Velocity Modulation Research Articles

直流グロー放電場による衝撃波速度局所変調効果

直流グロー放電場による衝撃波速度局所変調効果

Unveiling the Architecture of a Pulsar–Binary Black Hole Triple System with Pulsar Arrival Time Analysis

Abstract A large number of binary black holes (BBHs) with longer orbital periods are supposed to exist as progenitors of BBH mergers recently discovered with gravitational wave (GW) detectors. In our previous papers, we proposed to search for such BBHs in triple systems through the radial velocity modulation of the tertiary orbiting star. If the tertiary is a pulsar, high-precision and high-cadence observations of its arrival time enable an unambiguous characterization of the pulsar–BBH triples located at several kiloparsecs, which are inaccessible with the radial velocity of stars. The present paper shows that such inner BBHs can be identified through the short-term Rømer delay modulation, on the order of 10 ms for our fiducial case, a triple consisting of a 20 M ⊙ BBH and 1.4 M ⊙ pulsar with P in = 10 days and P out = 100 days. If the relativistic time delays are measured as well, one can determine basically all the orbital parameters of the triple. For instance, this method is applicable to inner BBHs of down to ∼1 hr orbital periods if the orbital period of the tertiary pulsar is around several days. Inner BBHs with ≲1 hr orbital period emit the GW detectable by future space-based GW missions, including LISA, DECIGO, and BBO, and very short inner BBHs with subsecond orbital period can be even probed by the existing ground-based GW detectors. Therefore, our proposed methodology provides a complementary technique to search for inner BBHs in triples, if they exist at all, in the near future.

Fusion and fission phenomena for [formula omitted]-dimensional fifth-order KdV system

Based on N-soliton solutions, fusion and fission waves are obtained through a new constraint among parameters. With this new constraint, fusion and fission phenomena can be reduced from N-soliton solutions in most (2+1)-dimensional integrable systems. This paper takes the (2+1)-dimensional fifth-order KdV equation as an example to introduce how to use this constraint to generate these fusion and fission waves in detail. At the same time, by continuing to introduce constraints like velocity resonance, module resonance, and long-wave limit, we can generate all kinds of hybrid solutions for granted, such as a hybrid of fissionable waves and breather waves, and a nonlinear superposition between fissionable waves and higher-order lump waves.

Effect of particle concentration on turbulent modulation inside hydrocyclone using coupled MPPIC-VOF method

We discuss the implementation of a coupled Multi-phase particle in cell method (MPPIC) and Volume of Fluid (VOF) flow solver to simulate particles in a fluid flow field having a free surface. Using the solver developed using OpenFOAM 4.1 library, we study the flow of particles inside a highly anisotropic turbulent flow field of a hydrocyclone. The free surface from the air-core inside the hydrocyclone is resolved using the VOF method coupled with the LES turbulence model. We test multiple sub-grid scale model and find the dynamic k-equation model to have the best-predicting capability of the mean and turbulent flow field as well as the air-core shape. Using the established flow field, we study the particle flow properties and its effect on the fluid flow field using a four-way coupled description between MPPIC and VOF. Important flow properties such as the particle flow field velocity and turbulence modulation with varying particle concentration were studied. It was found that even with low solid concentration (0.3–1.5% by volume) there is a quite substantial increase in the fluctuating flow field (around 12%) and with a further increase (1.8%) we observe a decrease in the turbulent levels by approximately 6%.

Struktura bimodal'nosti napravleniya pribrezhnogo techeniya u Yuzhnogo berega Kryma v 2002–2008 godakh

