Measuring absorbed energy in the human auditory system using finite element models: A comparison with experimental results.

BACKGROUND: There are different ways to analyze energy absorbance (EA) in the human auditory system. In previous research, we developed a complete finite element model (FEM) of the human auditory system. OBJECTIVE: In this current work, the external auditory canal (EAC), middle ear, and inner ear (spiral cochlea, vestibule, and semi-circular canals) were modelled based on human temporal bone histological sections. METHODS: Multiple acoustic, structure, and fluid-coupled analyses were conducted using the FEM to perform harmonic analyses in the 0.1-10 kHz range. Once the FEM had been validated with published experimental data, its numerical results were used to calculate the EA or energy reflected (ER) by the tympanic membrane. This EA was also measured in clinical audiology tests which were used as a diagnostic parameter. RESULTS: A mathematical approach was developed to calculate the EA and ER, with numerical and experimental results showing adequate correlation up to 1 kHz. Another published FEM had adapted its boundary conditions to replicate experimental results. Here, we recalculated those numerical results by applying the natural boundary conditions of human hearing and found that the results almost totally agreed with our FEM. CONCLUSION: This boundary problem is frequent and problematic in experimental hearing test protocols: the more invasive they are, the more the results are affected. One of the main objectives of using FEMs is to explore how the experimental test conditions influence the results. Further work will still be required to uncover the relationship between middle ear structures and EA to clarify how to best use FEMs. Moreover, the FEM boundary conditions must be more representative in future work to ensure their adequate interpretation.

Microhardness and Microstructure Analysis of the LPBF Additively Manufactured 18Ni300.

This research focuses on analysing the 18Ni300 maraging steel produced through laser powder bed fusion. Specifically, it aims to examine the phase components using X-ray diffraction, the microstructure through scanning electron microscopy, and the hardness of the different structures present in the manufactured material. The primary goal is to meticulously analyse the material and its microstructures. By doing so, a correlation between the hardness and each structure type, be it cellular or columnar, can be established. This will allow us to pinpoint any defects in the material before any surface chemical treatment is carried out and facilitate a thorough examination of its microstructure. A consistent pattern emerges across the samples through systematic measurement of microhardness distribution in various locations and detailed examination of the structure. The findings of the study reveal that the hardness of cellular and columnar structures exhibits a significant variation based on the location of the measurement about cell boundaries. The hardness value is notably higher in the combination of cellular and multiple layers, as the data indicate.

Tomography of Laser Powder Bed Fusion Maraging Steel.

The presence of defects in additive manufactured maraging steel is a widespread problem as its dependence on processing parameters significantly influences it. Using X-ray computed tomography, along with optical microscope data limited to 2D images, quantifies the internal porosity present on a compact tension sample typically employed in fatigue testing. The primary goal of this research is to analyse the pores obtained after the fabrication of a compact tension sample and their main definition parameters, such as sphericity, aspect ratio, surface, and volume, and obtain validation of which method is valid for each of the parameters analysed. The current study aims to enhance the understanding of defects in maraging steel samples through non-destructive 3D analysis. Conventional 2D analyses are limited to surface measurements, providing incomplete information. The proposed method will provide a comprehensive understanding of the defects inside the maraging steel sample, thereby improving the reliability of this material for further applications. This study will contribute to academic and industrial communities by providing a novel approach to analysing maraging steel samples and, ultimately, developing improved materials for various applications. The study's findings reveal that most pores are produced by gases that are trapped in the fabrication process, and keyhole pores only appear near the surface.

Influence of Porosity on Fatigue Behaviour of 18Ni300 Steel SLM CT Specimens at Various Angles.

In order to improve understanding of the fatigue behaviour in additive manufactured samples, this research delves into the challenging interplay between building parameters, particularly fabrication angles, and the presence of pores. The primary objective is to explore the characterisation of these pores and unravel their relationship with the fatigue properties of the material under investigation. Through a systematic analysis of porosity distribution in various fabrication orientations, supplemented by a detailed examination of the elemental dispersion around specific porous structures using energy-dispersive X-ray spectroscopy, a consistent behavioural pattern emerges across the samples. In assessing fatigue behaviour, an examination of the variables reveals that only area and aspect ratio significantly influence the behaviour of the samples. Such studies can contribute substantially to academic research in the field of material science and engineering.

A Literature Review of Incorporating Crack Tip Plasticity into Fatigue Crack Growth Models.

This paper presents an extensive literature review focusing on the utilisation of crack tip plasticity as a crucial parameter in determining and enhancing crack growth models. The review encompasses a comprehensive analysis of various methodologies, predominantly emphasising numerical simulations of crack growth models while also considering analytical approaches. Although experimental investigations are not the focus of this review, their relevance and interplay with numerical and analytical methods are acknowledged. The paper critically examines these methodologies, providing insights into their advantages and limitations. Ultimately, this review aims to offer a holistic understanding of the role of crack tip plasticity in the development of effective crack growth models, highlighting the synergies and gaps between theoretical, experimental, and simulation-based approaches.

Electrospinning of Polyepychlorhydrin and Polyacrylonitrile Anionic Exchange Membranes for Reverse Electrodialysis.

