500MW气轮发电机滑环碳刷运行维护及调整

文章针对神头第二发电厂500MW气轮发电机滑环、碳刷的典型故障情况,从碳刷性能、运行条件及运行维护等方面进行了详细的分析,进而提出了防止滑环、碳刷损坏的措施,所得结论对生产实践有一定的指导意义。     

Data organization and management of mine typical object spectral libraries

With the development of mining industry,people have obtained profits from it,but they are facing environmental damages.In order to monitor these environmental changes,a spectral library is set up for the spectrum data organization and management of mine typical objects.Most of the spectrum data come from the long-term field measuring in mining area and other spectral libraries.For the data quality control and error detection in the measuring data,an inner precision calculation method is presented and a series of interactive graphical controls are developed for the spectrum visualization and analysis.Through extracting and saving spectrum characters for the mine typical objects,realizs spectrum matching and classification for new measured spectrum samples are realized by using Euclidean distance,Aitchison distance,Pearson correlation coefficient and vector angular cosine methods.Based on the matching result,this work is able to gather dynamically physicochemical environment parameters from the library and gives an early warning for the mine environmental changes.     

福州地铁1号线典型软土的工程性质

为研究福州地铁1号线典型软土的工程性质及其影响,用电子显微镜进行了典型软土试样的扫描、X射线衍射分析及室内物理力学试验.基于工程地质条件和施工经验,就软土对地层环境影响进行了ABAQUS数值模拟分析.研究结果表明:该软土是由含有较大孔隙的微团聚颗粒组成,不同放大倍数图像具有一定的自相似特征,试样含石英成分,工程性质较差;盾构隧道开挖20m后,沉降历时800d的地层沉降和管片应力符合工程实际,地表最大沉降达18.5mm,且没有完全收敛.     

简单系统热力学基本方程麦氏关系记忆方法及推广研究

热力学理论中涉及了大量公式和数学推导,使得这部分知识比较零散,脉络不清不利于学生理解掌握,本文通过归纳总结给出了系统函数微分方程和麦氏关系的记忆方法,并提纲要领的阐述了怎样应用这部分知识对热力学系统进行研究,最后推导出了几种典型系统的函数微分方程和麦氏关系,实现热力学知识体系系统化.     

近红外高光谱大米典型特征提取分类识别

针对大米近红外高光谱特征轮廓不清导致有效信息损失与有损化品质检测的问题, 提出一种基于掩膜下能量泛函活动轮廓波的大米高光谱典型特征区域提取算法组合模型. 该方法对目标样本形态学区域与几何形心点进行高光谱谱段信息对比寻优建模, 对4个产地、3种品质大米进行泛化性可视判别. MATLAB实验结果表明, 对不同品质大米典型特征区域的光谱信息进行建模对比, 形态学感兴趣区域识别准确率更高, 泛化预测集精度为94.84%, 优化了近红外高光谱大米典型特征区域择优建模问题, 实现了大米快速无损化品质检测.     

翁同龢“罢退”之原由

在变法风潮席卷中华大地的1898年,支持变法的一代帝师翁同龢却被罢黜,一方面因其所代表的帝党利益与以慈禧为首的后党利益互不相容,受到了顽固派官僚后党分子的排斥打击而至;另一方面因光绪皇帝经验不足造成与翁同龢的政见分歧,最终给了后党分子以可乘之机;再次勾心斗角的权力之争使李鸿章等人伺机报复了因变法动机不纯而且疏忽大意的翁同龢,导致最终以“揽权”的罪名被罢免。     

也谈我国的热带区域

用区域综合分析方法论述了热带区域若干特性,即:热带区域应受热带过程支配;区域内部的季节变化和地域差异不决定于热量而决定于水分;各种有机和无机物质变化急剧;是热带作物的垦殖基地.作者认为,我国的热带仅指琼雷、台南、滇南、南海诸岛等地,其中的海南岛南部及其以南区域为典型的热带区域,以北为热带边缘区域.     

Daily volatility forecasts: reassessing the performance of GARCH models

Volatility plays a key role in asset and portfolio management and derivatives pricing. As such, accurate measures and good forecasts of volatility are crucial for the implementation and evaluation of asset and derivative pricing models in addition to trading and hedging strategies. However, whilst GARCH models are able to capture the observed clustering effect in asset price volatility in‐sample, they appear to provide relatively poor out‐of‐sample forecasts. Recent research has suggested that this relative failure of GARCH models arises not from a failure of the model but a failure to specify correctly the ‘true volatility’ measure against which forecasting performance is measured. It is argued that the standard approach of using ex post daily squared returns as the measure of ‘true volatility’ includes a large noisy component. An alternative measure for ‘true volatility’ has therefore been suggested, based upon the cumulative squared returns from intra‐day data. This paper implements that technique and reports that, in a dataset of 17 daily exchange rate series, the GARCH model outperforms smoothing and moving average techniques which have been previously identified as providing superior volatility forecasts. Copyright © 2004 John Wiley & Sons, Ltd.     

新疆西天山典型岩石含矿性研究

通过对新疆西天山四种典型岩石类型的岩石学特征和含矿性分析 ,认为糜棱岩中相对富集金、银、铜 ,并且砷也较富 ,在区域寻找金、银、铜矿方面有较大的指导意义。火山碎屑岩对金、铜等成矿有利 ,但此类岩石中铜、金分布存在不均匀性 ,在一些具褐铁矿化、黄铁矿化、硅化、绿泥石化等现象的韧性剪切带 ,极可能呈富矿层位 ,这类岩石应是该区寻找铜金矿床的主要岩石类型     

我国极端温度事件的定义和趋势分析

 利用1961-2005年45 a中国日平均温度的站点资料和累积频率的统计方法,确定了以90%（10%）累积频率为标准的日、旬、月和季四种不同时间尺度的极端高（低）温事件的阈值。分析表明,日尺度阈值（简称“日阈值”）用于检测极端高（低）温事件最为合理。但在日阈值的季节变化中包含系统性的天气扰动,因此需对其进行低通滤波,滤去8日以下的波动,最终可得到较为合理的检测极端温度事件的日阈值。对用日阈值检测出的全国极端温度事件,定义频数（日平均温度等于或超过高阈值的次数）和平均强度（极端温度事件的日平均温度总和与频数的比值）两个参数进行分析,发现频数的线性趋势表现为：高温事件（大于等于高阈值）中,内蒙古和新疆北部均为大趋势区,而西南地区为小趋势区,低温事件（小于等于低阈值）则相反,趋势显著的地区为高温事件中的东北、华北和青藏高原一带。平均强度的线性趋势表现为：高温事件中,我国东北地区为负趋势的大值区,云南西北部和海南省大部分地区为正趋势的大值区。低温事件则相反,趋势显著区则为高、低温事件中25°N的以南地区。