• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.786-794
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• 2022

Green ammonia is a promising renewable energy carrier. Green ammonia can be used in various energy conversion devices (e.g., engine, fuel cell, etc.). Ammonia has to be fed with hydrogen for start-up and failure protection of some energy conversion devices. Ammonia can be converted into hydrogen by decomposition and partial oxidation. Especially, partial oxidation has the advantages of fast start-up, thermally self-sustaining operation and compact size. In this paper, thermodynamics, start-up and operation characteristics of ammonia partial oxidation were investigated. O₂/NH₃ ratio, ammonia flow rate and catalyst volume were varied as operation parameters. In thermodynamic analysis, ammonia conversion was maximized in the O₂/NH₃ range from 0.10 to 0.15. Ammonia partial oxidation reactor was successfully started using 12 V glow plug. At 0.13 of O₂/HN₃ ratio and 10 LPM of ammonia flow rate, ammonia partial oxidation reactor showed 90% of ammonia conversion over commercial Ru catalyst. In addition, Increasing O₂/NH₃ ratio from 0.10 to 0.13 was more effective for high ammonia conversion than increasing catalyst volume at 0.10 of O₂/NH₃.

• Carbon letters
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• 제4권3호
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• pp.121-125
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• 2003

The Pt-Ru/Carbon as an anode catalyst supported on the commercial activated carbon (AC) having high surface area and micropore was characterized for application of Direct Methanol Fuel Cell (DMFC). The Pt-Ru/AC anode catalyst used in this experiment showed the performance of $600\;mA/cm^2$ current density at 0.3 V. The borohydride reduction process using $NaBH_4$, denoted as a process A, showed much higher current and power densities than process B prepared by changing the reduction and washing process of process A. The particle sizes are strongly affected by the reduction process than the specific surface area of raw active carbon and the sizes are almost constant when the specific surface area of carbon are over than the $1200\;m^2/g$. Smaller particle size of catalyst and more narrow intercrystalite distance increased the performance of DMFC.

• BMB Reports
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• 제38권1호
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• pp.104-110
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• 2005

We extended the measurable time scale of DNA dynamics to microsecond using $[Ru(phen)_2(dppz)]^{2+}$ (phen = 1,10-phenanthroline, dppz = dipyrido[3,2-a:2',3'-c]phenazine) (RuPD), which displays a mean lifetime near 500 ns. To evaluate the usefulness of this luminophore (RuPD) for probing nucleic acid dynamics, its intensity and anisotropy decays when intercalated into supercoiled and linear pBluescript (pBS) II SK(+) phagemids were examined using frequency-domain fluorometry with a blue light-emitting diode (LED) as the modulated light source. The mean lifetime for the supercoiled phagemids (< $\tau$ > = 489.7 ns) was somewhat shorter than that for the linear phagemids (< $\tau$ > = 506.4 ns), suggesting a more efficient shielding from water by the linear phagemids. The anisotropy decay data also showed somewhat shorter slow rotational correlation times for supercoiled phagemids (997.2 ns) than for the linear phagemids (1175.6 ns). The slow and fast rotational correlation times appear to be consistent with the bending and torsional motions of the phagemids, respectively. These results indicate that RuPD can have applications in studies of both bending and torsional dynamics of nucleic acids.

• 한국정보통신학회논문지
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• 제16권10호
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• pp.2085-2094
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• 2012

본 논문에서는 다수 무선 접속 기술 (Radio Access Technology; RAT)이 통합되어 운용되는 셀룰러 네트워크에서 차세대 이동통신 네트워크 진화 방향인 디지털 유닛 (DU)-라디오 유닛 (RU) 분리 구조를 기본으로 무선 액세스 네트워크 가상화 알고리즘을 제안한다. 제안 무선 액세스 네트워크 가상화 알고리즘은 크게 기본 액세스 네트워크 가상화, RAT 가상화, 액세스 경로 이주 알고리즘으로 구성되고, 순차적인 수행을 통하여 최종 무선 액세스 네트워크 가상화가 이루어진다. 제안 무선 액세스 네트워크 가상화 알고리즘은 3GPP LTE와 WiMAX의 두 무선 접속 기술을 예제로 한 시스템 레벨 시뮬레이션을 통하여 시스템 수율 측면에서 성능이 평가된다. 이 때, 네트워크 트래픽 로드의 비대칭성에 따른 두 가지 시나리오를 고려하고, 제안 무선 액세스 네트워크 가상화 알고리즘은 비대칭적 네트워크 트래픽 로드와 사용자 분포 상황에서도 상당한 성능 이득을 성취한다.

