Nonlinear Rayleigh–Taylor instability of the cylindrical fluid flow with mass and heat transfer

The nonlinear Rayleigh–Taylor stability of the cylindrical interface between the vapour and liquid phases of a fluid is studied. The phases enclosed between two cylindrical surfaces coaxial with mass and heat transfer is derived from nonlinear Ginzburg–Landau equation. The F-expansion method is used to get exact solutions for a nonlinear Ginzburg–Landau equation. The region of solutions is displayed graphically.     

Heat and mass transfer in a coal-water fuel particle at the stage of “thermal” treatment

The problem of heat and mass transfer has been solved numerically under the conditions of coal-water fuel particle ignition. The concurrent processes of evaporation, filtration of steam, thermal decomposition of the organic part of coal, thermal and chemical interaction of steam and coke carbon, and oxidation of products of their reaction and volatiles by the external oxidizer have been taken into account. The scales of influence of individual thermophysical and thermochemical properties of coals on the characteristics and conditions of ignition of coal-water slurry have been determined.     

The influence of the “hot”-dimer adsorption mechanism on the kinetics of a monomer-dimer surface reaction

Hot dimers are molecules which after adsorption dissociate and each of the remaining hot monomers fly apart up to a maximum distance R from the original adsorption site. The influence of the hot-dimer adsorption mechanism on relevant aspects of the bimolecular catalyzed reaction of the type A – (1/2)B ₂(hot) AB is studied by means of the Monte-Carlo simulation technique. The temporal evolution of both the reactant's coverages as well as the rate of AB-production is evaluated and discussed. Due to the enhanced probability of hot species for encounters with other adsorbed particles, the rate of AB-production becomes faster when increasing R. This behavior may be relevant in the dynamic of some catalyzed reactions such as for example the oxidation of carbon monoxide on transition metal surfaces, i.e. ACO, B ₂O₂, and ABCO₂. Also the sticking coefficient of hot dimers and the average distance traveled by the hot monomers are evaluated and discussed.     

Effects of temperature,pH, and ionic strength on the adsorption of nanoparticles at liquid–liquid interfaces

The effects of temperature, pH and sodium chloride (NaCl) concentration on the equilibrium and dynamic interfacial tension (IFT) of 4.4-nm gold nanoparticles capped with n-dodecanethiol at hydrocarbon–water interfaces was studied. The pendant drop technique was used to study the adsorption properties of these nanoparticles at the hexane–water and nonane–water interfaces. The physical size of the gold nanoparticles was determined by TEM image analysis. The interfacial properties of mixtures of these nanoparticles, having different sizes and capping agents, were then studied. The addition of NaCl was found to cause a decrease of the equilibrium and dynamic IFT greater than that which accompanies the adsorption of nanoparticles at the interface in the absence of NaCl. Although IFT values for acidic and neutral conditions were found to be similar, a noticeable decrease in the IFT was found for more basic conditions. Increasing the temperature of the system was found to cause an increase in both dynamic and equilibrium IFT values. These findings have implications for the self-assembly of functionalized gold nanoparticles at liquid–liquid interfaces.     

Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble?s dynamics

A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with the experimental data and a good correspondence was observed. The dynamics of hydrofoil cavitation bubble were also investigated. It was concluded that the thermal radiation heat transfer rate strongly depended on the cavitation number, initial bubble radius and hydrofoil angle of attack.     

Effect of the shape of an organic water–coal fuel particle on the condition and characteristics of its ignition in a hot air flow

The results of experimental studies of the effect of the shape of an organic water–coal fuel (OCWF) particle on its ignition delay time and the time of its complete burnout in a hot air flow are reported. Three most common shapes of real particles, such as spherical, ellipsoidal, and irregular-polyhedron-like, are considered. It is shown that the shortest ignition delay time and the time of complete burnout correspond to polyhedron- shaped OCWF particles. Conditions are identified under which this factor significantly influences the ignition characteristics. The experiments were carried out at initial particle sizes (averaged maximum values) of 0.5–5 mm and temperatures and velocities of the oxidant flow of 600–900 K and 0.5–5 m/s, respectively. The main components of the studied fuels were coal processing wastes and waste motor, turbine, and transformer oils.     

