Mixture Of Waves Research Articles

Combustion Synthesis of Functionalized Carbonated Boron Nitride Nanoparticles and Their Potential Application in Boron Neutron Capture Therapy

In this research, we developed boron-rich nanoparticles that can be used for boron neutron capture therapy as potential carriers for boron delivery to cancerous tissues. Functionalized carbonated boron nitride nanostructures (CBNs) were successfully synthesized in self-propagating combustion waves in mixtures of high-nitrogen explosives and boron compounds. The products’ composition, morphology, and structural features were investigated using Fourier transform infrared spectroscopy, powder X-ray diffraction, low-temperature nitrogen sorption analysis, thermogravimetric analysis, high-resolution scanning electron microscopy, and high-resolution transmission electron microscopy. The extreme conditions prevailing in combustion waves favor the formation of nanosized CBN hollow grains with highly disordered structures that are properly functionalized on the surface and inside the particles. Therefore, they are characterized by high porosity and good dispersibility in water, which are necessary for medical applications. During biological tests, a concentration-dependent effect of the obtained boron nitride preparations on the viability of normal and neoplastic cells was demonstrated. Moreover, the assessment of the degree of binding of fluorescently labeled nanoparticles to selected cells confirmed the relationships between the cell types and the concentration of the preparation at different incubation time points.

Structure of Detonation Waves in Mixtures of Tetranitromethane with Acetone

Structure of Detonation Waves in Mixtures of Tetranitromethane with Acetone

Characterization of non-Boltzmann CN X2Σ+ behind shock waves in CH4-N2 via broadband ultraviolet femtosecond absorption spectroscopy.

This article describes the temporal evolution of rotationally and vibrationally non-Boltzmann CN X2Σ+ formed behind reflected shock waves in N2-CH4 mixtures at conditions relevant to atmospheric entry into Titan. A novel ultrafast (i.e., femtosecond) laser absorption spectroscopy diagnostic was developed to provide broadband (≈400 cm-1) spectrally resolved (0.02nm resolution) measurements of CN absorbance spectra belonging to its B2Σ+ ← X2Σ+ electronic system and its first four Δv = 0 vibrational bands (v″ = 0, 1, 2, 3). Measurements were acquired behind reflected shock waves in a mixture with 5.65% CH4 and 94.35% N2 at initial chemically and vibrationally frozen temperatures and pressures of 4400-5900K and 0.55-0.75bar, respectively. A six-temperature line-by-line absorption spectroscopy model for CN was developed to determine the rotational temperature of CN in v″ = 0, 1, 2, and 3, as well as two vibrational temperatures via least-squares fitting. The measured CN spectra revealed rotationally and vibrationally non-Boltzmann population distributions that strengthened with increasing shock speed and persisted for over 100 µs. The measured vibrational temperatures of CN initially increase in time with the increasing CN mole fraction and eventually exceed the expected post-shock rotational temperature of N2. The results suggest that strong chemical pumping is ultimately responsible for these trends and that, at the conditions studied, CN is primarily formed in high vibrational states within the A2Π or B2Σ+ state at characteristic rates, which are comparable to or exceed those of key vibrational equilibration processes.

A multicomponent multitemperature model for simulating laminar deflagration waves in mixtures of air and hydrogen

In this manuscript, a multicomponent multitemperature model is proposed for the simulation of laminar deflagration waves in mixtures of four gases: H2, 02, N2, and H20. The model is built following a thermodynamical approach and it inherits several interesting mathematical properties: the model is hyperbolic, there is a unique solution for the Rankine–Hugoniot relations (i.e. for weak solutions/shock waves), the source terms are in agreement with the second law of thermodynamics. The correct propagation of the flame front is ensured by using the classical technique of the artificial thickening of the flame. Simple numerical schemes and classical methods are used for computing the approximated solutions of the model and for assessing its behavior on some basic test cases. The results are encouraging and further improvements should be done, in particular by modeling the effect of the turbulence on the front propagation.

