• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.749-761
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• 2014

Improving spectrum utilization efficiency is a fundamental goal of dynamic spectrum access technology. The definition of spectrum holes determines how to detect and exploit them. Current definitions of spectrum holes are ineffective in exploiting spatial-temporal spectrum holes. In this paper, a novel definition of spectrum holes is proposed, in which throughput loss indicates the impact of secondary users on primary users. The definition specifies spectrum holes, unifies the impact of secondary users on primary users and is effective exploiting spatial-temporal spectrum holes. Theoretical analysis and numerical simulations show that the new definition proposed in this paper significantly improves the spectrum utilization efficiency.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.135-138
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• 2009

Most of the studies use model order reduction for low frequency (LF) response analysis due to their high computational efficiency. In LF response analysis, one of model order reduction, algebraic substructuring (AS) retains all LF modes when using the modal superposition. However, in mid-frequency (MF) response analysis, the LF modes make very little contribution and also increase the number of retained modes, which leads to loss of computational efficiency. Therefore, MF response analysis should consider low truncated modes to improve the computational efficiency. The current work is focused on improving the computational efficiency using a AS and a frequency sweep algorithm. Finite element simulation for a MEMS resonator array showed that the performance of the presented method is superior to a conventional method.

• The Korean Journal of Health Service Management
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• v.10 no.3
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• pp.1-12
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• 2016

Objectives : This study examined relations between investment efficiency and management performance as indexes related to productivity of Korean regional public hospitals. Methods : The analysis data are financial information of Korean regional public hospitals from 2011 to 2014. For the indicators, value added to total assets, value added to productive activity tangible fixed assets, and value added to personnel expenses, operating margin to revenues, net profit to total earnings, and ratio of value added. Results : Significant relevance was not shown among indicators of investment efficiency. However, Significant relevance was shown between value added to personnel expense and productivity per value added. Conclusions : It confirmed that outside support funds like subsidy did not have effect on improving the management performance. Also, it could be known that availability about input of capital and labor was not realized organically.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.69-76
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• 2015

This study investigates the thermal efficiency and the efficiency of heat transfer through thermal analysis when the same heat is applied to a mortar frame by firing with various configurations of mortar. As the inside diameter of the mortar increases, the additional material must be reinforced. In comparison with the extent of getting cold due to models, a mortar with the strut under the gun barrel becomes cooler than one with no strut. The thermal deformation at firing becomes different. According to the configuration of mortar and its inside diameter, the extent of getting cold becomes different. This study result can be effectively applied for improving the efficiency of the heat transfer of mortar.

• Asia pacific journal of information systems
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• v.10 no.3
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• pp.17-40
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• 2000

This study aims at proposing a direction of improving the efficiency in Korean information technology(IT) industry. In the face of re-engineering which has been done in most industries, it is very important to assess the validity of their restructuring or M&A based on the future efficiency. At first, by using the DEA/WINDOW, we will evaluate how the 30 firms are efficient for outputting their performance with respect to the profit realization and market ability. Then, in order to propose the direction of the efficiency improvement and suitable restructuring strategy, we will clarify how the efficiency of IT firms depends on their firm size. Finally, we will analyze their 'economy of scale' and also reveal how their economy of scale depends on the firm size based on return-to-scale(RTS).

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.2
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• pp.41-48
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• 2000

An experimental study is made to improve the efficiency of floating breakwaters. Wave transmission coefficients highly depend on the drafts of the floating breakwaters but not on the mooting chain weights. Array of two breakwaters can improve the efficiency of the floating breakwaters. Proper draft combination of the fore and the aft bodies may improve the performance of the floating breakwaters lot various wave periods.

• Journal of Distribution Research
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• v.1 no.2
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• pp.141-172
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• 1996

This study is to investigate global logistics strategies of Korean electronics companies. in terms of service parts. According to the survey, Korean electronics companies were pursuing multi-level global logistics network such as global, continental, national, regional and service center echelon for improving the efficiency of service parts global logistics. Especially there was a tendency of developing new continental distribution centers. And the companies were exploiting efficiency through inventory control by multi-level echelon, demand forecasting by the product life cycle and supply and service lead time management. But there were some insufficient factors for the efficiency of global logistics operation at the construction of worldwide real time logistics information system and pursuit of the efficiency on the whole network including subcontractors. For the future competitive advantage of the Korean electronics companies, the following are suggested: 1) the establishment of arranged logistics channel adjusting each company's global strategy, 2) the construction of worldwide real time logistics information system, 3) the reengineering of all logistics procedures such as order processing, shipping, inventory control, etc., 4) the enhancement of the ratio of the supply from the external companies and the internal manufacturing subsidiaries at each continent, 5) and the pursuit of operational internalization of external subcontractors.

• Korean Journal of Computational Design and Engineering
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• v.17 no.1
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• pp.54-61
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• 2012

In this paper, we performed numerical analysis to improve the heat exchange efficiency of wasted heat recovery ventilator which has a delivery and a exhaustion fan. One of the most important design factors that affect the efficiency of heat exchange is uniform counter-flow between inbound and outbound air flows. We had simulated several types of porous plates which were installed at air intake area. With plate having 45 degrees of installation angle and 15 mm diameter holes which are uniformly arranged, we can generate a uniform air flows at the area of porous media where inbound and outbound air flows are cross over. In addition, we installed a duct to reduce vortex flows at the outlet and to discharge exhaust airs rapidly. By using the proposed numerical assessment, we expect the improvement of the heat exchange efficiency of ventilator.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.11
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• pp.529-535
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• 2003

In this paper, we presents the characteristics of the new electrode structure in an AC Plasma Display Panel(PDP) that can generate dual mode discharges with a combination of short-gap and long-gap discharges. The experiment results show that the discharge voltage of the new electrode structure is mainly determined by short-gap discharge and the luminous efficiency is improved by 20% compared with the conventional electrode structure. The improvement of luminous efficiency is mainly caused by higher VUV generation and broader distribution from Ole ICCD camera measurements.

• Journal of ILASS-Korea
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• v.9 no.3
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• pp.15-21
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• 2004

The removal of the dusts in the subway stations, tunnels, factories and buildings becomes issue for comfortable indoor and outdoor conditions. There has been used an automatic self-cleaning filter system to collect the dusts. In general, the collected particles are removed by water spray nozzles. The new design for improving the cleaning efficiency of collected dusts and reducing the supplied water is the concept of the plane array of demister filters and the twin-fluid nozzle for mixing compressed air and water in the automatic self-cleaning filter system. Results show that the cleaning efficiency of twin-nozzle filter systems is 99.1%, compared to 47% in the conventional filter system. Therefore the automatic self-cleaning filter system using twin-fluid nozzle filter systems reduces water supplied in the filter system, and increases cleaning efficiency and drying efficiency.