Dynamic Pressure Research Articles

Turbulent particle-gas feedback exacerbates the hazard impacts of pyroclastic density currents

Causing one-third of all volcanic fatalities, pyroclastic density currents create destruction far beyond our current scientific explanation. Opportunities to interrogate the mechanisms behind this hazard have long been desired, but pyroclastic density currents persistently defy internal observation. Here we show, through direct measurements of destruction-causing dynamic pressure in large-scale experiments, that pressure maxima exceed theoretical values used in hazard assessments by more than one order of magnitude. These distinct pressure excursions occur through the clustering of high-momentum particles at the peripheries of coherent turbulence structures. Particle loading modifies these eddies and generates repeated high-pressure loading impacts at the frequency of the turbulence structures. Collisions of particle clusters against stationary objects generate even higher dynamic pressures that account for up to 75% of the local flow energy. To prevent severe underestimation of damage intensities, these multiphase feedback processes must be considered in hazard models that aim to mitigate volcanic risk globally.

The use of urodynamic to assess the mechanism of incontinence in patients with Yang-Monti based catheterizable cutaneous stomas.

To analyze the static and dynamic urodynamic parameters of reservoirs and continent conduits in continent cutaneous urinary diversion with catheterizable stoma. 76 patients had augmented ileocystoplasty or continent urinary diversion with catheterizable urinary stoma based on Mitrofanoff principle and Yang-Monti procedure using subserous tunnel as continence mechanism. They were followed up for at least 6 months post-operatively for continence through stoma and divided into two groups (continents vs non-continent) according to stomal continence. Both groups had urodynamic assessment performed via the stoma to assess reservoir capacity, pressure and contractions, efferent limb functional length, reservoir overactivity, static and dynamic maximal closure pressures and leak point pressure. Continence rate was 87%. Continent group included 66 patients and incontinent group included 10 patients. In both groups at rest, the reservoir pressure after filling did not exceed 25 cm H2O. During peristaltic contraction, the pressure did not exceed 30 cm H2O and the duct remained continent. After Valsalva maneuver, the reservoir pressure increased up to 34 (+ 7.4) cm H2O and leakage occur in 10 patients (13%). Reservoir (wall) overactivity was recorded in 54 patients, with insignificant rise in intraluminal pressure during the contractions. In both groups, the efferent tract closing pressure was always higher than the reservoir pressure. The mean of maximal closing pressure at Valsalva was 82.5 (+ 4.18) cm H2O in the continent group and 61.66 (+ 8.16) cm H2O in the incontinent group. The mean functional length of the conduit was 4.95 + 1.62 in the continent group and 2.80 + 1.50 cm in the incontinent group. Urodynamic evaluation of continent catheterizable cutaneous stoma after Yang-Monti procedure has a practical significance. Functional length of the conduit seems to be the most influential factor for continence reflecting static & dynamic maximal closure pressure. Higher conduit closing pressure is associated with better continence. Contractions of the pouch and peristaltic contraction of the conduit has no effect on continence mechanism.

Meningeal Damage and Interface Astroglial Scarring in the Rat Brain Exposed to a Laser-Induced Shock Wave(s).

In the past decade, signature clinical neuropathology of blast-induced traumatic brain injury has been under intense debate, but interface astroglial scarring (IAS) seems to be convincing. In this study, we examined whether IAS could be replicated in the rat brain exposed to a laser-induced shock wave(s) (LISW[s]), a tool that can produce a pure shock wave (primary mechanism) without dynamic pressure (tertiary mechanism). Under certain conditions, we observed astroglial scarring in the subpial glial plate (SGP), gray-white matter junctions (GM-WM), ventricular wall (VW), and regions surrounding cortical blood vessels, accurately reproducing clinical IAS. We also observed shock wave impulse-dependent meningeal damage (dural microhemorrhage) in vivo by transcranial near-infrared (NIR) reflectance imaging. Importantly, there were significant correlations between the degree of dural microhemorrhage and the extent of astroglial scarring more than 7 days post-exposure, suggesting an association of meningeal damage with astroglial scarring. The results demonstrated that the primary mechanism alone caused the IAS and meningeal damage, both of which are attributable to acoustic impedance mismatching at multi-layered tissue boundaries. The time course of glial fibrillary acidic protein (GFAP) immunoreactivity depended not only on the LISW conditions but also on the regions. In the SGP, significant increases in GFAP immunoreactivity were observed at 3 days post-exposure, whereas in the GM-WM and VW, GFAP immunoreactivity was not significantly increased before 28 days post-exposure, suggesting different pathological mechanisms. With the high-impulse single exposure or the multiple exposure (low impulse), fibrotic reaction or fibrotic scar formation was observed, in addition to astroglial scarring, in the cortical surface region. Although there are some limitations, this seems to be the first report on the shock-wave-induced IAS rodent model. The model may be useful to explore potential therapeutic approaches for IAS.

