825 research outputs found
On the equilibrium problem and infinitesimal mechanisms of class theta tensegrity systems
No full textThis work presents a study on the equilibrium problem and the infinitesimal mechanisms of class θ= 1 tensegrity prisms. Local solutions of the self-equilibrium problem are numerically obtained through Newton-Raphson iterations. The presented results suggest that the analyzed structures can be usefully employed as building blocks of novel tensegrity metamaterials, due to their rich kinematic response and the considerably large number of infinitesimal mechanisms. © 2019 Author(s)
Full 3D CAD procedure for the speedy evaluation of the seismic vulnerability of masonry towers
No full textA very straightforward 3D CAD approach for the speedy evaluation of the seismic vulnerability of existing masonry towers is presented. The procedure requires only the detailed 3D geometric model of the structure and automatically calculates the collapse acceleration on a user defined failure mechanism. In this paper, few pre-assigned mechanisms are tested, as for instance vertical splitting, simple overturning at the base, rocking with inclined yield lines and combined rocking and vertical splitting. The restriction of the possible tower failure within such a few mechanisms grounds on previous numerical research in the field and post-earthquake surveys experience. In any case, any user can define his own mechanisms according to the specificity of the case-study under consideration, directly shaping distinct volumes inside the CAD software. The procedure is automatized and the direct application of the principle of virtual works-assuming that masonry behaves as a no-tension material-allows the immediate evaluation of the horizontal acceleration at collapse. The mechanism associated to the minimum acceleration, in agreement with the kinematic theorem of limit analysis, is that most probably would occur in reality during a seismic event. The approach allows a straightforward evaluation of the seismic vulnerability of a tower and can be used even by practitioners not familiar with advanced FE computations and limit analysis concepts, so adapting well to the heterogeneous community involved in cultural heritage preservation. The automatized procedure is applied in this paper to a historical tower located in central Italy, to show the capabilities of the approach. © 2019 Author(s)
The Arab peoples of T.E. Lawrence's Seven Pillars of Wisdom in the light of post-colonial theory
No full textIt can be said that The Seven Pillars of Wisdom is a work whose true potential has not yet been discovered. That the work presents itself to be of greater value than may have previously seemed goes without question. However, during the more than eighty years of its existence, it was the author and not the work that created major interest in the academic world. The complicated character of T.E. Lawrence offered itself to psycho-analyst interpretation and most critiques have been built on these premises. Other works have concentrated on major historical events in Lawrence's life creating thorough biographies and numbers of fascinating approaches, some more, some less misleading were created. However. The Seven Pillars of Wisdom (from henceforth "Seven Pillars") foremostly survived in the shadows of David Lean's film "Lawrence of Arabia" and it was only during the late seventies, that concentration on the Seven Pillars as a text had begun to be cultivated. Additionally, it has only been during the past few years that works by writers such as Gertrude Bell, T.E. Lawrence or Charles M. Doughty have begun to gain a larger public interest. The aim of this work, however, is not to analyse the historical purpose of Lawrence's presence in the Middle East, nor to align the Seven Pillars with historical facts. Such..
The Arab peoples of T.E. Lawrence's Seven Pillars of Wisdom in the light of post-colonial theory
No full textIt can be said that The Seven Pillars of Wisdom is a work whose true potential has not yet been discovered. That the work presents itself to be of greater value than may have previously seemed goes without question. However, during the more than eighty years of its existence, it was the author and not the work that created major interest in the academic world. The complicated character of T.E. Lawrence offered itself to psycho-analyst interpretation and most critiques have been built on these premises. Other works have concentrated on major historical events in Lawrence's life creating thorough biographies and numbers of fascinating approaches, some more, some less misleading were created. However. The Seven Pillars of Wisdom (from henceforth "Seven Pillars") foremostly survived in the shadows of David Lean's film "Lawrence of Arabia" and it was only during the late seventies, that concentration on the Seven Pillars as a text had begun to be cultivated. Additionally, it has only been during the past few years that works by writers such as Gertrude Bell, T.E. Lawrence or Charles M. Doughty have begun to gain a larger public interest. The aim of this work, however, is not to analyse the historical purpose of Lawrence's presence in the Middle East, nor to align the Seven Pillars with historical facts. Such..
