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81.
Houshang Ardavan ArzhangArdavan John Singleton Mario R. Perez 《Monthly notices of the Royal Astronomical Society》2008,388(2):873-883
We show that the proportionately spaced emission bands in the dynamic spectrum of the Crab pulsar fit the oscillations of the square of a Bessel function whose argument exceeds its order. This function has already been encountered in the analysis of the emission from a polarization current with a superluminal distribution pattern: a current whose distribution pattern rotates (with an angular frequency ω) and oscillates (with a frequency Ω > ω differing from an integral multiple of ω) at the same time. Using the results of our earlier analysis, we find that the dependence on frequency of the spacing and width of the observed emission bands can be quantitatively accounted for by an appropriate choice of the value of the single free parameter Ω/ω . In addition, the value of this parameter, thus implied by Hankins & Eilek's data, places the last peak in the amplitude of the oscillating Bessel function in question at a frequency (∼Ω3 /ω2 ) that agrees with the position of the observed ultraviolet peak in the spectrum of the Crab pulsar. We also show how the suppression of the emission bands by the interference of the contributions from differing polarizations can account for the differences in the time and frequency signatures of the interpulse and the main pulse in the Crab pulsar. Finally, we put the emission bands in the context of the observed continuum spectrum of the Crab pulsar by fitting this broad-band spectrum (over 16 orders of magnitude of frequency) with that generated by an electric current with a superluminally rotating distribution pattern. 相似文献
82.
A digital earth platform for sustainability 总被引:1,自引:1,他引:0
Mario Hernandez 《International Journal of Digital Earth》2017,10(4):342-355
ABSTRACTBased on the experience of the International Society for Digital Earth (ISDE), this paper describes some challenges foreseen in order to develop a Digital Earth platform that can support the implementation of the Sustainable Development Goals. The use of ready-to-use derived geospatial information is essential. Future Earth’s methodology of ‘co-design’ aims to bring together natural, social scientists and decision makers to plan and carry out research for sustainability. Sustainability implies transdisciplinary research, but in order for scientists of different disciplines to work together, they will need to be able to share, access and use common data. This is by far not simple! While the good will to share data might exist, the associated technological, ethical and privacy issues are difficult to solve. An adequate e-infrastructure will be required. ISDE could consider to use the SDGs is the basis to develop the desired Digital Earth platform. This paper, by no means, covers everything for a Digital Earth platform, it aims to trigger research discussions and to have a good view about a starting point. 相似文献
83.
Mario Bossolasco 《Pure and Applied Geophysics》1951,20(1):46-49
Summary The comparison of the geomagneticK-indices for Mogadiscio with the correspondingK
p
for the whole earth, during the 2.nd Intern. Polar Year 1932–33, allows to deduce some features of the equatorial geomagnetic activity. Furthermore, evidence is adduced indicating that the geomagnetic disturbance at Mogadiscio is normal inH andD, while it appears slightly abnormal inZ.
Communication presentée à l'Association Internationale de Magnétisme et Electricité Terrestres, IXe Assemblée Générale de l'UGGI, Bruxelles, Séance du 28 Août 1951. 相似文献
Communication presentée à l'Association Internationale de Magnétisme et Electricité Terrestres, IXe Assemblée Générale de l'UGGI, Bruxelles, Séance du 28 Août 1951. 相似文献
84.
Mario Bossolasco 《Pure and Applied Geophysics》1947,10(1-2):41-53
Riassunto Si espongono i risultati delle osservazioni sulle correnti telluriche eseguite a Mogadiscio nel 1933 con misure delle due componenti NS ed EW, traendone alcune deduzioni che permettono di precisarne le caratteristiche, specie nei confronti del relativo andamento diurno.
Summary The paper deals with the results of the earth-current-observations made at Mogadiscio during 1933. The analysis reveal elements for a new picture of the distribution of the earth-currents in the equatorial regions, particularly concerning the daily variation.
Zusammenfassung Die Ergebnisse des Erdstrom-Beobachtungen durchgeführt in einigen Monaten des Jahres 1933 in Modagiscio sind angegeben. Aus des Diskussion folgen einige Elemente die eine Neubearbeitung des Darstellung des Erdstrom-Verteilung in dem äquatorialem Gürtel nötig machen und dazu dienen werden sollen. besonders in Beziehung auf den täglichen Gang.相似文献
85.
Mario Bossolasco 《Pure and Applied Geophysics》1952,22(3-4):255-261
Riassunto Vengono esaminati due esempi di spostamento retrogrado di depressioni nel Mediterraneo, illustrandone le cause. Per uno di essi si calcolano gli elementi energetici, dimostrando come il rapportoK/P fra l'energia cinetica e quella potenziale della depressione costituisca un indice della sua capacità di proseguire il moto lungo la rotta precedente.
Summary Two examples of retrograde displacement of depressions in the Mediterranean are being examined, explaining their causes. For one of them the energetic elements are calculated showing how the ratioK/P between the kinetic and the potential energy of the depression constitutes an index of its capacity to continue the motion along the preceding course.
