• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.75-81
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• 2013

We presents a novel (2, 2) secret sharing (SS) scheme for all grayscale images. Generally, a secret image is distribute more than two shadow images, which are dealt out among participants. In order to find out secret image, participants print shadow images to transparent papers. Then, a secret image will appear as stacking transparent papers. The secret sharing scheme in this paper distribute secret image into natural grayscale images using multiplexer and data hiding scheme. After then, two participant have two shadow images respectively. The merit of the proposed scheme is that shadow images have small loss in aspect of the quality with steganographic features. Therefore, the proposed secret sharing scheme in this paper is not easily detected by attackers. The experiment result verified that the proposed scheme, obviously outperforms previous SS schemes.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.943-948
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• 2018

In this paper, SSPA Module for X-band radar was designed and fabricated by using GaN MMIC. For the purpose of configuring the high power SSPA module, the drive steamers are composed of 2-layers of GaN MMIC with considering Gain Loss. In addition, the power divider and power combiner used a 4way approach by designing a 4-stage power amplifier. The power divider has a loss of -3.0dB or more, and the I/O has a loss of -0.2dB in the power combiner and the phase difference between the ports are good at $2^{\circ}$ on average. The fabricated SSPA module got the measurement results that satisfy a Gain 48dB, P(sat)=88.3W(49.46 dBm), PAE=30.3% or more efficiency in condition of frequency range 9~10GHz. The fabricated X-Band SSPA module can be applied in RF performance improvement for SSPA module whit improvement of power divider/combiner.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.6
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• pp.809-817
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• 2020

In the design and development process of Small-Sat power distribution and transmission module, the stability of dynamic resources was evaluated by a deep learning algorithm. The requirements for the stability evaluation consisted of the power distribution function of the power distribution module and demand module to the SAR radar in Small-Sat. To verify the performance of the switching power components constituting the power module PDM, the reliability was verified using a dynamic neural network. The adoption material of deep learning for reliability verification is the power distribution function of the payload to the power supplied from the small satellite main body. Modeling targets for verifying the performance of this function are output voltage (slew rate control), voltage error, and load power characteristics. First, to this end, the Coefficient Structure area was defined by modeling, and PCB modules were fabricated to compare stability and reliability. Second, Levenberg-Marquare based Two-Way NARX neural network Sigmoid Transfer was used as a deep learning algorithm.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.2
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• pp.211-215
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• 2008

the data-centric publish/subscribe middle-ware is suitable for a communication environment in which various devices dynamically forms a network domain and same type of data are frequently exchanged. For this purpose, OMG has standardized DDS (Data Distribution Service) specification. In this study, we designed the RiTiCoM, data distribution service system that observes the OMG DDS (Data Distribution Service) standard specification and supports the automation of system management, and analyzed the performance and compared with the JMS.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1114-1116
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• 2015

In this paper, we propose a load distribution scheme in SDN utilizing load redirection, enabling incoming messages to be migrated to another controller. Specifically, when the capacity of a controller reaches a threshold, the controller makes incoming packets be migrated to a less-loaded controller to prevent them from being blocked. Analytical result shows that our scheme has lower blocking probability than the conventional scheme.

• Aerospace Engineering and Technology
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• v.2 no.1
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• pp.108-116
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• 2003

This research presents the design and analysis of PCDU(Power Control & Distribution Unit) of communication satellite. The PCDU of a spacecraft must provide adequate power to each subsystem and payload during mission life, and it also needs high reliability and performance in space environment. A control circuit of the PCDU include bus sensing and filter circuits, error signal amplification circuit, error compensation circuit of SAS(Shunt Assembly Switch) and BPC(Battery Power Converter). The phase margin and DC gain for the designed circuits are analyzed through the frequency response characteristics of the compensated control circuit. And also the transfer function of the battery power converter circuit are discussed at the battery CCCM(Charge Continuous Conduction Mode) and battery C/DCCM(Continuous/Discontinuous Conduction Mode).

