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Flexible vibration has a great impact on flexible spacecraft attitude control, which will reduce the pointing accuracy of the spacecraft platform and bring severe challenges to the design of a high-precision attitude control system for flexible spacecraft. Aiming at the problem of attitude and vibration coupling control of flexible spacecraft, an anti-unwinding attitude coupling controller using the positive position feedback (PPF) control is proposed in this paper. The model compensation control term is constructed based on the prior information to improve the tracking performance. The proposed attitude coupling control method can effectively suppress the flexible vibration while achieving more accurate attitude control. The obtained closed-loop system under the proposed control scheme is asymptotically stable, which is proved by the Lyapunov stability theory. The numerical simulation illustrates that the proposed method can effectively improve the attitude control accuracy of the flexible spacecraft and is capable of large-angle attitude maneuver control because of its prominent performance in attitude tracking and its unwinding-free performance. • Coupling control for flexible spacecraft. • Active vibration control using positive position feedback. • Model compensation control term is constructed to improve the dynamic performance. • The obtained closed-loop system achieves the asymptotic stability and anti-unwinding performance. [ABSTRACT FROM AUTHOR]

Multilayer piezoelectric ceramics have wide application prospects in the fields of precision driving and intelligent sensing owing to their low driving voltages and large strains. However, high sintering temperatures and expensive noble metal electrodes limit their application as multilayer piezoelectric ceramic actuators (MLAs) in conventional devices. In this study, a modified piezoelectric ceramic powder and Ag inner electrode were used to prepare a low-cost MLA with a low sintering temperature of 900 °C. The MLA showed superior piezoelectric properties with d 33 = 3015 pC/N and a large electric-field-induced strain of 0.13% at 22.2 kV/cm. Moreover, the stator of the ultrasonic motor composed of this MLA produced the ideal vibration mode, and the maximum rotation speed of the ultrasonic motor was 192 r/min under a 50 g load, which verifies the applicability of this component in practical minimised devices. These results demonstrate a strategy for fabricating low-cost and high-precision micro-actuators for precision driving. [ABSTRACT FROM AUTHOR]

• The optical fiber coil with spool (OFCS) is a crucial tool for precise physics measurements. • To improve the seismic resistance of OFCSs in space applications, the vibration modes are thoroughly investigated through dynamic analysis, simulations, and experiments. • We establish a dynamic model of the OFCS based on the vibration transmission mechanism to characterize its vibration modes. • The vibration eigenfrequency and shapes are calculated under various conditions. • The experimental results validate the feasibility of the dynamic model and simulation, meanwhile, the discrepancies between the simulations and experiments are analyzed. • This study is the first of its kind to develop a comprehensive dynamic model for an OFCS, with simulations and experiments confirming its effectiveness. The optical fiber coil with spool (OFCS) is a crucial tool for precise physics measurements. To improve the seismic resistance of OFCSs in space applications, the vibration modes are thoroughly investigated through dynamic analysis, simulations, and experiments. We establish a dynamic model of the OFCS based on the vibration transmission mechanism to characterize its vibration modes. The vibration eigenfrequency and shapes are calculated and simulated under various conditions. The experimental results validate the feasibility of the dynamic model and simulation, meanwhile, the discrepancies between the simulations and experiments are analyzed. This study is the first of its kind to develop a comprehensive dynamic model for an OFCS, with simulations and experiments confirming its effectiveness. [ABSTRACT FROM AUTHOR]

• The analytical solution for free vibration of constrained arches is proposed. • The arches with lateral translational and/or rotational braces are considered. • Closed-form solutions are obtained for the maximum fundamental frequency. • The threshold bracing stiffness or stiffness requirements is investigated herein. • The influences of the lateral braces on free vibration of arch are discovered. Discrete lateral braces are commonly employed to enhance the out-of-plane stability of arches. However, these braces generate coupling effects among vibration modes, which significantly impact the vibration characteristics of the arches. This paper presents an analytical solution for the free vibration analysis of two-hinged arches with equally-spaced lateral translational and/or rotational braces. A simplified method of evaluating the fundamental frequency for the out-of-plane vibration of arches with equally-spaced lateral braces is introduced. The method relies on the conventional approach of representing arch braces through elastic springs, but here the out-of-plane deflection of the braced arch is constructed by adding related coupled sinusoidal functions to that of the unbraced arch, satisfying both the boundary and kinematic conditions. Subsequently, the fundamental frequency and threshold bracing stiffness or stiffness requirement are derived using the Rayleigh–Ritz method. Finite element analysis (FEA) is applied to investigate the flexural-torsional vibration mode and fundamental frequency of arches with discrete braces, and the results from FEA closely match the theoretical predictions. The effects of number of lateral translational and/or rotational brace, out-of-plane slenderness, included angle, bracing stiffness and bracing position on the fundamental frequency are comprehensively analyzed. It is found that when the fundamental frequency of the braced arch increases due to changes in bracing stiffness, the mode shape displays more intricate behavior, rather than following a straightforward low-to-high mode growth pattern. Furthermore, it is observed that in some cases, the addition of rotational bracing stiffness can markedly enhance the maximum fundamental frequency of the arch with both translational and rotational braces. [ABSTRACT FROM AUTHOR]

• A novel method for pressure prediction and cavitation evaluation of water jacket in engines is proposed. • The pressure amplification factor for a thin liquid layer under modal vibration is derived. • The nonlinear relationship between liner vibration and coolant pressure is investigated to reveal the mechanism of vibration-induced cavitation. • Effects of acoustic parameters and liner modal parameters on cavitation are discussed. • The correctness and rationality of the method is verified by experiment. Vibrations of the cylinder liner in internal combustion engines cause coolant cavitation, inducing cavitation erosion. Owing to the lack of a comprehensive understanding of vibration-induced cavitation, the cavitation erosion has been long an unresolved problem influencing engine lifetime and reliability and concerned more in recent years due to lightweight designs. This study proposes a novel pressure prediction method that considers the dynamic properties of a cylinder liner and the pressure amplification effect of a thin water jacket. A pressure amplification factor for a thin water jacket, defined as the ratio of the acoustic pressure to the plane progressive wave pressure generated by the same liner vibration, was derived for the first time. The pressure amplification mechanism in the thin water jackets was revealed. The cavitation risk area on the cylinder liner was predicted, and the effects of acoustic parameters and liner modal properties on cavitation were analysed. The theoretical analyses agreed with the experimental results, proving the accuracy of the proposed method. Moreover, it has found that the thin-layer configuration of the water jacket significantly reduced the vibration threshold for triggering cavitation. Vibration-induced cavitation in cylinder liners is closely related to the liner constraint modes and acoustic properties of the water jackets. The research results enrich the theoretical understanding of vibration-induced cavitation and provide theoretical support for the prediction and mitigation of cavitation erosion in internal combustion engines. [Display omitted] [ABSTRACT FROM AUTHOR]

