Pressure Medium Research Articles

Shaping the Future: Navigating Youth Ideology and Mental Health in a Digital Age

The rapid evolution of societal and cultural dynamics in the contemporary era presents both significant challenges and remarkable opportunities for the guidance of youth ideology and the promotion of mental health among young people. The pervasive influence of technology, especially social media, has transformed the way youth interact with the world and each other, impacting their ideological development and psychological well-being. This article examines the multifaceted challenges faced by today's youth, including the pressure of social media, the conflict between traditional values and modern norms, and the increased prevalence of mental health issues. Concurrently, it explores the opportunities that arise from these challenges—opportunities for leveraging technology for mental health support, the role of progressive education in shaping ideology, and the potential for family and community support structures to provide a nurturing environment. Through a review of diverse case studies, from the Finnish education system to digital platforms for mental health, this article provides insights into successful strategies and programs that address the complex needs of contemporary youth. These examples highlight the importance of a comprehensive and adaptive approach, emphasizing the need for collaboration across various sectors to foster a generation that is not only ideologically sound but also mentally resilient.

Nanocrystallization of Bi2O3 based system from the glassy state under high compression

This report presents the pressure-temperature (p-T) plane of Bi2O3-Al2O3-SiO2 ternary system in the context of nanocrystallite formation from its amorphous state. The diagram was constructed through differential thermal analysis (DTA) performed in situ under high-pressure-high-temperature (HP-HT) conditions, with nitrogen serving as the pressurizing medium. Above the glass transition temperature Tg, a wide ultraviscous, supercooled liquid state spanning approximately 150 K is observed. Later heating transforms this state into nanocrystallites embedded within an amorphous matrix, thereby keeping distinctive structural characteristics even after the decompression process. The p-T plane serves as a fundamental prerequisite for the design of nanocrystallites within a glass matrix, a well-established technique known as glass-ceramics. Various paths within the p-T plane, followed by annealing just below Tg, can be explored, potentially leading to the development of Bi2O3-based materials with enhanced electrical, dielectric, photonic, and mechanical properties, predicated on nanocrystallites formed by high-pressure treatment.

The microscopic Ampère formulation for the electromagnetic force density in linear dielectrics

We present a detailed derivation of the electromagnetic force density and pressure in linear dielectric media according to the so-called microscopic Ampère formulation, which considers the classical dipolar sources in matter along with the hidden momentum contribution. It is seen that, among the other formulations existing in the literature, our proposal is the only one universally compatible with the experimental works reported to date. A new radiation pressure equation for non-magnetic dielectrics under oblique illumination from p-polarized beams is also derived.

Expression, purification, and characterization of self-assembly virus-like particles of capsid protein L1 HPV 52 in Pichia pastoris GS115

BackgroundCervical cancer caused by the human papillomavirus (HPV) is one of the most frequent malignances globally. HPV 52 is a high-risk cancer-causing genotype that has been identified as the most prevalent type in Indonesia. Virus-like particles (VLP)-based vaccinations against HPV infection could benefit from self-assembled VLP of L1 capsid protein. ResultThe recombinant HPV 52 L1 was expressed in Pichia pastoris on a shake-flask scale with 0.5% methanol induction in this study. The copy number was used to compare the expression level and stability. The colony that survived on a solid medium containing 2000 μg/ml of Zeocin was selected and cultured to express HPV 52 L1. DNA was extracted from the chosen colony, and the copy was determined using qPCR. HPV 52 L1 protein was then purified through fast performance liquid chromatography. Transmission electron microscopy (TEM) evaluation confirmed the VLP self-assembly. The genomic DNA remained intact after 100 generations of serial cultivation under no selective pressure medium conditions, and the protein produced was relatively stable. However, the band intensity was slightly lower than in the parental colony. In terms of copy number, a low copy transformant resulted in low expression but produced a highly stable recombinant clone. Eventually, the L1 protein expressed in Pichia pastoris can self-assemble into VLP. Therefore, recombinant HPV possesses a stable clone and the ability to self-assemble into VLP. ConclusionThe recombinant L1 HPV 52 protein is successfully expressed in P. pastoris within a size range of approximately 55 kDa and demonstrated favorable stability. The L1 protein expressed in Pichia pastoris successful self-assembled of HPV VLPs, thereby establishing their potential efficacy as a prophylactic vaccine.

