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2021-11-02 | Objective Astrocytes participate in the local innate immune response of the central nervous system. In response to stress such as ischemia, activated cells release endogenous factors known as damage-associated molecular patterns (DAMPs). Self-extracellular RNA (eRNA) is such a ubiquitous alarm signal. However, it is unclear whether eRNA is involved in the early acute phase of cerebral ischemia and is sufficient to sensitize astrocytes towards a DAMP or PAMP (pathogen-associated molecular pattern) reaction. Methods Pro-inflammatory activation upon eRNA stimulation was characterized in primary murine astrocyte cultures. In vivo, an experimental stroke model was used to localize and quantify eRNA in murine brain sections. Using primary cortical neurons and the mouse hippocampal neuronal cell line HT-22, neuronal RNA release upon stress conditions related to cerebral hypoxia/ischemia was analyzed. Results While low-dose eRNA alone did not promote pro-inflammatory activation of astrocytes in culture, it strongly enhanced the expression of pro-inflammatory cytokines in the presence of either Pam2CSK4, a synthetic PAMP molecule that mimics bacterial infection, or high mobility group box 1 (HMGB1), a prominent DAMP. Synergism of eRNA/Pam2CSK4 and eRNA/HMGB1 was prevented by blockage of the astroglial toll-like receptor (TLR)-2. Inhibition of NF-κB- and mitogen-activated protein kinase-dependent signaling pathways hampered eRNA/Pam2CSK4-mediated pro-inflammatory activation of astrocytes. In vivo, the amount of non-nuclear, presumably extracellular ribosomal RNA in close proximity to neurons significantly accumulated across the infarct core and peri-infarct areas that was accompanied by transcriptional up-regulation of various pro-inflammatory factors. Accordingly, the exposure of neurons to hypoxic/ischemic stress in vitro resulted in the release of eRNA, partly mediated by active cellular processes dependent on the cytosolic calcium level. Conclusion The DAMP signal eRNA can sensitize astrocytes as active players in cerebral innate immunity towards exogenous and endogenous activators of inflammation (PAMPs and DAMPs) in a synergistic manner via TLR2-NF-κB-dependent signaling mechanisms. These findings provide new insights into the pathogenesis of ischemic stroke and other inflammatory neurological disorders. Further studies will clarify whether administration of RNase in vivo may serve as an effective treatment for inflammatory brain pathologies. | Self-extracellular RNA promotes pro-inflammatory response of astrocytes to exogenous and endogenous danger signals | 10.1186/s12974-021-02286-w |
2021-11-01 | Reinforced concrete shear walls are the structural elements that considerably increase the seismic performance of buildings. Fiber elements and fiber-spring elements are used for the modeling of the inelastic behavior of these elements. The Fiber Element Method provides a certain amount of accuracy for the modeling of reinforced concrete shear walls. However, the studies related to this method are still in progress. In this study, different damping ratios and different damping types used in the structural damping are investigated by using the force-based fiber element method for reinforced concrete shear wall structures. Two shear wall structures subjected to seismic loads are used to compare numerical analysis and experimental results. The comparisons are achieved according to the absolute maximum values of the overturning moment, the base shear force, and the roof displacement. Rayleigh damping and stiffness-proportional damping types for the damping ratios that vary between 2 and 3% provide better results than mass-proportional damping. Additionally, the optimum number of fiber elements for Rayleigh and stiffness-proportional damping types is determined for the optimum damping ratio that provides minimum differences between numerical analysis and experimental results. For these damping types, when the length of a fiber is smaller than 3% of the longitudinal length of the shear wall at the optimum damping ratios, the roof displacement differences between numerical analysis and experimental results are less than 2.5%. | Numerical simulation of reinforced concrete shear walls using force-based fiber element method: effect of damping type and damping ratio | 10.1007/s10518-021-01221-x |
2021-11-01 | This paper uses TRT-LBM coupled with the effective viscosity to predict squeeze film air damping (SQFD) of micro-beam in the transition regime. The result shows that, in the transition regime, recent MC model underestimates the quality factor for ignoring the gas viscosity effect and recent Reynolds model overestimates it for ignoring the rarefaction effect. The TRT-LBM model proposed in this paper is more accurate than Reynolds and MC models in the transition regime. In addition, the end effect on SQFD is discussed, which shows that the constant ambient pressure condition on the edges would overestimate the quality factor of SQFD. | A TRT-LBM model of squeeze film air damping of micro-beam in the transition regime | 10.1007/s00419-021-02024-x |
2021-11-01 | The subject of this study is a new Process Damping Model approach for milling with flat end milling cutter. Dynamic model of the cutting system was modeled and applied for the milling operation. The machining process is developed mathematically as a complex dynamic cutting model with two degree of freedom. This cutting model is designed according to both friction forces due to contact with wavy surface and shear angle ( φ ) oscillations. Considering Process Damping Ratios (PDRs), shearing force equations of the system are mathematically modeled. This created process damping model is a complex model, and it enables to obtain process damping values and rates both due to the deflection of the insert and the penetrating of the cutting edge to the wavy surface. It is also explained how the total process damping of the cutting system will change and how the equations will be arranged accordingly. Comparative process damping rates were obtained by making modal analyzes to obtain structural constants of different length cutting tools. The experimental results determined were applied to the developed model, and it was calculated that the rate of process damping varies depending on the factors. The most obvious difference that distinguishes this study from others is the change, and amount of the PDR is estimated by the analytical calculation procedure which runs in reverse to the conventional Stability Lobe Diagrams. | Process damping model approach in milling operations | 10.1007/s40430-021-03201-3 |
2021-11-01 | This paper investigates the steady-state response of a harmonically excited multi-degree-of-freedom (MDOF) system with a Coulomb contact between: (1) a mass and a fixed wall; (2) two different masses; (3) a mass and an oscillating base. Although discrete MDOF models are commonly used at early design stages to analyse the dynamic performances of engineering structures, the current understanding of the friction damping effects on MDOF behaviour is still limited due to the absence of analytical solutions. In this contribution, closed-form expressions of the continuous time response, the displacement transmissibility and the phase angle of each mass of the system are derived and validated numerically for 2DOF and 5DOF systems. Moreover, the features of the analytical response are investigated, obtaining the following results: (i) the determination of the minimum amounts of friction for which the resonant peaks become finite and (ii) for which stick-slip motion can be observed at high frequencies; (iii) an equation for the evaluation of invariant points for the displacement transmissibilities; (iv) a better understanding of phenomena such as the inversions of the transmissibility curves and the onset of additional resonant peaks due to the permanent sticking of the mass in contact. All these results show that MDOF systems exhibit significantly different dynamic behaviours depending on whether the friction contact and the harmonic excitation are applied to the same or different masses. | Dynamic response of multi-degree-of-freedom systems with a Coulomb friction contact under harmonic excitation | 10.1007/s11071-021-06966-3 |
2021-11-01 | A design for a gas foil bearing with springs for secondary stiffness is presented. The construction of a bearing test rig, designed and built for conducting the tests in order to determine the maximum load capacity of the bearing for various shaft speeds (under normal conditions), is considered. The results of the experimental research into maximum load capacity depending on the shaft rotation frequency are reported. The factors affecting the maximum load capacity are described. | Determination of the Maximum Load Capacity of a Gas Foil Journal Bearing | 10.1007/s10556-021-00990-1 |
2021-11-01 | This study is to present a novel way to achieve superior passive vibration isolation by employing a specially designed and compact linkage mechanism. The proposed anti-vibration system has beneficial nonlinear inertia, inspired by swinging motion of human arms, and is constructed with an adjustable nonlinear stiffness system inspired by animal or human leg skeleton. It is shown with comprehensive theoretical analysis and consequently validated by a series of well-designed experiments that the nonlinear stiffness, nonlinear damping and nonlinear inertia of the proposed system are very helpful for significantly reducing resonant frequency and enhancing damping effect in a beneficial nonlinear way. This results in excellent vibration isolation performance with lower resonant frequency and resonant peak of faster decay rate. This study provides an innovative solution to a cost-efficient vibration control demanded in various engineering systems. | Vibration isolation with passive linkage mechanisms | 10.1007/s11071-021-06878-2 |
2021-11-01 | Often, the responses of additive manufactured parts are studied only in the context of static loads, since most consumer-grade additive manufactured parts are not capable of supporting dynamic loads. Here, the effects of fabrication parameters on the vibratory properties of 3D-printed polymer composite beams were studied. A total of 420 vibratory system identification experiments were conducted on 70 additive manufactured cantilever beams. In addition, Euler-Bernoulli beam theory and the finite element method were used to estimate the first natural frequency of the beams. It was found that build parameters change not only the stiffness of the beam, but these build parameters also affect the damping ratio. Furthermore, the frequency response of the beams is amplitude-dependent; this nonlinear effect is important in predicting the behavior of 3D printed structures. The complex relationship between the build parameters and the nonlinear vibratory response points to the possibility of creating tailored vibratory responses of 3D-printed structures. Since vibrations can cause accelerated wear, this work could also be important in determining accurate life cycle predictions of additive manufactured parts. | Nonlinear vibratory properties of additive manufactured continuous carbon fiber reinforced polymer composites | 10.1007/s00170-021-07456-x |
2021-11-01 | Reductive perturbation method (RPM) is used to obtain damped forced Kadomtsev–Petviashvili (DFKP) equation for the ion acoustic waves (IAWs) in a magnetized dusty plasma comprising electrons abiding by q -nonextensive velocity distribution, in the presence of external periodic force along with a damping term. A nonstationary solitary wave solution of IAW under the influence of forcing and damping term is derived through the framework of KP equation. The influence of various plasma parameters such as electron velocity distribution parameter ( q ), collisional frequency ( $$\nu _{id0}$$ ν i d 0 ), initial wave velocity ( $$M_0$$ M 0 ), external periodic forcing term ( $$f_0$$ f 0 ) and periodicity of external force ( $$\omega $$ ω ) etc. on solitary wave structures are studied from a numerical standpoint. Significant effects in the variation of width and amplitude of the soliton are observed due to the change of the parameters $$f_0$$ f 0 , M and $$\omega $$ ω . It is found that there is a parametric regime of $$f_0$$ f 0 for which the solitary structure exists in the form of a Gaussian pulse and beyond a cut-off value of $$f_0$$ f 0 , the solitary structure collapses. | Non-stationary Solitary Wave Solution for Damped Forced Kadomtsev–Petviashvili Equation in a Magnetized Dusty Plasma with q-Nonextensive Velocity Distributed Electron | 10.1007/s40819-021-01168-2 |
2021-11-01 | Background The elastic wave propagation characteristics, especially the local plus resonance phenomenon, affect the stability and the accuracy of the electronic components mounted on the spacecrafts significantly, which implies that the layout of the electronic components in the spacecrafts should be away from the plus resonance domains. Thus, considering two electronic components set symmetrically on a plate fixed on the spacecrafts by eight bolts, the elastic wave propagation properties in the plate are investigated by a structure-preserving approach in this paper. Method A non-smooth dynamic model is presented to describe the elastic wave propagation in the non-homogeneous centrosymmetric damping plate excited by the impact series acting on the connecting bolts. Then, a structure-preserving approach is proposed to simulate the localized wave propagation phenomenon in the plate based on the generalized multi-symplectic theory. Accompanying with the structure preserving approach, both the local energy dissipation and the generalized multi-symplectic residual are formulated in detail. Results and Conclusions In the numerical examples, the local plus resonance domains are explored for several load cases. From the numerical results, it can be found that the steady plus resonance domains are symmetric if and only if the impact series is symmetric. It is interesting to observe that, in some cases of the uniform impact series, the local plus resonance domains may exhibit splitting phenomenon or degeneration phenomenon with the time increase. The above-mentioned novel findings can be used to guide the layout optimization of the electronic components in the spacecrafts directly. In addition, the structure-preserving approach developed in this paper proposes a new way to investigate the non-smooth dynamic systems. | Wave Propagation in Non-homogeneous Centrosymmetric Damping Plate Subjected to Impact Series | 10.1007/s42417-021-00355-1 |
2021-11-01 | A major source of electric vehicle energy loss is the vibration energy dissipated by the shock absorbers under irregular road excitation, which is particularly severe when active wheel systems are employed because their greater unsprung mass leads to greater shocks and vibrations. Therefore, a tubular linear energy harvester (TLEH) with a large stroke and low electromagnetic force ripple is designed to convert this vibration energy into electricity. The proposed TLEH employs a slotted external mover with three-phase winding coils and an internal stator with PMs to increase the stroke, adopts a fractional slot-per-pole configuration to reduce its size and improve the winding factor, and realizes significantly reduced cogging force by optimizing the incremental length of the armature core. A finite element model of the TLEH is first verified against a theoretical model and then used to investigate the influences of various road excitation frequencies and amplitudes on the electromotive force (EMF) waveforms and generated power, the efficiency and damping force according to load condition, and the energy recovery and nonlinear electromagnetic force characteristics of the TLEH. A resistance controller is then designed to realize a self-damping electromagnetic suspension. The results indicate that the EMF and the generated power waveforms depend on the excitation frequency and amplitude, the efficiency increases and the damping coefficient decreases with the increasing load resistance. | Design, Modeling, and Characterization of a Tubular Linear Vibration Energy Harvester for Integrated Active Wheel System | 10.1007/s42154-021-00144-2 |
