The key parameters that characterize the morphological quality of multi-layer and multi-pass metal laser deposited parts are the surface roughness and the error between the actual printing height and the theoretical m...The key parameters that characterize the morphological quality of multi-layer and multi-pass metal laser deposited parts are the surface roughness and the error between the actual printing height and the theoretical model height.The Taguchi method was employed to establish the correlations between process parameter combinations and multi-objective characterization of metal deposition morphology(height error and roughness).Results show that using the signal-to-noise ratio and grey relational analysis,the optimal parameter combination for multi-layer and multi-pass deposition is determined as follows:laser power of 800 W,powder feeding rate of 0.3 r/min,step distance of 1.6 mm,and scanning speed of 20 mm/s.Subsequently,a Genetic Bayesian-back propagation(GB-BP)network is constructed to predict multi-objective responses.Compared with the traditional back propagation network,the GB-back propagation network improves the prediction accuracy of height error and surface roughness by 43.14%and 71.43%,respectively.This network can accurately predict the multi-objective characterization of morphological quality of multi-layer and multi-pass metal deposited parts.展开更多
The increasing electrification of urban transportation,i.e.,subways and electric vehicles(EV),brings more interactions between the power system and transportation system and further results in fault propagation across...The increasing electrification of urban transportation,i.e.,subways and electric vehicles(EV),brings more interactions between the power system and transportation system and further results in fault propagation across them.To analyze vulnerability of the coupling system under extreme events,this paper establishes a multi-layer urban electric-transportation interdependent network(ETIN)model.First,a weighted coupled metro-road traffic network(CTN)model and network path planning approach are proposed.A prospect theory-based failure load redistribution(FLR)method is further established to account for uncertainty of TN link capacity affected by power supply.Second,topology and emergency control strategy of power network(PN)are modeled,followed by formulation of multi-layer ETIN model.In particular,the inter-layer fault propagation from PN to TN is modeled based on power supply correlation strength,while from TN to PN is modeled based on traffic flow.A few indexes are then defined to quantify vulnerability of ETIN under deliberate attack.Finally,the proposed method is verified on an electric-transportation system to show influence of fault propagations within ETIN on its vulnerability under extreme events.展开更多
To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.T...To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.This source is based on spontaneous four-wave mixing(SFWM)in a piece of shallow-ridge silicon waveguide.Theoretical analysis shows that the waveguide dispersion could be tailored by adjusting the ridge width,enabling broadband photon pair generation by SFWM across C band and O band.The spontaneous Raman scattering(SpRS)in silicon waveguides is also investigated experimentally.It shows that there are two regions in the spectrum of generated photons from SpRS,which could be used to achieve cross-band photon pair generation.A chip of shallow-ridge silicon waveguide samples with different ridge widths has been fabricated,through which cross-band photon pair generation is demonstrated experimentally.The experimental results show that the source can be achieved using dispersion-optimized shallow-ridge silicon waveguides.This cross-band quantum light source provides a way to develop new fiber-based quantum communication functions utilizing both C band and O band and extends applications of quantum networks.展开更多
Although multicrystalline Si photovoltaics have been extensively studied and applied in the collection of solar energy,the same systems suffer significant efficiency losses in indoor settings,where ambient light condi...Although multicrystalline Si photovoltaics have been extensively studied and applied in the collection of solar energy,the same systems suffer significant efficiency losses in indoor settings,where ambient light conditions are considerably smaller in intensity and possess greater components of non-normal incidence.Yet,indoor light-driven,stand-alone devices can offer sustainable advances in next-generation technologies such as the Internet of Things.Here,we present a non-invasive solution to aid in photovoltaic indoor light collection—radially distributed waveguide-encoded lattice(RDWEL)slim films(thickness 1.5 mm).Embedded with a monotonical radial array of cylindrical waveguides(±20°),the RDWEL demonstrates seamless light collection(FoV(fields of view)=74.5°)and imparts enhancements in JSC(short circuit current density)of 44%and 14%for indoor and outdoor lighting conditions,respectively,when coupled to a photovoltaic device and compared to an unstructured but otherwise identical slim film coating.展开更多
Improving the optoelectronic behavior and stress-deformation stability of conjugated materials is crucial for the realization of their potential applications in flexible optoelectronics.To tune the emission behavior a...Improving the optoelectronic behavior and stress-deformation stability of conjugated materials is crucial for the realization of their potential applications in flexible optoelectronics.To tune the emission behavior and mechanical property of molecular crystals simultaneously via supramolecular salt strategy is rarely reported,which is very important to improve their photophysical behavior and softness for the fabrication of flexible light-emitting device.Herein,supramolecular salt approach has been successfully applied to synthesize two elastic organic fluorescent crystals(CMOH-Py-Cl and CMOH-Py-Br)derived from non-emissive and brittle pyridine-substituted coumarin derivative(CMOH-Py).Their elastic properties can be attributed to the prevalent presence of numerous weak interactions introduced by halogen atoms,which are beneficial to the absorption and release of mechanical energy.Furthermore,density functional theory(DFT)calculations demonstrated a narrowing of the HOMO-LUMO energy gaps from CMOH-Py to CMOH-Py-Cl/CMOH-Py-Br via supramolecular salt approach.Finally,the application of flexible crystal materials in the field of optical waveguides has been investigated.The transformation of crystals in terms of photophysical and mechanical properties,achieved by the supramolecular salt approach,offers novel insights into the design and construction of flexible crystalline materials,providing a new path for the development of next-generation smart materials.展开更多
