• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.185.2-185.2
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• 2010

한반도 국가바람지도(김현구, 2009)는 한국에너지기술연구원에서 지식경제부의 부처임무사업으로 구축되었으며 현재 웹서비스(http://www.kier-wind.org)를 통하여 정보를 제공하고 있다. 국가바람지도는 수치기상예측(NWP; Numerical Weather Prediction) 모델을 이용하여 영토, 영해에 대해 $1km{\times}1km$의 고해상도로 작성한 뒤(이순환 등, 2009) 풍력자원 정보로 재가공되었다. 한반도 국가바람지도는 5년의 장기간에 대한 시계열 수치기상예측에 의하여 구축되었기 때문에 데이터베이스(DB; database)의 효율적 관리가 필연적으로 요구된다. MM5 또는 WRF 모델의 고유 출력포맷의 자료구조는 풍력자원분석에 필요한 기상요소 외에도 대기과학자에게 필요한 수많은 기상인자를 종합적으로 포함하고 있다. 따라서 2차원 층(layer) 또는 3차원 공간분포 분석 및 계산격자인 셀(cell)에서의 1차원 시계열 분석 등 다양한 자료축출에는 비효율적인 자료구조가 된다. 이러한 자료구조의 불편을 해소하기 위해서는 기상요소별로 독립적이고 빈번한 시계열 자료 추출에 효율성을 가지며 어떤 프로그래밍 언어를 사용하든지 직관적으로 쉽게 사용할 수 있는 바람지도 데이터베이스의 재구성이 요구된다. 이에 대용량 수치자료의 처리 측면에서 장점을 가지는 과학기술 프로그래밍 언어인 IDL을 기반으로 국가바람지도의 자료구조를 효율화하여 데이터베이스화 하였으며 IDL에 내재된 그래픽 기능을 활용하여 가시화를 구현함으로써 연구개발자의 입장에서 국가바람지도의 활용성 및 효율성을 향상시키고자 하였다.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.4
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• pp.3-9
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• 2017

Due to difficulties of continuous electric power provision to underwater communication nodes, the efficient power usage is highly required in underwater network protocol. In this paper, we studied the energy efficient MAC(Medium Access Control) protocol for underwater network supporting mobile nodes such as UUV(Unmanned Underwater Vehicle) and AUV(Autonomous Underwater Vehicle). The mobile nodes could waste the electric power in vain when the receiver moves out of the radio propagation coverage during the data exchange and thus the transmitted data fails in reaching the receiver. Expecially, such a failure is much more obvious in underwater acoustic channels since the propagation delay is about $10^5$ times slower than in terrestrial radio channels. This proposed mobility-MAC controls the data dropping stochastically in the Dropping Zone by considering the receiver's location and moving velocity. In conclusion, this selective dropping method not only improves latency and throughput by reducing invalid droppings but also boosts power efficiency by valid droppings.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.537-544
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• 2001

Anatase $TiO_2$thin films as a photocatalyst were prepared by the reactive magnetron sputtering process. The $TiO_2$thin films were deposited on Si substrates under the various conditions : oxygen partial pressure, working pressure, sputtering time, and D.C. power. The photocatalystic degradation of $TiO_2$thin film have been studied to examine the contribution of surface morphology and crystallinity. The thin films with a good crystallinity or a rough surface showed a high photocatalytic degradation rate on phenol and E.coli 078 experiment. Compared with that of only UV radiation, the photocatalytic efficiency of $TiO_2$thin film under the UV radiation and the $O_2$ flow increased. We found that the crystallity and the morphology were the important factors on the photocatalytic efficiency of TiO$_2$thin film.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2528-2534
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• 2011

This paper investigates the relationship between the change of age structure of population and the efficiency of education investment, using cross-section of 106 countries. Based on the existing theoretical arguments, we establish a hypothesis concerning the relationship between age structure and education investment efficiency. The regression results suggest that a country's with a higher ratio of young age to total population results in a lower level of the efficiency of education investment. However, there exists a positive and significant relationship between the ratio of old age to total population and the efficiency of education investment. Therefore, it does suggest that countries experiencing reducing in fertility rate and increasing in expected longevity, such as Korea, not only should be maximized the education efficiency but also contrived for the institutional system for maximization the efficiency of education performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2826-2832
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• 2012

A smart grid is an electric-power grid that employs a new information technology.This technology makes it possible to exchange real-time energy information between suppliers and consumers, finally resulting in high energy efficiency. The energy management system in smart grid provides up to date information on electricity consumption as well as dynamic electricity price to consumers of smart grid system. However, the existing energy management systems only focus on pricing system, for example, real-time electricity prices. In this paper, we try to improve the existing energy management system and propose the energy management system that mainly focuses on the efficiency of electricity consumption. In the proposed management system, PMU(Phasor Measurement Units) installed in switchboards gathers electricity data in a real time. We also propose to use data mining method, which is applied to analyzed electricity data for improving energy efficiency. Also, the proposed energy management system is designed to efficiently control the electricity between PMU and management system in case of a shortage of electricity or surplus electricity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11A
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• pp.1117-1123
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• 2008

