Variable Pressure Conditions Research Articles

Unified EOS incorporating the finite strain theory for explaining thermo elastic properties of high temperature superconductors, nanomaterials and bulk metallic glasses

In the present research paper, we have proposed a novel EOS, which is based on the concepts of finite strain theories for predicting the thermo elastic properties of various materials viz. bulk metallic glasses, nanomaterials, and high temperature superconductors. Development of the present EOS involved deriving an innovative mathematical framework that considers the effects of finite strain, enabling the prediction of essential properties like pressure and bulk modulus under different compression ratios. For validity and applicability of the proposed EOS, we have conducted an extensive analysis by comparing the calculated thermo elastic properties with existing theoretical models or equation of sates and experimental data available in the literature. The present comparison revealed a remarkable agreement between our predictions and the observed values for a wide range of compression of nanomaterials, bulk metallic glasses, and superconductors. Our research not only introduces a comprehensive equation of state for these advanced materials but also demonstrates its effectiveness in accurately capturing their unique thermodynamic behavior. This present derived EOS can serve as a valuable tool to predict and understand the response of nanomaterials, bulk metallic glasses, and superconductors to varying pressure conditions, aiding the design and development of innovative applications in fields such as materials science, nanotechnology, and condensed matter physics.

Enhanced CO2 capture potential of UiO-66-NH2 synthesized by sonochemical method: experimental findings and performance evaluation

The excessive release of greenhouse gases, especially carbon dioxide (CO2) pollution, has resulted in significant environmental problems all over the world. CO2 capture technologies offer a very effective means of combating global warming, climate change, and promoting sustainable economic growth. In this work, UiO-66-NH2 was synthesized by the novel sonochemical method in only one hour. This material was characterized through PXRD, FT-IR, FE-SEM, EDX, BET, and TGA methods. The CO2 capture potential of the presented material was investigated through the analysis of gas isotherms under varying pressure conditions, encompassing both low and high-pressure regions. Remarkably, this adsorbent manifested a notable augmentation in CO2 adsorption capacity (3.2 mmol/g), achieving an approximate enhancement of 0.9 mmol/g, when compared to conventional solvothermal techniques (2.3 mmol/g) at 25 °C and 1 bar. To accurately represent the experimental findings, three isotherm, and kinetic models were used to fit the experimental data in which the Langmuir model and the Elovich model exhibited the best fit with R2 values of 0.999 and 0.981, respectively. Isosteric heat evaluation showed values higher than 80 kJ/mol which indicates chemisorption between the adsorbent surface and the adsorbate. Furthermore, the selectivity of the adsorbent was examined using the Ideal Adsorbed Solution Theory (IAST), which showed a high value of 202 towards CO2 adsorption under simulated flue gas conditions. To evaluate the durability and performance of the material over consecutive adsorption–desorption processes, cyclic tests were conducted. Interestingly, these tests demonstrated only 0.6 mmol/g capacity decrease for sonochemical UiO-66-NH2 throughout 8 consecutive cycles.

Thermal Conductivity of Frozen and Unfrozen Gas-Saturated Soils

Arctic permafrost often contains gas-saturated horizons. The gas component in freezing and frozen soils can exist under different pressures, which are expected to affect their properties and behavior. The effect of pore gas pressure on the thermal conductivity of frozen and unfrozen silt loam saturated with methane or carbon dioxide at pressures below the hydrate formation conditions is observed in the current study. The variable gas pressure and temperature conditions are simulated in a specially designed pressure cell, which allows thermal conductivity measuring in pressurized samples at positive and negative temperatures. The experiments using natural samples collected near the gas emission crater (Yamal Peninsula) show that thermal conductivity is sensitive to pore gas pressure even at high moisture contents. The thermal conductivity of methane-saturated soil becomes 4% and 6% higher in frozen and unfrozen samples, respectively, as the gas pressure increases from 0.1 MPa to 2 MPa. In the case of CO2 saturation, the respective thermal conductivity increase in frozen and unfrozen samples reaches 25% and 15% upon pressure change from 0.1 to 0.9 MPa. The results stimulate further special studies of the effects of gas type and pressure on the thermal properties of closed gas-saturated taliks, of which the pore pressure is increasing during freezing up.

