Pseudo Velocity Research Articles

Optimal intensity measure for seismic performance assessment of shield tunnels in liquefiable and non-liquefiable soils

Relating the ground motion intensity measure (IM) and the structural engineering demand parameter is a crucial step in the performance-based earthquake engineering framework. This study investigates the selection of IM for development of probabilistic seismic demand model of urban shield tunnels subjected to earthquake ground motions in liquefiable and non-liquefiable soils. Nonlinear dynamic effective stress analyses are conducted to develop a database of the intensity measures and structural seismic responses exposed to ground shaking and soil liquefaction. Two advanced soil constitutive models (i.e., Pressure DependMultiYield03 and PressureIndependMultiYield for liquefiable and non-liquefiable soils, respectively) are employed to capture the nonlinear behavior. A suite of 23ground motion intensity measures is selected and assessed based on the evaluation criteria of correlation, efficiency, practicality and proficiency. Eventually, the multi-level fuzzy comprehensive evaluation method is employed to comprehensively consider the four evaluation criteria and establish the optimal ground motion IM suitable for probabilistic seismic demand analysis of shield tunnel structures. The obtained results show that the sustained maximum acceleration is the optimal IM for evaluating the structural seismic response, followed by the peak ground acceleration in both liquefiable and non-liquefiable soils. Peak pseudo velocity spectrum, displacement square integral and Housner spectral intensity are found to be not suitable for the probabilistic seismic demand analysis of shield tunnel structures.

A New Method Using Pseudovelocity-Based Fatigue Analysis to Determine the Effectiveness of Acoustic Fields Used for Acoustic Testing

Abstract This paper summarizes results from the use of advanced adaptive multiple-input, multiple-output (i.e., MIMO) control for direct field acoustic testing to excite an aluminum-honeycombed 1.22 m × 2.44 m (4 ft × 8 ft) test panel with MSI-DFAT's near-diffuse acoustic field and four nondiffuse acoustic fields using three panel orientations, and two speaker configurations. The five fields have the same overall sound pressure level (OASPL) and 1/3-octave sound-pressure-level (SPL) spectrum. Test and analysis results demonstrate a dependence of the test panel's response characteristics to each acoustic-field excitation, showing that the near-diffuse field excites experimental-modal-analysis-identified test panel modes effectively, whereas nondiffuse fields excite these modes ineffectively. Differences are attributed to the relative diffuseness of fields. Partial fatigue damage values from 20 accelerometer locations are determined from pseudovelocity (PV) outputs from single-degree-of-freedom (SDOF) models at each modal frequency excited by their response time histories, for each acoustic field, to quantify the relative ability of acoustic fields to detect workmanship flaws of typical test articles. Fatigue-damage values are obtained from PV response time histories of SDOF models at identified modal frequencies, which are rainflow-cycle counted with the partial-damage coefficients calculated using the Palmgren-Miner rule. A new form of vibro-acoustic gain based on PV power spectral densities (PSDs) is also introduced and correlated with these experimental results, since the PV response PSDs of a test article undergoing random vibration are proportional to modal stress at their frequencies. This paper shows that the modal stress caused by acoustic-field types is an important consideration for acoustic testing of satellites and other spacecraft, since using a nondiffuse field may result in an acoustic test that doesn't detect workmanship flaws in a test article, even though the acoustic environment is achieving the same specified OASPL and average acoustic 1/3-octave SPL spectrum.

Damage boundaries on shock response spectrum based on an elastic single-degree-of-freedom structural model

Damage boundary based on a single-degree-of-freedom (SDOF) structural model under shock environment is studied in the present paper. Shock environment applied to the SDOF structure is characterized by different shock-waveforms. For an SDOF model with small damping, its shock damage boundary consists of three characteristic lines intersecting at a point, i.e. the isodamage absolute acceleration asymptote, pseudo velocity horizontal line and relative displacement asymptote in different frequency regimes. The upper and lower damage bounds on 4-coordinate pseudo velocity shock response spectrum (PVSRS) graph are proposed, which are associated with generic shock-waveforms with sufficiently large and small shock-waveform coefficients, respectively. The validity of the upper and lower damage bounds proposed in this study is demonstrated using an idealized mass-plate model with pins subjected to shock loads characterized by various shock-waveforms. Particularly, the lower damage bound underpins the use of PVSRS ‘damage metric’ as a rule-of-thumb in various engineering fields. It also shows that the proposed method is suitable for real shock environment.

