4,835 research outputs found
MDL Convergence Speed for Bernoulli Sequences
The Minimum Description Length principle for online sequence
estimation/prediction in a proper learning setup is studied. If the underlying
model class is discrete, then the total expected square loss is a particularly
interesting performance measure: (a) this quantity is finitely bounded,
implying convergence with probability one, and (b) it additionally specifies
the convergence speed. For MDL, in general one can only have loss bounds which
are finite but exponentially larger than those for Bayes mixtures. We show that
this is even the case if the model class contains only Bernoulli distributions.
We derive a new upper bound on the prediction error for countable Bernoulli
classes. This implies a small bound (comparable to the one for Bayes mixtures)
for certain important model classes. We discuss the application to Machine
Learning tasks such as classification and hypothesis testing, and
generalization to countable classes of i.i.d. models.Comment: 28 page
Electron-phonon interaction in the solid form of the smallest fullerene C
The electron-phonon coupling of a theoretically devised carbon phase made by
assembling the smallest fullerenes C is calculated from first
principles. The structure consists of C cages in an {\it fcc} lattice
interlinked by two bridging carbon atoms in the interstitial tetrahedral sites
({\it fcc}-C). The crystal is insulating but can be made metallic by
doping with interstitial alkali atoms. In the compound NaC the
calculated coupling constant is 0.28 eV, a value much larger
than in C, as expected from the larger curvature of C. On the
basis of the McMillan's formula, the calculated =1.12 and a
assumed in the range 0.3-0.1 a superconducting T in the range 15-55 K is
predicted.Comment: 7 page
Stability of longitudinal coupling for Josephson charge qubits
For inductively coupled superconducting quantum bits, we determine the
conditions when the coupling commutes with the single-qubit terms. We show that
in certain parameter regimes such longitudinal coupling can be stabilized with
respect to variations of the circuit parameters. In addition, we analyze its
stability against fluctuations of the control fields.Comment: 5 pages, 2 figures; additional discussion and reference
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Experimental pool boiling investigations of vertical coalescence for FC-72 on silicon from an isolated artificial cavity
In this study bubble growth from an isolated artificial cavity micro-fabricated on a horizontal 380 ”m thick silicon wafer was investigated. The horizontally oriented boiling surface was heated by a thin resistance heater integrated on the rear of the silicon test section. The temperature was measured using an integrated micro-sensor situated on the boiling surface with the artificial cavity located in its geometrical centre. A resistive track was used as the sensor, which when calibrated, exhibited a near-linear behaviour with increasing temperature. To conduct pool boiling experiments the test section was immersed in degassed fluorinert FC-72. Bubble nucleation, growth and detachment at different pressures were observed using high-speed imaging. Coalescence was observed at the boundary between the isolated bubble and interference regimes. The occurrence of vertical coalescence was found to be more frequent, with increasing wall superheat and decreasing pressure.
The equivalent sphere volumes of two bubbles before and after coalescence were evaluated from area measurements. It was observed that the second nucleated bubble is always smaller than its predecessor. The vapour generation appears not to stop during coalescence as the volume of the merged bubble was typically 5-18% larger than the sum of the bubble volumes just before coalescence
OpenML Benchmarking Suites
Machine learning research depends on objectively interpretable, comparable,
and reproducible algorithm benchmarks. Therefore, we advocate the use of
curated, comprehensive suites of machine learning tasks to standardize the
setup, execution, and reporting of benchmarks. We enable this through software
tools that help to create and leverage these benchmarking suites. These are
seamlessly integrated into the OpenML platform, and accessible through
interfaces in Python, Java, and R. OpenML benchmarking suites are (a) easy to
use through standardized data formats, APIs, and client libraries; (b)
machine-readable, with extensive meta-information on the included datasets; and
(c) allow benchmarks to be shared and reused in future studies. We also present
a first, carefully curated and practical benchmarking suite for classification:
the OpenML Curated Classification benchmarking suite 2018 (OpenML-CC18)
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