FAST LINEAR ESTIMATION METHODS FOR VECTOR AUTOREGRESSIVE MOVING-AVERAGE MODELS

Abstract. Three linear methods for estimating parameter values of vector auto-regressive moving-average (VARMA) models which are in general at least an order of magnitude faster than maximum likelihood estimation are developed in this paper. Simulation results for different model structures with varying numbers of component series and observations suggest that the accuracy of these procedures is in most cases comparable with maximum likelihood estimation. Procedures for estimating parameter standard error are also discussed and used for identification of nonzero elements in the VARMA polynomial structures. These methods can also be used to establish the order of the VARMA structure. We note, however, that the primary purpose of these estimates is to generate initial estimates for the nonzero parameters in order to reduce subsequent computational time of more efficient estimation procedures such as exact maximum likelihood.     

无线传感器网络分簇拓扑控制算法

通过对经典的分簇算法HEED和EEUC进行研究与分析,对它们不足之处进行了改进,提出了一种新的基于双簇首节能的无线传感器网络分簇拓扑控制算法,即DCHEB算法。该算法提出了一种新的簇划分方案,通过此方案可以对无线传感器网络进行合理分簇,使得簇首节点位于合适的位置上,平均了各个簇的节点个数,可以避免簇内的边缘节点过早死亡。最后通过理论分析和仿真工具验证了该算法对减少无线传感器网络的能量消耗和延长其生存时间有很好的作用。     

基于Cortex M3的铝型材生产全自动牵引切割系统的研究与设计

分析了铝型材生产中对牵引切割的技术要求,建立了双牵引机运动模型,并根据该模型设计了一种基于Cortex M3的无双线牵引机控制系统,设计了硬件电路,编写相应的控制程序及设计了无线通信协议,使该系统具有良好的兼容性。该系统完全实现了双牵引机运动模型,并在某铝材生产厂家运行测试。试验证明,该系统完全符合厂家的要求,而且价格低廉,结构简单,性能稳定,具有良好的应用前景。     

Fluoroelastomers-dependence of relaxation phenomena on composition

The dynamic-mechanical properties of some fluoroelastomers were determined as a function of composition at low frequency (≈ 1 Hz), by means of a free oscillation torsion pendulum, between −180°C and the softening point. Vinylidenefluoride (VDF)-hexafluoropropene (HFP) copolymers of molar composition 0–39% HFP and terpolymers of VDF and HFP with up to 30mol% tetrafluoroethylene (TFE) and a constant VDF to HFP molar ratio of 3.4 were considered. Two relaxation processes typical of the amorphous phase were found. The first, located at about −87°C, is related to local motions and the transition temperature was found to be independent of composition for copolymers, while it depends on TFE molar content for terpolymers. The second is related to the glass transition and the transition temperature depends on the composition. However, for semicrystalline copolymers the double glass transition phenomenon was observed. When crystallinity goes to zero at about 20 mol% HFP, only one transition is observed. It was also found that ordered structures can take place for terpolymers when TFE molar concentration exceeds 20%. The crystal disorder transition of pure PVDF (75°C) is observed also for low HFP concentrations but the transition temperature is strongly reduced. Analogies between the VDF-HFP and E-P systems are also discussed.     

对边缘不突出的显微镜影像进行边缘特征提取与Hough直线检测

文章主要介绍如何对边缘不突出的显微镜进行边缘特征提取与Hough直线检测,其中涉及到数字图像处理中的边缘检测、图像二值化及Hough直线检测算法。     

无先验地图条件下电力管廊无人机自主巡检方法研究

针对无先验地图条件下电力管廊无人机自主巡检能力不足的问题,本文提出了一种不依赖先验地图的无人机巡检方法。首先,无人机搭载激光雷达,通过SLAM（Simultaneous Localization and Mapping）算法进行实时场景构图,并基于RRT（Rapidly-exploring Random Tree）算法对构建的全局栅格地图进行边界搜索;其次,针对传统RRT算法难以判断环境地图完整性、保障巡检全面性的问题,提出了一种基于数字图像处理的边界检测方法。通过Canny算子对实时构建的地图进行边缘检测,并对地图进行完整性评估。最后,为验证本文提出方法的有效性,在江苏无锡处某220kV电力管廊的仿真模型中进行验证,分别采用RRT算法和本文改进算法进行自主巡检测试,结果表明本文提出的算法相比RRT算法可提升21.8%的巡检覆盖率。     

基于云端协同计算架构的边缘端I/O密集型虚拟机资源分配方案

大型制造业生产车间业务流程复杂,传统固定资源配置方式将产生负载不均衡的问题。针对此问题,设计并实现了一种基于云端协同架构的边缘端I/O密集型虚拟机资源的分配算法,通过定义计算节点中每个I/O密集型虚拟机三个维度的信息计算得出I/O密集型虚拟机的优先级,并按最大优先级队列实时统一分配硬件资源。实验结果表明,该算法在应对工业机械设备高响应和高通量的要求上有较为明显的提升,为实际生产起到了优化资源配置的作用。     

基于遗传算法优化的OCSVM双轮廓模型异常检测算法

针对Modbus工业总线协议的特殊性及工控数据样本的不均衡性,利用单类支持向量机（OCSVM）分别构建正常OCSVM模型和异常OCSVM模型,即双轮廓模态来模拟系统通信的正常模式和异常模式,从而实现工控系统异常检测。同时将遗传算法优化自变量降维应用于工控网络入侵检测场景,实现对输入自变量的降维压缩处理,防止OCSVM模型出现过拟合现象及分类准确率低的问题,提高异常检测的精度,缩减建模时间。通过仿真验证了该算法对工控网络异常检测的有效性。     

对辊式造粒机在复混肥生产中的应用

对辊式造粒机生产粒状 ( 5 .5 m m)复混肥的原理及特点 :过程无温升 ,不需干燥 ,故采用原料广泛 ;该机可用含硝态氮的氮肥生产喜硝态氮的的作物专用肥 ;还可生产颗粒磷肥及颗粒碳铵。该机的主要消耗为对辊外壳 ,一对对辊外壳价值 80 0 0元 ,可生产 30 0 0 t肥料 ,每吨肥料的设备机物料损耗约 3元     

甲醇装置高效分醇技术及双"零"节能工艺

针对甲醇分离系统存在的普遍性问题 ,提出了“少醇无水”工艺技术并进行了工业实际应用。在“少醇无水”工艺的基础上 ,又提出双“零”工艺的构思。分别对该两种工艺进行了经济效益分析。结果表明 :“少醇无水”工艺可使入塔醇含量由0 .987%降至 0 .5 62 % ,装置能力提高 6.0 %～ 11.12 % ;双“零”工艺可使 10万t/a甲醇装置生产能力提高 2 2 .0 0 %。