改进的信息最大化语音盲分离算法

提出一种改进的基于信息最大化的语音盲分离算法,克服了以往算法收敛速度慢,串音误差大的缺点.新算法分析了多种非线性函数的转换特性,采用一种新的更合适的非线性函数,并依此推导出分离算法的学习规则.实验表明,改进的算法有效实现了混叠语音信号的盲源分离,收敛速度更快,串音误差更小,取得了良好、稳定的分离效果.     

基于投影变换与轨迹关联的目标检测算法

低信噪比条件下序列图像中微弱点状运动目标的检测是许多实时监视系统的关键算法,具有信息量大、目标轨迹组合复杂和实时处理难度大等特点。为有效检测出微弱点目标,提出了一种基于最大值投影与目标轨迹关联相结合的运动点目标检测算法,仿真试验表明该算法具有较好的检测性能,可有效地检测出低信噪比条件下图像序列中的运动点目标,同时也可检测出交叉运动的多个点目标。     

连续波雷达加速度和速度估计方法研究

针对连续波雷达测速过程中目标径向加速度对速度测量精度的影响,采用基于自相关函数与先验知识相结合的方法进行加速度估计和补偿。仿真试验结果表明,该方法能够有效地估计出目标的径向加速度,先验知识的引入进一步降低了正确估计对输入信噪比的要求,提高了估计精度,减小了计算量。     

异步协作通信中三协作方信道与延迟估计算法

无线通信是采用多节点协作分集方式发送信号的,故具有很大的优势,但缺点是所传输的信号是异步的,因此采用协作分集方式发送信号亟需消除这种异步的影响。为此,给出了块平坦衰落信道延迟估计算法,采用训练序列附加在信息码上作为循环前缀,通过循环前缀来获得已知符号,再利用已知符号来消除异步。结果表明,该方案完全能消除异步,信道估计达到了克拉默拉奥下限,误码率和MRC（最大比合并）方式相同,且带有完全的分集阶数,初步达到了消除信号异步影响的目的。     

基于图形处理器的时域有限差分算法研究

如何提高时域有限差分算法(FDTD)的运算效率一直是FDTD数值运算研究的核心问题之一.针对近年来图形处理器(GPU)运算能力的高速增长及GPU通用运算概念提出的背景,对GPU加速FDTD运算的潜力与研究现状进行了总结,并对GPU加速FDTD运算的并行实现原理进行了阐述,通过将其与其他典型硬件加速方式进行比较,指出了G...     

基于位移反馈控制的主动增加时滞补偿方法及其试验验证

时滞是结构振动主动控制系统中普遍存在的现象,时滞不仅会降低控制系统的性能,严重时会造成系统失稳、控制发散。针对此问题,本文研究以下三方面内容：首先基于单自由度系统时滞的稳定性理论分析,确定系统最大允许时滞量的解析解,该阈值可以作为确定何时应用时滞补偿技术的一个评判指标;其次,当作动器实际时滞量大于最大允许时滞量时,常规时滞补偿方法将会失效,提出了基于位移反馈的主动增加时滞的补偿新方法,并定性结合定量详细分析了主动控制算法的参数影响规律;最后,以单层剪切型框架结构为被控对象,进行了多种输入激励下基于位移反馈的主动增加时滞补偿试验验证。大量仿真分析和试验结果表明本文所提方法能够在保证系统稳定性的同时获得一定可观的控制效果     

基于纹理的影像分类的特征、波段与窗口选择问题研究

结合纹理特征进行分类是提高影像分类精度的重要手段之一。纹理分析结果的好坏直接影响到最终的影像分类精度,而纹理分析结果又与很多因素有关。本文选取武汉某地区的局部多光谱遥感影像,分别在不同纹理特征组合、不同波段组合以及不同分析窗口下利用灰度共生矩阵进行纹理分析,然后采用最大似然法进行影像分类。通过精度分析实验选取出最优纹理特征组合、波段组合以及纹理分析窗口。     

Sickle bush (Dichrostachys cinerea L.) field performance and physical–chemical property assessment for energy purposes

The sickle bush (Dichrostachys cinerea (L.) Wight & Arn.) comprises a woody legume shrub which is widely distributed throughout of the tropical areas of Africa, Asia and Oceania, being found as well in Cuba where it represents a difficult to control invasive plant. It holds great silvopasture and energy crop potentials. In southwestern Spain a two year field trial was conducted contemplating also another six hardwood taxa commonly used as energy crops. The sickle bush above ground dry biomass fraction was 60.4%; sickle bush displayed a high transpiration rate during hot days (3.02 kg m⁻² d⁻¹ to 6.82 kg m⁻² d⁻¹); cold winter temperatures (<−2 °C) together with hot and dry summer air (<20% relative humidity) committed survival and growth. The physical-chemical wood properties and the pellets thereof derived were analyzed and compared to those of the other energy crop taxa. The within other woody species normal chemical composition range coupled to a high wood density and energetic use properties (19.2 MJ kg⁻¹ higher heating value, 29 g kg⁻¹ ash content) all allow for an industrial use. Pellets evidenced also good physical and mechanical properties (690 kg m⁻³ bulk density, 42 g kg⁻¹ moisture content). However, the mechanical durability (93.9%) was slightly less than that required by the non-industrial use standards, therefore further improvements should be studied. All of the above could encourage scrubland cuts in Cuba as a mechanical control method, in addition to the expansion of plantations within of their tropical climate based natural habitats.     

Characterisation of solar cells and modules under actual operating conditions

A PC-based measuring system is presented for outdoor testing of solar cells and modules under real operating conditions. It consists of a sun-tracked sample holder, different electronic loads (including control), digital multimeters, a PC and a laser printer. Insolation is measured and recorded with pyranometers, pyrheliometers and a reference cell. Current-voltage curves are acquired in the range of irradiance from 10 W/m² to over 1000 W/m². Small single cells of size down to 3 mm by 3 mm as well as large modules and laminates up to 1 m by 1.5 m can be tested. The measurement time for one test can be varied between 5 to 15 seconds. The maximum power point (mpp) is normally detected on-line. However, it can also be determined in a subsequent mathematical analysis, if more precise mpp data are required. The maximum relative uncertainty in the efficiency (determined from mpp data) has been estimated to be less than ± 1 %, depending on type and size of cell or module and on the constancy of the insolation during the testing time. Using a new dynamic method, the temperature coefficient of the efficiency can be determined within a relative uncertainty of about ± 3 %. The coefficient is used to derive standard test condition data. Results are given for two commercial modules.     

GPS‐Based Orbit Determination for KOMPSAT‐5 Satellite

Korea Multi‐Purpose Satellite‐5 (KOMPSAT‐5) is the first satellite in Korea that provides 1 m resolution synthetic aperture radar (SAR) images. Precise orbit determination (POD) using a dual‐frequency IGOR receiver data is performed to conduct high‐resolution SAR images. We suggest orbit determination strategies based on a differential GPS technique. Double‐differenced phase observations are sampled every 30 seconds. A dynamic model approach using an estimation of general empirical acceleration every 6 minutes through a batch least‐squares estimator is applied. The orbit accuracy is validated using real data from GRACE and KOMPSAT‐2 as well as simulated KOMPSAT‐5 data. The POD results using GRACE satellite are adjusted through satellite laser ranging data and compared with publicly available reference orbit data. Operational orbit determination satisfies 5 m root sum square (RSS) in one sigma, and POD meets the orbit accuracy requirements of less than 20 cm and 0.003 cm/s RSS in position and velocity, respectively.