• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.783-786
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• 2000

In this paper, physical properties and dielectric characteristics of LLDPE and EVA which are used as a blending material to improve PE's performance are studied. LLDPE of 0.92[g/cm3] and EVA with the EVA contents of 12.5[%1 were selected as specimens, and X-ray diffraction(XRD) are used to analysis physical properties. We measured dielectric constant with the frequency range from 20[Hz] to 1 [MHz], applied voltage 6[V] and the temperature from 25[$^{\circ}C$] to 110[$^{\circ}C$]. From XRD, LLDPE has a crystallinity of 53[%] and, 46[%] for EVA. LLDPE has as low tan$\delta$ as of 10$^{-3}$ ~10$^{-4}$ and inflection point near 500[Hz]. At frequency region lower than 500[Hz], tan$\delta$ decreases with frequency and increases with temperature and it is considered to be caused by conductive carriers within specimen. Over 500[Hz], it is the reverse and we thought that it was caused by decrease of relaxation time due to Debye theory, EVA has tan$\delta$with the values of 10$^{-2}$ ~10$^{-3}$ , which is higher than that of LLDPE, and it has inflection point at 60[Hz]. It is shown that Dielectric characteristics of EVA are similar to LLDPE's.

• Journal of Korean Society of Forest Science
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• v.98 no.6
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• pp.646-651
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• 2009

In this study, it was intended to prepare a stem volume table (with or without bark) and a stand yield table for Juglans mandshurica, plantations in Chungju, located in Chungcheongbuk-do, Korea. For the calculation of stem volume, we applied Kozak's growth model, which showed the best fitness index (97%). With this model, it was able to prepare the first yield table for Juglans mandshurica in Korea. Site index model, an indicator of forest productivity, was derived by using the Chapman-Richard model, in which the basic stand age was set to 30 years. The resulted site index ranged between 16 and 22. Based on the yield table of Juglans mandshurica resulted from this study, the volume for a 70-year-old stand with a midium site index class was estimated to be $238m^3/ha$, which is $100m^3/ha$ higher than the volume estimated from the yield table of Quercus acutissima. The yield table of oak trees has been used in the estimation of most broadleaf stands in Korea. However, the result of this study indicated that it is necessary to generate a stand yield table for each broadleaf species. The annual $CO_2$ removals of 30-year-old Juglans mandshurica plantations in the ChungJu region was estimated to be $5.84tCO_2/ha$. The stem volume and stand yield table of Juglans mandshurica plantation resulted from this study would provide a good information in decision making for forest management in ChungJu region.

• Journal of Korea Water Resources Association
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• v.54 no.11
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• pp.999-1009
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• 2021

As the frequency and intensity of extreme weather events due to climate change are increasing in recent years, it is very important to evaluate and analyze climate conditions to manage and respond to the negative effects of climate change in advance. In this study, the trends and characteristics of regional climate change were analyzed by calculating the climate indices for the Chungcheong Province. Annual and monthly UNEP-MP, UNEP-PM and MDM indices were calculated using daily data from 1973-2020 collected from 10 synoptic meteorological stations operated by the Korea Meteorological Administration. The normality of climate data was analyzed through the KS test, and the climate change trend was analyzed by applying the Spearman and Pearson methods. The Chungcheongnam-do region had a relatively humid climate than the Chungcheongbuk-do region, and the annual climate indices showed a dry climate trend in Cheongju and Chungju, while the climate of Seosan and Buyeo was becoming humid. Based on the monthly trend change analysis, a humid climate trend was observed in summer and autumn, while a dry climate trend was observed in spring and winter. Comparison of climate indices during the past (2001-2010) and the recent (2011-2020) years showed a higher decrease in the average climate indices during the last 10 years and a gradually drying climate change trend was recorded.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.3
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• pp.291-302
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• 2024

Sustained meteorological drought can lead to hydrological drought, known as drought propagation. The propagated droughts cause more damage to the region than the non-propagated droughts. Recent studies on drought propagation have focused on identifying the lag time using correlation analysis. There is a lack of studies comparing damage patterns between propagated and non-propagated droughts. In this study, the overlap and pooling propagation between meteorological and hydrological droughts were analyzed using drought indices in Chungcheong Province to identify drought propagation, and the propagation characteristics such as pooling, attenuation, lag and extension were analyzed. The results showed that although Chungju-si experienced a meteorological drought in 2010, no damage was caused by the drought. However, a meteorological drought in 2017 and 2018 propagated into a hydrological drought of longer duration but less severity, resulting in drought-affected damage. Similarly, Cheongyang-gun experienced a meteorological drought in 2017, but no damage was reported from the drought. However, in the neighboring county of Buyeo-gun, a meteorological drought with a similar magnitude propagated to a hydrological drought during the same period, resulting in drought-affected damage. The overall results indicated that the damage from propagated drought events was more severe than the non-propagated drought events, and these results can be used as basic data for establishing drought response policies suitable for the region.

