• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.243-244
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• 2011

최근에 산화물 반도체를 평판 디스플레이와 태양 전지의 투명 전극으로 응용하기 위해 많은 연구가 진행중에 있다. 특히, $In_2O_3$ 박막은 투명 전도 산화막으로써 3.7 eV의 직접 전이 밴드갭 에너지를 갖고 가시광 영역에서 높은 투과도를 갖는 반도체이어서 다양한 영역에서 응용 가능하다. 본 연구는 낮은 비저항과 높은 투과율을 갖는 최적의 투명 전도막을 성장시키기 위하여 라디오파 반응성 마그네트론 스퍼터링 방법을 사용하여 질소 도핑된 $In_2O_3$ 박막을 유리 기판 상부에 증착하였고, 후열처리로 온도 400, 450, 500, 550$^{\circ}C$에서 급속 열처리를 수행하여, 증착된 박막의 구조, 표면, 광학, 전기적 특성을 조사하였다. 증착된 박막은 XRD를 사용하여 구조적 특성을 조사한 결과, $2{\theta}=30.2^{\circ}$와 43.95$^{\circ}$에서 상대적으로 강한 피크가 관측되었다(Fig. 1). 전자는 (222)면에서 회절된 피크이며, 후자는 (100)면에서 발생한 회절 피크이다. 열처리 온도가 0$^{\circ}C$에서 500$^{\circ}C$로 증가함에 따라 (222) 면의 회절 신호의 세기는 상대적으로 증가하였고, 550$^{\circ}C$에서 급격하게 감소하였다. 박막의 광학적 특성은 자외선-가시광선 분광기를 사용하여 광학 흡수율과 투과율을 측정하였다(Fig. 2). 열처리를 하지 않은 박막의 경우에, 파장 200~1,100 nm 범위에서 측정된 평균투과율은 76%이었다. 광학 흡수 계수와 광자 에너지의 관계를 나타내는 포물선 관계식을 기초로 하여 광학 밴드갭 에너지를 계산하였다. 박막의 전기적 특성의 경우에, Hall 효과를 측정하여 전하 운반자 농도, 홀 이동도, 전기 비저항을 조사한 결과, 전기적 특성은 열처리 온도에 상당한 의존성을 나타냄을 알 수 있었고, 열처리 온도 500$^{\circ}C$에서 박막의 비저항값은 $4.0{\times}10^{-3}{\Omega}cm$이었다.

• Korean Journal of Materials Research
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• v.16 no.4
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• pp.218-224
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• 2006

RF sputtering process was applied to produce thin hydroxyapatite(HAp) films on Ti-6Al-4V alloy substrates. The effects of different heat treatment conditions on the hardness between HAp thin films and Ti-6Al-4V alloy substrates were studied. Before deposition, the Ti-6Al-4V alloy substrates were heat treated for 1h at $850^{\circ}C\;under\;3.0{\times}10^{-3}torr$, and after deposition, the HAp thin films were heat treated for 1h at $400^{\circ}C,\;600^{\circ}C\;and\;800^{\circ}C$ under the atmosphere, and analyzed FESEM-EDX, FTIR, XRD, nano-indentor, micro-vickers hardness, respectively. Experimental results represented that the surface defects of thin films decreased by relaxation of internal stress and control of substrate structure followed by heat treatment of substrates before the deposition, and the HAp thin films on the heat-treated substrates had higher hardness than none heattreated substrates before the deposition, and the hardness properties of HAp thin films and Ti-6Al-4V alloy substrates appeared independent behavior, and the hardness of HAp thin films decreased by formation of $VTiO_3(OH),\;{\theta}-Al_{0.32}V_2O_5,\;Al_{0.33}V_2O_5$.

• Korean Journal of Materials Research
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• v.22 no.5
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• pp.215-219
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• 2012

Red phosphors $Ca_{1-1.5x}WO_4:{Eu_x}^{3+}$ were synthesized with different concentrations of $Eu^{3+}$ ions by using a solid-state reaction method. The crystal structure of the red phosphors was found to be a tetragonal system. X-ray diffraction (XRD) results showed the (112) main diffraction peak centered at $2{\theta}=28.71^{\circ}$, and the size of crystalline particles exhibited an overall decreasing tendency according to the concentration of $Eu^{3+}$ ions. The excitation spectra of all the phosphors were composed of a broad band centered at 275 nm in the range of 230-310 nm due to $O^{2-}{\rightarrow}W^{6+}$ and a narrow band having a peak at 307 nm caused by $O^{2-}{\rightarrow}Eu^{3+}$. Also, the excitation spectrum presents several strong lines in the range of 305-420 nm, which are assigned to the 4f-4f transitions of the $Eu^{3+}$ ion. In the case of the emission spectrum, all the phosphor powders, irrespective of $Eu^{3+}$ ion concentration, indicated an orange emission peak at 594 nm and a strong red emission spectrum centered at 615 nm, with two weak lines at 648 and 700 nm. The highest red emission intensity occurred at x = 0.10 mol of Eu3+ ion concentration with an asymmetry ratio of 12.5. Especially, the presence of $Eu^{3+}$ in the $Ca_{1-1.5x}WO_4:{Eu_x}^{3+}$ shows very effective use of excitation energy in the range of 305-420 nm, and finally yields a strong emission of red light.

