• 한국산학기술학회논문지
• /
• 제10권12호
• /
• pp.3761-3767
• /
• 2009

산업단지에서 발생하는 액상폐기물(폐유와 폐유기용제)을 고온반응기에서(온도 $1,250{\sim}1,400^{\circ}C$, 압력 1기압) 연소시키면서 연소 특성, 유해물질 분해정도 및 연소 후 배출가스 특성 등을 살펴보았다. 산소와 폐기물의 질량비($O_2$/waste mass fraction)가 1.53 이하로 줄어들 때 반응기는 산화분위기에서 환원분위기로 전환되었고 연소 후 배출가스는 NOx 배출량이 감소하고 합성가스의 발생비율이 증가하였으며 BTEX류는 99.99%이상 분해되는 것으로 나타났다. 본 연구에서 제안한 시스템 및 조업조건 하에서 고농도의 액상폐기물(폐유와 폐유기용제)을 처리한 결과 미량 오염물질의 배출농도는 매우 낮은 값을 보여 액상폐기물의 처리에 적합한 것으로 판단되며 또한 연소 후 합성가스도연료로 활용할 수 있을 것으로 사료된다.

• Biomolecules & Therapeutics
• /
• 제28권2호
• /
• pp.152-162
• /
• 2020

Cerebral ischemia exhibits a multiplicity of pathophysiological mechanisms. During ischemic stroke, the reactive oxygen species (ROS) concentration rises to a peak during reperfusion, possibly underlying neuronal death. Recombinant human erythropoietin (EPO) supplementation is one method of treating neurodegenerative disease by reducing the generation of ROS. We investigated the therapeutic effect of PEGylated EPO (P-EPO) on ischemic stroke. Mice were administered P-EPO (5,000 U/kg) via intravenous injection, and middle cerebral artery occlusion (MCAO) followed by reperfusion was performed to induce in vivo ischemic stroke. P-EPO ameliorated MCAO-induced neurological deficit and reduced behavioral disorder and the infarct area. Moreover, lipid peroxidation, expression of inflammatory proteins (cyclooxygenase-2 and inducible nitric oxide synthase), and cytokine levels in blood were reduced by the P-EPO treatment. In addition, higher activation of nuclear factor kappa B (NF-κB) was found in the brain after MCAO, but NF-κB activation was reduced in the P-EPO-injected group. Treatment with the NF-κB inhibitor PS-1145 (5 mg/kg) abolished the P-EPO-induced reduction of infarct volume, neuronal death, neuroinflammation, and oxidative stress. Moreover, P-EPO was more effective than EPO (5,000 U/kg) and similar to a tissue plasminogen activator (10 mg/kg). An in vitro study revealed that P-EPO (25, 50, and 100 U/mL) treatment protected against rotenone (100 nM)-induced neuronal loss, neuroinflammation, oxidative stress, and NF-κB activity. These results indicate that the administration of P-EPO exerted neuroprotective effects on cerebral ischemia damage through anti-oxidant and anti-inflammatory properties by inhibiting NF-κB activation.

• 한국재료학회지
• /
• 제3권4호
• /
• pp.319-326
• /
• 1993

Hydroxide법으로 ${\alpha}$-주산산(stannic acid)을 만든후, 하고온도를 $500^{\circ}C$~$1100^{\circ}C$로 조정하여 일차입자(Crystallite)크기가 8-54nm인 $SnO_2$ 분말을 제작하였다. 분말의 입자(drystalite)클기에 따른 분말특성와 $H_2$, CO가스(0.5v/o)에 대한 감응성 미치공기중에서의 저상변화특성에 미치는 영향을 조사하였다. 입자크기가 감소함에 따라, 분말의 FTIR 흡습특성은 증가하였으나, 격자상수는 일정하였다. 후막소자에서, $H_2$가스에 대해 최대감도를 나타내는 온도와 공기중에서 최소저항을 나타내는 온도는 입자크기가 미세해짐에 따라 점차 낮아졌다. 최소저항점과 최대감도점의 온도저하를 산소흡착종의 활성화에너지의 감소라고 유추하였고, 이러한 에너지의 감소가 미세입자에 의한 감도향상요인 중의 한가지라고 제의하였다.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 추계학술발표대회
• /
• pp.43.2-43.2
• /
• 2011

