Pressure Range Research Articles

Biomimetic Electronic Skin Based on a Stretchable Ionogel Mechanoreceptor Composed of Crumpled Conductive Rubber Electrodes for Synchronous Strain, Pressure, and Temperature Detection.

Electronic skin (e-skin) is showing a huge potential in human-computer interaction, intelligent robots, human health, motion monitoring, etc. However, it is still challenging for e-skin to realize distinguishable detection of stretching strain, vertical pressure, and temperature through a simple noncoupling structure design. Here, a stretchable multimodal biomimetic e-skin was fabricated by integrating layer-by-layer self-assembled crumpled reduced graphene oxide/multiwalled carbon nanotubes film on natural rubber (RGO/MWCNTs@NR) as stretchable conductive electrodes and polyacrylamide/NaCl ionogel as a dielectric layer into an ionotropic capacitive mechanoreceptor. Unlike natural skin receptors, the sandwich-like stretchable ionogel mechanoreceptor possessed a distinct ionotropic capacitive behavior for strain and pressure detection. The results showed that the biomimetic e-skin displayed a negative capacitance change with superior stretchability (0-300%) and a high gauge factor of 0.27 in 180-300% strain, while exhibiting a normal positive piezo-capacitance behavior in vertical pressure range of 0-15 kPa with a maximal sensitivity of 1.759 kPa-1. Based on this feature, the biomimetic e-skin showed an excellent synchronous detection capability of planar strain and vertical pressure in practical wearable applications such as gesture recognition and grasping movement detection without a complicated mathematical or signal decoupling process. In addition, the biomimetic e-skin exhibited a quantifiable linear responsiveness to temperature from 20-90 °C with a temperature coefficient of 0.55%/°C. These intriguing properties gave the biomimetic e-skin the ability to perform a complete function similar to natural skin but beyond its performance for future wearable devices and artificial intelligence devices.

Investigation of the Newtonian fluids flow in circular horizontal tubes at low inlet pressures

The issues of increasing hydrodynamic efficiency, improving the operational and technical characteristics of various apparatus and devices used in the fi eld of heat and mass transfer, as well as ensuring the required regime and flowow conditions of liquids of different viscosities do not lose their relevance. To solve these issues, in addition to studying the nature of the flowow of various liquids in round horizontal tubes (capillaries), it is necessary to determine the conditions when the flowow of liquid in capillaries and round tubes of small diameter is laminar and can be described by the Poiseuille equation. Experimental data on determining water flow ow through horizontal round tubes of various diameters are presented. Determining the patterns and features of such flow ows is mostly aimed at increasing hydrodynamic efficiency, improving the operational and technical characteristics of various apparatus and devices, as well as ensuring the required flow ow regime and conditions. Experimental data on determining the flow ow rate of water through horizontal tubes of circular cross-section with different diameters are presented in the article. The dependence of the volumetric flow ow rate on the pressure drop has been determined; it has been shown that the main parameters that determine the nature of the flow ow of liquids in horizontal tubes are the tube radius and the dynamic viscosity of the liquid. The flow ow of distilled water in tubes with diameters of 0.95, 1.6 and 2.0 mm at an overpressure of 0.266 kPa to 4 kPa is considered. It is shown that the dependence of the volumetric flow ow rate on the excess pressure remains linear at 0.95 mm in the entire considered pressure range. An increase in the tube radius increases the likelihood of velocity flow uctuations and the appearance of a radial velocity component, i.e. the occurrence of elements of a turbulent structure. In this regard, with tube diameters of 1.6 and 2.0 mm, a deviation of the water flow ow regime from the laminar character was established at pressures of more than 1.3 kPa and 1 kPa, respectively. The dependence of the volumetric flow ow rate on pressure for a 40 % aqueous solution of CaCl2, transformer, transmission and engine oils with dynamic viscosity coefficients from 0.002 Pa·s to 0.182 Pa·s remains linear up to pipe diameters of 5–6 mm. The experimental results are shown in the form of a nomogram of the dependence of the coefficient K* on the tube radius at different values of the viscosity coefficient. The results of studies of liquids of various viscosities are presented in the form of a nomogram of the dependence of the ratio of the radius of the tube to the fourth power to the viscosity of the liquid on the radius of the tube. The analysis of which makes it possible to predict the nature of the flow ow of the investigated liquid at the given values of the tube radius and the dynamic viscosity coefficient. Heat exchange devices for the design of which the presented results can be used include a variety of radiators that include tubes through which coolant circulates.

