• Korean Journal of Optics and Photonics
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• v.26 no.2
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• pp.103-109
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• 2015

In an amplitude-splitting interferometer, a beam splitter divides an input beam into two parts, which are superposed after propagating along separate paths, producing an interference effect. We have investigated the phase relation between the reflected and transmitted light waves at BS's made of lossless dielectric stacks. If we define the phases with proper reference planes, a definite phase relation exists, irrespective of the detailed structure of the layers in the BS. Although this results from the generalized Stokes relations, we have verified it numerically for two representative BS's with symmetric and asymmetric layer structures respectively. When we applied the phase relation to interferometers, we could determine the superposition state of the output beam (either constructive or destructive interference) for a general BS, and could verify that the light's energy was conserved.

• Journal of Soil and Groundwater Environment
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• v.18 no.5
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• pp.56-64
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• 2013

After the law has been enacted for the prevention and recovery of mining damage in 2005, efforts of remediation have been started to recover heavy metal contaminated soils in agricultural land near mining sites. As part of an effort, the upper part of cultivation layer has been treated through covering up with clean soil, but the heavy metal contamination could be still spreaded to the surrounding areas because heavy metals may be remained in the lower part of cultivation layers. In this study, the most frequently occurring arsenic (As) contamination was selected to study in agricultural land nearby an abandoned metal mining site. We applied separation technologies considering the differences in the physical characteristics of soil particles (particle size, density, magnetic properties, hydrophobicity, etc.). Based on physical and chemical properties of arsenic (As) containing particles in agricultural lands nearby mining sites, we applied sieve separation, specific gravity separation, magnetic separation, and flotation separation to remove arsenic (As)-containing particles in the contaminated soil. Results of this study show that the removal efficiency of arsenic (As) were higher in the order of the magnetic separation, flotation separation, specific gravity separation and sieve separation.

• Journal of Soil and Groundwater Environment
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• v.25 no.2_spc
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• pp.86-100
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• 2020

Analyzing and monitoring environmental contaminants based on geophysical exploration techniques have become important and it is now widely applied to delineate spatial distribution geophysical characteristics in wide area. Among the techniques, induced polarization (IP) method, which measures polarization effects on electrical potential distribution, has drawn much attention as an effective tool for environmental monitoring since IP is sensitive to changes in biochemical reactions. However, various reactions stemming from the presence of multiple contaminants have greatly enhanced heterogeneity of polluted sites to result in highly variable electrical characteristics of the site. Those contaminants influence chemical and physical state of soil and groundwater to alter electrical double layer, which in turn influences polarization of the media. Since biochemical reactions between microbes and contaminants result in various IP effects, IP laboratory experiments were conducted to investigate IP responses of the contaminated soil samples under various conditions. Field IP surveys can delineate the spatial distribution of contamination, while providing additional information about electrical properties of a target medium, together with DC resistivity. Reviewing IP effects of contaminants as well as IP surveys can serve as a good starting point for the application of IP survey in site assessment for environmental remediation.

• Journal of Plant Biology
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• v.25 no.2
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• pp.83-99
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• 1982

In this study, thirty-two stands in Kwangnung forest located in the central part of Korea were preferentially selected. In each stand, all stems for trees and shrubs were recorded by species and their girths were measured down to 5cm. In addition, several enviromental factors such as field soil pH, field soil moisture, soil compressibility, depth of soil, thickness of litter layer, elevation and basal area were measured. Three soil cores were sampled and various physical and chemcial properties was determined. The vegetational data were subjected to three kinds of multivariate ordination(PO, PCA, RA). The results suggested that Kwangnung forest was consisted of three forest types: coniferous, mixed and broad leaved forest communities. The relation between the stand scores of ordination and several environmental factors were investigated in terms of correlation analysis in order to examine the relationships between the vegetation and certain environmental factors. As a result of this analysis, the amount of sand content in A1 horizon decreased frm the coniferous to broad leaved forest, while maximum field capacity, pore space, exchangeable cations, loss on ignition, soil pH nad the amount of total nitrogen had a tendancy to increase significantly. However, easily soluble phosphorus appeared to have little to do with the forest types. The result of species ordination of centered-standardized PCA suggested that the major successional pathway in Kwangnung forest was; Pinus densifloralongrightarrowQuercus mongolica, Q. serrata, Q. alienalongrightarrowCarpinus laxifloralongrightarrowC. erosa in sequence. This trend is in good agreement with the past studies. In three kinds of ordination (centered PCA, centered-standardized PCA and RA) based on nineteen species and twenty-five stands, the total variances accounted for the first three axes were 77%, 46% and 63% respectively. The estimated beta diversity in Kwangnung forest assumed as a coenocline, was 1.5~1.8 HC. Increasing the effect of the sampling errors on ordination perfermance, this low heterogeneity seems to cause the poor concentration of the total variance. The results from the four kinds of ordination were in good agreement with each other, especially between PO, centered-standardized PCA and RA appeared robust. It seems to be worthy of applying multivariate method for analyzing other forest communities in Korea.

• Journal of the Korean institute of surface engineering
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• v.54 no.5
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• pp.230-237
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• 2021

In this study, the influence of silicon contents on the microstructure, mechanical and tribological properties of Ti-Al-Si-N coatings were systematically investigated for application of cutting tools. The composition of the Ti-Al-Si-N coatings were controlled by different combinations of TiAl₂ and Ti₄Si composite target powers using an arc ion plating technique in a reactive gas mixture of high purity Ar and N₂ during depositions. Ti-Al-Si-N films were nanocomposite consisting of nanosized (Ti,Al,Si)N crystallites embedded in an amorphous Si₃N₄/SiO₂ matrix. The instrumental analyses revealed that the synthesized Ti-Al-Si-N film with Si content of 5.63 at.% was a nanocomposites consisting of nano-sized crystallites (5-7 nm in dia.) and a three dimensional thin layer of amorphous Si₃N₄ phase. The hardness of the Ti-Al-Si-N coatings also exhibited the maximum hardness value of about 47 GPa at a silicon content of ~5.63 at.% due to the microstructural change to a nanocomposite as well as the solid-solution hardening. The coating has a low friction coefficient of 0.55 at room temperature against an Inconel alloy ball. These excellent mechanical and tribological properties of the Ti-Al-Si-N coatings could help to improve the performance of machining and cutting tool applications.

