Phase Stratification Research Articles

Giant vortex in a fast rotating holographic superfluid

In a holographic superfluid disk, when the rotational velocity is large enough, we find a giant vortex will form in the center of the system by merging several single charge vortices at some specific rotational velocity, with a phase stratification phenomenon for the order parameter. The formation of a giant vortex can be explained as there is not enough space for a standard vortex lattice. Keep increasing the rotational velocity the giant vortex will disappear and there will be an appearance of a superfluid ring. In the giant vortex region, the number of vortices measured from winding number and rotational velocity always satisfies the linear Feynman relation. However, when the superfluid ring starts to appear, the number of vortices in the disk will decrease though the rotational velocity is increasing, where most of the order parameter is suppressed.

Preparation and characterization of CaCl2·6H2O based binary inorganic eutectic system for low temperature thermal energy storage

As a cost-effective phase change thermal storage material, calcium chloride hexahydrate exhibits high heat capacity and holds tremendous promise in building energy savings. However, as a kind of hydrated salt, it also suffers from the issues of phase stratification and high degree of supercooling. Thus, present work has studied the inorganic mixtures of hydrated chloride salts and prepared a novel kind of binary eutectic phase change thermal storage material via replacing calcium chloride hexahydrate by various mass ration of magnesium chloride hexahydrate. The initial research results showed that both the components liquefied simultaneously during melting and the phase stratification of eutectic system could be effectively alleviated. Nucleating agent led to a good restrain to the supercooling of inorganic eutectic and the subcooling degree could be found as small as 1 °C.Meanwhile, the small amount of additive would little affect the melting point and enthalpy of fusion of energy storage material. The thermal cycling tests showed that our as-prepared eutectic salts exhibited good thermal reliability with fixed phase transition temperature and almost no diminution of enthalpy, which indicated that this novel binary eutectic material possessed excellent and stable performance suitable for heat storage in building energy savings.

Development of novel predictive equations for local flow asymmetry within control valves using a distribution parameter-based method under multiphase conditions

When designing control valves for multiphase applications using conventional valve sizing methodologies, it is assumed that the flow properties such as mixture density and volume fraction of phases are uniform throughout the valve trim. In reality, however, the properties may be different due to the difference in the gas and liquid densities as well as velocities within the valve which cause phase stratification. Furthermore, complex geometric effects can also cause phase non-uniformity within the valve. Current valve sizing methodologies are based on global parameters such as overall valve coefficient (Cv) which do not consider local phase non-uniformities within the trim during the design phase. Among these methodologies, it has previously been shown that the harmonised Cvs method is the most accurate method of sizing control valves under multiphase flow conditions across a wide range of flow regimes. The current study provides additional equations to be used with the harmonised Cvs method to ensure that the local flow quality compliance is achieved, which seems to be the major weakness of the existing method. In order to obtain local gas and liquid flow rates, pressure drops and phase fractions, well-validated computational fluid dynamics (CFD) simulations were carried out. Two valve opening positions of 60% and 100% were considered each with 5, 10, and 15% inlet air volume fractions to simulate real life conditions. The results show that there is severe non-uniformity in the local gas and liquid distributions within the valve trim. To quantify the phase non-uniformities observed, a distribution parameter (Co) based on the drift-flux model was used. The harmonised Cv method was used to calculate the local Cvs and the local equivalent area factor (Ψ). A new equation was derived that considers the local variation of the Ψ factor within the trim and which incorporates the distribution parameter. Based on the foregoing analyses, additional flow distribution equations have been proposed that when used with the harmonised Cvs valve design method for multiphase flow applications will ensure that the deviation in performance of the valve is minimal from the design conditions.

Transition of a binary solution into an inhomogeneous phase

ABSTRACT The thermodynamics of phase transitions of binary solutions into spatially inhomogeneous one-dimensional states is studied theoretically by taking into account nonlinear effects. It is shown that below the spinodal decomposition temperature there first occurs a phase stratification, and at a lower temperature, after reaching the maximum possible stratification, there occurs a second-order transition into the phase with concentration waves. The contribution of inhomogeneity to the entropy and heat capacity of phases is calculated and the phase diagram in the coordinates temperature – average concentration is constructed.

