Peak Pressure Research Articles

Induced fatigue impact on plantar pressure in females with mild hallux valgus

Fatigue has been established to change plantar pressure distribution, yet its impact on hallux valgus (HV) patients, who exhibit morphological and biomechanical changes in the foot, remains insufficiently studied. Twenty-eight female participants, comprising 16 with mild HV and 12 healthy controls, were recruited. Plantar pressures were recorded pre- and post-fatigue using the Footscan platform during self-selected-speed walking trials, fatigue protocol was performed on a treadmill. Foot was segmented into 10 anatomical regions for calculating parameters including maximal force, peak pressure, impulse, contact duration, contact area, and force time-series, alongside assessing the distribution of medial and lateral contact forces (Foot balance) across the groups. During post-fatigue, patients with mild HV demonstrated adaptive changes in plantar pressure distinct from healthy controls, with significant reductions in maximal force, peak pressure, and impulse in the M1 and M2 regions and increases in the M3–M5 regions. In contrast, the control group exhibited an opposite pattern, concentrating pressure in the M1 and M2 regions post-fatigue. The force time-series analysis revealed significant disparities between HV patients and controls, particularly in the M4 and M5 regions, where HV patients showed a less pronounced and lower passive peak in forces. Results show that women with mild HV demonstrate adaptive changes in plantar pressure post-fatigue, distinctly different from healthy individuals, aiding in preventive strategies for fatigue-induced foot injuries for HV patients.

Comparison of in-shoe plantar pressure between Korean combat boots and running shoes

IntroductionCombat boots are special shoes designed for soldiers to wear during activities in rough terrain, such as long marches or military training. Combat boots have been known to cause high...

The Impact of Upstream Static Deformation on Flow Past a Cylinder/Flare

Reynolds-averaged Navier–Stokes simulations are performed for supersonic turbulent flow over a cylinder/flare with upstream surface distortion representative of structural deformation induced via fluid–structural and fluid–thermal–structural behavior. Broad parametric analysis is carried out through the generation of Kriging-response surfaces from a database of general simulations. A posteriori simulations are then carried out at parametric combinations that correspond to extrema in the Kriging response surfaces to gain deeper insights into the interaction between the surface distortion and flow responses. Upstream distortions tend to decrease, rather than increase, the peak pressure and heat flux loads on the flare compared to an undeformed cylinder. Furthermore, decreases in these quantities reach up to O(10%) compared to up to O(1%) for increases. Integrated quantities over the flare are relatively insensitive to upstream distortion. The corner separation length is the most sensitive quantity to upstream distortion, with protrusions tending to increase the separation length and recessions reducing the separation length. Modifications in the separation length of up to 40% are observed. Reductions in peak loads tend to correspond to increases in the corner separation length. The movement of the surface distortion relative to the corner indicates a negligible impact beyond 1.5 distortion lengths from the corner, and the largest impact on the corner separation length occurs when distortion is directly adjacent. These results are an important step toward understanding and quantifying the impact of surface deformations on downstream components.

Investigation of Residual Stress Distribution and Fatigue of 7050-T7451 Alloy Hole Components with Laser Shock and Ultrasonic Extrusion

Small-hole structures, such as the millions of fastener holes found on aircraft, are typical stress-concentration structures prone to fatigue failure. To further improve the strengthening process of this small-hole structure, we make up for the limitations of laser shock processing (LSP) of small holes by combining it with the ultrasonic extrusion strengthening (UES) process to form a new strengthening method—laser shock and ultrasonic extrusion strengthening (LUE). The influence of the LUE process sequence and process parameters on residual stress distribution was studied through FEM, and the gain of fatigue life of specimens after LUE strengthening was also explored through tests. The results show that when using LUE technology, the friction force decreases with the increase in amplitude and decreases by 3.2% when the amplitude is maximum. The LUE process eliminates the thickness effect generated by LSP, which can achieve good stress distribution of small-hole components under smaller laser shock peak pressure, and reduces equipment power. LUE can significantly improve the fatigue life of small-hole components, and the maximum fatigue life gain can be up to 310.66%.

