Low-frequency Structures Research Articles

Optimizing tomato detection and counting in smart greenhouses: A lightweight YOLOv8 model incorporating high- and low-frequency feature transformer structures

ABSTRACT Tomato harvesting in intelligent greenhouses is crucial for reducing costs and optimizing management. Agricultural robots, as an automated solution, require advanced visual perception. This study proposes a tomato detection and counting algorithm based on YOLOv8 (TCAttn-YOLOv8). To handle small, occluded tomato targets in images, a new detection layer (NDL) is added to the Neck and Head decoupled structure, improving small object recognition. The ColBlock, a dual-branch structure leveraging Transformer advantages, enhances feature extraction and fusion, focusing on densely targeted regions and minimizing small object feature loss in complex backgrounds. C2fGhost and GhostConv are integrated into the Neck network to reduce model parameters and floating-point operations, improving feature expression. The WIoU (Wise-IoU) loss function is adopted to accelerate convergence and increase regression accuracy. Experimental results show that TCAttn-YOLOv8 achieves an mAP@0.5 of 96.31%, with an FPS of 95 and a parameter size of 2.7 M, outperforming seven lightweight YOLO algorithms. For automated tomato counting, the R2 between predicted and actual counts is 0.9282, indicating the algorithm’s suitability for replacing manual counting. This method effectively supports tomato detection and counting in intelligent greenhouses, offering valuable insights for robotic harvesting and yield estimation research.

Wavelet structure-texture-aware super-resolution for pedestrian detection

This study aims to tackle the challenge of detecting pedestrians in low-resolution (LR) images by using super-resolution techniques. The proposed Wavelet Structure-Texture-Aware Super-Resolution (WSTa-SR) method is a novel end-to-end solution that enlarges LR images into high-resolution ones and employs Yolov7 for detection, effectively solving the problems of low detection performance. The LR image is first decomposed into low and high-frequency sub-images with stationary wavelet transform (SWT), which are then processed by different sub-networks to more accurately distinguish pedestrian from background by emphasizing pedestrian features. Additionally, a high-to-low information delivery mechanism (H2LID mechanism) is proposed to transfer the information of high-frequency details to enhance the reconstruction of low-frequency structures. A novel loss function is also introduced that exploits wavelet decomposition properties to further enhance the network’s performance on both image structure reconstruction and pedestrian detection. Experimental results show that the proposed WSTa-SR method can effectively improve pedestrian detection.

Wall-mounted circular cylinder flows

The flow over wall-mounted circular cylinders is influenced by variations in aspect ratio, Reynolds number, and boundary layer thickness, all of which affect the vortical structures in the wake. In this study, we conducted direct numerical simulations and data-driven techniques, including proper orthogonal decomposition (POD) and dynamic mode decomposition, to examine vortical flows behind wall-mounted circular cylinders with aspect ratios of 4, 8, and 12 at Reynolds numbers ranging from 60 to 800, based on cylinder diameter. The incoming boundary layer thickness varied from 0.05 to 0.25. Our findings reveal that a thicker boundary layer promotes the development of low-frequency symmetric vortical structures along the wall surface, suppressing antisymmetric wake shedding. Consequently, the induced upwashing motion of the flow behind the cylinder pushes the wake shedding region closer to the free-end side, facilitating quadrupole mean streamwise vortices. The wake shedding frequency is significantly altered as the symmetric low-frequency mode intensifies along the boundary. POD analysis demonstrates the coexistence of symmetric and antisymmetric vortical structures in the wake region. The presence of either antisymmetric or symmetric wake shedding is determined by the dominant frequency in the instantaneous flow. These findings substantiate previous conjectures about the simultaneous presence of symmetric and antisymmetric wake shedding modes and enhance our understanding of vortical flows around wall-mounted circular cylinders.

Theoretical and experimental investigation of flexible air spring stiffness in a tuned liquid column gas damper for vertical vibration control

