Mutual Energy Transfer Research Articles

Non-equilibrium Thermodynamics of Rayleigh–Taylor Instability

Here, the fundamental problem of Rayleigh–Taylor instability (RTI) is studied by direct numerical simulation (DNS), where the two air masses at different temperatures, kept apart initially by a non-conducting horizontal interface in a 2D box, are allowed to mix. Upon removal of the partition, mixing is controlled by RTI, apart from mutual mass, momentum, and energy transfer. To accentuate the instability, the top chamber is filled with the heavier (lower temperature) air, which rests atop the chamber containing lighter air. The partition is positioned initially at mid-height of the box. As the fluid dynamical system considered is completely isolated from outside, the DNS results obtained without using Boussinesq approximation will enable one to study non-equilibrium thermodynamics of a finite reservoir undergoing strong irreversible processes. The barrier is removed impulsively, triggering baroclinic instability by non-alignment of density, and pressure gradient by ambient disturbances via the sharp discontinuity at the interface. Adopted DNS method has dispersion relation preservation properties with neutral stability and does not require any external initial perturbations. The complete inhomogeneous problem with non-periodic, no-slip boundary conditions is studied by solving compressible Navier–Stokes equation, without the Boussinesq approximation. This is important as the temperature difference between the two air masses considered is high enough ( $$\Delta T = 70$$ K) to invalidate Boussinesq approximation. We discuss non-equilibrium thermodynamical aspects of RTI with the help of numerical results for density, vorticity, entropy, energy, and enstrophy.

Precise control and measurement of solid-liquid interfacial temperature and viscosity using dual-beam femtosecond optical tweezers in the condensed phase.

We present a novel method of microrheology based on femtosecond optical tweezers, which in turn enables us to directly measure and control in situ temperature at microscale volumes at the solid-liquid interface. A noninvasive pulsed 780 nm trapped bead spontaneously responds to changes in its environment induced by a co-propagating 1560 nm pulsed laser due to mutual energy transfer between the solvent molecules and the trapped bead. Strong absorption of the hydroxyl group by the 1560 nm laser creates local heating in individual and binary mixtures of water and alcohols. "Hot Brownian motion" of the trapped polystyrene bead is reflected in the corner frequency deduced from the power spectrum. Changes in corner frequency values enable us to calculate the viscosity as well as temperature at the solid-liquid interface. We show that these experimental results can also be theoretically ratified.

The effects of Ho3+ and Pr3+ ions on the spectroscopic properties of Er3+ doped SrGdGa3O7 crystals used in mid-infrared lasers

Ho3+ and Pr3+ ions were introduced into Er3+ : SrGdGa3O7 crystal, respectively, for enhanced 2.7 μm emissions. The effects of Ho3+ and Pr3+ on the spectroscopic properties and mutual energy transfer mechanisms were investigated. It is found that the introductions of Ho3+ and Pr3+ are helpful to achieve enhanced mid-infrared emissions and reduced near-infrared emissions. The up-conversion emission in Er3+/Ho3+ : SrGdGa3O7 crystal was stronger than that in Er3+ : SrGdGa3O7 crystal, while that in Er3+/Pr3+ : SrGdGa3O7 crystal was decreased. Introducing Ho3+ and Pr3+ depopulated the lower laser lever through energy transfer and thus reduced the fluorescence lifetime of Er3+ : 4I13/2 in Er3+/Ho3+ : SrGdGa3O7 and Er3+/Pr3+ : SrGdGa3O7 crystals to 1/2 and 1/10 of that in Er3+ : SrGdGa3O7 crystal without significantly affecting the fluorescence lifetime of the upper laser level Er3+ : 4I11/2, which greatly reduces the self-saturation problem. However, with reduced up-conversion emission and a weaker self-termination effect, Pr3+ is a more appropriate sensitizer than Ho3+ for Er3+ in this crystal. All the results imply that Er3+/Pr3+ : SrGdGa3O7 crystal could act as a potential gain media for an enhanced 2.7 μm MIR laser.

