5,828 research outputs found
Orthogonal learning particle swarm optimization
Particle swarm optimization (PSO) relies on its
learning strategy to guide its search direction. Traditionally,
each particle utilizes its historical best experience and its neighborhood’s
best experience through linear summation. Such a
learning strategy is easy to use, but is inefficient when searching
in complex problem spaces. Hence, designing learning strategies
that can utilize previous search information (experience) more
efficiently has become one of the most salient and active PSO
research topics. In this paper, we proposes an orthogonal learning
(OL) strategy for PSO to discover more useful information that
lies in the above two experiences via orthogonal experimental
design. We name this PSO as orthogonal learning particle swarm
optimization (OLPSO). The OL strategy can guide particles to
fly in better directions by constructing a much promising and
efficient exemplar. The OL strategy can be applied to PSO with
any topological structure. In this paper, it is applied to both global
and local versions of PSO, yielding the OLPSO-G and OLPSOL
algorithms, respectively. This new learning strategy and the
new algorithms are tested on a set of 16 benchmark functions, and
are compared with other PSO algorithms and some state of the
art evolutionary algorithms. The experimental results illustrate
the effectiveness and efficiency of the proposed learning strategy
and algorithms. The comparisons show that OLPSO significantly
improves the performance of PSO, offering faster global convergence,
higher solution quality, and stronger robustness
On the Three-dimensional Lattice Model
Using the restricted star-triangle relation, it is shown that the -state
spin integrable model on a three-dimensional lattice with spins interacting
round each elementary cube of the lattice proposed by Mangazeev, Sergeev and
Stroganov is a particular case of the Bazhanov-Baxter model.Comment: 8 pages, latex, 4 figure
Atomistic Investigation of Titanium Carbide Ti8C5 under Impact Loading
Titanium carbides attract attention from both academic and industry fields because of their intriguing mechanical properties and proven potential as appealing candidates in the variety of fields such as nanomechanics, nanoelectronics, energy storage and oil/water separation devices. A recent study revealed that the presence of Ti8C5 not only improves the impact strength of composites as coatings, but also possesses significant strengthening performance as an interlayer material in composites by forming strong bonding between different matrices, which sheds light on the design of impact protection composite materials. To further investigate the impact resistance and strengthening mechanism of Ti8C5, a pilot Molecular Dynamics (MD) study utilizing comb3 potential is carried out on a Ti8C5 nanosheet by subjecting it to hypervelocity impacts. The deformation behaviour of Ti8C5 and the related impact resist mechanisms are assessed in this research. At a low impact velocity ~0.5 km/s, the main resonance frequency of Ti8C5 is 11.9 GHz and its low Q factor (111.9) indicates a decent energy damping capability, which would eliminate the received energy in an interfacial reflection process and weaken the shock waves for Ti8C5 strengthened composites. As the impact velocity increases above the threshold of 1.8 km/s, Ti8C5 demonstrates brittle behaviour, which is signified by its insignificant out-of-plane deformation prior to crack initiation. When tracking atomic Von Mises stress distribution, the elastic wave propagation velocity of Ti8C5 is calculated to be 5.34 and 5.90 km/s for X and Y directions, respectively. These figures are inferior compared with graphene and copper, which indicate slower energy delocalization rates and thus less energy dissipation via deformation is expected prior to bond break. However, because of its relatively small mass density comparing with copper, Ti8C5 presents superior specific penetration. This study provides a fundamental understanding of the deformation and penetration mechanisms of titanium carbide nanosheets under impact, which is crucial in order to facilitate emerging impact protection applications for titanium carbide-related composites
Etanercept Inhibits Pro-inflammatory Cytokines Expression in Titanium Particle-Stimulated Peritoneal Macrophages
