大容量气枪震源子波时频特性及其影响因素

通过分析福建街面水库气枪实验的近场水听器记录,研究气枪子波时频特性及其受沉放深度和工作压力的影响,并结合气泡模型解释气泡振荡过程。数据分析表明：①气枪子波由主脉冲和气泡脉冲组成。主脉冲振幅大,持时短,频带宽,通常应用于浅部探测;气泡脉冲能量集中在低频段,垂直穿透深,水平传播远,通常应用于深部探测。②随沉放深度的增加,主脉冲振幅变化很小,气泡脉冲振幅增加,初泡比减小,气泡周期减小,低频段主频增加。沉放深度为10m时,主脉冲振幅和初泡比最大,可应用于浅部探测;沉放深度为25m时,气泡脉冲振幅很大,初泡比最小,可应用于深部探测。③工作压力增加时,主脉冲振幅、气泡脉冲振幅、初泡比、气泡周期等随之增大,低频段主频则减小。     

水库大容量气枪震源激发条件优化实验研究

通过人工拾取震相,统计记录台站数、台站最远观测距离、接收能量等3个参数,自主研发了最优工况处理软件来研判工况激发效果,并确定棉花滩水库最优工况为水深25m,枪阵沉放深度9m,枪阵尺寸7m×7m。对定点300次激发的每10次累计叠加结果进行分析后发现,叠加1090次时激发效果快速增强,100150次时缓慢增强,160240次时快速增强,250300次时缓慢增强,即随着叠加次数的增加,激发效果增强,传播距离和记录台数也逐步增加。     

河南范县及邻区地震精定位及震源机制解分析

选取河南范县及邻区2008年1月~2015年9月M_L≥2.0地震78个,用双差定位法进行重新定位。结果显示,重定位的震中主要沿聊城-兰考断裂带呈NE向分布,较此前更集中。重定位后的震源深度82%位于7~8km,也比此前更集中。在此基础上,用CAP方法研究了该地区2008年以来M_L≥3.0地震的震源机制解。结果显示,节面Ⅰ的14个地震中有11个地震震中分布呈NE向,这与用双差法重新定位后的震中分布方向一致。此外,这14个地震中有9个地震的P轴方位在50°~100°,均值为75°,这与华北地区主压应力方向基本一致。综合分析认为,该区域的地震活动与聊城-兰考断裂有关。     

Probabilistic solution of floodplain inundation equation

Uncertainty in bed roughness is a dominant factor in providing a sufficiently accurate simulation of floodplain flows. This study describes a method to compute the transition probability density distribution of time-varying water elevations where the evolutionary process is based on a conventional one-dimensional storage cell model with governing stochastic differential equation. By including the random inputs (or noise terms) of bed roughness and initial water depth, time-dependent and spatially varying probability density function of the water surface leads to a Fokker–Planck equation. The model’s performance is evaluated by applying it to shallow water flow with a horizontal bed. Sensitivity of model predictions to variations in the bed friction parameters is shown. By comparing the result of the proposed method with that of conventional Monte Carlo simulation, the advantage of the former as a method for density function prediction is confirmed.     

Adjoint free four-dimensional variational data assimilation for a storm surge model of the German North Sea

In this paper, a data assimilation scheme based on the adjoint free Four-Dimensional Variational(4DVar) method is applied to an existing storm surge model of the German North Sea. To avoid the need of an adjoint model, an ensemble-like method to explicitly represent the linear tangent equation is adopted. Results of twin experiments have shown that the method is able to recover the contaminated low dimension model parameters to their true values. The data assimilation scheme was applied to a severe storm surge event which occurred in the North Sea in December 5, 2013. By adjusting wind drag coefficient, the predictive ability of the model increased significantly. Preliminary experiments have shown that an increase in the predictive ability is attained by narrowing the data assimilation time window.     