Liquid phase stratification induced by large temperature gradient during spinodal decomposition in Fe–Cr alloys: A phase-field study

The spinodal decomposition in Fe-40at.%Cr binary alloy is numerically studied by implementing the phase-field model based on Cahn–Hilliard equation. Effects of different temperature gradients on the solute distributing characteristics during the spinodal decomposition are investigated. In the system with a temperature gradient, the phase decomposition happens gradually from low temperature to high temperature, and a metastable stratification is achieved with specified temperature distribution. The critical temperature and corresponding temperature gradient are specified for the obvious solute stratification in the binary Fe–Cr alloy. The kinetics of the solute diffusion during the spinodal decomposition is discussed to reveal the liquid phase stratification induced by the anisotropic diffusion with the nonuniform temperature field. Therefore, tailoring the heat treatment during the spinodal decomposition in Fe–Cr binary alloys might be an efficient way to obtain nanometer coherent microstructures with specified solute distribution.

Microstructure and mechanical properties of the Ni-B-Ti composite coating on TA2 prepared by pre-plating and laser remelting

To improve the mechanical properties of TA2, a Ni-B-Ti composite coating on TA2 was synthesized by a two-step surface modification method. Firstly, a Ni-TiB2 pre-coating was electroplated on TA2; subsequently, the pre-coating was remelted by laser beam to synthesize the composite coating. Microstructure analysis reveals that: i) the composite coating shows the obvious phenomenon of phase stratification, TiNi and Ti2Ni phases occupy the top and bottom layer of the coating, respectively; ii) high aspect ratio TiB whiskers are formed in the composite coating; iii) good metallurgical bonding of the coating with the substrate is obtained. Nanoindentation tests indicate that the presence of TiB increased the hardness of the composite coating to as high as 9.07 GPa, which is about 3.4 times higher than that of TA2 substrate (2.08 GPa), and about 1.6 times higher than that of the coating without any reinforcement (3.51 GPa). The wear test results show that although the coatings have higher friction coefficients than TA2 substrate, the wear rate of the composite coating is 88.9% and 29.8% lower than that of TA2 substrate and the coating without any reinforcement respectively, indicating that the wear resistance of the coatings has been greatly improved, and the presence of ceramic reinforcement intensifies the increase of wear resistance of the coating.

Non-relaxor behaviour of low-frequency vibration spectra of relaxor ferroelectric PbCo1/3Nb2/3O3: evidences from Brillouin and Raman scattering measurements

This paper presents the results of studies of a low-frequency vibration spectrum of PbCo1/3Nb2/3O3 (PCN) relaxor ferroelectric crystal using the Brillouin and Raman light scattering in the temperature range from 80 to 750 K. The analysis of the temperature behaviour of the longitudinal acoustic phonon in Brillouin scattering spectra showed no anomalies in the vicinity of ‘diffuse phase transition’ (T m = 250 K) in PCN. Polarized Raman light scattering spectra were obtained in PCN over the entire temperature range studied. Analysis of low-frequency optical mode behaviour in PCN during temperature change also revealed no correlations with dielectric permeability anomaly in the vicinity of T m: softening of optical phonon at 43 cm−1 frequency in VV polarization is observed at 170 K. In the same temperature range, there are anomalies (a ‘narrow’ and weak component) in quasi-elastic light scattering (QELS) obtained in temperature behaviour with VH polarization in Raman spectra in PCN. A ‘wide’ and intense QELS component, obtained in Raman spectra with VV polarization, shows anomalies in the vicinity of T m. We associate the anomalies of optical phonons and QELS with structure distortions in the formation of phase stratification and the dynamics of polar nano-regions.

Effects of a Fluorinated Donor Polymer on the Morphology, Photophysics, and Performance of All-Polymer Solar Cells Based on Naphthalene Diimide-Arylene Copolymer Acceptors.

