Estimation Of Acceleration Research Articles

Direct loss‐based seismic design of low‐rise base‐isolated reinforced concrete buildings

AbstractThis paper proposes a procedure to design low‐rise base‐isolated structures achieving a specific target level of earthquake‐induced loss (e.g., dollars, downtime) while complying with a predefined minimum level of structural reliability. The procedure is “direct” since the target loss is specified at the first step of the process, and virtually no design iterations are required. Direct loss‐based design (DLBD) is enabled by a simplified loss assessment module involving: (1) surrogate probabilistic seismic demand models representing the probability distribution of peak horizontal displacements and accelerations on top of the isolation layer conditional on different ground‐motion intensity levels; (2) approximations of the superstructure response; (3) simplified consequence models for isolation system and superstructure based on damage‐to‐loss ratios (economic loss or repair time); (4) simplified consequence models for acceleration‐ and drift‐sensitive non‐structural components, based on storey loss functions of a potential inventory of components. Given some basic geometrical parameters of the superstructure, DLBD provides the isolation system's force‐displacement curve and the required superstructure's strength complying with a selected loss target. The members' structural detailing follows the principles of direct displacement‐based design, sectional analysis, and the general theory of base isolation. The procedure is illustrated by designing six reinforced concrete wall buildings (two‐, three‐, and four‐storeys) base isolated with lead rubber bearings, to achieve predefined targets of expected repair time. Repair time is benchmarked against a more refined method adopting a cloud‐based non‐linear time history analysis, finding a maximum underestimation of 17%, thus confirming the dependability of DLBD. Such error is almost entirely attributable to the simplified estimation of peak floor accelerations, and it could be potentially eliminated by refining such estimation.

Acceleration Estimation of Signal Propagation Path Length Changes for Wireless Sensing

Acceleration Estimation of Signal Propagation Path Length Changes for Wireless Sensing

A novel method for measuring three-axis dynamic centrifugal acceleration field: the matrix transformation method

Abstract When a three-axis dynamic centrifuge is used to test the performance of inertial equipment (accelerometer, gyroscope, gyro-accelerometer, etc.), accurate estimating of the acceleration at the sensing position of the tested sensors is a key step. To solve the problem of the lack of relevant suitable methods, first, the principle of rigid body kinematics is used to prove that the acceleration of each point on a rigid body changes linearly with respect to the position. Subsequently, a matrix transformation method for accurately measuring the acceleration field on the three-axis dynamic centrifuge is presented. In this method, the distribution law (expressed by a 3×3 matrix) of the acceleration field is calculated based on the measured acceleration at multiple positions. After that the acceleration estimation value at any point on the centrifuge can be calculated. Finally, the uncertainty of the estimated acceleration value is analysed, and a verification experiment is carried out. The results show that the accuracy of this method is mainly limited by the accuracy of the acceleration measurements. The preliminary verification experiment system shows that the mean deviation of the estimated value error obtained by this method is less than 0.024 g, the standard uncertainty is less than 0.015 g, the left and right endpoints of the 95% probability inclusion interval are less than -0.026 g and 0.036 g, respectively, and the half width of the interval is less than 0.028 g. In all, this paper provides a powerful tool for examining the precision performance of inertial equipment on a three-axis dynamic centrifuge, and can also be used for calibration of this kind of centrifuge.

Suitable engineering demand parameters for acceleration‐sensitive nonstructural components

