• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2008년도 하계학술발표대회 논문집
• /
• pp.154-159
• /
• 2008

Two-phase flow boiling heat transfer of R-410A in horizontal small tubes was reported in the present experimental study. The local heat transfer coefficients were obtained over a heat flux range of 5 to 40 kW/$m^2$, a mass flux range of 170 to 600 kg/$m^2s$, a saturation temperature range of 3 to $10^{\circ}C$, and quality up to 1.0. The test section was made of stainless steel tubes with inner diameters of 0.5 and 3.0 mm, and lengths of 330 and 3000 mm, respectively. The section was heated uniformly by applying a direct electric current to the tubes. The effects on heat transfer of mass flux, heat flux, inner tube diameter, and saturation temperature were presented. The experimental heat transfer coefficient is compared with six existing heat transfer coefficient correlations. A new boiling heat transfer coefficient correlation based on the superposition model for R-410A in small tubes was developed with mean deviation of 10.13%.

• 설비공학논문집
• /
• 제14권2호
• /
• pp.175-183
• /
• 2002

Flow Condensation heat transfer coefficients (HTCs) of Rl2, R22, R32, Rl23, Rl25, R134a, R142b were measured experimentally on a horizontal plain tube. The experi- mental apparatus was composed of three main parts; a refrigerant loop, a water loop and a water-glycol loop. The test section in a refrigerant loop was made of a copper tube of 8.8 mm inner diameter and 1000 mm length respectively. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. All tests were performed at a filed refrigerant saturation temperature of 4$0^{\circ}C$ with mass fluxes of 100, 200, 300 kg/$m^2$s. The experimental result showed that flow condensation HTCs increase as the quality, mass flux, and latent heat of condensation increase. At the same mass flux, the HTCs of R32 and R142b were higher than those of R22 by 35~45% and 7~14% respectively while HTCs of R134a and Rl23 were similar to those of R22. On the other hand, HTCs of Rl25 and Rl2 were lower than those of R22 by 28 ~30% and 15 ~25% respectively Finally, a new correlation for flow condensation HTCs was developed by modifying Dobson and Chato's correlation with the latent heat of condensation considered. The correlaton showed an average deviation of 13.1% for all pure fluids data indicating an excellent agreement.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 추계학술대회 논문집
• /
• pp.348-356
• /
• 2004

In this paper, Analysis of parameters effecting on the derailment factor was conducted in oder to deduce technical requisites have to be reflected in design of Track and rolling-stocks because it is important to grasp the risk of derailment quantitatively. And then go far toward becoming practical study with that select two section of sharp curved track of actual train in service, incheon Metro Line 1 and make field research in condition of vehicles and track and analysis As a result of parameter study, the following conclusions were obtained. The radius of curve and Cant is in inverse proportion to the derailment factor, but as train operation velocity, standard deviation of alignment irregularity and the ratio lateral force : wheel load of the inside track increase, the derailment factor rise. In the investigation for the derailment safety of incheon Metro Line 1, the derailment factor was below 0.43 in both section R=200 and R=300, so that it proved safe compare with allowance limits 0.8, but it appeared that risk of the derailment in second transition curve is the highest among the entire curve.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2015년도 추계학술대회
• /
• pp.964-966
• /
• 2015

분산 제어 (DM; dispersion management)와 광 위상 공액기 (OPC; optical phase conjugator)가 적용된 광전송 링크에서 송신단부터 OPC까지 중계 구간이 증가할수록 단일 모드 광섬유 (SMF; single mode fiber)의 길이와 중계 구간 당 잉여 분산 (RDPS; residual dispersion per span)은 감소하고, OPC부터 수신단까지는 중계 구간이 증가할수록 SMF 길이와 RDPS가 증가하는 분포에서 인접 중계 구간과의 SMF 길이와 RDPS 편차가 WDM 신호의 보상에 미치는 영향을 살펴보았다.

