• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.214-215
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• 2005

In this paper, in order to develop low temperature sintering piezoelectric ceramics for piezoelectric transformer, PMW-PMN-PZT ceramics using 0.25wt%$CaCO_3$ and 0.2wt%$Li_2CO_3$ as sintering aids were fabricated according to the variation of amount of PMW and Zr/Ti ratio. Specimens could be sintered at 900$^{\circ}C$ by adding sintering aids. As Zr/Ti ratio was increased, kp was increased and Qm was decreased by approaching MPB region, and kp showed the largest value of 0.58 at Zr/Ti:50/50. The variation of amount of PMN substitution affected the liquid phase sintering of the ceramics using sintering aids, and decreased piezoelectric properties.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.200-204
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• 2008

The curing kinetics of diglycidyl ether of bisphenol F (DGEBF) with an asymmetric cycloaliphatic amine curing agent were examined by thermal analysis in both isothermal and dynamic curing conditions. From the residual curing of the samples partially cured in isothermal condition and from the dynamic curing with various heating rates, it was found that there exist two kinds of reactions such as at low temperature and at high temperature regions. It was thus also found that the cure parameters obtained from the isothermal curing kinetic model hardly estimate experimental results for a degree of cure larger than 0.6. The activation energies and frequency factors of these two kinds of reactions were obtained from the dynamic curing experiments with various heating rates. From the curing analysis, it was verified that the total cure kinetics for low degrees of cure is dominated by the cure reaction in the low temperature region.

• International Journal of Automotive Technology
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• v.6 no.2
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• pp.125-131
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• 2005

This article reports the experimental and numerical results for free sprays under ultra-high injection pressure conditions to give us better understandings of spray characteristics and also to make clear a limit pressure condition in diesel sprays. The high pressure injection system developed in this work is devised to reach ultra-high pressure conditions in the range from 150 MPa to 355 MPa. The free spray injected from a single nozzle injector is visualized by the Schlieren technique and the high speed camera. In particular, it is found that the shock waves are present and propagated along the edge of spray in the downstream direction. The measured spray penetration length increases gradually with the injection pressure, but its increasing rate is decreased as the injection pressure increases. The Sauter mean diameter is also no longer augmented for the injection pressures higher than 300 MPa. In addition, the three­dimensional numerical simulations are conducted for comparing the measurements with the predictions based on two different breakup models. The TAB model results show better agreements with experimental data than the WAVE model under ultra-high injection pressure conductions. Moreover, the simulation results show that the gas-phase pressure increases substantially in the vicinity of the spray tip region. It supports the experimental observation that the shock waves are formed at the front of spray tip and are propagated downstream.

• The Korean Journal of Mycology
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• v.51 no.4
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• pp.491-504
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• 2023

To explore fungal diversity in orchard soil where fire-blighted apple trees are buried, we collected soil samples from apple orchards in Chungju, Korea. Fungal isolates were obtained from DG18 agar and identified at the species level based on morphological features and phylogenetic analyses. The colony characteristics and microstructures were examined using a light microscope and a scanning electron microscope after culturing on potato dextrose agar (PDA), malt extract agar (MEA), Czapek yeast agar (CYA), and oatmeal agar (OA) The PCR-amplified products of the ITS1-5.8S-ITS2 region and 28S large subunit of the nuclear ribosomal RNA gene, as well as partial sequences of the β-tubulin, calmodulin, and translation elongation factor 1-α genes were sequenced and analyzed phylogenetically. Seven previously unknown fungal species were explored in Korea. All samples, including Aspergillus aureolatus, Botryotrichum atrogriseum, Dactylonectria novozelandica, Fusarium denticulatum, Paecilomyces tabacinus, Sarcopodium tibetense and Talaromyces stollii, had ascomycetes. Herein, we report their descriptions and features.

