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Magneto-rheological (MR) materials can respond reversibly and quickly under the effect of an external magnetic field. MR materials contain micron-sized iron particles. These iron particles are typically dispersed in an elastomer or a liquid. These materials due to their properties constitute a kind of smart material in terms of engineering material. Such materials are used as isolators in various engineering applications, structures, and sound control subsystems. This study aimed to determine the mechanical properties for shear behavior of MR materials for under harmonic loading. Parameters such as matrix materials with different hardness values, powder types, magnetic field, frequency, and deformation were studied. The parameters related to the MR material itself were analyzed with the obtained data. The present study reveals that considering the sensitivity to magnetic field parameter, composite materials having the most suitable properties were produced with Shore 2 hardness value and SQ magnetic powder. It had been observed on increase about 200% at the rate of Shore A10 and A2 as a result of comparing the hardness scale. Also according to the powder rate while there was an increase on worth effect of relative MR, it is seen that the biggest increase had been in SQ powder with 199% worth. When looked some studies in literature, about comparing different hardness values such as matrix materials powder types etc. there aren't any studies. The state of magnetic field thinks that features such as MR effect, Storage, and Loss modulus haven't been examined yet. [ABSTRACT FROM AUTHOR]

The interaction of dual-micro-cavity defect modes in a one-dimensional photonic crystal consisting of graphene layers is studied by using the transfer matrix method. The numerical relation of resonances and splitting condition of them are determined in this structure. Results show that for specific repetition numbers of surrounding and middle cells of the structure, a defect mode is split into two completely separated modes. Also, threshold states for merging the defect modes are determined for different amounts of these parameters. In addition, the transmission coefficients and the Faraday rotation angles of these states are calculated and compared with each other. By calculation of light intensity distribution inside the structure at resonance wavelengths, we present consistent qualitative interpretation of the analytical results. The information achieved by this research can be useful to fabricate a variety of graphene-based photonic systems and magneto-optical integrated devices such as miniaturized isolators and circulators. [ABSTRACT FROM AUTHOR]

Most of the engineering vibrations are harmful, due to many unfavorable consequences caused by them, such as structural damage, poor working accuracy, etc., making it necessary to implement vibration isolation measures. Traditional linear vibration isolation methods have significant deficiencies regarding isolating low-frequency vibrations, in which the stiffness of the isolation system becomes a dominant factor. The quasi-zero-stiffness (QZS) vibration isolation technology, developed in recent decades, can greatly reduce the dynamic stiffness without reducing the static stiffness and thus extend the vibration isolation frequency band to low frequency region. A variety of approaches for constructing QZS isolators have been proposed based on geometric nonlinearity, magnetic nonlinearity, deformable components and so on. With higher demands and more complex operating conditions, many improvement strategies have been proposed to further enhance the overall performance of QZS isolators from various aspects. To date, a small portion of theoretical achievements in QZS vibration isolation have been applied in engineering fields, showing great advantages over linear vibration isolation methods. In these contexts, a comprehensive review of the QZS vibration isolation technology is essential. This paper is devoted to summarize the main research progress of QZS vibration isolation in terms of designs, improvement strategies and applications, to provide a general overview of the QZS vibration isolation technology for researchers in related fields. • Various approaches for constructing QZS isolators are elucidated. • Improvement strategies are expounded to further enhance the QZS isolators. • Some application examples of QZS isolators in engineering are presented. • Future prospects for QZS vibration isolation are provided. [ABSTRACT FROM AUTHOR]

This study is concerned with the problem of analysis and optimization of inerter-based systems. A main inerter system is generally composed of an inerter, a spring, and viscous damper. Series – parallel inerter system s and series inerter system s are two commonly used configurations of inerter-based system s. First , in this study , the H ∞ optimum parameters of inerter-based isolators are derived to minimize the compliance and mobility transfer function of a single-degree -of-freedom system under a harmonic ground acceleration excitation. Under the optimum tuning condition, it is shown that the proposed inerter-based isolators when compared with the traditional dynamic vibration absorber provide larger suppression of the peak value of the magnitude of compliance and mobility transfer function s of the primary system. For the studied cases, more than 40% and 45% improvement can be attained in terms of minimizing the compliance and mobility transfer function s , respectively, as compared with the traditional dynamic vibration absorber for the series – parallel inerter system and 15% and 11% improvement can be attained respectively , for the series inerter system. Finally, further comparison between the inerter-based isolators and traditional dynamic vibration absorber under white noise excitation also shows that the series – parallel inerter system and series inerter system s are superior to the traditional dynamic vibration absorber. The results of the studied systems show that m ore than 23% and 16% improvement are attained in terms of minimizing the compliance and mobility transfer function s respectively , as compared with the traditional dynamic vibration absorber for the series – parallel inerter system and 26% and 13% improvement can be attained respectively , for the series inerter system. The optimal parameters for different cases are obtained. It is shown that the optimal parameters obtained using the minimized mobility transfer function are smaller than those using the compliance transfer function at all mass ratios or inertance-to-mass ratio. The results of this study can provide theoretical basis for design of the optimal inerter-based isolators in engineering practice. [ABSTRACT FROM AUTHOR]

