Wind-driven power harvestings attract attentions since their target wind speeds are quite low less than the so-called cut-in wind speed, which is generally recognized as around 3 m/s. The extant power harvestings driv...Wind-driven power harvestings attract attentions since their target wind speeds are quite low less than the so-called cut-in wind speed, which is generally recognized as around 3 m/s. The extant power harvestings driven by wind-induced-air-column-resonations (i.e. acoustic-pressures) are still lacking simplicity, scale flexibility and solid strategies for practical applications. Therefore, the piezoelectric power harvesters via acoustic-pressures driven by low-speedwind-forces with resonating-tubes and wind-collectors were invented so as to complement all the lacks. The wind-collector as well as the resonating-tube contributed to upraise the power harvesting density. The champion power harvesting density of 19.5 nW/dm2 could be procured at 2.3 m/s of an artificial wind and the optimal resonating-tube and wind-collector. Power harvesting proofs from the natural wind with low mean speeds down to about 0.6 m/s were successfully obtained. The cut-in wind speed of the prototype piezoelectric power harvester was found to be quite low as about 0.4 m/s, signifying its ubiquity. Finally, a multi-bundle pendant-type piezoelectric power harvester was specifically presented together with professing the solid and multiple strategies for practical applications.展开更多
We review the predictions of quark models for multiquark configurations that are bound or resonant states,and compare different methods for estimating the properties of resonances.
Unlocking the full potential of integrated photonics requires versatile,multi-functional devices that can adapt to diverse application demands.However,confronting this challenge with conventional singlefunction resona...Unlocking the full potential of integrated photonics requires versatile,multi-functional devices that can adapt to diverse application demands.However,confronting this challenge with conventional singlefunction resonators often results in cumbersome system designs.We present an elegant solution:a versatile and reconfigurable dual-polarization Si_(3)N_(4)microresonator that represents a new perspective in on-chip photonic designs.Our device can be dynamically reconfigured into three distinct topologies:a Möbius-like microcavity,a Fabry-Pérot resonator,and a microring resonator.This unprecedented functionality is enabled by a tunable balanced Mach-Zehnder interferometer that facilitates controllable mutual mode coupling of counterpropagating light using a single control knob.We experimentally demonstrate that the device not only supports polarization-diverse operation on a compact footprint but also gives rise to a wide variety of physical phenomena,including a standing wave cavity,a traveling wave cavity,free spectral range multiplication,and the photonic pinning effect.These behaviors are accurately modeled using the transfer matrix method and intuitively explained by the temporal coupled-mode theory.Our results underscore the potential for a chip-scale platform to realize reconfigurable reconstructive spectrometers and on-chip synthetic dimensions for topological physics.展开更多
BACKGROUND Many conditions may affect left ventricular(LV)phenotypes which have been classified according to LV mass and geometry.There is limited data on the prognostic value of LV phenotypes classified by cardiac ma...BACKGROUND Many conditions may affect left ventricular(LV)phenotypes which have been classified according to LV mass and geometry.There is limited data on the prognostic value of LV phenotypes classified by cardiac magnetic resonance(CMR).This study aimed to determine the prognostic value of LV phenotypes in elderly and non-elderly patients with known or suspected coronary artery disease.METHODS This is a retrospective cohort study among patients who underwent stress or viability CMR.LV phenotypes were classified according to the LV mass index,the LV end-diastolic volume index and the LV mass/volume ratio,into normal,concentric remodeling,concentric hypertrophy,and eccentric hypertrophy.The primary outcome was a composite of death or heart failure.RESULTS A total of 3289 patients was studied.The average age was 68.0±12.7 years,52.2%of patients were women.Elderly were defined as age≥65 years accounting for 63.9%of the cohort.LV phenotypes were normal,concentric remodeling,concentric hypertrophy,and eccentric hypertrophy at 74.5%,5.8%,9.2%,and 10.5%,respectively.The median duration of follow-up was 41.4 months.The composite outcome of death or heart failure occurred in 7.3%of patients.The prognostic impact of LV phenotypes was more pronounced in the elderly,with eccentric hypertrophy showing the worst prognosis,followed by concentric hypertrophy and concentric remodeling with the adjusted hazard ratio(95%CI)of 2.37(1.72–3.25),1.53(1.12–2.08),and 1.14(0.76–1.71),respectively,compared to normal phenotype.Patients with eccentric hypertrophy also demonstrated abnormal global longitudinal LV strain,left atrial strain,and extracellular volume fraction.CONCLUSIONS LV phenotypes by CMR independently predict adverse clinical outcomes in elderly patients with known or suspected coronary artery disease.In non-elderly patients,the prognostic value of LV phenotypes was less evident.Assessment of LV phenotypes may be useful for risk stratification.展开更多
The output voltages for the capacitive elements of a neural circuit model can be mapped into dimensionless capacitive variables,which present firing patterns similar to the membrane potentials detected in biological n...The output voltages for the capacitive elements of a neural circuit model can be mapped into dimensionless capacitive variables,which present firing patterns similar to the membrane potentials detected in biological neurons.The inclusion of a memcapacitor also en‐ables consideration of membrane deformation effects,enhancing the model’s capacity to simulate neuronal behavior across varying physio‐logical and environmental conditions.In this study,a capacitor and a memcapacitor are connected through a linear resistor in parallel with other electric components in different branch circuits composed of an inductor and a nonlinear resistor.The electrical activities in a neuron with a double-layer membrane and two capacitive variables are discussed in detail after converting the nonlinear equations for the neural circuit into a theoretical neuron model.A dimensionless neuron model and its corresponding energy function are derived.The field energy function for the neural circuit is converted into an equivalent Hamilton energy function and further validated via the Helmholtz theorem.Furthermore,the average value of energy serves as an indicator for predicting stochastic resonance,as supported by analyzing the distribu‐tion of the coefficient of variation.The neuronal firing patterns are shown to be energy-dependent.An adaptive control strategy is proposed to regulate mode transitions in electrical activities of the neuron.An analog equivalent circuit is constructed to experimentally verify the nu‐merical results,thereby supporting the reliability of the proposed neuron model.展开更多
Biodegradable metals(BMs)have shown significant potential for applications in the field of orthopedic implants.These materials gradually degrade after implantation,eventually disappear without residue,provide necessar...Biodegradable metals(BMs)have shown significant potential for applications in the field of orthopedic implants.These materials gradually degrade after implantation,eventually disappear without residue,provide necessary mechanical support during degradation,and closely integrate with bone tissues.Fe-based BMs are particularly notable for their good mechanical properties and biocompatibility.However,their slow degradation rate is a limitation.The emergence of Mn-incorporated Fe-based alloys(Fe-Mn alloys)offers the possibilities for addressing issues of slow degradation rate and incompatibility of magnetic resonance imaging(MRI)for Fe alloys.This review summarizes the advantages of Fe-Mn alloys as orthopedic implants,and the cutting-edge advances in degradation,mechanical and magnetic properties,and osteogenic performance.The cytotoxicity issue is addressed for the porous structured Fe-Mn alloys caused by the enrichment of manganese ions,and thus the main challenge and the development are involved for the Fe-Mn alloys to achieve a balance among biocompatibility,structure,and degradation rate.Also the perspectives are proposed for Fe-Mn alloys as orthopedic implants.展开更多
