• Title/Summary/Keyword: Constant Correlation Model

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Adsorption Characteristics and Kinetic Models of Ammonium Nitrogen using Biochar from Rice Hull in Sandy Loam Soil

  • Choi, Yong-Su;Kim, Sung-Chul;Shin, Joung-Du
    • Korean Journal of Soil Science and Fertilizer
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    • v.48 no.5
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    • pp.413-420
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    • 2015
  • Objective of this study was to investigate adsorption characteristics and kinetic models of $NH_4-N$ to biochar produced from rice hull in respective to mitigation of greenhouse gases. $NH_4-N$ concentration was analyzed by UV Spectrophotometer. For the experiment, the soil texture used in this study was sandy loam soil, and application rates of chemical fertilizer and pig compost were $420-200-370kgha^{-1}$ (N-P-K) and $5,500kgha^{-1}$ as recommended amount after soil test for corn cultivation. Biochar treatments were 0.2-5% to soil weight. Its adsorption characteristic was investigated with application of Langmuir isotherm, and pseudo-first order kinetic model and pseudo-second order kinetic model were used as kinetic models. Adsorption amount and removal rates of $NH_4-N$ were $39.3mg^{-1}$ and 28.0% in 0.2% biochar treatment, respectively. The sorption of $NH_4-N$ to biochar was fitted well by Langmiur model because it was observed that dimensionless constant ($R_L$) was 0.48. The maximum adsorption amount ($q_m$) and binding strength constant (b) were calculated as $4.1mgg^{-1}$ and $0.01Lmg^{-1}$ in Langmuir isotherm, respectively. The pseudo-second order kinetic model was more appropriate than pseudo-first order kinetic model for high correlation coefficient ($r^2$) of pseudo-second order kinetic model. Therefore, biochar produced from rice hull could reduce $N_2O$ by adsorbing $NH_4-N$ to biochar cooperated in sandy loam soil.

Comparison of Customer Satisfaction Indices Using Different Methods of Weight Calculation (가중치 산출방법에 따른 고객만족도지수의 비교)

  • Lee, Sang-Jun;Kim, Yong-Tae;Kim, Seong-Yoon
    • Journal of Digital Convergence
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    • v.11 no.12
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    • pp.201-211
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    • 2013
  • This study compares Customer Satisfaction Index(CSI) and the weight for each dimension by applying various methods of weight calculation and attempts to suggest some implications. For the purpose, the study classified the methods of weight calculation into the subjective method and the statistical method. Constant sum scale was used for the subjective method, and the statistical method was again segmented into correlation analysis, principal component analysis, factor analysis, structural equation model. The findings showed that there is difference between the weights from the subjective method and the statistical method. The order of the weights by the analysis methods were classified with similar patterns. Besides, the weight for each dimension by different methods of weight calculation showed considerable deviation and revealed the difference of discrimination and stability among the dimensions. Lastly, the CSI calculated by various methods of weight calculation showed to be the highest in structural equation model, followed by in the order of regression analysis, correlation analysis, arithmetic mean, principal component analysis, constant sum scale and factor analysis. The CSI calculated by each method showed to have statistically significant difference.

Measurements of Microwave Polarimetric Backscattering from a Wet Soil Surface and Comparison with a Semi-empirical Scattering Model

  • Oh, Yi-Sok
    • Proceedings of the KSRS Conference
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    • 1999.11a
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    • pp.154-157
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    • 1999
  • Microwave polarimetric backscattering from a wet soil surface had been measured using a Ku-band polarimetric scatterometer at the incidence angles ranging from 10$^{\circ}$ to 70$^{\circ}$ Since the accurate target parameters as well as the radar parameters are necessary for radar scattering modeling, a complete and accurate set of ground truth data were also collected, from which accurate measurements were made of the rms height, correlation length, and dielectric constant. The measured polarimetric backscattering coefficients (vv-, hh-, vh-, hv-polarizations) were compared with theoretical models and empirical models. A new semi-empirical model for microwave polarimetric radar backscattering from bare soil surfaces was developed using polarimetric radar measurements and the knowledge based on the theoretical and numerical solutions. The model was found to yield very good agreement with the backscattering measurements of this study.

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Covariance Estimation and the Effect on the Performance of the Optimal Portfolio (공분산 추정방법에 따른 최적자산배분 성과 분석)

  • Lee, Soonhee
    • Journal of the Korean Operations Research and Management Science Society
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    • v.39 no.4
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    • pp.137-152
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    • 2014
  • In this paper, I suggest several techniques to estimate covariance matrix and compare the performance of the global minimum variance portfolio (GMVP) in terms of out of sample mean standard deviation and return. As a result, the return differences among the GMVPs are insignificant. The mean standard deviation of the GMVP using historical covariance is sensitive to the estimation window and the number of assets in the portfolio. Among the model covariance, the GMVP using constant systematic risk ratio model or using short sale restriction shows the best performance. The performance difference between the GMVPs using historical covariance and model covariance becomes insignificant as the historical covariance is estimated with longer estimation window. Lastly, the implied volatilities from ELW prices do not lead to superior performance to the historical variance.

