基于模型相似度拟合的海杂波统计方法

本文提出一种基于模型相似度拟合的海杂波统计方法。首先根据合成孔径雷达(SAR)图像计算瑞利分布、对数正态分布、韦布尔分布、K分布、G0分布5种经典的海杂波分布的概率密度函数,然后根据模型间的相似度准则拟合得到新的海杂波分布模型。文章利用四景不同类型的真实SAR数据对算法的拟合性能进行了评价,结果显示利用该算法得到的拟合模型与真实SAR数据的平均Kullback-Leibler距离仅为0.015 84,远优于其他分布模型。基于该拟合模型的恒虚警率舰船检测算法对四景SAR数据的平均检测精度达到95.75%,在控制虚警和漏检方面均优于采用其他模型的同类方法。     

Hierarchy property of traffic networks

The flourishing complex network theory has aroused increasing interest in studying the properties of real-world networks. Based on the traffic network of Chang--Zhu--Tan urban agglomeration in central China, some basic network topological characteristics were computed with data collected from local traffic maps, which showed that the traffic networks were small-world networks with strong resilience against failure; more importantly, the investigations of assortativity coefficient and average nearest-neighbour degree implied the disassortativity of the traffic networks. Since traffic network hierarchy as an important basic property has been neither studied intensively nor proved quantitatively, the authors are inspired to analyse traffic network hierarchy with disassortativity and to finely characterize hierarchy in the traffic networks by using the n-degree--n-clustering coefficient relationship. Through numerical results and analyses an exciting conclusion is drawn that the traffic networks exhibit a significant hierarchy, that is, the traffic networks are proved to be hierarchically organized. The result provides important information and theoretical groundwork for optimal transport planning.     

Hierarchy of Interrelationships in the Dynamics of Tropical Cyclones Activity

Izvestiya, Atmospheric and Oceanic Physics - The main task of this work was to reveal possible regression relations between parameters of an individual cyclone, inside groups of tropical cyclones...     

Acoustic imaging of an inhomogeneous sediment matrix

This paper presents and applies a new acoustic imaging approach to quantitatively determine geophysical parameters of complex inhomogeneous sediment layers. The concept is called an Acoustic Sub-seabed Interrogator or ASI and it is based on optimising the criteria of temporal and spatial resolution and of coherence by utilizing broadband, narrow beam calibrated sources and fixed receivers on a stationary platform.The ASI concept was experimentally tested over a complex pseudo-glacial till built at a scale of 20:1. Compressional velocity, attenuation losses and thickness values were easily attained using the ASI's coherent spatial scanning approach and through a discrete application of the Hilbert transform in the post processing of data. The simulations provided indepth insight into the model's physical and spatial variations and by statistical distribution emphasized the depositional processes involved in creating the layer. It is believed that the fundamental internal information elucidated by the ASI for the pseudo-till structure and illustrated in the resultant acoustic core cannot be attained using current marine geophysical and geotechnical techniques.     

Parametrization of turbulent fluxes over inhomogeneous landscapes

Reasons for the nonclosure of the heat balance in the atmospheric boundary layers over natural land surfaces are analyzed. Results of measuring the heat-balance components over different land surfaces are used. The Cabauw (Netherlands) data (obtained throughout 1996 over a grass surface with intermittent shrubs and single trees) and the data from the Anchor station in Germany (measured over coniferous forest in 2000–2001) are analyzed. In all, the analysis involves about fifty thousand independent values of the heat-balance components measured in the experiments, which should be indicative of the reliability of the results obtained in the paper. The data have shown that the heat balance is not closed and the imbalance is 50–250 W/m². The sum of the latent and sensible heat fluxes λE + H = STF is found to be systematically smaller than the difference between the net radiation and the heat flux into the ground R _n ? G. It is shown that the main cause of a systematic heat imbalance in the atmospheric boundary layers over inhomogeneous land surfaces is that the methods of surface-flux measurement and estimation are based on the theory that requires the hypothesis of stationarity and horizontal homogeneity. Direct data analysis has shown that the heat imbalance increases with landscape inhomogeneity. In the paper, a parametrization of the heat imbalance is carried out and the coefficient k _f (z ₀ ^ef /L ^ef ) is introduced as a measure of inhomogeneity. For this, data from the experiments FIFE, KUREX, TARTEX, SADE, etc., are also used. Empirical formulas are presented to refine the results of direct measurements and calculations of surface fluxes over natural (inhomogeneous) land surfaces from profile and standard (using bulk parametrizations) data. These formulas can also be used to determine surface fluxes over inhomogeneous underlying land surfaces in order to take into account so-called subgrid-scale effects in constructing prediction models.     

