• Journal of Elementary Mathematics Education in Korea
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• v.13 no.2
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• pp.285-304
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• 2009

The operations of fractions are the main contents of number and operations in the elementary mathematics curriculum. They are also difficult for students to understand conceptually. Nevertheless, there has been little study on the addition and subtraction of fractions. Given this, this paper explored the connection between the national mathematics curriculum and its concomitant textbooks, the adequacy of when to teach, and the method of constructing each unit to teach addition and subtraction of fractions. This paper then analyzed elementary mathematics textbooks and workbooks by three parts aligned with the general instructional flow: 'introduction', 'activity', and, 'exercise'. First, it was analyzed with regard to the introduction part whether the word problems of textbooks might reflect on students' daily lives as intended, how different meanings of operations would be expected to be taught, and how the subsequent activities were connected with the original word problems. Second, the main analysis of activity part of the textbooks dealt with how to use concrete or iconic models to promote students' conceptual understanding of operations and how to formalize the calculation methods and principles with regard to addition and subtraction of fractions. Third, the analysis of the part of exercise in the textbooks and workbooks was conducted with regard to problem types and meanings of operations. It is expected that the issues and suggestions stemming from this analysis of current textbooks and workbooks are informative in developing new instructional materials aligned to the recently revised mathematics curriculum.

• KSBB Journal
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• v.15 no.6
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• pp.664-669
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• 2000

Micellar aggregates are known to be useful for the selective isolation of biologically active materials such as amino acids, proteins, and enzymes from crude mixtures sparsely dispersed in water. In this study, the effects of pH, salt type and its concentration on the solubilization of $\alpha$-chymotrypsin into the organic micellar phase, which consisted of AOT (sodium 야(2-ethylhexy)sulfosuccinate) and iso-octane, were comprehensively examined. It was found that maximum extraction efficiency was attained at a pH below the isoelectric point of $\alpha$-chymotrypsin; at pH=5.0 for NaCl and KCl, and at pH=7.0 for $CaCl_2$and $MgCl_2$. In order to avoid complications stemming from the precipitationof protein at low pH interfaces, the protein concentrations in the organic and aqueous phases were directly measured. The size of the micelle water pool was estimated by measuring the molar ratio of the surfactant to the water, W(sub)o. The resulting values of W(sub)o were nearly constant at 30 and 19 for NaCl and KCl, respectively, and were independent of pH. The addition of 1:2 salts like $MgCl_2$and $CaCl_2$ led to much lower, but a constant value of, W(sub)o than the 1:1 salts.

• Explosives and Blasting
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• v.36 no.4
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• pp.1-8
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• 2018

This numerical study was intended to evaluate the applicability of the half charge blasting to mining and tunnelling. The half charge blasting is a method that two separate rounds are sequentially blasted for the rock burdens in which long blast holes have already been drilled at one operation. The aim of the method is to decrease the construction cost and period in mining and tunnelling projects as well as to increase the blasting efficiency. Several numerical analyses were conducted by using the Euler-Lagrange solver on ANSYS AUTODYN to identify the effects of the suggested method on the blasting results in underground excavations. The overall performance of the suggested method was also compared to an ordinary blasting method. The analysis model was comprised of the Eulerian parts (explosive, air, and stemming materials) and the Lagrangian parts (rock material). As a result, it was found that, owing to the air decks formed in the bottom parts of the long blast holes, the first round of the suggested method presented a higher shock pressure and particle velocities in the vicinity of the blast holes compared to the ordinary blasting method.

• Journal of the Daesoon Academy of Sciences
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• v.41
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• pp.179-217
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• 2022

Concerning the differences in the tales between the Investigation of Historical Remains of Patriarch Jinmuk (hereafter, IHRPJ), as well as those which appear in Jeungsanist Thought and Daesoon Thought, previous studies view such differences as Jeungsan's intentional modification of the original intent of the narratives or as indicating differences in beliefs and values. This style of interpretation seeks to reconcile both Korean Buddhism and Jeungsanist and Daesoon Thought based on the premise that the former and the latter two exhibit differences in values. This study accepts the above view of the differences in description according to values. However, the differences between the tales of Jinmuk that appears in IHRPJ versus those in The Canonical Scripture can be approached from a new perspective, i.e., the differences that exist between literary and oral traditions; rather than only stemming from potential differences in the world views espoused by Buddhism and Daesoon Thought. These refer to the IHRPJ, which was constructed first as literary narratives in the 19th century; however, there was also folklore that had been handed down from the 18th century. As a result of examining the relationship between Jinmuk and Bonggok via this interpretive horizon, the contents of the IHRPJ are found to reflect the values and intentions of the intellectual class, such those held by Master Cho-ui and Kim Ki-jong, whereas oral traditions can be seen as a reflection of the hopes of the people of the late Joseon Dynasty. Jeungsan should also be interpreted as having utilized folklore in his teachings. Meanwhile, the circumstances and intentions behind publishing the IHRPJ are analyzed in the context of the text's historical background and the relationship between Confucianism and Buddhism during the 16th through 19th centuries. In particular, through the Compilations of Wandang and the collection of writings of Buddhist monastics, I have evaluated that Confucianism needed to purify and correct materials according to the ideology of the times in order to promote a spirit of morality and courtesy. Likewise, Buddhist Master Cho-Ui also embellished records to benefit Buddhism and deleted oral records that could harm the reputation of Buddhism. On the other hand, when viewing Records of Shrine Renovation and existing oral traditions, it can be shown that some Jinmuk tales existed in the 18 th century which were not included in the IHRPJ. Thereby, Jeungsan's description of Jinmuk tales can be reappraised as accepting the oral secular tradition that conveyed the wishes of the people. In other words, compared to the IHRPJ, which reflects only the harmonious content of Confucianism and Buddhism due to political and social factors, The Canonical Scripture reflects oral traditions that were widespread during the late Joseon Dynasty. As evidence, it can be suggested that there are many narratives about the relationship between Jinmuk and Bonggok that center on Bonggok's jealousy and the murder of Jinmuk. Jeungsan aimed to encompass people of all classes according to their minds and wills rather than their political positions or statuses. Therefore, Jeungsan did not need to rewrite the narrative content that had been passed down via oral tradition. Instead he embraced those narratives as a projection of the voices of the people.