Small‐scale measurement of fracture toughness of muddy marine sediments via bubble injection

AbstractMuddy marine sediments are elastic materials in which bubbles grow and worms extend their burrows by fracture. Bubble growth and burrowing behavior are dependent on the stiffness and fracture toughness (KIc) of these muds. This article describes a custom laboratory apparatus to measure the fracture toughness of muddy, cohesive sediments using a bubble injection method. The system induces fracture in sediment samples by incrementally injecting air through a needle inserted into the sediment. The increasing pneumatic pressure is monitored until it drops abruptly, indicating bubble formation. Fracture toughness is then calculated from the peak pressure at which fracture occurred, following cavitation rheology methods developed for soft gels. The system has produced measurements that compare well to previous data but with better spatial resolution, allowing for characterization of spatial heterogeneity on small scales.

Effect of open crack on axial compressor performance

To investigate the effects and mechanisms of rotor open crack on axial compressor performance, a steady 3D single-passage numerical simulation is used on NASA Stage 35. The results show that the crack leakage flow can affect the compressor performance, and the crack at the middle span has the most serious effect. At 100% rotating speed, there is a 1.2% decrease in peak total pressure ratio and a 0.36% decrease in peak efficiency. Besides, the stability margin is reduced by 26.9% relatively. The effect of crack is not only limited to the span range near it, and the main phenomena of cracks at different spans are various, concentrating in the aspects of vortex structure and stator passage flow. From peak efficiency to near stall condition, the effect of crack leakage flow is gradually strengthened, which leads to the flow blockage and reduces the working flow range of compressor. With the decrement of rotating speed, the reduction of stability margin increases gradually, but the influence span range of crack at low-speed narrows.

Combustion Diagnosis in a Spark-Ignition Engine Fueled with Syngas at Different CO/H2 and Diluent Ratios

The gasification of residues into syngas offers a versatile gaseous fuel that can be used to produce heat and power in various applications. However, the application of syngas in engines presents several challenges due to the changes in its composition. Such variations can significantly alter the optimal operational conditions of the engines that are fueled with syngas, resulting in combustion instability, high engine variability, and misfires. In this context, this work presents an experimental investigation conducted on a port-fuel injection spark-ignition optical research engine using three different syngas mixtures, with a particular focus on the effects of CO/H2 and diluent ratios. A comparative analysis is made against methane, considered as the baseline fuel. The in-cylinder pressure and related parameters are examined as indicators of combustion behavior. Additionally, 2D cycle-resolved digital visualization is employed to trace flame front propagation. Custom image processing techniques are applied to estimate flame speed, displacement, and morphological parameters. The engine runs at a constant speed (900 rpm) and with full throttle like stationary engine applications. The excess air–fuel ratios vary from 1.0 to 1.4 by adjusting the injection time and the spark timing according to the maximum brake torque of the baseline fuel. A thermodynamic analysis revealed notable trends in in-cylinder pressure traces, indicative of differences in combustion evolution and peak pressures among the syngas mixtures and methane. Moreover, the study quantified parameters such as the mass fraction burned, combustion stability (COVIMEP), and fuel conversion efficiency. The analysis provided insights into flame morphology, propagation speed, and distortion under varying conditions, shedding light on the influence of fuel composition and air dilution. Overall, the results contribute to advancing the understanding of syngas combustion behavior in SI engines and hold implications for optimizing engine performance and developing numerical models.

Assessing lunar paleointensity variability during the 3.9 - 3.5 Ga high field epoch

Numerous paleomagnetic studies suggest that a lunar dynamo, with surface field intensities potentially as high as 40-100 µT, existed between ∼3.9 Ga and ∼3.5 Ga. This period is referred to as the High Field Epoch (HFE). However, the debate over the origin of magnetization recorded in lunar rocks still persists. In addition, whether the Moon could have sustained a continuously strong dynamo during the HFE remains unclear. To unravel the origin of magnetization preserved in lunar rocks and to better characterize the evolution of the ancient lunar dynamo, we conducted a comprehensive set of experiments including rock magnetic tests, electron microscopy, and paleomagnetic investigations on four HFE-aged Apollo 11 mare basalt samples: 10003, 10044, 10069, and 10071. Rock magnetic experiments and electron microscopy indicate that the remanence carriers are kamacite grains of varying sizes and domain states. Sample 10003 recorded a paleointensity of 54.10 ± 4.66 µT. Sample 10044, which was shocked (peak pressure >5 GPa), did not preserve a stable high coercivity remanent magnetization. Samples 10069 and 10071 recorded paleointensities of 61.46 ± 26.09 µT and 10.69 ± 2.87 µT, respectively. A series of hydrostatic pressure experiments, isothermal remanent magnetization (IRM) acquisition experiments, and viscous remanent magnetization (VRM) tests preclude the possibility of our samples containing shock remanent magnetization from transient impact-generated fields, IRM acquisition from exposure to spacecraft fields, and VRM acquisition from exposure to the Earth magnetic field. Overall, our study suggests that the source of these magnetizations was likely the lunar dynamo and may indicate nearly order-of-magnitude magnetic field fluctuations during the HFE.

