Environmental assessment of vegetation and hydrological conditions in Everglades freshwater marshes using multiple geochemical proxies     

Colin J. Saunders  Min Gao  Rudolf Jaffé 《Aquatic Sciences - Research Across Boundaries》2015,77(2):271-291

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An autonomous adaptive scheduling agent for period searching     

E.S. Saunders  T. Naylor  A. Allan 《Astronomische Nachrichten》2008,329(3):321-325

We describe the design and implementation of an autonomous adaptive software agent that addresses the practical problem of observing undersampled, periodic, time‐varying phenomena using a network of HTN‐compliant robotic telescopes. The algorithm governing the behaviour of the agent uses an optimal geometric sampling technique to cover the period range of interest, but additionally implements proactive behaviour that maximises the optimality of the dataset in the face of an uncertain and changing operating environment. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Cosmological evolution and hierarchical galaxy formation     

Will Percival  Lance Miller 《Monthly notices of the Royal Astronomical Society》1999,309(4):823-832

We calculate the rate at which dark matter haloes merge to form higher mass systems. Two complementary derivations using Press–Schechter theory are given, both of which result in the same equation for the formation rate. First, a derivation using the properties of the Brownian random walks within the framework of Press–Schechter theory is presented. We then use Bayes' theorem to obtain the same result from the standard Press–Schechter mass function. The rate obtained is shown to be in good agreement with results from Monte Carlo and N -body simulations. We illustrate the usefulness of this formula by calculating the expected cosmological evolution in the rate of star formation that is due to short-lived, merger-induced starbursts. The calculated evolution is well-matched to the observed evolution in ultraviolet luminosity density, in contrast to the lower rates of evolution that are derived from semi-analytic models that do not include a dominant contribution from starbursts. Hence we suggest that the bulk of the observed ultraviolet starlight at z >1 arises from merger-induced starbursts. Finally, we show that a simple merging-halo model can also account for the bulk of the observed evolution in the comoving quasar space density.  相似文献   

The Space Community Policing Makes and the Body That Makes It     

Ralph H. Saunders 《The Professional geographer》1999,51(1):135-146

This paper examines the ways that community policing organizes urban space in order to increase the police's ability to observe and to enforce. The logic of that organization, I argue, rests in the particular way that police are integrating civilians into police practice as part of community policing's police-community partnership, a partnership that is characterized by the concrete metaphor of a policing body. This paper presents the results of twenty months of field research with the Boston Police Department whose community policing program, Neighborhood Policing, is being hailed as a national model.  相似文献   

A new microsplitter for unconsolidated sediments     

John T. Guptill  Yvonne Herman  Sam C. Saunders 《Marine Geology》1976,20(2):15-23

Unrepresentative subsamples can be obtained from a sedimentary sample through repeated subdivision when using a mechanical microsplitter. Physical biases are often compounded by repetition and can result in wide variations among the estimates computed from the relative proportion of foraminifera of a given species. A new microsplitter, designed on a new principle, has been built to separate small representative subsamples. The device is based on the uniform distribution of unconsolidated sediments suspended in water. A subsample of the desired size is obtained by collecting sediment from an appropriate sedimentation area. Operation of this sampler is rapid and convenient and requires only one step, thus eliminating sampling biases introduced by repeated operations with other splitters. This new device was tested and found to be superior to the Otto Microsplitter according to some statistical goodness-of-fit tests conducted on the series.  相似文献   

The 2dF Galaxy Redshift Survey: Wiener reconstruction of the cosmic web     

Pirin Erdo&#;du  Ofer Lahav  Saleem Zaroubi  George Efstathiou  Steve Moody  John A. Peacock  Matthew Colless  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  Peder Norberg  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,352(3):939-960

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Preface     

Basilevsky  Alexander  Head  James  Pettengill  Gordon  Saunders  Steve 《Earth, Moon, and Planets》1990,(1):vii-x

'Geology and Tectonics of Venus', special issue edited by Alexander T. Basilevsky (USSR Acad. of Sci. Moscow), James W. Head (Brown University, Providence), Gordon H. Pettengill (MIT, Cambridge, Massachusetts) and R. S. Saunders (J.P.L., Pasadena).  相似文献   

