向日葵茎髓提取物的抑菌活性及机制

以向日葵茎髓为原料,制得3种不同极性向日葵茎髓提取物。采用琼脂扩散法测定3种不同极性向日葵茎髓提取物对4种受试菌的抑菌活性;并以其中的金黄色葡萄球菌和大肠杆菌为研究对象,探讨了乙酸乙酯萃取部位(EE)的抑菌机制。结果显示:不同极性萃取部位对4种受试菌均有一定抑制作用。其中,EE处理金黄色葡萄球菌和大肠杆菌的最低抑菌质量浓度(MIC)均为0.78 g/L,半数抑制质量浓度(IC50)分别为(1.11?0.01)和(1.59?0.03)g/L;抑菌作用与其总酚、总黄酮含量呈显著正相关性(P0.05)。通过SEM分析发现,EE处理引起菌体形态变化,破坏菌体的细胞膜结构;EE可增加金黄色葡萄球菌和大肠杆菌细胞膜结构的通透性,使菌体内的电解质、蛋白质、碱性磷酸酶向胞外泄露;应用4?,6-二脒基-2-苯基吲哚(DAPI)染色和荧光检测发现,EE能干扰细菌遗传物质(DNA)的复制,最终抑制受试菌增殖。     

电控LPG点燃式发动机冷起动过程瞬态NO排放特性研究

使用瞬态NO气体分析仪,结合其它发动机参数,研究缸内燃烧过程.试验结果表明NO排放可以成为判断缸内燃烧的新依据.冷起动过程中瞬态NO排放主要集中在初始的几个循环中,而发动机转速稳定后,后续循环瞬态NO排放逐渐降低.冷起动过程中,混合气浓度保持不变时,瞬态NO排放随点火角度的提前而增加.     

利用STAR-CD软件分析2气门直喷式柴油机的螺旋气道

简单叙述2气门直喷式柴油机发展现状，针对2气门直喷式柴油机的螺旋进气道的流场以及压力场等运用STAR-CD软件进行模拟并分析。     

两种透平叶栅流场二次流特性及其涡系结构的可视化实验研究

本文应用 Ｔｉ Ｃｌ４ 烟迹法和表面油膜法对两种透平叶栅二次流特性及其涡系结构进行了流场可视化研究,深入地分析了叶栅端壁及叶栅型面的流动,揭示了叶栅二次流涡系的结构与叶型形状的关系以及马蹄涡吸力面分支和吸力面角涡的发生演变情况。     

高氮量硝化棉的脱硝反应动力学研究(英文)

用实时测定凝聚相分解产物的固体原位反应池/快速扫描傅立叶变换红外光谱热技术研究了高氮量硝化棉(14.14%N)的脱硝反应动力学。该反应的动力学参数(活化能和指前因子)用改良的Coats-Redfern法计算。根据所得结果,提出了在403～465K温度范围内描述高氮量硝化棉脱硝反应的微分动力学方程。     

泡沫铝夹芯板粉末冶金发泡机理的SR-CT研究

利用同步辐射装置的SR-CT,通过图像的断层扫描及3D重建,对轧制复合-粉末冶金发泡工艺制备的泡沫铝夹芯板(AFS)进行了泡孔结构演化的研究,分析了发泡过程中孔隙率的变化及大尺寸连通孔的形成原因。研究结果表明:具有微米级空间分辨率的SR-CT可清晰地观测到泡孔萌生及生长各阶段的泡沫结构。泡孔在发泡15~30 s阶段生成,形状为垂直于轧制方向的类裂纹孔。发泡45 s时,泡孔开始发生明显合并,继续延长发泡时间易导致形成大尺寸连通孔。芯层泡沫铝的孔隙率在泡孔的萌生阶段及合并阶段增长幅度较大,减少混料时发泡剂的"团聚"及提高芯层粉末致密度可获得良好的芯层泡沫结构。     

High-Temperature Oxidation Behavior and Mechanism of a New Type of Wrought Ni–Fe–Cr–Al Superalloy up to 1300°C

The oxidation behavior of a new type of wrought Ni–Fe–Cr–Alsuperalloy has been investigated systematically in the temperature range of1100 to 1300°C. Results are compared with those of alloy 214, Inconel600, and GH 3030. It is shown that the oxidation resistance of the newsuperalloy is excellent and much better than that of the comparisonalloys. Scanning electron microscopy (SEM), electron probe microanalysis(EPMA), and X-ray diffraction (XRD) experiments reveal that the excellentoxidation resistance of the new superalloy is due to the formation of adense, stable and continuous Al₂O₃ and Cr₂O₃ oxide layer at hightemperatures. Differential thermal analysis (DTA) shows that the formationof Cr₂O₃ and Al₂O₃ oxide layers on the new superalloy reaches a maximum at1060 and 1356°C, respectively. The Cr2O3 layer peels off easily, and thesingle dense Al₂O₃ layer remains, giving good oxidation resistance attemperatures higher than 1150°C. In addition, the new superalloypossesses high mechanical strength at high temperatures. On-site testsshowed that the new superalloy has ideal oxidation resistance and can beused at high temperatures up to 1300°C in various oxidizing andcorrosion atmospheres, such as those containing SO₂, CO₂ etc., for longperiods.     

司盘-80辅助回流法提取红藤中的黄酮类物质

采用表面活性剂辅助回流法提取红藤中的黄酮类物质,考察了表面活性剂的种类、浓度,液料比,溶剂pH值以及回流时间等因素对红藤中黄酮类物质得率的影响,并用正交实验确定最佳工艺条件为：司盘-800．007g／mL,液料比50mL／g,溶剂pH值为6,回流时间60rain,此时红藤总黄酮的得率为19．5％。与传统水提法相比,得率提高了92．74％。     

低温空气源热泵实验台

实验台由热泵机组和室内外环境模拟系统组成。基于系统误差分析的基本原理,合理选择测量仪表。分析得知,温差对测量精度的影响大于流量的影响。重复测试的结果表明,制热量和制热COP的总误差分别为3.65%和3.79%,能满足试验精度要求。     

An improved fitting method for subgroup parameters based on the heterogeneous cells

An accurate subgroup parameters fitting method, where background cross sections obtained based on heterogeneous cells are used to fit the subgroup level and subgroup weight, is proposed in this paper. Due to the dependence of background cross section on the subgroup level, the calculation of the subgroup parameters is a nonlinear problem, which causes the iteration between fitting subgroup parameters and updating background cross sections. The cubic spline interpolation method is used to update the background cross sections to avoid frequently solving fixed source equations. In the fitting process, the negative subgroup parameters are often obtained, and the accuracy of the subgroup parameters is very sensitive to the iterative initial values of subgroup levels. To avoid these problems, additional constraints ensuring positive subgroup parameters and guaranteeing numerical stability are added to the optimization function. Penalty function method is used to convert the optimization problem with constraints into the one without constraints, making the problem easy to be solved. The proposed method is tested against the problems of pin cell, pressurized water reactor assemblies and plate-type assembly. The numerical results show that the self-shielded cross sections calculated by the proposed method agree well with those by Monte Carlo code.