The transfer characteristics of zinc tin oxide(ZTO) on silicon dioxide(SiO2) thin film transistor generally depend on the electrical properties of gate insulators. SiO2 thin films are prepared with argon gas flow rates of 25 sccm and 30 sccm. The rate of ionization of SiO2(25 sccm) decreases more than that of SiO2(30 sccm), and then the generation of electrons decreases and the conductivity of SiO2(25 sccm) is low. Relatively, the conductivity of SiO2(30 sccm) increases because of the high rate of ionization of argon gases. Therefore, the insulating performance of SiO2(25 sccm) is superior to that of SiO2(30 sccm) because of the high potential barrier of SiO2(25 sccm). The ZTO/SiO2 transistors are prepared to research the CO2 gas sensitivity. The stability of the transistor of ZTO/SiO2(25 sccm) as a high insulator is superior owing to the high potential barrier. It is confirmed that the electrical properties of the insulator in transistor devices is an important factor to detect gases.

본 논문은 고전적인 오일러-베르누이 보의 집중소성힌지 모델링을 위한 일반유한요소법을 제안한다. 이 기법에서 소성힌지는 해의 약불연속을 묘사하는 적절한 확장함수에 의해 모델링되며, 요소간의 연결성을 변화시키지 않으면서 임의의 위치에 소성힌지를 삽입하는 것이 가능하다. 대신 소성힌지는 이미 존재하는 요소에 위계적으로 자유도를 추가함으로써 형성된다. 제안된 기법의 유효성을 검증하기 위해 수치해석 예제에 대해 h-, p-확장과 같은 수렴성 해석을 수행하였다. 수렴성 해석의 결과가 제안된 기법이 소성힌지가 절점 및 요소 내의 임의의 위치에 존재하는 두 가지 경우 모두에 대하여 유한요소이론에 의한 수렴속도를 얻을 수 있음을 보여주어 기법의 정확성을 입증하였다.

Finite element analyses are carried out to understand the piezoelectric behaviors of ZnO nanowires. Three different types of ZnO nanowires, with aspect ratios of 1:2. 1:31, and 1:57, are analyzed for uniaxial compression, pure bending, and buckling. Under the uniaxial compression with a strain of 1.0 × 10−4 as the reference state, it is predicted that all three types of nanowires develop the same magnitude of the piezoelectric fields, which suggests that longer nanowires exhibit higher piezoelectric potential. However, this prediction is not in agreement with the experimental results previously reported in the literature. Such discrepancy is understood when the piezoelectric behaviors under bending and buckling are considered. When only the strain field due to bending is present in bending or buckling, the antisymmetric nature of the through-thickness stain distribution indicates that two piezoelectric fields, the same in magnitude and opposite in sign, develop along the thickness direction, which cancels each other out, resulting in a zero net piezoelectric field. Once additional strain contribution due to axial deformation is superposed on the bending, such field cancelling is compensated for due to the axial component of the piezoelectric field. Such numerical predictions seem to explain the reported experimental results while providing a guideline for the design of nanowire-based piezoelectric devices.

In this paper, we analyzed the safety on static and dynamic characteristics of a top-down evacuation instrument fixed on the exterior walls of a building using finite element analysis. For this purpose, the stress distribution characteristics of the H-beam structure were analyzed and the equivalent stress distribution, deflection displacement and natural frequency characteristics of the overall structure of the evacuation instrument were analyzed. The structures were applied with the materials of SS440 and SUS304. The static analysis results showed the elastic behavior with safety coefficients from 2.4 to 2.9, by confirming the structural safety. In addition, the analysis of the natural frequency characteristics confirmed that the vibration characteristics were higher than the external conditions of 20Hz.

