Internal Pressure Research Articles

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

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

Understanding delamination behavior of air electrode in solid oxide electrolysis cells through in situ monitoring of internal oxygen partial pressure

In this study, we monitored the development of internal pO2 in solid oxide electrolysis cells (SOECs) in situ using an embedded probe and a reference electrode. Three types of air electrode cells were compared: LSM (La0.8Sr0.2MnO3−δ) + YSZ (Y0.08Zr0.92O2−δ), LSCF (La0.6Sr0.4Co0.2Fe0.8O3−δ) + GDC (Gd-doped ceria) and LSM + GdCeScSZ ((Gd2O3)0.005(CeO2)0.005(Sc2O3)0.1(ZrO2)0.89). The rate of pO2 increase with the increase in current density was highest in the LSM + YSZ cell, reaching ∼32201 atm at 0.6 A cm−2, resulting in air electrode delamination and intergranular fractures. This physically developed delamination with high pO2 is akin to catastrophic failure, accelerating degradation. The LSCF + GDC cells exhibited a maximum pO2 of ∼12.25 atm and operated stably without increasing pO2 or delamination. In the LSM + GdCeScSZ cells, internal pO2 was substantially suppressed to ∼10−3 atm, with a degradation rate comparable to that of the LSCF + GDC cell. However, the air electrode delaminated without intergranular fractures. This chemically developed delamination without high internal pO2 does not significantly accelerate degradation. These results indicate that the delamination mechanism may vary even with the same LSM electrode, depending on its ionic conduction characteristics.

CEOs' narcissism and opportunistic insider trading

Narcissism is a multifaceted personality trait that profoundly influences individuals' cognition, emotions, and actions. This study investigates the relationship between narcissistic CEOs and their engagement in opportunistic insider trading. Utilizing a quantitative measure of CEOs' narcissism derived from textual analysis, we find that CEOs with a higher level of narcissism engage in opportunistic insider trading more intensely. To mitigate endogeneity concerns, we employ various rigorous approaches, including matching, instrumental variable, Heckman's two-step sample selection model, and falsification tests. Through cross-sectional analysis, we find that the impact of CEOs' narcissism on opportunistic insider trading is more pronounced among CEOs with limited legal knowledge, facing weaker external and internal monitoring pressure, working at larger firms, and being male. In addition, we demonstrate that the insider trades of narcissistic CEOs are less profitable and less informative than those of non-narcissistic CEOs, as evidenced by subsequent stock performance.

Effects of irregular holes on load-bearing mechanism and capacity in prestressed concrete cylinder pipes

This study investigates the effects of irregular holes on the load-bearing mechanism and capacity of prestressed concrete cylinder pipes (PCCP). An internal pressure test was performed on a PCCP specimen containing multiple irregular holes, and a finite element numerical simulation was conducted to explore the impact of these holes. The results indicated that the presence of irregular holes caused significant anisotropic stress distribution, particularly at the inner wall of the concrete core, with stress concentrations around the holes. Cracks were initiated near the spigot end and propagated axially as the internal pressure increased. The load-bearing process of the PCCP evolved in three stages: (1) the prestressed wires bore the majority of the load, (2) the concrete began sustaining a portion of the load as it experienced tensile stress, and (3) the concrete underwent plastic damage, transferring the load to the steel cylinder and prestressed wires. The internal pressure of PCCP model with multiple irregular holes associated with the serviceability limit-states was 0.23 MPa, representing only 26.4 % of the intact model, which was 0.87 MPa. However, the difference in ultimate load-bearing capacity between the two models was minimal. These findings underscore the necessity of timely repairs to prevent the worsening of erosion in PCCPs with irregular holes.

Identifying the Internal and External Pressures of Quantifying the Impacts of Sustainability-Oriented Innovation

The sustainability-oriented innovation (SOI) has emerged as a critical approach for an organisation that addresses environmental, social, and economic challenges. The proposed study aims to identify key internal and external pressures by uncovering the main factors within and outside the organisation influencing the quantification of SOI impacts. In the given study’s research design adopts a primary qualitative approach to explore internal and external pressures affecting the quantification of sustainability-oriented innovation (SOI) that impacts the economic context. Qualitative research was chosen for its ability to provide an in-depth insight into a complex phenomenon that captures the nuances of the participant’s experience, attitudes and perception. The findings show that a leadership team’s commitment to sustainability and the proactive mindset of our employees fosters an environment where innovation thrives. The conclusion is that the implementation of internal policies and incentives encouraged sustainable practices and continuous improvement. SOI has been influenced by concepts like a crucial economy that promotes a continuation use of resources through its recycling and remanufacturing and to share economy, emphasizing access to over ownership.

