Key Dynamic Parameters Research Articles

Investigation on the mechanical responses of shallow coral reef limestones under dynamic loads

Coral reef limestone (CRL) is found only in ocean reef islands. Deepening the investigation of the dynamic performances of CRL helps expand its utilization in reef engineering. This study studied the dynamic response of shallow weakly-cemented CRL (WCRL) using experimental and numerical methods. First, the impact performance of the WCRL was tested using the Split Hopkinson Pressure Bar apparatus. The dynamic peak stress and peak strain of WCRL exhibited rate-sensitivity. Subsequently, the impact process of the WCRL was calculated in the numerical software LS_DYNA, with key dynamic parameters of WCRL calibrated based on the Holmquist-Johnson-Cook (HJC) model for the first time. The accuracy of the numerical results was verified with the experimental results. Thereafter, the dynamic failure process and energy dissipation mechanism of the WCRL were numerically investigated. As the strain rate increased, the failure of the WCRL specimens intensified. The energy analysis demonstrated that the destruction of WCRL specimens consumed more energy at high strain rates, though the distribution proportion of energy was rate-independent. Finally, the sensitivity analysis revealed that the certain parameters (A, B, C, N, p c, and μc) of the HJC model played a crucial role in describing the material’s dynamic response.

A State Estimation of Dynamic Parameters of Electric Drive Articulated Vehicles Based on the Forgetting Factor of Unscented Kalman Filter with Singular Value Decomposition

In this paper, a state estimation method of distributed electric drive articulated vehicle dynamics parameters based on the forgetting factor unscented Kalman filter with singular value decomposition (SVD-UKF) is proposed. The 7DOF nonlinear dynamics model of a distributed electric drive articulated vehicle is established. The unscented Kalman filter algorithm is the foundation, with singular value decomposition replacing the Cholesky decomposition. A forgetting factor is introduced to dynamically adapt the observation noise covariance matrix in real time, resulting in a centralized parameter state estimator for the articulated vehicle. The proposed parameter state estimation method based on the forgetting factor SVD-UKF is simulated and compared with the unscented Kalman filter (UKF) estimation method. Key dynamic parameters are estimated, such as the lateral and longitudinal velocities and accelerations, angular velocity, articulated angle, wheel speeds, and longitudinal and lateral tire forces of both the front and rear vehicle bodies. The results show that the proposed forgetting factor SVD-UKF method outperforms the traditional UKF method. Furthermore, a prototype vehicle test is conducted to compare the estimated values of various dynamic parameters with the actual values, demonstrating minimal errors. This verifies the effectiveness of the proposed dynamic parameter estimation method for articulated vehicles.

Monocular vision-based key dynamic parameters measurement method used for typical bridge structures health monitoring

Monocular vision-based key dynamic parameters measurement method used for typical bridge structures health monitoring

Enhancing stability and safety: A novel multi‐constraint model predictive control approach for forklift trajectory

AbstractThe advancements in intelligent manufacturing have made high‐precision trajectory tracking technology crucial for improving the efficiency and safety of in‐factory cargo transportation. This study addresses the limitations of current forklift navigation systems in trajectory control accuracy and stability by proposing the Enhanced Stability and Safety Model Predictive Control (ESS‐MPC) method. This approach includes a multi‐constraint strategy for improved stability and safety. The kinematic model for a single front steering‐wheel forklift vehicle is constructed with all known state quantities, including the steering angle, resulting in a more accurate model description and trajectory prediction. To ensure vehicle safety, the spatial safety boundary obtained from the trajectory planning module is established as a hard constraint for ESS‐MPC tracking. The optimisation constraints are also updated with the key kinematic and dynamic parameters of the forklift. The ESS‐MPC method improved the position and pose accuracy and stability by 57.93%, 37.83%, and 57.51%, respectively, as demonstrated through experimental validation using simulation and real‐world environments. This study provides significant support for the development of autonomous navigation systems for industrial forklifts.

