Non-uniform Motions Research Articles

Large-scale semi-organized rolls in a sheared convective turbulence: Mean-field simulations

Based on a mean-field theory of a non-rotating turbulent convection [T. Elperin et al., Phys. Rev. E 66, 066305, (2002)], we perform mean-field simulations (MFS) of sheared convection that takes into account an effect of modification of the turbulent heat flux by the non-uniform large-scale motions. This effect is caused by the production of additional essentially anisotropic velocity fluctuations generated by tangling of the mean-velocity gradients by small-scale turbulent motions due to the influence of the inertial forces during the lifetime of turbulent eddies. These anisotropic velocity fluctuations contribute to the turbulent heat flux. As the result of this effect, there is an excitation of large-scale convective-shear instability, which causes the formation of large-scale semi-organized structures in the form of rolls. The lifetimes and spatial scales of these structures are much larger compared to the turbulent scales. By means of MFS performed for stress-free and no-slip vertical boundary conditions, we determine the spatial and temporal characteristics of these structures. Our study demonstrates that the modification of the turbulent heat flux by non-uniform flows leads to a strong reduction of the critical effective Rayleigh number (based on the eddy viscosity and turbulent temperature diffusivity) required for the formation of the large-scale rolls. During the nonlinear stage of the convective-shear instability, there is a transition from a two-layer vertical structure with two rolls in the vertical direction before the system reaches steady-state to a one-layer vertical structure with one roll after the system reaches steady state. This effect is observed for all effective Rayleigh numbers. We find that inside the convective rolls, the spatial distribution of the mean potential temperature includes regions with a positive vertical gradient of the potential temperature caused by the mean heat flux of the convective rolls. This study might be useful for understanding the origin of large-scale rolls observed in atmospheric convective boundary layers, as well as in numerical simulations and laboratory experiments.

Exact solutions to the Navier–Stokes equations for describing inhomogeneous isobaric vertical vortex fluid flows in regions with permeable boundaries

A family of exact solutions to the Navier–Stokes equations is constructed to describe nonuniform two-dimensional fluid motions. The superposition of the main unidirectional flow with the secondary flow is considered. The secondary flow is determined by suction or injection through permeable boundaries. This class of exact solutions is obtained by multiplicative and additive separation of variables. The flow of a viscous incompressible fluid is described by a polynomial of the horizontal (longitudinal) coordinate. The polynomial coefficients are functions of the vertical (transverse) coordinate and time. They are determined by a chain of homogeneous and inhomogeneous parabolic partial differential equations with a convective term. In the case of a steady flow, it is described by a system of ordinary differential equations with constant coefficients. An algorithm for integrating a system of ordinary differential equations for studying the steady motion of a viscous fluid is presented. In this case, all the functions defining the velocity are quasipolynomials since the system of ordinary differential equations has an Euler-form exact solution.

The personal Gravity of the Earth by HF modulating impulses, described according to the new axioms and laws

The theory of new axioms and laws describes nonparametric and nonlinear processes and contains 2 new axioms and 8 new laws. Unlike Classical Field Theory, it describes longitudinal or transverse non-uniform motions or complex longitudinal-transverse and transverse-longitudinal non-uniform motions with various parameters and with changing causes of the motion. According to the Axiom1 every unevenly rotation of one vector form open vortex which can be accelerating or decelerating and as well as transverse in 2D or longitudinal in 3D. From previous reports is understood that both the electron and the planet Earth are gravitational bodies as result. According Law1the reason for generating the electron is a transverse decelerating vortex in 2D coming from the proton which is rolled up from periphery to center and generates there longitudinal accelerating vortex in 3D. According Axiom2 the electron and the proton form resonance system. According Law2 the reason for the creation of the proton is a longitudinal vortex from outside in 3D to the center, which generates there transverse accelerating vortex in 2D from center to periphery, perpendicular to the longitudinal vortex. It is well known the Rutherford's model of the analogy between the atomic structure and the structure of the solar system. But according new axiom and laws the reason for the creation of the planet Earth is in the generation a complex vortex in 2D (inside the third cylindrical resonator in volume of the Sun) from a longitudinal vortex in 3D ( coming from outside) . This complex vortex acts the energy control and management of Earth. It carries low-frequency power energy as a base and high-frequency pulses modulated onto the base. As described in previous report, low-frequency energy generates the inner planets in the Solar System (including Earth) and its low-frequency pulsation transforms their circular orbits into elliptical orbits. This article will describe how high frequency pulses create the personal, self-gravity of planet Earth in particular, and why they cause both a gravitational push from the outside to the body and a gravitational pull from the body out. In this report is used 2 new Axiom and 3 new Laws only.

