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Large‐scale fatigue testing is very important to the research on scale effects, which occur in large cyclic loaded structures, such as wind turbine towers. However, such experimental testing has a very high energy consumption. As an efficient alternative, this paper presents a new resonant testing facility for large‐scale specimens under cyclic bending loads. The facility works as a 4‐point bending test, in which the specimen is supported in the nodes of its first normal bending mode, where theoretically no reaction forces occur. Two counter‐rotating imbalance motors with excitation frequencies near resonance generate a harmonic force acting on the specimen. Experimental trial fatigue tests on a steel pipe as a specimen were carried out, in order to validate the new testing setup. A great decrease in the support forces was reached by placing the supports at the normal mode nodes. Additionally, the behavior of the support forces under varying positions and excitation frequencies was also investigated. In summary, the resonant testing method combined with the supports at the normal mode nodes offers an efficient and energy‐saving testing setup for large‐scale fatigue tests. [ABSTRACT FROM AUTHOR]

The aspect of resonant vibrations due to pedestrian movement is of great significance in engineering practice. Therefore, understanding the variations in the natural frequency of bridge structures under varying positions of additional mass is of particular interest. This paper presents a procedure for the straightforward determination of the natural frequencies of a beam pedestrian bridge for various positions of pedestrians or a service vehicle based on derived analytical solutions. The calculation takes into account the inertial effects of the additional load mass, modeled as either uniformly distributed or concentrated. The importance of additional load mass effects on the fundamental frequency of a beam pedestrian bridge and its dynamic response to a moving pedestrian load is demonstrated on a bridge example. The proposed solutions are also applicable to other girder system structures with uniform mass and stiffness along their span. [ABSTRACT FROM AUTHOR]

The nonlinear resonance between the saturated inductance of a transformer and capacitance of the switching device in a substation induces overvoltages and overcurrents. The voltage transformer experience 2–4 pu overvoltages due to the different modes of nonlinear resonance. Though many overvoltage suppression circuits are being proposed, the transformer does not have a single suppression circuit against all modes. A memristor-based suppression circuit has been proposed already for the fundamental (periodic) mode of ferroresonance. In this paper, an aperiodic mode of ferroresonance has been addressed with same memristive circuit along with meminductive circuit. A subharmonic mode of ferroresonance overvoltage of 3.13 pu has been induced in a (400 kV/ √ 3 )/(110 V/ √ 3 ) CVT model according to IEC 61869 -5 standards. The primary current got increased from 23.3 mA to 1.56 A and has subharmonic frequency components. A meminductor circuit is proposed as a suppression circuit against ferroresonance for a Substation CVT. A gas discharge lamp T8 Philips 18 W with low-frequency magnetic ballast emulated peculiar pinched hysteretic characteristics of a memristor. The relation between charge and flux termed as memristance of the memristor circuit is used to mitigate the nonlinear resonance oscillations. A mutator circuit for mitigation requirement has been connected to the lamp model to emulate meminductor characteristics. The mitigation performance shows that the meminductor circuit dominantly recovers the secondary voltage of CVT in 0.188 s with a reduction of 1/3rd, 1/5th, and 1/7th harmonic components by 35.4%, 78.15%, and 90.41%, respectively. [ABSTRACT FROM AUTHOR]

In contemporary construction, the prevalence of vibration serviceability issues in lightweight and slender structures has become increasingly common, owing to advancements in building materials and construction methods. While these structures often meet the criteria for ultimate limit states, they can still elicit complaints due to excessive vibrations induced by human activity. To address this challenge, the integral resonant control (IRC) technique has emerged as a favored approach for actively damping vibrations in various systems. This study introduces a fresh perspective by proposing the implementation of a multi-input multi-output (MIMO) IRC scheme for active vibration control (AVC) specifically tailored for pedestrian structures utilizing inertial mass actuators. This application of MIMO IRC for AVC represents a novel advancement in the field, offering a new solution to address vibration issues in lightweight and slender structures. Building upon a common framework and design methodology outlined in previous research, this work presents a novel application of MIMO IRC for AVC. The designed controller undergoes rigorous testing and is implemented on a laboratory floor structure to validate its efficacy. The outcomes of this study demonstrate the effectiveness of the proposed MIMO IRC scheme in actively damping vibrations, thereby enhancing the serviceability and comfort levels of lightweight and slender structures subjected to human-induced excitations. [ABSTRACT FROM AUTHOR]

The paper deals with the problem of obtaining a given dynamic behavior of simply supported bridge beams from the impact of rolling stock. Resonant vibrations of beams become a reality at high speeds if the train is formed of identical cars, which is typical for passenger trains. The phenomenon of suppression of beam vibrations by a train, known from publications, is possible only with an exact ratio of the length of the car and the beam. This significantly reduces the possibilities of choosing the necessary spans of beams. Consideration of issues of interaction in the "bridge–track—train" system for security purposes requires the involvement of a rather complex mathematical apparatus and appropriate software. The paper proposes a new method for determining the specified dynamic behavior of bridge beams, suitable for any spans and available to engineers at the stage of pre-design assignment of dynamic parameters of beams. The requirements that are necessary and sufficient conditions for preventing the resonance of bridge beams on the HSR are determined. At the same time, it does not require the involvement of software based on a complex mathematical technique. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental modal analysis of a beam covered by polymer materials used as a passive vibration isolation. The main aim of this study was to determine the damping properties of selected viscoelastic materials. In order to check the damping properties of tested materials, an experimental modal analysis, with the use of an electrodynamic vibration system, was performed. In this study, four kinds of specimens were considered. In the first step of the work, the beam made out of aluminum alloy was investigated. Afterwards, a cantilever beam was covered with a layer of bitumen-based material acting as a damper. This method is commonly known as a free layer damping treatment (FLD). In order to increase the damping capabilities, the previous configuration was improved by fixing a thin aluminum layer directly to the viscoelastic core. Such a treatment is called constrained layer damping (CLD). Subsequently, another polymer (butyl rubber) in the CLD configuration was tested for its damping properties. As a result of the performed experimental modal analysis, the frequencies of resonant vibrations and their corresponding amplitudes were obtained. The experimental results were used to quantitatively evaluate the damping properties of tested materials. [ABSTRACT FROM AUTHOR]

The subsynchronous oscillation caused by the resonance between power electronic devices and series compensation devices or weak power grids introduced by large-scale renewable energy generation greatly reduces the transmission capacity of the system and may endanger the safe operation of the power system. It even leads to system oscillation instability. In this paper, based on the advantages of a simple solution, a small amount of calculation and anti-noise of ERA, a method of subsynchronous oscillation parameter identification based on the eigensystem realization algorithm (ERA) is proposed. The Hankel matrix in the improved ERA is obtained by splicing the real part matrix and the imaginary part matrix of the synchrophasor, thus solving the problem of angular frequency conjugate constraints of two fundamental components and two oscillatory components which are not considered in the existing ERA. The solution to this problem is helpful to improve the accurate parameter identification results of ERA under the data window of 200 ms and weaken the limitation caused by the assumption that the synchrophasor model is fixed. The practicability of the improved method based on PMU is verified by the synthesis of ERA and the actual measurement data. Compared with the existing ERA, the improved ERA can accurately identify the parameters of each component under the ultra-short data window and realize the dynamic monitoring of power system subsynchronous oscillation. [ABSTRACT FROM AUTHOR]

