This paper presents a semi-active strategy for seismic protection of a benchmark cable-stayed bridge with consideration of multiple-support excitations. In this control strategy, Magnetorheological (MR) dampers are pr...This paper presents a semi-active strategy for seismic protection of a benchmark cable-stayed bridge with consideration of multiple-support excitations. In this control strategy, Magnetorheological (MR) dampers are proposed as control devices, a LQG-clipped-optimal control algorithm is employed. An active control strategy, shown in previous researches to perform well at controlling the benchmark bridge when uniform earthquake motion was assumed, is also used in this study to control this benchmark bridge with consideration of multiple-support excitations. The performance of active control system is compared to that of the presented semi-active control strategy. Because the MR fluid damper is a con-trollable energy- dissipation device that cannot add mechanical energy to the structural system, the proposed control strategy is fail-safe in that bounded-input, bounded-output stability of the controlled structure is guaranteed. The numerical results demonstrated that the performance of the presented control design is nearly the same as that of the active control system; and that the MR dampers can effectively be used to control seismically excited cable-stayed bridges with multiple-support excitations.展开更多
In order to study the infl uence of the ground motion spatial eff ect on the seismic response of large span spatial structures with isolation bearings, a single-layer cylindrical latticed shell scale model with a simi...In order to study the infl uence of the ground motion spatial eff ect on the seismic response of large span spatial structures with isolation bearings, a single-layer cylindrical latticed shell scale model with a similarity ratio of 1/10 was constructed. An earthquake simulation shaking table test on the response under multiple-support excitations was performed with the high-position seismic isolation method using high damping rubber (HDR) bearings. Small-amplitude sinusoidal waves and seismic wave records with various spectral characteristics were applied to the model. The dynamic characteristics of the model and the seismic isolation eff ect on it were analyzed at varying apparent wave velocities, namely infi nitely great, 1000 m/s, 500 m/s and 250 m/s. Besides, numerical simulations were carried out by Matlab software. According to the comparison results, the numerical results agreed well with the experimental data. Moreover, the results showed that the latticed shell roof exhibited a translational motion as a rigid body after the installation of the HDR bearings with a much lower natural frequency, higher damping ratio and only 1/2~1/8 of the acceleration response peak values. Meanwhile, the structural responses and the bearing deformations at the output end of the seismic waves were greatly increased under multiple-support excitations.展开更多
This study focuses on the fluorescent thermometric properties of CaMoO4:5%Tb3+under different temperature excitations.At the detection wavelength of 544 nm,with the temperature varying from 293 K to 563 K,there is a b...This study focuses on the fluorescent thermometric properties of CaMoO4:5%Tb3+under different temperature excitations.At the detection wavelength of 544 nm,with the temperature varying from 293 K to 563 K,there is a broadband absorption peak in the range of 250 nm to 350 nm.The results indicate that this phenomenon is caused by the superposition of the 4f-5d transition of Tb3+ and the O2--Mo6+charge transfer.It is considered that as the temperature rises,the luminescent intensity of the material shows an obvious continuous decreasing trend,which reflects a significant luminescent thermal quenching trend;thus,this quenching belongs to the“strong coupling”type.Based on the excitation spectrum results,two excitation wavelengths,312 nm and 338 nm,were specifically selected to excite the samples,which correspond to the top of the charge transfer band,the redshift intersection of the charge transfer band,and the edge of the charge transfer band at 293 K,respectively.展开更多
This study investigates the nonlinear resonance responses of suspended cables subjected to multi-frequency excitations and time-delayed feedback.Two specific combinations and simultaneous resonances are selected for d...This study investigates the nonlinear resonance responses of suspended cables subjected to multi-frequency excitations and time-delayed feedback.Two specific combinations and simultaneous resonances are selected for detailed examination.Initially,utilizing Hamilton’s variational principle,a nonlinear vibration control model of suspended cables under multi-frequency excitations and longitudinal time-delayed velocity feedback is developed,and the Galerkin method is employed to obtain the discrete model.Subsequently,focusing solely on single-mode discretization,analytical solutions for the two simultaneous resonances are derived using the method of multiple scales.The frequency response equations are derived,and the stability analysis is presented for two simultaneous resonance cases.The results demonstrate that suspended cables exhibit complex nonlinearity under multi-frequency excitations.Multiple solutions under multi-frequency excitation can be distinguished through the frequency–response and the detuning-phase curves.By adjusting the control gain and time delay,the resonance range,response amplitude,and phase of suspended cables can be modified.展开更多
Fluid-conveying pipes generally face combined excitations caused by periodic loads and random noises.Gaussian white noise is a common random noise excitation.This study investigates the random vibration response of a ...Fluid-conveying pipes generally face combined excitations caused by periodic loads and random noises.Gaussian white noise is a common random noise excitation.This study investigates the random vibration response of a simply-supported pipe conveying fluid under combined harmonic and Gaussian white noise excitations.According to the generalized Hamilton’s principle,the dynamic model of the pipe conveying fluid under combined harmonic and Gaussian white noise excitations is established.Subsequently,the averaged stochastic differential equations and Fokker–Planck–Kolmogorov(FPK)equations of the pipe conveying fluid subjected to combined excitations are acquired by the modified stochastic averaging method.The effectiveness of the analysis results is verified through the Monte Carlo method.The effects of fluid speed,noise intensity,amplitude of harmonic excitation,and damping factor on the probability density functions of amplitude,displacement,as well as velocity are discussed in detail.The results show that with an increase in fluid speed or noise intensity,the possible greatest amplitude for the fluid-conveying pipe increases,and the possible greatest displacement and velocity also increase.With an increase in the amplitude of harmonic excitation or damping factor,the possible greatest amplitude for the pipe decreases,and the possible greatest displacement and velocity also decrease.展开更多
