Performance and Early Results from the Golf Instrument Flown on the Soho Mission     

A. H. Gabriel  J. Charra  G. Grec  J.-M. Robillot  T. Roca Cortés  S. Turck-Chièze  R. Ulrich  S. Basu  F. Baudin  L. Bertello  P. Boumier  M. Charra  J. Christensen-Dalsgaard  M. Decaudin  H. Dzitko  T. Foglizzo  E. Fossat  R. A. García  J. M. Herreros  M. Lazrek  P. L. Pallé  N. Pétrou  C. Renaud  C. Régulo 《Solar physics》1997,175(2):207-226

GOLF in-flight commissioning and calibration was carried out during the first four months, most of which represented the cruise phase of SOHO towards its final L1 orbit. The initial performance of GOLF is shown to be within the design specification, for the entire instrument as well as for the separate sub-systems. Malfunctioning of the polarising mechanisms after 3 to 4 months operation has led to the adoption of an unplanned operating sequence in which these mechanisms are no longer used. This mode, which measures only the blue wing of the solar sodium lines, detracts little from the detection and frequency measurements of global oscillations, but does make more difficult the absolute velocity calibration, which is currently of the order of 20%. Data continuity in the new mode is extremely high and the instrument is producing exceptionally noise-free p-mode spectra. The data set is particularly well suited to the study of effects due to the excitation mechanism of the modes, leading to temporal variations in their amplitudes. The g modes have not yet been detected in this limited data set. In the present mode of operation, there are no indications of any degradation which would limit the use of GOLF for up to 6 years or more.  相似文献   

Phase differences between luminosity and velocity measurements of the acoustic modes     

A. Jiménez  M. Álvarez  N. B. Andersen  V. Domingo  A. Jones  P. L. Pallé  T. Roca Cortés 《Solar physics》1990,126(1):1-19

With two photometric stations (Tenerife and Baja California) the luminosity p-mode spectrum at different wavelengths has been identified. After a coherence analysis between data from both stations to verify the solar origin of the peaks identified in luminosity, a comparative study with simultaneous velocity measurements (obtained at Tenerife only) has also been made. As a result the frequency dependence of the phase difference between luminosity and velocity p-modes has been obtained that is interpreted in terms of a nonadiabatic behaviour of the solar atmosphere. The amplitude ratios between luminosity and velocity p-modes have also been obtained. All these results are compared with theoretical expectations.  相似文献   

Comments On “Evaluating The Similarity Of Geographic Flows”     

Katherine Klink  Cort J. Willmott 《The Professional geographer》1985,37(1):56-58

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The geometry of the active strike-slip El Tigre Fault,Precordillera of San Juan,Central–Western Argentina: integrating resistivity surveys with structural and geomorphological data     

Sabrina Y. Fazzito  José M. Cortés  Augusto E. Rapalini  Carla M. Terrizzano 《International Journal of Earth Sciences》2013,102(5):1447-1466

The geometry and related geomorphological features of the right-lateral strike-slip El Tigre Fault, one of the main morphostructural discontinuities in the Central–Western Precordillera of Argentina, were investigated. Achievements of this survey include: recognition of structural and geometrical discontinuities along the fault trace, identification and classification of landforms associated with local transpressional and transtensional sectors, observation of significant changes in the fault strike and detection of right and left bends of different wavelength. In the Central Segment of the El Tigre Fault, 2D electrical resistivity tomography surveys were carried out across the fault zone. The resistivity imaging permitted to infer the orientation of the main fault surface, the presence of blind fault branches along the fault zone, tectonic tilting of the Quaternary sedimentary cover, subsurface structure of pressure ridges and depth to the water table. Based on this information, it is possible to characterize the El Tigre Fault also as an important hydro-geological barrier. Our survey shows that the main fault surface changes along different segments from a high-angle to a subvertical setting whilst the vertical-slip component is either reverse or normal, depending on the local transpressive or transtensive regime induced by major bends along the trace. These local variations are expressed as sections of a few kilometres in length with relatively homogeneous behaviour and frequently separated by oblique or transversal structures.  相似文献   

The Mesolithic–Neolithic transition in southern Iberia     

Miguel Cortés Sánchez  Francisco J. Jiménez Espejo  María D. Simón Vallejo  Juan F. Gibaja Bao  António Faustino Carvalho  Francisca Martinez-Ruiz  Marta Rodrigo Gamiz  José-Abel Flores  Adina Paytan  José A. López Sáez  Leonor Peña-Chocarro  José S. Carrión  Arturo Morales Muñiz  Eufrasia Roselló Izquierdo  José A. Riquelme Cantal  Rebecca M. Dean  Emília Salgueiro  Rafael M. Martínez Sánchez  Nuno F. Bicho 《Quaternary Research》2012,77(2):221-234

