• Journal of Educational Research in Mathematics
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• v.24 no.1
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• pp.83-102
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• 2014

The purpose of this study was to explore students' understanding on units embedded in multiple interpretations of fractions: (a) part-whole relationships, (b) measures, (c) quotients, (d) ratios, and (e) operators. A total of 150 sixth graders in elementary schools were surveyed by a questionnaire comprised of 20 tasks in relation to multiple interpretations of fractions. As results, students' performance on units varied depending on the interpretations of fractions. Students had a tendency to regard the given whole as the unit, which led to incorrect answers. This study suggests that students should have rich experience to identify and operate various units in the context of multiple fractions.

• Journal of The Korean Astronomical Society
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• v.47 no.1
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• pp.1-13
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• 2014

We analyze the dependence of disk morphology (arm class, Hubble type, bar type) of nearby spiral galaxies on the galaxy environment by using local background density (${\Sigma}_n$), projected distance ($r_p$), and tidal index (T I) as measures of the environment. There is a strong dependence of arm class and Hubble type on the galaxy environment, while the bar type exhibits a weak dependence with a high frequency of SB galaxies in high density regions. Grand design fractions and early-type fractions increase with increasing ${\Sigma}_n$, $1/r_p$, and T I, while fractions of flocculent spirals and late-type spirals decrease. Multiple-arm and intermediate-type spirals exhibit nearly constant fractions with weak trends similar to grand design and early-type spirals. While bar types show only a marginal dependence on ${\Sigma}_n$, they show a fairly clear dependence on $r_p$ with a high frequency of SB galaxies at small $r_p$. The arm class also exhibits a stronger correlation with $r_p$ than ${\Sigma}_n$ and T I, whereas the Hubble type exhibits similar correlations with ${\Sigma}_n$ and $r_p$. This suggests that the arm class is mostly affected by the nearest neighbor while the Hubble type is affected by the local densities contributed by neighboring galaxies as well as the nearest neighbor.

• East Asian Economic Review
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• v.22 no.4
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• pp.403-425
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• 2018

This paper documents the presence of "sensitive sectors" in Free Trade Agreements, defined as sectors for which the within-FTA tariffs remain positive. The paper includes some brief theoretical discussion of the welfare implications of these, but the main emphasis is on reporting two measures of this phenomenon for countries in FTAs that entered into force between 1994 and 2003. One measure is the percentage of tariff lines that remain dutiable, and the second is the change, from before the FTA to after, in the average maximum (across 6-digit products) positive tariffs. Both measures are derived from data in the UNCTAD TRAINS database, and are then related to measures of country characteristics that might explain them. Low per capita GDP countries tend to have larger fractions of dutiable tariff lines, while higher income countries tend to post larger increases in average maximum positive tariffs. Both suggest that the favored treatment of sensitive sectors is undermining the potential gains from trade that FTAs could provide.

• Journal of Soil and Groundwater Environment
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• v.22 no.6
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• pp.1-11
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• 2017

This study was conducted to investigate the performance of four commercial chemical agents in stabilizing arsenic (As) in soil at the forest area near the former Janghang smelter site. After amending the stabilizing agents (A, B, C, and D) into As-contaminated soil samples, synthetic precipitation leaching procedure (SPLP) and solubility bioavailability research consortium (SBRC)-extractable As concentrations significantly decreased except for agent D, which is mainly composed of fly ash and calcium carbonate. Increase of SPLP and SBRC-extractable As concentrations in four soil samples (S1, S2, S3, and J2) was attributed to desorption of As adsorbed on iron oxides due to high pH generated by agent D. It is therefore necessary to consider application conditions according to soil characteristics such as pH and buffering capacity. Results of sequential extraction showed that readily extractable fractions of As in soil (i.e., sum of $SO_4-$ and $PO_4-extractable$ As in soil) were converted into non-readily extractable fractions by amending agents A, B, and C. Such changes in the As distribution in soil resulted in the decrease of SPLP and SBRC-extractable As concentration. A series of follow-up monitoring and management plan has been suggested to assess the longevity of the stabilization treatments in the site.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.7
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• pp.819-824
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• 2007

