Method For Dynamic Characterization Research Articles

Kinematic and dynamic analysis of a 2DOF parallel robot arm for wind turbine blade fatigue testing

In response to the issues of low efficiency and significant impact on blade intrinsic frequency posed by the current biaxial resonance blade fatigue testing method, an innovative dynamic characterization method based on a 2-DOF (two-degree-of-freedom) planar parallel testing device is proposed in this paper. Firstly, the kinematic forward and inverse solution equations of the mechanism are established by scrutinizing the inherent positional relationships that govern its operation. The velocity Jacobian matrix is derived, and three types of singularities prevalent in the mechanism are analyzed. Secondly, based on the kinematics of the mechanism, an analysis of its workspace is undertaken to subsequently determine the range of its motion. Thirdly, by applying the Lagrange equations, the kinetic model of the mechanism is established, which can capture the dynamic interplay of forces and accurately calculate the changes in angular displacement, angular velocity, and angular acceleration of the active joint. Finally, a virtual prototype model and kinematics simulation are conducted based on the mechanism dimensions and assembly mode. The results show that the angular velocity, angular acceleration, and torque of the active joint all demonstrate smooth and uninterrupted curves that align with the actual testing trajectories, confirming the accuracy and effectiveness of our approach.

A Generalized Method for Dynamic Fracture Characterization Using Two-Phase Rate Transient Analysis of Flowback and Production Data

Summary This study presents a comprehensive method for characterizing reservoir properties and hydraulic fracture (HF) closure dynamics using the rate transient analysis of flowback and production data. The proposed method includes straightline analysis (SLA), type-curve analysis (TCA), and model history matching (MHM), which are developed for scenarios of two-phase flow in fracture, stimulated reservoir volume (SRV), and nonstimulated reservoir volume (NSRV) domains. HF closure dynamics are characterized by two key parameters, which are pressure-dependent permeability and porosity controlled by fracture permeability modulus and compressibility. The above techniques are combined into a generalized workflow to estimate iteratively the five parameters (including four optional parameters and one fixed parameter) by reconciling data in different domains of time (single-phase water flow, two-phase flow, and hydrocarbon-dominated flow), analysis methods (SLA, TCA, and MHM), and phases (water and hydrocarbon phase). We used flowback and production data from a shale gas well in the US and a shale oil well in China to verify the practicability of the method. The analysis results of the field cases confirm the good performance of the newly developed comprehensive method and verify the accuracy in estimating the static fracture properties [initial fracture pore volume (PV) and permeability] and the HF dynamic parameters using the proposed generalized workflow. The accurate prediction of the decreasing fracture permeability and porosity, fracture permeability modulus, and compressibility demonstrates the applicability of the comprehensive method in quantifying HF dynamics. The field application results suggest a reduction of the fracture PV by 15% and 20%, and a reduction of the fracture permeability by 80% and 90% for shale gas and shale oil wells, respectively.

Quantitative analysis on resistant forces at oil-surfactant-rock interfaces with dynamic wettability characterization

Adhesion of oil at rock surface plays an important role in the liberation of oil from micro-/nano-pores, especially for heavy oil that has extremely high viscosity. Although molecular dynamics simulation is widely used to study the interfacial interaction for some specific oil-water-rock systems, experimental measurements provide more realistic and reliable evidence. In this work, we propose a dynamic wettability characterization method to indirectly measure resistant forces at oil-surfactant-rock interfaces, including frictional force, wettability hysteresis force, and viscous force, which are parallel with the oil-solid interface. The adhesive force, which is normal to the oil-solid interface is calculated through measurement of work of adhesion. The results show that work of adhesion instead of contact angle can better describe the adhesion of oil at solid surface. The effect of surfactant concentration on work of adhesion is different for water-wet and oil-wet surfaces. Moreover, average viscous forces are calculated through force analysis on oil drops moving along solid surface in different surfactant environments. It is found that viscous force has a magnitude comparable to the frictional force during the movement, while the wettability hysteresis force is negligible. On the other hand, the adhesive force calculated from the work of adhesion is also comparable to the viscous force. Therefore, both the resistant forces parallel with and normal to the oil-solid interface should be minimized for the liberation of oil from rock surface. This work proposes a simple method to evaluate the wetting capability of different surfactants and measure the adhesive force between heavy oil and rock surfaces indirectly, which provides insight into the adhesion of heavy oil at rock surface and would be valuable for the development of surfactant-based oil recovery methods.

