• 한국컴퓨터정보학회논문지
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• 제27권3호
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• pp.71-77
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• 2022

본 논문에서는 mmWave 대역에서 이중 직선편파 특성을 갖는 1×2 배열안테나를 제안하였다. 제안된 안테나는 두 개의 마이크로스트립 선로 급전구조를 갖도록 하였으며 유전율은 4.3이고 두께가 0.4 mm인 RF-4 유전체 기판위에 설계되었다. 제안된 1×2 배열안테나의 패치안테나 크기는 각각 2.33 mm×2.33 mm이며 전체 기판의 크기는 13.0 mm×6.90 mm이다. 제작 및 측정결과, 급전 위치가 포트 1일 때 1.13 GHz (28.52~29.65 GHz) 그리고 급전위치가 포트 2일 때 1.08 GHz (28.45~29.53 GHz) 임피던스 대역폭을 얻었다. 급전위치가 포트가 1일 때 편파분리도는 수직편파의 경우, 7.68 dBi에서 16.90 dBi 범위의 수평편파의 경우, 7.46 dBi에서 15.97 dBi 범위의 측정값을 얻었다. 급전위치가 포트 2일 때 편파분리도는 수직편파의 경우, 8.59 dBi에서 13.72 dBi 범위의 수평편파의 경우, 03 dBi에서 14.0 dBi 범위의 측정값을 각각 얻었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.23-23
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• 2010

The $Bi_2Mg_{2/3}Nb_{4/3}O_7$ (BMNO)-Bi composite films sandwiched by an $Al_2O_3$ protection layer exhibited a linear increase of a dielectric constant with increasing thickness and the 1000nm-thick BMNO-Bi composite films showed a dielectric constant (~220) higher than that of its bulk material (~210), keeping a low leakage current density of about $0.1{\mu}A/cm^2$. An enhancement of the dielectric constant in the BMNO-Bi composite films was attributed to the hybrid model combined by a space charge polarization, dipolar response, and nano-capacitors. On the other hand, 1000nm-thick BMNO-Bi composite films sandwiched by 40nm-thick BMNO layer exhibited a dielectric constant of about 450 at 100 kHz and a leakage current density of $0.1{\mu}A/cm^2$ at 6V.

• 한국전자통신학회논문지
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• 제16권6호
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• pp.1037-1044
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• 2021

본 논문에서는 3.5 GHz 대역에 적용 가능한 DLP(Dual Linear Polarization) 배열 안테나를 제안하였다. 제안된 안테나는 1×4 배열 안테나로 구성되어 있으며 두 개의 입력포트를 갖도록 설계하였다. 또한 임피던스매칭을 위해 십자가 구조가 패치 아래 부분과 연결하였다. 각 안테나는 18.85 mm(W1)×18.85 mm(L1)의 크기를 갖으며 1×4 배열 안테나 전체 구조는 236.0 mm(W)×60.2 mm(L)의 크기를 갖으며 두께(h) 1.6 mm, 그리고 비유전율이 4.3인 FR-4 기판 위에 설계하였다. 제작 및 측정결과로부터, -10 dB 반사손실을 기준으로 입력포트 1에서 70 MHz (3.54~3.61 GHz), 입력포트 2에서 75 MHz (3.55~3.625 GHz)의 대역폭을 얻었으며 전달계수 S21은 -20dB 이하의 값을 얻었다. 또한 두 입력단자 사이의 교차편파의 값을 얻었다.

• 한국세라믹학회지
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• 제19권4호
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• pp.316-320
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• 1982

The effect of the additive on dielectric properties of $BaTiO_3$ containing 0.030 mol% $Dy_2O_3$ was investigated function of frequency from 5$\times$104 to 0.3$\times$107cps and temperature from 25 to 1$25^{\circ}C$. The dielectric constant increased with increasing $Dy_2O_3$ concentration from 0 to 0.05mol% due to space charge polarization. However, the dielectric constant decreased for further increase of $Dy_2O_3$ concentration due to density increase. The dielectric constant exhibits rapid change at the Curie temperature and the Curie temperature drops from 122 to 116$^{\circ}C$ with increasing amount of $Dy_2O_3$ concentration.

• 대한원격탐사학회지
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• 제24권5호
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• pp.445-452
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• 2008

Preliminary results are reported on ship detection using coherence images computed from cross-correlating images of multi-look-processed dual-polarization data (HH and HV) of ENVISAT ASAR. The traditional techniques of ship detection by radars such as CFAR (Constant False Alarm Rate) rely on the amplitude data, and therefore the detection tends to become difficult when the amplitudes of ships images are at similar level as the mean amplitude of surrounding sea clutter. The proposed method utilizes the property that the multi-look images of ships are correlated with each other. Because the inter-look images of sea surface are covered by uncorrelated speckle, cross-correlation of multi-look images yields the different degrees of coherence between the images and water. In this paper, the polarimetric information of ships, land and intertidal zone are first compared based on the cross-correlation between HH and HV images, In the next step, we examine the technique when the dual-polarization data are split into two multi-look images, It was shown that the inter-look cross-correlation method could be applicable in the performance improvement of small ship detection and the land masking, It was also found that a simple combination of coherence images from each co-polarised (HH) inter-look and cross-polarised (HV) inter-look data can provide much higher target-detection possibilities.