Reliable operation of Cr2O3:Mg/β-Ga2O3 p–n heterojunction diodes at 600 °C

Beta gallium oxide (β-Ga2O3)-based semiconductor heterojunctions have recently demonstrated improved performance at high voltages and elevated temperatures and are, thus, promising for applications in power electronic devices and harsh environment sensors. However, the long-term reliability of these ultra-wideband gap (UWBG) semiconductor devices remains barely addressed and may be strongly influenced by chemical reactions at the p–n heterojunction interface. Here, we experimentally demonstrate operation and evaluate the reliability of Cr2O3:Mg/β-Ga2O3 p–n heterojunction diodes during extended operation at 600 °C, as well as after 30 repeated cycles between 25 and 550 °C. The calculated pO2-temperature phase stability diagram of the Ga-Cr-O material system predicts that Ga2O3 and Cr2O3 should remain thermodynamically stable in contact with each other over a wide range of oxygen pressures and operating temperatures. The fabricated Cr2O3:Mg/β-Ga2O3 p–n heterojunction diodes show room-temperature on/off ratios >104 at ±5 V and a breakdown voltage (VBr) of −390 V. The leakage current increases with increasing temperature up to 600 °C, which is attributed to Poole–Frenkel emission with a trap barrier height of 0.19 eV. Over the course of a 140-h thermal soak at 600 °C, both the device turn-on voltage and on-state resistance increase from 1.08 V and 5.34 mΩ cm2 to 1.59 V and 7.1 mΩ cm2, respectively. This increase is attributed to the accumulation of Mg and MgO at the Cr2O3/Ga2O3 interface as observed from the time-of-flight secondary ion mass spectrometry analysis. These findings inform future design strategies of UWBG semiconductor devices for harsh environment operation and underscore the need for further reliability assessments for β-Ga2O3-based devices.

High-pressure structures of solid hydrogen: Insights from abinitio molecular dynamics simulations.

Understanding the structural behavior of solid hydrogen under high pressures is crucial for uncovering its unique properties and potential applications. In this study, starting from the phase I of solid hydrogen-free-rotator hcp structure, we conduct extensive abinitio molecular dynamics calculations to simulate the cooling, heating, and equilibrium processes within a pressure range of 80-260GPa. Without relying on any structure previously predicted, we identify the high-pressure phase structures of solid hydrogen as P21/c for phase II, P6522 for phase III, and BG1BG2BG3 six-layer structure for phase IV, which are different from those proposed previously using the structure-search method. The reasonability of these structures are validated by Raman spectra and x-ray diffraction patterns by comparison with the experimental results. Our results actually show pronounced changes in the c/a ratio between phases I, III, and IV, which hold no brief for the experimental interpretation of an isostructural hcp transformations for phases I-III-IV.

Low Viscosity of Peridotite Liquid: Implications for Magma Ocean Dynamics

AbstractTransport properties of silicate melts control magma ocean dynamics on the early terrestrial planets and rocky exoplanets. Here we calculate the viscosity (transport of momentum) of peridotite liquid at potential magma ocean conditions (0–159 GPa, 2,200–6,000 K) using ab initio molecular dynamics simulations. We find that, unlike MgSiO3 or basaltic melts, the viscosity of the highly depolymerized peridotite liquid (a) increases monotonically with pressure without an anomalous drop and (b) is lower than those of other melts over the entire mantle pressure range. Low viscosity would promote fractional crystallization in a less polymerized magma ocean and thus contribute to mantle heterogeneity from its earliest stage. Given the compositional dependence of magma ocean properties, emphasis on multicomponent bulk silicate Earth‐like composition, instead of simple end‐members, are rendered necessary, in order to better understand high‐energy planetary accretion processes and their aftermaths.

