Nanoporous BiVO;thin films were deposited using reactive magnetron sputtering in Ar and O;atmosphere, on various substrates, employing pulsed direct-current(DC) power supplies applied to metallic Bi and V targets for ...Nanoporous BiVO;thin films were deposited using reactive magnetron sputtering in Ar and O;atmosphere, on various substrates, employing pulsed direct-current(DC) power supplies applied to metallic Bi and V targets for rapid deposition. The procedure was followed by a post-annealing treatment in air to crystallize the photoactive monoclinic scheelite structure. The influence of total pressure and substrate on the crystal structure, morphology, microstructure, optical and photocatalytic properties of the films was investigated. The crystallization of monoclinic scheelite structure deposited on fused silica substrate starts at 250 ℃ and the films are stable up to 600 ℃. The morphology of the films is rather dense, despite at the high sputtering pressure(>2 Pa), with embedded nanopores. Among the thin films deposited on fused silica, the one deposited at 4.5 Pa exhibits the highest porosity(52%), with the lowest bandgap(2.44 eV) and it shows the highest photocatalytic activity in the degradation of Rhodamine-B(26% after 7 h) under visible light irradiation. The film deposited on the silicon substrate exhibits the highest photoactivity(53% after 7 h). Lack of hypsochromic shift in the UV-Vis temporal absorption spectra shows the dominance of the chromophore cleavage pathway in the photodecomposition.展开更多
The characterization of finite length Surface Acoustic Wave (SAW) and Bulk acoustic Wave (BAW) resonators is addressed here. The Finite Element Analysis (FEA) induces artificial wave reflections at the edges of the me...The characterization of finite length Surface Acoustic Wave (SAW) and Bulk acoustic Wave (BAW) resonators is addressed here. The Finite Element Analysis (FEA) induces artificial wave reflections at the edges of the mesh. In fact, these ones do not contribute in practice to the corresponding experimental response. The Perfectly Matched Layer (PML) method, allows to suppress the boundary reflections. In this work, we first demonstrate the basis of PML adapted to FEA formalism. Next, the results of such a method are depicted allowing a discussion on the behavior of finite acoustic resonators.展开更多
Infrared camouflage based on artificial thermal metasurfaces has recently attracted significant attention.By eliminating thermal radiation differences between the object and the background,it is possible to hide a giv...Infrared camouflage based on artificial thermal metasurfaces has recently attracted significant attention.By eliminating thermal radiation differences between the object and the background,it is possible to hide a given object from infrared detection.Infrared camouflage is an important element that increases the survivability of aircraft and missiles,by reducing target susceptibility to infrared guided threats.Herein,a simple and practicable design is theoretically presented based on a multilayer film for infrared stealth,with distinctive advantages of scalability,flexible fabrication,and structural simplicity.The multilayer medium consists of silicon substrate,carbon layer and zinc sulfide film,the optical properties of which are determined by transfer matrix method.By locally changing the thickness of the coating film,the spatial tunability and continuity in thermal emission are demonstrated.A continuous change of emissive power is further obtained and consequently implemented to achieve thermal camouflage functionality.In addition,other functionalities,like thermal illusion and thermal coding,are demonstrated by thickness-engineered multilayer films.展开更多
We propose in this paper the design of artificial nanostructure chirality obtained by oblique illumination. This structure is based on anisotropic metamaterial having an optical activity induced by the special geometr...We propose in this paper the design of artificial nanostructure chirality obtained by oblique illumination. This structure is based on anisotropic metamaterial having an optical activity induced by the special geometry of the pattern and the incident beam. Starting from a non-chiral material, the artificial chirality is obtained thanks to the rectangular apertures which form the periodic perfect metal nanostructure （one layer） and the oblique incidence of the light beam. An extraordinary light transmission （93%） through the metal nanostructure is achieved by exciting the cavity modes. The extrinsic chirality obtained can be granted to the desired value by appropriately adjusting the geometric parameters and the angle of incidence.展开更多
Proton Exchange Membrane(PEM)electrolysis stands as a cornerstone technology in the clean energy sector,driving the production of hydrogen and oxygen from water.A critical aspect of ensuring the efficiency and safety ...Proton Exchange Membrane(PEM)electrolysis stands as a cornerstone technology in the clean energy sector,driving the production of hydrogen and oxygen from water.A critical aspect of ensuring the efficiency and safety of this process lies in the precise monitoring and control of temperature at the electrolysis outlet.However,accurately characterizing temperature changes within the PEM electrolysis system can be challenging due to the fluctuation of renewable energies.This study introduces an approach integrating data with fundamental physics principles known as Physics-Informed Neural Networks(PINNs).This method solves differential equations and estimates the unknown parameters governing the temperature dynamics within the PEM electrolysis system.We consider two distinct scenarios:a zero-dimensional model and a one-dimensional model.The results demonstrate the PINN’s proficiency in accurately identifying the parameters and solving for temperature fluctuations within the system with different input conditions.Furthermore,we compare the PINN with the Long Short-Term Memory(LSTM)method to predict the outlet temperature of the electrolysis.The PINN outperformed the LSTM method,highlighting its reliability and precision,achieving a Mean Squared Error(MSE)of 0.1596 compared to 1.2132 for LSTM models.The proposed method shows a high performance in dealing with sensor noises and avoids overfitting problems.This synergy of physics knowledge and data-driven learning opens new pathways towards real-time digital twins,enhanced predictive control,and improved reliability for PEM electrolysis and other complex,data-scarce energy systems.展开更多
