• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8A
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• pp.1238-1246
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• 2000

In a multi-channel network based on wavelength division multiplexing (WDM), an efficient protocol is needed for transmitter and receiver to be tuned to same wavelength during message transmission time. This paper proposes a message scheduling protocol that can efficiently support variable-sized messages, where tunable transceiver has nonzero tuning time. In this protocol, once a node reserves one data channel, it can persistently use the reserved channel till message transmission is finished. Therefore, overhead due to tuning time of the tunable transceiver can be reduced. Moreover, the protocol does not require any global information. Therefore, it can operate independently of the change of the number of nodes, and any new node can join the network at anytime without requiring network initialization. With this protocol, one can avoid data channel and destination conflicts. The protocol is analyzed with a finite population model and the throughput-delay characteristics are investigated as performance measures.

• Journal of KIISE:Computing Practices and Letters
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• v.9 no.3
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• pp.227-240
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• 2003

When we develop and use the java-based distributed object system, the system developer must deploy distributed object, which is implemented to predefined interface, to network and the system user acquires reference about distributed object and changes reference to interface type. Sharing of interface is essential for these works In this paper, we propose the IRSJ(interface repository service based on jim) to improve efficiency of interface sharing at the JINI system development. the IRSJ is consisted of the java classes for JINI system and interface sharing service. If development teams perform collaborative work in short distance, the IRSJ can search interface file without information of lookup server or interface writer If development teams perform collaborative work in long distance, the IRJS can search interface with only an address of server that executes lookup service. Although the interface object not requires additional search, the interface object that failed search interface can download interface and use interface using remote event model. When the message service fails in interface search, the message service sends interface request message to a development team member who use the IRSJ automatically, so that interface sharing may be possible in short time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.451-457
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• 2006

A peer-to-peer(P2P) network is inherently vulnerable to malicious attacks from participating peers because of its open, flat, and autonomous nature. This paper addresses the problem of effectively defending from active attacks of malicious peers at bootstrapping phase and at online phase, respectively. We propose a secure membership handling protocol to protect the assignment of ID related things to a newly joining peer with the aid of a trusted entity in the network. The trusted entities are only consulted when new peers are joining and are otherwise uninvolved in the actions of the P2P networks. For the attacks in online phase, we present a novel message structure applied to each message transmitted on the P2P overlay. It facilitates the detection of message alteration, replay attack and a message with wrong information. Taken together, the proposed techniques deter malicious peers from cheating and encourage good peers to obey the protocol of the network. The techniques assume a basic P2P overlay network model, which is generic enough to encompass a large class of well-known P2P networks, either unstructured or not.

• Journal of Digital Convergence
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• v.10 no.6
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• pp.225-230
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• 2012

When a car accident happened, the accident vehicle should broadcast a safe message to its neighbors in multi-hop. However, the pure flooding is difficult to protect a chain-reaction collision because of the frequent collision and the communication delay. To solve this problem, we proposes a back-off algorithm applied to the estimation of the neighbor node count using the t-distribution. And we proposes a MAC protocol preventing the communication delay by separating the neighbor's count collection channel and data channel. As a result, we show the frame reception success rate of our protocol improved more 10% than the previous protocol.

• Journal of the Korea Computer Industry Society
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• v.7 no.5
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• pp.487-494
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• 2006

By development of the superhigh speed network and the Networked appliance, a home network environment was equipped quickly around the cyber apartment. The home network environment provides the abundant family life style which numerous appliance and tools are connected with the network. Recently it is caused by with appearance of the Networked appliance which is connected with the network, the service demand is augmented to hacking, wrong operation, breakdown, crime prevention in home automation, fire, and break-in. This paper planned and proposed the integrated crisis management service model in the environment of home network and Networked appliance. Namely, it classifies the Networked appliance crisis management service and it defines a crisis management message with the XML. The message where the crisis situation occurs is notified and controlled in wireless PDA or the hand phone or the specific authorization.

• Journal of computational fluids engineering
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• v.13 no.1
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• pp.35-40
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• 2008

Generally flight vehicles have many cavities such as wheel wells, bomb bays and windows on their external surfaces and the flow around these cavities makes separation, vortex, shock and expansion waves, reattachment and other complex flow phenomenon. The flow around the cavity makes abnormal and three-dimensional noise and vibration even thought the aspect ratio (L/D) is small. The cavity giving large effects to the flow might make large noise, cause structural damage or breakage, harm the aerodynamic performance and stability, or damage the sensitive devices. In this study, numerical analysis was performed for cavity flows by the unsteady compressible three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with Wilcox's $\kappa-\omega$ turbulence model. The MPI(Message Passing Interface) parallelized code was used for calculations by PC-cluster. The cavity has the aspect ratios of 2.5, 3.5 and 4.5 with the W/D ratio of 2 for three-dimensional cavities. The Sound Pressure Level (SPL) analysis was done with FFT to check the dominant frequency of the cavity flow. The dominant frequencies were analyzed and compared with the results of Rossiter's formula and Ahuja& Mendoza's experimental datum.

• Journal of Internet Computing and Services
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• v.9 no.3
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• pp.103-117
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• 2008

General customer uses internet, SMS(Short Message Service), ATM(Automated Teller Machine), DM(Direct Mail), and telephony services, etc, for service of big businesses and small and medium enterprises, securities, financial institutions, bank. In particular, the case of Fire insurance & Securities, financial institutions, banks must meet Real-Time constrain control through QoS(Quality of Service) ensure. In this paper, we design and implement a system model about Fault-Tolerance IVR(Interactive Voice Response) of Multi Channel Service based on CRM(Customer Relationship Management) environment for the first inbound position of customer. The proposed model can be widely used in Large-scale Customer Response service.

• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.74-80
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• 2016

In this paper, the modeling and implementation results of the operational test and evaluation tool of the KASS up-link station composed of the GEO(Geostationary Earth Orbit) satellite signal analysis tool model that analyzes the GEO satellite signal and the GEO message analysis tool model that analyzes the GEO satellite navigation message. In addition, we describe the results of software modeling and implementation of some software models of GEO satellite and KASS up-link stations that can generate and provide simulated signals to operational test and evaluation tools of these KASS up-link stations.

• Journal of IKEEE
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• v.19 no.3
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• pp.327-334
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• 2015

Various types of middle-ware were created for integration between legacy systems and newly built systems. RPC(Remote Procedure Call), MOM(Message Oriented Middle-ware) and TM(Transaction processing Monitor) are the typical types of middle-ware. One of the most known MOM type middle-ware is PS(Publish/Subscribe). PS enables to create a system which has low coupling and high scalability. But PS based systems also have low cohesiveness. On the contrary, RPC has high cohesiveness but also has high coupling. This paper proposed design and implementation of hybrid model which offset disadvantages of RPC and PS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3629-3647
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• 2017

Certificate-based cryptography is a useful public key cryptographic primitive that combines the merits of traditional public key cryptography and identity-based cryptography. It not only solves the key escrow problem inherent in identity-based cryptography, but also simplifies the cumbersome certificate management problem in traditional public key cryptography. So far, four short certificate-based signature schemes have been proposed. However, three of them fail in achieving the existential unforgeability under adaptive chosen-message attacks and the remaining one was not constructed in the normal framework of certificate-based signature. In this paper, we put forward a new short certificate-based signature scheme. The proposed scheme is devised in the normal framework of certificate-based signature and overcomes the security weaknesses in the previous short certificate-based signature schemes. In the random oracle model, we formally prove that it achieves the existential unforgeability against adaptive chosen-message attacks. Performance comparison shows that it is efficient and practical.