2021-11-01 | Purpose The negative stiffness integrated tuned mass damper (NS-TMD) is considered as an interesting and efficient device for passive vibration control. However, design/optimization of NS-TMD may not always lead towards robust performance if there exist uncertainties. In this study, a stochastic design of NS-TMD is proposed taking into account various types of uncertainties. Methods Taylor-expansion is used to perturb the objective function facilitating a stochastic design/optimization. Besides, an interval-extension is used to observe the effect of uncertainties with different intensities. The Lyapunov equation is used in the proposed design of NS-TMD by minimizing the dispersion of displacement of primary system. The present work takes into account a standard model of NS-TMD in view of wider applicability of the present study. Random vibration is considered in both the cases of: (a) base-excitation and (b) superstructure loading. Results A numerical investigation is further carried out to observe the consequences of uncertainties on optimum design of NS-TMD parameters for both the cases of base-excitation and superstructure loading. Efficiency of NS-TMD is compared under various levels of uncertainties. Besides, some significant earthquake records and white noise (WN) samples are utilized towards more realistic understanding on the performance of stochastic design of NS-TMD under seismic excitation with different level of uncertainties. NS-TMD appears to be effective in robustness against uncertainties in structural parameters in comparison with the frequently used TMD system. Conclusion The proposed methodology may be considered as a useful alternative for stochastic design of the NS-TMD under both superstructure loading and base-excitation. | On Stochastic Design of Negative Stiffness Integrated Tuned Mass Damper (NS-TMD) | 10.1007/s42417-021-00356-0 |
2021-11-01 | Prothymosin alpha (ProTα) is involved in multiple cellular processes. Upon serum-free stress, ProTα lacking a signal peptide sequence is non-classically released from C6 glioma cells as a complex with Ca^2+-binding cargo protein S100A13. Thus, ProTα and S100A13 are conceived to be members of damage-associated molecular patterns (DAMPs)/alarmins. However, it remains to be determined whether stress-induced release of ProTα and S100A13 involves SNARE proteins in the mechanisms underlying membrane tethering of the multiprotein complex. In the present study, we used C6 glioma cells as a model of ProTα release. In pull-down assay, p40 synaptotagmin-1 (Syt-1), a vesicular SNARE, formed a hetero-oligomeric complex with homodimeric S100A13 in a Ca^2+-dependent manner. The interaction between p40 Syt-1 and S100A13 was also Ca^2+-dependent in surface plasmon resonance (SPR). Immunoprecipitation using conditioned medium (CM) revealed that p40 Syt-1 was co-released with ProTα and S100A13 upon serum-free stress. In in situ proximity ligation assay (PLA), Syt-1 interacted with S100A13 upon serum-free stress in C6 glioma cells. The intracellular delivery of anti-Syt-1 IgG blocked serum free-induced release of ProTα and S100A13. Serum free-induced ProTα-EGFP release was significantly blocked by botulinum neurotoxin/C1 (BoNT/C1), which cleaves target SNARE syntaxin-1 (Stx-1). In immunocytochemistry, the cellular loss of ProTα-EGFP, S100A13, and Syt-1 was also blocked by BoNT/C1. Furthermore, the intracellular delivery of anti-Stx-1 IgG or Stx-1 siRNA treatment blocked Syt-1, S100A13 and ProTα release from C6 glioma cells. All these findings suggest that SNARE proteins play roles in stress-induced non-classical release of DAMPs/alarmins proteins, ProTα and S100A13 from C6 glioma cells. | Involvement of SNARE Protein Interaction for Non-classical Release of DAMPs/Alarmins Proteins, Prothymosin Alpha and S100A13 | 10.1007/s10571-020-00950-y |
2021-10-28 | In this paper, the controllability analysis is proposed for both linear and nonlinear higher-order fractional damped stochastic dynamical systems with distributed delay in Hilbert spaces which involve fractional Caputo derivative of different orders. Based on the properties of fractional calculus, the fixed point technique, and the construction of controllability Gramian matrix, we establish the controllability results for the considered systems. Finally, examples are constructed to illustrate the applicability of obtained results. | Controllability of higher-order fractional damped stochastic systems with distributed delay | 10.1186/s13662-021-03625-0 |
2021-10-22 | The Generalized Reduced Gradient (GRG) and Grey Relation Analysis (GRA) optimization techniques are used to optimize the parameters of shear mode magneto-rheological (MR) damper design to achieve the defined objectives. The purpose is to develop a smart damper for washing machine application. The main objective is to optimize parameters like magnetic coil height, width, radius of piston road and optimum fluid volume (as this contributes to 60% cost of MR damper). The anisotropic-particle-based MR fluid (having high stress at low magnetic field strength) properties are used in optimization. GRG and GRA gave similar results for the optimized parameter values. GRA method gives additional advantages in design validation. ANOVA Minitab software is used to analyse significant contributions of each parameter in the design part. The practical shear mode MR damper was fabricated using optimized design parameters. The force–displacement curve was recorded using the damper test rig. The obtained force values at each magnetic field strength agree well with the calculated ones. The fluid volume used was 1.5 ml, and power and force values were, respectively, 5 W and 55 N. The reduced volume of MR fluid and power will help in commercializing this damper for washing machines. | Design and optimization of shear mode MR damper using GRG and GRA methods: experimental validation | 10.1007/s12046-021-01746-6 |
2021-10-19 | This work is concerned with a semilinear non-homogeneous Timoshenko system under the effect of two nonlinear localized frictional damping mechanisms. The main goal is to prove its uniform stability by imposing minimal amount of support for the damping and, as expected, without assuming any relation on the non-constant coefficients. This fact generalizes substantially the previous papers by Cavalcanti et al. (Z Angew Math Phys 65(6):1189–1206, 2014) and Santos et al. (Differ Integral Equ 27(1–2):1–26, 2014) at the levels of problem and method. It is worth mentioning that the methodologies of these latter cannot be applied to the semilinear case herein, namely when one considers the problem with nonlinear source terms. Thus, differently of Cavalcanti et al. (Z Angew Math Phys 65(6):1189–1206, 2014), Santos et al. (Differ Integral Equ 27(1–2):1–26, 2014), the proof of our main stability result relies on refined arguments of microlocal analysis due to Burq and Gérard (Contrôle Optimal des équations aux dérivées partielles, http://www.math.u-psud.fr/~burq/articles/coursX.pdf , 2001). As far as we know, it seems to be the first time that such a methodology has been employed to 1-D systems of Timoshenko type with nonlinear foundations. | Uniform stability for a semilinear non-homogeneous Timoshenko system with localized nonlinear damping | 10.1007/s00033-021-01622-7 |
2021-10-19 | In earlier days, the only way to resist the lateral loads was to increase the lateral strength of the structure obtained by making larger cross sections and massive buildings. Structural control is one of the solutions and important topics in both points of view of security and comfort in recent years. To reduce the effect of seismic energy, one of the structural forms used is the outrigger. In recent years, supplementary devices are installed into the outrigger structure so that damping of the structure increases and helps in mitigating the vibration, this concept is called damped outrigger. In this study, a damped outrigger structure replicating St. Francis Shangri-La Place skyscraper is excited for the El-Centro earthquake, and the Kobe earthquake is numerically modeled with viscous dampers and Magneto-Rheological damper to compare its effectiveness. The finite element approach is used for the analysis of the structure using Bernoulli’s Euler beam theory in modeling the core of the structure as a beam element. The state-space approach is used in modeling the structure, dampers, and controller interface in MATLAB and Simulink, then results are obtained for the peak value of displacement, acceleration, and mean values of the response of the structure. The results are discussed, which shows the significant distinction between uncontrolled and controlled responses. | Damped outrigger semi-active control for seismic vibration mitigation | 10.1007/s41062-021-00645-3 |
2021-10-18 | In a Hilbert space H $\mathcal{H}$ , we study a dynamic inertial Newton method which aims to solve additively structured monotone equations involving the sum of potential and nonpotential terms. Precisely, we are looking for the zeros of an operator A = ∇ f + B $A= \nabla f +B $ , where ∇ f is the gradient of a continuously differentiable convex function f and B is a nonpotential monotone and cocoercive operator. Besides a viscous friction term, the dynamic involves geometric damping terms which are controlled respectively by the Hessian of the potential f and by a Newton-type correction term attached to B . Based on a fixed point argument, we show the well-posedness of the Cauchy problem. Then we show the weak convergence as t → + ∞ $t\to +\infty $ of the generated trajectories towards the zeros of ∇ f + B $\nabla f +B$ . The convergence analysis is based on the appropriate setting of the viscous and geometric damping parameters. The introduction of these geometric dampings makes it possible to control and attenuate the known oscillations for the viscous damping of inertial methods. Rewriting the second-order evolution equation as a first-order dynamical system enables us to extend the convergence analysis to nonsmooth convex potentials. These results open the door to the design of new first-order accelerated algorithms in optimization taking into account the specific properties of potential and nonpotential terms. The proofs and techniques are original and differ from the classical ones due to the presence of the nonpotential term. | Asymptotic behavior of Newton-like inertial dynamics involving the sum of potential and nonpotential terms | 10.1186/s13663-021-00702-7 |
2021-10-12 | A tall building comprised of tubular frame, central shear core, and outrigger-belt truss systems is considered as an equivalent flexural hollow box beam with lumped masses at each floor level. Natural frequencies and mode shapes of the un-damped hybrid system are obtained by forming mass and stiffness matrices and solving the eigenvalue problem. Previous researches did not deal with the overall intrinsic damping of the structure or the damping added by external instruments, nor they considered the hybrid structure comprised of a tubular frame with geometrical discontinuous and damped outrigger systems in free vibration studies. By utilizing the achieved frequencies, first to fifth mode shape vectors, mass matrix, and modal participant mass and considering 5% modal damping ratio for each mode, the classically damping matrix of the hybrid system is achieved to fill these gaps. Then the non-classical damping matrix of the hybrid system with damped outriggers is obtained by adding the viscosity of passive linear viscous dampers to the classical damping matrix at the level of damped outrigger-belt truss systems. The eigenvalue problem is solved, and natural frequencies and mode shapes are obtained. 3-D finite element models of two 60- and 70-story buildings with conventional and damped outrigger systems are analyzed, and comparing the results of the proposed method and those of SAP2000 models reveals the correctness, reliability, and robustness of the method. Moreover, calculating natural frequencies by the proposed method is much less time consuming in comparison with finite element models. | An innovative approach for evaluating mode shapes and natural frequencies of tubular frame and damped outriggers | 10.1007/s41062-021-00634-6 |
2021-10-12 | Considering the linked structure concept, a single damper enhances the response of two adjoining structures, becomes an economic alternative for seismic performance enhancement of the adjoining connected structure. A high force-to-volume damper offers a sufficient amount of resistive force by comparatively small size device, which is more suitable application for space-restricted situation. The seismic ground motion excitation is random in nature. The seismic behavior of the structure depends on attributes of the structural system and ground excitation. The random response analysis gives a more appropriate estimation of functioning of the control device and structure. The performance of lead damper linking two adjoining single-degree-of-freedom structures subjected to non-stationary and stationary random excitations is studied. The efficacy of lead damper is evaluated by analyzing the adjoining interconnected structures applying 500 ground excitation realizations using Monte Carlo simulation. The act upon of quantities like damper constant, frequency ratio and a mass ratio of linked structure on the functioning of interconnected structure is inquired. The results indicate that lead damper with appropriate parameter is effective for response enhancement of adjoining coupled structure. The closed-form formula for optimal damper constant and the corresponding mean square response of undamped interconnected structures considering stationary excitations with uniform modulating function are derived. | Response control of adjoining structures interconnected with Lead damper | 10.1007/s41062-021-00660-4 |
2021-10-09 | In this work, we consider a quasilinear system of viscoelastic equations with degenerate damping and general source terms. According to some suitable hypothesis, we study the blow-up of solutions. This is the general case of the recent results of Boulaaras’ works (Bull. Malays. Math. Sci. Soc. 43:725–755, 2020 ) and (Appl. Anal. 99:1724–1748, 2020 ). | Blow-up of solutions for a quasilinear system with degenerate damping terms | 10.1186/s13662-021-03609-0 |
2021-10-05 | We introduce and analyze a space-time least-squares method associated with the unsteady Navier–Stokes system. Weak solution in the two dimensional case and regular solution in the three dimensional case are considered. From any initial guess, we construct a minimizing sequence for the least-squares functional which converges strongly to a solution of the Navier–Stokes system. After a finite number of iterations related to the value of the viscosity coefficient, the convergence is quadratic. Numerical experiments within the two dimensional case support our analysis. This globally convergent least-squares approach is related to the damped Newton method. | A Fully Space-Time Least-Squares Method for the Unsteady Navier–Stokes System | 10.1007/s00021-021-00627-6 |
2021-10-01 | Abstract The damping properties of the polymer composite materials based on a rubber mixture and thermoplastic elastomer are studied at dynamic compressing loads at temperatures of 23 and –40°C. The ratio of the tangential to the secant dynamic stiffness at temperatures above the polymer crystallization points is found to be related to the material microstructure and to affect the mechanical losses per deformation cycle and, hence, the damping capacity of the material. | Influence of Structure on the Dynamic Properties of Polymer Damping Composite Materials | 10.1134/S0036029521100189 |
2021-10-01 | Similar to synchronous generators (SGs), the phenomenon of low-frequency oscillation (LFO) may occur when virtual synchronous generator (VSG) is involved in power grid, thereby negatively affecting the stability of the power system. In this paper, the oscillation mechanism of the power system composed of a VSG and infinite grid (single-VSG infinite-bus system) is analyzed, the conditions for the occurrence of LFO are unveiled, and a simplified damping selection method to suppress the LFO is provided, considering the adjustable damping of VSG. First, a small-signal model of the single-VSG infinite-bus system is established. The order of this system model is reduced using the damping torque analysis. Then, the mechanism of LFO under various dampings is analyzed. On this basis, a reasonable selection method of damping is drawn. The range of damping, where LFO converges, can be determined and the appropriate damping coefficient can be selected using this method. Finally, the effectiveness of the proposed method is verified by simulations and experiments. | Simplified damping analysis and suppression method for low-frequency oscillation introduced by virtual synchronous generator | 10.1007/s43236-021-00293-x |
