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
This work investigated the dynamic behavior of vertical pipes conveying gas-liquid two-phase flow when subjected to external excitations at both ends.Even with minimal excitation amplitude,resonance can occur when the...This work investigated the dynamic behavior of vertical pipes conveying gas-liquid two-phase flow when subjected to external excitations at both ends.Even with minimal excitation amplitude,resonance can occur when the excitation frequency aligns with the natural frequency of the pipe,significantly increasing the degree of operational risk.The governing equation of motion based on the Euler-Bernoulli beam is derived for the relative deflection with stationary simply supported ends,with the effects of the external excitations represented by source terms distributed along the pipe length.The fourth-order partial differential equation is solved via the generalized integral transform technique(GITT),with the solution successfully verified via comparison with results in the literature.A comprehensive analysis of the vibration phenomena and changes in the motion state of the pipe is conducted for three classes of external excitation conditions:same frequency and amplitude(SFSA),same frequency but different amplitudes(SFDA),and different frequencies and amplitudes(DFDA).The numerical results show that with increasing gas volume fraction,the position corresponding to the maximum vibration displacement shifts upward.Compared with conditions without external excitation,the vibration displacement of the pipe conveying two-phase flow under external excitation increases significantly.The frequency of external excitation has a significant effect on the dynamic behavior of a pipe conveying two-phase flow.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 paper presents a numerical investigation of nonlinear sloshing in a prismatic tank.A three-dimensional,twophase flow model based on Cartesian grid is developed to simulate the phenomenon.The model solves incompre...This paper presents a numerical investigation of nonlinear sloshing in a prismatic tank.A three-dimensional,twophase flow model based on Cartesian grid is developed to simulate the phenomenon.The model solves incompressible Navier-Stokes equations,utilizing the fractional step method for velocity-pressure decoupling.The finite difference method discretizes spatial derivatives,with specific schemes implemented to enhance model robustness.Model validation involves simulating benchmark cases,and comparing wave profiles and pressure results with published experimental data and numerical findings.The model demonstrates robustness and accuracy in simulating violent sloshing.The validated model examines sloshing in a partially filled prismatic tank under combined surge and roll excitations.The study employs eight frequencies encompassing the natural frequencies of tank roll and surge motions.Roll motion excitation is fixed at 2°,while surge motion considers three excitation amplitudes(0.0 m,0.01 m,and 0.02m).Analysis reveals the effects of surge amplitude and excitation frequency on wave patterns,amplitudes,and pressure peaks.Results indicate the presence of multi-component waves,including transverse,diagonal,and longitudinal waves.Furthermore,the findings demonstrate a reduction in the natural frequency for surge motion through pressure peak analysis.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
The low-energy excited states in the neutron-deficient nucleus^(91)Ru were populated via the^(58)Ni(^(36)Ar,2p1nγ)^(91)Ru reaction at a beam energy of 111 MeV.Charged particles,neutrons,andγrays were emitted in the ...The low-energy excited states in the neutron-deficient nucleus^(91)Ru were populated via the^(58)Ni(^(36)Ar,2p1nγ)^(91)Ru reaction at a beam energy of 111 MeV.Charged particles,neutrons,andγrays were emitted in the reactions and detected using a DIAMANT CsI ball,neutron wall,and EXOGAM Ge clover array,respectively.Angular-correlation and linear polarization measurements were performed to determine the spins and parities of the excited states unambiguously.In addition to the previously reported states,a new low-energy-level structure of^(91)Ru,including one 7/2^(+)and two 11/2^(+)states,was established.Similar structures have also been reported in lighter N=47 even-odd isotones down to85Sr,which were expected to come from the three-neutron-holevg_(9/2)^(-3)configuration.A semiempirical shell model was used to explain the level systematics of the N=47 even-odd isotones.Calculated results indicated that the 7/2^(+)and the vg_(9/2)^(-3)states~are mainly associated with the seniority-threeν(g_(9/2))-3excitations,while the vg_(9/2)^(-3)level is most likely interpreted as a seniorityυ=1 configuration of three neutron holes in theνg_(9∕2)orbital_weakly coupled to a 2^(+)excitation of the^(88)Sr core.A comparison between the calculation and experiment shows that the two 11/2^(+)excited states display an increase in mixing with proton number Z added from^(87)Zr up to^(91)Ru.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