Dynamics and control of a high-altitude balloon with slung load

Abstract The high-altitude balloon proposed in this paper is a long-life balloon carrying a payload through a cable that flies at 20km altitude in near space. A dynamic model of the system, including the thermodynamics of the buoyancy body coupled with a hanging model of the pod, is developed using the Newton–Euler method. The buoyancy body consists of a helium balloon and a ballonet. A differential pressure difference-based altitude adjustment is achieved by tracking the pressure difference at the target altitude. A dynamic simulation of the buoyancy body with a slung pod in autonomous vertical takeoff and altitude regulation processes is presented. The internal thermodynamic variations and pressure differential of the buoyancy body are given. The air mass exchange and blower flow control of the ballonet are validated. The altitude holding error is analysed. The maximum pull force that the cable can withstand is calculated, and the maximum attitude angles of the pod during the ascending and descending processes are depicted. Simulation results provide basic knowledge for the structural design and payload installation of pods.

Security Length Associated with the Risk of Ammonia Tank Leak Using CTOA Criterion and ALOHA Software

Ammonia is a toxic gas and can cause tragic consequences for humans. The damage level depends on concentration and duration of exposure. The security length associated with the risk of a tank leak at the acute exposure level of 30 ppm (AEGL-1) has been computed. Two tools have been combined: the CTOA criterion and the ALOHA software. The CTOA, a measure of fracture resistance against ductile crack propagation, is implemented in Abaqus software to compute the size of a breach in a tank submitted to internal pressure. This breach is assumed to be initiated by a gouge-dent defect provoked by a shock. The ALOHA software introduces the tank's characteristics, contents, and breach size. This allows us to determine and visualize the security length. The security length depends on geographic and climatic conditions, and for an incident localized in Metz (France), a value of 436 m was found. The effects of internal temperature, wind speed, and breach position are studied. A comparison for the same reference state with hydrogen is also made.

Surface Strain Measurement for Non-Intrusive Internal Pressure Evaluation of a Cannon

Abstract Recent cutting-edge designs for gun barrels, projectiles, and propellants require testing, such as measuring the internal pressure during firing. However, there are concerns with the current drilling method to mount pressure transducers near the breech and chamber of the gun barrel where pressure is highest. To address this challenge, the team hereby presents an alternative, nonintrusive strain measurement method. This method focuses on determining the feasibility and accuracy of relating tangential strain along the sidewall of a gun barrel to the drastic internal pressure rise created during combustion. A transient structural, numerical model of a 155 mm gun barrel was created using ansys. The pressure was derived using the outline in Interior Ballistics of High Velocity Guns, version 2, and the model was validated using published experimental tangential strain testing data from a gun of the same caliber. The model was then used to demonstrate the ideal location for strain measurement along the sidewall of the chamber. Furthermore, three different pressure ranges were simulated in the model. The behavior of the tangential strain in each case indicates a similar trend to the internal pressure rise and oscillation due to a dominant frequency of the barrel. A method to predict internal pressure from external tangential strain was developed. The internal pressure predicted is within 4% of the pressure applied in the model. In the sensitivity study, the thickness and elastic modulus of the gun barrel were found to be the primary factors affecting tangential strain. Overall, this work helps to understand tangential strain behavior on the sidewall of a large-caliber gun barrel and lays the ground for an accurate prediction of internal pressure from external tangential strain.

Evaluation of thermal stresses in transversely isotropic piezoelectric disc with rotation and internal pressure

The paper deals with the analytical solution of transitional stresses in thin rotating disc composed of piezoelectric material under temperature and internal pressure. The stresses are evaluated in the rotating disc by using transition theory of Seth. The electric displacement relations and stresses are computed by using stress strain relations. The non-homogeneous differential equation is derived by substituting the obtained relations into the equilibrium equation. The formulated differential equation is solved with specified boundary conditions, applied pressure, electric displacement and stresses. Obtained results are exhibited graphically, analysed numerically and it is then concluded that transversely isotropic beryl is better than transversely isotropic magnesium material and transversely isotropic piezoelectric materials BaTiO4 and PZT-4.