2021-10-01 | The damping behavior of continuous SiC fiber reinforced aluminum matrix (SiC_f/Al) composite is still poorly understood. This paper examined the temperature dependence and strain amplitude dependence of damping capacities in 30 vol% SiC_f/Al composites including SiC_f/2024Al, SiC_f/6061Al and SiC_f/AlFe5Si2 composites, and the unreinforced aluminum alloys. Microstructure characterization was performed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscattered diffraction (EBSD) and X-ray diffraction (XRD) analysis to investigate the operative damping mechanisms in the SiC_f/Al composites. The results show that uniform dispersion of SiC_f and good interface bonding were achieved with these SiC_f/Al composites. The damping capacity and dynamic modulus of these composites were greatly improved as compared with that of the unreinforced aluminum alloys. The dominant damping mechanisms for SiC_f/Al composites were dislocation damping at low temperatures (< 150 ℃), and grain boundary damping and interface damping at high temperatures (> 150 ℃). This work indicated that the SiC_f/AlFe5Si2 composite simultaneously exhibited good damping capacity and high dynamic modulus, having potential for aerospace applications. | Microstructure and Damping Behavior of Continuous W-Core-SiC Fiber-Reinforced Aluminum Matrix Composites | 10.1007/s10443-021-09920-z |
2021-10-01 | In this study, the use of high damping rubber bearing (HDRB) with various design properties in mitigating the seismic effects for steel buildings was investigated. For this, a generalized demand on the analytical model of HDRB was introduced and eighteen different models of HDRB were examined comparatively. These models were created by considering three significant isolation parameters of HDRB such as isolation period T (2, 2.5, and 3 s), effective damping ratio β (0.05, 0.10, 0.15), and post-yield stiffness ratio λ (3 and 6). The benchmark low (3-storey), mid (6-storey), and high-rise (9-storey) steel buildings were equipped with different isolation systems of HDRB and then subjected to a set of earthquake ground motions through nonlinear time history analyses in order to evaluate the actual nonlinear behaviour of the bearings in the base-isolated steel buildings in service. The base-isolated frames were assessed by the variation of the selected structural response parameters such as isolator displacement, relative displacement, inter-storey drift ratio, absolute acceleration, base shear, hysteretic curve, and dissipated energy. The effectiveness of the isolation parameters on the nonlinear response of the steel buildings with HDRB under earthquakes was comparatively evaluated to generate alternatively innovative isolation system. It was shown that the seismic performance of the base-isolated structure was remarkably influenced by the isolation parameters. The most favourable base isolation model was obtained when the higher value of the isolation period and effective damping ratio combined with the low post-yield stiffness ratio. | Effect of Using High Damping Rubber Bearings for Seismic Isolation of the Buildings | 10.1007/s13296-021-00530-w |
2021-10-01 | A novel resilient variable friction damper (RVFD) with a simple construction was proposed. To analyze the effects of loading rate on the stability and energy dissipation performance of the RVFD, two RVFDs were tested under different loading rates and the hysteretic behaviors of the compared with that of the traditional constant friction dampers. Then the peak force, energy dissipation behavior, uneven gap opening of the grooved outer plates (GOPs), and performance of the disc springs under different loading rates were studied. The results show that although no self-centering system was provided, only the RVFDs without a self-centering system still can exhibit stable self-centering performance and effective energy dissipation behaviors, especially with due to the using e of athe grooved steel plates with greater groove angle. When the loading rate is less than 10 mm/s, the peak forces of the RVFD slightly decrease with the increase in loading rates, while when the loading rate is greater than 10 mm/s, its effects could be neglected. The uneven gap opening of the GOPs influences the clamping forces of the disc springs in the bolts under different loading amplitudes. The disc springs in the RVFDs not only provide the increasing clamping forces for energy dissipation and the restoring forces for self-centering behavior, but also dissipate the energy, which accounts for about 10% of the total energy dissipation of the RVFD. | Effects of Loading Rates on the Hysteretic Response of Resilient Variable Friction Dampers | 10.1007/s13296-021-00519-5 |
2021-10-01 | A damping model of fiber reinforced composites was established in this study. Meanwhile, the accuracy of the damping model was verified through experiments. Subsequently, the factors affecting the damping ratio and dynamic response under sinusoidal excitation force of fiber reinforced composites were explored and the measures improving the damping ratio were proposed. The damping model of the fiber reinforced composite was applied to its dynamic equation, and then the dynamic response curves were calculated by the direct time integration method, and the calculated dynamic response curves were compared with the experimental dynamic response curves. The two groups of curves almost coincided, verifying the excellent accuracy of the damping model. Additionally, this study discussed the effects of the fiber volume fraction, the thickness of each layer, the number of layers, the orientation of laying-up, and the sequence of layers on the damping ratio and dynamic response of composite material laminates. The damping model proposed in this paper was suitable for calculating the response curves of composite laminates under sinusoidal concentrated loads. The damping model can be used to calculate the response of the laminate in the elastic range. The accuracy of the model was verified through experiments in the frequency range of 10–200 Hz. The method of calculating the dynamic response of fiber reinforced composites proposed in this study can be easily inserted into the finite element analysis software and directly applied to engineering practice. | Damping Model of Fiber Reinforced Composites and Factors Affecting Damping and Dynamic Response | 10.1007/s10443-021-09924-9 |
2021-10-01 | The investigated hybrid carbon fiber reinforced plastics-elastomer-metal laminates (HyCEML) offer the potential of tailored structural materials with adaptable damping properties. Conventional fiber metal laminates, like glass laminate aluminum reinforced epoxy are already widely spread in the aviation industry owing to their outstanding fatigue behavior. By integrating an elastomeric interlayer, the glass fibers can be substituted by carbon fibers and damping properties of these laminates can be adjusted. The viscoelastic interlayer dissipates energy within the laminate by inducing shear strain during bending, which is commonly known as constrained layer damping. The aim of this paper is the description of the vibration and damping behavior of HyCEML over a wide temperature and frequency range by using different test methods. Dynamic mechanical analysis is used for the individual polymeric constituents and coupon specimens and modal analysis is used with different specimen geometries up to a component sized panel. In addition, analytical and numerical approaches complement the experiments and lead to a deeper understanding of the vibration and damping behavior. Owing to the high damping, already at frequencies of 5 kHz only running waves can be detected for the investigated panel size. The discussion of different test methods helps to identify material and wavelength dependent effects, but also possible adverse effects of certain methods. | Wide Scale Characterization and Modeling of the Vibration and Damping Behavior of CFRP-Elastomer-Metal Laminates—Comparison and Discussion of Different Test Setups | 10.1007/s10443-021-09934-7 |
2021-10-01 | Design of retaining walls (RWs) in earthquake (EQ)-prone areas requires the knowledge of the distribution of lateral earth pressure behind it. The lateral earth pressure acting on RW in case of dynamic/ seismic loading comprises of two components: (a) earth pressure due to static loading and (b) dynamic incremental pressure due to seismic forces. Pseudo-static and pseudo-dynamic methods are mostly preferred methods used to estimate the seismic earth pressure acting on the RW. Analysis based on pseudo-static approach (PSA) assumes seismic forces as equivalent constant inertial force acting on the wall, whereas pseudo-dynamic approach (PDA) includes the effect of phase change and dynamic amplification of seismic waves. This state-of-the-art paper presents a systematic review on the methodologies available for the determination of seismic active thrust, which are based on PSA and PDA. In addition, several other methods, e.g. methods involving numerical techniques, methods based on arching effect, etc., are also reviewed in this paper. While doing so, various limitations of above-stated approaches are pointed out. Further, it is found that there is scarcity of any rational method for the determination of seismic coefficients used in the analysis based on PSA. In addition, the effect of damping characteristics and excess pore pressure ratio, on seismic active thrust, is attempted in very limited studies. | Methodologies Available for the Determination of Seismic Active Thrust Acting on Retaining Walls: A Critical Review | 10.1007/s40098-020-00495-3 |
2021-10-01 | A forced damped harmonic oscillator model of the dipole plasmon mode is illustrated by the theoretical derivation and the simulation based on the metal ellipsoids. The analytical expression of the restoring force is derived. The displacement of the oscillator, which is the phenomenological relative displacement of the free negative and positive charge systems in solids, can be represented by the accumulated charges on the surface of the nanoparticles based on the derived results. With the help of the finite-difference time-domain method, the dependence of the resonance wavelengths and the surface charge distributions on the geometric parameters and the materials has been verified by the ellipsoids evolved from 10 nm radius spheres. As an essential feature of an oscillator, the phase shifts, which are between the accumulated surface charges (the displacement of the oscillator) and the electric field of the incident light, are also illustrated by the numerical simulation. For the silver nanoparticle with the radius of 10 nm, the phase shifts are consistent with the feature of a forced damped harmonic oscillator. For the large silver nanoparticle with the radius of 50 nm, the magnitudes of the phase shifts have some deviations due to the nonuniform electric field along the light propagation. By this oscillator model, we confirm that localized surface plasmon resonance arises from the collective motion of free charges modulated by the bound charges of the lattice background and the dielectric medium. The forced damped harmonic oscillator model is a clear picture for the dipole localized surface plasmon resonance. | Forced Damped Harmonic Oscillator Model of the Dipole Mode of Localized Surface Plasmon Resonance | 10.1007/s11468-021-01408-7 |
2021-10-01 | The magnetorheological damper has variable damping characteristic and the damping force is controllable, which made them employable in the semi-active suspension system of various engineering applications. Basically, there are three types of MR damper i.e monotube, twin-tube and double end. In this paper, a double-ended damper has been chosen to model and evaluated its dynamic behaviour through a computational approach. Electromagnetic circuit analysis and design have been carried out through Finite element analysis. The magnetic force induced in the fluid flow region is calculated at different currents. Later by using the Herschel Bulkley model the FEA and CFD analysis are coupled, which has been achieved by establishing communication between the Navier stokes and Maxwell equations. The damping force versus displacement characteristics are evaluated at different input currents and response were plotted. It has been observed that the compressive force and rebound forces are same in magnitude and opposite in sign which is due to negligible variation in the control volume of the damper. | Estimation of Damping Force of double Ended Magnetorheological Damper through one way coupled CFD and FEA Analysis | 10.1007/s40032-021-00737-0 |
2021-10-01 | Impact dampers (ID) are one of the passive dampers for controlling undesirable vibration and are suitable to operate in harsh environments and effective over a wide range of frequencies. These dampers can be classified as single-unit or multi-unit. The multiple-unit impact damper where is composed of one cavity and some impact mass can be used in various engineering applications. The disadvantage of single-mass impact dampers is high noise level after repeated impacts, because of high contact forces during the impact process. This noise causes discomfort in humans. The contact forces relatively reduced in multiple-mass impact dampers, so the noise generated during the damper’s impact process is reduced in multiple-unit impact damper. The effect of multiple-unit impact damper in vibration and noise reducing is related to the configurations of impact masses. These configurations can be classified as uniform, linear, eight, and diamond. A way for studying the effect of various layouts of masses is using balls with different material properties together. In this paper, three various materials are selected to perform multiple-mass impact damper, the stainless steel, glass and the pearl balls. All of these balls have the same diameter. The results show that the effect of diamond mass configuration in impact damper performance is better than the other configurations. The major innovation of this paper is to investigate the effect of different mass layouts on the performance of multi-mass impact damper experimentally. | Experimental Investigation of Vibratory and Acoustical Behavior of Multiple-Unit Impact Dampers in Free Vibration Reduction | 10.1007/s13296-021-00518-6 |
2021-10-01 | This paper studies the optimization design of sandwich structures with lattice core and viscoelastic layers for suppressing structural resonance response in the frequency domain. A concurrent optimization scheme is proposed to simultaneously optimize the damping material topology in the viscoelastic layers and the size distribution of the lattice core. The damping effect of the viscoelastic layers is simulated as hysteretic damping model, and the full method is used to accurately calculate the dynamic responses. Based on the adjoint method, the corresponding design sensitivities are analytically derived efficiently and the Globally Convergent Method of Moving Asymptotes algorithm is adopted. To ensure a smooth convergence in case of mode switching, the mode tracking technique based on the Modal Assurance Criteria is introduced to track the targeted resonant mode. Numerical examples demonstrate the effect of the concurrent optimization in suppressing structural resonance response. | Concurrent optimization of sandwich structures lattice core and viscoelastic layers for suppressing resonance response | 10.1007/s00158-021-02943-x |
