Hydrostatic Pressure Variation Research Articles

Enlightening the hydrostatic pressure variation effect on physical properties of mechanically stable La2Ge2O7 pyrochlore oxide: Insights from first principles for solar cell advancement

Herein this manuscript, we examine the structural, electronic, optical, elastic, mechanical, and thermoelectric attributes of the La2Ge2O7 under varying hydrostatic pressure (0–100 GPa). Comprehensive calculations were performed using GGA-PBE based on DFT in conjunction with the CASTEP program. Lattice parameters and unit cell volume both show a propensity to decrease as pressure increases. The degree of localized electrons in different bands was confirmed by examining the pressure-induced total and partial density of states. The optical characteristics of La2Ge2O7 up to the 50eV energy range have been fully investigated. Interestingly, the material is mechanically stable following Boron stability conditions and exhibits ductile behavior under pressure ranging from 0 to 100 GPa. Thermoelectric properties like electrical and thermal conductivities, the Seebeck coefficient, and other related parameters are computed through BoltzTraP code analysis under varying pressure. Thus, La2Ge2O7 is suitable for future research in photovoltaic and thermoelectric device applications.

TCT-720 Physiologic Effects of Hydrostatic Pressure Variations Caused by Height Difference on Fractional Flow Reserve Under Stenosis Condition: An Experimental Study Using Various Stenosis Models

TCT-720 Physiologic Effects of Hydrostatic Pressure Variations Caused by Height Difference on Fractional Flow Reserve Under Stenosis Condition: An Experimental Study Using Various Stenosis Models

Impact of variable hydrostatic pressure and intermittent operation on filtration performance and biofouling layer in gravity-driven membrane system for practical decentralized water supply

The gravity-driven membrane (GDM) systems offer a promising solution for decentralized drinking water supply due to its low maintenance and energy consumption. However, research on the practical application of GDM under variable hydrostatic pressure (variable load) and intermittent operation conditions, particularly in response to high-turbidity water, remains limited. This study investigates the long-term performance and characteristics of the biofouling layer of GDM under ultra-low variable hydrostatic pressure (20–60 mbar) and intermittent operation (8–12 h) conditions in practical decentralized water supply. The results indicate that the membrane flux (1.9–6.0 L∙m−2∙h−1, LMH) remained relatively stable despite variations in gravity-driven pressure (ΔP). Long-term operation of GDM can stably remove turbidity and potential pathogens from raw water. The total protein/polysaccharide ratios of extracellular polymeric substances (EPS) in the biofouling layer were below 0.50, reducing contaminant adhesion on the membrane surface. The 0.2–0.4 μm transparent exopolymer particles (TEP) fraction might be crucial for biofouling layer formation. The key species, belong to Proteobacteria and Patescibacteria, significantly alleviated membrane fouling by degrading polysaccharide and proteins in biofouling layer. Comammox Nitrospira were significantly enriched, contributing to efficient nitrification. GDM with variable load maintained a stable flux of 2.2–5.2 LMH under high-turbidity water conditions (300–1200 NTU), and simple forward flushing combined with sludge discharge can quickly restore ΔP. Overall, the variable load GDM system effectively manages membrane fouling and maintains stable filtration performance through the combined effects of variable load and intermittent operation, ensuring long-term and low-maintenance operation for decentralized water supply.

Optimizing the Influence of Fly Ash as an Anti-Sagging Additive in Highly Deviated Geothermal Well Drilling Fluids Using Surface Response Method

Weighting materials such as barite and ilmenite are crucial for controlling fluid density during deep or ultra-deep drilling operations. However, sagging poses significant challenges, especially in highly deviated high-pressure and high-temperature (HP/HT) wells. This leads to inadequate well control, wellbore instability, and variations in hydrostatic pressure in extended-reach wells. Given the challenges of experimental research, reliable prediction models are imperative for evaluating the interaction between the ratio of anti-sagging additives, temperature, and wellbore inclination on sag factor (SF). This research presents statistical-based empirical models for predicting the SF at various wellbore inclinations (0°, 30°, 45°, 60°, 70°, 80°, and 90°) and assessing the influence of fly ash on the SF. The regression equations, developed using the Response Surface Methodology in Minitab 18 software, show high reliability, with R2 values approaching unity. Contour and surface response plots provide a clear understanding of the variable interactions. The analysis reveals that sagging is most severe at 60° to 65° inclination. At 400 °F and 60° inclination, adding 4 lb/bbl of fly ash reduces sagging in barite and ilmenite-densified fluid by 63.9% and 63.1%, respectively. Model validation shows high accuracy, with percentage errors below 3%. This study offers valuable insights for optimizing drilling fluid formulations in HP/HT well environments.

