• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.1
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• pp.24-29
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• 2002

In this paper, the microstructure and the dielectric properties of Sr$\_$1-x/CaxTiO$_3$(0$\leq$x$\leq$0.2)-based grain boundary layer ceramics were investigated. The sintering temperature and time were 1420∼152 0$\^{C}$ and 4 hours in N$_2$ gas, respectively. The average grain size and the lattice constant were decreased with increasing content of Ca, but the average grain size was increased with increase of sintering temperature. The second phase foamed by the thermal diffusion of CuO from the surface leads to verb high apparent dielectric constant, $\xi$$\_$r/>50000 and low dielectric loss, tan$\delta$<0.05. X-ray diffraction patterns of Sr$\_$1-x/CaxTiO$_3$ exhibited cubic structure, and the peaks shifted upward and the peak intensity were decreased with x. This is due to the lattice contraction as Sr is replaced by Ca with a smaller ionic radius. The specimens treated thermal diffusion for 2hrs in 1150$\^{C}$ exhibited nonlinear current-voltage characteristic, and its nonlinear coefficient(a) was overt 7.

• Current Optics and Photonics
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• v.7 no.6
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• pp.701-707
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• 2023

In laser imaging, accurate extraction of the laser's center is essential. Several methods exist to extract the laser's center in an image, such as the geometric mean, the parabolic curve fitting, and the Gaussian curve fitting, etc. The Gaussian curve fitting is the most suitable because it is based on the physical properties of the laser. The width of the Gaussian laser beam depends on the distance from the laser source to the target object. It is assumed in general that the distance remains constant at a laser spot resulting in a symmetric Gaussian model for the laser image. However, on a curved surface of the object, the distance is not constant; The laser beam is narrower on the side closer to the focal point of the laser light and wider on the side closer to the laser source, which causes the distribution of the laser beam to skew. This study presents a modified Gaussian model in the laser imaging to incorporate the slant angle of a curved object. The proposed method is verified with simulation and experiments.

• Journal of Korean Physical Therapy Science
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• v.18 no.3
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• pp.87-92
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• 2011

Purpose : The purpose of this study is to have examined the influence on the blood circulation by comparing the differences between stimulating the sympathetic ganglion and the muscle group among the stimulation variables in interferential current stimulation and to have found out the most effective stimulating mode for the improvement the peripheral blood circulation in the interferential current stimulation. Method : The subjects of the study is the men and women in the twenties, who are in great condition and have no pathological report for the blood circulation influence. The intensity of the inferential current stimulation is the medium degree, 100 bps constant current, which is the comfort and overt degree to confirm the muscle contraction. The areas stimulated by the interferential current stimulation are the stellate ganglion area in the seventh cervical vertebrae and the forearm muscle area. The stimulating time is twenty minutes long. After stimulating the two areas, the change of the blood circulation has been measured. Results : Both stimulating the sympathetic ganglion and stimulating the muscle, before and after interferential current stimulation, we have seen that the amount of blood circulation was increased significantly and statistically in both two groups(p<.01) and that the amount of blood circulation was increased significantly and statistically in the case of stimulating the sympathetic ganglion(p<.01). Conclusion : The conclusion we received that inferential current stimulation had the clear influence on increasing the peripheral blood circulation. And stimulating the sympathetic ganglion area is more effective than stimulating muscle area directly.

• The Korean Journal of Physiology and Pharmacology
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• v.26 no.5
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• pp.313-323
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• 2022

Atrial fibrillation (AF) is the most common supraventricular arrhythmia, and it corresponds highly with exercise intensity. Here, we induced AF in mice using acetylcholine (ACh)-CaCl₂ for 7 days and aimed to determine the appropriate exercise intensity (no, low, moderate, high) to protect against AF by running the mice at different intensities for 4 weeks before the AF induction by ACh-CaCl₂. We examined the AF-induced atrial remodeling using electrocardiogram, patch-clamp, and immunohistochemistry. After the AF induction, heart rate, % increase of heart rate, and heart weight/body weight ratio were significantly higher in all the four AF groups than in the normal control; highest in the high-ex AF and lowest in the low-ex (lower than the no-ex AF), which indicates that low-ex treated the AF. Consistent with these changes, G protein-gated inwardly rectifying K⁺ currents, which were induced by ACh, increased in an exercise intensity-dependent manner and were lower in the low-ex AF than the no-ex AF. The peak level of Ca²⁺ current (at 0 mV) increased also in an exercise intensity-dependent manner and the inactivation time constants were shorter in all AF groups except for the low-ex AF group, in which the time constant was similar to that of the control. Finally, action potential duration was shorter in all the four AF groups than in the normal control; shortest in the high-ex AF and longest in the low-ex AF. Taken together, we conclude that low-intensity exercise protects the heart from AF, whereas high-intensity exercise might exacerbate AF.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.300-308
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• 2004