A three-dimensional seismic isolation device that is effective in isolating both horizontal and vertical earthquake components has drawn the interest of researchers in recent years. This paper proposes a new three-dimensional isolator for large-scale dome structures, which is composed of a quintuple friction pendulum component and a stacked disc spring component in series in the vertical direction. The complex working characteristics of these components are investigated in detail. Numerical modeling methods are proposed to simulate this isolator for engineering application purposes, and the model accuracy is validated based on theory and experiments. Thus, the isolator is applied to a large-scale dome structure subjected to near- and far-fault ground motions. Numerical analysis shows that the proposed modeling methods can efficiently analyze the isolation performance of the isolator in a large-scale structure. The numerical results demonstrate that the isolator has excellent isolation performance not only for displacement and axial force demands but also for velocity and acceleration demands in all three directions. In addition, according to the comparative study of this paper, the isolation performance of the proposed isolator is better than that of other types of isolators under major earthquakes due to the adaptive sliding characteristics of the quintuple friction pendulum component and the flexibility of the stacked disc spring component prolonging the structural periods. • A multidimensional isolator was proposed. • The working characteristics of the quintuple friction pendulum were investigated. • Numerical modeling methods were proposed for the multidimensional isolator. • Different kinds of isolators were compared in isolation performance. [ABSTRACT FROM AUTHOR]

A X‐band aperture‐coupled patch antenna based on backed substrate integrated cavity (SIC) and pins‐loaded cross slot with dual linear polarization and high isolation is investigated. Loaded pins are applied to cross aperture to reduce the mutual coupling between the slots. SIC is used to reduce the coupling caused by parallel plate mode. Moreover, one‐cross‐point structure of feed networks is used to further improve the isolation. A prototype of the dual‐polarized antenna is fabricated and measured. The measured results show that the dual‐polarized antenna exhibits impedance bandwidths better than 30% (voltage standing wave ratio ≤2), cross polarizations better than −27 dB. And the isolation between the two ports is above 51 dB. To the best knowledge of the authors, this is the highest isolation yet achieved for a patch antenna with wide bandwidth. [ABSTRACT FROM AUTHOR]

When an impact drive mechanism (IDM) is subjected to a heavy load, the large inertia of that load will seriously decrease the moving efficiency of the IDM. To solve this problem, a method of dynamic mass isolation is introduced in this article. The influence of load inertia is decreased to a minute value by adopting a light slider and using a spring between the load and the IDM. Thus, the moving efficiency can be increased. Kinematic models have been established and calculated by MATLAB/Simulink. Two prototypes have been fabricated and used to conduct a series of experiments. With a load of 1.8 g, the prototype with dynamic mass isolation presents a moving efficiency of 50.6%, whereas the other prototype without isolation presents a moving efficiency of only 11.9%. As a result, the average step size of the former is approximately four times larger than that of the latter. Moreover, the prototype with dynamic mass isolation can hold almost the same average step size with a wide range of load mass. The proposed method is low cost and may have practical significance for application in any known IDM-based actuating system to improve the performance. [ABSTRACT FROM AUTHOR]

We perform a theoretical study of the nonreciprocal reflection of high-frequency microwave radiation from ferromagnetic films with thin overlayers. Reflection from metallic ferromagnetic films is always near unity and shows no nonreciprocity. In contrast, reflection from a structure which has a dielectric overlayer on top of a film composed of insulated ferromagnetic nanoparticles or nanostructures can show significant nonreciprocity in the 75-80 GHz frequency range, a very high value. This can be important for devices such as isolators or circulators. [ABSTRACT FROM AUTHOR]

Dynamic substructuring (DS) is a research field that has gained a great deal of attention in both science and industry. The aim of DS techniques is to provide engineers in structural vibrations and sound practical solutions for analyzing the dynamic behavior of complex systems. This paper addresses the singularity problem that occurs when flexible joints are implemented as substructures into the Lagrange Multiplier Frequency-Based Substructuring (LM-FBS) coupling process. For illustration, we use rubber bushings from an automotive application. Considering the rubber isolators to exhibit hysteretic damping, we assume that only the property of the dynamic stiffness of material is given. To avoid singularity appearing in the admittance when inverting the impedance of a massless joint, we compare three different approaches to include rubber bushings in the framework of LM-FBS. One method consists in including the dynamic stiffness of material directly in the space of the interface constraints and add it to the assembled interface flexibility of the LM-FBS equation. This corresponds to a relaxation of the interface compatibility condition. In the second method, the rubber bushing is treated as a substructure by adding small masses to the equation of the joint. As a result, we obtain a nonsingular total dynamic stiffness matrix that can be included in the coupling process. The third method describes a novel extension of the LM-FBS approach, based on a solution for singular problems. If the applied forces are self-equilibrated with respect to the rigid body modes, a solution for the singular dynamic stiffness matrix exists. The methods are outlined, both mathematically and conceptually, based on a notation commonly used in LM-FBS. They facilitate the integration of connecting elements together with experimental or numerical determined system dynamics of substructures in order to predict the assembled system behavior. [ABSTRACT FROM AUTHOR]

