Cushion Effect Research Articles

Enhanced anti-icing and anticorrosion properties of nano-SiO2 composite superhydrophobic coating constructed by a large-scale micropillar array approach

The ordinary superhydrophobic coating exhibits insufficient anti-icing properties in the low temperature and high humidity environment and poor corrosion resistance after long-term immersion. In this work, the modified nano-silica superhydrophobic coating with the large area micropillar array structure was constructed innovatively on the fluorocarbon varnish coating by a straightforward net embossing method and layer-by-layer assembly techniques to remedy these deficiencies. The anti-icing test results showed that the micropillar array structures could reduce the contact area between water droplets and cold surfaces. It also generates a stronger air cushion effect, which effectively delayed the freezing time and decreased the deicing shear force. Meanwhile, a larger microgroove density per unit area was achieved by reducing the micropillar widths, which further increased the freezing delay time, enhanced icephobic stability, and decreased the deicing shear force. The results of electrochemical impedance spectroscopy test showed that the infiltration of the corrosive medium was delayed by a large amount of air trapped in the microgrooves, so the impedance modulus values were still above 1011 Ω·cm2 after 26 days of immersion in 3.5 wt% NaCl solution. This work provides a new idea for improving the anti-icing properties and corrosion resistance of superhydrophobic coatings by constructing a large area of micropillar array structures on organic coatings.

A study on obstetric and perinatal outcome in a pregnancy complicated with oligohydramnios

Oligohydramnios, defined as when the AFI is less than 5. Definition of increased or decreased amniotic fluid volume are based on sonographic criteria. Oligohydramnios complicates approximately 1 to 2% of pregnancies Amniotic fluid provides the cushion effect against the constricting confines of the gravid uterus. It creates space and helps in musculoskeletal development of foetus, helps in normal fetal lung development and prevents compression of umbilical cord, placenta and hence protects the foetus from vascular and nutritional compromises. Oligohydramnios is associated with high risk adverse perinatal outcome like fetal distress, meconium aspiration, low APGAR, joint contracture, pulmonary hypoplasia etc., and associated with maternal morbidity in the form of increased rates of induction and/or operative interference. This study is conducted to find out the effects of oligohydramnios in determining the obstetric and perinatal outcome.To study, 1) Primary outcome- Obstetric outcome in terms of mode of delivery, indication for operative interference. 2) Secondary outcome- Neonatal outcome in terms of birth weight, Apgar score, colour of liquor, admissions to NICU. This is a prospective observational study conducted on 80 patients presenting to Department of Obstetrics and Gynecology at KIMS hospital, Bengaluru from January 2019 to June 2020 who were diagnosed with oligohydramnios with intact membranes with AFI<5cms using sonographic criteria. A total of 80 cases of Isolated Oligohydramnios were assessed. 38.7% cases delivered vaginally, 61.2% of cases underwent Cesarean section, 15% had meconium stained liquor, 15% had APGAR score of <7 at 1 minute, 42.5% had birth weight <2.5kgs and 37.5% of babies required NICU admissions. The present study was conducted to know the fetomaternal outcome in pregnancies with oligohydramnios. The study showed oligohydramnios was associated with higher rates of induction and Cesarean section and associated with Low birth weight babies.

Seismic response of nuclear power station with disconnected pile-raft foundation using dynamic centrifuge tests

The typical foundation type for a nuclear power station is the raft foundation in rock areas. With the power demand, it is possible that a nuclear power station located in soft soil areas. Traditional connected pile raft foundation (CPRF) has been successfully used in soft soil areas. However, under earthquake loads, high horizontal shear stresses and bending moments are generated in the pile head. Accordingly, researchers have sought to develop an innovative disconnected pile raft foundation (DPRF), and the benefits of DPRF have simulated increasing researches on it in the last two decades. In this study, a series of dynamic centrifuge tests were carried out to identify the effect of cushion and its thickness on the dynamic characteristics of the nuclear power station with DPRF. A withe noise excitation and three earthquake waves with different seismic intensities were adopted as ground motion. The seismic responses of soil, structure, and bending moment of piles were analysed. A cushion thickness equal to the diameter of piles is recommended. Comparing with the CPRF, the cushion layer of DPRF has an isolation benefit. With the gravel cushion, attention must be paid to the horizontal displacement, inclination and rocking of the superstructure.

