• Title/Summary/Keyword: microscopic structure

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Multi-scale simulation of drying process for porous materials using molecular dynamics (part 1 : homogenization method) (분자동역학을 이용한 다공성 물질 건조공정 멀티스케일 시뮬레이션(1부 : 균질화법 해석))

  • 오진원;백성민;금영탁
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.14 no.3
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    • pp.115-122
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    • 2004
  • When porous materials are dried, the particles flocculate into fish-net structure in gel phase. In order to exactly analyze the stress distribution of porous materials during drying process, the elastic tensor of microscopic gel structures has to be predicted considering pore shapes as well as porosities of porous materials. The elastic characteristics of porous materials associated with porosities were predicted analyzing microscopic gel structures with circular and cross pores via homogenization method and the drying processes of the electric porous ceramic insulator were simulated using finite element method (FEM). Comparing analysis results between consideration and negligence of pores, the deformed shape and distributions of temperature and moisture were similar but the residual stress was significantly different.

The effects of Graphene Oxide flakes on the mechanical properties of cement mortar

  • Kim, Boksun;Taylor, Lawrence;Troy, Andrew;McArthur, Matthew;Ptaszynska, Monika
    • Computers and Concrete
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    • v.21 no.3
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    • pp.261-267
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    • 2018
  • This paper discusses a study of cement mortar reinforced with Graphene Oxide (GO) flakes carried out at the University of Plymouth. Over 60 specimens were prepared and tested to obtain the tensile, compressive and flexural strengths of cement mortar with/without 0.5% GO flakes by weight of cement. The dispersion of the GO flakes and the effect of the use of polycarboxylate ether superplasticizer (0.2% by weight of cement) on the material strength are discussed. Images of the particle sizes of GO are presented from the transmission electron microscopy analysis. In addition, the images from the field emission scanning electron microscope analysis are also presented to show the difference of the microscopic structure of cement mortar with/without GO. The results of the strength tests are presented. It is shown that the inclusion of the GO flakes in general led to positive results, which suggest that GO improved the tensile, compressive and flexural strengths of cement mortar.

Light Scattering from Microscopic Structure and Its Role on Enhanced Haze Factor

  • Kang, Junyoung;Park, Hyeongsik;Yi, Junsin
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.340-340
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    • 2016
  • We have prepared alumina (Al2O3) doped zinc oxide (AZO) films by DC magnetron sputtering (MS) technique and obtained higher self surface texturing at a high target angle (f). We have characterized the films and applied it as a front electrode of a single junction amorphous silicon solar cell. At a lower f the deposited films show higher values of optical gap (Eg), charge carriers mobility & concentration, crystallite grain size and wider wavelength range of transmission. At higher target angle the sheet resistance, surface roughness, haze factor etc for the films increase. For f=72.5o the haze factor for diffused transmission becomes 6.46% at 540 nm wavelength. At f=72.5o the material shows a reduction in crystallinity and evolution of a hemispherical-type sub-micron surface textures. A Monte Carlo method (MCM) of simulation of the AZO film deposition shows that such an enhanced self-surface texturing of the films at higher f is possible.

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Spray Characteristics on the Electrostatic Rotating Bell Applicator

  • Im, Kyoung-Su;Lai, Ming-Chia;Yoon, Suck-Ju
    • Journal of Mechanical Science and Technology
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    • v.17 no.12
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    • pp.2053-2065
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    • 2003
  • The current trend in automotive finishing industry is to use more electrostatic rotating bell (ESRB) need space to their higher transfer efficiency. The flow physics related with the transfer efficiency is strongly influenced by operating parameters. In order to improve their high transfer efficiency without compromising the coating quality, a better understanding is necessary to the ESRB application of metallic basecoat painting for the automobile exterior. This paper presents the results from experimental investigation of the ESRB spray to apply water-borne painting. The visualization, the droplet size, and velocity measurements of the spray flow were conducted under the operating conditions such as liquid flow rate, shaping airflow rate, bell rotational speed, and electrostatic voltage setting. The optical techniques used in here were a microscopic and light sheet visualization by a copper vapor laser, and a phase Doppler particle analyzer (PDPA) system. Water was used as paint surrogate for simplicity. The results show that the bell rotating speed is the most important influencing parameter for atomization processes. Liquid flow rate and shaping airflow rate significantly influence the spray structure. Based on the microscopic visualization, the atomization process occurs in ligament breakup mode, which is one of three atomization modes in rotating atomizer. In the spray transport zone, droplets tend to distribute according to size with the larger drops on the outer periphery of spray. In addition, the results of present study provide detailed information on the paint spray structure and transfer processes.

