微小尺度射流流量传感器的设计与仿真分析

在许多新型传感器和微系统中均存在微量流体自动、精确地驱动和控制问题,而这有赖于微小尺度下对流量的精确测量。基于射流振荡原理设计了一种新型的无反馈通道微小尺度流量传感器,采用计算流体动力学(CFD)方法对该流量传感器的测量特性进行了仿真研究。通过观测振荡腔内部流场,分析了振荡器内部流动形态和射流振荡过程。通过对监测点压力变化曲线的分析,获得了不同入口速度下流体振荡频率,建立了流体流速与振荡频率的函数关系。研究结果表明,该微小尺度射流振荡器振荡平稳,主射流切换灵活,在较宽的流速范围内,流速与振荡频率具有线性关系,具有0.3%的较低的相对压力损失并可达到较小的测量下限,易于加工成型。     

数字压力传感器BP5607应用实现

基于MEMS技术的数字压力传感器技术正处于一个迅猛发展的阶段,数字压力传感器目前的灵敏度可以做到0.01mbar,高灵敏度、高分辨率的数字压力传感器在日常生活中越发扮演着重要的角色。介绍了高分辨率数字压力传感器BP5607的设计思想;基于ARM处理器LPC1768+BP5607的架构,结合改进型差分气压测高的高程算法实现了BP5607的气压测高仪,克服了在“国际标准大气”模型下大气压无规则变化带来的高程测量误差,提高了高程测量精度。实验表明,该测高仪具有优于0.2m的高程测量分辨率和较高的灵敏度,对导航定位形成良好的辅助效果。     

两种典型扭振式粘度测头的灵敏度对比分析

针对扭振式粘度测量中,不同测头形状所受到的粘性力不同,进而对测量灵敏度产生影响的问题,基于FBG扭矩微振粘度测量原理,研究柱形与球面两种测头装置的测量精度及灵敏度.通过对不同形状的测头建立数学模型,得出相应的电压-粘度关系式,在实验室环境下通过标定实验确定待定系数,并比较两种测头的测量特性.实验数据表明,柱形测头的测量精度及灵敏度高于球面测头,验证了理论分析.同时,对测量误差来源进行了分析,为后续研究提供了理论基础.     

光纤Bragg光栅温度传感器在硅橡胶绝缘子温度特性研究中的应用

当硅橡胶绝缘子长期工作在恶劣的环境中时,会导致硅橡胶绝缘子产生发热现象.为了检测硅橡胶绝缘子的工作温度,将光纤Bragg光栅分别粘贴于硅橡胶绝缘子的上、下两端和伞群部分.温度特性实验结果表明:在15 kV电压作用下,硅橡胶绝缘子温度发生变化,从而使得光纤Bragg光栅中心波长产生相应的移位.金属棒上、下两端和伞群部分在无污染情况下温升分别为1.8℃、2.1℃和0.5℃;在凝露情况下温升分别为2.3℃、2.7℃和0.7 ℃;在Ⅱ级污秽等级情况下温升分别为3.5℃、4.1℃和0.9℃;破坏后的伞群部分在三种情况下的温升分别为4.9℃、5.5℃和7.1℃.光纤Bragg光栅温度传感器可有效的检测硅橡胶绝缘子的工作温度,反映硅橡胶绝缘子的工作状态.     

基于多传感器不完全量测下的机动目标跟踪算法

针对传感器探测概率小于1的不完全量测情况下的非机动目标跟踪问题,提出一种基于多传感器不完全量测下的扩展Kalman滤波算法。首先,利用残差检测的野值剔除方法,确定目标状态估计过程中传感器是否接收到正确的量测数据;其次,基于每个传感器的量测数据,在不完全量测下采用改进的扩展卡尔曼滤波算法分别对目标运动状态进行估计;进而结合多传感器最优加权融合方法求解基于多传感器观测数据的状态估计;最后,将算法应用到光电跟踪系统中。仿真实验得到不完全量测下传感器探测概率对滤波效果的影响,验证了算法的有效性,其跟踪精度接近完全量测下的状态估计精度。     

基于图像处理的晶体生长直径检测技术

针对单晶硅生长过程中的直径测量,提出一种“不在同一条直线上的三点确定圆”的直径测量算法.首先对获取到的单晶生长图像进行图像预处理,提取单晶体的边缘信息,然后基于“不在同一条直线上的三点确定圆”的原理,对部分“释热光环”提取特征点,从而获取硅单晶直径像素值,再通过量纲转化把直径像素值转化为长度值.试验表明,该算法获得的硅单晶直径的准确率满足直径检测系统的要求.     

