• Geomechanics and Engineering
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• v.17 no.6
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• pp.565-572
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• 2019

Spatial variability is an inherent characteristic of soil, and auto-correlation length (ACL) is a very important parameter in the reliability or probabilistic analyses of geotechnical engineering that consider the spatial variability of soils. Current methods for estimating the ACL need a large amount of laboratory or in-situ experiments, which is a great obstacle to the application of random field theory to geotechnical reliability analysis and design. To estimate the ACL reasonably and efficiently, we propose a micro-structure based numerical simulation method. The quartet structure generation set algorithm is used to generate stochastic numerical micro-structure of soils, and scanning electron microscope test of soil samples combined with digital image processing technique is adopted to obtain parameters needed in the QSGS algorithm. Then, 2-point correlation function is adopted to calculate the ACL based on the generated numerical micro-structure of soils. Results of a case study shows that the ACL can be estimated efficiently using the proposed method. Sensitivity analysis demonstrates that the ACL will become stable with the increase of mesh density and model size. A model size of $300{\times}300$ with a grid size of $1{\times}1$ is suitable for the calculation of the ACL of clayey soils.

• Economic and Environmental Geology
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• v.27 no.5
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• pp.499-505
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• 1994

Local stress concentrations often cause new micro-damaging induced by a healed pre-existing defects, and the macro-damage is developed by propagation and coalescence of the micro-damage. The micro-damage causes non-linear deformation in rock material. Considerable work has also been applied to describe mathematically the behavior of cracks under stress. Although these mathematical models can usually be made to agree quite well with the measured data, but it is questionable how well the models describe real rock including microcracks in pre-failure state, such as their micro-damage mechanisms. In the present study, micro-damage initiation and propagation in granitic rock under increasing stress were observed directly. Furthermore, a stress analysis considering the bisphere model was carried out using the homogenization theory to analyze the mechanics of the stress-induced micro-damage.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.E
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• pp.29-38
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• 2000

For the detailed characterization of atmospheric aerosol, the analysis of single particle is highly valuable. In this study, to investigate the characteristics of single Asian dust storm particles, scanning electron microscope(SEM) coupled with and energy dispersive X-ray microanalyzer(EDX) and micro-PIXE were applied. Sampling was performed at Kyoto University located in Kyoto, Japan, in spring of 1999. Mass concentration during Asian dust storm events was higher roughly 3∼5 times than measured in the season of the highest concentration. Single particles were generally sharp-edged and irregular in shape and contained mostly crustal elements. Significant amount of S in coarse fraction was detected in individual particles. A large particles in coarse fraction existed as the mixture of soil components and S. A good agreement between the result of SEM-EDX analysis and that iof micro-PIXE analysis was obtained in this study.

• 대한예방의학회:학술대회논문집
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• 2004.02a
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• pp.65-69
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• 2004

• Journal of the Korean GEO-environmental Society
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• v.15 no.11
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• pp.29-42
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• 2014

This paper investigates the effects of micro-tunneling on buried pipelines parametrically. A simplified numerical approach was developed and various parametric studies have been conducted to evaluate the effects of ground settlements on the response of buried pipelines. The controlled parameters included the pipe stiffness, ground loss magnitude, and pipe location with respect to a micro-tunnel. Maximum settlement and curvature along a pipeline have been investigated and compared among others for different conditions. In addition, the numerical results have been compared with a theoretical method by Attewell et al. (1986), which is based on a Winkler type linear-elastic solution. The comparison indicated that the response of buried pipes to micro-tunneling-induced ground settlements highly depends on the soil-pipe interaction including the separation and slippage of pipe from soil with the effects of the investigated parameters. Therefore, rather than using the theoretical method directly, it would be a better assessment of the response of buried pipelines to consider the soil-pipe interaction in more realistic conditions.

• The Journal of Industrial Distribution & Business
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• v.9 no.12
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• pp.23-29
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• 2018

Purpose - The purpose of this study is to apply a cost effective ultrasonic odor reduction method that generated micro-bubbles using ejector to the Southeast Asian wastewater market. Research design, data, and methodology - A leather maker located in Ansan-city, Gyunggi-do, South Korea was sampled from the collection tank to select experimental materials. Experimental setup consisted of circulating water tank-air ejector-ultrasonic device, and circulating wastewater. Sample analysis was performed by CODcr, T-N, T-P, and turbidity by the National Environmental Science Institute. Results - Experimental results show that it is most effective in removing odors when the frequency range of ultrasonic wave is 60~80 Khz and the output is 200 W. It showed that the concentration of complex odor dropped from a maximum of 14,422 times to a minimum of 120 times. Also, analysis of ammonia and hydrogen sulfide in specific odor substances has shown that they were reduced from 1.5 ppm to 0.4 ppm and from 0.6 ppm to 0.1 ppm, respectively. Conclusions - It is possible to shorten more than 12 hours in the treatment of micro-organisms. It can be seen that the processing time of odor after ultrasonic treatment in the pre-treatment facility is reduced by 25% when compared to the resultant micro-organisms after the chemical treatment, that is, the time of the bio-treatment of micro-organisms. Based on the results, it was confirmed that the pre-treatment method using the ultrasonic and the air ejector device of the experiment shows the effect of reducing the water pollutants and odor more effectively in a relatively short time than the conventional advanced oxidation method.