The precise excitation of molecular vibrational states is critical for ad-vancing chemical dynamics,preci-sion spectroscopy,and trace gas sensing.This objective,however,is often hindered by the weak oscilla-tor streng...The precise excitation of molecular vibrational states is critical for ad-vancing chemical dynamics,preci-sion spectroscopy,and trace gas sensing.This objective,however,is often hindered by the weak oscilla-tor strengths of ro-vibrational tran-sitions,which render conventional continuous-wave(cw)lasers ineffec-tive due to their limited power.This fundamental challenge is overcome by cavity-enhanced excitation(CEE),a technique that locks a cw laser to a high-finesse optical cavity.This configuration amplifies the intra-cavity light intensity by several orders of magnitude while preserving a narrow spectral linewidth.The resulting synergy enables highly efficient,state-selective population transfer and high-resolution spectroscopy previously considered impractical.This review elucidates the core technique of laser-cavity locking and highlights its applications,notably in the quantitative detection of trace isotopes and the investigation of highly excited vibrational states with kilo-hertz-level accuracy.展开更多
Modern/distributed electric energy systems,with ever larger penetration of renewable(photovoltaic,wind,wave,and hydro)energy sources and time-variable outputs,are in need of stronger/higher frequency and alternating c...Modern/distributed electric energy systems,with ever larger penetration of renewable(photovoltaic,wind,wave,and hydro)energy sources and time-variable outputs,are in need of stronger/higher frequency and alternating current(AC)(direct current(DC))voltage control.In fact,faster and more stable active and reactive power in the presence of frequency and voltage sags and swells is needed.Power electronics-controlled variable speed generators do not have enough energy storage(inertia)for the scope(static synchronous compensators(STATCOMs)included).This is because power electronics tends to decouple the generator from the power system.While virtual inertia control in doubly fed induction generators(DFIGs)offers a partial solution to these problems,a more robust and comprehensive framework is required for advanced grid support.This is how,by extending the dual-excitation principles,the dualaxis excited electric synchronous generators(DE-SG)provide superior flexibility in two variants summarized here:as a multifunctional DFIG and dual-axis vs.single-axis excited synchronous generator(SG),and as a synchronous condenser(SC),with dual DC and AC excitation(as a no-load DFIG with inertia wheel),where variable speed is used to accelerate/decelerate the SC and thus provide additional assistance in frequency stabilization.These solutions,good for short-time transients,are not meant,however,to replace the large bidirectional energy storage systems(pump-hydro,hydrogen,batteries,etc.)which are crucial for the daily inherent variations of output energy in modern power systems with multiple power sources.The present paper offers a summary of techniques used in the dual-axis excited vs.single-axis excited SGs(SE-SGs),and SCs topologies,modeling,and control for better stability in modern multiple-source energy systems.This survey includes multiple case studies to shed light on prominent methods.展开更多
In this paper,electrically excited synchronous machines(EESMs)using copper(Cu)and aluminum(Al)windings are compared for the feasibility of replacing Cu windings with Al windings in electric vehicle(EV)applications sin...In this paper,electrically excited synchronous machines(EESMs)using copper(Cu)and aluminum(Al)windings are compared for the feasibility of replacing Cu windings with Al windings in electric vehicle(EV)applications since Al windings have lower mass density and cost per weight,but higher resistivity and lower thermal conductivity than Cu windings.The EESMs with four winding configurations are optimized with an electromagnetic-thermal co-optimization method.The optimized EESM with only Cu windings is considered as the baseline in this study.Results show that the EESM with stator-Cu/rotor-Al windings has the least torque reduction(12.1%)compared to the baseline among the three EESMs with Al windings and the highest torque mass density among all EESMs.Meanwhile,although the new European driving cycle efficiency of the stator-Cu/rotor-Al EESM is 1.8%lower than that of the baseline,the torque per cost is 71%higher,and the maximum rotor mechanical stress is 8%lower.Therefore,the EESMs with stator-Cu/rotor-Al windings are prospective substitutions of those with only Cu windings for EV applications considering the trade-off between performance and cost.展开更多
