• Journal of the Korean Mathematical Society
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• v.36 no.5
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• pp.923-943
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• 1999

In this paper we consider functionals of the empirical age distribution of supercritical Bellman-Harris processes. Let f : R+ longrightarrow R be a measurable function that integrates to zero with respect to the stable age distribution in a supercritical Bellman-Harris process with no extinction. We present sufficient conditions for the asymptotic normality of the mean of f with respect to the empirical age distribution at time t.

• Journal of Oral Medicine and Pain
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• v.43 no.4
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• pp.118-124
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• 2018

Purpose: Age estimation is often used in the identification of living persons. Various methods are used for age estimation using teeth, and there are many studies on the methodology. But the study of changes in the social aspects of age estimation with the passage of times is still insufficient. Therefore, the purpose of this study is to analyze the age estimation cases in the social aspects and to investigate the changes of age estimation cases in Jeollabuk-do. Methods: From January 2008 to December 2015, 76 cases of age estimation were collected. The collected data were organized and analyzed. The distribution of patients by age and year, the difference between alleged and registered age, the purpose of age estimation, and regional distribution were examined. In addition, we compared the previous study which analyzed the age estimation cases in Jeollabuk-do from 2000 to 2007. Results: According to the distribution by age, the age distribution was the largest in the 50s and 60s, with 69.8%. The most reason to correct age was related to welfare benefits (38.2%), and most of the people who corrected for welfare benefits were over 50 years old. The age correction for purpose of welfare benefits existed every year during the study period. As the result of comparison with previous study, total number of age estimation cases was decreased very sharply, and distribution by age group was also changed. Conclusions: Changes in age estimation cases were observed when compared to the previous study. A significant decrease in the total number of age estimation cases was observed, but the number of age estimation in the 50s did not decrease. Although the total number of age estimation requests decreases, age estimation in the elderly are likely to persist. Thus, it is necessary to study new age estimation methods suitable for the elderly.

• Journal of Applied Reliability
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• v.17 no.3
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• pp.188-196
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• 2017

Purpose: The purpose of this research is to determine optimal replacement age using non-informative prior information and Bayesian method. Methods: We propose a novel approach using Bayesian method to determine the optimal replacement age in block replacement policy by defining the prior probability with data on failure time and repair time. The Marcov Chain Monte Carlo simulation is used to investigate the asymptotic distribution of posterior parameters. Results: An optimal replacement age of block replacement policy is determined which minimizes cost and nonoperating time when no information on prior distribution of parameters is given. Conclusion: We find the posterior distribution of parameters when lack of information on prior distribution, so that the optimal replacement age which minimizes the total cost and maximizes the total values is determined.

• Industrial Engineering and Management Systems
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• v.3 no.2
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• pp.134-139
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• 2004

During the last three decades, a few attentions have been paid for investigating the cost distribution for the optimal maintenance problems. In this article, we derive the moment of the discounted cost distribution over an infinite time horizon for the basic age replacement problem. With first two moments of the discounted cost distribution, we approximate the underlying distribution function by three theoretical distributions. Through a Monte Carlo simulation, we conclude that the log-normal distribution is the best fitted one to approximate the discounted cost distribution.

• Journal of the Korean Mathematical Society
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• v.36 no.6
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• pp.1115-1132
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• 1999

We consider a supercritical multitype age dependent branching process. We define a stochastic process Zf(t) which is a functional of the empirical age distribution. When the limit of the expectation of this functional vanishes we4 find some sufficient conditions for the asymptotic normality of the mean of f with respect to the empirical age distribution at time t.

• Journal of Korean Society of Forest Science
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• v.94 no.5 s.162
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• pp.321-329
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• 2005

Based on the data representing four typical Korean pine forest types, the age structure, DBH distribution, species composition, and forking rule were systemically analyzed for old-growth Korean pine forest in Liangshui Nature Reserve, northeast China. The age structure of Korean pine trees was strongly uneven-aged with one dominated peak following normal distribution, and age of trees varied from 100 to 180 years within a stand. The DBH and height differences in same age class (20 years) varied from 28 cm~64 cm and 5 to 20 m, respectively. Many conifer and hard wood species, such as spruce, fir, costata birch, basswood, oak, and elm, were mixed with dominated trees of Korean pine. The canopy of the old-growth Korean pine forest can be divided into two layers, and differences of mean age and height between Layer I and Layer II were ranged 80~150 years and 7~13 m, respectively. The Weibull function was used to model the diameter distribution and performed well to describe size-class distribution either with a single peak in over-story canopy and inverse J-shape in under-story canopy for old-growth Korean pine stands. The forking height of Korean pine trees ranged from 16m to 24 m (mean 19.4 m) and tree age about 120 to 160 years old. The results will provide a scientific basis to protect and recover the ecosystem of natural old-growth Korean pine and also provide the model in management of Korean pine plantation.