Abundant analytical soliton solutions and different wave profiles to the Kudryashov-Sinelshchikov equation in mathematical physics

The generalized exponential rational function (GERF) method is used in this work to obtain analytic wave solutions to the Kudryashov-Sinelshchikov (KS) equation. The KS equation depicts the occurrence of pressure waves in mixtures of liquid-gas bubbles while accounting for thermal expansion and viscosity. By applying the GERF method to the KS equation, we obtain analytic solutions in terms of trigonometric, hyperbolic, and exponential functions, among others. These solutions include solitary wave solutions, dark-bright soliton solutions, singular soliton solutions, singular bell-shaped solutions, traveling wave solutions, rational form solutions, and periodic wave solutions. We discuss the two-dimensional and three-dimensional graphics of some obtained solutions under the accurate range space by selecting appropriate values for the involved arbitrary parameters to make this research more praiseworthy. The obtained analytic wave solutions specify the GERF method’s dependability, capability, trustworthiness, and efficiency.

Structure of Detonation Waves in Mixtures of Tetranitromethane with Nitrobenzene and Methanol

Experimental studies of the structure of detonation waves in mixtures of tetranitromethane with methanol and nitrobenzene have been performed. Particle velocity profiles at the arrival of detonation waves at the interface with a water window were measured by a laser interferometer. It has been shown that the flow pattern in the reaction zone changes sharply at a concentration of diluents in the vicinity of stoichiometry, resulting in a decrease in the amplitude of the von Neumann spike up to its complete disappearance. The detonation waves are stable to the formation of a cellular structure of the front over almost the entire concentration range, except in the range near the limiting values. At the same time, the amplitude values of particle velocity show poor reproducibility from experiment to experiment performed under the same conditions. The obtained experimental dependences of detonation velocity on the concentrations of methanol and nitrobenzene are in good agreement with thermodynamic calculations.

Structure of Detonation Waves in Mixtures of Tetranitromethane with Nitrobenzene and Methanol

Structure of Detonation Waves in Mixtures of Tetranitromethane with Nitrobenzene and Methanol

Faraday waves and droplets in quasi-one-dimensional Bose gas mixtures

Faraday waves in mixtures of Bose gases are studied by taking into account quantum fluctuations beyond the Gross–Pitaevskii mean-field formalism with the Lee–Huang–Yang term. For that, a Bose–Einstein condensed binary atomic mixture is assumed trapped in cigar-type geometry, having the inter- and intra-species scattering lengths periodically varying in time. The period of the Faraday patterns is shown to be quite sensitive to the estimated value obtained by the beyond mean-field contribution, which can be used to measure quantum fluctuations in the ground state of the quasi-one-dimensional mixture. By studying the influence of the above nonlinear periodic modulations on quantum droplet dynamics, we also show that nonlinear resonances are excited in the oscillation widths of the quantum droplets. Variational predictions confirm numerical simulations for the corresponding formalism.

Physical and mathematical modeling of interaction of detonation waves in mixtures of hydrogen, methane, silane, and oxidizer with clouds of inert micro- and nanoparticles

ABSTRACTThe physical and mathematical models for the description of the detonation process in mixtures of hydrogen–oxygen, methane–oxygen, and silane–air in the presence of inert nanoparticles were proposed. On the basis of these models, the dependencies of detonation wave (DW) velocity deficit versus the size and concentration of inert nanoparticles were found. Three regimes of detonation flows in gas suspensions of reactive gases and inert nanoparticles were revealed: (1) stationary propagation of weak DW in the gas suspension, (2) galloping propagation of detonation, (3) destruction of the detonation process and transformation to wave of turbulent burning. It was determined that the mechanisms of detonation suppression by micro- and nanoparticles are closed and lie in the splitting of a DW to frozen shock wave and ignition and combustion wave. Concentration limits of detonation were calculated. It turned out that concentration limits (on particle volume concentration) of detonation are quite similar for particles with diameters ranging from 10 nm to 1 µm.

Dynamics of Waves in Multifractional Bubble Liquids

A study has been made of pulsed waves in mixtures of a liquid and a dispersed phase consisting of vapor–gas and gas bubbles that differ in radii and thermophysical properties. A system of differential equations has been proposed for description of the motion of such a mixture and a dispersion relation has been derived for it. A comparison has been made of the dynamics of acoustic waves in mixtures of water with vapor–air bubbles, bubbles of carbon dioxide with steam, and helium bubbles, and also in monodisperse mixtures of water with bubbles of one gas. In the investigations, the qualitative composition of the dispersed phase varied due to the buildup in the volume content of the bubbles of one fraction and the relevant decrease in the content of the bubbles of the other fraction, with the total volume content of the bubbles being constant.

Tunable emergent structures and traveling waves in mixtures of passive and contact-triggered-active particles.

