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41.
In our previous work (Hu et al., 2014), a method has been proposed to detect gas compositions by locating the acoustic spectral peaks, which can be detected only by two-frequency acoustic measurements in practice. However, as a ‘Detection Calibration’, the effective relaxation area (ERA) constructed by existing theoretical model cannot match the two-frequency measurements when there are more than one strong relaxational components in gas mixtures. This paper proposes a method to construct the ERA by coupling the decoupled single relaxation times together to a whole relaxation time. For gas mixtures with only one single relaxation process, the predicted ERA results match with the experimental data better than those predicted by the existing model. Moreover, for gas mixtures in which more than one relaxation process are significant, the ERA results predicted by the proposed method also match with the detection results of two-frequency measurements better than the existing model. This relaxation time coupling based ERA constructing method is validated by the application in low-quality natural gas detection. 相似文献
42.
It is well known that β-ketoesters are useful intermediates for the synthesis of a range of heterocyclic templates. While there are many useful synthetic methods available to access these intermediates, there are still opportunities for the discovery of useful methodologies for their construction from novel starting materials. In this regard, we report on the discovery of a facile Pd-catalyzed Mizoroki–Heck coupling of ethyl 3-ethoxyacrylate with aryl and heteroaryl halides to form substituted alkoxyacrylates which can be hydrolyzed to form novel aryl and heteroaryl β-ketoesters. 相似文献
43.
Yashwantsinh S. Jadeja Khushal M. Kapadiya Hetal J. Jebaliya Anamik K. Shah Ranjan C. Khunt 《Magnetic resonance in chemistry : MRC》2017,55(6):589-594
Hesperidin is flavonoid molecule found in citrus fruits (Citrus reticulata), especially difficult to extract, classify and characterize. Present work is to study the unresolved relative configuration of Hesperidin through the dihedral angle, coupling constant and different NMR techniques. The Karplus equation and its modifications have been originated from the valence bond theory and associated with dihedral angle and coupling constant. The result data set of calculated dihedral angle can probe significant method to assign the virtual configuration of natural products and also resolved stereochemistry of Hesperidin at C‐2 position in. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
44.
J. Chevallier A. Duarte E. Löcherbach G. Ost 《Stochastic Processes and their Applications》2019,129(1):1-27
We consider spatially extended systems of interacting nonlinear Hawkes processes modeling large systems of neurons placed in and study the associated mean field limits. As the total number of neurons tends to infinity, we prove that the evolution of a typical neuron, attached to a given spatial position, can be described by a nonlinear limit differential equation driven by a Poisson random measure. The limit process is described by a neural field equation. As a consequence, we provide a rigorous derivation of the neural field equation based on a thorough mean field analysis. 相似文献
45.
Results of molecular dynamics are presented for a simple model of cyanoadamantane crystal. Rotator cubic phase was simulated over a wide range of temperatures. In this system, glass formation is not induced by quenched diluted disorder, but it occurs similarly to conventional glasses. Simulations have shown that the system evolves from free small-step rotational diffusion to jump like motion. The results obtained with this model are used to discuss the validity of the Mode Coupling Theory (MCT) predictions. 相似文献
46.
2,5- and 2,6-dideuterobenzoquinone-1,4 were prepared by a direct catalytic (NaBD4/PdCl2) exchange of bromine in the corresponding dibromo derivatives and the subsequent oxidation with Ag2O. The structure of the products was unambiguously established by proton-carbon and deuteron-carbon splitting pattern of their NMR spectra. 相似文献
47.
Numerical and experimental studies of a magnetic levitation harvester are presented in the paper. The idea is based on the motion of permanent cylinder magnet in a coil exploited for energy harvesting. The novel model is based on a new definition of the coupling coefficient (inductive coefficient) which relates mechanical and an electrical components. The performed static and dynamics experimental tests show that this coefficient is a nonlinear function of the magnet position, and highly depends on the magnet coordinate in the coil, in such a way that the maximum energy is obtained in a coil ends. The comparison between classical – fixed value model – and novel nonlinear model of the inductive coefficient is presented for selected cases. The most essential differences are presented. 相似文献
48.
Frank Hoffmann Lothar Jäger Carola Griehl 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):299-309
The reactions of diphenoxyphosphoryl chloride ((PhO) 2 P(O)Cl) and different chlorophosphonium salts ([R 3 PCl]X, R = (CH 3 ) 2 N, pyrrolidine, X = PF 6 m , BF 4 m ), respectively, with 7-aza-1-hydroxybenzotriazole (HOAt), 1-hydroxybenzotriazole (HOBt), hydroximinomalonitrile (HOxDCO), and ethyl hydroximinocyanoacetate (HOxO) are described. The structures of the new compounds, which are useful coupling reagents for epimerization-free peptide segment condensation, are discussed on the basis of their 1 H, 13 C, 31 P NMR, and IR spectra. The reactions of (PhO) 2 P(O)Cl lead to mixtures of O - and N -phosphorylated isomers of varying ratios. Contrary, reactions of chlorophosphonium salts yield exclusively one isomer. 相似文献
49.
Microwave-assisted tandem reaction of(Z)-arylvinyl bromides involving an elimination and homocoupling in the presence of DBU and Cul in DMF affords a variety of symmetrical 1,3-diynes in good to excellent yields.This tandem process,eliminating the need of volatile and savory terminal alkynes,provides an alternative to the conventional homocoupling methods for the synthesis of symmetrical 1,3-diynes. 相似文献
50.
《合成通讯》2013,43(19):3317-3325
Abstract We report a new application of the Suzuki-Miyaura reaction whereas two bifunctional reactants, 3,8-dibromo-1,10-phenanthroline and 3,5-diethynylheptyloxylbenzene (9), yield 3,8-bis(3-ethynyl-5-heptyloxyphenylethynyl)-1,10-phenanthroline (2) efficiently (74% yield) without polymerization. This was achieved by reacting a stoichiometric amount of 9 and (Me3Si)2NLi to obtain quantitatively the monoacetylide anion of 9 (10). The latter was activated with B-methoxy-9-BBN and reacted in analogy to the alkynyl copper complex of a Sonogashira route. However, in the Sonogashira reaction, the alkynyl copper complex is present in small equilibrium concentrations and polymerization takes place even when reagents are mixed slowly. Actually the Sonogashira route gave no desired product 2, as the latter polymerizes easily via homo-coupling in the presence of air and Cu(I). 相似文献