Break junctions are important in generating nanosensors and single molecular devices. The mechanically con- trollable break junction is the most widely used method for a break junction due to its simplicity and stabil...Break junctions are important in generating nanosensors and single molecular devices. The mechanically con- trollable break junction is the most widely used method for a break junction due to its simplicity and stability. However, the bandwidths of traditional devices are limited to about a few hertz. Moreover, when using traditional methods it is hard to allow independent control of more than one junction. Here we propose on-chip thermally controllable break junctions to overcome these challenges. This is verified by using finite element analysis. Adopting microelectromechanical systems produces features of high bandwidth and independent controllability to this new break junction system. The proposed method will have a wide range of applications on on-chip high speed independent controllable and highly integrated single molecule devices.展开更多
In this paper,we present a circuit model of single-quantum-well InGaN/GaN light-emitting diodes based on the standard rate equations.Two rate equations describe carrier transport processes occurring in sep-arate confi...In this paper,we present a circuit model of single-quantum-well InGaN/GaN light-emitting diodes based on the standard rate equations.Two rate equations describe carrier transport processes occurring in sep-arate confinement heterostructure and quantum well respectively,and the third equation describes the varied photons in quantum well.By using the presented model,impacts of quantum well thickness on the static and dynamic performances are investigated.Simulated results show that LED with 4 nm well exhibits better lightcurrent(L-I)performance,but LED with 3 nm well presents wider 3 dB modulation bandwidth.It reveals that high carrier density in quantum well is detrimental to the static performance,but beneficial to the dynamic performance.展开更多
In this paper,the authors study a class of weighted version of probability density estimator.It is shown that the weighted estimator contains some existing estimators of probability density,no matter they are recursiv...In this paper,the authors study a class of weighted version of probability density estimator.It is shown that the weighted estimator contains some existing estimators of probability density,no matter they are recursive or non-recursive.Some statistical results including weak consistency,strong consistency,rate of strong consistency,and asymptotic normality are established under some mild conditions.Moreover,the random weighted estimator is also investigated.Some numerical simulations and a real data analysis are presented to study the numerical performances of the estimators.展开更多
The rapid growth in available network bandwidth has directly contributed to an exponential increase in mobile data traffic,creating significant challenges for network energy consumption.Also,with the extraordinary gro...The rapid growth in available network bandwidth has directly contributed to an exponential increase in mobile data traffic,creating significant challenges for network energy consumption.Also,with the extraordinary growth of mobile communications,the data traffic has dramatically expanded,which has led to massive grid power consumption and incurred high operating expenditure(OPEX).However,the majority of current network designs struggle to efficientlymanage a massive amount of data using little power,which degrades energy efficiency performance.Thereby,it is necessary to have an efficient mechanism to reduce power consumption when processing large amounts of data in network data centers.Utilizing renewable energy sources to power the Cloud Radio Access Network(C-RAN)greatly reduces the need to purchase energy from the utility grid.In this paper,we propose a bandwidth-aware hybrid energypowered C-RAN that focuses on throughput and energy efficiency(EE)by lowering grid usage,aiming to enhance the EE.This paper examines the energy efficiency,spectral efficiency(SE),and average on-grid energy consumption,dealing with the major challenges of the temporal and spatial nature of traffic and renewable energy generation across various network setups.To assess the effectiveness of the suggested network by changing the transmission bandwidth,a comprehensive simulation has been conducted.The numerical findings support the efficacy of the suggested approach.展开更多
This paper proposes two types of integrated sound absorbing-insulating metamaterials with low thickness and efficient sound attenuation in the low-frequency bandwidth,i.e.,labyrinth-type metamaterial and multi-order r...This paper proposes two types of integrated sound absorbing-insulating metamaterials with low thickness and efficient sound attenuation in the low-frequency bandwidth,i.e.,labyrinth-type metamaterial and multi-order resonator metamaterial.The labyrinth-type metamaterial is designed through spatial dimension transfer,transferring the required dimension in the thickness direction to the planar thin layer.Based on the Helmholtz resonance,the metamaterial achieves noise reduction through the reflection of sound waves and the thermoviscous dissipation of holes and cavities.This mechanism enables its sound insulation performance to produce the same gain effect as absorption,thereby accomplishing the broadband absorbing-insulating integrated design.With a thickness of only 33 mm,it achieves both sound absorption and insulation effects over more than one octave.The multi-order resonator metamaterial has a larger working bandwidth than the labyrinth-type metamaterial.It is designed based on the multiorder resonance absorption mechanism,and consists of 9 different orders of resonator units.The metamaterial obtains a continuous sound absorption coefficient curve in the low-frequency range of 362–1712 Hz,and possesses high transmission loss(TL)above 346 Hz.In addition,this paper deeply explores the sound absorbing-insulating mechanism through the correlation analysis between the sound absorption coefficient and TL curves.The experimental results verify the continuous and efficient absorption effects of the two metamaterials,as well as their insulation performance that breaks the mass law.In low-frequency engineering applications,the two designed metamaterials demonstrate great potential and value at sub-wavelength dimensions.展开更多
