Determination of the change of flavonoid components as the defence materials of Citrus unshiu Marc. fruit peel against Penicillium digitatum by liquid chromatography coupled with tandem mass spectrometry

A healthy fruit peel of Citrus unshiu Marc. and one infected by Penicillium digitatum were analysed for flavonoids via high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC–MS/MS) in the positive mode with selected ion monitoring (SIM). Among 16 flavonoid components characterised in C. unshiu Marc., four flavanones and nine flavones were identified for the first time. The identified compounds were quantified by HPLC–UV. To investigate the function of the flavonoids as defence materials, the flavonoid content change of the fruit peel inoculated with P. digitatum was monitored by HPLC. The flavonoid concentration in the infected fruit peel decreased initially after the infection and then gradually increased before finally progressively decreasing.     

无缝钢管定减径过程的有限元模拟

利用非线性有限元分析软件MSC．Marc对无缝钢管连轧工艺中的定减径过程进行了有限元模拟,分析了变形过程中金属的流动、管子的变形以及轧制力的变化等规律,得到了定减径过程中应力与变形的分布与变化以及各个轧制道次和最终成品管的结构形状,并通过实验的结果验证了所建立的钢管定减径过程有限元分析模型的正确性。研究的结果为生产实际提供了有益的依据。     

3-D distribution of tensile stress in rock specimens for the Brazilian test

It is claimed that the formula used for calculating the tensile strength of a disk-shaped rock specimen in the Brazilian test is not accurate, because the formula is based on the 2-dimensional elastic theory and only suitable for very long or very short cylinders. The Matlab software was used to obtain the 2-dimensional distribution of stress in the rock specimen for Brazilian test. Then the 2-dimensional stress distribution in Brazilian disk was analyzed by the Marc FEM software. It can be found that the results obtained by the two software packages can verify each other. Finally, the 3-dimensional elastic stress in the specimen was calculated. The results demonstrate that the distribution of stress on the cross section of the specimen is similar to that in 2-dimension. However, the value of the stress on the cross section varies along the thickness of the specimen and the stress is bigger when getting closer to the end of the specimen. For the specimen with a height-to-diameter ratio of 1 and a Poisson＇s ratio of 0.25, the tensile strength calculated with the classical 2-D formula is 23.3% smaller than the real strength. Therefore, the classical 2-D formula is too conservative.     

大型转炉倾动机构扭力杆有限元分析

应用有限单元法对大型转炉倾动装置的重要部件扭力杆进行应力应变分析,通过对正常工作状态和事故状态两种工况下扭力杆的变形及最大剪应力状态分析,确定出变截面扭力杆的强度,为产品设计提供依据.     

钢板仓输料桁架动力特性的有限元分析

应用有限元分析理论对钢板仓输料桁架进行动力分析,得到输料桁架的应力分布和位移变化过程图. 通过分析,能对钢板仓输料桁架的结构设计提供有益的参考.     

浮钳盘式制动器制动块有限元分析及结构优化

应用运用MSC Marc对制动块进行接触分析,得到其应力分布云图和接触状态云图,在此基础上进行结构优化,使之受力分散、接触均匀.     

有限元软件解决土-结构物动力相互作用的问题

1引言土体材料性质的复杂性和动力问题的复杂性,使得土-结构动力相互作用问题成为一个十分复杂的问题。通过解析方法分析土-结构动力相互作用问题具有相当的难度。利用计算机技术,进行数值模拟分析,就成为分析土-结构动力相互作用问题的一个有效途径。本文对大型非线性有限元软     

应用Marc分析气体静压轴承静态性能

依据气体润滑理论,建立了环面节流气体静压轴承数学模型。利用通用有限元软件Marc中的滑动轴承模块,结合气体静压润滑问题的有限元理论分析方法,对该模块进行二次开发,求得气体静压轴承的静态特性,并通过实验加以验证。     

基于Marc的风力发电机主轴动力学特性研究

本文根据振动理论建立了某型风力发电机主轴的振动方程。针对轴承弹性支撑对主轴固有频率影响的问题,建立了两种有限元模型,运用Marc有限元软件进行模态分析,并对计算结果做了对比。通过对比得出,考虑轴承弹性支撑方案计算出来的各阶固有频率值均有降低,说明轴承的弹性支撑对主轴固有频率有着较大的影响。这为以后进行进一步动力学研究提供了依据。     

弧齿锥齿轮准静态啮合仿真分析

利用大型有限元软件MSC.Marc,建立了弧齿锥齿轮副三齿啮合的三维有限元非线性接触模型.该模型可以实现转速和转矩的传递,基于该模型对齿轮副进行了准静态啮合仿真分析,并对啮合过程中的齿面接触应力及齿根弯曲应力变化规律进行了研究.数值计算结果符合弧齿锥齿轮的实际啮合规律,为进一步分析高速情况下弧齿锥齿轮的啮合状态提供了基础和依据.