• 한국수소및신에너지학회논문집
• /
• 제33권5호
• /
• pp.566-573
• /
• 2022

In this study, the mechanical properties of the polymer electrolyte membrane according to the temperature were studied. The test specimens of polymer electrolyte membrane were heat treated at 40℃, 60℃, 80℃, 100℃, and 120℃, and then the tensile tests were performed. As results of this study, the residual stress of the polymer electrolyte membrane was removes by the heat treatment and the elastic modulus decreased due to the decrease in internal energy. In addition, in the plastic region, the mechanical properties and crystallization rate of the polymer electrolyte membrane increased in proportion according to increase of the heat treatment temperature.

• KIEAE Journal
• /
• 제15권1호
• /
• pp.155-160
• /
• 2015

The annual average of energy sources is continuously increasing at a rate of 5.8%, and particularly, the power generation proportion of new/renewable energy is increasing significantly. Furthermore, South Korea has established a national energy master plan for 2008-2030 and is aiming at obtaining approximately 11% of total energy production from the wind turbine sector. Although offshore wind turbines are similar to wind turbines installed on land, they require materials with excellent dynamic properties and durability to prevent damage due to seawater at the lower parts and connecting parts. The lower parts of wind turbines are submerged in seawater, and the upper and lower parts are connected by filling the connecting part with grout. This paper describes the test results of the process of determining the mix ratios to develop ultra-high grout for offshore wind turbines. There is virtually no relevant technology regarding grout for offshore wind turbines in South Korea that can be referenced for the process of determining the mix ratios. Therefore, tests were conducted for determining compression strength, elastic modulus, flexural strength, density, constructability (floor test), and early strength by referencing a high-performance grout produced in South Korea, and the mixing process for achieving the goal strengths was described using the Korean Industrial Standards (KS) as the reference.

• 한국식품영양학회지
• /
• 제17권4호
• /
• pp.356-367
• /
• 2004

This study was performed to evaluate the effectiveness of a nutritional education program conducted by public health center in Jinju city for obese women. The subjects of this study consisted of 27 obese women(BMI $\geq$ 25) aged 35∼55 years in Jinju area, and the educational period was 6 weeks. We evaluated the anthropometric parameters and biochemical indices, dietary habits, dietary behaviors, nutritional attitude of obese women before and after the nutritional education. And also daily intake during the educational period were measured. Weight, obesity index, BMT, waist circumferences and hip circumferences of obese women were significantly decreased(p<0.001) after nutritional education, but changes of WHR, systolic blood pressure and diastolic blood pressure were not significant. There were no significant difference in total cholesterol, HDL-cholesterol, LDL-cholesterol, triglyceride, LDH and blood glucose level in serum before and after the nutritional education, but the indices tend to decrease after the nutritional education. There was significantly different change of dietary behaviors in 3 items among the dietary behavior after the nutritional education. Their dietary habit, dietary behavior and nutritional attitude scores were significantly improved after the nutritional education. Mean daily energy intakes was low compared with the RDA as 78.88%. The average carbohydrates, protein, fat ratio on the energy intakes was 63 : 17 : 20. The proportion of energy intake from snacks the was 12.91${\pm}$6.15%.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제8권2호
• /
• pp.326-354
• /
• 2014

In this paper, a new green clustering algorithm is proposed to be as a first approach in the framework of an energy efficient strategy for centralized enterprise high-density WLANs. Traditionally, in order to maintain the network coverage, all the APs within the WLAN have to be powered-on. Nevertheless, the new algorithm can power-off a large proportion of APs while the coverage is maintained as its always-on counterpart. The two main components of the new approach are the faster procedure based on K-means and the more accurate procedure based on Evolutionary Algorithm (EA), respectively. The two procedures are processes in parallel for different designed requirements and there is information interaction in between. In order to implement the new algorithm, EA is applied to handle the optimization of multiple objectives. Moreover, we adapt the method for selection and recombination, and then introduce a new operator for mutation. This paper also presents simulations in scenarios modeled with ray-tracing method and FDTD technique, and the results show that about 67% to 90% of energy consumption can be saved while it is able to maintain the original network coverage during periods when few users are online or the traffic load is low.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
• /
• pp.80.2-80.2
• /
• 2011

