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1.
The “global” representation of the geomagnetic field in terms of ordinary spherical harmonics (SHs) and its corresponding set {g,h} of coefficients has been studied extensively, but the “local” representation in terms of spherical cap harmonics (SCHs) and its corresponding set {G,H} of coefficients is not yet well understood. This paper clarifies some of the main properties of the SCHs and their proper use along with their relationship with the SHs. In particular, it shows that for the spherical cap part of a global field specified by spherical harmonics there is a strict relation between the ordinary Legendre functions of the global representation and the fractional functions of the local expansion; hence we can express the set of coefficients {G,H} in terms of the set {g,h}. Finally, some attention will be given to the role of the leading (n = 0, m = 0) term of the SCH expansion.  相似文献   

2.
3.
The hexagonal to orthorhombic phase transition in synthetic Mg-cordierite has been studied by (i) measuring the spontaneous strain associated with the transition using Synchrotron X-ray powder diffraction and (ii) measuring the degree of Al, Si order in terms of the number of Al-O-Al bonds per formula unit using solid state NMR spectroscopy. This defines the two order parametersQ andQ od respectively, and their relationship as a function of annealing temperature and time is used to define the structural states of cordierite during the ordering sequence. The formation of modulated hexagonal cordierite within which a high degree of Al, Si order can be attained, results in a strongly non-linear relationship betweenQ andQ od .The transition from modulated to orthorhombic cordierite is strongly first-order under all temperature conditions studied and involves a large step inQ, whileQ od changes continuously throughout the ordering sequence with no marked discontinuity at the phase transition. The lattice distortion, traditionally defined in cordierite by the Δ index provides no full information on the degree of Al, Si order in anhydrous Mg-cordierite, and both order parameters must be used to define its structural state. Transmission electron microscopy has been used to study the mechanism of the transformation from hexagonal to modulated to orthorhombic cordierite.  相似文献   

4.
The theory and practice of sustainability involves the understanding and management of the coupled relationship between the environment and humans. This relationship is very evident in respect to mining where the impacts of operations, both positive and negative, are environmental and socioeconomic in nature. In recent years, evaluating the sustainability of a mining operation has grown within the literature due to the impacts that mining has upon a local community. However, the literature has been often characterised by a variety of case study-specific approaches to define and evaluate the sustainability of mining operations. This is due to the fundamental problem of defining what is sustainability. The paper applies, based on our previous research, a mathematical model of sustainability to the environmental impact assessment (EIA) of a proposed bauxite mining project in the Andhra Pradesh province, India. The model??s application to the impact assessment, which used the rapid impact assessment matrix, was undertaken for the purpose of determining the level and nature of sustainability (if appropriate) of the proposed project. The results indicated that the project was considered as unsustainable in its current form, based on an obtained E value of 0.249 and an H NI value of 0.500. The results suggested that the project would greatly benefit from an environmental management plan in order to mitigate the extensive negative environmental and social impacts of the project. The results also indicated the potential of the model in assisting in the resolution of questions of the sustainability of local projects, which are assessed through quantitative-based EIA.  相似文献   

5.
《Journal of Structural Geology》1999,21(8-9):1057-1063
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6.
The world over, neoliberal modes of conservation are hybridising with, or even replacing, other forms of conservation. Under the banner of ‘win–win’ policies, planners actively work to commoditize natural resources and the social relations that determine the use and conservation of these resources. While these general processes seem to hold sway globally, it is crucial not to lose sight of the context specific ways in which neo-liberalism influences conservation practice and local outcomes. The paper examines how neo-liberalism’s global pervasiveness becomes manifest across different levels and scales in South Africa and the Philippines. The conclusion suggests that as a result of these neoliberal pressures, emphasis is shifting from local constructions of ‘nature’ by communities to what the environment should mean for communities in terms of commodified resources and growing capitalist markets.  相似文献   