Asymmetric stators,featuring nonuniform pitches,have demonstrated effectiveness in mitigating the forced response of the adjacent compressor rotor blades.However,the lack of comprehensive understanding of their vibrat...Asymmetric stators,featuring nonuniform pitches,have demonstrated effectiveness in mitigating the forced response of the adjacent compressor rotor blades.However,the lack of comprehensive understanding of their vibration reduction mechanisms hinders the development of optimal designs.Typically,the evaluation of rotor blades forced response using asymmetric stators requires fluid–structure interaction methods and full-annulus computational domains;however,these methods are time-consuming and resource-intensive,making them unsuitable for rapid engineering applications.To address these issues,the present study first develops a Fourier-based prediction method for the excitation spectrum and blade forced response that considers the impacts of multiple excitation components.To verify the accuracy of the prediction method,two typical asymmetric stator configurations are selected,and the forced response analyses with single-passage computational domains are conducted on their downstream rotor blades based on the rapid time inclination method.The results are then compared with those obtained using the dual time stepping method with whole-annulus computational domains.The results indicate that the proposed Fourier-based method can accurately predict the impacts of asymmetric stators on the forced response of the rotor blades.Moreover,the rapid evaluation approach based on the time inclination method provides comparable accuracy to the dual time stepping method,but with greater computational efficiency and reduced memory consumption.展开更多
The concept of the brain cognitive reserve is derived from the well-acknowledged notion that the degree of brain damage does not always match the severity of clinical symptoms and neurological/cognitive outcomes.It ha...The concept of the brain cognitive reserve is derived from the well-acknowledged notion that the degree of brain damage does not always match the severity of clinical symptoms and neurological/cognitive outcomes.It has been suggested that the size of the brain(brain reserve) and the extent of neural connections acquired through life(neural reserve) set a threshold beyond which noticeable impairments occur.In contrast,cognitive reserve refers to the brain's ability to adapt and reo rganize stru cturally and functionally to resist damage and maintain function,including neural reserve and brain maintenance,resilience,and compensation(Verkhratsky and Zorec,2024).展开更多
The overgeneralization of fear is associated with psychiatric disorders and cognitive decline.Recent studies have shown that engram cells in the dorsal dentate gyrus are integrated into functionally heterogeneous ense...The overgeneralization of fear is associated with psychiatric disorders and cognitive decline.Recent studies have shown that engram cells in the dorsal dentate gyrus are integrated into functionally heterogeneous ensembles that are involved in contextual fear memory generalization and discrimination.However,the intracellular signals that promote fear generalization remain to be fully elucidated.In this study,we labeled and manipulated the c-Fos+and Npas4+ensembles in the dorsal dentate gyrus that are activated by contextual fear conditioning using a robust activity marking system.The results showed that increasing the excitability of Fos-dependent robust activity marking by overexpressing NaChBac or decreasing the excitability of Npas4-dependent robust activity marking by overexpressing Kir2.1 promoted fear memory generalization.Furthermore,CRISPR-mediated downregulation of the autophagy-related Atg5 or Atg7 genes in dorsal dentate gyrus neurons inhibited activation of c-Fos,but not Npas4.Knockdown of Atg5 or Atg7 in the Fos-dependent robust activity marking or Npas4-dependent robust activity marking ensemble led to an increase in neuronal excitability and a decrease in spine density in both ensembles.However,Atg7 knockdown in the Fos-dependent robust activity marking ensemble promoted memory generalization,while knockdown of Atg5 or Atg7 in the Npas4-dependent robust activity marking ensemble increased anxiety levels.These results contribute to our understanding of how the varying plasticity of memory engrams is involved in regulating fear memory generalization and anxiety.展开更多
