[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
The proposed mass model of vocal fold vibration holds a significant importance in the auxiliary diagnosis and treatment of human vocal fold disorders.Mathematical models are proposed in aerodynamics and acoustics to s...The proposed mass model of vocal fold vibration holds a significant importance in the auxiliary diagnosis and treatment of human vocal fold disorders.Mathematical models are proposed in aerodynamics and acoustics to simulate vocal fold vibration during phonation.This has always been a hot topic in pathological linguistics research.Over the past few decades,researchers have designed various types of mass models of vocal fold vibration based on experiments.These models differ in principles,computational complexity,and degrees of freedom.Therefore,we classify and describe the mass models according to modeling methods.We summarize the research status and characteristics of different models,and based on this,we look forward to future research directions for vocal fold mass models.展开更多
This research investigates the bending response of folded multi-celled tubes(FMTs)fabricated by folded metal sheets.A three-point bending test for FMTs with circular and square sections is designed and introduced.The ...This research investigates the bending response of folded multi-celled tubes(FMTs)fabricated by folded metal sheets.A three-point bending test for FMTs with circular and square sections is designed and introduced.The base numerical models are correlated with physical experiments and a static crashworthiness analysis of six FMT configurations to assess their energy absorption characteristics.The influences of thickness,sectional shape,and load direction on the bending response are studied.Results indicate that increasing the thickness of the tube and radian of the inner tube enhances the crashworthiness performance of FMT,yielding a 20.50%increase in mean crushing force,a 55.53%increase in specific energy absorption,and an 18.05%decrease in peak crushing force compared to traditional multi-celled tubes(TMTs).A theoretical analysis of the specific energy absorption indicates that FMTs outperform TMTs,particularly when the peak crushing force is prominent.This study highlights the innovative and practical potential of FMTs to improve the crashworthiness of thin-walled structures.展开更多
An efficient strategy has been developed to reconstruct chain folding and traversing of poly(L-lactide)(PLLA)during melt crystallization based on the selective hydrolysis of its amorphous regions.The molecular weights...An efficient strategy has been developed to reconstruct chain folding and traversing of poly(L-lactide)(PLLA)during melt crystallization based on the selective hydrolysis of its amorphous regions.The molecular weights of the pristine PLLA(crystalline part),single stem,and single cluster were determined by gel permeation chromatography(GPC)according to their evolution during alkali hydrolysis.The maximum-folding-number(in a single cluster)and minimum-cluster-number(in one polymer chain)were obtained using these molecular weights.With the help of two numbers,the chain folding and traversing during the melt crystallization process(at 120℃)of PLLA can be described as follows.Statistically,in a single polymer chain,there are at least 2 clusters consisting of up to 6.5 stems in each of them,while the rest of the polymer chain contributes to amorphous regions.Our results provide a new strategy for the investigation and fundamental understanding of the melt crystallization of PLLA.展开更多
Spectrin domains,characterized by a distinctive triple helix structure,are crucial in physiological processes,particularly in maintaining membrane shape and crosslinking cytoskeletons.Previous research on the 16th dom...Spectrin domains,characterized by a distinctive triple helix structure,are crucial in physiological processes,particularly in maintaining membrane shape and crosslinking cytoskeletons.Previous research on the 16th domain of a-spectrin repeats(R16)has yielded conflicting results:bulk experiments showed an unfolding rate approximately two orders of magnitude faster than the zero-force result extrapolated from single-molecule force spectroscopy experiments using atomic force microscopy(AFM).To address this discrepancy,we investigated the folding and unfolding rates of R16 across a broader range of forces using magnetic tweezers(MT).Our findings reveal that AFM results at higher forces cannot be directly extrapolated to the low-force regime due to a nonlinear relationship between force and the logarithm of the unfolding rate.We demonstrated that two-dimensional model,structural-elastic model,and two-pathway model can all effectively explain the experimental data when they capture the core physics of the short unfolding distance at low forces.Our study provides a more comprehensive understanding of the unfolding dynamics of the spectrin domain,resolves previous contradictory experimental results,and highlights the common basis of different theoretical models.展开更多
Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent ...Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent a key research aspect for morphing aircraft,since they can lead to potential improvements in flight range,maneuverability,load alleviation and airport compatibility.This paper proposes a hinge mechanism design for folding wingtips based on the shape memory alloy torsion tube,aiming to achieve successful folding using the actuation effect of the shape memory alloy.The proposed design employs a shape memory alloy torsion tube as the actuator for the active folding of the wingtip,which is motivated by the characteristics of the tube,enabling a simplified structure for the integration with high energy density.Through numerical simulation and testing of the folding wingtip structure,the concept is verified,which shows its potential as an actuator for folding wingtips.展开更多
