• 센서학회지
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• 제25권6호
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• pp.440-446
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• 2016

This study introduces the characteristics of current-voltage (I-V) and impedance variance for $ZnO-Zn_2BiVO_6-Co_3O_4$ (ZZCo), which is sintered at $900^{\circ}C$, according to temperature changes. ZZCo varistor demonstrates dramatic improvement of non-linear coefficient, ${\alpha}=66$, with lower leakage current and higher insulating resistivity than those of ZZ ($ZnO-Zn_2BiVO_6$) from the aspect of I-V curves. While both systems are thermally stable up to $125^{\circ}C$, ZZCo represents a higher grain boundary activation energy with 1.05 eV and 0.94 eV of J-E-T and from IS & MS, respectively, than that of ZZ with 0.73 eV and 0.82 eV of J-E-T and from IS & MS, respectively, in the region above $180^{\circ}C$. It could be attributed to the formation of $V^*_o$(0.41~0.47 eV) as dominant defect in two systems, as well as the defect-induced capacitance increase from 781 pF to 1 nF in accordance with increasing temperature. On the other hand, both the grain boundary capacitances of ZZ and ZZCo are shown to decrease to 357 pF and 349 pF, respectively, while the resistances systems decreased exponentially, in accordance with increasing temperature. So, this paper suggests that the application of newly formed liquid phases as sintering additives in both $Zn_2BiVO_6$ and the ZZCo-based varistors would be helpful in developing commercialized devices such as chips, disk-type ZnO varistors in the future.

• Journal of Pharmaceutical Investigation
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• 제37권2호
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• pp.79-84
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• 2007

This study was aimed to establish analytical method of Bi to develop a guideline of the bioequivalence test of tripotassium dicitrato bismuthate (TDB). For this purpose, a simple, specific and sensitive inductively coupled plasma-mass spectrometry (ICP/MS) method were developed and validated in human plasma. Various concentrations of bismuth standard solution (0-25ng/mL) were prepared with distilled water and human blank plasma. To 10mL of the volumetric flasks, 2mL of blank plasma was added with 8ml of distilled water. Bi standard solution was added to prepare the calibration samples and injected into ICP-MS. The plasma samples obtained from volunteers given 3 tablets of bismuth (total 900mg as TDB) were analyzed as described above. As a result, the coefficients of variation were <20% in quantitation limit (0.2 ng/mL) and <15% at the rest of concentrations. The stability test by repeated freezing-thawing cycles showed that the samples were stable only for 24hr. The stability tested for samples with a short-term period of storage at room temperature and pre-treatment prior to the analysis showed very stable over 24hr. In 8 healthy Korean subjects received Denol tablets at the dose of 900mg bismuth, AUC, $C_{max},\;T_{max}$ and half-life $(t_{1/2})$ were determined to be $198.33{\pm}173.78 ng{\cdot}hr/mL,\;64.48{\pm}27.06 ng/mL,\;0.52{\pm}0.21 hr,\;and\;5.15{\pm}2.67 hr$, respectively, from the plasma bismuth concentration-time curves. In conclusion, the method was suitable for the determination of bismuth in human plasma samples and could be applied to bioequivalence test of bismuth tablet.

• 폴리머
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• 제39권2호
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• pp.225-234
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• 2015

In this study, we proposed to synthesize thermally stable, soluble and conjugated Schiff base polymer (SbP). For this reason, a specific molecule namely 4,4'-thiodiphenol which has sulfur and oxygen bridge in its structure was used to synthesize bi-functional monomers. Bi-functional amino and carbonyl monomers namely 4,4'-[thio-bis(4,1-phenyleneoxy)] dianiline (DIA) and 4,4'-[thiobis(4,1-phenyleneoxy)]dibenzaldehyde (DIB) were prepared from the elimination reaction of 4,4'-thiodiphenol with 4-iodonitrobenzene and 4-iodobenzaldehyde, respectively. The structures of products were confirmed by elemental analysis, FTIR, $^1H$ NMR and $^{13}C$ NMR techniques. The molecular weight distribution parameters of SbP were determined by size exclusion chromatography (SEC). The synthesized SbP was characterized by solubility tests, TG-DTA and DSC. Also, conductivity values of SbP and SbP-iodine complex were determined from their solid conductivity measurements. The conductivity measurements of doped and undoped SbP were carried out by Keithley 2400 electrometer at room temperature and atmospheric pressure, which were calculated via four-point probe technique. When iodine was used as a doping agent, the conductivity of SbP was observed to be increased. Optical band gap ($E_g$) of SbP was also calculated by using UV-Vis spectroscopy. It should be stressed that SbP was a semiconductor which had a potential in electronic and optoelectronic applications, with fairly low band gap. SbP was found to be thermally stable up to $300^{\circ}C$. The char of SbP was observed 29.86% at $1000^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• 제24권1호
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• pp.19-25
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• 2014

