Dust ion-acoustic wave oscillations in single-walled carbon nanotubes

In this paper, a charged single-walled carbon nanotube that surrounded by charged nanoparticles is modeled as a cylindrical shell of electron–ion–dust plasma. By employing the fluid theory for electron–ion–dust plasma, the dispersion relation of the dust ion-acoustic wave oscillations in the composed system is studied. For negatively charged dust particles, with increasing dust charge density, the phase velocity of the dust ion-acoustic wave will increase in comparison to the pure ion-acoustic wave oscillations.     

Lateral heat diffusion in layered structures: Theory and photothermal experiments

It is very important to understand how the heat diffuses in the case of nano objects and of layered structures. We will demonstrate that the lateral diffusion could be very different in the case of a good conductor layer deposited on a bad one and for the reverse (bad one on good substrate). Moreover, we will show how a thermoreflectance experiment can reveal both the thermal conductivity and the thermal diffusivity of thin layers deposited on substrates.     

Prediction of total loss factors of structures,I: Theory and experiments

A method for calculating the total loss factors of a complex structure has been derived by using Statistical Energy Analysis (SEA). The derived formulae have been simplified on the assumption that coupling between substructures except for the measured substructure is very weak. In two limiting situations, “damping addition” formulae have been obtained. The formula has been applied to predict the total loss factors of a steel box and these results are compared with actual experimental measurements. The agreement between estimated and measured values was in most cases quite good.     

Collisionless shocks: Simulation and laboratory experiments

Summary In the laboratory the conditions can be created that are necessary for reproducing typical shock waves that have been observed in the interplanetary plasma. There is also the possibility of changing the experimental conditions over a wide range and thus of considering the effect of different mechanisms of energy dissipation. With small Mach numbers, the anomalous increase of resistance at the shock front prevents the shock front from steepening. At high Mach numbers, the anomalous resistivity cannot stop the steepening and the two-stream instability occurs.

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Riassunto In laboratorio possono essere create le condizioni necessarie per riprodurre tipiche onde d'urto che sono state osservate nel plasma interplanetario. C'è anche la possibilità di cambiare le condizioni sperimentali in un ampio intervallo e quindi di considerare l'effetto di meccanismi diversi di dissipazione dell'energia. Con piccoli numeri di Mach l'aumento anomalo di resistenza sul fronte d'urto impedisce a questo di divenire più inclinato. Per alti numeri di Mach, la resistività anomala non può fermare l'inclinazione, e si verifica l'instabilità a due correnti.

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Резюме В лаборатории создаются условия. Необходимые для воспроизведения типичных ударных волн, которые наблюдаются в межпланетноИ плазме. Имеется также возможностъ для изменения зкспериментальных условиИ в широкоИ области и, следовательно, для исследования влияния различных механизмов диссипации знерчии. При малых числах Маха аномальное увеличение сопроти-вления на фронте удароИ волны прерятствует увеличению крутизны фронта ударноИ волны. При больших часлах Маха аномальное сопротивление не может остановить увеличение крутизны и возникает двух-струИная неустоичивость.

     

Dust ion-acoustic rogue waves in a three-species ultracold quantum dusty plasmas

Dust ion-acoustic (DIA) rogue waves are reported for a three-component ultracold quantum dusty plasma comprised of inertialess electrons, inertial ions, and negatively charged immobile dust particles. The nonlinear Schrödinger (NLS) equation appears for the low frequency limit. Modulation instability (MI) of the DIA waves is analyzed. Influence of the modulation wave number, ion-to-electron Fermi temperature ratio ρ$\rho$ and dust-to-ion background density ratio N_d$N_d$ on the MI growth rate is discussed. The first- and second-order DIA rogue-wave solutions of the NLS equation are examined numerically. It is found that the enhancement of N_d$N_d$ and carrier wave number can increase the envelope rogue-wave amplitudes. However, the increase of ρ$\rho$ reduces the envelope rogue-wave amplitudes.     

Rarefactive ion-acoustic electrostatic solitary structures in nonthermal plasmas

An investigation has been made of ion-acoustic solitary waves in an unmagnetized nonthermal plasma whose constituents are an inertial ion fluid and nonthermally distributed electrons. The properties of stationary solitary structures are briefly studied by the pseudo-potential approach, which is valid for arbitrary amplitude waves, and by the reductive perturbation method which is valid for small but finite amplitude limit. The time evolution of both compressive and rarefactive solitary waves, which are found to coexist in this nonthermal plasma model, is also examined by solving numerically the full set of fluid equations. The temporal behaviour of positive (compressive) solitary waves is found to be typical, i.e., the positive initial disturbance breaks up into a series of solitary waves with the largest in front. However, the behaviour of negative (rarefactive) solitary waves is quite different. These waves appear to be unstable and produce positive solitary waves at a later time. The relevancy of this investigation to observations in the magnetosphere of density depressions is briefly pointed out. Received 12 October 1999     

Partial pole placement in structures by the method of receptances: Theory and experiments

The theory and practical application of the receptance method for vibration suppression in structures by multi-input partial pole placement is described. Numerous advantages of the receptance method over conventional matrix methods such as state-space control based on finite elements have been demonstrated, in particular there is no need to know or to evaluate the structural matrices M, C, K and in practical experimentation the measurement of ‘receptance’ may be generalised so that explicit modelling of actuator dynamics becomes unnecessary. Active vibration control is demonstrated experimentally using two test rigs. In the first set of experiments partial pole placement is applied to a lightweight glass-fibre beam using macro fibre composite (MFC) actuators and sensors. In the second set of experiments active vibration control is implemented on a heavy modular test structure representative of systems of differing dynamic complexity using electromagnetic actuators and piezoelectric (ICP) accelerometers. It is demonstrated that chosen poles may be assigned to predetermined values without affecting the position of other poles of interest.     

