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Megasonic cleaning is one of the promising technologies to remove the particles during semiconductor processing. Acoustic bubble cavitation plays a key role in removing the particles. In this work, the effect of an anionic surfactant sodium dodecyl sulfate (SDS) on a bubble in the presence of hydrogen dissolved DIW water was studied. The bubble dynamics were observed using a high-speed camera. It was found that with the increase of surfactant the bubble characteristics were changed very significantly. Several parameters affecting the bubble dynamics were investigated.

We employ molecular dynamics simulations to investigate the evolution dynamics of {101¯2} twinning in single-crystal Ti under shock loading. The shock compression applied perpendicular to the c-axi...

The investigation of planetary gear dynamics including dynamic modeling and dynamic response analysis is a crucial approach in vibration reduction of industrial power transmission systems. In this paper, the nonlinear, time-varying dynamic model of a spur planetary gear system under consideration of the translational and rotational motions is investigated. The three subsystems for sun-planet, ring-planet and planet-carrier are analyzed subsequently, and the dynamic equations of the system are obtained. Moreover, different planet phasing and spacing configurations can be described by means of this model. In addition, the dynamic response is investigated by the multiple-scale method. First, the analytical solutions of the primary, superharmonic and subharmonic resonances are obtained. Then the frequency amplitude curves of different resonance modes are compared and the influence of some parameters on the vibration amplitude is studied. Meanwhile, the accuracy of the analytical solutions is evaluated by the numerical integration simulations. The results show that the frequency-amplitude curves of the primary and superharmonic resonance are similar in shape, the three solutions coexist, and the types of unstable solutions and stable solutions are identical. Furthermore, the softening nonlinearity of the subharmonic amplitude-frequency curve is more obvious under the three-dimensional model. This research is an important development of three-dimensional dynamic modeling and vibration prediction of planetary gears, and also improves the efficiency and accuracy of dynamic response calculation.

This study is concerned with modelling and analyses of a vibro-impact system consisting of a crank-slider mechanism and one oscillator attached to it, where the system is exposed to a non-ideal excitation. The impact occurs during the motion of the oscillator when it fits a base, and the excitation of the driving source is affected by this behaviour. The aim is to determine the interaction between a driving torque and the motion of the oscillator. To achieve this aim in a methodologically sound manner, both vibrating and vibro-impact systems with an ideal and non-ideal excitation are analysed. Analytical and numerical solutions are obtained for the vibrating system with the ideal excitation. Numerical analyses of the vibrating system with the non-ideal excitation is then conducted, where the characteristic curves for this system are found analytically. Numerical simulations are also carried out for other two systems and the results obtained are shown in terms of frequency–response diagrams, time-displacement diagrams and basins of attraction. The results found for different systems are compared mutually, and the differences between them are pointed out. Impact solutions for different regions of the excitation frequency are shown. For the vibro-impact system with the non-ideal excitation, the average value of its frequency is used.

We present an experimental study combining particle tracking, active microrheology, and differential dynamic microscopy (DDM) to investigate the dynamics and rheology of an oil-water interface during biofilm formation by the bacteria Pseudomonas Aeruginosa PA14. The interface transitions from an active fluid dominated by the swimming motion of adsorbed bacteria at early age to an active viscoelastic system at late ages when the biofilm is established. The microrheology measurements using microscale magnetic rods indicate that the biofilm behaves as a viscoelastic solid at late age. The bacteria motility at the interface during the biofilm formation, which is characterized in the DDM measurements, evolves from diffusive motion at early age to constrained, quasi-localized motion at later age. Similarly, the mobility of passively moving colloidal spheres at the interface decreases significantly with increasing interface age and shows a dependence on sphere size after biofilm formation that is orders-of-magnitude larger than that expected in a homogeneous system in equilibrium. We attribute this anomalous size dependence to either length-scale-dependent rheology of the biofilm or widely differing effects of the bacteria activity on the motion of spheres of different sizes.

