Showing papers by "University of Science and Technology Beijing published in 2020"
TL;DR: Bridging the gap, to some extent, between precise design from theory and practical modulation in experiments, the proposed strategy extends defect engineering to a more sophisticated level for further unlocking the potential of catalytic performance enhancement.
Abstract: Defect engineering is widely applied in transition metal dichalcogenides (TMDs) to achieve electrical, optical, magnetic, and catalytic regulation. Vacancies, regarded as a type of extremely delica...
481 citations
TL;DR: In this article, the authors review the thirty-year history of ML by elaborating on supervised learning, unsupervised learning, reinforcement learning and deep learning and investigate their employment in the compelling applications of wireless networks, including heterogeneous networks, cognitive radios (CR), Internet of Things (IoT), machine to machine networks (M2M), and so on.
Abstract: Future wireless networks have a substantial potential in terms of supporting a broad range of complex compelling applications both in military and civilian fields, where the users are able to enjoy high-rate, low-latency, low-cost and reliable information services. Achieving this ambitious goal requires new radio techniques for adaptive learning and intelligent decision making because of the complex heterogeneous nature of the network structures and wireless services. Machine learning (ML) algorithms have great success in supporting big data analytics, efficient parameter estimation and interactive decision making. Hence, in this article, we review the thirty-year history of ML by elaborating on supervised learning, unsupervised learning, reinforcement learning and deep learning. Furthermore, we investigate their employment in the compelling applications of wireless networks, including heterogeneous networks (HetNets), cognitive radios (CR), Internet of Things (IoT), machine to machine networks (M2M), and so on. This article aims for assisting the readers in clarifying the motivation and methodology of the various ML algorithms, so as to invoke them for hitherto unexplored services as well as scenarios of future wireless networks.
413 citations
TL;DR: An unsymmetrical Cu-S1N3 single atom site on porous carbon with high performance in the oxygen reduction reaction is prepared and provides a universal scheme for the controllable synthesis and performance regulation of single metal atom catalysts toward energy applications.
Abstract: Atomic interface regulation is thought to be an efficient method to adjust the performance of single atom catalysts. Herein, a practical strategy was reported to rationally design single copper atoms coordinated with both sulfur and nitrogen atoms in metal-organic framework derived hierarchically porous carbon (S-Cu-ISA/SNC). The atomic interface configuration of the copper site in S-Cu-ISA/SNC is detected to be an unsymmetrically arranged Cu-S1N3 moiety. The catalyst exhibits excellent oxygen reduction reaction activity with a half-wave potential of 0.918 V vs. RHE. Additionally, through in situ X-ray absorption fine structure tests, we discover that the low-valent Cuprous-S1N3 moiety acts as an active center during the oxygen reduction process. Our discovery provides a universal scheme for the controllable synthesis and performance regulation of single metal atom catalysts toward energy applications. Engineering the coordination environment of single atom catalysts offers to opportunity to optimize electrocatalytic activity. In this work, the authors prepare an unsymmetrical Cu-S1N3 single atom site on porous carbon with high performance in the oxygen reduction reaction.
407 citations
TL;DR: In this paper, a review of recent advances in the measurement and modeling of thermophysical properties at the nanoscale (from the solid state to colloids) is presented, including thermal conductivity, dynamic viscosity, specific heat capacity, and density.
322 citations
293 citations
TL;DR: A H 2 O 2 /O 2 self-supplying nanoagent, (MSNs@CaO 2 -ICG)@LA, which consists of manganese silicate-supported calcium peroxide and indocyanine green with further surface modification of phase-change material lauric acid, is reported, which is effective in inhibiting tumor growth both in vitro and in vivo.
Abstract: The therapeutic effect of reactive oxygen species (ROS)-involved cancer therapies is significantly limited by shortage of oxy-substrates, such as hypoxia in photodynamic therapy (PDT) and insufficient hydrogen peroxide (H2O2) in chemodynamic therapy (CDT). Here, we report a H2O2/O2 self-supplying nanoagent, (MSNs@CaO2-ICG)@LA, which consists of manganese silicate (MSN)-supported calcium peroxide (CaO2) and indocyanine green (ICG) with further surface modification of phase-change material lauric acid (LA). Under laser irradiation, ICG simultaneously generates singlet oxygen and emits heat to melt the LA. The exposed CaO2 reacts with water to produce O2 and H2O2 for hypoxia-relieved ICG-mediated PDT and H2O2-supplying MSN-based CDT, acting as an open source strategy for ROS production. Additionally, the MSNs-induced glutathione depletion protects ROS from scavenging, termed reduce expenditure. This open source and reduce expenditure strategy is effective in inhibiting tumor growth both in vitro and in vivo, and significantly improves ROS generation efficiency from multi-level for ROS-involved cancer therapies.
