163,377 research outputs found
Orbital tuning and re-tuning: art and science (abstract of paper presented at AGU Fall Meeting, San Francisco, 6-10 Dec 2002)
No full textIt is difficult to imagine a situation wherein (a) a geological record built up at a constant rate or (b) a geological deposit built up at a rate that was independent of climate. In addition all geological proxies for climate parameters are subject to both observational noise, and variability in their relationship with climate. Hence considerable judgement is needed in first selecting geological records that will be amenable to "tuning" to a record of changing distribution of solar insolation as calculated by an astronomer, and then in carrying out the operation. Tuning a geological record to an incorrect insolation record, or to the wrong time interval in a correct insolation record, or to a simplified "caricature" of the true insolation record can all provide considerable insights in some circumstances. Nevertheless from the point of view of the geological time scale it is important to carry out the procedure correctly, with the best available astronomical data. It is also important that one can utilize the tuning in order to verify the astronomical calculations. We have recently re-tuned a number of records on the basis of the new calculations discussed by Laskar (2001). Astronomical Solutions for Paleoclimates Studies. Eos Trans. AGU, 82(47), Fall Meet. Suppl. Abstract U11A-01. In the Pliocene re-tuning is generally straightforward and uninformative because the astronomical changes are small and the tuning is so unambiguous that little judgement is required. In the Early Miocene and Oligocene the situation is more interesting. During this time available data suggests that the climatic variability is dominated by 41-ky obliquity cycles but attaining a correct tuning requires identification of the weaker precession signal and making use of the longer-term (100-ky and 400-ky) eccentricity modulation. A surprising aspect of the tuning published by us in 1999 was that between 20Ma and 24Ma there was long-term (about 1.1My) modulation of the obliquity signal that matched that predicted; this match broke down in the earlier part of the record.Re-tuning the records for this interval required a slight "stretching" to take account of the fact that 400-ky eccentricity maxima in the Oligocene are around 100ky older than in the previous astronomical solution. This obviously required the addition of a very small number of additional obliquity cycles; thus it was necessary to make a judgement anew regarding the interpretation of each cycle. This in turn enables us to assess the degree of robustness of the tuning. The fact that in the new tuning the amplitude modulation of the obliquity signal in the 20Ma to 24Ma time window still matches the calculated modulation is not surprising since in this time-window the amplitude envelope of obliquity moved back in age to the same extent as the eccentricity signal, as a result of the new calculations. However, the fact that the re-tuned data now demonstrates an amplitude modulation of the obliquity signal that remains in phase with the calculated signal back to 30Ma, despite the fact that the re-tuning did not entail significant re-interpretation of the record, strongly suggests both that the new solution represents an "improvement" and that the coherence with this long-term modulation constitutes a very strong independent validation of this approach to geological time scale development
Stability of the long period terms in the La2011 astronomical solution.
No full textInternational audienceThe obtention of an accurate astronomical solution for the orbital motion of the Earth in the Solar System is an essential step for the elaboration of geological time scales that are based on the correlation of sedimentary cycles with insolation variations on the Earth's surface. The widely used La2004 (Laskar et al, 2004) solution has a time validity of about 40 Myr. Since, a large effort has been undertaken in order to improve this solution and to extend its time of validity to 50 Myr (Laskar et al, 2011a). On the other hand, it was demonstrated that asteroid close encounters set an absolute limit for the possibility of precise prediction of the Earth's orbit to about 60 Myr (Laskar et al, 2011b). In this context, we will report the latest development of the orbital solutions La2011 which present a noticeable improvement with respect to La2010. We will specially focus on the stability of the long period terms of 2.4 Myr in eccentricity and 1.2 Myr in obliquity. Refs : Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A. C. M., Levrard, B.: 2004, A long-term numerical solution for the insolation quantities of the Earth, A&A, 428, 261-285 Laskar, J., Fienga, A., Gastineau, Manche, H.: 2011a, La2010: a new orbital solution for the long-term motion of the Earth, A&A, 532, A89 Laskar, J., Gastineau, M., Delisle, J.-B. , Farrés, A., and Fienga, A. : 2011b, Strong chaos induced by close encounters with Ceres and Vesta, A&A, 532, L
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Geologic constraints on the chaotic diffusion of the Solar System
