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731.
SYNTHESIS OF BRANCHED POLYETHYLENE USING (α-DIIMINE)NICKEL(Ⅱ) -TiCl4 COMBINED AND SUPPORTED CATALYST
(a-Diimine)nickel(Ⅱ) {[C6H5 - N = C(CH3) - C(CH3) = N - C6H5]NiBr2}-TiCl4 abbreviated as NiL-TiCl4combined catalyst which is supported on MgCl2-SiO2 carrier has been prepared, by using alkyl aluminum (AlR3) as the cocatalyst in place of methylaluminoxane (MAO) to catalyze ethylene oligomerization and copolymerization in situ. The influences of procedure for supporting NiL-TiCl4, the molar ratio of NiL to TiCl4, cocatalyst type and polymerization temperature on the catalytic performance were studied. The degree of branching and the composition of the branched chain of polymers produced have been investigated by IR and 13C-NMR spectra. The results show that the combined catalyst can synthesize the branched polyethylene with various banched chains .The polymerization reaction was monitored by gas chromatography and mass spectrometry (GC-MS). The results show that this catalyst promotes the oligomerization and copolymerization in situ for ethylene. 相似文献
732.
A theoretical model and signal processing of acoustic correlation measurements to estimate current velocity are discussed. The sonar space-time correlation function of volume reverberations within Fraunhofer zone is derived. The function, which is in exponential forms, is the theoretical model of acoustic correlation measurements. The characteristics of the correlation values around the maximum of the amplitude of the correlation function, where most information about current velocity is contained, are primarily analyzed. Localized Least Mean Squares (LLMS) criterion is put forward for velocity estimation. Sequential Quadratic Programming (SQP) method is adopted as the optimization method. So the systematic signal processing method of acoustic correlation techniques for current velocity measurement is established. A prototype acoustic correlation current profiler (ACCP) underwent several sea trials, the results show that theoretical model approximately coincides with experimental re- sults. Current profiles including the speed and direction from ACCP are compared with those from acoustic Doppler current profiler (ADCP). The current profiles by both instruments agree reasonably well. Also, the standard deviation of velocity measurement by ACCP is statistically calculated and it is a little larger than predicted value. 相似文献
733.
References: 《声学学报:英文版》2008,27(1):23-33
The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results. 相似文献
734.
Vrielinck H De Cooman H Tarpan MA Sagstuen E Waroquier M Callens F 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,195(2):196-205
For the analysis of the angular dependence of electron paramagnetic resonance (EPR) spectra of low-symmetry centres with S=1/2 in three independent planes, it is well-established-but often overlooked-that an ambiguity may arise in the best-fit g<--> tensor result. We investigate here whether a corresponding ambiguity also arises when determining the hyperfine coupling (HFC) A<--> tensor for nuclei with I=1/2 from angular dependent electron nuclear double resonance (ENDOR) measurements. It is shown via a perturbation treatment that for each set of M(S) ENDOR branches two best-fit A<--> tensors can be derived, but in general only one unique solution simultaneously fits both. The ambiguity thus only arises when experimental data of only one M(S) multiplet are used in analysis or in certain limiting cases. It is important to realise that the ambiguity occurs in the ENDOR frequencies and therefore the other best-fit result for an ENDOR determined A<--> tensor depends on various details of the ENDOR experiment: the M(S) state of the fitted transitions, the microwave frequency (or static magnetic field) in the ENDOR measurements and the rotation planes in which data have been collected. The results are of particular importance in the identification of radicals based on comparison of theoretical predictions of HFCs with published literature data. A procedure for obtaining the other best-fit result for an ENDOR determined A<--> tensor is outlined. 相似文献
735.
Nóra Kucska 《哲学杂志》2018,98(18):1708-1730
A 2D square, two-bands, strongly correlated and non-integrable system is analysed exactly in the presence of many-body spin–orbit interactions via the method of Positive Semidefinite Operators. The deduced exact ground states in the high concentration limit are strongly entangled, and given by the spin–orbit coupling are ferromagnetic and present an enhanced carrier mobility, which substantially differs for different spin projections. The described state emerges in a restricted parameter space region, which however is clearly accessible experimentally. The exact solutions are provided via the solution of a matching system of equations containing 74 coupled, non-linear and complex algebraic equations. In our knowledge, other exact results for 2D interacting systems with spin–orbit interactions are not present in the literature. 相似文献
736.
董文堂 《应用数学和力学(英文版)》1995,16(3):293-299
ANANALYTICALSOLUTIONTOLARGEDEFLECTIONEQUATIONSOFSIMPLY-SUPPORTEDRECTANGULARHYPERBOLOIDALSHALLOWSHELLSOFORTHOTROPICCOMPOSITESD... 相似文献
737.
马如云 《应用数学和力学(英文版)》1993,14(2):193-200
This paper deals with multiplicity results for nonlinear elastic equations of the type-d~4u/dx~4+π~4u+g(x,u)=e(x)(0results under suitable condition. 相似文献
738.
739.
THERMOCHROMIC EFFECTS OF LEUCO DYES STUDIED IN POLYPROPYLENE 总被引:1,自引:0,他引:1
Arno Seeboth Detlef Lǒtzsch Elvira Potechius Renate Vetter 《高分子科学》2006,24(4):363-368
A series of thermochromic polypropylene foils were prepared by embedding various leuco dye-developer-solvent systems in the polymer matrix. Bisphenol A, laurylgallate, ethylgallate and p-hydroxybenzoic acid methyl ester were used as developers, crystal violet lactone and 3,3-bis-(1-n-butyl-2-methyl-3-indolyl)-phthalide as dyes and l-octanoic acid methyl ester as solvent. The molar ratio between the three components of the investigated leuco dye-developer-solvent systems was kept constant. All obtained polypropylene foils exhibit an excellent thermochromic behavior. The foils, prepared by extrusion technology, switch from color to colorless with increasing temperature. The influence of molecular structure of the developer on the intensity of the colored state and the influence of a developer-surfactant complex on the resulting thermochromic properties were investigated. The results are presented and discussed in detail according to a molecular model suggesting that the ring-opening process of the leuco dye is triggered by the formation of dye-developer complexes via H-bondings. 相似文献
740.
Junjun Wang 《Numerical Methods for Partial Differential Equations》2023,39(1):30-44
A three step backward differential formula scheme is proposed for nonlinear reaction–diffusion equation and superconvergence results are studied with Galerkin finite element method unconditionally. Energy stability is testified for the constructed scheme with an artificial term. Splitting technique is utilized to get rid of the ratio between the time step size and the subdivision parameter . Temporal error estimate in H2-norm is derived, which leads to the boundedness of the solutions of the time-discrete equations. Unconditional spatial error estimate in L2-norm is deduced which help bound the numerical solutions in L∞-norm. Superconvergent property of in H1-norm with order is obtained by taking difference between two time levels of the error equations unconditionally. The global superconvergent property is deduced through the above results. Two numerical examples show the validity of the theoretical analysis. 相似文献