Pressure Curves Research Articles

Impact of Influence of Piston Design Parameters on the Hydrodynamic Characteristics of Internal Combustion Engines—A Numerical Study

Piston top rings in the combustion engine play a crucial role in the overall hydrodynamic performance of engines, such as power loss, minimum film thickness and friction forces, by ensuring sealing and minimizing the leakage of burnt gases. This present paper examines the influence of four key parameters of the top ring, such as ring width, ring temperature, ring tension, and ring surface roughness on the hydrodynamic behavior at the ring/cylinder contact. These parameters play a significant role in the formation and maintenance of the oil film, directly influencing hydrodynamic indicators such as the minimum oil film thickness, friction force, power loss, oil pressure, and the ring angle twist. This article relies on hydrodynamic models and numerical simulations performed using GT-SUITE version 6 software to analyze these effects. The pressure curve used in this simulation is experimentally validated for an engine speed of 2000 RPM. It was found that an increase in the top ring temperature reduces the oil’s viscosity, decreasing the film thickness and increasing the risk of metal-to-metal contact. Increasing the roughness of the ring enhances oil film stability, especially at the bottom dead center (BDC) points during each phase of the operating cycle. Further, three different types of ring profiles were investigated for friction forces by varying the speed of the engine.

Airfoil Design and Flow Analysis of a Multi-Blade Centrifugal Fan: An Experimental and Simulation Study

To overcome the technical challenges of the multi-blade centrifugal fan, such as low efficiency and insufficient total pressure, the blades of the fan were optimally designed in this study. The flow field of the multi-blade centrifugal fan with a single-arc blade and an airfoil blade was simulated and compared using Computational Fluid Dynamics (CFDs). Under steady-state conditions, the total pressure, velocity field distribution, and aerodynamic performance of a multi-blade centrifugal fan were analyzed. The numerical results showed that there were vortices, secondary flows, and boundary layer separation phenomena in the flow passage of the single-arc multi-blade centrifugal fan. Based on the lift-to-drag ratio theory of airfoil in aerodynamics, four different airfoil blades were designed for the multi-blade centrifugal fan. The study found that the lift-to-drag ratio of the airfoil blades was positively correlated with the fan efficiency; among them, the A-type airfoil exhibited the highest lift-to-drag ratio within the 0–10 degree angle of attack range. The three-dimensional simulation results indicated that, except for the initial operating point B, the A-type airfoil showed higher fan efficiency under other operating conditions, and its total pressure curve was the most stable. In addition, the use of airfoil blades effectively suppressed the aforementioned adverse flow phenomena and improved the flow within the blade passage. Experimental verification further confirmed the effect of airfoil blades on improving fan performance: compared to single-arc blades, the efficiency of the multi-blade centrifugal fan increased by 3–7% after using airfoil blades, and the upper limit of high-efficiency flow increased from 450 m3/h to 650 m3/h. Meanwhile, the total pressure and power of the airfoil fan were also significantly improved. The results of this work are significant for guiding the optimal design of the fan.

Klotho protein: a new insight into the pathogenesis of essential hypertension

BackgroundEssential hypertension is a most prevalent global health concern. Despite extensive research, the exact mechanisms contributing to essential hypertension remain unclear. Several factors contribute to the pathogenesis of essential hypertension. Klotho, a membrane-bound and soluble protein, has been found to modulate hypertension through physiological processes like vascular function and sodium balance. This study aimed to determine the association of klotho protein with essential hypertension.MethodsThe study included 164 hypertensive cases and 164 normotensive controls, after imposing certain inclusion and exclusion criteria with written consent from all subjects. Subject’s details were obtained using structured proforma to account for potential confounding variables. To estimate klotho protein activity using sandwich enzyme-linked immunosorbent assay, 2 mL blood was collected in a plain vial. All data were tested at a 5% significance level.ResultsThe analysis revealed a significant decrease in klotho protein levels in cases compared to controls (1.52 ± 0.87 vs. 2.45 ± 0.90, P < 0.001), suggesting an inverse relationship of klotho protein with risk of essential hypertension. All indices in the structural equation model have suggested that the final model fitted the data reasonably (chi-square to df ratio, 1.153; goodness of fit index, 0.990; adjusted goodness of fit index, 0.945; normed fit index, 0.936; standardized root mean square residual, 0.953; root mean square error of approximation, 0.031). Also, klotho was negatively associated with blood pressure. The area under the receiver operating characteristic curve for klotho and blood pressure was 0.765 (95% confidence interval, 0.716–0.815; P < 0.001).ConclusionsKlotho levels were significantly reduced in essential hypertension cases compared to controls, Also, klotho had a negative direct association with essential hypertension indicating a potential role for klotho as a prognostic and predictive marker for essential hypertension. This suggests that klotho may have a role in the pathogenesis of essential hypertension. Understanding klotho’s role in essential hypertension may lead to the development of novel therapeutic strategies for this disease.Graphical

