• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.83-87
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• 2009

The MAC protocol of HiperLAN/2 is based on TDMA/TDD. Mobile terminal acquires a data transmission opportunity as successfulness in channel competition through RCH (Random CHannel) phase. Therefore, AP (Access Point) be able to dynamically assign optimum RCH at next frame according to the number of success and collision. In this paper, we suggest scheme that fluctuate RCH (Random CHannel) number as fixed value considering success and collision for improvement of performance in HiperLAN/2. To prove efficiency of proposed scheme, a lots of simulations are conducted and analyzed in view of throughput and access delay.

• KDI Journal of Economic Policy
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• v.9 no.2
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• pp.89-108
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• 1987

우리나라 공기업경영(公企業經營)의 효율성제고(效率性提高)를 위하여 1984년 25개정부투자기관(個政府投資機關)에 도입한 책임경영제도(責任經營制度)와 그에 따른 경영실적평가제도(經營實績評價制度)의 효과(效果)를 측정하기 위하여 매출원가율(賣出原價率) 개선정도(改善程度)에 관한 계량분석과 경영개선 전반에 관한 설문분석(設問分析)을 실시하였다. 정부투자기관(政府投資機關) 임직원(任職員)을 대상으로 한 설문조사(設問調査)에서 전체 응답자의 79%가 정부투자기관(政府投資機關) 최고경영진(最高經營陣)의 경영개선 의지가 과거보다 새로워졌거나 아주 참신해졌다고 응답하였고 사장(社長) 이외 일반직원들의 경영개선을 위한 의식구조 변화에 있어서도 전체 응답자의 72%가 어느 정도 변하였거나 크게 변하였다고 응답하는 등 경영분위기(經營雰圍氣)가 전반적으로 크게 변화를 겪고 있음을 나타냈다. 또한 새로운 공기업정책(公企業政策)의 경영개선(經營改善) 효과(效果)를 계량적으로 분석한 결과 산업은행 등 25개정부투자기관(個政府投資機關)의 1984~86년간 원가절감액은 단순평균치 기준으로는 1조(兆) 1,281억(億)원으로 추정되었으나 신뢰구간 등을 고려한 순원가절감액(純原價節減額)은 2,983억(億)원으로 나타났다. 이러한 성과에도 불구하고 인사관리제도(人事管理制度) 운영(運營)에 대한 불만 잔존 및 경영계획의 실효성 미흡 등의 문제가 제기되고 있는바, 관련 정책당국의 보다 적극적인 책임경영제도(責任經營制度) 운영이 요청되고 있다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.100-109
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• 1995

철도는 대량수송 및 정시제 운행이라는 중요한 역할을 하면서도 다른 한편으로는 철도연변에 거주하고 있는 사람들에게 상당한 소음공해를 미쳐 정온한 생활환경을 누릴 권리를 침해하고 있음에도 불구하고 철도소음을 관리하는 기준이나 대책등이 아직 미미한 실정이다. 향후 5년 내에는 고속철도의 등장도 확실하지만 기존 재래식 철도에 대한 소음 실태 자료마저 충분치 않아 철도연변의 소음진동 문제를 해결하기 위한 기본적 수단인 소음 기준 제시를 위해서는 폭넓은 기초 자료확보와 새로운 관련연구가 요청되었다. 이러한 필요성에 따라 전기기관차를 중심으로 영동선, 중앙선, 태백선, 경인선, 경원선 및 대도시 도심지를 관통하는 호남선 및 경부선 중에서 측정환경이 양호한 22개 지역을 선정하여 기존 철도의 구간별 30분, 1시간, 2시간, 3시간 등가소음도를 측정하였고 선로의 조건, 열차의 종류 및 속도, 거리권별 등에 따른 개별열차 통행시의 소음특성을 조사하여 철도소음의 기준 설정과 방지대책 강구시에 활용할 수 있도록 하며, 열차 통행속도로부터 최고소음도를 추정하여 주변지역의 등가소음도를 산정할 수 잇는 예측식을 도출하여 측정방법 개정에 활용하고, 그리고 선로변에 위치한 공동주택을 대상으로 층별 철도소음 노출도와 열차통과시의 공동주택 실내.외의 소음도를 비교조사하여 벽체 차음 효과를 조사하였고 철도소음에 대한 주민반응 조사를 하였다.