In this paper,a set of distributed secondary controllers is introduced that provide active regulation for both steady-state and transient-state performances of an islanded DC microgrid(MG).The secondary control for di...In this paper,a set of distributed secondary controllers is introduced that provide active regulation for both steady-state and transient-state performances of an islanded DC microgrid(MG).The secondary control for distributed converter interfaced generation(DCIG)not only guarantees that the system converges to the desired operating states in the steady state but also regulates the state variations to a prescribed transient-state performance.Compared with state-of-the-art techniques of distributed secondary control,this paper achieves accurate steady-state secondary regulations with prescribed transient-state performance in an islanded DC MG.Moreover,the applicability of the proposed control does not rely on any explicit knowledge of the system topology or physical parameters.Detailed controller designs are provided,and the system under control is proved to be Lyapunov stable using large-signal stability analysis.The steady-state and transient-state performances of the system are analyzed.The paper proves that as the perturbed system converges,the proposed control achieves accurate proportional power sharing and average voltage regulation among the DCIGs,and the transient variations of the operating voltages and power outputs at each DCIG are regulated to the prescribed transient-state performance.The effectiveness of the proposed control is validated via a four-DCIG MG system.展开更多
Impedance metasurfaces enable accurate regulation of acoustic fields.However,they can hardly supply a flexible response as such perfect operation is accompanied by stringent requirements on the design of unit cells.Ac...Impedance metasurfaces enable accurate regulation of acoustic fields.However,they can hardly supply a flexible response as such perfect operation is accompanied by stringent requirements on the design of unit cells.Actually,an arbitrary lossless and passive target impedance matrix requires the tuning of 3 independent real parameters.The set composed of a reflection phase,a transmission amplitude,and a transmission phase,enables the representation of an arbitrary impedance matrix,possibly possessing singular elements.In this paper,a mechanism of phase-amplitude-phase modulation(PAP modulation)is developed for the generic design of the unit cells of acoustic impedance metasurfaces.Adjustable acoustic impedance metasurfaces are further available under this framework.An impedance unit with 3 mobile parts is designed based on this idea.The assembled metasurface can handle different incidences for acoustic field manipulation at a given frequency.Beam steering and beam splitting are considered as demonstration examples and are verified by numerical simulation and experiment.PAP modulation enriches the design of acoustic impedance metasurfaces and extends the range of application of impedance theory.展开更多
With the growing global energy demand and the pursuit of sustainable energy,solar energy has received widespread attention as a clean and renewable energy source.A structural design of an inflatable,large-scale solar ...With the growing global energy demand and the pursuit of sustainable energy,solar energy has received widespread attention as a clean and renewable energy source.A structural design of an inflatable,large-scale solar concentrating reflector based on in-orbit assembly is proposed in this paper.The axisymmetric inflated reflector surface is inversely designed through membrane mechanics,and the internal pressures to maintain the reflector surface morphology at different orbital positions and the tiny deformation produced by the reflecting surface under the action of the uniform pressure are determined.A inflatable-rigidizable support structure is prepared by using a rigidizable aramid fabric-reinforced composite.The support structure used to the parabolic reflecting surface is designed,and the diameter and spacing distance of the resistance wire of the heating layer are determined by electrothermal simulation;the combination of solar radiation and electric heating is used to rigidize the reflector in orbit,and the corresponding electric heating time at different orbital positions is also analyzed by in orbit simulation.The heating voltage,folding radius and folding method of the rigidizable support structure are determined through the experimental design,and the folding and deployment experiments are carried out by using the heating and internal pressure and the final shape recovery rate of the support tube is approximately 100%,which verifies the feasibility of its folding and deployment.展开更多
As part of the 4th industrial revolution,programmable mechanical metamaterials exhibit great application potential in flexible robotics,vibration control,and impact protection.However,maintaining a programmed state wi...As part of the 4th industrial revolution,programmable mechanical metamaterials exhibit great application potential in flexible robotics,vibration control,and impact protection.However,maintaining a programmed state without sustaining the external stimulus is often challenging and leads to additional energy consumption.Inspired by Rubik’s cube,we design and study an in-situ programmable and distribution-reconfigurable mechanical metamaterial(IPDR-MM).A matrix model is developed to model IPDR-MMs and describe their morphological transitions.Based on this model,the reinforcement learning method is employed to find the pathways for morphological transitions.We find that IPDR-MMs have controllable stiffness across several orders of magnitude and a wide range of adjustable anisotropies through morphology transformation.Additionally,because of the independence of the directions of morphology transformation and bearing,IPDR-MMs exhibit good stability in bearing and can readily achieve high stiffness.The Rubik’s cube-inspired design concept is also instructive for other deformable structures and metamaterials,and the current version of the proposal should be sufficiently illustrative to attract and broaden interdisciplinary interests.展开更多