This investigation focuses on the nonlinear dynamic behaviors in the trans- verse vibration of an axiMly accelerating viscoelastic Timoshenko beam with the external harmonic excitation. The parametric excitation is ca...This investigation focuses on the nonlinear dynamic behaviors in the trans- verse vibration of an axiMly accelerating viscoelastic Timoshenko beam with the external harmonic excitation. The parametric excitation is caused by the harmonic fluctuations of the axial moving speed. An integro-partial-differential equation governing the transverse vibration of the Timoshenko beam is established. Many factors are considered, such as viscoelasticity, the finite axial support rigidity, and the longitudinally varying tension due to the axial acceleration. With the Galerkin truncation method, a set of nonlinear ordinary differential equations are derived by discretizing the governing equation. Based on the numerical solutions, the bifurcation diagrams are presented to study the effect of the external transverse excitation. Moreover, the frequencies of the two excitations are assumed to be multiple. Further, five different tools, including the time history, the Poincaré map, and the sensitivity to initial conditions, are used to identify the motion form of the nonlinear vibration. Numerical results also show the characteristics of the quasiperiodic motion of the translating Timoshenko beam under an incommensurable re- lationship between the dual-frequency excitations.展开更多
Starting from an improved mapping approach and a linear variable separation approach, a new family of exact solutions （including solitary wave solutions, periodic wave solutions and rational function solutions） with...Starting from an improved mapping approach and a linear variable separation approach, a new family of exact solutions （including solitary wave solutions, periodic wave solutions and rational function solutions） with arbitrary functions for a general （2＋1）-dimensional Korteweg de solutions, we obtain some novel dromion-lattice solitons, system Vries system （GKdV） is derived. According to the derived complex wave excitations and chaotic patterns for the GKdV展开更多
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
By improved projective equation approach and a linear variable separation approach, a new family of exact solutions of the （2＋1）-dimensional Boiti-Leon-Pempinelli （BLP） system is derived. Based on the derived sol...By improved projective equation approach and a linear variable separation approach, a new family of exact solutions of the （2＋1）-dimensional Boiti-Leon-Pempinelli （BLP） system is derived. Based on the derived solitary wave solution, some dromion and solitoff excitations and chaotic behaviours are investigated.展开更多
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financially supported by the Key Research and Development Program of Shandong Province(Grant Nos.2022CXGC020405,2023CXGC010415 and 2025TSGCCZZB0238)the National Natural Science Foundation of China(Grant No.52171288)the financial support from CNPq,FAPERJ,ANP,Embrapii,and China National Petroleum Corporation(CNPC).
文摘This work investigated the dynamic behavior of vertical pipes conveying gas-liquid two-phase flow when subjected to external excitations at both ends.Even with minimal excitation amplitude,resonance can occur when the excitation frequency aligns with the natural frequency of the pipe,significantly increasing the degree of operational risk.The governing equation of motion based on the Euler-Bernoulli beam is derived for the relative deflection with stationary simply supported ends,with the effects of the external excitations represented by source terms distributed along the pipe length.The fourth-order partial differential equation is solved via the generalized integral transform technique(GITT),with the solution successfully verified via comparison with results in the literature.A comprehensive analysis of the vibration phenomena and changes in the motion state of the pipe is conducted for three classes of external excitation conditions:same frequency and amplitude(SFSA),same frequency but different amplitudes(SFDA),and different frequencies and amplitudes(DFDA).The numerical results show that with increasing gas volume fraction,the position corresponding to the maximum vibration displacement shifts upward.Compared with conditions without external excitation,the vibration displacement of the pipe conveying two-phase flow under external excitation increases significantly.The frequency of external excitation has a significant effect on the dynamic behavior of a pipe conveying two-phase flow.
