Multiphase State Research Articles

High temperature phase transition and multiphase state formation in K3H(SO4)2 superprotonic conductor

EPR spectra of K3H(SO4)2 (KHS) doped with VO2+ or Mn2+ recorded at the temperature higher than about 440K are time-dependent and indicate on anomalously slow kinetics of the paraelastic/ferroelastic phase transition which takes place far below the temperature proposed by Baranov et al. (TII=463K). The formation of a multidomain state upon heating below TII is manifested as irreversible changes in EPR spectra after sample cooling to room temperature. The angular dependence of EPR spectra indicates that K3H(SO4)2 undergoes a ferroelastic phase transition between the point groups 2/m and 3¯m. The EPR spectra of KHS doped with VO2+ or Mn2+ are rapidly changed into the pseudo-powder ones after annealing above TI=480K. This points to a decomposition of the KHS crystal and a multiphase state formation at TI=480K, rather than at superprotonic phase transition, which is typical for the majority of compounds of the M3H(XO4)2 type.

Fe-Cr鋼の熱間加工における多相組織状態の流動応力に及ぼす温度履歴の影響

Fe-Cr鋼の熱間加工における多相組織状態の流動応力に及ぼす温度履歴の影響

Structure and properties of cast and splat-quenched high-entropy Al–Cu–Fe–Ni–Si alloys

The effect of the composition and cooling rate of the melt on the microhardness, phase composition, and fine-structure parameters of as-cast and splat-quenched (SQ) high-entropy (HE) Al–Cu–Fe–Ni–Si alloys was studied. The quenching was performed by conventional splat-cooling technique. The cooling rate was estimated to be ~106 K/s. Components of the studied HE alloys were selected taking into account both criteria for designing and estimating their phase composition, which are available in the literature and based on the calculations of the entropy and enthalpy of mixing, and the difference between atomic radii of components as well. According to X-ray diffraction data, the majority of studied Al–Cu–Fe–Ni–Si compositions are two-phase HE alloys, the structure of which consists of disordered solid solutions with bcc and fcc structures. At the same time, the Al0.5CuFeNi alloy is single-phase in terms of X-ray diffraction and has an fcc structure. The studied alloys in the as-cast state have a dendritic structure, whereas, after splat quenching, the uniform small-grained structure is formed. It was found that, as the volume fraction of bcc solid solution in the studied HE alloys increases, the microhardness increases; the as-cast HE Al–Cu–Fe–Ni–Si alloys are characterized by higher microhardness compared to that of splat-quenched alloys. This is likely due to the more equilibrium multiphase state of as-cast alloys.

Aluminum surface layer strengthening using intense pulsed beam radiation of substrate film system

The paper presents formation of the substrate film system (Zr-Ti-Cu/Al) by electric arc spraying of cathode having the appropriate composition. It is shown that the intense beam radiation of the substrate film system is accompanied by formation of the multi-phase state, the microhardness of which exceeds the one of pure A7 aluminum by ≈4.5 times.

Feasibility of Quantifying Arterial Cerebral Blood Volume Using Multiphase Alternate Ascending/Descending Directional Navigation (ALADDIN).

Arterial cerebral blood volume (aCBV) is associated with many physiologic and pathologic conditions. Recently, multiphase balanced steady state free precession (bSSFP) readout was introduced to measure labeled blood signals in the arterial compartment, based on the fact that signal difference between labeled and unlabeled blood decreases with the number of RF pulses that is affected by blood velocity. In this study, we evaluated the feasibility of a new 2D inter-slice bSSFP-based arterial spin labeling (ASL) technique termed, alternate ascending/descending directional navigation (ALADDIN), to quantify aCBV using multiphase acquisition in six healthy subjects. A new kinetic model considering bSSFP RF perturbations was proposed to describe the multiphase data and thus to quantify aCBV. Since the inter-slice time delay (TD) and gap affected the distribution of labeled blood spins in the arterial and tissue compartments, we performed the experiments with two TDs (0 and 500 ms) and two gaps (300% and 450% of slice thickness) to evaluate their roles in quantifying aCBV. Comparison studies using our technique and an existing method termed arterial volume using arterial spin tagging (AVAST) were also separately performed in five subjects. At 300% gap or 500-ms TD, significant tissue perfusion signals were demonstrated, while tissue perfusion signals were minimized and arterial signals were maximized at 450% gap and 0-ms TD. ALADDIN has an advantage of visualizing bi-directional flow effects (ascending/descending) in a single experiment. Labeling efficiency (α) of inter-slice blood flow effects could be measured in the superior sagittal sinus (SSS) (20.8±3.7%.) and was used for aCBV quantification. As a result of fitting to the proposed model, aCBV values in gray matter (1.4–2.3 mL/100 mL) were in good agreement with those from literature. Our technique showed high correlation with AVAST, especially when arterial signals were accentuated (i.e., when TD = 0 ms) (r = 0.53). The bi-directional perfusion imaging with multiphase ALADDIN approach can be an alternative to existing techniques for quantification of aCBV.

