2,245 research outputs found
Polyethylene/silica nanocomposites: absorption current and the interpretation of SCLC
No full textThe topic of nanodielectrics continues to receive significant attention from today’s dielectrics community, due to the property enhancements that can stem from the unique interfacial features within such material systems. Nevertheless, understanding of the interfacial phenomena that occur in nanodielectrics and which determine their electrical behaviour is challenging. In this paper, we report on an investigation into the absorption current behaviour of two nanocomposite systems, one containing an untreated nanosilica and the other containing the same nanofiller chemically modified using trimethoxy(propyl)silane. The results indicate that the absorption current behaviour of all the nanocomposites is very different from that of the reference, unfilled polymer; while the current flowing through the unfilled polyethylene decreased monotonically with time in a conventional manner, all nanocomposites revealed an initial decrease followed by a period in which the current increased with increasing time of electric field application. Possible mechanisms leading to the observed absorption current behaviour in the nanocomposites are discussed with the aid of space charge measurements. The presence of space charge limited conduction (SCLC) and its trap-filled limit is proposed.
This data supports the article Lau,K.Y. et al (2016) Polyethylene/silica nanocomposites: absorption current and the interpretation of SCLC J. Phys. D: Appl. Phys.</span
Optimum structures of digital controllers in sampled-data systems: a roundoff noise analysis
Full text linkIn this paper, the effect of roundoff noise in a digital controller is analyzed for a sampled-data system in which the digital controller is implemented in a state-space realization. A new measure, called averaged roundoff noise gain, is derived. Unlike the traditionally used measure, where the analysis is done based on an equivalent digital control system, this newly defined averaged roundoff noise gain allows us to take consideration of the inter-sample behavior. It is shown that this measure is a function of the state-space realization. Noting the fact that the state-space realizations of a digital controller are not unique, the problem of optimum controller structure is to identify those realizations that minimize the averaged roundoff noise gain subject to the -scaling constraint which is for preventing the signals in the controller from overflow. An analytical solution to the problem is presented and a design example is given. Both theoretical analysis and simulation results show that the optimum controller realizations obtained with the proposed approach are superior to those obtained with the traditional analysis based on a digital control system
Multicultural Experience Fosters Creative Conceptual Expansion
No full textEdited by Angela K.Y. Leung, Chiu Chi-Yue and Hong Ying-Yi</p
On the dielectric response of silica-based polyethylene nanocomposites
No full textThe dielectric response of silica-based polyethylene nanocomposites is studied by dielectric spectroscopy. The results indicate that nanocomposites absorb significantly more water than unfilled polyethylene, with the consequence that both permittivity and loss tangent increase with increasing duration of water immersion. However, appropriate surface treatment of nanosilica is found to reduce the water absorption effect and to modify the dielectric response of the nanocomposites compared with those containing untreated nanosilica. While water absorption may not be a technologically desirable characteristic, our results indicate that water molecules can act as effective dielectric probes of interfacial factors
Nanodielectrics: opportunities and challenges
No full textThis article highlights recent findings and issues concerning nanodielectric research and outlines possible future work on nanodielectrics, in particular in relation to nanofiller/polymer interface
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