• 한국병원경영학회지
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• 제16권4호
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• pp.35-66
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• 2011

This study analyzed efficiency by utilizing DEA analytical technique centering on materials for 2009 of 20 major university hospitals in capital area. Input variables were utilized professor & full-time doctor, resident, nurse & number of bed hospitals. Output variables were analyzed by dividing number of annual outpatients & number of annual inpatients, and annually total outpatient profit & inpatient profit into a model of the standard for number of patients and the standard for medical profit. DEA analysis was elicited efficiency score by applying CCR, BCC, BFG, scale profit, and SE model. Through t-test after eliciting efficiency score, the implications were suggested by comparing efficiency between DMU in Seoul and DMU in capital area, by comparing between high-class general hospitals and general hospitals, and by comparing between high-class general hospitals in Seoul and 5 big hospitals. As a result of analysis, the major university hospitals in capital area showed high efficiency as a whole close to "1," but indicated low efficiency relatively in CCR field. Thus, the expansion in scale within capital area was indicated to reach the limit. Second, in a model of analyzing the standard for number of patients, the medical institutions, which are being operated efficiently, were indicated to be 10 DMUs. In the standard for medical profit, 12 DMUs were analyzed to be operated efficiently. Third, the efficiency in general hospital was higher than high-class general hospital. Thus, the efficiency of operation was indicated to be more important than scale. Also, large high-class hospitals(big 5) where are located in downtown Seoul showed the higher efficiency than other general high-class general hospitals, but were indicating very low efficiency in some DMUs. Fourth, as a result of generalizing and evaluating the number of patients and the medical profit, the efficient DMU was indicated to be more when analyzing on the basis of medical profit than the standard for number of patients. Thus, major university hospitals in capital area were indicated to make more effort for section in medical profit. Based on the analytical results of efficiency, a strategy for reinforcing efficiency in inefficient DMU was indicated to be needed a strategy of creating customers for promoting number of patients and a strategy for making operation efficient for increasing profitability.

• 한국문헌정보학회지
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• 제44권1호
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• pp.117-135
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• 2010

본 연구는 이미지의 시맨틱 검색을 위해서 동등어, 동의어 및 관련어를 질의 확장시에 사용하여 태그를 통제한 구조화된 폭소노미 시스템의 모형을 제안하였다. 그런 다음 제안한 시스템의 효율성을 평가하기 위해서 실험을 통해서 이 시스템을 태그를 전혀 통제하지 않은 태그 기반 시스템과 검색 효율성(재현율과 정확률)과 만족도 측면에서 비교해 보았다. 이외에 검색 효율성이 질의 확장 방식에 따라서 어떤 차이를 보이는지 조사해 보았다. 실험 결과, 제안된 구조화된 폭소노미 시스템이 태그 기반 시스템 보다 재현율, 정확률 및 만족도에서 더 높게 나타났으며 그 차이도 통계적으로 유의미한 것으로 나타났다. 한편 질의 확장 방식에 따라서 재현율은 차이가 없었지만 정확률은 부분적으로 차이가 있는 것으로 나타났다. 본 연구 결과는 라이브러리 2.0 시대의 디지털 도서관 시스템에 적용되어 디지털 자원에 대한 접근성을 향상시킬 수 있을 것이다.

• 한국자동차공학회논문집
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• 제15권2호
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• pp.8-14
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• 2007

Compression ignition of homogeneous charges in IC engines indicates possibilities of achieving the high efficiency of DI diesel engines with low level of NOx and particulate emissions. The objectives of this study are to further understand the characteristics of the HCCI(Homogeneous charge compression ignition) combustion and to find ways of extending the rich HCCI operation limit in an engine-like environment. DME fuel is supplied either in the form of premixture with air or directly injected in the combustion chamber of a rapid compression and expansion machine under the conditions of various equivalence ratio and injection timing. The cylinder pressure is measured and the rate of heat release is computed from the measured pressure for the analysis of the combustion characteristics. The experimental data show that the RCEM can operate without knock on mixtures of higher equivalence ratio, when DME is directly injected in the combustion chamber than introduced as a fraction of a perfect or nearly perfect premixture. Very early fuel injection timings usually employed in HCCI operation are seen to have only insignificant effects in control of ignition timing.

