Three-dimensional carbon dioxide-induced strain distribution within a confined bituminous coal     

J. Denis N. Pone  Michael Hile  Phillip M. Halleck  Jonathan P. Mathews 《International Journal of Coal Geology》2009,77(1-2):103-108

Sequestration of carbon dioxide in unmineable coal seams is an option to reduce carbon dioxide emissions. It is well known that the interaction of carbon dioxide with unconfined coal induces swelling. This paper contributes three-dimensional strain distribution in confined coal at microstructural level using high-resolution X-ray computerized tomography data and image analysis. Swelling and compression/compaction of regions in the coal matrix occurs with CO₂ uptake. Normal strain varies between ? 1.15% and 0.93%, ? 3.11% and 0.94%, ? 0.43% and 0.30% along x, y and z axes respectively. Volumetric strain varies between ? 4.25% and 1.25%. The positive strains reported are consistent with typical range for unconstrained swelling. However, the average volumetric strains value (? 0.34%) reflect overall volume reduction. Overall swelling is apparently influenced by the confining stresses. The magnitudes of normal strains are heterogeneous and anisotropic. The swelling vs. compression/compaction observed after CO₂ uptake is localized and likely lithotype dependant.  相似文献   

Mapping the Internet using GIS: The death of distance hypothesis revisited     

Yong?Wang  Phillip?Lai  Daniel?Suisui@geog.tamu.edu" title="yong  sui@geog.tamu.edu" itemprop="email" data-track="click" data-track-action="Email author" data-track-label="">Email author 《Journal of Geographical Systems》2003,5(4):381-405

This paper revisits the death of distance hypothesis. To explore the role of distance in the information age, three methods – web scan, hyperlink, and trace-route – are used to map the Internet for the US educational network. Statistical analysis is conducted to evaluate whether physical distance has any impact on the Internet information access. The cartographic and statistical results indicate that geography in general and distance in particular are still important factors in shaping the spatial pattern of Internet activities. For the most popular fifty-three US educational web sites, the physical distance within one thousand miles has positive effects on Internet access while access to international hosts heavily depends on the response time, link speed and other Internet infrastructures and interconnections such as the availability of domain name servers, network access points, backbones, etc. Implications of absolute, relative, and virtual distance in mapping the Internet are discussed. It is concluded that the death of distance hypothesis is premature, even misguided in most cases.  相似文献   

Epidemic modelling of HIV/AIDS transfers between Eastern and Western Europe   总被引：1，自引：0，他引：1  

Phillip Smith  Richard Thomas 《GeoJournal》2001,53(4):373-383

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Karst depressions in a time context     

Phillip R. Kemmerly  Susan K. Towe 《地球表面变化过程与地形》1978,3(4):355-361

A study of karst depression enlargement through time on the Western Highland Rim (physiographic province), based on two sets of aerial photography (1937, 1972) and field work, indicates that areal growth rates (dA/dt, m²/a) depend upon the surficial geologic setting. Areal growth rates were calculated from rates of long axis (dL/dt) and mean width (dW/dt) enlargement assuming an elliptical plan shape. Areal growth rates averaged 40, 70, and 100 m²/century for loessial, clayey residual, and silty colluvial surficial material, respectively. Estimates of average apparent age of karst depressions in each of the three surficial materials, based on linear growth rates, varied from 25,000 to 65,000 years B.P. An occurrence of mastodon (Mammut americanum) and ground sloth (Megalonyx jeffersoni) from the Darks Mill depression as well as a pollen record from another depression dating from the Late Wisconsin glacial maximum in the same geomorphic setting yielded dates compatible with estimates of depression age.  相似文献   

Carbon-13 NMR spectra of macerals separated from individual coals     

Ronald J. Pugmire  Kurt W. Zilm  Warner R. Woolfenden  David M. Grant  Gary R. Dyrkacz  Carol A.A. Bloomquist  E.Phillip Horwitz 《Organic Geochemistry》1982,4(2):79-84

The density gradient centrifugation technique has recently been applied to the separation of macerals from whole coals. Sufficient quantities have been separated to permit examination of pure exinite, vitrinite and inertinite fractions by combined cross polarization and magic angle sample spinning (CP/MASS) carbon-13 NMR techniques. The similarities and differences observed in the maceral groups of two coals are discussed. Diversity in precursors or in differential chemical maturation or a combination of both of these factors can be used to account for subtle spectral differences in the two coals and macerals studied even though the gross spectral features are very similar for a given maceral type. The data show that CP/MASS is a technique that can address such interesting geochemical questions.  相似文献   