This paper aims at improvement of knowledge about the structure of bimodal distribution of coastal current direction repeatability at Cape Kikineiz of the Southern coast of Crimea as per monitoring data obtained at the stationary oceanographic platform of the Black Sea hydrophysical sub-satellite testing area of the MHI RAS. Used for monitoring, a vertical measuring antenna with a fixed aperture of Euler testers of the current horizontal component provided verifiable and synchronic isolation of the current's structural characteristics with a vertical velocity shift and multiscale coherent oscillations of the current. New results of analysis of in situ data are presented regarding characteristics of the coastal current and its variability. The data were obtained within the period from November 2001 to 2008. Change patterns of the long-term coastal current regime are noted. The current's characteristics are matched to the results obtained at Cape Kikineiz of the Southern coast of Crimea for the period from September 2008 to 2019. Regular intense oscillations of the coastal current at the local inertial (17 hrs) and daily component as well as current oscillations with a period of 11.6 day are defined. Evolution is analyzed of probability density distribution of the velocity module and current vector direction after calculations, during which a corresponding vector distribution of intensive inertial-gravitational, mesoscale and synoptic oscillations was excluded in the original vector series of dynamics using a digital filtration method. When excluding the contribution of daily and inertial oscillations, the backward and primary mode ratio in the histograms of the coastal current direction repeatability decreases by more than three times. When excluding the contribution of mesoscale and synoptical oscillations, the backward mode of current is almost absent and there exists only a large-scale coastal current coinciding with a cyclonic direction of the coastal edge of the Black Sea Rim Current. Bimodal distribution of the coastal current direction repeatability is a result of superposition of velocity vectors of a large-scale current and variable contribution of existing orbital velocities of multiscale wave and vortex formations present in the coastal-shelf area.

Autotuning procedure for energy modulation in Mössbauer spectroscopy

An autotuning procedure for driving energy modulation in Mössbauer spectroscopy is described in details. This procedure is applicable for those velocity modulation units which provide a signal proportional to the velocity, e.g. double speaker linear motors. It eliminates manual tuning of PID parameters and, moreover, allows to operate the velocity modulation unit on any frequency, i.e. above, below or in a resonance. The proper performance of the procedure is demonstrated by the measurement of 12 μm α-iron Mössbauer spectra.

Analogue Hawking radiation from black hole solitons in quantum Josephson transmission lines

The nonlinear LC circuit dual to the Toda lattice (voltage) soliton is studied using the reductive perturbation method. It is found that the current flowing through the circuit obeys the defocusing modified Korteweg--de Vries equation with shock-wave-type (current) solitons. The current soliton spatially modulates the nonlinear inductance, equivalently the spatial modulations of electromagnetic wave velocity in the circuit, resulting in the generation of analogue black holes. Hawking radiation from the black holes is also discussed based on the tunneling models.

Turbulent transport dissimilarity with modulated turbulence structure in channel flow of viscoelastic fluid

This experimental study investigated the turbulent transport dissimilarity with a modulated turbulence structure in a channel flow of a viscoelastic fluid using simultaneous particle image velocimetry and planar laser-induced fluorescence measurements. An instantaneous dye concentration field with fluctuating velocity vectors showed that mass was transferred by hierarchically large-scale wavy motions with inclination. A co-spectral analysis showed that the spatial phase modulation of the streamwise velocity and dye concentration fluctuations for the wall-normal velocity fluctuation corresponded to the relaxation time. The occurrence of intense dye concentration fluctuation and small streamwise velocity fluctuation in a thin boundary layer caused dissimilar turbulent transport because of the non-zero negative correlation of the streamwise velocity and dye concentration fluctuations for the wall-normal velocity fluctuation only on large scales. This explains the turbulent transport dissimilarity which leads to the zero averaged Reynolds shear stress and non-zero wall-normal turbulent mass flux.

Effect of fuel line acoustics on the flame dynamics of H2/CH4 syngas in a partially premixed gas turbine combustor

This paper investigates the dynamic response of flames, considering H2-enriched CH4 fuels that are submitted to upstream mechanical perturbations in a model gas turbine combustor, resulting in fuel velocity oscillations. Flame transfer function (FTF) and cold-flow transfer function (CTF), which represent, respectively, the dynamic responses in the flow of the flame and fuel induced by a velocity modulation in the fuel feed line (FFL), are derived. The gain of FTF shows a low-pass behavior and gradually increases until a specific modulation frequency is reached, which is identical to the frequencies of the corresponding peak gains of the CTF. The periodic variation of OH* intensity is observed from the images collected with a high-speed OH-PLIF. The high oscillation near the injector indicates that the fuel velocity perturbation leads to the amplification of the heat release fluctuation at specific modulation frequencies. The singularity frequencies corresponding to the peaks of the gain of both transfer functions coincide with the resonance frequencies in the FFL. The phase of FTF and CTF decreases as the H2 ratio increases and the phase of FTF is well fitted into a single line by nondimensionalization through Strouhal number. Most of these findings on the characteristics of combustion instability and acoustical characteristics of FFL can be used as a crucial methodology of H2 combustor design, such as an anti-resonance fuel/air feed line, which can ensure the stable operation of combustion system by avoiding H2 induced combustion instability failure.

