Pressure Phase Research Articles

Coupled droplet dynamics: Investigation of acoustic-spray interactions in a reacting flow field

Droplet dynamics in a self-excited thermoacoustic instability are not well understood due to the tight coupling of competing effects and difficulty in taking high-quality data. In this investigation, droplet data from a combustion instability is used to illustrate how a spray couples with a thermoacoustic instability. Commonly accepted ensemble averaging techniques such as the Sauter mean diameter (D32) is shown to be inadequate in describing the coupling phenomena, and instead, a new approach based on droplet surface area is used to characterize the spray. The present study extends literature concerning nonreacting acoustic-spray interactions and considers these in a fully self-excited instability. A lean direct injection (LDI) geometry is used at atmospheric pressure and phased averaged Phase Doppler Particle Analyzer (PDPA) measurements, acoustic pressure measurements, and OH* chemiluminescence images are taken to characterize the flow field. It is shown that while some of the trends found in nonreacting experiments apply to reacting systems, the mechanisms are notably different due to the presence of a flame. Flame response is shown to be important due to its influence on the evaporation of droplets.

Comments on forward pressure and other reflectance-based quantities for delivering stimuli to the ear.

The forward pressure has been proposed as an "optimal" reflectance-based quantity for delivering stimuli to the ear during evoked otoacoustic-emission measurements and audiometry. It is motivated by and avoids detrimental stimulus-level errors near standing-wave antiresonance frequencies when levels are adjusted in situ. While enjoying widespread popularity within research, the forward pressure possesses certain undesirable properties, some of which complicate its implementation into commercial otoacoustic-emission instruments conforming to existing international standards. These properties include its inability to approximate the total sound pressure anywhere in the ear canal and its discrepancy from the sound pressure at the tympanic membrane, which depends directly on the reflectance. This paper summarizes and comments on such properties of the forward pressure. Further, based on previous published data, alternative reflectance-based quantities that do not share these properties are investigated. A complex integrated pressure, with magnitude identical to the previously proposed scalar integrated pressure, is suggested as a suitable quantity for avoiding standing-wave errors when delivering stimuli to the ear. This complex integrated pressure approximates the magnitude and phase of the sound pressure at the tympanic membrane and can immediately be implemented into standardized commercial instruments to take advantage of improved stimulus-level accuracy and reproducibility in the clinic.

Behaviour of alkali-activated concrete at elevated temperatures: A critical review

Alkali-activated concrete (AAC) is recognised as a novel sustainable construction material to substitute Portland cement concrete with superior thermal and mechanical performance. However, AAC would suffer significant deterioration when subjected to elevated temperatures due to different damage mechanisms, including thermal incompatibility caused by different thermal coefficients between matrix and aggregates, pore pressure build-up and phase transformation. This paper presents a systematic and comprehensive review on the behaviour of different types of AAC such as alkali-activated fly ash, alkali-activated slag, alkali-activated metakaolin and alkali-activated fly ash-slag systems at elevated temperatures in terms of phase stability and microstructural evolution as well as thermal and mechanical performance. The effective strategies for improving the high-temperature resistance of AAC are reviewed and discussed from the perspectives of AAC matrix, aggregates and fibre incorporation, with special focus on how these strategies can tackle different damage mechanisms. This paper summarises the recent advances in the field and identifies the remaining challenges and opportunities for future research.

Numerical Assessment of Terrain Relief Influence on Consequences for Humans Exposed to Gas Explosion Overpressure

