拉曼光谱法快速检测猪肉脯中的掺伪鸡肉

目的建立拉曼光谱法快速、准确、无损地检测猪肉脯样品中掺假鸡肉的方法。方法制备33份猪肉中掺入不同比例鸡肉的肉脯样品,采集拉曼光谱数据,分别采用标准正态变换、多元散射校正、卷积平滑、归一化、一阶导数等5种不同预处理方法,对原始光谱数据进行预处理,采用连续投影算法、竞争性自适应重加权算法及随机蛙跳算法对光谱数据进行特征波长筛选,建立偏最小二乘法(partial least squares,PLS)模型对猪肉脯进行定性定量判别。结果拉曼光谱数据经过多元散射校正处理的效果最佳,竞争性自适应重加权算法竞筛选效果更佳,构建猪肉脯中猪肉含量的PLS定量模型,其预测集决定系数和预测均方根误差分别为0.9762、7.2998。建立的PLS判别模型的校正集和预测集总判别正确率分别为100.00%和98.33%。结论拉曼光谱分析技术可有效用于定性鉴别猪肉脯是否掺伪及定量分析猪肉肉脯中掺入鸡肉的比例,为肉脯掺假的快速无破坏性检测的应用提供支持。

Quantifying soil nitrous oxide emissions in spring freezing-thawing period over different vegetation types in Northeast China

Environmental changes significantly alter the structure,diversity and activity of soil microbial communities during spring freezing-thawing period,leading to changes in the soil microbial nitrogen cycle.Changes in N_(2)O fluxes after land use conversion from primary forest to secondary forest,Korean pine plantation and cropland in northeast China have not been quantified.Field experiments were conducted to measure soil N_(2)O fluxes in a primary forest,two secondary forests,a Korean pine plantation,and one maize field in a temperate region in northeast China from 2017-03-06 to 2017-05-28.During the experimental period,the soil was exclusively a nitrogen source for all land uses.We found that N_(2)O emissions ranged from 15.63 to 68.74μg m^(-2) h^(-1),and cumulative N_(2)O emissions ranged from 0.33 to 2.10 kg ha^(-1) during the period.Cumulative N_(2)O emissions from the maize field were significantly higher than that from primary forest,Korean pine plantation,hardwood forest,and Betula platyphylla forest by 262.1% to 536.4%.Compared with other ecosystems in similar studies,the N_(2)O emission rates of all ecosystem types in this study were low during the spring thaw period.Stepwise multiple linear regression indicated that there were significant correlations between N_(2)O emissions and environmental factors(air temperature and soil temperature,soil water content,soil p H,NH_(4)^(+)-N,NO_(3)^(-)-N,and soil organic carbon).The results showed that conversion of land use from primary forest to hardwood forest,Korean pine plantation or maize field greatly increased soil N_(2)O emissions during spring freezing-thawing period,and N_(2)O emissions from primary forest were almost the same as those from Betula platyphylla forest.

供水循环泵的振动研究与噪声优化

供水泵广泛应用于家居,工业等不同领域,随着其系统运行产生的振动和噪声是不可避免的,本文综合概述了对于降低供水泵的不必要振动带来的噪声的方法,简单介绍其应用方式。在我们的供水系统运行中经常面临的一个问题是振动和噪音。特别是近些年来变频供水技术的发展其在技术上的凸显越发明显。设计上的缺陷,以及施工人员错误的安装,都可能带来危害,长期的振动必将导致故障率的提升,最终影响工作效率乃至机器元件的使用周期,最严重的是恶化我们的生活环境,影响我们的身心健康。泵存在振动是不可避免的,我们只能减轻振动,通过措施减轻振动。

柔性陶瓷涂层与牙本质的结合强度及耐磨性研究

目的:将柔性陶瓷涂于经不同方法处理的牙本质表面,研究其结合强度、耐磨性,以寻求预防和治疗牙齿磨损的新方法。方法:结合强度实验中将牙本质试件随机分为A(表面不处理)、B(37%正磷酸处理)、C(超级粘接剂处理)3组,每组14个试件,A、B两组表面刷涂柔性陶瓷为实验组,C组表面刷超级粘接剂作为对照组。扫描电镜观察涂层表面及结合面形貌,划痕试验仪检测涂层与牙本质的结合强度。耐磨性试验中将表面涂有柔性陶瓷涂层的牙本质试件(柔性陶瓷组)作为实验组,牙釉质和牙本质试件作为对照组,在摩擦磨损实验机上与滑石瓷进行对磨。比较各组间的摩擦系数及磨损前后的质量损失量,扫描电镜观察磨损前后表面形貌。结果:扫描电镜显示陶瓷涂层表面致密平整,B、C两组涂层与基底间无明显界限,过渡自然;B、C两组的结合强度分别为(36.3±3.8)N、(29.0±3.3)N,差异无统计学意义。柔性陶瓷组的摩擦系数与牙釉质组接近;柔性陶瓷组质量损失量(0.288±0.049)mg最小,牙釉质组(0.346±0.028)mg次之,且两组间差异无统计学意义。结论:在本实验条件下,37%正磷酸处理的牙本质表面制备的柔性陶瓷涂层,表面结构致密,与牙本质结合牢固,具有与牙釉质相近的耐磨损性能。