基于自适应滤波的微弱GPS信号跟踪方法

针对全球定位系统(GPS)传统跟踪算法在接收信号很微弱的条件下跟踪误差大,为保持跟踪精度,提出了一种新的跟踪方法.同时考虑了多普勒频移和码相位偏移量作为观测模型,然后采用自适应卡尔曼滤波算法,有效减轻了系统噪声和观测噪声对信号跟踪的影响;并通过列文伯格-马夸尔特方法,优化迭代过程,进一步提高自适应卡尔曼滤波算法的稳定性和收敛速度.仿真结果显示,利用新的算法对载噪比低至21dB-Hz的微弱GPS信号取得了良好的跟踪精度和极高的灵敏度.     

Modeling of Energy Consumption and Effluent Quality Using Density Peaks-based Adaptive Fuzzy Neural Network

Modeling of energy consumption (EC) and effluent quality (EQ) are very essential problems that need to be solved for the multiobjective optimal control in the wastewater treatment process (WWTP). To address this issue, a density peaks-based adaptive fuzzy neural network (DP-AFNN) is proposed in this study. To obtain suitable fuzzy rules, a DP-based clustering method is applied to fit the cluster centers to process nonlinearity. The parameters of the extracted fuzzy rules are fine-tuned based on the improved Levenberg-Marquardt algorithm during the training process. Furthermore, the analysis of convergence is performed to guarantee the successful application of the DPAFNN. Finally, the proposed DP-AFNN is utilized to develop the models of EC and EQ in the WWTP. The experimental results show that the proposed DP-AFNN can achieve fast convergence speed and high prediction accuracy in comparison with some existing methods.      

基于神经网络的二次测爆仪传感器故障诊断方法

在全面分析智能二次测爆仪中传感器主要故障的基础上,提出了基于L-M算法的神经网络诊断方案.通过模拟矿井中各种气体体积分数所占比例的仿真实验证明:基于L-M算法的神经网络故障诊断系统具有良好的故障监测与诊断能力.     

Convergence rate of the Levenberg-Marquardt method under Hölderian local error bound

ABSTRACT

In this paper, we study the convergence rate of the Levenberg-Marquardt (LM) method under the Hölderian local error bound condition and the Hölderian continuity of the Jacobian, which are more general than the local error bound condition and the Lipschitz continuity of the Jacobian. Various choices of the LM parameter are also discussed.     

超塑性本构模型材料参数识别方法研究

金泉林等提出的超塑性本构关系考虑了三种微观变形机制和晶粒生长过程,但单纯依靠实验很难准确的测定该本构关系的材料参数.应用遗传算法和Levenberg-Marquardt算法,以Ti-6Al-4V为例,识别该超塑性本构关系中的材料参数.计算结果和实验结果符合的很好.最后讨论了各种微观变形机制的体积分数与应变、应变率和晶粒尺寸之间的关系,发现在大部分情况下扩散蠕变机制对超塑变形的贡献可以忽略.     

Self-adaptive Green-Ampt infiltration parameters obtained from measured moisture processes

The Green-Ampt(G-A) infiltration model(i.e., the G-A model) is often used to characterize the infiltration process in hydrology. The parameters of the G-A model are critical in applications for the prediction of infiltration and associated rainfall-runoff processes. Previous approaches to determining the G-A parameters have depended on pedotransfer functions(PTFs) or estimates from experimental results, usually without providing optimum values. In this study, rainfall simulators with soil moisture measurements were used to generate rainfall in various experimental plots. Observed runoff data and soil moisture dynamic data were jointly used to yield the infiltration processes, and an improved self-adaptive method was used to optimize the G-A parameters for various types of soil under different rainfall conditions. The two G-A parameters, i.e., the effective hydraulic conductivity and the effective capillary drive at the wetting front, were determined simultaneously to describe the relationships between rainfall, runoff, and infiltration processes. Through a designed experiment, the method for determining the GA parameters was proved to be reliable in reflecting the effects of pedologic background in G-A type infiltration cases and deriving the optimum G-A parameters. Unlike PTF methods, this approach estimates the G-A parameters directly from infiltration curves obtained from rainfall simulation experiments so that it can be used to determine site-specific parameters. This study provides a self-adaptive method of optimizing the G-A parameters through designed field experiments. The parameters derived from field-measured rainfall-infiltration processes are more reliable and applicable to hydrological models.     