This study is concerned with structural vibration reduction using a four-parameter isolator designed as a scissor-like structure, which can induce geometric nonlinearity during the deformation process. The displacement transmissibility of the isolator including the geometric nonlinearity under base excitations is thoroughly investigated. First, the dynamic model of the four-parameter isolator is presented. Then, by utilizing the harmonic balanced method (HBM), the steady-state solutions of the inertia mass and auxiliary spring of the proposed isolator are derived. The analytical solutions are validated by comparing with those obtained by the direct numerical integrating method. Besides, the natural frequency of the nonlinear isolation system is presented and investigated. Moreover, the isolation performance of the four-parameter isolator is assessed in terms of the relative and absolute displacement transmissibilities, and compared with that of the linear Zener model, by which the advantages of the present isolator have been clearly revealed. The effects of various design parameters on the displacement transmissibility of the isolator are also analyzed. Finally, a further comparison between the analytical and experimental results under base excitation also shows that the mechanical model used for the four-parameter isolator is accuracy enough. The present results may provide a useful theoretical basis for the design of the four-parameter isolator in engineering practice. [ABSTRACT FROM AUTHOR]

The selection of cold-tolerant forms was carried out during seed germination at a temperature of 9°C. Root material was grown in flowerpots, seeds were obtained by self-pollination in individual isolators. After repeated selections, the combining ability of the most valuable forms was studied as the parent components of the cross when creating new hybrids. The offspring of genotypes selected with the help of a cold background exceeded the control on the basis of germination and length of the seedling. The effectiveness of such studies is shown by the example of new hybrids Azimut, Kuban MS-95, and Uspekh. [ABSTRACT FROM AUTHOR]

High precision measurements in various applications rely on active seismic isolation to decouple the experiment from seismic motion; therefore, closed feed-back control techniques such as sensor blending and sensor correction are commonly implemented. This paper reviews the active isolation techniques of the Albert Einstein Institute seismic attenuation system (AEI-SAS). Two approaches to improve the well known techniques are presented. First, the influence of the sensor basis for the signal-to-noise ratio in the chosen coordinate system is calculated and second, a procedural optimization of blending filters to minimize the optical table velocity is performed. Active isolation techniques are adapted to the mechanical properties and the available sensors and actuators of the AEI-SAS. The performance of the final isolation is presented and limitations to the isolation are analyzed in comparison to a noise model. The optical table motion reaches approximately at 1 Hz, reducing the ground motion by a factor of approximately 100. [ABSTRACT FROM AUTHOR]

Tuned Mass Damper (TMD) with magneto-rheological elastomer isolators (MRE-TMD) is a novel control device for suppressing structural vibration caused by earthquakes. It is a nonlinear hybrid vibration absorber and the stiffness & damping can be controlled by changing the current of isolators' coil. Using MRE-TMD as an adaptive frequency TMD to mitigate vibration and treating it as only a passive damper is the focus of most nowadays researches. In this paper, semi-active control theory is introduced to the MRE-TMD-structure system which means that the control force can be obtained through variable stiffness & damping technology, and MRE-TMD is a semi-active damper instead of a passive one. A control system sketch, as well as principles and control strategies of a semi-active MRE-TMD-structure system for vibration control is designed. An improved limited sliding (ILSL) algorithm based on linear quadratic optimal theory is also introduced. Numeric simulations of a five-story benchmark building model equipped with semi-active MRE-TMD subjected to several benchmark earthquake records are conducted to investigate the control performance of the proposed semi-active MRE-TMD. Control force characteristics of the structural MRE-TMD systems are also evaluated. The results indicate that semi-active MRE-TMD can provide control force to the system and it shows superior ability to suppress the structural vibrations of comparing to the passive MRE-TMD. [ABSTRACT FROM AUTHOR]

A novel four-port circulator is presented which uses an inline ferromagnetic element to allow for transmission or reflection depending on the sense of the incident circularly polarized wave. This configuration has been shown to reduce the dependency on ferrite anisotropy and support higher power, low rf loss, operation. An analytic analysis of this device is presented alongside corroborating cold test data of the first prototype. High-power operation was performed at 2.856 GHz, with input power levels up to 8 MW for $3.5~\mu \text{s}$ in a pressurized nitrogen environment. The results from this research not only demonstrate ability to eliminate the use of greenhouse insulators, such as SF6, but also provide conceptual groundwork for a new class of ultrahigh power (50 MW+) nonreciprocal networks including circulators, isolators, phase shifters, and rf switches. [ABSTRACT FROM AUTHOR]

The absolute gravimeter plays an important role in metrology, geophysics, and geological exploration. Seismic and environmental vibration has been one of the most serious factors limiting its performance. Consequently, an ultralow-frequency vertical vibration isolator is required to significantly improve its measurement precision. A novel active vertical vibration isolator employing geometric antispring (GAS) structure is proposed in this paper. The payload is supported by a GAS structure fixed on an inner frame, and the inner frame is hung by coil springs from the base. The relative movement of the payload with respect to the inner frame is detected, and the inner frame is driven by a voice coil actuator controlled by a feedback circuit to track the payload’s motion. The new isolator has a compact size, and it can be used for different load ranges by tuning the GAS structure. The practical closed-loop system has a resonant period of 19.2 s, compared with the period of 0.74 s in an open-loop system. Experiments showed that the new isolator has great performance in a homemade T-1 absolute gravimeter, reducing the measurement deviation by a factor of 32. It is expected to be used in both free-falling and atomic-interference absolute gravimeters. Future improvements may include optimizing the mechanical structure and integrating a temperature control subsystem. [ABSTRACT FROM AUTHOR]