We investigate emergent behavior in binary mixtures comprised of passive particles and contact-triggered active particles (CAPs), where a propulsion force is applied on CAPs towards passive particles when the two are in contact. We show that such mixtures phase separate into distinct dense and dilute phases with as few as 10% CAPs. Furthermore, the structure of the dense phase can be tuned by varying the fraction of CAPs and the strength of their propulsion force. The dense phase is classified into seven structure types, which includes both 6-fold and 4-fold ordered crystals, and kinetically arrested gels and clusters. Mixtures with fewer than 35% CAPs exhibit traveling density waves such that one end of the dense phase recedes while the other propagates. This phenomenon results from the spontaneous symmetry breaking of particle flux at the dense-dilute interface. We show that contact-triggered activity can be employed to develop materials with a wide range of structures and dynamics.

Stabilization of unstable detonation waves in mixtures of nitromethane with inert diluents

Mass velocity profiles of detonation waves in mixtures of nitromethane with acetone and methanol with added diethylenetriamine sensitizer were measured using a VISAR laser interferometer. It was found that even small, about 1%, concentrations of acetone and methanol, inert diluents, led to instability of the one-dimensional detonation front in nitromethane. The results of the experiment show that the use of the sensitizer is an effective method of flow stabilization and if the concentration of the inert diluent does not exceed 10%, the detonation front becomes stable with the addition of 1% diethylenetriamine. At a higher diluent concentration, the sensitizer does not suppress the instability but decreases the oscillation amplitude by several times. The addition of diethylenetriamine to the mixture has been found to increase the detonation velocity.

Acoustic waves in multifractional gas mixture with the inclusion of different materials and dimensions without Phase Transformations

The propagation of acoustic waves in mixtures of gas and particle fractions of different materials and sizes is studied. A mathematical model is presented, the dispersion equation is obtained, dispersion curves are calculated. The influence of the particle size and the parameters of the dispersed phase for multifractional gas mixture with ice particles, aluminum and sand on dissipation and dispersion of sound waves is analyzed. A comparison with experiment is conducted.

Molecular Dynamics Simulations of Shock Waves in Mixtures of Noble Gases

We study the structure of a normal shock wave in noble gas mixtures (Xe-He and Ar-He) of various compositions using molecular dynamics and direct simulation Monte Carlo. The molecular dynamics simulations are first validated against experimental data. Good agreement is found between the molecular dynamics solutions and the experimental measurements, with the exception of the parallel temperature profile in the 24.7% Ar-He mixture, despite the satisfactory agreement between the parallel velocity profiles. Secondly, a validation against direct simulation Monte Carlo solutions obtained with the accurate generalized hard sphere model is presented. As expected, the generalized hard sphere direct simulation Monte Carlo and molecular dynamics solutions are in near-perfect agreement. Finally, molecular dynamics results are compared to those obtained with the lower fidelity variable hard sphere model, which, if inappropriately parametrized, fails to describe the shock wave structure. This work exemplifies how full molecular dynamics solutions could be used to precisely discern differences between phenomenological models of various accuracy.

Effect of an axial electric field on detonation waves

The present study reports the results of an investigation of the effects of an axial electric field (200–8000V/cm) on the propagation of detonation waves in mixtures of 2CO+O2 and C2H2+O2+85%Ar. High speed streak camera and photodiodes were used for detonation velocity measurements. In addition, the voltage across the axial electrodes and the current are monitored as the detonation traverses the electric field region. The present results show that the neither the detonation structure nor its velocity are influenced by the electric field as it traverses the region between electrodes except when a breakdown occurs ahead of the detonation. The breakdown is due to the progressively increasing electric field between the detonation (which acts like a travelling quasi-neutral conducting plasma slug) and the downstream electrode. For a sufficiently strong electric field an arc discharge develops between the detonation and the charged electrode. When a discharge occurs in the unburned mixture ahead of the detonation wave, the mixture is ignited prior to the detonation arrival. This leads to the failure of the detonation since it now propagates into burnt products. Re-initiation of the failed detonation may occur downstream of the discharge section. The present results provide an explanation of the previous observations of Bone et al. [2].

