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1.
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   
2.
The application of single‐atom catalysts (SACs) to high‐temperature hydrogenation requires materials that thermodynamically favor metal atom isolation over cluster formation. We demonstrate that Pd can be predominantly dispersed as isolated atoms onto TiO2 during the reverse water–gas shift (rWGS) reaction at 400 °C. Achieving atomic dispersion requires an artificial increase of the absolute TiO2 surface area by an order of magnitude and can be accomplished by physically mixing a precatalyst (Pd/TiO2) with neat TiO2 prior to the rWGS reaction. The in situ dispersion of Pd was reflected through a continuous increase of rWGS activity over 92 h and supported by kinetic analysis, infrared and X‐ray absorption spectroscopies and scanning transmission electron microscopy. The thermodynamic stability of Pd under high‐temperature rWGS conditions is associated with Pd‐Ti coordination, which manifests upon O‐vacancy formation, and the artificial increase in TiO2 surface area.  相似文献   
3.
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   
4.
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   
5.
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   
6.
我们给出了关于六元gcd封闭集S的充分必要条件,使得在整数矩阵环M_6(Z)中,定义在S上的e次幂GCD矩阵(S~e)整除e次幂LCM矩阵[S~e].这部分解决了Hong在2002年提出的一个公开问题.  相似文献   
7.
This work presents (in a wider perspective), some of our recent developments in the mathematical modeling and control of bulk polymerization for the production of HIPS. The recent model by Casís assumes the polymerization to be heterogeneous, and it calculates (in two phases) the global molecular structure of the three polymeric components of HIPS (free polystyrene, unreacted polybutadiene, and graft copolymer). At present, a model is being developed capable of estimating the average particle morphology (salami or core‐shell). Assuming a continuous bulk HIPS process as homogeneous, Luciani estimated the evolution of the MFI of the final product during changes of grade, with the aim of minimizing the intermediate off‐spec product. Finally, an unpublished simulation is presented that describes the transitions between the steady state of a HIPS‐grade and that of a general‐purpose polystyrene.

  相似文献   

8.
Novel Cu-Ni/C has been prepared and utilized as an efficient catalyst system in direct synthesis of DMC from CH3OH and CO2.  相似文献   
9.
Poly(trimethylene terephthalate)(PTT) is an excellent fiber material.Its thermal degradation and isothermal crystalline behaviors were in this study investigated using thermogravimetric analysis(TGA),thermogravimetric analysis-Fourier transform infrared spectroscopy(TGA-FTIR) analysis,differential scanning calorimetry(DSC) and X-ray diffraction(XRD).The thermal degradation mechanism of PTT follows Mclafferty rearrangement principle.The PTTwithintrinsicviscosity(Ⅳ) of 0.74 dL/g has a maximum crystallinity...  相似文献   
10.
A series of novel benzimidazole derivatives was synthesized and their anti-Coxsackie virus B_3(CVB_3) activity was evaluated in VERO cells.Compounds 9 and 10 exhibited better inhibitory activity than those of ribavirin(RBV) with IC_(50) values of 5.30 and 1.06μg/mL,respectively.  相似文献   
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