• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.1
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• pp.91-98
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• 2016

In order to apply Kriging methods for geostatistics of spatial data, an estimation of spatial coherency functions is required priorly based on the spatial distance between measurement points. In the study, the typical coherency functions, such as semi-variogram, homeogram, and covariance function, were estimated using the national geoid model. The test area consisting of 2°×2° and the Unified Control Points (UCPs) within the area were chosen as sampling measurements of the geoid. Based on the distance between the control points, a total of 100 sampling points were grouped into distinct pairs and assigned into a bin. Empirical values, which were calculated with each of the spatial coherency functions, resulted out as a wave model of a semi-variogram for the best quality of fit. Both of homeogram and covariance functions were better fitted into the exponential model. In the future, the methods of various Kriging and the functions of estimated spatial coherency need to be studied to verify the prediction accuracy and to calculate the Mean Squared Prediction Error (MSPE).

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.51-60
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• 2020

Estimation of passive earth pressure is an important factor in anchor block, temporary retaining wall and support block of raker that resist lateral earth pressure. In practice, due to ease of use, it is common to estimate the earth pressure using the theory of Coulomb and Rankine, which assumes the failure plane as a straight line. However, the passive failure plane generated by friction between the wall surface and the soil forms a complex failure plane: a curve near the wall and a flat plane near the ground surface. In addition, the limit displacement where passive earth pressure is generated is larger compared to where the active earth pressure is generated. Thus, it is essential to calculate the passive earth pressure that occurs at the allowable displacement range in order to apply the passive earth pressure to the design for structural stability reasons. This study analyzed the mobilized passive earth pressured to various displacement ranges within the passive limit displacement range using the semi-empirical method considering the complex failure plane.

• Earthquakes and Structures
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• v.12 no.3
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• pp.321-332
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• 2017

The reverse fault is a dangerous geological hazard faced by buried steel pipelines. Permanent ground deformation along the fault trace will induce large compressive strain leading to buckling failure of the pipe. A hybrid pipe-shell element based numerical model programed by INP code supported by ABAQUS solver was proposed in this study to explore the strain performance of buried X80 steel pipeline under reverse fault displacement. Accuracy of the numerical model was validated by previous full scale experimental results. Based on this model, parametric analysis was conducted to study the effects of four main kinds of parameters, e.g., pipe parameters, fault parameters, load parameter and soil property parameters, on the strain demand. Based on 2340 peak strain results of various combinations of design parameters, a semi-empirical model for strain demand prediction of X80 pipeline at reverse fault crossings was proposed. In general, reverse faults encountered by pipelines are involved in 3D oblique reverse faults, which can be considered as a combination of reverse fault and strike-slip fault. So a compressive strain demand estimation procedure for X80 pipeline crossing oblique-reverse faults was proposed by combining the presented semi-empirical model and the previous one for compression strike-slip fault (Liu 2016). Accuracy and efficiency of this proposed method was validated by fifteen design cases faced by the Second West to East Gas pipeline. The proposed method can be directly applied to the strain based design of X80 steel pipeline crossing oblique-reverse faults, with much higher efficiency than common numerical models.

• Journal of the Korean Chemical Society
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• v.39 no.3
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• pp.150-156
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• 1995

Molecular orbital calculations at the ab initio, AM1, and PM3 levels have been carried out to investigate the lactam-lactim tautomerism of 1,2,4-triazolidine-3,5- dione(1) and 1,3,4-oxa(or thia)diazolidine-2,5-dione(2, 3). Most stable tautomer in 1 compound has been calculated to be a dilactam 1a and next one is lactam-lactim 1b. The relative energies between 1a and 1b are 4.1~12.6 kcal/mol depending on computational methods. The optimized 1a structure at ab initio level is in good agreement with X-ray structure. While the stabilities of 2 tautomers are in order of 2a>2b>2c, the stabilities of 3 tautomers are dependent on methods. According to 3-21G basis set, 3a tautomer is more stable by 4.9 kcal/mol over 3b tautomer. In contrast, the heat of formation of 3a at AM1 is higher by 2.71 kcal/mol than 3b.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.4
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• pp.32-42
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• 2007

The substrate resistance is modeled to estimate the performance degradation of analog circuits by substrate noise in a $0.35{\mu}m$ twin-well non-epitaxial CMOS process. The substrate resistance model equations are applied to the P+ guard-ring isolation structure and a good match was achieved between measurements and models. The substrate resistance is divided into four types and a semi-empirical model equation is obtained for each type of substrate resistance. The rms(root-mean-square) error of the substrate resistance model is below 10% compared with the measured resistance. To apply this substrate resistance model to the P+ guard ring structure, ADS(Advanced Design System) circuit simulation results are compared with the measurement results using Network Analyzer, and relatively good agreements are obtained between measurements and simulations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.11
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• pp.849-859
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• 2020

The semi-empirical equation and commercial computational tool were used to predict the base drag of a guided missile with free-stream Mach numbers and chamber pressures, and the results were generally agree each other. Differences in flow characteristics and base drags were observed with over/under expansion conditions by the nozzle. Under the over-expansion condition, the base pressure decreased as the expansion fan was generated at upper region of the base, and base pressure decreased further with increasing free-stream Mach number as the expansion becomes strong. Under the under-expansion conditions, a shock wave was generated around the base by the influence of the nozzle flow, which increased the base pressure, and the effect increased as the chamber pressure increased. Under the same chamber pressure condition, as the free-stream Mach number increases, the characteristic that the base pressure decreases as the shock wave generated at the base moves downstream was observed.

