Effects of Sonic Waves at Different Frequencies on Propagation of Chlorella pyrenoidosa

[Objective] The aim was to investigate the effects of sound wave on propagation of Chlorella pyrenoidosa to explore the optimal frequency for Chlorella pyrenoidosa.[Method] In the research,Chlorella pyrenoidosa was cultured for 7 d with sound waves at different frequencies and a control group was set to study effects of sound wave at different frequencies on growth of Chlorella pyrenoidosa.[Result] Growth of Chlorella pyrenoidosa was significantly improved by sound wave,especially for wave at 400 Hz.[Conclusion] Chlorella pyrenoidosa propagation would be promoted by sound wave at certain frequencies.

Blasting cumulative damage effects of underground engineering rock mass based on sonic wave measurement

The principle of sonic wave measurement was introduced, and cumulative damage effects of underground engineering rock mass under blasting load were studied by in situ test, using RSM-SY5 intelligent sonic wave apparatus. The blasting test was carried out for ten times at some tunnels of Changba Lead-Zinc Mine. The damage depth of surrounding rock caused by old blasting excavation （0.8-1.2 m） was confirmed. The relation between the cumulative damage degree and blast times was obtained. The results show that the sonic velocity decreases gradually with increasing blast times, hut the damage degree （D） increases. The damage cumulative law is non-linear. The damage degree caused by blast decreases with increasing distance, and damage effects become indistinct. The blasting damage of rock mass is anisotropic. The damage degree of rock mass within charging range is maximal. And the more the charge is, the more severe the damage degree of rock mass is. The test results provide references for researches of mechanical parameters of rock mass and dynamic stability analysis of underground chambers.

Effects of wave propagation anisotropy on the wave focusing by negative refractive sonic crystal flat lenses

In this study, wave propagation anisotropy in a triangular lattice crystal structure and its associated waveform shaping in a crystal structure are investigated theoretically. A directional variation in wave velocity inside a crystal structure is shown to cause bending wave envelopes. The authors report that a triangular lattice sonic crystal possesses six numbers of a high symmetry direction, which leads to a wave convergence caused by wave velocity anisotropy inside the crystal. However, two of them are utilized mostly in wave focusing by an acoustic fiat lens. Based on wave velocity anisotropy, the pseudo ideal imaging effect obtained in the second band of the flat lens is discussed.

Theoretical demonstration of the hybrid focusing points of sonic crystal flat lenses and possible applications

We demonstrate the hybrid focusing points of sonic crystals for a multi-source array applied to flat sonic crystal lenses. The contributions of different point source couples form hybrid focusing points. Ray-trace analyses are conducted for acoustic flat lenses with multi-source configurations. The finite-difference time-domain （FDTD） simulation of flat lenses with multi-source configurations demonstrates the establishment of pure and hybrid focusing points in a pyramidal constellation. The number of focusing points in the pyramidal constellation depends on the number of point sources. We propose an acoustic device for fine-tuning the location of a far-field hybrid focusing point and discuss its benefits for acoustic energy focusing application.

Negative refractions by triangular lattice sonic crystals in partial band gaps

This study numerically demonstrates the effects of partial band gaps on the negative refraction properties of sonic crystal. The partial band gap appearing at the second band edge leads to the efficient transmissions of scattered wave envelopes in the transverse directions inside triangular lattice sonic crystal, and therefore enhances the refraction property of sonic crystal. Numerical simulation results indicate a diagonal guidance of coupled scattered wave envelopes inside crystal structure at the partial band gap frequencies and then output waves are restored in the vicinity of the output interface of sonic crystal by combining phase coherent scattered waves according to Huygens＇ principles. This mechanism leads to two operations for wavefront engineering： one is spatial wavefront shifting operation and the other is convex-concave wavefront inversion operation. The effects of this mechanism on the negative refraction and wave focalization are investigated by using the finite difference time domain （FDTD） simulations. This study contributes to a better understanding of negative refraction and wave focusing mechanisms at the band edge frequencies, and shows the applications of the slab comer beam splitting and SC-air multilayer acoustic system.

