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2023-01-01 | Energy dissipation devices are usually used to absorb or consume a portion of input energy from earthquake or wind, for reducing the structural response and to protect structural members. Steel Slit Shear Wall SSSW is one type of metallic damper having advantages of better ductility, easier installation and repair and higher energy dissipation. It is an excellent yield type energy dissipation device which doesn’t require any welding. It could be used in structures as energy dissipation fuses. This work focus on the development of economic shear wall with high yielding capacity without buckling failure to ensure the shear resistance of the building by varying the parameters like slit spacing and slit gap and are tested under the quasi static cyclic loading condition. | Study on Steel Slit Shear Walls with Different Characteristics of Hysteretic Behavior | 10.1007/978-3-031-12011-4_41 |
2023-01-01 | Current trends in the construction industry demand taller and lighter structures, which are also more flexible. Tuned liquid dampers (TLDs) are a relatively newer concept that can be used to reduce wind or seismic induced vibrations prevalent in these structures. TLD is essentially a liquid filled tank that uses liquid sloshing action to dampen the oscillations of a structure. They are cost effective and have low maintenance compared to dynamic vibration absorbers that are commonly used in flexible and lightly damped structures. This research used experiments employing models and software simulations to understand the effect of tank shape on the effectiveness of a roof mounted TLD that uses water as liquid damper media. Experimental investigations were carried out on a scaled model of single bay two storied structure using a shake table with harmonic sinusoidal input of 0.16 g at a frequency of 1 Hz. The effects of four different tank shapes using water depths corresponding to frequency ratios varying from 0.8 to 1.35 were investigated using this setup. The performance of each tank shape was compared with that of the rectangular tank. Further, the experimental results were compared with a numerical model developed in SAP 2000. The studies indicated that the shape of the tank plays an important role in the response reduction, and the sloped bottom tank was the most effective among the different shapes used. TLDs with different tank shapes may be effectively implemented as a damping mechanism through further research. | A Study on the Effect of Tank Shape on the Performance of Tuned Liquid Dampers | 10.1007/978-981-19-3371-4_21 |
2023-01-01 | Modern machining processes have been rapidly evolving into much more sophisticated forms. However, even with such sophistication in hand, the effect of chatter remains to be a significant problem. To date, engineers keep referring to the traditional chatter stability lobe to address the problem of limiting themselves in creativity to achieve high efficiency. The research aims to observe the vibration reduction along the boring process achieved by adding one type of DVA called Spring Radial Vibration Damper (SRVD) onto the workpiece. The workpiece is a cylindrical rod with the ratio of overhang length to a diameter at 6:1. The experiment conducted in different depths of cut (DoC) varies at 0.25 mm, 0.2 mm, and 0.15 mm. The experiment results show a comparison between the main system and without the SRVD in a graphical representation of the dynamic response, percentage of RMS reduction in each parameter, and surface finish of each parameter. This paper concludes that SRVD can be beneficial for the cutting process within the unstable area of the chatter stability lobe. It will worsen the cutting process if the parameters still lie within the stable area. | Analysis of the Reduction of Vibration and Chatter Effect in Boring Process Due to the Addition of Spring Radial Vibration Damper (SRVD) on the Workpiece | 10.1007/978-981-19-0867-5_8 |
2023-01-01 | Moisture is one of the main factors affecting the insulation performance of transformer oil paper in operation, and it is of great engineering value to carry out diagnostic analysis of the moisture state of the paper. In order to study the partial discharge characteristics of oil-impregnated paper after dampness, this paper selects the turn-to-turn discharge models as normal model and damp model according to the actual situation of valve-side winding of the converter. The experimental platform of AC-DC composite voltage partial discharge test is built. Through the experimental study, it is found that the partial discharge characteristics of the two models are different under the action of AC-DC compound voltage. The partial discharge onset voltage of the damped model is 7.69% lower than that of the normal model, and the discharge volume and pulse repetition rate of different discharge stages are higher than those of the normal model as the discharge develops. The types of gas production in the two models were also not the same, and the methane content was higher in the damped model. The electrical strength of the oil-impregnated paper after dampness is lower than normal, and the results of this paper can provide some reference for the operation and maintenance of the converter transformer. | Partial Discharge Characteristics of Damp Oil-Immersed Paper Under Combined AC and DC Voltage | 10.1007/978-981-99-1576-7_19 |
2023-01-01 | In the energy-based approach the effect of the earthquake on the structures is characterized in terms of an energy input and a its proper estimation is of key importance. This energy input, E _ I , flows into the structure and is partially dissipated through the inherent mechanism of damping of the structure, W _ ξ , and the rest ( E _ I − W _ ξ ) is what Housner defined as the energy that contributes to damage E _ D . This inherent damping of the structure results from internal friction in materials and, in case of RC structures, to light cracking in regions that remain essentially elastic, but does not accounts for the energy dissipated through plastic deformations. E _ D can be estimated from E _ I by using empirical expressions proposed in the literature, or from the relative velocity response spectrum of the ground motion. This paper compares the results of several shake table tests conducted by the authors on different types of structures (i.e. RC frames and RC waffle flat plates without and with energy dissipation devices) with the prediction provided by the two approaches above in terms of the ratio E _ D /E _ I . The evolution of E _ D /E _ I as a the dissipated plastic strain energy increases is also examined. | Experimental Assessment of the Energy that Contributes to Damage | 10.1007/978-3-031-36562-1_10 |
2023-01-01 | The inelastic response of structural components and systems is typically used in seismically active locations to dissipate the energy that an earthquake imparts to a structure. Response spectra are frequently used to assess how seismic waves affect structures built with civil engineering. As the effect of seismic waves cannot be controlled completely, some strategies can be adopted to prevent the structural failure and collapse. The installation of seismic dampers in place of structural parts is suggested as a method for reducing seismic damage to buildings and enhancing their seismic performance. These dampers function similarly to the hydraulic shock absorbers found in automobiles and the suspension in motorbikes, where the hydraulic fluids can absorb the majority of unexpected and sudden jerks. To adopt environment-friendly approach for controlling the effects of seismic waves, special dampers are designed on the software E-Tabs v18.0.2 as per the parameters of Taylor Devices Inc. and these dampers are applied at optimum location in particular zone which resists the seismic energy and control the effects of seismic waves. As a result, the dampers lessen the energy that may be used to shake the building. As a result, the building deforms less and the likelihood of damage is decreased. This research aims at a high-rise residential building which is seismically designed as per IS 1893:2016 Part-1 for a particular seismic prone zone on E-Tabs v18.0.2 Ultimate as per latest and modified IS codal provisions. The storey displacement was found very high in the seismic prone zone without damper consideration. After designing of special dampers and placing them into the building, structure improved and reduced the extent of maximum storey displacement to a minimised value and made the structure comparatively safe. | Optimising Structures for Earthquake Impact in Seismic Prone Zone | 10.1007/978-981-99-1886-7_36 |
2023-01-01 | Protection of structures to frequently occurring earthquake has been an active area of research due to devastating effects of an earthquake. Energy-dissipating devices undergoing inelastic deformation have been developed and implemented successfully for protection of various types of structures. The present paper aims to perform numerical study of hysteretic behavior of laboratory-based scaled model of ADAS-type metallic damper under increasing cyclic loading. A parametric study is conducted for ADAS-type metallic damper in terms of thickness and number of plates under predefined yield load/displacement. Nonlinear Chaboche model is considered for defining metal plate behavior in the post-yield region. FE model of ADAS-type metallic damper is developed and is subjected to increasing cyclic loading. It has been found that ADAS-type metallic damper has good energy dissipation capability. Equivalent viscous ratio, ζ , for the damper is of the order of 47% following yielding of the X-shaped steel plate. Parametric study in terms of thickness and numbers of plates for ADAS-type metallic damper shows marginal improvement in energy dissipation capacity. | Parameter Study on ADAS Metallic Damper | 10.1007/978-981-99-1608-5_47 |
2023-01-01 | The seismic response of a five-storey building with soil-structure interaction (SSI) utilising semi-active tuned mass damper (SATMD) is obtained. A magneto-rheological (MR) damper with friction type damping scheme is used alongside a tuned mass damper to constitute a semi-active tuned mass damper. To study the effect of SSI, the seismic response of the building with a fixed base is compared with that of the building resting on soft soil. The soft soil is considered to have a shear wave velocity of 100 m/s. The optimum damper parameters of SATMD considering four different ground motions are obtained, and these parameters are utilised to show the superiority of SATMD with friction type damping scheme in terms of efficiency and robustness. It was observed that the SATMD could significantly decrease the response of the building subjected to ground motions, but the reduction varied widely with the ground motion considered. | Effect of Semi-active Tuned Mass Damper on Seismic Response of Structure with Soil-Structure Interaction | 10.1007/978-981-99-1608-5_24 |
2023-01-01 | This paper deals with the modelling and simulation of magneto-rheological fluid in a damper using COMSOL software. MR dampers provide an edge over air or hydraulic dampers due to their variable viscous damping properties, which can be controlled with a magnetic field. This continuous controllability allows the MR damper to be optimized to give the best damping coefficient. In order to understand the functioning of an MR damper, we will have to simulate the flow of the MR fluid and understand how the rheological properties vary. In this study, a model of the MR damper will be first developed and the flow of MR fluid in the MR damper will be simulated using COMSOL. This study will aid us in designing an MR damper which will then be used in a dynamic vibration absorber. | Modelling and Simulation of Magneto-rheological Fluid in a Damper Using COMSOL | 10.1007/978-981-99-1288-9_48 |
2023-01-01 | This report presents the application of a Tuned-Mass Damper system to effectively reduce external vibrations experienced by the driver, caused by the random vibrations of the track conditions. The aim of this study is to investigate the impact of a tuned mass-damper (TMD) system on external vibrations endured by a vehicle under random vibration conditions. A quarter car model is used to simulate vehicle vibrations under random conditions and the TMD system is modeled as an additional mass-spring-damper system connected to the vehicle body. Simulation results show that the TMD system effectively reduces root mean square (RMS) value of the vehicle’s acceleration by 19.804%, and its effectiveness increases with the TMD mass. The study’s results indicate that a TMD system can be an effective method to improve a vehicle's ride comfort under random vibrations. The analysis was performed by modeling the system on Simulink, and the results were derived from the same model. | Investigation of the Effect of Tuned Mass-Damper System on the External Vibrations Endured by a Vehicle | 10.2991/978-94-6463-252-1_105 |
2023-01-01 | This paper proposes analytical solutions of the mass-spring-damper systems described by conformable fractional differential transform method. Conformable fractional transform method is based on new relation between fractional calculus and calculus based on basic limit definition were used. The behaviors of the analytical solutions of the mass-spring-damper systems described by conformable fractional transform method were represented analytically and graphically. Then the effect of the orders of the fractional derivative on the system was analyzed. The results obtained by this approach provide new explanation on the importance of fractional calculus on mechanical systems and showed clearly the amplitude of steady state solution depends on time; with contrary to what is known. | Fractional Mass-Spring-Damper System Described by Conformable Fractional Differential Transform Method | 10.1007/978-3-031-15758-5_12 |
2023-01-01 | With the development of high-speed rail, the requirements for control the motion of rail vehicle bogies are increasing. The chassis setting is responsible for the safety and comfort of the vehicle. The main problem is the conflict of the damping requirements for different driving modes. On one hand, it is necessary to ensure the stability of the bogie on a fast straight track and, on the other hand, it is good curving performance. The contribution will discuss the possibilities of mechatronic control of high-speed rail vehicle bogies to solve this conflict. There are two ways: control of the individual wheelsets and control of the entire bogie. The control can be implemented by actuators or dampers in adaptive or semi-active mode. | Mechatronically Controlled Bogie of High Speed Train | 10.2991/978-94-6463-182-1_30 |
2023-01-01 | In this paper, a damped one degree-of-freedom system equipped with a friction dynamic vibration absorber is considered. The optimal parameters: tuning frequency ratio and friction slip load are derived for various excitations: harmonic force, random force, harmonic base acceleration, and random base acceleration. The random excitation is modeled as Gaussian white noise, with constant power spectral density. First, a linearization technique is used to solve the equations of motion. Then, the optimization is conducted analytically for the undamped system, it is based on viscous absorber parameters. Finally, explicit formulas for the damped system are determined using curve fitting methods. The present paper has the advantage of determining analytically the optimal parameters of the friction absorber. It is found that the proposed formulas lead to optimal response, rapidly and accurately. | Explicit Formulas for Optimal Parameters of Friction Dynamic Vibration Absorber Attached to a Damped System Under Various Excitations | 10.1007/s42417-022-00560-6 |
