Shear-wave splitting in the crust:Regional compressive stress from polarizations of fast shear-waves

When propagating through anisotropic rocks in the crust, shear-waves split into faster and slower components with almost orthogonal polarizations. For nearly vertical propagation the polarization of fast shear- wave （PFS） is parallel to both the strike of the cracks and the direction of maximum horizontal stress, therefore it is possible to use PFS to study stress in the crust. This study discusses several examples in which PFS is applied to deduce the compressive stress in North China, Longmenshan fault zone of east edge of Tibetan plateau and Yunnan zone of southeast edge of Tibetan plateau, also discusses temporal variations of PFS orientations of 1999 Xiuyan earthquake sequences of northeastern China. The results are consistent to those of other independent traditional stress measurements. There is a bridge between crustal PFS and the crustal principal compressive stress although there are many unclear disturbance sources. This study suggests the PFS results could be used to deduce regional and in situ principal compressive stress in the crust only if there are enough seismic stations and enough data. At least, PFS is a useful choice in the zone where there are a large number of dense seismic stations.

Seismic anisotropy of the crust in Yunnan,China:Polarizations of fast shear-waves

Using seismic data recorded by Yunnan Telemetry Seismic Network from January 1, 2000 to December 31, 2003, the dominant polarization directions of fast shear-waves are obtained at 10 digital seismic stations by SAM technique, a systematic analysis method on shear-wave splitting, in this study. The results show that dominant directions of polarizations of fast shear-waves at most stations are mainly at nearly N-S or NNW direction in Yunnan. The dominant polarization directions of fast shear-waves at stations located on the active faults are consistent with the strike of active faults, directions of regional principal compressive strains measured from GPS data, and basically consistent with regional principal compressive stress. Only a few of stations.show complicated polarization pattern of fast shear-waves, or are not consistent with the strike of active faults and the directions of principal GPS compressive strains, which are always located at junction of several faults. The result reflects complicated fault distribution and stress field. The dominant polarization direction of fast shear-wave indicates the direction of the in-situ maximum principal compressive stress is controlled by multiple tectonic aspects such as the regional stress field and faults.

Blind Joint DOA and Polarization Estimation for Polarization Sensitive Coprime Planar Arrays via a Fast-Convergence Quadrilinear Decomposition Approach

The problem of joint direction of arrival(DOA)and polarization estimation for polarization sensitive coprime planar arrays(PS-CPAs)is investigated,and a fast-convergence quadrilinear decomposition approach is proposed.Specifically,we first decompose the PS-CPA into two sparse polarization sensitive uniform planar subarrays and employ propagator method(PM)to construct the initial steering matrices separately.Then we arrange the received signals into two quadrilinear models so that the potential DOA and polarization estimates can be attained via quadrilinear alternating least square(QALS).Subsequently,we distinguish the true DOA estimates from the approximate intersecting estimations of the two subarrays in view of the coprime feature.Finally,the polarization estimates paired with DOA can be obtained.In contrast to the conventional QALS algorithm,the proposed approach can remarkably reduce the computational complexity without degrading the estimation performance.Simulations demonstrate the superiority of the proposed fast-convergence approach for PS-CPAs.

Power System State Estimation Solution With Zero Injection Constraints Using Modified Newton Method and Fast Decoupled Method in Polar Coordinate

如何保证零注入节点的注入功率在状态估计结果中严格为0是电力系统状态估计研究中的重要问题。在直角坐标下,由于零注入约束为线性约束,可使用修正牛顿法来有效地解决这一问题。因此,借鉴直角坐标下修正牛顿法的思路,提出了极坐标下的修正牛顿法和修正快速解耦估计。这些方法的计算流程与传统的极坐标下的牛顿法和快速解耦估计非常相似,计算速度与大权重法相当,同时能够保证零注入约束严格满足。仿真结果验证了所得结论。

Towards 640 Gbit/s wavelength conversion based on nonlinear polarization rotation in a semiconductor optical amplifier

Taking into account ultra-fast carrier dynamics, this paper models 640 Gbit/s wavelength conversion scheme based on nonlinear polarization rotation （NPR） in a single semiconductor optical amplifier （SOA） and investigates the performance of this kind of wavelength conversion scheme in detail. In this model, two carrier temperature equations are introduced to substitute two energy density equations, which reduce the complexity of calculation in comparison with the previous model. The temporary gain and phase shift dynamics induced by ultra-short optical pulses are numerically simulated and the simulated results are qualitatively in good agreement with reported experimental results. Simulated results show that non-inverted and inverted 640 Gbit/s wavelength conversions based on NPR are achieved with clear open eye diagrams. To further investigate the performance of the non-inverted wavelength conversion scheme, the dependence of output extinction ratio （ER） on some key parameters used in simulation is illustrated. Furthermore, simulated analyses show that high performance non-inverted wavelength conversion based on NPR can be achieved by using a red-shifted filtering scheme.

