小麦抗倒性研究进展

倒伏是严重影响小麦子粒产量和品质的一个重要因素。本文系统阐述了小麦茎秆形态和结构特性、茎秆化学成分与抗倒伏关系以及抗倒性的遗传和分子标记等方面的最新研究进展。株高、基部节间长度与抗倒性呈负相关;而基部节间粗度、秆壁厚、单位长度干重与抗倒性呈正相关。茎秆机械组织细胞层数、厚度,维管束数目、面积以及髓腔大小与抗倒性密切相关。茎秆化学成分中纤维素、木质素以及碳水化合物含量和硅、钾元素含量与抗倒性呈正相关。小麦抗倒性呈数量性状遗传特征,除受多对主基因控制外,可能还受微效修饰基因作用。采用分子标记技术已将抗倒性以及与抗倒性相关的茎秆形态性状进行了QTL定位。

荞麦抗倒性研究进展

旨在为荞麦抗倒性研究领域的科研人员提供评价方法和理论依据。本研究归纳了荞麦茎秆和根系形态、茎秆化学成分和生理生化特征等方面与倒伏的关系,总结了荞麦茎秆抗倒性的遗传规律和荞麦抗倒性的评价方法,提出了评价荞麦抗倒性的主要指标和防治荞麦倒伏的生产措施。最后,对荞麦抗倒性QTL定位、肥料运筹和耕作方式等有待拓宽和深入研究的内容做出了展望。

Shape-sizing nested optimization of deployable structures using SQP

The potential role of formal structural optimization was investigated for designing foldable and deployable structures in this work.Shape-sizing nested optimization is a challenging design problem.Shape,represented by the lengths and relative angles of elements,is critical to achieving smooth deployment to a desired span,while the section profiles of each element must satisfy structural dynamic performances in each deploying state.Dynamic characteristics of deployable structures in the initial state,the final state and also the middle deploying states are all crucial to the structural dynamic performances.The shape was represented by the nodal coordinates and the profiles of cross sections were represented by the diameters and thicknesses.SQP(sequential quadratic programming) method was used to explore the design space and identify the minimum mass solutions that satisfy kinematic and structural dynamic constraints.The optimization model and methodology were tested on the case-study of a deployable pantograph.This strategy can be easily extended to design a wide range of deployable structures,including deployable antenna structures,foldable solar sails,expandable bridges and retractable gymnasium roofs.

Effect of liquid-solid ratio on the morphology,structure,conductivity,and electromagnetic characteristics of iron particles

Using a ball-milling technique,polymorphous iron particles were prepared by changing only the liquid-solid ratioλ.Effects of λon their morphology,structure,conductivity,and electromagnetic properties were studied.The results show that an increase ofλfrom 0 to 0.25 causes a nonlinear decrease of the conductivity in the ranges of 88.50-2.25 S cm-1 and a regular variation of the electromagnetic parameters,corresponding to the as-obtained iron particles.This is ascribed to a combination of the increased shape anisotropy and the decreased fresh surface with active atoms deriving from the weakened welding-on action and the enhanced micro-malleation action in the ball-milling process.Hereinto,the iron flakes formed at wet-milling with λ=0.08-0.25 have lower conductivity,higher permittivity and permeability,and more excellent absorption property compared with the irregular iron particles obtained at dry-milling withλ=0.It is a consequence of the synergistic effect of dielectric relaxation loss,exchange energy and conductance loss originating from the flake-shape structures.This indicates that the morphology,structure,conductivity,and electromagnetic properties of the products can be effectively controlled by changingλ.

船用柴油机轴系不对中在线检测与自愈调控方法

船用柴油机及其动力轴系受力状态复杂,结构装配、船体变形等影响相互耦合,常发生轴系不对中故障,易导致轴承严重磨损、联轴器断裂、发动机曲轴断裂等严重事故。受结构、工况等条件影响,传统的振动时频特征分析方法难以实现轴系不对中故障的准确定量检测,工频、二倍频特征频率也易与其他故障特征混叠并造成误判。基于不对中状态下的轴系结构形态特性,建立一种不对中形态特征计算模型,针对不对中形式、机械结构影响提出了在线检测方案;以柴油机输出轴为研究对象,建立6自由度故障模拟试验台,完成了不对中检测方法的试验验证;进一步提出一种轴系不对中故障自愈调控方案并完成试验验证,实现了轴系不对中故障的在线自愈调控。数据表明:基于轴系形态特征的不对中检测方法实现了不同工况条件下的不对中在线检测,准确率超过90%;伺服电缸驱动的自愈调控装置可在10 s内使轴系不对中量降低超过75%。