Large-scale circulations in a shear-free convective turbulence: Mean-field simulations

It has been previously shown [Elperin et al., “Formation of large-scale semi-organized structures in turbulent convection,” Phys. Rev. E 66, 066305 (2002)] that a non-rotating turbulent convection with nonuniform large-scale flows contributes to the turbulent heat flux. As a result, the turbulent heat flux depends explicitly not only on the gradients of the large-scale temperature, but also on the gradients of the large-scale velocity. This is because the nonuniform large-scale flows produce anisotropic velocity fluctuations, which modify the turbulent heat flux. This effect causes an excitation of a convective-wind instability and formation of large-scale semi-organized coherent structures (large-scale convective cells). In the present study, we perform mean-field numerical simulations of shear-free convection, which take into account the modification of the turbulent heat flux by nonuniform large-scale flows. We use periodic boundary conditions in horizontal direction as well as stress-free or no-slip boundary conditions in vertical direction. We show that the redistribution of the turbulent heat flux by the nonuniform large-scale motions in turbulent convection plays a crucial role in the formation of the large-scale semi-organized coherent structures. In particular, this effect results in a strong reduction of the critical effective Rayleigh number (based on the eddy viscosity and turbulent temperature diffusivity) required for the formation of the large-scale convective cells. We demonstrate that the convective-wind instability is excited when the scale separation ratio between the height of the convective layer and the integral turbulence scale is large. The level of the mean kinetic energy at saturation increases with the scale separation ratio. We also show that inside the large-scale convective cells, there are local regions with the positive vertical gradient of the potential temperature, which implies that these regions are stably stratified.

Dynamic ISAR Imaging Method for Multiple Moving Vehicles Based on OMP-CADMM

Inverse synthetic aperture radar (ISAR) technology has attracted considerable attention in smart traffic monitoring, owing to the superiority of high-resolution imaging and tracking for moving targets in all-weather. However, in practical application cases, it is hard to obtain a globally-focused image of multiple vehicles by traditional ISAR imaging techniques due to the nonuniform motions of vehicles. Hence, a dynamic ISAR imaging method for multiple moving vehicles based on the joint of orthogonal matching pursuit (OMP) and consensus alternating direction method of multipliers (CADMM) is proposed in this paper. First, the preprocessing for raw data is performed in the wavenumber domain to simplify the imaging task into linear phase error estimation and distributed image recovery. Based on the sparsity of moving vehicles, the OMP method is utilized to estimate the dynamic motion phase error of consecutive frames data for different moving vehicles with less computational overhead. Then, the dynamic ISAR imaging problems of multiple moving vehicles can be transformed into the distributed imaging problem with variously estimated phases. Motivated by this fact, the CADMM optimization framework is exploited for the distributed ISAR imaging problem to obtain a globally-focused result according to the consensus constraint characteristic of multiple vehicles. Lastly, both the simulation and real data experiments are conducted to verify the performance and feasibility of the OMP-CADMM method. Furthermore, the experimental results show that the proposed method is capable of dynamic imaging and de-noising for multiple vehicles without signal separation.

Free-field soil response to bidirectional horizontal non-uniform ground motion from multi-point shaking table tests

This paper assesses the dynamic nonlinear free-field soil response under bidirectional horizontal non-uniform excitation through a series of multi-point 1 g shaking table tests. The soil bed was enclosed in an innovative soil box supported by an array of three shake tables and was subjected to uniform and non-uniform ground motions in one and two horizontal directions. The soil response to bidirectional and unidirectional excitations, both uniform and non-uniform, were compared and discussed in terms of acceleration time history and Fourier spectra, acceleration amplification factor and soil settlement, as well as shear stress-shear strain behavior. The comparison of soil responses to bidirectional and unidirectional shakings demonstrated that the trends of peak acceleration amplification factors are similar along soil depth, but the response difference between bidirectional and unidirectional shaking is increasingly higher along the soil profile towards the ground surface, especially for uniform excitation. The variations of soil settlement, shear stress-strain and damping curves under bidirectional excitation were similar to that under longitudinal excitation; however, they were much different than those observed under transverse excitation. The soil damping in Y-direction under non-uniform excitation was larger than that under uniform excitation. These different site response characteristics under bidirectional non-uniform excitation should be properly considered in the seismic design of extended infrastructure.

