• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.4
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• pp.321-327
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• 2008

The shock tunnel as a hypersonic ground test facility was designed, constructed and its performance test was conducted to reproduce the high speed flow which the hypersonic propulsion system is encountered. The design points were understood and the conceptual design was completed using the quasi one dimensional operation analysis code. After that, the specific performance and compartment design were completed using CFD simulation as the part analysis. The facility was then constructed according to those design results and the performance test was conducted for various operation conditions. In this paper, we suggested the design method of hypersonic shock tunnel including the conceptual and performance design using theoretical analysis and the quasi 1D Multi-species computational fluid dynamics code.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.939-940
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• 2015

In this paper, a design method for a quasi-Yagi antenna (QYA) suitable for UHF band is studied. Due to the mutual coupling between a coplanar strip (CPS)-fed planar dipole and a conducting strip director placed close to the dipole, the dipole obtains broadband characteristics. A ground reflector improves gain in the lower frequency band, and the antenna size might be reduced by employing a bent reflector. The balun between the CPS line and the microstrip(MS) line is constructed by connecting the end of MS line and the CPS line through a shorting pin. In addition, a ring-type conductor connects the CPS line and reflector. The effects of various geometrical parameters and balun on the antenna characteristics are examined. An antenna, as an design example for the proposed antenna, is designed for the operation in the frequency band of 470-806 MHz for terrestrial DTV.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.37-45
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• 2018

A two-axis gimbal-type antenna for a Compact Advanced Satellite (CAS) is used to efficiently transmit high resolution image data to a ground station. In this study, we designed the structure of a two-axis gimbal-type antenna while applying a launch lock device to secure its structural safety under a launch environment. To validate the effectiveness of the structural design, a structural analysis of the antenna was performed. First, a modal analysis was performed to investigate the dynamic responses of the antenna with and without the mechanical constraints of the launch lock device. In addition, a quasi-static analysis was performed to confirm the structural safety of the antenna structure and bolt I/Fs between the antenna base and the satellite. The suitable range of constraint force on the launch lock device was also determined to ensure the structural safety and mechanical gapping of the ball & socket interfaces, which places multi-constraints on the azimuth and elevation stage of the antenna.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.567-579
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• 2011

Scirpus planiculmis is one of the most dominant species found in the Nakdong River estuary. In order to understand the recent changes in S. planiculmis and the environmental characteristics of the estuary, from 2005 to 2010, an analysis of the density, total dry biomass, tuber biomass, and distribution pattern of S. planiculmis as well as an analysis of the temperature, salinity, precipitation, barrage discharge, and soil texture of the estuary were conducted. In 2006, the density ranged from 10.1 to $87.6no./m^2$, but in 2009, it ranged from 0.4 to $2.2no./m^2$ in 2009 and drastic reductions were observed throughout the sampled areas in the Nakdong river estuary. In 2010, S. planiculmis was observed on the tidal flats of Myungji and Mangummerydeung, at a density of $18.3{\pm}7.7no./m^2$ and $17.5{\pm}20.7no./m^2$, respectively. Hence, S. planiculmis is considered to be in a recovery phase. The aboveground/belowground ratio reduced from $4.54{\pm}0.70$ in 2005 to $1.91{\pm}0.35$ in 2009, clearly showing a large decrease in the biomass amount of the aboveground than of the belowground. Tubers were distributed in the soil, with only 36.0% at the 0~15 cm depth but 64.0% at the 15~30 cm depth. Apparently, tubers were more likely to be found at 15~30 cm below the soil in the Nakdong River estuary. A drastic reduction in the S. planiculmis biomass in 2009 is possibly due to the high salinity in S. planiculmis habitats.

• Journal of Broadcast Engineering
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• v.18 no.4
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• pp.572-588
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• 2013

In this paper, 4K-UHDTV or 8K-UHDTV and UHD-3DTV that the next generation broadcasting implementation and the possibility of direct receiving environment construction is analyzed on the terrestrial broadcasting. Particularly, we investigated the possibility by analyzing the previous and related works with regard to UHDTV transmission by DVB-T2 that is one of the best commercialized transmission mode. In order that the UHDTV broadcasting succeeds once again after completion of digital terrestrial switch over at the end of 2012, the ultra high resolution image transfer is important. However, the direct, the indoor and ubiquitous receiving environment is important in not only TV but also the personal type multimedia terminal in the sense of UHDTV service penetration. Therefore, in this paper, by using SFN and high error-correcting mode in DVB-T2 standard, the efficient frequency utilization and effective reception environment construction is illustrated. Particularly, SFN network constitution by 2 mutually different frequencies including the VHF bandwidth and UHF band, and etc. is shown. And the method that builds the free wireless receive environment by using SFN low power radio repeater and for home use gap filler is proposed. And the effect and frequency amount required are presented, when UHDTV broadcasting use 10MHz bandwidth.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1908-1914
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• 2013

In this paper, we introduce a design method for a broadband planar quasi-Yagi antenna (QYA) for terrestrial digital television (DTV) reception. The coplanar strip line which feeds the driver dipole is connected to a microstrip line and is terminated by short circuit. By appending a wide strip-type rectangular director at a location close to the driver dipole, broadband impedance matching and gain enhancement in a high frequency region are obtained. The gain characteristics in a low frequency region are improved by adding a reflector formed by a truncated ground plane. To reduce the antenna size, the strip-type dipole and reflector are modified to half bow-tie (V)-shaped elements. The effects of various parameters on the antenna characteristics are examined. An antenna, as a design example for the proposed antenna, is designed for the operation in the frequency band of 470-806 MHz for terrestrial DTV. The optimized antenna is fabricated on an FR4 substrate and the experimental results show that the antenna has a good performance such as a frequency band of 450-848 MHz for a VSWR < 2, gain > 4.1 dBi, and front-to-back ratio > 10.4 dB.

