无缓凝剂磷酸镁修补砂浆的力学性能实验研究

磷酸镁水泥(Magnesium phosphate cement,MPC)是一种快速修补型胶凝材料,具备快硬、早强、高强、粘结力强、耐久性好等优点。首先运用正交试验方法,通过控制胶砂比、氧化镁与磷酸二氢盐的物质的量比(M/P)和水胶比,确定了基准MPC修补砂浆的最优配合比。然后研究了粉煤灰和磨细矿渣对MPC修补砂浆抗压强度和抗折强度的影响,分析了其强度特征。结果表明,MPC修补砂浆的最佳M/P比为6∶1,胶砂比1∶1。掺加粉煤灰的MPC修补砂浆具有较高的强度尤其是抗折强度,适宜作为道路与机场道面的快速修补材料。掺加磨细矿渣的MPC修补砂浆,其力学性能不如掺加粉煤灰的MPC修补砂浆。此外,MPC修补砂浆的抗折强度和抗压强度之间具有密切的线性相关关系,且与养护龄期、原材料来源与烧结温度、是否掺加缓凝剂和矿物掺合料、M/P比和水胶比等因素无关。     

A fast and automatic full-potential finite volume solver on Cartesian grids for unconventional configurations

To meet the requirements of fast and automatic computation of subsonic and transonic aerodynamics in aircraft conceptual design,a novel finite volume solver for full potential flows on adaptive Cartesian grids is developed in this paper.Cartesian grids with geometric adaptation are firstly generated automatically with boundary cells processed by cell-cutting and cell-merging algo rithms.The nonlinear full potential equation is discretized by a finite volume scheme on these Cartesian grids and iteratively solved in an implicit fashion with a generalized minimum residual (GMRES) algorithm.During computation,solution-based mesh adaptation is also applied so as to capture flow features more accurately.An improved ghost-cell method is proposed to implement the non-penetration wall boundary condition where the velocity-potential of a ghost cell is modified by an analytic method instead.According to the characteristics of the Cartesian grids,the Kutta condition is applied by specially computing the gradients on Kutta-faces without directly assigning the potential jump to cells adjacent wake faces,which can significantly improve the solution con verging speed.The feasibility and accuracy of the proposed method are validated by several typical cases of sub/transonic flows around an ONERA M6 wing,a DLR-F4 wing-body,and an unconventional figuration of a blended wing body (BWB).The validation cases demonstrate a fast convergence with fully automatic grid treatment and computation,and the results suggest its capacity in application for aircraft conceptual design.     

基于大数据的民用飞机未来运营模式探索

大数据作为一种新兴的IT实现方式,在深刻影响IT业变革的同时,也为航空业带来了新的发展机遇。飞机运行过程中产生的海量运营数据最能体现民机的大数据基因,基于大数据的飞机运营支援将会是其在航空产业施展拳脚的主要战场之一。首先通过对航空大数据的梳理与分析,获得运营数据的种类、结构、数据流程以及相关特点。然后结合航空公司的具体业务需求,针对飞机典型复杂系统,分别以健康监控中的故障诊断、性能退化预测以及维修辅助决策几大关键技术作为大数据应用的切入点介绍技术研究路线,利用数据挖掘、机器学习等方法识别运营数据在系统不同健康状态下的特征表达,准确预测系统退化趋势,设置风险预警模型以提前预知潜在故障,最后从工程应用角度探讨这些关键技术的大数据实现平台以及基于大数据的运营业务流程。     

基于改进Johnson-Cook模型的5083P-0铝合金动态本构关系研究

为研究5083P-0铝合金在高应变率下的力学行为及本构模型,通过RPL100材料试验机和分离式霍普金森压杆(SHPB),对5083P-0铝合金进行了准静态及应变率范围950～3000 s-1的冲击动态压缩实验.结果 显示随着应变率的增加,5083P-0铝合金的屈服强度、流动应力增加,应变硬化率减小,具有应变硬化效应,正...     

日照边缘区域电离层对耀斑的响应特点研究

利用MSIS模型和背景太阳辐射谱模型,在一定大耀斑辐射谱假设的前提下,计算了耀斑期间日照边缘区域的电子产生率,分析了这一区域电离层电子密度的变化特点.结果表明,大耀斑期间在日照边缘区域,甚至大于太阳天顶角90°的区域都有明显的电子产生率的增加.从不同太阳天顶角处的电子产生率剖面的形态来看,随着天顶角的增加最大电离率减少,但高度增加.计算还显示了在太阳天顶角小于90°的区域内电子产生率的垂直分布有明显的双峰结构,这种结构对应着电离层的E区和F区,但在天顶角大于90°区域,F区的电子产生率要大得多.考虑到离子和电子的复合过程,这一区域的总电子含量的增加主要产生在高F区.      

高精度、超低频标准振动台

振动测量应用愈来愈多,做为振动测量标准的的标准振动台的幅度和频率的精度显得尤为重要,而现有标准振动台的精度难以突破1%。本文提供一种新型高精度、超低频标准振动台,其精度可高达0.005%,还可实现频率低达0.002778Hz的超低频标准振动台。     

RELATIONSHIPS FOR MOTION DESCRIBED IN ANY TWO ROTATIONAL REFERENCE FRAMES

In this paper the definitions of the relative derivatives of a vector with respect to time in any reference frame by using the notation of vectrix are proposed. It is further shown that with the help of vectrix one can treat the relative derivatives more clearly and more rigorously when multiple reference frames are concerned. Very useful relationships between the first order relative derivatives described in any two reference frames are derived. Relationships for the second order relative derivatives are also presented in detail. A new concept called "rotation induced acceleration" which is caused by the rotation of two reference frames when motion is necessarily described in them is presented. The result obtained in this paper is the generalization of the acceleration theorem given in conventional theoretical mechanics.     

一种扩展的比例导引规律及其弹道方程的构建

在传统的动力学微分方程的基础上提出了一种扩展的比例导引法 ,并给出了该导引规律下的相对弹道方程。文中的推理过程表明 ,这种导引规律对导弹、目标的运动速度几乎没有限制 ,理论上说明运用该制导规律的导弹将能对付高机动大速度目标 ,其弹道方程的建立 ,使得研究该制导规律下的弹道特性成为可能。     

装备维修保障能力评估精确化研究

论文就维修保障能力评估中木桶现象引起的评估不精确问题,深入分析了影响因素,提出了切实可行的解决方法,为装备维修保障能力精确评估决策提供了理论依据,并可以适用于其他类似的评估.     

“任务驱动”下的计算机专业课程教学实践与探索

本文总结了“任务驱动”在教学中的应用，提出了“任务”设计要全方位立体化进行考虑；评价要全方位多样化。指出了“任务驱动”必须与多种教学法优化组合，才能发挥其最大教学效率。