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2021-01-01 | The multi-criteria problem of transverse vibrations attenuation of a cantilever beam is considered by the active and passive damping methods. The mathematical model of beam is provided by Bernoulli–Euler’s hypotheses with the linear viscosity. Perturbation acting on the beam belongs to a class L_2 of functions. The beam mode is described by Krylov functions. The normal form method is used to convert to the main coordinates. A model of active vibration isolation applied along the entire length of the cantilever beam and a model connected to a vertical base at one point were constructed. The beam model connected to a viscoelastic base within the passive vibration isolation is considered. The task of transverse vibrations attenuation is a state feedback control problem with two controlled outputs. Two criteria are introduced, namely the maximum beam deflection and the control force. The generalized H_2 norm is used as a measure of functional evaluation in the synthesis of optimal regulators. The search for optimal feedback is based on the use of linear matrix inequalities and efficient algorithms for solving, implemented in the MATLAB package. Synthesis of Pareto-optimal control is implemented on the basis of Germeyer convolution. The optimal values of the functional under distributed and concentrated forces are given with respect to two criteria for active and passive damping methods. The paper includes a comparison of vibration isolation for different attenuation methods. | Optimal Attenuation of Transverse Vibrations for a Cantilever Beam | 10.1007/978-3-030-54928-2_3 |
2021-01-01 | Let’s extend our free vibration analysis from Chap. 2 to include two degrees of freedom in the model. This would make sense, for example, if we completed a measurement to determine the frequency response function (FRF) for a system and saw that there were obviously two modes of vibration within the frequency range of interest; see Fig. 4.1. | Two Degree of Freedom Free Vibration | 10.1007/978-3-030-52344-2_4 |
2021-01-01 | The present work aims to study the free vibration and damping properties of pure bamboo bioepoxy composites (B), pure basalt bioepoxy composites (b), and bamboo/basalt fiber reinforced hybrid bioepoxy composites. The pure and hybrid composites were fabricated by hand layup technique with different layering sequences such as BBBB, bbbb, BbBb, BBbb, BbbB, and bBBb. Experimental modal analysis was performed to obtain the natural frequency and the damping characteristics of the fiber reinforced composites. Variations in the natural frequency and damping characteristics were noticed with different layering sequences of the fiber in the composites. For instance, a higher natural frequency was obtained when bamboo fiber was stacked on the top surface and an enhanced damping behavior was noticed when basalt fibers were used as skin layer in hybrid composites. Numerical analysis was performed and the results were compared with the experimental results. | Free Vibration Analysis of Bamboo Fiber-Based Polymer Composite | 10.1007/978-981-15-8489-3_6 |
2021-01-01 | The woven fabric carbon/epoxy composite is one of the commercially well-recognized composite materials for structural applications like aerospace systems, automobiles and also in ship building industries. In the present investigation, dynamic mechanical behavior of woven fabric carbon epoxy composite laminate fabricated, by blending micron sized rubber and nanosized silica particles of varying weight fraction in epoxy matrix was studied. Silica in nanosize was added in two different weight fractions say 6 and 11% by weight in 9 wt% rubber particle blended epoxy matrix. The composite plates were fabricated by hand layup method with 40% of fiber volume fraction. The storage modulus, loss modulus and tan delta values were evaluated by conducting dynamic mechanical analysis for all the specimens as per the ASTM standards. Results from the DMA tests under temperature sweep for the constant frequency range of 1 Hz reveals that there is significant increase in the tested parameters like storage modulus and loss modulus of the hybrid composite. | Study on the Influence of Nanosized Silica Reinforcement in Microrubber Blended Epoxy Carbon Composite Laminate Subjected Under Dynamic Mechanical Analysis | 10.1007/978-981-15-6267-9_42 |
2021-01-01 | In this paper, a seismic analysis of the Menta dam is briefly described. The Menta dam is a bituminous-faced rockfill dam located in Southern Italy, lying in the heart of Aspromonte Massif at an elevation of about 1400 m a.s.l. The embankment is about 90 m high at its deepest point, and the reservoir impounds 1.8 × 107 m^3 of water. This dam was designed in the late seventies and built between 1987 and 2000. In the seismic analysis, the dam material has been modelled with an elasto-plastic constitutive law which is characterized by a Young’s modulus dependent on the stress level and on the distortional strain and by a curvilinear yielding surface. Both the calibration of the model and the dynamic analysis has been carried out by means of the FDM code FLAC (Fast Lagrangian Analysis of Continua [ 1 ]) version 8.1 which adopts an explicit time-integration scheme. | Seismic Analyses of Menta Embankment Dam: An Elasto-Plastic Model with a Stress-Strain Dependent Stiffness and a Composite Yielding Surface | 10.1007/978-3-030-51085-5_34 |
2021-01-01 | Determination of dynamic properties of soil is a difficult, complex, and time-consuming task but an essential and important aspect in geotechnical earthquake engineering problems. Dynamic soil properties are important to predict the ground motion, site response, and probability of seismic hazards in seismic zones. Seismically, shear wave velocity is the best indicator for site characterization and also to evaluate the liquefaction potential of soils. The piezoceramic bender element test was conducted to study the effect of artificial cementation on low strain dynamic properties of sand. Artificially cemented specimens were prepared using 10% of Portland pozzolana cement by weight. Then, sample having dimension of 50 mm × 100 mm was prepared in relative densities of 30%, 50%, and 85%, and the samples were tested with the confining pressure of 100 kPa, 200 kPa, 300 kPa, and 400 kPa after 7, 14, and 28 days of curing. It is determined that shear wave velocity and maximum shear modulus increases with increase in the density, confining pressure and curing periods. | Small Strain Stiffness of Cemented Sand | 10.1007/978-981-33-6564-3_55 |
2021-01-01 | Advancement in vehicle technology has explored many possibilities for improvement, keeping customer satisfaction in mind. One major criterion which a passenger always wishes to possess is ride comfort. But the suspension parameters suitable for a good ride comfort may not support another salient feature called road holding. Hence, in this work an attempt has been made to simultaneously improve the ride comfort and road holding, using a quarter car test model using MATLAB Simulink for a commercial light motor vehicle. Initially, a commercially available passive damper of light motor vehicle has been characterized using dynamic testing machine (DTM) in order to obtain its force–displacement behavior and damping nature. A design of experiment (DOE) has been conducted by taking vehicle velocity, sprung mass, spring stiffness and damping coefficient into consideration, for experimentation using quarter car model. Regression equations have been extracted for relating the problem parameters to both ride comfort and road holding. Analysis of variance (ANOVA) has been used to know the influence of each parameter toward the target response. In the later stage, response surface methodology optimization technique has been used in order to optimize the parameters for better ride comfort and road holding. Optimized parameters are substituted again in the quarter car model, to validate the results obtained during optimization. The present work concluded with an optimal ride comfort and road holding and proved the effectiveness of optimization technique in achieving so. | Optimal Parameters Identification of Quarter Car Simulink Model for Better Ride Comfort and Road Holding | 10.1007/978-981-15-8315-5_53 |
2021-01-01 | In structural engineering aspect, the inherent structural property of the building is not sufficient to control the structural response when it comes to strong earthquakes. The common control strategy used by researchers makes use of energy dissipating devices that absorb the energy imparted to the structure due to earthquake and dissipate the energy by their hysteresis nature. In this study, seismic response of a G + 4 storey building installed with a hybrid damper has been investigated. The hybrid damper system comprises of Viscous Fluid Damper (VFD) and Shape Memory Alloy (SMA). The performance of the building under near-field earthquakes, Tabas, Kobe, and Gebze earthquakes has been evaluated. The dampers have been installed at the base of the superstructure. SMA exhibits a good self-centering capability and is known for its superior super-elasticity properties. It is capable of dissipating energy through its hysteresis nature while maintaining a low level of residual displacement. VFD dissipates energy through the movement of fluid inside it, which minimizes both stress and displacement the structure due to seismic effect. The time history analysis result shows the effectiveness of hybrid damper for controlling the seismic forces acting on the structure. In this present study, there is a significant reduction in base shear and displacement by about 16% and 8% by using Hybrid damper when compared to VFD and SMA dampers. A comparative study is made showing the effect of the Hybrid damper in reducing the seismic responses for the selected near-field earthquakes. | Seismic Control and Performance of Passive Hybrid Damper Under Near-Field Earthquakes | 10.1007/978-981-15-5235-9_1 |
2021-01-01 | The tall building is always prone to environmental loads like wind pressure and earthquake. As height of the structure increases, the effect of wind pressure also increases based on the region where the building is placed. There are many structural forms developed to overcome the lateral loads, one of the system is called outrigger structure. Conventional outrigger structural system consists of a core in its interior and outrigger arms that connect the core and perimeter column, which resists the overturning moment of the core and reduces the drift due to the reduction of bending moment in the structure. The problem identified in this research is to develop damped outrigger structure which further enhances the outrigger structural performance by increasing stiffness and damping. With the addition of external damping devices to outrigger structure, response control can be further increased. In this study, mathematical model of outrigger structure is simulated in MATLAB by placing viscous damper as external damping device. The response of the structure is determined against the wind load, which shows the mitigation of the vibration response of outrigger structure which is a multi-approach method. The simulation model of outrigger structural parameters is continuous process owing to its importance in improvement of structural response, and the outcome of this research can immensely contribute to the ‘body of knowledge’ in this area. | Response Control of Wind-Excited Outrigger Structural System | 10.1007/978-981-16-0336-5_34 |
2021-01-01 | This work is based on the optimum design of performance parameters of MR damper piston which is used in semi-active suspension system using Taguchi method based on grey relational analysis (GRA) and ANOVA (analysis of variation). For better ride comfort and great control over vehicle, suspension system plays a main role. Semi-active suspension is a combination of controllable magneto-rheological damper and passive spring. The conventional passive suspension’s damper is replaced by controllable MR damper for provide better resistive damping. The semi-active suspension is more accommodative and convenient to changes easily in its design parameters to enhance its performance. In this work, the design parameters of piston are change in order to determine the better value of affecting parameters of MR damper performance. Grey relational analysis is the process optimization used to find out the optimal performance parameters. The magneto-rheological damper uses the excitation of magnetic field produced by the maximum current of 0.7 A, and the annular gap between piston and cylinder is kept constant as 0.5 mm. As the maximum magnitude of current and less gap between piston and cylinder can produce maximum resistive damping force, the different design parameters are used to find out their effect on performance of suspension. Using design parameters like piston pole length, distance between two poles and piston velocity, the design is optimized. The optimization shows the pole length of piston, and distance between poles is the most considerable performance parameters of the piston design. | Performance Parameter Optimization of MR Damper Piston Using Taguchi Method and Grey Relational Analysis | 10.1007/978-981-16-0942-8_18 |
2021-01-01 | Tuned sloshing damper is a well-established and popular passive control device for vibration mitigation of structures subjected to excitations such as wind, earthquake, wave, etc. However, being a long period system, the applicability of this type of control device is restricted to flexible structures. To overcome this, a new kind of translational spring-connected sloshing damper is introduced in the present research paper and its applicability to short period structures is explored. First, a time-domain formulation of a linear single-degree-of-freedom (SDOF) structure with spring-connected sloshing damper system is developed. A nonlinear model based on the shallow water wave theory is utilized for modelling the liquid motion in the sloshing damper. Further, a numerical study on the performance of the damper system attached to a short period structure subjected to harmonic input is carried out. The performance of the damper system is examined on the basis of reduction in the peak value of the structural displacement. The performance of the proposed damper system indicates that the spring-connected sloshing damper has great potential as a vibration mitigation device for short period structures. | A Novel Sloshing Damper for Vibration Control of Short Period Structures | 10.1007/978-981-15-8138-0_26 |
2021-01-01 | Purpose The magnetorheological (MR) damping devices have attracted an increasing amount of attention in the field of vibration control for their excellent performance of the vibration absorption. Systematically, the constitutive mechanical models of the MR fluids affect the control accuracy for the control strategies and the applications of the MR dampers. Methods This work elaborately gives a systematic review on the control issues with the MR devices, thus, covering the dynamic models of the MR dampers, the state-of-the-art research, and the damping control strategies and its applications, which provide the necessary fundamental theories and the references for the damping control design of an MR damping device. Results According to the advanced degree of the control algorithms that are discussed in detail, they can be classified into three categories, namely, the classical control algorithms, the advanced control algorithms, and the intelligent control algorithms. The damping control strategies determine the control quality, which is the soul of an MR damping control system. There is still room to improve the algorithm for the controller for MR dampers. Conclusions Employing the smart algorithms of machine learning, the work directs much more attention to the foundational research on the application of the artificial intelligence algorithms in damping control, outlining a perspective to combine the advantages of the individual different intelligent algorithms that could be an alternative solution to control of an MR damping device for the complex problems. | The Dynamic Models, Control Strategies and Applications for Magnetorheological Damping Systems: A Systematic Review | 10.1007/s42417-020-00215-4 |