• Journal of the Korean Geographical Society
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• v.29 no.1
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• pp.84-104
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• 1994

The migration of population into the city has been on the increase according as Korea has been industrialized repidly since the 1960's. And there is a steady decrease in rural population. Thus lack of the number of the students forced many elementary Schools to be abolished. The aim of this study is to grasp the abolition types and the regional characteristics with the subject region of Chungbuk province. From the viewpoint of the increasing abolition of the elementary schools, I think it is very important to understand how the elementary schools have been abolished so far and predict how the subject region will have been changed in geography. Data for this study are based on Annual Establishment-Abolition Situation of the Schools published by Chungbuk office of Education in 1992, and many Kinds of the statistical reports, and the interview with the related. The results are as follows: 1. By examining the change of the number of the elementary schools and students in Chnugbuk, the numder of the students had also decreased since 1969 and was less than the half in 1990. As the number of the schools began to decrease ten years later than the students began to, the abolition of the elementary schools has started in reality from 1980's. 2. The 72 elementary schools were aboilshed between 1980 and 1992: the principal school is 9.7%, the branch school is 90.3%. The most fifteen schools are abolished in Yongdong-county and Chechon-county, and the least one school is abolished in Chechon-city and Okchon-county, and there is no abolition in Chongju-city and Chungju-city: According to the type of the abolition process, the least seven principal schools are abolished, and the principal school is reorganized as a branch school and twenty eight branch schools are abolished, and the most thirty seven branch schools are abolished. 3. When special change of the abolition is classified into the first perio (1980-1986) and the second period (1987-1992), in the first period the principal and branch schools were abolished and they are 13.9% of total abolition. The abolition out of them by building a dam is 60%. The principal schools in the submerged area though they have many students, were abolished. In the second period sixty two branch schools are abolished and they are 86.1% of total abolition. The most fifteen schools are abolished in Yongdong-county, thirteen in Chechon-county, seven in Tanyang-county, six in Chongwon-county, five in Chungwon-county and Koesan-county. Unlike the first period, the schools were abolished in this period because the number of students was so small. In this period sixty branch schools were abolished. All the students in the abolished schools except six schools transfered to the principal schools. The 58 school authorities help the students attend school by bus or support the expenses for attending school after that. 4. The abolition types of city, county and myon are classified into five types by the number of the abolished schools. The most forty nine abolished schools in type II are 68.1 of the total abolition. The least three abolished ones in type I are 12.5%. Considering the relation between the abolition type ane the number of schools and students, the number of the schools, increased in type I, II, III, V except IV from 1980 and then have decreased by abolition since 1980, while the more students decreased than they did in 1970 and the more the abolished school increases, the less the students decreases. The average students per school decreased in every abolition type and the most students decreased in type IV. 5. Considering the relation between the abolition type and the regional characteristics, most abolished schools were located between 100m and 300m above the sea level and it is 71% of the total abolition. The region without the abolition is high in the ratio of the cultivate land, ratio of rice field, and the part-time farmer, but the region with many abolition is low in the ratio of cultivated land. As for the manufacturing there are the most city, county and myon in the abolition type in Youngdong-county and Chechon-county where the manufacturing ratio of employing is low but Chongju-city without the abolition is a region where the manufacturing ratio is high. Consequently the development of the manufacturing causes the population to emigation out and the decrease of the population leads the transport is difficult of access, the facilities sold after being abolished are not being used in many ways. 7. Take an example of Youndong-county where the most schools were abolished, I have examined the school district and the population characteristics of the abolition. Though there were more villages, households, populations in the region that is higher than low above the sea level, the schools were abolished. Therefore we know that above the sea level had a great effect on the abolition. As a result of the regional analysis of the abolition, many schools were abolished by the artificial buildings such as a dam in the early 1980's but the schools in the late 1980's were abolished ten years later after the students decreased. More schools were abolished in the region where the manufacturing industry didn't develop. And the higher the school position was above the sea level, the sooner the school was abolished. It is also proved that both the beautiful natural scenery and accessibility are the important factor in using the abolished facilities practically.

• Korean Journal of Agricultural and Forest Meteorology
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• v.14 no.3
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• pp.124-131
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• 2012

This study was carried out to evaluate a possible change in freeze risk for 'Changhowon Hwangdo' peach buds in three major peach growing areas under the future climate projected by RCP8.5 emission scenario. Mean values of the monthly temperature data for the present decade (2000s) and the future decades (2020s, 2050s, 2080s) were extracted for farm lands in Icheon, Chungju, and Yeongcheon-Gyeongsan region at 1km resolution and 30 sets of daily temperature data were generated randomly by a stochastic process for each decade. The daily data were used to calculate a thermal time-based dormancy depth index which is closely related to the cold tolerance of peach buds. Combined with daily minimum temperature, dormancy depth can be used to estimate the potential risk of freezing damage on peach buds. When the freeze risk was calculated daily for the winter period (from 1 November to 15 March) in the present decade, Icheon and Chungju regions had high values across the whole period, but Yeongcheon-Gyeongsan regions had low values from mid-December to the end of January. In the future decades, the frequency of freezing damage would be reduced in all 3 regions and the reduction rate could be as high as 75 to 90% by 2080's. However, the severe class risk (over 80% damage) will not disappear in the future and most occurrences will be limited to December to early January according to the calculation. This phenomenon might be explained by shortened cold hardiness period caused by winter warming as well as sudden cold waves resulting from the higher inter-annual climate variability projected by the RCP8.5 scenario.