Guidance for structural integrity assessment of smooth pipe elbows containing defects using R6

Recently, guidance for fracture assessment of defective elbows using the R6 failure assessment diagram (FAD) method has been included in R6 Revision 4 Amendment 13 (2023). This paper provides an overview of the new guidance and supporting validation. The guidance is validated using 75 cases of 3-D finite element (FE) elastic-plastic J results of smooth pipe elbows of various geometries with axial/circumferential internal/external semi-elliptical/extended/fully-circumferential surface cracks under internal pressure, in-plane/out-of-plane bending moment, torsion and various load combinations, by comparing the FE-based Option 3 failure assessment curves (FAC) with the R6 Option 2 FAC. The results show that, for 74 out of 75 cases, the FE-based Option 3 data points are above the R6 Option 2 FAC with reasonable conservatism when the guidance for evaluating the elbow stress intensity factor and limit load is followed. In other words, following the new guidance can lead to reasonably conservative assessment results.

Analytical evaluation of the elastic stresses in a multilayer spherical pressure vessel

An explicit-form solution is constructed for a problem on elastic deformation of a multilayer spherical vessel due to uniform internal pressure. The vessel is assembled of perfectly connected elastic layers whose material properties may arbitrarily vary across their thickness. The solution is constructed through the use of the single solid approach along with the modified scheme of the direct integration method which allow for the consideration of the multilayer vessel as a composite sphere with piecewise-variable profiles of the material properties. As a result, the original problem is reduced to solving a governing integral equation of the second kind whose solution is constructed in the form of the explicit dependence on the internal pressure. The solution is verified by the comparison with exact solutions derived by making use the method of tailored solutions for specific benchmark problems. By comparing our with the one for a functionally-graded sphere, whose material properties are evaluated through the use of the micromodular homogenization technique, the specific features of the circumferential stress are analyzed.

Plant cell wall structure and dynamics in plant-pathogen interactions and pathogen defence.

Plant cell walls delimit plant cells from their environment and provide mechanical stability to withstand internal turgor pressure as well as external influences. Environmental factors can be beneficial or harmful for the plants and vary substantially depending on prevailing combinations of climate conditions and stress exposure. Consequently, the physicochemical properties of plant cell walls need to be adaptive, and their functional integrity needs to be monitored by the plant. One major threat to plants is posed by phytopathogens, which employ a diversity of infection strategies and lifestyles to colonise host tissues. During these interactions, the plant cell wall represents a barrier that impedes the colonisation of host tissues and pathogen spread. In a tussle over maintenance and breakdown, plant cell walls can be rapidly and efficiently remodelled by enzymatic activities of plant and pathogen origin, heavily influencing the outcome of plant-pathogen interactions. We review the role of locally and systemically induced cell wall remodelling and the importance of tissue-dependent cell wall properties for the interaction with pathogens. Furthermore, we discuss the importance of cell wall-dependent signalling for defence response induction and the influence of abiotic factors on cell wall integrity and cell wall-associated pathogen resistance mechanisms.

Thermal stress distribution in a tube of natural rubber/ polyurethane and subjected to internal pressure and mechanical load

This article deals with the study of thermal stress distribution in a tube made of natural rubber/polyurethane material and subjected to internal pressure and mechanical load. From the obtained results, it is noticed that natural rubber material of the tube requires higher pressure to yield at the internal surface in comparison to tube made of polyurethane, for the initial yielding stage. Moreover, the tube of natural rubber material requires maximum hoop stress at the external surface as compared to the tube of polyurethane material. Values of the hoop/radial stress also increase with increasing temperature/mechanical loads in the contraction/extension region of the tube. The tube of natural rubber material is more comfortable than that of polyurethane.

