• Journal of Welding and Joining
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• 제7권4호
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• pp.56-67
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• 1989

In this study, the possibility of evaluating the peculiar fracture strength of weldment in high strength steels was investigated by means of a small punch(SP) test. In order to obtain the ductile-brittle transition temperature(DBTT) of SP energy by which the fracture strength of weldment in structural steels such as SS41 and SM53B steels had been evaluated in our preceding publication, the effects of notches and loading rates on SP energy were discussed. It was found that the correspondence of SP energy to critical COD at test temperature -196.deg. C showed a linear relation with some deviation. The empirical correlation with scatter band, Esp/(Esp)p = 1.67[.delta./(.delta./sub c//(.delta./sub c/)/sub p/]-0.55, was developed between the SP energy ratio and critical COD ratio of each weld structure compared with parent material at test temperature -196.deg. C. In addition, there did not appear to be a significant effect of test materials and specimen size etc. on the correlation.

• Elastomers and Composites
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• 제59권1호
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• pp.17-21
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• 2024

Solution styrene-butadiene rubber (S-SBR) is used to improve the wet grip and rolling resistance properties of tire treads. As blending of SBRs can improve the physical properties of tire treads, we investigated the effects of SBR type and blending ratio on the physical properties. Twelve SBR/SBR biblend composites were prepared using four SBRs with different microstructures. The glass transition temperature (T_g), tanδ at 0℃ (wet grip predictor), and tanδ at 60℃ (rolling resistance predictor) were obtained from dynamic mechanical analysis, and were compared to the expected values obtained from the results of single SBR samples. Most of the SBR/SBR biblend composites exhibited crosslink densities lower than the expected values. The tanδ values at 0℃ and 60℃ of the SBR/SBR blend composites deviated from the expected values, with many of the deviations being disadvantageous. Of the twelve composites, six samples had higher 0℃ tanδ values than the corresponding expected values, and four exhibited superior wet grip properties to those of the SBR single samples. In addition, two of the twelve samples exhibited improved rolling resistance properties as compared with the single SBR samples. Finally, four samples exhibited lower T_g values than expected, and the T_g of one composite was lower than those of the single SBR samples.

• 대한화학회지
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• 제36권4호
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• pp.504-510
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• 1992

L-${\alpha}$-lecithin vesicle, bacteriorhodopsin(BR) 그리고 인지질로 재구성된 BR vesicle(InBR vesicle)의 각각의 수용액에서 methylene blue(MB)의 흡수성질을 $20^{\circ}C$에서 $60^{\circ}C$까지 흡수분광법으로 측정하였다. 인지질 vesicle에서 묽은 농도의 MB는 단위체와 이합체 사이에 평형을 이루었고, 고농도의 MB는 oligomer를 형성하였다. 대부분의 경우에 지질(vesicle)의 농도가 매우 높아지면 점점 단위체로 재분배 되었다. 일정한 MB 농도에 BR를 첨가할 때 흡광도비(${\alpha}/{\beta}$)는 감소되며 oligomer가 형성되었다. MB는 InBR vesicle의 상전이 온도 부근에서 흡광도비(${\alpha}/{\beta}$)가 증가했으나 인지질 vesicle에서는 상전이에 무관했다. 이것은 InBR vesicle 표면 위에서 회합하는 MB 분자들은 지질의 상전이에 영향을 받아 단위체로 재분배되는 것으로 사료된다.

• 한국전기전자재료학회논문지
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• 제22권6호
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• pp.506-511
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• 2009

For the application of the photosensitive barrier ribs with optimal properties such as glass transition temperature, refractive index and coefficient thermal expansion, the boro-silicate glasses was studied. The glass transition temperature, coefficient thermal expansion, and refractive index of the glasses based on the $B_2O_3-Al_2O_3-Al_2O_3-SiO_2$ glass system have been investigated with the different ratio of BaO/$Na_2O$ and $B_2O_3/Na_2O$. Increasing the ratio of $B_2O_3/Na_2O$ was led to the increase of coefficient thermal expansion and the decrease of glass transition temperature. The increase of refractive index of boro-silicate glasses increased with the density of glasses. We suggest the empirical equation for the prediction of refractive index with the glass density, $n=0.123{\rho}+1.182$ with 0.042 as the standard deviation in the boro-silicate glass system. The aim of the present paper is to give a basic result of the thermal and optical properties for designing the composition of photosensitive barrier ribs in PDP.

• Current Optics and Photonics
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• 제1권3호
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• pp.239-246
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• 2017

A compact plasmonic switching scheme, based on the phase change of a thin-film chalcogenide material ($Ge_2Sb_2Te_5$), is proposed and numerically investigated at optical-communication wavelengths. Surface plasmon polariton modal analysis is conducted for various thicknesses of dielectric and phase-change material layers, and the optimized condition is induced by finding the region of interest that shows a high extinction ratio of surface plasmon polariton modes before and after the phase transition. Full electromagnetic simulations show that multiple reflections inside the active region may conditionally increase the overall efficiency of the on/off ratio at a specific length of the active region. However, it is shown that the optimized geometrical condition, which shows generally large on/off ratio for any length of active region, can be distinguished by observing the multiple-reflection characteristic inside the active region. The proposed scheme shows an on/off switching ratio greater than 30 dB for a length of a few micrometers, which can be potentially applied to integrated active plasmonic systems.