Summary: An innovative subsystem with the incorporation of eddy current (EC) damping and magnetic negative stiffness spring (MNSS) is proposed to develop feasible strategies for performance improvement of existing base isolation techniques. The concept of integrating the eddy current damping mechanism and the nonlinear negative stiffness spring is firstly introduced for better energy transition behavior under earthquake excitations. The analytical expressions of the force characteristics of the EC and the MNSS components are presented accordingly, and a parametric study is conducted to evaluate the inherent properties of the integrated magnetic subsystem. To demonstrate the advantages of the EC–MNSS subsystem, an illustrative example of a two‐DOF model simulating both the superstructure and the isolation layer is numerically investigated by adopting two representative isolators and the proposed subsystem. The EC–MNSS subsystem is illustrated to significantly and simultaneously improve the isolation performances in terms of base drift and structural acceleration. The energy exchange and dissipation behavior are further revealed by employing time history analysis and energy‐displacement‐velocity plots. Furthermore, the proposed EC–MNSS subsystem is implemented in a benchmark isolation problem adopting an eight‐story frame structure subjected to bidirectional earthquake excitations. The simulation results indicate the superior and the comparable performances of the integrated isolation system as compared to those of the passive and the control‐augmented isolations, respectively. [ABSTRACT FROM AUTHOR]

This paper proposes a low-loss and high-isolation transformer (TF)-based mm-wave single-pole double-throw (SPDT) switch. The center-tapped technique is employed at the secondary coil of TF to improve isolation performance. The TF is implemented with the metals in redistribution layers (RDLs) in integrated fan-out (InFO) wafer level packaging technology to obtain low insertion loss (IL) and small chip size as the TF usually dominates the area of SPDT. The control device of the SPDT is realized in 40 nm bulk CMOS process. The simulated result shows the proposed SPDT achieves a minimum IL of 1.34 dB and the IL is less than 2.2 dB at 24–31 GHz. The isolations are better than 27 dB between two double-throw ports and better than 20 dB between single-pole and double-throw ports, respectively. The proposed SPDT has a compact silicon size of 220 μ m × 1 4 0 μ m (with PADs) and its return losses are better than − 9 dB at 24–31 GHz and. This work explores a new chip-package co-design method for the SPDT and may have some guidance for the co-design of SPDT and antenna in package (AiP). [ABSTRACT FROM AUTHOR]

The 2008 Wenchuan earthquake brought numerous issues to the attention of researchers of seismic mitigation in Chinese museums. After the Wenchuan earthquake, the structural design team of Chengdu Museum conducted a series of research projects on seismic mitigation and subway vibration control design of buildings. These projects included the following topics: optimization of design, numerical simulation of seismic performance, analysis of key technologies for the base isolation structure, in-depth studies on structural vibrations caused by the nearby subway, and proposals for reducing structural vibrations. In 2015, after the superstructure of Chengdu Museum was completed, conservators evaluated the safety of permanent exhibitions under earthquake conditions. Seismic protection devices were installed on the showcases according to the preventive conservation requirements for museum collections. Reinforced measures were used for museum collections according to the methods suggested in the document 'Specification for seismic protection of museum collection' (WW/T 0069-2015). The conservators also built a systematic platform for earthquake monitoring for museum collections. Preventive conservation studies on seismic protection and subway vibration control in Chengdu Museum are summarized and forecasted. [ABSTRACT FROM AUTHOR]

This article deals with structural vibration attenuation and control using periodic materials for isolation of structures. An innovative approach to achieve wider low-frequency attenuation zones using a combination of different one-dimensional periodic units has been explored to provide close to a vibration-free environment for civil engineering structures subjected to seismic and other excitations. The wave attenuation regions for the base isolation system made of periodic materials have been derived from the theory of phononic materials and investigated using parametric studies and finite element modelling. The concept of combined periodicity is implemented on bridges to achieve wider attenuation zone and higher response reduction. A novel concept of using a hollow-shell periodic isolation system on bridges has been presented to minimize the effect of seismic waves on these structures. A substantial reduction in the seismic response of a bridge model has been observed over the entire frequency domain with the introduction of the proposed isolation systems. The proposed hollow-shell periodic isolation system reduces the seismic response of structures with efficient material utilization as compared to the typical solid-periodic isolation systems. The proposed isolation systems thus open up new directions for research and potential implementation of periodic materials for seismic response reduction and earthquake-resistant design of structures. [ABSTRACT FROM AUTHOR]

A polarization rotator based on substrate integrated waveguide (SIW) is proposed in this article. The rotator is designed as a dual-band, single-layer, frequency-selective surface (FSS) that transmits a wave rotated of 90° with respect to the incident one in one of the two bands maintaining unchanged the polarization in the other one. Other than the design and characterization of the rotator, its application to a linear-to-circular dual-band polarizer is also investigated. To this purpose, the rotator is coupled to a conventional meander line polarizer generating orthogonal circular polarizations (CP) in the two bands. This configuration is useful in SatCom applications where the required high isolation between TX and RX channels is obtained assigning orthogonal polarizations to the two bands. As a design example, a prototype is designed and experimentally validated in the SatCom K-/Ka-bands. Measured performance shows an isolation between the TX and RX channels of more than 35 dB and insertion losses which do not exceed 1.5 dB in the two operating bands. [ABSTRACT FROM AUTHOR]

