Since the beginning of 2020, coronavirus disease 2019 (COVID-19) has spread throughout China. This study explains the findings from lung computed tomography images of some patients with COVID-19 treated in this medical institution and discusses the difference between COVID-19 and other lung diseases. RésuméDepuis le début de l'année 2020, la maladie à coronavirus 2019 (COVID-19) s'est répandue dans toute la Chine. Cetteétude analyse les résultats tirés des images de TDM pulmonaire de certains patients atteints de COVID-19 traités dans cetétablissement médical et examine la différence entre le COVID-19 et d'autres maladies pulmonaires.

Effects of postdensification annealing upon microstructures and microwave dielectric characteristics in Ba((Co 0.6Àx/2 Zn 0.4Àx/2 Mg x ) 1/3 Nb 2/3 )O 3 (x = 0, 0.1, 0.2, and 0.3) complex perovskite ceramics have been investigated. Long-time annealing at temperatures below the order-disorder transition temperature enhances the cation ordering degree and promotes the ordering domain growth. The most significant improvement of Qf value is obtained together with the suppressed temperature coefficient of resonant frequency in the samples annealed at 1400°C for 12 h, while the dielectric constant decreases slightly. The Qf value of ceramics annealed at 1400°C mainly attributes to the enhanced cation ordering degree, because their low-energy domain boundaries are not detrimental to the Qf value. As the annealing temperature increases close to the transition temperature, coarse ordering domains with high-energy boundaries are formed, and then the Qf value steadily decreases because of the inferior domain structure, even the cation ordering degree increases. The microwave dielectric characteristics of Ba((Co 0.6Àx/2 Zn 0.4Àx/2 Mg x ) 1/3 Nb 2/3 )O 3 ceramics are affected by the common function of ordering degree and domain structure. The best combination of microwave dielectric characteristics is obtained in the composition of x = 0.3 after annealing at 1400°C for 12 h: e r = 33.2, Qf = 117 200 GHz, and s f = 8.6 ppm/°C. II. Experimental ProceduresBa((Co 0.6Àx/2 Zn 0.4Àx/2 Mg x ) 1/3 Nb 2/3 )O 3 (x = 0, 0.1, 0.2, 0.3) ceramics were prepared by a routine solid-state reaction process from high-purity powders of BaCO 3 (99.93%), CoO (99.9%), ZnO (99.95%), MgO (99.9%), and Nb 2 O 5 (99.99%). The weighed starting materials were mixed by ball milling with zirconia media in ethanol for 24 h, and P. K. Davies-contributing editor Manuscript No. 33012.

Effects of Mg substitution on order/disorder transition, microstructure, and microwave dielectric characteristics of Ba((Co0.6Zn0.4)1/3Nb2/3)O3 complex perovskite ceramics have been investigated. The ordered complex perovskite solid solutions are obtained in Ba((Co0.6−x/2Zn0.4−x/2Mgx)1/3Nb2/3)O3 ceramics (x = 0, 0.1, 0.2, and 0.3), and the ordering degree in the as‐sintered dense ceramics increases with increasing Mg‐substitution amount. The significantly improved Qf value is obtained in the present ceramics with increasing x, whereas the dielectric constant decreases slightly together with some increase of temperature coefficient of resonant frequency. The best combination of microwave dielectric characteristics is obtained in the composition of x = 0.3: εr = 33.7, Qf = 93 800 GHz, and τf = 9.6 ppm/°C. In the Mg‐substituted compositions, clear domain boundaries are obtained and the domain size increases as x increases, the highest Qf value is obtained when the domain size is about 40–60 nm in the ceramics with x = 0.3. The increased ordering degree and the fine ordering domain structure are considered to primarily contribute to the significant increase of Qf value in the Mg‐substituted Ba((Co0.6Zn0.4)1/3Nb2/3)O3 complex perovskite ceramics.

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