• 한국지구과학회지
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• 제41권6호
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• pp.684-694
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• 2020

이 연구에서는 이슬점에 대한 중학생들의 개념 이해를 평가하기 위한 루브릭을 개발하였다. 이를 위해 국가 수준 학업성취도 평가의 다층 서답형 문항에 대한 중학생의 응답을 분석하였다. 학생들의 응답 특성에 따라 유형을 분류하고, 성취도 점수 평균에 따른 응답 유형의 분포를 분석하였다. 이를 토대로 이슬점 개념 이해를 평가하기 위한 루브릭을 작성하였다. 연구 결과 다음과 같다: 첫째, 포화수증기량 곡선에서 이슬점 찾기에 대한 학생 응답을 분석한 결과, 다수의 학생들이 이슬점에 대한 개념이 없거나 부족한 것으로 나타났다. 둘째, 이슬점에서 수증기 응결과정에 대한 학생 응답을 분석한 결과, 과학적 개념 유형의 비율은 매우 낮았으며, 오개념 유형의 비율이 상대적으로 높았으며 유형 또한 다양하였다. 셋째, 성취도 점수 평균에 따른 학생 응답 유형 분포 분석을 토대로 4수준의 평가 루브릭을 작성하였다. 이러한 연구 결과를 토대로 지구과학 분야에서 개념 이해 평가를 위한 루브릭 개발과 활용 측면에서 제언을 하였다.

• Architectural research
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• 제10권1호
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• pp.33-39
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• 2008

Condensation has mainly occurred in corridor type apartment door which is exposed to the outside air and is made of steel, which has high thermal conductivity. As a result, the total costs of repair have increased with the number of disputes with residents. In this study, therefore, we investigate materials and construction methods used in apartment door, perform a computer simulation to find out possible improvements, and then suggest the dew point to prevent the occurrence of condensation throughout simulation. The results indicate that the temperature that condensation does not occur is $15.4^{\circ}C$, and the optimum method of achieving this dew point is shown to be a door frame system including a large vertical slot to decrease the area of thermal conduction between the outer and inner portions of the door frame. Mock-up tests show that the surface temperature of the door frame was higher than the dew point, and the system can withstand severe cold conditions of $-20^{\circ}C$. In application test, the surface temperature of door frame with vertical slots is $5.9^{\circ}C$in average, which is higher than the existing door frame. Furthermore, in the temperature distribution of the surrounding door measured with infrared ray camera, the existing door shows the high temperature distribution indicating lack of insulation, but the improved door shows the low temperature distribution indicating higher insulation.

• 한국대기환경학회지
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• 제21권3호
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• pp.303-313
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• 2005

In this study, meteorological characteristics concerning the occurrence of fog are analyzed using 4-years $(2000\~2003)$ data at Chuncheon and the probability of prediction is investigated. From the analysis of meteorological characteristics, the fog at Chuncheon occurred before sunrise time and disappeared after that time and lasted for $2\~4$ hours. When fog occurred, on the whole, wind direction was blew the northerly and wind speed was below 2.1m/s. Especially, about $42\%$ of foggy day fell on the calm $(0\~0.2\;ms^{-1})$ conditions. The difference between air temperature and dew point temperature near the surface were mainly less than $2^{\circ}C$. For the lack of water surface temperature, the water surface temperature was calculated by using Water Quality River Reservoir System (WQRRS) and then it was used as the surface boundary condition of MM5. The numerical experiment was carried out for 2 days from 1300 LST on 14 October 2003 to 1300 LST on 16 October 2003 and fog was simulated at dawn on 15 and 16 October 2003. Simulated air temperature and dew point temperature indicate the similar tendency to observation and the simulated difference between air temperature and dew point temperature has also the similar tendency within $2^{\circ}C$. Thus, the occurrence of fog is well simulated in the terms of the difference between air temperature and dew point temperature. Horizontal distribution of the difference between air temperature and dew point temperature from the numerical experiment indicates occurrence, dissipation and lasting time of fog at Chuncheon. In Chuncheon, there is close correlation between the frequency of fog day and outflow from Soyang reservoir and high frequency of occurrence due to the difference between air and cold outlet water temperature.

• 한국농림기상학회지
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• 제2권3호
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• pp.75-79
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• 2000

Calibrations of fast-response krypton hygrometers were carried out using a dew-point hygrometer to investigate the changes in their absorption coefficients due to long-term field operation. Absorption coefficients changed proportionally with the number of hours of field operation. The increase in absorption coefficient indicates that the water vapor flux, calculated with the original absorption coefficient, would underestimate the true flux in the field. To minimize the uncertainty in quantifying evapotranspiration and surface energy budget studies, frequent calibrations (for example, every 1500 hours of field operation) of krypton hygrometer are recommended.

• Journal of Mechanical Science and Technology
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• 제16권5호
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• pp.696-702
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• 2002

In the present paper, the effects of inlet pressure on the heat and mass transfer rates of an air cooler are numerically predicted by a local analysis method. The pressures of the moist air vary from 2 to 4 bars. The psychrometric properties such as dew point temperature, relative humidity and humidity ratio are employed to treat the condensing water vapor in the moist air when the surface temperatures are dropped below the dew point. The effects of the inlet pressures on the heat transfer rate, the dew point temperature, the rate of condensed water, the outlet temperature of air and cooling water are calculated. The condensation process of water vapor is discussed in detail. The results of present calculations are compared with the test data and shows good agreements.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.839-840
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• 2006

Sintering behavior of the Fe-0.8Mn-0.5C powder system was studied on the specimens with a density of ${\sim}7.0g/cc$ sintered at $1120^{\circ}C$ for 30 min in a gas mixture of $7%H_2/93%N_2$ with the inlet dew point of $-60^{\circ}C$. During the atmosphere monitoring ($CO/CO_2$-content and dew point) was showed, that carbothermical reduction occurs in two different temperature ranges; three peaks of dew point profile also can be distinguished during sintering cycle as well. Following sintering the Mn-content distribution and microstructures around the Mn-source were micro-analytical evaluated; the results showed that manganese travels through porous iron matrix up to ${\sim}60{\mu}m$.