Perinatal exposure to infection/inflammation is highly associated with neural injury,and subsequent impaired cortical growth,disturbances in neuronal connectivity,and impaired neurodevelopment.However,our understandin...Perinatal exposure to infection/inflammation is highly associated with neural injury,and subsequent impaired cortical growth,disturbances in neuronal connectivity,and impaired neurodevelopment.However,our understanding of the pathophysiological substrate underpinning these changes in brain structure and function is limited.The objective of this review is to summarize the growing evidence from animal trials and human cohort studies that suggest exposure to infection/inflammation during the perinatal period promotes regional impairments in neuronal maturation and function,including loss of high-frequency electroencephalographic activity,and reduced growth and arborization of cortical dendrites and dendritic spines resulting in reduced cortical volume.These inflammation-induced disturbances to neuronal structure and function are likely to underpin subsequent disturbances to cortical development and connectivity in fetuses and/or newborns exposed to infection/inflammation during the perinatal period,leading,in the long term,to impaired neurodevelopment.The combined use of early electroencephalography monitoring with neuroimaging techniques that enable detailed evaluation of brain microstructure,and the use of therapeutics that successfully target systemic and central nervous system inflammation could provide an effective strategy for early detection and therapeutic intervention.展开更多
Purpose:Ankle proprioception deficits have been widely reported in patients with chronic ankle instability(CAI),but their central neuropathological mechanisms have not been fully discussed.So,we aimed to figure out wh...Purpose:Ankle proprioception deficits have been widely reported in patients with chronic ankle instability(CAI),but their central neuropathological mechanisms have not been fully discussed.So,we aimed to figure out whether the structural and functional features of the cerebellar vermis differed between patients with CAI and healthy controls,and are associated with proprioception deficits in patients.Methods:Twenty-two patients and 25 control individuals were enrolled in a cross-sectional investigation.All participants underwent structural and resting-state functional magnetic resonance imaging scanning to calculate voxel-based morphometry(VBM)and fractional amplitude of low-frequency fluctuation(fALFF)of the vermis.Between-group comparisons of the ankle instability-related subregions of the vermis were performed.Correlation analyses were performed between the outcomes of the surviving subregions and the proprioceptive scores of the ankle inversion discrimination apparatus for landing test.Results:The subregion of vermis Ⅳ/Ⅴ survived the multiple comparison correction to reveal a lower VBM value in patients than in healthy controls(Cohen's d=-0.968).The patients also showed significantly higher fALFF(Cohen's d=0.666)in this subregion.After controlling the demographic features,the proprioceptive scores were significantly correlated with VBM(r=0.622)and fALFF values(r=-0.512)in the group of patients.Conclusions:Patients with CAI have lower gray matter volume and higher activity intensity in the cerebellar vermis than healthy control.The more severe proprioception deficits were significantly associated with the vermal volume and activity,which might be able to facilitate future diagnoses and treatments for CAI.展开更多
This study explores the nonlinear resonance of a rotating solar sail membrane exposed to time-varying solar thermal and solar radiation pressure.The sail membrane is modeled using a cantilever membrane,applying the vo...This study explores the nonlinear resonance of a rotating solar sail membrane exposed to time-varying solar thermal and solar radiation pressure.The sail membrane is modeled using a cantilever membrane,applying the von Kármán theory for membrane large deflection.The membrane’s nonlinear equation is derived by employing the Lagrange equation while accounting for excitations from solar thermal and radiation pressure.The equation is solved via the Rayleigh-Ritz method.The bifurcation diagram of membrane motion is applied to reveal membrane resonance responses under different solar sail rotating frequencies.The displacement time history,phase portrait,Poincarémap,frequency spectrum,and the largest Lyapunov exponent are used to study nonlinear vibrations that occur near resonance regions.The results indicate that time-varying thermal loading excites membrane motions with multiple natural frequencies by the parametric resonance mechanics,leading to the onset of membrane chaotic motion.The membrane’s primary resonance is stimulated in harmonic oscillation by the time-varying radiation pressure.The divergence instability caused by thermal excitation is also illustrated by comparing the membrane’s vibration amplitude with and without thermal excitation.The membrane’s nonlinear vibration characteristics vary significantly with solar illumination angles,the membrane’s thermal expansion coefficients,and structural damping.展开更多
Local resonant acoustic metamaterials have broad applications in sound insulation,yet their single-configuration designs often exhibit limited and discontinuous bandgap widths,hindering full-frequency noise attenuatio...Local resonant acoustic metamaterials have broad applications in sound insulation,yet their single-configuration designs often exhibit limited and discontinuous bandgap widths,hindering full-frequency noise attenuation across the human auditory range.This study presents a double-phase fidget-spinner-shaped acoustic metamaterial(DFAM),specifically designed to achieve an ultra-broad,low-frequency continuous bandgap by means of synergistic structural optimization,enabling effective and robust control of audible noise.Based on Bloch's theorem and the finite element method,the dispersion relation of the DFAM structure is calculated and verified by the transmission loss curves.The propagation characteristics of sound waves within the structure are further analyzed for noise frequencies that fall within the passband.The influence of the geometric and physical parameters on the bandgap is investigated,and the corresponding transmission loss in the propagation direction is further calculated.A hybrid collaborative design strategy,leveraging multi-parameter optimization and bandgap complementarity,is developed to construct a metastructure with continuous bandgap coverage from 20 Hz to 1000 Hz.The resulting metastructure demonstrates exceptional broadband noise attenuation,achieving a total bandgap width of 876.3 Hz(87.63% of the target range)with the transmission loss up to-762.78 d B in a three-periodic arrangement.The simulation and experimental results for the transmission loss of the DFAM metastructure show strong agreement in the low-frequency range.This work provides a novel framework for designing ultra-wide low-frequency continuous bandgap metastructures,offering significant potential for noise mitigation in complex environments.展开更多
In this paper,a theoretical model is established for locally resonant plates with general resonators,and the corresponding governing equation is derived.The model provides a mathematical demonstration of the locally r...In this paper,a theoretical model is established for locally resonant plates with general resonators,and the corresponding governing equation is derived.The model provides a mathematical demonstration of the locally resonant effect,which contains two parts:the first part is induced by translation coupling,and the second part is induced by rotation coupling.The second part cannot be reflected by most existing theoretical models.The analytical solutions of the dynamic response are compared with the direct numerical simulation(DNS)results for two locally resonant plates with different resonator types,thereby validating the general applicability of the present model.The rotation coupling effect leads to the frequency-dependent effective rotational inertia density and anisotropic dispersion relation of the locally resonant plate,as well as the enhancement of the structural vibration suppression ability.展开更多
