部件有两类故障状态且修理设备可更换的并联可修系统分析

本文考虑由两个同型部件组成的并联可修系统,每个部件有两类故障状态,部件故障后立即修理,且修理设备在修理故障部件的过程中也可能发生故障.假定部件的寿命和修理设备的寿命均服从指数分布,部件发生故障后的修理时间和修理设备故障后的更换时间均服从一般分布,利用马尔可夫更新过程理论,求得系统的有关可靠性指标和修理设备的闲期长度和"广义忙期"长度等一系列结果.     

一类基于模糊T-S模型的有执行器故障的自适应容错跟踪控制

研究了一类带有执行器故障的T-S模糊系统的容错跟踪控制问题。设计中,把模糊控制与自适应控制相结合,提出了一种新的容错控制方法。该控制器由正常控制器和一个自适应控制器组成,能够使得闭环系统稳定,故障状态模型渐近跟踪正常模型,并获得优化的控制性能。应用Lyapunov函数和线性矩阵不等式方法,给出和证明了带有执行器故障的T-S模糊系统的稳定的充分条件。仿真结果进一步验证了所提出的方法的有效性。     

Hénon混沌系统的模糊广义预测控制与同步

针对Hénon混沌系统,本文给出了一种基于T-S模糊模型的混沌系统广义预测控制算法。该方法将模糊辨识和广义预测控制结合起来应用到Hénon混沌系统中。首先,应用T-S模糊模型对Hénon混沌系统进行辨识,模糊聚类法辨识模型的前件参数,递推最小二乘法辨识结论参数。基于辨识模型,采用广义预测控制算法对其进行控制,实现了系统的跟踪与同步。仿真结果表明,与其它算法相比,该算法能够保证系统输出快速、有效地跟踪设定值。     

基于多元分析的人民币汇率波动率预测

对人民币汇率波动率建立了BEKK,CCC,O-GARCH,IC-GARCH模型。针对人民币汇率波动率的非对称性,改进了IC-GARCH模型,建立了IC-GJRGARCH,IC-IGARCH模型。给出了以上各模型的预测结果及评价,并分析IC情形下,残差类型及降维技术对预测效果的影响。人民币汇率波动率的预测实证表明,BEKK模型和IC-GJRGARCH模型比其他模型的预测效果要理想;残差类型为广义误差分布与t分布的预测效果都要优于高斯分布的预测效果;模型降维后预测效果与降维前的预测效果相差不大,甚至优于后者。     

Propulsive matrix of a helical flagellum

We study the propulsion matrix of bacterial flagella numerically using slender body theory and the regularized Stokeslet method in a biologically relevant parameter regime. All three independent elements of the matrix are measured by computing propulsive force and torque generated by a rotating flagellum, and the drag force on a translating flagellum. Nu- merical results are compared with the predictions of resistive force theory, which is often used to interpret micro-organism propulsion. Neglecting hydrodynamic interactions between different parts of a flagellum in resistive force theory leads to both qualitative and quantitative discrepancies between the theoretical prediction of resistive force theory and the numerical results. We improve the original theory by empirically incorporating the effects of hydrodynamic interactions and propose new expressions for propulsive matrix elements that are accurate over the parameter regime explored.     

改进灰导数和时间响应函数的新灰色预测模型

以白化方程为基础,利用梯形公式白化灰导数,同时根据最小二乘法求出时间响应函数中的常数c,得到一种改进的灰色预测模型.应用实例说明改进模型具有较高的预测和拟合精度.     

Sequential Observation of Alkali-halide Gas Phase Clusters in High Resolution TOF-MS and Prediction of Their Structures

Alkali halide clusters are interesting model systems that can provide information about how crystal properties evolve. To study these properties, a high-resolution atmospheric pressure inlet time-of-flight mass spectrometry （APi-TOF-MS） study of the sequential sodium halides series, C1-（NaC1）n and Br-（NaBr）m, has been reported, and the viability of the APi-TOF- MS equipped with an electrospray ionization source in determining cluster compositions has been demonstrated. The isotopic patterns were well resolved, as n=4 and 7 were determined to be the magic numbers for C1-（NaC1）n clusters, which were particularly abundant in the mass spectra. A global minimum search based on density functional theory enabled basin hopping yield the most stable structures for the mentioned series. The structures exhibit several distinct motifs which can be roughly categorized as linear chain, rock salt, and hexag- onal ring. This work provides an effective way to discover and elucidate the nonstoichiometry sodium halide clusters. These clusters possess very high vertical detachment energies and are generally called as superhalogens, which play important roles in chemistry because they are widely used in the synthesis of new classes of charge-transfer salts.     

PDS算法进行近红外定量模型更新的效果评估

以不同厂家阿莫西林胶囊及其内容物近红外(Near infrared,NIR)光谱为例,寻找评价分段直接标准化算法(Piecewise direct standardization,PDS)进行光谱校正是否成功的量化指标。本研究共涉及76批阿莫西林胶囊样品,其中54批用于建立胶囊剂的定量模型。通过聚类分析,所有胶囊的NIR光谱分成5类,每类视为一个均质样本;分别计算每个均质样本的平均光谱,从该样本中选择10~15张光谱作为PDS校正的目标光谱,对76批阿莫西林胶囊内容物粉末光谱进行校正,利用阿莫西林胶囊定量模型对校正后的光谱进行含量预测;计算校正后的光谱与PDS校正中目标光谱所属均质样本的平均光谱的相似系数,分析其与预测误差的关系。结果表明,校正结果与所选择的目标光谱关系密切。PDS校正光谱与模型中不同均质样本平均光谱的相似系数(r)越大,通常校正效果越好;当r<99%时,一般可判断PDS校正失败(预测误差>5%)。因此,可以用PDS校正后光谱与校正时使用的目标光谱所属的均质样本的平均光谱的相似系数作为判断PDS校正是否成功的标志。     

喷砂冲蚀实验中颗粒轨迹的数值预测

针对冲击磨损实验研究中磨粒群体的运动轨迹难以准确表征的问题,在负压喷射砂粒群冲击Q235钢板的实验中宏观测量了砂粒撞击的速度与位置分布,并使用数值方法模拟了实验砂粒与空气在喷嘴内外的双向耦合过程,以实现负压喷射砂粒群的轨迹预测。计算中提出了非球形粒子在相对马赫数接近1时的曳力模型,以反映空气可压缩引起砂粒表面流动分离的现象,并合理选择Magnus升力模型及壁面反射模型,最终数值预测的砂粒碰撞速度以及撞击位置与实验情况吻合良好。