2023-01-01 | Energy exchange takes place between turbine and generator in the power system during subsynchronous resonance (SSR) which leads to torsional interaction between the shafts. Resonance in the power system is caused by the series capacitors connected to the transmission line. This paper aims to present an electromechanical approach to analyse and interpret subsynchronous resonance using the Finite element method. Subsynchronous resonance is introduced in two test rigs consisting of turbine, generator, shaft, and coupler with capacitors. Experiments and simulations (torque analysis and frequency response analysis) are conducted in test rigs and ANSYS workbench 16.0. Moreover, a spring damper is modelled to improve the stability of the shaft. From the results, it is clear that mechanical stress is increased when capacitors are connected to the test rig. A spring damper is installed at the point where the deformation is high. The damper reduced the stress and the vibration. | Experimental Investigations on Turbine-Generator Shaft Under Subsynchronous Resonance | 10.1007/978-981-19-7753-4_53 |
2023-01-01 | Many studies have been conducted on energy dissipation walls for small houses to improve the earthquake resistance of structures in Japan. Oil dampers, a main damper, is installed in studs to increase their strength. However, this method tends to deform each member and joint—“support members”—owing to tensile force, and therefore, the energy absorption performance of the damper tends to decrease. In this study, we propose an energy-dissipation wall that increases the overall stiffness by prestressing the support members to prevent tensile deformation. From 2020 to 2021, two types of specimens using laminated veneer lumber (LVL) as supporting members—Type 1 and Type 2—were tested to understand the mechanical behavior of the wall. Both types were subjected to static loading tests. Additionally, dynamic loading tests were applied to Type 2. Moreover, the dynamic behavior of the one-story wooden structure installed on the Type 1 wall was investigated by subjecting it to artificial earthquake waves. In state R which the damper part of the energy dissipation wall is restrained the load-deformation relationships obtained from the static loading tests for the two types of specimens using LVL as support members showed almost linear behavior up to the assumed damper load level for both specimens. In the dynamic loading test on Type 2, a stable load-deformation history with almost no slip was obtained. In shaking table test on Type 1, it was found that the energy dissipation wall incorporated into the wooden structure absorbed the energy of the artificial earthquake shaking and prevented the deterioration of its bearing capacity. | Development of Energy Dissipation Walls with Oil Dampers and Totally Reinforced Support Members Using Pre-stress | 10.1007/978-981-19-7331-4_10 |
2023-01-01 | Tuned liquid damping devices are a low-cost, passive control system that does not require an external energy source and is effective in damping the dynamic vibrations of structures. Tuning the damper tank geometry and device parameters is important in optimizing the efficiency to be obtained from the control. In this study, tuned liquid damper (TLD) device parameters were optimized with algorithms created by hybridizing metaheuristic algorithms to minimize the structure movement. For this purpose, Jaya (JA) and Teaching-Learning Based Optimization (TLBO) algorithms were hybridized. By optimizing the properties of the TLD, the maximum displacement and total acceleration values of the structure under the critical earthquake record were reduced. In light of the results obtained, it was determined that hybrids may increase the performance of the algorithm in some cases. | Design Optimization of Tuned Liquid Dampers with Hybrid Algorithms | 10.1007/978-3-031-50151-7_19 |
2023-01-01 | The usage of the passive energy dissipative system is increasing nowadays in the high seismic risk zones, particularly in the important buildings. In this context, the effectiveness of the nonlinear fluid viscous dampers (FVDs) in the seismic performance enhancement of RC buildings is analysed in this study. This research compares the engineering response parameters such as total displacement, drift ratio, residual displacement and the floor acceleration between bare frame only model and the same with the addition of nonlinear fluid viscous dampers for Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE). The study is done in three categories of regular buildings from the perspective of Nepalese cities; five-storeyed, ten-storeyed and fifteen-storeyed buildings as this covers the typical high-rise buildings in Nepal. The building is modelled in the 3-D finite element analysis software SAP2000 developed by Computers and Structures Inc. The results show that nonlinear fluid viscous dampers are highly effective in reducing the storey displacement, drift and residual displacement whereas less effective in reducing floor acceleration as compared to the others and the efficacy of the dampers reduces with increasing building height. | Effectiveness of fluid viscous dampers in the seismic performance enhancement of RC buildings | 10.1007/s42107-022-00504-1 |
2023-01-01 | The idea of a tuned mass damper emerges due to a common vibration problem existed in mechanical and civil structures applications. Vibration turns out to be a hazard that can reduce the life of the structure, thus tuned mass damper is considered as one of the most practical methods in the engineering branches since it can be used as vibration attenuator. The present paper investigated the design of tuned mass damper (TMD) to reduce the vibration amplitude of a building structure model. In the initial stage, the frequency of the building model and tuned mass damper were determined by using the theoretical equations. This is followed by the finite element modal analysis to determine the natural frequency and mode shape and then compared with the calculation. It was found that the percentage error of natural frequency between the theoretical and the simulation result was less than 15% for building model (without tuned mass damper) and 2% for building model with attached tuned mass damper. The simulation analysis was further carried out by utilizing tuned mass damper to suppress vibration on the building model when subjected to a 10 N force. The results demonstrated that the attachment of TMD on the building model could significantly reduce the vibration amplitude by more than half. | Finite Element Analysis of Tuned Mass Damper | 10.1007/978-981-19-4425-3_25 |
2023-01-01 | The work presents a novel Prestressed LEad Damper with Straight Shaft (PS-LED), which incorporates several desirable characteristics, namely high stiffness and damping capability in a compact design, and low manufacturing cost, which make it suitable for social housing. The device provides a resistive force by the friction activated between a lead core and a shaft, showing a consistent rigid-plastic behavior without significant strength degradation; the shape of the hysteresis loops is essentially rectangular, resulting in an equivalent damping ratio of 0.55. A modelling procedure is suggested to represent in the OpenSees framework the non-linear behavior of the PS-LED for both static and dynamic analyses. In particular, for dynamic analyses, a finite element object of the PS-LED is formulated by means of a simple rheological model comprising a parallel of a non-linear spring and a viscous model. In order to show the effectiveness of the PS-LED device for the retrofit of reinforced concrete structures, a case-study is chosen as paradigmatic of a category of existing buildings in Italy designed according to outdated codes. The structure is retrofitted with the PS-LED in order to maintain an elastic behavior, with no plastic hinges, during the earthquake. Non-linear static analyses are performed on the upgraded building, showing a fair agreement between the design target and the actual performance. To provide a deeper insight, bidirectional non-linear dynamic analyses are further performed considering a suite of artificial bidirectional ground motions in accordance with the provisions of the Eurocode 8. | Modelling of a Novel Lead Damper and Application to an Existing RC Structure | 10.1007/978-3-031-30125-4_5 |
2023-01-01 | Stockbridge dampers are the most widely used in wind induced vibration control of overhead power transmission lines. This dynamic absorber comprises a carrier cable with a mass at each end and a bolted clamp that can be attached to a conductor or a guard wire, with the purpose of supplementing the energy dissipated by the cable related to its self-damping. The maximum response of this type of absorber is associated with the frequencies of its different oscillation modes. The masses are designed in such a way to obtain moments of inertia and location of their center of gravity such that, with the vibration of the clamp, their various characteristic bending and torsional modes are excited. In this work, the calibration of a nonlinear finite element model using Bayesian inference is presented to evaluate the dynamic behavior of the damper for all excitation frequencies and displacement amplitudes. To this end, an inverse problem was posed in which the probability distributions of the parameters of interest are obtained from backward uncertainty propagation of experimental measurements performed in laboratory tests. Finally, the uncertainty of the calibrated model was propagated and contrasted with the experimental data. The developed model is a powerful tool when defining the quantity and distribution of dampers in the span of a line. | Bayesian Inversion of a Non-linear Dynamic Model for Stockbridge Dampers | 10.1007/978-3-031-38563-6_1 |
2023-01-01 | The rotor-bearing-squeeze film damper coupling (RBSC) system is the core part of aero-engines, determining operation safety and reliability. The dynamic behavior of the RBSC system is easily affected by the bearing outer race localized defect, which is difficult to identify accurately. Inappropriate dynamic analysis of system behavior will further affect monitoring and diagnosis of the system. This paper presents a mathematical model of the RBSC system with bearing outer race localized defect to study the dynamic behavior of the system. The model develops a smooth spalling path in the bearing outer race to simulate the successive passage of the balls. The model also considers the effect of centrifugal load on the bearing force. The impact of the bearing outer race localized defect on the RBSC system during the acceleration process is analyzed. The numerical results show the bearing outer race localized defect will aggravate the nonlinear behavior of the RBSC system and is prone to chaotic motion. Meanwhile, affected by the bearing outer race localized defect, the vibration of the RBSC system will increase in the speed range of relatively low and relatively high. Especially in the high-speed range, the impact of a bearing outer race localized defect on system vibration covers more speeds. This study provides a theoretical basis for condition monitoring and fault diagnosis of the RBSC system. | Dynamic Behavior Analysis of a Rotor-Bearing-Squeeze Film Damper Coupling System with Bearing Outer Race Localized Defect | 10.1007/978-3-031-07322-9_51 |
2023-01-01 | For the offshore platform located in an active fault zone, earthquakes are a significant additional burden to the wave load. When mining and producing resources from the ocean, jacket platforms are frequently exposed to a variety of environmental stresses, including waves, strong winds, earthquakes, tsunamis, etc. Jacket platforms are more susceptible to seismic loads because of their inflexible design. The goal of the current investigation is to determine how well tuned liquid dampers (TLDs) manage the earthquake-induced responses of jacket platforms. A linear time-history analysis is performed in SAP2000, with and without TLDs. The TLD behavior has been simulated using a simplified lumped mass model. The efficiency of TLD was evaluated for three different seismic excitations in order to determine its durability. For the purpose of examining the impact of various factors on the functionality of the TLD, the effectiveness of TLDs is explored for variable depth ratio, mass ratio, and structural damping. The general conclusions of the numerical investigation show that TLD has the ability to regulate the jacket deck vibrations under seismic excitation. | Seismic Vibration Control of Jacket Platform with the Aid of Tuned Liquid Dampers | 10.1007/978-981-99-1608-5_8 |
2023-01-01 | In this work, optimum parameters of the tuned inerter damper (TID) are obtained using equal eigenvalue (EEV) criterion. Performance of this TID is compared with that of other optimum TID available in the literature. EEV criteria are loading independent, whereas other criteria available in the literature are loading dependent. TID uses an inerter, a mechanical device with two terminals that appears to have a mass amplification effect. TID performance is first assessed for harmonic loading. Frequency response function (FRF) from both the TIDs is compared. Robustness, i.e., sensitivity to mistuning is also assessed, and it is found that TID with EEV parameters is more robust. Under seismic excitation, both the TIDs are found to give similar reduction in response. | Optimum Parameters for Tuned Inerter Damper | 10.1007/978-981-99-1608-5_34 |
2023-01-01 | In this section, as well as explaining the building control systems and their properties, the displacement and acceleration values were found in the case that TMD is not used and TMD is placed, according to the earthquake record that affects the building most negatively, by affecting past earthquake records on the single degree of freedom system. By using the Matlab & Simulink programs, the displacement optimization was performed according to the time history domain using the Hybrid (TLBO-Jaya) and Jaya algorithms. In this optimization process, firstly, the TMD mass was determined as 5% of the mass of the structure, after that. the constant values, constraint values and the necessary information for the algorithm were entered to solve the system. Optimal intervals were determined by assigning the TMD period and damping ratio as variables. In the case of optimization of the single degree of freedom system, it is seen that there are great differences in displacement and acceleration in the system. Furthermore, while for the same system operated using different algorithms, the values of the Hybrid algorithm and the Jaya algorithm for variables under loadings were compared for system. | Structural Control Systems and Tuned Mass Damper Optimization by Using Jaya and Hybrid Algorithms | 10.1007/978-3-031-34728-3_6 |
2023-01-01 | Damper failures are generally brittle mechanisms, which can compromise the capacity of the structure to withstand the seismic action, leading to a lack of robustness of the overall system. The brittle failure is due to the attainment of the maximum force capacity, because of end-stroke impacts, which causes an arising of the forces, or to an excessive velocity of the piston (over-velocity). Moreover, anti-seismic devices need to be designed with proper safety margins against their failure in order to reach a target safety level. Seismic standards generally prescribe safety factors (reliability factors), that in the case of Fluid Viscous Dampers (FVDs) are applied to stroke and velocity, with values that are not homogenous among seismic codes. The effect of damper failure and different reliability factors on both the fragility and the seismic risk of the structural system is investigated by performing multiple-stripe analysis and monitoring different global and local demand parameters of a medium-rise steel moment-resisting frame building, widely studied in literature, thanks to an advanced model implemented in OpenSees, which considers the brittle mechanism. Moreover, the problem of damper failure is also analysed in terms of fragility functions, providing information about the dependency of the probability of failure with the seismic intensity. | The Brittle Failure of Fluid Viscous Dampers and the Related Consequences on the Reliability of a Medium-Rise Steel Building | 10.1007/978-3-031-21187-4_83 |
