随机微分系统关于时变集的几乎必然稳定性

本文借助于Lyapunov-like函数及比较方法研究了It随机微分系统关于状态空间的时变集的几乎必然(a.s.)稳定性,得到了a.s.稳定性、a.s.不稳定性以及a.s.渐近稳定性的判别定理。这些结果均为确定性常微系统关于时变集的相应稳定性结果(见[1,2]),对于随机微分系统的直接推广。

集群时变拓扑下的链路修复

针对集群拓扑的时变特性引起的网络分割问题,设计了一种多目标的协同修复方法。基于拓扑修复模型,将链路修复节点引入,建立了信道链路模型。通过多目标链路约束,设计了多目标链路优化算法。结果表明:该算法通过解密集度策略以及速率约束策略,实现了最优的通信位置规划。通过扩大种群数,该算法取得较为精确的帕累托最优解集,能够在两个分割网络间确定最优的通信位置,实现了分割网络间的数据投递。

一种改进的鲁棒约束预测控制器的综合设计方法

针对多包描述的不确定系统,提出一种新的鲁棒约束预测控制器.离线设计多包系统worst-case情况下性能最优的不变集,在线求解多包系统无穷时域性能指标的min-max优化问题.设计方法采用了时变的终端约束集,扩大了初始可行域,并能获得较优的控制性能.仿真结果验证了该方法的有效性.

Improving the simulation of terrestrial water storage anomalies over China using a Bayesian model averaging ensemble approach

The ability to estimate terrestrial water storage(TWS)is essential for monitoring hydrological extremes(e.g.,droughts and floods)and predicting future changes in the hydrological cycle.However,inadequacies in model physics and parameters,as well as uncertainties in meteorological forcing data,commonly limit the ability of land surface models(LSMs)to accurately simulate TWS.In this study,the authors show how simulations of TWS anomalies(TWSAs)from multiple meteorological forcings and multiple LSMs can be combined in a Bayesian model averaging(BMA)ensemble approach to improve monitoring and predictions.Simulations using three forcing datasets and two LSMs were conducted over China's Mainland for the period 1979–2008.All the simulations showed good temporal correlations with satellite observations from the Gravity Recovery and Climate Experiment during 2004–08.The correlation coefficient ranged between 0.5 and 0.8 in the humid regions(e.g.,the Yangtze river basin,Huaihe basin,and Zhujiang basin),but was much lower in the arid regions(e.g.,the Heihe basin and Tarim river basin).The BMA ensemble approach performed better than all individual member simulations.It captured the spatial distribution and temporal variations of TWSAs over China's Mainland and the eight major river basins very well;plus,it showed the highest R value(>0.5)over most basins and the lowest root-mean-square error value(<40 mm)in all basins of China.The good performance of the BMA ensemble approach shows that it is a promising way to reproduce long-term,high-resolution spatial and temporal TWSA data.

Generic reconstruction technology based on RST for multivariate time series of complex process industries

In order to effectively analyse the multivariate time series data of complex process,a generic reconstruction technology based on reduction theory of rough sets was proposed,Firstly,the phase space of multivariate time series was originally reconstructed by a classical reconstruction technology.Then,the original decision-table of rough set theory was set up according to the embedding dimensions and time-delays of the original reconstruction phase space,and the rough set reduction was used to delete the redundant dimensions and irrelevant variables and to reconstruct the generic phase space,Finally,the input vectors for the prediction of multivariate time series were extracted according to generic reconstruction results to identify the parameters of prediction model.Verification results show that the developed reconstruction method leads to better generalization ability for the prediction model and it is feasible and worthwhile for application.

基于参数李雅普诺夫函数的鲁棒预测控制器

针对多包描述的不确定系统,提出一种新的鲁棒约束预测控制器.离线设计时引入参数Lyapunov函数以减少单一Lyapunov函数设计时的保守性,得到多包系统Worst-case情况下性能最优的不变集,在线求解多包系统无穷时域性能指标的min-max优化问题.设计采用了时变的终端约束集,扩大了初始可行域,而且能够获得较优的控制性能.仿真结果验证了该方法的有效性.

Temporal and Spatial Characteristics and Optimization of the Intensive Use of Cultivated Land in Maoming City

Improving the level of intensive cultivated land use is an important measure to ensure food security and promote the sustainable development of the regional society and economy.Based on data from the statistical yearbook of Maoming City and its counties and districts from 2005 to 2018 and the land use change database of Maoming City for 2018,this study constructed an evaluation index system for four aspects:cultivated land use intensity,cultivated land use degree,cultivated land output benefit and cultivated land sustainable use status.The level of intensive use of cultivated land in Maoming City from 2004 to 2017 was evaluated by AHP,the range method and the comprehensive evaluation model,and its temporal and spatial characteristics were evaluated.The results revealed three major points.(1)The intensive use of cultivated land in Maoming City in the past 14 years was good,and its level showed an overall upward trend,with the intensive use degree of cultivated land rising from 0.4045 in 2004 to 1.3148 in 2017.(2)The levels of intensive use of cultivated land in each county and district of Maoming City were generally on the rise,with no significant differences between them.However,according to the regional distribution,the intensive use level of cultivated land was highest in Maonan District,while it was relatively low in Dianbai County.The largest increase in the level of cultivated land intensive use was in Gaozhou,and the smallest was in Dianbai County.(3)According to the existing problems of cultivated land utilization in Maoming City,combined with the current international and domestic measures to effectively improve the level of intensive use of cultivated land,four suggestions are put forward:to improve the efficiency of cultivated land utilization and effectively protect basic farmland;to improve the overall urban planning and rationally adjust the layout of construction land;to raise farmers’awareness of the intensive use of cultivated land;and to increase agricultural investment and improve agricultural infrastructure.

