Embedded system design is the core course of the telecommunication major in engineering universities,which combines software and hardware through embedded development boards.Aiming at the problems existing in traditio...Embedded system design is the core course of the telecommunication major in engineering universities,which combines software and hardware through embedded development boards.Aiming at the problems existing in traditional teaching,this paper proposes curriculum teaching reform based on the outcome-based education(OBE)concept,including determining course objectives,reforming teaching modes and methods,and improving the curriculum assessment and evaluation system.After two semesters of practice,this method not only enhances students’learning initiative but also improves teaching quality.展开更多
TheUAV pursuit-evasion problem focuses on the efficient tracking and capture of evading targets using unmanned aerial vehicles(UAVs),which is pivotal in public safety applications,particularly in scenarios involving i...TheUAV pursuit-evasion problem focuses on the efficient tracking and capture of evading targets using unmanned aerial vehicles(UAVs),which is pivotal in public safety applications,particularly in scenarios involving intrusion monitoring and interception.To address the challenges of data acquisition,real-world deployment,and the limited intelligence of existing algorithms in UAV pursuit-evasion tasks,we propose an innovative swarm intelligencebased UAV pursuit-evasion control framework,namely“Boids Model-based DRL Approach for Pursuit and Escape”(Boids-PE),which synergizes the strengths of swarm intelligence from bio-inspired algorithms and deep reinforcement learning(DRL).The Boids model,which simulates collective behavior through three fundamental rules,separation,alignment,and cohesion,is adopted in our work.By integrating Boids model with the Apollonian Circles algorithm,significant improvements are achieved in capturing UAVs against simple evasion strategies.To further enhance decision-making precision,we incorporate a DRL algorithm to facilitate more accurate strategic planning.We also leverage self-play training to continuously optimize the performance of pursuit UAVs.During experimental evaluation,we meticulously designed both one-on-one and multi-to-one pursuit-evasion scenarios,customizing the state space,action space,and reward function models for each scenario.Extensive simulations,supported by the PyBullet physics engine,validate the effectiveness of our proposed method.The overall results demonstrate that Boids-PE significantly enhance the efficiency and reliability of UAV pursuit-evasion tasks,providing a practical and robust solution for the real-world application of UAV pursuit-evasion missions.展开更多
Second harmonic generation(SHG),a fundamental and widely-studied phenomenon in nonlinear optics,has attracted significant attention for its ability to convert fundamental frequencies into their second harmonics.While ...Second harmonic generation(SHG),a fundamental and widely-studied phenomenon in nonlinear optics,has attracted significant attention for its ability to convert fundamental frequencies into their second harmonics.While the dominant SHG research has been focused on the optical and infrared regimes,its investigation in the microwave range presents challenges due to the requirements of materials with higher nonlinear coefficients and high-power microwave sources.Here,we provide an overview of methods together with underlying mechanisms for SHG in microwave frequencies,and discuss prospects and insights into the future developments of SHG-based technologies.The discussions on both numerical analyses and experimental studies will offer guidance for further SHG research and communication advancements in microwave regime.展开更多
The authors report the development of aλ~4.1μm quantum cascade laser grown by metal-organic chemical vapor deposition using strain-balanced In Ga As/In Al As materials.A device with a 7.5 mm cavity length and 6.5μm...The authors report the development of aλ~4.1μm quantum cascade laser grown by metal-organic chemical vapor deposition using strain-balanced In Ga As/In Al As materials.A device with a 7.5 mm cavity length and 6.5μm ridge width,bonded to an aluminum nitride heatsink,achieves maximum output powers of 3.4 W at 288 K in pulsed mode and 1.6 W at288 K in continuous-wave(CW)operation,with corresponding maximum wall-plug efficiencies of 14.8%and 9.3%.A kink is observed in the power–current curve under CW operation,which is absent in pulsed operation.Near-field results show that in CW operation,the horizontal beam quality factor M2fluctuates with current,indicating mode instability and highorder lateral mode excitation,while in pulsed mode,the horizontal M2remains stable around 1.3 as the current increases from 1.4 A to 1.9 A.展开更多
THE development of agriculture faces significant challenges due to population growth,climate change,land depletion,and environmental pollution,threatening global food security[1].This necessitates the development of s...THE development of agriculture faces significant challenges due to population growth,climate change,land depletion,and environmental pollution,threatening global food security[1].This necessitates the development of sustainable agriculture,where a fundamental step is crop breeding to improve agronomic or economic traits,e.g.,increasing yields of crops while decreasing resource usage and minimizing pollution to the environment[2].展开更多
Optical singularities are topological defects of electromagnetic fields;they include phase singularity in scalar fields,polarization singularity in vector fields,and three-dimensional(3D)singularities such as optical ...Optical singularities are topological defects of electromagnetic fields;they include phase singularity in scalar fields,polarization singularity in vector fields,and three-dimensional(3D)singularities such as optical skyrmions.The exploitation of photonic microstructures to generate and manipulate optical singularities has attracted wide research interest in recent years,with many photonic microstructures having been devised to this end.Accompanying these designs,scattered phenomenological theories have been proposed to expound the working mechanisms behind individual designs.In this work,instead of focusing on a specific type of microstructure,we concentrate on the most common geometric features of these microstructures—namely,symmetries—and revisit the process of generating optical singularities in microstructures from a symmetry viewpoint.By systematically employing the projection operator technique in group theory,we develop a widely applicable theoretical scheme to explore optical singularities in microstructures with rosette(i.e.,rotational and reflection)symmetries.Our scheme agrees well with previously reported works and further reveals that the eigenmodes of a symmetric microstructure can support multiplexed phase singularities in different components,such as out-of-plane,radial,azimuthal,and left-and right-handed circular components.Based on these phase singularities,more complicated optical singularities may be synthesized,including C points,V points,L lines,Néel-and bubble-type optical skyrmions,and optical lattices,to name a few.We demonstrate that the topological invariants associated with optical singularities are protected by the symmetries of the microstructure.Lastly,based on symmetry arguments,we formulate a so-called symmetry matching condition to clarify the excitation of a specific type of optical singularity.Our work establishes a unified theoretical framework to explore optical singularities in photonic microstructures with symmetries,shedding light on the symmetry origin of multidimensional and multiplexed optical singularities and providing a symmetry perspective for exploring many singularity-related effects in optics and photonics.展开更多