文摘目的:探究血清D二聚体(D-dimer,D-D)、白细胞介素-6(Interleukin 6,IL-6)、红细胞沉降率(Erythrocyte sedimentation rate,ESR)水平联合检测对大叶性肺炎患儿预后的预测价值。方法:选取2021年2月至2024年2月长垣市人民医院儿一科收治的472例大叶性肺炎患儿作为研究对象,根据其预后情况分为预后良好组(n=409)和预后不良组(n=63)。对比2组治疗7 d血清D-D、IL-6、ESR水平,分析治疗7 d血清D-D、IL-6、ESR水平与大叶性肺炎患儿预后的相关性及对大叶性肺炎患儿预后不良的预测价值。结果:预后不良组治疗7 d血清D-D、IL-6、ESR水平明显高于预后良好组(P<0.05);大叶性肺炎患儿血清D-D、IL-6、ESR水平与其预后情况均呈正相关(P<0.05);血清D-D、IL-6、ESR水平是大叶性肺炎患儿预后不良的危险因素(P<0.05);血清D-D、IL-6、ESR水平联合预测患儿预后不良的曲线下面积(Area under the curve,AUC)分别为0.614、0.665、0.703、0.841(P<0.05);血清D-D、IL-6、ESR高水平患儿预后不良的危险度是低水平的2.268倍、2.505倍、3.311倍(P<0.05)。结论:血清D-D、IL-6、ESR水平与大叶性肺炎患儿预后关系密切,各指标联合检测可为临床预测患儿预后不良提供有效参考。
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financially supported by the Shandong Provincial Natural Science Foundation(Grant No.ZR2023QE063)。
文摘This paper presents a numerical investigation of nonlinear sloshing in a prismatic tank.A three-dimensional,twophase flow model based on Cartesian grid is developed to simulate the phenomenon.The model solves incompressible Navier-Stokes equations,utilizing the fractional step method for velocity-pressure decoupling.The finite difference method discretizes spatial derivatives,with specific schemes implemented to enhance model robustness.Model validation involves simulating benchmark cases,and comparing wave profiles and pressure results with published experimental data and numerical findings.The model demonstrates robustness and accuracy in simulating violent sloshing.The validated model examines sloshing in a partially filled prismatic tank under combined surge and roll excitations.The study employs eight frequencies encompassing the natural frequencies of tank roll and surge motions.Roll motion excitation is fixed at 2°,while surge motion considers three excitation amplitudes(0.0 m,0.01 m,and 0.02m).Analysis reveals the effects of surge amplitude and excitation frequency on wave patterns,amplitudes,and pressure peaks.Results indicate the presence of multi-component waves,including transverse,diagonal,and longitudinal waves.Furthermore,the findings demonstrate a reduction in the natural frequency for surge motion through pressure peak analysis.
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.
文摘The low-energy excited states in the neutron-deficient nucleus^(91)Ru were populated via the^(58)Ni(^(36)Ar,2p1nγ)^(91)Ru reaction at a beam energy of 111 MeV.Charged particles,neutrons,andγrays were emitted in the reactions and detected using a DIAMANT CsI ball,neutron wall,and EXOGAM Ge clover array,respectively.Angular-correlation and linear polarization measurements were performed to determine the spins and parities of the excited states unambiguously.In addition to the previously reported states,a new low-energy-level structure of^(91)Ru,including one 7/2^(+)and two 11/2^(+)states,was established.Similar structures have also been reported in lighter N=47 even-odd isotones down to85Sr,which were expected to come from the three-neutron-holevg_(9/2)^(-3)configuration.A semiempirical shell model was used to explain the level systematics of the N=47 even-odd isotones.Calculated results indicated that the 7/2^(+)and the vg_(9/2)^(-3)states~are mainly associated with the seniority-threeν(g_(9/2))-3excitations,while the vg_(9/2)^(-3)level is most likely interpreted as a seniorityυ=1 configuration of three neutron holes in theνg_(9∕2)orbital_weakly coupled to a 2^(+)excitation of the^(88)Sr core.A comparison between the calculation and experiment shows that the two 11/2^(+)excited states display an increase in mixing with proton number Z added from^(87)Zr up to^(91)Ru.
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supported by the Chinese Acade-my of Sciences(Grant Nos.YSBR-055,XDB0970100)the National Natural Science Foundation of China(Nos.22241302,12393825).
文摘The precise excitation of molecular vibrational states is critical for ad-vancing chemical dynamics,preci-sion spectroscopy,and trace gas sensing.This objective,however,is often hindered by the weak oscilla-tor strengths of ro-vibrational tran-sitions,which render conventional continuous-wave(cw)lasers ineffec-tive due to their limited power.This fundamental challenge is overcome by cavity-enhanced excitation(CEE),a technique that locks a cw laser to a high-finesse optical cavity.This configuration amplifies the intra-cavity light intensity by several orders of magnitude while preserving a narrow spectral linewidth.The resulting synergy enables highly efficient,state-selective population transfer and high-resolution spectroscopy previously considered impractical.This review elucidates the core technique of laser-cavity locking and highlights its applications,notably in the quantitative detection of trace isotopes and the investigation of highly excited vibrational states with kilo-hertz-level accuracy.
