用INGLADA与GEIGER方法实现近震精定位

介绍了一种近震定位方法,即利用INGLADA方法实现近震初定位,并对初定位结果利用GEIGER方法进行校正,最终取得精确定位结果的近震定位方法。通过使用虚拟台网测试此定位方法以及该定位方法在实际中的应用表明,将INGLADA与GEIGER方法相结合,在区域地震台网中是一种较理想的近震定位方法。作者已经在MATLAB下实现了此定位方法。

Geiger型碳纤维索穹顶结构连续倒塌性能非线性分析

为了研究Geiger型碳纤维索穹顶结构的连续倒塌路径及破坏模式,基于备用传力路径(alternate path,AP)方法,采用等效荷载瞬时卸载法来模拟初始失效构件的拆除,对矢跨比为0.1的索穹顶结构的连续倒塌全过程进行了非线性动力数值分析。提出结构重要性矩阵和构件重要性系数的概念,建立了倒塌控制方程。依据倒塌控制方程将构件分为:关键构件、重要构件和一般构件。上述三类构件分别对应于在拆除该构件后结构发生整体连续倒塌、局部连续倒塌和不发生连续倒塌三种倒塌结果。通过参数分析,得出结论:对倒塌结果影响较大构件为内环索、内圈和中圈压杆。针对Geiger型碳纤维索穹顶结构提高抗连续倒塌性能提出设计建议。

Geiger索穹顶结构自振特性及地震响应分析研究

Geiger索穹顶结构是由索杆膜结构组成的柔性体系,该结构属于对振动敏感的结构,膜结构作为索穹顶的一部分在受力分析中必不可少,并且膜面初始预应力的大小直接影响结构的内力,因此本文以两种不同的膜面预应力作为初始条件进行非线性有限元找形,对索杆膜结构的整体找形结果进行自振特性分析和El Centro波作用下的地震时程分析,结果表明改变膜结构的初始预应力可以有效地增强结构的刚度,提高结构的抗震能力。

联合采用Inglada算法和Geiger算法确定地震精确位置

Inglada定位算法具有全局反演地震位置的优点,但只能采用均匀地壳结构求解地震位置,Geiger定位算法能够采用不均匀地壳结构进行定位,但给定的真解必须在实际解附近才能得到全局最优的震源位置。本研究结合Inglada和Geiger算法的各自优点,提出了地震定位算法的策略,即先采用Inglada算法得到接近真解的初始震源位置,然后采用Geiger算法对Inglada算法得到的解进行修改,以便得到考虑不均匀速度模型的震源位置。数值试验表明这种策略可以很好地约束地震的位置。我们将该算法应用于2008年2月11日江西瑞金ML2.3地震,得到了残差更小的地震精确位置。

基于Geiger-mode APD的激光雷达性能分析

针对基于盖革模式雪崩光电二极管(Gm-APD)阵列的激光雷达,提出一种分析其探测性能的方法。以分析单个Gm-APD像元产生的初始光电子和暗计数噪声为基础,对Gm-APD像元的探测概率、虚警概率和漏警概率进行研究,并进一步提出一种多脉冲阈值探测法,并对其探测概率、虚警概率进行了研究和仿真。结果表明,对2～10 km外的目标,采用128×128像元面阵探测器,单脉冲能量小于200 mJ时,探测概率随脉冲能量提高而提高;单脉冲能量大于200 mJ时,探测概率保持不变;当采用多脉冲阈值探测、信号较弱时,探测概率总是随脉冲能量提高而提高,虚警概率总是随脉冲能量提高而降低。

基于全相位多次互相关的Geiger声发射源定位方法

直接互相关在岩石声发射源定位中,会出现多次峰值与波形密集的问题,在求解过程中会出现无解的情况且定位精度不足,为了解决这些问题,提出一种基于全相位快速傅里叶变换(FFT)分析及多次互相关的岩石声发射源定位的算法。通过对50 mm×100 mm×50 mm的花岗岩进行断铅试验,利用小波变换对互相关分析的频谱进行预处理,同时发挥全相位FFT的相位不变性的优点,找出波形峰值,得到时间差,最后利用最小二乘法得到定位初始点,再通过Geiger迭代,得到最终定位坐标。在选取8个测点的基础上,经声发射监测试验结果表明:该方法比单独直接互相关更容易找到波峰,且波形清晰,初始点的选择有效解决了Geiger迭代法对初始值要求严格的问题,通过全相位分析及多次互相关计算,然后Geiger程序迭代,得到的定位结果比直接互相关精度更高,平均绝对误差比美国生产PCI–2型声发射仪器Geiger定位的结果低2.40 mm,比基于多次互相关和Geiger算法的声发射源定位结果低3.31 mm,比全相位相位差法声发射测试时间延迟定位结果低1.74 mm。

