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âVoyagerâ: An educational card game
âVoyagerâ is an educational card game involving scientific satellites, developed for use in schools with children aged 9 to 13 years. The idea of the game is to improve pupilsâ knowledge about the large number of scientific satellites there are in space in a fun way, while also practising numeracy skills. Several copies of the game were produced using funding obtained from the Particle Physics and Astronomy Research Council (PPARC) as a Public Understanding of Science (PUS) award. These initial âtrialâ versions of the game were taken to three different schools where feedback obtained from both pupils and staff was used to produce a final copy of the game that can be distributed to other schools along with a set of companion notes to form the basis of a science lesson. This article reports the findings of the school trials and indicates possible future developments of other scientific card games that could be beneficial to the classroom.http://www.iop.org/EJ/abstract/0031-9120/38/1/30
Multifluid, Magnetohydrodynamic Shock Waves with Grain Dynamics II. Dust and the Critical Speed for C Shocks
This is the second in a series of papers on the effects of dust on
multifluid, MHD shock waves in weakly ionized molecular gas. We investigate the
influence of dust on the critical shock speed, v_crit, above which C shocks
cease to exist. Chernoff showed that v_crit cannot exceed the grain
magnetosound speed, v_gms, if dust grains are dynamically well coupled to the
magnetic field. We present numerical simulations of steady shocks where the
grains may be well- or poorly coupled to the field. We use a time-dependent,
multifluid MHD code that models the plasma as a system of interacting fluids:
neutral particles, ions, electrons, and various ``dust fluids'' comprised of
grains with different sizes and charges. Our simulations include grain inertia
and grain charge fluctuations but to highlight the essential physics we assume
adiabatic flow, single-size grains, and neglect the effects of chemistry. We
show that the existence of a phase speed v_phi does not necessarily mean that C
shocks will form for all shock speeds v_s less than v_phi. When the grains are
weakly coupled to the field, steady, adiabatic shocks resemble shocks with no
dust: the transition to J type flow occurs at v_crit = 2.76 v_nA, where v_nA is
the neutral Alfven speed, and steady shocks with v_s > 2.76 v_nA are J shocks
with magnetic precursors in the ion-electron fluid. When the grains are
strongly coupled to the field, v_crit = min(2.76 v_nA, v_gms). Shocks with
v_crit < v_s < v_gms have magnetic precursors in the ion-electron-dust fluid.
Shocks with v_s > v_gms have no magnetic precursor in any fluid. We present
time-dependent calculations to study the formation of steady multifluid shocks.
The dynamics differ qualitatively depending on whether or not the grains and
field are well coupled.Comment: 43 pages with 17 figures, aastex, accepted by The Astrophysical
Journa
Nonlinear adaptive control using non-parametric Gaussian Process prior models
Nonparametric Gaussian Process prior models, taken from Bayesian statistics methodology are used to implement a nonlinear adaptive control law. The expected value of a quadratic cost function is minimised, without ignoring the variance of the model predictions. This leads to implicit regularisation of the control signal (caution), and excitation of the system. The controller has dual features, since it is both tracking a reference signal and learning a model of the system from observed responses. The general method and its main features are illustrated on a simulation example
Kolmogorov-Burgers Model for Star Forming Turbulence
The process of star formation in interstellar molecular clouds is believed to
be controlled by driven supersonic magnetohydrodynamic turbulence. We suggest
that in the inertial range such turbulence obeys the Kolmogorov law, while in
the dissipative range it behaves as Burgers turbulence developing shock
singularities. On the base of the She-Leveque analytical model we then predict
the velocity power spectrum in the inertial range to be E_k ~ k^{-1.74}. This
result reproduces the observational Larson law, ~ l^{0.74...0.76},
[Larson, MNRAS 194 (1981) 809] and agrees well with recent numerical findings
by Padoan and Nordlund [astro-ph/0011465]. The application of the model to more
general dissipative structures, with higher fractal dimensionality, leads to
better agreement with recent observational results.Comment: revised, new material added, 8 page
Teaching Students to Fish: Creating a Sustainable Student Peer Research Program
A Peer Research Mentor (PRM) program was developed at Musselman Library, Gettysburg College to augment traditional reference services and expand library outreach. Goals included enhancing these studentsâ information literacy skills helping them become better researchers, as well as sharing that knowledge with peers. This poster will highlight the initial and on-going training, their involvement at the reference desk, and outreach projects to date
Neural networks for modelling and control of a non-linear dynamic system
The authors describe the use of neural nets to model and control a nonlinear second-order electromechanical model of a drive system with varying time constants and saturation effects. A model predictive control structure is used. This is compared with a proportional-integral (PI) controller with regard to performance and robustness against disturbances. Two feedforward network types, the multilayer perceptron and radial-basis-function nets, are used to model the system. The problems involved in the transfer of connectionist theory to practice are discussed
Rubber-coated bellows improves vibration damping in vacuum lines
Compact-vibration damping systems, consisting of rubber-coated metal bellows with a sliding O-ring connector, are used in vacuum lines. The device presents a metallic surface to the vacuum system and combines flexibility with the necessary stiffness. It protects against physical damage, reduces fatigue failure, and provides easy mating of nonparallel lines
Black hole singularities: a numerical approach
The singularity structure of charged spherical collapse is studied by
considering the evolution of the gravity-scalar field system. A detailed
examination of the geometry at late times strongly suggests the validity of the
mass-inflation scenario~\cite{PI:90}. Although the area of the two-spheres
remains finite at the Cauchy horizon, its generators are eventually focused to
zero radius. Thus the null, mass-inflation singularity {\em generally}\/
precedes a crushing singularity deep inside the black hole core. This
central singularity is spacelike.Comment: 4 pages Phys. Rev. style including five figures, provided as
compressed postscript files. To appear in Physical Review Letter
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