Zusammenfassung Es werden zwei Fälle rückläufiger Bewegungen, von Mittelmeerdepressionen untersucht und die Ursachen derselben erläutert. Für einen dieser Fälle werden die Grössen der Energie berechnet: und es wird gezeigt, dass das VerhältnisK/P zwischen kinetischer und potentieller Energie massgebend ist für die Fähigkeit der Depression, ihre Bewegung in der ursprünglichen Richtung fortzusetzen.相似文献
86.
Mario Bossolasco 《Pure and Applied Geophysics》1948,12(1-2):53-60
Riassunto Vengono esposti e discussi i risultati di alcune misure della suscetività magnetica di minerali magnetitiferi italiani. Fra
l'altro si dimostra l'impossibilità di una legge generale di interdipendenza fra i valori della suscettività ed il carattere
genetico dei giacimenti, indicando nuovi orientamenti per approfondire con successo simili indagini.
Summary The results of some measures of magnetic susceptibility of italian magnetic ores are reported and discussed. It is proved the impossibility of a general relation between the magnitude of the susceptibility and the genetic character of the ores; however, new views are pointed out to successfully deepen the results.
Zusammenfassung Die Ergebnisse einiger Suszeptibilit?ts-Messungen von ital. Magnetit-Mineralien verschiedener Genesis werden angegeben und erl?utert. U. a. beweist man, dass ein allgemeine Gesetz für eine einfache Zusammenhang zwischen den Werte der Suszeptibilit?t und die genetischen Eigentümlichkeiten der Lagerst?tten nicht bestehen kann. Neue Forschungsrichtungen dafür werden vorgeschlagen.相似文献
87.
Mario Bossolasco 《Pure and Applied Geophysics》1948,11(1):132-141
Riassunto Richiamate le condizioni pluviometriche medie cui è soggetta la regione milanese, vengono illustrati e discussi i risultati ottenuti nel biennio 1946–1947 per la distribuzione della pioggia nell'area cittadina, durante la primavera, l'estate e l'autunno. L'influenza alteratrice delle città in tale distribuzione appare evidente, particolarmente nella primavera.
Zusammenfassung Ausgehend von den mittleren Niederschlagsverhältnissen in der Region von Mailand, wird die Verteilung der Niederschläge im Frühjahr, Sommer und Herbst der Jahre 1946 und 1947 im Stadtareal von Mailand dargestellt und diskutiert. Der Einfluss der Stadt auf die Niederschlagsverteilung tritt deutlich in Erscheinung, besonders im Frühjahre.相似文献
88.
Riassunto Si espongono ed illustrano i valori medi dei principali elementi meteorologici osservati a Moncalieri senza alcuna interruzione nell'ottantennio 1865–1945 e durante il quarantennio 1907–1946 per il vento. L'analisi delle medie quinquennali ed annuali pone in luce qualche caratteristica della variazione secolare dei medesimi fattori.
Zusammenfassung Die Mittelwerte der wichtigsten meteorologischen Elemente die in Moncalieri ohne Unterbrechung gesammelt worden sind, werden angegeben und zwar für den Zeitraum 1865–1945, ausgenommen für den Wind, deren Beobachtungen auf die Periode 1907–1946 sich beziehen. Die Gänge der fünfjährigen und jährlichen Mitteln zeigen einige Eigentümlichkeiten der sekularen Variation für denselben Elemente, die herausgehoben werden.相似文献
89.
90.
Christopher A. Tout Mario Livio Ian A. Bonnell 《Monthly notices of the Royal Astronomical Society》1999,310(2):360-376
The position of pre-main-sequence or protostars in the Hertzsprung–Russell diagram is often used to determine their mass and age by comparison with pre-main-sequence evolution tracks. On the assumption that the stellar models are accurate, we demonstrate that, if the metallicity is known, the mass obtained is a good estimate. However, the age determination can be very misleading, because it is significantly (generally different by a factor of 2 to 5) dependent on the accretion rate and, for ages less than about 106 yr, the initial state of the star. We present a number of accreting protostellar tracks that can be used to determine age if the initial conditions can be determined and the underlying accretion rate has been constant in the past. Because of the balance established between the Kelvin–Helmholtz, contraction time-scale and the accretion time-scale, a pre-main-sequence star remembers its accretion history. Knowledge of the current accretion rate, together with an HR-diagram position, gives information about the rate of accretion in the past, but does not necessarily improve any age estimate. We do not claim that ages obtained by comparison with these particular accreting tracks are likely to be any more reliable than those from comparisons with non-accreting tracks. Instead, we stress the unreliability of any such comparisons, and use the disparities between various tracks to estimate the likely errors in age and mass estimates. We also show how a set of coeval accreting objects do not appear coeval when compared with non-accreting tracks. Instead, accreting pre-main-sequence stars of around a solar mass are likely to appear older than those of either smaller or larger mass. 相似文献