• 전자공학회논문지
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• 제51권11호
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• pp.33-39
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• 2014

본 논문에서는 다중 사용자 다중 안테나 하향링크 시스템에서 maximal ratio transmission (MRT) 기법 사용 시, 에너지 효율을 최대화하는 최적의 송신 안테나 수에 대해 알아본다. Full channel state information at the transmitter (CSIT) 환경에서 평균 채널 이득, 각 단말 간 채널 독립성, 평균 path loss를 사용하여 최적화 식을 근사하고 편미분을 이용하여 closed form으로 최적의 송신 안테나 수를 구한다. 또한 limited feedback 환경에서는 동일한 방법으로 근사한 목적함수에 대하여 bisection method를 이용하여 최적의 송신 안테나 수를 찾는다. 모의실험 결과를 통해, 구해진 최적의 송신안테나 수가 exhaustive search로 찾은 최적의 송신안테나 수에 비해 오차가 크지 않음을 확인하고, 단말의 피드백 비트 수가 최적의 송신 안테나 수에 미치는 영향을 분석한다.

• 한국경영과학회지
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• 제32권4호
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• pp.89-99
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• 2007

In this paper, an analytic model of a sleep mode operation in the IEEE 802.16e is investigated. A mobile subscriber station(MSS) goes to sleep mode after negotiations with the base station(BS) and wakes up periodically for a short interval to check whether there is downlink traffic to it. If the arrival of traffic is notified, an MSS returns to wake mode. Otherwise, it again enters increased sleep interval which is double as the previous one. In order to consider the situation more practically, we propose the sleep mode starting threshold, during which MSS should await packets before it enters the sleep mode. By modifying the M/G/l with multiple vacations model, energy consumption ratio(ECR) and average packet response time are calculated. Our analytic model provides potential guidance in determining the optimal parameters values such as sleep mode starting threshold, minimal sleep and maximal sleep window.

• 대한의용생체공학회:의공학회지
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• 제27권6호
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• pp.301-309
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• 2006

The main purpose of this study is to derive a regression equation that predicts the individual differences in activity energy expenditure (AEE) using accelerometer during different types of activity. Two subject groups were recruited separately in time: One is a homogeneous group of 94 healthy young adults with age ranged from $20\sim35$ yrs. The other subject group has a broad spectrum of physical characteristics in terms of age and fat ratio. 226 adolescents and adults of age ranged from $12\sim57$ yrs and fat ratio from $4.1\sim39.7%$ were in the second group. The wireless 3-axis accelerometers were developed and carefully fixed at the waist belt level. Simultaneously the total calorie expenditure was measured by gas analyzer. Each subject performed walking and running at speeds of 1.5, 3.0, 4.5, 6.0, 6.5, 7.5, and 8.5 km/hr. A generalized sensor-independent regression equation for AEE was derived. The regression equation was developed fur walking and running. The regression coefficients were predicted as functions of physical factors-age, gender, height, and weight with multivariable regression analysis. The generalized calorie estimation equation predicts AEE with correlation coefficient of 0.96 and the average accuracy of the accumulated calorie was $89.6{\pm}7.9%$.

• 신재생에너지
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• 제5권2호
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• pp.9-14
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• 2009

Automobile Shredder Residue (ASR) is very appropriate in a gasification melting system. Gasification melting system, because of high reaction temperature over than $1,350^{\circ}C$, can reduce harmful materials. To use the gasification processes for hydrogen production, the high concentration of CO in syngas must be converted into hydrogen gas by using water gas shift reaction. In this study, the characteristics of shift reaction of the high temperature catalyst (KATALCO 71-5M) and the low temperature catalyst (KATALCO 83-3X) in the fixed - bed reactor has been determined by using simulation gas which is equal with the syngas composition of gasification melting process. The carbon monoxide composition has been decreased as the WGS reaction temperature has increased. And the occurrence quantity of the hydrogen and the carbon dioxide increased. When using the high temperature catalyst, the carbon monoxide conversion ratio ($1-CO_{out}/CO_{in}$) rose up to 95.8 from 55.6. Compared with average conversion ratio from the identical synthesis gas composition, the low temperature catalyst was better than the high temperature catalyst.