In this work, a dynamic model considering time-varying mesh stiffness and backlash was proposed and a test rig was built to investigate the vibration behavior of the idle gear set in a gerotor pump. The effects of input shaft speed, torque fluctuation, and gear tooth backlash on the dynamic performance of gerotor pump were analyzed according to the numerical and experimental results. Results demonstrate that when the torque fluctuation is neglected, the dynamic transmission error of drive gear is dominated by the first three mesh harmonic components; however, the RMS values of vibration acceleration have high frequency characteristics. When the torque fluctuation is considered, the dynamic responses of gerotor pump are modulated by the torque fluctuation. The effect of tooth backlash on the dynamic performance of gerotor pump is limited and mostly depended on the torque fluctuation condition. The gerotor pump noise is dominated by the low frequency component around the mesh frequency. The vibration energy can be divided into two parts in the frequency domain. In the low frequency band, the vibration energy is caused by the mechanical vibration. However, in the high frequency band, the cavitation phenomena may cause the concentration of the vibration energy and resonant of pump structure. [ABSTRACT FROM AUTHOR]

The levered-dual response (LEDAR) Coulomb-damped system attains near resonant vibration isolation by differential preloads/offsets in linear springs. It takes the advantages of both the preloads/offsets in linear springs and the guiderail friction for realizing different levels of vibration isolation. The isolation capacities are investigated on the strategies with both the horizontal and vertical guiderails, with the horizontal rail only, and without guiderails. The compressive preloads generally result in the consumption of most of the initial excitation energy so as to overcome the potential threshold. The isolation onsets at the frequency ratio of 1 ∓ 0.095 on the left-hand side (LHS) and the right-hand side (RHS) of the lever are relative to the load plate connector. The observed near resonant isolation thus makes the LEDAR system a candidate for the isolation of the mechanical systems about resonance while opening a path for simultaneous harvester-isolation functions and passive functions at extreme frequencies. [ABSTRACT FROM AUTHOR]

The safe and stable operation of the transformer is the key to ensure the reliable operation of the power grid. Loose windings will produce a vibration acceleration signal with twice the power supply frequency signal, i.e., 100 Hz, as the main spectral component. The realization of transformer winding vibration acceleration detection can effectively determine the operating status of the transformer winding. In this report, a dual-cantilever beam Fiber Bragg Grating (FBG) vibration acceleration sensor for transformer winding with a two-point package structure was designed based on theoretical analysis and finite element simulation of COMSOL Multiphysics software. Through the demodulation of the center wavelength change to achieve the detection of external vibration acceleration and to achieve the vibration acceleration sensitivity of 37.813 pm/g at 100 Hz, linearity up to 99.97%, cross-sensitivity is less than 17.4%. The resonant frequency of the sensor is 134 Hz, and the sensitivity of the vibration acceleration at the resonant frequency point is 425.52 pm/g. The sensor is installed under the transformer to measure the vibration acceleration of the transformer winding. The vibration component under 100 Hz frequency could be obviously captured, and the FFT of the center wavelength captured the amplitude signal to realize the measurement of the vibration acceleration of the transformer winding less than 0.02 g micro-vibration acceleration, which could satisfy the general vibration range of the transformer winding. [ABSTRACT FROM AUTHOR]

A top-down design methodology and implementation of a time domain sensor is presented in this paper. The acceleration resolution of the time domain sensor is equal to the time-measurement accuracy divided by the sensor sensitivity. Combined with the sensitivity formula, the acceleration resolution is proportional to the vibration amplitude, the time-measurement accuracy, and the third power of the resonant frequency. According to the available time-measurement accuracy and the desired acceleration resolution, the parameters including the vibration amplitude and the resonant frequency were theoretically calculated. The geometrical configuration of the time domain sensor device was designed based on the calculated parameters. Then, the designed device was fabricated based on a standard silicon-on-insulator process and a matched interface circuit was developed for the fabricated device. Experimental results demonstrated that the design methodology is effective and feasible. Moreover, the implemented sensor works well. In addition, the acceleration resolution can be tuned by adjusting the time-measurement accuracy and the vibration amplitude. All the reported results of this work can be expanded to other time domain inertial sensors, e.g., a gyroscope or tilt sensor. [ABSTRACT FROM AUTHOR]

The application of nonlinear vibration absorbers in a variety of dynamic systems is attracting significant attention. The so-called nonlinear energy sink (NES) has the ability to provide high vibration attenuation in a broad frequency with robustness. However, the effectiveness of this device can be limited with the increase of excitation, as it may induce high amplitude (i.e., detach zone) oscillation and leading to sudden failure. To address these limitations, this work proposes an investigation into an electromagnetic-enhanced nonlinear energy sink (NES-EH) aiming to combine hybrid vibration control and energy harvesting. The device comprises the conventional NES, with a cubic stiffness spring, coupled with a magnet-coil assembly. The electro-magneto-mechanical coupling provides nonlinear damping dynamics allowing mitigation of the detached zone and an efficient conversion of the absorbed energy into electrical power. Two different assemblies, varying the relative static position of the magnet coil, are considered to explore alternative nonlinear damping models. The harmonic balance method is used to build analytical solutions to characterize the dynamics of coupled systems. After a numerical validation of the analytical approach, a complete characterization of the system dynamics is performed regarding frequency-response and slow invariant manifold (SIM) curves. Parametric analysis and optimization procedure are employed to design the NES-EH parameters. The performance of the designed absorber is compared with the classical NES solution, and their robustness is also investigated. [ABSTRACT FROM AUTHOR]

A theoretical approach was applied to study the vibration of simple-supported submerged horizontal plate. The derived analytical solution was used to determine natural frequencies for a horizontal plate vibrating in fluid. The investigations were conducted for a very wide range of material density and elasticity modulus covering all materials used in engineering practice. Analysis shows that plate vibration frequency decreases with increasing plate width and draft, and decreases with decreasing plate thickness. Moreover, the results show that a substantial effect on vibration of submerged plate has mass of water above plate. The results also show that plate vibration frequency decreases with increasing plate material density and decreases with decreasing elasticity modulus. The dominant factors affecting the vibration of the submerged plate are the plate width, the plate thickness, and elasticity modulus. For moderate and low values of elasticity modulus, vibration frequency is becoming lower than frequency of water waves. This is very important because wave frequencies overlap with the natural plate vibration frequencies, which may lead to resonance and failure of a structure. The problem is that the overlap of plate vibration frequencies and wave frequencies occurs for very wide range of wave and plate parameters. Laboratory experiments confirm theoretical results. [ABSTRACT FROM AUTHOR]