2022-12-30 | In this paper, we consider semilinear wave equations with critical power and scale invariant damping term $$2(1+t)^{-1}u_{t}$$ 2 ( 1 + t ) - 1 u t in exterior domain in high dimensions ( $$n\ge 3$$ n ≥ 3 ). Upper bound lifespan estimates of solution are established by employing test function method. The novelty is that we show the asymptotic behavior of the test function by using maximum principle. Comparing with the method utilized in Sobajima (J Math Anal Appl 484:123667, 2019), we avoid using the modified Bessel functions to construct the test function. It is worth to mention that the method employed in this paper is also different from the one in Lai (Nonlinear Anal 125: 550–560, 2015) and Lai (Nonlinear Anal. 143: 89–104, 2016). | Lifespan estimates for critical semilinear wave equations and scale invariant damped wave equations in exterior domain in high dimensions | 10.1007/s00028-022-00857-9 |
2022-12-26 | In this study, a half-space 13-degree-of-freedom vehicle model, a double track model, and a train-bridge interaction model were integrated to form a combined people-train-rail-bridge interaction model to analyze the vertical Sperling index of the train body and passengers as realistically as possible. In this bigger, more complete, and novel model, the separation between the vehicle and bridge is considered. By comparing measured data and simulated results obtained using the proposed model with the Newmark-Beta algorithm, the effectiveness of the model was verified, and the results demonstrated that these two values were very close. Upon further numerical analysis, the dynamic responses of the train and the three equivalent human bodies at different train speeds were computed using the developed vehicle-structure dynamic analysis program with different abruptness values in the random rail irregularities. The results of these four dynamic responses revealed that the rail irregularities affected the vertical acceleration of the three equivalent human bodies and train, and the best Sperling index evaluation standard for the train was not fixed (as assumed when only considering the train body) but varied with the passenger position as the train traveled over irregularities. | Dynamic Train Vertical Sperling Index Evaluation Model Considering Wheel-Rail Contact Loss | 10.1007/s12204-022-2551-1 |
2022-12-26 | We analyse the evolution of a generalized bosonic oscillator in the near horizon geometry of the BTZ black hole by analytically obtaining a solution of the associated Klein–Gordon equation. We show that it is possible to obtain relativistic frequency expression in closed-form for the system in question. Here, we observe that such a system decays in time without any real oscillation and the damped modes depend explicitly on the parameters of the oscillator coupling besides the parameters of the background geometry. This result allows us to analyse the influences of both oscillator coupling and spacetime parameters on the evolution of such a test field. Also, the results indicate that the spacetime background is stable under this perturbation field. | Damped modes for a bosonic quantum oscillator in the near-horizon geometry of the BTZ black hole | 10.1007/s10714-022-03058-4 |
2022-12-19 | In this paper, we discuss the asymptotic stability as well as the wellposedness of the viscoelastic damped wave equation posed on a bounded domain $$\Omega $$ Ω of $${\mathbb {R}}^2,$$ R 2 , $$\begin{aligned} \partial _{t}^2u - \Delta u+ \displaystyle \int _0^\infty g(s)\hbox {div}[a(x)\nabla u(\cdot ,t-s)]\,\mathrm{{d}}s + b(x) \partial _{t}u + f(u)=0, \hbox { in }\Omega \times {\mathbb {R}}_+, \end{aligned}$$ ∂ t 2 u - Δ u + ∫ 0 ∞ g ( s ) div [ a ( x ) ∇ u ( · , t - s ) ] d s + b ( x ) ∂ t u + f ( u ) = 0 , in Ω × R + , subject to a locally distributed viscoelastic effect driven by a nonnegative function a ( x ) which is positive around the entire neighborhood of $$\partial \Omega $$ ∂ Ω and supplemented with a frictional damping $$b(x)\ge 0$$ b ( x ) ≥ 0 acting effectively on $$\partial A$$ ∂ A where $$A=\{x\in \Omega \big / a(x)=0\}$$ A = { x ∈ Ω / a ( x ) = 0 } . Assuming that well-known geometric control condition $$(\omega ^\prime , T_0)$$ ( ω ′ , T 0 ) holds, supposing that the relaxation function g is bounded by a function that decays exponentially to zero and the function f possesses an arbitrary growth, we show that the solutions to the corresponding partial viscoelastic model decay exponentially to zero. We can also treat the focusing case for those solutions with energy less than d of the ground state, where d is the level of the Mountain Pass Theorem. | Exponential Stability for the 2D Wave Model with Localized Memory in a Past History Framework and Nonlinearity of Arbitrary Growth | 10.1007/s12220-022-01085-w |
2022-12-16 | The modal parameters identification of bridges under non-stationary environmental excitation has caught the attention of researchers. This paper studies the non-stationarity of wind velocity, and extracts the time-varying mean wind velocity based on a discrete wavelet transform and recursive quantitative analysis. The calculated turbulence intensity and turbulence integral scale under the non-stationary model are smaller than those under the stationary model, especially the turbulence integral scale. The empirical wavelet transform is used to identify the modal parameters of long-span bridges, and the power spectral density spectrum is proposed as a replacement for the Fourier spectrum as the basis of the frequency band selection. The bridge modal parameters are then compared using the covariance-driven stochastic subspace system identification method (SSI-COV) and the Hilbert transform method based on an improved empirical wavelet transform (EWT-HT). Both methods can accurately identify the modal frequency, and the absolute difference between these two methods is equal to 0.003 Hz. The wind velocity results in a change of less than 1% in the modal frequency. The absolute difference between the modal damping ratios identified using SSI-COV and EWT-HT is significant and can reach 0.587%. The modal damping ratios are positively correlated with the mean wind velocities, which aligns with the quasi-steady assumption. In addition, the applicability of SSI-COV and EWT-HT is also evaluated using the standard deviation, coefficient of variation, and range dispersion indicators. The results show that the EWT-HT is more applicable to the identification of the modal parameters of long-span bridges under non-stationary wind velocities. | Identification of modal parameters of long-span bridges under various wind velocities | 10.1186/s43251-022-00071-0 |
2022-12-16 | In a Hilbert setting, we study the convergence properties of the second order in time dynamical system combining viscous and Hessian-driven damping with time scaling in relation to the minimization of a nonsmooth and convex function. The system is formulated in terms of the gradient of the Moreau envelope of the objective function with a time-dependent parameter. We show fast convergence rates for the Moreau envelope, its gradient along the trajectory, and also for the system velocity. From here, we derive fast convergence rates for the objective function along a path which is the image of the trajectory of the system through the proximal operator of the first. Moreover, we prove the weak convergence of the trajectory of the system to a global minimizer of the objective function. Finally, we provide multiple numerical examples illustrating the theoretical results. | A fast continuous time approach with time scaling for nonsmooth convex optimization | 10.1186/s13662-022-03744-2 |
2022-12-02 | A multilevel design toolchain is used for the development of particle dampers for vertical transient vibrating structures. Thereby various experimental tests and numerical models are combined. The design toolchain consists of three levels. The first level deals with the micro-mechanical behavior of single particle–particle and particle–wall impacts. The resulting coefficient of restitution is then used on the second level. Within, the second level the properties of vertical vibrated granular matters inside a container under harmonic motion are analyzed. The resulting motion modes and energy dissipation of the granular matter strongly depend on the excitation conditions, i. e. the excitation amplitude and excitation frequency. Multiple analytical formulations for the different motion modes, i. e. solid-like state and collect-and-collide motion mode, are derived to describe the energy dissipation within the particle damper. These analytical descriptions are in good agreement with numerical discrete element simulations. Finally, the third level of the design toolchain deals with designing a damper for a desired structure. The analytical formulations describing the energy dissipation within the particle damper are used to optimize a particle damper configuration for a simple beam-like structure undergoing a vertical transient vibration. The efficiency of the optimized particle damper dissipation is proven experimentally. | Systematic design of particle dampers for transient vertical vibrations | 10.1007/s10035-022-01290-y |
2022-12-01 | Conventional and earlier versions of the cyclic simple shear tests employed specimens confined within stacked rings or wire reinforced membranes or rigid boundary platens. A new type of cyclic simple shear where the specimens are tested within the confines of a flexible membrane as in the case of the conventional cyclic triaxial testing system is presented and described. The principles, the advantages, and the stated limitations in the past studies related to conventional testing systems are discussed. This paper assesses the advantages of the new type (confining pressure type) of a cyclic simple shear system over the previous versions and the need for using it to determine the dynamic response of soils. | A review of cyclic simple shear test on soils: challenges and new solutions | 10.1007/s12572-022-00321-4 |
2022-12-01 | This paper compared the mechanical properties and damping capacity of homogeneous welded joints of Mn-36Cu-3Al-2Zn-2Ni-2Fe (wt.%) cast damping alloy by pulsed and non-pulsed current TIG welding. The results show that the pulsed current makes the microstructure finer in the welded seam due to its rapid solidification of the welding pool and fragmentation of the rough dendrite arm. Tensile and impact tests show that pulsed current welded joints have better mechanical properties than non-pulsed current welded joints, as the strength and toughness of the joints increased by 6.6 and 25.2%, respectively. In addition, according to damping capacity test results, the larger Mn-rich regions in the pulsed current welded seam result in a larger f.c.c-f.c.t phase transformation and more fine martensitic twins. Thus, the damping capacity of the welded joint under pulsed current is 27.6% higher than that under non-pulsed current and far higher than that of the base metal. The addition of pulsed current significantly improves the mechanical properties and damping capacity of the alloy welded joint. | Increase in Mechanical Properties and Damping Capacity of a Cast Mn-Cu Damping Alloy Welded Joint by Pulsed Current TIG Welding | 10.1007/s11665-022-07001-1 |
2022-12-01 | It is widely known that a coupled system of nonlinear wave equations with a polynomial nonlinearity can be stabilized by a frictional damping or by a viscoelastic one under some restrictive conditions. In this paper, we study the asymptotic behavior of coupled system of nonlinear wave equations with a damping of fractional order. We show that under the condition that the fractional order is less than one and the initial data are so large, the system blows up in some finite time. | Well-Posedness and a Blow up Result for a Fractionally Damped Coupled System | 10.1007/s40840-022-01405-x |
2022-12-01 | In this article, a new class of stochastic exponential Runge-Kutta (SERK) methods is developed for solving stochastic differential equations. The proposed SERK methods can preserve conformal quadratic invariants and conformal symplectic structure automatically under certain coefficient conditions. Stochastic B-series theory is generalized, which allows the study of the mean-square convergence order conditions of the SERK methods. Some low stage stochastic exponential integrators with 1 order mean-square convergence and structure-preserving properties are given. For damped Hamiltonian systems with additive noise terms, a class of stochastic exponential integrators with 1.5 order mean-square convergence and conformal symplectic structure preservation is constructed. Numerical tests show the efficacy of the stochastic exponential integrators. | A new class of structure-preserving stochastic exponential Runge-Kutta integrators for stochastic differential equations | 10.1007/s10543-022-00924-0 |
2022-12-01 | Abstract The problem of active damping of cylindrical shell vibrations with free boundary conditions is considered. The shell is supported by rings. An example of the identification of the source and damping of bending vibrations of a shell is presented. | Problem of the Active Damping of Cylindrical Shell Vibrations by Discrete Forces | 10.3103/S1052618822080131 |
2022-12-01 | Abstract In this paper, we are concerned with the stabilization of a laminated beam with one discontinuous local internal fractional damping. We reformulate the system into an augmented model and prove the well-posedness of it by using semigroup method. Based on a general criteria of Arendt-Batty, we show that the system is strongly stable. By combining frequency domain method and multiplier techniques, we establish a polynomial energy decay rate of type $${{t}^{{\frac{{ - 2}}{{1 - \alpha }}}}}$$ for the case of equal wave speeds, and obtain a polynomial decay rate of type $${{t}^{{\frac{{ - 2}}{{5 - \alpha }}}}}$$ when the wave speeds are different. | Polynomial Stability of the Laminated Beam with One Discontinuous Local Internal Fractional Damping | 10.3103/S0025654422060024 |
2022-12-01 | Ink transfer is achieved by the squeezing and rotation of two rollers, one of which is a roller coated with a viscoelastic rubber layer. In this study, the force caused by ink hydrodynamic pressure on the rubber roller during the rotation is considered, the viscoelasticity of ink and rubber is equivalently substituted by spring-damping unit, and a rolling squeezing theoretical model of two rollers is established to study the node deformation of the rubber roller. The validity of the theoretical model is verified by experiments. Results show that the deformation of the rubber roller is greatly affected by the roller rotational speed, rubber layer thickness, and nip width. The rotational speed and nip width have a significant influence on the stiffness-damping of the ink layer and the ink force, and the rubber layer thickness has a remarkable effect on the squeezing deformation between the rollers. | Deformation of the ink roller of an offset press based on a simplified model of ink-rubber viscoelasticity | 10.1007/s12206-022-1119-1 |
