Behavior Of Gas Research Articles

Adsorption and sensing behavior of Cr-doped WS2 monolayer for hazardous gases in agricultural greenhouses: A DFT study

This study used Density functional theory (DFT) to analyze the adsorption behavior of the Cr-doped WS2 monolayer on five hazardous gases (NH3, SO2, NO, NO2, and CO) in agricultural greenhouses. The optimal stable doped site for the Cr atom was identified, and various adsorption parameters such as adsorption energy, adsorption distance, charge transfer and desorption time were calculated. Results indicated that intrinsic WS2 had limited adsorption capacity for five target gases. Moreover, Cr doped significantly enhanced WS2 monolayer conductivity, shifting NH3, SO2, NO and NO2 adsorption from physisorption to chemisorption with Eads <0.6 eV, while CO remained physisorbed. The conductivity of the five gases underwent significant changes after adsorption on Cr-WS2. Desorption times at four temperatures (298 K, 398 K, 498 K and 598 K) indicate that Cr-WS2 demonstrates ideal gas sensor behavior for NH3 gas. However, the physisorbed and short desorption at room temperature suggested unsuitability for CO detection in practical applications. Conversely, the extended desorption time at 598 K made Cr-WS2 more appropriate as a gas scavenger for SO2, NO and NO2 gases. These findings underscore the potential of Cr-WS2 monolayers as novel gas warning or adsorbent materials, offering crucial applications in detecting and removing hazardous gases in agricultural greenhouses.

Extracting the electronic structure of light elements in bulk materials through a Compton scattering method in the readily accessible hard x-ray regime

Our Compton profile measurements of Ti and TiH2 using readily available hard X-ray radiation at 27.5 keV, detected by both a Hitachi Vortex silicon-drift detector and a high-resolution superconducting transition-edge sensor array, are found to be in excellent accord with state-of-the-art density functional theory based calculations. The spherically averaged difference between the Compton profiles of TiH2 and Ti is well described by an inverted parabola, supporting an itinerant behavior of the electron gas screening the protons in the Ti matrix. Our experimental approach, validated by two different detectors, extends the applicability of Compton scattering technique to the readily accessible hard x-ray regime (below 30 keV). Our study suggests possibilities for experiments at low-flux bending magnet synchrotron beamlines and paves the way for the development of tabletop Compton experiments with x-ray tubes.

Effect of different regions on fatigue crack growth behavior of 6005-T6 aluminum alloy metal inert gas (MIG) butt welded joint: experimental and numerical study

Effect of different regions on fatigue crack growth behavior of 6005-T6 aluminum alloy metal inert gas (MIG) butt welded joint: experimental and numerical study

A theory and analysis of the impact of gas in the dynamical behavior of the molten salt research reactor leading to the computation of the "gas coefficients of reactivity"

Background Molten salt reactors, and other types of circulating, liquid fueled, nuclear reactors contain a certain amount of gas entrained in their liquid nuclear fuel. This gas induces an effect on the nuclear and dynamical behavior of the reactor as a whole. Gas voids respond to variation in temperature and pressure differently than liquids. When the gas voids in the reactor working fluid expand, the nuclear fuel is pushed from the core. Likewise, when the gas voids contract, more nuclear fuel enters into the core. Methods This paper examines the interplay of gas void fraction and reactivity in a molten salt reactor, and attempts to elucidate the dynamical response of the void fraction and the reactivity of the system to perturbation in system temperature, pressure, and gas quantity. A theory is presented that aims at describing the relationship between reactivity and gas behavior. This theory is then applied to the Molten Salt Research Reactor (MSRR) design, a facility currently under construction at Abilene Christian University campus. Results A result of this paper is the temperature and void fraction parameterized gas coefficients of reactivity for the Molten Salt Research Reactor. Conclusions The presence of voids accounts for 5-30% of the total temperature coefficient of reactivity, demonstrating their non-trivial contribution. Additionally, the study emphasizes the importance of considering gas content in MSR physics, especially in the context of pressure transients and system reactivity during pump trips. The initial system pressure, particularly in designs like the MSRR operating at sub-atmospheric pressures, is crucial due to its influence on reactivity changes during rapid pressure increases.

