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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Electric Field Enhancement from Semiconductive Protrusions in Extruded Power Cables
摘要： The paper deals with calculation of the field enhancement from semiconductive protrusions in high voltage polymeric cables. The scientific community has traditionally used two different equations: The Larmor formula assuming spheroidal shape of the protrusion and the Mason formula assuming hyperboloidal shape. The Larmor equation can only be used for sharp protrusions (small tip radius) that are not representative for the majority of the protrusions found in power cables. On the other hand, the Mason equation has not this restriction, but can give values very much different from those obtained by the Larmor formula. It will be emphasized in the paper that the Mason formula was derived for needle-plane geometries and is therefore not valid for estimation of the field enhancement of protrusions extending into the insulation from a conductive plane. On the other hand, the Larmor formula follows from the analytical solution of the Laplace equation for the electric field outside a spheroidal-shaped protrusion in a plane-plane geometry. It is thus the best available formula for calculating field enhancement from semiconductive protrusions in high voltage cables. The paper will also introduce a new solution to the Laplace equation making it possible to extend the Larmor equation to spheroidal protrusions of all shapes, including those typical for modern cables.
关键词： Power cables,field enhancement,protrusions
更新于2025-09-23 15:21:01
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Evolution of microstructures on stainless steel induced by ultra-short pulsed laser ablation
摘要： Ultra-short pulsed laser ablation of stainless steel is accompanied by the evolution of different microstructures. Depending on the fluence, accumulated energy and number of laser passes cones from impurities, laser induced periodic surface structures, cone-like protrusion (CLP), and thermal bumps evolve at the surface. These often unwanted morphologies can be induced or inhibited by carefully choosing the strategy and laser parameters. The investigated range reveals a small processing window for defined 515 nm sub 1 ps ablation leading to low surface roughness using circular polarization. Hitherto, the origin and dependencies of CLP are still not well understood and for the first time a precursor ripple structure reported. These precursor ripples reveal supra-wavelength periodicity with about 2 μm spacing and evolve earliest after the second layer of ablation. Potentially, low spatial frequency laser-induced periodic surface structure generated with the first laser pass with pulse and hatch overlap are the root cause of CLP evolution. Moreover, the CLP growth is grain orientation and strongly polarization state dependent. Preferentially, CLP start to evolve at the {110} planes of the face-centered cubic crystals of the inspected austenitic stainless steel and linear polarized laser radiation revealing a 1:1 aspect ratio of 10 μm. A nanoindentation study at the interface near region on cross-sections reveals robust mechanical properties of this CLP structure.
关键词： Laser machining,Laser induced periodic surface structures,Ultra-short laser pulses,Orthogonal processing,Nanoindentation,Self-assembled structures,Cone-like protrusions
更新于2025-09-23 15:19:57
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Remarkable Improvement in Foldability of Polya??Si Thina??Film Transistor on Polyimide Substrate Using Blue Laser Crystallization of Amorphous Si and Comparison with Conventional Polya??Si Thina??Film Transistor Used for Foldable Displays
摘要： Highly robust poly-Si thin-film transistor (TFT) on polyimide (PI) substrate using blue laser annealing (BLA) of amorphous silicon (a-Si) for lateral crystallization is demonstrated. Its foldability is compared with the conventional excimer laser annealing (ELA) poly-Si TFT on PI used for foldable displays exhibiting field-effect mobility of 85 cm2 (V s)-1. The BLA poly-Si TFT on PI exhibits the field-effect mobility, threshold voltage (VTH), and subthreshold swing of 153 cm2 (V s)-1, -2.7 V, and 0.2 V dec-1, respectively. Most important finding is the excellent foldability of BLA TFT compared with the ELA poly-Si TFTs on PI substrates. The VTH shift of BLA poly-Si TFT is ±0.1 V, which is much smaller than that (±2 V) of ELA TFT on PI upon 30 000 cycle folding. The defects are generated at the grain boundary region of ELA poly-Si during folding. However, BLA poly-Si has no protrusion in the poly-Si channel and thus no defect generation during folding. This leads to excellent foldability of BLA poly-Si on PI substrate.
关键词： grain boundary,polyimide substrates,protrusions,flexible low-temperature poly-Si thin-film transistors,blue laser annealing
更新于2025-09-16 10:30:52