• The classification of saturated, supersaturated and undersaturated cavitation clouds was proposed. • The vibration mode of the radiation surface of transducer is investigated experimentally. • The characteristics and formation mechanism of supersaturated cavitation cloud structure were investigated. • A new approach is proposed to measure the vibration mode of transducer operating at high power and large amplitude in real time. The vibration mode of the radiation surface of transducer (or structure of supersaturated cavitation cloud in thin liquid) is investigated experimentally by high-speed photography. The classification of saturated, supersaturated and undersaturated cavitation clouds was proposed, and a comparison was made between saturated and supersaturated cavitation cloud structures in liquid thin layers. The characteristics and formation mechanism of supersaturated cavitation cloud structure were investigated. Based on the close correspondence and rapid response between the distribution of supersaturated cavitation clouds and vibration modes of radiation surface, a new approach is proposed to measure the vibration mode of transducer operating at high power and large amplitude in real time. [ABSTRACT FROM AUTHOR]

• The subdiced transducer (SDT) was fabricated and its performance was studied. • For lower frequency, SDT can achieve a smaller size and shorter transmission pulse. • SDT may have great potential for miniaturization and close-range imaging. Structure design of medical ultrasonic transducers is of prime importance, as it not only affects the transducer's imaging performance, but also limits its application scene and scope. In this paper, a single element transducer with subdicing is fabricated and its performance is studied using finite element method. In addition, the comparison transducers (CPTs) are fabricated as well as single element transducers with and without subdicing the element. The experimental results show that by subdicing the element with cut width 120 μm and cut depth 500 μm of the single transducer with a center frequency of 8 MHz and dimension of 2 mm × 0.9 mm × 1.2 mm, the center frequency reduced by up to 58.3 %, the −6 dB bandwidth increased by up to 48.7 %, but the echo signal amplitude reduced by 52.4 %. Compared to CPT-5, the volume of the subdicing transducer reduced by 94.6 %, the center frequency reduced by 4.3 %, the −6 dB bandwidth increased by 1.26 times, the transmitted pulse signal length decreased by 50 %, and the echo signal amplitude achieved 28 % of CPT-5. Therefore, the proposed subdicing transducer may have great potential for miniaturization and close-range imaging. [ABSTRACT FROM AUTHOR]

As a sub-process of flotation, the bubble-particle detachment plays a critical role in final flotation recovery. In this short communication, the effect of vibration mode, i.e., sine wave, triangle wave and square wave, on the detachment of low-rank coal particle from oscillating bubble was investigated using a home-made bubble-particle detachment measurement system. The critical detachment amplitude was used to evaluate the stability of bubble-particle aggregate. Three coal size fractions, i.e., 0.25–0.5, 0.5–1, and 1–1.5 mm, were used as the experimental samples, respectively. The results show that the critical amplitude decreased as particle size increased under different vibration modes due to the increased inertia. The critical amplitude at three different size fractions always decreased in the following order: sine wave, triangle wave and square wave, indicating the bubble-particle aggregate was the most stable under sine wave vibration. Square wave vibration has the most dramatic movement path changes, causing a highest instantaneous impulse and detachment force. Unlabelled Image • Effect of vibration mode on detachment of low-rank coal was studied. • The critical amplitude decreased with increasing particle size. • The critical amplitude decreased as follows: sine, triangle and square wave. [ABSTRACT FROM AUTHOR]

• Flow induced vibration of four-span tube is tested. • FEI critical velocity for tube with AVB is obtained. • FEI critical velocity for tube with TSP is obtained. • Five correlations for predicting onset of FEI are evaluated. Flow induced vibrations in steam generator and other heat exchangers can result in tube failure and lead to large economic losses. Tube supports such as tube support plates (TSP) or anti-vibration bars (AVB) are commonly used to suppress the flow induced vibration. Knowledge on the tube dynamic characteristics and instability phenomena under these support conditions is therefore essential, when fluid flows across the multi-span tubes. In this paper, flow induced vibration of a four-span rotated triangular tube array with a pitch-to-diameter ratio of 1.4 under three sets of AVB or TSP supports is experimentally studied. Part of the middle segment of the tube is subjected to cross flow. The vibration displacements and frequency spectra of a tube on first row are analyzed. It was found that the vibration mode for four-span tube bundle with TSP is different from that of the tube supported by AVB when fluid elastic instability (FEI) happens. The effective FEI critical velocities for the tube with TSP and that with AVB is 6.8 m/s and 3.0 m/s, respectively. Five correlations for predicting the onset of FEI of the tube bundle tested are compared with experimental results. Weaver and El-Kashlan correlation (1981b) is best. The effective FEI critical velocities predicted by Weaver and El-Kashlan correlation (1981b) are 15% and 27% higher than the experimental results for tube with TSP and tube with AVB, respectively. The vortex shedding responses are analyzed for the two tube-support structures. The Strouhal number for non-resonant vortex shedding response is calculated and compared with expectations from literature. The turbulent buffeting response for tube under different supports are compared with each other and discussed. [ABSTRACT FROM AUTHOR]

