Papers by Keyword: Electro-Thermal Effect

Abstract: Considering physical mechanisms, an electro-thermal effect model of GaAs pseudomorphic high electron mobility transistor (PHEMT) was proposed. The model included PAD capacitances, intrinsic elements and extrinsic elements, which represented the relationship of performance parameters to physical structure and temperature. By using this model, the effects of temperature to devices performance parameters could be analyzed, and the device's structure and materials' parameters could be optimized. A typical GaAs PHEMT was simulated in the EDA software. Thus, DC I-V characteristics and small-signal S parameters of PHEMT under varied temperatures could be given.

Abstract: Based on the functional characteristics of carbon fiber reinforced concrete (CFRC), an improved infrared nondestructive testing method, to detect crack in CFRC by using infrared thermography, is presented in this paper. The principle is that when a CFRC specimen is applied a low voltage, crack existing in the specimen will result in non-homogeneous surface temperature distribution due to the electro-thermal effect of the material. Monitoring the temperature difference on the surface, the crack under the observed surface can be inspected by using infrared thermography. In theory, the mechanism causing the temperature difference comes down to an unsteady heat transfer problem with internal energy sources. In the case of the thermo-physical property of CFRC as given, the sensitivity of this method to the depth of the crack is analyzed by numerical computation.

Abstract: Cement structures such as bridges and dams often come into being distortion or exhibit excessive thermal stresses due to the sun radiation or freeze-thaw cycle. Therefore, temperature especially inner temperature difference or deformation of structures must be controlled or regulated sometimes in order to reduce thermal stresses or excessive deformation and to extend the life-span of structures. In this paper, the electro-thermal effects of smart cement are used to adjust temperature difference or deformation of concrete beams without the need of peripheral non-structural materials. Concrete beams for temperature and deformation adjustment were fabricated, and some experimental results as well as the related conclusions about temperature difference and deformation were produced. Based on these results, experiments of temperature difference or deflection adjustment are further conducted successfully. The research results in this paper are the bases of temperature and deformation adjustment for mass concrete structures. A new path will be broken to adjust temperature or deformation easily for some structures.