Critical Gas Research Articles

The mutual interactions among ozone, fine particulate matter, and carbon dioxide on summer monsoon climate in East Asia

Ozone (O3) and fine particulate matter (PM2.5) are the major air pollutants, and CO2 is a critical greenhouse gas in East Asia. They three are active species in terms of radiation. Most importantly, both O3 and PM2.5 can interact with CO2 through the terrestrial ecosystem, thus having effects on the regional climate. This study investigated the mutual interactions among O3, PM2.5, and CO2 on the East Asia summer monsoon climate using the coupling regional climate-chemistry-ecology model, RegCM-Chem-YIBs. Two numerical experiments were performed with and without involving the interactions among the three species. The investigations showed that the mutual interactions finally resulted in changes to surface PM2.5, O3, and CO2 of -6∼-2 μg/m3, 4∼6 μg/m3, and 3∼5 ppm, respectively, in northern China. While in southern China, surface PM2.5, O3, and CO2 varied in the range of 2∼4 μg/m3, 1∼2 μg/m3, and -4∼-2 ppm. Surface downward shortwave radiation flux (SWF) and longwave radiation flux (LWF) increased in northern China, whereas showed decreasing in southern China. The lower atmosphere was warmed by 1∼2 K in north China, enlarging the air temperature gradient between land and sea, inducing easterly and southerly winds at 850 hpa in the region. On the contrary, surface cooling (-2∼-1K) exhibited northerly wind anomalies in southern China. The results indicated that the mutual interactions among the three species could significantly impact regional climate. We argue that future simulations should consider these interactions to better predict air pollution and climate changes in the target region. This work could help to comprehensively understand the climate effects of the mutual interactions among O3, PM2.5, and CO2. The findings provide a scientific reference for the collaborative governance of regional climate and air pollution in East Asia.

Accuracy of Critical Care Ultrasonography Plus Arterial Blood Gas Analysis Based Algorithm in Diagnosing Aetiology of Acute Respiratory Failure.

Lung ultrasound when used in isolation, usually misses out metabolic causes of dyspnoea and differentiating acute exacerbation of COPD from pneumonia and pulmonary embolism is difficult, hence we thought of combining critical care ultrasonography (CCUS) with arterial blood gas analysis (ABG). The objective of this study was to estimate accuracy of Critical Care Ultrasonography (CCUS) plus Arterial blood gas (ABG) based algorithm in diagnosing aetiology of dyspnoea. Accuracy of traditional Chest X-ray (CxR) based algorithm was also validated in the following setting. It was a facility based comparative study, where 174 dyspneic patients were subjected to CCUS plus ABG and CxR based algorithms on admission to ICU. The patients were classified into one of five pathophysiological diagnosis 1) Alveolar( Lung-pneumonia)disorder ; 2) Alveolar (Cardiac-pulmonary edema) disorder; 3) Ventilation with Alveolar defect (COPD) disorder ;4) Perfusion disorder; and 5) Metabolic disorder. We calculated diagnostic test properties of CCUS plus ABG and CXR based algorithm in relation to composite diagnosis and correlated these algorithms for each of the defined pathophysiological diagnosis. The sensitivity of CCUS and ABG based algorithm was 0.85 (95% CI-75.03-92.03) for alveolar (lung) ; 0.94 (95% CI-85.15-98.13) for alveolar (cardiac); 0.83 (95% CI-60.78-94.16) for ventilation with alveolar defect; 0.66 (95% CI-30-90.32) for perfusion defect; 0.63 (95% CI-45.25-77.07) for metabolic disorders.Cohn's kappa correlation coefficient of CCUS plus ABG based algorithm in relation to composite diagnosis was 0.7 for alveolar (lung), 0.85 for alveolar (cardiac), 0.78 for ventilation with alveolar defect, 0.79 for perfusion defect and 0.69 for metabolic disorders. CCUS plus ABG algorithm is highly sensitive and it's agreement with composite diagnosis is far superior. It is a first of it's kind study, where authors have attempted combining two point of care tests and creating an algorithmic approach for timely diagnosis and intervention.

