Fluorescent probes based on intramolecular charge transfer(ICT) have obvious advantages for accurate quantitative analysis.To obtain high-performance ratiometric probes requires distinct photophysical properties durin...Fluorescent probes based on intramolecular charge transfer(ICT) have obvious advantages for accurate quantitative analysis.To obtain high-performance ratiometric probes requires distinct photophysical properties during recognition reaction process,which is closely related to their ICT characteristics.1,8-Naphthalimide is known as a typical fluorophore with desirable ICT property when functionalized with an electron-donating moiety at the para-position of the naphthalene chromophore.Although the photophysical properties of para-substituted 1,8-naphthalimide have been well studied,its meta-substituted counterpart has not been fully evaluated since the meta-position is conventionally thought to be weakly conjugated.Herein,combined experimental and theoretical studies are performed which consistently indicate that stronger charge transfer(CT) is exhibited by the meta-amino substituted 1,8-naphthalimide(m-NH_(2)) compared to the para-amino substituted one(p-NH_(2)).The ratiometric response of fluorescence with significant changes in wavelength and intensity upon acetylation(m-NAc and p-NAc) can be attributed to the larger ICT and stronger-NH_(2) vibrations.This observation is further demonstrated by deuterium oxide experiments,viscosity experiments and quantum chemical calculations.The practical application of meta-amino-1,8-naphthalimide ICT-based probes is also confirmed.This research is expected to bring an in-depth understanding of π-conjugated systems with ICT characteristics,and facilitates the design of sensitive ICT fluorescent probes with meta-amino substitution.展开更多
Tactile sensing of subcutaneous organ vibrations provides a promising route toward human-machine interfaces and wear-able diagnostics,particularly for voice rehabilitation and silent-speech communication.Here,we prese...Tactile sensing of subcutaneous organ vibrations provides a promising route toward human-machine interfaces and wear-able diagnostics,particularly for voice rehabilitation and silent-speech communication.Here,we present a bioinspired piezoelectric vibration sensor that mimics the graded stiffness and stress-based transduction mechanism of otolithic cilia in the human vestibular system.The device consists of a trapezoidal cantilever array with tip inertial masses,fabricated through a hybrid stereolithography 3D printing and laser micromachining process for rapid prototyping without cleanroom facilities.Finite-element modeling and experimental measurements demonstrate a fundamental resonance near 1.2 kHz,a 5%flat-bandwidth of 350 Hz,and an in-band charge sensitivity of 3.17 pC/g.A wearable proof-of-concept test further verifies the sensor's ability to reproducibly distinguish phoneme-specific vibration patterns in both time and frequency domains.This work establishes a foundation for bioinspired tactile sensing front-ends in wearable voice interfaces and other intelligent diagnostic systems integrated with machine-learning algorithms.展开更多
Time-delayed blasting is widely utilized in engineering to mitigate induced vibration hazards and enhance fragmentation.The underlying vibration reduction principle is the decrease of the charge weight per delay,while...Time-delayed blasting is widely utilized in engineering to mitigate induced vibration hazards and enhance fragmentation.The underlying vibration reduction principle is the decrease of the charge weight per delay,while the potential for further vibration reduction remains debated,largely due to unclear underlying mechanisms.In light of the popularization of electronic detonators and the representativeness of double-hole configurationsfor multiple blastholes,it is essential to investigate the vibration characteristics induced by time-delayed double blastholes.Therefore,a series of doubleborehole experimental blasts was conducted in an underground roadway to clarify the variation in vibration from single-hole to dual-hole conditions.Based on the experimental data and inherent limitations,an exact full-fieldtheoretical model was further employed to systematically analyze the effects of delay time,charge length,and borehole inclination angle on vibrations induced by various doublehole configurations.The experimental data and theoretical analysis reveal that the general scaled distance effectively predicts vibrations in delayed blasting but does not reflectvibration reduction.Increasing delay time causes fluctuatingPPVs,which stabilize slightly above single-hole PPVs as delay times exceed a certain value.The delayed blasting primarily reduces near-fieldfrequencies.Longer charge lengths in double boreholes increase PPV levels and attenuation rates within a certain length,and the vibration behavior of combined long and short charge lengths is governed by the long blasthole.Larger blasthole inclination angles enhance vibration amplitude and reduce PPV attenuation rates.Optimizing inclination angles is more critical than adjusting delay times,and parallel boreholes offer the best vibration control.展开更多
