A Local Deviation Constraint Based Non-Rigid Structure From Motion Approach

In many traditional non-rigid structure from motion(NRSFM)approaches,the estimation results of part feature points may significantly deviate from their true values because only the overall estimation error is considered in their models.Aimed at solving this issue,a local deviation-constrained-based column-space-fitting approach is proposed in this paper to alleviate estimation deviation.In our work,an effective model is first constructed with two terms:the overall estimation error,which is computed by a linear subspace representation,and a constraint term,which is based on the variance of the reconstruction error for each frame.Furthermore,an augmented Lagrange multipliers(ALM)iterative algorithm is presented to optimize the proposed model.Moreover,a convergence analysis is performed with three steps for the optimization process.As both the overall estimation error and the local deviation are utilized,the proposed method can achieve a good estimation performance and a relatively uniform estimation error distribution for different feature points.Experimental results on several widely used synthetic sequences and real sequences demonstrate the effectiveness and feasibility of the proposed algorithm.

Seismic Response Analysis of Steel Structure Isolation System Under Long-Period Seismic Motion

To analyze the seismic response of steel structure isolation systems under long-period seismic motion,a 9-story steel frame building was selected as the subject.Five steel structure finite element models were established using SAP2000.Response spectrum analysis was conducted on the seismic motion to determine if it adhered to the characteristics of long-period seismic motion.Modal analysis of each structural model revealed that the isolation structure significantly prolonged the structural natural vibration period and enhanced seismic performance.Base reactions and floor displacements of various structures notably increased under long-period seismic motion compared to regular seismic activity.Placing isolation bearings in the lower part of the structure proved more effective under long-period seismic motion.In seismic design engineering,it is essential to consider the impact of long-period seismic motion on structures and the potential failure of isolation bearings.

Selection and modification of ground motion records using Newmark-Hall spectrum as target spectrum for long-period structures

Input ground motions have significant impacts on the uncertainty of structural responses in time-history analysis.In this study,records were selected and scaled for the evaluation of mean structural responses according to the target spectrum.The Newmark-Hall spectrum is closely related to seismic response of short,medium and long-period structures,so it was taken as the target spectrum here.The nonlinear time-history analyses of 9-story and 20-story steel moment-resisting frame structures were carried out as examples.They represent medium and long-period buildings,respectively.Three target spectra with risk of 50%,10%and 2%probabilities for exceedance in 50 years were calculated by the average Newmark-Hall spectrum method for three ground motion sets developed in the SAC Steel Project.The predicted structural mean responses of these Newmark-Hall spectra were compared with those calculated by the average spectral acceleration method for the same record set.It is found that both methods have similar accuracy for estimating the structural mean response.However,the method proposed herein is more effective in reducing the variability of the structural responses.Also,the proposed method is more advantageous for the time-history analysis of long-period structures or structures with more severe nonlinear responses under strong seismic excitations.

Impact of resonant magnetic perturbation on blob motion and structure using a gas puff imaging diagnostic on the HL-2A tokamak

The impact of resonant magnetic perturbation(RMP)on blob motion and structure in the SOL of the HL-2A tokamak is studied using a gas puff imaging diagnostic.Ellipse fitting is applied to study the structure and motion of blobs quantitatively.The radial locations,amplitudes and scale sizes of blobs are obtained based on the fitted ellipse.Furthermore,based on the measurement of blob location,the radial and poloidal velocities of blobs are calculated.With the application of RMP,the edge poloidal shear flow is significantly weakened and the wave number spectrum changes from quasisymmetric to significantly up-down asymmetric.The application of RMP also causes the detected blob location to be much further into the far scrape-off layer(SOL)and increases the blob amplitude.Blob poloidal velocity in the SOL is slowed.Larger-size and longer-lifetime blobs are observed with RMP.With the application of RMP,stronger-amplitude and larger-size blobs are detected in the far SOL and they may cause a more serious erosion problem to the first wall.