Background:Sarcomatoid carcinoma of the ureter(SCU)is a highly aggressive and relatively uncommon malignant tumor of the urinary tract.Its frequency is quite low,and its prognosis is very bad when compared to other ca...Background:Sarcomatoid carcinoma of the ureter(SCU)is a highly aggressive and relatively uncommon malignant tumor of the urinary tract.Its frequency is quite low,and its prognosis is very bad when compared to other cancers of the urinary system.SCU clinical reports are still hard to come by.MRI and PEI/CT imaging of ureteral sarcomatoid cancer is presented in this case to promote diagnostic awareness and comprehension of the imaging characteristics of this uncommon illness.Method:The patient had ureteral sarcomatoid cancer,which was verified by pathological investigation after ureteroscopic biopsy.The patient’s clinical information,imaging results,surgical outcomes,and pathological findings were gathered.A retrospective study was carried out in combinationwith pertinent national and international literature.Results:An 84-year-old female patient was admitted for“left flank discomfort lasting over one month.”MRI revealed an irregular soft tissue mass in the middle-lower segment of the left ureter.T2-weighted imaging showed an unevenly slightly hyperintense signal.Diffusion-weighted imaging demonstrated restricted diffusion.Contrastenhanced imaging exhibited heterogeneous enhancement.PET/CT demonstrated significantly increased fluorodeoxyglucose metabolism in the mass with secondary left upper urinary tract obstruction.Concurrent findings included a solitary metastatic lesion in hepatic segment S6 and multiple lymph node metastases along the left common iliac and external iliac arteries.Preoperative diagnosis suggested a malignant tumor of the ureter.The patient underwent left nephroureteroscopy with biopsy,and the postoperative pathological diagnosis was ureteral sarcomatoid carcinoma.Conclusion:Ureteral sarcomatoid carcinoma is a rare,highly malignant,and aggressive tumor with nonspecific imaging features,typically presenting as an invasively growing mass.Diagnosis relies on postoperative pathology and immunohistochemical examination.MRI and PET/CT scans are valuable for preoperative localization and characterization,tumor staging,treatment planning,and postoperative follow-up.The prognosis is extremely negative.The main treatment option is radical surgery,although constant monitoring is necessary since early recurrence and metastases are frequent after surgery.展开更多
Energy-regenerative suspension combined with piezoelectric and electromagnetic transduction has evolved into a core technological pathway in advancing automotive design paradigms.With the aim of improving energy harve...Energy-regenerative suspension combined with piezoelectric and electromagnetic transduction has evolved into a core technological pathway in advancing automotive design paradigms.With the aim of improving energy harvesting performance,time-delayed feedback control is widely used in an energy-regenerative suspension system under different external disturbances in this paper.Meanwhile,limited research has addressed the stochastic dynamics of time-delayed nonlinear energy-regenerative suspension systems.Different from previous studies,this work studies the stochastic response and P-bifurcation of the nonlinear energy-regenerative suspension system with time-delayed feedback control.Firstly,an approximately equivalent dimension reduction system is established by the variable transformation method,and then the stationary probability density function of amplitude is obtained by the stochastic averaging method.Secondly,the precision of the method used in this work is verified by comparing the numerical solutions with the analytical results.Finally,based on the stationary probability density function,the influence of system parameters on stochastic P-bifurcation and the mean output power is discussed.展开更多
AIM:To summarize publication trends in the field of strabismus over the past 30y and predict future research hotspots.METHODS:A total of 2915 English-language articles and reviews on strabismus,published between 1993 ...AIM:To summarize publication trends in the field of strabismus over the past 30y and predict future research hotspots.METHODS:A total of 2915 English-language articles and reviews on strabismus,published between 1993 and 2022,were retrieved from the Web of Science Core Collection.Bibliometric analyses were performed using VOSviewer and CiteSpace software to explore publication trends,as well as the contributions and collaborative networks of countries/regions,authors,institutions,and journals.RESULTS:The annual number of publications on strabismus showed a consistent upward trend.The United States(USA)maintained a leading position in this research field while Republic of Korea and China emerged as rapidly advancing contributors over the last decade.The University of California,Los Angeles ranked as the most productive institution,and Jonathan M.Holmes from USA was the most productive author.Journal of AAPOS was the leading journal with the most strabismus publications,whereas the two most highly cited articles were both published in Ophthalmology.Co-occurrence analysis identified pivotal keywords and burst terms,including intermittent exotropia(IXT),acute acquired comitant esotropia(AACE),functional magnetic resonance imaging(fMRI),and surgical treatment,which were confirmed as predominant and frontier topics.CONCLUSION:This study provides a comprehensive bibliometric analysis of strabismus research,revealing the evolution of research hotspots over the past 30y and outlining several cutting-edge directions for future investigation.展开更多
In a rapid cycling synchrotron(RCS),the magnetic field is synchronized with the beam energy,creating a highly dynamic magnetic environment.A ceramic chamber with a shielding layer(RF shield),composed of a series of co...In a rapid cycling synchrotron(RCS),the magnetic field is synchronized with the beam energy,creating a highly dynamic magnetic environment.A ceramic chamber with a shielding layer(RF shield),composed of a series of copper strips connected to a capacitor at either end,is typically employed as a vacuum chamber to mitigate eddy current effects and beam coupling impedance.Consequently,the ceramic chamber exhibits a thin-walled multilayered complex structure.Previous theoretical studies have suggested that the impedance of such a structure has a negligible impact on the beam.However,recent impedance measurements of the ceramic chamber in the China Spallation Neutron Source(CSNS)RCS revealed a resonance in the low-frequency range,which was confirmed by further theoretical analysis as a source of beam instability in the RCS.Currently,the magnitude of this impedance cannot be accurately assessed using theoretical calculations.In this study,we used the CST Microwave Studio to confirm the impedance of the ceramic chamber.Further simulations covering six different types of ceramic chambers were conducted to develop an impedance model in the RCS.Additionally,this study investigates the resonant characteristics of the ceramic chamber impedance,finding that the resonant frequency is closely related to the capacitance of the capacitors.This finding provides clear directions for further impedance optimization and is crucial for achieving a beam power of 500 kW for the CSNS Phase-Ⅱ project(CSNS-Ⅱ).However,careful attention must be paid to the voltage across the capacitors.展开更多
