• Journal of Korean Society for Atmospheric Environment
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• 제24권E2호
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• pp.63-73
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• 2008

In this study, neural network models (NNMs) were examined as alternatives to dispersion models in predicting the short-term $SO_2$ concentrations in a coastal area because the performances of dispersion models in coastal areas have been found to be unsatisfactory. The NNMs were constructed for various combinations of averaging time and prediction time in advance by using the historical data of meteorological parameters and $SO_2$ concentrations in 2002 in the coastal area of Boryeung, Korea. The NNMs were able to make much more accurate predictions of 1 hr $SO_2$ concentrations at ground level in the morning in coastal area than the atmospheric dispersion models such as fumigation models, ADMS3 and ISCST3 for identical conditions of atmospheric stability, area, and weather. Even when predictions of 24-h $SO_2$ concentrations were made 24 hours in advance, the predictions and measurements were in good accordance(correlation coefficient=0.65 for n=216). This accordance level could be improved by appropriate expansion of training parameters. Thus it may be concluded that the NNMs can be successfully used to predict short-term ground level concentrations averaged over time less than 24 hours even in complex terrain. The prediction performance of ANN models tends to improve as the prediction lagging time approaches the concentration averaging time, but to become worse as the lagging time departs from the averaging time.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 추계학술대회
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• pp.23-30
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• 2000

A calculation technique which estimates natural recharge was proposed and prepared with the existing techniques. And the necessity to obtain representative averages of 'specific yield' was discussed.

• 정보관리학회지
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• 제32권3호
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• pp.183-197
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• 2015

이 이론적 논문의 목적은 도서관서비스 시장을 확인하고 일반 상품시장과 대비되는 도서관서비스 시장의 특성을 파악하여 연구 및 실천 부분에서 도서관 마케팅 및 경영의 논의를 더욱 풍성하게 하는 데에 있다. 도서관서비스 시장은 일반 시장의 모형을 기반으로 확인하였으며, 일반 상품시장과 비교하여 도서관서비스 시장은 간접 교환, 제한 경쟁, 그리고 시차적 교환이라는 특성이 있음을 밝혔다. 이러한 특성에 기반하여 도서관 경영의 목표 및 목적의 개발과 도서관 마케팅에의 적용이라는 두 가지 연구방향을 제안하였다.

• 농촌계획
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• 제20권4호
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• pp.45-54
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• 2014

The main purpose of this study is to provide the back-from-city farmers with the information about the melon cultivation technology by surveying 268 farm houses in the major melon producing districts such as Seongju and Chilgok. For the purpose, this study classifies the essential technologies that the melon experts think as most important into 6 categories: size of plastic film house, covering film, varieties of oriental melon, lagging cover, ventilation method and ways to reduce repeated-cultivation damage. The result of the study shows that the back-from-city farmers should consider the following items when they choose to cultivate oriental melons. For the size of plastic film house, the ventilation method and the covering film of plastic film house, it is better to choose the latest technology. Even though it may require larger initial investment, the latest technology can increase the production and lower the cost. In case of variety, it is better to choose popular or the most widely grown ones rather than the new ones. The lagging cover should be selected in consideration of climate conditions such as average temperature and humidity, transplant time and harvest time of the farming region.

• 대한안전경영과학회지
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• 제16권3호
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• pp.451-469
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• 2014

The purpose of this study is to implement and develop the integrated Economic Value Added (EVA) and Time-Driven Activity-Based Costing (TDABC) model to seek both improvement of Net Operating Profit Less Adjusted Tax (NOPLAT) and reduction of Capital Charge (CC). Net Operating Profit Less Adjusted Tax (NOPLAT) can be maximized by reducing the indirect cost of an unused resource capacity increased by Cost Capacity Ratio (CCR) of TDABC. On the other hand, Capital Charge (CC) can be minimized by improving the efficiency of Invested Capital (IC) considered by Weighted Average Cost of Capital (WACC) of EVA. In addition, the integrated system of TDABC using Balance Scorecard (BSC) and EVA is developed by linking between the lagging indicators and the three leading indicators. The three leading indicators include customer, internal process and growth and learning perspectives whereas the lagging indicator includes NOPLAT and CC in terms of financial perspective. When the Critical Success Factor (CSF) of BSC is cascading as a cause and an effect relationship, time driver of TDABC and capital driver of EVA can be used efficiently as Key Performance Indicator (KPI) of BSC. For a better understanding of the proposed EVA/TDABC model and BSC/EVA/TDABC model, numerical examples are derived from this paper. From the proposed model, the time driver of TDABC and the capital driver of EVA are known to lessen indirect cost from comprehensive income statement when increasing the efficiency of operating IC from the statement of financial position with unified KPI cascading of aligned BSC CSFs.

