• Journal of Korea Multimedia Society
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• v.9 no.4
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• pp.490-504
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• 2006

It needs to control each objects on various platform and transmit multimedia data to multiple receivers which are for developing a multimedia service with multimedia live streaming in a distributed environment. In this paper, we present a DLS (Distributed Live Streaming) package which support l:N multimedia live streaming in a distributed environment. Also, it has extended RMI which is a distributed object technology and JMF using multimedia transmission/processing. A java-based DLS package has been designed to separate a transmission and a control for more efficient distributed processing. It is possible to apply in development of multimedia service supported 1:N transmission and runned independently to any platform.

• Journal of Korea Multimedia Society
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• v.19 no.3
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• pp.567-572
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• 2016

N-screen is an emerging technology to support multimedia multicasting, content sharing and content mobility. N-screen service providers should obtain the technology that provides the highest quality content seamlessly. Distributed nature of WiMedia distributed-MAC protocol can provide full mobility support, and achieves seamless medium access method in contrast to IEEE 802.15.3. So, in this paper, WiMedia distributed-MAC protocol is adopted and an asynchronous multicast transmission (AMT) technology is proposed to enhance performance of seamless N-screen wireless service based on distributed-MAC. The ACK frame transmissions are not required for multicast transmissions. By using this property in AMT, if a device is a multicast receiver, its reserved time slots can be reserved by the other devices with 1-hop distance. Furthermore, each N-screen device broadcasts and shares the information including an order in asynchronous traffic reservations to reduce conflicts in determining the transmission order of asynchronous N-screen packets. Therefore, AMT scheme expands the number of time slots available and throughputs for multicast and asynchronous traffic reservations when comparing with the distributed-MAC standard system. N-screen communications based on distributed-MAC with the proposed AMT shows a new framework for realizing N-screen wireless service with the full content mobility.

• Journal of information and communication convergence engineering
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• v.8 no.5
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• pp.473-478
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• 2010

Today's engineering design is carried out in a distributed fashion geographically or physically. This places new requirements on the computational environments such as efficient integration and collaboration. With the advances of the Internet and Network environment recently, many researches have been proposed and at the same time, Web-based distributed design gives to a new paradigm in design and manufacturing fields. That is, Web-based technologies lead to reduce the product development times and to ensure a competitive product in order to exchange and interact of real-time design information that integrates the distributed design environment between departments as well as companies via Internet and Web. So, an efficient data communication for design information sharing is the foundation for collaborative systems in the distributed environment. Design data communication techniques such as CORBA, DCOM and RMI have been considered in the existing research but they have some problems that are limitations of interoperability and firewall problems in the Web. Therefore, this paper presents a Web-based distributed design application where distributed design information resources are integrated and exchanged using Web Services for supporting XML and HTTP without the interoperability and firewall problems through the 330K VLCC case.

• Journal of computational fluids engineering
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• v.11 no.2 s.33
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• pp.19-24
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• 2006

A research to evaluate the efficiency of design optimization was carried out for aerodynamic design optimization problem in distributed computing environment. The aerodynamic analyses which take most of computational work during design optimization were divided into several jobs and allocated to associated PC clients through network. This is not a parallel process based on domain decomposition in a single analysis rather than a simultaneous distributed-analyses using network-distributed computers. GBOM(gradient-based optimization method), SAO(Sequential Approximate Optimization) and RSM(Response Surface Method) were implemented to perform design optimization of transonic airfoils and evaluate their efficiencies. dimensional minimization followed by direction search involved in the GBOM was found an obstacle against improving efficiency of the design process in the present distributed computing system. The SAO was found fairly suitable for the distributed computing environment even it has a handicap of local search. The RSM is apparently the most efficient algorithm in the present distributed computing environment, but additional trial and error works needed to enhance the reliability of the approximation model deteriorate its efficiency from the practical point of view.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.39 no.2
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• pp.1-9
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• 2002