Sonic Scanner声波扫描测井在碳酸盐岩储层裂缝有效性评价中的应用——以四川盆地震旦系为例

电成像测井探测深度较浅,无法判定井壁上识别出的裂缝在地层中的延伸情况。利用电成像测井识别出的裂缝走向与Sonic Scanner声波扫描测井确定的横波各向异性方位进行综合建模,以确定地层中裂缝引起的各向异性和井壁内裂缝的延伸情况,进而评价裂缝的有效性。该方法在四川盆地震旦系灯影组缝洞型碳酸盐岩地层中取得了较好的应用效果。通过Sonic Scanner声波扫描测井和电成像测井结合能够准确评价井筒周围裂缝的有效性,为储层评价及试油层段优选提供可靠依据。

Parallel Simulation of 3D Wave Propagation by Domain Decomposition

In order to perform large scale numerical simulation of wave propagation in 3D heterogeneous multiscale viscoelastic media, Finite Difference technique and its parallel implementation based on domain decomposition is used. A couple of typical statements of borehole geophysics are dealt with—sonic log and cross well measurements. Both of them are essentially multiscales, which claims to take into account heterogeneities of very different sizes in order to provide reliable results of simulations. Locally refined spatial grids help us to avoid the use of redundantly tiny grid cells in a target area, but cause some troubles with uniform load of Processor Units involved in computations. We present results of scalability tests together with results of numerical simulations for both statements performed for some realistic models.

Simple waves for two-dimensional compressible pseudo-steady Euler system

A simple wave is defined as a flow in a region whose image is a curve in the phase space. It is well known that ＂the theory of simple waves is fundamental in building up the solutions of flow problems out of elementary flow patterns＂ see Courant and Friedrichs＇s chassical book ＂Supersonic Flow and Shock Waves＂. This paper mainly concerned with the geometric construction of simple waves for the 2D pseudo-steady compressible Euler system. Based on the geometric interpretation, the expansion or compression simple wave flow construction around a pseudo-stream line with a bend part are constructed. It is a building block that appears in the global solution to four contact discontinuities Riemann problems.

地下煤火分维—分级探测预警技术研究

为实现煤自燃隐蔽火源的高效监测预警和防治,本文对地下煤火分维—分级探测预警技术展开研究。首先,揭示煤自燃受热升温及燃烧过程的煤自燃的电磁—声波—温—气变化特征,形成电磁—声波—氡气—红外多维探测方法,实现井上井下联合多维探测应用;其次,根据大尺寸煤自燃指标气体产生规律,建立基于正压输运的煤自燃监测预警体系,实现地下煤自燃发火的分级精准预警;最后,依据复杂区域综放面煤层自燃发火特点、影响因素及变化规律,提出复杂开采煤自燃灾害综合防治技术体系。研究成果可为井下煤自燃灾害预警防治提供依据与参考。

声波法测试玻璃纤维杨氏模量

声波法是一种无损检测玻璃材料模量的方法,但对被测样品的形状、尺寸等有所限制。在测试玻璃纤维模量时,声波法会因发射信号的传递效率、接收灵敏度以及样品的差异性等因素影响测试结果。通过调整声波振动的频率和纱线的纤维数量,研究声波法测试玻璃纤维模量的可行性。结果表明,波频增高后(5 kHz),经过玻璃纤维的信号强度减弱;200 Hz的振动波具有良好的精度(变异系数≤3.73%),以及拟合优度(R^(2)=0.9999)。此外,通过与拉伸法对比,发现测试结果均保持一致性:随着纱线纤维数量的增加,弹性模量下降,且单丝的弹性模量高于复丝的弹性模量。该研究可为纤维材料模量的无损检测提供参考。

基于声波测井资料的波动方程走时层析反演速度建模

地震勘探目标逐渐由浅层(<2000 m)转向中深层(2000~3500 m),高精度速度建模是实现精确地震成像的关键手段之一.目前,初至波或早至波速度层析建模方法已较为成熟,然而对深层速度建模更为重要的反射波层析建模方法依然面临走时拾取困难及计算量大等难题.针对当前中深层走时层析速度建模方法面临的难题,本文提出了一种基于声波测井资料的波动方程全波走时层析速度建模方法及策略.该方法首先通过早至波层析反演获得浅层及大尺度速度信息;其次,通过提取初次成像剖面的构造倾角信息,利用声波测井资料进行稀疏反演,进一步获得更高精度的速度模型;最后,以此为初始模型,进行全波层析反演获得最终偏移速度模型.数值结果表明,本文所提出的速度建模方法及策略不仅可以避免传统反射波层析建模方法因采用Born近似反偏移所带来的大计算量问题,且大幅提高了中深层速度建模的精度,进而能有效地提高中深层复杂构造区域的地震成像质量.

