• Korean Journal of Environment and Ecology
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• v.28 no.6
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• pp.715-724
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• 2014

Tongdosa, which is located in Gajisan(Mt.) Provincial Park of Yangsan City, is one of three representative temple in Korea. The purpose of this study was to investigate a relation between plants community and environmental factors in Tongdosa(Temple) District of Gajisan(Mt.) Provincial Park. In order to find out vegetation structure of Gajisan(Mt.) Provincial Park, thirty one plots(unit size: $200{\sim}300m^2$) were set up and surveyed. For environmental factors, it were surveyed and analyzed physical factors such as altitude, aspect etc. and soil characteristics such pH, organic content, total nitrogen content, exchangeable cation and so on. Using DCCA technique, a relation between plants community and environmental factors were analyzed. The surveyed plots were divided into five groups which are Pinus densiflora - Quercus aliena, Carpinus tschonoskii - Q. spp., P. densiflora - C. tschonoskii, P. densiflora - Q. variabilis, and Q. variabilis - Q. mongolica community. Vegetation succession was progressed from Pinus densiflora toward Carpinus tschonoskii and Quercus spp. It was found out that the distribution of vegetation was affected by altitude. Pinus densiflora - Quercus aliena community is located lower altitude and Q. variabilis - Q. mongolica community is located higher area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.444-455
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• 2019

The purpose of this research was to analyze technological trends of 「Military Small Giant Venture Tech-Fi Net」 from Defense Technology Information Service via social network analysis. 「Military Small Giant Venture Tech-Fi Net」, which was constituted for their fine technology for application to the military field, registered 847 technologies of 388 companies. In this research, we analyzed 847 technologies for the relations between "Military System" and "Military Technology Category" via centrality measurement, one of the social network analysis methods. The results indicate that the major technologies of domestic military small giant venture companies were "Sensor" and "ICT" for "C4I System" and "Surveillance and Reconnaissance System" and "Platform/Structure" for "Land System", "Aeronautical System" and "Naval Sea System". In contrast, we recognized inadequate technologies, such as "Propellant" and "Material" for "Missile and Ammunition system" and "Sensor" and "ICT" for "Defense System", We hope that our results and method will be conducive to the technological development of Small Giant Venture companies.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.329-330
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• 2017

본 논문에서는 계통 연계 단상 인버터의 양방향 모드 전환을 위한 새로운 제어 기법을 제안하였다. 일반적으로 DC 측과 AC 측 사이의 전력 흐름은 d-q 동기 회전 좌표계에서 계통 연계 인버터의 전류 지령치에 의해 제어된다. 따라서 전력 흐름의 방향이 변경되면 전류 지령치를 반전하는 것이 일반적이다. 그러나 전류의 급격한 변화를 초래하고 과도상태가 길어지는 등 AC 측의 전력 품질을 악화시킨다. 따라서 본 논문에서는 동기 회전 좌표계에서의 원활한 모드 전환을 위한 향상된 제어 기법을 제안한다. 이론적 분석과 시뮬레이션 결과로 제안된 제어 기법의 타당성을 입증한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2022.05a
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• pp.52-55
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• 2022

5G 시대에 스마트 모바일 기기가 기하급수적으로 증가하면서 멀티 액세스 엣지 컴퓨팅(MEC)이 유망한 기술로 부상했다. 낮은 지연시간 안에 계산 집약적인 서비스를 제공하기 위해 MEC 서버로 오프로딩하는 특히, 태스크 도착률과 무선 채널의 상태가 확률적인 MEC 시스템 환경에서의 오프로딩 연구가 주목받고 있다. 본 논문에서는 차량의 전력과 지연시간을 최소화하기 위해 로컬 실행을 위한 연산 자원과 오프로딩을 위한 전송 전력을 할당하는 심층 강화학습 기반의 오프로딩 기법을 제안하였다. Deep Deterministic Policy Gradient (DDPG) 기반 기법과 Deep Q-network (DQN) 기반 기법을 차량의 전력 소비량과 큐잉 지연시간 측면에서 성능을 비교 분석하였다.

• Journal of Korean Library and Information Science Society
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• v.51 no.4
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• pp.101-119
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• 2020

The study aims to understand major topics and concerns of gender identity-related questions expressed by the users of the NAVER social Q&A site. To achieve this goal, we analyzed 2,120 questions created from 2010 to 2018 using natural language- and information retrieval-based methods. Results indicated that the major topics discussed by the users include interpersonal relationships, doubts about gender identity, sexual orientation, feelings and relationships, and concerns about gender identity. In addition, users mainly expressed concerns regarding general issues of gender identity; sexual orientation; negative cognition about gender identity; confession, coming-out, homosexuality; future, heterosexual relationships, military enlistment; and causes of gender identity confusion. The present study effectively derives information needs from real-world concerns about sexual identity by employing topic modeling techniques, and by comparing the advantages of exact match and tf-idf-based information retrieval methods extends methodology of Library and Information Science. Further, it has contributed to the academic maturity of the study of information behavior by observing the information needs or information-seeking behaviors of online community users with specific interests.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.558-565
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• 2013

In this paper, modeling and simulation for performance analysis of high resolution SAR system has been carried out in the time, frequency and numeric domain using ADS Ptolemy simulation tool of Agilent corporation. SAR system consists of antenna, controller and transceiver. Error parameters affecting SAR system performances have been defined, modeled and simulated such as phase noise of frequency synthesizer, amplitude and phase characteristic of TWTA, sampling frequency of waveform generator and I/Q imbalance. Finally, the development requirements of SAR system based on the impulse response function have been derived.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.188-196
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• 2021

