Source time functions of the Gonghe，China earthquake retrieved from long－period digital waveform data using empirical Green＇s function technique

An earthquake of Ms= 6, 9 occurred at the Gonghe, Qinghai Province, China on April 26, 1990. Three larger aftershocks took place at the same region, Ms= 5. 0 on May 7, 1990, Ms= 6. 0 on Jan. 3, 1994 and Ms= 5. 7on Feb. 16, 1994. The long-period recordings of the main shock from China Digital Seismograph Network (CDSN) are deconvolved for the source time functions by the correspondent0 recordings of the three aftershocks asempirical Green's functions (EGFs). No matter which aftershock is taken as EGF, the relative source time functions (RSTFs) Obtained are nearly identical. The RSTFs suggest the Ms= 6. 9 event consists of at least two subevents with approximately equal size whose occurrence times are about 30 s apart, the first one has a duration of 12 s and a rise time of about 5 s, and the second one has a duration of 17 s and a rise time of about & s. COmParing the RSTFs obtained from P- and SH-phases respectively, we notice that those from SH-phases are a slightly more complex than those from p-phases, implying other finer subevents exist during the process of the main shock. It is interesting that the results from the EGF deconvolution of long-Period way form data are in good agreement with the results from the moment tensor inversion and from the EGF deconvolution of broadband waveform data. Additionally, the two larger aftershocks are deconvolved for their RSTFs. The deconvolution results show that the processes of the Ms= 6. 0 event on Jan. 3, 1994 and the Ms= 5. 7 event on Feb. 16,1994 are quite simple, both RSTFs are single impulses.The RSTFs of the Ms= 6. 9 main shock obtained from different stations are noticed to be azimuthally dependent, whose shapes are a slightly different with different stations. However, the RSTFs of the two smaller aftershocks are not azimuthally dependent. The integrations of RSTFs over the processes are quite close to each other, i. e., the scalar seismic moments estimated from different stations are in good agreement. Finally the scalar seismic moments of the three aftershocks are compared. The relative scalar seismic moment Of the three aftershocks deduced from the relative scalar seismic moments of the Ms=6. 9 main shock are very close to those inverted directly from the EGF deconvolution. The relative scalar seismic moment of the Ms =6. 9 main shock calculated using the three aftershocks as EGF are 22 (the Ms= 6. 0 aftershock being EGF), 26 (the Ms= 5. 7 aftershock being EGF) and 66 (the Ms= 5. 5 aftershock being EGF), respectively. Deducingfrom those results, the relative scalar sesimic moments of the Ms= 6. 0 to the Ms= 5. 7 events, the Ms= 6. 0 tothe Ms= 5. 5 events and the Ms= 5. 7 to the Ms= 5. 5 events are 1. 18, 3. 00 and 2. 54, respectively. The correspondent relative scalar seismic moments calculated directly from the waveform recordings are 1. 15, 3. 43, and 3. 05.

Source time functions of the 1999, Jiji (Chi-Chi) earthquake from GDSN long period waveform data using aftershocks as empirical Green's functions

A large earthquake (Mw=7.6) occurred in Jiji (Chi-Chi), Taiwan, China on September 20, 1999, and was followed by many moderate-size shocks in the following days. Two of the largest aftershocks with the magnitudes of Mw=6.1 and Mw=6.2, respectively, were used as empirical Green's functions (EGFs) to obtain the source time functions (STFs) of the main shock from long-period waveform data of the Global Digital Seismograph Network (GDSN) including IRIS, GEOSCOPE and CDSN. For the Mw=6.1 aftershock of September 22, there were 97 pairs of phases clear enough from 78 recordings of 26 stations; for the Mw=6.2 aftershock of September 25, there were 81 pairs of phases clear enough from 72 recordings of 24 stations. For each station, 2 types of STFs were retrieved, which are called P-STF and S-STF due to being from P and S phases, respectively. Totally, 178 STF individuals were obtained for source-process analysis of the main shock. It was noticed that, in general, STFs from most of the stations had similarities except that those in special azimuths looked different or odd due to the mechanism difference between the main shock and the aftershocks; and in detail, the shapes of the STFs varied with azimuth. Both of them reflected the stability and reliability of the retrieved STFs. The comprehensive analysis of those STFs suggested that this event consisted of two sub-events, the total duration time was about 26 s, and on the average, the second event was about 7 s later than the first one, and the moment-rate amplitude of the first event was about 15% larger than that of the second one.