Impact analysis of the four-party evolutionary game in renewable portfolio standard under dynamic parameters

Renewable portfolio standard has become the primary policy tool to improve the integration of renewable energy. The motivation of the parties involved and the formulation of the policy parameters are crucial for the rapid development of renewable energy industry. However, the role of large consumers has often been neglected as the main party for renewable energy consumption, and the policy parameters have been dominated by static parameters. This paper innovatively introduces large consumers into the evolutionary game, constructs a four-party revenue matrix and the replicated dynamic equations, analyzes the equilibrium conditions of the evolutionary game, and constructs the functions of the key dynamic parameters over time, then simulates the behavioral strategies of the game players under the dynamic parameters with a system dynamics model. The optimal strategy is regulators waive regulation, while power plants, large consumers and power sales companies fulfill their quotas. Dynamic fines, dynamic quotas, and dynamic consumption prices have a large impact on each player, while dynamic TGC prices have a limited impact on them. Reasonably high fines in the initial stage are effective in facilitating each player to its stable state more quickly than static fines. Even if the fine is reduced in the later stages, it will not affect their strategies. High quotas and low consumption prices will significantly accelerate the exit of regulators from regulation, while power sales companies and large consumers will quickly fulfill their quota tasks. Only power generators prefer low quotas and high consumption prices. These results provide some recommendations for the setting of policy parameters.

Transient temperature and pressure coupling model of cementing injection stage in ultra deep wells considering segmental rheological model, casing eccentricity and U-tube effect

The geological environments of ultra deep wells such as high temperature and high pressure (HTHP), narrow safety density window pose significant challenges to cementing operation. Considering segmental rheological model and density model, casing eccentricity, U-tube effect and viscous dissipation, this paper established a transient temperature and pressure coupling model during cementing injection stage of ultra deep wells. The segmental rheological model can describe the rheological properties of cementing fluids under HTHP much better. Considering casing eccentricity and viscous dissipation can accurately model the variation of temperature and pressure profiles. Taking U-tube effect into the model, the formation process of vacuum section at top of the casing can be simulated. The fully implicit finite-difference approach was used to solve the coupling model, and the calculation results were compared with field measurement data and simulation data to verify its accuracy. The calculation errors of the developed model are respectively 10% and 5% compared to field measurement data and Wellplan’s simulation data. Numerical simulations were conducted to reveal the cementing fluid distribution, transient temperature distribution and pressure distribution during the cementing injection stage. The simulation results show that the variety of cementing fluids with different density, rheological properties and thermophysical parameters complicates the change mechanism of temperature and pressure. The temperature and pressure distributions both present unsteady characteristics during cementing injection stage, which puts forward higher requirements of pressure control for narrow safety density window formation. The influence of temperature and pressure on rheology of cementing fluids cannot be ignored, and segmental rheological model should be considered for accurate pressure prediction. Also the casing eccentricity cannot be ignored for cementing pressure calculation in deviated or horizontal wells. Managed pressure cementing (MPC) has a greater advantage in dealing with narrow density window formation. The synergistic control of cementing fluid density and back pressure can keep the equivalent circulating density (ECD) within the safe density window. Through the application of the transient temperature and pressure coupling model, we can simulate the variations of key dynamic parameters during cementing injection stage and optimize the cementing parameters.

Profiles and some dynamic parameters of a layered inhomogeneous elliptical galaxy

Several new models of a layered inhomogeneous elliptical galaxy (EG) having the shape either a triaxial ellipsoid or an oblate or prolate spheroid and consisting of baryonic mass and dark matter with different laws of density distribution — profiles. Based on these models, some key dynamic parameters of the EG were determined: gravitational (potential) energy and rotational kinetic energy, total surface brightness, total luminosity, and velocity dispersion depending on the distance to the EG center. The relationships between the important dynamic parameters of the galaxy have been established: “mass-dimensions”, “mass-velocity dispersion”, “size-dispersion speeds–luminosity” (surface brightness). Evolutionary scenarios for the formation of EG were studied according to these models. The results obtained were applied to sixty model EGs with parameters exactly matching those that actually exist and are presented in the form of tables.