For the tactical vehicles operated by the Korean army, the hub-reduction portal axle was applied considering Korea's topographical characteristics. Hub-reduction was applied to a Korean military vehicle to increase the vehicle body to secure ground clearance and improve the driving capability on rough roads, such as unpaved and field land by increasing the torque. The Korean military is operating tactical vehicles after various performance tests, including durability driving, but wheel damage occurred in one of the vehicles operating in the front units. Failure analysis revealed many damaged parts, including the hub, making it difficult to determine the cause. Therefore, an analysis of the failure occurrence mechanism for each damaged part was conducted, which confirmed that the cause of wheel breakage was a hub. Furthermore, the root cause of the hub breakage was a crack due to internal pores and foreign matters. In addition, a realistic improvement plan that can be applied throughout the design, manufacture, and shipping stages was presented using the fishbone diagram analysis. The derived improvement plan was verified through unit performance tests, including CAE and actual vehicle tests, and by reflecting this, the driving safety of Korean tactical vehicles was improved. Finally, it is expected that the proposed method for analyzing the failure occurrence mechanism will be used as reference material when analyzing the quality problems of similar military vehicles in the future.

• Korean Journal of Environment and Ecology
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• v.34 no.4
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• pp.304-317
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• 2020

This study conducted selected two sites in Geumnamhonam and four sites in Honam-Jeongmaek for vegetation survey with consideration to the location environment and anthropogenic impacts to investigate the vegetation structures of the Geumnamhonam-Jeongmaek·Honam-Jeongmaek ridge areas. Using TWINSPAN (two-way indicator species analysis), each of the two ridge areas were categorized into seven plant communities. The differential species in the TWINSPAN technique indirectly represent the environmental factors of plant communities, and the community types of the two ridge areas were divided based on environmental factors such as altitudes above sea level, soil moisture, and disturbance. These results were in harmony with the environmental factors of the DCA (detrended correspondence analysis) axis 1. In the low-lying areas of both ridge areas, afforestation tree species such as Pinus rigida and P. thunbergii were in competition with native tree species. As such, in the low-lying areas, artificial vegetation disturbance was severe due to afforestation and development projects. In relatively highland areas, such as upper slopes, and top areas, in the ridge, the vegetation type with the dominance of Quercus mongolica, Q. variabilis, and P. densiflora was preserved well. As for differences between the two ridge areas, communities dominated by Q. mongolica were distributed widely in Geumnamhonam-Jeongmaek because of the altitudes above sea level, and the latitude of this ridge area are higher than those of Honam-Jeongmaek. On the other hand, communities dominated by P. densiflora were distributed along with communities dominated by Q. mongolica, and communities dominated by Q. variabilis appeared in Honam-Jeongmaek because it is adjacent to the south coast. In quantitative vegetation analysis such as TWINSPAN and DCA, changes in species composition and the extracting environmental factors that cause the changes are important. To that end, the removal of accidental emergent species, the establishment of an investigation plan that assumes environmental factors, and the selection of the optimal analytical method suitable for the characteristics of the survey data are necessary.

• Journal of KIISE:Software and Applications
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• v.29 no.11
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• pp.785-794
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• 2002

Automatic stock trading systems should be able to solve various kinds of optimization problems such as market trend prediction, stock selection, and trading strategies, in a unified framework. But most of the previous trading systems based on supervised learning have a limit in the ultimate performance, because they are not mainly concerned in the integration of those subproblems. This paper proposes a stock trading system, called R-Trader, based on reinforcement teaming, regarding the process of stock price changes as Markov decision process (MDP). Reinforcement learning is suitable for Joint optimization of predictions and trading strategies. R-Trader adopts two popular reinforcement learning algorithms, temporal-difference (TD) and Q, for selecting stocks and optimizing other trading parameters respectively. Technical analysis is also adopted to devise the input features of the system and value functions are approximated by feedforward neural networks. Experimental results on the Korea stock market show that the proposed system outperforms the market average and also a simple trading system trained by supervised learning both in profit and risk management.

• Korean Journal of Environment and Ecology
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• v.8 no.2
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• pp.121-134
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• 1995

To investigate the plant community structure in Pinus densiflora forest of Chuwangsan National Park, twenty five plots were set up and surveryed. The classification by TWINSPAN and DCA ordination techniques were applied to the study area. The plant community were divided into five groups in twenty five plots by DCA and the dividing groups were Pinus densiflora-Quercus variabilis community(I), P. densiflora-Q. serrata community(II), P. densiflora-Fraxinus sieboldiana community(III), P. densiflora-F. sieboldiana-Q. spp. community(IV) and P. densiflora-mixed deciduous forest community(V). The successional trends of tree species by DCA ordination techniques and DBH class distribution analysis seems to be from P. densiflora through Q. mongolica, Q. serrata to Carpinus laxiflora in the canopy layer group. And in the subtree and shrub layer, it was expected that Lespedeza maximowiczii, L. cytobotrya, Rhododendron mucronulatumlongrightarrowStyrax obassia, Stephandra insisa, Zanthoxylum schinifolimlongrightarrowAcer pseudo-sieboldianum, Lindera obtusiloba. There was no difference between the stand scores of DCA and soil pH, and soil moisture.