Heat transfer coefficient evolution of boron steel during hot forming die quenching

Based on a novel calculation model that considers microstructural changes and latent heat release, evolution of heat transfer coefficients of boron steel in different metallographic states during hot forming die quenching are investigated. Results demonstrate that the evolution of the coefficients in the different metallographic states is significantly different in each state. As blank temperature decreases, no evident fluctuations emerge in the austenitic state, a significant sharp increase followed by a gradual decrease is detected in the multiphase state during martensitic transformation and a slight decrease is observed in the martensitic state. A simulation model for temperature predicting is established by integrating the coefficient data with the finite element software ABAQUS. The numerical results showed good agreement with the experimental results.

Multi-Phase State Estimation Featuring Industrial-Grade Distribution Network Models

This paper proposes a novel implementation of a multiphase distribution network state estimator which employs industrial-grade modeling of power components and measurements. Unlike the classical voltage-based and current-based state estimators, this paper presents the implementation details of a constrained weighted least squares state calculation method that includes standard three-phase state estimation capabilities in addition to practical modeling requirements from the industry; these requirements comprise multiphase line configurations, unsymmetrical and incomplete transformer connections, power measurements on ${ \triangle }$ -connected loads, cumulative-type power measurements, line-to-line voltage magnitude measurements, and reversible line drop compensators. The enhanced modeling equips the estimator with capabilities that make it superior to a recently presented state-of-the-art distribution network load estimator that is currently used in real-life distribution management systems; comparative performance results demonstrate the advantage of the proposed estimator under practical measurement schemes.

Entropy-stabilized oxides.

Configurational disorder can be compositionally engineered into mixed oxide by populating a single sublattice with many distinct cations. The formulations promote novel and entropy-stabilized forms of crystalline matter where metal cations are incorporated in new ways. Here, through rigorous experiments, a simple thermodynamic model, and a five-component oxide formulation, we demonstrate beyond reasonable doubt that entropy predominates the thermodynamic landscape, and drives a reversible solid-state transformation between a multiphase and single-phase state. In the latter, cation distributions are proven to be random and homogeneous. The findings validate the hypothesis that deliberate configurational disorder provides an orthogonal strategy to imagine and discover new phases of crystalline matter and untapped opportunities for property engineering.

Structure of the surface layer of a wear-resistant coating after treatment with a high-intensity electron beam

Transmission electron microscopy is used to investigate the carbon extraction replicas of a wearresistant surface layer formed on Hardox 400 steel and its phase composition. The formation of a multiphase state is revealed, which includes a-iron grains and inclusions of carbide phases based on iron, chromium, and niobium. The surface layer is additionally treated by a high-intensity pulsed electron beam. The relative position of α-iron grains and particles of carbide phases is examined by the electron-diffraction microscopy of thin foils. The main carbide phase is iron carbide located as extended interlayers which separate a-iron grains. Nanoscale particles of chromium and niobium carbides are located at the interfaces of the a-iron–iron-carbide system and in the body of the a-iron grains. It is established that the surface layer is in the elastic-stress state during pulsed electron-beam treatment due to ultrahigh heating and cooling rates. It is shown that stress concentrators are the interphase boundaries between the carbide and the a-phase of iron.

Nanostructural States and Properties of the Surfacing Formed on Steel by a Cored Wire

Structural-phase states and mechanical properties of electric arc surfacing by an EnDOtec DO*33 cored wire on a Hardox 400 steel are investigated. Formation of the multiphase state of the surfacing represented by grains of α-iron and inclusions of carbide phases based on iron, chromium, and niobium is revealed by the methods of electron diffraction microscopy and x-ray phase analysis. The additional treatment of the surfacing by a high-intensity electron beam is performed. Mutual arrangement of the grains of α-iron and particles of carbide phases is investigated. It is found that the surfacing layer is in the elastic-stressed state formed as a result of super-high heating and cooling rates initiated by the pulsed electron beam treatment. It is shown that the microhardness of the surfaced layer remains constant with the depth down to 4 mm and exceeds by a factor of 2.4 the microhardness of the substrate; the wear resistance of the surfacing is 3 times higher than that of the steel, and the friction coefficient of the surfacing is half that of the steel.