• Journal of the Korean Society of Safety
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• v.15 no.2
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• pp.111-117
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• 2000

In this study, the bearing capacity behavior of strip footing located above a continuous cavity in sand was investigated experimentally. The model footing test was performed in a model box made by using raining method in sand. The model footing test results were compared with those obtained from theoretically proposed equations. The results of the analysis indicate that there is a critical region under the footing. For strip footing, there exists a critical depth below which the presence of the cavity has negligible influence on the footing performance. Only when the cavity is located within this region will the footing performance be significantly affected by the presence of the cavity. The size of the critical region depends on several factors such as footing shape, soil property, cavity size and cavity shape. When the cavity is located within the critical region, the bearing capacity of the footing varies with various factors, such as the size and location of the cavity and the depth of foundation. Based on the experimental study, the following conclusions were induced. 1. The ultimate bearing capacity due to the eccentricity of a underground cavity increases at the rate of the small rather than that due to the depth of a underground cavity. This indicates that the bearing capacity of a strip footing is influenced on the depth rather than the eccentricity of a underground cavity. 2. The critical $depth(D/B)_{cr}$, by underground cavity in sand soil ground that is made by the relative density($D_r$)=55%, 65%, 75%, approaches a range of about 8~10 in case of W/B=1, and about 11~13 in case of W/B=2. 3. In case of the relative density($D_r$) 75%, the most outstanding differential settlement trend is shown in the depth of 4~8cm regardless of the size of cavity, namely, when the value of D/B is 1~2. Therefore, a underground cavity influences on not only the decrease of the bearing capacity but also the differential settlement of a strip footing.

• Korea journal of population studies
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• v.24 no.1
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• pp.5-40
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• 2001

We have approached this study on the basis of population and family changes. We have selected two suburban and two general rural areas for this research. The suburban rural areas are located next to Chungju City, which is the biggest city in Chungbuk Province, and the residents are able to commute to Chungju. The general rural areas are located in Boeun Gun, which is a typical agricultural county in Chungbuk Province. We have conducted two round surveys at the research areas: 1995-1996 for the first round and 1999-2000 for the second round surveys. Since the surveys were completed ones interviewed by enumerators, we have used the survey data directly for the analysis by year and region. The population structure by age and sex in general rural areas is shaped as a reverse triangle, which is becoming more serious because of the continuing emigration of young generation. Most of the young generation moves to the urban areas and their old parents only are left in their hometown, rural areas. When the parents become old and die, the number of households in the areas decreases rapidly. If there are no more new family formations, therefore, the rural society itself would cease to exist in near future. However, the situation of suburban rural areas was a different case. Although the rural young generation has moved to urban areas, other young age groups have moved into the areas with their small enterprises and for the low living costs. The original residents become older and the young age groups are replaced with the new immigrants continuously. Therefore, the traditional agricultural society will be replaced with a non-agricultural society, which will have more characteristics of urban areas.

• Journal of Society of Preventive Korean Medicine
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• v.21 no.2
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• pp.117-126
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• 2017

Objectives : The use of health functional foods is gradually increasing. On the other hand, the use of the Korean herbal medicine is gradually decreasing. Especially children are known to have a high percentage of taking a health functional food. This study was designed to compare the use of health functional food with the reason for taking the Korean herbal medicine. Methods : The participants were 453 parents who have kids age between 3 to 6 years old from day care center in Wonju and Chungju. The questionnaire consisted of 17 questions and the survey was conducted by self-entry method. This study analyzed 374 participants' questionnaires who agreed to the survey. Results : The percentages of children's health functional food intake experience were 82.9% and they usually bought products which contain lactic acid bacteria(55.6%). The reason for consuming health functional food was to strengthen the immune system and enhance the physical strength. Most of the participants purchased health functional food from pharmacy through inaccurate information such as the internet. The percentages of children's health functional food preference were 58.5% because it is easy to take. The percentages of children's herbal medicine preference were 41.7%. There are inconveniences of taking herbal medicine because of taste and smell(68.8%). Conclusions : Therefore, it is necessary to change the formulation of the herbal medicine and increase convenience for use of the herbal medicine to preschooler(3-6 years old). In additionary, it is necessary to supply accurate and up to date information of herbal medicine taking.

