• Journal of Communications and Networks
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• 제11권6호
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• pp.615-625
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• 2009

Worldwide inter-operability for microwave access (WiMAX) is a promising technology that provides high data throughput with low delays for various user types and modes of operation. While much research had been conducted on physical and MAC layers, little attention has been paid to a comprehensive and efficient security solution for WiMAX. We propose a hybrid security solution combining identity-based cryptography (IBC) and certificate based approaches. We provide detailed message exchange steps in order to achieve a complete security that addresses the various kind of threats identified in previous research. While attaining this goal, efficient fusion of both techniques resulted in a 53% bandwidth improvement compared to the standard's approach, PKMv2. Also, in this hybrid approach, we have clarified the key revocation procedures and key lifetimes. Consequently, to the best of knowledge our approach is the first work that unites the advantages of both techniques for improved security while maintaining the low overhead forWiMAX.

• 한국항만학회지
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• 제8권1호
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• pp.49-63
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• 1994

The introduction of high speed railway system a significant impact on the conventional inter-urban transport systems by inducing a significant traffic from the existing modes as well as generating a new traffic. It is also closely related to intra-urban transport systems as the inter-urban traffic has its origin and destination in a city. In the context of mode choice, for high speed transport systems, it has been argued that the accessibility is the most important attribute conceived by users. Thus this study attempts to analysis the importance of the accessibility for the planned high speed railway systems particularly with respect to the location of Busan Station. For this Stated-Preference approach, which is considered appropriate for such study, is adopted, and disaggregate binary logit models for mode choice between the high speed railway and air service in Busan-Seoul corridor are developed. The elasticities for cost and service variables are also derived. The results disclose that cost is the most important which is inconsistent with most previous studies ; accessibility has considerable impact on the choice ; and frequency however has a little impacts. Concerning location of the high speed railway station the results suggest that the longer the access distance is, the more important the accessibility is. This implies that the connection of reliable access transport services such as underground are essential between the terminal and urban center.

• 대한교통학회지
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• 제21권4호
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• pp.17-27
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• 2003

공항여객 처리시설의 혼잡해소에 관한 연구는 주로 공항접근교통시스템의 확충이나 터미널의 확장 등 물리적인 방법에 집중되어 왔다. 물리적인 확장은 막대한 투자비용이 뒤따라야 하는 문제가 있기 때문에 공항운영과 같은 소프트웨어 측면에 대한 접근방식을 적극 도입하여 투자비용을 줄이고 효율적인 공항운영을 꾀하는 것이 필요하다. 본 연구는 공항운영의 효율성 증진을 위한 대안 중 하나로서 여객들이 공항에 도착하는 행태가 어떻게 나타나는 지를 분석하여. 향후 여객터미널 운영에 적용할 수 있는 유용한 정보를 제공하는데 그 목적이 있다. 서로 다른 접근소요 시간을 가진 여객들이 항공기 출발예정시간(STD:scheduled time of departure) 이전에 도착하는 확률함수를 도출하고, 이를 이용하여 STD 이전시간 임의구간에서 여객이 도착하는 확률을 구할 수 있는 모형을 개발코자 하였다. 또한 이 모형을 공항 여객터미널에 적용하여 운영시간대별 도착 여객수를 산출하는 과정을 제시하고자 하였다. 본 연구에서 분석된 공항접근시간에 따른 STD 이전시간대별 공항도착 확률모형은 공항운영자 및 항공사가 공항의 체크인 카운터 운영시간 및 수량 결정, 수하물 처리시스템, 검색보안서비스 등의 운영시점을 결정하는 도구로 이용될 수 있다. 이와 같이 분석된 결과를 토대로 공항운영 상 비효율성을 제거하고 보다 합리적인 인력 투입이나 시설 운영이 가능하게 되는 것이다.

• 정보보호학회논문지
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• 제27권6호
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• pp.1307-1315
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• 2017

DTLS의 PSK 모드는 DTLS 핸드쉐이크의 성능 측면에서 가장 효율적이지만 센서 디바이스의 개수가 증가함에 따라 대칭키 쌍을 미리 배포하는 것과 관리하는 것이 용이하지 않다. 반면에 RPK 모드와 인증서 모드는 키 관리가 용이하지만 계산상의 효율성은 매우 떨어진다. 본 논문에서는 자원 제약적인 센서 디바이스에 적합한 인증서인 ECQV를 통한 인증서 모드와 PSK 모드를 사용하여 그룹 환경에서의 종단 간 보안을 달성하기 위한 프로토콜을 제안한다. Initial DTLS 핸드쉐이크는 ECQV 인증서 모드를 사용하고, 이후 동일 그룹에 속한 CoAP 서버와의 Subsequent DTLS 핸드쉐이크는 PSK 모드를 사용하기 때문에 그룹내 CoAP 서버들과의 전체적인 계산 부담을 감소시킬 수 있다. 제안 프로토콜에서는 특정 CoAP 클라이언트가 그룹의 제한된 CoAP 서버에 접근 할 수 있게끔 세밀한 접근제어가 행해진다.

