1,052 research outputs found

    Zooarqueolog铆a hist贸rica: la necesidad de un enfoque tafon贸mico integral en Argentina

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    Animal bones remains are usual parts of the archaeological records of any chronology and its study is important to all investigation. It鈥檚 well known that there are different processes that can modify the cultural information that bones can provide, but in archaeology of historical moments these processes are ignored when archaeofaunal remains are analyzed. When doing an integral research, it is necessary to take into account that zooarchaeology shares methods and common problems in any given historical time. Nevertheless, the tendency in historical zooarchaeology in general (and in Argentina particularly) was that taphonomy processes can were ignored, which produced misleaded or incomplete 聽interpretations of his-torical remains. Some aspects connecting with natural and cultural process that affect the zooarchaeology-cal remains of historical sites are presented in this paper, in order to provide more accurate interpretations about the past human behavior.Los restos 贸seos de animales conforman una parte habitual del registro de sitios arqueol贸gicos de cualquier cronolog铆a, y su estudio es relevante para m煤ltiples intereses de investigaci贸n. Si bien es sabido que existe una variedad de procesos que tienen el potencial de alterar u obliterar la informaci贸n cultural que pudieren contener los materiales 贸seos, en la arqueolog铆a de momentos hist贸ricos muchas veces estos procesos son dejados de lado a la hora de analizar los restos arqueofaun铆sticos. Se considera que la zooarqueolog铆a, m谩s all谩 del per铆odo temporal del que se ocupe comparte m茅todos y problem谩ticas que deben ser abordadas en toda investigaci贸n para poder dar una mirada integral del registro que estudia. Sin embargo en zooarqueolog铆a hist贸rica la tendencia general (y particularmente en Argentina) es la de ignorar la posibilidad de sesgos introducidos por procesos tafon贸micos, lo que conlleva un potencial considerable para interpretaciones err贸neas o al menos incompletas de conjuntos hist贸ricos. Se presentan aqu铆 algunos aspectos vinculados a los factores naturales y culturales que modelan conjuntos zooarqueol贸gicos hist贸ricos, los cuales constituyen una contribuci贸n importante a la hora de hacer m谩s y mejores interpretaciones acerca de las acciones humanas del pasado

    Technology requirements of exploration beyond Neptune by solar sail propulsion

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    This paper provides a set of requirements for the technology development of a solar sail propelled Interstellar Heliopause Probe mission. The mission is placed in the context of other outer solar systems missions, ranging from a Kuiper Belt mission through to an Oort cloud mission. Mission requirements are defined and a detailed parametric trajectory analysis and launch date scan performed. Through analysis of the complete mission trade space a set of critical technology development requirements are identified which include an advanced lightweight composite High-Gain Antenna, a high-efficiency Ka-band travelling-wave tube amplifier and a radioisotope thermoelectric generator with power density of approximately 12 W/kg. It is also shown that the Interstellar Heliopause Probe mission necessitates the use of a spinning sail, limiting the direct application of current hardware development activities. A Kuiper Belt mission is then considered as a pre-curser to the Interstellar Heliopause Probe, while it is also shown through study of an Oort cloud mission that the Interstellar Heliopause Probe mission is the likely end-goal of any future solar sail technology development program. As such, the technology requirements identified to enable the Interstellar Heliopause Probe must be enabled through all prior missions, with each mission acting as an enabling facilitator towards the next

    Optimal low-thrust trajectories to asteroids through an algorithm based on differential dynamic programming

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    In this paper an optimisation algorithm based on Differential Dynamic Programming is applied to the design of rendezvous and fly-by trajectories to near Earth objects. Differential dynamic programming is a successive approximation technique that computes a feedback control law in correspondence of a fixed number of decision times. In this way the high dimensional problem characteristic of low-thrust optimisation is reduced into a series of small dimensional problems. The proposed method exploits the stage-wise approach to incorporate an adaptive refinement of the discretisation mesh within the optimisation process. A particular interpolation technique was used to preserve the feedback nature of the control law, thus improving robustness against some approximation errors introduced during the adaptation process. The algorithm implements global variations of the control law, which ensure a further increase in robustness. The results presented show how the proposed approach is capable of fully exploiting the multi-body dynamics of the problem; in fact, in one of the study cases, a fly-by of the Earth is scheduled, which was not included in the first guess solution

    Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

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    This paper presents measurements of the W++W^+ \rightarrow \mu^+\nu and WW^- \rightarrow \mu^-\nu cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

    Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in 鈭歴=13鈥塗eV pp collisions with the ATLAS detector