At present,the emerging solid-phase friction-based additive manufacturing technology,including friction rolling additive man-ufacturing(FRAM),can only manufacture simple single-pass components.In this study,multi-laye...At present,the emerging solid-phase friction-based additive manufacturing technology,including friction rolling additive man-ufacturing(FRAM),can only manufacture simple single-pass components.In this study,multi-layer multi-pass FRAM-deposited alumin-um alloy samples were successfully prepared using a non-shoulder tool head.The material flow behavior and microstructure of the over-lapped zone between adjacent layers and passes during multi-layer multi-pass FRAM deposition were studied using the hybrid 6061 and 5052 aluminum alloys.The results showed that a mechanical interlocking structure was formed between the adjacent layers and the adja-cent passes in the overlapped center area.Repeated friction and rolling of the tool head led to different degrees of lateral flow and plastic deformation of the materials in the overlapped zone,which made the recrystallization degree in the left and right edge zones of the over-lapped zone the highest,followed by the overlapped center zone and the non-overlapped zone.The tensile strength of the overlapped zone exceeded 90%of that of the single-pass deposition sample.It is proved that although there are uneven grooves on the surface of the over-lapping area during multi-layer and multi-pass deposition,they can be filled by the flow of materials during the deposition of the next lay-er,thus ensuring the dense microstructure and excellent mechanical properties of the overlapping area.The multi-layer multi-pass FRAM deposition overcomes the limitation of deposition width and lays the foundation for the future deposition of large-scale high-performance components.展开更多
Miniaturized erbium-doped waveguide amplifiers attracted great interests in recent decades due to their high gain-efficiency and function-scalability in the telecom C-band.In this work,an erbium-doped thin film lithiu...Miniaturized erbium-doped waveguide amplifiers attracted great interests in recent decades due to their high gain-efficiency and function-scalability in the telecom C-band.In this work,an erbium-doped thin film lithium niobate waveguide amplifier achieving>10 dB off-chip(fiber-to-fiber)net gain and>20 mW fiber-output amplified power is demonstrated,thanks to the low-propagation-loss waveguides and robust waveguide edge-couplers prepared by the photolithography assisted chemomechanical etching technique.Systematic investigation on the fabricated waveguide amplifiers reveals remarkable optical gain around the peak wavelength of 1532 nm as well as the low fiber-coupling loss of-1.2 dB/facet.A fiber Bragg-grating based waveguide laser is further demonstrated using the fabricated waveguide amplifier as the external gain chip,which generates>2 mW off-chip power continuous-wave lasing around the gain peak at 1532 nm.The unambiguous demonstration of fiber-to-fiber net gain of the erbium-doped thinfilm lithium niobate(TFLN)waveguide amplifier as well as its external gain chip application will benefit diverse fields demanding scalable gain elements with highspeed tunability.展开更多
In the process of power scaling large-area Quantum Cascade Lasers(QCLs),challenges such as degradation of beam quality and emission of multilobed far-field modes are frequently encountered.These issues become particul...In the process of power scaling large-area Quantum Cascade Lasers(QCLs),challenges such as degradation of beam quality and emission of multilobed far-field modes are frequently encountered.These issues become particularly pronounced with an increase in ridge width,resulting in multimode problems.To tackle this,an innovative multi ridge waveguide structure based on the principle of supersymmetry(SUSY)was proposed.This structure comprises a wider main waveguide in the center and two narrower auxiliary waveguides on either side.The high-order modes of the main waveguide are coupled with the modes of the auxiliary waveguides through mode-matching design,and the optical loss of the auxiliary waveguides suppresses these modes,thereby achieving fundamental mode lasing of the wider main waveguide.This paper employs the finite difference eigenmode(FDE)method to perform detailed structural modeling and simulation optimization of the 4.6μm wavelength quantum cascade laser,successfully achieving a single transverse mode QCL with a ridge width of 10μm.In comparison to the traditional single-mode QCL(with a ridge width of about 5μm),the MRW structure has the potential to increase the gain area of the laser by 100%.This offers a novel design concept and methodology for enhancing the single-mode luminous power of mid-infrared quantum cascade lasers,which is of considerable significance.展开更多
[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,...[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,with multi-channel slow-wave structures(SWSs)forming the foundation for their realization in high-power vacuum electronic devices.[Purpose]To provide design insights for multi-channel TWTs and simultaneously enhance their output power,a W-band folded-waveguide TWT with dual electron beams and H-plane power combining was proposed.[Methods]Three-dimensional electromagnetic simulations in CST were conducted to verify the highfrequency characteristics,electric field distribution,and amplification performance of the proposed SWS,thereby confirming the validity of the design.[Results]Results indicate that the designed TWT achieves a transmission bandwidth of 10 GHz.With an electron beam voltage of 17.9 kV and a current of 0.35 A,the output power reaches 450 W at 94 GHz,corresponding to an efficiency of 7.18%and a gain of 23.5 dB.Moreover,under fixed beam voltage and current,the TWT delivers over 200 W output power across 91–99 GHz,with a 3 dB bandwidth of 91–98.5 GHz.The particle voltage distribution after modulation further validates the mode analysis.[Conclusions]These results demonstrate the feasibility of compact dual-beam power-combining structures and provide useful guidance for the design of future multi-channel TWTs.展开更多
This study involved a comprehensive investigation aimed at achieving efficient multi-millijoule THz wave generation by exploiting the unique properties of cylindrical GaAs waveguides as effective mediators of the conv...This study involved a comprehensive investigation aimed at achieving efficient multi-millijoule THz wave generation by exploiting the unique properties of cylindrical GaAs waveguides as effective mediators of the conversion of laser energy into THz waves.Through meticulous investigation,valuable insights into optimizing THz generation processes for practical applications were unearthed.By investigating Hertz potentials,an eigen-value equation for the solutions of the guided modes(i.e.,eigenvalues)was found.The effects of various param-eters,including the effective mode index and the laser pulse power,on the electric field components of THz radia-tion,including the fundamental TE(transverse electric)and TM(transverse magnetic)modes,were evaluated.By analyzing these factors,this research elucidated the nuanced mechanisms governing THz wave generation within cylindrical GaAs waveguides,paving the way for refined methodologies and enhanced efficiency.The sig-nificance of cylindrical GaAs waveguides extends beyond their roles as mere facilitators of THz generation;their design and fabrication hold the key to unlocking the potential for compact and portable THz systems.This trans-formative capability not only amplifies the efficiency of THz generation but also broadens the horizons of practical applications.展开更多
