Sonic Regime Research Articles

Making Dementia Matter Through Sound

This paper investigates the working practices of the Genetic Choir and the “Stem&Luister” project, in which the ensemble uses voice, sound and improvisation to explore and develop ways of connecting with people with dementia, thereby seeking to improve the experience of care. Their musical sessions are multilayered. First, through listening they develop a sense of the people and the environment. Then through introducing their vocal practices, they breach the prevailing sonic regime. Second, through immersing the residents in sound-making and singing, they draw on the material and sensorial qualities of sound. This gives access to those who were difficult to reach and offers both an alternative means of communication and enables the recognition of selves. A third layer concerns the strategic use of improvisation, of which the deployment of “ensemble” and “instant composition” are analysed. Recognising the compositional efforts in improvisation shows their work to be a form of design. It facilitates attention to personhood, relations, and diversity. This specific practice appears as an untapped resource for the health and wellbeing of people with cognitive and speech impairments. Theoretically, the findings have implications for the notion of care and provide support from practice to existing neurological evidence of the significance of music as a fundamental faculty for survival and wellbeing.

Density jump as a function of magnetic field strength for parallel collisionless shocks with anisotropic upstream pressure

ABSTRACTThe properties of collisionless shocks are frequently assessed in the magnetohydrodynamics (MHD) model. Yet, in a collisionless plasma, an ambient magnetic field can sustain a stable anisotropy in the upstream or the downstream, resulting in a departure from the MHD predicted behaviour. We present a model allowing to derive the downstream anisotropy, hence the shock density jump, in terms of the upstream quantities. For simplicity, the case of a parallel shock in pair plasma is considered. Contrary to previous works where the upstream was assumed isotropic, here the upstream anisotropy A = T⊥/T∥ is a free parameter. The strong sonic shock regime is formally identical to the isotropic upstream case. Yet, for intermediate sonic Mach numbers, a variety of behaviours appear as a result of the anisotropy of the upstream.

Time Dependent Effect of flow properties on addition of heat to the air flow at Compressible Subsonic Speeds

Heat addition process is a governing phenomenon in turbojet and ramjet burners, where heat is added to the flow during the fuel-air combustion process. In the present work, an analytical study has been performed to investigate the effect of heat addition on the basic flow properties based on compressible Rayleigh flow model between the subsonic and sonic flow regime. The unsteady nature of flow properties in these regimes have been evaluated analytically by adding heat through the walls of a constant area, frictionless duct in which air flow occurs over different periods of time. Sudden variation of temperature, pressure, velocity and kinetic energy of the flow were found at flow Mach number M = 0.94. Flow velocity and kinetic energy increases until the flow approaches M = 0.94, afterwards there is a rapid increase in the flow velocity and kinetic energy until it reaches sonic conditions. Conversely, pressure decreased till the flow reaches M = 0.94, there after a sudden drop was observed. Flow enthalpy increased initially, reached maximum at flow M = 0.845 and then reduced till sonic conditions. Based on the observations, it has been concluded that the heat energy contributed to increase the kinetic energy thereby reducing the temperature of the flow.

Characterization of a 100 micrometer-scale cryogenically cooled gas jet for near-critical density laser-plasma experiments

We present the design and characterization of a thin, high density pulsed gas jet for use in the study of near critical laser plasma interactions with ultrashort Ti:sapphire laser pulses. The gas jet uses a range of capillary nozzles with inner diameters between 50 and 150 μm and is operated in the sonic regime. Cryogenic cooling of the gas valve body to −160 °C provides the necessary density enhancement for reaching overcritical plasma densities at λ = 800 nm (Ncr ≈ 1.7 × 1021 cm−3) using hydrogen gas at jet backing pressures below 1000 psi. Under certain conditions, fast expansion of the gas from a nozzle can lead to formation of clusters; here, we use our previously demonstrated all-optical method to estimate the cluster mean size and density. For the jets studied here, we find that cluster formation only begins at distances from the nozzle exit greater than a few times the nozzle orifice diameter.

Wake effects of a stationary charged grain in streaming magnetized ions.

A systematic numerical study of wake potential and ion density distribution of a single grain in flowing ions under the influence of a magnetic field applied along the flow is presented. A strong magnetic field introduces ion focus depletion behind grains, facilitating the entrance of electrons far in the downstream towards the grain. It is shown that the magnetic field suppresses the amplitude of the wake potential and modifies the ion density distribution substantially. The wake peak potential and position characteristics and density distribution of plasma constituents in the presence of a magnetic field and charge-exchange collisions for the subsonic, sonic, and supersonic regime are also delineated. In the subsonic regime, simulations demonstrate the accumulation of ions near the dust grain in the transverse direction, while complete suppression of oscillations in the transverse direction takes place for the sonic and supersonic regime.