291 citations
TL;DR: In order to improve the electrochemical performance of various kinds of rechargeable batteries, such as lithium-ion batteries, lithium-sulfur batteries, sodium- ion batteries, and other types of emerging batteries, the strategies for the design and fabrication of layered TMD-based electrode materials are discussed.
Abstract: The rapid development of electrochemical energy storage (EES) systems requires novel electrode materials with high performance. A typical 2D nanomaterial, layered transition metal dichalcogenides (TMDs) are regarded as promising materials used for EES systems due to their large specific surface areas and layer structures benefiting fast ion transport. The typical methods for the preparation of TMDs and TMD-based nanohybrids are first summarized. Then, in order to improve the electrochemical performance of various kinds of rechargeable batteries, such as lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, and other types of emerging batteries, the strategies for the design and fabrication of layered TMD-based electrode materials are discussed. Furthermore, the applications of layered TMD-based nanomaterials in supercapacitors, especially in untraditional supercapacitors, are presented. Finally, the existing challenges and promising future research directions in this field are proposed.
263 citations
TL;DR: In this paper, Al2O3 coating by an atomic layer deposition (ALD) technique was developed to improve the rechargeability of Zn anodes for rechargeable aqueous zinc-ion batteries.
Abstract: Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted increasing attention as an energy storage technology for large-scale applications, due to their high capacity (820 mA h g−1 and 5854 A h L−1), inherently high safety, and their low cost. However, the overall performance of ZIBs has been seriously hindered by the poor rechargeability of Zn anodes, because of the dendrite growth, passivation, and hydrogen evolution problems associated with Zn anodes. Herein, Al2O3 coating by an atomic layer deposition (ALD) technique was developed to address the aforementioned problems and improve the rechargeability of Zn anodes for ZIBs. By coating the Zn plate with an ultrathin Al2O3 layer, the wettability of Zn was improved and corrosion was inhibited. As a result, the formation of Zn dendrites was effectively suppressed, with a significantly improved lifetime in the Zn–Zn symmetric cells. With the optimized coating thickness of 100 cycles, 100Al2O3@Zn symmetric cells showed a reduced overpotential (36.5 mV) and a prolonged life span (over 500 h) at 1 mA cm−2. In addition, the 100Al2O3@Zn has been verified in Zn–MnO2 batteries using layered δ-MnO2 as the cathode and consequently exhibits superior electrochemical performance with a high capacity retention of 89.4% after over 1000 cycles at a current density of 1 mA cm−2 (3.33C for MnO2) was demonstrated. It is expected that the novel design of Al2O3 modified Zn anodes may pave the way towards high-performance aqueous ZIBs and shed light on the development of other metal anode-based battery systems.
259 citations
TL;DR: In this article, a boundary control approach is used to control a two-link rigid-flexible wing, which is based on the principle of bionics to improve the mobility and the flexibility of aircraft.
Abstract: A boundary control approach is used to control a two-link rigid-flexible wing in this article. Its design is based on the principle of bionics to improve the mobility and the flexibility of aircraft. First, a series of partial differential equations (PDEs) and ordinary differential equations (ODEs) are derived through the Hamilton's principle. These PDEs and ODEs describe the governing equations and the boundary conditions of the system, respectively. Then, a control strategy is developed to achieve the objectives including restraining the vibrations in bending and twisting deflections of the flexible link of the wing and achieving the desired angular position of the wing. By using Lyapunov's direct method, the wing system is proven to be stable. The numerical simulations are carried out with the finite difference method to prove the effectiveness of designed boundary controllers.
