P-wave Research Articles

Central Hemodynamics in African American Women: Examining the Role of Superwoman Schema Endorsement.

African American women bear a disproportionate burden of cardiovascular diseases, potentially due to altered central hemodynamics. Racism and sexism often lead to African American women taking on numerous caretaking roles and overall increases their use of the Strong Black Woman (ie, Superwoman) mindset, which may have negative health consequences. We hypothesized that endorsing the Superwoman role and its Obligation to Help Others dimension would be associated with a deleterious central hemodynamics profile in African American women. Using cross-sectional data, we examined central systolic blood pressure (mm Hg; n=408), augmentation index (percentage, adjusted for height and heart rate; n=408), and pulse wave velocity (m/s; n=368) in African American women aged 30 to 46 years. The Giscombe Superwoman Schema (SWS) questionnaire assessed endorsement of Overall SWS (range, 0-105) and SWS-Obligation to Help Others (range, 0-3). Multiple linear regression modeled associations between Overall SWS (10-unit increments) and SWS-Obligation to Help Others (1-unit increments) and central hemodynamics while adjusting for pertinent sociodemographic, clinical, and psychosocial factors. In fully adjusted models, central systolic blood pressure was significantly associated with Overall SWS (β=0.83 [95% CI, 0.19-1.47]) and SWS-Obligation to Help Others (β=2.03 [95% CI, 0.39-3.67]). Augmentation index was associated with Overall SWS (β=0.66 [95% CI, 0.02-1.30]) and SWS-Obligation to Help Others (β=2.21 [95% CI, 0.58-3.84]). Significant associations were not observed between pulse wave velocity and SWS. Greater endorsement of the Superwoman role and prioritizing caregiving over self-care were associated with higher central systolic blood pressure and augmentation index, which may contribute to adverse cardiovascular health among African American women.

Seasonal nitrate variation as a tracer of preferential flow in bedrock aquifers

Short-term nitrate variations in streams are common, but the extent of groundwater contributions to such variability has been unclear. Analysis of well, spring and stream nitrate concentrations plus well water levels and stream flow for a chalk aquifer in Dorset (UK) shows that nitrate variation in streams lags discharge peaks by days to weeks. Spring monitoring also shows a short lag time, showing that high nitrate concentrations are rapidly transmitted from aquifers to streams. The lag time reflects the difference between the celerity (pressure wave speed) and the advective velocity of groundwater flow through the fracture network. Results give celerities of ∼500 m/d, advective velocities of 100–200 m/d, and kinematic porosities of ∼0.001. In addition, long-term nitrate data gives time lags of several decades, reflecting the matrix porosity of ∼0.3. Consequently, nitrate can be used an environmental tracer for both preferential flow through fracture networks and for retarded matrix flow and storage in this dual-porosity bedrock aquifer. Dual porosity is common in bedrock aquifers, so it is possible that this methodology may be widely applicable to understand the hydraulic characteristics of bedrock aquifers and to explain short-term nitrate variation in streams.

Drag Modeling Effects on Simulations of Supersonic Jet-Induced Cratering in a Soil

The impact of the drag model in the simulation of turbulent granular flows is studied using databases here created through simulations of supersonic jet-induced cratering in granular soil. The simulations are based on a previously developed model, which was shown to be hyperbolic, thus permitting the unhindered propagation of pressure waves critical to craters produced by supersonic plumes. The goal is to identify predicted quantities from these simulations that show sufficient differences among simulations performed with different drag models; these quantities would warrant future experimental investigations determining which model is correct. Among all drag models examined, only two models are found applicable to the regime of investigation. Examination of the databases is conducted from the viewpoint of global quantities and detailed quantities. The results show that isocontours and characteristic length scales are minimally affected by the employed drag law. In contrast, azimuthally averaged and root mean square ejecta-related quantities are more sensitive to the drag model employed, but only in the central part of the crater. This sensitivity is much larger for shallow craters having a parabolic cross section than for deep craters having a conical cross section, thus indicating the experimental configuration best suited to experimentally evaluating drag models.