Mechanism of adsorption and gas-sensing of hazardous gases by MoS2 monolayer decorated by Pdn (n=1–4) clusters

The adsorption behaviors of hazardous gases (NO2 and SO2) on MoS2 monolayer decorated by Pdn (n=1–4) clusters (Pdn-MoS2) are investigated by first-principles calculations, and the performance of Pdn-MoS2 gas sensors has also been studied in this work. Our results show that Pdn nanocluster can enhance the electrical conductivity of MoS2 monolayer with band gaps of Pdn-MoS2 (n=1–4) sharply decreased, and the adsorption performance of NO2 and SO2 with higher adsorption energy and larger charge transfer. Thus, Pdn-MoS2 show higher sensitive to NO2 and SO2 molecules compared with pristine MoS2. The band gaps of Pdn-MoS2 can be further decreased upon the adsorption of NO2 and SO2 (except for SO2/Pd4-MoS2), indicating Pdn-MoS2 (n=1–3) gas sensor shows improved gas-sensitive response to both NO2 and SO2, and Pd4-MoS2 shows improved gas-sensitive response only to NO2. The recovery time analysis indicates that Pdn-MoS2 (n=1–4) is applicable to be utilized as NO2 and SO2 scavenger at ambient temperature, and the recovery process can be realized simply by heating. Our results indicate that Pdn-MoS2 (n=1–4) monolayer is a favorable candidate as adsorbent for detection and removal of NO2 and SO2, and also provides guidance for further study of the MoS2 monolayer decorated by transition metal clusters.

Amine-impregnated natural inorganic nanotubes via layer-by-layer electrostatically self-assembly approach for efficient CO2 adsorption

Developing cost-effective and high-performance solid amine adsorbents has considered as an important way to alleviate the greenhouse effect. How to precisely regulate its pore structure and surface interface characteristics, and how to cooperate to optimize the dynamic mass transfer and adsorption–desorption behavior of gas in the adsorbent are still challenging work. Herein, we demonstrated a facile and efficient approach to construct polyethyleneimine (PEI) impregnated halloysite nanotubes (HNTs) as an emerging nanocomposite for CO2 capture. Based on the natural electrostatic differences of inner and outer walls for HNTs, the hollow tubular structures of adsorbents were constructed by selective surface modification and layer-by-layer electrostatic self-assembly technology to improve the CO2 uptake capacity and cyclic stability, in which poly(sodium-p-styrene sulfonate) (PSS) and PEI were used as polyanionic and polycationic layer, respectively, to coat the inner walls of HNTs. The loading capacity of PSS-PEI composite ionic layers in HNTs and the influence of PSS polyanionic layer on PEI dispersion were specifically discussed according to the CO2 uptake capacity, adsorption heat, thermodynamics and kinetics of the adsorbents. The optimal PEI20-0.5PHNTs adsorbent exhibited a higher CO2 uptake of 0.87 mmol/g at 80 °C in the flow of 40 vol% N2/60 vol% CO2 than that of PEI20-HNTs, owing to the high amine efficiency due to the uniform dispersion of PEI in the electrostatic composite ionic layers. Furthermore, PEI20-0.5PHNTs reached 75 % of the maximum adsorption capacity at the 5th min of the adsorption process and released the most heat during adsorption at − 18.28 kJ/mol due to the presence of electrostatic composite ionic layers. PEI20-0.5PHNTs showed excellent cyclic stability with a slight loss of 7.4 %. The electrostatic self-assembled adsorbent obtained by layer-by-layer loading of PSS and PEI based on the unique surface charge characteristics of HNTs is an inspiration for the synthesis of cost-effective solid amine adsorbents for practical CO2 capture and separation.

