912 research outputs found
Innovative all composite multi-pultrusion truss system for stressed arch deployable shelters
Trusses are one of the successful structural forms that have been utilised, at extended scale, since the nineteen century. Fibre composite materials are relatively new to civil engineering applications. The increased interest in using composites in civil applications can be attributed to advantages when compared to other construction materials that offset their associated costs. Using conventional approaches for truss systems in composite materials can undermine their efficiency. This is mainly due to concentration of stresses at connections which usually govern the truss design.
The Military Modular Shelter System (M2S2) initiative is a research project that aims to develop a fibre composite re-deployable arched shelter system with rigid PVC or fabric cladding. The main frames are formed from modular fibre composite panels that are connected and stressed into position by prestressing cables. Different geometries can be obtained using this system by changing the number of panels per frame and the packer sizes between panels.
This paper presents the development and testing of innovative fibre composite truss modules that were investigated as part of this project. The truss system is based on using multi-pultrusion sections for the chord and vertical members. Truss bracing is provided by a double skin laminated web. This structure offers many advantages including semi-ductile failure that occurred outside the joint area and ease of manufacturing. In spite of being developed for the M2S2 system, the concept is similarly applicable as a general purpose truss system
Aubry transition studied by direct evaluation of the modulation functions of infinite incommensurate systems
Incommensurate structures can be described by the Frenkel Kontorova model.
Aubry has shown that, at a critical value K_c of the coupling of the harmonic
chain to an incommensurate periodic potential, the system displays the
analyticity breaking transition between a sliding and pinned state. The ground
state equations coincide with the standard map in non-linear dynamics, with
smooth or chaotic orbits below and above K_c respectively. For the standard
map, Greene and MacKay have calculated the value K_c=.971635. Conversely,
evaluations based on the analyticity breaking of the modulation function have
been performed for high commensurate approximants. Here we show how the
modulation function of the infinite system can be calculated without using
approximants but by Taylor expansions of increasing order. This approach leads
to a value K_c'=.97978, implying the existence of a golden invariant circle up
to K_c' > K_c.Comment: 7 pages, 5 figures, file 'epl.cls' necessary for compilation
provided; Revised version, accepted for publication in Europhysics Letter
THE EFFECT OF CORE ARCHITECTURE ON THE BEHAVIOUR OF SANDWICH COLUMNS UNDER EDGEWISE COMPRESSION LOADING
ABSTRACT Sandwich structures are a form of construction that offers high performance and low-weight. This type of construction became popular by the mid of the twenty century where different metallic faces and core materials were used for the construction of aircrafts and marine vessels. The development of high-strength, high-modulus, light-weight fibres and new forms of core materials has opened a new horizon for sandwich structures. Using sandwich structures for columns was investigated by different researchers. However, none of the located literature reported using strong-weak core (mixed-core) materials in sandwich columns. To investigate the effect of using mixed-core on the column behaviour was investigated by testing five sets of prototype columns under edgewise compression. The column cores were made of PVC low-density foam, end-grain balsa wood or a combination of both materials. The column skins were laminated by using glass/epoxy composites. The test results showed that the mixed-core can lead to having a failure mode that has not been reported previously. This paper presents the experimental work conducted in testing these columns. It highlights the effect of core structure on the failure mode and capacity of the sandwich columns
Innovative Piloting Technique for a Semi-Autonomous UAV Lighter-Than-Air Platform Simulator
UAS design has in these years reached a point in which trends and objectives are well beyond the actual test capabilities. The tendency of the past to build and test has clearly been overridden by new design concepts for many reasons, one of these being the scarce or null possibility of testing safety-critical systems such as UAV systems. This is the context in which the Elettra-Twin-Flyer (ETF) Simulator is constantly upgraded and rearranged to incorporate new features and more advanced capabilities. In this paper it is shown how the piloting modes have been differentiated, to improve the airship autonomy and allow path following operations. Innovative piloting tools have been introduced and a new Human-Machine-Interface has been proposed along
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Dit artikel geeft een overzicht van de mogelijkheden met de voor- en nadelen en kosten
Towards structured sharing of raw and derived neuroimaging data across existing resources
Data sharing efforts increasingly contribute to the acceleration of
scientific discovery. Neuroimaging data is accumulating in distributed
domain-specific databases and there is currently no integrated access mechanism
nor an accepted format for the critically important meta-data that is necessary
for making use of the combined, available neuroimaging data. In this
manuscript, we present work from the Derived Data Working Group, an open-access
group sponsored by the Biomedical Informatics Research Network (BIRN) and the
International Neuroimaging Coordinating Facility (INCF) focused on practical
tools for distributed access to neuroimaging data. The working group develops
models and tools facilitating the structured interchange of neuroimaging
meta-data and is making progress towards a unified set of tools for such data
and meta-data exchange. We report on the key components required for integrated
access to raw and derived neuroimaging data as well as associated meta-data and
provenance across neuroimaging resources. The components include (1) a
structured terminology that provides semantic context to data, (2) a formal
data model for neuroimaging with robust tracking of data provenance, (3) a web
service-based application programming interface (API) that provides a
consistent mechanism to access and query the data model, and (4) a provenance
library that can be used for the extraction of provenance data by image
analysts and imaging software developers. We believe that the framework and set
of tools outlined in this manuscript have great potential for solving many of
the issues the neuroimaging community faces when sharing raw and derived
neuroimaging data across the various existing database systems for the purpose
of accelerating scientific discovery
A stitch in time: Efficient computation of genomic DNA melting bubbles
Background: It is of biological interest to make genome-wide predictions of
the locations of DNA melting bubbles using statistical mechanics models.
Computationally, this poses the challenge that a generic search through all
combinations of bubble starts and ends is quadratic.
Results: An efficient algorithm is described, which shows that the time
complexity of the task is O(NlogN) rather than quadratic. The algorithm
exploits that bubble lengths may be limited, but without a prior assumption of
a maximal bubble length. No approximations, such as windowing, have been
introduced to reduce the time complexity. More than just finding the bubbles,
the algorithm produces a stitch profile, which is a probabilistic graphical
model of bubbles and helical regions. The algorithm applies a probability peak
finding method based on a hierarchical analysis of the energy barriers in the
Poland-Scheraga model.
Conclusions: Exact and fast computation of genomic stitch profiles is thus
feasible. Sequences of several megabases have been computed, only limited by
computer memory. Possible applications are the genome-wide comparisons of
bubbles with promotors, TSS, viral integration sites, and other melting-related
regions.Comment: 16 pages, 10 figure
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