RESULTS OF MONITORING THE SETTLEMENT OF SILO FOUNDATIONS REINFORCED WITH SOIL-CEMENT ELEMENTS

During the first cycle of loading and in the subsequent process of steel silos operation to store grain, special attention goes to the observation of base settlement under silo foundations and their tilting. Traditionally, silo settlement tends to be monitored by geodetic measurements. To analyse the results of monitoring for the silos base settlement, we used the linearity changing of the base stiffness approach. The base stiffness is the ratio of the average pressure p (in kPa) under the foundation sole to the average settlement S (in mm). This approach relies on the following assumption: in the process of silo loading, thus gradually increasing the average pressure under the sole of the foundation, the modulus of deformation of the base soil gradually decreases, and the deformability of the base increases until the stresses in the soil mass under the foundation do not exceed the values of the calculated resistance and the development of plastic deformations begins. For grain storage elevator silos 10.1–10.12 located in the Khmelnytskyi region, we obtained the ratio of the average pressure p (in kPa) under the foundation sole to the average settlement S (in mm) during the geodetic monitoring, and then, we used it to construct the stiffness graphs of the silo base. The base stiffness indicators of silos 10.2 and 10.3 most closely match the calculated base stiffness. The specified values of base stiffness exceeding the measured ones by 3–5% are probably due to the higher calculated mechanical characteristics of the base reinforced with soil-cement elements. The rigidity of the silo base and the average pressure in the base under the foundations calculated based on geodetic measurement data are independent random variables, as evidenced by the graphs of the rigidity of the silo base 10.1–10.12. The study of the correlation between the specified random variables is of practical interest. The obtained value of the sample correlation coefficient r = –0.4687 indicates a negative correlation between the samples of the average pressure p (in kPa) under the foundation sole and the stiffness of the base (p / S, kPa/mm). The existence of negative correlation dependence has a clear physical meaning, such as when the pressure on the base increases, its stiffness decreases while increasing the deformability of the base, as confirmed by the results of silo geodetic monitoring. The calculated stiffness of the base decreases with increasing pressure due to the involvement of a greater depth of the compressible stratum, and, accordingly, the calculated deformability of the base increases. To determine the physical and mechanical properties of the base soil, the generally accepted pressure range during the tests does not exceed 250 kPa. A priori, this pressure range corresponds to the elastic section of the soil deformation diagram and the gradual decrease in mechanical characteristics. The average stresses under the foundations of the studied silos did not exceed 125 kPa. Therefore, the proposed method makes it possible to obtain not only quantitative conclusions – the magnitude of base settlement, but also to analyse qualitative indicators related to the stiffness characteristics (р / S, kPa/mm) of the base and to assess its deformation indicators acceptability. Keywords: foundation settlement, geodetic monitoring, reinforced concrete foundation, steel silo, base stiffness.

Impact of densification process on unprocessed biomass and post-hydrothermal carbonization

The pulp and paper industry use biomass residues, such as paper sludge and bark as fuel to provide energy for their plants. However, issues such as high-water content or low heating value limit the amount of energy that can be utilized. Processes to improve heat generation include biomass densification, which facilitates transportation and handling and can increase energy yield. However, the technical feasibility of briquetting is a function of the feedstock and preprocessing. This study introduces a novel approach to briquette production from biomass residues by utilizing wet biomass with water as a natural binder, contrasting with conventional methods that require forced drying and/or the addition of binders. The objective of this research was to investigate the impact of briquetting both unprocessed biomass and post-hydrothermal carbonization. The study focused on manufacturing briquettes derived from different sources, including bark (Balsam fir), paper sludge, and hydrochar of paper sludge. The feedstock was characterized for ash content and higher heating value. Biomass particle size (range), moisture content (range), process temperature (range), process pressure (range), and process residence time (range) were varied in briquetting experiments to determine conditions to produce high-quality briquettes with minimal energy input. Moisture content as high a 50 wt% in feedstock produced technically feasible briquettes, with appropriate physical-mechanical properties (durability, volumetric expansion and apparent density), and energetic potential (calorific value). The addition of heat (pressing temperature of 150 °C) during the pressing process resulted in briquettes with enhanced physical-mechanical, and energetic properties, surpassing those produced at room temperature. Further tests with additional steps in the production process are required to meet commercialization standards in Canada, but the treatments conducted in this study effectively improved the energy potential of biomass for internal industrial energy gains.

