危岩体崩塌灾害监测预警试验研究

岩体崩塌破坏的突发性使其成为最难预防的地质灾害之一, 严重威胁人类的生命财产安全. 边坡岩块体崩塌破坏多是系统不稳定导致的动力破坏, 因此应用动力学指标进行监测预警更为有效. 本研究通过引入多种时域动力学监测指标, 开展了岩体崩塌破坏全过程的监测预警实验研究. 通过振动幅值、峭度指标等时域动力学指标监测, 可有效识别岩体分离破坏前兆现象, 提前55 s实现岩块体崩塌的早期预警. 多个时域动力学指标均可识别岩体破坏前的非协调性动力特征, 其中变异系数在识别这一振荡特征上优势明显, 可通过识别这一震荡特征实现崩塌灾害的早期预警. 此外, 破坏前岩体的振动速度是稳定岩体的2.1倍, 岩体破坏发生时刻赋存较大的冲击能量, 是岩体启程剧动的主要原因之一, 可通过综合分析峭度指标等时域动力学指标, 实现分离破坏前兆更为合理的判识. 本研究不仅为岩体崩塌灾害早期预警提供了新的数据与技术方法支持, 也为崩塌岩体启程剧动机制与破坏后运动特性研究提供了新的启示.      

A novel memcapacitor and its application in a chaotic circuit

Nonlinear Dynamics - In this paper, a novel memcapacitor is designed by the SBT ( $$\hbox {Sr}_{0.95}\hbox {Ba}_{0.05}\hbox {TiO}_{{3}}$$ ) memristor and two capacitors. A fifth-order memcapacitor...     

基于无人机高光谱特征参数和株高估算马铃薯地上生物量

地上生物量（above-ground biomass, AGB）是评价作物长势及其产量估测的重要指标,对指导农业管理具有重要的作用。因此,快速准确地获取生物量信息,对于监测马铃薯生长状况,提高产量具有重要的意义。于马铃薯现蕾期、块茎形成期、块茎增长期、淀粉积累期、成熟期获取成像高光谱影像、实测株高（heigh, H）、地上生物量和地面控制点（ground control point, GCP）的三维空间坐标。首先基于无人机高光谱灰度影像结合GCP生成试验田的DSM（digital surface model, DSM）,利用DSM提取马铃薯的株高（H_dsm）;然后利用无人机高光谱影像计算一阶微分光谱、植被指数和绿边参数,进而分析高光谱特征参数（hyperspectral characteristic parameters, HCPs）和绿边参数(green edge parameters, GEPs)与马铃薯AGB的相关性,每个生育期筛选出相关性较高的前7个高光谱特征参数和最优绿边参数(optimal green edge parameters, OGEPs);最后基于HCPs,HCPs加入OGEPs,HCPs加入OGEPs和H_dsm的组合利用偏最小二乘回归（partial least square regression, PLSR）和随机森林（random forest, RF）估算不同生育期的AGB。结果表明：（1）提取的H_dsm与实测株高H高度拟合（R2=0.84,RMSE=6.85 cm,NRMSE=15.67%）;（2）每个生育期得到的最优绿边参数不完全相同,现蕾期、块茎增长期和淀粉积累期OGEPs为R_sum,块茎形成期和成熟期OGEPs分别为Dr_min和SDr;（3）与仅使用HCPs估算AGB相比,使用HCPs加入OGEPs,HCPs加入OGEPs和H_dsm在马铃薯不同生育期可以提高AGB估算精度,且以后者为自变量提高精度的幅度更大;（4）每个生育期利用PLSR和RF估算AGB的建模和验证R2从现蕾期到块茎增长期呈上升趋势,随后开始降低,整体上R2呈先上升后下降的趋势,通过PLSR方法构建的估算AGB模型效果优于RF方法,其中块茎增长期表现效果最好。因此,高光谱特征参数中结合最优绿边参数和株高,并使用PLSR方法可以改善马铃薯AGB的估算效果。     

