• 한국문헌정보학회지
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• 제42권1호
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• pp.273-294
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• 2008

이 연구에서는 학문분야별 연구자들이 연구를 수행하는 과정에서 참고하는 주요 정보원을 자료 형태별로, 그리고 7개 학문분야별로 비교. 분석해 보고 이 가운데 회색문헌에 대한 학문 분야별로 선호도에서 어떠한 차이가 있는가를 인용분석을 통하여 확인해 보았다. 분석결과 연구자들의 회색문헌과 백색문헌에 대한 선호도가 분야별로 차이가 나타났으며, 분야와 상관없이 국내에서 발간되는 국, 영문 학술지 사이에서도 그 선호도에 차이가 발견되었다. 또한 동일한 분야 내에서 영문학술지와 국문학술지 사이에 인용된 문헌에 대한 회색문헌과 백색문헌의 두 집단 간에도 선호도 차이가 있음을 보였다. 마지막으로 분야와 언어 변수를 통제한 후 자료 형태별로 편상관계수 값을 통하여 분석한 결과 회의록 자료와 기타자료 사이의 편상관계수 값이 타 형태의 자료에 비해 높은 것으로 나타나 회의록 자료를 많이 인용한 논문은 기타자료도 동시에 인용하는 경향이 있음을 보여 주었다.

• 동력기계공학회지
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• 제13권5호
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• pp.52-58
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• 2009

A gas turbine consists of an upstream compressor and a downstream turbine with a combustion chamber, and also the compressor and the turbine are generally coupled using a single shaft. Many casing bolts are used to assemble two horizontally separated casings, the gas turbine casing and the compressor casing, in both of axial and vertical directions. Because drilled holes for casing bolts in vertical direction are often too close to drilled holes for casing bolts in axial direction, one can observe cracks in the area frequently during operations of a gas turbine. In this study of the root cause analysis for the cracking initiating from the drilled holes of the casings of a gas turbine, the finite element analysis(FEA) was applied to evaluate the thermal and mechanical characteristics of the casings. By applying the field operation data recorded from combined cycle power plants for FEA, thermal and thermo-mechanical characteristics of a gas turbine are analyzed. The crack is initiated at the geometrical weak point, but it is found that the maximum stress is relieved when the same type of cracks is introduced on purpose during FEA. So, it is verified that the local fracture could be delayed by machining the same type of defects near the hole for casing flange bolts of the gas turbine, where the crack is initiated.

• 대기
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• 제32권1호
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• pp.71-84
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• 2022

This paper describes verification results for the ocean analysis field produced by the Nucleus for European Modelling of the Ocean (NEMO) of the Korea Meteorological Administration (KMA) against observed Argo floats and drift buoys over the western Pacific Ocean and the equatorial Pacific during 2020~2021. This is confirmed by a comparison of the verification for the newly updated version of the HYbrid Coordinate Ocean Model/Navy Coupled Ocean Data Assimilation (HYCOM/NCODA) against same observations. NEMO shows that the vertical ocean temperature is much closer to the Argo floats than HYCOM for most seasons in terms of bias and root mean square error. On the other hand, there are overall considerable cold biases for HYCOM, which may be due to the more rapid decreasing temperature at the shallow thermocline in HYCOM. Conclusion demonstrated that the NEMO analysis for ocean temperature is more reliable than the analysis produced by the latest version of HYCOM as well as by the out-of-date HYCOM applied to the precedent study. The surface ocean current produced by NEMO also shows 14% closer to the AOML (Atlantic Oceanographic and Meteorological Laboratory) in situ drift buoys observations than HYCOM over the western Pacific Ocean. Over the equatorial Pacific, however, HYCOM shows slightly closer to AOML observation than NEMO in some seasons. Overall, this study suggests that the resulting information may be used to promote more use of NEMO analysis.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.965-968
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• 2005