• Steel and Composite Structures
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• 제36권3호
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• pp.339-353
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• 2020

This study investigates the seismic performance of steel reinforced concrete (SRC) T-shaped columns under low cyclic loading tests. Based on test results of ten half-scale column specimens, failure patterns, hysteretic behavior, skeleton curves, ultimate strength, ductility, stiffness degradation and energy dissipation capacity were analyzed. The main variables included loading angles, axial compression ratios and steel ratios. The test results show that the average values of the ductility factor and the equivalent viscous damping coefficient with respect to the failure of the columns were 5.23 and 0.373, respectively, reflecting good seismic performance. The ductility decreased and the initial stiffness increased as the axial compression ratio of the columns increased. The strength increased with increasing steel ratio, as expected. The columns displaced along the web had higher strength and initial stiffness, while the columns displaced along the flange had better ductility and energy dissipation capacity. Based on the test and analysis results, a formula is proposed to calculate the effective stiffness of SRC T-shaped columns.

• 한국태양에너지학회 논문집
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• 제36권5호
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• pp.1-8
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• 2016

In this paper, we evaluated the effect of a silica-based Anti-Reflection(AR) coating for PV modules. The coating technique can be easily applied to large-scale PV modules at room temperature with improvements of the optical properties that is qualified by the optical transmission measurements on the coated cover glass of the modules. The power improvement of the large-scale PV modules shows the increasing about 2.4% at standard condition of the coating technique on average. To improve the AR coating effect of the PV modules, we have characterized the individual PV modules by the measurements of DC power output, modified performance ratio(PRm) and the regression. The results show that the significant improvements of the AR coating effect are 6.4%, 5.5% and 4.5% of increasing of the performances by using the measurements of DC power output, modified performance ratio(PRm) and the regression, respectively.

• The Korean Journal of Ecology
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• 제23권1호
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• pp.39-43
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• 2000

1996년 7월 하순부터 9월 하순에 걸쳐 동경농공대학 농학부 부속부중농장(동경도 부중시)의 대두(Glycine max)개체군을 대상으로 미기상학적 플럭스측정방법의 하나인 열수지법을 이용하여 CO₂ 플럭스와 O₃ 플럭스를 측정하였다. CO₂ 플럭스와 O₃ 플럭스는 엽면적지수(LAI)의 변화에 영향을 받았으며, LAI가 2.0이상일 경우 CO₂ 플럭스는 광합성유효발사량(PAR)과 정비례관계가 있었다. O₃ 플럭스는 측정 기간 중 항상 양의 수치를 나타냈으며, 평균치는 0.5 mol m/sup -2/S/sup -1/이었다. 또한 CO₂와 O₃ 침착속도사이에는 정비례관계가 있었다 (LAI>2.0).

• 동아시아식생활학회지
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• 제17권2호
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• pp.192-197
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• 2007

The purpose of this study was to evaluate the energy intake and energy expenditure of obese children. The body weight and height were measured, and the daily energy intake and activity pattern assessed for one day, using the 24 hour recall method and interviews in 83 elementary school children (59 boys and 24 girls). The average age, height, weight, ideal body weight and obesity index in boys and girls were 11.8 years, 144.8 cm, 54.2 kg, 39.9 kg and 35.9% and 11.5 years, 140.8 cm, 48.9 kg, 36.9 kg and 33.7%, respectively. The mean daily energy intakes of boys and girls were 1,670.5 and 1,656.5 kcal; these being 76.4 and 88.5% of estimated energy requirement for Koreans, respectively. The energy intake ratio from carbohydrates, proteins and fats in boys and girls were 61.5:14.7:23.6 and 62.0:14.7:23.7, respectively. The resting energy expenditure, as estimated by the Harris-Benedict, WHO/NAO/FAO and Korean DRI formulae in boys and girls were 1,452.7, 1,239.2 and 1,629.2 kcal and 1,323.9, 1,156.0 and 1,252.4 kcal, respectively. The activity coefficient for both the boys and girls was 1.39. The daily energy expenditure of boys (1,990.7 kcal) was significantly higher than that of girls (1712.1 kcal). No significant correlations were found between the obesity index, energy intake and energy expenditure. These results suggested that a nutrition and exercise program is required to increase the energy expenditure of elementary school children. Further research will be needed to assess multiple dietary factors and dove]lop a standard method for assessing the energy expenditure of obese children.