Comparison of different methods for dynamic characterization of porous-elastic materials

Acoustical simulation of porous-elastic materials requires several properties to be characterized, one of them is the dynamic mechanical behavior of the structure. For this goal, quasi-static mechanical analysis (QMA) is the generally used method executed in the ca. 20-60 Hz frequency range, resulting constant (averaged) mechanical properties. Polymer-based materials, however, are well-known from their time- and frequency-dependent behavior. This implies the need for having frequency-dependent data in a wider frequency range, but the error induced by the fluid motion inside the pores increases with frequency. For that reason, dynamic mechanical analysis (DMA) together with frequency-temperature superposition method was chosen to analyze the possibility of extending the evaluable frequency range. Different measurement setups and strategies were tested and evaluated to minimize the errors coming from machine resonances and other influencing factors, and results were compared to those obtained from the classical QMA measurements. It was finally proven, that with thoroughly chosen technique, DMA can give high quality results for porous-elastic materials as well, in a remarkably wide frequency range.

DynH 2 O: Aufbau zur metrologischen Charakterisierung der dynamischen Eigenschaften von Hygrometern

Abstract A novel flow switching setup for the dynamic generation and metrological detection of fast, isolated H2O concentration changes is presented and characterized. Based on this flow setup, very accurate, static H2O concentrations as well as highly dynamic H2O step changes of several 1000 ppmv (µmol/mol) can be generated and repeated. First experiments show that temporal water vapor concentration gradients of up to 10000 ppmv/s can be generated and measured. Based on this setup, a dynamic hygrometer characterization method was developed and demonstrated using a polymer-based hygrometer as device under test (DUT). The polymer hygrometer (with about 180 ppmv/s) proved to be more than 15 times slower than the optical reference hygrometer (with 3000 ppmv/s) and could be modeled and described well with a first order lowpass. To estimate the dynamics of the spatial and temporal H2O-profile, a fast, traversable, local sampling probe was developed and used in combination with a fast, extractive laser hygrometer (called SEALDH-II). The modeling of the H2O distribution in the dynamically operated flow channel enables the calculation of the dynamic concentration at the position of the DUT based on the data of the spatially averaging open-path laser reference hygrometer. In the future, this calculation will be used to determine a transfer function between the optical, open path reference hygrometer and the position of the DUT in order to extract the ideal step response of the DUT from the measured data of the flow channel.

Dynamic response characterization and simplified analysis methods for viscoelastic dampers considering heat transfer

AbstractViscoelastic (VE) dampers are sensitive to temperature, excitation frequency, and strain level. As they dissipate the kinetic energy from earthquake or wind‐induced structural vibrations, their temperature increases from the heat generated, consequently softening their VE materials and lowering their dynamic mechanical properties. Temperature increase can be significant for long‐duration loading, but can be limited by heat conduction and convection which depend on damper configuration. The writers analytically explored such effect on the six different dampers by using their previously proposed three‐dimensional finite‐element analysis method. Results provided better understanding of how heat is generated within the VE material, conducted and stored in different damper parts, and dispersed to the surrounding air. These results also led to characterization of both local (e.g., temperatures, properties, and strain energy density) and global (e.g., hysteresis loops, and stiffness) behavior of VE dampers, and provided a framework for a new simplified one‐dimensional (1D) modeling approach for time‐history analysis. This new proposed 1D method greatly improves the computation time of the previously proposed long‐duration method coupling fractional time‐derivatives VE constitutive rule with 1D heat transfer analysis. Unlike the previous method, it idealizes uniform shear strain and VE material property distributions for computational efficiency, but still simulating non‐uniform temperature distribution along the thickness direction of the VE material. Despite the approximations, it accurately predicts VE damper global responses.

