Accuracy Of Dynamic Measurements Research Articles

A novel framework and validation for the dynamic characterization of civil structures via ground-based lidar

While there has been substantial research conducted on the use of Ground-Based Lidar (GBL; i.e., Terrestrial Laser Scanners) in monitoring the static deformation of civil structures, its application in monitoring dynamic vibrations of structures, which is critical for structural health monitoring (SHM), has only been studied to a limited extent. Traditional contact-based SHM frameworks are constrained by a limited number of sensors and the need for physical access for instrumentation placement. Although recent case studies demonstrate GBL's potential in quantifying dynamic displacements, there is a need for more comprehensive research to validate the accuracy of GBL-based dynamic measurements under various GBL- and structure-based parameters in an autonomous and scalable framework. Therefore, the main objective of this study is to develop and comprehensively validate a novel end-to-end framework to monitor the dynamic vibrations of structures using GBL through extensive experimentation in a controlled laboratory environment. In this study, a novel two-step spatio-temporal algorithm was developed to extract the dynamic vibrations of structures from the dynamic point clouds. The framework leverages the Density-based Spatial Clustering of Applications with Noise (DBSCAN) and change detection algorithms. The impact of several GBL-based parameters on the accuracy of the operational modal analysis results was investigated across six single-degree-of-freedom structures with unique natural frequencies. The GBL-based parameters included the resolution, quality, and point-to-point distance of the dynamic point clouds. Accelerometers and infrared-based sensors were used for the validation of GBL measurements and operational modal analysis results. To validate GBL's full-field mode shapes across the tested specimen configurations, analytical and finite element models were constructed to provide high-fidelity mode shapes as ground-truth data. The results show that the GBL can detect sub-millimeter structural vibrations, and that the resulting natural frequencies and operational deflected shapes closely match those of traditional sensing modalities, and the analytical and finite element models. This study concludes that GBL can be used reliably for remotely monitoring the dynamic response of structures at a high spatial resolution. However, further research is warranted to evaluate the full extents of the proposed framework.

Modelling and estimating trajectory points from RTK-GNSS based on an integrated modelling approach

The sparse Gaussian process regression (GPR) has been used to model trajectory data from Real time kinematics-global navigation satellite system (RTK-GNSS). However, upon scrutinizing the model residuals; the sparse GPR model poorly fits the data and exhibits presence of correlated noise. This work attempts to address these issues by proposing an integrated modeling approach called GPR-LR-ARIMA where the sparse GPR was integrated with the linear regression with autoregressive integrated moving average errors (LR-ARIMA) to further enhance the description of the trajectory data. In this integrated approach, the predicted trajectory points from the GPR were further described by the LR-ARIMA. Simulation of the GPR-LR-ARIMA on three sets of trajectory data indicated better model fit, revealed in the normally distributed model residuals and symmetrically distributed scatter plots. Correlated noise was also successfully eliminated by the model. The GPR-LR-ARIMA outperformed both the GPR and LRARIMA by its ability to improve mean-absolute-error in 2-dimension positioning by up to 86%. The GPR-LR-ARIMA contributes to enhancement of positioning accuracy of dynamic GNSS measurements in localization and navigation system with good model fit.

Reducing the Uncertainty of the Moving Object Location Measurement with the Method of Quasi-Multiple Measurement in GNSS Technology in Symmetrical Arrangement

The article presents a solution to the problem of limited accuracy of dynamic measurements performed with GNSS receivers. The proposed measurement method is a response to the needs related to the assessment of the measurement uncertainty of the position of the track axis of the rail transport line. However, the problem of reducing the measurement uncertainty is universal for many different situations where high accuracy of positioning of objects is required, especially in motion. The article proposes a new method to determine object's location using geometric constraints of a number of GNSS receivers arranged in symmetric configuration. The proposed method has been verified by comparing signals recorded by up to five GNSS receivers during stationary and dynamic measurements. The dynamic measurement was made on a tram track within the framework of a cycle of studies upon effective and efficient methods to catalogue and diagnose tracks. A detailed analysis of the results obtained with the quasi-multiple measurement method confirms remarkable reduction in their uncertainty. Their synthesis shows the usability of this method in dynamic conditions. The proposed method is expected to find application in measurements requiring high accuracy, and in case of deterioration of the signal quality from satellites by one or more of GNSS receivers due to the appearance of natural obstacles.