The development of collinear resonance ionization spectroscopy for studying the nuclear structure of nickel isotopes far from the stability line relies on high-efficiency two-color two-step photoionization pathways.We...The development of collinear resonance ionization spectroscopy for studying the nuclear structure of nickel isotopes far from the stability line relies on high-efficiency two-color two-step photoionization pathways.We systematically investigated the even-parity autoionization spectrum of atomic nickel through resonance ionization mass spectrometry(RIMS).Fifteen intense single-color photoionization lines and corresponding transitions in the 300-325 nm range were identified and excluded as potential interference peaks for subsequent two-color studies.Fifty-one even-parity autoionization states in the 64000-66800 cm^(-1)range were identified for the first time by scanning from five intermediate excited states of the3d^(8)(^(3)F)4s4p(^(3)P^(o))configuration.Forty-eight of these states were assigned unique total angular momentum quantum numbers(J)based on electric dipole transition selection rules.The autoionization state at 64437.77 cm^(-1)was identified as an optimal final state for enhancing photoionization efficiency in two-color two-step pathways.This study provides comprehensive datasets of even-parity autoionization states of nickel,supporting both the advancement of collinear resonance ionization spectroscopy for exotic nickel isotopes and theoretical modeling of autoionization states.The datasets are openly available at https://doi.org/10.57760/sciencedb.j00113.00280.展开更多
This study investigated the effects of periodic high-frequency stress disturbances on the creep behavior of sandstone and analyzed the microstructural changes using nuclear magnetic resonance(NMR)technology.High-frequ...This study investigated the effects of periodic high-frequency stress disturbances on the creep behavior of sandstone and analyzed the microstructural changes using nuclear magnetic resonance(NMR)technology.High-frequency disturbance creep experiments were conducted on sandstone under different disturbance frequencies,disturbance cycles and loading stresses,and the following findings were obtained.Firstly,with the increase of loading stress and disturbance cycles,the total porosity increments,and damage value of sandstone increase,while the fractal dimension of sandstone pore structure presents the opposite trend.Secondly,during the disturbance creep process,the volumes of all three types of pores increase,but the proportion of micropores(T_(2)<10 ms)decreases,while the proportion of mesopores(10 ms<T_(2)<100 ms)and macropores(T_(2)>100 ms)increases.Thirdly,the fractal dimension difference has a good linear relationship with the damage,strain and porosity increment of sandstone during the disturbance creep process.Finally,the higher the disturbance frequency,the smaller the creep strain and creep strain rate during the steady-state creep stage.The study offers valuable theoretical insights for understanding rock creep behavior in complex stress environments.展开更多
This study investigates the frequency-temperature behaviors in AT-cut quartz crystal resonators(QCRs).First,the dispersion relations of an infinite quartz plate are obtained through a semi-analytical finite element(SA...This study investigates the frequency-temperature behaviors in AT-cut quartz crystal resonators(QCRs).First,the dispersion relations of an infinite quartz plate are obtained through a semi-analytical finite element(SAFE)analysis,which explicitly reveals the intrinsic frequency-temperature dependence of different vibration modes.Subsequently,we address practical resonator configurations by examining finite quartz plates,where numerical simulations uncover critical interactions between the operational thickness-shear(TS)mode and coupling modes,i.e.,the flexure(F),face-shear(FS),and extension(E)modes.Through the frequency spectra analysis,we demonstrate that both the plate aspect ratio and thermal variations affect mode-coupling behaviors.Unstable frequency-temperature variations(activity dips)are observed at critical resonator dimensions.Validation through the free-vibration eigen-frequency analysis and forced-vibration admittance characterization confirms the stable or unstable states predicted by the frequency spectra.The established framework not only reveals the origin of temperatureinduced activity dips but also provides the crucial design criteria for suppressing the mode-coupling interference in high-stability resonators.展开更多
The complex chaotic behavior of a quasi-zero-stiffness(QZS)double-winged system with symmetric impact boundaries is investigated with Melnikov functions and numerical simulations.The analysis reveals the coexistence o...The complex chaotic behavior of a quasi-zero-stiffness(QZS)double-winged system with symmetric impact boundaries is investigated with Melnikov functions and numerical simulations.The analysis reveals the coexistence of multiple attractors.As a key mass parameter varies,the mechanism underlying degenerate singular closed orbits is elucidated,based upon which five distinct types of singular closed orbits are discovered,exhibiting both smooth and discontinuous(SD)characteristics.The chaotic threshold of each singular orbit is obtained by Melnikov functions and verified by numerical simulations.The numerical results further demonstrate the coexistence of SD motions.For zero damping systems,the Kolmogorov-Arnold-Moser(KAM)structures are exhibited to present the complex quasi-periodic and resonant behavior coexisting with chaotic and periodic motions.These findings advance the understanding of chaotic dynamics in nonsmooth multi-well impact systems.展开更多
This study explores theoretical insights and experimental results on monitoring load-carrying capacity degradation in bridge spans through frequency analysis.Experiments were conducted on real bridge structures,includ...This study explores theoretical insights and experimental results on monitoring load-carrying capacity degradation in bridge spans through frequency analysis.Experiments were conducted on real bridge structures,including the Binh Thuan Bridge,focusing on analyzing the power spectral density(PSD)of vibration signals under random traffic loads.Detailed digital models of various bridge spans with different structural designs and construction periods were developed to ensure diversity.The study utilized PSD to analyze the vibration signals from the bridge spans under various loading conditions,identifying the vibration frequencies and the corresponding response regions.The research correlated the observed frequency changes of PSD with the actual deterioration of the bridges over time,identifying patterns that indicate a reduction in stiffness.Experiments demonstrated that frequency changes,particularly in high-frequency regions,are directly related to a reduction in the stiffness of bridge spans.This supports the hypothesis that natural frequencies can serve as effective indicators of structural damage.Furthermore,the emergence and shift of resonant frequency regions provide valuable insights into the extent of damage in actual bridge spans,highlighting the potential for using changes in resonant frequency regions as a new tool for structural damage detection.展开更多
文摘Wind-driven power harvestings attract attentions since their target wind speeds are quite low less than the so-called cut-in wind speed, which is generally recognized as around 3 m/s. The extant power harvestings driven by wind-induced-air-column-resonations (i.e. acoustic-pressures) are still lacking simplicity, scale flexibility and solid strategies for practical applications. Therefore, the piezoelectric power harvesters via acoustic-pressures driven by low-speedwind-forces with resonating-tubes and wind-collectors were invented so as to complement all the lacks. The wind-collector as well as the resonating-tube contributed to upraise the power harvesting density. The champion power harvesting density of 19.5 nW/dm2 could be procured at 2.3 m/s of an artificial wind and the optimal resonating-tube and wind-collector. Power harvesting proofs from the natural wind with low mean speeds down to about 0.6 m/s were successfully obtained. The cut-in wind speed of the prototype piezoelectric power harvester was found to be quite low as about 0.4 m/s, signifying its ubiquity. Finally, a multi-bundle pendant-type piezoelectric power harvester was specifically presented together with professing the solid and multiple strategies for practical applications.
