一种基于GPU和内存映射文件的高分辨率遥感图像快速处理方法     

马秀丹  崔宾阁  钟勇  张永辉  费东 《海洋科学》2018,42(1):139-146

高分辨率遥感图像处理经常面临程序执行时间过长和内存空间不足的问题,虽然并行计算技术可以提高遥感图像的处理速度,但是无法降低算法占用的巨大内存空间。为了解决这一问题,本文提出了一种利用CUDA和内存映射文件的高分辨率遥感图像快速处理方法,并以K-Means算法为例进行了实现。其中,CUDA技术可以有效利用GPU强大的并行计算能力,而内存映射文件技术降低了磁盘I/O速度较慢对算法性能的影响。实验结果表明,本文方法比传统K-Means聚类算法计算速度提高了30倍左右,内存使用量降低了90%以上。  相似文献   

Risk identification and perception in the fisheries sector: Comparisons between the Faroes,Greece, Iceland and UK     

Diana Tingley  Jóhann Ásmundsson  Edward Borodzicz  Alexis Conides  Ben Drakeford  Ingi Rúnar Eðvarðsson  Dennis Holm  Kostas Kapiris  Sakari Kuikka  Bogi Mortensen 《Marine Policy》2010

This paper presents the findings of risk identification and risk perception research conducted in relation to the fisheries systems of four distinct and diverse European countries: Faroes, Iceland, Greece and the UK. Risk research traditionally attempts to quantify the potential threat or consequences from a range of risk events or hazards. This research, however, adopted a social sciences perspective and so assumed that a risk event or hazard can mean different things to different people and that these perceptions are also context and culturally dependent. Risk perceptions were examined and risk registers developed in each country for a range of stakeholder groups. A ‘mental modelling’ approach was adopted in a series of qualitative interviews. Findings were examined in terms of a wide range of psychological, social and cultural risk theories. Differences in risk perceptions were noted between stakeholder groups and countries and contextual influences were examined such as the widely differing fisheries management systems used in each country. This research provides one of the first attempts to systematically evaluate risks and perceptions across a range of fisheries-systems. The findings support social science theories which argue that risk is a subjective, as opposed to objective, concept and that this subjectivity will therefore affect our attempts to assess and manage those hazards we think we can potentially influence or control.  相似文献   

Fast numerical solution of the linearized Molodensky problem     

R. Klees  M. van Gelderen  C. Lage  C. Schwab 《Journal of Geodesy》2001,75(7-8):349-362

 When standard boundary element methods (BEM) are used in order to solve the linearized vector Molodensky problem we are confronted with two problems: (1) the absence of O(|x|⁻²) terms in the decay condition is not taken into account, since the single-layer ansatz, which is commonly used as representation of the disturbing potential, is of the order O(|x|⁻¹) as x→∞. This implies that the standard theory of Galerkin BEM is not applicable since the injectivity of the integral operator fails; (2) the N×N stiffness matrix is dense, with N typically of the order 10⁵. Without fast algorithms, which provide suitable approximations to the stiffness matrix by a sparse one with O(N(logN) ^s ), s≥0, non-zero elements, high-resolution global gravity field recovery is not feasible. Solutions to both problems are proposed. (1) A proper variational formulation taking the decay condition into account is based on some closed subspace of co-dimension 3 of the space of square integrable functions on the boundary surface. Instead of imposing the constraints directly on the boundary element trial space, they are incorporated into a variational formulation by penalization with a Lagrange multiplier. The conforming discretization yields an augmented linear system of equations of dimension N+3×N+3. The penalty term guarantees the well-posedness of the problem, and gives precise information about the incompatibility of the data. (2) Since the upper left submatrix of dimension N×N of the augmented system is the stiffness matrix of the standard BEM, the approach allows all techniques to be used to generate sparse approximations to the stiffness matrix, such as wavelets, fast multipole methods, panel clustering etc., without any modification. A combination of panel clustering and fast multipole method is used in order to solve the augmented linear system of equations in O(N) operations. The method is based on an approximation of the kernel function of the integral operator by a degenerate kernel in the far field, which is provided by a multipole expansion of the kernel function. Numerical experiments show that the fast algorithm is superior to the standard BEM algorithm in terms of CPU time by about three orders of magnitude for N=65 538 unknowns. Similar holds for the storage requirements. About 30 iterations are necessary in order to solve the linear system of equations using the generalized minimum residual method (GMRES). The number of iterations is almost independent of the number of unknowns, which indicates good conditioning of the system matrix. Received: 16 October 1999 / Accepted: 28 February 2001  相似文献   

