Downlink multiple access schemes for transmitted reference pulse cluster UWB systems

Transmitted reference pulse cluster (TRPC) signaling was recently proposed for low data rate ultra‐wideband communications. Compared with the conventional transmitted reference (TR), TRPC has a more compact and uniform spacing for the reference and data pulses and therefore solves the implementation problem posed by the long delay line requirement in the conventional TR. In this paper, downlink multiple access issue is further investigated for TRPC systems. According to the TRPC signaling structure, both code division multiple access (CDMA) and time division multiple access (TDMA) methods are discussed. Theoretical analysis and simulation results show that TDMA outperforms CDMA in both bit error rate performance and throughput. Copyright © 2010 John Wiley & Sons, Ltd.     

Driver sensitivity to brake pulse duration and magnitude

Adaptive cruise control (ACC) requires that the driver intervene in situations that exceed the capability of ACC. A brake pulse might provide a particularly compatible means of alerting the driver to situations in which the acceleration authority of the ACC has been exceeded. This study examined the sensitivity of the driver to brake pulses of five different amplitudes (0.01–0.025 g) and five different durations (50–800 ms). Drivers were sensitive to accelerations as low as 0.015 g. Pulse duration interacted with pulse amplitude, such that moderate duration pulses were more detectable than long and short duration pulses at intermediate levels of pulse amplitude. A power function with an exponent of 1.0 accounted for 99% of the variance in drivers' sensitivity to pulse amplitude; however, a power function with an exponent of 0.23 accounted for only 70% of the variance in drivers' sensitivity to pulse duration. These results can help designers create ACC algorithms and develop brake pulse warnings.     

Research on forecasting model of sandstone deformation rate during sine wave loading segment under the lag effect

To reduce data variance caused by individual differences of different samples,a new experimental method is proposed by loading and unloading the axial forces with different frequencies and different waves of a certain load amplitude to the same rock sample without damaging it.Lag time segments are defined and fractionized into segments I and Ⅱ.Criterions for seg-mentation,definitions of relevant parameters and empirical analysis are also offered afterwards.In the course of sinusoidal loading,the serious pea...     

退耕还林对志丹水文站水沙量影响浅析

通过对志丹水文站径流量、输沙量的分析,探讨了退耕还林对志丹水文站水沙量的影响,并对志丹县退耕还林的可持续性等方面提出建立生态补偿机制等,同时得到了沙量、水量变化规律。     

Application of step‐response test for evaluation of uncertainty of standard measuring system for lightning‐impulse high voltage

In evaluating the uncertainty of the standard measuring system for lightning‐impulse high voltages, which is composed of a standard voltage divider, a digital recorder, and calibrators, step‐response tests of the standard voltage divider may be useful. In this paper, a convolution algorithm is employed to calculate the output impulse voltage waveforms from measured step‐response waveforms. The uncertainties of peak‐value measurement due to the influence of the nominal epoch, uncertainty of the peak‐value measurement due to dispersion of the AC scale factor, and uncertainty of the virtual front‐time measurement due to long‐term stability are evaluated. Furthermore, the error of the virtual front time of the output waveforms is discussed. The front part of the step‐response waveform, t≤ T₃₀%, does not influence the error of the virtual front time. Therefore, for the standard voltage divider, the step‐response parameters, that is, the experimental response time, partial response time, settling time, and overshoot, have almost nothing to do with the error of the virtual front time. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(2): 24–32, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21279     

用 CPLD实现的高精度脉冲干扰抑制电路

提出了一种用CPLD实现的高精度新型脉冲干扰抑制电路。仿真分析和实际应用结果表明，该电路简单可靠，能有效地抑制数字信号中的脉冲干扰，明显提高电路的抗干扰能力，保证数据传输的可靠性，是一种有实用价值和重复利用潜力的电路。     

联合蚁群算法和PCNN的脑部MRI图像分割方法

采用蚁群算法(ACO)联合脉冲耦合神经网络(PCNN)的脑部磁共振成像(MRI)图像分割方法。其中利用ACO解决了PCNN参数设置困难的问题,同时能够克服图像的低对比度和噪声对图像分割的影响,实现图像的精确分割。首先利用ACO的全局搜索能力,以图像信息熵与灰度期望值的和作为ACO的目标函数,对PCNN的3个关键参数β、αE和VE进行设定;然后基于PCNN简化模型,结合最大熵值准则对脑部MRI图像进行分割;最后对分割结果进行面积滤波,得到最终的分割结果。实验结果表明,本文方法能够实现脑部MRI图像的自动分割,具有较高的精度和较强的鲁棒性。对于没有噪声的图像,本文方法分割结果的平均正确提取率达到97.0%以上,平均错误提取率达到0.4%以下,平均杰卡德相似系数达到94.8%以上;对于添加了不同级别噪声的图像,本文方法的分割效果也优于FCM和自适应PCNN。     

基于加速度传感器的运动步数检测算法研究

为解决人体运动过程中手腕摆动对步数检测干扰的影响,提出了一种区域峰值步数检测算法。该算法根据人体运动时的加速度信号特征,使用高斯滤波去除噪声对加速度信号的影响,基于三轴合加速度数据采用区域峰值检测方法判定有效步伐,同时利用提取的加速度信号幅值的变化量作为特征值,准确实现了稳定状态下的跑步、走路两种动作的自动识别,并根据人体不同的运动状态自动调整采样速率,有效降低了系统功耗。实验结果表明,区域峰值算法相比于动态阀值和单一峰值的算法具有更高的步数检测精确度,可达到95%以上。     

脉冲雷达的优化设计

常规脉冲雷达基于回波时延距离变换原理,工作比一般较小,存在许多缺点。提出了一种基于回波时延频率距离变换原理的脉冲雷达,给出了这种雷达发射信号的选择、雷达诸参数优化设计原则及主要分机技术。     

机载干扰系统对信号处理的需求

机载干扰设备工作平台特殊,资源有限。此类设备要保证快速有效地实施干扰,信号处理必须为系统提供有针对性的处理结果。本文通过对几批不同的外场雷达数据的分析,提出分类与并行处理等需求,以提高机载干扰设备信号处理的时效。