This study introduces the development advances and trend of power semiconductors used in hybrid and electric vehicles (HEV/EV). The status and forecast of power electronics' requirement in HEV/EV are discussed along with a review of the automotive standard of power semiconductor devices. The advances in automotive semiconductor technologies such as Sibased insulated-gate bipolar transistor (IGBT) and freewheeling diode (FRD) and SiC-based metal oxide semiconductor fieldeffect transistor (MOSFET) and Schottky barrier diode are presented. The advances in automotive semiconductor packaging technologies are illustrated from three considerations, which are the low inductance in high-power density packaging, lower thermal resistance designing, and advanced packaging technologies. The challenges and development trend of more reliable power semiconductors for HEV/EV are discussed. The challenges in Si devices are focused on power density, efficiency, reliability, and packages, while the high temperature and low inductances are the main challenges for SiC devices. Lastly, the development trend is discussed in terms of four aspects, the new generation Si IGBT for HEV/EV, such as recessed-emittertrench, reverse-conduction-IGBT, and smart IGBT; next generation SiC MOSFET; new packaging technology and material, such as planar packaging.
Super-hydrophobic surfaces are quite common in nature, inspiring people to continually explore its water-repellence property and applications to our lives. It has been generally agreed that the property of super-hydrophobicity is mainly contributed by the microscale or nanoscale (or even smaller) architecture on the surface. Besides, there is an energy barrier between the Cassie-Baxter wetting state and the Wenzel wetting state. An optimized square post micro structure with truncated square pyramid geometry is introduced in this work to increase the energy barrier, enhancing the robustness of super-hydrophobicity. Theoretical analysis is conducted based on the wetting transition energy curves. Numerical simulation based on a phase-field lattice Boltzmann method is carried out to verify the theoretical analysis. The numerical simulation agrees well with the theoretical analysis, showing the positive significance of the proposed micro structure. Furthermore, another novel micro structure of rough surface is presented, which combines the advantages of truncated pyramid geometry and noncommunicating roughness elements. Theoretical analysis shows that the novel micro structure of rough surface can effectively hinder the Cassie-Baxter state to Wenzel state transition, furtherly enhancing the robustness of the surface hydrophobicity.
Emissivity variations are one of the most critical challenges in thermography technologies; this is due to the temperature calculation strongly depending on emissivity settings for infrared signal extraction and evaluation. This paper describes an emissivity correction and thermal pattern reconstruction technique based on physical process modelling and thermal feature extraction, for eddy current pulsed thermography. An emissivity correction algorithm is proposed to address the pattern observation issues of thermography in both spatial and time domains. The main novelty of this method is that the thermal pattern can be corrected based on the averaged normalization of thermal features. In practice, the proposed method brings benefits in enhancing the detectability of the faults and characterization of the materials without the interference of the emissivity variation problem at the object’s surfaces. The proposed technique is verified in several experimental studies, such as the case-depth evaluation of heat-treatment steels, failures, and fatigues of gears made of the heat-treated steels that are used for rolling stock applications. The proposed technique can improve the detectability of the thermography-based inspection methods and would improve the inspection efficiency for high-speed NDT&E applications, such as rolling stock applications.
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