• Communications of the Korean Mathematical Society
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• v.31 no.4
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• pp.857-868
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• 2016

Let (X, ${\mu}$) be a generalized topological space (GTS) and $\mathcal{H}$ be a hereditary class on X due to $Cs{\acute{a}}sz{\acute{a}}r$ [8]. In this paper, we define an operator $()^{\circ}:\mathcal{P}(X){\rightarrow}\mathcal{P}(X)$. By setting $c^{\circ}(A)=A{\cup}A^{\circ}$ for every subset A of X, we define the family ${\mu}^{\circ}=\{M{\subseteq}X:X-M=c^{\circ}(X-M)\}$ and show that ${\mu}^{\circ}$ is a GT on X such that ${\mu}({\theta}){\subseteq}{\mu}^{\circ}{\subseteq}{\mu}^*$, where ${\mu}^*$ is a GT in [8]. Moreover, we define and investigate ${\mu}^{\circ}$-codense and strongly ${\mu}^{\circ}$-codense hereditary classes.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.103-104
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• 2016

차량용 영구자석형 동기전동기는 벡터제어를 사용한다. 이때 사용 되는 벡터제어는 3상의 전류를 2상으로 변경 후 정지좌표계의 값을 동기좌표계로 변환 시켜줌으로써 순시제어를 실시한다. 이때 벡터제어 정지/동기 좌표계의 변환 시 위치 정보 ${\theta}$는 정지/동기 좌표계 변환의 기준으로 매우 중요한 정보이다. 따라서 정확한 제어를 위한 위치정보를 얻기 위해 이용되는 센서로 엔코더, 레졸버, 레치형 홀센서 등이 사용된다. 일반적으로 낮은 가격의 BLDC 모터의 경우 레치형 홀센서가 많이 이용된다. 그러나 레치형 홀센서의 경우 위치 정확도가 $60^{\circ}^C$로 한정되어 정확한 전기각을 추출하는데 문제가 있다. 본 논문에서는 BLDC 모터의 레치형 홀센서를 대신하여 리니어 홀센서를 이용함으로써 신호의 불균형 및 옵셋 등 문제를 보안, 이전의 시스템보다 더욱 정확한 전기각을 추출하여 벡터제어를 실시한다. 검증방법으로는 700[W]급 범용 영구자석형동기전동기를 이용 시험을 실시함으로써 검증하였다.

• Bulletin of the Korean Chemical Society
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• v.14 no.1
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• pp.38-42
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• 1993

Factor analysis was applied to study the thermal decomposition of barium titanyl oxalate (BTO) which is used as the precursor of barium titanate. BTO was synthesized in $H_2O$ solvent and calcined at various temperatures. The X-ray diffraction patterns were obtained to make the data matrix of peak intensity vs. 2${\theta}$. Abstract factor analysis and target transformation factor analysis were applied to this data matrix. It has been found that the synthesized BTO consists of the crystals of $BaC_2O_4{\cdot}0.5H_2O\;and\;BaC_2O_4{\cdot}2H_2O$ as well as the amorphous solid of TiO-oxalate. The results also indicate that the BTO was transformed via $BaCO_3\;to\;BaTiO_3\;and\;Ba_2TiO_4$ during the thermal decomposition.

• Bulletin of the Korean Chemical Society
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• v.6 no.1
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• pp.7-11
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• 1985

The crystal structure of phlorizin, a ${\beta}$ -D-glucopyranoside of a flavonoid dihydrochalcone phloretin, has been determined by single crystal diffraction methods using diffractometer data obtained by the ${\omega}-2{\theta}$ scan technique with Cu $K{\alpha}$ radiation from a crystal with space group symmetry $P2_12_12_1$ and unit cell parameters a = 4.9094 (2), b = 19.109 (1), c = 23.275 (4) $\AA$. The structure was solved by direct methods and refined by full-matrix least-squares to a final R = 0.047 for the 1697 observed reflections. The dihydrochalcone moiety is flat and fully extended. The glucose ring has the $^4C_1$ chair conformation and the conformation of the primary alcohol group is gauche-gauche. The crystal packing is dominated by an extensive hydrogen bonding pattern. There are one strong and two weak intramolecular hydrogen bonds in the phlorizin molecule.