Li–Na interdiffusion and diffusion-driven lithium isotope fractionation in pegmatitic melts

Abstract. In this study, we investigate the diffusion of Li and its stable isotopes (6Li and 7Li) in flux-rich (1.8 % Li2O, 2.6 % B2O3, 2.3 % P2O5 and 3 % F) pegmatitic melts in order to contribute to the understanding of Li enrichment in such systems. Two glasses were synthesized with a model pegmatitic composition, one of which is highly enriched in Li (> 1 wt %, PEG2-blue) and the other one essentially Li-free (PEG2-Li-free). Diffusion couple experiments were performed to determine the chemical diffusivity of Li in dry pegmatitic melts. Experiments were conducted using rapid-heat and rapid-quench cold-seal pressure vessels in a temperature range of 650–940 ∘C at 100 MPa with Ar as the pressure medium. We observed rapidly formed diffusion profiles, driven by an interdiffusive exchange of the monovalent alkalis Li and Na, while the other elements are immobile on the timescale of experiments (1–30 min). From these experiments, activation energies for Li–Na interdiffusion were determined as 99 ± 7 kJ mol−1 with a pre-exponential factor of log D0 = −5.05 ± 0.33 (D0 in m2 s−1). Li and Na partitioning between the stronger depolymerized PEG2-blue and the less depolymerized PEG2-Li-free leads to a concentration jump at the interface; i.e. Na is enriched in the more depolymerized PEG2-blue. Li–Na interdiffusion coefficients in the studied melt composition are in a similar range as Li and Na tracer diffusivities in other dry aluminosilicate melts, confirming little to no effect of aluminosilicate melt composition on Li diffusivity. Thus, added fluxes do not enhance the Li diffusivity in the same way as observed for H2O (Holycross et al., 2018; Spallanzani et al., 2022). Using melt viscosity as a proxy for the polymerization of the melt shows that water has a stronger potential to depolymerize a melt compared to other fluxing elements. Faster diffusion of 6Li compared to 7Li leads to a strong Li isotope fractionation along the diffusion profile, resulting in δ7Li as low as −80 ‰ relative to the diffusion-unaffected regions. This diffusive isotope fractionation can be quantified with an empirical isotope fractionation factor (β) of 0.20 ± 0.04, similar to previously observed β values for Li diffusion in melts. This suggests in accordance with previously published data that a β value of ca. 0.2 seems to be universally applicable to diffusive Li isotope fractionation in aluminosilicate melts.

Tube explosion during continuous supercritical water oxidation of sludge: An incident investigation

Supercritical water oxidation (SCWO) is well known as a promising end-of-pipe technology for treatment of hazardous wastes. Safety is undoubtedly the first concern as the SCWO should be operated under a harsh chemical and physical environment, including high temperature, high pressure, and high corrosive medium and plugging risk. This paper is the first report about a tube explosion incident that encountered during continuous SCWO treatment of industrial sludge. 3D imaging, Scanning Electron Microscope - Energy Dispersive Spectroscopy (SEM-EDS) and 3D finite element analysis are used to analyze the incident tube comprehensively. The results indicate that the incident tube was working at a hash corrosive environment of subcritical water and chloride, which leads to all of general, pitting and intergranular corrosions. Of which, the pitting is the most severe one that finally results to perforation. Then, leakage took place. Soon afterwards, the hard inorganic particle from sludge plugged the leaking pore for a second, but immediately split it as a big hole due to the local high pressure around the leaking pore. Finally, explosion occurred. Three lessons are drawn for the future safe design and operation of SCWO, i.e., selecting suitable pressure bearing material, checking regularly, and executing safety regulations.