Application of graph neural networks to predict explosion-induced transient flow

We illustrate an application of graph neural networks (GNNs) to predict the pressure, temperature and velocity fields induced by a sudden explosion. The aim of the work is to enable accurate simulation of explosion events in large and geometrically complex domains. Such simulations are currently out of the reach of existing CFD solvers, which represents an opportunity to apply machine learning. The training dataset is obtained from the results of URANS analyses in OpenFOAM. We simulate the transient flow following impulsive events in air in atmospheric conditions. The time history of the fields of pressure, temperature and velocity obtained from a set of such simulations is then recorded to serve as a training database. In the training simulations we model a cubic volume of air enclosed within rigid walls, which also encompass rigid obstacles of random shape, position and orientation. A subset of the cubic volume is initialized to have a higher pressure than the rest of the domain. The ensuing shock initiates the propagation of pressure waves and their reflection and diffraction at the obstacles and walls. A recently proposed GNN framework is extended and adapted to this problem. During the training, the model learns the evolution of thermodynamic quantities in time and space, as well as the effect of the boundary conditions. After training, the model can quickly compute such evolution for unseen geometries and arbitrary initial and boundary conditions, exhibiting good generalization capabilities for domains up to 125 times larger than those used in the training simulations.

Analysis of the Impact of Multiple Explosion Source Layouts on the Kinetic Characteristics of Gas Explosions in Blind Roadways

To investigate the changes in conditions within a blind roadway when multiple gas explosion sources are simultaneously detonated, the fluid dynamics software Fluent14.0 was used to conduct numerical simulation experiments with different numbers (2 and 3) and varying intervals (5 m, 10 m, and 15 m) of explosion sources. The results revealed that multiple explosion sources in gas explosions generate shock waves that propagate in opposite directions, creating pressure overlap zones within the roadway. The pressure waves and shock waves in these overlap zones continuously couple within the roadway. The number of overlap zones decreases incrementally with each encounter of opposing shock waves in the roadway. Unlike single explosion source models, the pressure at various positions within the roadway in multiple explosion source models oscillates due to the coupling of multiple shock waves, with significant peak pressures occurring at the closed end of the roadway and in the pressure overlap zones. Additionally, the propagation patterns of shock waves and flames within the roadway are not associated with the interval distance between explosion sources, whereas the encounter time, speed, and pressure of shock waves increase with the interval distance.

Seismic Imaging of the Arctic Subsea Permafrost Using a Least-Squares Reverse Time Migration Method

High-resolution seismic imaging allows for the better interpretation of subsurface geological structures. In this study, we employ least-squares reverse time migration (LSRTM) as a seismic imaging method to delineate the subsurface geological structures from the field dataset for understanding the status of Arctic subsea permafrost structures, which is pertinent to global warming issues. The subsea permafrost structures in the Arctic continental shelf, located just below the seafloor at a shallow water depth, have an abnormally high P-wave velocity. These structural conditions create internal multiples and noise in seismic data, making it challenging to perform seismic imaging and construct a seismic P-wave velocity model using conventional methods. LSRTM offers a promising approach by addressing these challenges through linearized inverse problems, aiming to achieve high-resolution, subsurface imaging by optimizing the misfit between the predicted and the observed seismic data. Synthetic experiments, encompassing various subsea permafrost structures and seismic survey configurations, were conducted to investigate the feasibility of LSRTM for imaging the Arctic subsea permafrost from the acquired seismic field dataset, and the possibility of the seismic imaging of the subsea permafrost was confirmed through these synthetic numerical experiments. Furthermore, we applied the LSRTM method to the seismic data acquired in the Canadian Beaufort Sea (CBS) and generated a seismic image depicting the subsea permafrost structures in the Arctic region.

