• Journal of Korean Society for Atmospheric Environment
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• v.24 no.E2
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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.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.11a
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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.

• Journal of the Korean Society for information Management
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• v.32 no.3
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• pp.183-197
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• 2015

The purpose of this conceptual paper is to identify the library services market and its characteristics versus the common commodity market so that marketing and management in library services can be more fruitful in terms of research and development. Based on the developed hypothetical market, a library services market is identified; the market is then characterized in comparison to the common commodity market using three theoretical characteristics of the library services market: indirect exchange, limited competition, and time-lagging exchange. Based on these characteristics, two possible research directions are suggested: development of goals for library management and consideration of applications in library marketing.

• Journal of Korean Society of Rural Planning
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• v.20 no.4
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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.

• Journal of the Korea Safety Management & Science
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• v.16 no.3
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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.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.10
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• pp.10-16
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• 2005

In this paper, a three-dimensional Euler aeroelastic analysis program is developed with a second-order staggered algorithm to reduce the lagging errors between the fluid and structural solvers. In the unsteady aerodynamic analysis, a dual-time stepping method based on the diagonalized-ADI algorithm is adopted to improve the time accuracy and a parallelized multi-grid method is used to save the computing time. The aeroelastic analyses of AGARD 445.6 wing model have been performed to verify the Euler aeroelastic analysis code. The analysis results are compared with the experimental data and other computational results. The results show comparatively good correlation when they are compared with other references.

• Electronics and Telecommunications Trends
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• v.39 no.3
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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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• v.11 no.1
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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.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.6
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• pp.1177-1182
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• 2018

We designed a 500W zero voltage switching DC / DC converter operating at 100Mhz with phase shift topology using UCC3895 driver. The dead time of the UCC3895 driver is designed so that the leading and lagging leg of the full bridge can be driven separately. So, the dead time can be given between the two legs separately. The dead time, which is an asymmetrical relationship between the two legs, enables the implementation of zero voltage switching. This paper proposed a negative feedback circuit design method for stable output voltage. The maximum efficiency of the prototype was 95.5% at $500{\Omega}$ load.

• Journal of Power Electronics
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• v.15 no.3
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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.