• The Journal of the Acoustical Society of Korea
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• v.26 no.8
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• pp.426-431
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• 2007

In this paper we have studied the underwater vector channel modeling for MIMO(Multiple Input Multiple Output) to increase the performance and efficiency for ultrasound communication in underwater channel environments. Also we have analyzed the MIMO techniques using the proposed channel modeling. For underwater MIMO channel modeling. experiments were done in real channel environments and the data were analyzed to estimate parameters such as fading, Doppler, time delay, angle of arrival, and receiving power. These were used for modeling of underwater vector channel modeling for MIMO. Additionally, we have analyzed the performance of MIMO systems using our proposed channel models. As a result we could see that the BER has decreased severely with the same SNR when using the MIMO system.

• Journal of Korean Society of Disaster and Security
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• v.15 no.3
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• pp.67-77
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• 2022

In South Korea, U-type girder development was attempted as a means to increase the length of I-type girder, but due to the large self-weight according to the post-tension method, the application of rail bridges of 30m or less is typical. There are not many examples of application of pre-tension type girder. This study does not limit the post-tension method, but applies the pre-tension method to induce a reduction in self-weight and materials used due to the reduction of the cross-section. In addition, we intend to apply the on-site pre-tensioning method using the internal reaction arm of the U-type girder. The prestressed concrete U-type girder bridge is composed of a concrete deck slab and a composite section. Compared to the PSC I-type, which is an open cross-section because the cross section is closed, structural performance such as resistance and rigidity is improved, the safety of construction is increased during the manufacturing and erection stage, and the height ratio is reduced due to the reduction of its own weight. Therefore, it is possible to secure the aesthetic scenery and economical of the bridge. As a result, it is expected that efficient construction will be possible with high-quality factory-manufactured members and cast-in-place members. In this paper, the introduction of the pre-tension method on-site and the analytical performance verification of the anchoring block for tension are included.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.46-52
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• 2011

A study on the improvement for cycle efficiency of closed-type ocean thermal energy conversion (OTEC) was studied to obtain the basic data for the optimal design of cycle. For that, OTEC cycle with a generator, a reheater and a multi-turbine was simulated and analyzed. The basic thermodynamic model for OTEC is Rankine cycle and the surface seawater of $26^{\circ}C$ and deep seawater of $5^{\circ}C$ were used for the heat source of evaporator and condenser, respectively. Ammonia is used as the working fluid. The cycle efficiency increased when generator is added with 0.9 generator effectiveness. When the reheater and multi-turbine are applied in the basic cycle, the cycle efficiency showed 3.14% and the capacity of heat exchanger decreased for same total cycle power. For the OTEC cycle with the generator, the reheater and the multi-turbine showed the highest cycle efficiency and increased the efficiency by more than 6.5% comparing with the basic OTEC cycle.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.355-357
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• 2003

본 논문은 기존에 제시되었던 협동적 캐슁 프록시 서버의 구조에 프록시 서버에 독립적인 prefix 배치와 프록시 서버간의 suffix 공유라는 동작을 추가하여, 무선 상에서의 효율적인 멀티미디어 콘텐츠 스트리밍이 가능하도록 하였다. 제안한 구조에 적합한 동작방법과 알고리즘 및 이에 따른 prefix의 특성을 제시하며, 콘텐츠 초기 지연 시간의 감소와 서버저장 능력 향상에 대한 성능 개선 효과를 기술한다.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.362-363
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• 2018

태양광 발전시스템에서 태양광 모듈은 고압의 발전전압 형성을 위해 직렬로 구성한 스트링을 사용하고 있다. 그러나 직렬로 연결된 태양광 모듈 중 한 개의 모듈이라도 노후화가 발생하면 노후화가 발생한 스트링의 발전 효율이 감소하는 문제점이 있다. 따라서 본 논문에서는 태양광 스트링에서 노후화 모듈을 판정을 위해 순시 PV 특성곡선을 계측할 수 있는 토포로지를 제안하고 계측된 PV 특성곡선을 이용한 노후화 판정 알고리즘을 제안한다.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.12a
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• pp.356-359
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• 2003

본 논문에서는 제안하는 Grid Computing은 PMI(Privilege Management Infrastructure)를 이용하여 효율적으로 컴퓨팅 파워의 분산 관리하고 네트？의 트래픽을 분산시키는 모델을 제시한다. 또한 Agent 간 통신 및 Agent와 Server 간 통신에서 Soap Protocol과 SSL Protocol을 접목하여 보안 RPC통신을 기반으로 데이터의 무결성과 기밀성을 보장한다. 본 논문에서 제안한 모델은 Agent를 효과적으로 관리하고 네트워크의 트래픽을 감소시킴과 더불어 Grid Computing의 성능이 개선될 것으로 기대된다.

