基于MVDR高分辨算法的时反定位技术研究

最小方差无畸变响应(MVDR)算法突破了瑞利限的限制,具有较高的分辨能力,但其容易受到复杂的水声环境的影响,宽容性差,因而难被应用到实际水下系统中.时间反转镜作为一种新的定位方法,可自适应修正各种多途引起的畸变,实现目标的检测和定位.针对MVDR算法宽容性差的问题,将时间反转镜和MVDR算法相结合,用于水声被动检测和定位,可充分利用水声信道的多径信息,减小复杂的水声环境对高分辨算法的影响.并研究了固定对角加载和基于RCB算法的宽容时反MVDR的被动定位性能.仿真、水池和海试实验数据处理结果证明了时反MVDR用于被动目标进行检测和定位的可行性和宽容时反MVDR的稳健性.     

基于免疫遗传算法的煤与瓦斯突出预测研究

根据影响煤与瓦斯突出的各个因素与突出强度之间存在的复杂的非线性映射关系,建立了突出强度预测的BP网络模型.针对BP网络收敛速度慢和易陷入局部极小值及基于遗传算法的BP网络易出现未成熟收敛问题,提出了一种基于免疫遗传算法(IGA)的BP网络,即利用IGA实现对BP网络的优化.IGA在遗传算法(GA)的基础上引入生物免疫系统中的多样性保持机制和抗体浓度调节机制,有效地克服了GA算法的搜索效率低、个体多样性差及早熟现象,提高了算法的收敛性能.结果表明:将基于IGA的BP网络应用于煤与瓦斯突出强度预测,该算法设计的BP网络具有较快的收敛速度和较强的全局收敛性能,在煤与瓦斯突出预测中取得了良好效果.     

Deformation resistance effect of PAN-based carbon fibers

The deformation resistance effect of polyacrylonitrile (PAN)-based carbon fibers was investigated, and the variatipn law of electrical resistivity under tensile stress was analyzed. The results show that the gauge factor (fractional change in resistance per unit strain) of PAN-based carbon fibers is 1.38, which is lower than that of the commonly-used resistance strain gauge. These may due to that the electrical resistivity of carbon fibers decreases under tensile stress. In addition when the carbon fibers are stretched, the change of its resistance is caused by fiber physical dimension and the change of electric resistivity, and mainly caused by the change of physical dimension. The mechanical properties of carbon fiber monofilament were also measured. Funded by the National Natural Science Foundation of China (No. 10672128 and 50878170)     

结构损伤识别的残余向量法及数值仿真

为了找到对小损伤较敏感的参数,在结构自由振动微分方程基础上,利用广义逆和矩阵投影定理,导出了识别效果很好的残余向量投影范数.确定了损伤单元,计算了该损伤单元的损伤因子.算例分析发现,该参数对结构损伤非常敏感,能识别出结构中的微小损伤,而且不受损伤位置的约束,仅需要结构的前几阶模态就能达到很好的效果.     

一种块递推实时FFT算法模块设计与实现

文中提出了一种基于FPGA-IP核的FFT算法硬件模块的设计方案,该方案采用四分块递推FFT算法,具有结构规范、递推性好、实时性强等特点,结合DSP对模块的数据输入和输出的软件控制,实现了一种硬件和软件相结合的实时FFT模块.对该模块性能进行测试,FFT模块运行稳定,输出的计算结果正确,与DSP软件实现的标准FFT算法程序库相比,文中的FFT模块实时性能提高了35倍,该模块已被用于实时信号处理系统中.     

改进灰色模型在中长期电力负荷预测中的应用

针对中长期电力系统负荷预测,在前人已有成果的基础之上,对普通灰色模型进行了改进.一方面对历史数据进行二次平滑处理,大大消除了干扰因素;另一方面利用带有马尔可夫链符号估计的残差修正技术对未来残差的符号进行预测以修正灰色模型的预测结果.以某地区多年以来的历史数据为基础,建立了数学模型,通过实际数据计算表明:改进后的灰色负荷预测方法可以应用于电力系统中长期负荷预测,而且较普通灰色预测模型在预测精度上有着明显的提高,尤其是对于较远时间的负荷预测有着较为理想的预测精度,表明了该种方法的有效性和实用性.     

利用弯管测量流体流量的实验研究

利用火力发电厂中循环水管道与凝汽器之间连接所形成的弯管,首先从弯管流量测量基本理论入手,分别用自由涡流理论和强制涡流理论,建立了循环水在弯管内流动过程中,弯管内外径的压力差与循环水流量之间关系的数学关系模型.其次,利用实验室实验确定循环水流量与弯管内外径之间压差的关系,实现了利用弯管对流体流量进行测量.     

Temperature distribution and dynamic control of secondary cooling in slab continuous casting

To predict and optimize the temperature distribution of slab continuous casting in steady operational state, a three-dimensional model (named offline model) based on the heat transfer and solidification theories was developed. Both heat transfer and flux distribution characteristics of the nozzle sprays on the slab were considered, and the complicated boundary condi-tions, such as spray cooling, natural convection, thermal radiation as well as contact cooling of individual rolls were involved in the model. ...     

Numerical analysis on Joule heating of double-loop channel induction furnaces

In order to investigate Joule heating power, a three-dimensional finite element model (FEM) was developed to predict Joule heating power in the channels of double-loop inductor. The simulated results were compared with experimental data from low load trials for a 400 kW inductor. The results, such as power factor and Joule heating power, show reasonable correlation with experimental data, and Joule heating rate reaches the maximum at the corners and the minimum at the centre of the cross-section area. With increasing relative permeability of iron core, length of coils, current frequency and resistivity of metal melt, the power factor and Joule heating power change. It is concluded that current frequency, the resistivity and length of the coil play a critical role in determining the power factor and Joule heating power, whereas relative permeability of the magnetic core shows no significant influence on them.     

考虑冷变形加工硬化的翻边力理论计算

在分析现有计算公式存在不足的基础上,根据翻边变形区材料的应力应变特点,考虑了冷变形加工硬化(取幂函数硬化规律)和变形区材料厚度变化(翻边为变薄)两个因素的影响,利用金属塑性成形问题求解理论中的主应力法,推导和提出了圆孔翻边力计算的一个新公式.通过用钢板(SPCC)和铜板(T1)进行了翻边工艺试验的验证,并与经验公式和现有理论公式的计算结果进行了比较,表明新公式计算结果能接近于实际,且原理上更为科学合理.