A finite-deformation isotropic non-associative viscoplasticity/damage coupled thermodynamic model for ductile fracture of thick adhesive composite joint

This paper develops a finite-deformation isotropic non-associative viscoplasticity/damage coupled model to predict ductilefracture behaviors of thick adhesive composite joint within the framework of irreversible thermodynamics. First, a damage variable is introduced into the elastic constitutive model, along with the Drucker-Prager’s type yielding function and plastic potential function which take into account the variable hydrostatic pressure and non-associative plasticity. An exponential damage potential function is developed to derive the damage evolution law relating to the thermodynamic force. Second, both kinematic hardening and isotropic hardening are considered that are represented by the back stress, hardening stress and their conjugate relationships with the corresponding internal variables, derived by the Helmholtz free energy. Third, an extended version of the Perzyna’s type model is developed by incorporating an over-stress function to derive the consistency plasticity factor for the viscoplasticity/damage coupled model. Fourth, the strain, stress, back stress, thermodynamic force, damage variable and tangent modulus are updated within the corotated configuration in the integration procedure. To simplify numerical computation, the stress and strain at time n + 1 are initially updated using the frozen damage variable and the back stress at time n, and the latter two values are independently updated at time n + 1. Finally, the developed model and numerical algorithm by implicit FEA are employed to predict the strain, stress, back stress, damage and fracture behaviors of the dog-bone MMA specimens under tensile loads and the thick MMA ductile adhesive specimens under shear loads.

Dissolved nutrient gas uptake and fluid mixing by bubble-mediated mass transfer in tall fermenters — A theoretical study

A laminar flow perturbation theory for small gas volume fraction in high aspect ratio bubble columns is developed. The model captures the approximate hydrodynamics, mass transfer, microbicidal gas consumption as well as the hydrostatic head appropriate to vessels in the range of 10–50 m heights. The model is validated against a finite element multiphysics two fluid bubbly flow model for limiting cases of low heights. The key parameter in the mixing is found to be the ratio between stripping length scale, and the hydro-static pressure variation. If this is small, the mixing efficiency in the unaerated region increases like the bubble radius to the -3rd power, but for large values it is independent of the bubble radius. The overall mass transfer continues to increase as the bubble radius decreases. We find that decreasing the bubble radius from 1 cm scale to 1 mm results in an order of magnitude increase in our mixing metric.

The Effect of Hydrostatic Pressure on Coronary Flow and Pressure-Based Indices of Coronary Stenosis Severity.

Background: To assess whether hydrostatic pressure gradients caused by coronary height differences in supine versus prone positioning during invasive physiological stenosis assessment affect resting and hyperaemic pressure-based indices or coronary flow. Methods: Twenty-three coronary stenoses were assessed in twenty-one patients with stable coronary artery disease. All patients had a stenosis of at least 50% visually defined on previous coronary angiography. Pd/Pa, iFR, FFR, and coronary flow velocity (APV) measured using a Doppler were recorded across the same stenosis, with the patient in the prone position, followed by repeat measurements in the standard supine position. Results: When comparing prone to supine measurements in the same stenosis, in the LAD, there was a significant change in mean Pd/Pa of 0.08 ± 0.04 (p = 0.0006), in the iFR of 0.06 ± 0.07 (p = 0.02), and in the FFR of 0.09 ± 0.07 (p = 0.003). In the Cx, there was a change in mean Pd/Pa of 0.05 ± 0.04 (p = 0.009), iFR of 0.07 ± 0.04 (p = 0.01), and FFR of 0.05 ± 0.03 (p = 0.006). In the RCA, there was a change in Pd/Pa of 0.05 ± 0.04 (p = 0.032), iFR of 0.04 ± 0.05 (p = 0.19), and FFR of 0.04+-0.03 (p = 0.004). Resting and hyperaemic coronary flow did not change significantly (resting delta APV = 1.6 cm/s, p = 0.31; hyperaemic delta APV = 0.9 cm/s, p = 0.85). Finally, 36% of iFR measurements and 26% of FFR measurements were re-classified across an ischaemic threshold when prone and supine measurements were compared across the same stenosis. Conclusions: Pd/Pa, iFR, and FFR were affected by hydrostatic pressure variations caused by coronary height differences in prone versus supine positioning. Coronary flow did not change signifying a purely pressure-based phenomenon.