Manual hierarchical clustering of regional geochemical data using a Bayesian finite mixture model     

《Applied Geochemistry》2016

Interpretation of regional scale, multivariate geochemical data is aided by a statistical technique called “clustering.” We investigate a particular clustering procedure by applying it to geochemical data collected in the State of Colorado, United States of America. The clustering procedure partitions the field samples for the entire survey area into two clusters. The field samples in each cluster are partitioned again to create two subclusters, and so on. This manual procedure generates a hierarchy of clusters, and the different levels of the hierarchy show geochemical and geological processes occurring at different spatial scales. Although there are many different clustering methods, we use Bayesian finite mixture modeling with two probability distributions, which yields two clusters. The model parameters are estimated with Hamiltonian Monte Carlo sampling of the posterior probability density function, which usually has multiple modes. Each mode has its own set of model parameters; each set is checked to ensure that it is consistent both with the data and with independent geologic knowledge. The set of model parameters that is most consistent with the independent geologic knowledge is selected for detailed interpretation and partitioning of the field samples.  相似文献   

基于聚类的极光形态分类的探索性研究          下载免费PDF全文

王倩  胡泽骏丘琪 《极地研究》2016,28(3):353-360

极光形态为研究日地物理过程提供了显著、直观和具有可识别性的特征。合理分类对研究各类极光现象与磁层动力学过程之间的关系尤为重要。极光形态分类机制的选择问题是极光有监督分类研究被主要诟病的问题之一。有监督分类实验中人工标记的工作量非常浩大,而且不能保证标记的准确性。更重要的是,高分类正确率只能说明自动分类符合人的认识,有监督分类结果无法验证分类机制的正确性。现有的分类机制是否为极光数据空间的真实划分,是否存在更为合理的分类机制都是我们应该探讨的问题。针对该问题,基于已有的全天空极光图像表征方法,引入聚类算法探究极光特征空间的结构,利用了9种聚类有效性函数选择适合极光数据的聚类个数。实验结果表明,对于从2003—2004年北极黄河站观测的全天空极光数据中随机选取的6 000幅极光图像,两类和四类的划分方式最为合适。两类的划分可以看作是分离度较好的极光类型,并且根据两类分布曲线呈现午前-午后双峰的分布特点,这一类极光可能是弧状极光。对于四类的情况,虽然通过肉眼观察无法用一幅典型的极光图像代表每一类,但是这些由聚类得出的极光类型具有各自的时间分布特点,这一结果从无监督的角度证明了极光类型在形态上是可分的。  相似文献   

The space/time behaviour of dwelling burglars: Finding near repeat patterns in serial offender data     

《Applied geography (Sevenoaks, England)》2013

Whilst analysis of crime for tactical and strategic reasons within the criminal justice arena has now become an established need, predictive analysis of crime remains, and probably always will be, a goal to be desired. Opening a window on this over the last 2 decades, prominent research from academia has focused on the phenomenon of repeat victimisation and more recently ‘near repeat’ victimisation, both firmly grounded in the geography of crime. Somewhat limited to the establishment of near repeat behavioural patterns in whole area data, these can be utilised for crime prevention responses on a local scale. Research reported here however, explores the phenomenon through the examination of serial offending by individual offenders to establish if such spatio-temporal patterns are apparent in the spatial behavioural patterns of the individual burglar, and if so how they may be defined and therefore utilised on a micro rather than macro scale. It is hypothesised that offenders' responsible for more than one series of offences will display consistency across their crime series within time and distance parameters for their closest offences in space. Results improve upon current knowledge concerning near repeat offending being the actions of common offenders. Testing of the extracted data indicates that offenders maintain personal boundaries of ‘closeness’ in time and space even when actions are separated by significant time spans, creating stylised behavioural signatures appertaining to their use of and movement through space when offending.  相似文献   

云闪辐射脉冲序列的丛集特征     

苟学强  张义军  董万胜  陈明理 《高原气象》2008,27(3):644-647

根据2002年夏季那曲地区野外观测的宽带干涉仪资料, 应用变异系数CV、 Allan因子分析(AFA)和Fano因子分析(FFA)等统计方法, 对33个云闪辐射脉冲事件序列的时间丛集特征进行了分析.结果显示, 放电过程呈现强的分形丛集性, 变异系数平均为5.2, AFA和FFA标度指数αAF及αFF平均分别为1.42和0.81; 同时发现, 初始强K脉冲前CV增加到明显>1.  相似文献   