• Tribology and Lubricants
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• v.37 no.4
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• pp.144-150
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• 2021

The most cost-effective method of reducing abrasive wear in mechanical parts is increasing their hardness with thin hard coatings. In practice, the composite hardness of the coated substrate is more important than that of the substrate or coating. After full unloading of the load applied to an indenter, its indentation hardness evaluated based on the dent created on the test piece was almost dependent on plastic deformation of the substrate. Following the first part of this study, which proposes a new Brinell hardness test method for a coated surface, the remainder of the study is focused on practical application of the method. Indentation analyses of a rigid sphere and elastic-perfect plastic materials were performed using finite element analysis software. The maximum principal stress and plastic strain distributions as well as the dent shapes according to the substrate yield stress and coating thickness were compared. The substrate yield stress had a significant effect on the dent size, which in turn determines the Brinell hardness. In particular, plastic deformation of the substrate produced dents regardless of the state of the coating layer. The hardness increase by coating behaved differently depending on the substrate yield stress, coating thickness, and indentation load. These results are expected to be useful when evaluating the composite hardness values of various coated friction surfaces.

• Molecules and Cells
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• v.44 no.10
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• pp.736-745
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• 2021

Although various marine ingredients have been exploited for the development of cosmetic products, no previous study has examined the potential of seaweed extracellular vesicles (EV) in such applications. Our results revealed that EV from Codium fragile and Sargassum fusiforme effectively decreased α-MSH-mediated melanin synthesis in MNT-1 human melanoma cells, associated with downregulation of MITF (microphthalmia-associated transcription factor), tyrosinase and TRP1 (tyrosinase-related proteins 1). The most effective inhibitory concentrations of EV were 250 ㎍/ml for S. fusiforme and 25 ㎍/ml for C. fragile, without affecting the viability of MNT-1 cells. Both EV reduced melanin synthesis in the epidermal basal layer of a three-dimensional model of human epidermis. Moreover, the application of the prototype cream containing C. fragile EV (final 5 ㎍/ml) yielded 1.31% improvement in skin brightness in a clinical trial. Together, these results suggest that EV from C. fragile and S. fusiforme reduce melanin synthesis and may be potential therapeutic and/or supplementary whitening agents.

• International journal of advanced smart convergence
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• v.10 no.3
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• pp.257-278
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• 2021

As the definition of the vendor-oriented implementation method, which was utilized in adopting an ERP system, has been centered around the project construction business, it was difficult for the EPR adopting organization to systematically prepare ERP projects and have enough deliberative opportunities to change-related policies. Furthermore, this method does not have a fully standardized construction process. Accordingly, by defining an organization that wants to adopt an ERP system as a customer, this paper develops the customer-based ERP construction process framework that assists both customers and developers who construct the system. For this purpose, this paper reviews the previous research and collects the construction processes of the commercial ERP SW vendor and ERP construction cases while proposing the three-layer process framework to construct ERP through the KJ method. The ERP process framework consists of 7 processes, 32 activities, 141 tasks while providing definitions for concepts of each component. Furthermore, the proposed processes and phases were set in order of the recommended execution, while the activities were suggested as an open-ended type so that the application and usability can be increased and polished by reflecting experts' opinions. The contribution of this study is to standardize the ERP project process by transforming the previous supplier-based ERP construction method into the customer-based one while providing important procedure and activity frameworks that apply to diverse ERP solutions per vendor. At the same time, this study provides an theoretical foundation to develop the construction process for the customer -based Cloud ERP. In practice, At the beginning of the ERP system construction project, it provides communication or process tailoring tools for the stakeholder.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.279-286
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• 2021

Recently, the effort of enterprises are visualized to correspond for 4th industrial revolution and climate change. Reaching the operation of industrial facilities are one of these efforts and is actively progressing under identical condition between real and virtual world through introduction of cyber-physical system (CPS). However, the problem on no unified definition for CPS still exists. Thus, in this paper, we review the previous concept of CPS. We propose new concept of CPS with four sections such as real world section, communication section, virtual world section and management section. We also propose definite concept by classifying the layer of each section. In order to confirm the possibility of application for proposed concept of CPS, we applied simple motor. We compare the result for torque between real motor and virtual motor. Finally we confirm that the applicability of proposed concept of CPS is very high.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.3
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• pp.207-212
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• 2019

A flat-type piezoelectric ceramic ultrasonic transmitter was successfully fabricated for application in acoustic devices with cone-free diaphragms. The transmitter, possessing a center frequency of 40.6 kHz, exhibited a higher displacement characteristic for a multilayer type compared with a single layer type. Surface roughness treatment of an Al elastic diaphragm influenced a slight increase (1.1 dB) in the sound pressure level (SPL) at $10V_{rms}$ due to the enlarged surface area. The fabricated multilayer piezoelectric ceramic ultrasonic transmitter showed increasing SPL with increasing input voltage, with a maximum SPL of approximately 123.6 dB at $10V_{rms}$. This implies a doubly increased SPL density of $3.6dB/mm^3$, superior to that of a commercial open-type transmitter with a cone.