Damping characteristics of helicon and Trivelpiece–Gould waves in high density and low magnetic field helicon plasma

By employing a warm plasma model and considering a cyclotron harmonic effect in dielectric tensor elements, the power deposition properties of the azimuthally symmetric mode of the helicon and Trivelpiece–Gould (TG) waves due to collisional and kinetic damping in high density (∼1 × 1013 cm−3), low magnetic fields (∼30–50 G), and low to moderate neutral gas pressure (∼0.5–10 mTorr) helicon plasma are investigated. Theoretical calculations indicate that the magnetic field imposed a significant influence on the mode coupling surface properties between the helicon and TG waves; in a typical helicon plasma electron temperature range, Te ∈ (3, 5) eV, there exists the critical neutral gas pressure, below or above which different waves due to different damping mechanisms play the dominant role in the power deposition; meanwhile, in low neutral gas pressure (∼0.5 mTorr) circumstances, TG waves due to Landau damping dominate the power deposition and this dominance gradually becomes intensified as the magnetic field increases.

Experimental demonstration of >20 kJ laser energy coupling in 1-cm hydrocarbon-filled gas pipe targets via inverse Bremsstrahlung absorption with applications to MagLIF

Laser propagation experiments using four beams of the National Ignition Facility to deliver up to 35 kJ of laser energy at 351 nm laser wavelength to heat magnetized liner inertial fusion-scale (1 cm-long), hydrocarbon-filled gas pipe targets to ∼keV electron temperatures have demonstrated energy coupling >20 kJ with essentially no backscatter in 15% critical electron density gas fills with 0–19 T applied axial magnetic fields. The energy coupling is also investigated for an electron density of 11.5% critical and for applied field strengths up to 24 T at both densities. This spans a range of Hall parameters 0 < ωceτei≲2, where a Hall parameter of 0.5 is expected to reduce electron thermal conduction across the field lines by a factor of 4–5 for the conditions of these experiments. At sufficiently high applied field strength (and therefore Hall parameter), the measured laser propagation speed through the targets increases in the measurements, consistent with reduced perpendicular electron thermal transport; this reduces the coupled energy to the target once the laser burns through the gas pipe. The results compare well with a 1D analytic propagation model for inverse Bremsstrahlung absorption.

Variability in exercise tolerance and physiological responses to exercise prescribed relative to physiological thresholds and to maximum oxygen uptake.

What is the central question of this study? Does prescribing exercise intensity using physiological thresholds create a more homogeneous exercise stimulusthanusing traditional intensity anchors? What is the main finding and its importance? Prescribing exercise using physiological thresholds, notably critical power, reduced the variability in exercise tolerance and acute metabolic responses. At higher intensities, approaching or exceeding the transition from heavy to severe intensity exercise, the imprecision of using fixed % as an intensity anchor becomes amplified. The objective of this study was to determine whether the variability in exercise tolerance and physiological responses is lower when exercise is prescribed relative to physiological thresholds (THR) compared to traditional intensity anchors (TRAD). Ten individuals completed a series of maximal exercise tests and a series of moderate (MOD), heavy (HVY) and severe intensity (HIIT) exercise bouts prescribed using THR intensity anchors (critical power and gas exchange threshold) and TRAD intensity anchors (maximum oxygen uptake; ). There were no differences in exercise tolerance or acute response variability between MODTHR and MODTRAD . All individuals completed HVYTHR but only 30% completed HVYTRAD . Compared to HVYTHR , where work rates were all below critical power, work rates in HVYTRAD exceeded critical power in 70% of individuals. There was, however, no difference in acute response variability between HVYTHR and HVYTRAD . All individuals completed HIITTHR but only 20% completed HIITTRAD . The variability in peak (F=0.274) and average (F=0.318) blood lactate responses was lower in HIITTHR compared to HIITTRAD . The variability in W' depletion (the finite work capacity above critical power) after the final interval bout was lower in HIITTHR compared to HIITTRAD (F=0.305). Using physiological thresholds to prescribe exercise intensity reduced the heterogeneity in exercise tolerance and physiological responses to exercise spanning the boundary between the heavy and severe intensity domains. To increase the precision of exercise intensity prescription, it is recommended that, where possible, physiological thresholds are used in place of .

