• Journal of Science Education
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• v.47 no.3
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• pp.273-285
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• 2023

Measurement in elementary school mathematics is one of the mathematical concepts that is directly used in real life. This study is based on the fact that mathematics textbooks for 3-4 and 5-6 graders were developed as the government designed and authorized textbooks and the general measurement instruction process is condensed and presented considering the limitation of the textbook's space for the capacity and weight. Its contents were analyzed. The results are as follows. The contents of authorized textbooks and government designed textbook are different in detail but similar overall in comparative activities, recognition, and situation of the need for the introduction of standard unit and estimation activities. Through this, it is proposed that efforts are needed to reform national textbook policies and develop textbooks that can highlight the meaning of each measurement activity and focus on students' activities.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.112-112
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• 2015

유기 분자들은 대부분 전기가 잘 통하지 않아, 그 응용이 매우 제한적이었으나, 1985년의 C. W. Tang 교수의 다층 구조 전자소자의 보고를 기점으로 급격한 발전을 이루었다. 현재는 유기분자를 이용한 디스플레이인 AMOLED(아몰레드)를 적용한 스마트폰, TV등이 상용화 되었을 정도로 기술 성숙도가 매우 높아졌다. 그러나 여전히 분자 시스템에서의 전하 수송에 대해서는 하나의 정립된 모델이 없다. 일례로, 밴드 수송과 호핑 수송 등 두 가지 다른 전하수송 특성이 보고되고 있다. 본 발표에서는 계면 에너지레벨 접합과, 분자층 내부의 분자간 상호작용(호핑 수송 위주로) 측면에서 분자 시스템의 전하 수송에 대해 논의한다.

• Journal of the Korean Vacuum Society
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• v.10 no.2
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• pp.252-256
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• 2001

We performed spectroscopic ellipsometry measurement to obtain dielectric function(DF) of ZnSe at room temperature. Proper wet chemical etching procedure was carried out to remove overlayers on top of ZnSe, and our result indicates that the previous reports on the pure DF of ZnSe have inaccurate interpretations. We constructed DF of oxide on ZnSe by using reported DFs of amorphous-Se, $GaAsO_3$, and voids through Bruggeman effective-medium approximation.

• Progress in Medical Physics
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• v.9 no.4
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• pp.195-200
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• 1998

Purpose: When an elongated x-ray field is used for treating a patient, the equivalent- field method is commonly used for the output calculation. This study is intended for investigating potential factors such as, beam quality, field elongation ratio, and depth of measurement, which might effect on the applicability of the equivalent square technique for output calculation. The derivation of a 'rule of thumb' for the application criteria of the equivalent-field method is also aimed. Materials and Methods: Three x-ray beams, 4-, 6- and 10-MV, were employed for this study. Width of the rectangular field was ranged from 5-40 cm and the elongation ratio (length/width) 1:0 to 10:0. An elongation effect was measured in a water phantom at three different depths, dmax, 5-cm, and 10-cm. For an elongated field and its equivalent square field, the output factor was measured and the difference in the output factor were examined between two fields. Results and Discussions: As the elongation ratio increases, a larger discrepancy in outputs is observed between the elongated rectangular field and its corresponding equivalent square field. Output was measured larger for an elongated field than for its corresponding equivalent square field and the maximal difference over 10 % was found. The difference was found larger for the smaller field with the same elongation ratio. The effect of the beam quality and the depth of measurement on the output difference was minimal. Conclusion: Based on the study, there is criteria for the application of the method for output calculation. For the combination of long axis and elongation ratio whose relationship satisfies Elongation ratio < (0.48) (Long axis) - 0.5, the equivalent-field method is valid for output calculation within 2 % for the field whose long axis < 25-cm. For other combinations, instead of using the equivalent-field method, direct output measurement is recommended. This criteria can be applied for 4-10 MV x-ray beams up to 10-cm depth.