2021-10-01 | Utilization of a communication network to transmit remote-control signals might introduce time delay into the control loop, which degrades the controller efficacy. This paper proposes a new design of wide-area damping controller based on scattering transformation to enhance power system stability. The proposed control approach is comprised of a classical structure in addition to two scattering transformation ports. These ports are inserted between the power system and the wide-area damping controller (WADC) to regulate the signal exchanging between them. Since the WADC is a centralized controller, the time-delay imperfections are considered in the design stage. The proposed controller improves the system damping performance thanks to the achieved time-delay compensation. The effectiveness of the proposed controller is demonstrated by implementing the controller in several case studies under different disturbance scenarios. The proposed controller performance is benchmarked with the classical WADC based on lead-lag structure. The efficacy of the proposed controller is confirmed to reduce the time delay resulting in a better power system stability. | Delay-Independent Wide-Area Damping Control Using Scattering Transformation | 10.1007/s13369-020-05209-8 |
2021-10-01 | The LCL type active power filter (APF) with a traditional repetitive controller has drawbacks in terms of poor dynamic performance, large steady-state error, and difficult digital implementation. A fast repetitive control (RC) algorithm was proposed in this paper in an effort to improve the APF dynamic performance without worsening its stability. To eliminate the non-integer delay of the traditional RC, a fractional-order RC algorithm based on the Lagrangian Interpolation was developed. The proposed fast fractional-order RC (FFORC) strategy only needs 1/6 delay time when compared to the traditional RC. In addition, it can track the error signal quickly and obtain a higher steady-state accuracy. Furthermore, the double current loops control method with grid side current and inverter side current feedback is proposed to achieve active damping of the resonance peak of the LCL filter, which ensures that the APF system is stable. Simulation and experimental results are presented to verify the performance of the dynamic response and steady-state accuracy of the proposed FFORC strategy. | LCL APF based on fractional-order fast repetitive control strategy | 10.1007/s43236-021-00301-0 |
2021-10-01 | The present study is an attempt to investigate structures equipped with friction dampers under the influence of near-field earthquakes based on Stribeck friction behavior of velocity function. At present, the cyclic behavior of friction dampers in structural design engineering software is simple and based on the Coulomb friction force that is independent of velocity, which should be estimated and considered in terms of Stribeck velocity-dependent friction. Their sliding and vibration methods, including displacement, velocity, and acceleration, are calculated using numerical analysis and differential equation. For this purpose, the representative of the near-field records affects the structure with Stribeck frictional behavior of velocity function as a pulse of Ricker wavelet stimulation. The response of the structure is evaluated in the transition phase from impending motion with a friction coefficient of μ _s to kinetic motion with μ _k and vice versa, which makes the poor results of previous simplifications more accurate. Due to the nonlinear behavior of the damping force, programming has been used to perform nonlinear analytical dynamics. Also, behavioral models in OpenSees software are used to investigate the behavior of Stribeck friction for friction damper and to compare its results with the results obtained from accurate analysis. | Effects of Stick-Slip in Behavior of Structures with Friction Damper under Near-Field Earthquakes | 10.1007/s12205-021-1324-y |
2021-10-01 | Abstract This paper considers and analyzes the properties and characteristics of electromechanical magnetorheological dampers that are able to quickly change their rigidity in variable operating conditions. It is shown that the correct development of these dampers and the refined definition of their characteristics are complicated by the need to take into account the interrelated electromagnetic, hydrodynamic, and thermal processes. Approaches to describing the properties of magnetorheological dampers and taking into account the ongoing physical processes are analyzed. Mathematical models of different complexity are considered. The results of calculating the performance indicators and properties of magnetorheological dampers by different models are presented, and the findings are discussed. Comparative results of the calculations and the experimental studies of the damper resistance force are presented. It is revealed that the most correct results of defining the characteristics of magnetorheological dampers at significant piston speeds are provided by the calculation methods taking into account the mutual influence of magnetic, hydrodynamic, and thermal processes. The difference between the results obtained by these methods and the experimental results does not exceed 7%. The failure to take into account the initial shear stress of the magnetorheological suspension and the influence of the magnetic field and temperature on it can lead to an error of more than 50% in defining the initial effort. | Analysis of Properties and Refined Definition of Characteristics of Electromechanical Magnetorheological Dampers | 10.3103/S1068371221100084 |
2021-10-01 | The optimum damping and tuning frequency ratio of the tuned inerter damper (TID) for the base-isolated structure is obtained using the numerical searching technique under stationary white-noise and filtered white-noise earthquake excitation. The criterion selected for optimality is the minimization of the mean-square relative displacement and absolute acceleration of the isolated structure and maximization of the energy dissipation index. Explicit formulae for TID damping and tuning frequency for white-noise excitation are then derived using a curve-fitting technique that can be conveniently used for applications in dynamical systems. The error in the proposed empirical expressions is found to be negligible and hence these expressions are quite useful for the effective design of the base-isolated structure with supplemental TID. An optimally designed TID was found to be more effective for the base-isolated structures under soft soil conditions in comparison to the firm soils. Further, a comparison of the seismic response of the flexible base-isolated structure with and without TID was made under non-stationary earthquake excitation. It was observed that an optimally designed TID was found to be effective in controlling the displacement and acceleration response of the base-isolated structure and the effectiveness is observed to be increased for a higher inertance mass ratio. Finally, the close form expression for the bearing displacement of base-isolated structure with TID subjected to broadband earthquake excitation is proposed which will be helpful for initial optimal design. | Optimum Tuned Inerter Damper for Base-Isolated Structures | 10.1007/s42417-021-00309-7 |
2021-10-01 | Purpose Sloshing is undesirable phenomenon and may invite instability in any type of tank partially filled with liquid. For a specially designed circular cylindrical container filled with an inviscid, incompressible, and homogenous liquid, if an annular baffle is attached to the outer cylinder wall in the annular region of the cylinder at some depth, the natural frequencies and the response of the liquid in the container undergo a drastic change. The purpose of this study is to report the sloshing modes and sloshing frequencies in the annular region of two coaxial vertical circular cylinders. Methods An introduction of a baffle divides the liquid region into four. Boundary value problems are set up for the potential in each of these regions, and with the help of the matching conditions across the virtual interfaces, we set up a system of linear equations by solving which we determine the natural frequencies. Results and conclusions The fundamental natural frequency of the liquid is determined for different width and positions of the baffle in addition to different configurations. It is observed that effect of baffle position on frequency is non-monotonic. It is also observed that when a baffle is placed nearer to the free surface, it has a greater significance on frequency. It is observed that frequency decreases with increasing baffle depth. The effect of the inner radius of the baffle on frequency is almost monotonic while with increasing inner radius of container, frequency increases monotonically. ANSYS is used to report the first modes of the sloshing. All our observations are supported by relevant graphs. | Study on Liquid Sloshing in an Annular Rigid Circular Cylindrical Tank with Damping Device Placed in Liquid Domain | 10.1007/s42417-021-00314-w |
2021-10-01 | A vibrating screen is widely used in raw coal screening, but intensive resonance in the startup and shutdown stages shortens the service life of the vibrating screen and generates vibration damage to surrounding buildings. Therefore, we designed a novel vibration isolator based on a magnetorheological damper, aiming to improve the vibration isolation performance of the vibrating screen. The rheological mechanical model of damping force was analyzed based on the Bingham model, and a magnetic circuit was designed according to electromagnetic theory. Then, an experiment was designed to evaluate the vibration isolation performance of the vibration isolator. The results show that the novel vibration isolator, compared with the metal spring ones, reduces the maximum resonance amplitude by 64 % in the resonance region. In addition, the time of passing through the resonance region in startup and shutdown stages is also reduced by 50 % and 60 %, respectively. This study can provide a new method to improve the vibration isolation performance of vibrating screens. | A novel vibration isolator for vibrating screen based on magnetorheological damper | 10.1007/s12206-021-0906-4 |
2021-10-01 | The effectiveness of the series tuned mass dampers (STMDs) in reducing the dynamic vibrations of the structures under the ground motion is investigated, and their optimum parameters are obtained based on the simulated annealing (SA) optimization. The STMD is one of the most well-known passive control devices which consists of two TMD units arranged in series. However, only a few studies are available on the control performance and optimum parameters of the STMDs for structural systems subjected to ground motion. Thus, the goal of this study is to carry out a thorough optimization analysis based on the SA algorithm for the structures equipped with an STMD under the effect of ground motion. The objective function is selected as the reduction of the displacement response of the structure. It is proved that the optimum STMD has better effectiveness than the optimum TMD in suppressing the maximum story displacement of the structure. Further, the effect of the frequency shift on the effectiveness of the optimally designed STMD is investigated. | Design of series tuned mass dampers for seismic control of structures using simulated annealing algorithm | 10.1007/s00419-021-02013-0 |
2021-10-01 | We study the dissipative dynamics of a single quantum harmonic oscillator subjected to parametric driving within an effective Hamiltonian approach. Using the Liouville–von Neumann approach, we show that the time evolution of a parametrically driven dissipative quantum oscillator has a strong connection with the classical, damped Mathieu equation. Based on the numerical analysis of the Monodromy matrix, we demonstrate that the dynamical instability generated by the parametric driving is reduced by the effect of dissipation. Furthermore, we obtain a closed relationship between the localization of the Wigner function and the stability of the damped Mathieu equation. | Role of dissipation in the stability of a parametrically driven quantum harmonic oscillator | 10.1007/s40042-021-00260-6 |
2021-09-30 | The quality factor is a key parameter of micro-electro-mechanical system resonators, and the internal friction of structural materials in the micro resonator caused by thermoelastic damping has been limiting the improvement of the quality factor. In this paper, thermoelastic damping models of trilayered composite microplates with three kinds of boundary conditions are studied. Then the convergence of thermoelastic damping with different material combinations is analyzed, and that with three kinds of boundary conditions is also analyzed. Next, the finite element model is compared with the analytical model, and the accuracy of the analytical model is verified. Finally, the effects of the coating material and the coating thickness on thermoelastic damping of micro resonators are analyzed. The results show that the Zener modulus of the coating material has a great influence on the convergence of the analytical model; the boundary condition has little effect on the convergence of the analytical model; the maximum thermoelastic damping of composite plates is related to Zener modulus of coating; the maximum thermoelastic damping of composite plates is related to the thickness of coating. | Analysis of thermoelastic damping in trilayered composite microplates based on three-dimensional heat conduction | 10.1007/s40430-021-03182-3 |
2021-09-29 | This manuscript focuses on the study of the existence of a solution for an abstract Cauchy problem involving a wave equation with a monotone operator damping and nonlinear source term. We apply the potential well and prove the global weak solutions and the exponential stability for initial data in the set of stability created from the Nehari Manifold. A more general framework is presented focusing on the damping, which must satisfy the monotonicity condition, and then, some previous works to second-order differential equations of hyperbolic type can be considered as a particular case. | Abstract Wave Equation with Monotone Operator Damping in Banach Spaces | 10.1007/s00025-021-01514-2 |
2021-09-29 | The double-beam system finds many applications in various engineering fields due to its light-weight, sufficient rigidity (flexibility), and robust and reliable performance. The concentrated masses are frequently attached to the double-beam system, yet few related studies are available in the literature. This paper investigates a special configuration of the double-beam system with pair-wise concentrated masses. The equations of motion are reformulated, and the mode shape solutions are obtained by the shape function method. The frequency equations can be built by substituting the mode shape solutions into the boundary conditions. A new form of orthogonality condition for the double-beam system carrying masses is derived, which is combined with the classical modal expansion technique to derive the dynamical responses under exciting forces. Numerical examples for both the free and forced vibrations are presented and verified, which may serve as the benchmark problems for future studies. | Free and forced vibration analysis of double-beam systems with concentrated masses | 10.1007/s40430-021-03167-2 |
2021-09-21 | Background A shock-absorbing pylon (SAP) is a modular prosthetic component designed to attenuate impact forces, which unlike traditional pylons that are rigid, can compress to absorb, return, or dissipate energy. Previous studies found that walking with a SAP improved lower-limb prosthesis users’ comfort and residual limb pain. While longitudinal stiffness of a SAP has been shown to affect gait kinematics, kinetics, and work done by the entire lower limb, the energetic contributions from the prosthesis and the intact joints have not been examined. The purpose of this study was to determine the effects of SAP stiffness and walking speed on the mechanical work contributions of the prosthesis (i.e., all components distal to socket), knee, and hip in individuals with a transtibial amputation. Methods Twelve participants with unilateral transtibial amputation walked overground at their customary (1.22 ± 0.18 ms^−1) and fast speeds (1.53 ± 0.29 ms^−1) under four different levels of SAP stiffness. Power and mechanical work profiles of the leg joints and components distal to the socket were quantified. The effects of SAP stiffness and walking speed on positive and negative work were analyzed using two-factor (stiffness and speed) repeated-measure ANOVAs (α = 0.05). Results Faster walking significantly increased mechanical work from the SAP-integrated prosthesis (p < 0.001). Reducing SAP stiffness increased the magnitude of prosthesis negative work (energy absorption) during early stance (p = 0.045) by as much as 0.027 Jkg^−1, without affecting the positive work (energy return) during late stance (p = 0.159), suggesting a damping effect. This energy loss was partially offset by an increase in residual hip positive work (as much as 0.012 Jkg^−1) during late stance (p = 0.045). Reducing SAP stiffness also reduced the magnitude of negative work on the contralateral sound limb during early stance by 11–17% (p = 0.001). Conclusions Reducing SAP stiffness and faster walking amplified the prostheses damping effect, which redistributed the mechanical work, both in magnitude and timing, within the residual joints and sound limb. With its capacity to absorb and dissipate energy, future studies are warranted to determine whether SAPs can provide additional user benefit for locomotor tasks that require greater attenuation of impact forces (e.g., load carriage) or energy dissipation (e.g., downhill walking). | Reducing stiffness of shock-absorbing pylon amplifies prosthesis energy loss and redistributes joint mechanical work during walking | 10.1186/s12984-021-00939-8 |
