• Survey Research
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• v.11 no.2
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• pp.1-28
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• 2010

This paper reports the results of the 2009 Internet volunteer panel version of the social survey conducted by Statistics Korea (Korea National Statistical Office). Authors identify socio-psychological characteristics of Internet survey volunteers and present quantitative evaluation of the propensity adjustment weighting method intended to remove Internet sample bias. The nine criteria used for propensity adjustment were regions, urban/rural, gender, age, education, consumer satisfaction, views on income distribution, newspaper access and Internet news access. Propensity adjustment weighting based on the logit model and rim weights were applied to the online survey of 2,903 respondents using the face-to-face area sample data of 37,049 respondents as reference. A total of 106 items were used for evaluating the propensity adjustment weighting methods. The results showed that in 80% of survey items the propensity adjustment weighting yielded better estimates compared to simple demographic weighting. This suggests that Internet surveys by volunteer panels are useful for conducting the general social study in Korea. The reference survey data for this study contains several items on social-psychological behaviors and attitudes, is large in size and obtained by probability sampling. Thus it may be utilized in propensity adjustment of other Internet surveys.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.753-761
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• 2009

This paper presents the test results of total 24 beam-end specimens to investigate the effect of high-strength concrete and cover thickness on the development resistance capacity in tensile lap splice length regions. Based on bond characteristics that an increase in concrete strength results in higher bond stress and shortening of the transfer length, cracking behavior that thin cover thickness induced a splitting crack easily and brittle crack propagation, current design code that development length provisions as uniform bond stress assumption was investigated apply as it. The results showed that as higher strength concrete was employed, not only development resistance capacity was influenced by cover thickness, but also more sufficient safety factor reserved shorter than the lap splice length provision in current design code. From experimental research results, high-strength concrete development length was not inverse ratio of $\sqrt{f_{ck}}$ but directly inverse of $f_{ck}$, and it is also said that there is a certain limit length of the embedded steel over which the assumption of uniform bond stress distribution is valid specially for high-strength concrete not having a same embed length such as normal-strength concrete in current design criteria hypothesis.

• Journal of Korea Water Resources Association
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• v.51 no.5
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• pp.395-404
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• 2018

This research evaluated the change in rainfall quantile during S1, S2, and S3 by using Representative Concentration Pathways (RCP) 4.5 climate scenario HadGEM3-RA Regional Climate Model (RCM) produced by downscaling and bias correlation compared to the past standard observation data S0. Also, the maximum flood peak volume and flood area were calculated by using the urban runoff model and the impact of climate change was analyzed in each period. For this purpose, Gumbel distribution was used as an appropriate model based on the method of maximum likelihood. As a result, in the case of the 10 year-frequency which is the design of most urban drainage facilities, the rainfall quantile is in increased about 10% if we assume 50 years from now with the $3^{rd}$ quarter value and about 20% if we assume 70 years from now. This result implies that the installed urban drainage facility based on the currently set design flood volume cannot be met the design criteria in the future. Therefore, it is necessary to reflect future climate conditions to current urban drainage facilities.

• Journal of Food Hygiene and Safety
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• v.34 no.1
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• pp.58-64
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• 2019

In the current study, 109 commercial nut samples were collected from different Korean markets and analyzed for the contamination of 5 different mycotoxins (aflatoxin, ochratoxin A, deoxynivalenol, zearalenone, and T-2 toxin) using ELISA kits. The results revealed that the most frequently detected mycotoxin was zearalenone (n=36, 33%), followed by aflatoxin (n=31, 28.4%) and ochratoxin A (n=30, 27.5%). Deoxynivalenol and T-2 toxin were also detected in 22 (20.3%) samples, respectively. Among 109 nut samples, 33 samples (30.3%) were contaminated only with one kind of mycotoxin, whereas 43 samples had at least 2 kinds of mycotoxins. Two samples were contaminated with as many as 4 different mycotoxins, and they were both walnuts. Although the monitoring results revealed the amount of aflatoxin contamination was under the safety criteria, there is no current safety guideline for other kinds of mycotoxins or multiple contaminations in Korea. Therefore, further studies should be performed to reveal the distribution of mycotoxin in different foods and propose appropriate safety guidelines for Korean markets.

• The Journal of Bigdata
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• v.4 no.1
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• pp.63-72
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• 2019

For power energy, optimal generation and distribution plans based on accurate demand forecasts are necessary because it is not recoverable after they have been delivered to users through power generation and transmission processes. Failure to predict power demand can cause various social and economic problems, such as a massive power outage in September 2011. In previous studies on forecasting power demand, ARIMA, neural network models, and other methods were developed. However, limitations such as the use of the national average ambient air temperature and the application of uniform criteria to distinguish seasonality are causing distortion of data or performance degradation of the predictive model. In order to improve the performance of the power demand prediction model, we divided Korea into five major regions, and the power demand prediction model of the linear regression model and the neural network model were developed, reflecting seasonal characteristics through regional characteristics and migration period learning techniques. With the proposed approach, it seems possible to forecast the future demand in short term as well as in long term. Also, it is possible to consider various events and exceptional cases during a certain period.