Gas–Liquid Flow Behavior in Condensate Gas Wells under Different Development Stages

The phase state prediction methods of condensate gas are relatively mature, but the effect of phase changes on gas–liquid mixture flow behavior and the liquid-carrying capacity of gas has not been researched in detail. This study applied PIPESIM software to predict the fluid phase properties under different development stages of a condensate gas reservoir in Shengli Oilfield and determined the phase diagram and physical properties of the well stream on the basis of the optimized equation of state (EOS). Then the influence of phase change characteristics on wellbore flow behavior and critical liquid-carrying gas velocity was analyzed. The study showed that compared with the early development stage, fewer heavy components are produced and the produced gas–liquid ratio is increased in the late stage of the condensate gas reservoir. In addition, the pressure loss of fluid is decreased, the critical liquid-carrying gas velocity and flow rate are reduced, and the liquid-lifting difficulty is reduced for gas. The reason is that the liquid density decreases obviously due to the phase change, while the gas density is almost unchanged, and the oil–gas surface tension decreases obviously, resulting in a decrease in the critical liquid-carrying gas velocity. At the same time, the variation in the gas compressibility factor is very small, which leads to a decrease in the critical liquid-carrying gas flow rate.

Evaluation of Liquid Loading in Gas Wells Using Machine Learning

The inevitable result that gas wells witness during their life production is the liquid loading problem. The liquids that come with gas block the production tubing if the gas velocity supplied by the reservoir pressure is not enough to carry them to surface. Researchers used different theories to solve the problem naming, droplet fallback theory, liquid film reversal theory, characteristic velocity, transient simulations, and others. While there is no definitive answer on what theory is the most valid or the one that performs the best in all cases. This paper comes to involve a different approach, a combination between physics-based modeling and statistical analysis of what is known as Machine Learning (ML). The authors used a refined ML algorithm named XGBoost (extreme gradient boosting) to develop a novel full procedure on how to diagnose the well with liquid loading issues and predict the critical gas velocity at which it starts to load if not loaded already. The novel procedure includes a combination of a classification problem where a well will be evaluated based on some completion and fluid properties (diameter, liquid density, gas density, liquid viscosity, gas viscosity, angle of inclination from horizontal (alpha), superficial liquid velocity, and the interfacial tension) as a “Liquid Loaded” or “Unloaded”. The second practice is to determine the critical gas velocity, and this is done by a regression method using the same inputs. Since the procedure is a data-driven approach, a considerable amount of data (247 well and lab measurements) collected from literatures has been used. Convenient ML technics have been applied from dividing the data to scaling, modeling and assessment. The results showed that a wellconstructed XGBoost model with an optimized hyperparameters is efficient in diagnosing the wells with the correct status and in predicting the onset of liquid loading by estimating the critical gas velocity. The assessment of the model was done relatively to existing correlations in literature. In the classification problem, the model showed a better performance with an F-1 score of 0.947 (correctly classified 46 cases from 50 used for testing). In contrast, the next best model was the one by Barnea with an F-1 score of 0.81 (correctly classified 37 from 50 cases). In the regression problem, the model showed an R2 of 0.959. In contrast, the second best model was the one by Shekhar with an R2 of 0.84. The results shown here prove that the model and the procedure developed give better results in diagnosing the well correctly if properly used by engineers.

Gas Lift Modeling: A Viable Option for Oil Production Optimization

Gas lift optimization is very challenging even in the mist of availability of gas assets as this involves modeling reservoirs accurately. Non availability of good software hinders best results such as obtaining critical gas lift design parameters like appropriate absolute open flow (AOF), skin factor, formation productivity index and the skin factor or even the reservoir pressure. The aim of this work is to design a model to gas lift an oil well in the Niger Delta for improved oil optimization. In other to achieve this aim the following objectives are considered; determine the maximum production rate achievable using gas lift, determine the optimum lift gas injection rate and depth and design the operating and unloading valves. Integrated Production Management (IPM) software was used with data from an oil well in the Niger Delta. Results show that the AOF gave 18026.3STB/day, formation PI gave 10.56STB/day/psi while the skin factor gave a positive value of 2. Pipe correlation used is Beggs and Brill. The maximum and minimum gases available are both 15mmscf/day. Water cut is 80%. The use of gas lift is very appropriate when the gas cap is a major source of reservoir energy