Enhancement of the small- and large-signal modulation performance of wavelength tunable laser diode (TLD) transmitters under strong optical injection locking (OIL) is investigated numerically in back-to-back and optical-fiber transmission schemes. Our model is based on the spatiotemporal description of laser dynamics as due to the composite cavity design of TLDs, the usual rate equation formalism is not directly applicable. We demonstrate that TLD transmission strongly depends on wavelength tuning, which was investigated over a 21-nm range between 1529 and 1550 nm emission wavelengths. The best performance for both free-running (FR) and OIL TLDs is achieved at shorter wavelengths, 1529 nm for our device. Although in both cases this is due to larger differential material gain at shorter wavelengths, the underlying physics of the effect is completely different. For an FR TLD, it is the resonance oscillation frequency (ROF) that defines the best modulation speed, while for an OIL TLD, the achievable modulation speed depends on the cavity mode shift due to optical injection. Both the ROF and the cavity mode shift increase when the differential gain increases. However, the ROF is the device's fixed parameter, while the cavity mode shift is defined by the OIL conditions, and thus, it can be optimized. The superior performance of the optical fiber digital data transmission with the OIL TLD is demonstrated at around 20-Gb/s modulation speed for standard fibers. This result is attributed to an enhanced modulation response and suppressed frequency chirping of the OIL TLD, and it is important for practical utilization of TLD transmitters. [ABSTRACT FROM AUTHOR]

The regulation of mass is essential for the development and homeostasis of cells and multicellular organisms. However, cell mass is also tightly linked to cell mechanical properties, which depend on the time scales at which they are measured and change drastically at the cellular eigenfrequency. So far, it has not been possible to determine cell mass and eigenfrequency together. Here, we introduce microcantilevers oscillating in the Ångström range to monitor both fundamental physical properties of the cell. If the oscillation frequency is far below the cellular eigenfrequency, all cell compartments follow the cantilever motion, and the cell mass measurements are accurate. Yet, if the oscillating frequency approaches or lies above the cellular eigenfrequency, the mechanical response of the cell changes, and not all cellular components can follow the cantilever motions in phase. This energy loss caused by mechanical damping within the cell is described by the quality factor. We use these observations to examine living cells across externally applied mechanical frequency ranges and to measure their total mass, eigenfrequency, and quality factor. The three parameters open the door to better understand the mechanobiology of the cell and stimulate biotechnological and medical innovations. There is increasing interest in measuring the mechanical properties of living cells. Here, the authors develop a method to simultaneously measure the cell mass and two parameters related to its natural oscillation or resonance frequencies. [ABSTRACT FROM AUTHOR]

Resonators are passive time-invariant components that do not produce a frequency shift. However, they respond to an excitation signal close to resonance with an oscillation at their natural frequencies with exponentially decreasing amplitudes. If resonators are connected to antennas, they form purely passive sensors that can be read remotely. In this work, we model the external excitation of a resonator with different excitation signals and its subsequent decay characteristics analytically as well as numerically. The analytical modeling explains the properties of the resonator during transient response and decay behavior. The analytical modeling clarifies how natural oscillations are generated in a linear time-invariant system, even if their spectrum was not included in the stimulation spectrum. In addition, it enables the readout signals to be optimized in terms of duration and bandwidth. [ABSTRACT FROM AUTHOR]

This paper presents a solution to the problem of forced bending vibrations of a flat rod with two cantilevers and a finite-length fixed region on one of the outer surfaces. The cantilever deformation processes are described using the Timoshenko model with no account for transverse compression and the fixed region: the same deformation model with allowance for transverse compression, modified by considering the presence of an unmoving fixed region. Conditions for the kinematic coupling of the cantilevers and the fixed region are formulated. The Hamilton–Ostrogradsky variational principle serves as a basis for equations of motion, boundary conditions, and force conditions for the coupling of the rod regions. Exact analytical solutions to the equations of motion under the influence of a harmonic transverse force at the end of one of the cantilevers are obtained. The passage of resonant vibrations through a finite-length fixed region in duralumin and fiber composite rods with and without account for the transverse compression of the fixed region is studied in numerical experiments. There is a significant increase in the vibration amplitude of the end of the unloaded cantilever of a duralumin rod due to transverse compression of the fixed region. The vibration amplitude for the composite rod increases slightly. [ABSTRACT FROM AUTHOR]

Controlling robots in space with necessarily low material and structural stiffness is quite challenging at least in part due to the resulting very low structural resonant frequencies or natural vibration. The frequencies are sometimes so low that the very act of controlling the robot with medium or high bandwidth controllers leads to excitation of resonant vibrations in the robot appendages. Biomimetics or biomimicry emulates models, systems, and elements of nature for solving such complex problems. Recent seminal publications have re-introduced the viability of optimal command shaping, and one recent instantiation mimics baseball pitching to propose control of highly flexible space robots. The readership will find a perhaps dizzying array of thirteen decently performing alternatives in the literature but could be left bereft selecting a method(s) deemed to be best suited for a particular application. Bio-inspired control of space robotics is presented in a quite substantial (perhaps not comprehensive) comparison, and the conclusions of this study indicate the three top performing methods based on minimizing control effort (i.e., fuel) usage, tracking error mean, and tracking error deviation, where 96%, 119%, and 80% performance improvement, respectively, are achieved. [ABSTRACT FROM AUTHOR]

The resonance phenomena of a weakly nonlinear, damped, Duffing-van der Pol oscillation is studied analytically and numerically. The methods of multiple scales is used to obtain uniformly valid asymptotic approximate solutions of the governing equation for various cases of primary harmonic resonance, super-harmonic resonance and sub-harmonic resonance respectively. The study shows that the steady amplitudes in the solutions of the nonlinear equation demonstrate the nonlinear phenomena involving jump and bistability at some bifurcation points. The quantitative relations of Frequency-Amplitude involving the parameters of damping, nonlinear, external force in the oscillator are obtained. The asymptotic approximation and numerical solutions are in vertically perfect agreement for all the cases considered. The results enrich previous researches just for Duffing or van der Pol oscillation respectively. [ABSTRACT FROM AUTHOR]