• Journal of Korean Society of Forest Science
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• v.96 no.1
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• pp.70-76
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• 2007

The main purpose of this study was to realize Mountain Search and Rescue System based on Ubiquitous Sensor Network for applying search and rescue operations in the mountains. The on-site survey was conducted in order to test the possibility of data reception rate and sensor network stability, ten nodes was installed on the trail at 100m intervals Unson waterfall to Kwanumbong in Kyeryongsan national park. The results showed that the data reception rate was over 90.0% at least. To test sensor network stability, nodes were randomly turned off one by on. The result was 100% functionality.

• Journal of KIISE:Computing Practices and Letters
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• v.11 no.6
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• pp.531-537
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• 2005

The Tunnel Broker is to provide dedicated servers and to automatically manage tunnel requests coming from the users. This approach is useful to stimulate the growth of IPv6 interconnected hosts and to provide easy access to their IPv6 networks. However, the existing tunnel broker is vulnerable to attacks of malicious users about network resources and services. Therefore, to solve the secure problem of tunnel broker, this paper presents secure IPv6 tunnel broker based on TSP(Tunnel Setup Protocol). The clients and the tunnel broker are communicated based on SHTTP(Secure HTTP) and the XML message of plain text is converted to XML signature by encryption and decryption. finally, Clients and tunnel server use the IPsec method to protect the important information.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.1215-1218
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• 2008

IEEE 802.15.4 기반의 무선 센서 네트워크는 다양한 종류의 센서들로 구성된다. 이러한 센서들은 각각 다양한 주기들로 중심 노드에게 데이터를 전송하고자 한다. 슈퍼프레임마다의 주기적인 전송을 위해 IEEE 802.15.4에서는 GTS(Guaranteed Time Slot) 메커니즘을 제공한다. 하지만 하나의 센서 네트워크에서 슈퍼프레임 길이는 모두 동일하기 때문에 이보다 긴 주기를 갖는 센서들은 GTS를 할당받고도 데이터를 전송하지 않는 경우가 발생할 수 있다. 때문에 IEEE 802.15.4의 GTS 메커니즘에서는 낮은 사용 효율의 문제가 발생한다. 본 논문은 이러한 문제를 보완하고자 주기적 GTS 할당 방법(PGTS: Periodic Guaranteed Time Slot)을 제안한다. 주기적 GTS 할당 방법에서는 단말들이 GTS 요청 시 자신의 데이터 전송 주기를 PAN 코디네이터에게 보고하고, PAN 코디네이터는 이를 고려하여 단말의 주기에 따른 슈퍼프레임에서만 GTS 구간을 할당한다. 이를 통해 주기적 GTS 할당 방법은 기존 GTS 할당 방법보다 대역의 낭비를 줄여 GTS를 효율적으로 사용가능하도록 하고 더 많은 수의 단말들에게 GTS를 배정할 수 있게 한다. 본 논문에서는 시뮬레이션 결과를 통해 주기적 GTS 할당 방법이 IEEE 802.15.4의 GTS 할당 방법보다 효율적이며 더 많은 수의 단말에게 GTS를 할당할 수 있음을 확인하였다.

• Science of Emotion and Sensibility
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• v.14 no.3
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• pp.435-444
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• 2011

The development of ubiquitous healthcare technology and portable electronic devices requires new energy sources for providing continuous power supply. This study particularly focuses on an energy harvesting system capable of charging energy using clothing. One of the sources for energy harvesting is heat energy, which is the difference in temperature of the body and the surrounding environment. In this study, the skin temperature distribution of the human body was empirically measured to determine the basic materials needed to develop heat energy harvesting clothing. The distribution of skin temperature in different sections of the human body was analyzed. The analysis found that the skin temperature of the upper body was higher than that of the lower body. The area close to the heart with a lot of blood flow was especially high. The skin temperature of the back side of the body, such as the back of the neck, upper back, and waist, was higher than that of the front side of the body. As for the arms, the skin temperature of the upper arms was higher than that of the lower arms, and the skin temperature of the back side of the arms was lower than that of the front and the flank side of the arms. The difference in the average skin temperature and the environment temperature was highest at the back of the neck, and thereby is considered to be the most appropriate section to integrate the heat energy harvesting function and structure. The following sections had the next highest difference in values, listed in descending order: the back of the waist, the sides of shoulders, the front chest area, the front side of the upper arms, and the front abdomen. Based on the skin temperatures of the different sections of the human body, this study outlines the basic guidelines for developing heat energy harvesting clothing.

