http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Kim, Chungman,Kim, Soohyun,Hong, Yang-Ki,Oh, Min-Wook,Jung, Myung-Hwa Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.690 No.-
<P><B>Abstract</B></P> <P>Single crystals of Mg<SUB>2−<I>x</I> </SUB>Mn<SUB> <I>x</I> </SUB>Si (<I>x</I> = 0, 0.1, 0.2, 0.3, and 0.4) were prepared using a vertical Bridgman method. The formation of desired materials was confirmed using single-crystal and powder X-ray diffraction. The thermoelectric and magnetic properties were investigated for various Mn contents in the temperature range between 2 and 300 K and in magnetic fields up to 70 kOe. For various <I>x</I> values, Mg<SUB>2−<I>x</I> </SUB>Mn<SUB> <I>x</I> </SUB>Si with <I>x</I> = 0.2 possesses the highest figure of merit. The experimental results revealed that the substitutional Mn atoms exhibit mixed valences of +3 (majority) and +2, giving rise to dramatic changes of carrier density and magnetic interaction. At the same time, the Seebeck coefficient and magnetic susceptibility show a sudden change at the same temperature. These results imply that the thermoelectric properties are correlated with the magnetic properties in the Mg<SUB>2−<I>x</I> </SUB>Mn<SUB> <I>x</I> </SUB>Si crystals.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Single crystals of Mg<SUB>2−x</SUB>Mn<SUB>x</SUB>Si were prepared by using a vertical Bridgman method. </LI> <LI> The thermoelectric performance was improved as doping Mn into Mg<SUB>2</SUB>Si. </LI> <LI> The magnetic properties were enhanced with Mn dopants. </LI> <LI> The thermoelectric and magnetic properties were strongly correlated in Mg<SUB>2−x</SUB>Mn<SUB>x</SUB>Si. </LI> </UL> </P>
Continuous performance of hydrogenotrophic methanogenic mixed cultures: Kinetic and SMP analysis
Kim, Mi-Sun,Moon, Chungman,Kang, Seoktae,Kim, Dong-Hoon Elsevier 2017 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.42 No.45
<P><B>Abstract</B></P> <P>To investigate the characteristics of hydrogenotrophic methanogenic (HM, 4H<SUB>2</SUB> + CO<SUB>2</SUB> → CH<SUB>4</SUB> + 2H<SUB>2</SUB>O) mixed cultures, continuous stirred-tank reactors (CSTRs) were operated at various H<SUB>2</SUB> loading rates (HLR, 2.8–14.0 m<SUP>3</SUP> H<SUB>2</SUB>/m<SUP>3</SUP>/d) and hydraulic retention times (HRTs, 5–30 d). The feeding gas was composed of H<SUB>2</SUB>/CO<SUB>2</SUB> (80:20 on volume basis), and HRT was controlled by the continuous pumping of a nutrient medium. At a fixed HLR of 4 kg COD/m<SUP>3</SUP>/d (1 kg COD = 1.4 m<SUP>3</SUP> H<SUB>2</SUB>), complete H<SUB>2</SUB> conversion to CH<SUB>4</SUB> (> 98% on a COD basis) was observed up to the HRT decrease to 6 d. However, at HRT 5 d, the H<SUB>2</SUB> conversion gradually decreased, reaching 30% within 30 d, and the H<SUB>2</SUB> content in the head space increased to 70%, which triggered the production of acetate with an increased concentration to 3 g COD/L. When the HLR was increased at a fixed HRT of 10 d, the maximum CH<SUB>4</SUB> production rate of 2.75 m<SUP>3</SUP> CH<SUB>4</SUB>/m<SUP>3</SUP>/d was achieved at 8 kg COD/m<SUP>3</SUP>/d. A kinetic analysis conducted using the Monod equation showed that HM cultures had a maximum specific growth rate of 0.18 d<SUP>−1</SUP> and a half-saturation coefficient of 1.73 g COD/L. Though, successful hydrogenotrophic CH<SUB>4</SUB> conversion was achieved, the broth contained soluble microbial products (SMPs) at a concentration of 80–250 mg/L, which exceeded the effluent regulation standard. Most of the organic matters in SMPs consisted of humic-like and fulvic-like organic matters with a low molecular weight (<1 kDa).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Investigate the characteristics of hydrogenotrophic methanogens. </LI> <LI> CSTR operation at various H<SUB>2</SUB> loading rates and HRTs. </LI> <LI> Complete H<SUB>2</SUB> conversion to CH<SUB>4</SUB> up to the HRT decrease to 6 d. </LI> <LI> Maximum CH<SUB>4</SUB> production rate of 2.75 m<SUP>3</SUP> CH<SUB>4</SUB>/m<SUP>3</SUP>/d at 8 kg COD/m<SUP>3</SUP>/d. </LI> <LI> Maximum specific growth rate = 0.18 d<SUP>−1</SUP>, half-saturation coefficient = 1.73 g COD/L. </LI> </UL> </P>
Effect of the accuracy of pH control on hydrogen fermentation
Moon, Chungman,Jang, Sujin,Yun, Yeo-Myeong,Lee, Mo-Kwon,Kim, Dong-Hoon,Kang, Won-Seok,Kwak, Seung-Shin,Kim, Mi-Sun Elsevier 2015 Bioresource technology Vol.179 No.-
<P><B>Abstract</B></P> <P>pH, known as the most important parameter in H<SUB>2</SUB> fermentation, cannot be precisely controlled in a scaled-up fermenter as in a lab fermenter. In the preset work, to assess the effect of pH control accuracy on H<SUB>2</SUB> fermentation, the pH was controlled at 6.0±0.1, 6.0±0.3, 6.0±0.5, 6.0±0.7, and 6.0±0.9 during batch fermentation of food waste. Up to deviation of ±0.3, a high H<SUB>2</SUB> yield of 1.67–1.73molH<SUB>2</SUB>/mol hexose<SUB>added</SUB> was attained with producing butyrate as a major metabolite (>70% of total organic acids produced). A huge drop of H<SUB>2</SUB> production, however, was observed at deviation >±0.5 with lowered substrate utilization and increased production of lactate. Next generation sequencing results showed that <I>Clostridium</I> was found to be the dominant genus (76.4% of total number of sequences) at deviation of ±0.1, whereas the dominant genus was changed to lactic acid bacteria such as <I>Streptococcus</I> and <I>Lactobacillus</I> with increase of deviation value.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A significant effect of pH control accuracy on H<SUB>2</SUB> fermentation performance. </LI> <LI> High H<SUB>2</SUB> yield and substrate utilization at deviation of ±0.1 and ±0.3. </LI> <LI> Low H<SUB>2</SUB> production with lowered substrate utilization at deviation >±0.5. </LI> <LI> Lactic acid bacteria became dominant with increase of deviation value. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>