Temporal Variations and Driving Factors of Cultivated Land Use Intensity in Shandong Province from 1980 to 2015

Based on the cost-income data of agricultural products and relevant statistical data, taking major grain crops and economic crops in the process of cultivated land use as study cases, we studied characteristics of the temporal variation of cultivated land use intensity and its composition in Shandong Provinee from 1980 to 2015, and then analyzed its main driving factors. The results showed that:(1) The total intensity of major crops in Shandong Province showed a rising trend from 919.73 Yuan ha^-1 in 1980 to 3285.06 Yuan ha^-1 in 2015, and the average annual in tensity of economic crops was higher than that of grain crops. The labor cost and material cost of major crops both showed an increasing trend, but the material input was much higher than labor input for grain crops, while the labor in put was much higher tha n material in put for economic crops.(2) The labor intensity of major crops in Shandong Province showed a decreasing trend from 501.75 man-day ha^-1 in 1980 to 161.93 man-day ha^-1 in 2015. The labor intensity of grain crops was lower than that of economic crops and its decline rate was fast. On the contrary, the capital intensity showed an increasing trend from 518.33 Yuan ha^-1 in 1980 to 1159.95 Yuan ha^-1 in 2015. In the internal composition of capital internsity, the proportion of yield-increasing inputs such as seed, farm-yard manure, fertilizer, pesticide and drainage and irrigation decreased gradually, while the proportion of la-bor-saving inputs such as agricultural machinery increased significantly.(3) The cultivated land use intensity in Shandong Provinee had significant negative correlations with the amount of agricultural labor and cultivated land area per capita. The primary direct driving factor was the net income per unit cost of major crops, but the time re-sponse lagged by 1-3 years. The main indirect driving factor was the reform of agricultural policy.

OPTIMAL ALLOCATION FOR ESTIMATING THE CORRELATION COEFFICIENT OF MORGENSTERN TYPE BIVARIATE EXPONENTIAL DISTRIBUTION BY RANKED SET SAMPLING WITH CONCOMITANT VARIABLE

Ranked set sample is applicable whenever ranking of a set of sample units can be done easily by a judgement method of the study variable or of the auxiliary variable. This paper considers ranked set sample based on the auxiliary variable X which is correlated with the study variable Y, where （X, Y） follows Morgenstern type bivariate exponential distribution. The authors discuss the optional allocation for unbiased estimators of the correlation coefficient p of the random variables X and Y when the auxiliary variable X is used for ranking the sample units and the study variable Y is measured for estimating the correlation coefficient. This paper first gives a class of unbiased estimators of p when the mean 0 of the study variable Y is known and obtains an essentially complete subclass of this class. Further, the optimal allocation of the unbiased estimators is found in this subclass and is proved to be Bayes, admissible, and minimax. Finally, the unbiased estimator of p under the optimal allocation in the case of known θ is reformed for estimating p in the case of unknown θ, and the reformed estimator is shown to be strongly consistent.

Revisit of constraints on holographic dark energy:SNLS3 dataset with the effects of time-varying β and different light-curve fitters

Previous studies have shown that for the Supernova Legacy Survey three-year （SNLS3） data there is strong evidence for the redshifl- evolution of color-luminosity parameter β of type Ia supernovae （SN Ia）. In this paper, we explore the effects of varying β on the cosmological constraints of holographic dark energy （HDE） model. In addition to the SNLS3 data, we also use Planck distance prior data of cosmic microwave background （CMB）, as well as galaxy clustering （GC） data extracted from Sloan Digital Sky Survey （SDSS） data release 7 and Baryon Oscillation Spectroscopic Survey （BOSS）. We find that, for the both cases of using SN data alone and using SN＋CMB＋GC data, involving an additional parameter of β can reduce χ^2 by - 36; this shows that β deviates from a constant at 6σ- confidence levels. Adopting SN＋CMB＋GC data, we find that compared to the constant β case, varying β yields a larger fractional matter density Ωm0 and a smaller reduced Hubble constant h; moreover, varying β significantly increases the value of HDE model parameter c, leading to c ≈ 0.8, consistent with the constraint results obtained before Planck. These results indicate that the evolution of β should be taken into account seriously in the cosmological fits. In addition, we find that relative to the differences between the constant β and varying β（z） cases, the effects of different light-curve fitters on parameter estimation are very small.