• The Journal of the Acoustical Society of Korea
• /
• v.32 no.1
• /
• pp.14-21
• /
• 2013

The erosion, suspension, and transport of sediment frequently occur in the coastal waters and estuarine. These processes often generate the so-called fluid mud layer, which is defined as a high-concentration aqueous suspension of fine grained sediment (> 10 g/l), consisting mainly of silt and clay-size particles. Therefore the high-resolution ultrasound is mostly used to detect or monitor the fluid mud layer. Because the sound attenuation tends to increase rapidly with the suspended sediment concentration, it is necessary to consider the accurate attenuation correction to estimate the backscattering strengths from the suspended sediment layers. In this paper, the volume backscattering strengths with various suspended sediment concentrations were measured using 5-MHz ultrasound signal in a small-scale water tank. The sound attenuation due to the viscosity and scattering from suspended sediment particles was predicted by the Richard's model and applied to the sonar equation to estimate the volume backscattering strengths from the suspended sediment concentrations. For the case that the additional attenuation was not considered, the volume backscattering strengths increased to the concentration of 20 g/l, and over this point, the backscattering strengths were roughly constant. However, for the case that the attenuation due to the suspended sediment concentration was considered, the backscattering strengths increased with the concentration.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.12 no.1
• /
• pp.47-54
• /
• 2009

This research is about the inherent optical properties(IOPs) of algae which is collected from Nam-Hae for basic research of red tide remote sensing technique development. 21 kinds of red tide organisms were cultivated to investigate IOPs of them in the level of laboratory, and specific absorption coefficient of phytoplankton($a^*$) and backscattering coefficient of phytoplankton(${b_b}^*$) are estimated by using spectrophotometer. Absorption spectrums according to species appeared to range from 0.005 to 0.06 ($m^2{\cdot}mg^{-1}$), and the shapes of spectrums were also different. The range of ${b_b}^*$ appeared to be $10^{-2}{\sim}10^{-4}\;m^2{\cdot}mg^{-1}$, which had about 100 times differences between species, and the shape of spectrum have significant difference between species. These results will input as a remote sensing reflectance model input parameter from ocean color.

• Journal of Korea Water Resources Association
• /
• v.53 no.11
• /
• pp.973-983
• /
• 2020

Recently, SAR (Synthetic Aperture Radar) is being highlighted as a solution to the coarse spatial resolution of remote sensing data in water resources research field. Spatial resolution up to 10 m of SAR backscattering coefficient has facilitated more elaborate analyses of the spatial distribution of soil moisture, compared to existing satellite-based coarse resolution (>10 km) soil moisture data. It is essential, however, to multilaterally analyze how various hydrological and environmental factors affect the backscattering coefficient, to utilize the data. In this study, soil moisture estimated by WCM (Water Cloud Model) and linear regression is compared with in-situ soil moisture data at 5 soil moisture observatories in the Korean peninsula. WCM shows suitable estimates for observing instant changes in soil moisture. However, it needs to be adjusted in terms of errors. Soil moisture estimated from linear regression shows a stable error range, but it cannot capture instant changes. The result also shows that the effect of soil moisture on backscattering coefficients differs greatly by land cover, distribution of vegetation, and water content of vegetation, hence that there're still limitations to apply preexisting models directly. Therefore, it is crucial to analyze variable effects from different environments and establish suitable soil moisture model, to apply SAR to water resources fields in Korea.

• Proceedings of the Optical Society of Korea Conference
• /
• 2004.02a
• /
• pp.46-47
• /
• 2004

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.18 no.6
• /
• pp.841-847
• /
• 1993

The evaluation methods of the splicing loss in attenuation characteristics of optical fiber were measured and analyzed presently, the splicing loss of single mode optical fiber is measured by the cut-back technique and the backscattering technique. Comparing the splicing loss measured by above two technique, evaluation method of splicing loss measured by backscattering technique (OTDR) shall be calculated by the splicing loss is occurred due to difference of the backscattering coefficient in the spliced fibers. Thus. this analysis of the splicing loss is certainly applied in installation of the optical fiber cables for management of the data.

• Proceedings of the KSRS Conference
• /
• v.1
• /
• pp.479-482
• /
• 2006

The absorption coefficient and backscattering properties of phytoplankton were calculated from the Mie theory. Given a simple case that phytoplankton and mineral particles are the only constitutions in seawater, the reflectance $b_b({\lambda})/[a({\lambda})+b_b({\lambda})]$was analyzed. Then the chlorophyll concentrations were estimated from remote sensing OC2 algorithm. The results show that reflectance in short wavelength region is more sensitive to the Chl variation; High mineral concentrations in seawater have significant influence on the reflectance spectrum; the existence of high mineral concentration may result in the mistake in chlorophyll estimation from OC2 algorithm.