To investigate the vibration response of the comprehensive transportation hub structure under multiple-source excitations,an on-site vibration measurement was carried out at Wuhan Railway Station in China.The characte...To investigate the vibration response of the comprehensive transportation hub structure under multiple-source excitations,an on-site vibration measurement was carried out at Wuhan Railway Station in China.The characteristics of each floor vibration were obtained through the time domain and frequency domain analyses.Based on the vibration characteristic under multiple-source excitations,the proposed attenuation model was derived.In addition,a vibration comfort evaluation on the Wuhan Railway Station was conducted.The results show that the effect of the number of vibration sources on horizontal acceleration is more significant than that regarding vertical acceleration.When the structure is under the effects two vibration sources with different frequencies,a high-frequency vibration can amplify a low-frequency vibration.The derived attenuation model can precisely predict the vibration attenuation and reduce the subsequent vibration test workload.Based on the annoyance rate model result,the annoyance rate of Wuhan Railway Station is high,which is harmful to the staff of the station.展开更多
Antiferromagnetic spin fluctuation is regarded as the leading driving force for electron pairing in high-Tc superconductors.In iron-based superconductors,spin excitations at low energy range,especially the spin-resona...Antiferromagnetic spin fluctuation is regarded as the leading driving force for electron pairing in high-Tc superconductors.In iron-based superconductors,spin excitations at low energy range,especially the spin-resonance mode at ER~5kBTc,are important for understanding the superconductivity.Here,we use inelastic neutron scattering(INS)to investigate the symmetry and in-plane wave-vector dependence of low-energy spin excitations in uniaxial-strain detwinned Fe Se.The low-energy spin excitations(E<10 meV)appear mainly at Q=(±1,0)in the superconducting state(T9K)and the nematic state(T90 K),confirming the constant C_(2) rotational symmetry and ruling out the C_(4) mode at E≈3 meV reported in a prior INS study.Moreover,our results reveal an isotropic spin resonance in the superconducting state,which is consistent with the s±wave pairing symmetry.At slightly higher energy,low-energy spin excitations become highly anisotropic.The full width at half maximum of spin excitations is elongated along the transverse direction.The Q-space isotropic spin resonance and highly anisotropic low-energy spin excitations could arise from dyz intra-orbital selective Fermi surface nesting between the hole pocket aroundΓpoint and the electron pockets centered at MX point.展开更多
By applying the mastersymmetry of degree one to the time-independent symmetry K_(1), the fifth-order asymmetric Nizhnik-Novikov-Veselov system is derived. The variable separation solution is obtained by using the trun...By applying the mastersymmetry of degree one to the time-independent symmetry K_(1), the fifth-order asymmetric Nizhnik-Novikov-Veselov system is derived. The variable separation solution is obtained by using the truncated Painlevé expansion with a special seed solution. New patterns of localized excitations, such as dromioff, instanton moving on a curved line, and tempo-spatial breather, are constructed. Additionally, fission or fusion solitary wave solutions are presented,graphically illustrated by several interesting examples.展开更多
While the geodetic excitationχ(t)of polar motion p(t)is essential to improve our understanding of global mass redistributions and relative motions with respect to the terrestrial frame,the widely adopted method to de...While the geodetic excitationχ(t)of polar motion p(t)is essential to improve our understanding of global mass redistributions and relative motions with respect to the terrestrial frame,the widely adopted method to deriveχ(t)from p(t)has biases in both amplitude and phase responses.This study has developed a new simple but more accurate method based on the combination of the frequency-and time-domain Liouville's equation(FTLE).The FTLE method has been validated not only with 6-h sampled synthetic excitation series but also with daily and 6-h sampled polar motion measurements as well asχ(t)produced by the interactive webpage tool of the International Earth Rotation and Reference Systems Service(IERS).Numerical comparisons demonstrate thatχ(t)derived from the FTLE method has superior performances in both the time and frequency domains with respect to that obtained from the widely adopted method or the IERS webpage tool,provided that the input p(t)series has a length around or more than 25 years,which presents no practical limitations since the necessary polar motion data are readily available.The FTLE code is provided in the form of Mat Lab function.展开更多
The fluorescence imaging (FLI) in the second near-infrared window (NIR-II, 1000–1700nm) has attracted considerable attention in the past decade. In contrast to conventional NIR-I window excitation (808nm/980nm), FLI ...The fluorescence imaging (FLI) in the second near-infrared window (NIR-II, 1000–1700nm) has attracted considerable attention in the past decade. In contrast to conventional NIR-I window excitation (808nm/980nm), FLI with NIR-II window excitation (1064nm/other wavelength beyond 1000nm) can afford deeper tissue penetration depth with high clarity due to the merits of suppressed photon scattering and diminished autofluorescence. In this review, we have summarized NIR-II window excitable/emissive organic/polymeric fluorophores recently developed. The characteristics of these fluorophores such as chemical structures and photophysical properties have also been critically discussed. Furthermore, the latest development of noninvasive in vivo FLI with NIR-II excitation was highlighted. The ideal imaging results emphasized the importance of NIR-II excitation of these fluorophores in enabling deep tissue penetration and high-resolution imaging. Finally, a perspective on the challenges and prospects of NIR-II excitable/emissive organic/polymeric fluorophores was also discussed. We expected this review will be served as a source of inspiration for researchers, stimulating the creation of novel NIR-II excitable fluorophores and fostering the development of bioimaging applications.展开更多
Background:Acupuncture is widely used in modulating brain excitability and motor function,as a form of complementary and alternative medicine.However,there is no existing meta-analysis evaluating the effectiveness and...Background:Acupuncture is widely used in modulating brain excitability and motor function,as a form of complementary and alternative medicine.However,there is no existing meta-analysis evaluating the effectiveness and safety of acupuncture on corticospinal excitability(CSE),and the credibility of the evidence has yet to be quantified.Objective:This study was designed to assess the efficacy and safety of electroacupuncture(EA)and manual acupuncture(MA)in enhancing brain excitability,specifically focusing on CSE as measured by transcranial magnetic stimulation(TMS).Search strategy:This study followed a systematic approach,searching 9 databases up to August 2024 and examining grey literature,in compliance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.Inclusion criteria:Studies were included if they compared the clinical efficacy of EA or MA with sham acupuncture,no treatment or usual training.Data extraction and analysis:Three