Nonlinear Behavior of RC Columns Subjected to Cyclic Loadings (반복하중을 받는 철근콘크리트 기둥의 비선형 거동)

  • 곽효경;김선필
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2002.10a
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    • pp.475-482
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    • 2002
  • A moment-curvature relationship to simulate the behavior of reinforced concrete (RC) columns under cyclic loading is introduced. Unlike previous moment4curvature models and the layered section approach, the proposed model takes into account the bond-slip effect by using a monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The pinching effect caused by axial force is considered with an assumption that the absorbing energy corresponding to any deformation level maintains constant regardless of the magnitude of applied axial lone. The advantages of the proposed model, comparing to layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures. Finally, correlation studies between analytical result and experimental studies are conducted to establish the validity of the proposed model.

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Analysis of asymmetric flow in annulus with square ribs by linearly- varying shear stress model (線型 亂流剪斷應力모델에 의한 直四角形 조도를 갖는 二重圓管內의 非對稱流動의 解析)

  • 이병곤;최영돈
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.11 no.1
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    • pp.88-96
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    • 1987
  • A method is presented to calculate the fiction factor and velocity distribution of asymmetric flow in rough channels and annuli. This method is derived from an assumption of linearly-varying shear stress which is different from Maubach's constant shear stress assumption. This method gives continuous velocity gradient at the position of maximum velocity and the predicted velocity profiles are in better agreements with experimental data than those obtained by Maubach's method. In this paper, a new correlation of roughness function is proposed and the predictions of friction factors by this correlation agree well with experimental data.

Comparative Analysis of Models for Free Convective Film Condensation on an Isothermal Vertical Wall (등온 수직벽의 자연대류 막응축 모델에 관한 비교분석)

  • Sung, Hyun-Chan;Kim, Kyoung-Hoon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.10
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    • pp.1380-1387
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    • 2000
  • The existing theoretical models for steady two-dimensional free convective laminar film condensation of pure saturated or superheated vapor under atmospheric pressure on isothermal vertical wall have been reviewed. To investigate the effects such as inertia, thermal convective and liquid-vapor interface shear stress, the models of constant or variable properties in liquid film for condensation of saturated vapor are compared in detail with Nusselt model. Also, for condensation of superheated vapor, the effects of superheated temperature and variable properties in liquid and vapor layers are examined and then a new correlation is proposed to predict the heat transfer. The results are in good agreement with the Shang's correlation within 2% errors.

Effect of Specimen Thickness on the Statistical Properties of Fatigue Crack Growth Resistance in BS4360 Steel

  • Kim, Seon-Jin;Itagaki, Hiroshi;Ishizuka, Tetsuo
    • Journal of Mechanical Science and Technology
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    • v.14 no.10
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    • pp.1041-1050
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    • 2000
  • In this paper the effect of specimen thickness on fatigue crack growth with the spatial distribution of material properties is presented. Basically, the material resistance to fatigue crack growth is treated as a spatial stochastic process, which varies randomly on the crack surface. The theoretical autocorrelation functions of fatigue crack growth resistance with specimen thickness are discussed for several correlation lengths. Constant ${\Delta}K$ fatigue crack growth tests were also performed on CT type specimens with three different thicknesses of BS 4360 steel. Applying the proposed stochastic model and statistical analysis procedure, the experimental data were analyzed for different specimen thicknesses for determining the autocorrelation functions and probability distributions of the fatigue crack growth resistance.

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Comparative Analysis of Models for Free Convective Film Condensation on an Isothermal Vertical Wall (등온 수직벽의 자연대류 막응축 모델에 관한 비교분석)

  • Sung, Hyun-Chan;Kim, Kyoung-Hoon
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.31-36
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    • 2000
  • The existing theoretical models for steady two-dimensional free convective laminar film condensation or pure saturated or superheated vapor under atmospheric pressure on isotheraml vertical wall have been reviewed. To investigate the effects of inertia, thermal convective and liquid-vapor interface shear stress, the models of constant or variable properties in liquid film for condensation of saturated vapor are compared in detail with Nusselt model. Also, for condensation of superheated vapor the effects of superheated temperature and variable properties in liquid and vapor layer are examined and then new correlation is proposed to predict the heat transfer. The results are in good agreement with the Shang's correlation within 2% errors.

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Dynamic bivariate correlation methods comparison study in fMRI

  • Jaehee Kim
    • Communications for Statistical Applications and Methods
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    • v.31 no.1
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    • pp.87-104
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    • 2024
  • Most functional magnetic resonance imaging (fMRI) studies in resting state have assumed that the functional connectivity (FC) between time series from distinct brain regions is constant. However, increased interest has recently been in quantifying possible dynamic changes in FC during fMRI experiments. FC study may provide insight into the fundamental workings of brain networks to brain activity. In this work, we focus on the specific problem of estimating the dynamic behavior of pairwise correlations between time courses extracted from two different brain regions. We compare the sliding-window techniques such as moving average (MA) and exponentially weighted moving average (EWMA), dynamic causality with vector autoregressive (VAR) model, dynamic conditional correlation (DCC) based on volatility, and the proposed alternative methods to use differencing and recursive residuals. We investigate the properties of those techniques in a series of simulation studies. We also provide an application with major depressive disorder (MDD) patient fMRI data to demonstrate studying dynamic correlations.