• Journal of KIISE:Databases
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• v.31 no.2
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• pp.140-149
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• 2004

Data broadcast has received much attention as a very efficient method for disseminating data items in mobile environment with large number of mobile clients. In this approach, a database server periodically and continuously broadcasts data items through wireless channels and clients perform read-only transactions by accessing necessary data items from the air. While broadcasting, the server must also process update transactions on the database, which raises an obstacle for client's accessing consistent data. In this research, we propose a new algorithm SCDSC(Serialization Checking with DirtySet on Commit) which is an alternative for solving the concurrency control problem efficiently. The SCDSC is a kind of optimistic concurrency control in that a client checks the consistency of data using a DirtySet as a part of data broadcast when it commits its transaction. In each broadcast cycle, the server updates and disseminates the DirtySet with newly changed data items for last few cycles in the sliding window approach. We perform an analysis and a simulation study to evaluate the performance of our SCDSC algorithm in terms of data consistency and data currency.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1229-1233
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• 2007

국내에서의 수제는 하안 및 제방의 보호, 유로제어 및 주운 등의 목적에 의해 설치되기 보다는 수제로 인해 발생되는 수제역(recirculation zone)의 다양한 흐름이 수중생물의 다양한 서식처 및 홍수 시 어류의 피난처 제공한다는 환경적인 목적이 지배적이다. 따라서 홍수시 하천의 통수능 감소영향이 상대적으로 작고 국부세굴에 대해 안정적인 경사형 수제에 대한 관심이 크며 몇몇 곳에서는 시공되어 졌다. 하지만 경사수제에 대한 설계기법은 현재 미미한 상태이며 선행되어져야할 구조물 주변의 흐름해석에 관한 연구도 미미하다. 이에 본 연구에서는 3차원 수치모형을 적용하여 주수로와 수제역의 흐름해석을 수행하였다. 연구내용은 수리모형변화와 수치모형실험을 병행하여 수행하여 수치모형결과를 검증하였으며 그 결과를 적용하여 경사형 수제주변의 흐름을 해석하였다. 수치모형은 Flow 3D모형을 이용하여 경사형 수제조건에 따른 흐름해석을 수행하였고 수리모형실험은 수치모형과 동일한 2가지 조건에 대해 수행하여 수치모형결과와 비교 분석 하였다. 본 연구의 목적은 경사형 수제설치로 변화되는 수제역 흐름을 3D 수치해석으로 분석하여 수제역의 환경적 효과(수중생물의 서식처 등)에 대한 기초자료를 제공하는 것이다. 연구결과, 수치모형실험은 수리모형결과와 일치하였으며 경사형 수제특성에 따라 수심별 흐름변화를 분석할 수 있었으며 기존 불투과 및 투과수제와 다른 결과를 도출하였다.

• Journal of Korean Society of Transportation
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• v.20 no.2
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• pp.135-148
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• 2002

In this paper, a queue length calculation algorithm using image detectors has been proposed. The algorithm produces the queue length using a pair of image detectors installed both on upstream and on downstream of a corridor. In addition, a new framework for controlling the traffic signal system based on queue length has been presented. More specifically, the scheme of determining the cycle time and green split using the queue lengths has been proposed. To validate the results, a simulation study was conducted with a network environment. Results showed that the proposed method gave better operational performance than a traditional method. However, additional validation effort is necessary in order to apply the real traffic conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.2
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• pp.1-6
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• 2005

This paper studies the OF-LED(Optical Fiber-LED) illuminated display board system for energy saving. The OF-LED illuminated display board system has PV module, batteries, charge 8t discharge system and dynamic full color display controller. Both maximum power point tracker (MPPT) and constant current & constant voltage controls (CCVC) are used to govern the charging system. This system. improves the charging efficiency of battery. The system is compact and operates only by PV except the rainy days when the sun is unfavorable. in the system display control and charging-discharging control by on-chip microprocessor are simultaneously carried out. To verify the unposed system, me simulation and experiment results show the operating characteristics with a laboratory prototype.

