• Journal of the Korean institute of surface engineering
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• v.34 no.1
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• pp.25-32
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• 2001

$TiB_2$ ceramics were oxidized at 800, 900 and $1000^{\circ}C$ in air for 40 hr, and their oxidation property was investigated using TGA, XRD, SEM and EPMA. The oxidation resistance decreased with an increase in oxidation temperature. The scale was essentially composed of $TiO_2$ only. $B_2$$O_3$ formed during oxidation escaped from the $TiO_2$ oxide scale owing to its high vapor pressure. This made the oxide scale highly porous and thick. The oxidation reaction was mainly governed by the inward transport of oxygen.$ TiO_2$ existing at the outermost scale grew into peculiarly shaped blades, as the reaction progressed.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.463-469
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• 2016

In this paper, the use of a dual composite right/left-handed coplanar waveguide (CPW) transmission line is proposed for the design of a band rejection filter. The notch property of the filter is achieved by combining the convex signal line with the shorted concave meander line, and the equivalent circuit model is extracted from the geometry of the unit cell for organizing the band rejection property. Then the equivalent parameters of the unit cell are analyzed to identify those behaviors. And the dispersion characteristics and energy distributions are simulated. In the end, the band rejection filter is manufactured by cascading two proposed unit cells. We show that the measurement result for the resonant frequency demonstrates good agreement with the simulation result and the band rejection filter provides a rejection performance of 17.5 dB at the stopband frequency ranging from 869 MHz to 894 MHz.

• Progress in Superconductivity
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• v.9 no.1
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• pp.11-17
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• 2007

Magnetization studies have been carried out on $MgB_2$ polycrystalline samples in the temperature range of 5 - 44 K and in the magnetic field up to 7 Tesla. The critical current density was calculated from hysteresis loops using the Bean's critical state model, and the highest value of $J_c$ at 20 K was $2.7{\times}10^5\;A/cm^2$ at 2 Tesla. The hysteresis loops were carefully examined to determine the temperature and magnetic field range where flux jumps appeared. The first jump occurred typically at 1 Tesla. Due to the strong pinning, we observed the presence of flux jump below H = 1 Tesla at temperature below 30 K.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.173-173
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• 2010

$Bi_4Ti_3O_{12}$ ($B_4T_3$) is a unique ferroelectric material that has a relatively high dielectric constant, high Curie temperature, high breakdown strength, and large spontaneous polarization. As a result this material has been widely studied for many applications, including nonvolatile ferroelectric random memories, microelectronic mechanical systems, and nonlinear-optical devices. Several reports have appeared on the use of Mn dopants to improve the electrical properties of $B_4T_3$ thin films. Mn ions have frequently been used for this purpose in thin films and multilayer capacitors in situations where intrinsic oxygen vacancies are the major defects. However, no systematic study of the optical properties of $B_4T_3$ films has appeared to date. Here, we report optical data for these films, determined by spectroscopic ellipsometry (SE). We also report the effects of thermal annealing and Mn doping on the optical properties. The SE data were analyzed using a multilayer model that is consistent with the original sample structure, specifically surface roughness/$B_4T_3$ film/Pt/Ti/$SiO_2$/c-Si). The data are well described by the Tauc-Lorentz dispersion function, which can therefore be used to model the optical properties of these materials. Parameters for reconstructing the dielectric functions of these films are also reported. The SE data show that thermal annealing crystallizes $B_4T_3$ films, as confirmed by the appearance of $B_4T_3$ peaks in X-ray diffraction patterns. The bandgap of $B_4T_3$ red-shifts with increasing Mn concentration. We interpret this as evidence of the existence deep levels generated by the Mn transition-metal d states. These results will be useful in a number of contexts, including more detailed studies of the optical properties of these materials for engineering high-speed devices.

• Korean Journal of Materials Research
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• v.14 no.1
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• pp.52-58
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• 2004

The surface property and formation behavior of a boride layer formed on Ni-Cr-Mo steel in a plasma paste boronizing treatment were investigated. The plasma paste boronizing treatment was carried out at 973～1273 K for 1-7 hrs under the gas ratio of Ar:H$_2$ (2:1). The thickness of the boride layer increased with increasing temperature and time in the boronizing treatment. The cross-section of the boride layer was a tooth structure and the hardness was Hv 2000～2500. XRD analysis revealed that the compound was identified as FeB, $Fe_2$B, and mixed phase of FeB/$Fe_2$B in the boride layer formed at 973～1073 K, 1173K, and 1273K, respectively. The Ni-Cr-Mo alloy boronized at 1173-1273 K showed the best excellent wear resistance against the sand. As a results of corrosion test in 1 M $H_2$$SO_4$ solution, $Fe_2$B formed on the matrix alloy exhibited higher corrosion resistance than FeB.