2021-01-01 | Poorly damped systems exhibit a high oscillatory behavior making them harder to control. The paper explores the possibilities of controlling a poorly damped system using different fractional order control approaches such as the Fractional Order Internal Model Control (FOIMC) and the Fractional Order Proportional Integral (FOPI) controllers. The case study is chosen to be a highly nonlinear experimental platform consisting of a vertical take-off and landing platform. The performances of the closed loops with the two fractional order controllers are compared experimentally by analyzing reference tracking, disturbance rejection and robustness. | Comparison of Various Fractional Order Controllers on a Poorly Damped System | 10.1007/978-3-030-77314-4_18 |
2021-01-01 | In this research, we describe the design of a seismic isolation system with power generation performance. There are three main types of anti-vibration measures: earthquake resistance, vibration control, and seismic isolation. Recently, seismic isolation structures that do not transmit vibrations by insulating them from the ground attract attention. In addition, various seismic isolation devices have been proposed and applied to actual buildings. We incorporated an inertial mass damper (inerter) into a seismic isolation device and designed the mechanism with response reduction effect and power generation. The design proposal is described in detail. Furthermore, the vibration experiment using a sine wave was performed on this seismic isolation system, and we measured the acceleration response of the input wave and the seismic isolation layer and the voltage obtained from the motors at that time and evaluated its performance. Also, in the simulation, we examined the influence of parameters on the acceleration response using a mass point model. | Experimental Vibration Analysis of Seismic Isolation System Using Inertial Mass Damper | 10.1007/978-3-030-48153-7_33 |
2021-01-01 | In recent mechanical systems, vibration problems have become obvious as the size and working speed of the equipment become smaller and faster. Much attention has been paid to develop vibration control devices, e.g., the vibration isolators and absorbers. The size of the absorbers is expected to be smaller in view of space saving and weight reduction. However, constitutive physical characteristics limit realization of the compact design without sacrificing the required damping performance. Specifically, it is difficult to attenuate low-frequency vibration by a miniaturized vibration control device. In the present study, we propose a novel active-type mass damper for vibration control of structures. By using a relatively small, high-frequency-driven actuator to drive the mass with an amplitude-modulated control signal, the low-frequency damping force can be demodulated. Mathematical formulation of the driving principle, both numerical and experimental verification of the low-frequency acceleration component to be used for the inertial control force, is shown. | Development of an Active Mass Damper Driven by an Amplitude-Modulated Signal | 10.1007/978-3-030-47618-2_34 |
2021-01-01 | A magnetorheological (MR) fluid is one of functional fluids whose rheological properties vary in response to a magnetic fluid. The change of the properties is so drastic and quick that it is applied to controllable dampers for semi-active vibration suppressions. However, conventional cylindrical dampers using MR fluid have two problems: the performance degradation caused by the particle settling and the narrow dynamic range due to sliding frictions of sealing elements. In order to overcome them, we propose a shear-type damper using MR grease. Owing to the high dispersion stability of MR grease and the absence of sealing elements, it realizes the long-lasting performance and the wide dynamic range. In this study, its damping effect was investigated by the vibration suppression test. The novelty is that the suppression target is 2DOF structure model. The vibration response was reduced by using a control law based on skyhook damper scheme. Furthermore, our calculation suggested that the proposed change of the control law can further reduce the vibration response. | Semi-active Vibration Suppression of a Structure by a Shear-Type Damper Using Magnetorheological Grease | 10.1007/978-3-030-47618-2_30 |
2021-01-01 | This paper shows test and analyses results of a new oil damper, “The Oil Damper with Stiffness”. It was developed to solve some issues around seismic retrofit. There are difficulties in reinforcing buildings which were designed before 1981 in accordance with The Old Buildings Standards Act and many buildings have low stiffness. Therefore, it has become common to retrofit old buildings using braces and oil dampers, but this requires many areas to be reinforced. It causes some problems relating to construction period, cost, and convenience of access. This paper confirms that the test specimens have sufficient capabilities regarding stiffness, constant slip force, durability, etc. in test results and advantages of this damper in analyses using the factory model and the high-rise building model. | Development of New Oil Damper with Stiffness for Architectural Vibration Control and Experimental Research on Structural Characterization | 10.1007/978-981-15-8079-6_126 |
2021-01-01 | If a response (that is, an output) can be described by a second-order differential equation, this circuit is referred to as a second-order circuit. An RLC circuit is a second-order circuit. Sometimes (but not always), the order of the circuit can be estimated by the total number of inductors and capacitors in the circuit. | Second-Order Circuits | 10.1007/978-3-030-60515-5_25 |
2021-01-01 | Ferromagnetic resonance spectroscopy (FMR) is a versatile characterization technique that probes the magnetization dynamics in the frequency domain. Despite its long history, there continues to be significant improvement regarding the sensitivity and frequency range achievable in ferromagnetic resonance experiments. In this chapter we will briefly introduce the basic principles of ferromagnetic resonance spectroscopy and the long history of this technique. We will discuss the equation of motion for the magnetization that leads to the ferromagnetic resonance condition in the form of the Kittel equation and the Smit-Beljers equation, followed by a discussion of the resonance lineshape. We will cover four different experimental methods that are used to detect ferromagnetic resonance: cavity-based, shorted waveguide, transmission line, and electrically detected ferromagnetic resonance. We will give three examples that highlight some of the unique capabilities of broadband ferromagnetic resonance spectroscopy. | Ferromagnetic Resonance | 10.1007/978-3-030-70443-8_16 |
2021-01-01 | With the increasing penetration rate of the renewable energy sources in the microgrid, the state-of-stability (SoS) in the system is decreasing. The deep-down issue is rooted in the loss of inertia. Eventually, in recent time, the research in the field of virtual inertia emulation schemes has gained a lot of momentum. The virtual inertia can potentially improve the SoS in the microgrid. However, another major concern in the static generator-based microgrid, the frequency recovery rate, cannot be improved through virtual inertial support. Therefore, concerned with this issue, an auxiliary dynamic damping loop (ADDL) has been introduced in the study to work synchronously with the existing virtual inertial loop. The performance of the ADDL-based scheme has been evaluated in the ARM Cortex A-72 processor-driven prototype hardware model and found a significant improvement. | Auxiliary Dynamic Damping Loop in the Microgrid for Enhancing Frequency Recovery Rate | 10.1007/978-981-15-8218-9_6 |
2021-01-01 | This article discusses the end-to-end design of electric machines (EM) for their use in the composition of shock absorbers with a regenerative effect (SARE) and its stages. It describes the implementation and end-to-end design of synchronous EM with permanent magnets (PM) with the help of the developed methods of design and modern methods of technical systems analysis. The authors apply the methods of finite elements and simulation analysis in a virtual operation using MATLAB. The process of designing shock absorbers with a regenerative effect is cyclic and iterative. The design includes the formation of the necessary damping characteristics, calculation of the main dimensions of the generator and their optimization, as well as the study of electromagnetic fields arising during the operation of the shock absorber using finite element methods and subsequent virtual operation of the device, simulating the operation in real operating conditions. The development is completed when all the necessary technical and economic requirements are met with the subsequent development of design documentation. | Design Methodology for Shock Absorbers with Regenerative Effect for Springing Systems of Wheeled Vehicles | 10.1007/978-3-030-54814-8_3 |
2021-01-01 | Foundation in case of industries and high-rise buildings where turbines, generators, and compressors are installed undergoes vibration. This paper presents the experimental and numerical study on an isolated square shallow foundation under vertical periodic machine vibrations. To excite the foundation with vertical dynamic loading, the eccentric mass shaker is utilized. The eccentric mass shaker essentially consists of two counter-rotating shafts capable of creating vertical periodic loading. A series of block vibration tests are conducted on a square-reinforced cement concrete of size 1 m × 1 m × 0.3 m on field site near western laboratory at IIT Kanpur campus. The shallow foundation is excited with vertical periodic loading of different magnitudes and frequencies. The responses are measured using sensors like accelerometers. The variation in the dynamic responses is recorded, and the same is plotted with varying eccentric force. The resonant amplitude, natural frequency of soil and damping ratio are plotted with frequency. Further, the experimental results are compared with the experimental findings earlier reported in the available literature for the IIT Kanpur campus soil. The numerical simulation of shallow foundation–soil system is done with built-in finite element package ABAQUS and compared to experimental amplitude values. | Experimental and Numerical Study of Shallow Foundation Subjected to Vertical Dynamic Load | 10.1007/978-981-33-4001-5_32 |
2021-01-01 | The problem of dynamic deformation of structures damping elements made of metal hollow spheres (MHS) filler is considered. MHS filler is a porous material obtained by joining homogeneous metal hollow spheres. The MHS filler is modeled by a continually homogeneous, orthotropic, physically nonlinear medium. The solution of the determining equation system is based on the finite element method moment scheme and the explicit finite-difference time integration “cross” type scheme. The problem of stability loss and supercritical behavior of a titanium spherical shell under compression loading between two non-deformable plates approaching with a constant velocity is considered. According to the problem numerical solution results, the dependence of the contact force on the plates movement was built, on the basis of which the deformation diagram and the parameters of the MHS filler mathematical model of the were determined. The problem of plate falling on a spherical shells’ set located on a fixed base is solved using the obtained data. As it is shown by the calculation results analysis, the developed computational model allows to determine with acceptable accuracy the integral deformation parameters of the MHS filler (contact forces, displacements, displacement velocities) and to evaluate its damping properties. | Finite Element Method Study of the Protection Damping Elements Dynamic Deformation | 10.1007/978-3-030-53755-5_4 |
2021-01-01 | The development of traditional CMOS-based logic circuits in terms of speed and energy consumption is approaching the limit. Memristor is a kind of bio-inspired hardware with a special structure, which has the advantages of simple structure, low power consumption and easy integration. It has good application prospects in high performance memory and neural network. The invention of memristor provides a new way to develop a more efficient circuit design. In this paper, the second order damping system based on memristor is used to realize the function of human body perceptron. By taking advantage of the variable resistance of memristors, the function of real-time perception can be realized. The second order underdamped state itself is used to realize the sensory adaptation ability of perceptrons. Through theoretical analysis and Pspice simulation, the feasibility of the second order damped system perceptron based on memristor is verified. The human body sensor based on memristor provides a reference for more future intelligent robots. It also provides support for the development and application of bio-inspired hardware. | Perceptron Circuit Design of Second Order Damped System Based on Memristor | 10.1007/978-981-16-1354-8_24 |
2021-01-01 | A new proposed control based on the modified Riccati-like equation is developed in this study. The interval type 2 fuzzy model is applied and embedded in the controller for control the uncertainty and also support for calculation progress of the proposed control. To design of the control, the first sliding surface based on the conventional model is established and its elements using for combine with the other elements of the Riccati-like equation. The robustness control is designed including three components of PID control and matrices of the traditional model of Riccati equation. Model of the proposed control is evaluated by applying to the bus suspension system. In the suspension, a magneto-rheological (MR in short) damper with its stiffness following the variation of applied current is used. The main input control is applied to change the value of the applied current. Belong to the magnitude of vibration, the current is also changed. The results of simulation of the proposed control are shown that the proposed control is better for control real system. | A New Adaptive Hybrid PID Controller for Severe Disturbance of Bus Suspension Featuring Smart Damper | 10.1007/978-3-030-69610-8_4 |
2021-01-01 | Active or passive control strategies are developed for the control of civil structures. Since the structures are huge systems as a mechanical system, the control must be feasible for application proposals and cost efficiency performance. For that reason, structural control methods are still an active research area by optimum tuning of system parameters. The tuning of control systems is the most essential subject in performance of control systems. Also, the classical methods are not effective for civil structures subjected to seismic activities. In this chapter, a state-of-the-art review about active, passive, semi-active, and hybrid control studies is presented especially for seismic structures. Then, two active control models are compared via metaheuristics. These models are active tuned mass damper (ATMD) and active tendon control (ATC). Advantages and disadvantages are given in the conclusion. | Metaheuristic-Based Structural Control Methods and Comparison of Applications | 10.1007/978-981-33-6773-9_12 |
2021-01-01 | The increasing renewables penetration leads to reduction in system inertia and may have negative impact on damping of low-frequency oscillations (LFOs). In this paper, a technique to improve the system small signal stability is proposed using a robust coordinated tuning approach of damping controllers. An improved fitness function is proposed to simultaneously maximize the LFO modes damping ratio and shift the eigenvalues to left-hand side of s-plane. The coordinated tuning is achieved using an advanced meta-heuristic technique Marine Predators Algorithm (MPA). The results of MPA are compared with other techniques to prove its superiority in handling this complex problem. The study has been carried out on benchmark IEEE 39-bus test system. Further, eigenvalue analysis and time-domain simulations are executed to demonstrate the capability of suggested control approach. The critical scenarios are simulated to test the robustness of the coordinated tuning. The results substantiate the potency of proposed strategy and robustness in improving the LFOs damping under varying system operating conditions. | Damping Enhancement of DFIG Integrated Power System by Coordinated Controllers Tuning Using Marine Predators Algorithm | 10.1007/978-981-15-8815-0_15 |
