• 한국정보처리학회논문지
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• 제6권11S호
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• pp.3278-3288
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• 1999

This paper proposes a security platform, called SCAP(Security platform for CORBA based APplication), to cope with potential threats in a distributed object system. SCAP supports CORBA security specification announced by OMG. SCAP is comprised of four functional blocks, which co-work with ORB to provide security services: Authentication Block, Association Block, Access Control Block, and Security Information Management Block. It is designed to support Common Secure Interoperability Functionality Level 2, which is useful for large-scale intra-, or inter-network based applications. Actual security services, which are dependent on supporting security technology, will be provided as external security service for replace ability. Implementation issues such as how to simulate an interceptor mechanism using a commercial ORB product without source code, and how to extend Current object required for security services are also described. At the end of the paper, the SCAP applied to the web environment is described to show its practical utilization.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.258-261
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• 2005

In this paper, experimental and numerical attempts are made fur application of powder metallurgy forming technology to making the cylinder block of a hydraulic pump of which height reaches nearly 70 mm and is ten times larger than the wall thickness. Leak tests with several compositions are carried out in order to find allowable powder composition to prevent leak under high pressure in service and CAE techniques are applied to finding proper process conditions. Through the research, the possibility of the powder formed cylinder block that is very competitive from the point of both cost and mass production has been shown, even though its thickness exceeds the recommended limit considering heterogeneous density distribution caused by the friction between a powder compact and dies.

• Journal of information and communication convergence engineering
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• 제20권1호
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• pp.1-7
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• 2022

Herein, a new space-time block coding technique is proposed for a MIMO 2 × 2 multiple-input multiple output (MIMO) system to minimize the bit error rate (BER) in Rayleigh fading channels with reduced decoding complexity using ZF and MMSE linear detection techniques. The main objective is to improve the service quality of wireless communication systems and optimize the number of antennas used in base stations and terminals. The idea is to exploit the correlation product technique between both information symbols to transmit per space-time block code and their own orthogonal Walsh-Hadamard sequences to ensure orthogonality between both symbol vectors and create a full-rate orthogonal STBC code. Using 16 quadrature amplitude modulation and the quasi-static Rayleigh channel model in the MATLAB environment, the simulation results show that the proposed space-time block code performs better than the Alamouti code in terms of BER performance in the 2 × 2 MIMO system for both cases of linear decoding ZF and MMSE.

• 정보처리학회논문지B
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• 제8B권5호
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• pp.507-514
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• 2001

VOD(Video-On-Demand) 시스템에서 실시간 서비스 및 대화형 서비스의 제공 여부는 QoS(Suality of Service)를 결정하는 중요한 요소이다. 본 논문에서는 지연이나 단절 업서는 대화형 서비스를 제공하기 위하여 서버로부터 단지 하나의 비디오 스트림만을 수신하여 복수 사용자들에게 서비스를 제공하는 스위칭 에이전트(Switching Agent)의 종단노드(Head-End Node)로 구성된 종단시스템(Head-End System)을 제안한다. VCR 서비스는 클라이언트 및 종단노드의 버퍼가 동적으로 확장되어 비디오 데이터를 저장하기 때문에 사용자에게 제한 없이 제공되어진다. 또한 제안된 알고리듬은 버퍼의 사용 효율을 증대시키는 방법을 제공하며 모든 클라이언트들의 서비스 요청을 지연 없이 즉시 처리하므로 사용자들에게 진정한 대화형 VOD 서비스를 제공하게 된다. 본 논문에서는 종단시스템을 구현하여 서버로부터 단지 하나의 비디오 스트림만을 수신하여 지연이나 단절 없는 VCR 기능을 갖춘 VOD 시스템을 구현하였으며, 시뮬레이션 결과는 제안된 알고리듬이 VCR 서비스 요청수와 시간에 대하여 매우 우수한 성능을 갖고 있음을 보여주고 있다.

• 보건행정학회지
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• 제18권3호
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• pp.128-146
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• 2008

Nonlinear pricing abounds in practice because it is a potentially powerful pricing method to explore consumer surplus. The various forms of nonlinear pricing are feasible within a given industry. In this context, it is important for manufacturers and retailers to understand which nonlinear pricing scheme is appropriate to apply in their specific situation and which nonlinear pricing schedule is the most profitable in their market situation. Although the merits of nonlinear pricing are well documented, the attempt to apply nonlinear pricing in medical service has been relatively rare. The researcher aims to try to full this gap by applying a practice-oriented simulation model to health examination data. We compare the sales volumes among nonlinear pricing scheme such as n-block tariff, two-part tariff, and uniform pricing. We found that n-block tariff outperforms two-part tariff and uniform pricing.