investigators independently conducted literature screening,data extraction,and risk of bias assessment.The primary outcome focused on motor-evoked potentials as measured by TMS,with treatment effects quantified using mean differences or standardized mean differences between pre-and post-treatment.Subgroup analyses were conducted using mixed-effects models,while random-effects or fixed-effects models were used to estimate average treatment differences across studies.Results:Based on 34 studies involving 1031 adults,acupuncture techniques significantly enhanced CSE.EA had a greater impact than MA,with effect sizes of 0.53 mV vs 0.43 mV(95%confidence interval[CI]:[0.30,0.76],P<0.00001 vs 95%CI:[0.28,0.59],P<0.00001).The 5 most frequently used acupoints were LI4(Hegu,32 times),ST36(Zusanli,10 times),LI11(Quchi,7 times),TE5(Waiguan,6 times),and GB34(Yanglingquan,5 times).Conclusion:This systematic review indicates that both EA and MA could effectively and safely enhance CSE,bringing the corticospinal pathway closer to the threshold for firing,which may ultimately improve motor function.LI4,ST36,LI11,TE5 and GB34 are the most commonly used acupoints.展开更多
The ultrafast excitation dynamics of atoms and molecules exposed to circularly polarized two-color(CPTC)laser fields constitute a fascinating topic in attosecond science. Although extensive research has established th...The ultrafast excitation dynamics of atoms and molecules exposed to circularly polarized two-color(CPTC)laser fields constitute a fascinating topic in attosecond science. Although extensive research has established the relationship between the Rydberg state excitation(RSE) yields and the CPTC field parameters, such as field amplitude ratios and helicity of two components, the role of the relative phase(φ) in modulating RSE efficiency remains unclear. In this work, we theoretically investigate the φ dependence of RSE and ionization yields in the co-rotating and counter-rotating circularly polarized two-color(CPTC) few-cycle laser fields by a semiclassical model. We find that, in co-rotating CPTC fields, both RSE and ionization yields display pronounced oscillations as a function of φ and these oscillations are significantly suppressed in the counter-rotating configuration, particularly for ionization yields. Moreover, the ratio of RSE to ionization yields exhibits an out-of-phase oscillatory pattern between low-and high-intensity regimes. These results can be comprehended by the unique feature of φ dependence of CPTC few-cycle fields, based on our semiclassical analysis. Our results demonstrate that phase-controlled CPTC fields offer a versatile tool for steering ultrafast ionization and RSE dynamics of atoms and molecules.展开更多
Hydro-pneumatic near-zero frequency(NZF)vibration isolators have better performance at isolating vibration with low frequencies and heavy loadings when the nonlinear fluidic damping is introduced and the pressurized g...Hydro-pneumatic near-zero frequency(NZF)vibration isolators have better performance at isolating vibration with low frequencies and heavy loadings when the nonlinear fluidic damping is introduced and the pressurized gas pressure is properly adjusted.The nonlinear characteristics of such devices make their corresponding dynamic research involve chaotic dynamics.Chaos may bring negative influence and disorder to the structure and low-frequency working efficiency of isolators,which makes it necessary to clarify and control the threshold ranges for chaos generation in advance.In this work,the chaotic characteristics for a class of hydro-pneumatic NZF vibration isolators under dry friction,harmonic,and environmental noise excitations are analyzed by the analytical and numerical methods.The parameter ranges for the generation of chaos are obtained by the classical and random Melnikov methods.The chaotic characteristics and thresholds of the parameters in the systems with or without noise excitation are discussed and described.The analytical solutions and the influence of noise and harmonic excitation about chaos are tested and further analyzed through many numerical simulations.The results show that chaos in the system can be induced or inhibited with the adjustment of the magnitudes of harmonic excitation and noise intensity.展开更多
Vicinal diamines are key motifs widely-found in many pharmaceuticals and biologically active molecules.An appealing approach for synthesizing these molecules is the amination of enamines,but few examples have been exp...Vicinal diamines are key motifs widely-found in many pharmaceuticals and biologically active molecules.An appealing approach for synthesizing these molecules is the amination of enamines,but few examples have been explored.With the utilization of nitrogen-centered radicals(NCRs),here we present the development of a dual bio-/photo-catalytic system for achieving enantioselective hydroamination of enamides,which can give easy access to diverse enantioenriched vicinal diamines.These reactions progress efficiently under green light excitation and exhibit excellent enantioselectivities(up to>99%enantiomeric excess).Mechanistic studies uncovered the synergistic effect of the enzyme and the externally added organophotoredox catalyst Rhodamine B(RhB).This work demonstrates the effectiveness of photobiocatalysis to generate and control high-energy radical intermediates,addressing a long-standing challenge in chemical synthesis.展开更多
Inflammation plays a crucial role in the initiation and progression of sepsis and induces alterations in brain neurotransmission, thereby contributing to the development of sepsis-associated encephalopathy(SAE).Parval...Inflammation plays a crucial role in the initiation and progression of sepsis and induces alterations in brain neurotransmission, thereby contributing to the development of sepsis-associated encephalopathy(SAE).Parvalbumin(PV) interneurons are pivotal contributors to cognitive processes and have been implicated in various central nervous system dysfunctions, including SAE. Oxytocin, known for its ability to augment the firing rate of gamma-aminobutyric acid(GABA)-ergic interneurons and directly stimulate inhibitory interneurons to enhance the tonic inhibition of pyramidal neurons, has prompted an investigation into its potential therapeutic effects on cognitive dysfunction in SAE. In the current study, we administered intranasal oxytocin to SAE mice induced by lipopolysaccharide. Behavioral assessments, including open field, Y-maze, and fear conditioning, were used to evaluate cognitive performance. Golgi staining revealed hippocampal synaptic deterioration, local field potential recordings showed weakened gamma oscillations, and immunofluorescence staining demonstrated decreased PV expression in the cornu ammonis 1(CA1) region of the hippocampus following lipopolysaccharide treatment, all of which were alleviated by oxytocin administration. Furthermore, immunofluorescence staining of PV co-localization with vesicular glutamate transporter 1 or vesicular GABA transporter indicated a balanced excitation/inhibition effect of neurotransmitters on PV interneurons after oxytocin administration in the SAE mice, leading to an improved cognitive function. In conclusion, oxytocin treatment improved cognitive function by increasing the number of PV^(+) neurons in the hippocampal CA1 region, restoring the balance of excitatory/inhibitory synaptic transmission on PV interneurons, and enhancing hippocampal CA1 local field potential gamma oscillations. These findings suggest a potential mechanism underlying the beneficial effects of oxytocin in SAE.展开更多