• Aerospace Engineering and Technology
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• v.1 no.1
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• pp.84-96
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• 2002

The major goal of this research is to use as a baseline guide for a flight model design of power system of next domestic communication satellite. For this purpose, the EPS(Electrical Power Subsystem) is designed to compliance performance requirements specified in EPS subsystem specification during all expected spacecraft operations. The regulated electrical power bus gives 42.5V to the various spacecraft loads from PCDU(Power Control & Distribution Unit) and the solar arrays are composed of 6 panel, each panel has 3 circuits including 7 string. The battery system is comprised of two batteries consisting of 26 IPV(Individual-Pressure-Vessel) NiH2 cells. Each battery can be capable of delivering 2878Watt-hours at a 80% maximum DOD(Depth of Discharge) based on the nameplate capacity of 150 amper-hours.

• The KIPS Transactions:PartC
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• v.9C no.1
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• pp.115-122
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• 2002

This paper presents a new web cluster scheme based on dispatcher which does not depend on operating system for server and can examine server's status interactively. Two principal functions are proposed for new web cluster technique. The one is self-controlled load distribution and the other is transaction fail-safe. Self-controlled load distribution function checks response time and status of servers periodically, then it decides where the traffic goes to guarantee rapid response for every query. Transaction fail-safe function can recover lost queries including broken transaction immediately from server errors. Proposed new web cluster scheme is implemented by C language on Unix operating system and compared with legacy web cluster products. On the comparison with broadcast based web cluster, proposed new web cluster results higher performance as more traffic comes. And on the comparison with a round-robin DNS based web cluster, it results similar performance at the case of traffic processing. But when the situation of one server crashed, proposed web cluster processed traffics more reliably without lost queries. So, new web cluster scheme Proposed on this dissertation can give alternative plan about highly increasing traffics and server load due to heavy traffics to build more reliable and utilized services.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.605-608
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• 2006

본 논문에서는 SLA(Service Level Agreement)와 같이 차별화 서비스를 지원하는 웹서버 시스템의 가동성 척도를 향상시키기 위해 기존의 동적 성능 분리 기법에 퍼지 기법을 접목하였다. 특히, 클러스터 기반 웹서버 시스템의 부하량에 대한 판단기준 혹은 사용자 요청률 및 동적요청 비율 변화시에 발생하는 애매모호한 상황을 효과적으로 반영하기 위해, 퍼지제어 기법에 기초한 부하분배 메커니즘을 제안하였다. 이를 통해, 기존의 퍼지 기법을 활용하지 않은 성능분리 기법과 퍼지기법을 활용한 경우에 대해 응답시간(95-percentile of response time) 성능 비교 평가를 통해 퍼지기반의 성능분리 기법이 차별화 서비스 시스템의 성능을 더욱 강건하고 효율적으로 향상시킬 수 있다는 점을 검증하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.12
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• pp.108-116
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• 2009

In this paper, we propose a Ethernet based audio distribution system with a new L1/L2 hybrid switching scheme, and evaluate its performance. The proposed scheme not only offers guaranteed low latency and jitter characteristics that are essentially required for the distribution of high-quality uncompressed audio traffic, and but also provide an efficient transmission of data traffic on the Ethernet environment. The audio distribution system with a proposed scheme consists of a master node and a number of relay nodes, and all nodes are mutually connected as a daisy-chain topology through up and downlinks. The master node generates an audio frame for each cycle of 125us, and the audio frame has 24 time slotted audio channels for carrying stereo 24 channels of 16-bit PCM sampled audio. On receiving the audio frame from its upstream node via the downlink, each intermediate node inserts its audio traffic to the reserved time slot for itself, then relays again to next node through its physical layer(L1) transmission - repeating. After reaching the end node, the audio frame is loopbacked through the uplink. On repeating through the uplink, each node makes a copy of audio slot that node has to receive, then play the audio. When the audio transmission is completed, each node works as a normal L2 switch, thus data frames are switched during the remaining period. For supporting this L1/L2 hybrid switching capability, we insert a glue logic for parsing and multiplexing audio and data frames at MII(Media Independent Interlace) between the physical and data link layers. The proposed scheme can provide a good delay performance and transmission efficiency than legacy Ethernet based audio distribution systems. For verifying the feasibility of the proposed L1/L2 hybrid switching scheme, we use OMNeT++ as a simulation tool with various parameters. From the simulation results, one can find that the proposed scheme can provides outstanding characteristics in terms of both jitter characteristic for audio traffic and transmission efficiency of data traffics.