The head change coefficient for branched flows: Why “losses” due to junctions can be negative

In this study, the phenomenon of negative “loss”-coefficients reported in various studies about turbulent branched flows through combining junctions is investigated systematically. It turns out, that the “loss” for one branch of a junction and its adjacent ducts only in parts is due to devaluation of mechanical energy, which would be a real loss, so that the term energy change is more appropriate. The other part of the energy change which is not due to a loss is due to a mutual energy transfer between the two partial flows. As a consequence, non-dimensional coefficients should be called energy change coefficients rather than head loss coefficients whenever branching of flows occurs. Furthermore, a method is introduced by which losses and the energy transfer are determined directly in the flow field. The field values allow a quantification and visualization of the local loss and work transfer, while their integral values can be used to quantify the individual contributions of losses and energy transfer within the energy change of a flow through a junction.

Correction: Corrigendum: Tunable negligible-loss energy transfer between dipolar-coupled magnetic disks by stimulated vortex gyration

A wide variety of coupled harmonic oscillators exist in nature. Coupling between different oscillators allows for the possibility of mutual energy transfer between them and the information-signal propagation. Low-energy input signals and their transport with negligible energy loss are the key technological factors in the design of information-signal processing devices. Here, utilizing the concept of coupled oscillators, we experimentally demonstrated a robust new mechanism for energy transfer between spatially separated dipolar-coupled magnetic disks - stimulated vortex gyration. Direct experimental evidence was obtained by a state-of-the-art experimental time-resolved soft X-ray microscopy probe. The rate of energy transfer from one disk to the other was deduced from the two normal modes' frequency splitting caused by dipolar interaction. This mechanism provides the advantages of tunable energy transfer rates, low-power input signals and negligible energy loss in the case of negligible intrinsic damping. Coupled vortex-state disks might be implemented in applications for information-signal processing.

Interaction and dispersion of waveguide modes in an optical fiber with microirregularities of the core surface

A self-consistent linear model is proposed for the transformation of the average intensity of the mode spectrum I(z) of the waveguide field in a multimode optical fiber with a stepped refractive index profile and the core having a rough surface. The model is based on the concept of the intermodal dispersion matrix of an elementary segment of the fiber, ∆, whose elements characterize the mutual transfer of energy between the waveguide modes, as well as their conversion to radiation modes on the specified interval. On this basis, the features of the transformation of the mode spectrum I(z) in a multimode optical fiber with a stepped refractive index profile are considered that is due to the effects of multiple dispersion of the signal by the stochastic irregularities of the duct. The effect of self-filtering of I(z) is described that results in the formation of a stable (normalized) distribution I*. The features of the normalization of the radiative damping of a group of modes I i (z) in an optical fiber are considered.

Tunable negligible-loss energy transfer between dipolar-coupled magnetic disks by stimulated vortex gyration

A wide variety of coupled harmonic oscillators exist in nature. Coupling between different oscillators allows for the possibility of mutual energy transfer between them and the information-signal propagation. Low-energy input signals and their transport with negligible energy loss are the key technological factors in the design of information-signal processing devices. Here, utilizing the concept of coupled oscillators, we experimentally demonstrated a robust new mechanism for energy transfer between spatially separated dipolar-coupled magnetic disks - stimulated vortex gyration. Direct experimental evidence was obtained by a state-of-the-art experimental time-resolved soft X-ray microscopy probe. The rate of energy transfer from one disk to the other was deduced from the two normal modes' frequency splitting caused by dipolar interaction. This mechanism provides the advantages of tunable energy transfer rates, low-power input signals and negligible energy loss in the case of negligible intrinsic damping. Coupled vortex-state disks might be implemented in applications for information-signal processing.

Spin-relaxation Process of Excited Triplet States of Ir(ppy)3

The phosphorescence intensities of the green phosphor, fac tris(2-phenylpyridine) iridium [Ir(ppy)3], in a polymethylmethacrylate [PMMA] host matrix are independent of temperature, while the phosphorescence lifetimes increase significantly at temperatures below T ∼ 50 K. In this paper, to rationalize the characteristic temperature dependence of the transient phosphorescence of Ir(ppy33, we propose a model where the triplet excited states split by spin-orbital interaction, forming three levels in which mutual energy transfer between the sub-levels of triplet states occurs. We discuss the validity of this numerical model by comparing with the experimental result of the transient phosphorescence in a PMMA host matrix and demonstrate that the model well explains the characteristic temperature dependence.

