P-GMAW电源外特性对焊接过程稳定性的影响

设计了一套具有阶梯外特性的脉冲熔化极气体保护焊(P-GMAW)电源,可根据负载工作点自动选择恒流、恒压、短路或空载特性. 研究了P-GMAW电源外特性对Q235低碳钢焊接过程稳定性的影响. 结果表明,基值为恒压特性时,电弧稳定性差,易熄弧或短路. 基值为恒流特性可减少飞溅及熄弧现象,但不能消除短路倾向. 基值为阶梯外特性,可有效减少甚至消除短路或熄弧现象,焊接过程稳定性好. 采用基值阶梯特性加峰值恒压特性组合时电弧稳定,抗干扰能力强,无飞溅及断弧现象,焊缝成形均匀.     

Static mixers for laminar flow reactors with low aspect ratios

Conventional static mixers typically require high length to diameter ratios to be effective. This paper considers static mixers design to increase first appearance times in short, fat reactors. Three types are considered: conical baffles and annular baffles for tubular reactors and axial baffles for reactors with a rectangular cross-section. Relatively simple designs allow production increases (or reactor volume decreases) on the order of 20–50%.     

Investigation on vermilion,gingiva, and tooth color of young Uygur and Han populations in Xinjiang,China

This study examines oral tissue color in Uygur and Han Chinese populations. The color of oral tissues is of great significance in dental field. It remains uncertain whether there is any difference in the color of oral tissues between different nationalities or ethnicities. Little is known about the color of oral tissues in different Chinese populations. The study included 263 Uygur and Han students aged 18–22 years. The color of anterior teeth, vermilion, and attached gingiva in the subjects was measured by spectrophotometry and expressed through the CIELCh system. The t test and ANOVA was used to analyze color difference between groups. Distribution ranges for L (lightness), C (chroma) and h (hue angle) of anterior teeth, vermilion, and attached gingiva in these two ethnicities were obtained. Significant differences in color of oral tissues between Uygur and Han Ethnicities were found out. The Uygur and Han populations have similar spatial distribution ranges for the color of oral tissues, with slight differences that displayed strong regularities, suggesting that the color of oral tissues was associated with race. In addition, there was a trend of decreasing lightness (especially for maxillary anterior teeth), increasing chroma and redder hue from the center of teeth toward the sides in both ethnicities. There were differences in the color of teeth and attached gingiva between sexes in the Uygur and Han populations. The color of the upper vermilion differed significantly from that of the lower vermilion. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2010     

运用QC小组活动提升发电厂房主机间排架柱混凝土施工外观质量

阐述了QC小组在发电厂房主机间排架柱混凝土施工过程中的外观质量控制,从基础资料入手,调查存在的质量缺陷,并对质量缺陷的产生原因进行了讨论和分析,做出了因果分析图和要素确认表,从图表中可以得出产生表面不平整质量缺陷的主要原因,同时也以这几项原因作为主要的改进目标,起到了良好的效果。     

Milk fat composition modifies the texture and appearance of Cantal-type cheeses but not their flavor

