网站访问速度量化指示系统的设计

为了统一用户和网管人员对网络速度的评判标准 ,文章介绍并实现了一种通过测量网站访问速度来指示网络速度的方法 ,使用户可以具体地了解网络运行状态 ,为网络的规划建设提供了量化的依据     

“机械精度设计与检测技术”教学改革与实践

"机械精度设计与检测技术"是我国高等院校机械类学科重要的专业基础必修课程,该课程的良好掌握是学生成为本领域专门技术人才的前提。提出一种基于自主实践的教学新模式,将精度指标检测与分析的现代先进测试设备引入课堂,增设实践实验课程,旨在通过学生自主实践激发其对本专业知识的学习兴趣,为课程内容的深度掌握提供保障,为后续专业课程的学习奠定扎实基础。     

一种基于改进替代数据法的图形化混沌判据

替代数据法是非线性系统分析的一种有效方法. 该方法不能直接判断信号是否处于混沌状态,而是基于排除法思路,提高混沌识别的置信度. 文中引入一种针对类周期信号混沌识别的伪周期替代数据法,在数值实验中发现了该算法的3个缺陷:一是相空间重构在实际信号分析中效果不佳;二是替代数据直线化;三是检验统计量容错性较差. 针对这些问题分别提出了改进方法. 使用改进算法对不同类别信号（包括由Logistic模型产生的周期信号和混沌信号以及其它典型混沌信号等）进行数据实验. 发现所有混沌信号在各噪声半径下的复杂度都呈线性增长趋势;而周期信号在噪声半径小于0.1时,复杂度的取值保持平稳,噪声半径大于0.1时,复杂度取值开始单调增长. 对数据实验的结果分析表明:在各噪声半径下复杂度的线性增长趋势是混沌信号的共同特征,可作为一种有效的图形化混沌判据.     

Photoshop的核心——通道

本文针对Photoshop软件中的重要组成部分——通道进行讨论。主要分为"什么是通道""通道的种类"和"通道的应用"三大部分探讨。其中,前两个部分将以文字形式进行讨论,第三个部分将以实例进行说明。     

Metagenomic and functional analysis of hindgut microbiota of a wood-feeding higher termite

From the standpoints of both basic research and biotechnology, there is considerable interest in reaching a clearer understanding of the diversity of biological mechanisms employed during lignocellulose degradation. Globally, termites are an extremely successful group of wood-degrading organisms and are therefore important both for their roles in carbon turnover in the environment and as potential sources of biochemical catalysts for efforts aimed at converting wood into biofuels. Only recently have data supported any direct role for the symbiotic bacteria in the gut of the termite in cellulose and xylan hydrolysis. Here we use a metagenomic analysis of the bacterial community resident in the hindgut paunch of a wood-feeding 'higher' Nasutitermes species (which do not contain cellulose-fermenting protozoa) to show the presence of a large, diverse set of bacterial genes for cellulose and xylan hydrolysis. Many of these genes were expressed in vivo or had cellulase activity in vitro, and further analyses implicate spirochete and fibrobacter species in gut lignocellulose degradation. New insights into other important symbiotic functions including H2 metabolism, CO2-reductive acetogenesis and N2 fixation are also provided by this first system-wide gene analysis of a microbial community specialized towards plant lignocellulose degradation. Our results underscore how complex even a 1-microl environment can be.     

The origin of spontaneous activity in the developing auditory system

Spontaneous activity in the developing auditory system is required for neuronal survival as well as the refinement and maintenance of tonotopic maps in the brain. However, the mechanisms responsible for initiating auditory nerve firing in the absence of sound have not been determined. Here we show that supporting cells in the developing rat cochlea spontaneously release ATP, which causes nearby inner hair cells to depolarize and release glutamate, triggering discrete bursts of action potentials in primary auditory neurons. This endogenous, ATP-mediated signalling synchronizes the output of neighbouring inner hair cells, which may help refine tonotopic maps in the brain. Spontaneous ATP-dependent signalling rapidly subsides after the onset of hearing, thereby preventing this experience-independent activity from interfering with accurate encoding of sound. These data indicate that supporting cells in the organ of Corti initiate electrical activity in auditory nerves before hearing, pointing to an essential role for peripheral, non-sensory cells in the development of central auditory pathways.     

交换环上辛代数和正交代数的抛物子代数的导子

设R是有1的交换环,L是R上的辛代数或正交代数,h是L的极大环面子代数,b是L中包含h的标准Borel子代数.在2∈R可逆的条件下,本文详细描述了b与L之间的中间李代数,并且证明这些中间李代数的导子都是内导子.