All-sapphire fiber-optic sensor for the simultaneous measurement of ultra-high temperature and high pressure

An all-sapphire fiber-optic extrinsic Fabry-Perot interferometric (EFPI) sensor for the simultaneous measurement of ultra-high temperature and high pressure is proposed and experimentally demonstrated. The sensor is fabricated based on all-sapphire, including a sapphire fiber, a sapphire capillary and a sapphire wafer. A femtosecond (fs) laser is employed to drill a through hole at the side wall of the sapphire capillary to allow gas flow. The sapphire fiber is inserted from one side of the sapphire capillary. The sapphire wafer is fixed at the other side of the sapphire capillary. The first Fabry-Perot (FP) cavity, composed of the end face of the sapphire fiber and the front surface of the sapphire wafer, is used for measuring pressure, while the second FP cavity, composed of the two surfaces of the sapphire wafer, is used for measuring temperature. Experimental results show that the sensor can simultaneously measure ultra-high temperature and gas pressure within the temperature range of 20 - 1400 °C and the pressure range of 0 - 5 MPa. The temperature sensitivity is 0.0033 µm/°C, and the pressure sensitivity decreases as the temperature increases, reaching 1.8016 µm/MPa and 0.3253 µm/MPa at temperatures of 20 °C and 1400 °C, respectively.

GET 43-2022 State Primary Standard for the unit of excess pressure within the static pressure range of 10–1600 MPa and the pulse pressure range of 1–1200 MPa and the effective area of piston-cylinder assemblies in deadweight testers within the range of 0.05–1 cm2

GET 43-2022 State Primary Standard for the unit of excess pressure within the static pressure range of 10–1600 MPa and the pulse pressure range of 1–1200 MPa and the effective area of piston-cylinder assemblies in deadweight testers within the range of 0.05–1 cm2

Molecular Insights into the Wettability and Adsorption of Acid Gas-Water Mixture.

Sequestration of acid gas in geological formations is a disposal method with potential economic and environmental benefits. The process is governed by variables such as gas-water interfacial tension, wetting transition, and gas adsorption into water, among other things. However, the influence of the pressure and temperature on these parameters is poorly understood. This study investigates these parameters using coarse-grained molecular dynamics (CG-MD) simulations and density gradient theory (DGT). Simulations were carried out at 313.15 K and a pressure range of 0-15 MPa. A comparison was made against H2S-water systems to clarify the effects of adsorption on interfacial tension due to vapor-liquid-liquid equilibrium. The predicted H2S-water interfacial tension and phase densities by CG-MD and DGT matched the experimental values well. The adsorption can be quantified via the Gibbs Adsorption function Γ12, which correlated well with the three-phase transition. On the one hand, pressure increments below the three-phase transition revealed a significant adsorption of H2S. On the other hand, above the three-phase transition, the Gibbs Adsorption capacity remained constant, which indicated a saturation of H2S at the water surface due to liquid-liquid equilibrium. Finally, H2S behaves markedly differently in wetting transition, rather than the involved for CO2 to different molecular layers beneath the surface of aqueous solutions. In this respect, H2S is represented by a first-order wetting transition while CO2 presents a critical wetting. Finally, it has also been found that the preferential adsorption of H2S over the H2O interface is greater if compared to that of CO2, due to its strong interaction with water. In fact, we have also demonstrated that CO2 under triphasic conditions strongly influences the wetting of the ternary system.

