• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.4
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• pp.239-245
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• 2014

Finite element modeling of composite structures may be cumbersome due to complex distributions of reinforcements. In this paper, an efficient scheme is proposed that can generate periodic meshes for the composite structures. Regular meshes with hexahedral finite elements are first prepared, and the elements are then trimmed to fit external surfaces of reinforcements in the composite structures. The trimmed hexahedral finite elements located at interfaces between the matrix and the reinforcements correspond to polyhedral finite elements, which allow an arbitrary number of nodes and faces in the elements. Because the trimming process is consistently conducted by means of consistent algorithms, the elements of the reinforcements are automatically compatible with those of the matrices. With the additional consideration of periodicity of reinforcements in a representative volume element(RVE), the proposed scheme provides periodic meshes in an efficient manner, which are compatible for each pair of periodic boundaries of the RVE. Therefore, periodic boundary conditions for the RVE are enforced straightforwardly. Numerical examples demonstrate the effectiveness of the proposed scheme for finite element modeling of complex composite structures.

• Journal of Radiation Protection and Research
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• v.16 no.2
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• pp.41-54
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• 1991

This paper aimed to analyse dose sensitivity to the controllable parameters of indoor radon $(^{222}Rn)$ and its decay products (Rn-D) by applying the input~output linear system theory. Physical behaviors of $^{222}Rn\;&\;Rn-D$ were analyzed in terms of $(^{222}Rn)$ gas -generation, -migation and -infiltration to indoor environments, and the performance output-function, i. e. mean dose equivalent to Tracho-Bronchial (TB) lung region, was assessed to the following extented ranges of the controllable paramenters; a) the ventilation rate $constant({\lambda}_v)\;:\;0{\sim}50[h^{-l}].\;b)$ the attachment rate $constant({\lambda}_a)\;:\;0{\sim}500[h^{-l}].\;c)$ the unattached-deposition rate constant (${\lambda}^u_d)\;:\;0-50[h-l]$. A linear input-output model was reconstructed from the original models in literatures, as follows, which was modified into the matrices consisting of 111 nodal equations; a) indoor $^{222}Rn\;&\;Rn-D$ Behaviour; Jacobi-Porstendoerfer-Bruno model.

• Child Health Nursing Research
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• v.21 no.1
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• pp.20-27
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• 2015

Purpose: The purpose of this study was to investigate factors affecting childhood asthma and atopic dermatitis. Methods: For this study, data for 1,170 children (1-11 years) from the Fifth Korean National Health and Nutrition Examination Survey (KNHANES V-2, 2011) were analyzed. First correlation matrices were computed to test the normality of every data set and then to be in accordance with the real demographic composition, data were added weight before being analyzed. Results: The child with asthma of a three generation family (OR=3.91, 95% CI [1.33, 11.45], p=.013) compared with a two generation family showed higher asthma development, and maternal asthma (OR=9.71, 95% CI [2.66, 35.40], p=.001) showed higher asthma development in child. The only factor affecting atopic dermatitis was parental perceptions of child health: poor (OR=3.40, 95% CI [1.29, 8.98], p=.014). Conclusion: These results suggest that childhood asthma and atopic dermatitis are both affected by parental perceptions of child health. Accordingly, management and support programs for children who have asthma and/or atopic dermatitis and their families should be comprehensive and also give attention to any other health problems because health perception represents quality of life.

• Journal of Adhesion and Interface
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• v.7 no.2
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• pp.1-11
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• 2006

Interfacial evaluation of the untreated and treated Jute and Hemp fibers reinforced different matrix polypropylene-maleic anhydride polypropylene copolymer (PP-MAPP) composites were investigated by micromechanical technique and dynamic contact angle measurement. For the statistical tensile strength of Jute and Hemp fibers, bimodal Weibull distribution was fitted better than the unimodal distribution. The acid-base parameter on the interfacial shear strength (IFSS) of the natural fiber composites was characterized by calculating the work adhesion, $W_a$. The effect of alkaline, silane coupling agent on natural fibers were obtained with changing MAPP content in PP-MAPP matrices. Alkaline treated fibers made the surface energy to be higher due to removing the weak boundary layers and thus increasing surface area, whereas surface energy of silane treated Jute and Hemp fibers decreased due to blocked high energy sites. MAPP in the PP-MAPP matrix caused the surface energy to increase due to introduced acid-base sites. Microfailure modes of two natural fiber composites were observed clearly differently due to different tensile strength of natural fibers.

• Korean Journal of Environmental Agriculture
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• v.22 no.4
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• pp.284-289
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• 2003

Titanium mesoporous materials have received increasing attention as a new photocatalyst in the field for photocatalytic degradation of organic compounds. The photocatalytic degradation of chlorothalonil by mesoporous titanium oxo-phoswhate (Ti-MCM) was investigated in aqueous suspension for comparison with $TiO_2$, (Degussa, P25) using as an effective photocatalyst of organic pollutants. Mesoporous form of titanium Phosphate has been prepared by reaction of sulfuric acid and titanium isopropoxide in the presence or n-hexadecyltrimethylammonium bromide. The XRD patterns of Ti-MCM are hexagonal phases with d-spacings of 4.1 nm. Its adsorption isotherm for chlorothalonil reached at reaction equilibrium within 60 min under dark condition with 28% degradation efficiency. The degradation ratio of chlorothalonil after 9 hours under the UV radiation condition (254 nm) exhibited 100% by Ti-MCM and 88% by $TiO_2$. However, these degradation kinetics in static state showed a slow tendency compared to that of stirred state because of a low contact between titanium matrices and chlorothalonil. Also, degradation efficiency of chlorothalonil was increased with decreasing initial concentration and with increasing pH of solution. As results of this study, it was clear that mesoporous titanium oxo-phosphate with high surface area and crystallinity could be used to photo- catalytic degradation of various organic pollutants.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.4
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• pp.349-356
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• 2010