On the induced charge density distribution in streaming plasmas

Motivated by experiments on the generation of streaming plasmas in high energy density facilities,industrial setups, and fundamental dusty plasma research, the plasma polarization around a test charge instreaming plasmas is considered in this work. The induced charge density distribution of the plasmaconstituents is discussed for the subsonic, sonic, and supersonic regime taking into account the non-Maxwellian distribution of the flowing ions. It is shown that the plasma polarization (the plasmawakefield) in the vicinity of the test charge shows different scaling in the subsonic and supersonicregimes, where Mach number is defined as the ratio of the ion streaming velocity and the ion soundspeed. In contrast to the wake potential, the density decays strongly monotonically in the plasma wakeand does not exhibit an oscillatory pattern or trailing maxima. Therefore, the picture of an ion focusingeffect creating a separated ion region downstream was not confirmed.

Tunable sub-wavelength acoustic energy harvesting with a metamaterial plate

We report theoretically on sub-wavelength acoustic energy harvesting (AEH) using a thin acoustic metamaterial (AM) made of spring-mass resonators attached to the surface of a homogeneous elastic thin plate. Considering an incident acoustic wave hitting the AM plate, tunable and highly efficient AEH is achieved by introducing a sub-wavelength defect inside the AM structure to confine the elastic energy into a spot which is then electromechanically converted into electrical power using a ceramic PZT patch. Several types of sub-wavelength cavities capable of confining acoustic energy at the sonic regime are extensively investigated for the optimization of AEH. Three analytical approaches—band structure, sound transmission loss and electrical-to-mechanical energy conversion—are proposed to fully describe the system interaction with the acoustic wave and quantify the AEH performance. The computed results show that an average power of 18 μW can be harvested using a specific cavity design of only size from an incident acoustic wave with a sound pressure level of 100 dB at 520 Hz. Such a system can open up a way through the design of effective tunable sub-wavelength acoustic energy harvesters based on AM applied to scavenge energy from sound.

Acoustic beam splitting at low GHz frequencies in a defect-free phononic crystal

The directional waveguiding in a 2D phononic crystal is simulated based on the analysis of equifrequency contours. This approach is utilized to investigate acoustic beam splitting in a defect-free nanostructure in the low GHz range. We find relaxed limitations regarding the source parameters compared to similar approaches in the sonic regime. Finally, we discuss the possibility to design an acoustic interferometer device at the nanoscale at GHz frequencies.

Features of primary damage by high energy displacement cascades in concentrated Ni-based alloys

Alloying of Ni with Fe or Co has been shown to reduce primary damage production under ion irradiation. Similar results have been obtained from classical molecular dynamics simulations of 1, 10, 20, and 40 keV collision cascades in Ni, NiFe, and NiCo. In all cases, a mix of imperfect stacking fault tetrahedra, faulted loops with a 1/3⟨111⟩ Burgers vector, and glissile interstitial loops with a 1/2⟨110⟩ Burgers vector were formed, along with small sessile point defect complexes and clusters. Primary damage reduction occurs by three mechanisms. First, Ni-Co, Ni-Fe, Co-Co, and Fe-Fe short-distance repulsive interactions are stiffer than Ni-Ni interactions, which lead to a decrease in damage formation during the transition from the supersonic ballistic regime to the sonic regime. This largely controls final defect production. Second, alloying decreases thermal conductivity, leading to a longer thermal spike lifetime. The associated annealing reduces final damage production. These two mechanisms are especially important at cascades energies less than 40 keV. Third, at the higher energies, the production of large defect clusters by subcascades is inhibited in the alloys. A number of challenges and limitations pertaining to predictive atomistic modeling of alloys under high-energy particle irradiation are discussed.

Parallel Kelvin-Helmholtz instability in edge plasma

In the scrape-off layer (SOL) of tokamaks, the flow acceleration due to the presence of limiter or divertor plates rises the plasma velocity in a sonic regime. These high velocities imply the presence of a strong shear between the SOL and the core of the plasma that can possibly trigger some parallel shear flow instability. The existence of these instabilities, denoted as parallel Kelvin-Helmholtz instability in some works [1, 2] have been investigated theoretically in [3] using a minimal model of electrostatic turbulence composed of a mass density and parallel velocity equations. This work showed that the edge plasma around limiters might indeed be unstable to this type of parallel shear flow instabilities. In this work, we perform 3D simulations of the same simple mathematical model to validate an original finite volume numerical method aimed to the numerical study of edge plasma. This method combines the use of triangular unstructured meshes in the poloidal section and structured meshes in the toroidal direction and is particularly suited to the representation of the real complex geometry of the vacuum chamber of a tokamak.The numerical results confirm that in agreement with the theoretical expectations as well as with other numerical methods, the sheared flows in the SOL are subject to parallel Kelvin-Helmholtz instabilities. However, the growth rate of these instabilities is low and these computations require both a sufficient spatial resolution and a long simulation time. This makes the simulation of parallel Kelvin-Helmholtz instabilities a demanding benchmark.