Two types of bound states in continuum(BICs),symmetry-protected and Brillouin zone folding driven,are identified in hollow Si nanorod arrays.By modulating the direction and distance of the air holes from the center of...Two types of bound states in continuum(BICs),symmetry-protected and Brillouin zone folding driven,are identified in hollow Si nanorod arrays.By modulating the direction and distance of the air holes from the center of the nanorods,it is possible to achieve either a single quasi-BIC or three quasi-BICs.The transmission spectra exhibit ultra-narrow lines,and the quasi-BICs demonstrate ultra-high Q factors.Additionally,efficient third-harmonic generation occurs at low pump intensities.The results indicate that the proposed nanostructures of two types of BICs with a flexible modulation hold great potential applications for nonlinear photonic devices.展开更多
Extensional fault-bend folds,also called rollovers,are one of the most common structures in extensional settings.Numerous studies have shown that oblique simple shear is the most appropriate mechanism for quantitative...Extensional fault-bend folds,also called rollovers,are one of the most common structures in extensional settings.Numerous studies have shown that oblique simple shear is the most appropriate mechanism for quantitative modeling of geometric relations between normal faults and the strata in their hanging walls.However,the oblique simple shear has a rather serious issue derived from the shear direction,particularly above convex bends.We use geometric and experimental methods to study the deformation of extensional fault-bend folds on convex bends.The results indicate that whether the fault bends are concave or convex,the shear direction of the hanging wall dips toward the main fault.On this basis,we improve the previous geometric model by changing the shear direction above the convex bends.To illustrate basin history,our model highlights the importance of the outer limit of folding instead of the growth axial.Moreover,we propose a new expression for the expansion index that is applicable to the condition of no deposition on the footwall.This model is validated by modeling a natural structure of the East China Sea Basin.展开更多
The folded-cascode structure is used to realize the low-voltage low-power consumption mixer, whose performance parameters have big influence on the navigation radio receiver＇s performance. Adopting the folded-cascode...The folded-cascode structure is used to realize the low-voltage low-power consumption mixer, whose performance parameters have big influence on the navigation radio receiver＇s performance. Adopting the folded-cascode structure, the folded-cascode mixer （FCM） has a lower power supply voltage of 1.2 V and realizes the design trade-offs among the high transconductance, high linearity and low noise. The difficulties of realizing the trade-offs between the linearity and noise performance, the linearity and conversion gain, the conversion gain and noise performance are reduced. Fabricated in an radio frequency （RF） 0.18 μm CMOS process, the FCM has an active area of about 200 μm ×150 μm and consumes approximate 3.9 mW. The test results show that the FCM features a conversion gain （Gc） of some 14.5 dB, an input 1 dB compression point （Pin-1dB） of almost -13 dBm and a dual sideband （DSB） noise figure of around 12 dB. The FCM can be applied to the navigation radio receivers and electronic systems for aviation and aerospace or other related fields.展开更多
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.
基金the Shanghai Educational Sciences Research Program(No.C2021016)。
文摘The proposed mass model of vocal fold vibration holds a significant importance in the auxiliary diagnosis and treatment of human vocal fold disorders.Mathematical models are proposed in aerodynamics and acoustics to simulate vocal fold vibration during phonation.This has always been a hot topic in pathological linguistics research.Over the past few decades,researchers have designed various types of mass models of vocal fold vibration based on experiments.These models differ in principles,computational complexity,and degrees of freedom.Therefore,we classify and describe the mass models according to modeling methods.We summarize the research status and characteristics of different models,and based on this,we look forward to future research directions for vocal fold mass models.
基金supported by the National Natural Science Foundation of China(Grant No.52475277)2022 Guangxi University Young and Middle-aged Teachers’Basic Research Ability Improvement Project(Grant No.2022KY0781)Scientific Research Funds of Guilin University of Aerospace Technology(Grant No.XJ22KT29).
文摘This research investigates the bending response of folded multi-celled tubes(FMTs)fabricated by folded metal sheets.A three-point bending test for FMTs with circular and square sections is designed and introduced.The base numerical models are correlated with physical experiments and a static crashworthiness analysis of six FMT configurations to assess their energy absorption characteristics.The influences of thickness,sectional shape,and load direction on the bending response are studied.Results indicate that increasing the thickness of the tube and radian of the inner tube enhances the crashworthiness performance of FMT,yielding a 20.50%increase in mean crushing force,a 55.53%increase in specific energy absorption,and an 18.05%decrease in peak crushing force compared to traditional multi-celled tubes(TMTs).A theoretical analysis of the specific energy absorption indicates that FMTs outperform TMTs,particularly when the peak crushing force is prominent.This study highlights the innovative and practical potential of FMTs to improve the crashworthiness of thin-walled structures.
