排序方式: 共有23条查询结果,搜索用时 15 毫秒
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单独提取滚动轴承振动信号的时域或频域特征进行故障诊断,是目前常用的轴承诊断方法,诊断精度有待提高。以时域和频域的多维振动特征参量为指标,以历史诊断正确率作为特征参量权值,分别对滚动轴承的无故障和经常出现的滚珠故障、内环故障和外环故障工况进行特征提取和故障识别。多维时频域振动特征是单维特征依据诊断精度权重的集合。运用BP神经网络分别对信号的时域特征(TDF)、IMF能量矩(IEM)、小波包能量矩(WPEM),以及多维时频域特征进行智能故障判别。实验验证用多维时频域振动特征参量综合诊断的方法进行滚动轴承故障诊断,比单维特征的诊断结果精确且效率较高,该方法可以在滚动轴承故障诊断领域展开应用。 相似文献
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异常威克汉姆酵母(Wickerhamomyces anomalus)是一种产子囊孢子的酵母,广泛存在于各类水果表面及传统酒曲中,该酵母能够分泌β-D-葡萄糖苷酶、β-D-木糖苷酶、α-L-鼠李糖苷酶等多种糖苷酶,并且具有一定的产香、产酯和产酒精的能力,可以显著提升酒体感官品质,是酒醅发酵过程中重要的功能性微生物。该文对异常威克汉姆酵母的来源、对酒类风味的影响及其在酒类酿造中的应用进行综述,并对异常威克汉姆酵母在酿酒中的应用前景提出展望,旨在为筛选优良酵母菌株,优化酒类发酵条件,提高酒体品质提供参考借鉴。 相似文献
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以面包酵母细胞不对称还原苯乙酮合成S-α-苯乙醇为模型反应,研究了水-有机溶剂两相体系促进面包酵母细胞催化芳香酮的不对称还原情况.首先研究了适合于活性细胞催化的两相溶剂体系,实验表明合适的有机溶剂为logp3的溶剂,这与有机相中的酶催化对溶剂的要求相一致.在所选用的溶剂中,正辛烷获得的效果最好.在此基础上进一步考察了两相之间的比率、辅助溶剂、底物浓度以及水相体系的pH等对反应的影响.实验表明两相之间的比率和辅助溶剂对反应有显著的影响,合理改变这些因素可以改善底物在两相之间的分配进而促进反应的进行.反应对底物浓度的敏感性较单相水相体系反应要小得多,而pH对反应的影响与水相中反应相同.在有机溶剂与水相体积比为1:4、添加1%乙醇以及底物浓度为30 mmol·L-1时,产物得率可达到45%左右,这较在水相中反应有显著的提高. 相似文献
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在含糖量高、酵母可同化氮不足的葡萄汁中,研究不同发酵时期添加安琪发酵营养剂NutrienFast对葡萄酒发酵的影响。结果表明,在发酵第3天(糖消耗36.26%)、第4天(糖消耗到达44.18%)时添加发酵营养剂NutrienFast对葡萄酒发酵的影响最大,此时CO2累积质量损失最高,分别为129.62 g/L和128.82 g/L;葡萄汁中的酵母干物质含量达到最高值,分别为3.57 g/L、3.62 g/L;葡萄酒相对密度、残糖含量最低;酒精度最高,分别为16.5%vol、16.4%vol,酒精发酵完全(残糖<4 g/L),可有效解决或者预防葡萄酒的发酵停止或停滞问题。 相似文献
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Chiral aromatic alcohols are the key chiral building block for many important enantiopure pharmaceu-ticals. In this work,we studied asymmetric reduction of prochiral aromatic ketone to produce the corresponding chiral alcohol using vegetables as the biocatalyst. Acetophenone was chosen as the model substrate. The results in-dicate that acetophenone can be reduced to the corresponding chiral alcohols with high enantioselectivity by the chosen vegetables,i.e. apple(Malus pumila),carrot(Daucus carota),cucumber(Cucumis sativus),onion(Allium cepa),potato(Soanum tuberosum),radish(Raphanus sativus),and sweet potato(Ipomoea batatas) . In the reaction,R-1-phenylethanol is produced with apple,sweet potato and potato as the catalyst,while S-1-phenylethanol is the product with the other vegetables as the catalyst. In term of the enantioselectivity and reaction yield,carrot(D. ca-rota) is the best catalyst for this reaction. Furthermore,the reaction characteristics were studied in detail using car-rot(D. carota) as the biocatalyst. The effects of various factors on the reaction were investigated and the optimal reaction conditions were determined. Under the optimal reaction conditions(reaction time 50 h,substrate concen-tration 20 mmol·L-1,reaction temperature 35 °C and pH 7),95% of e.e.(to S-1-phenylethanol) and 85% chemical yield can be obtained. This work extends the biocatalyst for the asymmetric reduction reaction of prochiral aromatic ketones,and provides a novel potential route to produce enantiopure aromatic alcohols. 相似文献
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