Observations of Hipparcos short-period red giant stars     

Chris Koen  Dave Laney  Francois van Wyk 《Monthly notices of the Royal Astronomical Society》2002,335(1):223-232

Optical UBV(RI) _C and infrared JHK photometry is presented of a small sample of giant stars with short periods in the Hipparcos catalogue. Observations were limited, but were sufficient to rule out most of the Hipparcos periods. Radial velocity measurement were also made for a few stars, over six successive nights. Low-level variability was detected in a few stars. It is argued that in most cases the brightness variations are primarily due to temperature changes. These findings show that high-overtone pulsations in M giant stars occur, if at all, in a far more limited number of stars than proposed in the authors' previous discussion of the Hipparcos data alone.  相似文献   

The Canada–UK Deep Submillimetre Survey – VIII. Source identifications in the 3-hour field     

Dave Clements  Steve Eales  Kris Wojciechowski  Tracy Webb  Simon Lilly  Loretta Dunne  Rob Ivison  Henry McCracken  Min Yun  Ashley James  Mark Brodwin  Olivier Le Fèvre  Walter Gear 《Monthly notices of the Royal Astronomical Society》2004,351(2):447-465

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First XMM-Newton observations of strongly magnetic cataclysmic variables – II. Timing studies of DP Leo and WW Hor     

Dirk Pandel  France A. Cordova  Robert E. Shirey  Gavin Ramsay  Mark Cropper  Keith O. Mason  Rudi Much  Dave Kilkenny 《Monthly notices of the Royal Astronomical Society》2002,332(1):116-126

XMM-Newton was used to observe two eclipsing, magnetic cataclysmic variables, DP Leo and WW Hor, continuously for three orbital cycles each. Both systems were in an intermediate state of accretion. For WW Hor we also obtained optical light curves with the XMM-Newton Optical Monitor and from ground-based observations. Our analysis of the X-ray and optical light curves allows us to constrain physical and geometrical parameters of the accretion regions and derive orbital parameters and eclipse ephemerides of the systems. For WW Hor we directly measure horizontal and vertical temperature variations in the accretion column. From comparisons with previous observations we find that changes in the accretion spot longitude are correlated with the accretion rate. For DP Leo the shape of the hard X-ray light curve is not as expected for optically thin emission, showing the importance of optical depth effects in the post-shock region. We find that the spin period of the white dwarf is slightly shorter than the orbital period and that the orbital period is decreasing faster than expected for energy loss by gravitational radiation alone.  相似文献   

Data acquisition, control, communication and computation system of solar X-ray spectrometer (SOXS) mission     

Amish B. Shah  N. M. Vadher  Rajmal Jain  Hemant Dave  Vishal Shah  K. S. B. Manian  Satish Kayasth  Vinod Patel  Girish Ubale  Kirit Shah  Chirag Solanki  M. R. Deshpande  Ramkrishna Sharma  C. N. Umapathy  N. Viswanath  Ravi Kulkarni  P. S. Kumar 《Journal of Astrophysics and Astronomy》2006,27(2-3):299-304

The Solar X-ray Spectrometer (SOXS) mission onboard GSAT-2 Indian Spacecraft was launched on 08 May 2003 using GSLV-D2 rocket by Indian Space Research Organization (ISRO). SOXS aims to study solar flares, which are the most violent and energetic phenomena in the solar system, in the energy range of 4–56 keV with high spectral and temporal resolution. SOXS employs state-of-the-art semiconductor devices, viz., Si-Pin and CZT detectors to achieve sub-keV energy resolution requirements. In this paper, we present an overview of data acquisition, control, communication and computation of low energy payload of the SOXS mission.  相似文献   

Modelling the Earth's Geomagnetic Field to High Degree and Order     

Dave R. Schmitz§  J. Meyer  Joseph C. Cain 《Geophysical Journal International》1989,97(3):421-430

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Spectral multigrid and collocation methods for barotropic nondivergent flow over irregular coastal topography     

Dave Broutman  Roger Grimshaw 《地球物理与天体物理流体动力学》2013,107(1-3):1-23

Abstract

We describe the high-resolution spectral modelling of nondivergent barotropic linearized flow over steep irregular topography. We use collocation to evaluate spatial derivatives in the barotropic vorticity equation, and a spectral multigrid technique to accelerate the iterative solution of the vorticity—stream function relation. The computational domain is a rectangular channel, which can be conformally mapped into more interesting shapes, as we also discuss. A Fourier-series representation is used in the (periodic) direction parallel to the walls of the channel, and a sine series in the cross-channel direction. For much of the paper we concentrate on the numerical techniques, though results are provided, including an application to the Bass Strait region of southeast Australia.  相似文献   