A Modified Discrete-Time Jacobi Waveform Relaxation Iteration

In this paper, we investigate an accelerated version of the discrete-time Jacobi waveform relaxation iteration method. Based on the well known Chebyshev polynomial theory, we show that significant speed up can be achieved by taking linear combinations of earlier iterates. The convergence and convergence speed of the new iterative method are presented and it is shown that the convergence speed of the new iterative method is sharper than that of the Jacobi method but blunter than that of the optimal SOR method. Moreover, at every iteration the new iterative method needs almost equal computation work and memory storage with the Jacobi method, and more important it can completely exploit the particular advantages of the Jacobi method in the sense of parallelism. We validate our theoretical conclusions with numerical experiments.

Photonic generation of arbitrary waveforms based on incoherent wavelength-to-time mapping

We demonstrate experimentally a radio frequency arbitrary waveform generator using the incoherent wavelength-to-time mapping technique. The system is implemented by amplitude modulation of a broadband optical resource whose spectrum is reshaped by a programmable optical pulse shaper and transmitted over a single mode fiber link. The shape of the generated waveform is controlled by the optical pulse shaper, and the fiber link introduces a certain group velocity delay to implement wavelength-to-time mapping. Assisted by the flexible optical pulse shaper, we obtain different shapes of optical waveforms, such as rectangle, triangle, and sawtooth waveforms. Furthermore, we also demonstrate ultra-wideband generation, such as Gaussian monocycle, doublet, and triplet waveforms, using the incoherent technique.

Photonics Improvement of the Time-Bandwidth Product for a Linearly Chirped Waveform

A photonics approach to generate a linearly chirped waveform with increased TBWP is proposed and investigated. The time bandwidth product (TBWP) of the linearly chirped waveform is improved based on optical microwave frequency multiplying combined with temporal synthesis. An integrated dual-polarization modulator and an optical filter are utilized to perform frequency doubling operation by generating an orthogonally polarized optical signal, which consists of an optical carrier in one polarization direction and a second-order chirped optical sideband in another. Then the orthogonally polarized optical signal puts into a polarization modulator (PolM) to perform phase coding process. By driving a Pseudorandom (PN) sequence to the PolM, the time duration of the generated bandwidth doubled linearly chirped waveform can be synthesized to arbitrary length. The approach is verified by simulation. A linearly chirped waveform with central frequency of 8.25 GHz, bandwidth of 500 MHz, time duration of 6.4 ns is used to generate a synthesized waveform with central frequency of 16.5 GHz, bandwidth of 1 GHz, time duration of 819.2 ns. The TBWP of the linearly chirped signal is improved from 3.2 to 819.2. The proposed method features arbitrary large TBWP, and it can be used in a radar system to improve its resolution.

新型连续B/J类功率放大器设计

为满足无线通信技术对高性能功率放大器的需求,提出一种新型宽带高效率B/J类功率放大器的设计方法。区别于传统连续B/J模式,设计中引入变量因子重塑其时域电压波形表达式,推导出扩展的阻抗设计空间。扩展的阻抗设计空间增加了阻抗匹配的灵活度,拓展了带宽,同时仿真表明可获得与传统连续B/J类功率放大器相同的功率和效率。基于此新型阻抗匹配技术,设计了一款工作频段为1.5~2.5 GHz的GaN HEMT宽带功率放大器。测试结果表明,在该频率范围内,输出功率大于40.6 dBm,漏极效率为72.4%~79.1%,增益为10.6~11.9 dB表明,所提出方法具有有效性.

脉内频率 时延捷变雷达抗间歇采样转发干扰方法

间歇采样转发干扰凭借快速准确的采样和转发手段,利用脉压雷达的匹配滤波特性形成假目标群,严重影响目标检测和跟踪性能。针对这一问题,结合波形设计和滤波思想,设计一种脉内频率时延捷变波形,并在此基础上提出一种基于时频分析的抗间歇采样转发干扰方法。首先,将线性调频信号划分为多个子脉冲,并在子脉冲之间增加随机时延。然后,提取未被干扰的子脉冲进行目标位置的准确判断,结合子脉冲的频率和随机时延等先验信息,利用迭代阈值分割算法去除强干扰信号。最后,通过构造时频域和时域带通滤波器分别进行子脉冲滤波和时域滤波处理。仿真实验结果表明,所提方法在不同干信比、信噪比和非同步采样情况下具有较好的抗间歇采样转发干扰性能。