To explore atomic-level phenomena in the Cu-Ni-Sn alloy,a second nearest-neighbor modified embedded-atom method(2NN MEAM)potential has been developed for the Cu-Ni-Sn system,building upon the work of other researchers...To explore atomic-level phenomena in the Cu-Ni-Sn alloy,a second nearest-neighbor modified embedded-atom method(2NN MEAM)potential has been developed for the Cu-Ni-Sn system,building upon the work of other researchers.This potential demonstrates remarkable accuracy in predicting the lattice constant,with a relative error of less than 0.5%when compared to density functional theory(DFT)results,and it achieves a 10%relative error in the enthalpy of formation compared to experimental data,marking substantial advancements over prior models.The bulk modulus is predicted with a relative error of 8%compared to DFT.Notably,the potential effectively simulates the processes of melting and solidification of Cu-15Ni-8Sn,with a simulated melting point that closely aligns with the experimental value,within a 7.5%margin.This serves as a foundation for establishing a 2NN MEAM potential for a flawless Cu-Ni-Sn system and its microalloying systems.展开更多
Seasonal precipitation has always been a key focus of climate prediction.As a dynamic-statistical combined method,the existing observational constraint correction establishes a regression relationship between the nume...Seasonal precipitation has always been a key focus of climate prediction.As a dynamic-statistical combined method,the existing observational constraint correction establishes a regression relationship between the numerical model outputs and historical observations,which can partly predict seasonal precipitation.However,solving a nonlinear problem through linear regression is significantly biased.This study implements a nonlinear optimization of an existing observational constrained correction model using a Light Gradient Boosting Machine(LightGBM)machine learning algorithm based on output from the Beijing National Climate Center Climate System Model(BCC-CSM)and station observations to improve the prediction of summer precipitation in China.The model was trained using a rolling approach,and LightGBM outperformed Linear Regression(LR),Extreme Gradient Boosting(XGBoost),and Categorical Boosting(CatBoost).Using parameter tuning to optimize the machine learning model and predict future summer precipitation using eight different predictors in BCC-CSM,the mean Anomaly Correlation Coefficient(ACC)score in the 2019–22 summer precipitation predictions was 0.17,and the mean Prediction Score(PS)reached 74.The PS score was improved by 7.87%and 6.63%compared with the BCC-CSM and the linear observational constraint approach,respectively.The observational constraint correction prediction strategy with LightGBM significantly and stably improved the prediction of summer precipitation in China compared to the previous linear observational constraint solution,providing a reference for flood control and drought relief during the flood season(summer)in China.展开更多
Fluorine(F)substitution in polymers modulates both molecular energy levels and film morphology;however,its impact on exciton–vibrational coupling and molecular reorganization energy is often neglected.Herein,we syste...Fluorine(F)substitution in polymers modulates both molecular energy levels and film morphology;however,its impact on exciton–vibrational coupling and molecular reorganization energy is often neglected.Herein,we systematically investigated F-modified polymers(PBTA-PSF,PBDB-PSF)and their nonfluorinated counterparts(PBTA-PS,PBDB-PS)through simulations and experiments.We found that F atoms effectively lower the vibrational frequency of the molecular skeleton and suppress exciton–vibration coupling,thereby reducing the nonradiative decay rate.Moreover,introducing F atoms significantly decreases the reorganization energy for the S_(0)→S_(1) and S_(0)→cation transitions while increasing the reorganization energy for the S_(1)→S_(0) and cation→S_(0) transitions.These changes facilitate exciton dissociation and reduce the energy loss caused by dissociation and nonradiative recombination of excitons.Additionally,introducing F atoms into polymers enhances theπ–πstacking strength and the crystal coherence length in both neat and blended films,ultimately resulting in improvements in the power conversion efficiency of PBTA-PSF:L8-BO and PBDB-PSF:L8-BO are 16.51%and 17.59%,respectively.This study provides valuable insights for designing organic semiconductor materials to minimize energy loss and achieve a higher power conversion efficiency.展开更多
For constrained linear parameter varying(LPV)systems,this survey comprehensively reviews the literatures on output feedback robust model predictive control(OFRMPC)over the past two decades from the aspects on motivati...For constrained linear parameter varying(LPV)systems,this survey comprehensively reviews the literatures on output feedback robust model predictive control(OFRMPC)over the past two decades from the aspects on motivations,main contributions,and the related techniques.According to the types of state observer systems and scheduling parameters of LPV systems,different kinds of OFRMPC approaches are summarized and compared.The extensions of OFRMPC for LPV systems to other related uncertain systems are also investigated.The methods of dealing with system uncertainties and constraints in different kinds of OFRMPC optimizations are given.Key issues on OFRMPC optimizations for LPV systems are discussed.Furthermore,the future research directions on OFRMPC for LPV systems are suggested.展开更多
