On Reflectionless Nature of Self-Consistent Multi-Soliton Solutions in Bogoliubov–de Gennes and Chiral Gross–Neveu Models

Recently the most general static self-consistent multi-soliton solutions in Bogoliubov–de Gennes and chiral Gross–Neveu systems were derived by the present authors (Takahashi and Nitta, Phys. Rev. Lett. 110:131601, 2013). Here we show a few complementary results, which were absent in our previous work. We prove directly from the gap equation that the self-consistent solutions need to have reflectionless potentials. We also give the self-consistent condition for the system consisting of only right-movers, which is more used in high-energy physics.     

Phase Diagram of a ^6Li–^{40}K Mixture in a Square Lattice

We calculate the mean-field phase diagram for an attractive interacting Fermi mixture of Lithium-6 ( \(^6Li\) ) and Potassium-40 ( \(^{40}K\) ) atoms in a two-dimensional optical lattice at finite temperatures. The polarization versus temperature diagrams show that there are three phases: the Sarma phase (in which the condensed pairs have zero net momentum), the Fulde–Ferrell (FF) phase (in which the pairs have non-zero net momentum), and the normal phase (in which the Helmholtz free energy is minimized for gapless phase). The zero polarization line is the conventional Bardeen–Cooper–Schrieffer state. The phase diagram contains a Lifshitz point. When the interaction strength is increased, the Lifshitz point moves toward the higher temperatures and larger polarizations. Moreover, contrary to the phase diagram of population-imbalanced \(^6Li\) Fermi gas, where the phase separation appears for low polarizations, we found the existence of a polarization window for the FF phase. This means that as soon as the system is polarized it goes into the FF phase if the temperature is low enough. This polarization window is larger for a majority of \(^{40}K\) atoms compared to the majority of \(^6Li\) atoms. We also find that the largest polarization that the system can support before it becomes a normal fluid is larger for majority of \(^6Li\) atoms.     

Phase Relations in the Reduction of Solid Solutions in the Co–Mn–Ti–O System

The hydrogen reduction of spinel solid solutions in the Co–Mn–Ti–O system was investigated by a static method. Six phase regions were identified in which the gas phase is in equilibrium with various combinations of -Co, TiO₂ (rutile), and solid solutions of variable composition: Co _A Mn _B Ti_{3 – A – B} O₄ (spinel), Co _m Mn_{2 – m} TiO₄ (spinel), Co _N Mn_{1 – N} TiO₃ (ilmenite), and Co _n Mn_{1 – n} O (NaCl). The equilibrium compositions of the solid solutions and the corresponding oxygen partial pressures were determined, and the general trends of the reduction of spinel solid solutions in the Co–Mn–Ti–O system were established.     

The Effect of Impurities on the Evolution of the Melting Front Analyzed in a Two-Dimensional Representation for the Eutectic Pt–C

The paper discusses the effect of two-front melting on the liquidus temperature of the eutectic Pt–C and the eutectic temperature of the system in its pure state. This influence factor has not been considered thus far in the uncertainty budget associated with the assignment of thermodynamic temperatures to the eutectics Co–C (1597.15 K), Pt–C (2011.05 K), and Re–C (2747.35 K), selected in the European Metrology Research Programme project Implementing the New Kelvin. For Pt–C, simulation of the effect of two-front melting on the melting process has been done before in a 1D analytical model, and this formed the starting point to the present study. In this study the melting process is analyzed by means of a 2D axisymmetrical finite-volume model. In the model, freezing and melting are considered for an impure ingot and for a pure ingot. As to the impure ingot, the impurity concentrations are the concentrations met in current practice of the realization of the high-temperature reference fixed point, but formulated in terms of an effective concentration and associated effective distribution coefficient \(k< 1\) , related to a Scheil fit to the melting curve at given melting conditions as measured for the eutectic Pt–C. Heat injection rates for melting varied from 15 000 W \({\cdot }\) m \(^{-2}\) down to 3000 W \({\cdot }\)  m \(^{-2}\) . In any case for the impure system, two melting fronts are showing up. For the pure system, only one melting front is generated, traveling from the outside of the ingot toward its inside.     

Numerical Analysis of the Jet‐Vortex Pattern of Flow in a Rectangular Trench

Numerical simulation of the vortex structure of threedimensional laminar flow in a rectangular trench of square cross section has been carried out on the basis of the finitevolume solution of steadystate Navier–Stokes equations.     