• Journal of Korea Multimedia Society
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• v.1 no.1
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• pp.67-79
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• 1998

In this paper, we present the design and analyze the transmission rate of a control algorithm for the client buffer on the VOD systems. The design is based on the server's data transmission rate and clients' data consumption rate. The proposed algorithm stabilizes the client's buffer by reducing the oscillation phenomena of the buffer. And it uses the BCT (Buffer Check Time) to reduce the scheduling load of the client system. The client's data consumption rate and the buffer size are calculated on the basis of BCT. In case that the predicted buffer size operates in the overrun or starvation the buffer. As the load fluctuation of the network, the transmission rate control policy cannot stabilize the client's buffer alone. The media scaling policy, therefore, also performs its complementary part in stabilizing the client's buffer, and performance evaluation of the proposed algorithm is provided through simulation.

• 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.

• Journal of KIISE:Software and Applications
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• v.29 no.12
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• pp.883-894
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• 2002

Classical deterministic testing controls the execution of concurrent programs based on the equivalence between specifications and programs. However, it is not directly applicable to a situation in which synchronization sequences, being valid but infeasible, are taken into account. To resolve this problem, we had proposed automata-based deterministic testing in our previous works, where a concurrent program is executed according to one of the sequences accepted by the automaton recognizing all sequences semantically equivalent to a given sequence. In this paper, we present the automata-based testing environment for Java multi-thread programs, and we design and implement "Deterministic Executor" in the testing environment. "Deterministic Executor" transforms a Java multi-thread program by applying automata-based deterministic testing, the transformed program presents testing results. "Deterministic Executor" uses "Automata Generator", which generates an equivalent automaton of a test sequence, and "Replay Controller", which controls the execution of programs according to the sequence accepted by the automaton. By illustrating automata-based testing procedures with a gas station example, we show how the proposed approach does works in a Java multi-threaded program.roach does works in a Java multi-threaded program.

• Journal of Korea Multimedia Society
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• v.2 no.4
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• pp.367-377
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• 1999

Nowadays, the number of database applications which need fast transaction processing are increasing. One way to improve the performance of transaction processing is to reside the whole database in main memory As semiconductor memory becomes cheaper and chip densities increase, the research to improve transaction throughput rates of transaction processing system, using main memory databases, has begun In this thesis, how to implement a high performance transaction processing system based on main memory databases, new concurrency control scheme, recovery scheme and storage structure is presented. The objective of the proposed schemes is to improve the transaction processing system performance measured by transaction throughput and response times.

• Proceedings of the KAIS Fall Conference
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• 2007.05a
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• pp.158-161
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• 2007

본 연구는 고속으로 회전하는 축류압축기(송풍기)의 설계 및 운전에 기초가 되는 축류회전 익렬에서의 유동계산과 유동측정, 그리고 고속회전에 따른 진통해석과 안전진단을 위한 이상 진단 시스템개발에 관해 연구한 것이다. 따라서 회전날개의 진통해석, 선회실속시의 회전날개의 진통해석, 전 체계의 동력학적 해석, 그리고 회전축의 비틀림 진동 및 선회진동의 제어로 나누어 수행하였다. 또한 각각의 연구에 대하여 수치해석과 실험을 병행하여 이론해석과 설정한 모델의 타당성을 검증하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10a
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• pp.30-32
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• 2000

최근 메타데이타의 주요 논쟁점으로 메타데이타의 표준화 문제가 등장하고 있다. 새로운 표준화 방향으로 인한 메타데이타의 확장성은 기존 메타데이타 관리 기법의 변화를 요구하게 되었다. 즉, 사용자의 질의에 대한 신속한 정보 제공과 동적인 자료의 일관성 있는 저장과 유지방 안을 필요로 한다. 이에 본 논문에서는 디지털 라이브러리 환경에서 메타데이타 속성을 정의하고, 이러한 요구사항을 만족하는 병행수행 제어 기법인 2VL(Two Version using the Latch)을 제안한다. 2VL은 래치를 사용하여 2버전을 유지함으로써 판독과 기록 연산간의 충돌로 인한 지연을 최소화하며 판독 연산에 있어서의 빠른 응답시간과 높은 최근성 반영율을 보인다.