토목섬유로 보강한 연약지반의 정$\cdot$반복하중 모형실험에 의한 평가

김영수,권성목,김연욱,김형준,Kim Young-Su,Kwon Sung-Mok,Kim Yeun-Wook,Kim Hyoung-Jun 한국지반공학회 2005 한국지반공학회논문집 Vol.21 No.5

Each static and cyclic load test was performed in a laboratory model test. As a result, ground displacement decreased and bearing capacity of the soil increased owing to the sheer strength of geosynthetics in general. In addition, numerical analysis was operated using Mohr-Coulomb, Modified Cam-Clay models, and FLAC 4.0 2D and compared with the laboratory model test. The results were shown to be of a great difference because the existing equations had not considered the characteristics that sheer strength increases with a load increment. Therefore, this paper proposes an equation of cable elements considering an effect of load given through repeated tests. 실내 모형실험으로 정,반복하중 재하 실험을 실시하여 하중과 침하, 지중 측방변위, 토목섬유 변위 등을 측정한 결과 지반과의 마찰과 토목섬유 인장력의 영향으로 전반적으로 지반의 변위가 줄고 지지력이 증가하였다. 또한 Mohr-coulomb 및 수정Mohr-Coulomb 모델들과 FLAC 4.0 2D을 사용하여 수치해석을 실시하였고 실내 모형 실험결과와 비교하였다. 기존식들은 토목섬유 모델링시 FLAC의 케이블 요소는 하중증가에 따른 전단강도를 증가되는 특성을 고려할수 없었기 때문에 실험 결과치와 상이하게 나타났다. 따라서 본 연구에서는 반복적인 학습으로 상재 하중의 영향을 고려한 케이블 구성요소의 적절한 식을 제시하였다.

MILC 성장 속도에 비정질 실리콘의 기하학적 형상이 미치는 영향

김영수,김민선,주승기,Kim Young-Su,Kim Min-Sun,Joo Seung-Ki 한국재료학회 2004 한국재료학회지 Vol.14 No.7

High quality polycrystalline silicon is very critical part of the high quality thin film transistor(TFT) for display devices. Metal induced lateral crystallization(MILC) is one of the most successful technologies to crystallize the amorphous silicon at low temperature(below $550^{\circ}C$) and uses conventional and large glass substrate. In this study, we observed that the MILC behavior changed with abrupt variation of the amorphous silicon active pattern width. We explained these phenomena with the novel MILC mechanism model. The 10 nm thick Ni layers were deposited on the glass substrate having various amorphous silicon patterns. Then, we annealed the sample at $550^{\circ}C$ with rapid thermal annealing(RTA) apparatus and measured the crystallized length by optical microscope. When MILC progress from narrow-width-area(the width was $w_2$) to wide-width-area(the width was $w_1$), the MILC rate decreased dramatically and was not changed for several hours(incubation time). Also the incubation time increased as the ratio, $w_1/w_2$, get larger. We can explain these phenomena with the tensile stress that was caused by volume shrinkage due to the phase transformation from amorphous silicon to crystalline silicon.

실트질 함유량에 따른 낙동강 모래의 비배수 반복전단거동 특성

김영수,김대만,Kim, Young-Su,Kim, Dae-Man 한국지반공학회 2008 한국지반공학회논문집 Vol.24 No.11

In this study, a series of undrained cyclic triaxial tests were performed with three different consolidation stress ratios ($K_c$=1.0, 1.5, 2.0) to investigate the undrained shear strength characteristics of sands with respect to the amount of contained silt located around the basin of Nak-dong River. The test results show that the more the sand has silt, the lower is cyclic shear stress ratio (CSR) in all $K_c$ and that the higher $K_c$ goes, the larger CSR decreases due to the increase of contained silt. The excessive pore pressure caused during shearing has an influence on the decrease of CSR by the high initial pore pressure in proportion to the amount of contained silt regardless of the $K_c$ value. After consolidation, the analysis of the skeleton void ratio of the sample reveals that the main cause of the decrease of CSR as well as the increase of the initial excessive pore pressure is the increase of the skeleton void ratio in proportion to the amount of contained silt.