文摘We review the predictions of quark models for multiquark configurations that are bound or resonant states,and compare different methods for estimating the properties of resonances.
基金supported by the National Natural Science Foundation of China(Grant Nos.62105061,12374301,and 62225404)the Jiangsu Provincial Frontier Technology Research and Development Program(Grant No.BF2024070)+1 种基金the National Key R&D Program of China(Grant No.2024YFA1210500)the Key Lab of Modern Optical Technologies of Education,Ministry of China,Soochow University。
文摘Unlocking the full potential of integrated photonics requires versatile,multi-functional devices that can adapt to diverse application demands.However,confronting this challenge with conventional singlefunction resonators often results in cumbersome system designs.We present an elegant solution:a versatile and reconfigurable dual-polarization Si_(3)N_(4)microresonator that represents a new perspective in on-chip photonic designs.Our device can be dynamically reconfigured into three distinct topologies:a Möbius-like microcavity,a Fabry-Pérot resonator,and a microring resonator.This unprecedented functionality is enabled by a tunable balanced Mach-Zehnder interferometer that facilitates controllable mutual mode coupling of counterpropagating light using a single control knob.We experimentally demonstrate that the device not only supports polarization-diverse operation on a compact footprint but also gives rise to a wide variety of physical phenomena,including a standing wave cavity,a traveling wave cavity,free spectral range multiplication,and the photonic pinning effect.These behaviors are accurately modeled using the transfer matrix method and intuitively explained by the temporal coupled-mode theory.Our results underscore the potential for a chip-scale platform to realize reconfigurable reconstructive spectrometers and on-chip synthetic dimensions for topological physics.
文摘BACKGROUND Many conditions may affect left ventricular(LV)phenotypes which have been classified according to LV mass and geometry.There is limited data on the prognostic value of LV phenotypes classified by cardiac magnetic resonance(CMR).This study aimed to determine the prognostic value of LV phenotypes in elderly and non-elderly patients with known or suspected coronary artery disease.METHODS This is a retrospective cohort study among patients who underwent stress or viability CMR.LV phenotypes were classified according to the LV mass index,the LV end-diastolic volume index and the LV mass/volume ratio,into normal,concentric remodeling,concentric hypertrophy,and eccentric hypertrophy.The primary outcome was a composite of death or heart failure.RESULTS A total of 3289 patients was studied.The average age was 68.0±12.7 years,52.2%of patients were women.Elderly were defined as age≥65 years accounting for 63.9%of the cohort.LV phenotypes were normal,concentric remodeling,concentric hypertrophy,and eccentric hypertrophy at 74.5%,5.8%,9.2%,and 10.5%,respectively.The median duration of follow-up was 41.4 months.The composite outcome of death or heart failure occurred in 7.3%of patients.The prognostic impact of LV phenotypes was more pronounced in the elderly,with eccentric hypertrophy showing the worst prognosis,followed by concentric hypertrophy and concentric remodeling with the adjusted hazard ratio(95%CI)of 2.37(1.72–3.25),1.53(1.12–2.08),and 1.14(0.76–1.71),respectively,compared to normal phenotype.Patients with eccentric hypertrophy also demonstrated abnormal global longitudinal LV strain,left atrial strain,and extracellular volume fraction.CONCLUSIONS LV phenotypes by CMR independently predict adverse clinical outcomes in elderly patients with known or suspected coronary artery disease.In non-elderly patients,the prognostic value of LV phenotypes was less evident.Assessment of LV phenotypes may be useful for risk stratification.
基金supported by the National Natural Science Foundation of China(No.12072139).
文摘The output voltages for the capacitive elements of a neural circuit model can be mapped into dimensionless capacitive variables,which present firing patterns similar to the membrane potentials detected in biological neurons.The inclusion of a memcapacitor also en‐ables consideration of membrane deformation effects,enhancing the model’s capacity to simulate neuronal behavior across varying physio‐logical and environmental conditions.In this study,a capacitor and a memcapacitor are connected through a linear resistor in parallel with other electric components in different branch circuits composed of an inductor and a nonlinear resistor.The electrical activities in a neuron with a double-layer membrane and two capacitive variables are discussed in detail after converting the nonlinear equations for the neural circuit into a theoretical neuron model.A dimensionless neuron model and its corresponding energy function are derived.The field energy function for the neural circuit is converted into an equivalent Hamilton energy function and further validated via the Helmholtz theorem.Furthermore,the average value of energy serves as an indicator for predicting stochastic resonance,as supported by analyzing the distribu‐tion of the coefficient of variation.The neuronal firing patterns are shown to be energy-dependent.An adaptive control strategy is proposed to regulate mode transitions in electrical activities of the neuron.An analog equivalent circuit is constructed to experimentally verify the nu‐merical results,thereby supporting the reliability of the proposed neuron model.
