• Journal of Ocean Engineering and Technology
• /
• v.15 no.3
• /
• pp.9-19
• /
• 2001

In this paper we present the aspect of inertial oscillation typically observed in the spin-up of fluids at low Rossby numbers in a circular cylinder. Numerical computations for the quasi three-dimensional equation as well as one-dimensional equation are performed to estimate the predictability of the one-dimensional equation with Ekman pumping/suction models. It is assumed that the discrepancy between the two results may be attributed to the inertial oscillation The detailed analysis to the numerical results reveals that the axial plane is dominated by a comparatively strong oscillatory flows caused by the inertial oscillation. In view of the fact that the time-averaged flow field however agrees to the Taylor-Proudman theorem, it is recommended that further analysis is needed to obtain an improved one-dimensional model like the Reynolds-averaged Navier-Stokes equation for turbulent flows.

• Korean Journal of Materials Research
• /
• v.17 no.1
• /
• pp.1-5
• /
• 2007

GaN thin fan were grown by spin coated colloidal GaOOH precursor. Polycrystalline GaNs with crystalline size of $10{\sim}100nm$ were grown on $SiO_2$ substrate. The shape of crystallite above $900^{\circ}C$ had the hexagonal plate and column type. X-ray diffraction patterns for them correspond to those of the hexagonal wurtzite GaN. With increasing droplets. i.e, thickness of deposited layers, XRD intensity increased. PL (photoluminescence) spectrum consisted with an weak near band-edge emission at 3.45 eV and a broad donor-acceptor emission band at 3.32 eV. From the low temperature PL measurement on GaN grown at $800^{\circ}C$ that the shallow donor-acceptor recombination induced emission was more intense than the near band-edge excitonic emission.

• Journal of Magnetics
• /
• v.13 no.1
• /
• pp.30-33
• /
• 2008

A highly sensitive, giant magnetoresistance-spin valve (GMR-SV) biosensing device with high linearity and very low hysteresis was fabricated by photolithography. The detection of magnetic nanoparticles and Fe-hemoglobin inside red blood cells using the GMR-SV biosensing device was investigated. When a sensing current of 1 mA was applied to the current electrode in the patterned active devices with an area of $2{\times}6{\mu}m^2$, the output signals were about 13.35 mV. The signal from even one drop of human blood and nanoparticles in distilled water was sufficient for their detection and analysis.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.51 no.2
• /
• pp.82-86
• /
• 2002

A series of $Ni_xZn_yFe_{3-x-y}O_4$ films were prepared by spin-spray ferrite plating on glass substrates from aqueous solution at $90[^{\circ}C]$. The magnetic properties in terms of contents of Ni and Zn in the plated films are presented. All the films are polycrystalline with spinel structure. At x+y=0.58, the film presents preferential orientation. As composition of y in the films increases grain size and void in the films increases, while saturation magnetization and coercive force of the films decrease.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.3
• /
• pp.418-422
• /
• 2005

By introducing spin-coating method to the evaporation induced self-assembly (EISA) process, a simple and reproducible route in controlling the mesophase of silica thin films has been developed for the first time in this work. When a comparatively solvent-rich Si-sol (The atomic ratio of TEOS : F127 : HCl : $H_2O$ : EtOH = 1 : 0.006 : 0.2 : 9.2 : 30) was used as coating solution, the mesophase of resultant silica films was selectively controlled by adjusting the spin-on speed. The cubic mesophase has been obtained from the coating at a low rpm, such as 600 rpm, while the 2-D hexagonal mesophase is formed at a high rpm, such as 2,500 rpm. At a medium coating speed, a mixture of cubic and hexagonal mesophase has been found in the fabricated films. The present results confirm that the evaporation rate of volatile components at initial step is critical for the determination of mesopore structures during the EISA process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.8
• /
• pp.652-657
• /
• 1998

We have performed spin-spray ferrite plating of $Fe{_3}{-X}-Ni_XO_4$(X=0.17~0.26) films in the temperature region $T=80~95[^{\circ}C]$. A reaction solution and an oxidizing solution were supplied to a reaction chamber by supply pump. The solubility limit of Ni increases as the substrate temperature increase, from X=0.17 at $80[^{\circ}C]$ to X=0.26 at $95[^{\circ}C]$. All the films are polycrystalline with no preferential orientation, and the magnetization exhibits no definite anisotropy. Grain size in the films increases as X increases, reaching $0.87[\mu{m}]$ at X=0.26.

• Journal of Magnetics
• /
• v.12 no.2
• /
• pp.68-71
• /
• 2007

Even a pure bulk Fe has a complicated magnetic phase and its magnetism is still needed to be clarified. In this study we investigated the magnetism of bcc and fcc bulk Fe with total energy calculations as functions of atomic volume. The full-potential linearized augmented plane wave method was adopted within a generalized gradient approximation. The ground state of bulk Fe is confirmed to be of ferromagnetic (FM) bcc. For fcc structured Fe an antiferromagnetic (AFM) state is more stable compared to FM states which exist as low spin and high spin states. The stable AFM states were found to accompany a tetragonal distortion, while the FM states remained in a cubic symmetry. At an expanded lattice constant a high spin FM state was calculated to be able to be stabilized with significant enhanced magnetic moment compared to the value of the ground state, bcc FM.

• Journal of the Semiconductor & Display Technology
• /
• v.17 no.3
• /
• pp.27-30
• /
• 2018

In this study, ZnO film was deposited on polycarbonate substrate by spin-spray method at low substrate temperature of $85^{\circ}C$. Surface morphology of ZnO films was changed by adding citrate from rod to dense structure. As-deposited ZnO film indicated high transmittance above 80%. In case of the resistivity, as-deposited ZnO film had high resistivity due to the existence of organic substance in the film. However, organic substance was removed and resistivity was decreased to $3.9{\times}10^{-2}{\Omega}{\cdot}cm$, after UV irradiation.

• KEPCO Journal on Electric Power and Energy
• /
• v.4 no.1
• /
• pp.19-24
• /
• 2018

The long-term research and development for the production of domestic blades has been consistently performed. As the direct and indirect results of its nationwide technologies in precision casting have been improved as well as maintenance costs for turbine machinery has been reduced. Whereas, there are still not a few concerns about the reliability of newly manufactured blades in spite of the quality certificate in metallurgical and mechanical properties. A spin tester is a machine that gives centrifugal loading to a rotating part, and its practical application is the overspeed test that is usually used to check the quality of products. A new spin rig has been constructed in KEPCO Research Institute for the purpose of evaluating the reliability of blades. In this paper, the test methodology for low cycle fatigue damage mechanism as well as the overspeed test for newly developed blades is described, and their reliability is evaluated too.

• Journal of the Korean Chemical Society
• /
• v.33 no.6
• /
• pp.607-613
• /
• 1989

The chemical equilibria of Ni(II)-tetraamine (tetraamine = 2,12-dimethyl-3,7,11,17-tetraazabicyclo-11,3,1-heptadeca-1(17),2,11,13,15-pentaene) complex ion in water, acetonitrile, acetone and nitromethane were investigated using spectrophotometric method, respectively. The equilibria between low-spin ($D_{4h}$) and high-spin ($O_h$) structures of Ni-tetraamine complex ion were presented in water, acetonitrile and acetone, but not in nitromethane. The eqilibrium constants, the reaction enthalpies and the reaction entropies were determined from analysis of the temperature dependence of the electronic spectra. The formation of the triplet species ($O_h$) was found to be exothermic. The solvent and electrolyte effects on the equilibrium constants could be explained by the dielectric constants of solvents and the reaction entropies.