Roll drafting operation causes variations in the linear density of bundles because the bundle flow cannot be controlled completely by roll pairs. Defects occurring in this operation bring about many problems successively in the next processes. In this paper, we attempt to analyze the draft dynamics and the linear density irregularity based on the governing equation of a bundle motion that has been suggested in our previous studies. For analyzing the dynamic characteristics of the roll drafting operation, it is indispensable to investigate a transient state in time domain before the bundle flux reaches a steady state. However, since governing equations of bundle flow consisting of continuity and motion equations turn out to be nonlinear, and coupled between variables, the solutions for a transient state cannot be obtained by an analytical method. Therefore, we use the Finite Difference Method(FDM), particularly, the FTBS(Forward-Time Backward-Space) difference method. Then, the total equations system yields to an algebraic equations system and is solved under given initial and boundary conditions in an iterative fashion. From the simulation results, we confirm that state variables show different behavior in the transient state; e.g., the velocity distribution in the flow field changes more quickly the linear density distribution. During a transient flow in a drafting zone, the output irregularity is influenced differently by the disturbances, e.g., the variation in input bundle thickness, the drafting speed, and the draft ratio.

• Journal of Korean Society for Atmospheric Environment
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• 제18권E1호
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• pp.1-12
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• 2002

One technique for determining dry acid deposition fluxes involves measurement of time - averaged ambient concentrations of dry acid deposition species using filter packs (FP) coupled with estimates of mean deposition velocities for the exposure period. A critical problem associated with filter pack data comparisons between various field sampling networks is the use of diverse sampling flow rates and duration protocols. Field experiments were conducted to evaluate the effects of varying sampling flow rates, from 1.5 to 10 standard liters per minute, on total nitrate and sulfate measurements of specific dry acid deposition species . Collocated FP samplers were used to determine sampling and analysis data reproducibility and representativeness . Ambient air samples were simultaneously collected using groups of filter packs operated at various flow rates over identical 7 day periods. The species measured were sulfur dioxide, particulate sulfate , nitric acid and particulate nitrate. Statistical results (ANOVA; alpha level 5%) showed that neither the low nor high sampling flow rates caused a significant difference in the measurements of total sulfate and adjusted total nitrate (ATN) . However, it was concluded that for high flow rate sampling measurements, total nitrate (TN) could be affected during extended sampling durations because of potential nitric acid overloading and breakthrough. Although the previous workers (Costello, 1990; Quillian, 1990) used much higher sampling flow rates (~ 17 sLpm) than employed here, it was assumed that for a high loading (> 50$\mu\textrm{g}$ HNO$_3$) of nitric acid on the Nylon filters, a significant fraction (~10%) of nitric acid could pass through the Nylon filters and be collected on the carbonate impregnated filters. It was concluded that even at the highest sampling flow rate employed (10 sLpm) at the Cary Forest site, nitric acid breakthrough was less than 10% of the total HNO$_3$ collected. However, for a heavily polluted urban airshed or with longer sampling times , higher filter loadings could result in substantial nitric acid breakthrough and HNO$_3$concentrations would be underestimated.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.471-474
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• 2006

Several planktonic dinoflagellates, including Cochlodinium polykrikoides (p), are known to produce red tides responsible for massive fish kills and serious economic loss in turbid Northwest Pacific (Korean and neighboring) coastal waters during summer and fall seasons. In order to mitigate the impacts of these red tides, it is therefore very essential to detect, monitor and forecast their development and movement using currently available remote sensing technology because traditional ship-based field sampling and analysis are very limited in both space and temporal frequency. Satellite ocean color sensors, such as Sea-viewing Wide Field-of-view Sensor (SeaWiFS), are ideal instruments for detecting and monitoring these blooms because they provide relatively high frequency synoptic information over large areas. Thus, the present study attempts to evaluate the red tide index methods (previously developed by Ahn and Shanmugam et al., 2006) to identify potential areas of red tides from SeaWiFS imagery in Korean and neighboring waters. Findings revealed that the standard spectral ratio algorithms (OC4 and LCA) applied to SeaWiFS imagery yielded large errors in Chl retrievals for coastal areas, besides providing false information about the encountered red tides in the focused waters. On the contrary, the RI coupled with the standard spectral ratios yielded comprehensive information about various ranges of algal blooms, while RCA Chl showing a good agreement with in-situ data led to enhanced understanding of the spatial and temporal variability of the recent red tide occurrences in high scattering and absorbing waters off the Korean and Chinese coasts. The results suggest that the red tide index methods for the early detection of red tides blooms can provide state managers with accurate identification of the extent and location of blooms as a management tool.

