• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2005년도 춘계 종합학술대회 논문집
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• pp.346-351
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• 2005

인터넷의 급속한 보급과 대용량 멀티미디어 서비스에 대한 요구 증가로 댁내 또는 중소사업장에 대한 광대역 무선 액세스(Broadband Wireless Access) 수요가 증가하고 있다. 기존의 무선랜은 도달거리가 짧아서 이동 중일 때나 AP(Access Point)에서 멀어지면 통화품질이 저하되고, 무선인터넷은 사용 비용이 높다. 이를 보안한 광대역 무선 인터넷 시스템인 와이브로(WiBro: Wireless Broadband Internet)는 휴대폰과 무선랜의 중간 영역에 위치한 이동초고속인터넷서비스이다. 본 논문에서는 IEEE 802.16 BWA을 기반으로 멀티미디어 서비스를 제공하기 위해서 서비스별 트래픽 모델과 특성을 분석하고, 다양한 트래픽 혼합 비율에 따라 시뮬레이션을 수행하였으며, 이를 토대로 최종적으로는 WiBro 시스템에서 수용 가능한 최대 가입자 수를 산출하였다.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2001년도 추계학술대회(제116회) 및 13회 Workshop 제3회 한ㆍ일 치과보존학회 공동학술대회 초록집
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• pp.553-553
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• 2001

The purpose of this study is to identificate root canal system including ideal access placement, root curvature, canal configuration, incidence of isthmus in mandibular incisors for success of endodontic treatment. 200 mandibular incisors were selected. The ideal access placement was determimed as follows. The teeth were radiographed from mesiodistal and buccolingual views using intraoral dental film. The image was divided into coronal, middle and apical third using the proximal film. Straight line access was determined by measuring the faciolingual canal width and placing points at midway point between the buccal and lingual wall at the junction of the middle and apical third and at the juntion of coronal and middle third of the root canal.(omitted)

• 한국IT서비스학회:학술대회논문집
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• 한국IT서비스학회 2002년도 추계학술대회
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• pp.355-359
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• 2002

웹 서비스의 등장으로 XML이 기반 기술로서 자리 매김하고 있는 현재, XML을 이용하여 여러 표준기술을 제정하려는 움직임이 많아지고 있다. XACML은 접근제어 리스트 (access control list)를 통해 보안이 요구되는 자원에 대해 미세한 접근 제어 서비스를 제공 할 수 있는 XML 기반의 언어이다. XACML은 SAML PDP(Policy Decision Point)의 일부로서 역할을 수행 할 수 있으며 각 정의에 따라 각각의 사용자 별 XML 문서 접근 정책을 수립하고 적용 할 수 있다. 본 논문에서는 XML기반의 Access Control 표준인 XACML에 대하여 분석하고 적용 방법에 대하여 연구하였다.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2001년도 추계학술대회(제116회) 및 13회 Workshop 제3회 한ㆍ일 치과보존학회 공동학술대회 초록집
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• pp.562.2-562
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• 2001

The purpose of this study is to identificate root canal system including ideal access placement, root curvature, canal configuration, incidence of isthmus in mandibular incisors for success of endodontic treatment. 200 mandibular incisors were selected. The ideal access placement was determined as follows. The teeth were radiographed from mesiodistal and buccolingual views using intraoral dental film. The image was divided into coronal, middle and apical third using the proximal film. Straight line access was determined by measuring the faciolingual canal width and placing points at midway point between the buccal and lingual wall at the junction of the middle and apical third and at the juntion of coronal and middle third of the root canal.(omitted)

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2004년도 가을 학술발표논문집 Vol.31 No.2 (3)
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• pp.109-111
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• 2004