Laser-induced plasmas of dual-pulse fiber-optic laser-induced breakdown spectroscopy with different pulse energy ratios are studied by using the optical emission spectroscopy(OES)and fast imaging.The energy of the two...Laser-induced plasmas of dual-pulse fiber-optic laser-induced breakdown spectroscopy with different pulse energy ratios are studied by using the optical emission spectroscopy(OES)and fast imaging.The energy of the two laser pulses is independently adjusted within 0–30 m J with the total energy fixed at 30 m J.The inter-pulse delay remains 450 ns constantly.As the energy share of the first pulse increases,a similar bimodal variation trend of line intensities is observed.The two peaks are obtained at the point where the first pulse is half or twice of the second one,and the maximum spectral enhancement is at the first peak.The bimodal variation trend is induced by the change in the dominated mechanism of dual-pulse excitation with the trough between the two peaks caused by the weak coupling between the two mechanisms.By increasing the first pulse energy,there is a transition from the ablation enhancement dominance near the first peak to the plasma reheating dominance near the second peak.The calculations of plasma temperature and electron number density are consistent with the bimodal trend,which have the values of 17024.47 K,2.75×10^(17)cm;and 12215.93 K,1.17×10^(17)cm;at a time delay of 550 ns.In addition,the difference between the two peaks decreases with time delay.With the increase in the first pulse energy share,the plasma morphology undergoes a transformation from hemispherical to shiny-dot and to oblate-cylinder structure during the second laser irradiation from the recorded images by using an intensified charge-coupled device(ICCD)camera.Correspondingly,the peak expansion distance of the plasma front first decreases significantly from 1.99 mm in the single-pulse case to 1.34 mm at 12/18(dominated by ablation enhancement)and then increases slightly with increasing the plasma reheating effect.The variations in plasma dynamics verify that the change of pulse energy ratios leads to a transformation in the dual-pulse excitation mechanism.展开更多
Compared with first-order surface-related multiples from marine data,the onshore internal multiples are weaker and are always combined with a hazy and occasionally strong interference pattern.It is usually difficult t...Compared with first-order surface-related multiples from marine data,the onshore internal multiples are weaker and are always combined with a hazy and occasionally strong interference pattern.It is usually difficult to discriminate these events from complex targets and highly scattering overburdens,especially when the primary energy from deep layers is weaker than that from shallow layers.The internal multiple elimination is even more challenging due to the fact that the velocity and energy difference between primary reflections and internal multiples is tiny.In this study,we propose an improved method which formulates the elimination of the internal multiples as an optimization problem and develops a convolution factor T.The generated internal multiples at all interfaces are obtained using the convolution factor T through iterative inversion of the initial multiple model.The predicted internal multiples are removed from seismic data through subtraction.Finally,several synthetic experiments are conducted to validate the effectiveness of our approach.The results of our study indicate that compared with the traditional virtual events method,the improved method simplifies the multiple prediction process in which internal multiples generated from each interface are built through iterative inversion,thus reducing the calculation cost,improving the accuracy,and enhancing the adaptability of field data.展开更多
Both the modeling and the load regulation capacity prediction of a supercritical power plant are investigated in this paper. Firstly, an indirect identification method based on subspace identification method is propos...Both the modeling and the load regulation capacity prediction of a supercritical power plant are investigated in this paper. Firstly, an indirect identification method based on subspace identification method is proposed. The obtained identification model is verified by the actual operation data and the dynamic characteristics of the system are well reproduced. Secondly, the model is used to predict the load regulation capacity of thermal power unit. The power, main steam pressure, main steam temperature and other parameters are simulated respectively when the unit load is going up and down. Under the actual constraints, the load regulation capacity of thermal power unit can be predicted quickly.展开更多
Retinal diseases pose significant challenges to global healthcare systems,necessitating accurate and efficient diagnostic methods.Optical Coherence Tomography(OCT)has emerged as a valuable tool for diagnosing and moni...Retinal diseases pose significant challenges to global healthcare systems,necessitating accurate and efficient diagnostic methods.Optical Coherence Tomography(OCT)has emerged as a valuable tool for diagnosing and monitoring retinal conditions due to its noncontact and noninvasive nature.This paper presents a novel retinal layering method based on OCT images,aimed at enhancing the accuracy of retinal lesion diagnosis.The method utilizes gradient analysis to effectively identify and segment retinal layers.By selecting a column of pixels as a segmentation line and utilizing gradient information from adjacent pixels,the method initiates and proceeds with the layering process.This approach addresses potential issues arising from partial layer overlapping,minimizing deviations in layer segmentation.Experimental results demonstrate the efficacy of the proposed method in accurately segmenting eight retinal boundaries,with an average absolute position deviation of 1.75 pixels.By providing accurate segmentation of retinal layers,this approach contributes to the early detection and management of ocular conditions,ultimately improving patient outcomes and reducing the global burden of vision-related ailments.展开更多
The reported electrocaloric(EC)effect in ferroelectrics is poised for application in the next generation of solidstate refrigeration technology,exhibiting substantial developmental potential.This study introduces a no...The reported electrocaloric(EC)effect in ferroelectrics is poised for application in the next generation of solidstate refrigeration technology,exhibiting substantial developmental potential.This study introduces a novel and efficient EC effect strategy in(1-x)Pb(Lu_(1/2)Nb_(1/2))O_(3)-xPbTiO_(3)(PLN-xPT)ceramics for low electric-fielddriven devices.Phase-field simulations provide fundamental insights into thermally induced continuous phase transitions,guiding subsequent experimental investigations.A comprehensive composition/temperature-driven phase evolution diagram is constructed,elucidating the sequential transformation from ferroelectric(FE)to antiferroelectric(AFE)and finally to paraelectric(PE)phases for x=0.10-0.18 components.Direct measurements of EC performance highlight x=0.16 as an outstanding performer,exhibiting remarkable properties,including an adiabatic temperature change(ΔT)of 3.03 K,EC strength(ΔT/ΔE)of 0.08 K cm kV-1,and a temperature span(Tspan)of 31℃.The superior EC effect performance is attributed to the temperature-induced FE to AFE transition at low electric fields and diffusion phase transition behavior contributing to the wide Tspan.This work provides valuable insights into developing high-performance EC effect across broad temperature ranges through the strategic design of continuous phase transitions,offering a simplified and economical approach for advancing ecofriendly and efficient solid-state cooling technologies.展开更多
