26,612 research outputs found
Connected subgroups of SO(2,n) acting irreducibly on R^{2,n}
We classify all connected subgroups of SO(2, n) that act irreducibly on R^{2, n
Optimality conditions and regularity results for time optimal control problems with differential inclusions
We study the time optimal control problem with a general target
for a class of differential inclusions that satisfy mild smoothness and
controllability assumptions. In particular, we do not require Petrov's
condition at the boundary of . Consequently, the minimum time
function fails to be locally Lipschitz---never mind
semiconcave---near . Instead of such a regularity, we use an
exterior sphere condition for the hypograph of to develop the
analysis. In this way, we obtain dual arc inclusions which we apply to show the
constancy of the Hamiltonian along optimal trajectories and other optimality
conditions in Hamiltonian form. We also prove an upper bound for the Hausdorff
measure of the set of all nonlipschitz points of which implies that
the minimum time function is of special bounded variation.Comment: 23 pages, 1 figur
Numerical analysis of suction embedded plate anchors in structured clay
As offshore energy developments move towards deeper water, moored floating production facilities are increasingly preferred to fixed structures. Anchoring systems are therefore of great interest to engineers working on deep water developments. Suction embedded plate anchors (SEPLAs) are rapidly becoming a popular solution, possessing a more accurate and predictable installation process compared to traditional alternatives. In this paper, finite element analysis has been conducted to evaluate the ultimate pullout capacity of SEPLAs in a range of post-keying configurations. Previous numerical studies of anchor pullout capacity have generally treated the soil as an elastic-perfectly plastic medium. However, the mechanical behaviour of natural clays is affected by inter-particle bonding, or structure, which cannot be accounted for using simple elasto-plastic models. Here, an advanced constitutive model formulated within the kinematic hardening framework is used to accurately predict the degradation of structure as an anchor embedded in a natural soft clay deposit is loaded to its pullout capacity. In comparison with an idealised, non-softening clay, the degradation of clay structure due to plastic strains in the soil mass results in a lower pullout capacity factor, a quantity commonly used in design, and a more complex load–displacement relationship. It can be concluded that clay structure has an important effect on the pullout behaviour of plate anchors.Peer ReviewedPostprint (author's final draft
Light pseudo-Goldstone bosons without explicit symmetry breaking
A mechanism is discussed to obtain light scalar fields from a spontaneously
broken continuous symmetry without explicitly breaking it. If there is a
continuous manifold of classical vacua in orbit space, its tangent directions
describe classically massless fields that may acquire mass from perturbations
of the potential that do not break the symmetry. We consider the simplest
possible example, involving a scalar field in the adjoint representation of
SU(N). We study the scalar mass spectrum and its RG running at one-loop level
including scalar and pseudoscalar Yukawa couplings to a massive Dirac fermion.Comment: minor typographical changes, 12 pages, 4 figure
An estimate of theta_14 independent of the reactor antineutrino flux determinations
In a previous paper [Phys. Rev. D 83, 113013 (2011)] we have shown that the
solar sector data (solar and KamLAND) are sensitive to the parameter theta_14,
encoding the admixture of the electron neutrino with a fourth (essentially)
sterile mass eigenstate. In that work we evidenced that such data prefer a
non-zero value of theta_14 and that such a preference is completely degenerate
with that of non-zero theta_13. In this report we show how the evidence of
theta_13 > 0, recently emerged from global neutrino data analyses, lifts such a
degeneracy and disfavors the case of sterile neutrino mixing. By excluding from
our analysis the total rate information coming from the reactor experiments we
untie our results from any assumption on their flux normalization. In this way,
we establish the robust upper bound sin^2 (theta_14) < 0.04 at the 90% C.L.Comment: 4 pages, 1 figure, minor changes, matches version accepted by PR
How Do Research Projects Influence the Design of Local Policies for Environmental and Natural Resource Management?
This paper documents and analyzes interactions between environmental and natural resource (ENR) management research and local governance. It draws from the experiences of the Philippine-based Sustainable Agriculture and Natural Resource Management Collaborative Research Support Program (SANREM CRSP) to address the following questions: How do research projects influence ENR policy and design? What are the institutional arrangements necessary to sustain interactions between research and governance? The authors offer important methodological insights as well as lessons for practical efforts to link research and policy.environmental and natural resource management, research-policy relationship
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