• 한국수학교육학회지시리즈E:수학교육논문집
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• 제23권1호
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• pp.129-144
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• 2009

본 연구에서는 초등학교 3학년 학생들을 대상으로 Lesh 표상 변환 모델을 적용한 RNP 교재의 사용이 분수에 대한 아동의 개념 이해와 문제 해결력에 어떤 영향을 미치는지를 알아보았다. RNP 교재의 사용은 아동들의 분수에 대한 개념적 이해를 향상시켰을 뿐 아니라 그들의 문제해결 능력 또한 향상시켰다. RNP 교재가 제공하는 다양한 구체적 조작 활동 및 표상 변환 활동을 통해서 아동들은 등분할로서의 분수의 개념에 대한 이해를 더욱 명확히 하였고, 개념적 이해를 토대로 다양한 문제 상황에서 적절한 문제 해결 전략을 사용하여 문제를 해결하였다. 특히, 후속 학습 내용인 분수의 크기 비교에 관한 문제 상황에서 아동들은 선행 학습 과정에서 만들어진 심상이나 수학적 경험을 토대로 올바른 추론 과정을 보여주었다.

• Ecology and Resilient Infrastructure
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• 제6권3호
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• pp.137-144
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• 2019

본 연구는 수공구조물 주변에서 발생하는 폭기 흐름의 기포분율을 측정하는 실험 연구를 수행하였다. 그림자기법을 이용한 영상측정기법을 적용하여 기포분율을 측정하고 이를 통해 폭기 정도를 정량화하였다. 제안된 영상기법을 이용하여 경사보와 계단보 주변에서 발생하는 흐름을 측정하였다. 흑백 영상으로부터 얻어진 공간적으로 분포한 기포분율은 친환경 수공구조물 주변에서 폭기 정도를 제시할 수 있었다. 얻어진 결과로부터 계단보의 전면경사부와 하류부에서 상대적으로 강한 폭기 현상이 발생함을 알 수 있었다.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2005년도 추계학술대회 논문집
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• pp.6-10
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• 2005

PIV(Particle image velocimetry) presents the flow velocity of whole flow fields in a fraction of a second. Conventional PIV method uses two optical axis configuration during the image grabbing process. That is, the illumination plane and the recording plane must be parallel. This configuration is very natural to grab the whole field without the image distortion. In the real problem, it is often to meet the situation which this configuration is hard to be fulfilled. In this study, we developed new PIV method which only uses single optical axis to grab the particle images. This new PIV method become possible by utilizing the scanning method similar to echo PIV technique. One particle image of scanning PIV consists of scanned several line images and by repeating this scanning process, two particle images were grabbed and processed to produce the velocity vectors.

• Journal of Biosystems Engineering
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• 제41권2호
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• pp.126-137
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• 2016

Purpose: The overall objective of this study was to evaluate the vegetation fraction of soybeans, grown under different cropping conditions using an unmanned aerial vehicle (UAV) equipped with a red, green, and blue (RGB) camera. Methods: Test plots were prepared based on different cropping treatments, i.e., soybean single-cropping, with and without herbicide application and soybean and barley-cover cropping, with and without herbicide application. The UAV flights were manually controlled using a remote flight controller on the ground, with 2.4 GHz radio frequency communication. For image pre-processing, the acquired images were pre-treated and georeferenced using a fisheye distortion removal function, and ground control points were collected using Google Maps. Tarpaulin panels of different colors were used to calibrate the multi-temporal images by converting the RGB digital number values into the RGB reflectance spectrum, utilizing a linear regression method. Excess Green (ExG) vegetation indices for each of the test plots were compared with the M-statistic method in order to quantitatively evaluate the greenness of soybean fields under different cropping systems. Results: The reflectance calibration methods used in the study showed high coefficients of determination, ranging from 0.8 to 0.9, indicating the feasibility of a linear regression fitting method for monitoring multi-temporal RGB images of soybean fields. As expected, the ExG vegetation indices changed according to different soybean growth stages, showing clear differences among the test plots with different cropping treatments in the early season of < 60 days after sowing (DAS). With the M-statistic method, the test plots under different treatments could be discriminated in the early seasons of <41 DAS, showing a value of M > 1. Conclusion: Therefore, multi-temporal images obtained with an UAV and a RGB camera could be applied for quantifying overall vegetation fractions and crop growth status, and this information could contribute to determine proper treatments for the vegetation fraction.

