Regular Velocity Research Articles

An improved LTI algorithm for multiphase raytracing in undulating surface model

Abstract Based on the linear traveltime interpolation (LTI) algorithm, we propose an improved LTI (referred as ILTI) algorithm for multiphase seismic ray tracing, which uses a velocity node in model parameterization and introduces secondary nodes between adjacent velocity nodes. To better fit the undulating surface model, an irregular velocity node is used in near the irregular interface, and regular velocity nodes are still used in the region far away from the irregular interface. We derive an iterative fixed-point formula for calculating traveltime. By combining multistage computational technology and wavefront narrowband expansion technology, the proposed ILTI algorithm can efficiently trace the multiphase seismic raypath and compute the corresponding traveltime field. Through comparison and analysis with the traditional LTI algorithm, its computational accuracy can be highlighted by at least one order of magnitude. Compared with the popular fast marching method (FMM) and irregular shortest-path (ISPM) algorithms, it also has the advantages in terms of computational accuracy and efficiency. Numerical simulations in the Marmousi model show that the algorithm is also suitable for tracking multiphase seismic rays in the complex velocity model.

Nernst–Planck–Navier–Stokes Systems far from Equilibrium

We consider ionic electrodiffusion in fluids, described by the Nernst-Planck-Navier-Stokes system. We prove that the system has global smooth solutions for arbitrary smooth data: arbitrary positive Dirichlet boundary conditions for the ionic concentrations, arbitrary Dirichlet boundary conditions for the potential, arbitrary positive initial concentrations, and arbitrary regular divergence-free initial velocities. The result holds for any positive diffusivities of ions, in bounded domains with smooth boundary in three space dimensions, in the case of two ionic species, coupled to Stokes equations for the fluid. The result also holds in the case of Navier-Stokes coupling, if the velocity is regular. The global smoothness of solutions is also true for arbitrarily many ionic species, if all their diffusivities are the same.

Influence of design anode and cathode channel on (PEMFC) fuel cell performance

Abstract This paper is focussed on investigating into some key aspects relating to design of an integrated proton exchange membrane fuel cell. Analysis of all currently utilised storage mediums was undertaken. High and low inlet operating conditions were studied by determining the distributions of over potentials, velocity distribution, and pressure. At entrance and exit, a triangle channel flow-field was predicted to have better polarization performance and regular velocity distribution, whereas for rectangular that was performance differences among four serpentine flow-fields for hydrogen and air. The pressure in the triangle channels were monitored to have periodically similar plots and showed important low pressure drop. Considering low pressure drop of rectangular channel has mid effect between triangles and rectangular for the same dimension that depends on the hydraulic diameter, these flow-fields would be beneficial for the larger inlet channel area. The study found that the triangular channels produced a better performance than their square flow path counterparts.

Galaxy-scale ionised winds driven by ultra-fast outflows in two nearby quasars

We used MUSE adaptive optics data in narrow field mode to study the properties of the ionised gas in MR 2251−178 and PG 1126−041, two nearby (z ≃ 0.06) bright quasars (QSOs) hosting sub-pc scale ultra-fast outflows (UFOs) detected in the X-ray band. We decomposed the optical emission from diffuse gas into a low- and a high-velocity components. The former is characterised by a clean, regular velocity field and a low (∼80 km s−1) velocity dispersion. It traces regularly rotating gas in PG 1126−041, while in MR 2251−178 it is possibly associated with tidal debris from a recent merger or flyby. The other component is found to be extended up to a few kpc from the nuclei, and shows a high (∼800 km s−1) velocity dispersion and a blue-shifted mean velocity, as is expected from outflows driven by active galactic nuclei (AGN). We estimate mass outflow rates up to a few M⊙ yr−1 and kinetic efficiencies LKIN/LBOL between 1−4 × 10−4, in line with those of galaxies hosting AGN of similar luminosities. The momentum rates of these ionised outflows are comparable to those measured for the UFOs at sub-pc scales, which is consistent with a momentum-driven wind propagation. Pure energy-driven winds are excluded unless about 100× additional momentum is locked in massive molecular winds. In comparing the outflow properties of our sources with those of a small sample of well-studied QSOs hosting UFOs from the literature, we find that winds seem to systematically lie either in a momentum-driven or an energy-driven regime, indicating that these two theoretical models bracket the physics of AGN-driven winds very well.

