Dynamic Resonance Research Articles

Response of structure models to sinusoidal dynamic action

The use of small-sized models of structures printed on 3-D printers is possible due to the electroelastic properties of ABS plastic. A comparison of their reactions with analogs made of plexiglas, used in studies of concrete structures, was made. The influence of the environment - water or sea sand, support conditions - free support or pinching, shape - simple or complex in planon the response of models from two different materials was investigated. The laboratory setup simulated a dynamic sinusoidal effect using: a digital frequency generator from 1 to 10000 Hz, an acoustic system diffuser, a microphone amplifier, two electrodes, and a computer in a two-channel oscilloscope mode. The vibration characteristics at the base and top of the models were recorded. The experimental system turned out to be sensitive to the shape, methods of fastening elements, the structure as a whole, and the medium of wave propagation. The response was analyzed in terms of the dynamic compliance coefficient and resonance frequencies, reflecting the similarity of the responses of the plexiglas and ABS models. Printing will allow you to adjust the shape and connections of the elements of the models so that they work like mechanical resonators – filters - in a narrow band. No resonances are expected outside this band. In the operated structures, the quality of the element connections is reproduced. Changing the existing rigidity to obtain resonances in a narrow band can serve as a criterion for choosing an effective amplification method.

Contribution to Harmonic Depollution Control by the Use of Adaptive Hybrid Filter Type TLC: Case of Control by Modulated Hysteresis

In this article, we propose a topology of a TLC-HAPF power filter as a harmonic compensator for an optimization of the pollution control of electrical networks. This filter consists of an active part and a passive part in order to reduce or limit switching losses during current injection into networks thanks to its TLC module. This topology also provides solutions dynamic performance issues, resonance and lack of compensation capacity for imbalance cases. It also offers a greater range of compensation than conventional active models which do not offer as well as an intermediate circuit voltage in the order of 105 V to 109 V relatively lower than others models (600 v). A modulated hysteresis control of this topology is therefore also developed in this article and allows to obtain a network analysis on the three phases at three levels: source side, load side, and finally at the connection of the filter to the network, allowing to specify for these different positions the value of the current spectrum and its THD at this well-defined moment.

Horizontal stress increase induced by deep vibratory compaction

Compaction by vertically or horizontal oscillating probes increases not only the soil stiffness but also the horizontal effective stress. An important, but often neglected, consequence is that compaction also causes preloading of the soil. The change in horizontal stress following vibratory compaction can be measured independently by two in situ methods – a cone penetration test (CPT) and a flat dilatometer test (DMT). Values of sleeve resistance (CPT) and horizontal stress index (DMT) can be determined prior and after compaction. In this work, five case histories reported in the literature where different vibratory compaction methods were used (dynamic compaction, vibroflotation, VibroWing, TriStar and resonance compaction) were re-analysed. For each test site, the change in CPT cone resistance and sleeve resistance was determined and compared with the increase in horizontal stress index from DMTs. The preloading effect due to vibratory compaction was estimated using empirical correlations.

Multidimensional characterization of the conical intersection seam in the normal mode space.

Multidimensional conical intersection seam has been characterized by utilizing the dynamic resonances in the nonadiabatic transition probability experimentally observed in the predissociation of thioanisole isotopomers. The nonadiabatic bifurcation behavior of the reactive flux into either the Herzberg type-I (electronic) or type-II (vibrational) predissociation pathway is found to be strongly dependent on the quantum nature of the S1/S2 vibronic eigenstate, providing the essential information about structure and dynamic character of the conical intersection seam projected onto the normal mode space. By modifying the nature of the normal mode space through partial or full H/D substitution of the molecule, multiple aspects of the conical intersection seam could be characterized from different viewpoints set by the adjusted normal mode space. Theoretical calculations of potential energy curves along selected normal mode displacements support the experiment.

Spectral analysis of Morse-Smale flows, II: Resonances and resonant states

The goal of the present work is to compute explicitely the correlation spectrum of a Morse-Smale flow in terms of the Lyapunov exponents of the Morse--Smale flow, the topology of the flow around periodic orbits and the monodromy of some given flat connection. The corresponding eigenvalues exhibit vertical bands when the flow has periodic orbits. As a corollary, we obtain sharp Weyl asymptotics for the dynamical resonances.

