Jitter-approximation tradeoff for periodic scheduling

We consider an asymmetric wireless communication setting, where a server periodically broadcasts data items to different mobile clients. The goal is to serve items into a prescribed rate, while minimizing the energy consumption of the mobile users. Abstractly, we are presented with a set of jobs, each with a known execution time and a requested period, and the task is to design a schedule for these jobs over a single shared resource without preemption. Given any solution schedule, its period approximation is the maximal factor by which the average period of a job in the schedule is blown up w.r.t. its requested period, and the jitter is roughly the maximal variability of times between two consecutive occurrences of the same job. Schedules with low jitter allow the mobile devices to save power by having their receivers switched off longer. In this paper we consider a scenario where clients may be willing to settle for non-optimal period approximation so that the jitter is improved. We present a parametric jitter-approximation tradeoff algorithm that allows us to choose various combinations between jitter optimality and period optimality for any given set of jobs. Zvika Brakerski was born in 1981. He received a masters’ degree from Tel-Aviv University in 2002 and is currently employed as an Electric Engineer. Boaz Patt-Shamir received his PhD from MIT in 1995. He was an assistant professor in Northeastern University until 1997, and then he joined the Dept. of Electrical Engineering in Tel Aviv University, where he directs the Computer Communication and Multimedia Laboratory. He held visiting positions at MIT, Boston University, Bellcore, and HP Labs.     

在调制域中观察数字信号的抖动

本文介绍了一种测量抖动的新方法，即在调制域中观察数字信号的抖动。并将此种方法与会峰－峰抖动测试法作了较为详细的比较。     

Effects of initial consonant, pneumotachographic mask, and oral pressure tube on vocal perturbation, harmonics-to-noise, and intensity measurements

Vocal perturbation, harmonics-to-noise, and intensity measures were obtained for 10 subjects during three experimental tasks: (a) prolonged /a/, (b) /pa/ with vowel prolonged, and (c) same as (b) with subjects wearing a pneumotachographic mask and oral pressure tube inserted between the lips. There were no statistically significant differences among the experimental conditions for any of the measures. The findings suggest that a single task may be used to obtain airflow, oral pressure, and acoustic measures of vocal performance. Observed differences in jitter and harmonic-to-noise means for the male and female speakers are discussed.     

Clinical relevance of the fractal dimension of F0perturbations computed by the box-counting method

The box-counting method for determining the fractal dimension (D_fj)was applied to the fundamental frequency (F₀) perturbations in normal and pathological voices in order to assess its clinical value. The upper limit of these D_fj values was similar for both groups, but the distribution for pathological voices extended to lower values than for the normal voices. However, these lower values were most probably the result of one or a few outlying frequency points due to incorrect determination of the vocal period. The D_fj of normal voices were within the range of values found for randomly varying F₀ values. It was concluded, that the vocal perturbations in pathological voices are also more or less randomly distributed. So, the D_fj, at that least determined with the box-counting method, do not contain clinically relevant information in addition to the traditional measures for the extent of the vocal period perturbations. An exception is special perturbation types like diplophonia. The result of the computation is very sensitive for voice breaks and vibrato and depends on the number of periods.     

Comparisons of jitter, shimmer, and signal-to-noise ratio from directly digitized versus taped voice samples

The purpose of this study was to compare jitter, shimmer, and signal-to-noise ratio (SNR) measures obtained from tape-recorded samples with the same measures made on directly digitized voice samples, with use of the CSpeech acoustic analysis program. Subjects included 30 young women who phonated the vowel /a/ at a comfortable pitch and loudness level. Voice samples were simultaneously recorded and digitized, and the resulting perturbation measures for the two conditions were compared. Results indicated that there were small but statistically significant differences between percent jitter, percent shimmer, and SNR calculated from taped samples compared with the same measures calculated from directly digitized samples. It was concluded that direct digitization for clinical measures of vocal perturbation was most desirable, but that taped samples could be used, if necessary, with some caution.     

低抖动小漂移开关脉冲发生器研究

开关脉冲发生器输出的稳定性是影响大口径电光开关可靠性的关键因素,而输出脉冲的触发延时和抖动则是其稳定性的两大重要指标。利用国产VE-4073氢闸管进行了分析和实验研究,通过采用直流加热氢闸管灯丝和氢储存器,以及精确、稳定的双脉冲触发技术,大幅减小了开关脉冲发生器触发延时的抖动和漂移,48 h内开关脉冲发生器输出漂移仅6.1 ns。     

高功率激光装置中超快电脉冲发生器的研究

报导了一种基于雪崩晶体管和阶跃恢复二极管的超快前沿、低触发晃动方波电脉冲产生技术.利用雪崩晶体管的电触发雪崩导通特性得到脉冲主体,再用阶跃恢复二极管的超快阶跃恢复特性对脉冲前沿整形,从而得到输出脉冲幅度23 V、输出阻抗50Ω、脉冲前沿小于160 ps的方波脉冲,脉冲触发晃动小于4.5 ps(rms),脉冲宽度5 ns,幅度稳定性优于3%,顶部不平坦度优于5%.该脉冲发生器在“神光Ⅲ”高功率激光原型装置前端系统中获得成功应用.