Doping of lead halide perovskites (LHPs) with the targeted impurities has emerged as an additional lever, a dimension beyond structural perfection and compositional distinction, for the alteration of ...many properties of halide perovskites. The past several years has seen an explosive increase in our knowledge of doped halide perovskites, which exhibit distinct optical and electronic properties with respect to undoped counterparts and improve performance of perovskite optoelectronic devices. However, there are still a series of fundamental scientific issues unresolved in the domain of doped perovskites. In this review, we present a critical overview of recent advances in the synthesis, property, and functional applications of metal-doped halide perovskites. We lay a particular focus on three-dimensional LHPs and discuss the influence of doped metal ions on the properties of these perovskites, including main group metal cations, transition metal cations, and rare earth (RE) metal cations. We thoroughly summarize the synthesis methods used, doping-induced variation in optoelectronic properties, and benefit of doping engineering for optimization of device performance. We highlight the milestone achievements in this field and emphasize new properties arising from dopants in halide perovskites. We also address controversies encountered during the development of doped perovskites and examine the remaining challenges in this exciting field of science. Finally, we present our perspectives for further investigation of this star material by doping engineering.
This paper presents a novel (SPC) scheme for the path following of autonomous vehicles (AVs) subject to denial of service (DoS) attacks. First, by considering the energy constraints of DoS attacks, ...bounded but arbitrary packet dropouts is used to characterize the effects of DoS attacks. Then, a switched control system model is established to describe the path following control of AVs under DoS attacks. In what follows, the SPC scheme, which depends on the detection of packet dropout from actuator side, is developed to compensate the packet dropout while there are no feedback measurements available. The main advantage of the proposed SPC scheme is that the predictive control design only depends on the latest available measurement and not affected by external disturbance. This is important to the control of networked systems under DoS attacks. At last, the corresponding experiments on path following control of the AVs are carried out in order to verify the validity of theory results.
This paper is concerned with the event-triggered adaptive security control (ET-ASC) for the path following of networked unmanned ground vehicles (UGVs) subject to sensor attacks. Firstly, a security ...model is well established to capture the dynamics of path following control of UGVs under sensor attacks. Then, the ET-ASC with respect to correction signal is proposed to mitigate the effects of such sensor attacks. In what follows, two theorems, which include both input to state stability (ISS) criterion and controller design method, are carefully derived for the path following control of UGVs under the proposed ET-ASC scheme. The advantage of the proposed ET-ASC scheme lies in that it can actively amend the sensor attacks in an adaptive way and exclude Zeno phenomenon naturally. At last, a verification simulation experiment are conducted to show the effectiveness of the proposed ET-ASC method.
The malicious physical attacks from both sensor and actuator sides make real threats to the security and safety of autonomous ground vehicles (AGVs). This paper focuses on the problem of ...neural‐network‐based event‐triggered adaptive security control (ET‐ASC) scheme for path following of AGVs subject to arbitrary abnormal actuator signal. First, we assume that an arbitrary abnormal signal is caused by arbitrary malicious attacks or disturbances from actuators. Then, radial basis function neural network (RBF‐NN) is used to reconstruct such abnormal actuator signal. Second, modelling issues on security path following control of AGVs with Sigmoid‐like ETC scheme are shown when the AGV is suffering from abnormal actuator signal. In what follows, an ET‐ASC scheme is developed to mitigate the adverse effects of abnormal actuator signal with the reconstructed abnormal signal based on a novel Sigmoid‐like event‐triggered communication scheme. By using the proposed RBF‐NN‐based ET‐ASC scheme, H∞$$ {H}_{\infty } $$ control performance can be guaranteed under arbitrary malicious actuator signal rather than such attacks following a specific probability distribution. Final, some simulation experiments are provided to verify the effectiveness of proposed ET‐ASC scheme.
Abstract
Multitudinous topological configurations spawn oases of many physical properties and phenomena in condensed-matter physics. Nano-sized ferroelectric bubble domains with various polar ...topologies (e.g., vortices, skyrmions) achieved in ferroelectric films present great potential for valuable physical properties. However, experimentally manipulating bubble domains has remained elusive especially in the bulk form. Here, in any bulk material, we achieve self-confined bubble domains with multiple polar topologies in bulk Bi
0.5
Na
0.5
TiO
3
ferroelectrics, especially skyrmions, as validated by direct Z-contrast imaging. This phenomenon is driven by the interplay of bulk, elastic and electrostatic energies of coexisting modulated phases with strong and weak spontaneous polarizations. We demonstrate reversable and tip-voltage magnitude/time-dependent donut-like domain morphology evolution towards continuously and reversibly modulated high-density nonvolatile ferroelectric memories.