External rotation of the foot position during plantarflexion increases non-uniform motions of the Achilles tendon

The medial (GM) and lateral gastrocnemius (GL) muscles enroll to different subparts of the Achilles tendon to form their respective subtendons. The relative gastrocnemii activations during submaximal plantarflexion contraction depend on the position of the foot in the horizontal plane: with toes-in, GL activation increases and GM activation decreases, compared to toes-out. The aim of the current study was to investigate whether horizontal foot position during submaximal isometric plantarflexion contraction differently affects the subtendons within the Achilles tendon in terms of their (i) length at rest, and (ii) elongations and distal motions. Twenty healthy subjects (12 females/8 males) participated in the study. Three-dimensional ultrasound images were taken to capture subtendon lengths at rest and during isometric contraction. Ultrasound images were recorded at the distal end of Achilles tendon (sagittal plane) during ramped contractions and analyzed using a speckle tracking algorithm. All tasks were conducted twice, ones with toes-in and ones with toes-out. At rest, subtendons were shorter with toes-out compared to toes-in. During contraction, the GM subtendon lengthened more in toes-out, compared to the GL, and vice versa (all p <.01). The relative motions within the Achilles tendon (middle minus top layers displacements) were smaller in toes-in compared to toes-out (p =.05) for higher contraction intensity. Our results demonstrated that the horizontal foot position during plantarflexion contraction impacts Achilles tendon motions. Such findings may be relevant in a clinical context, for example in pathologies affecting Achilles tendon motions such as Achilles tendinopathy.

Designing Physics Problems with Mathematica Example II

Customarily in the physics of sound, static-acoustic-related topics are addressed. For instance, the change in the sound level vs discrete change in the distance. In dynamic cases, e.g. the Doppler shit although the relative motion of the components, i.e. the source and the sensor are essential, the movements are limited to uniform motions. In this investigating report, scenarios departed from these limitations are considered. For the former case, time dependent sound level and for the latter case, nonuniform motions are analyzed. Aside from light long-hand mathematical formulations, the majority of the analysis is carried out utilizing a Computer Algebra System (CAS) specifically Mathematica. The analysis and format of the development are crafted flexibly conducive opportunities for furthering quests for the “what if” scenarios.

Multi-angle and nonuniform ground motions on cable-stayed bridges

The definition of the spatial variability of the ground motion (SVGM) is a complex and multi-parametric problem. Its effect on the seismic response of cable-stayed bridges is important, yet not entirely understood to date. This work examines the effect of the SVGM on the seismic response of cable-stayed bridges by means of the time delay of the ground motion at different supports, the loss of coherency of the seismic waves, and the incidence angle of the seismic waves. The focus herein is the effect of the SVGM on cable-stayed bridges with various configurations in terms of their length and of design parameters such as the pylon shape and the pylon–cable system configuration. The aim of this article is to provide general conclusions that are applicable to a wide range of canonical cable-stayed bridges and to contribute to the ongoing effort to interpret and predict the effect of the SVGM in long structures. This work shows that the effect of the SVGM on the seismic response of cable-stayed bridges varies depending on the pylon shape, height, and section dimensions; on the cable-system configuration; and on the response quantity of interest. Furthermore, the earthquake incidence angle defines whether the SVGM is important to the seismic response of the cable-stayed bridges. It is also confirmed that the SVGM excites vibration modes of the bridges that do not contribute to their seismic response when identical support motion is considered.