Investigating the crystal structure of ZrB2 under varied conditions of temperature, pressure, and swift heavy ion irradiation

The influence of temperature, pressure, and swift heavy ions on the structural characteristics of a nano-sized zirconium diboride crystal (43 nm) was investigated using X-ray diffraction and Small-Angle X-ray Scattering/Wide-Angle X-ray Scattering (SAXS/WAXS) powder diffraction methods. Within the temperature range of 300–773 K, alterations in lattice parameters, lattice volume, coefficient of thermal expansion, and the kinetics of water molecule absorption on the active surface of the zirconium diboride crystal were comprehensively analyzed. Furthermore, the mechanism responsible for the structural degradation of absorbed water molecules was elucidated. The degree of amorphization in the ZrB2 nano crystal reached its maximum when subjected to irradiation by fast 132Xe26+ ions with an energy of 167 MeV, at fluences of up to 3.0 × 1014 ions/cm2. Additionally, the expansion mechanism of lattice parameters and the kinetics of the phase transformation process under the influence of swift heavy ions were studied. Notably, pressure variations did not induce a phase transition within the lattice structure. However, when exposed to an 8.0 GPa pressure, the lattice underwent substantial maximum contraction, reducing by up to 20.5 Å3.

Design and evaluation of a novel process for green hydrogen production in the iodine–sulfur cycle via pressure-swing distillation of HIx (HI-I2-H2O)

In striving for carbon neutrality, hydrogen energy serves as a sustainable solution, and the iodine–sulfur (IS) cycle stands out as the most promising method for hydrogen production. The separation and purification of HI from the HIx (HI-I2-H2O) mixture holds significant research value, as they constitute the crucial aspect of the iodine–sulfur cycle in hydrogen production. Due to the azeotropic behavior of HI and H2O, the HIx system poses a considerable challenge. In this research, a technique for purifying HI via pressure-swing distillation was developed, exploiting the changes in azeotropic points under varying pressure conditions. The most effective method for HI purification was determined to be a three-column pressure-swing distillation configuration, as revealed by Aspen Plus phase diagrams and process topology mapping. It yielded H2O and I2 at the top of the first column, I2 at the bottom of the second column, and HI at the top of the third column with an HI recovery rate of 97 %. By analyzing the Bunsen reaction kinetics of the core reaction in the IS system, a comprehensive method for evaluating the separation and reaction coupling quality network of HIx cycle system using Bunsen-factor (B-factor) was proposed. The B-factor elucidates the correlation between the Bunsen reaction rate and the concentrations of [H+], [I-], [I3-], as well as the pH level. A comprehensive analysis of the B-factor was conducted for the pressure-swing distillation topologies of the HIx system, and the results were contrasted with those of alternative separation processes. The findings indicated that the three-column pressure-swing distallation is the most suitable option for both separation and reaction quality in a recycled network. The total energy consumption of the newly designed HIx three-column process is 352 MJ/kmol, rendering it more economical and beneficial than other processes. This study presents a pressure-swing distillation method for HI separation and purification, which is broadly applicable in IS cycles and aids in achieving large-scale production of green H2. This method enables the achievement of the dual-carbon objective, which seeks to mitigate carbon emissions while safeguarding the environment.

Non-monotonic effect of growth pressure on the responsivity of AlGaN ultraviolet Schottky detectors

Three AlGaN-based Schottky detector samples grown with varying pressure conditions are prepared and their responsivity is investigated. It is found that the responsivity of the three samples first increases and then decreases with the increase of pressure. In addition, the vacancy defect concentration increases and carbon impurities concentration decreases when the reactor pressure increases from 100 mbar to 200 mbar during the i-AlGaN layer growth. It is assumed that carbon impurities and vacancy defects play a negative role in detector’s performance, which increase the recombination of photogenerated carriers and reduce detector responsivity. The relationship between growth pressure and detector responsivity is not linear. It is necessary to select a suitable growth pressure to improve the performance of AlGaN detectors.

