• Journal of the Korean Ceramic Society
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• v.38 no.2
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• pp.143-151
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• 2001

Ca/LiCl-KCl/CaCrO$_4$열 전지계의 양극재료로서 BCT(Body-Centered Tetragonal) 결정구조를 갖는 CaCrO$_4$분말을 GNP로 합성하고, SEM, TEM, XRD를 이용하여 그 미세구조를 분석하였다. GNP 공정에 의한 CaCrO$_4$분말은 단일상으로 0.5$mu extrm{m}$ 이하의 입자 크기를 가지며 균일하게 분포한 반면, 기존의 분말 혼합법은 높은 하수 온도 및 장시간의 하소 조건을 필요하므로 미세한 분말 합성이 어렵고 pellet 형태로 만들었을 때 GNP 분말에 비해 비표면적이 현저하게 작기 때문에 전극 재료로써 유리하지 못하다. Ca/LiCl-KCl/CaCrO$_4$계의 전기 화학적인 특성을 평가해본 결과 전지셀을 Ca/DEB(LiCl-KCl+CaCrO$_4$+SiO$_2$)와 같은 DEB 형태로 만들었을 때 $600^{\circ}C$의 온도에서 2.0 V이상 (<100 mA/㎤)의 안정한 전압이 5분 이상 유지되었다. 그러나 3층 전극 셀(Ca/LiCl/KCl/ CaCrO$_4$)에서는 동일한 온도에서 2.0 V이상 (<100 mA/㎤)의 전압이 7분 이상 유지되었으나 불안정한 전압 변동 및 낮은 peak voltage로 인해 DEB 셀의 전지 특성이 더 우수한 것으로 생각된다. 양극 재료의 제조 방법의 관점에서 볼 때, 동일한 DEB(Depolarizer : Electrolyte : Binder=25 : 70 : 5 wt%) 조성의 셀 구성시, GNP 분말은 분말 혼합법에 의한 분말보다 반응 표면적이 훨씬 크기 때문에 GNP 양극 활 물질의 DEB 셀에서의 전지 수명이 더 길었다.

• Journal of computational fluids engineering
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• v.18 no.4
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• pp.25-34
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• 2013

A numerical study of a laminar natural convection of the CuO-water nanofluid in a square cavity using the Buongiorno's nonhomogeneous model is presented. All the governing equations including the volume fraction equation are discretized on a cell-centered, non-uniform grid employing the finite-volume method with a primitive variable formulation. Calculations are performed over a range of Rayleigh numbers and volume fractions of the nanopartile. From the computed results, it is shown that both the homogeneous and nonhomogeneous models predict the deterioration of the natural convection heat transfer well with an increase of the volume fraction of nanoparticle at the same Rayleigh number, which was observed in the previous experimental studies. It is also shown that the differences in the computed results of the average Nusselt number at the wall between the homogeneous and nonhomogeneous models are very small, and this indicates that the slip mechanism of the Brown diffusion and thermophoresis effects are negligible in the laminar natural convection of the nanofluid. The degradation of the heat transfer with an increase of the volume fraction of the nanoparticle in the natural convection of nanofluid is due to the increase of the viscosity and the decrease of the thermal expansion coefficient and the specific heat. It is clarified in the present study that the previous controversies between the numerical and experimental studies are owing to the different definitions of the Nusselt number.

• Journal of Microbiology and Biotechnology
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• v.15 no.3
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• pp.551-559
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• 2005

The recent rapid increase in genomic data related to many microorganisms and the development of computational tools to accurately analyze large amounts of data have enabled us to design several kinds of simulation approaches for the complex behaviors of cells. Among these approaches, dFBA (dynamic flux balance analysis), which utilizes FBA, differential equations, and regulatory events, has correctly predicted cellular behaviors under given environmental conditions. However, until now, dFBA has centered on substrate concentration, cell growth, and gene on/off, but a detailed hierarchical structure of a regulatory network has not been taken into account. The use of Boolean rules for regulatory events in dFBA has limited the representation of interactions between specific regulatory proteins and genes and the whole transcriptional regulation mechanism with environmental change. In this paper, we adopted the operon as the basic structure, constructed a hierarchical structure for a regulatory network with defined fundamental symbols, and introduced a weight between symbols in order to solve the above problems. Finally, the total control mechanism of regulatory elements (operons, genes, effectors, etc.) with time was simulated through the linkage of dFBA with regulatory network modeling. The lac operon, trp operon, and tna operon in the central metabolic network of E. coli were chosen as the basic models for control patterns. The suggested modeling method in this study can be adopted as a basic framework to describe other transcriptional regulations, and provide biologists and engineers with useful information on transcriptional regulation mechanisms under extracellular environmental change.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.654-660
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• 1998