Supine Sleep-Promoting Baby Mattress: SIDS Prevention and Athlete Injury Relief

Sudden Infant Death Syndrome (SIDS) is a leading cause of death in infants aged one to 12 months, primarily occurring during sleep. Consequently, there is considerable interest among researchers and healthcare professionals regarding the sleeping environment and potential risk factors. One identified risk factor is infants sleeping prone (on their stomach), making supine (on the back) sleeping the recommended position. Associate Research Fellow Shing-Jye Chen from the Department of Sports Science Research at the Taiwan Institute of Sports Science (TISS) is developing a hammock-like air-based baby mattress covered with breathable mesh. This mattress is designed to promote supine sleeping and prevent babies from rolling onto their stomachs during sleep. It features air tubing within tensioned mesh fabric that automatically adjusts to suspend and support the baby’s weight. This design increases the contact surface area between the baby and the mattress, reduces contact pressure, and provides evenly distributed support as the baby grows. Chen takes an interdisciplinary approach, collaborating with experts in baby breathing, sleeping patterns, and biomechanics to develop solutions aimed at reducing the risk of SIDS based on scientific evidence, safety, and effectiveness. In a pilot study, Chen collected data on the mattress’s performance using weights to simulate babies of different ages. His team will explore the relationship between weight and the measured pressure values at different internal air pressures within the inflatable tubing design. The potential application of this product design may extend to injured athletes, particularly in areas where injuries contact the mattress surface, thereby reducing stress.

Case of colon perforation due to segmental absence of intestinal musculature accompanied by cancer treated with colonic resection and anastomosis

BackgroundSegmental absence of intestinal musculature (SAIM) is a partial defect of intestinal muscularis propria without diverticulum. Many reports indicate that the increase in intestinal pressure caused by enemas or endoscopic examinations leads to bowel perforation, but there are few reports involving malignant tumors. Moreover, few reports have had good outcomes after performing one-stage intestinal anastomosis.Case presentationA 60-year-old male came to the office with right-side abdominal pain, and was diagnosed with acute generalized peritonitis caused by ascending colon perforation. Emergency laparotomy was performed, and oval and smooth perforation at the ascending colon was observed, which caused ascites with feces. In addition, there was a tumor on the distal side. The terminal ileum was not dilated, so the cause of the perforation was more likely the SAIM-related thin intestinal wall rather than increased internal intestinal pressure due to obstruction of the tumor. Therefore, a right hemicolectomy with functional end-to-end anastomosis (FEEA) between the ascending colon and ileum was performed, rather than creating a stoma. On pathological examination, the resected bowel segments had a partial defect of intestinal muscularis propria around the perforation, leading to the diagnosis of SAIM. The patient had a favorable postoperative course without anastomotic issues and was discharged safely.ConclusionsThis case implies that initial intestinal anastomosis can be performed without creating a stoma when SAIM is suspected from the shape of the perforation and proximal intestine. This case report suggests surgeons should keep SAIM in mind during operations for colon perforations.

Analysis of multi-phase lag gradients for a spherical cavity due to prescribed internal pressure

A refined multi-phase lag model is proposed here for a homogeneous unbounded thermoelastic spherical cavity in a curvilinear coordinate system. The associated solutions are obtained by forming non-dimensional vector matrix equations and applying Eigen value approach in the transform domain. The results have been verified using the valid boundary conditions associated with physical and field variables. Mathematica and MATLAB platforms are used for numerical analysis and graphical representation.

Optimizing performance of hybrid fiber reinforced overwrapped pressure vessel

Composite overwrapped pressure vessels (COPVs) offer significant weight advantages over traditional all-metal vessels particularly in industries like aerospace, automotive and pharmaceutical, but pose unique challenges in mechanical design, fabrication, and testing. Despite their benefits, COPVs are susceptible to stress rupture failure, which can lead to catastrophic consequences during operation. This failure mode is not fully understood, with burst pressure-induced extreme stress concentrations and dynamic loading primarily contributing to rapid deformation and strain. To address these concerns, a comprehensive investigation was conducted, focusing on optimizing and examining the effects of optimum winding angle and lay-up pattern configuration on burst pressure in vessels under internal pressure. Finite element modeling analyzed the burst pressure behavior of COPVs with a 4 mm thick aluminum core cylinder and varying layers of carbon/fiber epoxy, each with a constant thickness. ABAQUS composite modeler generated 18 COPV models with carbon fiber/epoxy plies, ensuring uniform thicknesses while exploring different fiber orientations. The effects of ply stacking sequence were analyzed through finite element analysis for all models, comprising varying layers with uniform thicknesses. Attention was paid to failure criteria, methodically evaluating the burst strength of the Al/CFRPC COPVs This exhaustive analysis yielded an optimal COPV design profile characterized by a precisely calibrated ply stacking sequence of [24.50, −24.50] PP winding pattern and six (6) arranged layers. The stress-strain distribution analysis of the Composite Overwrapped Pressure Vessel (COPV) revealed both a uniform distribution of stress across its surface and extreme stress concentration, particularly peaking towards the polar boss region. This concentration is discernible due to variations in ply thickness induced by the overwrapped fiber orientation. This investigation provides valuable insights for optimizing COPV design and enhancing its performance and reliability in various applications.