Evaluating the adequacy of dynamic pressure remote sensing method in a model gas turbine combustor

Direct measurement of dynamic pressure in a combustor using a flush sensor mounting generally shortens the lifetime and lowers the measurement accuracy of the sensor due to its direct exposure to hot-burnt gases. Thus, indirect remote sensing methods are typically employed in combustion systems; however, the measurements may contain errors. Therefore, in this study, the feasibility of a remote sensing method for measuring dynamic pressure is verified by conducting an acoustic forcing experiment in a model gas turbine combustor. Sensing performance of the sensor adapters are evaluated based on their measurement locations for a driving frequency of 50–5000 Hz. In an experiment with different measurement locations, mode shapes corresponding to a resonant frequency of 160 Hz are clearly observed. Furthermore, in a sensor-adapter performance experiment, the effects of hole-size and length of a dynamic pressure propagation tube on the sensing characteristics are investigated and the optimum design shape is obtained. The results indicate an increase in the accuracy of dynamic pressure measurements and a subsequent decrease in the risk of combustion instability accidents. Therefore, the findings of this study and optimal design methodology for remote sensing equipment could positively contribute to the safe operation of gas turbines.

Effects of T2 * on accuracy and precision of dynamic T1 measurements using the single reference variable flip angle method: a simulation study.

To study in simulation and in theory the accuracy and precision of dynamic T1 measurements obtained using the previously published single-reference variable flip angle (SR-VFA) technique, with a focus on the effects of dynamic changes in T2 * on the calculation. Monte Carlo simulations were performed over 1000 noisy iterations for the VFA method, the SR-VFA method, and a proposed method, SR-VFA with a T2 * correction (SR-VFA-T2 *). Dynamic T1 estimates were calculated analytically for each method, with signals modeled by the steady-state spoiled gradient echo equation. The mean and standard deviation of these estimates were calculated and compared to truth, while varying repetition time (TR), baseline and dynamic T1 , echo time (TE), baseline and dynamic T2 *, flip angles, and the number of averages on baseline scans. Additionally, the variance of T1 in the SR-VFA and SR-VFA-T2 * methods was derived analytically based on the theory of propagation of errors. This equation was used to produce an inverse-variance weighted linear combination to improve T1 mapping precision in the SR-VFA-T2 * method. Flip angle sensitivity of dynamic T1 precision in the SR-VFA and SR-VFA-T2 * methods was also performed. Substantial bias can be produced by the SR-VFA method when the ratio of the T2 * decay of the dynamic signal versus that of the baseline signals deviates from 1, with a 0.01 deviation leading to approximately a 1% bias in cases of high SNR and TR ≫ T1 . This bias can be corrected by estimating the baseline and dynamic T2 * values in this ratio via multiecho measurements. The bias and precision of the SR-VFA-T2 * method, when normalized to scan time, is found to rival and sometimes improve upon the two flip angle VFA method when an inverse variance weighted linear combination is applied across its multiecho T1 maps. The analytic variance equation presented is found to be accurate within 1% relative to the Monte Carlo simulations over a broad parameter space. Flip angle ranges that maximize SR-VFA and SR-VFA-T2 *T1 precision over a broad parameter space are given, and each is defined relative to TR and T1 . Multiecho SR-VFA-T2 * T1 mapping is found in simulation and theory to be a promising alternative to the VFA method that maintains speed of the SR-VFA method with accuracy and precision similar to the VFA method.

Results of experimental studies of the mutual influence of tenometric sensors on the plane elements of the road machine design

Analysis of the use of road vehicles in recent years shows an increasing trend continuous mode of their operation. In these circumstances, it is important to know the current technical status condition of the road machine. To a large extent, this is determined by the reliability of the measurement information about dynamic loads on the structural elements of a road machine. In order to increase the accuracy and reliability of dynamic measurements of loads, the authors conducted a number of experimental studies. Experimental studies of the mutual influence of strain gauges on the errors of dynamic load measurements on the structure of the road machine were carried out using a model of the planar element of the structure of the road machine. A computerized four-channel spatially distributed measurement information system was used in the experimental studies. Research results are presented mutual influence of strain gauges under various static and dynamic loads. It is established that due to the action of inertia forces and acceleration, the interaction between the sensors is manifested to a greater extent. Using the methods of comparison, comparison and complex analysis of the results of experimental studies, the dependences of the errors of dynamic load measurements on the angle of action and load removal were established. According to the results of research, the functions of dependence of dynamic loads on the direction and force of action on each of the 4 strain gauges, taking into account their mutual location, are obtained. It is shown that the experimentally obtained coefficient of the interconnection of strain gauges depends on both the mutual location of the sensors and the spatial direction of the force and has a nonlinear dependence. The experimentally determined error function between the four strain gauges was 3%. The reason for the increase in measurement errors of dynamic planar loads is the displacement of the operating point upwards by the transformation function at positive load, or downwards at negative load. The magnitude of the displacement depends on both the magnitude of the load and its removal.The results obtained will allow optimizing the placement and number of strain gauges on board Measuring Information System on the structure of of the road machine. As a result, the accuracy and reliability of measuring the parameters of the dynamic loads of the road machine will significantly increase.