본 논문은 IEEE 802.11 네트워크 환경에서 MN(Mobile Node)이 핸드오버를 수행하기 전에 미리 이동 정보를 예측함으로써, 유연하게(Seamless) 서비스를 계속 받을 수 있는 예측 방법을 제안한다. 특히, MN이 속한 AP(Access Point)가 중첩된 상황에서 발생할 수 있는 여러 가지 문제점을 해결한다. MN은 이동성 패턴 레코드를 저장하고, 또한 각 이웃 AR(Access Router)은 AP의 AP-ID(BSSID, Basic Service Set ID)와 채널을 저장한다. MN이 AP의 영역의 경계를 벗어나기 전, 새로운 AP로부터 AP-lD를 획득하면, MN이 저장하는 이동성 패턴 레코드에서, AP-ID와 맞는 정보를 비교하여 확률이 높은 AP를 선택한다. 이러한 정보를 PAR(Previous Access Router)에게 정보를 보내어 신속하게 새로운 링크에서 서비스를 받을 수 있음으로써 손실.지연을 최소화 할 수 있다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
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• pp.191-194
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• 2003

In IEEE 802.11b, Medium Access Control Sublayer consists of DCF (Distributed Coordination Function) and PCF (Point Coordination Function). DCF provides contention based services and PCF provides contention free services for QoS satisfaction. DCF uses CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) as an access protocol. And PCF uses Polling Scheme. In this paper, a modified New-PCF, which gives weights to channels with heavier traffic load, was suggested. NS-2 simulations were conducted to compare the service performances with original DCF, PCF and the modified New-PCF respectively. Simulation results has shown the increased overall throughput with the proposed New-PCF compared with other cases.

• ETRI Journal
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• 제36권4호
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• pp.625-634
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• 2014

This paper studies a dual-hop multiple-access relay network where two independent source nodes transmit information to a common destination node with the aid of multiple single-antenna amplify-and-forward relays. Each relay node is subject to an individual power constraint. We focus on the design of distributed beamforming schemes for the relays to support the transmission rate requirements of the two sources. To this end, we first characterize the achievable rate region for this network via solving a sequence of corner point optimization problems proposed in this paper. We also develop several low-complexity suboptimal schemes in closed form. Two inner bounds of the achievable rate region are theoretically shown to be approximately optimal in two special scenarios. Finally, numerical results demonstrate the effectiveness of our proposed approaches.

• International Journal of Railway
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• 제1권4호
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• pp.134-142
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• 2008

Serving as a strategic crossing point for major corridors in Central Europe, Railnet Austria's Infrastructure Network incurs continual increases in international traffic flows and is therefore subject to accumulating traffic congestion with potential restrictions to infrastructure access. This imposes challenges towards preserving open access to Railnet Austria's existing railway network and hinders quality infrastructure service during maintenance, repair, and upgrading. Through Railnet Austria's experiences, the economic viability of a railway network can be sustained through maintaining open access with good quality service of planned trainpaths, thus representing new challenges for future infrastructure maintenance and capacity planning. Railnet Austria's Capacity Management Department has proven that these challenges can be accommodated more effectively through recent technological developments in data warehousing and software development.

• Journal of Communications and Networks
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• 제15권6호
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• pp.606-613
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• 2013

This paper proposes a complete solution of a contention-based medium access control in wireless local networks to provide station level quality of service guarantees in both downstream and upstream directions. The solution, based on the mature distributed coordination function protocol, includes a new fixed contention window backoff scheme, a tuning procedure to derive the optimal parameters, a super mode to mitigate the downstream bottleneck at the access point, and a simple admission control algorithm. The proposed system guarantees that the probability of the delay bound violation is below a predefined threshold. In addition, high channel utilization can be achieved at the same time. The numerical results show that the system has advantages over the traditional binary exponential backoff scheme, including efficiency and easy configuration.

• 한국IT서비스학회지
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• 제9권3호
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• pp.145-161
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• 2010

Recently, identifying user locations is becoming important as the society evolves into an ubiquitous society with the innovation of information technology. Particularly, many researches on identifying user locations are headed in direction to identify locations of users in the indoors, because a GPS that is widely used to identify the locations of users in the outdoors is inapplicable in the indoors. However, those researches are mostly not useful to general indoor environment because they are performed in a specific environment with specialized or customized devices such as UWB, RFID. Therefore, in this paper we propose a effective method to identify user locations in general indoor environments with wireless local network access points. Our approach enables to identify user location efficiently by measuring signal power of access points around the user and using the FRIIS formula which is used to calculate the distance among the things.