• Journal of Periodontal and Implant Science
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• v.48 no.2
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• pp.103-113
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• 2018

Purpose: The purpose of this retrospective study with 4-12 years of follow-up was to compare the marginal bone loss (MBL) between external-connection (EC) and internal-connection (IC) dental implants in posterior areas without periodontal or peri-implant disease on the adjacent teeth or implants. Additional factors influencing MBL were also evaluated. Methods: This retrospective study was performed using dental records and radiographic data obtained from patients who had undergone dental implant treatment in the posterior area from March 2006 to March 2007. All the implants that were included had follow-up periods of more than 4 years after loading and satisfied the implant success criteria, without any peri-implant or periodontal disease on the adjacent implants or teeth. They were divided into 2 groups: EC and IC. Subgroup comparisons were conducted according to splinting and the use of cement in the restorations. A statistical analysis was performed using the Mann-Whitney U test for comparisons between 2 groups and the Kruskal-Wallis test for comparisons among more than 2 groups. Results: A total of 355 implants in 170 patients (206 EC and 149 IC) fulfilled the inclusion criteria and were analyzed in this study. The mean MBL was 0.47 mm and 0.15 mm in the EC and IC implants, respectively, which was a statistically significant difference (P<0.001). Comparisons according to splinting (MBL of single implants: 0.34 mm, MBL of splinted implants: 0.31 mm, P=0.676) and cement use (MBL of cemented implants: 0.27 mm, MBL of non-cemented implants: 0.35 mm, P=0.178) showed no statistically significant differences in MBL, regardless of the implant connection type. Conclusions: IC implants showed a more favorable bone response regarding MBL in posterior areas without peri-implantitis or periodontal disease.

• The Korean Journal of Applied Statistics
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• v.26 no.5
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• pp.797-806
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• 2013

Meta-analysis is used in variety of areas to synthesize the results of previous studies. Among the methods for Meta-analysis, combining p-values is the simplest method; in addition Tippett (1931), Fisher (1932), Stuoffer at al. (1949), proposed various methods to combine p-values. We propose a new method to combine p-values based on exponential distribution. A Monte Carlo simulation study compares the power of the proposed methods with previous methods.

• The Korean Journal of Applied Statistics
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• v.10 no.2
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• pp.339-352
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• 1997

Chi-square test based on large sample theory is inappropriate for testing the row homogeneity in two-way contingency table with several sparse cells. For that case, exact testing methods has been developed in the literature and implemented in StatXact(1991). However, considerable computing time is inevitable for moderate size tables. So, Monte Carlo approximation is recommended frequently. In this study, we propose a simple algorithm for generating two-way random tables with fixed row and column margins for small sample chi-square test. Also, we develop “Turkey-type” method for multiple between-row comparisons.

• Applied Microscopy
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• v.44 no.2
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• pp.41-46
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• 2014

In this study, the vegetative and reproductive morphology and anatomy of two Hawaiian endemic Portulaca species were examined. Specifically, P. molokiniensis and P. sclerocarpa were compared to closely related species in the genus. The comparisons were both qualitative and quantitative, using characteristics of leaves, stems, roots, and fruits. Tissue organizations of vegetative and reproductive parts of the plants were assessed using microtechnique procedures, statistical analysis, and scanning electron microscopy. The most notable features of these two species were (1) the size and frequency of stomata in P. molokiniensis, and (2) the large number of sclerenchymatous cell layers in the thickest fruit walls of P. sclerocarpa. These findings may imply that stomata development in P. molokiniensis and thick fruit wall development in P. sclerocarpa are evolved features of survival. In particular, the development of thickened walls in indehiscent fruits likely has evolutionary implications of ecological tolerance for better adaptation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.5
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• pp.607-617
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• 1998

Comparisons of joint probability density distribution obtained from the raw data of measured droplet sizes and velocities in a transient diesel fuel spray with computed joint probability density function were made. Simultaneous droplet sizes and velocities were obtained using PDPA. Mathematical probability density functions which can fit the experimental distributions were extracted using the principle of maximum likelihood. Through the statistical process of functions, mean droplet diameters, non-dimensional mass, momentum and kinetic energy were estimated and compared with the experimental ones. A joint log-hyperbolic density function presents quite well the experimental joint density distribution which were extracted from experimental data.

