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Aortic dissecting aneurysm is one of the most catastrophic cardiovascular emergencies that carries high mortality. It was pointed out from clinical observations that the aneurysm development is likely to be related to the hemodynamics condition of the dissected aorta. In order to gain more insight on the formation and progression of dissecting aneurysm, hemodynamic parameters including flow pattern, velocity distribution, aortic wall pressure and shear stress, which are difficult to measure in vivo, are evaluated using numerical simulations. Pulsatile blood flow in patient-specific dissecting aneurismal aortas before and after the formation of lumenal aneurysm (pre-aneurysm and post-aneurysm) is investigated by computational fluid dynamics (CFD) simulations. Realistic time-dependent boundary conditions are prescribed at various arteries of the complete aorta models. This study suggests the helical development of false lumen around true lumen may be related to the helical nature of hemodynamic flow in aorta. Narrowing of the aorta is responsible for the massive recirculation in the poststenosis region in the lumenal aneurysm development. High pressure difference of 0.21kPa between true and false lumens in the pre-aneurismal aorta infers the possible lumenal aneurysm site in the descending aorta. It is also found that relatively high time-averaged wall shear stress (in the range of 4–8kPa) may be associated with tear initiation and propagation. CFD modeling assists in medical planning by providing blood flow patterns, wall pressure and wall shear stress. This helps to understand various phenomena in the development of dissecting aneurysm.

In the past two decades, acoustic metamaterials have garnered much attention owing to their unique functional characteristics, which are difficult to find in naturally available materials. The acoustic metamaterials have demonstrated excellent acoustical characteristics that paved a new pathway for researchers to develop effective solutions for a wide variety of multifunctional applications, such as low-frequency sound attenuation, sound wave manipulation, energy harvesting, acoustic focusing, acoustic cloaking, biomedical acoustics, and topological acoustics. This review provides an update on the acoustic metamaterials’ recent progress for simultaneous sound attenuation and air ventilation performances. Several variants of acoustic metamaterials, such as locally resonant structures, space-coiling, holey and labyrinthine metamaterials, and Fano resonant materials, are discussed briefly. Finally, the current challenges and future outlook in this emerging field are discussed as well.

Additive manufacturing (commonly known as 3D printing) is defined as a family of technologies that deposit and consolidate materials to create a 3D object as opposed to subtractive manufacturing methodologies. Fused deposition modeling (FDM), one of the most popular additive manufacturing techniques, has demonstrated extensive applications in various industries such as medical prosthetics, automotive, and aeronautics. As a thermal process, FDM may introduce internal voids and pores into the fabricated thermoplastics, giving rise to potential reduction on the mechanical properties. This paper aims to investigate the effects of the microscopic pores on the mechanical properties of material fabricated by the FDM process via experiments and micromechanical modeling. More specifically, the three-dimensional microscopic details of the internal pores, such as size, shape, density, and spatial location were quantitatively characterized by X-ray computed tomography (XCT) and, subsequently, experiments were conducted to characterize the mechanical properties of the material. Based on the microscopic details of the pores characterized by XCT, a micromechanical model was proposed to predict the mechanical properties of the material as a function of the porosity (ratio of total volume of the pores over total volume of the material). The prediction results of the mechanical properties were found to be in agreement with the experimental data as well as the existing works. The proposed micromechanical model allows the future designers to predict the elastic properties of the 3D printed material based on the porosity from XCT results. This provides a possibility of saving the experimental cost on destructive testing.

This manuscript offers a concise overview of paper microfluidics, emphasizing its sustainable sensing applications in healthcare, environmental monitoring, and food safety. Researchers have developed innovative sensing platforms for detecting pathogens, pollutants, and contaminants by leveraging the paper’s unique properties, such as biodegradability and affordability. These portable, low-cost sensors facilitate rapid diagnostics and on-site analysis, making them invaluable tools for resource-limited settings. This review discusses the fabrication techniques, principles, and applications of paper microfluidics, showcasing its potential to address pressing challenges and enhance human health and environmental sustainability.

Battery pack casings with a total energy of 12.432 kWh were designed using two types of materials: aluminum alloy and carbon fiber reinforced composite filament based on polyphthalamide or high-performance/high-temperature nylon (PPA-CF). The effectiveness of mechanical metamaterials (lattice and auxetic structures) in mitigating the levels of random vibrations in the battery pack casings was studied using a numerical method. Both structures demonstrate outstanding capabilities with a 97% to 99% reduction in vibration levels in the aluminum casing. However, the capabilities of these structures in mitigating vibration levels in the PPA-CF casing are very limited, in that they can only mitigate approximately 63.8% and 92.8% of the longitudinal vibrations at the top cover of the casing and center of its front and back walls, respectively. Compared to PPA-CF, aluminum alloy shows better vibration mitigation performance with or without structural modification.