基金financially supported by the Shandong Province Natural Science Foundation(No.ZR2023ME181)the National Natural Science Foundation of China(No.52305313)the Natural Science Foundation of Hunan Province(Nos.2023JJ40553 and 2023JJ60433)。
文摘Biodegradable metals(BMs)have shown significant potential for applications in the field of orthopedic implants.These materials gradually degrade after implantation,eventually disappear without residue,provide necessary mechanical support during degradation,and closely integrate with bone tissues.Fe-based BMs are particularly notable for their good mechanical properties and biocompatibility.However,their slow degradation rate is a limitation.The emergence of Mn-incorporated Fe-based alloys(Fe-Mn alloys)offers the possibilities for addressing issues of slow degradation rate and incompatibility of magnetic resonance imaging(MRI)for Fe alloys.This review summarizes the advantages of Fe-Mn alloys as orthopedic implants,and the cutting-edge advances in degradation,mechanical and magnetic properties,and osteogenic performance.The cytotoxicity issue is addressed for the porous structured Fe-Mn alloys caused by the enrichment of manganese ions,and thus the main challenge and the development are involved for the Fe-Mn alloys to achieve a balance among biocompatibility,structure,and degradation rate.Also the perspectives are proposed for Fe-Mn alloys as orthopedic implants.
基金supported by National Health and Medical Research Council of Australia(APP1090890 and APP1164954)Cerebral Palsy Alliance(ERG02123)the Victorian Government’s Operational Infrastructure Support Program。
文摘Perinatal exposure to infection/inflammation is highly associated with neural injury,and subsequent impaired cortical growth,disturbances in neuronal connectivity,and impaired neurodevelopment.However,our understanding of the pathophysiological substrate underpinning these changes in brain structure and function is limited.The objective of this review is to summarize the growing evidence from animal trials and human cohort studies that suggest exposure to infection/inflammation during the perinatal period promotes regional impairments in neuronal maturation and function,including loss of high-frequency electroencephalographic activity,and reduced growth and arborization of cortical dendrites and dendritic spines resulting in reduced cortical volume.These inflammation-induced disturbances to neuronal structure and function are likely to underpin subsequent disturbances to cortical development and connectivity in fetuses and/or newborns exposed to infection/inflammation during the perinatal period,leading,in the long term,to impaired neurodevelopment.The combined use of early electroencephalography monitoring with neuroimaging techniques that enable detailed evaluation of brain microstructure,and the use of therapeutics that successfully target systemic and central nervous system inflammation could provide an effective strategy for early detection and therapeutic intervention.
基金supported by the National Natural Science Foundation of China[grant numbers 82372492,82072510]National Key R&D Program of China[grant numbers 2018YFC1312900]+1 种基金Shanghai Natural Science Foundation[grant numbers 20ZR1406400]Science and Technology Commission of Shanghai Municipality[grant numbers 22dz1204700].
文摘Purpose:Ankle proprioception deficits have been widely reported in patients with chronic ankle instability(CAI),but their central neuropathological mechanisms have not been fully discussed.So,we aimed to figure out whether the structural and functional features of the cerebellar vermis differed between patients with CAI and healthy controls,and are associated with proprioception deficits in patients.Methods:Twenty-two patients and 25 control individuals were enrolled in a cross-sectional investigation.All participants underwent structural and resting-state functional magnetic resonance imaging scanning to calculate voxel-based morphometry(VBM)and fractional amplitude of low-frequency fluctuation(fALFF)of the vermis.Between-group comparisons of the ankle instability-related subregions of the vermis were performed.Correlation analyses were performed between the outcomes of the surviving subregions and the proprioceptive scores of the ankle inversion discrimination apparatus for landing test.Results:The subregion of vermis Ⅳ/Ⅴ survived the multiple comparison correction to reveal a lower VBM value in patients than in healthy controls(Cohen's d=-0.968).The patients also showed significantly higher fALFF(Cohen's d=0.666)in this subregion.After controlling the demographic features,the proprioceptive scores were significantly correlated with VBM(r=0.622)and fALFF values(r=-0.512)in the group of patients.Conclusions:Patients with CAI have lower gray matter volume and higher activity intensity in the cerebellar vermis than healthy control.The more severe proprioception deficits were significantly associated with the vermal volume and activity,which might be able to facilitate future diagnoses and treatments for CAI.
基金supported by the Science Fund of NPU-Duke China Seeds Program(Grant No.119003067)the CAST-BISEE Fund(Grant No.MC010175)+1 种基金the Project of National Natural Science Foundation of China(Grant No.12372233)the“111”project of China(Grant No.B17037).
文摘This study explores the nonlinear resonance of a rotating solar sail membrane exposed to time-varying solar thermal and solar radiation pressure.The sail membrane is modeled using a cantilever membrane,applying the von Kármán theory for membrane large deflection.The membrane’s nonlinear equation is derived by employing the Lagrange equation while accounting for excitations from solar thermal and radiation pressure.The equation is solved via the Rayleigh-Ritz method.The bifurcation diagram of membrane motion is applied to reveal membrane resonance responses under different solar sail rotating frequencies.The displacement time history,phase portrait,Poincarémap,frequency spectrum,and the largest Lyapunov exponent are used to study nonlinear vibrations that occur near resonance regions.The results indicate that time-varying thermal loading excites membrane motions with multiple natural frequencies by the parametric resonance mechanics,leading to the onset of membrane chaotic motion.The membrane’s primary resonance is stimulated in harmonic oscillation by the time-varying radiation pressure.The divergence instability caused by thermal excitation is also illustrated by comparing the membrane’s vibration amplitude with and without thermal excitation.The membrane’s nonlinear vibration characteristics vary significantly with solar illumination angles,the membrane’s thermal expansion coefficients,and structural damping.
基金Project supported by the National Natural Science Foundation of China(No.12572020)the Key Project of Natural Science Foundation of Hebei Province of China(No.A2023210064)。
文摘Local resonant acoustic metamaterials have broad applications in sound insulation,yet their single-configuration designs often exhibit limited and discontinuous bandgap widths,hindering full-frequency noise attenuation across the human auditory range.This study presents a double-phase fidget-spinner-shaped acoustic metamaterial(DFAM),specifically designed to achieve an ultra-broad,low-frequency continuous bandgap by means of synergistic structural optimization,enabling effective and robust control of audible noise.Based on Bloch's theorem and the finite element method,the dispersion relation of the DFAM structure is calculated and verified by the transmission loss curves.The propagation characteristics of sound waves within the structure are further analyzed for noise frequencies that fall within the passband.The influence of the geometric and physical parameters on the bandgap is investigated,and the corresponding transmission loss in the propagation direction is further calculated.A hybrid collaborative design strategy,leveraging multi-parameter optimization and bandgap complementarity,is developed to construct a metastructure with continuous bandgap coverage from 20 Hz to 1000 Hz.The resulting metastructure demonstrates exceptional broadband noise attenuation,achieving a total bandgap width of 876.3 Hz(87.63% of the target range)with the transmission loss up to-762.78 d B in a three-periodic arrangement.The simulation and experimental results for the transmission loss of the DFAM metastructure show strong agreement in the low-frequency range.This work provides a novel framework for designing ultra-wide low-frequency continuous bandgap metastructures,offering significant potential for noise mitigation in complex environments.