ENVIRONMENTAL LANDSCAPE ART DESIGN USING DYNAMIC NONLINEAR PARAMETERIZATION

For the problem of parametric design of anisotropic curves and cambers in the practical application field of environmental landscape design, in this exploration, the modeling of design object is carried out through computer parametric technology. It is based on the information collection and data extraction of design object and the formulation of logical relationship between parametric variable factors related to design. For nonlinear systems, a necessary condition to judge parameters is proposed. This criterion is a natural extension of the PBH criterion, which makes it easy to identify the parameters of the pseudo-linear system in the generalized case, and avoids a lot of complex operations; at the same time, a parametric design method of dynamic environment landscape is proposed systematically. In the first order, second order, high order and generalized nonlinear model, the complete parametric optimization method of environmental landscape design is established. The [Formula: see text] search function in MATLAB optimization toolbox is used to solve the generalized nonlinear system. The performance of the algorithm is tested by the examples of pseudo velocity, pseudo velocity uniformity and parameter optimization of the parametric curve called by the software environment. The results show that system dynamic process to simulate the dynamic environmental changes in landscape design by using the optimized parameter method is faster than that by using the unoptimized method. Meanwhile, the optimization method in this exploration can reduce the amplitude of change when external factors interfere, which shows that the optimized parametric design model has better transient performance; the curve generated by calling the drawing function provided in this exploration is smoother when the number of drawing points is the same.

Use of the Velocity Intensity Spectrum to Characterize Transient Data

Abstract This paper introduces and develops the Velocity Intensity Spectrum as an analytical tool for examining transient data in the frequency domain. The Velocity Intensity Spectrum is then compared with three common alternatives: the Shock Response Spectrum, the Pseudo Velocity Spectrum, and the lesser-known Shock Intensity Spectrum, upon which it is based. The various techniques are applied to an experimental data set and compared and discussed in a practical manner.

Explosion Shock Measurement System of the Precursor Warhead for the Tandem Projectile

This paper presents a system that measures the acceleration of the shock caused by the explosion of the precursor warhead for the tandem projectile. The proposed system, which is implemented based on the MIL-STD-810G, Method 517.1, consists of a miniaturized shock measurement device, a cable, accelerometers, and a trigger circuit. The shock measurement device has a size of ￠102 x 171 mm and cable has a length of 3 m. The operational confirmation test is conducted by implementing the measurement system. The Analysis of shock data(accelerometer output data) is carried out using Shock Response Spectrum(SRS), pseudo velocity and plot of acceleration time transient. Through measurement analysis, one can predict the damage of electronics in projectile when precursor warhead is exploded.

A well-balanced lattice Boltzmann model for the depth-averaged advection–diffusion equation with variable water depth

A well-balanced lattice Boltzmann model for the depth-averaged advection–diffusion equation is developed to solve the solute transport problem in shallow water flows with obvious gradient changes in water depth. The flow field is simulated by the lattice Boltzmann model for shallow water equations with the central moments (CMs) collision operator and D2Q9 lattice pattern. In this model, the diffusion term of the depth-averaged advection–diffusion equation is divided into two parts by the product rule, one part of which is combined into the advection term to produce the pseudo velocity. The relaxation time is independent of the diffusion coefficient, and the remaining value of (3+3)∕6 derived from the Chapmann–Enskog expansion reduces the third-order error. According to the different treatments of the water depth gradient in the equilibrium distribution function, center scheme and linked scheme are developed. Both schemes can ensure the conservation of the solute mass. Numerical tests show that these two schemes give predictions in good agreement, but the linked scheme works better at the breakpoint. Comparisons with the reference indicate that this model is advantageous with respect to both stability and efficiency.

MPC-Based Cooperative Control Strategy of Path Planning and Trajectory Tracking for Intelligent Vehicles

In this paper, we propose a progressive model predictive control scheme (PMPCS) by considering the cooperative control of local planning and path tracking for intelligent vehicles. An improved particle swarm optimization (IPSO) based model predictive control (MPC) method is developed to solve the planning and tracking problem. With the PMPCS, the total computational burden can be reduced sharply because of the seamless connection and mutual promotion between the optimization of two layers. Besides we also propose a novel planning algorithm, which can take traffic lights and overtaking time constraint into account. To solve these problems, we first combine model predictive control with artificial potential field (APF) to get a collision-free path by treating the time-varying safety constraints as the scope of the repulsive force and an asymmetrical lane potential field function. Furthermore, the pseudo velocity planning method is adopted to take traffic lights into account in the planning module. Simulation results show the reliability of the proposed algorithm and the advantages of the scheme compared with general hierarchical algorithm.

