引入EXCEL编程的单跨梁内力及位移计算教学探索

在结构力学中利用EXCEL软件的数据分析功能,能批量处理相似结构的计算。本文介绍了两个EXCEL表格,一个用于绘制简支梁在较复杂荷载条件下的剪力图、弯矩图、挠度图、转角图,另一个利用单位荷载法进行指定位置位移的辅助数据计算。在结构力学教学中引入EXCEL编程,不仅能提高学生的学习效率,还可以培养学生的自学能力和独立思考能力,增加学生对结构力学课程的兴趣和信心。     

带指定微商值特殊形式的插值

文章给出了节点处函数值与微商值个数不相等的特殊形式的插值的不同计算方法 ,特别是解决了找基函数的难题     

关于代数精确度

文章主要对代数精确度的结论和应用进行了研究、探讨 ,并给出了一些有用的结果。     

割集电流混合方程法

本文提出的方法用来求解含理想电压源及理想受控电压源支路的网络,克服了改进节点法通过增加网络变量来求解网络的缺点,大大减少网络方程系数矩阵中的零元素,扩大了计算机解题的规模。     

The finite element method and earthquake engineering: The 2006 Benjamin Franklin Medal in civil engineering presented to Ray W. Clough

The Franklin Institute, Philadelphia, PA awarded the 2006 Benjamin Franklin Medal in civil engineering to Ray W. Clough for revolutionizing engineering and scientific computation, and engineering design methods through his formulation and development of the finite element method, and for his innovative leadership in applying the method to the field of earthquake engineering with special emphasis on the seismic performance of dams.     

饱和土体中圆柱体对弹性波的散射

考虑土颗粒与孔隙流体的压缩以及孔隙流体与土骨架之间的粘性耦合作用,采用修正的Biot模型,研究了入射平面P1波在饱和土中饱和圆柱体上的散射问题,得到了散射和折射波场势函数的幅值方程,并对背向散射形函数随无量纲频率的变化曲线以及不同无量纲频率的径向位移沿周向的分布曲线进行了数值模拟。     

计算梁弯曲变形的位移合成法

位移合成法是指由梁弯曲变形的近似微分方程导出梁截面间转角及挠度的关系，并利用这种关系来计算截面位移的一种计算方法。这种方法与各种材料力学教科书中所提出的方法都有所不同。它利用弯矩图使得计算更为方便、实用。     

Virtual internal thermal work evaluation in the multifield variational statements for the analysis of multilayered structures

The principle of virtual displacements (PVDs) extended to elasto-thermo-electric problems includes virtual internal elastic, thermal and electric works. The governing equations have displacement vector, temperature and electric potential as primary variables of the problem, and the elasto-thermal, elasto-electric and pure elastic problems are obtained as particular cases by deleting the appropriate contributions in the general elasto-thermo-electric variational statement. The most sensitive issue is given by thermal coupling because the thermo-elastic and thermo-electric effects change depending on the type of load and analysis considered (mechanical load, temperature or electric potential imposed and free vibration analysis). This feature means that the form of the virtual internal thermal work in such variational statements changes depending on the analysis performed and the load applied. Results about multilayered plates and shells suggest the appropriate extension of the variational statement for each analysis, and they give an exhaustive explanation for several forms of the PVD proposed.     

基于施工过程的路基水平位移特征分析

基于非线性有限元方法，对路堤各施工阶段路基体内水平位移的变化特性进行了考察，对比分析表明：在各施工阶段路基体内最大水平位移的位置并不是固定不变的，其随着填筑和固结阶段的不同而发生变化。最大水平位移的位置一般位于坡趾处竖向断面与坡中竖向断面之间的范围附近，故建议把测斜仪布置在该范围内(为了施工方便，可布置在坡中竖向断面或坡趾竖向断面处)。分析还表明，工程中通常采用的利用测斜仪来量测路基深部水平位移发展情况的技术存在一定的缺陷，故需发展更精密的仪器来考察路基水平位移的基本特性。     

Improving micropropagation of some grape cultivars via boron,calcium and phosphate

BackgroundAn efficient regeneration protocol is a priority for the successful application of plant biotechnology. Grape nodal explants were used to develop a micropropagation protocol for Thompson Seedless and Taify cvs. Explants were cultured on MS medium supplemented with Kinetin or benzylaminopurine (BA) and indolebutyric acid (IBA).ResultsFor both cultivars, axillary buds were grown, only, on a medium enriched with kinetin, moreover, shoot tip necrosis and callus formation were observed on Thompson Seedless cv. cultures grown on a medium with BA. Supplementing the growth medium with 100 mM (boron) B and 2.5 mM (calcium) Ca successfully help overcome these phenomena. The highest regenerated shoot numbers (14 and 6.2 explant⁻¹) for Taify and Thompson Seedless cvs., respectively, were on media supplemented with 13.2 µM BA + 4.9 µM IBA and BA 13.2 µM + 5.8 µM IBA, respectively. Moreover, these media supported the developing shoots to have the heaviest dry weights (1.46 and 0.72 mg explant⁻¹) for Taify and Thompson Seedless cvs., respectively. Thompson Seedless cv. regenerated shoot numbers and their dry weights were significantly increased by increasing the MS medium PO₄⁻ concentration. However, these two parameters were significantly decreased for Taify cv. Developing shoots were elongated and rooted on MS medium enriched with 4.9 µM, IBA 100 mM B and 2.5 mM Ca. Plantlets were acclimatized and successfully transferred to the greenhouse conditions.ConclusionsA novel promising protocol for Thomson Seedless and Taify cvs. micropropagation using single nodes has been developed.How to cite: Al-Aizari AA, Al-Obeed RS, Mohamed MA-H. Improving micropropagation of some grape cultivars via boron, calcium and phosphate. Electron J Biotechnol 2020;49. https://doi.org/10.1016/j.ejbt.2020.10.001