Non-invasive FBG-based contact lens for continuous intraocular pressure monitoring

The intraocular pressure (IOP), or pressure inside the eye, is one of the key indicator for glaucoma diagnosis and treatment. The present work shows the design and fabrication of a non-invasive Fiber Bragg Grating (FBG) based contact lens for continuous IOP monitoring. By employing wet etching to reduce the FBG diameter, FBG based contact lens sensitivity and mechanical flexibility are enhanced. The contact lens is made of an optical fiber with a small core diameter that has an inscribed FBG of length 3 mm and is etched for a length of 40 mm to facilitate coiling the eFBG during fabrication. The soft contact lens was fabricated using flexible thin film technology with a transparent and flexible etched Fiber Bragg Grating (eFBG) integrated within flexible polydimethylsiloxane (PDMS) for sensing corneal deformations brought about by IOP variations. Experimental studies on the bionic eyeball model show that the Bragg wavelength shift is highly linear (r2 = 0.9694), with a very good sensitivity of 49.243 pm/mmHg in the IOP pressure range of 0 to 50 mmHg. Due to its ease of fabricating, simplicity of design, and ability to continuously measure pressure with good repeatability and stability, the proposed sensor thus offers a potential solution for IOP monitoring.

A preliminary study of ecosmart intra venous system on patients’ comfort

Intravenous fluid therapy may cause discomfort to patients most of the time. More research and innovation are needed to develop infusion devices to provide a more comfortable feeling for patients receiving the therapy. This preliminary study analyzed the effect of economical and smart (ecosmart) infusion systems on comfort in healthy adults. The one-group post-test-only design was used in this pre-experimental investigation. A range of ages, gender, body weight, body temperature, and normal blood pressure selected participants. An independently created, valid, and reliable tool was used to measure comfort. Data analysis employed a t-test on a single sample. Fifteen nursing students are participating as sampling objects. The average comfort score for the study's participants was 11.2 (SD = 2.5967; p < 0.05). The result indicates that the participants are at ease using the ecosmart system. The respondents' sense of comfort related to the instrument showed comfort or relaxation.
 Keywords: Nursing care; ecosmart; comfort; patient-centered care; hospital; fluid therapy

Flexible Piezoresistive Sensors Based on PPy Granule-Anchored Multilayer Fibrous Membranes with a Wide Operating Range and High Sensitivity.

The employment of flexible piezoresistive sensors has sparked growing interest within the realm of wearable electronic devices, specifically in the fields of health detection and e-skin. Nevertheless, the advancement of piezoresistive sensors has been impeded by their limited sensitivity and restricted operating ranges. Consequently, it is imperative to fabricate sensors with heightened sensitivity and expanded operating ranges through the utilization of the appropriate methodologies. In this paper, piezoresistive sensors were fabricated utilizing electrospun polyvinylidene fluoride/polyacrylonitrile/polyethylene-polypropylene glycol multilayer fibrous membranes anchored with polypyrrole granules as the sensing layer, while electrospun thermoplastic polyurethane (TPU) fibers were employed as the flexible substrate. The sensitivity of the sensor is investigated by varying the fiber diameter of the sensing layer. The experimental findings reveal that a concentration of 14 wt % in the spinning solution exhibits high sensitivity (996.7 kPa-1) within a wide working range (0-10 kPa). This is attributed to the favorable diameter of the fibers prepared at this concentration, which facilitates the uniform in situ growth of pyrrole. The highly deformable TPU flexible fibers and multilayer sensing layer structure enable different linear responses across a broad pressure range (0-1 MPa). Furthermore, the sensor demonstrates good cyclic stability and can detect human movements under different pressures. These results suggest that the piezoresistive sensor with a wide operating range and high sensitivity has significant potential for future health monitoring and artificial intelligence applications.

Effect of pressure on the structural properties of tantalum carbide

In this study, tantalum carbide (TaC) samples were placed in a diamond anvil cell to study the equation of state at room temperature and high pressure using synchrotron radiation X-ray diffraction. By fitting the data at ambient pressure and up to the highest pressure of 38.5[Formula: see text]GPa, we obtained the bulk modulus and first derivative of TaC as [Formula: see text] (6.8) GPa and [Formula: see text] (0.49), respectively. In addition, we calculated the bulk modulus and band structure of TaC under high pressure using density functional theory. The obtained bulk modulus is 267 (3)[Formula: see text]GPa. TaC is metallic in nature throughout the entire pressure range. We studied the high-pressure deviatoric stress of TaC using linewidth analysis method. We found that TaC can support a maximum differential stress of up to 18.6[Formula: see text]GPa at the highest pressure of 38.5[Formula: see text]GPa.