Controlling parameters of co-current and counter-current imbibition in naturally fractured reservoirs

Naturally fractured formations are complex petroleum reservoirs that are poor candidates for waterflooding due to difficulties in controlling sweep. Injected water can readily propagate through the fracture system, bypassing the hydrocarbon stored in the matrix. Instead, such systems rely on spontaneous imbibition (SI) from the matrix into the extensive fracture gathering system. SI is a crucial recovery mechanism that relies on capillary pressure-dominated fluid movement. SI can occur through two modes, co-current (COSI) and counter-current (COUSI), depending on the relative direction of fluid movement in response to prevailing boundary conditions. Analytical solutions that incorporate the diffusivity coefficient, which combines relative permeability and capillary pressure curves, are used to describe co-current and counter-current imbibition mechanisms. The perturbation method is one approach in solving these analytical equations. In-situ water saturation profiles, ascertained through experimental CT scanning, serve as validation benchmarks for both co-current and counter-current models. The understanding of the SI process can give more details about the fracture-matrix interactions and the exchange function. Sensitivity studies with respect to the parameterization of the driving force for imbibition, capillary pressure, and the resistive forces, captured in relative permeability curves, can guide experimental study planning and aid in inverse problem analysis in the characterization of naturally fractured reservoirs. The results of a parametric study show that capillary pressure curve parameters, such as capillary entry pressure and capillary exponent, significantly affect the position of the waterfront which indicates the imbibition rate. In addition, the water relative permeability exponent has greater impact on both shape and position of water profile than other relative permeability parameters. The nonwetting phase parameters, like oil endpoint relative permeability and oil exponent, have the least influence on water saturation profile.

Modeling and Simulation of Multi‐Material and Complex‐Shaped Gun Propellant Combustion in Closed Vessels

AbstractThe geometric shape and material structure of gun propellant grains control the pressure evolution during combustion and, consequently, the performance of the ammunition. Due to the large number of degrees of freedom, additive manufacturing offers novel opportunities for grain shape and structure design. However, this new freedom necessitates the development of new algorithms for modeling and simulation of surface regression. In traditional combustion models, it is assumed that the propellant′s burn rate is a global quantity on its surface, which enables separate simulation of the surface regression and pressure evolution. To exploit the full potential of additive manufacturing and optimize designs for different applications, it is necessary to simulate grain structures with locally different burn rates on the surface. This work presents a model to simulate quantitatively the combustion of multi‐material and complex‐shaped solid propellant grains in a closed vessel for the first time. A lumped parameter pressure model is coupled with a surface regression simulation based on the level set method. The model is validated by comparison to analytical surface regression. Then, for the first time, a combustion simulation of a multi‐material ball propellant grain consisting of two hemispheres in a closed vessel is presented. Compared to a combustion simulation using global and weighted mean burn rate values, the pressure and vivacity curve shows significant differences. This demonstrates impressively that for predicting the performance potential of multi‐material and complex‐shaped solid gun propellant grains, a quantitative and accurate combustion simulation is indispensable.