2021-09-18 | We study the influence of the factor of electron-ion collisions on the solution of the Cauchy problem in the one-dimensional relativistic model of cold plasma and show that, depending on their intensity and initial data, two scenarios are possible: either the solution remains smooth and stabilizes to a stationary state, or during a finite time the oscillations blowup. In contrast to the nonrelativistic model, when exact conditions can be obtained separating the two behaviors, in a much more complicated relativistic situation, it turns out to be possible to analytically estimate from below the time during which the existence of a smooth solution and the guaranteed number of oscillations during this time. In addition, we show that in contrast to the relativistic case without taking into account collisions, when oscillations corresponding to arbitrarily small deviations from the zero equilibrium position blow up, the presence of electron collisions can suppress the blowup of sufficiently small oscillations. Further, based on the analysis of characteristics, a numerical algorithm is constructed, the order of accuracy of which is determined only by the smoothness of the initial data. Numerical experiments are presented to illustrate the theoretical results. The initial conditions are chosen as reasonably as possible from the point of view of full-scale physical experiments. | Stabilization and blowup in the relativistic model of cold collisional plasma | 10.1007/s00033-021-01615-6 |
2021-09-01 | In the present work, we investigate the global existence and uniform decay rates of solutions to the Cauchy problem in $$\mathbf {R}^{n}$$ R n ( $$n\ge 1)$$ n ≥ 1 ) related to the dynamic behavior of evolution equations accounting for rotational inertial forces along with a linear viscoelastic memory damping arising in viscoelastic materials. Under certain conditions on the initial data and on the kernel, the global existence and decay estimates of the solutions are established. Furthermore, time decay estimates in higher Sobolev space of the solution are provided. The proof is carried out by means of the point-wise decay estimates of the solution in the Fourier space. | Energy Decay Estimates of Solutions for Viscoelastic Damped Wave Equations in
$$\mathbf {R}^{n}$$
R
n
| 10.1007/s40840-021-01097-9 |
2021-09-01 | Due to increase in population, industrialisation and a lack of space in the urban areas of Surat city in Gujarat (India), numerous buildings are being constructed in the vicinity of the railway tracks. The perspective is further aggravated by the proposal for a high-speed corridor (≥ 200 kmph) connecting two key Indian cities, Mumbai and Ahmedabad. These structures need to be evaluated for their susceptibility to the dynamic stresses induced by such high-speed locomotives. However, before the assessment of such dynamic stresses, geometrical and material damping properties of the in situ soil must be determined as the stresses induced in the structure also depend on the attenuation characteristics of the subsoil. With the objective to determine attenuation characteristics of the soil due to high-speed trains, the current study uses modelling capabilities of SAP2000 to prepare a vehicle-track-soil interaction model for dynamic analysis of the site in Surat city (India). A quarter car model (lumped mass model) prepared in SAP2000 environment is used to replicate CHR3-type high-speed train. The passage of train over the track structure is represented as a sinusoidal harmonic load. The study establishes that the statistical analysis of the attenuation of the waves is exponentially related to the distance from the source and follows the Bornitz equation. The frequency-independent damping ratio is computed considering near-field and far-field effect of induced vibration in the soil. Finally, the damping ratio and transmissibility are used to derive the critical velocity for the given track near the proposed site. | Application of Quarter Car Model for Assessment of Attenuation Characteristics of Soil at Low Strain | 10.1007/s40515-020-00139-2 |
2021-09-01 | We study the dynamics of perturbations around an inhomogeneous stationary state of the Vlasov-HMF (Hamiltonian Mean-Field) model, satisfying a linearized stability criterion (Penrose criterion). We consider solutions of the linearized equation around the steady state, and prove the algebraic decay in time of the Fourier modes of their density. We prove moreover that these solutions exhibit a scattering behavior to a modified state, implying a linear damping effect with an algebraic rate of damping. | On Linear Damping Around Inhomogeneous Stationary States of the Vlasov-HMF Model | 10.1007/s10884-021-10044-y |
2021-09-01 | Background Magneto-rheological (MR) dampers have a promising future for application in automotive semi-active suspensions. The damping force produced by MR dampers can be modulated by controlling the electric current supplied to it. Purpose The present work explores a twin-tube MR damper working in valve mode for application in a semi-active SUV suspension system. Further, the performance of a single sensor control scheme is evaluated. Methods The MR damper is characterized in a damper testing machine to demonstrate the MR behaviour and also to show that it develops similar magnitude of force as a passive damper used in SUV suspension. To prove the superiority of semi-active suspension, a single degree of freedom quarter car test rig is built and ground excitation is given in the form of displacement input from a hydraulic actuator. Constant current control, Skyhook control and Rakheja-Sankar (RS) control method are employed as three different control strategies and compared with passive suspension to study the advantages. Peak acceleration response of the sprung mass is studied for better passenger ride comfort and peak ground force is studied for preventing damage to road surface as well as to vehicle suspension elements. Results RS control provides much lower sprung mass vertical acceleration than Skyhook control and constant current control. RS control method led to 36% reduction of peak ground force when compared to Skyhook control. Conclusion For a semi-active suspension using twin-tube MR damper, RS control method provides better ride comfort to passengers due to lower peak vertical acceleration when compared to constant current control or Skyhook control method. Moreover, for preventing damage to road surface as well as to vehicle suspension elements, RS control method, requiring a single sensor, is a much better choice. | Performance Evaluation of a Single Sensor Control Scheme Using a Twin-Tube MR Damper Based Semi-active Suspension | 10.1007/s42417-021-00290-1 |
2021-09-01 | Abstract The movement of an elastic panel is considered in an ideal liquid flow. It is assumed that the panel vibrates with small amplitude and is subject to external mechanical effects to resist these vibrations. The problem of optimizing the vibration damping process is formulated followed by solving through estimation using the quadratic energy criterion. The necessary optimum conditions are derived and applied to suppress hydroelastic vibrations within a finite time interval. An iteration vibration damping algorithm is presented based on sequential solution of direct problems of interaction between the moving liquid and the panel. The algorithm also involves solving adjoint problems of inverse integration of a homogeneous equation consisting of sequential determination of the corresponding approximation to obtain the optimum control to suppress vibrations. The algorithm proposed to optimize vibration damping is illustrated by an example of determining the stabilizing effect in analytical form. | Optimum Damping Vibrations in a Panel Undergoing Translational Movement in Liquid Flow | 10.3103/S0025654421070062 |
2021-09-01 | The response behavior of two adjacent single-degree-of-freedom structures connected with Friction damper is investigated. The ground motion acceleration is modeled as non-stationary random process as well as stationary white-noise random excitation. The governing equations of motion of the connected structures are formulated and root mean square responses (relative displacement and absolute acceleration) are obtained. The responses are obtained considering 500 ground motion realization using Monte Carlo simulation. An optimum value of the damper slip force for which the root mean square response attains a minimum value is observed. The influence of parameters such as frequency ratio and mass ratio of the connected structures on performance of the damper is investigated. The closed-form expressions for the optimum damper slip force and corresponding mean square responses of the undamped coupled structures under stationary white-noise excitation are derived using equivalent linearization technique. | Random response analysis of adjacent structures connected with friction damper | 10.1007/s42107-021-00369-w |
2021-09-01 | Abstract This article investigated the effect of Mg content (4.5, 6.5 and 9.2, in wt%) on the damping capacities of Al–Mg alloys. The results indicate that the damping behavior can be divided into three regions. Region I refers to the low strain amplitude region ( ε < 5 × 10^−5), where the damping capacity decreases with increasing the Mg content and has almost no relation with the strain amplitude. Region II is the middle strain amplitude region (5 × 10^−5 < ε < 8 × 10^−4), where the damping capacity increases rapidly with the strain. Region III refers to the high strain amplitude region (8 × 10^−4 < ε < 2 × 10^−3), where the damping capacity remains constant and is independent of the strain when the strain is high enough, but increases with the Mg content. The damping values Q ^−1 of Al–4.5Mg, Al–6.5Mg and Al–9.2Mg alloys are 0.01501 ± 0.00032, 0.01633 ± 0.00032 and 0.01862 ± 0.00119 at the strain of 1 × 10^−3, respectively. The damping capacity in Region I is mainly determined by the lattice distortion caused by Mg addition and the restoring force caused by pinning points and Suzuki segregation. The extended dislocations break away from the pinning effect of Mg atoms and become moveable in Region II, and the movement of extended dislocations is the dominant damping mechanism in Region III. Graphic Abstract The damping behavior associated with the movement of extended dislocations and the force diagram of the extended dislocation segment. | Effect of Mg Content on the Damping Behavior of Al–Mg Alloys | 10.1007/s12540-020-00695-9 |
2021-09-01 | In this work, we consider a system of two wave equations coupled by velocities in a one-dimensional space, with one boundary fractional damping. First, we show that the system is strongly asymptotically stable if and only if the coupling parameter b of the two equations is outside a discrete set of exceptional real values. Next, we show that our system is not uniformly stable. Hence, we look for a polynomial decay rate for smooth initial data. Using a frequency domain approach combined with the multiplier method, we prove that the energy decay rate is greatly influenced by the nature of the coupling parameter b , the arithmetic property of the wave propagation speed a and the order of the fractional damping $$\alpha $$ α . Indeed, under the equal speed propagation condition, i.e., $$a=1$$ a = 1 , we establish an optimal polynomial energy decay rate of type $$t^{-\frac{2}{{1-\alpha }}}$$ t - 2 1 - α if the coupling parameter $$b\notin \pi {\mathbb {Z}}$$ b ∉ π Z and of type $$t^{-\frac{2}{{5-\alpha }}}$$ t - 2 5 - α if the coupling parameter $$b\in \pi {\mathbb {Z}}$$ b ∈ π Z . Furthermore, when the wave propagates with different speeds, i.e., $$a\not =1$$ a ≠ 1 , we prove that, for any rational number $$\sqrt{a}$$ a and almost all irrational numbers $$\sqrt{a}$$ a , the energy of our system decays polynomially to zero like as $$t^{-\frac{2}{{5-\alpha }}}$$ t - 2 5 - α . This result still holds if $$a\in {\mathbb {Q}}$$ a ∈ Q , $$\sqrt{a}\notin {\mathbb {Q}}$$ a ∉ Q and b small enough. | The influence of the coefficients of a system of wave equations coupled by velocities on its stabilization | 10.1007/s40324-020-00233-y |
2021-09-01 | This paper aims to study the well-posedness and the stability of two thermoelastic systems. The derivation of the first system is based on a classical coupling between the mechanical equations of Timoshenko and the thermal effects which are based on the conductivity of Fourier’s law. Whereas, the second system is derivable through a thermal coupling on the shear force. Furthermore, the damping of Kelvin–Voigt type is simultaneously presented in both the shear stress and the bending moment for the two systems. | Well-posedness and energy decay for some thermoelastic systems of Timoshenko type with Kelvin–Voigt damping | 10.1007/s40324-021-00239-0 |
2021-09-01 | A steel slit damper has been used to enhance the seismic performance of structures with several advantages. The damper can be easily manufactured at a low cost. Furthermore, it can dissipate a significant amount of seismic energy through the stable hysteretic behavior of steel. This study presents a preliminary investigation of the development of a composite steel slit damper that can respond effectively at multiple levels of seismic loading. The performance of the prototype composite steel slit damper is investigated in both experimental and analytical ways. In the experiments, the specimen shows the stable hysteretic response with sufficient ductility, where the multi-phased response is observed in the incremental-amplitude cyclic loading case. Furthermore, a nonlinear numerical analysis that combines both kinematic hardening and isotropic hardening models can reliably describe such characteristics. | Preliminary study on a composite steel slit damper | 10.1007/s12206-021-0806-7 |
2021-09-01 | Abstract We have investigated a class of materials whose experimental stress–strain behavior does not allow them to be considered plastic or elastic. They are not elastic since unloading occurs along a curve significantly different from the loading curve; nor are they plastic since in a full loading–unloading cycle, there are no residual deformations. As such materials we investigate so-called metal rubbers — materials made from twisted wire pressed into an almost homogeneous body. The propagation of shock waves in these materials is studied using a one-dimensional model. | NUMERICAL STUDY OF WAVE PROPAGATION IN NONLINEAR DISSIPATIVE MATERIAL | 10.1134/S0021894421050126 |
2021-09-01 | In this paper, we investigate the existence of a local solution in time and discuss the exponential asymptotic behavior to a weakly damped wave equation involving the variable-exponents u t t − M ∇ u t 2 Δ u + ∫ 0 t g t − s Δ u s d s + γ 1 u t + u t k x − 1 u t = u p x − 1 u in Ω × ℝ + $$ \begin{array}{@{}rcl@{}} &&u_{tt}-M\left( \left\vert \nabla u\left( t\right) \right\vert^{2}\right) {\Delta} u+{{\int}_{0}^{t}}g\left( t-s\right) {\Delta} u\left( s\right) ds+\gamma_{1}u_{t}+\left\vert u_{t}\right\vert^{k\left( x\right) -1}u_{t}\\ &=&\left\vert u\right\vert^{p\left( x\right) -1}u \text{ in }{\Omega} \times \mathbb{R}^{+} \end{array} $$ with simply supported boundary condition, where Ω is a bounded domain of ℝ n $\mathbb {R}^{n}$ , g > 0 is a memory kernel that decays exponentially, and M ( s ) is a locally Lipschitz function. This kind of problem without the memory term when k (.) and p (.) are constants models viscoelastic Kirchhoff equation. | Existence and Asymptotic Behavior of Solutions for Degenerate Nonlinear Kirchhoff Strings with Variable-Exponent Nonlinearities | 10.1007/s40306-021-00420-7 |