The mass and surface stress loadings in microcantilever-based sensors, caused by surface adsorption of target analytes/biomolecules, change their resonance behavior. Despite numerous efforts, the mechanisms of surface stress impact on the resonance behavior of microcantilevers are not fully understood. This results in substantial discrepancies between theoretically predicted and experimentally measured resonance frequency shifts in wide microcantilevers with aspect ratios (width-to-thickness) larger than 10, commonly found in chemical and biological sensing applications. This also impedes the proper decoupling of the effects of mass and surface stress loading and hinders the development of accurate microcantilever-based sensors. In this work, we attempt to decrease the discrepancy found between theoretical models and experiments by introducing a new mechanism that correlates the nonlinear geometric effects associated with surface stress-induced variation of microcantilever biaxial curvature to its frequency and modal responses, with a correlation intensity that strongly depends on the microcantilever aspect ratio. A new comprehensive analytical model combining the new mechanism with currently available theoretical models is proposed and used to study the resonance behavior of microcantilevers with different deformations and sizes. Using the new model, it is shown that in wide microcantilevers, the theoretically predicted resonance frequency shifts agree with experimental and finite element simulations results within 30% whereas the predictions by other currently available theoretical models are off by more than one order of magnitude. The new model is also used to investigate the modal response of microcantilevers where it anticipates the bending-extensional mode coupling associated with the flexural vibration modes of microcantilevers with a coupling strength that depends on the microcantilever curvature. The presented model is expected to provide a new tool to decouple the effects of mass and surface stress loadings on the resonance behavior of microcantilevers used in chemical and biological sensors. [ABSTRACT FROM AUTHOR]

Numerous papers deal with the Equivalent Plate Model (EPM) for corrugated panels. Comparison of published formulas for the four relevant equivalent bending stiffnesses D 11 eq , D 22 eq , D 66 eq , and D 12 eq revealed ambiguities: Three different formulas were found for D 22 eq , which describes the bending of the ridges and troughs; for D 66 eq two ‘competing’ formulas emerged. Expressions not converging to the flat-plate values in the limit of vanishing corrugation height were discarded. All discussed formulas are written in a uniform notation for general one-dimensionally periodic shapes. Formulas derived for isotropic panel materials were generalized to the orthotropic case. In order to resolve the ambiguities and assess the EPM with regard to its range of applicability, vibration modes of six rectangular corrugated panels were measured. While agreement with numerical results obtained with COMSOL was fair, the EPM predictions of natural frequencies were satisfactory only for low-order modes. Finally, equivalent bending stiffnesses were determined numerically from COMSOL results for a few low-order modes by inverse methods. Thus the ambiguities with regard to D 22 eq and D 66 eq could be resolved. However, the D 12 eq values determined numerically came out significantly larger than the EPM prediction, in particular for stronger corrugations. Even though this discrepancy had little effect on the natural frequencies tested in the present paper, it remains a theoretical challenge. [ABSTRACT FROM AUTHOR]

Non-linear static procedure (NSP) has been considered as a popular method to predict seismic force and deformation demands for performance evaluation of the structures, in recent years. However, this evaluation tool is restricted to low-rise and regular buildings in which the fundamental vibration mode dominates the structural behavior. Recently, some advanced procedures have been presented to oversee these conventional procedure deficiencies. In the current study, a new nonlinear static procedure considering the effects of higher modes in structural responses is presented. This approach assigns a contribution factor for each mode based on modal shear distribution. The offered contribution factor can be applied for determining the importance of each mode in lateral load pattern formation. In order to verify the results, some other types of pushover-based analysis are also performed and the responses obtained from each NSP are compared with those of rigorous non-linear response history analysis (NL-RHA). Results demonstrated the efficiency of the proposed method in accurate prediction of the seismic demands of high-rise buildings. [ABSTRACT FROM AUTHOR]

Vibration modes of MEMS piezoelectric diaphragms responding to an ultrasound pulse were investigated and influence of top electrodes to the vibration modes was discussed. The top electrode has a centrosymmetric shape divided into inner part for ultrasonic sensing and outer part for resonant frequency tuning. Piezoelectric output signal is generated in the inner electrode by centrosymmetric vibrations. The piezoelectric diaphragms were fabricated in flat or buckled shape and the top electrodes of various thickness were formed on them. Pulse-induced vibration modes were evaluated by using scanning laser Doppler vibrometry. The buckled diaphragms showed resonant peaks in a narrower frequency range compared to the flat diaphragm. The top electrode showed an influence on the vibration modes so that vibrations with a large amplitude spontaneously concentrated in the sensing electrode area, even in the case of a thin electrode film around 10nm. [ABSTRACT FROM AUTHOR]

The maximum root mean square (RMS) of the displacement of a long tensioned mooring tether undergoing vortex-induced vibration (VIV) as the flow velocity varies was experimentally investigated, and an evaluation model was established to predict the maximum RMS value of the displacement by a dimensionless analysis. The results showed that the maximum RMS of the displacement linearly increased with the increasing of the flow velocity if only the low order modes were excited at the corresponding flow velocities. This kind of maximum RMS of displacement was evaluated by the proposed model, which is more reliable when it was used to predict the maximum RMS of the total displacement. [ABSTRACT FROM AUTHOR]

A new dynamic model for double-helical star gearing system is proposed in this research. The dynamic model can used to analysis double-helical star gearing system in any condition. A equivalent meshing error analysis on different types of gear errors in the external and internal meshing line for star gearing system respectively. Axial, transverse, torsional and rotational motions of gears are included in the dynamic model. Establishes a refined new dynamic model for vibration and natural characteristic analysis of double-helical star gearing system. A type of gearing system for aero-engine was researched and calculated to demonstrate the validity of the dynamic model, obtained the values and the vibration mode for different order. It is revealed that the vibration characters for left side and right side of double-helical star gears have a nice distinction, which can provide scientific theory evidence for dynamic design and vibration control for precision double-helical star gearing system. [ABSTRACT FROM AUTHOR]