With the advent of deep learning,self-driving schemes based on deep learning are becoming more and more popular.Robust perception-action models should learn from data with different scenarios and real behaviors,while ...With the advent of deep learning,self-driving schemes based on deep learning are becoming more and more popular.Robust perception-action models should learn from data with different scenarios and real behaviors,while current end-to-end model learning is generally limited to training of massive data,innovation of deep network architecture,and learning in-situ model in a simulation environment.Therefore,we introduce a new image style transfer method into data augmentation,and improve the diversity of limited data by changing the texture,contrast ratio and color of the image,and then it is extended to the scenarios that the model has been unobserved before.Inspired by rapid style transfer and artistic style neural algorithms,we propose an arbitrary style generation network architecture,including style transfer network,style learning network,style loss network and multivariate Gaussian distribution function.The style embedding vector is randomly sampled from the multivariate Gaussian distribution and linearly interpolated with the embedded vector predicted by the input image on the style learning network,which provides a set of normalization constants for the style transfer network,and finally realizes the diversity of the image style.In order to verify the effectiveness of the method,image classification and simulation experiments were performed separately.Finally,we built a small-sized smart car experiment platform,and apply the data augmentation technology based on image style transfer drive to the experiment of automatic driving for the first time.The experimental results show that:(1)The proposed scheme can improve the prediction accuracy of the end-to-end model and reduce the model’s error accumulation;(2)the method based on image style transfer provides a new scheme for data augmentation technology,and also provides a solution for the high cost that many deep models rely heavily on a large number of label data.展开更多
Fully homomorphic encryption is faced with two problems now. One is candidate fully homomorphic encryption schemes are few. Another is that the efficiency of fully homomorphic encryption is a big question. In this pap...Fully homomorphic encryption is faced with two problems now. One is candidate fully homomorphic encryption schemes are few. Another is that the efficiency of fully homomorphic encryption is a big question. In this paper, we propose a fully homomorphic encryption scheme based on LWE, which has better key size. Our main contributions are： （1） According to the binary-LWE recently, we choose secret key from binary set and modify the basic encryption scheme proposed in Linder and Peikert in 2010. We propose a fully homomorphic encryption scheme based on the new basic encryption scheme. We analyze the correctness and give the proof of the security of our scheme. The public key, evaluation keys and tensored ciphertext have better size in our scheme. （2） Estimating parameters for fully homomorphic encryption scheme is an important work. We estimate the concert parameters for our scheme. We compare these parameters between our scheme and Bral2 scheme. Our scheme have public key and private key that smaller by a factor of about logq than in Bral2 scheme. Tensored ciphertext in our scheme is smaller by a factor of about log2q than in Bral2 scheme. Key switching matrix in our scheme is smaller by a factor of about log3q than in Bra12 scheme.展开更多
This paper focuses on fixed-interval smoothing for stochastic hybrid systems.When the truth-mode mismatch is encountered,existing smoothing methods based on fixed structure of model-set have significant performance de...This paper focuses on fixed-interval smoothing for stochastic hybrid systems.When the truth-mode mismatch is encountered,existing smoothing methods based on fixed structure of model-set have significant performance degradation and are inapplicable.We develop a fixedinterval smoothing method based on forward-and backward-filtering in the Variable Structure Multiple Model(VSMM)framework in this paper.We propose to use the Simplified Equivalent model Interacting Multiple Model(SEIMM)in the forward and the backward filters to handle the difficulty of different mode-sets used in both filters,and design a re-filtering procedure in the model-switching stage to enhance the estimation performance.To improve the computational efficiency,we make the basic model-set adaptive by the Likely-Model Set(LMS)algorithm.It turns out that the smoothing performance is further improved by the LMS due to less competition among models.Simulation results are provided to demonstrate the better performance and the computational efficiency of our proposed smoothing algorithms.展开更多
Localized surface plasmon resonance(LSPR) has caused extensive concern and achieved widespread applications in optoelectronics. However, the weak coupling of plasmons and excitons in a nanometal/semiconductor system r...Localized surface plasmon resonance(LSPR) has caused extensive concern and achieved widespread applications in optoelectronics. However, the weak coupling of plasmons and excitons in a nanometal/semiconductor system remains to be investigated via energy transfer. Herein, bandgap tunable perovskite films were synthesized to adjust the emission peaks,for further coupling with stable localized surface plasmons from gold nanoparticles. The degree of mismatch, using steadystate and transient photoluminescence(PL), was investigated systematically in two different cases of gold nanoparticles that were in direct contacting and insulated. The results demonstrated the process of tuning emission coupled to LSPR via wavelength-dependent photoluminescence intensity in the samples with an insulating spacer. In the direct contact case,the decreased radiative decay rate involves rapid plasmon resonance energy transfer to the perovskite semiconductor and non-radiative energy transfer to metal nanoparticles in the near-field range.展开更多
This paper presents a tunable multi-threshold micro-electromechanical inertial switch with adjustable threshold capability.The demonstrated device combines the advantages of accelerometers in providing quantitative ac...This paper presents a tunable multi-threshold micro-electromechanical inertial switch with adjustable threshold capability.The demonstrated device combines the advantages of accelerometers in providing quantitative acceleration measurements and g-threshold switches in saving power when in the inactive state upon experiencing acceleration below the thresholds.The designed proof-of-concept device with two thresholds consists of a cantilever microbeam and two stationary electrodes placed at different positions in the sensing direction.The adjustable threshold capability and the effect of the shock duration on the threshold acceleration are analytically investigated using a nonlinear beam model.Results are shown for the relationships among the applied bias voltage,the duration of shock impact,and the tunable threshold.The fabricated prototypes are tested using a shock-table system.The analytical results agree with the experimental results.The designed device concept is very promising for the classification of the shock and impact loads in transportation and healthcare applications.展开更多
基金This paper is one of the phased achievements of the Education and Teaching Reform Project of Guangdong University of Petrochemical Engineering in 2022(71013413080)the Research and Practice Project of Teaching and Teaching Reform of University-Level Higher Vocational Education in 2023(JY202353).