2021-09-01 | Abstract The hydrodynamic action on long thin beams executing bending resonance vibrations in a fluid near a plane rigid surface (surface) is investigated. The model of quasi-two-dimensional interaction between the fluid and the beam is used, according to which the hydrodynamic action on any beam cross-section can regarded as a result of plane flow around it. The fluid flow in the planes orthogonal to the beam plane is modeled using the time-dependent system of Navier—Stokes equations, whose solution is determined numerically on the basis of the finite volume method. The solutions are determined in a wide range of the governing parameters of the oscillation process, namely, the dimensionless frequency, the vibration amplitude, and the distance to the surface. The dependences for the hydrodynamic forces thus obtained are used to assess the surface effect on the vibrations of cantilevers with actual physical parameters. | Hydrodynamic Damping of Beam Oscillations near a Surface | 10.1134/S0015462821050050 |
2021-09-01 | Inter-storey seismic isolation is increasingly gaining attention. One of the main related issues is the need to limit the relative displacement between substructure and superstructure, while maintaining a good seismic performance of the superstructure. As shown in some studies, fluid viscous dampers (FVDs) mounted in isolation systems are effective in reducing isolator deflection but can be harmful by amplifying inter-storey drifts and floor accelerations. Additionally, the effectiveness of FVDs for inter-storey applications was investigated only recently, and specific approaches for their optimisation and performance evaluation are missing. Therefore, this paper proposes a method for the optimal multi-objective design of FVDs, based on the definition of appropriate surrogate response models, which allows for rationally comparing the FVD effects for a wide range of dampers and structures. In particular, the optimal FVD parameters are provided in a dimensionless form, so that they can be predicted by design equations of general validity within the range of the structures analysed. This method is applied to a stock of regular structures with various vibration periods of superstructure, isolation and substructure, examining a linear and a non-linear isolation system and a set of natural records, in order to comprehensively assess the effects of FVDs and their non-linearity on the seismic performance of these structures. Finally, prediction models of optimal FVD parameters are provided based on the results obtained and are applied to three case studies as an example. | Evaluation of optimal FVDs for inter-storey isolation systems based on surrogate performance models | 10.1007/s10518-021-01134-9 |
2021-09-01 | The study aims at vibration control of laminated plates by the active constraining layer damping ( ACLD ) treatment incorporating the Murakami zig-zag function ( MZZF ) while deriving the displacement fields. The control is achieved by activating the ACLD patches by supplying the control voltage. The ACLD patch has two component layers, namely 1–3 piezoelectric composite ( PZC ) constraining material layer and the viscoelastic constrained material layer. The complete ACLD plate system is modelled as a three layered structure using a MZZF in the displacement fields of the individual layers, and the FE model is obtained by the virtual work principle. A MATLAB FE code has been developed considering the closed loop feedback system for the control of the input parameters. The present method of modelling the ACLD system has proven to be accurate and cost effective for damping the vibrations of the composite plates. Also, the change in piezo fiber orientation angle on the control and performance of the ACLD patches has been effectively studied in detail. | Smart control of laminated plates using Murakami zig-zag functions | 10.1007/s10999-021-09542-0 |
2021-09-01 | Abstract One-dimensional isolated quantum rings in a perpendicular magnetic field with the Rashba spin–orbit coupling parameter changing along the ring are investigated. The electronic spectra and non-damping (persistent) currents of such ring structures are calculated at different structural parameters and magnetic fluxes. It is shown that the inhomogeneity of the Rashba parameter leads to anticrossing of the energy levels and smoothing of the flux dependence of the persistent charge current. The effect of the inhomogeneity on the persistent spin current turns out to be more significant: the spin-current projection onto the ring axis stops being retained during motion along the ring and additional extrema or zeros appear in the magnetic-flux dependence of the absolute value of the spin current at a specified number of electrons in the ring. | Electronic States and Persistent Currents in Rings with Inhomogeneous Rashba Spin–Orbit Coupling | 10.1134/S106378262109013X |
2021-09-01 | Conventional dynamic positioning (DP) systems on larger ships compensate primarily for slowly time-varying environmental forces. In doing so, they use wave filtering to prevent the DP from compensating for the first-order wave motions. This reduces wear and tear of the thruster and machinery systems. In the case of smaller autonomous vessels, the oscillatory motion of the vessel in waves may be more significant, and the thrusters can be more dynamic. This motivates the use of DP to compensate for horizontal wave motions in certain operations. We study the design of DP control and filtering algorithms that employ acceleration feedback, roll damping, wave motion prediction, and optimal tuning. Six control strategies are compared in the case study, which is a small autonomous surface vessel where the critical mode of operation is launch and recovery of an ROV through the wave zone. | Wave motion compensation in dynamic positioning of small autonomous vessels | 10.1007/s00773-020-00765-y |
2021-09-01 | Sound radiation from thin metal plates has consistently been recognized as a severe noise problem. One of the most popular approaches to suppressing this noise is applying viscoelastic layers, also called free layer damping (FLD), on the plate surface, which can damp the structural motion and minimize the radiated sound. The thickness of the FLD is an important parameter. It needs to be optimized for the target acoustic limits through numerical simulations, as the total mass and the costs may rise unnecessarily. This paper investigates the sound radiation from thin metals of particular sizes with different thickness values of FLD. A unique test setup was established to measure vibration and sound for three different sized plates, with each one having three different FLD thicknesses, namely, 0.5 mm, 0.75 mm, and 1 mm. In parallel, vibro-acoustic analyses were performed for the same configurations using the finite element method. The damping of the FLD was defined using the Rayleigh damping model, of which coefficients were obtained through a prediction formula developed earlier by the authors. After validating the model with the test, the effect of FLD on the extended acoustic parameters (radiated sound power, directivity) was also analyzed. | Experimental and Numerical Investigation of Sound Radiation from Thin Metal Plates with Different Thickness Values of Free Layer Damping Layers | 10.1007/s40857-021-00241-6 |
2021-09-01 | Design sensitivity analysis (DSA) of transient responses, which are indispensable in gradient-based time domain optimization, often requires excessive computational resources for viscoelastically damped systems to directly differentiate and integrate the full-order model (FOM). In this paper, an efficient model-order reduction (MOR)–based DSA framework is developed for capturing the 1st- and 2nd-order derivatives of the transient responses and response functions for viscoelastically damped systems. The damping force is represented by a non-viscous damping model, which depends on the past history of motion via convolution integrals over suitable kernel functions. The direct differentiation method (DDM) is used to derive the DSA. Three robust modal reduction bases, namely multi-model (MM) method, modal strain energy modified by displacement residuals (MSER) method and improved approximation method (IAM) are introduced to reduce the system dimension. Based on a generalized damping model in expression of fraction formula, a reduced state-space formulation without convolution integral term is derived. The 1st- and 2nd-order derivatives of the transient responses and response functions are calculated using a modified precise integration method and the DDM on the reduced stage. The computational efficiency and accuracy of the presented methods are illustrated and compared by two examples. The results indicate that the computational time is significantly reduced by the proposed MOR methods maintaining fairly good accuracy. Among these methods, the MM method represents the most compromise between precise and efficiency and would be the best candidate to be the reduction basis for calculating the time domain DSA of large-scale viscoelastically damped systems. | Design sensitivity analysis for transient responses of viscoelastically damped systems using model order reduction techniques | 10.1007/s00158-021-02937-9 |
2021-09-01 | Chaotic neural networks are versatile systems that attract the attention of researchers while the control of their output is a challenging problem. The objective of this paper is to control chaotic neural networks by a novel combinatorial method adopted from two controlling strategies: the threshold and the damping mechanisms. In one sense, the threshold mechanism restricts the refractoriness internal states with a time varying threshold. The limiting threshold depends on a control signal which is a control signal provided by an inner loop as a function of the network internal state. In another sense, the damping mechanism modifies the network’s dynamics to stabilize the chaotic behaviour basically when the threshold mechanism fails. This mechanism is an outer feedback control loop evaluated when the model is chaotic and exponentially stabilizes it. Two simulation examples are considered in this paper which checks the performance of the proposed method compare to the results of the conventional methods. Comparative results imply the superiority of the proposed controlling method compare to the counterparts on both benchmarks. | State Feedback Method to Control Chaotic Neural Network Based on the Dynamic Phase-Space Constraint | 10.1007/s40998-021-00407-y |
2021-09-01 | The nonlinear dynamic characteristics of a rod fastening rotor-bearing system considering internal damping are investigated in this paper. The governing equations of motion of the rod fastening rotor system, in consideration of nonlinear oil-film force and internal damping, are derived by using finite element method based upon Timoshenko beam theory. On the basis of the mathematical model developed, the rotational speed, contact feature and internal damping are the variables considered in the performed simulations. This work mainly focuses on the internal damping effects on the response amplitude and rotor stability. The obtained results obviously show that the internal damping has a dual effect on the nonlinear dynamic response, i.e., low-speed attenuation and high-speed amplification. In addition, internal damping reduces the threshold of instability by 24.14%. Overall, in order to ensure the operating speed less than the onset speed of whip instability but greater than the critical speed, the internal damping should be strictly considered in dynamic modeling and analysis for such complicated rotors. The research can give a new guidance to the dynamic design and vibration control for such types of rod fastening rotors. | Nonlinear dynamic response and stability of a rod fastening rotor with internal damping effect | 10.1007/s00419-021-01981-7 |
2021-09-01 | In the study of the cross-flow vortex-induced vibration of the cylinder, it is found that with the increase in the Reynolds number, the upper branch of the vibration amplitude and the lock-in region show an increasing trend. Currently, there are relatively few studies on two-degree-of-freedom VIV at high Reynolds number. In this paper, the Launder and Sharma low Reynolds number k – ɛ turbulence model is modified by limiting the kinetic energy generation term and dissipation term, which is similar with the limiter used in SST k – ω model. Based on the modified turbulence model, the two-degree-of-freedom vortex-induced vibration of the cylinder with different Reynolds numbers is simulated with the two-dimensional RANS method. The accuracy of the improved turbulence model and its applicable Reynolds number range are verified by comparing with experiments and relevant numerical simulations. The effects of Reynolds number on the vibration characteristics of cylinder with low mass damping ratio are discussed, which provide a theoretical reference for the study of vortex-induced vibration under high Reynolds number. | Modification and application of low Reynolds number k–ɛ turbulence model to vortex-induced vibration at subcritical Reynolds number range | 10.1007/s00773-020-00749-y |
2021-09-01 | In this paper, a new Kelvin-Voigt type beam model of a microelectromechanical resonator made of power-law materials taking into account internal strain-rate damping is proposed and the corresponding lumped-parameter model is derived. Analytical formulas of the lumped parameters in the model are presented. And the pull-in solution is analyzed based on the lumped-parameter model. It is demonstrated analytically and numerically that the internal damping plays an important role in the pull-in solution as well as in determination of the amplitudes and frequencies of the resonator. The hysteresis loops are provided for this model with initial conditions using numerical simulations. The approximation of the electrostatic force in the lumped-parameter model can describe the relations between amplitudes and frequencies with different values of the stiffness and damping coefficients quite well. | Nonlinear dynamical analysis of some microelectromechanical resonators with internal damping | 10.1007/s10409-021-01114-x |
2021-09-01 | Dissipative kinetic models inspired by neutron transport are studied in a (1 + 1)-dimensional context: first, in the two-stream approximation, then in the general case of continuous velocities. Both are known to relax, in the diffusive scaling, toward a damped heat equation. Accordingly, it is shown that “uniformly accurate” L ${\mathscr{L}}$ -splines discretizations of this parabolic asymptotic equation emerge from well-balanced schemes involving scattering S -matrices for the kinetic models. Moreover, well-balanced properties are shown to be preserved when applying IMEX time-integrators in the diffusive scaling. Numerical tests confirm these theoretical findings. |
L
${\mathscr{L}}$
-Splines as Diffusive Limits of Dissipative Kinetic Models | 10.1007/s10013-020-00461-9 |
2021-09-01 | This article deals with free and forced vibration responses of the viscoelastic parabolic arches of variable thickness. Firstly, considering the effects of shear deformation and damping, time-dependent motion equations of in-plane loaded parabolic arches are obtained. Subsequently, the Laplace transform is applied to the obtained equations and solved by a powerful numerical method. Furthermore, the Kelvin viscose model is used to describe the viscoelastic material. Using an effective and suitable inverse numerical Laplace transform method, the results were transferred back to time space. The verification of the presented method is performed by comparing its results with the results of ANSYS. It has been shown in several examples that the proposed method is highly accurate and efficient compared to step-by-step time integration methods. | In-plane vibration analysis of parabolic arches having a variable thickness | 10.1007/s40435-020-00727-7 |