基于小波分析的马铃薯地上生物量估算

地上生物量（AGB）是作物长势评价及产量预测的重要指标,因此快速准确地估算AGB至关重要。由于传统植被指数（VIs）估算多生育期的AGB存在饱和现象,因此,利用VIs结合基于离散小波转换（DWT）的影像小波分解（IWD）技术提取的高频信息和连续小波转换（CWT）技术提取的小波系数,探究VIs,VIs+IWD和VIs+CWT对于AGB的估算能力。首先,基于无人机平台分别获取马铃薯现蕾期、块茎形成期、块茎增长期、淀粉积累期的数码影像和成像高光谱影像以及地面实测的AGB数据。其次,利用数码影像通过IWD技术提取3种高频信息和利用高光谱反射率数据通过CWT技术提取小波系数以及构建6种高光谱植被指数。然后,将植被指数、高频信息和小波系数分别与AGB进行相关性分析,并挑选出不同尺度下相关系数绝对值较高的前10波段。最后,以VIs,VIs+IWD和VIs+CWT这3种变量分别使用偏最小二乘回归（PLSR）方法构建AGB估算模型,并对比不同模型估算AGB的效果。结果表明: （1）每个生育期选取的6种植被指数、3种高频信息和10种小波系数与AGB的相关性均达到0.01显著水平,整个生育期相关性均呈现先升高后降低的趋势,其中以小波系数得到的相关性最高、高频信息次之,植被指数最低。（2）对比分析每个生育期的3种估算模型,以VIs+CWT为输入变量的估算效果最好,VIs+IWD的估算效果次之,而VIs的估算效果最差,说明基于小波分析构建的模型适用性较广、稳定性较强。（3）每个生育期分别以3种变量利用PLSR方法构建的AGB估算模型均在块茎增长期达到最高精度（VIs：建模R2=0.70,RMSE=98.88 kg·hm-12,NRMSE=11.63%;VIs+IWD：建模R2=0.78,RMSE=86.45 kg·hm-12,NRMSE=10.17%;VIs+CWT：建模R2=0.85,RMSE=74.25 kg·hm-12,NRMSE=9.27%）。通过VIs分别结合IWD和CWT技术利用PLSR建模方法,可以提高AGB估算精度,为农业指导管理提供可靠参考。     

How do mutative events modify moments evolution in thermostatted kinetic models?

This short communication aims at developing a thermostatted kinetic framework which includes conservative and nonconservative interactions. Specifically nonconservative interactions refer to proliferative/destructive and mutative events. The thermostatted kinetic framework is a set of autonomous partial integro-differential equations with quadratic nonlinearity. How the moments evolution is modified by mutative interactions is explored in the present communication. Applications refer to the cancer-immune system competition.     

Attitude control of rigid spacecraft with disturbance generated by time varying exosystems

This paper is concerned with the problem of attitude control and disturbance rejection of rigid spacecraft in the presence of parameter uncertainty. It is assumed that the external disturbance is generated by some time varying exosystems. The unit quaternion is used as the kinematic variables since it is free of singularity. An internal model and an adaptive control law are proposed. The parameter uncertainty caused by the unknown inertia matrix is handled by combining the semi-tensor product and adaptive control method. The asymptotical stability of the closed-loop system is given via backstepping and Lyapunov analysis. Finally, an illustrative example is provided to show the effectiveness of the proposed approach.     

Vortical and self-similar flows of 2D compressible Euler equations

This paper presents the vortical and self-similar solutions for 2D compressible Euler equations using the separation method. These solutions complement Makino’s solutions in radial symmetry without rotation. The rotational solutions provide new information that furthers our understanding of ocean vortices and reference examples for numerical methods. In addition, the corresponding blowup, time-periodic or global existence conditions are classified through an analysis of the new Emden equation. A conjecture regarding rotational solutions in 3D is also made.     

Integrability and exact solutions of the nonautonomous mixed mKdV–sinh–Gordon equation

In this paper, a nonautonomous mixed mKdV–sinh–Gordon equation with one arbitrary time-dependent variable coefficient is discussed in detail. It is proved that the equation passes the Painlevé test in the case of positive and negative resonances, respectively. Furthermore, a dependent variable transformation is introduced to get its bilinear form. Then, soliton, negaton, positon and interaction solutions are introduced by means of the Wronskian representation. Velocities are found to depend on the time-dependent variable coefficient appearing in the equation and this leads to a wide range of interesting behaviours. The singularities and asymptotic estimate of these solutions are discussed. At last, the superposition formulae for these solutions are also constructed.     

An explicit recursive formula for computing the normal forms associated with semisimple cases

This paper presents an explicit, computationally efficient, recursive formula for computing the normal forms, center manifolds and nonlinear transformations for general n-dimensional systems, associated with semisimple singularities. Based on the formula, we develop a Maple program, which is very convenient for an end-user who only needs to prepare an input file and then execute the program to “automatically” generate the result. Several examples are presented to demonstrate the computational efficiency of the algorithm.