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71.
A chiral ionic liquid-catalyzed, efficient and unprecedented version of the Biginelli reaction using new variants of its active methylene component, viz. 2-phenyl-1,3-oxazol-5-one/2-methyl-2-phenyl-1,3-oxathiolan-5-one, with aromatic aldehydes and urea/thiourea enantio- and diastereoselectively, yields 5-amino-/mercaptoperhydropyrimidines. This three-component domino cyclocondensation reaction is effected via ring transformation of an isolable intermediate in a one-pot procedure. 相似文献
72.
73.
The reactions of dimethyltin dichloride with nitrogen and sulfur donor ligands derived by condensation of S‐benzyldithiocarbazate with indol‐3‐carboxylaldehyde, thiophene‐2‐aldehyde and furfuraldehyde have been investigated in 1:1 and 1:2 molar ratios in anhydrous alcohol. These ligands act as mononegatively charged bidentate species and coordinate to the central tin(IV) atom through the thiosulfur by proton exchange with the azomethine nitrogen. The newly synthesized complexes have been characterized by elemental analysis, conductance measurements and molecular weight determinations. The mode of bonding and the geometry of the complexes have been suggested on the basis of infrared, electronic and 1H, 13C and 119Sn NMR spectroscopy, and probable structures have been assigned to these complexes. A few representative ligands and their tin(IV) complexes have also been screened for their antifungal and antibacterial activities and found to be quite active in this respect. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
74.
M. Lal 《Il Nuovo Cimento D》1986,7(4):551-558
Summary In the present work the axially symmetric thermal-stress distribution in an infinite elastic solid containing an annular crack
under torsion has been studied. The problem is reduced to triple integral equations which in their turn are reduced to simultaneous
algebraic equations by using Hankel transform technique. The quantities of physical interest have also been computed and illustrated
graphically for different values of the inner and outer radius of the crack.
Riassunto In questo lavoro si studia la distribuzione a simmetria assiale dello stress termico in un solido elastico infinito che contiene un crack annulare sotto torsione. Il problema è ridotto alle equazioni integrali triple che per contro sono ridotte ad equazioni algebriche simul tanee usando la tecnica di trasformazione di Hankel. Sono state calcolate ed illustrate graficamente per valori differenti del raggio interno ed esterno del crack anche le quantità di interesse fisico.
Резюме В работе исследуется аксиально симметричное распределение термических напряжений в бесконечном упрутом твердом теле, содержащем кольцевые трещины при кручении. Рассматриваемая проблема сводится к интегральным уравнениям с тройными интегралами, которые, в свою очередь, сводятся к совместным алгебраическим уравнениям, испрльзуя технику преобразований Ганкеля. Вычисляются величины, представляющие физический интерес. Полученные величины иллюстрируются графически для различных значений внутреннего и внешнего радиусов трещин.相似文献
75.
76.
THEESTIMATIONOFPRIORFROMFISHERINFORMATION¥LIYUANZHANG;K.M.LALSAXENAANDQIANGWENJIUAbstract:InBayesiananalysis,themaximumentrop... 相似文献
77.
Santosh K. Shrestha Heiko Timmers Aidan P. Byrne Wayne D. Hutchison Don H. Chaplin Rakesh Dogra 《Hyperfine Interactions》2004,158(1-4):407-411
A radioisotope ion implanter has been developed using a cesium-sputtering, negative ion source, which offers versatility and
sustained operation. Employing the molecular 111In16O− ion, μCi activities of the radioisotope probe 111In/Cd have been implanted into different material hosts. The implanted tracer activity has been shown to be sufficient for
LTNO, NMRON and PAC. A new NMRON resonance for 111InAg was observed at 75.08 MHz. In2O3 powder performed well as the radioisotope carrier in the ion source, with the ratio of radioisotope and parasitic ion current
being typically 4 × 10−4. 相似文献
78.
79.
When a soft elastic cylinder is bent beyond a critical radius of curvature, a sharp fold in the form of a kink appears catastrophically at its compressed side while the tensile side remains smooth. The critical radius increases linearly with the diameter of the cylinder but remains independent of its material properties such as modulus; the maximum deflection at the location of the kink depends on both the material and geometric properties of the cylinder. The catastrophic dynamics of evolution of the kink depicts propagation of a shear wave from the location of the kink towards the edges signifying that kinking is an elastic response of the material which results in extreme localization of curvature. We have rationalized this phenomenon in the light of the classical Euler's buckling instability in slender elastic rods. 相似文献
80.
A parametric investigation of the friction performance of PC‐ABS parts processed by FDM additive manufacturing process 下载免费PDF全文
The friction performance is an important factor of parts processed by fused deposition modeling (FDM) for various engineering applications. It is one type of failure made of surface contact. The proper use of FDM process parameters can bring a significant reduction in friction and the amount of wear, thereby leading to a reduction in the material waste. To date, very little studies have been performed in this area. This paper investigates the effect of FDM manufacturing parameters on the friction performance of polycarbonate‐acrylonitrile butadiene styrene prototypes processed by FDM using definitive screening design and partial least squares method. The observation of surface morphology was obtained by the scanning electron microscopy to examine the effect of process parameters on the microstructure. The experimental results have shown that layer thickness, air gap, raster angle, and build orientation are the most influential factors affecting the friction performance of FDM manufactured parts. The proposed approach presented in this study provides an impetus to develop analytical modeling and functional relationships between FDM manufacturing parameters and friction performance. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献