基于模糊理论的舰船航迹控制器

着重介绍如何从航向控制的模糊规则扩展到航迹控制的模糊规则 ,并应用此模糊控制规则实现对舰船航迹的控制 .仿真表明 ,在此模糊控制器的控制下 ,船舶转向动态性能、航迹保持精度、抗干扰性能以及船舶参数发生变化时的鲁棒性均明显优于 PID控制器     

偏心加筋板大变形梁板单元

给出了偏心加筋板大变形分析的理论公式和相应的梁板单元模型 .在肋骨和板的运动方程中引用 Von Karman形变方程 ;按照 Mindlin板理论计及横向剪切变形的影响 ;对横向剪应变和薄膜应变重新插值修正克服 Mindlin型单元在薄板应用时的“锁定”行为 ,此模型可适合于薄板和厚板的非线性分析 .     

模拟转子不平衡响应数值分析及实验研究

对模拟转子进行了不平衡响应的有限元计算,并进行了相应的实验研究.在转速为960r/min和1568r/min时,不平衡响应的计算结果与实验结果的误差近似为1.7%和2.1%,计算结果与实验结果相符.     

基于改进EMD的信号降噪方法

经验模态分解(Empirical Mode Decomposition,EMD)算法作为新型时频分析方法受到广泛关注,它基于信号的极值特性处理信号,具有自适应强、无需预先确定基函数的优点。但EMD算法本身仍存在模态混叠及EMD强制降噪法易导致信号失真等一系列问题。针对EMD算法的缺陷,提出基于自相关函数的集合经验模态分解方法(Ensemble Empirical Mode Decomposition,EEMD)与小波阈值降噪相结合的改进算法。首先利用自相关函数对高频固有模态函数(Intrinsic Mode Function,IMF)进行选择,然后利用小波阈值降噪法为EEMD设定阈值,最后将改进算法用于信号降噪,并与快速傅里叶变换(FFT)算法、小波阈值算法以及EMD强制降噪算法进行比较。该方法的优点是克服了EMD算法的不足,避免了模态混叠现象,有效地保留了高频信号中分量,降噪效果更好。     

Coordinated pricing and inventory control problems with capacity constraints and fixed ordering cost

This article addresses a single‐item, finite‐horizon, periodic‐review coordinated decision model on pricing and inventory control with capacity constraints and fixed ordering cost. Demands in different periods are random and independent of each other, and their distributions depend on the price in the current period. Each period's stochastic demand function is the additive demand model. Pricing and ordering decisions are made at the beginning of each period, and all shortages are backlogged. The objective is to find an optimal policy that maximizes the total expected discounted profit. We show that the profit‐to‐go function is strongly CK‐concave, and the optimal policy has an (s,S,P) ‐like structure. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012     

SNR准则下的认知MIMO雷达波形设计

研究了MIMO雷达信号模型下基于最大化信噪比(SNR)准则的最优和稳健波形设计问题.根据对目标冲击响应功率谱密度(PSD)确定和不确定两种条件的分析,推导了最优波形和稳健波形的闭式表达式.仿真结果表明,当目标冲激响应PSD的先验知识准确时,使用最优波形作为发射波形,在接收端获得在给定条件下最优的SNR;当目标冲击响应PSD的先验知识不准确时,使用稳健波形作为发射波形,能够降低目标冲激响应PSD的不确定性对输出端信噪比(SNR)的负面影响.     