Mineralogy, petrology, and oxygen isotopic compositions of chondritic and achondritic lithologies in the anomalous CB carbonaceous chondrites Sierra Gorda 013 and Fountain Hills

AbstractThe CB (Bencubbin‐like) metal‐rich carbonaceous chondrites are subdivided into the CBa and CBb subgroups. The CBa chondrites are composed predominantly of ~cm‐sized skeletal olivine chondrules and unzoned Fe,Ni‐metal ± troilite nodules. The CBb chondrites are finer grained than the CBas and consist of chemically zoned and unzoned Fe,Ni‐metal grains, Fe,Ni‐metal ± troilite nodules, cryptocrystalline and skeletal olivine chondrules, and rare refractory inclusions. Both subgroups contain exceptionally rare porphyritic chondrules and no interchondrule fine‐grained matrix, and are interpreted as the products of a gas–melt impact plume formed by a high‐velocity collision between differentiated planetesimals about 4562 Ma. The anomalous metal‐rich carbonaceous chondrites, Fountain Hills and Sierra Gorda 013 (SG 013), have bulk oxygen isotopic compositions similar to those of other CBs but contain coarse‐grained igneous clasts/porphyritic chondrule‐like objects composed of olivine, low‐Ca‐pyroxene, and minor plagioclase and high‐Ca pyroxene as well as barred olivine and skeletal olivine chondrules. Cryptocrystalline chondrules, zoned Fe,Ni‐metal grains, and interchondrule fine‐grained matrix are absent. In SG 013, Fe,Ni‐metal (~80 vol%) occurs as several mm‐sized nodules; magnesiochromite (Mg‐chromite) is accessory; daubréelite and schreibersite are minor; troilite is absent. In Fountain Hills, Fe,Ni‐metal (~25 vol%) is dispersed between chondrules and silicate clasts; chromite and sulfides are absent. In addition to a dominant chondritic lithology, SG 013 contains a chondrule‐free lithology composed of Fe,Ni‐metal nodules (~25 vol%), coarse‐grained olivine and low‐Ca pyroxene, interstitial high‐Ca pyroxene and anorthitic plagioclase, and Mg‐chromite. Here, we report on oxygen isotopic compositions of olivine, low‐Ca pyroxene, and ±Mg‐chromite in Fountain Hills and both lithologies of SG 013 measured in situ using an ion microprobe. Oxygen isotope compositions of olivine, low‐Ca pyroxene, and Mg‐chromite in these meteorites are similar to those of magnesian non‐porphyritic chondrules in CBa and CBb chondrites: on a three‐isotope oxygen diagram (δ17O vs. δ18O), they plot close to a slope‐1 (primitive chondrule mineral) line and have a very narrow range of Δ17O (=δ17O–0.52 × δ18O) values, −2.5 ± 0.9‰ (avr ± 2SD). No isotopically distinct relict grains have been identified in porphyritic chondrule‐like objects. We suggest that magnesian non‐porphyritic (barred olivine, skeletal olivine, cryptocrystalline) chondrules in the CBas, CBbs, and porphyritic chondrule‐like objects in SG 013 and Fountain Hills formed in different zones of the CB impact plume characterized by variable pressure, temperature, cooling rates, and redox conditions. The achondritic lithology in SG 013 represents fragments of one of the colliding bodies and therefore one of the CB chondrule precursors. Fountain Hills was subsequently modified by impact melting; Fe,Ni‐metal and sulfides were partially lost during this process.