The need for recognition and implementation of a sinkhole-floodplain hazard designation in urban karst terrains     

Phillip Kemmerly 《Environmental Geology》1981,3(5):281-292

Soluble rock terrains pose increased flood hazards because of a demographic shift from the upper Middle West and metropolitan Northeast to the “Sun Belt.” Approximately one-half of the soluble rock terrains in the continental United States occur in the Sun Belt. Urbanization of karst terrains generally increases the frequency and magnitude of sinkhole flooding and the probability of collapse. Soil erosion attendant with urbanization results in silt deposition in depressions, reducing sinkhole runoff storage capacity and regolith hydraulic conductivity. A new flood-hazard designation termed the sinkhole flood-plain is advocated for use by federal mortgage agencies in karst terrains so that sinkhole-related flooding can be minimized. A four-phase methodology for assessing sinkhole flood hazards in a rapidly urbanizing karst terrain is developed, using examples from central Tennessee and southern Kentucky.  相似文献   

A study of small aftershocks of the Oroville California, earthquake sequence of August 1975     

William U. Savage  Don Tocher  Phillip C. Birkhahn 《Engineering Geology》1976,10(2-4):371-385

The August 1, 1975 earthquake near Oroville, California, occurred along the Sierra foothills in a region characterized by occasional moderate earthquakes. Several earthquakes in the general region, including those in 1869, 1875, and 1909, appear to have had significant aftershock sequences. The general character of the aftershock sequence of the Oroville earthquake thus does not appear to be anomalous when measured against the known seismic history of this area.

Four smoked-paper micro-earthquake recorders were deployed immediately following the occurrence of the main earthquake to attempt to define the structural associations of the principal earthquake by location and analysis of aftershocks. Focal locations for 243 micro-earthquakes in the magnitude range of 1–3 were selected from the 30-day period (August 2–September 1), during which monitoring was continued. The aftershocks clearly define a planar surface striking north–south and dipping west at 62° from the surface to a depth of about 12 km. Aftershocks during the first two days of monitoring defined a surface of active faulting of approximately 100 km². Extension of this surface both to the north and south began on August 5 at focal depths of 5–10 km, resulting in a total ruptured area of approximately 125 km². The number of aftershocks per day decreased at the rate oft^−1.1, but the decay curve was punctuated by several secondary aftershock sequences. No. direct relationship between the aftershock sequence and the presence of Oroville Reservoir was observed.  相似文献   

3D Geographic Reconstruction and Visualization Techniques Applied to Land Resource Management   总被引：1，自引：0，他引：1  

Sabine Grunwald  & Phillip Barak 《Transactions in GIS》2003,7(2):231-241

Optimized land resource management depends on reliable and detailed information describing the spatial distribution of soils, geology, topography, and land use. Soil–landscapes are three–dimensional (3D) systems commonly represented using 2D maps utilizing geographic information systems. Addressing 3D soil–landscape reality is crucial for land resource management in terms of crop growth and transport processes (e.g. nitrate leaching) that are driving soil and water quality. Our objective was to investigate the usefulness of 3D geographic information technology (GIT) applied to land resource management. Our approach is based on 2D and 3D ordinary kriging interpolating surface and subsurface attributes to reconstruct soil–landscapes. We used Virtual Reality Modeling Language, which is a web–based 3D graphics language, to visualize objects (e.g. voxels, polyhedrons) representing soil and landscape attributes. We produced a 3D block model showing the spatial distribution of bulk densities and relief for a site in southern Wisconsin and a 3D stratigraphic model showing the spatial distribution of soil horizons and relief for a site in northern Florida. Emerging GIT was used to develop 3D soil–landscape models describing continuous changes of soil and landscape attributes. Combining multimedia elements (e.g. WWW, 3D visualization, and interactivity) can produce insight that would not arise from use of the elements alone. Three–dimensional scientific visualization is a powerful tool to help us see what is invisible from above the ground.  相似文献   

The petrographic and compositional character of variably K-enriched magmatic suites associated with Ordovician porphyry Cu–Au mineralisation in the Lachlan Fold Belt,Australia   总被引：1，自引：0，他引：1  