Multi-planar 3D breast segmentation in MRI via deep convolutional neural networks.

Nowadays, Dynamic Contrast Enhanced-Magnetic Resonance Imaging (DCE-MRI) has demonstrated to be a valid complementary diagnostic tool for early detection and diagnosis of breast cancer. However, without a CAD (Computer Aided Detection) system, manual DCE-MRI examination can be difficult and error-prone. The early stage of breast tissue segmentation, in a typical CAD, is crucial to increase reliability and reduce the computational effort by reducing the number of voxels to analyze and removing foreign tissues and air. In recent years, the deep convolutional neural networks (CNNs) enabled a sensible improvement in many visual tasks automation, such as image classification and object recognition. These advances also involved radiomics, enabling high-throughput extraction of quantitative features, resulting in a strong improvement in automatic diagnosis through medical imaging. However, machine learning and, in particular, deep learning approaches are gaining popularity in the radiomics field for tissue segmentation. This work aims to accurately segment breast parenchyma from the air and other tissues (such as chest-wall) by applying an ensemble of deep CNNs on 3D MR data. The novelty, besides applying cutting-edge techniques in the radiomics field, is a multi-planar combination of U-Net CNNs by a suitable projection-fusing approach, enabling multi-protocol applications. The proposed approach has been validated over two different datasets for a total of 109 DCE-MRI studies with histopathologically proven lesions and two different acquisition protocols. The median dice similarity index for both the datasets is 96.60 % (±0.30 %) and 95.78 % (±0.51 %) respectively with p < 0.05, and 100% of neoplastic lesion coverage.

Chromium effects on the microstructural, mechanical and thermal properties of a rapidly solidified eutectic Sn-Ag alloy

PurposeThis study aims to investigate the chromium (Cr) effects on the microstructural, mechanical and thermal properties of melt-spun Sn-3.5Ag alloy.Design/methodology/approachTernary melt-spun Sn-Ag-Cr alloys were investigated using X-ray diffractions, scanning electron microscope, dynamic resonance technique, instron machine, Vickers hardness tester and differential scanning calorimetry.FindingsThe results revealed that the Ag3Sn intermetallic compound (IMC) and ß-Sn have been refined because of the hard inclusions’ (Cr atoms) effects, causing lattice distortion increasing these alloys. The tensile results of Sn96.4-Ag3.5-Cr0.1 alloy showed an improvement in Young’s modulus more than 100 per cent (42.16 GPa), ultimate tensile strength (UTS) by 9.4 per cent (23.9 MPa), compared with the eutectic Sn-Ag alloy due to the high concentration of Ag3Sn and their uniform distribution. Shortage in the internal friction (Q−1) of about 54 per cent (45.1) and increase in Vickers hardness of about 7.4 per cent (142.1 MPa) were also noted. Hexagonal Ag3Sn formation led to low toughness values compared to the eutectic Sn-Ag alloy, which may have resulted from the mismatching among hexagonal Ag3Sn phase with orthorhombic Ag3Sn and ß-Sn phases. Mechanically, the values of Young’s modulus have been increased, with increasing chromium content, whereas the UTS and toughness values have been decreased. The opposite of this trend appeared in Sn95.8-Ag3.5-Cr0.7 alloy, which may have been due to high lattice distortion (ƹ = 16.5 × 10−4) compared to the other alloys. Increase in the melting temperature Tm, ΔH, Cp and ΔT was because of Ag3Sn IMC formation. The low toughness of Sn96-Ag3.5-Cr0.5 and Sn95.8-Ag3.5-Cr0.7 (109.56 J/m3 and 35.66 J/m3), relatively high melting temperature Tm (223.22°C and 222.65°C) and low thermal conductivity and thermal diffusivity (32.651 w.m−1.k−1 and 0.314 m2/s) make them undesirable in the soldering process. The high UTS, high E, high thermal conductivity and diffusivity, low creep rate and low electrical resistivity, which have occurred with “0.1 Wt.%” of Cr, make this alloy desirable and reliable for soldering applications and electronic assembly.Originality/valueThis study provides chromium effects on the structure of the eutectic Sn-Ag rapidly solidified by melt-spinning technique. In this paper, the authors compared the elastic modulus of the melt-spun compositions, which have been resulted from the Static method with that have been resulted from the Dynamic method. This paper presents new improvements in mechanical and thermal performance.