Engineering Properties of Commercially Available Hermetic Storage Bag Liners

Highlights Fundamental engineering properties of hermetic bag liners were identified and measured to establish specifications for a new ASABE X657 standard for measurement and rating the performance of gas barrier liners in hermetic storage bags. Results showed strong evidence of differences in properties among six types of commercially available hermetic bag gas barrier liners (P<0.05). Critical gas barrier properties (OTR and WVTR) were measured to assess their ability to maintain initial conditions (“hermeticity”). Critical mechanical properties, such as impact failure weight, penetration resistance, and tear strength, were measured to determine their durability during handling and storage. Abstract. The impacts of hermetic storage bag technology on food security are well established. However, understanding the hermetic bag liner's mechanical and barrier properties with its useful life and efficacy are needed to ensure the continued successful adoption of this critically important storage technology to control biological activity. The goals of this study were to identify and quantify fundamental engineering properties as a basis for establishing an American Society of Agricultural and Biological Engineers (ASABE) engineering standard for testing and rating the hermeticity of gas barrier liners in storage bags for smallholder farmers. Six commercially available hermetic storage bag liners (AgroZ, Elite, PICS, GrainPro, Storezo, Zerofly) were evaluated for mechanical properties (tensile, impact, tear, penetration resistance) and barrier properties (oxygen transmission rate and water-vapor transmission rate) following American Society for Testing and Materials (ASTM) test methods. Results indicate significant differences (P< 0.05) in material properties among brands of storage bag liners. Values for oxygen and water vapor transmission rates were determined to ensure hermetic conditions can be achieved. Values for mechanical properties (yield and tensile strength, elongation, and toughness, tear strength, penetration resistance and impact failure weight) of gas barrier liners were quantified to ensure acceptable performance of hermetic storage bags. Keywords: Elongation, Hermetic storage, Hermetic storage bags, Impact failure weight, Oxygen Transmission Rates (OTR), Penetration resistance, Tear strength, Tensile strength, Toughness, Water Vapor Transmission Rate (WVTR), Yield strength.

Dynamic Simulation Approach for Liquid Loading in Horizontal Gas Well X Field Indonesia

There has been intensive investigation on the understanding of the liquid loading phenomenon lately via experiment and transient approach. This is driven due to the limitation of the traditional approach using steady state Turner correlation to be used over a wide range of actual conditions (i.e such as under various tubing diameters, fluid condition (CGR/WGR), and horizontal or deviated trajectory of the well) which can lead to underpredict critical gas rate and mitigation action which directly impact the production and economics limit of the field. By nature, the liquid loading phenomena classified as transient or dynamic phenomena and hence couldn’t be able to be explained under the steady state approach. The application of dynamic well modeling itself has been applied worldwide recently. Therefore, utilizing this new approach for estimating the critical gas rate for horizontal well bring benefit by reducing the uncertainty of the outcome and providing more accurate prediction compare to the traditional approach. The selection of the de-liquification method which uses the bullheading for the horizontal gas well in X field provides the highest production optimization and the most economical approach to the field as there is no additional opex cost required.

Gas pressure evolution characteristics of deep true triaxial coal and gas outburst based on acoustic emission monitoring

Coal and gas outburst is one of the geological disasters that seriously threaten the safety of coal mines production. In recent years, with the increase of mining depth, outbursts become frequent. To further explore the occurrence mechanism of deep coal and gas outburst, a self-developed true triaxial coal and gas outburst simulation device was used to simulate the coal and gas outburst at different depths. The results show that with the increase of simulation depth, the critical gas pressure of outburst gradually decreases, and the unit outburst intensity increases sharply. The gas threshold of deep coal and gas outburst is lower. During the incubation and excitation, gas pressure has three special variation rules, namely self-increasing characteristic, stage and instantaneous. In the early incubation, acoustic emission (AE) energy is at a low level, low energy frequency is dominant; in the later incubation, AE energy increases greatly, high energy frequency is dominant. From the perspective of AE energy, a quantitative index that reflects the danger of coal and gas outburst in the incubation is defined, which provides a scientific reference for the prediction and prevention of disasters of coal and gas outburst in deep mining.