Data-Driven Identification of Nonlinear Power System Dynamics Using Output-Only Measurements

In this paper, we propose a novel approach for the data-driven characterization of power system dynamics. The developed method of Extended Subspace Identification (ESI) is suitable for systems with output measurements when all the dynamics states are not observable. It is particularly applicable for power systems dynamic identification using Phasor Measurement Units (PMUs) measurements. As in the case of power systems, it is often expensive or impossible to measure all the internal dynamic states of system components such as generators, controllers and loads. PMU measurements capture voltages, currents, power injection and frequencies, which can be considered as the outputs of system dynamics. The ESI method is suitable for system identification, capturing nonlinear modes, computing participation factor of output measurements in system modes and identifying system parameters such as system inertia. The proposed method is suitable for measurements with a noise similar to realistic system measurements. The developed method addresses some of the known deficiencies of existing data-driven dynamic system characterization methods. The approach is validated for multiple network models and dynamic event scenarios with synthetic PMU measurements.

Dynamic characterization of breast cancer response to neoadjuvant therapy using biophysical metrics of spatial proliferation

Current tools to assess breast cancer response to neoadjuvant chemotherapy cannot reliably predict disease eradication, which if possible, could allow early cessation of therapy. In this work, we assessed the ability of an image data-driven mathematical modeling approach for dynamic characterization of breast cancer response to neoadjuvant therapy. We retrospectively analyzed patients enrolled in the I-SPY 2 TRIAL at the Atrium Health Wake Forest Baptist Comprehensive Cancer Center. Patients enrolled on the study received four MR imaging examinations during neoadjuvant therapy with acquisitions at baseline (T0), 3-weeks/early-treatment (T1), 12-weeks/mid-treatment (T2), and completion of therapy prior to surgery (T3). We use a biophysical mathematical model of tumor growth to generate spatial estimates of tumor proliferation to characterize the dynamics of treatment response. Using histogram summary metrics to quantify estimated tumor proliferation maps, we found strong correlation of mathematical model-estimated tumor proliferation with residual cancer burden, with Pearson correlation coefficients ranging from 0.88 and 0.97 between T0 and T2, representing a significant improvement from conventional assessment methods of change in mean apparent diffusion coefficient and functional tumor volume. This data shows the significant promise of imaging-based biophysical mathematical modeling methods for dynamic characterization of patient-specific response to neoadjuvant therapy with correlation to residual disease outcomes.

Comparison of extraction methods for extracellular polymeric substances (EPS) and dynamic characterization of EPS from sessile microorganisms during pyrite bioleaching

Extracellular polymeric substances (EPS) have many beneficial functions in the bioleaching process. A mixed culture of moderate thermophilic microorganisms was used to bioleach pyrite concentrate in a stirred tank reactor at a pulp density of 6%. Three physical methods (heating, ultrasound and vibration with glass beads) and three chemical methods (NaOH, H2SO4 and formaldehyde) were assessed for the extraction of EPS from sessile microorganisms. The parameter conditions for each method were optimised to obtain the optimal settings. The EPS content of each extract varied depending on the extraction method used. Cell lysis can be minimised by optimizing the extraction conditions. Results indicated that heating method outperformed other methods with low cell lysis and yielded 355.56 ± 116.56 ug/108 cells of protein and 16.72 ± 1.45 ug/108 cells of polysaccharides. Thereafter, this method was applied to extract EPS from pyrite surface during the bioleaching process. During pyrite bioleaching, extracellular proteins were the major component of EPS extracted from sessile strains. Confocal laser scanning microscope and scanning electron microscope showed that pyrite grains were wrapped by many extracellular proteins. Therefore, this research can provide a reference for the extraction of EPS from moderate thermophilic bioleaching systems by analysing the potential impact of extraction methods.