In this paper,a terahertz slotted waveguide array antenna is designed based on photonic crystal,which can realize efficient radiation of terahertz waves.The electromagnetic wave is fed from the rectangular waveguide a...In this paper,a terahertz slotted waveguide array antenna is designed based on photonic crystal,which can realize efficient radiation of terahertz waves.The electromagnetic wave is fed from the rectangular waveguide at the bottom of the antenna,coupled to photonic crystal waveguide through photonic crystal cavity,and radiated outward through slots at the top layer of antenna.The simulation results show that the antenna achieves a peak gain of 13.45 dBi at 360 GHz,a half-power beam width of 10.9°,and a side lobe level of−13.9 dB.The antenna based on photonic crystal has the advantages of low profile,low loss,and high radiation efficiency,which can be applied to terahertz wireless communication systems.展开更多
A plasmonics waveguide structure that consist of a non-through metal–insulator–metal(MIM)waveguide coupled with a D-shaped cavity was designed.And the transmission properties,magnetic field distribution,and refracti...A plasmonics waveguide structure that consist of a non-through metal–insulator–metal(MIM)waveguide coupled with a D-shaped cavity was designed.And the transmission properties,magnetic field distribution,and refractive index sensing functionality were simulated using the finite element method(FEM).A multi-Fano resonance phenomenon was clearly observable in the transmission spectra.The Fano resonances observed in the proposed structure arise from the interaction between the discrete states of the Dshaped resonant cavity and the continuum state of the non-through MIM waveguide.The influence of structural parameters on Fano resonance modulation was investigated through systematic parameter adjustments.Additionally,the refractive index sensing properties,based on the Fano resonance,were investigated by varying the refractive index of the MIM waveguide's insulator layer.A maximum sensitivity and FOM of 1155 RIU/nm and 40 were achieved,respectively.This research opens up new possibilities for designing and exploring high-sensitivity photonic devices,micro-sensors,and innovative on-chip sensing architectures for future applications.展开更多
Ferrimagnetic materials exhibiting remanence can be used to achieve unidirectional electromagnetic-field propagation in the form of magnetoplasmons(MPs)in the subwavelength regime.This study investigates the MP proper...Ferrimagnetic materials exhibiting remanence can be used to achieve unidirectional electromagnetic-field propagation in the form of magnetoplasmons(MPs)in the subwavelength regime.This study investigates the MP properties and various guiding modes in a hollow cylindrical waveguide made of materials that exhibit remanence.Pattern analysis and numerical simulations are used to demonstrate that dispersion relationships and electromagnetic-field distribution are strongly affected by the operating frequency and physical dimensions of the structure.In addition,the existence of two different guiding modes is proved,namely regular and surface-wave modes.By adjusting the operating frequency and reducing the diameter of the hollow cylinder,the regular mode can be suppressed so as to only retain the surface-wave mode,which enables unidirectional MP propagation in the cylindrical waveguide.Moreover,the unidirectional surface-wave mode is robust to backscattering due to surface roughness and defects,which makes it very useful for application in field-enhancement devices.展开更多
The huge impact kinetic energy cannot be quickly dissipated by the energy-absorbing structure and transferred to the other vehicle through the car body structure,which will cause structural damage and threaten the liv...The huge impact kinetic energy cannot be quickly dissipated by the energy-absorbing structure and transferred to the other vehicle through the car body structure,which will cause structural damage and threaten the lives of the occupants.Therefore,it is necessary to understand the laws of energy conversion,dissipation and transfer during train collisions.This study proposes a multi-layer progressive analysis method of energy flow during train collisions,considering the characteristics of the train.In this method,the train collision system is divided into conversion,dissipation,and transfer layers from the perspective of the train,collision interface,and car body structure to analyze the energy conversion,dissipation and transfer characteristics.Taking the collision process of a rail train as an example,a train collision energy transfer path analysis model was established based on power flow theory.The results show that when the maximum mean acceleration of the vehicle meets the standard requirements,the jerk may exceed the allowable limit of the human body,and there is a risk of injury to the occupants of a secondary collision.The decay rate of the collision energy along the direction of train operation reaches 79%.As the collision progresses,the collision energy gradually converges in the structure with holes,and the structure deforms when the gathered energy is greater than the maximum energy the structure can withstand.The proposed method helps to understand the train collision energy flow law and provides theoretical support for the train crashworthiness design in the future.展开更多
A triple-band miniaturized end-fire antenna based on the odd modes of spoof surface plasmonic polariton(SSPP)waveguide resonator is proposed in this paper.To meet the ever increasing demand for more communication chan...A triple-band miniaturized end-fire antenna based on the odd modes of spoof surface plasmonic polariton(SSPP)waveguide resonator is proposed in this paper.To meet the ever increasing demand for more communication channels and less antenna sizes,multi-band antennas are currently under intensive investigation.By a novel feeding method,three odd modes are excited on an SSPP waveguide resonator,which performs as an end-fire antenna operating at three bands,7.15-7.26 GHz,11.6-12.2 GHz and 13.5-13.64 GHz.It exhibits reasonably high and stable maximum gains of 5.26 dBi,7.97 dBi and 10.1 dBi and maximum efficiencies of 64%,92%and 98%at the three bands,respectively.Moreover,in the second band,the main beam angle shows a frequency dependence with a total scanning angle of 19°.The miniaturized triple-band antenna has a great potential in wireless communication systems,satellite communication and radar systems.展开更多
The growing incidence of cyberattacks necessitates a robust and effective Intrusion Detection Systems(IDS)for enhanced network security.While conventional IDSs can be unsuitable for detecting different and emerging at...The growing incidence of cyberattacks necessitates a robust and effective Intrusion Detection Systems(IDS)for enhanced network security.While conventional IDSs can be unsuitable for detecting different and emerging attacks,there is a demand for better techniques to improve detection reliability.This study introduces a new method,the Deep Adaptive Multi-Layer Attention Network(DAMLAN),to boost the result of intrusion detection on network data.Due to its multi-scale attention mechanisms and graph features,DAMLAN aims to address both known and unknown intrusions.The real-world NSL-KDD dataset,a popular choice among IDS researchers,is used to assess the proposed model.There are 67,343 normal samples and 58,630 intrusion attacks in the training set,12,833 normal samples,and 9711 intrusion attacks in the test set.Thus,the proposed DAMLAN method is more effective than the standard models due to the consideration of patterns by the attention layers.The experimental performance of the proposed model demonstrates that it achieves 99.26%training accuracy and 90.68%testing accuracy,with precision reaching 98.54%on the training set and 96.64%on the testing set.The recall and F1 scores again support the model with training set values of 99.90%and 99.21%and testing set values of 86.65%and 91.37%.These results provide a strong basis for the claims made regarding the model’s potential to identify intrusion attacks and affirm its relatively strong overall performance,irrespective of type.Future work would employ more attempts to extend the scalability and applicability of DAMLAN for real-time use in intrusion detection systems.展开更多