• 전자통신동향분석
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• 제35권3호
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• pp.55-65
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• 2020

With the development of nonvolatile memory technology, Intel has released the Optane datacenter persistent memory module (DCPMM) that can be deployed in the dual in-line memory module. The results of research and experiments on Optane DCPMMs are significantly different from the anticipated results in previous studies through emulation. The DCPMM can be used in two different modes, namely, memory mode (similar to volatile DRAM: Dynamic Random Access Memory) and app direct mode (similar to file storage). It has buffers in 256-byte granularity; this is four times the CPU (Central Processing Unit) cache line (i.e., 64 bytes). However, these properties are not easy to use correctly, and the incorrect use of these properties may result in performance degradation. Optane has the same characteristics of DRAM and storage devices. To take advantage of the performance characteristics of this device, operating systems and applications require new approaches. However, this change in computing environments will require a significant number of researches in the future.

• 대한치과의사협회지
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• 제48권8호
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• pp.587-593
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• 2010

The management of malignant tumors of the oral cavity requires that the resection should be performed with adequate negative margins. To this end, the surgeon is sometimes required to increase the access to the oral cavity to resect with clear margins although most of our resections can be carried via the transoral route. This article highlights some of the most common surgical accesses to the oral cavity: Peroral approach, mandibulotomy and mandibular swing approach, visor flap approach, upper & lower cheek flap approach, pull-through technique. Also, various modes of management are grossly described according to primary site, size, and stage of the tumors.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.794-798
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• 2002

This paper deals with a moving coil type linear motor for fast access of the miniature ODD. This slim-line motor is composed of the mover supported by guide mechanism, the coil wound into it, and the yoke attached to the permanent magnet for stator. The driving force is generated by the PM of the stator and the current in the coils of the mover. Magnetic circuit analysis and Finite Element Method are applied to estimate the thrust force at air gap. In order to compare the force characteristics between two methods, various experiment results are applied to verify on a prototype. Also the flexible modes of the motor are predicted through the FEM and the structural components are modified to locate this on high frequency region.

• 대한전기학회논문지:전력기술부문A
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• 제53권1호
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• pp.43-55
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• 2004

This paper presents a study on evaluating the reliability indices considering a transmission system. Because successful operation of electric power under the deregulated electricity market depends on transmission system reliability management, quantity evaluation of transmission system reliability is very important. This paper introduces features and operation modes of the Transmission Reliability Evaluation for Large-Scale Systems(TRELSS) Version 6.0, a commercial program made in EPRI, and TranRel-I V3.2, a educational program made in GSNU(GyeongSang National University) for assessing reliability indices of composite power system. The packages access not only bulk but also bus indices for reliability evaluation of composite powers system. The practicality, effectiveness and future works of this methodology are illustrated by demonstrations of two case studies of modified IEEE 25 buses reliability test system using TRELSS and TranRel-I and a brief case study for the KEPCO size system using TranRel-II made in GSNU.

• 천문학회보
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• 제39권2호
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• pp.40-40
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• 2014

Through KASI, Korean astronomers will have access to the Gemini Observatory starting in 2015. Gemini operates two optical/infrared 8m-class telescopes: one on the northern hemisphere in Hawaii, one on the southern hemisphere in Chile. Both are equipped with state of the art instruments and adaptive optics systems that will be presented. Gemini also offers the opportunity for instrument development and welcomes visiting instruments. In terms of operations, Gemini offers to its partners three ways of applying for time: through semester-basis calls for standard programs, through yearly calls for Large and Long Programs, and through monthly calls for fast turnaround programs. Gemini operates in queue mode (observing for the principal investigators and allowing flexibility in the time domain), as well as in the classical visitor mode (where principal investigators come to the telescope). I will explain the requirements and advantages of all these modes as well as a full update on the Gemini Observatory.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 추계학술대회 논문집
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• pp.104-110
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• 2001

During the last several years, the high speed railway system has been constructed and it is scheduled to open sometime in 2004. To fulfil its duties, it is essential to view intermodalism in the context of broader technological developments in easy access to high speed railway station. And also, to understand the economic importance of intermodal transportation, continual research is needed on the costs and distributional effects of alternative intermodal mechanisms for public works, including direct service to local station or easy transfer to other mass transportation modes. In this paper, necessary courses for local governments involvement are taken, and additional resources must be found that will benefit the entire railway system.