文摘Embedded system design is the core course of the telecommunication major in engineering universities,which combines software and hardware through embedded development boards.Aiming at the problems existing in traditional teaching,this paper proposes curriculum teaching reform based on the outcome-based education(OBE)concept,including determining course objectives,reforming teaching modes and methods,and improving the curriculum assessment and evaluation system.After two semesters of practice,this method not only enhances students’learning initiative but also improves teaching quality.
文摘TheUAV pursuit-evasion problem focuses on the efficient tracking and capture of evading targets using unmanned aerial vehicles(UAVs),which is pivotal in public safety applications,particularly in scenarios involving intrusion monitoring and interception.To address the challenges of data acquisition,real-world deployment,and the limited intelligence of existing algorithms in UAV pursuit-evasion tasks,we propose an innovative swarm intelligencebased UAV pursuit-evasion control framework,namely“Boids Model-based DRL Approach for Pursuit and Escape”(Boids-PE),which synergizes the strengths of swarm intelligence from bio-inspired algorithms and deep reinforcement learning(DRL).The Boids model,which simulates collective behavior through three fundamental rules,separation,alignment,and cohesion,is adopted in our work.By integrating Boids model with the Apollonian Circles algorithm,significant improvements are achieved in capturing UAVs against simple evasion strategies.To further enhance decision-making precision,we incorporate a DRL algorithm to facilitate more accurate strategic planning.We also leverage self-play training to continuously optimize the performance of pursuit UAVs.During experimental evaluation,we meticulously designed both one-on-one and multi-to-one pursuit-evasion scenarios,customizing the state space,action space,and reward function models for each scenario.Extensive simulations,supported by the PyBullet physics engine,validate the effectiveness of our proposed method.The overall results demonstrate that Boids-PE significantly enhance the efficiency and reliability of UAV pursuit-evasion tasks,providing a practical and robust solution for the real-world application of UAV pursuit-evasion missions.
基金supported by the National Natural Science Foun-dation of China(No.12274339).
文摘Second harmonic generation(SHG),a fundamental and widely-studied phenomenon in nonlinear optics,has attracted significant attention for its ability to convert fundamental frequencies into their second harmonics.While the dominant SHG research has been focused on the optical and infrared regimes,its investigation in the microwave range presents challenges due to the requirements of materials with higher nonlinear coefficients and high-power microwave sources.Here,we provide an overview of methods together with underlying mechanisms for SHG in microwave frequencies,and discuss prospects and insights into the future developments of SHG-based technologies.The discussions on both numerical analyses and experimental studies will offer guidance for further SHG research and communication advancements in microwave regime.
文摘The authors report the development of aλ~4.1μm quantum cascade laser grown by metal-organic chemical vapor deposition using strain-balanced In Ga As/In Al As materials.A device with a 7.5 mm cavity length and 6.5μm ridge width,bonded to an aluminum nitride heatsink,achieves maximum output powers of 3.4 W at 288 K in pulsed mode and 1.6 W at288 K in continuous-wave(CW)operation,with corresponding maximum wall-plug efficiencies of 14.8%and 9.3%.A kink is observed in the power–current curve under CW operation,which is absent in pulsed operation.Near-field results show that in CW operation,the horizontal beam quality factor M2fluctuates with current,indicating mode instability and highorder lateral mode excitation,while in pulsed mode,the horizontal M2remains stable around 1.3 as the current increases from 1.4 A to 1.9 A.
基金supported by Research Fund for Young Talent Plans of Xi’an Jiaotong University(KZ6J007)the National Natural Science Foundation of China(62303372,GYKP034)
文摘THE development of agriculture faces significant challenges due to population growth,climate change,land depletion,and environmental pollution,threatening global food security[1].This necessitates the development of sustainable agriculture,where a fundamental step is crop breeding to improve agronomic or economic traits,e.g.,increasing yields of crops while decreasing resource usage and minimizing pollution to the environment[2].
基金supported by the National Natural Science Foun-dation of China(62301596 and 62288101)Shaanxi Provincial Science and Technology Innovation Team(23-CX-TD-48)+4 种基金the KU Leuven internal funds:the C1 Project(C14/19/083)the Interdisciplinary Network Project(IDN/20/014)the Small Infrastructure Grant(KA/20/019)the Research Foundation of Flanders(FWO)Project(G090017N,G088822N,and V408823N)the Danish National Research Foundation(DNRF165).
文摘Optical singularities are topological defects of electromagnetic fields;they include phase singularity in scalar fields,polarization singularity in vector fields,and three-dimensional(3D)singularities such as optical skyrmions.The exploitation of photonic microstructures to generate and manipulate optical singularities has attracted wide research interest in recent years,with many photonic microstructures having been devised to this end.Accompanying these designs,scattered phenomenological theories have been proposed to expound the working mechanisms behind individual designs.In this work,instead of focusing on a specific type of microstructure,we concentrate on the most common geometric features of these microstructures—namely,symmetries—and revisit the process of generating optical singularities in microstructures from a symmetry viewpoint.By systematically employing the projection operator technique in group theory,we develop a widely applicable theoretical scheme to explore optical singularities in microstructures with rosette(i.e.,rotational and reflection)symmetries.Our scheme agrees well with previously reported works and further reveals that the eigenmodes of a symmetric microstructure can support multiplexed phase singularities in different components,such as out-of-plane,radial,azimuthal,and left-and right-handed circular components.Based on these phase singularities,more complicated optical singularities may be synthesized,including C points,V points,L lines,Néel-and bubble-type optical skyrmions,and optical lattices,to name a few.We demonstrate that the topological invariants associated with optical singularities are protected by the symmetries of the microstructure.Lastly,based on symmetry arguments,we formulate a so-called symmetry matching condition to clarify the excitation of a specific type of optical singularity.Our work establishes a unified theoretical framework to explore optical singularities in photonic microstructures with symmetries,shedding light on the symmetry origin of multidimensional and multiplexed optical singularities and providing a symmetry perspective for exploring many singularity-related effects in optics and photonics.
