• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.174-179
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• 1998

In this paper, the radar altimeter for topographic mapping over land is introduced and the characteristics of the return signals are analyzed. The radar system is described briefly and the requirements to get the fine resolution of the terrain surface height are considered. The designed radar altimeter was tested on the landscape in the near of Stuttgart. The measured data shows very fine profile of the test landscape and the height errors induced from different geometrical structure of the land surface are acquired in the measurement. In the test area, most characteristics of radar return signals over land could be tested and the results of the topographic mapping using our radar altimeter can be used for future radar altimeter development for land applications.

• 전기전자학회논문지
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• 제5권1호
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• pp.75-84
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• 2001

도로 노면상태와 관련된 신뢰성 있는 데이터는 도로 유지 및 관리 당국과 운전자에게 도로 노면상태에 대한 정보를 제공하기 위해 그 중요성이 날로 증대하고 있다. 본 논문은 새로운 고속의 자동 노면 데이터 획득장치의 개발에 관한 것이다. 개발된 장치는 100km/h의 주행속도에서 도로노면 청단 전체 폭에 대해 30cm 간격으로 종단 노면 데이터를 수집하고, 수집된 데이터로부터 국제평탄성지수(IRI)를 계산하여 노면요철 데이터와 함께 스크린상에 디스플레이 한다. 이 같은 시스템의 구현을 위해 광학적 거리측정기, 계측차량의 진행거리 및 움직임 계측기, 데이터 처리 및 디스플레이 모듈을 고안하였다. 70km/h의 주행 속도로 측정한 결과, 개발된 시스템의 측정 정확도는 표준 노면에 대해 IRI에서 ${\pm}0.1m/km$ 정도의 오차를 보이는 것으로 나타났다. 또한, 개발된 장비의 성능을 검증하기 위해 이미 포설된 노면에 대한 측정을 수행하여 기존 장비 및 육안 측정 결과와 비교하였다.

• Ocean and Polar Research
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• 제29권2호
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• pp.113-121
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• 2007

The sound wave in the sea propagates under the effect of water depth, sound speed structure, sea surface roughness, bottom roughness, and acoustic properties of bottom sediment. In shallow water, the bottom sediments are distributed very variously with place and the sound speed structure varying with time and space. In order to investigate the seasonal propagation characteristics of low-frequency sound wave in the Yellow Sea, propagation experiments were conducted along a track in the middle part of the Yellow Sea in spring, summer, and autumn. In this paper we consider seasonal variations of the sound speed profile and propagation loss based on the measurement results. Also we quantitatively investigate variation of bottom loss by dividing the propagation loss into three components: spreading loss, absorption loss, and bottom loss. As a result, the propagation losses measured in summer were larger than the losses in spring and autumn, and the propagation losses measured in autumn were smaller than the losses in spring. The spreading loss and the absorption loss did not show seasonal variations, but the bottom loss showed seasonal variations. So it was thought that the seasonal variation of the propagation loss was due to the seasonal change of the bottom loss and the seasonal variation of the bottom loss was due to the change of the sound speed profile by season.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.275-275
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• 2012

The relative composition of $Cu(InGa)Se_2$ solar cells is one of the most important measurement issues. However, quantitative analysis of multi-component alloy films is difficult by surface analysis methods due to severe matrix effect. In this study, quantitative depth profiling analysis of CIGS films was investigated by secondary ion mass spectrometry (SIMS). The compositions were measured by SIMS using the alloy reference relative sensitivity factors derived from the certified compositions and the total counting numbers of each element. The compositions measured by SIMS were linearly proportional to those by inductively coupled plasma-mass spectrometry (ICP-MS) using isotope dilution method. In this study, the quantification measured by ICP-MS method is compared with the composition calculated by SIMS depth profiles with AR-RSFs obtained from the reference. The SIMS depth profile of CIGS thin films according to the manufacturing condition was converted into compositional depth profile.

• 대한조선학회논문집
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• 제50권6호
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• pp.399-406
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• 2013

In the present study, the flat plate model test method is developed to evaluate the skin friction of the marine coating in the cavitation tunnel. Six-component force balance is used to measure the profile drag of the flat plate and strut. LDV(laser Doppler velocimetry) technique is also employed to evaluate the drag and to figure out the reason of the drag reduction. The flow velocities above the surface can be used to assess the skin friction, combined with direct force measurement. Since the vortical structure in the coherent turbulence structure influences on the skin friction in the high Reynolds number regime, the interaction between the turbulence structure and the surface wall is paying more attention. This sort of thing is important in the passive control of the turbulent boundary layer because the skin friction can't be determined only by wall condition. As complicated flow phenomena exist around a paint film, systematic measurement and analysis are necessary to evaluate the skin friction appropriately.

