Damped Method Research Articles

Silencing the rolling thunder: An almost unthinkable acoustic isolation facade solution

Situated along a popular motorcycle route, the Lindemann Performing Arts Center at Brown University posed a unique challenge to its design team — isolating the performance space from external road noise while adhering to the demanding RC 15 performance standard. This presentation provides a comprehensive exploration of the intricate development and testing of a robust yet relatively lightweight acoustic isolation façade system. The ultimate approach employed unconventional damping methods, ensuring compliance with dew point requirements. The paper delves into the nuances of the design process, with a focus on key elements such as glazing systems, roofing solutions, access doors, and gypsum buildups that push the boundaries of conventional construction, challenging the possible maximum length of a drywall fastener. Attendees will gain valuable insights into the innovative strategies implemented to achieve effective acoustic isolation without compromising the high-performance standards demanded by the Lindemann Performing Arts Center. This presentation serves as a valuable case study, offering a deeper understanding of the intersection between architecture, acoustics, and the practical challenges encountered in the design of performance spaces.

A reweighted damped singular spectrum analysis method for robust seismic noise suppression

(Multichannel) Singular spectrum analysis is considered as one of the most effective methods for seismic incoherent noise suppression. It utilizes the low-rank feature of seismic signal and regards the noise suppression as a low-rank reconstruction problem. However, in some cases the seismic geophones receive some erratic disturbances and the amplitudes are dramatically larger than other receivers. The presence of this kind of noise, called erratic noise, makes singular spectrum analysis (SSA) reconstruction unstable and has undesirable effects on the final results. We robustify the low-rank reconstruction of seismic data by a reweighted damped SSA (RD-SSA) method. It incorporates the damped SSA, an improved version of SSA, into a reweighted framework. The damping operator is used to weaken the artificial disturbance introduced by the low-rank projection of both erratic and random noise. The central idea of the RD-SSA method is to iteratively approximate the observed data with the quadratic norm for the first iteration and the Tukeys bisquare norm for the rest iterations. The RD-SSA method can suppress seismic incoherent noise and keep the reconstruction process robust to the erratic disturbance. The feasibility of RD-SSA is validated via both synthetic and field data examples.

Application of amplified damped outrigger in seismic design of high‐rise buildings

SummaryThe application of the outrigger technology effectively improves the lateral stiffness of buildings, reduces harmful deformation, enhances the seismic resistance of structures, and contributes to the rapid development of high‐rise buildings. To improve the response speed and energy dissipation of a viscous damping outrigger under seismic excitation, a viscous damping outrigger with an amplifier was proposed, and its effectiveness was verified by combining it with the seismic design of a 149.2 m high‐rise building in an 8.5‐degree intensity area. To determine the additional damping ratio of the building structure, investigations were carried out using both the code method and energy ratio method to evaluate the contribution of the damping outrigger. The damped outrigger equivalent stiffness determination method was studied, and the simplified engineering calculation method was compared against the refined finite element analysis results for engineering design purposes. The displacement amplification technique incorporated into the viscously damped outrigger can enhance the damper response speed, and increase the energy dissipation of the damped outrigger system. The application of an enlarged damped outrigger in engineering can result in an additional damping ratio of approximately 1% while simplifying the calculation method based on the additional damping and equivalent damper cut‐line stiffness, which can be useful in engineering design.

Damage Spectra of SDOF Structures Under Tsunami Actions Considering the Nonlinear Dynamic Analysis Method

This paper studies the damage spectra of single-degree-of-freedom (SDOF) systems for tsunami loading. The 2011 Tohoku tsunami wave traces are computed and obtained by adopting the Cornell Multi-grid Coupled Tsunami (COMCOT) model and are further verified by the Tohoku Tsunami Joint Survey (TTJS) data. The tsunami response analyses of SDOF systems are conducted taking into account the dynamic analysis method. The classical ductility damage is considered as the damage performance. The damage spectra are computed for five force reduction factors and 791 tsunami loadings. The effects of inundation depths, hysteretic model, post-yield stiffness ratio, [Formula: see text], viscous damping ratio, [Formula: see text], are explored and interpreted scientifically and statistically. The results demonstrate that the effect of the hysteretic model, force reduction factor, R, post-yield stiffness ratio, [Formula: see text], viscous damping ratio, [Formula: see text], on the damage of the structure is evident. Comparison with the static method and influence analysis of structural damping indicate the necessity for the application of the dynamic method. A simplified predictive formulation is developed for the evaluation of structural damage for tsunami loadings.

