共查询到20条相似文献，搜索用时 161 毫秒
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南海东北部受黑潮入侵、季风等动力因素的影响,背景剪切流场复杂,涡旋众多,水体垂向层结季节性变化明显,同时又因吕宋海峡的复杂底地形和强潮流的影响,内潮、内孤立波现象显著。但是,以往关于内潮、内孤立波的研究很少考虑到背景剪切流场和涡旋对其影响,因而难以揭示内波的生成、传播和演变规律。主要概述了南海东北部的剪切流、涡旋和内波等多种中尺度物理现象及其之间的相互作用的研究进展,进而提出未来关于南海东北部剪切流场对内波生成、传播和演变影响研究中的一些问题和研究思路。 相似文献
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太古宙岩群构造的研究是鉴别古构造型式的基础,也是研究古构造型式对矿带、矿田、矿床及矿体的生成与分布规律的基础.辽宁省鞍本地区是太古宙鞍山群典型发育地区之一,也是我国钢铁工业发展的重要原料基地,尽管这个地区开展工作较早,地质研究程度甚高,但是过去多侧重于地层划分和岩石学等方面的研究,在构造研究方面则缺乏系统性而又局限于传统构造学观点,因此许多复杂的地质构造问题长期没有得到解决.如该区的构造格架、构造期次划分、构造变形特征及其对铁矿的控制等,这些都是地质勘探及矿山开发部门所急待解决的问题.近几年来我们在鞍山冶金地质勘探公司及其所属研究所、地质队以及鞍钢、本钢所属矿山等部门的大力支持和协助下,对本区开展了专题研究工作,并取得一些认识上的新进展. 相似文献
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有关煤层气几个基本问题的认识 总被引：6，自引：1，他引：6
目前国内兴起了煤层气热，对有关煤层气的若干基本问题需要认真加以思考。笔者就煤层气的生成、赋存、运移及其影响因素的一些基本概念和煤层气勘探开发研究、评价的方法途径问题谈了一些独到的认识。 相似文献
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由于转换波本身的特殊性,在处理过程中需要采用不同于纵波的处理方法。分析了转换波处理过程中的一些问题,即面波衰减、静校正、各向异性动校正,以及方位各向异性校正,提出相应的解决方法。采用极化滤波方法,实现了转换波上的面波衰减。采用综合静校正技术,切实解决转换波静校正问题。各向异性速度分析及动校正方法,用于拉平转换波资料的近、中和远偏移距同相轴。通过横波分裂分析及分量校正补偿,提高了转换波径向剖面质量。根据实际资料处理效果,说明了这些方法的有效性。 相似文献
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有关煤层气八个基本问题的认识 总被引：6，自引：0，他引：6
目前国内兴起了煤层气热，对有关煤层气的若干基本问题需要认真加以思考，笔者就煤层气的生成，赋存，运移及其影响因素的一些基本概念和煤层气勘控开发研究，评价的方法途径问题谈了一些独到的认识。 相似文献
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当前环境工程地质领域的几个主要问题及研究对策 总被引：9，自引：2，他引：9
本文总结了当前环境工程地质领域几个急待研究解决的主要问题, 分析了这些问题的研究现状, 主要科学问题及研究对策。最后, 提出了研究解决这些问题的基本技术路线。 相似文献
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北太平洋Rossby波研究进展 总被引：3，自引：0，他引：3
系统地阐述了北太平洋Rossby波在卫星观测、理论扩展及模型应用3个方面的研究成果.随着卫星观测技术的发展,明显地探测到海表面信号的Rossby波特征,且观测到波速在热带外大于自由Rossby波理论值.为解释这个波动加速现象,在自由Rossby渡理论的基础上,考虑了大气强迫、非静止基流及海底地形等因子的作用,使得Rossby波的波动理论得到了扩展.而关于风应力强迫Rossby波的线性理论模型主要有3类:一阶斜压Rossby波模型、局地Ekman抽吸模型和Svetdrup平衡模型.这些模型被广泛地应用到北太平洋海表面高度和温度/密度跃层深度等要素变化的机理研究中,得到了不同的模型在大洋的不同区域有不同的作用等结论.最后,对线性Rossby波研究存在的问题进行了初步探讨,提出了需要进一步解决的新课题. 相似文献
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The case of a freak wave collision with the ship in the Agulhas current is described. The explanation of the appearance of the freak wave as a result of wind-wave transformation in the Agulhas current is given. Swell is captured and intensified by the counter-current and is located in the neighbourhood of the maximum value of the current velocity, as a result of which there is a great concentration of wave-energy density. The superposition of wind and sea with swell transformed by the current promotes the formation of the freak waves. Using a simple mathematical analysis, an optimal ship track is proposed which could reduce the risk of collision with a freak wave. 相似文献
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S. M. Bawiskar M. D. Chipade D. K. Paul S. S. Singh 《Journal of Earth System Science》1995,104(4):613-634
Kinetic energy exchange equations (Saltzman 1957) in wave number domain are partitioned into standing, transient and standing-transient
components following Murakami (1978, 1981). These components are computed for the 1991 summer monsoon using dailyu andv grid point data at 2.5° latitude-longitude interval between the equator and 40°N at 200 hPa and 850 hPa levels for the period
June through August. The data are obtained from NCMRWF, New Delhi.