• The LPBF Ti-6Al-4V has shown better tensile strengths than the wrought Ti-6Al-4V. • The LPBF bracket has achieved the expected frequency and "g" capacity targets. • The LPBF bracket has exhibited expected redundancy in the structural load path. • The modified KT diagram has been used for safe life zone of LPBF Ti-6Al-4V parts. • The work has shown feasibility of using LPBF for safety load bearing applications. Due to the stringent certification requirements and complex engine operating environment, the design of AM components for aero-engine application remains a challenging task. The high cycle fatigue performance of a weight-optimised bracket made using the Laser Powder Bed Fusion (LPBF) process was studied through shaker table testing. The results are discussed together with the observed mechanical and fatigue strengths in conjunction with material characterisation of microstructure, surface roughness, defects, micro-hardness and fracture surfaces. The debits in mechanical and fatigue strengths are expected due to process dependent surface roughness and the density of defects present. From the shaker table test results, it was concluded that the proposed weight-optimised LPBF bracket is capable of meeting the performance targets. The fundamental vibration mode of the bracket assembly was 84 Hz, which was much higher than the 1st Low Pressure shaft speed (48 Hz) of the target engine and thus avoids potential resonance. The bracket achieved its target inertial g load capability of 20 g and it was demonstrated that the bracket had enough redundancy in its load transfer paths should a strut fail during service of the engine. Lack of fusion voids and micro-cracks present on or near the surface were the prime sites for crack initiation. It has been shown that the as-built surface can cause a significant reduction (up to 40%) in the fatigue strength when compared to machined Ti-6Al-4V. A safe life regime for LPBF component design has been presented based on the Kitagawa-Takahasi diagram, modified using the Chapetti curve, which effectively links the material fatigue properties and performance of LPBF parts with intrinsic defects. [ABSTRACT FROM AUTHOR]

Aluminum foam sandwiches (AFS) with metallic bonding between face sheets and aluminum foam have been produced by the method of fluxless soldering with surface abrasion assisted by vibrations. The effects of vibration modes on mechanical properties and interfacial characterization are analyzed via microstructural observation, tension tests and static three-point bending tests. The average bending strength increases sharply with the increase of vibration frequency and can reach 571% of that of aluminum foam when AFS is made with assisted ultrasonic vibration. Excellent metallic bonding has been informed between face sheets and foam core. The delaminations between face sheets and foam core are not observed and good wetting and spreading process are realized. Particularly, ultrasonic vibration helps to make the microstructure more uniform and reduce the defects of soldering seam. The joining mechanism of Al plate and aluminum foam is explained. A model based on thermodynamic equations is built up to explain interdiffusion process, and the relation between diffusion depth and spreading radius has been discussed. Fluxless soldering with surface abrasion assisted by vibrations has been proven to be suitable for fabricating AFS. [ABSTRACT FROM AUTHOR]

The paper presents an experimental study on the key characteristics of a magnetostrictive vibrator being developed for polishing application. Firstly, the actuation principle is systematically illustrated by a general model and experimentally verified by measuring magnetic fluxes flowing in the legs of the vibrator. Then the vibration mode is analyzed by finite element method and proved by node position test. It is found that the experiment result shows good consistent with that of simulation. After that, the effect of external stress on vibration amplitude is tested and the result indicates that under the stress of 0–1 N, the vibration amplitude shows in a rough proportion relationship to the stress. However, when the stress is less than 100 mN, vibration amplitude is almost not changed. Finally, the heat generation of the vibrator is evaluated, and a cooling device is developed for effectively decreasing the operating temperature. [ABSTRACT FROM AUTHOR]

Based on surface reaction technology, electrochemical sensing methods are well suitable for small-volume samples, such as droplets. However, rapid mass transfer of analytes within droplets is usually hard to achieve due to small fluid volumes and minimal convection. Here, we present a mass transfer enhancement method achieved by actuating a sessile droplet into certain vibration modes. Electrodes for electrochemical detection, each with a droplet retainer, are placed on a vertically vibrating platform. The vibrational and mass transfer properties of the sessile droplets are experimentally tested with optical and electrochemical methods. Internal flows generated by the droplet vibration are visualized to explain the enhancement in mass transport. Compared with a static case, measurements with droplet vibration in the (0, 2) mode demonstrate an increase in mass transfer rate of over five times. Finally, improvement in sensing performance of electrochemical sensors caused by vibration is experimentally verified by detecting heavy metal ions and large molecules (proteins) using a gold working electrode. • Propose a simple and low-cost strategy to accelerate transport of analytes in sessile droplet sample towards sensing surface. • Mass transfer coefficient from droplet to electrode is experimentally investigated under various droplet vibrating conditions. • By driving sessile droplet sample into a certain vibration mode, over 5 times enhancement in mass transfer rate is observed. [ABSTRACT FROM AUTHOR]

• Rigid-body displacements of time-varying models can be eliminated in modal coordinates. • Some modal responses of split-path transmissions can be suppressed by mesh phasing. • Vibrations in some directions can also be suppressed for different parameters. • The suppression phenomenon is interpreted as decoupling from excitations. This paper studies the effectiveness of adopting mesh phasing for suppressing several particular modal responses in a typical split-path transmission. The dynamic model admits three planar degrees of freedom for each gear and considers time-varying mesh stiffnesses, which captures the effect of mesh phasing. The vibration modes of the system are analyzed for the time-invariant case with average mesh stiffnesses, and the characteristics of each mode shape are summarized. Then, according to the characteristic of rigid-body modes, a new method for eliminating the rigid-body displacement of a time-variant system is proposed. This method has a clear physical interpretation and is convenient to use. The modal equations are solved numerically after removal of the equation of the rigid-body mode. It is found that appropriate mesh phasing can effectively suppress several different modal responses, and a physical interpretation of this phenomenon is provided by using the modal equations and the modal analysis results. [ABSTRACT FROM AUTHOR]

