On the form of interfacial surface at evaporation front propagation along the heater in the layer of metastable liquid

Within the framework of approximate physical and mathematical model, we considered the stationary problem of propagation of evaporation front in superheated liquid along the flat heater. The analytical dependence of the vapor layer thickness on the coordinate and physical parameters has been obtained. The solution is presented in invariant dimensionless form. Satisfactory agreement between theoretical results and new experimental data is shown.     

Spin-dependent electron dynamics in front of a ferromagnetic surface

Exchange splitting and dynamics of image-potential states in front of a 3 monolayer iron film on Cu(100) have been studied with time-, energy-, and spin-resolved bichromatic two-photon photoemission. For the first image-potential state n=1 we observe an exchange splitting of 56 +/- 10 meV and spin-dependent lifetimes of 16 +/- 2 fs for majority-spin and of 11 +/- 2 fs for minority-spin electrons, respectively. The time-resolved studies of both the population and the linewidth of image-potential states manifest that at the magnetic surface not only inelastic but also quasielastic scattering processes are spin dependent.     

Wave front reversal of surface magnetostatic waves

The wave front reversal (WFR) of non-reciprocal waves has been investigated. The experiment was performed using surface magnetostatic waves (SMSW) excited by a pulsed microwave signal of the carrier frequency ∼4.7 GHz in an epitaxial yttrium–iron garnet (YIG) film. The WFR was realized by pulsed parametric pumping of a double frequency. It was shown that WFR with high efficiency can be achieved for SMSW having relatively small wavenumbers k∼10² rad/cm.     

Modeling of a surface plasmon polariton interferometer

We model the operation of a micro-optical interferometer for surface plasmon polaritons (SPPs) that comprises an SPP beam-splitter formed by equivalent scatterers lined up and equally spaced. The numerical calculations are carried out by using a relatively simple vectorial dipolar model for multiple SPP scattering [Phys. Rev. B 67 (2003) 165405]. The SPP beam-splitter is simulated elucidating the influence of system parameters, such as the angle of SPP beam incidence, scattering particle size, and inter-particle distance, on the splitting efficiency and phase difference between the transmitted and reflected beams. It is found that the splitting efficiency is very sensitive to the size of scatterers and angle of incidence. Comparing our simulations with experimental data available in the literature, we conclude that this approach can be used, with certain limitations, for modelling of SPP components assembled of individual scatterers, e.g., beam-splitters and interferometers, and suggest further improvements of the model used.     

Thermal dynamics-based mechanism for intense laser-induced material surface vaporization

Laser material processing involving welding, ablation and cutting involves interaction of intense laser pulses of nanosecond duration with a condensed phase. Such interaction involving high brightness radiative flux causes multitude of non-linear events involving thermal phase transition at soild-liquid-gas interfaces. A theoretical perspective involving thermal dynamics of the vaporization process and consequent non-linear multiple thermal phase transitions under the action of laser plasma is the subject matter of the present work. The computational calculations were carried out where titanium (Ti) was treated as a condensed medium. The solution to the partial differential equations governing the thermal dynamics and the underlying phase transition event in the multiphase system is based on non-stationary Eulerian variables. The Mach number M depicts significant fluctuations due to thermal instabilities associated with the laser beam flux and intensity. A conclusive amalgamation has been established which relates material surface temperature profile to laser intensity, laser flux and the pressure in the plasma cloud.      

The n-type Si-based materials applied on the front surface of IBC-SHJ solar cells

Interdigitated back contact silicon hetero-junction(IBC-SHJ) solar cells exhibit excellent performance owing to the IBC and SHJ structures.The front surface field(FSF) layer composed of electric field passivation and chemical passivation has been proved to play an important role in IBC-SHJ solar cells.The electric field passivated layer n~+-a-Si: H, an n-type Si alloy with carbon or oxygen in amorphous phase, is simulated in this study to investigate its effect on IBC-SHJ.It is indicated that the n~+-a-Si: H layer with wider band gap can reduce the light absorption on the front side efficaciously,which hinders the surface recombination of photo-generated carriers and thus contributes to the improvement of the short circuit current density J_(sc).The highly doped n~+-a-Si: H can result in the remakable energy band bending, which makes it outstanding in the field passivation, while it makes little contribution to the chemical passivation.It is noteworthy that when the electric field intensity exceeds 1.3 × 10~5 V/cm, the efficiency decrease caused by the inferior chemical passivation is only 0.16%.In this study, the IBC-SHJ solar cell with a front n~+-a-Si: H field passivation layer is simulated, which shows the high efficiency of 26% in spite of the inferior chemical passivation on the front surface.     

