岩石中诱发脉冲的声发射场的频谱分析及应用     

Roza.  AO 《CT理论与应用研究》1999,8(1):47-51

本文用光弹性的方法记录岩石中诱发脉冲的自然振动场,并做频谱分析,这种方法可以测量波动的应力,用以显示在有限尺寸的非均匀固体或岩层结构中,由于破裂成核结构的形成而激发的声发射频谱。地声频谱方法的一个应用,是探测宏观破碎断裂面或不同岩性的断裂面。本文的结果,可导致对不同频率波的层析成像;可对矿山的岩体断层定位作出贡献,从而有助于预测矿井的灾害。在实验室中岩层破裂时声发射系列的频谱模式,可能转用于天然强震系列频谱作模拟类比。  相似文献   

高阶seislet变换及其在随机噪声消除中的应用   总被引：13，自引：6，他引：7       下载免费PDF全文

刘洋  FOMEL Sergey  刘财  王典  刘国昌  冯晅 《地球物理学报》2009,52(8):2142-2151

Seislet变换是一种小波类数学变换方法,主要根据不同小波级数上地震同相轴的局部倾角的不同来分析数据.一般意义上,测线方向上的离散小波变换（DWT）是一种特殊的零局部地震倾角的seislet变换.早期的工作基于低阶版本的离散小波变换来构建seislet变换,在本文中,通过使用Cohen-Daubechies-Feauveau (CDF) 9/7双正交小波变换（常用于JPEG2000压缩标准）作为框架,扩展高阶seislet变换方法.通过分析理论模型和实际数据的处理结果,并对比傅里叶变换、离散小波变换和低阶seislet变换,高阶seislet变换可以为地震数据提供更好的压缩比.因此更加适用于地震数据去噪处理.  相似文献   

Initiation and Propagation of Compaction Bands in Dry and Wet Bentheim Sandstone     

Sergei Stanchits  Jerome Fortin  Yves Gueguen  Georg Dresen 《Pure and Applied Geophysics》2009,166(5-7):843-868

We investigated initiation and propagation of compaction bands (CB) in six wet and four dry Bentheim sandstone samples deformed in axial compression tests with strain rates ranging from 3.2 × 10^?8 s^?1 to 3.2 × 10^?4 s^?1. Circumferential notches with 0.8-mm width and 5-mm depth served to initiate CB at mid-sample length. Wet samples were saturated with distilled water and deformed at 195 MPa confining pressure and 10 MPa pore pressure. Dry samples were deformed at 185 MPa confining pressure. Twelve P-wave sensors, eight S-wave sensors and two pairs of orthogonally oriented strain-gages were glued to the sample surface to monitor acoustic emission (AE), velocities and local strain during the loading process. Nucleation of compaction bands is indicated by AE clusters close to the notch tips. With progressive loading, AE activity increased and AE hypocenters indicated propagation of a single CB normal to the sample axis. CB propagation from the sample periphery towards the centre was monitored. Microstructural analysis of deformed samples shows excellent agreement between location of AE clusters and CBs. In both dry and wet samples the lateral propagation of CBs was about 100 times faster than axial shortening rates. At the slowest displacement rate, AE activity during band propagation was reduced and CB nucleation in wet samples occurred at 20% lower stresses. This may indicate an increasing contribution of stress corrosion processes to the formation of the compaction bands. In dry and wet samples inelastic compaction energy per area ranged between 16 and 80 kJ m^?2. This is in good agreement with previous estimates from laboratory and field studies.  相似文献   

July 2020 heavy rainfall in Japan: effect of real-time river discharge on ocean circulation based on a coupled river-ocean model     

Chang  Yu-Lin K.  Varlamov  Sergey M.  Guo  Xinyu  Miyama  Toru  Miyazawa  Yasumasa 《Ocean Dynamics》2023,73(5):249-265

Ocean Dynamics - In July 2020, a stationary atmospheric front over Japan caused persistent, nearly continuous rain for most of the month that resulted in new historical highest rainfall records in...  相似文献   

Pattern-guided dip estimation with plane-wave destruction filters     

Zhiguang Xue  Houzhu Zhang  Yang Zhao  Sergey Fomel 《Geophysical Prospecting》2019,67(7):1798-1810

We propose to use pattern-guided dip estimation to mitigate aliasing problem that possibly exists in structure-oriented data processing. A straightforward and effective approach of generating pattern-guided dip is presented, which generally involves three rounds of standard dip estimation with plane-wave destruction filters. The first use of plane-wave destruction filter is for generating a mask operator distinguishing aliased and non-aliased data, based on measuring the uncertainty of the first dip estimation. The second plane-wave destruction filter uses the aliasing-free portions of the input data, and the dip in the aliasing-affected area is automatically padded with the ‘pattern’ dip by smoothing regularization. The result of the second plane-wave destruction filter is used as the initial dip for the inversion of the last-pass plane-wave destruction filter, which produces a pattern-guided dip. For some specific applications, the mask operator can be easily generated through other methods, and we can skip the first dip estimation. Two numerical examples, related to picking information using predictive painting and structure-oriented interpolation, respectively, demonstrate that our pattern-guided dip can effectively mitigate the aliasing problem in structure-oriented data processing.  相似文献   

Role of nitrates in the adaptation of fish to hypoxic conditions     

Sergey Dolomatov  Walery Zukow  Maciej Dzierzanowski  Jan Mieszkowski  Radoslaw Muszkieta  Mariusz Klimczyk 《Water Resources》2016,43(1):177-183

