• Earthquakes and Structures
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• v.24 no.2
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• pp.91-96
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• 2023

In this article, the vibration response of elastic nanocomposite beams with enhanced damping by nanoparticles is presented based on the mathematical model. Damp construction is considered by spring and damper elements based on the Kelvin model. Exponential shear deformation beam theory (ESDBT) has been used to model the structure. The mixed model model is used to obtain the effective properties of the structure including compaction effects. Using the energy method and Hamilton's principle, the equations of motion are calculated. The beam frequency is obtained by analytical method. The purpose of this work is to investigate the effect of volume percentage of nanoparticles and density, length and thickness of the beam on the frequency of the structure. The results show that the frequency increases with the increase in volume percentage of nanoparticles.

• Journal of the Korean Data and Information Science Society
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• v.28 no.1
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• pp.1-10
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• 2017

Longitudinal data of Korean child academic achievement have been used to find the significant exploratory variables under the assumption of independent repeated measured data. Using the exploratory variables in previous research works, we analyze the linear mixed model incorporating the fixed and random effects for child academic achievement to detect the significant exploratory variables. Korea welfare panel study data observed three times between 2006 and 2012 by additional survey for children. The child academic achievement is evaluated by the sum of academic achievements of Korean, English and Mathematics. We also investigate the multicollinearity and the missing mechanism and select some popular correlation matrices to analyze the linear mixed model.

• Journal of the Korean Chemical Society
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• v.37 no.6
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• pp.562-569
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• 1993

The pseudophase separation model is used to describe the effects of pH and n-propanol on the mixed micellar formation of protonated and unprotonated dimethyldodecylamine oxides. Dimethyl-dodecylamine oxide surfactant molecules may exist in aqueous solution in either nonionic (unprotonated) or cationic (protonated) form, and they can be modeled thermodynamically as a binary mixture of cationic and nonionic surfactants. The composition of the binary mixture is varied by adjusting the solution pH. And activities, micellar compositions, and monomeric compositions of two surfactant species can be calculated directly from the experimental titration data by applying pseudophase separation model to the micellar system of DDAO in water/n-propanol. The critical micellar concentrations and the p$K_a$ values of the binary mixture systems are dependent on the micellar composition of the protonated cationic surfactant (X); especially they show the minimum phenomena when they are plotted against the micellar composition of the protonated cationic surfactant (X). The critical micellar concentration of the binary mixed DDAO system is generally decreased when n-propanol is added to the binary mixture system, and the degree of decrease is dependent on the concentration of n-propanol.

• Journal of the Society of Disaster Information
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• v.8 no.4
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• pp.384-390
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• 2012

This study attempts to test the effects of neighborhoods on children and adolescents' alcohol, cigarette and marijuana use. Theoretically, this study was guided by Akers' (1998) SSSL model as potential explanations for understanding the linkage and provided partial test of the model. More specifically, it aims to test the mediation effects of one of core propositions of the SSSL model; whether differential association with deviant peers as well as with conforming peers mediates social disorganization of neighborhoods on adolescent substance and drug use in a different direction. Using multilevel regression techniques with robust standard error, this study utilized data from 1,791 children and adolescents who were nested in 80 neighborhoods in Chicago. The findings of the study provide mixed supports for the SSSL model. That is, it found that there are not only mediation effects but also moderation effects of differential association on children and adolescents' substance and drug use.

• The Journal of Fisheries Business Administration
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• v.36 no.1 s.67
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• pp.81-101
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• 2005

This article is to estimate the fishing frequency function in Korean recreational fishery with respect to socio-economic characteristics of anglers. First, the study described the characteristics of the entire angler population on the view points of 9 socio-economic variables. And then, the study divided the total angler population into three groups of in-land, sea, and mixed angler populations in order to investigate the differences in their characteristics. The study could confirm the existence of differences in regions, size of regions, and educational levels between the in - land and the sea angler populations by testing heterogeneity in the frequency table. The fishing frequency function is estimated using Poisson regression model in order to accomodate the count data(non-negative discrete random variable) aspects of the fishing frequency. However, the model specification error is found due to overdispersion of data. The model exhibits the lack of goodness of fit. The negative binomial regression model is adopted to cure the overdispersion of the data as an alternative estimation methodology. Finally, the study can confirm overdispersion does not exist in the model any more and the goodness of fit improved significantly to the reasonable level. The results of estimation of fishing frequency population modeled by the negative binomial regression models are following. The three variables of region, sex, and education have effects on the decision making process of fishing frequency in the case of in-land recreation fishery. On the other hand, the three variables of sex, age, and marriage status do the same job in the case of sea angler population. Among the left-over variables, both income and use of Internet variables now affect on the process in mixed angler population. Finally, the results of whole angler population show that all of the previous variables are proven to be statistically significant due to the summation of data with all three sub-groups of angler population.