Flexible Display용 Low Temp Process를 이용한 ZnO TFT의 제작 및 특성 평가

김영수,강민호,남동호,최광일,이희덕,이가원,Kim, Young-Su,Kang, Min-Ho,Nam, Dong-Ho,Choi, Kang-Il,Lee, Hi-Deok,Lee, Ga-Won 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.10

Recently, transparent ZnO-based TFTs have attracted much attention for flexible displays because they can be fabricated on plastic substrates at low temperature. We report the fabrication and characteristics of ZnO TFTs having different channel thicknesses deposited at low temperature. The ZnO films were deposited as active channel layer on $Si_3N_4/Ti/SiO_2/p-Si$ substrates by RF magnetron sputtering at $100^{\circ}C$ without additional annealing. Also, the ZnO thin films deposited at oxygen partial pressures of 40%. ZnO TFTs using a bottom-gate configuration were investigated. The $Si_3N_4$ film was deposited as gate insulator by PE-CVD at $150^{\circ}C$. All Processes were processed below $150^{\circ}C$ which is optimal temperature for flexible display and were used dry etching method. The fabricated devices have different threshold slop, field effect mobility and subthreshold slop according to channel thickness. This characteristics are related with ZnO crystal properties analyzed with XRD and SPM. Electrical characteristics of 60 nm ZnO TFT (W/L = $20\;{\mu}m/20\;{\mu}m$) exhibited a field-effect mobility of $0.26\;cm^2/Vs$, a threshold voltage of 8.3 V, a subthreshold slop of 2.2 V/decade, and a $I_{ON/OFF}$ ratio of $7.5\times10^2$.

지진하중에 의한 액화의 가능성과 간극수압의 발생에 관한 확률론적 연구

김영수,이송,조우철,Kim, Young-Su,Lee, Song,Cho, Woo-Chul 한국지반공학회 1992 지반 : 한국지반공학회지 Vol.8 No.2

지진하중을 받는 완전포화된 모래지반위에 구조물이 있을 경우(비등방상태) 또는 없을 경우 (등방상태)에 대하여 액화의 가능성을 평가하고 간극수압의 발생을 예측하기 위하여 확률론적 그리고 통계적 방법을 사용하였다. 본 연구를 수행하기 위하여 포화된 모래지반의 등방, 비등방상태하의 전단강도와 반복하중과 의 관계를 나타내는 동적전단강도계수들이 제시되었다. 이 전단강도계수들을 사용하여 지진에 의하여 발생되는 간극수압을 예측하는 프로그램과 그리고 저항과 하중계수들에 내포되어 있는 불확실성을 고려하여 액화가 일어날 확률을 구하는 프로그램을 3차원 Random Field Model을 사용하여 개발 하였다. 개발된 프로그램을 하나의 예제에 적용하였다. 그결과 등방상태가 비등방상태보다도 액화의 가능성이 높았고 상재하중이 커질수록 액화의 가능성은 낮았다. 또한 간극수압비는 Kc 값이 증가함에 따라 감소하는 경향을 나타내었다. The probabilistic and statistical model is used to estimate the probability of liquefaction potential and pore water pressure build up due to earthquake in fully saturated sand deposit for each case of being structure(anisotropic) or not(isotropic). To execute this paper, dynamic shear strength parameters to show the relationship between shear strength and cyclic loading under isotropic or anisotropic condition in saturated sand deposit are presented. Using these parameters, the program which Predicts Pore water Pressure build up due to earthquake is developed. Using the 3-dimensional Random Field Model considering uncertainty of resistance and strength parameter, the program which computes the probability of liquefaction potential is developed. The developed program is applied to a case study, and then the result shows that the probability of liquefaction in isotropic condition is higher than in anisotropic condition. The ratio of pore water pressure tends to decrease as Kc increases.

Probabilistic Analysis of the Stability of Soil Slopes

김영수,Kim, Young Su Korean Society of Civil Engeneers 1988 대한토목학회논문집 Vol.8 No.3

균질토 사면에서 파괴에 대한 확률론적모델이 제시되었다. 사면의 안전은 관례적인 안전을 보다는 파괴확률로써 측정된다. 사면파괴의 Safety Margin은 정규분포라 가정하였다. 어떤 균질한 흙층에 있어서 흙의 특성에 영향을 주는 불확실성의 원인은 본래의 공간적인 가변성, 불충분한 시료에서 오는 판단오차 그리고 실험오차등이 었다. 파괴면을 따라 존재하는 전단강도의 불확실성은 1차원 Random Field Madels로 표현되었다. 파괴aus의 양상은 대수나선 곡선을 따른다고 가정하였다. 파괴면과 그것을 따라 작용하는 힘의 통계적 특성을 유도하여 사면의 파괴확률을 계산하였다. 마지막으로 개발된 절차가 사면의 신뢰성 해석에 대한 하나의 예제 연구에 적용되었다. A probabilistic model for the failure in a homogeneous soil slope is presented. The Safety of the slope is measured through its probability of failure rather than the customary factor of safety. The safety margin of slope failure is assumed to follow a normal distribution. Sources of uncertainties affecting characterization of soil property in a homogeneous soil layer include inherent spatial variability., estimation error from insufficient samples, and measurement errors. Uncertainties of the shear strength-along potential failure surface are expressed by one-dimensional random field models. The rupture surface, created at toe of a soil slope, has been considered to propagate towards the boundary along a path following an exponential (log-spiral) law. Having derived the statistical characteristics of the rupture surface and of the forces which act along it, the probability of failure of the slope was found. Finally the developed procedure has been applied in a case study to yield the reliability of a soil slope.

