Study on the uniformity of water film in a transpiring wall reactor for supercritical water oxidation

A three-dimensional computational fluid dynamic model of a transpiring wall reactor for supercritical water oxidation has been built to optimize the uniformity of water film. Results show that the temperature and species distributions at the nozzle outlet deviate from the reactor centre. The inner wall of the porous tube near the transpiring water injection tube displays low temperatures, while high temperatures are recorded far from the injection tube. The circumferential temperature distribution on the inner wall of the porous tube is uneven. This phenomenon is due to the uneven injection of the transpiring water, leading to the uneven protection of the water film and local overheating of the porous wall. The injection velocity of the transpiring water significantly decreases when the number of injection tubes is increased, and the circumferential velocity and temperature distributions on the porous wall gradually become even. Moreover, high pressure drops across the porous wall at low porosities are useful for the uniform injection of the transpiring water. This characteristic is also conducive to obtaining a more uniform water film protection.     

Effect of <i>Lycopus lucidus</i> Turcz. supplementation on gut microflora and short chain fatty acid composition in Crj: CD-1 mice

We investigated the diversity and composition of microflora in feces of Lycopus lucidus Turcz.-fed mice. In addition, we evaluated the production of major cytokines (Interleukin-6 and -10) which are related to inflammation and fatty acid composition of several tissues. 16S ribosomal DNA sequencing-based microbiome taxonomic profiling analysis was performed utilizing the EzBioCloud data base. Male mice fed on L. lucidus showed a significantly reduced number of lactic acid bacteria and coliform in the feces compared with the control group (p < 0.05). 16S rDNA sequencing analysis of fecal samples showed that L. lucidus supplementation decreased the community of harmful microflora (Enterobacteriaceae including Escherichia coli and Bacteroides sp.) in feces compared with the control group (p < 0.05). There were no significant differences in mRNA expression of cytokine IL-6 and IL-10 between the control and L. lucidus fed groups. The fecal fatty acid composition in the L. lucidus group had percentages of 4:0, 6:0, 8:0 and 10:0 in the intestine but those short chain fatty acids were not detected in the control group. Our results showed that L. lucidus supplementation influenced gut environment by decreasing harmful microflora and increased the percentages of several short fatty acids.     

真空热处理炉布料矩阵优化仿真分析

为了获得更高的加热效率和更好的温度均匀性,采用有限元软件建立了真空热处理炉加热过程仿真模型,并耦合PID算法用于温度控制。通过与实测温度对比,验证了仿真模型的准确性。借助该模型,模拟研究了布料矩阵对两种典型形状零件在真空热处理炉内加热特性的影响。模拟装炉时基于零件几何形状特征,对圆棒形工件采用顺排、叉排和环形排列3种形式,对圆盘形工件采用横排式和竖排式。研究结果表明:尽管零件形状和数量相同,但是随着布料矩阵的变化,加热效率和温度均匀性都会改变。对于圆棒形工件,采用环形排列不仅可以提高内部工件的加热速率,而且相较于叉排式可以将最大温差减小36 ℃;对于圆盘形工件,由水平式改为竖直式布料可以将最大温差由248 ℃减小至171 ℃。     

Rational design of thermally stable polymorphic layered cathode materials for next generation lithium rechargeable batteries

Classical layered transition metal oxides have remained the preferred cathode materials for commercial lithium-ion batteries. Variation in the transition metal composition and local ordering can greatly affect the structure stability. In classical layered cathodes, high concentrations of electrochemically inert Mn elements usually act as a pillar to stabilize the structure. When excess amount of Li and Mn are present in the layered structure, the capacity of the Li-rich layered oxide (molar ratio of lithium over transition metal is larger than one by design) can exceed that expected from transition metal redox. However, the over lithiation in the classical layered structure results in safety issues, which remains challenging for the commercialization of Li-rich layered oxides. To characterize the safety performance of a series of Li-rich layered cathodes, we utilize differential scanning calorimeter and thermal gravimetric analysis; this is coupled with local structural changes using in situ temperature dependent synchrotron X-ray diffraction and X-ray adsorption spectroscopy. These methods demonstrate that the gradual decrease of the Mn–M (M = Ni, Co, Mn and Li) coordination number directly reduces structural stability and accelerates oxygen release. For safety characterization tests in practice, we evaluate the thermal runaway process through accelerating rate calorimeter in 1.0 Ah pouch cells to confirm this trend. Using the insights obtained in this work, we design a polymorphic composition to improve the thermal stability of Li-rich layered cathode material, which outperforms Ni-rich layered oxides in terms of both electrochemical and safety performances.     

