• Journal of the Korean Data and Information Science Society
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• v.17 no.2
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• pp.619-631
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• 2006

When X and Y have independent Poisson distributions, we develop a Bayesian one-sided testing procedures for the ratio of two Poisson means. We propose the objective Bayesian one-sided testing procedures for the ratio of two Poisson means based on the fractional Bayes factor and the intrinsic Bayes factor. Some real examples are provided.

• 한국데이터정보과학회:학술대회논문집
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• 2006.04a
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• pp.295-306
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• 2006

When X and Y have independent Poisson distributions, we develop a Bayesian one-sided testing procedures for the ratio of two Poisson means. We propose the objective Bayesian one-sided testing procedures for the ratio of two Poisson means based on the fractional Bayes factor and the intrinsic Bayes factor. Some real examples are provided.

• Journal of the Korean Data and Information Science Society
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• v.13 no.2
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• pp.201-207
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• 2002

In this paper, Jeffrey's and reference priors are derived when the parameter of interest is the ratio of means of two in dependent Poisson distribution. To achieve the parameter orthogonality in the sense of Cox and Reid (1987), non-trivial orthogonal transformation is provided. The orthogonal transformation makes to find noninformative priors easy. Our simulation study indicates that the reference prior meet very well the target coverage probabilities in a frequentist sense. Using the real data, we compute Bayes estimator and MLE for the ratio of means based on the reference prior.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.387-388
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• 2006

The influence of porosity (P) on Young's modulus (E) and Poisson's ratio $(\upsilon)$ of sintered steels produced from four types of steel powders was investigated. The values of E and $(\upsilon)$ depend mainly on the value of P, and those were a little affected by alloying elements. The relationships between E, $(\upsilon)$, and P were described as following equations: $E\;=\;E_0{\cdot}(1\;-\;k_E{\cdot}P)^2$ and $\upsilon\;=\;({\upsilon}_0\;-\;\upsilon_{sub}){\cdot}(1\;-\;k_{\upsilon}{\cdot}P)2+\upsilon_{sub}$, where subscript 0 means P = 0, and $k_E,\;k_{\upsilon}$ and ${\upsilon}_{sub}$ are empirical constants. These approximate equations showed good agreement with empirical results.

• The Korean Journal of Applied Statistics
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• v.10 no.1
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• pp.105-119
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• 1997

Barnwal and Paul(1988) derived the likelihood ratio statistic and $C(\alpha)$ statistic for testing the equality of the means of several groups of count data in the presence of a common dispersion parameter. These tests are generalized to be applicable without the restriction of a common dispersion parameter. And the assumed model of data is also extended from negative binomial to double exponential Poisson model. Monte Carlo simulations show the superiority of $C(\alpha)$ statistic based on the double exponential Poisson family which has a very simple form and requires estimates of the parameters only under the null hypothesis.

• Advances in nano research
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• v.10 no.5
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• pp.423-435
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• 2021

This paper examines the thermal post-buckling behaviors of graphene-reinforced metal matrix composite (GRMMC) laminated cylindrical panels which possess in-plane negative Poisson's ratio (NPR) and rest on an elastic foundation. A panel consists of GRMMC layers of piece-wise varying graphene volume fractions to obtain functionally graded (FG) patterns. Based on the MD simulation results, the GRMMCs exhibit in-plane NPR as well as temperature-dependent material properties. The governing equations for the thermal post-buckling of panels are based on the Reddy's third order shear deformation shell theory. The von Karman nonlinear strain-displacement relationship and the elastic foundation are also included. The nonlinear partial differential equations for GRMMC laminated cylindrical panels are solved by means of a singular perturbation technique in associate with a two-step perturbation approach and in the solution process the boundary layer effect is considered. The results of numerical investigations reveal that the thermal post-buckling strength for (0/90)_5T GRMMC laminated cylindrical panels can be enhanced with an FG-X pattern. The thermal post-buckling load-deflection curve of 6-layer (0/90/0)_S and (0/90)_3T panels of FG-X pattern are higher than those of 10-layer (0/90/0/90/0)_S and (0/90)_5T panels of FG-X pattern.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.228-233
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• 2016

