336 research outputs found
Topological plasma transport from a diffusion view
Recent studies have identified plasma as a topological material. Yet, these
researches often depict plasma as a fluid governed by electromagnetic fields,
i.e., a classical wave system. Indeed, plasma transport can be characterized by
a unique diffusion process distinguished by its collective behaviors. In this
work, we adopt a simplified diffusion-migration method to elucidate the
topological plasma transport. Drawing parallels to the thermal
conduction-convection system, we introduce a double ring model to investigate
the plasma density behaviors in the anti-parity-time reversal (APT) unbroken
and broken phases. Subsequently, by augmenting the number of rings, we have
established a coupled ring chain structure. This structure serves as a medium
for realizing the APT symmetric one-dimensional (1D) reciprocal model,
representing the simplest tight-binding model with a trivial topology. To
develop a model featuring topological properties, we should modify the APT
symmetric 1D reciprocal model from the following two aspects: hopping amplitude
and onsite potential. From the hopping amplitude, we incorporate the
non-reciprocity to facilitate the non-Hermitian skin effect, an intrinsic
non-Hermitian topology. Meanwhile, from the onsite potential, the quasiperiodic
modulation has been adopted onto the APT symmetric 1D reciprocal model. This
APT symmetric 1D Aubry-Andr\'e-Harper model is of topological nature.
Additionally, we suggest the potential applications for these diffusive plasma
topological states. This study establishes a diffusion-based approach to
realizing topological states in plasma, potentially inspiring further
advancements in plasma physics.Comment: This letter has been published on Chinese Physics Letters as an
express letter.Comments are welcome
The strengthened Brou\'{e} abelian defect group conjecture for and
We show that each -block of and over
an arbitrary complete discrete valuation ring is splendidly Rickard equivalent
to its Brauer correspondent, hence give new evidence for a refined version of
Brou\'{e}'s abelian defect group conjecture proposed by Kessar and Linckelmann
Recent developments in biofeedback for neuromotor rehabilitation
The original use of biofeedback to train single muscle activity in static positions or movement unrelated to function did not correlate well to motor function improvements in patients with central nervous system injuries. The concept of task-oriented repetitive training suggests that biofeedback therapy should be delivered during functionally related dynamic movement to optimize motor function improvement. Current, advanced technologies facilitate the design of novel biofeedback systems that possess diverse parameters, advanced cue display, and sophisticated control systems for use in task-oriented biofeedback. In light of these advancements, this article: (1) reviews early biofeedback studies and their conclusions; (2) presents recent developments in biofeedback technologies and their applications to task-oriented biofeedback interventions; and (3) discusses considerations regarding the therapeutic system design and the clinical application of task-oriented biofeedback therapy. This review should provide a framework to further broaden the application of task-oriented biofeedback therapy in neuromotor rehabilitation
Expanded-plane bilayer thermal concentrator for improving thermoelectric conversion efficiency
Thermoelectric devices are pivotal in the energy sector, with enhancing their
conversion efficiency being a longstanding focal point. While progress has been
made, overcoming the inherent low efficiency and heat management issues remains
challenging. The advent of thermal metamaterials, particularly thermal
concentrators, holds promise for improved thermoelectric efficiency. The
concentrator has the potential to amplify the temperature gradient within the
working region without altering the temperature gradient of the background,
thereby enhancing thermoelectric conversion efficiency through this
concentrating effect. Nevertheless, the efficacy of this effect is contingent
upon the structural parameters of the concentrator. Systematically
investigating the impact of metamaterials on thermoelectric conversion
efficiency, particularly in terms of quantifying the enhancement, presents a
significant challenge. Additionally, the intrinsic thermal conductivity of the
material imposes constraints on the applicability of the concentrator in this
regard. In this context, drawing inspiration from the recently proposed passive
ultra-conductive heat transport scheme, we have devised expanded-plane bilayer
thermal concentrators. We substantiate the prospective performance of our
design through analytical demonstration, further validated through
finite-element simulations and experiments. Notably, through direct
calculation, we illustrate an efficiency improvement of about 38\% when
utilizing the expanded-plane concentrator comparing with not using
expanded-plane structure. The expanded-plane geometrical configuration of the
outer layer can also attain large-scale value. These findings not only present
a novel avenue for the functional transformation of thermal metamaterials but
also hold significant implications for the field of thermoelectrics
Convective meta-thermal concentration for ultrahigh efficient Stirling engine with waste heat and cold utilization
The Stirling engine, which possesses external combustion characteristics, a
simple structure, and high theoretical thermal efficiency, has excellent
potential for utilizing finite waste heat and cold resources. However,
practical applications of this technology suffered from thermal inefficiency
due to the discontinuity and instability of waste resources. Despite advances
in energy storage technology, temperature variations in the heat-exchanging
fluids at the hot and cold ends of the Stirling engine remained significant
obstacles. In this work, convective meta-thermal concentration (CMTC) was
introduced between the heating (cooling) fluids and the hot (cold) end of the
Stirling engine, employing alternating isotropic materials with high and low
thermal conductivities. It was demonstrated that CMTC effectively enhanced the
temperature difference between the hot and cold ends, leading to a remarkable
improvement in Stirling engine efficiency. Particularly, when the Stirling
engine efficiency tended to zero due to the limited availability of waste heat
and cold resources, CMTC overcame this limitation, surpassing existing
optimization technology. Further analysis under various operating conditions
showed that CMTC achieved a significant thermal efficiency improvement of up to
1460%. This work expanded the application of thermal metamaterials to heat
engine systems, offering an exciting avenue for sustainable energy utilization
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