2,649 research outputs found
Classical quarks in dual electromagnetic fields
Electromagnetic properties of quark-like particles are examined in a
classical field model involving extended dual electromagnetic fields. These can
have fractional charges and a confining potential that derives essentially
completely from a short-range weaker potential. The combined potentials exhibit
an asymptotically free spherical surface and contribute to the masses of the
particles. The quarks are shown to have an intrinsic symmetry that describes
their structures in hadrons. Multi- quark solutions are easily obtained for
both stable and unstable particles. Each quark can undergo simple harmonic
motion in a range of frequencies
Capacity formulas in MWPC: some critical reflexions
An approximate analytical expression for "capacitance" of MWPC configurations
circulates in the literature since decades and is copied over and over again.
In this paper we will try to show that this formula corresponds to a physical
quantity that is different from what it is usually thought to stand for
Non-Archimedean character of quantum buoyancy and the generalized second law of thermodynamics
Quantum buoyancy has been proposed as the mechanism protecting the
generalized second law when an entropy--bearing object is slowly lowered
towards a black hole and then dropped in. We point out that the original
derivation of the buoyant force from a fluid picture of the acceleration
radiation is invalid unless the object is almost at the horizon, because
otherwise typical wavelengths in the radiation are larger than the object. The
buoyant force is here calculated from the diffractive scattering of waves off
the object, and found to be weaker than in the original theory. As a
consequence, the argument justifying the generalized second law from buoyancy
cannot be completed unless the optimal drop point is next to the horizon. The
universal bound on entropy is always a sufficient condition for operation of
the generalized second law, and can be derived from that law when the optimal
drop point is close to the horizon. We also compute the quantum buoyancy of an
elementary charged particle; it turns out to be negligible for energetic
considerations. Finally, we speculate on the significance of the absence from
the bound of any mention of the number of particle species in nature.Comment: RevTeX, 16 page
Recommended from our members
Electric power system concepts for integration of advanced sensor and pulsed loads in the DDG-51 class ships
Advanced weapons and sensors increase demand on the electric power systems of Navy surface combatants, driving the need for fully Integrated Power Systems (IPS) such as those found in the DDG-1000 Zumwalt class of ships. The goal of this paper is to introduce novel power system configurations that could potentially be integrated into future flights of the DDG-51 class to support expanded electric power system capability at reasonable cost. Two concepts are presented: the first addresses the need for additional power for advanced sensor systems and the second addresses the need for a more significant increase in capacity to support higher power electric loads.Center for Electromechanic
A lumped conceptual model to simulate groundwater level time-series
Lumped, conceptual groundwater models can be used to simulate groundwater level time-series quickly and efficiently without the need for comprehensive modelling expertise. A new model of this type, AquiMod, is presented for simulating groundwater level time-series in unconfined aquifers. Its modular design enables users to implement different model structures to gain understanding about controls on aquifer storage and discharge. Five model structures are evaluated for four contrasting aquifers in the United Kingdom. The ability of different model structures and parameterisations to replicate the observed hydrographs is examined. AquiMod simulates the quasi-sinusoidal hydrographs of the relatively uniform Chalk and Sandstone aquifers most efficiently. It is least efficient at capturing the flashy hydrograph of a heterogeneous, fractured Limestone aquifer. The majority of model parameters demonstrate sensitivity and can be related to available field data. The model structure experiments demonstrate the need to represent vertical aquifer heterogeneity to capture the storage-discharge dynamics efficiently
Using statistically designed experiments for safety system optimization
This paper describes the method of statistically designed experiments (SDE's), used as a
structured method to investigate the best setting for a number of decision variables in a
system design problem. Traditionally, in the design of safety critical systems, a trial and
error type approach is undertaken to achieve a final system that meets the design
objectives. This approach can be time consuming and often only an adequate design is
found rather than the optimal design for the available resources. Optimal use of
resources should be imperative when possible lives are at risk. To demonstrate the
practicality of this new structured approach for optimising a safety system design, a high