We utilize conventional wave-vector-resolved Brillouin light scattering technology to investigate the spin wave response in YIG thin films under high-power microwave excitation. By varying the microwave frequency, ext...We utilize conventional wave-vector-resolved Brillouin light scattering technology to investigate the spin wave response in YIG thin films under high-power microwave excitation. By varying the microwave frequency, external bias magnetic field, and in-plane wave vector, in addition to observing the dipole-exchange spin waves excited by parallel parametric pumping, we further observe broadband spin wave excitation within the dipole-exchange spin wave spectrum. This broadband excitation results from the combined effects of parallel and perpendicular parametric pumping, induced by irregularities in the excitation geometry, as well as magnon–magnon scattering arising from the absence of certain spin wave modes. Our findings offer new insights into the mechanisms of energy dissipation and relaxation processes caused by spin wave excitation in magnetic devices operating at high power.展开更多
This paper deeply discusses the causes of gear howling noise,the identification and analysis of multi-source excitation,the transmission path of dynamic noise,simulation and experimental research,case analysis,optimiz...This paper deeply discusses the causes of gear howling noise,the identification and analysis of multi-source excitation,the transmission path of dynamic noise,simulation and experimental research,case analysis,optimization effect,etc.,aiming to better provide a certain guideline and reference for relevant researchers.展开更多
Long-period free oscillations provide robust information for the spatio-temporal characteristics of large earthquakes.In this study,we employ a normal-mode summation algorithm to generate threecomponent seismograms wi...Long-period free oscillations provide robust information for the spatio-temporal characteristics of large earthquakes.In this study,we employ a normal-mode summation algorithm to generate threecomponent seismograms within an aspherical,anelastic,and rotating Earth model,focusing on the excitation of seismic normal modes by the 2011 Tohoku megathrust earthquake.Specifically,we analyze the effects of seismic source parameters,including fault geometry,focal depth,and rupture duration.By comparing synthetic free oscillation spectra with observed data,we validate several source mechanisms and emphasize the need for horizontal observations to improve seismic mechanism inversions.Our quantitative analyses reveal that among fault geometry parameters,dip and slip angles have a more pronounced impact on excitation amplitudes than fault strikes.Certain fault configurations enhance the detectability of specific modes,underscoring the relationship between fault geometry and mode excitation.Normal modes also exhibit varying sensitivity to focal depth,with significant excitation amplitude changes at discontinuity boundaries.Additionally,we demonstrate that while rupture duration can be inferred by minimizing differences between observed and synthetic spectra,more extensive records and modes should be included.展开更多
Physical layer authentication(PLA)in the context of the Internet of Things(IoT)has gained significant attention.Compared with traditional encryption and blockchain technologies,PLA provides a more computationally effi...Physical layer authentication(PLA)in the context of the Internet of Things(IoT)has gained significant attention.Compared with traditional encryption and blockchain technologies,PLA provides a more computationally efficient alternative to exploiting the properties of the wireless medium itself.Some existing PLA solutions rely on static mechanisms,which are insufficient to address the authentication challenges in fifth generation(5G)and beyond wireless networks.Additionally,with the massive increase in mobile device access,the communication security of the IoT is vulnerable to spoofing attacks.To overcome the above challenges,this paper proposes a lightweight deep convolutional neural network(CNN)equipped with squeeze and excitation module(SE module)in dynamic wireless environments,namely SE-ConvNet.To be more specific,a convolution factorization is developed to reduce the complexity of PLA models based on deep learning.Moreover,an SE module is designed in the deep CNN to enhance useful features andmaximize authentication accuracy.Compared with the existing solutions,the proposed SE-ConvNet enabled PLA scheme performs excellently in mobile and time-varying wireless environments while maintaining lower computational complexity.展开更多
Exploring advanced techniques capable of probing nanometric acoustic waves in nanostructures is critically important for the development of miniaturized acoustic devices.In this study,we probe the optically-excited ac...Exploring advanced techniques capable of probing nanometric acoustic waves in nanostructures is critically important for the development of miniaturized acoustic devices.In this study,we probe the optically-excited acoustic waves in a single silicon nanowire(NW)using the time-resolved(tr-)high-order Laue-zone(HOLZ)lines under convergent-beam electron diffraction(CBED)conditions in an ultrafast transmission electron microscope(UTEM).We devise an experimental scheme to obtain tr-HOLZ lines under off-zone-axis CBED conditions.We also propose a geometric description of HOLZ line formation and use this alternative description to quantitatively evaluate the dynamics of optically-excited silicon NW.Using part of the deformation gradient tensor,our simulations of the dynamics of Si NW reproduce the experimental results.We further discuss the feasibility of a full retrieval of the deformation gradient tensor by using a set of HOLZ lines from three zone axes.Our findings illustrate a strategy for the quantitative access to dynamical acoustic waves optically excited in micro-and nano-structures using UTEM.展开更多
文摘This paper presents a semi-active strategy for seismic protection of a benchmark cable-stayed bridge with consideration of multiple-support excitations. In this control strategy, Magnetorheological (MR) dampers are proposed as control devices, a LQG-clipped-optimal control algorithm is employed. An active control strategy, shown in previous researches to perform well at controlling the benchmark bridge when uniform earthquake motion was assumed, is also used in this study to control this benchmark bridge with consideration of multiple-support excitations. The performance of active control system is compared to that of the presented semi-active control strategy. Because the MR fluid damper is a con-trollable energy- dissipation device that cannot add mechanical energy to the structural system, the proposed control strategy is fail-safe in that bounded-input, bounded-output stability of the controlled structure is guaranteed. The numerical results demonstrated that the performance of the presented control design is nearly the same as that of the active control system; and that the MR dampers can effectively be used to control seismically excited cable-stayed bridges with multiple-support excitations.
