Orientation dependence of primary dendrite spacing

The orientation dependence of the primary dendrite spacing is examined through the solidification of a succinonitrile-3.61 wt pct acetone alloy with a Bridgman-type device. Primary dendrite spacing has been studied as a function of the primary dendrite trunk orientation with respect to the thermal gradient direction under different growth rate conditions. The observations show that the orientation dependence of the primary dendrite spacing can be related to the formation of new primary dendrites at divergent grain boundariesvia the branching mechanism. A branching-based model is developed to study the interaction between secondary and tertiary dendrite arms. Based on this model, a simple analytical relationship is proposed to account for the orientation dependence of the primary dendrite spacing.     

小间距平行顶管管道土压力计算方法研究

小间距顶管过程中,由于管?管相互作用的影响,使得管周土压力分布与单管顶进土压力分布模式产生差异,从而造成小间距顶管荷载确定、结构计算及顶力估算与控制等设计施工难题。结合数值模拟反分析,基于太沙基土压力理论和极限平衡理论,假设了土体松动线和上部既有顶管的支挡作用线,进一步构建了小间距平行顶管管道拱顶垂直土压力的计算方法。基于构建的土压力计算方法,分析了土体抗剪强度、管径、管间距等对新建顶管拱顶土压力的影响,并与不考虑既有顶管影响的土柱理论和太沙基理论计算值进行了对比。计算结果表明:土体抗剪强度越大,新建顶管拱顶垂直土压力越大,而其侧面的土压力越小;抗剪强度较大时,新构建方法计算拱顶土压力小于太沙基理论计算结果,抗剪强度较小时,新构建方法计算拱顶土压力大于太沙基理论计算结果;顶管埋深增加时,新建顶管拱顶土压力增加,相较于土柱理论和太沙基理论,新构建方法计算的新建顶管拱顶土压力增量最小;随着管间距增加,新建顶管拱顶土压力越来越大。      

Size, style, and vertical spacing in the legibility of small typefaces.

Conducted 3 experiments with a total of 264 18-77 yr. old adults to determine whether the minimum legible size of lowercase Univers, found previously to be 6.6 point (pt.), generalizes to other typefaces and to printing in capitals. Times New Roman and Perpetua were found to be as legible as 6.6 pt. Univers when the "x" heights were the same, about 1.2 mm. (1 pt. = .35 mm.), i.e., when the Times was 6.6 pt., and the Perpetua was 8.6 pt. Univers capitals with a vertical space between lines equal to 60% of the letter height were as legible as 6.6 pt. lowercase Univers when they occupied about the same vertical height of paper. Reducing the height of the capitals from 1.4-1.2 mm made them reliably (p