AbstractEarly earthquake design codes used peak ground accelerations (PGAs) as intensity measures (IMs) to characterize the demands of ground motions on structures, but have since shifted towards using spectral accelerations because they provide a better indication of demand. The design of acceleration‐sensitive nonstructural components has followed a similar approach, with modern codes being based on an estimate of the spectral acceleration at the period of the nonstructural component. However, most fragility curves for loss assessment of acceleration‐sensitive nonstructural components, including the existing FEMA P58 library, continue to be based on peak floor accelerations (PFAs). Similar to PGAs as an IM for buildings, a limitation of PFA as an engineering demand parameter (EDP) for nonstructural components is its lack of dependence on the period of those components. In this study, fifteen alternative EDPs suggested in the literature are evaluated as potential candidates for developing seismic damage fragility curves. Acceleration‐sensitive nonstructural components are simulated by single‐degree‐of‐freedom (SDOF) components with elastic perfectly plastic behavior, with a period range of 0.01 to 1 s, and varying strength levels. Nonlinear response history analyses are conducted for the SDOFs, using floor motions obtained from both the first floor and the roof of buildings designed with four distinct seismic force‐resisting systems. Ductility demands for each SDOF are taken as an indicator of damage and are predicted using a linear regression model developed for each specific EDP. The suitability of candidate EDPs is evaluated based on their efficiency and relative sufficiency. Furthermore, a comparison is made between the expected annual loss calculated using fragility curves derived from the selected EDPs to quantify how the EDP used for a fragility curve can affect the seismic loss assessment. The results reveal that the PFA is a suitable EDP only for nonstructural components with very short periods (i.e., less than 0.1 s). Moreover, although the spectral acceleration at the period of the SDOF nonstructural component is a suitable EDP for components that are nearly elastic and are located on the roof of buildings, the peaks that develop in the floor spectra can grossly overstate the demands on nonstructural components that experience significant nonlinearity in their response. In such situations, an average of the spectral accelerations in a range of periods near the period of the SDOF nonstructural component is more appropriate. Moreover, although the spectral acceleration at the period of the SDOF nonstructural component is a suitable EDP for components that are nearly elastic and are located on the roof of the buildings, an average of the spectral accelerations near the period of the SDOF nonstructural component is more appropriate when the component encounters higher levels of nonlinear behavior or is installed on a lower floor.

Impact of ground motion uncertainty evolution from post-earthquake data on building damage assessment

Accurate damage assessment after an earthquake is crucial for effective emergency response. Using ground motion information enables rapid building damage assessment when detailed damage data are unavailable. While uncertainty in earthquake parameters plays a significant role in the accuracy of rapid estimations, it is usually treated as a constant parameter rather than as a dynamic parameter that considers the amount of ground motion data collected that evolve over time. This work investigates the impact of incorporating evolving ground motion uncertainty in ground motion estimations from US Geological Survey’s (USGS) ShakeMap on post-disaster damage assessments from two methodologies: the revised Thiel–Zsutty (TZR) model and Federal Emergency Management Agency’s (FEMA) Hazus. Using data from the 2020 Indios earthquake in Puerto Rico and the 2014 Napa earthquake, we find that changes in uncertainty in estimates of peak ground acceleration reach 65% between early and late versions of the ShakeMap. We propose a process to integrate this evolution with the two damage assessment methodologies through a Monte Carlo simulation-based approach, demonstrating that it is critical to introduce dynamic ground motion uncertainty in the damage assessment process to avoid propagating unreliable measures. Both methodologies show that resulting damage estimates can be characterized by narrower distributions, indicative of reduced uncertainty and increased precision in damage estimates. For the TZR model, an improved estimate of post-disaster loss is achieved with narrower bounds in distributions of expected high scenario loss. For Hazus, the results show potential changes in the most probable damage state with an average change of 13% in the most probable damage state. The described methodology also demonstrates how uncertainty in the resulting damage state distributions can be reduced compared with the use of the current Hazus methodology.

Locating quark-antiquark string breaking in QCD through chiral symmetry restoration and Hawking-Unruh effect

The relationship between QCD and the string model offers a valuable perspective for exploring the interaction potential between quarks. In this study, we investigate the restoration of chiral symmetry in connection with the Unruh effect experienced by accelerating observers. Utilizing the Schwinger model, we analyze the critical point at which the string or chromoelectric flux tube between quark-antiquarks breaks with increasing separation between quarks. In this study, the critical distance for quark-antiquark chromoelectric flux tube or string breaking is determined to be rc=1.294±0.040 fm. The acceleration and Unruh temperature corresponding to this critical point signify the transition of the system's chiral symmetry from a broken to a restored state. Our estimates for the critical acceleration (ac=1.14×1034 cm/s2) and Unruh temperature (Tc=0.038 GeV) align with previous studies. This analysis illuminates the interplay between chiral symmetry restoration, the Unruh effect, and the breaking of the string or chromoelectric flux tube within the context of quark interactions.

