Study of reflection and transmission on the moving interface of medium

The laws of refection and transimission on a moving interface between two nonvacuum medium are studied and the new method, which can be used for handling reflection and transimission on the moving interfaces between the vacuum-nonvacuum media and between two nonvacuum medium is suggested. The formula of reflection and transmission coefficients that suitable for both cases are derived. The present paper not only enriches electrodynamical theory, but also laies the foundation of optical waveguide modulators and other similar device.     

Study of reflection and transmission on the moving interface of medium

The laws of refection and transimission on a moving interface between two nonvacuum medium are studied and the new method, which can be used for handling reflection and transimission on the moving interfaces between the vacuum-nonvacuum media and between two nonvacuum medium is suggested. The formula of reflection and transmission coefficients that suitable for both cases are derived. The present paper not only enriches electrodynamical theory, but also laies the foundation of optical waveguide modulators and other similar device.     

Statistical properties of ultrasound speckles reflected from an interface

The first- and second-order statistical properties of ultrasound -speckles reflected from an interface are studied theoretically and experimentally. A theoretical model for predicting statistical properties of ultrasound speckles is constructed based on the Fresnel-Huygens principle and three basic assumptions. Distributions of amplitude and phase of ultrasound speckles in a scattering space are studied. And the study shows that they are in the form of Rayleigh and uniform distribution respectively. Using the proposed model, the average transverse size of the speckles within a scattering domain which are received by a focus probe is investigated. The average transverse size is found to be dependent on the characteristics of the measuring system only, and does not vary with the position in the domain. To verify the applicability of the theoretical model, a special experimental set-up was designed and the corresponding experiments were conducted for measuring the sound pressure of the ultrasound speckles     

Behavior of an oppositely charged oil–water interface

Abstract  

This paper virtually presents induced behavior of an oppositely charged oil–water interface with the use of a high-speed camera. The elevation behavior of an oil–water interface is demonstrated experimentally, using a transparent acrylic cylindrical container (176 mm in inner diameter, 450 mm in height) with the bottom half (100 mm) filled with deionized water and the top half (between 50 and 150 mm) with an immiscible oil (viscosity 1 or 5 cSt). Copper fragments are inserted into each liquid (at top and bottom) to serve as electrodes, i.e., the oil layer is negatively charged, and the water layer is positively charged. A high-DC-voltage power supply provides potential difference of the order between about 1 and 30 kV. As a result, three kinds of behavior are observed, i.e.: (1) rotary motion on the interface in lower electric field supplied about E = 0.013 kV/mm; (2) fluctuation on the interface in medium electric field supplied about E = 0.021 kV/mm; (3) elevation of the interface in higher electric field supplied between E = 0.04 and 0.65 kV/mm (which depends on the depth of the oil layer).     

Impact of nitrogen plasma passivation on the interface of germanium MOS capacitor

Nitrogen plasma passivation(NPP) on(111) germanium(Ge) was studied in terms of the interface trap density,roughness, and interfacial layer thickness using plasma-enhanced chemical vapor deposition(PECVD). The results show that NPP not only reduces the interface states, but also improves the surface roughness of Ge, which is beneficial for suppressing the channel scattering at both low and high field regions of Ge MOSFETs. However, the interfacial layer thickness is also increased by the NPP treatment, which will impact the equivalent oxide thickness(EOT) scaling and thus degrade the device performance gain from the improvement of the surface morphology and the interface passivation. To obtain better device performance of Ge MOSFETs, suppressing the interfacial layer regrowth as well as a trade-off with reducing the interface states and roughness should be considered carefully when using the NPP process.     