Janus Conductive Mechanism: An Innovative Strategy Enabling Ultra‐Wide Linearity Range Pressure Sensing for Multi‐Scenario Applications

AbstractThe wide range of pressure detection and the exceptional linearity are essential performance parameters for flexible pressure sensors, enabling them to adapt to diverse scenarios and acquire information accurately. However, currently available “ultra‐wide range” piezoresistive sensors lack an optimal solution that effectively balances sensing properties, device thickness, and process cost. This study proposes a distinctive approach by introducing a Janus conductive structure assembled with dual resistive sensitive layers. The design allows for a pressure‐induced staged transformation of the current transport path, effectively mitigating variations and saturation in sensor resistance over a wide pressure range. The resulting piezoresistive sensor demonstrates an unprecedented detection range of 0–3800 kPa, showcasing remarkable sensitivity of 4.11 kPa−1 and outstanding linearity of 99.9% within the range of 0–1000 kPa. Additionally, the sensor boasts a thickness of only ≈200 µm, made possible through the utilization of a cellulose nanofibers material matrix. These performance achievements stand at the forefront when compared to existing reports. This research explores the potential applications of these sensors and extended arrays in the domains of human health and motion monitoring. It investigates their utility in gait analysis for assisted posture correction, as well as in the assessment and rehabilitation of gait instability.

Pressure and non-ideal axial ratio effects on thermodynamic properties of hexagonal close-packed Mg and Zn metals

ABSTRACT The Debye model has been developed to study the pressure dependence of the extended X-ray absorption fine structure Debye–Waller factor, the Debye frequency and temperature of hexagonal close-packed (hP2) metals. The effects of the non-ideal axial ratio c/a of hP2 structure on these thermodynamic quantities at high pressures have also been considered. Additionally, based on the combination of the Debye model and the Lindemann melting law, we derive the analytic expression of melting temperature of hP2 metals as a function of pressure. Numerical calculations have been implemented for Mg and Zn metals up to 20 and 50 GPa, respectively. We have shown that Debye frequency and temperature, as well as melting temperature of these two metals increase robustly with pressure and non-ideal axial ratio plays important role in these thermodynamic quantities. The remarkable consistency observed between our calculations and various experimental results validates the reliability of the currently presented melting curve. Meanwhile, at high pressure non-ideal axial ratio gives a small contribution to pressure-dependent Debye–Waller factor of Mg (up to 20 GPa) and Zn (beyond 20 GPa), and can be safely neglected in the suggested pressure range.

Linear Capacitive Pressure Sensor with Gradient Architecture through Laser Ablation on MWCNT/Ecoflex Film.

The practical application of flexible pressure sensors, including electronic skins, wearable devices, human-machine interaction, etc., has attracted widespread attention. However, the linear response range of pressure sensors remains an issue. Ecoflex, as a silicone rubber, is a common material for flexible pressure sensors. Herein, we have innovatively designed and fabricated a pressure sensor with a gradient micro-cone architecture generated by CO2 laser ablation of MWCNT/Ecoflex dielectric layer film. In cooperation with the gradient micro-cone architecture and a dielectric layer of MWCNT/Ecoflex with a variable high dielectric constant under pressure, the pressure sensor exhibits linearity (R2 = 0.990) within the pressure range of 0-60 kPa, boasting a sensitivity of 0.75 kPa-1. Secondly, the sensor exhibits a rapid response time of 95 ms, a recovery time of 129 ms, hysteresis of 6.6%, and stability over 500 cycles. Moreover, the sensor effectively exhibited comprehensive detection of physiological signals, airflow detection, and Morse code communication, thereby demonstrating the potential for various applications.