• The KIPS Transactions:PartC
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• v.11C no.6 s.95
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• pp.787-798
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• 2004

High performance net재rking is one of key factors to provide support for data intensive applications in the Internet. Extended frame size has a major impact on end to-end performance with increasing effective TCP throughput and decreasing system overhead. Most of the research about extended frames has focused on local area network performance and the impact that extended frame size has on the system elements including memory, network interface card and so forth. In the paper, we analyse the effects of the extended frames to the other traffic flows sharing Internet paths for the wide area performance of TCP by conducting various network simulations. Results show that securing available bandwidth in no loss and low delay networks is indispensable to exploit the efficiency of extended frames.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4C
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• pp.207-216
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• 2011

Motion compensated extrapolation (MCE) techniques show inferior performance compared to motion compensated interpolation techniques, since only past frames are used in MCE. MCE techniques are used for the reconstruction of corrupted frames, the up-conversion of frame rates and the generation of side information in the distributed video coding system. In this paper, the performance of various MCE techniques are evaluated and an efficient MCE technique using the forward and backward motion estimation is proposed. In the proposed technique, the present frame is extrapolated by averaging two frames which are generated by forward and backward motion estimation respectively. It is shown that the proposed method produces better PSNR results and less blocking phenomena than conventional methods.

• The KIPS Transactions:PartC
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• v.11C no.6 s.95
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• pp.755-764
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• 2004

Recently 'Banking IC Card Standard' and EMV Standard by the domestic standard is selected, and it is situation that is developing infrastructure vigorously to alternate Magnetic Stripe card by IC card. This paper analyzes EMV standard that is selecting public key cipher, and research wishes to study unexhausted EMV PKI relatively than internet PKI, WAP PKI etc. This paper propose utilizable EMV base Payment PKI model in IC card base payment system development, and developed EMV CA system with this. Also, this paper supplemented IC card Authentication mechanism that is defined in EMV standard, and propose 'Efficient smart card Authentication mechanism' to improve performance of this mechanism, and estimate performance.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.227-227
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• 2014

OLED 소자에 사용되는 유기물들은 대부분 전자에 비해 정공의 이동속도가 매우 빨라 소자 효율의 손실이 일어난다. 본 연구에서는 이러한 전하 이동도의 불균형에 의한 OLED 소자 성능의 감소를 개선하기 위해 HBL (hole blocking layer) 물질로 BCP (HOMO : 6.5 eV, LUMO : 2.83 eV)를 도입하였다. 그러나 BCP의 LUMO 값이 약 3 eV를 가지기 때문에 전자의 이동에 영향을 미치는 것으로 예상되어 더 높은 효율을 가지는 소자를 제작하기 위해 host 물질을 상용물질(PGH02)로 교체하였다. PGH02의 HOMO 값은 약 5.86 eV로 소자에 사용된 HTL (hole transport layer)의 HOMO 값(5.54 eV)에 비해 높은 값을 가지기 때문에 HBL의 역할 역시 가능하여 소자의 성능이 상당히 개선되는 것을 확인할 수 있었다. 또한 전하 이동도의 균형을 맞추기 위해 ETL 물질로는 기존에 많이 사용되고 있는 Alq3 (${\mu}{\sim}10-5cm2/Vs$)에 비해 이동도가 10배 이상 빠른 Bebq2 (${\mu}{\sim}10-4cm2/Vs$)를 사용하였다. HTL (hole transport layer) 물질로는 상용물질(LHT 259)를 사용하였고, LHT 259의 전하 이동도는 FET (field effect transistor)를 제작하여 측정하였다. 이를 기반으로 하여 ETL과 HTL의 두께를 조절하여 전하 이동도가 균형을 이루는 OLED 소자를 제작하기 위해 실험을 진행하였다.