基于径向基函数响应面的机翼有限元模型修正

用ANSYS三维实体单元SOLID45建立机翼基准有限元模型并计算其自由振动的前6阶模态频率.用均匀设计方法将结构参数分组并分别计算各组结构参数对应的模态频率,建立高斯径向基函数响应面模型.用最小二乘法则拟合系数并检验响应面拟合精度,对基准模型的结构参数施加摄动量建立待修正有限元模型.用响应面模型和基准模型计算所得模态频率的相对误差建立适应度函数的表达式,将混沌搜索机制引入粒子群算法对结构参数的摄动量进行寻优计算,搜索所得优化解代入即得修正后模型,将修正后模型与基准模型在测试频段内段外的模态频率近似度进行比较,证实了修正后模型的有效性.      

复杂结构振动控制设计与仿真方法研究

为了避免在建立结构数学模型过程中因简化和降阶引起的模型误差,解决复杂结构建模难的问题,提高控制器设计的准确性,提出了一种新的基于有限元法(FEM)的结构振动控制设计方法.该方法可借助于商用结构有限元分析软件来实现,简便易行,在PATRAN/NASTRAN环境中利用PATRAN命令语言PCL(Patran Command Language)建立了通用结构控制仿真平台.通过对压电自适应桁架结构的振动控制进行控制设计仿真和实验验证,证明了新方法的有效性;与Simulink使用简化模型的仿真结果相比,新方法的结果与实验结果更为接近,表明其准确性更高.该方法适用于对处在设计阶段的复杂结构进行控制设计与仿真评估.      

Ti-15-3环板的翻孔成型研究

针对Ti—15—3环板零件的形状特点,分析了成型工艺的几种可能性,说明了翻孔成型的优点。详细介绍了钛合金环板翻孔成型工艺过程,对成型中遇到的工艺技术难题提出了解决办法,如工艺参数的选取、成型模具的结构设计及零件回弹量的确定方法等。对此类零件的成型生产具有一定的借鉴作用。     

利用模态编码进行结构损伤位置识别的自联想储存器神经网络方法

 提出了一种基于自联想储存器神经网络的结构损伤识别方法,该网络的训练数据为经编码后的结构模态向量。和传统BP网络相比,这种方法收敛性能较好且不易陷入局部极小值。另外,为判断识别结果的正确性,提出了一种基于向量间距离的可靠性分析方法。最后,以一个悬臂梁为算例验证了该方法的有效性和可行性。     

Polysaccharide from Loquat Leaves to Prepare Hierarchical Porous Carbon as a Matrix for Active Sulfur

Fossil fuel exhaustion and overdevelopment usually lead to a recession,which is worsened by the environmental pollution.So it is of high priority to develop high-efficiency energy storage device.Here,agreen and environment-friendly strategy is devised to fabricate carbon materials from biomass.By water extraction and alcohol precipitation,polysaccharide is extracted from loquat leaves.After calcining under high temperature,hierarchical porous carbon materials(HPCM)are obtained,possessing a variety of macropores,mesopores and micropores.Such ample and hierarchical pores enable the electrolyte infiltration and the buffering of the volume expansion of sulfur in repeated electrochemical reactions.The structure stability of the entire electrode can thus be well maintained.When evaluated as the scaffold for sulfur,the electrochemical performance of carbon/sulfur composite was tested.Even after 500 cycles,the reversible capacity is retained as high as 485.4 mA·h/g at the current density of 1.6 A/g.It also offers a notable rate capability,attaining the discharge capacity of 700.7 mA·h/g at 2 C.All the electrochemical performance results prove the feasibility of the proposed strategy.     

Optimal trajectory planning of free-floating space manipulator using differential evolution algorithm

The existence of the path dependent dynamic singularities limits the volume of available workspace of free-floating space robot and induces enormous joint velocities when such singularities are met. In order to overcome this demerit, this paper presents an optimal joint trajectory planning method using forward kinematics equations of free-floating space robot, while joint motion laws are delineated with application of the concept of reaction null-space. Bézier curve, in conjunction with the null-space column vectors, are applied to describe the joint trajectories. Considering the forward kinematics equations of the free-floating space robot, the trajectory planning issue is consequently transferred to an optimization issue while the control points to construct the Bézier curve are the design variables. A constrained differential evolution (DE) scheme with premature handling strategy is implemented to find the optimal solution of the design variables while specific objectives and imposed constraints are satisfied. Differ from traditional methods, we synthesize null-space and specialized curve to provide a novel viewpoint for trajectory planning of free-floating space robot. Simulation results are presented for trajectory planning of 7 degree-of-freedom (DOF) kinematically redundant manipulator mounted on a free-floating spacecraft and demonstrate the feasibility and effectiveness of the proposed method.     