• A novel non-resonant harmonic piezoelectric motor is proposed. • The electromechanical coupling dynamic models and equations of the proposed non-resonant piezoelectric motor are developed. • The influence of parameters on natural frequency and resonant response is analyzed. • The natural frequencies of the motor are tested by building an experimental platform. Most of the traditional piezoelectric motors are driven by the resonance of piezoelectric ceramics and can achieve a large output torque. However, these motors also have the defects of high speed and difficulty to adjusting the speed when working. To overcome these issues, a novel non-resonant harmonic rotary piezoelectric motor operating at low speed is presented. Electromechanically coupled vibration has a great influence on the dynamic performance of the piezoelectric motor, which may lead to instability of the output performance of the motor. Therefore, the electromechanical coupling dynamic characteristics of the proposed non-resonant piezoelectric motor are studied in this paper. The working principle of the motor is illustrated, and the electromechanical dynamic model and nonlinear dynamic equations are established. Utilizing the dynamic equations, the coupled natural frequencies, amplitude-frequency characteristics, and dynamic responses of the motor are developed. Meanwhile, the influence of parameters on natural frequency and nonlinear response is analyzed. What's more, the natural frequencies of the system are tested by building an experimental platform. Results show the minimum coupled natural frequency of the motor is 11231 rad/s. The length of the piezoelectric stack, the length, and mass block of the harmonic rod have an important influence on the natural frequency of the proposed non-resonant harmonic piezoelectric motor. The nonlinear piezoelectric effect has a larger effect on the forced response amplitude when the excitation frequency is far away from resonance, but a smaller effect on the forced response amplitude when the excitation frequency is near resonance. What's more, the maximum error between the theoretical natural frequencies and the test frequencies is 3%, which verifies the correctness of the theoretical model. [ABSTRACT FROM AUTHOR]

Periodic monitoring of large industrial and civil structures is carried out through static and dynamic measurements. The monitoring, carried out over many years, offers important information for evaluating the health of structures and their management. Dynamic tests are carried out starting from measurements of the vibrations of the structure induced by mechanical devices or by the surrounding environment. If a ground support element is available, it is possible to exert a forcing action on the structure using actuators fixed to the support. When a ground support is unavailable, the structure can be forced using devices comprised of masses with rotary or reciprocating translational motion. These masses must be large enough to excite appreciable mechanical vibrations of the structure. In this paper, a vibration exciter, based on a mass suspended on an air spring and forced to vibrate at the resonant frequency, is proposed. Thanks to the resonant condition, the force transmitted to the structure is amplified compared to that applied to the mass. The excitation frequency can be adjusted by altering the inflation pressure of the air spring to modify the natural frequency of the system. In the paper, after the presentation of some mechanical devices used as vibration exciters for large structures, the proposed device is described and the first experimental results are reported. [ABSTRACT FROM AUTHOR]

In this paper, transient dynamic responses and frequency characteristics of a rotating internally connected laminated piezoelectric beam are analyzed and studied. Since the beam is compressed by the centrifugal force, frequencies decrease with the increase in the rotating speed (and centrifugal force), which can be called as the dynamic softening effect. When the frequency of increasing speed is gradually close to the decreasing the first frequency, the system resonance will occur. Nevertheless, the resonant rotating speed was rarely accurately calculated in the previous studies owing to ignoring the foreshortening effect that plays a significant role in the dynamic softening. To this end, a novel dynamic model of rotating internally connected laminated piezoelectric beams is developed. In this model, constitutive equations for metallic and piezoelectric material are considered, and the axial shortening displacement caused by the bending deformation is calculated for the foreshortening effect. The buckling rotating speeds obtained from the presented model show good agreement with those presented by the research considering the foreshortening effect, which well validates the model. Several examples are presented for investigating effects of radius, foreshortening effect, rotating speed on transient dynamic responses and frequency characteristics. The results show that beat and resonant vibrations can be orderly observed when the rotating speed is gradually close to the resonant speed. The resonant rotating speed is smaller than the buckling one. The simplified model ignoring the foreshortening effect leads to imprecise results including dynamic responses, buckling and resonant speeds. [ABSTRACT FROM AUTHOR]

High-performance internal combustion engines are subject to severe torsional vibrations which result from uneven gas and inertial loads. Fatigue damage occurs if the frequency of these undesired oscillations matches the resonance frequency of the crankshaft and the driven engine elements. This phenomenon can be avoided by the application of visco-dampers whose working fluid is high-viscosity silicone oil. Since silicone oil is exposed to a significant amount of heat load during operation, it is essential to calculate the temperature distribution in a relatively easy, quick, and cost-efficient way for lifetime estimation purposes. The aim of this article is to develop a reliable, fast, and accurate finite difference-based numerical method for steady-state thermal calculations for arbitrary damper sections. The developed MATLAB code calculates the temperature field of the damping fluid together with all components in a radial cross-section at given operational conditions. The accuracy of the developed thermal calculation method has been tested in a 3-dimensional – 2-dimensional two-step verification process by finite element and finite volume-based advanced engineering software in ANSYS environment. Furthermore, the original Iwamoto equation available in the literature has been updated to provide more accurate surface temperature results based on the simulations' outcome gained by the finite volume method. [ABSTRACT FROM AUTHOR]

A popular dynamical model for the vortex induced vibration (VIV) of a suspended flexible cable consists of two coupled equations. The first equation is a partial differential equation governing the cable vibration. The second equation is a wake oscillator that models the lift coefficient acting on the cable. The incoming wind acting on the cable is usually assumed as the uniform wind with a constant velocity, which makes the VIV model be a deterministic one. In the real world, however, the wind velocity is randomly fluctuant and makes the VIV of a suspended flexible cable be treated as a random vibration. In the present paper, the deterministic VIV model of a suspended flexible cable is modified to a random one by introducing the fluctuating wind. Using the normal mode approach, the random VIV system is transformed into an infinite-dimensional modal vibration system. Depending on whether a modal frequency is close to the aeolian frequency or not, the corresponding modal vibration is characterized as a resonant vibration or a non-resonant vibration. By applying the stochastic averaging method of quasi Hamiltonian systems, the response of modal vibrations in the case of resonance or non-resonance can be analytically predicted. Then, the random VIV response of the whole cable can be approximately calculated by superimposing the response of the most influential modal vibrations. Some numerical simulation results confirm the obtained analytical results. It is found that the intensity of the resonant modal vibration is much higher than that of the non-resonant modal vibration. Thus, the analytical results of the resonant modal vibration can be used as a rough estimation for the whole response of a cable. [ABSTRACT FROM AUTHOR]

Thin-shell models offer important insights into the complex process of sound-structure interaction but are found to be inconsistent with the rigorous thick-shell theory for fluid-loaded spherical shells. Here, linearized equations of motion of fluid-loaded, thin, spherical shells are re-derived from the first principles. The shell may be prestressed due to the difference in the static pressures in the internal and external fluids. Differences in the fluid-loading terms from previously proposed ad hoc models are identified and their significance is analyzed. Analytic solutions are derived of the problems of spherical sound wave scattering by a fluid-filled, prestressed spherical shell and resonant vibrations of the shell. The results reduce to a number of known exact and asymptotic solutions in appropriate limiting cases. The mathematical model of the shell vibrations is applied to characterize the influence of the shell's material properties and the prestress on passive suppression of low-frequency underwater sound radiation due to diffraction on an acoustically compliant sphere, such as an encapsulated gas bubble. Using soft rubber as the encapsulating membrane is found to preserve the sound suppression qualities of the free gas bubble. [ABSTRACT FROM AUTHOR]

