• Korean Journal of Remote Sensing
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• v.27 no.5
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• pp.613-623
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• 2011

This study assessed the feasibility to apply Two-band and Three-band reflectance models for chlorophyll-a estimation in turbid productive waters whose scale is smaller and narrower than ocean using a high spatial resolution image. Those band ratio models were successfully applied to analyzing chlorophyll-a concentrations of ocean or coastal water using Moderate Imaging Spectroradiometer(MODIS), Sea-viewing Wide Field-fo-view Sensor(SeaWiFS), Medium Resolution Imaging Spectrometer(MERIS), etc. Two-band and Three-band models based on band ratio such as Red and NIR band were generally used for the Chl-a in turbid waters. Two-band modes using Red and NIR bands of RapidEye image showed no significant results with $R^2$ 0.38. To enhance a band ratio between absorption and reflection peak, We used red-edge band(710 nm) of RapidEye image for Twoband and Three-band models. Red-RE Two-band and Red-RE-NIR Three-band reflectance model (with cubic equation) for the RapidEye image provided significance performances with $R^2$ 0.66 and 0.73, respectively. Their performance showed the 'Approximate Prediction' with RPD, 1.39 and 1.29 and RMSE, 24.8, 22.4, respectively. Another three-band model with quadratic equation showed similar performances to Red-RE two-band model. The findings in this study demonstrated that Two-band and Three-band reflectance models using a red-edge band can approximately estimate chlorophyll-a concentrations in a turbid river water using high-resolution satellite image. In the distribution map of estimated Chl-a concentrations, three-band model with cubic equation showed lower values than twoband model. In the further works, quantification and correction of spectral interferences caused by suspended sediments and colored dissolved organic matters will improve the accuracy of chlorophyll-a estimation in turbid waters.

• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.401-408
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• 2022

As research on a controlled environment system based on crop growth environment sensing for sustainable production of horticultural crops and its industrial use has been important, research on how to properly utilize soil moisture sensors for outdoor cultivation is being actively conducted. This experiment was conducted to suggest the proper method of utilizing the TEROS 12, an FDR (frequency domain reflectometry) sensor, which is frequently used in industry and research fields, for each orchard soil in three regions in Korea. We collected soils from each orchard where fruit trees were grown, investigated the soil characteristics and soil water retention curve, and compared TEROS 12 sensor calibration equations to correlate the sensor output to the corresponding soil volumetric water content through linear and cubic regressions for each soil sample. The estimated value from the calibration equation provided by the manufacturer was also compared. The soil collected from all three orchards showed different soil characteristics and volumetric water content values by each soil water retention level across the soil samples. In addition, the cubic calibration equation for TEROS 12 sensor showed the highest coefficient of determination higher than 0.95, and the lowest RMSE for all soil samples. When estimating volumetric water contents from TEROS 12 sensor output using the calibration equation provided by the manufacturer, their calculated volumetric water contents were lower than the actual volumetric water contents, with the difference up to 0.09-0.17 m³·m^-3 depending on the soil samples, indicating an appropriate calibration for each soil should be preceded before FDR sensor utilization. Also, there was a difference in the range of soil volumetric water content corresponding to the soil water retention levels across the soil samples, suggesting that the soil water retention information should be required to properly interpret the volumetric water content value of the soil. Moreover, soil with a high content of sand had a relatively narrow range of volumetric water contents for irrigation, thus reducing the accuracy of an FDR sensor measurement. In conclusion, analyzing soil water retention characteristics of the target soil and the soil-specific calibration would be necessary to properly quantify the soil water status and determine their adequate irrigation point using an FDR sensor.

• Journal of the Korean Magnetics Society
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• v.9 no.3
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• pp.136-142
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• 1999

$Ni_{0.65}Zn_{0.35}Cu_{0.3}Fe_{1.7}O_4$ has been studied with x-ray diffraction, Mossbauer spectroscopy, and vibrating sample magnetometer. The crystal structure is found to be a cubic spinel with the lattice constant $a_0=8.403{\AA}$. Mossbauer spectra of have been taken at various temperatures ranging from 12 K to 665 K. as the temperature increases toward $T_N$ a systematic line broadening effect in the Mossbauer spectrum is observed and interpreted to originate from different temperature dependencies of the magenetic hyperfine fields at various iron sites. Also, by using binomial distribution equation we obtained the hyperfine fields of tetrahedral[A] and octahedral sites[B], $H_{hf}(A)=470\;kOe,\; H_{hf}(B0)=495 \;kOe,\; H_{hf}(B1)=485\;kOe, \;H_{hf}(B2)=453\;kOe,\; H_{hf}(B3)=424\;kOe,\; H_{hf}(B4)=390\;kOe,\; H_{hf}(Bavr)=451\;kOe$ respectively at room temperature. The isomer shift indicates that the iron ions are ferric at tetrahedral[A] and octahedral sites[B], respectively. The Neel temperature is determined to be $T_N=665\;K$. The results of the VSM data gave the magnetic moment and coercivity values of $M_S=66\; emu/g\;and\;H_C=36\;Oe$.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.1
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• pp.45-53
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• 1991

The nonlinear forward diffraction of a modulated wave train by a thin wedge has been studied analytically. Since the physical variables involved in the problem have vastly different scales, the multiple scale expansion method has been used to obtain an approximate solution. To simplify the problem. the wedge is assumed to be thin and the parabolic approximation is utilized. The wave evolution can be described by a kind of the cubic Schrodinger equation. which consists of the linear time evolution. the lateral dispersion and the nonlinearity. Numerical results indicate that the nonlinearity. which it defined by the ratio of the ratio of the incident wave to the wedge angle. governs the amplitude and the stability of diffracted waves. The instability of dirffracted waves becomes more pronounced as the nonlinearity increases and the modulation ratio decreases. It is also found that the stem waves. initially developed along the wedge. can not sustain for a long time.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.43-53
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• 2011