• 폴리머
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• 제24권4호
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• pp.488-498
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• 2000

주쇄로 poly(4-vinylpyridine) (P4VP)과 양친매성 측쇄로 3-pentadecylphenol (PDP)의 수소결합을 통해서 molecular bottle-brush를 제조하였다. 제조된 bottle-brush에 대하여 P4VP의 pyridine기 대 PDP의 몰비 (x)와 P4VP 분자량에 따른 액정성의 구조, 상전이온도( $T_{ODT}$)와 bottle-brush 층간거리 ( $L_{p}$)변화에 대하여 고찰하였다. P4VP-PD $P_{x}$ bottle-brush는 상온영역에서 미세상분리를 이루고 있는 라멜라구조로 조사되었다. Bottle-brush의 온도에 따른 상거동에 대한 조사에서 상한임계온도(UCST)거동을 나타내었다. 또한 P4VP의 분자량별로 x가 0.8-0.9일때 최대온도를 나타내었으며, P4VP의 분자량이 증가함에 따라서 상전이가 높은 온도에서 일어났다. 이러한 결과는 주쇄긴 P4VP의 유동성과 라멜라구조의 크기와 규칙성에 영향을 받음을 알 수 있었다. Bottle-brush의 라멜라구조 분석시 bottle-brush의 $L_{p}$는 35 $\AA$에서 40 $\AA$로 x보다는 P4VP의 분자량에 더 큰 영향을 받았다. P4VP의 분자량이 증가함에 따라서 $L_{p}$도 증가하였으나, 일정 크기이상으로 분자량이 커졌을 경우, 오히려 거리가 감소하거나 증가하지 않는 결과를 얻었다.결과를 얻었다.다.

• Advances in materials Research
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• 제8권4호
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• pp.337-359
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• 2019

Shape Memory Polymer Composites (SMPC) have gained popularity over the last few decades due to its flexible shape memory behaviour over wide range of strains and temperatures. In this paper, non-linear bending analysis has been carried out for SMPC beam under the application of uniformly distributed transverse load (UDL). Simplified C⁰ continuity Finite Element Method (FEM) based on Higher Order Shear Deformation Theory (HSDT) has been adopted for flexural analysis of SMPC. The numerical solutions are obtained by iterative Newton Raphson method. Material properties of SMPC with Shape Memory Polymer (SMP) as matrix and carbon fibre as reinforcements, have been calculated by theory of volume averaging. Effect of temperature on SMPC has been evaluated for numerous parameters for instance number of layers, aspect ratio, boundary conditions, volume fraction of carbon fiber and laminate stacking orientation. Moreover, deflection profile over unit length and behavior of stresses across thickness are also presented to elaborate the effect of glass transition temperature (T_g). Present study provides detailed explanation on effect of different parameters on the bending of SMPC beam for large strain over a broad span of temperature from 273-373K, which encompasses glass transition region of SMPC.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.197-201
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• 2009

대향류확산화염에서 수축하는 화염디스크로부터 화염구멍으로 천이에 대한 실험 연구가 수행되었다. 이러한 연구는 버너직경, 전체신장율 그리고 속도비에 따라 묘사된다. 적절히 작은 버너 직경을 사용한 경우 고신장율 화염임에도 반경방향의 전도 열손실의 효과가 기여하는 것을 실험적으로 입증하였다. 그리고 화염소화 모드는 세 가지로 분류되며 특히, 충분히 큰 고신장율 화염의 표면에서 화염구멍 또는 줄무늬로 나타났다. 그리고 버너직경에 따라 화염소화모드를 구분 짓는 임계화염반경이 존재한다.

• 대한전자공학회논문지SD
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• 제45권9호
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• pp.57-64
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• 2008

본 논문은 높은 압축 성능을 가진 테스트 데이터 압축 기법을 제안한다. 제안하는 기법은 돈 케어 리맵핑을 이용한 천이 추가 단계와 천이 이전 단계로 구성된다. 실험 결과는 새로운 기법이 가장 높은 성능의 기법들 중 하나인 RL-huffman보다 높은 압축률을 제공하고 더 작은 하드웨어 면적을 필요로 함을 보여준다. 따라서 이 기법은 테스트 데이터 압축을 위한 실제적인 해법으로 널리 쓰일 수 있다.

• 천문학회지
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• 제33권1호
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• pp.57-73
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• 2000

We have done a spectroscopic study of the solar transition region using high resolution UV & EUV data obtained by SUMER(Solar Ultraviolet Measurements of Emitted Radiation) on board SOHO(Solar and Heliospheric Observatory). Optically thin and conspicuous emission lines observed at the solar limb are carefully selected to acquire average values of physical parameters for the quiet region as a function of radial distance. Our main results found from the present study can be summarized as follows. 1) Nonthermal velocities estimated from various UV lines do not decrease with height at least within one total line intensity scale height above the limb. 2) Nonthermal velocity distribution with temperature is very similar to that of the disk center, in the sense that its peak is located around $2{\times}10^5 K$, but the value is systematically larger than that of the disk. 3) It is found that nonthermal velocity is inversely proportional. to quadratic root of electron density up to about 10 arc seconds above the limb, i.e. ${\xi}\~N_e^{-1/4}$, implying that the observed nonthermal broadening can be attributed to Alfven waves passing through the medium. 41 Electron density estimated from the O V 629/760 line ratio is found to range from about $1{\times}10^{10}cm^{-3}$ to $2{\times} 10^{12}cm^{-3}$ in the transition region.