This work studies a haptotaxis system proposed as a model for oncolytic virotherapy, accounting for interaction between uninfected cancer cells, infected cancer cells, extracellular matrix (ECM) and oncolytic virus. In addition to random movement, both uninfected and infected tumor cells migrate haptotactically toward higher ECM densities; moreover, besides degrading the non-diffusible ECM upon contact the two cancer cell populations are subject to an infection-induced transition mechanism driven by virus particles which are released by infected cancer cells, and which assault the uninfected part of the tumor. The main results assert global classical solvability in an associated initial-boundary value problem posed in one- or two-dimensional domains with any given suitably regular initial data. This is achieved by discovering a quasi-Lyapunov functional structure that allows to appropriately cope with the presence of nonlinear zero-order interaction terms which apparently form the most significant additional mathematical challenge of the considered system in comparison to previously studied haptotaxis models. [ABSTRACT FROM AUTHOR]

Summary: Due to their low inherent damping and high lateral flexibility, stay cables are prone to large amplitude vibrations governed by either a single or multiple cable modes. Among the practical measures, the installation of transverse passive dampers near the cable‐deck anchorage is a popular choice. Compared to conventional positive stiffness and zero stiffness dampers, negative stiffness damper (NSD) manifests superior performance in mitigating cable vibrations, especially in the case of long cables. In this study, a novel design approach is proposed to optimize NSD for multimode cable vibration control. Two design scenarios are considered. In the former, the damper size is optimized for a predetermined negative damper stiffness; whereas in the latter, the size and negative stiffness of the NSD are both optimized to achieve a required damping ratio for the dominant modes. The applicability of the proposed NSD optimum design approach is validated using 15 sample real stay cables. A numerical example is presented, of which a NSD is designed based on the proposed approach to optimize wind‐induced multimode vibration control of a 460‐m stay cable, and the performance is compared with that of a linear‐quadratic regulator (LQR) control. Results show that the selected NSD can effectively suppress the dominant modes and has a controlling effect comparable with an active control using LQR. In addition, it is found that when there exist more than two dominant modes in vibration, designing NSD for the lowest and the highest dominant modes would also adequately control the mid‐range modes. [ABSTRACT FROM AUTHOR]

This article investigates the possibility of using active control devices for the seismic protection of museum artifacts subjected to sliding and rocking. An actively base isolated system is compared to a passively base isolated one constituted by a spring-dashpot system that can represent a simplified modeling of both a base isolator or a flexible case-supporting system. Results show that active base isolation has superior performance than the passive one for the seismic protection of museum's artifacts. Moreover, due to their adaptability and robustness, active control devices can be adopted for different works of art in different site exposure conditions. [ABSTRACT FROM AUTHOR]

This paper presents a parametric study of the collapse performance of two-story residential buildings equipped with a simple spherical concave deformable rolling isolation system cast in high strength concrete. The collapse performance follows the procedures of FEMA P695 with direct evaluation of the spectral shape effects and accounts for uncertainties. The isolation system consists of isolators with fixed dimensional parameters that include a displacement restraint system and have a displacement capacity of 650 mm. The designs considered in the study have properties that are representative of highly ductile reinforced concrete two-story residential buildings consisting of moment frames and/or shear walls designed in Turkey for a lateral force under elastic conditions corresponding to a spectral acceleration of 1 g. This is representative of areas of the highest seismic hazard in Turkey except for areas controlled by near-fault conditions. The simplicity in the design of the structural system and of the isolation system intend to facilitate application of the system without sophisticated analysis. The seismic collapse performance evaluation demonstrates that residential buildings designed by this procedures and using this isolation system have acceptable collapse performance as stipulated in the ASCE/SEI 7-16 standard. [ABSTRACT FROM AUTHOR]

In this article, a novel tunable isolation network and a novel ring-type reconfigurable single-to-balanced (SE-BAL), power-dividing (PD), and single-to-single-ended (SE) bandpass filter is proposed. The tunable isolation network consists of a simple $\pi $ -type resistive network with tunable varactors, while the proposed filter consists of three ring-type stepped impedance resonators (SIRs) connected by varactors in between. By simply combining the proposed tunable isolation network and the proposed ring-type reconfigurable filter, it can achieve multiple reconfigurable functions among SE-BAL filtering, PD filtering, and conventional SE filtering with fully matched three ports, arbitrary power-division ratios (PDRs), high output isolations, and excellent amplitude and phase balance, in addition to continuous frequency and independent bandwidth tuning. The proposed filter is demonstrated using the microstrip line technology. The measured results show that the SE-BAL, PD, and two SE filtering functions can continuously cover the frequency ranges of 1.03–1.61, 1.01–1.53, 1.03–1.56, and 1.06–1.48 GHz with −1-dB bandwidth tuning of 35–80, 50–140, 60–130, and 70–140 MHz, respectively; the 1-, 3-, and 5-dB PDRs have been demonstrated for both SE-BAL and PD filtering modes. The measured output return losses and isolation are better than 19 and 18 dB, respectively, for SE-BAL filtering mode and 20 and 16 dB, respectively, for PD filtering mode. Good agreement is obtained between the simulated and measured results. [ABSTRACT FROM AUTHOR]

Seismic isolation devices were designed to protect three similar building structures, containing different objects with different fragilities, in a strong earthquake region. And a performance-based assessment framework, established by the PEER, was used to identify the seismic isolation efficiency of these devices. It optimized the ratios of spring part, viscous damping part and friction part in the seismic isolation devices, aiming at different functional buildings. Results show that a spatially concave friction distribution, combined with a weak spring, not only can reduce the structural acceleration response during earthquakes, but also decrease the structural residual displacement after earthquakes. Moreover, the spatially concave friction distribution can dissipate earthquake energy, but cannot hinder the recentering of structure like that of general uniform friction distributions. Consequently, the spatially concave friction distribution can partly or fully replace the viscous dampers, which are more expensive and short-lived. The reasonable combination of different components in the seismic isolation devices can satisfy different seismic requirements, aiming at different functional buildings. [ABSTRACT FROM AUTHOR]