• Each LN-based device produced peak water particle sizes in the range 3.2–4.2 µm. • Larger transducer area increased atomization volume but decreased efficiency. • The optimal LN size for efficient atomization area was found to be 8 mm × 10 mm. • FEM results and impedance analysis suggested that mode mixing reduced atomization. In recent years, individual control of one's personal environment has been drawing increasing attention due to the growing interest in health care. Wearable devices are especially useful because of their controllability regardless of location. Humidity is one of the inevitable factors in the personal environment as a preventive against infectious diseases. Although atomization devices are commonly used as a method of humidity control, at present, there are no wearable humidity control devices. Vibration of a lithium niobate (LN) device in the thickness mode is a promising piezoelectric method for miniaturization of atomization devices for humidity control. To miniaturize the atomization device, the transducer size needs to be small not so much as to decrease the atomization efficiency. However, the effect of the device area on the atomization efficiency of LN at a size suitable for mounting in wearable devices has not been studied. Here, we conducted an atomization demonstration of LN devices with different sizes to evaluate particle size and atomization efficiency. Furthermore, to reveal the relationship between vibration behavior and atomization efficiency, resonance vibration in the MHz frequency band was evaluated by the finite element method and an impedance analyzer. The results showed that the peak size of water particles atomized by each device was in the range of 3.2 to 4.2 µm, which is smaller than particles produced by typical piezoelectric ceramics. Moreover, the best LN size for efficient atomization was found to be 8 mm × 10 mm among the five LN device sizes used in experiments. From the relationship between vibration behavior and atomization efficiency, the size of the transducer was suggested to affect the vibration mode. The obtained result suggested that the LN device is suitable for small wearable nebulizer devices. [ABSTRACT FROM AUTHOR]

• Improvement of tapered beam vibration theories in which geometric matrix is developed. • The theory which verifies the structural reliability and methodological advancement of variable-section beams. • Predicting differences in stability from the frequencies and vibration responses of the shafts system with changing loads. To examine the geometric relationships and mechanical characteristics of a variable-section beam, a Timoshenko beam model was selected. The finite element method (FEM) was applied to derive each coefficient matrix of the bending-torsional axial vibrations of a variable-section shaft system and the geometric matrix constructed by the axial load. The differential equations of motion of the variable-section shaft system were constructed by combining the bearing characteristics. The frequencies of single-stage and multi-stage beams under different boundary conditions were investigated separately, verifying the correctness of the simulations. Furthermore, the analysis methodology of the rotating shaft system was proposed, the vibration characteristics of the rotating variable-section shaft system and the rotating stepped-shaft system were analyzed and compared, the vibration mode shapes of the shaft system under different axial loads were studied, and the unbalanced response characteristics of the rotating shaft system were obtained. This work provides guidelines for improving the stability of shaft system operation. The results of this study provide a dynamic description of shaft systems. [ABSTRACT FROM AUTHOR]

Highlights: [•] An old 50m tall masonry chimney damaged by the 2012 Emilia earthquake was analyzed. [•] A survey put in evidence diagonal cracks and mortar degradation in the upper part. [•] Traditional pushover methods yielded unrealistic bending failure mechanisms. [•] Modal pushover analysis (MPA) detected a shear failure mechanism of the upper part. [•] Refined nonlinear dynamic analyses confirmed that the shear mechanism is crucial. [Copyright &y& Elsevier]

The main objective of the femur bone analysis is to know the natural frequencies, natural vibration modes and identify the fracture location of the bone through the computer simulation based on the FEA. Finite element Method or Finite Element Analysis is an approximation techniques used for the analysis of complex objects and geometries. The femur bone analysis is subjected to free- free and fixed-fixed boundary conditions. For these two different boundary conditions natural frequencies and natural vibration modes are identified. The mode shape shows that the natural frequency of free-free boundary condition varies from 0 Hz to 1381.1 Hz and for fixed-fixed boundary condition 1211 Hz to 7856.4 Hz. On the bases of these two boundary conditions mode shape is determined and fracture location can be easily notified. To prevent the fracture of femur bone external excitation frequency must be avoided to coincide with these natural frequencies. The results were compared with experimental results available in literature. For the design of femur bone model Solid Edge software is used and the model is imported in ANSYS R 14.5 (FEA based software) for the free vibration analysis. [ABSTRACT FROM AUTHOR]

• Three optimal anisotropic LRSs are obtained through the topology optimization. • These optimal LRSs can efficiently attenuate impact load. • The mechanism of energy absorption and conversion in impact is analyzed. • The attenuation and natural frequencies of these optimal LRSs are in good agreement. • The application of multiple LRSs proves their impact attenuation effect again. This study explored a new impact protection method based on three-phase locally resonant structures (LRSs), and this method did not rely on large structural deformation and material destruction. The performances of three LRSs with a steel cylindrical oscillator (LSCYO), aluminium cylindrical oscillator (LACYO), and steel cubic oscillator (LSCUO) were studied. A design with an optimised topology with the goal of maximising the impact attenuation was introduced to further improve the performance. The nonlinearities of the material, geometry, and contact were simultaneously considered in the optimisation of the design. The analysis results indicated that these optimal LRSs were anisotropic and could efficiently attenuate the impact load and absorb the impact energy. The attenuation effects of these optimal LRSs were better than those of the original and LRS models. In addition, the mechanisms of the energy absorption and conversion in the impact attenuation process were analysed. The vibration modes and propagation behaviours of the waves of these optimal LRSs were also studied. The attenuation frequencies of the waves and natural frequencies of these optimal LRSs were in good agreement, and the attenuation frequencies of the waves were all within the spectral range of the impact loads. In addition, multiple optimal LRSs were applied simultaneously to study their impact response, and the attenuation effect of the impact force was demonstrated. In short, this study investigated the attenuation mechanism of LRSs from the perspective of energy conversion, explored the new application scenarios of LRSs, and provided a novel solution for the impact problem, which is of significance in the field of functional structure design and impact protection. [Display omitted]. [ABSTRACT FROM AUTHOR]

Abstract: Many design requirements need to be considered in designing an ultrasonic motor. To solve the multi-objective optimization problem, sequential quadratic programming and finite element method are applied to the design process. The finite element method is used for modal analysis and harmonic response analysis of the ultrasonic motor. The sequential quadratic programming is employed to determine the optimal design solution. To validate the effectiveness of the proposed method, it is applied to the optimization of a rod shape ultrasonic motor. Design results show that all the requirements of motor design are satisfied and the design indexes related to motor performance show significant improvements after optimization. A prototype motor with 15mm in diameter is manufactured using the optimization results. The stator vibration characteristics and the motor performance are tested. The results show that this design method is available and effective for the design of ultrasonic motors. [Copyright &y& Elsevier]

