• Journal of KSNVE
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• v.5 no.3
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• pp.284-291
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• 1995

본 글에서와 같이 SMA 작동기는 전류 압력만으로 유연 구조물 시스템의 형상 이나 전동을 제어할 수 있으므로 작동기의 구조를 매우 간단히 할 수 있으머, 또한 작동기의 무게에 비하여 큰힘이나 변위를 제어할 수 있다는 장점이 있다. 이를 이용 하여 각종 제조분야 및 첨단 항공우주 산업에 이르기까지 매우 다양한 분야에 응용이 가능하다. 그러나, 현재 우리나라의 경우 SMA에 대한 연구는 미미한 상태이다. 새로운 SMA 재료와 이를 응용한 매카니즘에 대한 연구와 개발이 절실하며 이를 위한 과감한 투자가 요구된다. 또한 정확하고 견실한 제어를 위하여 SMA 작동기의 다양한 특성을 보다 심도있게 파악하고, 강건한 제어기를 적용하여 외부 환경의 영향을 최소화하는 연구가 필요하다. 나아가서 제어 메카니즘의 구동 장치 등의 적용을 위한 이방향성 SMA의 특성과 제어기법에 대한 연구도 병행해서 수행되어야 할 것으로 생각된다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04a
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• pp.349-351
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• 2000

이동 방송 환경(mobile broadcasting environment)은 정보를 가지고 있는 서버가 다수의 이동 클라이언트에게 모든 데이터를 주기적으로 방송하면 클라이언트가 자신이 원하는 데이터가 방송 채널에 나타날 때 이를 검색하는 환경을 말한다. 이 때 클라이언트는 일관적이면서 가장 최근에 갱신된 데이터를 필요로 하기 때문에, 병행성 제어 기법을 사용하여 이러한 요구 조건을 충족시켜야 한다. 이동 방송 환경에서는 클라이언트가 여러 가지 제약점을 가지고 있기 때문에 서버가 클라이언트의 일관성 검사를 위한 제어 정보를 데이터와 함께 방송해야 한다. 그러나, 매 방송 주기마다 방송해야 하는 제어 정보의 양이 크기 때문에 일관성 검사에 영향을 주지 않는 범위에서 이를 줄일 필요가 있다. 본 논문에서는 제어 정보의 양을 줄이기 위하여 데이터를 그룹화(grouping)하는 기법을 제시하고, 시뮬레이션을 통해 데이터 그룹화가 클라이언트의 트랜젝션 중단(abort)에 미치는 영향을 알아본다. 서로 다른 데이터들을 하나의 그룹으로 묶으면 클라이언트가 일관성을 검사할 때 트랜잭션이 불필요하게 중단되는 경우가 더 많아질 수 있다. 그러나, 실험 결과 전체 데이터 수의 20% 정도 크기로 데이터를 그룹화하면 불필요하게 트랜잭션이 중단되는 경우가 거의 없으면서 제어 정보의 크기를 줄일 수 있다는 사실을 알 수 있었다.

• Journal of KIISE:Databases
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• v.32 no.6
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• pp.628-640
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• 2005

The XML is well accepted in several different Web application areas. As soon as many users and applications work concurrently on the same collection of XML documents, isolating accesses and modifications of different transactions becomes an important issue. When an XML document correctly corresponds to the rules laid out in a DTD or XML schema, it is also said to be valid. The valid XML document's validity should be guaranteed after the document is updated. The validation method mentioned above, however, results in lower degree of concurrency. For getting higher degree of concurrency and minimizing the range of the XML document validity, a new validation method based on a specific locking method is required. In this paper we propose the sequence group validation method for minimizing the range of the XML document validity. We also propose the boundary locking method for isolating accesses and modifications of different transactions while supporting the valid XML document's validity. Finally, the results of some experiments show the validation and locking methods increase the degree of transaction concurrency.

• The KIPS Transactions:PartD
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• v.9D no.1
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• pp.11-20
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• 2002

We propose a new concurrency control algorithm for enhancing the degree of parallelism of the transactions in fully replicated databases designed to improve the availability and the reliability. The update transactions can be logically decomposed of a read-only transaction and a write-only transaction. In our algorithm, a set of read operations of an update transaction is treated as a read-only transaction and the read-only transaction reads data items in the site to which it is submitted. And a set of write operations of the update transaction is treated as a write-only transaction and it is submitted to all corresponding sites after the update transaction has been completed. By using the proposed update protocol, all write-only transactions can execute at all sites atomically. The proposed algorithm can have transactions execute concurrently at the site to which they are submitted and, after the completion of each transaction, the update protocol is performed for updating their data items and checking their serializability. Therefore, the degree of parallelism of the transactions can be improved. Especially, if the probability of conflict among transactions is low, we can expect the higher degree of their parallelism.