245 citations
TL;DR: It is unveiled that the superior performances of FeP@CNs anode originate from its prominent structural and compositional merits, which render fast electron/ion transport kinetics and abundant active sites for charge storage, thus enabling high-rate and highly durable lithium storage.
Abstract: Conversion-type transition-metal phosphide anode materials with high theoretical capacity usually suffer from low-rate capability and severe capacity decay, which are mainly caused by their inferior electronic conductivities and large volumetric variations together with the poor reversibility of discharge product (Li3P), impeding their practical applications. Herein, guided by density functional theory calculations, these obstacles are simultaneously mitigated by confining amorphous FeP nanoparticles into ultrathin 3D interconnected P-doped porous carbon nanosheets (denoted as FeP@CNs) via a facile approach, forming an intriguing 3D flake-CNs-like configuration. As an anode for lithium-ion batteries (LIBs), the resulting FeP@CNs electrode not only reaches a high reversible capacity (837 mA h g-1 after 300 cycles at 0.2 A g-1) and an exceptional rate capability (403 mA h g-1 at 16 A g-1) but also exhibits extraordinary durability (2500 cycles, 563 mA h g-1 at 4 A g-1, 98% capacity retention). By combining DFT calculations, in situ transmission electron microscopy, and a suite of ex situ microscopic and spectroscopic techniques, we show that the superior performances of FeP@CNs anode originate from its prominent structural and compositional merits, which render fast electron/ion-transport kinetics and abundant active sites (amorphous FeP nanoparticles and structural defects in P-doped CNs) for charge storage, promote the reversibility of conversion reactions, and buffer the volume variations while preventing pulverization/aggregation of FeP during cycling, thus enabling a high rate and highly durable lithium storage. Furthermore, a full cell composed of the prelithiated FeP@CNs anode and commercial LiFePO4 cathode exhibits impressive rate performance while maintaining superior cycling stability. This work fundamentally and experimentally presents a facile and effective structural engineering strategy for markedly improving the performance of conversion-type anodes for advanced LIBs.
225 citations
TL;DR: A brief overview of the structural features of PBDB-T congeners and the strategies used to design these polymers is given in this article, where a meta-analysis of a library of high-performance polymers, which are compared with other types of conjugated polymers are suggested.
14 Jun 2020
TL;DR: Focal Convolution Layer, a new applying of convolution, is presented to enhance the fine-grained learning of the part-level spatial features and the Micro-motion Capture Module is proposed, which is a novel way of temporal modeling for gait task, which focuses on the short-range temporal features rather than the redundant long-range features for cycle gait.
Abstract: Gait recognition, applied to identify individual walking patterns in a long-distance, is one of the most promising video-based biometric technologies. At present, most gait recognition methods take the whole human body as a unit to establish the spatio-temporal representations. However, we have observed that different parts of human body possess evidently various visual appearances and movement patterns during walking. In the latest literature, employing partial features for human body description has been verified being beneficial to individual recognition. Taken above insights together, we assume that each part of human body needs its own spatio-temporal expression. Then, we propose a novel part-based model GaitPart and get two aspects effect of boosting the performance: On the one hand, Focal Convolution Layer, a new applying of convolution, is presented to enhance the fine-grained learning of the part-level spatial features. On the other hand, the Micro-motion Capture Module (MCM) is proposed and there are several parallel MCMs in the GaitPart corresponding to the pre-defined parts of the human body, respectively. It is worth mentioning that the MCM is a novel way of temporal modeling for gait task, which focuses on the short-range temporal features rather than the redundant long-range features for cycle gait. Experiments on two of the most popular public datasets, CASIA-B and OU-MVLP, richly exemplified that our method meets a new state-of-the-art on multiple standard benchmarks. The source code will be available on https://github.com/ChaoFan96/GaitPart.
TL;DR: Cryogenic atom probe observations map hydrogen to a variety of interfaces, providing insight into hydrogen embrittlement, and direct observation of hydrogen at carbon-rich dislocations and grain boundaries provides validation for embrittlements models.
