Narrow Results

We present the results from simulation studies of evaporation of a single fluid in a capillary porous medium. Employing a three-dimensional site-bond correlated network model to represent a porous medium, namely Clashac sandstone, we analyze different aspects of the phase distribution by evaporation of a single fluid in the porous medium. As a direct consequence of the porous medium utilized, we analyze the influence of a strongly disordered porous media with a broad range of pore and throat size distributions in the evaporation process. Experimental data togheter with throat and pore size distributions were used to build and match the network model, allowing us to determine the porosimetric curve for the Clashac sandstone for different degrees of correlation. Also, the correlation length was obtained from the percolation theory. In our case study the evaporation process modeled was insensitive to the different degrees of correlation that might occur between pores and throats. In addition, it was observed that the evaporation pattern was the same for all analyzed networks above the correlation length.

In this study, the effect of different arrangements of injectors on the injection of liquid water into the hot supersonic crossflow of cylindrical geometry on the performance and the rate of evaporation has been studied using a numerical method. The crossflow has a Mach of about 2 and a total temperature of 800K. At first, the penetration height and droplets produced by atomization in the supersonic flow are validated using the Lagrangian technique, and the results have been compared with the experiments. The usage of heat transfer equations and the evaporation model for the spray evaporation of droplets in the hot flow is also performed in the validation process, and the results are compared with the experimental results. Then, the injection into the examined geometry with four, six and eight injectors in three different arrangements was evaluated. The results indicate that employing an arrangement of eight injectors leads to the most significant reduction in total temperature, with average total temperatures decreasing to below 550K. The results demonstrate a 40% decrease in total pressure, with a decrease in Mach number to about 1 at the end of the cylinder. Additionally, the evaporation rate shows higher evaporation of water in the eight-injector arrangement compared to other arrangements.

In this paper, we generalize the Parikh–Wilczek scheme to a holographic screen in the framework of the ultraviolet self-complete quantum gravity. We calculate that the tunneling probability depends on the energy of the particle and the mass of the holographic screen. The radiating temperature has not been the standard Hawking temperature.

A toy model based upon the q-deformation description for studying the radiation spectrum of black hole is proposed. The starting point is to make an attempt to consider the space–time noncommutativity in the vicinity of black hole horizon. We use a trick that all the space–time noncommutative effects are ascribed to the modification of the behavior of the radiation field of black hole and a kind of q-deformed degrees of freedom are postulated to mimic the radiation particles that live on the noncommutative space–time, meanwhile the background metric is preserved as usual. We calculate the radiation spectrum of Schwarzschild black hole in this framework. The new distribution deviates from the standard thermal spectrum evidently. The result indicates that some correlation effect will be introduced to the system if the noncommutativity is taken into account. In addition, an infrared cutoff of the spectrum is the prediction of the model.

In this paper, we employ a new form of the extended uncertainty principle to investigate the thermal properties of the Schwarzschild and Reissner–Nordström. After we construct the formalism, we obtain the mass-temperature function for the Schwarzschild black hole. We follow a heuristic method to derive the entropy function after we obtained the heat capacity function. Then, we derive the mass-temperature and mass-charge-temperature functions of the Reissner–Nordström black hole in the new formalism. After we obtain the heat capacity and entropy functions, we present a comprehensive and comparative analysis of all these functions. We find that the deformation parameter changes drastically some of the thermodynamic function characteristics.

In this invited review, we discuss the evaporation of a black hole, with emphasis on the resulting macroscopically distinct patterns of Hawking radiation. The density matrix of this radiation can approach a pure final state in the form of a highly entangled macroscopic superposition state. We note that this exact property is exhibited in replica wormhole calculations, and also in quantum hair effects on Hawking radiation amplitudes. Finally, we revisit the information paradox (Mathur’s theorem and firewalls), showing that it can be resolved by macroscopic entanglement.

