置换还原法制备银包铜粉工艺及性能研究

采用EDTA为络合剂,利用置换还原法制备银包铜粉。研究了还原剂的浓度,分散剂以及络合剂的浓度对银包铜粉性能的影响。实验结果表明,采用EDTA为络合剂,所得粉末表层结构致密,包覆均匀。当c(EDTA)为0.12mol/L,c(葡萄糖)为0.12mol/L,同时采用超声波分散,所得银包铜粉导电性最好,镀银层致密,粉末为银白色,包覆率高,抗氧化性最佳。     

响应面法优化黑胡萝卜红色素双水相萃取工艺

采用聚乙二醇（PEG）/硫酸铵双水相体系萃取纯化黑胡萝中的花青素。通过单因素实验考察了硫酸铵、PEG6000、粗提液的质量分数对花青素选择性系数和萃取率的影响,并以花青素的萃取率为响应值,结合响应面试验优化萃取工艺。结果表明,各因素对萃取率的影响程度由大到小依次为硫酸铵质量分数>粗提液质量分数>PEG6000质量分数。以双水相体系的总质量为基准,实验最佳萃取条件为:硫酸铵质量分数为20.0%、粗提液质量分数为12.0%、PEG6000质量分数为14.0%,黑胡萝卜红色素的平均萃取率为94.17%。此萃取方法得到的黑胡萝卜红色素具有一定的抗氧化活性,对DPPH自由基清除能力的IC₅₀值为30.51 mg/L。     

Preparation of diamond/SiC composites by the liquid silicon infiltration method and their microstructure and properties

Diamond/SiC composites have long been recognized as advanced materials for thermal management as they exhibit excellent thermal and mechanical properties. The objective was to investigate and understand the phase composition, diamond graphitization behavior, microstructure, and properties of diamond/SiC composites developed following the liquid silicon infiltration process. The results revealed that the incorporation of α-SiC particles increased the degree of uniformity of the microstructure of the diamond/SiC composites. The acoustic mismatch model was used to analyze the samples before and after diamond graphitization to evaluate the interfacial thermal resistance of the composites. The results indicated that the interfacial thermal resistance of the graphitized composites was 11.9 times higher than the interfacial thermal resistance of the un-graphitized composites. Finally, the correlation between the diamond content of the composites and their thermal and mechanical properties was investigated.     

双权法LSSVM在旋转设备故障诊断中的应用

由于旋转设备故障数据样本存在不平衡性,导致传统的LSSVM无法对异常值样本正确分类,为了解决这一问题,首先采用LSSVM从训练集中提取错分样本及其分类的支持向量,再根据各类故障样本数量对惩罚因子进行加权,以减少样本数量不平衡对分类结果的影响;然后根据错分样本到本类边界支持向量的距离,对松弛系数设置不同的权值,使错分的异常值样本分类得以修正。通过煤矿风机故障数据集验证了该算法分类效果明显优于传统的LSSVM方法。它有效地消除了因故障样本数据不平衡、样本分布异常对分类器造成的影响,提高了设备故障诊断的正确率。     

激光干扰CCD系统的实验研究

为了验证激光辐照CCD系统的干扰效果,进行了视场内和视场外He-Ne激光干扰面阵CCD探测器系统的实验研究,测得了像元饱和阈值和局部受辐照时的CCD饱和功率街度阈值.使用Matlab编程处理了视场内干扰图像,得到了激光入射能量与CCD饱和面积比的关系曲线,并对实验中出现的光饱和串音现象进行了理论分析.对视场外干扰图像进...     

户式中央空调系统的复合控制器设计

针对空调系统纯滞后、多干扰的特性,提出了一种复合控制方案。首先,建立了被控对象的数学模型,并基于此模型初步设计了一个常规PID控制器;然后,针对对象的滞后环节对系统产生大超调量问题,加入了Smith补偿器,有效地减小了超调量;最后,通过引入前馈控制,有效地消除了干扰对系统产生的不良影响。通过仿真实验结果,不仅验证了各设计方案的正确性和有效性,也充分展示出该复合控制器的优良特性。     

基于根轨迹校正法的倒立摆控制系统设计

针对倒立摆系统的稳定控制问题,提出了一种根轨迹校正方案.建立控制对象的数学模型,运用经典控制理论的根轨迹校正法完成控制系统的设计,在Matlab环境下对控制系统进行了仿真实验,并对该方案的要点进行了归纳性总结.仿真结果表明,该方法不仅成功实现了系统的稳定控制,也满足了期望的性能指标,从而充分证明了方案的正确性与有效性.     

新型植物皮革鞣剂的研究进展

就目前所使用的植物鞣剂的优缺点进行了概述,并且就几种具有应用前景的新型植物鞣剂做了简单的介绍。     

A comparison of the influence of eight commercial yeast strains on the chemical and sensory profiles of freshly distilled Chinese brandy

The current study examined eight commercial Saccharomyces cerevisiae strains [Lalvin ICV‐D80, Lalvin FC9 EDV, Lalvin QA23, Lalvin RHST, Uvaferm 43, Enoferm Burgundy (BGY), Lalvin EC1118 and Lalvin M69] for their influence on young brandies, with a special emphasis on chemical, volatile and sensory characteristics. Results of the chemical analysis of the fermented wines showed that all of the strains exhibited a similar performance for ethanol production, but titratable acidity was more variable, with the highest being found in the yeast BGY‐derived wine and the lowest in the yeast QA23‐derived wine. Spirits produced using yeast FC9 EDV showed a significantly higher content of volatile alcohols, esters and acids, and conveyed to the brandy typical fruity and rosy notes. Brandies derived using yeast Uvaferm 43 presented the highest content of total benzene compounds and this brandy was characterized by rosy and onion attributes. Higher levels of varietal compounds and a medium rosy and slightly acidic and rancid nuances were produced when yeast QA23 was used. When using principal component analysis to classify the samples, there were four groups: group 1 ( ICV‐D80, Uvaferm 43 and BGY), group 2 (FC9 EDV), group 3 (QA23, RHST and EC1118) and group 4 (M69). This work sheds some light on the flavour complexity owing to the use of different commercial yeasts and provides useful information for the brandy‐maker regarding the choice of yeast for the fermentation based on the volatile profile. Copyright © 2012 The Institute of Brewing & Distilling