Dynamic failure evolution of surrounding rock in a long tunnel with different unfavorable geological structure zones under non-uniform seismic input

Earthquake damage investigations show that damage often occurs in complex geological sections with unfavorable geological structures along a long tunnel. And the unique earthquake damage phenomena are the result of non-uniform ground motion generally. In order to study dynamic failure evolution of surrounding rock in a long tunnel with different unfavorable geological structure zones under earthquake. Therefore, a variety of schemes for dynamic analysis of a long tunnel with different lithology and thickness unfavorable geological structure zones is carried out through non-uniform ground motion input. Firstly, based on stochastic process theory, multiple time history curves of different ground motions that can reflect the traveling wave effect and attenuation effect for long tunnels are generated. Then, the dynamic response of the surrounding rock in the tunnel is analyzed through inputting these non-uniform ground motions. By analyzing the variation of shear plastic strain increment and plastic volume in surrounding rock, the characteristics of the potential failure surface with the earthquake time history in the surrounding rock of the tunnel with different unfavorable geological structure zones are studied. On this basis, the main influencing factors and the degree of influence on the dynamic damage of the surrounding rock of the long tunnel with unfavorable geological structure zone under non-uniform ground motions are evaluated. The results show that the unfavorable geological structure zone has a controlling effect on the seismic dynamic response and destruction of the surrounding rock of the tunnel. Further, the lithology of unfavorable geological structures and the time history of ground motions have a significant impact on the response and damage of surrounding rock.

Visualizing how inclusion of higher reciprocal space in SWAXS data analysis improves shape restoration of biomolecules: case of lysozyme

Query remains whether use of increased resolution data from X-ray scattering aids in better understanding of the dynamic shape of the biomolecule in solution? To address this, we acquired Small/Wide angle X-ray scattering (SWAXS) data in the q range of 0.008 − 1.72 Å−1 from dilute solutions of lysozyme (0.9 to 5 mg/ml). Samples lacked any interparticulate effect and datasets showed Bragg peaks at q∼0.325, 0.65 and 1.4 Å−1, as reported before by other authors. Considering an averaged profile, we estimated shape parameters and distance distribution profiles of interatomic vectors by gradually increasing input qmax value. Interestingly, use of higher resolution led to emergence of new peaks amongst smaller vectors. Deconvolution of these peaks provided positions of smaller peaks which correlated well with an earlier theoretical work. These peaks arise from secondary structures or due to non-uniform internal motions within the larger shape of this protein. Dummy residue modeling considering uniform density yielded model(s) with holes or cavities when considering higher q values implying limitations of this method. Employing normal mode calculations, we searched for better fitting model of lysozyme using differentially ranged SWAXS data and a crystal structure of lysozyme as starting structure. Comparison of refined models with structures from crystallography and NMR data showed that use of data till mid q region resulted in adjustments near the center of mass of starting structure, and inclusion of higher resolution induced pan-structure adjustments. We conclude that high resolution SWAXS data analysis provides additional dimension towards understanding biomolecular structural dynamics. Communicated by Ramaswamy H. Sarma

Gravity Field (Low Frequency) of Planet Earth Described by Theory of New Axioms and Laws

The theory of new axioms and laws is published by the same author. It describes nonparametric and nonlinear processes and contains 2 new axioms and 8 new laws. Unlike Classical field theory, it describes longitudinal or transverse non-uniform motions which are accelerating or decelerating. According to the Axiom 1 every unevenly rotation of one vector forms open vortex which can be transverse or longitudinal and accelerating or decelerating. From the planetary model of Rutherford it is known that there is analogy between the electrons and an planets including the planet Earth. By analogy - the electrons and the internal planets are similar Gravitational bodies. According the Law 1 the model of the electron or the Earth represents a decelerating transverse vortex rolled into a plane (2D) and generating in its center accelerating longitudinal Gravity Funnel in (3D), perpendicular to the same plane. Inside- the primary accelerating longitudinal Gravity vectors are with decreasing dimensions and forms the decelerating Magnetic Field as a Back wave passing through the center of Earth. Outside- because of resistance of environment in periphery, is formed Back wave or decelerating Gravity vortex that passes outside the body of Earth. According Axiom 2 the reason for the creation of the electron is the generation by the corresponding proton. By analogythe reason for the creation of internal planets, including the planet Earth is in the generation of a specific vortex inside the corresponding for Earth resonator in the volume of the Sun. It is Low Frequency vortex which is formed in the third cylindrical resonator that corresponds to Earth. According Law 2 the proton or the resonator inside Sun is generated by a decelerating longitudinal vortex with direction from outside to inside which creates an accelerating transverse vortex from inside to outside in the perpendicular plane. As it is strongly accelerated this vortex from inside to outside it shoots itself into space in direction to the Earth. Due to the friction it decelerates and according to the previous Law 1 it winds into as a decelerating transverse vortex generating the body of Earth. According Law 5 decelerating vortex emits decelerating cross vortices from itself to outside. This decelerating vortices in periphery of the Earth emit energy and warm the center of the Earth. That is why the periphery of Earth is cool ,but the center of Earth is hot . According Law 6 the accelerating cross vortex sucks accelerating cross vortices to itself . This accelerating cross vortex at center of the Sun sucks energy and warm from center and emits them to periphery of Sun. That is why the center of Sun is cool but the periphery is extremely accelerated and hot. The described generating mechanism only applies to the inner planets. For the outer planets, the generation algorithm is orthogonal and will be described further.