On the effect of “Dead Water” in a stratified liquid on a solid bottom

The influence of a solid bottom on the ??dead water?? effect for gravitational and fluctuation waves (having the same dispersion law), as well as capillary waves, is calculated in a linear statement. It is found that the presence of a solid bottom aggravates the dead water effect.     

The Δ mass dependence of the M matrix and its influence on the NΔ→NN cross-sections

TheΔmass dependence of the M matrix and its influence on the NΔ→NN cross-sections are investigated in the one-boson exchange model.Our calculations show that theΔmass dependence of the momentum of the outgoingΔand the M matrix affects the calculations ofσNΔ→NN,especially around the threshold energy.     

Comment on “On the Anomalon Interpretation of 40Ar + Cu Collisions at 0.9 and 1.8 AGeV”

A recent article interpreted the experiment by Dersch et al. on the formation of ²⁴Na in ⁴⁰Ar + Cu interactions in a very simple manner. The results from emulsion experiments performed with 3.6 AGeV ²²Ne were adapted for the interpretation of the experiments with 1.8 AGeV ⁴⁰Ar. The model used the same mean value for the energy of minimum ionizing protons and pions at all angles. It is argued that a more complex approach is needed for a satisfactory interpretation.     

Reduction of noxious substance emissions at the pulverized fuel combustion in the combustor of the BKZ-160 boiler of the Almaty heat electropower station using the “Overfire Air” technology

The computational experiments using the “Overfire Air” (OFA) technology at the coal dust torch combustion in the combustor of the BKZ-160 boiler of the heat power plant No. 2 in Almaty have been conducted. The results show a possibility of reaching a reduction of the emission of noxious nitrogen oxides NO _x and minimizing the energy losses. The results of numerical experiments on the influence of the additional air supply on the main characteristics of heat and mass transfer are presented. A comparison with the base regime of the solid fuel combustion when there is no supply of the additional air (OFA = 0 %) has been made.     

On the “Equivalence” of the Maxwell and Dirac Equations

It is shown that Maxwell's equation cannot be put into a spinor form that is equivalent to Dirac's equation. First of all, the spinor in the representation of the electromagnetic field bivector depends on only three independent complex components whereas the Dirac spinor depends on four. Second, Dirac's equation implies a complex structure specific to spin 1/2 particles that has no counterpart in Maxwell's equation. This complex structure makes fermions essentially different from bosons and therefore insures that there is no physically meaningful way to transform Maxwell's and Dirac's equations into each other.     

“Quasi-Planck” spectra of capillary turbulence on the surface of liquid hydrogen

We report the first observation of “quasi-Planck” spectra of capillary turbulence on the surface of liquid hydrogen in the dissipation domain. Capillary waves have been driven by low-frequency random force. We have observed that the frequency spectrum of surface elevation changes its dependence from power-like 〈|η_ω²|〉 ∼ ω^−2,8 at middle-frequency domain to “quasi-Planck” distribution ∼e ^ω/ω _d at higher frequencies. The frequency ω _d is proportional to the boundary frequency between inertial interval and dissipation domain and it is scaled up with the increase of driving force.     

Comment on “On the analytical solution of the optical Bloch equations”

In a recent paper [P.J. Colmenares and J.L. Paz, Opt. Commun. 284 (2011) 5171], analytical solutions of the optical Bloch equations are presented. This paper follows the same procedures as presented in the paper by the authors [H.R. Noh and W. Jhe, Opt. Commun. 283 (2010) 2353] but concludes that their results are substantially different from the results of the authors. We find that the discrepancy results from the wrong initial conditions employed by those authors for one of the Bloch vector components (w), whose initial value must be 1 not 0. We also find that if proper initial conditions are used, there are no discrepancies between the two results.     

