• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.06a
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• pp.246-247
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• 2014

케이블 방송망에서 최대 10Gbps 테이터 전송을 위해 최근 북미에서 표준화된 DOCSIS 3.1(Data over Cable Service Interface Specifications Version 3.1)에서는 고차 혼합 변조(Mixed Modulation) 방식을 제시하였다. DOCSIS 3.1 은 하향 데이터 전송을 위해 최대 192MHz 의 대역에서 4K 또는 8K 다중 직교 반송파를 사용한다. 특히 채널 오류 정정을 위한 채널 부호화 방법으로 유럽의 차세대 케이블 방송 표준인 DVB-C2(Digital Video Broadcasting - Cable Version 2)에 정의된 BCH(Bose, Chaudhuri, and Hocquenghem)와 LDPC(Low Density Parity Check) 연접부호를 사용한다. 단, DOCSIS 3.1 에서는 DVB-C2 와 달리 부호율 8/9 의 Short Mode 부호만을 사용하며 최대 16384-QAM 까지 사용한다. 하나의 부호율을 사용하기 때문에 QAM 차수에 따른 요구 SNR 의 차가 크게 된다. 주어진 채널 상황에서 최적의 전송용량을 얻기 위해 QAM 차수에 따른 요구 SNR 의 차를 줄일 수 있는 방법으로 혼합 변조가 도입되었으며, 본 논문에서는 혼합 변조에 따른 수신 성능을 제시한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.140-143
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• 2006

Load/Unload(L/UL) technology includes the benefits, that is, increased areal density, reduced power consumption and improved shock resistance. The main issues of L/UL are no slider-disk contact and no media damage. To make sure L/UL stability, we consider many design parameters in L/UL systems. This paper is focused on disk design parameters through designing a disk bump in outer guard band(OGB). In the case of bump design on the disk, we create a bump by changing bump design parameters as like size and amplitude. From dynamic analysis, we choose optimal bump model with the highest flying height and the longest rising time. When a slider passes over a bump in dynamic system, the slider rise above bump according to bump shape. On the basis of this rising effect on the bump, we apply bump design to classical L/UL system having slider-disk contact possibility. This study is based on the simulation, we finally realize improved slider unloading performance by applying slider dynamic result on unload simulation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.127-129
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• 2003

Recently. the efforts for the development of DVD concentrate on the high storage and multi-media. DVD has been manufactured by assembling many parts and it causes the vibration and noise. In this paper, one body rotor is proposed, which can make the nose and vibration be decreased. The injection mould for DVD rotor is designed by finite element analysis and the rotor is manufactured in the mould. The magnetic flux density is measured on the surface and it is compared with the design criteria.

• Journal of Broadcast Engineering
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• v.12 no.1 s.34
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• pp.28-40
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• 2007

In this paper, we proposes an idea for improved sound characteristic which decreasing a problem in previous reverberation algorism structure. To later reflection sound, proposed new reverberation structure, using a lopped and nested all-pass delay line, and it is designed to improve an natural concert hall sound. In addition, In order to have best imaginary sound effect, we extracted the factors by controlling each delay line's delay time, and we realized a proposed new algorithm by using general-purpose DSP. Through several experimental cases, we observed better effect on improvement of linear flatten and reverberation density and decreasing about colorlessness and non-linear sound at previous proposed model about impulse input.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.336-340
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• 2009

This paper presents experimental results carried out on the purge characteristic of the anodic dead-end mode fuelcell and how to improve the cell performance by pulsation effects. The dead-end mode fuelcell has some merits that a fuel supplying device is not needed and the cell power is higher than that in the open mode fuelcell. However, the purge is necessary for preventing the porous media from being flooded by liquid water formed in the channel. At this time, the un-reacted fuel is discharged with the liquid water together in purge process. The discharged fuel can make the fuel efficiency lower. Therefore, the number of purge times should be decreased for the better fuel efficiency. In this study, the outlet of the anode channel was equipped with a purge solenoid valve and a pulsation generator. The purge times was decreased when the current density decreased and operation pressure increased without the pulsation effects. In addition, when the pulsation effects such as various frequencies or amplitudes were applied, purge times was alleviated up to 40%.

• Journal of Broadcast Engineering
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• v.4 no.1
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• pp.22-31
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• 1999

Moving object tracking improves the efficiency and qualification for observation system, broadcasting system, video conference, etc. This paper propcses an improved Bayes decision method for detecting and tracking moving objects in active camera environment. The Bayes decision based tracking approach finds the region of moving objects by analyzing the image sequences statistically. The propcsed algorithm regenerates the probability density function to accord with moving objects and background for active camera. Experimental results show that the algorithm is accurate. reliable and noise resistant. The result is compared with those of the conventional methods.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.07a
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• pp.301-302
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• 2015

