• Education of Primary School Mathematics
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• v.5 no.2
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• pp.111-119
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• 2001

Over the years, the benefits of instructional manipulatives in mathematics education have been verified by classroom practice and educational research. The purpose of this paper is to introduce how the instructional material, specifically, geoboard could be used and integrated in elementary mathematics classroom in order to develop student's mathematical concepts and process in terms of the following areas: (1) Number '||'&'||' Operation : counting, fraction '||'&'||' additio $n_traction/multiplication (2) Geometry : geometric concepts (3) Geometry : symmetry '||'&'||' motion (4) Measurement : area '||'&'||' perimeter (5) Probability '||'&'||' Statistics : table '||'&'||' graph (6) Pattern : finding patterns Further, future study will continue to foster how manipulatives will enhance children's mathematics knowledge and influence on their mathematics performance.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.595-599
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• 2003

We have studied the phase transition to look for molecular structure by using several different techniques for new banana-shaped liquid crystals shown in Fig. 1. Based on the similarities to recently observed fluro-contaning materials (switching involves layer structure rearrangement, increasing threshold with increasing temperature) for HC sample (where x is H), we assume that the phase C has a triclinic symmetry corresponding to the double tilted $smC_G$ Phase. The observation that the polarization peak appears at lower field ($E_o{\sim}15V/{\mu}m$) than the amplitude of the threshold ($E_{th}$) can be explained assuming a field induced $SmC_G$ - SmCP (or SmAP) transition at $E_{th}$

• Bulletin of the Korean Chemical Society
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• v.20 no.12
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• pp.1399-1408
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• 1999

Geometrical structures for the dimerization of (NO)₂ from (NO + NO) have been calculated using ab initio Har-tree-Fock (SCF), second-order Møller-Plesset perturbation (MP2), and coupled cluster with the single, double, and triple substitution [CCSD(T)] methods with a triple zeta plus polarization (TZP) basis set including diffuse Rydberg basis functions. The structure of (NO)₂ can be described by two interactions (N…N, N…O). One is the ONNO structure with an (N…N) interaction. In this structure, acyclic cis-ONNO with $C_{2v}$-symmetry, acyclic trans-ONNO with $C_{2h}$, and cyclic ONNO with trapezoidal structure ($C_{2v}$) are optimized at the MP2 level. The other structure is the ONON structure with an (N…O) interaction. In the structure, acyclic cis-ONON with Cs$^{-symmetry}$ and cyclic ONON of the rectangular ($C_{2h}$), square $(D_{2h})$, rhombic $(D_{2h})$, and parallelogramic $(D_{2h})$ geometries are also optimized. It is found that acyclic cis-ONNO (¹A₁) is the most stable structure and cyclic ONNO (³A₁) is the least stable. Acyclic trans-ONNO (³A₁) with an (N…N) interaction, acyclic trans-ONON and bicyclic ONON $(C_{2v})$ with (N…O) interaction, and acyclic cis- and trans-NOON with an (O…O) interaction can not be optimized at the MP2 level. Particularly, acyclic trans-ONNO with $C_{2h}$-symmetry can not be optimized at the CCSD(T) level. Meanwhile, acyclic NNOO (¹A₁, $C_s)$ and trianglic NNOO (¹A₁,$C_{2v})$ formed by the (O…N) interaction between O₂ and N₂ are optimized at the MP2 level. The binding energies and the relative energy gaps among the isomers are found to be relatively small./sec. Spiral CT scans during the arterial phase were obtained 35 seconds after the injection of contrast medium. CT findings of 78 lesions less than 4cm in diameter were correlated with angiographic findings. Results : The attenuation of lesions was high(n = 69), iso(n = 5), and low(n = 4) compared with liver parenchyma during the arterial phase of spiral CT. In lesions with high-, iso-, and low-attenuation during the arterial phase of spiral CT, hypervascularity on angiograms was found in 63 of 69(91.3%), three of five(60%), and three of four lesions(75%), respectively. Six lesions with high-attenuation on the arterial phase of spiral CT were not seen on angiography. Two iso-attenuated and one low-attenuated lesion were hypovascular on angiograms. Conclusion : The results of this study suggest that with some exceptions there was good correlation between the arterial phase of spiral CT and angiography.

• Progress in Superconductivity
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• v.9 no.1
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• pp.111-114
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• 2007

We have investigated the effect of different heat treatment processes on electrical and magnetic properties of Bi2212/Ag ROSAT wire. The ROSAT wire was fabricated by stacking and arranging 12 filaments Bi2212/Ag tapes in triple rotation symmetry in a Ag tube. ROSAT wires have been prepared using a partial melting method with changing $T_{max}$ and $T_a$ in oxygen atmosphere. The highest critical current density($J_c$) at 65 K under 0 T was $21,158\;A/cm^2$ for wire prepared $890\;^{\circ}C(T_{max})$ and $840\;^{\circ}C(T_a)$, respectively. SEM results indicated that the wire prepared at $890\;^{\circ}C(T_{max})$ and $840\;^{\circ}C(T_a)$ showed better directional phases than the other samples. However the result of magnetic susceptibility measurement indicates that the wire prepared $890\;^{\circ}C(T_{max})$ and $835\;^{\circ}C(T_a)$ had better superconducting phases than the other samples. It was revealed that heat treatment temperature was important factor for superconducting properties of the ROSAT wire.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.59-68
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• 2017

The flower and woman are beautiful but Euler's theorem and the symmetry are the best. Shannon applied his theorem to information and communication based on Euler's theorem. His theorem is the root of wireless communication and information theory and the principle of today smart phone. Their meeting point is $e^{-SNR}$ of MIMO(multiple input and multiple output) multiple antenna diversity. In this paper, Euler, who discovered the most beautiful formula($e^{{\pi}i}+1=0$) in the world, briefly guided Shannon's formula ($C=Blog_2(1+{\frac{S}{N}})$) to discover the origin of wireless communication and information communication, and these two masters prove a meeting at the Shannon limit, It reveals something what this secret. And we find that it is symmetry and element-wise inverse are the hidden secret in algebraic coding theory and triangular function.

• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.177-180
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• 2005

Ferroelectric $LiTaO_3$ single crystals, grown by the Czochralski method, were thermally treated at temperature $1000^{\circ}C\;and\;1100^{\circ}C$. Electron paramagnetic resonance (EPR) study of stoichiometric $LiTaO_3$ and thermally treated $LiTaO_3$ crystals has been investigated by employing an X-band spectrometer. From the $Fe^{3+}$ EPR spectra, it turned out that there is no change of site location and local site symmetry around $Fe^{3+}$ impurity ion between stoichiometric and thermally treated $LiTaO_3$ single crystals. We confirmed that the ionic state of $Fe^{3+}$ ion changed after thermal treatment. The EPR parameters of $Fe^{3+}$ ion in $LiTaO_3$ single crystals are determined with effective spin Hamiltonian.

• Bulletin of the Korean Chemical Society
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• v.22 no.11
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• pp.1231-1235
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• 2001

Pseudotetragonal ZrO0.75S whose space group is P212121 was synthesized and the cell dimensions were a=5.110(2) $\AA$, b=5.110(7) $\AA$, and c=5.198(8) $\AA.$ The space group P212121 seems to be resulted from lowering the symmetry of cubic ZrOS structure with P213 space group by lattice distortion due to the oxygen defects. In the distorted structure, bond shortening between metal-nonmetal by reduction of cell volume and alternation of Zr-Zr distance were observed. Dielectric constant and loss data of the bulk material in temperature range -170 to 20 $^{\circ}C$ and frequency range 50 Hz to 1 MHz showed that there was dielectric transition at around -70 $^{\circ}C$ originated from the relaxation of Zr-S segment. Comparing with ZrO2 exhibited the dielectirc constants, 9.0 at room temperature, ZrO0.75S showed high dielectric constant, k = 200.2 at 100 kHz. The activation energy of relaxation time due to dielectric relaxation of Zr-S was 0.47 eV (11.3 kcal/mole). According to the impedance spectra, ZrO0.75S showed more parallel circuit character between the resistance and capacitance components at the temperature (-70 $^{\circ}C)$ that the Zr-S dielectric relaxation was observed.

• Korean Journal of Crystallography
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• v.6 no.2
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• pp.75-79
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• 1995

The crystal structure of Tris(ethylenediamine)nickel(II)Chromate has been determined by X-ray crystallography. Crystal data : a=9.027(2)Å, c=9.751(5)Å이며, Z=2, V=687.9(2)Å3, Dc=1.714gcm-3, μ=21.635-1. The intensity were collected with Mo-Kα radiation (λ=0.7107Å) on an automatic four-circle diffractometer with a graphite monochromator. The structure was solved by Patterson method and refined by full matrix least-square methods using unit weights. The final R and S values were R=0.029, Rw=032, Rall=0.049 andS=0.018 for 342 observed reflections. The chromate ions are located at position of point of point symmetry 32 and their oxygens are sixfold disodered in an unusual way. Extensive strong hydrogen bonds between complex cations and chromatic anions are found in axial and equatorial directions.

• Korean Journal of Crystallography
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• v.15 no.1
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• pp.29-34
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• 2004

The crystal structure of cholesteryl hemisuccinate ($C_{31}H_{50}O_4$) was investigated by X-ray diffraction method. The cholesterol fragment of the title compound were in good agreement with those for related cholesterol derivatives. The unit cell contains four cholesteryl hemisuccinate molecules that are not related by crystal symmetry and have their tetracyclic system almost parellel to each other. There are two pairs of hydrogen-bonded dimer between A and D molecules and B and C molecules. These two hydrogen-bonded dimers are parallel to the c-axis, and are closely packed.

• Korean Journal of Crystallography
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• v.9 no.2
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• pp.120-124
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• 1998

N-tert-Butyl-2-(1-acetoxy-2-fluoro-1-butyl)benzenesulfonamide의 분자 및 결정구조를 X-선회절법으로 연구하였다. 결정의 공간군은 P21/c이고, 단위포 상수는 a=8.583(2) , b=14.674(2) , c=14.703(2) , β=103.23(1)0, Z=4, V=1802.6(5) 3, Dc=1.27 Mgm-3이다. 회절반점들의 세기는 Rigaku AFC-5 Diffractometer로 얻었으며, graphite로 단색화한 Cu-KαX-선을 사용하였다. 분자구조는 직접법으로 풀었으며 최소자승법으로 정밀화하였다. 최종신뢰도 R값은 2472개의 회절반점에 대하여 0.069였다. 분자 내에 N(7)과 O(4)사이에 1개의 수소결합[2.990(4) ]을 갖으며, C(14)와 C(15)는 반대배열을 갖고 있다. 분자간 가장 인접한 거리는 3.465(5) [C(19) O(5)] (symmetry code: -x, y+1/2, -z+1/2)로 분자간 접촉은 van der Waals 힘에 의해 결합되어 있다.