Toroidicity effects on the absorption of IC waves by electrons

Poloidal modulation of the parallel velocity of charged particles in a tokamak magnetic field modifies the strength of electron absorption of the compressional wave in the ion cyclotron range of frequencies. We have developed a model of this effect which is sufficiently simple to be numerically tractable, and we have implemented it in TORIC full-wave code, which solves the wave equation in toroidal axisymmetric geometry. We find that the effect is normally negligible in present-day devices, but its importance increases with the dimensions and the temperature of the plasma, and should be taken into account when estimating the competition between electron and ion heating and the efficiency of the current drive in future reactor-grade plasmas.

Soliton molecules and some novel hybrid solutions for the (2+1)-dimensional generalized Konopelchenko–Dubrovsky–Kaup–Kupershmidt equation

Soliton molecules have become one of the hot topics in recent years. In this article, we investigate soliton molecules and some novel hybrid solutions for the (2+1)-dimensional generalized Konopelchenko–Dubrovsky–Kaup–Kupershmidt (gKDKK) equation by using the velocity resonance, module resonance, and long wave limits methods. By selecting some specific parameters, we can obtain soliton molecules and asymmetric soliton molecules of the gKDKK equation. And the interactions among N-soliton molecules are elastic. Furthermore, some novel hybrid solutions of the gKDKK equation can be obtained, which are composed of lumps, breathers, soliton molecules and asymmetric soliton molecules. Finally, the images of soliton molecules and some novel hybrid solutions are given, and their dynamic behavior is analyzed.

Criticality across the energy spectrum from random artificial gravitational lensing in two-dimensional Dirac superconductors

We numerically study weak, random, spatial velocity modulation ["quenched gravitational disorder" (QGD)] in two-dimensional massless Dirac materials. QGD couples to the spatial components of the stress tensor; the gauge-invariant disorder strength is encoded in the quenched curvature. Although expected to produce negligible effects, wave interference due to QGD transforms all but the lowest-energy states into a quantum-critical "stack" with universal, energy-independent spatial fluctuations. We study five variants of velocity disorder, incorporating three different local deformations of the Dirac cone: flattening or steepening of the cone, pseudospin rotations, and nematic deformation (squishing) of the cone. QGD should arise for nodal excitations in the $d$-wave cuprate superconductors (SCs), due to gap inhomogeneity. Our results may explain the division between low-energy "coherent" (plane-wave-like) and finite-energy "incoherent" (spatially inhomogeneous) excitations in the SC and pseudogap regimes. The model variant that best matches the cuprate phenomenology possesses quenched random pseudospin rotations and nematic fluctuations. This model variant and another with pure nematic randomness exhibit a robust energy swath of stacked critical states, the width of which increases with increasing disorder strength. By contrast, quenched fluctuations that isotropically flatten or steepen the Dirac cone tend to produce strong disorder effects, with more rarified wave functions at low- and high-energies. Our models also describe the surface states of class DIII topological SCs.

