• Title, Summary, Keyword: 후방산란

Search Result 271, Processing Time 0.05 seconds

Prediction of rice growth parameters by X-band automatic scatterometer system (X-band 자동관측시스템을 이용한 벼 생육인자 추정)

  • Kim, Yi-Hyun;Hong, S.Young;Choe, Eun-Young;Lee, Hoon-Yol
    • Proceedings of the KSRS Conference
    • /
    • /
    • pp.40-45
    • /
    • 2009
  • 본 연구에서는 기후 등의 영향을 받지 않고 레이더 산란 측정을 할 수 있는 X-band antenna 기반의 자동관측 시스템을 이용하여 벼 생육시기에 따른 후방산란계수와 벼 생육인자와의 관계를 분석하여 후방산란계수를 이용한 벼 생육인자를 추정한 것을 목적으로 하였다. 2008년도 국립농업과학원 시험포장 ($37^{\circ}$15'28.0"N, $126^{\circ}$59'21.5"E)에서 추청벼를 대상으로 생육시기별 후방산란계수를 관측하였는데 모든 편파별 후방산란계수가 벼 유수형성기 (7월 말경)까지 증가하다가 그 후 감소하다가 수확기가 가까워지는 9월 중순이후 다시 증가하는 dual-peak 현상을 보였고 특히 W-편파의 경우 9월 초순부터 후방산란계수 증가가 다른 polarization에 비해 크게 나타났다. 후방산란계수와 작물생육인자와의 관계를 분석한 결과 고주파수인 X-band는 상대적으로 바이오메스, 엽 면적지수와의 상관이 낮게 나타났지만 이삭 건물중은 VV-편파 후방산란계수와 상관관계를 보였다. 이삭 건물중과 상관관계가 높게 나타난 X-band의 W-편파 후방산란계수를 이용하여 수확기 이삭 건물중을 추정하였는데 VV-편파 후방산란계수와 이삭 건물중과는 결정계수 $(R^2)$가 0.85이었고, 이삭 건물중 실측값과 추정값을 비교해 본 결과 1:1 line에 근접하게 분포하였다 ($R^2$=0.85).

  • PDF

Estimation of Soil Moisture Content from Backscattering Coefficients Using a Radar Scatterometer (레이더 산란계 후방산란계수를 이용한 토양수분함량 추정)

  • Kim, Yi-Hyun;Hong, Suk-Young;Lee, Jae-Eun
    • Korean Journal of Soil Science and Fertilizer
    • /
    • v.45 no.2
    • /
    • pp.127-134
    • /
    • 2012
  • Microwave remote sensing can help monitor the land surface water cycle, crop growth and soil moisture. A ground-based polarimetric scatterometer has an advantage for continuous crop using multi-polarization and multi-frequencies and various incident angles have been used extensively in a frequency range expanding from L-band to Ka-band. In this study, we analyzed the relationships between L-, C- and X-band signatures and soil moisture content over the whole soybean growth period. Polarimetric backscatter data at L-, C- and X-bands were acquired every 10 minutes. L-band backscattering coefficients were higher than those observed using C- or X-band over the period. Backscattering coefficients for all frequencies and polarizations increased until Day Of Year (DOY) 271 and then decreased until harvesting stage (DOY 294). Time serious of soil moisture content was not a corresponding with backscattering over the whole growth stage, although it increased relatively until early August (R2, DOY 224). We conducted the relationship between the backscattering coefficients of each band and soil moisture content. Backscattering coefficients for all frequencies were not correlated with soil moisture content when considered over the entire stage ($r{\leq}0.50$). However, we found that L-band HH polarization was correlated with soil moisture content (r=0.90) when Leaf Area Index (LAI)<2. Retrieval equations were developed for estimating soil moisture content using L-band HH polarization. Relation between L-HH and soil moisture shows exponential pattern and highly related with soil moisture content ($R^2=0.92$). Results from this study show that backscattering coefficients of radar scatterometer appear effective to estimate soil moisture content.