Phillip L. Blevin 《Mineralium Deposita》2002,37(1):87-99

Mineralised igneous complexes of Ordovician age from New South Wales range in composition from quartz-rich medium-K dacites (e.g. Copper Hill), to quartz-poor, high-K to 'shoshonitic' monzodioritic to monzonitic complexes (Goonumbla and Cadia). Despite Ordovician igneous suites being considered mostly 'shoshonitic' by some authors, only the Cadia Igneous Complex is potassic in the sense of having molecular K/Na greater than unity. A feature of the intrusive complexes is that each is spatially associated with volcanic rocks of similar compositional character, and that these relationships may occur over long periods of time within local regions (e.g. Goonumbla Volcanic Complex), or show progressive compositional evolution over probably shorter time periods as in the case of the Cadia District. The igneous suites are variably enriched in K and LILE elements, with uniformly high K/Rb ratios, low mantle-compatible element abundances and marked depletions in Ti, Nb and Ta, which is consistent with a subduction-related tectonic setting. Patterns of enrichment and depletion between each suite are similar, and are consistent with the magmas having been derived from sources variably enriched by slab derived materials prior to fusion. Recent dating results from the Goonumbla Volcanic Complex suggest that this enrichment was not progressive over time, and that the oldest intrusions in the Ordovician are not necessarily the least compositionally evolved. These results confirm the overall 'calc-alkaline' nature of Ordovician magmatism and do not support models that argue against contemporaneous subduction on the grounds that Ordovician magmatism was almost exclusively shoshonitic in character. Economic size and significance of associated deposits increase with the degree of K-enrichment (but not total alkali contents) observed in the associated igneous complexes, and supports conceptual models that link mineralisation potential and fertility with processes related to the production of K-enriched protoliths.  相似文献   

Middle Miocene to present plate tectonic history of the southern Central American Volcanic Arc   总被引：1，自引：0，他引：1  

Ian MacMillan  Phillip B. Gans  Guillermo Alvarado 《Tectonophysics》2004,392(1-4):325

New mid Miocene to present plate tectonic reconstructions of the southern Central American Volcanic Arc (CAVA) reveal that the inception of Cocos Ridge subduction began no earlier than 3 Ma, and possibly as late as 2 Ma. The Cocos Ridge has been displaced from the Malpelo Ridge to the southeast since 9 Ma along the Panama Fracture Zone (PFZ) system. Ambiguous PFZ and Coiba Fracture Zone (CFZ) interaction since 9 Ma precludes conclusively establishing the age of initial Cocos Ridge subduction. Detailed reconstructions based on magnetic anomalies offshore reveal several other variations in subduction parameters beneath southern Central America that preceded subduction of the Cocos Ridge, including southeastward migration of the Nazca–Cocos–Caribbean triple junction along the Middle America Trench (MAT) from 12 Ma to present, and subduction of ≤2 km high scarps both parallel and perpendicular to the trench from 6 to 1 Ma.The timing of changes in subduction processes has commonly been determined by (and correlated with) geologic changes in the upper plate. However, reliable ⁴⁰Ar/³⁹Ar dating of these events has become available only recently [Abstr. Programs-Geol. Soc. Am. (2002)]. These new dates better constrain the magmatic and structural history of southern Costa Rica. Observations from this data set include: a gap in the volcanic record from 11 to 6 Ma, which coincides temporally with emplacement of most plutons in southern Costa Rica, normal arc volcanism ceased after 3.5 Ma in southern Costa Rica, and Pliocene (mostly 1.5 Ma) adakite volcanism was widely distributed from central Panama to southern Costa Rica (though volumetrically insignificant).This new data reveals that many geologic phenomena, commonly attributed to subduction and underplating of the buoyant Cocos Ridge, in fact precede inception of Cocos Ridge subduction and seem to correlate more favorably in time with earlier tectonic events. Adakite volcanic activity corresponds in space and time with the subduction of a large scarp associated with a tectonic boundary off southern Panama. Regional unconformities and an 11–6 Ma gap in arc volcanism match temporally with oblique subduction of the Nazca plate beneath central and southern Costa Rica. Cessation of volcanic activity, low-temperature cooling of plutons in the Cordillera de Talamanca (CT), and rapid increases in sedimentation in the fore-arc and back-arc basins coincide with passage of the Nazca–Cocos–Caribbean triple junction and initiation of subduction of “rough” crust associated with Cocos–Nazca rifting 3.5 Ma, closely followed by initial subduction of the Cocos Ridge 2–3 Ma. None of the aforementioned geologic events occurred at a time that would allow for underplating by the Cocos Ridge. Rather they are probably related to complex interactions with subduction of complicated plates offshore. All of the aforementioned events indicate that the southern Central American subduction system has been in flux since at least 12 Ma.  相似文献