ЦИФРОВЫЕ МОДЕЛИ ИНТЕЛЛЕКТУАЛЬНЫХ РАСПРЕДЕЛЕННЫХ ИЗМЕРИТЕЛЬНЫХ СИСТЕМ

The issues of the information organization of the measurement control system of a distributed object based on digital models of its main blocks, databases reflecting the functional organization of each block, its input and output values aimed at increasing the accuracy of static and dynamic measurements are considered.

Non-Invasive Estimation of the Mean Right Atrial Pressure Using Sonographic Measurements of the Right Internal Jugular Vein

Introduction Right ventricular dysfunction (RVD) is associated with increased morbidity and mortality. RVD is detected clinically by elevated JVP on physical exam, a reflection of the high mean right atrial pressure (mRAP). The sensitivity and specificity of mRAP estimation by JVP assessment is limited. Non-invasive techniques that can reliably estimate mRAP are thus useful to supplement physical exam findings. Sonographic measurement of the IVC has emerged as the most utilized non-invasive estimate of the mRAP but the IVC is visualized only 75-90% of the time. Objectives In this study, we prospectively tested the diagnostic accuracy of various static and dynamic ultrasound measurements of the right internal jugular vein (RIJV) in estimating the mRAP and compared this to mRAP measured by right heart catheterization (RHC). The best identified RIJV parameter was then compared to simultaneous measurements of IVC and JVP assessment by HF cardiologists. Methods This is a single center prospective study that enrolled patients scheduled to undergo RHC. IRB approved consents were obtained. JVP assessment was performed by a HF cardiologist, the IVC and RIJV ultrasound measures were obtained by author KH, and these were performed prior to right heart catheterization. RIJV measurements were done w/ the patient lying flat. Categorical variables were reported as percentages, mean ± standard deviation if normally distributed data, and as median ± interquartile range for non-normally distributed data. Area under the curve (AUC) of various static and dynamic RIJV measures was calculated using the receiver operator characteristic (ROC) curves. The best RIJV parameter that best estimated mRAP was then compared against IVC and JVP assessment by HF cardiologists using mRAP measured by RHC as gold standard. Results We enrolled 100 patients, 8 of whom were excluded due to incomplete data. The patients were 63.6 ± 13.8 y/o, mostly males (65%), 20% had heart transplants, and 38% were obese. The RIJV of all subjects were well visualized in all cases. Of the various static and dynamic RIJV parameters tested, the expansibility index calculated as (CSA on end-expiration- CSA with Valsalva)/CSA on end-expiration best correlated with the mRAP [AUC 0.62, 95% CI (0.49-0.74)]. In this study, the IVC max diameter was superior to HF cardiologist exam > RIJV in estimating the mRAP (Figure). The findings were similar when applied to obese patients. Conclusion While the RIJV was visualized 100% of the time, the best RIJV parameter in estimating the mean right atrial pressure was inferior to IVC max diameter and HF cardiologist JVP assessment, even in obese patients.

Bayes filter for dynamic coordinate measurements – Accuracy improvment, data fusion and measurement uncertainty evaluation

This paper presents a novel methodology to improve the measurement accuracy of dynamic measurements. This is achieved by deducing an online Bayes optimal estimate of the true measurand given uncertain, noisy or incomplete measurements within the framework of sequential Monte Carlo methods. The estimation problem is formulated as a general Bayesian inference problem for nonlinear dynamic systems. The optimal estimate is represented by probability density functions, which enable an online, probabilistic data fusion as well as a Bayesian measurement uncertainty evaluation corresponding to the “Guide to the expression of uncertainty in measurement“. The efficiency and performance of the proposed methodology is verified and shown by dynamic coordinate measurements.

Study on the Parameters Influencing the Accuracy and Reproducibility of Dynamic Pressure Measurements at the Surface of a Rigid Body During Water Impact

Water wave slamming is known as one of the most important load which marine constructions encounter. Especially the large and spiky local pressures moving fast over the body surface during a slamming event can be harmful for the structure. Analytical and numerical research on these pressure loads has already been performed, but however, quantitative experimental information necessary for validation of these studies is restricted. This lack in experimental data may originate from the fact that accurate pressure measurements are difficult to perform. This paper investigates the reason why this type of measurements is so difficult by identifying the parameters affecting the pressure recordings during water impact. According to the authors’ knowledge, no other paper is available in the open literature which investigates all these influencing factors. It has been observed that the pressure signal sampling rate, sensor position, water temperature, object surface conditions and water surface conditions all have an effect on the measured pressures. Only by controlling these parameters, accurate and reproducible results are possible. Precautions in order to meet this goal are formulated.