Due to space constraints in mountainous areas,twin tunnels are sometimes constructed very close to each other or even overlap.This proximity challenges the structural stability of tunnels built with the drill-and-blas...Due to space constraints in mountainous areas,twin tunnels are sometimes constructed very close to each other or even overlap.This proximity challenges the structural stability of tunnels built with the drill-and-blast method,as the short propagation distance amplifies blasting vibrations.A case of blasting damage is reported in this paper,where concrete cracks crossed construction joints in the twin-arch lining.To identify the causes of these cracks and develop effective vibration mitigation measures,field monitoring and numerical analysis were conducted.Specifically,a restart method was used to simulate the second peak particle velocity(PPV)of MS3 delays occurring 50 ms after the MS1 delays.The study found that the dynamic tensile stress in the tunnel induced by the blast wave has a linear relationship with the of the product of the concrete wave impedance and the PPV.A blast vibration velocity exceeding 23.3 cm/s resulted in tensile stress in the lining surpassing the ultimate tensile strength of C30 concrete,leading to tensile cracking on the blast-facing arch of the constructed tunnel.To control excessive vi-bration velocity,a mitigation trench was implemented to reduce blast wave impact.The trench,approximately 15 m in length,50 cm in width,and 450 cm in height,effectively lowered vibration ve-locities,achieving an average reduction rate of 52%according to numerical analysis.A key innovation of this study is the on-site implementation and validation of the trench's effectiveness in mitigating vi-brations.A feasible trench construction configuration was proposed to overcome the limitations of a single trench in fully controlling vibrations.To further enhance protection,zoned blasting and an auxiliary rock pillar,80 cm in width,were incorporated to reinforce the mid-wall.This study introduces novel strategies for vibration protection in tunnel blasting,offering innovative solutions to address blasting-induced vibrations and effectively minimize their impact,thereby enhancing safety and struc-tural stability.展开更多
Unbalanced force produced by the unbalanced mass will affect vibrations of rotor systems,which probably results in the components failures of rotating machinery.To study the effects of unbalanced mass on the vibration...Unbalanced force produced by the unbalanced mass will affect vibrations of rotor systems,which probably results in the components failures of rotating machinery.To study the effects of unbalanced mass on the vibration characteristics of rotor systems,a flexible rotor system model considering the unbalanced mass is proposed.The time-varying bearing force is considered.The developed model is verified by the experimental and theoretical frequency spectrums.The displacements and axis orbits of flexible and rigid rotor systems are compared.The results show that the unbalanced mass will affect the vibration characteristics of rotor system.This model can be more suitable and effective to calculate vibration characteristics of rotor system with the flexible deformation and unbalanced mass.This paper provides a new reference and research method for predicting the vibrations of flexible rotor system considering the unbalanced mass.展开更多
For the first time,the linear and nonlinear vibrations of composite rectangular sandwich plates with various geometric patterns of lattice core have been analytically examined in this work.The plate comprises a lattic...For the first time,the linear and nonlinear vibrations of composite rectangular sandwich plates with various geometric patterns of lattice core have been analytically examined in this work.The plate comprises a lattice core located in the middle and several homogeneous orthotropic layers that are symmetrical relative to it.For this purpose,the partial differential equations of motion have been derived based on the first-order shear deformation theory,employing Hamilton’s principle and Von Kármán’s nonlinear displacement-strain relations.Then,the nonlinear partial differential equations of the plate are converted into a time-dependent nonlinear ordinary differential equation(Duffing equation)by applying the Galerkin method.From the solution of this equation,the natural frequencies are extracted.Then,to calculate the non-linear frequencies of the plate,the non-linear equation of the plate has been solved analytically using the method of multiple scales.Finally,the effect of some critical parameters of the system,such as the thickness,height,and different angles of the stiffeners on the linear and nonlinear frequencies,has been analyzed in detail.To confirmthe solution method,the results of this research have been compared with the reported results in the literature and finite elements in ABAQUS,and a perfect match is observed.The results reveal that the geometry and configuration of core ribs strongly affect the natural frequencies of the plate.展开更多
Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emp...Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emphasis on structural durability and monitoring is required.This study focuses on the mechanical vibrations that occur in rotary drilling systems,which have a substantial impact on the structural integrity of drilling equipment.The study specifically investigates axial,torsional,and lateral vibrations,which might lead to negative consequences such as bit-bounce,chaotic whirling,and high-frequency stick-slip.These events not only hinder the efficiency of drilling but also lead to exhaustion and harm to the system’s components since they are difficult to be detected and controlled in real time.The study investigates the dynamic interactions of these vibrations,specifically in their high-frequency modes,usingfield data obtained from measurement while drilling.Thefindings have demonstrated the effect of strong coupling between the high-frequency modes of these vibrations on drilling sys-tem performance.The obtained results highlight the importance of considering the interconnected impacts of these vibrations when designing and implementing robust control systems.Therefore,integrating these compo-nents can increase the durability of drill bits and drill strings,as well as improve the ability to monitor and detect damage.Moreover,by exploiting thesefindings,the assessment of structural resilience in rotary drilling systems can be enhanced.Furthermore,the study demonstrates the capacity of structural health monitoring to improve the quality,dependability,and efficiency of rotary drilling systems in the petroleum industry.展开更多