• Korean Journal of Environment and Ecology
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• v.28 no.6
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• pp.705-714
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• 2014

This text was analyzed and investigated the aerial part plants and buried seed plants at coniferous forest and broadleaved forest in Yesan-gun, in order to offer the basic data of potential natural vegetation change on secondary forest. Plants of buried seed germination were consisted of 29 taxa in coniferous forest (28 species, 1 varieties, of 27 genus, 20 families) and 36 taxa in broadleaved forest (34 species, 2 varieties, of 32 genus, 18 families). Family classification of buried seed plant was the most in Compositae, and emergent plot frequency was the highest of Cyperus amuricus in coniferous forest and Crepidiastrum sonchifolium in broadleaved forest. The soil depth of the most plants appearance was 0~10 cm in coniferous forest and 0~5 cm in broadleaved forest, and the soil depth of the most population appearance was 0~2 cm in coniferous forest and broadleaved forest. Population of buried seed germination was decreased according as soil is deep. Crepidiastrum sonchifolium was a plant that population of buried seed germination is the most. Similarity index of the aerial part plants and buried seed plants was low as 0.22, and coniferous forest and broadleaved forest was 0.40.

• Journal of Wetlands Research
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• v.12 no.1
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• pp.51-61
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• 2010

Changes in climate have largely increased concentrated heavy rainfall, which in turn is causing enormous damages to humans and properties. Therefore, it is important to understand the spatial-temporal features of rainfall. In this study, RADAR rainfall was used to calculate gridded areal rainfall which reflects the spatial-temporal variability. In addition, Kalman-filter method, a stochastical technique, was used to combine ground rainfall network with RADAR rainfall network to calculate areal rainfall. Thiessen polygon method, Inverse distance weighting method, and Kriging method were used for calculating areal rainfall, and the calculated data was compared with adjusted areal RADAR rainfall measured using the Kalman-filter method. The result showed that RADAR rainfall adjusted with Kalman-filter method well-reproduced the distribution of raw RADAR rainfall which has a similar spatial distribution as the actual rainfall distribution. The adjusted RADAR rainfall also showed a similar rainfall volume as the volume shown in rain gauge data. Anseong-Cheon basin was used as a study area and the RADAR rainfall adjusted with Kalman-filter method was applied in $Vflo^{TM}$ model, a physical-based distributed model, and ModClark model, a semi-distributed model. As a result, $Vflo^{TM}$ model simulated peak time and peak value similar to that of observed hydrograph. ModClark model showed good results for total runoff volume. However, for verifying the parameter, $Vflo^{TM}$ model showed better reproduction of observed hydrograph than ModClark model. These results confirmed that flood runoff simulation is applicable in domestic settings(in South Korea) if highly accurate areal rainfall is calculated by combining gauge rainfall and RADAR rainfall data and the simulation is performed in link to the distributed hydrological model.

• Korean Journal of Remote Sensing
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• v.34 no.6_1
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• pp.893-903
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• 2018

The necessity of automatic precise georeferencing is increasing with the increase applications of high-resolution satellite imagery. One of the methods for collecting ground control points (GCPs) for precise georeferencing is to use chip images obtained by extracting a subset of an image map such as an ortho-aerial image, and can be automated using an image matching technique. In this case, the importance of the image matching success rate is increased due to the limitation of the number of the chip images for the known reference points such as the unified control point. This study aims to propose a method to improve the success rate of image matching between KOMPSAT-3A images and GCP chip images from aerial ortho-images. We performed the image matching with 7 cases of band pair using KOMPSAT-3A panchromatic (PAN), multispectral (MS), pansharpened (PS) imagery and GCP chip images, then compared matching success rates. As a result, about 10-30% of success rate is increased to about 40-50% when using PS imagery by using PAN and MS imagery. Therefore, using PS imagery for image matching of KOMPSAT-3A images and aerial ortho-images would be helpful to improve the matching success rate.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2007.02a
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• pp.29-32
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• 2007

지상파 DMB 상용 서비스가 시작된 지 1년이 경과함에 따라 DMB 시청자의 수가 급격히 증가하였다. 그러나 DMB와 융합된 새로운 서비스가 활성화가 활발하지 못하고, 따라서 여러 가지 부가 수익서비스가 창출되지 못하고 있다. 그 이유 중의 하나는 기존에 제안된 양방향 데이터 서비스들은 모바일 홈페이지로의 연결하는 방식이라, 시청자가 DMB 단말기의 작은 화면에서 단말기의 버튼이나 터치스크린을 사용하기 불편하고, 방송시청이 불편하다. 또한, 기존의 방송참여 방식인 ARS, SMS 방식을 포용하지 못한다. 본 논문은 기존의 시청자 참여 방식을 분석하고 기존 방식의 약점을 보안하여 URL 방식 명령을 통한 양방향 서비스를 제안한다. 이 방법은 작은 디스플레이를 통해 홈페이지 방식을 고집하지 않고, 기존의 ARS, SMS를 포용하며, 단순한 동작으로 시청자 참여가 가능하다. 본 논문이 제안하는 방법은 서비스 방식 및 구조에 따라 ARS 서비스를 제공하는 URL방식 명령, SMS 서비스를 제공하는 URL 명령, 서버응용 호출서비스를 위한 URL방식 명령(SERVER-URL), 클라이언트 응용호출 서비스를 위한 URL방식 명령(CLIENT-URL)으로 분류된다. 본 방법들은 사용자의 참여가 단순하게 이루어지도록 방송시 송출되며, 이러한 방법은 ol동 방송에 특히 적합할 것으로 사료되어, 앞으로 보다 실용적인 DMB 기반의 융합 서비스에 사용될 것으로 사료된다.