Практические советы по выбору манометров

The areas were determined reiated to the state regulation in the field of ensuring the uniformity of measurements when using pressure gauges installed on potentially hazardous industrial equipment of hazardous production facilities were determined. Including — in the field of defense and safety of the Russian Federation, in nuclear energy, in the field of competence of the Ministry of Emergency Situations, the Ministry of Internal Affairs, the Federal Service for Technical and Export Control and the National Guard troops. An analysis of the requirements for pressure gauges was carried out, and the forms of state control were determined. The technical (metrological) characteristics of pressure gauges are analyzed in accordance with the requirements of the international and national standards of the Russian Federation. Special features of measuring the pressure of various media and the need to use special technical devices and tools are considered. Significant criteria for the selection of pressure gauges were identified. A simple and understandable algorithm for their selection was developed.

Flexibility for Intensity Dosing in Lingual Resistance Exercises: A Large Randomized Clinical Trial in Typically Aging Adults as Proof of Principle.

The objective of this study was to determine the effect of intensity dosing during tongue exercise on tongue pressure generation, adherence, and perceived effort. This was a five-site, prospective, randomized clinical trial. Outcome measures were obtained across multiple baselines, biweekly during exercise, and 4-weeks post-intervention. The general community at each study site. Typically aging adults between 55-82 years of age with no history of neurological or swallowing disorders. Eighty-four volunteers completed the study. Participants were randomly assigned to one of four exercise groups: (a) maximum intensity/no biofeedback, (b) progressive intensity/no biofeedback, (c) maximum intensity/biofeedback, and (d) progressive intensity/biofeedback. Half of the participants completed a maintenance exercise program. Maximum isometric pressure (MIP), regular effort saliva swallow pressure, adherence, and the Borg Rating of Perceived Exertion Scale. All exercise protocols were efficacious for gains in MIP (large effect sizes; Cohen's d). Group 3 made gains in regular effort saliva swallow pressure (medium effect size). There was a significant change in perceived exertion for regular effort saliva swallow pressure at 8 weeks. Tongue pressure gains were maintained at 1 month, regardless of maintenance group status. Mean adherence across groups was high. All groups improved pressure generation. Intensity dosing differences did not affect strength gains, adherence, or detraining. Regular effort saliva swallow pressure may be most responsive to maximum intensity with biofeedback. The findings suggest flexibility in approach to tongue exercise protocols. Tongue muscles may differ from limb muscles in terms of dose response and neuroplasticity principles.

Influence of chromium of low content on the corrosion behavior of SA106B carbon steels in high-temperature pressurized LiOH medium

The corrosion of carbon steel (CS) pipelines widely troubles the primary circuit system of pressurized heavy water reactors. The element chromium (Cr) plays a crucial role in resisting corrosion. However, the mechanism of oxide film formation and dissolution on low Cr-content CS remains unclear. A comparison study in corrosion behavior between SA106B with 0.02 wt% and 0.36 wt% Cr was carried out with weight loss tests, electrochemical measurements, and morphology observations. Immersion tests were performed in deaerated lithium hydroxide solution at 553 K and 6.3 MPa for 30 days. The results showed that although the content of Cr was as low as 0.36 wt%, it exhibited relatively high corrosion resistance to the SA106B with 0.02 wt% Cr. Two layers of oxide film were formed on both the two CSs and chromium oxide was present in the inner oxide layer of 0.36Cr CS. The possible formation mechanism of oxidation film with low content of Cr in high-temperature water was discussed.

Racial/ethnic and socioeconomic disparities in achievement of treatment goals within a clinical trial: a secondary analysis of the ACCORD trial.

