2,071 research outputs found
Homotopy Method for the Large, Sparse, Real Nonsymmetric Eigenvalue Problem
A homotopy method to compute the eigenpairs, i.e., the eigenvectors and eigenvalues, of a given real matrix A1 is presented. From the eigenpairs of some real matrix A0, the eigenpairs of
A(t) ⥠(1 â t)A0 + tA1
are followed at successive "times" from t = 0 to t = 1 using continuation. At t = 1, the eigenpairs of the desired matrix A1 are found. The following phenomena are present when following the eigenpairs of a general nonsymmetric matrix:
⢠bifurcation,
⢠ill conditioning due to nonorthogonal eigenvectors,
⢠jumping of eigenpaths.
These can present considerable computational difficulties. Since each eigenpair can be followed independently, this algorithm is ideal for concurrent computers. The homotopy method has the potential to compete with other algorithms for computing a few eigenvalues of large, sparse matrices. It may be a useful tool for determining the stability of a solution of a PDE. Some numerical results will be presented
Quiescent Prominence Dynamics Observed with the Hinode Solar Optical Telescope. II. Prominence Bubble Boundary Layer Characteristics and the Onset of a Coupled KelvinâHelmholtz RayleighâTaylor Instability
This is the author accepted manuscript. The final version is available from American Astronomical Society via the DOI in this record.We analyze solar quiescent prominence bubble characteristics and instability dynamics using Hinode/Solar
Optical Telescope (SOT) data. We measure bubble expansion rate, prominence downflows,
and the profile of the boundary layer brightness and thickness as a function of time. The largest
bubble analyzed rises into the prominence with a speed of about 1.3 km sâ1 until it is destabilized
by a localized shear flow on the boundary. Boundary layer thickness grows gradually as prominence
downflows deposit plasma onto the bubble with characteristic speeds of 20 â 35 km sâ1
. Lateral
downflows initiate from the thickened boundary layer with characteristic speeds of 25 â 50 km sâ1
,
âdrainingâ the layer of plasma. Strong shear flow across one bubble boundary leads to an apparent
coupled Kelvin-Helmholtz Rayleigh-Taylor (KH-RT) instability. We measure shear flow speeds above
the bubble of 10 km sâ1 and infer interior bubble flow speeds on the order of 100 km sâ1
. Comparing
the measured growth rate of the instability to analytic expressions, we infer a magnetic flux density
across the bubble boundary of âź 10â3 T (10 gauss) at an angle of âź 70âŚ
to the prominence plane.
The results are consistent with the hypothesis that prominence bubbles are caused by magnetic flux
that emerges below a prominence, setting up the conditions for RT, or combined KH-RT, instability
flows that transport flux, helicity, and hot plasma upward into the overlying coronal magnetic flux
ropeTEB was supported by NASA contracts NNM07AA01C (Solar-B FPP), NNG04EA00C (SDO/AIA) while at the Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), and by The National Weather Service (NWS) Office of Science and Technology Integration (OSTI) while at the National Oceanic and Atmospheric Administration (NOAA). A.H. was supported by his STFC Ernest Rutherford Fellowship grant number ST/L00397X/2. W.L. was supported by NASA HGI grant NNX15AR15G and NASA contract NNG09FA40C (IRIS) at LMSAL
How Does Competition Help Future Learning in Serious Games? An Exploratory Study in Learning Search Engine Optimization
Serious games, many of which are multi-player games, have been commonly used in information technology education and training. Competition can be intuitively associated with games; however, it is not always considered as a necessary attribute of serious games. Particularly, the learning impact results of competition are mixed. Challenge and control are two game attributes that are highly relevant to competition. With the use of a multi-player serious game, SEO War, this study aims to explore the relationships among competition, perceived control, perceived challenge, and self-efficacy in a game-based learning environment. Particularly, it investigates whether competition leads to self-efficacy. It also examines whether perceived challenge and perceived control mediate the relationship between competition and self-efficacy in serious games. This study contributes to the expanding literature on selecting important attributes for serious games, and it advances our understanding of the mechanism of how competition leads to self-efficacy. Moreover, it will help game designers decide on important game attributes through which games can be enhanced
The Role of Artificial Intelligence for Business Value
An increasing number of organizations are investing in Artificial intelligence (AI), but not all AI implementation leads to improved performance. To contribute to organizational business value, two components of AI resources, AI assets and AI capabilities, should be complementary in the business value creation process. In this study, based on IT business value literature and through the lens of dynamic capabilities, the role of AI resources in organizational value creation is explored. It is proposed that AI resources would enable organizations to develop process-oriented dynamic capabilities (PDCs), contributing to business value. This study will examine how organizations build AI capabilities and the roles of AI resources in creating business values through case studies. This research will offer a framework that guides and assists practitioners in utilising AI resources and building AI capabilities. A deeper understanding of the subject through this study also enriches the growing body of literature on AI
Numerical studies of the fractional quantum Hall effect in systems with tunable interactions
The discovery of the fractional quantum Hall effect in GaAs-based
semiconductor devices has lead to new advances in condensed matter physics, in
particular the possibility for exotic, topological phases of matter that
possess fractional, and even non-Abelian, statistics of quasiparticles. One of
the main limitations of the experimental systems based on GaAs has been the
lack of tunability of the effective interactions between two-dimensional
electrons, which made it difficult to stabilize some of the more fragile
states, or induce phase transitions in a controlled manner. Here we review the
recent studies that have explored the effects of tunability of the interactions
offered by alternative two-dimensional systems, characterized by non-trivial
Berry phases and including graphene, bilayer graphene and topological
insulators. The tunability in these systems is achieved via external fields
that change the mass gap, or by screening via dielectric plate in the vicinity
of the device. Our study points to a number of different ways to manipulate the
effective interactions, and engineer phase transitions between quantum Hall
liquids and compressible states in a controlled manner.Comment: 9 pages, 4 figures, updated references; review for the CCP2011
conference, to appear in "Journal of Physics: Conference Series
- âŚ