千分尺测量结果不确定度的计算

以用千分尺测量长度为L=45mm的工件为例,阐述了千分尺的测量不确定度的来源及计算方法,并给出用千分尺测量该工件的测量结果。     

Effects of particle size on the quality attributes of reconstituted whole-wheat flour and tortillas made from it

The objective of this study was to examine the effects of whole-wheat flour (WWF) particle size on the quality attributes of WWF tortillas. WWF samples of different particle size distributions from commercial U.S. hard white (median diameters: 175.7, 128.6, 120.0, 108.5 and 102.4 μm), hard red winter (median diameters: 173.7, 133.6, 124.3, 110.8 and 104.2 μm) and hard red spring (median diameters: 173.7, 132.1, 124.7, 112.9, 106.3 μm) wheat classes were obtained by fine grinding of bran and shorts and re-combining with the rest of fractions. For all three wheat classes, as WWF median particle size decreased, the L* (lightness) value decreased but the adjusted damaged starch, polyphenol oxidase activity, and a* and b* values increased. Mixolab data showed that development time decreased as WWF particle size was reduced, while stability time and starch retrogradation increased. As for WWF tortilla quality, the breaking force and extensibility increased with decreasing particle size from ∼175 to 129–134 μm, but diameter and thickness were not significantly affected. The results indicated that reducing the median particle sizes of WWFs from ∼175 μm to ∼130 μm would significantly improve the WWF tortilla quality.     

微米SiCp/Cu基复合材料的机械和耐磨性能

以微米级(14μm)SiCp和微米级(10μm)铜粉为原料，采用冷压烧结方法制备出SiCp(14μm)／Cu基复合材料，并进行了热挤压加工。研究了Sicp(14μm)／Cu基复合材料的组织、硬度、导电、拉伸和耐磨性能。并与6-6-3锡青铜进行了比较。结果表明：Sicp(14μm)／Cu基复合材料组织致密，SiCp(14μm)分布均匀；随着Sicp(14μm)含量增加，导电性下降，硬度增高，抗拉强度下降，伸长率下降；在Sicp(14μm)含量为1～10vol％时，导电率为95．9％～82．2％IACS。硬度为84．5～89．2HV，抗拉强度为243．3～166．6MPa，伸长率为50．6％～23．0％；Sicp(14μm)／Cu基复合材料具有良好的耐磨性，5vol％Sicp(14μm)／Cu基复合材料磨损质量损失是6．5-0．4锡青铜1／18．3；Sicp(14μm)对对磨件产生犁削，复合材料磨损表面形成混合中间层，提高了耐磨性。     

Theoretical computation and analysis of benefits of wood cutting power

This paper studies the problem of high energy waste in the course of the wood fiber processing in the wood-based panel industry. In the light of the energy economy principle, the cutting theory on the micron and long-slice wood fiber was put forward. In this paper, by means of analyzing the power waste in traditional processing, a series of analytical measures, such as, cytology, super precision work theory and fiber processing, and so on were utilized in the micron wood fiber formation process, and the cutting conception of the micron and long-slice wood fiber was put forward. Accordingly, the study of the micron and long-slice wood fiber was put into the microstructure study. This paper scientifically explains the reasons why the traditional wood fiber processing consumes more energy and the fiber quality low. In an example, the cutting power on the micron and long-slice wood fiber was calculated, which was compared with the traditional cutting power. The result showed that the energy waste by machining at micron is much lower than by heat grind and the high quality and long-slice wood fiber was gained. Thus, a revolutionary step was taken in the paper-making and wood-based panel industry of China. __________ Translated from Scientia Silvae Sinicae, 2006, 42(3): 44–46 [译自: 林业科学 2006, 42(3): 44–46]     

智能数字测微仪设计

智能数字测微仪是一种新型的高精度量仪。该量仪采用 MCS-51系列的80C31单片机。具有多种功能,如测量功能控制,求数据平均值,报警等。它体积小、功耗低、高精度和高分辨率,使用方便。本文介绍了该量仪的工作原理、技术指标、功能和设计特点等。     

白术、微米白术和白术多糖对断奶仔猪生长性能和肠道形态及微生态区系的影响

试验选用96头平均体重14.82 kg左右的杜×长×大断奶仔猪,随机分成4组,每组3栏,每栏8头(公母各半)。对照组饲喂基础日粮,试验1、2、3组分别添加1%80目白术、0.2%白术多糖和1%微米白术。试验期30 d。结果表明:在生长性能方面,与对照组相比,1%微米白术添加组可显著提高日增重(P0.05)、降低饲料增重比和腹泻率,而且效果优于1%80目白术组和0.2%白术多糖组,在肠道形态和肠道微生态区系方面,与对照组相比,日粮添加1%80目白术、0.2%白术多糖、1%微米白术均可不同程度的提高十二指肠和空肠的绒毛高度,加深十二指肠和空肠的隐窝深度,并且增加肠道微生态区系的多样性,其中以1%微米白术添加组的效果最佳。     

微米长薄片木纤维切削加工功率的理论计算方法与效益分析

对传统纤维加工的功耗进行分析,将细胞学、超精加工理论、纤维学等一系列现代分析手段运用到木纤维的形成过程中,提出微米长薄片木纤维切削的概念,从而将微米长薄片木纤维的研究上升到微观结构,并通过对纤维形状的产生和切削力变化的分析,解释传统木纤维加工消耗的能源高、产生纤维质量差的本质原因.示例对微米长薄片木纤维的加工功率进行计算,将其与传统加工方法的功率进行对比,得出结论:以微米级机械法加工木纤维耗能远远低于热磨法,且可以加工出质量较高的微米级长丝木纤维.     

纳微米科学与技术在木材工业的应用前景展望

本文对纳米和微米技术在木材工业上的应用前景进行展望，预测未来纳微米技术可能对木材工业产生的影响，利用纳微米技术可能形成造纸的高得浆率方法，木材在变成纳微米尺寸后，木材的材料特异性质、尺寸效应及其变化机理，以及木材改性的显微结构关系可能使木材改性出现突破性进展。当木粉变成纳微米的粒度后，原木材理化指标发生变化，在细粉状态下进行木材液化可以改变木材液化的方式和成本，使木材液化真正工业化。在复杂木雕制品加工中，采用RPM技术利用直接CAD将纳微米木酚形成复杂木雕制品，可能开创一种新的木材加工方法。利用木材细胞的自组装方式可形成新的木基复合材料，纳米木粉生产的无污染胶粘剂可能代替含甲醛的有毒胶、胶粘剂的绿色革命可能从木材的纳微米技术开始。     

玉米籽粒果皮厚度变化规律研究

采用显微测微法对3种不同基因型的7个玉米骨干系及由它们配制的4个杂交组合F1的果皮厚度变化规律进行了研究.结果表明:玉米籽粒发育过程中,果皮厚度呈曲线状态变化.即授粉后随着籽粒发育果皮逐渐变厚,到乳熟后期(超甜玉米)或蜡熟期(普甜玉米、普通玉米)达最大值,然后随着籽粒脱水,果皮细胞排列紧密而变薄;在广州地区春、秋正造种植时,环境不会从根本上改变果皮厚度这一性状;同一基因型内不同核背景材料间籽粒平均果皮厚度也有显著、极显著差异;杂交组合F1代种子果皮厚度似乎有母体效应.