Existing research on fault diagnosis for polymer electrolyte membrane fuel cells(PEMFC)has advanced significantly,yet performance is hindered by variations in data distributions and the requirement for extensive fault...Existing research on fault diagnosis for polymer electrolyte membrane fuel cells(PEMFC)has advanced significantly,yet performance is hindered by variations in data distributions and the requirement for extensive fault data.In this study,a cross-domain adaptive health diagnosis method for PEMFC is proposed,integrating the digital twin model and transfer convolutional diagnosis model.A physical-based high-fidelity digital twin model is developed to obtain diverse and high-quality datasets for training diagnosis method.To extract long-term time series features from the data,a temporal convolutional network(TCN)is proposed as a pre-trained diagnosis model for the source domain,with feature extraction layers that can be reused to the transfer learning network.It is demonstrated that the proposed pre-trained model can hold the ability to accurately diagnose the various fuel cell faults,including pressure,drying,flow,and flooding faults,with 99.92%accuracy,through the effective capture of the long-term dependencies in time series data.Finally,a domain adaptive transfer convolutional network(DATCN)is established to improve the diagnosis accuracy across diverse fuel cells by learning domain-invariant features.The results show that the DATCN model,tested on three different target domain devices with adversarial training using only 10%normal data,can achieve an average accuracy of 98.5%(30%improved over traditional diagnosis models).This proposed method provides an effective solution for accurate cross-domain diagnosis of PEMFC devices,significantly reducing the reliance on extensive fault data.展开更多
A coordinated scheduling model based on two-stage distributionally robust optimization(TSDRO)is proposed for integrated energy systems(IESs)with electricity-hydrogen hybrid energy storage.The scheduling problem of the...A coordinated scheduling model based on two-stage distributionally robust optimization(TSDRO)is proposed for integrated energy systems(IESs)with electricity-hydrogen hybrid energy storage.The scheduling problem of the IES is divided into two stages in the TSDRO-based coordinated scheduling model.The first stage addresses the day-ahead optimal scheduling problem of the IES under deterministic forecasting information,while the sec-ond stage uses a distributionally robust optimization method to determine the intraday rescheduling problem under high-order uncertainties,building upon the results of the first stage.The scheduling model also considers col-laboration among the electricity,thermal,and gas networks,focusing on economic operation and carbon emissions.The flexibility of these networks and the energy gradient utilization of hydrogen units during operation are also incor-porated into the model.To improve computational efficiency,the nonlinear formulations in the TSDRO-based coordinated scheduling model are properly linearized to obtain a Mixed-Integer Linear Programming model.The Column-Constraint Generation(C&CG)algorithm is then employed to decompose the scheduling model into a mas-ter problem and subproblems.Through the iterative solution of the master problem and subproblems,an efficient analysis of the coordinated scheduling model is achieved.Finally,the effectiveness of the proposed TSDRO-based coordinated scheduling model is verified through case studies.The simulation results demonstrate that the proposed TSDRO-based coordinated scheduling model can effectively accomplish the optimal scheduling task while consider-ing the uncertainty and flexibility of the system.Compared with traditional methods,the proposed TSDRO-based coordinated scheduling model can better balance conservativeness and robustness.展开更多
Femtosecond pulses from an ultrafast mode-locked fiber laser can be optimized in real time by combining single-shot spectral measurements with a smart genetic algorithm to actively control and drive the intracavity dy...Femtosecond pulses from an ultrafast mode-locked fiber laser can be optimized in real time by combining single-shot spectral measurements with a smart genetic algorithm to actively control and drive the intracavity dynamics.展开更多
In this paper, we present an ultra-compact 1D photonic crystal(Ph C) Bragg grating design on a thin film lithium niobate slot waveguide(SWG) via 2D-and 3D-FDTD simulations. 2D-FDTD simulations are employed to tune the...In this paper, we present an ultra-compact 1D photonic crystal(Ph C) Bragg grating design on a thin film lithium niobate slot waveguide(SWG) via 2D-and 3D-FDTD simulations. 2D-FDTD simulations are employed to tune the photonic bandgap(PBG) size, PBG center, cavity resonance wavelength, and the whole size of Ph C. 3DFDTD simulations are carried out to model the real structure by varying different geometrical parameters such as SWG height and Ph C size. A moderate resonance quality factor Q of about 300 is achieved with a Ph C size of only 0.5 μm× 0.7 μm× 6 μm. The proposed slot Bragg grating structure is then exploited as an electric field(E-field) sensor. The sensitivity is analyzed by 3D-FDTD simulations with a minimum detectable E-field as small as 23 m V∕m. The possible fabrication process of the proposed structure is also discussed. The compact size of the proposed slot Bragg grating structure may have applications in on-chip E-field sensing, optical filtering, etc.展开更多
The Year 2020 represents 60 years since the first successful operation of the laser.This anniversary provides an ideal occasion to reflect on the myriad ways that lasers have revolutionized society,and to consider the...The Year 2020 represents 60 years since the first successful operation of the laser.This anniversary provides an ideal occasion to reflect on the myriad ways that lasers have revolutionized society,and to consider the many new areas of research that continue to drive photonics in unexpected directions.Yet at the same time as we consider these exciting future perspectives,it is also interesting to see how the development of the laser traces a path that intertwines basic and applied science,and intersects with the recognition of many of the pioneers of optics through the Nobel Prize.Of course,an exhaustive history of such a rich topic cannot be given in a short Perspective,but it is perhaps possible to describe some of the key highlights.展开更多
