Fuzzy multi-criteria decision-making approach to prioritization of space debris for removal

As private companies and government space agencies begin to seriously consider the task of active space debris removal, it is becoming increasingly more important to determine the highest priority objects to deorbit. This work sets forth an approach for prioritization of space debris through the utilization of Multi-Criteria Decision-Making methodologies and fuzzy logic, as well as both quantitative and qualitative criteria. The proposed debris prioritization approach considers various criteria including the orbit, size, mass, pairwise and total collision probabilities, and decay timeframe of each debris object. The means of assigning attributes to each assessment criterion is discussed in detail. To determine the weighting scheme for the criteria, a questionnaire was prepared and shared with experts in the field of space situational awareness. The work examines over two thousand critical debris objects selected from the existing debris catalog with respect to these criteria. The quantified attributes for each debris object are then aggregated through the fuzzy versions of the Analytic Hierarchy Process and the Technique for Order Preference by Similarity to Ideal Solution. The results of the analysis identify high-priority debris objects for removal from Earth-bound orbits.     

移位寄存器分析方法的研究

研究了串行输入 ,并行输出单向移位寄存器的功能。利用所提出的分析方法对移位寄存器进行的分析 ,揭示了移位寄存器内在的联系。     

夹芯的典型参数对夹层板受迫振动影响分析

根据伽辽金法,用Matlab/Simulink软件对推导的经典板假设理论、一阶剪切理论蜂窝夹层板运动方程进行了数值仿真。简单算例的计算结果表明两者基本一致。基于一阶剪切理论讨论了蜂窝夹芯泊松比对蜂窝夹层板低阶频率的影响。发现当泊松比接近1时对频率响应有显著的影响。     

基于互相关向量估计的自适应盲均衡算法

基于互相关估计的盲MMSE均衡算法以批处理方式估计信道输出向量和信道输入信号之间不同延时的互相关向量,得到MMSE均衡器系数。由于涉及到大型矩阵乘积,若在线实现,计算量较大。根据该算法对信道阶数过估计不敏感特性,推导出基于互相关向量估计的盲MMSE均衡的自适应实现算法。自适应算法将矩阵和矩阵相乘转换为矩阵和向量的相乘,大大减少了均衡系数更新计算量,计算量仅为O(K2)(K为矩阵维数)。仿真结果显示自适应算法的收敛性能远远优于目前存在的自适应算法。     

用于失谐叶盘动力学特性分析的减缩计算方法

提出了一种用于失谐叶盘动力学特性分析的减缩计算方法.该方法采用基于周期对称的谐波平衡法,建立非线性的迭代方程,能够基于单扇区的矩阵求解整个失谐叶盘的强迫响应,且不存在任何截断误差,因而效率高于部件模态综合法但精度并不降低.从周期对称结构理论出发给出了方法原理的数学推导,在此基础上通过一个失谐叶盘有限元模型算例对该方法的效率与精度进行了讨论.结果表明:相较部件模态综合法,周期对称谐波平衡法矩阵维度减小59.5%,计算复杂度减少93.4%,计算时间节省57.4%.     

基于模糊分数阶PI~λD~μ的柔性结构振动主动控制

为防止翅翼结构因干扰而产生振颤,以柔性悬臂梁结构为被控对象,提出一种参数自整定的分数阶比例积分微分控制器,在利用遗传算法取得优化参数后,通过模糊规则第2次对控制器参数进行在线整定,以达到实时最优控制的目的.在Simulink软件环境下进行了数值仿真,结果表明:设计的分数阶比例积分微分控制器具有记忆性,动态表征能力强.与常规比例积分微分控制器相比,冲击激励下的系统响应稳态时间缩短0.9s;简谐激励下的系统响应衰减幅度从88%提升到96%;随机激励下系统响应抖动减小,提高了稳定性.     

High-order implicit discontinuous Galerkin schemes for unsteady compressible Navier–Stokes equations

Efficient solution techniques for high-order temporal and spatial discontinuous Galerkin(DG) discretizations of the unsteady Navier–Stokes equations are developed. A fourth-order implicit Runge–Kutta(IRK) scheme is applied for the time integration and a multigrid preconditioned GMRES solver is extended to solve the nonlinear system arising from each IRK stage. Several modifications to the implicit solver have been considered to achieve the efficiency enhancement and meantime to reduce the memory requirement. A variety of time-accurate viscous flow simulations are performed to assess the resulting high-order implicit DG methods. The designed order of accuracy for temporal discretization scheme is validate and the present implicit solver shows the superior performance by allowing quite large time step to be used in solving time-implicit systems. Numerical results are in good agreement with the published data and demonstrate the potential advantages of the high-order scheme in gaining both the high accuracy and the high efficiency.     

服务通告全面成本评估

从工作实际出发，提出了服务通告的全面成本评估方案，详细给出成本项分类和量化方法，应用投资收益率方法综合决策各成本项，帮助工程管理人员科学量化服务通告，得到更准确合理的评估结论。     

卫星导航和惯性导航与时间和空间的理论

从卫星导航和惯性导航的测速定位机理分析出发讨论了时间和空间理论的有关基本问题。提供了一种卫星导航的原理完备的观测方程形式,包括惯性和非惯性物理效应。着重讨论了洛伦兹一次项的效应,伽里略变换自然进化到洛伦兹变换,“同地性”的相对性自然导致“同时性”的相对性。从卫星导航的单程光（电磁）信号的特点出发讨论了爱因斯坦“往”和“返”双程光信号定义带来的困惑。指出哈勃红移是超低速度和超大距离的狭义相对论效应验证。用爱因斯坦对惯性质量和引力质量等效原理的论述,论证了惯性导航的理论基础和超过 3×10 8m/s的速度测量机理。     

航空发动机PI控制参数频域最优整定方法

针对航空发动机高、低压转速和压比的控制回路,研究满足幅值裕度和相角裕度要求的比例-积分(PI)控制参数稳定域确定方法.根据系统在频域的稳定域解析模型,建立考虑PI控制器的系统参数频域稳定域图形.根据典型的动态性能指标和鲁棒性指标定义的优化目标函数,在所得到的控制参数稳定域中寻找到一组最优的PI控制参数.该方法应用于航空发动机高、低压转速和压比回路控制器参数设计中,设计了不同状态下的PI控制器,仿真结果表明,这种整定方法能够使闭环系统满足性能指标和鲁棒性.