Characterization of nano-structure pyrolytic char for smart and sustainable nanomaterials

  • N. K. Karthikeyan;S. Elavenil
    • Advances in nano research
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    • v.16 no.1
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    • pp.53-69
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    • 2024
  • Advancements in the technology of building materials has led to diverse applications of nanomaterials with the aim to monitor concrete structures. While there are myriad instances of the use of nanoparticles in building materials, the production of smart nano cement-composites is often expensive. Thereupon, this research aims to discover a sustainable nanomaterial from tyre waste using the pyrolysis process as part of the green manufacturing circle. Here, Nano Structure Tyre-Char (NSTC) is introduced as a zero-dimension carbon-based nanoparticle. The NSTC particles were characterized using various standard characterization techniques. Several salient results for the NSTC particles were obtained using microscopic and spectroscopic techniques. The size of the particles as well as that of the agglomerates were reduced significantly using the milling process and the results were validated through a scanning electron microscope. The crystallite size and crystallinity were found to be ~35nm and 10.42%, respectively. The direct bandgap value of 5.93eV and good optical conductivity at 786 nm were obtained from the ultra violet visible spectroscopy measurements. The thermal analysis reveals the presence of a substantial amount of carbon, the rate of maximum weight loss, and the two stages of phase transformation. The FT-Raman confirms the presence of carboxyl groups and a ID/IG ratio of 0.83. Water contact angle around 140° on the surface implies the highly hydrophobic nature of the material and its low surface energy. This characteristic process assists to obtain a sustainable nanomaterial from waste tyres, contributing to the development of a smart building material.

Evaluation of Microscopic Degradation of Copper and Copper Alloy by Electrical Resistivity Measurement (전기비저항 측정에 의한 구리와 구리합금의 미시적 열화평가)

  • Kim, Chung-Seok;Nahm, Seung-Hoon;Hyun, Chang-Young
    • Journal of the Korean Society for Nondestructive Testing
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    • v.30 no.5
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    • pp.444-450
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    • 2010
  • In the present study, the microscopic degradation of copper and copper alloy subjected to cyclic deformation has been evaluated by the electrical resistivity measurement using the DC four terminal potential method. The copper (Cu) and copper alloy (Cu-35Zn), whose stacking fault energy is much different each other, were cyclically deformed to investigate the response of the electrical resistivity to different dislocation substructures. Dislocation cell substructure was developed in the Cu, while the planar array of dislocation structure was developed in the Cu-35Zn alloy increasing dislocation density with fatigue cycles. The electrical resistivity increased rapidly in the initial stage of fatigue deformation in both materials. Moreover, after the fatigue test it increased by about 7 % for the Cu and 6.5 % for the Cu-35Zn alloy, respectively. From these consistent results, it may be concluded that the dislocation cell structure responds to the electrical resistivity more sensitively than the planar array dislocation structure evolved during cyclic fatigue.

The structure analysis of iron relics excavated at dwelling site of Yangsoo-ri (양수리 주거지출토 철제유물의 금속조직과 분석-BC1-AD1 세기 추정 철제유물을 중심으로)

  • Kim, Soo-Ki
    • 보존과학연구
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    • s.27
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    • pp.165-180
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    • 2006
  • The research was conducted to understand type of iron used by those who lived at dwelling site of Yangsoo-ri in between the first century B.C. and the first century A.D. to make steel products and their technique such as steel making process and heat treatment, based on micro structure information obtained through microscopic metallographic structure analysis with SEM-EDS of six steel productsexhumed at the site. Key findings are summarized as below. In the sense that Si-Ca-Al style and less than 0.5% of Ti were found in the non-metallic inclusion, the material used for forged iron ware was magnetite resolved in that. It is, however, unclear whether magnetite was resolved at high temperature or at low temperature. Microscopic structure analysis revealed that forged steel products were made through repeated hot working, the technique of molding by hitting after heating in the process of resolving and molding iron. As a result, the iron used here for the products was not the iron ore which was produced through resolution from discarded cast iron axe, ingot iron. It is probable that to make those steel products, disposed-of cast iron was reused after being molded by decarburizing. Although a few of relics were analyzed for the research, they were of critical importance in defining the process of ironware production from the first century B.C. and the first century A.D. at the Yangsoo-ri region. Judging from the iron from A-19 dwellingsite, it is possible to conclude that the iron was manufactured from cast iron decarburized and yet more research has to be done into relics yetto be exhumed in order to ascertain the finding. All of these findings are believed to play a critical role in further studies to define the steel-manufacturing technique used on the central Korean peninsular in the ancient times.