Phosphorescence Decay Mechanism of Ir(ppy)3 in a Solid Matrix

The phosphorescence intensities of the green phosphor fac tris(2-phenylpyridine) iridium [Ir(ppy)3] in a polymethylmethacrylate [PMMA] host matrix are independent of temperature, while the phosphorescence lifetimes increase significantly at temperatures below T ∼ 50 K. In this paper, we propose a phosphorescence decay mechanism for Ir(ppy)3 to rationalize the characteristic temperature dependence of the transient phosphorescence. By comparing a numerical model with the experimental data, we demonstrate that mutual energy transfer between the sub-levels of triplet states can explain the characteristic temperature dependence.

CFD analysis of spray propagation and evaporation including wall film formation and spray/film interactions

Abstract Addressing the numerical simulation of complex two-phase flows in gas turbine combustors, this study features a comprehensive approach to the coupled solution of the interacting flow fields of the gas phase, evaporating fuel spray and evaporating, shear-driven fuel wall film. The gas flow and wall-film flow are described in Eulerian coordinates and are both calculated in the same computational unit. A second, separate program is based on Lagrangian particle tracking to model spray dispersion and evaporation. To account for interaction effects, an iterative procedure is applied considering mutual mass, momentum and energy transfer between the three flow regimes. For a realistic modeling of spray/wall and spray/film interaction, the droplet-trajectory computation comprises a set of droplet-impact models covering a broad range of impact conditions. The results of a two-phase flow simulation in a schematic LPP combustor premix duct demonstrate the effects of phase interaction as well as spray/wall and spray/film interaction.

Strings in Anisotropic Cosmological Spacetimes

We present a general method to reduce the full set of equations of motion and constraints in the conformal gauge for the bosonic string moving in a four-dimensional curved spacetime manifold with two spacelike Killing vector fields, to a set of six coupled first-order partial differential equations in six unknown functions. By an explicit transformation the constraints are solved identically and one ends up with only the equations of motion and integrability conditions. We apply the method to the family of inhomogeneous, non-singular cosmological models of Senovilla possessing two spacelike Killing vector fields, and show how one can extract classes of special exact solutions, even for this highly complicated metric. For the case of the same family of exact cosmological spacetimes, we give an explicit example, not previously encountered, where we have a direct and mutual transfer of energy between the string and the gravitational field.

Luminescence of Pb2+ and energy transfer from Pb2+ to rare earth ions in silicate oxyapatites

AbstractThe Pb2+ luminescence in a series of silicate oxyapatites Me2(Y, Gd)8(SiO4)6O2, Me4Y6(SiO4)6O(Me = Mg, Ca, Sr) is reported and discussed in relation to the crystal structure. The maximum wavelengths of the excitation (1S03P1) and emission (3P1−1S0) bands of Pb2+ are independent of the Me:Y ratio (2:8 or 4:6), but they have lower energies in MgY‐oxyapatites than in CaY‐ and SrY‐oxyapatites. The Stokes shift of Pb2+ luminescence amounts to 11100 to 11400 cm−1, which does not depend strongly on the host composition. There exists a mutual energy transfer between Pb2+ and Gd2+ in Sr2Gd8(SiO4)6O2. At last, the dependence of the energy transfer efficiency of Pb2+−Sm3+, Tb3+, Dy3+ in Sr2(La, Gd)8(SiO4)6O2 and Ca2(Y, Gd)8(SiO4)6O2 on their doping concentrations was studied in more detail.

Fluorescence study of the three tryptophan residues of the pore-forming domain of colicin A using multifrequency phase fluorometry.

