• 에너지공학
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• 제21권3호
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• pp.315-324
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• 2012

폐기물 저감 재활용 에너지화 기술은 27대 중점 녹색기술 중 하나로, 2012년까지 정부 R&D 투자가 증가해야 함에도 불구하고, 2008년~2010년 기간 동안 연평균 증가율이 오히려 감소하였다. 이에 따라 동 분야의 정부 R&D 투자 현황을 상세히 분석하였고, 그 결과 총 정부 R&D 투자는 감소하였지만, 동 분야에서 정의하는 전략제품 서비스 기술에 대한 투자는 증가하고 집중화 되는 추세로 나타나 투자의 질적인 측면은 양호했다고 판단된다. 특히 2010년에는 전략제품 서비스 기술 중 3개 기술군((1) 폐기물 에너지화설비, (2) 폐기물자원순환시설, (3) 폐기물기반 물질생산시설)의 비중이 24 ~ 28%로 비교적 균등하게 투자되어, 정부 R&D 투자는 질적으로 적절했다고 판단되어 진다. 이러한 분석틀은 향후 녹색기술 R&D 정책 추진점검에서 활용할 수 있을 것이다.

• 자원ㆍ환경경제연구
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• 제21권2호
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• pp.271-299
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• 2012

환경과 경제성장과의 관계는 환경경제학 분야에서 오랜 동안 논란이 되어왔으며, 논란의 핵심은 두 변수간의 내생성(endogeneity)과 생략변수(omitted variables)들에 관한 문제들이다. 본 연구는 논란의 핵심들을 고려하여 우리나라의 1981년~2008년까지의 시계열자료를 바탕으로 $CO_2$ 배출량과 경제성장 간의 인과관계 및 에너지믹스의 영향을 실증적으로 분석하였다. 에너지믹스와 계량경제학 문제들을 고려한 대부분의 모형에서 $CO_2$ 배출량과 경제성장의 관계가 역 U자형이라는 EKC 가설을 확인할 수 있었으며, 에너지믹스가 국내 온실가스 감축에 크게 기여하는 것으로 나타났다. 에너지믹스가 $CO_2$ 배출에 미치는 영향은 원자력에너지가 다른 에너지원에 비해 $CO_2$ 배출량 감축에 가장 큰 기여를 하였으나, 신재생에너지는 $CO_2$ 감축에 거의 기여하지 못한 것으로 분석되었다. 이는 지금까지 국내에서 신재생에너지 비중이 다른 에너지원에 비해 적었기 때문이다. 또한 최종 에너지 소비부문은 $CO_2$ 증가와 수송부문의 연관성이 통계적으로 유의한 것으로 나타났다.

• 한국지열·수열에너지학회논문집
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• 제17권3호
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• pp.13-20
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• 2021

The capacity optimization of the heat exchanger of the TEM dehumidifier was performed through numerical analysis. If the ratio of the size of heat exchangers on the cold and hot surfaces of the TEM is not appropriate, the larger the size of the heat exchanger results the lower performance and efficiency. Optimizing the ratio of heat exchangers on the cold surface of TEM can improve the performance and the efficiency compared to when the ratio is 50%. The optimal proportion of cold surface heat exchangers is inversely proportional to the sum of the size of the heat exchangers on the cold and hot surfaces. When the optimum ratio of cold surface heat exchanger was applied, the larger the sum of size of the two heat exchangers results the greater the improvement of the performance and efficiency, compared to when the ratio of cold surface heat exchangers is 50%.

• Asian-Australasian Journal of Animal Sciences
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• 제32권12호
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• pp.1907-1913
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• 2019

Objective: Homoacetogens play important roles in the production of acetate in the large intestine of monogastric mammals. However, their diversity in the porcine large intestine is still unknown. Marker gene analysis was performed to assess the effects of energy level on the diversity and population densities of homoacetogens in porcine feces. Methods: Crossbred pigs were fed high or low energy-level diets. The high-intake (HI) diet was sufficient to allow a daily gain of 1.2 kg. The low-intake (LI) diet provided 0.6 times the amount of energy as the HI diet. Genetic diversity was analyzed using formyltetrahydrofolate synthetase gene (FHS) clone libraries derived from fecal DNA samples. FHS DNA copy numbers were quantified using real-time polymerase chain reaction. Results: A wide variety of FHS sequences was recovered from animals in both treatments. No differences in FHS clone libraries between the HI and LI groups were found. During the experimental period, no significant differences in the proportion of FHS copy numbers were observed between the two treatment groups. Conclusion: This is the first reported molecular diversity analysis using specific homoacetogen marker genes from the large intestines of pigs. There was no observable effect of feed intake on acetogen diversity.

• Steel and Composite Structures
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• 제38권1호
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• pp.79-86
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• 2021

Due to the complex geological conditions, a large number of high quality coal seams was buried in the western of China which cannot be mining in open-pit methods. The dynamic properties of that coal cannot be studied easily in real site for the complex working condition. The compound coal blocks made on the basis of the real situation were studied in the laboratory. The physical and mechanical properties of the compound coal blocks and the raw coal were contrasted by using the UCS tests. The results show that the compound coal blocks made by mixing coal powder, cement and water in proportion of 2.5:2:1 are the closest to that of standard raw coal. Then the propagation of strain waves and crushing effects on the coal were studied in the compound coal blocks by using the super dynamic strain test system and the numerical calculated method of ANSYS/LS-DYNA. The results show that the diameter of the crushing zone in the compound coal blocks was similar to that in the numerical results. The fractures distribution in laboratory tests also has a similar trend to the calculation results. The measured strain waves at the distance of 50 cm, 100 cm, and 150 cm from the center of the charge are mainly concerned at -1.0×104 με and have a similar trend as that in the numerical simulation.

