• Information and Communications Magazine
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• v.13 no.9
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• pp.54-66
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• 1996

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1996.10a
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• pp.293-296
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• 1996

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1996.10a
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• pp.289-292
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• 1996

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1996.10a
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• pp.532-535
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• 1996

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.123-130
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• 2005

Zeolite X adsorbents with large surface area were prepared for using oxygen PSA adsorbent. Selective adsorption performance of nitrogen on the synthesized zeolite X adsorbent was improved by the cation exchange of adsorbent. The zeolite X which had over $650m^2/g$ surface area was synthesized at the conditions of $SiO_2\;:\;Na_2O\;:\;H_2O\;:\;Al_2O_3$ = 2.5 : 3.5 : 150 : 1 mole ratio, $98^{\circ}C$ temperature and 18 h synthesized time in 50 L reactor. The metal ions Li, Ag, Ca, Br, Sr, etc. were investigated for ion exchange with zeolite X. Ag ion was showed the highest ion exchange rate among these metal ions and all metal ions were exchanged with Na ion at equivalent rate. Compared with the NaX adsorbent, the ion exchanged zeolite X adsorbent remarkably improved its adsorption performance of nitrogen at the conditions of $10{\sim}40^{\circ}C$ temperature and 0~9 atm pressure. At an equilibrium pressure under 0.5 atm, adsorption performance of nitrogen on the ion exchanged zeolite adsorbent increased in the order of Ag > Li > Ca > Sr> Ba > K, whereas at an equilibrium pressure over 1 atm showed in the order of Li > Ag > Ca > Sr > Ba > K. Nitrogen/oxygen separation factor of Li ion exchanged zeolite X adsorbent was 13.023 at the partial pressure of nitrogen/oxygen gas mixture similar to air and $20^{\circ}C$ adsorption temperature.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.4
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• pp.421-429
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• 2000

In present, ATM integrated switching system has been developed to a mixed modules that complexed switching system including maintenance, operation based on B-ISDN/LAN service and plug-in module, , which runs on workstation computer system. Meanwhile, workstation has HMI operation system feature including file system management, time management, graphic processing, TMN agent function. The workstation has communicated with between ATM switching module and clients. This computer system architecture has much burden messages communication among processes or processor. These messages communication consume system resources which are socket, message queue, IO device files, regular files, and so on. Therefore, in this paper we proposed new performance modeling with this system architecture. We will analyze the system bottleneck and improve system performance. In addition, in the future, the system has many additional features should be migrated to workstation system, we need previously to evaluate system bottleneck and redesign it. In performance model, we use queueing network model and the simulation package is used PDQ and C-program.

• The Magazine of the IEIE
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• v.25 no.6
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• pp.69-78
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• 1998

