• 터널과지하공간
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• 제10권3호
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• pp.301-308
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• 2000

균열모형을 이용하여 압축 하중하에 있는 암석의 비선형 거동을 예측하는 것은 가능하다. 암석내의 균열의 성장은 암석의 이방성을 가져오며, 이러한 이방성의 정도는 단성계수의 변화로 표현될 수 있다. 본 연구에서는 균열의 성장에 따른 탄성계수의 변화를 이론적인 균열모형을 통해 예측하고, 이를 탄성파 속도 시험을 통해 구한 탄성계수와의 비교를 수행하였다. 또한, 균열모형에 사용되는 초기 암석내 존재하는 균열에 대한 정보는 암석표면의 이미지를 분석하여 구하였다.

• 한국세라믹학회지
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• 제50권1호
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• pp.82-86
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• 2013

A poled lead zirconate titanate (PZT) cube specimen is subjected to impulse-type compressive stress with increasing magnitude in parallel to the poling direction at four room and high temperatures. During the ferroelastic domain switching induced by the compressive stress, electric displacement in the poling direction and longitudinal and transverse strains are measured. Using the measured responses, linear material properties, namely, the piezoelectric and elastic compliance coefficients, are evaluated by a graphical method, and the effects of stress and temperature are analyzed. Finally, the dependency of the evaluated linear material properties on relative remnant polarization is analyzed and discussed.

• Structural Engineering and Mechanics
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• 제54권5호
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• pp.855-875
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• 2015

Many novel materials exhibit a property of different elastic moduli in tension and compression. One such material is graphene, a wonder material, which has the highest strength yet measured. Investigations on buckling problems for structures with different moduli are scarce. To address this new problem, firstly, the nondimensional expression of the relation between offset of neutral axis and deflection curve is derived based on the phased integration method, and then using the energy method, load-deflection relation of the rod is determined; Secondly, based on the improved constitutive model for different moduli, large deformation finite element formulations are developed and combined with the arc-length method, finite element iterative program for rods with different moduli is established to obtain buckling critical loads; Thirdly, material mechanical properties tests of graphite, which is the raw material of graphene, are performed to measure the tensile and compressive elastic moduli, moreover, buckling tests are also conducted to investigate the buckling behavior of this kind of graphite rod. By comparing the calculation results of the energy method and finite element method with those of laboratory tests, the analytical model and finite element numerical model are demonstrated to be accurate and reliable. The results show that it may lead to unsafe results if the classic theory was still adopted to determine the buckling loads of those rods composed of a material having different moduli. The proposed models could provide a novel approach for further investigation of non-linear mechanical behavior for other structures with different moduli.

• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2000년도 암반공학문제의 수치해석(Numerical Analysis in Rock Engineering Problems)
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• pp.47-55
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• 2000

균열모형을 이용하여 압축 하중하에 있는 암석의 비선형 거동을 예측하는 것은 가능하다. 암석내의 균열의 성장은 암석의 이방성을 가져오며 이러한 이방성의 정도는 탄성계수의 변화로 표현될 수 있다. 본 연구에서는 균열의 성장에 따른 탄성계수의 변화를 이론적인 균열모형을 통해 예측하고, 이를 탄성파 속도 시험을 통해 구한 탄성계수와의 비교를 수행하였다. 또한, 균열모형에 사용되는 초기 암석내 존재하는 균열에 대한 정보는 암석표면의 이미지를 분석하여 구하였다.

• Composites Research
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• 제18권2호
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• pp.30-37
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• 2005

본 논문에서는 평직구조를 갖는 성층권 비행선 기낭의 하중막재에 대한 비선형 유한요소 해석 결과를 기술하였다. 평직구조를 갖는 하중막재의 미세구조를 3차원적으로 구현하였고, Updated Lagrangian 방법을 사용하여 기하학적 비선형성을 고려하였다 계산결과, 큰 변형률에서 비선형해석으로부터 얻은 응력-변형률 곡선은 선형해석의 결과와 큰 차이를 보였다. 또한 응력-변형률 곡선으로부터 얻은 비선형 탄성계수 값은 선형 탄성계수보다 큰 값을 보였는데 그 차이는 섬유의 굴곡도가 작은 경우 더욱 두드러지게 나타났다

• 한국지반공학회지:지반
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• 제3권1호
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• pp.53-64
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• 1987

도로포장의 구조평가 및 유지관리를 위하여 매우 효율적인 장비로 알려진 Dynaflect의 이용이 날 로 증가하고 있어, 이에 대한 연구가 절실하다. 따라서 본 연구에서는 도로포장에 사용되는 재료의 탄성계수에 따른 해석모질을 설정하고, 이를 다층토 이론에 근거한 콤퓨터 프로그램을 통하여 Dyn select의 처짐곡선을 산출함으로써 표층 두께와 탄성계수에 따른 분산도의 특성을 연구하였다.

• 대한수학회지
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• 제61권1호
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• pp.65-90
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• 2024

In this paper, we introduce the notion of the stability of automorphic forms for the general linear group and relate the stability of automorphic forms to the moduli space of real tori and the Jacobian real locus.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.834-839
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• 2003

Previous research has been conducted on an ultrasonic wave reflection method that utilizes a steel plate embedded in the concrete to measure the reflection loss of shear waves at the steel-concrete interface. The reflection loss has been shown to have a linear relationship to compressive strength at early ages. The presented investigations continue this research by examining the fundamental relationship between the reflection loss, measured with shear waves, and the hydration kinetics of Portland cement mortar, represented by dynamic elastic moduli, compressive strength and degree of hydration. Dynamic elastic moduli are measured by fundamental resonant frequency and degree of hydration is determined by thermogravimetric analysis. The water/cement ratio was varied for the tested mixture compositions. The results presented herein show that compressive strength, dynamic shear modulus and degree of hydration have a linear relationship to the reflection loss for the tested mortars at early ages.

• Computers and Concrete
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• 제21권5호
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• pp.559-567
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• 2018

In this study alkali activation of Electric Arc Furnace Slag (EAFS) is studied with a comprehensive test program. Three different silicate moduli (1-1,5-2), three different sodium concentrations (4%-6%-8%) for each silicate module, two different curing conditions (45%-98% relative humidity) for each sodium concentration, two different curing temperatures ($400^{\circ}C-800^{\circ}C$) for each relative humidity condition and two different curing time (6h-12h) for each curing temperature variables are selected and their effects on compressive strength was evaluated then regression equations using multiple linear regressions methods are fitted. And then to select the best regression models confirm with using the variables, the regression models compared between itself. An Artificial Neural Network (ANN) models that use silicate moduli, sodium concentration, relative humidity, curing temperature and curing time variables, are formed. After the investigation of these ANN models' results, ANN and multiple linear regressions based models are compared with each other. After that, an explicit formula is developed with values of the ANN model. As a result of this study, the fluctuations of data set of the compressive strength were very well reflected using both of the methods, multiple linear regression with quadratic terms and ANN.

• 천문학회지
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• 제29권spc1호
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• pp.11-14
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• 1996

Super-inflation driven by dilaton/moduli kinetic energy is naturally realized in compactified string theory. Discussed are selected topics of recent development in string inflationary cosmology: kinematics of super-inflation, graceful exit triggered by quantum back-reaction, and classical and quantum power spectra of density and metric perturbations.