Physical mechanisms of sputtering

A review of experiment and theory concerned with the atomic mechanisms of the sputtering process.     

Classification of backscattering-enhancement mechanisms

A classification is provided for the principal backscattering-enhancement mechanisms, which are divided into singleparticle and collective mechanisms, which, in turn, consist of geometrical mechanisms and mechanisms associated with phase coherence. A distinction is made between dynamic mechanisms, which appear in nearly all realizations, and statistical mechanisms, which are observed only after averaging.     

Nonlinear dynamics of physiological function and control

Complex rhythms are observed in the physiological systems that control and carry out vital bodily functions. Theoretical approaches to analyze the physiological systems include control theory and computation theory. Complementary to these approaches is nonlinear dynamics, which offers ways to classify both normal and abnormal dynamics, and to analyze bifurcations occurring in physiological dynamics.     

Electrical charging of engines in the efflux of combustion products. Experimental results

The electrical charging of jet engines during efflux of combustion products is studied. Measurements are made of the electrical current beyond the exit section of a nozzle as a function of such parameters as the characteristic length of the space charge region, the electrical potential of the engine, and the pressure of the surrounding medium. Possible practical applications of the results (estimating the charging current and the rate of rise and maximum value of the potential on a flight vehicle) are discussed. Zh. Tekh. Fiz. 69, 55–59 (August 1999)     

Construction and control of a physiological articulatory model

A physiological articulatory model has been constructed using a fast computation method, which replicates midsagittal regions of the speech organs to simulate articulatory movements during speech. This study aims to improve the accuracy of modeling by using the displacement-based finite-element method and to develop a new approach for controlling the model. A "semicontinuum" tongue tissue model was realized by a discrete truss structure with continuum viscoelastic cylinders. Contractile effects of the muscles were systemically examined based on model simulations. The results indicated that each muscle drives the tongue toward an equilibrium position (EP) corresponding to the magnitude of the activation forces. The EPs shifted monotonically as the activation force increased. The monotonic shift revealed a unique and invariant mapping, referred to as an EP map, between a spatial position of the articulators and the muscle forces. This study proposes a control method for the articulatory model based on the EP maps, in which co-contractions of agonist and antagonist muscles are taken into account. By utilizing the co-contraction, the tongue tip and tongue dorsum can be controlled to reach their targets independently. Model simulation showed that the co-contraction of agonist and antagonist muscles could increase the stability of a system in dynamic control.     

面部视频非接触式生理参数感知

为了在非接触条件下检测受试者的各项生理参数,本文设计了一种基于成像式光电容积描记技术,从手机录制的人脸视频中估算生理参数的方法.首先,提出了"小波变换-主成分分析-盲源分离"算法,用于提取出高信噪比的RGB三通道脉搏波信号.然后,分别从频域和时域角度对绿色通道信号进行处理,估算出心率值和呼吸率值;对红蓝通道的脉搏波信号...     

Failure mechanisms of graphene under tension

Recent experiments established pure graphene as the strongest material known to mankind, further invigorating the question of how graphene fails. Using density functional theory, we reveal the mechanisms of mechanical failure of pure graphene under a generic state of tension at zero temperature. One failure mechanism is a novel soft-mode phonon instability of the K1 mode, whereby the graphene sheet undergoes a phase transition and is driven towards isolated hexagonal rings resulting in a reduction of strength. The other is the usual elastic instability corresponding to a maximum in the stress-strain curve. Our results indicate that finite wave vector soft modes can be the key factor in limiting the strength of monolayer materials.     

Charge redistribution mechanisms of ceria reduction

Charge redistribution at low oxygen vacancy concentrations in ceria have been studied in the framework of the density functional theory. We propose a model to approach the dilute limit using the results of supercell calculations. It allows one to reproduce the characteristic experimentally observed behavior of composition versus oxygen pressure dependency. We show that in the dilute limit the charge redistribution is likely to be driven by a mechanism different from the one involving electron localization on cerium atoms. We demonstrate that it can involve charge localization on light element impurities.     

Extinction mechanisms of hyperbolic h-BN nanodisk

We applied the finite element method to calculate the extinction spectrum of single hyperbolic hexagonal boron nitride(h-BN) nanodisk. We show that the hyperbolic h-BN nanodisk exhibits two extinction mechanisms in the mid-infrared region. The volume confined phonon polaritons resonances of the nanodisk give rise to a series of weak extinction peaks.The localized surface phonon polaritons lead to a robust dipolar extinction, and the extinction peak position is tunable by varying the size of the h-BN nanodisk. These findings reveal the mechanisms of the interaction between light and resonant h-BN nanodisk, which are essential for h-BN related opto-electromagnetic applications.     