• Journal of Practical Engineering Education
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• v.16 no.3_spc
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• pp.333-342
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• 2024

This study analyzes the curriculum applied to students of specialized high schools in 2025, when the 2022 revised curriculum is fully implemented, and proposes a curriculum to help schools and companies that are still organizing the curriculum. In addition, through a questionnaire on apprenticeship education by unit school students, parents, and corporate teachers, we will examine the requirements of each subject in the middle and further study ways to develop the current work-learning parallel system of apprenticeship students and ordinary students after pre-employment. As apprenticeship education continues to develop, continuous research, interest, and support are needed to establish apprenticeship education in the changed curriculum, which should continue to be studied as basic research in the parallel of national-level work-learning in the future.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.157-159
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• 2004

본 논문에서는 분산 일시간 객체 엔진을 내장하는 TMO-LINUX/ARM 커널 상에서, 각종 센서 및 모터 제어로 구성되는 로봇 제어 시스템을 동적 분산 실시간 객체인 TMO로 모델링하고 구현하였다. TMO(Time-triggered Message-triggered Object)는 시간적 조건에 의해 구동되는 객체 내의 실시간 스레드와 메시지에 의해 구동되어 주어진 데드라인 안에 작업을 수행하는 메시지 구동 실시간 스레드들의 동적 멤버들로 구성되는 실시간 객체로, 외부의 입출력에 반응하며 내부 장치에 대한 실시간 작업을 병행해야 하는 로봇 제어 시스템에 대해 매우 적합한 모델이다. 본 논문에서는 이러한 로봇 제어 시스템 설계에의 TMO의 적용이 잘 정의되고 규격적인 설계 모델을 제공함을 보인다.

• The Journal of Engineering Research
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• v.6 no.2
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• pp.39-46
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• 2004

In this paper, we carry out a performance study related to the Broadband Network. For this network, it has been proposed to use the leaky bucket as a way of controlling congestion within the network. On the top of leaky bucket type rate based congestion control scheme for high speed networks, a user will typically operate an error control scheme for retransmitting lost and erroneous packets. We propose a performance model in order to study the interaction between a user's error control scheme and the leaky bucket congestion control scheme for high speed networks. Simulation results show that parameters such as the window size and the token generation rate in the leaky bucket are key factors affecting the end-to-end delay.

• Journal of KIISE:Computing Practices and Letters
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• v.5 no.5
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• pp.574-582
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• 1999

Computer Supported Cooperative Work(CSCW) systems for cooperaton in distributed computing environment are used in many fields such as on-line approval, co-authoring, co-decision making, and so on. There have been many researches on co-drawing tools of the CSCW system, because they can be used in communication, co-design, and education. However, the existing tools are not flexible in system architecture and concurrency control. In this paper, we present "autonomous object," which includes concurrency control policy and information about its view. And we developed a new CSCW system with flexible system architecture.

• Journal of Korean Society for Geospatial Information Science
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• v.5 no.2 s.10
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• pp.193-205
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• 1997

It is required for multi-users to share massive mapping data effectively that distributed data model in the Client-Server environment is developed for the replication consistency. The existing model is not effective to the long transaction just like a mapping system, since it does not account lot consistency between GUI screen and database replications even though it emphasizes on the replication consistency. The performance of concurrency control is very important for those long transactions, especially the mapping systems. This model is to support consistency between GUI screen and replicas using display locks. It suggests consistency model improving process performance by modifying memory consistency model and optimistic concurrency control for mapping data's characteristics.

• Radiation Oncology Journal
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• v.13 no.4
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• pp.331-338
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• 1995

Purpose : To evaluate our clinical experience with the combination of teletherapy and intraluminal brachytherapy in patients with unresectable or inoperable esophageal cancers. Materials and Methods : From Nov 1989 to Mar 1993, twenty patients with esophageal cancer were treated with radical radiotherapy and intraluminal brachytherapy at Yonsei Cancer Center. All patients had squamous histolgy and stage distribution was as follows: stage II, 4($20{\%}$)patients; III, 15 ($75{\%}$)patients; IV, 1($5{\%}$)patients. A dose of S-12Gy/1-3weeks with intraluminal brachytherapy (3-5Gy/fraction) to 5mm from the outside of the esophageal tube using high dose rate Iridium-192 remotely afterloading brachytherapy machine was given 2 weeks after a total dose of 59-64Gy with external radiotherapy. Induction chemotherapy using cisplatin and 5-FU was performed in 13 patients with median 3 cycles(1-6 cycles), Response rate, local control rate, survival and complications were analysed retrospectively. Results : Two-year overall survival rate and median survival were $15.8{\%}$ and 13.5 months. Response rates were as follows complete remission(CR) 5($25{\%}$): partial remission a(PRa) 7($35{\%}$): partial remission b(PRb) 7($35{\%}$), no response(NR) 1($5{\%}$). Patterns of failure were as follows; local failure 13($65{\%}$), local and distant failure 3($15{\%}$), distant failure 0($0{\%}$). Ultimate local control rate was $20{\%}$. Treatment related complications included esophageal ulcer in two patients and esophageal stricture in one. Conclusion : Though poor local conrol rate, median survival was improved as compared with previous results of radiation therapy alone(8months) and chemoradiation combined treatment(11 months) in Yonsei Cancer Center High-dose-rate intraluminal brachytherapy following external irradiation is an effective treatment modality with acceptable toxicity in esophageal cancer.