GET 63–2019: Innovative Method for Stabilizing Liquid Flow Rate in a Reference Installation 3

Establishing the pinpoint accuracy of national primary standards for units of mass and volume flow rates (mass and volume) of liquid (water) is a priority in the national economy of most states. In Russia and abroad, the principle of operation of standards for units of flow rate and amount of liquid is based on the gravimetric weighing method, i. e., on measuring the mass of liquid entering a weighing container over a certain averaging time interval. The decisive condition for the accuracy of the result of the standard is the stabilization of liquid flow rate, as well as the choice of the optimal method for creating a forced flow of liquid in the pressure pipeline and measuring line. The widely accepted method of creating a forced flow of liquid by placing it at a height or supplying it using pumps has one inconvenient consequence – the bulkiness of the standard design. The creation of such a design entails economic, labor, and time costs, which can adversely affect the test conditions and results. The author’s innovative method of active damping of pressure and fluid flow fluctuations, which eliminates the need to place the pressure tank at a great height above ground level, allows minimizing inconveniences. This method is implemented in the pressure pipeline and measuring line of the reference installation 3 of the State Primary Special Standard of Units of Mass and Volume of Liquid in a Flow and of Mass and Volume Flow Rates of a Liquid GET 63–2019. The purpose of the article is to substantiate and experimentally confirm the high efficiency of this method. The results of experimental research of changes in the absolute pressure in the air cushion and the liquid level in the pressure tank of the stabilization module confirmed the efficiency of the proposed method based on the obtained minimum values of the relative deviations of the instantaneous and average liquid flow rates. The engineering solution presented in the article is of interest to economic entities and commercial organizations interested in reducing the costs of testing the volumetric flow rate (mass and volume) of liquid (water).

Differential ray tracing for an efficient computation of the Jacobian in the damped least-squares algorithm

We present a framework for the optimization of optical systems based up on the damped least-squares method and differential ray tracing. First, a mathematical description for the differentiation of the ray-surface intersection is introduced. It is observed that the structure of the optimization variables and operands can be exploited such that the Jacobian for the damped least-squares algorithm can be computed in the same computational complexity as the primal ray tracing for both forward and reverse mode algorithmic differentiation. To demonstrate the advantages of the method a freeform mirror system is analyzed.

An Innovative Method for Damping the Seismic Waves on Pile Foundations Using A Mixture of Rubber-Binder Jacketing

Earthquakes are sudden and unpredictable natural activity that causes severe damage. As a result of the increasing seismic activity in Iraq, it has become necessary to conduct a study on the impact of earthquakes and methods of damping them. Since traditional seismic damping methods for construction are very expensive, alternative solutions are necessary. Therefore, this research proposes a new damping method that depends on surrounding the piles with rubber crumbs, as the rubber works to dampen the seismic force before it reaches the piles before moving to the structure. This method is considered a type of sustainability. The study included a set of variables, including (the thickness of the rubber that surrounds the piles, and the position of placing the rubber that sleeved the piles). The tests were carried out using the shaking table device. The results showed that surrounding the piles with rubber gave distinct results in damping the seismic force and it is considered an easy damping method due to its ease of implementation, as well as its economic feasibility. The results showed for the models that surround the rubber in the upper part of the pile, an increase in the values of the acceleration of the structure and a decrease in the values of the movement speed of the structure, the values of the lateral displacement of the structure. The models in which the rubber surrounds the middle and bottom part of the pile, the results were close to the reference model.

Seismic reduction principle and response analysis of variable damping viscous damper system

PurposeA new type of variable damping viscous damper is developed to meet the settings of different damping parameter values at different working stages. Its main principle and design structure are introduced, and the two-stage and multi-stage controllable damping methods are proposed.Design/methodology/approachThe theoretical calculation formulas of the damping force of power-law fluid variable damping viscous damper at elongated holes are derived, aiming to provide a theoretical basis for the development and application of variable damping viscous dampers. For the newly developed variable damping viscous damper, the dynamic equations for the seismic reduction system with variable damping viscous dampers under a multi-degree-of-freedom system are established. A feasible calculation and analysis method is proposed to derive the solution process of time history analysis. At the same time, a program is also developed using Matlab. The dynamic full-scale test of a two-stage variable damping viscous damper was conducted, demonstrating that the hysteresis curve is complete and the working condition is stable.FindingsThrough the calculation and analysis of examples, the results show that the seismic reduction effect of high and flexible buildings using the seismic reduction system with variable damping viscous dampers is significant. The program developed is used to analyze the seismic response of a broadcasting tower using a variable damping TMD system under large earthquakes. The results indicate that the installation of variable damping viscous dampers can effectively control the maximum inter-story displacement response of TMD water tanks and can effectively consume seismic energy.Originality/valueThis method can provide a guarantee for the safe and effective operation of TMD in wind and vibration control.