A Planar InGaAs/InP Geiger Mode Avalanche Photodiode with Cascade Edge Breakdown Suppression

A Geiger mode planar InGaAs/InP avalanche photodiode （APD） with a cascade peripheral junction structure to suppress edge breakdowns is designed by finite-element analysis. The photodiode breakdown voltage is reduced to 54.3V by controlling the central junction depth, while the electric field distribution along the device central axis is controlled by adjusting doping level and thickness of the lnP field control layer. Using a cascade junction structure at the periphery of the active area, premature edge breakdowns are effectively suppressed. The simulations show that the quadra-cascade structure is a good trade-off between suppression performance and fabrication complexity, with a reduced peak electric field of 5.2 × 10^5 kV/cm and a maximum hole ionization integral of 1. 201. Work presented in this paper provides an effective way to design high performance photon counting InGaAs/InP avalanche photodiodes.

全相位与Geiger算法的岩石声发射源定位方法

Geiger定位算法在岩石定位分析中得到广泛应用,但是对初始值要求非常严格,若初始值选择不当,则很难进入收敛范围。为了提高定位精度,减少迭代次数,针对这些问题,提出全相位与Geiger算法的岩石声发射源定位方法。首先进行花岗岩(50 mm×100 mm×50 mm)断铅实验,接着充分利用全相位FFT相位不变性的优势分析断铅信号,通过相位差法求出时延同时反演声发射源求出Geiger迭代初始值,最后综合最小二乘法与Geiger算法,迭代求出最优解。实验仿真结果显示此算法的平均误差相比美国PCI-2型声发射仪器定位结果降低了约5 mm,有效解决了Geiger初始值选取的问题,能够迅速进入收敛范围,提高了收敛速度和定位精度。

Geiger型索穹顶的静力性能分析

针对Geiger型索穹顶的静力性能,采用ANSYS软件,根据试验过程,建立了索穹顶有限元模型,并对其进行验证.利用该建模方法,建立了直径为100m的大跨度模型,对其加载进行全过程力学分析.改变索穹顶结构的主要参数(初始预应力、高度、横截面积等),探讨了不同参数对静力性能的影响.研究表明:索穹顶由于预应力损失,结构存在一个失效荷载.当结构参数发生改变时,对应的失效荷载与挠度也随着有相应的变化.

基于Chan与Geiger混合算法的声发射源定位方法

Geiger定位算法是一种广泛应用的岩石损伤声发射源定位方法,但该算法受初始值影响较大,直接影响了算法的应用效果。文章充分挖掘Chan算法的特性,提出了一种混合Chan与Geiger算法的优化算法,利用Chan算法对损伤声源进行初始定位,再融合Geiger算法进行迭代解算。通过数值计算和断铅实验对所提出的混合算法进行理论分析和实验验证,结果表明:该混合算法简便、易行、结果可靠,能够有效提升声发射源定位算法的收敛速度和定位精度;在传感器数量较少时,该混合算法具有较强的适应性;在布设4个单维传感器的条件下,Chan与Geiger混合算法较最小二乘法与Geiger混合算法,定位结果更加精确,且迭代次数更少,能有效提高计算效率。该研究对于提高岩石、混凝土材料的损伤定位和健康监测的测算精度以及工作效率具有一定的促进意义。

基于时差定位线性算法和Geiger迭代算法的某铁矿声发射源定位精度分析

随着矿山开采逐渐向深部化发展,地压活动对开采的影响日益显著。声发射源定位技术的应用可以有效的实时监测地压,为安全生产提供指导。定位精度又是声发射源定位的重中之重。时差定位算法应用较为普遍,时差线性定位算法主要构建线性方程组进行代数方法求解,该法较为简单,缺点是方程组可能会出现无解导致定位计算失败。Geiger迭代定位算法在选取了合适迭代初值的基础上进行多次迭代得到定位结果,原理上比时差线性定位算法更精确,对时差定位中的线性定位和Geiger迭代定位两种算法结合云南某大型铁矿的声发射监测系统监测到的声发射事件进行了分析,通过两种定位算法得到的定位结果误差对比分析来具体说明两种方法对于工程实际的适用性和精确度。

