• Journal of the Mineralogical Society of Korea
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• v.21 no.4
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• pp.415-423
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• 2008

Earth outer core is composed of iron mainly with some diluent elements, which account for the observed ca. 10% density deficit compared to the pure iron. Among candidates as the light diluents, hydrogen and oxygen were selected, and the thermodynamic stability of the following reaction was calculated; hematite + hydrogen $\to$ goethite + iron. At ambient conditions, Gibb's free energy of this reaction is 12.62 kJ/mol. On increasing pressure at room temperature, it decreases to zero at 0.068 GPa. This energy decreases at constant rate down to 200 GPa, which shows -208.26 kJ/mol at that pressure. From these results, this chemical reaction prefers the reduction environment forming the iron element and iron oxyhydroxide, so possible presence of iron oxyhydroxide with iron at proto-core can not be ruled out.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.93-102
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• 2021

The analysis of the fluid flow characteristics in reactor pressure vessel is an important part of the hydraulic design of nuclear power plant, which is related to the structure design of reactor internals, the flow distribution at core inlet and the safety of nuclear power plant. The flow distribution and mixing characteristics in the pressurized reactor vessel for the 1000MWe advanced pressurized water reactor is analyzed by using Computational Fluid Dynamics (CFD) method in this study. The geometry model of the full-scaled reactor vessel is built, which includes the cold and hot legs, downcomer, lower plenum, core, upper plenum, top plenum, and is verified with some parameters in DCD. Under normal condition, it is found that the flow skirt, core plate holes and outlet pipe cause pressure loss. The maximum and minimum flow coefficient is 1.028 and 0.961 respectively, and the standard deviation is 0.019. Compared with other reactor type, it shows relatively uniform of the flow distribution at the core inlet. The coolant mixing coefficient is investigated with adding additional variables, showing that mass transfer of coolant occurs near the interface. The coolant mainly distributes in the 90° area of the corresponding core inlet, and mixes at the interface with the coolant from the adjacent cold leg. 0.1% of corresponding coolant is still distributed at the inlet of the outer-ring components, indicating wide range of mixing coefficient distribution.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.82-89
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• 2011

In this paper, we numerically study both band-pass and band-stop plasmonic filters based on Metal-Insulator-Metal (MIM) waveguides and circular ring resonators. The band-pass filter consists of two MIM waveguides coupled to each other by a circular ring resonator. The band-stop filter is made up of an MIM waveguide coupled laterally to a circular ring resonator. The propagating modes of Surface Plasmon Polaritons (SPPs) are studied in these structures. By substituting a portion of the ring core with air, while the outer dimensions of the ring resonator are kept constant, we illustrate the possibility of red-shift in resonant wavelengths in order to tune the resonance modes of the proposed filters. This feature is useful for integrated circuits in which we have limitations on the outer dimensions of the filter structure and it is not possible to enlarge the dimension of the ring resonator to reach to longer resonant wavelengths. The results are obtained by a 2D finite-difference time-domain (FDTD) method. The introduced structures have potential applications in plasmonic integrated circuits and can be simply fabricated.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.44.4-44.4
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• 2019

The supernova remnant Cassiopeia A (Cas A) provides a unique opportunity to observe the fine details of the explosion of core-collapse supernova (SN). Previous optical and near-infrared (NIR) observations of Cas A have shown that the spatial distribution of the metal-enriched SN ejecta is very complicated, indicating that the SN explosion should have been asymmetric and turbulent, especially near the core. Recently, we obtained a long-exposure (~10 hr) image of Cas A by using the UKIRT 3.6-m telescope with a narrow-band filter centered at [Fe II] 1.644 um emission. This 'deep [Fe II] image' provides an unprecedented panoramic view of Cas A, revealing the distribution of dense SN ejecta over the entire remnant. We have carried out NIR multi-object spectroscopic observations of the dense ejecta knots in the northeastern (NE) and eastern (E) outer regions of the remnant using the MMIRS attached on the MMT 6.5-m telescope. A total of 67 ejecta knots are detected. By analyzing their spectra, we have found that the knots in the NE area show strong [S II]/[S III] and [Fe II] lines but little or no [P II] line, while those in the E outer region show strong [Fe II] lines but weak [S II]/[S III] lines. In this talk, we present the preliminary results of our NIR spectroscopic observations and discuss the implications.