• Structural Engineering and Mechanics
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• v.71 no.5
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• pp.485-502
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• 2019

In this research, the nonlinear static, buckling and vibration analysis of viscoelastic micro-composite beam reinforced by various distributions of boron nitrid nanotube (BNNT) with initial geometrical imperfection by modified strain gradient theory (MSGT) using finite element method (FEM) are presented. The various distributions of BNNT are considered as UD, FG-V and FG-X and also, the extended rule of mixture is used to estimate the properties of micro-composite beam. The components of stress are dependent to mechanical, electrical and thermal terms and calculated using piezoelasticity theory. Then, the kinematic equations of micro-composite beam using the displacement fields are obtained. The governing equations of motion are derived using energy method and Hamilton's principle based on MSGT. Then, using FEM, these equations are solved. Finally the effects of different parameters such as initial geometrical imperfection, various distributions of nanotube, damping coefficient, piezoelectric constant, slenderness ratio, Winkler spring constant, Pasternak shear constant, various boundary conditions and three material length scale parameters on the behavior of nonlinear static, buckling and vibration of micro-composite beam are investigated. The results indicate that with an increase in the geometrical imperfection parameter, the stiffness of micro-composite beam increases and thus the non-dimensional nonlinear frequency of the micro structure reduces gradually.

• Journal of Microbiology and Biotechnology
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• v.26 no.12
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• pp.2116-2126
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• 2016

Bacterial biofilms are spatially structured communities that contain bacterial cells with a wide range of physiological states. The spatial distribution and speciation of copper in unsaturated Pseudomonas putida CZ1 biofilms that accumulated 147.0 mg copper per g dry weight were determined by transmission electron microscopy coupled with energy dispersive X-ray analysis, and micro-X-ray fluorescence microscopy coupled with micro-X-ray absorption near edge structure (micro-XANES) analysis. It was found that copper was mainly precipitated in a $75{\mu}m$ thick layer as copper phosphate in the middle of the biofilm, while there were two living cell layers in the air-biofilm and biofilm-medium interfaces, respectively, distinguished from the copper precipitation layer by two interfaces. The X-ray absorption fine structure analysis of biofilm revealed that species resembling $Cu_3(PO_4)_2$ predominated in biofilm, followed by Cu-Citrate- and Cu-Glutathione-like species. Further analysis by micro-XANES revealed that 94.4% of copper were $Cu_3(PO_4)_2$-like species in the layer next to the air interface, whereas the copper species of the layer next to the medium interface were composed by 75.4% $Cu_3(PO_4)_2$, 10.9% Cu-Citrate-like species, and 11.2% Cu-Glutathione-like species. Thereby, it was suggested that copper was initially acquired by cells in the biofilm-air interface as a citrate complex, and then transported out and bound by out membranes of cells, released from the copper-bound membranes, and finally precipitated with phosphate in the extracellular matrix of the biofilm. These results revealed a clear spatial pattern of copper precipitation in unsaturated biofilm, which was responsible for the high copper tolerance and accumulation of the biofilm.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.3
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• pp.274-278
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• 1999

Determination of soil texture, particularly the clay fraction, is an important measurement in most researches related with soil. In this study micro-pipette method For soil particle size analysis was compared with the standard hydrometer method. Micro-pipette method can eliminate the need for bulky laboratory equipment and long settling times associated with the standard hydrometer or pipette method. In the results of this investigation, the particle size data obtained with micro-pipette method were in good agreement with those found using standard hydrometer method. And with this method one person could run analysis much larger numbers of soil sample per day than with hydrometer method in relatively small laboratory space.

• Asian Journal of Atmospheric Environment
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• v.11 no.1
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• pp.54-60
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• 2017

Quantifying the trace elements in infinitesimal ambient liquid samples (e.g., single raindrop, cloud/fog water, and the soluble fraction extracted from the particles collected for a short time) is an important task for understanding formation processes, heating/cooling rates, and their health hazards. The purpose of this study is to employ an in-air micro PIXE system for quantitative analysis of the trace elements in a thimbleful of reference liquid sample. The bag type liquid sample holder originally designed with $10{\mu}m$ thick $Mylar^{(R)}$ film retained the original shape without any film perforation and apparent peaks of film blank by the end of the analysis. As one of tasks to be solved, the homogeneity of the elemental distribution in liquid reference species was verified by the X-ray line profiles for several references. It was possible to resolve the significant peaks for whole target elements corresponding to the channel number of micro-PIXE spectrum. The calibration curves for the six target elements (Si, S, Cl, Fe, Ni, and Zn) in standard solutions were successfully plotted by concentration (ppm) and ROI of interest net counts/dose (nC).