Dual-frequency carrier smoothed code filtering with dynamical ionospheric delay modeling

In GNSS applications, carrier-smoothed-code is a widely used technique to combine code pseudo-range and carrier phase measurements. A dynamical ionospheric delay modeling method is proposed based on Kalman filter and least-squares theory. The level of the process noise is adaptively tuned along with the real-time KF state estimation, based on the online variance component estimation method. Meanwhile, the correlations of the time differenced carrier phase measurements are considered. This approach avoids overly optimistically evaluating the estimate and improves the transient accuracy of the estimates. A real GPS dataset is employed to check the performance of the proposed method under different conditions. The results show that the new algorithm can model the ionospheric delay variation well with different sampling intervals or even in ionospheric abnormal environment. The positioning accuracy can be confirmed, about 21%, 35% and 16% better are obtained in the N, E, and U direction than raw dataset.     

Improving the estimation of zenith dry tropospheric delays using regional surface meteorological data

Global Navigation Satellite Systems (GNSS) are emerging as possible tools for remote sensing high-resolution atmospheric water vapour that improves weather forecasting through numerical weather prediction models. Nowadays, the GNSS-derived tropospheric zenith total delay (ZTD), comprising zenith dry delay (ZDD) and zenith wet delay (ZWD), is achievable with sub-centimetre accuracy. However, if no representative near-site meteorological information is available, the quality of the ZDD derived from tropospheric models is degraded, leading to inaccurate estimation of the water vapour component ZWD as difference between ZTD and ZDD. On the basis of freely accessible regional surface meteorological data, this paper proposes a height-dependent linear correction model for a priori ZDD. By applying the ordinary least-squares estimation (OLSE), bootstrapping (BOOT), and leave-one-out cross-validation (CROS) methods, the model parameters are estimated and analysed with respect to outlier detection. The model validation is carried out using GNSS stations with near-site meteorological measurements. The results verify the efficiency of the proposed ZDD correction model, showing a significant reduction in the mean bias from several centimetres to about 5 mm. The OLSE method enables a fast computation, while the CROS procedure allows for outlier detection. All the three methods produce consistent results after outlier elimination, which improves the regression quality by about 20% and the model accuracy by up to 30%.     

基于Multi—Agent的空中交通流量仿真研究

针对传统空中交通流量仿真过程中灵活性和智能性的不足，将分布式人工智能Multi—Agent的理论和方法应用到空中交通流量管理领域中，提出了基于Muhi-Agent的空中交通流量仿真方法。介绍了空中流量管理的体系结构和流量管理的具体措施，详细设计了与流量仿真相关的重要Agent，包括航班Agent、航路Agent、机场终端区Agent和区域流量管理Agent等，探讨了各Agent的内部运行机制和在流量管理中的职能，构建了基于Multi．Agent的空中交通流量仿真子系统的整体框架．为实际空中交通流量管理系统的建设提供重要的指导和拳者。     

Supertyphoon Hagibis action in the ionosphere on 6–13 October 2019: Results from multi-frequency multiple path sounding at oblique incidence

The purpose of the present paper is to describe the observations of the variations in the parameters of HF radio waves propagating through the ionosphere when the action of the super typhoon Hagibis on 6–13 October 2019 occurred. The observations have been made with the Harbin Engineering University (the People's Republic of China) multi-frequency multiple path radio system involving the software-defined technology. The action of the super typhoon has been shown to be accompanied by enhanced atmospheric wave activity acting to generate wave processes with periods of 10 to 120 min. Coupling in the atmosphere–upper-atmosphere–ionosphere system has been confirmed to be carried out with atmospheric gravity waves. The ionosphere underwent the greatest impact on those days when the supertyphoon had maximum energy, on 8, 10, and especially 9 October 2019, and when it was found to be in an ～2,500–3,000-km distance range from the propagation path midpoints. Under the action of wave processes, the height of the reflection region was observed to oscillate within the ±(30–90 km) limits. The amplitude of the quasi-periodic variations in the ionospheric F-region electron density was estimated to be 10–12% for periods of ～20 min, and 30–60% for periods of ～60–120 min. The joint action of the dusk terminator and the supertyphoon has been confirmed to enhance wave activity in the ionosphere. Similar effects for the dawn terminator have not been detected.