Modeling evaluation of physiochemical processes controlling gas migration in shallow groundwater systems

Gases may be released into shallow groundwater systems during energy development and geological carbon storage (commonly referred to as gas migration, GM) and can result in greenhouse gas emissions, safety concerns, and the reduction of groundwater quality. The physiochemical processes occurring during GM, including gas release, movement, partitioning, and dissolved-phase transport in the saturated groundwater zone, are difficult to characterize and model; however, modeling is important to develop strategies for detecting and monitoring GM and formulate conceptual models to describe GM at impacted sites. In this study, a previously developed numerical model, which coupled macroscopic invasion percolation (macro-IP) and multicomponent mass transfer, was enhanced to simulate gas releases in the shallow subsurface. Evaluation of the effects of the coupled physiochemical processes was performed by comparing model simulations to previously conducted bench-scale gas injection experiments. Results show that gas flow is highly sensitive to the entry pressures assigned within the model domain and the critical gas saturation (Sg,crit) used to model gas-water flow based on macro-IP; however, mass transfer and the resulting domain-scale dissolved-gas transport were relatively insensitive to these parameters. Multicomponent mass transfer, considering not only the partitioning of the released gas, but also the dissolved background gases ubiquitous in shallow groundwater, was vitally important to simulate dissolution and the resulting free-phase gas distribution within the experimental systems. The use of the local equilibrium assumption for gas-water mass transfer could not consistently describe the experimental observations. Overall, the modeling evaluation performed in this study provides improved understanding of the key processes controlling GM in the shallow subsurface and will advance efforts including up-scaling and scenario testing to accurately quantify the environmental impacts of GM.

Prediction model of critical liquid‐carrying gas velocity for high gas‐to‐liquid ratio gathering pipelines

As the pressure and temperature of natural gas pipelines decreases during operation, water and condensate accumulates form in the low areas of the pipelines, affecting the operational efficiency of the pipelines and even corroding them. The critical gas velocity is a key factor in predicting liquid loading onset in the pipeline, so that appropriate measures can be taken in advance and hazards can be reduced. This paper proposes a model for predicting pipeline liquid loading onset based on the liquid film and wall shear stress of zero, and applicable to different pipe diameters and different inclination angles. This model provides a more simplified and comprehensive prediction of pipeline fluid loading than other models with complex calculations. The critical gas velocity in this model is a function of the liquid holding rate rather than the liquid film thickness, and the critical gas velocity prediction in a phase-inclined pipe is carried out by an improved Belfroid angle correction term. The experimental data, field data and seven models in the published literature were compared and validated, and the errors were judged. The results showed that the new model outperformed the other models in terms of absolute mean error at full inclination angle, and was able to predict the pipeline liquid loading accurately.

A Review on the Incorporation of Diatomaceous Earth as a Geopolymer-Based Concrete Building Resource.

The development of geopolymer building composites at a lower cost with a smaller carbon footprint may lessen the growing concerns about global warming brought on by emissions of a critical greenhouse gas (CO2) paired with the high production costs in the cement sector. Diatomaceous earth, commonly used as an admixture or partial replacement of cement owing to its most effective pozzolanic properties, has been investigated as a precursor in geopolymer concrete development. Several studies have been examined to develop a greater understanding of its characterization, inclusion status, and impacts on the performance aspects of concrete. The literature review showed that using diatomaceous earth is one of the effective ways to create sustainable, insulating, lightweight building materials while minimizing the harmful economic and environmental effects of industrial solid wastes. However, since most studies have focused on its integration as a partial cement substitute or a replacement for fine aggregate, further research on diatomaceous earth-based clinker-free concrete is required. A lack of research on geopolymer concrete’s reinforcement with either natural or synthetic fibers, or a combination of the two, was also discovered. This review also showed that there has been remarkably little effort made towards theoretical property correlation modeling for predicting concrete performance. It is anticipated that the detailed overview presented herein will guide potential researchers in defining their future paths in the study area.