Simulation and experimental investigation of material removal profile based on ultrasonic vibration polishing of K9 optical glass

Ultrasonic vibration polishing (UVP) is an important method for the precision processing of optical glass, which is good for improving surface quality and processing efficiency. So far, the material removal mechanism in UVP is not well understood and the various process parameters involved are not considered. To achieve ultra-precision polishing under optical glass, this paper carries out the axial UVP method. The material removal profile (MRP) is critical to affect the surface accuracy. A new MRP is developed for UVP based on the Urick attenuation model and the proposed material removal coefficient distribution function, considering the dynamic pressure changes under ultrasonic vibration, the attenuation effect of the acoustic pressure propagation process and the inhomogeneous distribution of the abrasive particles in the contact area during the ultrasonic electro-spindle rotation. Through a series of polishing experiments and simulations, the results show that the maximum errors of the actual material removal depth (MRD) and the actual material removal rate (MRR) from the model simulation results are 8.54% and 9.92%, respectively. The accuracy of the model is further demonstrated by the Pearson correlation coefficient. When the amplitude of UVP is 9 µm, Sa and Ra are 60 nm and 68 nm, which are reduced by 37.50% and 22.73%, respectively, compared with conventional polishing. This research can contribute to the deterministic processing of UVP, and provide a theoretical basis for the application of optical glass.

Investigation of Thermo-Hydraulics in a Lid-Driven Square Cavity with a Heated Hemispherical Obstacle at the Bottom.

Lid-driven cavity (LDC) flow is a significant area of study in fluid mechanics due to its common occurrence in engineering challenges. However, using numerical simulations (ANSYS Fluent) to accurately predict fluid flow and mixed convective heat transfer features, incorporating both a moving top wall and a heated hemispherical obstruction at the bottom, has not yet been attempted. This study aims to numerically demonstrate forced convection in a lid-driven square cavity (LDSC) with a moving top wall and a heated hemispherical obstacle at the bottom. The cavity is filled with a Newtonian fluid and subjected to a specific set of velocities (5, 10, 15, and 20 m/s) at the moving wall. The finite volume method is used to solve the governing equations using the Boussinesq approximation and the parallel flow assumption. The impact of various cavity geometries, as well as the influence of the moving top wall on fluid flow and heat transfer within the cavity, are evaluated. The results of this study indicate that the movement of the wall significantly disrupts the flow field inside the cavity, promoting excellent mixing between the flow field below the moving wall and within the cavity. The static pressure exhibits fluctuations, with the highest value observed at the top of the cavity of 1 m width (adjacent to the moving wall) and the lowest at 0.6 m. Furthermore, dynamic pressure experiences a linear increase until reaching its peak at 0.7 m, followed by a steady decrease toward the moving wall. The velocity of the internal surface fluctuates unpredictably along its length while other parameters remain relatively stable.

Threshold capillary pressure of caprocks for CO2 storage: Numerical insight on the dynamic and residual method

The dynamic threshold pressure method and the residual capillary pressure method provide an estimate of the threshold capillary pressure for CO2 storage. In the dynamic method, the threshold capillary pressure is determined by comparing the discharge measured when the CO2 starts flowing into the sample with the one measured when only water is flowing. In the residual method, a high CO2 pressure is applied on the vessel at the inlet of a water-saturated sample while water cannot flow from the vessel at its end. The threshold capillary pressure is estimated as the difference between the CO2 and the water pressures at the sample boundaries at equilibrium conditions.Sensitive analyses showed the impact of material properties and experimental conditions on results. Both methods allow estimating the threshold capillary pressure within a few days and the estimates are influenced by the applied pressures. The dynamic method estimate is not precautionary, and it tends to the exact value as the applied CO2 overpressure decreases. The residual method estimate is influenced by the drainage conditions and the volume of the vessels: it is generally precautionary and tends to increase with the volume of the vessels and the applied pressure. Suggestions for test interpretation and planning are also provided.

