127,210 research outputs found
Periodicities in Solar Coronal Mass Ejections
Mid-term quasi-periodicities in solar coronal mass ejections (CMEs) during
the most recent solar maximum cycle 23 are reported here for the first time
using the four-year data (February 5, 1999 to February 10, 2003) of the Large
Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric
Observatory (SOHO). In parallel, mid-term quasi-periodicities in solar X-ray
flares (class >M5.0) from the Geosynchronous Operational Environment Satellites
(GOES) and in daily averages of Ap index for geomagnetic disturbances from the
World Data Center (WDC) at the International Association for Geomagnetism and
Aeronomy (IAGA) are also examined for the same four-year time span. Several
conceptual aspects of possible equatorially trapped Rossby-type waves at and
beneath the solar photosphere are discussed.Comment: Accepted by MNRAS, 6 figure
Integrate the GM(1,1) and Verhulst models to predict software stage effort
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2009 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.Software effort prediction clearly plays a crucial role in software project management. In keeping with more dynamic approaches to software development, it is not sufficient to only predict the whole-project effort at an early stage. Rather, the project manager must also dynamically predict the effort of different stages or activities during the software development process. This can assist the project manager to reestimate effort and adjust the project plan, thus avoiding effort or schedule overruns. This paper presents a method for software physical time stage-effort prediction based on grey models GM(1,1) and Verhulst. This method establishes models dynamically according to particular types of stage-effort sequences, and can adapt to particular development methodologies automatically by using a novel grey feedback mechanism. We evaluate the proposed method with a large-scale real-world software engineering dataset, and compare it with the linear regression method and the Kalman filter method, revealing that accuracy has been improved by at least 28% and 50%, respectively. The results indicate that the method can be effective and has considerable potential. We believe that stage predictions could be a useful complement to whole-project effort prediction methods.National Natural Science Foundation of
China and the Hi-Tech Research
and Development Program of Chin
From limit cycles to strange attractors
We define a quantitative notion of shear for limit cycles of flows. We prove
that strange attractors and SRB measures emerge when systems exhibiting limit
cycles with sufficient shear are subjected to periodic pulsatile drives. The
strange attractors possess a number of precisely-defined dynamical properties
that together imply chaos that is both sustained in time and physically
observable.Comment: 27 page
Radio observations of two intermittent pulsars: PSRs J1832+0029 and J1841-0500
We present long-term observations of two intermittent pulsars,
PSRs~J1832+0029 and J18410500 using the Parkes 64\,m radio telescope. The
radio emission for these pulsars switches "off" for year-long durations. Our
new observations have enabled us to improve the determination of the on-off
timescales and the spin down rates during those emission states. In general our
results agree with previous studies of these pulsars, but we now have
significantly longer data spans. We have identified two unexpected signatures
in the data. Weak emission was detected in a single observation of
PSR~J18320029 during an "off" emission state. For PSR~J18410500, we
identified a quasi-periodic fluctuation in the intensities of the detectable
single pulses, with a modulation period between 21 and 36 pulse periods.Comment: 7 pages, 7 figures, accepted for publication in Ap
Conduction mechanisms of epitaxial EuTiO3 thin films
To investigate leakage current density versus electric field characteristics,
epitaxial EuTiO3 thin films were deposited on (001) SrTiO3 substrates by pulsed
laser deposition and were post-annealed in a reducing atmosphere. This
investigation found that conduction mechanisms are strongly related to
temperature and voltage polarity. It was determined that from 50 to 150 K the
dominant conduction mechanism was a space-charge-limited current under both
negative and positive biases. From 200 to 300 K, the conduction mechanism shows
Schottky emission and Fowler-Nordheim tunneling behaviors for the negative and
positive biases, respectively. This work demonstrates that Eu3+ is one source
of leakage current in EuTiO3 thin films.Comment: 17 pages,4 figures, conferenc
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