• Journal of the Korean Data and Information Science Society
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• v.27 no.2
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• pp.363-372
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• 2016

Two-stage sample designs are commonly used for household surveys in Korea using as clusters the enumeration districts (EDs). Since clustering decomposes the population variation into within- and between-cluster variations, the sample sizes allocated in stages can affect the overall precision. Alternative clusters are often considered due to diverse reasons such as the EDs' limitation in size, being out-of-date, and in-assessibility to their household lists. In addition, the EDs are currently under development by the Statistics Korea as an joint effort toward their transition from the traditional practice to the register census from 2015. We present an approach for evaluating the difference in the precision of the mean estimators of the sets of the cluster units in between a hierachical and nested form, where the design effect is used to reflect the effect of the clustering and the sample allocation. We also demonstrate our approach using the U.S. Census counts from the year 2000 for Anne Arundel County in Maryland. Our research shows that the within-cluster variance can be significantly different for survey variables and thus the choice of cluster units and the associated sample allocation scheme should reflect the corresponding variance decomposition due to clustering.

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.52-60
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• 2005

In this study, low density polyethylene/organo-clay nanocomposites were prepared by melt blending. Thermal property, structure, and morphology of the LDPE/organo-clay nanocomposites were investigated. When the composition ratios of the compounds of LDPE/PE-g-MA/organo-clay were 90/10/1~10 (w/w/w), X-ray diffractograms of LDPE/organo-clay nanocomposites revealed that the intercalation of polymer chains lead to increase the spacing between clay layers. TEM microphotographs showed that LDPE was intercalated into organo-clay. TGA performed under air atmosphere demonstrated a great increase in thermal stability of the LDPE/organo-clay nanocomposties. The maximum decomposition temperature of LDPE/organo-clay nanocomposite was increased about $80^{\circ}C$ compared with pure LDPE. When the organo-clay contents were 1.0~5.0 wt%, the LOI values were increased with increasing the organo-clay content, but in the case of the contents more than 5.0 wt%, the LOI values were not increased any more.

• Journal of the Korean Society of Food Science and Nutrition
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• v.17 no.4
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• pp.312-319
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• 1988

The functional properties of plasteins have been compared with those of sardine protein concentrate and egg albumin. The solubility of plasteins was higher than that of FPG and the glu-plastein had 84% solubility in the range of pH 3-10. The dispersibility of plasteins was lower than that of egg albumin, however those of plasteins was higher than that of sardine protein concentrate. The water holding capacity of plasteins was higher than that of egg albumin. Lipid absorption of leu-papain plastein was the highest, holding 2.2m119, and that of the other plastein was higher than that of egg albumin. The emulsifying activity of leu-papain plastein was the highest, holding 66.4%, and that of glu-papain plastein was the lowest, holding 51.2%, The emulsifying stability of plasteins was similar to that of the emulsifying activity. The foaming capacitt of leu-papain plastein was the highest, holding 460%, and those of the other plasteins was higher than that of egg albumin. The foaming stability of plasteins was superior to that of egg albumin. The viscosity of plasteins was lower than that of see albumin. The in vitro digestibility of plasteins was 67.6-78.0% range. The digestibility by four pretense were somewhat lower in the glu-papain plastein than in the FPG. The digest of plasteins treated with the microbiol pretense such as molsin and pretense(from Streptomyces griceus), which had a storage broth taste.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.3
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• pp.151-156
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• 2009

The purpose of this study is to evaluate the affecting factors on Oil-Mineral Aggregates(OMA) for stranded oil on intertidal flat, because the OMA formation enhances the oil dispersion and biodegradation rates. We choose the affecting factors such as spilled oil concentrations(50, 100, 200, 300, 400, 500 mg/L), mineral concentration(100, 200, 500, 1,000, 2,000, 4,000 mg/L), salinity(10, 20, 30, 40 psu), shaking time(1, 2, 4, 8, 12, 24 hr) and applied dispersant volume(0, 5, 10, 15, 20%). Major conclusions derived from this study are as follows. It was observed that the kaolinite interacts three times strongly with crude oil than quartz. OMA formation was enhanced with increasing of spilled oil concentrations, whereas the increase of salinity rarely affected the OMA formation. The shaking time for OMA formation affected positively with kaolinite, but quartz was irrespective the shaking time. The applied dispersant enhanced the OMA formation by 13% in kaolinite and 56% in quartz experimental condition.

• Land and Housing Review
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• v.4 no.1
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• pp.43-54
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• 2013

This This paper investigates the variation of the factors to determinate housing price in Seoul metropolitan area after sub-prime financial crisis, in Korea, using a VAR model. The model includes housing price and housing rent (Jeonse) in Seoul metropolitan area from 1999 to 2011, and uses interest rate, real GDP, KOSPI, Producer Price Index and practices to impulse response and variance decomposition analysis to grasp the dynamic relation between a variable of macro economy and and a variable of housing price. Data is classified to 2 groups before and after the 3rd quater of 2008, when sub-prime crisis occurred; one is from the 1st quater of 1999 to the 3rd quater of 2008, and the other is from the 2nd quater of 1999 and the 4th quater of 2011. As a result, comparing before and after sub-prime crisis, housing price is more influenced by its own variation or Jeonse price's variation instead of interest rate and KOSPI. Both before and after sub-prime financial crisis, Jeonse price is also influenced by its own variation and housing price. While after sub-prime financial crisis, influences of Producer Price Index, KOSPI and interest rate were weakened, influence of real GDP is expanded. As housing price and housing rent are more influenced by real economy factors such as GDP, its own variation than before sub-prime financial crisis, the recent trend that the house prices is declined is difficult to be converted, considering domestic economic recession and uncertainty, continued by Europe financial crisis. In the future to activate the housing business, it ia necessary to promote purchasing power rather than relaxation of financial and supply regulation.

