581 research outputs found
Multilevel Diversity Coding with Secure Regeneration: Separate Coding Achieves the MBR Point
The problem of multilevel diversity coding with secure regeneration (MDC-SR)
is considered, which includes the problems of multilevel diversity coding with
regeneration (MDC-R) and secure regenerating code (SRC) as special cases. Two
outer bounds are established, showing that separate coding of different
messages using the respective SRCs can achieve the
minimum-bandwidth-regeneration (MBR) point of the achievable normalized
storage-capacity repair-bandwidth tradeoff regions for the general MDC-SR
problem. The core of the new converse results is an exchange lemma, which can
be established using Han's subset inequality
Composite Quantum Phases in Non-Hermitian Systems
Non-Hermitian systems have attracted considerable interest in recent years
owing to their unique topological properties that are absent in Hermitian
systems. While such properties have been thoroughly characterized in free
fermion models, they remain an open question for interacting bosonic systems.
In this Letter, we present a precise definition of quantum phases for
non-Hermitian systems and propose a new family of phases referred to as
composite quantum phases. We demonstrate the existence of these phases in a
one-dimensional spin- system and show their robustness against perturbations
through numerical simulations. Furthermore, we investigate the phase diagram of
our model, indicating the extensive presence of these new phases in
non-Hermitian systems. Our work establishes a new framework for studying and
constructing quantum phases in non-Hermitian interacting systems, revealing
exciting possibilities beyond the single-particle picture.Comment: 9 pages, 5 figure
Diversity is Strength: Mastering Football Full Game with Interactive Reinforcement Learning of Multiple AIs
Training AI with strong and rich strategies in multi-agent environments
remains an important research topic in Deep Reinforcement Learning (DRL). The
AI's strength is closely related to its diversity of strategies, and this
relationship can guide us to train AI with both strong and rich strategies. To
prove this point, we propose Diversity is Strength (DIS), a novel DRL training
framework that can simultaneously train multiple kinds of AIs. These AIs are
linked through an interconnected history model pool structure, which enhances
their capabilities and strategy diversities. We also design a model evaluation
and screening scheme to select the best models to enrich the model pool and
obtain the final AI. The proposed training method provides diverse,
generalizable, and strong AI strategies without using human data. We tested our
method in an AI competition based on Google Research Football (GRF) and won the
5v5 and 11v11 tracks. The method enables a GRF AI to have a high level on both
5v5 and 11v11 tracks for the first time, which are under complex multi-agent
environments. The behavior analysis shows that the trained AI has rich
strategies, and the ablation experiments proved that the designed modules
benefit the training process
Stability studies of ZnO and AlN thin film acoustic wave devices in acid and alkali harsh environments
Surface acoustic wave (SAW) devices based on piezoelectric thin-films such as ZnO and AlN are widely used in sensing, microfluidics and lab-on-a-chip applications. However, for many of these applications, the SAW devices will inevitably be used in acid or alkali harsh environments, which may cause their early failures. In this work, we investigated the behavior and degradation mechanisms of thin film based SAW devices in acid and alkali harsh environments. Results show that under the acid and alkali attacks, chemical reaction and corrosion of ZnO devices are very fast (usually within 45 s). During the corrosion, the crystalline orientation of the ZnO film is not changed, but its grain defects are significantly increased and the grain sizes are decreased. The velocity of ZnO-based SAW devices is decreased due to the formation of porous structures induced by the chemical reactions. Whereas an AlN thin-film based SAW device does not perform well in acid–alkali conditions, it might be able to maintain a normal performance without obvious degradation for more than ten hours in acid or alkali solutions. This work could provide guidance for the applications of both ZnO or AlN-based SAW devices in acid/alkali harsh environments
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