Minimal explanations of missing values by chasing acquisitional data

Acquisitional issues widely exist in GPS and sensor networks. They pertain to where, when, and how often data is physically acquired (sampled) and delivered to some query processing systems. Due to the dynamic environment that the data is acquired with the change of monitoring time, acquisitional data are typically a time-stamped stream where a time-stamped value could either contain noises or be missing. Aiming to improve the quality of data acquisition, we focus on the explanations of missing values in this paper. Several techniques have been developed to provide the explanation on relational data, however, they cannot be directly applied in acquisitional stream data due to its dynamic feature, such as the “change” of acquisitional stream data between two adjacent monitoring time is often constrained by some rules. We show that an explanation could be incorrect or unreasonable if those constraints are not taken into account. We propose one novel chasing technique by considering both spatial and temporal correlations to explain missing values and guarantee a minimal explanation. Experimental results show that our approach can efficiently return high-quality and minimal explanations of missing values.     

微气体传感器测试系统的恒流配气系统研究

针对恒流混合气体在微气体传感器实验中的重要性,根据道尔顿分压定律和阿马伽定律,采用质量比动态配气法,实现了实验用恒流配气系统.基于NI USB6215系列多功能数据采集卡,以LabVIEW8.5为软件开发平台,设计了恒流配气系统软件控制界面.通过计算机严格控制MFCs流量调节,配比出不同浓度氢气混合气体.气体流量始终保持在1L/min,上下波动不超过10mL/min.分析了气体流量值出现波动的原因,为进一步完善恒流配气系统提供了参考.     

对已有信息表二次利用的程序开发

Excel是OFFICE家族成员中一个功能强大、技术先进、使用方便的数据管理和分析系统。而在Excel中使用VBA(Visual Basicfor Application的简称)对已有的信息表进行宏编程,可以使用户高效地生成新的工作表,达到办公自动化的目的。文章用班级成绩表生成重考报名表的实例,揭示了利用VBA在Excel中进行二次开发,提高工作效率,保证数据准确性的强大功能。     

水和甲醇存在下MAMS的消失反应动力学研究

通过实验研究了甲基丙烯酰胺硫酸盐（ＭＡＭＳ）与甲醇、水进行反应的动力学，并对该反应的机理进行了探讨。     

广西北部湾经济区水资源管理对策研究

分析了广西北部湾经济区水资源开发利用的现状,对未来20年的需水态势进行了预测,针对经济区水资源开发利用和管理工作中存在问题,提出了相应的对策,为政府决策提供参考。     

两种水轮发电机组开机控制技术的比较及优化

本文建立了水轮发电机组仿真模型,并以某电站的水流特性、机组惯性等实际参数作为仿真模型参数,着重研究水轮发电机组的两种开机控制规律,分析了原有以空载开度为限制的机组开机控制技术,提出以恒转速变化率为控制目标的机组开机控制技术,并将两种开机控制技术进行了仿真比较。通过仿真波形分析比较表明,两种开机控制技术各自具有的优越动态性能。在工程实践中,将这两种开机控制技术都应用到水轮机调速器开机程序中,可以根据水电站现场对开机动态性能的不同要求在停机态切换两种开机控制流程。     

露天磷矿数字配矿模型

露天磷矿选矿厂采用合理的配矿方案,对稳定入选磷矿的品位,增加选矿产率,降低生产成本有着重要的意义.为了提高入选磷矿石品位的均匀性和稳定性,提出了针对以入选磷矿品位为目标的从采矿场配矿到精矿仓配矿的整个生产环节的配矿方法.将采场内原矿、选矿厂原矿矿堆和选矿厂精矿仓均定义为矿堆,按照生产实际需求设定其属性.通过设定目标函数,实现使采矿场的开采原矿量最大,配矿方案总的运输距离最小,运输成本最低等目标.同时建立约束条件,使采矿场的开采原矿量要保证选矿厂正常生产,使每一矿堆的品位达到目标要求.最后,采集企业生产实际数据对模型加以验证,证明模型在指导露天磷矿山的生产过程中有重要的实际意义,配矿过程应成为矿山生产组织、管理的一个重要环节.     

一种基于P系统的图像阈值分割方法

将P系统引入到图像阈值分割中,提出了一种基于P系统的图像阈值分割方法。采用一个两层膜的组织型P系统作为其计算框架,每个膜作为独立的并行计算单元,速度一位置模型作为进化规则,同时采用同向／反向转运规则交换和共享膜之间的对象。实验结果表明,这个基于P系统框架的阈值分割方法具有可用性和有效性,能为图像寻找最优的分割阈值。     

单通道TD-SCDMA射频拉远单元

该文设计了一种单通道TD-SCDMA射频拉远单元。首先根据系统要达到的性能指标要求,设计了系统拓扑结构,接着从该系统拓扑结构出发,分析了整个系统的设计思路及实现方案,选择相应的电路模块。测试结果表明设计的系统达到了预期的指标,临近通道功率比小于-40.64 dBc和误差向量幅度为5.08%rms。     

Global stabilization of a chain of integrators with input saturation and disturbances: A new approach

In this article, we solve the problem of global stabilization for a chain of integrators in the presence of input saturation and disturbances. A novel and elegant approach to solve this problem, in the absence of disturbances, was proposed by Teel (1992) using saturation functions and coordinate transformation. With Teel’s work as a foundation, many results have been proposed to improve the performance of controllers for a chain of integrators. Naturally, all such approaches also inherited the limitations of Teel’s approach. Most importantly, in the presence of uncertainties and disturbances, the transformation introduced in Teel (1992) would considerably shrink the region where the controller is unsaturated and, severely limit the level of uncertainties and disturbances which can be tolerated. In order to overcome these difficulties, a conceptually different approach which does not rely on the coordinate transformation is presented in this work. Specifically, modified saturation functions are directly applied to the tracking error of actual states as opposed to transformed fictitious states to develop a globally stable controller. The proposed controller is less conservative in terms of the level of uncertainties and disturbances which can be handled. In addition, arbitrarily good disturbance rejection in the unsaturated region can be achieved theoretically. Comparative simulation studies performed on a third order integrator chain verified the effectiveness of the proposed scheme.