Functional glass-ceramic foams from \u2018inorganic gel casting\u2019 and sintering of glass/slag mixtures

The here described investigation was essentially aimed at exploring the chemical stabilization and reutilization of iron-rich slag from copper metallurgy, by the manufacturing of glass-ceramic foams. The foams were developed according to a new method, recently reported for pure recycled soda-lime glass. Mixtures of soda-lime glass/slag powders (with slag content ranging from 10 to 30\u202fwt%), suspended in alkaline aqueous solution, underwent progressive low temperature (80\u202f\ub0C) hardening, owing to the formation of hydrated calcium silicate compounds (CSH). Before complete setting, an extensive foaming could be achieved by vigorous mechanical stirring, with the help of a surfactant. After foaming, glass/slag mixtures could be sintered at 800\u20131000\u202f\ub0C; the mutual interaction caused an extensive crystallization, with precipitation of CaFe silicates and iron oxides (hematite and magnetite), promoting the mechanical properties (up to 4.4\u202fMPa, with a porosity of about 80%). Leaching test confirmed the stabilization of pollutants, from the slag, in the final ceramics. Owing to the separation of iron oxides, particularly magnetite, the newly obtained foams exhibited a ferrimagnetic behavior, that could be exploited in electromagnetic shielding applications

Development of piezoelectric harvesters with integrated trimming devices

Piezoelectric cantilever harvesters have a large power output at their natural frequency, but in some applications the frequency of ambient vibrations is different fromthe harvester\u2019s frequency and/or ambient vibrations are periodicwith some harmonic components. To copewith these operating conditions harvesters with integrated trimming devices (ITDs) are proposed. Some prototypes are developed with the aid of an analytical model and tested with an impulsive method. Results show that a small trimming device can lower the main resonance frequency of a piezoelectric harvester of the same extent as a larger tip mass and, moreover, it generates at high frequency a second resonance peak. A multi-physics numerical finite element (FE) model is developed for predicting the generated power and for performing a stress-strain analysis of harvesters with ITDs. The numerical model is validated on the basis of the experimental results. Several configurations of ITDs are conceived and studied. Numerical results show that the harvesters with ITDs are able to generate relevant power at two frequencies, owing to the particular shape of the modes of vibration. The stress in the harvesters with ITDs is smaller than the stress in the harvester with a tip mass trimmed to the same frequency

A face-smoothed cell method for static and dynamic piezoelectric coupled problems on polyhedral meshes

Low-order discretization schemes are suitable for modeling 3-D multiphysics problems since a huge number of degrees of freedom (DoFs) is typically required by standard high-order Finite Element Method (FEM). On the other hand, polyhedral meshes ensure a great flexibility in the domain discretization and are thus suitable for complex model geometries. These features are useful for the multiphysics simulation of micro piezoelectric devices with a thin multi-layered and multi-material structure. The Cell Method (CM) is a low-order discretization scheme which has been mainly adopted up to now for electromagnetic problems but has not yet been used for mechanical problems with polyhedral discretization. This work extends the CM to piezo-elasticity by reformulating local constitutive relationships in terms of displacement gradient. In such a way, piecewise uniform edge basis functions defined on arbitrary polyhedral meshes can be used for discretizing local constitutive relationships. With the CM matrix assembly is completely Jacobian-free and do not require Gaussian integration, reducing code complexity. The smoothing technique, firstly introduced for FEM, is here extended to CM in order to avoid shear locking arising when low-order discretization is used for thin cantilevered beams under bending. The smoothed CM is validated for static and dynamic problems on a real test case by comparison with both second-order FEM and experimental data. Numerical results show that accuracy is retained even if a much lower number of DoFs is required compared to FEM

Low temperature upcycling of vitreous byproduct of the MSW plasma processing into multifunctional porous glass-ceramics

Mixtures of glass residues, deriving from the plasma processing of municipal solid waste (‘Plasmastone’), and recycled glasses have been already converted into highly porous glassceramics by application of an inorganic gel casting technique (foaming, by intensive mechanical stirring, of alkali activated slurries) followed by sintering at 1000°C. The full potential of recycled glass, however, has not been disclosed yet. The present investigation, infact, demonstrates that boro-alumino-silicate glass, from discarded pharmaceutical vials, may allow for sintering of cellular glass-ceramics at particularly low temperature, i.e. at 800°C. The full stabilisation of heavy metals from Plasmastone (already assessed for treatments at 1000° C) is not compromised, whereas the low processing temperatures favour the separation of magnetite, in turn imparting new functionalities (e.g. electromagnetic shielding) to wastederived glass-ceramic foams

On the Electrical and Optical Features of the Plasma Coagulation Controller Low Temperature Atmospheric Plasma Jet

