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51.
The model studies were designed to obtain information concerning wind loads on a tall building by placing the model in a turbulent
shear flow simulating expected atmospheric boundary-layer winds. Since current design codes are inadequate for predicting
all possible motions of tall buildings, it is important that better knowledge of mean and fluctuating loadings and their distributions
becomes available.
Experiments were conducted to determine the mean and fluctuating forces and twisting moments at several levels over the surface
of a model. By determining the effects at several levels simultaneously, it was possible to correlate forces and moments at
five levels with one common level.
A single model was tested at varying orientations. Tests were also conducted with an identical model placed upstream so that
its wake influenced the flow around the instrumented model.
Results are presented in terms of distributions of force and moment coefficients and correlations at different levels. The
spectral character of the force and moment components is illustrated for one case.
Paper was presented at 1977 SESA Spring Meeting held in Dallas, TX on May 15–20. 相似文献
52.
This work features an analysis for the acceleration technique DIIS that is standardly used in most of the important quantum
chemistry codes, e.g. in DFT and Hartree–Fock calculations and in the Coupled Cluster method. Taking up results from Harrison
(J Comput Chem 25:328, 2003), we show that for the general nonlinear case, DIIS corresponds to a projected quasi-Newton/secant method. For linear systems,
we establish connections to the well-known GMRES solver and transfer according (positive as well as negative) convergence
results to DIIS. In particular, we discuss the circumstances under which DIIS exhibits superlinear convergence behaviour.
For the general nonlinear case, we then use these results to show that a DIIS step can be interpreted as step of a quasi-Newton
method in which the Jacobian used in the Newton step is approximated by finite differences and in which the according linear
system is solved by a GMRES procedure, and give according convergence estimates. 相似文献
53.
Lechel T Gerhard M Trawny D Brusilowskij B Schefzig L Zimmer R Rabe JP Lentz D Schalley CA Reissig HU 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(27):7480-7491
Lithiated alkoxyallenes, nitriles, and carboxylic acids have been employed as precursors in a three-component reaction leading to highly substituted β-alkoxy-β-ketoenamides. Upon treatment with trifluoroacetic acid, these enamides could be easily cyclized to 5-acetyloxazole derivatives. The synthesis is very flexible with respect to the substitution pattern at C-2 and C-4 of the oxazole core. A mechanistic suggestion for the oxazole formation is presented on the basis of (18)O-labeled compounds and their mass spectrometric analysis. In several cases, 1,2-diketones are formed as side products or even as major components. The acetyl moiety at C-5 of the oxazole derivatives can efficiently be converted into alkenyl or alkynyl moieties, which allows a multitude of subsequent reactions. Condensation reactions of the acetyl group provided the expected oxime or hydrazone. By applying a Fischer reaction, the phenylhydrazone could be transferred into an indole, which emphasizes the potential of 5-acetyloxazoles for the preparation of highly substituted (poly)heterocyclic systems. The alkynyl group at C-2 is prone to addition reactions, providing an enamine with interesting photophysical properties. Sonogashira couplings were performed with 5-alkynyl-substituted oxazoles, furnishing the expected aryl-substituted products. This alkynyl unit was employed for the preparation of a new, star-shaped trisoxazole derivative. The ability of this multivalent compound to form self-assembled monolayers between the basal plane of highly oriented pyrolytic graphite and 1-phenyloctane was demonstrated by scanning tunneling microscopy (STM). The star-shaped compound seems to prefer the C(3)-symmetric arrangement in this two-dimensional crystal. Two 1,2-diketones were smoothly converted into functionalized quinoxaline derivatives. 相似文献
54.
Schon C Roth W Fischer I Pfister J Fink RF Engels B 《Physical chemistry chemical physics : PCCP》2011,13(23):11076-11082
The structure of the electronic ground- and first excited state of mono-hydroxy [2.2]paracyclophane (MHPC) and the S(1)← S(0) electronic transition have been investigated by resonance-enhanced multiphoton ionisation (REMPI) and by quantum chemical spin-component-scaled-approximate coupled cluster second order (SCS-CC2) computations. The origin of the S(1)← S(0) transition was located at 30,772 cm(-1) (3.815 eV) in the REMPI spectrum. The value has to be compared with a computed excitation energy of 3.79 eV. The vibrational structure of the spectrum confirms a significant geometry change upon excitation along the coordinates corresponding to twist- and shift-motions in the molecule. It gives rise to an experimentally observed progression with a fundamental of +30 cm(-1) and an inverse anharmonicity. From the experimental data a shallow potential along the twist coordinate was derived for the S(1) state. For the shift vibration a wavenumber of +91 cm(-1) was observed, while +85 cm(-1) was computed. The ionisation energy of MHPC was determined to be 7.63 ± 0.05 eV using synchrotron radiation. When compared to earlier results on the parent compound [2.2]paracyclophane and pseudo-ortho-dihydroxy[2.2]paracyclophane it can be seen that already small variations in the substitution pattern have a significant impact on the shapes of the involved potential energy surfaces leading to strong variations in ground and excited state geometries and opto-electronic properties governing the exciton transfer processes. 相似文献
55.
Reinhold Kienzler Frank Jablonski 《Archive of Applied Mechanics (Ingenieur Archiv)》2006,75(10-12):567-567
56.
57.
Reinhold Baer 《Mathematische Annalen》1966,165(2):163-180
Ohne Zusammenfassung
Ernst Hölder zum 65. Geburtstag gewidmet 相似文献
58.
Reinhold Baer 《Mathematische Zeitschrift》1977,152(3):207-222
Ohne ZusammenfassungFriedrich Karl Schmidt zum 22. September 1976 in alter Freundschaft gewidmet 相似文献
59.
60.
On the Relative Donor-Acceptor-Properties of Monodentate Ligands. An EHT-Study The relative donor-acceptor properties of some important monodentate ligands are investigated by means of the extended Hückel method and a suitable graduation is determined. Charge gradations are discussed and results compared with known facts. Acceptor properties of ligands with phosphorous and sulfur atoms are described in the best manner using charge iterations at the atoms mentioned. 相似文献