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951.
L. I. Kuncheva J. J. Charles N. Miles A. Collins B. Wells I. S. Lim 《Mathematical Geosciences》2008,40(6):639-652
We develop the classification part of a system that analyses transmitted light microscope images of dispersed kerogen preparation. The system automatically extracts kerogen pieces from the image and labels each piece as either inertinite or vitrinite. The image pre-processing analysis consists of background removal, identification of kerogen material, object segmentation, object extraction (individual images of pieces of kerogen) and feature calculation for each object. An expert palynologist was asked to label the objects into categories inertinite and vitrinite, which provided the ground truth for the classification experiment. Ten state-of-the-art classifiers and classifier ensembles were compared: Naïve Bayes, decision tree, nearest neighbour, the logistic classifier, multilayered perceptron (MLP), support vector machines (SVM), AdaBoost, Bagging, LogitBoost and Random Forest. The logistic classifier was singled out as the most accurate classifier, with an accuracy greater than 90. Using a 10 times 10-fold cross-validation provided within the Weka software, we found that the logistic classifier was significantly better than five classifiers (p<0.05) and indistinguishable from the other four classifiers. The initial set of 32 features was subsequently reduced to 6 features without compromising the classification accuracy. A further evaluation of the system alerted us to the possible sensitivity of the classification to the ground truth that might vary from one human expert to another. The analysis also revealed that the logistic classifier made most of the correct classifications with a high certainty. 相似文献
952.
Zinc–lead–barite deposits located in Lefan and Lower Banik localities of about 25 km northeast of Zakho City, Northern Iraq
consist of a group of strata-bound sulfides hosted in Upper Cretaceous (Upper Campanian–Maastrichtian) dolomitic limestone.
Carbonate-hosted ores contain 3.77% Zn, 2% Pb, and 5% Fe, while in lower Banik, they contain 1.5% Zn, 0.37% Pb, and 1.4% Fe.
Diagenetic processes, such as dolomitization and recrystalization in addition to the type of microfacies, provided appropriate
physical and chemical conditions that permitted the passage of ore-bearing fluids and participated in precipitation and ore
localization. These deposits are precipitated in a platform and developed within the Foreland Thrust Belt. Ore precipitated
as infill of intergranular dolomite porosity with replaced dolomite and rudist shells forming disseminated crystals that occupy
intergranular pore spaces around dolomite and calcite and as infill of dissolution spaces and fractures. 相似文献
953.
Experimental data are presented in this paper to study the strain-softening behaviour of sand under plane-strain conditions. K 0 consolidated strain path tests were conducted using a new plane-strain apparatus. The stress–strain behaviour of medium dense sand under plane-strain conditions was characterized. The test results show that the occurrence of pre-failure strain softening under plane-strain conditions is affected by the void ratio, the strain increment ratio and the initial effective confining stress. This is consistent with previous findings established under axisymmetric conditions. However, a pre-failure strain-softening behaviour in plane-strain tests conducted under high-confining stresses may consist of three stages, namely, material softening, banding softening, and ultimate state. This observation is different from that in triaxial tests where banding softening does not normally occur. 相似文献
954.
955.
S. P. Turner 《Mineralogy and Petrology》1996,56(1-2):51-89
Summary A group of funnel-shaped gabbroic plutons at Black Hill, South Australia, consist of a lower series of layered peridotite, troctolite and olivine gabbro cumulates overlain by gabbronorites and potassic gabbronorites, the latter yielding a Sm-Nd isochron of 489 ± 39 Ma. Mineral assemblages in the gabbros record an olivine compositional hiatus (Fo75-55) and a high temperature (1200-1000°C), low pressure (1 kbar), continental tholeiitic fractionation trend under moderate fO
2 (QFM) conditions. The liquid line of descent involved complex open system processes including recharge and crustal assimilation. In one pluton, fine-grained norites may reflect assimilation which resulted in an increaseda
SiO2
liquid
causing orthopyroxene to crystallize prior to plagioclase.All the gabbros, including the most primitive peridotites, are LREE and incompatible element enriched. Moreover, the calculated parental magma composition in equilibrium with the most primitive troctolite has high La/Yb, La/Nb, Ti/Y and low Rb/Ba, similar to that of basaltic dykes which cut the gabbroic complex. Such compositions are untypical of melts derived from the asthenosphere suggesting that the incompatible element enrichment is not simply due to small degrees of melting. Given the isotopic constraints (Ndi 3.4 to –4.6,87Sr/86Sri 0.7038-0.7065), this enrichment is not easily reconciled by crustal contamination either, and instead it is inferred to reflect an enriched lithospheric mantle source. Published data on mantle xenoliths from local Tertiary volcanoes overlap the isotopic and geochemical array of the gabbros and dykes, supporting this hypothesis.In conjunction with A-type granites and minor volcanic rocks, the gabbroic plutons form part of a high temperature, bimodal magmatic suite which intruded the Adelaide fold belt just after the cessation of convergent deformation during the Cambro-Ordovician Delamerian Orogeny. The appearance of such magmas is problematic since thick orogenic lithosphere severely restricts the likelihood of decompression melting in the asthenosphere. One solution to this dilemma is that convective thinning of the lithospheric mantle beneath the orogen promoted melting of hydrated, enriched regions within the lithospheric mantle. Such a model can reconcile the strong lithospheric mantle signature in the gabbros with the observation that their intrusion was coincident with uplift and the cessation of deformation.