Numerical Investigation of the Hydrodynamics of a Twisted Flow in a Vortex Chamber Based on the Two‐Parameter Model of Turbulence

An approach based on solution of complete averaged Navier–Stokes equations in vortex chambers using a lowReynolds k– model of turbulence is considered. The problem is solved in the variables vortex, stream function, and circular component of the velocity. The method of oriented pseudoconvection is used for problems of the dynamics of twisted flows. The method allows one to retain second order of accuracy of convective terms and provide stability of the solution for rather high Reynolds numbers. The problem of formulation of boundary conditions of second order of accuracy for vorticity on a solid wall at angular points is considered. An analysis of the results obtained shows that numerical calculations within the framework of the considered model of turbulence agree with experimental data rather well.     

Solution of the Landau–Ginzburg Equations Using Lattice–Boltzmann

In this paper, we solve the time dependent Ginzburg–Landau (TDGL) equations in two dimensions, using Lattice–Boltzmann (LB) technique and the velocity discretization scheme D2Q9, for a square region with periodic boundary conditions. In order to obtain the solution, we use three distribution functions, each of them obeying the LB equation, and making a proper redefinition of the tensor Π ⁰, we find the (TDGL) equations. Further, we obtain the equilibrium distribution functions for the three LB equations, and then the solution for the components of the magnetic potential vector and the order parameter.     

Demonstration of a Broadband Photodetector Based on a Two-Dimensional Metal–Organic Framework

Metal–organic frameworks (MOFs) are emerging as an appealing class of highly tailorable electrically conducting materials with potential applications in optoelectronics. Yet, the realization of their proof-of-concept devices remains a daunting challenge, attributed to their poor electrical properties. Following recent work on a semiconducting Fe₃(THT)₂(NH₄)₃ (THT: 2,3,6,7,10,11-triphenylenehexathiol) 2D MOF with record-high mobility and band-like charge transport, here, an Fe₃(THT)₂(NH₄)₃ MOF-based photodetector operating in photoconductive mode capable of detecting a broad wavelength range from UV to NIR (400–1575 nm) is demonstrated. The narrow IR bandgap of the active layer (≈0.45 eV) constrains the performance of the photodetector at room temperature by band-to-band thermal excitation of charge carriers. At 77 K, the device performance is significantly improved; two orders of magnitude higher voltage responsivity, lower noise equivalent power, and higher specific detectivity of 7 × 10⁸ cm Hz^1/2 W⁻¹ are achieved under 785 nm excitation. These figures of merit are retained over the analyzed spectral region (400–1575 nm) and are commensurate to those obtained with the first demonstrations of graphene- and black-phosphorus-based photodetectors. This work demonstrates the feasibility of integrating conjugated MOFs as an active element into broadband photodetectors, thus bridging the gap between materials' synthesis and technological applications.     

Isobaric–Isothermal Polyhedra of Solid Solutions in the Li–Ni–Mn–Co–O System

Inorganic Materials - Isobaric–isothermal composition polyhedra of solid solutions existing in the Li–Ni–Mn–Co–O system at a temperature of 800°C and oxygen...     

Thermally Assisted Flux Creep of a Driven Vortex Lattice in Untwinned YBa2Cu3O7−δ Single Crystals

We have studied the driven vortex lattice in untwinned, clean YBa ₂ Cu ₃ O _7– single crystals, showing the first order (melting) transition T _m . At high enough driving currents (j 10 ³ A/cm ² , j j _c ) and temperatures T < T _m , a clear distinction is found between two different behaviours of the moving vortex lattice. The onset of dissipation is characterized by a noisy flux creep with a temperature independent activation energy U(j). At higher temperatures, the creep regime crosses over into a flux flow regime with linear resistivity. Apart from the dip in resistivity at T _m , associated with the peak effect and usually assigned to a softening of the shear modulus, the resistivity of the flowing flux lattice continuously extends into the vortex-liquid.     

Control of an Error of a Finite‐Difference Solution of the Heat‐Conduction Equation by the Conjugate Equation

The results of the calculation of temperature by the finitedifference method can be verified and the value of the remaining error can be estimated by the conjugate problem with a moderate expenditure of computer resources.     

Errors in measuring the directivity of a field by the method of a reference field in the range of 25–400 MHZ

Conclusions The cited data on error components in measuring the field-strength lead to the conclusions that the reference field (provided that the distances are measured with an error of ±2%) can be determined with an error of 6%, at frequencies up to 150 MHz, and of ±7% in the range from 150 to 400 MHz. The error in determining the resulting field-strength is smaller for small angles of elevation, since the beam reflected from the ground has a substantial effect on the value of the field.     