Estimation of speed-related car body acceleration limits with quantile regression

PurposeThis study aimed to facilitate a rapid evaluation of track service status and vehicle ride comfort based on car body acceleration. Consequently, a low-cost, data-driven approach was proposed for analyzing speed-related acceleration limits in metro systems.Design/methodology/approachA portable sensing terminal was developed to realize easy and efficient detection of car body acceleration. Further, field measurements were performed on a 51.95-km metro line. Data from 272 metro sections were tested as a case study, and a quantile regression method was proposed to fit the control limits of the car body acceleration at different speeds using the measured data.FindingsFirst, the frequency statistics of the measured data in the speed-acceleration dimension indicated that the car body acceleration was primarily concentrated within the constant speed stage, particularly at speeds of 15.4, 18.3, and 20.9 m/s. Second, resampling was performed according to the probability density distribution of car body acceleration for different speed domains to achieve data balance. Finally, combined with the traditional linear relationship between speed and acceleration, the statistical relationships between the speed and car body acceleration under different quantiles were determined. We concluded the lateral/vertical quantiles of 0.8989/0.9895, 0.9942/0.997, and 0.9998/0.993 as being excellent, good, and qualified control limits, respectively, for the lateral and vertical acceleration of the car body. In addition, regression lines for the speed-related acceleration limits at other quantiles (0.5, 0.75, 2s, and 3s) were obtained.Originality/valueThe proposed method is expected to serve as a reference for further studies on speed-related acceleration limits in rail transit systems.

Kinematics of nonlinear waves over variable bathymetry. Part I: Numerical modelling, verification and validation

Fluid particle kinematics due to wave motion (i.e. orbital velocities and accelerations) at and beneath the free surface is involved in many coastal and ocean engineering applications, e.g. estimation of wave-induced forces on structures, sediment transport, etc. This work presents the formulations of these kinematics fields within a fully nonlinear potential flow (FNPF) approach. In this model, the velocity potential is approximated with a high-order polynomial expansion over the water column using an orthogonal basis of Chebyshev polynomials of the first kind. Using the same basis, original analytical expressions of the components of velocity and acceleration are derived in this work. The estimation of particle accelerations in the course of the simulation involves the time derivatives of the decomposition coefficients, which are computed with a high-order backward finite-difference scheme in time. The capability of the numerical model in computing the particle kinematics is first validated for regular nonlinear waves propagating over a flat bottom. The model is shown to be able to predict both the velocity and acceleration of highly nonlinear and nearly breaking waves with negligible error compared to the corresponding stream function wave solution. Then, for regular waves propagating over an uneven bottom (bar-type bottom profile), the simulated results are confronted with existing experimental data, and very good agreement is achieved up to the sixth-order harmonics for free surface elevation, velocity and acceleration.

Effect of Data-Processing Methods on Acceleration Summary Metrics of GNSS Devices in Elite Australian Football.

This study aimed to measure the differences in commonly used summary acceleration metrics during elite Australian football games under three different data processing protocols (raw, custom-processed, manufacturer-processed). Estimates of distance, speed and acceleration were collected with a 10-Hz GNSS tracking technology device from fourteen matches of 38 elite Australian football players from one team. Raw and manufacturer-processed data were exported from respective proprietary software and two common summary acceleration metrics (number of efforts and distance within medium/high-intensity zone) were calculated for the three processing methods. To estimate the effect of the three different data processing methods on the summary metrics, linear mixed models were used. The main findings demonstrated that there were substantial differences between the three processing methods; the manufacturer-processed acceleration data had the lowest reported distance (up to 184 times lower) and efforts (up to 89 times lower), followed by the custom-processed distance (up to 3.3 times lower) and efforts (up to 4.3 times lower), where raw data had the highest reported distance and efforts. The results indicated that different processing methods changed the metric output and in turn alters the quantification of the demands of a sport (volume, intensity and frequency of the metrics). Coaches, practitioners and researchers need to understand that various processing methods alter the summary metrics of acceleration data. By being informed about how these metrics are affected by processing methods, they can better interpret the data available and effectively tailor their training programs to match the demands of competition.

