Search Results (292)

High-entropy alloys (HEAs) possess multi-element composition and uniform structure, exhibiting superior microstructure and properties compared to traditional alloys. However, the multi-element composition of HEAs results in a complex internal composition configuration with exceptionally high hardness and strength, leading to various machining defects under cutting loading such as poor surface roughness, excessive machining temperature, and cutting tool wear. This study investigates the milling performance of FeCoNiCrMn_x HEAs with different elemental ratios subjected to various ultrasonic-assisted milling techniques, aiming to identify the better ultrasonic assisted technique and machining process parameters. The ultrasonic-assisted milling techniques include single-axis ultrasonic, dual-axis ultrasonic, and triple-axis ultrasonic. The side milling experiments were performed on three different elemental ratios of HEAs, e.g., FeCoNiCrMn_0.1, FeCoNiCrMn_0.5, and FeCoNiCrMn_1.0 workpieces. The study is divided into two phases. Each alloy workpiece undergoes side-milling experiments using two designated combinations of feed rate and radial cutting depth subjected to various ultrasonic-assisted milling techniques in the first phase. The purpose is to identify which ultrasonic-assisted milling technique may provide the better surface quality for different elemental ratios and to analyze the performance of various cutting condition combinations in terms of surface roughness and cutting tool wear. Based on the results of the first phase, the better ultrasonic-assisted milling technique is selected and an L₉ Taguchi orthogonal array is then employed for process parameter planning, by varying spindle speed, feed rate, and radial cutting depth to investigate the effects of different process parameter combinations on machining performance of HEAs with different elemental ratios. The results show that ultrasonic assistance significantly improves the cutting performance in aspects such as reduction of cutting force and cutting tool wear, and the surface quality of alloys with high Mn content. In the first phase experiment, as compared to milling without assistance, the surface roughness may be reduced up to approximately 17.86% by single-axis ultrasonic-assisted milling using the Set 1 process parameters for different elemental ratios, while it achieves up to approximately 34.4% in surface roughness and approximately 17.68% in cutting tool wear using the Set 2 process parameters. The results from the second phase of experiments reveal a more moderate fluctuation of surface roughness and an approximate reduction from 22.03% to 314.27%, with an approximate reduction from 3.64% to 54.45% in cutting force, and an approximate reduction from 0.58% to 94.77% in cutting tool wear for the higher Mn content alloy in contrast to the lower Mn content one. The integrity of the surface morphology is significantly improved as the elemental ratio, x, is increased to 1.0, resulting in a reduction in machined surface deformation and more consistent milling marks on the machined surface, which indicates a higher stable state of machining quality. Full article

This research focuses on the structural and bonding characteristics of the Al(111)/CrB2(0001) interface, aiming to clarify the adhesion mechanisms of CrB₂ coatings on aluminum composites. Utilizing first-principles calculations grounded in density functional theory (DFT), we systematically examined the interfacial properties of both clean and doped Al(111)/CrB₂(0001) systems. And key aspects such as binding energy, electron density distribution, and chemical bonding types were thoroughly evaluated. The results demonstrate that the Cr-terminated HCP stacking arrangement at the Al(111)/CrB₂(0001) interface achieves the maximum adhesion work and minimal interfacial energy. This is primarily due to the strong covalent interactions between Al-p and Cr-p orbitals, which contribute to exceptional interfacial strength and stability. Furthermore, the incorporation of Fe, Mg, and Mn at the interface not only markedly improves working adhesion but also effectively lowers the interfacial energy for the Cr-terminated HCP stacking configuration. This phenomenon significantly enhances the overall bonding performance of the Al/CrB₂ system. Conversely, the addition of Cu, Zn, and Si leads to an increase in interfacial energy, negatively impacting the bonding quality. Analysis of binding energies at the doped interface revealed a consistent trend among the elements: Fe > Mn > Mg > Si > Zn > Cu. These findings offer valuable guidance for the design and optimization of Al-based surface coatings with improved performance. Full article