Abstract: Hydrogen embrittlement of high-strength steel is an obstacle for using these steels in sustainable energy production. Hydrogen embrittlement involves hydrogen-defect interactions at multiple-length scales. However, the challenge of measuring the precise location of hydrogen atoms limits our understanding. Thermal desorption spectroscopy can identify hydrogen retention or trapping, but data cannot be easily linked to the relative contributions of different microstructural features. We used cryo-transfer atom probe tomography to observe hydrogen at specific microstructural features in steels. Direct observation of hydrogen at carbon-rich dislocations and grain boundaries provides validation for embrittlement models. Hydrogen observed at an incoherent interface between niobium carbides and the surrounding steel provides direct evidence that these incoherent boundaries can act as trapping sites. This information is vital for designing embrittlement-resistant steels.
TL;DR: A comprehensive review on recent important development and progress in fiber SCs is provided, with respect to the active electrode materials, device configurations, functions, integrations and the exploration of some functions including stretchability and self-healing.
Abstract: Fiber supercapacitors (SCs), with their small size and weight, excellent flexibility and deformability, and high capacitance and power density, are recognized as one of the most robust power supplies available for wearable electronics. They can be woven into breathable textiles or integrated into different functional materials to fit curved surfaces for use in day-to-day life. A comprehensive review on recent important development and progress in fiber SCs is provided, with respect to the active electrode materials, device configurations, functions, integrations. Active electrode materials based on different electrochemical mechanisms and intended to improve performance including carbon-based materials, metal oxides, and hybrid composites, are first summarized. The three main types of fiber SCs, namely parallel, twist, and coaxial structures, are then discussed, followed by the exploration of some functions including stretchability and self-healing. Miniaturized integration of fiber SCs to obtain flexible energy fibers and integrated sensing systems is also discussed. Finally, a short conclusion is made, combining with comments on the current challenges and potential solutions in this field.
TL;DR: A model of the impact of green finance on the relationship between economic development and environmental quality indicates that green finance can significantly improve this relationship, creating a win-win situation regardingEconomic development and the environment.
Abstract: The goal of green finance is to pursue the coordinated development of financial activities, environmental protection, and ecological balance. This study aims to examine the impact of green finance on economic development and environmental quality. Data concerning green finance, economic development, and environmental quality for 30 provinces and municipalities in China from 2010 to 2017 are used. First, the global principal component analysis is adopted to develop a green finance development index. Second, a model of the impact of green finance on economic development is constructed, which indicates that the development of green finance plays a role in promoting economic development. Next, emissions of industrial smoke (powder) dust, industrial solid waste, and carbon dioxide are used to represent the environmental variables, and a model of the impact of green finance on environmental quality is proposed. The model shows that green finance has a positive effect on environment improvement. However, the impact of green finance on environmental quality varies for different levels of economic development. Finally, based on the theory of the environmental Kuznets curve, a model of the impact of green finance on the relationship between economic development and environmental quality is developed. The model indicates that green finance can significantly improve this relationship, creating a win-win situation regarding economic development and the environment.
TL;DR: A novel hydrogel design is adopted by introducing two different chitosan chains via the simultaneous crosslinking of carbon–carbon double bonds and catechol‐Fe3+ chelation, which enhances mechanical performance including high compressive modulus and high ductility and can remarkably promote healing of bacteria‐infected wound.
TL;DR: In this paper, a 3D fiber-network-reinforced composite solid electrolyte (CSE) with a mechanically robust, porous polyimide (PI) film as a host, Li6.75La3Zr1.75Ta0.25O12 nanoparticles and polyvinylidene fluoride (PVDF) polymer matrix with bis-trifluoromethanesulfonimide lithium salt as electrolyte filler, is designed and fabricated.
10 Jun 2020
TL;DR: An endogenous enzyme-powered Janus platelet micromotor system prepared by immobilizing urease asymmetrically onto the surface of natural platelet cells leads to a biogenic microrobotic system capable of autonomous movement using biological fuel.
