• Tunnel and Underground Space
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• v.34 no.5
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• pp.599-618
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• 2024

This study investigated the effects of microwave irradiation on the physical properties of basalt to explore its potential as an efficient technique for lunar surface and deep excavation. Experiments were conducted to measure changes in P-wave velocity, Leeb hardness, Schmidt hammer rebound hardness, Cerchar Abrasivity Index (CAI), Uniaxial compressive strength (UCS), Young's modulus, and temperature of basalt specimens according to microwave irradiation time. Results showed that microwave irradiation induced microcracks in basalt and reduced its physical strength. Notably, after 5 minutes of microwave irradiation, UCS and Young's modulus decreased significantly. P-wave velocity also decreased markedly with increased irradiation time, indicating internal structural weakening of the rock. This is primarily attributed to thermal stress induced by microwave penetration into the rock and crack propagation due to differential thermal expansion between minerals. By confirming the rock weakening effect of microwave irradiation under conditions similar to the lunar environment, this study suggests the possibility of greatly improving the efficiency of lunar surface and deep excavation operations.

• Journal of the East Asian Society of Dietary Life
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• v.23 no.3
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• pp.297-310
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• 2013

This study was performed to investigate relationships among night eating and nutrient intakes status in university students. A total of 271 subjects (male=155, female=116) were divided by using 3-days food record method according to the percentage of energy from night eating: non-night eating, <25% night-eating and ${\geq}25$ night-eating group. There were no significant differences in age, height, weight, percent body fat and BMI among the groups. The proportion of morning anorexia and insomnia was below 2% and 10%, and no differences were observed among the groups by percentage of energy from night eating. In the male subjects, the intakes of energy in the '${\geq}25$ night-eating group' was significantly higher than those of the other groups; whereas, the nutrient density (ND, nutrient intakes per 1,000 kcal) and INQ (index of nutritional quality) of vitamin $B_1$, vitamin $B_2$, vitamin C, calcium and iron in the '${\geq}25$ night-eating group' was significantly lower than those of the other groups. In the female subjects, the intakes of energy in the '<25 night-eating group' was significantly higher than that of the 'non-night eating group'. And the ND and INQ of vitamin C in the '<25 night-eating group' was significantly higher than those of the 'non-night eating group'. In addition, within the male subjects, the INQ of vitamin $B_1$, vitamin $B_2$, vitamin C, calcium and phosphorous showed significantly negative correlations with food intakes, energy intakes and percentages of energy from night eating after the values were adjusted for age. These results suggest that among male university students, night snack intakes above 25% of energy have lower micronutrient qualities of vitamin $B_1$, vitamin $B_2$, vitamin C and calcium.

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.3
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• pp.202-210
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• 2013

As incomes increase, interest in ocean leisure picks up. As a result, a lot of research and developments on hull form design and production of planing boats, mostly used for ocean leisure, are needed. Analysis in researches on resistance of planing boats shows that resistance characteristic of planing boats is different from resistance characteristic of general boats because the former is fast, and its wetted surface is very small. Using Savitsky formula widely used in the calculation of effective horse power in shipbuildingyards, and propulsion system and engine manufacturers, this study calculated total resistance of a research planing boat. Then it analyzed the flow characteristics of the planing boat through theoretical analysis and wind tunnel experiment, and computed air resistance and lift force by changes of speed and trim angle. It also compared and analyzed result of theoretical analysis and experiment of the ratio of air resistance to total resistance under variations of velocity and trim angle. When the study is used to estimate more accurate effective horse power, it is expected to remedy abuses of unnecessarily installing high-powered engine. As nature disasters due to abnormal changes of weather increase, interest in greenhouse gas grows. International Maritime Organization (IMO) legislated Energy Efficiency Design Index (EEDI) and Energy Efficiency Operational Indicator (EEOI) to reduce ship greenhouse gas emissions. But this index will be applied to over 400 tons ships, small ships, emitting more greenhouse gases than larege ships per unit power, will dodge the regulations. Thus, this study indicated a problem by calculating greenhouse gas emissions of an ocean leisure planning boat (a small ship), and suggested the need for EEDI of small ships.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.42 no.2
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• pp.103-109
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• 2016