The keV scale sterile neutrino was a qualified candidate for dark matter particles in the Dodelson-Widrow mechanism. But the mixing angle, needed to provide enough amount of dark matter, is in contradiction with the astrophysical observations. To alleviate such tension, we introduce an effective interaction, i.e. g a (ϕ / Λ) ∂ μ a ν α ¯ γ μ γ 5 ν α , among Standard Model neutrino ν α , axion a, and singlet ϕ . The axial-vector interaction form is determined by the axion shift symmetry, and the singlet ϕ with dynamically varied vacuum expectation value is introduced to reinforce the axial-vector coupling strength and evade the stringent neutrino oscillation constraints. The effective potential generated by the new interaction could cancel the SM counterpart, resulting in an enhanced converting probability between SM neutrino and sterile neutrino. Hence, the production rate of sterile neutrinos can be substantially enlarged with smaller mixing compared to the DW mechanism. [ABSTRACT FROM AUTHOR]

We study the three-dimensional Morris–Lecar–Terman neuron model in the parametric region of tonic spiking oscillations close to the bifurcation of the torus birth. It is shown that in this region random disturbances can induce switching to the toroidal bursting mode from the tonic spiking regime. We approximate the probability of such switches as well as analyze temporal characteristics of produced oscillations. Moreover, we indicate a coherence resonance in the stochastic bursting regime and reveal the underlying reasons of these noise-induced phenomena. [ABSTRACT FROM AUTHOR]

This article presents a comparison of test results from two models of anti-vibration systems (I and II) made employing MJF 3D printing technology and two different materials. The research included laboratory tests and numerical simulations, assuming a linear nature of the mechanical properties for the materials and models of structures. The aim of this research was to assess the consistency between laboratory test and numerical simulation results. In addition, evaluation of the suitability of using MJF technology to produce antivibration systems was conducted. During the laboratory tests, the response of the two models of structures to vibrations generated by an exciter was recorded using a high-speed camera. Subsequent image analysis was performed using the MOVIAS Neo software. The obtained values of vibration displacements and resonant frequencies were used to validate the numerical model created in the Simcenter Femap software. Relative differences between the values of resonant frequencies obtained experimentally and through simulations were determined. In the case of the structural model I, creating its numerical model without considering the nonlinearity of mechanical parameters was found to be unjustified. The comparison of the displacements determined during numerical simulations showed relative differences of less than 16% for both models in relation to the laboratory test results. This comparison result indicates a satisfactory accuracy in simulating this parameter. An assessment of the quality and accuracy of MJF technology-produced prints, led to the conclusion that due to the formation of internal stresses during the print creation, the use of "soft" materials in this technology is problematic. [ABSTRACT FROM AUTHOR]

A single transistor preamplifier circuit was designed to facilitate electrical detection of mechanical oscillations in nanoelectromechanical systems (NEMSs) at low temperatures. The amplifier was integrated in the close vicinity of the nanowire inside the cryostat to minimize cabling load and interference. The function of the circuit was impedance conversion for current flow measurements in NEMSs with a high internal resistance. The circuit was tested to operate at temperatures as low as 5 K and demonstrated the ability to detect oscillations in double-clamped bismuth selenide nanowires upon excitation by a 0.1 MHz–10 MHz AC signal applied to a mechanically separated gate electrode. A strong resonance frequency dependency on temperature was observed. A relatively weak shift in the oscillation amplitude and resonance frequency was measured when a DC bias voltage was applied to the gate electrode at a constant temperature. [ABSTRACT FROM AUTHOR]

Detailed analysis of kinematics of the Milky Way disk in the solar neighborhood based on the GAIA DR3 catalog reveals the existence of peculiarities in the stellar velocity distribution perpendicular to the galactic plane. We study the influence of resonances—the outer Lindblad resonance and the outer vertical Lindblad resonance—of a rotating bar with stellar oscillations perpendicular to the plane of the disk, and their role in shaping the spatial and the velocity distributions of stars. We find that the Z and V Z distributions of stars with respect to L Z are affected by the outer Lindblad resonance. The existence of bar resonance with stellar oscillations perpendicular to the plane of the disk is demonstrated for a long (large semi-axis 5 kpc) and fast rotating bar with Ω b = 60.0 km s − 1 kpc − 1 . We show also that, in the model with the long and fast rotating bar, some stars in the 2:1 OLR region deviate far from their original places, entering the bar region. A combination of resonance excitation of stellar motions at the 2:1 OLR region together with strong interaction of the stars with the bar potential leads to the formation of the group of 'escapees', i.e., stars that deviate in R and Z—directions at large distances from the resonance region. Simulations, however, do not demonstrate any noticeable effect on V Z -distribution of stars in the solar neighborhood. [ABSTRACT FROM AUTHOR]

This study focuses on the performance validation of a wave energy converter (WEC) equipped with resonant frequency adjustment capability. Achieving resonance with the oscillation period of waves is crucial for maximizing the efficiency of wave energy conversion systems. For this purpose, we introduce a variable moment of inertia (VMI) device that allows for tuning of the resonant frequency by adjusting the position of the mass. For validation of the proposed approach, performance verification experiments were conducted using a vibration platform. Through free vibration experiments, we identified the system's resonant frequency and characteristics. In our forced vibration tests considering the wave frequency band of the coastal area, harmonic vibration experiments were performed over a range of 0.4–0.8 Hz. In these experiments, we considered three separate cases by adjusting the distance from the reel's center to the mass. As a result, we found that the resonant frequency of the WEC can be adjusted from 0.65 Hz when the mass is furthest away to 0.55 Hz when it is closer. This research confirms the benefits obtained by utilizing VMI to adjust the resonant frequency of WECs without changing the mass or springs. This offers a promising opportunity to enhance the energy conversion efficiency of resonant-type WECs utilizing wave energy. [ABSTRACT FROM AUTHOR]

Determining the resonance frequencies of sediment-filled basins is important in seismic site effects assessment and to infer information about the geometrical and mechanical properties of the basins. Being intrinsic properties of elastic bodies, resonance frequencies are not expected to change over time, at least in the short term and under small excitations, in this type of basins. By analysing multi-annual time-series at some seismic stations located on markedly alpine and subalpine 2-D basins, we first state under what type of exciting function (ambient noise) these resonances can be identified and with what uncertainty. The analysis will reveal a clear annual and daily oscillation of the resonance frequencies, increasing in the summertime and at daytime (i.e. directly correlated with temperature). We attempt to provide different explanations to this not yet so systematically documented experimental evidence. A clear and unique answer is yet to come. [ABSTRACT FROM AUTHOR]

