• Title/Summary/Keyword: Quasi-homogeneity

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Tests for homogeneity of proportions in clustered binomial data

  • Jeong, Kwang Mo
    • Communications for Statistical Applications and Methods
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    • v.23 no.5
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    • pp.433-444
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    • 2016
  • When we observe binary responses in a cluster (such as rat lab-subjects), they are usually correlated to each other. In clustered binomial counts, the independence assumption is violated and we encounter an extra-variation. In the presence of extra-variation, the ordinary statistical analyses of binomial data are inappropriate to apply. In testing the homogeneity of proportions between several treatment groups, the classical Pearson chi-squared test has a severe flaw in the control of Type I error rates. We focus on modifying the chi-squared statistic by incorporating variance inflation factors. We suggest a method to adjust data in terms of dispersion estimate based on a quasi-likelihood model. We explain the testing procedure via an illustrative example as well as compare the performance of a modified chi-squared test with competitive statistics through a Monte Carlo study.

Natural Frequencies of Laminated Composite Plates Attached Point Mass Under an Uniform Axial-Loading (등분포 축하중을 받고 첨가질량이 재하된 적충복합판의 고유진동수)

  • Park, Jae-Sean;Hong, Chang-Woo;Lee, Jung-Ho;Lee, Joo-Hyung
    • Journal of Industrial Technology
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    • v.19
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    • pp.235-243
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    • 1999
  • Vibration analysis for some of simple supported antisymmetric composite laminated plate loaded uniformly distributed axial force and attached mass was carried out. Because it is complicated to analysis this type of plate by theory of antisymmetric laminate, possibility for application of theory of special orthotropic laminate was studied, and natural frequency of laminated plate attached mass was calculated. Stiffness $B_{16}$, $B_{26}$, $D_{16}$, $D_{26}$ for this type of antisymmetric laminated plate converge on zero as the number of ply increases and it is possible to use classical theory by reason that considered plate has quasi-homogeneity without relevance to variation of angle. Difference between results by theory of antisymmetric and special orthotropic laminate is 0.36~1.96%, therefore it is convenient to analyze this by use of theory of special orthotropic laminate. When composite laminated plate with attached mass is analyzed range that was able to neglect self-weight of plate was proposed.

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Natural Frequencies of Laminated Composite Plates with Attached Mass Under an Uniform Axial-Loading (등분포 축하중을 받고 첨가질량이 재하된 적층복합판의 고유진동수에 관한 연구)

  • Hong, Chang-Woo;Kim, Kyeong-Jin
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.4 no.4
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    • pp.181-190
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    • 2000
  • Vibration analysis for some of simple supported antisymmetric composite laminated plate loaded uniform axial-loading and attached mass was carried out. Because it is complicated to analyze this type of plate by theory of antisymmetric laminate possibility for application of theory of special orthotropic laminate was studied, and natural frequency of laminated plate attached mass was calculated. Stiffness $B_{16}$, $B_{26}$, $D_{16}$, $D_{26}$ for this type of antisymmetric laminated plate converge on zero as the number of ply increases and it is possible to use classical theory by reason that considered plate has quasi-homogeneity without relevance to variation of angle. Difference between results by theory of antisymmetric and special orthotropic laminate is 0.36~1.96%, therefore it is convenient to analyze this by use of theory of special orthotropic laminate. When composite laminated plate with attached mass is analyzed range that Was able to neglect self-weight of plate was proposed.

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Visualizations for Matched Pairs Models Using Modified Correspondence Analysis

  • Lee, Chanyoon;Choi, Yong-Seok
    • Communications for Statistical Applications and Methods
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    • v.21 no.4
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    • pp.275-284
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    • 2014
  • Matched pairs are twice continuously measured data with the same categories. They can be represented as the square contingency tables. We can also consider symmetry and marginal homogeneity. Moreover, we can infer the matched pairs models; the symmetry model, the quasi-symmetry model, and the ordinal quasi-symmetry model. These inferences are involved in assumptions for special distributions. In this study, we visualize matched pairs models using modified correspondence analysis. Modified correspondence analysis can be used when square contingency tables are given; consequently, it is involved in the square and asymmetric correspondence matrix. This technique does not need assumptions for special distributions and is more helpful than the correspondence analysis to visualize matched pairs models.

Evaluation of thermal stability of quasi-isotropic composite/polymeric cylindrical structures under extreme climatic conditions

  • Gadalla, Mohamed;El Kadi, Hany
    • Structural Engineering and Mechanics
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    • v.32 no.3
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    • pp.429-445
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    • 2009
  • Thermal stability of quasi-isotropic composite and polymeric structures is considered one of the most important criteria in predicting life span of building structures. The outdoor applications of these structures have raised some legitimate concerns about their durability including moisture resistance and thermal stability. Exposure of such quasi-isotropic composite/polymeric structures to various and severe climatic conditions such as heat flux and frigid climate would change the material behavior and thermal viability and may lead to the degradation of material properties and building durability. This paper presents an analytical model for the generalized problem. This model accommodates the non-linearity and the non-homogeneity of the internal heat generated within the structure and the changes, modification to the material constants, and the structural size. The paper also investigates the effect of the incorporation of the temperature and/or material constant sensitive internal heat generation with four encountered climatic conditions on thermal stability of infinite cylindrical quasi-isotropic composite/polymeric structures. This can eventually result in the failure of such structures. Detailed critical analyses for four case studies which consider the population of the internal heat generation, cylindrical size, material constants, and four different climatic conditions are carried out. For each case of the proposed boundary conditions, the critical thermal stability parameter is determined. The results of this paper indicate that the thermal stability parameter is critically dependent on the cylinder size, material constants/selection, the convective heat transfer coefficient, subjected heat flux and other constants accrued from the structure environment.

