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941.
(TlMes2)[BF4] – A Salt with the Linear Cation (Mes‐Tl‐Mes)+ TlMes3 was reacted with [BF3(OEt2)] in Et2O at 20 °C to give (TlMes2)[BF4] ( 1 ). 1 was characterized by NMR techniques, IR spectroscopy as well as by an X‐ray structure determination. According to this, 1 is built‐up by ifinite chains of cations and anions along [001]. The linear cations are rotated 90° to each other along the chains due to the coordination of the [BF4]? ion. 相似文献
942.
943.
The interface between cold gas sprayed zinc-based coatings and selected light weight alloy substrates (aluminium AA7022 and
magnesium AZ91) has been investigated by scanning and transmission electron microscopy in combination with energy-dispersive
X-ray spectroscopy. In both cases a non-uniform interfacial zone with a thickness of up to 10 microns is evident. It consists
of coating and substrate phases as well as an approximately 1 micron thick, partially whirled layer. For the AA7022 substrate
the interfacial layer contains nano and submicron sized crystallites of the binary MgZn2 phase (η) which are embedded in an aluminium solid solution matrix. In the case of AZ91 substrate two ternary phases, Mg5Zn2Al2 (φ) and Mg11Zn11Al6 (τ) with particle size smaller than 50 nm are evident. The formation of these phases during spraying cannot be explained
by diffusion process only, but a local melting is needed. Consequently, the assumption that the high kinetic energy of cold
gas sprayed particles causes an intensive mechanical mixing of coating and substrate material accompanied by a high local
temperature rise is proved. 相似文献
944.
The Fu?ík spectrum for systems of second order ordinary differential equations with Dirichlet or Neumann boundary values is considered: it is proved that the Fu?ík spectrum consists of global C1 surfaces, and that through each eigenvalue of the linear system pass exactly two of these surfaces. Further qualitative, asymptotic and symmetry properties of these spectral surfaces are given. Finally, related problems with nonlinearities which cross asymptotically some eigenvalues, as well as linear-superlinear systems are studied. 相似文献
945.
946.
947.
Ian C. Watson Yuqiao Zhou Michael J. Ferguson Moritz Kränzlein Bernhard Rieger Eric Rivard 《无机化学与普通化学杂志》2020,646(13):547-551
The synthesis of new trialkylaluminum adducts with N-heterocyclic olefin (NHO) ligands is described. These well-defined complexes can catalyze the polymerization of various Michael-type monomers, such as 2-vinylpyridine, methylacrylate, and dimethylacrylamide. 相似文献
948.
David Maurer Prof. Dr. Bernhard Breit 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2643-2648
The design and synthesis of air-stable and conveniently crystallizable RhIII-cyclopentadienyl catalysts substituted with a urea moiety, which are able to accelerate the C−H olefination of benzoic acid derivatives, is reported. Through kinetic studies and NMR titration experiments, the catalysts’ substrate recognition ability mediated by hydrogen bonding was identified to be the reason for this effect. Introduction of pyridone-phosphine ligands capable of forming additional H-bond interactions increased the catalytic performance even further. By unveiling a proportionality between reaction rate and relative complex formation enthalpy the hypothesis of a supramolecular catalyst preformation was supported. Its application to a variety of substrates proved the catalyst system's advantages, generally increasing the yields when compared to the results obtained with widely used [RhCp*Cl2]2. 相似文献
949.
A high-order immersed boundary method is devised for the compressible Navier-Stokes equations by employing high-order summation-by-parts difference operators. The immersed boundaries are treated as sharp interfaces by enforcing the solid wall boundary conditions via flow variables at ghost points. Two different interpolation schemes are tested to compute values at the ghost points and a hybrid treatment is used. The first method provides the bilinearly interpolated flow variables at the image points of the corresponding ghost points and the second method applies the boundary condition at the immersed boundary by using the weighted least squares method with high-order polynomials. The approach is verified and validated for compressible flow past a circular cylinder at moderate Reynolds numbers. The tonal sound generated by vortex shedding from a circular cylinder is also investigated. In order to demonstrate the capability of the solver to handle complex geometries in practical cases, flow in a cross-section of a human upper airway is simulated. 相似文献
950.
Nowadays, mixed-model assembly lines are applied in a wide range of industries to mass-produce customized products to order, e.g., in automobile industry. An important decision problem in this context receiving a lot of attention from researchers and practitioners is the sequencing problem, which decides on the succession of workpieces launched down the line. However, if multiple departments with diverging sequencing objectives are to be passed or unforeseen disturbances like machine breakdowns or material shortages occur, a resequencing of a given production sequence often becomes equally essential. This paper reviews existing research on resequencing in a mixed-model assembly line context. Important problem settings, alternative buffer configurations, and resulting decision problems are described. Finally, future research needs are identified as some relevant real-world resequencing settings have not been dealt with in literature up to now. 相似文献