• Geomechanics and Engineering
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• v.18 no.6
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• pp.605-614
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• 2019

The present paper seeks to investigate propagation and reflection of waves at free surfaces of homogeneous, anisotropic and rotating micropolar fibre-reinforced medium with voids. It has been observed that, in particular when P-wave is incident on the free surface, there exist four coupled reflected plane waves traveling in the medium; quasi-longitudinal displacement (qLD) wave, quasi-transverse displacement (qTD) wave, quasi-transverse microrotational wave and a wave due to voids. Normal mode Analysis usually called harmonic solution method is adopted in concomitant with Snell's laws and appropriate boundary conditions in determination of solution to the micropolar fibre reinforced modelled problem. Amplitude ratios which correspond to reflected waves in vertical and horizontal components are presented analytically. Also, the Reflection Coefficients are presented using numerical simulated results in graphical form for a particular chosen material by the help of Mathematica software. We observed that the micropolar fibre-reinforced, voids and rotational parameters have various degrees of effects to the modulation, propagation and reflection of waves in the medium. The study would have impact to micropolar fibre-reinforecd rotational-acoustic machination fields and future works about behavior of seismic waves.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.268-277
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• 1998

The numerical procedure for calculating non-uniform residual stress fields by using relieved strain data from incremental hole drilling method is presented. Finite element calculations are described to evaluate the relieved coefficients required for the determination of residual stresses. From the results of simulations it is found that this numerical method is well adopted to measuring non-uniform residual stress in the hole depth range of 0.8 times of the hole diameter from the surface. In order to examine the practicability of this method, the hole drilling procedure for the four point bending test is performed. This method is applied to the measurement of residual stresses in the cold-rolled steel pipe. It is shown that the magnitude of residual stress in the pipe is not negligible when compared with yield stress and the residual stress should be duly considered in designing structures with this pipes.

• Journal of the Korean Society of Tobacco Science
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• v.31 no.1
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• pp.45-50
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• 2009

In this study, a simple gradient RRLC method for rapid determination of carbonyl compounds of cigarette smoke was developed. Within 10 min, 8 carbonyl compounds have been separated and identified on ZORBAX Eclipse XDB-C18 column ($4.6{\times}50\;mm$, $1.8\;{\mu}m$) with gradient elution using water and acetonitrile as a mobile phase. RRLC was used for the quantification of carbonyl compounds in mainstream smoke of 3R4F reference cigarette, and evaluated those efficiencies in the recovery, repeatability and reproducibility. The correlation coefficients ($r^2$) for calibration curves of carbonyl compounds were over 0.9998. The developed RRLC method was successfully applied to the analysis of smoke samples and the recoveries of carbonyl compounds were in the range of 97.5~102.1% with RSD<3.1%.

• Natural Product Sciences
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• v.24 no.3
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• pp.206-212
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• 2018

Xanthii Fructus has been traditionally used for the treatment of rhinitis, rheumatoid arthritis, and eczema. In this study, a high-performance liquid chromatography-photodiode array (HPLC-PDA) method was developed and then used for the simultaneous analysis of eight phenylpropanoids in Xanthii Fructus. The analytical column used for this separation was a $SunFire^{TM}$ $C_{18}$ column, maintained at $40^{\circ}C$. The mobile phase used was 1.0% acetic acid in distilled water and 1.0% acetic acid in acetonitrile with gradient elution. For identify of each component, the mass spectrometer (MS) was used a Waters triple quadrupole mass spectrometer requipped with electrospray ionization (ESI) source. The HPLC-PDA method showed good linearity: correlation coefficients were ${\geq}0.9996$. The limits of detection and quantification of the eight compounds were 0.02 - 0.04 and $0.06-0.14{\mu}g/mL$, respectively. The extraction recoveries ranged from 97.51 to 108.67%. The relative standard deviation values of intra- and inter-day precision were 0.06 - 1.55 and 0.09 - 1.68%, respectively. The validated HPLC-PDA method was applied to simultaneously analyse the amounts of eight phenlypropanoids in Xanthii Fructus.

• International Journal of Highway Engineering
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• v.16 no.2
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• pp.11-18
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• 2014

PURPOSES : This study aims to develop a strength test method for irregularly shaped concrete block paver. METHODS : Ten (10) different types of concrete block pavers including porous and dense blocks were tested for strength capacities. Destructive and non-destructive methods were used to develop a strength test method for irregularly shaped concrete block paver. The flexural strength evaluation was conducted in accordance to KS F 4419, while compressive strength was conducted with a 45.7mm-diameter core specimen. The impact echo test method was used to evaluate the elastic modulus. Finally, regression analysis was used to investigate the relationship between flexural strength, compressive strength and elastic modulus based on their corresponding test results. RESULTS : The flexural strength of the tested block pavers ranged from 4MPa to 10MPa. At 95% confidence level, the coefficients of determination between compressive-flexural strength relationship and compressive strength-elastic modulus relationship were 0.94 and 0.84, respectively. These coefficients signified high correlation. CONCLUSIONS : Using the test method proposed in this study, it will be easier to evaluate the strength of irregularly shaped concrete block pavers through impact echo test and compressive test, instead of the flexural test. Relative to the flexural strength requirement of 5MPa, the minimum values of compressive strength and elastic modulus, as proposed, are 13.0MPa and 25.0GPa, respectively.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.362-369
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• 2005