• Korean Journal of Plant Resources
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• v.25 no.2
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• pp.209-224
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• 2012

This study was carried out to survey the vascular plants of Namhan River located in Chungju-si, and the period of survey was from June, 2010 to June, 2011. The results are as follows. The vascular plants distributed in Neungam, Mokgye and Jangcheon around Namhan river were summarized as 225 taxa including 52 families, 164 genera, 200 species, 23 varieties and 2 forms. The rare plant designated by Korea Forest Service was $Aristolochia$ $contorta$ Bunge, and the endemic plant was identified as $Salix$ $koriyanagi$ Kimura. The specific plants by floristic region were 7 taxa including $Salix$ $chaenomeloides$ Kimura, $Aristolochia$ $contorta$ Bunge, $Actinostemma$ $lobatum$ Maxim., $Artemisia$ $selengensis$ Turcz., $Cirsium$ $pendulum$ Fisch., $Alisma$ $plantago-aquatic$ var. $orientale$ Samuels. and $Carex$ $versicaria$ L.. The naturalized plants were 47 taxa including $Fallopia$ $dumetorum$ (L.) Holub., $Chenopoidum$ $album$ L., $Silene$ $armeria$ L., $Brassica$ $juncea$ (L.) Czern., $Melilotus$ $alba$ Medicus, $Trifolium$ $pratense$ L., $Oenothera$ $erythrosepala$ Borb$\acute{a}$s, $Ipomoea$ $hederacea$ var. $integriuscula$ A.Gray, $Bidens$ $frondosa$ L., $Matricaria$ $inodora$ L., $Xanthium$ $canadense$ Mill., $Panicum$ $dichotomiflorum$ Michx. and so forth. In life forms, megaphanerophytes (M) were 13 taxa, 13 taxa in nanophanerophytes (N), 14 taxa inchamaiphytes (Ch), 40 taxa in hemicryptophytes (H), 20 taxa in geophytes (G), 103 taxa in therophytes (Th) and 22 taxa in hydrophytes (HH). The ratios of the naturalized index (NI), the urbanized index (UI) and the disturbed index (DI) were 20.9%, 14.6% and 18.2% in all sites.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.433-447
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• 2023

There is a growing demand for the stability of existing dams due to abnormal climate and the aging of dams. Emergency Action Plans (EAPs) for reservoir or dam failure only consider a single rainfall event. Therefore, this study simulates dam failure caused by continuous rainfall events, and proposes the establishment of EAP by selecting the optimal shelters. We define a mega rainfall event scenario caused by continuous rainfall events with 500-year frequency in the Chungju Dam watershed and estimate the mega flood. The mega flood event scenario is divided into two cases: scenario A represents the flooding case caused by discharge release from a dam, while scenario B is the case of a dam break. As a result of flood inundation analysis, the flooded damage area by the scenario A is 50.06 km² and the area by the scenario B is 6.1 times of scenario A (307.45 km²). We select optimal shelters for each administrative region in the city of Chungju, which has the highest inundation rate in the urban area. Seven shelter evaluation indicators from domestic and foreign shelter selection criteria are chosen, and Analytical Hierarchy Process (AHP) method is used to evaluate the alternatives. As a result of the optimal shelter selection, the six shelters are selected and five are schools. This study considers continuous rainfall events for inundation analysis and selection of optimal shelters. Also, the results of this study could be used as a reference for establishment of the EAP.

• Journal of the Korean earth science society
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• v.27 no.2
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• pp.159-176
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• 2006

Geographic factors and mathmatical location of the Korean Peninsula have great influences on the variation patterns and appearances over a period of ten days of summer precipitation. In order to clarify the influence of several climate factors on precise climate classification in the middle part region of the Korea, weather entropy and the information ratio were calculated on the basis of information theory and of the data of 25 site observations. The data used for this study are the daily precipitation phenomenon over a period of ten days of summer during the recent thirteen years (1991-2003) at the 25 stations in the middle part region of the Korea. It is divided into four classes of no rain, $0.1{\sim}10.0mm/day,\;10.1{\sim}30.0mm/day$, 30.1mm over/day. Their temporal and spatial change were also analyzed. The results are as follows: the maximum and minimum value of calculated weather entropy are 1.870 bits at Chuncheon in the latter ten days of July and 0.960 bits at Ganghwa during mid September, respectively. And weather entropy in each observation sites tends to be larger in the beginning of August and smaller towards the end of September. The largest and smallest values of weather representative ness based on information ratio were observed at Chungju in the beginning of June and at Deagwallyeong towards the end of July. However, the largest values of weather representativeness came out during the middle or later part of September when 15 sites were adopted as the center of weather forecasting. The representative core region of weather forecasting and climate classification in the middle part region of the Korea are inside of the triangle region of the Buyeo, Incheon, and Gangneung.