Effects of Dipole–Dipole Interaction on Vortex Motion in Bose–Einstein Condensates

In this paper, we study the dynamics of a single vortex and a corotating vortex pair in a quasi-two-dimensional Bose–Einstein condensate. The numerical results are obtained by solving the Gross–Pitaevskii equation. It is shown that the vortex motion is strongly dependent on the dipole–dipole interaction (DDI). For a single vortex, the periodic motion occurs with increasing dipole strength. The x-coordinate and y-coordinate as a function of time close to the shape of cosine wave and triangular wave when DDI is an isotropic repulsive interaction, respectively. In addition, it is evident that strong and anisotropic DDI makes the movement of vortex become fast and the amplitude enlarges. In the case of a corotating vortex pair, the dynamics is qualitatively consistent with a single vortex for weak dipole strength. Moreover, the periodic dynamics only appears for strong and anisotropic DDI and more rapid vortex motion is indicated.

     

Diameters of the Liquid–Liquid Coexistence Curves of Aqueous Solutions of Tetrahydrofuran

The diameters of the coexistence curves of aqueous solutions of tetrahydrofuran and two quasibinary, isotopically related mixtures near their lower consolute points are analyzed in terms of different composition variables including mole, mass, and volume fractions, using various possible definitions of the reduced temperature. A (1–) anomaly is observed for all choices of the temperature and concentration variables. In terms of mole fraction the diameters are free from a regular contribution as well as from a spurious 2 contribution arising from the inappropriate choice of the order parameter. The mass and volume fractions lead to an apparent symmetrization of the coexistence curve, but cause significant 2 contributions to the diameter that could mask the 1– anomaly. A reduced temperature that accounts for the presence of both upper and lower critical consolute points is found to be preferable, although the second critical point is 80 K away.     

Investigation of Thermal Resonance in Solution of a Two-Dimensional Singularly Perturbed Boundary-Value Problem of Nonstationary Heat Conduction with Nonlinear Boundary Conditions of the Stefan–Boltzmann Type

Data of the analytical-numerical parametric investigation of a singularly perturbed temperature field in the boundary layer of the side of a rectangle on which nonlinear boundary conditions of the Stefan–Boltzmann type are specified have been given. It has been established that a nonuniform initial temperature distribution of the Gaussian type causes the appearance of discontinuous traveling thermal waves in the corresponding boundary layer. A set of parameters for which the discontinuous traveling thermal waves, being superimposed, lead to a local nonlinear enhancement of the thermal field has been found. This effect can be considered as thermal resonance.     

Transport Properties of the Two-Dimensional Wigner Solid on Liquid Helium in the Presence of?a?High-Frequency Damaging Electric Field

Experimental studies of transport properties of the two-dimensional (2D) Wigner solid (WS) over a liquid helium surface are performed in the presence of an additional (damaging) high frequency electric field. Surface electrons are in the linear transport regime with regard to the driving electric field created by a potential of a small amplitude (about 1 mV) whose frequency varies in the range 3?C8 MHz. The damaging potential applied simultaneously has substantially higher amplitudes (30?C300 mV) and frequency 36 MHz. The evolution of resonance spectra of the coupled phonon-ripplon system, electron resistivity, and the effective mass of surface dimples caused by an increase in the damaging electric field amplitude is observed. At a certain damaging potential of about 300 mV the major electron-ripplon resonance is shown to disappear, which is accompanied by a sharp decrease in the dimple effective mass, and electron resistivity. Experimental data are explained by a theoretical model of high-frequency WS decoupling from surface dimples caused by the breakdown of the balance of forces applied to the WS.     

The Decay of a Quantized Vortex Ring and the Influence of Tracer Particles

We capture the decay of a quantized vortex ring in superfluid helium-4 by imaging particles trapped on the vortex core. The ring shrinks in time, providing direct evidence for the dissipation of energy in the superfluid. The ring with trapped particles collapses more slowly than predicted by an available theory, but the collapse rate can be predicted correctly if the trapping of the particles on the core is taken into account. We theoretically explore the conditions under which particles may be considered passive tracers of quantized vortices and estimate, in particular, that their dynamics on the large-scale is largely unaffected by the burden of trapped particles if the latter are spaced by more than ten particle diameters along the vortex core, at temperatures between 1.5 K and 2.1 K.     

Analysis of the Thinning Mechanism of an Aluminum Alloy in Friction Stir Welding Based on the Indirect Extrusion–Vortex Flow Filling Model

Strength of Materials - Different morphology and thinning cases of the weld zone of a 7022 aluminum alloy in friction stir welding were analyzed. Metal plastic flow processes in the contact zone...