京港高铁万安隧道音爆现象分析及缓解措施研究

列车运营速度不断提高容易引发高速铁路长大隧道音爆现象,对洞口声环境及行车秩序造成负面影响,而音爆发生机制及相关空气动力学指标特性尚不明确。基于京港高铁万安隧道实车试验,从音爆产生机制和原因、音爆声波频域特性、压力梯度与微气压波规律展开分析,并结合三维精细化数值仿真增补实车测试工况,针对测试隧道探究不同缓解措施的气动缓解效果。结果表明:1)压缩波在无砟轨道隧道内传播过程中,在非线性效应作用下发生激化,由此诱发了音爆的发生。2)音爆发生时,隧道洞外和洞内的音爆噪声中0~20 Hz的低频段占主要部分。3)列车时速低于300 km时,压缩波在隧道内激化较弱,隧道洞口未出现音爆噪声;当列车时速达到300 km时,压缩波在隧道内激化显著,洞口微气压波幅值较时速250 km时增长近5.5倍,洞口能够监测到明显的音爆噪声。4)对于测试隧道,3种缓冲结构型式缓解措施对于微气压波的缓解效果排序为进、出口同时增设动力学开孔<出口增设动力学开孔<开启3处斜井。

麦克风集群网络模型及其障碍物识别中的应用

基于声学基本原理和抽象空间的网络结构方法,开发了一种创新的障碍物检测系统,其结构包括硬件终端、多声路网络模型和分类器。硬件终端由立体式分布的麦克风节点、数据采集卡和工控机组成。多声路网络模型能够基于多路声波信号建立网络结构,并提取和计算多路声波复杂信号中的有效信息。分类器采用主成分分析方法(Principal Component Analysis,PCA)对提取的有效信息进行降维处理,再采用监督学习方法实现对环境的分类和识别。该系统的开发不仅为汽车自动驾驶、机器人导航和无人机等领域提供了重要的技术支持,而且为智能导航和自动化领域的技术发展提供了新的可能性。未来的工作将进一步优化系统性能,提高其应用的广泛性和经济效益。

裂缝性储层阵列声波成像测井响应模拟及速度频散特征研究

为分析裂缝性储层中裂缝发育带对阵列声波测井响应的影响,本文采用交错网格有限差分算法实现孔弹介质阵列声波测井波列响应的数值模拟。通过对模拟波形速度频散信息的提取,总结裂缝发育带与扩径井段不同模式波的吸收衰减与速度频散响应特征的差异性。首先基于Biot孔弹介质模型导出柱坐标下弹性波的速度-应力方程;其次,用交错网格有限差分方法对孔弹波动方程进行离散化,为提高模拟算法效率与精度,使用高阶差分格式与NPML;最后,基于含倾斜裂缝带模型与井壁坍塌地层模型的响应模拟,用前后向振幅相位估计法分析阵列声波的波形幅度相位响应特征与速度频散的差异性。结果表明,低速裂缝带纵横波波场时差会增大,且衰减幅度随裂缝带倾角变化;井壁塌陷在径向与轴向上扩大时,会增强斯通利波与伪瑞利波衰减。声波纵横波时差、速度频散与幅度衰减均可反映一定的裂缝带特征,这些影响对评价和开发裂缝性储层具有重要意义。

高速铁路长大隧道音爆现象及斜井辅助泄压缓解效果研究

随着高速铁路隧道运营速度不断增大,隧道空气动力学问题日益凸显。为此,首先调研整理国内外典型高速铁路隧道音爆案例,并在国内某隧道开展一系列实车测试试验,分析200,250和300 km·h^(-1)3个典型速度条件下隧道内初始压缩波压力梯度与洞口微气压波峰值变化规律,并对比不同斜井启闭条件下的辅助泄压缓解效果。结果表明:音爆现象主要发生在长度大于5.0 km隧道;当列车速度低于300 km·h^(-1)时,测试隧道内初始压缩波压力梯度峰值与隧道洞口微气压波峰值相对较小,此时压缩波未发生激化,测试隧道洞口未监测到音爆;当列车速度达到300 km·h^(-1)及以上时,压缩波发生激化,初始压缩波压力梯度峰值与洞口微气压波峰值分别超过90 kPa·s^(-1),150 Pa,此时在测试隧道洞口监测到明显音爆现象;相同速度条件下,不同动车组通过测试隧道时隧道内初始压缩波压力梯度峰值与洞口微气压波峰值存在一定差异,CRH380系列动车组测试数据低于CR400系列动车组;开启斜井能够缓解压力梯度及微气压波峰值,但开启压力梯度峰值达到最大值位置之前的斜井缓解效果更好,而同时开启隧道进口、出口处2个斜井对于压力梯度峰值缓解率最大可达到27.5%。