Research on the crack formation mechanism of shaped charge blasting and the new dual-shaped charge blasting technology

Shaped charges are extensively utilized in various rock engineering fields for directional fracturing. Numerous scholars have conducted extensive research on this topic, yielding significant results and widespread application in engineering projects. Efforts have focused on improving the directional fracture effects and fully utilizing the energy generated by the explosion to enhance the directional blasting effects of shaped charges and minimize damage to the rock mass in areas not targeted by the shaped energy. This approach aims to preserve the integrity and stability of the rock mass in the areas unaffected by the directional fracture, thereby reducing damage to the surrounding rock. This study builds on the foundations of explosion mechanics. It incorporates a novel digital laser dynamic caustic line experiment system and pressure fields, and numerical analysis techniques. The research systematically analyzes the process of explosive action in shaped charges and proposes a new type of dual polymer charge. This novel charge is compared to traditional and common charges. The findings revealed that, compared to standard-shaped charges, the new dual-shaped charge achieves a more effective directional fracturing, The rock damage is less in the direction of non-gathering energy. Under the conditions of the same amount of explosive and the same decoupling coefficient, The crack propagation length of common charge is 1.34 times of the diameter of the gun hole, the crack propagation length of shaped charge is 10.17 times of the hole diameter, The crack propagation length of the new dual-charge is 19.67 times of the hole diameter. HIGHLIGHTS In this paper, a new type of dual-charge is proposed. The findings revealed that, compared to standard-shaped charges, the new dual-shaped charge achieves a more effective directional fracturing, The rock damage is less in the direction of non-gathering energy. Under the conditions of the same amount of explosive and the same decoupling coefficient, The crack propagation length of common charge is 1.34 times of the diameter of the gun hole, the crack propagation length of shaped charge is 10.17 times of the hole diameter, The crack propagation length of the new dual-charge is 19.67 times of the hole diameter. 1.Following the charge explosion, influenced by the shaped charge tube, the detonation wave and explosive gas alter, expanding outward in an approximate "elliptical" shape. The explosion stress field distribution is approximately "one"-shaped in the direction of energy concentration. The primary explosive crack expands along the direction of energy accumulation, while the secondary cracks predominantly distribute in the perpendicular direction. The seam width and the transmission coefficient (material) influence the condenser’s concentration effect. 2.Compared to ordinary charge blasting, shaped charge blasting exerts a pronounced guiding effect on the explosion stress field. The stress field primarily transfers along the direction of energy concentration, with the stress being markedly greater in this direction than in the direction of non-concentrated energy. In comparison, dual charge blasting undergoes two convergence effects, with longer durations and distances of convergent action. The stress field generated by dual-charge blasting is significantly greater than that of the shaped and common charges, offering enhanced effects. 3.Agglomeration length is a crucial factor in the agglomeration effect. Explosion energy directly transfers to the solid medium via the coalseam, minimizing explosion energy loss in the air medium and controlling the detonation wave shape and explosive gas flow in the energy accumulation direction, resembling "one." The dipolymer charge notably extends crack propagation length in the polymer direction and mitigates damage in the non-polymer direction.

Effect of Body Mass Index on Pedobarographic and Patient-Reported Outcome Measures in Adolescent Flexible Flat Feet.