爆破振动强度、波形与频谱研究综述:预测及主动控制

岩石钻孔爆破不可避免地会产生爆破振动效应及危害,准确预测爆破振动效应并进行主动控制具有极大的现实意义。论文综述了近40年来,国内外研究人员在爆破振动预测及主动控制方面取得的研究成果。在爆破振动速度峰值(PPV)预测方面,经验模型预测方法体现出了较大的便捷性,但预测精度与效果较差,将概率统计理论引入经验模型预测方法,提高了PPV预测精度;而基波叠加预测方法可实现对振速、频率和持续时间的综合预测,但是该方法对振动基波的测试精度要求较高,同时亟须在行业内建立对爆破振动采集设备的定期标定与校核机制;人工智能预测方法极大提高了PPV预测精度,同时为多因素影响下的爆破振动效应预测提供了新思路,但需要建立在海量真实有效实测数据的基础上,目前还缺乏充实的振动测试样本数据库;PPV预测理论模型及数值模拟预测法对理论与专业知识、数值模拟技术等要求高,限制了两种方法在工程的普遍应用。在爆破振动速度主动控制上,可以确定合理的延期时间,采用毫秒延迟干扰减振法来降低PPV,但目前多为单一防护对象所提出的延期时间建议值;从调整爆破振动频谱结构的角度,通过主动改变延期时间调控爆破振动频率成分,可避开建(构)筑物自振频带,减小爆破振动危害,然而目前仅仅停留在理论层面或模型试验尺度条件下,缺乏大规模的现场应用实例。最后,对未来爆破振动预测及控制方面重点研究内容进行了展望。

柱坐标系下浅海传播声场时域有限差分预报方法

直角坐标系下的时域有限差分方法在水声传播仿真时由于计算量太大而较少应用。文章利用时域有限差分方法推导了柱坐标系下的声波方程的近似表达式,结合复频移完全匹配层建立浅海声传播模型,在减少计算量的同时准确预报了传播信号声压的时域波形、传播声场的时空演变过程以及频域传播损失曲线。在柱坐标系下使用时域有限差分方法仿真Pekeris传播环境声场并与简正波和波数积分模型进行对比,分析了时域有限差分水声传播模型的适用范围。结果表明,时域有限差分方法仿真浅海中近程传播声场精度较高。模型的稳定性与时间和空间网格大小有关,声源频率越高,空间和时间网格划分越小,计算量越大。数值离散带来的频散误差累积会导致远场传播声场计算不准确,因此时域有限差分水声传播模型更适用于低频中近程声场计算。

雪道点云时域波形特征分割及SLAM算法

为提升压雪车在滑雪场行驶与作业的夜间环境感知能力,提出了压雪车车载激光雷达点云时域波形阶跃值检测的雪道分割算法,并构建了适用于高山滑雪场的实时定位与建图算法(SLAM)。首先,对点云反射率分布进行统计并标记飘雪噪声点,利用邻近点线性插值方法对标记的飘雪噪声进行处理,保证点云的时域波形连续性,同时在特定扫描视角内划分栅格并以相邻网格高程值变化实时估计坡度。其次,根据山地滑雪场典型障碍设计了相应的时域波形阶跃值检测判据,筛选雪道-障碍分界点,划分扫描区间并对区间内的波形阶跃值进行包络,实现雪道点云特征分割。然后,根据雪道分割结果对特征进行分类匹配,并利用特征约束方法提高建图速度。最后,在张家口万龙滑雪场的高级和中级雪道进行算法效果验证测试。测试结果表明:所提出的雪道分割算法对单帧点云数据的处理平均耗时为2.36 ms,平均分割准确率可达98.54%,在基于雪道分割算法的改进SLAM方法中可以准确实现雪道-障碍分割,在建图精度方面表现更为优越且大幅缩减了计算耗时。

