2.4GHz MIMO 网状网络中一种固定信道分配方法（英文）     

王大鹏  杨寿保  胡云  滕达 《中国科学院研究生院学报》2007,24(4):506-515

由于无线网路中链路质量的不稳定、信号的广播传输模式和节点之间存在的相互干扰，针对提高无线网状网络性能的信道分配和路由选择将更加复杂。采用多信道成为一种可选的提高网络容量的方法。本文提出了一种基于2.4GHz 802.11无线网状网络的一种固定信道分配方法，采用了多输入多输出技术使得网络中的数据流以流水线的方式进行传输。在这个场景下多条并行的流可以同时被激活，以此来提升UDP和TCP的传输性能。通过对802.11b网络中1、6和11三个相互不重叠的信道的分配，该信道分配算法在空间上实现邻居节点之间的干扰最小化，其中信道1和11被分配给网状网络的主干传输部分，信道6被分配给用户接入网络。文章最后通过NS2仿真实验，并对本文提出的算法进行了分析。实验结果证明网络的平均吞吐率有大幅度提升，且多跳传输的延迟也被降低。  相似文献   

大数据背景下学术期刊评价标准研究     

庞达 《科技与管理》2016,(4):87-91

期刊评价标准的合理构建对学术期刊的健康成长具有重要意义,大数据时代的来临将给我国当前学术期刊评价带来巨大影响。在简要阐述我国当前主要学术评价系统、评价标准、基本特征及存在问题的基础上,对大数据给学术期刊评价标准带来的影响进行了细致分析,在此基础上提出大数据背景下学术期刊评价标准可能包含的具体指标及其计算公式。  相似文献   

多时相AVHRR数据的傅立叶分析   总被引：10，自引：0，他引：10  

郑玉坤  庄大方 《中国科学院研究生院学报》2003,20(1):62-68

傅立叶分析(FourierAnalysis)是一种常用的信号处理方法.将中国全年 36旬的NOAA AVHRR的 1km数据采用最大值合成法获得 1 2个月的NDVI时间序列数据,然后运用离散傅立叶变换检测该时间信号的频率分布状况.结果各频率分量与NDVI的累加值及不同周期的季节性变化等生物学特征相关.其中零频率分量为均值NDVI,而 1/1 2频率分量最大程度概括了中国地表覆盖类型的全年季节性变化模式.将提取出的这些生物学特征引入到地表覆盖分类的特征空间中,提高了类别间的可分性.这些研究表明了傅立叶变换是分析多时相AVHRR数据及提取植被的生物学特征的有用工具  相似文献   

Socio-cultural variation in reading comprehension development among fifth graders in Peru     

Silvia Morales Silva  Ludo Verhoeven  Jan van Leeuwe 《Reading and writing》2011,24(8):951-969

In this study, the socio-cultural variation in reading comprehension development was examined in 331 fifth graders from schools in Lima, Peru. Reading comprehension was measured using an adaptation of the PIRLS Reading Literacy test. The fifth graders?? reading comprehension results, measured over the course of fifth grade, were related to the development of word decoding, vocabulary, and motivation for reading. Children??s development in these domains was related to their gender, intellectual maturity, home literacy climate, and socio-economic status. Structural Equation Modelling showed that the development of reading comprehension was influenced by the children??s ability to decode words, their vocabulary, and reading motivation. Furthermore, gender and intellectual maturity as well as children??s home literacy climate and socio-economic status appeared to substantially predict reading comprehension development, directly or indirectly. More than half of the variance in reading comprehension by the end of the fifth grade could be explained based on these predictor variables.  相似文献   

Why Implementing History and Philosophy in School Science Education is a Challenge: An Analysis of Obstacles     

Dietmar H?ttecke  Cibelle Celestino Silva 《Science & Education》2011,20(3-4):293-316

Teaching and learning with history and philosophy of science (HPS) has been, and continues to be, supported by science educators. While science education standards documents in many countries also stress the importance of teaching and learning with HPS, the approach still suffers from ineffective implementation in school science teaching. In order to better understand this problem, an analysis of the obstacles of implementing HPS into classrooms was undertaken. The obstacles taken into account were structured in four groups: 1. culture of teaching physics, 2. teachers?? skills, epistemological and didactical attitudes and beliefs, 3. institutional framework of science teaching, and 4. textbooks as fundamental didactical support. Implications for more effective implementation of HPS are presented, taking the social nature of educational systems into account.  相似文献   

Child psychiatry takes to the streets: a developmental partnership between a university institute and children and adolescents from the streets of Sao Paulo, Brazil     

Scivoletto S  da Silva TF  Rosenheck RA 《Child abuse & neglect》2011,35(2):89-95

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School quality, child wellbeing and parents’ satisfaction   总被引：1，自引：0，他引：1  

Stephen Gibbons  Olmo Silva 《Economics of Education Review》2011,30(2):312-331

Child wellbeing at school and enjoyment of the learning environment are important economic outcomes, in particular because a growing body of research shows they are strongly linked to later educational attainments and labour market success. However, the standard working assumption in the economics of education is that parents choose schools on the basis of test-score performance, and concerns about child happiness are largely ignored. In this paper, we address this omission and investigate to what extent parents’ and children's views of their school are linked to test-score based performance, and to what extent parents’ judgements of school quality are linked to their child's happiness. To do so, we use information on stated attitudes from the Longitudinal Survey of Young People in England (LSYPE) matched to administrative records on pupil achievements in England. Our results suggest that test-score based measures of school quality tend to dominate parental satisfaction with the learning environment. However, school quality along this dimension is not strongly associated with pupil happiness and wellbeing at school.  相似文献   

Resilience does not predict academic performance in gross anatomy     

Rodrigo Enrique Elizondo‐Omaña  María de los Angeles García‐Rodríguez  José Miguel Hinojosa‐Amaya  Eliud Enrique Villarreal‐Silva  Rosa Ivette Guzmán Avilan  Juan José Bazaldúa Cruz  Santos Guzmán‐López 《Anatomical sciences education》2011,4(1):56-56

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云南契丹后裔研究述评     

达福兴 《保山学院学报》2018,(3):34-39

“云南契丹后裔”又称本人(或本族),是北方古老游牧民族——契丹族的遗裔;这一族群在内蒙古民族研究所和云南民族研究所等多方机构的协作下于1992年被发现,一时学界震惊;自此,云南契丹后裔便成为学界关注的焦点,众多学科研究闻风而来,各项研究成果颇丰,而针对这些研究成果分门别类地进行归纳和总结,则有助于对云南契丹后裔这一族群的研究工作更好地深入开展.  相似文献   

海峡西岸经济区民营企业职工体育特征与模式     

李健  刘英杰  蔡衍铿  张达  黄咏梅  郭升平 《哈尔滨体育学院学报》2011,29(2):22-25

对海峡西岸经济区民营经济较发达的福州、厦门、泉州3个城市28家大中型民营企业职工体育基本特征进行分析。提出既有时代特征又具地域特色的＂层级型＂、＂福利型＂、＂自治型＂、＂共建型＂、＂圈子型＂、＂营销型＂、＂带动型＂民营企业职工体育发展模式,为民营企业职工体育和谐发展提供参考。  相似文献