二维粘弹介质五点八阶超紧致有限差分声波方程数值模拟

本文首次将五点八阶超紧致有限差分格式(CCD8)用于粘弹介质声波方程的数值模拟中。此文根据泰勒级数展开粘滞声波方程,建立了位移场时间二阶离散格式,将CCD8用于对位移场空间导数的求取。然后,对CCD8格式进行稳定性研究,频散的压制效果对比分析,及截断误差对比。将CCD8格式运用于均匀介质模型以及水平层状介质模型中进行数值模拟,最后运用于对Marmousi模型的数值模拟中。研究结果表明：(1)CCD8与普通八阶紧致差分相比,具有更小的截断误差、更高的模拟精度以及低数值频散的优势;(2)CCD8具有较高稳定性;(3)采用完全匹配层(PML)对人工边界进行处理后对均匀介质、含有层状介质以及Marmousi模型进行粘弹声波方程的数值模拟,发现模拟效果不错,从而验证了方法的实用性和有效。     

耦合钻井液钻柱声波传播特性研究

钻井过程中非常规钻井液的应用,使得随钻数据无法通过传统的钻井液脉冲方式传输,迫切需要更高数据传输速率和受工作环境影响更小的井下随钻无线传输技术。基于钻柱信道的井下信息声波传输技术是较为理想的随钻数据无线传输方式,为给声波传输系统的设计提供理论依据,针对钻柱信道中的声波传播特性进行了研究。研究结果表明:钻柱信道具有通带和阻带相间的梳状滤波器特征,频带分布具有一定的周期性和对称性特征。钻柱结构决定了其信道通阻带的分布情况,随着钻杆根数的增加通带内小谱峰的个数增加,信道传输能力下降,结构尺寸不一致会使通带变窄,声波传输性能下降。     

电磁波CT揭露重大工程岩溶发育特征--以某地铁岩溶勘察为例

灰岩地区岩溶发育程度严重影响重大工程建设,以钻探为主的城市岩溶勘察,很难充分查明地下岩溶发育特征及规模,而高密度电法、浅层地震反射等其余地球物理方法因场地条件限制和干扰因素较多,在城市岩溶探测中很难实施。鉴于此,本文采用井间电磁波CT层析技术对某地铁进行岩溶探测,应用联合迭代重建技术（simultaneous iterative reconstruction technique 简称SIRT）进行反演,获取电磁波CT吸收系数等值线图,并通过吸收系数判断岩溶发育状态。研究结果表明：电磁波CT层析技术可较好揭露地下岩溶发育规模和特征,探测结果与钻孔资料揭露岩溶信息高度吻合。该方法的成功引入为重大工程岩溶探测提供了新思路,其探测成果结合钻孔信息可作为重大工程建设可靠的地质参考依据,具有较好的科学意义和推广价值。     

Auroral substorm response to solar wind pressure shock

Two cases of auroral substorms have been studied with the Polar UVI data, which were associated with solar wind pressure shock arriving at the Earth. The global aurora activities started about 1–2 min after pressure shocks arrived at dayside magnetopause, then nightside auroras intensified rapidly 3–4 min later, with auroral substorm onset. The observations in synchronous orbit indicated that the compressing effects on magnetosphere were observed in their corresponding sites about 2 min after the pressure shocks impulse magnetopause. We propose that the auroral intensification and substorm onset possibly result from hydromagnetic wave produced by the pressure shock. The fast-mode wave propagates across the magnetotail lobes with higher local Alfven velocity, magnetotail was compressed rapidly and strong lobe field and cross-tail current were built in about 1–2 min, and furthermore the substorm was triggered due to an instability in current sheet.     

一维空间中半线性波方程的整体解

研究Cauchy问题utt-uxx=εF(u),t＞0,0＜x＜+∞,u(0,x)=u0(x),ut(0,x)=u1(x),0＜x＜+∞,得到了初值和p满足一定的假设条件,ε充分小时,该Cauchy问题整体解的适定性.     

Elastic wave velocity in rocks from Dabieshan and its constraints for lithospheric composition and crust-mantle recycling

P-and S-wave velocities in eclogites and granulites from the Dabie ultrahigh pressures (UHP) meta morphic belt, China, were measured at room temperature under the hydrostatic pressures up to 1.0 GPa. The ultrahigh pressure eclogites had the highest densities (3.3 ～ 3.6 g.cm-3) , high velocities and the lowest anisotropy (1.4%c ～ 2.6 % ) . The lowest densities (2.8 ～ 3.1 g. cm-3 ) and the highest Poisson' s ratios (0.28 ～ 0.29) were found in gran ulites, whereas the strongest anisotropies (6. 1 % ～8.4% ) were found in the high-pressure (HP) eclogites. Compari son of the velocities in rocks with that observed in the deep seismic sounding profile crossing Dabieshan suggests that e clogites might exist in the lower crust of Dabieshan, but the quantity might be small. The upper mantle has very similar velocities as the UHP eclogites and serpentinizated/water-bearing dunite. The formation of eclogite represents the crust mantle recycling processes. Crustal material is delaminated and sinks into the mantle by way of eclogite, whereas only a small part of the eclogite could return to the crust.     

Shock wave diffraction and reflection around a dusty square cavity

The diffraction and reflection of planar shock wave around a dusty square cavity is investigated nuerically, which is embedded in the flat bottom surface of a two-dimensional channel, and the induced gas-particle twophase flow. The wave patterns at different times are obtained for three different values of the particle diameter. The computational results show that the existence of particles affects appreciably the shock wave diffraction and cavity flow.     

组合KdV-mKdV方程的函数变换和精确解析解

利用新的函数变换,得到了组合KdV-mKdV方程u1 2auux 3βu^2ux γuxxx=0的若干精确解析解,其中包含钟状孤波解、扭状孤波解,新的钟状和扭状组合型的孤波解以及周期波解,此外,也得到了其他类型非线性波方程的解。     

基于兰姆波技术的液体密度声传感器

在考虑晶体的压电性和各向异性基础上,从声的波动理论出发,对叉指换能器在液体－压电晶片界面上兰姆波的激发理论及基性质进行了研究,分析了兰姆波对液体密度变化的敏感情况,提出了一种基于兰姆波技术的测量液体密度微小变化声传感器,根据传感器敏感液体的特点,对其进行实验分析,取得了较好的效果。实验结果表明,这种传感器具有良好的性能。     

激发应力波在锚杆锚固体中传播规律的实验研究

通过理论分析和实验研究,证明了锚杆锚固体中弹性应力波的波速确实会发生变化,给出了锚杆锚固质量与锚固体中弹性应力波波速之间的定性关系。