• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.13-16
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• 1999

The terrestrial/satellite hybrid network may replace or supply the terrestrial network in some areas or certain application. Futhermore, it can play an important role in the development of B-ISDN due to their features of flexible wide coverage, independent of ground distances and geographical constraints, multiple access and multipoint broadcast. Also, satellite have the capability to supply terrestrial ATM and B-ISDN with flexible links for access networks as well as trunk networks. This paper describes the design and verification of the interworking protocol between terrestrial B-ISDN and satellite network. For the verification, the designed interworking protocol is modeled by Petri-net and analyzed by reachability tree.

• Electronics and Telecommunications Trends
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• v.13 no.2 s.50
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• pp.10-28
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• 1998

무선 ATM에서는 위치관리 기법으로는 PNNI 라우팅 프로토콜의 확장과 기존의 셀룰러 전화망의 위치 등록기 개념에 근거한 방식들이 제안되고 있는데 크게 Mobile PNNI 방식과 Location Register(LR) 방식으로 나누어진다. Mobile PNNI 방식은 기존의 PNNI 라우팅 프로토콜을 기반으로 하여 단말기의 이동성을 제공할 수 있도록 수정 확장한 위치 관리 기법이다. Mobile PNNI 방식에서는 단말기가 이동할 경우에 영역 변수(scope parameter) S에 의해 제한된 범위 내에서 교환국 간에 reachability information이 갱신되며, 이러한 정보를 이용하는 PNNI 라우팅 프로토콜을 기반으로 하여 위치 추적과 호 설정이 동시에 수행된다. LR 방식은 Mobile PNNI 방식과는 달리 발신호가 발생하게 되면, 계층적인 구조의 위치 등록기들의 추적을 통해 상대편 이동 단말기가 접속된 교환국의 위치 정보를 알아낸 다음, 호 설정 과정을 수행하게 된다. 본 연구에서는 무선 ATM에서의 여러 가지 위치관리 요구사항을 살펴보고, 위에서 언급한 두 가지 방식에 대하여 자세히 소개하고, 이들을 비교 분석한다.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.6
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• pp.811-821
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• 1998

A new scheduling algorithm for large scale semiconductor processes is addressed. The difficulties of scheduling for semiconductor fabrication processes are mainly due from repeating production of wafers that experience reentrant flows. Sequence branch algorithm (SBA) is proposed for large real scheduling problems when all processing times are deterministic. The SBA is based on the reachability graph of Petri net of which the several defects such as memory consumption and system deadlock are complemented. Though the SBA shows the solution deviating a little from the optimal solution of mixed integer programming, it is adjustable for large size scheduling problems. Especially, it shows a potential that is capable of handling commercial size problems that are intractable with mathematical programming.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.1
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• pp.15-18
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• 2007

We consider the problem of designing a static output feedback sliding mode control law for linear dynamical systems with mismatched uncertainties in the state matrix. We assume that an output dependent sliding surface guaranteeing the quadratic stability of the sliding mode dynamics is given, the reachability condition is not required to be satisfied globally, and the output feedback sliding mode control law complises both linear and discontinuous parts. We reduce the problem of designing the linear part of the sliding mode control law to a simple LMI problem which offers design flexibility for combining various useful convex design specifications. Our approach does not require state transformation and it can be applied to mismatched uncertain systems.

• 한국컴퓨터산업교육학회:학술대회논문집
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• 2003.11a
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• pp.17-22
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• 2003

The surge of Internet traffic makes the bottleneck nowadays. This problem can be reduced by substituting the media of network, routers and switches with more high-performance goods. However, we focused radically the server performance of processing the service requests. We prepose the method improving performance of server in the Linux kernel stack. This accelerator accepts the requests from many clients, and processes them using not user threads but kernel thread. To do so, we can reduce the overhead caused by frequent calling of system calls and the overhead of context switching between threads. Furthermore, we implement CPN(Coloured Petri Net) model. By using the CPN model criteria, we can analyze the characteristics of operation times in addition to the reachability of system. Benchmark of the system proves the model is valid.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.2
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• pp.169-177
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• 1993

In this paper an experimental microsatellite packet radio protocol based on the terrestrial AX.25 amateur packet radio protocol is introduced and its protocol is modeled by the extended Petri Nets with timers and counters. Finally, this protocol is validated in terms of correctness, recovery, boundness, deadlock, etc by its reachability tree.

• Journal of Communications and Networks
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• v.9 no.4
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• pp.350-355
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• 2007

Border gateway protocol allows autonomous systems(ASes) to apply diverse routing policies for selecting routes and for propagating reachability information to other ASes. Although a significant number of studies have been focused on the Internet topology, little is known about what routing policies network operators employ to configure their networks. In this paper, we infer and characterize routing policies employed in the Internet. We find that routes learned from customers are preferred over those from peers and providers, and those from peers are typically preferred over those from providers. We present an algorithm for inferring and characterizing export policies. We show that ASes announce their prefixes to a selected subset of providers to perform traffic engineering for incoming traffic. We find that the selective announcement routing policies imply that there are much less available paths in the Internet than shown in the AS connectivity graph, and can make the Internet extremely sensitive to failure events. We hope that our findings will help network operators in designing routing policies.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.271-276
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• 1997

Verification is a process aimed at demonstrating whether a system meets it's specified requirements. As expert systems are used in various applications, the knowledge base verification of systems fakes an important position. The conventional Petri net approach that has been studied recently in order to verify the knowledge base is found that it is inadequate to verify the knowledge base of large and complex system, such as alarm processing system of nuclear power plant. Thus, we propose an improved method that models the knowledge base as enhanced colored Petri net. In this study. we analyze the reachability and the error characteristics of the knowledge base and apply the method to verification of simple knowledge base.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.395-398
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• 2000

The method of Variable Structure Control (VSC) design of windmill power systems is proposed. In the design of sliding mode control, we use Riccati equations arising in linear H$\^$$\infty$/ control to decide a stable sliding surface. Then the reachability to the sliding surface is realized by designing a nonlinear controller for the windmill power system. The capability of the proposed controller to damp out the oscillations of power and the robustness with respect to the system parameter variations and model errors are evaluated in the simulation study.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.771-772
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• 2006

IPv6 nodes use the Neighbor Discovery Protocol (NDP) to discover other nodes on the link, to determine their link-layer addresses to find routers, and to maintain reachability information about the paths to active neighbors. If not secured, NDP is vulnerable to various attacks. This document specifies security mechanisms for NDP. Unlike those in the original NDP specifications, these mechanisms do not use IPsec.