Silicon nitride(Si_(3)N_(4))photonic platform has recently attracted increasing attention for Si_(3)N_(4) photonic integrated circuits(PIC).A diffraction grating with the only etched top-layer in tri-layer Si3N4 optic...Silicon nitride(Si_(3)N_(4))photonic platform has recently attracted increasing attention for Si_(3)N_(4) photonic integrated circuits(PIC).A diffraction grating with the only etched top-layer in tri-layer Si3N4 optical waveguides is proposed,which shows a simple fabrication process,high upward diffraction efficiency,and lower far-field divergence angle.The measured results of the diffraction grating at a wavelength of 905 nm show the average upward diffraction efficiency of 90.5% and average far-field divergence angle of 0.154°,which shows a good agreement with the design results with the upward diffraction efficiency of 91.6%and far-field divergence angle of 0.105°.展开更多
Research on supercontinuum sources on silicon has made significant progress in the past few decades.However,conventional approaches to broaden the spectral bandwidth often rely on complex and critical dispersion engin...Research on supercontinuum sources on silicon has made significant progress in the past few decades.However,conventional approaches to broaden the spectral bandwidth often rely on complex and critical dispersion engineering by optimizing the core thickness or introducing the cladding with special materials and structures.We propose and demonstrate supercontinuum generation using long-periodgrating(LPG)waveguides on silicon with a C-band pump.The LPG waveguide is introduced for quasi-phase matching,and the generated supercontinuum spectrum is improved greatly with grating-induced dispersive waves.In addition,the demonstrated LPG waveguide shows a low propagation loss comparable with regular silicon photonic waveguides without gratings.In experiments,when using a 1550-nm 75-fs pulse pump with a pulse energy of 200 pJ,the supercontinuum spectrum generated with the present LPG waveguide shows an ultrabroad extent from 1150 to 2300 nm,which is much wider by 200 nm than that achieved by dispersionengineered uniform silicon photonic waveguides on the same chip.This provides a promising option for on-chip broadband light source for silicon photonic systems.展开更多
In practical engineering construction,multi-layered barriers containing geomembranes are extensively applied to retard the migration of pollutants.However,the associated analytical theory on pollutants diffusion still...In practical engineering construction,multi-layered barriers containing geomembranes are extensively applied to retard the migration of pollutants.However,the associated analytical theory on pollutants diffusion still needs to be further improved.In this work,general analytical solutions are derived for one-dimensional diffusion of degradable organic contaminant(DOC)in the multi-layered media containing geomembranes under a time-varying concentration boundary condition,where the variable substitution and separated variable approaches are employed.These analytical solutions with clear expressions can be used not only to study the diffusion behaviors of DOC in bottom and vertical composite barrier systems,but also to verify other complex numerical models.The proposed general analytical solutions are then fully validated via three comparative analyses,including comparisons with the experimental measurements,an existing analytical solution,and a finite-difference solution.Ultimately,the influences of different factors on the composite cutoff wall’s(CCW,which consists of two soil-bentonite layers and a geomembrane)service performance are investigated through a composite vertical barrier system as the application example.The findings obtained from this investigation can provide scientific guidance for the barrier performance evaluation and the engineering design of CCWs.This application example also exhibits the necessity and effectiveness of the developed analytical solutions.展开更多
The phase-controlled single-photon transport properties of a giant atom coupled to a one-dimensional waveguide are investigated.The coupling between the giant atom and the waveguide is modeled as a multi-point interac...The phase-controlled single-photon transport properties of a giant atom coupled to a one-dimensional waveguide are investigated.The coupling between the giant atom and the waveguide is modeled as a multi-point interaction.The coupling strengths between the giant atom and the waveguide are represented as complex numbers with associated phases.Analytical expressions for the scattering amplitudes are obtained using the real-space Hamiltonian method.The results show that the characteristics of the scattering spectra,including the positions of peaks(or dips)and the full width at half maximum,can be tuned by adjusting the phase difference between the coupling strengths.Further calculations reveal that the scattering spectra can be either super-broadened or sub-broadened.The conditions for achieving perfect nonreciprocal single-photon transport in the Markovian regime are also discussed.Moreover,we demonstrate the control of single-photon transport through phase differences in the non-Markovian regime.Our results may find applications in the design of quantum devices operating at the single-photon level,based on waveguide quantum electrodynamics.展开更多
基金National Natural Science Foundation of China(52175237)。
文摘The key parameters that characterize the morphological quality of multi-layer and multi-pass metal laser deposited parts are the surface roughness and the error between the actual printing height and the theoretical model height.The Taguchi method was employed to establish the correlations between process parameter combinations and multi-objective characterization of metal deposition morphology(height error and roughness).Results show that using the signal-to-noise ratio and grey relational analysis,the optimal parameter combination for multi-layer and multi-pass deposition is determined as follows:laser power of 800 W,powder feeding rate of 0.3 r/min,step distance of 1.6 mm,and scanning speed of 20 mm/s.Subsequently,a Genetic Bayesian-back propagation(GB-BP)network is constructed to predict multi-objective responses.Compared with the traditional back propagation network,the GB-back propagation network improves the prediction accuracy of height error and surface roughness by 43.14%and 71.43%,respectively.This network can accurately predict the multi-objective characterization of morphological quality of multi-layer and multi-pass metal deposited parts.
