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최문규,김칠영,김종헌,김희수,서은경,장유순 공주대학교 과학교육연구소 2015 과학교육연구 Vol.45 No.1
A new light curve was obtained through photometric observation of GW-Cep, W UMa type eclipsing binaries using 152㎜ refractor telescope of Observatory of Kongju National University and BRC-250 telescope of Daejeon Science High School for 4 inconsecutive days; two days in October, 2014, two days in October, 2015 respectively. With new photometric observation of GW-Cep, period of variation of 0.318832907 day and four new eclipse timings were obtained. New light elements (Min I = HJD2449319.30711 + 0.318830911×E) were confirmed with the analysis between these results and the previous eclipse timings of GW-Cep and the variation of sinusoidal orbital period was identified from new (O-C) diagram made with these light elements.
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균일 기체 유동 속의 물방울의 증발에 복사열전달이 미치는 영향
최문규,김형석 한국화학공학회 1998 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.36 No.4
본 연구에서는 수치모사를 통하여 고온 균일 기체 흐름 속의 물방울에 대하여 증발현상을 고찰하였다. 기존의 연구에서는 액적의 증발에 복사가 미치는 영향을 고려하지 않거나 액적의 증발없이 복사 열전달에 의한 내부 열발생량만을 계산하였다. 고온 환경 속의 액적이 받는 복사열은 주로 적외선이므로 액적의 크기와 유사한 파장을 갖는다. 따라서 적외선은 액적 내부로 침투하여 액적 내부에서 열을 발생시킨다. 본 연구에서는 Mie의 해를 써서 열발생량을 구하여 액적 내부 및 회부의 유체 요동과 물질전달, 열전달을 포괄하여 동시에 풀었다. 수치모사가 올바르게 수행되었는지 검증하기 위하여 정상사태에서의 항력계수와 Nusselt 수, Sherwood 수를 수치적으로 구하여 실험으로부터 얻은 상관식과 매우 잘 일치함을 보여 주었다. 액적의 증발에 복사가 미치는 효과를 고찰하기 위하여 초기온도가 300K 인 물방울과 1,300K, 1,900K인 공기를 사용하여 Nusselt 수와 Sherwood 수를 계산하였다. 주위 기상의 온도가 상승할수록 복사로 인해 발생하는 열량이 증가하였다. 그러나 물방울의 경우에 굴절률의 허수부가 매우 작기 때문에 복사가 물방울의 내부유동이나 기-액 전달현상, 증발 등에 미치는 영향은 거의 없었다. The phenomenon of water droplet evaporation in hot gaseous flow is investigated numerically in the present study. In the past researches the effects of radiation on the droplet evaporation have not been taken into consideration or only the internal heat generation due to radiation was calculated without considering the droplet evaporation. Since the infrared light, which the droplet in hot environments is subject to, has a wavelength range comparable to the droplet size, the light transverses to heat generated in the droplet. By employing the Mie solution to obtain heat generation inside the droplet, the fluid flow, the heat transfer and the mass transfer inside and droplet are calculated simultaneously. To prove that the numerical algorithm has been correctly applied, the drag coefficient, the Nusselt number and the Sherwood number calculated numerically at steady state are shown to agree well with experimental correlations. To find out the effects of radiation on the droplet evaporation, the water drop at the initial temperature of 300K and the air of 1,300K or 1,900K are employed for case study, and Nu and Sh are calculated. The higher the gas phase temperature is, the more heat generation occurred inside the droplet. The radiation however, made no influence on the flow pattern inside the droplet, the transport phenomena, the evaporation, etc., since the imaginary part of the refractive index for water in very small, resulting in negligible heat generation.
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Light intensity fluctuations on a semiconductor microsphere calculated by boundary element method
최문규,Jungmoo Kim 한국물리학회 2007 Current Applied Physics Vol.7 No.6
which are transformed into Schro¨dinger equations through Debye potentials, are solved by the boundary element method, one of theintegral formulations. The resultant light intensities on the particle surface show noise-like uctuations depending on various parameterssuch as the light wavelength, the particle size, the numerical surface element size, etc. The more the numerical surface elements used, theare somehow made into shape numerically by Green’s function and surface integration. One can consider a numerical surface element asa crystalline or amorphous unit cell. Actually a few experiments with photon energy conversion devices give the consistent results withours that the energy conversion eciency is on the increase with the decreasing size of unit cells. It is thus proposed here that this noisefrom numerical computation may be modeled to be the real thermal uctuations of photon density on particle surface for photovoltaic.
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박층 에폭시 덧씌우기 포장의 부착성능과 미끄럼 저항 현장시험
최문규,이재훈,홍승호,성시완,정진훈 한국도로학회 2021 한국도로학회논문집 Vol.23 No.6
PURPOSES : On a thin epoxy overlay pavement, epoxy is placed on the existing bridge deck pavement, followed by the spraying of aggregates on it. The bond strength between the existing pavement and overlay pavement is an important factor representing the performance of the thin epoxy overlay pavement, in addition to the skid resistance and roughness. Therefore, the bond strength, skid resistance, and roughness of a thin epoxy overlay pavement constructed for field tests under various field conditions are examined in this study. METHODS : The usability of epoxy and aggregates on a thin epoxy overlay pavement is identified by testing their material properties in a laboratory. A construction test is performed using the pretreatment conditions of the existing pavement surface and the number of layers of overlay pavement as variables. The bond strength, skid resistance, and roughness are analyzed 3 d after constructing the test pavement, and immediately before and after applying repetitive traffic loadings at 6 months. RESULTS : When the existing pavement is in good condition, as in this study, the bond strength of the thin epoxy overlay pavement is affected more significantly by the existing pavement condition than the material properties of epoxy, in which destruction is indicated in the existing pavement. The skid resistance is affected primarily by the condition of the aggregates sprayed on the epoxy. The pavement on which the aggregates are well sprayed indicate a high skid resistance. The roughness is not affected by any variables, such as the pretreatment conditions, number of thin pavement layers, and repetitive traffic loadings. CONCLUSIONS : A long-term evaluation of the bond strength, skid resistance, and roughness will be conducted on a test pavement. In addition, another construction test will be performed to investigate the performance of a thin epoxy pavement overlaid on a bridge deck pavement under inferior conditions.
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시공 중인 시멘트 콘크리트 포장의 프로파일 측정 및 보정방법 개발
최문규,김동혁,김진수,나계주,정진훈 한국도로학회 2021 한국도로학회논문집 Vol.23 No.5
PURPOSES : For high driving performance and service life of cement concrete pavement, construction quality must be secured. The construction quality is to be measured after pavement construction, but in this case, it is difficult to improve construction quality. Therefore, it is necessary to develop a method for measuring and correcting the profile of the pavement and subbase so that the construction quality can be monitored immediately after construction. METHODS : The device that can measure the construction quality of cement concrete pavement has been developed. Through the experiment simulating the field situation, the profile of the pavement and subbase was measured and calibration method was developed. RESULTS : In the measured profile, an outlier by the sensor and noise by the sensor and vibration were measured, and a step-like profile was measured differently from the acture one. To remove outliers, the boxplot outlier removal method was applied by overlapping each data group. The noise were removed by a low pass filtering. And, it was calibrated to a profile similar to the acture one through the sampling interval adjustment and the weighted moving average method. CONCLUSIONS : The method that can measure and calibrate the profile that is almost identical to the actual one has been developed. Accordingly, it is expected that the performance of the pavement can be improved by accurately monitoring the construction quality immediately after construction.
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