This paper derived the expression to estimate the effective line moment mobility of a non-deterministic thin plate under moment excitation by a piezoelectric patch actuator. The piezoelectric patch actuator is assumed to generate purely line moments at each of its edges and regarded as a finite number of point moments acting on an infinite plate, which is achieved by integration method. The theoretical model is validated using MATLAB simulation and compared with experimental measurements on a randomized thin plate. The derived effective line moment mobility managed to closely estimate high-frequency response while cutting significant computational time and resource. Results from this study can be used in many applications ranging from vibration isolation where power transmission between the isolator with an area distribution and its host structure can be determined more accurately, and to design the optimal shunt circuit of a piezoelectric shunt damper for maximum power dissipation in order to reduce vibration of a non-deterministic thin plate. [ABSTRACT FROM AUTHOR]

This paper proposes a semi-active variable stiffness vibration isolation system based on electromagnetic spring for the low-frequency vibration isolation of mass-varying objects. It is achieved by four straight leaf springs in parallel to an electromagnetic spring system composed of a single electromagnet and a permanent magnet. The equivalent magnetic circuit method is used to compute electromagnetic force of the electromagnetic spring system, and mathematical model of the semi-active vibration isolation system is established according to Maxwell's equations. The nonlinear mathematical model is linearized at the equilibrium point by using the Taylor series expansion theorem to establish linear state-space representation of the system, and then using the traditional PID control method, a double closed-loop feedback control system of the inner current loop and outer location loop is designed. By controlling the current in the coil, the equivalent stiffness and electromagnetic force of the system are variable to achieve semi-active control. Furthermore, the control block diagram of the semi-active vibration isolation system is built based on Simulink software, then make a simulation analysis to the vibration isolation performance of the system and compare the effects of vibration isolation with inner current loop control and without inner current loop control, respectively. Finally, the experiments prove the correctness of the theory. It concludes that this semi-active vibration isolation system is a vibration isolation system with broad application prospects, which has fast current response, high vibration isolation efficiency, and an excellent vibration isolation effect for the low-frequency disturbance of mass-varying objects. [ABSTRACT FROM AUTHOR]

The use of friction pendulum devices has recently attracted the attention of both academic and professional engineers for the protection of structures in seismic areas. Although the effectiveness of these has been shown by the experimental testing carried out worldwide, many aspects still need to be investigated for further improvement and optimisation. A thermo-mechanical model of a double friction pendulum device (based on the most recent modelling techniques adopted in multibody dynamics) is presented in this paper. The proposed model is based on the observation that sliding may not take place as ideally as is indicated in the literature. On the contrary, the fulfilment of geometrical compatibility between the constitutive bodies (during an earthquake) suggests a very peculiar dynamic behaviour composed of a continuous alternation of sticking and slipping phases. The thermo-mechanical model of a double friction pendulum device (based on the most recent modelling techniques adopted in multibody dynamics) is presented. The process of fine-tuning of the selected modelling strategy (available to date) is also described. [ABSTRACT FROM AUTHOR]

This paper proposes a bioinspired reference model based fuzzy adaptive tracking control for active suspension systems. A general bioinspired nonlinear structure, which can present ideal nonlinear quasi-zero stiffness for vibration isolation, is adopted as tracking reference model. Fuzzy logic systems are used to approximate unknown nonlinear terms in nonlinear suspension systems. Particularly, a nonlinear damping is designed to improve damping characteristics of the bioinspired reference model. With beneficial nonlinear stiffness and improved nonlinear damping of the bioinspired reference model, the proposed fuzzy adaptive controller can effectively suppress vibration of suspension systems with less actuator force and much improved ride comfort, thus energy saving performance can be achieved. Finally, a quarter-vehicle active suspension system with considering payload uncertainties, general disturbance, and actuator saturation is provided for evaluating the validity and superiority of the bioinspired nonlinear dynamics based fuzzy adaptive control approach proposed in this paper. [ABSTRACT FROM AUTHOR]

Active electromagnetic isolator systems are used to isolate vibration with variable stiffness and damping, flexible controllability, varied control methods and fast response. In order to achieve better vibration isolation performance, an electromagnetic isolator system is designed with small volume and simple structure and the control block diagram with the nonlinear relationships and PID controller is proposed to simulate and verify in this paper. The structure of the electromagnetic isolator system can not only save space, but also provide the controllable electromagnetic force to counteract external disturbances quickly and actively. For improving the vibration isolation performance of the designed electromagnetic isolator system, a mathematical model which can accurately reflect the relationship between electromagnetic force and coil current and gap is established using structural information and experimental data. A control block diagram of the electromagnetic vibration isolator system containing nonlinear characteristics with PID controller is then designed. The PID control system shows the good performance of active anti-jamming of the designed isolator system. The experimental result demonstrates that the designed electromagnetic isolator system can effectively isolate vibration, and that the control block diagram with PID controller based on the nonlinear system can effectively describe and control the electromagnetic isolator system. The better vibration isolation performance, such as fast response, less overshoot and so on, can be achieved through deliberately designed controllers. [ABSTRACT FROM AUTHOR]