Efficacy of cosmetics has been mainly evaluated by qualitative and quantitative methods based on visual sense, tactile sense and skin structure until now. In this study, we suggested a novel evaluation method for skin status based on sound; measuring and analyzing the rubbing noise generated by applying cosmetics. First, the rubbing noise was measured at a close range by a high-sensitivity microphone in anechoic environment, and the noises were analyzed by 1/3 octave band analysis in frequency-domain. Three conditions, 1) before washing, 2) after washing and 3) after application of cosmetics, were compared. As a result, sound pressure level (SPL) of rubbing noise after washing was larger than that of before washing, and the SPL of rubbing noise after cosmetic application was the smallest. Furthermore, the energy of rubbing noise after application was higher than that of the before and after washing conditions in a low frequency band (lower than 2 kHz region). Conversely, the energy of rubbing noise after application was much lower than the others in a high-frequency band (upper than 2 kHz region). This change of energy distribution was described as a balloon-skin model. High SPL in the low frequency region after the cosmetic applications was due to the increase of "flexibility index", while SPL in the high frequency region significantly decreased because of the attenuation which is related to "softness index". Therefore, we developed two indices based on the spectrum-energy difference for evaluating skin conditions. This proposed method and indices were verified via skin flexibility and roughness measurement using cutometer and primos respectively. These results suggest that acoustic measurement of skin friction noise may be a new skin status evaluation method.

• The Journal of Korean Society for Radiation Therapy
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• v.30 no.1_2
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• pp.9-16
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• 2018

Purpose : Brain Stereotactic Radiosurgery can treat non-invasive diseases with high rates of complications due to surgical operations. However, brain stereotactic radiosurgery may be accompanied by radiation induced side effects such as fractionation radiation therapy because it uses radiation. The effects of Coplanar Volumetric Modulated Arc Therapy(C-VMAT) and Non-Coplanar Volumetric Modulated Arc Therapy(NC-VMAT) on surrounding normal tissues were analyzed in order to reduce the side effects caused fractionation radiation therapy such as head and neck. But, brain stereotactic radiosurgery these contents were not analyzed. In this study, we evaluated the usefulness of NC-VMAT by comparing and analyzing C-VMAT and NC-VMAT in patients who underwent brain stereotactic radiosurgery. Methods and materials : With C-VMAT and NC-VMAT, 13 treatment plans for brain stereotactic radiosurgery were established. The Planning Target Volume ranged from a minimum of 0.78 cc to a maximum of 12.26 cc, Prescription doses were prescribed between 15 and 24 Gy. Treatment machine was TrueBeam STx (Varian Medical Systems, USA). The energy used in the treatment plan was 6 MV Flattening Filter Free (6FFF) X-ray. The C-VMAT treatment plan used a half 2 arc or full 2 arc treatment plan, and the NC-VMAT treatment plan used 3 to 7 Arc 40 to 190 degrees. The angle of the couch was planned to be 3-7 angles. Results : The mean value of the maximum dose was $105.1{\pm}1.37%$ in C-VMAT and $105.8{\pm}1.71%$ in NC-VMAT. Conformity index of C-VMAT was $1.08{\pm}0.08$ and homogeneity index was $1.03{\pm}0.01$. Conformity index of NC-VMAT was $1.17{\pm}0.1$ and homogeneity index was $1.04{\pm}0.01$. $V_2$, $V_8$, $V_{12}$, $V_{18}$, $V_{24}$ of the brain were $176{\pm}149.36cc$, $31.50{\pm}25.03cc$, $16.53{\pm}12.63cc$, $8.60{\pm}6.87cc$ and $4.03{\pm}3.43cc$ in the C-VMAT and $135.55{\pm}115.93cc$, $24.34{\pm}17.68cc$, $14.74{\pm}10.97cc$, $8.55{\pm}6.79cc$, $4.23{\pm}3.48cc$. Conclusions : The maximum dose, conformity index, and homogeneity index showed no significant difference between C-VMAT and NC-VMAT. $V_2$ to $V_{18}$ of the brain showed a difference of at least 0.5 % to 48 %. $V_{19}$ to $V_{24}$ of the brain showed a difference of at least 0.4 % to 4.8 %. When we compare the mean value of $V_{12}$ that Radione-crosis begins to generate, NC-VMAT has about 12.2 % less amount than C-VMAT. These results suggest that if NC-VMAT is used, the volume of $V_2$ to $V_{18}$ can be reduced, which can reduce Radionecrosis.

