Time-series intervention analysis of pedestrian countdown timer effects

Pedestrians account for 40–50% of traffic fatalities in large cities. Several previous studies based on relatively small samples have concluded that Pedestrian Countdown Timers (PCT) may reduce pedestrian crashes at signalized intersections, but other studies report no reduction. The purposes of the present article are to (1) describe a new methodology to evaluate the effectiveness of introducing PCT signals and (2) to present results of applying this methodology to pedestrian crash data collected in a large study carried out in Detroit, Michigan.     

Determination of gas-tightness of containers using a pressure-decay timer

The most common measure of the gastightness of containers and vehicle bodies is the steady-state air flow rate required to produce a specified over-pressure. However, the pressure-decay test is in common use for coolstores, and is more easily performed. The theoretical relationship between these two types of test has been developed and is shown here to compare well with an experimental correlation obtained for integral refrigerated containers. This paper also describes an automatic timing device, ‘Contestor’, that simplifies the performance of the pressure-decay test for gas-tightness.     

MCS-51定时器/计数器在出租车计价器中的应用

本文对定时器/计数器的原理及应用方法进行了探讨，介绍了计价器利用这一特性实现计价器的计时收费。     

无线自组网TCP定时器的分析与改进

仿真并分析了无线自组网TCP数据流重传超时(RTO)与传输往返时间(RTT)的关系,指出在RTT剧烈振荡的无线多跳网络环境下RTO的变化会滞后于RTT的变化,导致根据RFC2988标准做出的RTO估计不准确。针对这种情况,利用网络演算理论推导出了TCP数据流的最小延迟上界(MDUB),并以此改进了RTO的估计算法。仿真实验表明,基于最小延迟上界的RTO估计算法能准确地估计数据包的最小传输往返时间上界,减少TCP数据传输中的伪重传,提升无线环境下TCP协议的性能。     

Measurement of small time intervals by means of an attachment to an electric timer

Conclusions Ferromagnetic materials with a rectangular hysteresis loop can be used for designing a short time-interval measuring instrument and providing it, as compared with existing instruments, with high sensitivity, small over-all size and weight, a large measuring range and a simple circuit consisting of static elements which are insensitive to shaking and vibrating and do not depend on humidity and temperature.     

基于双计时原理的水表和换向器检定方法研究

为提高水流量标准试验装置检测大口径机械式水表示值误差的检定精度,提出一种基于动态启停双计时原理的检定方法.依据两台计时器分别记录的被检水表通流时间和工作量器进水时间,可以方便地修正示值误差并对换向系统工作特性进行监测.研究结果证实,换向气动电磁阀不对称工作特性是换向系统不确定度的主要来源,双计时法能明显提高机械类流量仪表的示值误差检定不确定度.     

Measuring statistical literacy

This study considers the measurement of Statistical Literacy understanding that goes beyond the basic chance and data skills and knowledge in the mathematics curriculum. This understanding requires application of mathematical skills in a range of contextual situations and draws on aspects of statistics, such as variation and inference, which may not be explicit in the school curriculum. The study reports the outcomes from tests of Statistical Literacy given to 673 students from Grades 5 to 10. It confirms the nature and structure of a previously identified construct of Statistical Literacy and proposes three subgroups of items that address aspects of Statistical Literacy that might usefully be measured by classroom teachers.     

成像光学工程面临的光学问题

文章简单论述了现代成像光学主要领域的情况,指出非球面反射系统是发展的必然趋势。讨论了加工与检验方面的基本情况及应着重深入研究的问题。对镜坯材料也提了一点看法。     

Optical Bistability,Instability and Optical Computing

The formation of a cone-type light beam structure in an amplifying medium exhibiting the Kerr-type non-linearity and two-photon absorption is considered. The dependences of the relative diameter, contrast, and the position of the origin of a filamentary light region (that formed on the beam axis) on the active medium parameters are investigated. The effects of additional factors, such as a dielectric tube covering the active medium cylinder, the inhomogeneity of the medium amplification in the cross-section, and a saturable absorber mixed with the active medium on the light propagation pattern, are also discussed. Here, it is shown that a cone-type light beam structure is highly stable under the influence of such factors. It is noted that picosecond and sub-picosecond spectroscopy, including the study of multiphoton transitions and the measurement of the Kerr-type non-linearity constant in a medium on observation of a cone-type light beam structure, are possible.     

Optical Hygrometer

Results of creating an optical instrument for measuring gas humidity based on the principle of absorption of vacuum ultraviolet radiation in the wavelength range 110–190 nm are considered. A hygrometer of the TKA-MK type has been designed and fabricated making it possible to measure the dew point, and absolute and relative humidity. The instrument has passed type approval tests and it is included in the State Register for measuring instruments permitted for use in the territory of the Russian Federation. __________ Translated from Izmeritel'naya Tekhnika, No. 7, pp. 68–71, July, 2005.     

Composite Shewhart-EWMA statistical control schemes

A group of composite Shewhart-EWMA statistical control schemes were evaluated with simulations. The main results are given in terms of average run-length profiles for each scheme. Results in terms of suggested secondary criteria, percentile points of the run-length distribution of false out-of-control signals, are also given.

It is shown that Shewhart-EWMA control schemes using either time-dependent or constant control limits can be found that have better average run-length characteristics than standard Shewhart-Runs Rules schemes. When the secondary criteria are used, only the constant control limit schemes are better than the Shewhart-Runs Rules schemes.     

On a statistical h index

The measurement of the quality of academic research is a rather controversial issue. Recently Hirsch has proposed a measure that has the advantage of summarizing in a single summary statistics the information that is contained in the citation counts of each scientist. From that seminal paper, a huge amount of research has been lavished, focusing on one hand on the development of correction factors to the h index and on the other hand, on the pros and cons of such measure proposing several possible alternatives. Although the h index has received a great deal of interest since its very beginning, only few papers have analyzed its statistical properties and implications. In the present work we propose a statistical approach to derive the distribution of the h index. To achieve this objective we work directly on the two basic components of the h index: the number of produced papers and the related citation counts vector, by introducing convolution models. Our proposal is applied to a database of homogeneous scientists made up of 131 full professors of statistics employed in Italian universities. The results show that while “sufficient” authors are reasonably well detected by a crude bibliometric approach, outstanding ones are underestimated, motivating the development of a statistical based h index. Our proposal offers such development and in particular confidence intervals to compare authors as well as quality control thresholds that can be used as target values.