Aggregation behaviors of gradient and diblock copoly(2-oxazoline) monolayers at the air-water interface

This study reveals the different behavior of amphiphilic gradient and diblock copolymers based on aliphatic and aromatic 2-oxazolines. The copolymers were synthesized by the polymerization of hydrophilic 2-ethyl-2-oxazoline with hydrophobic 2-(4-octyloxyphenyl)-2-oxazoline. The aggregation behavior of gradient and diblock copolymers with different ratios between hydrophilic and hydrophobic units was explored. Surface pressure (Π)–surface area ( A ) isotherms were measured at the air-water interface. The gradient copolymers produced higher surface pressures and smaller limiting areas, while the diblock copolymers exhibit relatively flexible behaviors. Langmuir–Blodgett monolayers were transferred on the hydrophilic silicon wafer substrates at various surface pressure levels, and the nanostructure of the films was investigated by using atomic force microscopy and X-ray reflectivity measurements. It was observed that the morphologies of gradient and diblock copolymers were similar, indicating that the films form a uniform monolayer. The diblock copolymers produced relatively small changes in thickness upon the compression, compared to the changes in gradient copolymer monolayer films. The thickness of the gradient copolymers which have a high hydrophilic ratio at low surface pressure increases by increasing surface pressure and hydrophobic ratio. But the diblock copolymers do not change the thickness by increasing the surface pressure and hydrophobic ratio. The results indicate that the gradient copolymer monolayers have relatively rigid domains where hydrophilic and hydrophobic parts are smeared. On the other hand, the diblock copolymer has a flexible hydrophilic cushioning effect. This study provides insights into the development of novel materials based on hydrophilic-hydrophobic interactions. • The different behavior of amphiphilic gradient and diblock copolymers based on aliphatic and aromatic 2-oxazolines. • The aggregation behavior of gradient and diblock copolymers with different ratios between hydrophilic and hydrophobic units was explored. • The gradient copolymer monolayers have relatively rigid domains where hydrophilic and hydrophobic parts are smeared. • The diblock copolymer has a flexible hydrophilic cushioning effect.

Design feature combinations effects of running shoe on plantar pressure during heel landing: A finite element analysis with Taguchi optimization approach.

Large and repeated impacts on the heel during running are among the primary reasons behind runners’ injuries. Reducing plantar pressure can be conducive to reducing running injury and improving running performance and is primarily achieved by modifying the design parameters of running shoes. This study examines the effect of design parameters of running shoes (i.e., heel-cup, insole material, midsole material, and insole thickness) on landing peak plantar pressure and determines the combination of different parameters that optimize cushion effects by employing the Taguchi method. We developed the foot–shoe finite element (FE) model through reverse engineering. Model assembly with different design parameters was generated in accordance with the Taguchi method orthogonal table. The effectiveness of the model was verified using the static standing model in Ansys. The significance and contribution of different design parameters, and the optimal design to reduce plantar pressure during landing, were determined using the Taguchi method. In the descending order of percentage contribution was a conforming heel-cup (53.18%), insole material (25.89%), midsole material (7.81%), and insole thickness (2.69%). The more conforming heel-cup (p < 0.001) and softer insole (p = 0.001) reduced the heel pressure during landing impact. The optimal design of running shoe in this study was achieved with a latex insole, a 6 mm insole thickness, an Asker C-45 hardness midsole, and a 100% conforming heel-cup. The conforming heel-cup and the insole material significantly affected the peak plantar pressure during heel landing. The implementation of a custom conforming heel-cup is imperative for relieving high plantar pressure for long-distance heel-strike runners.