• Journal of Nutrition and Health
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• 제36권6호
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• pp.635-645
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• 2003

This study was conducted to investigate the effects of smoking on nutrient intake and blood mineral status. The subjects were composed of two groups.55 smokers and 52 non-smokers. A 24-hour recall method was used along with questionnaires and serum mineral levels were analyzed by ICP spectrometer. The average ages of the smokers and non-smokers were 55.5 and 59.3 years old, respectively. The height, obesity degree, BMI, and WHR of the smokers were significantly higher than those of the non-smokers (p < 0.05, p < 0.05, p < 0.05, p < 0.01) Approximately 45.5% of the smokers smoked 16-20 cigarettes per day. The average age that the smokers started smoking was 22.0 years old and their smoking history was 33.5 years. About 74.5% of the smokers drank alcoholic beverages, while 44.2% of the non-smokers did. The smokers tended to eat less meals and breakfast meal, but drink coffee more often compared to the non-smokers. The mean daily energy intake and CPF energy intake ratio were 1231.8 ㎉ and 69.8 : 14.8 : 14.7 in the smokers and 1210.2 ㎉ and 72.1 : 14.7 12.7 in the non-smokers, respectively. The results show that the smokers tended to consume more energy, lipid, and cholesterol compared to the non-smokers. The results also show that in both groups, nutrient intake was lower than the RDA. The two groups were not significantly different in terms of the intake frequency of green-yellow vegetables and fresh fruits. There were no significant differences in serum levels of Ca, P, Mg, Cu, Fe, Mn, and Zn. However, serum Se level of the smokers was significantly higher than that of the non-smokers. In conclusion, the subjects of this study showed a serious imbalance in the nutrient intake, and the smokers showed a more undesirable dietary intake in the light of their high intake of energy, lipid, cholesterol, alcoholic beverages, and coffee. The serum Se level of the smokers was higher than that of the non-smokers, showing that Se is involved in smoking, Therefore, it could be suggested that more systematic research be conducted with respect to Se and smoking and that increased nutrition education and guidelines for smokers are required.

• 한국콘텐츠학회논문지
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• 제13권12호
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• pp.9-18
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• 2013

최근 무선 센서 네트워크는 멀티미디어 센서 모듈을 활용한 멀티미디어 데이터 수집을 기반으로 하는 고품질의 모니터링에 대한 요구가 증가하고 있다. 그러나 기존 센서 네트워크에서 수집되는 수치 데이터와 달리 멀티미디어 센서 네트워크에서 수집되는 데이터는 크기가 매우 크므로 데이터를 수집하는 과정에서 특정 노드의 과도한 에너지 소모 및 네트워크 성능 저하 문제가 발생한다. 본 논문에서는 무선 멀티미디어센서 네트워크에서 에너지 효율적인 동적 영역 압축 기법을 제안한다. 제안하는 기법은 중국인의 나머지 정리와 동적 변화 영역 감지 및 분할 알고리즘에 기반을 둔 수집 데이터의 데이터 압축 및 전송을 수행함으로써 대용량 멀티미디어 데이터 전송에서 발생하는 에너지 소모를 최소화한다. 성능평가 결과, 제안하는 기법은 기존 기법에 비해 데이터 압축률은 평균 37% 향상되었고, 데이터 전송량은 평균 56% 감소하였으며, 그에 따른 노드 생존율은 평균 14% 증가함을 보임으로써 그 우수성을 확인하였다.