• School Mathematics
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• v.11 no.4
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• pp.723-743
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• 2009

This paper analyzed the main contents of multiplication and division of fractions in elementary mathematics textbooks and workbooks aligned to the national mathematics curriculum. This paper first explored the adequacy of when to teach the contents, the connection of instructional flow across grades, and the method of constructing a unit to teach multiplication or division of fractions. This paper then analyzed in detail the contents with regard to the types and frequency of word problems, the types of visual models and frequency, and the process of formalizing the calculation methods and principles. 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.

• School Mathematics
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• v.19 no.4
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• pp.713-729
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• 2017

It is the 6th curriculum that first officially mentioned the use of calculators in elementary mathematics education in Korea. Since then, the curriculum has been more widely used than in the beginning. However, in actual textbooks, it is still not enough to see the utilization situation, and guidance in this textbook is very scarce. In particular, there is no relevant study that meets the standards of achievement of the curriculum. The purpose of this study is to investigate the contents of the research on the use of the calculator in the course of the curriculum change after the 6th curriculum, and to present the complex calculation, mathematical concept, mathematical principles and rules, mathematical problem solving. In addition, the course is presented in the textbooks that are appropriate for the achievement criteria and the application process for each topic.

• Proceedings of the Korean Magnestics Society Conference
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• 2012.11a
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• pp.172-172
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• 2012

A Pt-skin $Pt_3Ni$(111) surface was reported to show high catalytic activity. In this study, we investigated the magnetic properties and electronic structures of the various oriented surfaces of bulk-terminated and Pt-segregated $Pt_3Ni$ by using a first-principles calculation method. The magnetic moments of Pt and Ni are appreciably enhanced at the bulk-terminated surfaces compared to the corresponding bulk values, whereas the magnetic moment of Pt on the Pt-segregated $Pt_3Ni$(111) surface is just slightly enhanced because of the reduced number of Ni neighboring atoms. Spin-decomposed density of states shows that the dz2 orbital plays a dominant role in determining the magnetic moments of Pt atoms in the different orientations. The lowering of the d-band center energy (-2.22 eV to -2.46 eV to -2.51 eV to -2.65 eV) in the sequence of bulk-terminated (100), (110), (111), and Pt-segregated (111) may explain the observed dependence of catalytic activity on surface orientation. Our d-band center calculation suggests that an observed enhanced catalytic activity of a $Pt_3Ni$(111) surface originates from the Pt-segregation.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.256-259
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• 2013

We investigate co-doping effects of conjugated P-N B-N with increasing of N concentration in the graphene sheets using a first principles based on the density functional theory. N doping sites of the graphene consider two possible sites (pyridinic and porphyrin-like). Energy calculation shows that additional doping of B atom in the porphyrin-like N doped graphene ($V+B-N_x$) is hard to form. At the low chemical potential of N, one N atom with additional doping in the graphene ($V+P-N_1$, $P/B-N_1$) has low formation energy on the other hand at high chemical potential of N, high concentration of N ($V+P-N_4$, $P/B-N_3$) in the graphene is governing conformation. From the results of electronic band structure calculation, it is found that $V+P-N_4$ and $P/B-N_3$ cases change the Fermi energy therefore type change is occurred. On the other hand, the cases of $V+P-N_1$ and N+B recover the electronic structure of pristine graphene.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.288-291
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• 2016

Recently, there has been a lot of researches related to two-dimensional (2D) materials due to their new properties and applications emerging upon 2D confinement. A new type of graphene like two-dimensional layer material, nitrogenated holey two-dimensional structure C2N-h2D, that is possession of evenly distributed holes and nitrogen atoms with proper bandgap has been synthesized. Previous calculation studies already have shown that the variance of the orbital interaction, band structure of few-layer C2N-h2D suggests that interlayer coupling does play an important role in its electronic properties. In this point, using first-principles density functional theory calculation, we here explore the effect of porous embedded iron atom and iron substrate on encapsulated few layer C2N-h2D. We show the atomic structures and the corresponding electronic structures of Fe@C2N to elucidate the effect of iron. Finally, this study demonstrates that embedded iron C2N has AA-stacking as most favorable stacked structure in contrast to pure C2N. In addition, iron substrate modifies its encapsulated C2N from semi-metallic states to metallic state.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.6
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• pp.556-561
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• 2022