Self-adaptive potential-based stopping criteria for Particle Swarm Optimization with forced moves

We study the variant of Particle Swarm Optimization that applies random velocities in a dimension instead of the regular velocity update equations as soon as the so-called potential of the swarm falls below a certain small bound in this dimension, arbitrarily set by the user. In this case, the swarm performs a forced move.In this paper, we are interested in how, by counting the forced moves, the swarm can decide for itself to stop its movement because it is improbable to find better candidate solutions than the already-found best solution. We formally prove that when the swarm is close to a (local) optimum, it behaves like a blind-searching cloud and that the frequency of forced moves exceeds a certain, objective function-independent value. Based on this observation, we define stopping criteria and evaluate them experimentally showing that good candidate solutions can be found much faster than setting upper bounds on the iterations and better solutions compared to applying other solutions from the literature.

Effect of primary magnetic intensity and rotation on wave propagation in generalized thermo-piezoelectric anisotropic smart materials

In this work, a mathematical system of wave propagation in generalized thermo-piezoelectric anisotropic smart material under primary magnetic field and rotation influence is considered. The system of equations for this phenomenon are given in the case of generalized thermoelasticity for three models, namely, Lord–Shulman (LS), Green–Lindsay (GL), and dual-phase-lag (DPL). Furthermore, it is assumed the whole medium is revolved with a regular angular velocity and perturbed magnetic field. Next, the normal mode technique is given to the set of partial differential equations to produce the corresponding ordinary differential equations whose exact analytical solutions will be found. The distributions of the considered variables such as the horizontal and vertical displacements, the temperature, the stress components, the electric potential, and the electric displacement are calculated numerically. Finally, the impacts of the rotation, primary magnetic field, and thermal relaxation times have been illustrated graphically which were noticeable on the various physical quantities.

Properties of galaxies with an offset between the position angles of the major kinematic and photometric axes

We derive the photometric, kinematic, and abundance characteristics of 18 star-forming MaNGA galaxies with fairly regular velocity fields and surface brightness distributions and with a large offset between the measured position angles of the major kinematic and photometric axes, ΔPA ≳ 20°. The aim is to examine if there is any other distinctive characteristic common to these galaxies. We found morphological signs of interaction in some (in 11 out of 18) but not in all galaxies. The observed velocity fields show a large variety; the maps of the isovelocities vary from an hourglass-like appearance to a set of straight lines. The position angles of the major kinematic axes of the stellar and gas rotations are close to each other. The values of the central oxygen abundance, radial abundance gradient, and star formation rate are distributed within the intervals defined by galaxies with small (no) ΔPA of similar mass. Thus, we do not find any specific characteristic common to all galaxies with large ΔPA. Instead, the properties of these galaxies are similar to those of galaxies with small (no) ΔPA. This suggests that either the reason responsible for the large ΔPA does not influence other characteristics or the galaxies with large ΔPA do not share a common origin, they can, instead, originate through different channels.