A three-dimensional(3D)analytical formulation is proposed to put together magnetic,electric and elastic fields to analyze the vibration modes of simply-supported layered piezo-electro-magnetic plates.The present 3D mo...A three-dimensional(3D)analytical formulation is proposed to put together magnetic,electric and elastic fields to analyze the vibration modes of simply-supported layered piezo-electro-magnetic plates.The present 3D model allows analyses for layered smart plates in both open-circuit and closed-circuit configurations.The secondorder differential equations written in the mixed curvilinear reference system govern the magneto-electro-elastic free vibration problem for multilayered plates.This set consists of the 3D equations of motion and the 3D divergence equations for the magnetic induction and electric displacement.Navier harmonic forms in the planar directions and the exponential matrix method in the transversal direction of the plate are applied to solve the second-order differential equations in terms of displacements.For these reasons,simply-supported boundary conditions are considered.Imposition of interlaminar continuity conditions on primary variables(displacements,magnetic potential,electric potential),and some secondary variables(transverse normal and transverse shear stresses,transverse normal magnetic induction/electric displacement)allows the implementation of the layer-wise approach.Assessments for both load boundary configurations are proposed in the results section to validate the present 3D approach.3D electro-elastic and 3D magneto-elastic coupling validations are performed separately considering different models from the open literature.A new benchmark involving a full magneto-electro-elastic coupling for multilayered plates is presented considering both load boundary configurations for different thickness ratios.For this benchmark,circular frequency values and related vibration modes through the transverse direction in terms of displacements,magnetic and electric potential,transverse normal magnetic induction/electric displacement are shown to visualize the magneto-electroelastic coupling and material and thickness layer effects.The present formulation has been entirely implemented in an academic Matlab(R2024a)code developed by the authors.In this paper,for the first time,the second-order differential equations governing the magneto-electro-elastic problem for the free vibration analysis of plates has been solved considering the mixed mode of harmonic forms and exponential matrix.The exponential matrix permits computing the secondary variable of the problem(stresses,electric displacement components and magnetic induction components)exactly,directly from constitutive and geometrical equations.In addition,the very simple and elegant formulation permits having a code with very low computational costs.The present manuscript aims to fill the void in open literature regarding reference 3D solutions for the free vibration analysis of magneto-electro-elastic plates.展开更多
The proposed mass model of vocal fold vibration holds a significant importance in the auxiliary diagnosis and treatment of human vocal fold disorders.Mathematical models are proposed in aerodynamics and acoustics to s...The proposed mass model of vocal fold vibration holds a significant importance in the auxiliary diagnosis and treatment of human vocal fold disorders.Mathematical models are proposed in aerodynamics and acoustics to simulate vocal fold vibration during phonation.This has always been a hot topic in pathological linguistics research.Over the past few decades,researchers have designed various types of mass models of vocal fold vibration based on experiments.These models differ in principles,computational complexity,and degrees of freedom.Therefore,we classify and describe the mass models according to modeling methods.We summarize the research status and characteristics of different models,and based on this,we look forward to future research directions for vocal fold mass models.展开更多