• Journal of the Korea Concrete Institute
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• v.15 no.5
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• pp.689-696
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• 2003

Recently, Appendix A of ACI 318∼02 Code introduced the Strut-and-Tie Model(STM) procedure in shear design of deep flexural members. The STM procedure is widely used in the design of concrete regions where the distribution of longitudinal strains is significantly nonlinear, such as deep beams, beams with large openings, corbels, and dapped-end beams. Experimental study included five high-strength reinforced concrete deep beams with different detailing schemes for the horizontal and vertical reinforcement. The specimens were designed as simply supported beams subjected to concentrated loads on the top face and supported on the bottom face. At failure, all specimen exhibited primary diagonal crack running from the support region to the point load. Specimens which had mechanical anchorages(terminators) gives better representation of the load-carrying mechanism than the specimen had standard 90-degree anchorage at failure in deep flexural members. Based on the test results, shear design procedures contained in the ACI 318-99 Code, Appendix A of the ACI 318-02 Code, CSA A23.3-94 Code and CIRIA Guide-2 were evaluated. The Shear design of ACI 318-99 Code, Appendix A of the ACI 318-02 Code and CIRIA Guide-2 shown to be conservative predictions from 10% to 36% in the shear strength of the single-span deep beam which was tested. ACI 318-99 Code was the lowest standard deviation.

• Journal of Korea Water Resources Association
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• v.32 no.5
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• pp.579-591
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• 1999

The operation of a reservoir system is necessary for establishing the operation rule as well as designing the reservoirs for water resources planning or management. Increasingly complex water resource systems require more advanced operation techniques. As a result, various techniques have been introduced and applied until now. In this study Linear Tracking model based on optimal control theory is applied to the operation of the largest scale multi-reservoir system in the Han river and its applicability proved. This system normally supplies the water resources required downstream for hydro-power and plays a role in satisfying the water demand of the Capital region. For the optimal use of the water resources the Linear Tracking model is designed with the objective to maximize the hydro-power energy subject to the water supply demand. The multi-reservoir system includes the seven main reservoirs in IIan river such as Hwachon, Soyanggang, Chunchon, Uiam, Cheongpyong, Chungju and Paldang. These reservoirs have been monthly operated for the past 21 years. Operation results are analyzed with respect to both hydro"power energy and water supply. Additionally the efficiency of the technique is assessed.sessed.

• Journal of the Korean GEO-environmental Society
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• v.18 no.6
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• pp.21-30
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• 2017

This study analyzed the ground characteristics region by designating 3 research areas, Anrim-dong in Chungju City, Busa-dong in Daejeon Metropolitan City and Sinan-dong in Andong City out of the areas subject to concentrated management to prepare for sediment disaster in downtown areas. The correlation between ground characteristics were observed by using characteristics (crown density, root cohesion, rainfall characteristics, soil characteristics) and the risk areas were predicted through sediment disaster prediction modeling. Landslide MAPping (LSMAP), Stability Index MAPping (SINMAP) and Landslide Hazard MAP (LHMAP) were used for the comparative analysis of the hazard prediction model for sediment disaster. As a result of predicting the sediment disaster danger, in case of SINMAP which was generally used, excessive range was predicted as a hazardous area and in case of the Korea Forest Service's landslide hazard map (LHMAP), the smallest prediction area was assessed. LSMAP predicted a medium range of SINMAP and LHMAP as hazardous area. The difference of the prediction results is that the analysis parameters of LSMAP is more diverse and engineering than two comparative models, and it is found that more precise prediction is possible.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5B
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• pp.415-429
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• 2011

Quantitative evaluation indexes for flood control effect of a multi-purpose reservoir used widely in Korea are the discharge control rate, reservoir release rate, reservoir storage rate, and flood control storage utilization rate. Because these indexes usually use and compare inflow, release, and storage data directly, the uncertainties included in these data are not considered in evaluation process, and the downstream flood control effects are not assessed properly. Also, since the acceptable partial failure in a design of water resources system is not considered, the development of a new flood control effect evaluation index is required. Fuzzy set theory is therefore applied to the development of the index in order to consider the data uncertainty, the downstream flood control effect, and the acceptable partial failure. In this study, the flood control effect of a multi-purpose reservoir is evaluated using the flood control effect index developed by applying fuzzy set theory. The Chungju reservoir basin was selected as a study basin and the storm events of July, 2006 are used to study the applicability of the developed index. The related factors for flood control effect are fuzzified, the acceptable failure region is divided from the system state to evaluate the flood control effect using developed flood control effect index. The flood control effect index were calculated by applying to the study basin and storm events. The results show that the developed index can represent the flood control effect of a reservoir more realistically and objectively than the existing index.