Impact of obesity on the incidence of postoperative pulmonary complications following laparoscopic colorectal surgery

Objective: To evaluate the effects of obesity on the incidence of postoperative pulmonary complications (PPCs) following laparoscopic colorectal surgery. Methods: A total of 150 patients with pathological diagnosis of colorectal cancer who accepted laparoscopic colorectal excision from January to May 2023 were retrospectively recruited. All the patients scored 26 points or more in the Assess Respiratory Risk in Surgical Patients in Catalonia (ARISCAT) model, making them all in intermediate to high risks of PPCs. Patients were divided into obesity group and non-obesity group depending on whether they were obese or not. Propensity score matching (1∶1) was performed to achieve the balance of clinicopathological characteristics with the matching factors of age, sex, respiratory complications and ARISCAT score. A total of 96 patients were eventually enrolled, with 48 patients in obesity group and 48 patients in non-obesity group. Besides, the patients were divided into 25°-30° Trendelenburg subgroup and ±10°-15° Trendelenburg subgroup according to surgical sites for further analysis. The incidence of PPCs, the intraoperative airway pressure and blood biomarker expression of lung injury, including soluble receptor for advanced glycation end products (sRAGE) and angiopoietin-2 (ANG2) at postoperative day (POD) 1 and POD3 between the two groups were compared. The relationship between obesity and incidence of PPCs within 30 postoperative days were analyzed with unifactorial Cox proportional hazard model. Results: The obesity group was comprised of 35 males and 13 females with a median age of 60 (49, 69) years, and the non-obesity group was comprised of 35 males and 13 females with a median age of 60 (52, 67) years. The incidence of PPCs was 50.0% (24/48) in the obesity group, which was higher than 20.8% (10/48) in the non-obesity group and the incidence of grade Ⅰ PPCs and microatelectasis were 31.3% (15/48) and 33.3% (16/48), higher than the 12.5% (6/48) and 12.5% (6/48) of the non-obesity group (all P<0.05). The peak airway pressure (Ppeak) and plateau airway pressure (Pplat) of patients in obesity group were 34.0(31.5, 36.5) and 30.0(27.0, 32.0) cmH2O(1 cmH2O=0.098 kPa), which were significantly higher than the 26.0 (24.0, 29.5) and 22.0 (21.0, 26.5) cmH2O of the non-obesity group (all P<0.001). The ANG2 level of the obesity group at POD3 was 11.9 (8.4, 16.5) μg/L, which was higher than 9.2 (6.0, 12.3) μg/L of the non-obesity group (P=0.045). In 25°-30°Trendelenburg subgroup, the incidence of PPCs in obese patients were significantly higher than that of non-obese patients [41.4% (12/29) vs 11.4% (4/35), P=0.005]. In ±10°-15°Trendelenburg subgroup, no significant difference was found in PPCs incidence between obese and non-obese patients [63.2% (12/19) vs 46.2% (6/13), P=0.215]. The unifactorial Cox proportional hazard model analysis showed that obesity was a risk factor of PPCs in 30 postoperative days (HR=3.015, 95%CI: 1.438-6.321, P=0.001). Conclusion: In patients undergoing laparoscopic colorectal surgery with intermediate to high risk of PPCs, obesity raises intraoperative airway pressure and aggravates intraoperative lung endothelial injury. Obesity is a risk factor of PPCs in 30 postoperative days.