Microstructure evolution and corrosion behavior of TIG welded joint of a new Mg[sbnd]Gd[sbnd]Nd[sbnd]Zn[sbnd]Zr alloy during post-weld heat treatment

The corrosion behavior of the tungsten inert gas (TIG) welded Mg3Nd3Gd0.2Zn0.5Zr alloy with different post-weld heat treatments was systematically investigated. The results show that the corrosion resistance of the sand-cast base material (BM) was inferior to that of the fusion zone (FZ), which was attributed to the larger grain size and exacerbated galvanic corrosion caused by coarser Mg3(Nd, Gd) eutectic phases and numerous β precipitates. It is found that post-weld solid-solution (T4) treatment could significantly enhance the corrosion resistance of the joint due to the dissolution of the cathodic second phases and the denser protective film abundant in RE oxides generated in corrosive solution. The precipitation of nanosized phases and ZnZr clusters would slightly increase the susceptibility to localized corrosion of the peak-aged (T6) joint. As the main corrosion products, MgO and Mg(OH)2 are distributed throughout the whole corrosion film, while RE oxides and RE hydroxides are mainly distributed in the inner layer, which can be explained by inward oxidation and replacement reactions between RE elements and MgO/Mg(OH)2. Based on the composition and structure of the corrosion product film, a physical model has been proposed for depicting the microstructure evolution associated with the corresponding corrosion behavior of the joints. This work could promote the applications of welded MgRE alloy joint in some corrosion environments.

Adsorption of toxic gases by Janus MoSeTe monolayers doped with transition metals and surface defects: A first-principles study

In recent years, two-dimensional TMDs materials have been proved to be high-performance gas sensor materials. Janus material is a member of the TMD family, and its gas sensing performance research is particularly important. Gas sensing mechanism of toxic gases on transition metal dichalcogenides based Janus MoSeTe monolayers is investigated using the density functional theory. Six transition metals are considered to modify the MoSeTe surface, by comparing the adsorption energies of the transition metal on both sides of the MoSeTe monolayer, it is found that the transition metal doping is more stable on the Se side. The MoSeTe surface is activated by transition metal modification, and the gas behavior is improved by transition metal modification, it is found that Ir-MoSeTe had the best sensing performance for NO2, Os-MoSeTe had the best sensing performance for CO, and Ru-MoSeTe had the best sensing performance for H2S, NO, and SO2. After that, we explain the adsorption mechanism of gas molecules by calculating the band structure, state density, differential charge density and work function of the adsorption structure, and the recovery time explain the reuse performance of the sensor. The results show that transition metal doped MoSeTe is a promising toxic gas sensor, which provides a theoretical basis for the development of new gas sensors.

Validation of the applicability of the ideal gas equation of state and its correction based on molecular simulation and statistical methods

The ideal gas equation of state is a theoretical model devised to simplify the behaviour of real gases, although its usefulness is limited in numerous realistic scenarios. The experimental subject of this study is the Ar atomic gas, and data is gathered using molecular simulation techniques to assess the suitability and scope of the ideal gas equation of state. Simultaneously, statistical techniques such as linear regression and polynomial regression are employed to construct a novel model. Additionally, the ideal gas equation of state is adapted under specific circumstances, leading to the proposition of a fresh empirical gas equation of state. The study determined that the ideal gas equation of state can be applied to Ar atomic gases within the temperature range of 300-500 K and gas densities ranging from 0.1-0.6 g/cm^3. However, when examining higher gas densities, specifically at temperatures of 300 K and densities exceeding 0.6 g/cm^3, a new empirical gas equation was derived. This equation demonstrates that the pressure of Ar atomic gas is influenced by the 1st and 6th power terms of its density.

Synthesis optimization and separation mechanism of ZSM-5 zeolite membranes for pervaporation dehydration of organic solvents