Lab-on-a-chip devices based on inertial microfluidics have emerged as a promising technique to manipulate particles in a precise way. Inertial microfluidics exploits internal hydrodynamic forces and the mechanical structure of particles to achieve separation and focusing. The article focuses on the hydrodynamic interaction of two particles. This will help to develop an understanding of the dynamics of particle trains in inertial microfluidics, which are typical structures in multi-particle systems. We perform three-dimensional lattice Boltzmann simulations combined with the immersed boundary method to unravel the dynamics of various mono- and bi-dispersed pairs in inertial microfluidics. We study the influence of different starting positions for mono- and bi-dispersed pairs. We also change their deformability from relatively soft to rigid and choose spherical and biconcave particle shapes. The observed two-particle motions in the present work can be categorized into four types: stable pair, stable pair with damped oscillations, stable pair with bounded oscillations, and unstable pair. We show that stable pairs become unstable when increasing the particle stiffness. Furthermore, a pair with both capsules in the same channel half is more prone to become unstable than a pair with capsules in opposite channel halves.

Numerical simulation of thermoelectric processes in a branch of a solid–state thermoelectric Peltier cooler in a non–stationary mode is performed. Some examples show the effect of changes in the amplitude of the current pulse over time on the temperature in the branch of the thermoelectric element.

In this paper, the dynamics of axially functionally graded (AFG) conical pipes conveying fluid are analyzed. The materials are distributed along the conical pipe axis as a volume fraction function. Either the elastic modulus or the density of the AFG conical pipe is assumed to vary from the inlet to the outlet. The governing equation of the AFG conical pipe is derived using the Hamiltonian principle and solved by the differential quadrature method. The effects of the volume fraction index, volume fraction function type and reduction factor on the natural frequency and critical velocity are analyzed. It is found that for a power function volume fraction type, the natural frequency and critical velocity increase with increasing volume fraction index and clearly increase when the volume fraction index is within the range (0, 10). For an exponential function volume fraction type, the natural frequency and critical velocity change rapidly within the range (−10, 10), besides the above range the relationship between the natural frequency, critical velocity and volume fraction index is approximate of little change. The natural frequency and critical velocity decrease linearly with increasing reduction factor.

A high-temperature superconducting (HTS) magnetic levitation (maglev), based on YBaCuO bulk superconductors and permanent magnet guideways, shows the potential to be applied in the future rail transportation. The maglev forces (levitation and guidance force) of the HTS maglev system, which bond the vehicle and the guideway, are the key factors of its dynamics studies. In practical operation, the HTS maglev vehicle moves in both the vertical and lateral directions, but the previous force models are in single degree of freedom. In this article, an experiment was designed to study the vertical–lateral coupled effect of the levitation and guidance force. A 2-D coupling model was proposed to fit the experimental data. Furthermore, the motion stability and the dynamical characteristics of the HTS maglev system in 2-D space were studied. The simulation results show that the vertical–lateral coupling effect in maglev forces cannot be neglected, and one direction motion can affect the motion in the other direction. It also shows that the proposed force model is suitable for HTS maglev dynamics’ calculations.

Binary amorphous alloys are the primary bulk metallic glasses (BMGs). Two binary BMGs Zr67Ni33 and Fe80B20 have been studied in the present work using the pseudo- alloy-atom (PAA) model based on the pseudopotential theory. Some important thermodynamic properties like Debye temperature and elastic properties like elasticity moduli and Poisson’s ratio at room temperature are theoretically computed with the help of pseudopotential theory from the elastic limit of the phonon dispersion curves (PDCs). The collective dynamics of longitudinal and transverse phonon modes are investigated in terms of eigenfrequencies of the localized collective modes. The presently computed results are compared with the other such data including theoretically generated results from the molecular dynamics at different temperatures as available in the literature and an acceptable agreement is found. BIBECHANA 18 (2021) 33-47

We employ molecular dynamics simulations to investigate the role of temperature on the evolution dynamics of the voids in single crystal iron. We simulate isotropic tension in single crystal iron a...

The field of micromotors has been growing exponentially with increased emphasis on biomedical applications, with various in vivo demonstrations of targeted drug delivery, biosensing, and gene deliv...