2021-01-01 | This paper focuses on evaluating whether a buckling-restrained brace (BRB) element should be replaced after an earthquake event. For this purpose, a damage index is proposed based on the experimental data obtained from a series of tests conducted on different BRB specimens. In total 19 full-scale BRB specimens were manufactured with local industry and workforce, and tested. 14 BRB specimens were tested using a low-cycle loading protocol, and five BRB specimens were tested using a high-cycle fatigue loading protocol. For the low-cycle protocol, the axial strain in the BRB core was continuously increased until failure, while for the fatigue protocol, the axial strain in the core was increased from zero to 1.5%, and continued at 1.5% strain until core failure occurred. The proposed damage index has been calibrated based on the experimental results, and is capable of considering the effect of the maximum core strain attained as well as the cumulative deformation effect. A qualification scale has been assigned to the proposed damage index as a tool for evaluating whether the BRB element should be replaced or left on site. Furthermore, a series of nonlinear dynamic analyses were carried out on a sample building in order to validate the proposed damage index when subjected to ground motions. Finally, the results suggest that the proposed damaged index can be useful in structural design practice. | A Damage Index for the Seismic Evaluation of Buckling-Restrained Braces | 10.1007/978-3-030-73932-4_12 |
2021-01-01 | Plants being the producers of food encounter various pests and pathogens, including microbes (virus, bacteria, fungi, protists, nematodes), insect and vertebrates with diverse modes of attack. Although some organisms have a mutualistic/symbiotic association with plants, others are harmful, may greatly impair plant productivity and threaten overall food security. In nature, plants and its enemies have coevolved for an interdependent co-existent. The plant defence mechanisms may vary when it encounters different attackers; however, they have evolved their defence mechanisms with a high degree of overlap to keep its resources allocated in an orderly fashion. The tripartite interactions between the microbe-plant-insect (MPI) form the basis for the plants to host the room for evolution and structure the communities of the interacting organisms along with the development of the host-vector relationship. Since, all the three interacting organisms (MPI) form a single system, the defence generated by plants is usually modified and may affect the microbes and insects up to a different degree, ranging from beneficial to detrimental. The early defensive strategies developed by plants against microbes and insects are almost similar and may involve the same mechanism; however, the difference lies at the molecular level. In this chapter, the biochemical and molecular aspect of defence mechanism regulating these interactions has been presented and discussed to gain an insight of practical applications for improving plant productivity and the plant immunity. | Microbe-Plant-Insect Interactions: A Comparative Dissection of Interactome | 10.1007/978-981-15-2467-7_15 |
2021-01-01 | Impact dampers of various designs are currently used for mitigating vibrations of industrial components. Although they may generate disturbing noise, these devices offer many advantages, as they are quite robust, exempt from fine-tuning and stand severe temperature and environmental conditions. Moreover, they can be applied to systems subjected to wideband excitations, which is a major advantage. However, they are highly nonlinear, hence the numerical modelling issues and the difficulties to predict their behaviour and to optimize their design. This work addresses some basic steps to increase our understanding of such devices, focusing on the family of “simple” chain impact dampers, composed of one or several spheres impacting inside a guide-tube. Damping of such 1-D device is related to the visco-elasticity of the impacting spheres, with only residual friction phenomena. In practice, this device can easily be coupled to any structure, such as the clamped-free vibrating beam as used in the present work. In this paper, we report the detailed dynamical modelling of the beam-damper coupled system and present preliminary simulation results obtained from a model calibrated based on experimental data stemming from modal analysis and drop test experiments. | Experimental Contact Model Calibration for Computing a Vibrating Beam Coupled to a Granular Chain Impact Damper | 10.1007/978-3-030-76517-0_28 |
2021-01-01 | Magnetorheological Dampers (MR) have the ability to mitigate seismic hazards caused to a structure by reducing its potential to undergo large displacements. The objective of the paper is to formulate an analytical modeling technique to perform the hybrid simulation. The seismic response of a single-story frame employed with an MR damper is analyzed for hybrid simulation. The paper compares the results of several parameters subjected to specific earthquake ground accelerations using an object-oriented programming software called OpenSees. A program source code developed by OpenSees is run with Active Tcl script and changes are made for specific models to validate the simulations for each model. The time-series data for ground accelerations of the earthquakes considered in the models (El Centro, Kobe, and Northridge earthquakes) is taken as an input to perform a simulation. OpenSees software is present as an executable file that runs this source code of the program, performs the simulation for each of the models, and saves the output. The simulated models give us several outputs like acceleration, displacement, damper force, etc., simultaneously after the program is run. The results of the output are deliberated in the form of graphs. | Studies on Modeling and Control of RCC Frame with MR Damper | 10.1007/978-981-15-5001-0_18 |
2021-01-01 | Tuned mass dampers (TMDs) and nonlinear energy sinks (NESs) are two viable options for passively absorbing structural vibrations. In seismic applications, a trade-off exists in their performance, because TMDs’ effectiveness varies with the structural stiffness while NESs’ effectiveness varies with the earthquake intensity. To investigate this trade-off systematically, a lifecycle cost- (LCC-) oriented robust analysis and design method is here proposed, in which the effectiveness of a solution is measured by the reduction it entails in the expected cost of future seismic losses. In it, structural stiffness variability is modelled using a worst-case approach with lower and upper bounds, while seismic intensity variability is inherently captured by the incremental dynamic analyses underlying every LCC evaluation. The resulting worst-case lifetime cost provides a rational metric for discussing pros and cons of TMDs and NESs, and becomes the objective function for their robust optimization. The method is applied to the design of TMDs and NESs on a variety of single- and multi-story linear building models, located in a moderate-to-high seismic hazard region. Mass ratios from 1 to 10% and structural stiffness reductions up to 4 times are considered. Results show that TMDs are consistently more effective than NESs even in the presence of large stiffness reductions, provided that structural stiffness uncertainty is considered in design. They also show that a conventional robust H_∞ design provides for TMDs a solution which is very close to that obtained by minimizing the proposed LCC metric. | Seismic effectiveness and robustness of tuned mass dampers versus nonlinear energy sinks in a lifecycle cost perspective | 10.1007/s10518-020-00973-2 |
2021-01-01 | Reciprocating compressors operated in gas transmission systems are equipped with passive pressure pulsation dampers protecting the system against the negative effects of excessive pulsation and the related dynamic phenomena. The transmission loss characteristics are determined by means of numerical simulations or measurements at test stands. Most often, however, both the simulations and the bench tests cover either only some assumed simplified operating conditions, e.g. experimental tests of acoustic characteristics, without taking into account the flow of medium, or numerical simulations without taking into account the geometry of the entire installation (the anechoic boundary condition). The article presents a proposed methodology for determining the transmission loss characteristics of pulsation dampers with allowance for variable operating parameters and with the use of a specially designed test stand equipped with a piston compressor and a variable volume damper. In addition, the influence of operational parameters (flow rate and pressure) on pressure pulsation attenuation was tested. The research results presented in the article may form the basis for the development of new improved mathematical models simulating the characteristics of pulsation dampers with allowance for the operational parameters of a system. | Experimental Research into the Influence of Operational Parameters on the Characteristics of Pressure Pulsation Dampers | 10.1007/978-3-030-59509-8_29 |
2021-01-01 | In this study, the analytical Herschel-Bulkley fluid model of a monotube mixed mode MR damper was examined. The MR damper was modeled and simulated by using computational fluid dynamics (CFD) and magnetic finite elements analysis (FEA). The magnetic effects were modeled in a coupled manner with CFD. The actual rheological data was used in the CFD solver to find the cell-based viscosity by using a shear stress interpolation method. The MR damper was manufactured, and experiments were conducted to find the force-displacement and force-velocity correlations, and a good agreement was found between the numerical results and experimental data. The experimental results were also compared with analytical and numerical models under various current values. The CFD results are valuable in predicting the actual characteristics of the non-Newtonian flow inside an MR damper, and it can be used for various non-Newtonian fluid CFD models. | Numerical analysis of a monotube mixed mode magnetorheological damper by using a new rheological approach in CFD | 10.1007/s00397-020-01252-2 |
2021-01-01 | In current work the unsteady MHD flow behaviour of a fluid of grade three between two infinitely long flat porous plates is scrutinized where the top lamina is fixed and the lower lamina moves with a velocity which vary with respect to time. Then the non linear p.d.e governing the flow behaviour are reduced to a system of algebraic equations using fully implicit finite difference scheme and numerical solution is obtained using damped-Newton method, which is then coded using MATLAB programming. Influence on velocity with variations in m , $$ \alpha $$ , $$ \gamma $$ , Re is interpreted through different graphical representation. | Computational Analysis of Unsteady MHD Flow of Third Grade Fluid Between Two Infinitely Long Porous Plates | 10.1007/978-981-15-4308-1_24 |
2021-01-01 | The COVID-19 outbreak has threatened human life and disrupted economies worldwide. With prepared healthcare systems and governments serving as our best defence, the forecasting of its spread has become imperative. The chapter applies a range of time series forecasting techniques—baseline methods, exponential smoothing, ARIMA and LSTM—to daily reports of total and new COVID cases in India, China and the USA. The analysis suggests that limited-sized time series datasets with contextual information are better forecasted with traditional methods like ARIMA, while large datasets render themselves more naturally to deep learning methods. | A Study of Time Series Forecasting Techniques for COVID-19 Trends | 10.1007/978-3-030-82079-4_1 |
2021-01-01 | This paper proposes a network of neural oscillators having lateral inhibition structures. Our previous research suggested a new control system for active mass dampers (AMDs) consisting of a neural oscillator network and a position controller. However, the proposed system required a large number of neural oscillators for robust operation, which made the implementation more difficult in microcomputers. Thus, there was a need to limit the number of oscillators for application. This research addressed this need by changing the internal structure of the network. This paper provides new structures that reduce the number of neural oscillators. The introduced lateral inhibition structures used in this work should be useful for the implementation of the network into the microcomputers. | Output Analysis of Neural Oscillator Networks Having Lateral Inhibition Structures | 10.1007/978-3-030-46466-0_44 |
2021-01-01 | In this paper, we discuss the influence of assuming L ^ m regularity of initial data, instead of L ^1, on a heat or damped wave equation with nonlinear memory. We find that the interplay between the loss of decay rate due to the presence of the nonlinear memory and to the assumption of initial data in L ^ m instead of L ^1, leads to a new critical exponent for the problem, whose shape is quite different from the one of the critical exponent for L ^ m theory for the corresponding problem with power nonlinearity | u |^ p . We prove the optimality of the critical exponent using the test function method. | A New Critical Exponent for the Heat and Damped Wave Equations with Nonlinear Memory and Not Integrable Data | 10.1007/978-3-030-61346-4_9 |
2021-01-01 | Neutrophils are the primary innate immune cell involved in acute inflammatory responses to trauma and injury. While the mechanisms used by neutrophils to cause inflammation are designed to protect the host and allow for recovery, many of these same processes can have pathologic outcomes, including contributing to the development of trauma-induced coagulopathy. Neutrophil priming, ROS production, degranulation, NETosis, and responses to damage-associated molecular patterns and how these phenomena drive interactions of the neutrophil with other host tissues and cells such as the endothelium will be reviewed here in the context of major trauma and the resulting development of coagulopathy and end-organ damage. Although neutrophil biology and innate immunity is an expansive topic, the goal of this chapter is to provide the reader with a broad understanding of neutrophil function focused within the context of trauma and trauma-induced coagulopathy. | Neutrophils, Inflammation, and Innate Immunity in Trauma-Induced Coagulopathy | 10.1007/978-3-030-53606-0_13 |
2021-01-01 | We consider the Cauchy problem on R 0 + × R n $$\mathbf {R_{0}^+} \times \mathbf {R^n}$$ for the semilinear damped wave equation u t t ( t , x ) − a 2 ( t ) Δ u ( t , x ) + b ( t ) u t ( t , x ) = | u ( t , x ) | p $$\displaystyle u_{tt}(t,x) - a^2(t) \Delta u(t,x) + b(t) u_t(t,x)= |u(t,x)|{ }^p $$ with decreasing in time coefficients, the propagation speed a ( t ) = (1 + t )^− ℓ , ℓ ∈ (0, 1), the scale-invariant dissipation b ( t ) = β (1 + t )^−1, β > 0, and a power nonlinearity of order p > 1. The solution u ^0 of the corresponding linear Cauchy problem will be represented in the explicit form using Fourier multipliers operators with multipliers expressed in terms of special functions. Our main goal is to prove a global in time existence result when initial data belongs to the space H ^ m ( R ^ n ) × H ^ m −1( R ^ n ), m ≥ 1. We are focused in finding the critical exponent p _ c ( n , ℓ ) such that if 1 < p < p _ c ( n , ℓ ) there exist small data for which u blow-up in finite time. We also prove that if p ≥ p _ c ( n , ℓ ) the global solution has the same long time behavior as u ^0. In order to estimate u we use Duhamel’s principle to represent u and then we apply L ^2 − L ^2 estimates of u ^0. | Critical Exponent for a Class of Semilinear Damped Wave Equations with Decaying in Time Propagation Speed | 10.1007/978-3-030-61346-4_11 |
