13,503 research outputs found
Image enhancement from a stabilised video sequence
The aim of video stabilisation is to create a new video sequence where the motions (i.e. rotations, translations) and scale differences between frames (or parts of a frame) have effectively been removed. These stabilisation effects can be obtained via digital video processing techniques which use the information extracted from the video sequence itself, with no need for additional hardware or knowledge about camera physical motion.
A video sequence usually contains a large overlap between successive frames, and regions of the same scene are sampled at different positions. In this paper, this multiple sampling is combined to achieve images with a higher spatial resolution. Higher resolution imagery play an important role in assisting in the identification of people, vehicles, structures or objects of interest captured by surveillance cameras or by video cameras used in face recognition, traffic monitoring, traffic law reinforcement, driver assistance and automatic vehicle guidance systems
Integration biases in the Ouchi and other visual illusions
A texture pattern devised by the Japanese artist H Ouchi has attracted wide attention because of the striking appearance of relative motion it evokes. The illusion has been the subject of several recent empirical studies. A new account is presented, along with a simple experimental test, that attributes the illusion to a bias in the way that local motion signals generated at different locations on each element are combined to code element motion. The account is generalised to two spatial illusions, the Judd illusion and the Zƶllner illusion (previously considered unrelated to the Ouchi illusion). The notion of integration bias is consistent with recent Bayesian approaches to visual coding, according to which the weight attached to each signal reflects its reliability and likelihood
Online identification and nonlinear control of the electrically stimulated quadriceps muscle
A new approach for estimating nonlinear models of the electrically stimulated quadriceps muscle group under nonisometric conditions is investigated. The model can be used for designing controlled neuro-prostheses. In order to identify the muscle dynamics (stimulation pulsewidth-active knee moment relation) from discrete-time angle measurements only, a hybrid model structure is postulated for the shank-quadriceps dynamics. The model consists of a relatively well known time-invariant passive component and an uncertain time-variant active component. Rigid body dynamics, described by the Equation of Motion (EoM), and passive joint properties form the time-invariant part. The actuator, i.e. the electrically stimulated muscle group, represents the uncertain time-varying section. A recursive algorithm is outlined for identifying online the stimulated quadriceps muscle group. The algorithm requires EoM and passive joint characteristics to be known a priori. The muscle dynamics represent the product of a continuous-time nonlinear activation dynamics and a nonlinear static contraction function described by a Normalised Radial Basis Function (NRBF) network which has knee-joint angle and angular velocity as input arguments. An Extended Kalman Filter (EKF) approach is chosen to estimate muscle dynamics parameters and to obtain full state estimates of the shank-quadriceps dynamics simultaneously. The latter is important for implementing state feedback controllers. A nonlinear state feedback controller using the backstepping method is explicitly designed whereas the model was identified a priori using the developed identification procedure
Results from a prototype chicane-based energy spectrometer for a Linear Collider
The International Linear Collider (ILC) and other proposed high energy e+eā machines aim to measure with unprecedented precision Standard Model quantities and new, not yet discovered phenomena. One of the main requirements for achieving this goal is a measurement of the incident beam energy with an uncertainty close to 10^(ā4). This article presents the analysis of data from a prototype energy spectrometer commissioned in 2006-2007 in SLAC's End Station A beamline. The prototype was a 4-magnet chicane equipped with beam position monitors measuring small changes of the beam orbit through the chicane at different beam energies. A single bunch energy resolution close to 5Ā·10^(ā4) was measured, which is satisfactory for most scenarios. We also report on the operational experience with the chicane-based spectrometer and suggest ways of improving its performance
Balancing selection response and inbreeding by including predicted stabilised genetic contributions in selection decisions
International audienc
Interfacing GHz-bandwidth heralded single photons with a room-temperature Raman quantum memory
Photonics is a promising platform for quantum technologies. However, photon
sources and two-photon gates currently only operate probabilistically.
Large-scale photonic processing will therefore be impossible without a
multiplexing strategy to actively select successful events. High
time-bandwidth-product quantum memories - devices that store and retrieve
single photons on-demand - provide an efficient remedy via active
synchronisation. Here we interface a GHz-bandwidth heralded single-photon
source and a room-temperature Raman memory with a time-bandwidth product
exceeding 1000. We store heralded single photons and observe a clear influence
of the input photon statistics on the retrieved light, which agrees with our
theoretical model. The preservation of the stored field's statistics is limited
by four-wave-mixing noise, which we identify as the key remaining challenge in
the development of practical memories for scalable photonic information
processing
Falling liquid films with blowing and suction
Flow of a thin viscous film down a flat inclined plane becomes unstable to
long wave interfacial fluctuations when the Reynolds number based on the mean
film thickness becomes larger than a critical value (this value decreases as
the angle of inclination with the horizontal increases, and in particular
becomes zero when the plate is vertical). Control of these interfacial
instabilities is relevant to a wide range of industrial applications including
coating processes and heat or mass transfer systems. This study considers the
effect of blowing and suction through the substrate in order to construct from
first principles physically realistic models that can be used for detailed
passive and active control studies of direct relevance to possible experiments.
Two different long-wave, thin-film equations are derived to describe this
system; these include the imposed blowing/suction as well as inertia, surface
tension, gravity and viscosity. The case of spatially periodic blowing and
suction is considered in detail and the bifurcation structure of forced steady
states is explored numerically to predict that steady states cease to exist for
sufficiently large suction speeds since the film locally thins to zero
thickness giving way to dry patches on the substrate. The linear stability of
the resulting nonuniform steady states is investigated for perturbations of
arbitrary wavelengths, and any instabilities are followed into the fully
nonlinear regime using time-dependent computations. The case of small amplitude
blowing/suction is studied analytically both for steady states and their
stability. Finally, the transition between travelling waves and non-uniform
steady states is explored as the suction amplitude increases
Forecasting Sales of Slow and Fast Moving Inventories.
Adaptations of simple exponential smoothing are presented that aim to unify the task of forecasting demand for both slow and fast moving inventories. A feature of the adaptations is that they are designed to ensure that the resulting prediction distributions have only a nonnegative domain. A parametric bootstrap approach is proposed for generating empirical approximations for the so-called lead-time demand distribution, something required for inventory control calculations. The proposed methods are illustrated and their performance compared on real demand data for car parts.demand forecasting, inventory control, simulation, parametric bootstrapping, time series analysis.
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