Pervaporation (PV), as an energy-efficient mixture separation technology, plays an important role in the chemical industry. In this work, no organic templates were needed to produce high-performance ZSM-5 membranes with an extremely low Si/Al ratio of 3.3 on α-Al2O3 tubular supports using 100 nm nanoseeds. The effects of preparation parameters on the crystalline phase structures, micromorphologies, and PV separation performance of ZSM-5 membranes were comprehensively investigated. The results revealed that the Si/Al ratio of gels significantly affected both the Si/Al ratio and the crystal orientation of the final ZSM-5 membrane. The optimized ZSM-5 membrane with a thickness of 1.8 μm was utilized to dehydrate various organic solvents via PV, and the influence of the operating parameters on PV dehydration performance was evaluated and is described herein. Furthermore, the permeation behaviors of single gases and PV were examined using permeate molecules within a similar size range to reveal the PV mechanism of the ZSM-5 membrane. The results demonstrated that gas permeation followed Knudsen diffusion, while PV permeation was decreased with decreases in the affinity of molecules, revealing an adsorption-diffusion mechanism that dominated PV dehydration through the ZSM-5 membrane. Moreover, the as-synthesized ZSM-5 membrane had good water permselectivity for water/acetone (e.g., total flux = 1.03 kg/(m2 h), α = 307) and for water/isopropanol (e.g., total flux = 1.49 kg/(m2 h), α = 1070) mixtures compared with other membranes reviewed in the literature. The synthesized ZSM-5 membrane also exhibited excellent reproducibility, high stability, and attractive PV separation performance, demonstrating its significant potential application in the PV dehydration of organic solvents.

Binary ion-exchanged ETS-4 (Sr/Ba-ETS-4): Synthesis, characterization, and selective nitrogen adsorption from methane for natural gas purification

Several variants of ETS-4 were synthesized through single-cation and binary-cation exchange, with a particular emphasis on Sr/Ba-ETS-4. The impact of binary-cation exchange on the structural characteristics was investigated using various analytical techniques, including XRD, FESEM, EDX, ICP-MS, TGA, and FT-IR analysis. The effect of mixed Sr and Ba exchange within ETS-4 on the adsorption, separation, and kinetic behavior of nitrogen and methane gases was explored utilizing the volumetric method at 30 °C and up to 100 kPa. Additionally, the investigation extended to examining the influence on diffusion coefficients employing the macropore-micropore kinetic model. ICP-MS results revealed a competitive advantage of barium in the exchange process among incoming cations. Notably, significant discrepancies in the adsorption capacity for nitrogen and methane gases were observed between the Sr-ETS-4 and Ba-ETS-4 samples. Experimental isotherm data suggested that the Sips model offered the most suitable fit, unlike the Langmuir or Freundlich models. Among the Sr/Ba-ETS-4 adsorbents investigated, the adsorbent with the highest barium content in the framework exhibited superior nitrogen adsorption capacity (0.33 mmol/g) and the lowest methane adsorption capacity (0.07 mmol/g), leading to high nitrogen over methane equilibrium selectivity (3.12) and kinetic selectivity (167.6).

Many-Body Quantum Systems

This workshop brought together experts on the analysis of quantum many-body problems and quantum statistical mechanics, with the goal of discussing the state-of-the-art of the field, recent developments as well as challenges for the future. The main topics of discussion concerned the equilibrium and dynamical behavior of (bosonic or fermionic) quantum gases, quantum spin systems, as well as quantum field theory models like the Nelson or Fröhlich model.

Comparison of Gas Signature and Void Fraction in Water- and Oil-Based Muds Using Fiber-Optic Distributed Acoustic Sensor, Distributed Temperature Sensor, and Distributed Strain Sensor

Summary Accurate estimation and prediction of gas rise velocity, length of the gas influx region, and void fraction are important for optimal gas kick removal, riser gas management, and well control planning. These parameters are also essential in monitoring and characterization of multiphase flow. However, gas dynamics in non-Newtonian fluids, such as drilling mud, which is essential for gas influx control, are poorly understood due to the inability to create full-scale annular flow conditions that approximate the conditions observed in the field. This results in a lack of understanding and poor prediction of gas kick behavior in the field. To bridge this gap, we use distributed fiber-optic sensors (DFOS) for real-time estimation of gas rise velocity, void fraction, and influx length in water and oil-based mud (OBM) at the well scale. DFOS can overcome a major limitation of downhole gauges and logging tools by enabling the in-situ monitoring of dynamic events simultaneously across the entire wellbore. This study is the first well-scale deployment of distributed acoustic sensor (DAS), distributed temperature sensor (DTS), and distributed strain sensor (DSS) for investigation of gas behavior in water and OBM. Gas void fraction, migration velocities, and gas influx lengths were analyzed across a 5,163-ft-deep wellbore for multiphase experiments conducted with nitrogen in water and nitrogen in synthetic-based mud, at similar operating conditions. An improved transient drift flux–based numerical model was developed to simulate the experimental processes and understand the gas dynamics in different wellbore fluid environments. The gas velocities, void fractions, and gas influx lengths estimated independently using DAS, DTS, and DSS showed good agreement with the simulation results, as well as the downhole gauge analysis.