B(G) denotes the bandwidth of graph G. For tree T, Ve(T)={v|v∈V(T) and dT(v)=1}. In this paper, we discuss bandwidths of trees and obtain that for any tree T,B(T)and the bounds is sharp. For two extreme cases, a tree...B(G) denotes the bandwidth of graph G. For tree T, Ve(T)={v|v∈V(T) and dT(v)=1}. In this paper, we discuss bandwidths of trees and obtain that for any tree T,B(T)and the bounds is sharp. For two extreme cases, a tree with a minimal number of internal vertices or one with a maximal number of internal vertices, that is, a star or a path, the equality holds.This bounds is much better than the previous one, B(G) .展开更多
Mechanical properties are critical to the quality of hot-rolled steel pipe products.Accurately understanding the relationship between rolling parameters and mechanical properties is crucial for effective prediction an...Mechanical properties are critical to the quality of hot-rolled steel pipe products.Accurately understanding the relationship between rolling parameters and mechanical properties is crucial for effective prediction and control.To address this,an industrial big data platform was developed to collect and process multi-source heterogeneous data from the entire production process,providing a complete dataset for mechanical property prediction.The adaptive bandwidth kernel density estimation(ABKDE)method was proposed to adjust bandwidth dynamically based on data density.Combining long short-term memory neural networks with ABKDE offers robust prediction interval capabilities for mechanical properties.The proposed method was deployed in a large-scale steel plant,which demonstrated superior prediction interval performance compared to lower upper bound estimation,mean variance estimation,and extreme learning machine-adaptive bandwidth kernel density estimation,achieving a prediction interval normalized average width of 0.37,a prediction interval coverage probability of 0.94,and the lowest coverage width-based criterion of 1.35.Notably,shapley additive explanations-based explanations significantly improved the proposed model’s credibility by providing a clear analysis of feature impacts.展开更多
With the boom in maritime activities,the need for highly reliable maritime communication is becoming urgent,which is an important component of 5G/6G communication networks.However,the bandwidth reuse characteristic of...With the boom in maritime activities,the need for highly reliable maritime communication is becoming urgent,which is an important component of 5G/6G communication networks.However,the bandwidth reuse characteristic of 5G/6G networks will inevitably lead to severe interference,resulting in degradation in the communication performance of maritime users.In this paper,we propose a safe deep reinforcement learning based interference coordination scheme to jointly optimize the power control and bandwidth allocation in maritime communication systems,and exploit the quality-of-service requirements of users as the risk value references to evaluate the communication policies.In particular,this scheme designs a deep neural network to select the communication policies through the evaluation network and update the parameters using the target network,which improves the communication performance and speeds up the convergence rate.Moreover,the Nash equilibrium of the interference coordination game and the computational complexity of the proposed scheme are analyzed.Simulation and experimental results verify the performance gain of the proposed scheme compared with benchmarks.展开更多
This study applies a double snap-through mechanism on a box-type oscillating buoy(OB)wave energy converter(WEC)-floating breakwater integrated system(OB WEC-FB)to simultaneously achieve efficient wave energy conversio...This study applies a double snap-through mechanism on a box-type oscillating buoy(OB)wave energy converter(WEC)-floating breakwater integrated system(OB WEC-FB)to simultaneously achieve efficient wave energy conversion and nearshore protection within a low-frequency bandwidth.This mechanism consists of four oblique springs and can operate in mono-stable,bi-stable,and tri-stable modes.A viscous-flow-based numerical model is established to investigate the hydrodynamic performance and dynamic behavior of the proposed multi-stable breakwater.The operational performance of the breakwater at different dynamic modes is first compared.The effects of the springs’original length and stiffness coefficient are then analyzed.The results show that the tri-stable breakwater has a wider resonance frequency tuning range than the bi-stable one,both of which outperform the mono-stable and linear ones in shifting the effective bandwidth to a lower frequency range.For a tri-stable breakwater,a large distance between outermost potential wells is conducive to tuning resonance frequency,whereas shallow potential wells limit this effect.The increase in spring stiffness distinctly causes a higher potential barrier and thus constrains the motion response of the breakwater.A well-designed double snap-through mechanism can excite large-amplitude inter-well motion,tune the resonance frequency of breakwater from 3.98 to 1.96 rad/s,and decrease the lower limit of the effective transmission bandwidth from 3.75 to 3.00 rad/s.It is crucial for improving the power absorption and wave attenuation capabilities of multi-stable OB WEC-FB.This study contributes to the limited research on the implementation of a double snap-through mechanism on multifunctional marine structures.It establishes the underlying connection between nonlinear dynamic behaviors and hydrodynamic coefficients.展开更多
Time Division Multiplexing-Passive Optical Networks(TDM-PONs)play a vital role in Fiberto-the-Home(FTTH)deployments.To improve the service quality of home networks,FTTH is expanding to the Fiber-to-the-Room(FTTR)scena...Time Division Multiplexing-Passive Optical Networks(TDM-PONs)play a vital role in Fiberto-the-Home(FTTH)deployments.To improve the service quality of home networks,FTTH is expanding to the Fiber-to-the-Room(FTTR)scenario,where fibers are deployed to connect individual rooms(i.e.,Fiber In-premises Network(FIN)in the ITU-T G.9940 standard).In this scenario,a point-to-multipoint(P2MP)fiber network is deployed as FTTR FIN to offer gigabit access to each room,which forms a two-tier cascaded network together with the FTTH segment.To optimize the capacity utilization of the cascaded network and reduce the overall system cost,a centralized architecture,known as Centralized Fixed Access Network(C-FAN),has been introduced.C-FAN centralizes the medium access control(MAC)modules of both the FTTH and FTTR networks at the FTTH’s Optical Line Terminal(OLT)for unified control and management of the cascaded network.We develop a unified bandwidth scheduling protocol by extending the ITU-T PON standard for both the upstream and downstream directions of C-FAN.We also propose a unified dynamic bandwidth allocation(UDBA)algorithm for efficient bandwidth allocation for multiple traffic flows in the two-tier cascaded network.Simulations are conducted to evaluate the performance of the proposed control protocol and the UDBA algorithm.The results show that,in comparison to the conventional DBA algorithm,the UDBA algorithm can utilize upstream bandwidth more efficiently to reduce packet delay and loss,without adversely impacting downstream transmission performance.展开更多
