• Journal of Elementary Mathematics Education in Korea
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• v.22 no.2
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• pp.199-220
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• 2018

This is a traditional education content that has been consistently handled in elementary school mathematics textbooks since the first curriculum in Korea. It has been mainly used to find out the properties of the solid figure or to save the surface area. However, as the importance of spatial ability is increasingly emphasized, the nets of solids can be a very suitable learning material for dealing with the spatial ability. Therefore, in this study, we examined how the nets of solids were taught in elementary school mathematics curriculum and textbooks in Korea, and based on the analysis, we analyzed the contents of the nets of solids covered in textbooks of Japan, Singapore, Finland and Hong Kong. Through this study, we suggested the enhancement of activities to find the right nets, the presentation of solid figure from various angles, and the nets of solids with patterns for improvement of spatial visualization and spatial orientation.

• The Mathematical Education
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• v.60 no.2
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• pp.159-172
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• 2021

The purpose of this study is to compare and analyze the effects of physical manipulative and exploratory geometry software on the spatial sense for 5^th grade elementary school students in learning nets. For this purpose, ton experimental group used Geofix, an operational learning tool, and the experimental group used Cabri 3D, an exploratory geometry software to learn the nets of solids. The comparison group was learned by worksheet only without any manipulative or software. Spatial sense tests were conducted before and after to determine the level, and eye tracking were used to analyze the strategies of students in solving nets problems. As a result, it was confirmed that the using Geofix group was the most effective for the spatial sense, and Cabri 3D could also be a good tool for learning the nets of solids. In addition, after learning the nets of solids, the analytical strategy, which was the most effective strategy for students' solving strategies, increased. In the process of solving spatial tasks such as the spatial sense tasks, eye tracking technology become a very useful tool for exploring students' strategies, so it is expected that objective and useful data will be collected through more active use in the future.

• Food Science and Preservation
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• v.14 no.1
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• pp.24-29
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• 2007

Quality changes in winter Chinese cabbages were evaluated during low temperature storage. Flesh and salt-treated Chinese cabbages were put into (a) polyethylene (PE) film sacks (size: $40cm{\times}60cm$, thickness: 0.03 mm, with four perforations each 8 mm in diameter), (b) plastic containers or (c) polypropylene (PP) nets and stored at $0^{\circ}C$. Also, Cabbages were also wrapped in newspapers and stored underground where the average temperature was $2.7^{\circ}C$. The weight loss rates of Chinese cabbages stored in PP nets and plastic containers were greater than those of cabbages stored with PE or wrapped in newspaper. Chinese cabbages wrapped in newspaper and stored underground needed much greater trimming compared to cabbages stored in other ways. The firmness and the soluble solid contents of Chinese cabbages were not affected by the various storage treatments. A better appearance was retained when Chinese cabbages were stored in PE film sacks. Chinese cabbages in PE film sacks stored at $0^{\circ}C$ showed delayed weight loss, less trimming loss, and less change in appearance. The quality changes in salted Chinese cabbages (desalting losses, pH changes, osmolarities, and crude fiber content) were not significantly different after the various treatments. No storage treatment was effective in maintaining a high quality of salted winter Chinese cabbage.

• Journal of Wetlands Research
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• v.12 no.2
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• pp.67-73
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• 2010

This study was performed to figure out what would be effective to maintain good water quality in the retention pond which was badly polluted before. In order to keep the good water quality of the retention pond it is necessary to prevent outer non-point source pollutants from flowing into the pond. In this study, we proposed to use porous slag as a blockage of the inflow into the pond from external non-point sources. We experimented with porous slag nets to see how the water is effected. With the results of the experiments, we found out there is a close correlation($r^2=0.9765$) between contact time and the removal rate of phosphorus, therefore we can conclude that contact time affects removal rate greatly. Synthetic wastewater, activated sludge effluent, and sewage were passed through a porous slag packed bed, both phosphorus and the suspended solid in water were removed highly. With the results of these tests, we proposed to set up a porous slag packed bed inside of the retention pond and revetment to prevent external non-point source pollutants flowing into the retention pond.

• Korean Journal of Radiology
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• v.19 no.6
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• pp.1066-1076
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• 2018

Objective: The reliability of size measurements of liver metastases from neuroendocrine tumors (NETs) on contrast-enhanced computed tomography (CT) phases made by different readers may be hampered due to transient, variable rim enhancement in arterial phase (AP) or portal venous phase (PVP) images. We aimed to assess the reliability of tumor size measurements in pre- and post-contrast scans. Materials and Methods: The study coordinator selected target lesions according to Response Evaluation Criteria in Solid Tumors 1.1 guidelines in 44 consecutive patients with pathologically confirmed NET liver metastases. Two blinded readers measured the longest diameters of target lesions on pre-contrast, AP, and PVP images twice with a 4-week interval. Inter- and intra-observer agreements were evaluated using Bland-Altman plots and 95% limit of agreement (LOA) calculations. Results: Of the 79 target lesions (approximate mean size of 3 cm), 45 showed rim enhancement. Inter-observer agreement assessed based on LOA was highest in pre-contrast CT images (-6.1-5.7 mm), followed by PVP (-7.9-7.1 mm) and AP (-8.5-7.4 mm) images. Intra-observer agreement showed the same trend: -2.8-2.9 mm and -2.9-2.9 mm for readers 1 and 2, respectively, on pre-contrast CT, -2.8-2.9 mm and -3.0-3.2 mm, respectively, on PVP, and -3.2-4.2 mm and -3.4-3.2 mm, respectively, on AP images. Mean tumor diameters differed significantly among the phases in the following increasing order: pre-contrast CT, PVP, and AP images. Conclusion: There was better inter- and intra-observer agreement in size measurements of NET liver metastases on pre-contrast scans than on AP and PVP scans. Pre-contrast CT may be the optimal for measuring NET liver metastases if its accuracy is proven.