• Journal of Technology Innovation
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• v.21 no.1
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• pp.27-57
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• 2013

The projects of agricultural R&D investments have been evaluated largely on the basis of efficiency better than equity although both criteria are equally critical in that major fund source of agricultural R&D investments is public budget. In this study, I focus on equity aspects by identifying the heterogeneous impacts of public knowledge created by R&D on farm efficiencies by farm income levels using bias-corrected DEA and quantile regression with panel data. The findings indicate that entire farms haven't been likely to be benefited evenly from public knowledge stock created by agricultural R&D, in particular high income farms can have enjoyed relatively more benefits of its in terms of efficiency gain. Those can imply agricultural R&D have functioned in the way analogue to digressive subsidies. In addition, the heterogeneous technological needs different among income level farms turns out to be main underlying factors affecting such the skewed benefit distribution of agricultural R&D over different income level farms.

• Journal of Korea Water Resources Association
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• v.49 no.8
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• pp.685-692
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• 2016

This study aimed to develop the indicator-based approach to assess water use vulnerability in watersheds and applied to the unit watershed within the Han River watershed. Vulnerability indices were comprised of three sub-components (exposure, sensitivity, adaptive capacity) with respect to water use. The indicators were made up of 16 water use indicators. Then we estimated vulnerability indices using the Technique for Order of Preference by Similarity to Ideal Solution approach (TOPSIS). We collected environmental and socio-economic data from national statistics database, and used them for simulated results by the Soil and Water Assessment Tool (SWAT) model. For estimating the weighted values for each indicator, expert surveys for subjective weight and data-based Shannon's entropy method for objective weight were utilized. With comparing the vulnerability ranks and analyzing rank correlation between two methods, we evaluated the vulnerabilities for the Han River watershed. For water use, vulnerable watersheds showed high water use and the water leakage ratio. The indices from both weighting methods showed similar spatial distribution in general. Such results suggests that the approach to consider different weighting methods would be important for reliably assessing the water use vulnerability in watersheds.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.135-139
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• 2017

The main reason for heat accidents occurring at the after stern tube bearing (STB) is excessive local pressure caused by the deflection of the propulsion shaft due to propeller loads. The probability of a heat accident is increased by the low flexibility of the shaft system in very large crude oil carriers (VLCCs) as the engine power and shaft diameter increase and the distance decreases between the forward and after STBs. This study proposed shaft system with only an after STB and no forward STB for a flexibility acquisition method for a VLCC shaft system under hull deformation. A Hertzian contact condition was applied, which assumes a half-elliptical pressure distribution along the contact width for the calculation of the local squeeze pressure. The propeller loads, heat effect, and hull deflection under engine operating conditions are also considered. The results show that the required design criteria were satisfied by building a partial slope at the white metal, which is the material at the axial contact side in the after STB. This system could reduce building cost by simplification of the shaft system.

• Journal of the Korean earth science society
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• v.24 no.3
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• pp.190-204
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• 2003

The PM (particulate matter) concentration data sets exceeding the Daily Air Quality Guidance Levels (i.e., established by the Korean Ministry of Environment) were selected from 31 air qality monitoring stations in Seoul from 1990 to 2000. (For reference, the 24hr environmental standard values of PM$_{10}$ and TSP are 150 and 300${\mu}$g/m$^{3}$, respectively.) When the data sets were compared between land use types, both PM fractions were exceeded most frequently in residential areas. However, the highest TSP concentration was measured at industrial areas (351.0${\pm}$35.9${\mu}$g m$^{3}$), while the highest PM$_{10}$ concentration was measured in residential areas (182.9${\pm}$42.4${\mu}$g m$^{3}$). When the temporal distribution patterns of the exceedance data sets were compared to those measured routinely (without any discrimination based on exceedance criteria), large differences were present. It was demonstrated that the occurrences of exceedance data sets increased rather significantly in recent years.

• Journal of Korean Library and Information Science Society
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• v.46 no.3
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• pp.301-323
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• 2015

This study was conducted to analyze the characteristics of records related to Korea shown in the cataloging records of major 10 Asia-Pacific university libraries. The results are as follows. To begin with, Korea-related records in most university libraries are very poor except for some libraries and are generally 2 times less than Japan related records. There are even 6 times less in 2 libraries. Second, most libraries organize records in MARC 21 format rather than UNIMARC, and apply subject headings of the national library, or go together with LCSH. Third, Korean materials usually write Korean in Roman characters, but 5 libraries are marked with the original Korean language and available Hangeul search. Forth, on investigation of the subject distribution in sub criteria of Korea-related records, subject related to 'history', 'economy', and 'politics' is largely shown in the highest rate. Fifth, Among the Korea-related subject heading, the terms such as 'Taekwondo', 'Kimchi', 'Dokdo', 'Donghae', 'Duman-gang', 'Baekdu-san' have different meanings in different libraries. However, these terms agree to LCSH in most libraries except for neighboring countries's libraries.