• 한국잠사곤충학회지
• /
• 제7권
• /
• pp.65-74
• /
• 1967

본 연구는 생사의 비균일성 섬도발생의 원인을 구명하기 위하여 견사형성에 관련되는 잠체기관의 해부학적 조사를 하였고 나아가서 그 비균일성을 개선하는 방안을 연구한 것이며 다음의 결과를 보았다. 1. 잠아의 토사관구조자체가 견사형성에 있어서 견사단면형태를 결정할뿐 아니라 견사선내의 견물질이 토사진행과 더불어 감소될 때 압출근육의 작용으로 섬도가 점차 가늘어져서 비균일성의 소인이 된다. 2. 우리나라 고치는 품종에 따라 다소의 차이는 있으나 견사종합섬도편차가 평균 0.58d로서 생사로 될 때 부득이 비균일성의 소인이 되고 있다. 3. 견사섬도가 생사목적섬도에 적합하지 못할때 더욱 비균일성이 악화된다. 4. 제사과정에서 작업부주의가 생사섬도의 비균일성에 크게 미치고 있으며 어느 조사법이 든간에 30％ 이상의 원인이 되고 있다. 5. 생사섬도 비균일성을 개선하는 데는 짐품종 선정을 심중히 하여 적절한 견사섬도를 택하여야 한다. 6. 정섬도조사법은 정립조사법에 비하여 섬도비균일성을 개선하게 되며 최소한 20％ 향상을 기할 수 있다. 7. 다조조사기에 사용할 수 있는 섬도감지기를 고안하여 시험조사한 결과 일반조사법에서 21 중사의 섬도편차가 1.57d인데 반하여 시험구는 1.30d이였으며 등급상으로 2격을 향상시킬 수 있었다.

• 한국ITS학회 논문지
• /
• 제10권6호
• /
• pp.74-83
• /
• 2011

하이패스 교통정보시스템은 프로브 차량을 이용하여 직접 구간정보를 수집함으로써, 보다 신뢰성 높은 정보를 운전자에게 제공할 수 있다. 그러나 프로브 차량의 운행상황과 특성, 그리고 통계처리 방법 등이 정보의 신뢰성에 영향을 미치며 특히, 도시부도로에서는 구간통행시간이 신호 지체시간 경험 유무에 의해 크게 영향을 받기 때문에, 수집되는 개별 프로브 데이터 간 많은 편차가 발생하게 된다. 따라서 구간정보의 신뢰도 제고를 위한 다각적인 방면에서의 연구가 필요하다. 그러나 하이패스 정보제공과 관련한 선행연구는, 주로 연속류 특성을 가지는 고속도로 구간을 대상으로 이루어져, 이를 단속류 교통 특성을 가지는 도시부도로에 적용시키기에 한계가 있었다. 따라서 본 연구에서는 도시부도로에서의 하이패스 교통자료 특성을 분석하고 적절한 가공방안을 마련하는데 의의를 두고자 하였다. 시공간도를 이용하여 RSE로부터 수집하는 도시부도로의 하이패스 자료 특성을 분석한 결과, 수집자료는 종료노드의 신호주기를 주기로 하여 도착 차량의 신호 대기 등에 따라 일정한 패턴을 나타내는 것을 알 수 있었다. 또한, 신호대기 횟수와 대기시간에 따라 수집데이터의 편차가 발생하는데, 혼잡 상황보다 비혼잡 상황에서 편차가 크게 나타났다. 이는 혼잡상황에서는 신호대기 횟수가 많아지면서, 편차가 일정부분 상쇄되기 때문인 것으로 분석되었다. 이러한 도시부도로의 하이패스 수집자료는 신호대기에 의한 교통특성을 반영하기 위해 평균값을 대표값으로 사용하는 것이 적절하며, 신호 및 도로 특성에 따라 지정체 판단기준을 조절할 필요가 있는 것으로 분석되었다. 본 연구에서 도출한 결과가 도시부도로에서의 하이패스 정보의 신뢰성을 향상 시킬 수 있는 초석이 되길 기대한다.

• Journal of Preventive Medicine and Public Health
• /
• 제11권1호
• /
• pp.14-23
• /
• 1978