An extracellular agarase was purified from Bacillus sp. BI-3, a thermophilic agar-degrading bacterium isolated from a hot spring in Indonesia. The purified agarase revealed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with an apparent molecular mass of 58 kDa. The optimum pH and temperature of the agarase were 6.4 and $70^{\circ}C$, respectively. The activity of the agarase was stable at high temperatures, and more than 50% activity was retained at $80^{\circ}C$ for 15 min. Furthermore, the enzyme was stable in the pH range of 5.8-8.0, and more than 60% of the residual activity was retained. Significant activation of the agarase was observed in the presence of $K^+$, $Na^+$, $Ca^{2+}$, $Mg^{2+}$, and $Sr^{2+}$; on the other hand, $Ba^{2+}$, $Zn^{2+}$, $Cu^{2+}$, $Mn^{2+}$, $Co^{2+}$, $Fe^{2+}$, and EDTA inhibited or inactivated the enzyme activity. The components of the hydrolytic product analyzed by thin-layer chromatography showed that the agarase mainly produced neoagarobiose. This study is the first to present evidence of agarolytic activity in aerobic thermophilic bacteria.

• 스마트미디어저널
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• 제11권10호
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• pp.65-75
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• 2022

딥러닝은 기존의 분석 모델이 갖는 한계를 극복하고 텍스트, 이미지, 음악 등 다양한 형태의 결과물을 생성할 수 있는 창의적인 도구로 활용되고 있다. 본 고에서는 Niko's MIDI Pack 음원 파일 1,609개를 데이터 셋으로 삼아 전처리 과정을 수행하고, 양방향 장단기 기억 순환 신경망(Bi-LSTM) 모델을 이용하여, 효율적으로 음악을 생성할 수 있는 전처리 방법과 예측 모델을 제시한다. 생성되는 으뜸음을 바탕으로 음악적 조성(調聲)에 적합한 새로운 시계열 데이터를 생성할 수 있도록 은닉층을 다층화하고, 디코더의 출력 게이트에서 인코더의 입력 데이터 중 영향을 주는 요소의 가중치를 적용하는 어텐션(Attention) 메커니즘을 적용한다. LSTM 모델의 인식률 향상을 위한 파라미터로서 손실함수, 최적화 방법 등 설정 변수들을 적용한다. 제안 모델은 MIDI 학습의 효율성 제고 및 예측 향상을 위해 높은음자리표(treble clef)와 낮은음자리표(bass clef)를 구분하여 추출된 음표, 음표의 길이, 쉼표, 쉼표의 길이와 코드(chord) 등을 적용한 다채널 어텐션 적용 양방향 기억 모델(Bi-LSTM with attention)이다. 학습의 결과는 노이즈와 구별되는 음악의 전개에 어울리는 음표와 코드를 생성하며, 화성학적으로 안정된 음악을 생성하는 모델을 지향한다.

• 한국항행학회논문지
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• 제25권6호
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• pp.536-542
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• 2021

본 논문에서는 WLAN(WiFi) 이중대역(2.4 ~ 2.484 / 5.15 ~ 5.825 GHz) 및 3.5 GHz 5G 대역(3.42~3.7 GHz) 을 위한 마이크로스트립 급전 구조를 가지는 굽은 가지 스트립을 가진 삼중대역 인쇄형 모노폴 안테나를 제안하였다. 3중 대역 안테나 구조로 수직으로 세워진 전형적인 λ/4 모노폴 스트립을 기반으로 하여 다중공진을 발생시키기 위한 굽은 스트립(strip)을 나무 가지(branch) 형태로 붙인 안테나 구조를 새롭게 제안하였다. 유전상수 4.3, 유전체 두께 1.6mm 의 FR4 기판에 28×40 mm²의 크기를 가진다. 측정 결과 2.4 GHz 대역에서 430 MHz (2.22~2.65 GHz), 3.5 GHz 5G 대역에서 450 MHz (3.38~3.83 GHz), 5 GHz 대역에서 2390 MHz (4.95~7.34 GHz)의 임피던스 대역폭을 나타냈다. 또한, 모든 대역에서 안정되고 무지향성 경향의 방사패턴을 얻을 수 있었으며, 각각 1.537 dBi, 1.878 dBi, 2.337 dBi의 이득을 가진다.