基于声波测试的矿柱稳定性模糊推理系统及其应用

分析了矿柱波速变化与载荷之间的关系以及矿柱破裂区分布与波速分布的对应关系,讨论了矿柱波速与其稳定性之间的模糊不确定性的特点,在此基础上,应用模糊数学理论建立了以完整系数为输入变量、矿柱稳定程度及局部破坏可能性为输出变量的模糊推理系统。将该推理系统应用于浙江遂昌金矿矿柱稳定性声波测试工程实践中,得到的推理结果与现场实际情况基本一致,即使在声波测点较少的情况下,系统仍具有良好的推理效果。

基于Hoek-Brown准则的开挖扰动引起围岩变形特性研究

Hoek-Brown经验准则(2002版)考虑施工扰动对岩体参数劣化效应,并提出扰动系数D,但仅为粗略定性化描述。现应用声波测试法获得的岩体波速降λ对扰动系数D进行优化处理,并将优化后的Hoek-Brown经验准则运用于开挖扰动引起岩体弹塑性变形特征方程的求解研究,进而可实现较精确表示围岩塑性圈半径。为验证该理论的合理性,综合运用声波测试法、位移监测法等监测手段及有限元数值模拟法予以对比分析。此外,考虑开挖扰动变形特征场地效应,提出可拟合不同岩性、不同开挖方式的变形与开挖扰动经验公式。工程实例计算结果表明:对Hoek-Brown经验准则(2002版)扰动系数D的优化合理,用其可计算开挖扰动引起的围岩弹塑性变形特征值。并可准确求得塑性圈半径值,同时,拟合得到变形与开挖扰动经验公式可满足不同工程需要,具有一定合理性。所获结果可为Hoek-Brown经验准则(2002版)及地下洞室开挖扰动引起岩体变形特性研究提供一定方法参考。

孔洞型碳酸盐岩地层超声波实验研究

为研究孔洞型碳酸盐岩储层的地震响应特征,利用基于地质模型的超声波实验观测方法,在孔洞系统中建立了单、多孔物理模型,通过大量的超声波透射实验,观测了不同孔洞模型的超声波响应特征,分析了探头频率、孔密度和孔排列方式对地震波属性参数的影响。结果表明:①探头频率与孔洞模型地震波的各项属性参数之间存在着一定的相关性;②孔密度对模型的地震波部分特征参数有明显影响,振幅和品质因子的衰减比速度对岩石孔密度变化更为敏感;③孔的排列方式对模型的地震波基本特征参数影响不明显,但在相同孔密度的条件下,轴向排列的孔状态明显小于其他径向孔状态的速度。该研究成果为地震资料解释及储层评价提供了依据。

低温超声波化学镀镍层的组织结构与性能

研究了低温（～４０℃）超声波化学镀镍层的初期析出行为、组织和相结构，并与常规化学镀镍层进行了比较，结果表明低温超声波化学镀镍层细密均匀，而常规化学镀镍层晶粒粗大且呈不均匀状态，在镀层的横截面上有分层现象。低温超声波化学镀镍层主要为非晶态，夹有少量微晶。

声波在高含蜡油生产中防蜡作用的实验研究

含蜡原油在生产过程中，蜡组分随井筒温度的降低而逐渐析出，这种结蜡现象导致原油粘度 急剧上升而影响油井的正常生产，因此采取防蜡措施在高含蜡原油生产中是必不可少的。利用声波 进行防蜡的实验研究表明，声波作用可以破坏蜡晶网状结构，降低原油粘度和凝固点，从而达到防蜡 的目的。声波防蜡以其独特的作用机理较其它防蜡方法具有更大的可靠性和更加广阔的应用前景。