Study of solid–liquid interface in water dispersions of microcrystalline celluloses

Interaction on the solid–liquid surface in dispersions of microcrystalline cellulose (MCC) with various particle sizes has been studied by means of rheological methods. It was shown that the MCC dispersions possess shear-thinning rheological properties. An inversely proportional relationship between the average particle size of the MCC particles and the viscosity of the dispersions was discovered. This phenomenon is explained by the decrease of water mobility with increase in the specific surface of the MCC particles. Irreversible closing of the MCC pores reduces the viscosity of water dispersions. Addition of some water-soluble polymers leads to a considerable increase in viscosity due to formation of macromolecular net composed of solid particles.     

Effect of temperature on the morphology of nanobubbles at mica/water interface

The great implication of nanobubbles at a solid/water interface has drawn wide attention of the scientific community and industries. However, the fundamental properties of nanobubbles remain unknown as yet. In this paper, the temperature effects on the morphology of nanobubbles at the mica/water interface are explored through the combination of AFM direct image with the temperature control. The results demonstrate that the apparent height of nanobubbles in AFM images is kept almost constant with the increase of temperature, whilst the lateral size of nanobubbles changes significantly. As the temperature increases from 28℃ to 42℃, the lateral size of nanobubbles increases, reaching a maximum at about 37℃, and then decreases at a higher temperature. The possible explanation for the size change of nanobubbles with temperature is suggested.     

Zonal PANS: evaluation of different treatments of the RANS–LES interface

The partially Reynolds-averaged Navier–Stokes (PANS) model can be used to simulate turbulent flows either as RANS, large eddy simulation (LES) or DNS. Its main parameter is f_k whose physical meaning is the ratio of the modelled to the total turbulent kinetic energy. In RANS f_k = 1, in DNS f_k = 0 and in LES f_k takes values between 0 and 1. Three different ways of prescribing f_k are evaluated for decaying grid turbulence and fully developed channel flow: f_k = 0.4, f_k = k^3/2 _tot/? and, from its definition, f_k = k/k_tot where k_tot is the sum of the modelled, k, and resolved, k_res, turbulent kinetic energy. It is found that the f_k = 0.4 gives the best results. In Girimaji and Wallin, a method was proposed to include the effect of the gradient of f_k. This approach is used at RANS– LES interface in the present study. Four different interface models are evaluated in fully developed channel flow and embedded LES of channel flow: in both cases, PANS is used as a zonal model with f_k = 1 in the unsteady RANS (URANS) region and f_k = 0.4 in the LES region. In fully developed channel flow, the RANS– LES interface is parallel to the wall (horizontal) and in embedded LES, it is parallel to the inlet (vertical). The importance of the location of the horizontal interface in fully developed channel flow is also investigated. It is found that the location – and the choice of the treatment at the interface – may be critical at low Reynolds number or if the interface is placed too close to the wall. The reason is that the modelled turbulent shear stress at the interface is large and hence the relative strength of the resolved turbulence is small. In RANS, the turbulent viscosity – and consequently also the modelled Reynolds shear stress – is only weakly dependent on Reynolds number. It is found in the present work that it also applies in the URANS region.     

SAXS andalysis of interface in organo—modified mesoporous silica

A small-angle x-ray scattering(SAXS)technique using synchrotron radiation as the x-ray source has been employed to characterize the microstructure of mesoporous silica prepared by one-pot template-directed synthesis methodology.The scattering of pure silica agreed with Porod’s law.the scattering of organomodified mesoporous silica showed a negative deviation from Porod’s law,suggesting that an interfacial layer exists between the pores and silica matrix.It was the organic groups comprising the interface,as shown by ^29Si cross-polarization magic-angle spinning nuclear magnetic resonance imaging (^29Si cp MAS/NMR) and Fourier transform infrared spectroscopy(FTIR),that caused this negative deviation of SAXS intensity from Porod’s law,and the average thichness of the interfacial layer could be deduced from this negative deviation.Copyright 2001 john Wiley and Sons,Ltd.     

