Earth rotation in the hipparcos reference frame     

J. Vondrak  C. Ron  I. Pešek 《Celestial Mechanics and Dynamical Astronomy》1996,66(1):115-122

New determination of the Earth orientation parameters (EOP), based on optical astrometry observations since the beginning of the century, is now under preparation by the Working group established by Commission 19 of the IAU. The Hipparcos catalog is to define the celestial reference frame in which the new series of EOP are to be described, The novelties of the prepared solution are the higher resolution (5 days) and more parameters estimated from the solution (celestial pole offsets, rheological parameters of the Earth, certain instrumental constants). The mathematical model of the solution is described, and the results based on the observations made with 46 instruments at 29 observatories and a preliminary Hipparcos catalog are presented.  相似文献   

Shoreface translation and the Holocene stratigraphic record: Examples from Nova Scotia, the Mississippi Delta and eastern Australia     

Ron Boyd  Shea Penland 《Marine Geology》1984,60(1-4):391-412

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Geomorphological evidence for upslope canyon-forming processes on the northern KwaZulu-Natal shelf,SW Indian Ocean,South Africa     

Andrew N. Green  John A. Goff  Ron Uken 《Geo-Marine Letters》2007,27(6):399-409

A geomorphological and statistical analysis of slope canyons from the northern KwaZulu-Natal continental margin is documented and compared with submarine canyons from the Atlantic margin of the USA. The northern KwaZulu-Natal margin is characterized by increasing upslope relief, concave slope-gradient profiles and features related to upslope growth of the canyon forms. Discounting slope-gradient profile, this morphology is strikingly similar to canyon systems of the New Jersey slope. Several phases of canyon incision indicate that downslope erosion is also an important factor in the evolution of the northern KwaZulu-Natal canyon systems. Despite the strong similarities between the northern KwaZulu-Natal and New Jersey slope-canyon systems, key differences are evident: (1) the concavity of the northern KwaZulu-Natal slope, contrasting with the ∼linear New Jersey slope; (2) the relative isolation of the northern KwaZulu-Natal canyons, rather than the dense clustering of the New Jersey canyons; and (3) the absence of strongly shelf-breaching canyons along the northern KwaZulu-Natal margin. In comparison with the New Jersey margin, we surmise a more youthful stage of canyon evolution, a result of either the canyons themselves being younger or the formative processes being less active. Less complicated patterns of erosion resulting from reduced sediment availability have developed in northern KwaZulu-Natal. The reduction in slope concavity on the New Jersey margin may be the result of grading of the upper slope by intensive headward erosion, a process more subdued—or less evident—on the KwaZulu-Natal margin.  相似文献   

Open source, spatial analysis, and activity-travel behaviour research: capabilities of the aspace package   总被引：2，自引：0，他引：2  

Ron N. Buliung  Tarmo K. Remmel 《Journal of Geographical Systems》2008,10(2):191-216

This paper reports on recent experience with the development of aspace, an Open Source (OS) library for the geographic visualization and analysis of activity-travel behaviour. The paper begins with an overview of recent progress with respect to the convergence of Open Source technology, spatial analysis, and travel behaviour research. The remainder of the paper focuses on aspace; a collection of functions that, when combined with data describing the geographical location of daily activities, can be used to visualize and describe spatial properties of individual and household activity spaces. These properties include: size, orientation, shape, and the geographical dispersion of activity locations contained within the activity space. Several planar geometries are used to transform measurable spatial properties into intuitive objects for visualizing spatial patterns of activity participation. Experiments are conducted, using data from the first wave of the 2003 Toronto Travel Activity Panel Survey, to demonstrate the potential application of aspace for basic and applied policy-based research into activity-travel behaviour. The toolkit is distributed as a downloadable ‘package’ from the Open Source R Project for Statistical Computing.   相似文献   

Geography (or geographers) and earth system science   总被引：1，自引：0，他引：1  

Ron Johnston 《Geoforum》2006,37(1):7-11

A response to Pitman’s recent arguments regarding a perceived invasion of geographers’ territory within the academic division of labour by earth system science. Geography is not the grand synthesiser, the only discipline which can explain the big picture, and arrogant claims that it is are counter-productive, both within and outwith the discipline. Geographers should just get on with what they are doing—well.  相似文献   

An investigation of upper mantle heterogeneity beneath the Archaean and Proterozoic crust of western Canada from Lithoprobe controlled-source seismic experiments     

Andrew R. Gorman  Balzs Nmeth  Ron M. Clowes  Zoltan Hajnal 《Tectonophysics》2006,416(1-4):187

