• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.778-779
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• 2015

전동기의 위치센서로 Variable Reluctance(VR) 레졸버의 구동 방식은 1차 권선에 여자신호가 인가됨과 동시에 2차 권선 COS, SIN의 유기된 기전력을 발생시키며, RDC(Resolover-to-Digital Converter)를 이용함으로써 위치 신호를 출력한다. 위치센서로서의 레졸버는 전동기 회전자의 정확한 위치를 정밀하게 측정하는 것이 중요하다. 그러나 다양한 외란으로 인해 위치 정보의 오차가 발생하며 레졸버 설계시 회전자 형상에 따라 오차가 다르게 나타난다. 본 논문은 레졸버의 설계 및 특성 해석을 용이하게 하기 위해 Visual Basic tool을 이용하여 자동화 설계 및 특성 해석 프로그램을 구성하였다. 또한 프로그램을 이용하여 레졸버 회전자 형상 변화에 따른 인덕턴스 변화로 유기된 전압의 크기변화와 그에 따른 위치 오차율을 분석하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1293-1302
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• 2001

It is generally known that radial vane blowers with vaneless diffuser may generate mostly only a rotating stall but backward curved vane blowers may do both an impeller and a diffuser rotating stalls. In this study, it was found from the numerical and experimental results that the diffuser rotating stall does not appear in a radial vane because of the suppression for the diffuser stall appearance by occurring of impeller rotating stall in a large flow rate coefficient. The diffuser rotating stalls occurring when the width of diffuser is broaden fur a backward curved vane blower are classified definitely by the diffuser flow rate coefficient defined by adopting the varying diffuser width.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.224-239
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• 2013

An exact performance analysis of an ML detector for a 2-dimensional rotation-transform aided QPSK system operating over an impulsive noise environment is presented using Rieman integrals of a two-dimensional Gaussian Q-function over Voronoi cells. A set of interesting features of the Voronoi cells is also characterised systematically. An optimum rotation angle yielding the minimum BER is also studied. The differences between the proposed exact method and the previous approximate analysis method are investigated in terms of the corresponding BERs and the derived optimum angles.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.234-241
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• 1999

The flow at the impeller exit is important to validate engineering design and numerical analysis of pumps. However, it is not easy to measure the flow at the impeller exit and evaluate the impeller performance since there is usually strong interaction between the impeller and the volute casing. We installed axisymmetric collector instead of the volute casing, so there is no interaction between the impeller and casing. A 3-hole Cobra probe is used to investigate the flow at impeller exit and vaneless diffuser region for design and on design flow rate. For a single suction centrifugal pump of low specific speed, the flow field such as velocity, flow angle, and total pressure are measured by traversing the probe across the vaneless diffuser. These data can be used for performance prediction, desist and numerical analysis of pumps.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.3
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• pp.49-55
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• 2011

For the purpose of the enhancement of the air conditioner performance and fuel effciency, several cases of centrifugal impeller for passenger car air conditioner have been numerically analyzed by changing central angle of blades and length of outlet for shape optimization of the impeller. Commercial CFD program Fluent 6.3.26 has been used to compute velocity, temperature, pressure and turbulence intensity that can lead numerous results. The central angles of two blades and three cases of outlet length led 4~12% and 3.5~6.4% differences of velocity and flow rate, respectively. The velocity distribution near the blade surface was axisymmetric and had a maximum value of 22.19 m/s and velocity of the vertical direction of the impeller showed linear increase with horizontal direction. At case 3 of oultet length, there existed a a minimum pressure value of -133320 Pa.

• The korean journal of orthodontics
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• v.33 no.2 s.97
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• pp.73-84
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• 2003

This study was performed to find out how much projection errors in the cephalometric measurements were made by vertical head rotation in taking posteroanterior cephalograms. 25 adults without any apparent facial asymmetry or severe sagittal skeletal discrepancy were selected and the posteroanterior cephalograms were taken with the head rotated $5^{\circ},\;10^{\circ}$ superior and inferior each to the reference $position(0^{\circ})$. The 7 height, 5 width and 6 angular measurements were taken at each 5 positions. Through the statistical analysis of all measurements taken at each rotated position, folowing results were obtained.1. The projection errors of height measurements were remarkably target than those of width or angular measure nents. f. Among the height measurements, the farther to the rotation axis the measurements were, the larger the projection errors were. 3. Among the width measurements, mandibular width and mandibular width of mandibular first molars showed significant differences between the values taken at each rotated position, while nasal width, maxillary width and intermolar width of maxillary first molars did not. 4. Among the angular measurements, the angle between horizontal reference line and the line that is connected to crista galli and antegonion or maxillare showed significant differences between the values taken at each rotated Position. The above results suggest that it is needed to the effort to keep constant head position for taking the useful posteroanterior cephalogra, because projection errors are caused by vertical head rotation.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.4
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• pp.1-9
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• 2012