7.
The systematic study of both natural and synthetic clinopyroxenes often indicates the presence in the difference Fourier map of a maximum of residual density of up to 0.8 electrons, here labelledM2′, close to theM2 site along the diad axis, defining a square pyramid co-ordination polyhedron. To investigate the nature and the crystalchemical implications of this feature, a limited but representative set of clinopyroxenes of volcanic, metamorphic and synthetic origin has been investigated by X-ray structure refinement (at 0.7 and 0.4 Å resolution), by microprobe analysis and by transmission electron microscopy. The most important results are: a) at increasing resolution, the height of theM2′ peak increases while its co-ordinates move towardM2; b) as (Ca + Na) content approaches 1.0 atom per formula unit,M2′ vanishes; c)M2′ has been found in clinopyroxenes which show differing incipient exsolution microstructures, from spinodal decomposition to non-periodic fluctuations, as well as in homogeneous specimens. The presence ofM2′ is interpreted in terms of the simultaneous coexistence in the crystals of two different structural models, approximately diopside and clinoenstatite. An accurate evaluation of the totalM2 + M2′ site occupancy is strongly suggested in XREF work, particularly when thermodynamic and kinetic considerations have to be obtained with accurate determinations of site occupancy factors as a starting point.  相似文献   

8.
Specific rates of flotation, K, as a function of particle size, d, and fractional mineral content, W, were measured for a quartz-hematite ore in a continuous flotation system using hydroxamate collector. The resulting K-d-W surface is explained in terms of flotation mechanisms and results of previous investigators. A K-d-W relationship will be of value to flotation models.  相似文献   

9.
The Van earthquake (M W 7.1, 23 October 2011) in E-Anatolia is typical representative of intraplate earthquakes. Its thrust focal character and aftershock seismicity pattern indicate the most prominent type of compound earthquakes due to its multifractal dynamic complexity and uneven compressional nature, ever seen all over Turkey. Seismicity pattern of aftershocks appears to be invariably complex in its overall characteristics of aligned clustering events. The population and distribution of the aftershock events clearly exhibit spatial variability, clustering-declustering and intermittency, consistent with multifractal scaling. The sequential growth of events during time scale shows multifractal behavior of seismicity in the focal zone. The results indicate that the extensive heterogeneity and time-dependent strength are considered to generate distinct aftershock events. These factors have structural impacts on intraplate seismicity, suggesting multifractal and unstable nature of the Van event. Multifractal seismicity is controlled by complex evolution of crustal-scale faulting, mechanical heterogeneity and seismic deformation anisotropy. Overall seismicity pattern of aftershocks provides the mechanism for strain softening process to explain the principal thrusting event in the Van earthquake. Strain localization with fault weakening controls the seismic characterization of Van earthquake and contributes to explain the anomalous occurrence of aftershocks and intraplate nature of the Van earthquake.  相似文献   

10.
Shock loading experiments on single crystal ilmenite (FeTiO3) are carried out up to peak pressures of 80 GPa using a newly built two-stage light gas gun. Shock effects are investigated by means of X-ray precission technique and Mössbauer spectroscopy. Shock effects are largely controlled by the anisotropic nature of the ilmenite structure. Considerable deformations are observed even in a pressure level of 30 GPa in the shocked crystal when the shock propagation direction is parallel to the c axis, whereas little effects are seen up to 55 GPa when the crystal is shocked parallel to the c plane (cleavage plane). The greatest deformation is introduced in the planes containing the c axis, while less remarkable effects are seen in the plane perpendicular to the c axis. Residual effects are favorably compared with the compression anomalies found in the Hugoniot measurements by King and Ahrens (1976). Mössbauer measurements also reveal that a fraction of highly disturbed regions increases with increasing shock loading pressure. These observations are explained in terms of current heterogeneous yielding model of brittle substances under shock loading, where internal fragmentation is preferentially formed so as to give c-platelet domains that are mutually misoriented with each other.  相似文献   

11.
L.W. Senger  S. Chang 《Geoforum》1975,6(2):164-167
Ecology is receiving increased attention as a research focus for geography and other academic disciplines. A consideration of basic concepts and the relationship of such ideas to the organizing frameworks of individual disciplines is needed to define the position of ecology as a substantive field or methodological approach. Geographers are concerned with the identification and explanation of the spatial patterning of earth phenomena. The ecosystem concept, with an emphasis on structure, networks of interaction, and function, is quite useful for conducting such geographical investigations. It acquires enhanced value within the subfields of geography by refining the approach through topical foci. Cultural ecology is one example; in this case a system is studied in terms of how its various cultural and biophysical components relate to a cultural characteristic (s) selected as the focus of investigation. Ecology is thus viewed as a methodological approach with significant applications for geographic research.  相似文献   

