Pressure Dependence Of Properties Research Articles

Measurement of Radiation Heat Transfer within Porous Material

This paper deals with heat transmission through porous material subjecting to high levels of radiation. In depth absorption of radiant energy would lead to increased in-depth temperature which would cause a thicker pyrolysis zone, that lead to uncontrolled material spallation and failure. Analytical treatments of such problems had been attempted by many researchers [, approaches vary from theoretical principles to engineering correlations, but unfortunately no appropriate temperature and pressure-dependent material properties are available which are needed for their estimations, and extensive experimental measurements would still be required for their evaluations. This paper describes an experimental system developed for direct measurement of radiation transport parameters which is developed with reference to the experimental setups of previous investigators.

Structural, elastic, electronic and optical properties of layered alkaline-earth halofluoride scintillators

A systematic investigation of structural properties at ambient as well as at high pressure has been carried out for layered scintillators CaClF, CaBrF, SrClF, SrBrF and SrIF based on density functional theory. Semi-empirical dispersion correction scheme has been used to account for the van der Waals interactions and the obtained results are in good agreement with experimental data. The pressure-dependent structural and elastic properties reveal that the c-axis is more compressible than the a-axis (C ) in all these materials due to weakly bonded layers stacked along the c-axis. In addition, the electronic structure and optical properties of these materials are calculated using Tran-Blaha-modified Becke-Johnson (TB-mBJ) potential. Among the five investigated compounds which are structurally anisotropic, a weak optical anisotropy is found in CaClF and SrClF and strong optical anisotropy in CaBrF, SrBrF and SrIF. The present study suggests that unlike alkaline-earth dihalides which are fast scintillators, these materials can act as storage phosphors and the possible reason is speculated from the band structure calculations.

Numerical modeling of steam injection in heavy oil reservoirs

In this communication, a three-dimensional, three-phase numerical model is presented for simulation of steam injection in heavy oil reservoirs. Formulation details, numerical solution method, and computational results are presented. The model includes the effects of three-phase relative permeability, capillary pressure, and temperature and pressure-dependent fluid properties. Interphase mass transfer of water-steam is allowed, but the oil is assumed nonvolatile and the hydrocarbon gas is insoluble in liquid phases. The three-phase mass balance and the energy balance equations are solved simultaneously using finite difference method. Some steam injection laboratory data are used for studying the accuracy of this model. Comprehensive and comparative studies together with extensive sensitivity analysis among various important parameters are conducted to understand steam injection performance in the heavy oil reservoir. This work indicates that steam injection can improve oil recovery from almost zero up to nearly 60% during a fixed period of time. In addition, it shows that only 30% of OOIP can be recovered by hot water injection method. The results demonstrate that there is an optimum time for oil production that is determined according to the flow of oil production and steam–oil ratio (SOR).

Seismic Response of Squat Rigid Bodies on Inclined Planes with Rigid Boundaries

AbstractA planar rigid-body dynamics formulation describing the seismic behavior of a squat rectangular rigid body initially resting on an inclined rigid plane is presented. The downslope motion of the body is limited by a rigid boundary perpendicular to the inclined plane. This type of problem appears in several practical applications. Coulomb and hysteretic friction with velocity- and pressure-dependent properties are considered at the body-to-ground interface. The weaknesses of hysteretic friction models incorporating static and kinetic velocity-dependent components are identified and remedied. Impact models for collision of the body with the rigid boundary and the inclined plane are also derived. The formulation is embodied in a numerical model through a dedicated computer code. A comparative study is conducted to demonstrate the effects on the body response of major model characteristics, including the rigid boundary; inclination angle; Coulomb, hysteretic, and combined Coulomb-hysteretic friction; a...