• Proceedings of the KSRS Conference
• /
• 2008.03a
• /
• pp.153-157
• /
• 2008

기상상태에 관계없이 데이터를 획득할 수 있는 Synthetic Aperture Radar (SAR)는 산림 분야에서 C, L, P 밴드의 자료가 많이 연구되어 왔다. 특히 밴드 간에 산림 지역에서 수관을 투과하는 특성이 뚜렷하게 나타나고 있다. X밴드의 경우는 C, L, P 밴드에 비하여 수관 표면에서 backscattering이 일어나게 되므로 수종을 분류하게 되는데 더 큰 장점을 가질 수 있으나 지금까지 산림 분야에서는 X 밴드의 SAR 자료가 활발히 연구되어 오고 있지 않다. 이 연구는 X밴드 SAR자료의 산림 분야의 활용성을 검토해보는 목적으로 1994년 10월 3일에 동시 촬영된 SIR-C/X-SAR 자료의 L, C와 X 밴드의 backscattering coefficients의 차이점을 통해서 수관 밀도나 다른 산림 특성과의 연관성을 살펴보고자 한다. 연구지역은 국립산림과학원에 의하여 관리되고 있는 광릉 지역으로서 그 지역의 산림에 대한 정밀한 자료를 분석에 활용하여 SAR 자료의 밴드별 파장과 산림피복의 특성에 따른 연관성에 대해 분석하였다.

• Transactions on Electrical and Electronic Materials
• /
• v.3 no.3
• /
• pp.1-7
• /
• 2002

The developed patterns by direct writing of electron beam are measured by AFM, FESEM and optical profiler of WYKO NT3300. From different measurement methods, the measured linewidths of the patterns are shown a little bit wider than designed pattern size due to electrons scattering effect during direct writing of electron beam. The optimized conditions of these experiments are suggested and explained for the forming of structures below 0.1 ㎛ dimension size. Because of electron scattering effects from the different under layers such as Si, Si$_3$N$_4$ and aluminum, the developed pattern size is also influenced by the accelerated energy of electrons, dose, resist and soft and hard bake conditions in PMMA. The distributions of electron beam and calculations of backscattering coefficient are demonstrated by Monte Carlo simulation. From the measured results, the developed linewidth of PMMA/Al /silicon is shown a little bit wider than that of PMMA/Si$_3$N$_4$/silicon structure due to the backscattering effects.

• Proceedings of the KSRS Conference
• /
• 2002.10a
• /
• pp.312-316
• /
• 2002

Satellite radar interferometry data shows a strong coherent signal on oyster sea farms where artificial structures installed on the bottom. We obtained 21 highly coherent interferograms from eleven JERS-1 SAR data sets despite of large orbital baseline (~2 km) or large temporal baseline (~l year). The phases observed in sea farms are probably induced by double bouncing on sea surface, and consequently reveal a tide height variation. To restore the absolute sea level changes we counted the number of wrapping by exploiting the intensity of backscattering. Backscattering intensity is closely correlated with the change in water surface height, while interferometry gives the detailed variation within the limit of 2$\pi$ (or 15.3 cm). Comparing the radar measurements with the tide gauge records yielded a correlation coefficient of 0.96 and an ms error of 6.0 cm. The results demostrate that radar interferometry is promising to measure sea level.

• Korean Journal of Remote Sensing
• /
• v.23 no.2
• /
• pp.145-152
• /
• 2007

The polarimetric backscattering coefficients of a wet-land rice field which is an experimental plot belong to National Institute of Agricultural Science and Technology in Suwon are measured using ground-based polarimetric scatterometers at 1.8 and 5.3 GHz throughout a growth year from transplanting period to harvest period (May to October in 2006). The polarimetric scatterometers consist of a vector network analyzer with time-gating function and polarimetric antenna set, and are well calibrated to get VV-, HV-, VH-, HH-polarized backscattering coefficients from the measurements, based on single target calibration technique using a trihedral corner reflector. The polarimetric backscattering coefficients are measured at $30^{\circ},\;40^{\circ},\;50^{\circ}\;and\;60^{\circ}$ with 30 independent samples for each incidence angle at each frequency. In the measurement periods the ground truth data including fresh and dry biomass, plant height, stem density, leaf area, specific leaf area, and moisture contents are also collected for each measurement. The temporal variations of the measured backscattering coefficients as well as the measured plant height, LAI (leaf area index) and biomass are analyzed. Then, the measured polarimetric backscattering coefficients are compared with the rice growth parameters. The measured plant height increases monotonically while the measured LAI increases only till the ripening period and decreases after the ripening period. The measured backscattering coefficientsare fitted with polynomial expressions as functions of growth age, plant LAI and plant height for each polarization, frequency, and incidence angle. As the incidence angle is bigger, correlations of L band signature to the rice growth was higher than that of C band signatures. It is found that the HH-polarized backscattering coefficients are more sensitive than the VV-polarized backscattering coefficients to growth age and other input parameters. It is necessary to divide the data according to the growth period which shows the qualitative changes of growth such as panicale initiation, flowering or heading to derive functions to estimate rice growth.