• Bulletin of the Korean Chemical Society
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• v.4 no.3
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• pp.123-127
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• 1983

The crystal structure of metoclopramide, $C_14H_22ClN_3O_2$, has been determined by X-ray diffraction techniques using diffractometer data obtained by the ${\omega}-2{\theta}$ scan technique with Mo $K\alpha$ radiation from a crystal with space group symmetry $P{\overline{1}}$ and unit cell parameters a = 7.500(1), b = 8.707(2), c = 13.292(2) ${\AA}$; ${\alpha}$ = 101.70(2), ${\beta}$ = 81.20(2), and ${\gamma}$ = $114.90(l)^{\circ}$. The sructure was solved by direct methods and refined by full-matrix least-squares to a final R = 0.055 for the 1524 observed reflections. The bent overall-conformation of the molecule seems to be determined mainly by the bifurcated intramolecular hydrogen bond from the amide nitrogen atom to the methoxy oxygen and the amine nitrogen atoms. The crystal packing consists of the hydrogen bonds, ${\pi}-{\pi}$ interaction and hydrophobic interaction.

• Journal of Radiation Industry
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• v.7 no.2_3
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• pp.167-170
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• 2013

Lignin can be a valuable natural chemical resource. Structurally, lignin is a three-dimensional polymer made up of condensed C-C bonds and some ether linkages, most of which are not readily degraded. In this study, lignin carbonization under various electron beam pretreatment conditions was characterized through a thermogravimetric analysis (TGA), X-ray diffraction (XRD) and Raman spectroscopy. Lignin stabilization was controlled by various doses of electron beam irradiation corresponding to 50, 100, 200, 500 and 1,000 kGy; the carbonization process was performed under a nitrogen gas atmosphere at $1000^{\circ}C$ for 1 h. The TGA results showed that a 1,000 kGy lignin dose increased the residue weight from 39.96% to 45.23%, compared to non-irradiated lignin. This observation is in agreement with the XRD and Raman spectroscopy results, in which the two theta degrees and the degree of crystallization were improved by increasing the electron beam irradiation.

• Bulletin of the Korean Chemical Society
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• v.13 no.6
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• pp.663-665
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• 1992

The superconducting $YBa_2Cu_4O_8$ was synthesized in oxygen condition at 1 atm. The starting material with 1 : 2 : 4 composition was obtained by pyrolysis of EDTA complex, which was converted to 1-2-3 phase during densification, followed by the 1-2-4 phase recovery at $810^{\circ}C$ . The phase presents were identified by XRD, TG, DTA and AC magnetic susceptibility. Our data indicated that considerable amounts of 1-2-4 phase formed but with the 1 : 2 : 3 phase or possibly 2-4-7 as visible. As the P($O_2$) increased with temperature, impurity peak, CuO ($2{\Theta}$ = 38.8), gradually decrease, and we conclude that the 1-2-4 phase is predominant bulk superconductor under the high oxygen pressure.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.73-74
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• 2019

In order to examine the chemical stabilization through DCG curing of cement paste exposed to high temperature environment, we produced a sample of 40% W/C cement paste and heated it for 180 minutes under the heating temperature of $800^{\circ}C$. The DCG curing time was 6, Three time conditions were divided into 12 and 18 hours. As a result of XRD analysis, Calcite ($CaCO_3$) was found in Theta 29.4, 40, and 46.5o. As the curing time increased, the peak of Calcite also increased, which is due to the increased reaction time with DCG. Therefore, Calcite produced through DCG curing seems to have stabilized chemically by filling the pores generated by heating.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.536-542
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• 2008

The rocket technology has the best reliability and the high acceleration performance currently. In addition, next generation propulsion system is acquired to low cost and high payload percentage at that same time. This work is to improve the performance of Diskshaped MHD accelerator which is expected as the one of the solution. In this study we have been focusing on the swirl vane. It is so important to know that how the swirl vane contribute the plasma and its performance. As results, the gas velocities of r-component with inlet swirl were increased about over 3000m/s at the channel exit. And then static gas pressure were also reduced, we found that the case with inlet swirl gives the good influence to the acceleration performance. And the difference of the acceleration by positive and negative inlet swirl is that gas velocity of $\theta$-component may operate to the electric field.

• Structural Engineering and Mechanics
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• v.3 no.1
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• pp.61-74
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• 1995

A linearly tapered, doubly symmetric thin-walled closed member, such as power-transmission towers and tourist towers, are often characterized by local variation in mass and/or rigidity, due to additional mass and rigidity. On the preliminary stage of design the closed-form solution is more effective than the finite element method. In order to propose approximate solutions, the discontinuous and local variation in mass and/or rigidity is treated continuously by means of a usable function proposed by Takabatake(1988, 1991, 1993). Thus, a simplified analytical method and approximate solutions for the free and forced transverse vibrations in linear elasticity are demonstrated in general by means of the Galerkin method. The solutions proposed here are examined from the results obtained using the Galerkin method and Wilson-${\theta}$ method and from the results obtained using NASTRAN.