The formation mechanism of anodic oxide films on Mg alloys when anodized in NaOH solution. was investigated by focusing on the effects of anodizing potential. Al content. and anodizing time. Pure Mg and Mg-Al alloys were anodized for 10 min at various potentials in NaOH solutions. $Mg(OH)_2$ was generated by an active dissolution reaction at the surface. and the product was affected by temperature. The intensity ratio of $Mg(OH)_2$ in the XRD analysis decreased with increasing applied potential. while that of MgO increased. The anti-corrosion properties of anodized specimens at each constant potential were better than those of non-anodized specimens. The specimen anodized at an applied potential of 3 V had the best anti-corrosion property. And the intensity ratio of $Mg_{17}Al_{12}$/Mg increased with aluminum content in Mg-Al alloys. During anodizing. the active dissolution reaction occurred preferentially in ${\beta}\;phase(Mg_{17}Al_{12})$ until about 4 mins. and then the current density increased radually until 7 mins. The dissolution reaction progressed in a phase(Mg) which not formed the intermetallic compound. which had a lower Al content. In the anodic polarization test of $0.017\;mol{\cdot}dm^-3$ NaCl and $0.1\;mol{\cdot}dm^-3\;Na_2SO_4$ at 298 K. the current density of Mg-15 mass% Al alloy anodized for 10 mins increased. since the anodic film that forms on the a phase is a non-compacted film. The anodic film on the phase for 30 mins was a compact film as compared with that for 10 mins.

• Journal of Biomedical Engineering Research
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• v.27 no.2
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• pp.64-72
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• 2006

The present study introduces a new cortical patch-based source model for EEG/MEG cortical source imaging to consider anatomical constraints more precisely. Conventional source models for EEG/MEG cortical source imaging have used coarse cortical surface mesh or sampled small number of vertices from fine surface mesh, and thus they failed to utilize full anatomical information which nowadays we can get with sub-millimeter modeling accuracy. Conventional ones placed a single dipolar source on each cortical patch and estimated its intensity by means of various inverse algorithms; whereas the suggested cortical patch-based model integrates whole cortical area to construct lead field matrix and estimates current density that is assumed to be constant in each cortical patch. We applied the proposed and conventional models to realistic EEG data and compared the results quantitatively. The quantitative comparisons showed that the proposed model can provide more precise spatial descriptions of neuronal source distribution.

• Journal of the Korean Ceramic Society
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• v.27 no.1
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• pp.35-42
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• 1990

In the present investigation, ceramic PZT and Polymer were prepared. The former is Pb[(Sn1/2Sb1/2)0.1 Ti0.27Zr0.63]O3 including Pb(Sn1/2Sb1/2)O3 with good pyroelectric effect, and the latter PVA(Poly Vinyl Alcohol) with good plasticity. Then, they were fabricated to be flat by using 0-3 connectivity which is rather easily fabricated and capable of making thin film, extending surface area among the connectivities. Such were applied to the sample as variation of intensity of poling field, poling temperature, volume fraction between ceramic and polymer. Then dielectric constant, pyroelectric current, pyroelectric coefficient and the figure of merit were measured. And then their effects on pyroelectric characteristics were observed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.42-42
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• 2010

Deep-trenched photonic crystals passing through InGaN/GaN quantum well structural layer have been fabricated on the surface of GaN-based light emitting diode(LED) using by electron beam nanolithography. The lattice constant and hole diameter of the photonic crystals are 230nm and 140nm, respectively. The structural and electro-optical properties have been investigated by scanning electron microscope(SEM) and power-current-voltage(L-I-V). Electroluminescence from GaN-based LED with deep-trenched photonic crystal shows the higher intensity than that without photonic crystal.

• Journal of the Semiconductor & Display Technology
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• v.7 no.1
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• pp.41-45
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• 2008

We studied the electrical characteristics of low-k SiOCR interlayer dielectric(ILD) films fabricated by plasma enhanced chemical vapor deposition (PECVD). The precursor bis-trimethylsilylmethane (BTMSM) was introduced into the reaction chamber with the various flow rates. The absorption intensities of Si-O-$CH_x$, bonding group and Si-$CH_x$, bonding group changed synchronously for the variation of precursor flow rate, but the intensity of Si-O-Si(C) responded asynchronously with the $CH_x$, combined bonds. The SiOCH films revealed ultra low dielectric constant around 2.1(1) and reduced further below 2.0 by heat treatments.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.59.3-59.3
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• 2019

The last two decades have seen an immense growth in our understanding of the physics of the birth and evolution of our Universe. However there are still many unanswered questions, such as: what is the nature of the dark energy, which drives the acceleration of the expansion of the Universe? Is the acceleration driven by a cosmological constant, some dynamical dark energy, or a modification of the gravitational force law on large scales? The next generation of radio observatories will conduct large area radio continuum and HI intensity mapping surveys, and so will make possible new and complimentary tests of these fundamental questions. In this talk I present the design of these next generation of surveys, current forecasts for the effectiveness of these cosmological probes, and results from precursor experiments.