2021-01-01 | Tuning of structures of short periods to the long period sloshing liquid of a tune liquid damper (TLD) possess difficulty. However, proper tuning of the tuned damper devices is must for the desired control efficiency. To overcome this difficulty, a new implementation is proposed contrary to the conventional rigidly connected TLD with relatively shallow water depth. Presently, flexible pads with lower time period of vibration are inserted between the structure and the TLD, for which, the depth of the liquid in water tank may allow to be relatively high. The frequency of the container (inclusive of impulsive mass of the liquid) vibration is tuned to the fundamental frequency of the structure, which is observed to allow sufficient sloshing. The elastomeric pads are designed for adequate tuning. The performance of the proposed implantation studied numerically. Two short period structures are chosen (0.3 and 0.5 s) for the present study. Six ground motions representing the various seismic hazard levels from SAC ground motion data base are employed as input excitation. The numerical study reveals that the damper system is effectively reducing the response of structure yet it allows a relatively larger depth of water in the tank that can be harnessed for storage purposes as well. | Modified Tuned Liquid Damper for Vibration Control of Short Period Structures | 10.1007/978-981-15-9976-7_24 |
2021-01-01 | Mitigation of pounding between closely spaced building structures, subjected to earthquake excitation, by interconnecting them by friction dampers is investigated. Considering the pounding force and damper frictional force, the non-linear equations of motion of two connected single-degree-of-freedom (SDOF) structural systems subjected to recorded earthquake base motions are formulated and solved for the stick and slip phases. The pounding and damper frictional forces are represented by the Hertzian impact model and by the Coulomb friction model, respectively. Different combinations of structural time periods are considered to examine the effect of the relative flexibility of the adjacent structures on the pounding occurrence and on the performance of the damper. Results indicate that by appropriately selecting the slip force in the friction damper, it is possible to completely mitigate pounding. However, this may entail an increased displacement of the stiffer structure over that of the uncontrolled response. It is seen that a judicious choice of the damper slip force will provide substantial pounding reduction, even in case of large earthquakes, while constraining the displacements to within the uncontrolled values. | Vibration Control of Seismically Excited Adjacent Buildings Prone to Pounding by Use of Friction Dampers | 10.1007/978-981-15-5862-7_22 |
2021-01-01 | In this paper, an intelligent control technique with ameliorated performance for active half car systems with nonlinearities is presented. In fact, nonlinear characteristics of mechanical items and exogenous environmental disturbances that may deteriorate stiffness-damping parameters are neglected in some applications. However, this kind of parameter uncertainty are always present and can deteriorate the behavior of controller. In order to enhance the car body displacement and ensure a good compromise between the suspension constraints, a new model free controller MFC based on non-asymptotic observer is created. The intelligent-Proportional–Integral-Derivative strategy (i-PID) can update online the actuator force without getting precise information’s about unpredictable malfunction in suspension items. Considering, an auxiliary block is implemented to compensate the endogenous phenomenon’s of parameter uncertainties and is able to cope with all of these based on online compensator. Furthermore, the simplicity of implementation is an observed feature of the i-PID. Finally, the effectiveness of proposed controller is verified by a comparative analysis with optimal control Linear Quadratic Gausien (LQR) and the traditional Proportional–Integral-Derivative control (PID). A deterministic road profile was used to test satisfaction constraints: ride comfort, road holding and rattle space.The numerical simulations illustrate the effectiveness and the robustness of proposed scheme against nonlinearities. | Online Adaptive MFC for Nonlinear Active Half Car System | 10.1007/978-3-030-76517-0_23 |
2021-01-01 | This study focuses on frame buildings equipped with hysteretic dampers, and presents an energy-based methodology to estimate the earthquake deformation demand after damper installation. The proposed methodology considers not only structural and dynamic characteristics of the main frame and dampers, but also input ground motion characteristics. For this purpose, five R/C building structures with 2, 4, 6, 8 and 10 stories were designed according to the Colombian seismic code, and further converted into equivalent single-degree-of-freedom (SDOF) system models. Hysteretic dampers with varying mechanical properties were then installed into the SDOF models, and the models were then subjected to a series of 30 input ground motions. The input motions were modified to represent the seismic intensity given in the Colombian code and to grant certain control over the input energy. Furthermore, a discussion over the results of a three-dimension sample R/C frame building is presented. The predicted deformation demand obtained from the proposed methodology was compared with that obtained from the analysis. The methodology was shown to be useful for the preliminary assessment of the earthquake response of frame buildings with dampers. | An Energy-Based Prediction of Deformation Demand on Low- to Mid-Rise R/C Buildings with Hysteretic Dampers | 10.1007/978-3-030-73932-4_13 |
2021-01-01 | In response spectrum method, the modal seismic response is a combination of the damped periodic part and a rigid part. In high-frequency modes, the damped periodic part of the response is negligible and the response becomes rigid. The proposed methods and the current practices that have been used to account the effect of rigid part of the response into the seismic analysis of structures and their modal response combination methods are reviewed. Case studies on (i) a squat shear wall with an aspect ratio less than unity to show the behavior of a structure in high-frequency region of a spectrum and (ii) a building with a stiff base supporting a tower to show the effect of “missing mass” on the seismic analysis of structures with rigid modes are presented. The paper concludes with a set of methods for considering the effect of rigidity in earthquake analysis of irregular structures based on the latest developments in the field. | Effect of Rigidity on Seismic Analysis of Structures | 10.1007/978-981-15-5644-9_62 |
2021-01-01 | In this study, a model of the friction force of dampers in a horizontal washing machine is proposed. A MATLAB program is used to determine the parameters for force-velocity relation curve according to Tustin model based on the experimental data of dampers. The two degree of freedom system of horizontal washing machines with new friction model is simulated. The validation of the model with the proposed friction force was verified by comparison with experimental results and previous studies. The result shown that the damping model with the force-velocity relations proposed for more accurate results especially when examining the vibration properties of the suspension when the washing machine works at high speed. | Force-Velocity Relation of Dampers in Horizontal Washing Machines | 10.1007/978-3-030-64719-3_52 |
2021-01-01 | Steel chimney is a kind of high-rise structure, which is usually built in areas with large wind loads. And the possibility of large deformation or even damage caused by wind vibration exists. Suspended tuned mass damper (STMD) has been proved to be an effective vibration control device, which can effectively reduce the dynamic response of high-rise structures caused by wind and ensure it meets the requirements of deformation and comfort. A STMD is designed in a seaside thermodynamic boiler chimney to reduce the wind-induced response of the structure. The AR method for simulating the time-course load of along-wind is firstly introduced, with Davenport wind speed spectrum used in fitting. It can be concluded that the fluctuating wind obtained by the AR method meets the requirements in statistical sense. Then the simulation of cross-wind is proposed according to the range of Reynolds number, and the coupling of along-wind and cross-wind is taken into consider. The effect of STMD on vibration reduction is proved by analysis and test on the spot by comparing the acceleration amplitude of the top of the chimney with or without the STMD. | Research on Suspended Tuned Mass Damper in Wind Vibration Control of the Steel Chimney | 10.1007/978-981-15-8079-6_84 |
2021-01-01 | Liquid column vibration absorber (LCVA) is very much useful to mitigate the responses generated by the dynamic forces due to its cost-effectiveness dynamic vibration absorbing property. LCVA is usually a U-shaped tube having different cross-sectional areas in the vertical and horizontal column, normally filled up with water. The basic working principle of LCVA is to dissipate the vibration energy by gravitational force and the viscous force generated by the water present in the column. The damping force generation by the liquid movement through the orifice is very less in case of LCVA. To overcome this aspect, a new system is introduced which is called tuned liquid column ball damper (TLCBD) where a metal ball is installed in the horizontal part of the tube instead of orifice present in the LCVA. In the present study, the optimum performance of the response reduction of the structure is compared for both these systems. The numerical study has been performed by considering a single degree of freedom (SDOF) structure with an LCVA and TLCBD attached on the top of it separately under non-stationary random earthquake. The stochastic structural optimisation has been performed for both the cases and their results are compared. The results are confirmed the disparity between the response reduction of these two damper systems and improved response reduction is achieved for TLCBD system over LCVA system. | Comparison of Effectiveness of TLCBD Over LCVA in Vibration Control of Structure Under Non-stationary Earthquake | 10.1007/978-981-15-4577-1_26 |
2021-01-01 | In this paper, a dual quaternion-based methodology for computing the forward and inverse kinematic models for a serial manipulator is presented. A dual quaternion-based forward kinematics model is developed for the Kuka LBR IIWA 7 R800 cobot. An inverse kinematics model is developed that uses dual quaternion differential kinematics and includes Jacobian transpose and damped least squares methods for determining Jacobian pseudo-inverse. Implementation of these methods on a given trajectory shows that, compared to damped least squares, the Jacobian transpose method is faster, but is less immune to singularity and gives more jerky motions. | Dual Quaternion-Based Kinematic Modelling of Serial Manipulators | 10.1007/978-981-15-3639-7_1 |
2021-01-01 | Sloshing of liquid in a partially filled container, subjected to higher amplitude of dynamic load, is a complex phenomenon. In shallow water conditions, the natural frequency of sloshing depends on the amplitude of excitation. Sloshing frequency tends to change with increase in amplitude of excitation. The change in natural frequency is critical if we use the sloshing tank as a passive damping device, such as Tuned Liquid Damper (TLD) for offshore structures or onshore structures. A small change in sloshing frequency in TLD may affect the structural vibration control significantly. Therefore, it is essential to comprehend the natural frequency of shallow water sloshing. Experimental study is one of the best ways to understand the physical insights of change in sloshing frequency. Experimental studies are conducted to study the jump in sloshing frequency at different excitation amplitudes. Several rectangular tanks (1163, 1064, 951, and 844 mm) under different water depths (60, 50, and 40 mm) are taken for the study to generalize the results. The liquid tank is mounted on a uni-directional horizontal shake table, which is subjected to simple harmonic motion. The amplitude of excitation varied from 5 to 50 mm. A single capacitance-type wave probe is used at the end of the tank wall to measure the wave surface elevation. The wave elevation increases as the excitation frequency reaches toward the natural frequency of sloshing. The measured liquid sloshing frequency, at the resonance condition, is considered as actual sloshing frequency of liquid in tank. This sloshing frequency changes with the amplitude of excitation and shows the sudden jump in frequency from a particular amplitude of excitation. The objective of this paper is to generalize the relation between the jump frequency ratio (ratio of jump frequency to linear frequency) and the non-dimensional amplitude of excitation. | Experimental Study on Shallow Water Sloshing | 10.1007/978-981-15-5862-7_46 |
2021-01-01 | An organism’s phenotype can be thought of as consisting of a set of discrete traits, able to evolve relatively independently of each other. This implies that the developmental processes generating these traits—the underlying genotype-phenotype map—must also be functionally organised in a modular manner. The genotype-phenotype map lies at the heart of evolutionary systems biology. Recently, it has become popular to define developmental modules in terms of the structure of gene regulatory networks. This approach is inherently limited: gene networks often do not have structural modularity. More generally, the connection between structure and function is quite loose. In this chapter, we discuss an alternative approach based on the concept of dynamical modularity, which overcomes many of the limitations of structural modules. A dynamical module consists of the activities of a set of genes and their interactions that generate a specific dynamic behaviour. These modules can be identified and characterised by phase space analysis of data-driven models. We showcase the power and the promise of this new approach using several case studies. Dynamical modularity forms an important component of a general theory of the evolution of regulatory systems and the genotype-phenotype map they define. | Dynamical Modularity of the Genotype-Phenotype Map | 10.1007/978-3-030-71737-7_11 |
2021-01-01 | A friction damper (FD) can be an effective energy dissipation device for the seismic protection of structural systems. The level of the constant slip force in a passive FD is a critical design parameter, since it will determine the amount of energy dissipated by the damper in an earthquake. A passive FD will behave like a bracing without energy dissipation capacity when the seismic load is lower than the slip force, while the amount of energy dissipated by the passive FD may not be sufficient if the seismic load is much higher than the designed slip force. In order to improve the control performance, a novel leverage-type variable friction damper (LVFD), whose friction force can be adjusted in real time through a leverage mechanism, depending on the earthquake intensity, is introduced in this study. Different from most existing variable FDs that are usually controlled by adjusting the clamping force applied on friction interfaces, the LVFD system combines a passive FD and a leverage mechanism with a movable central pivot. By simply controlling the pivot position, the frictional damping force generated by the LVFD can be adjusted in real time; therefore, precision control of the clamping force, which is usually substantially larger than the slip force, can be avoided. Furthermore, by considering 16 different ground motions with two different intensities, the adaptive feature and control performance of the LVFD for the seismic protection of a 3-story shear structure is further demonstrated numerically, by comparing with those of its counterpart passive FD systems. | A Leverage-Type Variable Friction Damper for Seismic Protection of Structural Systems | 10.1007/978-981-15-8079-6_78 |