With 15 Figures 相似文献
Die Petrogenese eines spätdelamerischen Gabbrokomplexes von Black Hill, Südaustralien: Schlußfolgerungen zur konvektiven Ausdünnung des lithospharischen Mantels
Zusammenfassung Eine Gruppe von trichterförmigen, gabbroiden Plutonen von Black Hill, Südaustralien, setzt sich aus einer unteren Serie von geschichteten Peridotiten, Troktoliten and Olivin-Gabbro-Kumulaten, die von Gabbro-Noriten und potassischen Gabbros überlagert werden, zusammen; letzgenannte Gesteine ergaben ein Sm-Nd Isochronenalter von 489 ± 39 Ma. Die Mineralzusammensetzungen der Gabbros belegen eine Mischungslücke bei Olivin (Fo75-55). Die Gesteine folgen einem kontinentalen, tholeiitischen Fraktionierungstrend und kristallisierten bei hohen Temperaturen (1200-1000°C), unter niedrigem Druck ( 1 kbar) and moderatem fo2 ( QFM). Wiederholte Magmenzufuhr und Krustenassimilation sind weitere zu beriicksichtigende, komplexe Prozesse, die sich in einem offenen System abspielten. Feinkörnige Norite von einem der Plutone könnten durch Assimilationsprozesse - she äußern sich in einer Erhöhung desa SiO2 liquid liquid - entstanden sein. In diesen Gesteinen kristallisierte Orthopyroxen vor Plagioklas.Alle Gabbros, einschließich der primitivsten Peridotite, sind an LREE und inkompatiblen Elementen angereichert. Die berechnete Zusammensetzung des Ausgangsmagmas, das im Gleichgewicht mit dem primitivsten Troktolit steht, weist hohe La/Yb, La/Nb, Ti/Y and niedrige Rb/Ba auf. Basaltische Dykes, die die Gabbros durchsetzen zeigen ähnliche Elementverhältnisse. Derartige Zusammensetzungen sind untypisch für astenosphärische Schmelzen und belegen, daß die Anreicherung an inkompatiblen Elementen nicht einfach nur mit geringen Aufschmelzungsraten zu erklären ist. Auf Grund der Isotopendaten (Ndi 3.4 to -4.6,87Sr/86 Sri 0.7038–0.7065) kann these Anreicherung auch nicht leicht mit Krustenkontamination erklärt werden. Vielmehr wird eine angereicherte, lithosphärische Mantelquelle vermutet. Publizierte Daten an Mantelxenolithen von tertiären Vulkanen zeigen sehr ähnliche isotopische und geochemische Zusammensetzungen and belegen these Hypothese.Gemeinsam mit A-Typ Graniten und untergeordnet, vorkommenden, vulkanischen Gesteinen sind die Gabbros Teil einer hochtemperierten bimodalen, magmatischen Serie, die den Adelaide Fold Belt postdeformativ, während der kambro-ordovizischen delamerischen Orogenese, intrudierten. Das Vorkommen solcher Magmen ist problematisch, da die Präsenz dicker, orogen gebildeter Lithosphäre die Möglichkeit der Dekompressions-Aufschmelzung der Astenosphäre stark vermindert. Eine mögliche Lösung dieses Dilemmas ist, daß konvektives Ausdünnen des lithosphärischen Mantels unterhalb der Orogenzone das Aufschmelzen von hydratisierten, angereicherten Regionen innerhalb der Lithosphäre förderte. Dieses Modell bringt die Beobachtungen, daß die Gabbros einerseits eine lithosphärische Signatur zeigen, andererseits aber während der Hebungsphase und am Ende des Deformationsgeschehens intrudierten, in Einklang.
With 15 Figures 相似文献
956.