Application of Vertical Electrical Sounding Method Using Damped Least-Square Inversion for Leachate Identification at Bakung Landfill, Lampung

This paper has reviewed the application of the damped least square inversion method for the VES (vertical electrical sounding) with Schlumberger array. The damped least squares solved using singular value decomposition were applied in Bakung Landfill to determine the aquifer contaminated by leachate. The ability of damped Least Squares inversion algorithm were verified using the resistivity variation of synthetic model which simulates aquifer layer of subsurface. Based on the results of 1D resistivity model, low resistivity zone can be used to identify the existence leachate contaminants of aquifer.

Ambient noise tomography of a linear seismic array based on an improved Voronoi tessellation

Ambient noise tomography, when applied to a dense linear seismic array, has the capability to provide detailed insights into the fine velocity structures across diverse tectonic settings. The linear station arrangement naturally generates parallel and concentrated ray paths along the array trend. This unique geometry requires specific optimization of the inversion methodology and model parameterization. The Bayesian-based transdimensional inversion method, characterized by its fully non-linear nature and high degree of freedom in parameter settings, offers a powerful tool for ambient noise inversion. To effectively adapt this method to a linear array layout, we propose a modification to the Voronoi cell tessellation built in the transdimensional method. By introducing spatial priority to the Voronoi kernels, we strategically increased the density of Voronoi cells along the direction of the array. We then applied the modified approach to a linear seismic array in the North China Craton and validated its robustness through phase velocity images and resolution tests. Our improved non-uniform sampling technique in the 2-D model space accelerates convergence while simultaneously enhancing model accuracy. Compared with the conventional damped least-squares method, the proposed algorithm revealed a shear-wave velocity map with notable low-velocity anomalies situated in the middle and lower crust beneath the borders of the Ordos block and its surrounding orogenic belt. Aligned with the crustal structures revealed by receiver function and electrical imaging, our findings indicated that the western and eastern margins of the Ordos block had experienced intensive crustal wedge deformation and re-melting, respectively.

A homogenization method for natural frequencies and damping of sandwich panels based on representative volume elements

The existing representative volume element (RVE) homogenization method, grounded in finite element analysis, assumes a planar configuration for the sections of sandwich panels, implying rigidity. To accommodate non-planar displacements, this study introduces a novel homogenization method reliant on the displacements obtained from four-point bending and four-point torsion. The present method is employed to investigate the mode shapes, natural frequencies, and loss factors of sandwich panels utilizing an equivalent single-layer shell model. Validation of the present method is conducted through the analysis of lattice sandwich panels and corrugated sandwich panels incorporating viscoelastic layers. Comparative analyses encompassing the results of the experiment, the conventional solid model method, the present method, and the conventional plane method are undertaken. The universality of the present method is substantiated. The present method enhances the precision of natural frequency prediction.

Research of the track irregularity spectrum of Shanghai high-speed transrapid demonstration line

High-speed maglev system is a hot research topic nowadays in the field of high-speed ground transportation. Characteristics of the track irregularity of high-speed maglev system is quite different due to its contactless vehicle-rail relationship and segmented track compared with traditional railway. However, research on maglev track irregularity is still insufficient. This paper summarises, for the first time, the track inspection data collected on Shanghai Maglev Demonstration Line (Shanghai Line) since 2006, and describes the main filtering methods and parameters for acceleration and gap signals, taking into account the characteristics of maglev track. Track irregularity is then determined using the inertial measurement principle. The measured track spectrum on Shanghai Line calculated by the Welch method obeys a chi-square distribution with 2 degrees of freedom, indicating that different track qualities can be transformed by probability methods according to the research requirements. Based on the samples obtained over the past 15 years, and referring to the seven-parameter model of the railway system, a high-speed maglev track spectrum is obtained by the fitting method, parameters of which are obtained by applying the damped least squares method. Preliminary vehicle dynamic analysis is conducted utilising the inverted excitations derived from the measured spectrum of the Shanghai Line.