• 천문학회지
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• 제33권2호
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• pp.89-95
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• 2000

As an efficient method to detect blending of general gravitational microlensing events, it is proposed to measure the shift of source star image centroid caused by microlensing. The conventional method to detect blending by this method is measuring the difference between the positions of the source star image point spread function measured on the images taken before and during the event (the PSF centroid shift, ${\delta}{\theta}$c,PSF). In this paper, we investigate the difference between the centroid positions measured on the reference and the subtracted images obtained by using the difference image analysis method (DIA centroid shift, ${\delta}{\theta}$c.DIA), and evaluate its relative usefulness in detecting blending over the conventional method based on ${\delta}{\theta}$c,PSF measurements. From this investigation, we find that the DIA centroid shift of an event is always larger than the PSF centroid shift. We also find that while ${\delta}{\theta}$c,PSF becomes smaller as the event amplification decreases, ${\delta}{\theta}$c.DIA remains constant regardless of the amplification. In addition, while ${\delta}{\theta}$c,DIA linearly increases with the increasing value of the blended light fraction, ${\delta}{\theta}$c,PSF peaks at a certain value of the blended light fraction and then eventually decreases as the fraction further increases. Therefore, measurements of ${\delta}{\theta}$c,DIA instead of ${\delta}{\theta}$c,PSF will be an even more efficient method to detect the blending effect of especially of highly blended events, for which the uncertainties in the determined time scales are high, as well as of low amplification events, for which the current method is highly inefficient.

• 설비공학논문집
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• 제17권4호
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• pp.355-363
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• 2005

A novel method for simultaneously measuring the fluid velocity and the large particle velocity in a particle-containing fluid flow is developed in this study. In this method, the fluid velocity and the large particle velocity are measured by PIV and PTV, respectively. The PIV and PTV images are obtained from the same flow images. Since a PIV result represents the average displacement of all particles in an interrogation area, it will include an error caused by the relative displacement between the large particles and the fluid. In order to reduce the false influence of large particles on the PIV calculation, the mean brightness of small PIV particle images is substituted to the locations of large particles in the PIV images. The simulation results showed that the new method significantly reduces the PIV error caused by the large particles even at the case where the large particles occupy area fraction as large as $20\%$ of the full image.

• 천문학회보
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• 제42권1호
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• pp.50.1-50.1
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• 2017

We present our study of the correlation between star formation rate(SFR) and merging activities of nearby galaxies(d<150Mpc). Our study uses 265 UV-selected galaxies which are not classified as AGN. The UV selection is made using the GALEX Atlas of Galaxies (Gil de Paz+07) and the updated UV catalog of nearby galaxies (Bai+15). We use deep R band optical images reaching to $1{\sigma}$ surface brightness detection limit ${\sim}27mag/arcsec^2$ to classify merger features by visual inspection. We also estimated unobscured SFR($SFR_{NUV}$) and obscured SFR($SFR_{W4}$) using Near-UV continuum and 22 micron Mid-IR luminosity respectively as a indicator of star forming activity. The fraction of galaxies with merger features in each SFR bin is obtained to see if how the fraction of galaxies with merging features($F_m$) changes as a function of SFR. As a result, for 203 late type galaxies(LTGs), we found that merger fraction increases from ~8% up to 50% with $SFR_{W4}$, while for 229 LTGs $SFR_{NUV}$ shows relatively consistent fraction(~18%) of merger fraction. For early type galaxies(ETGs), we could also find no significant correlation between $F_m$ and SFR(both $SFR_{NUV}$ and $SFR_{W4}$). This result suggests that a main driver of star forming activity of UV bright galaxies, especially for obscured late types, is mergers.

