• The Journal of Korean Institute of Next Generation Computing
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• v.15 no.4
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• pp.18-29
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• 2019

A dynamic adaptive streaming server consumes high processor power because it handles a large amount of transcoding operations at a time. For this purpose, multi-processor architecture is mandatory for which effective transcoding task distribution strategies are essential. In this paper, we present the design and implementation details of the transcoding workload distribution schemes at a 2-tier (frontend node and backend node) transcoding server. For this, we implemented four schemes: 1) allocation of transcoding tasks to appropriate back-end nodes, 2) task scheduling in the back-end node and 3) the communication between front-end and back-end nodes. Experiments were conducted to compare the estimated and the actual power consumption in a real testbed to verify the efficacy of the system. It also proved that the system can reduce the load on each node to optimize the power and time used for transcoding.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.219-220
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• 2016

A power management system (PMS) has been an important part in a ship integrated control system. To evaluate a PMS for a liquefied natural gas carrier (LNGC), this research proposes a real-time hardware-in-the-loop simulation (HILS), which is composed of major component models such as turbine generator, diesel generator, governor, circuit breaker, and 3-phase loads on MATLAB/Simulink. In addition, FPGA based control console and main switchboard (MSBD) are constructed in order to develop an efficient control and a similar real environment in an LNGC PMS. A comparative study on the performance evaluation of PMS functions is conducted using two test cases for sharing electric power to consumers in an LNGC. The result shows that the proposed system has a high verification capability for the operating function and failure insertion evaluation as a PMS simulator.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.5
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• pp.543-554
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• 2000

In the conventional distance education systems, all functions for the distance education were processed by a server. Therefore, the system of high capacity was required and there were various restrictions to provide many classes in real-time simultaneously. The group-based distance education system proposed in this study reduces a load of the main server by distributing its functions to client PCs. In the group-based education system, the establishment of lecture or discussion rooms is executed by main server, but on the other hand, the functions of the conventional server are executed by a lecturer's PC or a discussion administrator's PC The test results of the system implemented in this study show that a lecturer's PC can afford to provide fifty trainees a lecture, though they depend on the specification of systems. Therefore, the proposed system in this study can afford to simultaneously provide with the various distance discussions and lectures by reducing a load concentrated to the server.

• Journal of Korea Society of Industrial Information Systems
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• v.23 no.1
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• pp.31-41
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• 2018

This paper discusses a structure design and thermal analysis of cryogenic conduction cooling system for a high current HTS DC reactor. Dimensions of the conduction cooling system parts including HTS magnets, bobbin structures, current leads, support bars, and thermal exchangers were calculated and drawn using a 3D CAD program. A finite element method model was built for determining the optimal design parameters and analyzing the thermo-mechanical characteristics. The operating current and inductance of the reactor magnet were 1,500 A, 400 mH, respectively. The thermal load of the HTS DC reactor was analyzed for determining the cooling capacity of the cryo-cooler. Hence, we carried out the operating test of conduction cooling system of the 1st stage area with high current flow. The cooper bars was cooled down to 40 K and HTS leads operated stably. As a experiment result, the total heat load of the 1st stage area is 190 W. The study results can be effectively utilized for the design and fabrication of a commercial HTS DC reactor.

• Journal of Astronomy and Space Sciences
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• v.23 no.2
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• pp.153-160
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• 2006

A Protomodel Space Infrared Cryogenic System (PSICS) cooled by a stirling cry-ocooler has been designed. The PSICS has an IR sensor inside the cold box which is cooled by a stirling cryocooler with refrigeration capacity of 500mW at 80K in a vacuum vessel. It is important to minimize the heat load so that the background thermal noise can be reduced. In order to design the cryogenic system with low heat load and to reduce the remained heat load, we have performed numerical analyses. In this paper, we present the design factors and the results obtained by the thermal analysis of the PSICS.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.110-118
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• 2007

In multi-hop wireless network, multi-channel makes it possible to enhance network performance because it reduces channel interferences md contentions. Recently several schemes have been proposed in the literatures to use multi-channel. Especially, MCR(Multi channel routing protocol), which utilize hybrid interface assignment, is a prominent routing protocol. MCR uses simple way to change channel but efficiently reduce channel interferences. In this paper, we propose a load-aware channel selection algorithm called LCS that enhances the channel switching algerian used in MCR protocol. In LCS, channel of a node is assigned based on collected information about queue length of neighbors. Moreover this paper evaluates the performance of in by using simulation test and testbed demonstration. Test results show that the MCR with LCS outperforms the naive MCR.