A 5deg x 5deg deep H i survey of the M81 group

ABSTRACT A $25\, \rm deg^2$ region, including the M81 complex (M81, M82, and NGC 3077), NGC 2976, and IC2574, was mapped during ∼3000 h with the DRAO synthesis telescope. With a physical resolution of ∼1 kpc, these observations allow us to probe a large region down to column density levels of ${\sim }1\times 10^{18}\, \rm cm^{-2}$ over 16 km s−1, mapping the extent of the H i arm connecting the system and NGC 2976, and resolving the H i clouds adjacent to the arm. The observations also reveal a few clouds located between the system and IC 2574, probably tidally stripped from a past interaction between the two systems. Given the regular velocity distribution in the H i envelope of the system, we attempt and derive an idealized large-scale rotation curve of the system. We observe a flat trend for the rotation velocity of the overall system from 20 kpc out to 80 kpc, well beyond the outskirts of the M81 disk, although with asymmetries like a wiggle at the vicinity of M82. This supports the assumption that intergalactic gas and galaxies in the system participate to a large-scale ordered rotation motion which is dominated by M81. Also, our H i analysis of the group further supports the hypothesis that the galaxies forming the system moved closer from afar, in agreement with numerical simulations.

Effect of Mimic Vegetation with Different Stiffness on Regular Wave Propagation and Turbulence

Flume experiments were performed to test four plant mimics with different stiffness to reveal the effect of plant stiffness on the wave dissipation and turbulence process. The mimics were built of silica gel rod groups, and their bending elastic modulus was measured as a proxy for stiffness. The regular wave velocity distribution, turbulence characteristics, and wave dissipation effect of different groups were studied in a flume experiment. Results show that, when a wave ran through the flexible rod groups, the velocity period changed gradually from unimodal to bimodal, and the secondary wave peak was more apparent in the more flexible mimics. The change in the turbulence intensity in the different rod groups showed that the higher the rod stiffness, the greater the turbulence intensity. With an increase in the bending elastic modulus of a rod group, the wave dissipation coefficient increased. The increase in the wave dissipation coefficient was not linearly correlated with the bending elastic modulus, but it was sensitive within a certain range of the elastic modulus.

Non-Linear Convection in Chemically Reacting Fluid with an Induced Magnetic Field across a Vertical Porous Plate in the Presence of Heat Source/Sink

An investigation is carried out to observe the impacts of non-linear convection and induced magnetic field in the flow of viscous fluid over a porous plate under the influence of chemical reaction and heat source/sink. The plate is subjected to a regular free stream velocity as well as a suction velocity. The subjected non-linear problem is non-dimensionalized and analytic solutions are presented via perturbation method. The graphs are plotted to analyze the effect of relevant parameters on velocity, induced magnetic field, heat and mass transfer fields as well as friction factor, current density, Nusselt and Sherwood numbers. It is established that nonlinear convection aspect is destructive for thermal field and its layer thickness. The magnetic field effect enhances the thermal field while it reduces the velocity field. Also, the nonlinear effect subsides heat transfer rate significantly.

Neutral versus ionized gas kinematics at z ≃ 2.6: the AGN-host starburst galaxy PKS 0529-549

We present a multiwavelength study of the AGN-host starburst galaxy PKS 0529-549 at z~2.6. We use (1) new ALMA observations of the dust continuum and of the [CI] 370 um line, tracing molecular gas, (2) SINFONI spectroscopy of the [OIII] 5007 Ang line, tracing ionized gas, and (3) ATCA radio continuum images, tracing synchrotron emission. Both [CI] and [OIII] show regular velocity gradients, but their systemic velocities and position angles differ by ~300 km/s and ~30 degrees, respectively. The [CI] is consistent with a rotating disc, aligned with the dust and stellar continuum, while the [OIII] likely traces an outflow, aligned with two AGN-driven radio lobes. We model the [CI] cube using 3D disc models, which give best-fit rotation velocities V~310 km/s and velocity dispersions sigma<30 km/s. Hence, the [CI] disc has V/sigma>10 and is not particularly turbulent, similar to local galaxy discs. The dynamical mass (~10^11 Msun) is comparable to the baryonic mass within the errors. This suggests that baryons dominate the inner galaxy dynamics, similar to massive galaxies at z=0. Remarkably, PKS 0529-549 lies on the local baryonic Tully-Fisher relation, indicating that at least some massive galaxies are already in place and kinematically relaxed at z~2.6. This work highlights the potential of the [CI] line to trace galaxy dynamics at high z, as well as the importance of multiwavelength data to interpret gas kinematics.