Auxetic material is a material which has negative Poisson's ratio(NPR). Auxetic material shows some distinctive property like high energy absorbing property and high shear modulus. Among these, synclastic curvature is very interesting characteristic. When synclastic-curvature-material bends, it changes its shape like dome, contrary to non-auxetic material which changes its shape like saddle(anticlastic). This distinctive property could make it easy to manufacture curved structure like nose cone or wing panel in aerospace engineering. In this study, we studied a quantitative analysis about synclastic curvature of re-entrant panel with finite element model. We suggested a concept 'Degree of Synclasticity(DOS)', which means a ratio of curvature of load-direction and load-orthogonal direction. We studied the variation of DOS with two factor, unit cell inner angle(${\theta}$) and load position angle(${\phi}$). DOS decreases as ${\theta}$ increases because the unit cell goes out of auxetic-shape. As ${\phi}$ varies, DOS changes in a large range. So proper optimization of ${\phi}$ would be needed for application.

• Tunnel and Underground Space
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• v.25 no.1
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• pp.24-36
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• 2015

The Geochang granite widely used in construction works is one of the most popular dimension stones in Korea. In order to evaluate the physical properties of rock, a lot of laboratory tests for the Geochang granite were conducted to find unit weight, absorption ratio, P wave velocity, S wave velocity, uniaxial compressive strength, Young's modulus, Poisson's ratio, tensile strength, cohesion, friction angle and point load strength index. The uniaxial compressive strength of the Geochang granite was 19.5 times tensile strength and also 8.6 times cohesion, besides P wave velocity was 1.5 times S wave velocity. Correlation analyses were also conducted to find the correlation among 11 different physical properties, where the uniaxial compressive strength showed Pearson correlation coefficient of more than 0.8 with Poisson's ratio, point load strength index and Young's modulus, respectively. Regression analyses were finally conducted by means of both linear and multiple analysis and the brief results including coefficient of determination of more than 0.7 were presented.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.291-302
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• 2005

Due to the importance of the parameter in structural response, the uncertain elastic modulus was located at the center of stochastic analysis, where the response variability caused by the uncertain system parameters is pursued. However when we analyze the so-called stochastic systems, as many parameters as possible must be included in the analysis if we want to obtain the response variability that can reach a true one, even in an approximate sense. In this paper, a formulation to determine the statistical behavior of in-plane structures due to multiple uncertain material parameters, i.e., elastic modulus and Poisson's ratio, is suggested. To this end, the polynomial expansion on the coefficients of constitutive matrix is employed. In constructing the modified auto-and cross-correlation functions, use is made of the general equation for n-th moment. For the computational purpose, the infinite series of stochastic sub-stiffness matrices is truncated preserving required accuracy. To demons4rate the validity of the proposed formulation, an exemplary example is analyzed and the results are compared with those obtained by means of classical Monte Carlo simulation, which is based on the local averaging scheme.

• Tunnel and Underground Space
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• v.22 no.5
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• pp.354-364
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• 2012

In order to evaluate the physical properties of rock which might serve as a database for both mining and civil works, a lot of laboratory tests for Jecheon limestones were conducted to find unit weight, absorption ratio, porosity, elastic wave velocity, uniaxial compressive strength, Young's modulus, poisson's ratio, tensile strength, shore hardness, friction angle and cohesion. On investigation of the mechanical properties of both the gray limestone and the clayey limestone distributed in the studied region, the clayey limestone turned out to have more weak mechanical properties which might come from low unit weight, high absorption ratio and high porosity of rocks. The failure criteria of Jecheon limestones were discussed by means of both Mohr-Coulomb criterion and Hoek-Brown criterion. Regression analyses of the physical properties obtained from a lot of laboratory tests were also conducted by means of both linear and multiple regression analyses.