This study deals with the operation effectiveness of roundabout. The objective of this study was to analyze the operational effectiveness of roundabout based on the operation of pedestrian signal. For pursuing the above, VISSIM was as a traffic simulation program. this study gives particular attention to analyzing the 1,680 scenarios by operation of Pedestrian Signal(7 cases), roundabout type(2 cases), pedestrian volume(8 cases) and entering volume(15 cases). The main results analyzed are as follows. First, the operational effectiveness analyzed by 2 type of 4-legged 1-lane roundabout and 6 type of 4-legged 2-lane were evaluated to be better than that by the others type. Second, the average delay time analyzed by operation of pedestrian signal were evaluated to be less than that by unsignalized pedestrian crossing. Finally, the average delay time analyzed by pedestrian crossing were decreased 8.18% than that by staggered pedestrian crossing in 4-legged 1-lane. However, the average delay time analyzed by staggered pedestrian crossing were evaluated to be decreased 36.53% than that by pedestrian crossing in 4-legged 2-lane.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.208-209
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• 2000

라이다 방법을 이용한 대기의 온도 측정은 크게 1) DIAL 방법을 이용하는 방법 2) 공기분자의 밀도를 측정하는 진동 라만 산란을 이용하는 방법 3)공기분자의 회전 라만 산란을 이용하는 방법 4) Rayleigh 산란의 선폭을 이용하는 방법 등으로 나누어진다. 이 중에서 대류권의 온도 측정에 적용가능한 방법은 3 번째의 방법으로 질소나 산소의 회전 라만 산란(RRS:Rotational Raman Scattering)이 가장 흔히 사용되는 기술이다. 질소와 산소의 회전 라만 신호를 이용한 온도 측정 기술은 Cohen$^1$ 등에 의하여 처음 시도되었으며, 그 후 많은 사람들에 의하여 검증되었다.$^2$ (중략)

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.11a
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• pp.38-38
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• 2000

최근 개발되고 있는 고속회전기계들은 무게 절감과 성능을 높이기 위해 그 크기가 소형화되고, 높은 회전수를 갖는 경향이 있으며, 이로 인하여 기계의 운전속도가 회전체의 1차 굽힘 위험속도(Critical Speed) 이상에서 운전하는 경우가 빈번히 발생되고 있다. 위험속도를 통과하는 고속회전기계 개발에 있어 가장 중요하게 고려되고 있는 회전체진동 문제는 정밀 제작 및 조립, 좋은 성능의 댐퍼 설계, 그리고 고속회전체 밸런싱 (High Speed Balancing) 작업등을 통하여 더 이상 회전기계 개발의 장애요인이 아닌 것으로 점차 인식되어 가고 있다.(중략)

• Solar Energy
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• v.13 no.2_3
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• pp.120-132
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• 1993

The purpose of this research is to study the characteristics of heat transfer in composite rotary heat pipe as modeled turbine rotating by a finite element analysis and experiment. Nu number, Re number, Pr number and dimensionless condensate layer thickness by thermal input and revolutions per minute were given as analysis factors. The comparison between calculated and experimental data showed similar tendency. Therefore the analysis method may be useful to predict the performance of composite heat pipe. The resistance on heat pipe showed the best effect of heat transfer by film condensation, by decreasing film condensation, the heat transfer rate from condenser was increased rapidly. The dimensionless condensate layer thickness according to Re number at given Pr number showed constant values, the dimensionless condensate layer thickness is proportionate to the square root of inverse of revolution number per minute. In this study Nu=A$({\delta}({\omega}/v)^{-1/2}Re^B)$ is used to the convection heat transfer coefficient and A=0.963, B=0.5025 were obtained as analysis predicts.