内渐进多焦点镜片前表面光焦度匹配研究

研究内渐进多焦点镜片的前表面光焦度对该镜片的光焦度和散光的影响。设计出远用光焦度为2~10m-1,附加光焦度为2m-1的渐进表面数据,分别与1~10m-1的前表面光焦度匹配后输入Rotlex自由曲面检测仪转化为理论光焦度和散光度并进行统计分析。结果表明:在内渐进多焦点镜片的前表面光焦度匹配图中,存在扁椭圆区域,在该区域内匹配的内渐进多焦点镜片的远用区和近用区视觉清晰范围最大,且最大散光不大于附加光焦度。对于远用光焦度为非负的内渐进多焦点镜片,子午线上光焦度会随着前表面光焦度的增大而偏大。远用区为较大的正光焦度时,远用区和近用区清晰视觉范围明显较小。     

Explosive vaporization of a water layer on a flat microheater

Explosion vaporization of a water layer of different thickness, induced by pulse heating in an inhomogeneous temperature field on the surface of a flat microheater coated with a submicron silicon-carbide layer, is experimentally studied. An optical method is used for recording the vaporization time history and dynamics of the steam blanket. Pulsed laser irradiation is applied for high-time-resolution photography of the vaporization process. The dynamics of filling the heater surface with the vapor phase and the lifetime of the main vapor bubble and the satellite bubble are estimated. Dependences of the vaporization temperature on the heater temperature growth are obtained. The initial temperature is 30°C; the temperature growth rate on the heater surfaces is about 180 MK/s.     

Nearly perfect absorption in a single-layer metallic grating with rectangular grooves on its front surface

A subwavelength metallic grating can support horizontal surface plasmons (HSPs) at its horizontal metallic boundaries and vertical cavity modes (CMs) inside its slits. It has been shown that the coupling between these two resonant modes can enhance the absorption of the transverse magnetic polarized wave with the maximum absorption up to 75 % (Roszkiewicz et al. in Opt Lett 37(18):3759–3761, 2012). In this work, we propose and analyze a modified grating structure and show that it is possible to raise the absorption to nearly 100 %. The modified structure is a freestanding metallic grating with rectangular grooves on its front surface which can change the distribution of the HSPs on the same side, while leave those on the other side unaffected. When the HSPs on the front surface are changed to some certain situations, all incident energy can be launched into the grating slits by the CMs resonance and then be prohibited from transmitting through the grating by the HSPs on the back surface. Therefore, in such a single-layer metallic grating structure, all of the incident energy is absorbed, i.e., nearly 100 % absorption is obtained.     

Peculiarities of the variation of the detonation front surface area for DINA-Acetonitrile charges with a near-critical diameter

The previously revealed similarity between the passage of detonation in a weak liquid HE (a 68.5: 31.5 wt % DINA-A solution, close to the critical one) from a tube into a unconfined volume and in powerful liquid HE, such as nitroglycerin is discussed. It was concluded that the similarity in the behavior of liquid HEs so different in power is not associated with the kinetic stability of the detonation front and is determined by the phenomenon of the termination of the chemical reaction in the front of the corresponding waves by rarefaction waves.     

Laser acceleration of ion bunches at the front surface of overdense plasmas

The acceleration of ions in the interaction of high intensity laser pulses with overdense plasmas is investigated with particle-in-cell simulations. For circular polarization of the laser pulses, high-density ion bunches moving into the plasma are generated at the laser-plasma interaction surface. A simple analytical model accounts for the numerical observations and provides scaling laws for the ion bunch energy and generation time as a function of pulse intensity and plasma density.     

Modeling of the effect of a dielectric film on the electrode surface upon the discharge glow-to-arc transition

It is shown that when a dielectric film is on the cathode, the current density in the discharge sheath is raised due to the field emission of electrons from the cathode metal substrate under the effect of the electric field generated in the film by the surface charge that accumulates on it. This results in more intense cathode heating and faster glow-arc transitions.     

Modeling of a nanoscale flexoelectric energy harvester with surface effects

This work presents the modeling of a beam energy harvester scavenging energy from ambient vibration based on the phenomenon of flexoelectricity. By considering surface elasticity, residual surface stress, surface piezoelectricity and bulk flexoelectricity, a modified Euler-Bernoulli beam model for the energy harvester is developed. After deriving the requisite energy expressions, the extended Hamilton's principle and the assumed-modes method are employed to obtain the discrete electromechanical Euler-Lagrange's equations. Then, the expressions of the steady-state electromechanical responses are given for harmonic base excitation. Numerical simulations are conducted to show the output voltage and the output power of the flexoelectric energy harvesters with different materials and sizes. Particular emphasis is given to the surface effects on the performance of the energy harvesters. It is found that the surface effects are sensitive to the beam geometries and the surface material constants, and the effect of residual surface stress is more significant than that of the surface elasticity and the surface piezoelectricity. The axial deformation of the beam is also considered in the model to account for the electromechanical coupling due to piezoelectricity, and results indicate that piezoelectricity will diminish the output electrical quantities for the case investigated. This work could lead to the development of flexoelectric energy harvesters that can make the micro- and nanoscale sensor systems autonomous.     

Dynamic characteristics of a wind-tunnel ohmic heater

Dynamic characteristics of an ohmic heater intended for heating the working-gas flow in hot-shot wind tunnels have been experimentally studied. The experiments were performed on a specially designed test facility. Experimental data on the dynamic characteristics of the heater were obtained.