694 research outputs found
semigroup generation for Fokker-Planck operators associated with general L\'evy driven SDEs
We prove a new generation result in for a large class of non-local
operators with non-degenerate local terms. This class contains the operators
appearing in Fokker-Planck or Kolmogorov forward equations associated with
L\'evy driven SDEs, i.e. the adjoint operators of the infinitesimal generators
of these SDEs. As a byproduct, we also obtain a new elliptic regularity result
of independent interest. The main novelty in this paper is that we can consider
very general L\'evy operators, including state-space depending coefficients
with linear growth and general L\'evy measures which can be singular and have
fat tails
Theoretical studies of photoinduced dynamics and topological states in materials with strong electron-lattice couplings
First, we study the nonequilibrium dynamics of photoinduced phase transitions in charge ordered (CO) systems with a strong electron-lattice interaction and analyze the interplay between electrons, periodic lattice distortions, and a phonon thermal reservoir. Simulations based on a tight-binding Hamiltonian and Boltzmann equations reveal partially decoupled oscillations of the electronic order parameter and the periodic lattice distortion during CO melting, which becomes more energy efficient with lower photon energy. The cooling rate of the electron system correlates with the CO gap dynamics, responsible for an order of magnitude decrease of the cooling rate upon the gap reopening. The work also find that the time-dependent frequency of coherent oscillation reflects the dynamics of the energy landscape, such as transition between single-well and double-well, which sensitively depends on the photon energy and the pump fluence. The results demonstrate the intricate nonequilibrium dynamics in CO materials.
Second, a model for two-dimensional electronic, photonic, and mechanical metamaterial systems is presented, which has flat one-dimensional zero-mode energy bands and stable localized states of a topological origin confined within twin boundaries, antiphase boundaries, and at open edges. Topological origins of these flat bands are analyzed for an electronic system as a specific example, using a two-dimensional extension of the Su-Schrieffer-Heeger Hamiltonian with alternating shift of the chains. It is demonstrated that the slow group velocities of the localized flat band states are sensitively controlled by the distance between the boundaries and the propagation can be guided through designed paths of these boundaries. We also discuss how to realize this model in metamaterials.
Third, the study of topological mechanical metamaterials system made of 1D or 2D arrays of spinners, as an experimental realization of electron models in the second part. Compared with experimental data for 1D case and makes prediction for 2D case of ribbon with open edges. And also show how they slow group velocity of localized edge modes depend on the width of the ribbon
STEREOTYPE FILTER: A DIGITAL INTERFACE TO FOSTER CULTURAL AWARENESS
With the development of economic globalization, more and more people are immersed in a cross-cultural community. United States hosts the largest number of international students in the world. The cultural diversity of American college campuses makes them full of opportunity to learn about and from each other. However, huge portion of international students experience American colleges as culturally challenging. The cultural identities of international students are often stereotyped or misunderstood, causing barriers between students. Online questionnaires and analyzing related literatures suggests that the problem of stereotyping is a broad issue that is worth studying. Interaction design is a possible solution to help connect students on campus. However, as a communication medium, its application to solve the stereotype problem is still very limited. Therefore, the objective of this thesis is to explore how interaction design can foster cultural awareness and address stereotyping on college campuses. The “Stereotype Filter” was designed by developing a digital interface. Testing the prototypes of the design showed that the design effectively promotes cultural understanding among people of various backgrounds. It suggests that interaction design is a possible intervention to the cultural barriers that international students experience
Antioxidant activities of polyphenols extracted from Perilla frutescens varieties
Various cultivars of Perilla frutescens (L.) (var. crispa and var. frutescens) Britt. were harvested in China and Japan. They were easily differentiated on the basis of their foliage color, that varied from red to green. Water extracts of dried plants were investigated for their antioxidant activity (AA) and their polyphenolic compounds compared. Among them, cinnamic acid derivatives (coumaroyl tartaric acid, caffeic acid and rosmarinic acid), flavonoids (apigenin 7-O-caffeoylglucoside, scutellarein 7-Odiglucuronide, luteolin 7-O-diglucuronide, apigenin 7-O-diglucuronide, luteolin 7-Oglucuronide, and scutellarein 7-O-glucuronide) and anthocyanins (mainly cis-shisonin, shisonin, malonylshisonin and cyanidin 3-O-(E)-caffeoylglucoside-5-O-malonylglucoside) were quantified. AA assays are based on the inhibition of the free radical 2,2-diphenyl-1- picrylhydrazyl (DPPH). The DPPH radical scavenging activity was calculated as Trolox® [(±)-6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid] equivalent antioxidant capacity (TEAC). The mean amount of total phenolics of the water extracts (4-29 ?mol/100 mL) and the TEAC value calculated (23-167 ?mol TE/100 mL) confirmed the high antioxidant activity of these leaf water extracts. These results were highly correlated within some o-dihydroxylated polyphenolic compounds and AA. (Résumé d'auteur
Hidden vortices in a Bose-Einstein condensate in a rotating double-well potential
We study vortex formation in a Bose-Einstein condensate in a rotating
double-well potential. Besides the ordinary quantized vortices and elusive
ghost vortices, "hidden" vortices are found distributing along the central
barrier. These hidden vortices are invisible like ghost vortex but carry
angular momentum. Moreover, their core size is not given by the healing length,
but is strongly influenced by the external potential. We find that the
Feynman's rule can be well satisfied only after including the hidden vortices.
There is no critical rotating frequency for the formation of hidden vortex
while there is one for the formation of ordinary visible vortices. Hidden
vortices can be revealed in the free expansion of the Bose-Einstein
condensates. In addition, the hidden vortices in a Bose-Einstein condensate can
appear in other external potentials, such as a rotating anisotropic toroidal
trap.Comment: 6pages,5figure
Stationary states and quantum quench dynamics of Bose-Einstein condensates in a double-well potential
We consider the properties of stationary states and the dynamics of
Bose-Einstein condensates (BECs) in a double-well (DW) potential with pair
tunneling by using a full quantum-mechanical treatment. Furthermore, we study
the quantum quench dynamics of the DW system subjected to a sudden change of
the Peierls phase. It is shown that strong pair tunneling evidently influences
the energy spectrum structure of the stationary states. For relatively weak
repulsive interatomic interactions, the dynamics of the DW system with a
maximal initial population difference evolves from Josephson oscillations to
quantum self-trapping as one increases the pair tunneling strength, while for
large repulsion the strong pair tunneling inhibits the quantum self-trapping.
In the case of attractive interatomic interactions, strong pair tunneling tends
to destroy the Josephson oscillations and quantum self-trapping, and the system
eventually enters a symmetric regime of zero population difference. Finally,
the effect of the Peierls phase on the quantum quench dynamics of the system is
analyzed and discussed. These new features are remarkably different from the
usual dynamical behaviors of a BEC in a DW potential.Comment: 9 pages,7 figures,accepted for publication in Journal of Physics
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