• 한국지구과학회지
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• 제39권6호
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• pp.555-567
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• 2018

본 연구에서는 서해 연안에서의 실측-위성 해수면온도 차이를 규명하고 그 특성을 분석하기 위해 GCOM-W1/AMSR2 마이크로파 해수면온도 자료와 서해 연안에 위치한 덕적도, 칠발도, 외연도 해양기상 부이의 실측 수온 자료를 활용하여 2012년 7월부터 2017년 12월까지 총 6,457개의 일치점 자료를 생산하였다. 5년 이상의 덕적도, 칠발도, 외연도 해양 부이 수온 자료와 AMSR2 해수면온도를 비교하여 정확도를 제시하였다. 마이크로파 위성 해수면온도와 현장 관측 부이 해수면온도 간의 차이는 풍속과 수온 등 환경 요인에 대한 의존성을 가지는 것으로 나타났다. 낮시간 풍속이 약할 때 ($<6ms^{-1}$) AMSR2 해수면온도는 실측 해수면온도보다 높게 산출되며, 밤시간에 대해서는 풍속이 커질수록 양의 편차가 증가함을 밝혔다. 또한 AMSR2 해수면온도와 실측 해양부이 수온 간의 차이가 증가하는 경향은 낮은 온도에서 마이크로파 센서의 민감도의 저하와 육지에 의한 자료오염과 관련이 있는 것으로 나타났다. 실측-위성 해수면온도 차이를 월별로 도시해본 결과, 마이크로파 위성 해수면온도의 편차는 강한 바람이 부는 겨울철에 가장 커진다고 알려져 있던 기존의 경향성과는 달리 덕적도, 칠발도 부이에서는 여름철 가장 큰 해수면온도 편차값이 나타났다. 이러한 차이는 부이의 위치에 따른 조석 혼합의 공간적 차등에 기인한 것으로 사료된다. 본 연구는 인공위성 합성장에 기여도가 높은 마이크로파 위성 해수면온도를 사용할 때 한반도 서해안에서 발생할 수 있는 문제점과 제한점을 제시하였다.

• Environmental Engineering Research
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• 제25권3호
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• pp.281-289
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• 2020

Environmental fate of ionizable organic pollutants such as perfluoroalkyl acids (PFAAs) are of increasing interest but has not been well understood because of uncertain values for parameters related with atmospheric interphase partitioning behavior. In the present study, not only the values for air-water partition coefficient (K_AW) and dissociation constant (pKa) of PFAAs were induced by adjusting to in situ measurements of air-water distribution coefficient between vapor phase and rainwater but also gas-particle partition coefficients were also estimated using three-phase partitioning model of ionizable organic pollutants, in situ measurements of PFAAs in aerosol and air vapor phase, and obtained parameter values. The pKa values of PFAAs we obtained were close to the minimum values suggested in literature except for perfluorooctane sulfonic acids, and COSMOtherm-modeled K_AW values were assessed to more appropriate among suggested values. When applying parameter values we obtained, it was predicted that air particle-associated fate and transport of PFAAs could be negligible and PFAAs could distribute ubiquitously along the transection from urban to rural region by pH-dependent phase transfer in air. Our study is expected to have some implications in prediction of the environmental redistribution of other ionizable organic compounds.

• Earthquakes and Structures
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• 제22권4호
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• pp.345-353
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• 2022

The configuration of an open ground floor (pilotis) is a common and very critical irregularity observed in multistory reinforced concrete frame structures. The characteristics and the geometrical formation of the beams of the first story proved to be a critical parameter for the overall seismic behavior of this type of Reinforced Concrete (RC) structures. In this work the combination of open ground floor (pilotis) morphology with very strong perimetrical beams at the level of the first story is studied. The observation of the seismic damages and the in situ measurements of the fundamental period of four buildings with this morphology and Π-shaped plan view are presented herein. Further analytical results of a pilotis type Π-shaped RC structure are also included in the study. From the measurements and the analytical results yield that the open ground floor configuration greatly influences the fundamental period whereas this morphology in combination with strong beams can lead to severe local shear damages in the columns of the ground floor. The structural damage was limited in the columns of the ground floor and yet based on the changes of the in situ measured fundamental period the damaged level is assessed as DI=88%. Furthermore, due to the Π-shape of the plan view the tendency of the parts of the building to move independently strongly influences the distribution of the damages over the ground floor vertical elements.

• Journal of Magnetics
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• 제7권4호
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• pp.151-155
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• 2002

In situ stress changes at interfaces of ultrathin magnetic films were measured by means of a non-contact optical fiber bundle displacement detector. A bending of the substrate due to stress of a deposited film was detected in cantilever geometry. The highest sensitivity of 134 mV/$\mu$m for the displacement detector was realized with a help of computer simulation. The detector was applied to in situ stress measurements of Co/Pt and Ni/Pd magnetic multilayer films prepared on the glass substrates by dc magnetron sputtering. The detector turned out to have a submonolayer sensitivity that enables to observe coherent-to-incoherent transition in these mismatched multilayers and even detect the stress changes within the monoatomic coverage. This highly sensitive detector paves new way to probe the stress relaxation at an interface in ultrathin films.