케이블 방송망에서 멀티-Gbps(Giga bit per second) 초고속 인터넷 서비스 제공을 위해 최근 북미에서 DOCSIS 3.1(Data over Cable Service Interface Specifications Version 3.1) 표준을 발표하였다. DOCSIS 3.1 은 최대 10Gbps 하향 데이터 전송과 최대 2Gbps 의 상향 데이터 전송을 목표로 한다. DOCSIS 3.1 이 이전 DOCSIS 표준들과 다른 점은 전송 효율을 높이기 위해 물리계층 전송 방식에 큰 변화를 주었다는 점이다. 기존 6MHz 대역폭의 단일 반송파 전송 방식에서 최대 192MHz 광역 채널의 다중 반송파 전송 방식으로 변경하였다. 또한 채널 오류정정 방식으로 BCH(Bose, Chaudhuri, and Hocquenghem)와 LDPC(Low Density Parity Check) 연접부호를 적용하여, 이로 인한 SNR 성능 이득 통해 4096-QAM 의 고차 변조를 지원한다. 본 논문에서는 최대 192MHz 의 광역 채널로 전송되는 약 2Gbps 의 전송 데이터에 대한 채널 오류 정정을 위해 고속의 LDPC 복호기 구현 방법을 제시한다.

• Journal of KSNVE
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• v.9 no.2
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• pp.324-330
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• 1999

With the increase of track density, high rotational speed and the compatibility for various media such as CD-ROM, CD-R/RW, DVD-ROM/RAM/RW etc. in optical disk drive, the effective anti-vibration design is so crucial for robust operaton. Especailly when the drive is self-excited by unbalanced disk, internal sled base vibration and its external transmission to the case bring about so severe problem. Generally these two consideration points the practical anti-vibration design process to control thses two conflictive properties using finite element analysis. As an example of the design process, Duro 25 and 40 visco-elastic rubber mount was selected and analyzed. The stiffness obtained from FEM rubber model was well matched with the experiments. Also it was confirmed that the internal and external vibration induced from unbalanced disk have good agreement with experimental results. The proposed design process is adopted to the slim-type optical disk drive.

• Journal of The Korean Society of Grassland and Forage Science
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• v.25 no.2
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• pp.125-130
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• 2005

This study was conducted from March 16 to July 6 in 2004 at Jeju Island to investigate the influences of sowing dates(on March 16, March 26, April 5, April 15 and April 25) on creeping bentgrass vegetation. The result obtained were summarized as follows; Plant height was 22.7 cm at March 16 planting. It was longest but after that planting, plant height gradually shorted. Then it was shortest at April 25 planting(16.6 cm). Root length and Minolta SPAD-502 chlorophyll reading value were directly proportional plant height response. Leave and root weight were greatest at March 16 planting. It were 1,373 kg /10a and 2,374 kg /10a, respectively. These weight decreased gradually as planting was delayed from March 16 to April 25. Degree land cover and density of creeping bentgrass were $98.0\%$ and $99.3\%$, respectively, at March 16. After that planting they were decreased ($97.5\%$, $98.7\%$). But degree land cover and density of weed tended to increased gradually as the planting was delayed. The number of weed species were increased from March 16 to April 25. It showed increase that Poa annua, Stellaria media and Chenopodium album var. centrorubrum(at March 16 planting), Poa annua, Digitaria adscendens and Chenopodium album var. centrorubrum(at March 26 planting), Digitaria adscendens, Chenepodium album var. centrorubrum and Stellaria media(at April 5 planting), Digitaria adscendens, Stellaria media and Chenopodium album var. centrorubrum(at April 15 planting), Digitaria adscendens, Polygonum hydropiper, Chenopodium album var. centrorubrum(at April 25 planting). Based on the these findings, optimum sowing date for growth of creeping bentgrass seems to be about early seeding in atmospheric phenomena and volcanic ash soils of Jeju island.

• Journal of Korean Society of Forest Science
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• v.96 no.3
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• pp.307-316
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• 2007

Yellow poplar (Liriodendron tulipifera L.) has low germination rate relatively other species, so the seedling production of Yellow poplar is a hard task. Accordingly this study was conducted to determine the optimal germination conditions for healthy seedling production and to promote survival rate after afforestation. Gemination percentage was examined at different media and seed covering materials using planting flats in the greenhouse. The best germination percentage was observed in sand for media and compound soil for covering materials. But it was time to transplant, seedlings became a poor character (i.e. height, root length, number of root, dry weight) in sand for media. In order to produce healthy seedlings, each different medium was compounded with TKS-2 (this is a gardening bed soil.) in the ratio 1:1 (v/v.), and compared two conditions. Quality of seedling was better than not mixed TKS-2 into each medium. Transplanting seedlings from greenhouse to nursery grew up rapidly 2 months later (early in August~early in October). Growth amount during two months corresponded to 85.6% and 71.3% in total growth amount of height and diameter at root collar, respectively. In the case of the competition-density effect on yellow-poplar seedlings, direct seedling produced the maximum 35 standard seedlings above 8 mm of root collar diameter per $m^2$, while transplanting seedling produced the maximum 64 standard seedlings per $m^2$. And produced seedlings of two way were significantly different rootlet while axial root and lateral root was not significantly different.