Modelado numérico de las oscilaciones frontales y ocurrencia de formación de diques de hielo del Glaciar Perito Moreno, Campo de Hielo Patagónico Sur

En el presente estudio, se aborda el diseño y desarrollo de un modelo numérico computacional del comportamiento del ciclo oscilatorio estacional de avance y retroceso del glaciar Perito Moreno, denominado MO-ACAR. Dentro de su comportamiento oscilatorio, en algunos años el glaciar avanza y alcanza la Península de Magallanes formando un dique de hielo. Por ello, el objetivo del MO-ACAR es simular la posición frontal diaria del glaciar y la ocurrencia de eventos de formación de los diques de hielo durante el periodo 1994-2018. El modelo fue calibrado y validado a partir de un proceso de optimización iterativo, basado en la maximización de valores de correlación y minimización de errores de distancia. La simulación de la ocurrencia de la formación de diques de hielo y la oscilación de la posición frontal lograron altas prestaciones, alcanzando óptimos valores de correlación (0,99) y bajos errores de posición (9,56 ± 13,94 m), respectivamente. Los resultados demuestran que la dinámica del glaciar y la formación de los diques de hielo responden a distintas escalas temporales. En periodos cortos-intermedios de tiempo (escalas diarias-estacionales), la ocurrencia depende tanto de las características propias del evento, como de la fase e intensidad del evento previo. En periodos prolongados (escalas mayores a un año), la modulación de baja frecuencia de la velocidad del flujo de hielo, provocada por las variaciones de temperatura del aire, controla los periodos con formación de diques de hielo y libres de éstos.

Inference in Turbulent Molecular Information Channels Using Support Vector Machine

Inference of transmitter side information is essential to communication. In Molecular Communication (MC), whilst the Bayesian inference of mass diffusion channel parameters is well established, turbulent diffusion (TD) channels are not well-understood. Cascading vortices rapidly transform transmitted momentum (molecular information puffs) into heat, which raises the challenge of receiver inferring transmitter information. Our initial results found that in TD channels, inferring transmitted molecular concentration or timing is challenging. As such, we were motivated to infer transmitter velocity from a flexible receiver sample area. In this paper, we consider an unbounded scenario of Molecular Communication via Turbulent Diffusion (MCvTD) where a transmitter injects several molecular puffs with different velocities. We first developed a time difference concentration (TDC) method based on large-scale support vector machine (SVM) to distinguish the injection velocities. To trade-off the prediction accuracy and number of receiver spatial samples, we propose the stepwise maximum variance (SMV) algorithm to select the limited dominant receiver sampling locations. The overall performance can achieve 100% accuracy in transmitter velocity information recovery, with excellent error vs. receiver size trade-off (e.g., 5% error for 74% area reduction). The research results indicate that velocity modulation at transmitter and TDC with SVM receiver should be used in MCvTD channels.

Modulatory effects of magnetic vestibular stimulation on resting-state networks can be explained by subject-specific orientation of inner-ear anatomy in the MR static magnetic field

Strong static magnetic fields, as used in magnetic resonance imaging (MRI), stimulate the vestibular inner ear leading to a state of imbalance within the vestibular system that causes nystagmus. This magnetic vestibular stimulation (MVS) also modulates fluctuations of resting-state functional MRI (RS-fMRI) networks. MVS can be explained by a Lorentz force model, indicating that MVS is the result of the interaction of the static magnetic field strength and direction (called “B0 magnetic field” in MRI) with the inner ear’s continuous endolymphatic ionic current. However, the high variability between subjects receiving MVS (measured as nystagmus slow-phase velocity and RS-fMRI amplitude modulations) despite matching head position, remains to be explained. Furthermore, within the imaging community, an “easy-to-acquire-and-use” proxy accounting for modulatory MVS effects in RS-fMRI fluctuations is needed. The present study uses MRI data of 60 healthy volunteers to examine the relationship between RS-fMRI fluctuations and the individual orientation of inner-ear anatomy within the static magnetic field of the MRI. The individual inner-ear anatomy and orientation were assessed via high-resolution anatomical CISS images and related to fluctuations of RS-fMRI networks previously associated with MVS. More specifically, we used a subject-specific proxy for MVS (pMVS) that corresponds to the orientation of the individual inner-ear anatomy within the static magnetic field direction (also called “z-direction” in MR imaging). We found that pMVS explained a considerable fraction of the total variance in RS-fMRI fluctuations (for instance, from 11% in the right cerebellum up to 36% in the cerebellar vermis). In addition to pMVS, we examined the angle of Reid’s plane, as determined from anatomical imaging as an alternative and found that this angle (with the same sinus transformation as for pMVS) explained considerably less variance, e.g., from 2 to 16%. In our opinion, an excess variability due to MVS should generally be addressed in fMRI research analogous to nuisance regression for movement, pulsation, and respiration effects. We suggest using the pMVS parameter to deal with modulations of RS-fMRI fluctuations due to MVS. MVS-induced variance can easily be accounted by using high-resolution anatomical imaging of the inner ear and including the proposed pMVS parameter in fMRI group-level analysis.