Nonlinear modal interaction of an electrically actuated microbeam with flexible support

For the electrically actuated microbeam subjected to a combination of DC and AC voltage loadings, we studied the nonlinear dynamical responses and internal resonance analytically. The flexible boundary condition is considered. The modal interaction due to three-to-one internal resonance between the first and second modes is highlighted. The method of multiple scales is employed to get the modulation equation, which describes the amplitude and phases of the involving modes. Then, the equilibrium solutions of the modulation equation are calculated and their stability is examined. The frequency and force response curves reflecting the primary resonance (the first mode) are presented. We find that the first and second modes in the proposed model are coupled, and hence the energy transfer can occur between the involving modes. Moreover, it is found that the response of the system may encounter Hopf bifurcation for some specific parameters. As for simulation, the Galerkin scheme is applied to verify the analytical results in terms of time history, phase-plane portrait, Fourier spectrum, and Poincare section. The simulation results are in good agreement with the analytical ones.

Fatigue and extreme load reduction on two‐bladed wind turbines using the flexible hub connection

AbstractThe load reduction potential in regular operation and the design drivers of a flexible hub connection on two‐bladed turbines are presented in this paper. Developed for the two‐bladed Skywind 3.4 MW wind turbine, the flexible hub connection integrates an additional, multidirectional elasticity between the hub mount and the nacelle carrier to reduce the load transfer into the support structure. The stiffness and damping properties of the interface connection determine the load amplitudes of the system and influence the overall turbine dynamics. Consequently, the design relevant operating scenarios change due to a potential dynamic instability, resonance, or violation of deflection margins in comparison with a nonflexible hub connection. The system's capability to reduce fatigue and ultimate loads is assessed in several turbulent inflow conditions and transient operating states, while taking into account the operating limits of displacements. A permutation of the dynamic coupling parameters is conducted to characterize the sensitivity of load characteristics to the design variables. By identifying the critical operating conditions, it is possible to provide design guidelines for an effective optimization strategy.

Numerical Analysis on Mathieu Instability of a Top-Tensioned Riser in a Dry-Tree Semisubmersible

AbstractThe development of a dry-tree semisubmersible (DTS), a new type offshore hydrocarbon production system, is facing unconventional challenges in the issues of dynamic stability, structural integrity, and parametric resonance. The Mathieu equation is used to assess the dynamic stability of a top-tensioned riser (TTR) in order to prevent the parametric resonance which leads to detrimental effects on structural integrity. The objectives of this paper are to (i) study a Mathieu stability diagram and its coefficients for an assessment of the stability of a TTR, (ii) identify the effects of the dynamic tension variations in the Mathieu stability assessment, and (iii) analyze the stability of the TTR on a DTS, which is equipped with a long-stroke tensioner, by using numerical simulation. The dynamic tension variation in the DTS was identified to induce instability in the TTR. Hence, the Mathieu stability assessment is recommended to be included in an analysis of TTR behaviors in a dry-tree interface of semisubmersibles.

Thermo-mechanical stability of single-layered graphene sheets embedded in an elastic medium under action of a moving nanoparticle