Blockchain trends and analysis under the economic and financial fields in pharmaceutical sector

Block chain innovation has filled in prevalence as an examination theme and a specialized answer for various undertakings and enterprises. Blockchains disseminated, decentralized, and trustless can give associations new choices and benefits as higher effectiveness, lower costs, further developed honesty and straightforwardness, further developed security, and further developed discernibility. Low financial entrance, the exit of monetary players from specific business sectors, substantial interest for economic incorporation from the two people and private ventures, significant degrees of versatile infiltration, less created business foundation, and monetary area officeholders are on the whole attributes of developing business sectors. With the appearance of Bitcoin, the connection between blockchain innovation and the monetary business sectors will become more personal and incorporated. Then, at that point, as the pertinence of blockchain innovation became clear, more monetary organizations started to explore different avenues regarding its utilization in financial exchanges. These elements, taken together, can go about as a critical gas pedal for the reception of blockchain-based economic arrangements, laying the foundation for a specialized jump ahead and a lift to financial consideration and development. This article gives a prologue to blockchain innovation, investigates significant useful parts of blockchains, fosters a conventional definition, and examines and orders current and forthcoming blockchain applications in the monetary and financial areas.

Transient nuclear criticality excursion analysis of highly dispersed particulate three-phase fluidised systems

The aim of this study was to perform sensitivity analysis, investigating how different fluidisation and sedimentation characteristics of three-phase wetted UO2 powder beds, may affect a transient nuclear criticality excursion initiated through the addition of water into a fissile powder bed. This type of postulated nuclear criticality accident scenario may occur in nuclear fuel fabrication facilities when a fire is fought through the use of water, supplied via an automatic or manual fire-suppression system. A similar scenario may also develop as a result of water leaks or flooding of the process area housing UO2 powder. The article introduces a model for gas-bubble induced fluidisation of a UO2 powder bed and examines how this phenomenon may affect the neutron kinetic response of a three-phase fluidised fissile powder system. Empirical analysis has shown that fissile suspensions form agglomerated structures when suspended in water, at agglomerate sizes that range from 18 μm to 40 μm. Simulation results indicate that both the critical gas velocity and rate of fluidisation may significantly affect transient nuclear criticality excursion dynamics. The re-distribution of fissile mass into a highly dispersed suspension generally reduces the reactivity of the system, however, depending on the H/U ratio, a positive reactivity may be added to the system. Low Péclet numbers in the suspension suggest that gas-bubble induced motion of the suspension causes a highly dispersive flow field. An oscillatory power response is predicted for low critical gas velocities where the reactivity of the system is predominantly governed by the re-distribution of fissile mass within the system. The frequency of these oscillations is greater for a higher hindered settling rate of powder particles. At a higher critical gas velocity, the transient nuclear criticality excursion is governed by the voidage reactivity feedback, making the response quite independent of fluidisation. In all cases, large volumes of UO2 powder may leave the domain due to overflowing of the suspension. Transient nuclear criticality excursions in UO2 powder beds with a low critical gas velocity are terminated once the bed becomes fully saturated.

Free vibration and stability analysis of inclined pipes conveying gas-liquid slug flow

In this paper, the free vibration and stability of inclined pipes conveying gas-liquid slug flow are investigated, by considering the intermittency of slug flow and gravity effects of the system. A new lateral motion model has been established based on the stable slug flow dynamics model and the Euler–Bernoulli beam vibration model and is then truncated by the Galerkin approach. The natural frequencies, critical gas velocities, and responses to flow conditions are comprehensively investigated to show the basic dynamic characteristics of inclined pipes. The results show that the gravity effects caused by the inclined angle have a significant effect on the vibration characteristics. The system is less stable with lower critical gas velocity and natural frequency with the increase of inclined angle, due to the gravity-induced compression. For a given inclined angle, the system dynamic responses to superficial gas/liquid velocities are directly related to the mass of liquid per unit length. In addition, the fluctuation of natural frequency caused by the intermittency of slug flow decreases with the increase of inclined angle. This study contributes to understanding the complex dynamic behavior of inclined pipes conveying slug flow and promoting pipeline safety.