The present study describes the cytotoxic effect of Artemisia fukudo extracts. The extract from A. fukudo by 80% ethanol was fractionated with n-hexane, dichloromethane, ethylacetate, and butanol in serial. The cytotoxicity of A. fukudo extracts was examined for its effect on the growth of HL-60 cells by the colorimetric 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide (MTT) assay. In addition, we used the HL-60 cells to see what effects the A. fukudo extracts will have on apoptosis of cancer cells. We checked the cell activity, cell morphologic changes, DNA fragmentation, and DNA content after 24 hr incubation with administering 25 ${\mu}g/mL$ of the A. fukudo extracts. In the treatment of the low concentration of n-hexane and dichloromethane fractions, the survival rate of HL-60 cells is lower than that of the control. The laddering-pattern DNA fragmentation was observed in the treatment with n-hexane and dichloromethane fractions. The DNA content of the cells apoptosis measured as the density of sub-$G_{1}$ hypodiploid cells by flow cytometric analysis. The number of sub-$G_{1}$ hypodiploid cells increased in the treatment with n-hexane and dichloromethane fractions. These fractions obstructed the cell cohesion and caused the blebbing of the cell membrane and fragmentation of the nucleus, both of which are symptoms of apoptosis. These results suggest that A. fukudo has a great potential value as food additives, medicinal supplements for patients with chronic diseases, and preventive measures against cancer.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.1
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• pp.25-35
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• 2005

This study analyzed total concentrations and existing forms of heavy metals in soils of Ulsan using a sequential extraction method. Soil samples were collected from 6 categorized areas including green, residential, heavy traffic, petrochemical industrial complex(IC), mechanical and shipbuilding IC, and non-ferrous metal IC areas. which represent different emission characteristics. The highest total concentrations of heavy metals by a sequential extraction analysis were observed in the soils collected from the non-ferrous metal IC area, followed by the mechanical and shipbuilding IC and heavy traffic areas. Dominant(> 50%) existing forms of Cd, Cr and Ni were residual forms followed by Fe and Mn oxides in almost areas. Residual fractions in the non-ferrous metal IC areas were relatively lower than those in other areas. However, the fractions of organic and sulphides in the IC areas were higher. The dominant farms of Cu were much different with the investigated areas. In most areas, the dominant forms of Pb and Zn were Fe and Mn oxides, followed by residual fraction for Pb. The exchangeable and carbonate fractions represent mobility of metallic elements in soils. They are also significantly affected by the environmental renditions, such as pHs of soil and rainfall. In this study the exchangeable and carbonate fractions were lower than other fractions. Because the total concentrations of heavy metals in the soils of the non-ferrous metal IC area were extremely high, however, the mobile fractions of heavy metals in the IC area would be significant. Thus a large amount of heavy metals can be released into plants, water bodies, and soils. Therefore, urgent measures, such as source control for soil remediation of heavy metals, in the non-ferrous metal IC areas are essentially required. Analysis results obtained from the sequential extraction and the aqua regia extraction showed a high correlation, whose determination coefficients(R2) of heavy metals except Cd approximately ranged from 0.7 to 0.9.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.812-824
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• 2021

In order to reduce risks from the Steam Generator Tube Rupture (SGTR) accident and to meet safety targets, various measures have been analyzed to minimize the amount of fission product (FP) release. In this paper, we propose an introduction of a Containment Filtered Venting System (CFVS) connected to the steam generator secondary side, which can reduce the amount of FP release while minimizing adverse effects identified in the previous studies. In order to compare the effect of new equipment with the existing strategy, accident simulations using MELCOR were performed. As a result of simulations, it is confirmed that CFVS operation lowers FP release into the environment, and the release fractions are lower (minimum 0.6% of the initial inventory for Cs) than that of the strategy which intends to depressurize the primary system directly (minimum 15.2% for Cs). The sensitivity analyses identify that refill of the CFVS vessel is a dominant contributor reducing the amount of FP released. As the new strategy has the possibility of hydrogen combustion and detonation in CFVS, the installation of an igniter inside the CFVS vessel may be considered in reducing such hydrogen risk.

• Geomechanics and Engineering
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• v.23 no.6
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• pp.513-521
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• 2020

In this paper, due to the need for cutting cement-soil group pile composite foundation under the 7-story masonry structure of Zhenghe District and the shield tunnel of Zhengzhou Metro Line 5, a field test was conducted to directly cut cement-soil single pile composite foundation with diameter Ф=500 mm. Research results showed that the load transfer mechanism of composite foundation was not changed before and after shield tunnel cut the pile, and pile body and the soil between piles was still responsible for overburden load. The construction disturbance of shield cutting pile is a complicated mechanical process. The load carried by the original pile body was affected by the disturbance effect of pile cutting construction. Also, the fraction of the load carried by the original pile body was transferred to the soil between the piles and therefore, the bearing capacity of composite foundation was not decreased. Only the fractions of the load carried by pile and the soil between piles were distributed. On-site monitoring results showed that the settlement of pressure-bearing plates produced during shield cutting stage accounted for about 7% of total settlement. After the completion of pile cutting, the settlements of bearing plates generated by shield machine during residual pile composite foundation stage and shield machine tail were far away from residual pile composite foundation stage which accounted for about 15% and 74% of total settlement, respectively. In order to reduce the impact of shield cutting pile construction on the settlement of upper composite foundation, it was recommended to take measures such as optimization of shield construction parameters, radial grouting reinforcement and "clay shock" grouting within the disturbance range of shield cutting pile construction. Before pile cutting, the pile-soil stress ratio n of composite foundation was 2.437. After the shield cut pile is completed, the soil around the lining structure is gradually consolidated and reshaped, and residual pile composite foundation reaches a new state of force balance. This was because the condensation of grouting layer could increase the resistance of remaining pile end and friction resistance of the side of the pile.

