• 전기학회논문지
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• 제65권5호
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• pp.773-776
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• 2016

In the quasi-3D finite element(FE) anlysis, the overall characteristics of axial flux permanent magnet(AFPM) motor could be composed of each computation region. However, A drawback of quasi-3D FEM is not to consider the end effect on the stack end. To address this problem, an improved quasi-3D FE analysis which considers the end effect of the AFPM motor was proposed. From results the 3D FE analysis, the validity of the proposed method is verified.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.95-99
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• 2011

$CaTi_{1-x}Fe_xO_3(0{\leq}x{\leq}0.4)$ solid solution photocatalysts were synthesized by iron doping during the conventional solid state reaction at $1100^{\circ}C$ for 5 h and characterized by ultraviolet-visible (UV-vis) absorption spectroscopy, X-ray diffraction, morphological analysis. We found that $CaTi_{1-x}Fe_xO_3$ samples not only absorb UV but also the visible light photons. This is because the Fe substitution at Ti-site in $CaTi_{1-x}Fe_xO_3$ lattice induces the band transition from Fe3d to the Fe3d + Ti3d hybrid orbital. The photocatalytic activity of Fe doped $CaTiO_3$ samples for hydrogen production under UV light irradiation decreased with the increase in the Fe concentration. There exists an optimized concentration of iron in $CaTiO_3$, which yields a maximum photocatalytic activity under visible light ($\lambda\geq420nm$) photons.

• Advances in aircraft and spacecraft science
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• 제6권2호
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• pp.169-187
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• 2019

This work presents a practical detailed finite element (FE) approach for the three-dimensional (3D) free-vibration analysis of actual aircraft and spacecraft-type lightweight and thin honeycomb sandwich panels. It consists of calling successively in $MATLAB^{(R)}$, via a developed user-friendly GUI, a detailed 3D meshing tool, a macrocommands language translator and a commercial FE solver($ABAQUS^{(R)}$ or $ANSYS^{(R)}$). In contrary to the common practice of meshing finely the faces and core cells, the proposed meshing tool represents each wall of the actual hexagonal core cells as a single two-dimensional (2D) 4 nodes quadrangularshell element or two 3 nodes triangular ones, while the faces meshes are obtained simply using the nodes at the core-faces interfaces. Moreover, as the same 2D FE interpolation type is used for meshing the core and faces, this leads to an automatic handling of their required FE compatibility relations. This proposed approach is applied to a sample made of very thin glass fiber reinforced polymer woven composite faces and a thin aluminum alloy hexagonal honeycomb core. The unknown or incomplete geometric and materials properties are first collected through direct measurements, reverse engineering techniques and experimental-FE modal analysis-based inverse identification. Then, the free-vibrations of the actual honeycomb sandwich panel are analyzed experimentally under different boundary conditions and numerically using different mesh basic cell shapes. It is found that this approach is accurate for the first few modes used for pre-design purpose.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.301-308
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• 2004

The present study mainly focuses on the inelastic stress analysis of the 1/4 scale prestressed concrete containment vessel model(PCCV) under internal pressure and evaluates not only failure mode but also ultimate pressure capacity of the PCCV. Inelastic analysis is carried out 2D axisymmertic FE model and 3D FE model using four concrete material models which are Drucker-Prager Model, Chen-Chen Model, Damaged Plasticity Model and Menetrey-Willam Model. The uplift phenomenon of the basemat is considered in the 2D axisymmetric FE models. It is found from the 2D axisymmetric analysis results that both of Drucker-Prager model and Damaged Plasticity Model have a good performance and the uplift of the basemat is too small to influence on the global behavior of the PCCV. The FE analysis results on the ultimate pressure and failure mode have a good agreement with experimental results.

• Journal of Magnetics
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• 제11권4호
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• pp.151-155
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• 2006

The electromagnetic engine valve actuator is a key technology to achieve variable valve timing in internal combustion engine and the steel core and clapper of the electromagnetic engine valve actuator are laminated to reduce the eddy current loss. To design and characterize the performance of the electromagnetic engine valve actuator, FE (finite element) analysis is the most effective way, but FE (finite element) 3-D modeling of real lamination needs very fine meshes resulting in countless meshes for modeling and numerous computations. In this paper, the equivalent FE 2-D model of electromagnetic engine valve actuator is introduced and FE analysis is performed using the equivalent FE 2-D model.

• 한국식품영양학회지
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• 제27권3호
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• pp.406-413
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• 2014

The objective of this study was to identify the nutritional risk factors by blood analysis, in 1,083 preschool children of age 3 to 6 years. The frequency of anemic children was 7.3% with Hb<11.1 g/dL, 29.9% with ferritin<20 ng/mL, and 16.7% with transferrin Fe saturation(%)<15%. The prevalence of anemia in these children were 12.8% for those with MCV<79 fL, and it was 71% for those with TIBC> $400{\mu}g/dL$. Serum ferritin concentration was 20 ng/mL in the normal children. Thirty two percent of the children had anemia with Hb<12 g/dL, which is below the normal range of Hb. Exactly 15.4% of the children had serum Fe concentration of $60{\mu}g/dL$. The transferrin Fe saturation of the children (16.3%) was >15%. The serum ferritin concentration showed low correlations with Hb, Fe, transferrin Fe saturation, and MCV. The transferrin Fe saturation, higher Hb concentration, MCV, and Hct values were increased significantly. Consequently, iron-deficiency anaemia was thus defined as having Hb concentration <12 g/dL accompanied by ferritin concentration <20 ng/mL or Hct <33%.

