摘要 ：

In this paper, the decentralised tracking control (DTC) problem is investigated for a class of continuous-time large-scale systems with external disturbance by utilising adaptive dynamic programming (ADP). Firstly, the DTC problem is solved by designing corresponding optimal controllers of the isolated subsystems, which are formulated with N augmented subsystems consisting of the tracking error and the reference trajectory. Then, considering the external disturbance, we can effectively construct the DTC scheme by means of adding suitable feedback gains to the optimal control strategies associated with each augmented tracking isolated subsystems (ATISs). Due to the approximate nature, a series of critic neural networks are constructed to solve the Hamilton-Jacobi-Isaacs equation, so as to derive the estimation of the Nash equilibrium solution containing the optimal control strategy and the worst disturbance law. Herein, a modified weight updating criterion is developed by employing a stabilising term. Consequently, we remove the requirement of initial admissible control in the proposed algorithm. After that, stability analysis of the ATIS is performed through the Lyapunov theory, in the sense that tracking states and weight approximation errors are uniformly ultimately bounded. Finally, an experimental simulation is demonstrated to ensure the validity of the proposed DTC scheme.

关键词 ：

optimal control Adaptive dynamic programming (ADP) interconnected systems disturbance rejection decentralised tracking control (DTC) neural networks

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Case history investigations have shown that pile foundations are more critically damaged in liquefiable soils than non-liquefiable soils. This study examines the differences in seismic response of pile foundations in liquefiable and non-liquefiable soils and their sensitivity to numerical model parameters. A two-dimensional finite element (FE) model is developed to simulate the experiment of a single pile foundation centrifuge in liquefiable soil subjected to earthquake motions and is validated against real-world test results. The differences in soil-pile seismic response of liquefiable and non-liquefiable soils are explored. Specifically, the first-order second-moment method (FOSM) is used for sensitivity analysis of the seismic response. The results show significant differences in seismic response for a soil-pile system between liquefiable and non-liquefiable soil. The seismic responses are found to be significantly larger in liquefiable soil than in non-liquefiable soil. Moreover, the pile bending moment was mainly affected by the kinematic effect in liquefiable soil, while the inertial effect was more significant in non-liquefiable soil. The controlling parameters of seismic response were PGA, soil density, and friction angle in liquefiable soil, while the pile bending moment was mainly controlled by PGA, the friction angle of soil, and shear modulus of loose sand in non-liquefiable soil.

关键词 ：

pile foundation seismic response liquefiable sensitivity analysis non-liquefiable finite element analysis

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Multisource localization occupies an important position in the field of acoustic signal processing and is widely applied in scenarios, such as human-machine interaction and spatial acoustic parameter acquisition. The direction-of-arrival (DOA) of a sound source is convenient to render spatial sound in the audio metaverse. A multisource localization method in a reverberation environment is proposed based on the angle distribution of time-frequency (TF) points using a first-order ambisonics (FOA) microphone. The method is implemented in three steps. 1) By exploring the angle distribution of TF points, a single-source zone (SSZ) detection method is proposed by using a standard deviation-based measure, which reveals the degree of convergence of TF point angles in a zone. 2) To reduce the effect of outliers on localization, an outlier removal method is designed to remove the TF points whose angles are far from the real DOAs, where the median angle of each detected zone is adopted to construct the outlier set. 3) DOA estimates of multiple sources are obtained by postprocessing of the angle histogram. Experimental results in both the simulated and real scenarios verify the effectiveness of the proposed method in a reverberation environment, which also show that the proposed method outperforms reference methods.

关键词 ：

speech processing signal processing

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In this letter, we focus on the relationship between modification bioparticle density (N) and biological regulation ability in extended gate HEMT (EG-HEMT) biosensors. By analyzing, we demonstrate that under the same gate electrodes size (S (g)) and concentration, N is exponentially related to the area of sensing regions (y) and has fixed exponential magnification -0.65 +/- 0.05. This formula had been demonstrated to have perfect universality when testing protein and small molecules. Finally, we apply N to the structural design of EG-HEMT biosensors and projected that 10 y structure has both high biological regulation ability of biosensors and efficient utility of chips.

