•Crystalline clusters form in amorphous NiTi-based alloys during mechanical vibrations.•Clusters form during both low-frequency and ultrasonic vibrations at room temperature.•Temperature hardly ...affects the cluster size and distribution.•Clusters do not influence the crystallisation temperature but decrease the enthalpy.
The aim of the present work is to study the influence of the vibration temperature, frequency and amplitude on the structure of amorphous NiTi-based shape memory alloys. The Ti40.7Hf9.5Ni44.8Cu5, Ti40.7Hf9.5Ni41.8Cu8 and Ti50Ni25Cu25 melt-spun amorphous thin ribbons were subjected to low-frequency mechanical vibrations in a Dynamical Mechanical Analyser or ultrasonic vibrations in anvil. The results of the study have shown that the mechanical vibrations lead to a structural relaxation and initiate the beginning stage of the crystallisation in the amorphous NiTi-based shape memory alloys. During the vibrations with an amplitude of 4 μm, crystalline clusters, with a size of 4–6 nm, appear in the amorphous matrix. On an increase in the vibration temperature or frequency, the size of the crystalline clusters hardly changes. The clusters that form during the vibrations do not influence the crystallisation temperature but decrease the crystallisation enthalpy.
The aim of the study was to investigate the dependence of selected textural, rheological and mechanical vibration damping properties of restructured chicken breast ham (RCBH) on the concentration of ...furcellaran (FRC1 or FRC2) or κ-carrageenan (KC) during a 14-days storage period (at 4 ± 2 °C). The above-mentioned polysaccharides were used in concentrations of 0.25 g/100 g, 0.50 g/100 g, 0.75 g/100 g and 1.00 g/100 g. Control sample (CS) without any polysaccharide addition was also produced. The textural, rheological and mechanical vibration damping properties of RCBH samples were affected by the type and concentration of the polysaccharide used (p < 0.05) and the storage period (p < 0.05). Samples prepared with KC and FRC1 at a concentration level of 1.00 (g/100 g) presented the highest values of hardness, G′, G″ and G*. Values of G* and δ (in all tested frequency ranges) indicated a solid-like behavior for all the samples over the experimental range. It was found that the first resonance frequency peak position increased with an increase in the RCBH stiffness leading to lower vibration damping properties of the samples (p < 0.05).
•Restructured chicken breast hams with κ-carrageenan and furcellaran were developed.•The hardness of the samples increased with the rising level of added polysaccharides.•The use of polysaccharides resulted in higher G* values during the cooling stage.•The samples exhibited a solid-like character over the experiment.•The polysaccharides used influenced samples displacement transmissibility and stiffness.
Recently, there have been notable advancements in energy harvesting from various sources, including mechanical vibrations, thermal gradients, and electromagnetic and solar radiations, intending to ...achieve sustainable micro/nanosystems. Micro-electromechanical systems (MEMS) and microfluidics have facilitated the development of smaller energy harvesters that offer a stable and portable power supply. MEMS-based piezoelectric power generators can harvest power from low-level ambient vibration sources. Still, their usage is limited by their low power output in the microwatt range and restricted operation frequency. There is an increasing interest in vivo therapies in harnessing energy from sources like ambient or human bodies. While MEMS-based energy harvesters hold the potential for powering implantable biomedical devices (IMD), their performance is hindered by various factors. However, experimental results show advancements achieved in vibration-based MEMS piezoelectric energy harvesters. The progress of micro-energy harvesters for IMD applications indicates that MEMS-based energy harvesters could be promising for low-power applications soon.
Display omitted
•Discussed MEMS-based energy harvesting system.•Discussion on different types of energy harvesting system has been performed.•Portable power supply has been discussed.•Vivo therapies has been discussed.
Generalized Kelvin–Voigt and Maxwell models using Prony series are some of the most well-known models to characterize the behavior of polymers. The simulation software for viscoelastic materials ...generally implement only some material models. Therefore, for the practice of the engineer, it is very useful to have formulas that establish the equivalence between different models. Although the existence of these relationships is a well-established fact, moving from one model to another involves a relatively long process. This article presents a development of the relationships between generalized Kelvin–Voigt and Maxwell models using the aforementioned series and their respective relaxation and creep coefficients for one and two summations. The relationship between the singular points (maximums, minimums and inflexion points) is also included.
KWU-PWR reactors (SIEMENS design) are commonly exhibiting high neutron noise levels that can lead to costly operational issues. Recent analysis seems to indicate that, coolant flow, temperature ...oscillations, and mechanical vibrations have a key impact on neutron noise phenomena. In order to advance in understanding this phenomenon, the transient nodal code SIMULATE-3K (S3K) has been already utilized to simulate scenarios with individual or combined types of perturbation sources: mechanical vibrations of fuel assemblies and thermal-hydraulic fluctuations at the core inlet. In this work, new simulations are performed with all the perturbations applied simultaneously. The simulated neutron detectors responses are then analyzed with noise analysis techniques. All the simulated spectral features of neutron noise are compared to those obtained from real plant data. Results show that the simulated neutron noise phenomenology behaves similarly to that obtained from real plant data by increasing the fluctuation amplitude in the inlet coolant flow in the S3K calculations.
Large-amplitude longitudinal oscillations of solar filaments have been observed and explored for more than ten years. Previous studies are mainly based on the one-dimensional rigid flux tube model ...with a single magnetic dip. However, it has been noted that there might be two magnetic dips, and hence two threads, along one magnetic field line. Following previous work, we intend to investigate the kinematics of the filament longitudinal oscillations when two threads are magnetically connected, which is done by solving one-dimensional radiative hydrodynamic equations with the numerical code MPI-AMRVAC. Two different types of perturbations are considered, and the difference from previous works resulting from the interaction of the two filament threads is investigated. We find that even with the inclusion of the thread-thread interaction, the oscillation period is modified weakly, by at most 20% compared to the traditional pendulum model with one thread. However, the damping timescale is significantly affected by the thread-thread interaction. Hence, we should take it into account when applying the consistent seismology to the filaments where two threads are magnetically connected.
PDF