This study investigates the effectiveness of equivalent linear air spring stiffness in a Vertical Tuned Liquid Column Gas Damper (VTLCGD) for reducing vertical structural vibrations, particularly considering different sealing conditions. The VTLCGD system, designed with a single sealed vertical air column, allows flexible frequency tuning by adjusting the air spring stiffness. It aims to be used in low-frequency structures where conventional VTLCGD designs with two sealed ends are less efficient. The geometric configuration and working principle of the VTLCGD are first described. The equation of motion is derived using liquid dynamic equilibrium and the pressure-volume relationship, with expressions for natural frequency and control force validated through shaking table tests conducted with varying VTLCGD lengths. Experimental investigations are conducted to examine the parameters affecting damper performance using pressure data. The system's vibration reduction performance is then numerically evaluated on a cantilevered floor subjected to human walking. The numerical results, based on the equation of motion for liquid displacement and natural frequency, show good agreement with experimental data, which confirms the effectiveness of using linearized air spring stiffness for frequency tuning. The effects of total liquid length and height difference on control force are further investigated, and a polytropic index of 1.2 is determined for the VTLCGD frequency formula. The VTLCGD system achieves a maximum vibration reduction of 52.63 % in acceleration response on the cantilevered floor compared to the uncontrolled case. Moreover, the variation in stiffness due to changes in the sealing condition is presented to validate the damper's adaptability over a wide frequency range.

Reduction of turbulence by enhanced low-frequency zonal flow-like structures in HL-2A edge plasmas

Abstract A low-frequency zonal flow-like (LFZF-like) structure peaking at f ≈ 2.0 kHz has been observed in HL-2A ohmically heated deuterium plasmas using a combined Langmuir probe array. This time-varying potential structure, which has axisymmetric characteristics (n = 0) and a finite radial correlation length (less than 1 cm), was identified to be generated by the three-wave interaction in small-scale turbulence. The results illustrate that the amplitude of the LFZF-like structure dramatically increases with the influence of impurity ions, which is mainly due to the increased strength in the nonlinear energy transfer by the turbulence vortex symmetry-breaking process. Consequently, the enhanced LFZF-like structure has the ability to stabilize the local turbulence via the shearing decorrelation mechanism as demonstrated in this experiment. The observed results given here reveal the essential role played by the LFZF-like structure in the reduction of turbulence levels, which could advance our understanding of the multi-scale physics governing turbulence and the resulting transport in magnetically confined plasmas.

Electrical-Modulated Flexible Acoustic Metamaterial: Enhancing Low-Frequency Absorption via an Ionic Electroactive Polymer.

The growing concern over low-frequency noise pollution resulting from global industrialization has posed substantial challenges in noise attenuation. However, conventional acoustic metamaterials, with fixed geometries, offer limited flexibility in the frequency range adjustment once constructed. This research unveiled the promising potential of ionic electroactive polymers, particularly ionic polymer-metal composites (IPMCs), as a superior candidate to design tunable acoustic metamaterial due to its bidirectional energy conversion capabilities. The previously perceived limitations of the IPMC, including slow reaction and high energy expenditure, owning to its inherent sluggish intermediary ionic mass transport process, were astutely leveraged to expedite the attenuation of low-frequency sound energy. Both our experimental and simulation results elucidated that the IPMC can generate voltage potentials in response to acoustic pressure at frequencies significantly higher than those previously established. In addition, the peak absorption frequency can be effectively shifted by up to 45.7% with the application of a 4 V voltage. By further integration with a microperforated panel (MPP) structure, the developed metamaterial absorbers can achieve complete sound absorption, which was continuously tunable under minimal voltage stimulation across a wide frequency spectrum. In addition, a microslit structure IPMC metamaterial absorber was designed to realize modulation of the perforation rate, and the absorption peak can be shifted by up to 79.2%. These findings signify a pioneering application of ionic intelligent materials and may pave the way for further innovations of tunable low-frequency acoustic structures, ultimately advancing the pragmatic deployment of both soft intelligent materials and acoustic metamaterials.

Low-frequency broadband acoustic metamaterial absorber based on nested resonator and synergistic coupled weak resonances

