1,236 research outputs found
Grounding the Lexical Semantics of Verbs in Visual Perception using Force Dynamics and Event Logic
This paper presents an implemented system for recognizing the occurrence of
events described by simple spatial-motion verbs in short image sequences. The
semantics of these verbs is specified with event-logic expressions that
describe changes in the state of force-dynamic relations between the
participants of the event. An efficient finite representation is introduced for
the infinite sets of intervals that occur when describing liquid and
semi-liquid events. Additionally, an efficient procedure using this
representation is presented for inferring occurrences of compound events,
described with event-logic expressions, from occurrences of primitive events.
Using force dynamics and event logic to specify the lexical semantics of events
allows the system to be more robust than prior systems based on motion profile
Specific-to-General Learning for Temporal Events with Application to Learning Event Definitions from Video
We develop, analyze, and evaluate a novel, supervised, specific-to-general
learner for a simple temporal logic and use the resulting algorithm to learn
visual event definitions from video sequences. First, we introduce a simple,
propositional, temporal, event-description language called AMA that is
sufficiently expressive to represent many events yet sufficiently restrictive
to support learning. We then give algorithms, along with lower and upper
complexity bounds, for the subsumption and generalization problems for AMA
formulas. We present a positive-examples--only specific-to-general learning
method based on these algorithms. We also present a polynomial-time--computable
``syntactic'' subsumption test that implies semantic subsumption without being
equivalent to it. A generalization algorithm based on syntactic subsumption can
be used in place of semantic generalization to improve the asymptotic
complexity of the resulting learning algorithm. Finally, we apply this
algorithm to the task of learning relational event definitions from video and
show that it yields definitions that are competitive with hand-coded ones
The effectiveness of licence restriction for drink drivers: The Australian experience
In many jurisdictions, licence restriction is used as an alternative to full suspension for certain drink driving offenders. However, this may undermine both the specific and general deterrent effect of licence loss, by reducing the perceived certainty and severity of the sanction. To explore this proposition, an analysis was undertaken of the records of almost 22,000 male drivers initially convicted of drink driving during 1988 in Queensland, Australia. At a process level, it was found that licence restriction was relatively common, with 12% of offenders being granted a restricted licence for employment purposes. Contrary to legislative guidelines, these licences were sometimes granted to offenders with a recent history of drink driving. At an outcome level, it was found that the restricted drivers were involved in a similar proportion of alcohol-related crashes, but more non alcohol-related crashes, during the term of the sanction than drivers who had been fully suspended. This is consistent with previous research by the authors indicating that restricted drivers do not commit any more drink driving offences than suspended drivers. Therefore, while full suspension produces greater overall road safety benefits, restricted licences appear no less effective as a specific deterrent to drink driving
A low-altitude satellite interaction study
Two computer programs calculate interaction effects of high speed spacecraft on the environment at altitudes from 90 km to 150 km. EXT program determines fluid field in bodies of arbitrary geometries in transient flow regime. INT program uses EXT output and measures flow conditions inside spacecraft body
First-Class Nonstandard Interpretations by Opening Closures
We motivate and discuss a novel functional programming construct
that allows convenient modular run-time nonstandard interpretation
via reflection on closure environments. This map-closure construct
encompasses both the ability to examine the contents of a
closure environment and to construct a new closure with a modified
environment. From the user’s perspective, map-closure is a
powerful and useful construct that supports such tasks as tracing,
security logging, sandboxing, error checking, profiling, code instrumentation
and metering, run-time code patching, and resource
monitoring. From the implementor’s perspective, map-closure
is analogous to call/cc. Just as call/cc is a non-referentiallytransparent
mechanism that reifies the continuations that are only
implicit in programs written in direct style, map-closure is a nonreferentially-
transparent mechanism that reifies the closure environments
that are only implicit in higher-order programs. Just as
CPS conversion is a non-local but purely syntactic transformation
that can eliminate references to call/cc, closure conversion
is a non-local but purely syntactic transformation that can eliminate
references to map-closure. We show how the combination
of map-closure and call/cc can be used to implement set! as
a procedure definition and a local macro transformation
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