Sounding the Occupation: Joe Sacco’s Palestine and the Uses of Graphic Narrative for (Post)Colonial Critique

Working at the intersection of postcolonial literary studies and comics narratology, this paper argues that Joe Sacco’s graphic narrative Palestine contributes a spatial and sonic record of territorial occupation to the Palestinian national narrative. Sacco utilizes the comics form to represent the complex of physical borders and spatial narratives he encounters in the Occupied Palestinian Territories at the end of the first Intifada . Further, he renders graphically the epiphenomenal sonic regime resulting from spatial management. Rather than an absence or gap in the Palestinian narrative, Sacco understands spatialized sound as a presence or marker of materiality. Ultimately, Palestine suggests the rich potential of the comics form for postcolonial literary studies. Sacco’s graphic narrative reinvigorates the field’s engagement with literary representations of Israel-Palestine by demonstrating the continued utility of the (post)colonial paradigm and by challenging the fields’ scholars to forge new interdisciplinary links to comics studies.

MOLECULAR-KINETIC SIMULATIONS OF ESCAPE FROM THE EX-PLANET AND EXOPLANETS: CRITERION FOR TRANSONIC FLOW

The equations of gas dynamics are extensively used to describe atmospheric loss from solar system bodies and exoplanets even though the boundary conditions at infinity are not uniquely defined. Using molecular-kinetic simulations that correctly treat the transition from the continuum to the rarefied region, we confirm that the energy-limited escape approximation is valid when adiabatic expansion is the dominant cooling process. However, this does not imply that the outflow goes sonic. In fact in the sonic regime, the energy limited approximation can significantly under estimate the escape rate. Rather large escape rates and concomitant adiabatic cooling can produce atmospheres with subsonic flow that are highly extended. Since this affects the heating rate of the upper atmosphere and the interaction with external fields and plasmas, we give a criterion for estimating when the outflow goes transonic in the continuum region. This is applied to early terrestrial atmospheres, exoplanet atmospheres, and the atmosphere of the ex-planet, Pluto, all of which have large escape rates. The paper and its erratum, combined here, are published: ApJL 768, L4 (2013); ApJ, 779, L30 (2013).

Fast gas combustion in systems with hydraulic resistance

Various aspects of the sonic velocity regime, one of the steady-state regimes of filtration combustion of gases, is analyzed. The conditions and region of existence of the regime, the velocity and structural characteristics of the combustion wave, the gas ignition and combustion mechanisms, conditions for the stabilization of the wave velocity, and regime transitions are considered. A characteristic feature of the regime is the presence of a pressure wave in the zone of turbulent flame due to the choking of channels and narrowings. The main factors determining the nature and properties of the sonic velocity regime are the hydraulic resistance, piezo diffusion, the energetics of the mixture, the compressibility and turbulence of the gas, and the reactivity of the mixture at high pressures and temperatures. The sonic velocity regime is a unique and intriguing combustion regime which is promising for applications.

Solitary waves on tensegrity lattices

We study the dynamics of lattices formed by masses connected through tensegrity prisms. By employing analytic and numerical arguments, we show that such structures support two limit dynamic regimes controlled by the prisms’ properties: (i) in the low-energy (sonic) regime the system supports the formation and propagation of solitary waves which exhibit sech2 shape and (ii) in the high-energy (ultrasonic) regime the system supports atomic-scale localization. Such peculiar features found in periodic arrays of tensegrity structures suggest their use for the creation of new composite materials (here called “tensegrity materials”) of potential interest for applications in impact absorption, energy localization and in new acoustic devices.

Effect of an Internal Open Crack on Pipes Wave Propagation

Stress guided waves in the sonic and ultrasonic regime are acknowledged as a powerful too lto inspect pipes in a non-invasive manner.A key point of the inspection procedure is related to the dispersive behavior of guided waves, that for agiven pipe is defined by the so-called dispersion curves. Such behavior, is generally predicted bymeans ofanalytical formulations. However, when the geometry of the pipe cross-section is not axially symmetric,such as in the presence of an open internal crack running along the pipe length, analytical formulations fail. Here, the computation of the guided waves properties for such a scenario is addressed via a SemiAnalytical Finite Element (SAFE) formulation in which the open crack is modeled at the mesh level.Different crack depths are considered and their effect on the waves dispersion curves are highlighted.The results could be of interest in pipeline inspection and monitoring.

