Voice-band modem: A device to transmit data over telephone networks

Over the last 40 years, there has been continuous evolution in the design of voice-band modems-starting at a data rate of 300 bits per second in the late 1950s, a rate of 33,600 bits per second has been achieved in 1995. Realising such high data rates over the voice band of 3400 Hz is a remarkable feat, made possible by combining sophisticated techniques from three disciplines, communication theory, signal processing and information theory. In this article, we briefly describe certain advanced ideas, which led to data rates very close to the channel capacity limit, established by Shannon.     

32位并行数据的CRC-16编码器的FPGA实现

在数据通信中,提高数据在通信中的可靠性,以及快速的数据处理能力一直是人们所追求的,循环冗余校验CRC就是一种广泛采用的差错控制方法,也是一种最常用的信道编码方法。在介绍CRC码原理之后,以经典的LFSR电路为基础,推导出产生32位并行数据的CRC-16编码表达式,用EDA工具设计出CRC-16编码模块,并对其进行综合仿真,验证其可行性。     

CMOS图像传感器中A/D转换器的可测性设计

模拟或混合集成电路设计过程早期 ,应充分考虑电路的可测性。CMOS图像传感器系统集成A/D转换器设计中 ,每级 1.5位结构流水线A/D转换器适合于高分辨率、高速应用 ,同时具有良好的可测性。另外 ,位串行A/D转换器结构也具有较好的可测性 ,可应用于CMOS图像传感器系统     

MIMO—OFDM系统自适应算法的比较与分析

针对如何增加MIMO—OFDM系统数据传输速率的问题,本文研究了MIMO—OFDM系统中四种典型的自适应算法,并通过MATLAB仿真软件平台,对这四种自适应算法的性能进行比较分析,得出相应数据及结论．研究表明,在这四种算法中,自适应门限算法能分配到较多的比特数,且分配到高比特数情况的次数较多．另外还可看出,该算法能保证总发射功率恰如其分地运用到每个子载波上,而不是由于平均分配使得某些功率因不适当的运用而被浪费．     

图式理论在英语听力教学中运用的实验研究

文章通过调查分析了听力课堂存在的问题,在英语听力教学中引入一新的教学模式—图式理论,该理论在国外二语研究中已获成效。数据分析为SPSS计算机统计软件。实验结果表明图式理论对英语听力理解有影响能促进学生英语听力水平的提高,能提高学生学习英语的兴趣。     

Selective attention deficits in poor readers? Dichotic listening, speeded classification, and auditory and visual central and incidental learning tasks

Poor readers (PRs) and controls (i.e., normal readers) from the second, fourth, and sixth grades were compared on four tasks chosen to measure the development of selective attention. The PRs performed more poorly than controls on the central but not on the incidental portion of an auditory memory task. The differences on the central task were interpreted as a function of group differences in mnemonic skills rather than selective attention. There were no group differences on either central or incidental portions of a visual memory task. In a speeded classification task, PRs exhibited a slower rate of information processing, measured in bits of information transmitted per second, than controls, but this difference in rate was not affected by distraction. On a dichotic listening task, PRs performed more poorly than controls under a variety of conditions in which the presence of distraction, the rate of information presentation, and attended ear were manipulated; the pattern of differences obtained, however, was not readily interpretable as a function of greater distractibility on the part of PRs than controls. As a whole, the results did not support the hypothesis that PRs show deficits in selective attention relative to age-matched normal readers. In addition, correlations computed among indices of selectivity (residualized gain scores) derived from the four tasks were uniformly low, suggesting that the four tasks did not measure the same cognitive construct. The implications for the study of reading disabilities and for the construct of selective attention in developmental studies are discussed.     

