• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.415-415
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• 2012

ZnO nanostructures were synthesized by a vapor phase transport process in a single-zone furnace within a horizontal quartz tube with an inner diameter of 38 mm and a length of 485 mm. The ZnO nanostructures were grown on Au-catalyzed Si(100) substrates by using a mixture of zinc oxide and graphite powders. The growth of ZnO nanostructures was conducted at $800^{\circ}C$ for 30 min. High-purity Ar and $O_2$ gases were pushed through the quartz tube during the process at a flow rate of 100 and 10 sccm, respectively. The sequence of ON/OFF cycles of the Ar gas flow was repeated, while the $O_2$ flow is kept constant during the growth time. The Ar gas flow was ON for 1 min/cycle and that was OFF for 2 min/cycle. The structure and optical properties of the ZnO nanostructures were investigated by field-emission scanning electron microscope, X-ray diffraction, temperature-dependent photoluminescence. The preferred orientation of the ZnO nanostructures was along c-axis with hexagonal wurtzite structure.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.5
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• pp.218-225
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• 2021

In this study, damping capacities were comparatively investigated for Mg-9%Al alloy with as-cast (AC) and fully discontinuous precipitates (DPs) microstructures, respectively. The DPs microstructure was obtained by solution treatment at 678 K for 24 h, followed by furnace cooling to RT. The AC microstructure was typically characterized by partially divorced eutectic β(Mg₁₇Al₁₂) phase particles distributed along the α-(Mg) matrix cell boundaries. The DPs microstructure showed lamellar morphology consisting of α and β thin layers with various interlamellar spacings. The DPs microstructure had better damping capacity than the AC microstructure in the strain-amplitude independent region, while in the strain-amplitude dependent region, the damping behavior was reversed. In view of the microstructural features of AC and DPs, the lower concentration of Al in the α-(Mg) phase for the DPs microstructure and the lower β phase number density for the AC microstructure would be responsible for the higher damping capacities in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

• 대한관절경학회:학술대회논문집
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• 2009.10a
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• pp.74-74
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• 2009

• Proceedings of the Materials Research Society of Korea Conference
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• 1997.10a
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• pp.87-87
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• 1997

• Journal of Magnetics
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• v.19 no.1
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• pp.55-58
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• 2014

We have synthesized ferromagnetic ${\tau}$-phase $Mn_{54}Al_{46}/{\alpha}$-phase $Fe_{65}Co_{35}$ composite by annealing a mixture of paramagnetic ${\varepsilon}$-phase $Mn_{54}Al_{46}$ and ferromagnetic ${\alpha}$-phase $Fe_{65}Co_{35}$ particles at $650^{\circ}C$. The volume fraction ($f_h$) of hard ${\tau}$-phase $Mn_{54}Al_{46}$ of the composite was varied from 0 to 1. During the annealing, magnetic phase transformation occurred from paramagnetic ${\varepsilon}$-phase to ferromagnetic ${\tau}$-phase $Mn_{54}Al_{46}$. The magnetization and coercivity of the composite monotonically decreased and increased, respectively, as the $f_h$ increased. These results are in good agreement with our proposed composition dependent coercivity and modified magnetization equations.

• Journal of the Korean Institute of Telematics and Electronics
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• v.10 no.6
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• pp.25-44
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• 1973

The please relation between motive force and result is reviewed in view point of the correlation function as well as the redundancy in a continuous signal which permits the sampled treatment. A new correlation function (to be named Time Dependent Correlation Function) which is a functon of time, is defined in order to indicate the variation of the correlation between two signals. As application a phase looked loop is analysed which shows the increase of correlation between input signal and output signal of the loop after the application of the input signal. Finally again the T.D.Correlation Function method is used to show how the polyphase envelope detection-method is justifiable by this method.

• Journal of Photoscience
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• v.9 no.2
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• pp.243-245
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• 2002

Pigment-dispersing factor (PDF) is an octadecapeptide distributed in the optic lobe and the brain in a variety of insect species. There are lines of evidence suggesting possible involvement of PDF in the insect circadian system. However, its physiological roles in the circadian time keeping mechanism have not been clearly defined. In this study, we have examined the phase shifting effects of Gryllus-PDF on the circadian locomotor rhythm in the cricket Gryllus bimaculatus of which circadian clock is located in the optic lobe. Phase shifts in the circadian activity rhythm were measured following microinjection of 22nl of vehicle (Ringer's solution) or O.lmM PDF into the optic lobe through the compound eye at various circadian times. The results showed that PDF induced phase shifts of the circadian clock in a phase-dependent manner, suggesting that it may play a role as an input signal for the circadian clock.

• Transactions of the Society of Information Storage Systems
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• v.3 no.3
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• pp.118-122
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• 2007

Phase-change wet-etching technology using GeSbTe phase-change films is developed. Selective etching between an amorphous and a crystalline phase can be carried out with an alkaline etchant of NaOH. Etching selectivity is dependent not only on the concentration of the alkaline etchant but also on the film structure. Specifically, metal films for heat control cause marked effects on the etching properties of GeSbTe film. Surviving amorphous pits can be obtained with Al metal layer, however etched amorphous pits are seen with Ag metal layer. An opposite selective etching behavior can be observed between samples with two different metal layers.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.505-508
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• 2000

The success of target reconstruction in SAR(Synthetic Aperture Radar) imaging system is greatly dependent on the coherent detection. Primary causes of incoherent detection are uncompensated target or sensor motion, random turbulence in propagation media, wrong path in radar platform, and etc. And these appear as multiplicative phase error to the echoed signal, which consequently, causes fatal degradations such as fading or dislocation of target image. In this paper, we present iterative phase error estimation scheme which uses echoed data in all temporal frequencies. We started with analyzing wave equation for one point target and extend to overall echoed data from the target scene - The two wave equations governing the SAR signal at two temporal frequencies of the radar signal are combined to derive a method to reconstruct the complex phase error function. Eventually, this operation attains phase error correction algorithm from the total received SAR signal. We verify the success of the proposed algorithm by applying it to the simulated spotlight-mode SAR data.

• Journal of the Korean institute of surface engineering
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• v.50 no.3
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• pp.141-146
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• 2017

We investigated configuration of metallic and insulating domains in $VO_2$ thin films, while spanning metal-insulator phase transition. Kelvin probe force microscopy, of which spatial resolution is less than 100 nm, enables us to measure local work function (WF) at the sample surface. The WF of $VO_2$ thin films decreased (increased) as increasing (decreasing) the sample temperature, during the phase transition. The higher and lower WF regions corresponded to the insulating and metallic domains, respectively. The metallic fraction, estimated from the WF maps, well explained the temperature-dependent resistivity based on the percolation model. The WF mapping also showed us how the structural defects affected the phase transition behaviors.