Towards traceable dynamic pressure calibration using a shock tube with an optical probe for accurate phase determination

In this paper, we introduce a robust method for dynamic characterization of pressure measuring systems used in time-varying pressure applications. The dynamic response of the pressure measuring systems in terms of sensitivity and phase as a function of frequency at various amplitudes of the measurand can be provided. The shock tube which is the candidate primary standard for dynamic pressure calibration at the National Laboratory for pressure, Sweden, was used to realize the dynamic pressure. The shock tube setup used in this study can realize reference pressure with amplitudes up to 1.7 MPa in the frequency range from below a kilohertz up to a megahertz. The amplitude of the realized step pressure was calculated using the Rankine–Hugoniot step relations. In addition, the accurate time of arrival of the generated shock at the device under test (DUT) was measured using an optical probe based on shadowgraphy. The optical detector has a response time in nanosecond time scale which is several orders of magnitude faster than the response time of any pressure measuring system. Hereby, the latency between physical stimuli and response of the DUT can be measured. By the knowledge of the amplitude and the accurate time of arrival of the reference step pressure, the transfer function of the DUT can be calculated and presented in Bode diagrams of sensitivity and phase response versus frequency. The uncertainty in sensitivity and phase measurements was estimated. The information provided by this work is useful for developing reliable models of dynamic pressure measuring system and provide accurate information about their dynamic response. That in turn will contribute to establish a traceability chain for dynamic pressure calibration.

High-Force Application by a Nanoscale DNA Force Spectrometer.

The ability to apply and measure high forces (>10 pN) on the nanometer scale is critical to the development of nanomedicine, molecular robotics, and the understanding of biological processes such as chromatin condensation, membrane deformation, and viral packaging. Established force spectroscopy techniques including optical traps, magnetic tweezers, and atomic force microscopy rely on micron-sized or larger handles to apply forces, limiting their applications within constrained geometries including cellular environments and nanofluidic devices. A promising alternative to these approaches is DNA-based molecular calipers. However, this approach is currently limited to forces on the scale of a few piconewtons. To study the force application capabilities of DNA devices, we implemented DNA origami nanocalipers with tunable mechanical properties in a geometry that allows application of force to rupture a DNA duplex. We integrated static and dynamic single-molecule characterization methods and statistical mechanical modeling to quantify the device properties including force output and dynamic range. We found that the thermally driven dynamics of the device are capable of applying forces of at least 20 piconewtons with a nanometer-scale dynamic range. These characteristics could eventually be used to study other biomolecular processes such as protein unfolding or to control high-affinity interactions in nanomechanical devices or molecular robots.

Alternative experimental methods for machine tool dynamics identification: A review

An accurate machine dynamic characterization is essential to properly describe the dynamic response of the machine or predict its cutting stability. However, it has been demonstrated that current conventional dynamic characterization methods are often not reliable enough to be used as valuable input data. For this reason, alternative experimental methods to conventional dynamic characterization methods have been developed to increase the quality of the obtained data. These methods consider additional effects which influence the dynamic behavior of the machine and cannot be captured by standard methods. In this work, a review of the different machine tool dynamic identification methods is done, remarking the advantages and drawbacks of each method.

An Enhanced Method for Dynamic Characterization of High-Power LEDs for Visible Light Communication Applications

Visible light communications (VLC) have been proposed for several applications beyond the traditional indoor scenarios, from vehicular to underwater communications. The common element in all these applications is the use of light-emitting diodes (LEDs) in which the forward current that flows through each LED plays a major role. Therefore, knowing the electrical equivalent of the LEDs is a useful tool for the proper design of the VLC systems. Currently, some measurement instruments exist, such as the LCR (inductance, capacitance, and resistance) meters or impedance analyzers to characterize the main parameters of the LEDs. However, these instruments and measurement procedures are subject to satisfying some requirements, such as a minimum value of the input impedance or the maximum forward current. In this work, the LED LXHL-BW02 is used to obtain its equivalent circuit, using different measurement methods and traditional methods of measurement with our proposed method. The equivalent model is implemented on the simulation tool LTSPICE. Our alternative method can be used for determining the electrical equivalent circuit of LEDs subject to high current variations at very high frequencies, in the MHz range, i.e., in an operating range for VLC applications.