Mesoscale modelling of concrete for static and dynamic response analysis -Part 2: numerical investigations

  • Lu, Yong;Tu, Zhenguo
    • Structural Engineering and Mechanics
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    • v.37 no.2
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    • pp.215-231
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    • 2011
  • As a brittle and heterogeneous material, concrete behaves differently under different stress conditions and its bulk strength is loading rate dependent. To a large extent, the varying behavioural properties of concrete can be explained by the mechanical failure processes at a mesoscopic level. The development of a computational mesoscale model in a general finite element environment, as presented in the preceding companion paper (Part 1), makes it possible to investigate into the underlying mechanisms governing the bulk-scale behaviour of concrete under a variety of loading conditions and to characterise the variation in quantitative terms. In this paper, we first present a series of parametric studies on the behaviour of concrete material under quasi-static compression and tension conditions. The loading-face friction effect, the possible influences of the non-homogeneity within the mortar and ITZ phases, and the effect of randomness of coarse aggregates are examined. The mesoscale model is then applied to analyze the dynamic behaviour of concrete under high rate loading conditions. The potential contribution of the mesoscopic heterogeneity towards the generally recognized rate enhancement of the material compressive strength is discussed.

Effects of Calcium/Vitamin D Intake and Taekkyeon Exercise on the Elderly's Frailty (칼슘/비타민D 섭취와 택견운동이 노인 허약에 미치는 효과)

  • Lee, Kwang Ok
    • Journal of Korean Biological Nursing Science
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    • v.18 no.3
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    • pp.185-191
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    • 2016
  • Purpose: The purpose of this study is to understand the effect of taking calcium/vitamin D supplements and performing Taekkyeon exercises on the frailty of the elderly targeting a vulnerable senior social group. Methods: A total of 124 people aged 65 and older consisting of 60 persons in the experimental group, and 64 persons in the control group participated in this study, and this study is a non-equivalent control group pre/post-test design quasi-experimental study. This study analyzed the homogeneity between the experimental group and the control group using a chi-square test and t-test while analyzing the difference in the degree of frailty and bone density with the practice of Taekkyeon and a calcium agent using t-test and GEE. Results: The study results showed that the frailty and bone density of the experimental group significantly improved. Conclusion: Through this study, it was confirmed that calcium/vitamin D intake and Taekkyeon exercises were an effective intervention which strengthened the elderly's physical condition.

Effects of Meridian Massage on Menopausal Symptoms, Mood, $E_2$, and Pain in Post Menopausal Women with Hemodialysis : A Quasi-experimental Study (경락마사지가 혈액투석을 받고 있는 폐경여성의 폐경증상, 기분, $E_2$ 및 통증에 주는 효과)

  • Yang, Kyung-Hee;Park, Ok-Rae;Park, Kum-Sook
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.24 no.4
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    • pp.707-715
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    • 2010
  • In this study, meridian massage is developed and applied on post menopausal Women with Hemodialysis to identify the effects of Menopausal Symptoms, Mood, Estradiol($E_2$), and Pain. The study was a nonequivalent control group pre-post test Quasi-experimental design. There were 17 people in the experimental group and 17 people in the control group. Meridian massage was performed for 4 weeks, 3 times a week for 20 minutes each sessions. The data were collected at pretest and posttest. SPSS win. 11.5 program was used. Fisher's exact test and Mann Whitney U-test were used to analyze the Pre-treatment homogeneity. Wilcoxon Sign Rank test was used to find out the effectiveness within each groups. Mann Whitney U-test was used in comparing between the two groups. After meridian massage, there were significant differences in menopausal symptoms in experimental group(z=-2.583, p=.010) and pain between groups(U=86.00, p=.040). $E_2$ was not effective in both groups. The mood was effective in both groups, since the mood had influenced by interviewer's collecting data. Meridian massage was effective in alleviating menopausal symptoms and pain of post menopausal women with Hemodialysis, but it is desirable to perform meridian massage to the patients for enough time.

The Effects of Moxibustion on Chronic Back Pain and Activities of Daily Living in Aged (뜸 요법이 노인의 만성 요통과 일상생활 활동장애에 미치는 효과)

  • Ryu, Hye Sook;Park, Kyung Sook
    • The Korean Journal of Rehabilitation Nursing
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    • v.18 no.1
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    • pp.38-45
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    • 2015
  • Purpose: This study was attempted in order to verify the effects of moxibustion on aged back pain and activities of daily living. Methods: A research design is quasi-experiment with pre-post test design in nonequivalent control group. As for data collection and experimental treatment, it accidentally sampled totally 50 people with 24 people for the experimental group and 26 people for the control group who appeal for chronic back pain aged over 60 who visited 4 senior centers where are located in N city from November 7, 2012 to December 3, 2012. Experimental treatment was carried out moxibustion totally 12 times by 3 times for 4 weeks in the experimental group. Data analysis was made by using SPSS program. As an analytical technique, the experimental group and the control group were analyzed the homogeneity verification with t-test, Fisher's exact test and $x^2$ test and the hypothesis verification with t-test. Results: The back pain level was reduced in the experimental group than the control group. The disability of daily living activities was reduced in the experimental group than in the control group. Conclusion: Moxibustion was considered to be likely useful therapeutic method for effects of chronic back pain and disability of daily living activities in aged.