文摘Modern/distributed electric energy systems,with ever larger penetration of renewable(photovoltaic,wind,wave,and hydro)energy sources and time-variable outputs,are in need of stronger/higher frequency and alternating current(AC)(direct current(DC))voltage control.In fact,faster and more stable active and reactive power in the presence of frequency and voltage sags and swells is needed.Power electronics-controlled variable speed generators do not have enough energy storage(inertia)for the scope(static synchronous compensators(STATCOMs)included).This is because power electronics tends to decouple the generator from the power system.While virtual inertia control in doubly fed induction generators(DFIGs)offers a partial solution to these problems,a more robust and comprehensive framework is required for advanced grid support.This is how,by extending the dual-excitation principles,the dualaxis excited electric synchronous generators(DE-SG)provide superior flexibility in two variants summarized here:as a multifunctional DFIG and dual-axis vs.single-axis excited synchronous generator(SG),and as a synchronous condenser(SC),with dual DC and AC excitation(as a no-load DFIG with inertia wheel),where variable speed is used to accelerate/decelerate the SC and thus provide additional assistance in frequency stabilization.These solutions,good for short-time transients,are not meant,however,to replace the large bidirectional energy storage systems(pump-hydro,hydrogen,batteries,etc.)which are crucial for the daily inherent variations of output energy in modern power systems with multiple power sources.The present paper offers a summary of techniques used in the dual-axis excited vs.single-axis excited SGs(SE-SGs),and SCs topologies,modeling,and control for better stability in modern multiple-source energy systems.This survey includes multiple case studies to shed light on prominent methods.
基金supported in part by China Scholarship Council(CSC)under Grant 202206160023.
文摘In this paper,electrically excited synchronous machines(EESMs)using copper(Cu)and aluminum(Al)windings are compared for the feasibility of replacing Cu windings with Al windings in electric vehicle(EV)applications since Al windings have lower mass density and cost per weight,but higher resistivity and lower thermal conductivity than Cu windings.The EESMs with four winding configurations are optimized with an electromagnetic-thermal co-optimization method.The optimized EESM with only Cu windings is considered as the baseline in this study.Results show that the EESM with stator-Cu/rotor-Al windings has the least torque reduction(12.1%)compared to the baseline among the three EESMs with Al windings and the highest torque mass density among all EESMs.Meanwhile,although the new European driving cycle efficiency of the stator-Cu/rotor-Al EESM is 1.8%lower than that of the baseline,the torque per cost is 71%higher,and the maximum rotor mechanical stress is 8%lower.Therefore,the EESMs with stator-Cu/rotor-Al windings are prospective substitutions of those with only Cu windings for EV applications considering the trade-off between performance and cost.
基金supported by the Aeronautical Science Foundation of China(Nos.2023L039053002 and 2024M039053001)。
文摘Asymmetric stators,featuring nonuniform pitches,have demonstrated effectiveness in mitigating the forced response of the adjacent compressor rotor blades.However,the lack of comprehensive understanding of their vibration reduction mechanisms hinders the development of optimal designs.Typically,the evaluation of rotor blades forced response using asymmetric stators requires fluid–structure interaction methods and full-annulus computational domains;however,these methods are time-consuming and resource-intensive,making them unsuitable for rapid engineering applications.To address these issues,the present study first develops a Fourier-based prediction method for the excitation spectrum and blade forced response that considers the impacts of multiple excitation components.To verify the accuracy of the prediction method,two typical asymmetric stator configurations are selected,and the forced response analyses with single-passage computational domains are conducted on their downstream rotor blades based on the rapid time inclination method.The results are then compared with those obtained using the dual time stepping method with whole-annulus computational domains.The results indicate that the proposed Fourier-based method can accurately predict the impacts of asymmetric stators on the forced response of the rotor blades.Moreover,the rapid evaluation approach based on the time inclination method provides comparable accuracy to the dual time stepping method,but with greater computational efficiency and reduced memory consumption.
文摘The concept of the brain cognitive reserve is derived from the well-acknowledged notion that the degree of brain damage does not always match the severity of clinical symptoms and neurological/cognitive outcomes.It has been suggested that the size of the brain(brain reserve) and the extent of neural connections acquired through life(neural reserve) set a threshold beyond which noticeable impairments occur.In contrast,cognitive reserve refers to the brain's ability to adapt and reo rganize stru cturally and functionally to resist damage and maintain function,including neural reserve and brain maintenance,resilience,and compensation(Verkhratsky and Zorec,2024).