Fossil fuel was a major energy resource but the consumption of fossil fuel will decrease gradually because of limited deposits and non-environmental features. In contrast, because the renewable energy resources are infinite and sustainable, their consumption has increased annually. To promote the supply of these infinite natural energy we have to develop more efficient and inexpensive heat recovery system. In this study a simple device was designed as a heat exchanger, that is a direct contact heat exchanger. This heat exchanger was manufactured in cylindrical shape with height of 1,500 mm and diameter of 1,000 mm. To test the efficiency of this heat exchanger, it was connected to the evaporator of heat pump system. During the experimental tests, the humid air of $10{\sim}30^{\circ}C$ was supplied to this air-to-water heat exchanger and then the water flow rate was set to 2500~3500 L/h. Heat recovery rate of this heat exchanger increased in proportion to entering air temperature and water flow rate.

• 전기학회논문지
• /
• 제58권3호
• /
• pp.467-477
• /
• 2009

Renewable Portfolio Standard (RPS) is a regulatory policy that requires the generation companies to increase the proportion of renewable energy sources such as wind, solar, LFG, fuel cell, and small hydro. Recently, Korean government decided to increase the portion of renewable energy to 3% to total electricity generation by 2012 from the current level of 0.13%. To achieve this goal, an innovative plan for market competitiveness would be required in addition to the present Feed-In-Tariff (FIT). That is Korean government has taken it into consideration to introduce a Renewable Portfolio Standard (RPS) as an alternative to FIT. This paper reviews the impact of RPS on the long-term fuel mix in 2020. The studies have been carried out with the GATE-PRO (Generation And Transmission Expansion PROgram) program, a mixed-integer non-linear program developed by Hongik university and Korea Energy Economics Institute. Detailed studies on long-term fuel mix in Korea have been carried out with four RPS scenarios of 3%, 5%, 10% and 20%. The important findings and comments on the results are given to provide an insight on future regulatory policies.

• Nutrition Research and Practice
• /
• 제16권2호
• /
• pp.260-271
• /
• 2022

BACKGROUND/OBJECTIVES: The prevalence of obesity has been increasing in Korean children. As an unhealthy diet is known as one of the major determinants of childhood obesity, assessing and monitoring dietary fat intake of children is needed. SUBJECTS/METHODS: This analysis included 9,998 children aged 3-11 yrs from the 2007-2017 Korea National Health and Nutrition Examination Surveys. Dietary data were obtained from a single 24-h dietary recall. Intakes of total fat and fatty acids, including saturated fatty acid (SFA), monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), n-3 fatty acid (n-3 FA), and n-6 fatty acid (n-6 FA) were evaluated as the absolute amount (g) and proportion of energy from each fatty acid (% of energy). The total fat and SFA intake were also assessed according to compliance with dietary guidelines. Linear trends in the dietary fats intake across the survey period were tested using multiple regression models. RESULTS: Total fat intake significantly increased from 38.5g (20.3% of energy) to 43.4g (23.3% of energy) from 2007 to 2017. This increase was mainly accounted for the increases in intakes of SFA (7.2% to 8.4% of energy) and MUFA (6.2% to 7.5% of energy). PUFA intake increased from 4.4 to 4.7% of energy during the 11-yrs period: from 0.57 to 0.63% of energy for n-3 FA and from 3.8 to 4.1% of energy for n-6 FA. The proportions of children who consumed amounts exceeding the dietary guidelines for total fat and SFA significantly increased from 2007 to 2017, with increases from 9.8% to 17.4% for total fat and from 36.9% to 50.9% for SFA. CONCLUSIONS: Prominent increasing trends in the consumption of total fat and SFA but tiny change in n-3 FA intake were observed in Korean children. The healthy intake of dietary fats should be emphasized in this population.

