Nonparametric estimation of generalized covariances by modeling on-line data     

Paul Chiasson  Michel Soulié 《Mathematical Geology》1997,29(1):153-172

Structural analysis of data displaying trends may be performed with the help of generalized increments, the variance of these increments being a function of a generalized covariance. Generalized covariances are estimated primarily by parametric methods (i. e., methods searching for the best coefficients of a predetermined function), but also may be computed by one known nonparametric alternative. In this paper, a new nonparametric method is proposed. It is founded on the following principles: (1) least-squares residues are generalized increments; and (2) the generalized covariance is not a unique function, but a family of functions (the system is indeterminate). The method is presented in a general context of a k order trend in R^d, although the full solution is given only fork = I in Rⁱ. In Rⁱ, higher order trends may be developed easily with the equations included in this paper. For higher dimensions in space, the problem is more complex, but a research approach is proposed. The method is tested on soil pH data and compared to a parametric and nonparametric method.  相似文献   

Geochemistry, genesis, and health implications of fluoriferous groundwaters in the upper regions of Ghana   总被引：9，自引：2，他引：9  

W. B. Apambire  D. R. Boyle  F. A. Michel 《Environmental Geology》1997,33(1):13-24

 The most appropriate and widely used source of drinking water for the populations of the upper regions of Ghana is groundwater. In general, groundwater quality is acceptable except for some parts of the Bolgatanga and Bongo Districts, where there are occurrences of elevated levels of natural groundwater fluoride. Concentrations of groundwater fluoride in excess of the World Health Organization (WHO) maximum guideline value (1.5 mg/l) in the Bongo area have been known since 1978. However, the effect of fluoride on people ingesting the water did not receive public and medical attention until October 1993, when health personnel were asked to investigate the cause of stained teeth in school children. The investigation established that 62% of the total population of school children in the Bongo area had dental fluorosis. Against this background, a study was initiated to understand the geochemistry, genesis, and distribution of fluoride in relation to the geology of the area. Groundwater fluoride in the upper regions ranges from 0.11 to 4.60 ppm, with the highest concentrations associated with the fluorine-enriched Bongo coarse-grained hornblende granite and syenite suite. The source of groundwater fluoride within the Bongo granitoids is dissolution of the mineral fluorite and dissolution of and anion exchange with micaceous minerals and their clay products. Applying the WHO recommended guideline values for fluoride in drinking water reveals that 49% of wells in the area deliver water below the optimum level of 0.5 mg/l F^–; these populations are thus prone to dental caries. Twenty-eight percent of the wells fall within the optimum interval for good dental health (0.5–1.5 mg/l F^–). Twenty-three percent of the wells have concentrations above the recommended maximum guideline limit of 1.5 mg/l F^–; this population is susceptible to dental and possibly skeletal fluorosis. Climatic conditions of the area suggest that the individual water consumption is in the order of 3 to 4 l which is higher than the WHO estimate of 2 l/adult/day. In addition, dietary intake for the upper region population is probably higher than WHO baseline values (0.2–0.5 mg/day). This implies that a much higher population is susceptible to developing dental and skeletal fluorosis than originally suspected. Geochemical symbol plot maps help geochemists understand factors controlling the distribution and uptake of fluoride in the upper regions, but they are of minimal value to health officials responsible for planning epidemiological studies and dental health education programs in the region. By casting fluoride data into contoured 'geochemical health-risk maps' using intake interval guidelines more closely aligned to regional climatic and dietary conditions, health officals can better judge the impacts (regional and population based) of fluoride on segments of the population, such as various sex and age groups. Received: 11 March 1997 · Accepted: 17 June 1997  相似文献   

Late holocene level fluctuations of the Lake Ilay in Jura,France: sediment and mollusc evidence and climatic implications     

Michel Magny  Jacques Mouthon  Pascale Ruffaldi 《Journal of Paleolimnology》1995,13(3):219-229

The level fluctuations of Lake Ilay, Jura (France) during the last three millennia are reconstructed from sedimentological and malacological analyses of a core that is well-dated by tree-ring, radiocarbon and pollen datings. Changes in sediment facies, in carbonate concretion assemblages and in mollusc assemblages highlight a major lowering phase atc. 1550 BP and minor lowering phases atc. 2800 BP and shortly before AD 1394. Rises in lake level developed during the early Subatlantic and betweenc. 1500 and 1000 BP. These data are in good agreement with other proxy data from higher European and American latitudes. These correlations support the climatic origin of the level fluctuations of the Lake Ilay during the late Holocene. They suggest that the mediaeval climatic optimum is centred rather in the early than the late Middle Age.  相似文献   

High-frequency magnetotelluric investigation of crustal structure in north-central Abitibi, Quebec, Canada     

