• Steel and Composite Structures
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• v.49 no.6
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• pp.713-728
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• 2023

This paper aims to investigate the free vibration analysis of FG plates, taking into account the effects of even and uneven porosity. The study employs the Hellinger-Reisner functional and obtains the element's bending stress and membrane stress fields from the analytical solution of the governing equations of the thick plate and plane problem, respectively. The displacement field serves as the second independent field. While few articles on free vibration analysis of circular plates exist, this paper investigates the free vibration of both rectangular and circular plates. After validating the proposed element, the paper investigates the effects of porosity distributions on the natural frequency of the FG porous plate. The study calculates the natural frequency of thin and thick bending plates with different aspect ratios and support conditions for various porosity and volume fraction index values. The study uses three types of porosity distributions, X, V, and O, for the uneven porosity distribution case. For O and V porosity distribution modes, porosity has a minor effect on the natural frequency for both circular and rectangular plates. However, in the case of even porosity distribution or X porosity distribution, the effect of porosity on the natural frequency of circular and rectangular plates increases with an increase in the volume fraction index.

• Journal of the korean academy of Pediatric Dentistry
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• v.51 no.1
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• pp.40-54
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• 2024

This study aims to identify the regional distribution in the prevalence of dental caries and related multidimensional factors among 12-year-old children in Korea. Data from the 2018 Child Oral Health Survey were used to calculate the average DMFT index of 12-year-old children in metropolitan cities, and a multi-level regression model was applied to explain the regional distribution of dental caries prevalence and related factors. Factors were divided into two levels by administrative structure. This study finds a significant regional difference in the prevalence of dental caries in 12-year-old Korean children across metropolitan cities. Multilevel analysis showed that district-level factors (average number of pit and fissure-sealed permanent teeth, dental treatment demand rate, preventive treatment rate, sex ratio, and number of dentists per 100,000 people) and metropolitan-level factors (intakes of cariogenic beverages and number of pediatric dental hospitals and clinics per 100,000 people) had a significant effect on dental caries prevalence (p < 0.05). Individual characteristics and local socio-environmental factors influence the prevalence of dental caries. Especially considering the strong dependence on preventive treatment and accessibility to dental care services, it is necessary to provide adequate preventive treatment and expand health care resources in high-risk areas of dental caries.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.3
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• pp.171-176
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• 2016

The distribution shapes of air and water temperatures are basic and essential information, which determine the frequency patterns of their occurrence. It is also very useful to understand the changes in long-term air and water temperatures with respect to climate change. The typical distribution shapes of air and water temperatures cannot be well fitted using widely used/accepted normal distributions because their shapes show multimodal distributions. In this study, Gaussian mixture distributions and kernel distributions are suggested as the more suitable models to fit their distribution shapes. Based on the results, the tail shape exhibits different patterns. The tail is long in higher temperature regions of water temperature distribution and in lower temperature regions of air temperature distribution. These types of shape comparisons can be useful to identify the patterns of long-term air and water temperature changes and the relationship between air and water temperatures. It is nearly impossible to identify change patterns using only mean-temperatures and normal distributions.

• Journal of Distribution Science
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• v.14 no.10
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• pp.153-164
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• 2016