PURPOSES: The objective of this study was to develop an asphalt pavement response model for a subsurface cavity section using the 3D finite element method and a statistical approach. METHODS: It is necessary to analyze the structural behavior of asphalt pavement with a subsurface cavity to evaluate the degree of risk for a road cave-in. A 3D finite element model was developed to simulate the subsurface cavity underneath asphalt pavement and was verified using the ILLIPAVE program. Finite element analysis was conducted for asphalt pavement sections with different asphalt layer thickness/modulus, and cavity depth and length, to generate the artificial pavement response database. The critical pavement response considered in this study was the tensile strain at the bottom of the asphalt layer because fatigue cracking is the main cause of road cave-in. The relationship between the critical pavement response and influencing factors was investigated using the pavement response database. The statistical regression approach was adopted to develop the asphalt pavement response model for predicting the critical pavement response of asphalt pavement with a subsurface cavity. RESULTS : It was found from the sensitivity analysis that the asphalt layer thickness or modulus, and cavity depth or length, are the major factors affecting road cave-in incidents involving asphalt pavement. The asphalt pavement response model showed high accuracy in predicting the tensile strain at the bottom of asphalt layer. It was found from the verification study that the R square value between finite element model and pavement response model were 0.969 and 0.978 in the cavity and intact sections, respectively. CONCLUSIONS: The work reported in this paper was intended to figure out the pavement structural behavior and to develop a pavement response model for the occurrence of cavities underneath asphalt pavement using 3D finite element analysis. In the future, critical pavement response will be utilized to establish the criteria of risk of road cave-in based on various different conditions.

It is inevitable to use the distinct element method in the analysis of structural dynamics for stacked stone pagoda system. However, the experimental verification of analytical results produced by the discrete element method is not sufficient yet, and the theory of distinct element method is not universal in Korea. This study introduces how to model the stacked stone pagoda system using the distinct element method, and draws some considerations in the seismic analysis procedures. First, the rocking mode and sliding mode are locally mixed in the seismic responses. Second, the vertical stiffness and the horizontal stiffness on the friction surface have the greatest influence on the seismic behavior. Third, the complete seismic analysis of stacked stone pagoda system requires a set of the horizontal, vertical, and rotational velocity time histories of the ground. However, earthquake data monitored in Korea are limited to acceleration and velocity signals in some areas.

본 연구에서는 옹벽 구조물의 내진성능 평가를 위해 2차원 유한요소 해석을 수행하였다. 2차원 유한요소 모델은 실제로 시공된 옹벽 구조를 기반으로 2차원 평면변형 요소로 모델링되었으며, 지반은 각각 유한요소와 무한요소로 모델링 하였다. 지진하중은 총 38개의 인공 지진을 생성하여 사용하였고, 생성된 인공 지진파를 11개의 PGA로 나누어 총 418회의 시간이력해석을 수행하였다. 수치해석 결과를 바탕으로 옹벽 구조물의 지진에 대한 취약도를 분석하였다. 취약도 분석 결과 콘크리트 및 철근의 취약도 곡선이 낮은 PGA 수준에서 급격히 변하는 것을 관찰할 수 있었다. 유한요소 해석 결과를 바탕으로 실제 현장의 옹벽 구조에서 상대적으로 낮은 수준의 지진파가 발생하더라도 높은 파괴확률로 인해 지진에 상대적으로 취약함을 확인하였다.

UHPFRC 15 M 분절형 박스거더에 대한 비선형 재료 및 비선형 기하학적 유한요소해석을 수행하였다. UHPFRC의 인장 및 압축 영역에서의 구성방정식은 공시체 시험을 기반으로 하였고, 체적 대비 강섬유 혼입률이 각각 1.0%, 1.5% 및 2.0%에 대해 해석을 수행하였다. UHPFRC를 위한 3차원 8 node hexahedron brick model과 1차원 embedded steel element를 기반으로 모델링하였다. UHPFRC 박스거더 단면에서 하부플랜지에 14개, 24개, 32개의 15.2mm 강연선을 모델링하여 실험결과와 비교하였다. 하중과 변위관계, 선형거동에서 비선형거동으로 변하는 시점에서 하중 및 중립축 변화 과정이 실험결과와 비교해 볼 때 정확하게 산출되었다. 따라서, 압축 및 인장구역에서 구성방정식을 반영한 재료적 비선형해석, UHPFRC 분절형 박스의 기하학적 비선형 해석이 유효함을 알 수 있다.