Minimum MSE estimation of a regression model with fixed effects from a series of cross sections (Revised version)
No full textEstimation
Pathways to Industrial-Scale Fuel Out of Thin Air from CO<sub>2</sub> Electrolysis
No full textUsing renewable energy as an input, Power-to-X technologies have the potential to replace fossil fuels and chemicals with dense-energy carriers that are instead derived out of thin air. In this work, we put into context what the industrial-scale production of chemicals from ambient CO2 using CO2 electrolysis means in terms of future required operating conditions and the device and catalyst scales that will be needed for the technology to assume its role in our global energy system.Accepted Author ManuscriptChemE/Materials for Energy Conversion and StorageChemE/Transport Phenomen
Mechanical modeling of the bandgap response of tensegrity metamaterials
No full textWe investigate the acoustic band structure of tensegrity mass-spring chains as a function of the applied, local and global states of prestress. We first study the bandgap response of linear monoatomic chains, which show lumped masses connected to tensegrity prisms acting as mechanical springs. Next, we present a numerical study on the nonlinear wave dynamics of the examined systems in the geometrically nonlinear regime that is induced by the presence of moderately large relative displacements between the lumped masses. Such a study confirms the results of the linear analysis in the case of an elastically hardening system. © 2019 Author(s)
Publication models in a changing environment: bibliometric analysis of books and book chapters using publications by Surrey Beatty & Sons
No full textExpectations and patterns of publication have changed markedly with evolving online availability and associated development of new citation gathering databases. Perhaps the most vulnerable components of the scientific literature to ongoing change are books and book chapters, given their elongated publication timelines and generally more limited online availability. To test this, we applied citation analyses and assessments of library holdings to determine the use of the natural history books published by Surrey Beatty & Sons between 1987 and 2010. We (i) evaluated the relative use of book chapters and journal papers by comparing citations to chapters in the five books of the Nature Conservation series by Surrey Beatty & Sons to citations of journal chapters in four Australian journals published in the same years, (ii) determined the efficacy of four different databases in retrieving citations to book chapters by comparing their recovery of citations to the five books of the Nature Conservation series, and (iii) quantified noncitation measures related to library holdings to evaluate the use of the books on the entire Surrey Beatty & Sons list.
Mean citations/chapter to the first three books in the Nature Conservation series were similar to the mean citations/paper in four Australian journals published in the same years. However, the mean citations/chapter of the last two books declined relative to citations/paper for the journals, suggesting a fall in book use evident by early this century. Citation retrieval varied across databases; Google Scholar retrieved most citations, followed by Scopus, Web of Science (Cited Reference Search) and Web of Knowledge. Contrary to published concerns, no citations retrieved by Google Scholar were in questionable sources such as contents pages - many were from highly ranked journals.
Each book in the full Surrey Beatty & Sons list was held by an average of 45.3 libraries in Australia and 36.1 in the USA, and less than five in each of the UK, New Zealand, Hong Kong, Canada, Germany and South Africa. This was a similar coverage to another Australian publisher, the Royal Zoological Society of New South Wales, and indicated strong markets in Australia and the USA. It was less, though, than the number of libraries with current or past subscriptions to five Australian journals publishing nature conservation content.
We conclude that citation data for books and book chapters are available and that library holdings provide another measure of use. The online ‘visibility’ of books may be a problem, but can be improved through better marketing and improved author search techniques
Optimising Landing-site Selection for ExoMars
No full textOnly 6 out of 16 missions to the surface of Mars have been successful, all have been NASA missions. The landing sites of all the successful missions have been carefully selected in a process where: 1) scientists propose candidate landing sites, 2) engineers check whether these sites allow for a safe landing, and 3) over a few iterations, the number of sites is brought down to the final site and a back-up. ExoMars will be the first lander to Mars designed by the European Space Agency. It will explore Mars in search of signs of past and present life. An extensive landing-site selection process is required to find a landing site that is safe from both an engineering perspective and that will help to answer the mission’s science objectives. This research has identified four developments that decrease the efficiency of the current landing-site selection process: 1) there is more and more data available on Mars, which makes combining and analysing all this data manually no longer possible; 2) the technical capabilities of the landing system are increasing, which makes a larger part of the surface available; 3) the questions posed in the scientific and exploration objectives become more and more specific, which sets more stringent requirements on where these questions can be answered; and 4) the Martian surface turned out to be more variable in composition than was previously thought. This study recommends a set of improvements in the form of a decision support system (DSS) that assists experts in the landing-site selection process. The DSS developed for this research includes two prototypes 1) a method that emulates the pattern recognition of a trained, terrain-analysis expert (i.e. a geologist) on a computer, called the terrain fingerprinting method (TFM); and 2) a platform that provides the interface through which all stakeholders in the landing site selection process (scientists, engineers, students, managers) can efficiently interact. This study concludes that I) the TFM can be used to find a landing site that optimises both the safety of the mission and the possibility for scientific return at the site. II) A central platform is required in order to empower the landing site selection community by sharing higher level data products, tools (e.g. TFM software tools), a forum, and documentation. III) The United States Geological Survey (USGS) is the central authority in the planetary sciences community in the USA providing standardisation support, the lack of such a central authority in Europe will negatively affect the process of landing-site selection by European scientists for all future planetary landers. And IV) for the various stakeholders to effectively collaborate and interact in the process of landing-site selection, standardisation of elements related to geographically referenced planetary data is essential.Astrodynamics and Satellite SystemsAerospace Engineerin
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