• Proceedings of the Korean Information Science Society Conference
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• 2007.10c
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• pp.175-178
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• 2007

그리드 데이터베이스는 여러 사이트에 데이터베이스의 복사본을 두어 네트워크 전송 지연을 감소시킨다. 그러나 데이터베이스가 갱신될 때마다 모든 복사본들이 갱신되어야 하기 때문에 이로 인해 발생되는 네트워크 대역폭 소모와 시스템 부하 또한 무시할 수 없는 수준이다. 본 논문에서는 그리드에 사용되는 광대역 네트워크인 인터넷의 구조에 적합한 새로운 데이터베이스 갱신 정책을 제안한다. 본 정책은 인터넷의 구성요소인 AS(Autonomous System)와 ISP(Internet Service Provider)의 계층성과 네트워크의 속도 차를 고려하여 네트워크의 병목구간을 최대한 회피하고, 시스템 부하와 네트워크 부하의 균형을 조절함으로써 그리드 데이터베이스의 성능을 향상시킬 수 있다.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10b
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• pp.590-594
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• 2006

본 연구는 신뢰성 있는 유비쿼터스 프로그램을 개발하기 위한 보다 효율적인 프로그래밍 환경을 제공함을 목적으로 한다. 이 프로그래밍 환경은 정책 기술 언어와 이를 바탕으로 접근 제어와 상황 적응을 관리하는 실행시스템을 제공한다. 프로그래머는 정책 기술 언어를 통해 메소드에 대한 접근 권한과 변화되는 상황에 적응하는 규칙들을 쉽게 표현할 수 있다. 본 논문의 실행 시스템은 정책 파일의 규칙들에 따라 객체가 메소드에 대한 접근 권한이 있는지를 검사하는 접근 제어기(access controller)와 변화되는 상황에 적응하여 자동으로 반응하도록 해주는 적응 엔진(adaptation engine)의 형태로 구현되었다. 또한 이 시스템을 이용하여 개발된 유비쿼터스 프로그램을 시뮬레이션 할 수 있는 시뮬레이터를 제공한다.

• The Transactions of the Korea Information Processing Society
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• v.7 no.11
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• pp.3356-3371
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• 2000

본 논문에서는 분산시스템 환경에서 n개의 노드가 결함일 경우, 결함을 허용해 주고, 시스템의 안정성을 유지하면서, 결함 노드의 부하를 정상 노드로 조절하기 위하여 부하 조절 알고리즘 전송정책, 위치 정책, 선정 정책을 제안하였다. 이러한 메카니즘은 부하 상태의 정보를 효과적으로 획득하고, 응답 시간을 줄이기 위하여 자기 학습 경험을 기반으로 하는 최적의 알고리즘을 선정할 수 있었다. 결과적으로 이를 기반으로 유사한 상황에서도 최적의 알고리즘을 선정할 수 있음을 알 수 있었다. 각 기법들의 효율성에 영향을 미칠 수 있는 매개변수를 적용하여 성능평가를 하였다. 성능평가 결과 작업 도착 율, 서비스 율, 노드 결합 율은 서로간에 영향을 주지 못하고, 다만 결함 수리 율과 특히 부하의 이주에 대한 통신 지연 시간의 크기에 민감한 영향을 주었다.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.5
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• pp.412-421
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• 2009

Due to the physical characteristics of NAND flash memory, overwrite operations are not permitted at the same location, and therefore erase operations are required prior to rewriting. These extra operations cause performance degradation of NAND flash memory file system. Since it also has an upper limit to the number of erase operations for a specific location, frequent erases should reduce the lifetime of NAND flash memory. These problems can be resolved by delaying write operations in order to improve I/O performance: however, it will lower the cache hit ratio. This paper proposes a policy of page management using double cache for NAND flash memory file system. Double cache consists of Real cache and Ghost cache to analyze page reference patterns. This policy attempts to delay write operations in Ghost cache to maintain the hit ratio in Real cache. It can also improve write performance by reducing the search time for dirty pages, since Ghost cache consists of Dirty and Clean list. We find that the hit ratio and I/O performance of our policy are improved by 20.57% and 20.59% in average, respectively, when comparing them with the existing policies. The number of write operations is also reduced by 30.75% in average, compared with of the existing policies.

• KIPS Transactions on Computer and Communication Systems
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• v.9 no.3
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• pp.59-66
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• 2020

Content Centric Network(CCN) with architecture that is completely different from traditional host-based networks has emerged to address problems such as the explosion of traffic load in the current network. Research on cache replacement policies is very active to improve the performance of CCN with the characteristics that all routers cache on the network. Therefore, this paper proposes a cache replacement policy suitable for situations in which popularity is constantly changing, taking into account the actual network situation. In order to evaluate the performance of the proposed algorithm, we experimented in an environment where the popularity of content is constantly changing, and confirmed that we are superior to the existing replacement policy through comparing hit rates and analyzing server load.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.5
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• pp.703-711
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• 2018

Recently, as various metro lines have been constructed and connected to other lines the rate of utilization has also been increased. However, the existing fare policy which the government does still stick to causes not only inappropriate action to the demand pattern but aggravation of the profit of the operation company. This study reviewed rail fare policy of major countries such as Japan and U.K etc. to improve the rationality of fare policy in Korea. In order to systematical analysis of fare policy, such viewpoints as of fare decision method, the card fare discounting system, the structure of fare, and the government subsidy policy were reviewed. Based on the results from the review, various problems and improvement plans were drawn. Through this study, appropriate fare systems to urban railway users could be given to improve the chronic deficit problem of urban railway operators.