The saline gradient present in river mouths can be exploited using ion-exchange membranes in reverse electrodialysis (RED) for energy generation. However, significant improvements in the fabrication processes of these IEMs are necessary to increase the overall performance of the RED technology. This work proposes an innovative technique for synthesizing anion exchange membranes (AEMs) via electrospinning. The AEM synthesis was carried out by applying a high voltage while ejecting a mixture of polyepichlorohydrin (PECH), 1,4-diazabicyclo [2.2.2] octane (DABCO® 33-LV) and polyacrylonitrile (PAN) at room temperature. Different ejection parameters were used, and the effects of various thermal treatments were tested on the resulting membranes. The AEMs presented crosslinking between the polymers and significant fiber homogeneity with diameters between 1400 and 1510 nm, with and without thermal treatment. Good chemical resistance was measured, and all synthesized membranes were of hydrophobic character. The thickness, roughness, swelling degree, specific fixed-charge density and ion-exchange capacity were improved over equivalent membranes produced by casting, and also when compared with commercial membranes. Finally, the results of the study of the electrospinning parameters indicate that a better performance in electrochemical properties was produced from fibers generated at ambient humidity conditions, with low flow velocity and voltage, and high collector rotation velocity.

Effects of 12-Week Concurrent High-Intensity Interval Strength and Endurance Training Program on Physical Performance in Healthy Older People.

García-Pinillos, F, Laredo-Aguilera, JA, Muñoz-Jiménez, M, and Latorre-Román, PA. Effects of 12-week concurrent high-intensity interval strength and endurance training program on physical performance in healthy older people. J Strength Cond Res 33(5): 1445-1452, 2019-This study aimed to analyze the effect of 12-week low-volume high-intensity interval training (HIIT)-based concurrent training program on body composition, upper- and lower-body muscle strength, mobility, and balance in older adults, as well as to compare it with a low-moderate-intensity continuous training. Ninety active older adults were randomly assigned to experimental group (EG, n = 47) and control group (CG, n = 43). Body composition and physical functioning were assessed before (pretest) and after (posttest) a 12-week intervention. A 2-way repeated measures analysis of variance was used to test for an interaction between training program and groups. The time × group interaction revealed no significant between-group differences at pretest (p ≥ 0.05). The group × time interaction showed significant improvements for the EG in body composition parameters (p ≤ 0.05) and physical functioning (muscle strength: p < 0.001; mobility: p < 0.001; and balance: p ≤ 0.05); whereas the CG remained unchanged (p ≥ 0.05). This HIIT-based concurrent training program led to greater improvements in body composition, muscle strength, mobility, and balance in healthy older people than a regular low-moderate-intensity continuous training, despite the reduction in overall training volume.

Physical activity, weight and functional limitations in elderly Spanish people: the National Health Survey (2009-2014).

Background: The purpose of this study was to analyze physical activity (PA), functional limitations, weight status, self-perceived health status and disease or chronic health problems in older people aged 65 and over using the European Health Survey in Spain (EHSS) conducted one in 2009 and one in 2014. Methods: This study included 12,546 older people, 6026 [2330 men and 3696 women; age (Mean, SD) =75.61 ± 7.11 years old] in 2009 and 6520 [2624 men and 3896 women; age (Mean, SD) =75.90 ± 7.59 years old] in 2014. The sample was divided into three age groups: 65-74 years old, 75-84 years old and ≥85 years old. Results: In 2014, participants exhibited lower values for moderate PA, and self-perceived health status compared to 2009. Moreover, in 2014 more people with disease or chronic health problems, and severe difficulty walking 500 m without assistance were found and severe difficulty going up and down 12 stairs than people in 2009. In relation to weight status there were no significant differences between older people in 2009 and 2014. Conclusions: From 2009 to 2014, the PA levels of Spanish older people have decreased, while the BMI has not increased. That fact is in consonance with a worst perception of health status in 2014 and with an increase of their disease levels. The current data highlight the importance of incorporating exercise programmes at an early stage of ageing in order to preserve physical performance, and to prevent the negative consequences of ageing.

Blackberry (Rubus spp.): a pH-dependent oral contrast medium for gastrointestinal tract images by magnetic resonance imaging.

In this study, seven fruits have been tested on their magnetic properties, paramagnetic metal content and contrast enhancement in magnetic resonance imaging (MRI) of phantom and in vivo. Magnetic susceptibility was determined for the fruit pulps, as well as the contents of paramagnetic metals; iron, manganese and copper. The total content of these metals was 4.3, 8.6, 11.1, 10.9, 12.3, 8.3 and 29.3 mg/kg of fruit for plum, blueberry, apple (red), pineapple, beet, grape, blackberry, respectively, and with magnetic susceptibility of -2.29+/-0.07, -2.43+/-0.07, -2.13+/-0.07, -1.84+/-0.02, -1.75+/-0.01, -1.78+/-0.06, -2.18+/-0.07 SI, respectively. T(1)- and T(2)-weighted MR images were performed for the seven fruits and water (chi= -9.98 x 10(-3) SI) and in one subject. While there was no correlation between the magnetic susceptibility and contrast enhancement, there is a correlation with the total paramagnetic metal content determined with contrast enhancement in MRI. Thus, blackberry (Rubus spp.) contrast enhancement was the highest among the fruits in T(1)-weighted images. Furthermore, this fruit's contrast enhancement shows to be pH-dependent. These characteristics and the wide availability of the Rubus spp. suggest that it should be implemented as an oral contrast agent in images by MR to assess the function of the gastric section of the GI tract. Furthermore, it has the advantage of being a natural meal, so that it can be well tolerated by the patients and use as much as it is needed without side effects.