• 한국재료학회지
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• 제9권6호
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• pp.547-550
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• 1999

Optical and electrical properties of MgO-CaO films as a protective layer for AC plasma display panel were studied. When the [(CaO/(MgO+CaO)] ratio of evaporation starting materials was optimum composition, 0.1, firing voltage and memory margin of the film were 176V and 0.5, respectively. When [CaO/(CaO+MgO)] was 0, 0.1 and 0.2, memory margin was 0.39, 0.5 and 0.41, respectively, and surface roughness of films was $27.7\AA$, $21.1\AA$ and $40.3\AA$, respectively. It was thought that memory margin had a reverse-relation with surface roughness. The density of film was calculated by measuring the refractive index of film. The density of MgO film was 3.21g/㎤ and the density of film, when [CaO/(CaO+MgO)] was 0.1, was 3.632g/㎤. The mixture of MgO-CaO films showed a good transmittance property in the visual range.

• 대한금속재료학회지
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• 제50권9호
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• pp.669-675
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• 2012

Hot tearing was the most significant casting defect when the castability evaluation of the Al-Zn-Mg-Cu alloy system was conducted. It was related to the solidification range of the alloy. Therefore, the hot tear susceptibility of the AA7075 alloy, whose solidification range is the widest, was evaluated. The hot tear susceptibility was evaluated by using a mold for a hot tearing test designed to create the condition for the occurrence of hot tear in 8 steps. According to the tearing location and shape, a hot tear susceptibility index (HTS) score was measured. The solidification range of each alloy and hot tear susceptibility was compared and thereafter the microstructure of a near tear defect was observed. As a result, the HTS of the AA7075 alloy was found to be 67. Also, the HTS in relation to a change in Zn, Mg, Cu composition showed a difference of about 6-11% compared to the AA7075 alloy.

• Bulletin of the Korean Chemical Society
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• 제21권3호
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• pp.305-309
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• 2000

The cerium ion intercalated aluminosilicate was prepared by ion exchange reaction between $Na^+$ in montmorillonite and $Ce^{+4}$ in aqueous solution. The X-ray absorption near edge structrure(XANES) analyses indicate that the $Ce^{+4}$ ions are partially reduced to the $Ce^{+3}$ ones during the intercalation into layered aluminosilicate due to a charge transfer between host and intercalant. From the EXAFS analysis, two different (Ce-O) bonding pairs could be characterized with the distances and coordination numbers of 2.31 $({\pm}0.02){\AA}$ ${\times}$ 8.2 $({\pm}1.5)$ and 2.66 $({\pm}0.02){\AA}$ ${\times}$ 2.7 $({\pm}1.0)$, respectively, with the oxygen atoms as the first nearest neighbor, and two (Ce-Ce) pairs at 3.78 ${\AA}$ as the second neighbor. It is therefore concluded that the most probable Ce-species stabilized in the interlayer space of aluminosilicate after the intercalation is the tetrameric Ce-polyoxy/hydorxy cations with the mixed valent state of 0.75 $Ce^{+4}$.0.25 $Ce^{+3}$.

• Corrosion Science and Technology
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• 제19권6호
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• pp.288-295
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• 2020

This study investigated the erosion-corrosion characteristics of 5038-H321 aluminum alloy in a natural seawater solution through various electrochemical experiments and flow rate parameters. Cathodic polarization experiments were conducted at flow rates ranging from 4 to 12 knots. Considering the concentration polarization section representing a relatively low current density, the range of the potentiostatic experiment was determined to be -1.6 to -1.0 V. The potentiostatic experiment was conducted at various potentials for 180 minutes in seawater. After the experiment, the corrosion characteristics were evaluated by observing surface morphology and measuring surface roughness. As a result, as the applied potential was lower, the amount of calcareous deposits increased and the roughness tended to increase. On the other hand, it was confirmed that the roughness was larger in the static condition than the flow rate condition due to the influence of the flow velocity. Variations in the chemical composition with flow rate variations were analyzed by energy-dispersive spectroscopy (EDS). In conclusion, the cathodic potential of AA5083-H321 in seawater was determined to be -1.0 V.