• 동아시아식생활학회지
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• 제1권1호
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• pp.99-111
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• 1991

In each nuruk using today, effect of pH on glucoamylase activity and viable cell count of yeast and bacteria was measured. Common components during fermentation, alcohol, acetaldehyde and acetone, amino acid composition, and total sugars and mineral content were determined in yakju(korean wine) brewed from different ingredients and by different methods. Results are summarized as follows ; 1. The lower the pH, the lower the glucoamylase activity in JK, BK, JK-S BK-S and JN. But the higher the glucoamylase activity ratio in Koji and KN. 2. Yeast and bacteria cell count could not determined in nuruk inoculated of seed. In JK, BK and JN, yeast cell count was 50${\times}$104∼80${\times}$104, bacteria cell count was 5${\times}$106∼24${\times}$106. 3. In yakju during fermentation, pH was higher in RU, total acidity content was higher in ST-N, ST-K, RU and ST-RUPO and alcohol content was lower in RUPO and ST-RUPO. 4. Ethanol and acetaldehyde content were highest in dukyunju. Trace amount of acetone was determined only in ST-K, RUPO and ST-RUPO . n-Propyl alcohol content was higher in ST-K, ST-RUPO and ST-N, iso-butyl alcohol content was higher in L-RUPO, Dukyunju and Songyupju and iso-amyl alcohol content was higher in Songyupju, RU, L-RUPO and Dukyunju. 5. In amino acids composition of each yakju, Pro, Ala and Val content was higher than other amino acids. Total amino acids content was the highest in Dukyunju and second highest in ST-N, NH3 was higher in ST-N, Dukyunju, RUPO than other samples. 6. Total sugars content was the highest in ST-N and second highest in RU. 7. P, K and Mg content were higher in Dukyunju and ST-N than in other samples. In Dukyunju, Ca and P ratio was 0.075 because of low Ca content and high P content.

• 공업화학
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• 제34권2호
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• pp.180-185
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• 2023

물의 전기 분해 효율을 향상시키기 위해 산소발생반응(OER)의 반응 속도를 가속화하며 고성능과 장기 안정성을 가진 OER 전기촉매 개발이 필수적이다. 본 연구에서는 고효율의 OER 전기촉매를 합성하기 위해 중공 금속-유기골격체 (MOF)로부터 유도된 루테늄-코발트 산화물 촉매를 개발하였다. 합성된 촉매는 루테늄의 표면 노출을 증대시킴으로 낮은 Tafel 기울기와 10 mA/cm²의 전류밀도에서 386 mV의 낮은 과전위가 관찰되었다. 또한 상용 RuO₂ 촉매 대비 높은 질량 활성과 안정성을 보여, 귀금속 촉매를 대체할 수 있을 것으로 기대된다.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.421-425
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• 2013

The effect of pretreatment on indium-tin oxide (ITO) electrodes has been rarely studied, although that on metal and carbon electrodes has been enormously done. The electrochemical and surface properties of ITO electrodes are investigated after 6 different pretreatments. The electrochemical behaviors for oxygen reduction, $Ru(NH_3){_6}^{3+}$ reduction, $Fe(CN){_6}^{3-}$ reduction, and p-hydroquinone oxidation are compared, and the surface roughness, hydrophilicity, and surface chemical composition are also compared. Oxygen reduction, $Fe(CN){_6}^{3-}$ reduction, and p-hydroquinone oxidation are highly affected by the type of the pretreatment, whereas $Ru(NH_3){_6}^{3+}$ reduction is almost independent of it. Interestingly, oxygen reduction is significantly suppressed by the treatment in an HCl solution. The changes in surface roughness and composition are not high after each pretreatment, but the change in contact angle is substantial in some pretreatments.

• 전기학회논문지
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• 제67권4호
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• pp.543-548
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• 2018

Ferroelectric $Bi_4Ti_3O_{12}$ films were deposited on $SrTiO_3(100)$ and Si(100) substrate by using conductive $SrRuO_3$ films as underlayer, and their ferroelectric and electrical properties were investigated depending on crystal structure and orientation. C-axis oriented $Bi_4Ti_3O_{12}$ films were grown on well lattice-matched pseudo-cubic $SrRuO_3$ films deposited on $SrTiO_3(100)$ substrate, while random-oriented polycrystalline $Bi_4Ti_3O_{12}$ films were grown on $SrRuO_3$ films deposited on Si(100) substrate. The random-oriented polycrystalline film showed a good ferroelectric hysteresis property with remanent polarization ($P_r$) of $9.4{\mu}C/cm^2$ and coercive field ($E_c$) of 84.9 kV/cm, while the c-axis oriented film showed $P_r=0.64{\mu}C/cm^2$ and $E_c=47kV/cm$ in polarizaion vs electric field curve. The c-axis oriented $Bi_4Ti_3O_{12}$ film showed a dielectric constant of about 150 and lower thickness dependence in dielectric constant compared to the random-oriented film. Furthermore, the c-axis oriented $Bi_4Ti_3O_{12}$ film showed leakage current lower than that of the polycrystalline film. The difference of ferroelectric properties in two films was explained from the viewpoint of depolarization effect due to orientation of spontaneous polarization and layered crystal structure of bismuth-base ferroelectric oxide.