Mathematical model for the plastic flow and ductile fracture of polycrystalline solids

It is mathematically shown that ductile fracture after finite plastic strain is a necessary consequence of the polycrystalline nature of the materials. A closed–form equation for the plastic strain to fracture of a fine–grained polycrystal with no voids is derived. The mathematical model for the plastic deformation is grounded on the physical hypothesis that adjacent grains slide with a relative velocity proportional to the local shear stress resolved in the plane of the shared grain boundary, when exceeds a finite threshold. Hence plastic flow is governed predominantly by the in–plane shear forces making grain boundaries to slide, and the induced local forces responsible for the continuous grain reshaping are much weaker. The process is shown to produce a monotonic hydrostatic pressure variation with strain that precludes a stationary flow. The hydrostatic pressure dependence on strain has two solutions. One of them leads to superplasticity, the other one is shown to diverge logarithmically at a finite fracture strain and then represents ductile behaviour. Emphasis is done in the mathematical aspects of the deformation of the polycrystal up to the initiation of fracture. Although theoretical predictions agree well with mechanical tests of commercial alloys, technical issues like the effects of the presence and evolution of porosity and other imperfections, or how fracture evolves after initiation are left for a more specific communication.

Simulation and Experiment on Elimination for the Bottom-Sitting Adsorption Effect of a Submersible Based on a Submerged Jet

When a submersible is sitting on a seabed, it could lose buoyancy because of the bottom-sitting adsorption effect. In this article, a numerical calculation model and experimental scheme for eliminating the bottom-sitting adsorption effect of under-sea equipment were established. An analysis of the hydrostatic pressure variation on a submersible’s bottom was carried out, and a submerged water jet which was based on the method of soil liquefaction was proposed to solve the problem of reducing hydrostatic pressure. It was shown that a water jet could liquefy soil to restore hydrostatic pressure on the submersible’s bottom, and there was an optimal jet velocity to form the largest liquefied soil thickness. A rectangular pulsed jet was the best way to liquefy soil in terms of efficiency and the liquefaction degree, which can be seen from the calculation of the two-dimensional two-phase flow. Through the calculation of the three-dimensional two-phase flow, it was found that the soil liquefaction developed from the periphery to the center, and a variation in jet liquefaction with the top wall constraint was obtained. Finally, an experiment was carried out to prove that a submerged water jet could eliminate the bottom-sitting adsorption effect of a submersible. The results showed that the submerged jet was an efficient way to liquefy soil, and a submersible could quickly recover hydrostatic pressure on the bottom and refloat up independently.

A snap-through instability of cell adhesion under perturbations in hydrostatic pressure

The balance between stress and adhesion governs many behaviors of adherent cells such as cell migration. In certain microenvironments such as that of a tumor, variations in hydrostatic pressure be substantial compared to cell-generated stresses. These variations can affect stress-activated ion channels whose activation can in turn affect cell volume and adhesion. To study these effects, we developed a theoretical model to relate changes in hydrostatic pressure to the morphology and volume of adherent cells. The model predicted the bistability of cell morphology (i.e., a snap-through instability) under hydrostatic pressure for certain ranges of adhesion energy density. This snap-through instability can enable cells to spontaneously detach from their environment, and may have bearing on migration and metastasis.