Purpose of the article is to demonstrate that a high-speed electric locomotive, driven by asynchronous motors in a hollow shaft arrangement and swing-out couplings, can generate corrugation conditions on the surface of new and smooth rails on straight and curved track. Most studies carried out in this area is usually concerned with the response of the power train to kinematic excitation from a track where corrugations are already present. The novelty of the look presented in the article is to establish the influence of the vehicle's driveline and the parameters of a perfectly smooth formation track on the mechanism of corrugation. A four-axle EU11 electric locomotive, produced in Poland in the late 1990s, has been selected for analysis. A complete electro-mechanical model of the locomotive was built using the Vi-Rail software and prepared for simulation on straight and curved track. A non-linear model of wheel-rail contact was included and the contact forces were determined for the locomotive model in motion with the active power system. Unbalanced inertia forces generated by the scattering of stiffness characteristics of the coupling links, have been included to the propulsion system as an additional source of dynamic excitations. The complexity of the obtained results was influenced by the fact that simulation studies were carried out in both the time and frequency domains. The results obtained in the time domain were used to calculate the vertical and torsional vibration frequencies with respect to the driving wheelsets. One of the most important results of the simulation studies carried out is the determination of the effect of locomotive acceleration on the frequency of resonant torsional vibrations of the wheelsets in straight and curved track traffic. [ABSTRACT FROM AUTHOR]

For realizing ultrasonic elliptical vibration-assisted cutting, a single excitation elliptical vibration system was proposed in this work, which was composed of a giant magnetostrictive transducer and an asymmetrical stepped ultrasonic horn with arc transition (ASUH). The dynamic simulation of the vibration system was carried out using ANSYS, the output end of the vibration system produced longitudinal and transverse vibrations simultaneously due to the ASUH at the resonant frequency, and the influence of the transition arc of the ASUH on the elliptical vibration performance of the vibration system was studied. The impedance, elliptical vibration trajectory of the output end, and output amplitude of the vibration system were tested experimentally. The results show that the actual resonant frequency of the vibration system was 20.708 kHz, the mechanical quality factor was 106, and the longitudinal amplitude was slightly greater than the transverse amplitude of the output end. The theoretical calculations coincide with the experimentally tested results. [ABSTRACT FROM AUTHOR]

In this study, a plate‐type locally resonant metamaterial (PTLRM) is proposed to control bending vibrations and low‐frequency noise of civil members. Considering the ease of design, installation, and workability, the PTLRM was fabricated using high‐density and soft materials. The PTLRM design includes a resonance frequency calculation of the unit and band gap estimation of the PTLRMs‐coupled structure. Three indicators were developed and experimentally analyzed to evaluate the vibration attenuation performance of the PTLRM: the response suppression in the resonance of PTLRMs, peak response suppression ratio, and distance between peaks. Experimental results of a 5‐m long steel beam with PTLRMs indicated that the bending modal responses of the steel beam were suppressed at frequencies closer to the local resonance of the PTLRM. This showed reasonable agreement with the results of the estimation. The acceleration of the PTLRMs‐coupled beam was reduced by up to 98.58% in the frequency response function. The time history of acceleration also decreased significantly over the entire time period. The damping of the soft material had little effect on the bandwidth of the band gap. However, it was found that a proper increase in the damping of the soft material could increase the vibration suppression performance. [ABSTRACT FROM AUTHOR]

One of the important methods to prevent the intensification of the main vibration system is using a dynamic vibration absorber (DVA). A DVA is a mechanical subsystem used to reduce Vibration amplitude and prevent the main vibration system from resonance. This paper aims to use a nonlinear dynamic absorber as a cantilever beam with a concentrated mass at its end to reduce the amplitude of the intensified oscillator vibration. The primary vibration system consists of mass, nonlinear spring, and viscous damping, and a harmonic excitation force is applied to it, resonance the system. In this case, using a nonlinear dynamic absorber reduces the vibration amplitude. For this purpose, first, the kinetic energy and the potential energy of the vibration system are calculated, and then, using Lagrange equations, the governing equations are extracted. Due to the nonlinearity of the equations of motion, the multiple scales method is used to solve the governing equations. In the results, the effect of nonlinear DVA on reducing the amplitude of intensified oscillator vibration is well visible. The effect of the main parameters of nonlinear dynamic absorbers on the vibration amplitude of the initial system is also investigated. Finally, the vibration amplitude of the system is optimized as a target function by the genetic algorithm method, and the optimal parameters of the nonlinear dynamic absorber and the optimal vibration amplitude are studied. Considering the main resonant vibration system as a structure under earthquake, the results of this research in reducing the vibration amplitude can be widely used in earthquake engineering. [ABSTRACT FROM AUTHOR]

The problem of forced resonant vibrations and dissipative heating of a hinged viscoelastic elastomeric cylindrical shell under preliminary membrane loads is stated. The concept of complex moduli is used to describe the viscoelastic properties of the shell material under harmonic loading. The mechanical stationary and thermal (both stationary and nonstationary) behavior of the shell is studied. The axial distributions of kinematic and force parameters, as well as temperature are plotted. The dependence of the maximum self-heating temperature on the preliminary force was studied. The temperature curves are used to assess the endurance of the shell due to overheating during cyclic loading. The effect of the prestress level on the fatigue endurance of the shell is studied in detail. [ABSTRACT FROM AUTHOR]

Due to current architectural trends, contemporary public buildings are becoming open-plan spaces with much less weight and damping. Consequently, Vibration Serviceability Limit State (VSLS) due to human-induced vibrations has become an increasing concern for structural engineers, especially when designing offices, hospitals, or gymnasiums. When dealing with resonant vibrations, a slight increase in the floor-damping enables decreasing considerably the vibration level. The damping strategy studied in this work is usually known in the literature as Constrained Layer Damping (CLD) and consists of a viscoelastic layer constrained between the concrete slab and the steel beam of a lightweight composite floor. In this paper, a complete structural checking methodology has been developed for analyzing all the limit states that determine the final sizing of a steel–concrete composite floor treated with CLD, including a detailed analysis of the VSLS. The methodology has been used for setting a structural optimization problem for floors with and without CLD treatments. Thus, it has been demonstrated that the integration of CLD treatments at the design stage of the building allows the development of lighter floor structures with a smaller embodied carbon (EC) footprint, especially for long-span schemes with restrictive vibration limitations. [ABSTRACT FROM AUTHOR]