文摘The increasing electrification of urban transportation,i.e.,subways and electric vehicles(EV),brings more interactions between the power system and transportation system and further results in fault propagation across them.To analyze vulnerability of the coupling system under extreme events,this paper establishes a multi-layer urban electric-transportation interdependent network(ETIN)model.First,a weighted coupled metro-road traffic network(CTN)model and network path planning approach are proposed.A prospect theory-based failure load redistribution(FLR)method is further established to account for uncertainty of TN link capacity affected by power supply.Second,topology and emergency control strategy of power network(PN)are modeled,followed by formulation of multi-layer ETIN model.In particular,the inter-layer fault propagation from PN to TN is modeled based on power supply correlation strength,while from TN to PN is modeled based on traffic flow.A few indexes are then defined to quantify vulnerability of ETIN under deliberate attack.Finally,the proposed method is verified on an electric-transportation system to show influence of fault propagations within ETIN on its vulnerability under extreme events.
基金supported by the Quantum Science and Technology-National Science and Technology Major Project (Grant No.2024ZD0302502 for WZ)the National Natural Science Foundation of China(Grant No.92365210 for WZ)+1 种基金Tsinghua Initiative Scientific Research Program (for WZ)the project of Tsinghua University-Zhuhai Huafa Industrial Share Company Joint Institute for Architecture Optoelectronic Technologies (JIAOT,for YH)。
文摘To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.This source is based on spontaneous four-wave mixing(SFWM)in a piece of shallow-ridge silicon waveguide.Theoretical analysis shows that the waveguide dispersion could be tailored by adjusting the ridge width,enabling broadband photon pair generation by SFWM across C band and O band.The spontaneous Raman scattering(SpRS)in silicon waveguides is also investigated experimentally.It shows that there are two regions in the spectrum of generated photons from SpRS,which could be used to achieve cross-band photon pair generation.A chip of shallow-ridge silicon waveguide samples with different ridge widths has been fabricated,through which cross-band photon pair generation is demonstrated experimentally.The experimental results show that the source can be achieved using dispersion-optimized shallow-ridge silicon waveguides.This cross-band quantum light source provides a way to develop new fiber-based quantum communication functions utilizing both C band and O band and extends applications of quantum networks.
基金supported by the European Research Council(ERC)under the European Union's Horizon 2020 Research and Innovation Programme(Grant Agreement No.818762)the Engineering and Physical Sciences Research Council(Grant No.EP/V048953/1)and the Isaac Newton Trust(grant 22.39(m))。
文摘Although multicrystalline Si photovoltaics have been extensively studied and applied in the collection of solar energy,the same systems suffer significant efficiency losses in indoor settings,where ambient light conditions are considerably smaller in intensity and possess greater components of non-normal incidence.Yet,indoor light-driven,stand-alone devices can offer sustainable advances in next-generation technologies such as the Internet of Things.Here,we present a non-invasive solution to aid in photovoltaic indoor light collection—radially distributed waveguide-encoded lattice(RDWEL)slim films(thickness 1.5 mm).Embedded with a monotonical radial array of cylindrical waveguides(±20°),the RDWEL demonstrates seamless light collection(FoV(fields of view)=74.5°)and imparts enhancements in JSC(short circuit current density)of 44%and 14%for indoor and outdoor lighting conditions,respectively,when coupled to a photovoltaic device and compared to an unstructured but otherwise identical slim film coating.
基金supported by the National Natural Science Foundation of China(Nos.22205105,61874053,22075136)National Key Basic Research Program of China(No.2020YFA0709900)Jiangsu Provincial Postgraduate Scientific Research Innovation Program(No.KYCX24_1649).
文摘Improving the optoelectronic behavior and stress-deformation stability of conjugated materials is crucial for the realization of their potential applications in flexible optoelectronics.To tune the emission behavior and mechanical property of molecular crystals simultaneously via supramolecular salt strategy is rarely reported,which is very important to improve their photophysical behavior and softness for the fabrication of flexible light-emitting device.Herein,supramolecular salt approach has been successfully applied to synthesize two elastic organic fluorescent crystals(CMOH-Py-Cl and CMOH-Py-Br)derived from non-emissive and brittle pyridine-substituted coumarin derivative(CMOH-Py).Their elastic properties can be attributed to the prevalent presence of numerous weak interactions introduced by halogen atoms,which are beneficial to the absorption and release of mechanical energy.Furthermore,density functional theory(DFT)calculations demonstrated a narrowing of the HOMO-LUMO energy gaps from CMOH-Py to CMOH-Py-Cl/CMOH-Py-Br via supramolecular salt approach.Finally,the application of flexible crystal materials in the field of optical waveguides has been investigated.The transformation of crystals in terms of photophysical and mechanical properties,achieved by the supramolecular salt approach,offers novel insights into the design and construction of flexible crystalline materials,providing a new path for the development of next-generation smart materials.
基金supported by the National Key Research and Development Program of China(No.2022YFB3404700)the National Natural Science Foundation of China(Nos.52105313 and 52275299)+2 种基金the Research and Development Program of Beijing Municipal Education Commission,China(No.KM202210005036)the Natural Science Foundation of Chongqing,China(No.CSTB2023NSCQ-MSX0701)the National Defense Basic Research Projects of China(No.JCKY2022405C002).