The use of Object-Oriented Distributed Programming(OODP) environment such as DCOM, DSOM, Java RMI, CORBA to implement distributed applications is becoming increasingly popular. However, absence of a fault-tolerance feature in these middleware platforms complicates the design and implementation of reliable distributed object-based applications, although they greatly enhance the quality and reusability of the distributed object-based applications. In this paper, we propose a fault-tolerant programming environment based on RMI, namely Evergreen, for the reliable distributed computing with checkpoints and rollback-recovery mechanism. Based on a series of experiments, we evaluate the performance of Evergreen and find its possibility of extension to fully support our optimal design goal.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.11
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• pp.50-55
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• 2009

In this paper, a distributed amplifier is designed using distributed network synthesis that provides the optimum absorption capability of a capacitance. Transfer functions of filters, which consist of the amplifier, are synthesized by a low-pass Chebyshev approximation. Capacitances that a filter network can absorb are calculated as a function of its minimum insertion loss(MIL) and ripple. Active devices in a distributed amplifier are modeled as equivalent circuits by using their S-parameters, and their equivalent capacitances are absorbed into filter structures by properly adjusting the MIL and ripple of a transfer function. As an application example, a distributed amplifier with the gain of about 12.5dB is designed that operates over the frequency range between 0.1 and 7.5GHz. Experimental results prove that distributed network synthesis, which considers capacitance absorption capability, is useful to the design of distributed amplifiers.

• The Journal of the Korea Contents Association
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• v.12 no.2
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• pp.60-68
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• 2012

This paper describes design and implementation of a distributed rendering management system using existing rendering module. Currently, most of 3D commercial software provide modeling, rendering and distributed environment in the whole package. So, the server and client should use the given renderer as is, without the required features. In this paper, we propose a distributed rendering management system that consist of rendering module and distributed rendering client-server. The rendering module can be executed independently and managed by the distributed rendering client. The server requests rendering for each connected client. After the execution, the server gathers rendering result from each client. After gathering, the server provides the rendering result to the user.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.8
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• pp.1002-1008
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• 2018

Fault Ride Through(FRT) requirement prevents disconnections of distributed generations during the specific time on disturbance condition for system stability. However, since there is a limitation to the FRT capability of distributed generation, and the protection system needs to clear the fault quickly before the distributed generation is disconnected. Therefore, this paper proposes a novel optimal setting method of directional overcurrent relay considering FRT of distributed generation. The proposed method reduces the probability of disconnections of the distributed generation in disturbance without additional equipment considering the FRT capability of the distributed generation by calculating the optimal relay setting through the Genetic Algorithm(GA).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.298-305
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• 2010

In this paper, a new algorithm of optimal Volt/Var Control is proposed using Volt/Var control for the Distribution Automation System (DAS) with Distributed Generation (DG) based on the modeling of the distributed load and the distributed current. In the proposed, algorithm based on the modeling of the distributed load and the distributed current are estimated from constants of four terminals using the measurement of the current and power factor from a Feeder Remote Terminal Unit (FRTU) and DG data from RTU for DG. For the optimal Volt/Var Control, the gradient method is applied to find optimal solution for tap, capacity and power control of OLTC (On-Load Tap Changers), SVR (Step Voltage Regulator), PC (Power Condenser) and DG (Distributed Generation). In the case studies, the estimation and control of the voltages have been testified in a radial distribution system with DG using matlab program.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.5
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• pp.345-351
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• 2018

A distributed control method is proposed to improve the power sharing performance of bidirectional distributed generators and the voltage regulation performance of a DC bus in a DC microgrid. Voltage sensitivity analysis based on power flow analysis is conducted to analyze the structural characteristics of a DC microgrid. A distributed control method using a voltage sensitivity matrix is proposed on the basis of this analysis. The proposed method uses information received through the communication system and performs the droop gain variation method and voltage shift method without additional PI controllers. This approach achieves improved power sharing and voltage regulation performance without output transient states. The proposed method is implemented through a laboratory-scaled experimental system consisting of two bidirectional distributed generators, namely, a load and a non-dispatchable distributed generator in a four-bus ring-type model. The experimental results show improved power sharing accuracy and voltage regulation performance.