• 한국전자파학회논문지
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• 제18권7호
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• pp.819-827
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• 2007

본 논문은 논에 대한 전파 산란 특성을 측정하고, 수치적 계산 결과와 비교함으로써 벼의 수치적 모델링에 대한 전파 산란 알고리즘을 제시하고자 한다. 임피던스 경계 조건과 dyadic 그린함수로부터 임피던스 표면 위(수면)의 손실 있는 유전체(벼)에 대한 적분 방정식을 유도하였고, 모멘트 법을 이용하여 유전체의 체적 전류를 계산하였다. 또한, 몬테 카를로 방법을 적용하여 입사 각도 및 편파에 따른 후방 산란 계수를 수치적으로 계산하였다. 1.85 GHz의 측정 시스템을 이용하여 논의 후방 산란 계수를 측정하였으며, 본 논문에서 제시한 알고리즘의 계산 결과와 비교, 검증하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.359-359
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• 2014

In this study, surface plasmon resonance structures for the selective and the enhanced transmission of infrared light were designed. In order to relieve the large discontinuity of refractive index between air and metal hole array, $Si_3N_4$ was used as the impedance matching layer. Experimental parameter were calculated and determined in advance by the rigorous coupled wave analysis (RCWA) simulation, and then the experiment was carried out. A 2-dimensional metal hole array structures were patterned on the size of $1{\times}1cm^2$ GaAs substrate using photolithography process, and 5 nm thick Ti, 50 nm thick Au were deposited by E-beam evaporator, respectively. Subsequently, $Si_3N_4$ films with various thicknesses (150, 350, 550, and 750 nm) were deposited by plasma enhanced chemical vapor deposition (PECVD). For the comparison, transmittance of specimens with and without $Si_3N_4$ was measured using Fourier transform infrared spectroscopy (FTIR) in the range of $2.5-15{\mu}m$. Furthermore, the surface and the cross-sectional images were collected from the specimens by scanning electron microscopy (SEM). From the results, it was demonstrated that the transmittance was enhanced up to 80% by the deposition of 750 nm $Si_3N_4$ at $6.23{\mu}m$. It has advantage of enhanced transmission despite the simple fabrication process.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.159-159
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• 2017

Ti-6Al-4V alloy have been used for dental implant because of its excellent biocompatibility, corrosion resistance, and mechanical properties. However, the integration of such implant in bone was not in good condition to achieve improved osseointergraiton. For solving this problem, calcium phosphate (CaP) has been applied as coating materials on Ti alloy implants for hard tissue applications because its chemical similarity to the inorganic component of human bone, capability of conducting bone formation and strong affinity to the surrounding bone tissue. Various metallic elements are known to play an important role in the bone formation and also affect bone mineral characteristics. Especially, Zn is essential for the growth of the human and Zn coating has a major impact on the improvement of corrosion resistance. Plasma electrolytic oxidation (PEO) is a promising technology to produce porous and firmly adherent inorganic Zn containing TiO2(Zn-TiO2)coatings on Ti surface, and the a mount of Zn introduced in to the coatings can be optimized by altering the electrolyte composition. In this study, effect of Zn content on the corrosion behavior of Ti-6Al-4V alloy after plasma electrolytic oxidation were studied by SEM, EDS, XRD, AC impedance, and potentiodynamic polarization test. The potentiodynamic polarization and AC impedance tests for corrosion behaviors were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat with a scan rate of 1.67 mV/s and potential range from -1500 mV to +2000 mV. Also, AC impedance was performed at frequencies ranging from 10 MHz to 100 kHz for corrosion resistance.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.120-120
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• 2016

Ti-6Al-4V alloy have been used for dental implant because of its excellent biocompatibility, corrosion resistance, and mechanical properties. However, the integration of such implant in bone was not in good condition to achieve improved osseointergraiton. For solving this problem, calcium phosphate (CaP) has been applied as coating materials on Ti alloy implants for hard tissue applications because its chemical similarity to the inorganic component of human bone, capability of conducting bone formation and strong affinity to the surrounding bone tissue. Various metallic elements, such as strontium (Sr), magnesium (Mg), zinc (Zn), sodium (Na), silicon (Si), silver (Ag), and yttrium (Y) are known to play an important role in the bone formation and also affect bone mineral characteristics, such as crystallinity, degradation behavior, and mechanical properties. Especially, Zn is essential for the growth of the human and Zn coating has a major impact on the improvement of corrosion resistance. Plasma electrolytic oxidation (PEO) is a promising technology to produce porous and firmly adherent inorganic Zn containing $TiO_2(Zn-TiO_2)$coatings on Ti surface, and the a mount of Zn introduced in to the coatings can be optimized by altering the electrolyte composition. In this study, corrosion behavior of Ti-6Al-4V alloy after plasma electrolytic oxidation in solutions containing Ca, P and Zn were studied by scanning electron microscopy (SEM), AC impedance, and potentiodynamic polarization test. A series of $Zn-TiO_2$ coatings are produced on Ti dental implant using PEO, with the substitution degree, respectively, at 0, 5, 10 and 20%. The potentiodynamic polarization and AC impedance tests for corrosion behaviors were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat with a scan rate of 1.67mV/s and potential range from -1500mV to +2000mV. Also, AC impedance was performed at frequencies ranging from 10MHz to 100kHz for corrosion resistance.

