执行器故障参数不可测飞行系统的模型跟踪重构控制

针对具有二阶动态特性的执行器故障的飞控系统,在故障参数不可测、并伴有外界未知扰动和建模误差等不确定因素的情况下,克服已有的大部分模型跟踪重构控制所采用的自适应律都存在的双线性问题,研究一种新的直接自适应重构控制方案.在已有的重构控制器基础上,对状态反馈的形式进行改进,并利用Lyapunov稳定性定理,证明了在自适应重构控制器的作用下,故障后系统的跟踪误差渐近地收敛于零.仿真结果证明,存在不确定因素的飞控系统发生不可测的执行器故障后,本文给出的自适应重构控制器能够很好的对故障系统进行重构,证实了所提出的算法的有效性.     

锦屏一级水电站地下厂区非线性地应力场反演

以锦屏一级水电站地下厂区现场工程为依托,提出一种新的地应力场反演方法.该方法考虑了大型结构面对地应力场的影响特征,将含有大型结构面的工程地质模型分区进行处理.首先,在线弹性的状态下,确定边界位移的搜索范围.继而,建立初始应力场拟合优化问题的目标函数,并采用一阶优化算法,有效的避免了繁琐的运算.最后,拟合结果表明精度较好,满足了工程的需要,从而证实了提出的地应力场反演方法的可适用性与正确性.     

Fragmentation dynamics within shear bands--a model for aging tectonic faults?

A numerical model for packing of fragmenting blocks in a shear band is introduced, and its dynamics is compared with that of a tectonic fault. The shear band undergoes a slow aging process in which the blocks are being grinded by the shear motion and the compression. The dynamics of the model have the same statistical characteristics as the seismic activity in faults. The characteristic magnitude distribution of earthquakes appears to result from frictional slips at small and medium magnitudes, and from fragmentation of blocks at the largest magnitudes. Aftershocks to large-magnitude earthquakes are local recombinations of the fragments before they reach a new quasi-static equilibrium. The aftershocks satisfy Omori's law. Local precursor activity at a few times the normal background level appears at a short time before a major earthquake. Seismic gaps appear as a natural consequence of the aging process of a fault. Explanation of the heat flux and principal stress direction anomalies at the faults both involve the value of fracture stress of the blocks in the gouge. The final form of a tectonic fault is predicted to involve a gouge dominated by fine-grained and rather rounded blocks so that it cannot withstand large shear stresses. Received 26 July 2000     

缓倾角断裂隔震效应的定量研究

在对断裂分带研究的基础上 ,尝试对缓倾角断裂 (指倾角小于 45°断层 )建立起等效简化地质模型 ,针对各带的不同衰减机理 ,分别采用不同的力学模型和数值计算方法 ,分析了应力波通过断裂构造的动力响应 ,通过系统的定量研究 ,指出除断层各带自身材料力学性质 (如波阻抗等 )外 ,断层的倾角、各带的厚度、断层泥带的存在及构造透镜体带颗粒大小、拓扑结构是影响应力波传播的重要因素     

合成绝缘子的性能与缺陷检测

主要探讨了合成绝缘子的各种性能 ,指出运行中出现的问题 ,介绍了几种缺陷检测方法 ,并对今后的发展做了预测     

凸极同步发电机定子内部故障瞬态的仿真模型

随着凸极同步发电机单机容量的不断增加 ,其结构越来越复杂 ,造价也更加昂贵 ,一旦发生故障 ,会带来巨大的经济损失。运用多回路分析方法建立的凸极同步发电机定子绕组内部故障的数学模型及在此基础上编制的仿真程序 ,可以对凸极同步发电机定子绕组内部故障的瞬态和稳态过程进行仿真 ;通过对仿真结果与实验结果的比较 ,验证了数学模型的正确性。该仿真程序能够揭示凸极同步发电机定子绕组内部故障瞬态的运行特征及瞬态过程中各个故障量的变化规律。     

发动机气缸故障诊断的研究

在研究发动机瞬态转速波形和气压扭矩波形的基础上,定义几个诊断参数VI,API,TCI和PCI。利用这些诊断参数和简单的判断规则,可判断发动机各气缸的工作状态,并诊断出发动机气缸灭火和供油不足故障。     

原位合成MoSi2/SiC复合材料的组织缺陷

TEM和HREM研究表明,原位合成MoSi2基复合材料的组织中,基体MoSi2中存在较多的位错,而且尤以MoSi2与SiC的界面处位错最为集中,SiC颗粒的内部缺陷的主要形式为孪晶和层错,纳米力学探讨分析表明,MoSi/SiC界面附近存在明显的硬度梯度,在材料制备冷却过程中,因MoSi2基体与SiC颗粒之间的热膨胀系数（CTE）的差别而导致的其中的残余热应力是造成上述组织特征的原因。     

Zur Polymorphie von In5Br7

On the Polymorphism of In₅Br₇ The existence of two polymorphs of In₅Br₇ has been proved by single crystal structure determinations. In₅Br₇ (tP192) crystallizes with the tetragonal space group P4₁2₁2 and lattice parameters a_t = 1318.9(5) pm and c_t = 3723.8(9) pm (293 K). Concerning monoclinic In₅Br₇ (mC192), the centrosymmetric space group C2/c with lattice parameters a_m = 1867.3(4) pm, b_m=1867.0(5) pm, c_m = 1918.0(7) pm, and β_m = 103.96(2)° (293 K) has been confirmed. Both modifications of In₅Br₇ are built up from layers of the same type. These layers with a thickness of about 930 pm consist of structure fragments [InBr₂]⁴⁺ and [InBr₁₂]^4–. The anion is composed of two ethan‐like [InBr₆]^2– units, which contain In–In bonds. The stacking sequence of the layers with symmetry C 1 2 (1) differs for the two modifications of In₅Br₇. The tetragonal form is generated by applying a 4₁ screw axis; the monoclinic polymorph is formed by introducing inversion centers between the layers. The adequate name of In₅Br₇ = In[InBr₆]Br is triindium(I)‐hexabromodiindate(II)(In–In)‐bromide.     

TEM Investigation of Stacking Faults in the Superconducting Compound YNi2B2C

To evaluate the influence of composition and high-temperature heat treatment on the occurrence of stacking faults and intergrowths in the layered superconducting compound YNi₂B₂C a series of polycrystalline samples and a single crystal were investigated by TEM. Stacking faults were found in the most inhomogeneous sample only, which was annealed at 1100°C. Homogenisation at temperatures of 1450°C and higher results in a recovery of stacking faults. The observed faults should develop during crystallisation by formation of extra planes of YC or Ni₂B, resulting in a local deviation from the stoichiometric composition. In highly faulted areas the distance of stacking faults was about 50nm. These faults have apparently no influence on the superconduction transition temperature T_c.