Although the effects of cow diet on cheese sensory properties have been well documented, the putative interactions between the biochemical and microbial milk components and their respective roles in the development of the sensory properties of cheeses have yet to be explored in depth. The aim of this study was to evaluate the specific contribution of milk fat composition to the formation of cheese sensory properties. Two creams with different fat compositions were obtained from cows fed either pasture or maize silage. Cheeses were manufactured from the same skim milk (identical chemical and microbial composition) with either the pasture- or maize silage-origin pasteurized cream added. The gross composition and microbial composition of milks did not vary with cream origin. In milks and cheeses, the fatty acid (FA) profiles were modified by the origin of the cream. The concentrations of C18:0 and unsaturated FA such as cis-9 C18:1, trans-11 C18:1, C18:3n-3, total conjugated linoleic acids, and mono- and polyunsaturated FA were higher in milks and cheeses with the pasture-origin cream than in those with the maize-origin cream. In contrast, the maize milks and cheeses had higher concentrations of short- and medium-chain saturated FA, C16:0, and C18:2n-6. The level of lipolysis was 11% in the cheese rind and only 0.30% in the cheese core. The rind of pasture cheeses had a higher concentration of free C18:0 and C18:3n-3 and a lower concentration of free C14:0 and free C16:0 than the rind of maize cheeses. The levels of major microbial groups were similar in pasture and maize cheeses at different stages of ripening. The pasture cheeses had a more elastic and creamier texture, a yellower color, and a thinner rind than the maize cheeses, but the odor and aroma of cheeses were not affected by the origin of the cream, despite a few modifications in the balance of volatile compounds from FA catabolism. Based on these results, we conclude that milk fat composition modulated by cow diet had a direct role in the texture of the cheese but no effect on flavor. The high degree of lipolysis in cheese rind, along with the higher concentration of long-chain unsaturated free FA in pasture cheeses may be responsible for antimicrobial activity, which could explain differences in the appearance of cheese rind.     

多丝直缝埋弧焊管焊缝形貌对热影响区冲击功的影响

为了研究多丝直缝埋弧焊管焊缝形貌对热影响区冲击功的影响,分析了直缝埋弧焊管焊接接头不同区域的组织和韧性分布规律,得出由于热影响区冲击试样刻槽处焊缝宏观形貌的不同,冲击试样刻槽所经过的焊缝、热影响区（HAZ）及母材的比例各不相同,造成HAZ冲击功结果不稳定。试验结果表明,稳定的焊缝宏观形貌,应从坡口准备、成型各工序、焊接工艺及操作等方面进行严格规范及标准化操作。     

基于图像分析的织物外观质量综合评价

 针对织物外观质量主观评价结果不够准确的现况,本文构建一种基于图像灰度分析的方法,可数字化对织物外观质量进行描述及评价。通过构建灰度极差值、纹理均匀度、能量极差值、对比度极差值、粗糙度极差值等五个灰度特征描述织物各方面外观质量状况,给出一种基于数量级调整及可变权重的织物外观质量综合评价模型,将五种特征进行数字化综合计算,以精确对织物外观质量进行综合评价。实验及分析显示,该方法能较为合理的对织物外观质量进行数字化综合描述及评价,为织物外观质量的客观化、标准化评估提供了一种新的研究思路。     

微孔发泡PP材料的断口形貌分析

本文采用二次开模注射成型的方法制取PP微孔发泡材料,对其力学性能进行了测试,实验结果表明,除拉伸强度有所下降外,其它机械性能都得到了提高,尤其冲击强度得到显著提高。用扫描电子显微镜观察了PP微孔发泡材料试样的冲击断口,初步研究了其断口形貌,认为冲击强度提高的原因主要是裂纹扩展过程中微孔吸收了大量的能量和转移了裂纹扩展路径。     

涤纶DTY性能指标对后道织造的影响及控制

涤纶DTY产品多样,用途广泛,不同的织造机和织造技术对DTY有不同的要求,通过对涤纶DTY物化性能、染色性能、外观特性的分析,浅析主要指标对后道织造产生的影响,通过更新质量概念,以适应不同织物风格的要求,生产出符合后道织造要求的涤纶DTY产品。     

基于CIECAM02模型的均匀色貌空间研究

本文利用BFD-CP小色差评估数据构造色分辨椭圆和孟塞尔新标数据集检验的方法,对基于国际照明委员会2002年推荐的色貌模型CIECAM02的颜色空间进行均匀性分析,并用线性回归方法调整初始颜色空间明度、彩度坐标的量表,推导出新的均匀颜色空间。并再次利用构造色分辨椭圆的方法和孟塞尔新标数据集检验了CIECAM02原始空间和优化色貌空间的均匀性,分析和比较了两者的性能;本文利用线性优化新建的色貌空间取得了较理想的效果,新建的优化色貌空间Jab的均匀性与CIECAM02原始空间相比有了较大的提高。