基于红外测温的内部缺陷尺寸、方位的计算方法研究

对具有内部缺陷的平板试件的传热建立了三维物理和数学模型,提出了通过表面红外测温确定内部缺陷尺寸、方位的计算方法。同时,分析了测量误差和缺陷导热系数对计算结果的影响。通过计算分析可以得到结论：本方法可以精确地确定内部缺陷的尺寸和方位,测量误差对内部缺陷估计的影响较小;在试件的导热系数远大于缺陷的导热系数时,缺陷导热系数的微小变化对缺陷尺寸和位置的计算没有明显的影响;适用于任何尺寸、方位可用有限个参数描述的内部缺陷的检测。     

Application of artificial neural network method to predict the breakage properties of PGE bearing chromite ore

In the present investigation, systematic grinding experiments were conducted in a laboratory ball mill to determine the breakage properties of low-grade PGE bearing chromite ore. The population balance modeling technique was used to study the breakage parameters such as primary breakage distribution (B_{i, j}) and the specific rates of breakage (S_i). The breakage and selection function values were determined for six feed sizes. The results stated that the breakage follows the first-order grinding kinetics for all the feed sizes. It was observed that the coarser feed sizes exhibit higher selection function values than the finer feed size. Further, an artificial neural network was used to predict breakage characteristics of low-grade PGE bearing chromite ore. The predicted results obtained from the neural network modeling were close to the experimental results with a correlation of determination R² = 0.99 for both product size and selection function.     

瞬变电磁法反演效果分析

瞬变电磁法用于隐伏矿体勘探、采空区的探测等领域,是有效排查治理矿山安全隐患的关键。目前国内瞬变电磁数据处理与解释主要停留在一维阶段, 基于层状介质模型假设。本文采用均匀半空间模型进行正演模拟,充分验证了一维正演程序的精确性,然后分别采用电导率高低高(K型)模型与电导率低高低(H型)模型两个典型的三层模型,对一维Levenberg-Marquardt反演进行验证,保证了反演结果的可靠性,并对实际数据测量与解释提供一定的建议。     

Thermophysical properties of pure gases and mixtures at temperatures of 300-30 000 K and atmospheric pressure:thermodynamic properties and solution of equilibrium compositions

The equilibrium compositions and thermodynamic properties(density,enthalpy,etc at constant pressure)of plasma of pure gases and mixtures under local thermodynamic nonequilibrium have been calculated in this paper.The homotopy Levenberg-Marquardt algorithm was proposed to accurately solve nonlinear equations with singular Jacobian matrices,and is constructed by the Saha equation and Guldberg-Waage equation combined with mass conservation,the electric neutrality principle and Dalton's partial pressure law,to solve the problem of dependence on the initial value in the process of iteration calculation.In this research,the equations at a higher temperature were solved and used as the auxiliary equations,and the homotopy control parameters'sequence of the homotopy equations was selected by equal ratios.For auxiliary equations,the iterative initial value was obtained by assuming that there were only the highest-valence atomic cations and electrons at this temperature,and the plasma equilibrium composition distribution with the required accuracy was ultimately solved under the current conditions employing the Levenberg-Marquardt algorithm.The control parameter sequence was arranged according to the geometric sequence and the homotopy step was gradually shortened to ensure continuity of the homotopy process.Finally,the equilibrium composition and thermodynamic properties of pure N2,Mg(30％)-C02(70％)and Mg(40％)-CO(50％)-N2(10％)mixture plasma at atmospheric pressure were calculated and the calculation process of some specified temperatures was shown and analyzed.The calculation accuracy of equilibrium composition is higher than other findings in the literature.The results for the thermodynamic properties are in good agreement with data reported by the literature.