We report on the electrical and optical characterization of the Plasma Coagulation Controller (PCC) device, a low temperature atmospheric plasma source for biomedical applications. This device, designed for the study of plasma-induced blood coagulation, has been developed to operate flexibly in several operational conditions, since it is possible to vary the applied voltage V p and the pulse repetition rate f in a quite wide range ( V p range: 2–12 kV, f range: 1–40 kHz). Emission spectroscopy measurements were conducted by varying the line of sight along the axis of helium and neon plasma plumes. The increase of the Reactive Oxygen and Nitrogen Species (RONS) has been observed, as one moves from inside the gas pipe to the outside, as a consequence of the gas mixture with the surrounding air. Furthermore, high-speed photographs of the plasma jet were taken, showing that the plasma is not uniformly distributed in a continuous volumetric region, the plasma being concentrated in localized structures called Pulsed Atmospheric-pressure Plasma Streams (PAPS). The propagation velocities of these objects have been examined, noting that they are not related to the propagation of ion sound waves. Rather, we provide indications that the streamer propagation speed is proportional to the electron drift velocity

How future surgery will benefit from SARS-COV-2-related measures: a SPIGC survey conveying the perspective of Italian surgeons

COVID-19 negatively affected surgical activity, but the potential benefits resulting from adopted measures remain unclear. The aim of this study was to evaluate the change in surgical activity and potential benefit from COVID-19 measures in perspective of Italian surgeons on behalf of SPIGC. A nationwide online survey on surgical practice before, during, and after COVID-19 pandemic was conducted in March-April 2022 (NCT:05323851). Effects of COVID-19 hospital-related measures on surgical patients' management and personal professional development across surgical specialties were explored. Data on demographics, pre-operative/peri-operative/post-operative management, and professional development were collected. Outcomes were matched with the corresponding volume. Four hundred and seventy-three respondents were included in final analysis across 14 surgical specialties. Since SARS-CoV-2 pandemic, application of telematic consultations (4.1% vs. 21.6%; p < 0.0001) and diagnostic evaluations (16.4% vs. 42.2%; p < 0.0001) increased. Elective surgical activities significantly reduced and surgeons opted more frequently for conservative management with a possible indication for elective (26.3% vs. 35.7%; p < 0.0001) or urgent (20.4% vs. 38.5%; p < 0.0001) surgery. All new COVID-related measures are perceived to be maintained in the future. Surgeons' personal education online increased from 12.6% (pre-COVID) to 86.6% (post-COVID; p < 0.0001). Online educational activities are considered a beneficial effect from COVID pandemic (56.4%). COVID-19 had a great impact on surgical specialties, with significant reduction of operation volume. However, some forced changes turned out to be benefits. Isolation measures pushed the use of telemedicine and telemetric devices for outpatient practice and favored communication for educational purposes and surgeon-patient/family communication. From the Italian surgeons' perspective, COVID-related measures will continue to influence future surgical clinical practice

Development and commissioning of a test system based on a TEM cell for RF exposure

In the development of a low-cost two-port TEM cell, a new analytical model of the capacitance of the terminations has been performed. The model has been verified by calculating the termination capacitance by means of a commercial 3D code. A TEM cell modified in accordance with the obtained results has been tested, with reference to the voltage standing wave ratio (VSWR) parameter, and the obtained improvements on VSWR versus frequency are reported. The TEM cell is the principal part of a test system for RF exposure (up to 230 MHz), including signal generator, power amplifier, dual directional coupler, 50 \u3a9 load attenuator and 1 GHz bandwidth oscilloscope, whose commissioning has been performed. A numerical analysis has been performed also for calculating the stationary electric field in the TEM cell. Experimental measurements of electric field inside the TEM cell, by means of an electric field meter (100 kHz \u2013 6 GHz broadband) were done, and the results are in good agreement with the numerical data

Magnetic field emissions up to 400 kHz from a welding equipment

This paper reports on the experimental characterization of a commercial industrial welding equipment with respect to magnetic field emissions up to 400 kHz. The frequency range of this analysis is due to the fact that the equipment under test is a manual metal arc (MMA) welding power source using inverter technology and an active dynamic control, resulting in frequency components in the tens and hundreds of kHz range. A simple and low cost new measurement probe consisting of three mutually perpendicular concentric coils for magnetic field analysis up to 400 kHz has been developed. This equipment has been combined with a commercial one for the analysis at low frequencies down to 5 Hz. Experimental data have been obtained at 400 A, maximum current for the equipment under test, with a resistive load corresponding to an MMA conventional load voltage of 36 V, in agreement with Standard EN 60974-1. Further analysis has been performed on the emissions from the welding cables. Frequency-selective field measurements have been obtained and the results are discussed with respect to occupational exposure limits

Electric field under an MV line supported by concrete poles

This paper presents a study of the electric field under a three-phase medium voltage (MV) power line supported by concrete poles. The analyzed configuration is a pole-top-pin construction. An analytical model has been developed for the three-phase wires assuming three straight cylindrical conductors whose axes have been put parallel to each other and to the ground, and for the concrete pole a cylindrical conductor placed in a vertical position. Simple analytical formulas have been obtained for the three components of the electric field in the vertical plane containing the axis of the conductor representing the central top wire. The validity range of the model is from the ground to one quarter of the height of the concrete pole. The analytical expressions have been checked against the numerical data obtained by a 3-D numerical analysis performed by using the charge simulation method. Finally, the results have been experimentally validated. The analytical model reported here is a new easy tool for the evaluation of the electric field for the analyzed geometry