10,781 research outputs found
Autonomous Ticking Clocks from Axiomatic Principles
There are many different types of time keeping devices. We use the phrase
ticking clock to describe those which -- simply put -- "tick" at approximately
regular intervals. Various important results have been derived for ticking
clocks, and more are in the pipeline. It is thus important to understand the
underlying models on which these results are founded. The aim of this paper is
to introduce a new ticking clock model from axiomatic principles that overcomes
concerns in the community about the physicality of the assumptions made in
previous models. The ticking clock model in [arXiv:1806.00491] achieves high
accuracy, yet lacks the autonomy of the less accurate model in
[10.1103/PhysRevX.7.031022]. Importantly, the model we introduce here achieves
the best of both models: it retains the autonomy of [10.1103/PhysRevX.7.031022]
while allowing for the high accuracies of [arXiv:1806.00491]. What is more,
[10.1103/PhysRevX.7.031022] is revealed to be a special case of the new ticking
clock model.Comment: 14 + 14 page
Verifying Real-Time Systems using Explicit-time Description Methods
Timed model checking has been extensively researched in recent years. Many
new formalisms with time extensions and tools based on them have been
presented. On the other hand, Explicit-Time Description Methods aim to verify
real-time systems with general untimed model checkers. Lamport presented an
explicit-time description method using a clock-ticking process (Tick) to
simulate the passage of time together with a group of global variables for time
requirements. This paper proposes a new explicit-time description method with
no reliance on global variables. Instead, it uses rendezvous synchronization
steps between the Tick process and each system process to simulate time. This
new method achieves better modularity and facilitates usage of more complex
timing constraints. The two explicit-time description methods are implemented
in DIVINE, a well-known distributed-memory model checker. Preliminary
experiment results show that our new method, with better modularity, is
comparable to Lamport's method with respect to time and memory efficiency
Teaching Concurrent Software Design: A Case Study Using Android
In this article, we explore various parallel and distributed computing topics
from a user-centric software engineering perspective. Specifically, in the
context of mobile application development, we study the basic building blocks
of interactive applications in the form of events, timers, and asynchronous
activities, along with related software modeling, architecture, and design
topics.Comment: Submitted to CDER NSF/IEEE-TCPP Curriculum Initiative on Parallel and
Distributed Computing - Core Topics for Undergraduate
Illusory perceptions of space and time preserve cross-saccadic perceptual continuity
When voluntary saccadic eye movements are made to a silently ticking clock, observers sometimes think that the second hand takes longer than normal to move to its next position. For a short period, the clock appears to have stopped (chronostasis). Here we show that the illusion occurs because the brain extends the percept of the saccadic target backwards in time to just before the onset of the saccade. This occurs every time we move the eyes but it is only perceived when an external time reference alerts us to the phenomenon. The illusion does not seem to depend on the shift of spatial attention that accompanies the saccade. However, if the target is moved unpredictably during the saccade, breaking perception of the target's spatial continuity, then the illusion disappears. We suggest that temporal extension of the target's percept is one of the mechanisms that 'fill in' the perceptual 'gap' during saccadic suppression. The effect is critically linked to perceptual mechanisms that identify a target's spatial stability
The neurobiology of circadian rhythms
Purpose of review
There is growing awareness of the importance of circadian rhythmicity in various research fields. Exciting developments are ongoing in the field of circadian neurobiology linked to sleep, food intake, and memory. With the current knowledge of critical âclock genesâ (genes found to be involved in the generation of circadian rhythms) and novel techniques for imaging cyclic events in brain and peripheral tissue, this field of research is rapidly expanding. We reviewed only some of the highlights of the past year, and placed these findings into a mutual circadian perspective.
Recent findings
Recent findings on the organization of the circadian clock systems are addressed, ranging from the retina to the suprachiasmatic nucleus and peripheral organs. Novel developments in sleep, food intake, and memory research linked to circadian aspects are discussed.
Summary
The neurobiology of circadian rhythms is pivotal to the orchestration of the temporal organization of an individualâs physiology and behavior. Endogenous circadian timing systems underlie coupling and uncoupling mechanisms of many neuronal and physiological processes, the latter possibly inducing health risks to the organism. The integration of sleep, food intake and memory in a circadian setting has clear potential as a systems neurobiology line of research.
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Manual chronostasis: Tactile perception precedes physical contact
When saccading to a silent clock, observers sometimes think that the second hand has paused momentarily. This effect has been termed chronostasis and occurs because observers overestimate the time that they have seen the object of an eye movement. They seem to extrapolate its appearance back to just prior to the onset of the saccade rather than the time that it is actually fixated on the retina. Here, we describe a similar effect following an arm movement: subjects overestimate the time that their hand has been in contact with a newly touched object. The illusion's magnitude suggests backward extrapolation of tactile perception to a moment during the preceding reach. The illusion does not occur if the arm movement triggers a change in a continuously visible visual target: the time of onset of the change is estimated correctly. We hypothesize that chronostasis-like effects occur when movement produces uncertainty about the onset of a sensory event. Under these circumstances, the time at which neurons with receptive fields that shift in the temporal vicinity of a movement change their mappings may be used as a time marker for the onset of perceptual properties that are only established later
Ticking clocks in quantum theory
We present a derivation of the structure and dynamics of a ticking clock by
showing that for finite systems a single natural principle serves to
distinguish what we understand as ticking clocks from time-keeping systems in
general. As a result we recover the bipartite structure of such a clock: that
the information about ticks is a classical degree of freedom. We describe the
most general form of the dynamics of such a clock, and discuss the additional
simplifications to go from a general ticking clock to models encountered in
literature. The resultant framework encompasses various recent research results
despite their apparent differences. Finally, we introduce the information
theory of ticking clocks, distinguishing their abstract information content and
the actually accessible information.Comment: 16 pages + 3 pages appendix, 4 figure
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