Purpose: To investigate the inhibitory role of Etanercept in pro-inflammatory cytokines such as TNF-α, IL-1β and IL-6 production in titanium (Ti) particle stimulated macrophages.Methods: Peritoneal macrophages were stimulated with 1 × 109 Ti particles and treated simultaneously with or without 10, 100, or 1000 ng/mL Etanercept. The levels of TNF-α, IL-1β and IL-6 in the culture supernatants were measured using ELISA.Results: Titanium particles could stimulate TNF-α, IL-1β and IL-6 secretion in peritoneal macrophages. Etanercept inhibited Ti particle-induced TNF-α release by 29.7 % at 10 ng/ml (19.19 ± 4.72 pg/mL, p < 0.01), 49.3 % at 100 ng/mL (13.83 ± 3.72 pg/ml, p < 0.01) and 60.4 % at 1000 ng/mL (10.82 ± 3.87 pg/mL, p < 0.001), IL-1β release by 5.23 % at 10 ng/mL (34.79 ± 7.83 pg/mL, p > 0.05), 21.06 % at 100 ng/mL (28.98 ± 4.81 pg/mL, p < 0.01) and 29.83 % at 1000 ng/mL (25.76 ± 5.23 pg/ml, p < 0.001), and IL-6 release by 38.69 % at 10 ng/mL (256.8 ± 99.56 pg/mL, p < 0.01), by 42.13 % at 100 ng/mL (242.4 ± 33.26 pg/mL, p < 0.01) and 53.4 % at 1000 ng/ml (195.2 ± 48.82 pg/mL, p < 0.001).Conclusion: Etanercept has potent ability to prevent wear debris–induced osteolysis and may be valuable as a therapeutic agent for the treatment of prosthetic loosening in humans.Keywords: Etanercept; titanium particle; proinflammatory cytokines; peritoneal macrophage
Obvious enhancement of the total reaction cross sections for P with Si target and the possible relavent mechanisms
The reaction cross sections of P and the corresponding isotones on
Si target were measured at intermediate energies. The measured reaction cross
sections of the N=12 and 13 isotones show an abrupt increase at . The
experimental results for the isotones with as well as P can
be well described by the modified Glauber theory of the optical limit approach.
The enhancement of the reaction cross section for P could be explained
in the modified Glauber theory with an enlarged core. Theoretical analysis with
the modified Glauber theory of the optical limit and few-body approaches
underpredicted the experimental data of P. Our theoretical analysis
shows that an enlarged core together with proton halo are probably the
mechanism responsible for the enhancement of the cross sections for the
reaction of P+Si.Comment: 16 pages, 5 figures, to be published in Phys.Rev.
Forchheimer flow to a well-considering time-dependent critical radius
Previous studies on the non-Darcian flow into a pumping well assumed that
critical radius (RCD) was a constant or infinity, where RCD
represents the location of the interface between the non-Darcian flow region
and Darcian flow region. In this study, a two-region model considering
time-dependent RCD was established, where the non-Darcian flow was
described by the Forchheimer equation. A new iteration method was proposed
to estimate RCD based on the finite-difference method. The results
showed that RCD increased with time until reaching the quasi steady-state flow, and the asymptotic value of RCD only depended on the
critical specific discharge beyond which flow became non-Darcian. A larger
inertial force would reduce the change rate of RCD with time, and
resulted in a smaller RCD at a specific time during the transient flow.
The difference between the new solution and previous solutions were obvious
in the early pumping stage. The new solution agreed very well with the
solution of the previous two-region model with a constant RCD under
quasi steady flow. It agreed with the solution of the fully Darcian flow
model in the Darcian flow region
Hamiltonicity of 3-arc graphs
An arc of a graph is an oriented edge and a 3-arc is a 4-tuple of
vertices such that both and are paths of length two. The
3-arc graph of a graph is defined to have vertices the arcs of such
that two arcs are adjacent if and only if is a 3-arc of
. In this paper we prove that any connected 3-arc graph is Hamiltonian, and
all iterative 3-arc graphs of any connected graph of minimum degree at least
three are Hamiltonian. As a consequence we obtain that if a vertex-transitive
graph is isomorphic to the 3-arc graph of a connected arc-transitive graph of
degree at least three, then it is Hamiltonian. This confirms the well known
conjecture, that all vertex-transitive graphs with finitely many exceptions are
Hamiltonian, for a large family of vertex-transitive graphs. We also prove that
if a graph with at least four vertices is Hamilton-connected, then so are its
iterative 3-arc graphs.Comment: in press Graphs and Combinatorics, 201
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