To obtain the static shape of the continuous steel plate and vibration characteristic, we performed the analysis of the multi-body dynamics in which the continuous steel plate was discretized in many solid bodies. The shape of the steel plate obtained by the measurement experiment was agreement with the static shape of the steel plate obtained by the analysis. Then, dynamical analysis was performed when white noise input to the steel plate. It was confirmed that the vibration could be suppressed when the electromagnets were installed in consideration of the static shape of the steel plate.

The dynamics of ferroelectrics domain walls is modeled by the equation of a particle in a force field. It is considered that over the domain walls act the forces due to the interaction with an exte...

The article presents a spatial linkage composed of rigid and flexible links subjected to work dependent programmed constraints. The key tool used for the spatial linkage dynamics derivation is an a...

In this paper, we study the influence of unconventional current-phase relation (CPR) of Josephson junction on chaotic dynamics. The influence of the second term of CPR on an externally shunted Josephson junction with nonzero inductance has been studied. Using the circuit model, the time-dependent simulations are carried out for a variety of control parameters. It is shown that the presence of the second term on CPR leads to a change in the boundary of the chaotic region in the bifurcation diagram.

The dynamical evolution of smectic-C liquid crystals in the presence of a magnetic field is studied. The theoretical analysis is based on dynamic renormalisation group techniques. The starting poin...

Clearance joints and variable load have a great influence on the dynamic performance of shift manipulator for robot driver. In this article, a dynamics model of clearance joint and a simulation met...

In this present study, the detailed rotor dynamic evaluation of hybrid composite material rotating shaft of a power turbine high-speed rotor-bearing system is presented. The slender power turbine s...

A method for monitoring cell population movement in microscopic video-sequences based on integral optical flow and motion maps is proposed. Through adjustment and calibration of the optical system and averaging consecutive frames, high-quality subsequent images are obtained. Short-term dynamic characteristics are determined by optical flow. Based on optical flow, integral optical flow is calculated and used to create motion maps, and these maps are used to analyze and describe motions in any region of interest. Therefore, different types of cell movements, including directional motion, aggregation and dispersion can be identified. The proposed method does not require training, it can be used for situation monitoring and analysis, or as a component of comprehensive systems. Experiments performed on synthesized and real microscopic video images demonstrate the effectiveness of this method.

In order to explore methods for suppressing methane combustion and improve the safety of its engineering application. The effect of single-layer wire mesh on premixed methane-air flame behaviors and pressure dynamics in a closed pipe is experimentally investigated. Premixed methane-air mixture with stoichiometric ratio is used in our experiments. The wire mesh of seven different types are chosen. High-speed schlieren photography system and pressure transducers are adopted to record flame behaviors and pressure-time history, respectively. It is found that the flame can easily pass through the wire mesh of 12 and 20 mesh, but extinguishes under the effect of 30 mesh. For 40, 60, 80, and 100 mesh conditions, the flame presents salient quenching trend but finally passes through wire mesh. Meanwhile, the wire mesh has been seriously destroyed. The results indicate that anti-destructive is quite important for the fire resistance capacity of wire mesh. Moreover, the wire mesh significantly advances tulip flame formation time and makes flame front inversion extent weaker due to its effect on advancing and weakening the interactions between flame front and pressure waves. Furthermore, almost no suppression effect on flame tip speed is observed in the upstream pipe because the reduction of gas flow velocity is counteracted by the growth of gas combustion velocity. However, the flame propagation in the middle suppression section is significantly inhibited due to the great heat losses when touching wire mesh. Besides, the maximum pressure is decayed significantly. And the suppression effect is pretty enhanced as mesh of wire mesh increases.

We present a picture of flux-driven ITG turbulence and associated transport with heat source and sink which reveals resilience and stiffness coupled with SOC type intermittent bursts. The transport...

A detailed analysis of solutions to the Landau–Lifshitz equation describing solitons in a physically selected domain structure of a biaxial ferromagnet is presented. The structure and properties of new types of solitons that are strongly bound to the domain structure are investigated. Soliton behavior near the boundaries of their region of existence is considered. A comparative analysis of soliton cores in the domain structures of easy-axis and biaxial ferromagnets is performed, and their connection with solitons against a uniformly magnetized background is established.

Ultrafast laser-induced ablation is a complex function of many coupled parameters including laser intensity, pulse duration, optical wavelength, material thermophysical properties, and grain size. ...

