• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.966-973
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• 2005

The stress concentration ratio in accordance with area replacement ratios were considered as core elements of design. However, the stress concentration ratio will be vary depends on progress of consolidation in clay ground. And, since it is not sure to know the affecting factors accurately, the value is decided based on field experiences. To use SCP method more effective and correspond to soil improvement, the decision on proper area replacement ratio through the exact stress concentration ratio is very important. Accordingly, a numerical analysis on influence of various factors that needed to make rational designing guide for decision of proper area replacement ratio to stress concentration ratio was executed in this study.

• 한국해양공학회지
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• 제16권1호
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• pp.46-51
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• 2002

Fatigue life estimation by the theoretical stress concentration factors are, in general, considerably different from test results. And in calculating stress concentration factor, it is very difficult to consider actual geometry and material property which are the notch shapes, imperfections or defects of materials such as porosities inclusions and casting defects, etc. Therefore, the paper deals with the experimental method to find out the more exact stress concentration factors by measuring the strain distributions on each specimen by 3D-ESPI(Electronic Speckle Pattern Interferometry) System. Then the fatigue lives are compared between theoretical calculations using stress concentration factors determined by 3D-ESPI system and fatigue test results.

• 한국멀티미디어학회논문지
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• 제24권10호
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• pp.1414-1424
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• 2021

In this paper, the importance of input factors of a DNN (Deep Neural Network) PM_2.5 forecasting model using LRP(Layer-wise Relevance Propagation) is analyzed, and forecasting performance is improved. Input factor importance analysis is performed by dividing the learning data into time and PM_2.5 concentration. As a result, in the low concentration patterns, the importance of weather factors such as temperature, atmospheric pressure, and solar radiation is high, and in the high concentration patterns, the importance of air quality factors such as PM_2.5, CO, and NO₂ is high. As a result of analysis by time, the importance of the measurement factors is high in the case of the forecast for the day, and the importance of the forecast factors increases in the forecast for tomorrow and the day after tomorrow. In addition, date, temperature, humidity, and atmospheric pressure all show high importance regardless of time and concentration. Based on the importance of these factors, the LRP_DNN prediction model is developed. As a result, the ACC(accuracy) and POD(probability of detection) are improved by up to 5%, and the FAR(false alarm rate) is improved by up to 9% compared to the previous DNN model.

• 한국환경과학회지
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• 제9권5호
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• pp.429-436
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• 2000

In order to study on the variational characteristics of water quality and chlorolphyll a concentration the water samples were collected daily or three times a week during the period from April 1990 to November 1991 at Kukdong port located in the northern Kamak bay of Southern Korea I made an analysis on biological factor as chlorophyll a concentration as well as physico-chemical factors such as water temperature salinity sigma-t dissolved oxygen, nutrients (ammonia, nitrite, nitrate, phosphate, and silicate) N/P ratio and chemical oxygen demand. In Northern Kamak bay seasonal variations in physical factors such as water temperature salinity and sigma-t were very marked. On the other hand chemical factors such as nutrients concentration and COD were not so. Chemical factors, in particular silicate were influenced by input of freshwater. And the roles of silicate on the seasonal succession of phytoplankton species composition was very low. Phytoplankton biomass as measured by chlorophyll a concentration was very high all the year round and it was controlled by the combination of several factors especially of N/P ratio determined by dissolved inorganic nitrogen.

• 환경위생공학
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• 제13권2호
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• pp.128-138
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• 1998

This study was focused to find how each factors effect on the biological nitrification in wastewater treatment under high ammonia nitrogen concentration. Batch reactors in aerobic conditions were used to test the treatment efficiency of mixed liquor, nightsoil and piggery wastewater. The results are summeried as follows; Initial ammonia nitrogen concentration and pH were the direct influencing factors of nitrite build-up. More than 250 mg NH$_{4}$$^{+}$ - N/L in initial concentration built up nitrite and then the inhibition rate to Nitrobacter was above 70 percentage. And maximum nitritation rate was showed at pH 8.3 and nitrification could be completely achieved by pH control. Temperature and dissolved oxygen were the indirect influencing factors of nitrite build-up. These were a great effect on the activity of nitrifying microbes and ammonia nitrogen removal. Maximum nitritation rate was showed at 30 $\circ $C. The effect of DO concentration was negligible at more than 3 mg/L.

• 대한기계학회논문집A
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• 제28권7호
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• pp.1014-1020
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• 2004

The present work complies the elastic stress concentration factor for a pipe with local wall thinning, based on detailed three-dimensional elastic FE analysis. To cover practically interesting cases, a wide range of pipe and defect geometries are considered, and both internal pressure and global bending are considered. Resulting values of stress concentration factors are tabulated for practical use, and the effect of relevant parameters such as pipe and defect geometries on stress concentration factors are discussed. The present results would provide valuable information to estimate fatigue damage of the pipe with local wall thinning under high cycle fatigue.