Analysis of Barkhausen Noise Emissions and Magnetic Hysteresis in Multi-Phase Magnetic Materials

Ferromagnetic materials occur in single or multi-phase state and furthermore can undergo phase changes during processing or over time during service exposure. These phase changes can be attributed to physical processes or chemical reactions. In this paper, we examine the hysteresis and Barkhausen emission profiles of two-phase magnetic materials. Besides the shape of magnetic hysteresis curves that can reveal the presence of more than one phase, we demonstrate that the Barkhausen noise signatures for two-phase materials form two-peaks in their Barkhausen voltage profile. This can be used as a tool for non-destructive evaluation of ferromagnetic materials in industrial applications.

Structure and Properties of Wear-Resistant Weld Deposit Formed on Martensitic Steel Using the Electric-Arc Method

Studies on the structure and the phase composition of the deposited material were carried out using methods of X-ray structure analysis and electron diffraction microscopy of extract coal replicas and thin foils on steel Hardox 400. Formation of a multiphase state, represented by grains of α-iron and inclusions of carbide phases based on iron, chromium, and niobium, is revealed.

Magnetic, dielectric and transport characteristics of Ln2CoMnO6 (Ln=Nd and Sm) double perovskite ceramics

Magnetic and dielectric properties of Nd2CoMnO6 and Sm2CoMnO6 double perovskite ceramics have been investigated by comparing with those of La2CoMnO6 and Ln2NiMnO6 (Ln=La, Nd and Sm) ceramics. Differing from the single magnetic state of Ln2NiMnO6 (Ln=La, Nd and Sm) ceramics, both Nd2CoMnO6 and Sm2CoMnO6 are multiphase magnetic state with the monoclinic symmetry (space group P21/n). Ferromagnetic Curie point TC generally decreases with decreasing 〈Ni/Co–O–Mn〉 bond angles which depends on lanthanide ionic radius (RLn). This result indicates that the 〈Ni/Co–O–Mn〉 bond angle plays an important role in magnetic properties of Ln2MMnO6 (Ln=La, Nd and Sm, M=Ni and Co) ceramics. Meanwhile, only one relaxor-like dielectric peak with strong frequency dispersion is observed in Nd2CoMnO6 and Sm2CoMnO6 ceramics, which is similar with that of La2CoMnO6. The dielectric constant ε′ also decreases with decreasing RLn. Both magnetic and dielectric properties of Ln2CoMnO6 (Ln=La, Nd and Sm) ceramics have similar variation tendency with decreasing RLn, and have been correlated with cos2〈Co–O–Mn〉, demonstrating some coupling between magnetic and dielectric response. In addition, transport behaviors of the present ceramics conform to the three-dimensional variable-range hopping mechanism, which may be attributed to the phase separation nature.

105 Cardiac Mri Assessment Of Pulse Wave Velocity And Aortic Distensibility Following Treatment Of Aortic Stenosis

BackgroundArterial stiffness is an independent predictor of cardiovascular mortality and can be characterised by CMR measurement of aortic distensibility (AD) and pulse wave velocity (PWV).AimTo compare AD and PWV in...

The effect of high non-hydrostatic pressure on III-V semiconductors: zinc blende to wurtzite structural phase transition and multiphase generation

Raman scattering was employed to study structural phase transitions of InSb, GaSb and GaAs induced by highly non-hydrostatic pressures applied by mechanical impact, in which high compression/decompression rates are imposed to the sample. The results showed that is possible to produce several structural phases localized in different micrometric regions of the same sample: the zinc blende to possibly wurtzite structural phase transition and the generation of a multiphase state.

Numerical Simulation of Surfactant Flooding in Darcy Scale Flow

One of the methods that is used nowadays in enhanced oil recovery is surfactant flooding. The main mechanisms of surfactant flooding in reservoir consist of reduction of interfacial tension between water and oil and modification of rock wettability. In this study, the authors simulate the surfactant injection process in Darcy scale and in one-dimensional, multicomponent, multiphase state, and effects of physical phenomena such as adsorption, dispersion, convection, and exchange between fluids and solids are considered. Wettability alteration of reservoir rock due to presence of surfactant in injected fluid is detected in relative permeability and capillary pressure curves. First, the authors express the governing flow equations in the system and then discretize them. The variables consist of water and oil saturations, surfactant concentration in water phase, water and oil pressures, and velocities in each block. Second, the discretized equations are solved by IMPES method and pressure and saturation variables are calculated and after that, the concentration of surfactant in water phase is calculated. Finally, results of simulation are shown.