Calculation and Characteristic Analysis on Different Types of Shock Response Spectrum

Shock Response Spectrum (SRS) has been proved to be an effective standard tool for analyzing and quantifying shock environment in engineering, which is also the simplest tool for comparing shock severity and potential damage to structures. The calculation formulas of absolute acceleration spectrum, relative displacement spectrum, relative velocity spectrum and pseudo velocity spectrum are given respectively. The responses of different spectrum under typical semi-sinusoidal shock excitation are compared and analyzed, and some enlightening conclusions are obtained.

Strong ground motions from two moderate size (Mw5.5) Kachchh intraplate earthquakes, Gujarat, India

During 2006–2016, a strong motion seismic network of twenty 3-component accelerogarphs was deployed by the National Geophysical Research Institute, Hyderabad, India, in the epicentral region of the 2001 Mw7.7 Bhuj earthquake. On 7 March and 6 April 2006, two earthquakes of Mw5.5 have occurred in the Kachchh seismic zone, which led to an excellent dataset from 16 to 18 strong-motion accelerograph sites. This dataset enabled us to estimate strong motion parameters for these earthquakes that allowed us to examine the suitability of the design response spectra of BIS (criteria for earthquake-resistant design of structures, part I—general provisions and buildings, Bureau of Indian Standards, 2002) in Kachchh, Gujarat. Our study reveals that the estimated normalized response spectra at strong-motion accelerograph sites, which are lying in tertiary formations or near a zone of geological contact between Jurassic and tertiary formations, exceeded the design response spectra at 0.07–0.2 s, correlating with complete collapse of low-rise buildings, water tanks and dams in the area during the 2001 Bhuj earthquake. While the normalized acceleration spectrum of hard sediment (rock site) is found to not exceeding the design spectrum, correlating with the lack of damage in the Mesozoic hill zone. The estimated normalized acceleration spectra at SMA sites lying on hard sediments of Jurassic/Mesozoic formations are found to be lower than the design spectra, which suggests that these stations are less hazardous. We also notice that spectral acceleration values at few sites lying on quaternary formations have exceeded the design spectra at 3–4 s, suggesting these sites hazardous for engineered reinforced structures like bridges. Our estimated mean pseudo velocity spectra show peaks at 0.2, 0.5, 1.2 and 6 s. The peak at 6 s probably can cause damages to the reinforced engineered structures while the peak at 1.2 s could be causing damages to the multistoried reinforced buildings, as observed during the occurrence of the 2001 Bhuj mainshock. Thus, our estimated normalized acceleration spectra show peaks exceeding the design spectra at shorter (0.07–0.2 s, 0.5 s, 1–1.2 s) as well as longer periods (3–4 s, 6 s), which could be attributed to local site effects. We also notice that the modeled normalized response spectra for the shallow March event shows a better correlation with the NGA West2 model for tectonically active regions of US while the modeled normalized spectra for the deeper April event suggest a better correlation with the NGA east model for the stable parts of USA. We propose that the design spectra for the Kachchh region, Gujarat, India, should be modified incorporating local site, path and source effects.

Research on the UWB/IMU fusion positioning of mobile vehicle based on motion constraints

In a non-line-of-sight (NLOS) environment, high accuracy ultra-wideband (UWB) positioning has been one of the hot topics in studying indoor positioning. Aiming at the UWB and inertial measurement unit (IMU) fusion vehicle positioning, a constraint robust iterate extended Kalman filter (CRIEKF) algorithm has been proposed in this paper. It has overcome the innate defect of the extended Kalman filter against non-Gaussian noise and the shortcoming of the robust extended Kalman filter algorithm, which has just processed the non-Gaussian noise solely based on the prior information. Our algorithm can update the observation covariance based on the posteriori estimate of the system in each iteration, and then update the posteriori distribution of the system based on the obtained covariance to significantly reduce the influence of non-Gaussian noise on positioning accuracy. Also, with the introduction of motion constraints, such as zero velocity, pseudo velocity and plane constraints, it can achieve a smoother positioning result. The experimental result proves that through the CRIEKF-based UWB/IMU fusion robot positioning method, a mean positioning accuracy of around 0.21 m can be achieved in NLOS environments.