integrity safety system has been used. Each design is analysed using the Binary Decision
Diagram analysis technique to establish the system unavailability, which is penalised if
the system constraints are exceeded. System constraints indicate the limitations on the resources which can be utilised. The SDE approach highlights good and bad settings for
possible design variables. This knowledge can then be used by more sophisticated search
techniques. The latter part of this paper analyses the results from the best design
generated using the SDE, for further optimisation using localised optimisation
approaches
The 4D geometric quantities versus the usual 3D quantities. The resolution of Jackson's paradox
In this paper we present definitions of different four-dimensional (4D)
geometric quantities (Clifford multivectors). New decompositions of the torque
N and the angular momentum M (bivectors) into 1-vectors N_{s}, N_{t} and M_{s},
M_{t} respectively are given. The torques N_{s}, N_{t} (the angular momentums
M_{s}, M_{t}), taken together, contain the same physical information as the
bivector N (the bivector M). The usual approaches that deal with the 3D
quantities , , , ,
, etc. and their transformations are objected from the viewpoint of
the invariant special relativity (ISR). In the ISR it is considered that 4D
geometric quantities are well-defined both theoretically and
\emph{experimentally} in the 4D spacetime. This is not the case with the usual
3D quantities. It is shown that there is no apparent electrodynamic paradox
with the torque, and that the principle of relativity is naturally satisfied,
when the 4D geometric quantities are used instead of the 3D quantities.Comment: 13 pages, revte
Choosing a heuristic for the “fault tree to binary decision diagram” conversion, using neural networks
Fault-tree analysis is commonly used for risk assessment
of industrial systems. Several computer packages are
available to carry out the analysis. Despite its common usage there
are associated limitations of the technique in terms of accuracy
and efficiency when dealing with large fault-tree structures. The
most recent approach to aid the analysis of the fault-tree diagram
is the BDD (binary decision diagram). To use the BDD, the
fault-tree structure needs to be converted into the BDD format.
Converting the fault tree is relatively straightforward but requires
that the basic events of the tree be ordered. This ordering is
critical to the resulting size of the BDD, and ultimately affects
the qualitative and quantitative performance and benefits of
this technique. Several heuristic approaches were developed to
produce an optimal ordering permutation for a specific tree. These
heuristic approaches do not always yield a minimal BDD structure
for all trees. There is no single heuristic that guarantees a minimal
BDD for any fault-tree structure. This paper looks at a selection
approach using a neural network to choose the best heuristic from
a set of alternatives that will yield the smallest BDD and promote
an efficient analysis. The set of possible selection choices are 6
alternative heuristics, and the prediction capacity produced was
a 70% chance of the neural network choosing the best ordering
heuristic from the set of 6 for the test set of given fault trees
Efficient basic event orderings for binary decision diagrams
Over the last five years significant advances have been
made in methodologies to analyse the fault tree diagram.
The most successful of these developments has been the
Binary Decision Diagram (BDD) approach. The Binary
Decision Diagram approach has been shown to improve
both the efficiency of determining the minimal cut sets of
the fault tree ancl also the accuracy of the calculation
procedure used to determine the top event parameters. The
BDD technique povides a potential alternative to the
traditional approaches based on Kinetic Tree Theory.
To utilise the Binary Decision Diagram approach the
fault tree structure is first converted to the BDD format.
This conversion can be accomplished efficiently but
requires the basic events in the fault tree to be placed in an
ordering. A poor ordering can result in a Binary Decision
Diagram which is not an efficient representation of the fault
tree logic structure. The advantages to be gained by
utilising the BDD technique rely on the efficiency of the
ordering scheme. Alternative ordering schemes have been
investigated and no one scheme is appropriate for every
tree structure. Research to date has not found any rule
based means of determining the best way of ordering basic
events for a given fault tree structure.
The work presented in this paper takes a machine
learning approach based on Genetic Algorithms to select
the most appropriate ordering scheme. Features which
describe a fault tree structure have been identified and
these provide the inputs to the machine learning algorithm.
A set of possible ordering schemes has been selected based
on previous heuristic work. The objective of the work
detailed in the pap:r is to predict the most efficient of the
possible ordering alternatives from parameters which
describe a fault tree structure
- …