Effect of Surface Flaw Type on Ultrasonic Backscattering Profile (표면결함유형이 초음파 후방산란 프로파일에 미치는 영향)

  • Kwon, Sung-D.;Yoon, Seok-S.
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.21 no.6
    • /
    • pp.658-662
    • /
    • 2001
  • The classification of surface flaw types was performed on the basis of angular dependence of backscattered ultrasound. The copper line adhered on the surface, cower line filled in groove, pure groove and the normal edge were adopted as various surface flaw patterns of glass specimen. A backward longitudinal profile was formed probably by the longitudinal wane scattering at and near 1st critical angle. The wave trains at the peak angles of the backward radiation profiles showed different shapes according to the superposition ratio of scattered and leaky waves. The asymmetry of the backward radiation profile arose due to the scattering effect of flaw. The additive resonance effect of copper line appeared in the left side of the profile. The peak angles of both the longitudinal and radiation profiles were shifted toward small angle by the scattering effect.

  • PDF

Construction of X-band automatic radar scatterometer measurement system and monitoring of rice growth (X-밴드 레이더 산란계 자동 측정시스템 구축과 벼 생육 모니터링)

  • Kim, Yi-Hyun;Hong, Suk-Young;Lee, Hoon-Yol
    • Korean Journal of Soil Science and Fertilizer
    • /
    • v.43 no.3
    • /
    • pp.374-383
    • /
    • 2010
  • Microwave radar can penetrate cloud cover regardless of weather conditions and can be used day and night. Especially a ground-based polarimetric scatterometer has advantages of monitoring crop conditions continuously with full polarization and different frequencies. Kim et al. (2009) have measured backscattering coefficients of paddy rice using L-, C-, X-band scatterometer system with full polarization and various angles during the rice growth period and have revealed the necessity of near-continuous automatic measurement to eliminate the difficulties, inaccuracy and sparseness of data acquisitions arising from manual operation of the system. In this study, we constructed an X-band automatic scatterometer system, analyzed scattering characteristics of paddy rice from X-band scatterometer data and estimated rice growth parameter using backscattering coefficients in X-band. The system was installed inside a shelter in an experimental paddy field at the National Academy of Agricultural Science (NAAS) before rice transplanting. The scatterometer system consists of X-band antennas, HP8720D vector network analyzer, RF cables and personal computer that controls frequency, polarization and data storage. This system using automatically measures fully-polarimetric backscattering coefficients of rice crop every 10 minutes. The backscattering coefficients were calculated from the measured data at a fixed incidence angle of $45^{\circ}$ and with full polarization (HH, VV, HV, VH) by applying the radar equation and compared with rice growth data such as plant height, stem number, fresh dry weight and Leaf Area Index (LAI) that were collected at the same time of each rice growth parameter. We examined the temporal behaviour of the backscattering coefficients of the rice crop at X-band during rice growth period. The HH-, VV-polarization backscattering coefficients steadily increased toward panicle initiation stage, thereafter decreased and again increased in early-September. We analyzed the relationships between backscattering coefficients in X-band and plant parameters and predicted the rice growth parameters using backscattering coefficients. It was confirmed that X-band is sensitive to grain maturity at near harvesting season.

Investigation on backscatter According to Changed in Components of Linear Accelerator Using Monte Carlo Simulation (몬테카를로 시뮬레이션을 이용한 선형가속기 구성요소 변화에 따른 후방산란에 관한 연구)

  • Kim, Hwein;Chon, Kwonsu
    • Journal of the Korean Society of Radiology
    • /
    • v.9 no.4
    • /
    • pp.239-247
    • /
    • 2015
  • It should be accurate dose calculation to increase the efficiency of radiation therapy, and it is priority to figure out the beam characteristics for this purpose. The target and primary collimator in head components of the linear accelerator have the greatest influence on determining the beam characteristics which is caused by backscatter and it is the factor to consider the shielding structures and equipment management. In this study, we made modeling of the linear accelerator through the Geant4 Monte Carlo simulation and investigated backscatter according to the change of the size and shape in head components. For the scattered electrons, it showed the greatest number of distributions inside of the inner radius at primary collimator. But, for the scattered photons which have the high energy, it was mostly located outside of the inner radius at primary collimator. Scattered positrons showed a small occurrence in about 0.03%. According to the change of the inner radius at primary collimator, it was great changes in the inside of inner radius for all three scattered particles. According to the change of the outer radius at primary collimator, it was shown some considerable effects from more than 60 mm outer radius. It was no significant effect according to the change of target thickness. In this study, we found that backscatter should be considered, and figured out that geometric size and shape of the peripheral components are the factors that influences the backscatter effect.

