•A rotating Euler-Bernoulli beam vibration formulation is developed.•A tracking continuous scanning laser Doppler vibrometer system is developed.•A lifting method for processing measurement of a ...rotating structure is developed.•Modal parameters of a rotating fan blade with constant speeds are estimated.•Operating deflection shapes of a rotating fan blade are estimated.
A continuously scanning laser Doppler vibrometer (CSLDV) system is capable of rapidly obtaining spatially dense vibration measurement by continuously sweeping its laser spot along a path on a structure surface. This paper presents a new operational modal analysis (OMA) method for a rotating structure based on a rigorous rotating beam vibration theory, an image processing method, and a data processing method called the lifting method. A novel tracking CSLDV (TCSLDV) system was developed in this work to track and scan a rotating structure, and the real-time position of the rotating structure can be determined by image processing so that the TCSLDV system is capable of tracking a time-varying scan path on the rotating structure. The lifting method can transform raw TCSLDV measurement into measurements at multiple virtual measurement points as if they were measured by transducers attached to these measurement points. Modal parameters of the rotating structure with a constant speed, including damped natural frequencies, undamped mode shapes, and modal damping ratios, and operating deflection shapes (ODSs) of the structure with a constant or prescribed time-varying rotation speed can be determined by calculating and analyzing correlation functions with non-negative time delays among measurements at virtual measurement points. Experimental investigation is conducted using the TCSLDV system to study the OMA method with which modal parameters and ODSs of a rotating fan blade with different constant speeds, as well as an ODS of the rotating fan blade with a non-constant speed, are successfully estimated.
We previously demonstrated that fermitin family member 1 (FERMT1) was significantly overexpressed in colon cancer (CC) and associated with poor metastasis-free survival. This study aimed to ...investigate the precise role of FERMT1 in CC metastasis and the mechanism by which FERMT1 is involved in the epithelial-mesenchymal transition (EMT). Correlations between FERMT1 and EMT markers (E-cadherin, Slug, N-cadherin and β-catenin) were examined via immunohistochemistry in a cohort of CC tissues and adjacent normal colon mucosae. A series of in vitro and in vivo assays were performed to elucidate the function of FERMT1 in CC metastasis and underlying mechanisms. The upregulated expression of FERMT1 in CC tissues correlated positively with that of Slug, N-cadherin and β-catenin, but correlated inversely with E-cadherin expression. Altered FERMT1 expression led to marked changes in the proliferation, migration, invasion and EMT markers of CC cells both in vitro and in vivo. Investigations of underlying mechanisms found that FERMT1 interacted directly with β-catenin and activated the Wnt/β-catenin signaling pathway by decreasing the phosphorylation level of β-catenin, enhancing β-catenin nuclear translocation and increasing the transcriptional activity of β-catenin/TCF/LEF. Activation of the Wnt/β-catenin pathway by CHIR99021 reversed the effect of FERMT1 knockdown, whereas inhibition of the Wnt/β-catenin pathway by XAV939 impaired the effect of FERMT1 overexpression on EMT and cell motility. In conclusion, findings of this study suggest that FERMT1 activates the β-catenin transcriptional activity to promote EMT in CC metastasis.
•Nonlinear equations of a unit cell of transmission line systems are derived.•Complex boundary conditions due to rigid-flexible coupling are handled.•A comprehensive parametric study on band gaps is ...conducted.•Curve veering phenomena are observed among boundaries of band gaps.•A new design concept considering vibration and wave propagation is proposed.
Vibration analysis of periodic multi-span power transmission line systems is conducted and their band-gap characteristics are analyzed. Nonlinear partial differential equations of a unit cell of a periodic multi-span transmission line system are derived using the extended Hamilton principle along with their boundary conditions, where there is rigid-flexible coupling between an insulator and the cable. An accurate global spatial discretization method is used to deal with complex boundary conditions caused by sway of insulators and obtain spatially discretized, linearized equations of the unit cell. Two approaches are used: one spatially discretizes linearized governing partial differential equations and boundary conditions and the other applies Lagrange’s equations to spatially discretized, linearized energy and virtual work expressions. After obtaining spatially discretized, linearized equations, band gaps associated with wave propagation in a periodic infinite-span system are obtained using Bloch theory. Vibration transmissibility and energy distribution of a periodic finite-span system are studied using the transfer matrix method. From the relation between the wave frequency and characteristics of propagation constants, interaction between local vibration of the unit cell and global wave propagation among different spans is illustrated. Band gaps obtained from a finite-span system approach those from an infinite-span system when the number of cells becomes sufficiently large. A comprehensive parametric study is conducted to highlight effects of parameters of insulators and the cable on band gaps of the periodic multi-span transmission line system. Different types of curve veering phenomena that are related to the wave propagation problem of the periodic infinite-span transmission line system are observed for the first time among initial and cut-off frequencies of adjacent band gaps. Existence of band gaps and parametric study results can provide some support for design and vibration control of a power transmission line system.