The fundamental Lepage form in variational theory for submanifolds

The multiple-integral variational functionals for finite-dimensional immersed submanifolds are studied by means of the fundamental Lepage equivalent of a homogeneous Lagrangian, which can be regarded as a generalization of the well-known Hilbert form in the classical mechanics. The notion of a Lepage form is extended to manifolds of regular velocities and plays a basic role in formulation of the variational theory for submanifolds. The theory is illustrated on the minimal submanifolds problem, including analysis of conservation law equations.

Toward Understanding the B[e] Phenomenon. VII. AS 386, a Single-lined Binary with a Candidate Black Hole Component

Abstract We report the results of spectroscopic and photometric observations of the emission-line object AS 386. For the first time we found that it exhibits the B[e] phenomenon and fits the definition of an FS CMa type object. The optical spectrum shows the presence of a B-type star with the following properties: T eff = 11,000 ± 500 K, log L/L ⊙ = 3.7 ± 0.3, a mass of 7 ± 1 M ⊙, and a distance D = 2.4 ± 0.3 kpc from the Sun. We detected regular radial velocity variations of both absorption and emission lines with the following orbital parameters: P orb =131.27 ± 0.09 days, semiamplitude K 1 = 51.7 ± 3.0 km s−1, systemic radial velocity γ = −31.8 ± 2.6 km s−1, and a mass function of f(m) = 1.9 ± 0.3 M ⊙. AS 386 exhibits irregular variations of the optical brightness (V = 10.92 ± 0.05 mag), while the near-IR brightness varies up to ∼0.3 mag following the spectroscopic period. We explain this behavior by a variable illumination of the dusty disk inner rim by the B-type component. Doppler tomography based on the orbital variations of emission-line profiles shows that the material is distributed near the B-type component and in a circumbinary disk. We conclude that the system has undergone a strong mass transfer that created the circumstellar material and increased the B-type component mass. The absence of any traces of a secondary component, whose mass should be ≥7 M ⊙, suggests that it is most likely a black hole.

Hydraulic performance of abrupt outlet transition structure with strip guide vanes at subcritical flow

For some stream structures such as barrages, regulators, as well as change of channel cross section, the downstream expansion transitions structures are the common requirement. Eddies, as a result of the flow separation in such structures leads to destruction the bed and sides of the downstream channel. Head loss, on the other hand, produced through the expansion is important because it affects the stage at downstream. This study is restricted to developing the hydraulic performance of abrupt outlet transition at subcritical flow for both decreasing the head losses besides spreading the flow transversely to achieve regular velocity across the width as much as possible. New appurtenances, is adopting to install at specified configuration into a sudden transition. The appurtenances consisted of two successive rows of thin plates used as guide vanes to direct and spread the flow across the width with more uniformity. The guide vanes also keep the head losses at minimum possible. This attempt, through the results, proved that it has considerable hydraulic and economic advantages as compared to using a flared wall. Greater uniformity in velocity distributions of flow across the width, shorter length, and 70% lesser head loss are the results of the hydraulic performance of abrupt expansion transition equipped with two sets of strip vanes as compared to that with the plain one.