Understanding perioperative risk determinants in carotid endarterectomy: the impact of compromised circle of Willis morphology on inter-hemispheric blood flow indices based on intraoperative internal carotid artery stump pulse pressure and backflow patterns.

Carotid artery stenosis (CAS) often requires surgical intervention through carotid endarterectomy (CEA) to prevent stroke. Accurate cerebrovascular risk assessments are crucial in CEA, as poor collateral circulation can lead to insufficient interhemispheric blood flow compensation, resulting in ischemic complications. Therefore, understanding perioperative risk determinants is vital. This study aims to determine the impact of compromised circle of Willis (CoW) morphology on inter-hemispheric blood flow, focusing on indices based on intraoperative internal carotid artery stump pulse pressure and backflow patterns. In 80 CAS patients who underwent CEA, preoperative CT angiography for CoW was conducted. Patients were categorized into five subgroups based on their CoW anatomy and three additional groups based on intraoperative internal carotid artery (ICA) stump backflow patterns evaluated by the surgeon. Continuous blood pressure signals, including systolic, diastolic, mean, and pulse pressure values, were recorded during the procedure. The relationship between CoW anatomical variants and the systolic and diastolic segments of the averaged pressure waveforms, particularly diastolic pressure decay, was analyzed. The correlation between CoW anatomy and stump backflow intensity was also examined. Significant variability in ICA stump backflow and pressure values was evident across CoW variants. Patients with compromised CoW morphology exhibited weaker backflow patterns and lower ICA stump pulse pressure values, consistent with impaired interhemispheric blood flow. Notably, ICA stump diastolic pressure decay was consistent across most CoW variant groups, indicating developed collateral circulation in cases with CoW anomalies. Thus, impaired CoW integrity is associated with compromised interhemispheric blood flow indices based on intraoperative ICA stump pulse pressure and backflow patterns during CEA. Integrating intraoperative pulse waveform analysis with preoperative CT angiography provides a more detailed assessment of cerebrovascular risk, guiding the selective use of shunts. This combined approach may improve surgical outcomes and patient safety by identifying patients at increased risk of perioperative neurological events due to CoW anomalies.

Mechanical behaviour of rigid-flexible combined structures: Aluminium-inflated membrane beams for application in floating photovoltaic platform

This study aims to investigate the bending and failure behaviour of aluminium-inflated membrane beams for their applications in floating photovoltaic platforms. Four-point bending tests are conducted for a range of inflated pressures and two different deck heights to assess their effect on structural stiffness and ultimate bearing capacity. Meanwhile, the surface-based fluid cavity method is employed to develop the finite element model with the material properties determined by independent coupon-level tests. The bearing capacity of the aluminium-inflated membrane beam is positively correlated with the internal pressure and deck height. The midspan strain distribution is similar to those of the traditional four-point bending beam with the upper part undergoing compression and the lower part experiencing tension, however, the structural behaviour at the failure stage is different. Failure typically occurs due to localised depressions at the loading points on the aluminium deck, ultimately leading to structural failure. The numerical model closely matches the experimental data for the initial inflated and bending configurations, exhibiting a deviation of only 0.10 % to 0.46 % in diameter and 0.32 % to 5.57 % in equivalent bending stiffness. A parametric study shows that the loading properties of the beam are more sensitive to the internal pressure than the deck height and thickness.

Numerical Study on Effect of Overload and Unloading on Mechanical Properties of Shield Segmental Lining Bearing Internal Water Pressure

Numerical Study on Effect of Overload and Unloading on Mechanical Properties of Shield Segmental Lining Bearing Internal Water Pressure