Effect of the Interaction of Different Scale Vortices on the Structure and Motion of Typhoons

Five numerical experiments have been performed in this paper by using a quasigtostrophic barotropical model to investigate the interaction of different scale vortiCes on the structure and motion of typhoons.Results show that this interaction may arouse the irregular changes of the asymmetric structure of typhoons,thus leading to anomalous Phenomena such as meandering tracks and sudden changes in the motion speed of typhoons;the ￣t Of this interaction on the strucure and motion may be quite different when the smaller vortex is situated in different Posihons of the typhoon circulation.

Influence of earthquake ground motion incoherency on multi-support structures

A linear response history analysis method is used to determine the influence of three factors:geometric incoherency,wave-passage,and local site characteristics on the response of lnulti-support structures subjected to differential ground motions.A one-span frame and a reduced model of a 24-span bridge,located in Las Vegas,Nevada are studied,in which the influence of each of the three factors and their combinations are analyzed.It is revealed that the incoherency of earthquake ground motion can have a dramatic influence on structural response by modifying the dynamics response to uniform excitation and inducing pseudo-static response,which does not exist in structures subjected to uniform excitation.The total response when all three sources of ground motion incoherency are included is generally larger than that of uniform excitation.

Computation of Design Load and Motion for Floating Structures Navigating in Waves

Analytical and numerical investigation is made of the source potential for-floating structure with forward speed in waves. A particular form is selected for numerical applications, where the double integral of the Green function is transformed into the single one and the oscillation characteristics for integrands in the specific computation domain are treated numerically. A comparison of calculated examples with published data is given and it shows that the numerical simulation is satisfactory and the accuracy is adequate to engineering application.

Sedimentary structure of the western Bohai Bay basin and other basins in North China revealed by frequency dependent P-wave particle motion

High-resolution seismic models of sediment basins are critical inputs for earthquake ground motion prediction and petroleum resource exploration.In this study we employed a newly developed technique that utilizes the frequency-dependent nonlinear P-wave particle motion to estimate sedimentary structure beneath the Bohai Bay basin.A recent study suggests that the delay of the P wave on the horizontal component relative the vertical component and its variations over frequency are caused by interference of the direct P wave with waves generated at the sediment base.The frequency-dependent delay time can be used to constrain sediment thickness and seismic velocity beneath recording stations.We measured the particle motions of teleseismic P waves recorded by 249 broadband stations of the North China Array,which covers the western Bohai Bay basin and its surrounding areas.We found that the P waves of 90 stations inside the Bohai Bay basin and other local basins within the Taihang and Yanshan mountain ranges exhibit significant frequency-dependent nonlinear particle motions,and used the particle motion data to invert the sediment thickness(Z0)and surface S-wave velocity(β0).The estimated sediment thickness inside the Bohai Bay Basin varies from 1.02 km to 3.72 km,with an average of 3.20 km,which roughly agrees with previous active source studies.

Orthogonal expansion of ground motion and PDEM-based seismic response analysis of nonlinear structures

This paper introduces an orthogonal expansion method for general stochastic processes. In the method, a normalized orthogonal function of time variable t is first introduced to carry out the decomposition of a stochastic process and then a correlated matrix decomposition technique, which transforms a correlated random vector into a vector of standard uncorrelated random variables, is used to complete a double orthogonal decomposition of the stochastic processes. Considering the relationship between the Hartley transform and Fourier transform of a real-valued function, it is suggested that the first orthogonal expansion in the above process is carried out using the Hartley basis function instead of the trigonometric basis function in practical applications. The seismic ground motion is investigated using the above method. In order to capture the main probabilistic characteristics of the seismic ground motion, it is proposed to directly carry out the orthogonal expansion of the seismic displacements. The case study shows that the proposed method is feasible to represent the seismic ground motion with only a few random variables. In the second part of the paper, the probability density evolution method （PDEM） is employed to study the stochastic response of nonlinear structures subjected to earthquake excitations. In the PDEM, a completely uncoupled one-dimensional partial differential equation, the generalized density evolution equation, plays a central role in governing the stochastic seismic responses of the nonlinear structure. The solution to this equation will yield the instantaneous probability density function of the responses. Computational algorithms to solve the probability density evolution equation are described. An example, which deals with a nonlinear frame structure subjected to stochastic ground motions, is illustrated to validate the above approach.

