• Nuclear Engineering and Technology
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• v.38 no.2
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• pp.163-174
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• 2006

The $Ph{\acute{e}}bus$ FP project is an international reactor safety project. Its main objective is to study the release, transport and retention of fission products in a severe accident of a light water reactor (LWR). The FPT4 test was performed with a fuel debris bed geometry, to look at late phase core degradation and the releases of low volatile fission products and actinides. Post Test Analyses results indicate that releases of noble gases (Xe, Kr) and high-volatile fission products (Cs, I) were nearly complete and comparable to those obtained during $Ph{\acute{e}}bus$ tests performed with a fuel bundle geometry (FPT1, FPT2). Volatile fission products such as Mo, Te, Rb, Sb were released significantly as in previous tests. Ba integral release was greater than that observed during FPT1. Release of Ru was comparable to that observed during FPT1 and FPT2. As in other $Ph{\acute{e}}bus$ tests, the Ru distribution suggests Ru volatilization followed by fast redeposition in the fuelled section. The similar release fraction for all lanthanides and fuel elements suggests the released fuel particles deposited onto the plenum surfaces. A blockage by molten material induced a steam by-pass which may explain some of the low releases. The revaporisation testing under different atmospheres (pure steam, $H_2/N_2$ and steam /$H_2$) and up to $1000^{\circ}C$ was performed on samples from the first upper plenum. These showed high releases of Cs for all the atmospheres tested. However, different kinetics of revaporisation were observed depending on the gas composition and temperature. Besides Cs, significant revaporisations of other elements were observed: e.g. Ag under reducing conditions, Cd and Sn in steam-containing atmospheres. Revaporisation of small amounts of fuel was also observed in pure steam atmosphere.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.6
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• pp.43-50
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• 2011

The fractal method has recently been applied to a model for determining soil grain size distribution. The objective of this study is to review the applicability of the fractal method for a analysis of submarine sedimentary environments by comparing fractal constants with grain size statistical analysis for the soil samples of Pohang (PH) and Namhae (NH). The y-interception of log (grain size)-log (passing) equation was also used because grain size distribution couldn't be expressed with fractal dimension only. The result of comparison between fractal constants (dimension, y-interception) and grain size statistical indices, the fractal dimension was directly proportional to the mean and the sorting. And the y-interception showed high correlation with the mean. The fractal dimension and y-interception didn't show significant correlation with the skewness and the kurtosis. Thus regression equations between fractal constants and two statistical indices (mean, sorting) were derived. All classifications of the mean and the sorting could be determined using the regression equation based on the fractal dimension and y-interception. Therefore, fractal constants could be used as an alternative index representing the sedimentary environments instead of the mean and sorting.

• Journal of the Korean Geographical Society
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• v.30 no.4
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• pp.411-428
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• 1995

Intercountry adoption, one type of forced migration, has increased significantly in recent decades. The adoption of Korea-born children by Americans has been the strongest intercountry adoption linkage in the world. The intercountry adoption stream was strongly influenced by intercountry adoption policies, and socio-cultural settings in both South Korea and the United States. Socio-cultural factors in South Korea made local adoption undesirable and helped for abandoned children to be adopted by Americans, while socio-cultural factors in the United States had reduced the number of locally available infants for adoption, and increased the demand for infants from abroad. Distribution of Korea-born adoptees shows concentration in the Pacific Northwest, Upper Midwest and Northeast areas which have not attracted Korean immigrants so generally. The trend of concentration shows some increased importances in the outlying states in the northern United States. The location and activity of agencies shaped the spatial distribution of Korea-born adoptees in the United States.

• Korean Journal of Agricultural and Forest Meteorology
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• v.6 no.1
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• pp.30-37
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• 2004

This study investigated the structural characteristics of Taxus cuspidata communities on Mt. Hambaek. The vegetation consisted of 9 species in the T$_1$(tree) layer, 35 species in the T$_2$(subtall tree) layer, 28 species in the S(shrub) layer, and 69 species in the H(herb) layer. The dominant species of the T$_1$ layer was Taxus cuspidata and that of the T$_2$ layer was Acer tschonoskii var, rubripes. The dominant species of the S layer was Tripterygium regelii, and the dominant species of the H layer was Pseudostellaria palibiniana. The diameter distribution of the dominant five species in the T$_1$ and T$_2$ layers indicates that these Taxus cuspidata forests may be gradually dominated by Quercus mangolica and by Tripterygium regelii. The composition of biological type was Ph-D$_1$-R$_{5}$-e.

• Korean Journal of Plant Resources
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• v.17 no.1
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• pp.67-74
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• 2004

This study was carried out to investigate the structural characteristics of Taxus cuspidate communities in Mt. DuckYoo. The vegetation was consisted of 20 species in the T$_1$(tree) layer, 26 species in the T$_2$(subtall tree) layer, 26species in S(shrub) layer, and 56 species in the H(herb) layer. The dominant species of Mt. Duckyoo was Taxus cuspidata in the T$_1$ Layer, Acer tschonoskii var. rubripes in the T$_2$ Layer, Tripterygium regelii and Acer tschonoskii var. rubripes in the S Layer and Sasa borealis in the H Layer. According to the diameter distribution of high ranking five species in T$_1$, T$_2$ layer at natural Taxus cuspidata communities, these forests may be gradually replaced by Quercus mongolica, Tripterygium regelii. The composition of biological type was Ph-D$_1$-R$\sub$5/-e.

