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The accuracies of certain suboptimal solutions to the famous and still unsolved optimization problem known as ??Witsenhausen??s counterexample?? are investigated. The differences between the corresponding suboptimal values of the Witsenhausen functional and its optimum are estimated, too. The results give insights into the effectiveness of certain approaches proposed in the literature to face this hard optimization problem and into numerical results obtained by some researchers. 相似文献
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Maria Grazia De Angelis Giulio Cesare Sarti Aldo Sanguineti Patrizia Maccone 《Journal of Polymer Science.Polymer Physics》2004,42(10):1987-2006
The permeation, diffusion, and sorption of dimethyl ether into a series of commercial fluoroelastomers were characterized at various pressures and temperatures. The polymers under study were based on tetrafluoroethylene and contained various amounts of other perfluorinated monomers: perfluoromethylvinylether, hexafluoropropylene, and a partially fluorinated monomer, vinylidene fluoride (VDF). These polymers were also filled with inorganic particles and cured with different techniques. The permeation rate of dimethyl ether in the elastomers examined, as well as the solubility value, increased as the content of the nonperfluorinated monomer (VDF) increased, and this was consistent with the solubility parameter theory. The diffusion coefficients, at a fixed concentration, had rather similar values for most of the elastomers examined. Both the permeability and diffusivity increased with temperature, and the corresponding activation energies were obtained for two selected polymers. The solubility of dimethyl ether, at a fixed temperature and activity, showed a linear dependence versus the weight fraction of the partially fluorinated monomer (VDF) in the polymeric matrix. The effect of the filler on the sorption and transport properties was also considered: the addition of the filler lowered the permeability and diffusivity, whereas the solubility was generally increased with respect to the crosslinked rubber. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1987–2006, 2004 相似文献
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The reaction of primary nitroalkanes with magnesium or lithium amides provides a convenient, one-step synthesis of substituted amidoximes. 相似文献
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P. Fossati A. Sanguineti M. G. De Angelis M. G. Baschetti F. Doghieri G. C. Sarti 《Journal of Polymer Science.Polymer Physics》2007,45(13):1637-1652
An experimental analysis has been performed in this work, aimed to the characterization of thermodynamic and mass transport properties of a semicrystalline fluoro polymer (MFA) obtained from the copolymerization of tetrafluoroethylene (TFE) and perfluoromethylvinylether. Sorption and permeation experiments for two alkanes and corresponding perfluorinated compounds in MFA were performed at two different temperatures and solubility coefficients, as well as diffusivity and permeability, were determined. Experimental data were analyzed through different thermodynamic models to draw general conclusions about properties of MFA polymeric phases. Special attention was devoted to the glassy nature of MFA polymeric mixtures around room temperature. Indeed, analysis of experimental sorption data was performed through the use of specific models for glassy polymeric phases as well as by means of classical equilibrium models for fluid mixtures. Conclusions have been drawn from the aforementioned analysis, which significantly contributes to the discussion of correct location of glass‐transition temperature for PTFE and its copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1637–1652, 2007 相似文献
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The technique known as “weight decay” in the literature about learning from data is investigated using tools from regularization
theory. Weight-decay regularization is compared with Tikhonov’s regularization of the learning problem and with a mixed regularized
learning technique. The accuracies of suboptimal solutions to weight-decay learning are estimated for connectionistic models
with a-priori fixed numbers of computational units.
The Authors were partially supported by a PRIN grant from the Italian Ministry for University and Research, project “Models
and Algorithms for Robust Network Optimization”. 相似文献
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A. Alessandri C. Cervellera M. Sanguineti 《Journal of Optimization Theory and Applications》2007,134(3):445-466
The design of state estimators for nonlinear dynamic systems affected by disturbances is addressed in a functional optimization
framework. The estimator contains an innovation function that has to be chosen within a suitably defined class of functions
in such a way to minimize a cost functional given by the worst-case ratio of the ℒ
p
norms of the estimation error and the disturbances. Since this entails an infinite-dimensional optimization problem that
under general hypotheses cannot be solved analytically, an approximate solution is sought by minimizing the cost functional
over linear combinations of simple “basis functions,” represented by computational units with adjustable parameters. The selection
of the parameters is made by solving a constrained nonlinear programming problem, where the constraints are given by pointwise
conditions that ensure the well-definiteness of the functional and the existence of a solution. Penalty terms are introduced
in the cost function to account for constraints imposed on points that result from sampling the sets to which the trajectories
of the state and of the estimation error belong. To ensure an efficient covering of the sets, low-discrepancy sampling techniques
are exploited that generate samples deterministically spread in a uniform way, without leaving regions of the space undersampled.
Work supported by a PRIN grant from the Italian Ministry of University and Research (Project “New Techniques for the Identification
and Adaptive Control of Industrial Systems”) and by the EU and the Regione Liguria trough the Regional Programs of Innovative
Action of the European Regional Development Fund. 相似文献
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Bassi M Guarda PA Pagano E Sanguineti A Marchionni G 《The journal of physical chemistry. B》2006,110(24):12172-12178
After a broad scouting based on quantum chemical calculations, optical absorption measurements in the vacuum ultraviolet (VUV) wavelength region between 140 and 190 nm were performed on a narrower series of commercial and experimental liquids. By elimination of sources of external contamination, mainly due to atmospheric gases, the analysis of the contributions to the absorption related to the backbone structure and to the chain end composition allowed the synthesis of a novel family of linear perfluoropolyethers (PFPEs) with optical absorbance at 157 nm between 0.3 and 0.6 cm(-1) in a broad range of compositions and molecular weights. The dependence of the optical threshold on the PFPE composition demonstrates that -OCF2- is the most transparent segmental unit in the VUV region. 相似文献
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Paola Machetta Marco Lazzarino Valeri Kapeliouchko Tiziana Poggio Giorgio Canil Aldo Sanguineti Vincenzo Arcella 《Macromolecular Symposia》2002,179(1):347-358
Modern integrated circuits require insulating materials with a dielectric constant as low as possible in order to obtain device speed improvements through lower RC delay. We have investigated the electrical and structural properties of PTFE thin films obtained from Algoflon®-PTFE nanoemulsions, via spin coating deposition, followed by sintering. Films as thin as 160 nm with dielectric strength better than 4 MV/cm have been obtained. 相似文献