1,950 research outputs found
3D modeling of the vane test on a power-law cement paste by means of the proper generalized decomposition
The effective modeling of the flow of fresh concrete materials in settings such as that of the vane test is a challenging process that is the object of ongoing research. Previous works modeled concrete and cement pastes as solids subjected to yielding or as Bingham or power-law fluids, both in two or three dimensions [1, 2]. Of the existing models, those implementing power-law fluids in three dimensions carry the best predictive ability considering the typically heterogeneous composition of concrete suspensions and the relatively complex three-dimensional features of their flows.
In this work, we model the vane test in a power-law cement paste using the Proper Generalized Decomposition (PGD). In this framework, the three-dimensional problem is solved as a sequence of 2D × 1D problems, thus alleviating the curse of dimensionality. This choice is supported by experience from previous works using the PGD to simulate Non-Newtonian behavior using iterative resolutions [3, 4]. It is also particularly useful in addressing the inverse problem corresponding to the identification of the material properties of cement pastes from experimental data, as this requires many direct resolutions of the forward problem. The use of the PGD is also appealing because the model parameters can be introduced as extra coordinates of the problem [5]
Digital Ecosystems: Self-Organisation of Evolving Agent Populations
A primary motivation for our research in Digital Ecosystems is the desire to
exploit the self-organising properties of biological ecosystems. Ecosystems are
thought to be robust, scalable architectures that can automatically solve
complex, dynamic problems. Self-organisation is perhaps one of the most
desirable features in the systems that we engineer, and it is important for us
to be able to measure self-organising behaviour. We investigate the
self-organising aspects of Digital Ecosystems, created through the application
of evolutionary computing to Multi-Agent Systems (MASs), aiming to determine a
macroscopic variable to characterise the self-organisation of the evolving
agent populations within. We study a measure for the self-organisation called
Physical Complexity; based on statistical physics, automata theory, and
information theory, providing a measure of information relative to the
randomness in an organism's genome, by calculating the entropy in a population.
We investigate an extension to include populations of variable length, and then
built upon this to construct an efficiency measure to investigate clustering
within evolving agent populations. Overall an insight has been achieved into
where and how self-organisation occurs in our Digital Ecosystem, and how it can
be quantified.Comment: 5 pages, 5 figures, ACM Management of Emergent Digital EcoSystems
(MEDES) 200
Ecosystem-Oriented Distributed Evolutionary Computing
We create a novel optimisation technique inspired by natural ecosystems,
where the optimisation works at two levels: a first optimisation, migration of
genes which are distributed in a peer-to-peer network, operating continuously
in time; this process feeds a second optimisation based on evolutionary
computing that operates locally on single peers and is aimed at finding
solutions to satisfy locally relevant constraints. We consider from the domain
of computer science distributed evolutionary computing, with the relevant
theory from the domain of theoretical biology, including the fields of
evolutionary and ecological theory, the topological structure of ecosystems,
and evolutionary processes within distributed environments. We then define
ecosystem- oriented distributed evolutionary computing, imbibed with the
properties of self-organisation, scalability and sustainability from natural
ecosystems, including a novel form of distributed evolu- tionary computing.
Finally, we conclude with a discussion of the apparent compromises resulting
from the hybrid model created, such as the network topology.Comment: 8 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1112.0204, arXiv:0712.4159, arXiv:0712.4153, arXiv:0712.4102,
arXiv:0910.067
Digital Ecosystems: Ecosystem-Oriented Architectures
We view Digital Ecosystems to be the digital counterparts of biological
ecosystems. Here, we are concerned with the creation of these Digital
Ecosystems, exploiting the self-organising properties of biological ecosystems
to evolve high-level software applications. Therefore, we created the Digital
Ecosystem, a novel optimisation technique inspired by biological ecosystems,
where the optimisation works at two levels: a first optimisation, migration of
agents which are distributed in a decentralised peer-to-peer network, operating
continuously in time; this process feeds a second optimisation based on
evolutionary computing that operates locally on single peers and is aimed at
finding solutions to satisfy locally relevant constraints. The Digital
Ecosystem was then measured experimentally through simulations, with measures
originating from theoretical ecology, evaluating its likeness to biological
ecosystems. This included its responsiveness to requests for applications from
the user base, as a measure of the ecological succession (ecosystem maturity).
Overall, we have advanced the understanding of Digital Ecosystems, creating
Ecosystem-Oriented Architectures where the word ecosystem is more than just a
metaphor.Comment: 39 pages, 26 figures, journa
The impact of the unilateral EU commitment on the stability of international climate agreements
In this paper we analyze the negotiation strategy of the European Union regarding the formation of an international climate agreement for the post-2012 era. We use game theoretical stability concepts to explore incentives for key players in the climate policy game to join future climate agreements. We compare a minus 20 percent unilateral commitment strategy by the EU with a unilateral minus 30 percent emission reduction strategy for all Annex-B countries. Using a numerical integrated assessment climate-economy simulation model, we find that carbon leakage effects are negligible. The EU strategy to reduce emissions by 30% (compared to 1990 levels) by 2020 if other Annex-B countries follow does not induce participation of the USA with a similar 30% reduction commitment. However, the model shows that an appropriate initial allocation of emission allowances may stabilize a larger and more ambitious climate coalition than the Kyoto Protocol in its first commitment period.climate change, coalition theory, integrated assessment model, Kyoto protocol.
A technical note for the 91-clauses SAT resolution with Indirect QAOA based approach
This paper addresses the resolution of the 3-SAT problem using a QAOA-like
approach. The chosen principle involves modeling the solution ranks of the
3-SAT problem, which, in this particular case, directly represent a solution.
This results in a highly compact circuit with few gates, enabling the modeling
of large-sized 3-SAT problems. Numerical experimentation demonstrates that the
approach can solve instances composed of 91 clauses and 20 variables with an
implementation based on Qiskit
The largest reservoir of mitochondrial introns is a relic of an ancestral split gene
In eukaryotes, introns are located in nuclear and organelle genes from several kingdoms (ref. 1-4). Large introns (0.1 to 5 kbp) are frequent in mitochondrial genomes of plant and fungi (ref. 1,5) but scarce in Metazoa, despite these organisms are grouped with fungi among Opisthokonts. Introns are classified in two main groups (I and II) according to their RNA secondary structure involved in the intron self-splicing mechanism (ref. 5,6). Most of the group I introns carry a "Homing Endonuclease Gene" (ref. 7-9) encoding a DNA endonuclease acting in the transfer and site specific integration "homing") and allowing the intron spreading and gain after lateral transfer even between species from different kingdoms (ref. 10,11). Opposite to this "late intron" paradigm, the "early intron" theory indicates that introns, which would have been abundant in the ancestral genes, would mainly evolve by loss (ref. 12,13).

Here we report the sequence of the cox1 gene of the button mushroom _Agaricus bisporus_, the most worldwide cultivated mushroom. This gene is both the longest mitochondrial gene (29,902 nt) and the largest Group I intron reservoir reported to date. An analysis of the group I introns available in _cox1_ genes shows that they are ancestral mobile genetic elements, whose frequent events of loss (according to the "late theory") and gain by lateral transfer ("early theory") must be combined to explain their wide and patchy distribution extending on several kingdoms. This allows the conciliation of the "early" and "late intron" paradigms, which are still matters of much debate (ref. 14,15). The overview of the intron distribution indicates that they evolve towards elimination. In such a landscape of eroded and lost intron sequences, the _A. bisporus_ largest intron reservoir, by its singular dynamics of intron keeping and catching, constitutes the most fitted relic of an early split gene
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