Central configurations and relative equilibria in then-body problem inE 4     

Julian I. Palmore 《Celestial Mechanics and Dynamical Astronomy》1980,21(1):21-24

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Do Stable Isotope Data from Calcrete Record Late Pleistocene Monsoonal Climate Variation in the Thar Desert of India?     

Julian E. Andrews  Ashok K. Singhvi  Ansu J. Kailath  Ralph Kuhn  Paul F. Dennis  Sampat K. Tandon  Ram P. Dhir 《Quaternary Research》1998,50(3):240-251

Late Pleistocene terrestrial climate records in India may be preserved in oxygen and carbon stable isotopes in pedogenic calcrete. Petrography shows that calcrete nodules in Quaternary sediments of the Thar Desert in Rajasthan are pedogenic, with little evidence for postpedogenic alteration. The calcrete occurs in four laterally persistent and one nonpersistent eolian units, separated by colluvial gravel. Thermoluminescence and infrared- and green-light-stimulated luminescence of host quartz and feldspar grains gave age brackets for persistent eolian units I–IV of ca. 70,000–60,000, ca. 60,000–55,000, ca. 55,000–43,000, and ca. 43,000–25,000 yr, respectively. The youngest eolian unit (V) is <10,000 yr old and contains no calcrete. Stable oxygen isotope compositions of calcretes in most of eolian unit I, in the upper part of eolian unit IV, and in the nonpersistent eolian unit, range between −4.6 and −2.1‰ PDB. These values, up to 4.4‰ greater than values from eolian units II and III, are interpreted as representing nonmonsoonal¹⁸O-enriched “normal continental” waters during climatic phases when the monsoon weakened or failed. Conversely, 25,000–60,000-yr-old calcretes (eolian units II and III) probably formed under monsoonal conditions. The two periods of weakened monsoon are consistent with other paleoclimatic data from India and may represent widespread aridity on the Indian subcontinent during isotope stages 2 and 4. The total variation in δ¹³C is 1.7‰ (0.0–1.7‰), and δ¹³C covaries positively and linearly with δ¹⁸O. δ¹³C values are highest when δ¹⁸O values indicate the most arid climatic conditions. This is best explained by expansion of C₄grasses at the expense of C₃plants at low latitudes during glacial periods when atmosphericpCO₂was lowered. C₄dominance was overridingly influenced by global change in atmosphericpCO₂despite the lowered summer rainfall.  相似文献   

Three-dimensional seismic structure and moment tensors of non-double-couple earthquakes at the Hengill–Grensdalur volcanic complex, Iceland     

Miller  Julian  & Foulger 《Geophysical Journal International》1998,133(2):309-325

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Seismic image of a CO₂ reservoir beneath a seismically active volcano     

BruceR.Julian  A.M.Pitt  G.R.Foulger 《Geophysical Journal International》1998,133(1):F7-F10

Mammoth Mountain is a seismically active volcano 200 000 to 50 000 years old, situated on the southwestern rim of Long Valley caldera, California. Since 1989 it has shown evidence of unrest in the form of earthquake swarms (Hill et al. 1990), volcanic 'long-period' earthquakes (Pitt & Hill 1994), increased output of magmatic ³He (Sorey et al. 1993) and the emission of about 500 tonnes day ⁻¹ of CO₂ (Farrar et al. 1995; Hill 1996; M. Sorey, personal communication, 1997), which has killed trees and poses a threat to human safety. Local-earthquake tomography shows that in mid-1989 areas of subsequent tree-kill were underlain by extensive regions where the ratio of the compressional and shear elastic-wave speeds V_P/V_S was about 9 per cent lower than in the surrounding rocks. Theory (Mavko & Mukerji 1995), experiment (Ito, DeVilbiss & Nur 1979), and experience at other geothermal/volcanic areas (Julian et al. 1996) and at petroleum reservoirs (Harris et al. 1996) indicate that V_P/V_S is sensitive to pore-fluid compressibility, through its effect on V_P . The observed V_P/V_S anomaly is probably caused directly by CO₂, and seismic V_P/V_S tomography is thus a promising tool for monitoring gas concentration and movement in volcanoes, which may in turn be related to volcanic activity.  相似文献   

Mechanisms of hydrothermal crystallization of quartz at 250°C and 15 kbar     

Yukihiro Matsuhisa  Julian R. Goldsmith  Robert N. Clayton 《Geochimica et cosmochimica acta》1978,42(2):173-182

