2,668 research outputs found
Surface climatological information - Twenty selected stations for space shuttle studies
Surface climatological data for twenty selected launch, landing, and alternate landing sites for space shuttle syste
On the predictability of domain-independent temporal planners
Temporal planning is a research discipline that addresses the problem of generating a totally or a partially ordered sequence of actions that transform the environment from some initial state to a desired goal state, while taking into account time constraints and actions' duration. For its ability to describe and address temporal constraints, temporal planning is of critical importance for a wide range of real-world applications. Predicting the performance of temporal planners can lead to significant improvements in the area, as planners can then be combined in order to boost the performance on a given set of problem instances. This paper investigates the predictability of the state-of-the-art temporal planners by introducing a new set of temporal-specific features and exploiting them for generating classification and regression empirical performance models (EPMs) of considered planners. EPMs are also tested with regard to their ability to select the most promising planner for efficiently solving a given temporal planning problem. Our extensive empirical analysis indicates that the introduced set of features allows to generate EPMs that can effectively perform algorithm selection, and the use of EPMs is therefore a promising direction for improving the state of the art of temporal planning, hence fostering the use of planning in real-world applications.</p
Sub-femtosecond absolute timing precision with a 10 GHz hybrid photonic-microwave oscillator
We present an optical-electronic approach to generating microwave signals
with high spectral purity. By circumventing shot noise and operating near
fundamental thermal limits, we demonstrate 10 GHz signals with an absolute
timing jitter for a single hybrid oscillator of 420 attoseconds (1Hz - 5 GHz)
Inducing Probabilistic Grammars by Bayesian Model Merging
We describe a framework for inducing probabilistic grammars from corpora of
positive samples. First, samples are {\em incorporated} by adding ad-hoc rules
to a working grammar; subsequently, elements of the model (such as states or
nonterminals) are {\em merged} to achieve generalization and a more compact
representation. The choice of what to merge and when to stop is governed by the
Bayesian posterior probability of the grammar given the data, which formalizes
a trade-off between a close fit to the data and a default preference for
simpler models (`Occam's Razor'). The general scheme is illustrated using three
types of probabilistic grammars: Hidden Markov models, class-based -grams,
and stochastic context-free grammars.Comment: To appear in Grammatical Inference and Applications, Second
International Colloquium on Grammatical Inference; Springer Verlag, 1994. 13
page
Randomized Reference Classifier with Gaussian Distribution and Soft Confusion Matrix Applied to the Improving Weak Classifiers
In this paper, an issue of building the RRC model using probability
distributions other than beta distribution is addressed. More precisely, in
this paper, we propose to build the RRR model using the truncated normal
distribution. Heuristic procedures for expected value and the variance of the
truncated-normal distribution are also proposed. The proposed approach is
tested using SCM-based model for testing the consequences of applying the
truncated normal distribution in the RRC model. The experimental evaluation is
performed using four different base classifiers and seven quality measures. The
results showed that the proposed approach is comparable to the RRC model built
using beta distribution. What is more, for some base classifiers, the
truncated-normal-based SCM algorithm turned out to be better at discovering
objects coming from minority classes.Comment: arXiv admin note: text overlap with arXiv:1901.0882
Incommensurate Charge and Spin Fluctuations in d-wave Superconductors
We show analytic results for the irreducible charge and spin
susceptibilities, , where is the momentum
transfer between the nodes in d-wave superconductors. Using the BCS theory and
a circular Fermi surface, we find that the singular behavior of the irreducible
charge susceptibility leads to the dynamic incommensurate charge collective
modes. The peaks in the charge structure factor occur at a set of wave vectors
which form an ellipse around and in
momentum space with momentum dependent spectral weight. It is also found that,
due to the non-singular irreducible spin susceptibility, an extremely strong
interaction via random phase approximation is required to support the magnetic
peaks near . Under certain conditions, the peaks in the magnetic