文摘At present,the emerging solid-phase friction-based additive manufacturing technology,including friction rolling additive man-ufacturing(FRAM),can only manufacture simple single-pass components.In this study,multi-layer multi-pass FRAM-deposited alumin-um alloy samples were successfully prepared using a non-shoulder tool head.The material flow behavior and microstructure of the over-lapped zone between adjacent layers and passes during multi-layer multi-pass FRAM deposition were studied using the hybrid 6061 and 5052 aluminum alloys.The results showed that a mechanical interlocking structure was formed between the adjacent layers and the adja-cent passes in the overlapped center area.Repeated friction and rolling of the tool head led to different degrees of lateral flow and plastic deformation of the materials in the overlapped zone,which made the recrystallization degree in the left and right edge zones of the over-lapped zone the highest,followed by the overlapped center zone and the non-overlapped zone.The tensile strength of the overlapped zone exceeded 90%of that of the single-pass deposition sample.It is proved that although there are uneven grooves on the surface of the over-lapping area during multi-layer and multi-pass deposition,they can be filled by the flow of materials during the deposition of the next lay-er,thus ensuring the dense microstructure and excellent mechanical properties of the overlapping area.The multi-layer multi-pass FRAM deposition overcomes the limitation of deposition width and lays the foundation for the future deposition of large-scale high-performance components.
基金financial supports from National Key R&D Program of China(Grant No.2022YFA1205100,2022YFA1404600)National Natural Science Foundation of China(Grant Nos.12192251,12334014,12474325,12134001,12304418,12474378,12274133,12174107,12174113,12274130)+2 种基金the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301403)Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)Fundamental Research Funds for the Central Universities,the Engineering Research Center for Nanophotonics&Advanced Instrument,Ministry of Education,East China Normal University(No.2023nmc005).
文摘Miniaturized erbium-doped waveguide amplifiers attracted great interests in recent decades due to their high gain-efficiency and function-scalability in the telecom C-band.In this work,an erbium-doped thin film lithium niobate waveguide amplifier achieving>10 dB off-chip(fiber-to-fiber)net gain and>20 mW fiber-output amplified power is demonstrated,thanks to the low-propagation-loss waveguides and robust waveguide edge-couplers prepared by the photolithography assisted chemomechanical etching technique.Systematic investigation on the fabricated waveguide amplifiers reveals remarkable optical gain around the peak wavelength of 1532 nm as well as the low fiber-coupling loss of-1.2 dB/facet.A fiber Bragg-grating based waveguide laser is further demonstrated using the fabricated waveguide amplifier as the external gain chip,which generates>2 mW off-chip power continuous-wave lasing around the gain peak at 1532 nm.The unambiguous demonstration of fiber-to-fiber net gain of the erbium-doped thinfilm lithium niobate(TFLN)waveguide amplifier as well as its external gain chip application will benefit diverse fields demanding scalable gain elements with highspeed tunability.
基金Supported by the National Natural Science Foundation of China(62105039)。
文摘In the process of power scaling large-area Quantum Cascade Lasers(QCLs),challenges such as degradation of beam quality and emission of multilobed far-field modes are frequently encountered.These issues become particularly pronounced with an increase in ridge width,resulting in multimode problems.To tackle this,an innovative multi ridge waveguide structure based on the principle of supersymmetry(SUSY)was proposed.This structure comprises a wider main waveguide in the center and two narrower auxiliary waveguides on either side.The high-order modes of the main waveguide are coupled with the modes of the auxiliary waveguides through mode-matching design,and the optical loss of the auxiliary waveguides suppresses these modes,thereby achieving fundamental mode lasing of the wider main waveguide.This paper employs the finite difference eigenmode(FDE)method to perform detailed structural modeling and simulation optimization of the 4.6μm wavelength quantum cascade laser,successfully achieving a single transverse mode QCL with a ridge width of 10μm.In comparison to the traditional single-mode QCL(with a ridge width of about 5μm),the MRW structure has the potential to increase the gain area of the laser by 100%.This offers a novel design concept and methodology for enhancing the single-mode luminous power of mid-infrared quantum cascade lasers,which is of considerable significance.
基金National Key Research and Development Program of China(2022YFF0707602)National Natural Science Foundation of China(62471097,62471115,62471101)National Natural Science Foundation of Sichuan(2025ZNSFSC0537)。
文摘[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,with multi-channel slow-wave structures(SWSs)forming the foundation for their realization in high-power vacuum electronic devices.[Purpose]To provide design insights for multi-channel TWTs and simultaneously enhance their output power,a W-band folded-waveguide TWT with dual electron beams and H-plane power combining was proposed.[Methods]Three-dimensional electromagnetic simulations in CST were conducted to verify the highfrequency characteristics,electric field distribution,and amplification performance of the proposed SWS,thereby confirming the validity of the design.[Results]Results indicate that the designed TWT achieves a transmission bandwidth of 10 GHz.With an electron beam voltage of 17.9 kV and a current of 0.35 A,the output power reaches 450 W at 94 GHz,corresponding to an efficiency of 7.18%and a gain of 23.5 dB.Moreover,under fixed beam voltage and current,the TWT delivers over 200 W output power across 91–99 GHz,with a 3 dB bandwidth of 91–98.5 GHz.The particle voltage distribution after modulation further validates the mode analysis.[Conclusions]These results demonstrate the feasibility of compact dual-beam power-combining structures and provide useful guidance for the design of future multi-channel TWTs.