• 한국항공우주학회지
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• 제33권10호
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• pp.10-16
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• 2005

본 연구에서는 3차원 시간 정확도를 가진 오일러 공탄성 해석 기법을 개발하였다. 유체-구조를 연계 시 발생할 수 있는 지연(lagging) 오차를 감소시키기 위해서 2차의 staggered 알고리즘을 적용하였다. 비정상 공력 해석과정에서 시간 정확도와 계산 시간을 줄이기 위해 사용된 병렬화된 다중격자기법(parallelized multi-grid method)과 DADI 기법을 기반으로 된 이중시간전진기법(dual-time stepping method)을 사용하였다. 오일러 공탄성 코드의 검증을 위해서 AGARD 445.6 날개 모델의 공탄성 해석을 수행하였다. 해석 결과는 실험값 및 다른 참고문헌의 해석 결과와 비교하였으며, 본 연구의 해석 결과가 다른 참고 문헌의 해석 결과들과 비교하여 상대적으로 실험값에 근접하였다.

• 전자통신동향분석
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• 제39권3호
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• pp.69-78
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• 2024

Cloud computing technology based on centralized high-performance computing has brought about major changes across the information technology industry and led to new paradigms. However, with the rapid development of the industry and increasing need for mass generation and real-time processing of data across various fields, centralized cloud computing is lagging behind the demand. This is particularly critical in emerging technologies such as autonomous driving, the metaverse, and augmented/virtual reality that require the provision of services with ultralow latency for real-time performance. To address existing limitations, distributed and edge cloud computing technologies have recently gained attention. These technologies allow for data to be processed and analyzed closer to their point of generation, substantially reducing the response times and optimizing the network bandwidth usage. We describe distributed and edge cloud computing technologies and explore the latest trends in their standardization.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권1호
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• pp.237-252
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• 2017

In recent years, data centers have become the core infrastructure to deal with big data processing. For these big data applications, network transmission has become one of the most important factors affecting the performance. In order to improve network utilization and reduce job completion time, in this paper, by real-time monitoring from the application layer, we propose job-aware priority scheduling. Our approach takes the correlations of flows in the same job into account, and flows in the same job are assigned the same priority. Therefore, we expect that flows in the same job finish their transmissions at about the same time, avoiding lagging flows. To achieve load balancing, two approaches (Flow-based and Spray) using ECMP (Equal-Cost multi-path routing) are presented. We implemented our scheme using NS-2 simulator. In our evaluations, we emulate real network environment by setting background traffic, scheduling delay and link failures. The experimental results show that our approach can enhance the Hadoop job execution efficiency of the shuffle stage, significantly reduce the network transmission time of the highest priority job.

• 한국전자통신학회논문지
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• 제13권6호
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• pp.1177-1182
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• 2018

UCC3895 드라이버를 이용하여 위상천이방식의 100Mhz로 운용되는 500W급 영전압스위칭(Zero voltage switching) DC/DC 컨버터를 설계하였다. UCC3895 드라이버의 데드타임은 풀브리지의 리딩래그와 레깅래그가 별도로 구동 가능하도록 설계되어 있어 두 래그간에 데드타임을 별도로 부여하는 것이 가능하며, 이것은 두 래그간에 비대칭관계인 데드타임으로 영전압스위칭의 구현을 가능하게 하였다. 또한 본 논문에서는 안정된 출력전압을 위한 부귀환회로 설계방식이 제안되었다. 시제품의 최대 효율은 $500{\Omega}$의 부하에서 95.5% 정도를 나타냈다.

• Journal of Power Electronics
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• 제15권3호
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• pp.634-643
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• 2015

This paper presents a high frequency design approach for improving efficiency over a wide load range in the self-driven phase-shifted full-bridge converters for server power systems. In the proposed approach, a detailed ZVS analysis of the lagging leg switches in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM) is presented. The optimum dead time and the determination of the appropriate operation mode are given for high efficiency according to the load conditions. Finally, the optimum operation conditions are defined to achieve a high-efficiency. A laboratory prototype operating at 80 kHz, rated 1 kW (12 V-83.3 A), is built to verify proposed theoretical analysis and evaluations. The experimental results show that the maximum efficiency is achieved as 95% and 83.5% at full load and 5% load conditions, respectively.