Nonlinear Optical Properties of Al0.3Ga0.7As/GaAs Quantum Dots under Tunable Parameters

The nonlinear optical properties of quantum dots under multidimensional confinement potential are investigated. In the framework of the effective mass approximation, the analytical formula of the optical absorption coefficient in the quantum dots is derived using the density matrix method and the iterative procedure, and the numerical results of typical Al0.3Ga0.7 As/GaAs material are calculated. Through calculation and numerical fitting, it is found that increasing temperature and the depth of limiting potential will give rise to the absorption peak to move to the high‐energy region commonly referred to as the blueshift, within a certain range of parameter variations. While reducing the range of limiting potential, quantum dot radius and the hydrostatic pressure can achieve the same effect. It is important to emphasize that variations in hydrostatic pressure and the depth of the limiting potential result in significant changes to the peak value of the optical absorption coefficient. The research results have a certain guiding significance for further study of the optical properties of quantum dots under multidimensional confinement potential and their application in practical production.

Pressure-Induced Phase Transitions of Nonionic Polymer Brushes

While the temperature responsive behavior of nonionic polymers has been extensively studied and is nowadays one of the key mechanisms of smart materials, the pressure response of thin films remains basically unexplored. We investigate the conformational transition of nonionic brushes and semidilute solutions induced by hydrostatic pressure and temperature variations. Interestingly, the pressure–temperature phase diagram for the coil-to-globule transition of brushes, probed by neutron reflectometry, nearly coincides with that in semidilute solutions. We also show that the phase behavior can be understood and predicted with simple thermodynamic concepts employed so far for the denaturation of proteins. Fully atomistic molecular dynamics simulations provide molecular insight into the pressure-responsive behavior. Combining all three approaches allows us to demonstrate that pressure-induced hydration of nonionic polymers at low pressure is universal as it is dictated by water and is polymer-independent. In contrast, the pressure-induced dehydration at high pressure is strongly polymer-specific. The outcomes apply to a wide class of nonionic polymers and can aid the design of responsive coatings with the desired pressure-responsive behavior.

Design modification and performance evaluation of mini-hydrostatic pressure apparatus for inclined plane circular surface

Mini-Hydrostatic Pressure Apparatus (MHSPA), of spatial size 230×210×210 mm3, was developed for individual or limited number of users to promote Covid-19 social distance protocol. A solid hemisphere with an inclined circular segment made from gypsum material (CaSO2.0.5H2 O) and coated with filler putty and oil paint, is used in place of the regular quadrants. With the solid attached to a horizontal beam mounted over a pivot, hydrostatic forces due to liquids were measured at different heights of water. The results showed that the assembly could be used to demonstrate variation of hydrostatic pressure on circular surfaces at different heights of liquid with an average difference of 4.38% against average theoretical values. Compared to other results from the use of conventional quadrants in literature, the associated error is minimal, and indicates the possibility of adopting the apparatus in school laboratories for static pressure demonstration.

Application of Noise Attenuation on 2D Shallow Offshore Seismic Reflection Data: A Case Study from the Baltic Sea

Noise is always present in offshore seismic data, as there isn't a single method that could eliminate all the forms of noise. In this study, noise removal techniques were applied to attenuate different noises in 2D shallow-marine seismic data from the Baltic Sea area. Amplitude recovery should be applied before the noise attenuation stage as a preconditioning process for showing all noises in the deeper part of the seismic data. Frequency filters (notch filter and low-cut filter), frequency-wavenumber (FK) filter, and swell noise attenuation (Deswell) were applied as robust noise attenuation techniques. The method of directly modifying the amplitude spectrum of the seismic data is known as frequency filtering. A notch filter can be used to remove the harmonic noise of the power line harmonic noise (mono-frequency noise). A low-cut filter can be used to remove the low-frequency noises due to the influence of hydrostatic pressure variations. The linearly correlated events, such as tail-buoy and operational noise, were removed using the FK filter. Incoherent noise, such as swell noise, can be attenuated by swell noise attenuation (Deswell). The seismic results are displayed before and after the applied noise attenuation techniques to prove the validity of the applied filters. This study aimed to show the importance of shallow offshore seismic data processing in removing different types of noise, as it increases the value of data for seismic data interpretation and marine geohazard assessment.