For reinforced concrete members, the bond strength is one of the important factors between two materials: concrete and reinforcing element. This study concerns the bond strength of deformed bars in artificial lightweight aggregate concrete by pull-out test. 144 cubic specimens were manufactured for the test. concrete compressive strength, size of deformed bar and embedment lengths were considered as variables in this study. Normal concrete with W/C ratio 50% specimens were tested for the comparison. Test results included the bond stress-slip responses and modes of failure. Bond strength increased with an increase of compressive strength of concrete according to W/C ratio. The equation of bond stress of polymer-modified lightweight aggregate concrete were proposed by regression analysis based on the result.

• Journal of Educational Research in Mathematics
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• v.26 no.4
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• pp.715-730
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• 2016

The purpose of this study is to analyze Descartes's point of view on the mathematical connection of algebra and geometry which help comprehend the traditional frame with a new perspective in order to access to unsolved problems and provide useful pedagogical implications in school mathematics. To achieve the goal, researchers have historically reviewed the fundamental principle and development method's feature of analytic geometry, which stands on the basis of mathematical connection between algebra and geometry. In addition we have considered the significance of geometric solving of equations in terms of analytic geometry by analyzing related preceding researches and modern trends of mathematics education curriculum. These efforts could allow us to have discussed on some opportunities to get insight about mathematical connection of algebra and geometry via geometric approaches for solving equations using the intersection of curves represented on coordinates plane. Furthermore, we could finally provide the method and its pedagogical implications for interpreting geometric approaches to cubic equations utilizing intersection of conic sections in the process of inquiring, solving and reflecting stages.

• Journal of the Korean Institute of Gas
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• v.10 no.4 s.33
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• pp.6-10
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• 2006

In this study, gross heating value(GHV), density, vapor pressure and heat capacity of natural gas were estimated and their experimental data were compared with calculated ones, SRK method. A new alpha function was used to predict the vapor pressures of pure component of the natural gas constituents well instead of calculating vapor pressures with acentric factors. And binary adjustable parameters were determined by regressing binary vapor-liquid equilibria data. Through this study, our results showed good agreements with experimental data.

• Magazine of the Korean Society of Agricultural Engineers
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• v.29 no.3
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• pp.138-144
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• 1987

This study was conducted to pursue the normalization of frequency distribution by making approach the coefficient of skewness to nearly zero tbrough SMEMAX transformation and to get probable minimum flows can be acquired by means of transforrnation equation which has been derivated by SMEMAX method to the annual minimum flow series of five watersheds along Geum river basin. The results obtained through SMEMAX method were compared with probable minimum flows according to return periods by Type III extremal distribution which has been determined as the best fitted one among probablility distributions for the analysis of minimum flow. All the results obtained through this study are summarized as follows. 1.SMEMAX transformation based on median value was proved to be the best method when the coefficient of skewness has less reliability because of the short duration for the observation and were not affected by accidental outliers. 2.SMEMAX transformation has found to be the best one for the coefficient of skewness to be made nearly zero in comparison with log and cubic root transformation. 3.Probable minimum flows according to the return periods were derivated by transformation equations obtained through theoretical analysis of SMEM AX transformation. 4.In general, probable minimum flows by SMEMAX method were appeared as higher values in the range of five and twenty years and as lower ones in the range of below than five and more than fifty years in return periods respectively, in comparison with the results of type III extremal distribution. 5.Relative errors in the probable minimum flows of SMEMAX method to the results of type III extremal distribution were shown to be within ten percent except those of one hundred years in return periods. 6.SMEMAX method was also confirmed to be useful for the analysis of minimum flow frequency as well as flood frequency analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.3 s.43
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• pp.33-42
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• 2005

Frequency domain Volterra model is applied to nonlinear parameter identification procedure for dynamic systems modeled by nonlinear function. The frequency domain Volterra kernels, which correspond io linear, quadratic, and cubic transfer functions in lime domain, are incorporated in nonlinear parametric identification procedure. The nonlinear transfer functions, which can be derived from the Volterra series representation of the nonlinear differential equation of the system by Schetzen's method(1980), are directly used for modeling input output relation. The error is defined by the difference between the observed output and the estimated output which is calculated by substituting the observed input to nonlinear frequency domain model. The system parameters are searched by minimizing the error. Volterra model guarantees enough accuracy and convergence and the estimated coefficients have a good agreement with their actual values not only in the linear frequency region but also in the legion where the $2^{nd}\;or\;3^{rd}$ order nonlinearity is dominant.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12C
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• pp.1184-1193
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• 2006

Image interpolation has been widely used and studied in the various fields of image processing. There are many approaches of varying complexity and robustness. In this paper, a new distance weight is proposed for the conventional linear interpolation. In comparison with the conventional linear weight, the new distance weight uses a quadratic or cubic polynomial equation to reflect that the interpolated value should be influenced more by the value of closer pixels in an input image. In this paper, the new adaptive linear (NAL) interpolation, which considers patterns near the interpolated value, is also proposed. This algorithm requires a pattern weight, which is used to determine the ratio of reflection on local patterns, to obtain an interpolated image that exhibits better quality at various magnification factors (MF). In the computer simulation, not only did the NAL interpolation exhibit much lower computational complexity than conventional bicubic interpolation, it also improved peak signal-to-noise ratios (PSNR).