Mechanic-electric-thermal coupling simulation method of Lamb wave under variable temperature

The propagation mechanism of Lamb waves exhibits more intricate in the variable operational environment of high-speed trains. Simulation methods are widely used to study Lamb wave propagation characteristics due to economic and time constraints. A mechanic-electric-thermal coupling simulation method to study the propagation mechanism of Lamb waves under variable temperatures is proposed in this paper. To accurately simulate the dynamic behavior of Piezoelectric Transducer (PZT) under variable temperature, a nonlinear numerical model of the dynamic parameters (piezoelectric coefficient, dielectric constant) of PZTs has been developed based on the experiment of the temperature influence on Lamb wave. The model emphasizes the nonlinear pattern of change in the key dynamic parameters of the PZT with temperature fluctuations. In addition, a thermal expansion stress model of the PZT-bonding layers-structure is established to reveal the mechanical-thermal coupling mechanism. Based on the COMSOL, a mechanical-electrical-thermal direct coupling simulation model of PZT-bonding layers- structure under variable temperature is established. The simulation results at −40 °C to 80 °C are obtained and compared to the experiment. The results show that the simulation signal is highly consistent with the experimental measurement signal, and the simulation method proposed in this paper has high accuracy.

Design Considerations and Flow Characteristics for Couette-Type Blood-Shear Devices

Cardiovascular prosthetic devices, stents, prosthetic valves, heart-assist pumps, etc., operate in a wide regime of flows characterized by fluid dynamic flow structures, laminar and turbulent flows, unsteady flow patterns, vortices, and other flow disturbances. These flow disturbances cause shear stress, hemolysis, platelet activation, thrombosis, and other types of blood trauma, leading to neointimal hyperplasia, neoatherosclerosis, pannus overgrowth, etc. Couette-type blood-shearing devices are used to simulate and then clinically measure blood trauma, after which the results can be used to assist in the design of the cardiovascular prosthetic devices. However, previous designs for such blood-shearing devices do not cover the whole range of flow shear, Reynolds numbers, and Taylor numbers characteristic of all types of implanted cardiovascular prosthetic devices, limiting the general applicability of clinical data obtained by tests using different blood-shearing devices. This paper presents the key fluid dynamic parameters that must be met. Based on this, Couette device geometric parameters such as diameter, gap, flow rate, shear stress, and temperature are carefully selected to ensure that the device’s Reynolds numbers, Taylor number, operating temperature, and shear stress in the gap fully represent the flow characteristics across the operating range of all types of cardiovascular prosthetic devices. The outcome is that the numerical data obtained from the presented device can be related to all such prosthetic devices and all flow conditions, making the results obtained with such shearing devices widely applicable across the field. Numerical simulations illustrate that the types of flow patterns generated in the blood-shearing device meet the above criteria.

Insights into the fluid dynamics of the Bach impeller

The Bach impeller is a novel impeller that was purposefully designed to reduce power consumption as well as shear stress levels in stirred bioreactors. Contrary to conventional impellers where stirring is achieved by the pushing action of the blades, the Bach impeller relies on a central spiral element which induces an up-pumping central vortex and discharges the flow in the tangential direction through vanes. This feature is new and relevant to the field of biochemical engineering where cell culture and microbial fermentation often make use of shear-sensitive, living organisms to produce biopharmaceuticals and medicines. This article offers a thorough characterisation of the fluid mechanics of this impeller by means of 2D phased- and time-resolved particle image velocimetry (PIV) experiments. Key flow dynamics parameters including velocity magnitudes, kinetic energy, and shear stresses were estimated for different combinations of impeller size, clearance, and speed. The standard impeller size, D/T=0.52, performed most promisingly in combination with an off-bottom clearance of C=0.6 T, as the elevated impeller height allowed to pull high momentum fluid to the upper part of the tank and therefore improved overall transport phenomena in the entire reactor volume. For this impeller diameter-clearance combination peak ensemble-averaged shear stresses at the vessel base were lower due to the impeller greater distance from the bottom. A distinctive feature of the Bach impeller was its "smooth operation" mode, where velocity fluctuations due to the vane passages are nearly negligible (∼5 % of ensemble-averaged kinetic energy). These aspects make of the Bach impeller an appealing option in the context of stem cell bioprocess applications.

Nonlinear Growth Dynamics of Neuronal Cells Cultured on Directional Surfaces.