2021-09-01 | Storage racks are nonstructural components mainly designed to support the vertical load of goods. During strong external loads such as an earthquake, which acts in the lateral direction of the racks, stored goods become structurally vulnerable. To identify and reinforce the vulnerable parts of storage racks and improve their seismic performance, we developed a viscoelastic damper system with a capacity designed for storage racks. First, we performed an experiment to analyze the behavioral characteristics of a pallet rack — a representative storage rack used for large goods — under vibration. Based on the results of the experiment, we chose the members of storage racks that were vulnerable to vibration. For the proper seismic reinforcement of vulnerable members, we developed a viscoelastic damping system for storage racks by calculating the structural shear force on each floor of the rack and the capacity of the damper to distribute the shear force. First, three viscoelastic dampers of different capacities were fabricated using a viscoelastic material and subjected to cyclic loading tests to evaluate their mechanical performance. We determined the position on which the damper should be placed to improve the rack’s seismic performance by considering the shear force on each floor of the storage rack and its operational characteristics. Finally, we conducted a shaking table test to verify the new viscoelastic damper system. The system improves the seismic performance of storage racks by controlling their elastic and permanent deformations. | Development of Viscoelastic Damper System to Improve Seismic Performance of Storage Racks | 10.1007/s12205-021-1024-7 |
2021-09-01 | Abstract A model of dynamic deformation and fracture of composite materials is developed. This model accounts for the significant nonlinearity of shock loading diagrams with hardening, which depends on strain rate. An approach is used in which the dependence of ultimate strength on damage parameters and their variation rate is introduced in the form of constitutive relations. The proposed relations are similar to those of the Johnson—Cook model, but stresses are expressed via damage parameters and their variation rate rather than in terms of plastic deformations and the variation rate of plastic deformations. On the basis of the developed model, the impact fracture of a tubular profile made of a composite material based on carbon fiber and a polymer binder are numerically simulated. The influence of the orientation of unidirectional layers of a composite on specific absorption energy is investigated. | SIMULATING AN IMPACT ON COMPOSITE DAMPING ELEMENTS | 10.1134/S0021894421050102 |
2021-09-01 | We investigate the asymptotic properties of the trajectories generated by a second-order dynamical system with Hessian driven damping and a Tikhonov regularization term in connection with the minimization of a smooth convex function in Hilbert spaces. We obtain fast convergence results for the function values along the trajectories. The Tikhonov regularization term enables the derivation of strong convergence results of the trajectory to the minimizer of the objective function of minimum norm. | Tikhonov regularization of a second order dynamical system with Hessian driven damping | 10.1007/s10107-020-01528-8 |
2021-09-01 | Abstract A problem of damping vibrations of a smart structure consisting of elastic and viscoelastic materials and piezoelements with connected shunt circuits is considered. It is proposed to replace the classical resistor in the shunt circuit by an element made of an electroconducting material, in particular, a polymer material filled with graphene nanoparticles. This element plays the role of several resistors with different resistance values, which ensure multimodal damping of vibrations. A mathematical formulation of the problem of forced steady-state vibrations and natural vibrations of smart systems under consideration is provided, as well as results of numerical calculations, which show that graphene-based composites can be used for additional damping of vibrations of smart structures based on piezoelements. | APPLICATION OF ELECTROCONDUCTING COMPOSITE MATERIALS FOR ADDITIONAL DAMPING OF SMART SYSTEMS BASED ON PIEZOELEMENTS | 10.1134/S0021894421050059 |
2021-09-01 | Impact together with friction can be widely found in the mechanical engineering. Although some scholars have investigated the stochastic systems with impact and friction, they only involve the integer-order systems and do not consider the fractional-order cases. In fact, for the system with viscoelastic material, the damping term depends not only on the current time and position but also on the previous states. The memory property of viscoelastic material is characterized by a power-law kernel function which is associated with the fractional derivative. Based on this viewpoint, in this article, we focus on the friction-damped system with fractional derivative damping under Gaussian white noise excitation. We propose an approximate approach to investigate the stochastic response and bifurcation of a fractional-order friction-damped system with the help of variable transformations and stochastic averaging method. One example is employed to verify the effectiveness of the proposed approach. We also explore the stochastic bifurcation phenomenon induced by the fractional order, fractional coefficient and other system parameters through the critical conditions. At last, the difference of bifurcation regions for the fractional-order model and the integer-order model are presented. | Stochastic bifurcation analysis of a friction-damped system with impact and fractional derivative damping | 10.1007/s11071-021-06806-4 |
2021-09-01 | This study aims to present a method for matching the stiffness and damping of a magneto-rheological (MR) air suspension system that will ensure optimal ride comfort of a road vehicle traveling on roads with different roughness and speeds. The authors study the matching of the damping coefficient with the damping ratio, and obtain the adjustment range of the damping coefficient. Based on the linearization of the air spring, a suspension model with adjustable stiffness and adjustable damping has been established. To improve the ride comfort of the vehicle and to control the dynamic deflection and dynamic load, the optimal matching of stiffness and damping under different working conditions has been analyzed by using the stepwise optimal solution method. Then, the authors design four stiffness levels and five damping levels, and propose the parameter matching scheme of the MR air suspension system. The theoretical analysis shows that the proposed scheme can improve vehicle vertical dynamic performance. Four levels of adjustment for the width of the orifice between the air spring and auxiliary chamber and six levels of adjustment for the MR damper have been designed respectively. The findings of this study will inform other studies on vibration control. | Comfort-oriented Semi-active Matching Design with a Magneto-Rheological Air Suspension Mechanism | 10.1007/s40997-020-00393-2 |
2021-09-01 | This paper presents a practical multi-level performance-based optimisation method of nonlinear viscous dampers (NVDs) for seismic retrofit of existing substandard steel frames. A Maxwell model is adopted to simulate the behaviour of the combined damper-supporting brace system, with a fractional power-law force–velocity relationship for the NVDs, while a distributed-plasticity fibre-based section approach is used to model the beam-column members thus incorporating the nonlinearity of the parent steel frame in the design process. The optimum height-wise distribution of the damping coefficients of NVDs satisfying given performance requirements is identified via a uniform damage distribution (UDD) design philosophy. The efficiency of the proposed multi-level performance-based design optimisation is illustrated through nonlinear time-history analysis of 3-, 7- and 12-storey steel frames under both artificial and natural spectrum-compatible earthquakes. Sensitivity analysis is performed to investigate the effects of initial height-wise damping distribution, convergence factor and uncertainty in design ground-motion prediction on the optimisation strategy. The efficiency of the final optimum design solution is also investigated by using drift-based, velocity-based, and energy-based UDD approaches to identify the most efficient performance index parameter for optimisation purposes. It is found that regardless of the selected performance parameter, the optimum damping distribution identified by the proposed methodology leads to frames exhibiting lower maximum inter-storey drift, local damage (maximum plastic rotation) and global damage index compared to an equal-cost uniform damping distribution. However, using drift-based UDD approach generally results in a better seismic performance. It is shown that the proposed UDD optimisation method can be efficiently used to satisfy multiple performance objectives at different intensity levels of the earthquake excitation, in line with performance-based design recommendations of current seismic codes. The proposed method is easy to implement for practical design purposes and represents a simple yet efficient tool for optimum seismic retrofit of steel frames with NVDs. | Multi-level performance-based design optimisation of steel frames with nonlinear viscous dampers | 10.1007/s10518-021-01152-7 |
2021-09-01 | This paper introduces an eccentric brace system (EBS) based on an energy dissipation device for seismic retrofitting. Particularly, an EBS-based seismic reinforcement method (SRM) is proposed, and a damper system is constructed based on this method by considering performance enhancement and cost reduction. In a column reinforcement test, the yield strength and maximum strength of a direct web connection test piece (reinforced only via the direct bonding of the web) were marginally lower than those of a plate and web direct connection (PWC) test piece (reinforced by the direct bonding of the column and steel plate). However, the yield strength and maximum strength of the direct web connection test piece were 2.17–3.09 times those of the unreinforced specimen. In addition, it was verified that the strength decreased by approximately 13–18% compared with that of the PWC test piece. Moreover, a significant strength improvement effect could be achieved even when the web of the H-beam was attached directly to the reinforced column. The plate strength improved moderately because of the installation of the additional plate. In addition, in a reinforced frame test, the yield strengths of the SRM-I (simple reinforcement frame) and SRM-II (shear reinforcement frame with K-type inserts) test pieces were 1.27 and 2.47 times greater than that of the reinforced concrete frame specimen. Further, the maximum strengths of the SRM-I and SRM-II test pieces were 2.22 and 2.95 times greater than that of the reinforced concrete frame specimen. The rate of reduction in stiffness for the reinforced concrete frame specimen was the highest and that for the SRM-II test piece was the lowest. A review of the crack pattern, load–displacement relationship, accumulated energy dissipation, and stiffness reduction rate revealed that the SRM-II specimen displayed the highest seismic performance. | Seismic Reinforcement System of RC Structure Using Eccentric Brace Frame | 10.1007/s40999-021-00616-w |
2021-09-01 | This paper presents a displacement-based seismic design method for building structures equipped with viscoelastic dampers (VEDs) featuring strong nonlinear characteristics. First, major insights from recent analytical and experimental research on this type of VEDs, including their behavior and sources of nonlinearity, are briefly introduced. Then, a simplified response spectra-based method for estimation of the peak seismic response of the structure without and with VEDs is proposed. Here, the undamped and damped structures are reduced to equivalent single-degree-of-freedom (SDOF) systems through linearization procedures. The simplified analysis method allows for the assessment of the effects of VEDs on the structural response through a set of analytical expressions formulated in terms of two parameters controlling the design of the dampers: (1) the VED design strain; and (2) the stiffness ratio of the dampers to the main structure. In the displacement-based design procedure proposed here, the VED design strain is obtained from response history analyses of the base frame, whereas the stiffness ratio is determined through iterative calculations based on the simplified analysis method. Then, the design parameters are extended to the multi-degree-of-freedom (MDOF) system of the actual structure and VEDs are sized at each story. Finally, verification of the design layout is done through nonlinear time-history analysis. The use of time domain analysis procedures and simplified analysis tools to find the design parameters of the dampers provide the proposed methodology with a balance between accuracy and effectiveness. To illustrate the design process, the paper concludes with a design example of supplemental VEDs for the seismic retrofit of a 7-story reinforced concrete frame building. | A displacement-based seismic design method for building structures with nonlinear viscoelastic dampers | 10.1007/s10518-021-01135-8 |
2021-09-01 | Wave characteristics of solitons with damped structures in a four-component plasma fluid having positive and negative ions, nonthermal distributed positrons and electrons have been studied. The damped Kadomtsev–Petviashvili (DKP) equation has been obtained in a small amplitude limit. The nonlinear criticality of DKP is examined for related Earth’s ionosphere plasma parameters. The effects of the positron density ratio, the ionic mass ratio, the electron density ratio, the index of non-thermality and frequency parameters of collisions on the formation of both damped structures of compressive and rarefactive types are studied. It is a value mention that the results performed in this work may be used in the plasma of (D–F) Earth’s ionosphere regions. | Effects of the ionic masses and positron density on the damped behavior in nonthermal collisional plasmas | 10.1007/s12648-020-01831-2 |
2021-09-01 | In order to effectively suppress the resonance problem of photovoltaic grid-connected system, an optimization method of active damping resonance suppression is proposed by combining active damping notch control method and active damper method. The resonance mechanism of photovoltaic grid-connected system is analyzed based on frequency domain analysis method. The notch filter is added into the active damping control method, and the active damping of the system is enhanced by using the notch characteristics. The virtual impedance is introduced in parallel with the active damper at the common bus to increase the system damping, which can suppress the system resonance effectively. Finally, the Matlab/Simulink simulation results show that the resonance suppression of photovoltaic grid-connected system can obviously improve the voltage waveform of the common bus, and make the total harmonic distortion rate of the common bus reach 1.07%, which is 0.55% lower than that of the single active damping notch control method, and the higher harmonic suppression effect is more obvious. | Active Damping Resonance Suppression and Optimization of Photovoltaic Cluster Grid Connected System | 10.1007/s42835-021-00805-6 |
2021-09-01 | This paper focuses on the influence mechanism of magnetorheological damper (MR damper) on the dynamic characteristics of a rotor system and its damping effect. In this work, the structure of an MR damper in the form of a double coil is designed. The magnetic circuit of the MR damper is analysed by the finite element method and verified by experiments. Then, the MR damper is assembled into a rotor system and a general model of a rotor-bearing system supported by MR damper is proposed, in which the magnetorheological fluid (MR fluid) is modelled as lubricating oil with bilinear characteristics. The finite element model of the rotor system is established and solved by the Newmark-β method. The results indicate that the structure of the damper is reasonable and can reach the magnetic induction intensity required for MR fluid saturation. With an appropriate current, the MR damper has better performance in vibration suppression. However, if the applied current is not appropriate, the nonlinearity of the MR damper is excited, which results in the instability of the rotor system. This research discovers the influence mechanism of the MR damper to a rotor system, which is helpful for the vibration control of a rotor system and the design of the MR damper. | Vibration suppression of a rotor system with a nonlinear MR damper | 10.1007/s00419-021-01993-3 |