Patch-Clamp Characterization of the MscS-like Mechanosensitive Channel from Silicibacter pomeroyi

Based on sequence similarity, the sp7 gene product, MscSP, of the sulfur-compound-decomposing Gram-negative marine bacterium Silicibacter pomeroyi belongs to the family of MscS-type mechanosensitive channels. To investigate MscSP channel properties, we measured its response to membrane tension using the patch-clamp technique on either a heterologous expression system using giant spheroplasts of MJF465 Escherichia coli strain (devoid of mechanosensitive channels MscL, MscS, and MscK), or on purified MscSP protein reconstituted in azolectin liposomes. These experiments showed typical pressure-dependent gating properties of a stretch-activated channel with a current/voltage plot indicating a rectifying behavior and weak preference for anions similar to the MscS channel of E. coli. However, the MscSP channel exhibited functional differences with respect to conductance and desensitization behavior, with the most striking difference between the two channels being the lack of inactivation in MscSP compared with MscS. This seems to result from the fact that although MscSP has a Gly in an equivalent position to MscS (G113), a position that is critical for inactivation, MscSP has a Glu residue instead of an Asn in a position that was recently shown to allosterically influence MscS inactivation, N117. To our knowledge, this study describes the first electrophysiological characterization of an MscS-like channel from a marine bacterium belonging to sulfur-degrading α-proteobacteria.

Analytical Solution for Transient Thermal Response of an Insulated Structure

An analytical solution was derived for the transient response of an insulated aerospace vehicle structure subjected to a simplified heat pulse. This simplified problem approximates the thermal response of a thermal protection system of an atmospheric entry vehicle. The exact analytical solution is solely a function of two nondimensional parameters. A simpler function of these two parameters was developed to approximate the maximum structural temperature over a wide range of parameter values. Techniques were developed to choose constant, effective properties to represent the relevant temperature and pressure-dependent properties for the insulator and structure. A technique was also developed to map a time-varying surface temperature history to an equivalent square heat pulse. Using these techniques, the maximum structural temperature rise was calculated using the analytical solutions and shown to typically agree with finite element simulations within 10–20% over the relevant range of parameters studied.

A new velocity-pressure-compaction model for uncemented sediments

SUMMARY Knowledge of the pressure dependence of rock properties is useful for a wide range of earth science problems, especially related to pore pressure changes caused by fluid injection or withdrawal, as often occurs in groundwater, hydrocarbon and CO2 sequestration reservoirs. A long-standing problem is that theoretical models of velocity-pressure response often do not match laboratory measurements, and alternately, empirical regressions fit to such data do not extrapolate accurately to wider pressure ranges since they have little or no physical basis. Accurate determination of the dry rock frame properties at low effective pressure is a key aspect of the problem, particularly when ultrasonic laboratory measurements are not available in this pressure range. We present a new model to describe the pressure sensitivity of the bulk and shear moduli for uncemented sedimentary rocks. Our model incorporates effects of sedimentary compaction and critical porosity, including a relationship to account for porosityanddensitychangewithpressure.Themodelistestedonlaboratorymeasurementsfor various rock samples and fits well over a wide range of pressures. The new velocity‐pressure model should be useful for improved prediction and interpretation of pressure-dependent rock properties and seismic data.

Pressure-induced phase transformation of In2Se3

In2Se3 has potential as a phase-change material for memory applications. Understanding its phase diagram is important to achieve controlled switching between phases. Using x-ray diffraction and a diamond-anvil cell, the pressure-dependent structural properties of In2Se3 powder were studied at room temperature. α-In2Se3 transforms into the β phase at 0.7 GPa, an order of magnitude lower than phase-transition critical pressures in typical semiconductors. The β phase persists upon decompression to ambient pressure. Raman spectroscopy experiments confirm this result. The bulk moduli are reported and the c/a ratio for the β phase is shown to have a highly nonlinear dependence on pressure.

First-principles density functional calculation of mechanical, thermodynamic and electronic properties of CuIn and Cu2In crystals

The study aims at assessing the mechanical, thermodynamic and electronic properties of single-crystalline and polycrystalline CuIn and Cu2In intermetallic compound (IMC) crystals using first-principles calculation based on the density functional theory within the generalized gradient approximation. The lattice constants and the five independent elastic constants of the two hexagonal single crystal structures are first calculated as a function of hydrostatic pressure, and their elastic anisotropy is examined through the computation of the crystal direction-dependent elastic modulus and the Zener anisotropy factor. Subsequently, their associated pressure-dependent polycrystalline elastic properties are also predicted, by which the ductility or brittleness of the IMC materials is characterized. Moreover, the temperature-dependent Debye temperature and heat capacity of these two IMC nanocrystals are determined using a quasi-harmonic Debye model, and their electronic band structures and density of states profiles are examined through analysis of electronic characteristics.The calculation results show that these two IMC crystals are not only an elastically anisotropic, low stiff and very ductile material but also a conductor. The elastic anisotropy, Debye temperature and heat capacity of Cu2In single crystal all surpass those of CuIn, and also, Cu2In crystal tends to be much stiffer than CuIn. Besides, the heat capacity of these two nanocrystals strictly follows with the well-known T3-law at temperature below the Debye temperature and would reach the Dulong–Petit limit at temperature above the Debye temperature.