基金financially supported by"Pioneer"and"Leading Goose"R&D Program of Zhejiang(No.2023C03130)the National Natural Science Foundation of China(No.22373029)+1 种基金Interdisciplinary Research Project of Hangzhou Normal University(No.2024JCXK02)Open Project Program of Key Laboratory of Yarn Materials Forming and Composite Processing Technology of Zhejiang Province(No.MTC2022-09)。
文摘An efficient strategy has been developed to reconstruct chain folding and traversing of poly(L-lactide)(PLLA)during melt crystallization based on the selective hydrolysis of its amorphous regions.The molecular weights of the pristine PLLA(crystalline part),single stem,and single cluster were determined by gel permeation chromatography(GPC)according to their evolution during alkali hydrolysis.The maximum-folding-number(in a single cluster)and minimum-cluster-number(in one polymer chain)were obtained using these molecular weights.With the help of two numbers,the chain folding and traversing during the melt crystallization process(at 120℃)of PLLA can be described as follows.Statistically,in a single polymer chain,there are at least 2 clusters consisting of up to 6.5 stems in each of them,while the rest of the polymer chain contributes to amorphous regions.Our results provide a new strategy for the investigation and fundamental understanding of the melt crystallization of PLLA.
基金supported by the National Natural Science Foun-dation of China(Grant Nos.12174322,12474200,32271367,and 12204389)111 Project(B16029)Research Grant from Wenzhou Institute.
文摘Spectrin domains,characterized by a distinctive triple helix structure,are crucial in physiological processes,particularly in maintaining membrane shape and crosslinking cytoskeletons.Previous research on the 16th domain of a-spectrin repeats(R16)has yielded conflicting results:bulk experiments showed an unfolding rate approximately two orders of magnitude faster than the zero-force result extrapolated from single-molecule force spectroscopy experiments using atomic force microscopy(AFM).To address this discrepancy,we investigated the folding and unfolding rates of R16 across a broader range of forces using magnetic tweezers(MT).Our findings reveal that AFM results at higher forces cannot be directly extrapolated to the low-force regime due to a nonlinear relationship between force and the logarithm of the unfolding rate.We demonstrated that two-dimensional model,structural-elastic model,and two-pathway model can all effectively explain the experimental data when they capture the core physics of the short unfolding distance at low forces.Our study provides a more comprehensive understanding of the unfolding dynamics of the spectrin domain,resolves previous contradictory experimental results,and highlights the common basis of different theoretical models.
基金supported by the National Natural Science Foundation of China(No.52305262)the Aeronautical Science Foundation of China(No.20230015052002)the Fundamental Research Funds for the Central Universities(No.NT2024001)。
文摘Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent a key research aspect for morphing aircraft,since they can lead to potential improvements in flight range,maneuverability,load alleviation and airport compatibility.This paper proposes a hinge mechanism design for folding wingtips based on the shape memory alloy torsion tube,aiming to achieve successful folding using the actuation effect of the shape memory alloy.The proposed design employs a shape memory alloy torsion tube as the actuator for the active folding of the wingtip,which is motivated by the characteristics of the tube,enabling a simplified structure for the integration with high energy density.Through numerical simulation and testing of the folding wingtip structure,the concept is verified,which shows its potential as an actuator for folding wingtips.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12174228 and 12274271)。
文摘Two types of bound states in continuum(BICs),symmetry-protected and Brillouin zone folding driven,are identified in hollow Si nanorod arrays.By modulating the direction and distance of the air holes from the center of the nanorods,it is possible to achieve either a single quasi-BIC or three quasi-BICs.The transmission spectra exhibit ultra-narrow lines,and the quasi-BICs demonstrate ultra-high Q factors.Additionally,efficient third-harmonic generation occurs at low pump intensities.The results indicate that the proposed nanostructures of two types of BICs with a flexible modulation hold great potential applications for nonlinear photonic devices.
文摘Extensional fault-bend folds,also called rollovers,are one of the most common structures in extensional settings.Numerous studies have shown that oblique simple shear is the most appropriate mechanism for quantitative modeling of geometric relations between normal faults and the strata in their hanging walls.However,the oblique simple shear has a rather serious issue derived from the shear direction,particularly above convex bends.We use geometric and experimental methods to study the deformation of extensional fault-bend folds on convex bends.The results indicate that whether the fault bends are concave or convex,the shear direction of the hanging wall dips toward the main fault.On this basis,we improve the previous geometric model by changing the shear direction above the convex bends.To illustrate basin history,our model highlights the importance of the outer limit of folding instead of the growth axial.Moreover,we propose a new expression for the expansion index that is applicable to the condition of no deposition on the footwall.This model is validated by modeling a natural structure of the East China Sea Basin.
文摘The folded-cascode structure is used to realize the low-voltage low-power consumption mixer, whose performance parameters have big influence on the navigation radio receiver＇s performance. Adopting the folded-cascode structure, the folded-cascode mixer （FCM） has a lower power supply voltage of 1.2 V and realizes the design trade-offs among the high transconductance, high linearity and low noise. The difficulties of realizing the trade-offs between the linearity and noise performance, the linearity and conversion gain, the conversion gain and noise performance are reduced. Fabricated in an radio frequency （RF） 0.18 μm CMOS process, the FCM has an active area of about 200 μm ×150 μm and consumes approximate 3.9 mW. The test results show that the FCM features a conversion gain （Gc） of some 14.5 dB, an input 1 dB compression point （Pin-1dB） of almost -13 dBm and a dual sideband （DSB） noise figure of around 12 dB. The FCM can be applied to the navigation radio receivers and electronic systems for aviation and aerospace or other related fields.