Flat plate pressure impact on a still water surface: The effect of surrounding ambient pressure and plate size

The study of the impact between a rigid structure and water has raised the interest of many researchers in these recent years. This problem is relevant to various engineering applications, and particularly in the nautical environment (renewable energy, marine applications...). The present paper details an experimental investigation of rigid circular plates impacts into pure water. The analyses are based on impact pressure temporal signals, pressure impulses and frequency analysis recorded while the plates were impinging the still water surface. The measurement campaigns were carried out at the University Le Havre Normandy’s LOMC laboratory, in a recently developed experimental facility. In the previous experimental and numerical studies, it was observed that the magnitude of the peak slamming pressure is reduced if compared to the theoretical model predicted by von Karman (1929). Similar observations were made here and the decrease was partly attributed to the cushion effect resulting from the presence of an entrapped air layer between the rigid plate and the water free surface. This work aims to study the influence of the cushion effect on the impact pressure by using four rigid circular plates with different diameters in order to modify the volume of the air layer. Initially, the measurements were carried out for an ambient pressure equal to the atmospheric pressure. In a second part of the study, the same measurements were performed for two lower ambient pressures (about 75% and 50% of the atmospheric pressure) in order to minimise the cushion effect. And finally, a frequency analysis is presented with comparisons to theoretical results of Minnaert (1933) in order to correlate the air layer size to the pressure oscillation characteristics. The obtained results were compared with previous experimental and theoretical studies for low impact velocities (V≤1.2 m/s).

A tattoo-inspired electrosynthesized polypyrrole film: crossing the line toward a highly adherent film for biomedical implant applications

Polypyrrole (PPy) films have demonstrated promising application for implants due to their unique topographical and electronic properties. However, the limited PPy adhesiveness to metallic surfaces remains a challenge. Consequently, we propose a two-step technique for the surface modification of titanium (Ti) via a plasma electrolytic oxidation (PEO) step to serve as mechanical interlocking for the subsequent deposition of a highly adherent PPy film (PEO + PPy). Ti discs with machined and PEO-modified surfaces were used as controls. For the experimental groups, PPy film was deposited onto such surfaces by electrodeposition. Then, the role of machined and PEO surfaces in the synthesis, conductivity, microstructure, mechanical, electrochemical, microbiological, and biological properties of the PPy film was investigated. The results showed that a highly adherent “tattoo-inspired” PPy thin film was successfully achieved when the Ti surface was pretreated via PEO. PEO + PPy enhanced Ti mechanical and tribological properties by inducing a lower friction coefficient and wear loss due to the cushion effect of PPy film, besides promoting higher corrosion resistance. The “cauliflower-like” morphology of the PPy favored protein adsorption, calcium phosphate growth and demonstrated cell biocompatibility. The association between PEO and PPy film can be considered bioactive and is promising for the triggering of superior long-term stability of biomedical implants.

Vortical flow characteristics of a slender delta wing in ground effect

This study examined the ground effect on the vortical flow structures over a 70-deg-swept slender delta wing qualitatively and quantitatively using dye flow visualization and Particle Image Velocimetry techniques. The observations with dye visualization and PIV methods were conducted in the plan-view, side-view, and end-view planes with the angles of attack of α = 25° and 35°. The distance, h between the delta wing and the ground surface nondimensionalized with the chord, c of the delta wing, was considered as h/c = 0.1, 0.25 0.55 as well as the ground-free effect flow condition. Also, the experiments were performed at a normalized chordwise location of x/c = 0.8 over the end-view plane. The results demonstrate that magnitudes of leading-edge vortices progressively diminish when the delta wing moves from the ground-free effect region towards the wing location, h/c = 0.1. Also, the rate of inboard flow from the side leading-edge towards the central axis of the wing gets higher by the influence of the ground over the suction surface of the wing. When the wing altitude is lowered towards the ground surface, the size of the leading-edge vortex core region enlarges for both angles of attack, α = 25°, and 35°. The efficiency of the wing aerodynamics is positively affected by its closeness to the ground due to the air cushion effect that occurs as a result of the pressure increase on the suction surface of the wing due to the stagnation of air in the space between the delta wing and ground.

Protective Role of Obesity on Trauma Impact: A Retrospective Analysis of Patients with Surgical Blunt Bowel Mesenteric Injury Due to Road Traffic Accidents.