2021-01-01 | The STARDAMP software tool enables prediction and assessment of the performance of wheel and rail dampers. This paper supports ongoing validation and testing efforts by examining the use of STARDAMP in relation to assessing the performance of rail dampers on slab track with highly resilient fasteners. This track type is common on transit systems that are increasingly considering rail dampers for noise control. The normal assessment approach of summing a measured undamped TDR with a damped short rail DR may under-predict the rail damper benefit for some slab tracks. Alternatively the damper effect may be estimated by summing the predicted undamped TDRs with a damped DR from a short rail test, supported by investigations of the dominant rolling noise frequencies. The STARDAMP slab track model may limit the accuracy of rolling noise prediction by ignoring baseplate dynamic effects. | Track Decay Rate Analysis and Rail Damper Noise Reduction for Slab Tracks | 10.1007/978-3-030-70289-2_69 |
2021-01-01 | This paper introduces a novel adaptive inverse multilayer T-S fuzzy controller (AIMFC) optimally identified with an optimization soft computing algorithm available for a class of robust control applied in uncertain nonlinear SISO systems. The parameters of multilayer T-S fuzzy model are optimally identified by the differential evolution (DE) algorithm to create offline the inverse nonlinear plant with uncertain coefficients. Then, the adaptive fuzzy-based sliding mode surface is applied to ensure that the closed-loop system is asymptotically stable in which the stability is satisfied using Lyapunov stability concept. The control quality of the proposed AIMFC algorithm is compared with the three recent advanced control algorithms applied in the Spring-Mass-Damper (SMD) benchmark system. Simulation and experiment results with different control parameters show that the proposed algorithm is better than the inverse fuzzy controller and the conventional adaptive fuzzy controller comparatively applied in both SMD system and the coupled-liquid tank system with the performance index using the least mean squares (LMS) error, which is investigated to demonstrate the efficiency and the robustness of the proposed AIMFC control approach. | Adaptive inverse multilayer fuzzy control for uncertain nonlinear system optimizing with differential evolution algorithm | 10.1007/s10489-020-01819-9 |
2021-01-01 | Necroptosis is a regulated form of necrosis that depends on receptor-interacting protein kinase (RIPK)3 and mixed lineage kinase domain-like protein (MLKL). Necroptotic cells release a variety of cellular and nuclear factors, referred to as danger-associated molecular patterns (DAMPs). We recently developed a förster resonance energy transfer (FRET) biosensor, termed SMART (a sensor for MLKL activation based on FRET). SMART comprises a fragment of MLKL, and it monitors necroptosis, but not apoptosis or necrosis. We performed live-cell imaging for secretion activity (LCI-S) to observe the release of high-mobility group box 1 (HMGB1) from necroptotic cells at single-cell resolution. Moreover, we combined SMART and LCI-S imaging techniques and found two different modes of HMGB1 release from necroptotic cells. Thus, SMART and LCI-S are valuable tools for investigating intimate cross talk between necroptosis and DAMP release at single-cell resolution. | Time-Lapse Imaging of Necroptosis and DAMP Release at Single-Cell Resolution | 10.1007/978-1-0716-1258-3_29 |
2021-01-01 | There are numerous applications to evaluate the damage caused by subsynchronous resonance (SSR) to a turbine-generator shaft. Despite multiple applications, there are relatively few studies on shaft misalignment in the literature. In this paper, stresses in the existing turbine-generator shaft due to subsynchronous resonance were studied using finite element analysis (FEA). The 3D finite element model reveals that the most stressed part of the shaft is near the generator terminal. A new nonlinear damping scheme is modeled to reflect the torsional interaction and to suppress the mechanical vibration caused by subsynchronous resonance (SSR). Stresses developed due to the addition of capacitors in the system at high rotational speeds and deformation of the shaft during various modes of oscillations were evaluated. Experimental investigations are carried out in reaction turbine connected to a 3 kVA generator. Simulation is carried out for the experimental setup using ANSYS. According to the simulation results, the damper installed near the generator terminal provides satisfactory damping performance and the subsynchronous oscillations are suppressed. | Dampers to Suppress Vibrations in Hydro Turbine-Generator Shaft Due to Subsynchronous Resonance | 10.1007/978-981-15-4308-1_36 |
2021-01-01 | Research on the core technology has obtained a patent for invention authorization of hydraulic controlled vibration damper with vibration energy absorption. The hydraulic cylinder structure is designed by the principle of liquid incompressibility. The hydraulic circuit increases and the gap distance changes due to the movement of balance plate under the pressure difference between the two chambers of the hydraulic cylinder. With the damping effect and pressure drop of liquid flow, the purpose of efficient vibration reduction is achieved by absorbing the vibration energy into heat. The invention patent of the self-tuning hydraulic vibration energy absorption is suitable for the situations with high speed, precision, light load and small and medium energy level. For example, the measurement accuracy is improved by vibration reduction with dynamic weighing in instrument. And the processing precision is achieved by vibration reduction for precision machine tools. The invention patent of high power hydraulic emergency energy absorption for multistory parking area is applicable to the conditions with high altitude fall, impact, collision and large-scale energy absorption, such as elevator emergency energy absorption safety devices, the bases of forging press machine tools, high-speed rail locomotive vehicle chassis, and so on. | Research and Development of Hydraulic Controlled Vibration Damper with Vibration Energy Absorption | 10.1007/978-3-030-72795-6_39 |
2020-12-04 | The implementation of numerical squeeze film damper (SFD) models into rotordynamic study is a time-consuming work since it is challenging to efficiently calculate the SFD forces under a variety of different situations. This paper proposes a new scheme to incorporate SFD models into rotordynamic analysis. A polynomial interpolation technique is introduced to solve for SFD forces under different operating conditions. To evaluate the efficiency of the proposed method, a rotor shaft supported by an SFD at either end has been selected for vibration study, where a finite element model is created to describe the system. The transient response of the rotor at a steady state rotational speed is presented for an open SFD application. In addition, the frequency response is evaluated by the slow acceleration scheme. The prediction resulted from the interpolation method shows excellent agreement with that from the direct method. Moreover, the proposed method significantly reduces the simulation time for application using advanced SFD models. | Vibration analysis of rotor-bearing system using polynomial interpolation for squeeze film damper models | 10.1007/s42452-020-03783-y |
2020-12-01 | In this paper, we introduce a generalization of Lyapunov’s direct method for dynamical systems with fractional damping. Hereto, we embed such systems within the fundamental theory of functional differential equations with infinite delay and use the associated stability concept and known theorems regarding Lyapunov functionals including a generalized invariance principle. The formulation of Lyapunov functionals in the case of fractional damping is derived from a mechanical interpretation of the fractional derivative in infinite state representation. The method is applied on a single degree-of-freedom oscillator first, and the developed Lyapunov functionals are subsequently generalized for the finite-dimensional case. This opens the way to a stability analysis of nonlinear (controlled) systems with fractional damping. An important result of the paper is the solution of a tracking control problem with fractional and nonlinear damping. For this problem, the classical concepts of convergence and incremental stability are generalized to systems with fractional-order derivatives of state variables. The application of the related method is illustrated on a fractionally damped two degree-of-freedom oscillator with regularized Coulomb friction and non-collocated control. | The direct method of Lyapunov for nonlinear dynamical systems with fractional damping | 10.1007/s11071-020-05962-3 |
2020-12-01 | Natural slopes consist of non-homogeneous soil profiles with distinct characteristics from slopes made of homogeneous soil. In this study, the limit equilibrium modified pseudo-dynamic method is used to analyze the stability of two-layered c-ϕ soil slopes in which the failure surface is assumed to be a logarithmic spiral. The zero-stress boundary condition at the ground surface under the seismic loading condition is satisfied. New formulations derived from an analytical method are proposed for the predicting the seismic response in two-layered soil. A detailed parametric study was performed in which various parameters (seismic accelerations, damping, cohesion, and angle of internal friction) were varied. The results of the present method were compared with those in the available literature. The present analytical analysis was also verified against the finite element analysis results. | New pseudo-dynamic analysis of two-layered cohesive-friction soil slope and its numerical validation | 10.1007/s11709-020-0679-3 |
2020-12-01 | An analytical solution for the problem of an immersed flexible and vertical heavy rod subjected to a vertical top motion is developed using the multiple scales method directly applied to the partial differential equations of motion. The obtained results show good agreement with a numerical solution obtained using the finite element method for a study case. The analytical solution is then used to carry out some sensitivity studies. The effects of the structural nonlinearities, hydrodynamic and structural damping terms are investigated. It is shown that the nonlinearities play a role in defining the frequency of the top motion that causes the maximum amplitude of response, but not the value of the amplitude itself. In turn, the major role played by the hydrodynamic damping in defining the response amplitude is addressed. It is also shown that the structural damping have an important effect on the response amplitude even in the case of small damping ratio. This occurs due to the combined effect of the structural with the hydrodynamic damping. Finally, it is pointed out that small differences in the structural damping ratio can lead to significant differences in the response amplitude. | A detailed study of the parametric excitation of a vertical heavy rod using the method of multiple scales | 10.1007/s11012-020-01247-6 |
2020-12-01 | Abstract Damping methods for milling vibrations are studied. A mathematical model is developed for the ratio between the amplitude of the forced vibrations and the parameters of the perturbing pulse. The range of pulsed load parameters corresponding to stable milling is established. The parameters of cylindrical mills corresponding to minimum vibrational amplitude are determined. | Stable Milling | 10.3103/S1068798X20120217 |
2020-12-01 | In this study, a coke-shaped steel damper that exhibits in-plane resistance is introduced as a passive damper. The double-coke damper presented in this study applies the concept of reduced beam sections to increase the ductility in the case of a prolonged earthquake. Multiplastic hinges are placed on each strip by setting the radius-cut section. The fatigue performance of the damper during earthquake loading is verified through a constant cyclic loading test. The results indicate that, as the number of plastic hinges inside the strip increases, the damper ductility increases, producing a stable hysteresis graph. In addition, a new equation that considers the damage index using parameters such as maximum strength and effective stiffness is proposed, and the experimental results are found to be in excellent agreement with the number of failure cycles obtained from the proposed model. By comparing the results of applying the proposed equation with the machine learning results, it is demonstrated that machine learning can be used for estimating the damper performance against the fatigue of the resistive cycle. | Modified Low-Cycle Fatigue Estimation Using Machine Learning for Radius-Cut Coke-Shaped Metallic Damper Subjected to Cyclic Loading | 10.1007/s13296-020-00377-7 |
2020-12-01 | In this paper, we study the Riemann problem for a 2 × 2 $2 \times 2$ nonstrictly hyperbolic system with linear damping. We introduce the special time-dependent viscosity to obtain approximate solutions. Therefore, we solve the Riemann problem ( 1.1 )–( 1.2 ) by limiting viscosity approach. | Riemann Problem for a
2
×
2
$2 \times 2$
Hyperbolic System with Linear Damping | 10.1007/s10440-020-00350-w |
2020-12-01 | This paper combines the nonlinear Udwadia-Kalaba control approach with the Assumed Mode Method to model flexible structures and derives an attitude controller for a spacecraft. The study case of this paper is a satellite with four flexible cantilever beams attached to a rigid central hub. Two main topics are covered in this paper. The first one is the formulation of the equation of motion and the second one is the nonlinear controller design. The combination of these two techniques is able to provide a controller that damps the vibration of a flexible structure while achieving the desired rigid-motion state. | Nonlinear Controller Design for a Flexible Spacecraft | 10.1007/s40295-020-00234-z |
2020-12-01 | We consider the problem of maximal regularity for non-autonomous second order Cauchy problems $$\begin{aligned} \left\{ \begin{array}{l} u''(t)+{\mathcal {B}}(t)u'(t)+{\mathcal {A}}(t)u(t)=f(t) \quad t\text{-a.e.} \\ u(0)=u_{0},\quad u'(0)=u_{1}. \end{array} \right. \end{aligned}$$ u ′ ′ ( t ) + B ( t ) u ′ ( t ) + A ( t ) u ( t ) = f ( t ) t -a.e. u ( 0 ) = u 0 , u ′ ( 0 ) = u 1 . Here, the time dependent operator $${\mathcal {A}}(t)$$ A ( t ) is bounded from the Hilbert space $${\mathcal {V}}$$ V to its dual space $${\mathcal {V}}'$$ V ′ and $${\mathcal {B}}(t)$$ B ( t ) is associated with a sesquilinear form $$\mathfrak {b}(t,\cdot ,\cdot )$$ b ( t , · , · ) with domain $${\mathcal {V}}$$ V . We prove maximal $$L^p$$ L p -regularity results and other regularity properties for the solutions of the above equation under minimal regularity assumptions on the operators. Our result is motivated by boundary value problems. | Maximal regularity for the damped wave equations | 10.1007/s41808-020-00084-8 |
2020-12-01 | Consider the following damped vibration system $$\begin{aligned} \ddot{u}(t)+q(t)\dot{u}(t)-L(t)u(t)+\nabla W(t,u(t))=0,\ \forall t\in \mathbb {R} \qquad \qquad (1) \end{aligned}$$ u ¨ ( t ) + q ( t ) u ˙ ( t ) - L ( t ) u ( t ) + ∇ W ( t , u ( t ) ) = 0 , ∀ t ∈ R ( 1 ) where $$q\in C(\mathbb {R},\mathbb {R})$$ q ∈ C ( R , R ) , $$L\in C(\mathbb {R},\mathbb {R}^{N^{2}})$$ L ∈ C ( R , R N 2 ) and $$W\in C(\mathbb {R}\times \mathbb {R}^{N},\ \mathbb {R})$$ W ∈ C ( R × R N , R ) . Applying a Symmetric Mountain Pass Theorem, we prove the existence of infinitely many fast homoclinic solutions for (1) when L is not required to be either uniformly positive definite or coercive and W satisfies some general super-quadratic conditions at infinity in the second variable but does not satisfy the classical superquadratic growth conditions at infinity. | Infinitely many fast homoclinic solutions for a class of superquadratic damped vibration systems | 10.1007/s41808-020-00052-2 |
2020-12-01 | The aim of this paper is to study bounds for blow-up time to the following viscoelastic hyperbolic equation of Kirchhoff type with initial-boundary value condition: | u t | ρ u t t − M ( ∥ ∇ u ∥ 2 2 ) Δ u + ∫ 0 t g ( t − τ ) Δ u ( τ ) d τ + | u t | m ( x ) − 2 u t = | u | p ( x ) − 2 u . $$ |u_{t}|^{\rho }u_{tt}-M(\|\nabla u\|_{2}^{2})\Delta u+\int _{0}^{t}g(t- \tau )\Delta u(\tau )d\tau +|u_{t}|^{m(x)-2}u_{t}=|u|^{p(x)-2}u. $$ Compared with constant exponents, it is difficult to discuss the above problem due to the existence of a gap between the modular and the norm. The authors construct suitable function spaces to discuss the upper bound for blow-up time with positive initial energy by means of a differential inequality technique. In addition, lower bounds for blow-up time in different range of exponent are obtained. These improve and generalize some recent results. | Bounds for Blow-up Time to a Viscoelastic Hyperbolic Equation of Kirchhoff Type with Variable Sources | 10.1007/s10440-020-00357-3 |