Archaeal lipids, defining a primordial life domain alongside Bacteria and Eukarya, are distinguished by their unique glycerol-1-phosphate backbone and ether-linked isoprenoid chains. Serving as critical geochemical biomarkers, archaeal lipids like glycerol dialkyl glycerol tetraethers (GDGTs) underpin paleoclimate proxies, while their phylum-specific distributions illuminate phylogenetic divergence. Despite the maturity of Mass Spectrometry-based quantitative biomarkers—predominantly those with established structures—becoming well-established in geochemical research, systematic investigation of archaeal lipids as natural products has notably lagged. This deficit manifests across three key dimensions: (1) Extraction methodology lacks universal protocols adapted to diverse archaeal taxa and sample matrices. While comparative studies exist, theoretical frameworks guiding method selection remain underexplored. (2) Purification challenges persist due to the unique structures and complex isomerization profiles of archaeal lipids, hindering standardized separation protocols. (3) Most critically, structural characterization predominantly depends on decades-old foundational studies. However, the existing reviews prioritize chemical structural, biosynthetic, and applied aspects of archaeal lipids over analytical workflows. This review addresses this gap by adopting a natural product chemistry perspective, integrating three key aspects: (1) the clarification of applicable objects, scopes, and methodological mechanisms of various extraction technologies for archaeal lipids, encompassing both cultured and environmental samples; (2) the elucidation of separation principles underlying polar-gradient lipid fractionation processes, leveraging advanced chromatographic technologies; (3) the detailed exploration of applications for NMR in resolving complex lipid structures, with specialized emphasis on determining the stereochemical configuration. By synthesizing six decades of methodological evolution, we establish a comprehensive analytical framework, from lipids extraction to structural identification. This integrated approach constructs a systematic methodological paradigm for archaeal lipid analysis, bridging theoretical principles with practical implementation. Full article

The current commitment towards aviation climate neutrality and decarbonisation is boosting research programmes on disruptive aircraft configurations featuring sustainable powertrains and fuel-efficient airframes. This trend is pushing the design towards high-aspect-ratio wings made of lightweight structures housing distributed propulsion systems. Airframe preliminary sizing and mass estimation of non-conventional configurations, if performed using legacy methodologies based on experience, gathered with traditional configurations may result in non-optimised and non-viable designs. Therefore, a physics-based optimisation approach may allow more accurate sizing and airframe mass estimation. The methodology suggested in this paper is based on the automatic generation of a global finite element model to estimate the weight and determine a feasible material distribution for the wing box structure of a strut-braced wing configuration by means of size optimisation. Composite materials with defined stacking sequences were assigned to the wing components and structural weight minimised with the aim of offsetting the weight penalties associated with this non-conventional aircraft configuration. Preliminary results suggest that the composite strut-braced wing could achieve a weight reduction of up to 44% compared to a composite cantilever wing with equal aspect ratio of 20. The actual weight reduction is thought to be lower due to potential overestimation of the cantilever configuration. Full article

Compliant wing morphing devices deal with controlled and smooth adaptation of the subcomponents’ shape to external conditions. Their structural stiffness distribution, typically resulting from an optimization design process, is tailored to ensure large deformations and sufficient robustness while preserving a given form under the action of the aerodynamic loads and the internal force system. Within the European project HERWINGT (Hybrid Electric Regional Wing Integration Novel Green Technologies), supported by the Clean Aviation Joint Undertaking (CAJU), a compliant morphing flap (MF) concept has been developed by CIRA to implement adaptive capability for a strut-braced wing of the next generation Hybrid Electric Regional Aircraft. Its aim is to achieve remarkable high-lift performance improvement and related reduction of fuel consumption per flight. Specifically, the work focuses on the evolution of the conceptual architecture of the MF developed across the HERWINGT project, which was investigated in terms of preliminary design and has always accounted for actuation system integration aspects. A step-by-step design approach involving sensitivity finite elements analyses has been then carried out on two MF configurations; the technical outcomes resulting from the development of each of them have been critically analyzed and herein reported. Finally, justifications are provided for all the future adoptable engineering solutions. Full article

This paper reviews various design approaches for sensing schemes that utilize silicon nanowire (SiNW) ion-sensitive field-effect transistors (ISFETs) for pH-sensing applications. SiNW ISFETs offer advantageous characteristics, including a high surface-to-volume ratio, fast response time, and suitability for integration with complementary metal oxide semiconductor (CMOS) technology. This review focuses on SiNW ISFET-based biosensors in three key aspects: (1) major fabrication processes and device structures; (2) theoretical analysis of key performance parameters in readout circuits such as sensitivity, linearity, noise immunity, and output range in different system configurations; and (3) an overview of existing readout circuits with quantitative evaluations of N-type and P-type current-mirror-based circuits, highlighting their strengths and limitations. Finally, this paper proposes a modified N-type readout scheme integrating an operational amplifier with a negative feedback network to overcome the low sensitivity of conventional N-type circuits. This design enhances gain control, linearity, and noise immunity while maintaining stability. These advancements are expected to contribute to the advancement of the current state-of-the-art SiNW ISFET-based readout circuits. Full article