Acceleration of Subwavelength Polaritons by Engineering Dielectric-Metallic Substrates

By synchrotron infrared nanospectroscopy, we demonstrate modulation of momentum and group velocity of subdiffractional hyperbolic phonon-polaritons (HP2), in hexagonal boron nitride nanocrystals, b...

Effects of Fermi velocity engineering in magnetic graphene superlattices

In this work we investigate theoretically the influence of a Fermi velocity modulation in the electronic and transport properties of magnetic graphene superlattices. We solve the effective Dirac equation for graphene with a position dependent vector potential and Fermi velocity and use the transfer matrix method to obtain the transmission coefficient for the finite cases and the dispersion relation for a periodic superlattice. Our results reveals that the Fermi velocity modulation can control the resonance peaks of the transmittance and also works as a switch, turning on/off the transmission through the magnetic barriers. The results obtained here can be used for the fabrication of graphene-based electronic devices.

New observations of DW Cnc: where is the 38 min signal?

ABSTRACT We present extensive radial velocity observations of the intermediate polar DW Cnc during its 2018–2019 low state. We show that the 86 min signal associated with the orbital period is strong in our radial velocity analysis, power spectrum search, and in our Doppler tomography. However, we find that the velocity modulation associated with the 70 min beat period and the 38 min spin cycle is dramatically weaker than that previously observed. We put forward two interpretations for this change. The first is that a sudden drop into a low state detected in 2018–2019 caused an episode of low mass transfer from the companion, thus inhibiting the lighthouse effect produced by the rebound emission. The second is that this is a consequence of a rare outburst detected in 2007 by Crawford et al. (2008). We find this post-outburst hypothesis to be less likely. If the first scenario is correct, we predict that DW Cnc will recover its intermediate polar characteristics. A new ephemeris is presented by combining Patterson et al. (2004) radial velocities with ours.

Soliton molecules and some novel interaction solutions to the (2+1)-dimensional B-type Kadomtsev–Petviashvili equation

Soliton molecules may exists in both experimental and theotetical aspects. In this work, we investigate the (2+1)-dimensional B-type Kadomtsev–Petviashvili equation, which can be used to describe weakly dispersive waves propagating in the quasi media and fluid mechanics. Soliton molecules are generated by N-soliton solution and a new velocity resonance condition. Furthermore, soliton molecules can become to asymmetric solitons when the distance between two solitons of the molecule is small enough. Based on the N-soliton solution, we obtain some novel interaction solutions which component of soliton molecules, breather waves and lump waves by deal with part of parameters by applying velocity resonance, module resonance and long wave limit method, and the interactions are elastic. Finally, some graphic analysis are discussed to understand the propagation phenomena of these solutions.

Dispersion tuning and route reconfiguration of acoustic waves in valley topological phononic crystals.

The valley degree of freedom in crystals offers great potential for manipulating classical waves, however, few studies have investigated valley states with complex wavenumbers, valley states in graded systems, or dispersion tuning for valley states. Here, we present tunable valley phononic crystals (PCs) composed of hybrid channel-cavity cells with three tunable parameters. Our PCs support valley states and Dirac cones with complex wavenumbers. They can be configured to form chirped valley PCs in which edge modes are slowed to zero group velocity states, where the energy at different frequencies accumulates at different designated locations. They enable multiple functionalities, including tuning of dispersion relations for valley states, robust routing of surface acoustic waves, and spatial modulation of group velocities. This work may spark future investigations of topological states with complex wavenumbers in other classical systems, further study of topological states in graded materials, and the development of acoustic devices.