Approximation of waveforms and contours by one-dimensional pyramid linking

A method of segmenting an image was recently developed based on constructing links between the pixels at consecutive levels in a “pyramid” of successively reduced-resolution versions of the image. We develop here an analgous method of piecewise approximating a waveform or a closed curve by linking nodes in a one-dimensional “pyramid” of reduced-resolution versions of the curve. The method can be efficiently implemented in parallel on a one-dimensional cellular array or cellular “pyramid”.     

A systematic method for 3D mapping of mangrove forests based on Shuttle Radar Topography Mission elevation data, ICEsat/GLAS waveforms and field data: Application to Ciénaga Grande de Santa Marta, Colombia

Mangrove forests are found within the intertropical zone and are one of the most biodiverse and productive wetlands on Earth. We focus on the Ciénaga Grande de Santa Marta (CGSM) in Colombia, the largest coastal lagoon–delta ecosystem in the Caribbean area with an extension of 1280 km², where one of the largest mangrove rehabilitation projects in Latin America is currently underway. Extensive man-made hydrological modifications in the region caused hypersaline soil (> 90 g kg^− 1) conditions since the 1960s triggering a large dieback of mangrove wetlands (~ 247 km²). In this paper, we describe a new systematic methodology to measure mangrove height and aboveground biomass by remote sensing. The method is based on SRTM (Shuttle Radar Topography Mission) elevation data, ICEsat/GLAS waveforms (Ice, Cloud, and Land Elevation Satellite/Geoscience Laser Altimeter System) and field data. Since the locations of the ICEsat and field datasets do not coincide, they are used independently to calibrate SRTM elevation and produce a map of mangrove canopy height. We compared height estimation methods based on waveform centroids and the canopy height profile (CHP). Linear relationships between ICEsat height estimates and SRTM elevation were derived. We found the centroid of the canopy waveform contribution (CWC) to be the best height estimator. The field data was used to estimate a SRTM canopy height bias (− 1.3 m) and estimation error (rms = 1.9 m). The relationship was applied to the SRTM elevation data to produce a mangrove canopy height map. Finally, we used field data and published allometric equations to derive an empirical relationship between canopy height and biomass. This relationship was used to scale the mangrove height map and estimate aboveground biomass distribution for the entire CGSM. The mean mangrove canopy height in CGSM is 7.7 m and most of the biomass is concentrated in forests around 9 m in height. Our biomass maps will enable estimation of regeneration rates of mangrove forests under hydrological rehabilitation at large spatial scales over the next decades. They will also be used to assess how highly disturbed mangrove forests respond to increasing sea level rise under current global climate change scenarios.     

Orthogonal Discrete Frequency-Coding Waveform design for MIMO radar

Design of orthogonal code sets with ideal correlation properties is crucial for orthogonal Multiple Input Multiple Output（MIMO）radar.A modified Genetic Algorithm（GA）is proposed to numerically design orthogonal Discrete Frequency-Coding Waveforms（DFCWs）with good correlation properties for MIMO radar.Some of the designed results are presented,and their correlation properties are better than those presented in literatures.The effect of Doppler frequency shift on the performance of these signals is simply investigated.Simulation results and comparisons show that the proposed algorithm is more effective for the design of DFCWs with superior aperiodic correlation properties.     

波形相关矩阵未知情况下单基地MIMO雷达中一种改进MUSIC的DOA估计算法

该文研究了波形相关矩阵未知情况下多输入多输出(MIMO)雷达中的角度估计问题,提出了一种单基地MIMO雷达中改进多重信号分类(MUSIC)的到达角(DOA )估计算法。该算法可以在波形相关矩阵未知的情况下工作且性能优于传统的传播算子(PM)和借助旋转不变技术估计信号参数(ESPRIT)算法以及基于接收信号重构的MUSIC算法。该文算法可以扩展到任意阵列结构的MIMO雷达中进行角度估计。该文还给出了单基地MIMO雷达中DOA估计的克拉美罗界(CRB)。仿真结果验证了该算法的有效性。     

三角波信号波形参数的最小二乘评价

本文介绍了三角波信号时域波形参数的一种评价方法，通过使用波形测量手段和最小二乘直线拟合方法，对三角波信号的波峰，波谷，中值，幅度，频率，沿斜率，沿线性度，对称性等指标进行了精确评价，详细讨论了方法的实现过程以及有关技术问题，并对各项参数指标进行了误差分析，实验验证结果表明了该方法的有效性和实用性，该方法可应用到三角波信号源的性能指标评价中。     

准谐振及PWM型变流器开关工作波形平均建模法

本文提出一种适用于准谐振和ＰＷＭ型交流器的开关工作波形平均建模法。交流器中的开关元件被电压源或电流源替换，以建立一个等效时不变网络，使两类变流器的稳态及小信号动态分析得以统一和简化。文中给出两个建模实例，以及计算机仿真验证，并将结果与有关文献的结论进行了比较。     

变厚度曲面复合构件超声检测中的自动波形跟踪技术

针对变厚度曲面复合构件超声检测中,扫描程序难以根据各扫描点所采集的A型波进行缺陷自动识别的特点,从曲面构件的超声检测原理出发,进行了波形分析和推理运算,采用自动波形跟踪技术,提高了超声C扫描的定位精度和检测效率.     

Harmonic Analysis and Loss Comparison of Microcomputer-Based PWM Strategies for Induction Motor Drive

The results presented in this paper were specially chosen to provide a comparative basis for assessing the performance of induction motor drive operating on PWM strategies that have been suitably modified to facilitate real-time implementation using microcomputers. The comparison is made for harmonic copper loss with and without skin effect, end leakage losses, and stray load losses. The simulation results confirm that for low speed operation, Selective Harmonic Elimination (SHE) Technique is unsuited. The regular sampled strategies, in general, are superior to harmonic elimination technique in low and mid frequency range, and associated harmonic losses could be as low as one fourth of the losses occurring with SHE strategies. Sensitivity of the optimal regular sampled strategies for relative phase shift is also investigated. Reduction of 6% in harmonic copper losses occurs for phase shift of 180 at modulation depth of 1.2. teaching tool, and its open architecture would permit the expansion to customize specific requirements. More importantly, users can get     

Cr-doped DLC films in three mid-frequency dual-magnetron power modes

A series of Cr-doped diamond-like carbon (DLC) films were deposited using a mid-frequency dual-magnetron sputtering system, whose sputtering sources had three optional power modes of continuous DC, pulsed DC and AC (40 kHz). Morphology, microhardness, adhesion, and friction properties of the films were investigated using scanning electron microscopy, nano-indentation, scratch adhesion testing, ball-on-disc testing, etc. The results exhibited that the driving voltage waveforms played an important role in the properties of the films, and the properties of the films in pulsed DC mode were superior to those in AC mode and continuous DC mode.