Naphthalene diimide (NDI)-biselenophene copolymer (PNDIBS), NDI-selenophene copolymer (PNDIS), and the fluorinated donor polymer PM6 were used to investigate how a fluorinated polymer component affects the morphology and performance of all-polymer solar cells (all-PSCs). Although the PM6:PNDIBS blend system exhibits a high open-circuit voltage (Voc = 0.925 V) and a desired low optical bandgap energy loss (Eloss = 0.475 eV), the overall power conversion efficiency (PCE) was 3.1%. In contrast, PM6:PNDIS blends combine a high Voc (0.967 V) with a high fill factor (FF = 0.70) to produce efficient all-PSCs with 9.1% PCE. Furthermore, the high-performance PM6:PNDIS all-PSCs could be fabricated by various solution processing approaches and at active layer thickness as high as 300 nm without compromising photovoltaic efficiency. The divergent photovoltaic properties of PNDIS and PNDIBS when paired respectively with PM6 are shown to originate from the starkly different blend morphologies and blend photophysics. Efficient PM6:PNDIS blend films were found to exhibit a vertical phase stratification along with lateral phase separation, while the molecular packing had a predominant face-on orientation. Bulk lateral phase separation with both face-on and edge-on molecular orientations featured in the poor-performing PM6:PNDIBS blend films. Enhanced charge photogeneration and suppressed geminate and bimolecular recombinations with 99% charge collection probability found in PM6:PNDIS blends strongly differ from the poor charge collection probability (66%) and high electron-hole pair recombination seen in PM6:PNDIBS. Our findings demonstrate that beyond the generally expected enhancement of Voc, a fluorinated polymer component in all-PSCs can also exert a positive or negative influence on photovoltaic performance via the blend morphology and blend photophysics.

Study on performance optimization of sodium sulfate decahydrate phase change energy storage materials

In this paper, sodium sulfate decahydrate (SSD) with a phase transition temperature of 32 °C was selected as the phase change energy storage material. However, SSD has the problems of large degree of supercooling, obvious phase stratification, and low thermal conductivity. To address these issues, a new SSD composite phase change energy storage material was synthesized by adding certain amounts of nucleating agents, thickeners, and high thermal conductivity agent to SSD. The results showed that when the addition of nucleating agent Na2B4O7·10H2O and thickener carboxymethyl cellulose (CMC) reached an optimal formulation ratio of SSD:Na2B4O7·10H2O:CMC = 100:5:3, the supercooling degree of the SSD composite phase change material was only 1.5 °C. Moreover, the heat release time of the phase change process was 25 min, and no phase stratification occurred. When expanded graphite with high thermal conductivity was added with the mass ratio of 9%, the effect on the supercooling degree of the SSD composite energy storage material was small, and the thermal conductivity increased by 3.9 times, reaching 2.13 W m−1 K−1. Differential scanning calorimetry method and step cooling curve method were used to test the decay rate of the thermal properties of the new composite phase change energy storage material, and the results were relatively close.

Preparation and thermal properties of sodium acetate trihydrate as a novel phase change material for energy storage

As phase change thermal storage material, sodium acetate trihydrate (CH3COONa·3H2O) exhibits large thermal capacity and holds tremendous promise. However, main problems of undercooling of solidification and phase stratification constrained its application in energy storage. Thus, present work prepared a new composite phase change thermal storage material of sodium acetate trihydrate mixed with nucleating agent and thickening agent. The initial research results showed that addition of an appropriate proportion of nucleating agent tetrasodium pyrophosphate decahydrate led to a good restrain to the undercooling of CH3COONa·3H2O. A certain amount of thickening agent polyacrylamide could also avoid the phenomenon of phase stratification and maintain the heat storage capacity of samples. Meanwhile, the additions little affected the melting point and would not decrease the enthalpy of fusion of sodium acetate trihydrate as established from Differential Scanning Calorimetry study, which indicated that this novel composite material possessed excellent and stable performance suitable for its application for thermal energy storage systems.

Modeling centrifugal, multiphase, turbulent flows with a mixture-averaged drift-flux algorithm

A two-dimensional, axisymmetric, mixture-averaged multiphase flow model, developed to predict solid phase stratification arising from flow acceleration, has been generalized for three dimensions. The model is exercised, with results compared to a multiphase model having separate conservation equations for the gas phase and the solid phase, and momentum exchange between phases handled by source terms. Both models are exercised with a constant particle-gas drag coefficient, characteristic of turbulent flow, and a variable, Reynolds-based coefficient. Modeling results are compared against video data acquired at the Applied Research Laboratory at Penn State University. Qualitative comparisons data show comparable results using both models.