This study aims to reconstruct hazardous zones after the hydrogen explosion at a fueling station and to assess an influence of terrain landscape on harmful consequences for personnel with the use of numerical methods. These consequences are measured by fields of conditional probability of lethal and ear-drum injuries for people exposed to explosion waves. An “Explosion Safety®” numerical tool is applied for non-stationary and three-dimensional reconstructions of the hazardous zone around the epicenter of the explosion of a premixed stoichiometric hemispheric hydrogen cloud. In order to define values of the explosion wave’s damaging factors (maximum overpressure and impulse of pressure phase), a three-dimensional mathematical model of chemically active gas mixture dynamics is used. This allows for controlling the current pressure in every local point of actual space, taking into account the complex terrain. This information is used locally in every computational cell to evaluate the conditional probability of such consequences for human beings, such as ear-drum rupture and lethal outcome, on the basis of probit analysis. To evaluate the influence of the landscape profile on the non-stationary three-dimensional overpressure distribution above the Earth’s surface near the epicenter of an accidental hydrogen explosion, a series of computational experiments with different variants of the terrain is carried out. Each variant differs in the level of mutual arrangement of the explosion epicenter and the places of possible location of personnel. The obtained results indicate that any change in working-place level of terrain related to the explosion’s epicenter can better protect personnel from the explosion wave than evenly leveled terrain, and deepening of the explosion epicenter level related to working place level leads to better personnel protection than vice versa. Moreover, the presented coupled computational fluid dynamics and probit analysis model can be recommended to risk-managing experts as a cost-effective and time-saving instrument to assess the efficiency of protection structures during safety procedures.

Numerical methodology on prestressed reinforced concrete containment building: Creep, aging and leakage. Application to VERCORS mock-up

The containment building (CB) is known as the third and last safety barrier to protect the environment from diffusion of radioactive products. In 2014, Électricité de France (EDF) launched the VERCORS project to improve the knowledge of leak-tightness in the CB under air pressure loading and aging effects. VERCORS consists in a 1/3 scaled containment mock-up representing a 1300 MWe CB of a typical French pressurized water reactor (PWR). This paper presents the results of a numerical methodology applied on VERCORS mock-up. The simulation includes THM analysis in gusset, prestressing phase and pressurization phase, and is conducted through a finite element code, Cast3M. Concrete is modeled through 3D elements while rebars and tendons are modeled by 1D elements. Moreover, the delayed strains including creep and shrinkage are especially considered. The instantaneous prestress losses, which result from friction; relaxation and pull-in at wedge, are taken into account. Regarding the long-term prestress loss due to the delayed strains, it is achieved by a kinematic relationship at interface of concrete-tendons. To describe cracks in concrete, an elastic damage model is used for the concrete elements, and the post-processing of leak-tightness is based on the internal variable of the damage model and a hydric analysis. The mechanical results reveal different damage zones on the CB, which are distributed at gusset, hatch and dome.

Pressure induced modification of the electronic properties of stilbene by two-photon spectroscopy.

Carbon nanothreads are the most exciting carbon based nanomaterials recently discovered. Obtained by compressing aromatics around 20GPa, they are characterized by potentially exceptional mechanical properties. The reaction mechanisms have been partly elucidated through computational studies and x-ray diffraction experiments. However, in all these studies, the electronic modifications to which the molecule is subjected with increasing pressure are neglected as also if, and to which extent, the electronic excited states are involved in the high-pressure reactivity. In fact, the pressure increase induces remarkable changes in the electronic properties of molecular crystals, which are often directly related to the reaction's onset and path. We report the pressure evolution of the two-photon induced emission spectrum of crystalline stilbene, the archetype of a class of molecules from which double-core nanothreads are obtained, with the twofold purpose of gaining insight into the reaction mechanism and monitoring if the structural changes observed in x-ray diffraction studies have a detectable counterpart in the electronic properties of the system. The freezing of the spectral diffusion observed on rising pressure is ascribed to a hampered conformational rearrangement because of the larger stiffness of the local environment. The transition to the high pressure phase where the nanothreads form is revealed by the slope change of the pressure shift of all spectral components, while the progressive intensification with pressure of the 0-0 transition suggests a strengthening of the ethylenic bond favoring the charge delocalization on the benzene moieties, which is likely the trigger of the chemical instability.

