In this paper, we study generalized Douglas–Weyl(α, β)-metrics. Suppose that a regular(α, β)-metric F is not of Randers type. We prove that F is a generalized Douglas–Weyl metric with vanishing S-curvature if and only if it is a Berwald metric. Moreover, by ignoring the regularity, if F is not a Berwald metric, then we find a family of almost regular Finsler metrics which is not Douglas nor Weyl. As its application, we show that generalized Douglas–Weyl square metric or Matsumoto metric with isotropic mean Berwald curvature are Berwald metrics. 相似文献
In this study, multiwalled carbon nanotube (MWCNT) was modified by the pyridine group using a silane agent and characterized by infrared spectroscopy (IR), thermal analysis (TG/DTA), and elemental analysis (CHN) and scanning electron microscopy (SEM). The application of this sorbent was investigated in determination of lead ions in aqueous samples, using flame atomic absorption spectrometry (FAAS). Through this study, different parameters such as pH and sample flow rate on adsorption process and eluent concentration, volume and flow rate were optimized. The limit of detection (LOD), the relative standard deviation and the recovery of the method were 2 ng mL?1, 1.3% and 99.7%, respectively. Two standard reference materials (NIST 1571 and NIST 1572) were used to verify accuracy of this method. Finally, the sorbent was successfully applied for extraction and determination of low levels of Pb(II) ions in aqueous samples. 相似文献
Using two different types of the laddering equations realized simultaneously by the associated Gegenbauer functions, we show that all quantum states corresponding to the motion of a free particle on AdS2 and S2 are splitted into infinite direct sums of infinite-and finite-dimensional Hilbert subspaces which represent Lie algebras u(1, 1) and u(2) with infinite- and finite-fold degeneracies, respectively. In addition, it is shown that the representation bases of Lie algebras with rank 1, i.e., gl(2, C), realize the representation of nonunitary parasupersymmetry algebra of arbitrary order. The realization of the representation of parasupersymmetry algebra by the Hilbert subspaces which describe the motion of a free particle on AdS2 and S2 with the dynamical symmetry groups U(1, 1) and U(2) are concluded as well. 相似文献
Understanding the behaviour of short-chain hydrocarbons confined to porous solids informs the targeted extraction of natural resources from geological features, and underpins rational developments in separation, storage and catalytic conversion processes. Herein, we report the application of low-field (12.7 MHz) 1H nuclear magnetic resonance (NMR) relaxation measurements to characterise ethane dynamics within mesoporous silica materials exhibiting mean pore diameters between 6 and 50 nm. Our measurements provide NMR-based adsorption isotherms within the range 25–50 bar and at ambient temperature, incorporating the ethane condensation point (40.7 bar at our experimental temperature of 23.6 °C). The quantitative nature of the acquired data is validated via a direct comparison of NMR-derived excess adsorption capacities with ex situ gravimetric ethane adsorption measurements, which are demonstrated to agree to within 0.2 mmol g−1 of the observed ethane capacity. NMR relaxation time distributions are further demonstrated as a means to decouple interparticle and mesopore dominated adsorption phenomena, with unexpectedly rapid relaxation rates associated with interparticle ethane gas confirmed via a direct comparison with NMR self-diffusion analysis. 相似文献
The magnesium and calcium salts of acrylic acid have been polymerised in aqueous solution using ammonium persulphate as initiator. Both polymers were also prepared by the neutralisation of poly(acrylic acid) with metal oxide in the same medium.
The thermal degradation behaviour of magnesium and calcium polyacrylate was studied using thermogravimetry (TG), differential thermal analysis (DTA) and thermal volatilisation analysis (TVA). Degradation products were investigated by IR spectroscopy, mass spectrometry and GC-MS techniques, the volatile product fraction having first been separated by subambient TVA.
The decompositions of these materials show some similarities to the behaviour of the alkali metal salts of poly(acrylic acid) and to that of the alkaline earth metal salts of poly(methacrylic acid), but there are also important differences. Acetone and carbon dioxide are the most important volatile products and, in addition, there are various other carbonyl containing products. More carbon dioxide, resulting from side group scission, is evolved from magnesium polyacrylate than from calcium polyacrylate, because of the lower thermal stability of magnesium carbonate. 相似文献
N -isopropenylbenzimidazolone undergoes a smooth reaction with triphenylphosphine and dialkyl acetylenedicarboxylates to produce highly functionalized salt-free phosphorus ylides in good yields. These stabilized phosphorus ylides exist as a mixture of two geometrical isomers as a result of restricted rotation around the carbon-carbon partial double bond resulting from conjugation of the ylide moiety with the adjacent carbonyl group. These ylides are converted to dialkyl 2-(1-isopropenyl-1H-benzimidazol-2-yl)-but-2-enedioates in boiling toluene. 相似文献
In this work, neutron knockout reactions of 15C on a 9Be target at energy 103 and 250 MeV/nucleon are studied. Using the Eikonal approximation of the Glauber model, total neutron removal cross sections, the stripping and diffractive cross sections as well as 14C longitudinal momentum distributions are determined in both 15C ground state and exited states of the wave function. We compared the results of our calculations with the available experimental data obtained recently. The calculated cross sections of 15C and 14C reactions, as well as the momentum distribution are in relatively good agreement with available data. 相似文献