Abstract: Density functional theory (DFT) calculations using the different functional of PBE1PBE, PBEPBE, LSDA, B3LYP, MPW1PW91, B3P86 and B3PW91 have been carried out to study the adsorption of HCO3 − species on the Al2O3 catalyst. The geometrical structures and vibration spectra were obtained using DFT and compared with the corresponding experimental values. Theoretical calculations show that the calculated IR spectra for PBE1PBE and MPW1PW91 method are in good agreement with the experimental spectroscopic results. [Copyright &y& Elsevier]

Abstract: Laser ultrasonics was applied to the manufacturing control of the integrity (no failure) of coated spherical particles designed for High Temperature Reactors (HTR). This control is of major importance, since the coating of the nuclear fuel kernel is designed to prevent from the diffusion of fission products outside the particle during reactor operation. The SiC layer composing the coating is particularly important, since this layer must be an impenetrable barrier for fission products. The integrity of the SiC shell (no crack within the shell) can be assessed by the ultrasonic vibration spectrum of the HTR particle, which is significantly changed, compared to the reference spectrum of a defect-free particle. Spheroidal vibration modes of defect-free dummy particles with a zirconium dioxide (ZrO2) core were observed in the 2–5MHz range. A theoretical analysis is presented to account for the observed vibration spectra of defect-free or cracked HTR particles. [Copyright &y& Elsevier]

Abstract: This study develops a rotational degree of freedom model of general compound planetary gears. The model clarifies the conflicting gear mesh deflection expressions in prior research. For systems with identical, equally spaced planet trains in each stage, all vibration modes are classified into one of two types: overall modes and planet modes. In overall modes, all planet trains in the same planet set move identically. In planet modes, only one planet set has motion, and the motion of each planet train in this planet set is a scalar multiple of that of the arbitrarily chosen first planet train in this set. These structured vibration properties are analytically proven in this study. [Copyright &y& Elsevier]

Abstract: This paper develops a novel piezoelectric clutch mechanism, including a driving member and a driven member, and investigates the clutching performance of the clutch mechanism. Each member is based on a thin-disk piezoelectric buzzer as a frictional member under coupling mode and a mechanical vibrator under non-coupling mode. In doing so, the clutch mechanism and its experimental set-up namely a power transmission system are first expressed. Then, operating principles such as inverse piezoelectric effect and ultrasonic levitation for separating two facing surfaces of the members are stated, and a carbon-powder imaging method for observing the vibration mode of the piezoelectric buzzer is introduced. Moreover, a DC/AC resonant inverter for converting a DC source to a sinusoidal source applied to energize the piezoelectric buzzer is constructed. Finally, relationships between rotational speeds and electrical conditions as well as the transient response of the rotation speed with the condition of change are investigated. [Copyright &y& Elsevier]

Abstract: Slender footbridges are known to suffer excessive lateral vibration which is not well understood at present. A suspension footbridge model with reverse profiled cables is proposed to investigate the vibration characteristics of slender shallow suspension footbridges and two types of cable configurations are considered in this paper. It is found that suspension footbridges with shallow cable profiles often have coupled vibration modes which can be described by a “coupling coefficient” defined as the ratio of vertical component to the lateral one. Numerical results show that the coupling coefficient has a significant effect on the lateral dynamic amplification factor (DAF). Small coupling coefficients can induce large DAF in lateral modes. [Copyright &y& Elsevier]

Abstract: We developed a disk-type non-contact ultrasonic motor based on B22 vibration mode. The rotors of SU-8 photoresist are fabricated by the UV-LIGA process to control their shapes and thicknesses. So the structures of them are optimized by the experiments. It is found that the revolution speed of disk-type non-contact ultrasonic motor not only depends on the vibration amplitude of the stator, but also the weight and construction of the rotors. The maximum revolution speed of the optimal rotor is 3569rpm at the input voltage of 20V and the driving frequency of 45.6kHz. The exciting principle of traveling wave is presented with theoretical equations. The electric signals applied to the piezoelectric ceramic are designed by the principle. The natural frequency and corresponding vibration mode are calculated and analyzed using finite element method. It is shown that experimental results are in good agreement with simulation, which verifies the effectiveness of the finite element model. Moreover, the levitation distance between the stator and rotor is measured by a CCD laser displacement transducer. [Copyright &y& Elsevier]

Abstract: A new technique for crack detection in beam structures based on kurtosis is presented. The fundamental vibration mode of the cracked cantilever beam is analyzed and both the location and size of the crack are estimated. The location of the crack is determined by the abrupt changes in the spatial variation of the analyzed response, while the size of the crack is related to the estimate of kurtosis. The proposed prediction method was validated by experiments on cracked Plexiglas beams. The influence of added noise on the estimation accuracy of the method has been investigated. Compared to existing methods for crack detection, the proposed kurtosis-based prediction scheme is attractive due to low computational complexity and inherent robustness against noise. [Copyright &y& Elsevier]

Abstract: This paper deals with forced vibrations of two-DOF systems with more than one equilibrium positions. Such systems may be obtained by digitization of elastic post-buckling systems. A vibration mode, which is periodic at small force amplitudes and becomes chaotic as the force amplitudes are slowly increased, is selected. It is possible to formulate and solve the problem of stability of a periodic or chaotic vibration mode in a space with greater dimension using the classical Lyapunov stability definition and some calculating procedures. Instability of phase trajectories is used as a criterion of the chaotic behavior in dynamical systems. Trajectories with very close initial values are compared. Use of the Lyapunov stability definition shows mutual stability/instability of the trajectories. Calculations permit to observe an appearance and enlargement of the chaotic behavior regions. Specific results are obtained for the nonautonomous Duffing equation and pendulum system. [Copyright &y& Elsevier]