• 공업화학
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• 제9권6호
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• pp.846-851
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• 1998

w/o 에멀젼 내에서 균일용액침전반응을 진행시켜 산화아연 미세 입자를 제조하는 실험적 연구를 수행하였다. 질산아연 수용액에 hexamethylene tetramine (HMTA)을 침전제로 첨가한 침전액은 유화제 Span 80에 의해 kerosine과 안정한 w/o 에멀젼을 형성하였다. 얻어진 w/o 에멀젼을 HMTA 분해온도 이상($85^{\circ}C$)으로 가열하여 w/o 에멀젼 내에서 균일용액 침전반응을 진행시키면 산화아연 입자들이 제조되는 것을 확인하였다. 이렇게 제조된 산화아연 입자들은 이중분산 (bi-modal distribution)을 갖는 영역이 존재하기도 하였으나, 균일용액침전법에 비하여 높은 초기 아연농도와 높은 수율에서도 입자가 작고 입도분포가 비교적 좁은 산화아연 입자들을 얻을 수 있었다.

• 한국전자파학회지:전자파기술
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• 제12권3호
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• pp.2-11
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• 2001

L자 형태의 스트립 급전 구조는 두꺼운 유전체 기판 (두께${\approx}0.1\;{\lambda}$을 갖는 마이크로 스트립 안테나에 있어 적합한 구조이다. L자 형태의 스트립 급전 구조는 방사 패치와 결합하여 캐패시턴스 성분을 발생시켜 스트립 자체에 의해 발생되는 인덕턴스 성분을 억제시킨다. 본 논문에서는 PCS대역($1,750{\sim}1,870MHz$)과 IMT-2000대역($1,920{\sim}2,170MHz$의 광대역 주파수(420 MHz)를 모두 만족시킬 수 있는 L자 형태로 급전되는 광대역 마이크로 스트립 패치 안테나를 소개한다. 또한 L자 형태로 급전되는 안테나를 두 개 배열한 형태의 안테나도 소개한다. 이들 두 안테나는 모두 패스밴드에서 안정된 방사패턴을 가지며 임피던스 대역폭은 중심주파수 (1,960 MHz)의 31%(VSWR<1.5, 615 MHz) 이상을 가지고 약 7 dBi의 평균 이득을 갖는다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 기술교육위원회 창립총회 및 학술대회 의료기기전시회
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• pp.5-8
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• 2001

The $Sr_{0.8}Bi_{2.4}Ta_{2}O_{9}(SBT)$ thin films are deposited on Pt-coated electrode$(Pt/TiO_{2}/SiO_{2}/Si)$ using RF magnetron sputtering method. With increasing annealing tempera ture from $600[^{\circ}C]$ to $850[^{\circ}C]$, Bi-layered perovskite phase was crystallized above $650[^{\circ}C]$. The dielectric constant is 213 at annealing temperature of $750[^{\circ}C]$ and dielectric loss have a stable value within 0.1. Leakage current density is $1.01{\times}10^{-8} A/cm^{2}$ at annealing temperature of $750[^{\circ}C]$ The fatigue characteristics of SBT thin films did not change up to $10^{10}$ switching cycles.

• 한국세라믹학회지
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• 제28권4호
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• pp.261-268
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• 1991

The dielectric properties and microstructure of SrTiO3-based grain boundary layer (GBL) capacitor were investigated, and SrTiO3 GBL capacitor was made by penetrating the Frit (PbO-Bi2O3-B2O3 system). The Nb2O5-doped SrTiO3 ceramics were fired for 4-hours, at 145$0^{\circ}C$ in H2-N2 atomsphere to get semiconductive ceramics. The grain size of SrTiO3 sintered at reduction atmosphere had increased as the amount of Nb2O5 increases and then decreased as the amount of Nb2O5 exceeded 0.2 mole%. Insulating reagents which contained PbO-Bi2O3-B2O3 system frit and oxide mixture were printed on the each semiconductive ceramics and fired at varying temperature and for different holding time. The optimum dielectric properties could be obtained by second heat treatment at 110$0^{\circ}C$ for 1 hour, when frit paste was printed. A SrTiO3-based GBLC had the apparent permitivity of about 3.2$\times$104, the dielectric loss of 0.01~0.02 and the stable temperature coefficient of capacitance. The influence of frit paste on dielectric properties was similiar to that of oxide paste but the stability of temperature property of capacitance was improved.