• The KIPS Transactions:PartC
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• v.17C no.1
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• pp.1-14
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• 2010

IEEE 802.15.4[1] has been standardized for the physical layer and MAC layer of LR-PANs(Low Rate-Wireless Personal Area Networks) as a technology for operations with low power on sensor networks. The standardization is applied to the variety of applications in the shortrange wireless communication with limited output and performance, for example wireless sensor or virtual wire, but it includes vulnerabilities for various attacks because of the lack of security researches. In this paper, we analyze the vulnerabilities against the denial of sleep attacks on the MAC layer of IEEE 802.15.4, and propose a detection mechanism against it. In results, we analyzed the possibilities of denial of sleep attacks by the modification of superframe, the modification of CW(Contention Window), the process of channel scan or PAN association, and so on. Moreover, we comprehended that some of these attacks can mount even though the standardized security services such as encryption or authentication are performed. In addition to, we model for denial of sleep attacks by Beacon/Association Request messages, and propose a detection mechanism against them. This detection mechanism utilizes the management table consisting of the interval and node ID of request messages, and signal strength. In simulation results, we can show the effect of attacks, the detection possibility and performance superiorities of proposed mechanism.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.4
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• pp.135-140
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• 2015

The WDSS improves defensive capacity against web application layer DDoS attack by using web cache server and L7 switch which are added on the DDoS shelter system. When web DDoS attack occurs, security agents divert traffic from backbone network to sub-network of the WDSS and then DDoS protection device and L7 switch block abnormal packets. In the meantime, web cache server responds only to requests of normal clients and maintains stable web service. In this way, the WDSS can counteract the web DDoS attack which generates small traffic and depletes server-client session resource. Furthermore, the WDSS does not require IP tunneling because it is not necessary to retransfer the normal requests to original web server. In this paper, we validate operation of the WDSS and verify defensive capability against web application layer DDoS attacks. In order to do this, we built the WDSS on backbone network of an ISP. And we performed web DDoS tests by using a testing system that consists of zombie PCs. The tests were performed by three types and various amounts of web DDoS attacks. Test results suggest that the WDSS can detect small traffic of the web DDoS attacks which do not have repeat flow whereas the formal DDoS shelter system cannot.

• Korean Journal of Ecology and Environment
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• v.48 no.1
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• pp.68-76
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• 2015

There is no willow riparian vegetation in Jeju Island, Korea. Instead, a genetically-isolated population of Adina rubella is found in some parts of the riparian system. We describe its syntaxonomy and synecology. A total of 27 phytosociological relev$\acute{e}$s were collected, 11 relev$\acute{e}$s from 91 sites and 16 relev$\acute{e}$s from the previously published relevant materials. Data were analyzed by traditional Braun-Blanquet method and multivariate PCoA (Principal coordinates analysis). New syntaxa are distinguished, Adinion rubellae all. nov. and its type association Tripogono-Adinetum rubellae ass. nov. with two subassociations, typicum and rhododendretosum poukhanensae. Adino-Rhododendretum poukhanensae Itow et al. 1993 was discarded owing to mismatch of syntaxonomy and syngeography of Adina and Rhododendron phytocoena. The alliance Adinion is Jeju's regional and partly ombrotrophic vegetation occurring in pothole and rock crevice where are independent on ground-water table. We also suggest a revised alliance, Rhododendrion poukhanensae Lee 2004 ex. hoc loco in Korean peninsula, as a corresponding syntaxon to Adinion, which completely differs from Phragmito-Salicion. Finally we pointed out that Adina phytocoena requiring an absolutely monitoring has been threatened by river maintenance project of local government.