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This paper proposes a novel approach for fast human exposure absorbed power density assessment, based on a combination of over-the-air radiative field measurements and full-wave electromagnetic simulations. This so-called augmented OTA technique relies on the computation of an equivalent source or digital twin, which reproduces the radiation properties of the device under test. At short separation distances, the interaction between the human model and the device is however not negligible. A novel solution to model the influence of multiple reflections is introduced, where the inside of the equivalent source box is partially filled with a perfect electric conductor, thereby creating a reflective digital twin model. Simulation and measurement results demonstrate the relevance of this technique for enabling accurate absorbed power density evaluations. A discussion on aspects influencing the measurement time and uncertainty is also provided, where a new demonstration is delivered how spatial-averaging contributes positively to the accuracy of the method.

This study investigates the influence of cobalt (Co) alloying addition and heat treatment temperature on the phase transformation behaviour controlling the superelasticity and shape memory effect (SME) of Nickel-Titanium (Ni-Ti) alloys, commonly known as nitinol. The microstructural evolution upon heat treatment conducted at a temperature ranging from 440 to 560 °C was thoroughly analyzed via Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), and Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS). Increase in heat treatment temperatures from 470 °C up to 530 °C led to the dissolution of particles present in as-received (cold-worked) condition. It was determined that Co addition into the Ni-Ti alloy system resulted in a change in the nucleation and growth kinetics of Ti-rich precipitates, leading to the formation of larger and fewer particles during processing. Both binary and ternary alloys showed a decrease in austenite finish temperature (Af) with increasing heat treatment temperatures, however, the rate of decrease was found to be higher for Co containing ternary alloys. This is linked with faster structural relaxation when Co is present and evidenced by lattice size variation during heat treatment. It is highlighted that heat treatment methodology needs to be tailored to the specific alloy composition for controlling superelasticity and SME via alloy design.

To maximize the benefits of wire arc additive manufacturing (WAAM) processes, the effect of post-deposition heat treatment on the microstructure and mechanical properties of WAAM AZ80M magnesium (Mg) alloy was investigated. Three different heat treatment procedures (T4, T5 and T6) were performed. According to the results, after T4 heat treatment, the microsegregation of alloying elements was improved with the eutectic structure dissolved. Samples after T5 heat treatment inherited the net-like distribution of secondary phases similar to the as-deposited sample, where the eutectic structure covering the interdendritic regions and the β-phase precipitated around the eutectic structure. After T6 heat treatment, the tiny β-phases re-precipitated from the matrix and distributed in inner and outer of the grains. The hardness distribution of the samples went through T4 and T6 heat treatment was more uniform in comparison to that of T5 heat treated samples. The tensile test showed that the T6 heat treatment improved the strength and ductility, and the anisotropy between horizontal and vertical can be eliminated. Moreover, T4 treated samples exhibited highest ductility.

Magnesium alloys can be used in a wide range of applications, from lightweight structural and transport applications to biomaterials [...]

Abstract The effect of dislocation-RE atoms interactions on the creep behaviour has been studied via creep testing and HAADF-STEM analysis of two extruded alloys; Mg–0.5Ce and Mg–2Gd (wt%). Almost no Ce atoms are detected in the Mg matrix due to the low solid solubility and faster diffusion rate in as-extruded condition. However, Gd solute segregations are observed along dislocations and hexagonal dislocation patterns. Such segregations can not only pin the dislocation motion and enhance the creep strengthening via dislocation patterns, but also lead to dynamic precipitation. Thus, combing with the stress exponent values, the transition of creep mechanism between Mg–0.5Ce alloys and Mg–2Gd alloys has been found and dislocation-Gd atoms interactions are determined to be the main factor for superior creep resistance of Mg–2Gd alloys.

This article presents cyclic hardening/softening behaviors (experimental data) of the heat-treated aluminum-matrix nano-clay-composite (AlSi_N_HT6), compared to those of the piston aluminum alloy (AlSi) under strain-controlled loading. For such an objective, standard samples were fabricated by gravity and stir-casting methods. Low-cycle fatigue experiments were carried out under different strain amplitudes (0.20–0.45%) and at various temperatures (25–300°C). Obtained results implied that no obvious change was observed on material properties of aluminum alloy by reinforcements, but a decrement was observed due to increasing the temperature. Results also indicated that the increase of the temperature from 25°C to 200°C has changed the cyclic behavior of both materials (AlSi_N_HT6 and AlSi) from hardening to softening. Moreover, the temperature effect was more significant than the total strain amplitude influences in cyclic behaviors.