We have identified the steady-state and time-resolved fluorescence of the three tryptophan residues (Trp-86, Trp-130, and Trp-140) of the pore-forming domain of colicin A using site-directed mutagenesis in order to construct two- and one-tryptophan-containing mutant proteins. Fluorescence lifetimes were measured via multifrequency phase fluorometry. The fluorescence of the pore-forming domain of colicin A is dominated by Trp-140 which contributes almost 53% to the fluorescence intensity. Mutation of Trp-140 results in a decrease in fluorescence quantum yield and average lifetime. Colicin A wild-type and all mutant proteins display multiple lifetimes which belong to three different lifetime classes: 0.38-0.57 ns for tau 1, 1.6-1.87 ns for tau 2, and 3.6-4.41 ns for tau 3 at pH 5. At pH 7, the three classes are 0.64-0.89 ns for tau 1, 2.01-2.19 ns for tau 2, and 4.23-4.94 ns for tau 3. This pH effect influences all the lifetimes and must be attributed to a general conformational change. In wild-type colicin A, tau 3 originates mainly from Trp-140 while Trp-86 and Trp-130 both provide a major contribution to tau 2. The pH dependence of the fluorescence intensity gives rise to a pKa of 5.2. The different lifetime components of two of the three single-tryptophan-containing mutants show different quenching properties toward acrylamide, indicating that each lifetime is coupled to a different microenvironment. The linear combination of the lifetimes of the single tryptophans into pairs simulates very well the behavior of the two-tryptophan-containing mutants except for one, the mutant containing Trp-86 and Trp-130. The lifetimes of the wild-type protein can only be obtained by the linear combination of the lifetimes from the mutant containing the tryptophan pair Trp-86/Trp-130 and the mutant containing Trp-140. Mutual energy transfer between Trp-86 and Trp-130 is assumed to be the explanation of this deviation since the mutant proteins display no structural or dynamic aberrances. The calculated energy transfer efficiency amounts to 65% for energy transfer from Trp-86 to Trp-130 and 21% for the reverse transfer and is in agreement with our measurements.

Finite-Difference Modeling of Borehole Resonances

Abstract Most attempts at numerical synthesis of vertical seismic profiles ( VSPs) do not explicitly include the interaction of seismic waves with the borehole, the casing, or instruments located within the hole. Thus, borehole resonances, a type of tube wave that is prominent in many real VSPs, are typically missing in synthetic VSPs. Characteristics of generation and propagation of borehole resonances can be studied by including details of the borehole environment in acoustic and elastic finite-difference simulations. Specific models presented incorporate a variety of hole diameters, cased and uncased holes, the presence of geophones within a hole, a variety of source positions, the effects of local changes in hole diameter and lithology, and the mutual interaction of the response of two neighboring wells. The main conclusion is that the hole and the medium should be considered as a single coupled system as there is a continuous mutual transfer of energy between them.

Luminescence and mutual energy transfer between erbium(III) and manganese(II) in fluoride glasses

Glasses of mixed fluorides, contrary to the glasses formed by more conventional anions(such as silicate, phosphate and borate) have much greater propensity for luminescence of the excited J-levels of trivalent lanthanides. A major reason is the low vibrational frequencies (attenuating the competing non-radiative de-excitation). The composition ranges of stable glasses are quite narrow, and found pragmatically. They are wider in the presence of small amounts of Al(PO 3) 3 but this decreases the life-times of Er(III). The two main types used for spectroscopic studies contain GaF 3 PbF 2 and ZnF 2 (which can be replaced by MnF 2); or ZrF 4 and BaF 2. Here, incorporated erbium(III) is discussed. The narrow emission bands at 550 nm( 4S 3/2) and 668 nm( 4F 9/2) have life-times above 0.05 ms. Energy transfer from the former level to the lowest quartet level of manganese(II), and back transfer of energy stored in Mn(II) to Er(III) providing long-lived components of the 668 nm emission, are also described. Such fluoride glasses containing Nd(III) or Er(III) may be important for lasers, fiber optics communication, and luminescent solar concentrators based on total internal reflection of emitted photons travelling to the edge of a transparent plate.