• Korean Journal of Plant Resources
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• v.17 no.1
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• pp.58-66
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• 2004

This study was carried out to investigate the structural characteristics of Taxus cuspidate communities in Mt. DuckYoo. The vegetation was consisted of 20 species in the T$_1$(tree) layer, 26 species in the T$_2$(subtall tree) layer, 26species in S(shrub) layer, and 56 species in the H(herb) layer. The dominant species of Mt. Duckyoo was Taxus cuspidata in the T$_1$ Layer, Acer tschonoskii var. rubripes in the T$_2$ Layer, Tripterygium regelii and Acer tschonoskii var. rubripes in the S Layer and Sasa borealis in the H Layer. According to the diameter distribution of high ranking five species in T$_1$, T$_2$ layer at natural Taxus cuspidata communities, these forests may be gradually replaced by Quercus mongolica, Tripterygium regelii. The composition of biological type was Ph-D$_1$-R$\_$5/-e.

• Communications for Statistical Applications and Methods
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• v.28 no.5
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• pp.477-491
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• 2021

The Markov modulated Brownian motion is a substantial generalization of the classical Brownian Motion. On the other hand, the Markovian arrival process (MAP) is a point process whose family is dense for any stochastic point process and is used to approximate complex stochastic counting processes. In this paper, we consider a superposition of the Markov modulated Brownian motion (MMBM) and the Markovian arrival process of jumps which are distributed as the bilateral ph-type distribution, the class of which is also dense in the space of distribution functions defined on the whole real line. In the model, we assume that the inter-arrival times of the MAP depend on the underlying Markov process of the MMBM. One of the subjects of this paper is introducing how to obtain the first passage probabilities of the superposed process using a stochastic doubling algorithm designed for getting the minimal solution of a nonsymmetric algebraic Riccatti equation. The other is to provide eigenvalue and eigenvector results on the superposed process to make it possible to apply the GTH-like algorithm, which improves the accuracy of the doubling algorithm.

• The Korean Journal of Applied Statistics
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• v.28 no.5
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• pp.921-932
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• 2015

This study analyzed military personnel survivability in regards to offensive operations according to the scientific military training data of a reinforced infantry battalion. Scientific battle training was conducted at the Korea Combat Training Center (KCTC) training facility and utilized scientific military training equipment that included MILES and the main exercise control system. The training audience freely engaged an OPFOR who is an expert at tactics and weapon systems. It provides a statistical analysis of data in regards to state-of-the-art military training because the scientific battle training system saves and utilizes all training zone data for analysis and after action review as well as offers training control during the training period. The methodologies used the Cox PH modeling (which does not require parametric distribution assumptions) and decision tree modeling for survival data such as CART, GUIDE, and CTREE for richer and easier interpretation. The variables that violate the PH assumption were stratified and analyzed. Since the Cox PH model result was not easy to interpret the period of service, additional interpretation was attempted through univariate local regression. CART, GUIDE, and CTREE formed different tree models which allow for various interpretations.

• Proceedings of the Korean Society for Bioinformatics Conference
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• 2005.09a
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• pp.357-360
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• 2005

In this paper we consider the well-known semiparametric proportional hazards (PH) models for survival analysis. These models are usually used with few covariates and many observations (subjects). But, for a typical setting of gene expression data from DNA microarray, we need to consider the case where the number of covariates p exceeds the number of samples n. For a given vector of response values which are times to event (death or censored times) and p gene expressions (covariates), we address the issue of how to reduce the dimension by selecting the significant genes. This approach enable us to estimate the survival curve when n < < p. In our approach, rather than fixing the number of selected genes, we will assign a prior distribution to this number. The approach creates additional flexibility by allowing the imposition of constraints, such as bounding the dimension via a prior, which in effect works as a penalty. To implement our methodology, we use a Markov Chain Monte Carlo (MCMC) method. We demonstrate the use of the methodology to diffuse large B-cell lymphoma (DLBCL) complementary DNA(cDNA) data.

• Journal of Korean Institute of Industrial Engineers
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• v.31 no.4
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• pp.341-348
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• 2005

This paper is concerned with the question of servicing warranties for repairable items. During the warranty period, each time an item fails the manufacturer has the obligation to restore the item to operational condition either by repairing the item or by replacing it with a new item. In this paper, we consider repair-replacement strategies based on the condition of the failed item. For products with phase-type lifetime distributions where the phases represent the condition of the item, we develop algorithms to determine the expected cost of servicing a warranty and use it in making the repair-replacement decision. Illustrative numerical examples are presented. We also propose a dynamic strategy by taking the expected remaining warranty cost into consideration.