In this article, a 3D coupled Eulerian-Lagrangian (CEL) finite element method (FEM) model is presented for simulation of end milling processes based on Abaqus/Explicit. In the proposed model, the chip formation process does not rely on the degradation of material or continuous remeshing algorithms to achieve chip separation. The processes under investigation are the slot and shoulder milling of Al6061-T6. A linear motion of the workpiece is adopted as a simplification of the trochoidal motion of the end mill. The workpiece is given a sinusoidal profile to achieve a varying uncut chip thickness in the cutting process. With a stationary tool and a confined region of mesh refinement, the computational cost of the model can be minimized, which makes the proposed model compatible for parametric studies. The model demonstrates good accuracy in cutting force predictions. The prediction error of the resultant cutting forces can be controlled within 12% over various milling conditions. The proposed model also gives accurate predictions in terms of the morphology of chips. The excessive curling of chips in the early stages of chip formation can be predicted which has been compared with the shape of the actual chips collected during machining.

In this paper, the flexural wave propagation and its control of a novel piezoelectric composite pipe conveying fluid are investigated. Dual piezoelectric layers used as sensor and actuator are periodically arranged on the pipe, and a feedback amplifying circuit is applied from sensor to actuator, forming a self-powered phononic crystal (PC) control structure. The vibration reduction performance can be actively tuned by adjusting the feedback control gain instead of conventional changing the construction of pipe itself. The pipe is composed of functionally graded material (FGM), in which the material properties vary continuously along the radial direction, and a poroelastic medium is introduced. By using the Timoshenko beam theory and Hamilton’s principle, a set of electromechanical coupling equations governing flexural vibration of the pipe is deduced. The band structure, band gap (BG) distribution and frequency response are presented by applying the spectral element technology. Comprehensive parametric studies are carried out. The results obtained validate the excellent vibration control effect of the proposed design, and further demonstrate the significant impacts of material, piezoelectric layers, feedback control and flowing fluid on the BG characteristics. This paper is expected to provide a technological reference for the vibration and elastic wave control of engineering composite pipe structures.

Stethoscopes were originally designed for the auscultation of a patient’s chest for the purpose of listening to lung and heart sounds. These aid medical professionals in their evaluation of the cardiovascular and respiratory systems, as well as in other applications, such as listening to bowel sounds in the gastrointestinal system or assessing for vascular bruits. Listening to internal sounds during chest auscultation aids healthcare professionals in their diagnosis of a patient’s illness. We performed an extensive literature review on the currently available stethoscopes specifically for use in chest auscultation. By understanding the specificities of the different stethoscopes available, healthcare professionals can capitalize on their beneficial features, to serve both clinical and educational purposes. Additionally, the ongoing COVID-19 pandemic has also highlighted the unique application of digital stethoscopes for telemedicine. Thus, the advantages and limitations of digital stethoscopes are reviewed. Lastly, to determine the best available stethoscopes in the healthcare industry, this literature review explored various benchmarking methods that can be used to identify areas of improvement for existing stethoscopes, as well as to serve as a standard for the general comparison of stethoscope quality. The potential use of digital stethoscopes for telemedicine amidst ongoing technological advancements in wearable sensors and modern communication facilities such as 5G are also discussed. Based on the ongoing trend in advancements in wearable technology, telemedicine, and smart hospitals, understanding the benefits and limitations of the digital stethoscope is an essential consideration for potential equipment deployment, especially during the height of the current COVID-19 pandemic and, more importantly, for future healthcare crises when human and resource mobility is restricted.

Natural fibers and their composites differ in several aspects with carbon fibers, including higher scatter in strength and different tensile responses. The tensile and bending properties of flax fiber composites were experimentally studied and numerically simulated. Composite panels were fabricated from unidirectional flax fiber tapes and polypropylene films via hot pressing technique. The variation in the properties of flax/polypropylene composites was found to be relatively moderate as compared with that of single natural fibers. A multi-scale finite element analysis (FEA) strategy for the progressive damage prediction of natural fiber composites was developed. The FEA model started from micro-scale analysis which predicted the effective properties of unidirectional flax ply through representative volume element. Macro-scale analysis was conducted subsequently to predict the properties of composite coupons using the results of micro-scale analysis as inputs. The developed multi-scale FE model successfully predicted the tensile strength, bending behavior, and major failure modes of flax/polypropylene composites.

Referring to existing vibration transmissibility function-based approaches, which are frequently applied to diagnose fatigue crack and joint loosening faults in two-dimensional engineering structures such as aluminium plates and steel frames, a novel approach applying nonlinear vibration transmissibility functions is developed to diagnose potential loose pedestals in this paper. Firstly, the two-dimensional structural dynamic model, which simulates effects of loose pedestals as equivalent loads, is obtained through the lumped mass method. Secondly, exciting the dynamic model three times with different extra masses, the transmissibility function-based matrix of one sub-model to be diagnosed is obtained, and then a novel damage index is defined based on the matrix singularity. Lastly, a novel approach with particular procedures is proposed. Through three numerical cases on a two-dimensional dynamic model with multiple degrees of freedom (MDOFs), validity and applicability of the proposed approach are shown. As a result, this paper provides a totally new idea to diagnose loose pedestals, which can ensure structures’ smooth operation.