프레임 릴레이망을 백본으로 한 LAN과 LAN접속으로 형성되는 기업통신망이 현재 활발히 전개되면서 인터넷을 통한 광고, 전자거래가 중요한 서비스로 진행되고 있다. 국내의 프레임 릴레이 서비스 현황을 살펴보면 KT, 데이콤, 일부기업등에서 프레임 릴레이 교환기를 수입하여 주고객인 기업에 서비스를 제공하고 있다. 이들은 사용자 요구에 의해 주로 LAN과 LAN에 접속된 라우터 등의 종단 시스템간 PVC(영구가상회선: Permanant Virtual Circuit)접속을 통하여 다양한 서비스를 제공하면서 독자적인 기업통신체계를 구축하고 있는 실정이다. 이와같이 사용자 요구로 PVC등록시 프레임 릴레이망과 LAN을 연결하는 링크의 QoS(서비스 질: Quality of Service), 트래픽 파라메터는 수동적으로 설정된다. 현재 국내에서는 프레임 릴레이 교환기 개발은 전무하고 단지 그들을 수입하여 운용하는 수준이며 향후 ATM(비동기 전달모드: Asynchronous Transfer Mode)망의 중요 서비스 연동이 될 프레임 릴레이 기술은 심도있게 연구되고 있다. 향후 고속통신을 제공하는 백본망은 기존의 프레임 릴레이망과 ATM망이 공존할 추세이며 점진적으로 프레임 릴레이망은 사라질 것이다. 이때 ATM 망이 기존의 프레임 릴레이망을 백본으로 한 기업통신망 수용시 원할한 서비스 제공을 위해서는 프레임 릴레이망을 백본으로 채택한 기존의 기업통신망을 ATM망에서 수용시 야기되는 문제점의 제시와 이의 해결은 매우 중요하다고 생각된다. FR/ATM(Frame Relay/ATM)연동시 기업통신망 입장에서는 PVC뿐만 아니라 SVC(교환가상회선: Switched Virtual Circuit)호처리가 수용되어야 한다. 이와같이 PVC와 SVC 수용으로 기업통신망은 통신망의 구성 및 관리가 복잡, 다양해지며, 또 그 기업은 관련된 다양하고 수많은 고객과 접속될 수 있어야 한다. 이때 ATM망을 백본으로 한 공중망이 관련 기업의 사설 정보를 관리하도록 한다는 것은 그 서비스의 이용자에게 보안문제를 제기함은 물론 서비스 이용자가 자신의 망에서 동작하는 여러 서비스를 고객 스스로가 관리하는 것이 바람직하다. CNN(고객망관리 : Customer Network Management)은 이러한 고객에 의한 통신망, 공중망에 대한 부분적 관리 및 서비스에 대한 관리가 이루어 질수 있도록 수행하는 기능이다. 본 논문에서는 ATM망이나 프레임 릴레이망과 ATM 망이 공존시 기업통신망관점에서 야기되는 문제점의 제시와 이의 해결 방안을 살펴보았다. 우선 FR/ATM 연동에서 PVC설정뿐만 아니라 SVC 설정 방법의 연구, 이때 고려된 QoS,트래픽 처리과정을 살펴보았다. 또한 망관리 입장에서 기업통신망 관리자와 ATM망 관리자와의 온-라인 서비스를 제공하기 위해서는 변화된 통신망 차원서의 확장된 Managed Object(MO)를 근간으로한 체계적인 CNN-NMS(CNM-Network management System)연동을 살펴본후 결론에서는 추후 계속연구 및 조사 되어야 할 항목을 기업통신망 입장에서 서술하여 보았다.

• Journal of Korea Multimedia Society
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• v.10 no.4
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• pp.462-469
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• 2007

ATM protocol has the techniques such as cell discarding priority, traffic shaping and traffic policing. ATM based MPLS(Multiprotocol Label Switching) is discussed for its provisioning QoS commitment capabilities, traffic engineering and smooth migration for BcN using conventional ATM infra in Korea. This paper proposes preventive congestion control mechanism for detecting HTR(Hard To Reach) LSP(Label Switched Path) in ATM based MPLS systems. In particular, we decide HTR LSP using real time signaling information(etc., PTI,AIS/RDI) for applying HTR concept in circuit switching to ATM based MPLS systems and use those session gap and percentage based control algorithm that were used in conventional PSTN call controls. We concluded that it maximized the efficiency of network resources by restricting ineffective machine attempts. Proposed control can handle 208% call processing and more than 147% success call, than those without control. It can handle 187% BHCA(Busy Hour Call Attempts) with 100 times less than use of exchange memory.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.61
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• pp.33-39
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• 2000

In this paper, we present an algorithm for the multicast routing problem when there exit the cell replication limits of ATM switching nodes. This problem can be formulated as a Degree Constrained Minimum Steiner Tree Problem(DCSP). The proposed algorithm is a modification of the shortest path heuristic originally devised for minimum Steiner tree problem. From the experimental results, it can be seen that our algorithm is efficient to obtain a near optimal solution with comparatively low computational time.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.25-35
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• 1998

The control system architecture in switching systems have undergone numerous changes to provide various call processing capability needed in telecommunication services. During call processing in a distributed switching control environment, the delay effect due to communication among main processors or peripheral controllers is one of the limiting factors which affect the system performance. In this paper, we propose a performance model for an IPC(Inter Processor Communication) interface hardware block which is required on the ATM cell-based message processing in a distributed ATM exchange system, and analyze the primary causes which affect the processor performance through the simulation. Consequently, It can be shown that the local CPU of the several components(resources) related to the IPC scheme is a bottleneck factor in achieving the maximum system performance from the simulation results, such as the utilization of each processing component according to the change of the input message rate, and the queue length and processing delay according to input message rate. And we also give some useful results such as the maximum message processing capacity according to the change of the performance of local CPU, and the local CPU maximum throughput according to the change of average message length, which is applicable as a reference data for the improvement or expansion of the ATM control system.