Mega Low Earth Orbit(LEO)satellite constellations can provide pervasive intelligent services in the forthcoming Six-Generation(6G)network via the Free-Space Optical(FSO)InterSatellite Link(ISL).However,the challenges ...Mega Low Earth Orbit(LEO)satellite constellations can provide pervasive intelligent services in the forthcoming Six-Generation(6G)network via the Free-Space Optical(FSO)InterSatellite Link(ISL).However,the challenges posed by the mega LEO satellite constellations,such as limited onboard resources,high-speed movement and the vibration of satellite platforms,present significant obstacles for the existing Pointing,Acquisition and Tracking(PAT)schemes of FSOISL.To address these challenges,we propose a beaconless PAT scheme under satellite platform vibrations,employing a composite scanning approach combining an inner Archimedean spiral scan with an outer regular hexagon step scan.The proposed composite scanning approach covers a wide range of the Field of Uncertainty(FOU)and reduces the required scans by actuator,which can ensure a high Acquisition Probability(AP)while reducing the Average Acquisition Time(AAT)for the inner scan.Specifically,we model and analyze the effect of satellite platform vibrations on the acquisition performance of our beaconless PAT scheme,and derive closed-form expressions for both AP and AAT by utilizing a 2-track model where the acquisition happens on two adjacent spiral scan tracks.By utilizing the theoretical derivations,we can achieve a minimum AAT under diverse APs by selecting appropriate values of overlapping region and scanning range.Simulation results validate that our optimized composite scanning approach for beaconless PAT scheme outperforms the existing schemes.展开更多
The analysis of the dynamics of surface girders is of great importance in the design of engineering structures such as steel welded bridge plane girders or concrete plate-column structures.This work is an extension of...The analysis of the dynamics of surface girders is of great importance in the design of engineering structures such as steel welded bridge plane girders or concrete plate-column structures.This work is an extension of the classical deterministic problem of free vibrations of thin(Kirchhoff)plates.Themain aim of this work is the study of stochastic eigenvibrations of thin(Kirchhoff)elastic plates resting on internal continuous and column supports by the Boundary Element Method(BEM).This work is a continuation of previous research related to the random approach in plate analysis using the BEM.The static fundamental solution(Green’s function)is applied,coupled with a nonsingular formulation of the boundary and domain integral equations.These are derived using a modified and simplified formulation of the boundary conditions,inwhich there is no need to introduce theKirchhoff forces on a plate boundary.The role of the Kirchhoff corner forces is played by the boundary elements placed close to a single corner.Internal column or linear continuous supports are introduced using the Bezine technique,where the additional collocation points are introduced inside a plate domain.This allows for significant simplification of the BEM computational algorithm.An application of the polynomial approximations in the Least Squares Method(LSM)recovery of the structural response is done.The probabilistic analysis will employ three independent computational approaches:semi-analytical method(SAM),stochastic perturbation technique(SPT),and Monte-Carlo simulations.Numerical investigations include the fundamental eigenfrequencies of an elastic,thin,homogeneous,and isotropic plate.展开更多
To advance materials with superior performance,the construction of gradient structures has emerged as a promising strategy.In this study,a gradient nanocrystalline-amorphous structure was induced in Zr46Cu46Al8 bulk m...To advance materials with superior performance,the construction of gradient structures has emerged as a promising strategy.In this study,a gradient nanocrystalline-amorphous structure was induced in Zr46Cu46Al8 bulk metallic glass(BMG)through ultrasonic vibration(UV)treatment.Applying a 20 kHz ultrasonic cyclic loading in the elastic regime,controllable gradient structures with varying crystallized volume fractions can be achieved in less than 2 s by adjusting the input UV energy.In contrast to tradi-tional methods of inducing structural gradients in BMGs,this novel approach offers distinct advantages:it is exceptionally rapid,requires minimal stress,and allows for easy tuning of the extent of structural gradients through precise adjustment of processing parameters.Nanoindentation tests reveal higher hard-ness near the struck surface,attributed to a greater degree of nanocrystal formation,which gradually di-minishes with depth.As a result of the gradient dispersion of nanocrystals,an increased plasticity was found after UV treatment,characterized by the formation of multiple shear bands.Microstructural in-vestigations suggest that UV-induced nanocrystallization originates from local atomic rearrangements in phase-separated Cu-rich regions with high diffusional mobility.Our study underscores the tunability of structural gradients and corresponding performance improvements in BMGs through ultrasonic energy modulation,offering valuable insights for designing advanced metallic materials with tailored mechanical properties.展开更多
Moving-load induced vibrations can,in certain instances,exceed those caused by equivalent static loads,especially at the critical velocity of moving loads.Suppressing these vibrations is of critical practical importan...Moving-load induced vibrations can,in certain instances,exceed those caused by equivalent static loads,especially at the critical velocity of moving loads.Suppressing these vibrations is of critical practical importance in various engineering fields,including the design of precision robotics and advanced aerospace structures where components are subject to moving loads.In this paper,an inertial nonlinear energy sink(NES)is used for the first time to reduce the vibration response of graphene platelet(GPL)-reinforced nanocomposite beams with elastic boundaries under moving loads.Based on the von Kármán nonlinear theory,the governing equations of the beam-NES system are derived using the Lagrange equation.The Newmark-Newton method,in conjunction with the Heaviside step function,is used to obtain the nonlinear responses of the beam under moving loads.The effects of the boundary spring stiffness,the GPL parameters,as well as the velocity and frequency of the moving loads on the beam response and the performance of the NES are thoroughly studied.The results of this work provide insights into applying NESs to suppress the nonlinear vibrations induced by moving loads in composite structures with elastic boundaries.展开更多
