The relationship of human interest to immediate retention and to acceptability of technical material.

A different version of a 1206-word two-part lesson on aircraft mechanics was presented to each of 4 groups of 110 Ss. The versions differed with respect to level of human interest ("personal words" and "personal sentences") used in the two halves. "The results… indicate that a high level of human interest… of technical writing produced no significant difference in immediate retention test score, was consistently judged less acceptable, and showed a tendency to produce a greater amount read in a given time, compared to a low level of human interest.… " (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the hyper-singular boundary-element formulation for fracture-mechanics applications

The present paper discusses the application of the hyper-singular boundary-integral equation, the so-called traction formulation, to solve linear-elastic-fracture-mechanics (LEFM) problems. Emphasis is given to two-dimensional boundary-element implementations, combining continuous or discontinuous quadratic and quarter-point elements in order to identify the limitations and improvements for computing stress-intensity factors. The study shows the importance of considering displacement-derivative continuities into the numerical implementation and the use of quarter-point elements to improve results.     

2204滚动轴承的有限元分析与研究

为了寻找滚动轴承发生故障破坏的原因,选取以ANSYS为计算机工具,建立了有限元模型;以典型的径向载荷和边界条件为例,分析研究了其内部位移和载荷分布规律。分析和研究发生故障的内部机理,为深入研究滚动轴承破坏机理提供依据。     

研究型教学在材料力学教学中的应用

高校《材料力学》传统教学中,学生自主学习的能力较差,缺乏对知识的综合运用能力。为了克服传统教学模式的弊端,文章提出了《材料力学》教学中运用研究型的教学模式,这对提高学生的综合素质和能力具有重要意义。     

Knee extension moment arm variations relate to mechanical function in walking and running

The patellofemoral joint plays a crucial mechanical role during walking and running. It increases the knee extensor mechanism''s moment arm and reduces the knee extension muscle forces required to generate the extension moment that supports body weight, prevents knee buckling and propels the centre of mass. However, the mechanical implications of moment arm variation caused by patellofemoral and tibiofemoral motion remain unclear. We used a data-driven musculoskeletal model with a 12-degree-of-freedom knee to simulate the knee extension moment arm during walking and running. Using a geometric method to calculate the moment arm, we found smaller moment arms during running than during walking in the swing phase. Overall, knee flexion causes differences between running and walking moment arms as increased flexion causes a posterior shift in the tibiofemoral rotation axis and patella articulation with the distal femur. Moment arms were also affected by knee motion direction and best predicted by separating by direction instead of across the entire gait cycle. Furthermore, we found high inter-subject variation in the moment arm that was largely explained by out-of-plane motion. Our results are consistent with the concept that shorter moment arms increase the effective mechanical advantage of the knee and may contribute to increased running velocity.     

铝粉-空气混合物的燃烧转爆轰过程

利用自行设计的长29.6 m、内径199 mm配有40套喷粉扬尘装置的大型水平爆轰管,研究了细片状铝粉-空气混合物在40 J弱点火条件下火焰从发生到加速、最后实现爆轰转捩的全过程,探讨了铝粉浓度和点火延迟时间对爆轰参数的影响.结果表明,铝粉-空气混合物燃烧转爆轰(DDT)过程可分为慢速反应压缩阶段和快速反应冲击阶段.当点火延迟时间为370 ms,铝粉质量浓度为300 g/m~3时,在管道中距离点火位置83倍长径比处峰值超压为9.8 MPa,爆速为1 670 m/s,发生了DDT过程.在铝粉-空气混合物自持爆轰波的传播过程中,由于呈现螺旋爆轰波结构,爆速和峰值超压随着传播距离振荡.     

TNT装药水中爆炸的数值模拟

采用AUTODYN软件对不同起爆方式下TNT装药水中爆炸模型进行了数值计算,并对计算结果进行了实验验证.根据计算结果分析了中心起爆、端面中心起爆和端面面起爆情况下,在装药不同方位的水中冲击波压力峰值随距离的变化趋势.计算结果表明,端面起爆状态下,装药径向的冲击波压力峰值均大于端部;中心起爆状态下,一定距离处,装药端面的压力峰值大于径向.改变起爆方式,可以实现水中爆炸冲击波能量的定向增益,提高特定方位爆炸能量利用率.     

白竹磷矿地下开采岩体移动变形分析

根据鄂西山区白竹磷矿地下开采工程实际情况,利用随机介质理论模型,对地下开采引起的地表移动变形进行了具体的计算分析.将理论结果与实测资料进行了对比.二者吻合.所获结果表明.本文提出的分析方法可用于分析山区厚磷矿层地下开采岩体移动变形问题.     

双套管密相气力输运过程的数值模拟和能耗分析

基于计算流体力学理论,提出一种可用于预测双套管密相气力输送系统能耗的新方法. 与以往依靠经验的计算方法不同,本工作将输送管道分为起始段与充分发展段两部分,分别进行详细的计算流体力学模拟后汇总得出整个系统的总能耗. 压力梯度为750 Pa/m的情况下,计算所得物料输送速率为10 t/h,耗气量为290 m3/h,实验所得物料输送速率为8.0 t/h,耗气量240 m3/h,证明本数模方法是可靠的.     

Analysis of permeability and effective viscosity by CFD on isotropic and anisotropic metallic foams

Hydrodynamic properties of open-cell metallic foams are analyzed at the pore scale on a microtomographied sample from creeping flow to unsteady inertial flow. The influence of the anisotropy, obtained by shearing the initial sample, is also analyzed. The simulations show that the Darcy-Forchheimer law is valid at Re_dl>1 and that the inertial coefficient tensor can be asymmetric as proved by Whitaker [1996. The Forchheimer equation: a theoretical development. Transp. Porous Media 25, 27-61] and checked by the lattice Boltzmann method. Despite this property, the eigen vectors are nearly orthogonal to each other and their orientation follows the shear angle. To evaluate the accuracy of the results, the analysis of the REV leads to a REV size lower than 2.5d_p for the velocity and is lower than 4.5d_p for the inertial flow permeability tensor. It is shown also that the CFD approach, validated by MRI investigation [Graf von den Schulenburg et al., 2007. Flow through an evolving porous media-compressed foam. J. Mater. Sci. 42 6541-6548], matches the 3D-Brinkman-Forchheimer model if the effective viscosity is close to two.