Numerical study of detonation transmission in mixtures containing chemical inhibitors

In this article, we report on numerical simulations of the evolution of gaseous detonation waves in mixtures that contain chemical inhibitors. In general, these are compounds that consume the radicals that are produced during combustion, thereby inhibiting the exothermic chain-terminating reaction. Also, some of them participate in endothermic reactions, such as dissociation. These properties make them very efficient flame suppressants. In this study, we employ a chemical kinetics model that consists of a three-step chain-branching mechanism for the fuel combustion and a one-step mechanism for the reaction between inhibitor and radicals. Results from both one- and two-dimensional simulations are presented and discussed. It is shown that radical consumption and heat absorption due to the inhibitor's reaction result in longer induction zones. This, in turn, leads to a detachment of the reaction zone from the precursor shock. For small and medium inhibitor concentrations, this detachment is temporary. Eventually, the radical concentration behind the induction zone becomes sufficient to initiate rapid fuel consumption, thus producing pressure waves which reach the precursor shock and re-ignite the detonation. This is followed by large over-pressures and highly irregular oscillations of the shock. Nonetheless, sufficiently high inhibitor concentrations can yield permanent detonation quenching.

Modeling of reflection of detonation and shock waves from a rigid wall in mixtures of a reactive gas and chemically inert particles

An algorithm of approximate calculation of the reflection of detonation waves in mixtures of a reactive gas and chemically inert microparticles has been proposed. Consideration has been given to the case where the gas behind the wave front is in chemical equilibrium (D → D reflection). It has been shown that the presence of the condensed phase can substantially decrease the parameters of the reflected wave (its velocity, pressure, and temperature). Within the framework of a one-dimensional nonstationary approach and with allowance for the detailed kinetics of chemical reactions, the evolution of the shock wave in a stoichiometric hydrogen-oxygen mixture with sand particles in its reflection from a rigid wall has been calculated. The limiting particle concentration below which the reflected wave is of the detonation type and above which it is of the shock type has been found.

Multispecies laser measurements of n‐butanol pyrolysis behind reflected shock waves

AbstractTime histories of OH, H2O, and 306.8 nm absorbance were measured behind reflected shock waves in mixtures of 1% n‐butanol in Ar. Reflected shock conditions covered temperatures (T5) from 1274 to 1439 K and pressures (P5) near 1.5 atm. OH was measured using laser absorption of the R1(5) line of the A–X (0, 0) transition at 306.7 nm. Each experiment was repeated with the laser tuned off the narrow OH absorption feature to subtract broadband interference from CH2O and CH3CHO. Knowledge of the absorption coefficients of CH2O and CH3CHO at this nonresonant wavelength was then used to compare ultraviolet (UV) absorbance to model predictions. H2O was measured using DFB diode laser absorption of a well‐characterized absorption feature near 2.5 μm. These measured time histories, which should prove highly useful in reaction mechanism development, were then compared to simulations based on the comprehensive n‐butanol oxidation mechanism by Curran et al. (Combust Flame, 2010, 157, 363–373). Using that mechanism, it was determined that the n‐butanol decomposition pathways through C4H8OH(γ) should be strongly favored over C4H8OH(α) and that the C4H8OH(δ) pathway should also be increased by 25%. The specific rate adjustments inferred in this work were found to be highly mechanism dependent, though the overall reaction path analyses were very similar for all the mechanisms studied. In addition to Curran et al. (2010), two other mechanisms were examined, revealing the importance of four specific sets of reactions in n‐butanol pyrolysis. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 303–311, 2012

Auto-ignition of toluene-doped n-heptane and iso-octane/air mixtures: High-pressure shock-tube experiments and kinetics modeling

Toluene is often used as a fluorescent tracer for fuel concentration measurements, but without considering whether it affects the auto-ignition properties of the base fuel. We investigate the auto-ignition of pure toluene and its influence on the auto-ignition of n-heptane and iso-octane/air mixtures under engine-relevant conditions at typical tracer concentrations. Ignition delay times τ ign were measured behind reflected shock waves in mixtures with air at φ = 1.0 and 0.5 at p = 40 bar, over a temperature range of T = 700–1200 K and compared to numerical results using two different mechanisms. Based on the models, information is derived about the relative influence of toluene on τ ign on the base fuels as function of temperature. For typical toluene tracer concentrations ⩽10%, the ignition delay time τ ign changes by less than 10% in the relevant pressure and temperature range.

Solitary waves in mixtures of Bose gases confined in annular traps

A two-component Bose-Einstein condensate that is confined in a one-dimensional ring potential supports solitary-wave solutions, which we evaluate analytically in the limit of a large ring. The derived solutions are shown to be unique. The corresponding dispersion relation that generalizes the case of a single-component system shows interesting features.