基金financially supported by National Key Research and Development Programs (Nos.2022YFD1700403 and 2023YFD1700303)National Natural Science Foundation of China (Nos.12274128 and 12250003)+2 种基金Shanghai Rising-Star Program (No.21QA1402600)the support of NYU-ECNU Center for Computational Chemistry at NYU Shanghaithe University of Bath and the Open Research Fund of the School of Chemistry and Chemical Engineering,Henan Normal University (No.2020ZD01) for support。
文摘Fluorescent probes based on intramolecular charge transfer(ICT) have obvious advantages for accurate quantitative analysis.To obtain high-performance ratiometric probes requires distinct photophysical properties during recognition reaction process,which is closely related to their ICT characteristics.1,8-Naphthalimide is known as a typical fluorophore with desirable ICT property when functionalized with an electron-donating moiety at the para-position of the naphthalene chromophore.Although the photophysical properties of para-substituted 1,8-naphthalimide have been well studied,its meta-substituted counterpart has not been fully evaluated since the meta-position is conventionally thought to be weakly conjugated.Herein,combined experimental and theoretical studies are performed which consistently indicate that stronger charge transfer(CT) is exhibited by the meta-amino substituted 1,8-naphthalimide(m-NH_(2)) compared to the para-amino substituted one(p-NH_(2)).The ratiometric response of fluorescence with significant changes in wavelength and intensity upon acetylation(m-NAc and p-NAc) can be attributed to the larger ICT and stronger-NH_(2) vibrations.This observation is further demonstrated by deuterium oxide experiments,viscosity experiments and quantum chemical calculations.The practical application of meta-amino-1,8-naphthalimide ICT-based probes is also confirmed.This research is expected to bring an in-depth understanding of π-conjugated systems with ICT characteristics,and facilitates the design of sensitive ICT fluorescent probes with meta-amino substitution.
文摘Tactile sensing of subcutaneous organ vibrations provides a promising route toward human-machine interfaces and wear-able diagnostics,particularly for voice rehabilitation and silent-speech communication.Here,we present a bioinspired piezoelectric vibration sensor that mimics the graded stiffness and stress-based transduction mechanism of otolithic cilia in the human vestibular system.The device consists of a trapezoidal cantilever array with tip inertial masses,fabricated through a hybrid stereolithography 3D printing and laser micromachining process for rapid prototyping without cleanroom facilities.Finite-element modeling and experimental measurements demonstrate a fundamental resonance near 1.2 kHz,a 5%flat-bandwidth of 350 Hz,and an in-band charge sensitivity of 3.17 pC/g.A wearable proof-of-concept test further verifies the sensor's ability to reproducibly distinguish phoneme-specific vibration patterns in both time and frequency domains.This work establishes a foundation for bioinspired tactile sensing front-ends in wearable voice interfaces and other intelligent diagnostic systems integrated with machine-learning algorithms.
基金supported by the National Natural Science Foundation of China(Grant Nos.42407267 and 52374152)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20220975).
文摘Time-delayed blasting is widely utilized in engineering to mitigate induced vibration hazards and enhance fragmentation.The underlying vibration reduction principle is the decrease of the charge weight per delay,while the potential for further vibration reduction remains debated,largely due to unclear underlying mechanisms.In light of the popularization of electronic detonators and the representativeness of double-hole configurationsfor multiple blastholes,it is essential to investigate the vibration characteristics induced by time-delayed double blastholes.Therefore,a series of doubleborehole experimental blasts was conducted in an underground roadway to clarify the variation in vibration from single-hole to dual-hole conditions.Based on the experimental data and inherent limitations,an exact full-fieldtheoretical model was further employed to systematically analyze the effects of delay time,charge length,and borehole inclination angle on vibrations induced by various doublehole configurations.The experimental data and theoretical analysis reveal that the general scaled distance effectively predicts vibrations in delayed blasting but does not reflectvibration reduction.Increasing delay time causes fluctuatingPPVs,which stabilize slightly above single-hole PPVs as delay times exceed a certain value.The delayed blasting primarily reduces near-fieldfrequencies.Longer charge lengths in double boreholes increase PPV levels and attenuation rates within a certain length,and the vibration behavior of combined long and short charge lengths is governed by the long blasthole.Larger blasthole inclination angles enhance vibration amplitude and reduce PPV attenuation rates.Optimizing inclination angles is more critical than adjusting delay times,and parallel boreholes offer the best vibration control.