The effect of lactic acid bacteria and co-culture on structural, rheological, and textural profile of corn dough.

This study is aimed at assessing the effect of lactic acid bacteria (LAB) on corn flour using dynamic characterization methods including RVA, TPA, Rheometer, SEM, and DSC along with co‐culture technique in order to enhance its applicability by evaluating the variations in rheological, textural, morphological, thermal, and structural properties. Our findings suggested that bacterial incorporation both individually and in combination (co‐culture) revealed an improved corn dough profile with better properties. SEM showed irregular shape of particles having more grooves, indentations, and cracks. RVA demonstrated different pasting behavior on the dough. Bacterial inoculation in flour attributed to increase the TO (68.61–71.18), TP (73.74–78.42), TC (78.78–85.36), melting temperature (10.17–15.19), and ΔH (2.72–5.40). The hardness of corn was found approximately 75% of native dough. In treated corn, an increase was noted in both loss and storage modulus in correspondence with changes in the starch configuration and leaching of constituents. The results from DSC presented an increased melting temperature range and gelatinization enthalpy owing to bacterial treatment accredited to diversified morphological characteristics. The outcomes concluded in demonstration of a novel influence on structural, thermal, morphological, and rheological capabilities and capacities of corn dough. Lactic acid bacteria hydrolyzed part of the corn and flour had smaller, irregularly shaped particles with more holes in them, resulting in a reduced water retaining capacity. Textural, thermal, and pasting profile has also been improved due to degradation of macromolecules. Furthermore, the insight alterations induce various changes leading to improved corn flour. It may also develop the associations about the upright insurgence in the corn dough profile and its potential usage in industry and homes.

Near-Field Imaging and Time-Domain Dynamics of Photonic Topological Edge States in Plasmonic Nanochains.

Time-domain dynamic evolution properties of topological states play an important role in both fundamental physics study and practical applications of topological photonics. However, owing to the absence of available ultrafast time-domain dynamic characterization methods, studies have mostly focused on the frequency-domain-based properties, and there are few reports demonstrating the time-domain-based properties. Here, we measured the dynamic near-field responses of plasmonic topological structures of gold nanochains with the configuration of the Su-Schrieffer-Heeger model by using ultrahigh spatial-temporal resolution photoemission electron microscopy. The dephasing time of plasmonic topological edge states increases with increasing the bulk lattice number that has a threshold requirement and finally reaches saturation. We directly revealed through simulation that there is a transient bulk state in the evolution of topological edge states, that is, the energy undergoes relaxation from oscillation between the bulk lattice and the edge. This work shows a new perspective of time-domain dynamic topological photonics.

Printed silver contacts for Cd[formula omitted]Zn[formula omitted]Te radiation detectors

In this work, we evaluate a novel jetink printing method with silver nano particle ink for fabrication of metal–semiconductor–metal structures based on Cd1−xZnxTe for gamma-ray detector applications. Contact printing technology offers several advantages in terms of infrastructure and prototype cycle time. For comparison and reference similar samples with thermally evaporated silver and indium contacts were processed and analyzed. The MSM devices were investigated by various static and dynamic characterization methods including current–voltage (I–V), power spectral density of noise (PSD), transient current technique (TCT), and gamma-spectroscopy. In addition, impact of thermal annealing up to 200 °C was studied. The devices with the printed contacts exhibit comparable performance with the reference benchmark detectors. Preliminary study indicate that the printed contacts are immune to moderate thermal treatment, and moreover, show signs of improvement with annealing.