Surficial Sediment Classification using Backscattered Amplitude Imagery of Multibeam Echo Sounder(300 kHz) (다중빔 음향 탐사시스템(300 kHz)의 후방산란 자료를 이용한 해저면 퇴적상 분류에 관한 연구)

  • Park, Yo-Sup;Lee, Sin-Je;Seo, Won-Jin;Gong, Gee-Soo;Han, Hyuk-Soo;Park, Soo-Chul
    • Economic and Environmental Geology
    • /
    • v.41 no.6
    • /
    • pp.747-761
    • /
    • 2008
  • In order to experiment the acoustic remote classification of seabed sediment, we achieved ground-truth data(i.e. video and grab samples, etc.) and developed post-processing for automatic classification procedure on the basis of 300 kHz MultiBeam Echo Sounder(MBES) backscattering data, which was acquired using KONGBERG Simrad EM3000 at Sock-Cho Port, East Sea of South Korea. Sonar signal and its classification performance were identified with geo-referenced video imagery with the aid of GIS (Geographic Information System). The depth range of research site was from 5 m to 22.7 m, and the backscattering amplitude showed from -36dB to -15dB. The mean grain sizes of sediment from equi-distanced sampling site(50 m interval) varied from 2.86$(\phi)$ to 0.88(\phi). To acquire the main feature for the seabed classification from backscattering amplitude of MBES, we evaluated the correlation factors between the backscattering amplitude and properties of sediment samples. The performance of seabed remote classification proposed was evaluated with comparing the correlation of human expert segmentation to automatic algorithm results. The cross-model perception error ratio on automatic classification algorithm shows 8.95% at rocky bottoms, and 2.06% at the area representing low mean grain size.

Backscatter Data Processing of Multibeam Echo-sounder (300 kHz) Considering the Actual Bottom Slope (지형 경사를 고려한 다중빔 음향측심기(300 kHz) 후방산란 자료 처리에 관한 연구)

  • Kim, Tae-Heon;Lee, Jeong-Min;Park, Soo-Chul
    • Economic and Environmental Geology
    • /
    • v.48 no.5
    • /
    • pp.379-390
    • /
    • 2015
  • Multibeam backscatter strength is dependent not only on seafloor sediment facies but also on changed incidence angle due to the actual bottom slope. Therefore, the correction for actual bottom slope should be considered before the analysis of backscatter strength. This paper demonstrates the backscatter correction technique for the actual incidence angle and ensonified area. The target area is a part of the eastern Yellow Sea with water depths of 46~55 m. The area is located between the sand ridges and covered by large dunes with various bottom slopes. The dunes usually have the gentle slopes of about $1{\sim}3^{\circ}$, but show some steep slopes of $5{\sim}15^{\circ}$ on the crest. The backscatter strength values on the crest range from -34 to -23 dB, assuming that the bottom is flat. However, this study shows that the backscatter strength range was somewhat reduced (-32~-25 dB) after correction for actual bottom slope. In addition, the backscatter imagery was significantly improved; high and low backscatter strength values on the crest due to the actual bottom slope were normalized. The results demonstrate that the correction technique in this study is an effective tool for processing backscatter strength.

SNU 1.5-MV 직렬형 반데그라프 가속기를 이용한 러더포드 후방산란 분광법에 의한 소재의 표면적층 분석

  • 박혜일;배영덕;박준교;김명섭;곽종구;김창석
    • Nuclear Engineering and Technology
    • /
    • v.27 no.1
    • /
    • pp.141-153
    • /
    • 1995
  • SNU 1.5-MV 직렬형 반데그라프 가속기로부터 얻은 0.5~2.2 MeV He$^{++}$ 빔을 이용하여 러더포드 후방산란 분광법 (RBS, Rutherford Backscattering Spectrometry)으로 여러가지 시료의 표면적층을 분석하였다. 먼저 RBS 분석계통의 신뢰성을 확인하기 위하여 Micromatter사와 Charles Evans & Associates에서 제작한 14종 33개의 표준시료들에 대한 후방산란 실험을 수행하여, 각 층의 두께, 원소조성비 및 주입 이온의 깊이, 분포폭을 측정하였다. 결정된 이 값들은 제시된 값과 3% 이내로 일치하였다 이와 같이 본 RBS 분석계통의 신뢰성을 확인한 후, 분석을 의뢰받은 22종 87개의 시료에 대해, 빔에너지. 후방산란의 기하학적 구조 등의 최적 조건하에서 후방산란 실험을 수행하였다 그 결과, 분석가능한 두께의 한계를 벗어난 2종 3개의 시료를 제외한 나머지 모든 시료에 대해 각 층의 두께, 원소조성비 및 농도분포를 결정할 수 있었으며, 측정치의 통계오차는 8% 이내였다. 다양한 종류의 많은 시료들에 대한 표면적층 분석을 수행한 경험을 통하여, RBS 분석에서 신뢰도 높은 결과를 얻기 위해 분석계통에서 필수적으로 고려해야 할 요소들을 파악할 수 있었으며, 분석 결과에 대한 신뢰도는 분석 계통의 체계화뿐만 아니라 시료의 상태에 따라 크게 좌우됨을 알 수 있었다. 결론적으로 주의 깊은 시료준비와 RBS 분석계통의 최적화를 통해 신뢰도 높은 표면적층 분석이 가능함을 확인하였다.