• Korean Journal of Remote Sensing
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• v.27 no.3
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• pp.303-314
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• 2011

Surface albedo is an important parameter of the surface energy budget, and its accurate quantification is of major interest to the global climate modeling community. Therefore, in this paper, we consider the direct solution of kernel based bidirectional reflectance distribution function (BRDF) models for retrieval of normalized reflectance of high resolution satellite. The BRD effects can be seen in satellite data having a wide swath such as SPOT/VGT (VEGETATION) have sufficient angular sampling, but high resolution satellites are impossible to obtain sufficient angular sampling over a pixel during short period because of their narrow swath scanning when applying semi-empirical model. This gives a difficulty to run BRDF model inferring the reflectance normalization of high resolution satellites. The principal purpose of the study is to estimate normalized reflectance of high resolution satellite (RapidEye) through BRDF components from SPOT/VGT. We use semi-empirical BRDF model to estimated BRDF components from SPOT/VGT and reflectance normalization of RapidEye. This study used SPOT/VGT satellite data acquired in the S1 (daily) data, and within this study is the multispectral sensor RapidEye. Isotropic value such as the normalized reflectance was closely related to the BRDF parameters and the kernels. Also, we show scatter plot of the SPOT/VGT and RapidEye isotropic value relationship. The linear relationship between the two linear regression analysis is performed by using the parameters of SPOTNGT like as isotropic value, geometric value and volumetric scattering value, and the kernel values of RapidEye like as geometric and volumetric scattering kernel Because BRDF parameters are difficult to directly calculate from high resolution satellites, we use to BRDF parameter of SPOT/VGT. Also, we make a decision of weighting for geometric value, volumetric scattering value and error through regression models. As a result, the weighting through linear regression analysis produced good agreement. For all sites, the SPOT/VGT isotropic and RapidEye isotropic values had the high correlation (RMSE, bias), and generally are very consistent.

• Journal of the Korean Chemical Society
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• v.31 no.1
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• pp.3-13
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• 1987

Infrared absorption spectra of alkyl alcohols in the OH stretching region were obtained from varying the concentrations of alcohols in $CCl_4$. The OH stretching bands were broadened and shifted to lower frequencies due to the hydrogen-bond formation. Three bands were obtained from the breakdown of these bands by the simplex method. Each band was assigned to various types of hydrogen-bonded OH groups. The electronic structures and interaction energies of dimeric and trimeric alcohols were calculated by semi-empirical MO(CNDO/2, INDO) methods. These results were in good agreement with those of deconvoluted ir spectra. The EDA(electron donor-acceptor) effect of alkyl group on hydrogen-bond formation was in the decreasing order of butyl > propyl > ethyl > methyl group. On the other hand, the experimental results were in the order : propyl > ethyl > butyl > methyl group. This seemed to be ascribed to the bulkiness of butyl alcohol.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.177-183
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• 2013

As the development of available binder in the harsh conditions is needed, we propose the proper binder for high-voltage lithium-ion secondary batteries based on the quantum chemistry modeling. The optimized structures, HOMO (Highest Occupied Molecular Orbital) energies and ionization potentials of 4 binders, which were considered from monomer to tetramer, were investigated by the semi-empirical and DFT (Density Functional Theory) calculations. The results show that the ionization potential values by calculation tend to be close to the oxidation potentials from the measurement of linear sweep voltametry (LSV). The order of oxidative resistance from high value to low value is following: poly(hexafluropropylene), poly(vinylidene fluoride), poly(methyl acrylate) and poly(acryl amide). Also these results correspond with the experimental values. Thus, we find the reason why HOMO (Highest Occupied Molecular Orbital) energy of PHFP has the highest value than other binders by analysis of HOMO orbital structures.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.11
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• pp.901-907
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• 2021

The present study introduces an artificial neural network (ANN) that can predict the missile aerodynamic coefficients for various missile nose shapes and flow conditions such as Mach number and angle of attack. A semi-empirical missile aerodynamics code is utilized to generate a dataset comprised of the geometric description of the nose section of the missiles, flow conditions, and aerodynamic coefficients. Data normalization is performed during the data preprocessing step to improve the performance of the ANN. Dropout is used during the training phase to prevent overfitting. For the missile nose shape and flow conditions not included in the training dataset, the aerodynamic coefficients are predicted through ANN to verify the performance of the ANN. The result shows that not only the ANN predictions are very similar to the aerodynamic coefficients produced by the semi-empirical missile aerodynamics code, but also ANN can predict missile aerodynamic coefficients for the untrained nose section of the missile and flow conditions.