Estimation of consistent absolute acceleration and relative displacement floor response spectra in existing masonry-infilled reinforced concrete buildings

Estimation of consistent absolute acceleration and relative displacement floor response spectra in existing masonry-infilled reinforced concrete buildings

Velocity-field based load estimation of an unsteady actuator disc

Traditional methods for determining the load of an object in unsteady cases, such as Control-volume Momentum Integration (CMI) and Noca methods, encounter challenges related to near-body acceleration and pressure estimation. This prompts the need for innovative techniques to overcome these limitations. This study introduces a novel vorticity-based approach to expand classical load determination methods. The numerical results of an unsteady actuator disc (AD) CFD simulation are used to verify and quantify the uncertainty of the three methods. In the AD model, the load is prescribed and used as a source term. The velocity and pressure fields are solved from the Navier-Stokes equations using the open-source CFD package OpenFOAM, which offers a robust validation framework. Systematic examination of the robustness and accuracy of the three methods across various load and motion unsteady scenarios reveals that the proposed vorticity-based method excels in steady-state scenarios, exhibiting the highest level of robustness and accuracy. In contrast, the traditional CMI method proves more robust and accurate in pure motion cases. In scenarios involving static and moving AD with load variations, the new vorticity-based method demonstrates superior robustness and accuracy, mainly when moderate vorticity dynamics. Conversely, in cases with increased vorticity dynamics in the wake, the accuracy of the vorticity-based method decreases, with the CMI method showing superiority.

Angular acceleration estimation and aerodynamic parameter identification based on angular velocity equivalent model

Conventional angular acceleration estimation methods generate non-negligible errors when the control surface rapidly deflects; hence, the estimated angular acceleration cannot be used for aerodynamic parameter identification directly. This paper proposes an angular acceleration estimation method based on angular velocity equivalent model. The angular acceleration of the angular velocity equivalent model, whose angular velocity response is consistent with the flight test data, is used as the estimated angular acceleration. Firstly, the equivalent angular velocity model is established by combining the generic aerodynamic model with the rotational dynamic equations of aircraft. Secondly, the angular velocity data and the control surface deflection data are synchronized. Finally, the angular velocity response of the equivalent model is used as the predictor, and the estimated angular acceleration is obtained by extended Kalman filter. The aerodynamic parameter identification and validation are carried out using the estimated angular acceleration of a large civil aircraft flight test data. The results show that the angular acceleration obtained through the proposed angular acceleration estimation method meets the accuracy requirement of aerodynamic parameter identification.

Cooperative guidance law with maneuverability awareness: A decentralized solution

In this paper, we propose a cooperative guidance law aimed to achieve coordinated impact angles with limited observation on target information. The primary challenge lies in establishing an appropriate communication graph among all missiles and devising an algorithm to estimate target acceleration information during engagements. To address this, we propose a specific communication topology and employ a numerical integration-based estimation method. Additionally, a distributed algorithm is introduced to facilitate consensus on target acceleration estimation. Building upon these foundations, we design an optimal-control-based distributed guidance law for each missile. Performance of the proposed guidance law is validated through numerical simulations.