层次分析法在项目风险管理中的应用

针对现代项目风险管理涉及面广、技术复杂的特点，介绍了层次分析法(AHP)的理论及算法，对项目风险评估中出现的多指标、多方案的综合比较与选择问题提出了1种有效的解决方法；通过示例说明了在项目风险管理中如何应用该方法及其对提高项目管理水平所具有的重要意义。     

Modelling of the internal mechanics in ship collisions

A method for analysis of the structural damage due to ship collisions is developed. The method is based on the idealized structural unit method (ISUM). Longitudinal/transverse webs which connect the outer and the inner hulls are modelled by rectangular plate units. The responses are determined by taking into account yielding, crushing, and rupture. Some plates of the outer and the inner shell subjected to large membrane tensions are modelled by membrane tension triangular/rectangular plate units, while the remaining shell panels are modelled by the usual plate units. The effect of stiffeners on the stiffness and the strength is considered as well. In order to include the coupling effects between local and global failure of the structure, the usual non-linear finite-element technique is applied. In order to deal with the gap and contact conditions between the striking and the struck ships, gap/contact elements are employed. Dynamic effects are considered by inclusion of the influence of strain-rate sensitivity in the material model. On the basis of the theory a computer program has been written. The procedure is verified by a comparison of experimental results obtained from test models of double-skin plated structures in collision/grounding situations with the present solutions. As an illustrative example the procedure has been used for analyses of a side collision of a double-hull tanker. Several factors affecting ship collision response, namely the collision speed and the scantlings/ arrangements of strength members, are discussed.     

Experimental research on the evolution of wind waves in inhomogeneous currents

The results of an aircraft-ship experiment on the spatial variability of parameters of two-dimensional spectra of wind waves are discussed. The observed fields of wave parameters are compared with equations for wave refraction in the currents.Translated by Mikhail M. Trufanov.     

大洋岩石圈板块俯冲构造背景下流体的地质作用

地幔中存在着大量的“水”(存在形式:H₂O、H+和(HO)?)已是不争的事实,这些“水”既可以以流体或熔体的形式存在,又可以存在于含水矿物、名义上的无水矿物和致密含水镁硅酸盐中。在本文中,“流体”是指以水为主体包括溶解于水中或随水迁移的元素和化合物。在俯冲带的地震作用、地幔部分熔融、岩浆作用以及海底热液活动等重大地质作用过程中,流体都发挥着重要的作用。俯冲带是水化了的大洋岩石圈板块俯冲进入地球深处的关键部位,也是壳幔相互作用的重要地带。在俯冲带,流体随俯冲的岩石圈板块进入地球深部,部分在挤压和摩擦热的作用下脱逸俯冲的岩石圈板块,连同岩石矿物变质所产生的水进入上覆地幔楔,从而降低上覆地幔物质的熔点,产生岩浆;岩浆上升一方面加热了沿裂隙或物质间隙下渗的海水,另一方面也会因岩浆冷却产生岩浆作用后期热液流体,这些加热的下渗海水和岩浆作用后期流体构成了现代海底热液活动的物质基础;海底热液活动不仅将大量地下元素或物质输入大洋水体从而影响了大洋海水的物质组成及生态环境,而且在海底形成了具有重要经济价值的热液多金属矿体。因此,流体是贯穿板块俯冲及其所产生的各种重要地质作用过程的介质,从而成为研究这些重要地质作用的示踪剂。本文在分析了大洋岩石圈板块俯冲构造背景下流体的主要地质作用过程的基础上,探讨了流体在俯冲带地震发生机制、岩浆作用过程、现代海底热液活动模式及俯冲带流体成矿作用等方面的作用,并进一步提出近期研究工作应主要集中在4个方面:(1)进一步准确地定量评估通过板块俯冲作用进入地球深部的“流体”通量,为最终解决全球地球化学或物质循环问题作出贡献;(2)全面、准确地描述俯冲作用中流体的物理和化学行为,建立俯冲带流体地质作用的理论模型;(3)充分利用现代化的测试分析手段,重点获取矿物原位微区分析、矿物流体包裹体物理化学指标测试、稳定和放射性同位素分析等方面的精细准确数据,用于查明当前取样观测手段无法触及的地下深处物质状态和作用过程;(4)发展数值模拟技术,建立俯冲带流体地质作用的理论模型。     