This paper reports the elastic constants of the Ni-base single crystal superalloy (TMS-26) with a rafted (lamellar) structure having tetragonal symmetry. The elastic constants have been measured at room temperature with the resonance ultrasound spectroscopy method and the mode-selective electromagnetic acoustic resonance method. The value of the elastic constant c33 (250.4 GPa) is almost equal to that of c11 (252.5 GPa), which indicates that the rafted structure virtually has the elastic anisotropy of cubic system. [Copyright &y& Elsevier]

• Mesh phasing rules govern the presence/absence of sun, carrier, and ring motions. • Mesh phasing rules govern the forces/torques transmitted to surrounding components. • Mesh phasing suppresses many/most potential resonances. • All results are determined by a single mesh phasing parameter for easy design use. • Mesh phasing results do not depend on any mass/stiffness matrix model. This work analytically derives rules for how planet mesh phasing impacts the vibration of planetary/epicyclic gears. A key quantity is defined that depends on the mesh frequency harmonic number, ring gear tooth number, and total number of planets. This quantity dictates, for each harmonic of mesh frequency, which central member (sun, carrier, and ring) motions are present or absent, which force and moment components can be transmitted from the central members to their surrounding components, which modes are present in the response at the given harmonic, and which modes can experience resonance in the given harmonic. Neither the derivation nor the mesh phasing rules depend on a planetary gear model; only cyclic symmetry and periodicity of the response at the mesh frequency are required. The mesh phasing rules apply to spur/helical planetary gears where each component has six, three-dimensional rigid-body degrees of freedom. They apply to systems with high-speed, gyroscopic effects and those where rotational effects are neglected. Dynamic simulations using a finite element/contact mechanics model and an analytical model confirm the mesh phasing rules. Use of these mesh phasing rules for design and troubleshooting offers significant benefits to reduce vibration of planetary gears. [ABSTRACT FROM AUTHOR]

• Physical charge transfer mechanism between PEDOT and nitro group of secondary explosives. • Effect of Photo-excitation on explosive mixtures in Raman and absorption spectroscopy. • The ratios of As and S lines to ascertain the Photon-electron–phonon interaction. • Estimation of reduced mass of functional groups to ascertain the force constant of NO 2 group. • PEDOT as a new sensing medium at 532 nm wavelength. The paper reports the charge transfer mechanism between poly (3,4-ethylenedioxythiophene) (PEDOT) and high energy materials such as RDX, HMX and TNT, respectively in terms of ratios of anti-stokes (AS) and stokes(S) Raman lines of NO 2 bands. Generally it works as an effective sensing medium for the detection of explosives when mixed in an equal proportion and are subjected to 532 nm wavelength without any chemical treatment [1]. The pristine PEDOT is less sensitive to 532 nm wavelength (2.33 eV) but influences the Raman S and AS lines of explosives in the mixture. The study also reveals that a small quantity (one milligram) of PEDOT is sufficient to initiate the positive charge transfer mechanism between its oxidized state to the lone pairs of electrons on the oxygen atoms of the nitro group of the explosive molecules. Consequently, the intensity of the Raman spectra of RDX, HMX and TNT is dropped by an order of 22.5, 11.45 and 17.2 times, respectively along with the shift of the NO 2 vibrational modes. It is also attributed to Photon-electron–phonon interaction. Finally, we have estimated the reduced mass of the functional group to ascertain the force constant and the intensity ratios of AS /S lines to confirm the charge transfer mechanism. The effect of charge transfer mechanism is also reflected in drastic change in transmission /absorption characteristics of FTIR spectra of same PEDOT and explosive mixtures. [ABSTRACT FROM AUTHOR]

• New two-phases stress-based closed form solution for free vibrations is proposed. • Local/nonlocal model is defined by a convex combination through mixture parameter. • Normalised natural frequencies for four study cases are determined. • Effectiveness is discussed through a comparison with literature results. • Normalised frequency for higher vibrations modes is computed for each study case. In the present work, an innovative two-phases local/nonlocal constitutive mixture model based on the stress-driven model for free vibrations problems is presented. The above two-phases model has been formulated by defining a convex combination of local/nonlocal phases through a mixture parameter and the closed form solution for free vibrations problems is given. The proposed local/nonlocal model has been applied to compute the natural frequencies of four nanobeams study cases. The results are presented in terms of normalised natural frequency as function of both nonlocal and mixture parameters. First, the influence of the two parameters is studied. The effectiveness of the present model is discussed by comparing the results with those obtained by applying the Gradient Elasticity theory. Finally, the normalised natural frequencies for the second, third and fourth modes of vibrations are presented and discussed for each study case. [ABSTRACT FROM AUTHOR]

• We experimentally demonstrated both combinational logic function (half-adder) and fundamental AND and XOR logic gates. • The concept is based on selective modes activation for propagating the localization and delocalization of the vibration modes. • The F-shaped microstructure consists of two straight and arch in-plane microbeams connected to form a coupled resonator. • The designed F-shaped microstructure enables the demonstration of multi-inputs/outputs logic functions. • The logic input/output signals from the proposed device are AC-based signals at the same frequency that enable cascadability. In line with the rising demand for smarter solutions and embedded systems, Microelectromechanical systems (MEMS) have gained increasing importance for the Internet of Things (IoT) applications, most notably for mobile wearable devices. This is driven by their simplicity, sensitivity, reliability, and low power consumption. Hence, they are being explored for ultra-low-power computing machines. However, the realization of energy-efficient complex logic functions and the cascadability of MEMS resonator-based computing devices have introduced new challenges, such as using the outputs of logic units as inputs into others, which is necessary for realistic implementations. This study demonstrates a complex logic function (half-adder) and fundamental logic gates (XOR and AND) based on selective modes activation. The concept is based on the activation and deactivation of the vibration modes of an F-shaped coupled resonators. The proposed approach requires power for actuation only, and this results in significant improvement in energy efficiency because it does not need DC-based frequency modulations. It shows promising low consumed energy in femtojoules per logic operations. The proposed scheme provides prospects for cascadable MEMS resonator logic devices since it enables both the logic inputs and outputs to be in the same AC signal mode at the same frequency. [ABSTRACT FROM AUTHOR]