Magnetic resonance imaging(MRI)plays an important role in medical diagnosis,generating petabytes of image data annually in large hospitals.This voluminous data stream requires a significant amount of network bandwidth...Magnetic resonance imaging(MRI)plays an important role in medical diagnosis,generating petabytes of image data annually in large hospitals.This voluminous data stream requires a significant amount of network bandwidth and extensive storage infrastructure.Additionally,local data processing demands substantial manpower and hardware investments.Data isolation across different healthcare institutions hinders crossinstitutional collaboration in clinics and research.In this work,we anticipate an innovative MRI system and its four generations that integrate emerging distributed cloud computing,6G bandwidth,edge computing,federated learning,and blockchain technology.This system is called Cloud-MRI,aiming at solving the problems of MRI data storage security,transmission speed,artificial intelligence(AI)algorithm maintenance,hardware upgrading,and collaborative work.The workflow commences with the transformation of k-space raw data into the standardized Imaging Society for Magnetic Resonance in Medicine Raw Data(ISMRMRD)format.Then,the data are uploaded to the cloud or edge nodes for fast image reconstruction,neural network training,and automatic analysis.Then,the outcomes are seamlessly transmitted to clinics or research institutes for diagnosis and other services.The Cloud-MRI system will save the raw imaging data,reduce the risk of data loss,facilitate inter-institutional medical collaboration,and finally improve diagnostic accuracy and work efficiency.展开更多
In recent years,two-dimensional layered transition metal dichalcogenides-based multicomponent com-posites(MCCs)acting as electromagnetic wave(EMW)materials have received intensive investiga-tions.However,the vulcanica...In recent years,two-dimensional layered transition metal dichalcogenides-based multicomponent com-posites(MCCs)acting as electromagnetic wave(EMW)materials have received intensive investiga-tions.However,the vulcanication of metal greatly hindered their enhancement of EMW absorption per-formances(EMWAPs).Herein,a combined metal-organic frameworks-derived and hydrothermal strat-egy was presented to produce yolk-shell structure(YSS)CoNi@Air@C@MoS_(2) MCCs.The results showed that the thermal and hydrothermal treatments resulted in the generation of YSS and two-dimensional MoS_(2) nanosheets,which maintained the original morphology of CoNi Prussian blue analogues.The pro-tection of thick C layer well inhibited the vulcanization of inner CoNi alloy.The formed sheet-like MoS_(2) further optimized impedance matching characteristics,which led to the satisfactory EMWAPs of CoNi@Air@C@MoS_(2) MCCs.Furthermore,the EMWAPs could be further improved by optimizing the Ni:Co atom ratios CoNi@Air@C@MoS_(2) MCCs,which stemmed from their boosted impedance matching perfor-mances,EMW attention and polarization loss abilities.The absorption bandwidth and reflection loss val-ues for YSS CoNi@Air@C@MoS_(2) MCCs are 8 GHz and−60.83 dB,which covered almost all C-Ku bands.In general,our research work provided a valid strategy to produce YSS magnetic CoNi@Air@C@MoS_(2) MCCs with high efficiency,which well avoided the vulcanization of metal nanoparticles,made best of hollow engineering and atomic ratio optimization strategy to boost the comprehensive EMWAPs.展开更多
Terahertz(THz)switches are essential components of THz communication systems.THz switches based on conventional waveguides and photonic crystal structures are sensitive to manufacturing defects and sharp bending,resul...Terahertz(THz)switches are essential components of THz communication systems.THz switches based on conventional waveguides and photonic crystal structures are sensitive to manufacturing defects and sharp bending,resulting in high scattering losses.In addition,THz switches with tunable working bandwidths have not yet been demonstrated.Here,we design THz switches based on a topological valley photonic crystal(VPC)structure using magnetic materials,which can achieve high forward transmittance based on the unique spin–valley locking effect.The broad working bandwidth allows selective turning on and off at a designed wavelength region by controlling the applied magnetic field.The designed THz switch can achieve an extinction ratio of up to 31.66 dB with an insertion loss of less than 0.13 dB.The 3-dB bandwidth is up to 49 GHz.This tunable THz switch can be experimentally fabricated by current fabrication techniques and thus can find broad applications in THz communication systems.展开更多
Currently,the global 5G network,cloud computing,and data center industries are experiencing rapid development.The continuous growth of data center traffic has driven the vigorous progress in high-speed optical transce...Currently,the global 5G network,cloud computing,and data center industries are experiencing rapid development.The continuous growth of data center traffic has driven the vigorous progress in high-speed optical transceivers for optical interconnection within data centers.The electro-absorption modulated laser(EML),which is widely used in optical fiber communications,data centers,and high-speed data transmission systems,represents a high-performance photoelectric conversion device.Compared to traditional directly modulated lasers(DMLs),EMLs demonstrate lower frequency chirp and higher modulation bandwidth,enabling support for higher data rates and longer transmission distances.This article introduces the composition,working principles,manufacturing processes,and applications of EMLs.It reviews the progress on advanced indium phosphide(InP)-based EML devices from research institutions worldwide,while summarizing and comparing data transmission rates and key technical approaches across various studies.展开更多