Multifunctional cementitious composites have been widely recommended for transportation infrastructure due to their versatile applications. These advanced materials can serve multiple functions, including structural health monitoring (SHM), traffic management, de-icing and snow melting, cathodic protection, grounding, energy harvesting, and shielding against electromagnetic interference (EMI). Given their effectiveness in transportation infrastructure, the authors of this paper, as part of the In2Track2 and In2Track3 projects funded by the European Union, have conducted extensive research in this field. Complementary to the objectives of these projects, this review paper provides a comprehensive analysis of the key components of conductive pavements, including conductive fillers, matrix materials, electrode configurations, conductive mechanisms, and factors influencing the electrical properties of these systems. Additionally, it discusses the practical applications of conductive pavements. By integrating insights from various aspects of this advanced pavement technology, this paper serves as a valuable resource for researchers and practitioners seeking to advance the development and implementation of conductive pavements. Full article

Accurate separation in microfluidic devices is crucial for biomedical applications; however, enhancing their performance remains challenging due to computational and experimental constraints. This study aims to optimize microfluidic devices by systematically refining spiral microchannel configurations for the segregation of circulating tumor cells (CTCs) and red blood cells (RBCs) through detailed variable analysis and resource-efficient techniques. The spiral design was developed into six variations, considering loop numbers (2, 3, and 4), aspect ratios (2.333, 3.333, and 5), spiral radii (5, 6, and 7 mm), flow rates (1.5, 2, and 3 mL/min), surface roughness levels (0, 0.5, and 1 μm), and particle sizes (12, 18, and 24 μm). Simulations were conducted in COMSOL Multiphysics and evaluated using the Taguchi method to determine the optimal configuration, reducing the analysis set from 216 to 27 through an efficient experimental design approach. The results identified the optimal structure as having an aspect ratio of 3.333, four loops, a spiral radius of 6–7 mm, a flow rate of 3 mL/min, a surface roughness of 1 μm, and a particle diameter of 24 μm. Among the evaluated parameters, aspect ratio (61.2%) had the most significant impact, followed by the number of loops (13.9%) and flow rate (9.4%). The optimized design demonstrated high separation efficiency and purity, achieving 97.5% and 97.6%, respectively. The fabrication process involved 3D-printing the channel mold, followed by polydimethylsiloxane (PDMS) casting, validating the durability and scalability of the proposed design. This study integrates simulation and experimental results, providing a robust framework for developing next-generation microfluidic devices and advancing diagnostic and targeted therapeutic applications. Full article

In this paper, the geometric effect on flow structure and mixing performance of two miscible fluids (deionized water and glycerol) in a planetary centrifugal mixer (PCM) during the spin-up is numerically evaluated, using the OpenFOAM interMixingFoam solver. Six different aspect ratios, specifically 0.5, 1, 1.25, 1.5, 2, and 2.5, are considered. The flow structure in each geometric configuration is illustrated by the liquid interface and vorticity isosurface represented by the Q criterion, while the mixing performance is evaluated in terms of a mixing index $MI$. As the aspect ratio increases from small to large, $MI$ first increases and then decreases. The peak $MI$ at the end of spin-up reaches 0.196 for the aspect ratio of 1.25, rather than the other five aspect ratios in our study. The mechanism analysis shows that under an aspect ratio of 1.25, the vortex structure is most violently dissipated, the interface collapse degree is the largest, and the low-velocity region volume is the smallest, which enhances the chaotic convection mixing. Full article