2022-12-01 | In this article, a quasi-3D trigonometric shear deformation plate theory is utilized to study the vibration response of an advanced cross-ply multilayered composite plate that contains a homogenous core and viscoelastic faces subjected to a hygrothermal loading and embedded in a viscoelastic foundation. Two actuating layers of magnetostrictive material are employed for controlling and enhancing the vibration damping via a constant velocity feedback gain distributed control. The layers of the viscoelastic material are modelled using the Kelvin–Voigt model. The dynamic system is obtained employing Hamilton’s principle and solved analytically based on Navier’s approach. The influences of important factors on eigenfrequency values and deflection of the proposed multilayered plate are investigated. Of these, the effect of the feedback control gain magnitude, aspect ratio, magnetostrictive layer location, thickness ratio, viscoelastic layer thickness-to-core thickness ratio, half-wave numbers, magnetostrictive layer thickness-to-core thickness ratio, orientations of the viscoelastic layer’s fiber, and viscoelastic foundation and material. Numerical results proved that the stiffness of viscoelastic foundations, location of the smart layers, feedback control gain value, and magnetostrictive thickness-to-core thickness ratio have strong roles in the improvement of vibration damping characteristics. | Hygrothermal vibration of a cross-ply composite plate with magnetostrictive layers, viscoelastic faces, and a homogeneous core | 10.1007/s00366-021-01482-9 |
2022-12-01 | The functioning of adjoining similar two-degree-of-freedom structures interconnected by lead damper under random excitation is investigated. The governing equation of motion of the interconnected structure is derived, and responses (displacement and acceleration) are incurred. The response mitigation effectuality of lead damper is assessed by analyzing the linked structures using Monte Carlo simulation. The optimal measure of damper constant and representing response in closed-form formulation under stationary white-noise excitation is derived. The derived expressions can be utilized for preliminary optimal designing of damper interconnecting adjoining similar structures. The efficacy of lead damper interconnecting two adjoining multi-degree-of-freedom similar structures subjected to real earthquake excitations is also investigated. | Response control of adjoining similar structures interconnected by lead damper | 10.1007/s42107-022-00477-1 |
2022-12-01 | Abstract A mathematical model is derived for a two-chamber pneumatic suspension with internal air damping. The vibrational damping properties of the suspension are studied theoretically and experimentally. | Two-Chamber Pneumatic Suspension with Air Damping | 10.3103/S1068798X22120103 |
2022-12-01 | We prove that, under a suitable integrable condition, there is global stability of strong solutions for the 3D incompressible Navier–Stokes equations with a damping term which, consequently, provides a new class of global strong large solutions. Besides this, we prove that the system preserves helical symmetry and that, in this case, there is stability. Finally, if some parameters are small, we establish a connection between the stability of the system with and without the damping term. | Global stability of solutions with large initial conditions for the Navier–Stokes equations with damping | 10.1007/s40863-022-00298-9 |
2022-12-01 | A reaction–diffusion approximation is a method that solutions of multi-component reaction–diffusion systems approximate those of differential equations. We introduce the reaction–diffusion approximations of a semilinear wave equation and a semilinear damped wave equation under some assumptions of a reaction term. These approximation systems consist of a two-component reaction–diffusion system with a small parameter. In this paper, we prove that a first component of a solution for the system converges to a solution for the semilinear damped wave equation as the parameter tends to zero. Moreover, let us show the numerical results of reaction–diffusion approximation for the wave equation and the damped wave equation, respectively. | A reaction–diffusion approximation of a semilinear wave equation with damping | 10.1007/s13160-022-00536-9 |
2022-12-01 | Abstract The review summarizes the theoretical and numerical results of analysis of the dispersion equation of standing waves on the surface of a viscous liquid published by L.N. Sretensky in 1941. A mechanism for the viscous regularization of wave motion is proposed, according to which the effects observed in the experiment are associated with the presence of a short-wavelength cutoff region, where viscous dissipation becomes the predominant factor and short-wavelength perturbations responsible for the breaking of a standing wave are suppressed. | Standing Gravity Waves on the Surface of a Viscous Liquid | 10.1134/S0015462822070059 |
2022-12-01 | The response behavior of adjoining similar structures interconnected by friction dampers and subjected to non-stationary and stationary random excitations is studied. The response mitigation efficacy of friction damper is assessed by analyzing the adjoining interconnected structures using Monte Carlo simulation. The closed-form formulation for optimal slip force of friction damper and mean square response of undamped interconnected structures under stationary white-noise excitation are derived. The derived expressions can utilized for preliminary optimal designing of damper interconnecting adjoining similar structures. | Response Control of Adjoining Similar Structures Interconnected with Friction Dampers | 10.1007/s40030-022-00662-0 |
2022-12-01 | The present work deals with the study of the damping capacity of β-metastable Ti–(24–26) Nb alloys. In this work, several methods have been used to characterize this damping. The impact tests were carried out using two test benches: high-speed impacts were carried out using a vertical firing pressure gun and low-velocity impacts were studied with a bullet drop test. In addition, an original approach of a dynamic mechanical analysis (DMA) is proposed in order to obtain more in-depth understanding of the relationship between microstructure, deformation mechanisms, and damping capacity. The specimens are studied at different microstructure states: single β, dual-phase β + α″, and martensitic phase. A correlation is established between the evolution of the damping factor as function of the applied strain and the occurrence of the corresponding deformation mechanisms. The stress-induced martensite mechanism contributes to the improvement of the damping factor. The highest damping capacity is observed for the dual-phase specimen (β + α″). It is shown that the contribution of both the reorientation martensite variants and stress-induced martensitic transformation lead to a damping capacity higher than a single deformation mechanism one. | Damping Capacity of Ti–Nb Shape Memory Alloys Evaluated Through DMA and Single-Impact Tests | 10.1007/s40830-022-00398-7 |
2022-12-01 | Abstract The study compares seismic hazard assessments of the territory of Uzbekistan, obtained with the same input parameters, but using different methodological approaches: the Riznichenko approach based on the theory of macroseismic and spectral-time shaking and the classical Cornell probabilistic approach based on the full probability theorem. As seismic source models, linearly extended sources (seismogenic zones) and area sources (quasi-uniform seismological provinces) were considered. The authors used a number of their own damping dependences, established from analysis of isoseismic earthquake patterns in Central Asia, when assessing the seismic hazard of the study area in terms of macroseismic intensity, along with the Shebalin dependence, obtained from global data ( I = 1.5 M – 3.5 log R + 3). To estimate seismic hazard in engineering seismic indicators, the dependences built into the R-CRISIS software package, developed over the past 10–12 years for shallow active crust and stable regions, were used as the ground motion equation. For a 50-year seismic impact nonexceedance probability P = 0.90, the maximum differences in seismic hazard assessments using the two considered approaches for the entire seismically active part of the study area are ∆ I = 0.39; for P = 0.95, ∆ I = 0.54; for P = 0.98, ∆ I = 0.61; and for P = 0.99, ∆ I = 0.76. A similar comparison of seismic hazard assessments in the values of maximum ground motion accelerations leads to the following figures: for P = 0.90, ∆ a _max = 75 cm/s^2; for P = 0.95, ∆ a _max = 111 cm/s^2; for P = 0.98, ∆ a _max = 167 cm/s^2; for P = 0.99, ∆ a _max = 273 cm/s^2. | Comparison of Seismic Hazard Assessments Obtained with the Probabilistic and Probabilistic-Deterministic Approaches for the Territory of Uzbekistan | 10.3103/S0747923922070040 |
2022-12-01 | In this work, a new class of iron-based high entropy shape memory alloys (HE-SMAs) have been designed, characterized, and optimized. These FeCuNiMnV alloys (FeMn-like) with damping properties at low and high temperatures are developed; a methodology is proposed to demonstrate how to preserve this effect from the memory loss observed on conventional damping alloys. The developed alloys are analyzed using X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Their damping capacity is investigated using a drop weight test device instrumented with a digital image correlation system for the displacement measurement. It is compared with one of FeMnV, NiTi, CuAlNi, and 1050A alloys at different temperatures. The results show that the damping capacity is interesting over a wide range of operating temperatures. It has been established that the cocktail effect obtained by mixing Cu, Fe, Ni, Mn, and V elements allows for optimizing the damping capacity of the HE-SMAs. In addition, the sluggish diffusion may allow these HE-SMAs to prevent the premature aging that leads to a degradation of the damping behavior notably at high temperature. The variation of the composition of the Cu_ x Fe_ y Ni_ z Mn_20V_11 alloys enables the adjustment of the alloying element content by favoring the appearance of the non-thermally activated martensite keeping hence a stable damping behavior from − 40 to 200 °C. | Damping Behavior in a Wide Temperature Range of FeMn-Like High Entropy Shape Memory Alloys | 10.1007/s40830-022-00381-2 |
2022-12-01 | Stretchers are required whenever a life-threatening accident occurs. A patient’s journey from the place of accident to the hospital is a very critical factor in saving the patient life. The patient’s journey in the ambulance comes with vibrations occurring now and then which may cause the patient unnecessary pain and even increase the severity of the complications. The proposed work focuses on reducing these vibrations by isolating them. For doing so, stretchers with dampers are designed. The suggestive designing is carried out in SolidWorks whereas analysis is done using MATLAB Simulink. For validating the MATLAB model, analytical calculations are carried out in Scilab. A triple mass spring damper system based on a quarter car model is developed in MATLAB Simulink. Two suggestive CAD models are proposed in this work to achieve the objective of isolating vibrations. The results of the analysis successfully showed that the vibrations caused due to sudden impacts transmitted the shock directly to the patient, causing additional distress. By adding an additional damping system between the chassis and stretcher, we can reduce the impact of shock directly. | Design and Analysis of Stabilizing Ambulance Stretcher | 10.1007/s41403-022-00356-w |
2022-12-01 | Supercritical transmission shafts—those which have one or more critical speeds below their operation speeds—are becoming more popular in new armored vehicle and rotorcraft designs. To suppress the excessive transcritical vibration, dry friction damper is a prevailing choice. In this paper, we focus on the nonlinear dynamics, stability and bifurcation mechanism of the dry friction damper for supercritical transmission shaft. The harmonic balance method with alternating frequency-/time-domain technique (HB-AFT) and the numerical path continuation is employed to solve the nonlinear governing equations of the shaft/damper system where the rub-impact and dry friction phenomena are involved. The stability and bifurcation points of the solution branch are further determined with the help of Floquet theory. Besides, the effects of three damper parameters, that is, the clearance, the critical slip force and the circumferential friction coefficient, are investigated. Finally, prototypes of the dry friction damper are designed, manufactured and tested on a high-speed rotor dynamics test rig. The theoretical findings are in general agreement with the experimental results. | Nonlinear dynamics and stability analysis of dry friction damper for supercritical transmission shaft | 10.1007/s11071-022-07795-8 |
2022-12-01 | Filling layer self-compacting concrete (FLSCC) is an essential material used in the construction of China Rail Track System type III (CRTS III) slab track of high-speed rail. The mechanical properties of the filling layer are of paramount significance to the performance and serviceability of the track system. In this study, asphalt emulsion (AE) was incorporated into the FLSCC, and various properties related to workability, strength, durability, and damping performance were experimentally evaluated. The effect of AE on the durability of FLSCC was investigated through water absorption, sorptivity, and rapid chloride ion penetration tests; while damping properties were evaluated using impact resonance method. Results show that addition of AE decreases the compressive and split tensile strength while flexural strength increases, especially at lower AE content. The durability properties were greatly enhanced with the addition of AE, which results from the decreased permeability of FLSCC specimens due to the pore-filling effect of asphalt film that flows and fills the pores and cracks of the matrix. Damping ratio of FLSCC increased by 22.8%, 23.7%, 25%, and 30.6% through the addition of 5%, 10%, 15%, and 20% AE, respectively. According to the findings of this study, AE content up to 10% is recommended for FLSCC production. | Evaluation of the Influence of Asphalt Emulsion on the Strength, Durability, and Damping Performance of Filling Layer Self-Compacting Concrete | 10.1007/s12205-022-0155-9 |
2022-12-01 | Dynamic positioning (DP) for station-keeping control keeps the position and heading of the vessel constant regardless of environmental disturbances from wind, waves and currents. If the point of interest on the vessel has a significant vertical offset, it will be influenced also by the roll, pitch and heave motions. Although such motions are usually neglected in DP control, there is an opportunity to also influence these since thrusters will not only influence the horizontal plane motion of a vessel, but also generate roll and pitch moments. In this paper, we formulate the problem of DP control when explicitly considering the first-order wave-induced roll motion and thruster roll moment. It is shown that the control performance can be significantly improved when the DP system’s point of interest, and the location of the thrusters, have a significant vertical offset compared to the vertical position of the center of rotation. The proposed control algorithm is demonstrated in a realistic simulation of a relatively small ship during launch-and-recovery of a remotely operated vehicle (ROV) where the DP’s point of interest is at the lower end of the launch-and-recovery-system (LARS) that extends below the keel of the ship. It is shown that the positioning performance can be improved with 20–45 $$\%$$ % reduced error, depending on the sea state. | On compensation for wave-induced roll in dynamic positioning control | 10.1007/s00773-022-00906-5 |