Arterial stiffness in severe aortic stenosis following Transcatheter Aortic Valve Implantation (TAVI) compared to Surgical Aortic Valve Replacement (SAVR)

Methods Forty-eight patients underwent identical paired 1.5T CMR scans (Intera, Philips or Avanto, Siemens). Brachial artery blood pressure was recorded by Dinamap (Critikon, Tampa, Fl, USA). Multi-phase steady state free precession (SSFP) cine imaging (50 phases) was acquired in a axial plane to the thoracic aorta at the level of the pulmonary artery bifurcation (Ascending aorta (AA) and proximal descending aorta (PDA)). AD (mmHg-1) was calculated following the contouring of the aortic region of interest, Figure 1A (QMass V7.5, Medis, The Netherlands), using the equation; (Aortic max lumen areaAortic min lumen area)/(Aortic min lumen area × [Systolic BP Diastolic BP]). Aortic PWV was assessed using identical planning with retrospectively gated, through plane, phase-contrast velocity encoded images (breathhold, single slice, 10 mm thick, 40 phases, typical FOV 350, RFOV 85, VENC 200 cm/s). Offline analysis was performed using previously published algorithms implemented in the in-house software PMI 0.4. The velocity encoded images of the AA and PDA were manually contoured to derive velocity-time curves. The distance (mm) between AA and PDA was measured manually from in-plane saggital-oblique SSFP images of the aortic arch. PWV (m/s) was calculated using the transit-time method (foot-foot delay, Figure 1B).

Modeling of a nonisothermal flow with regard for the dependence of plastic properties on the microstructure of a material

On the basis of experimental data for 35KhМА steel, we have generalized the unified Bodner–Partom model of flow to take into account the influence of the phase composition of the material on its plastic properties. To determine parameters responsible for the yield strength and ultimate strength of the steel in the multiphase state, the rule of mixtures has been used. The reliability of the developed model has been confirmed by comparing with experimental data and results of other authors.

The structure of the interstellar medium of star-forming galaxies

We present numerical methods for including stellar feedback in galaxy-scale simulations. We include heating by SNe (I & II), gas recycling and shock-heating from O-star & AGB winds, HII photoionization, and radiation pressure from stellar photons. The energetics and time-dependence are taken directly from stellar evolution models. We implement these in simulations with pc-scale resolution, modeling galaxies from SMC-like dwarfs and MW analogues to massive z~2 starburst disks. Absent feedback, gas cools and collapses without limit. With feedback, the ISM reaches a multi-phase steady state in which GMCs continuously form, disperse, and re-form. Our primary results include: (1) Star forming galaxies generically self-regulate at Toomre Q~1. Most of the volume is in diffuse hot gas with most of the mass in dense GMC complexes. The phase structure and gas mass at high densities are much more sensitive probes of stellar feedback physics than integrated quantities (Toomre Q or gas velocity dispersion). (2) Different feedback mechanisms act on different scales: radiation & HII pressure are critical to prevent runaway collapse of dense gas in GMCs. SNe and stellar winds dominate the dynamics of volume-filling hot gas; however this primarily vents out of the disk. (3) The galaxy-averaged SFR is determined by feedback. For given feedback efficiency, restricting star formation to molecular gas or modifying the cooling function has little effect; but changing feedback mechanisms directly translates to shifts off the Kennicutt-Schmidt relation. (4) Self-gravity leads to marginally-bound GMCs with an ~M^-2 mass function with a cutoff at the Jeans mass; they live a few dynamical times before being disrupted by stellar feedback and turn ~1-10% of their mass into stars (increasing from dwarfs through starburst galaxies). Low-mass GMCs are preferentially unbound.

Features of the dynamics of the heavy bubble magma state in explosive volcanic eruptions

The explosive eruption of a volcano that occurs when a volcanic canal is suddenly depressurized is one of the mysterious phenomena of nature, the mechanism of which is associated with the sudden decompression of a high-pressure magma containing dissolved gas and microcrystallites and with its transition to a multiphase state. With the obvious lack of the possibility to directly investigate these processes, the problem of experimental and numerical modeling, and creation of mathematical models that would allow describing the state of magma during various stages of eruption with a certain degree of adequacy are becoming topical. A model combining systems of equations of the mechanics of multiphase media is proposed. The model is formulated on the basis of the modified Iordansky–Kogarko–van Wijngaarden model with the Navier-Stokes equation for the variable viscosity, and the full range of kinetic relationships, including spontaneous nucleation and saturation dynamics of magma with cavitation nuclei. An analysis of a pre-explosive state of a number of volcanoes was carried out, which showed that the structural features of explosive volcanoes are analogous to the schemes of hydrodynamic shock tubes (UT), such as Glass-Heuckroth. Experimental modeling of the flow structure demonstrates the probability of the formation of the projectile regime as a consequence of coalescence of bubbles in the flow. A physical model of combined explosive volcanic eruptions is proposed; the process of formation in the magma flux of an independent flow of crystalline clusters (magmatic ”bombs“) moving with respect to the flow of cavitating magma at a much higher rate is experimentally studied.