In the paper,a novel self-learning energy management strategy(EMS)is proposed for fuel cell hybrid electric vehicles(FCHEV)to achieve the hydrogen saving and maintain the battery operation.In the EMS,it is proposed to...In the paper,a novel self-learning energy management strategy(EMS)is proposed for fuel cell hybrid electric vehicles(FCHEV)to achieve the hydrogen saving and maintain the battery operation.In the EMS,it is proposed to approximate the EMS policy function with fuzzy inference system(FIS)and learn the policy parameters through policy gradient reinforcement learning(PGRL).Thus,a so-called Fuzzy REINFORCE algorithm is first proposed and studied for EMS problem in the paper.Fuzzy REINFORCE is a model-free method that the EMS agent can learn itself through interactions with environment,which makes it independent of model accuracy,prior knowledge,and expert experience.Meanwhile,to stabilize the training process,a fuzzy baseline function is adopted to approximate the value function based on FIS without affecting the policy gradient direction.More-over,the drawbacks of traditional reinforcement learning such as high computation burden,long convergence time,can also be overcome.The effectiveness of the proposed methods were verified by Hardware-in-Loop ex-periments.The adaptability of the proposed method to the changes of driving conditions and system states is also verified.展开更多
Acoustic wave resonators are promising candidates for gravimetric biosensing.However,they generally suffer from strong acoustic radiation in liquid,which limits their quality factor and increases their frequency noise...Acoustic wave resonators are promising candidates for gravimetric biosensing.However,they generally suffer from strong acoustic radiation in liquid,which limits their quality factor and increases their frequency noise.This article presents an acoustic radiation-free gravimetric biosensor based on a locally resonant surface phononic crystal(SPC)consisting of periodic high aspect ratio electrodes to address the above issue.The acoustic wave generated in the SPC is slower than the sound wave in water,hence it prevents acoustic propagation in the fluid and results in energy confinement near the electrode surface.This energy confinement results in a significant quality factor improvement and reduces frequency noise.The proposed SPC resonator is numerically studied by finite element analysis and experimentally implemented by an electroplating-based fabrication process.Experimental results show that the SPC resonator exhibits an in-liquid quality factor 15 times higher than a conventional Rayleigh wave resonator at a similar operating frequency.The proposed radiation suppression method using SPC can also be applied in other types of acoustic wave resonators.Thus,this method can serve as a general technique for boosting the in-liquid quality factor and sensing performance of many acoustic biosensors.展开更多
Strong nonlinear, electro-optical, and thermo-optical properties of lithium niobate(LN) have gained much attention. However, the implementation of LiNbO_3 in real devices is not a trivial task due to difficulties in m...Strong nonlinear, electro-optical, and thermo-optical properties of lithium niobate(LN) have gained much attention. However, the implementation of LiNbO_3 in real devices is not a trivial task due to difficulties in manufacturing and handling thin-film LN. In this study, we investigate an optical device where the Bloch surface wave(BSW) propagates on the thin-film LN to unlock its properties. First, access to the LN film from air(or open space) is important to exploit its properties. Second, for sustaining the BSW, one-dimensional photonic crystal(1DPhC) is necessary to be fabricated under the thin-film LN. We consider two material platforms to realize such a device: bulk LN and commercial thin-film LN. Clear reflectance dips observed in far-field measurements demonstrate the propagation of BSWs on top of the LN surface of the designed 1DPhCs.展开更多
In previous work, we have analyzed the feasibility of the estimation for a source term S（x, y, z） in a transversal section, The present study is concerned with a twodimensional inverse phase change problem. The goal...In previous work, we have analyzed the feasibility of the estimation for a source term S（x, y, z） in a transversal section, The present study is concerned with a twodimensional inverse phase change problem. The goal is the estimation of the dissipated heat flux in the liquid zone （reconstruction of a source term in the energy equation） from experimentally measured temperatures in the solid zone. This work has an application in the electron beam welding of steels of thickness about 8cm. The direct thermometallurgical problem is treated in a quasi steady two-dimensional longitudinal section （x, y）. The beam displacement is normally in the y direction. But in the quasi steady simulation, the beam is steady in the study section. The sample is divided in the axial direction z in few sections. At each section, a source term is defined with a part of the beam and creates a vaporized zone and a fused zone. The goal of this work is the rebuilding of the complete source term with the estimations at each section. In this paper, we analyze the feasibility of the estimation. For this work, we use only the simulated measurements without noise.展开更多
基金the supports of this study by the Iran National Science Foundation (No. 98001285)Pays de Montbéliard Agglomération (France) for the support of this work。
文摘Nanoporous BiVO;thin films were deposited using reactive magnetron sputtering in Ar and O;atmosphere, on various substrates, employing pulsed direct-current(DC) power supplies applied to metallic Bi and V targets for rapid deposition. The procedure was followed by a post-annealing treatment in air to crystallize the photoactive monoclinic scheelite structure. The influence of total pressure and substrate on the crystal structure, morphology, microstructure, optical and photocatalytic properties of the films was investigated. The crystallization of monoclinic scheelite structure deposited on fused silica substrate starts at 250 ℃ and the films are stable up to 600 ℃. The morphology of the films is rather dense, despite at the high sputtering pressure(>2 Pa), with embedded nanopores. Among the thin films deposited on fused silica, the one deposited at 4.5 Pa exhibits the highest porosity(52%), with the lowest bandgap(2.44 eV) and it shows the highest photocatalytic activity in the degradation of Rhodamine-B(26% after 7 h) under visible light irradiation. The film deposited on the silicon substrate exhibits the highest photoactivity(53% after 7 h). Lack of hypsochromic shift in the UV-Vis temporal absorption spectra shows the dominance of the chromophore cleavage pathway in the photodecomposition.