Abstract: Transforming natural cells into functional biocompatible robots capable of active movement is expected to enhance the functions of the cells and revolutionize the development of synthetic micromotors. However, present cell-based micromotor systems commonly require the propulsion capabilities of rigid motors, external fields, or harsh conditions, which may compromise biocompatibility and require complex actuation equipment. Here, we report on an endogenous enzyme-powered Janus platelet micromotor (JPL-motor) system prepared by immobilizing urease asymmetrically onto the surface of natural platelet cells. This Janus distribution of urease on platelet cells enables uneven decomposition of urea in biofluids to generate enhanced chemophoretic motion. The cell surface engineering with urease has negligible impact on the functional surface proteins of platelets, and hence, the resulting JPL-motors preserve the intrinsic biofunctionalities of platelets, including effective targeting of cancer cells and bacteria. The efficient propulsion of JPL-motors in the presence of the urea fuel greatly enhances their binding efficiency with these biological targets and improves their therapeutic efficacy when loaded with model anticancer or antibiotic drugs. Overall, asymmetric enzyme immobilization on the platelet surface leads to a biogenic microrobotic system capable of autonomous movement using biological fuel. The ability to impart self-propulsion onto biological cells, such as platelets, and to load these cellular robots with a variety of functional components holds considerable promise for developing multifunctional cell-based micromotors for a variety of biomedical applications.
TL;DR: Novel cellular membranes are designed based on a facile polydopamine-assisted metal (copper or silver) deposition on electrospun polymer nanofibers, and their interactions for excellent electrical conductivity, mechanical flexibility, and ultrahigh EMI shielding performance.
Abstract: Ultrathin, lightweight, and flexible electromagnetic interference (EMI) shielding materials are urgently demanded to address EM radiation pollution. Efficient design to utilize the shields' microstructures is crucial yet remains highly challenging for maximum EMI shielding effectiveness (SE) while minimizing material consumption. Herein, novel cellular membranes are designed based on a facile polydopamine-assisted metal (copper or silver) deposition on electrospun polymer nanofibers. The membranes can efficiently exploit the high-conjunction cellular structures of metal and polymer nanofibers, and their interactions for excellent electrical conductivity, mechanical flexibility, and ultrahigh EMI shielding performance. EMI SE reaches more than 53 dB in an ultra-broadband frequency range at a membrane thickness of merely 2.5 µm and a density of 1.6 g cm-3 , and an SE of 44.7 dB is accomplished at the lowest thickness of 1.2 µm. The normalized specific SE is up to 232 860 dB cm2 g-1 , significantly surpassing that of other shielding materials ever reported. More, integrated functionalities are discovered in the membrane, such as antibacterial, waterproof properties, excellent air permeability, high resistance to mechanical deformations and low-voltage uniform heating performance, offering strong potential for applications in aerospace and portable and wearable smart electronics.
Abstract: Electrocatalytic N2 reduction reaction (NRR) represents a sustainable and promising technology for producing NH3 at ambient conditions. Herein, we demonstrated that Mo-doping could change the MnO2 from an inert material into one that can efficiently and robustly catalyze NRR in neutral media. The developed Mo-doped MnO2 nanoflowers (Mo-MnO2 NFs) exhibited a significantly enhanced NRR performance with an NH3 yield of 36.6 μg h−1 mg−1 (-0.5 V) and an FE of 12.1 % (-0.4 V), far outperforming undoped MnO2 NFs and comparing favorably to most reported NRR catalysts. Density functional theory calculations revealed the electron-deficient character of Mo dopants that delivered multi-functions for NRR enhancement: (1) inducing a defect level to promote the conductivity of MnO2, (2) serving as the key NRR active sites, (3) activating the inert Mn sites for enhancing the intrinsic NRR activity of MnO2, (4) retarding the binding of Lewis acid H+ to suppress the hydrogen evolution reaction.
TL;DR: In this paper, a genetic algorithm was used to select the ML model and materials descriptors from a huge number of alternatives and demonstrated its efficiency on two phase formation problems in high entropy alloys (HEAs).
TL;DR: In this paper, an electric-field manipulation of skyrmions in a nanostructured ferromagnetic/ferroelectrical heterostructure at room temperature via an inverse magneto-mechanical effect was realized.
