14,180 research outputs found
Three-dimensional laser velocimeter simultaneity detector
A three-dimensional laser Doppler velocimeter has laser optics for a first channel positioned to create a probe volume in space, and laser optics and for second and third channels, respectively, positioned to create entirely overlapping probe volumes in space. The probe volumes and overlap partially in space. The photodetector is positioned to receive light scattered by a particle present in the probe volume, while photodetectors and are positioned to receive light scattered by a particle present in the probe volume. The photodetector for the first channel is directly connected to provide a first channel analog signal to frequency measuring circuits. The first channel is therefore a primary channel for the system. Photodetectors and are respectively connected through a second channel analog signal attenuator to frequency measuring circuits and through a third channel analog signal attenuator to frequency measuring circuits. The second and third channels are secondary channels, with the second and third channels analog signal attenuators and controlled by the first channel measurement burst signal on line. The second and third channels analog signal attenuators and attenuate the second and third channels analog signals only when the measurement burst signal is false
On the crosscorrelation between Gravitational Wave Detectors for detecting association with Gamma Ray Bursts
Crosscorrelation of the outputs of two Gravitational Wave (GW) detectors has
recently been proposed [1] as a method for detecting statistical association
between GWs and Gamma Ray Bursts (GRBs). Unfortunately, the method can be
effectively used only in the case of stationary noise. In this work a different
crosscorrelation algorithm is presented, which may effectively be applied also
in non-stationary conditions for the cumulative analysis of a large number of
GRBs. The value of the crosscorrelation at zero delay, which is the only one
expected to be correlated to any astrophysical signal, is compared with the
distribution of crosscorrelation of the same data for all non-zero delays
within the integration time interval. This background distribution is gaussian,
so the statistical significance of an experimentally observed excess would be
well-defined.
Computer simulations using real noise data of the cryogenic GW detectors
Explorer and Nautilus with superimposed delta-like signals were performed, to
test the effectiveness of the method, and theoretical estimates of its
sensitivity compared to the results of the simulation. The effectiveness of the
proposed algorithm is compared to that of other cumulative techniques, finding
that the algorithm is particularly effective in the case of non-gaussian noise
and of a large (100-1000s) and unpredictable delay between GWs and GRBs.Comment: 7 pages, 4 figures, 1 table. Submitted by Phys. Rev.
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Shifts of criteria or neural timing? The assumptions underlying timing perception studies
In timing perception studies, the timing of one event is usually manipulated relative to another, and participants are asked to judge if the two events were synchronous, or to judge which of the two events occurred first. Responses are analyzed to determine a measure of central tendency, which is taken as an estimate of the timing at which the two events are perceptually synchronous. When these estimates do not coincide with physical synchrony, it is often assumed that the sensory signals are asynchronous, as though the transfer of information concerning one input has been accelerated or decelerated relative to the other. Here we show that, while this is a viable interpretation, it is equally plausible that such effects are driven by shifts in the criteria used to differentiate simultaneous from asynchronous inputs. Our analyses expose important ambiguities concerning the interpretation of simultaneity judgement data, which have hitherto been underappreciated
Does Time Really Slow Down during a Frightening Event?
Observers commonly report that time seems to have moved in slow motion during a life-threatening event. It is unknown whether this is a function of increased time resolution during the event, or instead an illusion of remembering an emotionally salient event. Using a hand-held device to measure speed of visual perception, participants experienced free fall for 31 m before landing safely in a net. We found no evidence of increased temporal resolution, in apparent conflict with the fact that participants retrospectively estimated their own fall to last 36% longer than others' falls. The duration dilation during a frightening event, and the lack of concomitant increase in temporal resolution, indicate that subjective time is not a single entity that speeds or slows, but instead is composed of separable subcomponents. Our findings suggest that time-slowing is a function of recollection, not perception: 1a richer encoding of memory may cause a salient event to appear, retrospectively, as though it lasted longer
An Event-Driven Multi-Kernel Convolution Processor Module for Event-Driven Vision Sensors
Event-Driven vision sensing is a new way of sensing
visual reality in a frame-free manner. This is, the vision sensor
(camera) is not capturing a sequence of still frames, as in conventional
video and computer vision systems. In Event-Driven sensors
each pixel autonomously and asynchronously decides when to
send its address out. This way, the sensor output is a continuous
stream of address events representing reality dynamically continuously
and without constraining to frames. In this paper we present
an Event-Driven Convolution Module for computing 2D convolutions
on such event streams. The Convolution Module has been
designed to assemble many of them for building modular and hierarchical
Convolutional Neural Networks for robust shape and
pose invariant object recognition. The Convolution Module has
multi-kernel capability. This is, it will select the convolution kernel
depending on the origin of the event. A proof-of-concept test prototype
has been fabricated in a 0.35 m CMOS process and extensive
experimental results are provided. The Convolution Processor has