2022-12-01 | A new optimal control approach is presented for designing and controlling inelastic lateral load resisting systems. This paper uses the technique to develop a seismic retrofit procedure for inelastic shear-type resisting systems with stiffness changes and nonlinear fluid viscous dampers (FVDs). Generally, optimal control procedures aim to derive the optimal constant output feedback gains based on the weighting components assigned to the system's regulated outputs, which define their relative importance during the cost function minimization process. However, stiffness changes and FVD coefficients (the constant output feedback gains) are initially assigned in the reversed optimal control approach. Then, the consequent weighting matrices are calculated assuming the system is at its optimal state. Finally, a recurrence relation for updating the stiffness changes and added damping quantities is proposed based on the relative size between the weighting matrix components. While this paper addresses inelastic shear-type resisting systems, the reversed optimal control approach is suitable to other dynamic systems whose state vector trajectory can be determined. Two case studies examine and exemplify the developed procedure. The first case study analyzes a spectrum of single-degree-of-freedom (SDOF) systems and investigates the correlation between the weighting components and system configurations. The second case study applies the developed procedure to a five-story shear-type resisting system and demonstrates its reliability in sequentially minimizing the cost function while reducing relative interstory drifts and absorbed yield energy. | Reversed optimal control approach for seismic retrofitting of inelastic lateral load resisting systems | 10.1007/s40435-022-00939-z |
2022-12-01 | In the global optimization process of the firefly algorithm (FA), there is a need to provide a fast convergence rate and to explore the search space more effectively. Therefore, we conduct modular analysis of the FA and propose a novel enhanced exploration firefly algorithm (EE-FA), which includes an enhanced attractiveness term module and an enhanced random term module. The attractiveness term module can improve the exploration efficiency and accelerate the convergence rate by enhancing the attraction between fireflies. The random term module improves the exploration efficiency by introducing a damped vibration distribution factor. The EE-FA uses multiple parameters to balance its exploration efficiency and convergence rate. The parameters have a great influence on the performance of the EE-FA. In order to achieve the best performance of the EE-FA, each parameter of the EE-FA needs to be simulated to determine its optimal value. Compared to multiple variants of the FA, the EE-FA has better exploration efficiency and a faster convergence speed. Experimental results reveal that the EE-FA recreated consistently vanquishes the front for 24 benchmark functions and 4 real design case studies in terms of both convergence rate and exploration efficiency. | A novel enhanced exploration firefly algorithm for global continuous optimization problems | 10.1007/s00366-021-01477-6 |
2022-12-01 | The dynamic behaviour of unsaturated sand rubber chips mixtures at various gravimetric contents is evaluated through an experimental study comprising resonant column tests in a fixed-free device. Chips were irregularly shaped with dimensions ranging from 5 to 14 mm. Three types of sand with different gradation have been considered. Relative density amounted to 0.5 for all specimens. Due to the large size of the chips, the diameter of the specimens had to be equal to 100 mm, which in turn required a re-calibration of the device assuming a frequency-dependent drive head inertia. The effects of confining stress, rubber chips content, and sand gradation on shear modulus and damping ratio are determined over wide ranges of the shear strain. At small strains, as known for sands, increasing the confining stress stiffens the mixtures. Increasing the rubber chips content reduces significantly the shear modulus and increases the damping ratio. At higher strains, increasing the confining stress or the rubber content flattens the reduction of the shear modulus with strain. Damping at high strains does not show any appreciable dependence on rubber content. Unloading–reloading sequences are used to assess shear modulus degradation and threshold strains. Finally, design equations are derived from the test results to predict the dynamic response of the composite material. | Resonant Column Tests on Mixtures of Different Sands with Coarse Tyre Rubber Chips | 10.1007/s10706-022-02244-0 |
2022-12-01 | Abstract The influence of internal dissipative forces on rotational motion of a satellite in an elliptical orbit is studied in the context of the Lavrent’ev model. Evolution equations describing plane non-resonant rotations of the satellite are obtained. The conditions of existence and stability of plane resonant rotations of the satellite are determined. An analytical solution describing plane resonant rotations of the satellite in an elliptical orbit is obtained. | On the Plane Resonant Rotations of a Satellite with a Spherical Damper in an Elliptical Orbit | 10.3103/S0025654422070044 |
2022-12-01 | In this paper, magneto-rheological (MR) dampers are designed optimally for different control objectives by considering different distributions for dampers within structure stories. The modified Bouc–Wen model is used to model the MR dampers. For investigating the control algorithm efficiency in determining the dampers’ optimal voltage in each time step, different algorithms are used such that designing parameters of algorithms are determined based on defining an optimization problem and solving it using the genetic algorithm. For numerical example, a three-story benchmark shear structure is considered so that the MR dampers are designed optimally for different distributions of number and position in the structure under different objective functions including minimizing the structure’s maximum displacement, relative inter-story displacement (drift), and absolute acceleration. The results of the numerical analysis indicate that the MR dampers’ performance is highly dependent on the control algorithms, objective functions, and dampers’ distribution. The results also show the satisfactory performance of the proposed optimization method in the improvement in MR dampers’ efficiency under different objective functions. Moreover, the performance of the optimized MR dampers is evaluated under both the near-fault and far-fault earthquakes. | Optimal Design of MR Dampers by Considering Design Criteria and Dampers Distribution Effect | 10.1007/s40996-022-00945-3 |
2022-12-01 | The aim of the paper is to study the problem $$\begin{aligned} {\left\{ \begin{array}{ll} u_{tt}+du_t-c^2\Delta u=0 \qquad &{}\text {in}\, {\mathbb {R}}\times \Omega ,\\ \mu v_{tt}- \textrm{div}_\Gamma (\sigma \nabla _\Gamma v)+\delta v_t+\kappa v+\rho u_t =0\qquad &{}\text {on}\, {\mathbb {R}}\times \Gamma _1,\\ v_t =\partial _\nu u\qquad &{}\text {on}\, {\mathbb {R}}\times \Gamma _1,\\ \partial _\nu u=0 &{}\text {on}\, {\mathbb {R}}\times \Gamma _0,\\ u(0,x)=u_0(x),\quad u_t(0,x)=u_1(x) &{} \text {in}\, \Omega ,\\ v(0,x)=v_0(x),\quad v_t(0,x)=v_1(x) &{} \text {on}\, \Gamma _1, \end{array}\right. } \end{aligned}$$ u tt + d u t - c 2 Δ u = 0 in R × Ω , μ v tt - div Γ ( σ ∇ Γ v ) + δ v t + κ v + ρ u t = 0 on R × Γ 1 , v t = ∂ ν u on R × Γ 1 , ∂ ν u = 0 on R × Γ 0 , u ( 0 , x ) = u 0 ( x ) , u t ( 0 , x ) = u 1 ( x ) in Ω , v ( 0 , x ) = v 0 ( x ) , v t ( 0 , x ) = v 1 ( x ) on Γ 1 , where $$\Omega $$ Ω is a open domain of $${\mathbb {R}}^N$$ R N with uniformly $$C^r$$ C r boundary ( $$N\ge 2$$ N ≥ 2 , $$r\ge 1$$ r ≥ 1 ), $$\Gamma =\partial \Omega $$ Γ = ∂ Ω , $$(\Gamma _0,\Gamma _1)$$ ( Γ 0 , Γ 1 ) is a relatively open partition of $$\Gamma $$ Γ with $$\Gamma _0$$ Γ 0 (but not $$\Gamma _1$$ Γ 1 ) possibly empty. Here $$\textrm{div}_\Gamma $$ div Γ and $$\nabla _\Gamma $$ ∇ Γ denote the Riemannian divergence and gradient operators on $$\Gamma $$ Γ , $$\nu $$ ν is the outward normal to $$\Omega $$ Ω , the coefficients $$\mu ,\sigma ,\delta , \kappa , \rho $$ μ , σ , δ , κ , ρ are suitably regular functions on $$\Gamma _1$$ Γ 1 with $$\rho ,\sigma $$ ρ , σ and $$\mu $$ μ uniformly positive, d is a suitably regular function in $$\Omega $$ Ω and c is a positive constant. In this paper we first study well-posedness in the natural energy space and give regularity results. Hence we study asymptotic stability for solutions when $$\Omega $$ Ω is bounded, $$\Gamma _1$$ Γ 1 is connected, $$r=2$$ r = 2 , $$\rho $$ ρ is constant and $$\kappa ,\delta ,d\ge 0$$ κ , δ , d ≥ 0 . | The damped wave equation with acoustic boundary conditions and non-locally reacting surfaces | 10.1007/s00233-022-10319-w |
2022-12-01 | Abstract The issues of optimal damping of oscillations of the simplest nonlinear mechanical system, a mathematical pendulum, are considered. A parameter to be optimized is the dimensionless dissipative viscosity friction coefficient at the pendulum pivot point. Detailed optimization criteria are given, which are used in solving problems of optimal suppression of oscillations of mechanical systems and give a sense of the damping efficiency of these oscillations. The main advantages and disadvantages of these criteria are discussed, during which it is established that the most suitable criterion for the formulated nonlinear problem is the integral energy–time criterion. A graphical layout is constructed that makes it possible to find the best dimensionless dissipative coefficient for the worst set of initial conditions with energy not exceeding a given value, depending on the parameter characterizing this value. | Optimization of the Damping of Nonlinear Pendulum Oscillations | 10.3103/S1052618822090175 |
2022-12-01 | Combining a multi-stage circumferential flow mode in external valves, novel magnetorheological (MR) dampers have been devised by authors. For characterizing specific advantages generated by the combination of metal materials, magnetic field, non-Newton fluid and structure issues, a composite method including mathematical models and finite element models will be explained gradually. Therefore, beginning with mathematical models of magnetic field in an external valve, magnetic flux densities of circumferential channels at different currents can be obtained firstly. Secondly, establishing a computational fluid dynamics (CFD) model, associations between viscosity of magnetorheological fluid and pressure drops as well as flow rates will be revealed effectively. Finally, considering pressure drops along the entire flow path including an external valve, mathematical models for characterizing damping behaviors can be achieved, and numerical results will be also available based on two kinds of mathematical models and data of a CFD model. Further reflecting through simulated and experimental results, these dampers would be applied in diverse fields with a wide range of adjustment, the small energy consumption and a good versatility. | Design and modelling methodology for a new magnetorheological damper featuring a multi-stage circumferential flow mode | 10.1007/s10999-022-09607-8 |
2022-12-01 | Abstract This article considers a fundamentally new type of vibration protection devices for improving the reliability of overhead power lines, a magnetorheological damper. The calculation of the magnetorheological damper includes calculation of the mechanical, electromagnetic, magnetorheological, and damping subsystems. An autonomous control system was developed for the damper. A Prototype-up of the damper was developed, testing of which confirmed the operability and operational suitability of the device in relation to overhead power lines. | Calculation of a Magnetorheological Damper for Protection of Towers and Fittings of Overhead Power Lines | 10.3103/S1052618822090047 |
2022-12-01 | The modified Korteweg-de Vries equation (for short, mKdV) models the propagation of nonlinear water waves in the shallow water approximation. We consider the weakly damped and forced mKdV under the periodic boundary condition. We often study mKdV equation by using the Miura transformation, which converts solutions of mKdV to solutions of the Korteweg-de Vries equation (KdV). However, if mKdV has damping and external forcing terms, the Miura transformation does not work well. To see the asymptotic behaviour of the solutions of mKdV equation, the study of global attractor is important. We prove the existence of the global attractor for $$ {s > 9/10} $$ s > 9 / 10 in $$\dot{H}^{s}$$ H ˙ s for mKdV equation by applying the modified energies and almost conserved quantities. | Global attractor for weakly damped, forced mKdV equation in low regularity spaces | 10.1007/s40863-020-00207-y |
2022-12-01 | The working environment for agricultural machinery is complex and variable. Some weak characteristic damped oscillation signals are extremely difficult to extract and analyze because of their long-term operation in a strong noise environment. The vibration resonance (VR) phenomenon of a second-order Duffing bistable system driven by a weak characteristic damped oscillation signal and a high-frequency harmonic signal was studied. The results indicate that the cooperation between the Duffing damping ratio and attenuation coefficient can induce the VR occurrence of a small-parameter damped oscillation signal. As a result, the energy of the weak characteristic signal becomes stronger, and the VR numerical processing method of the high-frequency weak characteristic damped oscillation signal is provided. On this basis, aiming at the strong noise of agricultural machinery working, taking the weighted kurtosis index as the objective function and supplemented by variational mode decomposition (VMD) technology, a VR-VMD adaptive method based on quantum particle swarm optimization (QPSO) was proposed to extract the weak characteristic damped oscillation signal. Numerical simulation analysis and experiments show that the proposed VR-VMD method is effective in a strong noise environment for agricultural machinery. | Detecting the weak damped oscillation signal in the agricultural machinery working environment by vibrational resonance in the duffing system | 10.1007/s12206-022-1109-3 |
2022-12-01 | Different techniques are used to decrease structural responses under earthquakes. Base isolation system is a passive technique which reduces relative displacement and acceleration of the structure, simultaneously. However, it sometimes increases the absolute displacement. Using active control force in the isolated system is an effective method to overcome this problem. In this paper, the performance of an 8-story steel framed benchmark structure with base isolation is improved using a combination of multi-tuned mass damper (MTMD) and an active control force at the isolation level. The effects of proposed method in minimizing the response of the structure under four near-field ground motions are investigated. The control force is determined using the Fuzzy Type-1 algorithm. The MTMD consists of two TMDs, which are placed on the first floor and on the roof. In addition, the effects of pulse-like shape in near-field earthquakes on response of controlled structure are examined. Based on the results obtained from the time history response, it is revealed that MTMD reduces relative displacement and absolute acceleration in two directions ( x , y ) up to a maximum value of 66% and 47%, respectively. The hybrid base isolation controller reduces absolute displacement by a maximum of 33%. Based on the results, it is possible to reduce the twisting in the irregular structure by the placement of actuators in the four corners of the architectural plan. | The Effects of MTMD and HBI on the Performance of a Benchmark Building Against Near-Field Earthquakes Using Fuzzy Logic | 10.1007/s40996-022-00872-3 |
