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81.
Francisca Zamora Khalid Hakkou Abdelilah Alla Manuel Rivas Isaac Roff Manuel Mancera Sebastin Muoz‐Guerra Juan A. Galbis 《Journal of polymer science. Part A, Polymer chemistry》2005,43(19):4570-4577
The synthesis and characterization of a new series of aromatic polyesters based on D‐mannitol and galactitol are described. These polyesters were obtained by polycondensation reaction of the terephthaloyl chloride or isophthaloyl chloride and 2,3,4,5‐tetra‐O‐methyl‐D‐mannitol or 2,3,4,5‐tetra‐O‐methyl‐galactitol in o‐dichlorobenzene. All the new polyesters were characterized by elemental analyses, GPC, IR, and NMR. They were soluble in chloroform, but insoluble in water and other polar oxygenated solvents. They showed a notable hygroscopicity, lower for those containing isophthalic units. DSC and X‐ray diffraction studies showed that D‐mannitol‐based polyesters were stiffer and less crystalline than those derived from galactitol, which presented a noticeably lower thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4570–4577, 2005 相似文献
82.
Exact and approximate solutions for the reliability of a circular shaft, simultaneously subjected to a bending moment and a torque, are derived and compared. The closed-form solution is obtained in terms of an equivalent bending moment having a noncentral chi-square distribution, whereas the approximate solution is derived via the Hasofer-Lind reliability index. Comparison shows a remarkably high accuracy of the index.On leave from the Technion, Israel Institute of Technology, Haifa, Israel 相似文献
83.
We construct examples of Markov Decision Processes for which, for a given initial state and for a given nonstationary transient policy, there is no equivalent (randomized) stationary policy, i.e. there is no stationary policy which occupation measure is equal to the occupation measure of a given policy. We also investigate the relation between the existence of equivalent stationary policies in special models and the existence of equivalent strategies in various classes of nonstationary policies in general models. 相似文献
84.
An equivalent circuit model for analyzing the AC characteristics of power VDMOS transistors is presented. The model accounts for high field and saturation effects. This is achieved by incorporating dependent voltage and current sources in the device model. Results are given for the AC characteristics of a POLYFET F2001 Power VDMOSFET rated with a drain current of 1.4A, power out of 2.5W at 1GHz. The linear, quasi-saturation and saturation regions of the IV characteristics are accounted for in the analysis. The small signal device parasitics are extracted through s-parameter methods. The s-parameter results were used to extract the frequency dependent parasitics including parasitic capacitances, inductances and transconductances. 相似文献
85.
In this paper we introduce a new class of facet-inducing inequalities for the Windy Rural Postman Problem and the Windy General
Routing Problem. These inequalities are called Zigzag inequalities because they cut off fractional solutions containing a
zigzag associated with variables with 0.5 value. Two different types of inequalities, the Odd Zigzag and the Even Zigzag inequalities,
are presented. Finally, their application to other known Arc Routing Problems is discussed. 相似文献
86.
Kathlyn A. Parker Isaac D. Cohen Albert Padwa William Dent 《Tetrahedron letters》1984,25(43):4917-4920
Azomethine ylides, generated from cyanomethylamino silanes and excess silver fluoride, undergo cycloaddition with quinones to give, after oxidation , quinonoid isoindoles. This reaction provides the key step for a short, high yield synthesis of the isoindole 1a. 相似文献
87.
The addition of the benzylidine derivative of ethyl glycine to the enone system of a quinone monoacetal and subsequent aromatization provide a high yield preparation of intermediates for the synthesis of isoquinoline quinones. 相似文献
88.
We have found the two-phonon mode of the disorder-induced line at 1370 cm-1 for the single crystal and polycrystalline graphites having disorder. The degenerate E2g mode of the D6h symmetry for graphite is split for the disordered graphites, having frequencies at 1590 cm-1 and 1627 cm-1. Brewster angle measurements using lasers at 6328A and 10.6 μm yield n and k with good consistency even for surfaces with moderate roughness. Our results suggested that distortion of the crystal structure is present. 相似文献
89.
90.
Isaac Greber Raimo J. Hakkinen Leon Trilling 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1958,9(5-6):312-331
Résumé Ce mémoire décrit quelques recherches expérimentales et théoriques sur l'interaction des ondes de choc obliques avec les couches
limites laminaires. Une série de mesures détaillées de pressions et du frottement a été faite dans la région d'interaction
dans un écoulement le long d'une plaque plane. Un modèle du mécanisme en a été déduit, dont les prédictions s'accordent raisonnablement
bien avec les résultats des expériences. Les mêmes idées ont été appliquées à l'interaction sur une surface courbe, et les
résultats s'accordent encore avec les expériences. Une étude simplifiée de la région de stabilité de l'interaction sous l'action
d'oscillations de faible amplitude a été faite.
This work was supported by the National Advisory Committee for Aeronautics Contracts Nos. Naw-6320, 6412, 6452, 6507 and Air Force Contract No. 33-(616-3064) sponsored by the Wright Air Development Center, Wright Patterson Air Force Base. 相似文献
This work was supported by the National Advisory Committee for Aeronautics Contracts Nos. Naw-6320, 6412, 6452, 6507 and Air Force Contract No. 33-(616-3064) sponsored by the Wright Air Development Center, Wright Patterson Air Force Base. 相似文献