文摘The characterization of finite length Surface Acoustic Wave (SAW) and Bulk acoustic Wave (BAW) resonators is addressed here. The Finite Element Analysis (FEA) induces artificial wave reflections at the edges of the mesh. In fact, these ones do not contribute in practice to the corresponding experimental response. The Perfectly Matched Layer (PML) method, allows to suppress the boundary reflections. In this work, we first demonstrate the basis of PML adapted to FEA formalism. Next, the results of such a method are depicted allowing a discussion on the behavior of finite acoustic resonators.
基金supported by the EIPHI Graduate School(Grant No.ANR-17-EURE-0002)the U.S.National Science Foundation(Grant Nos.DMR-1823800,CMMI-2131760 and CMMI-1930873).
基金support by the China Scholarship Council(CSC).This research has additionally been funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)under Germany’s Excellence Strategy via the Excellence Cluster“3D Matter Made to Order”(Grant No.EXC-2082/1-390761711)which has also been supported by the Carl Zeiss Foundation through the“Carl-Zeiss-Foundation-Focus@HEiKA”,by the State of Baden-Württemberg,and by the Karlsruhe Institute of Technology(KIT).We further acknowledge support by the Helmholtz program“Materials Systems Engineering”(MSE).Muamer Kadic is grateful for support by the EIPHI Graduate School(Grant No.ANR-17-EURE-0002)Changguo Wang is grateful for support by the National Natural Science Foundation of China(Grant No.12172102).
基金supported by the EIPHI Graduate School(No.ANR-17-EURE-0002)the French Investissements d’Avenir program,project ISITEBFC(No.ANR-15-IDEX-03)+1 种基金the National Natural Science Foundation of China(Nos.12172102,11872160 and 11732002)the support of the Alexander von Humboldt Foundation through the Feodor Lynen Fellowship。
文摘Infrared camouflage based on artificial thermal metasurfaces has recently attracted significant attention.By eliminating thermal radiation differences between the object and the background,it is possible to hide a given object from infrared detection.Infrared camouflage is an important element that increases the survivability of aircraft and missiles,by reducing target susceptibility to infrared guided threats.Herein,a simple and practicable design is theoretically presented based on a multilayer film for infrared stealth,with distinctive advantages of scalability,flexible fabrication,and structural simplicity.The multilayer medium consists of silicon substrate,carbon layer and zinc sulfide film,the optical properties of which are determined by transfer matrix method.By locally changing the thickness of the coating film,the spatial tunability and continuity in thermal emission are demonstrated.A continuous change of emissive power is further obtained and consequently implemented to achieve thermal camouflage functionality.In addition,other functionalities,like thermal illusion and thermal coding,are demonstrated by thickness-engineered multilayer films.
文摘We propose in this paper the design of artificial nanostructure chirality obtained by oblique illumination. This structure is based on anisotropic metamaterial having an optical activity induced by the special geometry of the pattern and the incident beam. Starting from a non-chiral material, the artificial chirality is obtained thanks to the rectangular apertures which form the periodic perfect metal nanostructure （one layer） and the oblique incidence of the light beam. An extraordinary light transmission （93%） through the metal nanostructure is achieved by exciting the cavity modes. The extrinsic chirality obtained can be granted to the desired value by appropriately adjusting the geometric parameters and the angle of incidence.
文摘Proton Exchange Membrane(PEM)electrolysis stands as a cornerstone technology in the clean energy sector,driving the production of hydrogen and oxygen from water.A critical aspect of ensuring the efficiency and safety of this process lies in the precise monitoring and control of temperature at the electrolysis outlet.However,accurately characterizing temperature changes within the PEM electrolysis system can be challenging due to the fluctuation of renewable energies.This study introduces an approach integrating data with fundamental physics principles known as Physics-Informed Neural Networks(PINNs).This method solves differential equations and estimates the unknown parameters governing the temperature dynamics within the PEM electrolysis system.We consider two distinct scenarios:a zero-dimensional model and a one-dimensional model.The results demonstrate the PINN’s proficiency in accurately identifying the parameters and solving for temperature fluctuations within the system with different input conditions.Furthermore,we compare the PINN with the Long Short-Term Memory(LSTM)method to predict the outlet temperature of the electrolysis.The PINN outperformed the LSTM method,highlighting its reliability and precision,achieving a Mean Squared Error(MSE)of 0.1596 compared to 1.2132 for LSTM models.The proposed method shows a high performance in dealing with sensor noises and avoids overfitting problems.This synergy of physics knowledge and data-driven learning opens new pathways towards real-time digital twins,enhanced predictive control,and improved reliability for PEM electrolysis and other complex,data-scarce energy systems.