This study modeled the moving-vehicle-induced forcing excitation on a single-span prismatic bridge as a multiple frequency-multiplication harmonic load on the modal coordinates of a linear elastic simple Euler–Bernoulli beam, and investigated the forced modal oscillation and resonance behavior of this type of dynamic system. The forced modal responses consist of multiple frequency-multiplication steady-state harmonics and one damped mono-frequency complementary harmonic. The analysis revealed that a moving load induces high-harmonic forced resonance amplification when the moving speed is low. To verify the occurrence of high-harmonic forced resonance, numerical tests were conducted on single-span simple beams based on structural modeling using the finite element method (FEM) and a moving sprung-mass oscillator vehicle model. The forced resonance amplification characteristics of the fundamental mode for beam response estimation are presented with consideration to different end restraint conditions. The results reveal that the high-harmonic forced resonance may be significant for the investigated beams subjected to vehicle loads moving at specific low speeds. For the investigated single-span simple beams, the moving vehicle carriage heaving oscillation modulates the beam modal frequency, but does not induce notable variation of the modal oscillation harmonic structure for the cases that vehicle of small mass moves in low speed. [ABSTRACT FROM AUTHOR]

Ultracompact and soft pairwise grippers, capable of swift large-amplitude multi-dimensional maneuvering, are widely needed for high-precision manipulation, assembly and treatment of microscale objects. In this work, we demonstrate the simplest construction of such robotic structures, shaped via a single-nanowire-morphing and powered by geometry-tailored Lorentz vectorial forces. This has been accomplished via a designable folding growth of ultralong and ultrathin silicon NWs into single and nested omega-ring structures, which can then be suspended upon electrode frames and coated with silver metal layer to carry a passing current along geometry-tailored pathway. Within a magnetic field, the grippers can be driven by the Lorentz forces to demonstrate swift large-amplitude maneuvers of grasping, flapping and twisting of microscale objects, as well as high-frequency or even resonant vibrations to overcome sticky van de Waals forces in microscale for a reliable releasing of carried payloads. More sophisticated and functional teamwork of mutual alignment, precise passing and selective light-emitting-diode unit testing and installation were also successfully accomplished via pairwise gripper collaborations. This single-nanowire-morphing strategy provides an ideal platform to rapidly design, construct and prototype a wide range of advanced ultracompact nanorobotic, mechanical sensing and biological manipulation functionalities. A single nanowire morphing strategy has been established to construct ultracompact soft robotic grippers, capable of large amplitude multi-dimensional maneuvering and dexterous manipulation of microscale objects, under swift Lorentz forces driving. [ABSTRACT FROM AUTHOR]

A self-supplied circuit that is able to significantly increase the power delivered to a bridge rectifier by a Resonant Piezoelectric Vibration Energy Harvester (RPVEH) is presented and discussed. The proposed circuit, called the Energy Harvester Power Optimizer (EHPO), is implemented by means of a switch-mode converter that emulates a negative capacitance. Unlike switch-mode impedance emulators, based on sophisticated tracking algorithms requiring lossy microcontrollers, EHPO exploits a very light control circuit based on a hysteresis comparator. The EHPO is self-supplied since it does not need an external supply, but it draws the energy for its operation directly from the RPVEH. Moreover, it is developed without the assumption of purely sinusoidal vibrations. Experimental results show that the EHPO can significantly increase the power delivered to a rectifier, both in the case of sinusoidal vibrations (percent gain of the net extracted power up to about 190%) and non-sinusoidal vibrations (percent gain of the net extracted power up to about 245%), regardless of the shape of the forcing acceleration and regardless of the RPVEH resonance frequency. [ABSTRACT FROM AUTHOR]

The paper investigates the design and performance of an active horizontal seat suspension driven by an induction motor, with the aim of reducing harmful vibrations and enhancing energy efficiency. The physical model employs a permanent magnet synchronous motor (PMSM) as a modern actuator to generate the active force. Both passive and active seat suspensions are examined, revealing that the active system significantly reduces resonant vibration by applying electromagnetic torque from an induction motor. The motoring/braking principle is explored, where braking an induction motor returns electric energy to the servo drive system, and regenerative braking is utilized to charge batteries. However, the current regenerative braking system recovers only 3% of power. A novel control design methodology is proposed for the subsequent project to enhance suspension dynamics, attenuate vibrations transmitted to the human body, and minimize energy consumption during operation. The proposed energy-regenerative electromagnetic actuator model, in conjunction with advanced programmable micro-controller algorithms and inverter switching schemes, aims to optimize energy recuperation and vibration energy harvesting in the vibration reduction system. [ABSTRACT FROM AUTHOR]

Dynamic mesh atomizers have been widely used in various fields because of their compact structure, low energy consumption, and low production costs. The finite element method is an important technique to analyze the factors affecting the atomization performance of dynamic mesh atomizers. However, at present, there is a lack of decisive solutions to the basic problems of boundary setting in terms of the simulation and vibration displacement characteristics of atomizers under different vibration modes. In this paper, two errors were found in the Vibration Analysis of a Piezoelectric Ultrasonic Atomizer to Control Atomization Rate paper written by Esteban Guerra-Bravo et al. in 2021. First, in the finite element analysis, the boundary condition of the atomizing sheet was set to be fixed, which is inconsistent with the actual support situation and seriously affects the vibration of the atomizing sheet. Second, in the simulation result, from the first mode to the third mode, the growth rate of the maximum displacement at the center of the atomizing sheet was as high as 77.12%, even up to 221.05%, which is inconsistent with the existing vibration theory. In view of these errors, in this paper, the working principle of dynamic mesh atomizers is analyzed and the vibration equation of the atomizing sheet under peripheral simple support is derived. Through comparison with the literature, it was proven that the boundary setting and vibration displacement of the atomizing sheet in the original paper are unreasonable. By measuring the atomizing rate of the atomizing sheet under different boundary conditions, it was proven that the peripheral freedom of the atomizing sheet should be greater than or equal to 1, namely, peripheral freedom or peripheral simply supported. The vibration displacement theory was used for the simulation, and the relationship between the vibration displacement and resonant frequency of the atomizing sheet under peripheral simple support was measured. It was found that with the increase in the resonance frequency, the maximum displacement of vibration modes with only nodal circles was larger than that of the other vibration modes, and the maximum displacement increased slightly with the increase in the number of nodal circles by about 0.98%. [ABSTRACT FROM AUTHOR]

The problem of electrothermomechanical behavior and durability of inelastic shells of revolution with piezoelectric sensors and actuators under axisymmetric resonance vibrations is stated and a problem-solving method is presented. Numerical experiments for a round plate with a piezoelectric sensor were conducted to study the effect of geometric nonlinearity on the frequency dependences of deflection amplitudes, self-heating temperature, and electrical sensor index. The dependence of the service time of the system on extreme amplitudes of mechanical load and the thermal-transfer conditions on its surface is studied using a criterion of assessing local durability from the maximum self-heating temperature. [ABSTRACT FROM AUTHOR]