Single-walled carbon nanotubes (SWCNT) are transparent in the visible and show conductivity comparable to copper, and are environmentally stable. SWCNT films have high flexibility, conductivity and transparency approaching that indium tin oxide (ITO), and can be prepared inexpensively without vacuum equipment. Transparent conducting Films (TCF) of SWCNTs has the potential to replace conventional transparent conducting oxides (TCO, e.g. ITO) in a wide variety of optoelectronic devices, energy conversion and photovoltaic industry. However, the sheet resistance of SWCNT films is still higher than ITO films. A decreased in the resistivity of SWCNT-TCFs would be beneficial for such an application. We fabricated SWCNT sheet with $KAuBr_4$ on PET substrate. Arc-discharge SWCNTs were dispersed in deionized water by adding sodum dodecyl sulfate (SDS) as surfactant and sonicated, followed by the centrifugation. The dispersed SWCNT was spray-coated on PET substrate and dried on a hotplate at $100^{\circ}C$. When the spray process was terminated, the TCF was immersed into deionized water to remove the surfactant and then it was dried on hotplate. The TCF film was then treated with AuBr4-, rinsed with deionized water and dried. The surface morphology of TCF was characterized by field emission scanning electron microscopy. The sheet resistance and optical transmission properties of the TCF were measured with a four-point probe method and a UV-visible spectrometry, respectively. $HNO_3$ treated SWCNT films with Au nano-particles have the lowest 61 ${\Omega}$/< sheet resistance in the 80% transmittance. Sheet resistance was decreased due to the increase of the hole concentration at the washed SWCNT surface by p-type doping of $AuBr_4{^-}$.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 추계학술발표대회
• /
• pp.16.2-16.2
• /
• 2011

Graphene has attracted significant attention due to its unique characteristics and promising nanoelectronic device applications. For practical device applications, it is essential to synthesize high-quality and large-area graphene films. Graphene has been synthesized by eloborated mechanical exfoliation of highly oriented pyrolytic graphite, chemical reduction of exfoliated grahene oxide, thermal decomposition of silicon carbide, and chemical vapor deposition (CVD) on metal substrates such as Ni, Cu, Ru etc. The CVD has advantages over some of other methods in terms of mass production on large-areas substrates and it can be easily separated from the metal substrate and transferred to other desired substrates. Especially, plasma-enhanced CVD (PECVD) can be very efficient to synthesize high-quality graphene. Little information is available on the synthesis of graphene by PECVD even though PECVD has been demonstrated to be successful in synthesizing various carbon nanostructures such as carbon nanotubes and nanosheets. In this study, we synthesized graphene on $Ni/SiO_2/Si$ and Cu plate substrates with CH4 diluted in $Ar/H_2$ (10%) by using an inductively-coupled PECVD (ICPCVD). High-quality graphene was synthesized at as low as $700^{\circ}C$ with 600 W of plasma power while graphene layer was not formed without plasma. The growth rate of graphene was so fast that graphene films fully covered on substrate surface just for few seconds $CH_4$ gas supply. The transferred graphene films on glass substrates has a transmittance at 550 nm is higher 94%, indicating 1~3 monolayers of graphene were formed. FETs based on the grapheme films transferred to $Si/SiO_2$ substrates revealed a p-type. We will further discuss the synthesis of graphene and doped graphene by ICPVCD and their characteristics.

• Transactions on Electrical and Electronic Materials
• /
• 제8권6호
• /
• pp.260-264
• /
• 2007

We have studied stability in organic light-emitting diode depending on buffer layer and cathode. A transparent electrode of indium-tin-oxide(ITO) was used as an anode. An electron injection energy barrier into organic material is different depending on a work function of cathodes. Theoretically, the energy barriers for the electron injection are 1.2 eV, -0.1 eV, and 0.0 eV for Al, LiAl, and LiF/Al at 300 K, respectively. We considered the cases that holes are injected to organic light-emitting diode. The hole injection energy barrier is about 0.7 eV between ITO and TPD without buffer layer. For hole-injection buffer layers of CuPc and PEDOT:PSS, the hole injection energy barriers are 0.4 eV and 0.5 eV, respectively. When the buffer layer of CuPc and PEDOT:PSS is existed, we observed the effects of hole injection energy barrier, and a reduction of operating-voltage. However, in case of PVK buffer layer, the hole injection energy barrier becomes high(1.0 eV). Even though the operating voltage becomes high, the efficiency is improved. A device structure for optimal lifetime condition is ITO/PEDOT:PSS/TPD/$Alq_3$/LiAl at an initial luminance of $300cd/m^2$.

• 자원리싸이클링
• /
• 제12권5호
• /
• pp.29-35
• /
• 2003

국내의 화력발전소에서 발생되는 Fly ash와 활성탄을 원료로 사용하여 환원질화방법에 의해 $\beta$-Sialon 분말을 합성하였다. 분말합성은 $1,450^{\circ}C$에서 10시간 동안 질소분위기에서 합성하였으며, 또한 소결체 제조는 $1,550^{\circ}C$에서 3시간 동안 관상로에서 소결하였다. 본 실험에서 합성된 $\beta$-Sialon의 z value는 2.15이었으며 XRD 분석결과 $\beta$-Sialon 이외에 소량의 $SiO_2$와 $_FeSi{x}$ 가 일부 확인되었다. $\beta$-Sialon 소결체는 20시간 동안의 고온산화 결과 1,31$0^{\circ}C$까지는 열적으로 매우 안정하나 $1,360^{\circ}C$ 부근에서는 급격한 무게의 증가를 나타냈다. $1,360^{\circ}C$에서 10시간 고온산화 후 산화층은 mullite로 상전이가 일어났다.