• Progress in Superconductivity and Cryogenics
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• v.7 no.4
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• pp.1-3
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• 2005

Superconducting $MgB_2$ fibers are in-situ grown by a diffusion method. The fibers are prepared by exposing B filaments to Mg vapor inside a folded Ta foil over a wide range of temperature and growth time. The materials are sealed inside a quartz tube by gas welding. The as - grown fibers are characterized by scanning electron microscopy and energy dispersive x - ray analysis. The fibers have a diameter of about $110{\mu}m$. Surface morphology of the fibers looks dependent on growth temperature and mixing ratio of Mg and B. Radial distribution of Mg ions into B is observed and analyzed over the cross - sectional area. Transport properties of the $MgB_2$ fibers are examined by a physical property measurement system. The $MgB_2$ fibers grown at $900^{\circ}C$ for 2 hours show a superconducting transition at 39.8K with ${\Delta}T_c<$ 2.0 K. Resistance at room temperature $MgB_2$ is 3.745 $\Omega$ and residual resistivity ratio (RRR) is estimated as 4.723.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.14-18
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• 2023

We have investigated the behavior induced by Ga substitution in B-1212 system and observed an anomalous superconductor-like resistivity drop with an onset near 260 K and an offset at 248 K in the nominal (B_0.65Ga_0.35)(Ba_1.25Sr_0.75)(Er_0.5Ca_0.5)Cu₂O_z compound. However, this property degraded with repeated cycling. Systematic studies of the superconducting properties of the (B_1-xGa_x)(Ba_1.25Sr_0.75)(Er_0.5Ca_0.5)Cu₂O_z compounds are reported and discussed in the context of the anomalous resistivity transition.

• Journal of the Korea Fashion and Costume Design Association
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• v.12 no.3
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• pp.93-103
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• 2010

The results of comparison and analysis of dynamical features according to Jacquard structure are as follows. Regarding elongation(E) value in tensile property, the value in the direction of course was found to be larger in all Jacquard structure, except floating Jacquard, than the direction of wale. It could be found that, as to bending strength(B) in Bending Property, the value of bending strength in the direction of course smaller in all the textile(structure) except floating than the direction of wale, so that the ability of curve formation is excellent. And in case of floating Jacquard, it showed the smallest value in the direction of course and wale, so that it was interpreted as Jacquard having a soft feel. Blister Jacquard showed the highest value in both directions of course and wale, so that it was evaluated as Jacquard having the hardest touch. With regard to shearing character(G) and shearing hysteresis(2HG) in Shearing Property, Jacquard indicated the lowest value, so it was evaluated as the textile(structure) having high drape the transformation of whose fabric is easy. In addition, normal Jacquard, transfer Jacquard, blister Jacquard showed a high value, so that it could be known they are Jacquards having stiff touch. The study implies that normal Jacquard, bird's eye Jacquard, etc., which well stretch in the direction of a course like tubular Jacquard course, is better to make the margin a little shorter than the basic margin, and Jacquard that well stretches in the direction of wale like ladder's back Jacquard and floating Jacquard is better to make the margin longer and the length shorter than the basic margin.

• Progress in Superconductivity and Cryogenics
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• v.16 no.3
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• pp.7-9
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• 2014

Single-crystal like $MgB_2$ thin film was grown on (000l) $Al_2O_3$ substrate by using hybrid physical-chemical vapor deposition (HPCVD) system. Single crystal properties were studied by X-ray diffraction (XRD) and the full width at half maximum (FWHM) of the (0001) $MgB_2$ peak is $15^{\circ}$, which is very close to that has been reported for $MgB_2$ single-crystal. It indicates that the crystalline quality of thin film is good. Temperature dependence on resistivity was investigated by physical property measurement system (PPMS) in various applied fields from 0 to 9 T. The upper critical field ($H_{c2}$) and irreversibility field ($H_{irr}$) were determined from PPMS data, and the estimated values are comparable with that of $MgB_2$ single-crystals. The thin film shows a high critical temperature ($T_c$) of 40.4 K with a sharp superconducting transition width of 0.2 K, and a high residual resistivity ratio (RRR=21), it reflects that $MgB_2$ thin film has a pure phase structure.

• Honam Mathematical Journal
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• v.34 no.2
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• pp.289-295
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• 2012

In this note we prove the space (A, ${\parallel}.{\parallel}$) is a Banach space and ${\parallel}ab{\parallel}{\leq}{\parallel}a{\parallel}{\parallel}b{\parallel}$ for $a,b{\in}A$ where $A:=\{a:=(a_t)_{t{\in}G}:{\sum}_{t{\in}G}{\parallel}a_t{\parallel}_t<{\infty}\}$, $G=\mathbb{N}^*$. Also we show some property in (A, ${\parallel}.{\parallel}$).