Ultra-narrow bandwidth mode-locked lasers with tunable pulse duration can be versatile light sources for diverse applications.However,the spectral-temporal control of a narrow bandwidth mode-locked laser is challengin...Ultra-narrow bandwidth mode-locked lasers with tunable pulse duration can be versatile light sources for diverse applications.However,the spectral-temporal control of a narrow bandwidth mode-locked laser is challenging due to limited gain and nonlinearity,hindering practical applications of such lasers.We demonstrate a pulse duration widely tunable mode-locked ultra-narrow bandwidth laser using a composite filtering mechanism and a single-wall carbon nanotube.The laser pulse duration can be adjusted from 481 ps to 1.38 ns,which is the widest tuning range achieved in narrow-bandwidth passively mode-locked lasers.When the pulse duration is 1.38 ns,the corresponding spectral width reaches 4 pm(502 MHz).Numerical simulations support the experimental results and show that the evolution of long pulses in the laser cavity behaves similarly to a quasi-continuous wave with a low breathing ratio.We have not only designed a simple and flexible tunable scheme for the dilemma of spectral-temporal control in narrow-bandwidth mode-locked fiber lasers but also provided a unique and idealized light source for various applications that takes into account robust output.展开更多
Following publication of the original article[1],the authors found that they pasted the same data when drawing XRD for sample NCO-1 and NCO-2 in Fig.2a,however,the XRD of all four samples in the manuscript was tested,...Following publication of the original article[1],the authors found that they pasted the same data when drawing XRD for sample NCO-1 and NCO-2 in Fig.2a,however,the XRD of all four samples in the manuscript was tested,and XRD raw data were kept and can be offered.The correct Fig.2 has been provided in this Correction.展开更多
Maximize the resource utilization efficiency and guarantee the quality of service(QoS)of users by selecting the network are the key issues for heterogeneous network operators,but the resources occupied by users in dif...Maximize the resource utilization efficiency and guarantee the quality of service(QoS)of users by selecting the network are the key issues for heterogeneous network operators,but the resources occupied by users in different networks cannot be compared directly.This paper proposes a network selection algorithm for heterogeneous network.Firstly,the concept of equivalent bandwidth is proposed,through which the actual resources occupied by users with certain QoS requirements in different networks can be compared directly.Then the concept of network applicability is defined to express the abilities of networks to support different services.The proposed network selection algorithm first evaluates whether the network has enough equivalent bandwidth required by the user and then prioritizes network with poor applicability to avoid the situation that there are still residual resources in entire network,but advanced services can not be admitted.The simulation results show that the proposed algorithm obtained better performance than the baselines in terms of reducing call blocking probability and improving network resource utilization efficiency.展开更多
With the growing adoption of artificial intelligence algorithms and neural networks,online learning and adaptive methods for updating the bandwidth have become increasingly prevalent.However,the conditions required to...With the growing adoption of artificial intelligence algorithms and neural networks,online learning and adaptive methods for updating the bandwidth have become increasingly prevalent.However,the conditions required to ensure closed-loop stability when employing a time-varying bandwidth,as well as the supporting mathematical foundations,remain insufficiently studied.This paper investigates the stability condition for active disturbance rejection control(ADRC)with a time-varying bandwidth extended state observer(ESO).A new stability condition is derived,which means that the upper bound of rate of change for ESO bandwidth should be restricted.Moreover,under the proposed condition,the closed-loop stability of ADRC with a time-varying bandwidth observer is rigorously proved for nonlinear uncertainties.In simulations,the necessity of the proposed condition is illustrated,demonstrating that the rate of change of ESO bandwidth is crucial for closed-loop stability.展开更多
Achieving high-performance electromagnetic wave absorption(EMWA)capacity at thinner thicknesses remains a critical yet challenging objective.In this study,Dy_(2)O_(3)/Fe_(3)C/N-doped carbon(DFC)composites were synthes...Achieving high-performance electromagnetic wave absorption(EMWA)capacity at thinner thicknesses remains a critical yet challenging objective.In this study,Dy_(2)O_(3)/Fe_(3)C/N-doped carbon(DFC)composites were synthesized via a solvothermal process followed by high-temperature carbonization,with metal-organic frameworks(MOFs)used as precursors.By systematically adjusting the molar ratio of Dy^(3+)/Fe^(3+),the dielectric and magnetic properties of the materials were synergistically optimized.The EMWA performance exhibited a nonmonotonic dependence on the Dy^(3+)content,first increasing before decreasing at higher concentrations.At an optimal Dy^(3+)/Fe^(3+)molar ratio of 1.2:0.8,the DFC composites demonstrated a remarkable minimum reflection loss value of-56.08 dB at a mere 1.76 mm thickness,alongside an effective absorption bandwidth value of 5.12 GHz(12.56–17.68 GHz).The exceptional EMWA performance stems from optimized impedance matching,multiple scattering and reflections,dielectric loss,and magnetic loss.Furthermore,radar cross-section simulations validated the material’s practical applicability.Therefore,this work provides a novel strategy for designing next-generation EMWA materials with ultra-thin profiles and wideband absorption capabilities.展开更多
基金Supported by the National Key Basic Research Program of China under Grant No 2013CB921800the National Natural Science Foundation of China under Grant Nos 11227901,91021005,11274299,11104262 and 10834005the Strategic Priority Research Program(B)of the Chinese Academy of Sciences under Grant No XDB01030400
文摘Break junctions are important in generating nanosensors and single molecular devices. The mechanically con- trollable break junction is the most widely used method for a break junction due to its simplicity and stability. However, the bandwidths of traditional devices are limited to about a few hertz. Moreover, when using traditional methods it is hard to allow independent control of more than one junction. Here we propose on-chip thermally controllable break junctions to overcome these challenges. This is verified by using finite element analysis. Adopting microelectromechanical systems produces features of high bandwidth and independent controllability to this new break junction system. The proposed method will have a wide range of applications on on-chip high speed independent controllable and highly integrated single molecule devices.