One of the greatest challenges of researchers is to understand the behavior of base isolation systems and base-isolated buildings under the conditions of different ground motions. The specific objective of this study is to evaluate the seismic response of multi-story base-isolated buildings with lead core rubber bearings (LCRBs) and buildings that are not isolated when subjected to different types of ground motions with different components. Under these conditions, the equations of motion of buildings with isolation systems are obtained, and LCRB force–deformation behavior is modeled as bilinear in MATLAB. Then, the behaviors of the base isolation system and base-isolated buildings are evaluated for 45 different earthquake scenarios, which are categorized into three different groups with regard to the ratio of peak ground acceleration to peak ground velocity (PGA/PGV). The dissipation of energy by a base isolation system, which is induced by the earthquake, varies for three different ranges of the PGA/PGV ratio. Despite the fact that by increasing the number of stories, the effectiveness of the isolator system decreases, this paper shows the most important finding to be that the damage limitation requirement is kept below 1% according to Eurocode 8, which is the requirement for buildings at the upper limit on the inter-story drift ratio under seismic loading, and the inter-story drifts significantly decreases for the base-isolated buildings and even for high-rise buildings. [ABSTRACT FROM AUTHOR]

This paper presents a numerical method for analyzing the nonlinear structural and acoustic responses of a coupled stiffened composite laminated cylindrical shell and piecewise isolation system immersed in an infinite acoustic fluid. The cylindrical shell is reinforced by a series of circumferential rings and longitudinal stringers, which may be few or many in number, non-uniform or uniform in size, and arbitrarily distributed in space. The isolation system in the shell contains motion-limiting stops, and the restoring forces of the isolators are assumed as bi-linear functions of the isolator deformations. A modified variational approach for the shell combined with a discrete element method for the rings and the stringers is employed to establish the nonlinear dynamics model of the structural system. The exterior acoustic fluid is computed by a time-domain Kirchhoff boundary integral formulation. The structural and acoustic models are coupled together by considering the compatibility conditions on their interface. The validity of the present method for predicting the structural and acoustic responses of the coupled shell and isolator system is confirmed. The contribution of the grouped circumferential wave modes of the shell to the vibration and radiated sound of the coupled structural system is examined. The effects of the excitation frequency of the external load, as well as the stiffness ratio and the gap of the suspension springs in each isolator on the structural and acoustic responses of the coupled system are discussed. [ABSTRACT FROM AUTHOR]

The use of quasi-zero-stiffness isolators in vibration pickups is investigated in this study. For this purpose, a quasi-zero-stiffness mechanism is first investigated to extract optimal values of parameters guaranteeing these conditions. The frequency response of this type of pickups is then obtained and compared with their equivalent linear pickup to investigate the effects of damping and oscillation amplitude measured by the pickup on the pickup performance. To study the phase distortion, the phase difference between the oscillations exerted on the pickup and those measured by the pickup for various excitation frequencies are measured at quasi-zero-stiffness and their equivalent linear pickups. In this way, the effects of the pickup design parameters on the pickup performance are investigated, and the response of this type of pickups to a sum of two harmonic excitations is studied. Finally, the effects of uncertainties such as friction, noise, etc., on experimental results are investigated. [ABSTRACT FROM AUTHOR]

Gas turbine engines include a plethora of rotating modules, and each module consists of numerous components. A component's mechanical fault can result in excessive engine vibrations. Identification of the root cause of a vibration fault is a significant challenge for both engine manufacturers and operators. This paper presents a case study of vibration fault detection and isolation applied at a Rolls-Royce T-56 turboprop engine. In this paper, the end-to-end fault diagnosis process from starting system faults to the isolation of the engine's shaft that caused excessive vibrations is described. This work contributes to enhancing the understanding of turboprop engine behaviour under vibration conditions and highlights the merit of combing information from technical logs, maintenance manuals and engineering judgment in successful fault diagnosis. [ABSTRACT FROM AUTHOR]

• Test of an assembled isolation for slender composite equipment. • An equivalent simplified model for optimal selection of dampers. • Comparison between the wire rope isolation and the assembled isolation. • Discussion on the influence of seismic inputs on the effectiveness of isolation. Since the seismic performance of the bypass switch (BPS) cannot satisfy the stress safety factor requirement, an isolated combination of wire ropes with linear viscous dampers was employed. The assembled base isolation was designed using modal parameters, and the effectiveness of the isolation was validated numerically using finite element (FE) analysis and experimentally by the shaking table test. The numerical study shows that wire rope isolation can reduce the stress of a BPS considerably. Furthermore, the implementation of supplementary viscous dampers can further reduce the stress and, more importantly, displacement response, which is significant for UHV equipment. The middle section of BPS generates obvious high frequency vibration during test, although the root section still experiences the maximum stress response. Besides, testing verified the reliability of the FE model and confirmed that the stress safety factor requirement was satisfied. Therefore, the isolation comprised of wire ropes and a viscous damper is proposed to improve the seismic performance of the slender 800 kV composite BPS. [ABSTRACT FROM AUTHOR]