BackgroundThe “cushion effect” theory proposes that increased body mass index (BMI) is associated with less severe abdomen injury following blunt abdomen trauma, while the “obesity paradox” describes the protective effect of obesity against mortality. However, most previous studies used the abdominal abbreviated injury scale as the outcomes seemed to be inadequate owing to the injuries to the abdominal organs, such as the spleen and liver, which may be attributable to the force that caused the chest trauma. This study aimed to use adult trauma patients with surgical blunt bowel mesenteric injuries (BBMIs) to investigate the influence of obesity on the clinical outcomes and overall morbidities.MethodsThis retrospective study reviewed the data of all hospitalized trauma patients between 2009 and 2019 and included all patients with surgically proven small bowel, colon, or mesenteric injuries due to a road traffic accident. Comparison of the outcomes was performed among 123 patients with surgically proven BBMI, who were categorized by BMI into the normal-weight (n = 73, BMI<25 kg/m2), overweight (n = 37, 25≤BMI≤30 kg/m2), and obese groups (n = 13, BMI>30 kg/m2).ResultsThe obese group had a significantly lower incidence of isolated bowel injury (0%) compared with the normal-weight (35.6%) and overweight (16.2%) groups (p=0.005), but with higher incidence of isolated mesenteric injury or combined injury, although this was not significant. The obese group (92.3%) had a significantly higher percentage of overall morbidity than the normal-weight (61.6%) and overweight (70.3%) groups (p = 0.047). No significant difference was observed in the in-hospital mortality and 24-hour mortality among the three study groups.ConclusionThe study findings do not support the existence of a cushion effect and obesity paradox of obesity in blunt abdominal trauma.

Dynamic analysis of rock fall impact for a cantilever rock shed with geofoam cushion

In this study, the effect of geofoam compressible cushions on the impact response of the rockfall protection galleries located in a main artery highway connecting the southern Turkey to central Anatolia is investigated. Due to high occurrence risk of rockfall hazard at the mountainous region, permanent protection structures are required to prevent damage. Numerical analyses were carried out to evaluate the performance of EPS geofoam compressible layers with different stiffness characteristics on reducing the transmissibility of the impact forces caused by rockfalls. The kinetic energy levels, expected fall velocities for rock masses and the typical rockfall paths were assessed considering the topography of the hill. Dynamic explicit finite element analyses were performed to investigate the effect of the rockfall impact on a reinforced concrete rock shed. Stresses, strains and displacements on the structural section and the cushioning zone were monitored through the analyses. Based on the results, it was observed that geofoam has a significant effect on reducing the transmitted forces to the structure while increasing the impact duration. In terms of structural displacements, up to 75% reduction is observed when EPS cushions are placed on top of rock shed structure.

Numerical study of elbow erosion due to sand particles under annular flow considering liquid entrainment

Sand particle erosion is always a challenge in natural gas production. In particular, the erosion in gas–liquid–solid annular flow is more complicated. In this study, a three-phase flow numerical model that couples the volume of fluid multiphase flow model and the discrete phase model was developed for prediction of erosion in annular flow. The ability of the numerical model to simulate the gas–liquid annular flow is validated through comparison with the experimental data. On the basis of the above numerical model, the phase distribution in the pipe was analyzed. The liquid entrainment behavior was reasonably simulated through the numerical model, which guaranteed the accuracy of predicting the particle erosion. Additionally, four erosion prediction models were used for the erosion calculation, among them, the Zhang et al. erosion model predicted the realistic results. Through the analysis of the particle trajectory and the particle impact behavior on the elbow, the cushion effect of the liquid film on the particles and the erosion morphology generation at the elbow were revealed.

Cushioned on the way up, controlled on the way down during resuscitative endovascular balloon occlusion of the aorta (REBOA): investigating a novel compliant balloon design for optimizing safe overinflation combined with partial REBOA ability

BackgroundThere are a variety of devices capable of performing resuscitative endovascular balloon occlusion of the aorta (REBOA), with most containing compliant balloon material. While compliant material is ideal for balloon...

Investigating the Cushion Effect of Using Pebble Gravel in Bridge Foundations through Laboratory Cyclic Direct Shear Tests

Investigating the Cushion Effect of Using Pebble Gravel in Bridge Foundations through Laboratory Cyclic Direct Shear Tests