文摘In this paper,we present a circuit model of single-quantum-well InGaN/GaN light-emitting diodes based on the standard rate equations.Two rate equations describe carrier transport processes occurring in sep-arate confinement heterostructure and quantum well respectively,and the third equation describes the varied photons in quantum well.By using the presented model,impacts of quantum well thickness on the static and dynamic performances are investigated.Simulated results show that LED with 4 nm well exhibits better lightcurrent(L-I)performance,but LED with 3 nm well presents wider 3 dB modulation bandwidth.It reveals that high carrier density in quantum well is detrimental to the static performance,but beneficial to the dynamic performance.
基金supported by the National Natural Science Foundation of China under Grant Nos.12201079,12201004,and 11871072the National Social Science Foundation of China under Grant No.22BTJ059+1 种基金the Natural Science Foundation of Anhui Province under Grant Nos.2108085QA15 and 2108085MA06the“INSA Senior Scientist”scheme at the CR Rao Advanced Institute of Mathematics,Statistics and Computer Science,Hyderabad 500046,India.
文摘In this paper,the authors study a class of weighted version of probability density estimator.It is shown that the weighted estimator contains some existing estimators of probability density,no matter they are recursive or non-recursive.Some statistical results including weak consistency,strong consistency,rate of strong consistency,and asymptotic normality are established under some mild conditions.Moreover,the random weighted estimator is also investigated.Some numerical simulations and a real data analysis are presented to study the numerical performances of the estimators.
文摘The rapid growth in available network bandwidth has directly contributed to an exponential increase in mobile data traffic,creating significant challenges for network energy consumption.Also,with the extraordinary growth of mobile communications,the data traffic has dramatically expanded,which has led to massive grid power consumption and incurred high operating expenditure(OPEX).However,the majority of current network designs struggle to efficientlymanage a massive amount of data using little power,which degrades energy efficiency performance.Thereby,it is necessary to have an efficient mechanism to reduce power consumption when processing large amounts of data in network data centers.Utilizing renewable energy sources to power the Cloud Radio Access Network(C-RAN)greatly reduces the need to purchase energy from the utility grid.In this paper,we propose a bandwidth-aware hybrid energypowered C-RAN that focuses on throughput and energy efficiency(EE)by lowering grid usage,aiming to enhance the EE.This paper examines the energy efficiency,spectral efficiency(SE),and average on-grid energy consumption,dealing with the major challenges of the temporal and spatial nature of traffic and renewable energy generation across various network setups.To assess the effectiveness of the suggested network by changing the transmission bandwidth,a comprehensive simulation has been conducted.The numerical findings support the efficacy of the suggested approach.
基金Project supported by the National Natural Science Foundation of China(No.52250287)the Outstanding Youth Science Fund Project of Shaanxi Province of China(No.2024JC-JCQN-49)。
文摘This paper proposes two types of integrated sound absorbing-insulating metamaterials with low thickness and efficient sound attenuation in the low-frequency bandwidth,i.e.,labyrinth-type metamaterial and multi-order resonator metamaterial.The labyrinth-type metamaterial is designed through spatial dimension transfer,transferring the required dimension in the thickness direction to the planar thin layer.Based on the Helmholtz resonance,the metamaterial achieves noise reduction through the reflection of sound waves and the thermoviscous dissipation of holes and cavities.This mechanism enables its sound insulation performance to produce the same gain effect as absorption,thereby accomplishing the broadband absorbing-insulating integrated design.With a thickness of only 33 mm,it achieves both sound absorption and insulation effects over more than one octave.The multi-order resonator metamaterial has a larger working bandwidth than the labyrinth-type metamaterial.It is designed based on the multiorder resonance absorption mechanism,and consists of 9 different orders of resonator units.The metamaterial obtains a continuous sound absorption coefficient curve in the low-frequency range of 362–1712 Hz,and possesses high transmission loss(TL)above 346 Hz.In addition,this paper deeply explores the sound absorbing-insulating mechanism through the correlation analysis between the sound absorption coefficient and TL curves.The experimental results verify the continuous and efficient absorption effects of the two metamaterials,as well as their insulation performance that breaks the mass law.In low-frequency engineering applications,the two designed metamaterials demonstrate great potential and value at sub-wavelength dimensions.
文摘B(G) denotes the bandwidth of graph G. For tree T, Ve(T)={v|v∈V(T) and dT(v)=1}. In this paper, we discuss bandwidths of trees and obtain that for any tree T,B(T)and the bounds is sharp. For two extreme cases, a tree with a minimal number of internal vertices or one with a maximal number of internal vertices, that is, a star or a path, the equality holds.This bounds is much better than the previous one, B(G) .
