Postrzeganie wilków przez długie lata nie miało nic wspólnego z wiedzą o ich biologii i ekologii. Co mówią nam obserwacje wilczych rodzin o tych ssakach? Czy powinniśmy nadawać wilkom imiona i dlaczego wilki nie potrzebują naszej empatii?
Mathematical analysis for 3D Williamson nanofluid flow past a bi-directional stretched surface in Darcy-Forchheimer permeable media constitutes the focus of this study. The novelty of the proposed model is augmented by the addition of thermal and solutal stratification with chemical species and variable thermal conductivity. Calculations of the suggested model are conducted via the renowned homotopy analysis method (HAM). The results obtained are validated by comparing them in a limiting form with an already published article. Excellent harmony is achieved in this regard. Graphical structures, depicting impacts of assorted arising parameters versus the profiles involved are also provided. It is noticed that the velocity profile is a dwindling function of the Williamson parameter and Hartmann number. It is also stated that the Cattaneo-Christov heat flux exhibits conventional Fourier and Fick’s laws behavior when both coefficients of thermal and concentration relaxations are zero.
In this study, lead-free 0.94 Na0.5Bi0.5TiO3-0.06BaTiO3 (NBT-BT) compositions at morphotropic phase boundary were successfully synthesized by solid-state reaction method. The effects of the particle size for various milling time (12-24-48 hours) and sintering temperatures (1100-1125-1150-1175oC for 2h) on the electrical properties of the NBT-BT ceramics were evaluated. Experimental results showed that particle size and sintering temperatures significantly affect the electrical properties of NBT-BT ceramics. The particle size of the ceramic powders decreasing while milling time increases to 48 hours. Particle size values for 0, 12, 24 and 48 hours (h) milled powders were measured as nearly 1.5 µm, 1 µm, 700 nm, and 500 nm respectively. The bulk density enhanced with increasing sintering temperature and showed the highest value (5.73 g/cm3) at 1150oC for 48h milled powder. Similarly, the maximum piezoelectric constant (d33) = 105 pC/N, electromechanical coupling coefficient (kp) = 25.5% and dielectric constant (KT) = 575 were measured at 1150oC for 48 h milled powder. However, mechanical quality factor (Qm) was reduced from 350 to 175 with decreasing particle size. Similarly, remnant polarization was dropped by decreasing powder particle size from 56 μC/cm2 to 45 μC/cm2.
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