• Journal of Applied Reliability
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• v.16 no.4
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• pp.280-286
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• 2016

Purpose: Recently, Jiang defines the tradeoff B life to minimize a sum of life lost by preventive maintenance (PM) and corrective maintenance (CM) contribution parts and sets up an optimal replacement age of age replacement policy as this tradeoff life. In this paper, Jiang's model only considering the known lifetime distribution is extended by assigning different weights to two parts of PM and CM in order to reflect the practical maintenance situations in application. Methods: The new age replacement model is formulated and the meaning of a weight factor is expressed with the implied cost of failure under asymptotic expected cost model and also discussed with one-cycle expected cost criterion. Results: The proposed model is applied to Weibull and lognormal lifetime distributions and optimum PM replacement ages are derived with corresponding implied cost of failure. Conclusion: The new age replacement policy to escape the estimation of cost of failure in classical asymptotic expected cost criterion based on the renewal process is provided.

• Industrial Engineering and Management Systems
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• v.12 no.1
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• pp.41-45
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• 2013

Age replacement policy is a commonly policy in maintenance management of spare part. It means that a spare part is always replaced at failure or fixed time after its installation, whichever occurs first. An optimal age replacement policy of spare parts concerns with finding the optimal replacement time determined by minimizing the expected cost per unit time. The age of the part was generally assumed to be a random variable in the past literatures, but in many situations, there are few or even no observed data to estimate the probability distribution of part's lifetime. In order to solve this phenomenon, a new uncertain age replacement policy has been proposed recently, in which the age of the part was assumed to be an uncertain variable. This paper discusses the optimal age replacement policies by dealing with the parts' lifetimes as different distributed uncertain variables. Several results on the optimal age replacement time are provided when the lifetimes are described by the uncertain linear, zigzag and lognormal distributions.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.12 no.4
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• pp.40-46
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• 2016

In order to improve air quality of indoor environment, studies of the underfloor air distribution (UFAD) system for application in buildings are actively in progress based on temperature and air flow distribution. However, although the age of air is the major evaluation parameter, there has been very little study on this parameter for the UFAD system. In this study, we investigated the age of air to reach the air diffuser, which is installed at the bottom of the interior by the UFAD system. Computational fluid dynamics simulations showed no regular pattern to the maximum value of the age of air in accordance with air flow rate and the velocity at air diffuser. These factors can be deduced from air movement by considering that air emitted from air conditioners was rotated according to the bottom shape of the floor, and then, the age of air in the rotation center was increased. The average age of air of internal interior was reduced considerably as the flow velocity at the underfloor air diffuser was increased from 0.5 m/s to 1.0 m/s However, the age of air was not substantially affected with change in the air volume. Moreover, when the flow velocity at the underfloor air diffuser was higher than 1.0 m/s, the age of air showed no significant difference with change in air volume or height of measurement. These results imply that indoor air quality is more substantially influenced by flow velocity than air volume, and the appropriate flow velocity is 1 m/s or more.

• Fashion & Textile Research Journal
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• v.24 no.5
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• pp.618-627
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• 2022

This is a basic study to recommend a legging sizing system suitable for middle-aged women. This study aims to explore and analyze the sizing system of branded leggings for middle-aged women. Therefore, 40 pairs of leggings from 20 brands preferred by middle-aged women were first selected to compare their sizing systems. Thus, it was found that the size distribution of legging brands varied significantly, and the number of sizes or the size deviation also varied depending on the brands or products. Second, the adult female age groups were classified as 18-24 years, 25-34 years, 35-44 years, and 45-59 years. Additionally, the distribution of the waist and hip circumferences by age group was compared with the size specifications of the leggings. Leggings with large differences between size specifications and body size distribution were identified in each age group. In the case of women aged 45 to 59, the size distribution suitability of branded leggings was found to be the lowest among the four age groups. Furthermore, it was also found that it is important to reflect the body size distribution, especially the waist circumference, to establish a legging sizing system suitable for women aged 45 to 59 years.