Inelastic response of cable-stayed bridges subjected to non-uniform motions

This paper studies for the first time the effect of the spatial variability of ground motions (SVGM) with large intensities on the inelastic seismic response of the pylons which are responsible for the overall structural integrity of cable-stayed bridges. The svgm is defined by the time delay of the earthquake at different supports, the loss of coherency of the seismic waves and the incidence angle of the ground motion. An extensive study is conducted on cable-stayed bridges with ‘H’- and inverted ‘Y’-shaped pylons and with main spans of 200, 400 and 600 m. The svgm is most detrimental to the pylon of the 200-m span bridge owing to the large stiffness of this bridge compared to its longer counterparts. The stiff configuration of the inverted ‘Y’-shaped pylon makes it more susceptible against the multi-support excitation than the flexible ‘H’-shaped pylon, especially in the transverse direction of the response. Finally, the earthquake incidence angle is strongly linked with the svgm and should be included in the seismic design of cable-stayed bridges.

The effect of non-uniformity in ground motions on the seismic response of arch dams

Recorded ground accelerations at various locations of Karun III Dam during November 20, 2007, were recorded by an array of accelerometers located on the dam. In terms of amplitude and phase, these accelerations show non-uniformities in different elevations. In this paper, the effect of these non-uniform ground motions on the seismic response of the dam taking dam-reservoir-foundation interaction into account is investigated. The EACD-3D-2008 finite element program and ABAQUS Software are used for carrying out the seismic analyses. For this purpose, time histories of the earthquake accelerations are interpolated at nodal points located on the dam foundation interface. The analysis has been repeated, considering the common assumption of uniform ground motions. Comparing the results obtained from these two analyses reveals that the computed displacements in the crest due to the spatially varying excitations are in more conformity with the recorded information. Moreover, neglecting the non-uniform nature of ground motions in the model leads to underestimating the tensile stress values within the dam body.

Investigation of seismic response of topography under recorded excitation using boundary element method

Irregular topography induces non-uniform excitation in the supports of large structures such as dams and bridges. The present study employs the 3-dimensional boundary element method to achieve the seismic response of Pacoima Dam’s valley and compares the numerical results with the real responses recorded during the 2001 Pacoima earthquake. The horizontal components recorded on the bottom of the valley are used as the input wave for the analysis. The time history of displacements and amplifications of different points are examined. The results revealed that the amplification factor enhanced from bottom to the top of the valley for the most frequencies. The displacement amplification ratio reached approximately 3 along the valley, suggesting the necessity for considering the non-uniform motions effects on huge structures.

Fine-Grained Motion Estimation for Video Frame Interpolation

Recent advances in video frame interpolation have shown that convolutional neural networks combined with optical flow are capable of producing a high-quality intermediate frame between two consecutive input frames in most scenes. However, existing methods have difficulties dealing with large and non-uniform motions that widely exist in real-world scenes because they often adopt the same strategy to deal with different motions, which easily results in unsatisfactory results. In this article, we propose a novel fine-grained motion estimation approach (FGME) for video frame interpolation. It mainly contains two strategies: multi-scale coarse-to-fine optimization and multiple motion features estimation. The first strategy is to gradually refine optical flows and weight maps, both of which are used to synthesize the target frame. The second strategy aims to provide fine-grained motion features by generating multiple optical flows and weight maps. To demonstrate its effectiveness, we propose a fully convolutional neural network with three refinement scales and four motion features. Surprisingly, this simple network produces state-of-the-art results on three standard benchmark datasets and real-world examples, with advantages in terms of effectiveness, simplicity, and network size over other existing approaches. Furthermore, we demonstrate that the FGME approach has good generality and can significantly improve the synthesis quality of other methods.