2020-12-01 | Aiming to isolate disturbance vibration for heavy machines with low frequency, a novel hydro-pneumatic vibration isolator with high-static and low-dynamic (HSLD) stiffness is proposed, which contains bellows structure as elastic element and pressurized gas and incompressible liquid as working media. Due to that the natural frequency of isolation system with such isolator is close to zero and loading capacity can be adjusted by the gas pressure, the proposed device is termed as pneumatic near-zero frequency (NZF) vibration isolator. To obtain the mathematical model of isolator’s stiffness, the quasi-static derivation based on gas state equation is carried out first. Results prove that the presented isolator possesses ideal high-static and low-dynamic stiffness, which is also verified by the experimental data measured by a quasi-static test. The proportion of gas volume to total volume of gas and liquid media, respectively, in bellows and cylinder chambers are significant physical parameters, which dominate the nonlinearity extent of isolator’s stiffness. Different from most existing isolators, the proposed isolator includes fluidic damping and friction damping. The former is expressed by classic square-velocity-type nonlinear model, and the latter is modeled as Coulomb damping. To obtain dynamic response and vibration isolation transmissibility, the harmonic balance method is applied. A direct current term is added in the trial solution, which reflects the asymmetry of dynamic response. In respect of transmissibility analysis, square-velocity nonlinear damping brings a favorable advantage that it can ensure the fine force transmissibility in both resonance region and effective isolation band. This conclusion holds consistently under base motion excitation. Friction damping cannot give the same conclusion. Further comparison with a linear vibration isolator exhibits that the HSLD stiffness characteristics of the NZF isolator breaks through the trade-off between large loading capacity and small static deformation, and the square nonlinearity of fluid damping is able to overcome the dilemma that weak linear vicious damping is beneficial for isolation performance within the effective isolation frequency band, but cannot suppress resonance amplitude and transmissibility. And the experimental transmissibility is in good agreement with the analytical result. Besides, the influences of excitation variation on isolation performance are estimated theoretically. Due to the hardening stiffness, overload acceleration will cause the increase in linearized natural frequency of NZF isolator system, and thus, isolation effectiveness will be reduced. | Dynamics and isolation properties for a pneumatic near-zero frequency vibration isolator with nonlinear stiffness and damping | 10.1007/s11071-020-06063-x |
2020-12-01 | 将有限元与质量集中法相结合, 建立了具有橡胶阻尼环滚动轴承支承的柔性转子的动力学模型. 在该模型中, 转子通过 Timoshenko 梁单元离散建模, 支座和轴承外圈采用质量集中法建模, 同时考虑了转子重力、 不平衡力和非线性轴承力的影响. 动力学方程采用精确积分和 Runge-Kutta 混合数值算法求解. 为了验证建模方法的正确性, 在转子-轴承试验台上进行了理论和实验分析, 发现理论与实验研究的误差率小于 10%; 此外, 还分析了橡胶阻尼环对转子-轴承耦合系统动力学特性的影响, 所得结论与实际情况相吻合. 在此基础上, 分别研究了转速和橡胶阻尼环刚度对耦合系统的分岔和混沌行为的影响. 结果表明, 随着转速的增加, 系统进入混沌状态的路径有激变、 拟周期和间歇性分岔. 然而, 随着橡胶阻尼环刚度的变化, 发现了激变、 拟周期分岔和 Hopf 分岔到混沌的途径. 此外, 轴承间隙对转子系统的动态特性也有影响, 过大的轴承间隙会使系统的周期运动变为混沌; 橡胶阻尼环的刚度对系统的运动有很大的影响. A dynamic model of a flexible rotor supported by ball bearings with rubber damping rings was proposed by combining the finite element and the mass-centralized method. In the proposed model, the rotor was built with the Timoshenko beam element, while the supports and bearing outer rings were modelled by the mass-centralized method. Meanwhile, the influences of the rotor’s gravity, unbalanced force and nonlinear bearing force were considered. The governing equations were solved by precise integration and the Runge-Kutta hybrid numerical algorithm. To verify the correctness of the modelling method, theoretical and experimental analysis is carried out by a rotor-bearing test platform, where the error rate between the theoretical and experimental studies is less than 10%. Besides that, the influence of the rubber damping ring on the dynamic properties of the rotor-bearing coupling system is also analyzed. The conclusions obtained are in agreement with the real-world deployment. On this basis, the bifurcation and chaos behaviors of the coupling system were carried out with rotational speed and rubber damping ring’s stiffness. The results reveal that as rotational speed increases, the system enters into chaos by routes of crisis, quasi-periodic and intermittent bifurcation. However, the paths of crisis, quasi-periodic bifurcation, and Hopf bifurcation to chaos were detected under the parameter of rubber damping ring’s stiffness. Additionally, the bearing gap affects the rotor system’s dynamic characteristics. Moreover, the excessive bearing gap will make the system’s periodic motion change into chaos, and the rubber damping ring’s stiffness has a substantial impact on the system motion. | Dynamic analysis of a flexible rotor supported by ball bearings with damping rings based on FEM and lumped mass theory | 10.1007/s11771-020-4510-z |
2020-12-01 | Purpose The analysis of free vibrations of axisymmetric functionally graded isotropic viscothermoelastic hollow cylinder has been investigated in the radial direction. The material of viscothermoelastic cylinder has been assumed to be graded in the radial direction due to simple exponent law. The governing partial differential equations are transformed into ordinary differential equations with th e help of time harmonic vibrations. Methods The extended power series solution of matrix Fröbenius method has been applied to derive the analytical solutions for stresses, displacement and temperature change. The frequency equations of various types of modes of vibrations have been derived in a compact form. To investigate the numerical features of vibrations, the analytical results of frequency equations have been further solved with the help of fixed-point numerical iteration technique using MATLAB software tools. The polymethyl methacrylate material has been used for numerical computations. Results and Conclusions The numerical results have been presented for frequency shift, natural frequencies, thermoelastic damping, stresses, displacement and variation of temperature. With the increase in the values of grading index, variation of vibrations in field functions go on decreasing. The numerical results show alternate variations in homogenous materials in contrast to inhomogeneous materials. The behaviour of deformation, temperature change, frequency shift and thermoelastic damping have been monitored (increase or decrease) with the help of grading index (in-homogeneity parameter). | Analysis of Free Vibrations of Axisymmetric Functionally Graded Generalized Viscothermoelastic Cylinder Using Series Solution | 10.1007/s42417-019-00178-1 |
2020-12-01 | The friction at the contact surfaces of a vehicle body vibration damper, which are moved relatively to each other, influences its transmission behavior at the start of movement (breakaway force) as well as with excitation signals of higher velocity and thus has an impact on the comfort properties of the damper. According to Vibracoustic (Die wichtigsten Kriterien für deutsche Autofahrer beim Autokauf, Springer Fachmedien Wiesbaden GmbH, Wiesbaden, 2019), for most German drivers (63%) comfort (in addition to brand and appearance) before driving dynamics (53%) and environmental compatibility (48%) is the most important criteria when evaluating a new car, which explains the importance of this vehicle characteristics. Furthermore, the friction is present with any relative movement of the damper and is, therefore, relevant for the design of the damper and the associated vertical dynamics. The friction is generally determined in the fully assembled state of the damper, including oil filling and gas pressure at a very low movement velocity to eliminate the influence of the damping force. This measurement method allows no or only inadequate statements about the friction behavior at, e.g. more dynamic excitation scenarios. As a result, the aim should be to characterize the friction properties without the influence of hydraulic damping at the start of movement or reversal of movement, as well as at higher movement velocities. Another goal is to evaluate the influence of the internal pressure of the damper on its friction behavior. The test damper used here is a commercially available monotube damper that has been modified in accordance with the requirements for these tests. The results shown below can be used as starting variables for further investigations for the targeted optimization of the friction properties and thus for the improvement of driving comfort. The reduction in damper friction promises an increase in comfort due to the improved decoupling of the vehicle body from the road excitation. Furthermore, the data obtained enable the level of detail of simulation models to be increased and serve as a basis for comparing different friction pairings and contact surfaces in the damper. For the substitution of coatings (chrome-free piston rods → environmental protection) or tube materials (aluminum matrix composites → lightweight construction) as well as for changes in the surface structure and roughness, the results enable an evaluation of the friction properties compared to conventional dampers and the adjustment of the friction pairings in the sense of the best possible functionality. | Analysis and characterization of the friction of vehicle body vibration dampers | 10.1007/s41104-020-00060-3 |
2020-12-01 | This paper describes how overconsolidation affects the shear modulus at small strain ( G _0) for peat, as well as the strain dependence of the shear modulus ( G ) and the damping ratio ( h ) of overconsolidated peat. Hayashi et al. (Soils Found 52(2):299–311, 2012) pointed out that peat deposits tend to be overconsolidated as a result of seasonal changes in ground water levels, even when they have not been subjected to artificial stress. Therefore, it is necessary to carefully examine how overconsolidation affects G _0 and the strain dependence of G and h in order to determine these dynamic characteristics for peat under in-situ stress. In this study, cyclic torsional shear tests were conducted on peat samples with a stress history of overconsolidation in order to study the effect of overconsolidation in detail. Peat samples with a wide range of physical properties were collected in Hokkaido, Japan. This paper presents the relationship between the G _0 and the overconsolidation ratio ( OCR ), and proposes an experimental equation that expresses G _0 as a function of the ignition loss of peat and the OCR . The paper finds that the overconsolidation stress history does not significantly affect the strain dependence of G or h for peat. | Shear Modulus and Damping of Peat Subjected to Overconsolidation Stress History | 10.1007/s10706-020-01445-9 |
2020-12-01 | This study proposes Series Vectorial Compensator (SVeC) with Power System Stabilizers (PSSs) to mitigate oscillations in a network. SVeC is a novel Flexible Alternating Current Transmission Systems (FACTS) series device and is generally used for controlling the reactance of a line by varying the duty ratio of ac link. The optimal techniques based on state feedback for Coordinated Control (COC) are used to improve the dynamic stability. So, the first Optimal State Feedback Controller (OSFC) based on quadratic concept and second Optimal Sliding Mode Controller (OSMC) design on the sliding surface are used to develop the control strategy to COC of SVeC with PSSs. The analyses with proposed controllers are checked on Western System Coordinating Council (W.S.C.C) test system under nominal load operation. The damping characteristics of OSMC are compared with OSFC for COC and without control. The results show that system damping can be significantly improved by the OSMC compared to OSFC and without control. | Optimal Control Techniques Design to the Coordinated Control of Series Vectorial Compensator with Power System Stabilizers | 10.1007/s40031-020-00495-0 |
2020-12-01 | Abstract— At present, mechanics of damage media, which studies both the stress–strain state of media and the damage accumulation in materials, is being actively developed. In this study, a self-consistent problem, including the dynamic equation of the theory of elasticity and the kinetic equation of damage accumulation in a material, is formulated for an isotropic elastic half-space with damage in the material. It is assumed that damage is distributed uniformly over the medium. The surface-wave propagation along the free boundary of damaged half-space has been investigated. The wave propagates horizontally and decays in the vertical direction. All processes are assumed to be homogeneous along the third axis. It is shown that a self-consistent system with boundary conditions expressing the absence of stress at the half-space boundary is reduced to a complex dispersion equation in this case. In the limiting case (damage-free material), the obtained dispersion equation is reduced to the classical dispersion equation for a Rayleigh wave in the polynomial form (the surface wave propagates along the half-space boundary without dispersion and attenuation). If damage is present in the medium, the surface wave attenuates along the propagation direction, and low-frequency disturbances have frequency-dependent dissipation and dispersion. It is shown that dispersion has abnormal character. It is established that, in the high-frequency region, the phase and group velocities increase and decrease, respectively, with an increase in the damage coefficient. At low frequencies, both velocities increase with a decrease in the damage coefficient. | Influence of Material Damage on the Rayleigh Wave Propagation along Half-Space Boundary | 10.1134/S0021894420070020 |
2020-12-01 | This study proposes a hybrid control methodology that combines tuned liquid damper (TLD) and active mass damper (AMD) to suppress vibrations of multi-story building structure effectively. To this end, a dynamic model that can predict the vibration of multi-story building structure coupled with TLD and AMD is derived using the energy approach. The TLD that is mainly designed to suppress the main natural mode is developed with a multi-degree-of-freedom model to investigate the effect of the TLD on natural modes of structure numerically. The AMD is an active vibration controller that can suppress remaining resonant peaks, including ones resulting from the application of the TLD as well as other higher modes of interest. In this way, the proposed control can utilize the advantages of TLD and AMD simultaneously. We set up an experimental apparatus to verify the performance of the hybrid control methodology. The numerical and experimental results show that the proposed hybrid control method can successfully suppress the vibrations of multi-story building structure. The dynamic model derived in this study can also accurately predict the actual behavior of the system. | Vibration control of multi-story building structure by hybrid control using tuned liquid damper and active mass damper | 10.1007/s12206-020-1105-4 |