关键词 ：

biological detection extended gate HEMT biosensor bioparticle density

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The rapid development of neuromorphic computing has stimulated extensive research interest in artificial synapses. Optoelectronic artificial synapses using laser beams as stimulus signals have the advantages of broadband, fast response, and low crosstalk. However, the optoelectronic synapses usually exhibit short memory duration due to the low lifetime of the photo-generated carriers. It greatly limits the mimicking of human perceptual learning, which is a common phenomenon in sensory interactions with the environment and practices of specific sensory tasks. Herein, a heterostructure optoelectronic synapse based on graphene nanowalls and CsPbBr3 quantum dots was fabricated. The graphene/CsPbBr3 heterojunction and the natural middle energy band in graphene nanowalls extend the carrier lifetime. Therefore, a long half-life period of photocurrent decay - 35.59 s has been achieved. Moreover, the long-term optoelectronic response can be controlled by the adjustment of numbers, powers, wavelengths, and frequencies of the laser pulses. Next, an artificial neural network consisting of a 28 x 28 synaptic array was established. It can be used to mimic a typical characteristic of human perceptual learning that the ability of sensory systems is enhanced through a learning experience. The learning behavior of image recognition can be tuned based on the photocurrent response control. The accuracy of image recognition keeps above 80% even under a low-frequency learning process. We also verify that less time is required to regain the lost sensory ability that has been previously learned. This approach paves the way toward high-performance intelligent devices with controllable learning of visual perception.

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High slope efficiency 3 mu m laser output exceeding Stokes limit is demonstrated in Er:YAG crystals with lower doping concentration at room temperature. Based on cyclic cascaded cavity, several parameters affecting slope efficiency are optimized. Under the optimized configuration, slope efficiencies up to 36.5% and 37.2%, exceeding the Stokes efficiency of 33%, are achieved in 10at.% and 25at.% Er:YAG crystals, respectively. The realization of high slope efficiency paves the way for improving the average power of 3 mu m lasers.

关键词 ：

Er Cyclic cascade YAG crystals Mid -infrared lasers

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In this paper, a modified Leslie-type predator-prey model with simplified Holling type IV functional response is established, in which double Allee effect on prey and nonlinear prey harvesting are considered. The analysis of the model shows that there exists a Bogdanov-Takens singularity (focus case) of codimension 4, and also multiple other nonhyperbolic and degenerate equilibria. Bifurcations are explored and it is found that transcritical bifurcation, saddle-node bifurcation, Bogdanov-Takens bifurcation of codimension 2, degenerate cusp type Bogdanov-Takens bifurcation of codimension 3, and degenerate focus type Bogdanov-Takens bifurcation of codimension 4 occur as parameters vary. The bifurcations result in complex dynamic behaviors, such as double limit cycle, triple limit cycle, quadruple limit cycle, cuspidal loop, (multiple) homoclinic loop, saddle-node loop, and limit cycle(s) simultaneously with homoclinic loop. We run numerical simulations to verify the theoretical results, and it is found that the system admits bistability, tristability, or even tetrastability.(c) 2022 International Association for Mathematics and Computers in Simulation (IMACS). Published by Elsevier B.V. All rights reserved.