基金supported in part by Fundamental Research Funds for the Central Universities,Northwestern Polytechnical University,and in part by Xianyang Key R&D Program(No.L2023-Z DYF-QYCX-012)。
文摘In this paper,a set of distributed secondary controllers is introduced that provide active regulation for both steady-state and transient-state performances of an islanded DC microgrid(MG).The secondary control for distributed converter interfaced generation(DCIG)not only guarantees that the system converges to the desired operating states in the steady state but also regulates the state variations to a prescribed transient-state performance.Compared with state-of-the-art techniques of distributed secondary control,this paper achieves accurate steady-state secondary regulations with prescribed transient-state performance in an islanded DC MG.Moreover,the applicability of the proposed control does not rely on any explicit knowledge of the system topology or physical parameters.Detailed controller designs are provided,and the system under control is proved to be Lyapunov stable using large-signal stability analysis.The steady-state and transient-state performances of the system are analyzed.The paper proves that as the perturbed system converges,the proposed control achieves accurate proportional power sharing and average voltage regulation among the DCIGs,and the transient variations of the operating voltages and power outputs at each DCIG are regulated to the prescribed transient-state performance.The effectiveness of the proposed control is validated via a four-DCIG MG system.
基金supported by the National Natural Science Foundation of China(grant numbers 12072223,12122207,12021002,and 11991032)the EIPHI Graduate School(grant number ANR-17-EURE-0002).
文摘Impedance metasurfaces enable accurate regulation of acoustic fields.However,they can hardly supply a flexible response as such perfect operation is accompanied by stringent requirements on the design of unit cells.Actually,an arbitrary lossless and passive target impedance matrix requires the tuning of 3 independent real parameters.The set composed of a reflection phase,a transmission amplitude,and a transmission phase,enables the representation of an arbitrary impedance matrix,possibly possessing singular elements.In this paper,a mechanism of phase-amplitude-phase modulation(PAP modulation)is developed for the generic design of the unit cells of acoustic impedance metasurfaces.Adjustable acoustic impedance metasurfaces are further available under this framework.An impedance unit with 3 mobile parts is designed based on this idea.The assembled metasurface can handle different incidences for acoustic field manipulation at a given frequency.Beam steering and beam splitting are considered as demonstration examples and are verified by numerical simulation and experiment.PAP modulation enriches the design of acoustic impedance metasurfaces and extends the range of application of impedance theory.
文摘With the growing global energy demand and the pursuit of sustainable energy,solar energy has received widespread attention as a clean and renewable energy source.A structural design of an inflatable,large-scale solar concentrating reflector based on in-orbit assembly is proposed in this paper.The axisymmetric inflated reflector surface is inversely designed through membrane mechanics,and the internal pressures to maintain the reflector surface morphology at different orbital positions and the tiny deformation produced by the reflecting surface under the action of the uniform pressure are determined.A inflatable-rigidizable support structure is prepared by using a rigidizable aramid fabric-reinforced composite.The support structure used to the parabolic reflecting surface is designed,and the diameter and spacing distance of the resistance wire of the heating layer are determined by electrothermal simulation;the combination of solar radiation and electric heating is used to rigidize the reflector in orbit,and the corresponding electric heating time at different orbital positions is also analyzed by in orbit simulation.The heating voltage,folding radius and folding method of the rigidizable support structure are determined through the experimental design,and the folding and deployment experiments are carried out by using the heating and internal pressure and the final shape recovery rate of the support tube is approximately 100%,which verifies the feasibility of its folding and deployment.
基金the support of the National Natural Science Foun-dation of China(Grant No.12202084)the the Fundamental Re-search Funds for the Central Universities(Grant No.2024CDJXY009)+8 种基金the support of the National Natural Science Foundation of China(Grant No.12372127)the Fundamental Research Funds for the Central Uni-versities(Grant No.2022CDJQY-004)Chongqing Natural Science Foundation(Grant Nos.CSTB2024NSCQ-JQX0028 and CSTB2023NSCQ-LZX0083)the support of the National Natural Science Foundation of China(Grant No.12202085)the China Postdoctoral Science Foundation Funded Project(Grant No.2022M720562)the Special Fund for Postdoctoral Research Project of Chongqing(Grant No.2021XM3022)the support of the National Natural Science Foundation of China(Grant No.12302190)the Science Foundation of the National Key Laboratory of Science and Technology on Advanced Composites in Spe-cial Environments(Grant No.JCKYS2023603C018)the support of the EIPHI Graduate School(Grant No.ANR-17-EURE-0002).
