• Journal of Wetlands Research
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• v.20 no.1
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• pp.54-62
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• 2018

Nutrients generated from various land uses lead to eutrophication during the influx of water, and it is necessary to apply the LID techniques to reduce nutrients from nonpoint sources in order to mitigate the occurrence of the algal bloom. This study was carried out to derive the design factors of hybrid artificial wetland (HCW) to increase the removal efficiency of nutrients. HCW system was constructed in the year 2010 for the treatment of rainfall runoffs from parking lots and roads composed of 100% impervious floors in the Cheonan campus of Kongju University. The average nutrients removal efficiency of TN and TP was 74% and 72%, respectively. Both TN and TP removal efficiencies were higher than those of free surface wetlands and subsurface flow wetlands due to activated physical and ecological mechanisms. The critical design parameters for the efficient nutrients removal in the artificial wetlands were the ratio of the surface area to the catchment area (SA/CA), land use, the rainfall runoff, and the rainfall intensity. The optimal carbon to nitrogen (C/N) ratio was estimated at 5: 1 to 10.3: 1. The results of this study can be applied to the efficient design of hybrid artificial wetlands to treat nutrients in urban runoff with high efficiency.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.357-360
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• 2003

본 논문에서는 $90^{\circ}$ 하이브리드 결합기에 여파기 특성을 결합하여 전력분배와 하모닉 저지특성효과를 보여주고 있다. 일반적인 $90^{\circ}$ 하이브리드 결합기는 위상차를 갖고 전력을 분배, 합성하는 데에만 쓰이고 있기 때문에 비선형 소자와 결합함으로써 생기는 하모닉 성분을 억제하려면 여파기를 따로 설계해야 하는 단점이 있다. 그래서 본 논문에서는 하이브리드에 저역통과 여파기 특성을 결합함으로써 위상차와 전력분배는 물론 여파기 특성인 감쇠효과를 이용하여 하모닉 성분을 크게 감소시킬 수 있는 구조를 연구하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.356-359
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• 2011

최근 방송 시스템의 디지털화, 통신기술과 가전제품의 발전으로 스마트 TV 시대가 열리게 되었다. 이제 시청자들은 스마트 TV를 통해 기존의 디지털 방송과 IP(Internet Protocol) 통신이 융합한 하이브리드 방송 서비스가 가능해지면서 기존 방송망을 통한 실시간 콘텐츠 서비스와 더불어 IP망을 통한 VOD(Video on Demand) 서비스, 멀티뷰(Multi-view) 서비스의 이용이 가능하게 되었다. 그 중 멀티뷰 서비스는 시청자가 동일한 시간의 영상을 다양한 시점에서 동시에 볼 수 있는 서비스로서, 하이브리드 방송 환경 하에서 현 방송 규격인 MPEG-2 TS(Transport Stream) 콘텐츠와 IP망을 통해 전달되는 실시간/비실시간 콘텐츠가 멀티뷰 서비스가 이루어질 때 콘텐츠 간의 시간정보 규격이 서로 상이하여 동기화에 어려움이 있다. 따라서 본 논문에서 이종망을 기반으로 한 하이브리드 방송 환경내의 다시점 콘텐츠의 동기화 방안을 제안하고자 한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.692-693
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• 2010

In this study, we analyze the combustion characteristic of GOx/PE hybrid rocket, by changing port diameter of the propellant. To study combustion characteristics of hybrid rocket, GOx is used for oxidizer and PolyEthylene is used for solid propellant. Regression rate and O/F ratio of the rocket is measured and presented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.244-248
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• 2012

A series of hybrid rocket combustion experiments were carried out with PMMA/GOx changing diameter and length of the disk installed at pre-chamber. The disk can generate vortex shedding flow and change flow conditions prior to entering the fuel grain which could also alter the combustion characteristics and pressure oscillations. The interaction of vortex shedding in the pre-chamber and small-scale vortices adjacent to burning surfaces by using combustion test.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.7
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• pp.789-793
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• 2010