• Journal of Nutrition and Health
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• 제37권6호
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• pp.493-501
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• 2004

The purpose of this study was to evaluate weight control program provided by university health care center for female college students. The program was 8-week long and composed of diet, exercise, and behavioral modification. Evaluation was made on the completion of 8-week program and a follow-up survey was done at 3-24 months after the end of program by telephone or bye-mail. Total of 76 women completed the 8-week program and 51 for follow-up survey. On the completion of 8-week program, significant decreases in body weight, BMI, body fat (kg), ％ body fat, and WHR were resulted, however, no change in muscle mass was found. Even the subjects without weight change showed significant reduction in body fat (kg) and ％ body fat. Total food intake was decreased resulting in reduced intakes of most nutrients. Meal distribution of energy was changed; ％energy from snack decreased from 22％ to 14％, and proportion for breakfast increased. Blood values of hemoglobin, hematocrit, total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglyceride were within normal range, and no changes were observed by this program. The follow-up survey revealed that 88.3％ of the subjects continued to lose weight after completion of the program, while only 7.8％ gained weight. And 78.4％ of the subjects considered the program effective. In conclusion, the weight reducing regime with education is effective for long lasting weight control and health conscious behavior for female college student. Since the subjects reduced the size of meal, instead of cutting only calories down, food selection to meet all the nutrient requirements except energy should be emphasized.

• 설비공학논문집
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• 제25권1호
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• pp.14-19
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• 2013

The present study has been conducted for evaluating and comparing the performance of the underfloor air distribution system(UFAD) and the ceiling based air distribution system(CBAD) under cooling condition. Simulations and experiments were carried out for verifying the model by TRNSYS program about UFAD and CBAD. The results of simulation for various conditions of thermal load are summarized as followings. UFAD had an advantage for making thermal comfort because of lower temperature of the floor surface. Moreover, UFAD showed lower fan power about 30~50% than CBAD under the same conditions of thermal load. The energy saving rates of UFAD were increased to 17.7% in proportion to the thermal load on unoccupied zone(lighting). Ultimately, additional investigations should be done for analyzing optimized operating conditions of UFAD with considering the thermal performance of building envelop and the thermal load.

• 설비공학논문집
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• 제21권4호
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• pp.252-259
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• 2009

When various kinds of outputs are produced from a single energy system, the methodology which allocates the common cost to each output cost is very important because it is directly related with the profit and loss of producers and purchasers. In the cost allocation methodology of the heat and the electricity on a cogeneration, there are energy method, work method, proportional method, benefit distribution method, various exergetic methods, and so on. On the other hand, we have proposed a worth evaluation method which can be applied to any system. The definition of this methodology is that the unit cost of a product is proportion to the worth. Where, worth is a certain evaluating basis that can equalize the worth of products. In this study, we applied this methodology to a gas-turbine cogeneration which produces 119.2 GJ/h of electricity and 134.7 GJ/h of steam, and then we allocated 3,150 $/h of fuel cost to electricity cost and steam cost. Also, we compared with various cost allocation methods. As the result, we conclude that reversible work of various kinds of worth basis evaluates the worth of heat and electricity most reasonably.

• 전기학회논문지
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• 제65권7호
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• pp.1161-1168
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• 2016

Battery energy storage system(BESS) attract the attention of the power system operators with its fast response to a disturbance in spite of its limited energy capacity. This paper proposes the operating method of BESS for following the Automatic Generation Control(AGC) frequency control which is centrally distributed by a system operator. As BESS needs to just meet the control requirement from the system operator, it should be able to properly manage the state of charge(SOC) of BESS to be available to control signal. For doing these, the proposed method distributes the control requirement to available batteries in proportion to its SOC. In addition, unavailable batteries are controlled to recover the SOC to an appropriate range, and the recovering power is supplied by available batteries meeting the control requirement. Moreover, the proposed method manages the efficiency of power conversion system (PCS) by limiting the number of PCS to be assigned for the low control requirement. Finally, the case studies are carried out to verify the effectiveness of proposed strategy.

• 신재생에너지
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• 제18권1호
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• pp.1-16
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• 2022

Climatic characteristics were described using the LiDAR (Light Detection and Ranging) and the met-mast on Dongbok·Bukchon region. The influences of meteorological conditions on the power performance of wind turbines were presented using the data of Supervisory Control And Data Acquisition (SCADA) and met-mast of the Dongbok·Bukchon Wind Farm (DBWF) located in Jeju Island. The stability was categorized into three parameters (Richardson number, Turbulence intensity, and Wind shear exponent). DBWF was dominant in unstable atmospheric conditions. At wind speeds of 14 m/s or more, the proportion of slightly unstable conditions accounted for more than 50%. A clear difference in the power output of the wind turbine was exhibited in the category of atmospheric stability and turbulence intensity (TI). Particularly, a more sensitive difference in power performance was showed in the rated wind speeds of the wind turbine and wind regime with high TI. When the flow had a high turbulence at low wind speeds and a low turbulence at rated wind speeds, a higher wind energy potential was produced than that in other conditions. Finally, the high-efficiency of the wind farm was confirmed in the slightly unstable atmospheric stability. However, when the unstable state become stronger, the wind farm efficiency was lower than that in the stable state.