Importance of Renal Graft Reperfusion Thermoregulation in Living Donor Kidney Transplant Patients: Gasometrical and Hemodynamical Study

INTRODUCTION: Hypothermia, defined as a decrease in core body temperature below 36°C, has a notable influence on hemodynamic variables during anesthesia, which is of great interest in perioperative medicine. Temperature regulation is crucial in anesthetic management because hypothermia can significantly impact the patient's cardiovascular functioning. Accidental (uncontrolled) hypothermia during anesthetic and surgical procedures carries considerable risks such as: Increases the incidence of surgical site infections, prolongs the effects of drugs administered during anesthesia, and disrupts normal coagulation, potentially increasing the risk of bleeding. For these reasons, body temperature regulation is a critical aspect to monitor and control during anesthesia. MATERIAL AND METHODS: A descriptive, observational, single-center, and retrospective study was carried out in patients undergoing a related living donor kidney transplant between June 2022-2023 at the Juarez Hospital in Mexico. All data were collected from the demographic sheets, laboratories and trans anesthetic sheets of the patient's file. The data was integrated into an Excel database and statistical processing was performed in SPSS or STATSm software. The statistical analysis was tested for normality according to Kolmogorov-Smirnov with Lilliefors correction, where it was found that the population has a normal or non-normal distribution. The Mann-Whitney U test was performed to compare the difference of the means between the two groups. A correlation was made with Kendall´s Tau coefficient; All statistical analyzes were performed with a value of p&lt;0.05, considering these significantly. RESULTS: Of the 65 transplanted patients between Jun 2023 and June 2024 only 28 have appropriate inclusion criteria. Of the remaining 28, 16 were female (57.14%) and 12 were male (42.8%) with an average age of recipients of 30.2430.46 ±11.45 years with a weight of 58.23 ±10.47 kg, height 154.20 ±15.32 cm. Gasometrical and Hemodynamic Values upon Reperfusion with a Forced Air Turbine. The gasometrical variables before reperfusion were: Venous pH 7.41±0.05 (p=0.046); Arterial pH 7.40±0.04 (p=0.015); Venous Oxygen Saturation 68.2±9.74% (p = 0.039). Hemodynamic variables before reperfusion were: IC 3.67±1.77 lt/min/m2 (p=0.001); Stroke Volume 79.5±39.6 ml/beat (p=0.022), Oxygen Extraction 25.1±9.95% (p=0.001) and Myocardial Efficiency 0.28±0.06 (p=0.024); The gasometrical variables after reperfusion were: Venous pH 7.40±0.03; Arterial pH 7.380±0.04; Venous Oxygen Saturation 60.03±4.37%; The hemodynamic variables after reperfusion were: IC 2.88±0.48 liter/min/m2; Stroke Volume 65.4±16.01 ml/beat; Oxygen Extraction Rate 36.9±4.31% (p = 0.039) and Myocardial Efficiency 0.32±0.06 Gasometrical and Hemodynamic Values upon Reperfusion without Forced Air Turbine. The gasometrical variables before reperfusion were: Venous pH 7.32±0.04 (p=0.012); Arterial pH 7.30±0.04 (p=0.019); Venous Oxygen Saturation 64.7±8.27% (p = 0.026). Hemodynamic variables before reperfusion were Cardiac Index 3.28±1.66 lt/min/m2 (p=0.006); Stroke Volume 72.39±45.44 ml/beat (p=0.029); Oxygen Extraction 29.11±9.65% (p=0.001) and Myocardial Efficiency 0.268±0.08 (p=0.022). The gasometrical variables after reperfusion were: Venous pH 7.33±0.04; Arterial pH 7.320±0.05; Venous Oxygen Saturation 58.593±5.41%. The hemodynamic variables after reperfusion were: Cardiac Index 2.75±0.69 liter/min/m2, Stroke Volume 59.05±18.81 ml/beat, Oxygen Extraction Rate 38.47±6.17% and Myocardial Efficiency 0.31±0.05. CONCLUSIONS: Understanding the behavior of blood gas and hemodynamic variables upon reperfusion in transplant patients is essential for adequate kidney graft survival. In these patients, the use of a hot forced air turbine improves the conditions under which said reperfusion is performed, impacting not only at the blood gas level (venous pH, arterial pH and venous oxygen saturation) but also at the hemodynamic level (cardiac index, stroke volume, myocardial efficiency The limitations of the study are heterogeneity of the etiologies of CKD, sample size, and volume status prior to the procedure. To date the published works are consistent with the literature.