During the development of the nervous system, neuronal cells extend axons and dendrites that form complex neuronal networks, which are essential for transmitting and processing information. Understanding the physical processes that underlie the formation of neuronal networks is essential for gaining a deeper insight into higher-order brain functions such as sensory processing, learning, and memory. In the process of creating networks, axons travel towards other recipient neurons, directed by a combination of internal and external cues that include genetic instructions, biochemical signals, as well as external mechanical and geometrical stimuli. Although there have been significant recent advances, the basic principles governing axonal growth, collective dynamics, and the development of neuronal networks remain poorly understood. In this paper, we present a detailed analysis of nonlinear dynamics for axonal growth on surfaces with periodic geometrical patterns. We show that axonal growth on these surfaces is described by nonlinear Langevin equations with speed-dependent deterministic terms and gaussian stochastic noise. This theoretical model yields a comprehensive description of axonal growth at both intermediate and long time scales (tens of hours after cell plating), and predicts key dynamical parameters, such as speed and angular correlation functions, axonal mean squared lengths, and diffusion (cell motility) coefficients. We use this model to perform simulations of axonal trajectories on the growth surfaces, in turn demonstrating very good agreement between simulated growth and the experimental results. These results provide important insights into the current understanding of the dynamical behavior of neurons, the self-wiring of the nervous system, as well as for designing innovative biomimetic neural network models.

Identifying Damage in Structures: Definition of Thresholds to Minimize False Alarms in SHM Systems

In recent years, the development of quick and streamlined methods for the detection and localization of structural damage has been achieved by analysing key dynamic parameters before and after significant events or as a result of aging. Many Structural Health Monitoring (SHM) systems rely on the relationship between occurred damage and variations in eigenfrequencies. While it is acknowledged that damage can affect eigenfrequencies, the reverse is not necessarily true, particularly for minor frequency variations. Thus, reducing false positives is essential for the effectiveness of SHM systems. The aim of this paper is to identify scenarios where observed changes in eigenfrequencies are not caused by structural damage, but rather by non-stationary combinations of input and system response (e.g., wind effects, traffic vibrations), or by stochastic variations in mass, damping, and stiffness (e.g., environmental variations). To achieve this, statistical variations of thresholds were established to separate linear non-stationary behaviour from nonlinear structural behaviour. The Duffing oscillator was employed in this study to perform various nonlinear analyses via Monte Carlo simulations.

Variation characteristics of key dynamic measurement signals of anchor bolts with different anchorage qualities under pull-out loads

Pull-out load and the cement-sand ratio (CSR) can affect the non-destructive testing (NDT) results of anchor bolts. Therefore, in this article, NDT experiments were conducted on both fully and defectively grouted anchor bolts, and variation patterns of key dynamic testing signal parameters were analyzed. A longitudinal vibration model of defectively grouted anchor bolts considering dynamic and static damping was proposed, and simulated NDT of anchor bolts with varying qualities. The results indicated that grouting defects resulted in an increase in wave velocity, along with a decrease in the fundamental frequency and dynamic stiffness of anchor bolts. When grouting defects and pull-out load acted concurrently, the fundamental frequency, and dynamic stiffness of the defectively grouted anchor bolts were consistently smaller than those of fully grouted ones during the initial loading phase. With pull-out load increasing, wave velocity decreased first, then increased; fundamental frequency increased, followed by a decrease; dynamic stiffness rose. When the CSR of defectively grouted anchor bolts was reduced, wave velocity decreased, fundamental frequency increased slightly, and a substantial increase in dynamic stiffness was observed. Pull-out loads were more sensitive to anchor bolt key dynamic signals than defects and CSR. Simulated validation demonstrated the reliability of the proposed theory.