Clinical trial participation should theoretically reduce barriers to care by ensuring medication and healthcare access. We aimed to evaluate disparities in achieving diabetes treatment targets by race/ethnicity and educational attainment within the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial (ClinicalTrials.gov NCT00000620). The ACCORD trial included three interventions of varying participant burden: glycaemic (high burden), blood pressure (medium burden) and triglyceride-lowering (low burden). We examined adjusted odds ratios (aORs) for achievement of glycaemic targets, blood pressure targets and a ≥25% reduction in triglyceride levels (a proxy for adherence to fenofibrate therapy) in the first year, and for hypoglycaemia requiring medical assistance at any time, by treatment arm, race/ethnicity and educational attainment using multivariable models adjusted for demographics and clinical characteristics. We explored whether disparities in glycaemic goal achievement were mediated by hypoglycaemia, medication use, change in BMI or number of study visits attended. Compared with White participants, participants who identified as Black, Hispanic and Other race/ethnicity were less likely to achieve glycaemic targets (aOR [95% CI]) 0.63 [0.55,0.71], 0.73 [0.61, 0.88], 0.82 [0.71, 0.96], respectively); Black participants but not Hispanic and Other race/ethnicity participants were less likely to achieve blood pressure targets (aOR [95% CI] 0.77 [0.65, 0.90], 1.01 [0.78, 1.32], 1.01 [0.81, 1.26], respectively); and Black, Hispanic and Other race/ethnicity participants were equally or more likely to achieve triglyceride reduction (aOR [95% CI] 1.77 [1.38, 2.28], 1.34 [0.98, 1.84], 1.43 [1.10, 1.85], respectively). Differences in goal achievement by educational attainment were generally not significant after adjusting for baseline characteristics. Rates of hypoglycaemia requiring medical assistance were highest among Black individuals and those with lower educational attainment. Associations between race/ethnicity and glycaemic control were partially mediated by differences in insulin dosing and oral medication use. Racially/ethnically minoritised participants in the ACCORD trial were less likely to achieve high-burden (glycaemic) treatment goals but were generally similarly likely to achieve goals of less intensive interventions. Differences in glycaemic treatment goal achievement were partially mediated by differences in medication use but not mediated by hypoglycaemia, change in BMI or study visit attendance.

High-pressure fermentation of CO2 and H2 by a modified Acetobacterium woodii

Global warming due to the increased atmospheric carbon dioxide concentration is the driving force for developing strategies that exploit CO2 as raw material to produce interesting compounds for industry. According to this approach, Acetobacterium woodii was modified to convert CO2 and H2 into acetone. Gas fermentation was performed at high pressure to debottleneck the issue of the low availability of gaseous substrates in the liquid medium. This work aimed to investigate the catalytic performance of a modified A. woodii strain for acetone synthesis at 10 bar providing an H2-CO2 blend. First, tests were performed to assess the ability of the biocatalyst to survive heterotrophically at high pressure. Moreover, a reference test was set up in autotrophy at atmospheric pressure to confirm that it produced both acetate and acetone. Feeding the strain at 10 bar with the H2-CO2 mix resulted in growth inhibition and formic acid production. This outcome suggested a metabolism impairment due to bicarbonate build-up in the reactor at high CO2 partial pressure. Thus, bacteria were grown at atmospheric pressure in a medium with an augmented exogenous salt concentration. Results confirmed that formic acid production and growth inhibition could be due to HCO3–. Furthermore, the modified A. woodii grown at atmospheric pressure in a sterile medium pressurized before inoculation showed the same outcomes. Finally, tests at 10 bar lowering the CO2 partial pressure indicated that this gas was responsible for formic acid production but was not the only inhibitory factor for autotrophic cell growth at high pressure.

On Improving Sheet Metal Formability in Hydrodynamic Deep Drawing Process through a Solid‐Oil‐Type Mineral Grease Pressure Medium

In this research, the improvement in sheet metal formability obtained through the utilization of a mineral grease in solid‐oil‐type (SMG) pressure medium in the hydrodynamic deep drawing process assisted by radial pressure is investigated by experiments and finite‐element method (FEM) simulations on flat‐bottom cups realized with pure copper and DIN 1.0338 steel. To determine the process parameters ranges, an FEM model is developed in ABAQUS/Explicit and validated against experimental results. Afterward, experiments are carried out using two pressure mediums with different viscosities, i.e., water and SMG. Considering the results relevant for both sheet materials, the SMG medium allows an average reduction of the sheet metal thinning of 15% and 10% on the corner edges while also granting a negligible thickness variation on the cup walls. In contrast, the higher viscosity of the SMG, in comparison to the water medium, also results in an average 16% increase in the forming force when compared to the water pressure medium.