Ping Zhang  Michel Chouteau  Marianne Mareschal  Ron Kurtz  Claude Hubert 《Geophysical Journal International》1995,120(2):406-418

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Karst groundwater resources in the countries of eastern Mediterranean: the example of Lebanon   总被引：1，自引：0，他引：1  

Michel Bakalowicz  Massaad El Hakim  Ahmad El-Hajj 《Environmental Geology》2008,54(3):597-604

The hydrogeological study of some karst systems in Lebanon shows important storage capacity, up to 27 billions m³ for Zarka system, the spring of Orontes River. Their geological and morphological settings, as well as their hydrodynamic function, show structures developed below the level of present springs, probably up to several hundreds meters at depth. Since Miocene, those carbonate formations were subject to a remarkable instability of their base levels. Variations of sea level, of which the Messinian salinity crisis is the major phase, and effects of the alpine orogenesis, combined with climate variations to develop complex, multiphased karst systems. Karstification occurs frequently in the whole formation, often deeply below sea level or underneath sediment filling of continental basins. The surface karst landscape is often intensely eroded. Those multiple, superimposed karst phases give the carbonate aquifers their large extension and storage capacity. These karst aquifers show the typical easy restoration of storage. They have the ability to bear large interannual recharge variations and support exploitation under high pumping rates. However, these aquifers have some disadvantages for sustainable management. In some regions, successful boreholes, which allow high pumping rates also induce uncontrolled exploitation. Another consequence is natural seawater intrusion, as well as the submarine discharge of fresh groundwater, in coastal aquifers. Those carbonate aquifers are subject to important economical stress which jeopardizes their durability. The systematic study and understanding of carbonate aquifers in Eastern Mediterranean is a preliminary condition to any integrated and sustainable management of water resources. Studies in progress in Lebanon may serve as examples to the whole region.  相似文献   

Galactic evolution and star counts in the milky way     

Annie C. Robin  Michel Crézé  Vijay Mohan 《Astrophysics and Space Science》1989,156(1-2):9-18

A model of population synthesis for our Galaxy is used to estimate the constraints imposed by photometric and astrometric star counts. We construct a statistical method to compute the degree of compatibility of the model with the data in the form of a multidimensional functionf(V, B-V, U-B, ). We apply the method to the determination of the star formation history in the Galaxy from Schmidt plates towards the anticentre. Although the presently available data do not allow us to draw firm conclusions, we show that the same kind of data with a slightly better photometric accuracy and with proper motions would give new constraints on the past star formation rate of the Galaxy.  相似文献   

A Surface-Layer Study of the Transport and Dissipation of Turbulent Kinetic Energy and the Variances of Temperature,Humidity and CO$$_$$     

João A. Hackerott  Mostafa Bakhoday Paskyabi  Joachim Reuder  Amauri P. de Oliveira  Stephan T. Kral  Edson P. Marques Filho  Michel dos Santos Mesquita  Ricardo de Camargo 《Boundary-Layer Meteorology》2017,165(2):211-231

We discuss scalar similarities and dissimilarities based on analysis of the dissipation terms in the variance budget equations, considering the turbulent kinetic energy and the variances of temperature, specific humidity and specific CO\(_2\) content. For this purpose, 124 high-frequency sampled segments are selected from the Boundary Layer Late Afternoon and Sunset Turbulence experiment. The consequences of dissipation similarity in the variance transport are also discussed and quantified. The results show that, for the convective atmospheric surface layer, the non-dimensional dissipation terms can be expressed in the framework of Monin–Obukhov similarity theory and are independent of whether the variable is temperature or moisture. The scalar similarity in the dissipation term implies that the characteristic scales of the atmospheric surface layer can be estimated from the respective rate of variance dissipation, the characteristic scale of temperature, and the dissipation rate of temperature variance.  相似文献   

Impact of normal faulting and pre‐rift salt tectonics on the structural style of salt‐influenced rifts: the Late Jurassic Norwegian Central Graben,North Sea          下载免费PDF全文

Zhiyuan Ge  Rob L. Gawthorpe  Atle Rotevatn  Michel Bøgh Thomas 《Basin Research》2017,29(5):674-698