基金National Natural Science Foundation of China under Grant No.51278008the National Key Research and Development Plan of China under Grant No.2016YFC0701103
文摘In order to study the infl uence of the ground motion spatial eff ect on the seismic response of large span spatial structures with isolation bearings, a single-layer cylindrical latticed shell scale model with a similarity ratio of 1/10 was constructed. An earthquake simulation shaking table test on the response under multiple-support excitations was performed with the high-position seismic isolation method using high damping rubber (HDR) bearings. Small-amplitude sinusoidal waves and seismic wave records with various spectral characteristics were applied to the model. The dynamic characteristics of the model and the seismic isolation eff ect on it were analyzed at varying apparent wave velocities, namely infi nitely great, 1000 m/s, 500 m/s and 250 m/s. Besides, numerical simulations were carried out by Matlab software. According to the comparison results, the numerical results agreed well with the experimental data. Moreover, the results showed that the latticed shell roof exhibited a translational motion as a rigid body after the installation of the HDR bearings with a much lower natural frequency, higher damping ratio and only 1/2~1/8 of the acceleration response peak values. Meanwhile, the structural responses and the bearing deformations at the output end of the seismic waves were greatly increased under multiple-support excitations.
基金Basic Scientific Research Operating Expenses Project of Provincial Undergraduate Colleges and Universities in Heilongjiang Province:Study on Luminescent Properties and Fluorescent Temperature Characteristics of Rare Earth Luminescent Materials Based on Tungstates(YWK10236210223)Provincial General Project:College Students’Innovation and Entrepreneurship Training Program Project:Design of a Multifunctional Intelligent Car(202310236033)。
文摘This study focuses on the fluorescent thermometric properties of CaMoO4:5%Tb3+under different temperature excitations.At the detection wavelength of 544 nm,with the temperature varying from 293 K to 563 K,there is a broadband absorption peak in the range of 250 nm to 350 nm.The results indicate that this phenomenon is caused by the superposition of the 4f-5d transition of Tb3+ and the O2--Mo6+charge transfer.It is considered that as the temperature rises,the luminescent intensity of the material shows an obvious continuous decreasing trend,which reflects a significant luminescent thermal quenching trend;thus,this quenching belongs to the“strong coupling”type.Based on the excitation spectrum results,two excitation wavelengths,312 nm and 338 nm,were specifically selected to excite the samples,which correspond to the top of the charge transfer band,the redshift intersection of the charge transfer band,and the edge of the charge transfer band at 293 K,respectively.
基金supported in part by the National Natural Science Foundation of China(Grant No.12432001)Natural Science Foundation of Hunan Province(Grant Nos.2023JJ60527,2023JJ30152,and 2023JJ30259)the Natural Science Foundation of Changsha(KQ2202133).
文摘This study investigates the nonlinear resonance responses of suspended cables subjected to multi-frequency excitations and time-delayed feedback.Two specific combinations and simultaneous resonances are selected for detailed examination.Initially,utilizing Hamilton’s variational principle,a nonlinear vibration control model of suspended cables under multi-frequency excitations and longitudinal time-delayed velocity feedback is developed,and the Galerkin method is employed to obtain the discrete model.Subsequently,focusing solely on single-mode discretization,analytical solutions for the two simultaneous resonances are derived using the method of multiple scales.The frequency response equations are derived,and the stability analysis is presented for two simultaneous resonance cases.The results demonstrate that suspended cables exhibit complex nonlinearity under multi-frequency excitations.Multiple solutions under multi-frequency excitation can be distinguished through the frequency–response and the detuning-phase curves.By adjusting the control gain and time delay,the resonance range,response amplitude,and phase of suspended cables can be modified.
基金supported by the National Natural Science Foundation of China(Nos.12272211 and 12072181).
文摘Fluid-conveying pipes generally face combined excitations caused by periodic loads and random noises.Gaussian white noise is a common random noise excitation.This study investigates the random vibration response of a simply-supported pipe conveying fluid under combined harmonic and Gaussian white noise excitations.According to the generalized Hamilton’s principle,the dynamic model of the pipe conveying fluid under combined harmonic and Gaussian white noise excitations is established.Subsequently,the averaged stochastic differential equations and Fokker–Planck–Kolmogorov(FPK)equations of the pipe conveying fluid subjected to combined excitations are acquired by the modified stochastic averaging method.The effectiveness of the analysis results is verified through the Monte Carlo method.The effects of fluid speed,noise intensity,amplitude of harmonic excitation,and damping factor on the probability density functions of amplitude,displacement,as well as velocity are discussed in detail.The results show that with an increase in fluid speed or noise intensity,the possible greatest amplitude for the fluid-conveying pipe increases,and the possible greatest displacement and velocity also increase.With an increase in the amplitude of harmonic excitation or damping factor,the possible greatest amplitude for the pipe decreases,and the possible greatest displacement and velocity also decrease.