Estimating measurement system accuracy in researching nonstationary processes

The time dependence is considered for the measuring-system error in dynamic measurements associated with the nonstationarity of the process. Relationships are derived for estimating the accuracy of dynamic measurements, and lines are proposed for balancing out the additional error.

Dynamic light scattering in subdiffusive regimes

For describing the fluctuating signal scattered from a multiple-scattering system, diffusive-wave spectroscopy makes use of a diffusion model that provides the path-length distribution of scattered waves for a specific geometry. Using the recently introduced optical path-length spectroscopy, we show that the diffusion model fails to describe wave propagation in the low-order multiple-scattering regime. We propose a new methodology with which to obtain information about the dynamic properties of nondiffusive scattering systems. We use optical path-length spectroscopy to obtain experimentally the path-length distribution of optical waves scattered from dynamic colloids, which are multiply scattering but not in the diffusion limit. The experimental results show that, with this new technique, the accuracy of dynamic measurements is significantly improved in subdiffusive scattering regimes.

Accuracy of dynamic modulus measurements made with the dynamic mechanical thermal analyzer

The accurate determination of the complex moduli of viscoelastic materials is of great importance for the efficient design of many noise control devices. It is often the case that a design, in conjunction with its acoustic performance requirements, leads to a narrow band of acceptable dynamic modulus for the viscoelastic material. In such cases knowledge of the accuracy and reliability of the measurement apparatus is essential. Dynamic complex shear modulus is measured at Carderock Division Naval Surface Warfare Center (CDNSWC) with the Dynamic Mechanical Thermal Analyzer (DMTA), manufactured by Polymer Laboratories. An attempt to quantify the absolute accuracy of the DMTA measurement has been made through the consideration of errors including the accuracy of the beam solution used to infer the complex modulus, compliance of the sample mounts, measurement noise, temperature control, thermal stress, Poisson effects, and the implementation of time‐temperature superposition. With these considerations, an ad hoc error analysis is implemented to quantify absolute error bounds expected for DMTA measurements of a hypothetical material. These results are of direct interest to the ASA Committee on Standards S2WG79, ‘‘Characterization of the Dynamic Properties of Viscoelastic Polymers,’’ which has initiated round‐robin testing among committee participants. CDNSWC results from the DMTA tests of three round‐robin materials will be presented.

Frequency Response of Diaphragm Pore Pressure Transducers in Dynamic Centrifuge Model Tests

Abstract A theoretical relation for estimating the frequency response of diaphragm pore pressure transducers is derived by considering the interaction between the diaphragm, porous cap, air, and pore fluid inside the transducer. Using this relation, the frequency response of a pore pressure transducer under several centrifuge modeling environments is studied. The results indicate that the viscous drag imposed by the porous cap on the pore fluid can significantly reduce the sensitivity of the transducer to high frequency pore pressure fluctuation. This may impair the accuracy of dynamic pore pressure measurements in high-g centrifuge modeling of dynamic events if viscosity scaling is used.

Experimental comparison of dynamic mechanical testing facilities at several Navy laboratories

Dynamic mechanical spectroscopy provides valuable information on frequency‐dependent relaxation mechanisms in high polymers. The Young's modulus and loss tangent are often measured, due to the relative ease of experimental implementation. A variety of techniques is used, which often gives different results for samples that are supposedly of the same materials. A problem exists in interpreting such results in that one can never be sure if such differences are due to measurement techniques or to actual material property variations. Two systems, an automated resonance technique and the Polymer Laboratories DMTA, are now used at several Navy laboratories. To check the internal consistency of results obtained with these systems, a “round‐robin” evaluation was performed. Common batches of materials of several different types of rubbers were used to prepare samples for each of three different Navy laboratories. The results of this test will be presented, and factors that can affect the accuracy and reproducibility of dynamic mechanical property measurements will be discussed. Criteria for the applicability of the method of reduced variables will also be treated. [Work supported by NAVSEA.]

Dynamic DSC purity analysis studies of two component doped systems

Up to the present time, the accuracy and precision of dynamic DSC purity analysis measurements have been tested by using simple binary systems as models. For the most part, pure organic substances have served as host and eutectic-forming low level dopant. As a first step in considering whether the DSC method can be applied to multicomponent impure substances, the simple ternary model system, phenacetin doped with benzamide and p-aminobenzoic acid, has been studied. Separately, the two dopants form well defined eutectics with the host melting at 370 K (benzamide dopant) and 385 K ( p-aminobenzoic acid dopant). When the two dopants are combined, a third eutectic melting at 353 K is produced. Evidence is presented confirming the fact that in the range 100-98.5 mole % purity, the total DSC measured impurity is the sum of the two individual dopant levels, and is independent of their relative proportions.