基金sponsored by the Science and Technology Foundation of Guizhou Provincial Education Department(No.QJJ[2024]60)Guizhou Provincial Basic Research Program(Natural Science)(No.QKHJC[2024]Youth 214)+1 种基金Science and Technology Foundation of Guizhou Minzu University(No.GZMUZK[2024]QD21)Research Projects of Anshun University(No.asxybsjj202413).
文摘To explore atomic-level phenomena in the Cu-Ni-Sn alloy,a second nearest-neighbor modified embedded-atom method(2NN MEAM)potential has been developed for the Cu-Ni-Sn system,building upon the work of other researchers.This potential demonstrates remarkable accuracy in predicting the lattice constant,with a relative error of less than 0.5%when compared to density functional theory(DFT)results,and it achieves a 10%relative error in the enthalpy of formation compared to experimental data,marking substantial advancements over prior models.The bulk modulus is predicted with a relative error of 8%compared to DFT.Notably,the potential effectively simulates the processes of melting and solidification of Cu-15Ni-8Sn,with a simulated melting point that closely aligns with the experimental value,within a 7.5%margin.This serves as a foundation for establishing a 2NN MEAM potential for a flawless Cu-Ni-Sn system and its microalloying systems.
基金jointly supported by the National Natural Science Foundation of China(Grant Nos.42122034,42075043,42330609)the Second Tibetan Plateau Scientific Expedition and Research program(2019QZKK0103)+2 种基金Key Talent Project in Gansu and Central Guidance Fund for Local Science and Technology Development Projects in Gansu(No.24ZYQA031)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2021427)West Light Foundation of the Chinese Academy of Sciences(xbzg-zdsys-202215)。
文摘Seasonal precipitation has always been a key focus of climate prediction.As a dynamic-statistical combined method,the existing observational constraint correction establishes a regression relationship between the numerical model outputs and historical observations,which can partly predict seasonal precipitation.However,solving a nonlinear problem through linear regression is significantly biased.This study implements a nonlinear optimization of an existing observational constrained correction model using a Light Gradient Boosting Machine(LightGBM)machine learning algorithm based on output from the Beijing National Climate Center Climate System Model(BCC-CSM)and station observations to improve the prediction of summer precipitation in China.The model was trained using a rolling approach,and LightGBM outperformed Linear Regression(LR),Extreme Gradient Boosting(XGBoost),and Categorical Boosting(CatBoost).Using parameter tuning to optimize the machine learning model and predict future summer precipitation using eight different predictors in BCC-CSM,the mean Anomaly Correlation Coefficient(ACC)score in the 2019–22 summer precipitation predictions was 0.17,and the mean Prediction Score(PS)reached 74.The PS score was improved by 7.87%and 6.63%compared with the BCC-CSM and the linear observational constraint approach,respectively.The observational constraint correction prediction strategy with LightGBM significantly and stably improved the prediction of summer precipitation in China compared to the previous linear observational constraint solution,providing a reference for flood control and drought relief during the flood season(summer)in China.
基金supported by the National Natural Science Foundation of China(Grant No.62027822)the National R&D Program of China(Grant No.2019YFA0706402).
文摘Fluorine(F)substitution in polymers modulates both molecular energy levels and film morphology;however,its impact on exciton–vibrational coupling and molecular reorganization energy is often neglected.Herein,we systematically investigated F-modified polymers(PBTA-PSF,PBDB-PSF)and their nonfluorinated counterparts(PBTA-PS,PBDB-PS)through simulations and experiments.We found that F atoms effectively lower the vibrational frequency of the molecular skeleton and suppress exciton–vibration coupling,thereby reducing the nonradiative decay rate.Moreover,introducing F atoms significantly decreases the reorganization energy for the S_(0)→S_(1) and S_(0)→cation transitions while increasing the reorganization energy for the S_(1)→S_(0) and cation→S_(0) transitions.These changes facilitate exciton dissociation and reduce the energy loss caused by dissociation and nonradiative recombination of excitons.Additionally,introducing F atoms into polymers enhances theπ–πstacking strength and the crystal coherence length in both neat and blended films,ultimately resulting in improvements in the power conversion efficiency of PBTA-PSF:L8-BO and PBDB-PSF:L8-BO are 16.51%and 17.59%,respectively.This study provides valuable insights for designing organic semiconductor materials to minimize energy loss and achieve a higher power conversion efficiency.
基金supported in part by the National Natural Science Foundation of China(62103319,62073053,61773396)。
文摘For constrained linear parameter varying(LPV)systems,this survey comprehensively reviews the literatures on output feedback robust model predictive control(OFRMPC)over the past two decades from the aspects on motivations,main contributions,and the related techniques.According to the types of state observer systems and scheduling parameters of LPV systems,different kinds of OFRMPC approaches are summarized and compared.The extensions of OFRMPC for LPV systems to other related uncertain systems are also investigated.The methods of dealing with system uncertainties and constraints in different kinds of OFRMPC optimizations are given.Key issues on OFRMPC optimizations for LPV systems are discussed.Furthermore,the future research directions on OFRMPC for LPV systems are suggested.