A Simple Dynamic Characterization Method for Thin Stacked Dielectric Elastomer Actuators by Suspending a Weight in Air and Electrical Excitation

This paper proposes a simple but effective method for characterizing dielectric elastomer actuators (DEAs), especially for thin stacked DEAs, which are promising for haptic devices but which measure the dynamic elastic modulus with great difficulty. The difficulty of the measurement of such a thin stacked DEA arises from the friction and local deformation of the surface between the DEA and a contact, as shown in this paper. In the proposed method, a DEA is vertically suspended and a weight is attached to it. The proposed method requires no contact with the surface of a DEA and uses only a weighting mass. Experimental results demonstrated the proposed method can estimate almost essential constants, such as the dynamic elastic modulus (Young’s modulus and damping time constant), the electrical constants (permittivity and resistivity), and the coefficient of electromechanical coupling, through the forced vibration induced by voltage actuation.

Negative capacitance in epitaxial ferroelectric capacitors evidenced by dynamic dielectric characterization

A simple dynamic method was developed to evaluate the components in the equivalent circuit of a ferroelectric capacitor. The method is based on the application of short trapezoidal voltage pulses of variable amplitude and the analysis of the resulting current by considering the ferroelectric capacitor as a parallel Rp-Cp equivalent circuit. The values of Rp and Cp components are obtained in relation to different stages of polarization switching as the amplitude of the applied pulses increases. The most important result obtained by applying the present method is the evidence of an abrupt decrease of the Rp value (about 2 orders of magnitude) at the coercive voltage, while the equivalent Cp does not present a dramatic variation during polarization switching. This is interpreted in the context of negative capacitance obtained for ferroelectrics when polarization passes through zero value. The results obtained by using the proposed dynamic characterization method that will be referred to as “dynamic dielectric characterization”, are in good agreement with those obtained by classic capacitance-voltage measurements. A method to stabilize the negative capacitance for longer periods of time is also presented by adding an external resistance in series with the ferroelectric capacitor.

Magnetorheological elastomer dynamic characterization method considering temperature, frequency, and magnetic field

Magnetorheological elastomers (MRE) are composite materials, comprised of a viscoelastic matrix with ferromagnetic particles added to it, which enables variation in the dynamic properties through applied magnetic fields. The present work aims to experimentally identify the effects of frequency, temperature, and magnetic field on such properties. In the frequency domain, transmissibility tests of a single-degree-of-freedom system were performed, varying the applied magnetic field and temperature. An inverse optimization problem was used to fit the experimental transmissibility curves with an analytical model for the MRE. Thus, it was possible to obtain the parameters of the material that best describe the experimental data. Experimental results showed that MRE significantly increases the system stiffness, especially at higher temperatures. The comparison between experimental and analytical curves validated the mathematical model with R2 values above 0.96. A component of variation analysis showed that a variation in temperature has the most relevant effect on the MRE dynamic properties.

The multi-physic cell-based smoothed finite element method for dynamic characterization of magneto-electro-elastic structures under thermal conditions

This study was aimed to computationally investigate the thermal load combining the mechanical load effect on dynamic characteristics of intelligent composite structures. For this purpose, the cell-based smoothed finite element method (CS-FEM) was applied to the multi-physic coupling problem, and the coupled multi-physic CS-FEM (CPCS-FEM) integrating the magneto-electro-thermo-elastic (METE) coupling effect was put forward. Compared with standard FEM, this method with higher accuracy, lower mesh restriction and much less calculation for stochastic issues was more capable in handling severe mesh distortion and deformation. The convergence, accuracy and efficiency of CPCS-FEM were validated with three numerical cases. With CPCS-FEM integrating the modified Newmark scheme, the thermal effects on generalized displacement (x- and z-direction displacement components, electric and magnetic potentials) of magneto-electro-elastic sensors were explored. This study presents an effective approach to model the complicated multi-physic problem, and the simulation findings contribute to the design of intelligent structures in service under thermal conditions.