• Journal of Intelligence and Information Systems
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• v.23 no.4
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• pp.127-146
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• 2017

Services using artificial intelligence have begun to emerge in daily life. Artificial intelligence is applied to products in consumer electronics and communications such as artificial intelligence refrigerators and speakers. In the financial sector, using Kensho's artificial intelligence technology, the process of the stock trading system in Goldman Sachs was improved. For example, two stock traders could handle the work of 600 stock traders and the analytical work for 15 people for 4weeks could be processed in 5 minutes. Especially, big data analysis through machine learning among artificial intelligence fields is actively applied throughout the financial industry. The stock market analysis and investment modeling through machine learning theory are also actively studied. The limits of linearity problem existing in financial time series studies are overcome by using machine learning theory such as artificial intelligence prediction model. The study of quantitative financial data based on the past stock market-related numerical data is widely performed using artificial intelligence to forecast future movements of stock price or indices. Various other studies have been conducted to predict the future direction of the market or the stock price of companies by learning based on a large amount of text data such as various news and comments related to the stock market. Investing on commodity asset, one of alternative assets, is usually used for enhancing the stability and safety of traditional stock and bond asset portfolio. There are relatively few researches on the investment model about commodity asset than mainstream assets like equity and bond. Recently machine learning techniques are widely applied on financial world, especially on stock and bond investment model and it makes better trading model on this field and makes the change on the whole financial area. In this study we made investment model using Support Vector Machine among the machine learning models. There are some researches on commodity asset focusing on the price prediction of the specific commodity but it is hard to find the researches about investment model of commodity as asset allocation using machine learning model. We propose a method of forecasting four major commodity indices, portfolio made of commodity futures, and individual commodity futures, using SVM model. The four major commodity indices are Goldman Sachs Commodity Index(GSCI), Dow Jones UBS Commodity Index(DJUI), Thomson Reuters/Core Commodity CRB Index(TRCI), and Rogers International Commodity Index(RI). We selected each two individual futures among three sectors as energy, agriculture, and metals that are actively traded on CME market and have enough liquidity. They are Crude Oil, Natural Gas, Corn, Wheat, Gold and Silver Futures. We made the equally weighted portfolio with six commodity futures for comparing with other commodity indices. We set the 19 macroeconomic indicators including stock market indices, exports & imports trade data, labor market data, and composite leading indicators as the input data of the model because commodity asset is very closely related with the macroeconomic activities. They are 14 US economic indicators, two Chinese economic indicators and two Korean economic indicators. Data period is from January 1990 to May 2017. We set the former 195 monthly data as training data and the latter 125 monthly data as test data. In this study, we verified that the performance of the equally weighted commodity futures portfolio rebalanced by the SVM model is better than that of other commodity indices. The prediction accuracy of the model for the commodity indices does not exceed 50% regardless of the SVM kernel function. On the other hand, the prediction accuracy of equally weighted commodity futures portfolio is 53%. The prediction accuracy of the individual commodity futures model is better than that of commodity indices model especially in agriculture and metal sectors. The individual commodity futures portfolio excluding the energy sector has outperformed the three sectors covered by individual commodity futures portfolio. In order to verify the validity of the model, it is judged that the analysis results should be similar despite variations in data period. So we also examined the odd numbered year data as training data and the even numbered year data as test data and we confirmed that the analysis results are similar. As a result, when we allocate commodity assets to traditional portfolio composed of stock, bond, and cash, we can get more effective investment performance not by investing commodity indices but by investing commodity futures. Especially we can get better performance by rebalanced commodity futures portfolio designed by SVM model.

• Journal of Nutrition and Health
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• v.48 no.1
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• pp.46-57
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• 2015

Purpose: The aim of this study was to determine an appropriate energy level of breakfast with less risk of chronic disease for Korean adults. Methods: Using data from the 2007~2009 Korean National Health & Nutrition Examination Survey, from a total of 12,238 adults aged 19~64, the final 7,769 subjects were analyzed except subjects who were undergoing treatment for cancer or metabolic disorder. According to the percent of breakfast energy intake versus their estimated energy requirement (EER), the subjects were divided into four groups: < 10% (very low, VL), 10~20% (low, L), 20~30% (moderate, M), ${\geq}30%$ (sufficient, S). All data were analyzed on the metabolic risk and nutritional state after application of weighted value and adjustment of sex, age, residential area, income, education, job or jobless, and energy intake using a general linear model or logistic regression. Results: The subjects of group S were 16.9% of total subjects, group M 39.2%, group L 37.6%, and group VL 6.3%. The VL group included more male subjects, younger-aged (19 to 40 years), urban residents, higher income, higher education, and fewer breakfasts eaters together with family members. Among the 4 groups, the VL group showed the highest waist circumference, while the S group showed the lowest waist circumference, body mass index, and serum total cholesterol. The groups of VL and L with lower intake of breakfast energy showed high percent of energy from protein and fat, and low percent of energy from carbohydrate. With the increase of breakfast energy level, intake of energy, most nutrients and food groups increased, and the percentage of subjects consuming nutrients below EAR decreased. The VL group showed relatively higher intake of snacks, sugar, meat and eggs, oil, and seasonings, and the lowest intake of vegetable. Risk of obesity by waist circumference was highest in the VL group by 1.90 times of the S group and the same trend was shown in obesity by BMI. Risk of dyslipidemia by serum total cholesterol was 1.84 times higher in the VL group compared to the S group. Risk of diabetes by Glu-FBS (fasting blood sugar) was 1.57 times higher in the VL group compared to the S group. Conclusion: The results indicate that higher breakfast energy level is positively related to lower metabolic risk and more desirable nutritional state in Korean adults. Therefore, breakfast energy intake more than 30% of their own EER would be highly recommended for Korean adults.

