• Solar Energy
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• v.12 no.1
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• pp.59-71
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• 1992

The purposes of the present study are to investigate the characteristics of heat storage and emission of the PCM($CalCl_2{\cdot}6H_2O$) panel, and to analyze the distribution of indoor air temperature in a floor heating space with PCM panels for the heating system. Two identical unit test cells sized $1.8m^W{\times}1.8m^L{\times}1.8m^H$ were built and installed with specially designed aluminium Ondol-panels. It held 1.2kg of calcium chloride hexahydrate(CCH). It was found that PCM panels could reduce the indoor air temperature fluctuations and maintain the phase changing temperature for considerably long duration, $2{\sim}3$ times longer in heating hour over no-CCH one. When the elapsed time was 6 hours, the average temperature difference between PCM panel and Ondol panel was $7.7^{\circ}C$.

• Structural Engineering and Mechanics
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• v.50 no.4
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• pp.501-524
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• 2014

This paper presents a type of composite box girder with corrugated webs and concrete filled steel tube slab to overcome cracking on the web and reduce self-weight. Utilizing corrugated steel web improves the efficiency of prestressing introduced into the top and bottom slabs due to the accordion effect. In order to understand the loading capacity of such new composite structure, experimental and numerical analyses were conducted. A full-scale model was loaded monotonically to investigate the deflection, strain distribution, loading capacity and stiffness during the whole process. The experimental results show that test specimen has enough loading capacity and ductility. Based on experimental works, a finite element (FE) model was established. The load-displacement curves and stress distribution predicted by FE model agree well with that obtained from experiments, which demonstrates the accuracy of proposed FE model. Moreover, simplified theoretical analysis was conducted depending on the assumptions which were confirmed by the experimental and numerical results. The simplified analysis results are identical with the tested and numerical results, which indicate that simplified analytical model can be used to predict the loading capacity of such composite girder accurately. All the findings of present study may provide reference for the application of such structure in bridge construction.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.4
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• pp.427-432
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• 1999

Although importance of intrapancreatic neurons containing gastrin-releasing peptide (GRP) in control of exocrine secretion has been raised, the nature of GRP in the pancreas is unclear. Thus, the present study was undertaken to see distribution, content and molecular heterogeneity of immunoreactive GRP in the rat pancreas. Content of immunoreactive GRP in the rat pancreas was $2.99\;{\pm}\;0.66$ ng/g wet tissues determined by radioimmunoassay. Immunoreactive GRP was most abundantly expressed in the duodenal part among 3 parts of the pancreas; duodenal, body and splenic part. Vagotomy failed to change the content of immunoreactive GRP in the pancreas. Three distinct forms of immunoreactive GRP, very identical to GRP-27, bombesin-24 and neuromedin C, were observed in the rat pancreas by using reversed phase $C_{18}$ HPLC and Sephadex G-50 superfine column chromatography. Cell bodies of neurons containing immunoreactive GRP were scattered in pancreatic connective tissues and their nerve fibers innervated pancreatic acini and large ducts as determined by immunohistochemistry. The present results suggest that three distinct forms of GRP exist in intrapancreatic GRPergic neurons, which exert a stimulatory role in pancreatic exocrine secretion in rats.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.45-53
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• 2013

In this paper, we analyze the typical phase voltage and line current waveform characteristics of the distribution system with 3 phase small synchronous generation source in case with load and non-load group, in order to investigate the power quality for end load connected of generation source. As demonstrated by our experimental results, the distortion and power quality of phase voltage and line current waveform were relatively good for low voltage 3 phase model grids connected of 3 phase small synchronous generation source in case with non-load group. However, distortion and power quality of voltage and current waveform was poor for low voltage 3 phase model grids connected to 3 phase small synchronous generation source in the load group with some phase voltage and frequency difference. From the above results, we conclude that the phase voltage and frequency of 3 phase generation source must be identical to that of distribution system source to maximize the power quality. Also, special attention is required in case of having load group or non-load group to 3 phase generation source.

• Reproductive and Developmental Biology
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• v.30 no.4
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• pp.263-270
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• 2006

The Chinese Hamster Ovarian cells CHO-K1 are one of the most extensively used cells for the evaluation of gene expression and toxicology. However, these cells are frequently used for biomedical research without consideration of their cytogenetic characteristics. Therefore, we carried out to investigate the karyologic profiles, the frequency and type of chromosome aberration, and the distribution of telomeric DNA on chromosomes of the CHO-K1 cells. The GTG banding and fluorescence in situ hybridization on CHO-K1 cells were performed to characterize the karyotype and the distribution of telomeric DNA The present study revealed that the chromosome modal number of CHO-K1 cells was 2n=20; eight chromosomes appeared to be identical with those of the normal Chinese hamster, whereas the remaining 12 chromosomes were shown to be translocated, deleted, inversed, or rearranged from Chinese hamster chromosomes. The telomeric DNA on CHO-K1 chromosomes was intensively distributed at the centromeres rather than the ends of chromosomes. In addition, three chromosomes had interstitial telomeres and one marker chromosome entirely consisted of telomeric DNAs. The frequency and type of chromosome aberrations in CHO-K1 cells were examined. Of the 822 metaphase spreads, 68 (8.3%) cells resulted in chromosome aberrations of which the chromosome breakage was the most frequently occurred.