This survey was conducted on a total 672 pulmonary tuberculosis patients who were registered at certain health center in Busan, during the period from July 15th to August 31st, 1977, based on Modified Cornell Medical Index(CMI) consisting of 70 questions. Number of 'Yes' response of an individual patients was collected by each large section of Modified CMI. The each number of 'Yes' response was standardized by mean of Z scoring. Z score was obtained by following formula. Z=50+10(Xi-m)/s M : means of 'Yes' response by each section for all subjects s : standard deviation of the mean Xi : number of 'Yes' response by each section in an individual patients The results of obtained were as follows: 1. The number of investigated cases were 672 (459 males and 213 females). The most prevalent group was 20-24 years old group as 18.4% by age, moderate advanced group as 50.8% by radiological diagnosis, INH+PAS+SM group as 34.7% by antituberculotics and unemployed group as 59.9% by occupation. By bacteriological examination of sputum, the rate of negative group was 60.5% and positive group was 39.5%. 2. Z score of complaints by sex was higher in female as 52.4 than in male as 48.9 in general. By radiological diagnosis, there was decreasing tendency with age in male but increasing tendency with age in female. 3. By age group, Z score of complaints was increasing tendency with age in male but there was non-significant differences in female. 4. By bacteriological examination of sputum, the Z score of complaints was increasing tendency with the more discharged bacteria in both sex generally. 5. By antituberculotics, INH group was revealed the highest Z score of complaints as 50.4 in male and INH+PAS group was the highest as 51.21 in female. 6. By occupation, agricultural and fisherman group was the highest as 53.5 and the next group was professional, technical and related workers, unemployed and sales workers in that order.

• 대한기계학회논문집B
• /
• 제26권3호
• /
• pp.432-438
• /
• 2002

In order to design and analyze the performance of an axial-flow pump it is necessary to know the flow deviation, deflection angle and pressure loss coefficient as a function of the angle of incidence for the hydrofoil section in use. Because such functions are unique to the particular section, however, general correlation formulae are not available for the multitude of hydrofoil profiles, and such functions must be generated by either experiment or numerical simulation for the given or selected hydrofoil section. The purpose of present study is to generate design correlations for hydrofoils with double circular arc (DCA) camber by numerical analysis using a commercial code, FLUENT. The cascade configuration is determined by a combination of the inlet blade angle, blade thickness, camber angle, and cascade solidity, and a total of 90 cascade configurations are analyzed in this study. The inlet Reynolds number based on the chord and the inlet absolute velocity is fixed at 5${\times}$10$\^$5/. Design correlations are formulated, based on the data at the incidence angle of minimum total pressure loss. The correlations obtained in this way show good agreement with the experiment data collected at NASA with DCA hydrofoils.

• 전기학회논문지
• /
• 제67권6호
• /
• pp.695-701
• /
• 2018

For a power grid that has a high wind penetration level, when wind speeds are continuously fluctuating, the maximum power point tracking (MPPT) operation of a variable-speed wind turbine (VSWT) causes the significant output power fluctuation of a VSWT, thereby significantly fluctuating the system frequency. In this paper, an improved power-smoothing scheme of a VSWT is presented that significantly mitigates the frequency fluctuation caused by varying wind speeds. The proposed scheme employs an additional control loop based on the frequency deviation that operates in combination with the MPPT control loop. To improve the power-smoothing capability of a VSWT in the over-frequency section (OFS), the control gain of the additional loop, which is set to be inversely proportional to the rotor speed, is proposed. In contrast, the control gain in the under-frequency section is set to be proportional to the rotor speed to improve the power-smoothing capability while avoiding over-deceleration of the rotor speed of a VSWT. The proposed scheme significantly improves the performance of the power-smoothing capability in the OFS, thereby smoothing the frequency fluctuation. The results clearly demonstrate that the proposed scheme significantly mitigates the frequency fluctuation by employing the different control gain for the OFS under various wind penetration scenarios.

• 한국재난정보학회 논문집
• /
• 제16권3호
• /
• pp.550-557
• /
• 2020

연구목적:온실가스는 전 세계적인 재난인 지구 온난화의 주요 원인 중 하나이다.본 연구에서는 도로부문 온실가스 배출량 산정을 기존의 구간평균속도에서 개별차량의 속도기반으로 정밀하게 산정할 때 영향을 주는 우선순위를 판별할 수 있는 요인을 찾아내는 목적을 가진다. 연구방법:고속도로의 일반 통행구간, 휴게소 구간, 진입구간, 합류부 구간의 기존 방법과 개별차량의 속도기반 배출량 산정 방법의 비교 분석을 진행한다. 연구결과:경부 고속도로의 총 6 구간에 대해 분석을 진행한 결과 속도의 표준편차와 구간의 혼잡이 큰 영향을 주는 결과가 나왔다. 결론: 기존의 온실가스 배출량 산정 방법과 개별차량의 속도기반 배출량 산정 방법을 비교하면 개별차량의 속도기반 방법이 더 정밀한 것은 확실하다. 하지만 이를 전국에 일괄 적용하기는 어렵기 때문에 본 연구에서는 기존 방법과 개별차량의 속도기반 방법을 비교하여 크게 차이가 나게 영향을 주는 요인을 제시한다.