琼中抽水蓄能电站高压引水系统布置与设计

琼中抽水蓄能电站采用一洞三机的布置形式,岔管段最小覆盖层厚度与最小主应力条件满足规范要求,且运行期衬砌结构整体裂缝宽度处于可控范围内,检修期间,在外水压力作用下结构出现整体受压破坏的可能性较小,具备采用钢筋混凝土衬砌的条件。另外通过对不同钢岔管方案的比较,认为钢板衬砌需要的高强钢材用量较大,考虑到直接投资和工期方面的明显优势,最终推荐采用衬砌厚度为1.0 m的钢筋混凝土衬砌方案。     

基于PNDSC 的欠驱动AUV编队控制器设计

针对含有模型不确定与未知海洋环境扰动下的欠驱动自主水下航行器(AUV)的编队控制问题, 提出一种基于预估器的神经网络动态面(PNDSC) 控制算法. 将动态面法引入控制器的设计中, 采用神经网络逼近AUV模型中的不确定项与海洋环境的扰动, 并结合预估器设计了神经网络权值的离散迭代更新率. Lyapunov 稳定性分析表明, 闭环系统所有信号是一致最终有界的. 仿真结果验证了所提出方法的有效性.

     

Pseudo‐predictor feedback control of discrete‐time linear systems with a single input delay

This paper studies the problems of stabilization of discrete‐time linear systems with a single input delay. By developing the methodology of pseudo‐predictor feedback, which uses the (artificial) closed‐loop system dynamics to predict the future state, memoryless state feedback control laws are constructed to solve the problem. Necessary and sufficient conditions are obtained to guarantee the stability of the closed‐loop system in terms of the stability of a class‐difference equations. It is also shown that the proposed controller achieves semi‐global stabilization of the system if its actuator is subject to either magnitude saturation or energy constraints under the condition that the open‐loop system is only polynomially unstable. Numerical examples have been worked out to illustrate the effectiveness of the proposed approaches. Copyright © 2015 John Wiley & Sons, Ltd.     

Wide passband/stopband bandpass filter based on transversal signal interference concepts and modified branch‐line structure

A high selectivity wide passband filter with a broader stopband based on transversal signal‐interaction concepts and modified branch line structure (MBLS) is developed in this article. Two transmission paths, that is, one half‐wavelength transmission line and one MBLS, are used to realize signal transmission from Port 1 to Port 2. Then, two transmission zeros are introduced at both lower and upper sides of the passband, which are used to improve the passband selectivity greatly. The filter bandwidth can be easily controlled by reasonable adjusting the coupling coefficient of the coupled lines. Furthermore, with four stubs connected at the input/output ports, the stopband attenuation level is improved greatly. Finally, one prototype filter having 69.1% of 3 dB fractional bandwidth is fabricated with advantages of sharp selectivity and high out‐of‐band rejection. The EM simulated and measured results are presented, and an excellent agreement can be obtained. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:330–336, 2015.     

砂被筑坝技术在长江汊道封堵工程中的应用

抛投中小型土工织物充砂体一般用于修筑潜坝或填槽,在长江大型汊道封堵工程中的运用比较少见。大型汊道水流流速快、填筑工程量大,使坝体成型控制难度大、施工效率低,应在工程中不断优化和改进施工设计及工艺。通过加大土工织物袋体尺寸,采用边充砂边沉放的方法连续施工,形成了成熟的砂被筑坝技术。实践证明,该技术的施工机械化程度高、程序简单、施工高效、坝体成型易于控制,且运用该施工技术修筑而成的汊道封堵坝能起到预期的工程效果。     

On input‐to‐state stability‐based design for leader/follower formation control with measurement delays

This paper addresses the design of low‐level controllers for leader–follower formations of nonholonomic vehicles in the presence of bounded measurement delays. The concept of input‐to‐state stability is extended to encompass the effect of bounded delays and restrictions on the input. A method is proposed to integrate a Smith predictor in a backstepping design on the basis of nested saturations and nonlinear small‐gain assignment, which allows for time delays in the feedback loop. Robustness analysis under uncertain bounded time delays is provided, and design tradeoffs resulting from the use of bounded controls are discussed. Illustrative simulations are shown to validate the design and robustness analysis in the context of a simple leader–follower trailing control problem. Copyright © 2012 John Wiley & Sons, Ltd.     

