3,427 research outputs found
Practical applications of data mining in plant monitoring and diagnostics
Using available expert knowledge in conjunction with a structured process of data mining, characteristics observed in captured condition monitoring data, representing characteristics of plant operation may be understood, explained and quantified. Knowledge and understanding of satisfactory and unsatisfactory plant condition can be gained and made explicit from the analysis of data observations and subsequently used to form the basis of condition assessment and diagnostic rules/models implemented in decision support systems supporting plant maintenance. This paper proposes a data mining method for the analysis of condition monitoring data, and demonstrates this method in its discovery of useful knowledge from trip coil data captured from a population of in-service distribution circuit breakers and empirical UHF data captured from laboratory experiments simulating partial discharge defects typically found in HV transformers. This discovered knowledge then forms the basis of two separate decision support systems for the condition assessment/defect clasification of these respective plant items
Multidimensional integrable systems and deformations of Lie algebra homomorphisms
We use deformations of Lie algebra homomorphisms to construct deformations of
dispersionless integrable systems arising as symmetry reductions of
anti--self--dual Yang--Mills equations with a gauge group Diff.Comment: 14 pages. An example of a reduction to the Beltrami equation added.
New title. Final version, published in JM
Non equilibrium effects in fragmentation
We study, using molecular dynamics techniques, how boundary conditions affect
the process of fragmentation of finite, highly excited, Lennard-Jones systems.
We analyze the behavior of the caloric curves (CC), the associated thermal
response functions (TRF) and cluster mass distributions for constrained and
unconstrained hot drops. It is shown that the resulting CC's for the
constrained case differ from the one in the unconstrained case, mainly in the
presence of a ``vapor branch''. This branch is absent in the free expanding
case even at high energies . This effect is traced to the role played by the
collective expansion motion. On the other hand, we found that the recently
proposed characteristic features of a first order phase transition taking place
in a finite isolated system, i.e. abnormally large kinetic energy fluctuations
and a negative branch in the TRF, are present for the constrained (dilute) as
well the unconstrained case. The microscopic origin of this behavior is also
analyzed.Comment: 21 pages, 11 figure
Position Paper on Practicable Performance Criteria for the Removal Efficiency of Volatile Radionuclides
As a result of fuel reprocessing, volatile radionuclides may be released from the facility stack if no processes are put in place to remove them. The radionuclides that are of concern in this document are 3H, 14C, 85Kr, and 129I. The question we attempted to answer is how efficient must this removal process be for each of these radionuclides? To answer this question, we examined the three regulations that may impact the degree to which these radionuclides must be reduced before process gases can be released from the facility. These regulations are 40 CFR 61 (EPA 2010a), 40 CFR 190(EPA 2010b), and 10 CFR 20 (NRC 2012). These regulations apply to the total radionuclide release and to a particular organ - the thyroid. Because these doses can be divided amongst all the radionuclides in different ways and even within the four radionuclides in question, we provided several cases. We first looked at the inventories for these radionuclides for three fuel types (PWR UOX, PWR MOX, and AHTGR), several burn-up values, and time out of reactor extending to 200 y. We calculated doses to the maximum exposed individual (MEI) with the EPA code CAP-88 (Rosnick 1992). Finally, we looked at two dose cases. Allocating all of the allowable dose to be used by the volatile radionuclides is one case, but, perhaps, unrealistic. In lieu of this, we arbitrarily selected a value of 10% of the allowable dose to be assigned to the volatile radionuclides. We calculated the required decontamination factors (DFs) for both of these cases, including the case for the thyroid dose for which 14C and 129I were the main contributors. With respect to 129I doses, we found that the highest dose was calculated with iodine as a fine particulate. The dose scaled as the fraction of the total 129I that was particulate. Therefore, we assumed for all of our calculations that 100% of the 129I was particulate and allow the user of the results given here to scale our calculated doses to their needs
Effects of Self-field and Low Magnetic Fields on the Normal-Superconducting Phase Transition
Researchers have studied the normal-superconducting phase transition in the
high- cuprates in a magnetic field (the vortex-glass or Bose-glass
transition) and in zero field. Often, transport measurements in "zero field"
are taken in the Earth's ambient field or in the remnant field of a magnet. We
show that fields as small as the Earth's field will alter the shape of the
current vs. voltage curves and will result in inaccurate values for the
critical temperature and the critical exponents and , and can
even destroy the phase transition. This indicates that without proper screening
of the magnetic field it is impossible to determine the true zero-field
critical parameters, making correct scaling and other data analysis impossible.
