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High-ductile partial-strength composite beam-to-column joints: experimental analyses and comparisons
No full textA Cost Effective Approach for LARES Satellite
No full textLARES is a laser ranged satellite smaller and lighter with respect to its predecessor LAGEOS launched by NASA in 1976 and LAGEOS II launched by NASA and ASI in 1992. LARES experiment is not only a low cost evolution of the LAGEOS III mission proposed in 1986 [ ] but it will improve the scientific return by adding important contributions in Earth science and fundamental physics. The main objective of the LARES mission is to verify the Lense-Thirring effect which is a relativistic precession of the orbital plane induced by the Earth rotation and not predicted by the classical lows of gravitation. This effect is very small compared to the precession induced by the non gravitational perturbations as well as by the non perfectly spherical gravitational potential of the Earth. Other objectives in the field of gravity and general relativity include studies of the inverse square law for very weak-field, test of the equivalence principle and a more accurate evaluation of some PPN (Parametrized -Post-Newtonian) parameters. LARES is a passive satellite, very simple, reliable and low cost. It is a test particle with Cube Corner Retroreflectors (CCRs) on its surface. The orbit is reconstructed by analyzing the data collected from the Laser Ranging Station (LRS) that continuously send laser pulses towards the laser ranged satellites and evaluate the delay of the signals by very accurate atomic clocks. The total cost of a space mission is given by three main contributions: the ground segment, the launch system and the space segment. The ground segment is constituted by the International Laser Ranging Service that will provide at no extra cost the tracking and the ranging of the Satellite. The space segment is basically constituted by the separation system and the satellite only if the launcher is capable to inject the satellite into the final orbit. In order to keep the overall cost low a transfer module has to be avoided. Consequently the launcher should preferably be capable to put the satellite into the final orbit. As a consequence of what just said the total mission cost is mainly driven by the launch system which is in principle connected to the satellite mass and semimajor axis of the orbit. The orbit proposed both for LAGEOS III and LARES mission was supplementary to that one of LAGEOS, (i.e. 70 degrees and about 12.000 km for the semimajor axis)
The LARES mission revisited: an alternative scenario
No full textIn the original LARES mission, the general relativistic Lense-Thirring effect was to be detected using as an observable the sum of the residuals of the nodes of the existing passive geodetic laser-ranged LAGEOS satellite and of its proposed twin LARES. The proposed nominal orbital configuration of the latter would reduce the systematic error due to the mismodelling in the even zonal harmonics of the geopotential, which is the main source of error (to 0.3%) according to the most recent Earth gravity model EGM96. This observable turns out to be sensitive to possible departures of the LARES orbital parameters from their nominal values due to the orbital injection errors. By adopting a suitable combination of the orbital residuals of the nodes of LAGEOS, LAGEOS II and LARES and the perigees of LAGEOS II and LARES, it should be possible to reduce the error due to the geopotential by one order of magnitude, according to the EGM96 model. Moreover, the sensitivity to the orbital injection errors should be greatly reduced. According to a preliminary estimate of the error budget, the total error of the experiment should be reduced to less than 1%. In the near future, when the new data on, the terrestrial gravitational field from CHAMP and GRACE missions become available, a further increase in the accuracy should be obtained. The proposal to place LARES in a polar 2000 km altitude orbit and consider only its nodal rate would present the drawback that even small departures from the polar geometry would yield notable errors due to the mismodelled even zonal harmonics of the geopotential, according to the EGM96 model
Beam-to-column connections for steel-concrete composite moment resisting frame designed for S Ductility Class
No full textDesign, testing and analysis of high ductile partial-strength steel-concrete composite beam-to-column joints
No full textSteel-concrete composite structures, owing to their high capacity for prefabrication and rational use of materials can provide high levels of performance in terms of ductility and dissipation energy, while at the same time containing construction costs. Modern codes for frame structures in seismic areas allow high ductility structures to be conceived, without however providing designers with detailed specifications or prescriptions for designing partial-strength beam-to-column joints. This paper illustrates the methods that were conceived for the design of exterior and interior partial-strength beam-to-column joints in view of the construction of moment-resisting frame structures of ductility class high (DCH), where inelastic phenomena occur precisely in column web panel zones and beam-to-column connections. Successively, three-dimensional finite element models of an exterior and an interior joint subjected to horizontal loading are presented. The models take into account the non-linear material properties of columns, end plates, reinforced concrete slabs and reinforcing bars which represent critical points of joint performance. Then, the paper presents the basic joint modelling and its calibration on substructures tested experimentally. Finally, some parametric analyses focussing on the influence of a composite slab with strong and weak strength on the joint performance are illustrated. (c) 2005 Elsevier Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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