Using an energy-based method, this paper sought to analyze dynamic stability and parametric resonance of single-layered graphene sheets (SLGSs) embedded in thermal environment and elastic medium while carrying a nanoparticle moving along an elliptical path. In order to present a realistic model, all inertial effects of the moving nanoparticle are taken into account in the dynamic formulation of the system. Equations governing the transverse vibrations of the embedded SLGS are obtained using the Hamilton's principle. Small-scale effects based on the Eringen's nonlocal elasticity theory are considered in deriving the motion equations. The equations governing the reduced model are calculated based on the Galerkin method. To calculate the instability boundaries, the energy-rate method is applied on the ordinary differential equations (ODEs) governing the system oscillations. The effects of nonlocal parameter, the nanoparticle motion path radii, SLGS length-to-width ratio, temperature change of the thermal environment, stiffness of the elastic medium and boundary conditions of SLGS on the parametric instability regions are examined. The results show that these parameters influence the system stability, so that a decrease in the nonlocal parameter, the SLGS length-to-width ratio and the nanoparticle motion path radii and also an increase in the stiffness coefficients of the elastic medium improve the system stability. The model presented in this paper is validated by comparing the observations with those published in previous studies.

Dynamics of destructive Fano resonances

Based on the substantial difference in the response time for the resonant and background partitions at stepwise variations of the exiting signal, a simple exactly integrable model describing the dynamic Fano resonance (DFRs) is proposed. The model does not have any fitting parameters, may include any number of resonant partitions and exhibits high accuracy. It is shown that at the point of the destructive interference any sharp variation of the amplitude of the excitation (no matter an increase or a decrease) gives rise to pronounced "flashes" in the intensity of the output signal. In particular, the flash should appear behind the trailing edge of the exciting pulse, when the excitation is already over. The model is applied to explain the DFRs at the light scattering by a dielectric cylinder with two resonant modes excited simultaneously and exhibits the excellent agreement with the results of the direct numerical integration of the Maxwell equations.

Improved localized surface plasmon resonance responses of multi-metallic Ag/Pt/Au/Pd nanostructures: systematic study on the fabrication mechanism and localized surface plasmon resonance properties by solid-state dewetting

Multi-metallic nanoparticles (NPs) can offer dynamic and tunable localized surface plasmon resonance (LSPR) properties that are suitable for various catalysis, sensing and energy harvesting applications due to the wide range of tunability and applicability. In this work, the systematic fabrication and improved LSPR characteristics of multi-metallic alloy NP arrays are demonstrated based on the solid-state dewetting (SSD) of multi-layers of Ag/Pt/Au/Pd on sapphire (0001). The evolution of surface NPs in terms of configurational and elemental specifications yields vary strong and dynamic LSPR bands in the UV and VIS wavelengths based on the excitation of various plasmonic modes, i.e. dipolar (DR), quadrupolar (QR), multipolar (MR) and higher order (HO) bands, which is further exploited by the finite difference time domain simulations. Through the systematic control of multi-layer thickness, layer ratio and growth conditions, various nanostructures such as voided nanoclusters, network-like NPs and isolated semispherical NPs are obtained, which are unique in terms of morphology and elemental composition at each stage of dewetting process. The growth mechanism of multi-metallic alloy NP arrays is proposed based on the temperature driven thermal diffusion, alloying, Rayleigh-like instability and energy minimization mechanisms. Due to the subsequent sublimation of Ag atoms at above 650 °C, a sharp alteration in the elemental and morphological characteristics is demonstrated. In specific, the high percentage of Ag alloy NPs exhibits strong LSPR bands and gradually weakened along with the Ag sublimation. At the same time, however, the alloy or mono-metallic NPs without Ag still demonstrate much stronger LSPR bands as compared to the monometallic NPs by the SSD of pure films.