Improved Polar Decoder Utilizing Neural Network in Fast Simplified Successive-Cancellation Decoding

Polar codes using successive-cancellation decoding always suffer from high latency for its serial nature. Fast simplified successive-cancellation decoding algorithm improves the situation in theoretically but not performs well as expected in practical for the workload of nodes identification and the existence of many short blocks. Meanwhile, Neural network (NN) based decoders have appeared as potential candidates to replace conventional decoders for polar codes. But the exponentially increasing training complexity with information bits is unacceptable which means it is only suitable for short codes. In this paper, we present an improvement that increases decoding efficiency without degrading the error-correction performance. The long polar codes are divided into several sub-blocks, some of which can be decoded adopting fast maximum likelihood decoding method and the remained parts are replaced by several short codes NN decoders. The result shows that time steps the proposed algorithm need only equal to 79.8% of fast simplified successive-cancellation decoders require. Moreover, it has up to 21.2 times faster than successive-cancellation decoding algorithm. More importantly, the proposed algorithm decreases the hardness when applying in some degree.

RETRACTED: <i>Improved Polar Decoder Utilizing Neural Network in Fast Simplified Successive-Cancellation Decoding</i>

This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. The aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused. Please see the article page for more details. The full retraction notice in PDF is preceding the original paper which is marked "RETRACTED".

基于关键翻转集合的极化码Fast-SSC-Flip译码算法

为了降低极化码快速简化串行抵消翻转(Fast-SSC-Flip)译码算法的候选翻转比特集合大小,减小搜索复杂度,该文提出一种基于关键翻转集合的极化码Fast-SSC-Flip译码算法。基于快速简化串行抵消(Fast-SSC)译码过程中首位译码错误信息比特有极大的概率落于关键集合(CS)中,以及Fast-SSC-Flip译码算法的候选比特均为码字比特,所提算法利用极化码的生成矩阵得到与CS中信息比特相应的码字比特,并用这些码字比特构建关键翻转集合(CFS)作为候选翻转比特集合。实验结果表明,在使用相同候选比特可靠性度量准则的前提下,在码长N=1024及码率R=0.5时,该文所提基于关键翻转集合的Fast-SSC-Flip译码算法相较于传统Fast-SSC-Flip算法在不损失译码性能的情况下,候选翻转集合大小显著降低;相较于新的快速简化串行抵消翻转(N-Fast-SSC-Flip)算法有相近的译码性能,但候选翻转集合至少缩小了77.93%。

A Shear-wave Splitting Study of the Yingjiang M_S6.1 Earthquake Sequence Occurring on May 30,2014

Earthquakes of M_S5. 6 and M_S6.1 occurred in Yingjiang,Yunnan on May 24 and May 30,2014 respectively. In this paper,we use the waveform data recorded by mobile seismic stations( KAC) which were set up in the source area after the Yingjiang MS5. 6earthquake on May 24,2014 to study the shear-wave splitting characteristics of Yingjiang M_S6.1 earthquake sequence with the SAM method. The result shows that predominant polarization of fast shear-waves before the M_S6.1 earthquake is consistent with the direction of regional principal compressive stress,and predominant polarization of fast shear-waves before the M_S6.1 earthquake show better consistency and smaller dispersion compared to after the M_S6.1 earthquake,and there may be a deflection for the fast shearwaves predominant polarization between the M_S6.1 earthquake sequence and foreshock sequence. We found that the time-delays generally exhibited a lower level before the M_S6.1earthquake and a relatively higher value after the M_S6.1 earthquake.