The study shows that at 200 hPa wave number 1 over Region 3 (30°N to 40°N), wave number 2 over Region 2 (15°N to 30°N) and
wave number 3 over Region 1 (equator to 15°N) dominate the spectrum of transport of momentum and wave to zonal mean flow interaction.
Wave number 1 over Region 1 and Region 3 and wave number 2 over Region 2 are the major sources of kinetic energy to other
waves via wave-to-wave interaction. At 850 hPa wave number 1 over Region 3 has maximum contribution in the spectrum of transport
of momentum and kinetic energy and more than 90% of its contribution is from the standing component. This indicates that standing
wave number 1 over Region 3 plays a very important role in the dynamics of monsoon circulation of the lower troposphere.
The study further shows that although the circulation patterns at 200 hPa and 850 hPa levels are opposite in character, a
number of energy processes exhibit a similar character at these levels. For example, (i) transport of momentum by most of
the waves is northward, (ii) small scale eddies intensify northward, (iii) eddies are sources of kinetic energy to zonal mean
flow over Region 1 and (iv) standing eddies are sources of kinetic energy to transient eddies. Besides the above similarities
some contrasting energy processes are also observed. Over Region 2 and Region 3 standing and transient eddies are sources
of kinetic energy to zonal mean flow at 200 hPa, while at 850 hPa the direction of exchange of kinetic energy is opposite
i.e. zonal mean flow is a source of kinetic energy to standing as well as transient eddies. L(n) interaction indicates that at 200 hPa waves over R2 maintain waves over R1, while at 850 hPa waves over R1 maintain waves
over R2.
It has been found that the north-south gradient of zonal mean of zonal wind is the deciding factor of wave to zonal mean flow
interaction. 相似文献
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地球各向异性介质中地震波动理论、检测与应用研究 总被引：11，自引：0，他引：11
地下岩石的各向异性主要表现在地震波速度随传播方向发生变化,不同类型体波间相互耦合,横波发生分裂,波速度频散依赖于传播方向等。薄互层与裂隙定向分布等产生视各向异性,它在石油地震勘探、地震预测和岩石圈物理与动力学研究中有极大潜力和应用前景,并受到广泛重视。为此,文中讨论了地震各向异性研究在解决地球科学问题中的重要性与必要性;系统地介绍了中国在地震各向异性研究领域的各个方面,如波动传播、波场激发、数值模拟、偏移与反演成像,以及应用于油气资源探测、深部地球物理研究和地质灾害监测等方面所取得的新进展。结合笔者参加的第八届地震各向异性国际学术讨论会,及ＳＥＧ,ＩＡＳＰＥＩ,ＩＵＧＧ等有关学术会议情况,综述了国际上在该领域内的主要成果与发展动向,分析了国际上各国地震各向异性研究现状及存在问题,并对我国在该领域研究的进一步开展提供了主攻问题与相应建议。 相似文献
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深水沉积物波是一种海底普遍发育、规模较大的波状沉积体,大多数学者将它们解释为等深流沉积或浊流沉积。本文结合内波理论的研究进展，考虑内波沉积作用的水动力学特征，探讨了深水沉积物波的内波成因机制。得出以下几点认识：①海底流动单独作用无法满足沉积物波形成所需的流动层厚度及流动速度，较难解释沉积物波的迁移方向及规则的内部及外部形态。②内波可以引起海底流动，内波比表面波更容易形成更大规模范围内的沉积床形。③内波可以形成大型沉积物波，用内波可以较合理地解释内波的对称波形单元、非对称波形单元及上攀波形单元的成因。波动面离海底距离较大的行进内波及内驻波可以形成对称波形的沉积物波；波动面离海底距离较近的行进内波及内孤立波可以形成非对称波形的沉积物波；内波引起的海底流动进一步增强时，可形成上攀波形沉积物波。④行进内波可以形成向内波传播相反方向迁移的沉积物波，向海盆内部传播的内波可以形成向上坡方向迁移的沉积物波。 相似文献
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Doklady Earth Sciences - Cases of “freak waves” that occurred in the period from 2011 to 2018 and information on which is currently available are analyzed. In total, 210 cases of... 相似文献
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A laboratory experiment to monitor the contact state of a fault by transmission waves 总被引：1，自引：0，他引：1
We performed a series of laboratory experiments in which elastic waves were transmitted across a simulated fault. Two types of experiments were carried out: (1) Normal Stress Holding Test (NSHT): normal stress was kept constant for about 3 h without shear stress and transmission waves were observed. (2) Shear Stress Increasing Test (SSIT): shear stress was gradually increased until a stick-slip event occurred. Transmission waves were continuously observed throughout the process of stress accumulation. We focused on the change in transmission waves during the application