基金Science Fund for Distinguished Young Scholars of Hubei Province under Grant No.2023AFA103National Natural Science Foundation of China under Grant No.52078395+1 种基金Open Projects Foundation of State Key Laboratory for Health and Safety of Bridge Structures under Grant No.BHSKL19-07-GFYoung Top-Notch Talent Cultivation Program of Hubei Province。
文摘To investigate the vibration response of the comprehensive transportation hub structure under multiple-source excitations,an on-site vibration measurement was carried out at Wuhan Railway Station in China.The characteristics of each floor vibration were obtained through the time domain and frequency domain analyses.Based on the vibration characteristic under multiple-source excitations,the proposed attenuation model was derived.In addition,a vibration comfort evaluation on the Wuhan Railway Station was conducted.The results show that the effect of the number of vibration sources on horizontal acceleration is more significant than that regarding vertical acceleration.When the structure is under the effects two vibration sources with different frequencies,a high-frequency vibration can amplify a low-frequency vibration.The derived attenuation model can precisely predict the vibration attenuation and reduce the subsequent vibration test workload.Based on the annoyance rate model result,the annoyance rate of Wuhan Railway Station is high,which is harmful to the staff of the station.
基金Beijing Normal University was supported by the Fundamental Research Funds for the Central Universitiesthe National Key Projects for Research and Development of China(No.2021YFA1400400)+1 种基金the National Natural Science Foundation of China(Grant Nos.12174029 and 11922402)the neutron beamtimes from J-PARC(Proposal No.2019A0002)。
文摘Antiferromagnetic spin fluctuation is regarded as the leading driving force for electron pairing in high-Tc superconductors.In iron-based superconductors,spin excitations at low energy range,especially the spin-resonance mode at ER~5kBTc,are important for understanding the superconductivity.Here,we use inelastic neutron scattering(INS)to investigate the symmetry and in-plane wave-vector dependence of low-energy spin excitations in uniaxial-strain detwinned Fe Se.The low-energy spin excitations(E<10 meV)appear mainly at Q=(±1,0)in the superconducting state(T9K)and the nematic state(T90 K),confirming the constant C_(2) rotational symmetry and ruling out the C_(4) mode at E≈3 meV reported in a prior INS study.Moreover,our results reveal an isotropic spin resonance in the superconducting state,which is consistent with the s±wave pairing symmetry.At slightly higher energy,low-energy spin excitations become highly anisotropic.The full width at half maximum of spin excitations is elongated along the transverse direction.The Q-space isotropic spin resonance and highly anisotropic low-energy spin excitations could arise from dyz intra-orbital selective Fermi surface nesting between the hole pocket aroundΓpoint and the electron pockets centered at MX point.
文摘By applying the mastersymmetry of degree one to the time-independent symmetry K_(1), the fifth-order asymmetric Nizhnik-Novikov-Veselov system is derived. The variable separation solution is obtained by using the truncated Painlevé expansion with a special seed solution. New patterns of localized excitations, such as dromioff, instanton moving on a curved line, and tempo-spatial breather, are constructed. Additionally, fission or fusion solitary wave solutions are presented,graphically illustrated by several interesting examples.
基金supported by the National Natural Science Foundation of China(grant numbers 41874025 and 41474022)。
文摘While the geodetic excitationχ(t)of polar motion p(t)is essential to improve our understanding of global mass redistributions and relative motions with respect to the terrestrial frame,the widely adopted method to deriveχ(t)from p(t)has biases in both amplitude and phase responses.This study has developed a new simple but more accurate method based on the combination of the frequency-and time-domain Liouville's equation(FTLE).The FTLE method has been validated not only with 6-h sampled synthetic excitation series but also with daily and 6-h sampled polar motion measurements as well asχ(t)produced by the interactive webpage tool of the International Earth Rotation and Reference Systems Service(IERS).Numerical comparisons demonstrate thatχ(t)derived from the FTLE method has superior performances in both the time and frequency domains with respect to that obtained from the widely adopted method or the IERS webpage tool,provided that the input p(t)series has a length around or more than 25 years,which presents no practical limitations since the necessary polar motion data are readily available.The FTLE code is provided in the form of Mat Lab function.
基金supported by the National Nature Science Foundation of China(Nos.62075079,62305127,61975200)the Natural Science Foundation of Jilin Province(20230508135RC)the Science and Technology Development Foundation of Changchun City(23GZZ15).
文摘The fluorescence imaging (FLI) in the second near-infrared window (NIR-II, 1000–1700nm) has attracted considerable attention in the past decade. In contrast to conventional NIR-I window excitation (808nm/980nm), FLI with NIR-II window excitation (1064nm/other wavelength beyond 1000nm) can afford deeper tissue penetration depth with high clarity due to the merits of suppressed photon scattering and diminished autofluorescence. In this review, we have summarized NIR-II window excitable/emissive organic/polymeric fluorophores recently developed. The characteristics of these fluorophores such as chemical structures and photophysical properties have also been critically discussed. Furthermore, the latest development of noninvasive in vivo FLI with NIR-II excitation was highlighted. The ideal imaging results emphasized the importance of NIR-II excitation of these fluorophores in enabling deep tissue penetration and high-resolution imaging. Finally, a perspective on the challenges and prospects of NIR-II excitable/emissive organic/polymeric fluorophores was also discussed. We expected this review will be served as a source of inspiration for researchers, stimulating the creation of novel NIR-II excitable fluorophores and fostering the development of bioimaging applications.
