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NIKITIN S.; PR?TZEL-WOLTERS D. 《IMA Journal of Mathematical Control and Information》1991,8(4):431-439
In 1983 Morse proved, for unknown scalar one-dimensional linearsystems, the nonexistence of rational or polynomial universalstabilizers (UAS). In 1983, Nussbaum gave an example of an analyticUAS. In our paper, it is shown that there exist time-invariantpolynomial UAS's with multidimensional gain adaptation. Thedesign procedure is developed for linear, minimum-phase systemsof relative degree one. Convergence of the closed-loop systemis proved. Some numerical simulations are provided. 相似文献
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Liliana N. Trevani Jenene C. Roberts Peter R. Tremaine 《Journal of solution chemistry》2001,30(7):585-622
The spectra of copper(II)–ammonia solutions in 2 mol-kg–1 NH4NO3(aq) were recorded as a function of pH with a new UV–visible flow cell, capable of operating at conditions up to 325°C and 300 bars. Equilibrium constants for the formation of copper(II)–ammonia complexes Cu(NH3)n
2+, 1 n 4, from 30 to 150°C were determined by evolving factor analysis and nonlinear least-squares regression. Measurements at higher temperatures were limited by thermal decomposition of NH4NO3(aq). The formation constants of Cu(NH3)n
2+ decrease with temperature, consistent with extrapolations of literature data from measurements below 100°C. Measurements above 150°C were carried out in 0.5 mol-kg–1 CF3SO3H (aq), at the very high ammonia concentrations required to avoid the precipitation of CuO(s). The spectra are consistent with Cu(NH3)4
2+ as the predominant species, based on extrapolations of peak maxima and molar absorptivities from lower temperatures. Shifts in the spectra of Cu2+ and the Cu(NH3)n
2+ species to higher wavelength and increases in molar absorbance with increasing temperature are discussed in terms of the structure of the complexes. 相似文献
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An alternative approach to synthesize pedamide,a key building block of pederin was described.Iodine-induced asymmetric heterocyclization was used as the key step to construct the skeleton,a tetrahydropyran ring with three chiral centers.Brown's asymmetric allylation and Lewis acid-mediated allylation were investigated to introduce chains and chiral alcohols.Sharpless dihydroxylation decorated the side chain.And high optically pure target was obtained by removing the epimers formed in these reactions on c... 相似文献
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A convenient route for the synthesis of 3,4-dihydrocoumarin derivates from salicylaldehyde derivates and 1,3-dicarbonyl compounds under solvent-free microwave irradiation conditions was described. In this way, a range of compounds was obtained in moderate to good yields in a short reaction time. 相似文献
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Daniel E. Nieto Roca Carmen M. Romero Peter R. Tremaine 《Journal of solution chemistry》2017,46(2):388-423
The first and second ionization constants for the amino acids DL-2-aminobutyric acid (DL-2-aminobutanoic acid) and DL-norvaline (DL-2-aminopentanoic acid) were determined under hydrothermal conditions, from 175 to 275 °C at 10 MPa, using thermally-stable colorimetric pH indicators (acridine, 4-nitrophenol and 2-naphthoic acid). The measurements were carried out by UV–visible spectroscopy using a high-temperature, high-pressure platinum flow cell with sapphire windows, which minimized the effects of thermal decomposition. The results were combined with literature values from titration calorimetry at 25–130 °C to yield an extended van’t Hoff model for the temperature dependence of the ionization constants for the carboxylic acid and ammonium groups, \( K_{\text{a,COOH}} \) and \( K_{{{\text{a,NH}}_{3}^{ + } }} \), over the entire temperature range. The experimental results for the second ionization constant \( K_{{{\text{a,NH}}_{3}^{ + } }} \) at elevated temperatures are consistent with the predictions from the Yezdimer–Sedlbauer–Wood functional group additivity model, but for the first ionization constant \( K_{\text{a,COOH}} \) are not. This suggests that the group contribution parameters for the standard partial molar heat capacity of the carboxylic acid group are in error, or that nearest neighbor interactions between the –COOH and \( - {\text{NH}}_{3}^{ + } \) groups cause a breakdown in the functional group additivity relationship. 相似文献
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Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films
We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La0.7Ca0.3MnO3 (LCMO) and YBa2Cu3O7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO3 (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on
the LAO (control) and LCMO side of the substrate. Critical current, I
c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed
that while the control side showed a J
c of ∼ 2 × 106 A/cm2, the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J
c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of
J
c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection
length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length
has been quantified. A control experiment carried out with LaNiO3 deposited by PLD on YBCO did not show any evidence of self-injection. 相似文献
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Peter R. Tremaine J. D. Chen G. J. Wallace W. A. Boivin 《Journal of solution chemistry》1981,10(3):221-230
The solubility of carefully characterized UO2 in pOH 1.5 and pOH 2.5 aqueous solutions has been determined from 25°C to 300°C using a flow apparatus. Data were analyzed in terms of the reaction $$UO_2 + 2H_2 O + OH^ - \rightleftharpoons U(OH); log K = - 5.86 + 32/T$$ The extreme sensitivity of both the UO2 surface and aqueous U(IV) to oxidation is discussed. 相似文献
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