• Journal of Photoscience
• /
• 제1권1호
• /
• pp.31-37
• /
• 1994

Photoirradiation at > 300 nm onto a suspension of platinized TiO$_2$ (TiO$_2$-Pt) particles in an aqueous solution. of N$_{\varepsilon}$-carbamyI-L-lysine (Lys(CONH)$_2$) induced the selective N-cyclization of Lys(CONH$_2$) into almost optically pure L-pipecolinic acid (PCA) under argon atmosphere at ambient temperature. Among various TiO$_2$-Pt catalysts, a P-25 (Degussa) powder platinized via impregnation from chloroplatinic acid followed by hydrogen reduction at 753 K exhibited the highest photocatalytic activity for Lys(CONH$_2$) consumption and L-PCA production. GC-MS analyses of L-PCA obtained photocatalytically from $^{15}$N$\alpha$-Lys(CONH$_2$) revealed the selective formation $^{15}$N-substituted L-PCA. This implies that the mechanism for L-PCA production contains selective cleavage of C$_{\varepsilon}$-N bond and intramolecular alkylation at $\alpha$-amino group. Effect of pH on the rate of this photocatalytic reaction was investigated in detail and compared with the pH-dependent charge distribution in Lys(CONH$_2$) molecule. It is clarified that protonation-deprotonation of $\alpha$-amino group gives marked influence on the rate and selectivity of the photocatalytic reaction. On the basis of these results, it is concluded that the selective production of optically pure L-PCA, especially in an acidic suspension of TiO$_2$-Pt, was attributed to the enhanced protonation of $\alpha$-amino group to prevent undesirable oxidation by photogenerated positive holes and blocking of $\varepsilon$-amino group to yield racemic Schiff base intermediate.

• 대한한방내과학회지
• /
• 제26권2호
• /
• pp.379-389
• /
• 2005

Objectives: It is well known that aging and aging-related diseases are linked to the increased level of oxidative stress caused by reactive oxygen species(ROS) and reactive nitrogen species(RNS). Nonprotein-SH decreases during aging, while substances such as ROS, nitric oxide(NO), peroxynitrite($ONOO^-$), myeloperoxidase(MPO), and dityrosine show a significant increase. This study investigated the effect of Ichungwhan on the aging process by examining its effect on the generation of the above-mentioned substances. Methods: Four comparison groups of SD rats were used. They were 6 month-old rats, 24 month-old rats, and 24 month-old rats fed with food containing 0.1% and 0.3% of Ichungwhan extract. The amount of NO, $ONOO^-$, and ROS in the rats' kidneys were examined using a fluorescence microplate reader. The reagents used for this purpose include: dihydrorhodamine 123 (DHR 123), 2',7' -dichlorodihydrofluorescein, diacetate(DCFDA), and 4,5-diaminofluorescein(DAF-2). A spectrophotometer was used to investigate the reactivity of nonprotein-SH and myeioperoxidase(MPO), using reagents such as trichloroacetic acid(TCA) and tetramethylbenzidine(TMB). The amounts of MPO protein and dityrosine were measued by western blot. Results: The observed effects of Ichungwhan on rats were as follows: increase of nonprotein-SH; effective decrease of RNS level by suppression of the generation system of $ONOO^-$ and NO; decrease of ROS level; decrease of the MPO reactivity and the subsequent reduction of amount of MPO protein; retardation of dityrosine formation. It can be hypothesized, therefore, that Ichungwhan affects both the earlier and later phases of the molecular inflammatory process, and retards the aging process. Conclusions: Empirical evidence in this study supports a role for Ichungwhan in generation mechanisms of aging process-linked substances ROS, NO, $ONOO^-$, nonprotein-SH, MPO and dityrosine. Affects contrary to the aging process observed in rats beg further empiricism to investigate potential application of Ichungwhan as a medication for age-related diseases in humans.

• 센서학회지
• /
• 제23권5호
• /
• pp.337-341
• /
• 2014

For various additives doped-$VO_2$ critical temperature sensors using the nature of semiconductor to metal transition, the crystallinity, microstructure, and temperature vs. resistance characteristics were systematically investigated. As a starting material of $VO_2$ sensor, vanadium pentoxide ($V_2O_5$) powders were used, and CaO, SrO, $Bi_2O_3$, $TiO_2$, and PbO dopants were used, respectively. The $V_2O_5$ powders with dopants were mixed with a vehicle to form paste. This paste was silk screen-printed on $Al_2O_3$ substrates and then $V_2O_5$-based thick films were heat-treated at $500^{\circ}C$ for 2 hours in $N_2$ gas atmosphere for the reduction to $VO_2$. From X-ray diffraction analysis, $VO_2$ phases for pure $VO_2$, and CaO and SrO-doped $VO_2$ thick films were confirmed and their grain sizes were 0.57 to $0.59{\mu}m$. The on/off resistance ratio of the $VO_2$ sensor in phase transition temperature range was $5.3{\times}10^3$ and that of the 0.5 wt.% CaO-doped $VO_2$ sensor was $5.46{\times}10^3$. The presented critical temperature sensors could be commercialized for fire-protection and control systems.