基金the Foundation Research Project of Jiangsu Province,China(the Natural Science Fund No.BK20190187)。
文摘Laser-induced plasmas of dual-pulse fiber-optic laser-induced breakdown spectroscopy with different pulse energy ratios are studied by using the optical emission spectroscopy(OES)and fast imaging.The energy of the two laser pulses is independently adjusted within 0–30 m J with the total energy fixed at 30 m J.The inter-pulse delay remains 450 ns constantly.As the energy share of the first pulse increases,a similar bimodal variation trend of line intensities is observed.The two peaks are obtained at the point where the first pulse is half or twice of the second one,and the maximum spectral enhancement is at the first peak.The bimodal variation trend is induced by the change in the dominated mechanism of dual-pulse excitation with the trough between the two peaks caused by the weak coupling between the two mechanisms.By increasing the first pulse energy,there is a transition from the ablation enhancement dominance near the first peak to the plasma reheating dominance near the second peak.The calculations of plasma temperature and electron number density are consistent with the bimodal trend,which have the values of 17024.47 K,2.75×10^(17)cm;and 12215.93 K,1.17×10^(17)cm;at a time delay of 550 ns.In addition,the difference between the two peaks decreases with time delay.With the increase in the first pulse energy share,the plasma morphology undergoes a transformation from hemispherical to shiny-dot and to oblate-cylinder structure during the second laser irradiation from the recorded images by using an intensified charge-coupled device(ICCD)camera.Correspondingly,the peak expansion distance of the plasma front first decreases significantly from 1.99 mm in the single-pulse case to 1.34 mm at 12/18(dominated by ablation enhancement)and then increases slightly with increasing the plasma reheating effect.The variations in plasma dynamics verify that the change of pulse energy ratios leads to a transformation in the dual-pulse excitation mechanism.
基金the National Natural Science Foundation of China under Grant Nos.41974116 and 41930431Local Universities Reformation and Development Personnel Training Supporting Project from Central Authorities under Grant No.140119001 for supporting this work
文摘Compared with first-order surface-related multiples from marine data,the onshore internal multiples are weaker and are always combined with a hazy and occasionally strong interference pattern.It is usually difficult to discriminate these events from complex targets and highly scattering overburdens,especially when the primary energy from deep layers is weaker than that from shallow layers.The internal multiple elimination is even more challenging due to the fact that the velocity and energy difference between primary reflections and internal multiples is tiny.In this study,we propose an improved method which formulates the elimination of the internal multiples as an optimization problem and develops a convolution factor T.The generated internal multiples at all interfaces are obtained using the convolution factor T through iterative inversion of the initial multiple model.The predicted internal multiples are removed from seismic data through subtraction.Finally,several synthetic experiments are conducted to validate the effectiveness of our approach.The results of our study indicate that compared with the traditional virtual events method,the improved method simplifies the multiple prediction process in which internal multiples generated from each interface are built through iterative inversion,thus reducing the calculation cost,improving the accuracy,and enhancing the adaptability of field data.
文摘Both the modeling and the load regulation capacity prediction of a supercritical power plant are investigated in this paper. Firstly, an indirect identification method based on subspace identification method is proposed. The obtained identification model is verified by the actual operation data and the dynamic characteristics of the system are well reproduced. Secondly, the model is used to predict the load regulation capacity of thermal power unit. The power, main steam pressure, main steam temperature and other parameters are simulated respectively when the unit load is going up and down. Under the actual constraints, the load regulation capacity of thermal power unit can be predicted quickly.
基金the National Natural Science Foundation of China(62205120)the Project of State Key Laboratory of Radiation Medicine and Protection,Soochow University(GZK1202217)for supportthe Postgraduate Research&Practice Innovation Program of Jiangsu Province(HGYK202312,SJCX242149).
文摘Retinal diseases pose significant challenges to global healthcare systems,necessitating accurate and efficient diagnostic methods.Optical Coherence Tomography(OCT)has emerged as a valuable tool for diagnosing and monitoring retinal conditions due to its noncontact and noninvasive nature.This paper presents a novel retinal layering method based on OCT images,aimed at enhancing the accuracy of retinal lesion diagnosis.The method utilizes gradient analysis to effectively identify and segment retinal layers.By selecting a column of pixels as a segmentation line and utilizing gradient information from adjacent pixels,the method initiates and proceeds with the layering process.This approach addresses potential issues arising from partial layer overlapping,minimizing deviations in layer segmentation.Experimental results demonstrate the efficacy of the proposed method in accurately segmenting eight retinal boundaries,with an average absolute position deviation of 1.75 pixels.By providing accurate segmentation of retinal layers,this approach contributes to the early detection and management of ocular conditions,ultimately improving patient outcomes and reducing the global burden of vision-related ailments.
基金financially supported by the National Natural Science Foundation of China(Grant No.52261135548)the Key Research and Development Program of Shaanxi(Program No.2022KWZ-22)+2 种基金The research was made possible by Russian Science Foundation(Project No.23-42-00116)The equipment of the Ural Center for Shared Use“Modern nanotechnology”Ural Federal University(Reg.No.2968)which is supported by the Ministry of ScienceHigher Education RF(Project No.075-15-2021-677)was used.
文摘The reported electrocaloric(EC)effect in ferroelectrics is poised for application in the next generation of solidstate refrigeration technology,exhibiting substantial developmental potential.This study introduces a novel and efficient EC effect strategy in(1-x)Pb(Lu_(1/2)Nb_(1/2))O_(3)-xPbTiO_(3)(PLN-xPT)ceramics for low electric-fielddriven devices.Phase-field simulations provide fundamental insights into thermally induced continuous phase transitions,guiding subsequent experimental investigations.A comprehensive composition/temperature-driven phase evolution diagram is constructed,elucidating the sequential transformation from ferroelectric(FE)to antiferroelectric(AFE)and finally to paraelectric(PE)phases for x=0.10-0.18 components.Direct measurements of EC performance highlight x=0.16 as an outstanding performer,exhibiting remarkable properties,including an adiabatic temperature change(ΔT)of 3.03 K,EC strength(ΔT/ΔE)of 0.08 K cm kV-1,and a temperature span(Tspan)of 31℃.The superior EC effect performance is attributed to the temperature-induced FE to AFE transition at low electric fields and diffusion phase transition behavior contributing to the wide Tspan.This work provides valuable insights into developing high-performance EC effect across broad temperature ranges through the strategic design of continuous phase transitions,offering a simplified and economical approach for advancing ecofriendly and efficient solid-state cooling technologies.
