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S. Ó Tuairisg R. F. Butler A. Shearer R. M. Redfern D. Butler A. Penny 《Monthly notices of the Royal Astronomical Society》2003,345(3):960-980
We present the results of TRIFFID simultaneous V - and B -band observations of the cores of the globular clusters M15, M92 and NGC 6712. A variability search of their dense centres was made feasible through performing post-exposure image sharpening on the images, increasing the image resolution by a factor of ∼2. The isis implementation of the image subtraction technique developed by Alard & Lupton was then used to detect flux variations in our image sets. We have obtained periods for all observable variables (in our field of view) in NGC 6712 and we have found two new RR Lyrae variables (an RRab and an RRc). We have confirmed three variables in our field of view of the M92. For M15, we detect 48 variables in our field of view, 23 of which are new discoveries. We obtain periods and amplitudes for all variables and classify new ones based on the light-curve shape, the most significant period and the mean magnitude in the V band. Among the detected RR Lyrae we find 19 RRc, 12 RRab and two RRd types. In the subsequent analysis we find a marked increase in RRc over RRab variables in the core. In a refined procedure to search for fainter objects we find no dwarf novae in our field of view of M15. Simulations performed on the data set to quantify our sensitivity to such objects indicate that an upper limit of 10 dwarf novae (at 92 per cent probability) exist in our field of view. The implications this result has on globular clusters are discussed. 相似文献
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R. A.Street KeithHorne T. A.Lister A.Penny Y.Tsapras A.Quirrenbach N.Safizadeh J.Cooke D.Mitchell A.Collier Cameron 《Monthly notices of the Royal Astronomical Society》2002,330(3):737-754
We report on the discovery of 25 variable stars plus 13 suspected variables found in the field of the open cluster NGC 6819. The stars were identified from time-series photometric data obtained on the Isaac Newton Telescope, La Palma, during two observing runs covering the 19 nights between 1999 June 22–30 and 1999 July 22–31 . The variables found include 12 eclipsing binaries with an additional three suspected, nine BY Draconis systems, plus four variables of other types, including one star believed to be a Cepheid. Three of the 15 eclipsing binaries are believed to be cluster members. Details of a further 10 suspected variable stars are also included. 相似文献
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Modern social science is concerned with policing the ‘boundary’ between nature and culture, with limiting and excluding phenomena which threaten to challenge its account of the social determination of the attributes of human beings. The paper argues that this boundary defence is an unusually touchy and difficult matter because social science has inherited an Enlightenment conception of man as ‘unique’. Human culture is regarded as different in quality from any possible form of animal association or attainment. At the same time as supporting this ontology it supposes the ‘boundary’ is in some sense a matter of empirical science, capable of specification by reference to evidence. We try to show the confusions these two contradictory circumstances produce by considering two debates: those concerning the possibility of ‘feral’ children and those concerning the uniqueness of language to human beings. It is demonstrated that the modern debates develop theories, issues and lines of dispute which appeared in the eighteenth century. 相似文献
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Velocity images from stacking depth-slowness seismic wavefields 总被引：1，自引：0，他引：1
Geraint D. Jones Penny J. Barton Satish C. Singh 《Geophysical Journal International》2007,168(2):583-592
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The Inclusion of Stakeholder Knowledge and Perspectives in Integrated Assessment of Climate Change 总被引：1，自引：0，他引：1
Over the past few decades Integrated Assessment (IA) has emerged as an approach to link knowledge and action in a way that
is suitable to accommodate uncertainties, complexities and value diversities of global environmental risks. Responding to
the complex nature of the climate problem and to the changing role of climate change in the international climate policy process,
the scientific community has started to include stakeholder knowledge and perspectives in their assessments. Participatory
Integrated Assessment (PIA) is in its early stage of development. Methodology varies strongly across PIA projects. This paper
analyzes four recent IA projects of climate change that included knowledge or perspectives from stakeholders in one-way or
another. Approaches and methods used turn out to differ in whether stakeholders are involved actively or passively, whether
the approach is bottom-up or top-down, and whether the different functions in the IA process are open or closed to stakeholder
input. Also, differences can be seen in the degree to which boundaries are pre-set that limit the roles and domains of competencies
attributed to each scientific or non-scientific participant (so-called boundary work). The paper discusses pros and cons of
the various approaches identified, and outlines heuristics and considerations to assist those who plan, design or fund new
IA processes with stakeholder input on what approaches best to choose in view of the objectives for stakeholder involvement,
in view of the role that the IA plays in the overall risk management process and in view of considerations regarding boundary
work. 相似文献
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Butler Shearer Redfern Colhoun O'Kane Penny Morris Griffiths & Cullum 《Monthly notices of the Royal Astronomical Society》1998,296(2):379-391
The Galway/DIAS Image Sharpening Camera, TRIFFID, has been used to make observations in two colours of the centre of the post-core-collapse globular cluster M15. We present here our analysis of the photometry in B over two seasons. We have combined the complementary qualities of the HST 's high astrometric precision and TRIFFID's extended coverage and photometric precision, to perform crowded-field photometry in the innermost region of M15. Our technique virtually eliminates the problem of extreme crowding which has hitherto hampered studies of the variable star populations in globular cluster cores, and thereby provides an extension of the HST 's capability. Candidate variables detected with the HST have been confirmed and monitored over longer periods. We show that most of these are RR Lyrae stars, and that one is a short-period Type II Cepheid (the third to be discovered in M15). Our photometric study also produced evidence of a similar number of new variables. These also appear to be RR Lyrae stars, except for a possible eclipsing system. Further data from an upgraded version of TRIFFID have recently been obtained to help to refine the light curves of all these objects. 相似文献
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The boundary-element method has been widely used as a design tool in the offshore and ship building industry for more than 30 years. Its application to wave energy conversion is, however, more recent. This paper deals with the numerical modelling of a free-floating sloped wave energy device. The power take-off mechanism of the device consists of an immersed tube with a piston sliding inside. The modelling is done using the boundary-element method package WAMIT. The model is first worked out for the case where the axis of the tube is vertical. It is then derived for the tube inclined and successfully verified against numerical benchmark data. A companion paper presents results of a detailed comparison with a physical model study. 相似文献
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