Hydrothermal liquefaction of animal by product waste using zeolite catalyst: A Mini-review

In view of the worldwide challenges posed by rising pollution and fossil fuel usage, it is imperative that we adopt a new energy strategy that makes use of all available refuse and vegetation to generate electricity. This is the safest and most effective way to address this worldwide issue. The process of hydrothermal liquefaction converting dry and moist material, such as (agricultural and animal waste, algae, and foodstock waste) into bio-crude in the presence of high temps and pressure in a watery medium is a potential technology in the area of renewable energy. When producing bio-crude, it is better to use solvents and catalysts to improve biomass liquefaction and boost output. As such, this review provided a brief overview of the research into the mechanism of HTL processes and biomass represented by animal by-products, their transformation, and the production of bio-crude; the effect and effectiveness of zeolite used as a catalyst in the hydrothermal liquefaction process; the energy efficiency of the process; and the effect of parameters such as heat, pressure, and process residence time; all with the goal of developing better pathways.

Hyperosmotic stress and perfusion culture strategies increase the yield of recombinant adenoviral vector produced by HEK 293 cells

With various diseases ravaging internationally, the demands for recombinant adenoviral vector (Adv) vaccines have increased dramatically. To meet the demand for Adv vaccine, development of a new cell culture process is an effective strategy. Applying hyperosmotic stress in cells before virus infection could increase the yield of Adv in batch culture mode. Emerging perfusion culture can significantly increase the yield of Adv as well. Therefore, combining the hyperosmotic stress process with perfusion culture is expected to improve the yield of Adv at high cell density. In this study, a shake flask combined with a semi-perfusion culture was used as a scaled-down model for bioreactor perfusion culture. Media with osmotic pressure ranging from 300 to 405 mOsm were used to study the effect of hyperosmotic stress on cell growth and Adv production. The results showed that using a perfusion culture process with a hyperosmotic pressure medium (370 mOsm) during the cell growth phase and an isosmotic pressure medium (300 mOsm) during the virus production phase effectively increased the yield of Adv. This might be due to the increased expression of HSP70 protein during the late phases of virus replication. The Adv titer in a bioreactor with such a process reached 3.2×1010 IFU/mL, three times higher than that of the traditional perfusion culture process. More importantly, this is the first time that a strategy of combining the hyperosmotic stress process with perfusion culture is applied to the production of Adv in HEK 293 cells. It also reveals the reason why the hyperosmotic stress process increased the yield of Adv, which may facilitate the process optimization of for producing other Adv in HEK 293 cells.

Weathering the hunt: The role of barometric pressure in predator insects' foraging behaviour.

Abiotic factors strongly influence ecological interactions and the spatial distribution of organisms. Despite the essential role of barometric pressure, its influence on insect behaviour remains poorly understood, particularly in predators. The effect of barometric pressure variation can significantly impact biological control programs involving entomophagous insects, as they must efficiently allocate time and energy to search for prey in challenging environments. We investigated how predatory insects from different taxonomic groups (Coleoptera, Dermaptera and Neuroptera) adapt their foraging behaviour in response to variations in barometric pressure (low, medium and high). We also examined the response of different life stages to changes in pressure regimes during foraging activities. Our results showed that the searching time of Doru luteipes (Dermaptera: Forficulidae) was faster in a favourable high-pressure regime, whereas Chrysoperla externa (Neuroptera: Chrysopidae) and Eriopis connexa (Coleoptera: Coccinellidae) had similar searching times under varying pressure regimes. Although no differences in prey feeding time were observed among the studied species, the consumption rate was influenced by low barometric pressure leading to a decrease in the number of preyed eggs. Moreover, we provide novel insights into how hemimetabolous (D. luteipes) and holometabolous (E. connexa) species at different life stages respond to barometric pressure. Doru luteipes nymphs and adults had similar consumption rates across all pressure regimes tested, whereas E. connexa larvae consumed fewer eggs under low barometric pressure, but adults were unaffected. This highlights the importance of investigating how abiotic factors affect insects foraging efficiency and predator-prey interactions. Such studies are especially relevant in the current context of climate change, as even subtle changes in abiotic factors can have strong effects on insect behaviour. Barometric pressure is a key meteorological variable that serve as a warning signal for insects to seek shelter and avoid exposure to weather events that could potentially increase their mortality. Understanding the effects of barometric pressure on predatory insects' behaviour can help us develop more effective pest management strategies and promote the resilience of agroecosystems. We provide new insights into the complex relationship between barometric pressure and predator-prey interactions.

