图论在检修维护工期规划中的应用——关键路线法的证明与计算

本文证明出,在图G上一种新的求关键路线方法。该法便于编制程序与上机计算。通过工程实例检验证该实法简便及运算速度快。     

一种快速三轴全方位光电跟踪策略

为了消除两轴光电跟踪系统的跟踪盲区,提出了一种存在冗余自由度的三轴光电跟踪系统.先运用四元数方法,建立三轴光电跟踪系统的运动学模型,然后在此基础上,应用极小范数最小二乘算法,设计出一种快速三轴全方位的光电跟踪策略.该跟踪策略针对方程系数求取Moore-Pen-rose广义逆矩阵,通过对三轴光电跟踪系统的运动方程进行三角变换,得到了三轴角增量组合的极小范数最小二乘解.仿真和实验结果表明,该跟踪策略不需要复杂的寻优过程,即可真正实现三轴联动全方位连续跟踪运动,与其他跟踪策略相比,该跟踪策略在跟踪运动过程中所需的各轴转动角度更小,因此跟踪性能更加优越.     

囚禁离子的非线性对压缩效应的影响

从描述囚禁离子与驻波激光场相互作用的Jaynes-Cummings(J-C)模型出发,导出了囚禁离子谐振动单量子共振激发相互作用的非线性J-C模型.通过求解这一模型的系统状态随时间变化,利用数值模型研究了离子质心运动的压缩效应的规律.结果表明,离子压缩效应与Lamb-Dicke参数和离子在驻波激光场中的位置有关.     

ZNRF3 promotes Wnt receptor turnover in an R-spondin-sensitive manner

R-spondin proteins strongly potentiate Wnt signalling and function as stem-cell growth factors. Despite the biological and therapeutic significance, the molecular mechanism of R-spondin action remains unclear. Here we show that the cell-surface transmembrane E3 ubiquitin ligase zinc and ring finger 3 (ZNRF3) and its homologue ring finger 43 (RNF43) are negative feedback regulators of Wnt signalling. ZNRF3 is associated with the Wnt receptor complex, and inhibits Wnt signalling by promoting the turnover of frizzled and LRP6. Inhibition of ZNRF3 enhances Wnt/β-catenin signalling and disrupts Wnt/planar cell polarity signalling in vivo. Notably, R-spondin mimics ZNRF3 inhibition by increasing the membrane level of Wnt receptors. Mechanistically, R-spondin interacts with the extracellular domain of ZNRF3 and induces the association between ZNRF3 and LGR4, which results in membrane clearance of ZNRF3. These data suggest that R-spondin enhances Wnt signalling by inhibiting ZNRF3. Our study provides new mechanistic insights into the regulation of Wnt receptor turnover, and reveals ZNRF3 as a tractable target for therapeutic exploration.     

单桩式海上风力机支撑结构强度振动分析

以某型2MW海上风力机支撑结构为母型,运用有限元软件ANSYS建立了三维实体模型,并进行了模态、涡激振动及瞬态动力学等强度与振动特性分析.结果表明,非线性弹簧单元适用于模拟土壤对基础的约束,三维实体单元有限元模型在固有频率和应力分布计算上均比梁单元模型更为准确.在所提供的风况和海洋条件之下,海流涡激振动不会与支撑结构产生共振,支撑结构的应力水平主要受风载的影响,该结果可为海上风力机支撑结构强度与振动分析提供参考.针对不同环境,仅需调整载荷,所建模型宜可适用.     

全气膜冷却叶片表面换热系数和冷却效率研究

为了研究全气膜冷却涡轮导叶叶片的换热特性,采用瞬态液晶技术获得了叶片全表面的高分辨率换热系数和冷却效率.实验在三叶片两通道放大模型中完成,叶栅进口雷诺数是1.0×105. 叶片前缘有8排复合角孔,压力面有21排轴向角孔,吸力面有24排轴向角孔.气膜孔排由2个供气腔供气,前腔二次流与主流的质量流量比为4.56％,后腔为4.67％.结果表明:受叶栅通道涡作用,气膜出流在吸力面呈聚敛状,在压力面则呈发散状.气膜出流受气膜孔角度影响,气膜孔下游的换热系数和冷却效率都较高.叶片前缘受到冲击,换热强,冷却效率低;叶片吸力面冷却效率维持在0.4左右,压力面维持在0.35左右.该全气膜冷却叶片气膜覆盖效果较好,冷却效率和换热系数分布均匀,是一种较好的冷却结构.     

全反射相干自相关法测量飞秒脉冲的特性分析

 全反射相干自相关法在测量紫外-X光波段的超短脉冲和宽频带脉冲方面具有优势。借助数值模拟,比较了全反射相干自相关和传统相干自相关方法测量不同相位结构脉冲时信号特征的异同。利用自建的组合式自相关装置测量了钛宝石激光器输出的飞秒脉冲及经由40 mm厚BK7玻璃块展宽而成的啁啾脉冲。理论分析和实验结果表明,同一脉冲的两种自相关曲线是基本相似的,因而在传统自相关方法不适用或操作不便的情况下,可以用全反射相干自相关法来替代。     

新型催化剂对猪油制备生物柴油的研究

目的以猪油为原料,对新型催化剂SXL制备生物柴油的工艺进行探索。方法通过单因素试验研究了反应温度、醇油摩尔比、催化剂用量及反应时间对生物柴油的产率和转化率的影响,通过GC-MS技术对所得生物柴油成分进行分析,并以BD100的方法检测其性能。结果最佳工艺条件下,SXL催化猪油制备生物柴油的产率、转化率均能达到98%以上,其主要成分为脂肪酸甲酯,主要性能指标达到或接近国家标准。结论新型催化剂SXL对于猪油催化转化制取生物柴油具有良好的催化性能。     

Thermal degradation of BaAl2Si2O8：Eu2＋ phosphor excited by near ultraviolet light

Eu2+ doped BaAl2Si2O8 phosphor was synthesized by one-step calcination of precursors that were prepared by chemical co-precipitation.The thermal degradation properties of BaAl2Si2O8:Eu2+ were investigated by photoluminescence,lifetime and chromaticity coordinate measurements.BaAl2Si2O8:Eu2+ is efficiently excited by incident light of 250-400 nm,which matches the emission of near ultraviolet LED chips well.BaAl2Si2O8:Eu2+ exhibits broad blue emission at 470 nm because of the 4f65d1-4f7(8S7/2) transition of Eu2+ ions,and the emission band shows an unusual blue shift with bandwidth broadening and emission intensity decreasing as the annealing temperature is increased.The luminescence decay and CIE chromaticity coordinates of BaAl2Si2O8:Eu2+ were determined to investigate its application in white LEDs.