THE EFFECTS OF GLOBAL PANDEMIC ON STOCK LIQUIDITY IN THE NIGERIAN STOCK EXCHANGE

Stock liquidity plays important role in investors’ participation in any nation’s stock market. The global pandemic shock created market illiquidity especially among developing stock market like Nigerian stock market. However, the emergence of global pandemic via COVID-19 pandemic triggered declined market turnover (stock liquidity) which in turn created lack of confidence among stock investors in Nigeria. This study therefore examined the effects of Global pandemic on stock liquidity in the Nigerian stock market using stock turnover and COVID-19 pandemic as measure for stock market liquidity and global pandemic. The study employed expost facto research design using weekly data of both corona-virus pandemic and stock market turnover within the period of March, 2019 to February, 2022. The study employed Exponential GARCH (EGARCH) model and found a considerable negative consequence of Global Pandemic (Covid-19) on stock liquidity, implying that corona-virus pandemic has brought bad information (bad news) which deteriorate the liquidity in the stock exchange market. The study concluded that COVID-19 pandemic shock reduces stock liquidity in Nigerian stock exchange market. The study however recommended that government should put in place more palliative policies such as tax incentive and lowest interest rate on loan to individual and institutional investors which will cushion effect of COVID-19 pandemic and increase investors’ participation in the Nigerian stock market. Also, Nigeria stock market regulators should put in place sound measures that will enhance availability of stock information so as to arouse the interest more and new investors to the Nigerian Stock Market.

Ground Effect of a Two-Dimensional Flapping Wing Hovering in Inclined Stroke Plane

Abstract The ground effect aerodynamics and flow physics of a 2D dragonfly wing hovering (the Reynolds number is 157) in an inclined stroke plane are investigated via solving 2D unsteady incompressible laminar flow Navier–Stokes equations. An analysis road map is proposed to explain the influence of the ground on the flow field, pressure distribution on the wing surface, and the aerodynamic force. In the analysis road map, the flow relative to the wing surface induced by the wing motion and vortex is classified into vertical and parallel wing surface flows. The vertical flow impinges on the wing surface to form a positive pressure zone. In contrast, the parallel flow generates the boundary layer and further concentrated vortex and secondary vortex, which induce negative pressure on the wing surface. The ground impacts the flow relative to the wing in three ways: changing the trajectory of the shed vortex by the mirror effect, promoting the deformation and fusion of the vortices, and causing the cushion effect at extremely small ground clearance.

Fabrication of CL-20/HMX Cocrystal@Melamine-Formaldehyde Resin Core-Shell Composites Featuring Enhanced Thermal and Safety Performance via In Situ Polymerization.

Safety concerns remain a bottleneck for the application of 2,4,6,8,10,12-hexanitro- 2,4,6,8,10,12-hexaazaisowurtzitane (CL-20)/1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) cocrystal. Melamine–formaldehyde (MF) resin was chosen to fabricate CL-20/HMX cocrystal-based core–shell composites (CH@MF composites) via a facile in situ polymerization method. The resulted CH@MF composites were comprehensively characterized, and a compact core–shell structure was confirmed. The effects of the shell content on the properties of the composites were explored as well. As a result, we found that, except for CH@MF–2 with a 1% shell content, the increase in shell content led to a rougher surface morphology and more close-packed structure. The thermal decomposition peak temperature improved by 5.3 °C for the cocrystal enabled in 1.0 wt% MF resin. Regarding the sensitivity, the CH@MF composites exhibited a significantly reduced impact and friction sensitivity with negligible energy loss compared with the raw cocrystal and physical mixtures due to the cushioning and insulation effects of the MF coating. The formation mechanism of the core–shell micro-composites was further clarified. Overall, this work provides a green, facile and industrially potential strategy for the desensitization of energetic cocrystals. The CH@MF composites with high thermal stability and low sensitivity are promising to be applied in propellants and polymer-bonded explosive (PBX) formulations.

Physical modeling of floor failure above confined water: a case study in China

Coal mining in areas with deep confined water is very dangerous; to ensure safety, it is necessary to clarify the damage characteristics of the working face floor. To directly reflect the failure characteristics of the working face floor under the coupled effects of mining stress and confined water pressure, this study considers the mining above confined water in the deep coal seam of the II633 working face of the Hengyuan coal mine in the Huaibei mining area as the engineering background. With the use of the similar material simulation experimental method and a self-designed monitoring system for confined water diversion and a confined water loading system and a confined water lifting system that can directly reproduce the floor confined water lifting characteristics affected by floor failure during coal mining, the mining stress distribution patterns, deformation and failure characteristics of the overburden, and diversion characteristics of the confined water in the working face floor are investigated. The results show that the floor undergoes three stages of deformation in the horizontal direction: premining stress concentration-related compression (10–15 m ahead of the working face), postmining floor pressure relief-related expansion, and roof collapse-related stress recovery (the distance from the lagging working face is 15–20 m). In the vertical direction, a soft rock layer blocks the continuous transfer of mining stress to deeper layers and produces an important cushioning effect. In the process of coal mining, shear cracks easily develop in the coal wall in front of and behind the working face. After the coal seam is excavated, the length of the fractures that develop in the physical model is 27 cm. The confined water loading system can visually reproduce the hydraulic characteristics of the confined water during the mining process; that is, the confined water easily bursts at the front and back ends of the coal wall in the goaf. The error, as determined by comparison between the field measurement results and the theoretical calculation results, is only 0.617 m, verifying the reliability of the similar simulation method.

