• 에너지공학
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• 제6권2호
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• pp.145-151
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• 1997

전력산업의 연구개발투자는 국가경제에 미치는 영향뿐만 아니라 사회후생극대화측면에서도 그 영향은 상당히 크다. 이러한 연구개발투자가 얼마나 효율적으로 이루어져왔나를 분석하여 볼 필요가 있다. 따라서 규제하에서의 독점기업의 적정 연구개발투자규모는 연구개발탄력성과 가격탄력성의 비율로서 결정된다는 것을 수식으로 도출하여 전력산업의 연구개발투자의 효율성유무를 검증하였다. 그 결과 비용이 증가하면 전력판매랑은 증가하여 규모의 경제가 없는 것으로 나타났으며, 규모의 경제를 증가시키기 위해 투자되는 연구개발투자의 정도를 나타내는 연구개발투자집약도는 가격-비용 마진에 부의 효과를 나타내어 현재 전력산업은 연구개발투자가 비효율적으로 이루어지고 있음을 알 수 있다.

• 신재생에너지
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• 제16권2호
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• pp.47-53
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• 2020

The amount of food waste and its water content depends on both the season and region. In particular, the water content typically varies between 73.8 wt.% and 83.3 wt.%, depending on the proportion of vegetables. Current food waste drying technologies are capable of reducing the water content to less than 10 wt.%, while increasing the heating value. Ongoing studies aim to utilize dried food waste as fuel. Food waste can be used to produce solid refuse fuel (SRF) by mixing it with various solid fuels or other types of waste. The analysis of specimens is very important when considering the direct combustion of food waste or its co-firing with solid fuels. In this study, the weight reduction of specimens after burning them in a small combustor, and compared with the results of thermogravimetric analysis (TGA). The concentration of various chemicals was also measured to define the characteristics of waste generation. Performed proximate analysis, elemental analysis, TGA, combustion experiment, the heating value, and derivative thermogravimetry (DTG).

• 한국세라믹학회지
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• 제37권1호
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• pp.50-56
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• 2000

Precursor gels with the composition of xZrO2·(100-x)SiO2 systems (x=10, 20 and 30 mol%) were prepared by the sol-gel method. Kinetic parameters, such as activation energy, Avrami's exponent, n, and dimensionality crystal growth value, m, have been simultaneously calculated from the DTA data using Kissinger and Matusita equations. The crystallite size dependence of tetragonal to monoclinic transformation of ZrO2 was investigated using XRD, in relation to the fracture toughness. The crystallization of tetragonal ZrO2 occurred through 3-dimensional diffusiion controlled growth(n=m=2) and the activation energy for crystallization was calculated using Kissinger and Matusita equations, as about 310∼325±10kJ/mol. The growth of t-ZrO2, in proportion to the cube of radius, increased with increasing heating temperature and hteat-treatment time. It was suggested that the diffusion of Zr4+ ions by Ostwald ripening was rate-limiting process for thegrowth of t-ZrO2 crystallite size. The fracture toughness of xZrO2·(100-x)SiO2 systems glass ceramics increased with increasing crystallite size of t-ZrO2. The fracture toughness of 30ZrO2·70SiO2 system glass ceramics heated at 1,100℃ for 5h was 4.84 MPam1/2 at a critical crystaliite size of 40 nm.

• 상하수도학회지
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• 제28권2호
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• pp.161-170
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• 2014

It is essential to decrease energy consumption and excess sludge to economically operate sewage treatment plant. This becomes more important along with a ban on sea dumping and exhaustion of resource. Therefore, many researchers have been study on energy consumption reduction and strategies for minimization of excess sludge production from the activated sludge process. The aeration cost account for a high proportion of maintenance cost because sufficient air is necessary to keep nitrifying bacteria activity of which the oxygen affinity is inferior to that of heterotrophic bacteria. Also, additional costs are incurred to stabilize excess sludge and decrease the volume of sludge. There were anoxic, aerobic, membrane, deairation and concentration zone in this MBR process. Continuous aeration was provided to prevent membrane fouling in membrane zone and intermittent aeration was provided in aerobic zone through ammonia sensor. So, there was the minimum oxygen to remove $NH_4-N$ below limited quantity that could be eliminated in membrane zone. As the result of this control, energy consumption of aeration system declined by between 10.4 % and 19.1 %. Besides, we could maintain high MLSS concentration in concentration zone and this induced the microorganisms to be in starved condition. Consequentially, the amount of excess sludge decrease by about 15 %.

• 대한건축학회논문집:구조계
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• 제35권6호
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• pp.153-164
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• 2019

The presence of thermal bridges in a building envelope cause additional heat loss which increases the heating energy. Given that a higher building insulation performance is required in these cases, the heat loss via thermal bridges is a high proportion of the total heat energy consumption of a building. For the dry exterior insulation system that uses mullions and transoms to fix insulation and exterior materials such as stone and metal sheet, the occurrence of thermal bridges at mullions and transoms is one of the main reasons for heat loss. In this study, a dry exterior insulation system using the truss insulation frame (TIF) was proposed as an alternative to metal mullions. To evaluate the building envelope performance, structural, air-leakage, water-leakage, fire-resistance, thermal, and condensation risk tests were conducted. In addition, the annual energy consumption associated with heating and cooling was calculated, including the linear thermal transmittance of the thermal bridges. As a result, the dry exterior insulation system using TIF achieved the allowable value for all tests. It was also determined that the annual heating load of a building was reduced by 36.7 % when the TIF dry exterior insulation system was used, relative to the dry exterior insulation system using steel pipes without additional insulations.