Influence of nitrogen impurities on the characteristics of a patterned helium dielectric barrier discharge at atmospheric pressure

In this paper, a two-dimensional axisymmetric fluid model was established to investigate the influence of nitrogen impurity content on the discharge pattern and the relevant discharge characteristics in an atmosphere pressure helium dielectric barrier discharge (DBD). The results indicated that when the nitrogen content was increased from 1 to 100 ppm, the discharge pattern evolved from a concentric-ring pattern into a uniform pattern, and then returned to the concentricring pattern. In this process, the discharge mode at the current peak moment transformed from glow mode into Townsend mode, and then returned to glow mode. Further analyses revealed that with the increase of impurity level, the rate of Penning ionization at the pre-ionization stage increased at first and decreased afterwards, resulting in a similar evolution pattern of seed electron level. This evolution trend was believed to be resulted from the competition between the N₂ partial pressure and the consumption rate of metastable species. Moreover, the discharge uniformity was found positively correlated with the spatial uniformity of seed electron density as well as the seed electron level. The reason for this correlation was explained by the reduction of radial electric field strength and the promotion of seed electron uniformity as pre-ionization level increases. The results obtained in this work may help better understand the pattern formation mechanism of atmospheric helium DBD under the variation of N₂ impurity level, thereby providing a possible means of regulating the discharge performance in practical application scenarios.     

CaO-SiO2-FeO-Cr2O3-MgO-MnO渣系物相组成的热力学计算

摘要：在含铬铁水转炉冶炼过程中，Cr很容易被氧化成Cr2O3进入渣中，并与渣中其他成分反应生成高熔点含铬尖晶石。采用FactSage热力学软件计算了CaO-SiO2-FeO-Cr2O3-MgO-MnO转炉渣系在冶炼温度1300～1700℃下的物相组成，研究了Cr2O3、FeO和碱度对炉渣中尖晶石相含量的影响规律。研究结果表明，温度和渣系成分都会影响炉渣的物相组成。渣系中含有Cr2O3时，物相中均含有MgCr2O4、FeCr2O4和MgFe2O4尖晶石相，尖晶石相的总含量随着Cr2O3和碱度的增加而增加，随着炉温的升高而减少。温度为1300～1500℃时，炉渣中尖晶石含量随着FeO的增加而增加；温度为1500～1700℃时，尖晶石含量随着FeO的增加而略有减少。在温度小于1500℃的转炉冶炼前中期，炉渣物相组成中尖晶石相所占比例较大，易造成化渣不良或者炉渣粘稠，影响转炉冶炼工艺的顺行。     

烘烤条件对奇亚籽油理化性质及脂肪酸组成的影响

对奇亚籽进行烘烤、压榨取油,测定不同烘烤条件(温度、时间)下奇亚籽油的理化性质及脂肪酸组成,探讨烘烤温度和时间的影响。结果表明:随着烘烤温度的升高和烘烤时间的延长,奇亚籽油色泽加深,酸价、过氧化值、K_(232)、K_(268)均呈现上升趋势,且180℃烘烤50 min以上较其他条件下显著升高(p0.05);烘烤条件对脂肪酸组成无影响。故烘烤奇亚籽不宜在高温下进行,若采用180℃烘烤时,则时间不应超过50 min。     

Saccharomyces cerevisiae and Hanseniaspora uvarum mixed starter cultures: Influence of microbial/physical interactions on wine characteristics

The growing trend in the wine industry is the revaluation of the role of non-Saccharomyces yeasts, promoting the use of these yeasts in association with Saccharomyces cerevisiae. Non-Saccharomyces yeasts contribute to improve wine complexity and organoleptic composition. However, the use of mixed starters needs to better understand the effect of the interaction between these species during alcoholic fermentation. The aim of this study is to evaluate the influence of mixed starter cultures, composed by combination of different S. cerevisiae and Hanseniaspora uvarum strains, on wine characteristics and to investigate the role of cell-to-cell contact on the metabolites produced during alcoholic fermentation. In the first step, three H. uvarum and two S. cerevisiae strains, previously selected, were tested during mixed fermentations in natural red grape must in order to evaluate yeast population dynamics during inoculated fermentation and influence of mixed starter cultures on wine quality. One selected mixed starter was tested in a double-compartment fermentor in order to compare mixed inoculations of S. cerevisiae/H. uvarum with and without physical separation. Our results revealed that physical contact between S. cerevisiae and H. uvarum affected the viability of H. uvarum strain, influencing also the metabolic behaviour of the strains. Although different researches are available on the role of cell-to-cell contact-mediated interactions on cell viability of the strains included in the mixed starter, to our knowledge, very few studies have evaluated the influence of cell-to-cell contact on the chemical characteristics of wine.     

低压环境下航空电缆材料燃烧特性的研究

在高高原实验室(61 kPa、4 290 m)和广汉实验室(96 kPa、520 m),分别开展常低压条件下FXL型航空电缆的对比燃烧实验。通过热辐射加热箱、烟密度及成分测试仪和氧指数仪等设备,测量点燃时间、烟密度、质量损失速率和CO、CO2及O2等浓度变化。实验结果表明:在96 kPa和61 kPa两种实验环境下,低压下最小点燃时间及温度的数值更大,两者的温度和时间差分别为15℃和4.8 s;烟密度曲线快速升高后趋于平衡,61 kPa条件下的发烟量小于96 kPa;O2体积浓度随着加热时间先下降后升高,而CO2的变化趋势相反。在61 kPa条件下,CO曲线会出现双峰现象且更明显;随着氧浓度增加,质量损失速率加快且呈线性关系;压力因素对燃烧影响减弱且燃烧持续时间差值变小。研究结果揭示了低压环境对航空电缆的燃烧影响,为增强航空安全提供参考。