Bridge-bearing disengagement identification based on flexibility matrix diagonal matrix change rate: an indoor physical simulation experiment

The disengagement of bridge bearings is a pervasive issue encountered in the realm of bridges, which can potentially lead to changes in operational circumstances, diminished longevity, and compromised traffic safety. The current methods employed for detecting such disconnections primarily rely on force sensors, cameras, and acceleration sensors. However, their practical implementation on-site and effectiveness in accurately identifying disengagement require enhancement. To address the challenges associated with the installation and layout of conventional contact sensors, as well as the potential introduction of additional mass, a sophisticated “bridge-bearing disconnection detection system” has been devised. This innovative system is based on laser Doppler vibrometer technology, which eliminates the need for physical contact. The feasibility of employing non-contact laser Doppler vibration measurement technology in the detection of bridge-bearing disconnection has been successfully verified within the framework of this study. Furthermore, a comprehensive analysis of the sensitivity of key dynamic parameters, specifically natural frequencies and vibration modes, to bridge-bearing disengagement has been conducted. The verification process included evaluating the identification effectiveness of regularized combined absolute changes in vibration modes and flexibility matrix diagonal matrix change rate (FDMCR) under diverse working conditions simulating complete disconnection. This assessment involved using both finite element analysis and empirical measurements. The findings unequivocally demonstrate that the disconnection of bridge bearings results in a reduction in the natural frequencies for each mode order, with an observed cumulative effect. In addition, it is noteworthy that the vibration mode indices typically exhibit greater sensitivity toward the disconnection of outer bearings. By contrast, FDMCR demonstrates commendable positioning capabilities and exceptional noise resistance in identifying bridge-bearing disengagement. The empirical insights gleaned from these research findings hold significant value in terms of on-site identification of bridge-bearing disengagement, ultimately contributing to the preservation of bridges’ long-term operational integrity.

Thermal-vibration ageing characteristics of three thin-walled cylindrical shells covered with a functionally graded protective coating: Modeling, analysis and test

In this study, the thermal-vibration ageing characteristics of three thin-walled cylindrical shells (TCSs) covered with a functionally graded protective coating (FGPC) are investigated for the first time, including fiber reinforced polymer (FRP), metal and fiber metal hybrid (FMH) shell structures with the FGPC. Initially, a dynamic model of an FGPC-TCS structure in a thermal-vibration ageing environment is developed by employing the first-order shear deformation principle enriched by the improved exponential function approach, the complex modulus method, the Rayleigh-Ritz method, etc. In this model, the ageing-related material parameters of the FGPC and the TCS structure are assumed to be affected by both environmental temperature and aging time. After the solution procedures of the vibration parameters of the above three coated shells are clarified, the determining method of fitting coefficients of the coating and different materials in the shells studied is provided. Also, the detailed experimental validation is undertaken on the uncoated and coated FRP, metal, and FMH shell specimens, which indicates that the present model is reliable for predicting the key dynamic ageing parameters when the complex thermal-vibration ageing effect is considered. From the measured and calculated data, it is proved that the suppression contribution of the FGPC is obvious no matter whether these shell structures are at room temperature or thermal degradation environment. Furthermore, some important application suggestions of the FGPC are summarized to improve the degradation resistance of such coated shell structures.

Research on improved modal parameter identification method using Hilbert-Huang transform

In the wind tunnel test, the full-bridge aeroelastic model needs to simulate both the shape and dynamic characteristics of the real bridge, and modal parameters are key dynamic parameters. Therefore, it is essential to identify the modal parameters of the model accurately. To get accurate modal parameters of the long-span bridge model in the wind tunnel test, the applications of the Hilbert-Huang transform for modal parameter identification were analyzed in this paper. Then a band-pass filter is designed to filter the original signal so that the intrinsic mode function obtained by empirical mode decomposition can satisfy the single-component signal requirement and eliminate the mode mixing effect effectively. Meanwhile, the endpoint data extension method based on SVM (Support Vector Machine) was presented to restrain the end effects of empirical mode decomposition. Finally, taking the Oujiang Bridge as the engineering background, the improved algorithm was applied to modal parameter identification of the bridge under ambient excitation. The modal parameters such as modal frequency and damping ratio were obtained. The reliability of the improved method was verified by comparing the identified modal parameters with the results of the finite element method, and it turns out that the improved method can reduce the frequency identification error of vertical bend, lateral bend, and torsion to 1.01%, 4.07%, and 1.68%. The results indicated that the improved method based on the Hilbert-Huang transform can accurately identify the main modal parameters of the structure and can be better applied to identify the modal parameters of long-span bridge structures.

