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101.
In electron beams with high charge density there are observed anomalous shiftings and broadenings as well as symmetrizations of the energy distribution (Boersch 1954). Continuing former work, where these phenomena were ascribed to a relaxation process changing the energy distribution to a new equilibrium distribution, quantitative expressions are derived for the energy spread and the shape of this new energy distribution. Furthermore a relaxation degree is defined which measures the progress of relaxation. Measurements are described with the highest relaxation degrees reached up to now. In addition to the verification of former results up to these new limits the shape of the measured energy-distributions can be fitted to the derived one with suitable choice of a single parameter. Peculiarities of measurements with superposed axial magnetic fields are discussed. 相似文献
102.
103.
Werner Kerler Wolfgang Neuwirth Ekkehard Fluck Peter Kuhn Bodo Zimmermann 《Zeitschrift für Physik A Hadrons and Nuclei》1963,173(3):321-346
A number of complex and covalent iron compounds in the oxydation states 0, +2, +3, +6 and with coordination numbers 4, 5, 6 has been investigated at different temperatures. A source of Co57 in Pd has been made, which was shown to be well suited for such measurements. The influence of the cristalline environment has been studied by putting iron complexes in different lattices. Ligands of iron complexes have been exchanged to look for influences of different bonds. It has been shown that measurements are also possible in frozen solutions and applications of this method are discussed. It has been found that in Prussian blue and Turnbulls blue there is no socalled electron exchange between the different Fe. The Curie point of KFeS2 has been determined to be ?28° C and it was possible to study the fields and lineshifts in its neighbourhood. For some compounds indications for their structure and the sign of the electric field gradient could be derived from the data. The data are compiled in tables to allow further discussions from different points of view. 相似文献
104.
Bodo Volkmann 《Mathematische Annalen》1960,140(5):351-359
Ohne ZusammenfassungVorgetragen am 20. 10. 1959 auf der Tagung der DMV in Münster. 相似文献
105.
Christian Hasse Volker Sohm Bodo Durst 《International Journal of Heat and Fluid Flow》2009,30(1):32-43
Computational Fluid Dynamics using RANS-based modelling approaches have become an important tool in the internal combustion engine development and optimization process. However, these models cannot resolve cycle to cycle variations, which are an important aspect in the design of new combustion systems. In this study the feasibility of using a Detached Eddy Simulation (DES) SST model, which is a hybrid RANS/LES model, to predict cycle to cycle variations is investigated. In the near wall region or in regions where the grid resolution is not sufficiently fine to resolve smaller structures, the two-equation RANS SST model is used. In the other regions with higher grid resolution an LES model is applied. The case considered is a geometrically simplified engine, for which detailed experimental data for the ensemble averaged and single cycle velocity field are available from Boreé et al. [Boreé, J., Maurel, S., Bazile, R., 2002. Disruption of a compressed vortex, Physics of Fluids 14 (7), 2543–2556]. The fluid flow shows a strong tumbling motion, which is a major characteristic for modern turbo-charged, direct-injection gasoline engines. The general flow structure is analyzed first and the extent of the LES region and the amount of resolved fluctuations are discussed. Multiple consecutive cycles are computed and turbulent statistics of DES SST, URANS and the measured velocity field are compared for different piston positions. Cycle to cycle variations of the velocity field are analyzed for both computation and experiment with a special emphasis on the useability of the DES SST model to predict cyclic variations. 相似文献
106.
Nuno M. Santos Juergen Puls Bodo Saake Patrick Navard 《Cellulose (London, England)》2013,20(4):2013-2026
A commercial dissolving pulp was treated with aqueous solutions containing 3, 5 and 7 % of an organometalic complex (nitren) with the aim to selectively extract xylan and study its impact on the conventional physical–chemical properties of the pulp. The influence of these treatments on the pulp dissolution in a moderate solvent (8 % NaOH aqueous solution) was assessed by measuring the dissolution yields and the dissolution mechanisms. The results of this study show that nitren treatment has the effect of removing a large part of the xylan present in a dissolving pulp. It is also removing mannans and most important, it is influencing cellulose in two ways, (1) extracting it with more intensity when the nitren concentration increases, and (2) decreasing its mean molecular mass, also more evident with nitren concentration increase. The nitren extractions are favourable for the dissolution in cold NaOH–water, being more effective with higher concentrations. This chemical modification of the fiber surface leads to the disassembly of the primary wall. This allows an easier access of the NaOH reagent to regions not accessible on the initial fibres, which with the decrease of the cellulose molecular weight allows an easier dissolution and gives different dissolution mechanisms. 相似文献
107.
108.
The synthesis of long-chain 1,ω-diols with orthogonal cleavable protecting groups can be effectively performed with the use of the Grignard coupling reaction, successfully leading to the preparation of novel asymmetrical single-chain phosphoglycol-based bolaamphiphiles—a side-product that always occurred during the synthesis of symmetrical bolalipids.
[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] 相似文献
109.
The car following model under discussion is a system of ordinary differential equations describing N cars moving around a circular road. We extend the stability analysis of the model in two directions: variable reaction time (depending on the headway) and an additional part describing the aggressive driving tendency. We study the global bifurcation dynamics and in particular its dependence on these two new ingredients. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
110.