基于加权朴素贝叶斯分类器和极端随机树的蛋白质接触图预测

提出一个新的基于集成学习的预测器(TargetPCM),对蛋白质接触图(特别是中长程)进行高精度的预测。首先,TargetPCM使用加权朴素贝叶斯分类器(Weighted Nave Bayes classifier,WNBC)融合3个接触图预测器的输出,其中WNBC中的权重参数通过粒子群算法优化得到;其次,将WNBC融合后的输出和基于序列的特征进行组合,得到更具鉴别能力的特征;在此基础上,应用极端随机树训练得到最终的蛋白质接触图预测模型。为了验证TargetPCM的有效性,在包含98个非冗余蛋白质的数据集上进行了测试。结果表明:对于短程、中程和长程接触,TargetPCM的Top L/5精度比现有最好的集成预测器(NeBcon)分别提高了8.2%,16.1%和5.3%。在CASP11上进一步的验证表明,对于短程、中程和长程接触,TargetPCM的Top L/5精度比现有最好的基于协同进化的集成预测器(MetaPSICOV)分别提高了7.4%,9.1%和7.5%。实验结果验证了本文所提蛋白质接触图预测方法的有效性。     

圆柱厚壳混合状态等参元的半解析解

本文给出圆柱壳问题混合状态方程的一种强有力的半离散半解析方法－混合状态等参元，它沿壳厚方向未作任何位移及应力分布假设，采用状态控制方程给出解析解答，与通常壳体元相比减少了未知量数目，提高了计算效率。     

多源知识融合处理算法

多源知识融合可有效提高判决结果的可靠性和置信度.借鉴信息融合的思路,分析了知识融合方法和一般模型.重点讨论了基于Bayes准则、基于D-S(Dempster-Shafer)证据理论以及基于模糊集理论的知识融合算法,给出了基于3种知识融合算法的具体处理步骤,并从算法特点和适用性、实用性等方面对3种知识融合算法性能进行了对比分析.通过知识融合在合成孔径雷达(SAR,Synthetic Aperture Radar)图像融合中应用的仿真实验,验证了知识融合算法的有效性.     

Geometrically exact nonlinear analysis of pre-twisted composite rotor blades

Modeling of pre-twisted composite rotor blades is very complicated not only because of the geometric non-linearity, but also because of the cross-sectional warping and the transverse shear deformation caused by the anisotropic material properties. In this paper, the geometrically exact nonlinear modeling of a generalized Timoshenko beam with arbitrary cross-sectional shape, generally anisotropic material behavior and large deflections has been presented based on Hodges’ method. The concept of decomposition of rotation tensor was used to express the strain in the beam. The variational asymptotic method was used to determine the arbitrary warping of the beam cross section. The generalized Timoshenko strain energy was derived from the equilibrium equations and the second-order asymptotically correct strain energy. The geometrically exact nonlinear equations of motion were established by Hamilton’s principle. The established modeling was used for the static and dynamic analysis of pre-twisted composite rotor blades, and the analytical results were validated based on experimental data. The influences of the transverse shear deformation on the pre-twisted composite rotor blade were investigated. The results indicate that the influences of the transverse shear deformation on the static deformation and the natural frequencies of the pre-twisted composite rotor blade are related to the length to chord ratio of the blade.     

基于Wiener过程的民用航空发动机性能可靠性预测

通过对民用航空发动机性能退化数据的分析,提出了一种有效融合先验退化数据和现场退化数据的性能可靠性评估和剩余寿命预测方法.首先在先验退化数据的基础上确定Wiener过程参数的先验分布,然后利用贝叶斯方法融合新增的现场数据,对Wiener过程参数进行更新,并在此基础上对单台发动机进行性能可靠性评估和剩余寿命预测.该方法能根据现场退化数据不断地对可靠性和剩余寿命进行更新.最后通过某航空公司发动机性能退化数据验证文中提出的方法,结果表明41号发动机在2000循环和3000循环时预测的剩余寿命相对误差分别为0.060和0.018,可以满足航空公司发动机下发计划制定的实际需要.      

A critical evaluation of two Reissner–Mindlin type models for composite laminated plates

The purpose of this paper is to critically evaluate two Reissner–Mindlin type theories developed recently for composite laminated plates, namely, VAPAS (Variational Asymptotic Plate And Shell analysis) and EFSDT (Enhanced First-Order Shear-Deformation Theory). The fundamentals of both models are briefly summarized along with their unique features in comparison to most other existing models. The similarities and differences between VAPAS and EFSDT are also examined. Exact solutions of three-dimensional elasticity theory for the cylindrical bending problems are used as the arbiter to assess the accuracy of both models. Such a systematic assessment demonstrates that both models have achieved an excellent compromise between the layer-wise theories, which are accurate but computationally demanding, and the first-order shear deformation theories, which are computationally cheap but not accurate.     

Variational Bayesian Kalman filter using natural gradient

We propose a technique based on the natural gradient method for variational lower bound maximization for a variational Bayesian Kalman filter. The natural gradient approach is applied to the Kullback-Leibler divergence between the parameterized variational distribution and the posterior density of interest. Using a Gaussian assumption for the parametrized variational distribution, we obtain a closed-form iterative procedure for the Kullback-Leibler divergence minimization, producing estimates of...     

固体火箭发动机可靠性评定的影子理论及应用

首次提出可靠性评定的影子问题,证明了影子定理,并用影子定理对固体火箭发动机的结构可靠性进行了评定,表明其具有应用价值。     

评估导弹命中精度的一种工程实用方法

提供了一种工程适用的用贝叶斯方法评估导弹命中精度完整的数学模型。利用导弹飞行试验前制导器件误差标定的信息和飞行试验误差分离的信息，综合确定导弹落点偏差验前信息。最后给出了对某型导弹评估的算例，结果表明：本文方法既保证了验前信息的准确性和可靠性，又保证了用贝叶斯方法评估导弹命中精度的精确性和可靠性。     

基于性能退化数据的液体火箭发动机可靠性Bayes评定

性能退化表征的是产品的工作能力随时间逐渐降低的现象。对于液体火箭发动机等试验费用昂贵的高可靠性产品,失效时间数据难以得到,此时性能退化数据是评定其可靠性的重要信息。文章提出用线性随机过程模型来描述产品性能参数逼近临界值的过程,再根据产品的失效机理,推导出产品的失效分布函数形式。相对于传统的寿命分布模型,文中推导的失效分布函数中的参数因物理含义明确而易于通过实时跟踪测量性能参数时间序列数据估计得到。文中还通过一个数值实例说明了该方法在工程上应用的有效性。