Pressure-dependent dynamical properties of Zn-based II–VI semiconductors

The effect of pressure on optical phonons and polaron properties in ZnS, ZnSe, and ZnTe II–VI compound semiconductors has been investigated. The calculations are performed in the framework of ab initio pseudopotential approach based on the density functional perturbation theory . At zero pressure, a reasonable degree of agreement is generally found between our results and data available in the literature. It is found that when pressure is increased the phonon modes at Г in the Brillouin zone are shifted towards high energies. The pressure dependence of features such as Fröhlich coupling parameter, the Debye temperature of the longitudinal optical phonon frequency and the polaron effective mass showed that the polaron properties are sensitive to the pressure effect.

Pressure-dependent structure, mechanical and thermodynamic properties of tetragonal AsTiZr arsenide: A density functional theory study

Recent discoveries of the novel properties of arsenides prompt us to theoretically predict the tetragonal AsTiZr ternary compound under pressure, in order to exploit new functional materials. The structure, elastic and thermodynamic properties of AsTiZr have been investigated under various pressures, based on density functional theory (DFT). For the sake of consistency, the approach of the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) was used. The calculated structural data at zero pressure are in good agreement with previous report. The dependence of relative changes of lattice parameters (a0 and c0) and volume V0, elastic constants, bulk, shear and Young's modulus, and Debye temperature on pressure has been investigated. The thermodynamic properties like heat capacity C, enthalpy E, free energy F and entropy S with pressure are successfully obtained and discussed.

Pressure-dependent electronic properties of MgO polymorphs: a first-principles study of Compton profiles and autocorrelation functions

The first-principles periodic linear combination of atomic orbitals method within the framework of density functional theory implemented in the CRYSTAL06 code has been applied to explore effect of pressure on the Compton profiles and autocorrelation functions of MgO. Calculations are performed for the B1, B2, B3, B4, B8_1 and h-MgO polymorphs of MgO to compute lattice constants and bulk moduli. The isothermal enthalpy calculations predict that B4 to B8_1, h-MgO to B8_1, B3 to B2, B4 to B2 and h-MgO to B2 transitions take place at 2, 9, 37, 42 and 64 GPa respectively. The high pressure transitions B8_1 to B2 and B1 to B2 are found to occur at 340 and 410 GPa respectively. The pressure dependent changes are observed largely in the valence electrons Compton profiles whereas core profiles are almost independent of the pressure in all MgO polymorphs. Increase in pressure results in broadening of the valence Compton profiles. The principal maxima in the second derivative of Compton profiles shifts towards high momentum side in all structures. Reorganization of momentum density in the B1 to B2 structural phase transition is seen in the first and second derivatives before and after the transition pressure. Features of the autocorrelation functions shift towards lower r side with increment in pressure.

Structural Behavior of Symmetric Spindle-Shaped Tensairity Girders

AbstractThe load-bearing behavior of a symmetric spindle-shaped Tensairity girder with 5-m span and thin chords is studied experimentally, numerically, and analytically. The influence of the air pressure on the load-deflection behavior is investigated for homogeneous distributed load, asymmetric distributed load, and central local load. An m-shaped deflection with two maxima at about one- and three-quarter of the span was obtained for homogeneous distributed loads whose distribution is not linearly dependent on the applied load. The slope of the load-deflection curve as well as the maximal load increases with increasing air pressure, demonstrating the stabilizing role of the inflated hull. An analytical model based on two beams coupled by an elastic foundation with air pressure-dependent properties is presented for the homogeneous distributed load case, and simple predictions for the average displacement and the maximal load are given. The model reveals the subtle interplay between the chords and the infl...