基金supported by the National Key Research and Development Plan(Grant No.2023YFB3712400)the National Key Research and Development Plan(Grant No.2020YFB1713600).
文摘Mechanical properties are critical to the quality of hot-rolled steel pipe products.Accurately understanding the relationship between rolling parameters and mechanical properties is crucial for effective prediction and control.To address this,an industrial big data platform was developed to collect and process multi-source heterogeneous data from the entire production process,providing a complete dataset for mechanical property prediction.The adaptive bandwidth kernel density estimation(ABKDE)method was proposed to adjust bandwidth dynamically based on data density.Combining long short-term memory neural networks with ABKDE offers robust prediction interval capabilities for mechanical properties.The proposed method was deployed in a large-scale steel plant,which demonstrated superior prediction interval performance compared to lower upper bound estimation,mean variance estimation,and extreme learning machine-adaptive bandwidth kernel density estimation,achieving a prediction interval normalized average width of 0.37,a prediction interval coverage probability of 0.94,and the lowest coverage width-based criterion of 1.35.Notably,shapley additive explanations-based explanations significantly improved the proposed model’s credibility by providing a clear analysis of feature impacts.
文摘With the boom in maritime activities,the need for highly reliable maritime communication is becoming urgent,which is an important component of 5G/6G communication networks.However,the bandwidth reuse characteristic of 5G/6G networks will inevitably lead to severe interference,resulting in degradation in the communication performance of maritime users.In this paper,we propose a safe deep reinforcement learning based interference coordination scheme to jointly optimize the power control and bandwidth allocation in maritime communication systems,and exploit the quality-of-service requirements of users as the risk value references to evaluate the communication policies.In particular,this scheme designs a deep neural network to select the communication policies through the evaluation network and update the parameters using the target network,which improves the communication performance and speeds up the convergence rate.Moreover,the Nash equilibrium of the interference coordination game and the computational complexity of the proposed scheme are analyzed.Simulation and experimental results verify the performance gain of the proposed scheme compared with benchmarks.
基金supported by the National Natural Science Foundation of China Program(No.51739010).
文摘This study applies a double snap-through mechanism on a box-type oscillating buoy(OB)wave energy converter(WEC)-floating breakwater integrated system(OB WEC-FB)to simultaneously achieve efficient wave energy conversion and nearshore protection within a low-frequency bandwidth.This mechanism consists of four oblique springs and can operate in mono-stable,bi-stable,and tri-stable modes.A viscous-flow-based numerical model is established to investigate the hydrodynamic performance and dynamic behavior of the proposed multi-stable breakwater.The operational performance of the breakwater at different dynamic modes is first compared.The effects of the springs’original length and stiffness coefficient are then analyzed.The results show that the tri-stable breakwater has a wider resonance frequency tuning range than the bi-stable one,both of which outperform the mono-stable and linear ones in shifting the effective bandwidth to a lower frequency range.For a tri-stable breakwater,a large distance between outermost potential wells is conducive to tuning resonance frequency,whereas shallow potential wells limit this effect.The increase in spring stiffness distinctly causes a higher potential barrier and thus constrains the motion response of the breakwater.A well-designed double snap-through mechanism can excite large-amplitude inter-well motion,tune the resonance frequency of breakwater from 3.98 to 1.96 rad/s,and decrease the lower limit of the effective transmission bandwidth from 3.75 to 3.00 rad/s.It is crucial for improving the power absorption and wave attenuation capabilities of multi-stable OB WEC-FB.This study contributes to the limited research on the implementation of a double snap-through mechanism on multifunctional marine structures.It establishes the underlying connection between nonlinear dynamic behaviors and hydrodynamic coefficients.
基金supported by National Nature Science Founding of China(62101372)Open Fund of IPOC(BUPT,IPOC2022A07)+1 种基金State Key Laboratory of Advanced Optical Communication Systems and Networks(2023GZKF11)Leading Youth Talents of Innovation and Entrepreneurship of Gusu(ZXL2023162).
文摘Time Division Multiplexing-Passive Optical Networks(TDM-PONs)play a vital role in Fiberto-the-Home(FTTH)deployments.To improve the service quality of home networks,FTTH is expanding to the Fiber-to-the-Room(FTTR)scenario,where fibers are deployed to connect individual rooms(i.e.,Fiber In-premises Network(FIN)in the ITU-T G.9940 standard).In this scenario,a point-to-multipoint(P2MP)fiber network is deployed as FTTR FIN to offer gigabit access to each room,which forms a two-tier cascaded network together with the FTTH segment.To optimize the capacity utilization of the cascaded network and reduce the overall system cost,a centralized architecture,known as Centralized Fixed Access Network(C-FAN),has been introduced.C-FAN centralizes the medium access control(MAC)modules of both the FTTH and FTTR networks at the FTTH’s Optical Line Terminal(OLT)for unified control and management of the cascaded network.We develop a unified bandwidth scheduling protocol by extending the ITU-T PON standard for both the upstream and downstream directions of C-FAN.We also propose a unified dynamic bandwidth allocation(UDBA)algorithm for efficient bandwidth allocation for multiple traffic flows in the two-tier cascaded network.Simulations are conducted to evaluate the performance of the proposed control protocol and the UDBA algorithm.The results show that,in comparison to the conventional DBA algorithm,the UDBA algorithm can utilize upstream bandwidth more efficiently to reduce packet delay and loss,without adversely impacting downstream transmission performance.