The pipeline structure is prone to multi-dimensional vibration under the effect of external excitation, fluid pulsation and water hammer, which influences transportation efficiency and leads to accidents. In this paper, the multi-dimensional vibration isolation and mitigation device (MVIMD) is developed, which controls the vibration of the pipeline structure from two aspects simultaneously: isolating vibration and mitigating vibration. The device which consists of viscoelastic (VE) bearing, VE dampers and U-shaped springs, has energy dissipation capacities both in horizontal and vertical vibration due to employing VE material with high energy dissipation capacity. In order to investigate the mechanical properties of the device in the horizontal and vertical directions, the characterization tests under different frequencies and amplitudes are carried out. To accurately describe the nonlinear characteristics of the device caused by the complex viscoelasticity, the mathematical model for MVIMD is proposed for considering the effects of frequency and displacement amplitude based on the equivalent standard solid model. Finally, the numerical results are compared with the experimental data. It can be shown from comparison results that the proposed model can describe the properties of MVIMD precisely. [ABSTRACT FROM AUTHOR]

Two models have previously been commonly used to predict the isolation performance of a hydraulic leveraged dynamic anti-resonance vibration isolator. The models have deficiencies, however, in considering the volumetric stiffness of the isolator. In this paper, a new model is proposed to improve the accuracy by reasonably taking the volumetric stiffness into consideration. The model is validated by a carefully designed experiment. The influence of the volumetric stiffness on the isolation performance of the isolator is investigated by the validated model. The results indicate that the volumetric stiffness of the isolator and its location in a mathematical model have a significant influence on the isolation frequency and the second natural frequency of the isolator. The dependence of the volumetric stiffness on the isolation frequency, the attenuation capacity at the isolation frequency, and the bandgap of the isolator is presented. The investigation will enhance the understanding of the hydraulic leveraged dynamic anti-resonance vibration isolator, and facilitate the design and exploitation of this type of isolator in the field of vibration isolation. [ABSTRACT FROM AUTHOR]

Boring bars are widely used in deep hole machining. Due to the low stiffness of the long cantilever boring bar, vibration often occurs in the boring process. Vibration suppression can permit higher productivity and a better surface finish. To improve the performance of boring operations, a variable stiffness dynamic vibration absorber (DVA) is added inside the boring bar to reduce the vibration. The stiffness of the DVA is provided by two rubber bushes placed inside the DVA. By changing the axial compression, the stiffness of the DVA can be adjusted to accommodate different excitation frequencies. By establishing the relationship between the stiffness of the DVA and the axial compression of the rubber bush, the optimal stiffness for different excitation frequencies can always be found. A boring experiment is conducted, and the results show that, by selecting a reasonable axial compression, the vibration of the boring bar can be effectively suppressed. [ABSTRACT FROM AUTHOR]

Waveguide hybrid junctions, such as Magic-T and rat-race couplers, have been of great interest in microwave technology not only for their applications in power monitoring, but also for design and synthesis of various non-reciprocal devices including electromagnetic circulators and isolators. Here, an acoustic rat-race coupler is designed and demonstrated for the first time, working on the basis of constructive and destructive interferences between the clockwise and counterclockwise of a ring resonator. It is then shown how the sound isolation provided by such a coupler enables the realization of an acoustic four-port circulator, a device which has not been reported as yet. Many other promising acoustic devices comprising power combiners, power dividers, mixers, and modulators can be envisioned to be implemented based on the proposed rat-race coupler. [ABSTRACT FROM AUTHOR]

Intermediate isolation system (IIS) is currently spreading and gaining significant popularity, mainly in Japan. However, its potentials are not so well-known in European countries, and in USA only one application to building retrofit is registered. The dynamic behaviour of intermediate isolation systems, more complex than the two-degree-of-freedom behaviour of base isolation systems, gives rise to a twofold control mode, which combines isolation and mass damping strategies. However, the research contributions provided in the scientific literature usually concentrate on one single control mode, either isolation or mass damping, and the relevant design methods and criteria. This paper addresses the IIS design problem from a wider perspective and presents an explorative study on the vibration characteristics and dynamic behaviour of IIS, in order to identify the range of different behavioural modes and to propose relevant design guidelines. For these aims, a parametric analysis is carried out, varying the main design parameters, namely: isolation period and ratio, location of isolation layer and mass ratio, distributions of stiffness and mass in the upper and lower structures. A classical modal approach is initially assumed for assessing the contributions of each vibration mode on the global dynamic behaviour of IIS, with a particular focus on the effect of coupling of higher modes. However, since IIS is a non-proportionally damped system, a state space formulation is subsequently adopted for establishing the cases for which the simplified classical approach, only considering two damping values for the isolation and structural parts, can be adopted in a preliminary design stage. Finally, frequency response analysis is carried out for identifying the ranges of predominant isolation and mass damping behaviour and the effect of mode coupling both in terms of local and global response of the isolated models. Design implications are finally derived from the analysis results. [ABSTRACT FROM AUTHOR]

We proposed a design of a tunable optical isolator. The electro-optic (EO) effects in periodically poled lithium niobate (PPLN) with a defect were studied. EO effects and second harmonic generation (SHG) allow three-wave coupling in this nonlinear optics process. A defect is inserted in an asymmetrical position in PPLN to break the reciprocity of the fundamental-wave transmission in two reversed propagating directions. We numerically demonstrated that the contrast of this optical isolator can be tuned from -1 to 1 by simply changing the external dc electric field. With EO effects, the position of the defect can be designed more flexibly maintaining a high contrast of the optical isolation. [ABSTRACT FROM AUTHOR]