2022-11-28 | AN innovative amplified viscously damped outrigger (AVDO) is newly proposed to improve the seismic damping effect of conventional viscousl damped outrigger (VDO) on super high-rise structures by mechanically increasing the displacement of the viscous damper (VD). To investigate the advantages of the damping effect on AVDO over VDO, the dynamic cyclic tests on VDO and AVDO were conducted to verify the feasibility of AVDO and superiority of AVDO over VDO. On this basis, six finite element models of a 258 m-high building with two types of damped outriggers placed at different heights were established and analyzed by dynamic time-history method. By comparing the seismic responses of numerical models, it is shown that upgrading VDO to AVDO can improve the damping efficiency of VDs and effectively expand the applicable damping placement in structural height, thus, the structure can achieve a better damping effect. An equivalent theoretical model of AVDO was established and validated by numerical analysis, which contributes to facilitating the modelling work and analysis of AVDO. However, experimental results showed that the outrigger deformation reduced the working displacement of VD seriously, indicating that the stiffness of the outrigger should be designed reasonably to withstand the damping force in motion. On this basis, the relationship between the working efficiency of VD and the stiffness ratio of outrigger to VD was derived and verified. To ensure the high work efficiency of the damper, the recommended stiffness limit of the outrigger supporting nonlinear VD was put forward, which fills a gap in the specification for practical applications. | Investigation on seismic damping effect of an innovative amplified viscously damped outrigger for super high-rise structures | 10.1007/s43452-022-00574-7 |
2022-11-18 | Despite the long history of human treatments with the electromagnetic field, the topic has numerous unclear processes. Especially only a few investigations are devoted to the immune effects of the bioelectromagnetic interactions. Our recent review collects proven pieces of evidence of the immune-supportive activity of modulated electromagnetic fields. Modulated electro-hyperthermia (mEHT) applies a synergy of thermal and nonthermal factors to select malignant cells and degrade them with the intensive cooperation of the immune system. An amplitude-modulated radiofrequency carrier induces the suitable processes to optimize apoptosis toward immunogenic cell death, considering the inherent complexity of the living organism. The immunogenic information in spatiotemporal cooperation of the produced molecules during apoptotic damage maturates the dendritic cells. The antigen-presenting cells that are formed induce innate and adaptive immune responses, developing a tumor-specific immune reaction, which degrades the malignant cells across the entire system. The mEHT process broadens the effect of the local treatment to become systemic, assisting the immune recognition of cancer cells irrespective of the size of the malignant cellular cluster, attacking the metastases and the unobservable micro-clusters of the tumor. The harmonic cooperation of the electric field and the immune processes could form the basis of a new type of researches on the subject and apply the results in human oncotherapies. | Immunogenic Effect of Modulated Electro-hyperthermia (mEHT) in Solid Tumors | 10.1007/16833_2022_74 |
2022-11-18 | Recent developments have demonstrated that the brake pedal simulator (BPS) is becoming an indispensable apparatus for the break-by-wire systems in future electric vehicles. Its main function is to provide the driver with a comfortable pedal feel to improve braking safety and comfort. This paper presents the development and control of an adjustable BPS, using a disk-type magnetorheological (MR) damper as the passive braking reaction generator to simulate the traditional pedal feel. A detailed description of the mechanical design of the MR damper-based BSP (MRDBBPS) is presented in this paper. Several basic performance experiments on the MRDBBPS prototype are conducted. A return-to-zero (RTZ) algorithm is proposed to avoid hysteresis and improve the repeatability of the pedal force. In addition, an RTZ algorithm-based real-time current-tracking controller (RTZRC) is designed in consideration of the response lag of the coil circuit. Finally, an experimental system is established by integrating the MRDBBPS prototype into a self-developed automotive MR braking test bench (AMRBTB), and several control and braking experiments are performed. This research proposes a RTZRC control algorithm which can significantly increase the tracking accuracy of the brake pedal characteristic curve, particularly at a high pedal velocity. Additionally, the designed MRDBBPS prototype can achieve an effective and favorable control of the AMRBTB with a good repeatability. | Development and Control of a Magnetorheological Damper-Based Brake Pedal Simulator for Vehicle Brake-by-Wire Systems | 10.1186/s10033-022-00809-x |
2022-11-16 | The energy of a mechanical system as well as other invariants can be obtained using a complementary variable formulation. This approach is extended here to systems with a dissipative force. The damping coefficient depends linearly on the velocity, but is allowed to have an arbitrary time dependence. An invariant $$Q_{00}$$ Q 00 is obtained in terms of linearly independent solutions. A semipositive definite version of this quantity is the Ermakov invariant. This scenario including damping, allow us to give a physical meaning to a closely related quantity $$\mathcal {E}_{\omega }^{\textrm{ex}}=\frac{1}{2}mq_{00}$$ E ω ex = 1 2 m q 00 , which is the energy exchanged between the kinetic and potential energies per unit frequency, or $$\mathcal {E}_{t}^{\textrm{ex}}=\frac{1}{2}\kappa q_{00}$$ E t ex = 1 2 κ q 00 which is the energy exchange per period. The $$q_{00}$$ q 00 exchange energy is positive under light damping. Under critical or heavy damping, when no oscillations occur, $$q_{00}$$ q 00 is either zero or negative. Thus, $$q_{00}\ge 0$$ q 00 ≥ 0 is a measure of the back and forth energy exchange. This periodic energy transfer is compared with the usual oscillator energy of the damped system. To this end, the kinetic energy is split into conservative and dissipative terms. The energy ripples superimposed in the exponential decay are described by a dissipative modulation term. In the vein of Ermakov’s formalism, the amplitude and phase nonlinear differential equations are derived for a time-dependent damped system. The complementary variables and Ermakov formalisms are then compared. | Energy exchange in the dissipative time-dependent harmonic oscillator: Physical interpretation of the Ermakov invariant | 10.1007/s12043-022-02470-4 |
2022-11-07 | This paper is concerned with the multi-dimensional compressible Euler equations with time-dependent damping of the form $$-\frac{\mu }{(1+t)^\lambda }\rho {\varvec{u}}$$ - μ ( 1 + t ) λ ρ u in $${\mathbb {R}}^n$$ R n , where $$n\ge 2$$ n ≥ 2 , $$\mu >0$$ μ > 0 , and $$\lambda \in [0,1)$$ λ ∈ [ 0 , 1 ) . When $$\lambda >0$$ λ > 0 is bigger, the damping effect time-asymptotically gets weaker, which is called under-damping. We show the optimal decay estimates of the solutions such that $$\Vert \partial _x^\alpha (\rho -1)\Vert _{L^2(\mathbb R^n)}\approx (1+t)^{-\frac{1+\lambda }{2}\left( \frac{n}{2}+|\alpha |\right) }$$ ‖ ∂ x α ( ρ - 1 ) ‖ L 2 ( R n ) ≈ ( 1 + t ) - 1 + λ 2 n 2 + | α | , and $$\Vert \partial _x^\alpha {\varvec{u}}\Vert _{L^2({\mathbb {R}}^n)}\approx (1+t)^{-\frac{1+\lambda }{2}\left( \frac{n}{2}+|\alpha |\right) -\frac{1-\lambda }{2}}$$ ‖ ∂ x α u ‖ L 2 ( R n ) ≈ ( 1 + t ) - 1 + λ 2 n 2 + | α | - 1 - λ 2 , and see how the under-damping effect influences the structure of the Euler system. Different from the traditional view that the stronger damping usually makes the solutions decaying faster, here we recognize that the weaker damping with $$0\le \lambda <1$$ 0 ≤ λ < 1 enhances the faster decay for the solutions. The adopted approach is the technical Fourier analysis and the Green function method. The main difficulties caused by the time-dependent damping lie in twofold: non-commutativity of the Fourier transform of the linearized operator precludes explicit expression of the fundamental solution; time-dependent evolution implies that the Green matrix G ( t , s ) is not translation invariant, i.e., $$G(t,s)\ne G(t-s,0)$$ G ( t , s ) ≠ G ( t - s , 0 ) . We formulate the exact decay behavior of the Green matrices G ( t , s ) with respect to t and s for both linear wave equations and linear hyperbolic system, and finally derive the optimal decay rates for the nonlinear Euler system. | Optimal Decay Rates of the Compressible Euler Equations with Time-Dependent Damping in
$${\mathbb {R}}^n$$
R
n
: (I) Under-Damping Case | 10.1007/s00332-022-09865-y |
2022-11-07 | We study the stabilization and the wellposedness of solutions of the wave equation with subcritical semilinearities and locally distributed nonlinear dissipation. The novelty of this paper is that we deal with the difficulty that the main equation does not have good nonlinear structure amenable to a direct proof of a priori bounds and a desirable observability inequality. It is well known that observability inequalities play a critical role in characterizing the long time behaviour of solutions of evolution equations, which is the main goal of this study. In order to address this, we truncate the nonlinearities, and thereby construct approximate solutions for which it is possible to obtain a priori bounds and prove the essential observability inequality. The treatment of these approximate solutions is still a challenging task and requires the use of Strichartz estimates and some microlocal analysis tools such as microlocal defect measures. We include an appendix on the latter topic here to make the article self contained and supplement details to proofs of some of the theorems which can be already be found in the lecture notes of Burq and Gérard ( http://www.math.u-psud.fr/~burq/articles/coursX.pdf , 2001). Once we establish essential observability properties for the approximate solutions, it is not difficult to prove that the solution of the original problem also possesses a similar feature via a delicate passage to limit. In the last part of the paper, we establish various decay rate estimates for different growth conditions on the nonlinear dissipative effect. We in particular generalize the known results on the subject to a considerably larger class of dissipative effects. | Decay Rate Estimates for the Wave Equation with Subcritical Semilinearities and Locally Distributed Nonlinear Dissipation | 10.1007/s00245-022-09918-4 |
2022-11-01 | Background The background of this work is the classification of the broadband properties of particle dampers (PDs). This broadband characteristic has experienced little systematic investigation in experiments. Objective So the primary objective of this paper is to find a measure to quantify the broadband damping properties of PDs. Also the demonstration of applicability to technical structures is a desired goal and the experiments provide a sound basis. Methods The methods for evaluating the performance of particle dampers and tuned mass dampers target the reduction of vibration amplitudes over the frequency range. The test bench consists of a mechanical frame structure with multiple eigenfreqencies up to 200 Hz harmonically excited with an electrodynamic shaker. From the differences in the dynamic behaviour the performance metric will be derived and evaluated. Results As a result, a dynamic structure is set up as an effective test bench for different damper configurations. Differences of the tested concepts in regard to the dynamic behaviour over a wide frequency range are observed. From the experimental data a performance metric is deduced to quantify these differences. Conclusion The conclusions drawn from this paper are, that PDs provide high damping over a wide frequency range. Furthermore, with a suitable performance metric this broadband damping properties can be quantified for the use in further development of PDs. | Broadband Damping Properties of Particle Dampers Mounted to Dynamic Structures | 10.1007/s11340-022-00882-2 |
2022-11-01 | Magnetically optimization of mini-MR damper with focused on MR fluid properties and damper construction is investigated using dissipative particle dynamics method as a molecular scale modeling technique. To select a suitable MR fluid, the effect of diameter and weight of magnetic particles on damping force of 10 N as set point is studied. The results show damping force increases by increasing diameter of magnetic particles and finally trends to a constant value while changes nonparabolic by enhancement of their weight. The results of studies on structural parameters of damper show that by increasing gap size of flow passage, damping force increases while enhancement in inner diameter of cylinder and piston length has reverse effect. Optimum design of MR damper completed by investigation on electrical coils in terms of their arrangement and step wise distribution of magnetic field strength as our major innovation. To optimum operating conditions of MR damper at minimum electrical energy consumption and hysteresis level, the scenario of three segment coils in length of 3, 5, and 7 mm at base relative magnetic strength of 40% with 15% difference in steps by utilizing 140CG MR fluid as agent fluid are selected. | Dissipative particle dynamics modeling of MR fluid flow in a novel magnetically optimized mini-MR damper | 10.1007/s13367-022-00037-8 |
2022-11-01 | The effect of the container’s configuration on the performance of particle dampers is investigated considering different levels of random excitation. A single-story structure with low fundamental frequency with an attached particle damper was used for the experimental investigation. In all experiments, the same particles were used, placed in one layer. Different configurations of the container were examined considering dampers with either a single or two compartments. Considerable reduction in the structure’s response was observed when a single compartment was used with filling area ratio (defined as the corresponding squares around the projected spherical particles over the area of the compartment) equal to 60% for all excitation levels used. Similar results were obtained when the particles and the container were divided in equal parts while keeping the filling area ratio in each compartment at 60%. At large filling area ratios, the single-compartment damper was ineffective at the highest excitation level used while the damper with the two equal size compartments was ineffective for all excitation levels. When unequal compartment sizes were used, the damper was efficient when the filling area ratio was in the range of 50–70% for all excitation levels. | Effects of the Design Configuration on the Performance of Compartmental Particle Dampers | 10.1007/s40999-022-00739-8 |
2022-11-01 | In this paper, we are concerned with the asymptotic behavior of L ^∞ weak-entropy solutions to the compressible Euler equations with a vacuum and time-dependent damping $$ - \frac{m}{{{{(1 + t)}^\lambda }}}$$ . As $$\lambda \in (0,\tfrac{1}{7}]$$ , we prove that the L ^∞ weak-entropy solution converges to the nonlinear diffusion wave of the generalized porous media equation (GPME) in $${L^2}(\mathbb{R})$$ . As $$\lambda \in (\tfrac{1}{7},1)$$ , we prove that the L ^∞ weak-entropy solution converges to an expansion around the nonlinear diffusion wave in $${L^2}(\mathbb{R})$$ , which is the best asymptotic profile. The proof is based on intensive entropy analysis and an energy method. | L^2-convergence to nonlinear diffusion waves for Euler equations with time-dependent damping | 10.1007/s10473-022-0618-6 |
2022-11-01 | This paper considers a two-dimensional frictionally constrained joint to investigate the interfacial characteristics under periodic loadings with phase variations. Joints are pressed in contact by normal pressure, subjecting to tangential loading and bending moment. The tendency of contact behavior at the steady-state is investigated, subjected to various phase differences between the bending moment and the tangential loading. Total energy dissipation per cycle is obtained at steady-state to examine the overall frictional damping from the joint interface. It is found that friction damping is dominant during tensile loading, and the energy dissipates the most when the phase difference is near π / 2. | Effect of relative phase of periodic loading on frictionally constrained joints | 10.1007/s12206-022-1004-y |