The effect of compressive stress on cavitation-erosion corrosion behavior of 304 stainless steel

PurposeThe purpose of this paper is to clarify the effect of compressive stress on cavitation-erosion corrosion behavior of 304 stainless steel.Design/methodology/approachCompressive stresses of 60 MPa and 120 MPa were applied to 304 stainless steel through a self-designed loading device, and cavitation erosion-corrosion tests were performed using an ultrasonically vibratory apparatus. Scanning electron microscope and X-ray diffraction were used to analyze the microstructure evolution, and corrosion behavior was studied by electrochemical analysis.FindingsThe cavitation weight loss of 304 stainless steel decreased with the compressive stress. After cavitation corroded for 8 h, the weight loss for the specimen with 120 MPa compressive stress was 5.11 mg/cm2, which was reduced by 56.7% from that of the specimen without loading stress (11.79 mg/cm2). The reason can be attributed to that compressive stress promoted the deformation-induced martensitic transformation during the cavitation process, which could not only provide a cushioning effect by absorbing cavitation impact energy but also improve the hardness of 304 stainless steel.Originality/valueCompressive stress was found to restrain the cavitation damage on 304 stainless steel, and the corresponding mechanism was proposed.

Resolution of Intramolecular Dipoles and a Push-Back Effect of Individual Molecules on a Metal Surface

Molecules consisting of a donor and an acceptor moiety can exhibit large intrinsic dipole moments. Upon deposition on a metal surface, the dipole may be effectively screened and the charge distribution altered due to hybridization with substrate electronic states. Here, we deposit ethyl-diaminodicyanoquinone molecules, which exhibit a large dipole moment in the gas phase, on a Au(111) surface. Employing a combination of scanning tunneling microscopy and noncontact atomic force microscopy, we find that a significant dipole moment persists in the flat-lying molecules. Density functional theory calculations reveal that the dipole moment is even increased on the metal substrate as compared to the gas phase. We also show that the local contact potential across the molecular islands is decreased by several tens of meV with respect to the bare metal. We explain this by the induced charge-density redistribution due to the adsorbed molecules, which confine the substrate’s wavefunction at the interface. Our local measurements provide direct evidence of this so-called push-back or cushion effect at the scale of individual molecules.

Multi-phase moving particle semi-implicit method for violent sloshing flows

As a meshless technique, the moving particle semi-implicit (MPS) method has extensive applications in numerical studies on violent sloshing flows. However, most prevalent research in the area is based on the single-phase MPS method, which ignores the existence of the air phase. This study aims to illustrate the necessity of multi-phase simulations for representing violently sloshing liquid through a comparative analysis between single-phase and multi-phase MPS methods, and to better figure out the air effect in the violent sloshing flows The MMPS (multi-phase MPS) method is firstly developed by introducing various multi-phase models into the single-phase IMPS (improved MPS) method, and then verified through simulations of two classical examples: the static multi-fluid system and the Rayleigh–Taylor instability. Subsequently, both the MMPS and the IMPS methods are applied to simulate liquid sloshing with increasing intensities, and their numerical results are compared with each other and with experimental data. The comparisons show that as the intensity of sloshing increases, the effect of the air cushion become non-negligible and the accuracy of the single-phase simulation significantly decreases, whereas the simulation results obtained by the MMPS method agree well with the experimental results in all cases. In particular, the MMPS method fully considers the air cavity formed in case of a violent wave breaking as well as its influence on waves of the sloshing liquid, and rectifies the overestimation of impact pressures in single-phase simulations.