• 한국해양공학회지
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• 제22권1호
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• pp.13-21
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• 2008

In this study a method to predict CHF(Critical heat flux) in vertical round tubes with axially non-uniform cosine heat flux distribution for water was examined. For this purpose a local condition hypothesis based CHF prediction correlation for uniform heat flux in vertical round tubes for water was developed from 9,366 CHF data points. The local correlation consisted of 4 local condition variables: the system pressure(P), tube diameter(D), mass flux of water(G), and 'true mass quality' of vapor($X_t$). The CHF data points used were collected from 13 different published sources having the following operation ranges: 1.01 ${\leq}$ P (pressure) ${\leq}$ 206.79 bar, 9.92${\leq}$ G (mass flux) ${\leq}$ 18,619.39 $kg/m^2s$, 0.00102 ${\leq}$ D(diameter) ${\leq}$ 0.04468 m, 0.0254${\leq}$ L (length) ${\leq}$ 4.966 m, 0.11 ${\leq}$ qc (CHF) ${\leq}$ 21.41 $MVW/m^2$, and -0.87 ${\leq}X_c$ (exit qualities) ${\leq}$ 1.58. The result of this work showed that a uniform CHF correlation can be easily extended to predict CHF in axially non-uniform heat flux heater. In addition, the location of the CHF in axially non-uniform tube can also be determined. The local uniform correlation predicted CHF in tubes with axially cosine heat flux profile within the root mean square error of 12.42% and average error of 1.06% for 297 CHF data points collected from 5 different published sources.

• 마이크로전자및패키징학회지
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• 제28권2호
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• pp.45-50
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• 2021

Flip chip 제품의 난이도 증가에 따라 solder wetting 및 신뢰성 관점에서 강점을 갖는 flux 소재에 대한 관심이 높아지고 있다. 지용성 flux의 경우 별도의 세정 공정이 없기 때문에 공정 효율화 측면에서 유리하나, 리플로우 공정이후 반응을 마친 잔여물이 잔존하게 되는 경우 Cu migration 및 delamination을 발생시킬 수 있다. 본 연구에서는 저잔사 flux 구현을 위해 신규 resin에 적합한 solvent 및 activator를 변경 하였으며, package 환경에서 non-wet 및 신뢰성 개선 유무를 확인하였다. 저장 안정성 평가를 통해 신규 소재에 대한 안정성을 확보하였으며, boiling point가 상이한 solvent와 activator 2종 적용 및 activator 함량 증대를 통해 non-wet 미 발생 flux 소재를 확보하였다. 해당 소재에 대한 신뢰성 검증 이후 평면 분석 결과 flux residue 기인성 delamination 현상은 발견되지 않았으며, 이를 통해 저잔사 flux에 대한 최종 조성을 확보하였다.

• 한국농림기상학회지
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• 제5권2호
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• pp.138-149
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• 2003

KoFlux는 생태계와 대기 사이에 교환되는 이산화탄소, 수증기 및 에너지에 대한 우리의 이해를 높이고, FLUXNET과 CEOP등의 지역, 대륙 및 전구 규모의 관측망에 기여하기 위해서 시작되었다. 그거나 한반도의 지형적 특성 때문에 KoFlux의 대부분의 플럭스 타워는 관측에 이상적이지 못한 장소에 위치하고 있다. 탄소 및 에너지 교환의 정량화를 위해서 뿐만 아니라 군락 규모에서 지역 규모로 확장하기 위해서는 관측과 모델링을 병용한 다양한 접근 방법의 적용이 필요하다. 본 연구에서는 지역 규모의 현열 플럭스를 추정하기 위해 타워 플럭스 관측, 대류 경계층(CBL) 수지 방법, MM5 중규모 모형, 그리고 NCAR/NCEP 재분석 자료의 네 가지의 방법을 사용하여 다양한 면적을 대표하는 현열 플럭스를 산출하여 비교하였다. 비록 제한된 짧은 기간의 자료를 사용하였으나, 예비 분석을 통하여 (1) 해남 농경지 플럭스 타워에서 관측된 현열 플럭스가 지표의 불균질성을 보였고, (2) CBL 수지 방법으로 얻어진 지역 규모의 현열 플럭스는 수평 이류 효과의 계산 방법에 따라 다른 결과를 보였으며, (3) MM5 중규모 모형은 타워 플럭스 관측 값과 아주 유사한 현열 값을 수치 모사하였다. 그러나 관측지의 불균질성과 두 방법이 대표하는 면적의 근본적인 차이를 고려할 때, 플럭스 발자국 분석, 지리정보 시스템 및 관측지의 위성 영상 분석에 근거한 타워 플럭스의 공간 대표성을 정량화하는 것이 시급한 것으로 나타났다.