Comprehensive analysis of the structural, elastic, electronic, optical, and mechanical properties of orthorhombic CS(NH2)2 under pressure: A first-principles approach

This study provides a comprehensive theoretical assessment of the orthorhombic compound CS(NH2)2, examining its properties under varying pressure conditions. Employing the ultrasonic plane wave pseudopotential technique, first-principles calculations were conducted within the density functional theory (DFT) framework using the Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation (GGA) exchange-correlation functional. The study evaluates the compound's structural, elastic, electronic, optical, and mechanical properties. Simulations with hydrostatic pressure up to 20 GPa reveal changes in structural properties, elastic constants, and mechanical properties. The study estimates material brittleness and ductility based on Poisson's ratio and the B/G ratio. Elastic anisotropy is analyzed using various anisotropy indices. The compound exhibits a direct band gap along the (Z - Z) direction up to 2 GPa, transitioning to a direct band gap along the (U - Z) direction under higher pressures. Additionally, the band gap decreases from 3.817 eV to 2.38 eV as pressure increases from 0 GPa to 20 GPa. Optical properties are investigated by calculating dielectric functions, absorption coefficient, conductivity, reflectivity, and refractive indices for photon frequencies up to 40 eV. The HOMO-LUMO energy gap is estimated at approximately 5.548 eV. Hirshfeld surface analysis indicates significant contributions to crystal packing from interactions such as H···S/S···H (48%), H···H (35%), H···N/N···H (7.8%), and C···H/H···C (5.1%). This research presents the first quantitative theoretical prediction of the elastic, electronic, and optical properties of CS(NH2)2, contributing to our understanding of its behavior under pressure. Although experimental confirmation is required, these findings significantly advance the existing knowledge on the compound's properties and behavior under pressure.

Photoelectric and structural properties of super stable perovskite quantum dots glasses for contactless underwater electroluminescent LEDs

The photoelectric field has witnessed notable progress with the emergence of perovskite quantum dots. However, their practical utility is constrained by their susceptibility to degradation and malfunction when exposed to external environmental factors like light, heat, and humidity. To overcome these limitations, a potential solution lies in the growth of perovskite quantum dots within glasses, leveraging the dense network structure of inorganic glasses to achieve a seamless encapsulation of the quantum dots. This approach effectively addresses the challenges of quantum dot stability and the risk of lead contamination by isolating the quantum dots from the external environment. This study utilizes an in situ nanocrystallization approach to cultivate CsPbBr3 perovskite quantum dots within a matrix of glasses. The resulting CsPbBr3 perovskite quantum dots glasses (CsPbBr3 PQDs@glasses) demonstrate a vibrant green emission due to exciton recombination radiation. The investigation focused on the luminescent characteristics of CsPbBr3 PQDs@glasses subjected to pressures ranging from 0 to 7 GPa, which resulted in a significant red shift in the spectra, transitioning from 519 nm to 525 nm. Electronic structure, dispersion and vibrational properties of CsPbBr3 was investigated under varying pressure conditions through the utilization of first-principles methods. Furthermore, an examination of the pressure distribution within the diamond anvil cells was conducted from a macroscopic perspective employing the finite element method. Subsequently, contactless underwater electroluminescence devices incorporating CsPbBr3 PQDs@glasses were devised, employing the principle of electromagnetic induction. This study offers essential insights into the physics of perovskite materials subjected to high pressure, thereby establishing a groundwork for prospective applications.

Changing Law of Permeability of Coal Reservoirs under Variable Pressure Conditions and Its Influence on Extraction Efficiency of Coalbed Methane

Coal permeability data are critical in the prevention and control of coal and gas outbursts in mines and are an important reservoir parameter for the development of coalbed methane. The mechanism by which permeability is affected by gas pressure is complex. We used a self-developed true triaxial seepage experimental device that collects lignite and anthracite coal samples, sets fixed axial pressure and confining pressure, and changes gas pressure by changing the orientation of the coal seam to study the influence of the gas pressure on the permeability of the coal seam under the conditions of different coal types and different bedding orientations. Coal permeability decreased rapidly and then decreased slowly and tended to be stable with the increase in gas pressure. This conformed to the power exponential fitting relationship, and the fitting degree reached more than 99%. The comparison of the two anthracite coal samples showed that the sample’s permeability with a bedding plane vertical to the seepage direction was significantly lower than that of the bedding plane parallel to the seepage direction, indicating that gas seeped more easily along the bedding. The sensitivity coefficient of permeability with the change in gas pressure was calculated. The analysis showed that coal permeability was sensitive to changes in gas pressure during the low-pressure stage. When the gas pressure was greater than 0.8 MPa, the sensitivity coefficient was significantly reduced, which may have been related to the slow increase in the amount of gas absorbed by the coal seam in the high-pressure stage. A theoretical calculation model of coal seam permeability considering adsorption/desorption and seepage effects was proposed and then verified with experimental results showing that the theoretical model better reflected the permeability characteristics of coal and predicted its permeability. Using the finite element simulation software COMSOL, the extraction efficiency of the coal seam gas under different gas pressure conditions was simulated. The results showed that coal permeability and extraction efficiency decreased with an increase in gas pressure. In the low-pressure stage, the reduction in the extraction efficiency was more evident than that in the high-pressure stage.