Comparison of PCBs, organochlorine pesticides, and trace metals in cod liver from Georges Bank and Stellwagen Bank, USA and Canada     

Monosson E  Lincoln D 《Marine pollution bulletin》2006,52(5):591-597

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Application of Artificial Neural Network Model for the Prediction of Suspended Sediment Load in the Large River     

Gaur  Shishir  Mishra  Aryan  Gupta  Anurag  Jain  Arihant  Dave  Apurve  Eslamian  Saied  Dwivedi  S. B.  Graillot  Didier 《Water Resources》2021,48(4):565-575

Water Resources - Predicting the Suspended Sediment Load (SSL) of the river is a very significant and challenging task. Being a non-linearity in the SSL data, it requires a non-linear method to get...  相似文献   

Geochronology of unconformity-related uranium deposits in the Athabasca Basin,Saskatchewan, Canada and their integration in the evolution of the basin     

Paul Alexandre  Kurt Kyser  Dave Thomas  Paul Polito  Jim Marlat 《Mineralium Deposita》2009,44(1):41-59

The importance of geochronology in the study of mineral deposits in general, and of unconformity-type uranium deposits in particular, resides in the possibility to situate the critical ore-related processes in the context of the evolution of the physical and chemical conditions in the studied area. The present paper gives the results of laser step heating ⁴⁰Ar/³⁹Ar dating of metamorphic host-rock minerals, pre-ore and syn-ore alteration clay minerals, and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) U/Pb dating of uraninite from a number of basement- and sediment-hosted unconformity-related deposits in the Athabasca Basin, Canada. Post-peak metamorphic cooling during the Trans-Hudson Orogen of rocks from the basement occurred at ca 1,750 Ma and gives a maximum age for the formation of the overlying Athabasca Basin. Pre-ore alteration occurred simultaneously in both basement- and sandstone-hosted mineralizations at ca 1,675 Ma, as indicated by the ⁴⁰Ar/³⁹Ar dating of pre-ore alteration illite and chlorite. The uranium mineralization age is ca 1,590 Ma, given by LA-ICP-MS U/Pb dating of uraninite and ⁴⁰Ar/³⁹Ar dating of syn-ore illite, and is the same throughout the basin and in both basement- and sandstone-hosted deposits. The mineralization event, older than previously proposed, as well as several fluid circulation events that subsequently affected all minerals studied probably correspond to far-field, continent-wide tectonic events such as the metamorphic events in Wyoming and the Mazatzal Orogeny (ca 1.6 to 1.5 Ga), the Berthoud Orogeny (ca 1.4 Ga), the emplacement of the McKenzie mafic dyke swarms (ca 1.27 Ga), the Grenville Orogeny (ca 1.15 to 1 Ga), and the assemblage and break-up of Rodinia (ca 1 to 0.85 Ga). The results of the present work underline the importance of basin evolution between ca 1.75 Ga (basin formation) and ca 1.59 Ga (ore deposition) for understanding the conditions necessary for the formation of unconformity-type uranium deposits. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

A coupled mesoscale-model Fourier-method for idealized mountain-wave simulations over Hawaii     

John Lindeman  Dave Broutman  Stephen D. Eckermann  Jun Ma  Zafer Boybeyi 《Meteorology and Atmospheric Physics》2010,108(3-4):71-81

Mesoscale model simulations of representative trade winds impinging upon the Big Island of Hawaii are diagnosed for their mountain-wave characteristics by coupling a mesoscale model to a Fourier method. Localized phase-averaged wave momentum fluxes are calculated, which facilitates the study of wave generation from fine-scale topographic features. We find that the wave momentum fluxes are dominated by forcing from subsidiary topographic peaks, with the broader island topography controlling flow splitting and lee vortex generation. Waves also arise at the far northern and southern extremities of the island by acceleration of split flow. The strength of the local momentum fluxes proves to be sensitive to a small change in the incident flow direction. Areally integrated fluxes (wave drag) align closely with the incident flow direction and are an order of magnitude smaller than linear predictions and an order of magnitude larger than corresponding dividing streamline predictions. We briefly discuss the relevance of these results to the parameterization of subgrid-scale mountain-wave drag in climate and weather models.  相似文献