偏振三维成像仪的相对偏振方向定标方法

在介绍偏振三维成像机理、四孔径偏振三维成像仪组成的基础上,开展四孔径相对偏振方向对偏振三维成像精度影响分析,确定四孔径相对偏振方向精度要求。制定了四孔径镜头偏振片相对偏振方向定标方法和四孔径偏振三维成像仪相对偏振方向定标方法,搭建了定标装置,在实验室内开展了相对偏振方向定标。四孔径镜头偏振片相对偏振方向定标误差为±0.5o,四孔径偏振三维成像仪相对偏振方向误差为±1o,从而可保证偏振三维反演的法向量误差为-5.47%~5.80%,为偏振三维成像仪高质量成像提供保障。     

面向植被边坡的地基SAR高相干点选择

基于高相干点进行相位分析,才能有效保证地基SAR（Synthetic Aperture Radar,合成孔径雷达）形变测量的准确性。在差分干涉测量领域中,广泛使用幅度离差法,可以有效地选择出岩石、建筑物等PS（Permanent Scatterer,永久散射体）点作为高相干点,但对于植被边坡,采用该方法选择出高相干点数量较少,不利于差分干涉处理。在星载SAR领域,普遍采用StaMPS方法解决植被边坡的高相干点选择问题。本文探索了StaMPS方法在地基SAR领域的适用性,提出采用非PS点来计算相干系数门限,并引入DS（Distributed Scatterer,分布式散射体）选择技术,进一步提高了高相干点的数量。对一处植被边坡的实验结果表明,相比于幅度离差法和StaMPS方法,改进方法在提高高相干点数量的同时,有效保证了其相位质量。      

Research on encoding and decoding of non-binary polar codes over GF(2m)

Binary Polar Codes (BPCs) have advantages of high-efficiency and capacity-achieving but suffer from large latency due to the Successive-Cancellation List (SCL) decoding. Non-Binary Polar Codes (NBPCs) have been investigated to obtain the performance gains and reduce latency under the implementation of parallel architectures for multi-bit decoding. However, most of the existing works only focus on the Reed-Solomon matrix-based NBPCs and the probability domain-based non-binary polar decoding, which lack flexible structure and have a large computation amount in the decoding process, while little attention has been paid to general non-binary kernel-based NBPCs and Log-Likelihood Ratio (LLR) based decoding methods. In this paper, we consider a scheme of NBPCs with a general structure over GF(2^m). Specifically, we pursue a detailed Monte-Carlo simulation implementation to determine the construction for proposed NBPCs. For non-binary polar decoding, an SCL decoding based on LLRs is proposed for NBPCs, which can be implemented with non-binary kernels of arbitrary size. Moreover, we propose a Perfect Polarization-Based SCL (PPB-SCL) algorithm based on LLRs to reduce decoding complexity by deriving a new update function of path metric for NBPCs and eliminating the path splitting process at perfect polarized (i.e., highly reliable) positions. Simulation results show that the bit error rate of the proposed NBPCs significantly outperforms that of BPCs. In addition, the proposed PPB-SCL decoding obtains about a 40% complexity reduction of SCL decoding for NBPCs.     

An SPH-based mass transfer model for simulating hydraulic characteristics and mass transfer process of dammed rivers

Engineering with Computers - Aerated flow characterized by complex mass transfer processes with multiple hydraulic properties is a common enviro-hydraulics phenomenon, which have a variety of...     

An improved strategy for out-of-step oscillation separation devices based on apparent impedance angle applied to a series compensated line

Out-of-step oscillation separation devices based on apparent impedance angle trajectory are widely used in the power grid in China, and their reliability is of great importance. In this paper, the influence mechanism of series compensation on apparent impedance angle trajectory is analyzed. It reveals that series compensation capacitors reduce the equivalent impedance angle and consequently the apparent impedance angle cannot pass through all four zones, resulting in the risk of failure for the separation devices. A revised method of apparent impedance angle based on compensation principle is discussed, and then an improved out-of-step oscillation detection criterion is proposed. In view of the fact that the apparent impedance angle at the moment of maximum current is equal to the equivalent impedance angle during an oscillation process, a practical algorithm based on the compensated apparent impedance angle is proposed. RTDS tests are conducted to verify the effectiveness of the new criterion, considering transmission lines with a high series compensation level.     

双有源桥钳位变换器的简单PWM移相控制策略

针对传统移相控制方法下双有源桥变换器会产生较大电流应力和在宽电压范围下低效率运行的问题,提出一种面向双有源桥钳位变换器的简单PWM移相控制策略。首先,利用钳位开关的运行周期和占空比取代变换器内移相比,以简化原边H桥工作过程并提高控制自由度。然后,计算了副边H桥开关管的占空比。通过分析所提出的移相控制策略的工作原理和软开关特性,推导出以传输功率标幺值为控制量的线性大信号模型。最后,采用基于TMS320F2808为控制器的实验平台进行验证。实验结果展示了简单PWM移相控制降低了变换器的电压应力和电流应力,显著提升了变换器的传输效率。     

LD泵浦Pr∶YLF固体激光器

研究了LD泵浦Pr∶YLF固体激光器。激光器采用LD端面泵浦结构,通过建立激光器热效应模型,对激光晶体内部温度场进行了解析计算,模拟分析了不同掺杂浓度Pr∶YLF晶体的光吸收以及温度场分布,对激光器泵浦耦合系统和输出镜的透射率等参数进行了优化设计,实现了LD泵浦Pr∶YLF固体激光器的高功率、高效率输出。当LD泵浦功率为2W时,获得了最大输出功率为287mW,光光转换效率达16.1,光束质量因子为M2X=1.38,M2Y=1.35的640nm激光。     

静电喷印技术在太赫兹超表面制备中的应用

近年来,太赫兹技术快速发展,基于超表面的太赫兹器件受到广泛关注,并已应用于太赫兹成像、光谱和生物传感等诸多领域。但太赫兹超表面器件的制备复杂且成本高,而静电喷印技术无需掩模版,成本低、精度高且易于在异形曲面上制作。基于静电喷印技术设计和制备了太赫兹吸波器,并利用太赫兹时域光谱系统（THz-TDS）对样品进行了性能测试,实验与仿真结果基本相符,在0.098~0.353 THz频段内吸收大于90%。此外,还设计了太赫兹线极化转换器,在0.167~0.355 THz频段内的极化转换大于95%,相对带宽约72%,并分析了所设计样品的制备工艺条件,验证了静电喷印技术对于制备太赫兹极化转换器的可行性。研究成果表明,静电喷印技术在太赫兹超表面器件的制备中具有广泛的应用前景。     

基于全相位陷波器解析设计的啸叫去除

为了快速且精准地抑制助听器中的啸叫效应,该文提出一种中心频率可以精确控制的全相位有限脉冲响应(FIR)陷波器解析设计.首先,为了获得较高的陷波精度,引入了整数部分m和小数部分λ来控制陷波的中心频率.然后,设计了一个偶对称的闭式解析式来计算陷波器系数.最后,为了保证输出信号的连续性和线性相位,进行数据延拓和截取操作.该陷波器具有线性传输特性,避免了非线性失真.为了检验陷波器的滤波性能,将其应用在助听器中去除啸叫.实验结果表明,该滤波器在啸叫频率下的衰减值可达–330 dB,信噪比达22 dB,输出波形质量好,算法复杂度低,鲁棒性高,具有一定的应用前景.     

Extending $$\tau $$ τ -Lop to model MPI blocking primitives on shared memory

The Journal of Supercomputing - MPI communication optimization is essential for high-performance applications. The communication performance models have made some achievements in improving the...