• The Korean Journal of Air & Space Law and Policy
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• v.30 no.2
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• pp.249-277
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• 2015

Regulation (EC) No 261/2004 ("Regulation") is a common rule on compensation and assistance to passengers in the event of denied boarding and of cancellation or long delay of flights. In some recent cases of European nations, passengers sued the air carrier in order to obtain monetary compensation under Article 7(1) of the Regulation. Some courts dismissed the actions on the grounds that, unlike denied boarding or cancellation of the flight, the Regulation provides no compensation in relation to delayed flights. However, Court of Justice of the European Union(CJEU) ruled that Regulation 261/2004 must be interpreted to mean that passengers whose flights are delayed have a right to compensation in cases when the loss of time is equivalent to, or is in excess of three hours - where the passengers eventually reached their final destination three hours or more later than the originally scheduled arrival time. It is true that a strict interpretation of the regulation would suggest that passengers whose flight has merely been delayed are not entitled to compensation. They should only be offered assistance in accordance with the Articles 6 and 9. Nevertheless, the Court recognized the same right to the same compensation for passengers of flights delayed by more than three hours as that explicitly provided for passengers of cancelled flights. On the one hand, the Court bases this ruling on the recitals of the Regulation, in which the legislature links the question of compensation to that of a long delay, while indicating that the Regulations seek to ensure a high level of protection for passengers regardless of whether they are denied boarding or their flight is cancelled or delayed. On the other hand, the Court interprets the relevant provisions of the Regulation in light of the general principle of equal treatment. Furthermore, the Court delivered a ruling that the loss of time inherent in a flight delay, which constitutes an inconvenience within the intention of Regulation No 261/2004 and which cannot be categorized as 'damage occasioned by delay' within the meaning of Article 19 of the Montreal Convention, cannot come within the scope of Article 29 of that convention. Consequently, under this view, the obligation under Regulation No 261/2004 intended to compensate passengers whose flights are subject to a long delay is in line with Article 29 of the Montreal Convention. Although the above interpretation of the Court can be a analogical interpretation, the progressive attitude of the Regulation and the view of Court forward to protect passengers' interest is a leading role in the area of international air passenger transportation. Hopefully, after the model of the positive support in Europe, Korea can establish a concrete rule for protecting passengers' right and interest.

• The Korean Journal of Air & Space Law and Policy
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• v.35 no.2
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• pp.197-224
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• 2020

This paper reviews and criticizes some issues as to the case of A and Others v. Finnair Oyj [2020] Case C-832/18 by examining EU Regulations and practical point of views. Under this case, the travellers brought an action against Finnair in light of the Air Passenger Regulation12, seeking compensation for both the first cancelled flight, and the delayed re-routed flight. Finnair had paid the first compensation, but refused to grant the second claim, arguing that the regulation did not set out that passengers were eligible for a second claim in those situations, and that the delay of the second flight was a consequence of 'extraordinary circumstances' under the regulation. The Court of Appeal in Helsinki has asked the CJEU whether an air passenger is entitled to a further compensation where a re-routed flight they have agreed to take is delayed, where both the original and rerouted flight are operated by the same air carrier. The CJEU held that the regulation does not in any way limit the rights of passengers where they find their flights being re-routed. As such, under earlier CJEU case law, the relevant travellers here were entitled to compensation for cancellation of the first flight and delay of the second flight. It also disagreed with Finnair's assessment that the technical failure in the re-routing flight was a matter of extraordinary circumstances.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.75-82
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• 2008

Mobile IP was proposed to overcome identity problem of original IP address system caused by mobility of wireless mobile host. To complete its network handoff procedure, it must receive a mobile advertisement broadcasted by mobile agent. Generally, in a mobile IP system, mean time delay, 500ms, in a network handoff procedure is a critical problem of wireless service such as Voip, multimedia streaming. A caching agent caches a latest mobile advertisement, and replays it by receiving solicitation message from a mobile node finishing link layer detection. But, during the procedure of mobile registration, many packets from service provider to the mobile host would be lost and handoff time delay would be increased. In this thesis, we propose an unproved caching agent technique which can forward data packets while handoff procedure, and CoA pool for fast mobile IP registration.

• Journal of Digital Convergence
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• v.20 no.3
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• pp.389-397
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• 2022

As increasing the growth of the Internet in medical area, a new technology to transmit effectively massive medical data is required. In optical internet, all OBS nodes have fiber delay lines, hardware components. These components are calculated under some optimal traffic conditions, and this means that if the conditions change, then the components should be altered. Therefore, in this article a new service differentiation algorithm using the previously installed components is proposed, which is used although the conditions vary. When traffic conditions change, the algorithm dynamically recalculates the threshold value used to decide the length of data bursts. By doing so, irrelevant to changes, the algorithm can maintain the service differentiation between classes without replacing any fiber delay lines. With the algorithm, loss sensitive medical data can be transferred well.