• The Transactions of the Korea Information Processing Society
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• v.6 no.9
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• pp.2343-2349
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• 1999

The hyper-geometric distribution software reliability growth model (HGDM) was recently developed and successfully applied to real data sets. The HGDM considers the sensitivity factor as a parameter to be estimated. In order to reflect the random behavior of the test-and-debug process, this paper generalizes the HGDM by assuming that the sensitivity factor is a binomial random variable. Such a generalization enables us to easily understand the statistical characteristics of the HGDM. It is shown that the least squares method produces the identical results for both the HGDM and the generalized HGDM. Methods for computing the maximum likelihood estimates and predicting the future outcomes are also presented.

• Journal of Powder Materials
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• v.27 no.4
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• pp.300-304
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• 2020

In this paper, a durability study is presented to enhance the mechanical properties of an Fe-Si-Al powder-based magnetic core, through the addition of graphite. The compressive properties of Fe-Si-Al-graphite powder mixtures are explored using discrete element method (DEM), and a powder compaction experiment is performed under identical conditions to verify the reliability of the DEM analysis. Important parameters for powder compaction of Fe-Si-Al-graphite powder mixtures are identified. The compressibility of the powders is observed to increase as the amount of graphite mixture increases and as the size of the graphite powders decreases. In addition, the compaction properties of the Fe-Si-Al-graphite powder mixtures are further explored by analyzing the transmissibility of stress between the top and bottom punches as well as the distribution of the compressive force. The application of graphite powders is confirmed to result in improved stress transmission and compressive force distribution, by 24% and 51%, respectively.

• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1774-1786
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• 2018

Phenotypic variation among clones (individuals with identical genes, i.e. isogenic individuals) has been recognized both theoretically and experimentally. We investigate the effects of phenotypic variation on evolutionary dynamics of a population. In a population, the individuals are assumed to be haploid with two genotypes : one genotype shows phenotypic variation and the other does not. We use an individual-based Moran model in which the individuals reproduce according to their fitness values and die at random. The evolutionary dynamics of an individual-based model is formulated in terms of a master equation and is approximated as the Fokker-Planck equation (FPE) and the coupled non-linear stochastic differential equations (SDEs) with multiplicative noise. We first analyze the deterministic part of the SDEs to obtain the fixed points and determine the stability of each fixed point. We find that there is a discrete phase transition in the population distribution when the probability of reproducing the fitter individual is equal to the critical value determined by the stability of the fixed points. Next, we take demographic stochasticity into account and analyze the FPE by eliminating the fast variable to reduce the coupled two-variable FPE to the single-variable FPE. We derive a quasi-stationary distribution of the reduced FPE and predict the fixation probabilities and the mean fixation times to absorbing states. We also carry out numerical simulations in the form of the Gillespie algorithm and find that the results of simulations are consistent with the analytic predictions.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.4
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• pp.194-202
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• 2019

Reliability analysis of the components frequently starts with the data that manufacturer provides. If enough failure data are collected from the field operations, the reliability should be recomputed and updated on the basis of the field failure data. However, when the failure time record for a component contains only a few observations, all statistical methodologies are limited. In this case, where the failure records for multiple number of identical components are available, a valid alternative is combining all the data from each component into one data set with enough sample size and utilizing the useful information in the censored data. The ROK Navy has been operating multiple Patrol Killer Guided missiles (PKGs) for several years. The Korea Multi-Function Control Console (KMFCC) is one of key components in PKG combat system. The maintenance record for the KMFCC contains less than ten failure observations and a censored datum. This paper proposes a Bayesian approach with a Dirichlet mixture model to estimate failure time density for KMFCC. Trends test for each component record indicated that null hypothesis, that failure occurrence is renewal process, is not rejected. Since the KMFCCs have been functioning under different operating environment, the failure time distribution may be a composition of a number of unknown distributions, i.e. a mixture distribution, rather than a single distribution. The Dirichlet mixture model was coded as probabilistic programming in Python using PyMC3. Then Markov Chain Monte Carlo (MCMC) sampling technique employed in PyMC3 probabilistically estimated the parameters' posterior distribution through the Dirichlet mixture model. The simulation results revealed that the mixture models provide superior fits to the combined data set over single models.

• Journal of Korea Water Resources Association
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• v.35 no.1
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• pp.109-124
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• 2002

This study is an effort to develop a stochastic model of precipitation series that preserves the pattern of occurrence of precipitation events throughout the year as well as several characteristics of the duration, amount, and intensity of precipitation events. In this study an event cluster model is used to describe the occurrence of precipitation events. A logarithmic negative mixture distribution is used to describe event duration and separation. The number of events within each cluster is also described by the Poisson cluster process. The duration of each event within a cluster and the separation of events within a single cluster are described by a logarithmic negative mixture distribution. The stochastic model for hourly precipitation occurrence process is fitted to historical precipitation data by estimating the model parameters. To allow for seasonal variations in the precipitation process, the model parameters are estimated separately for each month. an analysis of thirty-four years of historical and simulated hourly precipitation data for Seoul indicates that the stochastic model preserves many features of historical precipitation. The seasonal variations in number of precipitation events in each month for the historical and simulated data are also approximately identical. The marginal distributions for event characteristics for the historical and simulated data were similar. The conditional distributions for event characteristics for the historical and simulated data showed in general good agreement with each other.