• Journal of Soil and Groundwater Environment
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• v.17 no.3
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• pp.21-31
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• 2012

This paper presents the short-term and long-term measures to determine the fugitive dust concentration in a contaminated site, which is a crucial step for the determination of particulate emission factor (PEF) for risk assessment. As a long-term measure, USEPA method employing Q/C value (inverse of the ratio of the geometric mean air concentration to the emission flux at center of a 0.5-acre square source) seems to be suitable as it reflects regional-specific meteorological conditions. However, it requires nation-wide database collection and interpretation. Use of ASTM method is an alternative as a short-term measure. The method is readily field-applicable as PEF calculation equation is simple and input parameters can be easily derived at the site of interest as well without the nation-wide efforts. Using ASTM method, PEF at the Former Janghang Smelter Site was determined. According to various mode of aggregate size distribution and fractions of vegetative cover, which are the most important factors in PEF calculation, PEF values at the Former Janghang Smelter Site varied greatly. When the mode of aggregate size distribution was set at 0.25 mm, PEF values at the Former Janghang Smelter Site was 5~20 times higher than the default PEF value (i.e., 35 ${\mu}g/m^3$) shown in the current Korean Soil Contamination Risk Assessment Guidance. On contrast, when the mode was set at 2 mm, PEF values at the Former Janghang Smelter Site was 160~640 times lower than the default PEF value in the Korean Guidance.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.6
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• pp.816-824
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• 2006

This study was conducted to evaluate the shoot height at which the yield and nutritive value of wormwood (Artemisia montana) is optimized in order to provide information on its potential to support animal production (Experiment 1). A second objective was to determine how the essential oil (EO) concentration in wormwood hay and silage differ (Experiment 2). In Experiment 1, Artemisia montana was harvested at five different shoot heights (20, 40, 60, 80 and 100 cm) from triplicate $1.8{\times}1.8m$ plots. Dry matter (DM) yield was measured at each harvest date and the harvested wormwood was botanically separated into leaf, stalk and whole plant fractions and analyzed for chemical composition and in vitro dry matter digestibility (DMD). Values for total digestible nutrients (TDN), digestible energy (DE) and metabolizable energy (ME) were subsequently calculated using prediction equations. Dry matter yields of stalk and whole plant increased linearly (p<0.001) and leaf yield increased quadratically (p<0.01) with shoot height, whereas the leaf/stalk ratio decreased linearly (p<0.001). As shoot height increased, there was a linear increase (p<0.001) in leaf DM, ether extract (EE) and neutral detergent fiber (NDF) contents and a quadratic increase (p<0.05) in leaf acid detergent fiber (ADF) and nitrogen free extract (NFE) contents, and stalk and whole plant DM (p<0.001), organic matter (OM, p<0.01 and p<0.05), NDF (p<0.001 and 0.05) and NFE (p<0.05) contents. However, there were decreases in leaf crude protein content (CP, quadratic, p<0.001) and stalk and whole plant EE content (linear, p<0.001), CP (quadratic, p<0.05) and ash (quadratic, p<0.05) contents. Digestibility of DM and TDN, and DE and ME value in leaves were not affected by increasing shoot height, but these measures linearly decreased (p<0.001) in stalk and whole plant. In Experiment 2, the hay had higher DM and CP concentrations, but lower EE concentration than the silage. Essential oil (EO) content in wormwood silage (0.49 g/100 g DM) was higher (p<0.05) than that in wormwood hay (0.32 g/100 g DM). Wormwood hay contained 25 essentail oils (EO) including camphor (10.4 g/100 g), 1-borneol (11.6 g/100 g) and caryophyllene oxide (27.7 g/100 g), and wormwood silage had 26 EO constituents including 3-cyclohexen-1-ol (8.1 g/100 g), trans-caryophyllene (8.6 g/100 g) and ${\gamma}$-selinene (16.8 g/100 g). It is concluded that the most ideal shoot height for harvesting wormwood is 60 cm based on the optimization of DM yield and nutritive value. Wormwood silage had a greater quantity and array of EO than wormwood hay.