Voice-band modems: 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 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 begin with a brief introduction of voice-band modems and then introduce the basic principles of data transmission.     

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.     

Higher Education in the Republic of Ireland: Participation and Performance

This paper describes the expansion and diversification of higher education in the Republic of Ireland and examines some of the principal characteristics of higher education entrants. It is estimated that in 1995, some 43 per cent of the age cohort entered the full-time higher education system in the Republic of Ireland with a further 5 per cent enrolling in UK colleges. While these increasing admission rates have been fuelled by rising completion rates at second level they reflect, primarily, rising transition rates into higher education from those who complete the Leaving Certificate. The greater part of the expansion has taken place in the non-university sector which is characterised by a preponderance of sub-degree programmes, heavily concentrated in the areas of Business Studies, Engineering and Applied Science. A noticeable feature of higher education admissions is the low percentage of older students. The great majority come directly from school with increasingly high levels of attainment in the Leaving Certificate reflecting stiff competition for places, especially in the university sector. While there continues to be large disparities by socioeconomic group in access to higher education, the most recent data point to some reduction in equality. Western counties have consistently had higher third level admission rates with lower rates in eastern counties, including Dublin, and border counties.     

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．     

Evaluating the impact of dyslexia laws on the identification of specific learning disability and dyslexia

Dyslexia is a specific learning disability that impacts word reading accuracy and/or reading fluency. Over half of the states in the USA have passed legislation intended to promote better identification of individuals with dyslexia. To date, no study has been conducted to investigate the potential impact of state laws on the identification of specific learning disability (SLD), and limited data has been presented on the rate at which students in public school settings are identified with dyslexia. The first aim of the current study was to determine if any detectable changes in the identification rates of SLD have occurred in states implementing dyslexia laws because most states do not report number of students identified as dyslexic but rather those students identified with an SLD. The second aim of the study was to characterize the rate of identifying dyslexia in the two states (Texas and Arkansas) that require public schools to report the number of students identified with dyslexia. The third aim was to characterize the identification rate across first to 12th grades. Current SLD rates range from 3.2 to 8.5% in all 50 states. Analysis of SLD prevalence rates did not vary between states with and without dyslexia laws in place. Moreover, there was no change in the identification of SLD once states had implemented these laws. Rates of dyslexia in Arkansas and Texas were less than 5%. Given the persistent levels indicating lack of reading proficiency, our review of data suggests that overall students with dyslexia are being underidentified.     

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.     

Do expenditures other than instructional expenditures affect graduation and persistence rates in American higher education?

During the last two decades, median instructional spending per full-time equivalent (FTE) student at American 4-year colleges and universities has grown at a slower rate than median spending per FTE student in a number of other expenditure categories, including academic support, student services and research. Our paper uses institutional level panel data and a variety of econometric approaches, including unconditional quantile regression methods, to analyze whether these non-instructional expenditure categories influence graduation and first-year persistence rates of undergraduate students.     

Teacher as token dispenser: Effect of an observer

Data were collected on rate per minute of administering token reinforcement for one male and six female teachers enrolled in a behavior modification course. Data were obtained from record cards maintained by pupils for tokens received during an observer-present condition and for an observer-absent condition. Comparison of reinforcement rates for observer-present vs. absent indicated significantly higher rates of token delivery (p <.025) in the observer-present condition. The observer effect has important implications for those programs in which assessment procedures introduce an observer into the classroom to collect data on changes in teacher behavior.     

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。     

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.     

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.     

An Improvement of MPEG-4 Rate Control Algorithm

Frame skipping in low bit video coding could significantly reduce the visual quality of reconstructed video. At the same time, if the complexity of the video sequence remains high for a long period, then driving up the long term average bit rate, the only resort of MPEG-4 Q2 rate control algorithm results in using a high quantization scale, which shows a poor visual quality of the reconstructed video. This paper analyzes the main causes of frame skipping in current MPEG-4 frame rate control scheme, and presents a new rate control algorithm based on the quadratic R-D model over a CBR channel. Key features of the present work are. 1) the bits allocated to each P-frame or B-frame are in proportion to its distance from the end of this GOP, i.e. more bits are allocated to the frames that are nearer to their reference Ⅰ -frame: 2) the target buffer level is changeable in the GOP, at the end of each GOP( five P-frames or B-frames), the target buffer level is linearly reduced from 1/2 to 1/4 of buffer size, to other frames, the target buffer level is set to 1/2 of buffer size: 3 ) a selective and judicious use of the reduced resolution mode, in addition to a modulation of the quantization scale parameter, is to control the average long term bit rate. Experimental results with different video sequences of varied complexity, encoded at low bit rates show better efficacy of the proposed algorithm than MPEG-4 Q2 rate control scheme, and the experimental results also show that the improved algorithm has significantly reduced the number of frame skipping, increased the overall PSNR, and improved the perceptual quality.     