• 한국세라믹학회지
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• 제53권2호
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• pp.215-221
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• 2016

In this study, the utilization of the by-products of various industries was examined using raw materials of CSA high-functional cement such as coal bottom ash, red mud, phosphate gypsum, etc. Technology to improve energy efficiency and reduce $CO_2$ was developed as part of the manufacturing process; this technology included lower temperature sintering ($150{\sim}200^{\circ}C$) than is used in the OPC cement manufacturing process, replacement of CSA cement with the main raw material bauxite, and a determination of the optimum mix condition. In order to develop CSA cement, a manufacturing system was established in the Danyang plant of the HANIL Cement Co. Ltd., in Korea. About 4,200 tons of low purity expansion agent CSA cement (about 16%) and about 850 tons of the lime-based expansion agent dead burned lime (about 8%) were produced at a rate of 60 tons per hour at the HANIL Cement rotary kiln. To improve the OPC cement properties, samples of 10%, 13%, and 16% of CSA cement were mixed with the OPC cement and the compressive strength and length variation rate of the green cement were examined. When green cement was mixed with each ratio of CSA cement and OPC cement, the compressive strength was improved by about 30% and the expansibility of the green cement was also improved. When green cement was mixed with 16% of CSA cement, the compressive strength was excellent compared with that of OPC cement. Therefore, this study indicates the possibility of a practical use of low-cost CSA cement employing industrial wastes only.

• 에너지공학
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• 제5권1호
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• pp.34-41
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• 1996

LNG의 기화열(냉열)은 NG액화시 소모된 동력으로서 생산된 NG의 약 14%에 달한다. 평택 인수기지의 경우 '93도입물량 기준으로 냉열량은 96MW에 달한다. 냉열을 이용하여 전력을 생산하는 방안으로, 저온 엑서지를 활용하는 Rankine 사이클, 압력 엑서지를 이용한 부분직접 팽창 사이클 및 이 두 사이클의 혼합 사이클인 Linde공정 냉열발전시스템의 성능을 비교연구하였다. 시뮤레이션은 ASPEN Plus를 이용하여 수행하였으며 현재 인수기지에서 운영되고 있는 각종 설비들의 설계데이타를 이용하였다. 시스템별 출력은 약 3∼6MW였으며 최적운전조건의 엑서지 효율은 37%로 계산되었다. 또한 부분직접팽창방식의 최적 시스템을 제시하였고 열교환기의 총 면적이 동일 할 경우 부분직접팽창과 랭킨사이클의 성능은 비슷한 것으로 확인되었다.

• 천문학회보
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• 제43권1호
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• pp.43.1-43.1
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• 2018

Star formation in galaxies predominantly takes place in giant molecular clouds (GMCs). While it is widely believed that UV radiation feedback from young massive stars can destroy natal GMCs by exciting HII regions and driving their expansion, our understanding on how this actually occurs remains incomplete. To quantitatively assess the effect of UV radiation feedback on cloud disruption, we conduct a series of theoretical studies on the dynamics of HII regions and its role in controlling the star formation efficiency (SFE) and lifetime of GMCs in a wide range of star-forming environments. We first develop a semi-analytic model for the expansion of spherical dusty HII regions driven by the combination of gas and radiation pressures, finding that GMCs in normal disk galaxies are destroyed by gas-pressure driven expansion with SFE < 10%, while more dense and massive clouds with higher SFE are disrupted primarily by radiation pressure. Next, we turn to radiation hydrodynamic simulations of GMC dispersal to allow for self-consistent star formation as well as inhomogeneous density and velocity structures arising from supersonic turbulence. For this, we develop an efficient parallel algorithm for ray tracing method, which enables us to probe a range of cloud masses and sizes. Our parameter study shows that the net SFE, lifetime (measured in units of free-fall time), and the importance of radiation pressure (relative to photoionization) increase primarily with the initial surface density of the cloud. Unlike in the idealized spherical model, we find that the dominant mass loss mechanism is photoevaporation rather than dynamical ejection and that a significant fraction of radiation escapes through low optical-depth channels. We will discuss the astronomical.

• 한국물환경학회지
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• 제22권5호
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• pp.905-912
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• 2006

In this paper, simulation methods of the system dynamics model developed by Das et al. (1997) for activated-sludge wastewater treatment plants are illustrated in an attempt to determine the operating rules and the policies related to capacity expansion of an activated-sludge wastewater treatment plant. For existing conditions, the analyses were performed by varying activated-sludge return rate to observe changes in effluent water quality and treatment efficiency. The effluent water quality is also analyzed for various average daily inflow conditions and activated-sludge return rates. As a result, without expanding the aeration tank, maximum average daily inflow that can satisfy the effluent water quality standard of BOD $0.02kg/m^3$ was determined as $2,840m^3/hr$, subject to 100% of activated-sludge return rate while other factors remain constant. When the activated-sludge return rate is less than 100%, expansion of the aeration tank is necessary and minimum sizes of the aeration tank to satisfy the effluent water quality standard were determined for various activated-sludge return rates. In addition, the total operating and maintenance as well as unit treatment cost regression equations for activated-sludge wastewater treatment plants are suggested by using the cost data that are obtained from Water and Wastewater Division, Ministry of Environment. The regression analyses showed that the economies of scale phenomena exist in the operating and maintenance costs of activated-sludge wastewater treatment plants.