Research on the impact of overflow well shut-in on wellbore integrity and safety

If an overflow occurs, the well must be closed immediately. To ensure the safety of the drilling wellbore in ultra-deep wells, it is critical to analyze the transient flow process and pressure fluctuations of the fluid in the annular space of the overflow well shut-in. This paper investigates the pressure fluctuation model of multi-phase fluid in the annular space after overflow occurs during gas well drilling, analyzes the influence factors of multi-phase fluid's pressure wave velocity, and simulates and analyses pressure fluctuation changes in the annular space in light of the impact of overflow well shut-in on wellbore safety. The model's correctness is verified by comparing it to experimental data published in the literature. The model is developed and examined using the example of a genuine gas well in western China. According to the study, as soon as the BOP closes, pressure rapidly increases to a high of 6.09 MPa at 5.89 s before falling to a valley of 4.68 MPa at 35.36 s. When the mild shut-in time lasts 20 s, the wellhead annular pressure reaches a maximum of 5.8 MPa. If the wellhead equipment can withstand the annular space's first pressure wave, a hard shut-in is recommended. To optimize the overflow well shut-in system and ensure wellbore safety, the change in pressure in the wellhead annular space as a result of varied shut-in timings and drilling fluid displacement is studied.

Modeling obliquely incident seismic wave propagation in rocks via the FDM-DEM coupling scheme: Algorithms and applications

The incidence angle of seismic waves plays a pivotal role in the stability analysis of structures in near-field zones. Despite its importance, the application of obliquely incident seismic waves within models of discontinuous media has been limited. This study introduces a novel approach that integrates the oblique incidence of seismic waves into a coupled model employing both the Finite Difference Method (FDM) and the Discrete Element Method (DEM). We validate the accuracy of seismic wave propagation under oblique incidence in two FDM-DEM coupling models—overlapping coupling and interface coupling—through comparisons with theoretical solutions. For vertically incident seismic P-waves, both models yield similar results. However, under oblique incidence, the overlapping coupling model demonstrates superior accuracy, with a maximum error of approximately 4.217 %, compared to about 10 % in the interface coupling model. Our findings also show that while the relative sizes of particle diameter and overlap length minimally affect accuracy, the arrangement of particles markedly influences the results. Furthermore, we apply this method to a slope model to investigate the failure process, revealing that the nature of the sliding body shifts from tensile sliding to tensile ejection as the incidence angle increases.

Numerical Study on the Excitation and Propagation of Surface/Internal Waves Due to Air Pressure Waves over Topography

Numerical Study on the Excitation and Propagation of Surface/Internal Waves Due to Air Pressure Waves over Topography

Assessment of aging degradation in rubber using quasi-static components of ultrasonic longitudinal waves

Abstract Aging degradation is the main form of failure of rubber in service, leading to a decline in its physical and mechanical properties. This paper presents an efficient method for assessing the aging degradation of rubber using the quasi-static component (QSC) of ultrasonic longitudinal waves induced by acoustic radiation. The experiments quantitatively observe the response of the QSC pulse to different levels of ageing degradation. A pulse-echo ultrasonic transducer is employed to simultaneously capture the primary longitudinal wave (PLW) and QSC echoes, enabling the determination of the acoustic nonlinearity parameter of QSC with a single transducer excitation. The results suggest that, in comparison to traditional linear ultrasonic techniques based on attenuation coefficient and wave velocity measurements, the relative acoustic nonlinear parameter of QSC proves to be more sensitive to aging degradation in rubber. Particularly, the amplitude of the QSC pulse undergoes a significant change with increasing aging degradation, even when the PLW tone burst is completely attenuated. These findings confirm the effectiveness of QSC as a method for evaluating aging degradation in highly attenuative materials.

A Bayesian detector-based approach for determining arrival and departure times of negative pressure waves in pipeline leakage localization

A Bayesian detector-based approach for determining arrival and departure times of negative pressure waves in pipeline leakage localization

Investigation of temperature field variations induced by the air thermodynamic behavior when trains pass through a high-speed railway tunnel in cold regions