Dynamical vector resonances from the EChL in VBS at the LHC: the WW case

In this work we study the phenomenology of the process pp → W+W−jj at the LHC, in the scenario of the resonant vector boson scattering subprocess W+W−→ W+W− which we describe within the effective field theory framework of the Electroweak Chiral Lagrangian. We assume a strongly interacting electroweak symmetry breaking sector in which dynamically generated resonances with masses in the TeV scale appear as poles in the Electroweak Chiral Lagrangian amplitudes unitarized with the Inverse Amplitude Method. The relevant resonance here, V0, is the neutral component of the triplet of vector resonances which are known to emerge dynamically at the TeV scale for specific values of the Electroweak Chiral Lagrangian parameters. With the aim of studying the production and possible observation of V0 at the LHC, via the resonant W+W−→ W+W− scatter- ing, a MadGraph 5 UFO model has been developed employing a phenomenological Proca Lagrangian as a practical tool to mimic the correct V0 properties that are predicted with the Inverse Amplitude Method. We choose to study the fully hadronic decay channel of the final gauge bosons W W → J (jj)J (jj) since it leads to larger event rates and because in the alternative leptonic decay channels the presence of neutrinos complicates the re- construction of the resonance properties. In this context, the 2 boosted jets from the W hadronic decays, jj, are detected as a single fat jet, J , due to their extreme collinearity. We perform a dedicated analysis of the sensitivity to these vector resonances V0 with masses between 1.5 and 2.5 TeV at the LHC with sqrt{s} = 13 TeV and the planned high luminosity of 3000 fb−1, paying special attention to the study of efficient cuts to extract the resonant vector boson fusion signal from the QCD background, which clearly represents the main challenge of this search.

Correlation of quantitative parameters of dynamic enhanced magnetic resonance imaging with Dukes stage, lymph node metastasis and tumor differentiation degree of rectal cancer

Objective To explore the correlation between quantitative parameters of dynamic enhanced magnetic resonance imaging (DCE-MRI) and Dukes stage, lymph node metastasis, tumor differentiation degree and molecular biological indicators [Ki67 and human epidermal growth factor receptor 2 (CerbB-2)] of rectal cancer. Methods This study was a prospective study. From October 2014 to October 2017, 168 cases of rectal cancer patients were selected as the research objects. DCE-MRI was performed preoperatively to obtain the quantitative parameter values of region of interest (ROI) [apparent diffusion coefficient (ADC)mean, Ktrans, Ve, and Kep] in tumor site. The expression of Ki67 and CerbB-2 were detected by immunohistochemical. Correlations of DCE-MRI quantitative parameter values and rectal cancer Dukes staging, lymph node metastasis, tumor differentiation degree to Ki67 and CerbB-2 expression level were analysised. Results With the increase of tumor differentiation, ADCmean was increasing, while Ktrans and Ve showed a downward trend, with significant difference (P 0.05). The ADCmean was statistically significant between different groups (P 0.05). The ADCmean of lymph node metastasis group was significantly lower than that of no lymph node metastasis group (P<0.001), while Ktrans, Ve and Kep were significantly higher than that of no lymph node metastasis group (P<0.001). With the increase of Dukes staging in rectal cancer, ADCmean was decreasing and Ktrans was increasing, with statistically significant difference (P<0.001); among which the ADCmean of Dukes A and B was significantly higher than that of Dukes C and D (P<0.05), and Ktrans was significantly lower than that of Dukes C and D (P<0.05). Ktrans and Kep were increased with the increased expression levels of Ki67 and CerbB-2, and the difference between Ktrans and Kep was statistically significant (P<0.05). The ADCmean decreased with the increase of Ki67 and CerbB-2 expression level, and the difference was statistically significant (P<0.05). Conclusions DCE-MRI quantitatively participates can reflect the biological behavior of rectal cancer, and can be used to evaluate the prognosis of tumors and guide the clinical selection of more appropriate treatment options. Key words: Rectal neoplasms; Magnetic resonance imaging; Diagnosis, computer-assisted; Ki-67 antigen; Receptor, erbB-2

Photoinduced Electron Transfer in Donor-Acceptor Complexes: Isotope Effect and Dynamic Symmetry Breaking.

Electron–nuclear (vibronic) coupling has emerged as an important factor in determining the efficiency of energy transfer and charge separation in natural and artificial photosynthetic systems. Here we investigate the photoinduced charge-transfer process in a hydrogen-bonded donor–acceptor molecular complex. By using real-time quantum–classical simulations based on time-dependent Kohn–Sham equations, we follow in detail the relaxation from the Franck–Condon point to the region of strong nonadiabatic coupling where electron transfer occurs. We elucidate how the charge transfer is coupled to specific vibrational modes and how it is affected by isotope substitution. The importance of resonance in nuclear and electron dynamics and the role of dynamic symmetry breaking are emphasized. Using the dipole moment as a descriptive parameter, exchange of angular momentum between nuclear and electronic subsystems in an electron–nuclear resonant process is inferred. The performed simulations support a nonadiabatic conversion via adiabatic passage process that was recently put forward. These results are relevant in deriving rational design principles for solar-to-fuel conversion devices.