Studies of salt‐influenced rift basins have focused on individual or basin‐scale fault system and/or salt‐related structure. In contrast, the large‐scale rift structure, namely rift segments and rift accommodation zones and the role of pre‐rift tectonics in controlling structural style and syn‐rift basin evolution have received less attention. The Norwegian Central Graben, comprises a complex network of sub‐salt normal faults and pre‐rift salt‐related structures that together influenced the structural style and evolution of the Late Jurassic rift. Beneath the halite‐rich, Permian Zechstein Supergroup, the rift can be divided into two major rift segments, each comprising rift margin and rift axis domains, separated by a rift‐wide accommodation zone – the Steinbit Accommodation Zone. Sub‐salt normal faults in the rift segments are generally larger, in terms of fault throw, length and spacing, than those in the accommodation zone. The pre‐rift structure varies laterally from sheet‐like units, with limited salt tectonics, through domains characterised by isolated salt diapirs, to a network of elongate salt walls with intervening minibasins. Analysis of the interactions between the sub‐salt normal fault network and the pre‐rift salt‐related structures reveals six types of syn‐rift depocentres. Increasing the throw and spacing of sub‐salt normal faults from rift segment to rift accommodation zone generally leads to simpler half‐graben geometries and an increase in the size and thickness of syn‐rift depocentres. In contrast, more complex pre‐rift salt tectonics increases the mechanical heterogeneity of the pre‐rift, leading to increased complexity of structural style. Along the rift margin, syn‐rift depocentres occur as interpods above salt walls and are generally unrelated to the relatively minor sub‐salt normal faults in this structural domain. Along the rift axis, deformation associated with large sub‐salt normal faults created coupled and decoupled supra‐salt faults. Tilting of the hanging wall associated with growth of the large normal faults along the rift axis also promoted a thin‐skinned, gravity‐driven deformation leading to a range of extensional and compressional structures affecting the syn‐rift interval. The Steinbit Accommodation Zone contains rift‐related structural styles that encompass elements seen along both the rift margin and axis. The wide variability in structural style and evolution of syn‐rift depocentres recognised in this study has implications for the geomorphological evolution of rifts, sediment routing systems and stratigraphic evolution in rifts that contain pre‐rift salt units.  相似文献   

Factors controlling stratal pattern and facies distribution of fluvio‐lacustrine sedimentation in the Sivas mini‐basins,Oligocene (Turkey)          下载免费PDF全文

Charlotte Ribes  Charlie Kergaravat  Philippe Crumeyrolle  Michel Lopez  Cédric Bonnel  André Poisson  Kaan S. Kavak  Jean‐Paul Callot  Jean‐Claude Ringenbach 《Basin Research》2017,29(Z1):596-621

The Sivas Basin, located in the Central Anatolian Plateau of Turkey, is a foreland basin that records a complex interaction between sedimentation, salt tectonics and regional shortening during the Oligo‐Miocene leading to the formation of numerous mini‐basins. The Oligocene sedimentary infill of the mini‐basins consists of a thick continental succession, the Karayün Formation, comprising a vertical succession of three main sub‐environments: (i) playa‐lake, (ii) fluvial braided, and (iii) saline lacustrine. These sub‐environments are seen as forming a large Distributive Fluvial System (DFS) modified through time as a function of sediment supply and accommodation related to regional changes in climate and tectonic regime. Within neighbouring mini‐basins and despite a similar vertical stratigraphic succession, subtle variations in facies assemblages and thickness are observed in stratigraphic units of equivalent age, thus demonstrating the local control exerted by halokinesis. Stratigraphic and stratal patterns reveal in great detail the complex interaction between salt tectonics and sedimentation including different types of halokinetic structures such as hooks, wedges and halokinetic folds. The regional variations of accommodation/sediment supply led to coeval changes in the architectural patterns recorded in the mini‐basins. The type of accommodation regime produces several changes in the sedimentary record: (i) a regime dominated by regional accommodation limits the impact of halokinesis, which is recorded as very small variations in stratigraphic thickness and facies distribution within and between mini‐basins; (ii) a regime dominated by localized salt‐induced accommodation linked to the subsidence of each individual mini‐basin enhances the facies heterogeneity within the DFS, causing sharp changes in stratigraphic thickness and facies assemblages within and between mini‐basins.  相似文献   

The anatomy of an active slide: the Gascons rockslide,Québec,Canada     

Catherine Cloutier  Jacques Locat  Réjean Couture  Michel Jaboyedoff 《Landslides》2016,13(2):241-258

A railroad crosses the coastal Gascons rockslide, in Quebec, Canada. This study improves the understanding of the rockslide’s failure mechanism and post-failure behaviour responsible for the deformation in the railroad. The slide is an asymmetrical wedge failure of 410,000 m³, in rocks made up of centimetre-scale beds of nodular calcilutite alternating with sandstones and limestone. The post-failure stage of the rockslide is characterised by continuous movement of blocks with speeds ranging from 6 to 110 mm/year. The main water table is just below the sliding surface, but precipitation and snowmelt can raise it above the sliding surface in the upper part of the slide. We propose a model for the rockslide, its failure mechanism, geometry and hydrogeology to provide a baseline for interpreting the near-real-time data collected since 2009.  相似文献