关键词 ：

Predator-prey model Degenerate focus type Bogdanov-Takens bifurcation of codimension 4 Nonlinear harvesting Double Allee effect

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Zeolitic imidazolate framework (ZIF) membranes have great potential applications in nanofiltration. However, preparing continuous and intact ZIF membranes on the surface of a substrate remains challenging. In this study, we assembled ZIF-8 nanoparticles in situ in the pores of a porous alumina substrate via a freezing-assisted counter-diffusion method. Although a continuous ZIF-8 membrane was not formed on the surface of the sub-strate, the obtained nano-confined composite membrane was dense enough to separate antibiotics and salt. The rejection rate of tetracycline was above 99 %, while that of sodium chloride was below 20 %, demonstrating good antibiotic desalination performance. The permeance of the ZIF-8 membrane reached 23.5 LMH/bar. Due to the nano-confined structure, the obtained ZIF-8 composite membrane was robust. Besides, polishing the surface layer did not reduce the separation performance. Moreover, sulfurizing the ZIF-8 membrane improved its sta-bility in water. It also improved the permeance to 31.3 LMH/bar, which remained stable for 100 h. Therefore, the obtained robust ZIF-8 membrane and its derivative composite membrane fabricated via freezing-assisted counter-diffusion have great potential in antibiotic desalination.

关键词 ：

ZnS membrane ZIF-8 membrane Counter-diffusion Freezing assistance Antibiotic desalination

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Beijing has experienced rapid economic development since the reforms and opening up. However, the traditional development model based on excessive energy consumption has posed great challenges to the ecological environment. To curb environmental degradation and achieve sustainable social development, Beijing has proposed to achieve carbon neutrality by 2050. As an important indicator of energy consumption, it is necessary to clarify how energy intensity (EI) affects carbon emissions (CE) to achieve carbon neutrality in Beijing by 2050. This study first decomposes the drivers of CE in Beijing from 2010 to 2020 using the logarithmic mean Divisia index (LMDI) method and comparatively analyses the impact of EI on CE. Then, the spatial Dubin model (SDM) is used to analyse the spatial spillover effect of EI on CE at the regional level. Finally, the macro moderating role of economic development in the effect of EI on CE is analysed. The results show that the effect of EI has been the main driver of CE reduction in Beijing. Among the industrial sectors, manufacturing and transportation have had the greatest success in reducing CE through EI reduction. At the regional level, there is a spatial spillover effect of EI on CE, and the effect of carbon reduction through the spillover effect of EI is greater than the direct effect of EI. Economic factors have an enhanced moderating effect on the process of EI affecting CE, and this moderating effect has threshold properties.

关键词 ：

spatial spill over effect energy intensity Beijing LMDI carbon emissions

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Due to the remarkable influence of aggregate characteristics on the mechanical behaviors of concrete materials, and in particular the microcracking development, complex aggregates shapes instead of widely used spherical -shape need to be considered in advanced numerical approaches. Apart from that, in numerical simulations, an extra consideration of the influences of concrete's heterogeneity on its softening behaviors is strongly recommended by the scientific community. In this context, the softening behaviors of concrete materials undergoing heterogeneous expansion in the aggregates due to fast neutron radiation were investigated in the present paper, and the influences of both aggregate shape and the heterogeneity of aggregate expansion were considered. According to the real shapes of aggregates, polygon-shaped aggregates with random orientation were placed into a 3D numerical concrete specimen, and a two-stage finite element (FE) approach allowing a coupled thermal-mechanical analysis was proposed. In the first stage, the temperature field evolves in time and the 3D concrete specimen was estimated. In the second stage, the temperature-and neutron fluence-dependent heterogeneous expansion in the aggregates was calculated and introduced into the 3D mesoscopic model, and the development of microcracks in the concrete, the resulting mechanical responses, the loss in mechanical properties of the radiation-induced concrete was evaluated. Surmounting the limitations due to the spherical-shape of aggregate and the homogeneous assumption of the aggregate expansion in the concrete, the present paper developed a new methodology in which the combined effects of aggregate's shape and the heterogeneous distribution of aggregate expansion on the mechanical properties of radiation-induced concrete were considered, permitting evaluating the changes in the dimensional and mechanical properties of radiation -induced concrete. The proposed model provides a reference to assess the long-term durability and the structural integrity of nuclear power plants.

关键词 ：

Residual mechanical properties Concrete material 3D mesoscale numerical model Fast neutron Radiation-induced volumetric expansion

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