基金the National Natural Science Foundation of China(51965008)Science and Technology projects of Guizhou[2018]2168Excellent Young Researcher Project of Guizhou[2017]5630.
文摘With the advent of deep learning,self-driving schemes based on deep learning are becoming more and more popular.Robust perception-action models should learn from data with different scenarios and real behaviors,while current end-to-end model learning is generally limited to training of massive data,innovation of deep network architecture,and learning in-situ model in a simulation environment.Therefore,we introduce a new image style transfer method into data augmentation,and improve the diversity of limited data by changing the texture,contrast ratio and color of the image,and then it is extended to the scenarios that the model has been unobserved before.Inspired by rapid style transfer and artistic style neural algorithms,we propose an arbitrary style generation network architecture,including style transfer network,style learning network,style loss network and multivariate Gaussian distribution function.The style embedding vector is randomly sampled from the multivariate Gaussian distribution and linearly interpolated with the embedded vector predicted by the input image on the style learning network,which provides a set of normalization constants for the style transfer network,and finally realizes the diversity of the image style.In order to verify the effectiveness of the method,image classification and simulation experiments were performed separately.Finally,we built a small-sized smart car experiment platform,and apply the data augmentation technology based on image style transfer drive to the experiment of automatic driving for the first time.The experimental results show that:(1)The proposed scheme can improve the prediction accuracy of the end-to-end model and reduce the model’s error accumulation;(2)the method based on image style transfer provides a new scheme for data augmentation technology,and also provides a solution for the high cost that many deep models rely heavily on a large number of label data.
基金The first author would like to thank for the Fund of Jiangsu Innovation Program for Graduate Education，the Fundamental Research Funds for the Central Universities,and Ningbo Natural Science Foundation，the Chinese National Scholarship fund,and also appreciate the benefit to this work from projects in science and technique of Ningbo municipal.The third author would like to thank for Ningbo Natural Science Foundation
文摘Fully homomorphic encryption is faced with two problems now. One is candidate fully homomorphic encryption schemes are few. Another is that the efficiency of fully homomorphic encryption is a big question. In this paper, we propose a fully homomorphic encryption scheme based on LWE, which has better key size. Our main contributions are： （1） According to the binary-LWE recently, we choose secret key from binary set and modify the basic encryption scheme proposed in Linder and Peikert in 2010. We propose a fully homomorphic encryption scheme based on the new basic encryption scheme. We analyze the correctness and give the proof of the security of our scheme. The public key, evaluation keys and tensored ciphertext have better size in our scheme. （2） Estimating parameters for fully homomorphic encryption scheme is an important work. We estimate the concert parameters for our scheme. We compare these parameters between our scheme and Bral2 scheme. Our scheme have public key and private key that smaller by a factor of about logq than in Bral2 scheme. Tensored ciphertext in our scheme is smaller by a factor of about log2q than in Bral2 scheme. Key switching matrix in our scheme is smaller by a factor of about log3q than in Bra12 scheme.
基金supported in part by the National Natural Science Foundation of China(No.61773306)the National Key Research and Development Plan,China(Nos.2021YFC2202600 and 2021YFC2202603)。
文摘This paper focuses on fixed-interval smoothing for stochastic hybrid systems.When the truth-mode mismatch is encountered,existing smoothing methods based on fixed structure of model-set have significant performance degradation and are inapplicable.We develop a fixedinterval smoothing method based on forward-and backward-filtering in the Variable Structure Multiple Model(VSMM)framework in this paper.We propose to use the Simplified Equivalent model Interacting Multiple Model(SEIMM)in the forward and the backward filters to handle the difficulty of different mode-sets used in both filters,and design a re-filtering procedure in the model-switching stage to enhance the estimation performance.To improve the computational efficiency,we make the basic model-set adaptive by the Likely-Model Set(LMS)algorithm.It turns out that the smoothing performance is further improved by the LMS due to less competition among models.Simulation results are provided to demonstrate the better performance and the computational efficiency of our proposed smoothing algorithms.
基金Project supported by the National Key R&D Program of China (Grant Nos. 2017YFA0700503 and 2018YFA0209101)the National Natural Science Foundation of China (Grant Nos. 61821002, 11734005, 62075041, and 61704024)。
文摘Localized surface plasmon resonance(LSPR) has caused extensive concern and achieved widespread applications in optoelectronics. However, the weak coupling of plasmons and excitons in a nanometal/semiconductor system remains to be investigated via energy transfer. Herein, bandgap tunable perovskite films were synthesized to adjust the emission peaks,for further coupling with stable localized surface plasmons from gold nanoparticles. The degree of mismatch, using steadystate and transient photoluminescence(PL), was investigated systematically in two different cases of gold nanoparticles that were in direct contacting and insulated. The results demonstrated the process of tuning emission coupled to LSPR via wavelength-dependent photoluminescence intensity in the samples with an insulating spacer. In the direct contact case,the decreased radiative decay rate involves rapid plasmon resonance energy transfer to the perovskite semiconductor and non-radiative energy transfer to metal nanoparticles in the near-field range.
基金supported by King Abdullah University of Science and Technology(KAUST).
文摘This paper presents a tunable multi-threshold micro-electromechanical inertial switch with adjustable threshold capability.The demonstrated device combines the advantages of accelerometers in providing quantitative acceleration measurements and g-threshold switches in saving power when in the inactive state upon experiencing acceleration below the thresholds.The designed proof-of-concept device with two thresholds consists of a cantilever microbeam and two stationary electrodes placed at different positions in the sensing direction.The adjustable threshold capability and the effect of the shock duration on the threshold acceleration are analytically investigated using a nonlinear beam model.Results are shown for the relationships among the applied bias voltage,the duration of shock impact,and the tunable threshold.The fabricated prototypes are tested using a shock-table system.The analytical results agree with the experimental results.The designed device concept is very promising for the classification of the shock and impact loads in transportation and healthcare applications.