• 한국자기학회지
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• 제15권6호
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• pp.315-319
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• 2005

본 연구에서는 자기터널접합(MTJs; magnetic tunnel junctions)의 스위칭 자기장($H_{SW}$)을 감소시키기 위하여 자유층으로 비정질 강자성 $Co_{70.5}Fe_{4,5}Si_{15}B_{10}$ 단일(single) 및 합성형 반강자성(SAF; synthetic antiferromagnet) 층을 사용하였다. $Si/SiO_2/Ta$ 45/Ru 9.5/IrMn 10/CoFe 7/AlOx/CoFeSiB 7 or CoFeSiB (t)/Ru 1.0/CoFeSiB (7-t)/Ru 60 (in nm) MTJs의 자기저항과 스위칭 특성을 CoFe 자유층과 NiFe 자유층을 갖는 MTJs와 비교하여 조사하였다. CoFeSiB은 포화자화($M_s$)가 $560\;emu/cm^3$으로 CoFe보다 낮고, 이방성 상수(Ku)는 $2800 erg/cm^3$으로 NiFe보다 높다. CoFeSiB SAF 구조에서 CoFeSiB 사이의 Ru 두께가 1.0 nm일 때 교환결합에너지($J_{ex}$)는 $-0.003erg/cm^2$였다. 이와 같이 비교적 작은 $J_{ex}$ 때문에, CoFeSiB SAF 자유층을 갖는 MTJs의 실험 및 Landau-Lisfschitz-Gilbert(LLG)식에 의한 시뮬레이션 결과 모두에서 $H_{SW}$가 접합크기에 의존하는 경향을 보였다. CoFeSiB SAF 자유층 MTJ의 $H_{SW}$는 CoFe, NiFe 또는 CoFeSiB single을 자유층으로 하는 MTJs에 비해 훨씬 낮게 나타났다. 따라서 CoFeSiB SAF를 자유층으로 사용한 MTJ는 micrometer에서 submicrometer 크기 영역 모두에서 보지적의 감소와 민감도 증가와 같은 우수한 스위칭 특성을 갖는 것을 확인하였다.

• Korean Chemical Engineering Research
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• 제48권2호
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• pp.275-282
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• 2010

아염소산나트륨($NaClO_2$)의 무격막 전기분해(un-divided electrolysis)에 의한 이산화염소(chlorine dioxide; $ClO_2$) 제조에서 양전극(anode) 재질에 따른 이산화염소수 발생특성을 조사하였다. 양전극으로는 $IrO_2$-coated Ti, $RuO_2$-coated Ti, DSA(dimensionally stable anode) 전극을 사용하였으며, 음전극으로는 Pt-coated Ti 전극을 사용하였다. 다양한 양전극을 사용한 무격막 전해셀(un-divided electrochemical cell) 시스템에서 이산화염소의 전구체인 아염소산나트륨 ($NaClO_2$) 농도, 전해질로 사용된 염화나트륨(NaCl) 농도 그리고 전구체 용액의 전해셀 체류시간(cell residence time;$t_R$), 전구체 용액의 초기 pH 그리고 무격막 전해셀에 공급된 전류(current; A)와 같은 운전 파라미터가 이산화염소수 발생에 미치는 영향을 조사하고 최적 운전조건을 도출하였다. $IrO_2$-coated Ti, $RuO_2$-coated Ti 그리고 DSA 양전극 시스템에서 최적 전해셀 체류시간은 각각 약 2.27, 1.52, 1.52 s, 전구체 용액의 초기 pH는 약 2.3, 최적 아염소산나트륨 농도는 $IrO_2$-coated Ti와 $RuO_2$-coated Ti 양전극 시스템이 약 0.43 g/L, DSA 양전극 시스템이 약 0.32 g/L 그리고 최적전해질 농도는 약 5.85 g/L로 나타났으며 무격막 전해셀에 공급된 최적 전류는 약 0.6 A로 나타났다. 산출된 최적 무격막 전해셀 조건에서 이산화염소수 발생을 위한 $IrO_2$-coated Ti, $RuO_2$-coated Ti 그리고 DSA 양전극 시스템의 전류효율(current efficiency; C.E.%)과 에너지 소모율(energy consumption; E.C. $W{\cdot}hr/g-ClO_2$)은 각각 약 79.80, 114.70, 70.99% 그리고 1.38, 1.03, $1.61W{\cdot}hr/g-ClO_2$로 나타났다.