Engineering Applications Research Articles

Microfluidic jet impacts on deep pools transition from capillary-dominated cavity closure to gas pressure-dominated closure at higher Weber numbers.

Studying liquid jet impacts on a liquid pool is crucial for various engineering and environmental applications. During jet impact, the free surface of the pool deforms and a cavity is generated. Simultaneously, the free surface of the cavity extends radially outward and forms a rim. Eventually the cavity collapses by means of gas inertia and surface tension. Our numerical investigation using an axisymmetric model in Basilisk C explores cavity collapse dynamics under different impact velocities and gas densities. We validate our model against theory and experiments across a previously unexplored parameter range. Our results show two distinct regimes in the cavity collapse mechanism. By considering forces pulling along the interface, we derive scaling arguments for the time of closure and maximum radius of the cavity, based on the Weber number. For jets with uniform constant velocity from tip to tail and We ⩽ 150 the cavity closure is capillary dominated and happens below the surface (deep seal). In contrast, for We ⩾ 180 the cavity closure happens above the surface (surface seal) and is dominated by the gas entrainment and the pressure gradient that it causes. Additionally, we monitor gas velocity and pressure throughout the impact process. This analysis reveals three critical moments of maximum gas velocity: before impact, at the instant of cavity collapse, and during droplet ejection following cavity collapse. Our results provide information for understanding pollutant transport during droplet impacts on large bodies of water, and other engineering applications, like additive manufacturing, lithography and needle-free injections.

Phototuning of Hyaluronic-Acid-Based Hydrogel Properties to Control Network Formation in Human Vascular Endothelial Cells.

In vitro network formation by endothelial cells serves as a fundamental model for studies aimed at understanding angiogenesis. The morphogenesis of these cells to form a network is intricately regulated by the mechanical and biochemical properties of the extracellular matrix. Here the effects of modulating these properties in hydrogels derived from phenolated hyaluronic acid (HA-Ph) and phenolated gelatin (Gelatin-Ph) are presented. Visible-light irradiation in the presence of tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate and sodium persulfate induces the crosslinking of these polymers, thereby forming a hydrogel and degrading HA-Ph. Human vascular endothelial cells form networks on the hydrogel prepared by visible-light irradiation for 45min (42W cm-2 at 450nm) but not on the hydrogels prepared by irradiation for 15, 30, or 60min. The irradiation time-dependent degradation of HA-Ph and the changes in the mechanical stiffness of the hydrogels, coupled with the expressions of RhoA and β-actin genes and CD44 receptors in the cells, reveal that the network formation is synergistically influenced by the hydrogel stiffness and HA-Ph degradation. These findings highlight the potential of tailoring HA-based hydrogel properties to modulate human vascular endothelial cell responses, which is critical for advancing their application in vascular tissue engineering.

DFT and TD‐DFT Study of Many‐Body and Hydrogen Bonding Interactions: Nitrosamine Oligomers

AbstractThis study focuses on the properties and intermolecular interactions of nitrosamine oligomers, which are important in both semiconductor manufacturing and nuclear waste management. The study explores various configurations of nitrosamine oligomers, ranging from monomers to pentamers in linear, ladder, and cyclic clusters, with the finding that dimer cyclic forms and hexamers and above are unstable. Many‐body analysis revealed that two‐body interaction energies made remarkable contributions to the binding energy, while the sum of 3‐, 4‐, and 5‐body energy contributed less, indicating the decrease in stability of nitrosamine from dimer to pentamer clusters. Using advanced computational techniques, such as dispersion‐corrected B3LYP‐D3 and TD‐DFT, the study investigates the vibrational modes and electronic absorption spectra of nitrosamine oligomers. The results reveal that different configurations can significantly affect the vibrational modes and electronic properties of nitrosamine oligomers. The NH2 symmetric and asymmetric modes were particularly intense in various forms of nitrosamine oligomers. The wavelengths of electronic transition, oscillator strength, and HOMO to LUMO gap were reported. Additionally, the study reports on nitrosamine oligomers’ hydrogen‐bonded cooperativity and binding energy contributions. Overall, these findings offer valuable insights into the stability and properties of nitrosamine oligomers, with potential applications in materials science and chemical engineering.