Preliminary analysis of the shear-wave splitting observations from the Qiaojia seismic array

A total of 351 shear-wave splitting results at 25 stations were obtained from the seismic data recorded in period of January,2013 to December,2016,by a broadband seismic array deployed in the northern segment of Xiaojiang Fault Zone(n-XJFZ).Meanwhile,the stress field of the n-XJFZ was determined by inverting 140 focal mechanism solutions of the small earthquakes within the study area which were recorded in the same period.This determination confirmed a compressive stress in NW-SE orientation and an extensional stress in the NE-SW orientation,with little difference from those released by previous studies.The shear-wave splitting results show a spatial complexity in polarization orientation,different from one site to another.How-ever,the polarization orientations integrated for the subareas suggest that the fault trends seemingly played important roles.All the subareas bear two dominant orientations,N10°E and N90°E,both of which are different from the azimuths of the principal compressive stress,due to the fault distribution.The time delay averaged over the entire region is 4.56 ms/km,close to that of the upper boundary of the generally accepted interval worldwide but larger than those in most of the investigated regions in the Chinese mainland,which probably implies an alignment of more micro-cracks in the n-XJFZ.Interestingly,the 2014 Ms6.5 Ludian earthquake was found to have caused a variation in the time delays of the slow shear waves within the study area though its epicenter was outside.This earthquake resulted in an evident drop of the time delays remaining for 4 months,however,lifted a bit the time-delay level with respect to that prior to the earthquake.

一种高性能极化码Fast-SSC译码器设计

为了进一步降低无线通信系统中信道编码极化码Fast-SSC译码器的译码延迟和硬件资源消耗,本文提出了两种对Fast-SSC译码算法的优化方法,基于FPGA硬件实现了码长N=1024优化的Fast-SSC译码器.基于Fast-SSC译码树上的四种特殊结点Rate0、Rate1、Rep和SPC,提出分别以Rate0结点和Rep结点为基础进行组合型特殊结点的拓展,使译码树上的特殊结点类型由原来的四种增加至十种以上,进一步加快了搜索译码树的速度;提出存储器资源复用的方法,相同译码树深度的结点使用相同的存储空间.综合结果表明最大工作频率为169 MHz,译码延迟为1.71μs,数据吞吐率为599 Mbps,存储器消耗为14.8 Kbit,有效提升了Fast-SSC译码器的整体性能.

FAST地锚基础工程中的若干问题探讨

FAST工程主动反射面为一半径300 m、口径500 m的球冠面,是一种基于柔性基底的预应力整体索网结构,索网包括2225个主索节点及下拉索驱动装置和地锚。由于台址岩土单元复杂,地锚点多、分布范围广、定位精度要求高、与场地其他基础设施的相互干涉大,给地锚基础的设计带来了一定的难题。本文针对FAST地锚基础中的特殊问题一一展开研究:以工程地质调查和测绘为基础,通过抓台址区主控因素,集合影响台址岩土性质的自然因素,对岩土单元进行了合理的分区;通过建立台址开挖后的BIM模型,利用极射投影技术实现了地锚中心点的精确定位;利用极射投影结果,对设备之间的相互干涉情况进行了调节和处理。研究成果最终确保了FAST地锚基础工程的顺利竣工。

基于复数FastICA的双极化干扰对消算法研究

为解决卫星通信中极化复用导致的交叉极化干扰问题,提出了一种基于复数快速独立成分分析方法,根据传输信道的对称性对算法作了简化处理,减少了计算量。该算法依据发送端的两个线极化信号的不相关性,在无源信号及混合矩阵的先验信息情况下,构造负熵函数并使其最大化来分离出独立成分,进而实现交叉极化信号对消。仿真实验以正交相移键控调制信号为例,从误差向量幅度、信干噪比、交叉极化隔离度、性能指数这几个指标上进行仿真,仿真结果显示基于复数快速独立成分分析方法对解决交叉极化干扰问题具有良好的性能。

Shear-wave Splitting in the Crust beneath Shandong and Its Adjacent Area

Based on the seismic data of near-field source from the Shandong Digital Seismic Network,this study obtained the shear-wave splitting parameters from multiple stations. The results show that dominant directions of polarizations of fast shear-waves reflect the spatial distribution characteristics of tectonic stress in this area,CHD and LIS stations show 2 dominant directions,and reveals that the crustal seismic anisotropy in the Shandong area is constrained by the regional stress background,local failure and structure.

基于FPGA的高速Fast-SSC译码器测试系统

为了满足Polar码高性能测试时大数据量的要求,设计了一种针对Fast-SSC译码器的FPGA硬件测试平台,包含信源、信道编码器、调制器、信道、解调器、译码器和统计模块,采用Verilog在Altera Stratix V 5SGXEA7N2F45C2上实现,并采用PCIe接口与上位机进行通信。该平台对码长1 024、码率1/2的Polar码进行测试,结果表明测试频率为300 MHz、测试数据为1.4×1010位时,译码耗时仅为19.18 s。

