• 전자공학회논문지
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• 제53권12호
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• pp.57-63
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• 2016

본 논문은 $0.18{\mu}m$ 실리콘 CMOS 기술을 이용한 IEEE802.15.4g SUN 체계의 센서노드 무선통신부에 적용할 수 있는 RF 주파수 합성기의 구현에 대하여 기술하였다. 제안한 주파수 합성기는 고속 저잡음 특성을 얻기 위하여 VCO, 프리스케일러, 1/N 분주기, ${\Delta}-{\Sigma}$ 모듈레이터 그리고 PLL 공통 회로 등의 설계 최적화가 이루어졌으며, 특히 VCO는 NP 코어 구조와 13단 캡 뱅크를 각각 적용하여 고속, 저잡음 및 광대역 튜닝 범위를 확보하였다. 제안된 주파수 합성기를 칩으로 제작하여 측정한 결과 출력 주파수 범위는 1483MHz~2017MHz, 위상잡음은 100KHz 오프셋에서는 -98.63dBc/Hz, 1MHz 오프셋에서는 -122.05dBc/Hz로 양호한 특성을 얻을 수 있었다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.21-21
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• 2010

AISI 316L 용접금속의 크롬/니켈 당량비에 따른 시그마상의 영향을 알아보기 위하여 응고모드가 다른 3종류의 플럭스 코어드 와이어를 제작하였다. AISI 316L 시편에 FCAW 프로세스를 적용한 용접재를 $650^{\circ}C$, $750^{\circ}C$, $850^{\circ}C$, $950^{\circ}C$에서 각 각 1H, 5H, 24H, 72H동안 열처리하였다. 크롬/니켈 당량비가 높을수록 즉, 크롬의 함량이 높아질수록 $\delta$-페라이트 함량은 증가하였으며, $\delta$-페라이트는 고온에서 시그마상으로 변태되었다. $\delta$-페라이트는 $650^{\circ}C$에서 가장 느리게 분해되었으며 $850^{\circ}C$에서 가장 활발히 분해되었다. 용접부의 특성상 크롬과 니켈 등의 합금원소에 의하여 응고온도범위가 넓어져 $950^{\circ}C$에서도 시그마상이 석출되었으며, 5시간 이상 유지 시 구형으로 존재하였다. 충격시험 시 시그마상에 의해 취약해진 inter-dendrite 를 따라 파면이 형성되었으며, $-100^{\circ}C$이하의 극저온에서는 시그마상의 양과 무관하게 충격흡수에너지는 0에 가까워졌다. 하지만 3%미만의 $\delta$-페라이트를 함유하는 AF모드에서 발생한 DDC와 미량의 시그마상은 충격흡수에너지에 결정적인 영향을 미치지 않았다.

• 대한전자공학회논문지SD
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• 제46권5호
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• pp.49-54
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• 2009

USN 센서노드 무선통신부에 내장하기 위한 1.9GHz RF 주파수 합성기를 $0.18{\mu}m$ 실리콘 CMOS 기술을 이용하여 구현하였다. 고속 저잡음 특성을 얻기 위하여 VCO, 프리스케일러, 1/N 분주기, ${\Sigma }-{\Delta}$ 모듈레이터 분수형 분주기, PLL 공통 회로 등의 설계 최적화에 중점을 두고 설계하였으며, 특히 VCO는 N-P MOS 코어 구조 및 캡 뱅크를 적용하여 고속 저전력 및 넓은 튜닝 범위를 확보하였다. 설계된 칩의 크기는 $1.2{\times}0.7mm^2$이며, IP로 활용하기 위한 코어 부분의 크기는 $1.1{\times}0.4mm^2$이다. 측정 결과 PLL 회로의 잡음 면에서도 문제가 될 만한 특정 스퍼는 발생하지 않았으며, 6MHz 기본 스퍼에 해당하는 잡음은 -63.06dB로 나타났다. 위상잡음 특성은 1MHz 오프셋에서 -116.17dBc/Hz로서 양호한 특성을 보였다.

