• 한국초전도ㆍ저온공학회논문지
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• 제9권4호
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• pp.16-18
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• 2007

We report the results of MOD-processed YBCO coated conductors on the IBAD-MgO template. The precursor solution was coated on the $CeO_2-buffered$ IBAD-MgO template using a slot-die coating method, calcined at a temperature of $550^{\circ}C$, and fired at high temperatures for 2.5 h in a reduced oxygen atmosphere. The $J_C$ value of YBCO coated conductors was found to be very sensitive to the microstructure, and thus higher $J_C$ value could be achieved when the in-plane texture was higher and the difference in $T_{C,zero}$. was negligible. Optimally processed YBCO coated conductor exhibited $J_C$ value of $0.75MA/cm^2$ at 77 K in self-field, which might be due to somewhat depressed $T_{C,zero}$ of 87.3 K caused by possible $Sm^{3+}$ substitution on the $Ba^{2+}$ site.

• Journal of Korea Trade
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• 제26권7호
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• pp.43-58
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• 2022

Purpose - Based on the telecommunication service trade data of China, Japan, and South Korea from 2009 to 2019, this paper compares and analyzes the international competitiveness of the three countries' telecommunication service trade, and finds the existing problems in China through the comparison, so as to make reasonable planning and industrial development strategy, and find away to catch up. Design/methodology - The comparative analysis method was used to compare and analyze the international competitiveness of telecommunication service trade among China, Japan, and South Korea from the three aspects of market share, trade surplus, and export proportion represented by MS, TC, G-L, RCA, and CA. Findings - The international competitiveness of telecommunication service trade among China, Japan, and South Korea does not have competitive advantages. China is larger than Japan and South Korea, but only close to average globally, and its share of trade in telecommunications services is lower than Japan and South Korea's. Originality/value - This paper tries to explore international competitiveness in the field of telecommunication service trade, and through the comparison of five indicators to find problems in China, so as to put forward countermeasures to improve the international competitiveness of China's telecommunication service trade, and lay a foundation for subsequent research on the source factors of international competitiveness.

• 한국지리정보학회지
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• 제6권4호
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• pp.122-134
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• 2003

최근 국가지리정보체계(NGIS) 사업을 통해 국가적 범위의 각종 주제도 개발사업이 이루어지고 있으며, 각 분야에서 이를 활용한 지리정보시스템 개발에 대한 노력이 활발히 이루어지고 있다. 또한 개발되는 시스템의 호환성을 높이기 위해 지리정보 데이터모델에 대한 연구가 여러 차례 수행되어 왔다. 수자원 분야에서 구축되는 시스템은 하천에서의 흐름의 동적특성을 반영할 수 있어야 한다. 이는 데이터 모델의 설계에서부터 고려되어야 하므로 본 연구에서는 하천 네트워크를 기반으로 선형참조 기능이 가능한 수자원 지리정보 데이터모델을 제안하였다. 제안된 데이터모델의 활용성을 검토하기 위해 네트워크 컴포넌트 기반의 시스템을 개발하였으며, 하천 네트워크를 이용한 시스템의 우수성과 효용성을 확인할 수 있었다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2017년도 춘계공동학술대회
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• pp.45-45
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• 2017

On-site monitoring of vegetable growth parameters, such as leaf length, leaf area, and fresh weight, in an agricultural field can provide useful information for farmers to establish farm management strategies suitable for optimum production of vegetables. Unmanned Aerial Vehicles (UAVs) are currently gaining a growing interest for agricultural applications. This study reports on validation testing of previously developed vegetable growth estimation models based on UAV-based RGB images for white radish and Chinese cabbage. Specific objective was to investigate the potential of the UAV-based RGB camera system for effectively quantifying temporal and spatial variability in the growth status of white radish and Chinese cabbage in a field. RGB images were acquired based on an automated flight mission with a multi-rotor UAV equipped with a low-cost RGB camera while automatically tracking on a predefined path. The acquired images were initially geo-located based on the log data of flight information saved into the UAV, and then mosaicked using a commerical image processing software. Otsu threshold-based crop coverage and DSM-based crop height were used as two predictor variables of the previously developed multiple linear regression models to estimate growth parameters of vegetables. The predictive capabilities of the UAV sensing system for estimating the growth parameters of the two vegetables were evaluated quantitatively by comparing to ground truth data. There were highly linear relationships between the actual and estimated leaf lengths, widths, and fresh weights, showing coefficients of determination up to 0.7. However, there were differences in slope between the ground truth and estimated values lower than 0.5, thereby requiring the use of a site-specific normalization method.

• 한국지하수토양환경학회지:지하수토양환경
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• 제21권6호
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• pp.192-203
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• 2016

A field investigation was conducted on an aquifer contaminated with trichloroethylene (TCE) for application of in situ reactive zone treatment using nanosized zero-valent iron (NZVI). The aquifer was an unconfined aquifer with a mean hydraulic conductivity of $5.14{\times}10^{-4}cm/sec$, which would be favorable for NZVI injection. Seasonal monitoring of TCE concentration revealed a presence of non-aqueous phase liquid form of TCE near IW (injection well). The hydrochemical data characterized the site groundwater to be a $Ca-HCO_3$ type. The average value of Langelier Saturation Index of the groundwater was -1.33, which implied that the site was favorable for corrosion of NZVI. Dissolved oxygen (DO) concentration varied between 2.5~11.5 mg/L, which indicated that DO would greatly compete with TCE as an electron acceptor. The hydrogeological and hydrochemical characterization reveals that the time around November would be appropriate for NZVI injection when water level and temperature are relatively high and DO concentration is low.