Quantum mechanisms of density wave transport

We report on new developments in the quantum picture of correlated electron transport in charge and spin density waves. The model treats the condensate as a quantum fluid in which charge soliton domain wall pairs nucleate above a Coulomb blockade threshold field. We employ a time-correlated soliton tunneling model, analogous to the theory of time-correlated single electron tunneling, to interpret the voltage oscillations and nonlinear current-voltage characteristics above threshold. An inverse scaling relationship between threshold field and dielectric response, originally proposed by Grüner, emerges naturally from the model. Flat dielectric and other ac responses below threshold in NbSe₃ and TaS₃, as well as small density wave phase displacements, indicate that the measured threshold is often much smaller than the classical depinning field. In some materials, the existence of two distinct threshold fields suggests that both soliton nucleation and classical depinning may occur. In our model, the ratio of electrostatic charging to pinning energy helps determine whether soliton nucleation or classical depinning dominates.     

Materials and mechanisms of hole superconductivity

The theory of hole superconductivity proposes that there is a single mechanism of superconductivity that applies to all superconducting materials. This paper discusses several material families where superconductivity occurs and how they can be understood within this theory. Materials discussed include the elements, transition metal alloys, high T_c cuprates both hole-doped and electron-doped, MgB₂, iron pnictides and iron chalcogenides, doped semiconductors, and elements under high pressure.     

Molecular mechanisms of the EHF bioeffect

A generalizing theoretical analysis of models of mechanisms of interaction of biological macromolecules with EHF electromagnetic fields is performed. It is shown that nonthermal EHF radiation has a biological effect when the dipole-active oscillation Q of the primary receptors is greater than or equal to 10³–10⁴, which is of the same magnitude as the corresponding characteristic of individual peaks in the radiation spectrum. From the analysis of model equations of the kinetics of synthesis and dissociation of molecular associates, an explanation of the EHF bioeffect is proposed that is based on the phenomenon of high sensitivity to external actions of responses in which high-molecular-weight aggregates participate.Institute of Theoretical Physics, Academy of Sciences of Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 1, pp. 93–102, January, 1994.     

Noise control mechanisms of inside aircraft

World trends in the development of methods and approaches to noise reduction in aircraft cabins are reviewed. The paper discusses the mechanisms of passive and active noise and vibration control, application of “smart” and innovative materials, new approaches to creating all fuselage-design elements, and other promising directions of noise control inside aircraft.     

Nucleation mechanisms of macrolocalized deformation bands

For the first time, a phenomenological classification of the nucleation mechanisms of bands of macrolocalized deformation is formulated that is based on data from the high speed optical monitoring of a surface of aluminum-magnezium alloy deformed with a uniformly growing rate of applied stress, [(s)\dot] ₀ = const\dot \sigma _0 = const. The classification includes eight nucleation mechanisms that depend on the applied stress: from the initial stage of formation of the Lüders band to the periodical nucleation of the conjugative bands in the structure of a neck prior to sample rupturing. The role of different mechanisms of band nucleation in the general picture of the jerky deformation of a metal is discussed.     

Atomic mechanisms of pure iron vitrification

It is shown on the basis of the model of iron with the Pak-Doyama paired potential of interatomic interaction in the framework of the molecular dynamics method that structural stabilization of the amorphous phase of pure iron during hardening from melt is ensured by the formation of a percolation cluster from mutually penetrating and contacting icosahedrons with atoms at vertices and centers.     

On the mechanisms of heavy-quarkonium hadroproduction

We discuss the various mechanisms potentially at work in hadroproduction of heavy quarkonia in the light of computations of higher-order QCD corrections both in the colour-singlet (CS) and colour-octet (CO) channels and the inclusion of the contribution arising from the s-channel cut in the CS channel. We also discuss new observables meant to better discriminate between these different mechanisms.     

Nanotribology: Microscopic mechanisms of friction

Friction is one of the oldest problems in physics with a huge practical significance. However, during the last decade this problem gets strong acceleration due to the development of new experimental techniques (surface-force apparatus, quartz-crystal microbalance technique, friction-force microscopy) and essentially due to the great progress in molecular dynamics (MD) simulation of tribological systems. In the present review we describe the modern state of the problem from the point of view of surface science physicists. The main accent is devoted to recent MD results in their connection with experiments.