• 한국산학기술학회논문지
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• 제16권10호
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• pp.7189-7195
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• 2015

모멘트법(MoM)인 TE(transversw electric) 전장 적분 방정식(EFIE)으로 완전 전기도체(PEC) 원통을 산란 해석하였다. 이 과정에서 나타나는 특이점(singlarity)과 과대 특이점(hypersingularity)을 포함한 적분 계산은 어렵기 때문에 수치해석 방법으로 특이점을 고립시켜 자체항(self-term)을 얻었다. 모멘트법에서 base 함수와 test 함수의 선택은 수치해석 결과의 정확도와 수렴에 있어 매우 중요한 요인이됨은 알려져 있는 사실이다. basis 함수와 test함수를 달리하여 세 가지 방법으로 PEC 원통에 유도된 전류를 구하였다. 이렇게 구한 결과를 해석학적 방법과 모멘트법에서 얻은 전류와 비교하여 상대 효율 전류 오차를 구하였으며 어떤 결합 방법이 효율적인지 확인하였다. 또한 각 결합방법에 따른 상대 효율 전류 오차의 수렴율을 구하여 가장 정확한 결과를 얻을 조건을 찾았다. 전류 오차의 가장 빠른 수렴오더(order of convergence) 2.528은 펄스 base 함수/델타 test 함수 결함 조건에서 얻었다.

• 자원환경지질
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• 제53권4호
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• pp.425-440
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• 2020

The study area is located in the southern part of the M'aider Paleozoic basin in the Moroccan Eastern Anti-Atlas. It is an arid region, characterized by minimal vegetation cover, which can provide an ideal environment to apply remote sensing. In this study, remote sensing and field investigations were integrated for lithological and structural lineaments mapping. The Landsat 8 OLI data were processed in order to understand the role of lithology and geological structures in the distribution of mineral deposits in the study area. To achieve this purpose, the Color Composite (CC), the Principal Component Analysis (PCA) and Band Rationing transformation (BR) tests were performed. The results of remote sensing techniques coupled with field investigations have shown that the zones of high lineaments densities are highly correlated with the occurrences of barite mineralization. These findings depict a spatial relationship between structural lineaments and the mineralization distribution zones. Therefore, the barite and Iron oxides mineralization veins, which occur mainly in the Ras Kammouna district, seem to have a structural control. The methodological approach used in this study examining lithological mapping and lineament extractions can be used to explore mineral deposits in arid regions to a high degree of efficiency.

• 대한기계학회논문집
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• 제14권3호
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• pp.725-733
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• 1990

본 연구에서는 Raju등의 연구의 확장으로 일정한 온도로 유지되는 경사진 평 판에 대하여 혼합대류 전 영역에 유효한 부력계수(.xi.)로서 (1+Gr$^{2}$$_{x}$cos.gamma./ Re$^{4}$$_{x}$)$_{-1}$를 적용하여 비상사 경계층 방정식을 유도하였다. 또한 적분 형 경계조건을 가진 편미분 경계층방정식을 유한차분법으로 Keller와 Cebeci의 Box scheme을 6차로 적용하여 수치해석하였다. 부력계수가 큰 영역에서 Mucoglu등의 해 석적 연구결과는 일정한 온도와 45˚의 경사를 유지하는 평판에 대한 Ramachandran의 실험적 연구결과와 약 10%정도 벗어난다. 이에 Ramachandran의 실험적 연구를 해석 적으로 재고찰하였다.하였다.

• 상하수도학회지
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• 제31권3호
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• pp.197-204
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• 2017

This study was carried out to apply the UAV(Unmanned Aerial Vehicle) coupled with Multispectral sensor for the algae bloom monitoring in river. The study acquired remote sensing data using UAV on the midstream area of Gum River, one of four major rivers in South Korea. Normalized difference vegetation index (NDVI) is used for monitoring algae change. This study conducted water sampling and analysis in the field for correlating with NDVI values. Among the samples analyzed, the chlorophyll concentration exhibited strong and significant linear relationships with NDVI, and thus NDVI was chosen for algae bloom index to identify emergence aspect of phytoplankton in river. Aerial remote sensing technology can provide more accurate, flexible, cheaper, and faster monitoring methods of detecting and predicting eutrophication and therefore cyanobacteria bloom in water reservoirs compared to currently used technology. As a result, there was high level of correlation in chlorophyll-a and NDVI. It is expected that when this remote water quality and pollution monitoring technology is applied in the field, it would be able to improve capabilities to deal with the river water quality and pollution at the early stage.