Abstract 4143219: Pressure-Volume Analysis by Three-Dimensional Echocardiography: A Novel Method to Estimate Left Ventricular Efficiency

Background: Left ventricular (LV) efficiency is a key pathophysiological marker in heart failure (HF). LV pressure curve estimation and three-dimensional (3D) volumes via echocardiography allows for non-invasive pressure-volume (PV) analysis and calculation of an index of efficiency (Figure 1). Aim: Validate efficiency index by 3D echocardiography by comparing it to invasive measurements and efficiency derived from Positron Emission Tomography (PET) metabolism. Methods: Two experimental models were utilized - one with canines (n=21) and another with sheep (n=12). In canines, echocardiography provided 3D LV volumes and valve event timings. The pressure curve was estimated by adjusting the time axis of a reference pressure curve to the valve events and its amplitude to measured peak LV pressure, which in clinical practice would be approximated as systolic brachial cuff pressure. Invasive pressure was measured by micromanometer and volume by subendocardial piezoelectric crystals. Non-invasive and invasive efficiency indices, calculated as the ratio of stroke work to total mechanical energy (Figure 1), were compared during baseline, right ventricular pacing, aortic constriction and dobutamine infusion. Twelve sheep implanted with a pacemaker underwent 8 weeks of rapid dyssynchronous DDD pacing to induce dilated HF. LV efficiency index was calculated as in Figure 1, using measurements from a PV-catheter calibrated to end-diastolic volume by cardiac MRI, and compared to efficiency calculated as stroke work divided by total LV glucose metabolism via PET/CT. Recordings were performed during AAI and DDD pacing, at baseline (n=3) and following 8 weeks pacing-induced HF (n=12). Results: In canines, non-invasive and invasive efficiency indices showed excellent agreement (r=0.95, p&lt;0.0001; mean difference 0.4%, SD 3.4%) (Figure 2). In sheep, the efficiency index showed similar decline compared to efficiency by PET/CT after induction of HF and after switching from AAI to DDD pacing (p&lt;0.05 for all interventions). Overall correlation between the methods was moderate (r=0.67, p=0.0001) but excellent in animals with longitudinal data (r=0.89, p=0.0001) (Figure 3). Conclusions: Efficiency index by 3D echocardiography is accurate and reflects changes in efficiency measured by PET/CT. It may thus be of interest for clinical use.

Effects of diesel pilot-injection strategy on a methanol/diesel dual-direct injection engine

To verify the effectiveness of dual-direct injection technology in enhancing the performance of methanol/diesel dual-fuel engines and the positive impacts of multiple-injection strategy on the in-cylinder mixture formation and combustion process, an experiment was conducted on a modified methanol/diesel dual-direct engine test platform in this paper. The research aimed to explore the effects of the diesel pilot-injection strategy, especially from the two aspects of diesel pilot-injection timing and diesel pilot-injection duration, on the operating range, combustion characteristics, performance and emissions. Results indicate that the pilot-injection strategy reduces the maximum pressure and pressure rise rate of the engine, alleviating the rough combustion in the cylinder and broaden the operating range. As the diesel pilot-injection timing advances, the in-cylinder pressure curve during the combustion process shifts leftward as a whole, and the pressure rise rate curve gradually becomes an approximate single-peak shape. The ignition delay almost increases linearly and CA50 first decreases and then increases with the advance of pilot-injection timing. When the pilot-injection duration increases, the ignition delay shortens and CA50 advances. Additionally, the diesel pilot-injection strategy can optimize engine emissions. As the pilot-injection timing advances and the duration increases, the HC, CO and soot emissions decrease, while the NOx emission increases. Using the pilot-injection strategy, the highest indicated thermal efficiency of 42.94 % is obtained at the diesel ignition injection timing and duration of −28 °CA aTDC and 0.25 ms respectively, which is 7.54 % relatively higher than that under a single injection strategy. The research results show that the pilot-injection strategy better adjusts the distribution of high reactivity and low reactivity fuels in the cylinder, which is beneficial for improving the combustion and performance of the methanol/diesel dual-fuel engine.