An energy transfer equilibrium between two identical copies of a ribosome-bound fluorescent transfer RNA analogue: Implications for the possible structure of codon-anticodon complexes

When yeast tRNA Pf Phe, a derivative of tRNA Phe in which proflavine replaces the Y base, is bound simultaneously to both the peptidyl and aminoacyl sites of a 70 S Escherichia coli ribosome, there is a rapid mutual energy transfer between the two bound tRNAs. Analysis of this energy transfer yields an upper limit for the proflavine-proflavine distance of 20 Å. It also allows an unequivocal measurement of the emission spectrum of tRNA Pf Phe bound at the aminoacyl site. In the presence of message this spectrum is very different from that seen in the peptidyl site, implying that in the two sites the hypermodified bases exist in significantly different environments. The rapid energy transfer leads to some loss of fluorescence anisotropy. This can be analyzed to obtain an estimate of the angle between the two proflavines: 28 ° ± 10 ° or 152 ° ± 10 °. Taken together all of these results place severe constraints on possible models of codon-anticodon complexes. The mutual energy transfer seen and analyzed on the ribosome is a convenient aspect of fluorescence spectroscopy, and it is one that should see broad application where multiple copies of a fluorescent ligand interact on a macromolecular substrate.

Ce3+ Luminescence in Hexagonal Aluminates Containing Large Divalent or Trivalent Cations

By analogy with earlier studies on Eu2+ phosphors the luminescence of the Ce3+‐doped hexagonal aluminates, containing large, divalent or trivalent cations, was also studied in relation to the crystal structure of the host lattices. The u.v. band ascribed to the luminescence of Ce3+ ions is found at a relatively short wavelength in the magnetoplumbites Ca‐, Sr‐, and aluminate: Ce and at a relatively long wavelength in the β‐aluminas Ba‐ and aluminate. The distorted magnetoplumbites which include La‐ and aluminate and Ce‐ and aluminates themselves occupy an intermediate position in between the above‐mentioned groups. The existence of various types of host lattices is also reflected in the shape and position of the excitation spectra of the Ce3+ luminescence. Differences in bond strength between Ce3+ ions and its surrounding oxygen ions, however, complicate the discussion of the position of the excited 5d levels of the Ce3+ ion. Apart from the u.v. band, a blue luminescence band was found in several Ce‐activated aluminates. This band occurs in phosphors where oxygen ions are thought to have partially replaced the large cations of the host lattice and is ascribed to Ce‐O associates. Next to direct excitation of these centers, the u.v.‐emitting Ce3+ ions transfer part of their energy of the associates. If Mg2+ ions are present in the lattice, the oxygen ions at large cation sites seem to be “screened” and no blue luminescence is found. The quantum efficiency of most Ce‐activated aluminate phosphors is 50–70%. Due to ineffective mutual energy transfer between u.v. emitting Ce3+ ions and between Ce‐O associates no concentration quenching occurs in the systems considered. For the same reason the influence of the preparation method on the luminescence properties is generally less drastic than that of the corresponding Eu2+ phosphors.

Statistical Characteristics of the Atmospheric Disturbances

The periods of the atmospheric phenomena are supposed to differ from each other according to their scales, e. g., there may be a positive correlation between the magnitude of scales and length of periods in the atmosphere.The purpose of this paper is to investigate the statistical characteristics of the atmospheric disturbances of various scales and further to find out the mechanism of mutual transfer of vorticity and kinetic energy of mean flow and disturbances. If we succeed in this attempt, the results obtained from are expected to be useful also for such a forecasting problem as numerical prediction. In the present study the following characteristics of the atmospheric phenomena are dealt with, that is, (1) the so-called “width of perturbations ”, (2) the stationarity of variations, (3) the spectral distribution of pressure and (4) the kinetic energy spectra, employing the 36 term harmonic coefficients calculated from the values of 500 mb level along 50°N, 45°N and 30°N latitude circles in the Historical Weather Maps. The periods subjected to analysis are January (1946,1949), May, June and July (1951).The results obtained are as follows. First the component waves of disturbances can be classified into three (or four) parts. Then let n and F(n) denote wave number and spectral function respectively. The motion of waves of small wave number is non-isotropic, oscillatory and moreover F(n)=const. Meanwhile the motion of waves of great wave number is isotropic, progressive and F(n) ∝ n-7/3 as expected. Further it may be concluded that the mean flow and the component waves of n=1,2 belong to the former and component waves of n=≤6 belong to the latter region. Accordingly the components of n=3, 4, 5 are considered to constitute the region of middle wave number in our case.Next, the energy spectra indicate three sources of kinetic energy in the atmosphere, i. e., mean flow, component wave of n=3 and of n=6 or 7.