Utilizing absorbers with sub-wavelength thickness for low-frequency broadband noise control is a challenging problem, and rapid on-demand design of structures based on target noise frequency has received continuous attention. In this work, nested cavities are introduced into the typical neck-embedded Helmholtz resonator (NEHR) to obtain the nested neck-embedded Helmholtz resonator (NNEHR), which exhibits better cavity partitioning volume fraction and covers wider sound absorption band. Both theoretical analysis and simulations demonstrate that NNEHR possesses superior acoustic properties: generating an additional absorption peak, lowering the position of the first absorption peak by 11 %, and increasing the absorption coefficient by 4.7 %. Instantaneous velocity fields and thermal-viscous energy dissipation density illustrate that the efficient sound absorption of NNEHR originates from resonant dissipation in the neck and surrounding areas. Furthermore, by combining the theoretical model with genetic algorithms, three sets of NNEHR metasurfaces are optimized. The optimized structures achieve average absorption coefficients of 0.831, 0.913, and 0.885 in the range of 250–550 Hz, 400–1000 Hz, and 500–2000 Hz, with a thickness of only 50 mm, reflecting sub-wavelength, low-frequency broadband sound absorption characteristics. The excellent absorption stems from synergistic coupled weak resonances and higher-order absorption peaks of constituent units, and the overdamping characteristic ensures the realization of the optimal structure with minimal thickness. The contribution of weak resonant units to the total sound absorption performance can be measured by the surface admittance normalized by the total incident area, and the essence of the coupling effect is the strong interaction between units with adjacent absorbing frequencies. The proposed structure exhibits good sound absorption performance and great adjustability, while the genetic algorithm optimization based on the theoretical model demonstrates high efficiency and robustness, providing a methodology for the design and on-demand optimization of low-frequency broadband structures.

Even laypeople use legalese

Whereas principles of communicative efficiency and legal doctrine dictate that laws be comprehensible to the common world, empirical evidence suggests legal documents are largely incomprehensible to lawyers and laypeople alike. Here, a corpus analysis (n = 59) million words) first replicated and extended prior work revealing laws to contain strikingly higher rates of complex syntactic structures relative to six baseline genres of English. Next, two preregistered text generation experiments (n = 286) tested two leading hypotheses regarding how these complex structures enter into legal documents in the first place. In line with the magic spell hypothesis, we found people tasked with writing official laws wrote in a more convoluted manner than when tasked with writing unofficial legal texts of equivalent conceptual complexity. Contrary to the copy-and-edit hypothesis, we did not find evidence that people editing a legal document wrote in a more convoluted manner than when writing the same document from scratch. From a cognitive perspective, these results suggest law to be a rare exception to the general tendency in human language toward communicative efficiency. In particular, these findings indicate law's complexity to be derived from its performativity, whereby low-frequency structures may be inserted to signal law's authoritative, world-state-altering nature, at the cost of increased processing demands on readers. From a law and policy perspective, these results suggest that the tension between the ubiquity and impenetrability of the law is not an inherent one, and that laws can be simplified without a loss or distortion of communicative content.

Studies of indium nanostructures growth models on A3B6 layered templates

This article explores the surface architecture formation on layered A3B6 semiconductors, such as In4Se3, InSe, and InTe, focusing on kinetics of surface roughness parameters, such as RMS, skewness and kurtosis, and power spectral density (PSD) under indium deposition studied through large-scale 1 × 1 µm2 and 150 × 150 nm2 scanning tunneling microscopy (STM) images analysis. Our findings reveal common kinetics of surface parameters across different crystals, suggesting fundamental similarities in their interface kinetics. Particularly, PSD analysis elucidates the role of low-frequency spatial structures, underscoring their significance in surface roughness kinetics to some extent independent of the specific layered crystal surface structure.

Package CovRegpy: Regularized covariance regression and forecasting in Python

Abstract This paper will outline the functionality available in the CovRegpy package which was written for actuarial practitioners, wealth managers, fund managers, and portfolio analysts in the language of Python 3.11. The objective is to develop a new class of covariance regression factor models for covariance forecasting, along with a library of portfolio allocation tools that integrate with this new covariance forecasting framework. The novelty is in two stages: the type of covariance regression model and factor extractions used to construct the covariates used in the covariance regression, along with a powerful portfolio allocation framework for dynamic multi-period asset investment management. The major contributions of package CovRegpy can be found on the GitHub repository for this library in the scripts: CovRegpy.py, CovRegpy_DCC.py, CovRegpy_RPP.py, CovRegpy_SSA.py, CovRegpy_SSD.py, and CovRegpy_X11.py. These six scripts contain implementations of software features including multivariate covariance time series models based on the regularized covariance regression (RCR) framework, dynamic conditional correlation (DCC) framework, risk premia parity (RPP) weighting functions, singular spectrum analysis (SSA), singular spectrum decomposition (SSD), and X11 decomposition framework, respectively. These techniques can be used sequentially or independently with other techniques to extract implicit factors to use them as covariates in the RCR framework to forecast covariance and correlation structures and finally apply portfolio weighting strategies based on the portfolio risk measures based on forecasted covariance assumptions. Explicit financial factors can be used in the covariance regression framework, implicit factors can be used in the traditional explicit market factor setting, and RPP techniques with long/short equity weighting strategies can be used in traditional covariance assumption frameworks. We examine, herein, two real-world case studies for actuarial practitioners. The first of these is a modification (demonstrating the regularization of covariance regression) of the original example from Hoff & Niu ((2012). Statistica Sinica, 22(2), 729–753) which modeled the covariance and correlative relationship that exists between forced expiratory volume (FEV) and age and FEV and height. We examine this within the context of making probabilistic predictions about mortality rates in patients with chronic obstructive pulmonary disease. The second case study is a more complete example using this package wherein we present a funded and unfunded UK pension example. The decomposition algorithm isolates high-, mid-, and low-frequency structures from FTSE 100 constituents over 20 years. These are used to forecast the forthcoming quarter’s covariance structure to weight the portfolio based on the RPP strategy. These fully funded pensions are compared against the performance of a fully unfunded pension using the FTSE 100 index performance as a proxy.