Plantar pressure distribution using personalised 3D printed lattice insoles with distributed stiffness

This work presents a proof-of-concept study on the use of additive manufacturing for developing customised lattice topology insoles, with the aim of redistributing plantar pressures. Four cubic lattice structures were applied to five sections of the moulded insole contours, which were based in 3D foot scans using Ansys material designer to predict material properties. The variation of the elastic modulus across the sections was controlled via the lattice cell structure volume ratio. The insole lattice structures were made from elastic photosensitive liquid resin resulting in flexible parts. A commercially available shoe was used to compare pressure distribution between the original and customised insole. Plantar pressure distribution and peak pressures were measured during standing, walking, and running. Pressure redistribution varied between insole conditions. During standing, the customised insole reduced peak pressure at the left heel, while the right foot experienced increased peak pressure compared to the control insole. Substantial peak pressure reduction was observed on the left foot during walking and running whilst the reduction was much less for the right foot. The study highlights the potential of additive manufacturing for cost-effective, accurate, and personalized insole production, offering material control and pressure redistribution benefits for various applications like injury prevention and rehabilitation.

Numerical investigation of blunt body's resistance and heat reduction with combination of airway spike and root jet

Aerodynamic heating and impact resistance present significant challenges for hypersonic aircraft. This study introduces a novel multi-jet strategy to enhance both resistance reduction and thermal protection performance of hypersonic aircraft. Computational Fluid Dynamics (CFD) analysis is employed for the aerodynamic evaluation. The results demonstrate that this novel strategy effectively mitigates the shock waves, the peak pressure coefficient and Stanton number have been reduced by 64.3 % and 73.2 %, respectively. Through a comprehensive analysis of the influencing factors, it has been found that increasing the pressure ratio of the root jet significantly lowers the heat flux and pressure on the blunt body, albeit at the cost of an increased total flight resistance. When the nozzle on the side of the airway is oriented perpendicularly to the incoming flow direction, a notable reduction in resistance and aerodynamic heating on the blunt body is noted. By increasing the length-diameter ratio of the spike, a significant decrease in the pressure coefficient of the blunt body is achieved, the Stanton number remains largely unaffected. This study offers insights into the engineering application of strategies for reducing resistance and heat in hypersonic aircraft.

How the multiplanar trunk resistance affects the dynamic postural control during single-leg vertical jumps in college athletes with poor movement quality

How the multiplanar trunk resistance affects the dynamic postural control during single-leg vertical jumps in college athletes with poor movement quality

Exposure of Undergraduate Nursing Students to Standing Environments: A Longitudinal Study on Plantar Force and Pressure Distribution.

Understanding the link between plantar force, pressure, and foot discomfort is important for nursing students' well-being, given the prevalence of foot and ankle musculoskeletal disorders among nurses. Assessing these factors can inform tailored self-care interventions, supporting holistic nursing education. To assess the plantar force and pressure distribution of third-year nursing students at baseline and after 5months of exposure to a clinical setting. A prospective cohort study in a Portuguese nursing school measured changes in podiatric profile at 5months, including peak pressure, maximum force, and contact area. Elevated mean peak pressure in the heel correlated positively with maximum force and contact area. Negative correlations were found between the contact area and edema. Peak pressure correlated positively with thigh pain, indicating pressure transfer to metatarsal heads. The findings underscore the importance of integrating ergonomic education into nursing curricula and raising awareness of self-care interventions.

High-pressure Phase Transition of Olivine-type Mg2GeO4 to a Metastable Forsterite-III type Structure and their Equation of States

Abstract Germanates are often used as structural analogs of planetary silicates. We have explored the high-pressure phase relations in Mg2GeO4 using diamond anvil cell experiments combined with synchrotron X-ray diffraction and computations based on density functional theory. Upon room temperature compression, forsterite-type Mg2GeO4 remains stable up to 30 GPa. At higher pressures, a phase transition to a forsterite-III type (Cmc21) structure was observed, which remained stable to the peak pressure of 105 GPa. Using a 3rd order Birch Murnaghan fit to the experimental data, we obtained V0 = 305.1 (3) Å3, K0 = 124.6 (14) GPa and K0′ = 3.86 (fixed) for forsterite- and V0 = 263.5 (15) Å3, K0 = 175 (7) GPa and K0′ = 4.2 (fixed) for the forsterite-III type phase. The forsterite-III type structure was found to be metastable when compared to the stable assemblage of perovskite/post-perovskite + MgO, as observed during laser-heating experiments. Understanding the phase relations and physical properties of metastable phases is crucial for studying the mineralogy of impact sites, understanding metastable wedges in subducting slabs and interpreting the results of shock compression experiments.