Paragenesis of fluids under evaporates in the Volga-Ural Basin

To unravel the mystery of the relationship between evaporates, Ca–Cl brines and accumulations of oil and N₂ in the basins of ancient cratons, their N₂, CH₄ and He concentration ratios, as well as the isotopic composition (δ¹⁵N, δ¹³C and ³He/⁴He) were compared within the Volga-Ural basin. The study allowed subsalt fluids from Volga-Ural Basin to divide into two genetic groups. The first one is found within the basin's platform area. It includes Ca–Cl brines, high-viscosity heavy oil, bitumen and N₂, which has concentrations higher than that of CH₄ and positive values of δ¹⁵N. The second one is tied to the edge of the platform, the Ural Foredeep and Peri-Caspian Depression. In this group, only the oil and gas reservoirs, which have more CH₄ than N₂, and possibly negative values of δ¹⁵N, were discovered. Interaction of gas components in compared fluids indicates great role of degassing in the formation of their composition. It is suggested that the fluids of the first group (N₂ > CH₄) is what remains, and the second group (N₂ < CH₄) is what is disappears from the rocks during their metamorphism and degassing.     

Temperature fluctuations in the atmospheric surface layer over the thermally inhomogeneous underlying surface

The influence of both spatial and temporal temperature inhomogeneities of the underlying surface on the temperature field in an unstably stratified atmospheric surface layer is considered. The methods of correlation and spectral analyses are proposed to estimate statistical characteristics of surface-air temperature fluctuations caused by both turbulent mixing and inhomogeneities in the temperature of the underlying surface. Analysis of experimental data obtained from measurements in the atmospheric surface layer yields estimates for the contribution made by the time-dependent thermal properties of the underlying surface to the total variance of air-temperature fluctuations. It is shown that the additional air-temperature fluctuations generated by surface-temperature inhomogeneities and unrelated to shear flow may reach 70% and 30% of the total variance of measured fluctuations under variable cloudiness and clear skies, respectively. For the height z = 2 m within the wave-number range 2 × 10^?3 rad m^?1 < k < 0.1 rad m^?1, the contribution made by a spatial surface-temperature inhomogeneity to the variance of air-temperature fluctuations does not exceed 10% of the total variance. Correlation and spectral analyses of experimental data make it possible to isolate the spectra of properly turbulent fluctuations from the measured fluctuations and thus to obtain more accurate values of the universal function of similarity theory for temperature in the range of small wave numbers beyond the inertial range.     

Wind wave breaking under the conditions of inhomogeneous currents and of the atmospheric boundary layer

As known fromin situ observations, inhomogeneities of flows and of the atmospheric boundary layer produce variations of the intensity of wind wave breaking. A relevant phenomenological model is suggested here, describingin situ data on the breaking of waves in the presence of internal waves. The response of the wave breaking to the flow's inhomogeneity enhances with the growth of its spatial or temporal scale. For the mesoscale (10–100 km) inhomogeneities, the model is essentially simplified—wave breakings depict the local energy inputs to wind waves. The model allows us to compute currents of various type in the wave breaking intensity field. The results may have practical implications, in terms of remote sensing of the ocean. Translated by Vladimir A. Puchkin.     