• 한국세라믹학회지
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• 제32권11호
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• pp.1292-1300
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• 1995

The ionic conductivity of NASICON solid electrolytes was simulated by using Monte Carlo Method (MCM). There were included two conduction paths: (1) Na1-Na2 and (2) Na1-Na2 including Na2-Na2. We assumed that mid-Na ions provde an additional driving force for Na mobile ions due to the interionic repulsion between Na1 and Na2 ions. The inflection point of vacancy availability factor, V has been shown at nearby x=2, the maximum mid-Na ions. The inflection point of vacancy availability factor, V has been shown at nearby x=2, the maximum mid-Na sites are occupied. The effective jump frequency factor, V has been shown at nearby x=2, the maximum mid-Na sites are occupied. The effective jump frequency factor, W increased rapidly with the composition at low temperature, but decreased at high temperature region. On Na1-Na2 conduction path, the minimum of charge correlation factor, fc and the maximum of $\sigma$T were appeared at x=2.0. this indicated that mid-Na ions affect on the high ionic conductivity behavior. At the whole range of NASICON composition, 1n $\sigma$T vs. 1/T* plots have been shown Arrhenius behavior but 1n (VWFc) vs. 1/T* have been shown the Arrhenius type tendency at x=2, which mid-Na is being the maximum. The results of MCM agreed with the experimental one when the chosen saddle point value was 6$\varepsilon$ : 3$\varepsilon$. Here the calculated characteristic parameter of materials, K and the phase transition temperature were -4.001$\times$103 and 178$^{\circ}C$ (1/T*=1.92, 1000/T=2.22), respectively.

• Journal of Microbiology
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• 제38권4호
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• pp.239-244
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• 2000

The cats gene encodes the major catalase in Sreptomyces coelicolor, whose production increases upon H$_2$O$_2$treatment. Besides the previously identified primary promoter (catApl), a minor promoter (catAp2) was newly assigned by S1 nuclease mapping. The catAp2 transcript was observed transiently upon entry into the stationary phase in liquid culture and upon differentiation on solid plates, whereas the level of catApl transcription did not chance significantly during this growth transition. ThecatApl promoter was transcribed by the major vegetative RNA polymerase holoenzyme containing $\sigma$$\^$HrdB/, whereas the catAp2 was transcribed in vitro by the holoenzyme containing $\sigma$$\^$R/ that is activated under oxidative conditions. The cia-element regulating the H$_2$O$_2$-inducibility of catApl was identified within the 23 bp inverted repeat sequence located between -65 and -43 of the catApl promoter. We roamed this sequence HRE (H$_2$O$_2$-responsive Element). The distal half of the inverted repeat was more crucial for H$_2$O$_2$-dependent induction of the catApl transcript than the proximal half. HRE most likely serves as a binding site for the H$_2$O$_2$-responsive repressor CatR.

• 한국재료학회지
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• 제9권1호
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• pp.57-64
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• 1999

The electrical conductivity of TiO$_2$ doped with 0.05~1.5mol% WO$_3$ was measured in the oxygen partial pressure range of 10\ulcorner~10\ulcorner atm and temperature range of 1100~130$0^{\circ}C$ to investigate the defect types and the electrical properties. The grain size and density were increased as the liquid phase was formed by the doped WO$_3$. The secondary phase and WO$_3$peaks at the sample doped up to 4.0 mol% were not detected from the XRD results. The data(log$\sigma$/logPo$_2$) over 110$0^{\circ}C$ were divided into the four regions. From these experimental results, we proposed the following defect regions. 1) Magneli phase(extended defect), 2) Reduced rutile region which is similar to the behavior of undoped rutile, 3) Nearly stoichiometric Ti\ulcornerW\ulcornerO$_2$region in which extra charge of W\ulcorner cation is expected to be compensated by an electron, 4) Overstoichiometric Ti\ulcornerW\ulcornerO\ulcorner region which is a metal deficiency not to be observed in pure TiO$_2$. The electrical conductivity of w-doped TiO$_2$ was influenced by the measuring temperature, oxygen partial pressure, and the dopig content.

