On buckling of cantilever rectangular plates under symmetrical edge loading

The stability of cantilever rectangular plates under the symmetrical edge loading will be studied in this paper by lite varialional calculus. We are going to find out the minimum critical loading for cantilever rectangular plates subjected to various edge loadings symmetrically on a pair of opposite free edges. We’ll discuss the least critical loadings when the buckling of rectangular plates acted on bv a pair of concentrated forces, uniformly distributed loads, locally uniform distributed loads, distributed loads in the form of triangle and a pair of concentrated couples occur respectively.     

车辆制动器制动力矩计算方法的研究

效能因数法是制动器制动力矩常用计算方法之一笔者对领从蹄式鼓式制动器制动力矩的效能因数法几种常见的计算公式进行了分析及计算验证结果表明：各公式虽然形式各异,但都是基于现今广泛使用的刚性假设,它们具有本质上的同一性文后对公式的选用提出了建议     

Computational fluid dynamics simulations of aerosol behavior in a high-speed (Heubach) rotating drum dustiness tester

Potential exposure from hazardous dust may be assessed by evaluating the dustiness of the powders being handled. Dustiness is the tendency of a powder to aerosolize with a given input of energy. Previously we used computational fluid dynamics (CFD) to numerically investigate the flow inside the European Standard (EN15051) rotating drum dustiness tester during its operation. The present work extends those CFD studies to the widely used Heubach rotating drum. Air flow characteristics are investigated within the Abe-Kondoh-Nagano k-epsilon turbulence model; the aerosol is incorporated via a Euler-Lagrangian multiphase approach. The air flow inside these drums consists of a well-defined axial jet penetrating relatively quiescent air. The spreading of the Heubach jet results in a fraction of the jet recirculating as back-flow along the drum walls; at high rotation rates, the axial jet becomes unstable. This flow behavior qualitatively differs from the stable EN15051 flow pattern. The aerodynamic instability promotes efficient mixing within the Heubach drum, resulting in higher particle capture efficiencies for particle sizes d < 80 μm.     

大理白族民间歌舞“八角鼓”引入地方小学体育课教学的思考

随着少数民族地区经济社会的快速发展,国家对少数民族地区基础教育校本课程研究与开发的工作力度不断加大,少数民族传统体育的研究进入了一个全新的发展时期,也为民族体育文化的传承和促进边疆民族地方基础教育事业发展提供了更为广阔的发展空间。文章拟探讨大理白族民间歌舞"八角鼓"的健身价值,把它引入云南省小学体育校本课程具有较高的开发价值,为进一步丰富地方小学体育课程资源的开发提供参考。     

Study on Airflow Field of Condensing Zone in Compact Spinning System with Perforated Drum

Negative pressure plays a very important role in compact spinning system. To know airflow field and its distribution is helpful to look into the condensing principle of fiber bundle. Therefore, computational fluid dynamics (CFD) software was used to simulate airflow field in this paper. Airflow velocity distributions both in different fiber layers and under different negative pressures were discussed. The results indicate that airflow velocity in upper layer of the fiber bundle is greater than that in lower layer.Airflow velocities in both X and Y axis directions have a positive correlation with negative pressure. It can provide a theoretical base to make high quality compact yarns in productive practice.     

浅谈电站锅炉汽包吊装施工

忻州广宇煤电有限公司锅炉汽包吊装,由于现场起重设备250t履带吊车无法直接吊装而成为工程的一大难点,经过多种方案比较后采用了卷扬机滑轮组倾斜提升的方案。详细论述了锅炉汽包吊装方案及采取的主要措施。     

滚筒结构参数对粉尘爆炸率的影响

通过假设与简化,建立了采煤工作面粉尘爆炸率与采煤机滚筒设计参数间关系的数学模型.以国产某型滚筒式采煤机为例,采用计算机模拟的方法得到了采煤机滚筒直径、螺旋叶片头数与粉尘爆炸率之间的关系曲线.通过分析,确定了各参数对粉尘爆炸率的影响,为预测不同结构滚筒参数的采煤机对粉尘爆炸率的影响,完善采煤机工作性能的评价体系,改进滚筒设计,减小采煤机的截割粉尘,降低粉尘爆炸率,提高煤炭生产的安全性提供理论依据.     

浅谈杯鼓实验中空气柱的选频作用

本文首先通过杯鼓实验得到了不同空气柱长度下杯内声波的频域图,然后基于波动理论解析分析了边界振动有衰减时空气柱的共振频率及振幅,结果表明空气柱长度在声波传播过程中具有明显的选频作用。     

网眼罗拉型集聚纺集聚区须条集聚机理分析

为深入研究网眼罗拉型集聚纺系统中纤维须条在流场作用下的运动规律,建立了集聚区域的计算流体动力学(CFD)模型,并运用Fluent软件对该区域的流场进行数值计算,然后建立了纤维微元在气流场中的动力学模型,利用自编的Matlab程序对其进行求解,最后获得了纤维在集聚区的运动轨迹.研究结果表明不同初始位置的纤维运动轨迹能够反映须条的集聚规律;气流的横向作用力能够使须条在集聚方向上发生集聚;上层纤维较网眼罗拉表面的纤维集聚速度快;y轴向气流力使须条贴伏在网眼罗拉表面.     

基于自适应神经模糊系统模型的锅炉汽包应力在线计算与监测

汽包寿命的在线监测是关系到自然循环锅炉运行安全与经济性的重要课题 .实现寿命监测的关键是寻找适合在线计算的应力模型 .针对建立模型的需要 ,制订了假想工况变动过程 ,并以此作为边界条件对锅炉汽包的温度、应力状况进行了三维有限元计算 .采用自适应神经模糊系统( ANFIS)再现有限元数值计算结果 ,从而建立了新的应力模型 .在所建模型的基础上对原有电站锅炉汽包应力监测系统的测点布置做出了相应的调整 .改进后的方法不仅提高了运算速度 ,减少了测点数量 ,而且继承了数值计算的精度 .由于数值计算的引入 ,克服了现场实验方法难以获得大样本数量的缺陷 ,并有利于进行事故状态的模拟 .