2022-11-01 | The literature, both scientific and commercial, already reports a large number of papers dealing with the dynamic properties of sports racquets and their influence on possible injuries caused to athletes. In particular, tennis players can suffer for the so called “tennis elbow” which is believed to depend also on the damping properties of racquets. In order to reduce injuries, to provide a better playing feeling, and to increase performances, producers of tennis equipment are keen to present ameliorations to their products, sometimes with great commercial echo. The same companies, together with a number of smaller firms, also sell minor components (grip, over-grip, strings dampers and so on) which should increase damping and limit annoying vibrations. The interest on the subject is also documented by the number of patents, easily acquired on the web. In this paper, the effects on the dynamic properties introduced by the granular damping technology and by a silicone ring are investigated. A finite element model of a generic racquet has been defined to study the effects of a silicone ring placed just above the end of the handle, i.e., at the base of the throat, and also to define the static stiffness of the structure. This stiffness and the forces computed by a discrete element model, aimed at quantifying the interactions among granules contained in two small boxes fixed to the racquet, have been introduced in a simplified single degree of freedom system to explore the effectiveness of the granular solution. Numerical conclusions are confirmed by experimental results, obtained by analysing (both in time and frequency domains) the free response of a racquet repeatedly impacted by tennis balls. | Experimental and numerical analysis of damping properties of tennis racquets | 10.1007/s11012-022-01601-w |
2022-11-01 | This paper primarily focuses on evaluation and adjustment methods for small signal analysis with wind farm integration. The connection of wind farms may affect the original oscillation modes of the system, and may also introduce new oscillation modes. To ensure the security and stability of the system, it is necessary to assess the running state of the system and evaluate the development direction of the small signal stability on the premise of taking volatility into account. It is also important to fast adjust the system when an unstable state happened. The method in this paper provides a new way to accurately evaluate and adjust the stability of the system integrated with wind farms. Broad learning system (BLS) is a non-fixed model and has the potential of incremental learning. A BLS model is trained to evaluate the damping ratio sensitivity in different operating states. The adjustment part will use the optimal adjustment model and damping ratio sensitivity to adjust unstable systems. The superior performance of the model proposed in this paper is tested by the case study based on the IEEE 3-machine, 9-bus, and the New-England 10-machine, 39-bus. The results demonstrate the feasibility, validity, and effectiveness of the method proposed in this article. | Evaluation and Adjustment Based on Broad Learning System for Small Signal Stability Analysis of Power System Integrated with Wind Farms | 10.1007/s42835-022-01111-5 |
2022-11-01 | We study the existence of fast homoclinic orbits for the following damped vibration system $$\ddot{u}(t)+q(t)\dot{u}(t)+\nabla V(t,u(t))=0$$ u ¨ ( t ) + q ( t ) u ˙ ( t ) + ∇ V ( t , u ( t ) ) = 0 ; where $$q\in C(\mathbb {R},\mathbb {R})$$ q ∈ C ( R , R ) and $$V\in C^{1}(\mathbb {R}\times \mathbb {R}^{N},\mathbb {R})$$ V ∈ C 1 ( R × R N , R ) is of the type V(t,x)=-K(t,x)+W(t,x). A map K is not a quadratic form in x and W ( t , x ) is superquadratic in x . | Fast homoclinic orbits for a class of damped vibration systems | 10.1007/s11587-020-00534-4 |
2022-11-01 | The microstructure and mechanical properties of a material are influenced by their fabrication method. This paper addresses how the fabrication process influences the damping behavior of pure aluminum. The samples were fabricated using two routes: powder metallurgy (PM) and casting (CT). Powder mixing, compacting, and sintering of the powder mixture are the basic manufacturing steps in PM, while in casting, the material is heated to liquidus condition and poured into the mold. The samples thus obtained were tested for damping measurements. Damping behavior was obtained at constant strain and at various frequencies of 0.1, 1, and 10 Hz from room temperature to 150°C under dual cantilever mode. Microstructural analysis was done using FESEM. Results demonstrated that the samples fabricated using powder metallurgy route exhibit high damping capacities and storage modulus. The related possible mechanisms for this behavior are analyzed and presented. | Powder Metallurgy versus Casting: Damping Behavior of Pure Aluminum | 10.1007/s11665-022-06886-2 |
2022-11-01 | The design of thermoelastic damping (TED) affected by the phase-lagging non-Fourier heat conduction effects becomes significant but challenging for enlarging the quality factor of widely-used microresonators operating in extreme situations, including ultra-high excitation frequency and ultra-low working temperature. However, there does not exist a rational method for designing the TED in the framework of non-Fourier heat conduction law. This work, therefore, proposes a design framework to achieve low thermoelastic dissipation of microresonators governed by the phase-lagging heat conduction law. The equation of motion and the heat conduction equation for phase-lagging TED microresonators are derived first, and then the non-Fourier TED design problem is proposed. A topology optimization-based rational design method is used to resolve the design problem. What is more, a two-dimensional (2D) plain-strain-based finite element method (FEM) is developed as a solver for the topology optimization process. Based on the suggested rational design technique, numerical instances with various phase lags are investigated. The results show that the proposed design method can remarkably reduce the dissipation of microresonators by tailoring their substructures. | Rational design of thermoelastic damping in microresonators with phase-lagging heat conduction law | 10.1007/s10483-022-2914-5 |
2022-11-01 | The propagation of normal waves in a prestrained incompressible half-space interacting with a layer of a viscous compressible fluid is studied. The study is based on the three-dimensional linearized equations of elasticity for the incompressible elastic half-space and the three-dimensional linearized Navier–Stokes equations for the viscous compressible liquid layer. A problem statement and an approach based on the general solutions of the linearized equations for the elastic body and the fluid are applied. A dispersion equation that describes the propagation of harmonic waves in the hydroelastic system is derived. The dispersion curves of surface waves in a wide range of frequencies are plotted. The effect of the finite prestrains of the elastic half-space and the thickness of the layer of viscous compressible fluid on the phase velocities, the dispersion of surface waves, and the surface instability of the hydroelastic waveguide are analyzed. Numerical results are plotted and analyzed. | Effect of a Viscous Compressible Liquid Layer on the Surface Instability of an Incompressible Elastic Half-Space with Finite Prestrains | 10.1007/s10778-023-01189-y |
2022-11-01 | Background Electromagnetic damper (EMD), which is regarded as an emerging type of damper, has drawn wide attention in vibration control fields. One of the main challenges of EMD is the design of controllers, many of which have adopted some unmeasured signals and have ignored the system's disturbance. Purpose To fill this research gap, a H _∞ controller based on state estimation and disturbance compensation is designed, and an EMD seat suspension system is applied in this research. Methods A two-degree-of-freedom (DOF) seat suspension and the EMD system models are introduced and established first. Then, the Bouc-Wen model is selected to represent the system's disturbance, including seat suspension friction and the EMD system's inertia force. A test bench is built to measure the system's force-displacement data, and the parameters of the Bouc-Wen model can be determined by parameter identification methods. Secondly, a robust H _∞ controller based on state estimation and disturbance compensation is proposed. A state observer is proposed to estimate unmeasurable state variables and is used in the design of the proposed H_∞ controller. Finally, another test bench, which consists of a six-DOF vibration platform and an EMD seat suspension system, is built. Three typical excitations, sinusoidal, bump, and random excitations, are selected to simulate the real road excitation. A commercial suspension with good vibration isolation capacity is selected to compare with the EMD seat suspension. Results Experimental results demonstrate that the H _∞ controller can improve vertical ride comfort and reduce suspension deflection effectively. Conclusion In addition, the designed controller can reduce vibration magnitude in all interested frequency ranges compared with the passive one. | Vibration Control of Electromagnetic Damper System Based on State Observer and Disturbance Compensation | 10.1007/s42417-022-00545-5 |
2022-11-01 | Linear mixed-effects models are commonly used when multiple correlated measurements are made for each unit of interest. Some inherent features of these data can make the analysis challenging, such as when the series of responses are repeatedly collected for each subject at irregular intervals over time or when the data are subject to some upper and/or lower detection limits of the experimental equipment. Moreover, if units are suspected of forming distinct clusters over time, i.e., heterogeneity, then the class of finite mixtures of linear mixed-effects models is required. This paper considers the problem of clustering heterogeneous longitudinal data in a mixture framework and proposes a finite mixture of multivariate normal linear mixed-effects model. This model allows us to accommodate more complex features of longitudinal data, such as measurement at irregular intervals over time and censored data. Furthermore, we consider a damped exponential correlation structure for the random error to deal with serial correlation among the within-subject errors. An efficient expectation-maximization algorithm is employed to compute the maximum likelihood estimation of the parameters. The algorithm has closed-form expressions at the E-step that rely on formulas for the mean and variance of the multivariate truncated normal distributions. Furthermore, a general information-based method to approximate the asymptotic covariance matrix is also presented. Results obtained from the analysis of both simulated and real HIV/AIDS datasets are reported to demonstrate the effectiveness of the proposed method. | Finite Mixture of Censored Linear Mixed Models for Irregularly Observed Longitudinal Data | 10.1007/s00357-022-09415-x |
2022-11-01 | The behavior of mechanical network consisting of discontinuous damped system oscillators elastically coupled with strong irrational nonlinearities, excited at one of its end by the modulated signal, is investigated. By using the Newton second law, the set of discrete damped equations governing the dynamics of this network are established. These set of equations have strong irrational nonlinearities, with smooth or discontinuous characteristics depending just to the inclination angles of strings. By using next the perturbation method, these set of discrete equations are reduced to the nonlinear cubic Landau–Ginzburg (CGL) equation governing the small dissipative amplitude modulated signal. As this CGL equation is not integrable, the dissipative modulated pulse and dark solitons as solutions are approximated via perturbation method, which is confirmed by using the conserved quantities as well as numerical investigations. Finally the conditions for modulational instability are found and proved to be sensitive both to inclination angle and dissipative coefficient. | Stability of modulated signals in the damped mechanical network of discontinuous coupled system oscillators with irrational nonlinearities | 10.1007/s00419-022-02259-2 |
2022-11-01 | Dual-volume Helmholtz dampers with two resonant frequencies are proposed to simultaneously attenuate longitudinal and azimuthal thermo-acoustic instabilities in annular combustors. Thermo-acoustic instabilities in a swirled annular combustor equipped with dual-volume dampers are numerically investigated by the Helmholtz method, combined with a measured flame transfer function and the established damper impedance model. Furthermore, the influences of the damper number and circumferential configurations on oscillation attenuations and mode structures are explored. The established dual-volume damper model is well validated by the impedance tube tests. Numerical results indicate velocity fluctuation levels of the longitudinal and azimuthal modes decline after installing Helmholtz dampers, whereas those of the azimuthal modes further decrease by around 16% after using four retuned dual-volume dampers. The eigenfrequencies of the first longitudinal and azimuthal modes decrease and increase after installing dampers, respectively. After installing dual-volume dampers, the difference between the pressure fluctuation in the plenum and combustion chamber is reduced, and pressure waveforms of the azimuthal modes along the circumferential direction shifts. The pressure distribution of azimuthal modes becomes more uniform after using more dual-volume dampers. The specific absorption frequency band for azimuthal modes introduced by the dual-volume damper may lead to decreased oscillations and mode evolutions. The maximal absorbing ability can be approached by installing dampers with the same angle between adjacent dampers. When dampers are unevenly distributed, the symmetry between two azimuthal modes is broken and standing modes will emerge. | Impact of Dual-Volume Helmholtz Dampers on Longitudinal and Azimuthal Thermo-Acoustic Instabilities in an Annular Combustor | 10.1007/s11630-022-1692-8 |
2022-11-01 | Purpose Among diverse Pattern Recognition Receptors (PRRs), Toll-like receptor-4 (TLR-4) is a key urothelial trigger for innate immune response impacting urothelial bladder carcinoma (BC). Androgen activation promotes immunotolerance, playing an immunoregulatory role by unknown mechanisms. We explored the castration impact on urothelial TLR-4 modulation in carcinogenesis and immunotherapeutic scenario. Methods Intact (SHAM) versus castrated male Fisher-344 rats were evaluated in 2 scenarios: (A) Carcinogenesis: After randomization to SHAM ( n = 5) and Castration ( n = 5), carcinogenesis was induced by four intravesical doses of 1.5 mg/kg n-methyl-n-nitrosourea (MNU) every 15 days. (B) Treatment: After ultrasonographic confirmed MNU-induced papillary BC on week 8, rats were randomized to SHAM ( n = 5) and Castration ( n = 5) and offered 6 weekly intravesical treatment of 10^6 CFU of bacillus Calmette Guerin (BCG) in 0.2 ml saline. After 15 weeks the urinary bladders underwent histopathology. Urothelial cell proliferation was measured by Ki-67 immunohistochemistry (IHC), and TLR-4 expression was quantified by IHC and WB. Results Castration induced higher TLR-4 urothelial expression (p = 0.007) and anticarcinogenic effect with fewer urothelial tumors (60 vs. 80%) and lower urothelial cell proliferation compared to intact animals ( p = 0.008). In the intravesical BCG treatment setting, castration has potentialized the BCG activation of TLR-4 ( p = 0.007) with no residual in situ carcinoma compared to intact animals, suggesting the potential to amplify the BCG immune response. Conclusion To our knowledge, this is the first description of TLR-4 urothelial expression hormonal modulation. The described castration-mediated immunomodulation will help to improve the knowledge of urothelial cancer gender diversities and PRRs modulations with treatment implications. | Castration immunoregulates toll-like receptor-4 in male bladder cancer | 10.1007/s11255-022-03336-9 |
