Phase estimation in data channelization for video transmitting

Channelization is one of the important techniques for sharing a single physical channel among the multiple videos. In channelization, the videos are partitioned into segments and the bandwidth of the physical channel is partitioned into logical channels. The first segment of each video is transmitted through the first logical channel, the second segment of each video is transmitted through the second logical channel, and so forth. The segments are transmitted periodically through the logical channels. In this paper, the video signals to be transmitted through the logical channels are estimated. Furthermore, the phase is estimated in terms of jitter delays that occur among the video segments, while transmitting them through the logical channels. The phase is an important parameter in video communication latency. Using the phase, the group delay can be estimated and based on the group delay, the storage space required at the client’s site can be determined so that the continuous and jerk-free delivery of the videos is provided to the users.     

Changes in riparian forests in the Kushiro Mire,Japan, associated with stream channelization

The Kushiro Mire, the largest mire in Japan, presently faces the serious problem of turbid water flooding. Shortening of stream channels associated with agricultural development is a major cause of streambed aggradation. This aggradation reduces the carrying capacity of the channel, resulting in sediment laden water spilling over the wetlands in a flood event. Sedimentation progresses with repeated inundation by turbid water, which significantly alters the edaphic conditions, and thereby the composition and structure of marsh forests. Aggradation of the geomorphic surfaces with sedimentation lowers the water level, and increases soil particle size and nutrient status. This situation was clearly displayed in an ordination of canonical correspondence analysis. Among the environmental variables, water level was related most strongly to the pattern of a forest community. Salix species dominated the flood areas, which were characterized by a low water level, coarse sediment, and high electrical conductivity. Alnus japonica, the most common tree species in the Kushiro Mire, favors soil conditions represented by high water table and organic content. A. japonica adapts to a higher water level by developing lenticels with hypertrophied and adventitious roots, multiple sprouting and regenerates vegetatively. Basal areas (BAs) of A. japonica, however, seem to be limited by high fluctuations in water levels, which are amplified by channelization. This raises serious concerns for the integrity of the Kushiro Mire. It is important to implement a conservation plan from a watershed perspective because most problems originate in upper basins. Creating riparian buffer strips, sediment‐filtering wetlands, and restoring the original meandering course may slow down sedimentation in the mire, and thus help to restore the natural hydrological regime. Copyright © 2002 John Wiley & Sons, Ltd.     

激光疏通周围血管的临床应用

我组于1984年开始进行了100条死体动物和人尸血管的基础实验,初步探索出激光疏通血管的方法、激光功率和发射时间等参数。接着进行了28条活体动物血管的激光疏通实验,成功率85％,1990年4月开始应用于临床,先后疏通了10条闭塞动脉。     

卫星通信中数字信道化方法及其对比

提出了几种应用于卫星通信中的数字信道化方法,即频域滤波(或FFT滤波)方法、多相/离散傅立叶变换(DFT)和信号分析方法(AS)。并分别对它们的原理、性能和特点进行了讨论和研究。在此基础上,还对三种方法的混合使用进行了较深入的研究。并对三种方法中的一种(AS)方法进行了有效的仿真,使这些方法的有效性得到了证明。     

基于FPGA的电力无线专网频谱感知系统

针对230 MHz频段的频谱感知实现,本文设计了基于AD9364及FPGA的硬件系统。为了实现较高的频谱分辨率,采用数字信道化的方法,增加FFT计算的点数,最终的频谱分辨率为100 Hz。系统中的频谱感知采取能量检测的方法,该方法有效且易于实现,当信噪比大于3 dBm时,可以判断该频谱被占用。数字信道化及FFT均在FPGA中实现,频谱拼接和能量检测则在MATLAB中实现。通过多次的仿真测试可以证明该系统有效。     

基于频域插值的信道化原型滤波器设计

针对信道化原型滤波器设计复杂度较高的问题,提出一种满足线性相位要求的原型滤波器频域插值设计算法。该算法采用无约束迭代优化办法获得了阻带衰减较高的低阶滤波器模型,然后根据所推导的频域插值模型构建满足线性相位特性的原型滤波器频谱,最后通过快速傅里叶逆变换获得了满足信道化滤波器组完全重构特性要求的原型滤波器。所提设计算法将频域插值与迭代优化相结合,有效地解决了设计高阻带衰减的原型滤波器时待优化参数数目较大的问题,并且不会产生镜像频谱,省去了镜像抑制滤波器的设计。仿真结果表明,所提算法相比传统的时域插值设计算法具有显著的性能改善,并且降低了设计复杂度。     

FACTORS CONTRIBUTING TO BANK STABILITY IN CHANNELIZED,ALLUVIAL STREAMS

Bank failure is a common fluvial process and can be a pervasive fluvial response to natural and anthropogenic disturbances. Previous research has identified causes and types of bank failure, but the conditions that lead to the cessation of bank failure remain poorly explained. This research examines differences between banks with active bank failure and banks that exhibit evidence of past bank failure that ceased (dormant) throughout three West Tennessee (USA) rivers to provide insight into the processes that cause bank failure to end. Bank characteristics were observed at 68 sites, and data from 55 banks were used to create a logistic regression model. Bank characteristics entered into the model included: vegetative cover, failure location, bar association, bank material, channel width‐to‐depth (w/d) ratio, and average bank angle. Results of the logistic regression suggest that bank angle best explains (p = 0.31 and odds ratio = 8.2) the difference between banks with active and dormant bank failure. Interestingly, vegetative cover and bank material composition, which have been found to be important in bank stabilization by previous researchers, were not significant predictors of bank stability according to the logistic regression model. These results suggest that in absence of drastic differences in bank material resistance (bedrock vs sediment): (1) spatial patterns of bank failure at the system‐scale will be diffuse, (2) bank stability can require a multiple decades, and (3) the potential for vegetation to stabilize banks may be limited in some alluvial systems because of positive feedbacks created by repeated human disturbance. Copyright © 2012 John Wiley & Sons, Ltd.     

分数傅里叶域宽带信道化侦察接收算法研究

数字信道化接收机是目前侦察接收机的主流。为降低频带折迭式信道化接收机对设备的要求,并有效弥补其输出信道模糊、灵敏度下降和截获概率降低的不足,以离散分数傅里叶变换为数字信号处理工具,提出了一种分数傅里叶谱折迭式数字信道化接收方法。分析了其基本原理及部分参数设置条件,给出了具体方法步骤。通过仿真进行了原理验证。研究结果表明：如果将接收信号划分成K个分波段,采用该方法能有效消除信道模糊问题,输出噪声总功率只有传统频带折迭式信道化的1/K,采样频率、设备量均可降低为纯信道化接收的1/K倍。     

无盲区数字信道化实现方法

通常的数字信道化方法,由于信道不重叠,相邻信道之间存在盲区,当信号落入盲区时,会造成信号畸变甚至丢失。利用信道重叠技术可以有效地解决信道之间的盲区问题,但需要研究高效算法。文中根据一般数字信道化高效算法的数学推导思路,推导出通带重叠的数字信道化的高效算法,并建立了算法模型,从而解决了无盲区数字信道化的高效实现问题。利用Mat1ab建立仿真模型,仿真结果验证了模型的正确性。     

相位测频法在数字信道化后续处理中的应用

讨论了基于相位测频法的数字信道化后的精测频方法,对相位测频性能进行了分析,利用相位测频法对信道化后的数据进行了仿真,并讨论了同一信道中同时多信号的处理方法。