• Corrosion Science and Technology
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• 제19권1호
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• pp.37-42
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• 2020

Even though 304 low-carbon (304L) stainless steel was developed to enhance the resistance to intergranular corrosion and stress corrosion cracking, it is occasionally subject to degradation in harsh environments. The degree of sensitization (DOS) of 304L stainless steel was studied as a function of sensitization using a double-loop electrochemical potentiokinetic reactivation (DL-EPR) method. Sensitizing heat treatment was performed in an Ar atmosphere at 500℃, 600℃, and 700℃, with heat treatment times varying from 0 to 96 h. DOS was measured by the ratio of the peak current density value of the forward scan to that of the reverse scan. After the EPR experiment, the specimen surface was observed by scanning electron microscopy and energy dispersive spectroscopy. The DOS of the specimens heat-treated at 600℃ increased with heat treatment times up to 48 h and then decreased due to a self healing effect. The DOS was higher in specimens heat-treated at 600℃ than those at 500℃ or 700℃. Corrosion of the sensitized specimens occurred mainly at the δ-γ phase boundary. The corrosion morphology at the δ-γ phase boundary changed with sensitizing heat-treatment conditions due to differences in chromium activity in γ austenite and δ ferrite.

• Corrosion Science and Technology
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• 제5권5호
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• pp.181-188
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• 2006

In this study, the characteristics of the experimentally produced high N-high Cr bearing stainless steels are discussed as a part of applications of materials for FGD (Fuel Gas Desulfurization) system of thermal power plants or for power plants using seawater as coolant. Corrosion resistance of developed alloys is especially investigated in detail. Corrosion characteristics of vacuum melted cast are shown to be superior to that of air melted one. From the viewpoint of CPT, It is estimated that the differences of corrosion resistance are $21.8^{\circ}C{\sim}24.6^{\circ}C$ at PRE 40 and $8^{\circ}C{\sim}12.4^{\circ}C$ at PRE 50, and the gaps becomes bigger as the PRE values are lower. In the evaluation of corrosion resistance in alloy A2501, Z3101, and A3301 according to Cr concentration, alloy A3301 shows a deviation from the general tendency in chloride solutions. It has relatively high PRE value as 48.6, but it has relatively poor pitting resistance. It is, however, difficult to observe a specific phase except ferrite in microstructure analysis and neither detects special phase such as sigma phase.

• 천문학논총
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• 제30권2호
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• pp.593-594
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• 2015

We present our analysis results for an updated orbital ephemeris for the dipping low mass X-ray binary 4U 1624-49, using the light curve collected by the All Sky Monitor (ASM) on board the Rossi X-ray Timing Explorer (RXTE) and the Monitor of All-Sky X-ray Image (MAXI). To make clear dip profiles, the light curve from the ASM and the MAXI were divided into ten 500d segments and four 400d segments for ASM and MAXI light curves, respectively, and folded with the linear ephemeris proposed by Smale et al. (2001). The phases of dip centers were determined by the method adopted from Hu et al. (2008). The phase drift was then fitted with a linear function. We obtained an updated orbital period of 0.869896(1) d and a phase zero epoch of JD 2450088.6618(57). No clear orbital period derivative is detected with a 2-sigma upper limit of $1.4{\times}10^{-6}(yr)^{-1}$ from a quadratic curve fitting of the dip phase evolution.

• Bulletin of the Korean Chemical Society
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• 제8권5호
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• pp.398-403
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• 1987

A general theory of polymer adsorption at a semi-permeable oil-water interface of the biphasic solution is presented. The configurational factor of the solution in the presence of the semi-open boundary at the interface is evaluated by the quasicrystalline lattice model. The present theory gives the feature of the bulk concentration equilibria between oil-water subsystems and the surface excesses of ${\Gamma}^{\alpha}$ and ${\Gamma}^\{beta}$ of the polymer segments as a function of the degree of polymerization $\gamma$, the Flory-Huggins parameter in $\beta$-phase $x_{\rho}^{{\beta}_{\rho}}$, the differential adsorption energy parameter in $\beta$-phase $x_{\sigma}^{{\beta}_{\rho}}$, the differential interaction energy parameter ${\Delta}x_{\rho}$ and the bulk concentration of the polymer in ${\beta}-phase ${\varphi}_2^{{\beta(*)}_2}$. From our numerical results, the characteristics of ${\Gamma}^{\alpha}$ are shown to be significantly different from those of ${\Gamma}^{\beta}$ in the case of high polymers, and this would be the most apparent feature of the adsorption behavior of the polymer at a semi-permeable oil-water interface, which is sensitively dependent on ${\Delta}x_{\rho}$ and r.