Improved Equivalent Strain Method for Fatigue Life of Automobile Aluminum Alloy

Improved Equivalent Strain Method for Fatigue Life of Automobile Aluminum Alloy

Physicochemical and biological characterization of propolis-loaded composite polyamide-6/soybean protein nanofibers for wound healing applications

Dressings are pivotal in aiding wound recovery, yet they are burdened by significant constraints. In addition to possessing antibacterial properties, the effectiveness of a wound dressing must be rigorously assessed for its potential utility across diverse medical applications. Propolis (Pro) is widely acknowledged for its antioxidant, antibacterial, and anti-inflammatory properties, positioning it as a promising candidate for wound healing and tissue engineering applications. This study presents a novel composite nanofiber (NF) material comprising polyamide-6 (PA6) and soybean protein as matrix components, incorporating Pro as a payload. We aimed to mimic the extracellular matrix, thus promotion the proliferation and adhesion of mouse embryonic fibroblast cells (NIH3T3) on the scaffold's surface. The morphology and composition of the NFs, examined through scanning electron microscopy (SEM) imaging and Fourier-transform infrared (FTIR) spectroscopy. The Pro-loaded fibers exhibited diameters ranging from 102 to 270 nm. Notably, the NFs demonstrated a dose-dependent increase in porosity, water vapor transmission rate, and fluid uptake capacity. However, the hydrophilic categorized nanofibers (NFs) did not exhibit a concentration-dependent effect on contact angle measurements. After a 15-day period, the Pro-loaded fibers experienced degradation within the range of 39–53 %. Using UV–visible spectrophotometry, the amount of pro released was measured. The rates of release were found to be 29.93 %, 41.02 %, and 60.06 % within 24 h for PA6/Soy/Pro5 %, PA6/Soy/Pro10 %, and PA6/Soy/Pro20 % NFs, respectively. Importantly, our study showcased the significant inhibitory effects of Pro-loaded fibers on the growth of E. coli and S. aureus, with inhibition increasing proportionally with higher Pro concentrations. This observation underscores the potential of Pro-based composite NFs as effective antimicrobial agents for wound dressings and tissue scaffolds. Furthermore, the biocompatibility of the fabricated nanofibrous mats was confirmed through the MTT test, affirming the non-toxic nature of all formulations. SEM imaging further demonstrated the optimal adhesion of cells on the NFs, confirming the findings of the MTT test and highlighting the suitability of Pro-loaded NFs for cell attachment and proliferation.

Elderberry (Sambucus nigra) and hawthorn (Crataegus oxyacantha) extract additives in carboxymethyl chitosan scaffolds for osteochondral tissue engineering applications

Elderberry (<i>Sambucus nigra</i>) and hawthorn (<i>Crataegus oxyacantha</i>) extract additives in carboxymethyl chitosan scaffolds for osteochondral tissue engineering applications

Non-linear modeling and parameter identification of a bolted joint using substructure synthesis theory

Engineering applications require accurate modeling and parameter identification to anticipate bolted joint behavior under different loading circumstances. Bolted joints are extensively used in civil and mechanical structures. In this research study, cubic stiffness non-linearity is examined and a comprehensive model, which can exhibit the non-linearity of joint behavior, is developed. This is achieved by modeling the bolted joint which is connected at one end of a cantilever beam. Mathematical model is established using concept of sub structure synthesis theory by considering non-linear translational stiffness and non-linear rotational stiffness as a boundary condition. Non-dimensional natural frequencies are estimated by assuming stiffness parameters and joint parameter estimation for translational spring having nonlinear stiffness is calculated using second order curve fitting technique. Furthermore, estimated and exact value of cubic stiffness coefficient are compared. The experimental results shows that the percentage error of estimation for all the modes are less than 8%. The experimentally determined natural frequencies are further contrasted with an analytical results to validate a precision of generated model. Present work contributes in improving the bolted joint analysis by providing a solid non-linear modeling and parameter identification methodology. This methodology enhances design practices and ensures the durability of engineering structures and mechanical systems by improving bolted joint comprehension.