Rapid zonation of abrupt mass movement hazard: Part I. General principles     

J.R. Ni  R.Z. Liu  Onyx W.H. Wai  Alistair G.L. Borthwick  X.D. Ge   《Geomorphology》2006,80(3-4):214-225

Hazards caused by mass movement cost many human lives and cause severe damage to property. Accurate zonation of such hazards provides an important tool for preventive measures. Previous approaches for mass movement hazard zonation are costly because they require large amounts of data, time and labor, and are only applicable to specific local areas. In this paper, a Rapid Zonation of Abrupt Mass-movement Hazard (RZAMH), applicable to large regions, is proposed. It involves the selection of appropriate zonation principles, routes, units, and indexes that can be used for the classification of reference groups, identification of matching groups of test sites, evaluation of blank test sites, and coalescence of sub-regions into specified zonation areas. The K-means clustering method is used in the classification processes. The applicability of the RZAMH approach to a large area implies that the number of reference sites required to build the reference groups is not of primary importance as long as the reference sites are representative. Therefore, for large areas, the RZAMH approach would be more economical than other conventional methods. The RZAMH approach is probably applicable to all abrupt mass movement hazards including rock falls, landslides, and debris flows.  相似文献   

Physical and stochastic models of earthquake clustering   总被引：4，自引：2，他引：4  

Rodolfo Console  Maura Murru  Flaminia Catalli 《Tectonophysics》2006,417(1-2):141

The phenomenon of earthquake clustering, i.e., the increase of occurrence probability for seismic events close in space and time to other previous earthquakes, has been modeled both by statistical and physical processes.From a statistical viewpoint the so-called epidemic model (ETAS) introduced by Ogata in 1988 and its variations have become fairly well known in the seismological community. Tests on real seismicity and comparison with a plain time-independent Poissonian model through likelihood-based methods have reliably proved their validity.On the other hand, in the last decade many papers have been published on the so-called Coulomb stress change principle, based on the theory of elasticity, showing qualitatively that an increase of the Coulomb stress in a given area is usually associated with an increase of seismic activity. More specifically, the rate-and-state theory developed by Dieterich in the ′90s has been able to give a physical justification to the phenomenon known as Omori law. According to this law, a mainshock is followed by a series of aftershocks whose frequency decreases in time as an inverse power law.In this study we give an outline of the above-mentioned stochastic and physical models, and build up an approach by which these models can be merged in a single algorithm and statistically tested. The application to the seismicity of Japan from 1970 to 2003 shows that the new model incorporating the physical concept of the rate-and-state theory performs not worse than the purely stochastic model with two free parameters only. The numerical results obtained in these applications are related to physical characters of the model as the stress change produced by an earthquake close to its edges and to the A and σ parameters of the rate-and-state constitutive law.  相似文献   

Evaluation of earthquake potential along the Northern Anatolian Fault Zone in the Marmara Sea using comparisons of GPS strain and seismotectonic parameters     

Ali. O. Oncel  Tom Wilson   《Tectonophysics》2006,418(3-4):205-218

Seismotectonic parameters including the Gutenberg-Richter b-value and multifractal dimensions D₂ and D₁₅ of seismicity patterns (both spatial and temporal) were compared to GPS-derived maximum shear and dilatation strains measured in the Marmara Sea region of western Turkey along the Northern Anatolian Fault Zone (NAFZ). Comparisons of seismotectonic parameters and GPS-derived maximum shear and dilatation strain along the NAFZ in the vicinity of the 1999 M7.4 Izmit earthquake reveal a positive correlation (r = 0.5, p = 0.05) between average dilatation and the Gutenberg-Richter b-value. Significant negative correlation (r = − 0.56, p = 0.03 and r = − 0.56, p = 0.02) was also observed between the spatial fractal dimension D₂ and GPS-derived maximum geodetic and shear strain. This relationship suggests that, as maximum geodetic and shear strains increase, seismicity becomes increasingly clustered.Anomalous interrelationships are observed in the Marmara Sea region prior to the Izmit event along a bend in the NAFZ near the eastern end of the Marmara Sea known as the Northern Boundary Fault (NBF). An asperity is located near the northwest end of the NBF. Along the 50-km length of the NBF, GPS strains become slightly compressive. The correlation between b-value and GPS-derived dilatation suggests that regions in compression have increased probability of larger magnitude rupture. The NBF appears to serve as an impediment to the transfer of strain from east to west along the NAFZ. Recurrence times for large earthquakes along the NBF are larger than in surrounding areas. Temporal clustering of seismicity in the vicinity of the NBF may represent foreshocks of an impending rupture.  相似文献