基金the STI2030-Major Projects,Nos.2021ZD0203500(to FW),2021ZD0202100(to XL)the National Natural Science Foundation of China,Nos.32222033(to FW),32330041(to LM)and 82021002(to LM),32171041(to XL)and 32450102(to XL)CAMS Innovation Fund for Medical Sciences,No.2021-I2M-5-009(to LM and XL).
文摘The overgeneralization of fear is associated with psychiatric disorders and cognitive decline.Recent studies have shown that engram cells in the dorsal dentate gyrus are integrated into functionally heterogeneous ensembles that are involved in contextual fear memory generalization and discrimination.However,the intracellular signals that promote fear generalization remain to be fully elucidated.In this study,we labeled and manipulated the c-Fos+and Npas4+ensembles in the dorsal dentate gyrus that are activated by contextual fear conditioning using a robust activity marking system.The results showed that increasing the excitability of Fos-dependent robust activity marking by overexpressing NaChBac or decreasing the excitability of Npas4-dependent robust activity marking by overexpressing Kir2.1 promoted fear memory generalization.Furthermore,CRISPR-mediated downregulation of the autophagy-related Atg5 or Atg7 genes in dorsal dentate gyrus neurons inhibited activation of c-Fos,but not Npas4.Knockdown of Atg5 or Atg7 in the Fos-dependent robust activity marking or Npas4-dependent robust activity marking ensemble led to an increase in neuronal excitability and a decrease in spine density in both ensembles.However,Atg7 knockdown in the Fos-dependent robust activity marking ensemble promoted memory generalization,while knockdown of Atg5 or Atg7 in the Npas4-dependent robust activity marking ensemble increased anxiety levels.These results contribute to our understanding of how the varying plasticity of memory engrams is involved in regulating fear memory generalization and anxiety.
基金Project supported by the State Key Program of National Natural Science Foundation of China(No.11232009)the National Natural Science Foundation of China(Nos.11372171 and 11422214)
文摘This investigation focuses on the nonlinear dynamic behaviors in the trans- verse vibration of an axiMly accelerating viscoelastic Timoshenko beam with the external harmonic excitation. The parametric excitation is caused by the harmonic fluctuations of the axial moving speed. An integro-partial-differential equation governing the transverse vibration of the Timoshenko beam is established. Many factors are considered, such as viscoelasticity, the finite axial support rigidity, and the longitudinally varying tension due to the axial acceleration. With the Galerkin truncation method, a set of nonlinear ordinary differential equations are derived by discretizing the governing equation. Based on the numerical solutions, the bifurcation diagrams are presented to study the effect of the external transverse excitation. Moreover, the frequencies of the two excitations are assumed to be multiple. Further, five different tools, including the time history, the Poincaré map, and the sensitivity to initial conditions, are used to identify the motion form of the nonlinear vibration. Numerical results also show the characteristics of the quasiperiodic motion of the translating Timoshenko beam under an incommensurable re- lationship between the dual-frequency excitations.
基金Project supported by the National Natural Science Foundation of China （Grant No 10172056）, the Natural Science Foundation of Zhejiang Province, China （Grant No Y604106）, the Foundation of New Century 151 Talent Engineering of Zhejiang Province, the Scientific Research Foundation of Zhejiang Provincial Education Department of China （Grant No 20070568） and the Natural Science Foundation of Zhejiang Lishui University （Grant No KZ04008）.
文摘Starting from an improved mapping approach and a linear variable separation approach, a new family of exact solutions （including solitary wave solutions, periodic wave solutions and rational function solutions） with arbitrary functions for a general （2＋1）-dimensional Korteweg de solutions, we obtain some novel dromion-lattice solitons, system Vries system （GKdV） is derived. According to the derived complex wave excitations and chaotic patterns for the GKdV
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Project supported by the Natural Science Foundation of Zhejiang Province of China (Grant Nos. Y6100257, Y6110140, and Y6090681)the Natural Science Foundation of Zhejiang Lishui University, China (Grant Nos. KZ09005 and KY08003)
文摘By improved projective equation approach and a linear variable separation approach, a new family of exact solutions of the （2＋1）-dimensional Boiti-Leon-Pempinelli （BLP） system is derived. Based on the derived solitary wave solution, some dromion and solitoff excitations and chaotic behaviours are investigated.
