• 한국토양비료학회지
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• 제46권5호
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• pp.391-398
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• 2013

Soil organic carbon (SOC) has the potential to promote the soil quality for sustainability and mitigation of global warming. There is little information on organic carbon composition despite of having resistance of carbon degradation in soil. In this study, to understand the effect of volcanic ash on organic carbon composition and quantity in soil, we investigated characteristics of volcanic soil and compared organic carbon composition of soil and humic extract by using $^{13}C$-CPMAS-NMR spectra under soil profiles of Namweon series in Jeju. SOC contents of inner soil profiles were 134.8, 101.3, and 27.4 g C $kg^{-1}$ at the layer of depth 10-20, 70-80 and 90-100 cm, respectively. These layers were significantly different to soil pH, oxalate Al contents, and soil moisture contents. Alkyl C/O-alkyl C ratio in soil was higher than that of humic extracts, which was decreased below soil depth. Aromaticity of soil and humic extract was ranged from 29-38 and 24-32%, which was highest at the humic extract of 70-80 cm in soil depth. These results indicate that the changes of SOC in volcanic ash soil resulted from alteration of organic composition by pyrolysis and stability of organic carbon by allophane in volcanic ash soil.

• 환경생물
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• 제18권3호
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• pp.299-305
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• 2000

본 연구는 울릉도 성인봉 주변에 생육하고 있는 너도밤나무군락의 섬조릿대하위군락, 전형하위군락, 일색고사리하위군락에 대한 토양단면 및 토양의 이화학적 특성을 조사하여 울릉도 산림토양의 기초자료를 제공하고, 하위군락별 토양특성의 차이를 조사하기 위해 실시되었다. 하위군락별 토양단면의 형태는 하위군락간에 큰 차이를 보이지 않았다. 하위군락간 토양의 이화학적 요인분석에 있어서 0-10cm 토양 깊이에서 Ca함량에서만 유의적인 차이가 나타났을 뿐, 다른 요인들은 하위군락 간에 큰 차이가 없는 것으로 나타났다. 울릉도 성인봉 주변의 토양특성 중 유기물함량은 0-10cm 토양 깊이에서 평균 21.6%로 매우 높게 나타났으며, 전질소함량도 0-10cm 토양 깊이에서 평균 0.74%로 높게 나타났다. 가비중은 0.43g/cm로 매우 낮게 나타났으며, pH는 평균 4.4로 강한 산성토양의 특성을 나타내어 우리나라의 일반 산림 토양과는 매우 다른 특성을 가지고 있는 것으로 나타났다.

• 분석과학
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• 제17권3호
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• pp.225-229
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• 2004

UV 경화반응에 의하여 형성된 코팅의 성질을 향상시키기 위하여 첨가제로 사용한 실리콘 아크릴레이트가 광중합 반응에 미치는 영향을 마이크로 라만 분광법을 사용하여 관찰하였다. 광중합 반응의 반응체는 아크릴계 올리고머와 모노머를 사용하였으며 광 개시제로는 Darocur 1173을 사용하였다. 첨가제 실리콘 아크릴레이트는 광 경화 수지에 각각 0-3 wt% 첨가하였으며, UV를 조사하여 중합 반응시킨 후 공기-박막 경계면으로부터 두께에 따른 라만 스펙트럼을 관찰하였다. 광중합 반응의 진행정도는 1410과 $1635cm^{-1}$에 나타나는 중합에 직접 관여하는 아크릴기 ($-C=CH_2$)와 관련된 띠의 세기로부터 구하였다. 관찰된 결과에 따르면 마이크로라만으로부터 얻은 심도 스펙트럼 (depth profile)은 두께에 따른 경화반응의 진행 정도를 관찰할 수 있을 뿐만 아니라 경화 반응에 미치는 여러 요인에 대한 이해를 돕는 좋은 방법이 될 수 있음을 알 수 있다.

• 대한방사선기술학회지:방사선기술과학
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• 제43권2호
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• pp.105-114
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• 2020