The end of the world: Huang Yong Ping’s intermedial art installations

ABSTRACT From 1987 to 1994, a period that overlapped with his move to France in 1989, Huang Yong Ping washed texts in washing machines as part of his ‘damp method’ series. His objective was to ‘cut off the tongue’ by destroying certain classics, while at the same time ‘nurtur[ing] the tongue’ by turning to other classics. This paradoxical strategy epitomises his practice and philosophy of art which privileges creation through destruction and showing over describing by questioning the possibilities of communication, whether within or across cultures. This article analyses three of Huang’s artworks that are inspired by texts (books, journals, newspapers, scripture) and their relationship to water and endings, whether linguistic, material, metaphysical, aesthetic or ecological. It focuses on his transformation of two-dimensional texts into three-dimensional structures which draws attention to the mediation of culture and knowledge. It also considers how these artworks resonate with Arne Næss’s concept of deep ecology and their correspondences with Bruno Latour’s concept of modes of existence, those networks of associations in which human and nonhuman entities are actors with agency in the processes of redistribution.

An Improved Active Damping Method for Enhancing Robustness of LCL-Type, Grid-Tied Inverters under Weak Grid Conditions.

The conventional proportional-gain-feedback link can only obtain the smallest effective damping region (EDR) due to the control delay among all the active damping methods regarding the capacitor current feedback. The digitally controlled system tends to be unstable when the system resonant frequency reaches the critical frequency caused by the grid impedance variation. To weaken the adverse effect on the system caused by the control delay, phase-lead feedback links are applied along the feedback path to provide phase compensation. By taking the simplicity and reliability of the feedback links into account, this paper proposes an alternative to an ideal differentiator, which consists of the Tustin discrete form of 's' and a digital low-pass filter. This proposed method has an identical phase frequency characteristic as an ideal differentiator but a better magnitude frequency characteristic, and its EDR can reach [0, fs/3]. The system stability analysis is conducted under different resonant frequencies, and under the condition of a weak grid, the co-design approach of the active damper and digital controller is presented. Finally, the experimental results are shown to verify the proposed method.

DRR: An open-source multi-platform package for the damped rank-reduction method and its applications in seismology

We present an open-source multi-platform package for the damped rank-reduction (DRR) method, that has been widely used in various problems in seismology. The DRR method is an optimally improved rank-reduction (RR) method by damping the singular values using an analytically derived threshold. The DRR method can separate the useful signal and unwanted noise in multi-channel seismic data better than the standard RR method, resulting in spatially more coherent seismic events without damaging the critical subtleties. There have been some advanced methodological improvements or ingenious implementations of the DRR method in the past decade, as well as dozens of new applications in different areas of seismology, most of which will be included in the presented package. The DRR package is composed of two parts: MATdrr and Pydrr, corresponding to the Matlab and Python versions, respectively. The current DRR package includes localized DRR, optimally damped rank-reduction (ODRR), off-the-grid reconstruction, de-aliased reconstruction, and many reproducible examples in different areas of seismology. The DRR package will be continuously developed to include more functionalities in the future.

High-fidelity CFD-trained machine learning to inform RANS-modelled interfacial turbulence

In aero-engine bearing chambers, two-phase shearing flows are difficult to predict as Computational Fluid Dynamics (CFD) RANS models tend to overestimate interfacial turbulence levels, leading to inaccuracies in the modelling of the flow. Turbulence damping methods have been developed to address this problem, such as Egorov’s correction, however, this method is mesh dependent and results differ considerably according to the choice of turbulence damping coefficient. In addition, this approach assumes a smooth interface between the air and oil phases when in reality they are wavy. In this paper, a Machine Learning method is used to inform an unsteady RANS turbulence modelling. It is trained using high fidelity quasi-DNS simulation data and used to provide an appropriate correction to the popular Wilcox’s standard RANS <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>k</mml:mi><mml:mo>−</mml:mo><mml:mi>ω</mml:mi></mml:math></inline-formula> turbulence model. The correction consists of a machine learning-predicted source term which is used to adjust the energy budget in the RANS transport equations. Demonstration of the approach is presented for a range of interfacial flow regimes.