• 대한토목학회논문집
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• 제26권3B호
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• pp.311-319
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• 2006

저면경계층에서 부유사와 소류사 flux를 포함하는 실제적인 표사이동에 기초한 지형변화모델(SED-FLUX)이 개발되었다. SED-FLUX는 파랑모듈, 동수역학 모듈 및 부유사농도, 순부상 flux($Q_s$)와 소류사 flux를 계산하는 표사수송 및 확산모듈을 포함하며, 소류사 flux는 파-흐름 공존장에서 검증된 van Rijn의 TRANSPOR 프로그램에 의해 평가되어진다. 저면에서 순부상 flux $Q_s$는 표사확산모듈에서 source/sink 항으로서 평가되어지며, 수심변화모듈은 수심변화량을 계산하고 시간에 따른 bed level의 변화를 계산한다. 모델의 검증을 위하여 소류사이동의 이동한계수심은 방사성 동위원소 추적자를 사용한 현장 실험자료와 파와 흐름에 의한 표사이동한계수심에 대한 몇몇 경험식과 비교되었다. 본 모델을 파에 의한 해빈 단면변화에 적용한 결과 입사파의 특성에 따른 명확한 침식과 퇴적분포를 나타내었다. 끝으로, 이안제 배후에서 파와 해빈류에 의한 수심변화를 계산한 결과 이안제의 배후에서 초기 tombolo의 형성을 보여주었다.

• 제어로봇시스템학회논문지
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• 제21권12호
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• pp.1142-1151
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• 2015

In this paper, High performance torque control based on the flux mapping of 48V Wound Rotor Synchronous Motor has been studied to improve torque control. Flux map considering MTPA (Maximum Torque Per Ampere), MFPT (Minimum Flux Per Torque), Maximum efficiency point at the same torque command and flux command for each field current was produced. Current map using flux mapping of Each field current was applied to the MTPA, MFPT. Generating a current vector locus was to determine the characteristics of the operation region. Through the Matlab/Simulink simulation, difference between speed-torque map and flux map was represented. The suggested flux map was tested actual experiments on a dynamometer.

• 설비공학논문집
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• 제8권4호
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• pp.527-536
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• 1996

Convective nucleate boiling and burnout heat flux have been studied on a flat, downward facing, constant heat flux surface cooled by an impinging water jet. The tests are progressed from low, nonboiling power to high, burnout heat flux power. The jet velocity and the subcooling do not affect the nucleate boiling curve of $q{\sim}{\Delta}T_{sat}$ diagram, but the supplementary water height affects the curve. For the case of dimensionless height of supplementary water S/D=1, the boiling curve shift to the heigher heat flux than that of S/D=0 or S/D=2. Burnout heat flux is enhanced with increasing jet velocity and subcooling. Also. by using the supplementary water(S/D=1 or S/D=2), burnout heat flux is larger than that of the simple water jet(S/D=0). A generalized correlation for the burnout heat flux data in the present boiling system with an impinging water jet is successfully evolved.