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．     

Student Loans: a Northern Ireland Perspective

The government's proposals for a student loans scheme has been inadequately thought-out and researched. Mr Baker's commitment to increase participation in higher education, and hence to increase the 'outflow' of much-needed graduates, may well be undermined by the proposed scheme. In particular, what has been missing in the debate on loans has been a regional perspective. Northern Ireland offers a useful example in that, despite being the most economically depressed region in the United Kingdom, recent participation rates have already come close to the rate Mr Baker is aiming for in other parts of the country.
We cannot predict the effect of the loans scheme on participation rates. However, in present circumstances and under present policies, our guess, based on extensive survey research, is that the proposed loans scheme will diminish participation rates, particularly among those Mr Baker has targeted for special attention. Secondly, the cost of the proposed scheme to the government will be much higher than envisaged. Regional evidence from Northern Ireland suggests that large numbers of graduates will take a long time to earn sufficient salaries to rise above the 85 per cent threshold, if, in fact, they ever do.     

An examination of trends in child sexual abuse investigations in Ontario over time

BackgroundChild sexual abuse (CSA) rates have been declining since the 1990s (Dunne et al., 2003; Finkelhor & Jones, 2004, 2012; Jones et al., 2001). Discrepancies in contexts and measures complicate comparing CSA rates across jurisdictions and studies, and there is limited literature about trends in CSA in Canada.ObjectiveUsing data from the Ontario Incidence Study of Reported Child Abuse and Neglect (OIS), the only source of provincially aggregated data in Ontario, Canada, that describes child welfare investigations, this paper provides information on reported and investigated CSA over the past 20 years.Participants and settingThe OIS uses a file review methodology; information is collected directly from investigating child welfare workers.MethodsA sample of child welfare agencies is selected for the study, and data are collected over a three-month period. Weights are applied to produce annual provincial estimates.ResultsThe rates of investigated CSA in Ontario decreased between 1993 and 2013, from 5.20 (95% CI [3.94, 6.47]) to 1.81 (95% CI [0.97, 2.66]) children per 1000. During this time, the rate of all child maltreatment-related investigations doubled, from 21.41 (95% CI [18.38, 24.42]) to 53.32 ([29.61, 77.03]) children per 1000.ConclusionsUnlike other forms of child maltreatment, the incidence of investigated CSA in Ontario declined since 1993. Substantiation rates for CSA investigations decreased more dramatically than the rate of all CSA investigations, which could indicate a true decline in rate or an inability to accurately identify cases of CSA.     

Selected schedules of reinforcement in the black-tailed prairie dog (Cynomys ludovicianus)

Wild black-tailed prairie dogs were run on FR, FI, VR, and VI schedules for Noyes pellet reinforcement. Cumulative barpress responses, postreinforcement pause lengths, and responses per second were recorded. The highest response rates occurred in the VR schedules, with the lowest response rates coming in the FI schedules. Fixed-ratio schedules had the longest postreinforcement pauses, VI schedules had the shortest. At the upper levels of the fixed-ratio schedules (FR 90–100), the animals ceased to respond consistently. Generally, data from prairie dogs were consistent with data reported in studies from other mammalian species.     

Rate Control for MPEG-4 Bit Stream

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

How much of a problem is resident mistreatment in child welfare institutions?

The purpose of this article is to provide information developed since 1980 by the Institutional Child Protection Project about the size and significance of the problem of mistreatment in child welfare residential institutions. In the 1.700 facilities surveyed, there are about 69.000 children and youths. Rates of utilization vary among Health and Human Services (H.H.S.) regions from 8 per 10.000 to 19 per 10.000 children and youths in the population. The average rate is 12 per 10.000. In 1961 this rate was estimated at 10 per 10,000. About 2,700 complaints were reported by facilities to the survey for 1979. Complaint rates range by H.H.S. region from 25 per 1.000 to 55 per 1.000 children and youth in care. The average complaint rate per 1.000 residents in care was 39. Observations of site visitors suggest that only one out of five complainable situations may be reported to child protection agencies. A list of complainable occurrences that came to the attention of site visitors is included to document the problem. An additional effort to assess the significance of this issue is made by comparing intrafamilial complaint rates with rates reported by child welfare facilities. The authors believe residential complaint rates may be twice as large as intrafamilial complaint rates.