Dynamical generation of resonances in the P33 partial wave

We investigate the formation of resonances in the P33 partial wave with the emphasis on possible emergence of dynamically generated quasi-bound states as a consequence of a strong $p$-wave pion attractive interaction in this partial wave, as well as their possible interaction with the genuine quark excited states. By using the Laurent-Pietarinen expansion we follow the evolution of the $S$-matrix poles in the complex energy plane as a function of the interaction strength. Already without introducing a genuine quark resonant state, two physically interesting resonances emerge with pole masses around 1200 MeV and 1400 MeV, with the dominant $\pi N$ and $\pi\Delta$ component, respectively. The added genuine resonant state in the $(1s)^3$ quark configuration mixes with the lower dynamically generated resonance forming the physical $\Delta(1232)$ resonance, and pushes the second dynamical resonance to around 1500 MeV, which allows it to be identified with the $\Delta(1600)$ resonance. Adding a second resonant state with one quark promoted to the $2s$ orbit generates another pole whose evolution remains well separated from the lower two poles. We calculate the helicity amplitudes at the pole and suggest that their $Q^2$ dependence could be a decisive test to discriminate between different models of the $\Delta(1600)$ resonance.

Vector mesons as dynamical resonances in the Bethe–Salpeter framework

We present the first dynamical calculation of the ρ-meson as a resonance in the Dyson–Schwinger/Bethe–Salpeter framework by including explicit two-pion exchange in addition to the t-channel one-gluon exchange of rainbow-ladder in the interaction kernel. The width is determined from the imaginary part of the resonance pole and is generated by the singularity structure of the integrand, treated by means of suitable path deformations. We find the resonant mass and width to be 640 MeV and 100 MeV respectively, corresponding to a coupling constant gρππ=5.7; repulsive corrections beyond rainbow-ladder are expected to bring these in line with experiment. Furthermore we present the dependence of these parameters on the pion mass and compare with results from lattice QCD.

Influence of imperfection on amplitude and resonance frequency of a reinforcement compositionally graded nanostructure

This article investigates the influences of nonuniform imperfection on the dynamic amplitude and resonance frequency of the nanoshell reinforced with graphene nanoplatelet (GNP). The novelty of the current study is to consider the effects of porosity, thermal loading and graphene platelet reinforced composites on the dynamic behavior of the nanostructure. Three-length scale parameters (l 0 = 5 h, l 1 = 3 h, l 2 = 5 h) in the modified strain gradient theory (MSGT) show a better agreement with MD simulation in comparison with other theories. Finally, the effects of different factors on the dynamic amplitude and resonance frequency of the porous nanostructure are examined in detail.

Luni-solar resonances and effect on long-term evolution of inclined geostationary transfer orbits

In this paper, a singly-averaged, semi-analytical orbital dynamic model in terms of Milankovitch elements is given for geostationary transfer orbits (GTOs), which includes the Earth's oblateness, luni-solar perturbations, atmospheric drag and solar radiation pressure (SRP). The orbital dynamic model is verified through a numerical simulation compared with the Semi-analytic Tool for End of Life Analysis software (STELA) by CNES. We find that if the area-to-mass ratio of the object is relatively large, the SRP will have a significant impact on the long-term evolution of GTOs. Then, the long-term dynamical evolution and orbital resonances of rocket upper stages in inclined geostationary transfer orbits (IGTOs) are studied. It has been found that the luni-solar secular resonances, which are inclination-dependent-only, play a leading role in the long-term evolution of IGTOs. By comparing and analyzing long-term dynamical evolution of orbits with different initial inclinations, the effects of luni-solar secular resonances are studied in details. Finally, a mitigation method for IGTO objects by utilizing luni-solar secular resonances is proposed, in which the eccentricity growth caused by the resonances is used for an early atmospheric re-entry.