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151.
152.
Class VII Flextensional Transducers (FTs) have been proposed as a means of overcoming the limitation of very high prestress in Class IV FTs. These transducers are made from shells shaped like dog bone and hence are also known as dog-bone shell transducers. In this work, we report design optimization of a low frequency aluminum shell Class VII FT, resonating at 2.5 kHz, using piezoelectric drive. Two and three dimensional Finite Element Modeling (FEM), with the help of a commercially available package ATILA have been used for the design optimization. Dimensional details of the base model have been adapted from previous literature. Parametric analyses have been done with respect to various aspects like type of rubber, shell height, shell material, etc. in order to optimize the design. Experimental results obtained from an initial prototype are also presented. The results match fairly well with the predicted values. 相似文献
153.
The electron paramagnetic resonance (EPR) parameters have been determined for the trivalent ions neodymium, erbium and ytterbium, at low abundance in lutetium vanadate. Crystal field splittings produce ground states which are Kramers doublets, and measurements were made of theg-values both parallel and perpendicular to the tetragonal axis; they are compared with previous measurements in yttrium vanadate. Two of the crystal field splitting parameters of the trivalent gadolinium ion (S = 7/2) in LuVO4 show noticeable difference from those in YVO4. 相似文献
154.
Langlet A Latypov NV Wellmar U Bemm U Goede P Bergman J Romero I 《The Journal of organic chemistry》2002,67(22):7833-7838
Nitration of some 2-substituted pyrimidine-4,6-diones in sulfuric acid was studied, which afforded previously unknown 5,5-gem-dinitropyrimidine-4,6-diones in high yields. The gem-dinitro products were easily attacked by nucleophiles with concomitant formation of gem-dinitroacetyl derivatives, which in turn could be further hydrolyzed to salts of dinitromethane and triureas. 相似文献
155.
Equations for the solubility of gases and vapours into dry alcohols from methanol to decan‐1‐ol and into water‐saturated alcohols from butan‐1‐ol to decan‐1‐ol have been compared through the use of the Abraham solvation equation. It is shown that there are noticeable differences in solvation into the dry and wet alcohols, and that these differences become larger as the alcohols become smaller and take up more water. The two main factors that lead to the differences in solvation are the solute hydrogen‐bond basicity, B, and solute size, L. Increase in solute hydrogen‐bond basicity favours the wet alcohols and increase in solute size favours the dry alcohols. Solute hydrogen‐bond acidity plays no part, because the hydrogen‐bond basicity of water, wet alcohols and dry alcohols is almost the same. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
156.
157.
Abraham Zaks 《Israel Journal of Mathematics》1971,9(3):285-289
The purpose of this note is to prove that a Dedekind domain R which contains a field k, and which is a subring ofk[x
1,…,x
n
] is a ring of polynomials. This generalizes similar results of A. Evyatar and A. Zaks on principal ideal domains, and of
P. M. Cohn for the casen=1. Our methods and proofs differ from those introduced previously.
This research was partially supported by the National Science Foundation, Grant GP-23861. 相似文献
158.
Canonical forms are found for all real four-dimensional matrices of the pseudo-orthogonal group which differs from the Lorentz group only in that its metric has twoplus signs and twominus signs. 相似文献
159.
The preparation of macrocyclic thiolactones by condensation of diacyl chlorides with siladithianes is described. 相似文献
160.
Raymond J. Abraham Fahimeh Eivazi R. Nayyir-Mazhir Harry Pearson Kevin M. Smith 《Magnetic resonance in chemistry : MRC》1978,11(1):52-54
Reproducible proton chemical shifts in the porphyrin series are obtained when the spectrum is measured in chloroform using the zinc (II) complex of the porphyrin in the presence of an excess of pyrrolidine. This method is specifically demonstrated for the case of 2,4-dicyanodeuteroporphyrin-IX dimethyl ester which, as the free base, shows dramatic effects due to aggregation phenomena. The shifts obtained using the zinc (II) complex plus pyrrolidine method, which allow compilation of substituent chemical shifts in the porphyrin series, are shown to be the same as the less easily accessible infinite dilution shifts of the porphyrin free bases. 相似文献