Oxygen isotopic exchange between quartz and water, using a novel technique in which both ¹⁸O/¹⁶O and ¹⁷O/¹⁶O fractionations were measured, yielded an equilibrium fractionation Δ¹⁸ = 9.0 at 250°C and 15 kbar. The reaction proceeds predominantly by solution of fine grains and growth of larger grains. Exchange by solid-state diffusion is immeasurably slow at this temperature. Under the same experimental conditions, cristobalite behaves quite differently, becoming transformed to sub-micron quartz crystals in a few minutes. The phase transformation is accompanied by a kinetic isotope effect yielding quartz in isotopic disequilibrium with water. It is possible that such disequilibrium products are also formed in other experiments involving phase transitions or mineral syntheses.  相似文献   

The Inverse Problem of Refraction Travel Times,Part II: Quantifying Refraction Nonuniqueness Using a Three-layer Model     

Julian?IvanovEmail author  Richard D.?Miller  Jianghai?Xia  Don?Steeples 《Pure and Applied Geophysics》2005,162(3):461-477

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Linkage between ocean climate, post-smolt growth, and survival of Atlantic salmon (Salmo salar L.) in the North Sea area   总被引：3，自引：0，他引：3  

Friedland  Kevin D.; Hansen  Lars P.; Dunkley  David A.; MacLean  Julian C. 《ICES Journal of Marine Science》2000,57(2):419-429

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The impacts of source structure on geodetic parameters demonstrated by the radio source 3C371     

Ming H. Xu  Robert Heinkelmann  James M. Anderson  Julian Mora-Diaz  Maria Karbon  Harald Schuh  Guang L. Wang 《Journal of Geodesy》2017,91(7):767-781

Closure quantities measured by very-long-baseline interferometry (VLBI) observations are independent of instrumental and propagation instabilities and antenna gain factors, but are sensitive to source structure. A new method is proposed to calculate a structure index based on the median values of closure quantities rather than the brightness distribution of a source. The results are comparable to structure indices based on imaging observations at other epochs and demonstrate the flexibility of deriving structure indices from exactly the same observations as used for geodetic analysis and without imaging analysis. A three-component model for the structure of source 3C371 is developed by model-fitting closure phases. It provides a real case of tracing how the structure effect identified by closure phases in the same observations as the delay observables affects the geodetic analysis, and investigating which geodetic parameters are corrupted to what extent by the structure effect. Using the resulting structure correction based on the three-component model of source 3C371, two solutions, with and without correcting the structure effect, are made. With corrections, the overall rms of this source is reduced by 1 ps, and the impacts of the structure effect introduced by this single source are up to 1.4 mm on station positions and up to 4.4 microarcseconds on Earth orientation parameters. This study is considered as a starting point for handling the source structure effect on geodetic VLBI from geodetic sessions themselves.  相似文献   

Data-driven estimation of building interior plans     

Julian F. Rosser  Gavin Smith  Jeremy G. Morley 《International journal of geographical information science》2017,31(8):1652-1674

This work investigates constructing plans of building interiors using learned building measurements. In particular, we address the problem of accurately estimating dimensions of rooms when measurements of the interior space have not been captured. Our approach focuses on learning the geometry, orientation and occurrence of rooms from a corpus of real-world building plan data to form a predictive model. The trained predictive model may then be queried to generate estimates of room dimensions and orientations. These estimates are then integrated with the overall building footprint and iteratively improved using a two-stage optimisation process to form complete interior plans.

The approach is presented as a semi-automatic method for constructing plans which can cope with a limited set of known information and constructs likely representations of building plans through modelling of soft and hard constraints. We evaluate the method in the context of estimating residential house plans and demonstrate that predictions can effectively be used for constructing plans given limited prior knowledge about the types of rooms and their topology.  相似文献   

Probing the Troodos Ophiolite: IGCP-649 Workshop and Field Excursion Held in Agros-Cyprus     

YANG Jingsui  Julian PEARCE  Yildirim DILEK 《《地质学报》英文版》2016,90(3):1041-1044

正The second IGCP-649 Workshop,held in Agros-Cyprus during 14-20 May 2016,brought together nearly fifty international scientists from around the world,and included a 5-day field excursion on the classic Troodos ophiolite.Organized by the IGCP-649 Project Leadership and the Geological Survey Department of Cyprus,the  相似文献