• Journal of Powder Materials
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• v.14 no.2 s.61
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• pp.123-126
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• 2007

In this work, the dispersion behavior of $Y_2O_3$ particles in binary aluminum (Al)-copper (Cu) cast alloy was investigated with respect to Cu contents of 20 (hypoeutertic), 33 (eutectic) and 40 (hypereutectic) wt.%. In cases of hypo and hypereutectic compositions, SEM images revealed that the primary Al and ${\theta}$ phases were grown up at the beginning, respectively, and thereafter the eutectic phase was solidified. In addition, it was found that some of $Y_2O_3$ particles can be dispersed into the primary Al phase, but none of them are is observed inside the primary 6 phase. This different dispersion behavior of $Y_2O_3$ particles is probably due to the difference in the val- ues of specific gravity between $Y_2O_3$ particles and primary phases. At eutectic composition, $Y_2O_3$ particles were well dispersed in the matrix since there is few primary phases acting as an impediment site for particle dispersion during solidification. Based on the experimental results, it is concluded that $Y_2O_3$ particles are mostly dispersed into the eutectic phase in binary Al-Cu alloy system.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1997.11a
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• pp.75-79
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• 1997

The present study was designed to investigate whether there is a consistint changes in the signals from the central and autonomic nervous systim due to olfactory stimulation. The olfactory stimuli were 0.6% orange and 2.5% valeric acid and the stimuli through the olfactory stimulator soth controlled consistint flow, controlled concentration, and saturated with vapour to prevent drying the nasal mucosa. A room air blunk served as the control stimulus, EEG was recorede from 4channels according to the international 10-20 systim. Additionally, ECG, EOG, heart rate, skin conductance and resputation were recorded comtinuously. The fast Fourier transform analysis of EEG waves was analysed with the power spectra. Averaged power spectra were computed for the following frequency bands ; delta(0-4.5Hz), theta (4.5-7Hz), alphal(7-9.5Hz), alpha2 (9.5-12.5Hz) and beta(12.5-30Hz). Withthe results of the subjective sensibility test for the ordor, the orange was related to pleasant and familiar and the valeric acid was realted to snpleasant and bothersome. There is the difference between orange and valeric acid in alphal at PG2-A2 channel. While the unpleasant stimuli seem to be increased in alphal, alpha2 and beta waves at all channels. Also, the heart rate, galvaric skin resistance seem to be decreased by pleasant stimuli and thd unpleasant stimuli shdwed the opposite. In respiration, respiration rate had been declinig tendency, and input/output ampoitued and duration showed an upward trend by olfactory stimulation with orange, while opposite by valeric acid. In conclusion, the consistent EEG changes and the autonomic responses suggests the possibilities of the subjective signal of human sensibility.

• Science of Emotion and Sensibility
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• v.1 no.2
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• pp.13-22
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• 1998

The sense of touch has both objective and subjective characteristics. During hand evaluation of the fabrics. psycho physiological processes such as emotion and stimulation. On other site, the mode of touch (passive vs. active) is also capable to modulate somatosensory responses. I.e., suppress somatocensory perception during active electrocortical responses to passive and active touch of the textiles with different subjective emotional preference. The study was carried out on 36 female college students. Physiological signals were acquired by Grass and BIOPAC 100 systems with AcqKnowledge variables, namely heart rate (HR), respiratory sinus arrhythmia (RSA), pulse transit time (PTT), respiration rate (RSP) and skin conductance parameters (SCL, amplitude, risetime and number of SCRs) were analyzed for baseline and stimulation conditions. Analysis was manifested in a form of moderate HR acceleration. RSP increase, RSA decrease (lowered vagal tone), decreased PTT and increased electrodermal activity (increased SCL, several SCRs) that reflects general sympathetic activation. Parietal EEG effects (on contra-lateral side to stimulated hand)were featured by short-term alpha-blocking, slightly reduced theta, significantly increased delta and enhanced fast beta activity with few variations across stimuli. The main finding of the study was that most and least preferred textures exhibited significant differences in autonomic (HR, RSP, PTT, SCR, and at less extent in RSA and SCL) and electrocortical responses (delta, slow and fast alpha, fast beta relative power). These differences were recorded both in passive and active stimulation modes, thus demonstrating reproducibility of distinction between most and least emotionally preferred tactile stimuli, suggesting influence of psychological factors, such as emotional property of stimulus, on physiological outcome.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.3
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• pp.178-184
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• 2007

The EEG signal in general can be categorized as the Alpha wave, the Beta wave, the Theta wave, and the Delta wave. The alpha wave, showed in stable state, is the dominant wave for a human EEG and the beta wave displays the excited state. The subject of this paper was to recognize the stable state of EEG quantitatively using wavelet transform and power spectrum analysis. We decomposed EEG signal into the alpha wave and the beta wave in the process of wavelet transform, and calculated each power spectrum of EEG signal, using Fast Fourier Transform. And then we calculated the stable state quantitatively by stable state ratio, defined as the power spectrum of the alpha wave over that of the beta wave. The study showed that it took more than 10 minutes to reach the stable state from the normal activity in 69 % of the subjects, 5 -10 minutes in 9%, and less than 5 minutes in 16 %.