Coherent pressure and acceleration estimation from triply decomposed turbulent bluff-body wakes

Coherent pressure and acceleration estimation from triply decomposed turbulent bluff-body wakes

Research on cascade control method for turboshaft engine with variable rotor speed

Abstract In order to realize high-quality control for turboshaft engine with variable rotor speed, a cascade control method based on the acceleration estimator of gas turbine speed (N gdot ) through Complementary filtering – incremental nonlinear dynamic inversion (CF-INDI)with Newton’s prediction is proposed. Firstly, an adaptive torsional suppression method based on the Recursive Least Square (RLS) algorithm and combined with the control index of power turbine speed is proposed and designed to solve the torsional instability of control system in turboshaft engine with variable rotor speed. Then, an online N gdot estimated method based on CF-INDI with Newton’s prediction is developed, and the complementary filtering method is applied to compensate for the inaccuracy of the state variable model available at a single working point, and Newton prediction is used to alleviate the problem of lagging acceleration estimate, which is accessible to realize the cascade control for turboshaft engine based on N gdot . The simulation results show that the RLS adaptive torsional filter can effectively suppress the low-order torsional components with frequencies of 1.2 Hz and 2.0 Hz mixing in power turbine speed, and the torsional suppression effect is remarkable. In addition, under different flight conditions, CF-INDI with Newton prediction is faster and more accurate than INDI N gdot estimate, and smoother than central difference method, which proves the feasibility of INDI N gdot estimator. Meanwhile, after the application of CF-INDI with Newton prediction N gdot estimator in cascade control, the anti-interference capacity of power turbine speed is stronger, and the dynamic control effect is superior, which has satisfactory robustness performance.

Estimating Rotational Acceleration in Shoulder and Elbow Joints Using a Transformer Algorithm and a Fusion of Biosignals.

In the present study, we used a transformer model and a fusion of biosignals to estimate rotational acceleration in elbow and shoulder joints. To achieve our study objectives, we proposed a mechanomyography (MMG) signal isolation technique based on a variational mode decomposition (VMD) algorithm. Our results show that the VMD algorithm delivered excellent performance in MMG signal extraction compared to the commonly used technique of empirical mode decomposition (EMD). In addition, we found that transformer models delivered estimates of joint acceleration that were more precise than those produced by mainstream time series forecasting models. The average R2 values of transformer are 0.967, 0.968, and 0.935, respectively. Finally, we found that using a fusion of signals resulted in more precise estimation performance compared to using MMG signals alone. The differences between the average R2 values are 0.041, 0.053, and 0.043, respectively. Taken together, the VMD isolation method, the transformer algorithm and the signal fusion technique described in this paper can be seen as supplying a robust framework for estimating rotational acceleration in upper-limb joints. Further study is warranted to examine the effectiveness of this framework in other musculoskeletal contexts.

Verification of regulatory formulas for assessing the level of accelerations in SP 286.1325800.2016 "Construction facilities of increased responsibility. Rules of detailed seismic zonation" based on real data

The normative formulas of SP 286.1325800.2016 for estimation of peak ground accelerations in earthquakes were checked on records obtained in the near-fault zones of strong earthquakes (MS ~6.9÷7.15) of Japan made by K-NET and KiK-net stations. It was found that the recorded values of peak accelerations have a fairly large scattering even in the selected narrow range of magnitudes, which is obviously due to local site effects (soil response, topographic effects, etc.), as well as to differences in the characteristics of the earthquake sources and the paths of seismic wave propagation. Calculations by the normative formulas produced estimates that are near the lower limit of the recorded peak accelerations, and in the near-source zones, they noticeably underestimate the recorded peak accelerations. In general, the formulas of SP 286.1325800.2016 give us only approximate estimates, and therefore, it is necessary to develop more reliable methods for estimating peak accelerations and other parameters of seismic motion, taking into account soil conditions and regional characteristics, with components of probabilistic analysis.