Phase Transitions of AlFeO3 and GaFeO3 from the Chiral Orthorhombic (Pna21) Structure to the Rhombohedral (R3̅c) Structure

AlFeO(3) and GaFeO(3), which crystallize in a chiral orthorhombic (Pna2(1)) structure, transform to a rhombohedral (R3c) structure when subjected to ball-milling. There is a distinct difference between the transformations of AlFeO(3) and GaFeO(3). AlFeO(3) first transforms to an orthorhombic P2(1)2(1)2(1) structure followed by its transformation to the R3c structure, while GaFeO(3) goes directly to the R3c structure. The transformations have been characterized by X-ray diffraction and Raman spectroscopy. Magnetic properties of Pna2(1) and the transformed phases show significant differences. It is noteworthy that partial substitution of aluminum by gallium in AlFeO(3) as in Al(0.5)Ga(0.5)FeO(3) eliminates the intermediate P2(1)2(1)2(1) phase, causing direct transformation of the Pna2(1) structure to the R3c structure. All of the transformations are thermodynamically first-order associated with significant changes in volume. We have used first-principles simulations to determine the pressure-dependent properties of AlFeO(3) and GaFeO(3) in orthorhombic and corundum structures and have estimated the critical pressures for the structural phase transition between the two structures. On the basis of this information, we also comment on the differences in the behavior of AlFeO(3) and GaFeO(3) under ball-milling.

Review of Zero-D and 1-D Models of Blood Flow in the Cardiovascular System

BackgroundZero-dimensional (lumped parameter) and one dimensional models, based on simplified representations of the components of the cardiovascular system, can contribute strongly to our understanding of circulatory physiology. Zero-D models provide a concise way to evaluate the haemodynamic interactions among the cardiovascular organs, whilst one-D (distributed parameter) models add the facility to represent efficiently the effects of pulse wave transmission in the arterial network at greatly reduced computational expense compared to higher dimensional computational fluid dynamics studies. There is extensive literature on both types of models.Method and ResultsThe purpose of this review article is to summarise published 0D and 1D models of the cardiovascular system, to explore their limitations and range of application, and to provide an indication of the physiological phenomena that can be included in these representations. The review on 0D models collects together in one place a description of the range of models that have been used to describe the various characteristics of cardiovascular response, together with the factors that influence it. Such models generally feature the major components of the system, such as the heart, the heart valves and the vasculature. The models are categorised in terms of the features of the system that they are able to represent, their complexity and range of application: representations of effects including pressure-dependent vessel properties, interaction between the heart chambers, neuro-regulation and auto-regulation are explored. The examination on 1D models covers various methods for the assembly, discretisation and solution of the governing equations, in conjunction with a report of the definition and treatment of boundary conditions. Increasingly, 0D and 1D models are used in multi-scale models, in which their primary role is to provide boundary conditions for sophisticate, and often patient-specific, 2D and 3D models, and this application is also addressed. As an example of 0D cardiovascular modelling, a small selection of simple models have been represented in the CellML mark-up language and uploaded to the CellML model repository http://models.cellml.org/. They are freely available to the research and education communities.ConclusionEach published cardiovascular model has merit for particular applications. This review categorises 0D and 1D models, highlights their advantages and disadvantages, and thus provides guidance on the selection of models to assist various cardiovascular modelling studies. It also identifies directions for further development, as well as current challenges in the wider use of these models including service to represent boundary conditions for local 3D models and translation to clinical application.

Effect of Si doping and applied pressure upon magnetostructural properties of Tb5(SixGe1−x)4magnetocaloric compounds

The composition- and pressure-dependent magnetostructural properties of Tb{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} (x = 0.4, 0.485, 0.625, and 0.7) were investigated using x-ray powder diffraction and x-ray magnetic circular dichroism in a diamond anvil cell, respectively. Substituting the smaller-size Si for Ge stabilizes a single-phase, ferromagnetic (FM) orthorhombic O(I) structure for x ? 0.7. Similarly, application of external pressure causes a canted antiferromagnetic orthorhombic O(II) sample (x = 0.4) to transform into an FM O(I) phase at 4 GPa. The element- and orbital-specific x-ray absorption data indicate that the Tb 4f orbital occupation changes with external pressure, likely through 4f-5d electronic mixing, yet no changes in Tb 4f electronic structure are observed with Si doping. The results point to different mechanisms behind the enhancement of FM exchange interactions in Tb{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} with chemical and applied pressure, respectively.