Analysis of the Site Effects in the North East Region of India Using the Recorded Strong Ground Motions from Moderate Earthquakes

ABSTRACT Site effect estimation using recorded ground motion is an effective approach to assess the seismic hazard of a region. Keeping the same thing in mind, an endeavor is being made to study the local site effects at different locations in the North East region of India through analysis of recorded strong ground motion data provided by Indian strong motion network. The data recorded at 25 sites from 37 earthquakes with a magnitude range 4.0–6.9 have been utilized. The estimated predominant frequencies ( using horizontal to the vertical spectral ratio (HVSR) is well observed for various sites placed in various geological formations like the Precambrian, Tertiary and Quaternary Consequently, the pseudo velocity response (PSV) for 5% critical damping is estimated and compared with the regional geological formations, especially in the Brahmaputra Valley region. It is further noticed that the HVSR, as well as PSV, show a noticeable correlation according to the geological set up of the region for most of the sites, giving a clear idea about the site effect evaluation. Analyzed strong motion data also show the effect of non-linearity, which is an important parameter as it explains the inelastic behavior of the soil causing a reduced or non-linear amplification. Since some of the sites used in present work do not correlate with geology, the sites used for HVSR estimation are used to classify them according to the classical approach employing . All the sites are classified in four different classes namely A, B, C, and D based on shear wave velocity in the upper 30 m. The outcome of the present study is being shown in the form of contour maps for and site amplification for various types of buildings in order to assess the seismic hazard and risk mitigation.

Investigations of the Dynamics of a Four-Element Machine-and-Tractor Aggregate

Abstract The paper presents a dynamic model of four-element machine-and-tractor designed on the basis of a combined soil-cultivating-sowing aggregate and a tractor with an articulated frame. The pseudo velocity of the first tractor half-frame was considered a generalised coordinate. The control impact upon the tractor was obtained by means of the bending angle of the tractor half-frames. The trajectories and movement speeds of the aggregate elements were calculated as a function of time for the driving mode along a straight-line path and the tractor movement according to the harmonic control law. By means of the measuring system, trajectories of the aggregate elements were obtained. It was established that the movement trajectories of the aggregate elements represent a complex assessment parameter of the mathematical model adequacy of the aggregate plane-parallel movement. There was found a regularity of the aggregate turning radius and the bending angle of the tractor half-frames.

Damage boundary of structural components under shock environment

This paper studies the damage of structural components (solid structures and electronics) under severe shock environment introduced by intensive impulsive loads. Two types of critical states of shock response spectrum (SRS) are identified, i.e. the critical SRS state governed by the maximum relative displacement and absolute acceleration, and the critical SRS state governed by the maximum pseudo velocity. The damage boundary of a given component under shock environment is determined analytically in a wide range of frequency domain, which shows good agreement with experimental and numerical results. The proposed method can be used to guide the shock environment adaptability design of aerospace and other structural components.

Brief communication: A nonlinear self-similar solution to barotropic flow over varying topography

Abstract. Beginning from the shallow water equations (SWEs), a nonlinear self-similar analytic solution is derived for barotropic flow over varying topography. We study conditions relevant to the ocean slope where the flow is dominated by Earth's rotation and topography. The solution is found to extend the topographic β-plume solution of Kuehl (2014) in two ways. (1) The solution is valid for intensifying jets. (2) The influence of nonlinear advection is included. The SWEs are scaled to the case of a topographically controlled jet, and then solved by introducing a similarity variable, η = cxnxyny. The nonlinear solution, valid for topographies h = h0 − αxy3, takes the form of the Lambert W-function for pseudo velocity. The linear solution, valid for topographies h = h0 − αxy−γ, takes the form of the error function for transport. Kuehl's results considered the case −1 ≤ γ < 1 which admits expanding jets, while the new result considers the case γ < −1 which admits intensifying jets and a nonlinear case with γ = −3.