Uniformity of low-pressure capacitively coupled plasmas: Experiments and two-dimensional particle-in-cell simulations

Radio-frequency capacitively coupled plasmas (CCPs) are one of the key technologies enabling the latest etching processes in 3D NAND and FinFET manufacturing. These processes rely crucially on the precise control of the uniformity of ion/radical fluxes and ion angular and energy distribution function (IAEDF) in CCPs. The plasma behavior and scaling properties are dependent on the plasma chemistry in these processes, e.g., electro-positive Ar plasmas vs highly electro-negative O2 plasmas. With the large number of process and design parameters influencing the plasma properties, computational modeling has become an important tool in conjunction with experimental diagnostics in understanding the intricate physical mechanisms in CCPs. In this paper, a 2D particle-in-cell plasma model is used to study the kinetic behavior of low-pressure (<5 Pa) CCPs in two different representative chemistries: Ar and O2. The low-frequency RF source is at 1.356 MHz while 27.12 MHz is used for the high frequency. Simulations show a shift of the peak in the plasma density from the center of the chamber to the edge as the pressure increases from 0.3 to 2.6 Pa. The computed magnitude and spatial profile of electron density compare reasonably with experimental measurements over a range of pressure. Comparison between electro-positive and electro-negative plasmas are discussed. Modeling results for the dual frequency CCP highlight the effect of plasma uniformity on the IAEDF, especially near the outer edge of the electrodes. Collisions in the sheath increase the population of low-energy ions as the pressure is increased to 2.6 Pa.

Turbulent Fluxes and Evaporation/Sublimation Rates on Earth, Mars, Titan, and Exoplanets

AbstractTurbulent fluxes of heat, momentum, and humidity in the atmospheric boundary layer are pivotal to the evolution of geology, weather and climate, and the possibility of life. Here we extend recent advances in calculating these near‐surface turbulent fluxes in the Earth's atmospheric boundary layer to any terrestrial planetary body with an atmosphere. These improvements include: (a) incorporating Monin‐Obukhov similarity functions that encompass the entire range of atmospheric stability expected on terrestrial planetary bodies, (b) accounting for the additional shear associated with buoyant plumes under unstable conditions, (c) using surface renewal theory to calculate transfer rates within the interfacial layer adjacent to the surface, and (d) explicitly accounting for key humidity effects that become especially important when a volatile is more buoyant than the ambient gas (e.g., on Mars where H2O is lighter than CO2). We tested and validated our model using in situ data collected on Earth, Mars, and Titan under a wide range of atmospheric stability, pressure, and surface roughness conditions. The model shows up to 71% better agreement with measurements compared to methods commonly used on Mars for evaporation/sublimation. Compared to previous estimates for H2O ice on Mars, our model predicts up to 1.5–190x lower latent heat fluxes under stable atmospheric conditions (depending on the wind speed) and 1.78x higher latent heat fluxes under unstable conditions. Our results provide improved constraints on the stability of ice on Mars and will help determine whether ice can melt under present‐day conditions.

Improved Flow Material Balance Equation for Dynamic Reserve Calculation Considering Variable Gas Drainage Radius in Shale Gas Reservoirs

Summary Based on the nonlinear relationship between the cumulative gas production and the total pressure difference, a segmental material balance equation was applied, and an improved flow material balance (FMB) equation was proposed to calculate the dynamic reserves of shale gas reservoirs with a variable gas drainage radius. In the early stage, the shale gas well drainage radius gradually increased. The spread range of the formation pressure increased, but fractures gradually closed because of the enhancement of the effective stress. This resulted in stress sensitivity. In the middle to late stages, the gas drainage radius can be regarded as unchanged. The rate of increase in the pressure spreading range decreased, and the rate of decrease in the fracture closure decreased. The stress sensitivity can be ignored. To explain these phenomena, a segmental material balance equation was established. Furthermore, an improved FMB equation was obtained based on the productivity equation using the potential superposition theorem, and the drainage radius of horizontal wells was regarded as a variable for the last dynamic reserve calculation. Finally, the dynamic reserves of four shale gas wells were calculated. The comparison indicated that the proposed improved equation predictions agreed more closely with actual development experience than the conventional models based on the dynamic recovery rate calculation and the correlation coefficient obtained by data fitting. The proposed method improves the dynamic reserve calculations and contributes to well productivity evaluation.