Control of the deflagration-to-detonation transition in systems with resistance

This paper develops an approach to controlling gas combustion, including deflagration-to-detonation transition, based on using systems with resistance, such as porous media, periodic obstacles, rough tubes, etc. Gas combustion in these systems involves various physicochemical interactions: interfacial heat transfer, including combustion failure, flame quenching in fast pulsations (jets), transition to turbulence, generation of pressure waves in the flame zone, formation of hotspots, etc. These interactions result in a number of steady-state regimes with a uniform velocity of propagation of thermal waves — low-, high-, and sonic-velocity regimes, low-velocity detonation, and normal detonation with heat and momentum losses. Systems with porous media and periodic obstacles are considered as examples of systems with resistance. It is shown that with the effects of Lewis numbers taken into account, the steady-state velocities in the high-velocity regime for CH4/Air, C3H8/air, and H2/air systems over wide parameter ranges can be represented by a single relation Re = 6 · 10−4Pe3 in the coordinates (Re-Pe) for systems with porous media. Steady-state velocities in the sonic velocity regime for C3H8/air and H2/air systems are described in the same coordinates by a single function Re = 120Pe4/3 for systems with porous media and periodic obstacles. A condition for pressure generation in the flame zone at sonic velocities was obtained analytically. Problems involved in the implementation of the approach of controlling high-velocity combustion processes in systems with resistance are discussed.

Hawking-Like Radiation Does Not Require a Trapped Region

We discuss the issue of quasiparticle production by "analogue black holes" with particular attention paid to the possibility of reproducing Hawking radiation in a laboratory. By constructing simple geometric acoustic models, we obtain a somewhat unexpected result: We show that, in order to obtain a stationary and Planckian emission of quasiparticles, it is not necessary to create a trapped region in the acoustic spacetime (corresponding to a supersonic regime in the fluid flow). It is sufficient to set up a dynamically changing flow asymptotically approaching a sonic regime with sufficient rapidity in laboratory time. This result is generic to curved-space quantum field theory, the "analogue spacetimes" we consider providing a guide to physical intuition, and a possible route to laboratory experiments.

Quasi-particle creation by analogue black holes

We discuss the issue of quasi-particle production by ‘analogue black holes’ with particular attention to the possibility of reproducing Hawking radiation in a laboratory. By constructing simple geometric acoustic models, we obtain a somewhat unexpected result: we show that in order to obtain a stationary and Planckian emission of quasi-particles, it is not necessary to create an ergoregion in the acoustic spacetime (corresponding to a supersonic regime in the flow). It is sufficient to set up a suitable dynamically changing flow. For instance, either a flow that eventually generates an arbitrarily small sonic region v = c, but without any ergoregion, or even a flow that just asymptotically, in laboratory time, approaches a sonic regime with sufficient rapidity.

Preliminary considerations in the use of industrial sonic nozzles

Preliminary considerations applying to the necessary instrumentation for the use of sonic nozzles is reviewed. A way to make sonic nozzles for industry, together with a method to determine the discharge coefficient of a convergent nozzle operating in the sonic regime in conditions of ideal flow is suggested. The results obtained for the behaviour of the discharge coefficient of sonic nozzles, in the range from 4×10 4 to 2×10 5 are compared with the standard ISO 9300 (Standard ISO 9300. Measurement of gas flow by means critical flow Venturi nozzles, 1990) and the curve proposed by Ishibashi et al. (M. Ishibashi, M. Takamoto, N. Wanatabe, Y. Nakao. Precise calibration of critical nozzles of various shapes at the Reynolds number of 0.2–2, 5×10 5. Proceedings of FLOMEKO 94).

Exciton Transport in Cu2O

The low temperature exciton transport in Cu2O shows a transition from a diffusive to sonic ballistic regime with increase of excitation power or decrease of temperature, and also well pronounced nonlinearities under two-pulse and under pulse plus cw excitation. These features have been interpreted by the authors of the experiments as a proof of Bose-Einstein condensation (BEC) in the exciton system and its superfluidity. However, we have shown previously that most of these transport phenomena in Cu2O can be quantitatively explained within the nonequilibrium phonon-assisted (phonon wind) model, whereas the superfluid interpretation meets multiple inconsistencies. In the present paper we show that the recent experiments by the same group with spatially separated and/or time delayed two-pulse excitation are as well fully explained by the phonon wind picture.