• 한국자기학회지
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• 제21권2호
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• pp.43-47
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• 2011

Fe-Al 계의 전이금속 화합물은 구조적 안정성과 자성에 대한 이견이 많은 것으로 알려져 있다. 본 연구에서는 B2, $L1_2$, 및 $D0_3$ 구조를 갖는 Fe-Al 계 화합물의 자성과 원자구조의 상관관계를 논의하기 위해 전전자 총퍼텐셜선형보강평면파(all-electron fullpotential linearized augmented plane wave; FLAPW) 방법을 이용하여 일반기울기 근사(generalized gradient approximation; GGA) 하에서 계산하였다. 고려한 모든 구조에서 강자성이 비자성에 비해 안정한 것으로 계산되었다. Fe 원자의 계산된 스핀 자기모멘트는 B2, $L1_2$ 구조에서 각각 0.771 ${\mu}_B$, 2.373 ${\mu}_B$의 값을 얻었고, $D0_3$ 구조의 Fe(I) 및 Fe(II) 원자들은 각각 2.409 ${\mu}_B$, 1.911 ${\mu}_B$로 계산 되었다. $Fe_3Al$의 같은 조성을 갖는 $L1_2$와 $D0_3$ 구조간의 안정성을 조사하기 위하여 형성 엔탈피 계산을 통해 강자성 상태에서 16 meV/atom의 에너지 차이로 $D0_3$ 구조가 $L1_2$ 구조보다 더 안정함을 확인하였다. 이 결과는 실험연구와 잘 일치하며, 원자구조와 전자구조의 분석을 통해 구조적 안정성과 자성에 대해 이해하였다.

• Geomechanics and Engineering
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• 제5권3호
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• pp.223-240
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• 2013

In the present study an attempt was made to predict the complex nonlinear parameters of the soil-pile system subjected to the vertical vibration of rotating machines. A three dimensional (3D) finite element (FE) model was developed to predict the nonlinear dynamic response of full-scale pile foundation in a layered soil medium using ABAQUS/CAE. The frequency amplitude responses for different eccentric moments obtained from the FE analysis were compared with the vertical vibration test results of the full-scale single pile. It was found that the predicted resonant frequency and amplitude of pile obtained from 3D FE analysis were within a reasonable range of the vertical vibration test results. The variation of the soil-pile separation lengths were determined using FE analysis for different eccentric moments. The Novak's continuum approach was also used to predict the nonlinear behaviour of soil-pile system. The continuum approach was found to be useful for the prediction of the nonlinear frequency-amplitude response of full-scale pile after introducing the proper boundary zone parameters and soil-pile separation lengths.

• 한국자기학회지
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• 제21권2호
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• pp.56-60
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• 2011

준강자성체(ferrimagnet) $Fe_3O_4$를 기반 물질로 하여 주기율표 상에서 Fe와 인접한 전이금속 원소 T(= V, Cr, Mn)가 도핑된 삼원화합물($T_{0.2}Fe_{2.8}O_4$) 박막 시료들을 제작하여 그 광학적 성질을 1~8 eV 범위 내에서 분광타원해석법(spectroscopic ellipsometry)을 이용하여 측정하고 $Fe_3O_4$에서의 결과와 비교하였다. V, Cr, Mn 도핑 시 선호되는 스피넬(spinel) 구조 상의 양이온 자리(site) 및 이온수(ionicity)와 연관된 전자구조 상의 변화에 근거하여 삼원화합물과 $Fe_3O_4$의 흡수 스펙트럼 차이의 원인을 분석하였다. $Fe_3O_4$ 및 전이금속 도핑된 화합물들에서 관측된 광학적 흡수 스펙트럼은 주로 Fe 이온의 d 전자가 관련된 이온 간의 전하이동전이(charge-transfer transition)에 의하여 발생하는 에너지 폭이 넓은 흡수구조들의 기여에 의한 것으로 해석된다. 또한, 흡수 스펙트럼에서 관측된 좁은 에너지 폭의 구조들은 사면체 자리에 존재하는 $Fe^{3+}(d^5)$ 이온 내의 d 전자들에 의한 결정장 전이(crystal-field transition)에 기인한 것으로 해석된다. 이와 같은 전이들과 관련된 전자상태들을 스핀편극된 $Fe_3O_4$ 전자구조를 토대로 기술하였다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2013년도 자성 및 자성재료 국제학술대회
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• pp.29-29
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• 2013

We predict agigantic perpendicular magnetocrystalline anisotropy (MCA) in Fe (001) capped by 5d transition metal (TM) overlayers by using first principles calculations. Analysis of atom-by-atom contribution to MCA reveals that gigantic MCA as large as 11 meV/TM originates not from Fe atoms but from the 5d TMs through the strong spin-orbit coupling. More specifically, it is the hybridization between TM and Fe d orbitals that also induces non-negligible magnetic moments in TM. Furthermore, spin-channel decompositions of MCA matrix with and without the presence of Fe substrate identify the electronic origin of the perpendicular MCA that the down-down channel contribution plays the most crucial role for the sign changes of MCA of TM overlayers upon the hybridization with Fe-3d.