基于多元非线性回归算法的动车组变压器温度预测研究

对动车组状态参数进行预测是实现动车组数字化精准维修的重要前提之一.目前对动车组数据的利用方式主要以定量观测和定性分析为主,缺乏准确的状态预测量.为此,文章提出了一种基于多元非线性回归的预测算法,通过建立变压器温度预测模型,实现了变压器温度值的次日预测,并以此指导由温度导向的变压器日常运维项目.通过对比CRH5A型动车组...     

不同围压下共面双裂隙脆性砂岩裂纹演化特性颗粒流模拟研究

岩体中含有大量节理、裂隙、断层等各类结构面,结构面在应力作用下的扩展与贯通是导致岩体破坏的重要原因。数值流形方法(NMM)可以有效模拟连续和非连续问题,然而,其在多裂纹动态扩展的模拟方面仍处于探索阶段。该文以线弹性断裂力学原理为基础,提出了一种基于高阶数值流形方法的多裂纹扩展模拟算法。通过在基函数中增加关键项来考虑裂纹尖端位移场的奇异性;裂纹尖端的应力强度因子则采用了J积分来计算;Ⅰ型-Ⅱ型混合裂纹的开裂和扩展方向依据最大周向拉应力准则来判断;采用假设-修正的多裂纹扩展算法解决了多裂纹的扩展问题。根据强化后的基函数,对于不符合单纯形积分形式的被积函数,采用了泰勒级数展开式计算近似解。通过多个静态裂纹扩展的经典问题的数值模拟对计算方法的合理性和计算精度及进行了验证。     

地面井抽采卸压瓦斯技术在新疆大倾角多煤组矿区的应用

针对新疆艾维尔沟矿区大倾角多煤组地表岩层移动与覆岩破坏特征,分析了大倾角多煤组地面井失稳机制,合理选择了地面井位置,优化了钻固井工艺及井身结构,并进行了适用性试验考察。试验工作面推过后井身结构稳定,套管基本未发生异常变形破坏,地面井抽采瓦斯持续稳定,可为新疆矿区大倾角多煤组地面井高效抽采瓦斯提供技术支撑及示范作用。     

A typology of different development and testing options for symbolic regression modelling of measured and calculated datasets

Data-driven modelling is used to develop two alternative types of predictive environmental model: a simulator, a model of a real-world process developed from either a conceptual understanding of physical relations and/or using measured records, and an emulator, an imitator of some other model developed on predicted outputs calculated by that source model. A simple four-way typology called Emulation Simulation Typology (EST) is proposed that distinguishes between (i) model type and (ii) different uses of model development period and model test period datasets. To address the question of to what extent simulator and emulator solutions might be considered interchangeable i.e. provide similar levels of output accuracy when tested on data different from that used in their development, a pair of counterpart pan evaporation models was created using symbolic regression. Each model type delivered similar levels of predictive skill to that other of published solutions. Input–output sensitivity analysis of the two different model types likewise confirmed two very similar underlying response functions. This study demonstrates that the type and quality of data on which a model is tested, has a greater influence on model accuracy assessment, than the type and quality of data on which a model is developed, providing that the development record is sufficiently representative of the conceptual underpinnings of the system being examined. Thus, previously reported substantial disparities occurring in goodness-of-fit statistics for pan evaporation models are most likely explained by the use of either measured or calculated data to test particular models, where lower scores do not necessarily represent major deficiencies in the solution itself.     

A dual-threshold up-down counter for GPS acquisition

In this work, the up-down counter detector for the acquisition of GPS signals is modified to use dual-thresholds for each trial. Closed form expressions for the mean and variance of the dwell time and the probabilities of detection and false alarm are derived. The new detector has a significantly smaller mean dwell time than the conventional single-threshold up-down counter and a lower dwell time variance when signals are weak. Further, the new detector has a low computational load, when compared to the optimal sequential probability ratio test (SPRT), whose main disadvantage is its computational complexity.     

New Linkage with Linear Actuator for Tracking PV Systems with Large Angular Stroke

This paper focuses on the development of an optimized photovoltaic tracking system involving low-cost, relative simple mechanisms, with linear actuators able to insure strokes comparable with those resulted when using gear rotary actuators. Starting with a rhombus linkage, with a linear actuator on the diagonal used for the elevation motion till 90°, a new performance solution is generated. This new linkage allows large angular strokes by using an asymmetric rhombus and an eccentrically positioned linear ac...     

Downlink multiple access schemes for transmitted reference pulse cluster UWB systems

Transmitted reference pulse cluster (TRPC) signaling was recently proposed for low data rate ultra‐wideband communications. Compared with the conventional transmitted reference (TR), TRPC has a more compact and uniform spacing for the reference and data pulses and therefore solves the implementation problem posed by the long delay line requirement in the conventional TR. In this paper, downlink multiple access issue is further investigated for TRPC systems. According to the TRPC signaling structure, both code division multiple access (CDMA) and time division multiple access (TDMA) methods are discussed. Theoretical analysis and simulation results show that TDMA outperforms CDMA in both bit error rate performance and throughput. Copyright © 2010 John Wiley & Sons, Ltd.     

Choice of a pertinent color space for color texture characterization using parametric spectral analysis

This article presents a comparison of different color spaces including RGB, IHLS and L?a*b* for color texture characterization. This comparison is based on the fusion of the independent spatial structure and color feature cues. In IHLS and L*a*b*, two channel complex color images are created from the luminance and the chrominance values. For such images, two dimensional complex multichannel linear prediction models are used to perform parametric power spectrum estimation and the structure feature cues are computed from this estimated power spectrum. Quantitative comparison of auto spectra of luminance and combined chrominance channels for different color spaces is done. This comparison is based on the degree of decorrelation between luminance and chrominance information provided by different color space transformations. Three dimensional histograms are used as color feature cues. Then, to classify color textures, Kullback-Leibler divergence based symmetric distance measures are calculated for pure color, luminance structure and chrominance structure feature cues. Individual as well as combined effect of information from all feature cues on classification results is then compared for different color spaces and different color texture data sets. The proposed color texture classification method performs better than the state of the art methods in certain cases. The L*a*b* color space gives us a better characterization of the chrominance spatial structure as well as the overall spatial structure for all of the chosen data sets. Experimental results on pixel classification of color textures are also presented and discussed.     

陶瓷湿敏电阻器静态校准曲线的线性拟合

陶瓷湿敏电阻器是湿度传感的重要元件,但因其阻-湿特性往往呈非线性而使用不便。本文利用最小二乘法对典型的铬镁钛系陶瓷湿敏电阻的阻-湿特性进行了线性拟合。结果表明,这种线性拟合方法简单可行,可用于非线性湿敏等敏感电阻器件的线性化处理。     

多机组集中控制技术在克拉玛依电厂的应用

介绍了克拉玛依电厂多机组集中控制系统的结构及说明,并对多机组集中控制、自动发电控制以及厂级监控信息系统进行了深入研究。