Three-dimensional admittance analysis of lithospheric elastic thickness over the Louisville Ridge

Using bathymetry and altimetric gravity anomalies, a 1° 9 1° lithospheric effective elastic thickness(Te) model over the Louisville Ridge and its adjacent regions is calculated using the moving window admittance technique. For comparison, three bathymetry models are used: general bathymetric charts of the oceans, SIO V15.1,and BAT_VGG. The results show that BAT_VGG is more suitable for calculating T e than the other two models. T e along the Louisville Ridge was re-evaluated. The southeast of the ridge has a medium Te of 10–20 km, while Te increases dramatically seaward of the Tonga-Kermadec trench as a result of the collision of the Pacific and IndoAustralian plates.     

Diet breadth and mortality patterns from Laoya Cave: A primary profile of MIS 3/2 hunting strategies in the Yunnan-Guizhou Plateau,southwest China

Laoya Cave is a long-term occupation site of Late Paleolithic humans in the Yunnan-Guizhou Plateau, southwest China, where abundant lithic, bone materials were recovered. Dating by the AMS technique showed a significant depositional process during marine isotope stage (MIS) 3/2. In this study, the species spectrum was presented from the perspective of zooarchaeology and the mortality profile of large Cervidae was examined to help increase our understanding of the subsistence strategy of local people dealing with climate and environmental changes. The main part of the diet was focused on large Cervidae, and the dominance of Ungulates indicates effective management of the cave and local fauna. On the other hand, the mortality profiles of large Cervidae varied correspondingly with climate change. The evidence indicates a specialized hunting strategy that was also flexible, depending on the prevailing climate and environment.     

适用于检测冻土的超声波测试系统的设计与研制

超声波波速测试作为一种无损检测已经广泛应用到岩土工程行业,该测试方法也是获得岩土体物理力学参数的有效方法.目前鲜有关于冻土的声波测试的技术和方法的报导,已有的冻土声波测试都是在垂直方向上忽略换能器的质量并在常温下快速测试声波通过时间,难以满足测试精度.鉴此,在购置常温声波测试主机的基础上,充分考虑冻土对温度敏感的特性、换能器在水平方向的测试以及土样与换能器之间的耦合程度,设计了一种适用于多种类型的冻土超声波换能器支架和恒温箱的测试系统,恒温箱意在提供适合不同温度下土体的测试环境（-30℃～+30℃）,换能器支架可供低温、提供多种尺寸冻土试样的横波和纵波的测试平台.为避免垂直测试中换能器和土样自身对测试的影响,除了支架提供水平测试平台外,在调节换能器与土样接触距离的螺杆顶端放置应变片测试冻土样与换能器之间的接触程度以提高冻土声波波速的测试精度.利用该测试系统对不同负温下冻土样品进行测试,数据结果证明了该测试系统的实用性和良好的测试精度.     

有孔管桩单桩承载性状试验及分析

有孔管桩能够有效地加速超静孔隙水压力时空消散,减轻沉桩效应对周围环境的不利影响,但桩身开孔引起的应力集中现象会削弱桩体承载力。为探讨桩身开孔对管桩承载性状的影响,采用室内模型试验方法,在软土地基中开展无孔管桩和3种不同布孔方式的有孔管桩单桩静载荷试验,对竖向荷载下引起桩顶沉降及桩身不同位置的应变进行了监测和分析,获得了各种管桩的Q-s曲线、桩身轴力及桩侧摩阻力的分布规律。对比分析可知,星状开孔有孔管桩的桩身轴力削弱情况最小,双向对穿有孔管桩的桩侧摩阻力最大。     

2000-2014年中国重特大煤矿事故时空分布分形特征

本文汇总整理了2000-2014年中国发生的472起重特大煤矿事故,获得其空间分布状况;基于分形理论,利用网格法统计不同网格尺度下覆盖重特大煤矿事故的非空网格中的事故数量,计算煤矿事故的全国、三大自然地理区以及干湿分区的分维值,分析其空间分布分形特征;利用R/S方法研究15年来重特大煤矿事故发生的时间分形特征。研究表明,从全国范围来看,重特大煤矿事故具有较好的空间分形特性,但不同区域的重特大煤矿事故的分形特性却具有很大差别。15年来发生重特大事故数量及事故死亡人数逐年下降,由R/S分析得到的Hurst指数表明事故时间序列的分形特征客观存在,并且年发生事故数量及事故死亡人数量减少趋势。