Liquid–vapour equilibrium of n -alkanes using interface simulations

Molecular Dynamics simulations were performed to calculate liquid–vapour coexisting properties of n-alkane chains up to 16 carbon atoms using interface simulations. The lattice sum or Ewald method on the dispersion forces of the Lennard–Jones potential was applied to calculate the full interaction. The liquid and vapour coexisting densities were obtained for two flexible force field models, NERD and TraPPE-UA, where the intermolecular interactions are of the Lennard–Jones type. We have recently shown [P. Orea, J. López-Lemus, and J. Alejandre, J. Chem. Phys. 123, 114702 (2005)] that the liquid–vapour densities for simple fluids do not depend on interfacial area and therefore it is possible to use a small number of molecules in a simulation. We show that the same trend is found on the simulation of these hydrocarbon molecules. The phase diagram of ethane/n-decane binary mixtures is also obtained at 410.95 K for the NERD model. The simulation results from this work were compared with those obtained using methods with interfaces using large cut-off distances and with methods without interfaces for the same potential model. In both comparisons, excellent agreement was found. The results of liquid density from the TraPPE-UA model are in good agreement with experimental data while those from the NERD model are underestimated at low temperatures. Our findings are consistent with results published by other authors for small hydrocarbons.     

Effect of an intermediate layer on the strength of an ice−substrate interface

The purpose of this investigation is quantitative determination of deformational changes in the ice structure immediately upon displacement under conditions of high hydrostatic pressure by the method of acoustic emission and estimation of the effect of the structure on the ice?substrate adhesive bond strength. The relation between the reciprocal acoustic compliance of ice, the size of mobile elements of its structure, their resonance eigenfrequency, and the density is established. The model is verified. The correlation of the amplitude?frequency spectra of the acoustic emission on the frictional contact with the acoustic spectra of eigenvibrations on glaciers from remote sources is confirmed. The results obtained can be used for distant study of the modes of motion of ice in glaciers.     

Laser-accelerated self-assembly of colloidal particles at the water–air interface

We experimentally demonstrate that optical tweezers can be used to accelerate the self-assembly of colloidal particles at a water–air interface in this Letter. The thermal flow induced by optical tweezers dominates the growth acceleration at the interface. Furthermore, optical tweezers are used to create a local growth peak at the growing front, which is used to study the preferential incorporation positions of incoming particles.The results show that the particles surfed with a strong Marangoni flow tend to fill the gap and smoothen the steep peaks. When the peak is smooth, the incoming particles incorporate the crystal homogeneously at the growing front.     

Solid–fluid diffuse interface model in cases of extreme deformations

Diffuse interface methods have been recently proposed and successfully used for accurate compressible multi-fluid computations Abgrall [1]; Kapila et al. [20]; Saurel et al. [30]. These methods deal with extended systems of hyperbolic equations involving a non-conservative volume fraction equation and relaxation terms. Following the same theoretical frame, we derive here an Eulerian diffuse interface model for elastic solid-compressible fluid interactions in situations involving extreme deformations. Elastic effects are included following the Eulerian conservative formulation proposed in Godunov [16], Miller and Colella [23], Godunov and Romenskii [17], Plohr and Plohr [27] and Gavrilyuk et al. [14]. We apply first the Hamilton principle of stationary action to derive the conservative part of the model. The relaxation terms are then added which are compatible with the entropy inequality. In the limit of vanishing volume fractions the Euler equations of compressible fluids and a conservative hyperelastic model are recovered. It is solved by a unique hyperbolic solver valid at each mesh point (pure fluid, pure solid and mixture cell). Capabilities of the model and methods are illustrated on various tests of impacts of solids moving in an ambient compressible fluid.     

Surface tension of hydrocarbon chains at the liquid–vapour interface

Molecular dynamics simulations were performed at constant temperature to obtain the surface tension of hydrocarbon chains at the liquid–vapour interface. The Ewald sum was used to calculate the dispersion forces of the Lennard–Jones potential to take into account the full interaction. The NERD and TraPPE_UA flexible force field models were used to simulate molecules from ethane to hexadecane along the coexistence curve. The simulation results for the TraPPE_UA model are in good agreement with experimental data, whereas the NERD model predicts slightly higher values.     