Low-frequency broadband vibration reduction based on a square spiral beam local resonance phononic crystal

Low-frequency vibration poses a great danger to both industrial production and human health. Therefore, the development of efficient low-frequency vibration reduction structures remains a focus of academic and engineering research. In this paper, a novel low-frequency vibration reduction local resonance phononic crystal (LRPnC) plate with a square spiral beam LRPnC design is proposed. Through finite element simulation, the band structure and vibration characteristics of the LRPnC are first analyzed. On this basis, a gradient LRPnC plate with rainbow trapping effect is constructed by gradient arranging unit cells with different structural parameters to achieve broadband vibration reduction. Finally, the vibration reduction performance of the designed structure is experimentally verified. The finite element analysis results show that the designed gradient LRPnC plate can provide more than 20 dB of transmission attenuation over the full frequency range of 20–200 Hz. And the experimental results are consistent with the simulation results.

Feasibility Study of a Novel Modal Decomposition Method for Low-Frequency Structure with Nonproportionally Distributed Rate-Independent Linear Damping

Compared with conventional linear viscous damping (LVD), rate-independent linear damping (RILD) mitigates floor response acceleration in low-frequency structures more effectively without compromising the control performance of displacement responses during long-period or low-frequency earthquakes. Although theoretical and experimental attempts have been made to overcome the noncausality of RILD devices and realize RILD using passive or semiactive devices, only a few studies have highlighted the impulse-response precursor and modal analysis method of multistory structures incorporated into RILD devices. This study investigated the impulse-response precursor of a noncausal RILD system and proposed a novel modal decomposition method for the structures equipped with nonproportionally distributed RILD devices. Additionally, real-time hybrid simulation was conducted to validate the effectiveness of the proposed modal analysis method and the feasibility of realizing ideal RILD using mechanical devices. This study is the first to demonstrate the differences between RILD and LVD devices in terms of controlling the modal responses of low-frequency structures and how RILD can lower the floor response acceleration more effectively compared to LVD.

Wavelet Approximation-Aware Residual Network for Single Image Deraining.

It has been made great progress on single image deraining based on deep convolutional neural networks (CNN). In most existing deep deraining methods, CNNs aim to learn a direct mapping from rainy images to clean rain-less images, and their architectures are becoming more and more complex. However, due to the limitation of mixing rain with object edges and background, it is difficult to separate rain and object/background, and the edge details of the image cannot be effectively recovered in the reconstruction process. To address this problem, we propose a novel wavelet approximation-aware residual network (WAAR), wherein rain is effectively removed from both low-frequency structures and high-frequency details at each level separately, especially in low-frequency sub-images at each level. After wavelet transform, we propose novel approximation aware (AAM) and approximation level blending (ALB) mechanisms to further aid the low-frequency networks at each level recover the structure and texture of low-frequency sub-images recursively, while the high-frequency network can effectively eliminate rain streaks through block connection and achieve different degrees of edge detail enhancement by adjusting hyperparameters. In addition, we also introduce block connection to enrich the high-frequency details in the high-frequency network, which is favorable for obtaining potential interdependencies between high- and low-frequency features. Experimental results indicate that the proposed WAAR exhibits strong performance in reconstructing clean and rain-free images, recovering real and undistorted texture structures, and enhancing image edges in comparison with the state-of-the-art approaches on synthetic and real image datasets. It shows the effectiveness of our method, especially on image edges and texture details.