2020-12-01 | A limited gap between closely spaced structural parts may induce internal pounding in seismically isolated structures, because of notable displacement at the level of the isolation system under severe earthquakes. A gap between a fixed-base elevator shaft and the surrounding building is presented here with reference to a reinforced concrete building located in the Sicilian town of Augusta. The building, comprising a basement and three storeys above the ground level, is seismically isolated at the top of rigid columns in the basement with a hybrid isolation system including elastomeric and sliding bearings, while a steel framed elevator shaft crosses the isolation level. Despite the gap, internal pounding may occur at all levels of the superstructure when the elevator with maximum load stops at the upper floors. To reduce structural pounding effects, a magnetic damped link (MDL) between adjacent corners of the elevator and the surrounding building is proposed. This is obtained as an in parallel combination of an eddy current damped link (ECDL) and an elastic helicoidal spring, and occupies less space than traditional passive dampers and transmits considerably less forces compared to a rigid link configuration. Specifically, an ECDL consists of an outer cylindrical copper tube, as conductor, and an inner tube, equipped with an array of axially magnetized and ring-shaped permanent magnets separated by iron pole pieces, as mover. The relative motion between conductor and magnets, during seismic loading, induces an eddy current producing electromagnetic damping. Given that viscoelastic linear behaviour can be hypothesized for the MDL, a simplified iterative design procedure of the ECDL is proposed, with optimization of the thickness and radius of the magnets, thereby enhancing magnetic flux and energy dissipation. The directionality of the near-fault ground motions is investigated through nonlinear seismic analysis, comparing no connection with four configurations of the interconnection: i.e., flexible and rigid elastic links, viscous and magnetic damped links. | Magnetic damped links to reduce internal seismic pounding in base-isolated buildings | 10.1007/s10518-020-00961-6 |
2020-12-01 | The study discusses the potential use of geosynthetics in isolating the ground vibration emanated from the vertical mode dynamic excitation. A field study was conducted to investigate the screening efficacy of reinforced foundation beds. In the field study, vibration was generated using a mechanical oscillator. Four different cases, namely, unreinforced, single layer geogrid, two layers of geogrid, and geocell reinforced cases were considered. The isolation efficacy was studied in terms of peak particle velocity and amplitude reduction ratio. The resonance response of different reinforced conditions was studied by varying the dynamic force, and frequency of the excitation. The effectiveness of the reinforced soil system was examined by comparing the performance of the reinforced system with the unreinforced system. From the field test results, a significant reduction in ground vibration was observed in the presence of geosynthetics. Maximum reduction was observed in the case of geocell reinforced condition as compared to other cases. In the presence of geocell, peak particle velocity and resonant amplitude were reduced by 48% and 61% respectively, as compared to the unreinforced condition. Similarly, 98% improvement in the stiffness of the foundation bed was observed in the presence of geocells. Further, the dynamic response obtained from the field study was compared with the mass spring dashpot analogy. The dynamic response predicted from the analytical study has shown reasonable agreement with the field test results. From the analytical comparison, 2.6 times improvement in the damping ratio of the foundation bed was noticed due to the inclusion of geocell reinforcement. | Isolation Prospects of Geosynthetics Reinforced Soil Beds Subjected to Vibration Loading: Experimental and Analytical Studies | 10.1007/s10706-020-01447-7 |
2020-12-01 | Purpose The dynamic response of pressure monitoring circuits must be evaluated to obtain true invasive blood pressure values. Since Gardner’s recommendations in 1981, the natural frequency and the damping coefficient have become standard parameters for anesthesiologists. In 2006, we published a new dynamic response evaluation method (step response analysis) that can plot frequency spectrum curves instantly in clinical situations. We also described the possibility of the defect of the standard parameters. However, the natural frequency and the damping coefficient are considered the gold standard and are even included in a major anesthesiology textbook. Therefore, we attempted to clarify the issues of these parameters with easy-to-understand pressure waves and basic numerical formulae. Methods A blood pressure wave calibrator, a single two-channel pressure amplifier, and personal computer were used to analyze blood pressure monitoring circuits. All data collection and analytical processes were performed using our step response analysis program. Results We compared two different circuits with almost the same natural frequency and damping coefficients. However, their amplitude spectrum curves and input/output pressure values were significantly different. Conclusions The natural frequency and the damping coefficient are inadequate for the dynamic response evaluation. These parameters are primarily obtained from the phase spectrum curve and not from the amplitude spectrum curve. We strongly recommend an evaluation using the amplitude spectrum curve with our step response analysis method. It is crucial to maintain an amplitude gain of 1 (input amplitude = output amplitude) in the pressure wave frequency range of 0–20 Hz. | Why the natural frequency and the damping coefficient do not evaluate the dynamic response of clinically used pressure monitoring circuits correctly | 10.1007/s00540-020-02843-2 |
2020-12-01 | Employing the methods of separation of variables and matched eigenfunction expansions for velocity potential, analytical solutions are proposed for a water wave radiation problem of a floating semi-porous compound cylinder in finite ocean depth. The configuration of the semi-porous compound cylinder is such that it consists of an impermeable inner cylinder rising above the free surface and a coaxial truncated porous cylinder around the lower part of the inner cylinder with the top of the porous cylinder being impermeable. The condition on the porous boundary is defined by applying Darcy’s law as in Williams et al. (Ocean Eng 27:1–28, 2000) . The translational motions in the x - and z -directions, i.e., surge and heave motions, are investigated. A mathematical model is developed which can be considered as an extension of a number of the earlier works, e.g., Kokkinowrachos et al. (Ocean Eng 13:505–538, 1986) and Calisal and Subancu (Ocean Eng 11(5):529–542, 1984), in which significance of porosity of the structure was neglected. Numerical investigation is taken up here in order to examine the influence of submerged depth, radii, porous coefficient, and water depth on added mass and radiation damping, two most important entities in radiation problems, with respect to surge and heave motions. It is found that the variation of porous coefficient, radii, and depth has a significant influence on the added mass and damping coefficients for the semi-porous compound cylinder. The added mass is found not sufficiently affected by lower values of porous coefficient G , but exhibits significant variation corresponding to higher values of G . Another important observation is that the damping coefficients oscillate alternately between negative and positive values which can be attributed to coupled behavior between different motions. The results establish that an appropriate optimal ratio of various parameters may be considered in designing ocean structures with minimum adverse hydrodynamic effect. The effectiveness of the present model is validated by comparing it with an available result which shows an excellent agreement. | Hydrodynamic coefficients for a floating semi-porous compound cylinder in finite ocean depth | 10.1007/s40868-020-00086-0 |
2020-12-01 | A high-speed rotating rotor system mounted on a moving vehicle is inevitably subjected to parametric excitations and exciting forces induced by base motions. Dynamic characteristics of a rotor-bearing system supported by squeeze-film damper with retainer spring subjected to unbalance and support motions are investigated. Using Lagrange’s principle, equations of motion for rotor system relative to a moving support are derived. Under base excitations, steady-state and transient responses are analyzed by frequency–amplitude curve, waveform, orbit, frequency spectrum, and Poincaré map. Changing with rotating speed or base harmonic frequency, journal motions are analyzed by bifurcation diagram. The results indicate that under base axial rotation, increasing base angular velocity, first two critical speeds decrease but resonant amplitudes increase slightly. The journal whirls around the static eccentricity with noncircular orbit. Under base lateral rotation, critical speeds, and resonant amplitudes remain essentially unchanged, but orbit’s deviation is related to base angular velocity. Excited by base harmonic translation, the integral multiples of fundamental frequency $$k{\varOmega }\left( {k = 1,2} \right)$$ k Ω k = 1 , 2 , base harmonic frequency $${\varOmega}^{z}$$ Ω z , and combined frequencies $$k{\varOmega } \pm j{\varOmega }^{z} { }\left( {k,j = 1,2} \right)$$ k Ω ± j Ω z k , j = 1 , 2 are stimulated, changing the motions from periodic to quasiperiodic. Overall, it provides a flexible approach with good expandability to predict dynamic characteristics of squeeze-film damped rotor system under base motions. | Nonlinear responses and bifurcations of a rotor-bearing system supported by squeeze-film damper with retainer spring subjected to base excitations | 10.1007/s11071-020-06052-0 |
2020-12-01 | The presented work deals with nonlinear dynamics of a three degree of freedom system with a spherical pendulum and a damper of the fractional type. Vibrations in the vicinity of the internal and external resonance are considered. The system consists of a block suspended from a linear spring and a fractional damper, and a spherical pendulum suspended from the block. The viscoelastic properties of the damper are described using the Caputo fractional derivative. The fractional derivative of an order of $$0 < \alpha \le 1$$ 0 < α ≤ 1 is assumed. The impact of a fractional order derivative on the system with a spherical pendulum is studied. Time histories, the internal and external resonance, bifurcation diagrams, Poincaré maps and the Lyapunov exponents have been calculated for various orders of a fractional derivative. Chaotic motion has been found for some system parameters. | Dynamics of a coupled mechanical system containing a spherical pendulum and a fractional damper | 10.1007/s11012-020-01203-4 |
2020-12-01 | Abstract Industrial by product dumped from iron making industry (slag) has been modified by various chemical agents, particularly, paraffin wax, liquid nitrile butadiene rubber (NBR) and silane coating agent. The modified slag powder samples were characterized by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA) and the corresponding differential thermal gravimetric (DTG). As further evidence on the effectiveness of the modification process, the modified slag samples were subjected to attenuated total reflectance infrared spectroscopy (ATR-IR). The potential of the modified slag as reinforcement for unsaturated polyester (UPE) composites were studied. The mechanical and dynamic mechanical properties of the fabricated composites were inspected as a function of modification type. | Modification of Mineral Powder by Various Organic Materials: Their Potential as Reinforcement for Unsaturated Polyester Composites | 10.1134/S1070427220120216 |
2020-12-01 | Applying an exponential damping to seismic wavefield generates artificial low frequencies. Therefore, full waveform inversion (FWI) of such data has a potential to yield long wavelength structures using its artificial low frequencies. If we apply a shifted exponential damping to trace according to the offset distance, it is not trivial to implement the adjoint-state method for FWI. Applying a non-shifted exponential damping, or what I refer to as a stationary exponential damping, to all traces, we can accommodate the adjoint-state method; however, the time-domain FWI using the L2 norm of data misfit might fail in updating subsurface velocity model since a stationary exponential damping incurs an exponential-decrease of the amplitudes along offset axis. To nullify this adverse effect in retrieving subsurface velocity model, I suggest the global correlation objective function for FWI of exponentially damped wavefield instead of the L2 treatment. | Full Waveform Inversion of Exponentially Damped Wavefield Using the Global-Correlation Norm | 10.1007/s00024-020-02593-y |
2020-12-01 | In this study, we have generalized the fractional action integral by using the Saigo-Maeda fractional operators defined in terms of the Appell hypergeometric function of two variables , F _3( a , a ′, β , β ′; γ ; z , ζ ) with complex parameters. We have derived the associated Euler-Lagrange equation and we have studied the harmonic oscillator problem. We have proved that a PT -symmetric quantum-mechanical Hamiltonian characterized by real and discrete spectra is obtained although the system is characterized by complex trajectories. The associated thermodynamical properties were discussed and it was revealed the entropy of the quantum system decreases with time toward an asymptotically positive value similar to what is observed in quantum Maxwell demon. | Saigo-Maeda Operators Involving the Appell Function, Real Spectra from Symmetric Quantum Hamiltonians and Violation of the Second Law of Thermodynamics for Quantum Damped Oscillators | 10.1007/s10773-020-04627-6 |
2020-12-01 | The effect of ultrasonic impact treatment (UIT) on the damping capacity of pure magnesium is revealed in this paper. The results show that after UIT, the metal underwent dynamic plastic deformation, the damping capacity of pure magnesium was greatly improved, however, as the UIT time and current intensity increased, the damping capacity of the impacted samples are decreased. Two internal friction peaks have been obtained in all tested samples, P _1 is considered to be related to the interaction between dislocations and weak pinners, and P _2 is caused by the grain boundaries sliding. After the UIT process, those internal friction peaks shift to a higher temperature, with the peak height decrease. The change in damping capacity is believed to be related to the increase in dislocation density and the number of vacancies and grain boundaries. | Study on Improving Damping Capacity of Pure Magnesium by Ultrasonic Impact Treatment | 10.1007/s11665-020-05249-z |
2020-12-01 | Recently, the construction of similar high-rise buildings has increased due to the increasing population. Moreover, due to space constraints, these structures are being built next to each other. When such tall buildings are located in high seismic zones, earthquake protection becomes essential. There have been many studies on vibration control by connecting dampers to adjacent dissimilar buildings. However, reviews with specific recommendations on damper connections to adjacent similar buildings are found to be scarce. This study aims to control the building vibration that is dynamically similar and adjacent to each other through damper connections. In this study, two adjacent ten-storied, dynamically similar RC buildings are considered. The buildings are modeled with shear frame and lumped mass for efficient yet straightforward analysis. The idealized shear buildings were connected with viscoelastic dampers using different damper configurations and then subjected to seven seismic ground motions. A numerical integration technique is used to obtain the seismic response, and a single objective particle swarm optimization technique is employed to optimize the position of dampers. The viscoelastic dampers provided at their optimal locations improved the seismic performance of coupled buildings in an economical way. | Vibration Control of Dynamically Similar Buildings Optimally Connected by Viscoelastic Dampers | 10.1007/s40030-020-00466-0 |
2020-12-01 | Constrained fourth-order latent differential equation (FOLDE) models have been proposed (e.g., Boker et al. 2020 ) as alternative to second-order latent differential equation (SOLDE) models to estimate second-order linear differential equation systems such as the damped linear oscillator model. When, however, only a relatively small number of measurement occasions T are available (i.e., $$T=50$$ T = 50 ), the recommendation of which model to use is not clear (Boker et al. 2020 ). Based on a data set, which consists of $$T=56$$ T = 56 observations of daily stress for $$N=44$$ N = 44 individuals, we illustrate that FOLDE can help to choose an embedding dimension, even in the case of a small T . This is of great importance, as parameter estimates depend on the embedding dimension as well as on the latent differential equations model. Consequently, the wavelength as quantity of potential substantive interest may vary considerably. We extend the modeling approaches used in past research by including multiple subjects, by accounting for individual differences in equilibrium, and by including multiple instead of one single observed indicator. | A Note on the Usefulness of Constrained Fourth-Order Latent Differential Equation Models in the Case of Small T | 10.1007/s11336-020-09738-x |