基金supported by the Shenzhen Stability Support Plan(Grant No.20231122095154003)National Natural Science Foundation of China(Grant Nos.51978671 and 52378425)Guizhou Provincial Department of Transportation Science and Technology Program(Grant No.2023-122-003)。
文摘Due to space constraints in mountainous areas,twin tunnels are sometimes constructed very close to each other or even overlap.This proximity challenges the structural stability of tunnels built with the drill-and-blast method,as the short propagation distance amplifies blasting vibrations.A case of blasting damage is reported in this paper,where concrete cracks crossed construction joints in the twin-arch lining.To identify the causes of these cracks and develop effective vibration mitigation measures,field monitoring and numerical analysis were conducted.Specifically,a restart method was used to simulate the second peak particle velocity(PPV)of MS3 delays occurring 50 ms after the MS1 delays.The study found that the dynamic tensile stress in the tunnel induced by the blast wave has a linear relationship with the of the product of the concrete wave impedance and the PPV.A blast vibration velocity exceeding 23.3 cm/s resulted in tensile stress in the lining surpassing the ultimate tensile strength of C30 concrete,leading to tensile cracking on the blast-facing arch of the constructed tunnel.To control excessive vi-bration velocity,a mitigation trench was implemented to reduce blast wave impact.The trench,approximately 15 m in length,50 cm in width,and 450 cm in height,effectively lowered vibration ve-locities,achieving an average reduction rate of 52%according to numerical analysis.A key innovation of this study is the on-site implementation and validation of the trench's effectiveness in mitigating vi-brations.A feasible trench construction configuration was proposed to overcome the limitations of a single trench in fully controlling vibrations.To further enhance protection,zoned blasting and an auxiliary rock pillar,80 cm in width,were incorporated to reinforce the mid-wall.This study introduces novel strategies for vibration protection in tunnel blasting,offering innovative solutions to address blasting-induced vibrations and effectively minimize their impact,thereby enhancing safety and struc-tural stability.
基金Support by Shanxi Provincial Key Research and Development Plan of China(Grant No.2024GH-ZDXM-29)National Natural Science Foundation of China(Grant No.52175120)Shaanxi Provincial Innovation Capability Support Program of China(Grant No.2024RS-CXTD-15)。
文摘Unbalanced force produced by the unbalanced mass will affect vibrations of rotor systems,which probably results in the components failures of rotating machinery.To study the effects of unbalanced mass on the vibration characteristics of rotor systems,a flexible rotor system model considering the unbalanced mass is proposed.The time-varying bearing force is considered.The developed model is verified by the experimental and theoretical frequency spectrums.The displacements and axis orbits of flexible and rigid rotor systems are compared.The results show that the unbalanced mass will affect the vibration characteristics of rotor system.This model can be more suitable and effective to calculate vibration characteristics of rotor system with the flexible deformation and unbalanced mass.This paper provides a new reference and research method for predicting the vibrations of flexible rotor system considering the unbalanced mass.
文摘For the first time,the linear and nonlinear vibrations of composite rectangular sandwich plates with various geometric patterns of lattice core have been analytically examined in this work.The plate comprises a lattice core located in the middle and several homogeneous orthotropic layers that are symmetrical relative to it.For this purpose,the partial differential equations of motion have been derived based on the first-order shear deformation theory,employing Hamilton’s principle and Von Kármán’s nonlinear displacement-strain relations.Then,the nonlinear partial differential equations of the plate are converted into a time-dependent nonlinear ordinary differential equation(Duffing equation)by applying the Galerkin method.From the solution of this equation,the natural frequencies are extracted.Then,to calculate the non-linear frequencies of the plate,the non-linear equation of the plate has been solved analytically using the method of multiple scales.Finally,the effect of some critical parameters of the system,such as the thickness,height,and different angles of the stiffeners on the linear and nonlinear frequencies,has been analyzed in detail.To confirmthe solution method,the results of this research have been compared with the reported results in the literature and finite elements in ABAQUS,and a perfect match is observed.The results reveal that the geometry and configuration of core ribs strongly affect the natural frequencies of the plate.
文摘Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emphasis on structural durability and monitoring is required.This study focuses on the mechanical vibrations that occur in rotary drilling systems,which have a substantial impact on the structural integrity of drilling equipment.The study specifically investigates axial,torsional,and lateral vibrations,which might lead to negative consequences such as bit-bounce,chaotic whirling,and high-frequency stick-slip.These events not only hinder the efficiency of drilling but also lead to exhaustion and harm to the system’s components since they are difficult to be detected and controlled in real time.The study investigates the dynamic interactions of these vibrations,specifically in their high-frequency modes,usingfield data obtained from measurement while drilling.Thefindings have demonstrated the effect of strong coupling between the high-frequency modes of these vibrations on drilling sys-tem performance.The obtained results highlight the importance of considering the interconnected impacts of these vibrations when designing and implementing robust control systems.Therefore,integrating these compo-nents can increase the durability of drill bits and drill strings,as well as improve the ability to monitor and detect damage.Moreover,by exploiting thesefindings,the assessment of structural resilience in rotary drilling systems can be enhanced.Furthermore,the study demonstrates the capacity of structural health monitoring to improve the quality,dependability,and efficiency of rotary drilling systems in the petroleum industry.