Autonomous methane seep site monitoring offshore western Svalbard: hourly to seasonal variability and associated oceanographic parameters

Abstract. Improved quantification techniques of natural sources are needed to explain variations in atmospheric methane. In polar regions, high uncertainties in current estimates of methane release from the seabed remain. We present unique 10- and 3-month time series of bottom water measurements of physical and chemical parameters from two autonomous ocean observatories deployed at separate intense seabed methane seep sites (91 and 246 m depth) offshore western Svalbard from 2015 to 2016. Results show high short-term (100–1000 nmol L−1 within hours) and seasonal variation, as well as higher (2–7 times) methane concentrations compared to previous measurements. Rapid variability is explained by uneven distribution of seepage and changing ocean current directions. No overt influence of tidal hydrostatic pressure or water temperature variations on methane concentration was observed, but an observed negative correlation with temperature at the 246 m site fits with hypothesized seasonal blocking of lateral methane pathways in the sediments. Negative correlation between bottom water methane concentration (and variability) and wind forcing, concomitant with signs of weaker water column stratification, indicates increased potential for methane release to the atmosphere in fall and winter. We present new information about short- and long-term methane variability and provide a preliminary constraint on the uncertainties that arise in methane inventory estimates from this variability.

DFT pressured BaTiO3 calculation using WC and HSE functionals and ONCV pseudopotentials

Theoretical BaTiO3 (BTO) single crystal with tetragonal phase was studied as a function of tensile and compressive pressure using Wu-Cohen (WC) and Heyd–Scuseria–Ernzerhof (HSE) exchange-correlational functional and the optimized norm-conserving Vanderbilt (ONCV) pseudopotentials. The results show different physical property anomalies associated with possible phase transitions. The lattice parameters evidence an anomaly at −7 GPa corresponding to the known super-tetragonality transition reported by Tinte et al. and Kvasov et al. [21]. The tetragonality coefficient indicates an apparent cubic phase at P= +2.17 GPa, however, the different Ti-O bond lengths and the phonons associated with the optical modes in the Brillouin zone center suggest that symmetric order of cubic phase is not reached in this pressure. While an additional anomaly at +7 GPa seems to be related to a well-ordered cubic structure. Furthermore, Löwdin atomic population analysis with variation in hydrostatic pressure provided information on the behavior of chemical bonds in BTO. Finally, the theoretical results are compared with those experimentally reported in the literature.

Correlation between anomalous thermal expansion coefficient and barocaloric effect: Application to spin crossover systems

We report the strong correlation between anomalous thermal expansion in solid-solid volumetric phase transition and the barocaloric effect. This investigation was carried out in {Fe[H2B(pz)2]2(bipy)} (pz = pyrazolyl; bipy = bipyridine) spin crossover system, in which the spin of Fe2+ changes from sLS = 0 to sHS = 2 coupled with high unit cell volume changes from VLS = 2356 to VHS = 2462 Å3, at T1/2–160 K. Giant barocaloric effect, through the isothermal entropy change (ΔST = 60 J kg−1 K−1) upon moderated hydrostatic pressure variation (ΔP = 1 kbar), was indirectly obtained from reported pressure dependence of magnetic susceptibility. Theoretical results, obtained from our microscopic model, updated with the reported metal-ligand asymmetrical stretching z-vibration modes, from DFT calculation, showed a remarkable agreement with the experimental data.

Refrigeration through Barocaloric Effect Using the Spin Crossover Complex {Fe[H2B(pz)2]2(bipy)}

Spin crossover complexes have a very striking signature of a huge volume change coupled with low–high spin conversion around a critical temperature, which can be pressure tuned in a large temperature interval. Herein, the barocaloric effect is reported in the spin crossover complex {Fe[H2B(pz)2]2(bipy)} (bipy = 2,2′‐bipyridine) from theoretical and applied points of view. The experimental data reveal a giant barocaloric effect, through the isothermal entropy change (ΔST = 83 J kg−1 K−1) around T = 273 K, upon moderated hydrostatic pressure variation (ΔP = 2 kbar). The high and linear behavior in the pressure dependence of the phase transition temperature (19 K kbar−1) leads to a huge relative cooling power (RCP = 7296 J kg−1) upon ΔP = 3 kbar, which is discussed using Ericsson's cooling cycle. Theoretical results, obtained from a microscopic model, updated with the vibration modes from density functional theory (DFT) calculation, show remarkable agreement with the experimental data.