Development of shock absorber with quasi-zero stiffness effect to reduce dynamic effects on pump unit

The article is devoted to the improvement of the vibration isolation and shockproof properties of the shock absorber used in the vibration isolation compensator system of the pumping unit (PU). The set task is to create an elastic damping system with the desired low (quasi-zero) stiffness, which makes it possible to reduce the detrimental effect of pumping unit vibrations both on human health and on the equipment itself. High internal dynamic (vibration) loads are the main causes of early failure of pumping units, which are transmitted to the equipment through pipelines and foundations, mainly due to various operational factors. A promising trend in increasing the operating reliability and efficiency of pumping and power equipment is the use of a vibration-isolating compensator system (VICS). To obtain greater efficiency of vibration isolation, it is proposed to apply a modern method of vibration damping – the use of elastic mechanical systems with quasi-zero stiffness. The damping devices with a quasi-zero stiffness effect were studied. An assessment of the operability and effectiveness of these dampers at oil and gas facilities was given. Based on the information studied, a new concept of a quasi-zero stiffness damping device is proposed. The method of mathematical analysis determined its power curve. A 3D model of the damper device was built using a simulation software. The functional check of the damper was performed with mathematical modeling carried out on the computing device with the help of a specialized Ansys software that allows performing a system analysis of an object using the finite element method. The following results were obtained: the design of the damper with the effect of quasi-zero stiffness allows to widen the range of basement load transmission coefficient reduction towards low frequencies. The low rigidity of the system at the operating point ensures low values of the frequency of natural oscillations, and, consequently, high vibration isolation qualities.

Experimental Investigation of the Frequency Response of an LC-Filter and Power Transformer for Grid Connection

The power delivered by a voltage source inverter needs to be filtered to fulfill grid code requirements. A commonly used filter technology is the LCL-filter. An issue with the LCL-filter is the occurrence of a resonance peak, which can be mitigated with active or passive damping methods. The transfer function of the filter is often used to investigate the frequency response of the system and propose damping methods. The use of an LC-filter combined with a power transformer to form an LCL-filter has not been extensively investigated. Therefore, the study in this article introduces a model for an LC-filter and power transformer for the grid connection and a derived transfer function for the model. The transfer function for the system is validated with simulations and experimental investigations. The results from simulations and the results from a direct solution of the derived analytical function overlap almost perfectly. The magnitudes of the experimental results are approximately 1 dB lower than the simulation and analytical results before the resonance frequency. At the resonance frequency, the experimental results are approximately 13.4 dB lower. The resonance frequency, however, occurs at approximately the same frequency. It is also concluded that the system is significantly damped.

Unified Active Damping Strategy Based on Generalized Virtual Impedance in LCL-Type Grid-Connected Inverter

Extensive solutions have been proposed to damp <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filter resonance. However, the time delay caused by computation and modulation process aggravates the complexity of current loop analysis. In this paper, a generalized virtual impedance model for six kinds of commonly used active damping methods is proposed, and the physical meaning is established by introducing the metric of “damping factor”. To ensure system robustness in a wide range of grid conditions, a hybrid active damping strategy that combines inverter current feedback and capacitor voltage feedforward is proposed. Importantly, this method only requires inverter current and capacitor voltage sensors, which are the basic variables for over-current protection, power control and synchronization. The superposition theorem is also utilized to analyze the damping capability provided by parasitic resistances, current feedback loop and voltage feedforward loop. Finally, experimental results verify the feasibility and robustness of the proposed damping method.

Hybrid Threshold Denoising Framework Using Singular Value Decomposition for Side-Channel Analysis Preprocessing.

The traces used in side-channel analysis are essential to breaking the key of encryption and the signal quality greatly affects the correct rate of key guessing. Therefore, the preprocessing of side-channel traces plays an important role in side-channel analysis. The process of side-channel leakage signal acquisition is usually affected by internal circuit noise, external environmental noise, and other factors, so the collected signal is often mixed with strong noise. In order to extract the feature information of side-channel signals from very low signal-to-noise ratio traces, a hybrid threshold denoising framework using singular value decomposition is proposed for side-channel analysis preprocessing. This framework is based on singular value decomposition and introduces low-rank matrix approximation theory to improve the rank selection methods of singular value decomposition. This paper combines the hard threshold method of truncated singular value decomposition with the soft threshold method of singular value shrinkage damping and proposes a hybrid threshold denoising framework using singular value decomposition for the data preprocessing step of side-channel analysis as a general preprocessing method for non-profiled side-channel analysis. The data used in the experimental evaluation are from the raw traces of the public database of DPA contest V2 and AES_HD. The success rate curve of non-profiled side-channel analysis further confirms the effectiveness of the proposed framework. Moreover, the signal-to-noise ratio of traces is significantly improved after preprocessing, and the correlation with the correct key is also significantly enhanced. Experimental results on DPA v2 and AES_HD show that the proposed noise reduction framework can be effectively applied to the side-channel analysis preprocessing step, and can successfully improve the signal-to-noise ratio of the traces and the attack efficiency.