Although adolescent flexible flatfoot deformity (FFD) is common, little is known regarding the effect of weight on associated symptomatology. This study uses pedobarography and patient-reported outcome measures (PROs) to determine if overweight adolescents with FFD have more severe alterations in dynamic plantar pressures than normal body mass index percentiles (wnBMI) with FFD and if such alterations correlate with pain and activity. A retrospective review of patients aged 10 to 18 years with nonsyndromic symptomatic FFD was performed. Overweight (BMI percentile ≥ 85%) patients were compared with wnBMI patients with regard to dynamic plantar pressure measures and PRO scores. Pedobarographic data were subdivided into regions: medial/lateral hindfoot and midfoot, and first, second, and third to fifth metatarsals. Plantar pressure variables were normalized to account for differences in foot size, body weight, and walking speed. Contact area (CA%), maximum force by body weight (MF%), and contact time as a percentage of the rollover process (CT%) were calculated. Two foot-specific PROs were assessed, including the Foot and Ankle Outcome Score and the Oxford Ankle Foot Measure for Children. Of the 48 adolescents studied, 27 (56%) were overweight and 21 (44%) were wnBMI. After normalization of the data, overweight patients had significantly greater medial midfoot MF%, whereas CT% was increased across the medial and lateral midfoot and hindfoot regions. Correlations showed positive trends: as BMI percentile increases, so will CA and MF in the medial midfoot, as well as CT in the medial and lateral midfoot and hindfoot. Significant differences were seen between groups, with the overweight group reporting lower sports and recreation subscores than the wnBMI group. No significant differences were seen in the pain and disability subscores. Although overweight adolescents with FFD exhibit greater forces and more time spent during the rollover process in the medial midfoot than normal-weight patients, they did not report worse pain or disability associated with their flat foot deformity. Therapeutic level 3.

The effect of continuous geomagnetic storms on enhancements of ultrarelativistic electrons in the Earth’s outer radiation belt

The effect of continuous geomagnetic storms on enhancements of ultrarelativistic electrons in the Earth’s outer radiation belt

Mechanism and deterioration pattern of sandstone surrounding rock voiding at bottom of heavy-haul railway tunnel

This study combines laboratory experiments and discrete element simulation methods to analyze the mechanism and deterioration patterns of sandstone surrounding rock voiding the bottom of a heavy-haul railway tunnel. It is based on previously acquired measurement data from optical fiber grating sensors installed in the Taihangshan Mountain Tunnel of the Wari Railway. By incorporating rock particle wastage rate results, a method for calculating the peak strength and elastic modulus attenuation of surrounding rock is proposed. Research indicates that the operation of heavy-haul trains leads to an instantaneous increase in the dynamic water pressure on the bottom rock ranging 144.4–390.0%, resulting in high-speed water flow eroding the rock. After 1–2 years of operation, the bottom water and soil pressures increase by 526.5% and 390.0%, respectively. Focusing on sandstone surrounding rock with high observability, laboratory experiments were conducted to monitor the degradation stages of infiltration, particle loss, and voiding of rock under the action of dynamic water flow. The impact of water flow on the “cone-shaped” bottom rock deformation was also clarified. The extent of rock deterioration and voiding was determined using miniature water and soil pressure sensors in conjunction with discrete element numerical simulations. The measured rock particle loss was used as a criterion. Finally, a fitting approach is derived to calculate the peak strength and elastic modulus attenuation of surrounding rock, gaining insight into and providing a reference for the maintenance and disposal measures for the bottom operation of heavy-haul railway tunnels.

One-dimensional model of manifold microchannels for embedded cooling: Prediction of thermal performance and flow non-uniformity

A one-dimensional model has been developed to accurately predict the thermal performance and flow non-uniformity of the manifold microchannels (MMC) for embedded liquid cooling. The model consists of one-dimensional governing equations derived from the integral relations of momentum and energy over appropriately-defined two separate control volumes. To validate the model, a series of 3-D numerical simulation is conducted over the wide ranges of the Reynolds number (Rem,in) at the manifold inlet from 560 to 3190, the dimensionless hydraulic flow length (x+) from 0.012 to 0.123, and the dimensionless thermal flow length (x∗) from 0.002 to 0.023. It is shown that the model provides accurate predictions of the thermal performance and flow non-uniformity (CV) of MMC heat sinks within the root mean square percentage error (RMSPE) of 6% and 26% for 50 data points, respectively. The significant improvement of the prediction accuracy is made over the earlier models with an error reduction of 82%. Finally, a design guideline for the uniform flow distribution is suggested for the first time based on a newly proposed explicit correlation for predicting the flow non-uniformity: the dynamic pressure at the manifold inlet should be kept smaller than the pressure drop across the microchannels.