基金supported by the National Natural Science Foundation of China(62122064,62331021,62371410)the Natural Science Foundation of Fujian Province of China(2023J02005 and 2021J011184)+1 种基金the President Fund of Xiamen University(20720220063)the Nanqiang Outstanding Talents Program of Xiamen University.
文摘Magnetic resonance imaging(MRI)plays an important role in medical diagnosis,generating petabytes of image data annually in large hospitals.This voluminous data stream requires a significant amount of network bandwidth and extensive storage infrastructure.Additionally,local data processing demands substantial manpower and hardware investments.Data isolation across different healthcare institutions hinders crossinstitutional collaboration in clinics and research.In this work,we anticipate an innovative MRI system and its four generations that integrate emerging distributed cloud computing,6G bandwidth,edge computing,federated learning,and blockchain technology.This system is called Cloud-MRI,aiming at solving the problems of MRI data storage security,transmission speed,artificial intelligence(AI)algorithm maintenance,hardware upgrading,and collaborative work.The workflow commences with the transformation of k-space raw data into the standardized Imaging Society for Magnetic Resonance in Medicine Raw Data(ISMRMRD)format.Then,the data are uploaded to the cloud or edge nodes for fast image reconstruction,neural network training,and automatic analysis.Then,the outcomes are seamlessly transmitted to clinics or research institutes for diagnosis and other services.The Cloud-MRI system will save the raw imaging data,reduce the risk of data loss,facilitate inter-institutional medical collaboration,and finally improve diagnostic accuracy and work efficiency.
基金supported by the Guizhou Provincial Science and Technology Projects for Platform and Talent Team Plan(No.GCC[2023]007)the Innovation Group of Guizhou University(No.[2024]08)+1 种基金Fok Ying Tung Education Foundation(No.171095)the National Natural Science Foundation of China(No.11964006).
文摘In recent years,two-dimensional layered transition metal dichalcogenides-based multicomponent com-posites(MCCs)acting as electromagnetic wave(EMW)materials have received intensive investiga-tions.However,the vulcanication of metal greatly hindered their enhancement of EMW absorption per-formances(EMWAPs).Herein,a combined metal-organic frameworks-derived and hydrothermal strat-egy was presented to produce yolk-shell structure(YSS)CoNi@Air@C@MoS_(2) MCCs.The results showed that the thermal and hydrothermal treatments resulted in the generation of YSS and two-dimensional MoS_(2) nanosheets,which maintained the original morphology of CoNi Prussian blue analogues.The pro-tection of thick C layer well inhibited the vulcanization of inner CoNi alloy.The formed sheet-like MoS_(2) further optimized impedance matching characteristics,which led to the satisfactory EMWAPs of CoNi@Air@C@MoS_(2) MCCs.Furthermore,the EMWAPs could be further improved by optimizing the Ni:Co atom ratios CoNi@Air@C@MoS_(2) MCCs,which stemmed from their boosted impedance matching perfor-mances,EMW attention and polarization loss abilities.The absorption bandwidth and reflection loss val-ues for YSS CoNi@Air@C@MoS_(2) MCCs are 8 GHz and−60.83 dB,which covered almost all C-Ku bands.In general,our research work provided a valid strategy to produce YSS magnetic CoNi@Air@C@MoS_(2) MCCs with high efficiency,which well avoided the vulcanization of metal nanoparticles,made best of hollow engineering and atomic ratio optimization strategy to boost the comprehensive EMWAPs.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1404201)Australia Research Council(Grant Nos.DP220100603 and FT220100559)+7 种基金the National Natural Science Foundation of China(Grant No.U23A20375)the Natural Science Foundation of Shanxi Province(Grant No.202403021211011)Research Project Supported by Shanxi Scholarship Council of China(Grant No.2024-032)Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province(Grant No.20240006)the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices(Grant No.KF202402)Basic Scientific Research Conditions and Major Scientific Instrument and Equipment Development of Anhui Science and Technology Department(Grant No.2023YFF0715700)Key Research Project of Shanxi Province(Grant No.202302150101001)Linkage Project Scheme(Grant Nos.LP210200345 and LP210100467).
文摘Terahertz(THz)switches are essential components of THz communication systems.THz switches based on conventional waveguides and photonic crystal structures are sensitive to manufacturing defects and sharp bending,resulting in high scattering losses.In addition,THz switches with tunable working bandwidths have not yet been demonstrated.Here,we design THz switches based on a topological valley photonic crystal(VPC)structure using magnetic materials,which can achieve high forward transmittance based on the unique spin–valley locking effect.The broad working bandwidth allows selective turning on and off at a designed wavelength region by controlling the applied magnetic field.The designed THz switch can achieve an extinction ratio of up to 31.66 dB with an insertion loss of less than 0.13 dB.The 3-dB bandwidth is up to 49 GHz.This tunable THz switch can be experimentally fabricated by current fabrication techniques and thus can find broad applications in THz communication systems.
基金supported by the Strategic Priority Research Program of CAS(Grant No.XDB43020202)the Natural Science Foundation of China(Grant Nos.61934007,62274153,62090053).
