丁酸苯酯Fries重排制备o-羟基苯丁酮

以丁酸苯酯为原料,探讨了丁酸苯酯Fries重排选择性制备o-羟基苯丁酮的工艺条件。通过正交实验考察了催化剂用量、反应温度、反应时间3个因素对o-羟基苯丁酮收率影响的显著性,通过单因素实验进一步考察了上述因素对丁酸苯酯重排制备o-羟基苯丁酮收率的影响。反应物中o/p-羟基苯丁酮的质量分数采用高效液相色谱定量分析。实验结果表明,当n(催化剂)∶n(丁酸苯酯)=1∶(1—1.2),反应温度为120℃,反应时间为2 h,丁酸苯酯转化完全,o-羟基苯丁酮收率为36%。在Zobarx SB-C18色谱柱(4.6 mm I.D.×150 mm,5μm)上,以V(甲醇)∶V(水)=75∶25混合溶剂为流动相,o/p-羟基苯丁酮达到基线分离。     

Halotolerance and Survival Kinetics of Lactic Acid Bacteria Isolated from Jalapeño Pepper (Capsicum annuum L.) Fermentation

The microbiota associated with spontaneous fermentation of vegetables in a saline substrate may represent an important group of bacteria in the food industry. In this work, the lactic acid bacteria (LAB) Weissella cibaria, Lactobacillus plantarum, Lactobacillus paraplantarum, and Leuconostoc citreum were identified by partial 16S rRNA gene sequence analysis. In addition, entophytic bacteria such as Pantoea eucalypti, Pantoea anthophila, Enterobacter cowanii, and Enterobacter asburiae were detected, but they were irrelevant for the fermentation process and were inhibited after 12 h of fermentation when the pH decreased from 6.5 to 4.9. Moreover, 2 species of yeast were isolated and identified as Hanseniaspora pseudoguilliermondii and Kodamaea ohmeri by their partial 26S rRNA gene sequence. The growth of LAB was evaluated at different sodium chloride contents. L. citreum was the most halotolerant species followed by L. plantarum and W. cibaria with a concentration index to obtain a 50% population reduction (IC₅₀) of 7.2%, 6.6%, and 5.2%, respectively. Furthermore, the growth of LAB and Escherichia coli O157:H7 was evaluated in the presence of the main phenylpropanoids from chilli peppers such as p‐coumaric and ferulic acid. It was determined that LAB can grow in both acids at 4 mM, unlike E. coli O157:H7, whose growth is inhibited in the presence of these acids.     

冰水二相流渠道流冰输移演变规律及其安全运行措施研究

针对我国新疆、青海地区为数众多且无法采用冰盖下输水的宽浅式渠道工程,开展冰水二相流输运机理及运行调控技术研究,对于解决这些地区冬季用水矛盾、节省工程改造投资具有重要意义。以新疆北部地区某电站引水渠为例,通过构建一维渠道冰水力学数学模型,研究渠道流冰输移和发展规律,分析气温、出库水温、输水流量等关键因素对渠道冰情的影响,并提出冰水二相流渠道的安全运行措施,对实现冰水二相流安全水力调控、解决我国西北地区冬季缺水问题具有一定参考价值。     

滨海地区水资源多目标优化调度模型研究

针对滨海地区水资源系统的特点,以加权相对总缺水深度最小和系统供水总成本最小为目标,建立了平原河网、平原水库群和远距离调水工程体系的水资源多目标优化调度模型;利用多目标粒子群算法(MOPSO)求解,提出了各类约束条件的处理方法,并得到非劣解集;采用距理想解欧拉距离最小准则,得到最好权衡两个目标的最佳协调解,并取得相应的调度结果。以江苏沿海为背景开展实证研究,验证了所建模型和求解方法的有效性。     