Aminopyrine is an inexpensive drug that is highly effective on analgesic and anti-inflammatory. However, it is found adulterated to traditional Chinese medicine by unscrupulous merchants though side effects, such as neutropenia, myelosuppression and formation of nitrosamine carcinogens, make it banned in many countries. In this work, terahertz time-domain spectroscopy has been proposed to perform characterization of aminopyrine in the range of 0.2∼2.4 THz. Characteristic absorption peaks of aminopyrine are found at 1.54 THz and 2.15 THz. To gain further insight, DFT studies have been carried out to simulate the THz spectrum and analyze molecular vibration mode of aminopyrine. The spectrum simulated is in good agreement with the experiments and the calcuated absorption peaks at 1.48 THz and 2.29 THz matches with the experimental result of 1.54 THz and 2.15 THz. The main vibrational modes of the characteristic peaks are the skeletal vibrations of the molecule, which is represented by the rotation and the swing of dimethylamino group, pyrazolone and benzene rings. This study shows that terahertz spectroscopy has potential application prospects for the detection of adulteration of aminopyrine in rheumatic Chinese patent medicines and the examination of counterfeit drugs. [ABSTRACT FROM AUTHOR]

Summary Objective The study aimed to investigate the physiological basis of vibration mode of sound source of a variety of Mongolian höömii forms of singing in China. Methods The participant is a Mongolian höömii performing artist who was recommended by the Chinese Medical Association of Art. He used three types of höömii, namely vibration höömii, whistle höömii, and overtone höömii, which were compared with general comfortable pronunciation of /i:/ as control. Phonation was observed during /i:/. A laryngostroboscope (Storz) was used to determine vibration source-mucosal wave in the throat. Results For vibration höömii, bilateral ventricular folds approximated to the midline and made contact at the midline during pronunciation. Ventricular and vocal folds oscillated together as a single unit to form a composite vibration (double oscillator) sound source. For whistle höömii, ventricular folds approximated to the midline to cover part of vocal folds, but did not contact each other. It did not produce mucosal wave. The vocal folds produced mucosal wave to form a single vibration sound source. For overtone höömii, the anterior two-thirds of ventricular folds touched each other during pronunciation. The last one-third produced the mucosal wave. The vocal folds produced mucosal wave at the same time, which was a composite vibration (double oscillator) sound source mode. Conclusions The Höömii form of singing, including mixed voices and multivoice, was related to the presence of dual vibration sound sources. Its high overtone form of singing (whistle höömii) was related to stenosis at the resonance chambers' initiation site (ventricular folds level). [ABSTRACT FROM AUTHOR]

Abstract: A novel 3 phase (ceramic, epoxy resin and decoupling material) piezoelectric composite with multi-elements in parallel connection has been developed by using dice-fill technology. The acoustic coupling between elements in composite was investigated. The vibration velocities curves of active element and close elements were measured by using Scanning Laser Vibrometer (Polytec PSV-400). The results exhibited that the decoupling material induced in multi-elements composite has a good decoupling effect. Vibration attenuations between adjacent elements are larger than 23.8 dB at resonance frequency. [Copyright &y& Elsevier]

Abstract: We report on picosecond ultrasonic measurements obtained on aluminum and platinum nanostructures with variable dot size and lateral periodicity which realized a 2D phononic crystal. Performing investigations at different resolution scales, we have identified individual modes of vibration depending on the dot size, and mode of vibration strongly correlated with the bi-dimensional organization. The platinum dots sputtered on an aluminum layer have shown a behavior of isolated oscillators without any coupling between neighbor elements in this phononic crystal. The frequency of such normal modes, extracted from time resolved measurements are in good agreement with 3D finite element simulations. In contrast, with aluminum dot systems where the coupling is more efficient we observe a complex spectrum of vibrational modes related to the band structure induced by the bi-dimensional patterning. [Copyright &y& Elsevier]

Abstract: A traveling wave ultrasonic motor of high torque with a new configuration is proposed in this paper. In the new design, a part of the motor serves as the stator. The rotor is the vibrator consisting of a toothed metal ring with piezoelectric ceramic bonded, which generates ultrasonic vibration. The rotor is in contact with the shell of motor and is driven by the friction between the rotor and the stator. This configuration not only removes the rotor in a conventional type of traveling wave ultrasonic motor but also changes the interaction between the rotor and the stator of the motor so that it improves the output performance of the motor. Although an electric brush is added to the ultrasonic motor, it is easy to be fabricated because of the low speed of motor. The finite element method was used to compute the vibration modes of an ultrasonic motor with a diameter of 100mm to optimize the design of the motor. A 9th mode was chosen as the operation mode with a resonance frequency about 25kHz. According to the design, a prototype was fabricated. Its performance was measured. The rotation speed–torque curves for various frequencies were obtained. The result shows that its stall torque is greater than 4Nm within a range of 400Hz. This ultrasonic motor was used to drive the window glass of a mobile car and the result was satisfactory. In the further the research on the friction material between the stator and the rotor is under way to improve the efficiency of the ultrasonic motor. [Copyright &y& Elsevier]

Abstract: Micro piezoelectric actuator using vibration mode B 11 (B mn , where m is the number of nodal circles, n is the nodal diameters) is designed. Different from conventional wobble-type ultrasonic motor using piezoelectric rod or cylinder, piezoelectric disc is used to excite wobble modes and metal cylinder stator is used to amplify the transverse displacement, metal rod rotor is actuated to rotate. The outer diameter of the actuator is 14mm. There are features such as low drive voltage, micromation, and convenient control of wobble state by modifying the structure of stator, etc. Finite element analysis (FEA) of the stator has been made. It is found that the resonant frequency of vibration mode B 11 is 49.03kHz, which is measured at 45.7kHz by the laser vibrometer and impedance analyzer. The rotation speed has been measured, which could be as high as 10,071rpm under an alternating current 100V. Such piezoelectric actuator can be optimized and adjusted to fit practical conditions. It can be applied in the fields of precise instrument, bioengineering and other micro actuator system. [Copyright &y& Elsevier]