Spatiotemporal Patterns of Risk Propagation in Complex Financial Networks

The methods of complex networks have been extensively used to characterize information flow in complex systems, such as risk propagation in complex financial networks. However, network dynamics are ignored in most cases despite systems with similar topological structures exhibiting profoundly different dynamic behaviors. To observe the spatiotemporal patterns of risk propagation in complex financial networks, we combined a dynamic model with empirical networks. Our analysis revealed that hub nodes play a dominant role in risk propagation across the network and respond rapidly, thus exhibiting a degree-driven effect. The influence of key dynamic parameters, i.e., infection rate and recovery rate, was also investigated. Furthermore, the impacts of two typical characteristics of complex financial systems—the existence of community structures and frequent large fluctuations—on the spatiotemporal patterns of risk propagation were explored. About 30% of the total risk propagation flow of each community can be explained by the top 10% nodes. Thus, we can control the risk propagation flow of each community by controlling a few influential nodes in the community and, in turn, control the whole network. In extreme market states, hub nodes become more dominant, indicating better risk control.

Идеи «слуховой филологии» в становлении отечественного теоретического музыкознания 1920-х годов: Б.В. Асафьев и исследователи «живого слова»

At a time of its institutionalization in post-revolutionary decade, Russian musicology was an active recipient of ideas, methods, and achievements of the related disciplines. The attention of the given article is drawn to one of such connections, significant for musicological thought of that period: an impact made on it by research of oral speech intonation carried out under the aegis of so called “Ohrenphilologie” (“auditory philology”). This impact is observed on the example of Boris Asafiev and, partly, his school at the Institute of Art History in Petrograd which maintained close collaboration with philologists and theater researchers from the Institute of the Live Word, one of the leading platforms of the Ohrenphilologie in Russia. A hypothesis is put forward that ideas of this direction influenced Asafiev’s concept of “sounding substance” which occupied an important place in his theoretical heritage of the 1920s. This phenomenon accumulated the key communicative, dynamic, and semantic parameters of music as well as sources of its psychphysiologic impact. In the course of comparative analysis it establishes continuity between ideas enunciated in the works of the specialists in Ohrenphilologie Vsevolod Vsesolodsky-Gerngross and Sergey Bernstein on the one hand, and Asafiev’s concept of the sounding substance on the other.

Synchrony and mental health: Investigating the negative association between interpersonal coordination and subclinical variation in autism and social anxiety

Interpersonal coordination forms an integral part of successful social interaction. Yet for psychopathologies that impact social functioning (e.g., autism, social anxiety), disruptions to coordination are widely documented. Little research however has considered the underlying mechanisms by which this association is sustained. To address this shortcoming, the current registered report investigated the extent to which key dynamical control parameters that govern interpersonal coordination (frequency matching and coupling) are impacted by traits associated with social anxiety and autism. In pairs, participants performed a pendulum swinging task known to reflect disruptions to the dynamics underlying coordination, while the level of task sociality was systematically varied (solo, observed, interactive). We quantified behaviour at both the individual (e.g., movement variability) and collective (e.g., coordination) levels via indices that are sensitive to changes in the parameters governing coordination. Consistent with past research, the results revealed negative associations between measures of coordination and symptoms of social anxiety and autism. Further, the findings highlighted disruption to the frequency matching parameter as a mechanism underlying the mental health-coordination link and identified coordination stability as a potential boundary condition of this relationship.

The Development of Emergency Communication Device for Tianwen-1 Probe

Mars is one of the most valuable planets for space exploration. After entering the entry descent and landing (EDL) phase, the spacecraft would carry out a series of procedural deceleration operations and achieve soft landing on the surface of Mars. In the process of EDL, the landing platform would encounter a series of irreversible incidents within environmental unpredictability, making this process highly risky. The emergency communication device plays an important role if in the Mars Exploration Program. It can capture and store key dynamic parameters during EDL phase, enabling a high probability of survival in the occurrence of a faulty condition. It can also send the stored data to the Mars obit probe when the communication condition is met. This paper presents a scheme design for the emergency communication device based on its functionality and performance requirements. It includes the design proposal, simulation results, reliability analysis, technical risks and control measures, inheritance and performance compliance which verifies the rationality and correctness of the design.