A neural network-based approach for dynamic quality prediction in a plastic injection molding process

This paper presents an innovative neural network-based quality prediction system for a plastic injection molding process. A self-organizing map plus a back-propagation neural network (SOM-BPNN) model is proposed for creating a dynamic quality predictor. Three SOM-based dynamic extraction parameters with six manufacturing process parameters and one level of product quality were dedicated to training and testing the proposed system. In addition, Taguchi’s parameter design method was also applied to enhance the neural network performance. For comparison, an additional back-propagation neural network (BPNN) model was constructed for which six process parameters were used for training and testing. The training and testing data for the two models respectively consisted of 120 and 40 samples. Experimental results showed that such a SOM-BPNN-based model can accurately predict the product quality (weight) and can likely be used for various practical applications.     

Accurate evaluation of Green’s functions in a layered medium by SDP-FLAM

Based on local Taylor expansions on the complex plane, a method for fast locating all modes (FLAM) of spectral-domain Green’s Functions in a planar layered medium is developed in this paper. SDP-FLAM, a combination of FLAM with the steepest descent path algorithm (SDP), is employed to accurately evaluate the spatial-domain Green’s functions in a layered medium. According to the theory of complex analysis, the relationship among the poles, branch points and Riemann sheets is also analyzed rigorously. To inverse the Green’s functions from spectral to spatial domain, SDP-FLAM method and discrete complex image method (DCIM) are applied to the non-near field region and the near filed region, respectively. The significant advantage of SDP-FLAM lies in its capability of calculating Green’s functions in a layered medium of moderate thickness with loss or without loss. Some numerical examples are presented to validate SDP-FLAM method. Supported by the National Natural Science Foundation of China (Grant No. 60621002), and the State Key Development Program for Basic Research of China (Grant No. 2009CB320200)     

基于模型参考自适应Smith预估器的反馈式AGC厚度控制系统

针对具有纯时间延迟特性的反馈式AGC(automatic gauge contro1)系统,利用Smith预估器对纯时间延迟具有补偿作用的原理,建立了模型参考白适应Smith预估器反馈式AGC控制系统模型,给出了控制系统结构.推导了自适应调节律和设计算法,结合预估器模型,计算得到轧件出口厚度偏差值的表达式.仿真结果表明,模型参考自适应Smith预估器反馈式AGC系统对铝薄板带材轧制出口厚度偏差控制具有很好的控制效果,解决了反馈式AGC厚度控制由于纯时间延迟特性对控制性能产生很大影响的问题,消除了出口厚度波动现象,响应速度加快,可以满足高精度铝薄板带材轧制生产的控制要求.     

一种基于YOLOv4-TIA的林业害虫实时检测方法

针对现有基于深度学习的林业昆虫图像检测方法存在检测精度低和检测速度慢的问题,提出一种结合改进PANet结构与三分支注意力机制的目标检测方法YOLOv4-TIA。通过对样本数量较少的昆虫类别进行数据增强,实现样本均衡分布。利用三分支注意力机制改进YOLOv4中的CSPDarkNet53骨干网络,同时通过旋转操作和残差变换建立维度间的依存关系,以提高有效的特征通道权重,在PANet结构上增加将跳跃连接与跨尺度连接相结合的特征融合方式,从而获取更丰富的语义信息和位置信息。在此基础上,采用Focal loss函数优化分类损失,解决正负样本不均衡的问题。实验结果表明,该方法的精确率和召回率分别达到85.9%和91.2%,相比SSD、Faster R-CNN、YOLOv4方法,其在保证检测速度的同时,能够有效提高检测精度,且实现对林业害虫的实时精确监测。