文摘Currently,the global 5G network,cloud computing,and data center industries are experiencing rapid development.The continuous growth of data center traffic has driven the vigorous progress in high-speed optical transceivers for optical interconnection within data centers.The electro-absorption modulated laser(EML),which is widely used in optical fiber communications,data centers,and high-speed data transmission systems,represents a high-performance photoelectric conversion device.Compared to traditional directly modulated lasers(DMLs),EMLs demonstrate lower frequency chirp and higher modulation bandwidth,enabling support for higher data rates and longer transmission distances.This article introduces the composition,working principles,manufacturing processes,and applications of EMLs.It reviews the progress on advanced indium phosphide(InP)-based EML devices from research institutions worldwide,while summarizing and comparing data transmission rates and key technical approaches across various studies.
基金supported by the National Natural Science Foundation of China(Grant No.61975107)the Natural Science Foundation of Shanghai(Grant Nos.24ZR1422000 and 20ZR1471500),and the“111”Project(Grant No.D20031).
文摘Ultra-narrow bandwidth mode-locked lasers with tunable pulse duration can be versatile light sources for diverse applications.However,the spectral-temporal control of a narrow bandwidth mode-locked laser is challenging due to limited gain and nonlinearity,hindering practical applications of such lasers.We demonstrate a pulse duration widely tunable mode-locked ultra-narrow bandwidth laser using a composite filtering mechanism and a single-wall carbon nanotube.The laser pulse duration can be adjusted from 481 ps to 1.38 ns,which is the widest tuning range achieved in narrow-bandwidth passively mode-locked lasers.When the pulse duration is 1.38 ns,the corresponding spectral width reaches 4 pm(502 MHz).Numerical simulations support the experimental results and show that the evolution of long pulses in the laser cavity behaves similarly to a quasi-continuous wave with a low breathing ratio.We have not only designed a simple and flexible tunable scheme for the dilemma of spectral-temporal control in narrow-bandwidth mode-locked fiber lasers but also provided a unique and idealized light source for various applications that takes into account robust output.
文摘Following publication of the original article[1],the authors found that they pasted the same data when drawing XRD for sample NCO-1 and NCO-2 in Fig.2a,however,the XRD of all four samples in the manuscript was tested,and XRD raw data were kept and can be offered.The correct Fig.2 has been provided in this Correction.
文摘Maximize the resource utilization efficiency and guarantee the quality of service(QoS)of users by selecting the network are the key issues for heterogeneous network operators,but the resources occupied by users in different networks cannot be compared directly.This paper proposes a network selection algorithm for heterogeneous network.Firstly,the concept of equivalent bandwidth is proposed,through which the actual resources occupied by users with certain QoS requirements in different networks can be compared directly.Then the concept of network applicability is defined to express the abilities of networks to support different services.The proposed network selection algorithm first evaluates whether the network has enough equivalent bandwidth required by the user and then prioritizes network with poor applicability to avoid the situation that there are still residual resources in entire network,but advanced services can not be admitted.The simulation results show that the proposed algorithm obtained better performance than the baselines in terms of reducing call blocking probability and improving network resource utilization efficiency.
基金supported partially by the National Natural Science Foundation(No.62473344)the T-Flight Laboratory in ShanXi Provincial(No.GSFC2024NBKY05)+1 种基金the Natural Science Basic Research Program of Shaanxi(No.2025JC-YBQN-035)the National Natural Science Foundation of China(Grant No.92471204).
文摘With the growing adoption of artificial intelligence algorithms and neural networks,online learning and adaptive methods for updating the bandwidth have become increasingly prevalent.However,the conditions required to ensure closed-loop stability when employing a time-varying bandwidth,as well as the supporting mathematical foundations,remain insufficiently studied.This paper investigates the stability condition for active disturbance rejection control(ADRC)with a time-varying bandwidth extended state observer(ESO).A new stability condition is derived,which means that the upper bound of rate of change for ESO bandwidth should be restricted.Moreover,under the proposed condition,the closed-loop stability of ADRC with a time-varying bandwidth observer is rigorously proved for nonlinear uncertainties.In simulations,the necessity of the proposed condition is illustrated,demonstrating that the rate of change of ESO bandwidth is crucial for closed-loop stability.
基金financially supported by the National Natural Science Foundation of China(Nos.52173267,21667019,22066017,and 51861006)the Key Laboratory of High-temperature Electromagnetic Materials and Structure of MOE(No.KB202402)+1 种基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX23_1867)the Cultivation Program for Excellent Master’s Theses(No.LWPY2414).
文摘Achieving high-performance electromagnetic wave absorption(EMWA)capacity at thinner thicknesses remains a critical yet challenging objective.In this study,Dy_(2)O_(3)/Fe_(3)C/N-doped carbon(DFC)composites were synthesized via a solvothermal process followed by high-temperature carbonization,with metal-organic frameworks(MOFs)used as precursors.By systematically adjusting the molar ratio of Dy^(3+)/Fe^(3+),the dielectric and magnetic properties of the materials were synergistically optimized.The EMWA performance exhibited a nonmonotonic dependence on the Dy^(3+)content,first increasing before decreasing at higher concentrations.At an optimal Dy^(3+)/Fe^(3+)molar ratio of 1.2:0.8,the DFC composites demonstrated a remarkable minimum reflection loss value of-56.08 dB at a mere 1.76 mm thickness,alongside an effective absorption bandwidth value of 5.12 GHz(12.56–17.68 GHz).The exceptional EMWA performance stems from optimized impedance matching,multiple scattering and reflections,dielectric loss,and magnetic loss.Furthermore,radar cross-section simulations validated the material’s practical applicability.Therefore,this work provides a novel strategy for designing next-generation EMWA materials with ultra-thin profiles and wideband absorption capabilities.