Abstract: Electrical manipulation of skyrmions attracts considerable attention for its rich physics and promising applications. To date, such a manipulation is realized mainly via spin-polarized current based on spin-transfer torque or spin–orbital torque effect. However, this scheme is energy consuming and may produce massive Joule heating. To reduce energy dissipation and risk of heightened temperatures of skyrmion-based devices, an effective solution is to use electric field instead of current as stimulus. Here, we realize an electric-field manipulation of skyrmions in a nanostructured ferromagnetic/ferroelectrical heterostructure at room temperature via an inverse magneto-mechanical effect. Intriguingly, such a manipulation is non-volatile and exhibits a multistate feature. Numerical simulations indicate that the electric-field manipulation of skyrmions originates from strain-mediated modification of effective magnetic anisotropy and Dzyaloshinskii–Moriya interaction. Our results open a direction for constructing low-energy-dissipation, non-volatile, and multistate skyrmion-based spintronic devices. Spin-polarized current manipulation of magnetic skyrmions is energy consuming. Here, the authors achieve an electric-field manipulation of individual skyrmions in a nanostructured ferromagnetic/ferroelectrical heterostructure at room temperature via an inverse magneto-mechanical effect.
TL;DR: In this article, an integrated review aims to sum up recent advances in current studies on fabrication of high efficiency BiaAOb photocatalysts to accelerate the developments of BiVO4, Bi2WO6, and Bi2MoO6 based materials in the photocatalysis field.
TL;DR: In this paper, two p-n junctions with different coupling facets of BiOI, denoted as B001/CN2 and B110/CN002+, were constructed by a simple precipitation method.
Abstract: Heterojunction photocatalyst fabrication benefits the improvement of photocatalytic activity. However, the influence of different coupling facets receives less attention. Herein, two p-n junctions with different coupling facets of BiOI, denoted as B001/CN002 and B110/CN002+, were constructed by a simple precipitation method. In B001/CN002, BiOI nanosheets parallel combined with g-C3N4 with the {001} facet of BiOI and (002) plane of g-C3N4. After being treated by CTAB, the (002) plane of g-C3N4 shows positive charge (g-C3N4+), and the BiOI nanosheets were vertically assembled onto g-C3N4+. The results of photodegradation on multiform industrial contaminants and antibiotic revealed that B001/CN002 shows much higher photoactivity than g-C3N4, g-C3N4+, BiOI and B110/CN002+. The substantially facilitated charge separation and transfer at the interface of B001/CN002 promote the generation of 1O2 and O2−, accounting for the excellent photocatalytic activity. The study may provide a new perspective on designing heterostructured photocatalytic materials via facet-charge-induced interfacial engineering strategy.
TL;DR: In this article, BaTiO3 (BT)-based lead-free ceramics are regarded as one kind of prospective candidates for next generation pulsed power capacitors due to their environmentally friendly and relatively high energy storage properties.
TL;DR: In this article, the relationship between structural attributes and photo-physical phenomena for broad-band emissions of metal halide perovskites (MHPs) has been reviewed from the perspective of both fundamental science and practical application.
Abstract: Metal halide perovskites (MHPs) are in a blossoming status where their inherent optoelectronic properties are being revisited from the perspective of both fundamental science and practical application. In an attempt to boost the manipulating photoluminescence performance of MHPs, it is timely and vital to review the relation between structural attributes and the photo-physical phenomena for their unique broad-band emissions. In this review, we highlight the luminescent mechanisms of MHPs from dopants, self-trapped excitons (STEs) and defects, and some progresses with an emphasis on how multi-color broad-band emitters can be designed in various classes of MHPs frameworks. We also summarize the integration of MHPs into optoelectronic devices including light-emitting diodes, X-ray scintillators, fluorescence sensors and thermometers. This review aims to provide an in-depth insights into the structure-luminescence relationships from mechanism, materials, and applications, and further pave a way to discuss the current challenges and future promising prospects in MHPs.
TL;DR: It is proved that all states of the closed-loop system are semiglobally uniformly ultimately bounded (SGUUB) by utilizing the Lyapunov stability principles.