The mass assembly of fossil groups of galaxies in the Millennium simulation     

Ali Dariush  Habib G. Khosroshahi  Trevor J. Ponman  Frazer Pearce  Somak Raychaudhury  Will Hartley 《Monthly notices of the Royal Astronomical Society》2007,382(1):433-442

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Interpretation of magnetic field perturbations in the earth's magnetopause boundary layers     

S.W.H. Cowley  D.J. Southwood  M.A. Saunders 《Planetary and Space Science》1983,31(11):1237-1258

Studies of the boundary layers in the vicinity of the Earth's dayside magnetopause are important in determining the nature of the processes which couple the magnetosphere to the flowing solar wind, thereby driving magnetospheric convection. In this paper we examine theoretically the magnetic field and plasma properties expected in the boundary regions for various models involving either diffusion or reconnection at the boundary. For diffusion models the transport of magnetosheath momentum across the magnetopause will result in field shears on either side of the boundary, the field rotations being in opposite senses on either side relative to the undisturbed fields. The directions of these rotations depend upon location at the magnetopause relative to the momentum transfer region and to the noon meridian. In reconnection models the effect of the tension of the open boundary layer field lines must be taken into account in addition to the magnetosheath flow, but on the super-Alfvénic flanks of the magnetosphere the latter still dominates, so that qualitatively similar effects will occur in the two models. More detailed, quantitative or statistical studies are then required to distinguish the two models in this regime. In the sub-Alfvénic dayside region, however, open field tension effects will dominate in reconnection models such that boundary layer field and plasma properties will then be determined mainly by the magnetosheath magnetic field configuration. In particular the East-West flow in the magnetospheric boundary layer will be controlled largely by the East-West field in the magnetosheath, leading to flow reversals across the magnetopause in some quadrants of the magnetopause. This behaviour is directly related to the Svalgaard-Mansurov effect and is a signature unique to reconnection models. The boundary layer fields are also expected to tilt towards the field on the opposite side of the boundary in these models on the dayside. “Toward” tilting can also occur in this regime in diffusion models, but “away” tilting, a signature unique to dayside diffusion, should also occur equally frequently. Finally, we briefly discuss previously published high-resolution ISEE 1 and 2 data from the boundary regions in the light of our results. We find that “toward” tilting generally occurs in boundary region crossings previously identified as being reconnection-associated and we present some examples in which the above unique reconnection signature has been observed. During impulsive FTE-like events, however, the field may tilt in either direction, possibly as a result of field line twists, thus complicating our simple picture in this case. We also show that the “reverse draping” observations presented by Hones et al. (1982) approximately satisfy the open magnetopause stress balance conditions.  相似文献   

International solar terrestrial energy programme and the UK participation     

M. Lester  A. J. Coates  R. A. Harrison  D. Rees  J. G. Roederer  M. J. Rycroft  M. A. Saunders 《Surveys in Geophysics》1993,14(6):555-583

The Solar Terrestrial Energy Programme (STEP) aims to improve our general understanding of how mass, energy and momentum are transferred between the various regions that form the Solar Terrestrial environment. STEP began in 1990 and will continue until 1997, during which time a number of major new spacecraft and ground-based projects will become operational. Six Working Groups form the basis of STEP, covering topics such as the Sun as a source of energy and disturbance, energy and mass transfer through the interplanetary medium and the magnetosphere-ionosphere system, ionosphere-thermosphere coupling and response to energy and momentum inputs, middle atmosphere responses to forcing from above and below, solar variability effects in the human environment, and informatics. A Royal Astronomical Society Geophysics Discussion meeting took place in March 1992 to draw to the attention of UK scientists the diverse nature of STEP and the opportunities offered by STEP. This paper consists of individual sections prepared by the speakers at the meeting and which cover most of the STEP Working Group topics. The main aims of each section are to provide a benchmark for the present status of the research area and to look ahead to the possible contributions that UK scientists can make during STEP.  相似文献