of shear stress and especially during precursory slips.It was found in NSHT that the amplitude of transmission waves linearly increased with the logarithm of stationary contact time. The increase amounted to a few percent after about 3 h. Creep at asperity contacts is responsible for this phenomenon. From a theoretical consideration, it was concluded that the real contact area increased with the logarithm of stationary contact time.We observed in SSIT a significant increase in wave amplitude with shear stress application. This phenomenon cannot be attributed to the time effect observed in NSHT. Instead, it can be explained by the mechanism of “junction growth” proposed by Tabor. Junction growth yields an increase in real contact area. It is required for junction growth to occur that the material in contact is already plastic under a purely normal loading condition. A computer simulation confirmed that this requirement was satisfied in our experiments. We also found that the rate at which the amplitude increased was slightly reduced prior to a stick-slip event. The onset time of the reduction well coincides with the onset of precursory slip. The cause of the reduction is attributed to the reset of stationary contact time due to displacement. This interpretation is supported by the result of NSHT. Taking the time of stationary contact in SSIT into account, we may expect the change in wave amplitude to be, at most, only a few percent. The observed slight reduction in increasing rate is, in this sense, reasonable. The static stiffness of the fault also decreases with precursory slip. It was also found that low frequency waves are a better indicator of precursory slip than high frequency waves. This might suggest that low frequency waves with longer wavelength are a better indicator of average behavior of faults. The problem, however, merits a further investigation. The shifts in phase were also found to be a good indicator of the change in contact state of the fault. The changes in both amplitude and phase of transmission waves are unifyingly understood through the theory of transmission coefficient presented by Pyrak-Nolte et al. Rough surfaces have a tendency to give larger stick-slips than smooth surfaces. The amount of precursory slip is larger for rough surfaces than for smooth surfaces. Although it was confirmed by a computer simulation that rough surfaces have larger contact diameters than smooth surfaces, the rigorous relationship between the surface roughness (contact diameter) and the amount of precursory slips was not established. 相似文献
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A simple compact equation for gravity water waves, which includes a nonlinear wave term and advection term, is derived. Numerical simulations in the framework of this equation demonstrate an initial stage of freak wave breaking. 相似文献
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饱和半无限体表面透水性会影响表面波（瑞利波和斯通利波）存在及其传播特性。在表面透水情况下,只有瑞利波存在,而在不透水情况,不仅有瑞利波而且还有斯通利波。表面波在工程勘探及声波测试中扮演很重要角色,因此,有必要研究表面透水性对表面波传播特性的影响。采用薄层法,将表面波频率方程根的搜索问题转换成求特征值问题。根据表面波沿深度衰减特性,从一组计算的特征值及特征向量中筛选出与表面波对应特征值、特征向量,由特征值得到表面波频率特性（频散和衰减特性）,由特征向量得到孔隙压力、骨架位移随深度变化,进而分析在表面不透水情况下瑞利波和斯通利波影响深度及程度。 相似文献
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利用高频面波反演横波速度一直是浅地表地震工程研究的热点。为深入认识利用高频面波（瑞雷波和勒夫波）评价横波速度的能力,本文首先采取高阶交错网格有限差分法实现两层模型的瑞雷波和勒夫波数值模拟,并应用τ-p变换形成频散能量图。相比瑞雷波,不同模式的勒夫波频散能量很接近,这说明易于实现多模式勒夫波反演。然后利用线性映射实现广义模式识别这种非线性反演方法对含软弱夹层的四层模型的基模式、多模式瑞雷波和勒夫波的变厚度反演。若初始模型很拙劣,相比勒夫波,瑞雷波基模式反演不能重建地层中含有软弱夹层这一特征,瑞雷波多模式反演则可以重建这一特征;勒夫波基模式和多模式反演都可以重建这一特征。即使在地层的泊松比与估计值相差很大时,瑞雷波多模式反演仍能重建地层结构,但其频散曲线总是存在"模式接吻"现象,容易模式误判;而勒夫波反演则不用估计地层泊松比,也不存在"模式接吻"现象。一系列算例表明：高模式瑞雷波的加入会显著提高横波速度评价结果的精度;而高模式勒夫波的加入会令反演系统对半空间以上异常层的参数过于敏感,造成参数过度估计,但也会显著提升对半空间横波速度的评价能力。最后,应用本文方法实现了对实测勒夫波数据的分析。 相似文献