• The KIPS Transactions:PartA
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• v.13A no.5 s.102
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• pp.435-444
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• 2006

Recently, various applications of location trigger service have been required and developed as users of location-based services are increasing. The location trigger is detecting event of entering in, existing in or leaving from pre-specified area, and then alerting by short message service, an e-mall or servicing other pre-defined action to mobile subscribers. The conventional methodology of supporting location trigger is detecting location trigger events as periodical requesting location of mobile communication terminal to location gateway server in mobile communication network. But these conventional methods cause mobile communication interruption when the location trigger services are overloaded; thereby inducing performance of core server to be fell off. So in this paper, we have studied a new location trigger technology, named multilevel location trigger, to reduce mobile core network sewer triggering bottleneck and power consumption caused embedded GPS device of mobile phone. Actually, as design and evaluating the performance of location trigger after building test-bed environment, we contribute toward improving echnology of location trigger.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.3049-3054
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• 2014

PST stands for the Premium Sales Tool for Product Consulting is customized product catalog system. In other words, the product classification categories of content for consulting and sales to customers by providing useful information for the maximization of an overall system. These problems with mobility and flexibility of updating the solution to integrate mobile with mobile devices, but high-performance high-resolutions era content data continuously, but still it is difficult to handle. In this paper, to solve this problem, depending on the user's gesture by allowing periodic allocation and release of a problem for load generation enhanced by improving the PST system has been designed and implemented. Implementation was a result of the test the performance of the system, that PA system that has been provided by the traditional DA system show the allocation and the average 78% of the rate of decrease the load is released in the frequency of page, CPU utilization was reduced an average 72% I was confirmed.

• Journal of Advanced Navigation Technology
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• v.28 no.3
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• pp.348-355
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• 2024

A current source capable of stably supplying current as a measurement medium is required in order to measure and test important facilities that require large-scale measurement current, such as a control element drive mechanism control system(CEDMCS), in case of dismantling a nuclear power plant. However, it can provides only voltage power as a source, not current, although direct voltage controlled constant current source is essential to test major equipment. That kind of source is not available to supply stable constant current regardless of load variation. It is just voltage supplier. Developing current source is not easy other than voltage source. Very large-scale current source up to ampere class more than such ten times of normal current is inevitable to test above mentioned equipment. So, we developed large-scale current source which is controlled by input DC voltage and supplies constant stable current to object equipment according to this requirement. We measured and tested nuclear power plant equipment using given real site data for a long time and afforded long period load test, and then proved its validity and verification. The developed invetion will be used future installed important equipment measuring and testing.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.10-12
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• 2006

인터넷의 발전으로 인한 사용자 욕구의 증가는 인터넷을 통해서 품질 좋은 멀티미디어 서비스를 요구하고 있다. 하지만 고품질의 멀티미디어 콘텐츠는 네트워크의 부하를 가중 시키고 그에 따라 서비스가 제한적일 수밖에 없다. 멀티캐스트 프로토콜은 이러한 멀티미디어 서비스에 적합하지만 비용, 보안, QoS와 같은 문제로 도입이 지연되고 있다. 오버레이 멀티캐스트는 기존의 망을 유지하면서 멀티캐스트 서비스가 가능하다는 장점으로 최근 주목받고 있는 방식이다. 이와 더불어 인터넷 프로토콜도 점차적으로 IPv6로 전환되어가고 있는 시점에서 IPv6에 적합한 오버레이 멀티캐스트 시스템이 필요하게 되었다. 본 연구에서는 IPv6 환경에서 동작하는 오버레이 멀티캐스트 시스템을 구현하고 실제 구축되어 있는 KOREN 망 위에서 다수의 사용자를 대상으로 테스트를 실시하여 본 시스템의 성능을 입증하고 있다.