238,435 research outputs found
Prompt Delay
Delay games are two-player games of infinite duration in which one player may
delay her moves to obtain a lookahead on her opponent's moves. Recently, such
games with quantitative winning conditions in weak MSO with the unbounding
quantifier were studied, but their properties turned out to be unsatisfactory.
In particular, unbounded lookahead is in general necessary. Here, we study
delay games with winning conditions given by Prompt-LTL, Linear Temporal Logic
equipped with a parameterized eventually operator whose scope is bounded. Our
main result shows that solving Prompt-LTL delay games is complete for
triply-exponential time. Furthermore, we give tight triply-exponential bounds
on the necessary lookahead and on the scope of the parameterized eventually
operator. Thus, we identify Prompt-LTL as the first known class of well-behaved
quantitative winning conditions for delay games. Finally, we show that applying
our techniques to delay games with \omega-regular winning conditions answers
open questions in the cases where the winning conditions are given by
non-deterministic, universal, or alternating automata
Delay Times and Rates for Type Ia Supernovae and Thermonuclear Explosions from Double-detonation Sub-Chandrasekhar Mass Models
We present theoretical delay times and rates of thermonuclear explosions that
are thought to produce Type Ia supernovae, including the double-detonation
sub-Chandrasekhar mass model, using the population synthesis binary evolution
code StarTrack. If detonations of sub-Chandrasekhar mass carbon-oxygen white
dwarfs following a detonation in an accumulated layer of helium on the white
dwarf's surface ("double-detonation" models) are able to produce thermonuclear
explosions which are characteristically similar to those of SNe Ia, then these
sub-Chandrasekhar mass explosions may account for at least some substantial
fraction of the observed SN Ia rate. Regardless of whether all
double-detonations look like 'normal' SNe Ia, in any case the explosions are
expected to be bright and thus potentially detectable. Additionally, we find
that the delay time distribution of double-detonation sub-Chandrasekhar mass
SNe Ia can be divided into two distinct formation channels: the 'prompt'
helium-star channel with delay times <500 Myr (~10% of all sub-Chandras), and
the 'delayed' double white dwarf channel, with delay times >800 Myr spanning up
to a Hubble time (~90%). These findings coincide with recent
observationally-derived delay time distributions which have revealed that a
large number of SNe Ia are prompt with delay times <500 Myr, while a
significant fraction also have delay times spanning ~1 Gyr to a Hubble time.Comment: MNRAS Accepted: 13 pages, shortened text, now 3 figure
Multipath noise reduction spread spectrum signals
The concepts of early-prompt delay tracking, multipath correction of early-prompt delay tracking from correlation shape, and carrier phase multipath correction are addressed. In early-prompt delay tracking, since multipath is always delayed with respect to the direct signals, the system derives phase and pseudorange observables from earlier correlation lags. In multipath correction of early-prompt delay tracking from correlation shape, the system looks for relative variations of amplitude across the code correlation function that do not match the predicted multipath-free code cross-correlation shape. The system then uses deviations from the multipath-free shape to infer the magnitude of multipath, and to generate corrections pseudorange observables. In carrier phase multipath correction, the system looks for variations of phase among plural early and prompt lags. The system uses the measured phase variations, along with the general principle that the multipath errors are larger for later lags, to infer the presence of multipath, and to generate corrections for carrier-phase observables
Synthesizing SystemC Code from Delay Hybrid CSP
Delay is omnipresent in modern control systems, which can prompt oscillations
and may cause deterioration of control performance, invalidate both stability
and safety properties. This implies that safety or stability certificates
obtained on idealized, delay-free models of systems prone to delayed coupling
may be erratic, and further the incorrectness of the executable code generated
from these models. However, automated methods for system verification and code
generation that ought to address models of system dynamics reflecting delays
have not been paid enough attention yet in the computer science community. In
our previous work, on one hand, we investigated the verification of delay
dynamical and hybrid systems; on the other hand, we also addressed how to