Structural and vibrational properties of GdTaO4 under compression: An insight from experiment and first principles simulations

Polycrystalline GdTaO4, synthesized by solid state reaction route at 1300°C, adopts an M′ fergusonite crystal structure (space group P2/c) with GdO8 and TaO6 as constituent units. The compression behavior of the compound has been investigated in a diamond anvil cell by powder x-ray diffraction and Raman spectroscopic techniques. Both the techniques indicate pressure driven first order isosymmetric phase transition in the compound around 19 GPa. X-ray diffraction data show nearly 6% volume discontinuity at the phase transition and a change in oxygen coordination around the Ta atom from six in the ambient phase to eight in a high pressure phase. Experimental data collected in the process of decompression confirm the reversible nature of phase transition. Bulk modulus obtained by fitting the pressure–volume data to the 3rd-order Birch–Murnaghan equation of state shows a higher value of bulk modulus for the high pressure phase compared to the low pressure phase, which is consistent with increased density due to volume collapse at the phase transition. The pressure dependence of unit cell parameters and Raman active modes along with Grüneisen parameters are also reported. Density functional theory based first principles simulations performed on compound corroborate the experimental findings. In low pressure phase, the simulated volumes of the constituent polyhedra under pressure indicate that the major contribution in the bulk modulus comes from lower valence rare earth polyhedra; however, for a high pressure phase, both the polyhedra units (GdO8 and TaO8) have almost similar contribution to the bulk modulus of the compound.

A rocky exoplanet classification method and its application to calculating surface pressure and surface temperature

ABSTRACT With over 5000 exoplanets currently detected, there is a need for a primary classification method to prioritize candidates for biosignature observations. Here, we develop a classification method to categorize rocky exoplanets based on their closest Solar system analogue using available data of observed stellar and planetary features, masses, and radii, to model non-thermal atmospheric escape, thermal atmospheric escape, and stellar irradiation boundaries. Applying this classification method to the 720 rocky exoplanets in our sample with uncertainties in planetary masses, radii, stellar temperatures, and fluxes propagated via a Monte Carlo model indicates that 22 per cent ± 8 per cent are Mercury analogues, 39 per cent ± 4 per cent are Mars analogues, 11 per cent ± 1 per cent are Venus analogues, 2 per cent ± 1 per cent are Earth analogues, and 26 per cent ± 12 per cent are without a known planetary counterpart in our Solar system. Extrapolating to conditions on LHS 3844b and GJ 1252b, our classification method gives results reasonably consistent with current observations. Subsequently, to demonstrate the functionality of this classification method, we plot our catalogued sample of exoplanets on an adjusted surface pressure versus temperature phase diagram, presenting more realistic estimates of the potential surface phases (gas, liquid, or ice). Our new classification method could help target selection for future exoplanet characterization missions.

Цифровизация как инструмент глобального партнерства: шоки и трансформации российской сферы IT

An example of the destructive influence of dependence on partners can be called the situation in the information and telecommunications (IT) sphere of Russia. Despite the aggravation of relations, the market share of some software and hardware components reached 100% of Russian market. Accordingly, with the beginning of the acute phase of station pressure, when Western partners began to leave the Russian market, the IT sphere turned out to be seriously destabilized. Equipment prices increased, many software developers were left without strategic partners and investments, customers without digital products. IT development budgets were urgently adjusted for the purchase of hardware. Moreover, an attempt was made to “capture” Russian personnel who were employed in Western IT companies. It is obvious that such a level of global openness for the IT sphere, which provides a number of basic needs for the population and business, as well as the authorities, is a threat to national security. The growth of self-sufficiency in all areas of the IT sphere will contribute to the sustainability of both the sphere itself and the whole country and will avoid the need for such emergency measures as it were required in 2022. IT is just an example and increasing self-sufficiency is relevant for the industry of mechanical engineering and tools, the production of components, energy and transport infrastructure and a number of other sectors of the Russian economy. The article examines the role of the state in the crisis management and strategic planning of the development of the IT sphere to ensure stability and security of work in the future.

Under pressure: offering fundamental insight into structural changes on ball milling battery materials

The dynamic impacts from the ball mill process inducing a pressure phase change.

High-pressure induced switching between halogen and hydrogen bonding regimes in 1,4-dioxane iodine monochloride

The crystal structures of two high pressure phases of 1,4-dixoane iodine monochloride are reported.