No full textThe correlation of Earth's orbital parameters with climatic variations has been used to generate astronomically calibrated geologic time scales of high accuracy. However, because of the chaotic behavior of the solar system, two initially close calculations of Earth's orbit diverge exponentially and have a large uncertainty beyond several million years in the past. This chaotic behavior is related to a combination of angles in the precession motion of the orbits of Earth and Mars, θ, which currently is in resonance. How long θ stays in libration critically depends on the dynamical model and initial conditions for the solar system. Here we show that geologic data can differentiate between astronomical solutions that do and do not exhibit a transition in θ since 40 Ma and that sediments can thus provide a history for the evolution of θ. We find that the chaotic transition of θ from libration to circulation did not occur after ca. 30 Ma. We can thus constrain the chaotic diffusion of the solar system in the past, and our results provide new and challenging constraints for astronomical models
Review of single particle dynamics for third generation light sources through frequency map analysis
No full textFrequency map analysis [J. Laskar, Icarus 88, 266 (1990)] is used here to analyze the transverse dynamics of four third generation synchrotron light sources: the ALS, the ESRF, the SOLEIL project, and Super-ACO. Time variations of the betatron tunes give additional information for the global dynamics of the beam. The main resonances are revealed; a one-to-one correspondence between the configuration space and the frequency space can be performed. We stress that the frequency maps, and therefore the dynamics optimization, are highly sensitive to sextupolar strengths and vary in a large amount from one machine to another. The frequency maps can thus be used to characterize the different machines
NILAI PENDIDIKAN, SOSIAL, BUDAYA, DAN RELIGIUS NOVEL LASKAR PELANGI KARYA ANDREA HIRATA
No full textThe purpose of this study was to describe the value of education, social, cultural, and religious in Laskar Pelangi novel by Andrea Hirata. This research used qualitative descriptive design. Educational values research findings in the novel Laskar Pelangi was essentially an attempt by the author to help readers realize the values it has. Social value was the lessons learned from social behavior such as attitudes towards events that occur in the vicinity that has to do with others, ways of thinking, and community social relations between individuals. Cultural values Belitong load of everyday citizens, and also about the diverse ethnic and cultural activities in Belitong. The religious value of the load; In terms of life outwardly, as well as the whole human self in total in its integration relationship to God. Furthermore, the findings are discussed in a comprehensive manner to be implied as teaching materials (Student Worksheet) for junior high school.Tujuan penelitian ini untuk mendeskripsikan nilai pendidikan, sosial, budaya, dan religius dalam novel Laskar Pelangi karya Andrea Hirata. Penelitian menggunakan desain deskriptif kualitatif. Temuan hasil penelitian Nilai Pendidikan di dalam novel Laskar Pelangi pada kahikatnya merupakan upaya penulis untuk membantu pembaca menyadari nilai-nilai yang dimilikinya. Nilai sosial merupakan hikmah yang dapat diambil dari perilaku sosial berupa sikap seseorang terhadap peristiwa yang terjadi di sekitarnya yang ada hubungannya dengan orang lain, cara berpikir, dan hubungan sosial bermasyarakat antar individu. Nilai budaya memuat tentang keseharian warga Belitong, kemudian juga tentang beragam etnis dan kegiatan kebudayaan yang ada di Belitong. Nilai religius memuat tentang; segi kehidupan secara lahiriah, serta keseluruhan diri pribadi manusia secara total dalam integrasinya hubungan terhadap Tuhan. Selanjutnya hasil temuan dibahas secara komprehensif untuk diimplikasikan sebagai bahan ajar (Lembar Kerja Siswa) untuk sekolah menengah pertama.Kata kunci: nilai (pendidikan, sosial, budaya, religius), novel, lembar kerja siswa
Efficiency enhanced and harmonic suppressed differential VCO with novel buffer scheme using transformers for IEEE 802.11a
No full textIs militant Islamism a busted flush in Indonesia?
No full textIn the late 1990s, Indonesia - the world’s most populous Muslim nation - began a transition from authoritarian rule. At the time, many commentators expressed concern about the security threat posed by militant Islamist extremists in the wake of Suharto’s downfall. Initially, Indonesia did witness a proliferation of Islamist paramilitary groups and a heightened security environment. Yet, in the decade and more since then, the dire threat predictions have largely failed to materialize. In fact, Indonesia today in coordination with international partners has reduced its potential climate of threat at least strategically. This outcome raises some interesting questions. First, has Indonesia really contained its paramilitary/extremist threat? Secondly, if so, how and what lessons, if any, can we draw from this? The following paper examines the ways in which Indonesia’s security concerns have actually diminished.Publisher PD
The measure of chaos by the numerical analysis of the fundamental frequencies. Application to the standard mapping
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