RÉSUMÉ
Personal physiological data is the digital representation of physical features that identify individuals in the Internet of Everything environment. Such data includes characteristics of uniqueness, identification, replicability, irreversibility of damage, and relevance of information, and this data can be collected, shared, and used in a wide range of applications. As facial recognition technology has become prevalent and smarter over time, facial data associated with critical personal information poses a potential security and privacy risk of being leaked in the Internet of Everything application platform. However, current research has not identified a systematic and effective method for identifying these risks. Thus, in this study, we adopted the fault tree analysis method to identify risks. Based on the risks identified, we then listed intermediate events and basic events according to the causal logic, and drew a complete fault tree diagram of facial data breaches. The study determined that personal factors, data management and supervision absence are the three intermediate events. Furthermore, the lack of laws and regulations and the immaturity of facial recognition technology are the two major basic events leading to facial data breaches. We anticipate that this study will explain the manageability and traceability of personal physiological data during its lifecycle. In addition, this study contributes to an understanding of what risks physiological data faces in order to inform individuals of how to manage their data carefully and to guide management parties on how to formulate robust policies and regulations that can ensure data security.
RÉSUMÉ
Recently, rapidly increased demands of integration and miniaturization continuously challenge energy densities of dielectric capacitors. New materials with high recoverable energy storage densities become highly desirable. Here, by structure evolution between fluorite HfO2 and perovskite hafnate, we create an amorphous hafnium-based oxide that exhibits the energy density of ~155 J/cm3 with an efficiency of 87%, which is state-of-the-art in emergingly capacitive energy-storage materials. The amorphous structure is owing to oxygen instability in between the two energetically-favorable crystalline forms, in which not only the long-range periodicities of fluorite and perovskite are collapsed but also more than one symmetry, i.e., the monoclinic and orthorhombic, coexist in short range, giving rise to a strong structure disordering. As a result, the carrier avalanche is impeded and an ultrahigh breakdown strength up to 12 MV/cm is achieved, which, accompanying with a large permittivity, remarkably enhances the energy storage density. Our study provides a new and widely applicable platform for designing high-performance dielectric energy storage with the strategy exploring the boundary among different categories of materials.
RÉSUMÉ
Transparent piezoelectric materials are capable of coupling several physical effects such as optics, acoustics, electricity, and mechanical deformation together, which expands applications for mechanical-electro-optical multifunctional devices. However, piezoelectricity, transparency, and Curie temperature restrict each other, so it is difficult to achieve high piezoelectricity with both good transparency and a high Curie point. In this paper, Sm-doped 24Pb(In1/2Nb1/2)O3-42Pb(Mg1/3Nb2/3)O3-34PbTiO3 (PIN-PMN-PT) transparent ceramic with a high piezoelectric coefficient of 905 pC/N, excellent electro-optical coefficient of 814 pm/V, and high Curie-point of 179 °C is fabricated. Sm doping effect on the phase structures, piezoelectricity, ferroelectricity, optical transparency, electro-optical properties, and thermal stability is systematically investigated. Compared with PMN-PT transparent ceramics, PIN-PMN-PT transparent ceramics exhibit better temperature stability. Electro-optical modulation and energy conversion are achieved using PIN-PMN-PT transparent piezoelectric ceramic, which indicates that it has great potential to develop mechanical-electrical-optical multifunctional coupling devices for optical communication, energy harvesting, photoacoustic imaging, and so on.
RÉSUMÉ
The 0.975[0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3]-0.025Eu2O3 ceramics were prepared by a two-step sintering process including oxygen sintering and hot-pressing. An ultrahigh piezoelectric charge coefficient of 1400 pC/N and a superior optical transmittance up to 68% were simultaneously achieved. The underlying mechanism was discussed from a microstructural perspective, where the watermark domain configuration with a small domain size is responsible for the high optical transmission, while the large remanent polarization and dielectric constant and the introduced tetragonal phase with a parallel stripe domain structure are believed to synergistically contribute to the high piezoelectric coefficients. This work demonstrates that the rare-earth dopant in the PMN-PT ceramic system is conducive to enhanced transparency and piezoelectricity.
RÉSUMÉ
The domain configuration of lead-free (K0.48Na0.52)(Nb0.96Sb0.04)O3-Bi0.50(Na0.82K0.18)0.50ZrO3 ceramics with rhombohedral-tetragonal morphotropic phase boundary, accounting for the high piezoelectric property and good thermal stability, were systematically studied. Short domain segments (before poling) and long domain stripes with wedge-shaped or furcated ends (after poling) were found to be typical domain configurations. The reduced elastic energy, lattice distortion, and internal stress, due to the coexistence of rhombohedral and tetragonal phases, result in much easier domain reorientation and domain wall motion, responsible for the high piezoelectric properties, being on the order of 460 pC/N, in which the extrinsic contribution from irreversible domain switching was estimated to be around 50% of the total piezoelectricity. Minor piezoelectric property variations (<6% over a temperature range from -50 to 100 °C) were observed as a function of temperature, showing a good thermal stability. In addition, nanodomains (50 ± 2 nm) were found to be assembled into domain stripes after poling, believed to benefit the high piezoelectric properties but not causing much thermal instability due to the small quantity.