Two hot to handle: How do we manage the simultaneous impacts of climate change and natural disasters on human health?

Climate change is one of the major challenges we face today. There is recognition alongside evidence that the health impacts of both climate change and natural disasters are significant and rising. The impacts of both are also complex and span well beyond health to include environmental, social, demographic, cultural, and economic aspects of human lives. Nonetheless integrated impact assessments are rare and so are system level approaches or systematic preparedness and adaptation strategies to brace the two simultaneously particularly in low and middle-income countries. Ironically the impacts of both climate change as well as natural disasters will be disproportionately borne by low emitters. Sufficiently large and long-term data from comprehensive weather, socio-economic, demographic and health observational systems are currently unavailable to guide adaptation strategies with the necessary precision. In the absence of these and given the uncertainties around the health impact projections alongside the geographic disparities even within the countries, the main question is how can countries then prepare to brace the unknown? We certainly cannot wait to obtain answers to all the questions before we plan solutions. Strengthening health systems is therefore a pragmatic “zero regrets” strategy and should be adopted hastily before the parallel impacts from climate change and associated extreme weather events (disasters thereof) become too hot to handle.     

Features of chemical reactions at vanishing kinetic energy: the presence of internally “hot” reagents

The reactions between vibrationally and rotationally excited H₂ and D₂ molecules and the F atom are analyzed at ultra-low collision energies using the Coupled Channels quantum approach. The aim of this work is to compare the relative efficiency of the reactive scattering event with that of the vibrational or rotational quenching process in the ultra-cold temperature regime in order to establish general trends, possibly amenable to experiments on this or on more complex systems. We have already compared the rotational de-excitation efficiency with the reactive one in the reaction [1] and we have seen in that case that rotational de-excitation is more efficient than reaction when going down to ultra-low energies. We are investigating here the vibrational excitation case when the internal energy of the molecule becomes large enough to be above the classical barrier, and we are also presenting new results for the rotationally hot H₂ partner. We find that, with vibrationally hot molecules, the reaction becomes more efficient than the relaxation process, while the relative efficiency of such processes when having rotationally hot molecular partners is much more system-dependent.Received: 15 June 2004, Published online: 7 September 2004PACS: 34.10. + x General theories and models of atomic and molecular collisions and interactions (including statistical theories, transition state, stochastic and trajectory models, etc.) - 34.50.Lf Chemical reactions, energy disposal, and angular distribution, as studied by atomic and molecular beams - 34.20.Mq Potential energy surfaces for collisions     

Reply to the comment on “On the Barut-Vigier model of the hydrogen atom”

It is shown that the main conclusion of Dragić and Marić [Phys. Lett. A 229 (1997) 130] about the ground state of the hydrogen atom in the Barut-Vigier potential is based on the wrong use of the radial wave function which cannot be normalized.     

Relativistic mass distribution in event-anti-event system and “realistic” equation of state for hot hadronic matter

We find the equation of state p, T ⁶,which gives the value of the sound velocity c ²7 = 0.20,in agreement with the realistic equation of state for hot hadronic matter suggested by Shuryak, in the framework of a covariant relativistic statistical mechanics of an event-anti-event system with small chemical and mass potentials. The relativistic mass distribution for such a system is obtained and shown to be a good candidate for fitting hadronic resonances, in agreement with the phenomenological models of Hagedorn, Shuryak, et al. This distribution provides a correction to the value of specific heat 3/2,of the order of 5.5%,at low temperatures.     

Erratum to “Boundary layer flow and heat transfer of a Casson fluid past a symmetric porous wedge with surface heat flux”

We would like to acknowledge the misprinted terms in our published paper “Boundary layer flow and heat transfer of a Casson fluid past a symmetric porous wedge with surface heat flux” [Chin. Phys. B 23 044702 (2014)]. Since only two misprints exist and the main results of the published paper are correct, we present the correct equations in this erratum.