文摘A three-dimensional(3D)analytical formulation is proposed to put together magnetic,electric and elastic fields to analyze the vibration modes of simply-supported layered piezo-electro-magnetic plates.The present 3D model allows analyses for layered smart plates in both open-circuit and closed-circuit configurations.The secondorder differential equations written in the mixed curvilinear reference system govern the magneto-electro-elastic free vibration problem for multilayered plates.This set consists of the 3D equations of motion and the 3D divergence equations for the magnetic induction and electric displacement.Navier harmonic forms in the planar directions and the exponential matrix method in the transversal direction of the plate are applied to solve the second-order differential equations in terms of displacements.For these reasons,simply-supported boundary conditions are considered.Imposition of interlaminar continuity conditions on primary variables(displacements,magnetic potential,electric potential),and some secondary variables(transverse normal and transverse shear stresses,transverse normal magnetic induction/electric displacement)allows the implementation of the layer-wise approach.Assessments for both load boundary configurations are proposed in the results section to validate the present 3D approach.3D electro-elastic and 3D magneto-elastic coupling validations are performed separately considering different models from the open literature.A new benchmark involving a full magneto-electro-elastic coupling for multilayered plates is presented considering both load boundary configurations for different thickness ratios.For this benchmark,circular frequency values and related vibration modes through the transverse direction in terms of displacements,magnetic and electric potential,transverse normal magnetic induction/electric displacement are shown to visualize the magneto-electroelastic coupling and material and thickness layer effects.The present formulation has been entirely implemented in an academic Matlab(R2024a)code developed by the authors.In this paper,for the first time,the second-order differential equations governing the magneto-electro-elastic problem for the free vibration analysis of plates has been solved considering the mixed mode of harmonic forms and exponential matrix.The exponential matrix permits computing the secondary variable of the problem(stresses,electric displacement components and magnetic induction components)exactly,directly from constitutive and geometrical equations.In addition,the very simple and elegant formulation permits having a code with very low computational costs.The present manuscript aims to fill the void in open literature regarding reference 3D solutions for the free vibration analysis of magneto-electro-elastic plates.
基金the Shanghai Educational Sciences Research Program(No.C2021016)。
文摘The proposed mass model of vocal fold vibration holds a significant importance in the auxiliary diagnosis and treatment of human vocal fold disorders.Mathematical models are proposed in aerodynamics and acoustics to simulate vocal fold vibration during phonation.This has always been a hot topic in pathological linguistics research.Over the past few decades,researchers have designed various types of mass models of vocal fold vibration based on experiments.These models differ in principles,computational complexity,and degrees of freedom.Therefore,we classify and describe the mass models according to modeling methods.We summarize the research status and characteristics of different models,and based on this,we look forward to future research directions for vocal fold mass models.
基金supported in part by the Major Key Project of PCL of China(No.PCL2024A01)in part by the National Natural Science Foundation of China(Nos.62071141,62027802)+1 种基金in part by the Shenzhen Science and Technology Program of China(Nos.JCYJ20241202123904007,GXWD20231127123203001,JSGG20220831110801003)in part by the Fundamental Research Funds for the Central Universities of China(No.HIT.OCEF.2024046)。
文摘Mega Low Earth Orbit(LEO)satellite constellations can provide pervasive intelligent services in the forthcoming Six-Generation(6G)network via the Free-Space Optical(FSO)InterSatellite Link(ISL).However,the challenges posed by the mega LEO satellite constellations,such as limited onboard resources,high-speed movement and the vibration of satellite platforms,present significant obstacles for the existing Pointing,Acquisition and Tracking(PAT)schemes of FSOISL.To address these challenges,we propose a beaconless PAT scheme under satellite platform vibrations,employing a composite scanning approach combining an inner Archimedean spiral scan with an outer regular hexagon step scan.The proposed composite scanning approach covers a wide range of the Field of Uncertainty(FOU)and reduces the required scans by actuator,which can ensure a high Acquisition Probability(AP)while reducing the Average Acquisition Time(AAT)for the inner scan.Specifically,we model and analyze the effect of satellite platform vibrations on the acquisition performance of our beaconless PAT scheme,and derive closed-form expressions for both AP and AAT by utilizing a 2-track model where the acquisition happens on two adjacent spiral scan tracks.By utilizing the theoretical derivations,we can achieve a minimum AAT under diverse APs by selecting appropriate values of overlapping region and scanning range.Simulation results validate that our optimized composite scanning approach for beaconless PAT scheme outperforms the existing schemes.
