• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.1
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• pp.19-28
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• 2016

In the case of structural analysis for building structures, the super-structure and the sub-structure are analyzed by using separate structural models in the field because of time saving, facile result interpretation and easy analysis of dynamic behavior. However this separate structural model violated the compatibility condition of structural analysis and it can not consider the interaction of superand sub- structures. In the present study, the analysis results of this separate model were compared to those of the unified model of super- and sub- structures which can consider the interaction of super- and sub- structures and reflect the realistic boundary conditions. According to the comparison results, the the analysis model using separate models can underestimate the member force and deflection of structural members in the super-structures and overestimate the deflection and member force of sub-structures. Therefore, in the case of high-rise buildings, irregular shaped buildings, buildings which are expected to be affected by large differential settlement and remodeling buildings, the unified structural model for super- and sub- structures was recommended for structural analysis instead of the separate structural model.

• Journal of Energy Engineering
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• v.26 no.4
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• pp.67-73
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• 2017

For the bio-fuel conversion of algae, several processes are needed including cultivating, agglomeration, extracting and conversion to the bio-fuel. The production cost for each process makes the total production cost of algae bio-fuel conversion. The production cost of algae bio-fuel has still higher than that of the other commercial bio-fuel. The reduction of production cost for each process enables the competitive price as a bio-fuel. It is difficult to separate the algae from water because of the similar magnitude of density each other. The agglomeration and extracting of algae using ultrasonic wave is rare effect of environmental hazard and also it is appropriate technology for the next generation energy resources. The present research is investigated for the elucidation of algae behavior in the water with the ultrasonics wave. For this purpose, the unsteady computational fluid dynamic analysis has been conducted in the ultrasonic pressure field. The velocity, pressure and algae concentration changes with time have been analysed to clarify the mechanism of algae separation by ultrasonic wave.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.87-94
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• 1992

The elution behavior of polystyrenes(PS), polymethylmethacrylates (PMMA), polybutadienes(PB), PS-PMMA(SM) block copolymers and PS-PB star shaped copolymers on the cross-linked polystyrene gels was studied. An interpretation was proposed for the plots of log hydrodynamic volume versus retention volume of solutes in the mobile phases such as tetrahydrofuran, toluene, chloroform, methylene chloride and tetrahydrofuran-cyclohexane mixture. In order to predict the retention of solutes from their physical properties, multiple stepwise regression analysis was applied to obtain the correlation. The distribution coefficients($K_p$) of solute-gel interactions in GPC for homopolymers and PS copolymers were also obtained in terms of network-limited separation mechanism. In the cases of PS and PB, $K_p$ values approach unity, while $K_p$ values for PMMA decrease as MW increase in the good solvent, but in poor solvent, $K_p$ values increase as MW increase. $K_p$ values of PS copolymers are dependent on their MW and composition, therefore, morohology of SM block copolymer is predicted to be random phase. A single universal plot of log[η]M vs. $(V_r-V_o)/K_p$

• Journal of the Korean Applied Science and Technology
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• v.24 no.2
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• pp.174-181
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• 2007

In this study, $SiO_2/poly(ethylene-co-vinyl$ alcohol)(EVOH) hybrid coating materials with gas barrier property could be produced using sol-gel method. The biaxially oriented polypropylene (BOPP) substrate with surface pretreatment was coated with the prepared hybrid sols containing various inorganic silicate component by a spin coating method. Crystallization behavior of the hybrids was investigated in terms of analysis of X-ray diffraction and cooling thermogram from DSC experiment. From the morphological observation of the $SiO_2/EVOH$ hybrid gel, it was confirmed that there existed an optimum content of inorganic silicate precursor, Tetraethylorthosilicate (TEOS), to produce hybrid materials with dense microstructure, exhibiting uniformly dispersed silica particles with average size below 100 nm. When TEOS was added at below or above the optimum content, particle clusters with large domain were observed, resulting in phase separation. This morphological result was found to be in good agreement with that of oxygen permeability of the hybrid coated films. In the case of film coated with hybrid prepared from addition of 0.01 - 0.02mol of TEOS, a remarkable improvement in barrier property could be obtained, however, with the addition of TEOS more than 0.04 mol, the barrier property was dramatically reduced because of phase separation and micro-crack formation on the film surface.