12.
Various statistical methods for predicting mineral potential from geological maps are reviewed. It is pointed out that, if the features are coded in more detail for relatively small cells, several new problems arise because of the dichotomous nature of the resulting variables. The objective of this paper is to present a method for the automatic contouring of both discovered and undiscovered deposits of a given type in terms of the geological framework. It is based on the assumption that the probability of occurrence of a deposit is fully determined by a combination of functions of the mappable geological attributes in a region. Application of the logistic model is proposed for the situation in which relatively few deposits of a given type are known to exist in the study region.  相似文献   

13.
A high rank coal was tested in terms of loading and unloading to characterize changes in the permeability and effective porosity of tectonically deformed coals. The coal sample, an anthracite, is subdivided into four types according to its structure, namely, the primary structure coal, cataclastic coal (the weakest deformation coal), granulated coal (the moderate deformation coal), and mylonitic coal (the intensest deformation coal); the latter three types are considered to be tectonic deformation coals. Permeability of tectonically deformed coals shows a negative exponential relation to stress. The intenser the structural deformation in coal is, the lower the permeability. Two evaluation parameters, namely, loss rate m (0.8318–0.9476) and damage rate n (0.447–0.6556), which are related to changes in permeability, increase with increasing structural deformation in coal. The cleat compressibility factor declines with increasing difference in effective stress and increases with increasing structural deformation in coal. This study proposes a calculation method for evaluating the porosity damage. Similar to the loss ratio and damage rate, this parameter (η) increases with increasing structural deformation in coal and reveals the relationship between the porosity damage and the structural deformation in coal.  相似文献   

14.
This paper explores audience engagements with popular television food media via a focus on UK based celebrity chef Jamie Oliver. One series, Jamie’s Ministry of Food (JMOF) is argued to form a common resource around which different audience positions are constructed and performed. This paper draws on focus group and interview data from two stereotypically contrasting UK towns, Rotherham and Tunbridge Wells. The paper identifies three key tropes: embarrassment, voyeurism and reflexive positioning. In Rotherham I show how the formation of embarrassment is premised upon an imagined social relationship between distant audiences, JMOF and an anxiously anticipating subject. In Tunbridge Wells I explore the recursive relationship between Voyeuristic class disgust and subsequent reflexive positioning. I argue that reflexive positioning works through exchanges of public self critique and public media critique in order to attain and maintain a position within a social group. Voyeuristic and reflexive audience positions are argued to be complementary to one another, forming two parts of a wider flexible relationship to media and the social, possessed by those in particular geographical, as well as subject, positions. The ostensible aims of JMOF are the improvement of health and culinary skill and yet these are complicated and interrogated in audience accounts. Matters of a moral nature, including discussions of social class, poverty, disgust, pleasure, and the ethics of spectatorship take prominence.  相似文献   

15.
The rich heritage of landscape history in Denmark enjoys a high degree of preservation through legislation. The new nature preservation law of 1969 is discussed in terms of its proposals for the establishment of nature parks in Denmark. Four relevance clusters — the village, the rural parish church, the landscape of enclosure, and the Bronze Age burial mound landscape — are proposed and discussed as they can contribute aspects of meaningful visible history within the recreational arena of the Danish nature park.  相似文献   

16.
The unconfined aquifer of the Continental Terminal in Niger was investigated by magnetic resonance sounding (MRS) and by 14 pumping tests in order to improve calibration of MRS outputs at field scale. The reliability of the standard relationship used for estimating aquifer transmissivity by MRS was checked; it was found that the parametric factor can be estimated with an uncertainty ≤150% by a single point of calibration. The MRS water content (θ MRS) was shown to be positively correlated with the specific yield (Sy), and θ MRS always displayed higher values than Sy. A conceptual model was subsequently developed, based on estimated changes of the total porosity, Sy, and the specific retention Sr as a function of the median grain size. The resulting relationship between θ MRS and Sy showed a reasonably good fit with the experimental dataset, considering the inherent heterogeneity of the aquifer matrix (residual error is ~60%). Interpreted in terms of aquifer parameters, MRS data suggest a log-normal distribution of the permeability and a one-sided Gaussian distribution of Sy. These results demonstrate the efficiency of the MRS method for fast and low-cost prospection of hydraulic parameters for large unconfined aquifers.  相似文献   