Discerning subtle high-pressure phase transitions in glyphosate

The partitioning of volumes into ‘occupied’ and ‘unoccupied’ space can recover a spectroscopic level of sensitivity in crystallographic measurements. This has revealed structural effects of two second order high pressure phase transitions in glyphosate.

Phase transition and bond symmetrization associated with noble gas bond in XeO3

The pressure-induced structural phase transition of XeO3 is studied by first principle calculations. The transition from P212121 to Pnma accompanied by a drastic reduction of volume is found at 2.18 GPa. The symmetrilized Xe−O2 bonds give rise to the better symmetry of high pressure phase. O-hopping between different possible local minima and the motion of Xe along the y axis may be responsible for phase transition. Results of electron localization function indicate that three ipsilateral Xe−O bonds lead to a lone-pair contour of Xe6+.

High pressure phase transition and strength estimate in polycrystalline alumina during laser-driven shock compression

Alumina (Al2O3) is an important ceramic material notable for its compressive strength and hardness. It represents one of the major oxide components of the Earth’s mantle. Static compression experiments have reported evidence for phase transformations from the trigonal α-corundum phase to the orthorhombic Rh2O3(II)-type structure at ∼90 GPa, and then to the post-perovskite structure at ∼130 GPa, but these phases have yet to be directly observed under shock compression. In this work, we describe laser-driven shock compression experiments on polycrystalline alumina conducted at the Matter in Extreme Conditions endstation of the Linac Coherent Light Source. Ultrafast x-ray pulses (50 fs, 1012 photons/pulse) were used to probe the atomic-level response at different times during shock propagation and subsequent pressure release. At 107 ± 8 GPa on the Hugoniot, we observe diffraction peaks that match the orthorhombic Rh2O3(II) phase with a density of 5.16 ± 0.03 g cm−3. Upon unloading, the material transforms back to the α-corundum structure. Upon release to ambient pressure, densities are lower than predicted assuming isentropic release, indicating additional lattice expansion due to plastic work heating. Using temperature values calculated from density measurements, we provide an estimate of alumina’s strength on release from shock compression.

Intra-aortic and Intra-caval Balloon Pump Devices in Experimental Non-traumatic Cardiac Arrest and Cardiopulmonary Resuscitation.

Intra-aortic balloon pump (IABP) use during CPR has been scarcely studied. Intra-caval balloon pump (ICBP) may decrease backward venous flow during CPR. Mechanical chest compressions (MCC) were initiated after 10min of cardiac arrest in anesthetized pigs. After 5min of MCC, IABP (n = 6) or ICBP (n = 6) was initiated. The MCC device and the IABP/ICBP had slightly different frequencies, inducing a progressive peak pressure phase shift. IABP inflation 0.15s before MCC significantly increased mean arterial pressure (MAP) and carotid blood flow (CBF) compared to inflation 0.10s after MCC and to MCC only. Coronary perfusion pressure significantly increased with IABP inflation 0.25s before MCC compared to inflation at MCC. ICBP inflation before MCC significantly increased MAP and CBF compared to inflation after MCC but not compared to MCC only. This shows the potential of IABP in CPR when optimally synchronized with MCC. The effect of timing of intra-aortic balloon pump (IABP) inflation during mechanical chest compressions (MCC) on hemodynamics. Data from12 anesthetized pigs.

Pressure-induced phase transition and band-gap decrease in semiconducting Na3Bi(IO3)6

We report a combined experimental/theoretical high-pressure study of Na3Bi(IO3)6 under compression to 11.2 GPa at ambient temperature. Through a combination of single-crystal and powder synchrotron X-ray diffraction, optical absorption measurements and ab initio density functional theory calculations we unambiguously show a first-order pressure-induced phase transition at around 9.5 GPa from the ambient pressure phase, referred to here as α-Na3Bi(IO3)6, to a new crystalline structure referred to here as β-Na3Bi(IO3)6. The triclinic (P-1) to triclinic (P1) phase transition is characterised by a doubling of the primitive cell volume, whereby the crystallographic b-axis doubles in length, and by a decrease in the volume per formula unit of approximately 3 %. The phase transition is also characterised by an indirect → indirect electronic bandgap decrease of approximately 0.1 eV as measured by absorption spectroscopy (3.44(1) → 3.32(1) eV) and calculated via density functional calculations (2.48 → 2.33 eV). We also report the pressure evolution of the crystal lattice parameters and isothermal compressibility tensor of the ambient pressure phase α-Na3Bi(IO3)6, which reveals highly anisotropic compressibility and a bulk modulus of 30.4(7) GPa.