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Structure of the Tripartite Multidrug Efflux Pump AcrAB-TolC Suggests an Alternative Assembly Mode

  • Kim, Jin-Sik;Jeong, Hyeongseop;Song, Saemee;Kim, Hye-Yeon;Lee, Kangseok;Hyun, Jaekyung;Ha, Nam-Chul
    • Molecules and Cells
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    • v.38 no.2
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    • pp.180-186
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    • 2015
  • Escherichia coli AcrAB-TolC is a multidrug efflux pump that expels a wide range of toxic substrates. The dynamic nature of the binding or low affinity between the components has impeded elucidation of how the three components assemble in the functional state. Here, we created fusion proteins composed of AcrB, a transmembrane linker, and two copies of AcrA. The fusion protein exhibited acridine pumping activity, suggesting that the protein reflects the functional structure in vivo. To discern the assembling mode with TolC, the AcrBA fusion protein was incubated with TolC or a chimeric protein containing the TolC aperture tip region. Three-dimensional structures of the complex proteins were determined through transmission electron microscopy. The overall structure exemplifies the adaptor bridging model, wherein the funnel-like AcrA hexamer forms an intermeshing cogwheel interaction with the ${\alpha}$-barrel tip region of TolC, and a direct interaction between AcrB and TolC is not allowed. These observations provide a structural blueprint for understanding multidrug resistance in pathogenic Gram-negative bacteria.

Effects of Anemarrhenae Rhizoma on anti-oxidative activities (서로 다른 품종 3종 지모(知母)의 항산화 효과)

  • Beak, Gwang-Hyun;Cho, Su-Jin;Cho, Hyun-Ju;Hong, Gwang-Hae;Kim, Hyung-Woo;Cho, Su-In
    • The Korea Journal of Herbology
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    • v.22 no.3
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    • pp.101-107
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    • 2007
  • Objective : This study was carried out to investigate diagnostic difference and anti-oxidative effect of 3 different Anemarrhenae Rhizoma (AR) extracts. Methods : Microscopic examination was used to distinguish histological differences. And eliminative ability of several kinds of free radicals was also measured. Results : In microscopic examination, we can distinguished three different lineage of AR with different structure of vascular bundles and secretory structures. The extract of AR show profitable abilities of elimination of DPPH free radical, ABTS free radical and hydrogen peroxide. Conclusion : So, it can be concluded that AR extract has an anti-oxidative effects. Especially indeciduous lineage was most effective to remove free radicals.

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Multiscale Stress Analysis of Palladium/Carbon Fiber Composites for the Hydrogen High Pressure Vessel (수소고압저장용기용 팔라듐 첨가 탄소섬유복합재에 대한 멀티스케일 응력해석)

  • Park, Woo Rim;Kwon, Oh Heon
    • Journal of the Korean Society of Safety
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    • v.33 no.2
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    • pp.1-7
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    • 2018
  • The multi-scale analysis is more proper and precise for composite materials because of considering the individual microscopic structure and properties of each material for composite materials. The purpose of this study is to verify the validity of using palladium particles in carbon/fiber composites by multi-scale analysis. The palladium is a material for itself to detect leaking hydrogen by using the property of adsorbing hydrogen. The macroscopic model material properties used in this study are homogeneous material properties from microstructure. Homogenized material properties that are calculated from periodic boundary conditions in the microscopic representative volume element model of each macroscopic analysis model. In this study, three macroscopic models were used : carbon fiber/epoxy, carbon fiber/palladium, palladium/epoxy. As a result, adding palladium to carbon/epoxy composite is not a problem in terms of strength.