An effective fingerprint orientation field estimation method using differential values of grayscale intensity.

Fingerprint orientation field (OF) estimation is important for basic fingerprint image processing and impacts the accuracy of fingerprint image enhancements, such as Gabor filters. In this article, we introduce an OF estimation algorithm based on differential values of grayscale intensity and examine the accuracy and reliability of the proposed algorithm by applying it to fingerprint images processed using Gaussian blurring and the Gaussian white noise process. The experimental results indicate that the OF estimation reliability of the proposed algorithm is higher than the gradient-based method and the power spectral density (PSD) based method in low quality fingerprints. The proposed algorithm is especially useful in noisy fingerprint images, where the OF estimation reliability of the algorithm is 6.46% and 32.93% higher than the gradient-based method and the PSD-based method, respectively.

The Enhanced Thermal Stability of (Mg0.95Ni0.05)2TiO4 Dielectric Ceramics Modified by a Multi-Phase Method.

The thermal stability of (Mg0.95Ni0.05)2TiO4 dielectric ceramics has been improved by mixing with CaTiO3 phases owing to higher positive temperature coefficients. The pure (Mg0.95Ni0.05)2TiO4 and the mixture phase systems of CaTiO3-modified (Mg0.95Ni0.05)2TiO4 were verified by XRD diffraction patterns to ensure the crystallite of different phases. The microstructures of the CaTiO3-modified (Mg0.95Ni0.05)2TiO4 were observed by SEM and EDS to investigate the relation between element ratios and grains. As a result, it can be seen that the thermal stability of the CaTiO3-modified (Mg0.95Ni0.05)2TiO4 can be effectively enhanced, compared with the pure (Mg0.95Ni0.05)2TiO4. Moreover, the radio frequency dielectric performances of CaTiO3-modified (Mg0.95Ni0.05)2TiO4 dielectric ceramics are strongly dependent upon the density and the morphology of the specimens. The champion sample with the ratio of (Mg0.95Ni0.05)2TiO4 and CaTiO3 of 0.92:0.08 showed an εr value of 19.2, an Qf value of 108,200 GHz, and a τf value of -4.8 ppm/°C, which may encourage (Mg0.95Ni0.05)2TiO4 ceramics to broaden the range of novel applications and match the requirements of 5G or next-generation communication systems.