2021-08-31 | This article performs an analytical study on the damping vibration behavior of metal foam nanocomposite plate reinforced with graphene oxide powders (GOPs) in thermal environment. The GOPs are dispersed through the thickness of the structure according to three functionally graded (FG) and one uniform distribution patterns. The Halpin–Tsai micromechanical model is chosen for estimating the effective material properties of the structure having GOPs as reinforcement phase. Also, different porosity types are taken into account for the metal foam matrix. The plate is resting on a three-parameter viscoelastic medium containing Winkler and Pasternak layers in combination with viscous dampers which can dissipate the oscillation of the structure in some special cases. The Governing differential equations are derived via Hamilton’s principle on the basis of refined higher order shear deformation theory and then solved with employing Galerkin solution method to obtain the natural frequencies of the proposed structure. Moreover, various boundary conditions (B.Cs) including simply supported, fully clamped and different combinations of these B.Cs are considered in this study. The influences and confrontation of different significant parameters such as GOPs’ weight fraction, foundation parameters, aspect and side-to-thickness ratios, porosity coefficients, thermal environment, and FG patterns are investigated through various graphical and numerical results. Our findings declare that the dynamic behavior of the graphene oxide powder reinforced metal foam (GOPRMF) plate remarkably depends on these parameters. | Analytical study of the damping vibration behavior of the metal foam nanocomposite plates reinforced with graphene oxide powders in thermal environments | 10.1007/s43452-021-00269-5 |
2021-08-21 | This paper studies the Cauchy problem of the 3D incompressible micropolar equations with a damping term σ | u | β − 1 u $\sigma |u|^{\beta -1}u$ ( σ > 0 , 1 ≤ β < 3 $\sigma >0, 1\le \beta <3$ ). It is shown that the strong solutions exist globally for any 1 ≤ β < 3 $1\le \beta <3$ . | A note on global existence of strong solution to the 3D micropolar equations with a damping term | 10.1186/s13661-021-01548-z |
2021-08-10 | The goal of the present paper is to study the viscoelastic wave equation with variable exponents $$\begin{aligned} u_{tt}-\Delta _{p(x)}u-\Delta u+\int _0^tg(t-s)\Delta u(s)\mathrm{{d}}s-\Delta u_t=|u|^{q(x)-2}u \end{aligned}$$ u tt - Δ p ( x ) u - Δ u + ∫ 0 t g ( t - s ) Δ u ( s ) d s - Δ u t = | u | q ( x ) - 2 u under initial-boundary value conditions, where the exponents of nonlinearity p ( x ) and q ( x ) are given functions. To be more precise, blow-up in finite time is proved, upper and lower bounds of the blow-up time are obtained as well. The global existence of weak solutions is presented, moreover, a general stability of solutions is obtained. This work generalizes and improves earlier results in the literature. | Study of a Viscoelastic Wave Equation with a Strong Damping and Variable Exponents | 10.1007/s00009-021-01826-1 |
2021-08-07 | By virtue of thermo-entangled state representation (TESR) and the technique of integration within an ordered product of operators, we solve the master equations of density operators in the amplitude damping model and examine firstly how the orthogonal coherent state (OCS) evolves in this model. The evolution formula of the field density operator is given. The effect of decoherence on the negativity of Wigner function (WF) is discussed. The results obtained by the numerical method are as follows: (1) its Wigner function displays negativity, which shows that unlike the coherent state, it has non-classical property and (2) the negativity of the Wigner function is gradually weakened, until it disappears with increased damping. | Decoherence of orthogonal coherent state in the amplitude damping model | 10.1007/s12043-021-02169-y |
2021-08-04 | This paper considers a one-dimensional piezoelectric beams with magnetic effect damped with a weakly nonlinear feedback in the presence of a nonlinear delay term. Under appropriate assumptions on the weight of the delay, we establish an energy decay rate, using a perturbed energy method and some properties of a convex functions. Our result generalizes the recent result obtained in Ramos et al. (Z Angew Math Phys 72:26, 2021). https://doi.org/10.1007/s00033-020-01457-8 . | Energy decay for a weakly nonlinear damped piezoelectric beams with magnetic effects and a nonlinear delay term | 10.1007/s00033-021-01593-9 |
2021-08-04 | An investigation on ion acoustic solitary waves has been presented in a weakly ionized plasma in the occurrence of ion-neutral collision with united effects of trapped and non-thermal electrons. Ion-neutral collision plays a very important role on the propagation of solitary waves in a weakly ionized plasma. In this work, damped Korteweg-de Vries-like Schamel equation has been derived using reductive perturbation technique and its approximate analytical solitary wave solution has been determined, for the first time, using momentum conservation law of Korteweg-de Vries-like equation. It has been observed that the structures of the solitary wave are highly dependent on ion-neutral collisional frequency ( $$\nu _0$$ ν 0 ), non-thermal parameter ( b ) and trapped to free electron temperature ratio ( $$\beta $$ β ). It has been shown that the amplitude of the solitary wave decreases prominently as the non-thermal parameter ( b ) and the ion-neutral collision frequency $$(\nu _0)$$ ( ν 0 ) enhance. But, only amplitude of the solitary wave increases with the increasing value of trapped to free electron temperature ratio $$(\beta )$$ ( β ) . It has been noticed that b and $$\nu _0$$ ν 0 affect the amplitude and width of the solitary wave but $$\beta $$ β affects only on the amplitude of the solitary wave. The obtained results are important to study the nonlinear waves in laboratory and in the universe where partially ionized plasma exists. | Ion-Neutral Collisional Effect on Solitary Waves in Weakly Ionized Plasma with Cairns–Gurevich Distribution of Electrons | 10.1007/s40819-021-01113-3 |
2021-08-01 | In this paper, we consider a wave equation with a time delay velocity and source terms. Using the semi-group theory, we establish the existence of solutions of the problem and we prove a decay rate estimate for the energy by introducing suitable Lyapunov functionals. We also prove that the solution blows up in finite time if the initial energy is negative. | Blow-up and asymptotic behavior for a wave equation with a time delay condition of fractional type | 10.1007/s12215-020-00545-y |
2021-08-01 | Magneto-rheological (MR) dampers using MR fluids with controllable rheological properties are mainly utilized in automobiles, structures, electrical transmission lines, medical applications, agricultural engineering, and military equipment. This paper presents a comprehensive review of bypass MR dampers. The principles of operation, design structures, analytical models, experimental analysis, and applications of MR dampers are classified and reviewed. The bypass MR dampers have better MR fluid stability and sedimentation control compared to MR dampers. This is important for maintaining homogeneous magnetic flux distribution throughout the fluid area. The advantageous features of external bypass MR dampers over internal bypass dampers are the higher shear stress, the damping force controllability, and the higher damping force they can generate. | State-of-the-art developments of bypass Magnetorheological (MR) dampers: A review | 10.1007/s13367-021-0018-9 |
2021-08-01 | This paper presents an online non-model-based scheme to voltage and frequency control of microgrids in the presence of inverter-based distributed energy resources (DERs). For developing proposed controller, considering adaptive control concept, a central controller is designed through aggregation distribution procedure which optimized using artificial adaptive neural network (AANN). In this case, based on the system dynamic variables, the DERs dynamical models are provided which following Lyapunov-based theory, the corresponding central controller is designed. In this way, the proposed Lyapunov theory is responsible to limit AANN weighted boundaries which following an optimization procedure, it is resulted in controller accuracy. By developing central controller, the intelligent AANN is provided which considering a set of offline training procedure, online values of dynamic variables are estimated through real-time working mode. By this way, it is not required to receive any initial information related to DER variables which based on the developing non-model-based dynamical model, the central damping controller (CDC) is extended. The effectiveness of proposed CDC scheme is verified on a typical microgrid test system consisting of several DERs which considering different fault event scenarios, CDC damping performances are evaluated. Simulation results prove the voltage and frequency damping performances of proposed controller in the presence of low-inertia suppliers. | Central Damping Controller for Microgrid Voltage and Frequency Dynamic Stability Using Adaptive Artificial Neural Network | 10.1007/s40313-021-00726-9 |
2021-08-01 | We study the Cauchy problem for quasilinear parabolic inequalities containing squares of the first derivatives of an unknown function (the so-called nonlinearities of the KPZ type). The coefficients of the leading nonlinear terms of the inequalities considered either can be continuous functions (the regular case) or can admit power singularities (the singular case) of degree no greater than 1. For the regular case, we prove the damping of global nonnegative solutions to the problem studied. By damping, we mean the boundedness of the support of a solution for each positive t , uniform (with respect to t ) convergence to zero as |x| → ∞ , and vanishing (for any x ) starting with a certain sufficiently large t . For the singular case, we proved that the problem considered has no global positive solutions. | On Qualitative Properties of Sign-Constant Solutions of Some Quasilinear Parabolic Problems | 10.1007/s10958-021-05472-6 |
2021-08-01 | Abstract— The formation of dusty plasma due to photoelectric and electrostatic processes in the near-surface layer of the illuminated part of Deimos, the satellite of Mars, is discussed. The parameters characterizing the trajectories of motion of dust grains are determined on the basis of a physico-mathematical model for a self-consistent description of densities of photoelectrons and dust grains above the illuminated part of Deimos. It is shown that the damping of oscillations of a dust grain above the Martian satellite’s surface is associated with variations in its charge that is consistent with the concept of anomalous dissipation that follows from processes associated with variations in the charges of dust grains. It is demonstrated that for the majority of dust grains that are lifted above Deimos’s surface due to photoelectric and electrostatic processes, the damping time of their oscillations turns out to be longer than the daylight time, i.e., the non-stationarity of the dusty plasma system above the illuminated surface of Deimos manifests almost during the entire duration of the day on it. The maximum altitudes to which dust grains lift and maximum charge numbers that can be achieved by dust grains of different sizes are determined, and the typical densities of dust grains and photoelectrons above Deimos are estimated. More detailed information on the properties of its soil, which is expected to be obtained in future space missions, is required to obtain more definite data about the parameters of the plasma–dust system in the vicinity of Deimos. | Non-Stationary Processes during the Formation of Dusty Plasma at the Surface of Deimos, the Satellite of Mars | 10.1134/S1063780X21070084 |
2021-08-01 | In this paper, we study the bounded traveling wave solutions for the Boussinesq equation with dissipative term by using the theory of planar dynamical systems, and reveal the relationships between the behaviors of bounded traveling wave solutions and the dissipation coefficient. The bell profile solitary wave solution and kink profile solitary wave solution can be obtained according to the undermined coefficients method. Meanwhile, the approximate oscillatory damped solutions can be obtained. Furthermore, the global error estimation of the approximate oscillatory damped solutions is given by establishing the integral equation which reflects the relationships between approximate and exact oscillatory damped solutions. | Qualitative analysis and bounded traveling wave solutions for Boussinesq equation with dissipative term | 10.1007/s11071-021-06750-3 |
2021-08-01 | This work presents the design optimization and numerical investigation results to evaluate the vibration control performance of a novel hybrid type magnetorheological (MR) damper. Since the proposed hybrid type MR damper has both an electromagnet and permanent magnets, it is possible to design a compact-sized damper with an improved damping force. After designing and characteristics analysis of the proposed hybrid type MR damper, optimization of design parameters is carried out to achieve enhanced damping force. The designed hybrid type MR damper is applied on both quarter and full vehicle models to evaluate its performance on suppressing the unwanted sprung mass motions such as heave and pitch motion. Skyhook and linear quadratic regulator (LQR) controllers are designed and incorporated to the vehicle system models to control the current input to the proposed hybrid type MR damper. The input current to this hybrid type damper is reduced while the damping force is enhanced compared with the conventional MR damper. All the numerically simulated results showed that the proposed hybrid type MR damper can improve the ride comfort and road holding capability on bump and random road conditions. | Design optimization and performance evaluation of hybrid type magnetorheological damper | 10.1007/s12206-021-0726-6 |
2021-08-01 | Magneto-Rheological (MR) fluid is a controllable material upon the applied magnetic field, and various MR dampers with different structures are designed to take advantage of this unique property. In the current paper, the squeeze mode MR damper is analyzed. The two-dimensional MR fluid squeeze flow in the damper is simulated using the Navier-Stokes’ equations. The shear stress of MR fluid is characterized by a non-convex constitutive relation, which is capable of capturing the solid-like to liquid-like switching. The two-dimensional velocity field and pressure distribution of MR fluid are obtained, from which the damping force of the MR damper is obtained. The unique hysteresis characteristic of the force versus velocity relation of the MR damper is captured. Further, the dependence on the loading rate and the field strength of the hysteresis characteristic is studied in the current paper. | Simulation on hysteresis characteristic of squeeze mode magneto-rheological damper based on non-convex constitutive relation | 10.1007/s13367-021-0020-2 |
2021-08-01 | Magnetorheological (MR) dampers are becoming popular smart devices with controllable higher damping properties. This paper presents an inclusive review of energy harvesting MR dampers. The classifications of energy harvesting MR dampers, operating principles, structural design, mathematical models, fluid models, experimental investigation, and applications are classified and reviewed. The regenerative MR dampers have self-power capability, and self-sensing capability to control higher performance and it is an important feature of regenerative MR dampers. The review indicates that regenerative MR dampers have enough power generation capacity to power MR dampers and higher damping performances. It has been found that a single-ended monotube regenerative MR (RMR) damper has maximum power generation capabilities than other RMR dampers. | Recent developments of regenerative magnetorheological (RMR) damper: A review | 10.1007/s13367-021-0017-x |
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