3차원(次元) 사면(斜面) 안정해석(安定解析)에 관한 확률론적(確率論的) 연구(?究)

김영수,Kim, Young Su 대한토목학회 1984 대한토목학회논문집 Vol.4 No.3

사면(斜面)의 3차원(次元) 파괴(破壞)의 신뢰성(信賴性) 해석(解析)에 안전율(安全率) 대신 파괴확률(破壞確率)이 사용(使用)되었다. 강도정수(强度定數)는 정규분포(正規分布)와 베타분포(分布)로 가정하였고 특정(特定)한 신뢰도(信賴度)와 최우추정법(最尤推定法)에 의하여 구간추정(區間推定) 하였다. 정규분포(正規分布)와 베타분포(分布)의 무작위변수(無作爲變數)는 중심극한정리(中心極限定理)와 Rejection방법(方法)에 따라 일양분포변환방법(一樣分布變換方法)을 사용(使用)하여 발생(發生)시켰고 몬테칼로방법(Monte-Carlo Method)에 의한 파괴확률(破壞確率)은 다음과 같이 정의(定義)된다. $P_f=M/N$ N: 시행회수(施行回數) M: 파괴회수(破壞回數) 본(本) 연구(硏究) 결과(結果)는 다음과 같다. 1. $F_3$는 $F_2$보다 일반적으로 더 컸으나 작은 경우도 나타났다. 2. $F_3/F_2$의 비(比)는 c, ${\phi}$와 3차원(次元) 파괴(破壞)형상 그리고 경사에 따라 민감하나 흙의 단위중량에는 그렇지 않았다. 3. 어떤 완전율(安全率)에 대한 파괴확률(破壞確率)은 배타분포(分布)가 정규분포(定規分布)보다 대체로 크게 나타났다. 4. 어떤 특정(特定)한 사면파괴(斜面破壞)형상과 토질조건(土質條件)에 대하여 허용안전율(許容安全率) $FS_a=1.25$에 해한 $P_f$는 0.23 (정규분포(正規分布)), 0.29(베타분포(分布))로 나타났다. The probability of failure is used to analyze the reliability of three dimensional slope failure, instead of conventional factor of safety. The strength parameters are assumed to be normal variated and beta variated. These are interval estimated under the specified confidence level and maximum likelihood estimation. The pseudonormal and beta random variables are generated using the uniform probability transformation method according to central limit theorem and rejection method. By means of a Monte-Carlo Simulation, the probability of failure is defined as; $P_f=M/N$ N: Total number of trials M: Total number of failures Some of the conclusions derived. from the case study include; 1. Three dimensional factors of safety are generally much higher than 2-D factors of safety. However situations appear to exist where the 3-D factor of safety can be lower than the 2-D factor of safety. 2. The $F_3/F_2$ ratio appears to be quite sensitive to c and ${\phi}$ and to the shape of the 3-D shear surface and the slope but not to be to the unit weight of soil. 3. From the two models (normal, beta) considered for the distribution of the factor of safety, the beta distribution generally provides lager than normal distribution. 4. Results obtained using the beta and normal models are presented in a nomgraph relating slope height and slop angle to probability of failure.

동적 하중을 받는 말뚝기호의 지반반력에 관한 연구

김영수,이송,백영식,Kim, Young-Su,Lee, Song,Paik, Young-Shik 한국지반공학회 1990 대한토질공학회지 Vol.6 No.4