Robust adaptive output feedback tracking control for flexible-joint robot manipulators based on singularly perturbed decoupling

SUMMARYThis paper presents a robust adaptive output feedback tracking controller for the flexible-joint robot manipulators to deal with the unknown upper bounds of parameter uncertainties and external disturbances. With applying the singular perturbation theory and integral manifold concept, the complex nonlinear coupled system of the flexible-joint robot manipulators is divided into a slow subsystem and a fast subsystem. A robust adaptive control scheme based on an improved linear parameterization expression is designed for the slow subsystem, and a saturation function is applied in the robust control term to make the torque output smooth. In the meantime, different from the previous approaches, the second-order derivative term of elastic torque is avoided by using the proposed computed torque method, which simplifies the implementation of the fast control law. Moreover, to carry out the whole control system with only position measurements, an approximate differential filter is involved to generate pseudo velocity signals for links and joint motors. In addition, an explicit but strict stability proof of the control system based on the theory of singularly perturbed systems is presented. Finally, simulation results verify the superior dynamic performance of the proposed controller.

Spreading behavior of quantum walks induced by random walks

In this paper, we consider the quantum walk on Z with attachment of one-length path periodically. This small modification to Z provides localization of the quantum walk. The eigenspace causing this localization is generated by finite length round trip paths. We find that the localization is due to the eigenvalues of an underlying random walk. Moreover we find that the transience of the underlying random walk provides a slow down of the pseudo velocity of the induced quantum walk and a different limit distribution from the Konno distribution.

Prediction of input energy spectrum: attenuation models and velocity spectrum scaling

SummaryRecent improvements in performance‐based earthquake engineering require realistic description of seismic demands and accurate estimation of supplied capacities in terms of both forces and deformations. Energy based approaches have a significant advantage in performance assessment because excitation and response durations, accordingly energy absorption and dissipation characteristics, are directly considered whereas force and displacement‐based procedures are based only on the maximum response parameters. Energy‐based procedures mainly consist of the prediction of earthquake input energy imposed on a structural system during an earthquake and energy dissipation performance of the structure.The presented study focuses on the prediction of earthquake input energy. A large number of strong‐ground motions have been collected from the Next Generation Attenuation (NGA) project database, and parametric studies have been conducted for considering the effects of soil type, epicentral distance, moment magnitude, and the fault type on input energy. Then prediction equations for input energy spectra, which are expressed in terms of the equivalent velocity (Veq) spectra, are derived in terms of these parameters. Moreover, a scaling operation has been developed based on consistent relations between pseudo velocity (PSV) and input energy spectra. When acceleration and accordingly velocity spectrum is available for a site from probabilistic seismic hazard analysis, it is possible to estimate the input energy spectrum by applying velocity scaling. Both of these approaches are found successful in predicting the Veq spectrum at a site, either from attenuation relations for the considered earthquake source or from the results of probabilistic seismic hazard analysis conducted for the site. Copyright © 2016 John Wiley & Sons, Ltd.

Strains Induced in Urban Structures by Ultra-High Frequency Blasting Rock Motions: A Case Study

This paper describes measurement and interpretation of strains induced in two, multiple story, older, urban structures by ultra-high frequency rock blast excitation from contiguous excavation. These strains are obtained from relative displacements found by integrating time correlated velocity time histories from multiple positions on the structures and foundation rock. Observations are based on ten instrumented positions on the structures and in the foundation rock during eight blast events, which provided over 70 time histories for analysis. The case study and measurements allowed the following conclusions: despite particle velocities in the rock that greatly exceed regulatory limits, strains in external walls are similar to or lower than those necessary to crack masonry structures and weak wall covering materials. These strains are also lower than those sustained by single story residential structures when excited by low frequency motions with particle velocities below regulatory limits. Expected relative displacements calculated with pseudo velocity single degree of freedom response spectra of excitation motions measured in the rock are similar to those measured.

Adaptive gravity compensation and region tracking control of an AUV without velocity measurement

In this paper, a region tracking controller has been proposed for an autonomous underwater vehicle (AUV) to ensure tracking within a constrained region. During tracking only position measurements are considered to be available. A pseudo velocity signal is generated using a filter to compensate for the velocity signal. For the mapping of the unknown persistent effects in AUV dynamics, i.e., to compensate these unknown forces, an adaptive signal has also been introduced. A Lyapunov function has been utilised to prove the stability of the closed-loop system. The controller ensures uniformly ultimately bounded stability of the system states. Simulation results prove the effectiveness of the proposed controller in terms of energy saving during region tracking.