The nonlinear vibration reduction in locally resonant cantilever thin plate with multi-frequency periodically distributed resonators is investigated, considering the geometric nonlinearity of the plate. Based on the von Kármán nonlinear plate theory, the strain and kinetic energy of the plated are constructed. The resonators are modeled by discrete mass–spring subsystems. The plate and resonators are combined by implementing their interactions at the connection point. The natural frequencies and modes of the cantilever plate are obtained via the Ritz method with modified characteristic functions in a linear analysis. The problem of nonlinear vibration for the locally resonant plate is discretized into a multi-degree-of-freedom system using the natural modes and Lagrange approach. The effects of multi-frequency periodically distributed resonators on the plate dynamics are demonstrated by studying the amplitude–frequency responses and the bifurcations in conjunction with the maximum Lyapunov exponents of the multi-frequency locally resonant plate. It is demonstrated that the complex nonlinear dynamic behavior of the plate in a specific frequency band can be suppressed by the periodically distributed linear resonators, and the vibration reduction over a wide frequency range can be achieved by appropriately setting the frequencies of the multi-frequency resonators. [ABSTRACT FROM AUTHOR]

If Ultra-light dark matter (ULDM) exists and couples to neutrinos, the neutrino oscillation probability might be significantly altered by a parametric resonance. This resonance can occur if the typical frequency of neutrino flavor-oscillations ∆m2/(2E), where ∆m2 is the mass-squared difference of the neutrinos and E is the neutrino energy, matches the oscillation frequency of the ULDM field, determined by its mass, mϕ. The resonance could lead to observable effects even if the ULDM coupling is very small, and even if its typical oscillation period, given by τϕ = 2π/mϕ, is much shorter than the experimental temporal resolution. Defining a small parameter ϵϕ to be the ratio between the contribution of the ULDM field to the neutrino mass and the vacuum value of the neutrino mass, the impact of the resonance is particularly significant if ϵϕmϕL ≳ 4, where L is the distance between the neutrino source and the detector. An outlier in the data collected by the KamLAND experiment which, until now, has been assumed to constitute a statistical fluctuation, or associated with the binning, can actually be explained by such narrow parametric resonance, without affecting the measurements of other current neutrino oscillation experiments. This scenario will be tested by the JUNO experiment. [ABSTRACT FROM AUTHOR]

This paper assessed the small-signal stability performance of a multi-converter-based direct current microgrid (DCMG). The oscillation and potential interactions between critical modes are evaluated. First, the complete analytical model of the DCMG is developed with the converter and associated controllers. Three methodologies, impedance scanning, eigenvalue analysis, and time-domain simulation, along with the fast Fourier transform (FFT) analysis, have been used to comprehensively investigate the oscillations and interactions. The simulation results show inherent weak modes, with a wide range of oscillations in the studied DCMG, which may destabilize the system under disturbances. Based on the sensitivity analysis, controller gains and DC-link capacitance are identified as the most critical parameters and substantially influence the weak modes leading to oscillations, interactions, and resonance. Finally, the performance of the various control synthesis methods is compared. This examination would help the researchers, planning, and design engineers to design and stably operate a multi converter-based DC microgrid. [ABSTRACT FROM AUTHOR]

In order to achieve its ultra-low vertical emittance (1 pm) and high luminosity (of up to 230 × 10 34 cm − 2 s − 1 per collision point), the e+e− Future Circular Collider (FCC-ee) requires a well-informed alignment strategy, powerful correction methods, and good understanding of the impact of vibrations. The large ring size, high natural chromaticity, small β ∗ , and the low coupling ratio make the FCC-ee design susceptible to misalignment and field errors, which if not properly addressed, threaten to increase the horizontal and vertical emittances and adversely affect the luminosity. Tight alignment tolerances around the 100 km ring would be a major cost driver and therefore alignment and stability need to be carefully studied. In this paper we present a status update, in which we apply analytical estimate methods, verified with simulation data, to determine the influence of the alignment of specific magnet types with the result informing the relative alignment tolerances. This is followed by simulations of a correction strategy that includes a large set of magnet misalignments and field errors. Finally, we also consider the tolerances on vibrations of quadrupoles through evaluating three cases: coherent vibration due to external seismic motion, vibrations resonant with the betatron frequency, and non-resonant, incoherent vibration. [ABSTRACT FROM AUTHOR]

Tsunami resonance excitation induces tsunami amplification, persistent oscillation, and strong current velocities, which may enlarge coastal hazards in tsunamigenic areas. Historically, the 2006 Pingtung earthquake doublet triggered tsunamis that affected the south Taiwan coast. Studying the resonance features based on past tsunamis is important for assessing tsunami hazards and obtaining critical disaster mitigation information. Here, we elucidate the tsunami resonance oscillation and its impacts along the south Taiwan coast based on synthetic assessment of tsunamis induced by the 2006 Pingtung earthquake doublet. A numerical simulation was performed to replicate the 2006 Pingtung earthquake doublet tsunamis. Then, spatially integrated spectra were obtained via spatiotemporal analysis. The results were compared to tsunami spectra at tide gauges to identify the main oscillation modes, suggesting the main oscillation modes had 13–50 min periods during the 2006 Pingtung earthquake doublet tsunamis. The tsunami resonance oscillations were analyzed based on the main oscillation modes. In the 2006 Pingtung earthquake doublet tsunamis, edge waves occurred along the south Taiwan west coast in most oscillation modes. The Hengchun Peninsula prevents tsunami oscillation transmission, and only part of the oscillation energy at certain periods propagates to the east coast. Furthermore, the spectral amplitude distribution migration across the period domain revealed that energy amplification is a frequency-dependent phenomenon and is responsible for the large tsunami heights and strong tsunami-induced current velocities distributed along the south Taiwan coast during this past tsunami. [ABSTRACT FROM AUTHOR]

• Nonlinear dynamic model of N - links flexible manipulator. • Consider link-joints flexibility and mobile platform. • Investigate the modal analysis of multi-link manipulator. • Demonstrate the dynamic characteristics under harmonic joint forces. • Investigate the stability analysis and bifurcation under resonance conditions. The present work theoretically demonstrates the dynamic analysis of a planar multi-link manipulator considering flexible links and joints mounted on a moving base. A nonlinear model of a multi-manipulator (N -links) has been developed accounting for an equivalent bi-directional mobile base. The nonlinear Euler-Bernoulli beam and spring-inertia/mass system have been introduced to demonstrate the flexibilities of links and joints, respectively. Modal analysis followed by trajectory analysis has been performed to investigate the behaviors of manipulator taking into account of accurate boundary conditions. Further, vibration characteristics, steady-state responses, and their stability at resonant situations due to joint motions and inertial coupling have been studied. Results of exploiting geometric and inertial coupling due to flexible arms on stability analysis of steady-state responses have been investigated and have been subsequently verified with the findings by directly solving the governing equations. Steady-state response characteristics to explore the dynamics of the multi-link manipulators under resonant states have been studied with the varying actuator mass, the flexibility of links, lifted payload, and joint parameters. The results thus obtained, deliver a useful insight into the position analysis and long-term behavior of multi-link flexible manipulators under harmonic hub-joint motions that shall further enable its proper vibration attenuation and control. [ABSTRACT FROM AUTHOR]