Titanium dioxide has been in close examination for application development due to its high index of refraction and transparency across the visible range. One of the most active researches is hydrophilicity and photocatalysis in TiO₂ films. In this study, a close investigation to TiO₂ films' microstructural transformation was examined. A number of thin film samples were prepared by ion-assisted electron-beam evaporation at 200-nm nominal thickness, 2.0 Å/s deposition rate and 250°C deposition temperature. The varying parameter was the oxygen flow rate at 2, 4, 6 and 8 sccm. The films were eventually annealed for three hours in air atmosphere. The crystalline structures of as-deposited (ASD) and annealed films were deduced by variable-angle spectroscopic ellipsometry (VASE), and supported by X-ray diffractometry (XRD) and atomic force microscopy (AFM). Film characterization based on VASE is desirable in order to understand physical and optical characteristics of the films. Transmittance spectra were derived from UV/Vis spectrophotometer. It was found that all as-deposited films were all amorphous with low luminous transmittance. Higher oxygen flow rate during the deposition, however, resulted in sub-oxide TiO₂ film. With this film, annealing at 300 and 500°C were presumed as transition temperatures for amorphous-to-anatase and anatase-to-rutile phases, respectively. The luminous transmittance also increased and was found to be the highest at 75.75% at 400°C annealing. The optical energy band gap for this film also increased up to 3.26 eV at 600°C annealing.

Nanocrystal indium tin oxide (ITO) thin films were grown by electron beam evaporation (e-beam). The ITO films were fabricated at substrate temperatures ranging from 100 to 400°C in O₂ partial pressure ranging from 0.10 to 100 mTorr. The surface morphology was monitored using atomic force microscopy (AFM). The charge in the surface morphology of ITO films was discussed in terms of grain size and crystallographic orientations. Grain size measurements of the solid dispersed and the AFM study for nanostructure showed that the oxides were in the nano range (20–30 nm). In general, the values of the optical bandgap for the films are consistently blue-shifted as compared with the crystal size. The average crystalline size determined from the shift of the optical gap were found to be in the range 20–30 nm, which is in excellent agreement with the data obtained from AFM. All ITO films average grain size was ~ 20 nm deposited by e-beam evaporation. The average optical transmittance was 90.50% in the visible range (400–700 nm) and the average bandgap was 3.98 eV. ESR spectrum of ITO film showed random oxygen vacancies which arise due to the changing crystal field effects.

We have proposed and investigated a model of drying colloidal suspension drop placed onto a horizontal substrate in which the sol to gel phase transition occurs. The temporal evolution of volume fraction of the solute and the gel phase dynamics were obtained from numerical simulations. Our model takes into account the fact that some physical quantities are dependent on volume fraction of the colloidal particles.

The evaporation of fluid on solid surface is an important process in nature and industry. The high-efficiency heat transport between the working fluid and the solid surface can enhance the energy conversion and utilization. Thus, it is of great significance to study the mechanism of the evaporation phenomenon at the liquid–solid interface. In this study, the evaporation of refrigerant R32 on Pt surface is investigated by molecular dynamics (MD) method. The effects of the substrate temperature on the evaporation behavior of R32 are discussed in detail. It is found that R32 molecules mainly enter the vapor region by evaporation when the substrate temperature is no larger than 300 K. The evaporation rate increases with the increase of substrate temperature. The nucleate boiling and film boiling clearly occur when the substrate temperature is 350 K. The nanobubble formation, growth and coalesce is observed in the simulation. The heat flux changes rapidly when the system is boiling. As time goes on, a vapor film forms and then it leads to the heat transfer deterioration.

A snapshot of the evidence of solution-mediated phase transition of glucose isomerase (GI) crystals more than 7 months after the start of an experiment was successfully captured. The transition to $\mathrm{\text{P}}{2}_1{2}_{1}2$ crystals started about 2 months after the first I222 crystals nucleated. To conduct such long-term experiments, we developed novel observation cells with liquid paraffin layers to prevent aqueous GI solutions from evaporation of water. Changes in the weights of cells were measured, and much less evaporation was successfully achieved by continuously adding liquid paraffin as a liquid sealant.

Recently, we have developed a phase field model to describe Marangoni convection with evaporation in a compressible fluid of van der Waals type away from criticality [Eur. Phys. J. B44 (2005)]. Using this model, we report now 2D fully nonlinear simulations where we emphasize the influence of evaporation on convective patterns.

This paper deals with the analysis of the steady flow of a semi-infinite expanse of rarefied gas bounded by its plane condensed phase by the methods of the discrete kinetic theory. The existence of the solutions of the corresponding boundary value problem is discussed. The relations among the parameters of the flow near the condensed phase and at infinity required for the existence of solutions are established. The problem of condensation of a vapor gas on its own condensed phase is then solved analytically for a particular discrete model and remarkable features of the flow are analyzed.