Ablation dynamics focusing exclusively on the thermal field without also considering electron emission and thermal stress is incomplete. The thermo-elasto-plastodynamic model developed in Part I of...

The present study is focussed upon vibration control of the weapon elevation and azimuth dynamics mathematical model under influence of the 20 degree of freedom integrated ride and cornering dynamics non-linear mathematical model of a military vehicle with trailing arm suspension. The PID, LQR and Backstepping control techniques are applied in the weapon dynamics model in order to achieve the desired level of gun stabilisation over different manoeuvring situations. The control methods are initially implemented in the weapon elevation dynamics mathematical model which is subjected to vehicle ride response inputs only. In the later section, the control methods are incorporated in the azimuth dynamics mathematical model which is subjected to the integrated ride and cornering dynamic response inputs from different manoeuvres. The control forces are incorporated in the governing equations of motion for the weapon elevation and azimuth dynamics. The equations of motion for the weapon elevation and azimuth dynamics with incorporated control parameters, are transformed into state space matrix domain and solved by using Matlab. The elevation and azimuth dynamic responses are observed over the random terrain and with variable track velocities, respectively and compared with the corresponding passive models. It is observed that adequate attenuation of the vehicle dynamic inputs could be attained with the control techniques which led to desired weapon stabilisation in both elevation and azimuth directions. Compared to other controllers, backstepping control strategy is observed to provide the maximum attenuation in weapon responses by directly considering the Lyapunov stability criterion in its formulation. Therefore, the basic focus is to evaluate the gun muzzle response reduction by implementing different control techniques under the influence of a non-linear vehicle dynamic platform. These studies would provide the motivation and foundation behind design and development of gun control system for the military vehicles with All Electric Drive.

Molecular dynamics (MD) simulation of an electrowetted nanodroplet is performed to understand the fundamental origin of the involved parameters resulted from the molecular movement in the vicinity of the three-phase contact line (TPCL). During the spreading of the droplet, contact line friction (CLF) force is found to be the controlling one among all other resistive forces. Being molecular in nature, MD study is required to unveil the CLF, which is manifested by the TPCL friction coefficient ζ. The combined effect of temperature, electric field, and surface wettability, manifested by the solid-liquid Lennard-Jones interaction parameter, is studied to explore the droplet spreading. The entire droplet wetting dynamics is divided into two different regimes, namely, spreading regime and equilibrium regime. The molecular frequency during the TPCL movement in the equilibrium regime is affected by the presence of any external perturbation and results in an alteration of ζ. The predetermined knowledge of the alteration of CLF due to the coupling effect of electric field and temperature will have a potential application towards designing electric field-inspired droplet movement devices.

Based on an algebraic model of Reynolds stresses and fluxes, a numerical model of the dynamics of a flat localized region of turbulent perturbations of non-zero buoyancy in a linearly stratified medium was constructed. The evolution of a weakly heated turbulent spot was considered. Presence of non-zero buoyancy leads to increase in the geometrical dimensions of the turbulent spot and generation of internal waves of greater amplitude.

The paper presents results of an experimental study of the effect of pin microstructures on the wetting front propagation and its structure under adiabatic conditions and on strongly pre-heated surfaces, as well as the heat transfer and critical heat fluxes under steady-state heat release with liquid nitrogen film flowing. The surface structuring was created by the deformational cutting method (DCM). Comparison with data obtained on a smooth heater is presented. It is shown that the microstructures created by the DCM may have a significant effect on the nature of the temperature curves, reducing the total time of plate cooling at rewetting up to 2 times, and significantly change the structure and dynamics of the wetting front under adiabatic conditions. At the same time, such microstructuring with preset parameters of microfinning has weak influence on the heat transfer under steady-state heat release. High-speed video data of the processes are presented.