Effects of annealing temperature on the alloying behavior of the AuGe-GaAs〈100〉 interface

UV(He I) and X-ray photoelectron spectroscopies (UPS and XPS) were used to examine the alloying behavior of AuGe ohmic contacts to silicon-doped 100 oriented n-type GaAs substrates. The reacted interface was then revealed by Ar ion sputter depth profiling at room temperature and after annealing in ultra high vacuum at 300°, 500°, or 700°C. The indiffusion of Au and the outdiffusion of Ga and As are evident. Instead of obtaining a maximum peak of the Ge profile on annealing in forming gas, we observed an increase of Ge indiffusion with temperature. The Au indiffusion results in a decrease in the Au 5d splitting and a shift of both levels to higher binding energy. Au-Ga alloy formation is indicated by the Au 4f levels, and is further supported by the observation of the metallic Ga peak. It has been concluded that the sample annealed at 500°C forms the Au-Ga alloy and the compound of As containing Ge more easily than the samples annealed at 300° or 700°C. This result is consistent with the observations of low contact resistance at the annealing temperature of 500°C for AuNiGe ohmic contacts to n-type GaAs.     

First principles study of behavior of helium at Fe(110)–graphene interface

Recently,metal-graphene nanocomposite system has aroused much interest due to its radiation tolerance behavior.However,the related atomic mechanism for the metal-graphene interface is still unknown.Further,stainless steels with Fe as main matrix are widely used in nuclear systems.Therefore,in this study,the atomic behaviors of point defects and helium(He) atoms at the Fe(110)-graphene interface are investigated systematically by first principles calculations.The results indicate that graphene interacts strongly with the Fe(110) substrate.In comparison with those of the original graphene and bulk Fe,the formation energy values of C vacancies and Fe point defects decrease significantly for Fe(110)-graphene.However,as He atoms have a high migration barrier and large binding energy at the interface,they are trapped at the interface once they enter into it.These theoretical results suggest that the Fe(110)-graphene interface acts as a strong sink that traps defects,suggesting the potential usage of steel-graphene with multiply interface structures for tolerating the radiation damage.     

Determination of interface layer thickness of a pseudo two—phase system by extension of the Debye equation

The Debye equation with slit-smeared small angle x-ray scattering(SAXS) data is extended form an ideal two-phase system to a pseudo two-phase system with the presence of the interface layer,and a simple accurate solution is proposed to determine the average thickness of the interface layer in porous materials.This method is tested by experimental SAXS data,which were measured at 25℃,of organo-modified mesoporous silica prepared by condensation of tetraethoxysiland(TEOS) and methyltriethoxysilane(MTES) using non-ionic neutral surfactant as template under neutral condition.     

Partially implicit motion of a sharp interface in Navier–Stokes flow

We develop a numerical method for the coupled motion of Navier–Stokes flow with an elastic interface of zero thickness which exerts tension and bending forces on the fluid. The interface motion is made partially implicit by approximating a backward Euler step in the high wavenumbers as in the small scale decomposition method of Hou, Lowengrub and Shelley. This modified step is combined with the method of Beale and Layton [J.T. Beale, A.T. Layton, A velocity decomposition approach for moving interfaces in viscous fluids, J. Comput. Phys. 228 (2009) 3358–67]; the fluid velocity is found by computing the Stokes velocity and a more regular remainder. The resulting scheme is second order in space and first order in time; it can be made second order in time by extrapolation. The discontinuities in the pressure and velocity gradient are preserved. The partially implicit method allows much larger time steps than an explicit method with negligible added effort. The formulas in the Fourier transform for the implicit approximation in high wavenumbers are similar to those derived in Hou and Shi [T.Y. Hou, Z. Shi, An efficient semi-implicit immersed boundary method for the Navier–Stokes equations, J. Comput. Phys. 227 (2008) 9138–69] in a different context.