Applications for mobile multimedia are testing the performance limits of present day CPUs with variety. However, hardwired solutions are inflexible and expensive to develop. CPUs with flexibility have limitation of performance. So, the requirement for both ASIC-like performance and CPU-like flexibility has led to reconfigurable processor. Mobile systems require low power and high performance concurrently. In this paper, we propose reconfigurable processor for mobile multimedia with high energy efficiency. Reconfigurable processor with 121MOPS/mW is developed by 130nm CMOS technology. And the processor was simulated for energy efficiency with 539MOPS/mW by 90nm CMOS technology and effective use of instructions. And we tested its applications for multimedia field. We tested the case of inverse MDCT for MP3 and DF for MPEG4 and ME for H.264.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.12
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• pp.59-70
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• 2003

Proposed CCRSVP (Candidate Casting RSVP) algorithm is a new fast handoff method which uses advanced multicasting method and RSVP for IEEE 802.11 Wireless LAN (WLAN) environments. The proposed algorithm shows good performance in the handoff latency and the B/W efficiency aspect and guarantees QoS because it uses L2 information (BSSID) of WLAN and starts to reserve resources and multicast packets before L2 handoff completes. We also propose a Markov chain performance analysis model in which we can analyze the handoff performance of various handoff algorithms. Using the model, we compare bandwidth efficiency of the proposed algorithm with existing handoff algorithms which use RSVP by analyzing blocking probability of session, resource usage, and the average number of ongoing session in a cell. The results show that the proposed algorithm shows better performance than the existing algorithms in the above three performance aspects.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.111-111
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• 2008

태양전지는 태양에너지를 직접 전기에너지로 변환시켜주는 광전 소자로서 구조적으로 단순하고 제조 공정도 비교적 간단하지만, 실용화를 위해서는 비용적인 측면이 많은 걸림돌이 되고 있다. 기존의 실리콘 태양전지는 낮은 광흡수율, 고비용임에도 불구하고 가장 많이 활용되고 있는 태양전지 기술이다. 그러나 태양전지의 경제성 향상과 실용화를 위해서는 기존의 실리콘 태양전지 보다 고효율 및 고신뢰도의 박막형 태양전지의 개발이 필요하다. 박막헝 태양전지의 재료로는 비정질 실리콘, 다결정 실리콘. CIGS, CdTe 등이 있다. 그 중에서도 박막형 태양전지에 광흡수층 물질로는 밴드갭 에너지 (l.4eV 부근), 변환 효율, 경제성 등을 고려했을 때 II-VI족 화합물인 CdTe가 가장 적합한 것으로 각광받고 있다. 하지만 아직까지 실리콘 태양전지에 비해 효율이 많이 떨어지는 단점을 가지고 있기 때문에 효율을 더 끌어올리기 위한 연구가 활발히 진행되고 있는 실정이다. 또한 CMP(chemical mechanical polishing) 공정은 반도체 박막 분야뿐만 아니라 물리, 화학 반응의 기초 연구에도 널리 응용이 되는 기술로써, 시료와 연마 패드 사이의 회전마찰에 의한 기계적 연마와 연마제 (abrasive) 에 의한 화학적 에칭으로 박막 표면을 평탄화하는 기술이다. 본 연구에서는 sputtering 법에 의해 증착된 CdTe 박막에 CMP 공정을 적용하여 표면 특성을 개선한 뒤 태양전지 변환 효율과 직접적인 연관성을 가지고 있는 표면 및 광특성의 변화를 CMP 공정 전과 후로 비교하였다. 표면의 변화를 관찰하기 위해서 AFM(atomic forced microscope) 과 SEM(scanning electron microscopy) 을 이용하였으며, 광특성의 비교를 위해서 흡수율과 PL특성을 측정하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.149-156
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• 2017

Nuclear fuel requires high reliability and safety and therefore contains debris filtering devices to prevent failure-inducing debris from entering it. The debris filtering performance of nuclear fuel is one of the most important factors for fuel integrity. Therefore, the performance must be evaluated and the measurement must be reasonable. In this study, a calculation method of the comprehensive filtering efficiency using the weighted mean was proposed to establish a standard filtering efficiency index. To confirm the suitability of the proposed method, representative debris specimens were selected and the filtering efficiency with the weighted mean was compared with the efficiency of the arithmetic mean. The weighting factor of the weighted mean was introduced to produce a fair evaluation. In addition, the analysis of the debris filtering mechanism was performed according to the size of debris specimens, and the main dimensions of the filtering feature for commercial nuclear fuel.

• Journal of Korean Society of Forest Science
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• v.101 no.4
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• pp.729-736
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• 2012

Korea Forest Service is recently focused on forest tending works for promoting in green jobs. The purpose of forest tending work is not only maintaining ecologically stable forest stand structure but also developing commercial forest. These trends are also emphasized by creation of various benefits and expanding carbon absorption in forest management. For achieving these purposes, Management efficiency of output was analized by the inputs such as labor cost, material cost and expense cost using DEA technique. The results show that, 19 sub-compartments are appeared to be the optimal in the efficiency of the forest tending works among total 52 sub-compartments. Among those there were 5 sub-compartment 8-0-3, 9-3-3, 6-0-3, 7-0-6, 1-0-5 and 3-0-3 to be considered in the high reference. The high reference areas mean those areas which is well accomplished in forest tending works as the desirable model.