• 한국수소및신에너지학회논문집
• /
• 제26권6호
• /
• pp.507-515
• /
• 2015

HI decomposition reaction requires a catalyst for the efficient production of hydrogen as a key reaction for hydrogen production in sulfur-iodine thermochemical water-splitting (SI) cycle. As a catalyst used in the reaction, the performance of platinum catalyst is excellent. While, the platinum catalyst is not economical. Therefore, studies of a nickel catalyst that could replace platinum have been carried out. In this study, the characteristics of the catalytic HI decomposition on the amount of loaded nickel (Ni = 0.1, 0.5, 1, 3, 5, 10 wt%) were investigated. As the supported Ni amount increased up to 3 wt%, HI decomposition was found to increase in linear proportion. However, the conversion of $Ni/Al_2O_3$ catalyst loaded above 3 wt% was not linear. It was thought that the different HI decomposition characteristics was caused in the size and metal dispersion of Ni particles of catalyst. The physical property of catalyst before and after HI decomposition reaction was characterized by BET, chemisorption, XRD and SEM analysis.

• 정보과학회 컴퓨팅의 실제 논문지
• /
• 제22권9호
• /
• pp.467-472
• /
• 2016

본 연구는 시스템의 부하 특성에 따라 에너지 절감을 최적화하여 에너지 인지형 웹 서비스에 관한 연구이다. 최근에 데이터 센터의 서비스 규모가 점점 커지고 그 응용 범위가 확대되어 이에 따른 에너지 절감에 대한 관심이 증가하고 있다. 특히 이러한 데이터 센터의 서비스 중에서 가장 많은 비중을 차지하는 서비스가 웹 서비스이다. 본 연구는 이처럼 비중이 높은 웹 서비스 부분에서 서비스의 성능을 보장하는 동시에 에너지 절감하는 새로운 기법을 제안한다. 그 제안된 기법은 시스템의 부하에 따른 에너지 소모율의 차이점을 통하여 최적화 하였다. 성능 평가는 실제 서비스에 매우 유사한 조건에서 평가되었고 제안하는 기법이 기존 방식에 비하여 크게는 약 30% 이상의 에너지를 절감을 보여준다.

• 방사성폐기물학회지
• /
• 제6권3호
• /
• pp.225-232
• /
• 2008

제3차 전력수급기본계획에 근거하여 현재 운영중이거나 계획중인 원자력발전소에서 발생할 사용후핵연료의 양과 특성을 추정하였다. 본 연구에서 고려된 대상 특성은 핵연료집합체에 대한 제원, 핵연료봉 배열, 무게, $^{235}U$ 초기 농축도 및 방출연소도이다. 이들은 파이로공정 시설을 설계하는데 필수적인 것이다. 2077년말까지 가압경수로 사용후핵연료의 예상발생량은 약 23,000 tU이 될 것으로 보인다. $^{235}U$ 초기 농축도 4.5 wt.% 이하를 갖는 사용후핵연료의 비율은 전체 발생량의 약 95%를 차지할 것이며, 16$\times$16 배열을 갖는 핵연료집합체는 74%를 차지할 것 같다. 현재 사용후핵연료의 평균연소도는 45 GWd/tU인데 반해, 2010년대 중 후반 이후 발생할 사용후 핵연료의 평균연소도는 55 GWd/tU이 될 것 같다. 이상의 결과에 따라 파이로공정 시설의 설계를 위한 기준 사용후핵연료를 도출하였다. 예상 사용후핵연료는 21.4 cm $\times$ 21.4 cm의 단면적, 453 cm의 길이, 672 kg의 질량, 4.5 wt.%의 $^{235}U$ 초기 농축도 및 55 GWd/tU의 방출연소도를 갖는 16$\times$16 한국표준형연료가 타당할 것으로 판단된다.