A Method for Determining Yield Stress of Unsaturated Soils from Lateral Pressure

Abstract Predicting the stress–strain behavior of unsaturated soils is essential for determining yield stress. This paper explores a new method for determining the yield stress of unsaturated soils from the lateral pressure curve. A series of earth pressure at rest (K0) ondometer tests were conducted on unsaturated Yangqin silt clay. Lateral stress was obtained under different saturations and compactness. The relationship curves between lateral and vertical net stress were drawn for each condition. An obvious turning point was observed in the curve, which can be used to determine the yield stress. The oedometer tests were conducted, and the Casagrande and the bilogarithmic methods were used for comparison purposes. The difference between the proposed and traditional methods was less than 17 %. The initial saturation and compactness influence on the yield stress was discussed. The yield stress increased with the decrease in saturation and increases in compactness, which is consistent with that of the classic method. The test results and comparison prove the rationality of the proposed method. No coordinate transformation is required in the proposed method, which is more convenient for data processing. It can be used to determine the yield stress of unsaturated soils from another perspective.

Thermodynamically consistent interfacial curvatures in real pore geometries: Implications for pore-scale modeling of two-phase displacement processes

In conventional Pore-network Modeling (PNM) approaches, fluid flow and transport are solved in a network of pore elements with idealized geometries. Such simplification can lead to inaccurate predictions when the original pore space features complex geometries. To overcome this limitation, this study introduces a novel workflow that integrates four key components: (i) an enhanced pore network extraction (PNE) platform capable of identifying and extracting pore cross-sections from high-resolution micro-computed tomography (micro-CT) images of the pore space, (ii) a computationally-efficient semi-analytical model that can faithfully predict capillary entry pressure and the corresponding fluid configuration of piston-like displacements using real two-dimensional cross-sections of pores, (iii) a PNM approach for two-phase flow modeling that utilizes the capillary entry pressure of pores predicted by the semi-analytical model, and (iv) an Artificial Intelligence (AI)-driven model that paves the way for future advancements in efficiently predicating fluid displacement properties in intricate pore structures. To validate this new workflow, we constructed various pore networks containing real pore and throat cross-sections over a diverse group of sandstone and carbonate rock samples. Subsequently, we simulate capillary pressure curves of Mercury Intrusion Capillary Pressure (MICP) and oil–water primary drainage displacements in Bentheimer and Berea sandstones, respectively, using both the conventional and enhanced PNM approaches. The latter demonstrated improved prediction accuracy compared to conventional methods. Next, primary drainage simulations are conducted for two carbonates, and the resulting capillary pressure curves from both PNM approaches are compared. In addition, we conduct an in-depth analysis of fourteen geometric features of the pore space, identifying key factors of hydraulic radius, circumradius, sphericity, and area, that significantly impact capillary entry pressure of pores. After that, we construct an Artificial Neural Network (ANN) to predict the capillary entry pressure of pores using their critical geometric features. This AI model, trained using data derived from the semi-analytical model, exhibits excellent predictive accuracy (with a R2 of 0.995 for the test data set) in estimating capillary entry pressure of pores. Overall, our newly proposed, integrated workflow represents a significant step forward in the field of digital rock technology (DRT), offering an accurate and efficient method for modeling fluid flow in rock samples with complex pore geometries.

Effect of concentration gradients on the explosion characteristics of methane/air premixed gases

Non-uniform concentration fields increase the risk of combustible gas explosions under practical industrial conditions. To investigate the effects of transverse and vertical concentration gradients on methane explosion characteristics, experiments were conducted near the stoichiometric ratio in a square pipeline, focusing on flame structure, velocity, pressure, and temperature. By adjusting ignition delay time and transverse methane concentration, a non-uniform concentration field was created, and CFD simulations were used to validate the gas distribution. Based on these simulations, the study found that at an ignition delay time of 0, flames propagated forward along the upper wall of the pipeline in an inclined 'tongue' structure. The flame evolved from 'multiple tulip' structures to a forward-moving 'tongue' shape as the ignition delay increased. The internal explosion pressure curve underwent three stages: rapid rise, slow rise, and rapid fall creating a “step” distribution with increased ignition delay. Temperature delays and peak reductions were observed with increased ignition delay and concentration gradients, indicating a decrease in flame propagation speed.

