RESUMO
Background: Cardiac auscultation is a traditional method that is most frequently used for identifying congenital heart disease (CHD). Failure to diagnose CHD may occur in patients with faint murmurs or obesity. We aimed to develop an intelligent diagnostic method of detecting heart murmurs in patients with ventricular septal defects (VSDs) and atrial septal defects (ASDs). Materials and methods: Digital recordings of heart sounds and phonocardiograms of 184 participants were obtained. All participants underwent echocardiography by pediatric cardiologists to determine the type of CHD. The phonocardiogram data were classified as normal, ASD, or VSD. Then, the phonocardiogram signal was used to extract features to construct diagnostic models for disease classification using an advanced optical coherence tomography network (AOCT-NET). Cardiologists were asked to distinguish normal heart sounds from ASD/VSD murmurs after listening to the electronic sound recordings. Comparisons of the cardiologists' assessment and AOCT-NET performance were performed. Results: Echocardiography results revealed 88 healthy participants, 50 with ASDs, and 46 with VSDs. The AOCT-NET had no advantage in detecting VSD compared with cardiologist assessment. However, AOCT-NET performance was better than that of cardiologists in detecting ASD (sensitivity, 76.4 vs. 27.8%, respectively; specificity, 90 vs. 98.5%, respectively). Conclusion: The proposed method has the potential to improve the ASD detection rate and could be an important screening tool for patients without symptoms.
RESUMO
The microstructures and microwave dielectric properties of (Mg0.6Zn0.4)0.95Ni0.05TiO3 with Ca0.6La0.8/3TiO3 and Ca0.8Sm0.4/3TiO3 additions prepared by the solid-state method has been investigated. The crystallization and microstructures of these two mixed dielectrics were checked by XRD, EDX, BEI, and SEM to demonstrate two phase systems. Furthermore, the tunable dielectric properties can be achieved by adjusting the amounts of Ca0.6La0.8/3TiO3 and Ca0.8Sm0.4/3TiO3 additions, respectively. After optimization of processed parameters, a new dielectric material system 0.88(Mg0.6Zn0.4)0.95Ni0.05TiO3-0.12Ca0.6La0.8/3TiO3 possesses a permittivity (εr) of 24.7, a Qf value of 106,000 (GHz), and a τf value of 3.8 (ppm/°C), with sintering temperature at 1225 °C for 4 h. This dielectric system with a near-zero temperature coefficient and appropriate microwave properties revealed a high potential for high-quality substrates adopted in wireless communication devices.
RESUMO
Mg0.95Ni0.05TiO3 ceramics were prepared by traditional solid-state route using sintering temperatures between 1300 and 1425 °C and holding time of 2-8 h. The sintered samples were characterized for their phase composition, micro-crystalline structure, unit-cell constant, and dielectric properties. A two-phase combination region was identified over the entire compositional range. The effect of sintering conditions was analyzed for various properties. Both permittivity (εr) and Q factor (Qf) were sensitive to sintering temperatures and holding times, and the optimum performance was found at 1350 °C withholding time of 4 h. The temperature coefficient of resonant frequency (τf) in a range from -45.2 to -52 (ppm/°C) and unit-cell constant were not sensitive to both the sintering temperature and holding time. An optimized Q factor of 192,000 (GHz) related with a permittivity (εr) of 17.35 and a temperature coefficient (τf) of -47 (ppm/°C) was realized for the specimen sintered at 1350 °C withholding time of 4 h. For applications of 5G communication device (filter, antennas, etc.), Mg0.95Ni0.05TiO3 is considered to be a suitable candidate for substrate materials.
