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31.
Michele Trenti Scott Ransom Piet Hut Douglas C. Heggie 《Monthly notices of the Royal Astronomical Society》2008,387(2):815-824
Though about 80 pulsar binaries have been detected in globular clusters so far, no pulsar has been found in a triple system in which all three objects are of comparable mass. Here, we present predictions for the abundance of such triple systems, and for the most likely characteristics of these systems. Our predictions are based on an extensive set of more than 500 direct simulations of star clusters with primordial binaries, and a number of additional runs containing primordial triples. Our simulations employ a number N tot of equal-mass stars from N tot = 512 to 19 661 and a primordial binary fraction from 0 to 50 per cent. In addition, we validate our results against simulations with N = 19 661 that include a mass spectrum with a turn-off mass at 0.8 M⊙ , appropriate to describe the old stellar populations of Galactic globular clusters. Based on our simulations, we expect that typical triple abundances in the core of a dense cluster are two orders of magnitude lower than the binary abundances, which in itself already suggests that we do not have to wait too long for the first comparable-mass triple with a pulsar to be detected. 相似文献
32.
Holger Baumgardt Douglas C. Heggie Piet Hut Junichiro Makino 《Monthly notices of the Royal Astronomical Society》2003,341(1):247-250
This paper considers the phenomenon of deep core collapse in collisional stellar systems, with stars of equal mass. The collapse takes place on some multiple, ξ−1 , of the central relaxation time, and produces a density profile in which ρ∝ r −α , where α is a constant. The parameters α and ξ have usually been determined from simplified models, such as gas and Fokker–Planck models, often with the simplification of isotropy. Here we determine the parameters directly from N -body simulations carried out using the newly completed GRAPE-6. 相似文献
33.
Helsen Samuel van Lipzig Nicole P. M. Demuzere Matthias Vanden Broucke Sam Caluwaerts Steven De Cruz Lesley De Troch Rozemien Hamdi Rafiq Termonia Piet Van Schaeybroeck Bert Wouters Hendrik 《Climate Dynamics》2020,54(3):1267-1280
Climate Dynamics - Convection-permitting models (CPMs) have been proven successful in simulating extreme precipitation statistics. However, when such models are used to study climate change,... 相似文献
34.
This study reports results from evaluation of the quality of digital elevation model (DEM) from four sources viz. topographic map (1:50,000), Shuttle Radar Topographic Mission (SRTM) (90 m), optical stereo pair from ASTER (15 m) and CARTOSAT (2.5 m) and their use in derivation of hydrological response units (HRUs) in Sitla Rao watershed (North India). The HRUs were derived using water storage capacity and slope to produce surface runoff zones. The DEMs were evaluated on elevation accuracy and representation of morphometric features. The DEM derived from optical stereo pairs (ASTER and CARTOSAT) provided higher vertical accuracies than the SRTM and topographic map-based DEM. The SRTM with a coarse resolution of 90 m provided vertical accuracy but better morphometry compared to topographic map. The HRU maps derived from the fine resolution DEM (ASTER and CARTOSAT) were more detailed but did not provide much advantage for hydrological studies at the scale of Sitla Rao watershed (5800 ha). 相似文献
35.
36.
Edward R. Valstar Rob G. H. H. Nelissen Johan H. C. Reiber Piet M. Rozing 《ISPRS Journal of Photogrammetry and Remote Sensing》2002,56(5-6)
Roentgen stereophotogrammetry is the most accurate Roentgen technique for three-dimensional assessment of micromotion of orthopaedic implants. The reported accuracy of Roentgen Stereophotogrammetric Analysis (RSA) ranges between 0.05 and 0.5 mm for translations and between 0.15° and 1.15° for rotations. Because of the high accuracy of RSA, small patient groups are in general sufficient to study the effect on prosthetic fixation due to changes in implant design, addition of coatings, or new bone cements. By assessing micromotion of a prosthesis in a short-term (i.e. 2 years) clinical RSA study, a prediction can be made on the chance of long-term (i.e. 10 years) loosening of the prosthesis. Therefore, RSA is an important measurement tool to screen new developments in prosthetic design, and to prevent large groups of patients from being exposed to potentially inferior designs.In this article, the basics of the RSA technique are explained, and the importance of clinical RSA studies is illustrated with two examples of clinical RSA studies which RSA delivered very valuable information. Thereafter, two recent developments in RSA that have been implemented at Leiden University Medical Center are presented: digital automated measurements in RSA radiographs and model-based RSA. 相似文献
37.
38.
Response of potential fish community indicators to fishing 总被引:3,自引:3,他引:3
39.
Piet Verburg 《Journal of Paleolimnology》2007,37(4):591-602
The change in dissolved inorganic δ13C in the ocean resulting from the change in δ13C in atmospheric CO2 owing to anthropogenic activities (the Suess effect) is well known. The need to correct for the Suess effect when applying
δ13C in organic matter in lacustrine sediment deposited during the anthropocene as a productivity proxy, is widely although not
universally acknowledged. This paper reviews conceptions about the Suess effect in lacustrine δ13Corg and methods to adjust for the Suess effect when δ13Corg is used to infer recent changes in aquatic productivity. Lake Tanganyika is used as an example to illustrate the necessity
of the correction. When the Suess effect is not considered, interpretations of sediment core data can result that are opposite
to those achieved with the correction applied, as is here shown in Lake Tanganyika and in other lakes. A new method to correct
for the Suess effect is provided which has the advantage of being applicable to data for a larger period (1700–2000) than
methods currently available. In addition, Lake Tanganyika is shown to be a net sink for CO2. 相似文献
40.
LAND USE SCANNER: An integrated GIS based model for long term projections of land use in urban and rural areas 总被引:9,自引:1,他引:8
This paper describes the structure of the LAND USE SCANNER model, a GIS based model developed to generate spatial forecasts
for various types of land use for a large number of grids. The model basically allocates land according to bid prices for
various types of land use. The possibility of government intervention in land use is taken into account among others by adding
aggregate constraints. The model includes all relevant land use types such as residential, industrial, agricultural, natural
areas and water. The model is driven by sectoral models providing forecasts of aggregate land use in various land use categories.
An application of the first version of the model is given for the Netherlands with some 200,000 grid cells. Further developments
and refinements of the model are planned for the near future.
Received: 18 February 1998/Accepted: 29 September 1998 相似文献