2020-12-01 | Non-linear dynamic model of a cable–mass system with a transverse tuned mass damper is considered. The system is moving in a vertical host structure therefore the cable length varies slowly over time. Under the time-dependent external loads the sway of host structure with low frequencies and high amplitudes can be observed. That yields the base excitation which in turn results in the excitation of a cable system. The original model is governed by a system of non-linear partial differential equations with corresponding boundary conditions defined in a slowly time-variant space domain. To discretise the continuous model the Galerkin method is used. The assumption of the analysis is that the lateral displacements of the cable are coupled with its longitudinal elastic stretching. This brings the quadratic couplings between the longitudinal and transverse modes and cubic nonlinear terms due to the couplings between the transverse modes. To mitigate the dynamic response of the cable in the resonance region the tuned mass damper is applied. The stochastic base excitation, assumed as a narrow-band process mean-square equivalent to the harmonic process, is idealized with the aid of two linear filters: one second-order and one first-order. To determine the stochastic response the equivalent linearization technique is used. Mean values and variances of particular random state variable have been calculated numerically under various operational conditions. The stochastic results have been compared with the deterministic response to a harmonic process base excitation. | Non-linear dynamic response of a cable system with a tuned mass damper to stochastic base excitation via equivalent linearization technique | 10.1007/s11012-020-01169-3 |
2020-11-27 | Abstract Over the past decades, experimental and theoretical studies on gas foil bearings have been conducted extensively. The essence of the operation of these bearings lies in the use of a unique underlying support mechanism, whose properties adapt to current operating conditions. The static and dynamic characteristics of the foil bearing structure depend not only on the geometry of the supporting structure but also on foil material, surface topology, the velocity of contact surfaces, load, etc. While the concept of stiffness is more intuitive and well described in the literature, the evaluation of the damping in foil bearings is not as obvious. The goal of this paper is to improve the understanding of the damping mechanism of the bump-type foil bearing structure under dynamic loads. At the beginning of the paper, the experimental studies of the foil bearing structure in a wide frequency range are discussed. Then, the experimental conditions were reproduced using an advanced numerical model that took into account the geometry of the top and bump foil, contact phenomena and dry friction. A new solution, unprecedented in the existing literature, is the inclusion of static and kinetic friction in the numerical model of the foil bearing structure. The developed numerical model made it possible to determine the system characteristics, including the evaluation of stiffness and damping. An important contribution of this work is the comparison of the results of calculations obtained with the use of an advanced numerical model with the results of experimental research. The paper gives clear guidelines for the experimental and numerical determination of dynamic characteristics for the bump-type foil bearing structure. The presented results of the experimental research can also be used to verify other numerical models. Graphic abstract | Experimental and numerical evaluation of the damping properties of a foil bearing structure taking into account the static and kinetic dry friction | 10.1007/s40430-020-02720-9 |
2020-11-19 | We consider the reduction of parametric families of linear dynamical systems having an affine parameter dependence that allow for low-rank variation in the state matrix. Usual approaches for parametric model reduction typically involve exploring the parameter space to identify representative parameter values and the associated models become the principal focus of model reduction methodology. These models are then combined in various ways in order to interpolate the response. The initial exploration of the parameter space can be a forbiddingly expensive task. A different approach is proposed here that requires neither parameter sampling nor parameter space exploration. Instead, we represent the system response function as a composition of four subsystem response functions that are non-parametric with a purely parameter-dependent function. One may apply any one of a number of standard (non-parametric) model reduction strategies to reduce the subsystems independently, and then conjoin these reduced models with the underlying parameterization to obtain the overall parameterized response. Our approach has elements in common with the parameter mapping approach of Baur et al. (PAMM 14 (1), 19–22 2014 ) but offers greater flexibility and potentially greater control over accuracy. In particular, a data-driven variation of our approach is described that exercises this flexibility through the use of limited frequency-sampling of the underlying non-parametric models. The parametric structure of our system representation allows for a priori guarantees of system stability in the resulting reduced models across the full range of parameter values. Incorporation of system theoretic error bounds allows us to determine appropriate approximation orders for the non-parametric systems sufficient to yield uniformly high accuracy across the parameter range. We illustrate our approach on a class of structural damping optimization problems and on a benchmark model of thermal conduction in a semiconductor chip. The parametric structure of our reduced system representation lends itself very well to the development of optimization strategies making use of efficient cost function surrogates. We discuss this in some detail for damping parameter and location optimization for vibrating structures. | Sampling-free model reduction of systems with low-rank parameterization | 10.1007/s10444-020-09825-8 |
2020-11-18 | In this paper, we consider a viscoelastic wave equation with Balakrishnan–Taylor damping and a delay term. Under suitable assumptions on relaxation functions, we establish general decay result for energy. | General decay result of solutions for viscoelastic wave equation with Balakrishnan–Taylor damping and a delay term | 10.1007/s00033-020-01426-1 |
2020-11-01 | A collision between two bodies is a usual phenomenon in many engineering applications. The most important problem with the collision analysis is determining the hysteresis damping factor or the hysteresis damping ratio. The hysteresis damping ratio is related to the coefficient of restitution. In this paper, an explicit expression is determined for this relation. For this reason, a parametric expression is considered for the relation between the deformation and its velocity of the contact process. This expression consists of two unknown constants. Using the energy balance, a new explicit parametric expression between the hysteresis damping factor and the coefficient of restitution is derived. For determining the unknown constants, the root mean square (RMS) of the hysteresis damping ratio of this new expression with respect to the numerical model is minimized. This new model is completely suitable for the whole range of the coefficient of restitution. So, the new model can be used in the hard and soft impact problems. Finally, three numerical examples of two colliding bodies, the classic bouncing ball problem, the resilient impact damper, and a planar slider–crank mechanism, are presented and analyzed. | A new model of the contact force for the collision between two solid bodies | 10.1007/s11044-020-09732-2 |
2020-11-01 | In this paper, we consider a viscoelastic plate equation in the presence of a strong time-varying delay, namely; $$\begin{aligned} u_{tt}+\Delta ^2 u-\int _0^t g(t-s)\Delta ^2 u(s)ds-\mu _1\Delta u_t-\mu _2\Delta u_t(\cdot ,t-\tau (t))=0. \end{aligned}$$ u tt + Δ 2 u - ∫ 0 t g ( t - s ) Δ 2 u ( s ) d s - μ 1 Δ u t - μ 2 Δ u t ( · , t - τ ( t ) ) = 0 . We proved a general and optimal decay result for the associated energy functional of the system. The following are novel achievements of the present work: A more general relaxation function g with minimal conditions is used, this allowed us to obtain exponential and polynomial decay rates as special cases. Furthermore, our results hold with lesser restriction on the values of $$\mu _1$$ μ 1 and $$\mu _2$$ μ 2 as against previous results which assume that $$|\mu _2|<\sqrt{1-d}\mu _1$$ | μ 2 | < 1 - d μ 1 . This work improves and generalizes previous results in the literature. | Decay estimate for a viscoelastic plate equation with strong time-varying delay | 10.1007/s11565-020-00346-2 |
2020-11-01 | The present study develops the dispersion and attenuation characteristics of Rayleigh wave regulations through a pre-stressed Voigt type viscoelastic strip of finite thickness. The displacement expressions of Rayleigh wave in the strip are introduced. The complex frequency equation of the wave motion is thus obtained. We have studied the effects of initial stress, attenuation coefficients and dissipation factor on the phase and damped velocities simultaneously. | Attenuation and dispersion characteristic of Rayleigh waves in a compressed viscoelastic strip: a comparative study | 10.1007/s40590-020-00279-y |
2020-11-01 | A method for constructing nonstationary vibration equations for electro-viscoelastic composite plates with their active damping is described. The problem is solved in an integral Fourier transform frequency space. To construct a multilayer plate model, a discrete structural approach was used, i.e., the plate is divided through the thickness into computational layers, within which the displacements and electric potentials are approximated by means of quadratic Lagrange polynomials. At the edges of the plate, the Navier conditions are met. The semi-analytical nonstationary vibration equations are derived by means of the variational convolutional Lagrange equation. To represent them in a frequency space, a direct integral Fourier transform is used, which makes it possible to use experimentally determined frequency-dependent complex characteristics directly in calculations of nonstationary vibrations of plates without additional transformations of integral physical relations. Solutions of the problem of active damping of nonstationary vibrations for the frequency images of displacements and electric potentials have been found, their convergence is analyzed. The procedure has been evaluated by analyzing the active damping of nonstationary vibrations of a three-layer edge-hinged square plate under the action of a blast wave impulse. The middle layer is made of a composite material, and the outer electro-viscoelastic layers act as a sensor and an actuator. The active damping of vibrations is provided by connecting these layers of the plate into a negative feedback circuit with the proportional-differential control law. The viscoelastic and electro-viscoelastic characteristics of the materials are taken into account by means of complex elastic, dielectric and piezoelectric moduli. The results of analyzing the active damping of nonstationary vibrations of a plate are presented. The values of the proportional and differential components of the controller as characteristics of this damping were chosen taking into account the permissible electric field strength of the actuator. The research results for the case of passive damping of vibrations are also given for comparison. The dependences of the decrement of plate vibrations on the differential component of the controller and of the maximum plate deflection on the reinforcement angle of the middle layer material have been established. The optimum reinforcement angle according to the minimum plate deflection criterion has been determined, which provides an increase in the efficiency of active damping of nonstationary vibrations of the plate owing to an increase in the differential component of the controller. | Active Damping of Nonstationary Vibrations of a Three-Layer Electro-Viscoelastic Composite Plate | 10.1007/s11223-021-00241-x |
2020-11-01 | In this manuscript, we present a system consisting of a three-level atom interacting with optical field. We investigate qualitatively the entanglement and atomic (field) geometric phase under the effect of cavity damping. The atom–field entanglement is measured by the negativity. We show that these quantifiers depend strongly on the variations of the initial settings of the atom, and this exhibits substantial phenomena that depend on the cavity damping effect. Finally, we explore the link between the entanglement and atomic (field) geometric phase of different physical parameters within the presence and absence of the cavity damping effect. | Some features of the geometric phase and entanglement of three-level atom under cavity damping effects | 10.1007/s12648-019-01613-5 |
2020-11-01 | The mechanical properties and vibration damping characteristics of cross-ply laminates ([90°/0°/90°] and [0°/90°/0°]), [0°/45°/0°], four-layered angle ply laminate ([90°/0°]_s) and Quasi-isotropic laminates ([0°/90°/45°]_s, [0°/45°/90°]_s,) containing 50 ± 2 wt% of banana fibres in polyester matrix were investigated. The experimental results indicate that the tensile strength, Young’s modulus, impact strength, and the natural frequency were superior for [0°/90°/0°] laminates. In the case of flexural properties, the Quasi-isotropic laminates displayed better performance than the other configurations. Tensile fractured specimens were examined under a scanning electron microscope (SEM) to understand the difference in failure behavior due to the inter-ply orientation in the laminate. | Influence of Fibre Inter-ply Orientation on the Mechanical and Free Vibration Properties of Banana Fibre Reinforced Polyester Composite Laminates | 10.1007/s10924-020-01814-8 |
2020-10-31 | In this paper we consider the blow-up of solutions to a weakly coupled system of semilinear damped wave equations in the scattering case with nonlinearities of mixed type. The proof of the blow-up results is based on an iteration argument. We find as critical curve for the pair of exponents ( p , q ) in the nonlinear terms the same one found for the weakly coupled system of semilinear wave equations with the same kind of nonlinearities. In the critical and not-damped case we combine an iteration argument with the so-called slicing method to show the blow-up dynamic of a weighted version of the functionals used in the subcritical case. | Nonexistence of global solutions for a weakly coupled system of semilinear damped wave equations in the scattering case with mixed nonlinear terms | 10.1007/s00030-020-00662-8 |
2020-10-28 | Water lubricated guide bearings for hydro turbines and pumps are conventionally designed with multiple axial grooves to provide effectively cooling and flushing away abrasives. Due to the variety of groove configuration in terms of number and size, a predication of their performance is difficult. This paper deals with an analytical procedure to investigate groove effect on load capacity, stiffness and damping for this type of bearing where it is considered as an assembly of many inclined slide bearings. The result can be applied to bearings made of hard materials combined with low bearing pressure. | A New Method to Calculate Water Film Stiffness and Damping for Water Lubricated Bearing with Multiple Axial Grooves | 10.1186/s10033-020-00492-w |
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