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Co-extruded multilayer films have been extensively investigated due to their broad range of applications in various industries, such as pipe and packaging. Ethylene vinyl alcohol (EVOH) is considered barrier polymer that is frequently co-extruded with polyethylene (PE) or polypropylene (PP) grafted with maleic anhydride (MA) to create films with multiple properties. While the combination of different polymers in a single structure offers unique mechanical, physical, and barrier properties, the quality of the bond between dissimilar polymers through co-extruded tie layer remains a challenge., Résumé de la communication présentée lors du congrès international tenu conjointement par Canadian Society for Mechanical Engineering (CSME) et Computational Fluid Dynamics Society of Canada (CFD Canada), à l’Université de Sherbrooke (Québec), du 28 au 31 mai 2023.

In this article, we report a wearable millimeter-size energy generator that yields instantaneous power of 2.1 W level from kinetic energy of human running motions. The generator, with a hybridization of piezoelectric and electromagnetic transductions, integrates mainly two major novel techniques: impact induced frequency up conversion effect for the piezoelectric generation and abrupt magnetic flux density change for the electromagnetic generation. The generator proves to be able to effectively harness energy from human motions, producing a power density over one order of magnitude higher than that of state-of-the-art work. This result is further validated by the charging performance, i.e. high charging rate and voltage into mF-level capacitors. Moreover, this wearable generator demonstrates the capability to charge a Li-on battery in dozens of minutes. This work can be of much significance for the development of self-charging battery powered wearable electronic devices. © 2020 Elsevier Ltd

The COVID-19 pandemic is one of the most challenging healthcare crises during the 21st century. As the virus continues to spread on a global scale, the majority of efforts have been on the development of vaccines and the mass immunization of the public. While the daily case numbers were following a decreasing trend, the emergent of new virus mutations and variants still pose a significant threat. As economies start recovering and societies start opening up with people going back into office buildings, schools, and malls, we still need to have the ability to detect and minimize the spread of COVID-19. Individuals with COVID-19 may show multiple symptoms such as cough, fever, and shortness of breath. Many of the existing detection techniques focus on symptoms having the same equal importance. However, it has been shown that some symptoms are more prevalent than others. In this paper, we present a multimodal method to predict COVID-19 by incorporating existing deep learning classifiers using convolutional neural networks and our novel probability-based weighting function that considers the prevalence of each symptom. The experiments were performed on an existing dataset with respect to the three considered modes of coughs, fever, and shortness of breath. The results show considerable improvements in the detection of COVID-19 using our weighting function when compared to an equal weighting function., Comment: 5 Pages, 1 Figure, To appear in The 7th International Conference on Wireless and Mobile Computing, Networking and Communication (IEEE eHPWAS - 17th IEEE WiMob - rank B), 2021

In this paper, we originally report an approach for cantilever piezoelectric energy harvesters (PEHs) for frequency tuning and performance improvement. The proposed scheme implements embedment of revolute joint(s) into PEH structure. We investigated two ways of embedment: the prior one is to replace the clamped edge partially with a joint and the other is to incorporate joint(s) into the substrate plane. Introducing joint mechanism reduces stiffness of the harvester, leading to more intense vibration and higher voltage of the piezoelectric element. We conducted FEA to validate hypothetical stiffness reduction by deriving resonant frequency considering parameters of joint width, length and number. Furthermore, experimental studies were conducted to compare open-circuit voltages in the frequency domain, power generation and capacitor-charging capabilities. The resonant frequencies from experiments display a good agreement with those from our simulation estimations. The embedded joint(s) effectively lowers resonant frequency by ∼43.1%. The output voltage of jointed cases increases ∼71.2 V, 2.83 times as high as that of the counterpart case. The mean power of the jointed cases reaches 0.49 mW, 7.3 times as high as that of the counterpart case. Furthermore, experimental charging results indicate remarkable improvement in charging capabilities regarding much higher charging rates and higher saturated voltage. © 2019