In previous papers and letters on quantum amplitudes in black-hole evaporation, a boundary-value approach was developed for calculating (for example) the quantum amplitude to have a prescribed slightly non-spherical configuration of a massless scalar field ϕ on a final hypersurface Σ_F at a very late time T, given initial almost-stationary spherically symmetric gravitational and scalar data on a space-like hypersurface Σ_I at time t = 0. For definiteness, we assumed that the gravitational data are also spherically symmetric on Σ_F. Such boundary data can correspond to a classical solution for the Einstein/scalar system, describing gravitational collapse from an early low-density configuration to a nearly Schwarzschild black hole. This approach provides the quantum amplitude (not just the probability) for a transition from an initial to a final state. For a real Lorentzian time-interval T, the classical boundary-value problem refers to a set of hyperbolic equations (modulo gauge), and is badly posed. Instead, the boundary-value approach of the previous letters and papers requires (following Feynman) a rotation into the complex: T → |T| exp(-iθ), for 0 < θ ≤ π/2, of the time-separation-at-infinity T. The classical boundary-value problem, for a complex solution of the coupled nonlinear classical field equations, is expected to be well-posed for 0 < θ ≤ π/2. For a locally supersymmetric Lagrangian, containing supergravity coupled to supermatter, the classical Lorentzian action S_class, a functional of the boundary data (which include the complexified T), yields a quantum amplitude proportional to exp(iS_class), apart from possible loop corrections which are negligible for boundary data with frequencies below the Planck scale. Finally (still following Feynman), one computes the Lorentzian quantum amplitude by taking the limit of exp(iS_class) as θ → 0₊. In the present paper, a connection is made between the above boundary-value approach and the original approach to quantum evaporation in gravitational collapse to a black hole, via Bogoliubov coefficients. This connection is developed through consideration of the radial equation obeyed by the (adiabatic) non-spherical classical perturbations. When one studies the probability distribution for configurations of the final scalar field, based on our quantum amplitudes above, one finds that this distribution can also be interpreted in terms of the Wigner quasi-probability distribution for a harmonic oscillator.

This paper presents a non-string-theoretic calculation of the microcanonical entropy of relic integer-spin Hawking radiation, at fixed total energy E, from an evanescent, neutral, non-rotating four-dimensional black hole. The only conserved macroscopic quantity is the total energy E which, for a black hole that evaporates completely, is the total energy of the relic radiation. Through a boundary-value approach, in which data for massless, integer-spin perturbations are set on initial and final space-like hypersurfaces, the statistical-mechanics problem becomes, in effect, a one-dimensional problem, with the "volume" of the system determined by the real part of the time separation at spatial infinity — the variable conjugate to the total energy. We count the number of field configurations on the final space-like hypersurface that have total energy E, assuming that initial perturbations are weak. We find that the density of states resembles the well-known Cardy formula. The Bekenstein–Hawking entropy is recovered if the real part of the asymptotic time separation is of the order of the semi-classical black-hole lifetime. We thereby obtain a statistical interpretation of black-hole entropy. Corrections to the microcanonical entropy are computed, and we find agreement with other approaches in terms of a logarithmic correction to the black-hole area law, which is universal (independent of black-hole parameters). This result depends crucially upon the discreteness of the energy levels. We discuss the similarities of our approach with the transition from the black-hole to the fundamental-string regime in the final stages of black-hole evaporation. In addition, we find that the squared coupling, g², which regulates the transition from a black hole to a highly-excited string state, and vice versa, can be related to the angle, δ, in the complex-time plane, through which we continue analytically the time separation at spatial infinity. Thus, in this scenario, the strong-coupling regime corresponds to a Euclidean black hole, while the physical limit of a Lorentzian space–time (the limit as δ → 0₊) corresponds to the weak-coupling regime. This resembles the transition of a black hole to a highly-excited string-like state, which subsequently decays into massless particles, thereby avoiding the naked singularity.