범용유한요소프로그램인 Abaqus의 확장유한요소법(XFEM)의 사용성 검증을 위하여 2차원 모델에 적용하여 수치해석을 수행하였다. 기존의 연구에 많이 사용되었던 응집요소(cohesive element) 모델은 균열 경로를 예측하고 요소를 삽입하여야 하는 단점 때문에 실제 균열을 모사하는데 한계가 있다. 이러한 이유로 응력의 방향성 및 특이성을 바탕으로 균열의 경로를 예측하는 확장유한요소법(XFEM)이 균열 해석에 있어서 더 발전된 방법으로 이용되어 왔다. 이번 연구에서는 균열의 경로가 자명한 2차원 모델에 사용하여 응집요소해석과 XFEM에 응집요소의 물성을 적용한 해석을 비교하고 XFEM 적용의 타당성을 확인하였다. 수치해석으로 균열 발생 직전의 응력분포 및 응력 특이성을 확인하고 실제 균열 발생경로와의 비교를 한다. 본 연구를 바탕으로 몇 가지의 한계를 극복하면 실제 복잡한 모델의 실제 균열진전해석을 수행하여 균열을 모사할 수 있을 것으로 기대된다.

1750년, 신경준이 저술한 『훈민정음운해(訓民正音韻解)』에 따라 순음(脣音) ㅁ･ㅂ을 水, 후음(喉音) ㅇ･ㅎ을 土로 오행을 배속하는 법이 성명학에서 다수설(多數說)로 정착되었으나 1940년에 발견된, 훈민정음 원본인 『훈민정음해례(訓民正音解例)』는 순음 ㅁ･ㅂ을 土, 후음 ㅇ･ㅎ을 水로 배속하고 있다. 본 연구는 이로 인해 야기된 혼란을 해소하고자 국어학과의 융합연구를 통해 훈민정음의 자음오행 배속원리를 궁구한 후, 『훈민정음운해』의 오행 배속법이 갖는 음운학(音韻學)적인 역사와 배경을 살펴보았다. 그 결과, 우리말 음운과 중국 한자음운의 오행배속을 각각 달리 본 신숙주의 인식체계가 신경준으로 이어졌으며 『훈민정음운해』의 궁극적 저술 목표는 중국의 한자 음운체계와 소통(疏 通)하기 위한 ‘한자음운도(漢字音韻圖)’에 있었다는 점에 주목하였다. 따라서 우리말 음운을 우리글로 적으려고 한 한글 창제의 주된 취지, 음운(音韻)이 시대･환경에 따라 분별되는 성향, 순 한글과 한자의 발음이 동일한 현대의 음운적 특징에 의거하여 『훈민정음해례』의 오행 배속이 더 합당하다는 결론을 이끌었다. 또한 한글이 발음기관의 동작이나 모습을 상형(象形)한 문자이므로 한글 자형오행(字 形五行)을 도입하고 오행배속은 『훈민정음해례』에 준(準)할 것을 제안하였다.

Subsurface cavities in the asphalt pavement which can cause road depression and cave-in accidents influence on the safety of pedestrians and vehicle drivers in the urban area. The existence of subsurface cavity can increase the tensile strain at the bottom of asphalt layer which is an indicator of fatigue cracking potential, and leads to the weakening of the pavement structural capacity. In this study, the finite element (FE) analysis was conducted to examine the relationship between the critical pavement responses and influencing factors, such as cavity depth and size, asphalt layer thickness, and asphalt concrete modulus. The surface deflections and tensile strains calculated from the ABAQUS FE program were compared to those from ILLIPAVE. It is found from this comparison that there are a good relationship between two analysis results. A three dimensional finite element model which is essential to simulate the hexahedral cavity were used to generate the synthetic database of critical pavement responses. To validate the developed model, the deflection data obtained from field Falling Weight Deflectometer (FWD) testing in four different locations were compared to FE deflections. It is found that the center deflections obtained from the FWD testing and FE analysis are similar to each other with an error values of 2.7, 4.4, 5.5, and 11.9 % respectively. The FE model developed in this study seems to be acceptable in simulating actual field cavity condition. On the basis of the data in the database, various analyses were conducted to estimate the effect of influencing factors on the critical pavement responses. It was found that the tensile strain at the bottom of asphalt layer is affected by all the factors but the most affected by the cavity depth and asphalt concrete modulus. Further studies are recommended to properly account for the effect of cavity’s geometry to pavement response.

When piles adjacent to deep excavations (i.e. tunnel operation), pile for slope stabilization, highway embankments near abutment piles in soft soil, the load generates lateral soil movement on pile. The lateral soil movement leads to develop the horizontal pressure between the pile and soil, also increase deflection as well as bending moment in the pile. In order to investigate a single pile subjected to horizontal loads due to the movement of the upper soil layer, the pile and soils are modelled by using 3D finite element analysis in this paper. The finite element analysis software used in this study is ANSYS. Furthermore, the soil's elastic behaviour follows the Mohr-Coulomb model and the pair of contact elements is used to simulate the pile-soil contact. A good correlation between laboratory and predicted results is observed in the validation analysis. The parametric study also demonstrates that soil Young's modulus and soil movement profile are key factors in predicting the behaviour of the pile.