Numerical Modeling of Two-Phase Fluid Filtration for Carbonate Reservoir in Two-Dimensional Formulation

This work considers the isothermal process of incompressible viscous fluid filtration in an oil-saturated, fractured-porous reservoir. A study of the pressure and water saturation distribution process is carried out for a case in which a production well is put into operation. For this problem, i.e., a mathematical model in a two-dimensional formulation, a numerical method and a parallel algorithm are proposed. The mathematical model of two-phase filtration is written in accordance with the classical laws of continuum mechanics and Darcy’s law and also includes a function of fluid exchange between low-permeability pores and high-permeability natural fractures within the framework of the Warren–Root model. The numerical solution is based on the finite-difference method and a splitting scheme of physical processes and spatial coordinates. For a split system with respect to piezoconductivity, an implicit finite-difference scheme with fixed saturations is constructed, and with respect to saturation transfer, explicit and implicit difference schemes are constructed. For parallel implementation of the developed numerical approach, a method based on geometric parallelism is selected. Testing of the developed method is performed using the example of calculating liquid mass transfer for a wide range of parameters. To verify the model, the obtained calculated pressure curves are compared with field data recorded by a deep-well measuring device. The results allow for estimation of the distribution of reservoir pressure and water saturation depending on the permeability of the fracture set and the pore part. The obtained results allow for monitoring of well operations, reducing unexpected accident risks and optimizing the development system in order to increase oil production in fractured-porous reservoirs. Computational experiments confirm the efficiency of the developed numerical algorithm and its parallel implementation.

Novel clinical method: left ventricular diastolic pressure curve by echocardiography

Abstract Background A non-invasive clinical method for construction of the systolic part of the left ventricular (LV) pressure curve was recently introduced. There is, however, no clinical method available to construct the LV diastolic pressure curve. Purpose The aim of this study was construction of patient-specific LV diastolic pressure curves from echocardiographic data and have initial validation against simultaneously acquired pressure curves by high-fidelity LV pressure catheters (micromanometers). Methods The study included 108 patients referred for diagnostic left heart catheterization due to suspected coronary artery disease. 81 patients were used as a training cohort. The construction of a diastolic pressure curve is based on a reference unitless pressure trace and seven key pressure-time diastolic events estimated in each patient. The reference diastolic pressure trace was generated from a group of 8 patients with LV pressures recorded by micromanometer. Each individual pressure trace from the reference cohort was first annotated with the occurrence of the key diastolic events: mitral valve (MV) opening, minimum LV pressure, peak of early-diastolic mitral flow velocity (E) and start and peak of atrial contraction-induced velocity (A), and MV closure. Then the temporal intervals between these events were normalized before calculating an averaged pressure curve (Figure 1, panels A-C). A patient-specific LV diastolic pressure curve was constructed by adjusting the standard curve according to estimated LV pressure at the key diastolic events (shown in Figure 1D). The estimation of the pressure-time instants is based on the LV volume temporal transient, used to estimate filling flow rate (Q=dV/dt) and flow acceleration and deceleration (dQ/dt=d2V/dt2), as well as a set of biomarkers including left atrial reservoir strain, peak systolic LV pressure, and body mass index. LV volume temporal traces were generated by combining global 2D volumes with global longitudinal strain. The ability to generate patient-specific diastolic LV pressure curves was validated in a second cohort of 7 patients studied with micromanometer-tipped catheters. Echocardiography and LV pressure were recorded from the same series of beats and recordings were done during breath-hold at end-expiration. The agreement was accessed qualitatively and considering the mean diastolic LV pressure. Results There was good agreement between measured and estimated LV diastolic pressure curves, qualitatively and quantitatively, via mean diastolic PLV: Bias 0.2 mmHg, limits of agreement &amp;lt;3.2 mmHg (Figure 1D-F). Conclusions The results suggest that the LV diastolic pressure curve can be estimated by echocardiography. The method needs validation in larger populations.Non-invasive diastolic LV pressure curve

Right ventricular myocardial work in heart failure with preserved ejection fraction: insights from invasive cardiopulmonary exercise testing

