Abstract-Ultra-Reliable and Low Latency Communications (URLLC) is a challenging class of services to be supported by the fifth generation of mobile networks (5G). Among the URLLC services, many use cases, especially those related to factory automation, involve communications with relatively static radio conditions and a periodic generation of control or data packets. The transmission of these packets requires extremely low latency and ultra-reliable communication to enable realtime control of automation processes. In this paper, we discuss a mechanism of deterministic resource allocation to meet the URLLC requirement in terms of reliability and latency, including initial transmissions and controlled retransmissions. A joint resource allocation and modulation and coding schemes selection is performed so that the resource consumption is minimized, subject to latency and reliability constraints. We show that when applying the proposed resource allocation technique it is possible to achieve very low error rates.
About 30% of the world’s primary energy consumption is in friction. The economic losses caused by friction energy dissipation and wear account for about 2%–7% of its gross domestic product (GDP) for different countries every year. The key to reducing energy consumption is to control the way of energy dissipation in the friction process. However, due to many various factors affecting friction and the lack of efficient detection methods, the energy dissipation mechanism in friction is still a challenging problem. Here, we firstly introduce the classical microscopic mechanism of friction energy dissipation, including phonon dissipation, electron dissipation, and non-contact friction energy dissipation. Then, we attempt to summarize the ultrafast friction energy dissipation and introduce the high-resolution friction energy dissipation detection system, since the origin of friction energy dissipation is essentially related to the ultrafast dynamics of excited electrons and phonons. Finally, the application of friction energy dissipation in representative high-end equipment is discussed, and the potential economic saving is predicted.
Moiré superlattices have emerged as an unprecedented manipulation tool for engineering correlated quantum phenomena in van der Waals heterostructures1-4. With moiré potentials as a naturally configurable solid-state that sustains high exciton density, interlayer excitons in transition metal dichalcogenide (TMDC) heterostructures are expected to achieve high-temperature exciton condensation and related superfluidity5. However, the exciton condensation is usually optically inactive due to the finite momentum of interlayer excitons. The experimental observation of dark exciton condensation in moiré potentials remains challenging with traditional optical techniques. Here we directly visualize the dark-exciton condensation in twisted TMDC heterostructures using femtosecond transient absorption microscopy. We observe a quantum transition from classical exciton gas to exciton condensation by imaging temperature-dependent exciton transport. With decreasing temperature, exciton diffusion rates exhibit an accelerating downwards trend under a critical degeneracy temperature, indicative of exciton condensation. This result is attributed to moiré potentials drastically suppressing exciton transport to promote exciton condensation. The ability to image exciton condensates opens the door to quantum information processing6 and high-precision metrology in moiré superlattices.
For non-contact friction, energy is usually dissipated through phonon excitation, Joule dissipation and van der Waals friction. Although some new dissipation mechanisms related to quantum phenomenon have been discovered, the...
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