A comprehensive dynamic model of a rotating hub–functionally graded material (FGM) beam system is developed based on a rigid–flexible coupled dynamics theory to study its free vibration ...characteristics. The rigid–flexible coupled dynamic equations of the system are derived using the method of assumed modes and Lagrange's equations of the second kind. The dynamic stiffening effect of the rotating hub–FGM beam system is captured by a second-order coupling term that represents longitudinal shrinking of the beam caused by the transverse displacement. The natural frequencies and mode shapes of the system with the chordwise bending and stretching (B–S) coupling effect are calculated and compared with those with the coupling effect neglected. When the B–S coupling effect is included, interesting frequency veering and mode shift phenomena are observed. A two-mode model is introduced to accurately predict the most obvious frequency veering behavior between two adjacent modes associated with a chordwise bending and a stretching mode. The critical veering angular velocities of the FGM beam that are analytically determined from the two-mode model are in excellent agreement with those from the comprehensive dynamic model. The effects of material inhomogeneity and graded properties of FGM beams on their dynamic characteristics are investigated. The comprehensive dynamic model developed here can be used in graded material design of FGM beams for achieving specified dynamic characteristics.
Background
In-plane vibration is significant to a structure and has been accurately solved by many numerical methods; however, there are still not enough studies on its experimental measurement.
...Objective
This work aims to propose a non-contact and fast way to measure dense full-field in-plane vibration of a plate structure, which has high frequencies and low response magnitudes.
Methods
A novel three-dimensional (3D) continuously scanning laser Doppler vibrometer (CSLDV) system that contains three CSLDVs is developed to conduct full-field scanning of a plate with free boundary conditions under sinusoidal excitation to measure its 3D vibrations. Calibration among the three CSLDVs in the 3D CSLDV system based on the geometrical model of its scan mirrors is conducted to adjust their rotational angles to ensure that three laser spots can continuously and synchronously move along the same two-dimensional scan trajectory on the plate. The demodulation method is used to process the measured response to obtain in-plane operating deflection shapes (ODSs) of the plate.
Results
Four in-plane ODSs are obtained in the frequency range of 0–5000 Hz. Modal assurance criterion (MAC) values between in-plane ODSs from 3D CSLDV and step-wise scanning laser Doppler vibrometer (SLDV) measurements are larger than 95%. MAC values between ODSs from 3D CSLDV measurements and corresponding mode shapes from the finite element model of the plate are larger than 91%.
Conclusions
Results from 3D CSLDV measurements have good accuracy compared to those from SLDV measurements and numerical calculation, and the 3D CSLDV system can scan much more measurement points in much less time than the SLDV system.
There are increasing concerns over the effects of veterinary antibiotics and heavy metals in agricultural soils. The widely used veterinary antibiotic oxytetracycline (OTC), Cu and their combination ...on soil microbial community function were assessed with the Biolog method. The microbial community was extracted from the soil and exposed to a 0.85% sodium chloride solution containing OTC (0, 1, 5, 11, 43, 109 and 217
μM), or Cu (0, 10, 20, 100 and 300
μM), or combination of the two pollutants (OTC 0, 5, 11
μM and Cu 0, 20
μM). Functional diversity, evenness, average well color development (AWCD) and substrate utilization decreased significantly with increasing concentrations of OTC or Cu (
p
<
0.005). The critical concentrations were 11
μM for OTC and 20
μM for Cu. The combination of OTC and Cu significantly decreased Shannon's diversity, evenness and utilization of carbohydrates and carboxylic acids compared to individual one of the contaminants. The antibiotic OTC and Cu had significant negative effects on soil microbial community function, particularly when both pollutants were present.
Oxytetracycline reduces the functional diversity of soil microbial community, and the combination of Cu and oxytetracycline leads to a further reduction.