Dual-mode biosensing platform for sensitive and portable detection of hydrogen sulfide based on cuprous oxide/gold/copper metal organic framework heterojunction

Hydrogen sulfide (H2S) can not only be regarded as a critical gas signal transduction substance, but also its excess levels can lead to a range of diseases. Currently, the accurate analysis combined with electrochemical (EC) or photothermal (PT) technology for H2S in a complex biological system remains a significant challenge. Herein, an endogenous H2S-triggered heterojunction cuprous oxide/gold/copper metal organic framework (Cu2O/Au/HKUST-1) nanoprobe is designed for dual-mode EC- second near-infrared (NIR-II)/PT analysis in tumor cells with high sensitivity and simplicity. Dual-mode EC quantification - PT is achieved through “off–on” mode of EC and PT signals based on electronic transfer and biosynthesis via an in situ sulfuration reaction. Under the optimum conditions, the EC quantification mode for trace H2S exhibits a wide linear range and an excellent limit of detection of 0.1 μM. More importantly, the dual-mode can display the selective detection of trace H2S in living tumor cells because of the specific interaction between copper ion and H2S. These results provide a new EC-PT promising biosensing platform for noninvasive intelligent detection of H2S in living tumor cells.

Characterizing Gas Hydrate–Bearing Marine Sediments Using Elastic Properties—Part 1: Rock Physical Modeling and Inversion from Well Logs

Gas hydrates are considered a potential energy source for the future. Rock physics modeling provides insights into the elastic response of sediments containing gas hydrates, which is essential for identifying gas hydrates using well-log data and seismic attributes. This paper establishes a rock physics model (RPM) by employing effective medium theories to quantify the elastic properties of sediments containing gas hydrates. Specifically, the proposed RPM introduces critical gas hydrate saturation for various modeling schemes. Such a key factor considers the impact of gas hydrates on sediment stiffnesses during the dynamic process of the gas hydrate accumulating as pore fillings and part of the solid components. Theoretical modeling illustrates that elastic characteristics of the sediments exhibit distinct variation trends determined by critical gas hydrate saturation. Numerical tests of the model based on the well-log data confirm that the proposed technique can be employed to rationally predict gas hydrate saturation using the elastic properties. The compressional wave velocity model is also developed to estimate the gas hydrate saturation, which gives reliable fit results to core measurement data. The proposed methods could improve our understanding of the elastic behaviors of gas hydrates, providing a practical approach to estimating their concentrations.

Visualization experiment and numerical simulation on behaviors of gas-liquid falling film flow on the air-side of two-row plain finned-tube heat exchanger

The frost-free air-source heat pump (ASHP) with integrated liquid desiccant dehumidification is a more promising energy-saving alternative to the conventional ASHP unit. The performance of spray-type finned-tube heat exchanger (FTHE), as one of the key equipment of this frost-free ASHP system, is affected by a combination of various factors including wall wettability, liquid film flow pattern, liquid film thickness, velocity distribution in a liquid film, interface wave, interface velocity and so on. To provide a theoretical basis for the operation, design and optimization of high-performance spray-type FTHE, a visualization experiment system and a three-dimensional (3D) numerical model are employed to study the behaviors of counter-current gas-liquid falling film flow on the air-side of two-row plain FTHE under different parameters in the present paper. According to the experimental results, the flow pattern of liquid film on the finned-tube surface is a mixture flow composed of the rivulet flow and the thin falling film flow, demonstrating that the assumption of the uniform distribution for liquid film thickness proposed in previous studies is not completely consistent with the actual situation. Meanwhile, the numerical results indicate that the transient-average film thickness on the surface of two-row plain finned-tube is significantly 18.3% – 32.5% higher than that on the vertical plate calculated by Nusselt's model. After that, the critical gas and liquid Reynolds numbers of the flow pattern transition for the liquid film are obtained, and it is pointed out that the wall contact angle of 10° is more conducive to the formation of complete film flow on the air-side of the two-row plain FTHE within the fin pitch range of 4.8 – 6.0 mm. The changes of the falling liquid film and gas-liquid interface characteristics are fundamentally attributed to the drag effect of the interfacial shear force. Furthermore, there is a cubic curve relationship between average interface shear force and gas Reg. A quadratic curve relation exists between average wall shear stress and gas Reg. At the same time, the velocity of falling film fluid at the bottom region of laminar flow is reduced, resulting from the inhibiting effect of the interfacial shear force.