synthesize SystemC code from a verified hybrid system modelled by Hybrid CSP
(HCSP) without delay. In this paper, we give a first attempt to synthesize
SystemC code from a verified delay hybrid system modelled by Delay HCSP
(dHCSP), which is an extension of HCSP by replacing ordinary differential
equations (ODEs) with delay differential equations (DDEs). We implement a tool
to support the automatic translation from dHCSP to SystemC
Empirical Delay Time Distributions of Type Ia Supernovae From The Extended GOODS/HST Supernova Survey
Using the Hubble Space Telescope ACS imaging of the GOODS North and South
fields during Cycles 11, 12, and 13, we derive empirical constraints on the
delay-time distribution function for type Ia supernovae. We extend our previous
analysis to the three-year sample of 56 SNe Ia over the range 0.2<z<1.8, using
a Markov chain Monte Carlo to determine the best-fit unimodal delay-time
distribution function. The test, which ultimately compares the star formation
rate density history to the unbinned volumetric SN Ia rate history from the
GOODS/HST-SN survey, reveals a SN Ia delay-time distribution that is tightly
confined to 3-4 Gyrs (to >95% confidence). This result is difficult to resolve
with any intrinsic delay-time distribution function (bimodal or otherwise), in
which a substantial fraction (e.g., >10%) of events are ``prompt'', requiring
less than approximately 1 Gyr to develop from formation to explosion. The
result is, however, strongly motivated by the decline in the number of SNe Ia
at z>1.2. Sub-samples of the HST-SN data confined to lower redshifts (z<1) show
plausible delay-time distributions that are dominated by prompt events, which
is more consistent with results from low-redshift supernova samples and
supernova host galaxy properties. Scenarios in which a substantial fraction of
z>1.2 supernovae are extraordinarily obscured by dust may partly explain the
differences in low-z and high-z results. Other possible resolutions may include
environmental dependencies (such as gas-phase metallicity) that affect the
progenitor mechanism efficiency, especially in the early universe.Comment: 12 pages, 9 figures, accepted to the Astrophysical Journa
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A comparison of the stimulus delay procedure and simultaneous stimulus presentation.
A comparison of a time delay and paired prompt (simultaneous stimulus presentation) procedure was conducted involving the teaching of a color identification task to two autistic adolescents. rime delay involved a gradual increase in the Lime between presentation of an instruction and prompt. Simultaneous stimulus presentation involved the concurrent presentation of instruct, ion and prompt. One subject met criterion with the color identification task assigned to the simultaneous stimulus presentation condition. The remaining subject failed to meet criterion with either procedure
Impact on mortality of prompt admission to critical care for deteriorating ward patients: an instrumental variable analysis using critical care bed strain.
PURPOSE: To estimate the effect of prompt admission to critical care on mortality for deteriorating ward patients. METHODS: We performed a prospective cohort study of consecutive ward patients assessed for critical care. Prompt admissions (within 4 h of assessment) were compared to a 'watchful waiting' cohort. We used critical care strain (bed occupancy) as a natural randomisation event that would predict prompt transfer to critical care. Strain was classified as low, medium or high (2+, 1 or 0 empty beds). This instrumental variable (IV) analysis was repeated for the subgroup of referrals with a recommendation for critical care once assessed. Risk-adjusted 90-day survival models were also constructed. RESULTS: A total of 12,380 patients from 48 hospitals were available for analysis. There were 2411 (19%) prompt admissions (median delay 1 h, IQR 1-2) and 9969 (81%) controls; 1990 (20%) controls were admitted later (median delay 11 h, IQR 6-26). Prompt admissions were less frequent (p < 0.0001) as strain increased from low (22%), to medium (15%) to high (9%); the median delay to admission was 3, 4 and 5 h respectively. In the IV analysis, prompt admission reduced 90-day mortality by 7.4% (95% CI 1.7-18.5%, p = 0.117) overall, and 16.2% (95% CI 1.1-31.3%, p = 0.036) for those recommended for critical care. In the risk-adjust survival model, 90-day mortality was similar. CONCLUSION: After allowing for unobserved prognostic differences between the groups, we find that prompt admission to critical care leads to lower 90-day mortality for patients assessed and recommended to critical care
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