Spectral Correlation Between the Non-uniform Input Ground Motion and the Dynamic Response of the Surrounding Rocks of a Long Tunnel

To generate several different time-history curves of ground motion, which have the ability to reflect local site effects, such as the traveling-wave effect and attenuation effect, for long circular tunnels, a random method for the synthesis of ground motion is employed. The dynamic response of the surrounding rocks of a long tunnel under the uniform and non-uniform input ground motions is analyzed using the vertical input method. Based on this, the spectral correlation between the input ground motion and the dynamic response of the surrounding rocks is investigated through the coherence function. Unlike the results under the uniform input ground motion, the transmission coefficient of the surrounding rock monitoring points of each section along the axial direction of the tunnel under the non-uniform input ground motion varies in the main frequency band. In addition, at the same frequency, the transmission coefficient of the monitoring points gradually increases along the tunnel’s axial direction, but the increasing magnitude is variable. The correlation function of each monitoring point along the tunnel axis under the non-uniform input ground motion generally decreases with frequency. Moreover, the further the distance from the tunnel entrance, the faster the attenuation of correlation. The maximum coherence coefficient and the axial distance of the tunnel are basically in conformity with the quadratic polynomial relationship. However, the maximum coherence coefficient of the non-uniform input ground motion is considerably greater than that of the uniform input ground motion. The gap increases with the distance, and the maximum gap is about 0.15.

Seismic Response and Vibration Reduction Analysis of Suspended Structure under Wave Passage Excitation

In order to study the influence of traveling wave effect on the seismic response and damping effect of suspended structure, a series of shaking table tests of the 1 : 20 suspended structure have been carried out to compare and analyze the dynamic responses of suspended structures under two points and a consistent input. The vibration damping effect and vibration reduction law of suspended structure are discussed at different apparent wave velocity and in the different connection. The research shows that the damping suspended structure has a good damping effect, and the amplitude reduction of the top displacement peak response is up to 15%, which corresponds to smaller apparent velocities. Moreover, the upper bound of the maximum acceleration response at the structures’ top under nonuniform input motions equals that of the uniform motion. However, there is a hysteresis in the acceleration response under wave travelling excitations, and the smaller the apparent wave velocity, the more obvious the hysteresis.

Element-Free Galerkin method for dynamic boundary flow problems

This paper focuses on the study of dynamic boundary flow problems based on the Element-Free Galerkin method. First, Navier–Stokes equation is discretized with the Galerkin method. The inertial term in the equation is discretized with the method of the speed term and direct deduction, respectively. The penalty function method is used to deal with the pressure and the essential boundary condition in the equation, and the discretization of two-dimensional N–S equation based on the EFG method is established. However, irregular changes in boundary conditions are often encountered in practical fluid problems. For example, the motion of flapping-foil is not uniform relative to the flow. In this paper, numerical experiments are carried out for the flow problems with non-uniform boundary motions. The problem which a plate with non-uniform drag movement above a rectangular tank filled with water is studied with the EFG method. The feasibility of the proposed algorithm is verified by comparison with the FEM method. Then, the procession of the water in the tank is stimulated. In the end, the influence of different calculation time steps on the accuracy of the solution is discussed.

Seismic performance evaluation of large-span offshore cable-stayed bridges under non-uniform earthquake excitations including strain rate effect

This paper presents a novel and precise seismic performance evaluation method for large-span offshore cable-stayed (LSOCS) bridge by considering the strain rate effect of RC materials and the spatial variation effect of seafloor seismic motions. Three-dimensional finite element (FE) model of a LSOCS bridge located in the southeast coast of China is constructed in the ABAQUS platform. The non-uniform ground motions at the offshore site beneath the bridge are stochastically simulated and used as seismic inputs. Moreover, a subroutine for considering the rate-dependent properties of RC materials in a fiber-based beam-column element model is developed to account for the strain rate effect of RC materials in the nonlinear time-history analysis. The numerical results indicate that seismic responses and fragilities of the LSOCS bridge are both considerably affected by the non-uniform seafloor seismic motions and strain rate effect. The seismic performance evaluation approach presented in this paper can provide vital support for earthquake resistant design of LSOCS bridges.