New data and a review of historiographic information from Neolithic sites of the Malaga and Algarve coasts (southern Iberian Peninsula) and from the Maghreb (North Africa) reveal the existence of a Neolithic settlement at least from 7.5 cal ka BP. The agricultural and pastoralist food producing economy of that population rapidly replaced the coastal economies of the Mesolithic populations. The timing of this population and economic turnover coincided with major changes in the continental and marine ecosystems, including upwelling intensity, sea-level changes and increased aridity in the Sahara and along the Iberian coast. These changes likely impacted the subsistence strategies of the Mesolithic populations along the Iberian seascapes and resulted in abandonments manifested as sedimentary hiatuses in some areas during the Mesolithic–Neolithic transition. The rapid expansion and area of dispersal of the early Neolithic traits suggest the use of marine technology. Different evidences for a Maghrebian origin for the first colonists have been summarized. The recognition of an early North-African Neolithic influence in Southern Iberia and the Maghreb is vital for understanding the appearance and development of the Neolithic in Western Europe. Our review suggests links between climate change, resource allocation, and population turnover.  相似文献   

Low Frequency End Performance of a Symmetrical Configuration Antenna for the Square Kilometre Array (SKA)     

Germán Cortés-Medellín 《Experimental Astronomy》2004,17(1-3):111-118

The frequency specifications of the Square Kilometre Array (SKA) call for an optimum operation of the antenna elements from 25 down to 100 MHz. The current 12 m diameter US-SKA design is specified from 500 up to 25 GHz, with an upper goal of 35 GHz. At the low frequency end of the band (i.e., 100 MHz), a 12 m reflector antenna is about four wavelengths in diameter. Then, the question is: how well can you do, at this low frequency end of the specified band of operation for the SKA, with a symmetric reflector configuration using an ultra-wide-band prime focus feed? This paper presents the analysis of the antenna performance, in terms of A _eff/T _A, of three symmetric configurations of the 12 m US-SKA antenna design between 100 and 200 MHz.  相似文献   

A More Rational Climatic Moisture Index*     

Cort J. Willmott  Johannes J. Feddema 《The Professional geographer》1992,44(1):84-88

A climatic moisture index (I_m) used extensively by C. W. Thornthwaite and others is examined, and a modified version of the index is proposed. Arbitrary limits [?100 ≤ I_m≤ 100 (∞? 1)], combined with its dimensionless property, make the original index difficult to interpret. Our refined version also is dimensionless, but the limits have been recast so that ?1 ≤ I_m≤ 1. Wet climates have positive values of I_m while dry climates are negative, and the index is symmetric about zero. The spatial distribution of our modified annual-average moisture index over the world's continents is mapped and described.  相似文献   

A SAMPLING FRAME FOR THE RURAL-URBAN FRINGE     

Robin J. Pryor 《The Professional geographer》1968,20(4):257-261

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Petrology of the Permian Yellow Sands of northeastern England and their North Sea Basin equivalents     

Wayne A. Pryor 《Sedimentary Geology》1971

The Permian Yellow Sands of northeastern England and the Permian Weissliegendes of the English North Sea Basin are petrologically defined as multicycle, moderately sorted, subrounded graywackes, subgraywackes and subarkoses with post-depositionally etched and overgrown grains. These sandstones were derived by the marine reworking of the Permian Rotliegendes and transported from the east to the southwest. Petrologic data show that these Upper Permian sandstones were deposited in a shallow marine environment and that the commonly held aeolian dune interpretation for them should be rejected. Their formation during the transgression of the Zechstein Sea places them within the Zechstein sequence and therefore they are Thuringian in age rather than Saxonian.  相似文献   

Accelerating the solution of linear systems appearing in two-phase reservoir simulation by the use of POD-based deflation methods     

Diaz Cortés  Gabriela Berenice  Vuik  Cornelis  Jansen  Jan-Dirk 《Computational Geosciences》2021,25(5):1621-1645

We explore and develop a Proper Orthogonal Decomposition (POD)-based deflation method for the solution of ill-conditioned linear systems, appearing in simulations of two-phase flow through highly heterogeneous porous media. We accelerate the convergence of a Preconditioned Conjugate Gradient (PCG) method achieving speed-ups of factors up to five. The up-front extra computational cost of the proposed method depends on the number of deflation vectors. The POD-based deflation method is tested for a particular problem and linear solver; nevertheless, it can be applied to various transient problems, and combined with multiple solvers, e.g., Krylov subspace and multigrid methods.

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