• 대한원격탐사학회지
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• 제34권1호
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• pp.127-139
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• 2018

The GOCI atmospheric correction overland surfaces is essential for the time-series analysis of terrestrial environments with the very high temporal resolution. We develop an operational GOCI atmospheric correction method over land surfaces, which is rather different from the one developed for ocean surface. The GOCI atmospheric correction method basically reduces gases absorption and Rayleigh and aerosol scatterings and to derive surface reflectance from at-sensor radiance. We use the 6S radiative transfer model that requires several input parameters to calculate surface reflectance. In the sensitivity analysis, aerosol optical thickness was the most influential element among other input parameters including atmospheric model, terrain elevation, and aerosol type. To account for the highly variable nature of aerosol within the GOCI target area in northeast Asia, we generate the spatio-temporal aerosol maps using AERONET data for the aerosol correction. For a fast processing, the GOCI atmospheric correction method uses the pre-calculated look up table that directly converts at-sensor radiance to surface reflectance. The atmospheric correction method was validated by comparing with in-situ spectral measurements and MODIS reflectance products. The GOCI surface reflectance showed very similar magnitude and temporal patterns with the in-situ measurements and the MODIS reflectance. The GOCI surface reflectance was slightly higher than the in-situ measurement and MODIS reflectance by 0.01 to 0.06, which might be due to the different viewing angles. Anisotropic effect in the GOCI hourly reflectance needs to be further normalized during the following cloud-free compositing.

• 한국분말재료학회지
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• 제10권4호
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• pp.275-280
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• 2003

Synthesis and characteristics of Cu nanopowder were considered by in-situ characterization method using SMPS in pulsed wire evaporation process. With increasing pressure in chamber, particle size and degree of agglomeration increased by increase of collision frequency. Also, it was found from the XRD analyses and BET measurements that crystallite size and particle size decreased with elevating applied voltage. However, SMPS measurements and TEM observation revealed the increase of particle size and degree of agglomeration with increase of applied voltage. These results suggested that particle growth and agglomeration depend on overheating factor in chamber at the early stage and thermal coagulation in filtering system during powder formation until collection.

• 한국지하수토양환경학회지:지하수토양환경
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• 제27권1호
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• pp.60-70
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• 2022

We evaluated the performance of in-situ capping to prevent the release of phenol, one of hazardous chemicals of concern for their impact on sediment. Sediment near the estuary of Hyeongsan River, Korea, and commercially-available sand were collected to evaluate their physical properties and phenol sorption characteristics. Biodegradation kinetics of phenol spiked into the sediment was evaluated under freshwater and estuarine salinity conditions. These experimental measurements were parameterized and used as input parameters for executing CapSim, a software predicting the performance of in-situ capping. The CapSim simulation demonstrated that capping with 50-cm sand reduced the phenol release by several orders of magnitude over 0.25- and 1-year duration for almost all simulation scenarios. The variables tested, i.e., cap thickness, pore-water movement, and biodegradation rate, showed high correlation to each other to influence the extent of phenol release from sediment to the water column. The findings and the framework employed to evaluate the performance of in-situ capping in this study can be adopted to determine whether in-situ capping is appropriate remedial approach at sediment sites impacted by hazardous chemicals due to accidental spills.

• 터널과지하공간
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• 제9권3호
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• pp.175-184
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• 1999

현장에서의 체계적인 측정자료는 최적의 안전한 설계를 위한 중요한 정보라 할 수 있다. 본 연구에서는 미국의 방사성폐기물 저장 시설인 Waste Isolation Pilot Plant(WIPP)에서 수행된 현장 측정 기법들에 대해 고찰하였다. 또한 지하구조물의 시간 의존적인 복잡한 거동을 이해하기 위해서 필요한 측정기기의 설치와 측정에 대하여 논의하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 말뚝기초 학술발표회
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• pp.85-106
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• 2000

The load distribution and deformation of drilled shafts subjected to axial loads were evaluated by a load transfer approach. The emphasis was on quantifying the load transfer mechanism at the interface between the shafts and surrounding highly weathered rocks based on a numerical analysis and small-scale tension load tests performed on nine instrumented piles. An analytical method that takes into account the soil coupling effect was developed using a modified Mindlin's point load solution. Based on the analysis, a single-modified hyperbolic model is proposed for the shear transfer function of drilled shafts in highly weathered rocks. Through comparisons with field case studies, it is found that the prediction by the present approach is in good agreement with the general trend observed by in-situ measurements.

• Journal of Korean Society for Atmospheric Environment
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• 제17권E4호
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• pp.169-181
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• 2001

To test the compatibility of differential optical absorption spectroscopy (DOAS) and conventional in-situ monitoring technique we conducted a comparative analysis of the two systems using hourly measurement data sets of three criteria pollutants including No$_{2}$O$_{3}$, and SO$_{2}$ collected in months between April and June of 2001 at Sung Man city, Kyung Gi Province, Korea. The results of our comparative analysis were useful to evaluate the various aspects of DOAS performance, of particular the level of agreement with the counterpart method through computation of percent differences and correlation analysis. Interpretation of the mixing ratio data for those chemical species was however confined in terms of explaining the differences affected by the changes in environmental conditions because measurements of important meteorological parameters were limited during most of the study period. Nevertheless, the overall results of this study strongly demonstrated that the mixing ratio of major pollutants measured by the two different systems maintain strong compatibility from various respects.