A comparative study of structural, electronic, magnetic, and pressure-dependent properties of Full-Heusler Fe2XSi (X=Mn and Co): first-principles calculation and Monte Carlo Simulation

This study investigates the structural, electronic, magnetic, and pressure-dependent properties of Fe2XSi (X=Mn and Co) full-Heusler alloy through a comprehensive computational approach. The structural stability of these alloys confirmed L21 and XA prototypes as favorable structures for Fe2MnSi and Fe2CoSi, respectively. In addition, Fe2MnSi exhibits 100% spin polarization suggesting its potential suitability for spintronics applications. Conversely, Fe2CoSi does not exhibit similar behavior. The calculated magnetic moments of these alloys revealed an increase due to Coulomb interaction (U). The magnetic moments satisfy the Slater-Pauling relation, with calculated values of 3 for Fe2MnSi and 5 for Fe2CoSi. Heisenberg exchange interaction parameters are calculated to illustrate distinct magnetic interactions within the alloys. The study further explores thermomagnetic properties through Monte Carlo simulations, including thermal magnetization, thermal magnetic susceptibility, and Curie temperature The calculated were found to be 294 K for Fe2MnSi and 1029 K for Fe2CoSi, showing close agreement with experimental data. We additionally investigate the pressure-dependent properties of these alloys, revealing a non-linear dependence of the band gap on pressure for Fe2MnSi, with values decreasing from 0.668 eV to 0.259 eV as pressure increased from −15.917 to 23.712 GPa. For Fe2CoSi, the band gap remained zero across varying pressure conditions, indicating its metallic conducting behavior.

Effect of Pressure Conditions in Uterine Decellularization Using Hydrostatic Pressure on Structural Protein Preservation.

Uterine regeneration using decellularization scaffolds provides a novel treatment for uterine factor infertility. Decellularized scaffolds require maximal removal of cellular components and minimal damage to the extracellular matrix (ECM). Among many decellularization methods, the hydrostatic pressure (HP) method stands out due to its low cytotoxicity and superior ECM preservation compared to the traditional detergent methods. Conventionally, 980 MPa was utilized in HP decellularization, including the first successful implementation of uterine decellularization previously reported by our team. However, structural protein denaturation caused by exceeding pressure led to a limited regeneration outcome in our previous research. This factor urged the study on the effects of pressure conditions in HP methods on decellularized scaffolds. The authors, therefore, fabricated a decellularized uterine scaffold at varying pressure conditions and evaluated the scaffold qualities from the perspective of cell removal and ECM preservation. The results show that by using lower decellularization pressure conditions of 250 MPa, uterine tissue can be decellularized with more preserved structural protein and mechanical properties, which is considered to be promising for decellularized uterine scaffold fabrication applications.