High-speed railway tunnels in the cold region, whose numbers are increasing, are widely exposed to the threat of frost damage caused by extremely negative temperatures. The operation of high-speed trains has made this problem even more pronounced. But there are fewer studies focusing on the dynamic changes in temperature during train operation. In this paper, the air thermodynamic behavior of trains passing through a tunnel and its consequences were investigated with the help of the CFD method. In numerical simulations, conditions of different natural airflows, different train speeds, different blockage ratios, as well as two trains intersecting in the tunnel were involved. The following valuable results were obtained. In cold environments, train-induced pressure wave effects will affect the air thermodynamic behavior, but the overall trend in air temperature is mainly influenced by the heat transfer between cold and warm air. The high-speed train will lead to massive cold air being carried into the tunnel and some warm air inside being pushed out. Heat transfer between cold and warm air will cause a significant decrease in tunnel air temperature. This air thermodynamic behavior is particularly prominent in the case of large blockage ratios. When there are same-direction natural airflows, they will be coupled with train-induced airflows, causing a greater decrease in tunnel air temperature. In contrast, opposite-direction natural airflows can reduce the negative effects of the train. Taking the case of opposite-direction natural airflow velocity of 5 m/s as an example, the temperature changes of the three cross-sections are only 16.7 %, 14.8 %, and 42.1 % of those in the case of no natural airflow. Whatever the direction of natural airflows, coupling effects between them and train-induced airflows will be more significant as the natural airflow speed increases. Greater train speed means more cold air entering the tunnel and stronger heat transfer between cold and warm air, causing a more significant temperature decrease. When two trains intersect through the tunnel, airflows caused by them will be coupled. As a result, only a little air enters the tunnel from the entrance and exit, and the heat transfer between air with different temperatures is weak. In this case, the air temperature doesn't decrease but slightly increases as the air is compressed.

Numerical Investigation on Dynamic Response of Carbon Fiber Honeycomb Sandwich Panels Subject to Underwater Impact Load

This study investigates the dynamic response and failure mechanisms of carbon fiber honeycomb sandwich structures under underwater impact loads using finite element numerical simulation. The geometric modeling was performed using HyperMesh, and the dynamic response simulations were carried out in ABAQUS, focusing on honeycomb core configurations with varying edge lengths, heights, and gradient forms. The Hashin damage model was employed to describe the damage evolution of the composite materials. The simulation results revealed that the dynamic response was significantly influenced by the initial shock wave pressure and the geometrical parameters of the honeycomb cells. Larger cell-edge lengths and heights generally resulted in improved energy absorption and reduced rear panel displacement. Among the different configurations, interlayer gradient honeycomb structures demonstrated superior impact resistance compared to homogeneous and in-plane gradient structures, particularly under higher initial shock wave pressures. These findings contribute to optimizing the design of carbon fiber honeycomb sandwich structures for enhanced impact resistance in relevant applications.

Flow field distribution and overpressure characteristics inside the crew compartment of a truck-mounted howitzer under the effect of muzzle blast

The muzzle blast overpressure induces disturbances in the flow field inside the crew compartment (FFICC) of a truck-mounted howitzer during the artillery firing. This overpressure is the primary factor preventing personnel from firing artillery within the cab. To investigate the overpressure characteristics of the FFICC, a foreign trade equipment model was used as the research object, and a numerical model was established to analyze the propagation of muzzle blast from the muzzle to the interior of the crew compartment under extreme firing condition. For comparative verification, the muzzle blast experiment included overpressure data from both the flow field outside the crew compartment (FFOCC) and the FFICC, as well as the acceleration data of the crew compartment structure (Str-CC). The research findings demonstrate that the overpressure–time curves of the FFICC exhibit multi-peak characteristics, while the pressure wave shows no significant discontinuity. The enclosed nature of the cab hinders the dissipation of pressure wave energy within the FFICC, leading to sustained high-amplitude overpressure. The frame-skin structure helps attenuate the impact of muzzle blast on the FFICC. Conversely, local high overpressure caused by the convex or concave features of the cab's exterior significantly amplifies the overpressure amplitude within the FFICC.

Phenomenological Aerodynamic Analysis of an Ejector Exposed to Large Inlet Pulsations

To enable the coupling of the unsteady, high-enthalpy flow exiting a Rotating Detonation Combustor (RDC) with a subsonic turbine, an ejector may be installed between the combustor and turbine. In the present work, a conventional ejector is investigated numerically using a Large-Eddy Simulation. Firstly, a stationary operating point is analyzed where sufficient agreement could be obtained with experimental data. Secondly, a new operating point is proposed where a sinusoidal acoustic pulsation is imposed at the primary ejector inlet. The pulsation generates a periodic fluctuation between sub- and supersonic velocity regimes at the primary nozzle exit, which is representative of local RDC exhaust velocities. In this first step, the exhaust gas temperature, flow angle, and gas composition are not considered. At this operating condition, a secondary normal shock appears periodically at the end of the constant-area mixing chamber and retracts upstream as a pressure wave. The shear layer, the boundary layer, the secondary shock, and the diffuser-induced separation are identified as kinetic energy loss sources within the ejector. The amplitude of total pressure fluctuations is reduced by 85% throughout the device, whereas the frequency is retained. The dampening characteristics are considered favorable for gas turbine integration.