$[Fe^{II}Fe^{III}BPLMP(OAc)_2](BPh_4)_2$ (1), a new model for the reduced form of the purple acid phosphatases, has been synthesized by using a dinucleating ligand, 2,6-bis[((2-pyridylmethyl)(6-methyl-2-pyridylmethyl)amino) methyl]-4-methylphenol (HBPLMP). Complex I has been characterized by X-ray diffraction method as having (μ-phenoxo)bis(acetato)diiron core. Complex 1 was crystallized in the monoclinic space group C2/c with the following cell parameters: a=41.620(6) Å, b=14.020(3) Å, c=27.007(4) Å, β=90.60(2)°, and Z=8. The iron centers in the complex 1 are ordered as indicated by the difference in the Fe-O bond lengths which match well with typical $Fe^{III}-O\; and\; Fe^{II}-O$ bond lengths. Complex 1 has been studied by electronic spectral, NMR, EPR, SQUID, and electochemical methods. Complex 1 exhibits strong bands at 592 nm, 1380 nm in $CH_3CN$ (ε = 1.0 × 103 , 3.0 × 102). These are assigned to $phenolate-to-Fe^{III}$ and intervalence charge-transfer transitions, respectively. Its NMR spectrum exhibits sharp isotropically shifted resonances, which number half of those expected for a valence-trapped species, indicating that electron transfer between $Fe^{II}\;and\;Fe^{III}$ centers is faster than NMR time scale. This complex undergoes quasireversible one-electron redox processes. The $Fe^{III}_2/Fe^{II}Fe^{III}\;and\;Fe^{II}Fe^{III}/Fe^{II}_2$ redox couples are at 0.655 and -0.085 V vs SCE, respectively. It has $K_{comp}=3.3{\times}10^{12}$ representing that BPLMP/bis(acetate) ligand combination stabilizes a mixed-valence $Fe^{II}Fe^{III}$ complex in the air. Complex 1 exhibits a broad EPR signal centered near g=1.55 which is a characteristic feature of the antiferromagnetically coupled high-spin $Fe^{II}Fe^{III}$ system $(S_{total}=1/2)$. This is consistent with the magnetic susceptibility study showing the weak antiferromagnetic coupling $(J= - 4.6\;cm^{-1},\; H= - 2JS_1{\cdot}S2)$ between $Fe^{II}\; and \;Fe^{III}$center.

• Journal of Ship and Ocean Technology
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• v.12 no.3
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• pp.36-54
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• 2008

A jet stream applied tangential to a curved surface in fluid increases lift force by strengthening circulation around the surface and this phenomenon is known as the Coanda effect. Many experimental and numerical studies have been performed on the Coanda effect and the results found to be useful in various fields of aerodynamics. Recently, preliminary studies on Coanda control surface are in progress to look for practical application in marine hydrodynamics since various control surfaces are used to control behaviors of ships and offshore structures. In the present study, the performance of a Coanda control surface with different geometries of the jet injection nozzle was surveyed to assess applicability to ship rudders. A numerical simulation was carried out to study flow characteristics around a section of a horn type rudder subjected to a tangential jet stream. The RANS equations, discretized by a cell-centered finite volume method were used for this computation after verification by comparing to the experimental data available. Special attentions have been given to the sensitivity of the lift performance of a Coanda rudder to the location of the slit (outlet) and intake of the gap between the horn and rudder surface at the various angles of attack. It is found that the location of the water intake is important in enhancing the lift because the gap functions as a conduit of nozzle generating a jet sheet on the rudder surface.

• Journal of the Korean Association of Geographic Information Studies
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• v.17 no.3
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• pp.68-81
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• 2014

This study aims to apply and evaluate the automatic DAD analysis method, which is able to establish the depth-area relationship more efficiently and accurately for point-to-areal rainfall conversion. First, the proposed automatic DAD analysis method tracks the expansion route of area from the storm center, and it is divided into Box-tracking, Point-tracking, Advanced point-tracking according to tracking method. After applying the proposed methods to 10 events occurred in Yongdam-watershed area, we confirmed that the Advanced point-tracking method makes it possible to estimate the maximum average areal rainfal(MAAR) more accurately with consideration of the storm movement and the multi-centered storm. In addition, Advanced point-tracking could reduce the errors of the estimated MAAR induced by increasing the area because it can estimate MAAR for each storm center and compare them at the same time. Finally, the DAD curve for the study area could be derived based on the DAD analysis of the selected 10 events.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.98-103
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• 2001

A new application of dirchroic mirror for the improvement of luminance and luminous efficacy in an AC-Plasma Display Panel (PDP) is suggested. Only about half of the Vacuum Ultraviolet (VUV) generated in the reflective PDP cell is used for the excitation of the phosphor. We are suggesting an idea of adopting a dichroic mirror which can reflect the VUV toward the phosphor which otherwise is absorbed by the front panel. The optical constants of the thin films of dirhroic mirror were determined from the photometric measurements through an iteration process of matching calculated and measured values of the reflectance and transmittance in the VUV wavelength region. From these results, we could design such a filter whose high reflection zone is centered at 147nm by a computer simulation accurately. The 147nm VUV is radiated from Xenon 3Pl state which is dominantly used to activate the phosphor in the PDP cell. The dichroic mirror was made with an electronbeam evaporator and its reflectance was measured by a reflectometer. We confirmed the usefulness of the dichroic mirror for the improvement of efficiency with experiments done by test panels. The panel with mirror shows improved luminance and luminous efficacy by 20∼30％.