文摘This study involved a comprehensive investigation aimed at achieving efficient multi-millijoule THz wave generation by exploiting the unique properties of cylindrical GaAs waveguides as effective mediators of the conversion of laser energy into THz waves.Through meticulous investigation,valuable insights into optimizing THz generation processes for practical applications were unearthed.By investigating Hertz potentials,an eigen-value equation for the solutions of the guided modes(i.e.,eigenvalues)was found.The effects of various param-eters,including the effective mode index and the laser pulse power,on the electric field components of THz radia-tion,including the fundamental TE(transverse electric)and TM(transverse magnetic)modes,were evaluated.By analyzing these factors,this research elucidated the nuanced mechanisms governing THz wave generation within cylindrical GaAs waveguides,paving the way for refined methodologies and enhanced efficiency.The sig-nificance of cylindrical GaAs waveguides extends beyond their roles as mere facilitators of THz generation;their design and fabrication hold the key to unlocking the potential for compact and portable THz systems.This trans-formative capability not only amplifies the efficiency of THz generation but also broadens the horizons of practical applications.
基金supported by the National Natural Science Foundation of China(No.62375031)the Basic Research Project of Chongqing Science and Technology Commission(No.CSTC-2021jcyj-bsh0194)the Science and Technology Research Program of Chongqing Municipal Education Commission(No.KJQN202200602)。
文摘In this paper,a terahertz slotted waveguide array antenna is designed based on photonic crystal,which can realize efficient radiation of terahertz waves.The electromagnetic wave is fed from the rectangular waveguide at the bottom of the antenna,coupled to photonic crystal waveguide through photonic crystal cavity,and radiated outward through slots at the top layer of antenna.The simulation results show that the antenna achieves a peak gain of 13.45 dBi at 360 GHz,a half-power beam width of 10.9°,and a side lobe level of−13.9 dB.The antenna based on photonic crystal has the advantages of low profile,low loss,and high radiation efficiency,which can be applied to terahertz wireless communication systems.
文摘A plasmonics waveguide structure that consist of a non-through metal–insulator–metal(MIM)waveguide coupled with a D-shaped cavity was designed.And the transmission properties,magnetic field distribution,and refractive index sensing functionality were simulated using the finite element method(FEM).A multi-Fano resonance phenomenon was clearly observable in the transmission spectra.The Fano resonances observed in the proposed structure arise from the interaction between the discrete states of the Dshaped resonant cavity and the continuum state of the non-through MIM waveguide.The influence of structural parameters on Fano resonance modulation was investigated through systematic parameter adjustments.Additionally,the refractive index sensing properties,based on the Fano resonance,were investigated by varying the refractive index of the MIM waveguide's insulator layer.A maximum sensitivity and FOM of 1155 RIU/nm and 40 were achieved,respectively.This research opens up new possibilities for designing and exploring high-sensitivity photonic devices,micro-sensors,and innovative on-chip sensing architectures for future applications.
文摘Ferrimagnetic materials exhibiting remanence can be used to achieve unidirectional electromagnetic-field propagation in the form of magnetoplasmons(MPs)in the subwavelength regime.This study investigates the MP properties and various guiding modes in a hollow cylindrical waveguide made of materials that exhibit remanence.Pattern analysis and numerical simulations are used to demonstrate that dispersion relationships and electromagnetic-field distribution are strongly affected by the operating frequency and physical dimensions of the structure.In addition,the existence of two different guiding modes is proved,namely regular and surface-wave modes.By adjusting the operating frequency and reducing the diameter of the hollow cylinder,the regular mode can be suppressed so as to only retain the surface-wave mode,which enables unidirectional MP propagation in the cylindrical waveguide.Moreover,the unidirectional surface-wave mode is robust to backscattering due to surface roughness and defects,which makes it very useful for application in field-enhancement devices.
基金Supported by the National Natural Science Foundation of China(Grant No.52172409)Postdoctoral Innovation Talents Support Program(Grant No.BX20240298)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2682024GF023)Heilongjiang Province Postdoctoral Foundation Project(Grant No.LBH-Z23041).
文摘The huge impact kinetic energy cannot be quickly dissipated by the energy-absorbing structure and transferred to the other vehicle through the car body structure,which will cause structural damage and threaten the lives of the occupants.Therefore,it is necessary to understand the laws of energy conversion,dissipation and transfer during train collisions.This study proposes a multi-layer progressive analysis method of energy flow during train collisions,considering the characteristics of the train.In this method,the train collision system is divided into conversion,dissipation,and transfer layers from the perspective of the train,collision interface,and car body structure to analyze the energy conversion,dissipation and transfer characteristics.Taking the collision process of a rail train as an example,a train collision energy transfer path analysis model was established based on power flow theory.The results show that when the maximum mean acceleration of the vehicle meets the standard requirements,the jerk may exceed the allowable limit of the human body,and there is a risk of injury to the occupants of a secondary collision.The decay rate of the collision energy along the direction of train operation reaches 79%.As the collision progresses,the collision energy gradually converges in the structure with holes,and the structure deforms when the gathered energy is greater than the maximum energy the structure can withstand.The proposed method helps to understand the train collision energy flow law and provides theoretical support for the train crashworthiness design in the future.
基金supported in part by the Natural Science Foundation of Tianjin(No.19JCYBJC16100)the Tianjin Innovation and Entrepreneurship Training Program(No.202210060027)。
文摘A triple-band miniaturized end-fire antenna based on the odd modes of spoof surface plasmonic polariton(SSPP)waveguide resonator is proposed in this paper.To meet the ever increasing demand for more communication channels and less antenna sizes,multi-band antennas are currently under intensive investigation.By a novel feeding method,three odd modes are excited on an SSPP waveguide resonator,which performs as an end-fire antenna operating at three bands,7.15-7.26 GHz,11.6-12.2 GHz and 13.5-13.64 GHz.It exhibits reasonably high and stable maximum gains of 5.26 dBi,7.97 dBi and 10.1 dBi and maximum efficiencies of 64%,92%and 98%at the three bands,respectively.Moreover,in the second band,the main beam angle shows a frequency dependence with a total scanning angle of 19°.The miniaturized triple-band antenna has a great potential in wireless communication systems,satellite communication and radar systems.