To investigate the effects of soil properties of the soft zone around a pile subjected 1,o the horizontal harmonic vibration, the parametric study is perfomed. The determination of the soil reaction or stiffness of the Winkler springs representing the soil around a pile is performed by dividing the soil profile into a number of homogeneous obtained from this study are as follows : 1) The real and imaginary parts of the stiffness show clear variations for the different shear modulus ratios, poisson's ratios, and distance retios to outer boundary as the dimensionless frequency increases. The differences are more pronounced for the imaginary part of the stiffness. 2) The stiffness of soil shows clear decrease. The real parts of the stiffness show larger as the frequency increases. On the other hand, the imaginary parts of the stiffness show smaller. 수평방향의 조화진동을 받는 말뚝주변의 지반특성에 관한 각종 계수들의 효과를 연구하였다. 그리고 비선형 해석을 위하여 말뚝주변의 흙을 성질이 같은 여러개의 동심고리 모양으로 나누어 지반반력 또는 흙의 강성을 계산하였으며 다음과 같은 결론을 얻었다. 1) 강성의 실수와 허수부분은 무차원 주파수가 증가함에 따라 전단 계수비, 포아슨비, 그리고 외부영역까지의 거리의 비에 대하여 큰 변화를 나타냈고 그 차이는 강성의 허수부분에 더 현저하게 나타났다. 2) 흙의 강성의 외부영역까지의 거리가 증가할수록 현저하게 감소하였는데 강성의 실수부분은 주파수가 작을수록 크게 나타났다. 반면에 허수부분은 작게 나타났다.

Pd에 의해 결정화 속도가 향상된 Ni-MILC에서 기하학적 형상이 결정화 속도에 미치는 영향

김영수,주승기,Kim Young-Su,Joo Seung-Ki 한국재료학회 2004 한국재료학회지 Vol.14 No.7

It is well-known that adjacent Pd-MILC enhanced the rate of Ni-MILC. And the phenomena can be explained by tensile stress propagation between amorphous silicon and Pd silicide which is catalyst of crystallization. In this study, we modified tensile stress by changing geometry of amorphous silicon to prove that there is a direct relation between tensile stress and Ni-MILC rate enhancement. When the tensile stress concentrated, the Ni-MILC rate was enhanced more(14.5 ${\mu}m/hr$) by Pd-MILC while the conventional Pd-MILC enhanced Ni-MILC rate was 11 ${\mu}m/hr$. As the result we can be sure that the tensile stress causes the enhancement of Ni-MILC rate.

사면(斜面)의 삼차원(三次元) 파괴확률(破壞確率)에 관한 연구(硏究)

김영수,임병조,백영식,Kim, Young Su,Lim, Byuong Zo,Paik, Young Shik 대한토목학회 1983 대한토목학회논문집 Vol.3 No.3

사면(斜面)의 3차원(次元) 파괴(破壞)의 신뢰성(信賴性) 해석(解析)에 안전율(安全率)대신 파괴확률(破壞確率)이 사용(使用)되었다. 강도정수(强度定數)는 정규분포(正規分布)와 베타분포(分布)(beta distribution)로 가정하였고 특별(特別)한 신뢰도(信賴度)와 최우추정법(最尤推定法)에 의하여 구간추정(區間推定)을 하였다. 정규분포(正規分布)와 베타분포(分布)의 의사무작위변수(擬似無作爲變數)는 중심극한정리(中心極限定理)와 Rejection방법(方法)에 따라 일양분포변환방법(一樣分布變換方法)을 사용(使用)하여 발생(發生)시켰고 몬테칼로방법 (Monte-Carlo Method)에 의한 파괴확률(破壞確率)은 다음과 같이 정의(定義)된다. $$P_f$$=M/N M: 파괴회수(破壞回數) N: 시행회수(施行回數) 본(本) 연구(硏究)의 결론(結論)은 강도정수(强度定數)를 정규분포(正規分布)로 가정한 경우에는 주어진 파괴표면(破壞表面)에 대하여 어떤 해석방법(解析方法)과 차원(次元)에 대해서도 안전율(安全率)과 파괴확률(破壞確率)과의 관계는 일정(一定)하였으나 베타분포(分布)로 가정 한 경우에는 일정(一定)한 관계가 나타나지 않았다. The probability of failure is used to analyze the reliability of three dimensional slope failure, instead of conventional factor of safety. The strength parameters are assumed to be normal variated and beta variated. These are interval estimated under the specified confidence level and maximum likelihood estimation. The pseudonormal and beta random variables are generated using the uniform probability transformation method according to central limit theorem and rejection method. By means of a Monte-Carlo Simulation, the probability of failure is defined as; $$P_f$$=M/N N: Total number of trials M: Total number of failures some of the conclusions derived from the case study include; 1. If the strength parameters are assumed to be normal variated, the relationship between safety factor and the probability of failure is fairly consistent, regardless of the procedures of analysis and dimensions of assumed rupture surfaces. 2. However if the strength parameters are beta variated, general relationship between $F_s$ and $P_f$ is hardly found.