• Journal of the Mineralogical Society of Korea
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• v.14 no.2
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• pp.99-110
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• 2001

A gem-quality yttria-stabilized zirconium oxide crystals were synthesized by the skull-melting method, using the RF electrical apparatus. Principal raw materials used were $ZrO_2$and 25 wt.% $Y_2O_3$as stabilizer and 0.03~0.05 wt.% $Nd_2O_3$decolorizing agent were added to it. The single crystals were approximately 20$\times$63 mm in size with chemical composition $Zr_{0.73}$ $Y_{0.27}$ $O_{1.87}$ . The crystals are isotropic with no appreciable anisotropism under a polarizing microscope. Their refractive indices are in the range of 2.15~2.18, specific gravity 5.85, Mohs' hardness 8~8.5, and reflectivity 13.47%. The zirconia crystals were confirmed to have cubic structure with Face-centered lattice(Z=4), space group Fm3m ($CaF_2$-type structure) and unit cell parameters are a=5.157 $\AA$. The optimal growing conditions for yttria-stabilized zirconia are 50 kW, 2.94 MHz in power and to use a crucible with 105 mm $\times$ 135 mm in size. When the lowering speed of the crucible was set 16mm/hr gave the best yield, 42%. Since the refractive index(2.15~2.18) of cubic zirconia is smaller than that of diamond, the angle between crown and pavilion should be fashioned to make it smaller than $40.5^{\circ}$ to show the maximum brilliancy and fire.

• Journal of Korean Home Economics Education Association
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• v.19 no.4
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• pp.91-117
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• 2007

This study was to compare the contents and practical problems addressed, the process of teaching-learning method, and evaluation method of Korean Home Economics curriculum and of the Oregon and Ohio's Practical Problem Focused Family & Consumer Sciences Curricula. The results are as follows. First, contents of Korean curriculum are organized by major sub-concepts of Home Economics academic discipline whereas curricular of both Oregon and Ohio states are organized by practical problems. Oregon uses the practical problems which integrate multi-subjects and Ohio uses ones which are good for the contents of the module by integrating concerns or interests which are lower or detailed level (related interests). Since it differentiates interest and module and used them based on the basic concept of Family and Consumer Science, Ohio's approach could be easier for Korean teachers and students to adopt. Second, the teaching-learning process in Korean home economics classroom is mostly teacher-centered which hinders students to develop higher order thinking skills. It is recommended to use student-centered learning activities. State of Oregon and Ohio's teaching-learning process brings up the ability of problem-solving by letting students clearly analyze practical problems proposed, solve problems by themselves through group discussions and various activities, and apply what they learn to other problems. Third, Korean evaluation system is heavily rely on summative evaluation such as written tests. It is highly recommended to facilitate various performance assessment tools. Since state of Oregon and Ohio both use practical problems, they evaluate students mainly based on their activity rather than written tests. The tools for evaluation include project documents, reports of learning activity, self-evaluation, evaluation of discussion activity, peer evaluation in a group for each students for their performance, assessment about module, and written tests as well.

• Archives of design research
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• v.19 no.4 s.66
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• pp.175-186
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• 2006

In the 21C, each nation controls exhaust fumes from automobiles and makes an effort to develop alternative energy because of serious environmental problem. Jechon area has many historical and cultural archeological sites. And Jechon city sponsors various cultural events. But the way of transportation which is connected with Jecheon and around sightseeing places is general and not ready yet. Therefore, if a special means of vehicle is developed, it could play an another role of sightseeing resources. Special identity of Jecheon area for establishment of green vehicle traffic system which gives Jecheon area specific character was investigated for theoretical background. Traffic system was studied for establishment of direction through existent successful case study. Moreover content, method, structure and advantage & shortcoming etc. of vehicle that use green energy resource such as solar car, fuel cell car, hybrid car, natural gas car etc. were examined. The suitable means of vehicle for Jechon area was proposed to three directions with research and investigation. After comparison and investigation by inquiry of each section's experts, the most suitable traffic system of which energy resource of car, form of vehicles, the complement, dimension of vehicles etc. were decided. Design proposal should be drawn according to process of automobile design in decided direction. Special Exterior design of vehicle that use green energy resource connecting Jecheon and around area should be suggested in Jecheon City Hall and Chungchong-bukdo provincial office for vivify image of cleanliness area.