2022-11-01 | The main goal of this study is to look at the motion of a damped two degrees-of-freedom (DOF) auto-parametric dynamical system. Lagrange’s equations are used to derive the governing equations of motion (EOM). Up to a good desired order, the approximate solutions are achieved utilizing the method of multiple scales (MMS). Two cases of resonance, namely; internal and primary external one are examined simultaneously to explore the solvability conditions of the motion and the corresponding modulation equations (ME). These equations are reduced to two algebraic equations, through the elimination of the modified phases, in terms of the detuning parameters and the amplitudes. The kind of stable or unstable fixed point is estimated. In certain plots, the time histories graphs of the achieved solutions, as well as the adjusted phases and amplitudes are used to depict the motion of the system at any instant. The conditions of Routh–Hurwitz are used to study the various stability zones and their analysis. The achieved outcomes are considered to be novel and original, in which the used strategy is applied on a particular dynamical system. The significance of the studied system can be observed in its applications in a number of disciplines, such as swaying structures and rotor dynamics. | On the solutions and stability for an auto-parametric dynamical system | 10.1007/s00419-022-02235-w |
2022-10-29 | In this paper, we investigate the direct and indirect stability of locally coupled wave equations with local viscous damping on cylindrical and non-regular domains without any geometric control condition. If only one equation is damped, we prove that the energy of our system decays polynomially with the rate $$t^{-\frac{1}{2}}$$ t - 1 2 if the two waves have the same speed of propagation, and with rate $$t^{-\frac{1}{3}}$$ t - 1 3 if the two waves do not propagate at the same speed. Otherwise, in case of two damped equations, we prove a polynomial energy decay rate of order $$t^{-1}$$ t - 1 . | Stabilization of Coupled Wave Equations with Viscous Damping on Cylindrical and Non-regular Domains: Cases Without the Geometric Control Condition | 10.1007/s00009-022-02164-6 |
2022-10-25 | In this paper, we investigate the stabilization of a system of piezoelectric beams under (Coleman or Pipkin)–Gurtin thermal law with magnetic effect. First, we study the piezoelectric Coleman–Gurtin system and we obtain an exponential stability result. Next, we consider the piezoelectric Gurtin–Pipkin system and we establish a polynomial energy decay rate of type $$t^{-1}$$ t - 1 . | Stability of piezoelectric beam with magnetic effect under (Coleman or Pipkin)–Gurtin thermal law | 10.1007/s00033-022-01867-w |
2022-10-20 | This research work proposes the conventional and novel eddy current damping systems (CECDS & NECDS) for an optimized multi-layer radial permanent magnet bearing, which is axially magnetized. Firstly, the design and optimization of a bearing are carried out by adopting the general procedure for maximum radial force and stiffness by selecting stator outer diameter, radial air gap, and length as parameters. The maximum radial force and stiffness concerning an optimized structure are also calculated using semi-analytical equations, and force results are validated with three-dimensional (3D) finite element analysis results. Then, the analysis of both damping systems is carried out for damping forces and coefficients using 3D electromagnetic transient analysis in ANSYS. The proposed dampers provide adequate damping to the bearing structure, and conductor plate thickness significantly affects the damping characteristics. The NECDS could be used to replace the conventional type as it eliminates the effect of reduced radial air gap on the performance of the bearing. | Optimized multi-layer radial permanent magnet bearing with an eddy current damping systems | 10.1007/s40430-022-03855-7 |
2022-10-19 | This paper is determined to investigate the low-velocity impact responses of functionally graded carbon nanotube reinforced composite viscoelastic beams with general boundary constraints. The beams considered are constructed by a multiplayer beam model with layer-wise CNT weight fraction in each individual layer in the thickness direction. The Mori–Tanaka micromechanics model with inclusions of CNT agglomerations is used to determine the effective elastic moduli and Poisson’s ratio of nanocomposites. The viscoelastic properties are assumed based on Kelvin–Voigt theory. An impactor drops vertically on the upper surface of the beams, and the contact force between impactor and beam is simulated based on the Hertz contact law. A new hyperbolic shear deformation theory in conjunction with the artificial spring method of quantifiably accounting for the elastic boundary conditions is developed to present energy expressions of the system. Governing equations of motions are derived by means of Lagrange method with the help of Gram–Schmidt process that used to produce admissible functions in a general orthogonal polynomial form. The low-velocity impact responses are solved using the Newmark- β method in time domain. Numerical examples are carried out to reveal the effects of CNT weight fractions, CNT distribution patterns, CNT agglomeration and artificial spring parameters as well as the impactor velocities on the damped dynamic responses of the beams. | Low-velocity impact response of agglomerated FG-CNTRC beams with general boundary conditions using Gram–Schmidt–Ritz method | 10.1007/s40430-022-03843-x |
2022-10-10 | We consider the strongly damped Klein–Gordon equation for defocusing nonlinearity and we study the asymptotic behaviour of the energy for periodic solutions. We prove first the exponential decay to zero for zero mean solutions. Then, we characterize the limit of the energy, when the time tends to infinity, for solutions with small enough initial data and we finally prove that such limit is not necessary zero. | Energy asymptotics for the strongly damped Klein–Gordon equation | 10.1007/s42985-022-00207-x |
2022-10-08 | In this work, ion acoustic solitary pulses are investigated in an electron-ion quantum plasma in the presence of neutrals and many-particle effect of exchange-correlations in local density approximation. Quantum hydrodynamics formulation is used to derive nonlinear evolution equation in the form of a damped Korteweg-de Vries equation. Linear dispersion relation is derived and profile of ion-neutral collision-induced weak dissipation of ion acoustic solitary pulses is obtained analytically and numerically. Time evolution of damping solitary pulse is shown for typical quantum plasma parameters with illustrations. It is noted that presence of species space charge effect, electron exchange-correlations and quantum corrections due to Fermi degeneracy and diffraction effects modify the weakly damping soliton profile significantly. It is found that such solitary pulses are stable and can withstand perturbations for a considerable time before damping. | Effect of Exchange-Correlation Potential on Weakly Dissipating Solitary Pulses in Quantum Plasmas | 10.1007/s13538-022-01197-2 |
2022-10-03 | In this paper, we prove a stability result for a nonlinear wave equation, defined in a bounded domain of $${\mathbb {R}}^N$$ R N , $$N\ge 2$$ N ≥ 2 , with time-dependent coefficients. The smooth boundary of $$\Omega $$ Ω is $$\Gamma =\Gamma _0\cup \Gamma _1$$ Γ = Γ 0 ∪ Γ 1 such that $$\Sigma ={\overline{\Gamma }}_0\cap {\overline{\Gamma }}_1\ne \emptyset $$ Σ = Γ ¯ 0 ∩ Γ ¯ 1 ≠ ∅ . On $$\Gamma _0$$ Γ 0 we consider the homogeneous Dirichlet boundary condition and on $$\Gamma _1$$ Γ 1 we consider the Neumann boundary condition with damping term. The presence of time-dependent coefficients and, moreover, of the singularities generated by the condition $$\Sigma \ne \emptyset $$ Σ ≠ ∅ brings some technical difficulties. The tools are the combination of appropriate functional with the techniques due to Bey, Loheac, and Moussaoui [ 2 ] and new technical arguments. | Stability for a nonlinear hyperbolic equation with time-dependent coefficients and boundary damping | 10.1007/s00033-022-01856-z |
2022-10-01 | Abstract A pneumatic suspension with a hybrid damping section is investigated, theoretically and experimentally. The suspension includes a hydraulic shock absorber, an inertial frictional shock absorber, and a dynamic damper. | Pneumatic Suspension with a Flywheel Damper and a Hydraulic Shock Absorber | 10.3103/S1068798X22100197 |
2022-10-01 | Purpose Non-ideal high-speed rotors often exhibit the Sommerfeld effect characterized by nonlinear jumps and eventually gets destabilized. This paper presents a bifurcation analysis to attenuate the jumps in a non-ideal internally damped DC motor-driven shaft-disk system via magnetorheological (MR) fluid damper. Methods A nonlinear hyperbolic tangent model of MR damper is proposed and linearized using equivalent linearization technique. To meet the demands of reliable engineering design, the system parameters of the proposed MR model are optimized using genetic algorithm (GA) with the consideration of parametric uncertainty. Then the system equations of the non-ideal rotor system are derived using Lagrangian formulation. Following, a characteristic equation of fifth-order polynomial in rotor speed is obtained through energy balance. The steady-state response is studied with the help of control current of the MR damper and subsequently verified through a bifurcation analysis with the help of root locus technique. A few results are also validated with earlier works. Results The nonlinear jumps are found to be attenuated as the control current of MR damper increases. The root locus technique confirms the jump phenomena though the existence of multiplicity of roots of the characteristic equation considering supply voltage as a gain. The proposed saddle-node bifurcation study confirms the cessation of the Sommerfeld effect when two unstable (saddle) points are found to be degenerated into a stable node at a specific bifurcation value of the MR control current. Conclusion The nonlinear jumps of non-ideal rotor can be attenuated by altering the control current of the MR damper. This study also suggests that MR-based semi-active strategy is more effective than the AMB-based active control as the former takes much lesser current to attenuate the jumps. MR-based attenuation is found to be safer and more reliable than its active counterpart, i.e., AMB as the overall natural frequency of MR-based non-ideal rotor is far more behind the instability threshold of the system. | Steady-State and Bifurcation Analysis of Nonlinear Jumps in a Non-ideal Rotor System Using Magnetorheological Fluid Dampers | 10.1007/s42417-022-00503-1 |
2022-10-01 | Taking LW10B-383W/YT4000 sulfur hexafluoride circuit breaker produced by Henan Pinggao Electric Co. LTD as the prototype, a 1/5 scale test model was designed and manufactured based on the similarity theory. Considering the seismic response characteristics and structural form of this electrical equipment, this paper discussed the method of damping control of circuit breaker model using SMA cables. First, the shaking table tests were carried out for the Y-shaped circuit breaker model with and without control under three scaled seismic records, and the ABAQUS finite-element analysis model was established by automatic surface meshing method. Then, the seismic response analysis was finished along X and Y directions, and the comparison between the finite element and the test results was adopted to examine the availability of the proposed analysis model. Finally, the dynamic response of the model and the damping effect of SMA cables under z direction earthquake excitation were discussed using finite-element method. The results show the finite-element analysis results of Y-shaped circuit breaker model are in good agreement with the test results, and the SMA cables can effectively suppress seismic response of circuit breaker. When the peak ground acceleration (PGA) is 800 gal, the maximum acceleration suppression ratio of the end of arcing porcelain bushing is about 35% and the maximum displacement suppression ratio is about 32.5%. Meanwhile, the root stress of porcelain casing is also efficiently decreased, the inhibition rate of peak root stress of supports porcelain casing is about 40% for horizontal seismic action, and that of arcing porcelain bushing is about 30% for vertical seismic action. | Experiment and Finite-Element Analysis on Seismic Response of Y-Shaped Porcelain Column Circuit Breaker Equipped with SMA Cables | 10.1007/s40999-022-00725-0 |
2022-10-01 | Use of phasor measurement units in power systems has emerged new real-time control techniques such as wide area damping control (WADC). WADC systems were shown to be very effective if the network induced time delay is handled properly. Delay compensation techniques based on constant delay assumption lack robustness and many of techniques assuming time variant delay are not suitable for real-time systems due to resulting complex structures of controllers or the strict requirements imposed on signal transmission. Handling time delay adaptively by switching among a set of lead controllers to provide required compensation based on online measurements shown to be both practical and robust. Here, frequent switching between the controllers should be avoided in order to avoid sustained oscillations. Putting a limit on switching period hinders proper delay compensation. This paper presents algorithms for adaptive selection of switching period based on the condition of network traffic in order to provide near real-time delay compensation. Network activity is observed by a metric defined as the difference of the average time delays measured in consecutive intervals. Based on this metric, switching period is decreased adaptively when time delay characteristics change fast. For slow changing dynamics of time delay, the algorithm picks longer switching periods in order to prevent sustained oscillations. Performance evaluation of the proposed algorithms are conducted by a WADC system designed for two-area, four-machine benchmark model. The algorithms are shown to be successful in tracking the fast changing dynamics of a communication network through simulations. | An adaptive network latency compensator design for wide area damping control of power system oscillations | 10.1007/s00202-022-01518-3 |
2022-10-01 | Introduction The radiation as well as diffraction issues involving a stationary spherical structure fully drenched in a fluid streaming on an infinitely extended flexible base surface, are investigated with support of the linear wave theory. The top surface of the fluid region is enclosed by a stiff horizontal sheet. In such a situation, the time-harmonic wave exists for any given frequency and proliferates over the flexible base surface of the fluid region. Methods The multipole expansion approach is utilized to resolve these two independent classical problems. Conclusions The hydrodynamic characteristics, such as added mass and damping coefficients associated with the radiation problem, and the exciting forces associated with the diffraction problem are calculated and drawn graphically against the wavenumbers for various submersion depths of the spherical structure and stiffness factors in the flexible base surface of the fluid region. | Influence of Bottom Flexibility on Radiation and Diffraction Problems Involving a Spherical Body in a Fluid | 10.1007/s42417-022-00521-z |
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