• 한국세라믹학회지
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• 제46권1호
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• pp.86-93
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• 2009

The crack formation and the resistance of ITO film on PET substrate with a thickness of 20 nm were investigated as a function of strain. The onset strain for the increase of resistance increased with increasing strain rate, suggesting the crack initiation is dependent on the strain rate. Electrical resistance increased at the strain of 1.6% at the strain rates below $10^{-4}/sec$ while it increased at ${\sim}2%$ at the strain rates above $10^{-3}/sec$. The critical strain at which the cracks were formed is close to the proportional limit. Upon loading, the initial cracks perpendicular to the tensile axis were observed and propagated the whole sample width with increasing strain. The spacing between horizontal cracks is thought to be determined by the fracture strength and the interfacial strength between ITO and PET. The crack density increased with increasing strain. However, the effect of the strain rate on the crack density was less pronounced in ITO/PET with 20 nm ITO thickness than ITO/PET with 125 nm ITO thickness, the strength of ITO film is thought to increase as the thickness on ITO film decreases. The absence of cracks on ITO film at a strain as close as 1.5% can be attributed to the compressive residual stress of ITO film which was developed during cooling after the coating process. The higher critical strain for the onset of the resistance increase and the crack initiation of ITO/PET with a thinner ITO film (20 nm) can be linked with the higher strength of the thinner ITO film.

• 융합보안논문지
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• 제19권4호
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• pp.133-142
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• 2019

토렌트 및 P2P 사이트나 웹 하드는 쉽고 편리하게 무료로 다운로드 받거나 가격을 저렴하게 이용할 수 있다는 이유만으로 사용자들은 자주 이용하지만 국내 토렌트 및 P2P 사이트나 웹 하드는 저작권과 관련되어 매우 민감하기 때문에 저작권 보호를 위한 기술들이 연구되고 적용 되어지고 있다. 이 중에서 파일의 제목이나 주요 단어의 조합 등 경우의 수를 금칙어로 설정하여 차단하는 제목 및 문자열 비교방식 필터링 기술은 제목 변경, 띄어쓰기 등을 통해 우회가 용이하다. 저작권 보호를 위한 불법저작물을 검색하고 차단하기 위해서는 변형된 파일 제목을 정규화 하는 기술이 필수적이다. 본 논문에서는 불법저작물의 변형된 파일 제목을 정규화 하는 기법과 파일 제목을 정규화를 진행 전과 후에 따른 검색에 의한 탐지율을 비교하였다. 정규화를 진행하기 전 탐지율은 77.72%로 아쉬운 탐지율이 보인 반면에 정규화를 진행한 후 90.23%로 정규화가 필수적이라고 말할 수 있다. 향후, 공통으로 나타나는 날짜와 화질 표시 같은 무의미한 용어들을 처리하면, 더욱 좋은 결과가 산출될 것으로 기대한다. 국문 요약입니다.

• Fibers and Polymers
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• 제2권2호
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• pp.98-107
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• 2001

The phase transition behavior isothermal micro-phase separation kinetics of polyester-based thermoplastic elastomer were studied using the synchrotron X-ray scattering(SAXS) method. The structural changes occurring during heating period were investigated by determining the changes of the one-dimensional correlation function, interfacial thickness and Porod constant. Based on the abrupt increases of the domain spacing and interfacial thickness, a major structural change occurring well below the melting transition temperature is suggested. Those changes are explained in terms of melting of the thermodynamically unstable hard domains or/and the interdiffusion of the hard and soft segments in the interfacial regions. SAXS profile changes during the micro-phase separation process were also clearly observed at various temperatures and the separation rate was found to be sensitively affected by the temperature. The peak position of maximum scattering intensity stayed constant during the entire course of the phase separation process. The scattering data during the isothermal phase separation process was interpreted with the Cahn-Hilliard diffusion equation. The experimental data obtained during the early stage of the phase separation seems to satisfy the Cahn-Hilliard spinodal mechanism. The transition temperature obtained from the extrapolation of the diffusion coefficient to zero value turned out to be about 147$\pm$$2^{\circ}$, which is close to the order-disorder transition temperature obtained from the Porod analysis. The transition temperature was also estimated from the inveriant growth rate. By extrapolating the inveriant growth rate to zero, a transition temperature of about 145$\pm$$\pm$$2^{\circ}$ was obtained.

• 설비공학논문집
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• 제17권10호
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• pp.898-906
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• 2005

The present study has been conducted to investigate convective heat/mass transfer in the cooling passage with bleed holes. The rotating square channel has 40.0 mm hydraulic diameter and the bleed holes on the leading surface of the channel. The hole diameter of bleed hole is 4.5mm and its spacing is ( p/d:4.9) about five times of hole diameter. Exit mass flow rate through bleed holes is $10\%$ of the main mass flow rate and relation number is changed form 0.0 to 0.4. A naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy The cooling performance is influenced by exit mass flow rate through bleed holes and Coriolis force of rotating channel for fixed Reynolds number. The heat transfer on the leading surface is decreased due to Coriolis force. However the total heat transfer is enhanced around holes on the leading surface because of trapping flow by bleeding.