Computational material science as an application of Density Functional Theory (DFT) to the discipline of material science has emerged and applied to the research and development of energy materials and electronic materials such as semiconductor. However, there are a few difficulties, such as generating input files for various types of materials in both the same calculating condition and appropriate parameters, which is essential in comparing results of DFT calculation in the right way. In this tutorial status report, we will introduce how to create crystal structures and to prepare input files automatically for the Vienna Ab initio Simulation Package (VASP) and Gaussian, the most popular DFT calculation programs. We anticipate this tutorial makes DFT calculation easier for the ones who are not experts on DFT programs.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.58
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• pp.3-33
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• 2013

The purpose of this paper is to examine the problems in exercising buyer's right to claim damages for the breach of contract by the seller in international sales contract and to suggest reasonable counter-measures. The main contents are as follows: First, this author analyzed the principles of the seller's liability for damages in detail and examined the methods for the calculation of damages on the basis of Arts.74~77. As these articles are found to be insufficient in practical application, this author further examined the UNIDROIT Principles(2004) to confirm whether these Principles can fill the gaps of CISG or not, which turned out their gap-filling functions. Second, this author tried to find any expected problems when the buyer resorts to the right to claim damages in case of the seller's breach of contract including the estimation of damages, the burden of proof, causation, the proof of appropriateness for avoidance, the proof of buyer's obligation to mitigate the loss and so on. The reason is that these problems may cause a lot of difficulties in real business. As result, many buyers have given up their reasonable rights to claim damages so far. Finally, from the buyer's perspective, this author would like to suggest a liquidated damage clause(LD Clause) which gives the buyer to received a specified sum in case of seller's non-performance and/or a demand guarantee(or standby L/C) which guarantees buyer to secure unconditional payment independent of the underlying contract. For these purposes, the buyer should try to insert the LD Clause and/or Guarantee Clause in the contract when the buyer and the seller negotiate the sales contract. Also there are a lot of considerations and limitations in using the LD Clause and the Guarantee Clause in their real business, mainly dependent up bargain power between the seller and the buyer, for which this author promise to examine in detail in the future.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.159-162
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• 2002

A software, called touch-one, is developed about the determination of short-circuit values and protective co-ordination in power system. The used solution algorithm reviewed intensively, and the protective co-ordination determination technique presented by using the circuit-breaker's current-limitation characteristic. The protective coordination concerns the behaviour of two devices placed in series in an electrical network, with a short-circuit downstream circuit-breaker. It has two basic principles: First, discrimination which is an increasing requirement of low voltage electrical distribution systems. Second, which is less well known: cascading, which consists of installing a device, whose breaking capacity is less than the three-phase short-circuit current at its terminals and helped by main circuit-breaker. With this software, we can construct a electric-power system which is reliable and economic according to user's purpose.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.442-442
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• 2011

Electronic and magnetic properties of bilayer zigzag graphene nanoribbon (bZGNR) are studied using pseudopotential density functional method. The edge atoms in the top and bottom layers of bZGNR make a weak hybridization, which leads to electronic structures different from monolayer ZGNR. For asymmetric bZGNR, where the top and bottom layers have different widths, one edge is pinched by the interlayer bonding and the other sustains antiferromagnetic ordering. A small amount of charge transfer occurs from narrower to wider layer, producing spin-polarized electron and hole pockets. External electric field produces asymmetric energy-gap opening for each spin component, inducing half-metallicity in bZGNR.

• Journal for History of Mathematics
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• v.27 no.6
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• pp.409-419
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• 2014

In school mathematics, the logarithmic function is defined as the inverse function of an exponential function. And the natural logarithm is defined by the integral of the fractional function 1/x. But historically, Napier had already used the concept of logarithm in 1614 before the use of exponential function or integral. The calculation of the logarithm was a hard work. So mathematicians with arithmetic ability made the tables of values of logarithms and people used the tables for the estimation of data. In this paper, we first take a look at the mathematicians and mathematical principles related to the appearance and the developments of the logarithmic tables. And then we deal with the confusions between mathematicians, raised by the estimation data which were known as proportional parts or mean differences in common logarithmic tables.