The paper reviews scientific and practical aspects of research on the metabolism of nitrates into nitrate (nitrite) reductase in the nitric oxide cycle in fish under hypoxic conditions. Literature data are given about enzymes involved in nitrate reductase reactions and how oxygen shortage affects their activity. The environmental factors that may participate in the processes of nitrate reduction to nitrites as well as the ones which may influence the kinetics of nitrate in fishes are considered. Examined results indicate that certain components of the conservative L-arginine-dependent nitric oxide cycle pass in a number of vertebrate animals. Then, the contour cycle of nitric oxide in the fish shows a wide range of diversity which is represented by phylogenetically ancient biochemical mechanisms of nitrite (nitrate) reductase. First of all, the presence or absence of hemoglobin is distinguished. Secondly, a wider range of expression of different myoglobin isoforms appears. Furthermore, the kinetics of nitrates in fish is distinctly dependent on abiotic environmental factors. The analysis of the literature confirms the thesis that nitrates are an important substrate for the nitrate (nitrite) reductase loop cycle of nitric oxide in fishes. Secondly, their role in the compensation of arginineindependent NO synthesis increases with decreasing oxygen levels in the environment. Thirdly, the provided research results are a basis for indicating xanthine oxidase and possibly the microflora of the digestive system as the basic units of the nitrate reductase system in the body of fish. The practical aspect of the question, in our opinion, is the most meaningful presence of numerous studies that emphasize the need to find physiological reactions that precede the formation of pathological changes induced by the influence of combined effects of nitrates and hypoxia on the organism of fish.  相似文献   

A robust approach to time‐to‐depth conversion and interval velocity estimation from time migration in the presence of lateral velocity variations          下载免费PDF全文

Sergey Fomel 《Geophysical Prospecting》2015,63(2):315-337

The problem of conversion from time‐migration velocity to an interval velocity in depth in the presence of lateral velocity variations can be reduced to solving a system of partial differential equations. In this paper, we formulate the problem as a non‐linear least‐squares optimization for seismic interval velocity and seek its solution iteratively. The input for the inversion is the Dix velocity, which also serves as an initial guess. The inversion gradually updates the interval velocity in order to account for lateral velocity variations that are neglected in the Dix inversion. The algorithm has a moderate cost thanks to regularization that speeds up convergence while ensuring a smooth output. The proposed method should be numerically robust compared to the previous approaches, which amount to extrapolation in depth monotonically. For a successful time‐to‐depth conversion, image‐ray caustics should be either nonexistent or excluded from the computational domain. The resulting velocity can be used in subsequent depth‐imaging model building. Both synthetic and field data examples demonstrate the applicability of the proposed approach.  相似文献   

北极圈数据库及为何需要     

JohnKimble SergeyGoryachkin 《冰川冻土》2002,24(5):532-537

Many factors, such the great changes of temperature, which will be expected at the high latitudes, increased pressure from humans to extract the natural resources in cold regions, seriously affect the cold environment. Many meetings have been held about the classification of cold soils, ideas and concepts of cold soils. These facilitate the need for developing a database of soils of the circumpolar region. The database can help offering information for potential problems in cold regions and for selecting the best areas for placement of new road and towns.  相似文献   

Understanding how physical-biological coupling influences harmful algal blooms,low oxygen and fish kills in the Sea of Oman and the Western Arabian Sea     

Paul J. Harrison  Sergey Piontkovski  Khalid Al-Hashmi 《Marine pollution bulletin》2017,114(1):25-34

In the last decade, green Noctiluca scintillans with its symbiont and other dinoflagellates such as Cochlodinium polykrikoides, Prorocentrum micans and Scrippsiella trochoidea have become the dominant HABs, partially replacing the previously dominant diatoms and red Noctiluca scintillans, especially during the northeast monsoon. Fish kills in the Sea of Oman are linked to a slow seasonal decline in oxygen concentration from January to November, probably due to the decomposition of a series of algal blooms and the deep, low oxygen waters periodically impinging the Omani shelf. In the western Arabian Sea, cyclonic eddies upwell low oxygen, nutrient-rich water and the subsequent algal bloom decays and lowers the oxygen further and leads to fish kills. Warming of the surface waters by 1.2 °C over the last 5 decades has increased stratification and resulted in a shoaling of the oxycline. This has increased the probability and frequency of upwelling low oxygen water and subsequent fish kills.  相似文献   

Data‐driven time–frequency analysis of seismic data using non‐stationary Prony method          下载免费PDF全文

Guoning Wu  Sergey Fomel  Yangkang Chen 《Geophysical Prospecting》2018,66(1):85-97

Empirical mode decomposition aims to decompose the input signal into a small number of components named intrinsic mode functions with slowly varying amplitudes and frequencies. In spite of its simplicity and usefulness, however, empirical mode decomposition lacks solid mathematical foundation. In this paper, we describe a method to extract the intrinsic mode functions of the input signal using non‐stationary Prony method. The proposed method captures the philosophy of the empirical mode decomposition but uses a different method to compute the intrinsic mode functions. Having the intrinsic mode functions obtained, we then compute the spectrum of the input signal using Hilbert transform. Synthetic and field data validate that the proposed method can correctly compute the spectrum of the input signal and could be used in seismic data analysis to facilitate interpretation.  相似文献