Multistage development of a hydrothermal W deposit during the Variscan late-orogenic evolution: the Puy-les-Vignes breccia pipe (Massif Central, France)

The Puy-les-Vignes W deposit, located in the northwestern French Massif Central (FMC), is a rare occurrence of a wolframite-mineralized hydrothermal breccia pipe hosted in high-grade metamorphic gneisses. We present an integrated study of this deposit aiming to characterize the ore-forming hydrothermal system in link with the Variscan late-orogenic evolution of the FMC. Based on a set of representative samples from the host rocks and mineralization, we describe a detailed paragenetic sequence and we provide the major and trace element geochemistry of the granitic rocks and W–Nb–Ta–Sn–Ti oxide minerals, in situ U/Pb and 40Ar/39Ar geochronology, and a fluid inclusion study of quartz and wolframite. We demonstrate that the formation of this W-mineralized breccia pipe results from a multistage development related to four major episodes during the late Carboniferous. The first episode corresponds to the emplacement of an unexposed peraluminous granite at ca. 324 Ma, which generated microgranite dykes exposed at the present-day surface. The second episode is the formation of the quartz-supported breccia pipe and wolframite mineralization at ca. 318 Ma at a paleodepth of 7 km. The mineralizing fluids have a H2O–NaCl–CO2–CH4–N2 composition, a moderate-salinity (< 9 wt.% NaCl eq) and were trapped at high-temperatures (> 400 °C) during lithostatic to hydrostatic pressure variations caused by hydrofracturing of the host rocks. Wolframite deposition is interpreted to result from a W-rich intermediate-density magmatic fluid that exsolved from an evolved leucogranite and interacted with volatile-rich metasedimentary country rocks and/or possibly mixed with low-salinity metamorphic fluids of deep origin. The third episode corresponds to magmatic-hydrothermal Nb–Ta mineralization overprinting the W-mineralized system interpreted to be related to the intrusion at ca. 311 Ma of a rare-metal granite, which is part of a regional peraluminous rare-metal magmatism during the 315–310 Ma period. Finally, the last episode corresponds to disseminated Bi ± Au–Ag mineralization emplaced at ca. 300 Ma, which shares similar mineralogical features with late Carboniferous orogenic gold deposits in the FMC. The Puy-les-Vignes W deposit records, therefore, a multistage and long-lived development that extends over a timespan of 25 million years in a regional setting dominated by protracted peraluminous magmatism and high-temperature and low-pressure metamorphism. Although the local environment of ore deposition is atypical, our results show that the mineral assemblages, alteration styles, and fluid characteristics of the Puy-les-Vignes breccia pipe are similar to those of other peri-granitic W deposits in the FMC.

UAV-based thermal imaging and heat output estimation of a coastal geothermal resource: La Jolla beach, Baja California, Mexico

The exploration of unexploited geothermal resources is required to encourage the use of renewable energy. This study focuses on La Jolla beach, Ensenada, Mexico. The beach hosts a thermal anomaly with temperatures of up to 52 °C at the surface and up to 93 °C at 20 cm depth. The objectives were to: map the thermal anomaly, understand the impact of tides, quantify the thermal water discharge rate and heat output, and discuss a direct use of the energy. The mapping was performed with Unmanned Aerial Vehicles equipped with optical and thermal cameras at two different dates. Additional temperature measurements were performed with a thermocouple, while the total fluid discharge was estimated from flow measurements. A comparison between the campaigns indicated that the highest surface temperature area was more than three times larger in 2019 than in 2018 (259 m2 vs. 69 m2). Such change was due to the tidal range and associated hydrostatic pressure variations. The total thermal water discharge is 330 ± 44 L s−1, which corresponds to an advective heat output of 40.5 ± 5.2 MWt. The use of this energy in a Multi-Effect Distillation desalinization plant can contribute to cover the shortage of freshwater in Ensenada.