11,977 research outputs found
Electron Impact Excitation Cross Sections for Hydrogen-Like Ions
We present cross sections for electron-impact-induced transitions n --> n' in
hydrogen-like ions C 5+, Ne 9+, Al 12+, and Ar 17+. The cross sections are
computed by Coulomb-Born with exchange and normalization (CBE) method for all
transitions with n < n' < 7 and by convergent close-coupling (CCC) method for
transitions with n 2s and 1s
--> 2p are presented as well. The CCC and CBE cross sections agree to better
than 10% with each other and with earlier close-coupling results (available for
transition 1 --> 2 only). Analytical expression for n --> n' cross sections and
semiempirical formulae are discussed.Comment: RevTeX, 5 pages, 13 PostScript figures, submitted to Phys. Rev.
Change detection in categorical evolving data streams
Detecting change in evolving data streams is a central issue for accurate adaptive learning. In real world applications, data streams have categorical features, and changes induced in the data distribution of these categorical features have not been considered extensively so far. Previous work on change detection focused on detecting changes in the accuracy of the learners, but without considering changes in the data distribution.
To cope with these issues, we propose a new unsupervised change detection method, called CDCStream (Change Detection in Categorical Data Streams), well suited for categorical data streams. The proposed method is able to detect changes in a batch incremental scenario. It is based on the two following characteristics: (i) a summarization strategy is proposed to compress the actual batch by extracting a descriptive summary and (ii) a new segmentation algorithm is proposed to highlight changes and issue warnings for a data stream. To evaluate our proposal we employ it in a learning task over real world data and we compare its results with state of the art methods. We also report qualitative evaluation in order to show the behavior of CDCStream
The effect of ionization on the populations of excited levels of C IV and C V in tokamak edge plasmas
The main populating and depopulating mechanisms of the excited energy levels
of ions in plasmas with densities <1023-1024 m-3 are electron collisional
excitation from the ion's ground state and radiative decay, respectively, with
the majority of the electron population being in the ground state of the
ionization stage. Electron collisional ionization is predominately expected to
take place from one ground state to that of the next higher ionization stage.
However, the question arises as to whether, in some cases, ionization can also
affect the excited level populations. This would apply particularly to those
cases involving transient events such as impurity influxes in a laboratory
plasma. An analysis of the importance of ionization in populating the excited
levels of ions in plasmas typical of those found in the edge of tokamaks is
undertaken for the C IV and C V ionization stages. The emphasis is on those
energy levels giving rise to transitions of most use for diagnostic purposes.
Carbon is chosen since it is an important contaminant of JET plasmas; it was
the dominant low Z impurity before the installation of the ITER-like wall and
is still present in the plasma after its installation. Direct electron
collisional ionization both from and to excited levels is considered.
Distorted-wave Flexible Atomic Code calculations are performed to generate the
required ionization cross sections, due to a lack of atomic data in the
literature.Comment: 29 pages, 5 figures. This is an author-created, un-copyedited version
of an article accepted for publication in Journal of Physics B. IOP
Publishing Ltd is not responsible for any errors or omissions in this version
of the manuscript or any version derived from i
Experimental Signatures of Anomaly Induced DCC Formation
We discuss characteristic experimental signatures related to the formation of
domains of disoriented chiral condensate (DCC) triggered by the axial anomaly
in relativistic heavy ion collisions. We predict that the enhancement of the
fraction of neutral pions compared to all pions depends on the angle of
emission with respect to the scattering plane and is concentrated at small
transverse momentum and small rapidity in the center-of-mass frame. The
anisotropy with respect to the reaction plane is also observable in the
inclusive photon distribution.Comment: 11 pages, 4 figures, REVTEX, discussion on photon distribution added,
one figure adde
In silico modeling and evaluation of Gordonia alkanivorans for biodesulfurization
10.1039/c3mb70132hMolecular BioSystems92530--254
From Physical to Cyber: Escalating Protection for Personalized Auto Insurance
Nowadays, auto insurance companies set personalized insurance rate based on
data gathered directly from their customers' cars. In this paper, we show such
a personalized insurance mechanism -- wildly adopted by many auto insurance
companies -- is vulnerable to exploit. In particular, we demonstrate that an
adversary can leverage off-the-shelf hardware to manipulate the data to the
device that collects drivers' habits for insurance rate customization and
obtain a fraudulent insurance discount. In response to this type of attack, we
also propose a defense mechanism that escalates the protection for insurers'
data collection. The main idea of this mechanism is to augment the insurer's
data collection device with the ability to gather unforgeable data acquired
from the physical world, and then leverage these data to identify manipulated
data points. Our defense mechanism leveraged a statistical model built on
unmanipulated data and is robust to manipulation methods that are not foreseen
previously. We have implemented this defense mechanism as a proof-of-concept
prototype and tested its effectiveness in the real world. Our evaluation shows
that our defense mechanism exhibits a false positive rate of 0.032 and a false
negative rate of 0.013.Comment: Appeared in Sensys 201
The STAR Photon Multiplicity Detector
Details concerning the design, fabrication and performance of STAR Photon
Multiplicity Detector (PMD) are presented. The PMD will cover the forward
region, within the pseudorapidity range 2.3--3.5, behind the forward time
projection chamber. It will measure the spatial distribution of photons in
order to study collective flow, fluctuation and chiral symmetry restoration.Comment: 15 pages, including 11 figures; to appear in a special NIM volume
dedicated to the accelerator and detectors at RHI
Maximizing Maximal Angles for Plane Straight-Line Graphs
Let be a plane straight-line graph on a finite point set
in general position. The incident angles of a vertex
of are the angles between any two edges of that appear consecutively in
the circular order of the edges incident to .
A plane straight-line graph is called -open if each vertex has an
incident angle of size at least . In this paper we study the following
type of question: What is the maximum angle such that for any finite set
of points in general position we can find a graph from a certain
class of graphs on that is -open? In particular, we consider the
classes of triangulations, spanning trees, and paths on and give tight
bounds in most cases.Comment: 15 pages, 14 figures. Apart of minor corrections, some proofs that
were omitted in the previous version are now include
- …