Study on the effect of ground motion direction on the response of engineering structure

Due to the randomness of earthquake wave magnitude and direction, and the uncertain direction of strong axis and weak axis in the construction of engineering structures, the effect of the direction of ground motion on a structure are studied herein. Ground motion records usually contain three vertical ground motion data, which are obtained by sensors arranged in accordance with the EW （East -West） direction, NS （South- North） direction and perpendicular to the surface （z） direction, referring to the construction standard of seismic stations. The seismic records in the EW and NS directions are converted to Cartesian coordinates in accordance with the rotation of θ = 0°-180°, and consequently, a countless group of new ground motion time histories are obtained. Then, the characteristics of the ground motion time history and response spectrum of each group were studied, resulting in the following observations： （1） the peak and phase of ground motion are changed with the rotation of direction θ, so that the direction θ of the maximum peak ground motion can be determined; （2） response spectrum values of each group of ground motions change along with the direction θ, and their peak, predominant period and declining curve are also different as the changes occur; then, the angle θ in the direction of the maximum peak value or the widest predominant period can be determined; and （3） the seismic response of structures with different directions of ground motion inputs has been analyzed under the same earthquake record, and the results show the difference. For some ground motion records, such as the Taft seismic wave, these differences are significant. Next, the Lushan middle school gymnasium structure was analyzed and the calculation was checked using the proposed method, where the internal force of the upper space truss varied from 25% to 28%. The research results presented herein can be used for reference in choosing the ground motion when checking the actual damage to structures following earthquakes and explaining the seismic damage. Meanwhile, it also provides a reference value for research into the most severe ground motion.

The effects of torsional ground motion on thin cylindric shell structures

The effects of torsional component of earthquake ground motion on thin cylindric shell structures were investigated qualitatively and quantitatively.The results show that the contributions of torsional component to structural response are related to the height,the radius-to-height ratio,and the stiffness of the structure.The structural response caused by torsional component can not be neglected for the containment structure of nuclear power plant and the industrial oil tank.

Seismic Responses of Asymmetric Base-Isolated Structures under Near-Fault Ground Motion

An inter-story shear model of asymmetric base-isolated structures incorporating deformation of each isolation bearing was built, and a method to simultaneously simulate bi-directional near-fault and far-field ground motions was proposed. A comparative study on the dynamic responses of asymmetric base-isolated structures under near-fault and far-field ground motions were conducted to investigate the effects of eccentricity in the isolation system and in the superstructures, the ratio of the uncoupled torsional to lateral frequency of the superstructure and the pulse period of near-fault ground motions on the nonlinear seismic response of asymmetric base-isolated structures. Numerical results show that eccentricity in the isolation system makes asymmetric base-isolated structure more sensitive to near-fault ground motions, and the pulse period of near-fault ground motions plays an import role in governing the seismic responses of asymmetric base-isolated structures.

Image Motion Deblurring Based on Salient Structure Selection and L0-2 Norm Kernel Estimation

Single image motion deblurring has been a very challenging problem in the field of image processing. Although there are many researches had been proposed to solve this problem, it still has problems on kernel accuracy. In order to improve the kernel accuracy, an effective structure selection method was used to select the salient structure of the blur image. Then a novel kernel estimation method based on L0-2 norm was proposed. To guarantee the sparse kernel and eliminate the negative influence of details L0-norm was used. And L2-norm was used to ensure the continuity of kernel. Many experiments were done to compare proposed method and state-of-the-art methods. The results show that our method can estimate a better kernel and use less time than previous work, especially when the size of blur kernel is large.

Numerical Simulation of the Water Entry of a Structure in Free Fall Motion

To solve the problems concerning water entry of a structure, the RANS equations and volume of fluid （VOF） method are used. Combining the user-defined function （UDF） procedure with dynamic grids, the water impact on a structure in free fall is simulated, and the velocity, displacement and the pressure distribution on the structure are investigated. The results of the numerical simulation were compared with the experimental data, and solidly consistent results have been achieved, which validates the numerical model. Therefore, this method can be used to study the water impact problems of a structure.