GPU-accelerated CFD-DEM modeling of gas-solid flow with complex geometry and an application to raceway dynamics in industry-scale blast furnaces

The coupling of Computational Fluid Dynamics (CFD) and Discrete Element Model (DEM) is a powerful tool for simulating dense particulate systems, yet the conventional CFD-DEM has limits for systems with large particle numbers and complex geometry. This paper reports a novel GPU-based CFD-DEM model to simulate the gas–solid flow with large particle numbers and complex geometry. A novel coupling strategy between the CFD solver and DEM solver is developed, featuring high efficiency and stability. The developed model is validated against the experimental measurements, and its efficiency is compared to the previous CFD-DEM simulations. Then, for demonstration, the model is employed to simulate the dynamic behavior of gas–solid flow in the raceway in ironmaking blast furnaces by considering complex tuyere structure details and the huge particle numbers involved. This model allows to study the effect of the tuyere angle in terms of raceway formulation and tuyere erosion. The results show that the largest and most stable raceway volume can be reached at 5° downward tuyere, although the −5° tuyere nose experiences more wear than 10° downward tuyere. The model provides a cost-effective tool to overcome the longstanding challenge of simulating dense fluid-particle systems with huge particle numbers and complex geometry.

Real Gas Effects in High-Pressure Ignition of n-Dodecane/Air Mixtures.

This work studies the real gas effects on the autoignition of hydrocarbon fuels under high pressures, using normal dodecane (n-dodecane) as the representative fuel and the Redlich-Kwong equation of state (EoS) as the real gas description. It is demonstrated that the real gas description yields a shorter ignition delay time (IDT) compared with the ideal gas description, especially in low-temperature regimes which could encompass the negative temperature coefficient (NTC) phenomena and has a stronger dependence on the molecular volume than the attractive potential. The study further shows that high pressure facilitates low-temperature reaction pathways, where the compressibility factors of key reactants contribute to real gas effects. Moreover, the results suggest that accounting for real gas behavior leads to an increase in the formation of polycyclic aromatic hydrocarbons (PAHs), which, in turn, promotes soot generation.

INFLUENCE OF SPRAY DISTANCE ON THE POROSITY OF Ni-BASED AMORPHOUS COATINGS: NUMERICAL SIMULATION AND EXPERIMENT

The influence of injection distance on the porosity of Ni-based amorphous coatings (AMCs) prepared with a high-velocity air fuel (HVAF) process is discussed based on a numerical analysis and experimental methods. A computational fluid dynamics model was established to demonstrate the gas flow field and behavior of particles in flight at different spraying distances during HVAF spraying. When analyzing the changes in the particle velocity and temperature, the spraying distance is less than 30 µm. The velocity and temperature changes of small particles have a significant impact, and the optimal spray distance (350 mm) for obtaining a low porosity coating is predicted. The calculation was validated experimentally by producing a Ni-based AMC with a low porosity (1.87 %) that was manufactured using the predicted HVAF optimal spraying distance.