• Geophysics and Geophysical Exploration
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• v.6 no.3
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• pp.119-125
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• 2003

The small-loop electromagnetic (EM) technique has been used successfully for many geophysical investigations, particularly for shallow engineering and environmental surveys. In conventional small loop EM operating at small induction numbers, geometric sounding has been widely used because the depth of penetration of EM energy depends only on the source-receiver separation. Recently developed small loop EM system, however, measures the secondary magnetic field, $H^S$, at multiple frequencies with a fixed source-receiver separation and frequency sounding is tried actively. In this study, we analyzed the behavior of in-phase and quadrature components of ${H^S}_z$, for horizonal coplanar (HCP) configuration over two-layer models. Through this theoretical analysis, it was found that the in-phase component of ${H^S}_z$ is more suitable for frequency sounding than the quadrature component. But, the in-phase component of ${H^S}_z$ is too small to measure, especially in resistive and noisy environment like Korea. Using the fact that the quadrature component is much greater than the in-phase component and the difference of quadrature component of ${H^S}_z$ measured at two frequencies shows the same behavoir as the in-phase component, we suggested an alternative frequency sounding technique. Also, we defined an apparent conductivity, which reflects well the conductivity of subsurface layers.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.5
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• pp.800-805
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• 2017

The accelerated thermal ageing of CSPE (chlorosulfonated polyethylene) was carried out for 16.82, 50.45, and 84.09 days at $110^{\circ}C$, equivalent to 20, 60, and 100 years of ageing at $50^{\circ}C$ in nuclear power plants, respectively. As the accelerated thermally aged years increase, the insulation resistance and resistivity of the CSPE decrease, and the capacitance, relative permittivity and dissipation factor of those increase at the measured frequency, respectively. As the accelerated thermally aged years and the measured frequency increase, the phase degree of response voltage vs excitation voltage of the CSPE increase but the phase degree of response current vs excitation voltage decrease, respectively. As the accelerated thermally aged years increase, the apparent density, glass transition temperature and the melting temperature of the CSPE increase but the percent elongation and % crystallinity decrease, respectively. The differential temperatures of those are $0.013-0.037^{\circ}C$ and, $0.034-0.061^{\circ}C$ after the AC and DC voltages are applied to CSPE-0y and CSPE-20y, respectively; the differential temperatures of those are $0.011-0.038^{\circ}C$ and $0.002-0.028^{\circ}C$ after the AC and DC voltages are applied to CSPE-60y and CSPE-100y, respectively. The variations in temperature for the AC voltage are higher than those for the DC voltage when an AC voltage is applied to CSPE. It is found that the dielectric loss owing to the dissipation factor($tan{\delta}$) is related to the electric dipole conduction current. It is ascertained that the ionic (electron or hole) leakage current is increased by the partial separation of the branch chain of CSPE polymer as a result of thermal stress due to accelerated thermal ageing.

• Magazine of the Korea Concrete Institute
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• v.7 no.4
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• pp.157-168
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• 1995

The structural performance of Slip-Form system was examined to make use of many advantages of fast construction and high quality c0ncret.e. However, the separate cor~struction of wall and slabs may cause some weaknesses around the wall-slab connection region. Thus, the purpose of the study is to examine the structural performance of wall-type structure constructed by Slip-Form method and to develop an efficient connection system between wall and slabs. In order to investigate the system, 7 wall specimens and 8 wall-slab joint specimens were tested and the experimental results were compared with the design equations and theoretical analysis. A satisfactory performance was obtained from the wall specimen tests. However, wall-slab joint specimens with rebar connection materials I Ilalfen] were shown that. the strength of' wall should be checked during design porocess.

