123,372 research outputs found
The effect of degassing on morphology and space charge
No full textIt is believed that space charge buildup in cross-linked polyethylene (XLPE) insulation is the main cause for premature failure of underground power cables. The space charge activities in XLPE depend on many factors such as additives, material treatment, ambient temperature, insulator/electrode interface, etc. Degassing is one of the material treatment process commonly employ in cable manufacturing to improve insulation performance. In this paper, investigation on the effect of degassing period has on the morphology and space charge was carried out. Planar XLPE samples of the same composite were subjected to different degassing time. It is discovered that apart from removing volatile by-products, degassing also anneal XLPE material; changing the morphology as a result
Temperature effect on space charge dynamics in XLPE insulation
No full textThis paper reports on space charge evolution in crosslinked polyethylene (XLPE) planar samples approximately 1.20 mm thick subjected to electric stress level of 30 kVdc/mm under four temperature 25 oC, 50 oC, 70 oC and 90 oC for 24 hours. Space charge profiles in both as-received and degassed samples were measured using the laser induced pressure pulse (LIPP) technique. The dc threshold stresses at which space charge initiates are greatly affected by testing temperatures. The results suggest that testing temperature has numerous effects on space charge dynamics such as enhancement of ionic dissociation of polar crosslinked by-products, charge injection, charge mobility and electrical conductivity. Space charge distributions of very different nature were seen at lower temperatures when comparing the results of as-received samples with degassed samples. However at higher temperature, the space charge distribution took the same form, although of lower concentration in degassed samples. Space charge distributions are dominated by positive charge when tested at high temperatures regardless of sample treatment and positive charge propagation enhances as testing temperature increases. This can be a major cause of concern as positive charge propagation has been reported to be related to insulation breakdown
Photoluminescence Quenching Phenomena of Different Surfactants on Core-Shell CdSe/ZnS Nanoparticles
No full textWhispering gallery modes in highly hexagonal symmetric structures of SBA-1 mesoporous silica
No full textEnhancement of random lasing based on the composite consisting of nanospheres embedded in nanorods template
No full text
A Rosary of Rubies: The Chronicle of the Gur-rigs mDo-chen Tradition from South-Western Tibet
Full text linkThe mDo-chen bKa’-brgyud-pa school represents a little known Buddhist tradition from Mang-yul Gung-thang in south-western Tibet. It goes back to a Buddhist yogin known as Ma-bdun-pa or Ma-bdun ras-chen (12th/13th c.) and was later mainly spread by members of the Gur family. Although belonging to the “Upper ’Brug” (stod ’brug) branch of the ’Brug-pa bKa’-brgyud-pa school, the mDo-chen tradition has always been deeply infused with the “spoken teachings” (bka’ ma) and “treasure teachings” (gter ma) of the rNying-ma-pa school, and the cult of the “Seven Ma-mo Sisters” (ma mo mched bdun) was particularly practised and transmitted by its members. This book presents a critical edition, an annotated translation and a photographic reproduction of a manuscript copy of a rare chronicle of the Gur-rigs mDo-chen tradition written by Brag-dkar rta-so sPrul-sku Chos-kyi dbang-phyug (1775–1837). The text provides us with an overview of the tradition’s development mainly through biographical accounts but also through prophecies, prayers and praises for individual masters. The study concludes with two appendices based on the mDo chen bka’ brgyud gser ’phreng, a lineage history composed in the 15th century, and the “records of teachings received” (thob yig) of three important members of the Gur family, thus allowing us to gain an insight into the transmissions of the mDo-chen bKa’-brgyud-pa school and the interactions of its representatives with other important Buddhist teachers up to the 18th century. The present work is a further outcome of the author’s investigations into the cultural and religious traditions of south-western Tibet and the neighbouring Himalayan valleys
Characterizations of material constraint effect for creep crack in center weldment under biaxial loading
Full text linkMaterial mismatch effect on the cracking behavior is an important topic for those welding structures. Characterization of the material constraint effect based on rigorously asymptotic solution is studied in this paper. Based on decomposition of the second order term, the constraint effect characterization parameter is decomposed as material constraint parameter and geometry constraint parameter. In general, the total constraint level for crack tip under undermatch condition is higher than overmatch condition. The specimen with positive biaxiality could lead to a higher constraint level compared with that of negative biaxiality. Geometry constraint effect and material constraint effect could not be separated independently from rigorously asymptotic solution for those cases with positive biaxiality. For a crack tip field under non-positive biaxiality, the material constraint effect can be characterized independently although it is approximate. For these conditions, the proposed material constraint effect and geometry constraint effected characterized are approximately independent on material mismatch factor, crack depth ratio and stress biaxiality. An empirical formula has been presented to characterize the geometry constraint effect and material constraint effect for the crack tip in the weldment under biaxial loading, which has been verified with fine accuracy. © 2021, The Author(s), under exclusive licence to Springer Nature B.V
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