郭兴福教学法的回顾与思考

郭兴福教学法是在20世纪60年代初人民解放军军事训练由战争年代"以战教战"向和平时期"以训备战"战略转变及贯彻"以我为主"军事训练方针的时代背景下诞生的。它经历了萌芽培育、成形提高、推广普及三个阶段。郭兴福教学法科学地反映了军事训练的客观规律,既有鲜明的时代特色,又有长久的价值和强大的生命力。在新形势下,继承和发展郭兴福教学法,重在把握其精髓实质,着力解决运用过程中遇到的新情况、新问题。     

Research on the influences of confining pressure and strain rate on NEPE propellant: Experimental assessment and constitutive model

In order to study the influences of confining pressure and strain rate on the mechanical properties of the Nitrate Ester Plasticized Polyether (NEPE) propellant, uniaxial tensile tests were conducted using the self-made confining pressure system and material testing machine. The stress-strain responses of the NEPE propellant under different confining pressure conditions and strain rates were obtained and analyzed. The results show that confining pressure and strain rate have a remarkably influence on the mechanical responses of the NEPE propellant. As confining pressure increases (from 0 to 5.4 MPa), the maximum tensile stress and ultimate strain increase gradually. With the coupled effects of confining pressure and strain rate, the value of the maximum tensile stress and ultimate strain at 5.4 MPa and 0.0667 s⁻¹ is 2.03 times and 2.19 times of their values under 0 MPa and 0.00333 s⁻¹, respectively. Afterwards, the influence mechanism of confining pressure on the NEPE propellant was analyzed. Finally, based on the viscoelastic theory and continuous damage theory, a nonlinear constitutive model considering confining pressure and strain rate was developed. The damage was considered to be rate-dependent and pressure-dependent. The constitutive model was validated by comparing experimental data with predictions of the constitutive model. The whole maximum stress errors of the model predictions are lower than 4% and the corresponding strain errors are lower than 7%. The results show that confining pressure can suppress the damage initiation and evolution of the NEPE propellant and the nonlinear constitutive model can describe the mechanical responses of the NEPE propellant under various confining pressure conditions and strain rates. This research can lay a theoretical foundation for analyzing the structural integrity of propellant grain accurately under working pressure loading.     

Maneuvering target tracking of UAV based on MN-DDPG and transfer learning

Tracking maneuvering target in real time autonomously and accurately in an uncertain environment is one of the challenging missions for unmanned aerial vehicles(UAVs).In this paper,aiming to address the control problem of maneuvering target tracking and obstacle avoidance,an online path planning approach for UAV is developed based on deep reinforcement learning.Through end-to-end learning powered by neural networks,the proposed approach can achieve the perception of the environment and continuous motion output control.This proposed approach includes:(1)A deep deterministic policy gradient(DDPG)-based control framework to provide learning and autonomous decision-making capa-bility for UAVs;(2)An improved method named MN-DDPG for introducing a type of mixed noises to assist UAV with exploring stochastic strategies for online optimal planning;and(3)An algorithm of task-decomposition and pre-training for efficient transfer learning to improve the generalization capability of UAV's control model built based on MN-DDPG.The experimental simulation results have verified that the proposed approach can achieve good self-adaptive adjustment of UAV's flight attitude in the tasks of maneuvering target tracking with a significant improvement in generalization capability and training efficiency of UAV tracking controller in uncertain environments.     

Recent progress on transition metal oxides and carbon-supported transition metal oxides as catalysts for thermal decomposition of ammonium perchlorate

As a main oxidizer in solid composite propellants, ammonium perchlorate (AP) plays an important role because its thermal decomposition behavior has a direct influence on the characteristic of solid com-posite propellants. To improve the performance of solid composite propellant, it is necessary to take measures to modify the thermal decomposition behavior of AP. In recent years, transition metal oxides and carbon-supported transition metal oxides have drawn considerable attention due to their extraor-dinary catalytic activity. In this review, we highlight strategies to enhance the thermal decomposition of AP by tuning morphology, varying the types of metal ion, and coupling with carbon analogue. The enhanced catalytic performance can be ascribed to synergistic effect, increased surface area, more exposed active sites, and accelerated electron transportation and so on. The mechanism of AP decom-position mixed with catalyst has also been briefly summarized. Finally, a conclusive outlook and possible research directions are suggested to address challenges such as lacking practical application in actual formulation of solid composite propellant and batch manufacturing.