328 research outputs found
Filling a blank on the map: 60Â years of fisheries in Equatorial Guinea
Despite a scarcity of pertinent information, it has been possible to reconstruct time series of marine fisheries catches for Equatorial Guinea from 1950 to 2010 using per capita fish consumption and population numbers for small-scale fisheries, catch rates and number of vessels for industrial fisheries and discard rates to estimate the discarded bycatch. Small-scale fisheries, industrial large-scale fisheries, domestic and legal and illegal foreign fisheries and their discards are all included. Total catches were estimated at 2.7 million tonnes over the time period considered, of which 653 000 t were caught domestically compared to 187 000 t reported by FAO. This shows that fisheries have more importance for Equatorial Guinea's food security than the official data suggest. In contrast to what is suggested by official figures, fisheries were shown to be strongly impacted by civil and political unrest; notably, they declined overall because of civil and political conflicts, socio-demographic dynamics, and a growing role of the newly discovered oil resources, which directly and indirectly threaten the food security of the people of Equatorial Guinea
Modeling, optimizing and simulating robot calibration with accuracy improvement
This work describes techniques for modeling, optimizing and simulating calibration processes ofrobots using off-line programming. The identification of geometric parameters of the nominalkinematic model is optimized using techniques of numerical optimization of the mathematicalmodel. The simulation of the actual robot and the measurement system is achieved by introducingrandom errors representing their physical behavior and its statistical repeatability. An evaluationof the corrected nominal kinematic model brings about a clear perception of the influence ofdistinct variables involved in the process for a suitable planning, and indicates a considerableaccuracy improvement when the optimized model is compared to the non-optimized one
Some Bianchi Type III String Cosmological Models with Bulk Viscosity
We investigate the integrability of cosmic strings in Bianchi III space-time
in presence of a bulk viscous fluid by applying a new technique. The behaviour
of the model is reduced to the solution of a single second order nonlinear
differential equation. We show that this equation admits an infinite family of
solutions. Some physical consequences from these results are also discussed.Comment: 12 pages, no figure. To appear in Int. J. Theor. Phy
A New Class of Inhomogeneous String Cosmological Models in General Relativity
A new class of solutions of Einstein field equations has been investigated
for inhomogeneous cylindrically symmetric space-time with string source. To get
the deterministic solution, it has been assumed that the expansion ()
in the model is proportional to the eigen value of the shear
tensor . Certain physical and geometric properties of the
models are also discussed.Comment: 12 pages, no figure. Submitted to Astrophys. Space Sci. arXiv admin
note: substantial text overlap with arXiv:0705.090
Implications of the Muon Anomalous Magnetic Moment for Supersymmetry
We re-examine the bounds on supersymmetric particle masses in light of the
E821 data on the muon anomalous magnetic moment. We confirm, extend and
supersede previous bounds. In particular we find (at one sigma) no lower limit
on tan(beta) or upper limit on the chargino mass implied by the data at
present, but at least 4 sparticles must be lighter than 700 to 820 GeV and at
least one sparticle must be lighter than 345 to 440 GeV. However, the E821
central value bounds tan(beta) > 4.7 and the lighter chargino mass by 690 GeV.
For tan(beta) < 10, the data indicates a high probability for direct discovery
of SUSY at Run II or III of the Tevatron.Comment: 20 pages LaTeX, 14 figures; references adde
Cylindrically Symmetric Inhomogeneous Universes with a Cloud of Strings
Cylindrically symmetric inhomogeneous string cosmological models are
investigated in presence of string fluid as a source of matter. To get the
three types of exact solutions of Einstein's field equations we assume , and . Some physical and geometric
aspects of the models are discussed.Comment: 9 page
Searching singlet extensions of the supersymmetric standard model in orbifold compactification of heterotic string
We search for supersymmetric standard model realizations with extra singlets
and extra using the heterotic string compactification on the orbifold with two Wilson lines. We analyze the vacuum restabilization
mechanism for three representative Pati-Salam string models obtained in the
literature and present detailed results for the effective superpotential
compatible with the string selection rules. An automated selection of
semi-realistic vacua along flat directions in the non-Abelian singlet modes
field space is performed by requiring the presence of massless pairs of
electroweak Higgs bosons having trilinear superpotential couplings with
massless singlet modes and the decoupling of color triplet exotic modes needed
to suppress and number violating processes.Comment: revtex4 format, 21 pages, 7 tables, shortened version added
reference
Selective quantum evolution of a qubit state due to continuous measurement
We consider a two-level quantum system (qubit) which is continuously measured
by a detector. The information provided by the detector is taken into account
to describe the evolution during a particular realization of measurement
process. We discuss the Bayesian formalism for such ``selective'' evolution of
an individual qubit and apply it to several solid-state setups. In particular,
we show how to suppress the qubit decoherence using continuous measurement and
the feedback loop.Comment: 15 pages (including 9 figures
CP Violation in Supersymmetric U(1)' Models
The supersymmetric CP problem is studied within superstring-motivated
extensions of the MSSM with an additional U(1)' gauge symmetry broken at the
TeV scale. This class of models offers an attractive solution to the mu problem
of the MSSM, in which U(1)' gauge invariance forbids the bare mu term, but an
effective mu parameter is generated by the vacuum expectation value of a
Standard Model singlet S which has superpotential coupling of the form SH_uH_d
to the electroweak Higgs doublets. The effective mu parameter is thus
dynamically determined as a function of the soft supersymmetry breaking
parameters, and can be complex if the soft parameters have nontrivial
CP-violating phases. We examine the phenomenological constraints on the
reparameterization invariant phase combinations within this framework, and find
that the supersymmetric CP problem can be greatly alleviated in models in which
the phase of the SU(2) gaugino mass parameter is aligned with the soft
trilinear scalar mass parameter associated with the SH_uH_d coupling. We also
study how the phases filter into the Higgs sector, and find that while the
Higgs sector conserves CP at the renormalizable level to all orders of
perturbation theory, CP violation can enter at the nonrenormalizable level at
one-loop order. In the majority of the parameter space, the lightest Higgs
boson remains essentially CP even but the heavier Higgs bosons can exhibit
large CP-violating mixings, similar to the CP-violating MSSM with large mu
parameter.Comment: 29 pp, 3 figs, 2 table
Learning and Action Alliance framework to facilitate stakeholder collaboration and social learning in urban flood risk management
Flood and water management governance may be enhanced through partnership working, intra- and cross-organisational collaborations, and wide stakeholder participation. Nonetheless, barriers associated with ineffective communication, fragmented responsibilities and âsiloed thinkingâ restrict open dialogue and discussion. The Learning and Action Alliance (LAA) framework may help overcome these barriers by enabling effective engagement through social learning, and facilitating targeted actions needed to deliver innovative solutions to environmental problems. By increasing the adaptive capacity of decision-makers and participants, social learning through LAAs may lead to concerted action and sustained processes of behavioural change. In this paper, we evaluate the LAA framework as a catalyst for change that supports collaborative working and facilitates transition to more sustainable flood risk management. We use a case study in Newcastle-upon-Tyne, UK, to demonstrate how the LAA framework brought together disparate City stakeholders to co-produce new knowledge, negotiate innovative actions and, ultimately, work towards implementing a new vision for sustainable urban flood risk management. The shared vision of Newcastle as a âBlue-Green Cityâ that emerged is founded on a strong platform for social learning which increased organisationsâ and individualsâ capacities to manage differences in perspectives and behaviours, reframe knowledge, and make collective decisions based on negotiation and conflict resolution. Broad recommendations based on lessons learned from the Newcastle LAA are presented to aid other cities and regions in establishing and running social learning platforms
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