文摘As part of the 4th industrial revolution,programmable mechanical metamaterials exhibit great application potential in flexible robotics,vibration control,and impact protection.However,maintaining a programmed state without sustaining the external stimulus is often challenging and leads to additional energy consumption.Inspired by Rubik’s cube,we design and study an in-situ programmable and distribution-reconfigurable mechanical metamaterial(IPDR-MM).A matrix model is developed to model IPDR-MMs and describe their morphological transitions.Based on this model,the reinforcement learning method is employed to find the pathways for morphological transitions.We find that IPDR-MMs have controllable stiffness across several orders of magnitude and a wide range of adjustable anisotropies through morphology transformation.Additionally,because of the independence of the directions of morphology transformation and bearing,IPDR-MMs exhibit good stability in bearing and can readily achieve high stiffness.The Rubik’s cube-inspired design concept is also instructive for other deformable structures and metamaterials,and the current version of the proposal should be sufficiently illustrative to attract and broaden interdisciplinary interests.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFB4005800)National Natural Science Foundation of China(grant No.52241702).
文摘Existing research on fault diagnosis for polymer electrolyte membrane fuel cells(PEMFC)has advanced significantly,yet performance is hindered by variations in data distributions and the requirement for extensive fault data.In this study,a cross-domain adaptive health diagnosis method for PEMFC is proposed,integrating the digital twin model and transfer convolutional diagnosis model.A physical-based high-fidelity digital twin model is developed to obtain diverse and high-quality datasets for training diagnosis method.To extract long-term time series features from the data,a temporal convolutional network(TCN)is proposed as a pre-trained diagnosis model for the source domain,with feature extraction layers that can be reused to the transfer learning network.It is demonstrated that the proposed pre-trained model can hold the ability to accurately diagnose the various fuel cell faults,including pressure,drying,flow,and flooding faults,with 99.92%accuracy,through the effective capture of the long-term dependencies in time series data.Finally,a domain adaptive transfer convolutional network(DATCN)is established to improve the diagnosis accuracy across diverse fuel cells by learning domain-invariant features.The results show that the DATCN model,tested on three different target domain devices with adversarial training using only 10%normal data,can achieve an average accuracy of 98.5%(30%improved over traditional diagnosis models).This proposed method provides an effective solution for accurate cross-domain diagnosis of PEMFC devices,significantly reducing the reliance on extensive fault data.
基金supported in part by the National Natural Science Foundation(51977181,52077180)Natural Science Foundation of Sichuan Province(2022NSFSC0027)+2 种基金Fok Ying-Tong Education Foundation of China(171104)14th Five-year Major Science and Technology Research Project of CRRC(2021CXZ021-2)Key research and development project of China National Railway Group Co.,Ltd(N2022J016-B).
文摘A coordinated scheduling model based on two-stage distributionally robust optimization(TSDRO)is proposed for integrated energy systems(IESs)with electricity-hydrogen hybrid energy storage.The scheduling problem of the IES is divided into two stages in the TSDRO-based coordinated scheduling model.The first stage addresses the day-ahead optimal scheduling problem of the IES under deterministic forecasting information,while the sec-ond stage uses a distributionally robust optimization method to determine the intraday rescheduling problem under high-order uncertainties,building upon the results of the first stage.The scheduling model also considers col-laboration among the electricity,thermal,and gas networks,focusing on economic operation and carbon emissions.The flexibility of these networks and the energy gradient utilization of hydrogen units during operation are also incor-porated into the model.To improve computational efficiency,the nonlinear formulations in the TSDRO-based coordinated scheduling model are properly linearized to obtain a Mixed-Integer Linear Programming model.The Column-Constraint Generation(C&CG)algorithm is then employed to decompose the scheduling model into a mas-ter problem and subproblems.Through the iterative solution of the master problem and subproblems,an efficient analysis of the coordinated scheduling model is achieved.Finally,the effectiveness of the proposed TSDRO-based coordinated scheduling model is verified through case studies.The simulation results demonstrate that the proposed TSDRO-based coordinated scheduling model can effectively accomplish the optimal scheduling task while consider-ing the uncertainty and flexibility of the system.Compared with traditional methods,the proposed TSDRO-based coordinated scheduling model can better balance conservativeness and robustness.
文摘Femtosecond pulses from an ultrafast mode-locked fiber laser can be optimized in real time by combining single-shot spectral measurements with a smart genetic algorithm to actively control and drive the intracavity dynamics.
基金National Natural Science Foundation of China(NSFC)(61405075)Natural Science Foundation of Guangdong Province(2015A030306046)
文摘In this paper, we present an ultra-compact 1D photonic crystal(Ph C) Bragg grating design on a thin film lithium niobate slot waveguide(SWG) via 2D-and 3D-FDTD simulations. 2D-FDTD simulations are employed to tune the photonic bandgap(PBG) size, PBG center, cavity resonance wavelength, and the whole size of Ph C. 3DFDTD simulations are carried out to model the real structure by varying different geometrical parameters such as SWG height and Ph C size. A moderate resonance quality factor Q of about 300 is achieved with a Ph C size of only 0.5 μm× 0.7 μm× 6 μm. The proposed slot Bragg grating structure is then exploited as an electric field(E-field) sensor. The sensitivity is analyzed by 3D-FDTD simulations with a minimum detectable E-field as small as 23 m V∕m. The possible fabrication process of the proposed structure is also discussed. The compact size of the proposed slot Bragg grating structure may have applications in on-chip E-field sensing, optical filtering, etc.