基金Project supported by the National Natural Science Foundation of China(No.12472062)。
文摘In this paper,a theoretical model is established for locally resonant plates with general resonators,and the corresponding governing equation is derived.The model provides a mathematical demonstration of the locally resonant effect,which contains two parts:the first part is induced by translation coupling,and the second part is induced by rotation coupling.The second part cannot be reflected by most existing theoretical models.The analytical solutions of the dynamic response are compared with the direct numerical simulation(DNS)results for two locally resonant plates with different resonator types,thereby validating the general applicability of the present model.The rotation coupling effect leads to the frequency-dependent effective rotational inertia density and anisotropic dispersion relation of the locally resonant plate,as well as the enhancement of the structural vibration suppression ability.
文摘Background:Sarcomatoid carcinoma of the ureter(SCU)is a highly aggressive and relatively uncommon malignant tumor of the urinary tract.Its frequency is quite low,and its prognosis is very bad when compared to other cancers of the urinary system.SCU clinical reports are still hard to come by.MRI and PEI/CT imaging of ureteral sarcomatoid cancer is presented in this case to promote diagnostic awareness and comprehension of the imaging characteristics of this uncommon illness.Method:The patient had ureteral sarcomatoid cancer,which was verified by pathological investigation after ureteroscopic biopsy.The patient’s clinical information,imaging results,surgical outcomes,and pathological findings were gathered.A retrospective study was carried out in combinationwith pertinent national and international literature.Results:An 84-year-old female patient was admitted for“left flank discomfort lasting over one month.”MRI revealed an irregular soft tissue mass in the middle-lower segment of the left ureter.T2-weighted imaging showed an unevenly slightly hyperintense signal.Diffusion-weighted imaging demonstrated restricted diffusion.Contrastenhanced imaging exhibited heterogeneous enhancement.PET/CT demonstrated significantly increased fluorodeoxyglucose metabolism in the mass with secondary left upper urinary tract obstruction.Concurrent findings included a solitary metastatic lesion in hepatic segment S6 and multiple lymph node metastases along the left common iliac and external iliac arteries.Preoperative diagnosis suggested a malignant tumor of the ureter.The patient underwent left nephroureteroscopy with biopsy,and the postoperative pathological diagnosis was ureteral sarcomatoid carcinoma.Conclusion:Ureteral sarcomatoid carcinoma is a rare,highly malignant,and aggressive tumor with nonspecific imaging features,typically presenting as an invasively growing mass.Diagnosis relies on postoperative pathology and immunohistochemical examination.MRI and PET/CT scans are valuable for preoperative localization and characterization,tumor staging,treatment planning,and postoperative follow-up.The prognosis is extremely negative.The main treatment option is radical surgery,although constant monitoring is necessary since early recurrence and metastases are frequent after surgery.
基金Project supported by the National Natural Science Foundation of China(Grant No.12002089)the Science and Technology Projects in Guangzhou(Grant No.2023A04J1323)UKRI Horizon Europe Guarantee(Marie SklodowskaCurie Fellowship)(Grant No.EP/Y016130/1)。
文摘Energy-regenerative suspension combined with piezoelectric and electromagnetic transduction has evolved into a core technological pathway in advancing automotive design paradigms.With the aim of improving energy harvesting performance,time-delayed feedback control is widely used in an energy-regenerative suspension system under different external disturbances in this paper.Meanwhile,limited research has addressed the stochastic dynamics of time-delayed nonlinear energy-regenerative suspension systems.Different from previous studies,this work studies the stochastic response and P-bifurcation of the nonlinear energy-regenerative suspension system with time-delayed feedback control.Firstly,an approximately equivalent dimension reduction system is established by the variable transformation method,and then the stationary probability density function of amplitude is obtained by the stochastic averaging method.Secondly,the precision of the method used in this work is verified by comparing the numerical solutions with the analytical results.Finally,based on the stationary probability density function,the influence of system parameters on stochastic P-bifurcation and the mean output power is discussed.
基金Supported by National Natural Science Foundation of China(No.82020108006,No.81730025).
文摘AIM:To summarize publication trends in the field of strabismus over the past 30y and predict future research hotspots.METHODS:A total of 2915 English-language articles and reviews on strabismus,published between 1993 and 2022,were retrieved from the Web of Science Core Collection.Bibliometric analyses were performed using VOSviewer and CiteSpace software to explore publication trends,as well as the contributions and collaborative networks of countries/regions,authors,institutions,and journals.RESULTS:The annual number of publications on strabismus showed a consistent upward trend.The United States(USA)maintained a leading position in this research field while Republic of Korea and China emerged as rapidly advancing contributors over the last decade.The University of California,Los Angeles ranked as the most productive institution,and Jonathan M.Holmes from USA was the most productive author.Journal of AAPOS was the leading journal with the most strabismus publications,whereas the two most highly cited articles were both published in Ophthalmology.Co-occurrence analysis identified pivotal keywords and burst terms,including intermittent exotropia(IXT),acute acquired comitant esotropia(AACE),functional magnetic resonance imaging(fMRI),and surgical treatment,which were confirmed as predominant and frontier topics.CONCLUSION:This study provides a comprehensive bibliometric analysis of strabismus research,revealing the evolution of research hotspots over the past 30y and outlining several cutting-edge directions for future investigation.
基金supported by the Guangdong Basic and Applied Basic Research Foundation,China(No.2021B1515140007).