• Journal of Elementary Mathematics Education in Korea
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• v.20 no.2
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• pp.215-238
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• 2016

The 2015 national revised curriculum was notified officially the last year. The intent and direction of the revision caused more or less change for mathematical contents to be taught and is expected to cause a considerable change in math class. In the level of elementary school mathematics, it turned that several contents were deleted or moved to the upper grades because the revision focused especially both on reducing students' burden of learning and on fostering the mathematical key competences. This study aims to examine the relevance of the change through investigation of the national curriculums for elementary school mathematics since 1946. The mathematical contents to be analyzed in this study were mixed calculation of natural numbers, mixed calculation of fractions and decimal fractions, position and direction of objects, are/hectare and ton, the range of numbers and estimating, surface and volume of cylinders, pattern and correspondence, and direct/inverse proportionality, which were changed in any aspect relative to 2009 national revised curriculum. Based on the results of these analyses, the discussion will provide some suggestions for setting the direction of elementary mathematics curriculum.

• East Asian mathematical journal
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• v.33 no.2
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• pp.177-197
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• 2017

The purpose of this study is to investigate and analyze the understandings of elementary pre-service teachers about 'estimation' in the elementary mathematics. Together with this analysis, we identify elementary pre-service teacher's Mathematical Pedagogical Contents Knowledge(MPCK), especially focusing to Subject Matter Knowledge(SMK). In order to this goals, we investigate contents relating to 'estimation' from $1^{st}$ curriculum to 2009 revised curriculum and compare 'rounding up', 'rounding off', 'rounding' in the elementary mathematics textbooks. As results of investigations, 'estimation' has been teaching at the 'Measurement' domain from $3^{rd}$ curriculum, but contexts of measuring weaken from $7^{th}$ curriculum. 'Rounding up(off)' is defined three types in the textbooks from $1^{st}$ to 2009 revised curriculum. And we examine elementary pre-service teachers through the questions on these 'estimation' contents. On the analysis of pre-service teacher's understanding relating MPCK, four themes is summarized as followings; the understanding of '0' in the 'rounding up', the cognitive gap between 'rounding up' and 'rounding off', the difference of percentage of correct answers according to types of question in the 'rounding up', and the difference between the definition of 'rounding up' and the definition of 'rounding'.

• Journal of Educational Research in Mathematics
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• v.21 no.1
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• pp.1-16
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• 2011

This study is to review division of whole numbers which is dealt in the revised elementary mathematics textbook and manual for teacher. The textbook and manual for teachers are most important documents to teach mathematics. And they are important to the would-be teachers who study the elementary mathematics with such documents. Therefore the textbook and manual for teachers should have no errors. But I found they have some errors and problems regarding division of whole numbers. In this paper, I discuss the problems and suggest the alternative plans.

• Applied Biological Chemistry
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• v.13 no.3
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• pp.261-268
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• 1970

1. A-value in the soils studied in this experiment were found to be about 40-50kg/10a (as $P_2O_5$) 2. Percentage of utilized phosphorus in Soybeans was 10%. 3. The utilization and A-value of phosphorus were very different among the varieties of soybean plants, and the range was about 30%. 4. A/M-value (A means maximum value of total amount of available phosphorus and M means minimum value of absorbed phosphorus by plants from soils) indicated the critical range of available phosphorus to the crops.

• Journal of the Korean School Mathematics Society
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• v.8 no.4
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• pp.423-444
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• 2005

Despite the importance of number sense, computational skills have been emphasized in elementary mathematics curriculum. There is lack of research on number sense. Against this background, this study analyzed the way 137 sixth grade students coped with routine computation problems and with problems requiring number sense. Students performed better on the computation tasks than on the number sense tasks. With regard to the number sense tasks, many students had a tendency to implement direct computation rather than to use number sense appropriate to the given contexts. Students also had difficulties in making use of effective benchmarks or applying the knowledge of number and operation to various problem contexts. An implication is that students should explore multiple tasks requiring number sense as an integral part of their mathematics learning in order to develop number sense.

• Journal of Elementary Mathematics Education in Korea
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• v.16 no.2
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• pp.227-252
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• 2012

Given the lack of research on the measurement domain, this paper analyzed the statements related to length and area in the curricular materials developed under the 7th and the current mathematics curriculum in terms of the degree of guidance and the key learning elements of measurement. The results showed that despite the similarity of the most prevalent guidance type and learning elements, the current materials used open-ended or combined types in place of guided types and employed measurement reasoning and components while decreasing mere calculation in measurement, in comparison with the previous textbooks and workbooks. This paper close with implications on the revision of curricular materials related to the measurement domain as well as methodological suggestions of textbook analysis.