used D2O+SDS+SWNT (5 %wt). The gap between upper electrode and nozzle is about 600 ㎛. Electrostatic drop-on-demand ejection is observed when a DC voltage of 1.5 ㎸ is applied between the control electrode and ground electrode. Droplet diameter is 100 ㎛.
3.3㎸(105A) COMPACT RACK TYPE 고압 인버터 시스템의 방열 성능 향상을 위한 열유동 해석
김선영(S.Y. Kim),김성대(S.D. Kim),유성열(S.R. Ryoo),유남규(N.K. You),김태범(T.B. Kim),홍찬욱(C.O. Hong),고한서(H.S. Ko) 한국전산유체공학회 2014 한국전산유체공학회지 Vol.19 No.3
With ever rising concerns about saving of fossil fuel resource, there have been an increasing demand for use of energy more efficiently. The electric motor driven inverters can be a great help to improve energy efficiency. They are also used to control the motor speed to the actual need. Therefore the use of them can lead to reduce energy consumption. In particular, the medium voltage(MV) drive systems used for pumps, fans, steel rolling mills and tractions have widespread applications in the industry. They cover power ratings from 0.4㎿ to 40㎿ at the ㎹ level of 2.3㎸ to 13.8㎸. The majority of the installed MV drive systems however, are in the 1㎿ to 4㎿ range with voltage rating from 3.3㎸ to 6.6㎸. But they are required to reduce size and weight like other power electronic equipments. In this paper, we studied on the 3.3㎸(105A) compact rack type inverter system for improving the cooling efficiency. At first, we confirmed the tendency of temperature with computational simulation using ANSYS ICEPAK and actual experimental tests. And then we researched thermal performance improvement designs in order to reduce temperature of the transformer for the safe operation. It can reduce temperature of transformer that using pipe type flow guide in the system. As a result, we found out more efficient solution by thermal-fluid analysis.
내부 온도 추정식 개발에 의한 LCD 모니터 내부의 열분포 분석
오석준(S. J. Oh),고한서(H. S. Ko),정두환(D. H. Chung) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
In these days, demand of a LCD monitor is remarkably increasing with development of the LCD technology. However, there are thermal problems for improvement of efficiency for the LCD monitor. Thus, this research analyzed thermal problems such as convection and conduction heat transfer characteristics in the LCD monitor using an infrared (IR) camera. Also, the results of the outer side of the front LCD panel using the IR camera have been compared with the results of the inner side of the front panel using T-type thermocouples. The equations have been derived for the temperature distribution of the inner side of the front LCD panel by a multiple regression method including variables for ambient temperature, humidity and temperature differences between the front and back panels of the LCD monitor.