文摘Background:Acupuncture is widely used in modulating brain excitability and motor function,as a form of complementary and alternative medicine.However,there is no existing meta-analysis evaluating the effectiveness and safety of acupuncture on corticospinal excitability(CSE),and the credibility of the evidence has yet to be quantified.Objective:This study was designed to assess the efficacy and safety of electroacupuncture(EA)and manual acupuncture(MA)in enhancing brain excitability,specifically focusing on CSE as measured by transcranial magnetic stimulation(TMS).Search strategy:This study followed a systematic approach,searching 9 databases up to August 2024 and examining grey literature,in compliance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.Inclusion criteria:Studies were included if they compared the clinical efficacy of EA or MA with sham acupuncture,no treatment or usual training.Data extraction and analysis:Three investigators independently conducted literature screening,data extraction,and risk of bias assessment.The primary outcome focused on motor-evoked potentials as measured by TMS,with treatment effects quantified using mean differences or standardized mean differences between pre-and post-treatment.Subgroup analyses were conducted using mixed-effects models,while random-effects or fixed-effects models were used to estimate average treatment differences across studies.Results:Based on 34 studies involving 1031 adults,acupuncture techniques significantly enhanced CSE.EA had a greater impact than MA,with effect sizes of 0.53 mV vs 0.43 mV(95%confidence interval[CI]:[0.30,0.76],P<0.00001 vs 95%CI:[0.28,0.59],P<0.00001).The 5 most frequently used acupoints were LI4(Hegu,32 times),ST36(Zusanli,10 times),LI11(Quchi,7 times),TE5(Waiguan,6 times),and GB34(Yanglingquan,5 times).Conclusion:This systematic review indicates that both EA and MA could effectively and safely enhance CSE,bringing the corticospinal pathway closer to the threshold for firing,which may ultimately improve motor function.LI4,ST36,LI11,TE5 and GB34 are the most commonly used acupoints.
基金supported by the National Natural Science Foundation of China (Nos. 12121004, 12274273, and 12450402)the Science and Technology Department of Hubei Province (No. 2020CFA029)+1 种基金CAS Project for Young Scientists in Basic Research (No. YSBR-091)the Youth Innovation Promotion Association CAS (No. 2021328)。
文摘The ultrafast excitation dynamics of atoms and molecules exposed to circularly polarized two-color(CPTC)laser fields constitute a fascinating topic in attosecond science. Although extensive research has established the relationship between the Rydberg state excitation(RSE) yields and the CPTC field parameters, such as field amplitude ratios and helicity of two components, the role of the relative phase(φ) in modulating RSE efficiency remains unclear. In this work, we theoretically investigate the φ dependence of RSE and ionization yields in the co-rotating and counter-rotating circularly polarized two-color(CPTC) few-cycle laser fields by a semiclassical model. We find that, in co-rotating CPTC fields, both RSE and ionization yields display pronounced oscillations as a function of φ and these oscillations are significantly suppressed in the counter-rotating configuration, particularly for ionization yields. Moreover, the ratio of RSE to ionization yields exhibits an out-of-phase oscillatory pattern between low-and high-intensity regimes. These results can be comprehended by the unique feature of φ dependence of CPTC few-cycle fields, based on our semiclassical analysis. Our results demonstrate that phase-controlled CPTC fields offer a versatile tool for steering ultrafast ionization and RSE dynamics of atoms and molecules.
基金Project supported by the National Natural Science Foundation of China(Nos.12172340 and12411530068)the Shenzhen Science and Technology Program(No.JCYJ20240813114012016)+2 种基金the High-Level Talent Introduction Plan of Guangzhou Citythe Fundamental Research Funds for the Central Universities-China University of Geosciences(Wuhan)(No.G1323524005)the Young Top-Notch Talent Cultivation Program of Hubei Province。
文摘Hydro-pneumatic near-zero frequency(NZF)vibration isolators have better performance at isolating vibration with low frequencies and heavy loadings when the nonlinear fluidic damping is introduced and the pressurized gas pressure is properly adjusted.The nonlinear characteristics of such devices make their corresponding dynamic research involve chaotic dynamics.Chaos may bring negative influence and disorder to the structure and low-frequency working efficiency of isolators,which makes it necessary to clarify and control the threshold ranges for chaos generation in advance.In this work,the chaotic characteristics for a class of hydro-pneumatic NZF vibration isolators under dry friction,harmonic,and environmental noise excitations are analyzed by the analytical and numerical methods.The parameter ranges for the generation of chaos are obtained by the classical and random Melnikov methods.The chaotic characteristics and thresholds of the parameters in the systems with or without noise excitation are discussed and described.The analytical solutions and the influence of noise and harmonic excitation about chaos are tested and further analyzed through many numerical simulations.The results show that chaos in the system can be induced or inhibited with the adjustment of the magnitudes of harmonic excitation and noise intensity.
文摘Vicinal diamines are key motifs widely-found in many pharmaceuticals and biologically active molecules.An appealing approach for synthesizing these molecules is the amination of enamines,but few examples have been explored.With the utilization of nitrogen-centered radicals(NCRs),here we present the development of a dual bio-/photo-catalytic system for achieving enantioselective hydroamination of enamides,which can give easy access to diverse enantioenriched vicinal diamines.These reactions progress efficiently under green light excitation and exhibit excellent enantioselectivities(up to>99%enantiomeric excess).Mechanistic studies uncovered the synergistic effect of the enzyme and the externally added organophotoredox catalyst Rhodamine B(RhB).This work demonstrates the effectiveness of photobiocatalysis to generate and control high-energy radical intermediates,addressing a long-standing challenge in chemical synthesis.
