Detecting Change Points by Fourier Analysis

The cumulative sum (CUSUM) is a basic diagnostic tool in the analysis of change-point data. It is shown that Fourier analysis of the CUSUM can be a useful supplementary tool in such analyses. The technique is applied to three data sets that have appeared previously in the statistical literature.     

Polynomial filtering for nonlinear stochastic systems with state‐ and disturbance‐dependent noises

This article is concerned with the polynomial filtering problem for a class of nonlinear stochastic systems governed by the Itô differential equation. The system under investigation involves polynomial nonlinearities, unknown‐but‐bounded disturbances, and state‐ and disturbance‐dependent noises ((x,d)‐dependent noises for short). By expanding the polynomial nonlinear functions in Taylor series around the state estimate, a new polynomial filter design method is developed with hope to reduce the conservatism of the existing results. In virtue of stochastic analysis and inequality technique, sufficient conditions in terms of parameter‐dependent linear matrix inequalities (PDLMIs) are derived to guarantee that the estimation error system is input‐to‐state stable in probability. Moreover, the desired polynomial matrix can be obtained by solving the PDLMIs via the sum‐of‐squares approach. The effectiveness and applicability of the proposed method are illustrated by two numerical examples with one concerning the permanent magnet synchronous motor.     

On the polynomial solvability of distributionally robust k-sum optimization

In this paper, we define a distributionally robust k-sum optimization problem as the problem of finding a solution that minimizes the worst-case expected sum of up to the k largest costs of the elements in the solution. The costs are random with a joint probability distribution that is not completely specified but rather assumed to be known to lie in a set of probability distributions. For k=1, this reduces to a distributionally robust bottleneck optimization problem while for k=n, this reduces to distributionally robust minimum sum optimization problem. Our main result is that for a Fréchet class of discrete marginal distributions with finite support, the distributionally robust k-sum combinatorial optimization problem is solvable in polynomial time if the deterministic minimum sum problem is solvable in polynomial time. This extends the result of Punnen and Aneja [On k-sum optimization, Oper. Res. Lett. 18(5)(1996), pp. 233–236] from the deterministic to the robust case. We show that this choice of the set of distributions helps preserve the submodularity of the k-sum objective function which is an useful structural property for optimization problems.     

Fixed points of an F-contraction on metric spaces with a graph

We introduce a new type of contraction on a metric space endowed with a graph and prove fixed point theorems that generalize some of the results related with G-contraction for a directed graph G. Examples are given to justify that our contractions are more general than many others in this area.     

化学示踪连通试验在矿井充水条件探查中的应用

为获取地下水流速和渗透系数等水文地质参数、查清含水层水力联系、查明矿井充水条件，在内蒙古某矿设计实施了化学示踪试验。通过对国内外化学示踪试验资料整理、统计分析，总结出化学示踪剂用量与投放距离、含水层性质的经验关系式，并对本次示踪剂用量做出了评价。同时，对试验中监测点水中均未出现Cl-浓度增高现象进行了科学解释，提出类似含Cl-示踪剂中的某些离子可能被地下岩层特定矿物质吸附时，只要化学试剂中的一种离子能达到试验效果，且具有成本低、易获取等特点，即可选择其作为示踪剂的观点。     

基于云管端一体化的车联网解决方案创新与实践

为满足客户日新月异的技术及运营需求,对车联网服务能力进行完善,发掘4G在新一代车联网应用中牵引作用,面向前装市场推出以云管端一体化为核心的和车连产品,引导车联网行业新变革.     

家用变频空调室外机控制器PFC电路设计

PFC电路是家用变频空调室外机控制器基本的单元电路之一,根据控制电路的不同,分为无源和有源PFC两大类,有源PFC电路因其优点多而得到很好的发展。目前,有源PFC的整流滤波电路通常用少量大容值的铝电解电容组成,存在成本高和寿命短的问题。本论文介绍一种新的有源PFC高压整流滤波电路,它由多数量小容值铝电解电容并联组成,辅以电流均流化设计,有效降低电容的ESR值,减小电容的发热,提升控制器寿命。     

风储联合并网发电系统的控制策略研究

并网运行控制方法是保证风储联合发电系统可靠运行需要解决的关键技术问题之一。本文首先建立了风力涡轮机和锂离子蓄电池的数学模型,并且给出了风力发电系统网侧和机侧变换器在两相同步旋转坐标系下的数学模型。详细研究了风力发电系统和储能逆变器的并网运行控制策略。最后通过仿真研究验证了本文研究方法的可行性和有效性。     

并联换流器高压直流输电系统控制策略

随着中国高压直流输电技术的发展,在直流工程分期建设和融冰方式运行方面,并联换流器结构受到越来越多的关注。文中详细分析了并联结构的四端直流输电系统特点,提出了整流站定直流电流控制、逆变站定直流电压控制且附加直流电流平衡控制功能的多端直流系统协调配合方式。该方式不仅最大程度地保持了双并联直流系统的相对独立性,简化了多端直流系统控制策略的设计,而且可以实现并联换流器间功率的灵活分配。由于换流器的并联和解并联是系统运行的关键技术,文中提出了详细的第二换流器解锁及第一换流器闭锁控制策略,并基于PSCAD/EMTDC搭建了四端并联直流系统的详细控制策略模型,验证了所提控制策略的有效性。     

含储能单元的分布式发电系统仿真研究

基于含有储能单元的分布式发电系统,分别设计了单相电流环控制逆变器并网运行方式,以及单相电压电流双环控制的储能逆变器的双向、双模运行方式。在此基础上提出了含储能单元的分布式发电系统运行控制策略,并对系统处于离网状态时的储能系统的三种工作状态做出了具体分析。同时,基于MATLAB/Simulink仿真平台,对系统多种运行方式、状态进行了仿真研究。仿真结果表明,控制策略系统可以准确的执行给定的电压、电流指令,验证了提出理论的正确性;同时,设计的系统在并网、离网状态及并/离网切换时都可以为重要负载提供持续高质量的电能,证明了设计构成的系统具有较强的可行性和稳定性。