Observations of upper mantle reflectivity at numerous locations around the world have been linked to the presence of a heterogeneous distribution of rock types within a broad layer of the upper mantle. This phenomenon is observed in wide-angle reflection data from Lithoprobe's Alberta Basement Transect [the SAREX and Deep Probe experiments of 1995] and Trans-Hudson Orogen Transect [the THoRE experiment of 1993]. SAREX and Deep Probe image the Archaean lithosphere of the Hearne and Wyoming Provinces, whereas THoRE images the Archaean and Proterozoic lithosphere of the Trans-Hudson Orogen and neighbouring areas.Finite-difference synthetic seismograms are used to constrain the position and physical properties of the reflective layer. SAREX/Deep Probe modelling uses a 2-D visco-elastic finite-difference routine; THoRE modelling uses a pseudospectral algorithm. In both cases, the upper mantle is parameterized in terms of two media. One medium is the background matrix; the other is statistically distributed within the first as a series of elliptical bodies. Such a scheme is suitable for modelling: (1) variations in lithology (e.g., a peridotite matrix with eclogite lenses) or (2) variations in rheology (e.g., lenses of increased strain within a less strained background).The synthetic seismograms show that the properties of heterogeneities in the upper mantle do not change significantly between the two Lithoprobe transects. Beneath the Trans-Hudson Orogen in Saskatchewan, the layer is best modelled to lie at depths between 80 and 150 km. Based on observations from perpendicular profiles, anisotropy of the heterogeneities is inferred. Beneath the Precambrian domains of Alberta, 400 km to the west, upper mantle heterogeneities are modelled to occur between depths of 90 and 140 km. In both cases the heterogeneous bodies within the model have cross-sectional lengths of tens of kilometers, vertical thicknesses less than 1 km, and velocity contrasts from the background of − 0.3 to − 0.4 km/s. Based on consistency with complementary data and other results, the heterogeneous layer is inferred to be part of the continental lithosphere and may have formed through lateral flow or deformation within the upper mantle.  相似文献   

EMRYS JONES 1920–2006     

Ron  Johnston 《The Geographical journal》2006,172(4):348-349

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The Port Mouton Shear Zone: intersection of a regional fault with a crystallizing granitoid pluton   总被引：2，自引：0，他引：2  

D. Barrie Clarke  Krista L. McCuish  Ron H. Vernon  Victor Maksaev  Brent V. Miller   《Lithos》2002,61(3-4):141-159

The peraluminous tonalite–monzogranite Port Mouton Pluton is a petrological, geochemical, structural, and geochronological anomaly among the many Late Devonian granitoid intrusions of the Meguma Lithotectonic Zone of southern Nova Scotia. The most remarkable structural feature of this pluton is a 4-km-wide zone of strongly foliated (040/subvertical) monzogranites culminating in a narrow (10–30 m), straight, zone of compositionally banded rocks that extends for at least 3 km along strike. The banded monzogranites consist of alternating melanocratic and leucocratic compositions that are complementary to the overall composition of that part of the pluton, suggesting an origin by mineral–melt and mineral–mineral sorting. Biotite and feldspar are strongly foliated in the plane of the compositional bands. These compositional variations and foliations originated by a process of segregation flow during shearing of the main magma with a crystallinity of 55–75%. Subsequent minor brittle fracturing of feldspars, twinning of microcline, development of blocky sub-grains in quartz, and kinking of micas demonstrate overprinting by a high-temperature deformation straddling the monzogranite solidus. Small folds and late sigmoidal dykes indicate dextral movement on the shear zone. This Port Mouton Shear Zone (PMSZ) is approximately co-linear with the only outcrops of Late Devonian mafic intrusions in the area, two of which are syn-plutonic with well-developed mingling textures in the marginal tonalite of the Port Mouton Pluton. Also closely co-linear with the mafic intrusions are a granitoid dyke that extends well beyond the outer contact of the Port Mouton Pluton, a swarm of large aligned angular xenolithic slabs, a zone of thin wispy schlieren banding, a large Be-bearing pegmatite, and a breccia pipe with abundant garnetiferous metapelitic xenoliths. In various ways, the shear zone may control all of these features. The Port Mouton Shear Zone is parallel to many other NE-trending faults and shear zones in the northern Appalachians, probably related to the docking of the Meguma Zone along the Cobequid–Chedabucto Fault system.  相似文献   

New Labour, new geography? The electoral geography of the 1997 British General Election     

Charles Pattie  Ron Johnston  Danny Dorling  Dave Rossiter  Helena Tunstall  Iain MacAllister 《Area》1997,29(3):253-259

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Inversion of potential field data by genetic algorithms     

Fabio Boschetti  Mike Dentith  Ron List 《Geophysical Prospecting》1997,45(3):461-478

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