• Structural Engineering and Mechanics
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• 제74권3호
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• pp.351-363
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• 2020

Based on the dynamic tests of recycled aggregate concrete (RAC) short columns confined by the hoop reinforcement, the dynamic failure mechanism and the mechanical parameters related to the constitutive relation of confined recycled aggregate concrete (CRAC) were investigated thoroughly. The fracturing sections were relatively flat and smooth at higher strain rates rather than those at a quasi-static strain rate. With the increasing stirrup volume ratio, the crack mode is transited from splitting crack to slipping crack constrained with large transverse confinement. The compressive peak stress, peak strain, and ultimate strain increase with the increase of stirrup volume ratio, as well as the increasing strain rate. The dynamic confining increase factors of the compressive peak stress, peak strain, and ultimate strain increase by about 33%, 39%, and 103% when the volume ratio of hoop reinforcement is increased from 0 to 2%, but decrease by about 3.7%, 4.2%, and 9.1% when the stirrup spacing is increased from 20mm to 60mm, respectively. This sentence is rephrased as follows: When the stirrup volume ratios are up to 0.675%, and 2%, the contributions of the hoop confinement effect to the dynamic confining increase factors of the compressive peak strain and the compressive peak stress are greater than those of the strain rate effect, respectively. The dynamic confining increase factor (DCIF) models of the compressive peak stress, peak strain, and ultimate strain of CRAC are proposed in the paper. Through the confinement of the hoop reinforcement, the ductility of RAC, which is generally slightly lower than that of NAC, is significantly improved.

• Geomechanics and Engineering
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• 제17권4호
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• pp.367-374
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• 2019

This study concluded the results of a research on the features of cement based permeation grout, based on some important grout parameters, such as the rheological properties (yield stress and viscosity), coefficient of permeability to grout ($k_G$) and the inject ability of cement grout (N and $N_c$ assessment), which govern the performance of cement based permeation grouting in porous media. Due to the limited knowledge of these important grout parameters and other influencing factors (filtration pressure, rate and time of injection and the grout volume) used in the field work, the application of cement based permeation grouting is still largely a trial and error process in the current practice, especially in the local construction industry. It is seen possible to use simple formulas in order to select the injection parameters and to evaluate their inter-relationship, as well as to optimize injection spacing and times with respect to injection source dimensions and in-situ permeability. The validity of spherical and cylindrical flow model was not verified by any past research works covered in the literature review. Therefore, a theoretical investigation including grout flow models and significant grout parameters for the design of permeation grouting was conducted in this study. This two grout flow models were applied for three grout mixes prepared for w/c=0.75, w/c=1.00 and w/c=1.25 in this study. The relations between injection times, radius, pump pressure and flow rate for both flow models were investigated and the results were presented. Furthermore, in order to investigate these two flow model, some rheological properties of the grout mixes, particle size distribution of the cement used in this study and some geotechnical properties of the sand used in this work were defined and presented.

• 대한금속재료학회지
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• 제50권12호
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• pp.897-905
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• 2012

Directional solidification experiments were carried out in a hypoeutectic Al-11.3Si-3.5Cu system to investigate the microstructural evolution with the solidification rate. At a fixed temperature gradient, a dendritic microstructure was observed at a constant speed of more than $25{\mu}ms^{-1}$, a cellular interface developed at $5{\mu}ms^{-1}$ and the growth rate of $0.5{\mu}ms^{-1}$ led to the stability of the planar interface. The results revealed that primary silicon phases formed among cells, even though the studied Al-Si alloy system formed the composition within a hypoeutectic silicon composition. This suggests that the liquid concentration among cells during solidification reached a higher concentration, i.e., the eutectic concentration. It is, however, interesting that primary silicon phases did not form during a dendritic growth of more than $25{\mu}ms^{-1}$. These experimental observations are explained using the theoretical models on the interface temperatures.

• 센서학회지
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• 제32권5호
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• pp.328-333
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• 2023

This study experimentally verified the etch rate of the SiO₂ sacrificial layer etching process with a single etch hole using vapor-phase hydrogen fluoride (VHF) etching. To fabricate small-sized polysilicon etch holes, both circular and triangular pattern masks were employed. Etch holes were fabricated in the polysilicon thin film on the SiO₂ sacrificial layer, and VHF etching was performed to release the polysilicon thin film. The lateral etch rate was measured for varying etch hole sizes and sacrificial layer thicknesses. Based on the measured results, we obtained an approximate equation for the etch rate as a function of the etch hole size and sacrificial layer thickness. The etch rates obtained in this study can be utilized to minimize structural damage caused by incomplete or excessive etching in sacrificial layer processes. In addition, the results of this study provide insights for optimizing sacrificial layer etching and properly designing the size and spacing of the etch holes. In the future, further research will be conducted to explore the formation of structures using chemical vapor deposition (CVD) processes to simultaneously seal etch hole and prevent adhesion owing to polysilicon film vibration.