高效液相色谱法分析对二甲苯的氧化残渣

采用高效液相色谱法测定了对二甲苯氧化残渣中的苯甲酸、对甲基苯甲酸、邻苯二甲酸、对苯二甲酸和间苯二甲酸。色谱柱为Ｐｈｅｎｏｍｅｎｅｘ５ＳＡＸ，２５０×４．６ｍｍ，磷酸盐缓冲液作流动相，紫外检测波长设在２３６ｎｍ。方法的回收率大于９７．２６％，相对标准偏差小于３．０２％，相关系数大于０．９９８５。     

R20S锌锰电池的质量问题及预防措施

分析了R20S锌锰电池生产过程中造成电池绿铜帽、锌筒穿孔以及电解液泄漏等重要质量问题的原因，并针对以上问题从电池生产工艺，机械设备和质量控制手段等方面提出了具体克服措施。     

开源世界里的面向对象数据库db4o

介绍了开源的,面向对象数据库db4o的优点及特性,通过c#语言展示其如何在程序设计中使用和操作.细致讲解db4o如何对数据库中的对象进行基本的加载,更新,删除操作及其三种十分重要的查询方式.     

分布时滞随机偏微分系统的均方指数稳定性

针对一类同时具有分布时滞和维纳过程的随机偏微分系统, 首先基于It?o微分公式, 通过计算弱无穷小算 子, 得到了随机微分导数; 其次利用Green公式和积分不等式及Schur补引理对矩阵不等式进行处理; 然后对微分两 边积分并同时取数学期望处理随机交叉项; 获得了分布时滞随机偏微分系统是均方指数稳定的充分条件. 在此基础 上, 进一步考虑了离散变时滞和分布变时滞在一定约束情形下的分布时滞随机偏微分系统的均方指数稳定性问题. 最后给出仿真实例, 仿真结果表明所获得的线性矩阵不等式条件保证了系统的稳定性, 验证了所得结论的有效性.     

Response of nearshore circulation outside Yangtze Estuary to El Nio events

With consideration of the comprehensive effects of runoff from the Yangtze River, East China Sea background circulation, and tidal currents,a regional circulation model, including the Yangtze Estuary, Hangzhou Bay, and adjacent sea areas was established. The 2002/2003 El Ni~no event was chosen for study of the anomalies of circulation outside the Yangtze Estuary. The coastal and ocean current systems of the East China Sea and the current structure outside the Yangtze Estuary were accurately described. The results of vertical circulation analysis basically coincide with those of horizontal circulation analysis, showing that the circulation outside the Yangtze Estuary is mainly affected by the Taiwan warm current, runoff from the Yangtze Estuary, and the tide-induced residual current. The El Ni~no event weakens Yangtze Estuary circulation to a certain degree, and the impacts are more significant in summer than in winter. During the 2002/2003 El Ni~no event, the flux of the Taiwan warm current decreases, and the northward component of the Taiwan warm current decreases by half in February 2003 compared to the previous year. However, its path is relatively stable.     

一种自适应特征地图匹配的改进VSLAM算法

从提高机器人视觉同时定位与地图构建（Visual simultaneous localization and mapping,VSLAM）算法的实时性出发,在VSLAM的视觉里程计中提出一种自适应特征地图配准的算法.首先,针对视觉里程计中特征地图信息冗余、耗费计算资源的问题,划分特征地图子区域并作为结构单元,再根据角点响应强度指标大小提取子区域中少数高效的特征点,以较小规模的特征地图配准各帧：针对自适应地图配准时匹配个数不满足的情况,提出一种区域特征点补充和特征地图扩建的方法,快速实现该情形下当前帧的再次匹配：为了提高视觉里程计中位姿估计的精度,提出一种帧到帧、帧到模型的g2o（General graph optimization）特征地图优化模型,更加有效地更新特征地图的内点和外点.通用数据集的实验表明,所提方法的定位精度误差在厘米级,生成的点云地图清晰、漂移少,相比于其他算法,具有更好的实时性、定位精度以及建图能力.