Вариативность результирующего поля микродеформаций в кристаллах Zn-=SUB=-1-x-=/SUB=-V-=SUB=-x-=/SUB=-Se (0.01≤ x≤0.10)

AbstractA detailed neutronographic study of the bulk ZnSe crystals doped with vanadium up to the content commensurate with the solubility limit in a semiconductor matrix has been carried out for the first time at room temperature. The data that characterize nonuniformly-deformed states based on the cubic structural modification of the II–VI compounds are obtained. A simplified analysis of the broadening patterns of the diffraction profiles of main Bragg reflexes of the studied crystals shows that the resulting deformation covers macroscopic volumes, and the distribution of vanadium ions in the given cases may significantly deviate from the uniform distribution over volume. Relative to the initial cubic lattice, dominating trends towards symmetry changes preceding the phase stratification in the ZnSe crystals heavily doped with vanadium are revealed.

Variability of the resulting microdeformation field in the Zn1 – xV x Se crystals (0.01 ≤ x ≤ 0.10)

A detailed neutronographic study of the bulk ZnSe crystals doped with vanadium up to the content commensurate with the solubility limit in a semiconductor matrix has been carried out for the first time at room temperature. The data that characterize nonuniformly-deformed states based on the cubic structural modification of the II–VI compounds are obtained. A simplified analysis of the broadening patterns of the diffraction profiles of main Bragg reflexes of the studied crystals shows that the resulting deformation covers macroscopic volumes, and the distribution of vanadium ions in the given cases may significantly deviate from the uniform distribution over volume. Relative to the initial cubic lattice, dominating trends towards symmetry changes preceding the phase stratification in the ZnSe crystals heavily doped with vanadium are revealed.

A simple LC–MS/MS method facilitated by salting‐out assisted liquid–liquid extraction to simultaneously determine trans‐resveratrol and its glucuronide and sulfate conjugates in rat plasma and its application to pharmacokinetic assay

A simple LC-MS/MS method facilitated by salting-out assisted liquid-liquid extraction (SALLE) was applied to simultaneously investigate the pharmacokinetics of trans-resveratrol (Res) and its major glucuronide and sulfate conjugates in rat plasma. Acetonitrile-methanol (80:20, v/v) and ammonium acetate (10 mol L-1 ) were used as extractant and salting-out reagent to locate the target analytes in the supernatant after the aqueous and organic phase stratification, then the analytes were determined via gradient elution by LC-MS/MS in negative mode in a single run. The analytical method was validated with good selectivity, acceptable accuracy (>85%) and low variation of precision (<15%). SALLE showed better extraction efficiency of target glucuronide and sulfate conjugates (>80%). The method was successfully applied to determine Res and its four conjugated metabolites in rat after Res administration (intragastric, 50 mg kg-1 ; intravenous, 10 mg kg-1 ). The systemic exposures to Res conjugates were much higher than those to Res (AUC0-t , i.v., 7.43 μm h; p.o., 8.31 μm h); Res-3-O-β-d-glucuronide was the major metabolite (AUC0-t , i.v., 66.1 μm h; p.o., 333.4 μm h). The bioavailability of Res was estimated to be ~22.4%. The reproducible SALLE method simplified the sample preparation, drastically improved the accuracy of the concomitant assay and gave full consideration of extraction recovery to each target analyte in bio-samples.

Preparation research of novel composite phase change materials based on sodium acetate trihydrate

As phase change thermal storage material, sodium acetate trihydrate (SAT) exhibits certain problems such as large undercooling, stratification in phase change, and small thermal conductivity. To overcome these problems, in this study, a new composite phase change thermal storage material was prepared by adding a certain amount of nucleating agent, thickening agent, and high thermal conductivity medium. The research results showed that addition of an appropriate proportion of nucleating agent disodium phosphate dodecahydrate(DSP) and thickening agent carboxymethyl cellulose(CMC) or gelatin led to a good restrain to the undercooling of SAT, while maintaining the heat storage capacity of sample, and avoiding the phenomenon of phase stratification at room temperature cooling. A certain proportion of expanded graphite could also be used in combination with the thermal storage materials, which resulted in relatively small undercooling of the SAT thermal storage materials and a relatively large thermal conductivity.

Ultrasound Flow-Monitoring and Flow-Metering of Air–Oil–Water Three-Layer Pipe Flows

The combined use of ultrasound pulse-echo intensity and Doppler shift frequency is examined as a means to measure strong unsteady three-phase pipe flows of a gas and two liquids. With air, oil, and water as components of the fluid media, particular attention is given to analyze ultrasound responses at the air–oil and oil–water interfaces. Reciprocating slugging is generated inside a 55-mm-diameter circular pipe, of which edges oscillate vertically at a controlled frequency. We use an ultrasound velocity profiler to obtain the 1-D cross-sectional distributions of the instantaneous flow velocity at the sampling rate of 60 Hz. All the measurements are realized by a single ultrasound transducer located outside the pipe. Measurement accuracy is validated using a high-speed camera coupled with particle image velocimetry that is synchronized with the profiler. The results demonstrate that the proposed technique works properly in sensing both interfaces as well as in-phase flow velocity distributions. In addition, multiphase volume flow rates for the constituents are obtained by velocity profile integration assuming vertical phase stratification in an approximation.