Recently, flash memory-based non-volatile cache (NVC) is emerging as an effective solution to enhance both I/O performance and energy consumption of storage systems. To get significant performance and energy gains by NVC, it would be better to use multi-level-cell (MLC) flash memories since it can provide a large capacity of NVC with low cost. However, the number of available program/erase cycles of MLC flash memory is smaller than that of single-level-cell (SLC) flash memory limiting the lifespan of NVC. To overcome such a limitation, SLC/MLC combined flash memory is a promising solution for NVC. In this paper, we propose an effective management scheme for heterogeneous SLC and MLC regions of the combined flash memory.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.5
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• pp.665-671
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• 2011

The Competitiveness of Hybrid hard disk drive(H-HDD) for solid state disk(SSD) comes from both lower power consumption and higher reading speed. This paper suggests a prefetching scheme that can improve the performance of Non-Volatile cache(NVCache) memory installed on the H-HDD through prefetching disk blocks as well as files to the NVCache. The proposed scheme makes the highly used data such as booting files copy to the NVCache as an unit of file and the frequently accessed blocks copy to the NVCache. This prefetching is done on the idle time of disk queue and the priorities of prefetched target blocks are based on both time and spatial locality of blocks. Experiments results show that the suggested method can improve response time of H-HDD and also lower the power consumption.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.5
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• pp.339-347
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• 2022

The post chamber in hybrid rocket is installed to induce additional increase in combustion enthalpy by allowing continuous burning of the liquefied fuels. When paraffin wax fuel is used, unsteady pressure oscillations are observed only at the beginning of combustion. This study intends to investigate the effect of additional combustion of liquefied fuel droplets on the occurrence of unsteady pressure fluctuations. For this, the combustion in post-chamber was visualized and image analysis using POD(Proper Orthogonal Decomposition) technique was performed. In addition, the hypothesis was proposed on the occurrence of unsteady pressure oscillations by identifying the modes including the behavior of droplets through mode reconstruction. Conducting a series of combustion tests, the amount of liquefied fuel flowing into the post chamber and the generation of fuel droplets were controlled. Also, the changes in frequency characteristic of unsteady pressure oscillation were monitored. As a result, the unsteady pressure oscillations observed in paraffin wax combustion were the result of additional combustion of fuel droplets generated in the post chamber.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.1
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• pp.40-47
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• 2013

The similarity in internal flow of solid and hybrid rocket suggests that hybrid rocket combustion can be susceptible to instability due to vortex sheddings and their interaction. This study focuses on the evolution of interaction of vortex generated in pre-chamber with other types of vortex in the combustor and the change of combustion characteristics. Baseline and other results tested with disks show that there are five different frequency bands appeared in spectral domain. These include a frequency with thermal lag of solid fuel, vortex shedding due to obstacles such as forward, backward facing step and wall vortices near surface. The comparison of frequency behavior in the cases with disk 1 and 3 reveals that vortex shedding generated in pre-chamber can interact with other types of vortex shedding at a certain condition. The frequency of Helmholtz mode is one of candidates resulting to a resonance when it was excited by other types of oscillation even if this mode was not discernable in baseline test. This selective mechanism of resonance may explain the reason why non-linear combustion instability occurs in hybrid rocket combustion.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.4
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• pp.86-93
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• 2008

A low-power, low-noise, highly-linear hybrid balun circuit is proposed for 2.4-GHz fully differential CMOS direct conversion receivers. The hybrid balun is composed of a passive transformer and loss-compensating auxiliary amplifiers. Design issues regarding the optimal signal splitting and coupling between the transformer and compensating amplifiers are discussed. Implemented in $0.18{\mu}m$ CMOS process, the 2.4 GHz hybrid balun achieves 2.8 dB higher gain and 1.9 dB lower noise figure than its passive counterpart and +23 dBm of IIP3 only at a current consumption of 0.67 mA from 1.2 V supply. It is also examined that the hybrid balun can remarkably lower the total noise figure of a 2.4 GHz fully differential RF receiver only at a cost of 0.82 mW additional power dissipation.