This study aimed to assess of beam-matching accuracy for an 8 MV beam between the same model linear accelerators(Linac) commissioned over two years. Two models were got the customer acceptance procedure(CAP) criteria. For commissioning data for beam-matched linacs, the percentage depth doses(PDDs), beam profiles, output factors, multi-leaf collimator(MLC) leaf transmission factors, and the dosimetric leaf gap(DLG) were compared. In addition, the accuracy of beam matching was verified at phantom and patient levels. At phantom level, the point doses specified in TG-53 and TG-119 were compared to evaluate the accuracy of beam modelling. At patient level, the dose volume histogram(DVH) parameters and the delivery accuracy are evaluated on volumetric modulated arc therapy(VMAT) plan for 40 patients that included 20 lung and 20 brain cases. Ionization depth curve and dose profiles obtained in CAP showed a good level for beam matching between both Linacs. The variations in commissioning beam data, such as PDDs, beam profiles, output factors, TF, and DLG were all less than 1%. For the treatment plans of brain tumor and lung cancer, the average and maximum differences in evaluated DVH parameters for the planning target volume(PTV) and the organs at risk(OARs) were within 0.30% and 1.30%. Furthermore, all gamma passing rates for both beam-matched Linacs were higher than 98% for the 2%/2 mm criteria and 99% for the 2%/3 mm criteria. The overall variations in the beam data, as well as tests at phantom and patient levels remains all within the tolerance (1% difference) of clinical acceptability between beam-matched Linacs. Thus, we found an excellent dosimetric agreement to 8 MV beam characteristics for the same model Linacs.

• 한국환경과학회지
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• 제23권4호
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• pp.543-552
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• 2014

Fixed Electromagnetic Wave Surface Velocimetry (Fixed EWSV) has been started to be used to measure flood discharge in the mountain stream, since it has various advantages such that it works well to continuously measure stream discharge even in the night time as well as very strong weather. On the contrary, the Fixed EWSV only measures single point surface velocity, thus it does not consider varying feature of the transverse velocity profile in the given stream cross-section. In addition, a conventional value of 0.85 was generally used as the ratio for converting the measured surface velocity into the depth-averaged velocity. These aspects could bring in error for accurately measuring the stream discharge. The capacity of the EWSV for capturing rapid flow velocity was also not properly validated. This study aims at conducting error analysis of using the EWSV by: 1) measuring transverse velocity at multiple points along the cross-section to assess an error driven by the single point measurement; 2) figuring out ratio between surface velocity and the depth-averaged velocity based on the concurrent ADCP measurements; 3) validating the capacity of the EWSV for capturing rapid flow velocity. As results, the velocity measured near the center by the fixed EWSV overestimated about 15% of the cross-sectional mean velocity. The converting ratio from the surface velocity to the depth-averaged velocity was 0.8 rather than 0.85 of a conventional ratio. Finally, the EWSV revealed unstable velocity output when the flow velocity was higher than 2 m/s.

• 자원환경지질
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• 제30권6호
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• pp.567-586
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• 1997

Concentrations of several heavy metals in soils derived from black shale and slate have been reported to be higher than the average concentrations in non-polluted soils. This study describes and characterizes soil minerals, and investigates the distribution of heavy metals in soils, and then examines their relationship. Soils in the study area are mainly consist of guartz and feldspars with minor amount of kaolin, illite, vermiculite, chlorite and illite-vermiculite interstratified minerals. Mineral compositions are similar in mountain-, farmland-, and paddy-soils. The residual soils derived from sandy phyllites contain less illites than those from black shale and black slate. Heavy metals appear to be more concentrated in soils than in rocks. The concentrate ratios in soils to rocks ranges 1.1 times for Cr, 2 for Cu, 1.4 for Ni. The contour maps of Cd, Zn, Pb, Cu contents using 0.43N $HNO_3$-extraction imply that these elements are highly concentrated in the soils near the past uranium exploration region, coal seams, black slate beds and tailings than other parts of the study area. The proportions of the day in most soils are less than 10%. In spite of small proportions of the clay, the concentrations of heavy metals from clay fractions to the total concentrations are high: 1~2.4 times for Co, 1.4~2.5 for Cu, 1.2~2.6 for Ni, 1~5 for Pb, 1~2.7 for Zn and 1.6~1.8 for Cr and V. The contents of organic carbons in clay fractions are also 1.5~3.9 times higher than in silt and sand fractions. Cu, Pb and organic carbons show positive relationship in all size fractions. In the size-fractionated soil profile samples, the contents of heavy metals and organic carbons show analogous trends with depth. For the clay fractions of soil profile samples, the contents of heavy metals with depth have analogous trends to abundances of vermiculites, which have the high CEC in main clay minerals.