文摘In a rapid cycling synchrotron(RCS),the magnetic field is synchronized with the beam energy,creating a highly dynamic magnetic environment.A ceramic chamber with a shielding layer(RF shield),composed of a series of copper strips connected to a capacitor at either end,is typically employed as a vacuum chamber to mitigate eddy current effects and beam coupling impedance.Consequently,the ceramic chamber exhibits a thin-walled multilayered complex structure.Previous theoretical studies have suggested that the impedance of such a structure has a negligible impact on the beam.However,recent impedance measurements of the ceramic chamber in the China Spallation Neutron Source(CSNS)RCS revealed a resonance in the low-frequency range,which was confirmed by further theoretical analysis as a source of beam instability in the RCS.Currently,the magnitude of this impedance cannot be accurately assessed using theoretical calculations.In this study,we used the CST Microwave Studio to confirm the impedance of the ceramic chamber.Further simulations covering six different types of ceramic chambers were conducted to develop an impedance model in the RCS.Additionally,this study investigates the resonant characteristics of the ceramic chamber impedance,finding that the resonant frequency is closely related to the capacitance of the capacitors.This finding provides clear directions for further impedance optimization and is crucial for achieving a beam power of 500 kW for the CSNS Phase-Ⅱ project(CSNS-Ⅱ).However,careful attention must be paid to the voltage across the capacitors.
基金supported by the China National Nuclear Corporation Basic Research Project(Grant No.CNNC-JCYJ-202327)。
文摘The development of collinear resonance ionization spectroscopy for studying the nuclear structure of nickel isotopes far from the stability line relies on high-efficiency two-color two-step photoionization pathways.We systematically investigated the even-parity autoionization spectrum of atomic nickel through resonance ionization mass spectrometry(RIMS).Fifteen intense single-color photoionization lines and corresponding transitions in the 300-325 nm range were identified and excluded as potential interference peaks for subsequent two-color studies.Fifty-one even-parity autoionization states in the 64000-66800 cm^(-1)range were identified for the first time by scanning from five intermediate excited states of the3d^(8)(^(3)F)4s4p(^(3)P^(o))configuration.Forty-eight of these states were assigned unique total angular momentum quantum numbers(J)based on electric dipole transition selection rules.The autoionization state at 64437.77 cm^(-1)was identified as an optimal final state for enhancing photoionization efficiency in two-color two-step pathways.This study provides comprehensive datasets of even-parity autoionization states of nickel,supporting both the advancement of collinear resonance ionization spectroscopy for exotic nickel isotopes and theoretical modeling of autoionization states.The datasets are openly available at https://doi.org/10.57760/sciencedb.j00113.00280.
基金supported by National Natural Science Foundation of China(Grant No.52404074)the National Key Research and Development Program(Fund for Young Scientists)(Grant No.2021YFC2900400)Postdoctoral Science Foundation of China(Grant No.2024M761706).
文摘This study investigated the effects of periodic high-frequency stress disturbances on the creep behavior of sandstone and analyzed the microstructural changes using nuclear magnetic resonance(NMR)technology.High-frequency disturbance creep experiments were conducted on sandstone under different disturbance frequencies,disturbance cycles and loading stresses,and the following findings were obtained.Firstly,with the increase of loading stress and disturbance cycles,the total porosity increments,and damage value of sandstone increase,while the fractal dimension of sandstone pore structure presents the opposite trend.Secondly,during the disturbance creep process,the volumes of all three types of pores increase,but the proportion of micropores(T_(2)<10 ms)decreases,while the proportion of mesopores(10 ms<T_(2)<100 ms)and macropores(T_(2)>100 ms)increases.Thirdly,the fractal dimension difference has a good linear relationship with the damage,strain and porosity increment of sandstone during the disturbance creep process.Finally,the higher the disturbance frequency,the smaller the creep strain and creep strain rate during the steady-state creep stage.The study offers valuable theoretical insights for understanding rock creep behavior in complex stress environments.
基金Project supported by the National Key Research and Development Program of China(No.2023YFE0111000)the National Natural Science Foundation of China(Nos.12102183,12172171,and U24A2005)the Shenzhen Science and Technology Program of China(No.JCYJ20230807142004009)。
文摘This study investigates the frequency-temperature behaviors in AT-cut quartz crystal resonators(QCRs).First,the dispersion relations of an infinite quartz plate are obtained through a semi-analytical finite element(SAFE)analysis,which explicitly reveals the intrinsic frequency-temperature dependence of different vibration modes.Subsequently,we address practical resonator configurations by examining finite quartz plates,where numerical simulations uncover critical interactions between the operational thickness-shear(TS)mode and coupling modes,i.e.,the flexure(F),face-shear(FS),and extension(E)modes.Through the frequency spectra analysis,we demonstrate that both the plate aspect ratio and thermal variations affect mode-coupling behaviors.Unstable frequency-temperature variations(activity dips)are observed at critical resonator dimensions.Validation through the free-vibration eigen-frequency analysis and forced-vibration admittance characterization confirms the stable or unstable states predicted by the frequency spectra.The established framework not only reveals the origin of temperatureinduced activity dips but also provides the crucial design criteria for suppressing the mode-coupling interference in high-stability resonators.
基金Project supported by the National Natural Science Foundation of China(No.11732006)the China Scholarship Council。
文摘The complex chaotic behavior of a quasi-zero-stiffness(QZS)double-winged system with symmetric impact boundaries is investigated with Melnikov functions and numerical simulations.The analysis reveals the coexistence of multiple attractors.As a key mass parameter varies,the mechanism underlying degenerate singular closed orbits is elucidated,based upon which five distinct types of singular closed orbits are discovered,exhibiting both smooth and discontinuous(SD)characteristics.The chaotic threshold of each singular orbit is obtained by Melnikov functions and verified by numerical simulations.The numerical results further demonstrate the coexistence of SD motions.For zero damping systems,the Kolmogorov-Arnold-Moser(KAM)structures are exhibited to present the complex quasi-periodic and resonant behavior coexisting with chaotic and periodic motions.These findings advance the understanding of chaotic dynamics in nonsmooth multi-well impact systems.
文摘This study explores theoretical insights and experimental results on monitoring load-carrying capacity degradation in bridge spans through frequency analysis.Experiments were conducted on real bridge structures,including the Binh Thuan Bridge,focusing on analyzing the power spectral density(PSD)of vibration signals under random traffic loads.Detailed digital models of various bridge spans with different structural designs and construction periods were developed to ensure diversity.The study utilized PSD to analyze the vibration signals from the bridge spans under various loading conditions,identifying the vibration frequencies and the corresponding response regions.The research correlated the observed frequency changes of PSD with the actual deterioration of the bridges over time,identifying patterns that indicate a reduction in stiffness.Experiments demonstrated that frequency changes,particularly in high-frequency regions,are directly related to a reduction in the stiffness of bridge spans.This supports the hypothesis that natural frequencies can serve as effective indicators of structural damage.Furthermore,the emergence and shift of resonant frequency regions provide valuable insights into the extent of damage in actual bridge spans,highlighting the potential for using changes in resonant frequency regions as a new tool for structural damage detection.