锂离子电池充放电过程声发射实验特征研究

锂离子电池在充放电过程的复杂电化学反应使得电池性能退化,导致电池使用容量减小。声发射技术作为一种精度高的无损检测方法可检测电池内部电极的变形行为。通过锂电池循环老化实验得到老化电池,与新电池进行多组充放电实验,收集充放电过程的声发射信号并分析。电池充放电过程中恒流充电阶段与放电第二阶段旧电池比新电池短,恒压充电阶段旧电池比新电池长。声发射信号主要在放电过程中稳定出现2个突发型波形,在放电过程中的电压稳定下降阶段中,锂电池的信号时间间隔与波形时间间隔都随着电压的降低而减小,相同放电倍率下老化电池的时间间隔大于新电池。

基于时域射线追踪算法的电场波形特性研究

利用时域射线追踪算法,构建出简化开关柜模型并模拟局部放电,仿真分析局放电磁波到达不同检测点的时域特性.由于多径传播,最短路径与其它路径存在到达时间差,通过叠加时间差相近路径的波形幅值,分析检测点时域波形混叠的原因,对比不同检测点的时域接收波形,分析波形畸变的原因.研究结果为开关柜内局部放电的电磁波传播规律提供新方法,为后续优化超高频检测天线的安装摆放提供参考依据.

超深水区基准面延拓驱动的反射波形反演成像

远离大陆架的海洋油气勘探与开发具有高风险、高投入的特征,对构造成像和储层预测精度要求很高,传统的基于射线理论的速度建模方法难以满足精细成像的需求。超深水探区地震观测受巨厚水层的影响,导致记录时间较长、数据规模和模型空间巨大,因此难以大规模应用基于波动理论的速度建模方法。为此,提出基准面延拓驱动的反射波形反演成像技术。该技术利用基准面延拓剥离水层影响,消除地震波在水中的传播效应,降低数据规模、压缩模型空间、缓解速度—深度多解性,使全波形反演在深海区的实际应用成为可能。考虑到超深水探区有限炮检距难以记录到穿透较深的初至波,无法利用初至波进行波形反演更新速度,因此选用反射波形反演对延拓后数据进行速度建模,以便得到高精度速度模型和成像结果。理论模型合成数据和南海A区块实际数据处理结果表明,该技术能够大规模缩减数据量,并提高高精度速度建模的效率,可在超深水油气勘探中发挥积极作用。

带有死区时间补偿及电容电压平衡功能的二极管钳位型三电平逆变器数字调制方法

针对二极管钳位型三电平逆变器存在的电容电压平衡问题和死区时间导致的输出波形失真问题,该文在分析死区时间对输出波形失真及电容电压平衡影响的基础上,提出一种可用于高频逆变器的数字调制方法及具体实现形式,分析量化与采样环节、数字隔离器件传输延时及采样时钟对所提方法的影响,并给出开关时钟分频倍数的设计准则。该方法独立于闭环控制系统其他环节,无需电流采样,实现容易且易于集成在数字控制器中;无需控制环路运算,可适用于更高开关频率和输出频率。仿真和实验表明,所提方法在不同开关频率、不同死区时间和不同负载类型下均能有效地降低死区时间导致的输出波形失真现象,且能够很好地解决电容电压平衡问题。此外,所提方法在开关频率高达400 kHz的情况下仍具有良好的效果。

脉冲负载下柴油发电机组建模优化与评价

针对柴油发电机组-三相不控整流器-DC/DC变换器-脉冲负载系统中柴油发电机组的输出特性,提出仿真模型与试验电源输出电压(流)波形契合度的评价指标,以判断模型的仿真程度;提出了基于反向(BP)传播神经网络算法的同步发电机励磁电压输出动态限幅方法,应用于脉冲负载下柴油发电机组的模型优化。试验验证表明:27组算例中,初始仿真模型有18组波形实时契合度值不足90%,优化仿真模型27组值均大于90%。说明本文提出的优化方法使仿真模型比初始模型更加有效,可应用于后续柴油发电机组带脉冲负载系统的研究。

常规直流逆变站交流送出线路距离保护适应性分析与对策

常规直流逆变站交流送出线路故障通常会引发换相失败,存在故障电压和电流波形畸变等问题,可能导致工频相量距离保护性能劣化。首先,分析了工程中广泛应用的正序电压极化距离保护在常规直流逆变站交流送出线路中的适应性,分析结果表明,当逆变站运行于单回交流出线工况时,传统正序电压极化距离保护不再适用;然后,基于交流线路的RL模型,提出了基于波形相关系数的时域距离元件,可以不受逆变站非线性输出特性的影响,并针对时域距离元件存在的出口近区故障方向判别问题,利用电流畸变程度判断故障方向;最后,通过仿真验证了时域距离保护方案的有效性。