also been combined with an Event-Driven Dynamic Vision Sensor
(DVS) for high-speed recognition examples. The chip can discriminate
propellers rotating at 2 k revolutions per second, detect symbols
on a 52 card deck when browsing all cards in 410 ms, or detect
and follow the center of a phosphor oscilloscope trace rotating at
5 KHz.Unión Europea 216777 (NABAB)Ministerio de Ciencia e Innovación TEC2009-10639-C04-0
RFI Identification and Mitigation Using Simultaneous Dual Station Observations
RFI mitigation is a critically important issue in radio astronomy using
existing instruments as well as in the development of next-generation radio
telescopes, such as the Square Kilometer Array (SKA). Most designs for the SKA
involve multiple stations with spacings of up to a few thousands of kilometers
and thus can exploit the drastically different RFI environments at different
stations. As demonstrator observations and analysis for SKA-like instruments,
and to develop RFI mitigation schemes that will be useful in the near term, we
recently conducted simultaneous observations with Arecibo Observatory and the
Green Bank Telescope (GBT). The observations were aimed at diagnosing RFI and
using the mostly uncorrelated RFI between the two sites to excise RFI from
several generic kinds of measurements such as giant pulses from Crab-like
pulsars and weak HI emission from galaxies in bands heavily contaminated by
RFI. This paper presents observations, analysis, and RFI identification and
excision procedures that are effective for both time series and spectroscopy
applications using multi-station data.Comment: 12 pages, 9 figures (4 in ps and 5 in jpg formats), Accepted for
publication in Radio Scienc
Production of -particle condensate states in heavy-ion collisions
The fragmentation of quasi-projectiles from the nuclear reaction +
at 25 MeV/nucleon was used to produce excited states candidates to
-particle condensation. The experiment was performed at LNS-Catania
using the CHIMERA multidetector. Accepting the emission simultaneity and
equality among the -particle kinetic energies as experimental criteria
for deciding in favor of the condensate nature of an excited state, we analyze
the and states of C and the state of O. A
sub-class of events corresponding to the direct 3- decay of the Hoyle
state is isolated.Comment: contribution to the 2nd Workshop on "State of the Art in Nuclear
Cluster Physics" (SOTANCP2), Universite Libre de Bruxelles (Belgium), May
25-28, 2010, to be published in the International Journal of Modern Physics
Being first matters: topographical representational similarity analysis of ERP signals reveals separate networks for audiovisual temporal binding depending on the leading sense
In multisensory integration, processing in one sensory modality is enhanced by complementary information from other modalities. Inter-sensory timing is crucial in this process as only inputs reaching the brain within a restricted temporal window are perceptually bound. Previous research in the audiovisual field has investigated various features of the temporal binding window (TBW), revealing asymmetries in its size and plasticity depending on the leading input (auditory-visual, AV; visual-auditory, VA). We here tested whether separate neuronal mechanisms underlie this AV-VA dichotomy in humans. We recorded high-density EEG while participants performed an audiovisual simultaneity judgment task including various AV/VA asynchronies and unisensory control conditions (visual-only, auditory-only) and tested whether AV and VA processing generate different patterns of brain activity. After isolating the multisensory components of AV/VA event-related potentials (ERPs) from the sum of their unisensory constituents, we run a time-resolved topographical representational similarity analysis (tRSA) comparing AV and VA ERP maps. Spatial cross-correlation matrices were built from real data to index the similarity between AV- and VA-maps at each time point (500ms window post-stimulus) and then correlated with two alternative similarity model matrices: AVmaps=VAmaps vs. AVmaps≠VAmaps. The tRSA results favored the AVmaps≠VAmaps model across all time points, suggesting that audiovisual temporal binding (indexed by synchrony perception) engages different neural pathways depending on the leading sense. The existence of such dual route supports recent theoretical accounts proposing that multiple binding mechanisms are implemented in the brain to accommodate different information parsing strategies in auditory and visual sensory systems
An analysis of recent studies of the effect of foreign exchange intervention
Two recent strands of research have contributed to our understanding of the effects of foreign exchange intervention: (i) the use of high-frequency data and (ii) the use of event studies to evaluate the effects of intervention. This article surveys recent empirical studies of the effect of foreign exchange intervention and analyzes the implicit assumptions and limitations of such work. After explicitly detailing such drawbacks, the paper suggests ways to better investigate the effects of intervention.Foreign exchange ; Time-series analysis
Event notification services: analysis and transformation of profile definition languages
The integration of event information from diverse event notification sources is, as with meta-searching over heterogeneous search engines, a challenging task. Due to the complexity of profile definition languages, known solutions for heterogeneous searching cannot be applied for event notification.
In this technical report, we propose transformation rules for profile rewriting. We transform each profile defined at a meta-service into a profile expressed in the language of each event notification source. Due to unavoidable asymmetry in the semantics of different languages, some superfluous information may be delivered to the meta-service. These notifications are then post-processed to reduce the number of spurious messages. We present a survey and classification of profile definition languages for event notification, which serves as basis for the transformation rules. The proposed rules are implemented in a prototype transformation module for a Meta-Service for event notification
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