• Journal of Information Technology Applications and Management
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• v.14 no.4
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• pp.43-59
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• 2007

The purpose of the study was to examine the effectiveness of Neuro Feedback training by observing the pre and post brainwave measurement results of about 50 (experimental group 25. comparative group 25) subjects who have shown psychological difficulties in studying. attention deficit, and personalities. The study took place at Neuro Feedback training Center B. in between the months of July 2006 and May 2007. The methodology involved in the study included the Coloring Analysis Program of the Brain Quotient Test. As the brain waves are adjusted by timeseries linear analysis. the brain function quotients can reflect the functional states of the brain. Through the test, three parameters relaxation, attention and concentration-were initially measured for one minute each and the lowest parameter out of the three was selected as the training mode or improvement target. The training took place two or three times a week. for about 40 to 60 minutes per session. Because the clients have come to the training center at different times. the researcher sampled the results of only those who had attended more than 30 training sessions. The tool used to measure the psychological reaction was POMS (Profile of Mood State). while the tool used to measure the emotional and attention-deficit characteristics was the Amen Clinic ADD Type questionnaire. Hypothesis testing included t-test. The result of the study showed the Theta: SMR ratio of (left)p = .013. (right) p = .019. The result also confirmed the differences of both ATQ(left) p = .011. (right)p = .030 and SQ(left) p = .017. (right) p = .022. The result confirmed of emotional p = .000. attention-deficit characteristics p = .000. The result of the study suggest Neuro Feedback technique's possibility in positively affecting the subjects' mental state and attention-deficit characteristics.

• Journal of Magnetics
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• v.19 no.2
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• pp.126-129
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• 2014

We report the crystallographic and magnetic properties of $Ni_{0.3}Fe_{0.7}Ga_2S_4$ by means of X-ray diffractometer (XRD), a superconducting quantum interference device (SQUID) magnetometer, and a M$\ddot{o}$ssbauer spectroscopy. In particular, $Ni_{0.3}Fe_{0.7}Ga_2S_4$ was studied by M$\ddot{o}$ssbauer analysis for evidence of spin reorientation. The chalcogenide material $Ni_{0.3}Fe_{0.7}Ga_2S_4$ was fabricated by a direct reaction method. XRD analysis confirmed that $Ni_{0.3}Fe_{0.7}Ga_2S_4$ has a 2-dimension (2-D) triangular lattice structure, with space group P-3m1. The M$\ddot{o}$ssbauer spectra of $Ni_{0.3}Fe_{0.7}Ga_2S_4$ at spectra at various temperatures from 4.2 to 300 K showed that the spectrum at 4.2 K has a severely distorted 8-line shape, as spin liquid. Electric quadrupole splitting, $E_Q$ has anomalous two-points of temperature dependence of $E_Q$ curve as freezing temperature, $T_f=11K$, and N$\acute{e}$el temperature, $T_N=26K$. This suggests that there appears to be a slowly-fluctuating "spin gel" state between $T_f$ and $T_N$, caused by non-paramagnetic spin state below $T_N$. This comes from charge re-distribution due to spin-orientation above $T_f$, and $T_N$, due to the changing $E_Q$ at various temperatures. Isomer shift value ($0.7mm/s{\leq}{\delta}{\leq}0.9mm/s$) shows that the charge states are ferrous ($Fe^{2+}$), for all temperature range. The Debye temperature for the octahedral site was found to be ${\Theta}_D=260K$.

• Corrosion Science and Technology
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• v.7 no.3
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• pp.139-144
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• 2008

The results of microstructure observations of the $Al_2O_3$ scale formed on a Fe-Cr-Al steel during high temperature oxidation in the $SO_2$ atmosphere are presented. Morphology of the scale has been studied by SEM and TEM techniques. Phase and chemical compositions have been studied by EDX and XRD techniques. The alumina oxide is a primary component of the scale. TEM observations showed that the scale was multilayer. The entire surface of the scale is covered with "whiskers", which look like very thin platelets and have random orientation. The cross section of a sample shows, that the "whiskers" are approximately $2{\mu}m$ high, however the compact scale layer on which they reside is $0.2{\mu}m$ thick. The scale layer was composed mainly of small equiaxial grains and a residual amount of small columnar grains. EDX analysis of the scale surface showed that the any sulfides were found in the formed outer and thin inner scale layer. A phase analysis of the scale formed revealed that it is composed mainly of the $\theta-Al_2O_3$ phase and a residual amount of $\alpha-Al_2O_3$.