A thermal contact model encompassing near-field effects of multi-interface TEGs in hypersonic conditions

High efficiency heat harvest of hypersonic vehicles claims elaborate design of thermoelectric (TE) conversion process. A thermoelectric generator (TEG) contains multi-interfaces in the heat transfer path and the interfacial thermal contacts with certain amount of nanoscale effects have significant influence on its TE conversion process. In this paper, a thermal contact model encompassing near-field thermal radiation (NFTR) effects of TEGs with heterogeneous interfaces between substrates, electrodes and TE legs is established and experimentally validated in hypersonic conditions. First, a real-topology-based thermal contact resistance (TCR) prediction model is developed and the far- and near-field radiative heat transfer at heterogeneous interfaces is considered by the fluctuational electrodynamics, and the model is validated by direct and indirect experimental measurements. Second, the effects of average interfacial temperature, clearance distance and opposite heat transfer paths on the thermal radiation are analyzed, and the influences of average interfacial temperature, loading pressure and clearance mediums on the TCR are then clarified. Third, the TCR is equivalently considered in a TEG performance evaluation model and the NFTR effects is quantitatively counted. The result shows that: with the consideration of the NFTR, the TCRs between TE legs and electrodes, substrates and electrodes decrease by about 3.90% to 17.0% and 0.510% to 6.40% under vacuum clearance, 1.30% to 5.50% and 0.220% to 2.00% under air clearance, respectively; and the maximum output power of the TEG increases by about 8.02% and 1.29% under vacuum and air clearance (0.1 MPa, 650 K), respectively.

Experimental study on brittle-to-ductile transition mechanism of lower Silurian organic-rich shale in south China

Brittle-ductile transition conditions and mechanisms are key scientific issues embedded in the reservoir deformation-related difficulties faced during shale gas exploration and exploitation. In this study, shale deformation experiments under different temperatures, confining pressure and differential stress were conducted using a NaCl solid confining pressure medium, taking the Lower Silurian marine shale from South China as an example. We aimed to clarify the characteristic textures and structures of brittle and ductile deformation in organic-rich shale and then, to reveal the conditions and mechanisms of the brittle-to-ductile transition under the deep in-situ environment of high-temperature, high-confining pressure and high-stiffness surrounding strata. Deformation characteristics of experimentally deformed shale showed significant differences between brittle and ductile deformed shale in terms of fracture development, failure combining form, deformation distribution homogeneity, shear angle and the structures and textures within intensely deformed zones. The micro-deformation structures of brittle deformed shale are characterized by the development of fractures and the simple mechanical crushing of shale blocks and mineral particles. The strong deformation zones of ductile deformed shale mainly show micro-deformation features, such as solid-state rheological deformation and accompanying fragmentation, rounding and directional arrangement of mineral particles. Comparison of control group experiments supported the conclusion that increasing confining pressure significantly improves the elastic modulus and compressive strength of shale and leads to a transition from large-area uniform deformation to narrow-band concentrated deformation. A confining pressure of 75–100 MPa is required for the brittle-to-ductile deformation transition of the target shale at 200 °C. An elevated temperature enhances shale deformation in the yield and creep stages. Finally, we revealed the progressive process and mechanism of brittle-to-ductile transition with the increase of confining pressure; that is, increasing confining pressure leads to a gradual transition of the shale micro-deformation mechanism, from brittle failures to ductile rheological deformation, by suppressing tension fracturing and enhancing friction.