• The Korean Journal of Applied Statistics
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• v.28 no.2
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• pp.151-158
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• 2015

This paper discusses how to use projections for the analysis of data from balanced incomplete block designs. A model is suggested as a matrix form for the interblock analysis. A second set of treatment effects can be found by projections from the suggested interblock model. The variance and covariance matrix of two estimated vectors of treatment effects is derived. The uncorrelation of two estimated vectors can be verified from their covaraince structure. The fitting constants method is employed for the calculation of block sum of squares adjusted for treatment effects.

• Steel and Composite Structures
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• v.39 no.5
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• pp.493-509
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• 2021

There is not enough mixed finite element method (MFEM) model developed for static and dynamic analysis of functionally graded material (FGM) beams in the literature. The main purpose of this study is to develop a reliable and efficient computational modeling using an efficient functional in MFEM for free vibration and static analysis of FGM composite beams subject to high order shear deformation effects. The modeling of material properties was performed using mixture rule and Mori-Tanaka scheme which are more realistic determination techniques. This method based on the assumption that a two phase composite material consisting of matrix reinforced by spherical particles, randomly distributed in the beam. To explain the displacement components of the shear deformation effects, it was accepted that the shear deformation effects change sinusoidal. Partial differential field equations were obtained with the help of variational methods and then these equations were transformed into a novel functional for FGM beams with the help of Gateaux differential derivative operator. Thanks to the Gateaux differential method, the compatibility of the field equations was checked, and the field equations and boundary conditions were reflected to the function. A MFEM model was developed with a total of 10 degrees of freedom to apply the obtained functional. In the numerical applications section, free vibration and flexure problems solutions of FGM composite beams were compared with those predicted by other theories to show the effects of shear deformation, thickness changing and boundary conditions.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.147-150
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• 2001

In the present work, a linear static analysis is presented for thin-walled prismatic box-beams made of generally anisotropic materials. A mixed beam theory has been used to model and carry out the analysis. Three different constitutive relations are assessed into the beam formulation. Simple layup cases having symmetric or anti-symmetric configuration have been chosen and tested to clearly show the effects of elastic couplings of the beam. Both 2D and 3D finite element structural analysis using the MSC/NASTRAN has been performed to validate the current analytical results. Results show that appropriate assumptions for the constitutive equations are important and prerequisite for the accurate prediction of beam stiffness constants and also for the beam behavior.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.3
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• pp.413-422
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• 2000

In the class of models which include random effects, the variance component estimates are important to obtain accurate predictors and estimators. Variance component estimation is straightforward for balanced data but not for unbalanced data. Since orthogonality among factors is absent in unbalanced data, various methods for variance component estimation are available. REML estimation is the most widely used method in animal breeding because of its attractive statistical properties. Recently, Bayesian approach became feasible through Markov Chain Monte Carlo methods with increasingly powerful computers. Furthermore, advances in variance component estimation with complicated models such as generalized linear mixed models enabled animal breeders to analyze non-normal data.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.212-217
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• 2000

The reliable determination of the stress intensity factors for cracks in bolted Joints is needed to evaluate the safety and fatigue life of them widely used in mechanical components. The weight function method is an efficient technique to calculate the stress intensity factors for various loading conditions using the stresses of an uncracked model. In this paper the mixed-mode stress intensity factors for cracks in bolted joints are obtained by weight function method, in which the coefficients of weight function are determined by finite element analyses far reference loadings. The effects of the magnitude of clearance and factional coefficient on the stress intensity factors are investigated.