• International Journal of Aeronautical and Space Sciences
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• 제13권2호
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• pp.188-198
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• 2012

An improvement to the k-${\varepsilon}$ turbulence model is presented and is shown to lead to better agreement with data regarding supersonic base flows. The improvement was achieved by imposing a grid-independent realizability constraint in the Launder-Sharma k-${\varepsilon}$ model. The effects of compressibility were also examined. The numerical results show that the modified Launder-Sharma model leads to some improvement in the prediction of the velocity and turbulent kinetic energy profiles. Compressibility corrections also lead to better agreement in both the turbulent kinetic energy and the Reynolds stress profiles with the experimental data.

• 자원ㆍ환경경제연구
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• 제9권5호
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• pp.811-827
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• 2000

Since improved thermal efficiency reduces capacity requirements and energy costs, electricity producers often treat thermal efficiency as a measure of management or economic performance. The conventional measure of the thermal efficiency of a fossil-fuel generation system is the ratio of total electricity generation to the simple sum of energy inputs. As a refined approach, we present a novel thermal efficiency measure using the concept of the Divisia index number. Application of this approach to the Korean power sector shows improvement of thermal efficiency of 1.1% per year during 1970-1998. This is higher than the 0.9% improvement per year given by the conventional method. The difference is attributable to the effect of fuel substitution. In the Divisia decomposition context, we also show the limitations of the popular $T{\ddot{o}}rnqvist$ index formula and the superiority of the Sato-Vartia formula.

• Applied Microscopy
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• 제41권1호
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• pp.75-79
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• 2011

For quantitative analysis of nano-crystal structure, we reported the accuracy improvement method of lattice parameters measured from electron diffraction. For calculation of Au lattice parameters used as a standard crystal structure, it was considered two different acquisition methods (detector and enegy-filter) and three different calculation methods (conventional, least-square and regression fit). As a result, the measurement reliability could be enhanced by using CCD camera which gives higher performance, while energy-filtering did not affect the improvement the camera constant accuracy. Also, the accuracy of lattice parameters could be improved up to $10^{-4}$ order by regression fitting with correction formula. Finally, it is expected that the combination of regression fitting and intensity extraction from energy-filtered precession electron diffraction gives a solution of quantitative structure analysis for unknown nano-crystals.

• 제어로봇시스템학회논문지
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• 제12권9호
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• pp.945-953
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• 2006

Though a fully thermally coupled distillation column consumes less energy than an original column, it is not widely implemented in practice due to its operational difficulty. A new fully thermally coupled distillation column is proposed for the operability improvement, and its performance is investigated. The main improvement is the separation of a main column to give an upper and lower columns and the installation of an intermediate heat exchanger between them to regulate the fluctuation of product compositions. A proper manipulation of column pressure in the separated main columns made easy vapor flow without a compressor. The operability improvement is examined in a hexane process from the dynamic simulation using a commercial design software HYSYS. The simulation results indicate that the coupling among inputs and outputs is loosened to make easy manipulation of product compositions in the proposed distillation system.

• Journal of Radiation Protection and Research
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• 제42권2호
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• pp.106-113
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• 2017

Background: Interfacing-system loss-of-coolant-accident (ISLOCA) has been identified as the most hazardous accident scenario in the typical PWR plants. The present study as an effort to improve the knowledge of the source term to the environment during ISLOCA focuses on an improvement of the estimation method. Materials and Methods: The improvement was performed to take into account an effect of broken pipeline and auxiliary building structures relevant to ISLOCA. An estimation of the source term to the environment was for the OPR-1000 plants by MELOCR code version 1.8.6. Results and Discussion: The key features of the source term showed that the massive amount of fission products departed from the beginning of core degradation to the vessel breach. Conclusion: The release amount of fission products may be affected by the broken pipeline and the auxiliary building structure associated with release pathway.

• Environmental Engineering Research
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• 제24권4호
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• pp.529-542
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• 2019

Nowadays, drying methods for municipal solid waste quality improvement have been adopted in the developed and developing countries to valorize wastes for a renewable energy source, reduce dependency on fossil fuel and keep safer disposal at landfills. Among them, biodrying, biostabilization, thermal drying and solar drying are the most common. Drying of municipal solid waste could offer several environmental and economic benefits. Therefore, this review highlighted the drying methods for municipal solid waste quality improvement around the world and compared them based on the reduction of moisture, weight and volume of municipal solid wastes against drying temperature and time by using statistical analysis. It was observed that the drying temperature of different drying methods accounted for 115 ± 40℃ for thermal drying, 59 ± 37℃ for solar drying, 55 ± 15℃ for biodrying and 58 ± 11℃ for biostabilization. Among the drying methods, thermal drying provided the shortest drying time. The moisture reduction, weight reduction, volume reduction and heating value increase of municipal solid waste could vary with drying temperature and time. Finally, the benefits and drawbacks of different drying methods were specified, and recommendations were made for the future efficient drying.

