• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.61-64
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• 2000

This paper analyzes a dynamic lot-sizing problem, in which the order size of multiple products and a single container type are simultaneously considered. In the problem, each order (product) placed in a period is immediately shipped immediately by containers in the period and the total freight cost is proportional to the number of each container type employed. Also, it is assumed that backlogging is not allowed. The objective of this study is to determine the lot-sizes and the shipping policy that minimizes the total costs, which consist of ordering costs, inventory holding costs, and freight costs. Because this problem is NP-hard, we propose a heuristic algorithm with an adjustment mechanism, based on the optimal solution properties. The computational results from a set of simulation experiment are also presented.

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.23-24
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• 2018

스마트 팩토리의 핵심 요소 중 하나인 AGV를 운용하기 위해서 스케줄링은 간과할 수 없는 문제이다. 기존의 정적인 휴리스틱 방식은 실시간으로 운용되는 스마트 팩토리에 다소 부적합한 면이 있다. 본 논문에서는 이러한 스케줄링에 관한 문제를 해결하고자 SLAM 기반의 자율주행 AGV를 운용 할 수 있는 3D 가상 환경을 설계하고 해당 환경에서 강화학습을 기반으로 한 스케줄링을 구현해 실시간으로 변화하는 공장에 적합한 동적인 스케줄링을 설계하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05c
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• pp.2045-2048
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• 2003

정보통신기술의 발전으로 유 무선 인터넷 사용자가 기하급수적으로 증가하고 있는 가운데 무선 인터넷을 이용한 m-Commerce 의 활성화가 기대되고 있다. 이와 더불어 무선 인터넷에서 안전한 m-Commerce를 제공하기 위해서는 다양한 모바일 기기 환경에 맞춘 무선 인터넷 PKI 서비스가 요구된다. 본 논문에서는 모바일 기기 성능, 네트워크 환경, 서비스 종류, 사용자의 보안 요구 사항에 맞추어 경제학 이론에서 출발한 MAUT(Multi-Attribute Utility Theory)와 간결한 휴리스틱스(Simple Heuristics) 알고리즘을 이용한 보안 등급 프로토콜을 동적으로 결정하는 적응적 보안 정책 알고리즘을 제안한다. 이를 바탕으로 PKI와 X9.59 기반의 보안 e/m-Commerce를 구축한다.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.440-442
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• 1999

본 연구에서는 전자연동장치의 확장성과 신뢰성 제고를 위해 전자연동장치의 실시간 연동전략으로 활용될 수 있는 연동 지식베이스를 자동 생성, 구축할 수 있는 지능형 연동지식베이스 자동 구축 소프트웨어(IIKBAGS)를 개발한다. IIKBAGS의 추론부는 주어진 역 모델의 동적탐색하에서 휴리스틱 규칙들의 우선순위에 따라 모든 진로를 탐색함은 물론 각 진로들에 대해 진로상 신호설비들간의 연쇄관계를 확인하여 연동패턴들을 자동생성하는 연동지식 자동생성기능을 가진다. 지식베이스는 전자연동장치상의 실시간 전문가 시스템이 직접적으로 활용할 수 있는 구조로 설계됨으로써 연동도표 입력과정에서 발생할 수 있는 오류를 배제, 연동장치의 정확성과 신뢰성을 높인다.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.11a
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• pp.84-87
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• 2020

최근, 응용 프로그램의 이식성, 확장성, 낮은 오버헤드 및 관리의 용이성 등을 제공하는 컨테이너 기술을 고성능 컴퓨팅 (high performance computing, HPC) 환경에 접목하려는 다양한 연구들이 진행되고 있다. 본 논문에서는 멀티 프로그램화된 환경, 즉, 컨테이너 기반의 다수개의 HPC 워크로드들이 동시에 실행되는 환경에서 멀티 프로그래밍 수준, 통신 패턴 및 비율에 따른 HPC 워크로드들의 성능 특성을 분석하고, HPC 워크로드가 실행되는 동일한 컨테이너 그룹에 속한 컨테이너들의 스케쥴링 시간 부조화가 데이터 교환 지연 시간을 증가시키고 그 결과 응용 성능을 크게 저하시킬 수 있음을 확인한다. 또한 HPC 워크로드가 수행되는 동일 그룹 컨테이너들의 CPU 점유 가능값(CPU Shares)을 동적으로 조절하는 휴리스틱을 제안, 적용함으로써, HPC 워크로드의 성능(통신소비시간 최대 약 42.5%, 워크로드 실행시간 최대 약 23.6% 감소)을 크게 향상시킬 수 있음을 확인한다.