Magnetic dynamics of iron oxyhydroxide akaganeite nanoparticles, functional building blocks of the newest generation iron deficiency drug Ferinject, has been studied. While magnetism of the involved nanoparticles relies in general on bulk properties of akaganeite, the low temperature magnetic dynamics of Ferinject differs a lot from large number of other iron-oxides-based intravenous drugs in pharmaceutical practice. Clear separation of the high-temperature (Curie) and the low-temperature (spin-freezing) regimes has been identified. Instead of standard single superparamagnetic blocking temperature we show that the spin freezing relies on the two dominant and superimposed relaxations, characterizing the temperature ranges 50–100 K and 4.2–10 K, respectively. Complex magnetic dynamics is interpreted to rely on presence of the two assemblies of nanoparticles differing significantly in their average sizes. Bimodal distribution of particle sizes has been confirmed using atomic force microscopy. The knowledge of the drug’s physicochemical characteristics has been thus significantly improved.

Perovskites are widely utilized either as a primary component or as a substrate in which the dynamics of charged oxygen vacancy defects play an important role. Current knowledge regarding the dynamics of vacancy mobility in perovskites is solely based upon volume- and/or time-averaged measurements. This impedes our understanding of the basic physical principles governing defect migration in inorganic materials. Here, we measure the ergodic and nonergodic dynamics of vacancy migration at the relevant spatial and temporal scales using time-resolved atomic force microscopy techniques. Our findings demonstrate that the time constant associated with oxygen vacancy migration is a local property and can change drastically on short length and time scales, such that nonergodic states lead to a dramatic increase in the migration barrier. This correlated spatial and temporal variation in oxygen vacancy dynamics can extend hundreds of nanometers across the surface in inorganic perovskites.

To ascertain the effect of transverse dissipative particle dynamics (DPD), which includes lateral dissipative forces in addition to the central ones in the standard DPD, on dynamics of systems involving interfaces, we compare dynamic properties derived from coarse-grained (CG) molecular dynamics simulations with the standard and transverse DPD for nanometer-thick liquid films on solid surfaces. The dynamic properties include relaxation times of the film thickness distribution and molecular rotational motion, and transport properties associated with molecular translational motion. Our results show that these dynamic properties are tuneable by changing friction coefficients in the transverse DPD, whereas this is not the case in the standard DPD. We also confirm that the transverse DPD applied to liquid–solid CG bead pairs can tune dynamic properties of nanometer-thick liquid films on solid surfaces, though it is less effective than when applied to liquid–liquid CG bead pairs. Moreover, we reveal that the dissipative forces are isotropic in transverse DPD, whereas the liquid–solid dissipative forces are highly anisotropic and nearly along the direction perpendicular to solid surfaces in standard DPD. This suggests that the transverse liquid–solid DPD might be crucial for modelling the in-plane energy dissipation at liquid–solid interfaces., ファイル公開：2021/09/16

The shaft and pedestal deformations can produce large misalignments and displacements of shaft-bearing-pedestal systems (SBPSs). The phenomena have a great influence on the working performances of the SBPS. Thus, the shaft and pedestal stiffness should be properly optimized to minimize the system vibrations during the design process of the SBPSs. To overcome this issue, a new shaft and pedestal stiffness optimization strategy of a SBPS based on both the time- and frequency-domain vibrations is conducted in this work, which cannot be addressed by the previous methods considering single shaft or pedestal stiffness. Moreover, this method can be used to avoid the unexpected resonance frequencies of the rotor system during the design processing. A dynamic model of the SBPS considering both the flexible deformations of shaft and pedestal is presented. The effects of the shaft and pedestal stiffness on the vibration performances of the SBPS are discussed. The results give that the shaft and pedestal stiffness have a great effect on the time-domain waveform, magnitude, and peak frequencies of the vibrations of the SBPS. The relationships between the peak frequencies in the spectra of SBPS and two stiffness coefficients are nonlinear ones. However, they have no effect on the bearing passing frequency and its harmonics in the envelop spectra. It represents that the SBPS with the larger shaft and pedestal stiffness has a smaller vibration level. The obtained results can provide some guidance for the SBPS design with a low vibration level.