• Journal of Advanced Marine Engineering and Technology
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• 제27권3호
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• pp.453-459
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• 2003

In this study, the effect of heat treatment to the electrochemical polarization resistance for the Ti-6Al-4V alloy was measured. The solution heat treatments were carried out at $1066^{circ}E, 966^{\circ}$E$, followed by aging heat treated $550^{circ}E, 600^{circ}E, and 650^{circ}E$. The electrochemical polarization resistance behavior was measured by potentio-dynamic polarization in the 1N $HNO_3$ + 15ppm HF solution. The obtained results were as follows. 1. As solution heat temperature increased. the corrosion potential was increased, whereas passive current density and critical current density were decreased. 2. As aging heat temperature increased, the corrosion potential was almost constant, but passive current density was decreased 3. The results of composition test measured by EDS at grain boundary and near $\gamma'$ precipitates indicated that S, Cl. and Si which originated from base metal were segregated at the grain boundaries Al and Ti which were the main alloying element in $\gamma'$ were depleted at the $\gamma'$ precipitated. The depletion of Al and Ti in $\gamma'$ was caused to early breakdown of passive film.

• Journal of Advanced Marine Engineering and Technology
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• 제17권1호
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• pp.55-65
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• 1993

Galvanic protection method is one the cathodic protection methods and is mostly used for corrosion prevention of heat exchangers and ship's hull. In this paper, it was investigated that how cathodic potential distribution was varied with according to the bare and painted steel plates in case of galvanic anode protection. The results obtained above were as follows. 1. Cathodic potential distribution of a painted steel plate was smoothed than that of the bare steel plate all over the cathodic surface area. 2. It was shown that polarization potential of the bare steel plate was somewhat shifted to negative potential, on the contrary that of the painted steel plate was somewhat shifted from negative potential to positive potential as time gone by beginning of galvanic anode method. 3. The applied current density in order to maintain constant protection potential(-770mv SCE) in the painted steel plate was less than that of the bare steel plate because of the high resistance polarization of the painted steel plate. 4. It was suggested that required number and life-time of anode for galvanic anode protection could be decided easily with corrosion prevention coefficient obtained by experimental data.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.94-98
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• 2000

Polycrystalline SBTN ferroelectric thin films were prepared by sol-gel method with various Nb mole ratios on Pt/ $SiO_2$/Si (100) substrates. The films were annealed at different temperatures and characterized in terms of phase and microstructure. Relatively a well saturated hysteresis pattern was obtained at x =0.2 in S $r_{0.8}$B $i_{2.3}$(T $a_{1-x}$ N $b_{x}$)$_2$ $O_{9+}$$\alpha$/ thin films. At an applied voltage of 5V, the dielectric constant ($\varepsilon$$_{r}$) and dissipation factor (tan $\delta$) of typical S $r_{0.8}$B $i_{2.3}$(T $a_{1-x}$ N $b_{x}$)$_2$ $O_{9+}$$\alpha$/ thin film (x=0.2) were about 236.2 and 0.034. Measured remanent polarization (2Pr) and coercive field (Ec) were 4.28C/c $m_2$, and 38.88kv/cm respectively. No fatigue was observed up to 6$\times$10$_{10}$ switching cycles at 5V and the normalized polarization reduced by a factor of only 4%.%. 4%.%. 4%.%.%.%.%.

• 한국결정성장학회지
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• 제25권6호
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• pp.239-244
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• 2015

에어로졸 증착법에 의해 실리콘 기판위에 $10{\sim}20{\mu}m$의 두께를 가진 PZT 후막을 제조한 후 $700^{\circ}C$에서 어닐링처리하였다. PZT 분말에 의해 제조된 막은 임피던스 분석기(impedance analyzer)와 쇼여-타워 서킷(Sawyer-Tower circuit)으로 분석하였다. PZT 분말은 통상적인 고상반응법 및 솔-젤 법으로 준비되었다. 고상반응법으로 만들어진 분말을 사용한 $10{\mu}m$ 두께 PZT 막의 잔류분극, 항전계 및 유전상수는 각각 $20{\mu}C/cm^2$, 30 kV/cm 그리고 1320이었다. 한편 솔-젤 법으로 제조된 분말을 사용한 경우의 유전상수는 635로 비교적 낮은 값을 나타낸다. 이는 어닐링시 생기는 발생하는 유기물에 의한 기공의 존재 때문이다.

• 한국결정성장학회지
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• 제12권4호
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• pp.178-183
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• 2002

용매제로서 polypropanediol을 사용한 sol-gel법으로, La의 함량을 1, 2, 5, 7 ㏖%로 변화시킨 PLZT(x/50/50) 박막을 제조하고 La 함량에 따른 유전특성의 변화를 연구하였다. 제조한 sol을 사용하여 $Pt/Ti/SiO_2$/Si 위에 10회 코팅한 후, 560~$600^{\circ}C$까지 10분간 열처리하여 600nm 두께의 박막을 얻을 수 있었다 $560^{\circ}C$ 이상에서는 조성에 관계없이 perovskite 단일 상만이 나타났고, La 함량이 증가함에 따라 입자 크기가 증가하였다. 모든 조성의 박막에서 열처리 온도가 증가함에 따라 유전상수 및 잔류분극 값이 증가되었으며 $600^{\circ}C$에서 열처리한 박막이 가장 우수한 유전 특성을 나타내었다. $600^{\circ}C$에서 열처리한 박막에서 La함량이 증가함에 따라 잔류분극, 항전계, 유전상수 모두 감소하였다.