structure factor occur near and .Comment: 5 pages, 3 figure
A Decision Tree Approach to Predicting Recidivism in Domestic Violence
Domestic violence (DV) is a global social and public health issue that is
highly gendered. Being able to accurately predict DV recidivism, i.e.,
re-offending of a previously convicted offender, can speed up and improve risk
assessment procedures for police and front-line agencies, better protect
victims of DV, and potentially prevent future re-occurrences of DV. Previous
work in DV recidivism has employed different classification techniques,
including decision tree (DT) induction and logistic regression, where the main
focus was on achieving high prediction accuracy. As a result, even the diagrams
of trained DTs were often too difficult to interpret due to their size and
complexity, making decision-making challenging. Given there is often a
trade-off between model accuracy and interpretability, in this work our aim is
to employ DT induction to obtain both interpretable trees as well as high
prediction accuracy. Specifically, we implement and evaluate different
approaches to deal with class imbalance as well as feature selection. Compared
to previous work in DV recidivism prediction that employed logistic regression,
our approach can achieve comparable area under the ROC curve results by using
only 3 of 11 available features and generating understandable decision trees
that contain only 4 leaf nodes.Comment: 12 pages; Accepted at The 2018 Pacific-Asia Conference on Knowledge
Discovery and Data Mining (PAKDD
Optimizing the linearity in high-speed photodiodes
Analog photonic links require high-fidelity, high-speed optical-to-electrical
conversion for applications such as radio-over-fiber, synchronization at
kilometer-scale facilities, and low-noise electronic signal generation.
Photodetector nonlinearity is a particularly vexing problem, causing signal
distortion and excess noise, especially in systems utilizing ultrashort optical
pulses. Here we show that photodetectors designed for high power handling and
high linearity can perform optical-to-electrical conversion of ultrashort
optical pulses with unprecedented linearity over a large photocurrent range. We
also show that the broadband, complex impedance of the circuit following the
photodiode modifies the linearity significantly. By externally manipulating the
circuit impedance, we extend the detector's linear range to higher
photocurrents, with over 50 dB rejection of amplitude-to-phase conversion for
photocurrents up to 40 mA. This represents a 1000-fold improvement over
state-of-the-art photodiodes and significantly extends the attainable microwave
power by a factor of four. As such, we eliminate the long-standing requirement
in ultrashort pulse detection of precise tuning of the photodiode's operating
parameters (average photocurrent, bias voltage or temperature) to coincide with
a nonlinearity minimum. These results should also apply more generally to
reduce nonlinear distortion in a range of other microwave photonics
applications
Collisional Dark Matter and the Origin of Massive Black Holes
If the cosmological dark matter is primarily in the form of an elementary
particle which has cross section and mass for self-interaction having a ratio
similar to that of ordinary nuclear matter, then seed black holes (formed in
stellar collapse) will grow in a Hubble time, due to accretion of the dark
matter, to a mass range 10^6 - 10^9 solar masses. Furthermore, the dependence
of the final black hole mass on the galaxy velocity dispersion will be
approximately as observed and the growth rate will show a time dependence
consistent with observations. Other astrophysical consequences of collisional
dark matter and tests of the idea are noted.Comment: 7 pages, no figures, LaTeX2e, Accepted for publication in Phys. Rev.
Lett. Changed conten
Spin effects in gravitational radiation backreaction III. Compact binaries with two spinning components
The secular evolution of a spinning, massive binary system in eccentric orbit
is analyzed, expanding and generalizing our previous treatments of the
Lense-Thirring motion and the one-spin limit. The spin-orbit and spin-spin
effects up to the 3/2 post-Newtonian order are considered, both in the
equations of motion and in the radiative losses. The description of the orbit
in terms of the true anomaly parametrization provides a simple averaging
technique, based on the residue theorem, over eccentric orbits. The evolution
equations of the angle variables characterizing the relative orientation of the
spin and orbital angular momenta reveal a speed-up effect due to the
eccentricity. The dissipative evolutions of the relevant dynamical and angular
variables is presented in the form of a closed system of differential
equations.Comment: 10 pages, 1 figur
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