• Transactions on Electrical and Electronic Materials
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• 제15권5호
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• pp.257-261
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• 2014

Multilayered CdTe/PSS films were prepared by the electrostatic self-assembly method in an aqueous medium. Positively-charged cadmium telluride (CdTe) nanoparticles and anionic polyelectrolyte, poly (sodium 4-styrene sulfonate) (PSS) were assembled alternately in order to build up a multilayered film structure. A linear proportion of absorbance to the number of bilayers suggests that an equal amount of CdTe was adsorbed after each dipping cycle, which resulted in the buildup of a homogenous film. The binding energies of elements (Cd and Te) in multilayered CdTe/PSS film shifted from those of the CdTe nanoparticles in the pure state. This result indicates that the interfacial electron densities were redistributed by the strong electrostatic interaction between the oppositely-charged CdTe and PSS. Electrochemical properties of the multilayered CdTe/PSS films were studied in detail by cyclic voltammetry (CV).

• 대한지역사회영양학회지
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• 제6권4호
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• pp.645-656
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• 2001

The relationship between socio-economic status and food and nutrient consumption patterns was studied in 7,370 Koreans aged 20 years and older in the 1995 Korean Health and Nutrition Survey. The aim of this study was to investigate the effect of rapid economic growth on food and nutrient consumption for Korean adults in the last 30 years. Monthly household income, and individual's educational level and occupation were chosen as variables of socio-economic status for individuals. A one day 24 hour recall method was used for the dietary survey. One way analysis of varience was adopted to test tole association between socio-economic variables and food and nutrient consumption patterns. Individuals who had a high socio-economic status had significantly higher daily intake of most of the nutrients including calcium, vitamin A, vitamin B$_2$which reached above the recommended dietary allowances(RDA) and a higher percentage energy consumption from fat. In addition, individual who belonged to a low socio-economic status consumed less animal foods, including meat, egg, milk and consumed low proportion of energy from fat. The results suggest that in spite of rapid economic growth during the last 30 years in Korea, individuals who belonged to low sorio-economic status categories are still nutritionally vulnerable. Among the sorio-economic variables, income and education except occupation were the influential factors on the food and nutrient consumption of Koreans. Therefore, nutrition policy should focus on influencing the dietary patterns of lower social class individuals to improve the health status of the population as a whole.

• 한국전기전자재료학회논문지
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• 제33권6호
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• pp.500-504
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• 2020

Heating films were prepared with composites of poly (methyl methacrylate) and conductive graphite. The as-prepared composite was deposited on a PET film and then fabricated using a bar coater to produce a film with uniform thickness. Copper electrodes were attached to both ends of the as-prepared film, and the heating characteristics of the film were analyzed while applying a DC voltage. The electrical conductivity and heating temperature of the heating films depended on the size, structure, content, and the dispersion characteristics of the graphite in the composite. The thermal energy was adjusted by controlling the electrical energy, based on the Joule heating theory. The electrical resistance of the film was altered in proportion to Ohm's law, and the heating temperature was changed according to the structure of the film (interelectrode spacing or electrode length) and the conductive graphite content. When the content of conductive graphite in the film increases, the electrical resistance decreases, and the heating temperature increases; however, there is no significant change above a certain content (50%).

• 수산해양기술연구
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• 제53권3호
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• pp.302-307
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• 2017

An electric steam boiler equipped with a condensate recovery system, which stores the condensate generated after using steam in steam washers, steam cookers, steam irons, and steam cleaners in a condensate tank and supplies compressed air to the condensate tank so that the condensate is recovered to the boiler by the pressure of the compressed air, was studied. In the results of this study, the heat energy balance between the quantity of the heat generated by the non-metallic surface heating element and the quantity of the heat absorbed by the water was good in a range of ${\pm}5%$. In addition, the heat transfer rate increased in proportion to the electric power of the surface heating element heater, the waste heat energy was normally recovered by the recovery of the condensate of the steam boiler equipped with the high compression waste heat recovery system, and the recovery rate of the waste heat exhibited 23%.

• 한국환경농학회지
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• 제24권2호
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• pp.169-179
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• 2005

With the industrialization in Korea, the economy has invested more resources on industry and less on agricultural production. However, agriculture is still an important industry, since the whole nation depends on rice for their living. And the proportion of agricultural land is relatively large, which leads issuing environmental aspects of agriculture in this country. This study was conducted to evaluate the environmental and economical aspects of agriculture in Korea, using system ecological concept, Emergy. The total Emergy inflow of Korean agriculture was $336.57{\times}10^{20}\;sej{\cdot}yr^{-1}$ in 2003. Emergy yield ratio, the ratio of non-renewable and imported Energy use to renewable Emergy use, was 5.21, which shows the agriculture in Korea has such a value as that of the world oil resources in 1986. Also, total agricultural product was $13.55{\times}10^{16}\;J{\cdot}yr^{-1}$ in 2003 and the Energy inflow was $121.09{\times}10^{20}\;sej{\cdot}yr^{-1}$. From these data, solar transformity of Korean agriculture was estimated as $8.68{\times}10^4\;sej{\cdot}J^{-1}$.