基于DSP的壁纸印刷花纹涂层厚度在线检测

在壁纸生产过程中,尤其是在花纹印刷过程中,有效地在线测量花纹涂层厚度,对于减少壁纸生产的次品率和提高生产效率至关重要。本课题针对壁纸印刷花纹涂层厚度在线检测问题进行了研究,利用激光传感器测厚原理,基于TI公司生产的TMS320F2812DSP芯片为硬件核心处理器,完成了花纹涂层厚度的非接触在线测量。     

基于uC/OS-II的数字电能表计量软件系统

首先介绍了将模拟小信号电能表与纯数字电能表的计量综合成一个系统以后的体系结构, 然后分析了在嵌入式实时操作系统uCOS-II环境下计量系统的实现: 包括任务的划分、任务间的通信以及数据的共享问题, 其中重点研究了任务间通信时数据的共享问题, 最后总结了任务间的总体通信情况, 为设计出高精度的数字电能表计量软件奠定了坚实的基础.     

Options analysis and knowledge management: Implications for theory and practice

Real options can be a powerful tool for quantifying the value of strategic and operational flexibility associated with uncertain IT investments. They also constitute a new way of thinking as to how knowledge management (KM) can be implemented and managed to maximize the upside potential while minimizing any downside risk. This paper explored how practitioners can incorporate options analysis into contemporary knowledge management. Options analysis is recognizing real options and then determines how they add value. The main issue here is to manage knowledge so that the theoretical option value is realized in practice. This paper developed a new metric, knowledge management performance index (KMPI), for evaluating the performance of a firm in its KM at any given point in time as follows: knowledge creation, knowledge conversion, knowledge circulation and knowledge completion. The higher the efficiency of the KM process, the higher the KMPI, thereby is enabling firms to become increasingly knowledgeable. To prove the contribution of the KMPI, a questionnaire survey was conducted among 121 firms listed on the Taiwan Stock Exchange Corporation (TSEC). This paper makes five important contributions: (1) it shows that if the KM process improves, the KMPI is enhanced. This finding is based on a survey of the questionnaires. As a result, the KMPI can effectively and efficiently represent the KM process; (2) it shows that when the KMPI increases, a company’s performance will be enhanced in five different areas This indicates a significant relationship between the KMPI and the company’s performance; (3) it also shows that the higher the KMPI, the higher the performance of the organization. This is especially valuable to any organization where knowledge is not being used optimally; (4) it provides an option analysis that may be helpful to managers for making the right decision in an uncertain environment; and (5) it presents the first application of the Black-Scholes model to use an actual business situation involving KM as its test bed. The results proved that the option pricing model can act as a measurement guideline for the entire knowledge of the whole company.     

A study of traffic, user behavior and pricing policies in a large campus network

Tsinghua University campus network is a large campus network in China, providing volume-based and flat-rate Internet access service for more than 31,000 students and staff. In order to better understand its traffic, user behavior and pricing policies to facilitate network planning and management, we collect a one-year-long flow-based traffic log and a 10-year-long user-based log at the boundary of this campus network, and then conduct an analysis study on these two data sets. In this paper, we first present characteristics of inbound traffic flows from the aspects of traffic prediction and inference. Then we analyze the geographical origins of incoming flows, and the result reveals that USA, Japan and Korea are the most important source countries of international traffic. Our user-based investigation shows that the properties of users have important influence on their behavior, e.g., major has stronger influence on users’ online time, while occupation has stronger influence on users’ international traffic volume. We also find that there are more and more users choosing flat rate pricing scheme instead of volume based pricing scheme, and these users tend to over-provision when they subscribe from tiered pricing options.