• 한국화재소방학회논문지
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• 제21권4호
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• pp.25-31
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• 2007

본 연구에서는 샌드위치 패널 심재에 대한 연소열과 일정한 외부 복사열에 의한 연소특성을 분석하였다. 일정한 외부 복사열원에 노출된 샌드위치 패널 심재의 착화시간, 임계열유속, 착화온도, 시료 표면 온도의 변화를 측정하기 위해 3가지 Type의 시료를 사용하였으며, 연소열을 측정하기 위해 Oxygen bomb calorimeter를, 연소특성을 측정하기 위해 Mass loss calorimeter를 사용하였다. 연소특성을 측정하기 위해 $100\;mm{\times}100\;mm{\times}50\;mm$ 크기의 시료를 사용하였다. 연구결과, 연소열과 착화온도에 있어서 가장 좋은 특성을 갖는 것은 Type B인 반면 임계열유속과 시료 표면온도 변화에 있어서는 Type C에서 가장 좋은 특성을 나타내었다. 모든 연구 데이터를 종합한 결과 Type C가 가장 좋은 화재안정성을 나타낸다는 것을 알 수 있었다. 향후, 샌드위치 패널 심재에 대한 열방출률 특성과 질량감소속도에 대한 실험연구가 필요할 것으로 판단된다.

• 한국기계가공학회지
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• 제19권2호
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• pp.69-74
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• 2020

In this study, we proposed a method for surface profiling aspheric lens molds using a precision displacement sensor with a spatial scanning mechanism. The precision displacement sensor is based on the confocal principle using a broadband light source, providing a 10 nm resolution over a 0.3 mm measurable range. The precision of the sensor, depending on surface slope, was evaluated via Allan deviation analysis. We then developed an automatic surface profiling system by measuring the cross-sectional profile of a lens mold. The precision of the sensor at the flat surface was 10 nm at 10 ms averaging time, while 200 ms averaging time was needed for identical precision at the steepest slope at 25 deg. When we compared the measurement result of the lens mold to a commercial surface profiler, we found that the accuracy of the developed system was less than 90 nm (in terms of 3 sigmas of error) between the two results.

• 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.

• 한국광물학회지
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• 제15권3호
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• pp.195-204
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• 2002

광물조성과 노출표면적(exposed surface area)은 토양풍화속도 계산모델에 영향을 미치는 중요한 요인들이다. PROFILE 등 기존의 풍화속도 계산모델에서는 입도분석자료에 기초한 기하학적 계산값이나 $N_2$-BET 비표면적 등을 그대로 노출표면적으로 적용하고 있다. 그러나, 토양은 광물과 유기물의 혼합체로써 노출표면적을 정확히 구하기는 상당히 어려운 것이 사실이다. 본 연구에서는 유기물의 영향에 의한 토양광물의 노출표면적변화를 토양 깊이에 따른 peroxidation 전후의 N2-BET 비표면적값을 통해 살펴보고, 토양칼럼실험을 이용하여 풍화속도의 차이를 살펴보았다. 실험결과 peroxidation 후의 $N_2$-BET 비표면적은 1.68~4.87 $m^2$/g의 범위에서 증가하였으며, 깊이에 따라 증가하는 범위가 감소하는 경향을 보여주었다 이는 부식산 등 토양표면에 농집되어 존재하는 다양한 형태의 유기산 등이 광물의 노출표면적을 감소시키고 있다는 것을 의미한다고 할 수 있다 기존의 토양풍화속도 모델에서 토양광물 노출표면적변화 계산에 있어서 광물-유기산간의 결합에 의한 영향을 결합세기 측면에서 고려하고 정량화 하는 것이 향후과제라고 생각된다.

• 대한원격탐사학회지
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• 제29권3호
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• pp.325-329
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• 2013

This present study describes an application of UV scanning spectrometer $O_4$ data for retrieval of aerosol vertical profiles in Seoul during the measurement period that includes two Asian dust event days. The results show large variations of aerosol load in vertical and temporal scales. Large variations in aerosol were observed at 1 km in height during the daytime in the measurement period when the Asian dust events took place. The aerosol load, however, was found to be largest at the surface compared to those retrieved at the higher atmospheric layers. The results also clearly identified the diurnal patterns of aerosol vertical distributions. The aerosol load was high in the morning and noon whereas it was low in the afternoon. This study demonstrates that UV scanning spectrometer observations of the oxygen dimer can serve as a potential method for determination of atmospheric aerosol vertical distributions and optical properties.