Dynamic Effect of Fluid–Structure Interaction and Modal Analysis of Crude–Pipeline Interaction System Considering the Fluctuating Pressure of Medium

This work explored the fluid–structure interaction (FSI) effect of crude oil and pipeline and the vibration characteristics of the pipe–crude oil structural system. A finite element computational analysis theory and corresponding simulation method were proposed for crude oil pipelines considering the FSI effect. Meanwhile, the spring model of the FSI interface between crude oil and pipeline was proposed. The experimental simulation and neural network were adopted to obtain the flow-excited pulsation pressure (FEPP), and the kinetic equations of the pipe–crude oil FSI were analyzed. The finite element computation (FEC) model for pipe–crude oil bi-directional FSI dynamics was established, which was composed of five support span lengths and four pipe liquid levels and can provide five different crude oil fluid velocities. One hundred orthogonal simulation test conditions were designed. In addition, the displacement response and acceleration response under FSI of the pipe wall were calculated, and the first six orders of inherent frequencies and main vibration patterns of the FEC model were analyzed. The results revealed that the dynamic effect of FSI between the crude oil transport medium and pipeline was complex and was influenced by the length of the pipeline crossing section, medium flow velocity, difference of liquid surface height, and displacement response. The acceleration response possessed prominent vibration decay characteristics, and the response peak in the same condition was about 8.2 times larger than that of the steady-flow state response. Therefore, the effect changed the inherent frequency and vibration pattern of the pipeline, to which the engineering design should pay sufficient attention.

Theoretical analysis of threshold pressure in tight porous media under stress

The threshold pressure is critical to characterizing multi-phase nonlinear flow through tight porous media under effective stress. Due to the complex and heterogeneous pore structures, the essential controls on the threshold pressure of tight porous media are not determined. In this study, based on the fractal theory, a theoretical model for the threshold pressure of gas–water two-phase flow through tight porous media is proposed. The derived model considers the effective stress, pore structures, gas–water capillary pressure, and boundary layer. The predicted threshold pressure from the developed model is in good agreement with the available experimental results, which validates the model. Moreover, based on the derived model, the effects of relevant parameters (e.g., gas–water surface tension, contact angle, initial porosity, and elastic modulus) on the threshold pressure are studied. Under a given effective stress, threshold pressure decreases as the initial porosity (or elastic modulus) increases. However, threshold pressure increases with the increase in gas–water surface tension (or contact angle). In addition, a positive relationship exists between threshold pressure and water saturation in tight porous media. From a practical standpoint, this model is of great significance in predicting threshold pressure and researching on the gas–water two-phase flow mechanism in tight sandstone gas reservoirs.

Numerical investigation on coupled heat transfer of an immersed tube with sCO2 working fluid in a fluidized bed at high temperature and pressure

Supercritical CO2 (sCO2) power cycle driven by pressurized fluidized bed (FB) boiler, reactor or heat exchanger is an advanced thermal power generation technology due to higher electrical efficiency and more compact system. However, as the main heating surface, the coupled heat transfer behavior of immersed tubes loaded within sCO2 is unclear. In this work, we developed a bed-tube-sCO2 heat transfer model and explored the effects of tube wall, furnace pressure, particle properties, bed temperature and fluidization medium on heat transfer of sCO2 loaded immersed tube in a FB at high temperature and pressure. Results showed that the thermal buffering effect of the immersed tube improved the heat transfer stability of sCO2. The bed-to-tube heat transfer coefficient (HTC) would not increase continuously with the furnace pressure. Therefore, using bed materials with better properties was an effective way to enhance the heat transfer of immersed tubes in high-pressure FBs. CO2 as a fluidization medium affected heat transfer mainly through convection rather than radiation. A new heat transfer correlation with an accuracy of ± 25% was proposed, which can be used to design and optimize immersed tubes in this advanced technology.