Studying unsaturated soil mechanics, determination of soil water characteristic curve and permeability equation is an essential factor but it is not easy. In this research a new testing apparatus was developed to determine soil water characteristic curve and permeability equation. The testing to get saturated permeability coefficients and soil water characteristic curves for two soils was performed by using the developed testing apparatus. First, a saturated permeability testing was performed and then the testing to get soil water characteristic curve of a drying process was performed. Next, the testing to get soil water characteristic curve of a wetting process was performed. Testing results showed hysteresis phenomena between soil water characteristic curve of a drying process and soil water characteristic curve of a wetting process. The permeability equations were determined by a theoretical method where a saturated permeability coefficient and a soil water characteristic curve were used.

• Bulletin of the Korean Chemical Society
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• v.22 no.7
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• pp.685-688
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• 2001

A gas chromatography/mass spectrometric assay method has been developed for the simultaneous determination of benzidine (BZ), N-acetyl benzidine (ABZ) and N,N-diacetyl benzidine (DABZ) in rat urine. BZ, ABZ and DABZ were extracted from urine at pH 8 with ethyl ether. Conjugated urinary metabolites were extracted at pH 8 after hydrolysis with 1 M HCl for 30 min at 100 $^{\circ}C.$ The dried extract was dissolved in 100 ${\mu}{\ell}$ of ethylacetate and then injected in gas chromatography-mass spectrometric (GC-MS) system without further purification or modification. BZ, ABZ and DABZ have good chromatographic properties and offer very sensitive response for the EI-MS (SIM) without any derivatization. The recoveries for BZ, ABZ and DABZ were about 98.0, 81.8 and 71.4%, respectively, at pH 8.0 and the concentration of 5.0 ng/mL. The coefficients of variation of BZ and ABZ were less than 9.5% from 0.1 to 100 ng/mL and that of DABZ was less than 13% in the same concentration range. The detection limits of the assay were 0.01 ng/mL for both BZ and ABZ, and 0.05 ng/mL for DABZ in urine or plasma 1.0 mL.

• Korean Journal of Veterinary Research
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• v.48 no.1
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• pp.33-38
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• 2008

In veterinary medicine amitraz has been used as an insecticide to eliminates mites, lice, and ticks in dogs, cats, goats, swine and cattle. The objective of present study was to developed an analytical method using one-step extraction and determination of the amitraz in veterinary drugs by liquid chromatography (LC). The amitraz was analyzed by LC equipped with Waters XTerra RP18 ($4.8{\times}250mm;\;5{\mu}m;\;Waters,\;USA$) analytical column, using 75% acetonitrile (acetonitrile/D.W; 75/25) at 1.0 ml/ min. The UV-VIS detection of amitraz was made at 290 nm. Calibration graphs were linear with very good correlation coefficients ($r^2>0.9999$) from $80{\sim}120{\mu}g/ml$. The limit of detection was $0.09{\mu}g/ml $ and limit of quantification was $0.27{\mu}g/ml $. The method showed good intra-day precision (CV 0.05~0.09%) and inter-day precision (CV 0.06~0.18%).

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.770-774
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• 2006

The determination of feasible design flood is the most important to control flood damage in river management. Model parameters should be calibrated using observed discharge but due to deficiency of observed data the parameters have been adopted by engineer's empirical sense. Storage coefficient in the Clark unit hydrograph method mainly affects magnitude of peak flood. This study is to estimate the storage coefficients based on the observed rainfall-runoff events at the four stage stations in the Hantan river basin. Model calibration is the process of adjusting model parameter values until model results match historical data. An objective function which is the percent difference between the observed and computed peak flows is available for measuring the goodness-of-fit between computed and observed hydrographs. By sensitivity analysis for the storage coefficient, it has been shown that the storage coefficients affect the peak flows. The Clark parameters adopted in the River Rectification Basic Plan have been estimated through an iterative process designed to produce a hydrograph with the peak flow.

• Korea Trade Review
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• v.46 no.1
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• pp.169-187
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• 2021

This paper analyzes the feasibility of using machine learning and deep learning methods to forecast the income and employment using the strategic industries as well as investment, export, and exchange rates. The decision tree, artificial neural network, support vector machine, and deep learning models were used to forecast the income and employment in Busan. The following were the main findings of the comparison of their predictive abilities. First, the decision tree models predict the income and employment well. The forecasting values for the income and employment appeared somewhat differently according to the depth of decision trees and several conditions of strategic industries as well as investment, export, and exchange rates. Second, since the artificial neural network models show that the coefficients are somewhat low and RMSE are somewhat high, these models are not good forecasting the income and employment. Third, the support vector machine models show the high predictive power with the high coefficients of determination and low RMSE. Fourth, the deep neural network models show the higher predictive power with appropriate epochs and batch sizes. Thus, since the machine learning and deep learning models can predict the employment well, we need to adopt the machine learning and deep learning models to forecast the income and employment.