• Journal of the Korea Society for Simulation
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• v.18 no.2
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• pp.29-38
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• 2009

In the computing environment with heterogeneous resources, a job scheduling model is necessary for effective resource utilization and high-speed data processing. And, the job scheduling model has to cope with a dynamic change in the condition of resources. There have been lots of researches on resource estimation methods and heuristic algorithms about how to distribute and allocate jobs to heterogeneous resources. But, existing researches have a weakness for system compatibility and scalability because they do not support the standard language. Also, they are impossible to process jobs effectively and deal with a variety of computing situations in which the condition of resources is dynamically changed in real-time. In order to solve the problems of existing researches, this paper proposes a semantic computing-based dynamic job scheduling model that defines various knowledge-based rules for job scheduling methods adaptable to changes in resource condition and allocate a job to the best suited resource through inference. This paper also constructs a resource ontology to manage information about heterogeneous resources without difficulty as using the OWL, the standard ontology language established by W3C. Experimental results shows that the proposed scheduling model outperforms existing scheduling models, in terms of throughput, job loss, and turn around time.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.11
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• pp.973-980
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• 2016

An air traffic management (ATM) has been studied in a variety of fields to utilize an air traffic capacity efficiently and solve a congested air traffic situation due to an increment of an air traffic demand. In this paper, an air traffic management, which is related with controlling and determining the sequencing of an aircraft approaching to an airport, in terminal control area is studied. This paper focuses on scheduling algorithms with a given problem for the air traffic management with operational constraints, such as a space separation, an overtaking on the same air-route, and a route merge point (a scheduling point). For a real-time calculation, the presented algorithms focus on dispatching heuristic rules which are able to assign tasks in a fast time period with an adequate performance, which can be demonstrated as a proper and realistic scheduling algorithm. A simulation result is presented to illustrate the validity and applicability of the proposed algorithm. Each scheduling rule is analyzed on the same static and dynamic air traffic flow scenario with the ATM Monte-Carlo simulation.

• Journal of Korean Society of Transportation
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• v.28 no.5
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• pp.107-116
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• 2010

The vehicle travel time between locations in a downtown is greatly influenced by both complex road conditions and traffic situation that changes real time according to various external variables. The customer's demands also stochastically change by time period. Most vehicle routing problems suggest a vehicle route considering travel distance, average vehicle speed, and deterministic demand; however, they do not consider the dynamic external environment, including items such as traffic conditions and stochastic demand. A realistic vehicle routing problem which considers traffic (smooth, delaying, and stagnating) and stochastic demands is suggested in this study. A mathematical programming model and hybrid genetic algorithm are suggested to minimize the total travel time. By comparing the results considering traffic and stochastic demands, the suggested algorithm gives a better solution than existing algorithms.

• Journal of KIISE:Computing Practices and Letters
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• v.12 no.3
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• pp.149-159
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• 2006

To provide on-demand video streaming services through the network, video objects with both high and low client request rates should be served efficiently. In this paper, we propose a dynamic on-demand streaming approach for providing services efficiently regardless of the client request rate. This approach can maintain QoS by transitioning the service scheme according to the request rate. The server provides services by the Heuristic broadcasting approach when the client request rate is low and by Striping broadcast, one of many Periodic broadcast approaches, when the client request rate is high. The server knows the variations of client request rates by the number of service channels and decides the transition to more efficient service schemes on its own. We simulated this scheme transition with various client request intervals and traces from a company providing streaming services. The results show that the performance of our approach is reasonable.

• Journal of KIISE:Information Networking
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• v.28 no.4
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• pp.517-526
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• 2001

In order to reduce the increasing packet loss rates caused by an exponential increase in network traffic, the IETF(Internet Engineering Task Force) is considering the deployment of active queue management techniques such as RED(Random Early Detection). While active queue management in routers and gateways can potentially reduce total packet loss rates in the Internet, this paper has demonstrated the inherent weakness of current techniques and shows that they are ineffective in preventing high loss rates. The inherent problem with these queue management algorithms is that they all use queue lengths as the indicator of the severity of congestion. In this paper, in order to solve this problem, a new active queue management algorithm called MRED(Modified Random Early Detection) is proposed. MRED computes the packet drop probability based on our heuristic method rather than the simple method used in RED. Using simulation, MRED is shown to perform better than existing queue management schemes. To analyze the performance, we also measure throughput of traffics under the FIFO control, and compared the performance with that of this MRED system.