Mechanical properties of scCu-rGO /Cu composites reinforced with Cu2O transition layer constructed by supercritical CO2 deposition

Reduced graphene oxide (rGO) with surface-loaded Cu particles (scCu-rGO) was prepared by supercritical CO2 deposition, and Cu matrix composites with scCu-rGO as a reinforcement (scCu-rGO/Cu composites) were successfully prepared by ball milling for different times and spark plasma sintering (SPS). The scCu-rGO/Cu composites prepared with a ball milling time of 20 h exhibited high electrical conductivity (96.3 % IACS), tensile strength (240 MPa), and elongation (37 %). The outstanding properties are mainly ascribed to the uniform distribution of rGO by the ball milling process and rGO promoted by loading Cu particles onto its surface through supercritical deposition, which led to an interfacial reaction between rGO and Cu, resulting in the formation of a Cu2O transition layer with a load-transferring effect that enhanced the mechanical properties of the composites. Based on the experimental results, the strength of scCu-rGO/Cu composites is mainly enhanced by synergistic strengthening through grain refinement, Orowan looping and load transfer strengthening. This study demonstrates that the use of supercritical deposition to construct Cu2O transition layers can result in a strength-plasticity and high electrical conductivity match in scCu-rGO/Cu composites. The findings presented here offer new insights for innovative design of Cu matrix composites for advanced engineering applications by using supercritical deposition.

Incorporation of self-heating effect into a thermo-mechanical coupled constitutive modelling for elastomeric polyurethane

Elastomeric polyurethane (EPU) is characterised by distinctive mechanical properties, including high toughness, low glass transition temperature, and high impact resistance, that render it indispensable in diverse engineering applications from soft robotics to anti-collision devices. This study presents a thermo-mechanically coupled constitutive model for EPU, systematically incorporating hyperelasticity, viscoelasticity, thermal expansion, and self-heating effect in a thermodynamically consistent manner. Experimental data, obtained from previous studies, are then used for parameter identification and model validation, including iterative updates for temperature parameters considering the self-heating effect. Subsequently, the validated model is integrated into finite element codes, i.e., user subroutine to define a material’s mechanical behaviour (UMAT) based on the commercial finite element software ABAQUS, for the computation of three-dimensional stress-strain states, facilitating the analysis of the structural response to various mechanical loads and boundary conditions. The results obtained from simulations are compared with analytical solutions to confirm the precision of Finite Element Method (FEM) implementation. The self-heating effect is further analysed under different strain rates and temperatures. To validate the engineering significance of the FEM implementation, a plate with a hole structure is also simulated. In conclusion, this research provides a robust tool for engineers and researchers working with soft materials, enhancing their understanding and predictive capabilities, notably addressing the self-heating effect in thermo-mechanical behaviours.

Exploring self-crosslinked hydrogel: Carboxymethyl chitosan and oxidized alginate for wound healing applications

This study reports the development and evaluation of self-healing hydrogel composed of carboxymethyl chitosan (CmCh) and oxidized alginate, with a focus on wound healing applications. Oxidized alginate was synthesized via metaperiodate oxidation and characterised. The hydrogels were formulated using Schiff base reactions with two weight ratios of oxidized alginate and CmCh, and their cross-linking mechanism was proposed. The developed hydrogels were characterised for their gelation, pH, self-healing capability, conductivity, and injectability. The optimized hydrogel was further evaluated for antibacterial activity, cytotoxicity, haemocompatibility, and in vitro wound healing studies. Results revealed that hydrogels with the lowest ratio of oxidized alginate to CmCh exhibited superior gelation, tensile strength, and injectability without needle clogging. Additionally, rapid self-healing of hydrogels was confirmed via Scanning Electron Microscope (SEM) analysis. The optimized hydrogel displayed good antibacterial activity against Staphylococcus aureus and Escherichia coli, alongside haemocompatibility. Additionally, in vivo studies demonstrated comparable wound healing efficacy to marketed formulations and significant improvement over control groups. These findings indicates the potential of self-healing hydrogels made up of oxidized alginate and CmCh for tissue engineering applications.

