2,336 research outputs found
Research 2.0 : improving participation in online research communities
Web 2.0 thinking and technologies create a number of new opportunities to conduct research broadly labeled as Research 2.0. Research 2.0 is a growing area of academic and commercial interest, which includes research undertaken in online research communities. This research in progress paper explores the practice of online research communities using a case study example operated by the commercial market research company Virtual Surveys Limited (VSL) in the UK on behalf of their client United Biscuits UK Ltd.
The preliminary findings are based on VSL and academics working together to improve the online research community participants’ response rate and the quality of contributions. Data collected for this study is based on meetings, participant observation, and a pilot survey of United Biscuits online research community (snackrs.com) members.
Using the responses of 112 snackrs.com community members, a preliminary typology of motivational factors is proposed. This can be used to refine the recruitment and development of activities in an online research community. Also, a model for supporting online research communities to ensure longitudinal engagement based on an adaptation of Salmon’s (2004) 5 Stage Model for e-moderation is proposed, extending the 5 stages to 7 – adding the stages of selection and disengagemen
Weather on Other Worlds. IV. H emission and photometric variability are not correlated in L0T8 dwarfs
Recent photometric studies have revealed that surface spots that produce flux
variations are present on virtually all L and T dwarfs. Their likely magnetic
or dusty nature has been a much-debated problem, the resolution to which has
been hindered by paucity of diagnostic multi-wavelength observations. To test
for a correlation between magnetic activity and photometric variability, we
searched for H emission among eight L3T2 ultra-cool dwarfs with
extensive previous photometric monitoring, some of which are known to be
variable at 3.6 m or 4.5 m. We detected H only in the
non-variable T2 dwarf 2MASS J125453930122474. The remaining seven objects do
not show H emission, even though six of them are known to vary
photometrically. Combining our results with those for 86 other L and T dwarfs
from the literature show that the detection rate of H emission is very
high (94) for spectral types between L0 and L3.5 and much smaller (20)
for spectral types L4, while the detection rate of photometric variability
is approximately constant (3055) from L0 to T8 dwarfs. We conclude
that chromospheric activity, as evidenced by H emission, and
large-amplitude photometric variability are not correlated. Consequently, dust
clouds are the dominant driver of the observed variability of ultra-cool dwarfs
at spectral types at least as early as L0.Comment: 12 pages, 4 figures, accepted for publication in Ap
A Variational Principle Based Study of KPP Minimal Front Speeds in Random Shears
Variational principle for Kolmogorov-Petrovsky-Piskunov (KPP) minimal front
speeds provides an efficient tool for statistical speed analysis, as well as a
fast and accurate method for speed computation. A variational principle based
analysis is carried out on the ensemble of KPP speeds through spatially
stationary random shear flows inside infinite channel domains. In the regime of
small root mean square (rms) shear amplitude, the enhancement of the ensemble
averaged KPP front speeds is proved to obey the quadratic law under certain
shear moment conditions. Similarly, in the large rms amplitude regime, the
enhancement follows the linear law. In particular, both laws hold for the
Ornstein-Uhlenbeck process in case of two dimensional channels. An asymptotic
ensemble averaged speed formula is derived in the small rms regime and is
explicit in case of the Ornstein-Uhlenbeck process of the shear. Variational
principle based computation agrees with these analytical findings, and allows
further study on the speed enhancement distributions as well as the dependence
of enhancement on the shear covariance. Direct simulations in the small rms
regime suggest quadratic speed enhancement law for non-KPP nonlinearities.Comment: 28 pages, 14 figures update: fixed typos, refined estimates in
section
Status and Recent Developments of the Analog Signal Observation System at CERN PS
The nAos (new Analog observation system) at CERN's PS complex allows visualization of some 1500 analog signals in any of the workstations connected to the controls network. Signals are digitized close to their source using VXI oscilloscope modules and sent to the users via Ethernet. A sophisticated application program conveys the signal selection and settings to the VXI front-ends and displays all the requested signals in one virtual oscilloscope window. The trigger pulses for the VXI oscilloscope modules are produced centrally near the Main Control Room of the PS and sent to the VXI crates oscilloscopes through long dedicated copper cables. To get to a sharper time definition, a new trigger production method has been tested with successful results. Timing events, encoded with an ultra-stable 10 MHz clock are sent as 32-bit messages through an optical fiber and converted locally into trigger pulses. The precision achieved with this method is better than 1 ns. The paper describes the current system, presents its performances in operation and details the recent development on the trigger generation
Pulsating Front Speed-up and Quenching of Reaction by Fast Advection
We consider reaction-diffusion equations with combustion-type non-linearities
in two dimensions and study speed-up of their pulsating fronts by general
periodic incompressible flows with a cellular structure. We show that the
occurence of front speed-up in the sense ,
with the amplitude of the flow and the (minimal) front speed, only
depends on the geometry of the flow and not on the reaction function. In
particular, front speed-up happens for KPP reactions if and only if it does for
ignition reactions. We also show that the flows which achieve this speed-up are
precisely those which, when scaled properly, are able to quench any ignition
reaction.Comment: 16p
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