Abstract Backgrounds Symptoms of heart failure with preserved ejection fraction (HFpEF) is closely related to elevated pulmonary capillary wedge pressure (PCWP) during exercise. The understanding of right ventricle myocardial work, assessing of right ventricular (RV) function utilizing RV pressure–strain loops, in HFpEF is lacking. Methods The study population underwent invasive cardiopulmonary exercise tests, measuring pressures at rest and during exercise to identify HFpEF. Echocardiography assessed LV and RV parameters. Right ventricular myocardial work was calculated using strain-rate and pressure curves, matching them with ECG data. RV global constructive work (RVGCW), RV global work index (RVGWI), RV global wasted work (RVGWW), and RV global work efficiency (RVGWE) were analysed and compared with invasively measured PCWP at resting and peak exercise. Results Between November 2017 and July 2023, 41 patients with adequate data were enrolled, and 21 were diagnosed with HFpEF. There were no significant differences in various echocardiographic parameters between HFpEF and non-HFpEF groups, except higher post-exercise PCWP and mean pulmonary artery pressure. HFpEF patients had higher RVGWW and lower RVGWE. RVGWW and RVGWE had higher predictive ability for HFpEF diagnosis compared to other echocardiographic parameters. While RVGCW (r = 0.0.504, P = 0.001 and r = 0.430, P = 0.006, respectively) and RVGWW correlated (r = 0.408, P = 0.008 and r = 0.621, P &amp;lt;0.001, respectively) with post-exercise ∆PCWP and exercise PCWP, only RVGWW (β=1.981, P=0.044 and β=4.323, p&amp;lt;0.001) being independently associated with both after adjustment for confounding factors. Conclusions RVGWW is a novel parameter that provides an integrative analysis of RV systolic function and correlates more closely with post-exercise ∆PCWP than other standard echocardiographic parameters in HFpEF.

An equivalent average shear stress yield criterion based on Simpson's numerical integration rule and its application in burst pressure analysis of thin-walled pipelines

Pipelines are a crucial transportation infrastructure for the long-distance transport of natural gas, oil, and other hydrocarbons, typically conducted through thin-walled pipes (D/t≥20). Accurate prediction of the burst pressure of thin-walled pipelines is essential for their safe and reliable operation. To enhance the prediction accuracy of the burst pressure for defect-free, straight, thin-walled pipes, a new numerical integration yield criterion was proposed between the Tresca and Mises criteria, using the mean value of Simpson's numerical integration (MSI) as the equivalent shear stress. A new burst pressure prediction formula was then constructed using the MSI yield criterion. The burst pressure predictions based on different yield criteria were compared with experimental data. Additionally, the burst pressure curves of the new prediction formula were plotted, and the relative errors between the new prediction formula and four existing prediction formulas were analyzed and compared. The results indicate that the new burst pressure prediction formula using the MSI yield criterion closely matches the experimental data, with the best relative error result within a confidence interval of ±1.3 %. The Lord parameter curve and plane stress curve of the MSI yield criterion exhibit good consistency with the experimental data of various ductile metal materials. The new burst pressure formula established by incorporating the MSI criterion provides a safe, economical, and reliable theoretical foundation for the design, manufacture, inspection, and safety assessment of thin-walled pipelines in production practice.

Obesity plays a key role in inducing myocardial and vascular dysfunction in a translational model of heart failure with preserved ejection fraction in rats