• 한국전산구조공학회논문집
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• 제21권4호
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• pp.325-334
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• 2008

표준 I형 프리스트레스트 콘크리트 거더교(I형 PSC 거더교)는 우리나라의 중 소 지간 교량에서 가장 많이 적용되는 교량형식이다. 이 교량 형식의 상부거더 안전성을 판단하기 위해 설계단면력을 결정할 때 유한요소법 등을 이용한 정밀한 해석보다는 설계기준들에서 제시한 활하중 분배계수나 단순화된 실용식을 일반적으로 이용하고 있다. 한편, 우리나라의 설계 실무에서 사용되는 활하중 분배계수는 대부분 외국의 연구결과나 설계기준이 그대로 반영된 것들이다. 따라서 표준 I형 PSC 거더교의 교량단면과 부재의 설계 기준강도 등을 고려한 우리나라의 설계여건에 적합한 활하증 분배계수식의 개발이 필요하였다. 본 연구에서는 활하중 분배계수식을 개발하기 위하여 교량의 폭, 지간길이, 주형간격과 차로폭 등에 대한 수많은 매개변수 해석과 민감도해석을 수행하였다. 그 결과 분배계수의 크기를 결정하는 주된 변수들로서 외측주형의 경우에는 주형간격, 내민길이와 지간길이를 선택하였다. 인접내측주형은 주형간격, 내민길이, 지간길이와 교폭으로 하였다. 내측주형은 주형간격, 교폭과 지간길이로 하였다 이어서 매개변수 해석결과들에 대한 다중선형회귀분석을 통하여 I형 PSC 거더교를 위한 활하중 분배계수식을 개발하였다. 본 연구에서 개발된 활하중 분배계수식을 가지고 설계실무자들은 교량 설계시 적절한 안전율이 보장된 설계단면력을 보다 쉽게 결정할 수 있을 것이다. 또한 예비설계시에 I형 PSC 거더교의 구조적인 효율을 향상시키기 위해 필요한 반복 설계에 소요되는 설계시간을 크게 줄일 수 것으로 기대된다.

• 한국약용작물학회지
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• 제5권2호
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• pp.95-101
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• 1997

결명자(決明子) 재배기술(栽培技術) 개발(開發)에 필요(必要)한 기초자료(基礎資料)를 얻기 위해 인력파종기(人力播種機)와 손파종(播種)을 비교(比較)하여 성력효과(省力效果)를 보고 조(條), 주간(株間)의 재식밀도(栽植密度)가 생육(生育)과 수량(收量)에 미치는 영향(影響)을 알고자 시험(試驗)한 바 그 결과(結果)를 요약(要約)하면 다음과 같다. 1. 파종량(播種量)은 손파종구(播種區)에 비해 인력파종기(人力播種機)의 주간거리(株間距離) 20 및 25cm 처리(處理)에서 적었다. 2. 파종(播種) 소요시간(所要時間)은 인력파종기(人力播種機) $60{\times}20cm$ 처리(處理)에서 손파종(播種)보다 ha당(當) 121시간(時間) 절약(節約) 되어 효율적(效率的)이었다. 3. 립모수(粒毛數)는 조간(條間) 및 주간(株間) 차이(差異)에 따라 그 밀도(密度)가 넓어질수록 적었고, 경장(莖長)은 년도(年度)에 따라 다르며, 주간(條間)이 넓어짐에 따라 다소(多少) 길어지는 경향(傾向)이었다. 주당(株當) 협수(夾數) 및 립중(粒重)은 조간(條間), 주간(株間)이 넓은 소식(疎植)에서 증가(增加)되었다. 4. 수량(收量)은 조간(條間) 60cm 주간(株間) 20cm 처리(處理)에서 가장 높았다. 5. 적산온도(積算溫度)는 경장(莖長), 주당(株當) 협수(夾數) 및 수량(收量)과 정(正)의 상관(相關)을 보인 반면(反面) 강수량(降水量)은 그들 형질(形質)과 부(負)의 상관(相關)을 보여 유의성(有意性)이 인정(認定)되었다. 6. $m^2$당(當) 립모수(粒毛數)는 분기수(分技數), 주당(株當) 협수(夾數), 립중(粒重)및 수량(收量)과 부(負)의 상관(相關)을 보였고, 수량(收量)은 분기수(分技數), 주당(株當) 협수(夾數), 립중(粒重)과 정(正)의 상관(相關)을 보였다.