A271 EFFECT OF ANTI-TNF AGENTS ON DNA METHYLATION IN PERIPHERAL BLOOD OF PATIENTS WITH INFLAMMATORY BOWEL DISEASE

Abstract Background Despite the success and ongoing use of tumor necrosis factor inhibitors (TNFi) in the treatment of inflammatory bowel disease (IBD), there are no predictors of response to therapy. While much research has gone into understanding genetic risks for IBD, less work has been done exploring epigenetic associations with treatment. Hence, we wondered whether epigenetic changes were associated with failure of TNFi in IBD. Aims Describe the association of TNFi response with DNA methylation in patients with IBD. Methods Participants ≥18 years with IBD (N=169) were selected from the Inflammation, Microbiome, and Alimentation: Gastro-Intestinal and Neuropsychiatric Effects (IMAGINE) Strategy for Patient Oriented Research (SPOR) Network. At enrollment participants completed a questionnaire that included their disease diagnosis, therapy, smoking history, and disease activity using the validated IBD Symptom Inventory (IBDSI). Patients provided whole blood samples that were processed for and run on Illumina DNA methylation arrays. Results The 169 patients were in three treatment groups: TNFi naïve (N=98, never exposed to an anti-TNF agent), TNFi responder (N=32, inactive disease on anti-TNF agent), and TNFi nonresponder (N=39, active disease not on any biologic at time of enrollment). The mean symptom score (SIBDSI) was different across the three groups (pampersand:003C0.001): TNFi nonresponders having a higher SIBDSI (24 ± 6.1) than the TNFi naïve (9.1 ± 5.5) or responder (8.3 ± 4.3) treatment groups. Relative proportions of leukocyte populations were estimated using DNA methylation. CD4 and CD8 T cell and B cell counts were higher (pampersand:003C0.05) in the nonresponders and responders versus TNFi naïve group. Neutrophil counts were lower (pampersand:003C0.05) in the TNFi nonresponders and responders compared to the TNFi naïve group (Figure 1). There was a trend towards increased epigenetic estimates of age acceleration (pampersand:003E0.05) in nonresponders versus responders and TNFi naïve patients, likely driven by disease activity (data not shown). Epigenome-wide analysis of the three groups revealed 16 CpGs for responder versus naïve (e.g. CDK5 regulatory subunit-associated protein 1-like 1 (CDKAL1), and two CpGs for nonresponders versus responders (Table 1). This includes a CpG for guanine nucleotide-binding protein subunit gamma-2 (GNG2) that was shared between the two comparisons. Conclusions Exposure to TNFi is associated with changes in peripheral leukocyte populations independent of response to treatment, indicating a TNFi effect. This implies that anti-TNF treatment is having some effect on patients even if there is clinical nonresponse. Differentially expressed CpGs implicates possible markers of response to treatment, particularly CDKAL1, a gene that has been associated with TNFi response in psoriasis. Funding Agencies Guts and Roses Charity

Dynamic characteristics analysis and robust transition control of tail-sitter VTOL UAVs

The strong nonlinear dynamics of tail-sitter vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs) have consistently constrained their applications. Particularly, the widely-varying flight speed and attitude during the transition flights pose substantial challenges for the controller design. In order to gain a clear understanding of the nonlinear transition flights, the long- and short- period dynamic characteristics of tail-sitter UAVs are investigated for the first time. The results reveal that the short-period mode exhibits either sluggish response or excessive overshoot in different transition stages, primarily due to the widely-varying damping ratio and natural angular frequency. Even worse, the long-period mode can diverge due to positive poles. To address these issues, a systematic controller is proposed. First, the transition trajectory is optimized and the optimal control inputs are employed in a feedforward manner to trim the nominal forces and moments. On this basis, a discrete-time linear quadratic regulation (LQR) controller with a predefined decay rate is developed to position the desired poles, and a novel angular acceleration estimation method is introduced to compensate for unmodeled dynamics. Simulations under different uncertainties indicate that the proposed control method performs better in both transition trajectory tracking and uncertainty suppression, compared to the PID and incremental nonlinear dynamic inversion (INDI) controllers.

Quick estimation of critical acceleration of slopes through a single prediction equation

Quick estimation of critical acceleration of slopes through a single prediction equation