Ohishi M Ishikawa SI Amano T Oka H Irvine WM Dickens JE Ziurys LM Apponi AJ 《The Astrophysical journal》1996,471(1):L61-L64
A new interstellar molecular ion, H2COH+ (protonated formaldehyde), has been detected toward Sgr B2, Orion KL, W51, and possibly in NGC 7538 and DR21(OH). Six transitions were detected in Sgr B2(M). The 1(1,0)-1(0,1) transition was detected in all sources listed above. Searches were also made toward the cold, dark clouds TMC-1 and L134N, Orion (3N, 1E), and a red giant, IRC + 10216, without success. The excitation temperatures of H2COH+ are calculated to be 60-110 K, and the column densities are on the order of 10(12)-10(14) cm-2 in Sgr B2, Orion KL, and W51. The fractional abundance of H2COH+ is on the order of 10(-11) to 10-(9), and the ratio of H2COH+ to H2CO is in the range 0.001-0.5 in these objects. The values in Orion KL seem to be consistent with the "early time" values of recent model calculations by Lee, Bettens, & Herbst, but they appear to be higher than the model values in Sgr B2 and W51 even if we take the large uncertainties of column densities of H2CO into account. We suggest production routes starting from CH3OH may play an important role in the formation of H2COH+. 相似文献
957.
S. N. Arteha 《Astrophysics and Space Science》1996,246(1):51-64
A self-consistent statistical approach to the problem of planetary and stellar magnetism is suggested. The mechanism of magnetic field generation in the astronomical objects, where the existence of fields is associated with the axial rotation of objects, is discussed. In the general case the light pressure, the centrifugal, gravitational and other forces produce partial -separation of the charges. As a result of the system rotation, the magnetic fields of the currents of these charges are not compensated. The influence of various factors on the magnetic field of some object is analysed. 相似文献
958.
James R. Coull 《GeoJournal》1996,39(2):185-194
Shetland, as an isolated group of islands on the north-west margin of Europe, has always depended in its economy on marine-based resources, and current trends suggest that this will continue for the future. Up to the oil era Shetland depended mainly on the fisheries around it, although for centuries externally-based fishermen have profited more from these fisheries than have the Shetland people. As well as the development of oil from the 1970s there has been the other major economic innovation of fish farming. The oil industry is on massive scale and has greatly changed the economy of the islands and brought notable social benefits; but the direct employment it provides is considerably exceeded by the fish-related industries, which include employment in fish processing and packing plants as well as in fish catching and fish farming. With the oil industry in Shetland now on a settled downward trajectory, the islands are inevitably now having to look more to fish-related employment for their future. In the internal structure of Shetland, fish farming has a notable effect in distributing employment throughout the islands. Activity in fishing and fish processing is more selectively located: fishing is mainly concentrated in certain islands in the archipelago, particularly Whalsay and Burra; and fish processing is mainly in central locations, especially Lerwick and Scalloway. A prominent problem for fish processors is getting reliable supplies in face of higher fish prices at markets on the Scottish mainland. The processors also now face the challenge of putting more value added on their products in an outlying location. For the future there is a major issue in getting more effective measures for conservation of fish stocks in the Shetland area; there is also the related issue of whether Shetland fishermen should get preference in the allocation of fish quotas in this area. For fish farming there is the basic issue of maintaining a pollution-free environment: this was emphasised by the oil spill from the Braer oil tanker, and there is also concern about potential polluution from the prospective development of oil fields in the more difficult deep-water environment to the west of the islands. 相似文献
959.
Croatia is a Central European and Mediterranean state, located in contact with and under the influence of various spheres of civilization, which for centuries have penetrated and conflicted on and around the territory of Croatia. Such a position has resulted in various influences which did not always have a positive effect on the development of Croatia. The gradual narrowing and decrease of the Croatian ethnic territory, as well as the presence of national minorities in it, was also a result of the aforementioned position and outside influences (ulji 1993/1994).The demographic structure of Croatia indicates a series of specificities which were primarily conditioned by the historical development of Croatia and which is particularly expressed in constant emigration since the end of the nineteenth century, the relatively large direct and indirect losses to the population during and immediately after the First and Second World Wars, emigration as a type of population movement in all inter-census periods after 1945, the appearance of a natural decline and the aging of the population on almost one half of the state territory. 相似文献
960.
A quadtree-based image segmentation procedure (HQ) is presented to map complex environmental conditions. It applies a hierarchical nested analysis of variance within the framework of multiresolution wavelet approximation. The procedure leads to an optimal solution for determining mapping units based on spatial variability with constraints on the arrangement and shape of the units. Linkages to geostatisiics are pointed out, but the HQ decomposition algorithm does not require any homogeneity criteria. The computer implementation can be parameterized by either the number of required mapping units or the maximum within-unit variance, or it can provide a spectrum of significances of nested ANOVA. The detailed mathematical background and methodology is illustrated by a salt-affected grassland mapping study (Hortobágy, Hungary), where heterogeneous environmental characteristics have been sampled and predicted based on remotely sensed images using these principles. 相似文献