利用小尺寸缺口试样测定延性材料的单轴本构关系

提出了一种利用三点弯曲试样获取延性材料本构关系的测试方法：针对小尺寸缺口试样的三点弯曲线载荷-位移曲线,采用有限元辅助测试（Finite-element-analysis aided tests,FAT）方法,迭代获得材料代表性体积单元（Representative volume element,RVE）本构关系。研究表明,两种延性材料的有限元迭代反求结果和单轴拉伸试验结果吻合较好。应用该方法,可以采用小尺寸缺口试样来获取延性材料的本构关系。     

基于三维裂纹尖端应力场的应力强度因子计算方法

提出一种基于无限大体裂纹尖端弹性应力场理论解的前几项多项式函数,对实际裂纹体弹性应力场有限元解进行拟合来计算应力强度因子的方法.该方法在计算应力强度因子时不需要预先假设裂纹尖端的应力应变状态,应力强度因子计算结果更符合三维裂纹体裂纹尖端实际的应力应变状态.首先基于二维无限大板中心穿透裂纹应力场理论解验证了方法的有效性,探讨了拟合确定应力强度因子需要的多项式应力函数的项数.然后分别以二维大板中心穿透裂纹、三维大体内埋圆裂纹和三维有限厚板中心穿透裂纹的应力强度因子计算为例,通过与无限大板和无限大体应力强度因子理论解以及基于位移外推法和1/4节点张开位移法的应力强度因子有限元解的对比分析,验证了该方法的有效性和合理性.研究表明该方法能够合理反映三维裂纹体裂纹尖端的实际应力应变状态,计算得到的应力强度因子数值更合理.      

一种基于蜂拥策略的分布式无人机编队控制方法

在无人机编队控制中,传统的主从式集中编队控制方式需要大量信息交互,对机间通信的要求较高.针对具有虚拟领航者的分布式无人机自组织编队跟踪问题,运用有界蜂拥算法对无人机模型进行求解.首先,提出了一种有界控制输入的蜂拥算法,并对算法的稳定性进行了分析;其次,对无人机进行了建模,提出了虚拟受力点的概念,并对虚拟受力点进行受力分析,将算法中的加速度转化成无人机径向速度与偏航速度的更新,以达到分布式无人机编队自组织以及跟踪虚拟领航者的目的;最后,通过仿真验证了算法和模型的有效性.     

风车状态下转子性能及通道内流动分析

为探究低展弦比压气机转子在风车状态下由压气机模式向涡轮模式转化过程中性能、内部流场结构以及气动损失的演化过程,提出了一种基于叶片和流体间能量传递的简化数值计算方法,以获得某转速下的风车状态临界流量点。在数值模拟的基础上,重点对比了同一转速线上压气机工况点(小流量工况)、风车临界点和涡轮工况点下叶尖泄漏损失的演化机制,同时探究了叶片通道内流动分离的演化过程。 结果显示,随着转速的增加,转子风车状态临界流量呈现近似线性的变化趋势。而同转速下随流量增大,叶尖泄漏流从吸力面流向压力面,并与压力面上的低能量流体进行掺混,造成了流动堵塞。同时,从压气机模式转向涡轮模式的过程中,叶尖区域的流动分离从吸力面分离转变为压力面分离,随后分离强度和尺寸逐渐增大,造成的气动损失显著增加;而在轮毂区域,流动分离始终保持吸力面分离,其分离尺度沿径向有所发展。     

民用涡轴发动机进气系统结冰试验

围绕中国民航规章CCAR-33部R2版中第33.68条款适航要求,针对涡轴发动机提出了一种满足适航要求的试验方法,包括结冰关键点分析、结冰取证试验点选定、整机结冰取证试验三部分。结合涡轴发动机工作包线,开展结冰关键点分析以选定结冰取证试验点。在结冰包线内选择了若干结冰计算点,并计算每个点的结冰位置与结冰量。计算结果显示:温度接近0 ℃且海拔高度较低的区域是涡轴发动机结冰量显著的区域。结冰试验时在-4~-1 ℃的温度区间寻找刚出现结冰的温度点与结冰量最大的温度点。试验结果显示:结冰量最大的温度点是最严酷的结冰试验点。     