• Communications for Statistical Applications and Methods
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• 제30권5호
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• pp.517-530
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• 2023

Recent studies revealed that fine dust in ambient air may cause various health problems such as respiratory diseases and cancer. To prevent the toxic effects of fine dust, it is important to predict the concentration of fine dust in advance and to identify factors that are closely related to fine dust. In this study, we developed a Bayesian network model for predicting PM10 concentration in Seoul, Korea, and visualized the relationship between important factors. The network was trained by using air quality and meteorological data collected in Seoul between 2018 and 2021. The study results showed that current PM10 concentration, season, carbon monoxide (CO) were the top 3 effective factors in 24 hours ahead prediction of PM10 concentration in Seoul, and that there were interactive effects.

• 대한기계학회논문집A
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• 제40권5호
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• pp.513-523
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• 2016

단순보와 외팔보의 U-노치 및 균열에 대한 응력집중계수 및 응력확대계수를 유한요소법 및 광탄성실험에 의해 해석하였다. 해석결과를 사용하여 응력집중계수 및 응력확대계수의 추정 그래프를 얻었다. 노치의 응력집중계수해석을 위하여 무차원 노치 길이 H(시편의 높이)/h=1.1~2, 무차원 틈 간격 r(노치선단의 반경)/h=0.1~0.5로 하였다. 여기서 h=H-c, c=노치길이이다. 해석결과 틈 길이가 증가할수록 그리고 틈 간격이 좁아질수록 응력집중계수는 증가 한다. 응력집중계수는 단순보가 외팔보다 더 크게 나타나나, 실제 일정한 하중과 노치길이 및 틈 간격 하에서 최대 응력값은 단순보보다 외팔보에서 크게 발생함을 알 수 있었다. 균열해석을 위하여 무차원 균열길이 a(균열길이)/H=0.2~0.5로 하였다. 균열의 길이가 증가 할수록 무차원 응력확대계수는 증가한다. 일정한 하중과 일정한 균열길이하에 응력확대계수값은 단순보 보다 외팔보에서 크게 발생함을 알 수 있었다.

• Journal of Preventive Medicine and Public Health
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• 제27권3호
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• pp.505-516
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• 1994

For the purpose of preparing the fundamental data on air pollution in underground shopping center and also contributing to the health improvement of residents, the authors measured the level of $SO_2,\;NO_2,\;TSP,\;CO,\;CO_2$ and also some related factors as air temperature, air movement, relative humidity and mean radiation temperature at inside and outside of underground shopping center in Pusan from January to February and from July to August 1994. The results were as follows : 1. The mean concentration of CO within the underground shopping center was $3.1{\pm}1.3ppm$ in winter and $2.1{\pm}0.9ppm$ in summer. There was a negative correlation (p<0.01) between inner CO concentration and temperature in summer and no correlation between inner CO concentration and outer CO concentration in underground shopping center 2. The mean concentration of COE within the underground shopping center was $876{\pm}353ppm$ in winter and $757{\pm}125ppm$ in summer. There was a negative correlation (p<0.01) between inner $CO_2$ concentration and air movement in summer and positive correlation (p<0.05) between inner $CO_2$ concentration and outer $CO_2$ concentration in underground shopping center. 3. The mean concentration of $SO_2$ within a underground shopping center was $0.036{\pm}0.019ppm$ in winter and $0.040{\pm}0.013ppm$ in summer. There was a positive correlation(p<0.01) between inner $SO_2$ concentration and temperature in summer and positive correlation between inner $SO_2$ concentration and outer $SO_2$ concentration in summer and winter in underground shopping center. 4. The mean concentration of $NO_2$ within a underground shopping center was $0.052{\pm}0.038ppm$ in winter and $0.042{\pm}0.016ppm$ in summer. There was a no correlation between inner $SO_2$ concentration and thermal factors in summer and winter and low correlation between inner $SO_2$ concentration and outer $SO_2$ concentration in underground shopping center 5. The mean concentration of TSP within a underground shopping center was $430{\pm}214{\mu}g/m^3$ in winter, $366{\pm}73{\mu}g/m^3$ in summer, and very in excess of the atmospheric environmental quality standards of Korea ($150{\mu}g/m3{\downarrow}$). There was low correlation between inner TSP concentration and temperature in summer and high correlation between inner TSP concentration and outer TSP concentration in underground shopping center.

• 동력기계공학회지
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• 제11권4호
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• pp.44-49
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• 2007

Generally, the economic concept of optimized design and operating conditions in fluidized bed heat exchangers can hardly be realized. Because the lack of fundamental knowledge about the particle flows, the optimum design of the fluidized bed heat exchanger is rather limited. In the present work, measurements are made on pressure drops and friction factors in the horizontal circular tube with solid particles in the circulating water. Two different solid particles of diameters of 3mm and 4mm are covered. The Reynolds numbers are ranged from 10,000 to 45,000. It is concluded that the friction factors for the particles of 4mm diameter are much higher than those for the particles of 3mm diameter. And at the lower particle concentration, the friction factors are strongly influenced by the fluid velocity rather than the particle concentration; However, the effect of the particle concentration on friction factors is also significantly higher at a higher particle concentration operating condition.