Bismuth is one of the most thoroughly investigated main group elements, which has been regarded as 'the wonder metal' because of its diverse oxidation states and profound propensities to form bismuth ...clusters, resulting from the easy involvement in chemical combinations for the electrons in the p orbital. This peculiarity allows them to behave as smart optically active centers in diverse host materials. Remarkable progress in the research of bismuth activated photonic materials has been seen over the last ten years owing to their unique properties and important applications in areas of telecommunication, biomedicine, white light illumination and lasers. The aim of this review is to present a critical overview of the current state of the art in bismuth activated photonic materials, their features, advantages and limitations as well as the future research trends. We first shortly introduce the fundamental properties of bismuth element including principles of bismuth-related luminescence and characterization techniques available. This is followed by a detailed discussion on the recent progress in the synthesis and characterization of bismuth-activated photonic materials, with an emphasis on material systems emitting in the near-infrared (NIR) spectral region. Furthermore, we describe the representative achievements regarding their prospective applications in broadband NIR optical amplifiers, fiber lasers, bioimaging, and white light-emitting diodes. Finally, we point out what key scientific questions remain to be answered, and present our perspectives on future research trends in this exciting field of sciences.
In this study, a bandwidth allocation-based distributed event-triggering load frequency control (LFC) has been developed for smart grids to deal with hybrid cyber-attacks, for example, ...denial-of-service (DoS) attacks and false data injection (FDI) attacks. Firstly, to prevent hybrid cyber-attacks from causing open-loop unstable operation of the LFC systems, we propose a distributed event-triggering communication (ETC) strategy. To attain the maximum usage of bandwidth, a dynamic bandwidth allocation mechanism is integrated with the ETC approach on the basis of resource availability and error between the current state and equilibrium state. This bandwidth reservation and allocation approach aim at detecting attacks and assigning bandwidth to the different channels of distribution networks. Then, by virtue of the Lyapunov approach, the exponential stability criteria are established. Further, the exclusion of Zeno behavior of the designed systems is proved during the control process. Finally, comprehensive case studies show that the proposed method can improve the utilization rate of the network resource.
The large specific surface area of perovskite nanocrystals (NCs) increases the likelihood of surface defects compared to that of bulk single crystals and polycrystalline thin films. It is thus ...crucial to comprehend and control their defect population in order to exploit the potential of perovskite NCs. This Perspective describes and classifies recent advances in understanding defect chemistry and avenues toward defect density reduction in perovskite NCs, and it does so in the context of the promise perceived in light-emitting devices. Several pathways for decreasing the defect density are explored, including advanced NC syntheses, new surface-capping strategies, doping with metal ions and rare earths, engineering elemental compensation, and the translation of core–shell heterostructures into the perovskite materials family. We close with challenges that remain in perovskite NC defect research.
Halide perovskites, in the form of thin films and colloidal nanocrystals, have recently taken semiconductor optoelectronics research by storm, and have emerged as promising candidates for ...high‐performance solar cells, light‐emitting diodes (LEDs), lasers, photodetectors, and radiation detectors. The impressive optical and optoelectronic properties, along with the rapid increase in efficiencies of solar cells and LEDs, have greatly attracted researchers across many disciplines. However, most advances made so far in terms of preparation (colloidal nanocrystals and thin films), and the devices with highest efficiencies are based on Pb‐based halide perovskites, which have raised concerns over their commercialization due to the toxicity of Pb. This has triggered the search for lower‐toxicity Pb‐free halide perovskites and has led to significant progress in the last few years. In this roadmap review, researchers of different expertise have joined together to summarize the latest progress, outstanding challenges, and future directions of Pb‐free halide perovskite thin films and nanocrystals, regarding their synthesis, optical spectroscopy, and optoelectronic devices, to guide the researchers currently working in this area as well as those that will join the field in the future.
This roadmap review summarizes the latest progress, outstanding challenges, and future directions of Pb‐free halide perovskites regarding their synthesis, optical spectroscopy, and optoelectronic devices.
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