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81.
82.
T. Di Salvo A. D'Aí R. Iaria L. Burderi M. Doviak V. Karas G. Matt A. Papitto S. Piraino A. Riggio N. R. Robba A. Santangelo 《Monthly notices of the Royal Astronomical Society》2009,398(4):2022-2027
Iron emission lines at 6.4–6.97 keV, identified with fluorescent Kα transitions, are among the strongest discrete features in the X-ray band. These are therefore one of the most powerful probes to infer the properties of the plasma in the innermost part of the accretion disc around a compact object. In this paper, we present a recent XMM–Newton observation of the X-ray burster 4U 1705−44, where we clearly detect a relativistically smeared iron line at about 6.7 keV, testifying with high statistical significance that the line profile is distorted by high-velocity motion in the accretion disc. As expected from disc reflection models, we also find a significant absorption edge at about 8.3 keV; this feature appears to be smeared, and is compatible with being produced in the same region where the iron line is produced. From the line profile, we derive the physical parameters of the inner accretion disc with large precision. The line is identified with the Kα transition of highly ionized iron, Fe xxv , the inner disc radius is R in = 14 ± 2 R g (where R g is the Gravitational radius, GM / c 2 ), the emissivity dependence from the disc radius is r −2.27±0.08 , the inclination angle with respect to the line of sight is i = 39°± 1° . Finally, the XMM–Newton spectrum shows evidences of other low-energy emission lines, which again appear broad and their profiles are compatible with being produced in the same region where the iron line is produced. 相似文献
83.
Matt Bradshaw 《The Australian geographer》2001,32(2):241-257
The focus in this paper is on the shifting optimum location for a newsprint mill in Australia, factors influencing this shift, and the implications for a particular manufacturing site that is becoming increasingly outdated and out-of-place. Shipping times and schedules for high-volume, high-density tonnages of commodities such as newsprint have altered insufficiently over the last 60 years to affect competitive relations among various newsprint manufacturers around the world. With sea transport held roughly constant, changes in other aspects of the international newsprint industry can be investigated as part of unpacking the concept of globalisation. Globalisation for the former Australian Newsprint Mills Ltd meant becoming more open to new and closer competition, as well as becoming more exposed to acquisition by increasingly transnational enterprises. In the global newsprint industry at least, the world is less a smaller place than a more open one, with tonnes of newsprint moving at similar speeds to 60 years ago but among different and changing locations in terms of geography, ownership and market preference. 相似文献
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Since the occasion of the Thompson Symposium in 1979, two new members have joined OEEPE. These are France and the United Kingdom. The possibility of membership had been considered by the UK over the last decade on more than one occasion but, for one good reason or another, no application had been made. In 1980, however, W. P. Smith (Director General, Ordnance Survey) circulated organisations and individuals who might be interested and received an almost unanimous expression of support for an application for membership. This was also in line with the Ordnance Survey's intent to increase its links with other organisations, both nationally and internationally. The Foreign Office agreed that the UK should apply for membership and this was done. The UK became a full member of OEEPE in time for the Oslo meeting of the Steering Committee in 1981.
There follows a background paper on the work of OEEPE and accounts of current OEEPE Commission activities. 相似文献
There follows a background paper on the work of OEEPE and accounts of current OEEPE Commission activities. 相似文献
86.
Gustav Visser 《GeoJournal》2004,60(3):283-299
South Africa has recorded considerable growth in tourism activity over the past decade. In the light of the vast range of
economic sectors that gain from tourism development, the national government has instituted a range of incentives and initiatives
to stimulate tourism development, with the expansion of tourism infrastructure aimed at high-end tourists forming a key component
of this strategy. Little investment has, however, been made in tourism infrastructure targeting those markets that prefer
to avoid high-end tourism facilities. In this respect backpacker tourists and their preferred accommodation type, backpacker
hostels, are a case in point. Despite backpacker tourism being largely ignored in national tourism development initiatives,
backpacker tourism is increasingly popular in South Africa. This paper focuses on the recent proliferation of backpacker tourism
in this country and seeks to convey the results of the first nation-wide exploration in this regard. The paper has two main
objectives. Firstly, it seeks to present broad-ranging empirical data concerning this tourist cohort and their preferred accommodation
type- backpacker hostels — in the South African context. Secondly, it aims to demonstrate why backpacker tourists and hostels
hold much potential for local development initiatives in South Africa. In the light of the findings of this study, the paper
concludes that the expansion of backpacker tourism to this country might form an appropriate means by which to achieve a range
of local development objectives. 相似文献
87.
Precise GRACE baseline determination using GPS 总被引:13,自引:1,他引:13
Precision relative navigation is an essential aspect of spacecraft formation flying missions, both from an operational and a scientific point of view. When using GPS as a relative distance sensor, dual-frequency receivers are required for high accuracy at large inter-satellite separations. This allows for a correction of the relative ionospheric path delay and enables double difference integer ambiguity resolution. Although kinematic relative positioning techniques demonstrate promising results for hardware-in-the-loop simulations, they were found to lack an adequate robustness in real-world applications. To overcome this limitation, an extended Kalman Filter modeling the relative spacecraft dynamics has been developed. The filter processes single difference GPS pseudorange and carrier phase observations to estimate the relative position and velocity along with empirical accelerations and carrier phase ambiguities. In parallel, double difference carrier phase ambiguities are resolved on both frequencies using the least square ambiguity decorrelation adjustment (LAMBDA) method in order to fully exploit the inherent measurement accuracy. The combination of reduced dynamic filtering with the LAMBDA method results in smooth relative position estimates as well as fast and reliable ambiguity resolution. The proposed method has been validated with data from the gravity recovery and climate experiment (GRACE) mission. For an 11-day data arc, the resulting solution matches the GRACE K-Band Ranging System measurements with an accuracy of 1 mm, whereby 83% of the double difference ambiguities are resolved. 相似文献
88.
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90.
The central theme of this paper is the issue of the governance of cooperation within the Chilean wine industry. The effects of the internationalization of this industry for the importance and the quality of governance of intra-cluster cooperation involving firms and other actors are analysed. Two questions stand central. First, what has been the relative importance of external and internal factors in improving the export performance of the Chilean wine industry over the past 20 years? Second, to what extent have collective actions and investments played a part in this growth, and what has been the quality of the various governance regimes dealing with the associated collective action problems? Empirical evidence suggests that world-market developments and upgrading efforts by individual wineries largely explain the good export performance of the Chilean wine industry until the year 2000. The evidence also shows that the industry’s success in world markets is stimulating cooperation between firms and other actors in areas where the industry needs to improve: marketing and promotion, internationalization, innovation and training. The enhanced cooperation has not only stimulated cluster development, but has also turned the quality of cluster governance into a central variable for future export growth. Nevertheless, several collective action problems await resolution before essential intra-cluster cooperation can develop. Overall, the evidence suggests that, in the case of the Chilean wine industry, industrial and cluster development do not automatically follow enhanced integration in world markets, but depend on the strategic skills of actors within the industry, in particular their ability to identify, prioritize, and realize collective investments while effectively managing the associated collective action problems. Internationalization stimulates firms to consider such investments, however, and provides them with an incentive to upgrade strategic skills at the local level as new opportunities arise and the pressure is there to exploit them in world markets. 相似文献