The noncovalent intercalation of amphiphilic molecules in the lipid membrane can be exploited to modulate efficiently the physical status of the membrane. Such effects are largely employed in a range of applications, spanning from drug-delivery to therapeutics. In this context, we have very recently developed an intramembrane photo-actuator consisting of an amphiphilic azobenzene molecule, namely ZIAPIN2. The selective photo-isomerization occurring in the lipid bilayer induces a photo-triggered change in the membrane thickness and capacitance, eventually permitting to evoke light-induced neuronal firing both in vitro and in vivo. Here, we present a study on the dynamical perturbation in the lipid membrane caused by ZIAPIN2 and its vehicle solvent, dimethyl sulfoxide. Effects on the dynamics occurring in the picosecond time range and at the molecular level are probed using quasi-elastic neutron scattering. By coupling experiments carried out both on model membranes and intact cells, we found that DMSO leads to a general retardation of the dynamics within a more dynamically ordered landscape, a result that we attribute to the dehydration at the interface. On the other hand, ZIAPIN2 partitioning produces a general softening of the bilayer owing to its interaction with the lipids. These data are in agreement with our recent studies, which indicate that the efficacy of ZIAPIN2 in triggering cellular signalling stems from its ability to mechanically perturb the bilayer as a whole, by forming light-sensitive membrane spanning dimers.

Relaxation dynamics of unentangled polymer melts (with a chain length below N = 100 for polyethylene) can be studied by performing either Rouse mode or relaxation mode analysis, such as proper orth...

Nucleate boiling is an important part of the pool boiling phenomenon which occurs in various processes involving heat transfer, such as, steam production, chemical processes, etc. The inclination of the heated surface, where bubbles nucleates, significantly affects the bubble growth dynamics as well as the heat transfer rate from the microlayer underneath the bubble during the nucleate boiling. In this study, the effect of the surface inclination on the bubble growth and detachment during the nucleate boiling is investigated numerically. For this purpose, the proposed model of Lay and Dhir for the microlayer is modified to include the effect of the inclination of the heated surface. The resulting equations are solved numerically, and the effect of varying the inclination of the heated surface on the bubble growth and heat transfer is investigated. The results show that the largest bubble size and the highest heat transfer from the heated surface occur when the inclination of the heated surface is 30°; while, the smallest bubble size and the lowest heat transfer from the heated surface are observed for the horizontal surface. Furthermore, the total heat transfer from the inclined surface during the bubble growth increases up to 32% compared to that for the horizontal surface.

The change in the carrier mobility in GaAs structures after irradiation is numerically simulated. For each investigated scattering potential, the model parameters are determined at which the calculation data are consistent with the results of the experiment. It is shown for the first time that the form of the potential of scattering at radiation-induced defects determines the time and space dynamics of the velocity overshoot in short structures.

Results of experimental investigation of the floating-up of a cluster of air bubbles in a viscous fluid by an optical method are presented. A setup has been developed for formation of a compact cluster of monodisperse bubbles with assigned diameter and volume concentration. It is shown that the velocity of the floating-up of a cluster of bubbles is higher than the velocity of the floating-up of a single bubble and depends on their number, diameter, and the distance between the bubbles. An empirical dependence of the resistance coefficient of a cluster of air bubbles floating up in glycerin on the Reynolds number has been obtained.

Scripta materialia 186, 268 - 271 (2020). doi:10.1016/j.scriptamat.2020.05.002, We reveal a slow-to-fast dynamics transition in the as-cast Cu$_{46}$Zr$_{46}$Al$_8$ (at.%) metallic glass (MG) at a temperature below the glass transition upon heating, which depends on the competition between free volume annihilation and thermally-activated atomic mobility, well consistent with the bond-length change of Cu-Cu pairs. The activation of $��$-relaxation at high temperatures could be related to the bond-length extension of Cu-Cu and Zr-Zr like-atom pairs together with the shortening of Cu-Zr unlike-atom pairs. Our results provide new insights into the correlation of dynamics with atomic structure in MGs and will be helpful to the understanding of ageing behaviors in MGs., Published by Elsevier Science, Amsterdam [u.a.]

Theoretical investigations into the dynamics and destruction of magmatic bombs forming during the eruption of submarine volcanos have been conducted. Continuum mechanics methods have been used for mathematical modeling of the dynamics and destruction of objects under investigation. In this case, it has been assumed that the mechanical behavior of the magmatic bomb material obeys the law of linear elastic deformation of a solid body.