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61.
Electrical model of a liquid crystal pixel with dynamic, voltage history-dependent capacitance value
The voltage history-dependent nature of a liquid crystal pixel capacitance becomes an important issue in active matrix addressing as large storage capacitors are replaced with more intelligent circuitry such as in-pixel frame buffers. In this paper, a simple but flexible Spice macro model is introduced that allows accurate simulations of the electrical behaviour of a nematic liquid crystal pixel capacitance. The model correctly predicts voltage drops caused by the increasing dielectric constant when liquid crystal molecules align themselves to the electric field. An internal node of the macro model represents the average director orientation and can also be used to predict the optical response. In its basic embodiment, the model uses a first-order, low pass RMS filter to implement the dynamic behaviour of the pixel, which suffices to predict response delays and asymmetric rise and fall times. However, the model also supports more elaborated filters that offer more control over the simulated dynamic behaviour. A number of simulations are performed that illustrate the usefulness of the new model during the design of novel 'smart' pixel architectures. 相似文献
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63.
MØrup Steen Frandsen Cathrine BØdker Franz Klausen Stine Nyborg Lefmann Kim LindgÅrd Per-Anker Hansen Mikkel Fougt 《Hyperfine Interactions》2002,144(1-4):347-357
Hyperfine Interactions - The magnetic properties of antiferromagnetic nanoparticles have been studied by Mössbauer spectroscopy and neutron scattering. Temperature series of Mössbauer... 相似文献
64.
J.R. Owen W.C. Maskell B.C.H. Steele T.Steen Nielsen O.Toft Sørensen 《Solid State Ionics》1984,13(4):329-334
LiAl thin film electrodes were formed by cathodic conversion of the surface of a 50 micron Al foil in a propylene carbonate based electrolyte. The films were cycled both in Li-doped poly(ethylene oxide) and propylene carbonate. On charging, an overpotential of 40 mV was required to sustain growth of the LiAl phase, but the diffusional overpotential was minimal. A simple diffusional model for the discharge predicted serious rate limitation due to slow diffusion in the α phase. However, measurements of the diffusion coefficient gave values many orders higher than previously reported and even greater values were required to explain the discharge rates. Cycling behaviour showed that the electrode degradation was less severe in the polymeric electrolyte than in propylene carbonate. 相似文献
65.
Steen Hildebrandt 《European Journal of Operational Research》1977,1(5):289-294
The aim of this article is to point out some basic aspects of the OR/MS implementation problem and to outline a frame of reference for dealing with the OR/MS process. The model proposed includes a decomposition of the OR/MS process. Phases, interest groups, strategies, and variables in the OR/MS process are considered as being important. The first part of the article is a summary of some important recent contributions by others, whereas the second part represents contributions resulting from the author's own research. 相似文献
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68.
Steen Yde-Andersen Jørgen S. Lundsgaard Lone Møller John Engell 《Solid State Ionics》1984,14(1):73-79
Nasicon ceramics have been prepared from gel-derived raw materials both by conventional sintering and by hot-pressing. For several compositions the ionic conductivity have been determined by the AC-method. The properties of ceramics based on the ZrO2-poor composition Na2.94Zr1.49P0.8Si2.2O10.85 have been studied in greater detail. Durability test in Na/Na-cells so far indicate good stability at 300°C, and corrosion tests in molten sodium (400°–700°C) indicate that at 400°, 350° and 300°C it will take respectively at least 100 h, 7 weeks and 3 years to dissolve a 1 micron thich layer of the ceramic. The fracture strenght of the ceramics have been determined by the three point bending method. Weibul statistics indicate an average fracture strength of 168 MPa and a m-value of 8.3 (sample vol. 0.07 cm3) for the best ceramics prepared so far. 相似文献
69.
Niels Olhoff Steen Hφjlund Rasmussen 《International Journal of Solids and Structures》1977,13(7):605-614
We study the problem of determining the optimum shape of a thin, elastic, clamped column of given length and volume, such that the fundamental buckling load is a maximum. The column cross-sections are assumed to be geometrically similar, and a minimum allowable value is specified for the cross-sectional area.Investigating the optimization problem parametrically in terms of this minimum constraint, we reveal a significant feature. There exists a threshold value for the constraint, beyond which the optimum columns are all associated with single mode optimum buckling loads, whereas, for any value of the constraint less than the threshold value, the optimum columns are associated with bimodal fundamental buckling loads.This bimodal behaviour necessitates an extension and a mathematical reformulation of the current optimization problem, which is outlined and solved in the paper. In particular, we revise the result hitherto considered to be the optimum solution for an unconstrained column with clamped ends. 相似文献
70.
Steen Honoré Hansen Per Helboe Mogens Thomsen 《Trends in analytical chemistry : TRAC》1985,4(9):233-237
A new approach to reversed-phase high-performance liquid chromatography has been developed and investigated in some detail. Bare silica is used as the column packing material with an aqueous eluent containing a buffer, an organic solvent as the modifier and a long-chain quaternary ammonium ion. The eluent exhibits a high affinity to the silica surface at pH values above 5, thus, dynamically, forming a nonpolar stationary phase. 相似文献