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Short wavelength instability in the vortex ring during impingement onto a solid wall
Data quality: Some comments on the NASA software defect datasets
Background-Self-evidently empirical analyses rely upon the quality of their data. Likewise, replications rely upon accurate reporting and using the same rather than similar versions of datasets. In recent years, there has been much interest in using machine learners to classify software modules into defect-prone and not defect-prone categories. The publicly available NASA datasets have been extensively used as part of this research. Objective-This short note investigates the extent to which published analyses based on the NASA defect datasets are meaningful and comparable. Method-We analyze the five studies published in the IEEE Transactions on Software Engineering since 2007 that have utilized these datasets and compare the two versions of the datasets currently in use. Results-We find important differences between the two versions of the datasets, implausible values in one dataset and generally insufficient detail documented on dataset preprocessing. Conclusions-It is recommended that researchers 1) indicate the provenance of the datasets they use, 2) report any preprocessing in sufficient detail to enable meaningful replication, and 3) invest effort in understanding the data prior to applying machine learners
On the nature of the lightest scalar resonances
We briefly review the recent progresses in the new unitarization approach
being developed by us. Especially we discuss the large
scatterings by making use of the partial wave matrix parametrization form.
We find that the pole may move to the negative real axis on the second
sheet of the complex plane, therefore it raises the interesting question
that this `' pole may be related to the in the linear
model.Comment: Talk presented by Zheng at ``Quark Confinement and Hadron
Spectroscopy VI'', 21--25 Sept. 2004, Cagliari, Italy. 3 pages with 2 figure
Brueckner-Hartree-Fock and its renormalized calculations for finite nuclei
We have performed self-consistent Brueckner-Hartree-Fock (BHF) and its
renormalized theory to the structure calculations of finite nuclei. The
-matrix is calculated within the BHF basis, and the exact Pauli exclusion
operator is determined by the BHF spectrum. Self-consistent occupation
probabilities are included in the renormalized Brueckner-Hartree-Fock (RBHF).
Various systematics and convergences are studies. Good results are obtained for
the ground-state energy and radius. RBHF can give a more reasonable
single-particle spectrum and radius. We present a first benchmark calculation
with other {\it ab initio} methods using the same effective Hamiltonian. We
find that the BHF and RBHF results are in good agreement with other
methods
On universal partial words
A universal word for a finite alphabet and some integer is a
word over such that every word in appears exactly once as a subword
(cyclically or linearly). It is well-known and easy to prove that universal
words exist for any and . In this work we initiate the systematic study
of universal partial words. These are words that in addition to the letters
from may contain an arbitrary number of occurrences of a special `joker'
symbol , which can be substituted by any symbol from . For
example, is a linear partial word for the binary alphabet
and for (e.g., the first three letters of yield the
subwords and ). We present results on the existence and
non-existence of linear and cyclic universal partial words in different
situations (depending on the number of s and their positions),
including various explicit constructions. We also provide numerous examples of
universal partial words that we found with the help of a computer
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