Method to Measure Indoor Radon Concentration in an Open Volume with Geiger-Mueller Counters: Analysis from First Principles

A simple method employing a pair of pancake-style Geiger-Mueller (GM) counters for quantitative measurement of radon activity concentration (activity per unit volume) is described and demonstrated. The use of two GM counters, together with the basic theory derived in this paper, permit the detection of alpha particles from decay of and progeny ( 218Po, 214Po) and the conversion of the alpha count rate into a radon concentration. A unique feature of this method, in comparison with standard methodologies to measure radon concentration, is the absence of a fixed control volume. Advantages afforded by the reported GM method include: 1) it provides a direct in-situ value of radon level, thereby eliminating the need to send samples to an external testing laboratory;2) it can be applied to monitoring radon levels exhibiting wide short-term variability;3) it can yield short-term measurements of comparable accuracy and equivalent or higher precision than a commercial radon monitor sampling by passive diffusion;4) it yields long-term measurements statistically equivalent to commercial radon monitors;5) it uses the most commonly employed, overall least expensive, and most easily operated type of nuclear instrumentation. As such, the method is par-ticularly suitable for use by researchers, public health personnel, and home dwellers who prefer to monitor indoor radon levels themselves. The results of a consecutive 30-day sequence of 24 hour mean radon measurements by the proposed GM method and a commercial state-of-the-art radon monitor certified for radon testing are compared.

Passive Quenching Electronics for Geiger Mode 4H-SiC Avalanche Photodiodes

We design and fabricate 4H-SiC UV avalanche photodiodes （APDs） ~qth positive beveled mesa, which exhibit low leakage current and high avalanche gain when working in the Geiger mode. The single photon counting performance of the SiC APDs is studied by using a passive-quenching circuit. A new method to determine the exact breakdown voltage of the APD is proposed based on the initial emergence of photon count pulses. The photon count rate and dark count rate of the APD are also evaluated as a function of quenching resistance.

New Geiger-Nuttall law of odd-Z nuclei and long-lived island beyond the stable line

Recently,we analyze the α-decay data of even-Z nuclei and propose the new Geiger-Nuttall law where the effects of the quantum numbers of α-core relative motion are naturally embedded in the law [Physical Review C 85,044608(2012)].In this paper,we firstly test whether the new law without any change of parameters can be applied to the α-decays of odd-Z nuclei which are more complicated than those of even-even nuclei.Then the nuclear shell effect around N=126 is analyzed for very proton-rich nuclei with Z=85-92 based on the data of α-decay energies and half-lives.A long-lived island beyond the stable line is proposed where the half-lives of nuclei on this island are abnormally long.The mechanism of the appearance of the island and its significance to other mass ranges are discussed.

基于多次互相关和Geiger算法的声发射源定位研究

为了解决岩石声发射源定位中,迭代法初始值的选取对定位精度和收敛速度的影响问题,提出了一种基于多次互相关的Geiger优化迭代的组合算法,充分利用互相关法可以提高信号信噪比和改善信号质量的优势,有效解决了声发射源定位初始迭代值的选取问题和传统互相关容易出现无解的问题,花岗岩断铅试验仿真结果表明:基于多次互相关与Geiger的组合算法定位结果的平均绝对误差比单独使用多次互相关降低了2.935 mm,比机器定位结果的平均绝对误差降低了1.834mm。

El Nio and the Kppen–Geiger Classification: A Prototype Concept and Methodology for Mapping Impacts in Central America and the Circum-Caribbean

The aim of this pilot study conducted by the consortium for capacity building was to develop a prototype concept and methodology for the classification and visualization of the geographic impacts of El Nio on annual climates and seasonality. Our study is based on the Kppen–Geiger climate classification scheme for a set of selected countries affected by strong El Nios in Latin America. By identifying and visualizing the annual and seasonal changes in regional, national, or subnational climate regimes that generally accompany an El Nio event,this research proposes an efficient way to detect and describe climate shifts and variability across time and space. Such knowledge provides a support tool for risk analysis and can potentially enhance government efforts of climate risk management, including disaster risk reduction activities that prevent, mitigate, and improve coping responses to El Nio-related hydrometeorological threats.Details of the conceptual approach and methodology to classifying and mapping El Nio's impacts are described and explained using the Central American and circumCaribbean region as a case study. The potential applications for disaster risk reduction as well as its limitations and future work are also discussed.