• 한국문헌정보학회지
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• 제45권4호
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• pp.77-102
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• 2011

본 연구의 목적은 이용자의 자신의 성향 정보에 맞는 정확한 검색결과를 제공하기위한 개인화 검색시스템을 설계, 구현, 평가하는 것이다. 이를 위해서 주제 분류와 하이브리드기반의 이용자 프로파일을 구성하였다. 제안한 개인화 검색시스템의 성능 평가를 위해서 전문가들이 직접 국내과학기술 DB의 논문의 적합성을 판별하기위해서 MRR, MAP과 사용성 평가를 측정하였다. 그 결과 전문가가 직접 "컴퓨터공학"과 "문헌정보학" 분야에서 평가한 국내과학기술논문 결과에서도 제안한 개인화 검색시스템이 일반 검색시스템보다 정확도가 더 높았다. 특히 중의성을 가진 키워드 부분에서 더 높은 정확도를 보였다. 질적 평가인 심층면담을 통한 평가에서도 개인화 검색시스템이 이용자가 선호하는 문서들을 우선적으로 제공함으로써 정보검색 시간 및 정보 획득에 용이하다고 응답하였다. 또한 다양한 추천 시스템을 제공함으로써 새로운 정보 탐색에 도움이 된다하였으며, 개인화 검색시스템이 일반 검색시스템보다 이용자의 만족도가 높음을 알 수 있었다. 따라서 본 연구에서 전문가 직접 평가 결과 모두 제안한 개인화 검색시스템이 일반 검색시스템보다 더 높은 효율성을 제공하는 것을 입증하였다.

• Structural Monitoring and Maintenance
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• 제6권4호
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• pp.365-387
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• 2019

This study aims to provide useful information on the fatigue assessment of a top-tensioned riser (TTR) subjected to vortex-induced vibration (VIV) by performing parametric study. The effects of principal design parameters, i.e., riser diameter, wall thickness, water depth (related to riser length), top tension, current velocity, and shear rate (or shear profile of current) are investigated. To prepare the base model of TTR for parametric studies, three (3) riser modelling techniques in the OrcaFlex were investigated and validated against a reference model by Knardahl (2012). The selected riser model was used to perform parametric studies to investigate the effects of design parameters on the VIV fatigue damage of TTR. From the obtained comparison results of VIV analysis, it was demonstrated that a model with a single line model ending at the lower flex joint (LFJ) and pinned connection with finite rotation stiffness to simulate the LFJ properties at the bottom end of the line model produced acceptable prediction. Moreover, it was suitable for VIV analysis purposes. Findings from parametric studies showed that VIV fatigue damage increased with increasing current velocity, riser outer diameter and water depth, and decreased with increasing shear rate and top tension of riser. With regard to the effects of wall thickness, it was not significant to VIV fatigue damage of TTR. The detailed outcomes were documented with parametric study results.

• Journal of Forest and Environmental Science
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• 제39권3호
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• pp.180-194
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• 2023

This study characterize, classify and evaluates the function of topography on spatial variability of some selected soil properties to assist in designing land management that support uniform agricultural production. The study site, an agricultural land, was part of the derived savanna zone in southwest Nigeria. Four soil profile pits each were established along two delineated toposequence and described following the FAO/UNESCO guidelines. Samples were collected from the identified genetic horizons. Properties of four soil series developed on different positions of the two delineated Toposequence viz upper, middle, lower slopes and valley bottom positions respectively were studied. The soil samples were analysed for selected physical and chemical properties and data generated were subjected to descriptive and inferential statistics. The results showed that soil colour, depth and texture varied in response to changes in slope position and drainage condition. The sand content ranged from 61 to 90% while the bulk density ranged between 1.06 g cm^-3 to 1.68 g cm^-3. The soils were neutral to very strongly acid with low total exchangeable bases. Available phosphorus value were low while the extractable micronutrient concentration varied from low to medium. Soils of Asejire and Iwo series mapped in the study area were classified as Typic isohyperthermic paleustult, Apomu series as Plinthic isohyperthermic paleustult and Jago series as Aquic psamment (USDA Soil Taxonomy). These soils were correlated as Lixisol, Plinthic Lixisol and Fluvisol (World Reference Based), respectively. Major agronomic constraints of the soils associations mapped in the study area were nutrient availability, nutrient retention, slope, drainage, texture, high bulk density and shallow depth. The study concluded that the soils were not homogenous, shows moderate spatial variation across the slope, had varying potentials for sustainable agricultural practices, and thus, the agronomic constraints should be carefully addressed and managed for precision agriculture.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.302-306
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• 1993

In this study, a new model for flexible disk grinding process will be proposed. A grinding mechanism with a grinding disk attached to the rubber platen has been introduced. Since the spinning axis is fixed and only the disk is deflected with respect to this axis, earlier model is not adequate to represent this proces. A new dynamic process model includes an assumption that the disk is deflected locally around the middle of its radial span between the spinning axis and the disk tip instead of several continuous deflection points along the radial span of the disk. Detailed kinematic analysis is proposed as for the removed portion during the process. Cutting force comonent and depth of cut profile trend is compared with the measured result.