• Journal of Nutrition and Health
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• v.24 no.3
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• pp.157-165
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• 1991

The purpose of this study was to investigate differences in body fat distribution between normal and obese subjects and the relationship between risk factors(fasting blood sugar, blood pressure. fasting serum lipids) and obesity. Measurements of height. weight, skinfold thickness. body circumference. percent body fat. blood pressure, fasting blood sugar and serum lipids were made and a dietary survey was performed on 120(Males 61. Females 59) adult subjects. 1) Among the female subjects, the obese group appeared to have significantly higher centrality of body fat than the normal group. Obese groups of both sexes appeared with higher blood pressure than normal groups. No differences in daily average nutrient intake, fasting blood sugar and fasting serum lipids concentrations were observed between obese and normal groups. 2) In males. the serum triglyceride concentration was observed to have a significantly positive correlation to body weight, body mass index and body circumference, additionally concentrations of total cholesterol and LDL-cholesterol were observed to have significantly positive correlations to the skinfold thickness. but the ratio of HDL-cholesterol/total cholesterol was observed to be significantly negatively correlated to the skinfold thickness. 3) In females. the obese group consumed about 47% of total energy intake at lunch. whereas the normal group consumed about 29% . The food habit score of males appeared to be negatively related to body weight, percent ideal body weight. But the food habit score of females appeared to be negatively related to percent body fat(r=-0.32, p<0.05) .

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.56.1-56.1
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• 2010

결정질 실리콘 태양전지의 표면 ARC(Anti-reflection Coating)layer는 반사도를 줄여 광 흡수율을 증가시키고, passivation 효과를 통하여 표면 재결합을 감소 시켜 태양전지의 효율을 높이는 중요한 역할을 한다. Silicon nitride 박막은 외부 stress 요인에 대해 안정성을 담보할 수 있어야한다. 따라서, 본 연구에서는 굴절률 가변에 따른 silicon nitride 박막을 PECVD를 이용하여 증착하고, 항온/항습 stability test를 통해 박막의 안정성을 확인하였다. Silicon nitride 증착을 위해 PECVD를 이용하였고, 공정압력 0.8Torr, 증착온도 $450^{\circ}C$, 증착파워 300W에서 실험을 진행하였다 박막의 굴절률은 1.9~2.3의 범위로 가변하였다. 항온/항습에 대한 신뢰성을 test 하기 위하여 5시간동안의 test를 1cycle로 하여 20회 동안 실험을 실시하였다. 증착된 silicon nitride 박막의 lifetime은 firing 이후 57.8us로 가장 높았으며, 항온/항습 test 이후에도 유사한 경향을 확인 할 수 있었다. 또한, 100h 동안의 항온/항습 test 결과 silicon nitride 박막의 lifetme 감소는 8.5%에 불과했다. 본 연구를 통하여 온도와 습도의 변화에 따른 결정질 실리콘 태양전지의 SiNx 박막의 증착 공정 조건에 대한 신뢰성을 확인 할 수 있었다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.197-202
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• 2008

In this paper, a hybrid vibration-impedance approaches is newly proposed to detect the occurrence of damage, the location of damage, and extent of damage in steel plate-girder bridges. The hybrid scheme mainly consists of three sequential phases: 1) to alarm the occurrence of damage, 2) to classify the alarmed damage, and 3) to estimate the classified damage in detail. Damage types of interest include flexural stiffness-loss in girder and bolts-loose in supports. In the first phase, the global occurrence of damage is alarmed by monitoring changes in acceleration features. In the second phase, the alarmed damage is classified into subsystems by recognizing patterns of impedance features. In the final phase, the location and the extent of damage are estimated by using modal strain energy-based damage index method and root mean square deviation method. The feasibility of the proposed system is evaluated on a laboratory-scaled steel plate-girder bridge model for which hybrid vibration-impedance signatures were measured for several damage scenarios.