基于一种有效攻击的蓝牙E0加密算法的改进

介绍蓝牙协议所采用的E0加密算法的基础上，对E0算法的安全性能进行了详细的分析．并针对E0算法弱点提出了一种有效的攻击手段．最后给出了基于该攻击手段的E0算法的改进方案。及改进后的算法的理论分析和实验数据．     

带权图Laplacian矩阵次小特征根下界

谱图理论是图论的重要研究分支,其思想广泛应用于计算机科学的各个领域.带权图Lap lac ian矩阵的次小特征根λn-1的估计被应用于在图像分割和图数据表示中.用代数方法对λn-1的下界进行估计,并讨论非带权图情况下λn-1的下界.     

Rate Control for MPEG-4 Bit Stream

Totransmitthemultimediadataovertheinternet ,pre encodedvideobitstreamsarepreferablebecauseofthelimitofthenetworkbandwidth .Inmostcases ,theencodershouldknowthechannelcharacteristicsinad vanceandencodethemasparameters .Consequently ,theflexibilityisreduced .Theratecontrolisemployedtocontroltheoutputbitrateaccordingtonetworkcondi tions.Forwirelessnetworks ,theirbandwidthsaremuchmorelimitedthanwirenetworks.Soratecontrolbecomesespeciallyimportantfortransmittingmultimediaoverthewirelessdomains[1- …     

EWMA算法在无线通信协议速率选择中的应用

如何根据无线环境的变化实时选择一个可靠的发送速率,进而保证数据传输的可靠性是无线通信研究的热点。针对传统累积和平均法（Cumulative Sum Average,CUSUMA）由于计算机存储数据位数的有限性可能导致的数据值超过计算机最大数据类型表示范围,进而造成统计数据丢失的问题,提出基于指数加权移动平均（Exponentially Weighted Moving Average, EWMA）算法,计算对应速率下的数据发送成功率,并根据计算出的成功率实现动态速率选择。该算法可用于解决通用平均值算法导致的因数据过大造成的统计数据丢失问题。     

开放的课堂：对文学概论课教学困境的探索与思考

文学概论课一直是中文专业教学的难点。其原因与中国原发性文艺学学科尚未完全建立、文学概论的互文性、整合性与抽象性以及文学概论课的教学体系发展的相对滞后有着密切的关系。我们从建构开放的课堂入手,试图为解决这一教学困境提供有益的思考。     

Frame-layer bit allocation for multi-view video coding based on frame complexity estimation

Current multi-view video coding （MVC） reference model in joint video team （JVT） does not provide efficient rate control schemes. This paper presents a rate control algorithm for MVC by improving the quadratic rate-distortion （R-D） model. We reasonably allocate bit-rate among views based on the correlation analysisl The proposed algorithm consists of three levels to control the rate bits more accurately, of which the frame layer allocates bits according to the frame complexity and the temporal activity. Extensive experiments show that the proposed algorithm can control the bit rate efficiently.     

Exploration of Factors Affecting the Added Value of Test Subscores

Recently, interest in test subscore reporting for diagnosis purposes has been growing rapidly. The two simulation studies here examined factors (sample size, number of subscales, correlation between subscales, and three factors affecting subscore reliability: number of items per subscale, item parameter distribution, and data generating model) that affected the value of reporting subscores within the classical test theory framework. Results showed that a higher proportion of subscores of added value was related to lower correlation between subscales, more items per subscale, no guessing in responses, smaller variability in difficulty parameters, and matched average item difficulty and average examinee ability.     

论第二语言习得中的母语迁移及其对英语学习的影响

母语迁移在第二语言习得理论中占重要地位.时至今日,母语迁移在第二语言习得中的作用得到了广泛的承认,并已形成了较为全面的理论:行为主义的刺激-反应论,对比分析假说,心灵主义的迁移最小论和普遍语法理论.母语迁移对二语学习者的影响主要表现在语音、词汇、语法以及文化四个方面.因此,要合理的运用母语的正迁移,尽量消除或降低母语的负迁移,达到促进第二语言学习与教学.     

