A comparison of traditional and adaptive control strategies for systems with time delay

A recently developed tuning method is compared to an adaptive Smith Predictor control strategy. The robustness of each method is considered for time-varying plant parameters. Examples with simulations are provided to compare the methods and present conclusions on the advantages and disadvantages of each.     

Forecasting Thailand’s rice export: Statistical techniques vs. artificial neural networks

Forecasting the international trade of rice is difficult because demand and supply are affected by many unpredictable factors (e.g., trade barriers and subsidies, agricultural and environmental factors, meteorological factors, biophysical factors, changing demographics, etc.) that interact in a complex manner. This paper compares the performance of artificial neural networks (ANNs) with exponential smoothing and ARIMA models in forecasting rice exports from Thailand. To ascertain that the models can reproduce acceptable results on unseen future, we evaluated various aggregate measures of forecast error (MAE, MSE, MAPE, and RMSE) during the validation process of the models. The results reveal that while the Holt–Winters and the Box–Jenkins models showed satisfactory goodness of fit, the models did not perform as well in predicting unseen data during validation. On the other hand, the ANNs performed relatively well as they were able to track the dynamic non-linear trend and seasonality, and the interactions between them.     

演播教学模式中视频压缩技术分析

随着多媒体技术的兴起。演播教学模式越来越多地取代了传统教学模式。在这种模式中，多媒体信息传输的主要瓶颈便是视频，拥有如此庞大数据量的视频，是限制多媒体技术发展的重要障碍。视频经过压缩后，存储会更方便，且并不影响作品的最终视觉效果。基于此目的。系统地研究了如何利用时间线＋事件＋帧的流来记录演示内容，从而尽可能地将视频数据压缩到最小，在文件大小和画面质量之间达到最佳平衡的问题。     

Making clustering in delay-vector space meaningful

Sequential time series clustering is a technique used to extract important features from time series data. The method can be shown to be the process of clustering in the delay-vector space formalism used in the Dynamical Systems literature. Recently, the startling claim was made that sequential time series clustering is meaningless. This has important consequences for a significant amount of work in the literature, since such a claim invalidates these work’s contribution. In this paper, we show that sequential time series clustering is not meaningless, and that the problem highlighted in these works stem from their use of the Euclidean distance metric as the distance measure in the delay-vector space. As a solution, we consider quite a general class of time series, and propose a regime based on two types of similarity that can exist between delay vectors, giving rise naturally to an alternative distance measure to Euclidean distance in the delay-vector space. We show that, using this alternative distance measure, sequential time series clustering can indeed be meaningful. We repeat a key experiment in the work on which the “meaningless” claim was based, and show that our method leads to a successful clustering outcome. Jason R. Chen received the B.E. degree from Sydney University, Australia, in 1991 and then worked mainly in the banking and finance industry until 1997. From 1997 to 2001, he completed the Ph.D. at Australian National University, Canberra, Australia, in robotics. From 2001 to the present, he has been a Research Engineer in the Research School of Information Science and Engineering, at Australian National University. His research interests broadly include robotics, data mining, and AI.     

基于实时监测的供水管防泄漏报警研究

采用嵌入式MCU和GSM技术,设计了基于实时监测的供水管防泄漏自动控制和报警系统,能很好地解决无人值守情况下,当供水管停水并重新给水后,因下游阀门未关而造成的泄漏问题,在最大程度上减少了生产和生活重此类损失的发生。     

基于PLC的火电厂调速液力耦合系统设计

针对火电厂的调速型液力耦合器,介绍了基于西门子S7-200PLC的控制系统,包括测控对象分析、系统硬件组成和控制程序设计等。运用PID算法调节水泵转速,控制系统提高了整机运行的可靠性和经济性。     

无线局域网实时业务优先的调度算法

该文在无线局域网的MAC协议上,基于时分多址技术,提出了分离缓冲器调度控制算法,将业务分为实时性要求的和非实时性要求两类,并给实时性业务以高的优先级.仿真结果表明该算法满足了实时性业务的失效概率要求,一定程度上保证了网络的QoS.     

RSA密码系统有效实现算法

大整数模幂乘运算一直是制约RSA广泛应用的瓶颈,在对传统算法剖析的基础上,提出了一种新的快速模乘算法,借鉴生成Wallace tree的思想,结合查找表和并行乘法运算进行RSA模幂运算。理论分析和试验证明新算法时间复杂度降低到O(logn)。     

高层住宅变频调速恒压供水系统设计

结合一工程实例,介绍了PLC控制的变频调速恒压供水系统的工作原理及其特点;探讨了主副泵切换的阀值流量、阀值频率;并时住宅建筑变频调速恒压供水系统存在主泵不能自动切换为副泵工作的问题,提出了引入流量控制元的改进方法。实际运行表明:该变频调速恒压供水系统可进行主副泵切换,运行可靠且节能。     

基于微处理器的数字超声波流量计

研究设计了一种以微计算机处理器为核心，根据时差法原理来测量流量的数字超声波流量计，该数字超声波流量计具有测量精度高、测量范围大、工作稳定可靠的特点。具体的实现过程是利用信号相关的数字处理方法计算出超声波在流体中的上行信号和下行信号的时间差，从而可换算出所测量的流量值。实验结果显示，这种数字超声波流量计能达到很高的精度。随着数字处理技术和处理器件的发展，数字超声波流量计将具有越来越大的优势。