基金funded by research grant OPUS no.2021/41/B/ST8/02432 entitled Probabilistic entropy in engineering computations sponsored by The National Science Center in Polandthe Institute of Structural Analysis of Poznan University of Technology in the framework of the internal research grant 0411/SBAD/0010.
文摘The analysis of the dynamics of surface girders is of great importance in the design of engineering structures such as steel welded bridge plane girders or concrete plate-column structures.This work is an extension of the classical deterministic problem of free vibrations of thin(Kirchhoff)plates.Themain aim of this work is the study of stochastic eigenvibrations of thin(Kirchhoff)elastic plates resting on internal continuous and column supports by the Boundary Element Method(BEM).This work is a continuation of previous research related to the random approach in plate analysis using the BEM.The static fundamental solution(Green’s function)is applied,coupled with a nonsingular formulation of the boundary and domain integral equations.These are derived using a modified and simplified formulation of the boundary conditions,inwhich there is no need to introduce theKirchhoff forces on a plate boundary.The role of the Kirchhoff corner forces is played by the boundary elements placed close to a single corner.Internal column or linear continuous supports are introduced using the Bezine technique,where the additional collocation points are introduced inside a plate domain.This allows for significant simplification of the BEM computational algorithm.An application of the polynomial approximations in the Least Squares Method(LSM)recovery of the structural response is done.The probabilistic analysis will employ three independent computational approaches:semi-analytical method(SAM),stochastic perturbation technique(SPT),and Monte-Carlo simulations.Numerical investigations include the fundamental eigenfrequencies of an elastic,thin,homogeneous,and isotropic plate.
基金supported by the Key Basic and Applied Research Program of Guangdong Province,China(Grant No.2019B030302010)the NSF of China(Grant Nos.52122105,52271150,52201185,52201186,52371160)+1 种基金the Science and Technology Innovation Commission Shenzhen(Grants Nos.RCJC20221008092730037,20220804091920001)the Research Team Cultivation Program of Shenzhen University,Grant No.2023QNT001.
文摘To advance materials with superior performance,the construction of gradient structures has emerged as a promising strategy.In this study,a gradient nanocrystalline-amorphous structure was induced in Zr46Cu46Al8 bulk metallic glass(BMG)through ultrasonic vibration(UV)treatment.Applying a 20 kHz ultrasonic cyclic loading in the elastic regime,controllable gradient structures with varying crystallized volume fractions can be achieved in less than 2 s by adjusting the input UV energy.In contrast to tradi-tional methods of inducing structural gradients in BMGs,this novel approach offers distinct advantages:it is exceptionally rapid,requires minimal stress,and allows for easy tuning of the extent of structural gradients through precise adjustment of processing parameters.Nanoindentation tests reveal higher hard-ness near the struck surface,attributed to a greater degree of nanocrystal formation,which gradually di-minishes with depth.As a result of the gradient dispersion of nanocrystals,an increased plasticity was found after UV treatment,characterized by the formation of multiple shear bands.Microstructural in-vestigations suggest that UV-induced nanocrystallization originates from local atomic rearrangements in phase-separated Cu-rich regions with high diffusional mobility.Our study underscores the tunability of structural gradients and corresponding performance improvements in BMGs through ultrasonic energy modulation,offering valuable insights for designing advanced metallic materials with tailored mechanical properties.
基金Project supported by the National Natural Science Foundation of China(No.12472003)the Key Research Project of Zhejiang Market Supervision Administration(No.ZD2024013)the Technical Project of Research Institute of Highway Ministry of Transport of China(No.0225KF12SC1002)。
文摘Moving-load induced vibrations can,in certain instances,exceed those caused by equivalent static loads,especially at the critical velocity of moving loads.Suppressing these vibrations is of critical practical importance in various engineering fields,including the design of precision robotics and advanced aerospace structures where components are subject to moving loads.In this paper,an inertial nonlinear energy sink(NES)is used for the first time to reduce the vibration response of graphene platelet(GPL)-reinforced nanocomposite beams with elastic boundaries under moving loads.Based on the von Kármán nonlinear theory,the governing equations of the beam-NES system are derived using the Lagrange equation.The Newmark-Newton method,in conjunction with the Heaviside step function,is used to obtain the nonlinear responses of the beam under moving loads.The effects of the boundary spring stiffness,the GPL parameters,as well as the velocity and frequency of the moving loads on the beam response and the performance of the NES are thoroughly studied.The results of this work provide insights into applying NESs to suppress the nonlinear vibrations induced by moving loads in composite structures with elastic boundaries.