• Journal of the Korean Society of Clothing and Textiles
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• v.11 no.3 s.25
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• pp.111-119
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• 1987

The main purposes of the study were to categorize the clothing items into product groups according to their product characteristics, and to find out the differences of consumer perception on clothing Product groups among different age and socioeconomic groups. A questionnaire about characteristics It?as constructed on the basis of Lipton, Darling, and Miracle's theories on product categorisations. The questionnaires were administered to female subjects in two age groups (20's and 40's) living in Seoul. Subjects were classified into 3 socioeconomic groups for the analysis. The Analysis of variance, post-hoc comparisons (Scheffe test and Tuckey test) were employed for the statistical inferences. The results were as follows ; Group I : none Group II : socks, undershirts, T-shirts (20's age group) Group III : blouse, sweater, blue jean, pajama, langerie, T-shirts (40's age group), skirt Group IV : jacket, skirt (high class of 40's age group) two-piece, half coat, long coat, Korean folk costume Group V : none Some of the clothing items were categorized into different product groups by different age and socioeconomic groups.

• Journal of the Ergonomics Society of Korea
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• v.16 no.3
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• pp.61-70
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• 1997

This study is undertaken to investigate the differences of accident characteristics between occupational deaths and nonfatal injuries in overall industry of Korea. The national statistics of industrial accidents in the years 1991-1994 were extracted from the annual publications of Ministry of Labor. To make the statistical comparisons for the accident characteristics, we derived the destributions of occupational deaths and injuries in terms of injured person's age, work experience, tiem of accident, activity at time of accident, accident type, injury type, injured part of body, and agency of accident. The results show that the distributions of the occupational deaths are significantly different from those of the nonfatal injuries in all characteristics investigated in this study. These findings indicate that the accident prevention programs should be developed and implemented by taking into account the characteristics of working environments based on accident analysis.

• The Korean Journal of Applied Statistics
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• v.23 no.6
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• pp.1245-1253
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• 2010

There are two main approaches for estimating the discontinuous regression function nonparametrically. One is the direct approach, the other is the indirect approach. The major goal of the two approaches are different. The direct approach focuses on the overall good estimation of the regression function itself, whereas the indirect approach focuses on the good estimation of jump locations. Apparently, the two approaches are quite different in nature. Gijbels et al. (2007) argue that the comparison of two approaches does not make much sense and that it is even difficult to choose an appropriate criterion for comparisons. However, it is obvious that the indirect approach also has the regression curve estimate as the subsidiary result. Therefore it is necessary to verify the appropriateness of the indirect approach as the estimator of the discontinuous regression function itself. Park (2009a) compared the performance of two approaches through a simulation study. In this paper, we consider a more general case and draw some useful conclusions.

• The Korean Journal of Applied Statistics
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• v.6 no.1
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• pp.41-52
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• 1993

In this paper we study numerical behavior of the adjustments for the variances of the pearson and deviance type dispersion statistics in two overdispersed mixture models; negative binomial and beta-binomial distribution. They are important families of an extended quasi-likelihood model which is very useful for the joint modelling of mean and dispersion. Comparisons are done for two types of dispersion statistics for various mean and dispersion parameters by simulation studies.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1033-1036
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• 2001

The object of this paper is to find out a coolant level, which is economic and similar to the conventional level, high level, in cutting temperature. For this, new coolant level, called a low level, was proposed, which is about 1/4 of conventional level. And the cutting temperature of each coolant level in turning was analyzed using statistical method. Firstly, it was analyzed that the temperature mean of each coolant level is not equal by ANOVA-test. Secondly by Tukey's HSD, one of multiple comparisons, it was analyzed that the temperature mean of low level is similar to that of high level and different from that of none level.