Dual Sensing Signal Decoupling Based on Thermoelectric Polymer Aerogels for Precise Temperature and Pressure Recognition

AbstractThe capability to emulate skin‐like temperature and pressure sensing is fundamental for next‐generation artificial intelligence products. However, detecting temperature and pressure simultaneously with a single sensor without signal interference is challenging. Herein, a novel PCC aerogel sensor composed of PEDOT:PSS, CNTs, and CNF via directional freezing technology is developed. The PCC sensor can decouple temperature and pressure stimuli into individual voltage and resistance signals. It exhibits high‐precision temperature sensing capabilities, boasting an exceptionally high Seebeck coefficient of 30.4 µV K‐1 and the ability to detect temperature variations as low as 0.1 K. PCC sensors show excellent sensitivity and fast response times for detecting static and dynamic pressures, as well as high stability after 1000 cycles. Its maximum pressure sensitivity can reach 159.1% kPa−1, and the lowest detection limit is 10 Pa. Additionally, its excellent thermoelectric properties also enable to generating thermopower from human skin for self‐powered pressure sensing. A 3×3 PCC sensor array has been proposed to simulate the unique features of human skin in temperature and pressure recognition. This work provides a scalable manufacturing strategy for multi‐functional tactile sensors.

Dynamic responses of reinforced concrete silo considering pile–soil‐structure–granular solid interaction

SummaryThe columned‐supported reinforced concrete silo models with different filling conditions considering soil‐structure dynamic interaction (SSI) are established based on the finite element program ANSYS to thoroughly investigate the complex interaction mechanism of the soil–pile–silo structure with granular solid. The dynamic characteristics and seismic responses of the SSI system and fixed‐base condition are analyzed and compared when the filling conditions are empty‐filled state, half‐filled state and full‐filled state. The numerical results reveal that the SSI effect reduces the seismic acceleration response of columned‐supported silos effectively. However, in terms of displacement, the SSI effect often amplifies the relative deformation of the supporting column and the cylindrical silos. Furthermore, the SSI effect often increases the relative dynamic lateral pressure of the storage material in the half‐filled silo condition. In the full‐filled silo condition, the relative dynamic lateral pressure at the top and bottom of the storage material is increased by the SSI effect; while it is decreased in the middle part of the granular solid, demonstrating that the SSI effect could change and increase the seismic responses of the silo structure in certain areas. Therefore, the investigation provides a comprehensive insight into the interaction mechanism of the pile–soil–silo structure with different filling conditions.

Deformation mechanism of gob‐side entry at top coal caving mining face: A numerical study

AbstractTo investigate the significant deformation of the surrounding rock within the dynamic pressure zone of the gateroad, this study utilized the tailgate of the 1506 longwall face in Anyang Coal Mine as the engineering context. A combined approach of field measurement and numerical analysis was employed to explore the deformation and failure mechanisms of the surrounding rock under dynamic pressure. The findings indicate that before the exploitation of the 1506 longwall face, there was a notable reduction in stress across the floor and immediate roof, with minimal stress concentration observed in the coal pillar and the entity rib side. The plastic zone surrounding the tailgate was limited, suggesting a high degree of stability in the entry's surrounding rock. However, during the extraction of the 1506 longwall face, the tailgate, extending 60 m ahead of the working face, was subjected to dynamic pressure, leading to a marked increase in stress within the floor, coal pillar, and immediate roof. Stress concentration was more pronounced on the entity rib side than on the pillar rib side. This resulted in significant fissuring and severe deformation of the entry's surrounding rock. The primary failure mechanism involved damage to both the roof and floor corners, with the severity of damage escalating alongside the stress in the surrounding rock. This culminated in the failure of roof corner bolts and anchor cables, thereby compromising the stability of the entry within the dynamic pressure zone.

A comprehensive approach for understanding debris flow interaction with pipelines through dynamic impact pressure modeling

The interaction of debris flows, and impacted structures is still not well understood due to the complex mechanisms of the flows. Although several methodologies from experimental to numerical have developed so far, a thorough assessment of impact mechanism necessitates multiphase modelling approaches. Therefore, this paper presents a dynamic impact pressure modelling approach of debris flows using experimental and numerical techniques. The experimental investigations involved seven type of debris flows based on solid volume fraction (αs), that being released on an inclined flume, impacting a 2″(52 mm) pipe model. The numerical investigations were performed in Computational Fluid Dynamics (CFD) environment by utilising the Spalart-Allmaras turbulence and Hershel- Bulkley rheological models by considering different inclined angle (β) impact scenarios. The findings revealed that all debris flows produced were in supercritical flows regime and characterized as dilute, medium viscous, and highly viscous flows, based on Froude (Fr) and Reynold (Re) numbers. Drag coefficients (CD-90/CD-0) were behaved non-linearly with respect to Fr and Re. The proposed refined dynamic normal (pd-90) and axial (pd-0) impact models using different set of Fr, Re and β will offer valuable insight for pipeline operators seeking to comprehend the complex interaction between debris flows and pipelines.