Abstract Background Exploring experimental models of heart failure with preserved ejection fraction (HFpEF) may help to understand the mechanisms leading to this challenging condition. Purpose In a translational model, we aimed to assess the relative contribution of hypertension and obesity in inducing structural, functional and hemodynamic changes associated to the HFpEF phenotype. Methods We investigated 3 groups of male 40 weeks old rats: control Wistar Kyoto (WKY, n=10), Spontaneous Hypertensive Rats (SHR, n=10) and SHR with obesity induced by consumption of cafeteria diet during 28 weeks (Ob-SHR, n=9). Animals were submitted to assessment of: body weight, systolic (SBP) and diastolic (DBP) blood pressure; in vivo structural and functional changes evaluated by high resolution Echocardiography including left atrial dimension (LA), left ventricle (LV) diastolic dimension (LVDD), LV posterior wall thickness (LVPW), LV wall relative thickness (LVWRT), LV ejection fraction (LVEF). Invasive hemodynamic evaluation assessed the intraventricular pressure curves obtaining LV end diastolic pressure (LVEDP) and calculation of LV diastolic time constant (Tau). After euthanasia, thoracic aorta was used for vascular function assessment by measuring the maximal cumulative concentration-effect curves of contraction to phenylephrine (PE), expressed as Emax (%). Protein expression of Intercellular Adhesion Molecule 1 (ICAM-1) was determined in myocardial tissue (% in relation to WKY). Results were expressed as mean ± SEM and effects of groups vs time were compared with mixed ANOVA. Results The results are shown in the table. We observed higher levels of SBP and DBP in SHR and Ob-SHR when compared to WKY, but with similar values between SHR and Ob-SHR groups. Regarding the structural LV changes, we observed LV remodeling and LA dilation in both SHR and Ob-SHR groups, but with no difference between both hypertensive groups. The Ob-SHR was the only group showing increased LVEDP in comparison to other groups. The Tau was also increased in the Ob-SHR animals. Concordantly, the Ob-SHR group showed increased expression of ICAM-1 (figure - A) that was concomitant to abnormal vascular response with increased contraction to PE (figure - B) as compared to SHR and WK groups. Conclusions In this translational model of HFpEF in rats, the structural changes related to LV remodeling were similar in SHR and Ob-SHR, probably reflecting comparable higher levels of blood pressure observed in both groups. In contrast, elevated EDP, a hallmark of HFpEF, was only seen in the Ob-SHR group and this was concomitant to diastolic dysfunction, endothelial inflammatory activation and altered vascular function. Our results indicate that obesity is a key factor inducing vascular and myocardial changes that triggers HFpEF phenotype in this model.

Artificial intelligence-enabled reconstruction of the right ventricular pressure curve using the peak pressure value: a proof-of-concept study

Abstract Aims Conventional echocardiographic parameters of right ventricular (RV) function are afterload-dependent. Therefore, incorporating RV pressures may enable the formulation of new parameters that reflect intrinsic RV function accurately. Accordingly, we sought to develop an artificial intelligence–based method to reconstruct the RV pressure curve based on the peak RV pressure. Methods and Results We invasively acquired RV pressure in 29 heart failure patients before and after implanting a left ventricular (LV) assist device. Using these tracings, we trained various machine learning models to reconstruct the RV pressure curve of the entire cardiac cycle based on the peak value of the curve. The best-performing model was compared with two other methods that estimated RV pressures based on a reference LV and RV pressure curve, respectively. Seventeen consecutive patients from another centre who underwent right heart catheterization and simultaneous echocardiography served as an external validation cohort. Among the evaluated algorithms, multilayer perceptron (MLP) achieved the best performance with an R2 of 0.887 (0.834–0.941). The RV and LV reference curve–based methods achieved R2 values of 0.879 (0.815–0.943) and 0.636 (0.500–0.771), respectively. During external validation, MLP exhibited similarly good performance [R2 0.911 (0.873–0.948)], which decreased only modestly if the echocardiography-derived peak RV pressure was used instead of the invasively measured peak RV pressure [R2 0.802 (0.694–0.909)]. Conclusions The proposed method enables the reconstruction of the RV pressure curve using only the peak value as input. Thus, it may serve as a fundamental component for developing new echocardiographic tools targeting the afterload-adjusted assessment of RV function.

Anesthetic Gas Scavenging System for Gas Evacuation in the ICU.

Inhaled sedation is increasing in ICUs, with active carbon filters (ACFs) commonly used for evacuating halogenated gases. However, the potential benefits of a waste anesthetic gas system (WAGS) similar to the ones used in operating rooms should be explored. To limit the suction over the flow sensor where the WAGS is connected on ICU ventilators, an anesthetic gas receiving system (AGRS) is required, constituting with the WAGS an active gas receiving and scavenging system (AGRSS). Ensuring that this whole device does not compromise the flow sensor reliability is crucial. The aim of this study was to compare various gas evacuation devices and assess the reliability of AGRSS on ICU ventilators. In this experimental study, pressures and flows were recorded during the ventilation of a test lung using various ventilator settings and gas evacuation methods: no device (reference condition), ACF, the WAGS alone, AGRSS (WAGS and AGRS together), and the expiratory valve connected to the medical vacuum system with the AGRS in between. Visual comparisons of the pressure and flow curves followed by a statistical analysis comparing median pressures and flows of each device to the reference were performed. The test lung model demonstrated consistent comparability in pressures and flows among all devices, except for the WAGS alone, which exhibited discordance through significant overestimation or underestimation. These findings indicate that using a WAGS with the AGRS system appeared to be reliable for managing gas evacuation in ICUs without compromising pressure or flow delivery. The data from this experimental trial should be confirmed with clinical studies involving human subjects. Given the increasing use of inhaled sedation in ICUs, these results support the daily application of the WAGS with the AGRS for gas evacuation, similar to its established use in anesthesiology.