Ion chromatography (IC) coupled with conductivity detector (CD) is a common system for the determination of perchlorate in water samples. Although the IC method with CD has been widely used for the determination of trace level perchlorate ion in water, sensitivity decreases dramatically as the complexity of the matrices increases. Here we proposed the application of ion chromatography coupled with mass spectrometry (IC-MS/MS) to significantly improve selectivity of perchlorate. The mean recovery of the method was 104.4 ${\pm}$ 5.7% and the relative standard deviation (RSD%) was 1.9 ${\pm}$ 1.3%. The alculated method detection limit (MDL) was 0.0207 ${\pm}$ 0.0099 ${\mu}g/L$. The concentrations of perchlorate were minimum <0.1 ${\mu}g/L$ and maximum 18.3 ${\mu}g/L$ in source water (Namhan, Bukhan and Han River). Hongreung showed higher concentrations ($1^{st}$-14.3 ${\mu}g/L$, $2^{st}$-18.3 ${\mu}g/L$) than the other places. And the concentrations of perchlorate were 0.18~0.34 ${\mu}g/L$ in the samples taken from the six water treatment plants and six intake stations in Seoul.

• Journal of Broadcast Engineering
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• v.13 no.1
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• pp.174-184
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• 2008

Complementary color filter array (CCFA) is widely used in consumer-level digital video cameras, since it not only has high sensitivity and good signal-to-noise ratio in low-light condition but also is compatible with the interlaced scanning used in broadcast systems. However, the full-color images obtained from CCFA suffer from the color artifacts such as false color and zipper effects. These artifacts can be removed with edge-adaptive demosaicking (ECD) approaches which are generally used in rrimary color filter array (PCFA). Unfortunately, the unique array pattern of CCFA makes it difficult that CCFA adopts ECD approaches. Therefore, to apply ECD approaches suitable for CCFA to demosaicking is one of the major issues to reconstruct the full-color images. In this paper, we propose a new ECD algorithm for CCFA. To estimate an edge direction precisely and enhance the quality of the reconstructed image, a function of spatial variances is used as a weight, and new color conversion matrices are presented for considering various edge directions. Experimental results indicate that the proposed algorithm outperforms the conventional method with respect to both objective and subjective criteria.

• The Korean Journal of Pesticide Science
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• v.9 no.4
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• pp.292-302
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• 2005

Condition of Ion-Trap gas chromatography-mass spectrometry (GC-MS) for rapid screening of 206-pesticides residues in agricultural foodstuffs was optimized. As applying a wide-bore column (10 m${\times}$0.53 mm, DF 0.25 um) connected with a fused silica restrictor (0.6 m${\times}$0.1 mm), a significant retention time reduction was obtained. Additionally, the shape of peaks was sharper and higher than classical GC's and GC-MS's, which allowed lower detection limits. To easily manage many spectral data, both of Electron Ionization(EI) and Chemical Ionization(CI) techniques were adopted in screening procedure. At the following steps, MS-MS technique were used to confirm screened analytes in complicated matrices.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.151-163
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• 2008

A formulation of three-dimensional model of articulated train-b ridge dynamic interaction has been made for the Korean eXpress Train (KTX). Semi-periodic profiles of rail irregularities consisting of elevation, alignment, cross and gauge irregularities have also been proposed using FRA maximum tolerable rail deviations. The effects of rail joints and sleeper step were also included. The resulting system matrices of train and bridge are very spare, and thus, are stored in one-dimensional arrays, yielding a time-efficient solution. A numerical algorithm for computing bridge-train response including an iterative scheme is also formulated. A program simulating train-bridge interaction and solving this problem using the new algorithm is implemented as new modules for the f inite element analysis software named XFINAS. Computed results using the new program are then checked by that of the validated 2-D bridge-train interaction model. This new 3D analysis provides more detailed train responses such as swaying, bouncing, rolling, pitching and yawing accelerations, which are useful inevaluating passenger riding comfort. Train operation safety and derailment could also be directly investigated by relative wheel displacements computed from this program.

• Korean Journal of Food Science and Technology
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• v.48 no.5
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• pp.454-460
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• 2016

In this study, we investigated the possibility of Droplet digital PCR (ddPCR) for detection of foodborne pathogens. ddPCR combines partitioning of PCR reactions into several thousands or millions of individual droplets in a water-oil emulsion, and counting of positive PCR reaction using flow cytometry. Four species of foodborne pathogens, Bacillus cereus, Staphylococcus aureus, Salmonella Typhimurium and Escherichia coli O157:H7, were used to quantify the target sequence with each of the designed primers and double stranded DNA-binding Evagreen dye. All tested foodborne pathogens showed a detection limit ranging from $100fg/{\mu}L$ to $10ng/{\mu}L$. It was concluded that ddPCR could be used to detect very low concentrations of foodborne pathogens from complex food matrices. For multi-detection of target pathogens, we also tested the samples using multiplex ddPCR and obtained successful results.