High-Energy Facet Engineering for Electrocatalytic Applications.

The design of high-energy facets in electrocatalysts has attracted significant attention due to their potential to enhance electrocatalytic activity. In this review, the significance of high-energy facets in various electrochemical reactions are highlighted, including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), nitrogen reduction reaction (NRR), and carbon dioxide reduction reaction (CRR). Their importance in various electrochemical reactions and present strategies for constructing high-energy facets are discussed, including alloying, heterostructure formation, selective etching, capping agents, and coupling with substrates. These strategies enable control over crystallographic orientation and surface morphology, fine-tuning electrocatalytic properties. This study also addresses future directions and challenges, emphasizing the need to better understand fundamental mechanisms. Overall, high-energy facets offer exciting opportunities for advancing electrocatalysis.

Highly Fault-Tolerant Systolic-Array-Based Matrix Multiplication

Matrix multiplication plays a crucial role in various engineering and scientific applications. Cannon’s algorithm, executed within two-dimensional systolic arrays, significantly enhances computational efficiency through parallel processing. However, as the matrix size increases, reliability issues become more prominent. Although the previous work has proposed a fault-tolerant mechanism, it is only suitable for scenarios with a limited number of faulty processing elements (PEs). This paper introduces a pair-matching mechanism, assigning a fault-free PE as a proxy for each faulty PE to execute its tasks. Our fault-tolerant mechanism comprises two stages: in the first stage, each fault-free PE completes its designated computations; in the second stage, computations intended for each faulty PE are executed by its assigned fault-free PE proxy. The experimental results demonstrate that compared to the previous work, our approach not only significantly improves the fault tolerance of systolic arrays (applicable to scenarios with a higher number of faulty PEs) but also reduces circuit areas. Therefore, the proposed approach proves effective in practical applications.

Constructing hydroxyoxime-functionalized ionic liquid [BHIB][NTf2] for the separation of Mo(VI) from U(VI)

We describe here a hydroxyoxime-functionalized ionic liquid, 1-butyl-3-(4-hydroxy-3-((hydroxyimino)methyl)benzyl)-1H-imidazol-3-ium bis((trifluoromethyl)sulfonyl)amide ([BHIB][NTf2]), for the isolation and purification of 99Mo from 235U. This material exhibits remarkable extraction efficiency for Mo(VI) from 0.1 to 2 M HNO3 and can effectively distinguish Mo(VI) from U(VI). The attained highest separation factor (SF) of Mo(VI) over U(VI) exceeds 104, thus setting a new record for their separation. Additionally, the extracted Mo(VI) can be efficiently recovered using either NH4OH or the mixture of NH4OH and (NH4)2CO3. This excellent extraction performance is sustained even after five cycles. The extraction efficiency remains stable following exposure to 150 kGy gamma irradiation, thus providing robust experimental support for potential engineering applications. Slope analysis and EXAFS results indicate that [BHIB][NTf2] forms a 2:1 complex with Mo(VI) during the extraction process primarily driven by a cation exchange mechanism. When one equivalent of Mo(VI) migrates from the aqueous phase to the organic phase, each of two equivalents [BHIB][NTf2] remove one of H+ and migrate to the aqueous phase to maintain charge balance. This investigation introduces a highly efficient and environmentally benign method for separation, alongside providing novel insights into ligand design for the efficacious differentiation of Mo(VI) and U(VI) under HNO3 conditions, potentially streamlining current methodologies.