基金Nourah bint Abdulrahman University for funding this project through the Researchers Supporting Project(PNURSP2025R319)Riyadh,Saudi Arabia and Prince Sultan University for covering the article processing charges(APC)associated with this publication.Special acknowledgement to Automated Systems&Soft Computing Lab(ASSCL),Prince Sultan University,Riyadh,Saudi Arabia.
文摘The growing incidence of cyberattacks necessitates a robust and effective Intrusion Detection Systems(IDS)for enhanced network security.While conventional IDSs can be unsuitable for detecting different and emerging attacks,there is a demand for better techniques to improve detection reliability.This study introduces a new method,the Deep Adaptive Multi-Layer Attention Network(DAMLAN),to boost the result of intrusion detection on network data.Due to its multi-scale attention mechanisms and graph features,DAMLAN aims to address both known and unknown intrusions.The real-world NSL-KDD dataset,a popular choice among IDS researchers,is used to assess the proposed model.There are 67,343 normal samples and 58,630 intrusion attacks in the training set,12,833 normal samples,and 9711 intrusion attacks in the test set.Thus,the proposed DAMLAN method is more effective than the standard models due to the consideration of patterns by the attention layers.The experimental performance of the proposed model demonstrates that it achieves 99.26%training accuracy and 90.68%testing accuracy,with precision reaching 98.54%on the training set and 96.64%on the testing set.The recall and F1 scores again support the model with training set values of 99.90%and 99.21%and testing set values of 86.65%and 91.37%.These results provide a strong basis for the claims made regarding the model’s potential to identify intrusion attacks and affirm its relatively strong overall performance,irrespective of type.Future work would employ more attempts to extend the scalability and applicability of DAMLAN for real-time use in intrusion detection systems.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFB2802401)the Beijing Municipal Natural Science Foundation(Grant No.Z221100006722002).
文摘Silicon nitride(Si_(3)N_(4))photonic platform has recently attracted increasing attention for Si_(3)N_(4) photonic integrated circuits(PIC).A diffraction grating with the only etched top-layer in tri-layer Si3N4 optical waveguides is proposed,which shows a simple fabrication process,high upward diffraction efficiency,and lower far-field divergence angle.The measured results of the diffraction grating at a wavelength of 905 nm show the average upward diffraction efficiency of 90.5% and average far-field divergence angle of 0.154°,which shows a good agreement with the design results with the upward diffraction efficiency of 91.6%and far-field divergence angle of 0.105°.
基金supported by the UK’s Engineering and Physical Sciences Research Council(Grant Nos.EP/V000624/1,EP/X03495X/1,EP/X041166/1,and EP/T02643X/1)the Royal Society(Grant No.RG\R2\232531).
文摘Research on supercontinuum sources on silicon has made significant progress in the past few decades.However,conventional approaches to broaden the spectral bandwidth often rely on complex and critical dispersion engineering by optimizing the core thickness or introducing the cladding with special materials and structures.We propose and demonstrate supercontinuum generation using long-periodgrating(LPG)waveguides on silicon with a C-band pump.The LPG waveguide is introduced for quasi-phase matching,and the generated supercontinuum spectrum is improved greatly with grating-induced dispersive waves.In addition,the demonstrated LPG waveguide shows a low propagation loss comparable with regular silicon photonic waveguides without gratings.In experiments,when using a 1550-nm 75-fs pulse pump with a pulse energy of 200 pJ,the supercontinuum spectrum generated with the present LPG waveguide shows an ultrabroad extent from 1150 to 2300 nm,which is much wider by 200 nm than that achieved by dispersionengineered uniform silicon photonic waveguides on the same chip.This provides a promising option for on-chip broadband light source for silicon photonic systems.
基金Project(2023YFC3707800)supported by the National Key Research and Development Program of China。
文摘In practical engineering construction,multi-layered barriers containing geomembranes are extensively applied to retard the migration of pollutants.However,the associated analytical theory on pollutants diffusion still needs to be further improved.In this work,general analytical solutions are derived for one-dimensional diffusion of degradable organic contaminant(DOC)in the multi-layered media containing geomembranes under a time-varying concentration boundary condition,where the variable substitution and separated variable approaches are employed.These analytical solutions with clear expressions can be used not only to study the diffusion behaviors of DOC in bottom and vertical composite barrier systems,but also to verify other complex numerical models.The proposed general analytical solutions are then fully validated via three comparative analyses,including comparisons with the experimental measurements,an existing analytical solution,and a finite-difference solution.Ultimately,the influences of different factors on the composite cutoff wall’s(CCW,which consists of two soil-bentonite layers and a geomembrane)service performance are investigated through a composite vertical barrier system as the application example.The findings obtained from this investigation can provide scientific guidance for the barrier performance evaluation and the engineering design of CCWs.This application example also exhibits the necessity and effectiveness of the developed analytical solutions.
基金supported by the National Natural Science Foundation of China(Grant Nos.12475010 and 119075023)the Major Project of the Natural Science Foundation of Anhui Provincial Department of Education(Grant No.2022AH040053)the Key Natural Scientific Research Projects of Universities in Anhui Province(Grant Nos.2023AH051078 and 2023AH051125)。
文摘The phase-controlled single-photon transport properties of a giant atom coupled to a one-dimensional waveguide are investigated.The coupling between the giant atom and the waveguide is modeled as a multi-point interaction.The coupling strengths between the giant atom and the waveguide are represented as complex numbers with associated phases.Analytical expressions for the scattering amplitudes are obtained using the real-space Hamiltonian method.The results show that the characteristics of the scattering spectra,including the positions of peaks(or dips)and the full width at half maximum,can be tuned by adjusting the phase difference between the coupling strengths.Further calculations reveal that the scattering spectra can be either super-broadened or sub-broadened.The conditions for achieving perfect nonreciprocal single-photon transport in the Markovian regime are also discussed.Moreover,we demonstrate the control of single-photon transport through phase differences in the non-Markovian regime.Our results may find applications in the design of quantum devices operating at the single-photon level,based on waveguide quantum electrodynamics.