• 한국안광학회지
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• 제11권3호
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• pp.259-265
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• 2006

우리는 하이드로겔 렌즈의 단점을 보완하기 위해 AA(Acrylic acid) and BMA(butyl methacrylate)의 재료를 중합하였다. 실리콘의 합성과정은 다음과 같다. Disocynate를 HEMA(2-hydroxyethylmethacrylate)와 촉매 하에서 반응시킨 후 다시 고 산소 투과성 특성을 가지는 bis(hydroxyalkyl)terminated poly(dimethylsiloxane)를 반응시켜 Acrylate-PDMS(Polydimethylsiloxane)-Urethane prepolymer를 합성하였다. HEMA(2-hydroxyet-hylmethacrylate)는 중합 가능한 prepolymer를 만들기 위해서 사용하였으며, Urethane의 도입은 탄성이 좋고 산소투과성을 높이기 위해 사용하였다. 이렇게 만들어진 prepolymer를 기존 하이드로겔 콘택트렌즈의 재료들과 공중합하여 산소투과성이 좋은 실리콘 하이드로겔 렌즈(silicone hydrogel contact lens)를 제조하였다. 콘택트렌즈 제조를 위해 기존에 사용된 콘택트렌즈 재료에 탄성과 유연성이 좋은 BMA(Butyl methacrylate), 습윤성이 좋은 AA(Acrylic acid)를 첨가하였다. 개시제로는 AIBN(Azobis2-methylpropionitrile)을, 교차결합제로 EGDMA(Ethylene Glycol Dimethacrylat)를 사용하였다. 각 monomer의 특징에 따라 여러 가지 조합을 시도하여 기본적인 콘택트렌즈 물성을 만족하면서 동시에 산소투과성과 습윤성이 좋은 렌즈를 제조하였다. SILICONE, HEMA, NVP과 EGDMA등이 포함된 SN은 팽윤율(swelling ratio) 9.38%, 함수율(water content) 23.72%로 나타났고, 가시광선 투과율은 88%로 나타났다. AA를 첨가한 SA는 팽윤율(swelling ratio) 9.38%, 함수율(water content) 23.72%로 나타났고, 가시광선 투과율은 88%로 나타났다. SN에 BMA를 첨가한 SB는 팽윤율(swelling ratio) 12.50%, 함수율(water content) 18.56%로 나타났고, 가시광선 투과율은 88%로 나타났다. SN에 AA와 BMA를 첨가한 SAB는 팽윤율(swelling ratio) 8.33%, 함수율(water content) 12.93%로 나타났고, 가시광선 투과율은 88%로 나타났다.

• 천문학회지
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• 제37권1호
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• pp.41-53
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• 2004

It has been a big mystery what drives filament eruptions and flares. We have studied in detail an X1.8 flare and its associated filament eruption that occurred in NOAA Active Region 9236 on November 24,2000. For this work we have analyzed high temporal (about 1 minute) and spatial (about 1 arcsec) resolution images taken by Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory, Hoc centerline and blue wing ($-0.6{\AA}$) images from Big Bear Solar Observatory, and 1600 ${\AA}$ UV images by the Transition Region and Corona Explorer (TRACE). We have found that there were several transient brightenings seen in H$\alpha$ and, more noticeably in TRACE 1600 ${\AA}$ images around the preflare phase. A closer look at the UV brightenings in 1600 ${\AA}$ images reveals that they took place near one end of the erupting filament, and are a kind of jets supplying mass into the transient loops seen in 1600 ${\AA}$. These brightenings were also associated with canceling magnetic features (CMFs) as seen in the MDI magnetograms. The flux variations of these CMFs suggest that the flux cancellation may have been driven by the emergence of the new flux. For this event, we have estimated the ejection speeds of the filament ranging from 10 to 160 km $s^{-1}$ for the first twenty minutes. It is noted that the initiation of the filament eruption (as defined by the rise speed less than 20 km $s^{-1}$) coincided with the preflare activity characterized by UV brightenings and CMFs. The speed of the associated LASCO CME can be well extrapolated from the observed filament speed and its direction is consistent with those of the disturbed UV loops associated with the preflare activity. Supposing the H$\alpha$/UV transient brightenings and the canceling magnetic features are due to magnetic reconnect ion in the low atmosphere, our results may be strong observational evidence supporting that the initiation of the filament eruption and the preflare phase of the associated flare may be physically related to low-atmosphere magnetic reconnection.

• Asian-Australasian Journal of Animal Sciences
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• 제15권2호
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• pp.247-253
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• 2002