基于关键简化集合的极化码SSRFSC翻转译码算法

为提高基于简化序列重复节点的快速串行抵消(SSRFSC)译码算法的译码性能,提出了基于关键简化集合(CSS)和简化序列重复(SSR)节点的CSS-SSR-Flip译码算法。所提算法首先选取SSR中最长重复(REP)节点的信息位作为候选比特(CB),从而构造了基于SSR的CSS;然后针对SSR节点的译码特点设计了相应的翻转度量和翻转准则,通过考虑SSR节点中重复序列和源节点对译码的影响来度量CB可靠性,在特定CB翻转时选择次优的重复序列完成SSR节点翻转操作。实验数据表明,当误帧率FER=10-3时,所提出的CSSSSR-Flip译码算法与传统的快速简化串行抵消翻转(Fast-SSC-Flip)译码算法相比能够获得超过0.1 dB的性能增益,且具有与新型Fast-SSC-Flip(New-Fast-SSC-Flip)译码算法相同的译码性能;与传统翻转集合大小K相比,CSS大小缩减最多达79.5%,与关键集合(CS)相比集合大小最多可缩减23.1%。

基于滤波算法的隧道全时域激发极化超前探测正演方法

为进一步提高隧道全时域激发极化多参数超前探测的效果,采用滤波算法进行计算时间域等效电阻率,采用有限单元法进行计算,提出一种基于滤波算法的隧道全时域激发极化超前探测正演方法。该方法针对时间域Cole-Cole表达式计算收敛性差的问题,引入滤波算法进行时间域激发极化等效电阻率的计算,提高算法的收敛性;针对正演过程中大型矩阵求解影响计算效率的问题,引入OpenMP并行算法,实现隧道全时域激发极化超前探测正演的加速运算。最后,开展数值算例和物理模型试验。研究结果表明:该正演方法对异常体有敏感响应,且在加快正演速度具有显著优势。通过基于滤波算法的隧道全时域激发极化超前探测获得的观测数据与实际探测数据较为相符,这为基于全时域激发极化隧道超前探测提供了一种可行的正演算法。

青藏高原东北部上地壳剪切波分裂特征

由羌塘、巴颜喀拉、柴达木和祁连等几个二级块体组成的青藏高原东北部与华南块体及华北块体接触,产生强烈的构造变形。文中利用青藏高原东北部2010年1月—2021年9月的小地震波形事件,使用剪切波分裂分析方法计算得到快波偏振方向与慢波时间延迟2个各向异性参数,并对参数的空间分布进行分析。快波偏振方向以NEE为主导,与区域主压应力方向大致平行,祁连块体北部和东南部、羌塘块体北部存在NNW、NWW或近EW等多个相对较弱的第2快波偏振方向,与区域内广泛分布的NW走向断裂近平行。柴达木块体东北缘的快波偏振方向较离散,受到应力、断裂、岩石性质等因素的共同作用。祁连块体北部逆冲断裂系东部的时间延迟大于西部,体现了两者应力环境的差异。祁连块体东南部及柴达木块体东北缘大致相当的时间延迟分布可能与其具有类似的岩石类别物性及构造环境相关。柴达木盆地北缘存在NWW向快波优势偏振方向和相对一致的时间延迟,可能是断裂在深部高压变质作用的响应。羌塘块体北部的时间延迟小于拉脊山断裂周缘(祁连块体东南部与柴达木块体东北缘),可能与岩石类别物性与构造环境的差异有关。

云母晶体快慢轴方向及折射率的光谱测量

根据偏光干涉原理,对云母在可见光波段内进行连续波长扫描,得到云母快慢轴两条偏振光的透过率曲线.由两条曲线的相对位置可以判断云母的快慢轴方向,并由透过率曲线计算出云母波片的折射率n o、n e,得到整个可见光范围内的折射率.对比光学手册中云母的折射率值,测量误差小于5%.

Large capacitance and fast polarization response of thin electrolyte dielectrics by spin coating for two- dimensional MoS2 devices

A spin-coating method was applied to obtain thinner and smoother poly（ethylene oxide） （PEO）/LiC104 polymer electrolyte films （EFs） with a lower level of crystallization than those obtained using a drop-casting method. When the applied frequency was as high as 10 kHz, the specific capacitance of such EFs with thicknesses of 1.5 μm was on the order of I μF·cm^-2 a value larger than most of the previously reported results achieved from the same material. We then combined the thin EFs with two-dimensional （2D） materials to fabricate a MoS2 transistor with a top gate right above the channel, defined by a shadowmask method, and an inverter device. This transistor showed excellent static characteristics and the inverter device showed excellent switching performance at 100 Hz, which indicates a fast polarization response of the thin EFs. Such device architecture is suitable for future low power and flexible electronics based on 2D materials.