ACCURACY AND BLOOD PRESSURE THRESHOLD CONTROL ANALYSIS OF UNATTENDED AUTOMATED OFFICE BLOOD PRESSURE MEASUREMENT: A CROSS-SECTIONAL STUDY BASED ON MULTICENTER POPULATIONS

Objective: The emergence of unattended automated office blood pressure (u-AOBP) measurement, facilitated by the flourishing development of electronic blood pressure monitors, has been proposed as a potential alternative or complementary approach for assessing patients’ blood pressure status within clinical settings. However, robust evidence is lacking to determine its application in diagnosing hypertension within the clinical practice in China. This study aims to compare u-AOBP values with standard office blood pressure data, assess the correlation between u-AOBP and diagnostic thresholds. Design and method: The study involved participants recruited from October 2023 to February 2024 in three hospitals: People's Hospital of Gongyi City in Henan Province, Nangong City Hospital in Hebei Province, and Fuwai Hospital of the Chinese Academy of Medical Sciences. Standardized validated upper arm blood pressure monitors were used to measure blood pressure. Baseline demographic data, anthropometric measurements, u-AOBP, and standard office blood pressure data were collected, along with additional examination results, including echocardiograms and 24-hour ambulatory blood pressure monitoring. Results: 1. The difference between u-AOBP and awake dynamic average blood pressure was 1.34 mmHg (95% confidence interval: 0.88-3.55 mmHg), and the difference was not statistically significant (P = 0.236). 2. The optimal cutoff values for diagnosing elevated blood pressure using u-AOBP, determined by ROC curve analysis based on awake dynamic blood pressure measurements, were 130.75/83.75 mmHg (sensitivity 89.73%, specificity 27.27%). 3. In participants with a dipper blood pressure diurnal rhythm, there was no statistically significant difference between standard office blood pressure and u-AOBP measurements (P > 0.05). However, in the group including non-dipper rhythm participants, standard office blood pressure was higher than u-AOBP by 5.84/4.98 mmHg (P < 0.05). Conclusions: 1. Unattended automated blood pressure measurements can reduce, but not eliminate, the white coat effect, with an optimal cutoff value for diagnosing elevated blood pressure determined as 130.75/83.75 mmHg. 2. In individuals with a normal dipper blood pressure diurnal rhythm, standardized u-AOBP values are equivalent to standard office blood pressure.

Effects of Coronary Stenosis on Coronary Vascular Impedance

Introduction: The impedance analysis for circulation system is a powerful tool to comprehensively measure the afterload of the entire circulation system. The spectrum of vascular mechanical parameters derived from the impedance analysis can reveal the compliance and resistance changes in proximal and distal vessels, as well as the wave reflections. However, the similar investigation in the opposition of the coronary circulation is limited, and it is unknown how coronary stenosis affects the vascular impedance of the coronary circulation. In this study, we aimed to quantify and compare the changes in the vascular impedance of coronary circulation from the dynamic pressure and flow relations in healthy and patients with stenosis. Method: The pressure and flow rate waveforms from the main coronary artery were obtained from a lumped-parameter computational model that coupled the systemic circulation with the coronary perfusion within a closed system. Both healthy and diseased (coronary stenosis) pressure-flow relations were examined. A Fourier transform was performed to analyze the pressure and flow data, and the resistance (Z0), characteristic impedance (ZC), wave reflections (RW), total arterial compliance (C), and other hemodynamic parameters were derived. Results: Compared to the healthy subject, the diseased subject presented an increased resistance (Z0 was elevated from 0.44 mmHg ▪ min/ml to 0.59 mmHg ▪ min/ml), increased characteristic impedance (ZC was elevated from 0.07 mmHg ▪ min/ml to 0.14 mmHg ▪ min/ml), and reduced wave reflection (RW was decreased from 0.72 to 0.6). These changes indicate elevated distal arteries and arterioles narrowing and proximal artery stiffening in the entire coronary vasculature. Moreover, the coronary flow and the total arterial compliance (stroke volume divided by pulse pressure) were reduced with the disease progression. These data suggest a reduced coronary perfusion and stiffening of the artery in the coronary circulation. Discussion: The impedance analysis has been widely used for systemic and pulmonary circulations previously to quantify the total afterload of the left and right ventricles, respectively. The distribution of the impedance in different frequencies reflects the anatomical and mechanical properties of the vasculature in the circulation system. This study originally found that the coronary artery impedance is altered by coronary stenosis. The key characteristics include the narrowing of distal coronary arteries and stiffening of proximal coronary arteries. However, since both proximal and distal arteries are altered, the wave reflection was reduced, and this may explain a reduced pulse pressure observed in the diseased subject. The reduction in overall coronary perfusion indicates an impaired blood supply to the ventricle and may be responsible for the dysfunction of the heart. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Investigation of dynamic characteristics of hydrofoil with leading-edge tubercles