Экспериментально-аналитические исследования пожарной опасности материалов, применяемых в оборудовании с обогащенными кислородом средамипри повышенных давлениях, и пути снижения их горючести

Introductio n. Sealed equipment (hereinafter referred to as hermetic chambers) is used in various branches of economy. Atmospheres enriched with oxygen (in some cases under variable pressure conditions) are used. It was shown that the main reason of the fires in the pressurized chambers was the unregulated use of the electrical equipment, as well as combustible substances and materials on the basis of organic compounds included in the materials used in the pressurized chambers. Objective. To find ways to decrease combustibility of materials used in pressurized chambers and to study fire risk parameters of pressurized chambers with high oxygen content and increased pressure. Obje ctives. To determine the boundary conditions of applying materials with increased values of temperature, oxygen content and pressure and analyze the results of experimental studies of combustibility of materials used in sealed chambers. Research met hods. Investigation of the characteristics of the combustion process of non-metallic materials under increased pressure was carried out on an original setup represented by a stainless steel vessel with a height of 750 mm and an inner diameter of 155 mm. A spiral of nichrome wire was used to ignite the sample. The pressure was fixed with a manometer. Results and th eir discussion. As a result of experimental research of fire hazard of construction and construction materials in oxygen-enriched media and under increased pressure the ways of increasing the oxygen concentration limit (OCL) and reduction of combustibility of materials were determined: application of heat-removing surface, incombustible shell; putting inhibitors in their composition and structure; surface treatment with different fire protective compositions and impregnations. When studying the parameters of fire hazard (flame propagation velocity, heat of combustion, autoignition temperature) of materials under the conditions of changes in the composition of nitrogen-oxygen atmosphere and pressure, it was found that the OCL for all materials decreases at higher pressures. Conc lusions. It is found that the limiting oxygen concentration depends on the geometrical dimensions of the sample, as well as on the speed of the gas flow. At higher pressures the OCL for all the materials decreases. The presence of a heat-removing surface also leads to higher OCL, which increases with increasing substrate thickness and decreasing thickness of the material on it. For materials not containing substances that inhibit the combustion reaction, a decrease in the LOC value with an increase in the number of hydrogen atoms in the polymer macromolecule is characteristic.

Genetic implications, composition, and structure of trioctahedral micas in xenoliths related to Plinian eruptions from the Somma-Vesuvius volcano (Italy)

Abstract The present work is part of a systematic mineralogical and petrographic characterization of mica-bearing xenoliths from Somma-Vesuvius volcano (Roman Magmatic Province, southern Italy). Skarns, composite skarns-marbles and cumulates from Pompeii Plinian eruption (AD 79), and skarns and syenite from Avellino eruption (3945 ± 10 cal yr BP) were investigated to define the crystal chemistry of the Somma-Vesuvius trioctahedral micas and to draw inferences on petrogenetic processes to which they were subjected. Xenoliths were characterized by means of polarized optical microscopy, scanning electron microscopy (SEM-EDS), X-ray powder diffraction (XRPD), and bulk-rock geochemical analyses. Mica crystals were studied using electron microprobe analysis (EMPA) and single-crystal X-ray diffraction (SCXRD). Micas from skarns are variably associated with Mg ± Ca silicates (clinopyroxene, vesuvianite, humite, clinohumite, chondrodite, forsterite, and garnet), other sporadic silicates (anorthite, sodalite, titanite, and britholite), apatite, calcite, various types of oxides, as well as rare sulfides and halides. In composite skarn-marble rocks, the mineral assemblages show some differences compared to skarns, as a lack of clinopyroxene and the presence of dolomite. Cumulate samples consist of mica and clinopyroxene, whereas syenite is mainly composed of mica, K-feldspar, feldspathoids, and clinopyroxene. Together with mica, apatite occurs in all the lithotypes. Trace element arrays are scattered for skarn and composite skarn-marble samples. The REE patterns have a general enrichment in light (La, Ce, Pr, Nd) and medium (Sm, Eu, Gd, Tb, Dy) rare earth elements, in some cases with slight positive Gd anomaly. Cumulate samples generally have low amounts of Ba, Sr, Zr, and Th, while syenite exhibits low concentrations of trace elements, except for Rb, Cs, and Tl. Mica crystals occurring in the studied xenoliths are phlogopite with different Al and Mg contents at the octahedral site, a negligible tetraferriphlogopite component and variable dehydrogenation degree. All samples belong to the 1M polytype (C2/m and C2 space group) and have a wide range of unit-cell parameters, especially of the c axis [5.3055(1) ≤ a ≤ 5.3218(1) Å, 9.1893(1) ≤ b ≤ 9.2188(4) Å, 10.1803(2) ≤ c ≤ 10.2951(2) Å]. The shortest c-cell parameter pertains to de-hydrogenated phlogopite from Avellino skarn, whereas OH-rich phlogopite from Pompeii composite skarns-marbles has a c-cell parameter that approximates that of the end-member phlogopite. Overall, it is observed that the crystal chemistry of the micas studied here extends the known range of the other Vesuvian micas from the literature. The Ti-depletion and the wide degree of dehydrogenation of phlogopites from skarns and composite skarns-marbles suggest that the studied samples originated under variable pressure conditions. In addition, the presence of humite in the mineral assemblage seems to indicate the occurrence of devolatilization reactions. The scarce mica occurrence in cumulate and mainly in syenite, instead, may depend on pressure conditions in the magma storage system exceeding the mica stability.