Dynamic reliability analysis of angular contact ball bearing based on maximum entropy quadratic fourth moment method*

ABSTRACT Bearing failure occurs when the dynamic contact stress exceeds the yield strength of the bearing material during operation. To minimise the risk of bearing failure, a new reliability theory method is proposed based on the stress-strength model of bearings, incorporating random input variables to analyse the reliability of angular contact ball bearings (ACBBs) and quantify their dynamic performance. The maximum entropy quadratic fourth moment method is used to calculate the probability distribution of maximum orthogonal shear stress-strength of bearing, and the maximum entropy principle is used to obtain the approximation of the minimum human error factors. Additionally, reliability-based sensitivity indices are derived to investigate the parametric significance of random input variables. Using B218 bearing as an example, the engineering application of this method in dynamic reliability and reliability-based sensitivity analysis is illustrated. Monte Carlo simulation is performed to verify the accuracy and effectiveness of the method to provide benchmark results. The results show that the Poisson’s ratio have a greater influence on the dynamic reliability of ACBBs than other parameters. Improving parameters such as ball diameter, raceway groove curvature radius and contact angle can also improve the reliability of bearings to some extent.

Ground Tire Rubber as a Sustainable Additive: Transforming Desert Sand Behavior

AbstractManaging waste tires presents a significant challenge globally, particularly in regions experiencing high temperatures and shortage of landfill sites. This issue is affecting countries like Kuwait, where the abundance of waste tires is a major source of environmental and safety risks, particularly during the intensely hot summer months. This extreme heat has sparked numerous fires, leading to substantial air pollution due to thick black smoke. Given the limited disposal options, recycling waste tires and finding practical applications for ground tire rubber (GTR) is essential. To address the challenge, a comprehensive laboratory testing program was conducted, using locally produced rubber aggregates as an additive to Kuwait's local surface sands. Two new variables were examined namely the size and gradation of the GTR, and the density of the compacted mixes. For this purpose, two different sizes of rubber aggregates, fine and coarse produced locally, were utilized, and the impact of relative compaction on the strength and compressibility of the mixtures was investigated by testing samples compacted to the maximum density and to 95% of the maximum density. The results suggest that combining local surface sands with rubber tire additives results in a lighter, more permeable, and compressible material, contributing significantly to sustainable waste management. With 20% rubber additive the maximum dry density decreased by nearly 20%, and the permeability increased by 1.74–3.11 times and the compression index increased by 6.15 and 3.8 times with fine and coarse rubber respectively. The angle of friction remained unchanged at 36° with the addition of coarse rubber and decreased by 3°–4° with fine rubber. The change in behavior although not an increase in the strength and stiffness, offers a range of suitable practical applications in civil engineering and environmental management, including use as a drainage layer, embankment construction on soft ground, earth fill around retaining walls, an additive in asphalt mixes, and in manufacturing compressible tiles for sports facilities.

Alendronate releasing silk fibroin 3D bioprinted scaffolds for application in bone tissue engineering: Effects of alginate concentration on printability, mechanical properties and stability

3D bioprinting uses biomaterials combined with cells to develop living constructs. This study explores the optimization of natural polymers, including silk fibroin, gelatin, and alginate, as bioink for 3D bioprinting in bone tissue engineering. The physicochemical properties of the bioink were thoroughly examined, revealing high water uptake and reduced degradation rate due to the addition of silk fibroin. The compressive modulus increased with higher alginate concentration. Rheological analysis confirmed shear-thinning properties and viscoelasticity of the ink. Through meticulous parameter optimization, the ink achieved the highest print accuracy with 4 % w/v alginate content. The printed scaffolds exhibited both macro and micro porosity, making them suitable for bone tissue regeneration. Furthermore, the scaffolds remained stable in culture medium for 36 days. The optimal composition for the hydrogel was determined to be a blend of 5 % fibroin, 7 % gelatin, and 4 % alginate in equal ratios. The bioink demonstrated excellent biocompatibility and, when supplemented with alendronate, enhanced alkaline phosphatase activity in MG-63 osteoblast-like cells. This finding indicates the commitment of cells toward the osteoblastic phenotype. Overall, this study successfully optimized the bioink and bioprinting process for bone tissue engineering applications, highlighting its promising potential for future advancements in the field.