• Environmental and Resource Economics Review
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• v.19 no.2
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• pp.283-301
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• 2010

This study estimated the paper demand and supply using VAR model. And the variance decomposition and impulse response were analyzed using the model. In the model of paper demand, the own price change accounts for about seventeen percent of variation in the demand, and the gross domestic product change accounts for about twenty eight percent of variation in the demand. And the impacts of a shock to the own price and gross domestic product are significant for about six months on the demand for paper. In the model of paper supply, the own price change accounts for about twenty nine percent of variation in the supply, and the pulp price change accounts for about twelve percent of variation in the supply. And the impacts of a shock to the own price and pulp price are significant for about six months on the supply of paper.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.106-111
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• 2008

Polypropylene (PP)/corn starch master batch (starch-MB)/silicate composites with different corn starch compositions of 10, 20, 30, 40 and 50 were prepared by melt compounding at $200^{\circ}C$, using lab scale Brabender mixer. The content of silicate was fixed at 5 wt%. The composition of starch-MB in composites was confirmed by the existence of hydroxy group and peak intensity in fourier-transform-infrared (FT-IR) spectrum. The thermal properties of the PP/starch-MB/silicate composites were investigated by differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). There was no district change in melting temperature, and TGA curve indicates a decrease in degradation temperature with the increase of starch-MB content. The silicate dispersion of the composites was measured by X-ray diffraction (XRD) and transmission electron microscope (TEM). The degree of silicate dispersion in PP/starch-MB/silicate composites depended on the content of starch-MB. There was detectable change in d-spacing and peak intensity of the composite when the content of starch-MB was higher than 20 wt%. The rheological behavior of the composites was explained by both shear thinning effect and elastic property with the starch-MB amount. These effects were remarkable when the content of starch-MB was higher than 20 wt%. These were confirmed by an oscillatory viscometer at $200^{\circ}C$.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.634-638
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• 1998

Monodisperse, spherical $PMSQ/TiO_2$ composite fine powders were prepared by modified sol-gel process where 300 nm $TiO_2$ fine powders were used as seed particles for hetero-condensation with hydrolyzed MTMS (Methyltrimethoxysilane). The reaction was carried out under $N_2$ atmosphere at ambient temperature using $NH_3$ as a catalyst. Methanol was used as a solvent. Powder was obtained by the filtration of the solution with a glass filter and washing with acetone. The stirring rate, reaction temperature, $[H_2O]/[MTMS]$ and $[MTMS]/[TiO_2]$ ratio were varied to investigate shapes and sizes of particles. Monodisperse particles of $1-2{\mu}m$ diameter were obtained with [MTMS]=0.2 M, $[NH_3]=0.6M$, $[H_2O]/[MTMS]=100$, $[MTMS]/[TiO_2]=10-50$ at ambient temperature with mild stirring condition. These composite particles had a contact angle of almost 180 degree contact angle with water, which proves their excellent hydrophobicity. The study of UV absorption spectra showed that they have UV protecting effect.

• Journal of Navigation and Port Research
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• v.46 no.3
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• pp.289-296
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• 2022

The purpose of this study was to investigate the inter-correlation between crude oil prices and Dry Bulk Freight rates. Eco-friendly shipping fuels has being actively developed to reduce carbon emission. However, carbon neutrality will take longer than anticipated in terms of the present development process. Because of OVID-19 and the Russian invasion of Ukraine, crude oil price fluctuation has been exacerbated. So we must examine the impact on Dry Bulk Freight rates the oil prices have had, because oil prices play a major role in shipping fuels. By using the VAR (Vector Autoregressive) model with monthly data of crude oil prices (Brent, Dubai and WTI) and Dry Bulk Freight rates (BDI, BCI and (BP I) 2008.10~2022.02, the empirical analysis documents that the oil prices have an impact on Dry bulk Freight rates. From the analysis of the forecast error variance decomposition, WTI has the largest explanatory relationship with the BDI and Dubai ranks seoond, Brent ranks third. In conclusion, WTI and Dubai have the largest impact on the BDI, while there are some differences according to the ship-type.

• Korea Trade Review
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• v.48 no.3
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• pp.69-88
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• 2023

This study analyzes the dynamic characteristics of cargo volume (demand), ship fleet (supply), and freight rate (price) of container, dry bulk, and tanker shipping markets by using the VAR and VECM models. This analysis is expected to enhance the statistical understanding of market dynamics, which is perceived by the actual experiences of market participants. The common statistical patterns, which are all shown in the three shipping markets, are as follows: 1) The Granger-causality test reveals that the past increase of fleet variable induces the present decrease of freight rate variable. 2) The impulse-response analysis shows that cargo shock increases the freight rate but fleet shock decreases the freight rate. 3) Among the three cargo, fleet, and freight rate shocks, the freight rate shock is overwhelmingly largest. 4) The comparison of adjR² reveals that the fleet variable is most explained by the endogenous variables, i.e., cargo, fleet, and freight rate in each of shipping markets. 5) The estimation of co-integrating vectors shows that the increase of cargo increases the freight rate but the increase of fleet decreases the freight rate. 6) The estimation of adjustment speed demonstrates that the past-period positive deviation from the long-run equilibrium freight rate induces the decrease of present freight rate.