A calibration method of discrete element contact model parameters for bulk materials based on experimental design method

This study proposes a method to address the issues of large amount of calculation and low efficiency in the calibration of discrete element method (DEM) contact model parameters for rockfill, which is based on the experimental design method. Plackett-Burman design method was used to analyze the significance of each contact model parameter to the macro-mechanical parameters. Second-order response surface regression models were developed to analyze the relationship between macro-mechanical parameters and contact model parameters that have significant impact on them. The contact model parameters in the rockfill DEM were calibrated using a multi-objective optimization method based on laboratory triaxial tests. The calibrated parameters were then used to simulate discrete element triaxial tests of the rockfill under varying pressure conditions. The study demonstrates that calibrated parameters can accurately predict the macroscopic behavior of rockfill under different confining pressures. Additionally, the calibration method has good applicability and effectiveness.

Experimental Study on Coal Seam Gas Desorption Characteristics Caused by Moisture under Stepwise Depressurization

Expansion energy is the main factor of coal and gas outbursts, and the gas desorption around the outburst hole is developed in variable pressure conditions. While studying the impact of moisture on gas desorption characteristics, atmospheric pressure desorption is usually used, but its characteristics under variable pressure conditions have not been thoroughly investigated. In this study, typical outburst coal samples with different water contents from the Jincheng mining area of China were selected as research objects, and the effects of water on gas displacement, desorption, desorption rate, and gas desorption index (K1) of drilling cuttings under step-by-step depressurization were analyzed by means of stepwise depressurization and atmospheric desorption experiments. The research conclusions suggest that (1) the amount of gas replacement, which augments rapidly during the inception, increases with the growth of water content under the experimental conditions, and then the rate decreases; (2) the gas desorption falls gradually at different depressurization stages when the humidity is constant, while the total desorption and the drop amplitude taper with the increasing water content; (3) the additional water enhances the desorption rate significantly only at the initial stage, but scarcely has an impact later on; and (4) the value of the drilling cuttings’ gas desorption index (K1) shows a downward trend with the developing humidity in each stage of stepwise depressurization desorption. We take humidity as a variable to simulate the desorption process of coal gas around the hole when coal and gas outbursts occur in the laboratory and study the influence of water on the desorption characteristics under desorption conditions of stepwise depressurization. This provides a reference for the purpose of studying the mechanism of coal and gas outbursts from the perspective of energy.

Is isochoric vitrification feasible?

This study investigates the feasibility of ice-free isochoric vitrification for cryopreservation applications using mathematical modeling, computation tools, and the underlying principles of thermo-mechanics. This study is triggered by an increasing interest in the possibility of isochoric vitrification, following promising experimental results of isochoric cryopreservation. In general, isochoric cryopreservation is the preservation of biological materials in subzero temperatures in a rigid-sealed container, where some ice crystallization creates favorable pressure elevation due to the anomaly of water expansion upon ice Ih formation. Vitrification on the other hand is the transformation of liquid into an amorphous solid in the absence of any crystals, which is typically achieved by rapid cooling of a highly viscous solution. The current study presents a mathematical model for vitrification under variable pressure conditions, building upon a recently published thermo-mechanics modeling approach for isochoric cryopreservation. Using the physical properties of dimethyl sulfoxide (DMSO) as a representative cryoprotective agent (CPA), this study suggests that vitrification under isochoric conditions is not feasible, essentially since the CPA solution contracts more than the isochoric chamber by an order of magnitude. This differential contraction can lead to absolute zero pressure in the isochoric chamber, counteracting the premise of the isochoric cryopreservation process. It is concluded that the only alternative to prevent ice formation while benefiting from the potential advantages of higher pressures is to create the required pressures by external means, and not merely by passively enclosing the specimen in an isochoric chamber.