Detection performance of trigger-controlled Geiger-mode avalanche photodiodes in weak optical signal detection

This Letter introduces a trigger-controlled Geiger-mode avalanche photodiode （GM-APD）. A hierarchical look- back-upon tree recurrence method is given to predict the performance of trigger-controlled GM-APDs under different trigger-count upper limits. In addition, the normalized detection probability is defined to evaluate the detection performance of trigger-controlled GM-APDs in typical weak optical signal detection （impulse noise and continuous noise situations）. Theoretical analyses show that the trigger-controlled GM-APD improves the detection performance of GM-APDs in weak optical signal detection via the optimization of the trigger-count upper limit, compared with single-trigger and multi-trigger GM-APDs.

New Geiger-Nuttall law for cluster radioactivity half-lives

In this study,derived from Balasubramaniam’s formula[Phys.Rev.C 70,017301(2004)]and further considering the effect of the parent nucleus mass,blocking effect,and effect of reduced mass on cluster radioactivity half-lives,we propose a new Geiger-Nuttall law that is model-independent to systematically evaluate the halflives of this process for 16 even-even nuclei and 10 odd-A nuclei.For comparison,a single universal curve for cluster radioactivity andαdecay proposed by Poenaru[Phys.Rev.C 83,014601(2011)],a scaling law proposed by Horoi[J.Phys.G:Nucl.Part.Phys.30,945(2004)],an extension of the Viola-Seaborg formula fromαdecay to cluster radioactivity proposed by Ren et al.[Phys.Rev.C 70,034304(2004)],a new semi-empirical formula for exotic cluster decay proposed by Balasubramaniam et al.[Phys.Rev.C 70,017301(2004)],and a unified formula for the half-lives ofαdecay and cluster radioactivity proposed by Ni et al.[Phys.Rev.C 78,044310(2008)]are also used.The calculated results of our new Geiger-Nuttall law are in good agreement with the experimental half-lives,with the least rms being 0.606,and are better than the compared values.Moreover,we extend this formula to predict the cluster radioactivity half-lives of 51 nuclei whose decay energies are energetically allowed or observed but not yet quantified in NUBASE2020.

一种基于选权迭代法的震中估计方法

强震仪提取P波到时容易出现误判现象,导致地震到时观测信息不准确,造成Geiger方法的震中估计精度降低。针对该问题,首先采用STA/LTA+AIC方法,提取地震P波到时;其次,基于选权迭代法的抗差估计进行震中位置解算,抵抗P波到时信息可能存在的粗差影响。利用6次地震事件对本文方法进行验证,结果表明,Geiger方法的震中平均偏差为22.48 km、均方根误差RMSE为19.44 km,获取的发震时刻平均偏差为4.1 s、RMSE为4 s;基于选权迭代法的震中估计新方法的震中平均偏差为12.59 km、RMSE为11.00 km,获取的发震时刻平均偏差为2.3 s、RMSE为2 s。相较于传统Geiger方法,新方法的震中估计精度提高43%,发震时刻获取精度提高50%,可有效减弱P波到时粗差对震中估计结果的影响,提高计算结果的准确性。

32×32 Si盖革模式激光焦平面探测器

为了满足350 nm~1100 nm波长范围内远距离及微弱激光3维成像探测的需求,提出了一种规模为32×32的盖革模式硅激光焦平面阵列探测器,它主要由硅雪崩光电二极管阵列、读出电路芯片、微透镜阵列、半导体制冷器、引脚网格阵列壳体等元件组成。硅雪崩光电二极管焦平面阵列采用拉通型N^(+)-Π_(1)-P^(-)-Π_(2)-P^(+)结构,工作在盖革模式下,通过Si片背面抛磨减薄及盲孔刻蚀技术,实现了纤薄光敏区的加工;读出电路采用主动模式淬灭设计,使电路单元的死时间控制在50 ns以内,并利用一种带相移技术的时间数字转换电路优化方案,在满足时间分辨率不大于2 ns的同时,降低了读出电路芯片的功耗。结果表明,在反向过偏电压14 V、工作温度-40℃的条件下,该探测器在850 nm的目标波长可实现20.7%的平均光子探测效率与0.59 kHz的平均暗计数率,时间分辨率为1 ns,有效像元率优于97%。该研究为纤薄型背进光Si基激光焦平面探测器的研制提供了参考。