电源网络低频段S参数拓展方法

电源网络S参数与芯片电源模型(Chip Power Module,CPM)级联可实现电源时域噪声仿真,完成电源完整性设计签核。当下部分仿真工具在AC阻抗优化过程中导出的S参数存在低频段无法覆盖的问题,影响时域纹波仿真精度,如果重新对S参数进行提取,又会增加仿真时间降低仿真效率。针对AC阻抗优化过程中导出的S参数无法覆盖低频段的问题,提出了一种电源网络S参数低频段拓展方法,结合电压调节模块(Voltage Regulator Module,VRM)的R-L模型,推导出低频段的S参数可以借用抽取的S参数中最低频点处的S参数实现低频段S参数的拓展。仿真和实验结果表明,通过对低频段S参数进行拓展,电源时域纹波噪声仿真的精度提升31%。同时,低频段的S参数直接借用已抽取的S参数中低频点的数值无须重复提取,在8 GB内存的配置下,仿真时间节约14%左右,提高了仿真效率。

基于时频变换和波形整形的跳频信号参数估计方法

针对噪声对跳频信号参数估计造成的困难,提出了基于时频变换和波形整形的跳频信号参数估计方法。对跳频信号进行短时傅里叶变换,计算得到时频脊线,对时频脊线进行波形整形处理,消除噪声造成的虚假跳频时刻干扰,通过跳频时刻序列得到跳周期序列,对跳周期序列计算其直方图,选出出现次数最多的值来计算跳频信号的跳频速率。根据跳周期序列分别取出每段信号,再进行频率估计。通过实验验证了提出方法的有效性,综合利用时频变换及波形整形处理技术,保证了在低信噪比下跳频信号跳频时刻、跳频速率及跳频频率的理想估计结果。

网络心电图诊断临床应用价值研究

目的分析网络心电图在心血管疾病临床诊断中的价值。方法选取2021年3月至2023年3月于医院接受网络心电图检查的1000例心血管疾病患者作为网络心电图组,另取2018年1月至2021年1月于医院接受常规心电图检查的1000例心血管疾病患者作为常规心电图组。比较两组的诊断效果。结果网络心电图组的检查所需时间、检查报告完成时间及就诊等待时间均短于常规心电图组,差异具有统计学意义(P<0.05)。网络心电图组的异常心电图、心律失常及心肌缺血检出率分别为65.30%、41.20%、12.00%,均高于常规心电图组的39.30%、20.50%、2.10%,差异具有统计学意义(P<0.05)。两组患者的Q-T间期、T时限、QRS时限、P-R间期及P波时限比较,差异无统计学意义(P>0.05)。网络心电图组的就医满意度为98.80%,高于常规心电图组的90.20%,差异具有统计学意义(P<0.05)。结论在心血管疾病诊断过程中,选用网络心电图检查可获得明显优于常规心电图检查的效果,其能够为患者争取更多诊治时间,从而促进患者早日康复,提升就医满意度。

多导睡眠测量仪质量控制检测与性能评估

目的:研究多导睡眠测量仪质量控制检测方法,确保其使用中性能的安全性与有效性。方法:针对多导睡眠测量仪的脑电信号、肌电信号、心电信号和脉搏血氧饱和度主要指标参数,设计质量控制检测方法。选取2023年8月陆军军医大学大坪医院临床在用的2台同品牌不同型号的多导睡眠测量仪(标记为测试设备A和测试设备B),采用心脑电图机检定仪和生命体征模拟仪进行多导睡眠测量仪质量控制检测,评估多导睡眠测量仪性能的可靠性。结果:针对多导睡眠测量仪的脑电信号、肌电信号、心电信号和脉搏血氧饱和度示值重复性制定质量控制检测方法进行多导睡眠测量仪质量控制检测,记录数据除测试设备B电压测量模拟仪输出值2 mV时,相对误差为-11%,出现参数超差,测试设备A和测试设备B的其余检测数据均满足国家计量检定规程和设备生产厂家技术要求的最大极限输出值。结论:多导睡眠测量仪质量控制检测方法能够对选取的测试设备A和测试设备B多导睡眠测量仪进行性能参数评估,为该类设备质量控制检测和使用安全提供技术支持。