• 제어로봇시스템학회논문지
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• 제16권5호
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• pp.433-439
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• 2010

This paper proposes a beacon color code scheduling algorithm for the localization of multiple robots in a multi-block workspace. With the developments of intelligent robotics and ubiquitous technology, service robots are applicable for the wide area such as airports and train stations where multiple indoor GPS systems are required for the localization of the mobile robots. Indoor localization schemes using ultrasonic sensors have been widely studied due to its cheap price and high accuracy. However, ultrasonic sensors have some shortages of short transmission range and interferences with other ultrasonic signals. In order to use multiple robots in wide workspace concurrently, it is necessary to resolve the interference problem among the multiple robots in the localization process. This paper proposes an indoor localization system for concurrent multiple robots localization in a wide service area which is divided into multi-block for the reliable sensor operation. The beacon color code scheduling algorithm is developed to avoid the signal interferences and to achieve efficient localization with high accuracy and short sampling time. The performance of the proposed localization system is verified through the simulations and the real experiments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권5호
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• pp.1484-1502
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• 2023

The medical sector actively changes and implements innovative features in response to technical development and revolutions. Many of the most crucial elements in IoT-connected health services are safeguarding critical patient records from prospective attackers. As a result, BlockChain (BC) is gaining traction in the business sector owing to its large implementations. As a result, BC can efficiently handle everyday life activities as a distributed and decentralized technology. Compared to other industries, the medical sector is one of the most prominent areas where the BC network might be valuable. It generates a wide range of possibilities and probabilities in existing medical institutions. So, throughout this study, we address BC technology's widespread application and influence in modern medical systems, focusing on the critical requirements for such systems, such as trustworthiness, security, and safety. Furthermore, we built the shared ledger for blockchain-based healthcare providers for patient information, contractual between several other parties. The study's findings demonstrate the usefulness of BC technology in IoHT for keeping patient health data. The BDSA-IoHT eliminates 2.01 seconds of service delay and 1.9 seconds of processing time, enhancing efficiency by nearly 30%.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(I)
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• pp.151-155
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• 2003

In this paper, as the first step to assess and enhance the reliability of Korea High Speed Train, electric traction system is selected and reliability analysis is carried out. The electric traction system is classified into subsystems and functional block diagrams and reliability block diagrams are drawn. Expressions to calculate the reliability are deducted and Mean Kilometer Between Service Failure is calculated using the trial test results on the track. Calculated results show reliability growth of the electric traction system.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(3)
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• pp.75-78
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• 2002

In this paper, we present the design and implementation of a Fault Tolerant VOD system. The system uses the double striping policy that a original file is sequentially striped to multiple streaming server with constant data block size and the data block of one streaming server is re-striped to the other streaming server. When a fault occurs in one streaming server, automatically the other streaming server will service.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.75-81
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• 2005

GNUnet은 모든 피어에게 익명성(출판자, 저장자, 요구자) 지원방법을 제안한 대표적인 P2P 시스템이다. GNUnet은 익명성 제공을 위하여 파일을 1 Kbyte 블록 단위로 분리하여 인코딩하였고, 인코딩된 정보를 주변 피어에게 분산시키는 방법으 ㄹ채택하였다. 그러나, 대용량화 되는 멀티미디어 파일을 1 Kbyte의 크기로 분리하는 것은 추가적인 블록의 생성을 의미한다. GNUnet에서 제안하고 있는 파일 분리 방법을 분석한 결과 피어들의 검색을 위하여 제공하는 R블록, I블록등이 원본 파일의 4%에 해당되는 저장공간을 추가적으로 요구하고, 분리된 블록을 전송하기 위하여 추가적은 네트워크 트래픽이 발생하였다. 본 논문에서는 이러한 문제점 해결을 위한 새로운 인코딩과 라우팅 방안을 제안하였다. 제안 인코딩 방법은 블록을 생성할 때 발생하는 추가적인 블록을 기존의 4%에서 1%이내으로 최소화 하였고, 분리된 블록을 분산할 때 발생하는 네트워크 트래픽 최소화를 위한 구조적 위상 방법을 채택하였다. 결론적으로 저장공간의 낭비 및 네트워크 트래픽을 최소화할 수 있다.