Abstract: In this article, an admittance-based controller for physical human–robot interaction (pHRI) is presented to perform the coordinated operation in the constrained task space. An admittance model and a soft saturation function are employed to generate a differentiable reference trajectory to ensure that the end-effector motion of the manipulator complies with the human operation and avoids collision with surroundings. Then, an adaptive neural network (NN) controller involving integral barrier Lyapunov function (IBLF) is designed to deal with tracking issues. Meanwhile, the controller can guarantee the end-effector of the manipulator limited in the constrained task space. A learning method based on the radial basis function NN (RBFNN) is involved in controller design to compensate for the dynamic uncertainties and improve tracking performance. The IBLF method is provided to prevent violations of the constrained task space. We prove that all states of the closed-loop system are semiglobally uniformly ultimately bounded (SGUUB) by utilizing the Lyapunov stability principles. At last, the effectiveness of the proposed algorithm is verified on a Baxter robot experiment platform. Note to Practitioners —This work is motivated by the neglect of safety in existing controller design in physical human–robot interaction (pHRI), which exists in industry and services, such as assembly and medical care. It is considerably required in the controller design for rigorously handling constraints. Therefore, in this article, we propose a novel admittance-based human–robot interaction controller. The developed controller has the following functionalities: 1) ensuring reference trajectory remaining in the constrained task space: a differentiable reference trajectory is shaped by the desired admittance model and a soft saturation function; 2) solving uncertainties of robotic dynamics: a learning approach based on radial basis function neural network (RBFNN) is involved in controller design; and 3) ensuring the end-effector of the manipulator remaining in the constrained task space: different from other barrier Lyapunov function (BLF), integral BLF (IBLF) is proposed to constrain system output directly rather than tracking error, which may be more convenient for controller designers. The controller can be potentially applied in many areas. First, it can be used in the rehabilitation robot to avoid injuring the patient by limiting the motion. Second, it can ensure the end-effector of the industrial manipulator in a prescribed task region. In some industrial tasks, dangerous or damageable tools are mounted on the end-effector, and it will hurt humans and bring damage to the robot when the end-effector is out of the prescribed task region. Third, it may bring a new idea to the designed controller for avoiding collisions in pHRI when collisions occur in the prescribed trajectory of end-effector.
TL;DR: In this article, the authors established relationships between rare-earth ions doping and intrinsic emission of lead-free double perovskite Cs2 AgInCl6 NCs to impart and tune the optical performances in the visible light region.
Abstract: The incorporation of impurity ions or doping is a promising method for controlling the electronic and optical properties and the structural stability of halide perovskite nanocrystals (NCs). Herein, we establish relationships between rare-earth ions doping and intrinsic emission of lead-free double perovskite Cs2 AgInCl6 NCs to impart and tune the optical performances in the visible light region. Tb3+ ions were incorporated into Cs2 AgInCl6 NCs and occupied In3+ sites as verified by both crystallographic analyses and first-principles calculations. Trace amounts of Bi doping endowed the characteristic emission (5 D4 →7 F6-3 ) of Tb3+ ions with a new excitation peak at 368 nm rather than the single characteristic excitation at 290 nm of Tb3+ . By controlling Tb3+ ions concentration, the emission colors of Bi-doped Cs2 Ag(In1-x Tbx )Cl6 NCs could be continuously tuned from green to orange, through the efficient energy-transfer channel from self-trapped excitons to Tb3+ ions. Our study provides the salient features of the material design of lead-free perovskite NCs and to expand their luminescence applications.
TL;DR: Control experiments and theoretical calculations demonstrate that the superior ORR catalytic performance of Cu1-SA/NC(meso)-7 catalyst is attributed to the atomically dispersed Cu1+ sites in catalyzing the reaction and the advantage of the introduced mesoporous structure in enhancing the mass transport.
Abstract: Herein, we report efficient single copper atom catalysts that consist of dense atomic Cu sites dispersed on a three-dimensional carbon matrix with highly enhanced mesoporous structures and improved...
TL;DR: This brief addresses the fixed-time event/self-triggered leader–follower consensus problems for networked multi-agent systems subject to nonlinear dynamics and proposes two new self-Triggered control strategies to avoid continuous triggering condition monitoring.
Abstract: This brief addresses the fixed-time event/self-triggered leader–follower consensus problems for networked multi-agent systems subject to nonlinear dynamics. First, we present an event-triggered control strategy to achieve the fixed-time consensus, and a new measurement error is designed to avoid Zeno behavior. Then, two new self-triggered control strategies are presented to avoid continuous triggering condition monitoring. Moreover, under the proposed self-triggered control strategies, a strictly positive minimal triggering interval of each follower is given to exclude Zeno behavior. Compared with the existing fixed-time event-triggered results, we propose two new self-triggered control strategies, and the nonlinear term is more general. Finally, the performances of the consensus tracking algorithms are illustrated by a simulation example.