Simulations of the explosive eruption of superheated fluids through deformable media

The sudden release of superheated fluids at depth can cause surface disturbances in the form of vents, mud volcanoes, or seafloor pockmarks. I have performed calculations with the Sage hydrocode (from Los Alamos and Science Applications International) of superheated venting in an idealised geometry, varying the pressure and velocity of hot fluid injected at depth. The simulations show several different patterns of propagation and fracturing in the deformable overburden. The simulations performed so far show, for different conditions, upward-propagating cylindrical pipes with hardened walls, narrowly diverging conical pipes, cone sheets, downward-propagating cracks, and funnel-shaped craters.     

Dynamics of Rossby waves in an ocean with inhomogeneous currents

A model for a two-layer ocean is applied to consider, in terms of the geometrical optics approximation, the effect of mean flows propagating within the upper layer upon the dynamics of Rossby waves. The case is theoretically analysed, with the depth of the ocean's upper layer much smaller than that of the underlying layer. In this case, the flow's impact upon the baroclinic mode of Rossby waves is ubiquitous, with the exception of synchronicity. Depending on the parameters, four types of wave packets' behaviour in the vicinity of synchronicity points are singled out, namely, the elimination of the peculiarity, shadowing, and convective/absolute instability. For the mean flow profile simulating cyclonic and anticyclonic gyres, we have obtained wave packet trajectories and have studied the wave packet's interaction with the current. Specifically, it has been demonstrated that, given some modulus of the wave packet, vigorous energy exchange between the wave vector and the flow takes place. Translated by Vladimir A. Puchkin.     

Structure and mechanics of nonpiscine control surfaces

Animals display a variety of control surfaces that can be used for propulsion and maneuvering devises. For nonpiscine vertebrates, these control surfaces are primarily evolutionary modifications of the paired appendages (i.e., legs). The diversity of control surfaces can be classified with regard to the forces used for stability and maneuverability. For animals, the pertinent forces are pressure drag, acceleration reaction, and lift. These forces can be generated actively by motion of the control surfaces or passively from flows produced by movements of the body or external flow fields. Drag-based control surfaces are associated with paddling and rowing movements, where the limbs are oriented either in the vertical parasagittal plane or horizontal plane, respectively. The paddle is unstreamlined and has a triangular design with a broad distal end, thereby affecting a large mass of water. Appendages, which are used to generate lift-based forces, are relatively stiff hydrofoils. To maximize lift, the hydrofoil should have a crescent wing-like design with high aspect ratio. This shape provides the hydrofoil with a high lift-to-drag ratio and high propulsive efficiency. The tail flukes of cetaceans are streamlined control surfaces with a wing-like design. The flukes of cetaceans function in the hydrodynamic generation of forces for thrust, stability, and maneuverability. The three-dimensional geometry of flukes is associated with the production of lift and drag. Previous studies of fluke geometry have been limited in the number of species examined and the resolution of measurements.     

Similarity parameters and a centrifugal convective instability of horizontally inhomogeneous circulations of the Hadley type

The stability of the zonal axisymmetric quasi-geostrophic hydrostatic solution to the equations of atmospheric dynamics that is determined by the horizontal temperature gradient is studied. Time-dependent regions of unstable solutions specified by the Rayleigh number describe ordinary convective (baroclinic) processes and the long-term weak growth of disturbances under the action of the centrifugal forces arising from the Earth’s rotation. Comparison with a centrifugal hydrodynamic instability is made. The spatiotemporal structure of the corresponding geophysical fields is described.     

一种基于数据层次性分析的水深综合研究

在分析和借鉴传统的水深综合理论和方法的基础上,开展水深数据的层次性分析,对水深数据进行分类、定级和聚合等处理方法研究。在满足制图综合规范的基础上,按照水深分类数据的重要性和特征性排序,重组综合方法使用顺序和结构,从而构建层次水深综合模型。该模型能够实现水深综合的流程控制,兼顾水深综合的质量要求,为进一步开展水深自动综合的实用性研究提供了理论和技术支持,具有一定实用价值。