• Composites Research
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• 제28권5호
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• pp.311-315
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• 2015

섬유체적비에 따라 복합재료의 기계적 열적 특성이 크게 달라지기 때문에, 복합재료 설계시 섬유체적비를 올바르게 측정하는 것이 매우 중요하다. 일반적으로 섬유체적비를 측정하는 여러 방법은 산화되지 않는 유리섬유나 세라믹섬유를 사용한 복합재료의 경우에는 적합하고 효율적이다. 하지만 산화현상이 있는 탄소섬유의 경우에는 산화 방법과 조건에 따라서 다른 결과를 가져오게 되며 그러므로 올바른 섬유체적비를 측정이 어렵다. 본 연구에서는 Thermogravimetric analysis를 수행하여 산화되는 탄소섬유의 질량 감소량을 보정하여 탄소섬유 복합재료의 섬유체적비를 측정하였고 현미경 단면 이미지를 이용하여 그 결과를 검증하였다.

• 한국약용작물학회지
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• 제25권5호
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• pp.282-289
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• 2017

Background: To investigate the possibility of using Asarum sieboldii as an environment-friendly fumigant for protecting organic cultural heritages, the inhibitory effect of A. sieboldii extract against wood rot fungi on Hanji was examined. Methods and Results: The physical, optical, and morphological properties of Hanji inoculated with Trametes versicolor and Tyromyces palustris, and exposed to the n-hexane fraction of A. sieboldii extract, were measured. The physical properties were expressed as weight loss, zero-span tensile strength and viscosity and the optical properties were depicted by luminance and chromaticity ($L^*$, $a^*$, and $b^*$). The results showed that, the n-hexane fraction of A. sieboldii extract inhibited the growth of fungi on Hanji, and preserved its condition. At a concentration of 25 mg, the n-hexane fraction of A. sieboldii extract maintained zero-span tensile strength, increased viscosity, and restricted discoloration of Hanji. It also was confirmed that the weight of fungi infested Hanji exposed to the extract did not decrease. Scanning electron microscopic images revealed that the spores and hyphae of T. versicolor and T. palustris were not present on Hanji during treatment with > 25 mg of the n-hexane fraction of A. sieboldii extract. Conclusions: These results indicate that the n-hexane fraction of A. sieboldii extract by virtue of its antifungal effectiveness may help in preserving Korean paper cultural heritages, including Hanji.

• Journal of Magnetics
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• 제17권3호
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• pp.229-232
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• 2012

This study examined the correlation between MR cine and myocardium Single-photon emission computed tomography (SPECT) by comparing the measured cardiac ejection fractions. The usefulness of cardiac MRI was also evaluated. Ten patients (8 men, 2 women and average age of 58.6 years), who underwent a myocardium SPECT scan and cardiac cine MRI scan among patients who visited the hospital for the chief complaint of cardiac disorder from June 1, 2010 to February 10, 2011, were enrolled in this study. The cardiac ejection fraction was calculated from the images obtained in both scans. The data was used to examine the correlation. The regression equation the cardiac ejection fraction values of the 10 patients obtained in myocardium SPECT and MRI cine was Y = 1.12X-8.91 ($R^2$ = 0.78, significance of F = 0.001639, and confidence level of 95%). The results were significant when the cardiac ejection fraction obtained from MRI cine was compared with that obtained from myocardium SPECT. Overall, a cardiac examination using MRI enables an investigation of not only the ejection fraction but also the ED and ES volumes, stroke volume, wall thickness, and wall thickening in a higher spatial resolution despite the examination being conducted once. This examination is believed to be very useful for diagnosing patients with cardiac disease.