• 한국안전학회지
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• 제32권6호
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• pp.34-39
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• 2017

Vapor-liquid equilibrium calculation is required to properly design and operation of distillation process. The general calculation method is to use binary interaction parameter. Lower flash points of cyclohexanol+aniline and cyclohexanol+cyclohexanone were measured by using Seta-flash closed cup apparatus. The measured flash points were compared with those calculated by the method based on Raoult's law and the optimization method using Wilson equation. The absolute average errors(A.A.E.) of the results calculated by Raout's law are $0.25^{\circ}C$ and $1.07^{\circ}C$ for cyclohexanol+aniline and cyclohexanol+cyclohexanone, respectively. The absolute average errors of the results calculated by the optimization method are $0.22^{\circ}C$ and $0.65^{\circ}C$ for cyclohexanol+aniline and cyclohexanol+cyclohexanone, respectively. As can be seen from A.A.E., the calculated values based on the optimization method were found to be better than those based on the Raoult's law. The binary interaction parameters calculated by the optimization method are used to predict the dew points of cyclohexanol+aniline and cyclohexanol+cyclohexanone. The A.A.E. for these mixtures show that there is an acceptable agreement between experimental and calculated dew poins.

• 한국지구과학회지
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• 제40권6호
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• pp.624-638
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• 2019

절대 습도와 이슬점 온도의 관계에 대한 예비 교사들의 인식을 조사하기 위하여 설문지를 투입하였다. 설문 결과 예비 교사들이 "절대 습도와 이슬점 온도는 비례한다.", "이슬점 온도는 공기 중의 수증기의 질량에 비례한다."와 같은 견고한 오개념을 갖고 있음을 발견하였다. 예비 교사들이 갖는 이러한 오개념은 절대 습도와 이슬점 온도의 관계에 대한 7차 교육과정과 2007 개정 교육과정 중학교 과학 교과서의 부정확한 서술 내용에서 기인하는 것으로 사료된다. 한편, 2015 개정 교육과정 중학교 1학년 과학 교과서는 증발, 응결, 압력과 온도 변화에 따른 기체의 부피 변화를 분자운동의 관점에서 다루기 때문에, 중학교 교육과정에서 이러한 관점을 유지하기 위해 수증기량과 이슬점 온도의 척도로서 수증기압의 도입은 예비 교사와 학습자의 오개념을 방지할 수 있으며, 과학 교육과정을 보다 일관되고 논리적으로 만들 수 있을 것으로 사료된다.

• 한국도로학회논문집
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• 제14권2호
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• pp.55-61
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• 2012

도로표지는 운전자에게 정보제공의 역할을 하는 도로시설물로서 주행경로에 대한 운전자의 판단을 도와준다. 그러나, 주 야간의 온도, 습도 변화로 인한 도로표지판에 결로발생 시, 정보전달의 결함이 발생하여 교통사고 가능성을 높이는 원인으로 작용한다. 따라서, 도로표지판의 결로발생을 예방하기 위한 기술이 필요하다. 본 연구에서는 도로표지판의 결로발생을 예방하는 대안의 효과를 비교하기 위해 단열소재가 삽입된 시편, 결로방지필름이 부착된 시편을 선정하고 결로방지처리가 되지 않은 일반시편과 비교하였다. 분산분석과 사후검정(Tukey HSD)을 통해 각 시편에 발생한 측정시간에 따른 결로량을 비교 했으며, 결로량과 재귀반사도의 관계를 Pearson의 상관분석으로써 검증하였다. 분석결과, 결로방지필름이 부착된 시편에서 결로량이 적게 나타났으며, 결로발생 90초 후에는 결로방지필름의 부착 시편과 단열소재가 삽입된 시편에서 나타나는 결로량은 결로방지 처리가 되지 않은 시편에서 발생한 결로량과의 통계적인 차이가 존재하였다. 또한, 상관분석결과로써 결로량과 재귀반사도는 반비례하는 것으로 나타났다. 따라서, 도로표지판에 발생된 결로량과 재귀반사 변화율에 대하여, 결로방지필름의 부착과 단열소재의 삽입은 결로방지에 효과가 존재하는 것으로 판단된다.

• 조명전기설비학회논문지
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• 제29권1호
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• pp.64-69
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• 2015

This study investigates the Horizontal surface discharge characteristics of solid insulators by varying their materials, and the dew-point of dry-air. The methodology of this study is that a quasi-uniform field is first applied to a test chamber. Then, the chamber is filled with dry-air as an insulation gas which pressure is varied from 1 to 6atm while applying an AC voltage to the chamber. The used solid insulators are teflon, polyethlene and polyurethane. As the dew-point is lower and the pressure of dry-air is higher, the flashover voltage of all solid insulators increases more. When each characteristic of the solid insulators is compared under the same gas pressure, the flashover voltage of teflon is the highest. Then, the flashover voltage of polyethlene is higher than that of polyurethane. Moreover, it is observed that the flashover voltage increases as the horizontal distance between the electrodes of each solid insulator become larger, respectively. However, as the pressure is increased, flashover voltage of the solid insulators is saturated. Therefore, selection of cost-effective insulation is needed in order to appropriate pressure.