  • PDF

Distribution of Seagrass (Zostera marina) Beds and High Frequency Backscattering Characteristics by Photosynthesis (잘피 서식지의 분포와 광합성에 의한 고주파 후방산란 특성)

  • Yoon Kwan-Seob;La Hyoung Sul;Na Jungyul;Lee Jae-Hyuk
    • The Journal of the Acoustical Society of Korea
    • /
    • v.23 no.8
    • /
    • pp.562-569
    • /
    • 2004
  • An experiment for observation of the distribution of the seagrass (zostera marina) beds and characteristics of high-frequency backscattering by the photosynthesis was conducted off the coast. Acoustic data were taken as a function of the grazing angles and the relative azimuth angles on the seagrass beds of which bottom type was sandy-mud. The transmitted source signal was a 120 kHz CW waveform. Mapping of the seagrass beds distribution was drawn up using the seagrass backscattering strength with azimuth and grazing angles. The result of the comparison backscattering strength distribution of the seagrass beds was shown to be the similar to the photograph of real seagrass beds. The seagrass backscattering strength was also compared between day and night to verify the effects of the acoustical scattering by the bubbles of Photosynthetic oxygen formed on the seagrass. In these results. it is clear that observation of the seagrass beds between day and night showed the different characteristics because the bubbles of Photosynthetic oxygen affect the acoustical scattering.

Prediction of Backscattering Strength and Volume (동물플랑크톤에 의한 후방산란강도 및 체적복반사음의 예측)

  • 나정열
    • Proceedings of the Acoustical Society of Korea Conference
    • /
    • /
    • pp.127-130
    • /
    • 1992
  • 한국 근해에서 능동소나 (active sonar) 사용시 사용되는 environmental parameters 가운데 하나인 volume reverberation(REv)을 산출하기 위하여 플랑크톤에 의한 후방산란 강도(backscattering strength)에 대한 연구를 하였다. 이를 위하여 수산진흥원 자료(80-89년)중 부유생물조사표에서 후방산란 강도가 다른 종에 비하여 큰 copepoda의 개체수를 평균한 후, 수심별 개체수를 계산하여 수심별, 주파수별(10, 50kHz), 계절별(2월, 8월) 후방산란 강도와 multipath eigenray model을 이용하여 REv를 산출하였다. 예로 사용한 동남해역(zone:S3), 서해중부해역(zone:W3)에서 주파수별 REv는 일반적인 형태인 포기에는 고주파가 높고, 1.5초 이후에는 저주파가 높게 나타났다. 그러나 여름이 겨울보다 플랑크톤 개체수가 많아 후방산란 강도가 크지만(2-5dB), REv는 겨울이 더 크게 나타났다. 이러한 이유는 SVP profile에 의한 pressure 계산결과, 여름에는 ray가 down-ward이고 겨울에는 duct를 형성하여 ray가 거의 direct로 진행하므로 transmission loss가 여름이 크기 때문이다. 또한 ray tracing결과 여름철에는 ray crossing이 많아 겨울에 비하여 fluctuation이 심하게 나타나는 현상을 보이고 있다. 두 지역 이외에도 한국근해의 정확한 REv을 예측하기 위해서는 플랑크톤의 정확한 측정과, 이론적인 수치와 비교할 수 있는 실측치를 얻는 것이 필요하다고 볼 수 있다.

  • PDF