3,226 research outputs found
Emergent Recurrent Extension Phase Transition in a Quasiperiodic Chain
We study -wave superconducting quasiperiodic chains with staggered
potential. The result shows a counter-intuitive phase transition phenomenon,
i.e., recurrent extension phase transition (REPT). By analyzing the
participation ration and scaling behavior, we prove the existence of REPT
phenomenon, which, in concrete terms, means that the system will repeatedly
return from the intermediate phase to the extended phase as the quasiperiodic
or staggered strength grows. Furthermore, our finding is also quite different
from the traditional understanding of intermediate phase (composed only of the
pure extended phase and pure localized phase) in that, the new intermediate
phase described here, stemming from the competition between staggered potential
and -wave pairing, actually falls into three types by bringing in the
critical phase. To be specific, the new intermediate phases are composed of the
critical + extended states, the critical + localized states, and the critical +
extended + localized states, respectively.Comment: 12 pages, 8 figure
Streaming Video over HTTP with Consistent Quality
In conventional HTTP-based adaptive streaming (HAS), a video source is
encoded at multiple levels of constant bitrate representations, and a client
makes its representation selections according to the measured network
bandwidth. While greatly simplifying adaptation to the varying network
conditions, this strategy is not the best for optimizing the video quality
experienced by end users. Quality fluctuation can be reduced if the natural
variability of video content is taken into consideration. In this work, we
study the design of a client rate adaptation algorithm to yield consistent
video quality. We assume that clients have visibility into incoming video
within a finite horizon. We also take advantage of the client-side video
buffer, by using it as a breathing room for not only network bandwidth
variability, but also video bitrate variability. The challenge, however, lies
in how to balance these two variabilities to yield consistent video quality
without risking a buffer underrun. We propose an optimization solution that
uses an online algorithm to adapt the video bitrate step-by-step, while
applying dynamic programming at each step. We incorporate our solution into
PANDA -- a practical rate adaptation algorithm designed for HAS deployment at
scale.Comment: Refined version submitted to ACM Multimedia Systems Conference
(MMSys), 201
Valley-Layer Coupling: A New Design Principle for Valleytronics
We introduce the concept of valley-layer coupling (VLC) in two-dimensional
materials, where the low-energy electronic states in the emergent valleys have
valley-contrasted layer polarization such that each state is spatially
localized on the top or bottom super-layer. The VLC enables a direct coupling
between valley and gate electric field, opening a new route towards
electrically controlled valleytronics. We analyze the symmetry requirements for
the system to host VLC, demonstrate our idea via first-principles calculations
and model analysis of a concrete 2D material example, and show that an
electric, continuous, wide-range, and switchable control of valley polarization
can be achieved by VLC. Furthermore, we find that systems with VLC can exhibit
other interesting physics, such as valley-contrasting linear dichroism and
optical selection of the electric polarization of interlayer excitons.Comment: 6 pages, 4 figure
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