Purpose - In general, large companies have larger organizations, funds, and systems to provide more effective and efficient services in the market. However, development needs to support the livelihood of ordinary citizens who work for small businesses as well. This research suggests that a new distribution channel, called a "foothold style Kosa mart," that cooperates jointly with a distribution center and a large discount mart can provide direct solutions to small and mid-size distributors. This new distribution channel can achieve a limited type of "Nadle shop (small supermarket) foster project" related to building a joint distribution center and improvement in wholesale supply. Research design, data, and methodology - Data about the Korea distribution situation, the Nadle stores, and the logistics centers were collected from literature, Statistics Korea, journals, and reports. Specifically, we investigated information about Kosa Mart and Nadle stores. We focused on the redesign of the distribution center for the Nadle store. Results - The Kosa Mart distribution center now includes 18 warehouses, and has been handling 2000-3000 items. Most of the warehouses have been simply designed and items loaded and stored without refrigeration; thus, it is possible to store only products of certain manufactured goods. The current logistics center has no wholesale function because it failed to resolve the joint purchasing and product supply issues of competitively priced products. Conclusions - This study aimed to identify ways to strengthen the competitiveness of small- and medium-sized retailers. A Kosa Mart redesign aims to unifying the logistics center, stores, and customers. First, the joint wholesale logistics system, equipped with an integrated ordering system, needs to process customer orders and store orders at the same time. Second, excellent small business product development has to connect with production. Third, the store composition needs to support a shipping hub. Fourth, the Mart differentiates itself from convenience store goods by supplying regional and specialized products to customers. Fifth, a service buying agent and direct transactions between producers and consumers need to be established, and exhibits and displays of goods need to be improved.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.527-530
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• 2002

The frequencies for HAPS used in fixed wireless access are allocated in the millimeter wave bands. The systems using these frequencies can have a serious impact on the radio communication qualities due to rain. In this paper, we compare the specific rain attenuation using CM(combined) raindrop size distribution with those using different sevral raindrop size distributions for the frequency bands 28/48㎓. The rain attenuations using CM raindrop size distribution for the path between the earth and HAPS platform according to the elevation angle are described.

• The Korean Journal of Ecology
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• v.17 no.2
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• pp.159-170
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• 1994

The geographical distribution and soil characteristics of Korean Elaeagnus plants were investigated by literatures, field survey and soil analysis. Deciduous E. umbellata was distributed throughout the Korean peninsula including western and southern islands. Distribution area of evergreen Elaeagnus plants was classified into three groups; E. macrophylla and E. glabra belonged to group l occurring in the southern, western and eastern islands; E. submacrophylla to group 2 occurring in the southern and western islands; E. maritima and E. ankaii to group 3 in the southern islands only. Deciduous E. umbellata appeared euryeciously from poor soil to rich one, whereas evergreen Elaegnus plants appeared stenoeciously in haline soil near coast.

• Communications for Statistical Applications and Methods
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• v.14 no.1
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• pp.255-266
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• 2007

A Bayesian estimation of the four-parameter gamma distribution is considered under the noninformative prior. The Bayesian estimators are obtained by the Gibbs sampling. The generation of the shape/power parameter and the power parameter in the Gibbs sampler is implemented using the adaptive rejection sampling algorithm of Gilks and Wild (1992). Also, the location parameter is generated using the adaptive rejection Metropolis sampling algorithm of Gilks, Best and Tan (1995). Finally, the simulation result is presented.

• The Korean Journal of Applied Statistics
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• v.19 no.2
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• pp.369-377
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• 2006

This paper considers moving variance ratio (MVR) for valiance detection problem with time series data in progress. For testing purpose, parametric method based on F distribution and nonparametric method based on empirical distribution are compared via simulation study.

• Communications for Statistical Applications and Methods
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• v.14 no.2
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• pp.355-363
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• 2007

In this paper a Bayesian estimation of the two-parameter kappa distribution was discussed under the noninformative prior. The Bayesian estimators are obtained by the Gibbs sampling. The generation of the shape parameter and scale parameter in the Gibbs sampler is implemented using the adaptive rejection Metropolis sampling algorithm of Gilks et al. (1995). A Monte Carlo study showed that the Bayesian estimators proposed outperform other estimators in the sense of mean squared error.

• Communications for Statistical Applications and Methods
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• v.17 no.5
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• pp.725-731
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• 2010

Economic Reliability test plans(ERTP) are proposed considering that the life time of the submitted items follow the Pareto distribution of the second kind. For various specified acceptance number, sample size and producer's risk, a minimum test termination time is obtained. A comparison of proposed plan has been made with the existing plan developed by Aslam et al. (2010). The results are explained by tables and example.