• 공업화학
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• 제9권5호
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• pp.667-673
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• 1998

염분이 함유된 콘크리트 모사 세공용액 중에서의 철근 부식반응을 Tafel 분극법과 교류 임피던스법에 의해 비교 고찰하였으며, 철근 표면의 거칠기와 산화피막층에 의한 부식거동을 연구하였다. 전기화학적 교류 임피던스법에 의한 철근부식의 진단은 매우 유용하며, 제안된 모델과 실험결과가 잘 일치하였다. 염분농도가 증가할수록 부식전위는 cathodic-방향으로 이동하여 부식확률이 증가하였으며, 부식전류도 동일한 양상을 보였다. 철근 표면의 산화피막은 주사전자현미경과 AES (Auger electron spectroscopy)로 분석하였다. Torch로 15초간 열처리하여 형성된 철근표면의 산화피막은 오히려 철근부식을 촉진하였으며, 철근 표면의 거칠기가 증가할수록 부식속도는 증가하였다. 또한, 초기 콘크리트 모사세공 용액의 온도 증가는 철근 부식속도의 증가를 가져왔다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 춘계학술대회 논문집
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• pp.219-219
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• 2009

In this study, electrochemical impedance characteristics of anodic oxide layer formed on titanium ternary alloy surface have been investigated, Titanium oxide layers were grown on Ti-29Nb-xZr(x=3, 5, 7, 10 and 15 wt%) alloy substrates using phosphoric acid electrolytes.

• 한국표면공학회지
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• 제36권6호
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• pp.437-443
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• 2003

The effects of additive(grain refiner, GR) on process efficiency of the Ni-Fe-P alloy electrodeposition and the material properties of the deposit were investigated. Electrochemical properties of the deposits were investigated using polarization and electrochemical impedance techniques, and the material properties of the deposits were characterized through inductively coupled plasma(ICP), spiral contractometer, XRD, SEM and TEM. When the additive was added into the electrodeposition bath, current efficiency, Ni content and corrosion resistance of the deposit increased, whereas residual stress, surface roughness and grain size of the deposit decreased.

• 전기학회논문지P
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• 제60권4호
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• pp.267-271
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• 2011

The insulating characteristics and temperature rise behaviors of porcelain suspension insulators were investigated. The testing insulators had used in the distribution systems normally and were sampled. Firstly, leakage current was measured and its impedance was calculated. The leakage current of good insulators is 0.2 mA and its impedance is 66 $M{\Omega}$. The worse insulators have lower impedance and the insulators having below 15 $M{\Omega}$ take place flashover at the high frequency voltage flashover test. Secondly, the temperature rise characteristics were analyzed depending on leakage current and its impedance. Surface temperature of insulators was measured for 30 minutes and until its saturation after voltage was applied. The temperature rise of insulators having 15 $M{\Omega}$ is about $14.5^{\circ}C$ above the ambient temperature. Lastly, the heating behaviors of 3 insulators in a string was analyzed. Any insulator in the string does not generate heat so far as it has at least one sound insulator. On the other hand, all the insulators in the string are bad if the string have any heating insulator.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.481-484
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• 2004

다중 채널 전극 위에 세포를 성장시켜 전극면을 통해 검출되는 신경 신호의 손실을 줄이고 주파수의 변형을 줄이기 위해서 전극과 전해질의 사이의 impedance를 줄이는 것이 바람직하다. 전하 이동을 증대시키기 위해서는 낮은 impedance가 요구되며 이를 위한 전극의 개선 방안으로 전극면이 증착될 기판의 표면을 거칠게 하여 결과적으로 전극면의 표면적을 넓히는 방법을 모색하였다. 기판으로 사용되는 glass(Pyrex#7740)의 구성 물질 중에서 4%를 차지하는 $N^+$ 이온을 황산 용액으로 표면 처리하여 제거함으로써 매끈한 표면을 거칠게 하여 표면적을 넓힐 수 있다. 기판으로 사용되는 glass (pyrex#7740) $1cm{\times}1cm{\times}0.05cm$를 50%, 95% 농도의 황산 용액 내에서 각각 30분, 60분 동안 상온에서 표면처리를 진행하였다. AFM을 이용하여 표면을 관찰한 결과 황산 용액 95%에서 30분간 표면 처리를 진행한 시편에서 최대 $4000{\AA}$정도의 조도를 얻었다. 이후 동일 시편에 대해 전극으로 사용될 Ti/Au를 각각 $500{\AA}/2500{\AA}$ 증착 후 사진식각 공정으로 MEA(Multi-channel electrode array)를 제작하여 impedance를 측정한 결과, 표면 처리 후 impedance가 70% 개선되었음을 측정하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.1341-1346
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• 2001

In this study, the acoustic properties of steel-wire sound absorbing materials with different thickness and bulk density were investigated in terms of characteristic impedance, propagation constant, and absorption coefficient. The well-known two-cavity method was used for evaluating those acoustic parameter values in experiments. Also, in order to validate the experimentally measured values, the results were compared with the results obtained from Chung and Blaser's transfer function method and SWR method. The experimentally measured values of normal absorption coefficients were generally agreed well with the corresponding values from the transfer function method and the SWR method. Based on the experimental results, the following conclusions could be made. The magnitude of the absorption coefficient and the frequency range of the maximum absorption coefficient were controllable by changing the thickness and bulk density of the sound absorbing materials. Also, the magnitude of the absorption coefficient depended on the characteristic impedance and the propagation constant. As large as the air cavity depth at the rear side of the steel-wire sound absorbing materials, the maximum magnitude of the absorption coefficient occurred at the lower frequency ranges.