文摘The Year 2020 represents 60 years since the first successful operation of the laser.This anniversary provides an ideal occasion to reflect on the myriad ways that lasers have revolutionized society,and to consider the many new areas of research that continue to drive photonics in unexpected directions.Yet at the same time as we consider these exciting future perspectives,it is also interesting to see how the development of the laser traces a path that intertwines basic and applied science,and intersects with the recognition of many of the pioneers of optics through the Nobel Prize.Of course,an exhaustive history of such a rich topic cannot be given in a short Perspective,but it is perhaps possible to describe some of the key highlights.
基金This work has been supported by the ANR DEAL(contract ANR-20-CE05-0016-01)This work has also been partially funded by Region Sud Provence-Alpes-Cote d’Azur via project AMULTI(2021_02918).
文摘In the paper,a novel self-learning energy management strategy(EMS)is proposed for fuel cell hybrid electric vehicles(FCHEV)to achieve the hydrogen saving and maintain the battery operation.In the EMS,it is proposed to approximate the EMS policy function with fuzzy inference system(FIS)and learn the policy parameters through policy gradient reinforcement learning(PGRL).Thus,a so-called Fuzzy REINFORCE algorithm is first proposed and studied for EMS problem in the paper.Fuzzy REINFORCE is a model-free method that the EMS agent can learn itself through interactions with environment,which makes it independent of model accuracy,prior knowledge,and expert experience.Meanwhile,to stabilize the training process,a fuzzy baseline function is adopted to approximate the value function based on FIS without affecting the policy gradient direction.More-over,the drawbacks of traditional reinforcement learning such as high computation burden,long convergence time,can also be overcome.The effectiveness of the proposed methods were verified by Hardware-in-Loop ex-periments.The adaptability of the proposed method to the changes of driving conditions and system states is also verified.
基金funded by NPRP grant no.NPRP10-0201-170315 from the Qatar National Research Fund(a member of Qatar Foundation)supported by the EIPHI Graduate School(contract“ANR-17-EURE-0002”)。
文摘Acoustic wave resonators are promising candidates for gravimetric biosensing.However,they generally suffer from strong acoustic radiation in liquid,which limits their quality factor and increases their frequency noise.This article presents an acoustic radiation-free gravimetric biosensor based on a locally resonant surface phononic crystal(SPC)consisting of periodic high aspect ratio electrodes to address the above issue.The acoustic wave generated in the SPC is slower than the sound wave in water,hence it prevents acoustic propagation in the fluid and results in energy confinement near the electrode surface.This energy confinement results in a significant quality factor improvement and reduces frequency noise.The proposed SPC resonator is numerically studied by finite element analysis and experimentally implemented by an electroplating-based fabrication process.Experimental results show that the SPC resonator exhibits an in-liquid quality factor 15 times higher than a conventional Rayleigh wave resonator at a similar operating frequency.The proposed radiation suppression method using SPC can also be applied in other types of acoustic wave resonators.Thus,this method can serve as a general technique for boosting the in-liquid quality factor and sensing performance of many acoustic biosensors.
基金Collgium SMYLE(SMart SYstems for a better LifE)Agence Nationale de la Recherche(ANR)ASTRID project Esencyal(ANR-13-ASTR-0019-01)+1 种基金French RENATECH NetworkFEMTO-ST Technological Facility
文摘Strong nonlinear, electro-optical, and thermo-optical properties of lithium niobate(LN) have gained much attention. However, the implementation of LiNbO_3 in real devices is not a trivial task due to difficulties in manufacturing and handling thin-film LN. In this study, we investigate an optical device where the Bloch surface wave(BSW) propagates on the thin-film LN to unlock its properties. First, access to the LN film from air(or open space) is important to exploit its properties. Second, for sustaining the BSW, one-dimensional photonic crystal(1DPhC) is necessary to be fabricated under the thin-film LN. We consider two material platforms to realize such a device: bulk LN and commercial thin-film LN. Clear reflectance dips observed in far-field measurements demonstrate the propagation of BSWs on top of the LN surface of the designed 1DPhCs.
文摘In previous work, we have analyzed the feasibility of the estimation for a source term S（x, y, z） in a transversal section, The present study is concerned with a twodimensional inverse phase change problem. The goal is the estimation of the dissipated heat flux in the liquid zone （reconstruction of a source term in the energy equation） from experimentally measured temperatures in the solid zone. This work has an application in the electron beam welding of steels of thickness about 8cm. The direct thermometallurgical problem is treated in a quasi steady two-dimensional longitudinal section （x, y）. The beam displacement is normally in the y direction. But in the quasi steady simulation, the beam is steady in the study section. The sample is divided in the axial direction z in few sections. At each section, a source term is defined with a part of the beam and creates a vaporized zone and a fused zone. The goal of this work is the rebuilding of the complete source term with the estimations at each section. In this paper, we analyze the feasibility of the estimation. For this work, we use only the simulated measurements without noise.