Sound absorption performance analysis of perforated panel resonator with tube bundles based on independent adjustment impedance

A method of independent adjustment of acoustic resistance and acoustic reactance is proposed for the problem of coupling of acoustic resistance and acoustic resistance affecting impedance matching in sound resonant absorbers. Combining theoretical analysis model and finite element simulation model, the modulation mechanism of independent adjustment impedance is revealed. Theoretical and simulation results show that for the same structural thickness and perforation rate, the acoustic resistance of the perforated panel resonator with tube bundles (PPTB) varies with the inner diameter of the tube, but the acoustic resistance remains constant. The PPTB can exhibit different damping states at the same resonant frequency and show different sound absorption performances. The experiment verifies that independent adjustment impedance can improve the impedance matching effect and enhance the sound absorption performance. In addition, the influence of structural parameters on the sound impedance is discussed. Moreover, independent adjustment impedance can be expected to design low-frequency broadband sound absorption structures and optimize sound absorption bandwidth.

Study on the acoustic performance of bending metasurface with ultra-thin broadband quasi-perfect sound absorption

In order to achieve low-frequency broadband noise control under subwavelength thickness, this paper established a theoretical model for calculating the sound absorption coefficient of curled acoustic metasurface (CAM) composed of embedded hole, equal width curled channel, and gradient width curled channel, which is based on the thermal viscosity equivalent model and impedance equivalent model. Considering the over resistance effect caused by multi-unit composite structure, a multi-parameter control strategy was used to design bending acoustic metasurface (BAM) units for perfect sound absorption at four discrete frequencies of 546 Hz, 563 Hz, 585 Hz, and 601 Hz, which is based on the complex frequency plane method. and the thicknesses of these unites are only (1.2 cm). The broadband and efficient sound absorption effect of the four parallel composite BAM units was theoretically studied. The simulation and experiment verified that the composite BAM not only achieved perfect sound absorption at 573 Hz with a subwavelength thickness of 12 mm, but also had an efficient sound absorption(α > 0.8) frequency band of 512Hz-621Hz, with a bandwidth up to 109 Hz. The research in this paper provides a certain theoretical basis for the design of low-frequency broadband compact acoustic structures, and has certain reference value for low-frequency broadband noise control.

Seismic control of base-isolated structures using rate-independent damping devices

Rate-independent linear damping (RILD) is a viable option for addressing excessive displacement challenges in low-frequency structures, particularly those subjected to ground motions containing many low-frequency components. RILD can mitigate the floor response acceleration of base-isolated structures more effectively than linear viscous damping (LVD) because of the larger damping force generated in the low-frequency region. However, RILD is an ideal element that exhibits noncausal characteristics. Many researchers have attempted to find approaches to realizing RILD, including both theoretical and mathematical investigations. Thus far, the physical realization of RILD remains challenging. In this study, a tuned inertoviscous-negative-stiffness Maxwell−Weichert (IvNsMW) model and a tuned inerter-viscous damper-negative-stiffness Maxwell−Weichert (IVdNsMW) model are proposed to promote progress in the application of RILD. These models differ in terms of the connection between the inerter and viscous damper. A direct design method is presented to determine the coefficients of these two devices. The efficiency of the proposed RILD-based devices for seismic control of low-frequency structures was examined using a multistory base-isolated structure. The results demonstrate that the proposed RILD devices are promising tools for both displacement and acceleration control of low-frequency structures.

Large eddy simulation investigation of S-shaped intake distortion and swirl characteristics

Curvature change of an S-duct wall naturally causes total pressure and swirl distortions in a compressor inlet. In this study, the large eddy simulation (LES) method is used to investigate the internal flow of a continuous variable curvature S-duct without a downstream compressor. A comparison between the numerical results and the experimental data verifies the effectiveness of the LES method in analyzing the internal flow mechanism of an S-duct. Based on the SAE standard, the transient distortion descriptors of the research cross-section are quantitatively analyzed, and the distortion characteristics of the total pressure and swirl in the aerodynamic interface plane (AIP), downstream outlet plane, and their spatial–temporal variation processes are revealed. Furthermore, the proper orthogonal decomposition and sparsity-promoting dynamic mode decomposition methods are used to decompose the flow structures of the AIP velocity fields, and the main coherent structures affecting the flow and their corresponding frequency/attenuation characteristics are obtained. The results indicate that the twin two swirl pattern near the wall annulus of the S-duct is dominant at high Reynolds numbers, and turbulent mixing downstream inhibits the development of distortion and swirl. In addition, some stable low-frequency mode structures exist near the Starboard, exhibiting multi-spiking frequency properties. Thus, this study reveals the generation, development, and evolution mechanisms of distortion and swirl at the upstream of a compressor inlet, and the analysis results of distortion and swirl characteristics can provide important input conditions for subsequent compressor distortion research and influence analysis of mass injection pre-compressor cooling technology.