On the structure dynamic response induced by the dam-break surge impact using multivariate copulas

In this study, the dam-break induced surge impact pressure data on a vertical wall are used to investigate the corresponding structure dynamic response. Both the hydrodynamic and structure parameters are confirmed to be crucial in assessing the structure dynamic responses. The surge peak pressure pk, the pressure rise time Tr, the surge impact duration Td, and the structure natural period Tn are considered to establish the statistical model. The present study determines the dependencies among these parameters which describe the structure dynamic response due to the complexity of dam breaking. Accordingly, two multivariate copulas, i.e., the Gaussian copula and the Vine copula, are used to simulate the statistical properties of the maximum dynamic amplification factor ψm, allowing a better understanding of the dependencies and correlations among different parameters. The tail dependence of variable pairs (pk, Tr) and (pk, ψm) are not significant, while the variable pairs (Tr, ψm) and (Td/Tn, ψm) show lower and upper tail dependence. With respect to the experiment data, simulation using the Gaussian copula shows good results regarding variable pairs of symmetric dependence structures, whereas the Vine copula is more suitable for variable pairs of asymmetric dependence structures.

Changes in the state of matter of KCIO4 to improve thermal and combustion properties of Al/MoO3 nanothermite

To improve the thermal and combustion properties of nanothermites, a design theory of changing the state of matter and structural state of the reactants during reaction was proposed. The Al/MoO3/KClO4 (Kp) nanothermite was prepared and the Al/MoO3 nanothermite was used as a control. SEM and XRD were used to characterize the nanothermites; DSC was used to test thermal properties; and constant volume and open combustion tests were performed to examine their combustion performance. Phase and morphology characterization of the combustion products were performed to reveal the mechanism of the aluminothermic reaction. The results show that the Al/MoO3/Kp nanothermite exhibited excellent thermal properties, with a total heat release of 1976 J·g− 1, increasing by approximately 33% of 1486 J·g− 1 of the Al/MoO3 nanothermite, and activation energy of 269.66 kJ·mol− 1, which demonstrated higher stability than the Al/MoO3 nanothermite (205.64 kJ·mol− 1). During the combustion test, the peak pressure of the Al/MoO3/Kp nanothermite was 0.751 MPa, and the average pressure rise rate was 25.03 MPa·s− 1, much higher than 0.188 MPa and 6.27 MPa·s− 1 of the Al/MoO3 nanothermite. The combustion products of Al/MoO3 nanothermite were Al2O3, MoO, and Mo, indicating insufficient combustion and incomplete reaction, whereas, the combustion products of Al/MoO3/Kp nanothermite were Al2O3, MoO, and KCl, indicating complete reaction. Their “coral-like” morphology was the effect of reactants solidifying after melting during the combustion process. The characterization of reactants and pressure test during combustion reveals the three stages of aluminothermic reaction in thermites. The excellent thermal and combustion performance of Al/MoO3/Kp nanothermite is attributed to the melt and decomposition of Kp into O2 in the third stage. This study provides new ideas and guidance for the design of high-performance nanothermites.

Effects of H2/CO ratio and CO2 dilution on the explosion behavior and flame evolution of syngas/air mixtures

Syngas, which is used as both a fuel and a raw material, presents numerous safety risks during its utilization. In this paper, the effects of H2/CO ratio (R = 0%, 30%, 50%, 70% and 100%) and CO2 dilution ([CO2] = 0%–20%) on the explosion behaviors of syngas/air mixtures with different equivalence ratios (φ = 0.8, 1.0, 1.6, and 2.5) are examined via experiments and numerical calculations. The results show that the peaks of explosion pressure and OH* spectral intensity are significantly influenced by the H2 percentage in the syngas. The introduction of CO2 notably decreases these parameters in oxygen-rich and severe oxygen-poor states. Additionally, the flame propagation speed noticeably increases with increasing H2 proportion in the syngas. The influence of CO2 on the buoyancy instability of the spherical flame of syngas is considered negligible when compared to that of other combustible gases, such as CH4. Nevertheless, the presence of CO2 decreases the density ratio between the unburned gas and burned gas and increases the flame thickness of syngas/air mixtures. This trend reduces the cellular instability of the spherical flame, particularly in severe oxygen-poor states. Notably, there is a definite correlation between the formation of cellular flames and the rise rate of explosion pressure. The cellular structure on the flame surface becomes more pronounced when the rise rate of explosion pressure increases. Conversely, it develops later or is noticeably inhibited. Furthermore, the main reaction pathways are H2 → ∙OH → H2O2 → H2O and H2 → ∙OH → CO → CO2 during the syngas explosion process. ∙OH is critical in the entire chain reaction because it promotes the conversion of H2 to H2O and acts as a vital connection between the reactants H2 and CO in the explosion process.