• Macromolecular Research
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• v.16 no.8
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• pp.725-733
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• 2008

Polyimide (PI) multilayer thin films were prepared by spin-coating from a poly(amic acid) (PAA) and poly(amic acid) ammonium salt (PAAS). PI was prepared from pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA) PAA. Different compositions of PAAS were prepared by incorporating triethylamine (TEA) into PMDA-ODA PAA in dimethylacetamide. PI multilayer thin films were spin-coated from PMDA-ODA PAA and PAAS. The PAAS comprising cationic and anionic moieties were spherical with a particle size of $20{\sim}40\;nm$. Some particles showed layers with ammonium salts, despite poor ordering. Too much salt obstructed the interaction between the polymer chains and caused phase separation. A small amount of salt did not affect the interactions of the interlayer structure but did interrupt the stacking between chains. Thermogravimetric analysis (TGA) showed that the average decomposition temperature of the thin films was $611^{\circ}C$. All the films showed almost single-step, thermal decomposition behavior. The nanostructure of the multilayer thin films was confirmed by X -ray reflectivity (XRR). The LF 43 film, which was prepared with a 4:3 molar ratio of PMDA and ODA, was comprised of uniformly spherical PAAS particles that influenced the nanostructure of the interlayer by increasing the interaction forces. This result was supported by the atomic force microscopy (AFM) data. It was concluded that the relationship between the uniformity of the PAAS particle shapes and the interaction between the layers affected the optical and thermal properties of PI layered films.

• Journal of the Korean Magnetics Society
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• v.3 no.4
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• pp.305-309
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• 1993

Thermal stability of Co/Cu artificial superlattice (AS) prepared by RF-magnetron sputtering and the effect of low temperature annealing on the magnetoresistance of the AS have been investigated in this work. Dependence of annealing behavior on the Cu spacer thickness, Fe underlayer thickness, and kind of the underlayer was examined and the relationship between the interfacial reaction and magnetoresistance was studied. It turned out that when Co/Cu AS was annealed at low temperature ($<450^{\circ}C$), the magnetoresistance could increase in the case of AS with thick spacer Cu ($20~25\AA$) layer, whereas it decreased in the case of AS with thin spacer Cu ($7\AA$) layer, which of the former is in contrast with previous reports and the latter in consistent with them. The increase of magnetoresistance is due to increase of interfacial atomic sharpness, which is supported by low angle X-ray diffraction analysis. The thermal stability of Co/Cu AS was better in the case of thick Fe underlayered AS. Interfacial reaction (separation of intermixed Co and Cu) could be observed at lower temperature for (200)-textured samples than for (111)-textured samples, which can be interpreted in terms of interdiffusion kinetics depending on the crystallographic orientation.

• Korean Journal of Remote Sensing
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• v.21 no.1
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• pp.91-98
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• 2005

On board satellite magnetometer measures all possible magnetic components, such as the core and crustal components from the inner Earth, and magnetospheric, ionospheric and' its coupled components from the outer Earth. Due to its dipole and non-dipole features, separation of the respective component from the measurements is most difficult unless the comprehensive knowledge of each field characteristics and the consequent modeling methods are solidly constructed. Especially, regional long wavelength magnetic signals of the crust are strongly masked by the main field and dynamic external field and hence difficult to isolate in the satellite measurements. In particular, the un-modeled effects of the strong auroral external fields and the complicated behavior of the core field near the geomagnetic poles conspire to greatly reduce the crustal magnetic signal-to-noise ratio in the polar region relative to the rest of the Earth. We can, however, use spectral correlation theory to filter the static lithospheric and core field components from the dynamic external field effects that are closely related to the geomagnetic storms affecting ionospheric current disturbances. To help isolate regional lithospheric anomalies from core field components, the correlations between CHAMP magnetic anomalies and the pseudo-magnetic effects inferred from satellite gravity-derived crustal thickness variations can also be exploited, Isolation of long wavelengths resulted from the respective source is the key to understand and improve the models of the external magnetic components as well as of the lower crustal structures. We expect to model the external field variations that might also be affected by a sudden upheaval like tsunami by using our algorithm after isolating any internal field components.