We also show, theoretically and experimentally, that the self-field generated
by the current flowing in the sample has no effect on the current vs. voltage
isotherms.Comment: 4 pages, 4 figure
The dispersive self-dual Einstein equations and the Toda lattice
The Boyer-Finley equation, or -Toda equation is both a reduction
of the self-dual Einstein equations and the dispersionlesslimit of the
-Toda lattice equation. This suggests that there should be a dispersive
version of the self-dual Einstein equation which both contains the Toda lattice
equation and whose dispersionless limit is the familiar self-dual Einstein
equation. Such a system is studied in this paper. The results are achieved by
using a deformation, based on an associative -product, of the algebra
used in the study of the undeformed, or dispersionless,
equations.Comment: 11 pages, LaTeX. To appear: J. Phys.
Normal-Superconducting Phase Transition Mimicked by Current Noise
As a superconductor goes from the normal state into the superconducting
state, the voltage vs. current characteristics at low currents change from
linear to non-linear. We show theoretically and experimentally that the
addition of current noise to non-linear voltage vs. current curves will create
ohmic behavior. Ohmic response at low currents for temperatures below the
critical temperature mimics the phase transition and leads to incorrect
values for and the critical exponents and . The ohmic response
occurs at low currents, when the applied current is smaller than the
width of the probability distribution , and will occur in both the
zero-field transition and the vortex-glass transition. Our results indicate
that the transition temperature and critical exponents extracted from the
conventional scaling analysis are inaccurate if current noise is not filtered
out. This is a possible explanation for the wide range of critical exponents
found in the literature.Comment: 4 pages, 2 figure
Probing the limits of superconductivity
DC voltage versus current measurements of superconductors in a magnetic field
are widely interpreted to imply that a phase transition occurs into a state of
zero resistance. We show that the widely-used scaling function approach has a
problem: Good data collapse occurs for a wide range of critical exponents and
temperatures. This strongly suggests that agreement with scaling alone does not
prove the existence of the phase transition. We discuss a criterion to
determine if the scaling analysis is valid, and find that all of the data in
the literature that we have analyzed fail to meet this criterion. Our data on
YBCO films, and other data that we have analyzed, are more consistent with the
occurrence of small but non-zero resistance at low temperature.Comment: 13 page pdf file, figures included To be published in conference
proceedings of SPIE 200
Automatic analysis of Pole Mounted Auto-Recloser data for fault diagnosis and prognosis
Fault diagnosis is a key part of a control and protection engineer’s role to ensure the effective and stable performance of electrical power networks. One challenge is to support the analysis and application of expert judgement to the, often, large data sets generated. To assist engineers with this task and improve network reliability, this research focuses on analysing previous fault activity in order to obtain an early-warning report to assist fault diagnosis and fault prognosis. This paper details the design of an integrated system with a fault diagnosis algorithm utilising available Supervisory Control And Data Acquisition (SCADA) alarm data and 11kV distribution network data captured from Pole Mounted Auto-Reclosers (PMARs) (provided by a leading UK network operator). The developed system will be capable of diagnosing the nature of a circuit’s previous fault activity, underlying circuit activity and evolving fault activity and the risk of future fault activity. This will provide prognostic decision support for network operators and maintenance staff
Gate Coupling to Nanoscale Electronics
The realization of single-molecule electronic devices, in which a
nanometer-scale molecule is connected to macroscopic leads, requires the
reproducible production of highly ordered nanoscale gaps in which a molecule of
interest is electrostatically coupled to nearby gate electrodes. Understanding
how the molecule-gate coupling depends on key parameters is crucial for the
development of high-performance devices. Here we directly address this,
presenting two- and three-dimensional finite-element electrostatic simulations
of the electrode geometries formed using emerging fabrication techniques. We
quantify the gate coupling intrinsic to these devices, exploring the roles of
parameters believed to be relevant to such devices. These include the thickness
and nature of the dielectric used, and the gate screening due to different
device geometries. On the single-molecule (~1nm) scale, we find that device
geometry plays a greater role in the gate coupling than the dielectric constant
or the thickness of the insulator. Compared to the typical uniform nanogap
electrode geometry envisioned, we find that non-uniform tapered electrodes
yield a significant three orders of magnitude improvement in gate coupling. We
also find that in the tapered geometry the polarizability of a molecular
channel works to enhance the gate coupling
- …