Deformation constraints of graphene oxide nanochannels under reverse osmosis

Nanochannels in laminated graphene oxide nanosheets featuring confined mass transport have attracted interest in multiple research fields. The use of nanochannels for reverse osmosis is a prospect for developing next-generation synthetic water-treatment membranes. The robustness of nanochannels under high-pressure conditions is vital for effectively separating water and ions with sub-nanometer precision. Although several strategies have been developed to address this issue, the inconsistent response of nanochannels to external conditions used in membrane processes has rarely been investigated. In this study, we develop a robust interlayer channel by balancing the associated chemistry and confinement stability to exclude salt solutes. We build a series of membrane nanochannels with similar physical dimensions but different channel functionalities and reveal their divergent deformation behaviors under different conditions. The deformation constraint effectively endows the nanochannel with rapid deformation recovery and excellent ion exclusion performance under variable pressure conditions. This study can help understand the deformation behavior of two-dimensional nanochannels in pressure-driven membrane processes and develop strategies for the corresponding deformation constraints regarding the pore wall and interior.

Experimental Study of Complex Resistivity Characteristics of a Sandstone Reservoir under Different Measurement Conditions

Due to the variability of fluid properties and saturation of reservoirs, large differences in formation temperature and pressure, and the diversity of rock and mineral compositions, the petrophysical response of reservoirs is often complex. This study explored a new method of reservoir fluid identification and evaluation based on the complex resistivity response characteristics of sandstone reservoirs under different measurement conditions. The complex resistivity of the five sandstone samples was measured under normal temperature and pressure and variable pressure, temperature, and formation conditions and under different oil saturations. Furthermore, the reservoir was comprehensively analyzed and evaluated based on the mineral composition, porosity, and permeability parameters. The results show that the resistivity of the sandstone increases logarithmically with pressure and oil saturation but decreases logarithmically with temperature and depth. The polarizability decreases slightly with increasing pressure and increases slightly with increasing temperature. With increasing depth, the polarizability decreases obviously, and with increasing oil saturation, the polarizability decreases moderately. Under different measurement conditions, the complex resistivity data for the sandstone reservoir and the IP parameters extracted through inversion are regular. The results of this study provide a new method for the identification and evaluation of complex reservoir fluids and have important reference value.

Leak detection and size identification in fluid pipelines using a novel vulnerability index and 1-D convolutional neural network

This paper proposes a leak detection and size identification technique in fluid pipelines based on a new leak-sensitive feature called the vulnerability index (VI) and 1-D convolutional neural network (1D-CNN). The acoustic emission hit (AEH) features can differentiate between normal and leak operating conditions of the pipeline. However, the multiple sources of acoustic emission hits, such as fluid pressure on the joints, interference noises, flange vibrations, and leaks in the pipeline, make the features less sensitive toward leak size identification in the pipeline. To address this issue, acoustic emission hit features are first extracted from the acoustic emission (AE) signal using a sliding window with an adaptive threshold. Since the distribution of the acoustic emission hit features changes according to the pipeline working conditions, a newly developed multiscale Mann–Whitney test (MMU-Test) is applied to the acoustic emission hit features to obtain the new vulnerability index feature, which shows the pipeline's susceptibility to leak and changes according to the pipeline working conditions. Finally, the vulnerability index is provided as input to a 1-D-CNN for leak detection and size identification, whose experimental results show a higher accuracy as compared to the reference state-of-the-art methods under variable fluid pressure conditions.