Pressure Behaviour of Hot Gases and Smoke in Fires of Large Enclosures with Different Ventilation Systems

This study investigates numerically the pressure behavior of hot gases and smoke in fires of large enclosures. It mainly covers the effectiveness of using natural and mechanical ventilation in changing the pressure behaviour of hot gases and smoke inside different structures. Fire Dynamics Simulator (FDS), provided by NIST, has been used to run the simulations for all proposed cases. For the assumed scenarios, the values of hot gas pressure and temperature are extracted at different points, especially in the hot layer close to the ceiling, for further analysis. The effect of changing the location of the fire source has been investigated, too. Final results show noticeable changes in the behavior of pressure, and temperature, in the presence of different ventilation systems, both natural and mechanical. Thus, appropriate ventilation systems can improve the pressure behaviour inside the place, which offers a better environment and higher safety level, in case of fire, in such large enclosures, open plan offices,

Adsorption behavior of formaldehyde gas on two-dimensional semiconductor monolayers MS2 (M=W, Mo)

Detecting methanal molecule, an indoor air pollutant and potential carcinogen, is crucial for safeguarding human health, ensuring occupational safety, and maintaining environmental quality. In this study, density functional theory calculations have been performed to explore the adsorption behavior of formaldehyde (methanal) gas on the surface of two-dimensional semiconductor monolayers MS2 (M=W, Mo). Using the Computational DFT-based Nanoscope tool, we compute binding energies and determine configurations at global minimum energy of molecule adsorbed monolayer MS2. Five nonlocal van der Waals functionals; revPBE-vdW, optPBE-vdW, vdW-DF2, optB88-vdW, and optB86b-vdW are used to compute the adsorption energy profiles. The calculated results show that: (i) the optPBE-vdW functional products the largest adsorption energy magnitude, (ii) Methanal molecule exhibits physical adsorption on both MoS2 and WS2 materials (iii) Adsorption of methanal molecules may enhance the electrical conductivity of MoS2 and WS2 upon the electron donation to molecule by substrates. The adsorption energy magnitude, bandgap reduction, and charge transfer of the methanal-MoS2 adsorption system are respectively 1.04, 1.27, and 1.47 times larger than those of the methanal-WS2 adsorption system, while the diffusion barrier energy is 0.25 times smaller. These characteristic adsorption parameters imply that methanal exhibits higher sensitivity to the MoS2 substrate. This study also provides an in-depth discussion regarding the interaction between methanal and the MS2 substrate, focusing on aspects of relaxed geometrical structures, potential energy surface, adsorption energy, response length, recovery time, work function, charge transfer, density of states, and energy band structure.

Study on the Flow Behavior of Gas and Water in Fractured Tight Gas Reservoirs Considering Matrix Imbibition Using the Digital Core Method

Tight gas reservoirs possess unique pore structures and fluid flow mechanisms. Delving into the flow and imbibition mechanisms of water in fractured tight gas reservoirs is crucial for understanding and enhancing the development efficiency of such reservoirs. The flow of water in fractured tight gas reservoirs encompasses the flow within fractures and the imbibition flow within the matrix. However, conventional methods typically separate these two types of flow for study, failing to accurately reflect the true flow characteristics of water. In this study, micro-CT imaging techniques were utilized to evaluate the impact of matrix absorption and to examine water movement in fractured tight gas deposits. Water flooding experiments were conducted on tight sandstone cores with different fracture morphologies. Micro-CT scanning was performed on the cores after water injection and subsequent static conditions, simulating the process of water displacement gas in fractures and the displacement of gas in matrix pores by water through imbibition under reservoir conditions. Changes in gas–water distribution within fractures were observed, and the impact of fracture morphology on water displacement recovery was analyzed. Additionally, the recovery rates of fractures and matrix imbibition at different displacement stages were studied, along with the depth of water infiltration into the matrix along fracture walls. The insights gained from this investigation enhance our comprehension of the dynamics of fluid movement within tight gas deposits, laying a scientific foundation for crafting targeted development plans and boosting operational efficiency in such environments.