17.
Hubert Cochet 《Geoforum》2012,43(1):128-136
Among the many concepts used in farming systems research, the agrarian system—système agraire—stands out in the works of francophone agronomists, agricultural economists and geographers. It is an all-encompassing concept, capable of making sense of agricultural activities at a regional scale in a way that accounts for both ecological and socio-economic dimensions. The objective of this article is to trace the evolution of this original concept, reflect on the difficulties inherent to its use, and examine its relevance to agricultural research. After exploring its origins and development within the French school of Comparative Agriculture, the author analyzes its components in terms of constituting sub-systems. Next, the challenges associated with the agrarian system approach are addressed, particularly in terms of boundaries and scales of analysis. Part four discusses the similarities and differences between this approach and others, more commonly used by non-francophones. The article concludes with a discussion of the usefulness of the approach in terms of identifying obstacles to agricultural development.  相似文献   

18.
Dear and others associated with the ‘Los Angeles School of Urbanism’ have presented a series of challenging ideas regarding changes in urban form as a consequence of the shift from modernism to post-modernism. Some of those challenges relate to a city’s ethnic diversity and residential segregation, with Los Angeles presented as a paradigm exemplar of an emerging new urban form. This paper evaluates the arguments that Los Angeles in particular, and Californian metropolitan areas more generally, differ from metropolitan areas elsewhere in the United States in the nature of ethnic residential segregation there. Regression analyses provide little support for the argument, but graphical analyses show that although Los Angeles does not differ from the general, US-wide trends, its almost unique nature in terms of its ethnic diversity means that it clearly stands out as a place with a different pattern shared by very few others.  相似文献   

19.
Crustal deformation in front of an indenter is often affected by the indenter’s geometry, rheology, and motion path. In this context, the kinematics of the Jaufen- and Passeier faults have been studied by carrying out paleostress analysis in combination with crustal-scale analogue modelling to infer (1) their relationship during indentation of the Adriatic plate and (2) their sensitivity in terms of fault kinematics to the geometry and motion path of Adria. The field study reveals mylonites along the Jaufen fault, which formed under lower greenschist facies conditions and is associated with top-to-the-west/northwest shear with a northern block down component. In addition, a brittle reactivation of the Jaufen shear zone under NNW–SSE to NW–SE compressional and ENE–WSW tensional stress conditions was deduced from paleostress analysis. The inferred shortening direction is consistent with fission track ages portraying Neogene exhumation of the Meran-Mauls basement south of the fault. Along the Passeier fault, deformation was only brittle to semi-ductile and paleostress tensors record that the fault was subjected to E–W extension along its northern segment varying into NW–SE compression and sinistral transpression along its southern segment. In the performed analogue experiments, a rigid, triangular shaped indenter was pushed into a sand pile resulting in the formation of a Passeier-like fault sprouting from the indenter’s tip. These kinds of north-trending tip faults formed in all experiments with shortening directions towards the NW, N, or NE. Consequently, we argue that the formation of the Passeier fault strongly corresponds to the outline of the Adriatic indenter and was only little affected by the indenter’s motion path due to induced strain partitioning in front of the different indenter segments. The associated fault kinematics along the Passeier fault including both E–W extension and NNW to NW shortening, however, is most consistent with a northward advancing Adriatic indenter.  相似文献   

20.
This preliminary petrographic study of a Paleozoic carbonate section (Upper Ordovician to Silurian) in the Lone Mountain district in east-central Nevada provides new information on its microfacies and dolomitization. The occurrence of diversified microfacies in rocks from this section reveals the complex nature of their depositional history, as well as the subsequent diagenesis. Most microfacies from these rocks fall into two general groups: (1) dolomite facies which predominates in the Hanson Creek Formation (Upper Ordovician to Lowest Silurian) and the Lone Mountain Unit 1; and (2) dolomitized limestone facies which is common in the Lone Mountain Formation (Upper Silurian).The dolomite in the mid-Paleozoic carbonate section of the Lone Mountain is overwhelmingly diagenetic in origin. The early diagenetic dolomite is characterized by its homogeneous texture, uniform medium-to-coarse grain size and poorly preserved fossil impressions. The fossil content in this type of dolomite indicates its original calcareous nature. On the other hand, the late-diagenetic dolomite is characterized by its heterogeneous texture, non-uniform grain-size, detrital-quartz content and the presence of partly or incompletely altered fossil structures.  相似文献   

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