We demonstrate that there exists an equilibrium description of thermodynamics on the apparent horizon in the expanding cosmological background for a wide class of modified gravity theories with the Lagrangian density f(R,ϕ,X), where R is the Ricci scalar and X is the kinetic energy of a scalar field ϕ. This comes from a suitable definition of an energy momentum tensor of the "dark" component obeying the local energy conservation law in the Jordan frame. It is shown that the equilibrium description in terms of the horizon entropy S is convenient because it takes into account the contribution of the horizon entropy Ŝ in non-equilibrium thermodynamics as well as an entropy production term.

For distant observers, black holes are trapped spacetime domains bounded by apparent horizons. We review properties of the near-horizon geometry emphasizing the consequences of two common implicit assumptions of semiclassical physics. The first is a consequence of the cosmic censorship conjecture, namely, that curvature scalars are finite at apparent horizons. The second is that horizons form in finite asymptotic time (i.e. according to distant observers), a property implicitly assumed in conventional descriptions of black hole formation and evaporation. Taking these as the only requirements within the semiclassical framework, we find that in spherical symmetry only two classes of dynamic solutions are admissible, both describing evaporating black holes and expanding white holes. We review their properties and present the implications. The null energy condition is violated in the vicinity of the outer horizon and satisfied in the vicinity of the inner apparent/anti-trapping horizon. Apparent and anti-trapping horizons are timelike surfaces of intermediately singular behavior, which manifests itself in negative energy density firewalls. These and other properties are also present in axially symmetric solutions. Different generalizations of surface gravity to dynamic spacetimes are discordant and do not match the semiclassical results. We conclude by discussing signatures of these models and implications for the identification of observed ultra-compact objects.

A droplet of nanoparticle suspension is deposited on a specially designed dual wettable surface. Half diagonal of SiO₂ substrate was oil coated and other half stayed unchanged. The droplet forms contact angle of 35^∘ on the unchanged dry portion whereas it reaches to 60^∘ on the oil coated region. Nanoparticle dried in stick–slip fashion where such effect was more pronounced on the oil-wet region. Scanning electron microscope (SEM) images revealed large ribbon-like nanorod assembly on the dry-region and short monolayer ribbons on the oil-wet part of the substrate. On both surfaces, shape-separation effect produced rod-rich and sphere-rich regions. The assemblies formed over the dry portion were dense whereas significantly small number of nanoparticles were observed on the oil-wet region. The droplet contact-line remained partially dynamic owing to the dual wettable design of the surface. Such contact-line dynamics facilitated the shape-separation effect induced by the surfactant molecules and dictated the deposition process over the surface. This work will be helpful to study shape-separation effect of small biological entities and multisystem of nanoparticles.

We review thermodynamic properties of modified gravity theories, such as $F(R)$ gravity and $f(T)$ gravity, where $R$ is the scalar curvature and $T$ is the torsion scalar in teleparallelism. In particular, we explore the equivalence between the equations of motion for modified gravity theories and the Clausius relation in thermodynamics. In addition, thermodynamics of the cosmological apparent horizon is investigated in $f(T)$ gravity. We show both equilibrium and nonequilibrium descriptions of thermodynamics. It is demonstrated that the second law of thermodynamics in the universe can be met, when the temperature of the outside of the apparent horizon is equivalent to that of the inside of it.

A three-dimensional simulation study is performed for investigating the hydrodynamic behaviors of a cross-flow liquid nitrogen spray injected into an air-fluidized catalytic cracking (FCC) riser of rectangular cross-section. Rectangular nozzles with a fixed aspect ratio but different fan angles are used for the spray feeding. While our numerical simulation reveals a generic three-phase flow structure with strong three-phase interactions under rapid vaporization of sprays, this paper tends to focus on the study of the effect of nozzle fan angle on the spray coverage as well as vapor flux distribution by spray vaporization inside the riser flow. The gas-solid (air-FCC) flow is simulated using the multi-fluid method while the evaporating sprays (liquid nitrogen) are calculated using the Lagrangian trajectory method, with a strong two-way coupling between the Eulerian gas-solid flow and the Lagrangian trajectories of spray.

Our simulation shows that the spray coverage is basically dominated by the spray fan angle. The spray fan angle has a very minor effect on spray penetration. The spray vaporization flux per unit area of spray coverage is highly non-linearly distributed along the spray penetration. The convection of gas-solid flow in a riser leads to a significant downward deviation of vapor generated by droplet vaporization, causing a strong recirculating wake region in the immediate downstream area of the spray.