A theory of self-organized zonal flow with fine radial structure in tokamak

The (low frequency) zonal flow-ion temperature gradient (ITG) wave system, constructed on Braginskii's fluid model in tokamak, is shown to be a reaction-diffusion-advection system; it is derived by making use of a multiple spatiotemporal scale technique and two-dimensional (2D) ballooning theory. For real regular group velocities of ITG waves, two distinct temporal processes, sharing a very similar meso-scale radial structure, are identified in the nonlinear self-organized stage. The stationary and quasi-stationary structures reflect a particular feature of the poloidal group velocity. The equation set posed to be an initial value problem is numerically solved for JET low mode parameters; the results are presented in several figures and two movies that show the spatiotemporal evolutions as well as the spectrum analysis—frequency-wave number spectrum, auto power spectrum, and Lissajous diagram. This approach reveals that the zonal flow in tokamak is a local traveling wave. For the quasi-stationary process, the cycle of ITG wave energy is composed of two consecutive phases in distinct spatiotemporal structures: a pair of Cavitons growing and breathing slowly without long range propagation, followed by a sudden decay into many Instantons that carry negative wave energy rapidly into infinity. A spotlight onto the motion of Instantons for a given radial position reproduces a Blob-Hole temporal structure; the occurrence as well as the rapid decay of Caviton into Instantons is triggered by zero-crossing of radial group velocity. A sample of the radial profile of zonal flow contributed from 31 nonlinearly coupled rational surfaces near plasma edge is found to be very similar to that observed in the JET Ohmic phase [J. C. Hillesheim et al., Phys. Rev. Lett. 116, 165002 (2016)]. The theory predicts an interior asymmetric dipole structure associated with the zonal flow that is driven by the gradients of ITG turbulence intensity.

A Sub-Riemannian Modular Framework for Diffeomorphism-Based Analysis of Shape Ensembles

Deformations, and diffeormophisms, in particular, have played a tremendous role in the field of statistical shape analysis, as a proxy to measure and interpret differences between similar objects but with different shapes. Diffeomorphisms usually result from the integration of a flow of regular velocity fields, whose parameters have not enabled, so far, a full control of the local behavior of the deformation. In this work, we propose a new mathematical and computational framework, in which these velocity fields are constrained to be built through a combination of local deformation modules with few degrees of freedom. Deformation modules contribute to the global velocity field, and interact with it during integration so that the local modules are transported by the global diffeomorphic deformation under construction. Such modular diffeomorphisms are used to deform shapes and to provide the shape space with a sub-Riemannian metric. We then derive a method to estimate a Frechet mean from a series of observat...

Chronic intestinal pseudo-obstruction in a child with Treacher Collins syndrome

Treacher Collins syndrome (TCS) mainly presents with severe craniofacial developmental abnormalities characterized by a combination of bilateral downward-slanting palpebral fissures, colobomas of the lower eyelids, hypoplasia of the facial bones, cleft palate, malformation of the external ears, atresia of the external auditory canals, and bilateral conductive hearing loss. It is due to mutations in Treacher Collins syndrome 1 (TCOF1) (5q32-q33.1) and Polymerase RNA 1 polypeptides D and C (POLR1D [13q12.2], and POLR1C [6p21.1]) genes, which are responsible for increased neuroepithelial apoptosis during embryogenesis resulting in the lack of neural crest cells involved in facial bone and cartilage formation. Altered function of the upper digestive tract has been reported, whereas severe dysmotility disorders have never been reported. We describe here the first case of TCS associated with histologically proven chronic intestinal pseudo-obstruction (CIPO) in humans. Case presentatios A 12-year-old boy with TCS due to TCOF1 gene deletion experienced nutritional difficulties and digestive intolerance from birth. CIPO was suspected during childhood because of severe intestinal dysmotility leading to enteral-jejunal nutrition intolerance and dependence on total parenteral nutrition. Diagnosis of CIPO with nervous abnormalities was histologically confirmed on a surgical rectal biopsy that showed enlarged ganglionic myenteric plexus. At the age of 9 years, an isolated colonic stenosis without dilatation responsible for severe abdominal pain and altered quality of life led to digestive derivation contributing to rapid disappearance of chronic abdominal pain. At the age of 12 years, the patient was still dependent on total home parenteral nutrition 7 days a week to maintain regular growth velocity. Recently, mice studies have pointed out the role played by TCOF1 in ganglionic cell migration in the foregut, suggesting that the synergistic haploinsufficiency of Tcof1 and Pax3, a transcription factor regulating the RET gene involved in disorders of neural crest cell development, probably results in colonic aganglionosis and may explain the association described here between TCS and CIPO. This case may correspond to this possible mechanism in humans. These findings and our clinical report suggest that CIPO may be assessed as unusual digestive manifestations in TCS with TCOF1 deletion.