Student injuries in the dissecting room

Cadaver dissection is the first opportunity for many students to practice handling human tissue and is their first exposure to the occupational hazards involved with this task. Few studies examine dissection room injuries to ascertain the dangers associated with dissecting. We performed a retrospective cohort analysis of dissection room injuries from four student cohorts over an eleven‐year period (2001–2011), including second‐year medical students, third‐year medical students, second‐year dental students, and third‐year science students. Injury data included activity causing injury, object responsible, and injury site. A total of 163 injuries during 70,039 hours of dissection were recorded, with 66 in third‐year medical students, 42 in second‐year medical students, 36 in third‐year science students, and 16 in second‐year dental students. The overall rate was 2.87 injuries per 1,000 dissection hours, with second‐year medical students most frequently injured (5.5 injuries per 1,000 hours); third‐year medical students were least frequently injured (1.3 injuries per 1,000 hours). A significant difference in injury rates between student groups indicated a higher than expected injury rate to second‐year medical students and lower than expected rates to third‐year medical students. Injury rates increased for most groups between 2001–2006 and 2007–2011 periods. Most injuries (79%) were from scalpel cuts to the finger or thumb. This study provides injury rates for dissection room injuries to students, indicating differences in injury frequency between cohorts and an increase in injury rate over time. As scalpel cuts were the most likely injury mechanism, targeting scalpel handling with preventative strategies may reduce future injury risk. Anat Sci Educ 6: 404–409. © 2013 American Association of Anatomists.     

交际能力理论及其对英语教学的启示

自交际能力理论问世以来,许多学者从不同的角度对知识和能力的关系,交际能力的内涵等开展了广泛的研究。尽管观念不尽一致,但对交际能力理论的发展都有着深刻的影响。本文着重阐述了Hymes和Chomsky的关于交际能力的理论观点及其对外语教学方法的启示,认为交际能力是英语教学中的一个重要概念,它既引发教学观念上的变革,导致教学目的和内容上的更新,更引起教学原则和方法上的一场革命,从而创设新的教学组织形式,是值得我们借鉴的有效教学手段。     

标记理论与词汇搭配迁移

对于词汇搭配的研究已经进行了几十年了,同时,母语迁移在二语习得中的作用也已经被广泛接受,因此,本文从影响语言迁移的一个因素——标记性着手,分析了词汇搭配的标记程度,进而利用标记理论分析了词汇搭配的迁移过程,以更好的预测了外语学习的困难点。     

非凝聚态粒子对超流临界速度实验值的影响

超流关键的物理量就是临界速度,MIT（麻省理工学院）实验组用激光来同扫描凝聚体的方法测出BEC超流体的临界速度,但是与理论值相比小得多．考虑到非凝聚态粒子的影响,发现MIT组测得的实验值并不是临界速度,而是玻色气体获得能量的最小速度,实际临界速度比测得的速度要大．通过修正玻色气体获得能量的速率公式从而得出临界速度与实验测量数据的关系,并发现修正后的临界速度的实验值符合理论值．     

社会性别理论视域下的女性继续教育

社会性别理论在西方第二次女性运动高潮中被提出来并成为西方女性主义的中心理论,这一理论的引入和运用为女性继续教育的研究提供了新的视角和方法。继续教育作为一种特殊的教育形式,为提高女性综合素质,促进女性发展创造了条件。本文阐述了社会性别理论的基本内容,分析了传统性别意识对女性继续教育的影响,并提出了相应的发展策略。     

图式理论在高职英语听力教学中的应用研究

在高职英语教学中,听力教学一直是教学中的难点,也是学生在二语学习中的薄弱环节,听力教学策略的研究已成为英语教学改革的焦点之一.通过图式理论在高职英语听力教学中的应用研究,我们发现以认知心理学为基础的图式理论为改革传统的英语听力教学模式开辟了一条新途径,为高职英语听力教学提供了理论指导.实践证明:图式理论在教学中的运用对调动学生听力学习的积极性和主动性,提高其听力水平是至关重要的.