This paper reviews the potential of Wire Arc Additive Manufacturing (WAAM) for architecture. It uniquely addresses its feasibility by evaluating existing large-scale, real-world prototypes developed to date and compiling critical gaps identified in the literature. Although previous review papers concerning WAAM for architecture exist, they focus on the technical aspects of the technology, such as the mechanical properties, defects, and process parameters. No existing review analyzes which architectural applications are being implemented nor the scale and degree prototyping accomplished for each application. WAAM, a form of metal additive manufacturing using an electric arc to melt and deposit wire, offers unique advantages for the construction industry. It allows for high deposition rates, structural integrity, and cost-efficiency using steel. However, challenges such as producing large-scale components and limited design freedom and lower resolution compared to other additive manufacturing processes remain. This review first contextualizes WAAM within the broader landscape of additive manufacturing technologies for construction and examines its proposed architectural applications, such as steel connections, columns, trusses, and bridge elements. This study emphasizes the need for real-world experimentation through large-scale prototypes to assess the practicality and scalability of WAAM in architecture. The results of this study reveal that 36 architectural projects using WAAM exist in the literature, whose application range from structural (such as beams, columns, and nodes) to nonstructural components (such as facades and ornamental elements). Based on these, a classification for WAAM in architecture is proposed: (1) stand-alone WAAM structures, (2) printed connector pieces to join standard steel parts, and (3) reinforcement for conventional steel elements using WAAM. The size of typical functional prototypes to date averages 200 × 200 × 200 mm, with exceptional cases such as the diagrid column of 2000 mm height and the MX3D Bridge, which spans over 12 m. A detailed analysis of seven projects documents the scale and development of the prototypes, functional lab configuration, and process parameters. Through this review, the current technical feasibility of WAAM in architecture is established. Full article

Although dental resin composite restoratives offer a widely used direct-placement treatment option aimed at replacing the form and function of a natural tooth, there are several clinically relevant performance aspects of these materials that can be improved. The formulation of the resin matrix phase of dental composites for high-efficiency photopolymerization leading to polymers with excellent mechanical properties has always been a challenge that is addressed here through the use of structurally new and more reactive monomers as well as the formation of polymer networks that incorporate non-covalent reinforcing interactions. The purpose of this study was to validate that a set of tetraurethane diacrylates (TUDAs) with a novel configuration of their urethane linkages in coordination with acidic comonomers could be devised to obtain highly robust new composite materials. Due to the novel molecular design, this exploratory approach was conducted using reaction kinetics and three-point bend testing to assess the performance. Conversion and mechanical properties were measured to refine these formulations prior to the addition of filler. The initial formulations demonstrated outstanding dry mechanical test results that subsequently showed a major intolerance to water storage, which led to a model study using urethane diacrylate (UDA) followed by the addition of hydrophobic TUDA monomers. Once the resin formulations were optimized, silane-treated particulate filler was added to determine the effectiveness as composite materials. The final formulation used a hydrophobic, aromatic TUDA along with 4-methacryloxyethyl trimellitic anhydride (4-META) as a latent acidic comonomer and a mixture of acrylic acid (AA) and methacrylic acid (MAA). This formulation achieves a very high level of both reactivity and mechanical properties relative to current dental composite restoratives. Full article

Geoenvironmental engineered barriers, such as geotechnical and hydraulic layered structures called liners, are essential for protecting the environment from pollution. Liners are usually compacted clay liners (CCL), geomembranes (GM), geosynthetic clay liners (GCL), or a combination of these liners (composite liners), which require significant attention concerning materials, techniques, and procedures to perform adequately. This work reviews the function of geotechnical and hydraulic barriers as liners and highlights the lack of investigation and problematic aspects of them. In addition, the work provides an overview of the literature around earthworks which are liners’ specific configurations, such as landfills, dams, ponds, wastewater lagoons, and vertical barriers. Furthermore, the main investigations, issues, and perspectives are demonstrated, and are discussed alongside the trending research areas and sustainable new materials. This work highlights different directives in several countries for liner construction standards and testing program specifications, analyzing their economic aspects. The main studies on the subject have been compiled, and a bibliometric analysis was performed. Thus, this paper concludes by pointing out gaps in the research regarding alternative materials and structures within geoenvironmental investigations on liners, and signposts future scientific threads related to sustainable development. Full article