Optimal design of broadband, low-directivity graded index acoustic lenses for underwater communication.

Manipulating underwater pressure waves is crucial for marine exploration, as electromagnetic signals are strongly absorbed in water. However, the multi-path phenomenon complicates the accurate capture of acoustic waves by receivers. Although graded index lenses, based on metamaterials with smoothly varying properties, successfully focus pressure waves, they tend to have high directivity, which hinders practical application. This work introduces three 2D acoustic lenses made from a metamaterial composed of solid inclusions in water. We propose an optimization scheme where the pressure dynamics is governed by Helmholtz's equation, with control parameters affecting each lens cell's density and bulk modulus. Through an appropriate cost function, the optimization encourages a broadband, low-directivity lens. The large-scale optimization is solved using the Lagrangian approach, which provides an analytical expression for the cost gradient. This scheme avoids the need for a separate discretization step, allowing the design to transition directly from the desired smooth refractive index to a practical lattice structure. As a result, the optimized lens closely aligns with real-world behavior. The homogenized numerical model is validated against finite elements, which considers acoustic-elastic coupling at the microstructure level. When homogenization holds, this approach proves to be an effective design tool for achieving broadband, low-directivity acoustic lenses.

Oscillation mechanism and predictive model of explosion load for natural gas in confined tube

Gas explosion in confined space often leads to significant pressure oscillation. It is widely recognized that structural damage can be severe when the oscillation frequency of the load resonates with the natural vibration frequency of the structure. To reveal the oscillation mechanism of gas explosion load, the experiment of gas explosion was conducted in a large-scale confined tube with the length of 30 m, and the explosion process was numerically analyzed using FLACS. The results show that the essential cause of oscillation effect is the reflection of the pressure wave. In addition, due to the difference in the propagation path of the pressure wave, the load oscillation frequency at the middle position of the tunnel is twice that at the end position. The average sound velocity can be used to calculate the oscillation frequency of overpressure accurately, and the error is less than 15%. The instability of the flame surface and the increase of flame turbulence caused by the interaction between the pressure wave and the flame surface are the main contributors to the increase in overpressure and amplitude. The overpressure peaks calculated by the existing flame instability model and turbulence disturbance model are 31.7% and 34.7% lower than the numerical results, respectively. The turbulence factor model established in this work can describe the turbulence enhancement effect caused by flame instability and oscillatory load, and the difference between the theoretical and numerical results is only 4.6%. In the theoretical derivation of the overpressure model, an improved model of dynamic turbulence factor is established, which can describe the enhancement effect of turbulence factor caused by flame instability and self-turbulence. Based on the one-dimensional propagation theory of pressure wave, the oscillatory effect of the load is derived to calculate the frequency and amplitude of pressure oscillation. The average error of amplitude and frequency is less than 20%.

P084 BLOOD PRESSURES MEASUREMENT WITH SITTING ON THE FLOOR POSITION FOR THE HOME BLOOD PRESSURE MONITORING FOR ASIAN LIFESTYLE

Objectives: The current standard method for home blood pressure (BP) measurement involves taking measurements while sitting in a chair. In cultures where floor sitting is common as like in Asian countries, the protocol only using sitting on the chair position can not be applied because of a lack of research for interchangeability. Methods & Materials: Among the participants who visited for evaluation of central blood pressure or pulse wave velocity, a total of 116 participants who agreed to participate in the study were randomly selected. All subjects rested for 5 minutes, and BP measurements were taken at 1-minute intervals according to a randomly assigned order of standard method (chair-sitting) and BP in a seated on the floor (floor-sitting). Results: Of the 116 participants, the median age was 67.5 (with an interquartile range of 59.0 to 75.0), and 82% were male. There were no significant differences in systolic BP (SBP, 127.0 [115.0, 142.2] mmHg in chair-sitting and 129.0 [115.5, 142.2] mmHg in floor-sitting, P = 0.228) and diastolic BP (DBP, 73.5 [66.0, 83.0] mmHg in chair-sitting and 72.0 [66.8, 81.3] mmHg in floor-sitting, P = 0.839) between the two positions. Conclusions: These findings provide important insights into securing the reliability of home BP measurements through the commonly practiced floor-sitting posture in cultures where floor sitting is common. Furthermore, this could serve as substantial evidence for providing specific home BP measurement guidelines to patients who adhere to a floor-sitting lifestyle.