In this paper, we present a 0.33 W piezoelectric and electromagnetic hybrid energy harvester to tackle the problem of efficiently harnessing energy from low-frequency vibrations. Two types of transduction cores-one piezoelectric element and two sets of magnets and coils, are embedded into a compact design. Several techniques are employed to enhance the performance of the harvester. A pair of truss mechanisms are added into the system to amplify the strain of the piezoelectric element. A stopper is used to induce impact to take advantage of the frequency up conversion effect as well as nonlinearity. We used an array made of multiple small cubic magnets and alternative magnet arrangement rather than one magnet block, for abrupt magnetic flux density changes. Experimental results based on a fabricated prototype validate the proposed techniques that work collectively and enable the harvester to yield a maximum peak power more than 0.33 W at resonance under an excitation of 0.70 g. We also examined the capability of the harvester for self-powered applications. The harvester displays excellent charging performance to millifarad or farad-scale capacitors. An LED array consisting of 99 diodes was lit up in real time. More importantly, experimental results indicate that not just can the harvester simultaneously power a temperature and humidity sensor, and a calculator, but also when the excitation stops, the remaining charges stored can power them for ~20.38 min and ~8.33 min, respectively. This study can be of great significance for high-performance energy harvesting and further development of self-powered sensing and battery-free electronic systems. © 2019 Elsevier Ltd

A quantitative calibration of an existing phenomenological model for polycrystalline ferroelectric ceramics is presented. The model relies on remnant strain and polarization as independent variables. Innovative experimental and numerical model identification procedures are developed for the characterization of the coupled electro-mechanical, multi-axial nonlinear constitutive law. Experiments were conducted on thin PZT-5A4E plates subjected to cross-thickness electric field. Unimorph structures with different thickness ratios between PZT-5A4E plate and substrate were tested, to subject the piezo plates to coupled electro-mechanical fields. Material state histories in electric field-strain-polarization space and stress-strain-polarization space were recorded. An optimization procedure is employed for the determination of the model parameters, and the calibrated constitutive law predicts both the uncoupled and coupled experimental observations accurately.

In this paper, we propose a truss-based compressive-mode piezoelectric energy harvester to harness energy from low frequency vibrations with a wide bandwidth and a high-power output. The design is an integration of mainly three modules: separated excitation mechanism from transduction mechanism for low resonant frequency, truss mechanism for magnification of the applied force onto the piezoelectric element, and amplitude limit mechanism to induce impact forces. We then formulate the harvester as a two-degrees-of-freedom system featured by superposition of harmonic and impact-induced nonlinear responses. Based on our structure design, we fabricate a prototype to conduct experimental studies. The experimental results show that the harvester is capable of harnessing energy efficiently from vibrations at the resonant frequencies of 3.3 and 6.09 Hz. The total bandwidth is expanded to 4.2 Hz owing to the structure nonlinearity and bifurcation. The open circuit voltage reaches 83.3 V and maximum power gets up to 38.2 mW with the matching impedance. Also, the harvester exhibits excellent charging performance in terms of saturated voltage and charging time. © 1996-2012 IEEE.

Complex morphology of open cell porous media makes it difficult to link microstructural parameters and acoustic behavior of these materials. While morphology determines the overall sound absorption and noise damping effectiveness of a porous structure, little is known on the influence of microstructural configuration on the macroscopic properties. In the present research, a novel bimodal porous structure was designed and developed solely for modeling purposes. For the developed porous structure, it is possible to have direct control on morphological parameters and avoid complications raised by intricate pore geometries. A semi-empirical model is developed to relate microstructural parameters to macroscopic characteristics of porous material using precise characterization results based on the designed bimodal porous structures. This model specifically links macroscopic parameters including static airflow resistivity (σ)(σ), thermal characteristic length (Λ′)(Λ′), viscous characteristic length (Λ)(Λ), and dynamic tortuosity (α∞)(α∞) to microstructural factors such as cell wall thickness (2t)(2t) and reticulation rate (Rw)(Rw). The developed model makes it possible to design the morphology of porous media to achieve optimum sound absorption performance based on the application in hand. This study makes the base for understanding the role of microstructural geometry and morphological factors on the overall macroscopic parameters of porous materials specifically for acoustic capabilities. The next step is to include other microstructural parameters as well to generalize the developed model. In the present paper, pore size was kept constant for eight categories of bimodal foams to study the effect of secondary porous structure on macroscopic properties and overall acoustic behavior of porous media.