Transport properties of Ag 0.8Pb 18SbTe 20 prepared by high pressure and high temperature

In this paper, N-type thermoelectric materials Ag 0.8Pb 18SbTe 20 with enhanced power factor were prepared by high pressure and high temperature (HPHT) method. The synthetic pressure-dependent transport properties including electrical resistivity, Seebeck coefficient and power factor were studied at room temperature. The maximum power factor of 15.4 μW cm −1 K −2 was obtained at the synthetic pressure of 4.0 GPa, which is much higher than that of the same sample prepared by other methods.

The effect of peripheral vascular disease on structure and function of resistance arteries isolated from human skeletal muscle

Peripheral vascular disease (PVD) is associated with numerous pathophysiological adaptations of the microvasculature. Considering this, active and passive pressure-dependent and pressure-independent mechanisms of vascular control were studied in small resistance arteries isolated from patients with PVD. Using pressure myography and confocal microscopy, human skeletal muscle arteriolar structure and function were compared between paired arteries; one isolated from the healthy non-diseased proximal skeletal muscle vascular bed (PSM, internal control) and the other from the diseased ischaemic part of the leg [distal skeletal muscle (DSM)]. Structurally, arteries isolated from the diseased part of the leg displayed significant atrophy compared with the non-diseased arteries. Functionally, no differences were observed in the fundamental ability small resistance arteries to contract or relax. However, active pressure-dependent myogenic contraction was significantly reduced in DSM arteries compared with PSM arteries. DSM versus PSM; 3 +/- 1% versus 22 +/- 4% and 3.4% +/- 1.1% versus 25 +/- 4% at 80 and 120 mmHg, respectively. Furthermore, structural remodelling in DSM arteries could also be correlated with significant changes in vascular wall mechanics. DSM arteries displayed significantly greater incremental dispensability, wall stress and wall strain compared with PSM arteries as a product of pressure-dependent distension. These alterations in pressure-dependent active myogenic tone and passive mechanical properties goes some way to explain uncontrolled orthostatic-dependent changes in leg fluid volume and oedema formation experienced by these patients.

High-pressure XRD study of β-Na0.33V2O5

We have investigated the pressure-dependent structural properties of the quasi-one-dimensional metal at room temperature by high-resolution angle-dispersive powder X-ray diffraction. According to our structural data, the crystal lattice of β-Na0.33V2O5 remains monoclinic (space group C2/m) up to 20 GPa. The smallest compressibility is found along the conducting b-axis. We observe an anomaly in the pressure dependence of the lattice parameters and the volume of the unit cell in the range 12–15 GPa, in agreement with the pressure-dependent optical properties.

Mn-Substituted [Zn1−xMnxSe](DETA)0.5 (x = 0−0.3) Inorganic−Organic Hybrid Nanobelts: Synthesis, Electron Paramagnetic Resonance Spectroscopy, and Their Temperature- and Pressure-Dependent Optical Properties

Mn-substituted 1D [Zn1−xMnxSe](DETA)0.5(DETA = diethylenetriamine, x = 0−0.3) inorganic−organic hybrid nanobelts have been synthesized by a solvothermal reaction in a mixed solvent media. Strong Mn2+ internal transition (4T1 → 6A1) emission peaks at 585 nm (2.12 eV) are detected at room temperature photoluminescence (PL) spectra, and the highest emission intensity is obtained when the nominal Mn content x = 0.15. Temperature- and pressure-dependent photoluminescent properties as well as the electron paramagnetic resonance (EPR) spectra of [Zn1−xMnxSe](DETA)0.5 nanobelts have been studied for the first time. Temperature-dependent PL spectra show that the lower the temperature, the higher the intensity of the emission intensity. Under high pressure, a large red shift of Mn2+-related orange luminescence is observed and luminescent intensity is greatly decreased as the pressure increases to 10.5 GPa. Pressure dependence of the Mn2+ PL integrated intensity and energy have the same kink point at 2.54 GPa, which...