As typical and significant structural elements, double-beam systems widely exist in practical engineering applications such as some subgrades and highway bridges. This paper focuses on presenting the ...closed-form solutions of the forced transverse vibration of a coupled Timoshenko double-beam system under compressive axial load. The solutions are generalized and can be suitable for any boundary conditions. The present model is generalized and can be reduced to any existing double-beam systems. Timoshenko model is employed to express the two beams of the double-beam system. Using the Laplace transform, the steady-state Green's functions of the coupled double-beam system can be derived. Since the Green's functions are fundamental solutions of the system, the steady-state forced vibration solutions can be obtained with the help of the superposition principle. In the numerical section, the present solutions are compared with the other known results along with FEM solutions for verification. In addition to the influences of the stiffness modulus of Winkler elastic layer and axial force on the present solutions that should be discussed, the influences of some physical parameters, such as the height-to-length ratio, external frequency, shearing effect, rotational inertia, on the closed-form solutions will also be presented. The effect of the compressive axial load is studied in this work.
The forced transverse vibration of a coupled Timoshenko double-beam system under compressive axial load, and the boundary conditions are generalized ones. Display omitted
•Forced vibration solutions for Timoshenko double-beam systems are obtained.•A generalized model that can be reduced to a Double-Euler beam model is proposed.•The solutions are generalized and can be suitable to any boundary conditions.•Green's function method is used to obtain the closed-form solutions.•Dynamic buckling phenomena induced by the axial force are studied.
ZnO thin films were prepared in Ar and Ar+H2 atmospheres by rf magnetron sputtering, and then they were annealed in vacuum and Ar+H2 atmosphere, respectively. The structure and optical–electrical ...properties of the films were investigated by X-ray diffraction, transmittance spectra, and resistivity measurement, and their dependences on deposition atmosphere, annealing treatment, and aging were studied. The results showed that adding H2 in deposition atmosphere improved the crystallinity of the films, decreased lattice constant, increased band gap, decreased the resistivity by the order of 104Ωcm, but exhibited poor conductive stability with aging. After Ar+H2 and vacuum annealing, crystallinity of the films deposited in Ar and Ar+H2 was further improved; their resistivity was decreased by the order of 105 and 101Ωcm, respectively, and exhibited high conductive stability with aging. We suggest that the formed main defect is VO and Hi when H2 is introduced during deposition, which decreases the resistivity but cannot improve the conductive stability; hydrogen would remove negatively charged oxygen species near grain boundaries during Ar+H2 annealing to decrease the resistivity, and grain boundaries are passivated by formation of a number of VO–H complex (HO) to improve the conductive stability at the same time. Under vacuum annealing, the hydrogen that is introduced non-intentionally from deposition chamber maybe plays an important role; it exists as HO in the films to improve the conductive stability of the films.
Controlling and guiding elastic waves in solids is more complicated compared with electromagnetic and acoustic waves; design and fabrication of an elastic wave cloak with non-singular, homogeneous, ...and isotropic material parameters is a challenging task. Recent studies in the literature that focus on manipulating flexural waves in elastic thin plates mainly use a linear transformation with a linear radial-dependent mapping function, which has drawbacks of being narrowly banded or even having negative cloaking efficiency that results from singular material parameters on the internal boundary of the cloak. This paper presents a theory of nonlinear transformation-based flexural waves and derives the nonlinear ray-tracing equation for flexural waves. A broadband cylindrical cloak for flexural waves in an elastic thin plate is realized based on a nonlinear transformation, whose materials can be simplified as layered non-singular, homogeneous, and isotropic materials using an effective medium theory. Some advantages and improvements of the invisibility nonlinear-transformation cloak are analyzed by comparison with the linear-transformation cloak. The invisibility capability of the nonlinear-transformation cloak can be tuned by adjusting an impact parameter that is shown to have influence on flexural wave energy emitting into the region inside the cloak. Numerical simulations show that the nonlinear-transformation cloak is more effective for guiding flexural waves that propagate in the region outside the cloak than the linear-transformation cloak in a broad frequency range. They also show that the nonlinear-transformation cloak can accurately control ray tracing of different types of flexural waves under disturbances outside the cloak. The methodology developed here can be used to construct nonlinear-transformation cloaks for other types of waves.
•A nonlinear-transformation cloak is proposed to control flexural wave propagation.•A nonlinear ray trajectory equation is derived to construct a cylindrical cloak.•Two parameters are introduced to adjust efficiency of the cylindrical cloak.•Qualities of the invisibility nonlinear-transformation cloak were analyzed.•Control of flexural waves under disturbances outside the cloak is confirmed.
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