14,398 research outputs found
Examples of mesoscale structures and short-term wind variations detected by VHF Doppler radar
The first of three wind profilers planned for operation in central and western Pennsylvania began full-time, high-quality operation during July 1985. It is located about 20 km south-southeast of University Park and operates at 50 MHz. Another 50-MHz radar and a 400-MHz radar are to be installed over the next few months, to complete a mesoscale triangle with sides of 120 to 160 km. During the period since early July, a number of weather systems have passed over the wind profiler. Those accompanied by thunderstorms caused data losses either because the Department computer system lost power or because power went out at the profiler site. A backup power supply and an automatic re-start program will be added to the profiler system to minimize such future losses. Data have normally been averaged over a one-hour period, although there have been some investigations of shorter-period averaging. In each case, preliminary examinations reveal that the profiler winds are indicative of meteorological phenomena. The only occasions of bad or missing data are obtained when airplane noise is occasionally experienced and when the returned power is nearly at the noise level, at the upper few gates, where a consensus wind cannot be determined. Jets streams, clouds, and diurnal variations of winds are discussed
Theta Graph Designs
We solve the design spectrum problem for all theta graphs with 10, 11, 12, 13, 14 and 15 edges
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Completing the design spectra for graphs with six vertices and eight edges
Apart from two possible exceptions, the design spectrum has been determined for every graph with six vertices and at most eight edges. The purpose of this note is to establish the existence of the two missing designs, both of order 32
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Designs for graphs with six vertices and nine edges
The design spectrum has been determined for eleven of the 21 graphs with six vertices and nine edges. In this paper we completely solve the design spectrum problem for the remaining ten graphs
Icosahedron designs
It is known from the work of Adams and Bryant that icosahedron designs of order v exist for v ≡ 1 (mod 60) as well as for v = 16. Here we prove that icosahedron designs exist if and only if v ≡ 1, 16, 21 or 36 (mod 60), wit
Bayesian Target Zones
Several authors have postulated econometric models for exchange rates restricted to lie within known target zones. However, it is not uncommon to observe exchange rate data with known limits that are not fully 'credible'; that is, where some of the observations fall outside the stated range. An empirical model for exchange rates in a soft target zone where there is a controlled probability of the observed rates exceeding the stated limits is developed in this paper. A Bayesian approach is used to analyse the model, which is then demonstrated on Deutschemark-French franc and ECU-French franc exchange rate data.
The development of a rich multimedia training environment for crisis management: using emotional affect to enhance learning
PANDORA is an EU FP7-funded project developing a novel training and learning environment for Gold Commanders, individuals who carry executive responsibility for the services and facilities identified as strategically critical e.g. Police, Fire, in crisis management strategic planning situations. A key part of the work for this project is considering the emotional and behavioural state of the trainees, and the creation of more realistic, and thereby stressful, representations of multimedia information to impact on the decision-making of those trainees. Existing training models are predominantly paper-based, table-top exercises, which require an exercise of imagination on the part of the trainees to consider not only the various aspects of a crisis situation but also the impacts of interventions, and remediating actions in the event of the failure of an intervention. However, existing computing models and tools are focused on supporting tactical and operational activities in crisis management, not strategic. Therefore, the PANDORA system will provide a rich multimedia information environment, to provide trainees with the detailed information they require to develop strategic plans to deal with a crisis scenario, and will then provide information on the impacts of the implementation of those plans and provide the opportunity for the trainees to revise and remediate those plans. Since this activity is invariably multi-agency, the training environment must support group-based strategic planning activities and trainees will occupy specific roles within the crisis scenario. The system will also provide a range of non-playing characters (NPC) representing domain experts, high-level controllers (e.g. politicians, ministers), low-level controllers (tactical and operational commanders), and missing trainee roles, to ensure a fully populated scenario can be realised in each instantiation. Within the environment, the emotional and behavioural state of the trainees will be monitored, and interventions, in the form of environmental information controls and mechanisms impacting on the stress levels and decisionmaking capabilities of the trainees, will be used to personalise the training environment. This approach enables a richer and more realistic representation of the crisis scenario to be enacted, leading to better strategic plans and providing trainees with structured feedback on their performance under stress
Bulge Globular Clusters in Spiral Galaxies
There is now strong evidence that the metal-rich globular clusters (GC) near
the center of our Galaxy are associated with the Galactic bulge rather than the
disk as previously thought. Here we extend the concept of bulge GCs to the GC
systems of nearby spiral galaxies. In particular, the kinematic and metallicity
properties of the GC systems favor a bulge rather than a disk origin. The
number of metal-rich GCs normalized by the bulge luminosity is roughly constant
(i.e. bulge S_N ~ 1) in nearby spirals, and this value is similar to that for
field ellipticals when only the red (metal--rich) GCs are considered. We argue
that the metallicity distributions of GCs in spiral and elliptical galaxies are
remarkably similar, and that they obey the same correlation of mean GC
metallicity with host galaxy mass. We further suggest that the metal-rich GCs
in spirals are the direct analogs of the red GCs seen in ellipticals. The
formation of a bulge/spheroidal stellar system is accompanied by the formation
of metal-rich GCs. The similarities between GC systems in spiral and elliptical
galaxies appear to be greater than the differences.Comment: 5 pages, Latex, 2 figures, 1 table, Accepted for publication in ApJ
Letter
Improved approach to Fowler-Nordheim plot analysis
This article introduces an improved approach to Fowler-Nordheim (FN) plot
analysis, based on a new type of intercept correction factor. This factor is
more cleanly defined than the factor previously used. General enabling theory
is given that applies to any type of FN plot of data that can be fitted using a
FN-type equation. Practical use is limited to emission situations where slope
correction factors can be reliably predicted. By making a series of
well-defined assumptions and approximations, it is shown how the general
formulas reduce to provide an improved theory of orthodox FN-plot data
analysis. This applies to situations where the circuit current is fully
controlled by the emitter characteristics, and tunneling can be treated as
taking place through a Schottky-Nordheim (SN) barrier. For orthodox emission,
good working formulas make numerical evaluation of the slope correction factor
and the new intercept correction factor quick and straightforward. A numerical
illustration, using simulated emission data, shows how to use this improved
approach to derive values for parameters in the full FN-type equation for the
SN barrier. Good self-consistency is demonstrated. The general enabling
formulas also pave the way for research aimed at developing analogous
data-analysis procedures for non-orthodox emission situations.Comment: Paper is extended version of poster presented at the 25th
International Vacuum Nanoelectronics Conference, Jeju island, South Korea,
July 2012. Third version includes small changes made at proof correction
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