• 한국환경복원기술학회지
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• 제14권3호
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• pp.101-113
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• 2011

The purpose of this study are to develop a SDSS (Spatial Decision Support System) that can incorporate diverse opinions of stakeholders related the designation of protected areas (PA), and to employ the model for the readjustment of the boundary line of the Jirisan National Park of Korea. The SDSS would lead to more rational and less controversial decision-making during the expansion or removal of PA in Korea. Research methods are as follows. Firstly, to select evaluation criteria for SDSS for PA designation by using expert interview and literature survey. Secondly, to measure their preferences on the designation of additional PA or the removal of a part of PA based on the opinions of various stakeholders such as local residents, environmental groups, or public officials. Thirdly, to produce conservation priority maps based on a multi-criteria decision making technique. The SDSS would be used to rational decision making for the expansion of PA or the release of a certain part of PA by reflecting diverse preferences on biodiversity conservation and economic interest of residents. The visualization of conservation priority maps would also increase the efficiency of such decision making processes. The evaluation criteria for the expansion of PA for biodiversity conservation includes vegetation conservation value, wildlife conservation value, and the habitats of key species. The evaluation criteria for the removal of PA includes the proximity to roads and the boundary of PA, land use types, and conservation zoning of the PA. Preference weights are based on data collected from the Jirisan National Park. Both the conservation priority and removal priority maps are based on land parcels so that property rights of all parcels would be correctly represented.

• 한국정보시스템학회지:정보시스템연구
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• 제29권1호
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• pp.75-91
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• 2020

Purpose Retrofit, defined to be addition of new technologies or features to the old system to increase efficiency or to abate GHG emissions, is considered as an important alternative for the old coal-fired power plant. The purpose of this study is to propose mathematical method to model multiple alternative retrofit in Generation Capacity Expansion Planning(GCEP) problem, and to get insight to the retrofit patterns from realistic case studies. Design/methodology/approach This study made a multi-alternative retrofit GECP model by adopting some new variables and equations to the existing GECP model. Added variables and equations are to ensure the retrofit feature that the life time of retrofitted plant is the remaining life time of the old power plant. We formulated such that multiple retrofit alternatives are simultaneously compared and the best retrofit alternative can be selected. And we found that old approach to model retrofit has a problem that old plant with long remaining life time is retrofitted earlier than the one with short remaining life time, fixed the problem by some constraints with some binary variables. Therefore, the proposed model is formulated into a mixed binary programming problem, and coded and run using the GAMS/cplex. Findings According to the empirical analysis result, we found that approach to model the multiple alternative retrofit proposed in this study is comparing simultaneously multiple retrofit alternatives and select the best retrofit satisfying the retrofit features related to the life time. And we found that retrofit order problem is cleared. In addition, the model is expected to be very useful in evaluating and developing the national policies concerning coal-fired power plant retrofit.

• 한국인터넷방송통신학회논문지
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• 제22권1호
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• pp.181-186
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• 2022

세계 전기자동차 분야는 기술적 환경변화를 넘어서 시장 환경에까지 영향을 미치는 단계로 전환하여 완성차업체들은 "기술 우위 → 브랜드 제고 → 기존 내연기관 차량의 판매 확대"라는 기존 전략에서 시장경쟁력 제고라는 전기자동차 시장 자체의 확대로 전환되고 있다. 또한 전기자동차 부품시장은 기존 부품업체들의 사업영역 확대와 신규업체들의 진입으로 경쟁이 심화될 전망이며, 전기자동차 주요 부품의 효율성 향상을 위해 개발 협력도 활발히 진행될 전망이다. 이러한 전망과 함께 전기자동차가 성장할수록 자동차 산업의 전반적인 구조적 변화가 예상됨에 따라 배터리, 파워트레인(모터, 전력관리 제어시스템), 전기차 생산, 충전 인프라 등 전기자동차 Value Chain 전반의 성장이 예상된다. 따라서 본 논문에서는 변화되고 있는 전기자동차 산업의 발맞춰 기업이 원하는 다양한 고급인력을 양성하기 위해 전기자동차의 에너지 및 전기 요소기술을 선도하는 인력양성 알고리즘을 연구한다.