Sex differences and role of lysyl oxidase-like 2 in angiotensin II-induced hypertension in mice.

Hypertension, a disease with known sexual dimorphism, accelerates aging-associated arterial stiffening, partly because of the activation of matrix remodeling caused by increased biomechanical load. In this study, we tested the effect of biological sex and the role of the matrix remodeling enzyme lysyl oxidase-like 2 (LOXL2) in hypertension-induced arterial stiffening. Hypertension was induced by angiotensin II (ANG II) infusion via osmotic minipumps in 12- to 14-wk-old male and female mice. Blood pressure and pulse wave velocity (PWV) were measured noninvasively. Wire myography and uniaxial tensile testing were used to test aortic vasoreactivity and mechanical properties. Aortic wall composition was examined by histology and Western blotting. Uniaxial stretch of cultured cells was used to evaluate the effect of biomechanical strain. LOXL2's catalytic function was examined using knockout and inhibition. ANG II infusion-induced hypertension in both genotypes and sexes. Wild-type (WT) males exhibited arterial stiffening in vivo and ex vivo. Aortic remodeling with increased wall thickness, intralamellar distance, higher LOXL2, and collagen I and IV content was noted in WT males. Female mice did not exhibit increased PWV despite the onset of hypertension. LOXL2 depletion improved vascular reactivity and mechanics in hypertensive males. LOXL2 depletion improved aortic mechanics but worsened hypercontractility in females. Hypertensive cyclic strain contributed to LOXL2 upregulation in the cell-derived matrix in vascular smooth muscle cells (VSMCs) but not endothelial cells. LOXL2's catalytic function facilitated VSMC alignment in response to biomechanical strain. In conclusion, in males, arterial stiffening in hypertension is driven both by VSMC response and matrix remodeling. Females are protected from PWV elevation in hypertension. LOXL2 depletion is protective in males with improved mechanical and functional aortic properties. VSMCs are the primary source of LOXL2 in the aorta, and hypertension increases LOXL2 processing and shifts to collagen I accumulation. Overall, LOXL2 depletion offers protection in young hypertensive males and females.NEW & NOTEWORTHY We examined the effect of sex on the evolution of angiotensin II (ANG II)-induced hypertension and the role of lysyl oxidase-like 2 (LOXL2), an enzyme that catalyzes matrix cross linking. While ANG II led to hypertension and worsening vascular reactivity in both sexes, aortic remodeling and stiffening occurred only in males. LOXL2 depletion improved outcomes in males but not females. Thus males and females exhibit a distinct etiology of hypertension and LOXL2 is an effective target in males.

Nonlinear interaction of Lamb waves with fatigue cracks in metal plates under the condition of phase-velocity mismatching

Abstract Nonlinear Lamb waves have been widely acknowledged as an efficient method for evaluating material damage at an early stage. However, due to the dispersive and multimode natures of Lamb waves, nonlinear Lamb waves with exact/approximate phase-velocity matching have been employed in previous research solely for the evaluation of fatigue cracks. Second harmonic Lamb waves can be generated from the contact acoustic nonlinearity (CAN) induced by the “breathing” effect of fatigue cracks. This paper presents a verification of the second harmonic S0 mode Lamb waves due to fatigue crack CAN, despite the mismatch in phase velocity between this mode and the primary S0 mode Lamb waves. This verification is achieved through both simulation and experiment. Consequently, the generation of double-frequency Lamb waves by fatigue cracks under conditions of phase velocity mismatching is validated. Furthermore, the phase-velocity mismatching method is anticipated to exclude material nonlinearity in the detection of fatigue cracks. This method offers a potential for accurate detection and evaluation of fatigue cracks.