基金supported by grants from the general project of Nanjing Medical University Science and Technology Development Foundation (Grant No.NMUB20210112)。
文摘Inflammation plays a crucial role in the initiation and progression of sepsis and induces alterations in brain neurotransmission, thereby contributing to the development of sepsis-associated encephalopathy(SAE).Parvalbumin(PV) interneurons are pivotal contributors to cognitive processes and have been implicated in various central nervous system dysfunctions, including SAE. Oxytocin, known for its ability to augment the firing rate of gamma-aminobutyric acid(GABA)-ergic interneurons and directly stimulate inhibitory interneurons to enhance the tonic inhibition of pyramidal neurons, has prompted an investigation into its potential therapeutic effects on cognitive dysfunction in SAE. In the current study, we administered intranasal oxytocin to SAE mice induced by lipopolysaccharide. Behavioral assessments, including open field, Y-maze, and fear conditioning, were used to evaluate cognitive performance. Golgi staining revealed hippocampal synaptic deterioration, local field potential recordings showed weakened gamma oscillations, and immunofluorescence staining demonstrated decreased PV expression in the cornu ammonis 1(CA1) region of the hippocampus following lipopolysaccharide treatment, all of which were alleviated by oxytocin administration. Furthermore, immunofluorescence staining of PV co-localization with vesicular glutamate transporter 1 or vesicular GABA transporter indicated a balanced excitation/inhibition effect of neurotransmitters on PV interneurons after oxytocin administration in the SAE mice, leading to an improved cognitive function. In conclusion, oxytocin treatment improved cognitive function by increasing the number of PV^(+) neurons in the hippocampal CA1 region, restoring the balance of excitatory/inhibitory synaptic transmission on PV interneurons, and enhancing hippocampal CA1 local field potential gamma oscillations. These findings suggest a potential mechanism underlying the beneficial effects of oxytocin in SAE.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 52471200, 12174165, and 52201219)。
文摘We utilize conventional wave-vector-resolved Brillouin light scattering technology to investigate the spin wave response in YIG thin films under high-power microwave excitation. By varying the microwave frequency, external bias magnetic field, and in-plane wave vector, in addition to observing the dipole-exchange spin waves excited by parallel parametric pumping, we further observe broadband spin wave excitation within the dipole-exchange spin wave spectrum. This broadband excitation results from the combined effects of parallel and perpendicular parametric pumping, induced by irregularities in the excitation geometry, as well as magnon–magnon scattering arising from the absence of certain spin wave modes. Our findings offer new insights into the mechanisms of energy dissipation and relaxation processes caused by spin wave excitation in magnetic devices operating at high power.
文摘This paper deeply discusses the causes of gear howling noise,the identification and analysis of multi-source excitation,the transmission path of dynamic noise,simulation and experimental research,case analysis,optimization effect,etc.,aiming to better provide a certain guideline and reference for relevant researchers.
基金supported by the National Natural ScienceFoundation of China(42204003,42274011,42388102,42192533,42192531)the Natural Science Foundation of Wuhan(2024040701010027)+1 种基金the Open Fund Supported by the State KeyLaboratory of Precision Geodesy,Innovation Academy for PrecisionMeasurement Science and Technology,Chinese Academy of Sci-ences(SKLGED2024-1-1)the Open Fund Supported by KeyLaboratory of Polar Environment Monitoring and Public Gover-nance(Wuhan University),Ministry of Education(202401)。
文摘Long-period free oscillations provide robust information for the spatio-temporal characteristics of large earthquakes.In this study,we employ a normal-mode summation algorithm to generate threecomponent seismograms within an aspherical,anelastic,and rotating Earth model,focusing on the excitation of seismic normal modes by the 2011 Tohoku megathrust earthquake.Specifically,we analyze the effects of seismic source parameters,including fault geometry,focal depth,and rupture duration.By comparing synthetic free oscillation spectra with observed data,we validate several source mechanisms and emphasize the need for horizontal observations to improve seismic mechanism inversions.Our quantitative analyses reveal that among fault geometry parameters,dip and slip angles have a more pronounced impact on excitation amplitudes than fault strikes.Certain fault configurations enhance the detectability of specific modes,underscoring the relationship between fault geometry and mode excitation.Normal modes also exhibit varying sensitivity to focal depth,with significant excitation amplitude changes at discontinuity boundaries.Additionally,we demonstrate that while rupture duration can be inferred by minimizing differences between observed and synthetic spectra,more extensive records and modes should be included.
基金supported in part by the National Key R&D Program of China under grant no.2022YFB2703000in part by the Young Backbone Teachers Support Plan of BISTU under grant no.YBT202437+1 种基金in part by the R&D Program of Beijing Municipal Education Commission under grant no.KM202211232012in part by the Educational Innovation Program of BISTU under grant no.2025JGYB19。
文摘Physical layer authentication(PLA)in the context of the Internet of Things(IoT)has gained significant attention.Compared with traditional encryption and blockchain technologies,PLA provides a more computationally efficient alternative to exploiting the properties of the wireless medium itself.Some existing PLA solutions rely on static mechanisms,which are insufficient to address the authentication challenges in fifth generation(5G)and beyond wireless networks.Additionally,with the massive increase in mobile device access,the communication security of the IoT is vulnerable to spoofing attacks.To overcome the above challenges,this paper proposes a lightweight deep convolutional neural network(CNN)equipped with squeeze and excitation module(SE module)in dynamic wireless environments,namely SE-ConvNet.To be more specific,a convolution factorization is developed to reduce the complexity of PLA models based on deep learning.Moreover,an SE module is designed in the deep CNN to enhance useful features andmaximize authentication accuracy.Compared with the existing solutions,the proposed SE-ConvNet enabled PLA scheme performs excellently in mobile and time-varying wireless environments while maintaining lower computational complexity.
基金supported by the Guangxi Natural Science Foundation(Grant No.2024GXNSFDA010014)the National Natural Science Foundation of China(Grant Nos.12364018 and U22A6005)+1 种基金the Guangxi Science and Technology Major Program(Grant No.AA23073019)the Innovation Project of Guangxi Graduate Education(Grant Nos.YCBZ2022049 and YCBZ2023015)。
文摘Exploring advanced techniques capable of probing nanometric acoustic waves in nanostructures is critically important for the development of miniaturized acoustic devices.In this study,we probe the optically-excited acoustic waves in a single silicon nanowire(NW)using the time-resolved(tr-)high-order Laue-zone(HOLZ)lines under convergent-beam electron diffraction(CBED)conditions in an ultrafast transmission electron microscope(UTEM).We devise an experimental scheme to obtain tr-HOLZ lines under off-zone-axis CBED conditions.We also propose a geometric description of HOLZ line formation and use this alternative description to quantitatively evaluate the dynamics of optically-excited silicon NW.Using part of the deformation gradient tensor,our simulations of the dynamics of Si NW reproduce the experimental results.We further discuss the feasibility of a full retrieval of the deformation gradient tensor by using a set of HOLZ lines from three zone axes.Our findings illustrate a strategy for the quantitative access to dynamical acoustic waves optically excited in micro-and nano-structures using UTEM.