• 대한건축학회논문집:구조계
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• 제34권5호
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• pp.59-67
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• 2018

G-SEED's evaluation of existing buildings is an important point because the energy consumption and CO2 emissions of existing buildings are continuously increasing due to the aging of buildings over time. However, as G-SEED certification is concentrated on new buildings and the standards are not yet available, we will make improvements to evaluate the existing buildings of G-SEED. In order to improve G-SEED for EB, two research procedures were carried out. First, LEED EBOM and LEED for NC compare and analyze evaluation items and methods, and LEED EBOM focuses on evaluation of existing buildings. Second, we analyzed the certification evaluation contents of eight domestic LEED EBOM accredited buildings and obtained items that can be applied or need to be applied when revising G-SEED for EB. LEED EBOM is focused on improving the performance and utilization of data that track and manage the energy and environmental effects of building operations. As a result of the case analysis, the evaluation of G-SEED for EB requires quantitative evaluation items such as environmental management of buildings, energy performance status of building, improvement plan and improvement of performance according to tracking value. Although G-SEED for EB is not structured yet and there are few cases of certification, it is expected that quantitative evaluation of existing buildings will be made through continuous research.

• 한국농촌건축학회논문집
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• 제23권1호
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• pp.9-18
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• 2021

In this study, surveys and data collection on new profit-sharing measures were carried out in order to improve the residential environment and residents' participation in 65 MW large-scale solar power complex located at Munhye 5-ri, Galmal-eup, Cheorwon-gun, Gangwon-do province. From May to September 2018, the presentation and meetings for residents were held and a survey for 67 households were carried out in order to collect profit-sharing data which is sharing profits from solar power project improving residential environment. The results of the survey shows that it needs to improve some obstacles of residential environment in rural areas, such as improvement of living infrastructure at village level, improvement of monotonous leisure activities from the residents' point of view, improvement of economic income sources depending on farm income and Basic Old-age Pensions, inconvenience factors in the unsuitable residential environment due to aging. Based on these findings, this paper suggests that Profit-Sharing solar power complex project has possibilities to improve living environment in rural areas by sharing profits from power generation and residents participating in the project with consensus for need of renewable energy.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.679-680
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• 2011

This paper is developed to Energy Balance Flow show the flow of total energy resource be used nationally. The Energy Balance Flow is applicable of demand management factor through the analysis of foreign energy model of supply and demand and energy statistic data in the country. This study is based on and developed to Energy system management model is able to appraisal efficient of energy cost cutting, CO2 emission reduction and Energy saving at the national level calculated effect reached amount of primary energy to change of energy flow followed application of demand side management factor is able to appraisal quantitatively at the total energy to model of demand and supply.

• 한국인터넷방송통신학회논문지
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• 제20권2호
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• pp.179-185
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• 2020

DRAM은 메인 메모리 시스템을 구성하는 주요한 요소로서 운영체제의 발전, 응용 프로그램의 복잡도와 용량의 증가에 맞추어 DRAM의 용량과 속도 역시 증가하는 추세이다. DRAM은 주기적으로 저장된 값을 읽은 후 다시 저장하는 리프레시 동작을 수행해야 하며, 이에 수반되는 성능 및 파워/에너지 오버헤드는 용량이 증가할수록 더 악화되는 특성을 내재하고 있다. 본 연구는 전하의 보존 시간이 가장 낮은 셀들에 대해서 블룸 필터를 사용하여 64ms, 128ms 이내에 리프레시를 수행해야 하는 로우들을 효율적으로 저장하여 선택적 리프레시를 수행하는 에너지 효율 향상 기법을 제안한다. 실험 결과에 따르면 제안 기법을 통하여 평균 5.5%의 성능 향상이 있었으며, 리프레시 에너지는 평균 76.4% 절감되었고, 평균 EDP는 10.3% 절감된 것으로 나타났다.