Measurement Of Spatial-Temporal Waves In The Laboratory Using Computer Vision Technolog

Given the complexity of ocean wave phenomena, physical modeling continues to be essential in various engineering and research applications. Wave height, a characteristic measured in nearly all projects, is commonly assessed using resistance/capacitance wave gauges. However, a significant limitation of these traditional wave gauges is their point-based nature, which restricts their ability to describe detailed spatial wave characteristics, especially during wave nonlinearity or when waveforms change. Furthermore, to reconstruct the 3D wave field, an array of wave gauges is often employed alongside an appropriate interpolation algorithm. Additionally, wave gauges may alter flow/wave conditions in specific scenarios. To address these limitations, various non-intrusive measurement techniques have been proposed. Gomit et al. (2022) classified these into stereoscopic, projection, and light-based methods, including LiDAR (Blenkinsopp et al., 2012), RGB-D cameras (Martínez-Aranda et al., 2018), and binocular stereo vision (Li et al., 2022). However, their applicability is constrained by factors such as optical setup complexity and device cost. With the rapid advancement of computer vision technology, it is possible to improve these issues and better describe temporal and spatial wave field variations using such techniques. This conference contribution details the reconstruction of the temporal and spatial 3D free water surface using photogrammetry techniques applied to images from consumer webcams. It also compares these results with measurements obtained from a wave gauge.

Electromagnetic Transverse Modes in Periodic Structures: Mathematical Analysis and Engineering Applications

This study explores the electromagnetic transverse modes in periodic structures, combining mathematical analysis with practical engineering applications. We showcase how the deliberate arrangement of materials, using Maxwell's equations and Bloch's theorem, may control and guide electromagnetic waves for novel applications in devices. We emphasize the progress made in photonic crystals and metamaterials, which have resulted in significant developments in fields such as optical computing and stealth technologies. The debate encompasses the potential of computational methods to further improve the functions of materials and devices. This paper highlights the important interaction between theoretical physics and applied engineering, which lays the foundation for future technical advancements in wave manipulation.

Postprocessing Workflow for Laboratory Diffraction Contrast Tomography: A Case Study on Chromite Geomaterials.

Texture stands as a fundamental descriptor in the realms of geology and earth and planetary science. Beyond offering insights into the geological processes underlying mineral formation, its characterization plays a pivotal role in advancing engineering applications, notably in mining, mineral processing, and metal extraction, by providing quantitative data for predictive modeling. Laboratory diffraction contrast tomography (LabDCT), a recently developed 3D characterization technique, offers nondestructive measurement of grain phases including their morphology, distribution, and crystal orientation. It has recently shown its potential to assess 3D textures in complex natural rock samples. This study looks at improving on previous work by examining the artifacts and presents a novel postprocessing workflow designed to correct them. The workflow is developed to rectify inaccurate grain boundaries and interpolate partially reconstructed grains to provide more accurate results and is illustrated using multi-scan examples on chromite sands and natural chromitite from the Upper Group 2 Reef layer in South Africa. The postcorrected LabDCT results were validated through qualitative and quantitative assessment using 2D electron back-scattered diffraction on polished sample surfaces. The successful implementation of this postprocessing workflow underscores its substantial potential in achieving precise textural characterization and will provide valuable insights for both earth science and engineering applications.

Effect of cell diameter variations on the mechanical behavior of aluminum foams: Experiments and modeling

Aluminum foams can be manufactured in a variety of cell sizes; however, existing models focus primarily on density and neglect the effect of cell size. Furthermore, aluminum foams with different cell diameters exhibit diverse mechanical properties. In this study, a quasi-static/dynamic compression test was performed to investigate the mechanical behavior, damage patterns, and damage mechanisms of aluminum foams with different cell diameters. The results demonstrate that the compressive properties of aluminum foams undergo significant changes. As the cell diameter increases, normalized initial damage stress and Young's modulus also increase, leading to enhanced energy absorption. However, this increase in cell diameter negatively affects the energy absorption efficiency, resulting in increased instabilities. A finite element analysis was conducted using the LS-DYNA finite element software to investigate the behavior of aluminum foils under all the experimentally tested loading regimes. The simulation results reveal that the deformation zone formed due to collapse diminishes with increasing cell diameter. More importantly, a new damage mechanism named central cell cleavage was reported, which increased the energy absorption capacity and amplified the instability during deformation. This study offers novel insights into the mechanical behaviors exhibited by aluminum foams, thereby facilitating their application in structural engineering.