Research on Air Cushion Flow Field and Bearing Characteristics of Single Row Hole Air Cushion Belt Conveyor

In order to obtain information regarding changes in the air cushion flow field and load-bearing characteristics of a single row hole air cushion belt conveyor, a structural model of the air cushion of the belt conveyor was established, with the single row hole air cushion belt conveyor as the research object. Firstly, according to the theory of fluid lubrication, a mathematical model of the air cushion was established. Then, the effects of air cushion thickness, pore velocity, and belt velocity on the pressure and bearing characteristics of the air cushion flow field were studied using FLUENT software. In addition, the equivalent stress, displacement, and pressure curves between the air cushion flow field and the conveyor belt and the material were analyzed using the two-way fluid–solid coupling method. Finally, the experimental platform of a single row hole air cushion belt conveyor was built, and the flow field and bearing characteristics of the belt were verified through experiments. The results show that reducing the thickness of the air cushion and increasing the pore flow rate can improve the pressure and bearing characteristics of the air cushion, while speed has little effect at lower belt speeds.

Prediction of Capillary Pressure Curves Based on Particle Size Using Machine Learning

Capillary pressure curves are usually obtained through mercury injection experiments, which are mainly used to characterize pore structures. However, mercury injection experiments have many limitations, such as operation danger, a long experiment period, and great damage to the sample. Therefore, researchers have tried to predict capillary pressure data based on NMR data, but NMR data are expensive and unstable to obtain. This study aims to accurately predict capillary pressure curves. Based on rock particle size data, various machine learning methods, such as traditional machine learning and artificial neural networks, are used to build prediction models and predict different types of capillary pressure curves, aiming at studying the best prediction algorithm. In addition, through adjusting the amount of particle size characteristic data, the best amount of particle size characteristic data is explored. The results show that three correlation coefficients of the four optimal algorithms can reach more than 0.92, and the best performance is obtained using the Levenberg–Marquardt method. The prediction performance of this algorithm is excellent, with the three correlation coefficients being all higher than 0.96 and the root mean square error being only 5.866. When partial particle size characteristics are selected, the training performance is gradually improved with an increase in the amount of feature data, but it is far less than the performance of using all the features. When the interpolation increases the particle size characteristics, the best performance is achieved when the feature data volume is 50 groups and the root mean square error is the smallest, but the Kendall correlation coefficient decreases. This study provides a new way to obtain capillary pressure data accurately.

Molecular insight into the interfacial microstructural and miscible behavior of CO2 flooding in tight reservoir

In this study, the interfacial microstructure of CO2 flooding in tight reservoirs was investigated by molecular dynamics simulations. Initially, the study focused on four systems: membrane, cluster, dead-end and channel. The evolving properties of the oil-gas and oil-solid interfaces within the static swelling system were analyzed. By examining interaction energy and pressure curves, it was revealed that CO2 permeability at the oil-gas interface and accumulation at the oil-solid interface play crucial roles in the swelling process, subsequently impacting competitive adsorption behaviors with alkanes. Secondly, the oil-gas interface characteristics of the dynamic driving system are analyzed through comparison of tangential and vertical drive. The mechanism underlying the degradation of miscibility is revealed by evaluating the interfacial thickness and energy. Moreover, the addition of different co-solvents identifies key influencing factors on miscible zone stability, which serve as an improvement for the subsequent miscible optimization. The study provides certain guiding significance for improving oil recovery in CO2 flooding projects.