Study on tubing string safety during perforation detonation in ultra-deep wells

ABSTRACT To address the challenge of quantitatively predicting the wellbore pressure and the force of the tubing string below the packer during the perforation detonation, a prediction model for the wellbore pressure and the axial force of the tubing string is established. The evolution laws of the wellbore pressure and the axial force of the tubing are analyzed. The sensitivity analysis of four primary controlling factors is further studied. The obtained results indicate that the peak pressure of the wellbore at the bottom of the perforating gun is the cause of the tubing string failure. The relative error of the predicted peak pressure of the wellbore is 2.22%. The major sensitive parameters affecting the peak pressure of the wellbore at the bottom of the perforating gun and the peak axial force at the bottom of the tubing are ranked as follows: the initial wellbore pressure, the shot density, the explosive mass, and the perforating fluid density. The work presented can provide a theoretical foundation and technological basis for the quantification of the wellbore pressure and the force of the tubing string during the perforation detonation, which is critical for well completion design and wellbore safety evaluation.

Behavior of steel liner tray walls under external blast: Experimental testing and numerical simulations

Explosions produced in urban or industrial areas due to accidental or intentional detonation of explosives are low-probability but high-impact events. If standoff distance from buildings or other constructions is small, explosions can cause structural failures and serious injuries or deaths of occupants. Although heavy/stiff enclosure systems were long considered appropriate to protect buildings against explosive threats, lighter and flexible steel-based systems, which are increasingly used for modern buildings, may also provide satisfactory performance. The study presents the results of full-scale blast tests on liner tray walls attached to a steel frame building. Walls were tested against increasing blast charges until failure. Due to very high peak pressures and very short durations, the loading regime could be classified as impulsive. The ultimate strength is given by the failure of the end fasteners, after large bolt hole elongations coupled with the pull-through of the end fasteners. If the insulation and outer cladding are lost, the liner trays are directly exposed to blast and the seaming fasteners at overlapping sheets are prematurely lost. As a result, the wall panels work mostly independently, as one-way elements. On the contrary, if the outer cladding protects the seaming fasteners, the overlapping provides additional capacity due to membrane effect (two-way behavior). Numerical models were calibrated using test data and were further used to obtain more information about liner tray behavior under blast.

Development of a numerical model for disassembly phase of hypothetical core disruptive accident and application to a medium-sized mixed oxide fuelled fast reactor

Safety assessment of fast reactors involves analyzing Hypothetical Core Disruptive Accidents (HCDA) that could result in reactor core disassembly. HCDA is generally analyzed in three distinct phases that include pre-disassembly, disassembly and post-disassembly phases. In the present work, a new coupled neutronics-hydrodynamics computer code called FAst Reactor DISassembly (FARDIS-1) is developed in 2-D cylindrical coordinate geometry to model the super-prompt critical power excursion during the disassembly phase of HCDA in a sodium-cooled fast reactor (SFR). The modelling approach followed is essentially similar to the one used in VENUS-II code but with a few improvements. The code is benchmarked against the predictions of VENUS-II for a sample case of HCDA in the FFTF reactor model. This is followed by an analysis of the disassembly phase in a medium-sized (500 MWe) mixed oxide fuelled fast reactor. Two cases are assumed at the beginning of the disassembly phase: a sodium voided core (conservative) and a partially voided core (realistic) and the influence of several core neutronics parameters on the transients is elucidated through parametric studies. The peak power, thermal energy release, peak pressure, maximum temperature and work-potential are estimated and their trends are discussed.