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1.
2.
We consider the least squares approximation of gridded 2D data by tensor product splines with free knots. The smoothing functional to be minimized—a generalization of the univariate Schoenberg functional—is chosen in such a way that the solution of the bivariate problem separates into the solution of a sequence of univariate problems in case of fixed knots. The resulting optimization problem is a constrained separable least squares problem with tensor product structure. Based on some ideas developed by the authors for the univariate case, an efficient method for solving the specially structured 2D problem is proposed, analyzed and tested on hand of some examples from the literature. 相似文献
3.
TorstenLinB 《计算数学(英文版)》2003,21(4):401-410
We consider a singularly perturbed semilinear convection-diffusion problem with a boundary layer of attractive turning-point type. It is shown that its solution can be decomposed into a regular solution component and a layer component. This decomposi-tion is used to analyse the convergence of an upwinded finite difference scheme on Shishkin meshes. 相似文献
4.
We study a model linear convection-diffusion-reaction problem where both the diffusion term and the convection term are multiplied by small parameters εd and εc, respectively. Depending on the size of the parameters the solution of the problem may exhibit exponential layers at both end points of the domain. Sharp bounds for the derivatives of the solution are derived using a barrier-function technique. These bounds are applied in the analysis of a simple upwind-difference scheme on Shishkin meshes. This method is established to be almost first-order convergent, independently of the parameters εd and εc. 相似文献
5.
Summary N-Benzoylphenylhydroxylarnine complexes of some metals have been investigated by HPLC. The green chromium complex formed by this reagent shows conclusive evidence of the presence of geometrical isomers. It is photosensitive and changes to a brown modification when irradiated with ultra violet or visible light. Elution behaviour of the complexes has been studied with different solvent mixtures. Attempts have been made to characterize the complexes from different measurements.
Untersuchung von isomeren Chrom-N-benzoylphenylhydroxylaminaten durch HPLC相似文献
6.
Torsten Küppers Martin Köckerling Prof. Dr. Helge Willner Prof. Dr. 《无机化学与普通化学杂志》2007,633(2):280-284
The new tetracyanoborate K[B(CN)4]·CH3CN was synthesized by dissolution of the solvent‐free K[B(CN)4] in acetonitrile and subsequent careful crystallization. The crystal structure has been determined by single‐crystal X‐ray diffraction. It crystallizes in the orthorhombic space group P212121 with Z = 4. Some comparisons with related structures are made, and the vibrational spectrum is discussed. 相似文献
7.
8.
Sablinskas V Hegelund F Ceponkus J Bariseviciute R Aleksa V Nelander B 《The journal of physical chemistry. A》2005,109(39):8719-8723
Ozonization reaction of ethene in neat film at 77 K was performed. Separation of ethene secondary ozonide from the other products of the reaction was performed by continuous pumping of the reactor. Only the products, which evaporated from the walls of the reactor at 185 K, were transferred to the gas cell. The high-resolution infrared absorption spectrum of gaseous ethene secondary ozonide (C(2)H(4)O(3)) in a static gas long-path absorption cell has been recorded in the 900-1100 cm(-1) spectral region at 185 K. The spectral resolution was 0.003 cm(-1). Analyses of the nu(7)(A) band at 1037.0 cm(-1), the nu(8)(A) band at 956.1 cm(-1), and the nu(18)(B) band at 1082.1 cm(-1) have been performed using the Watson Hamiltonian model (A, reduction; III(r), representation). A set of ground-state rotational and quartic centrifugal distortion constants have been obtained, and upper state spectroscopic constants have been determined for the bands investigated. A local resonance observed in nu(18) is explained as c-Coriolis interaction with nu(10) + nu(11). 相似文献
9.
B. W. Wenclawiak Torsten Hees Corinna E. Z?ller Hans-Peter Kabus 《Fresenius' Journal of Analytical Chemistry》1997,358(4):471-474
An on-line system of supercritical fluid extraction (SFE) and high performance liquid chromatography (HPLC) via solid phase
extraction (SPE) is described for the determination of palladium and rhodium 2,2,6,6-tetramethyl-3,5-heptanedione-(thd) as
well as rhodium-acetylacetonate-(acac) and benzylacetonate-(bzac) chelates. The chelates were extracted with supercritical
CO2 from sand and humic acid, concentrated on SPE cartridges and analysed with HPLC. Two cartridge materials were tested and
compared to off-line trapping. The percentage of the breakthrough and cartridge retained material were measured in liquid
dichloromethane. The SFE conditions could be optimized to separate metal chelates during the extraction. The supercritical
fluid (SF) behaviour of different ligands on rhodium were investigated.
Received: 19 July 1996/Revised: 11 December 1996/Accepted: 14 December 1996 相似文献
10.
Torsten Meyer Thomas Hellweg Stefan Spange Stephanie Hesse Christian Jger Cornelia Bellmann 《Journal of polymer science. Part A, Polymer chemistry》2002,40(18):3144-3152
Polyvinylamine hydrogels with silica particles encapsulated (PVAm/silica) were produced by a two‐step synthesis. In the first step, polyvinylformamide/silica (PVFA/silica) hybrids were synthesized from vinylformamide (VFA) and 1,3‐divinylimidazolidin‐2‐one (1,3‐bisvinylethyleneurea, BVU), as the crosslinker, by radical copolymerization in silica/water suspensions using different compositions of VFA/BVU. The target product PVAm/silica was obtained by acidic hydrolysis of the PVFA/silica hydrogels in a second step. The chemical structures of both hydrogels, PVFA/silica and PVAm/silica, respectively, were revealed by solid‐state 13C(1H) cross‐polarity/magic‐angle spinning NMR spectroscopy. Both hydrogels swelled significantly in water. The swelling capacity of the two systems was characterized by the correlation length ξ (or hydrodynamic blob size) of the network meshes with small‐angle neutron scattering experiments. ξ is significantly larger for PVAm/silica than for PVFA/silica, which corresponds to the observed higher swelling capacity of this polyelectrolyte material. Furthermore, the swelling behavior of the hybrid hydrogels was quantitatively described in terms of free swell capacity, centrifuge‐retention capacity, adsorption against pressure, and free swell rate as compared with values of the corresponding copolymer hydrogels. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3144–3152, 2002 相似文献