Digital image correlation (DIC) techniques were used to evaluate strain distributions along tensile gage lengths immediately after yielding of a medium manganese steel (7 wt% Mn) in samples cold rolled in the range of 1–6 pct. With an increase in cold work, DIC confirmed that the yielding behavior transitioned from nucleation and propagation of a single localized deformation zone (Lüders band) to uniform deformation, that is, no evidence of strain localization. At intermediate amounts of cold work, a unique yielding behavior was evident where the initially-low positive strain hardening rate increased with tensile strain until conventional strain hardening (i.e., decrease in strain hardening rate with strain). The intermediate yielding behavior was associated with the development of multiple non‑propagating regions of strain localization, an observation not previously evident without the use of DIC.

Philippine natural bentonite is characterized using X-ray diffractometer (XRD), scanning electron microscope (SEM), chemical analysis, thermogravimetric-differential scanning calorimetry (TG-DSC), and Fourier transform infrared (FTIR) analysis. The cation exchange capacity (CEC) was also measured. XRD shows that the mineral is composed primarily of mordenite, hectorite, and montmorillonite. SEM shows the flaky and porous structure of the bentonite powder. Chemical analyses show that SiO2 (47.90 wt%) and Al2O3 (14.02 wt%) are the major components of the clay. TG-DSC shows that the mineral contains 15.55% moisture. IR transmittance spectrum shows the common vibration bands present in the sample which include O–H stretching of inter-porous water, symmetric and asymmetric stretching of hydroxyl functional groups, asymmetrical stretching of internal tetrahedra (O–Si–O and O–Al–O), symmetrical stretching of external linkages, and so on. The measured CEC were found to be 91.37 and 43.01 meq/100 g according to the ammonium acetate method and barium acetate method, respectively.

Abstract Purpose: To investigate the effect of subcutaneous sildenafil on random flap survival. Methods: Fourteen Wistar rats, which were divided in to two groups, were used for this experimental study. Rats in the sildenafil group received subcutaneous sildenafil injections daily for seven days before flap elevation. At the end of the treatment period, 9x3 cm dorsal skin flaps were elevated and reinserted back into their place in all of the animals. Necrotic and whole flaps areas were recorded on graph papers. Seven days after the flap elevation samples for histological examination were taken and angiographies were performed to visualize the flap vascularization. Results: The calculated average percentage of necrotic flap areas were 18.29% and 42.26% in the sildenafil and control group respectively.(p=0.0233). In selected angiography images, vessels were found to be more prominent in the sildenafil group. The average number of capillary formations under light microscopy was higher in the sildenafil group (p= 0.0286). Conclusion: The subdermal high dose sildenafil has a positive effect on flap survival.

While the potential use of energy harvesters as structural health monitors show promise, numerical models related to the design, deployment and performance of such monitors often present significant challenges. One such challenge lies in the problem of leak detection in fluid-carrying pipes. Recent advances in experimental studies on energy harvesters for such monitoring has been promising but there is a paucity in existing literature in linking relevant fluid–structure interaction models around such applications. This paper addresses the abovementioned issue by developing a numerical model with Computational Fluid Dynamics (CFD) and Finite Element (FE) tools and carries out extensive analyses to compare it with existing experiments under controlled laboratory conditions. Conventional Polyvinylidene Fluoride (PVDF) films for leak detection and monitoring of water pipes were considered in this regard. The work provides guidelines on parameter selection and modeling for experimental design and repeatability of results for these types of experiments in future, around the demands of leak monitoring. The usefulness of such models is also demonstrated through the ability to estimate the optimum distribution frequency of these sensors that will enable the detection of the smallest leak of consequence under a known or established flow condition.

Objectives. Premature myocardial infarction (PMI) is an uncommon disease, and its incidence varies between 2% and 10%, rising, depending on genetic susceptibility under the influence of lifestyle. The purpose of this study was to investigate the association between SIRT1 single nucleotide polymorphisms (SNPs), SIRT1, and eNOS (endothelial nitric oxide synthase) protein expressions, total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) in young patients with premature ST-elevation myocardial infarction (STEMI). Methods. Genotyping of the three single-nucleotide polymorphisms (rs7895833 A > G in the promoter region, rs7069102 C > G in intron 4, and rs2273773 C > T in exon 5) in SIRT1 gene was performed in 108 consecutive patients (87.0% were men with a mean age of 40.74 ± 3.82 years) suffering from ST-elevation myocardial infarction at the age of ≤45 and 91 control subjects. Results. The risk for myocardial infarction was increased by 2.31 times in carriers of CC or CG genotypes. SIRT1 protein levels were enhanced and endothelial nitric oxide synthase levels were diminished in ST-elevation myocardial infarction patients regardless of the underlying gene variant. There was no correlation between SIRT1 expression and the amount of endothelial nitric oxide synthase, total antioxidant status, total oxidant status, and oxidative stress index levels in patients and in the control group either. Conclusions. SIRT1 single-nucleotide polymorphisms were associated with premature myocardial infarction, which affected the SIRT1 and endothelial nitric oxide synthase protein expression, irrespective of the underlying SIRT1 genotype.