The convex structure of a humpback whale flipper is included in the airfoil design to investigate the control principle of the dynamic stall process. The effect of two different types of tubercles on the dynamic stall process of airfoils was investigated. The distribution of dynamic hysteresis loops and pressure fields with streamlines was used to explain the properties of the dynamic flow field and the emergence of dynamic stall vortices. The results demonstrate that the airfoils with tubercles have stronger hysteretic characteristics in the pre-stall region, and the ζ CM of mod-1 is increased by 51.33%, indicating stronger torsional hydroelastic stability. In the post-stall region, mod-2 is always in a condition of significant flow separation, which impairs the torsional hydrodynamic stability of the airfoil and has the potential to cause flutter. These findings suggest that leading-edge tubercles offer a negligible advantage in reducing airfoil dynamic stall, and their significance warrants further investigation.

Feedback and Galaxy Dynamics: A Study of Turbulence and Star Formation in 34 Galaxies Using the PHANGS Survey

The correlation between interstellar turbulent speed and local star formation rate surface density, ΣSFR, is studied using CO observations in the PHANGS survey. The local velocity dispersion of molecular gas, σ, increases with ΣSFR, but the virial parameter, α vir, is about constant, suggesting the molecular gas remains self-gravitating. The correlation arises because σ depends on the molecular surface density, Σmol, and object cloud mass, M mol, with the usual molecular cloud correlations, while ΣSFR increases with both of these quantities because of a nearly constant star formation efficiency for CO. Pressure fluctuations with ΔΣSFR are also examined. Azimuthal variations of molecular pressure, ΔP mol, have a weaker correlation with ΔΣSFR than expected from the power-law correlation between the total quantities, suggesting slightly enhanced star formation rate (SFR) efficiency per molecule in spiral arms. Dynamical equilibrium pressure and SFR correlate well for the whole sample, as PDE∝ΣSFR1.3 , which is steeper than in other studies. The azimuthal fluctuations, ΔP DE(ΔΣSFR), follow the total correlation P DE(ΣSFR) closely, hinting that some of this correlation may be a precursor to star formation, rather than a reaction. Galactic dynamical processes correlate linearly such that ΣSFR∝(ΣgasR)1.0±0.3 for total gas surface density Σgas and galactic dynamical rates, R, equal to κ, A, or Ω, representing epicyclic frequency, shear rate A, and orbit rate Ω. These results suggest important roles for both feedback and galactic dynamics.

Slope stability analysis based on rate-dependent soil-water characteristic curve

Rainfall-induced landslides are a common geological hazard. Analyzing this problem necessitates the use of the unsaturated soil theory, with the soil-water characteristic curve (SWCC) being a crucial component. Most existing unsaturated soil seepage models are established based on the static soil-water characteristic curve model. However, the dynamic capillary pressure has been observed in experiments conducted in previous studies. In this study, experiments were performed to explore the dynamic impact of the SWCC. The influence of different infiltration rates was studied, and a rate-dependent SWCC model under dynamic conditions was established. The model was validated through experiments. The behavior of an unsaturated soil slope under different rainfall intensities was analyzed based on the equivalent model. The equation for the slope safety factor was then derived using the Bishop method. The slope safety factors based on both the rate-independent and rate-dependent SWCC models were compared. The results indicated that the safety factor continuously decreased with increasing rainfall intensity. The dynamic effect reduced the safety factor, making the slope more susceptible to instability.