• Steel and Composite Structures
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• v.30 no.2
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• pp.81-96
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• 2019

The behavior of a new Three-Tube Buckling-Restrained Brace (TTBRB) with circumference pre-stress (${\sigma}_{{\theta},pre}$) in core tube are investigated through a verified finite element model. The TTBRB is composed of one core tube and two restraining tubes. The core tube is in the middle to provide the axial stiffness, to carry the axial load and to dissipate the earthquake energy. The two restraining tubes are at inside and outside of the core tube, respectively, to restrain the global and local buckling of the core tube. Based on the yield criteria of fringe fiber, a design method for restraining tubes is proposed. The applicability of the proposed design equations are verified by TTBRBs with different radius-thickness ratios, with different gap widths between core tube and restraining tubs, and with different levels of ${\sigma}_{{\theta},pre}$. The outer and inner tubes will restrain the deformation of the core tube in radius direction, which causes circumference stress (${\sigma}_{\theta}$) in the core tube. Together with the ${\sigma}_{{\theta},pre}$ in the core tube that is applied through interference fit of the three tubes, the yield strength of the core tube in the axial direction is improved from 160 MPa to 235 MPa. Effects of gap width between the core tube and restraining tubes, and ${\sigma}_{{\theta},pre}$ on hysteretic behavior of TTBRBs are presented. Analysis results showed that the gap width and the ${\sigma}_{{\theta},pre}$ can significantly affect the hysteretic behavior of a TTBRB.

• International Journal of High-Rise Buildings
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• v.3 no.2
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• pp.99-106
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• 2014

This paper presents the determination of the structural system of the Changsha IFC T1 tower with 452 m in architectural height and 440.45 m in structural height. Sensitivity analyses are carried out by varying the location of belt trusses and outriggers. The enhancement of seismic capacity of the outer frame by reasonably adjusting the column size is confirmed based on parametric studies. The results from construction simulation including the non-load effect of structures demonstrate that the deformation of vertical members has little effect on the load-bearing capacity of belt trusses and outriggers. The elastoplastic time-history analysis shows that the overall structure under rare earthquake load remains in an elastic state. The influence of the frame shear ratio and frame overturning moment ratio on the proposed model and equivalent mega column model is investigated. It is found that the frame overturning moment ratio is more applicable for judging the resistance of the outer frame against lateral loads. Comparison is made on the variation of these two effects between a classical frame-core tube-outrigger structure and a structure with diagonal braces between super columns under rare earthquakes. The results indicate that plasticity development of the top core cube of the braced structure may be significantly improved.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.268-271
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• 2007

A sandwich tube is a structured material that has two inner and outer circular tubes and light material between them. In this paper, a sandwich tube with a pyramidal truss core is introduced. Fabrication method and example made by brazing are shown. The behavior of the sandwich tube under lateral loading is predicted by analytical and numerical method. Comparative study between the sandwich and the monocoque tube is performed at a point of view such as strength and weight saving. As a result, proposed tube is appropriate for application to lightweight structural material

• Journal of the Korean earth science society
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• v.38 no.6
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• pp.427-441
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• 2017

Theory of Earth's free oscillation is revisited. Firstly, we summarized the underlying formulations, such as the equation of motion and its conversion into numerically integrable form and then explained computational procedures including the treatment of inner core-outer core boundary and core-mantle boundary, while the latter information has not been explicitly given in most publications. Secondly, we re-calculated the periods of Earth's free oscillation modes (period >200 s) for PREM model. In doing so we acquired the values of modes missing in Dziewonski and Anderson (1981). As a case observation, one seismogram after 2011 Tohoku earthquake recorded at Daejeon, Korea (KIGAM seismic station) was briefly analyzed to identify free oscillation mode excitations on its spectra. The material in this article will be most clear guide for those on calculating the Earth's free oscillation mode.

• Journal of Magnetics
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• v.11 no.4
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• pp.160-163
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• 2006

We have prepared crystalline Ag nanoparticles with an average size of 4 nm in diameter by using an inductively coupled plasma reactor equipped with the liquid nitrogen cooling system. Our magnetic data show that the nano-sized effect of Ag nanoparticles on the magnetic properties is ferromagnetic, instead of a diamagnetic component of the Ag bulk and a superparamagnetic component of magnetic nanoparticles. We have also studied the magnetic properties of Ag-Cu nanocomposites with an opposite concentration profile between surface and core. These comparisons indicate that the ferromagnetic component strongly depends on the surface of Ag nanoparticles, while the paramagnetic component is strongly affected by the outer oxide layer, with the background of a diamagnetic component from the core of Ag.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.818-819
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• 2008

본 논문은 영구자석 횡자속 전동기의 고정자 코어구조에 따른 특성을 비교하였다. 즉 전동기의 고정자를 inner core와 outer core로 분리했을 때 사용하는 재질을 SMC-SMC로 제작하는 경우와 SMC-S12로 제작하는 경우에 대해 정특성 해석과 정특성 실험을 통해 비교했다.