Nonlinear dynamic modeling of planar moving Timoshenko beam considering non-rigid non-elastic axial effects

Due to the importance of vibration effects on the functional accuracy of mechanical systems,this research aims to develop a precise model of a nonlinearly vibrating single-link mobile flexible manipulator.The manipulator consists of an elastic arm,a rotary motor,and a rigid carrier,and undergoes general in-plane rigid body motion along with elastic transverse deformation.To accurately model the elastic behavior,Timoshenko’s beam theory is used to describe the flexible arm,which accounts for rotary inertia and shear deformation effects.By applying Newton’s second law,the nonlinear governing equations of motion for the manipulator are derived as a coupled system of ordinary differential equations(ODEs)and partial differential equations(PDEs).Then,the assumed mode method(AMM)is used to solve this nonlinear system of governing equations with appropriate shape functions.The assumed modes can be obtained after solving the characteristic equation of a Timoshenko beam with clamped boundary conditions at one end and an attached mass/inertia at the other.In addition,the effect of the transverse vibration of the inextensible arm on its axial behavior is investigated.Despite the axial rigidity,the effect makes the rigid body dynamics invalid for the axial behavior of the arm.Finally,numerical simulations are conducted to evaluate the performance of the developed model,and the results are compared with those obtained by the finite element approach.The comparison confirms the validity of the proposed dynamic model for the system.According to the mentioned features,this model can be reliable for investigating the system’s vibrational behavior and implementing vibration control algorithms.

STRUCTURES AND CONDITIONS OF EXISTENCE FORA KIND OF ATMOSPHERIC MOTIONS

With the method of phase plane, the ρ-coordinated equation sets have been derived that include no friction without the introduction of the kdv equation and the structure of atmospheric motions, conditions for existence and movement are studied for all individual solutions. The result shows that a weak high or low pressure system isjointly affected by the atmospheric static stability, latent heating due to condensation and sensible heating for the conditions for existence, state of movement, structural features.

A NUMERICAL ANALYSIS ON TYPHOON ASYMMETRIC STRUCTUREAND MOTION

Five prediction experiments are carried out with two typhoons in 1992 using a limited -arca primitiveequations and two-way interactive model in a movable ,nested mesh. The result indicates good agreementin terms of motion between the prediction and observation. Studying the asymmetric structure in the cas-es selected, a close link is uncovered between the temporal evolutions of the structure and the track of motion in a tropical cyclone. Understanding of real asymmetric structure will help to improve the skill offorecasting tropical cyclones.

Real-Time Structure and Motion by Fusion of Inertial and Vision Data for Mobile AR System

The performance of adding additional inertial data to improve the accuracy and robustness of visual tracking is investigated. For this real-time structure and motion algorithm, fusion is based on Kalman filter framework while using an extended Kalman filter to fuse the inertial and vision data, and a hank of Kalman filters to estimate the sparse 3D structure of the real scene. A simple, known target is used for the initial pose estimation. Motion and structure estimation filters can work alternately to recover the sensor motion, scene structure and other parameters. Real image sequences are utilized to test the capability of this algorithm. Experimental results show that the proper use of an additional inertial information can not only effectively improve the accuracy of the pose and structure estimation, but also handle occlusion problem.

Dynamic Positioning Control of Surge−Pitch Coupled Motion for Small-Waterplane-Area Marine Structures

For general dynamic positioning systems,controllers are mainly based on the feedback of motions only in the horizontal plane.However,for marine structures with a small water plane area and low metacentric height,undesirable surge and pitch oscillations may be induced by the thruster actions.In this paper,three control laws are investigated to suppress the induced pitch motion by adding pitch rate,pitch angle or pitch acceleration into the feedback control loop.Extensive numerical simulations are conducted with a semi-submersible platform for each control law.The influences of additional terms on surge−pitch coupled motions are analyzed in both frequency and time domain.The mechanical constraints of the thrust allocation and the frequency characters of external forces are simultaneously considered.It is concluded that adding pitch angle or pitch acceleration into the feedback loop changes the natural frequency in pitch,and its performance is highly dependent on the frequency distribution of external forces,while adding pitch rate into the feedback loop is always effective in mitigating surge−pitch coupled motions.