Specifics of heat and mass transfer in spherical dimples under the effect of external factors

The specifics are examined of heat transfer enhancement with spherical dimples under the effect of factors important for practice and characteristic of cooling systems of gas-turbine engines and power units. This experimental investigation deals with the effect of the following factors on the flow in a channel with hemispherical dimples: continuous air swirl in an annulus with dimples on its concave wall, dimples on the convex or concave wall of a curved rectangular channel, imposition of regular velocity fluctuations on the external flow in a straight rectangular channel, and adverse or favorable pressure gradient along the flow direction. The flow is turbulent. Reynolds numbers based on the channel hydraulic diameter are on the order of 104. Results of the investigation of a model of a two-cavity diffuser dimple proposed by the authors are presented. It has been found that results for channels with spherical dimples and for smooth channels differ not only quantitatively but also qualitatively. Thus, if the effect of centrifugal mass forces on convex and concave surfaces with hemispherical dimples and in a smooth channel is almost the same (quantitative and qualitative indicators are identical), the pressure gradient in the flow direction brings about the drastically opposite results. At the same time, the quantitative contribution to a change in heat transfer in hemispherical dimples is different and depends on the impact type. The results are discussed with the use of physical models created on the basis of the results of flow visualization studies and data on the turbulence intensity, pressure coefficient, etc. Results of the investigations suggest that application of spherical dimples under nonstandard conditions requires the calculated heat transfer to be corrected to account for one or another effect.

Revealing a spiral-shaped molecular cloud in our galaxy: Cloud fragmentation under rotation and gravity

The dynamical processes that control star formation in molecular clouds are not well understood, and in particular, it is unclear if rotation plays a major role in cloud evolution. We investigate the importance of rotation in cloud evolution by studying the kinematic structure of a spiral-shaped Galactic molecular cloud G052.24+00.74. The cloud belongs to a large filament, and is stretching over ~ 100 pc above the Galactic disk midplane. The spiral-shaped morphology of the cloud suggests that the cloud is rotating. We have analysed the kinematic structure of the cloud, and study the fragmentation and star formation. We find that the cloud exhibits a regular velocity pattern along west-east direction - a velocity shift of ~ 10 km/s at a scale of ~ 30 pc. The kinematic structure of the cloud can be reasonably explained by a model that assumes rotational support. Similarly to our Galaxy, the cloud rotates with a prograde motion. We use the formalism of Toomre (1964) to study the cloud's stability, and find that it is unstable and should fragment. The separation of clumps can be consistently reproduced assuming gravitational instability, suggesting that fragmentation is determined by the interplay between rotation and gravity. Star formation occurs in massive, gravitational bound clumps.

Radiated flow of chemically reacting nanoliquid with an induced magnetic field across a permeable vertical plate

Impact of induced magnetic field over a flat porous plate by utilizing incompressible water-copper nanoliquid is examined analytically. Flow is supposed to be laminar, steady and two-dimensional. The plate is subjected to a regular free stream velocity as well as suction velocity. Flow formulation is developed by considering Maxwell–Garnetts (MG) and Brinkman models of nanoliquid. Impacts of thermal radiation, viscous dissipation, temperature dependent heat source/sink and first order chemical reaction are also retained. The subjected non-linear problems are non-dimensionalized and analytic solutions are presented via series expansion method. The graphs are plotted to analyze the influence of pertinent parameters on flow, magnetism, heat and mass transfer fields as well as friction factor, current density, Nusselt and Sherwood numbers. It is found that friction factor at the plate is more for larger magnetic Prandtl number. Also the rate of heat transfer decayed with increasing nanoparticles volume fraction and the strength of magnetism.