Two experiments were conducted to investigate the impact of high temperature and dietary tryptophan (Trp) on performance, selected organ weights and plasma free amino acid (AA) concentrations in broiler chickens. In Experiment 1, exposure to $27-33^{\circ}C$ of chickens for 2 weeks from 2 weeks of age did not affect growth and plasma free AA concentration except for a decrease in the concentration of plasma tyrosine (Tyr). In Experiment 2, 2-week-old birds were allocated to one of three temperature treatments; $24^{\circ}C$ (control), $36^{\circ}C$ (heat stress, HS) and $24^{\circ}C$ pair-fed (24PF) for 2 weeks and fed on diets containing 50, 100 and 300% of NRC requirement for Trp. Heat stress caused a reduction of weight gain and feed intake irrespective of dietary Trp levels compared with control counterparts, while feeding of 300% Trp diet did not attenuate the reduced performance by HS exposure. In groups fed the 100% Trp diets, plasma aromatic AA (AAA) and Tyr concentrations were decreased in the HS birds compared with the 24PF group. Plasma concentrations in most of AA groups were increased by HS in chickens fed the 50% Trp diet, while those were not changed by HS in chickens fed the 300% Trp diet, compared with 24PF counterparts. The plasma Trp/LNAA (LNAA=large neutral AAs, which are comprised of BCAA, AAA and Trp) ratio was increased by HS in chickens fed the 100% Trp diet, while it was decreased in chickens fed on 50% Trp diet as compared with 24PF group. From these results, it is suggested that performance and plasma amino acid profile deranged by heat stress are modulated, at least, to be relieved from the heat stress by feeding 50% Trp diet but not at all by feeding 300% Trp diet. The involvement of altered plasma AA profiles, in particular plasma Tyr concentrations and Trp/LNAA ratio, is discussed in association with the performance characteristics of HS chickens.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2011년도 춘계학술발표대회
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• pp.590-593
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• 2011

Time goes on, Ad Hoc network is hot issues. So far, there are a lot of protocols have been proposed for Ad Hoc routing protocol to support the mobility. This paper presents an enhanced DSDV(Destination-Sequenced Distance Vector) routing protocol which nominates one node to take care of a specific area. Simply Area-Aware(AA) DSDV routing protocol has one nominee to take care of some area. It has two jobs. One is to take care of its neighbour and another is to transfer the routing table to its other node as it works. It is called as Area Nominee(AN). The new scheme extends the routing table to include the nominee in the area. The general node is the same as the previous DSDV routing protocol. In the other hands, the node which is nominated has two routing protocols. One is for Regional Routing(RR) table which is the same routing table in DSDV. Another is Global Routing(GR) table which is about the area round its area which it cares nearby. GR table is the table for the designated node like the nominee. Each area has one nominee to transfer between ANs. It has only nominee's information about every area. This concept decreases the topology size and makes the information of topology more accurate.

• Carbon letters
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• 제14권1호
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• pp.55-57
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• 2013

The development of hollow carbon balls by $CO_2$ oxidation of two types of carbon blacks was studied. Super P (SP) and Denka Black (DB) were used for this study. Specific surface area (SSA), structural parameters, and microstructures were examined using Brunauer, Emmett and Teller apparatus, X-ray diffraction spectroscopy, and transmission electron microscope (TEM), respectively. The SSAs of both oxidized carbon blacks increased after oxidation. The SSAs of raw DB and SP were 73 $m^2/g$ and 60 $m^2/g$, respectively. Maximum SSAs of oxidized DB and SP were 152 $m^2/g$ and 253 $m^2/g$, respectively. The $d_{002}$ of DB and SP showed almost no change after oxidation. The Lc of raw DB ($38{\AA}$) and SP ($19{\AA}$) increased with increasing weight loss. The $L_c$ of SP increased up to $254{\AA}$ at 96% weight loss. The SSA increased about twice in DB (148 $m^2/g$) and about four times in SP (254 $m^2/g$) after 3 h oxidation compared with the original carbon blacks. Through TEM observation the outer parts of the oxidized carbon blacks showed a rigid shell structure and the inner parts looked empty. Generally it looked like an angular soccer ball, so we named it 'hollow carbon ball'. It is expected that the hollow carbon ball can be used as catalyst supports.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권1호
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• pp.1-7
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• 2000

The SNOSFET memory devices with ultrathin ONO(tunnel oxide-nitride-blocking oxide) gate dielectric were fabricated using n-well CMOS process and investigated its characteristics. The thicknesses of tunnel oxide, nitride and blocking oxide were $23{\AA},\; 53{\AA}\; and\; 33{\AA}$, respectively. Auger analysis shows that the ONO layer is made up of $SiO_2(upper layer of blocking oxide)/O-rich\; SiO_x\N\_y$. It clearly shows that the converting layer with $SiO_x\N\_y(lower layer of blocking oxide)/N-rich SiO_x\N\_y(nitride)/O-rich SiO_x\N\_y(tunnel oxide)$. It clearly shows that the converting layer with $SiO_x\N\_y$ phase exists near the interface between the blocking oxide and nitride. The programming condition of +8 V, 20 ms, -8 V, 50 ms is determined and data retention over 10 years is obtained. Under the condition of 8 V programming, it was confirmed that the modified Fowler-Nordheim tunneling id dominant charge transport mechanism. The programmed threshold voltage is distributed less than 0.1 V so that the reading error of memory stated can be minimized. An $8\times8$ NAND type flash EEPROM with SONOSFET memory cell was designed and simulated with the extracted SPICE parameters. The sufficient read cell current was obtained and the upper limit of $V_{TH}$ for write state was over 2V.