Water surface response to turbulent flow over a backward-facing step

The water surface response to subcritical turbulent flow over a backward-facing step (BFS) is studied via high-resolution large-eddy simulation (LES). The LES method is validated first using data of previously reported experiments. The LES-predicted water surface is decomposed into different types of gravity waves as well as turbulence-driven forced waves. Analysis of the LES data reveals the interplay between low-frequency large-scale turbulence structures, which are the result of flow separation from the step and reattachment behind the step, and the dynamics of the water surface. The water surface deformation is mainly the result of freely propagating gravity waves and forced waves, owing to turbulence in the form of rollers and/or hairpin vortices. Gravity waves with zero group velocity define the characteristic spatial and temporal scales of the surface deformations at higher frequencies, while large eddies determine their low-frequency modulation. These deformations are mainly confined in lateral bands that propagate downstream following the advection of the near-surface streamwise vortices (rollers) that are shed from the step. Steeper surface waves are observed in regions of negative perturbation velocity gradient and down-welling, downstream of the larger rollers, and are associated with thin isolated regions of high vorticity near the surface. The investigation of such a complex flow has shown that the decomposition of the water surface fluctuations into its different physical components may be used to identify the dynamics of the underlying flow structure.

Theoretical and experimental research on damping performance of suspended multiple mass pendulums damper

Conventional suspended mass pendulum damper (SMPD) include suspended single mass pendulum damper (SSMPD), tandem suspended multiple mass pendulums damper without springs (TSMP), and parallel suspended multiple mass pendulums damper without springs (PSMP), these types of SMPD have the advantages such as clear mechanism, simple construction, and good damping effect, but they have a narrow tuning frequency band and the pendulum length needs to be set too long for low-frequency super tall structures and too short for high-frequency tall structures, limiting their application in practical engineering. Because of this, the paper proposes connecting the spring to the mass pendulum, forming a tandem suspended multiple mass pendulums damper with spring (TSMP-S) and a parallel suspended multiple mass pendulums damper with spring (PSMP-S), and establishing structural system dynamics equations and performing the dynamic characterization of the TSMP-S and PSMP-S, obtain their frequency resolved solutions to explain the damping mechanism. In order to study the vibration-damping performance of these two types of SMPD, through numerical simulations to compare the damping effect of the conventional SMPD, TSMP-S, and PSMP-S on the controlled structures, and a series of shaking table tests on controlled and uncontrolled structures to verify the effectiveness of SSMPD, TSMP, PSMP, TSMP-S and PSMP-S for damping control of controlled structures under conventional earthquake and earthquake at four types of sites. Numerical simulations and shaking table test results in both show that the TSMP-S has the best damping effect, with the advantages of increasing the tuning frequency band, achieving multi-order vibration control, and flexible adjustment of the pendulum length, which is suitable for actual engineering.

Experimental realization of rate-independent linear damping using a semiactive damper to enhance the seismic performance of low-frequency structures

Rate-independent linear damping (RILD) has been shown to simultaneously reduce the displacement and acceleration responses of low-frequency structures. However, previous studies on RILD have focused on its theoretical aspects and have almost excluded experimental approaches. Among the existing causal RILD models, the tuned Maxwell–Wiechert model can provide constant loss stiffness in a specified frequency range, thus offering a viable option as a control device intended to be incorporated into a base-isolated structure. A challenge remains regarding its undesired storage stiffness that compromises the flexibility of the base-isolated structure. This study eliminates the undesired storage stiffness via a negative stiffness-tuned Maxwell-Wiechert (NSTMW) model and experimentally investigates its feasibility to enhance the seismic performance of low-frequency structures. However, it is impossible to realize the NSTMW model using mechanical devices owing to the need for the negative damping coefficient of the Maxwell elements in some special cases. Therefore, the NSTMW model's frequency-domain expressions were transformed into time-domain differential equations using a bilinear transformation, and a small-scale magnetorheological damper was designed and fabricated to realize the NSTMW model. A series of real-time hybrid simulations were then conducted to examine the effectiveness of the NSTMW model for the protection of low-frequency structures. The experimental results confirmed that the NSTMW model could effectively control the dynamic response of low-frequency structures, compared with ideal RILD and linear viscous damping.