Dust ion-acoustic solitary waves in a hot adiabatic magnetized dusty plasma

The basic features of obliquely propagating dust ion-acoustic (DIA) solitary waves in a hot adiabatic magnetized dusty plasma (containing adiabatic inertia-less electrons, adiabatic inertial ions, and negatively charged static dust) have been investigated. The reductive perturbation method has been employed to derive the Korteweg-de Vries (KdV) equation which admits a small amplitude solitary wave solution. The combined effects of plasma particle (electron and ion) adiabaticity, ion-dust collision, and external magnetic field (obliqueness), which are found to significantly modify the basic features of the small but finite-amplitude DIA solitary waves are explicitly examined. The implications of our results in space and laboratory dusty plasmas are briefly discussed.     

Droplet spreading: Theory and experiments

A hypothesis is presented that distinguishes the characteristics of spreading by hydrodynamic forces from those driven by molecular/kinetic effects, demarking the regimes by contact-line speeds and contact angles. Several applications of the criterion to experiments are discussed.     

A study of near-critical states of metals in shock-wave experiments

Methods for creating near-critical states of the liquid-vapor phase transition during shock wave impact and optical methods for determining the positions of the boundaries of the two-phase region and the parameters of the critical point of the liquid-vapor phase transition (temperature, pressure) are described.     

Soliton and chaotic structures of dust ion-acoustic waves in quantum dusty plasmas

The quantum hydrodynamic model is employed to study the soliton and chaotic structures of dust ion-acoustic waves in quantum dusty plasmas consisting of electrons, ions, and negatively/positively charged dust particles. By means of the reductive perturbation technique, two-dimensional Davey-Stewartson (DS) system is derived. By improving the extended projective method and the extended tanh-function method, a separation of variables solution with arbitrary functions for the Davey-Stewartson system is obtained. Many soliton and chaotic structures such as localized nonlinear coherent structure, line-soliton structure, periodic wave pattern structure, Rössler and Lorenz chaotic structures are given. It is found that these structures are effected by the quantum effects.     

Guided ionization waves: Theory and experiments

This review focuses on one of the fundamental phenomena that occur upon application of sufficiently strong electric fields to gases, namely the formation and propagation of ionization waves–streamers. The dynamics of streamers is controlled by strongly nonlinear coupling, in localized streamer tip regions, between enhanced (due to charge separation) electric field and ionization and transport of charged species in the enhanced field. Streamers appear in nature (as initial stages of sparks and lightning, as huge structures—sprites above thunderclouds), and are also found in numerous technological applications of electrical discharges. Here we discuss the fundamental physics of the guided streamer-like structures—plasma bullets which are produced in cold atmospheric-pressure plasma jets. Plasma bullets are guided ionization waves moving in a thin column of a jet of plasma forming gases (e.g., He or Ar) expanding into ambient air. In contrast to streamers in a free (unbounded) space that propagate in a stochastic manner and often branch, guided ionization waves are repetitive and highly-reproducible and propagate along the same path—the jet axis. This property of guided streamers, in comparison with streamers in a free space, enables many advanced time-resolved experimental studies of ionization waves with nanosecond precision. In particular, experimental studies on manipulation of streamers by external electric fields and streamer interactions are critically examined. This review also introduces the basic theories and recent advances on the experimental and computational studies of guided streamers, in particular related to the propagation dynamics of ionization waves and the various parameters of relevance to plasma streamers. This knowledge is very useful to optimize the efficacy of applications of plasma streamer discharges in various fields ranging from health care and medicine to materials science and nanotechnology.     

Dust ion-acoustic shock waves due to dust charge fluctuation in a superthermal dusty plasma

The nonlinear propagation of dust ion-acoustic (DIA) shock waves is studied in a charge varying dusty plasma with electrons having kappa velocity distribution. We use hot ions with equilibrium streaming speed and a fast superthermal electron charging current derived from orbit limited motion (OLM) theory. It is found that the presence of superthermal electrons does not only significantly modify the basic properties of shock waves, but also causes the existence of shock profile with only positive potential in such plasma with parameter ranges corresponding to Saturn?s rings. It is also shown that the strength and steepness of the shock waves decrease with increase of the size of dust grains and ion temperature.     

Localized structures in convective experiments

In this work we review localized structures appearing in thermo-convective experiments performed in extended (large “aspect ratio”) fluid layers. After a brief general review (not exhaustive), we focus on some results obtained in pure fluids in a Bénard-Marangoni system with non-homogeneous heating where some structures of this kind appear. The experimental results are compared in reference to the most classical observed in binary mixtures experiments or simulations. In the Bénard-Marangoni experiment we present the stability diagram where localized structures appear and the typical situations where these local mechanisms have been studied experimentally. Some new experimental results are also included. The authors want to honor Prof. H. Brand in his 60th. birthday and to thank him for helpful discussions.     

Internal solitons in laboratory experiments: comparison with theoretical models

Nonlinear internal solitary waves observed in laboratory experiments are discussed from the standpoint of their relation to different soliton theories, from the classical integrable models such as the Korteweg-de Vries, Gardner, Benjamin-Ono, and Joseph-Kubota-Ko-Dobbs equations and their modifications, through the nonintegrable models describing higher-order nonlinear effects, viscosity, rotation, and cylindrical spreading, to the strongly nonlinear models. First, these theoretical models are briefly described and, then, laboratory data and their comparison with the theory are presented.