Novel phase transition for XSnN2 (X = Mg, Zn) under uniaxial compression

The behavior of ternary nitrides MgSnN 2 and ZnSnN 2 were computationally explored under uniaxial compressions in [100] direction. It was found that at 20 GPa MgSnN 2 transforms from the P n a 2 1 structure into a Pnma phase, while this new phase can remain with compression fully released. Similar phase transition was observed for ZnSnN 2 at 41 GPa, while the high pressure phase will recover to the original lattice when compression is removed. In addition, the band gap increases along with an enhancing compression in the investigated pressure range for MgSnN 2 , accompanied with a sudden increase at the critical point of the phase transition. While for ZnSnN 2 , it shows a drop at the phase transition and continues to decrease with even larger compression. The light absorption will basically be suppressed for MgSnN 2 and ZnSnN 2 in visible and near ultraviolet region under compression, while enhanced at high frequency above 14 eV. Moreover, the metastable Pnma phase of MgSnN 2 is studied at ambient conditions and shows promising conductive properties, comparing to the P n a 2 1 structure.

Film formation kinetics of Methane-propane hydrate on gas bubble in MEG and luvicap EG solutions

Hydrate plugging in deep sea oil & gas transportation is the final result of morphological evolution of hydrate growth. However, effect of hydrate morphological evolution in the presence of hydrate inhibitors with respect to flow assurance is rarely studied. In this work, methane-propane hydrate forming system by suspending gas bubbles in pressurized aqueous phase was studied to evaluate the hydrate film growth kinetics in the presence of thermal and kinetic inhibitors (MEG, LuviCap EG) at subcooling levels of 10–15 K. Along with morphological observations with optical microscope, the results suggested that: (1) KHI showed better inhibition performance on hydrate growth with hydrate film as a barrier for mass transfer; (2) 4000 ppm performed as a threshold concentration of hydrate film formation on bubble; (3) crater structures, as potential mass transfer channels, are the morphological characteristics of KHIs adsorbing to the hydrate film. In addition, the effects of environmental factors on the growth kinetics of hydrate on bubble showed that the subcooling determined the lateral growth rate of hydrate film, the inhibitor concentration determined whether a film was formed, and the craters structure on the hydrate film determined the mass transfer in the initial thickening stage of hydrate film growth. The research could shed new light on fine-tuning of the inhibitor concentration and level of subcooling to effectively inhibit the growth of hydrate in gas pipelines and assure the multiphase flow in deep sea oil & gas transportation.

Phase transition and properties of ternary MgGeN2 under pressure: a first principles investigation

In this work the structural, electronic, mechanical and optical properties of MgGeN2 under pressure are investigated through the density functional theory based first principles computations using the recently proposed Strongly Constrained and Appropriately Normed (SCAN) functional. It was found that the orthorhombic structure is energetically stable at ambient conditions and a phase transition from orthorhombic phase to a newly found tetragonal phase occurs at about 23 GPa under hydrostatic compression. In addition, in the investigated pressure range, MgGeN2 does not follow the rule that the materials will become more metallic under pressure due to that the strengthened covalent bond will enlarge the band gap and enable the system more insulating. Therefore, for both the orthorhombic phase and the high pressure tetragonal phase, the band gap shows a monotonic increment along increasing pressure. A reduction of the band gap was accompanied with the phase transition. In addition, the high pressure phase has a much larger bulk modulus and shear modulus than the orthorhombic phase, together with an enhanced optical absorption and conductivity. Finally, the potential applications of pressure induced structural change and band tuning are interpreted.

High pressure phase transitions in diglycine perchlorate: a Raman spectroscopic study

High pressure phase transitions in diglycine perchlorate: a Raman spectroscopic study