Pavement performance usually depends on the pavement’s material property, traffic and environmental conditions. Current pavement design programs such as the Mechanistic Empirical Pavement Design Guide use these factors in assessing the pavement life and performance in terms of different distresses like rutting and fatigue cracking. Theoretically, the cracking and rutting behaviour of pavements are based on accumulated strains experienced by the pavement which is brought by the weight and loading speed of vehicles. A steady state loading device was used in the field to evaluate pavement deflection’s behaviour in varying loading frequencies. It was observed that the pavement deflection increases as the loading frequency also increases until it approaches a certain frequency wherein the deflection decreases thereafter. In this study, a three-dimensional finite element pavement model was established using ABAQUS wherein the effect of the vehicle’s loading frequencies was analysed. The calculated static deflection and stress from the finite element (FE) model were found to have good correlation with the KENPAVE measured deflection and stress. The deflections of different pavement conditions were further studied and analysed by generating several pavement geometries and strength from the FE model using a frequency sweep response analysis. It was found that the geometric condition and the current modulus of the pavement can amplify the pavement deflection by a factor, β, depending on the loading frequency. The peak deflection was found to be occurring when the loading frequency approaches one of the pavement’s natural frequencies. Based on the finding from this study, the natural frequency is an important factor to be considered in designing pavements. Further study is recommended to understand more on how to minimize the effect of natural frequency to pavement life.

In this study, proposed how to design an airport concrete pavement expansion joint considering the weather conditions and material properties. Currently, expansion joint spacing of airport concrete pavement in korea is not designed according to a clear standard, but it is designed to an empirical level. Various types of Admixture are used in concrete pavement and depending on the material characteristics or local environmental factors, there is a substantial difference in the extent and shrinkage to which the package is inflated. Significant differences are made in the extent to which the pavement expands or shrinkage depending on the material characteristics used or the local environmental factors. But, expansion joint design performed on empirical criteria cannot reflect these materials and environmental characteristics, resulting in unpredictable damage such as blow-up. To analyzing behavior of airport concrete pavement, horizontal displacement gauges, static strain gauges and thermometers are installed in the 3rd phase construction sites at Incheon International Airport. In this study, the relationship between the temperature and horizontal displacement of the concrete pavement was analyzed using the measured depth temperatures and the horizontal displacement data at the expansion joints at the Incheon airport site. The Finite Element Analysis Model of Incheon International Airport pavement was used to compare the difference between actual behavior and analytical behavior. In addition, it is proposed to design a suitable expansion joint spacing by considering the maximum expansion of concrete pavement and shrinkage caused by material expansion (e.g., ASR) and shrinkage due to water loss. This study was supported by Incheon International Airport Corporation (BEX00625).

In this study, the effect of dry shrinkage of concrete pavement due to seasonal changes was analyzed by comparing the results of finite element analysis with the temperature and strain measurements at Incheon airport pavement. To measure the behavior of slab by environmental condition in site, static strain gauges and thermometers were installed. To predict changes in the properties of concrete slab, experiments were conducted in site as well as in the lab. The considered parameters of FEA were pavement conditions according to seasonal and material properties change. The results of field measurements and the strain by FEA analysis were different in terms of the effects of drying shrinkage. This is due to humidity changes not applied to input values during FEA analysis. In this study, the difference between the results of field measurements and the results of the finite element model analysis was used to identify the drying shrinkage occurring on the concrete slab. Long-term data analysis in the future will enable the analysis of the trends in drying shrinkage in airport concrete pavement. This study was supported by Incheon International Airport Corporation(BEX00625).

Recently, the incidence and magnitude of earthquakes have been continuously increasing. NFPA 13 requires that hydroponics fire extinguishing system pipelines apply seismic isolation. Stainless steel joints have been newly developed to replace these seismic isolation joints. Therefore, in this study, a nonlinear finite element model of a pipeline with Stainless Power Joint was developed based on experimental data, and finite element analysis was performed by applying hydrostatic pressure and cyclic loading.