METHOD OF REDUCING THE PRESSURE OF HIGH VISCOSITY OIL PUMPING IN OILFIELD PIPELINES

The article considers the results of pilot testing of successive oil and water pumping by centrifugal pumps. It was defined that at achieving the pumped production water cut of 80 % and more the effectiveness of pumping of water and oil by alternate batches is actually absent due to a fast phase stratification in the pipelines.

Effect of phase stratification into electro- and magnetotransport in heteroepitaxial La2/3Ca1/3MnO3 films

The La2/3Ca1/3MnO3 films 25-nm thick biaxially compressed in the substrate plane, grown quasi-coherently on the (001) surface of the LaAlO3 single crystal, were studied using laser vaporization. It was found that mechanical stresses acting during nucleation and growth promoted calcium enrichment of the cation sublattice of the manganite layer, which caused a decrease in its unit cell volume. Crystalline grains in manganite films were distinctly oriented along the normal to the substrate plane; the grain size in the substrate plane was within 20–40 nm, and the relative grain misorientation in the substrate plane did not exceed 0.2°. In zero magnetic field, the maximum in the temperature dependence of the resistivity ρ of La2/3Ca1/3MnO3 films was observed at temperatures close to 210 K. At T < 100 K and μ0H = 2 T, the magnetoresistance of manganite films was negative, weakly depended on temperature, its value was about–0.45. The magnetic field caused transformation of nonferromagnetic phase inclusions to ferromagnetic ones, which resulted in a decrease in the La2/3Ca1/3MnO3 film resistivity with increasing magnetic field. At low temperatures (T < 100 K), a hysteresis was observed in the dependences of the film resistivity on the magnetic field.

Accurate inference of local phased ancestry of modern admixed populations.

Population stratification is a growing concern in genetic-association studies. Averaged ancestry at the genome level (global ancestry) is insufficient for detecting the population substructures and correcting population stratifications in association studies. Local and phase stratification are needed for human genetic studies, but current technologies cannot be applied on the entire genome data due to various technical caveats. Here we developed a novel approach (aMAP, ancestry of Modern Admixed Populations) for inferring local phased ancestry. It took about 3 seconds on a desktop computer to finish a local ancestry analysis for each human genome with 1.4-million SNPs. This method also exhibits the scalability to larger datasets with respect to the number of SNPs, the number of samples, and the size of reference panels. It can detect the lack of the proxy of reference panels. The accuracy was 99.4%. The aMAP software has a capacity for analyzing 6-way admixed individuals. As the biomedical community continues to expand its efforts to increase the representation of diverse populations, and as the number of large whole-genome sequence datasets continues to grow rapidly, there is an increasing demand on rapid and accurate local ancestry analysis in genetics, pharmacogenomics, population genetics, and clinical diagnosis.

Fluctuation conductivity and pseudogap in [formula omitted] single crystals under pressure with transport current flowing under an angle 45° to the twin boundaries

The influence of hydrostatic pressure up to 0.48GPa on the fluctuation conductivity σ′(T) and pseudogap (PG) Δ∗(T) of slightly doped HoBa2Cu3O7-δ single crystals with Tc≈ 62K and δ≈0.35 is studied with current passing under an angle 45° to the twin boundaries. It is shown that near Tc the conductivity σ′(T) is well described by the Aslamasov–Larkin and Hikami–Larkin fluctuation theories demonstrating 3D–2D crossover with the increase of temperature. Δ∗(T) displays two representative maxima at Tmax1≈219K and Tmax2≈241K likely caused by the phase stratification of the single crystal. Pressure leads to disappearance of these maxima and linear Δ∗(T) with a positive gradient at high temperatures. Essentially, with the removal of pressure the maxima are restored. The comparison of our results with those obtained for YBa2Cu3O7-δ sheds more light on the role of magnetic subsystem in the high-Tc superconductors.