• 천문학회보
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• 제38권2호
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• pp.96.2-96.2
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• 2013

The solar images are taken by the CCD detectors of the Sun monitoring satellites. The solar images are constructed after removing the traces of cosmic rays on the raw CCD data files. Thus, while applying the method of removing the cosmic rays traces, we can estimate the cosmic rays flux by counting the number of traces. The cosmic ray flux in the steady state might be the sum of the solar and galactic cosmic rays. However, the abrupt change in the flux could be assumed to be originated from the Sun. Therefore, we can identify the solar origins of the sudden solar cosmic ray flux changes from the phenomena shown in the processed solar images taken by SOHO/EIT. As the results, the estimated cosmic ray flux in the steady state is the anti-correlated with sunspot numbers, which shows the minima in cosmic ray flux at the solar cycle maxima defined by the sunspot numbers. The profiles of estimated solar cosmic ray associated with the ground level enhancements have the significant increase in the cosmic ray flux with good correlation. Thus, the solar images are valuable data useful in estimating the solar cosmic ray long term and transient flux variations.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1991년도 추계학술대회 논문집
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• pp.80-86
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• 1991

In this study an the development of the heat flux sensor with thermocouple, the heat-treated adhesive type film nickel gauge(Ni-Gauge) for measuring temperature was used. and this Ni-Gauge is not only comparable for platinum gauge(Pt-Gauge) in linearity, but also economically cheap. And from this viewpoint. numerical analysis is essential to investigate charateristics of sensor, since this analysis is capable of simulating precise boudary condition and practical conditions and so on. By the way. there are many types of heat flux sensor. of which adhesive type flux sensor is common, in the study this type of heat flux sensor was chogen. and analysis of the sensor is considered as a kind of open cavity figure. performed by SIMPLER algorithm. As a result. through temperature distributial of the sensor by numerical analysis in steady and unsteady state, the dracteristics of the acdhesive type heat flux sensor(lst heat flux sensor) acooodinge to heat flux, that is, outvoltage, sensitivity. and responsibilty could be evaluated. in addition, time of improved heat flux sensor(2nd heat flux sensor) could be predicted fran the reflectian of proper operating temperature(l50 $^{\circ}C$)of theNi-Gauge.

• 한국전기전자재료학회논문지
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• 제24권5호
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• pp.410-415
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• 2011

In this paper, we investigated the fault current limiting and the load voltage sag suppressing characteristics of the flux-lock type SFCL, designed with the additive polarity winding, according to the variations of turn number's ratio and the comparative analysis between the resistive type and the flux-lock type SFCLs were performed as well. From the analysis for the short-circuit tests, the flux-lock type SFCL designed with the larger turn number's ratio was shown to perform more effective fault current limiting and load voltage sag suppressing operations compared to the flux-lock type SFCL designed with the lower turn number's ratio through the fast quench occurrence of the high-$T_C$ superconducting (HTSC) element comprising the flux-lock type SFCL. In addition, the recovery time of the flux-lock type SFCL after the fault removed could be confirmed to be shorter in case of the flux-lock type SFCL designed with the lower turn number ratio.

• 한국전기전자재료학회논문지
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• 제24권2호
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• pp.141-146
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• 2011

When the current of the superconducting element exceeds its critical current by the fault occurrence, the quench of the high-$T_C$ superconducting fault current limiter (HTSC) comprising the flux-lock type superconducting fault current limiter (SFCL) occurs. Simultaneously, the magnetic flux in the iron core induces the voltage in each coil, which contributes to limit the fault current. In this paper, the fault current limiting characteristics of the flux-lock type SFCL as well as the load voltage sag suppressing characteristics according to the flux-lock type SFCL's winding direction were investigated. To confirm the fault current limiting and the voltage sag suppressing characteristics of the this SFCL, the short-circuit tests for the simulated power system with the flux-lock type SFCL were carried out. The flux-lock type SFCL designed with the additive polarity winding was shown to perform more effective fault current limiting and load voltage sag suppressing operations through the fast quench occurrence right after the fault occurs and the fast recovery operation after the fault removes than the flux-lock type SFCL designed with the subtractive polarity winding.