This paper deals with developing a comparative study of the principal time-domain system identification methods suitable for performing an experimental modal analysis of structural systems. To this end, this work focuses first on analyzing and reviewing the mathematical background concerning the analytical methods and the computational algorithms of interest for this study. The methods considered in the paper are referred to as the AutoRegressive eXogenous (ARX) method, the State-Space ESTimation (SSEST) method, the Numerical Algorithm for Subspace State-Space System Identification (N4SID), the Eigensystem Realization Algorithm (ERA) combined with the Observer/Kalman Filter Identification (OKID) method, and the Transfer Function ESTimation (TFEST) method. Starting from the identified models estimated through the methodologies reported in the paper, a set of second-order configuration-space dynamical models of the structural system of interest can also be determined by employing an estimation method for the Mass, Stiffness, and Damping (MSD) matrices. Furthermore, in practical applications, the correct estimation of the damping matrix is severely hampered by noise that corrupts the input and output measurements. To address this problem, in this paper, the identification of the damping matrix is improved by employing the Proportional Damping Coefficient (PDC) identification method, which is based on the use of the identified set of natural frequencies and damping ratios found for the case study analyzed in the paper. This work also revisits the critical aspects and pitfalls related to using the Model Order Reduction (MOR) approach combined with the Balanced Truncation Method (BTM) to reduce the dimensions of the identified state-space models. Finally, this work analyzes the performance of all the fundamental system identification methods mentioned before when applied to the experimental modal analysis of flexible structures. This is achieved by carrying out an experimental campaign based on the use of a vibrating test rig, which serves as a demonstrative example of a typical structural system. The complete set of experimental results found in this investigation is reported in the appendix of the paper. Full article

Optical fiber-based acoustic detectors for ultrasound imaging in medical field feature plano-concave Fabry–Perot cavities integrated on fiber tips, realized via dip-coating. This technique imposes constraints on sensor geometry, potentially limiting performance. Lab-on-Fiber technology enables complex three-dimensional structures with precise control over geometric parameters, such as the curvature radius. A careful investigation of the optical and mechanical aspects involved in the sensors’ performances is crucial for determining the design rules of such probes. In this study, we numerically analyzed the impact of curvature on the optical and acoustic properties of a plano-concave cavity using the Finite Element Method. Performance metrics, including sensitivity, bandwidth, and directivity, were compared to planar Fabry–Perot configurations. The results suggest that introducing curvature significantly enhances sensitivity by improving light confinement, especially for cavity thicknesses exceeding half the Rayleigh zone (∼45 μm), reaching an enhancement of 2.5 a L = 60 μm compared to planar designs. The curved structure maintains high spectral quality (FOM) despite 2% fabrication perturbations. A mechanical analysis confirms no disadvantages in acoustic response and bandwidth (∼40 MHz). These findings establish curved plano-concave structures as robust and reliable for high-sensitivity polymeric lab-on-fiber ultrasound detectors, offering improved performance and fabrication tolerance for MHz-scale bandwidth applications. Full article

The technologically advanced learning ocean system—wave energy converter (TALOS-WEC) project addresses the urgent need for sustainable and efficient energy solutions by leveraging the vast potential of wave energy. This project presents a pioneering approach to wave energy capture through its unique multi-axis and omnidirectional point absorber design. Featuring a fully enclosed power take-off (PTO) system, the TALOS-WEC harnesses energy across six degrees of freedom (DoFs) using an innovative internal reaction mass (IRM) mechanism. This configuration enables efficient energy extraction from the relative motion between the IRM and the hull, aiming for energy conversion efficiencies ranging between 75–80% under optimal conditions, while ensuring enhanced durability in harsh marine environments. The system’s adaptability is reflected in its versatile geometric configurations, including triangular, octagonal, and circular designs, customised for diverse marine conditions. Developed at Lancaster University, UK, and supported by international collaborations, the TALOS-WEC project emphasises cutting-edge advancements in hydrodynamic modelling, geometric optimisation, and control systems. Computational methodologies leverage hybrid frequency-time domain models and advanced panel codes (WAMIT, HAMS, and NEMOH) to address non-linearities in the PTO system, ensuring precise simulations and optimal performance. Structured work packages (WPs) guide the project, addressing critical aspects such as energy capture optimisation, reliability enhancement, and cost-effectiveness through innovative monitoring and control strategies. This paper provides a comprehensive overview of the TALOS-WEC, detailing its conceptual design, development, and validation. Findings demonstrate TALOS’s potential to achieve scalable, efficient, and robust wave energy conversion, contributing to the broader advancement of renewable energy technologies. The results underscore the TALOS-WEC’s role as a cutting-edge solution for harnessing oceanic energy resources, offering perspectives into its commercial viability and future scalability. Full article