• 한국터널지하공간학회 논문집
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• 제15권3호
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• pp.321-331
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• 2013

이 연구는 TBM의 디스크커터 관입깊이에 대하여 실질적인 현장을 통하여 평가한 것이다. 연구를 위하여 설계시 적용되는 디스크커터 관입깊이에 대하여 검토하였다. 또한 대상 현장에 대한 지반특성에 대하여 검토하고 현장에 투입된 장비에 대한 적용성에 대하여 분석하였다. 특히 장비의 용량분석을 실시하여 적합성에 대하여 평가하였다. 이러한 평가결과와 현장 공사자료를 근거로 실질적인 TBM의 공사량과 굴진속도를 분석하였다. 이 결과로부터 설계시 적용된 TBM의 디스크커터 관입깊이에 대하여 재평가 하였다. 연구 결과로부터 설계시 적용되는 디스크커터 관입깊이는 특히 극경암 지반($S_c$ >150 MPa)에 있어서 적용값의 변경이 필요하다는 것을 명백히 보여주었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제10권2호
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• pp.59-65
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• 2005

단공 수리시험으로서의 단계양수시험은 일반적으로 대수층 및 우물의 생산성 혹은 효율을 평가하기 위해 수행되어 왔다. 단계양수시험은 기본적으로 초기에 저양수량으로 양수를 하며 양수관정의 수위가 안정되면 다음 단계의 고양 수량으로 다시 수위가 안정될 때까지 양수를 지속한다. 이러한 과정은 최소 3단계 이상 반복되며 각 단계별 양수지속시간을 동일하여야 한다. 본 기술자료에서는 그 동안 국내에서 수행된 단계양수시험의 해석과 관련하여 몇 가지 문제점들을 살펴보았다. 그 결과 단계양수시험에 대한 부적절한 해석결과는 주로 잘못된 해석개념 및 불완전한 현장 양수자료와 관계가 큰 것으로 파악되었다.

• 한국철도학회논문집
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• 제20권4호
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• pp.500-511
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• 2017

최근 경주지진이 일어나게 되면서 지진의 진동에 의한 구조물의 안정성에 대한 관심이 증가하고 있다. 하지만 국내 앵커분야의 경우 설계하중에 대한 안정성만 고려하고 있을 뿐 진동에 대한 안정성에 대한 연구는 미미한 실정이다. 마찰형 앵커의 경우 시공 중 발생하는 발파진동 등으로 인하여 앵커의 저항능력을 상실한 경우가 종종 보고되고 있다. 이에 반하여 지압형 앵커의 경우 구조적으로 마찰형 앵커에 비하여 진동저항능력이 우수할 것으로 판단되나 이러한 특성에 대한 연구는 거의 진행되지 않았다. 본 연구에서는 새롭게 개발한 지압형 앵커의 발파진동과 지진에 대한 안정성을 검증하기 위하여 현장시험을 수행하였으며 수치해석을 통하여 내진안정성을 검증하였다. 그 결과 현장시험의 경우에는 마찰형 앵커보다 발파진동에 대한 저항성능이 우수하였으며, 수치해석을 이용한 내진해석의 경우 또한 마찰형 앵커에 비하여 저항성능이 우수한 것으로 분석되었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제19권6호
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• pp.80-90
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• 2014

The laboratory and field studies were conducted to identify an optimal injection concentration of nanoscale zero-valent iron particles (NZVI) and to evaluate the applicability of NZVI-based reactive zone technology to the site contaminated with trichloroethylene (TCE) DNAPL (Dense Non-Aqueous Phase Liquid). The laboratory test found an optimal injection concentration of NZVI of 5 g/L that could remove more than 95% of 0.15 mM TCE within 20 days. Eleven test wells were installed at the aquifer that was mainly composed of alluvial and weathered soils at a strong oxic condition with dissolved oxygen concentration of 3.50 mg/L and oxidation-reduction potential of 301 mV. NZVI of total 30 kg were successfully injected using a centrifugal pump. After 60 days from the NZVI injection, 86.2% of the TCE initially present in the groundwater was removed and the mass of TCE removed was 405 g. Nonchlorinated products such as ethane and ethene were detected in the groundwater samples. Based on the increased chloride ion concentration at the site, the mass of TCE removed was estimated to be 1.52 kg. This implied the presence of DNAPL TCE which contributed to a higher estimate of TCE removal than that based on the TCE concentration change.

• Journal of Astronomy and Space Sciences
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• 제36권1호
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• pp.35-43
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• 2019

The Optical Wide-field patroL-Network (OWL-Net) is a global optical network for Space Situational Awareness in Korea. The primary operational goal of the OWL-Net is to track Low Earth Orbit (LEO) satellites operated by Korea and to monitor the Geostationary Earth Orbit (GEO) region near the Korean peninsula. To obtain dense measurements on LEO tracking, the chopper system was adopted in the OWL-Net's back-end system. Dozens of angle-only measurements can be obtained for a single shot with the observation mode for LEO tracking. In previous work, the reduction process of the LEO tracking data was presented, along with the mechanical specification of the back-end system of the OWL-Net. In this research, we describe an integrity assessment method of time-position matching and verification of results from real observations of LEO satellites. The change rate of the angle of each streak in the shot was checked to assess the results of the matching process. The time error due to the chopper rotation motion was corrected after re-matching of time and position. The corrected measurements were compared with the simulated observation data, which were taken from the Consolidated Prediction File from the International Laser Ranging Service. The comparison results are presented in the In-track and Cross-track frame.