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The manipulation of a ferroelectric vortex under the boundary condition of inhomogeneous screening is simulated by phase-field calculations. It is revealed that the vortex chirality can be tuned by utilizing uniform electric fields under inhomogeneous screening boundary conditions in which the switching mechanism is distinct from that under boundary conditions of asymmetric screening previously reported. The influence of the screening inhomogeneity and the ambient temperature on the vortex switching is further studied. The results indicate that inhomogeneous screening conditions are of vital importance to the switching behaviors of vortex chirality in a ferroelectric nanodot under the influence of a uniform electric field. Furthermore, the critical electric field is inextricably linked to the screening inhomogeneity and the ambient temperature. [ABSTRACT FROM AUTHOR]

The coupling calculation model of tunnel and surrounding rock is established by the finite difference method, and the main design parameters of lining structure of single-track ballasted tunnel under 40-ton axle load, heavy train load, are studied in combination with cumulative damage mechanism of surrounding rock at tunnel bottom and the fatigue life characteristics of concrete structure at tunnel bottom. The results show that (1) inverted arch shall be set in sections of III-grade and above. Whether an invert is set in sections of II-grade and below shall be determined according to lithology and groundwater conditions. When the surrounding rock condition is good and the tunnel bottom structure (without invert structure) is adopted, the thickness is recommended to be more than 20 cm, and the concrete strength grade should not be lower than C35. (2) Connection mode: the inverted arch and side wall of the tunnel should be connected in sequence to reduce the stress concentration and improve the stress state of the connection part between the inverted arch and the side wall. (3) It is suggested that the rise-span ratio of invert of single-track tunnel should be 1/6 ∼ 1/8; the larger value should be taken when the surrounding rock condition is poor and the small value should be taken when the surrounding rock condition is good. (4) The thickness of inverted arch is recommended to be no less than 20 cm under the condition of V-grade surrounding rock, to be no less than 15 cm under IV-grade surrounding rock, and to be no less than 10 cm under the condition of III-grade surrounding rock and II-grade surrounding rock sections requiring inverted arch. (5) The recommended value of bedding thickness meeting the design service life is 20 cm under the condition of II-grade surrounding rock. [ABSTRACT FROM AUTHOR]

The ceramics of 0·5Ba(ZrxTi1-x)O3-0·5(Ba0·75Ca0·25)TiO3(x = 0·15, 0·20, 0·25 and 0·30) (BZT-BCT) were synthesized by the conventional solid-state reaction method. And then, the dielectric, ferroelectric and electrostrictive properties of the ceramics were investigated near morphotropic phase boundary (MPB). Meanwhile, its crystallographic structure had been found to change from tetragonal phase to pseudocubic phase by the raising Zr4+ content from 0·15 to 0·30. And the grains morphology was observed from SEM. Finally, when the ceramics sintered at 1400°C for 2h with x = 0·15, The excellent properties were obtained: The electrostrictive strain reaches 0·16% under 40 kV cm− 1, and Tm=102°C, which demonstrated that the BZT-BCT has superior strain capacity as a lead-free system. [ABSTRACT FROM AUTHOR]

Empirical modeling is an essential and economical tool for estimating solar radiation. Based on statistical error tests, a model with relative sunshine duration, difference between average maximum and minimum air temperatures, relative humidity, and rainfall as parameters is recommended for estimating monthly average daily global solar radiation in Guangzhou. The present study can be used to encourage similar studies in the region that have the same climatic conditions as Guangzhou. [ABSTRACT FROM PUBLISHER]