Evolution of periodic orbits near the Lagrangian point L2

A study of the evolution of the periodic and the quasi-periodic orbits near the Lagrangian point L₂, which is located to the right of the smaller primary on the line joining the primaries and whose distance from the more massive primary is greater than the distance between the primaries, in the framework of restricted three-body problem for the Sun–Jupiter, Earth–Moon (relatively large mass ratio) and Saturn–Titan (relatively small mass ratio) systems is made. Two families of periodic orbits around the smaller primary are identified using the Poincaré surface of section method – family I (initially elliptical, gradually becomes egg-shaped with the increase in the Jacobi constant C and elongated towards the more massive primary) and family II (initially egg-shaped orbits elongated towards L₂ and gradually becomes elliptical with the increase in C). The family I in the Sun–Jupiter and Saturn–Titan systems contains two separatrix caused by third-order and fourth-order resonances, while the Earth–Moon system has only one separatrix which is caused by third-order resonances. Also in the Sun–Jupiter and the Saturn–Titan systems, family I merge with family II, around Jacobian constant 3.0393 and 3.0163, respectively, while in the Earth–Moon system, family II evolves separately from two different branches. The two branches merge at C = 3.184515. In the Earth–Moon system, the family II contains a separatrix due to third-order resonances which is absent in the other two systems.     

刍议构建凸显高职院校特色的任选课体系

以长沙航空职业技术学院为背景,就高职院校任选课课程体系的构建进行研究探索,以求综合高职教育背景、学院行业背景、学院办学理念以及专业结构特点等因素,合理的划分出课程模块,并进一步制定任选课课程教学标准,构建既能体现学院行业特色、传承学院校园文化,又能服务学院专业教学的新的任选课课程体系。     

Matching suitable feature construction for SAR images based on evolutionary synthesis strategy

In the paper,a set of algorithms to construct synthetic aperture radar（SAR）matching suitable features are frstly proposed based on the evolutionary synthesis strategy.During the process,on the one hand,the indexes of primary matching suitable features（PMSFs）are designed based on the characteristics of image texture,SAR imaging and SAR matching algorithm,which is a process involving expertise;on the other hand,by designing a synthesized operation expression tree based on PMSFs,a much more flexible expression form of synthesized features is built,which greatly expands the construction space.Then,the genetic algorithm-based optimized searching process is employed to search the synthesized matching suitable feature（SMSF）with the highest effciency,largely improving the optimized searching effciency.In addition,the experimental results of the airborne synthetic aperture radar ortho-images of C-band and P-band show that the SMSFs gained via the algorithms can reflect the matching suitability of SAR images accurately and the matching probabilities of selected matching suitable areas of ortho-images could reach 99±0.5%.     

复杂曲面零件散乱点云特征点提取

复杂曲面零件的几何特征提取对加工质量的检测及逆向重构具有重要意义。提出了一种复杂曲面零件散乱点云特征点提取方法。首先,提出了基于高斯权重的邻域主成分分析的方法,通过估计每一点邻域的局部变化程度对点云模型进行初始标记;然后,采用基于标记的自动识别法实现特征点的提取;最后,通过特征点聚类的方式去除了特征点集中的异常点,完善了提取的点云特征。该方法直接操作于散乱点云,无需任何的拓扑连接信息。试验结果表明:该方法简单、有效,不需要过多地人为调节参数,特征点提取完整。     

微分对策理论及其研究现状分析

本文阐述了微分对策在经济和军事领域中的研究和应用,详尽地叙述了微分对策的分类,并采用定量和定性方法对微分对策进行了分析,指出了微分对策的研究难点,对发展趋势作了较为详细的探讨。