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81.
82.
83.
Friedrich Pfeiffer 《Archive of Applied Mechanics (Ingenieur Archiv)》2010,80(1):47-56
Many machine and mechanism processes are accompanied by impacts with friction. They arise by short-time contacts between two
or more bodies, and they generate energy losses mainly due to friction in tangential contact directions. During the last two
decades, a couple of impact models based on the theory of rigid body contact were established connected with the names of
Moreau, Frémond, and Glocker, which all work quite satisfactorily with respect to practical applications, although some examples
indicate deviations requiring more investigations with respect to the impact models and the type of examples considered. We
shall focus on Glocker’s model, for which some experimental verifications are available by Beitelschmidt. A missing link are
energy considerations, which are available, but nevertheless do not provide us with a complete information for all possible
cases. The paper tries to fill a bit this gap by founding the investigations on a combined phenomenological and theoretical
basis. 相似文献
84.
Coupling fermions to gravity necessarily leads to a non-renormalizable, gravitational four-fermion contact interaction. In this essay, we argue that augmenting the Einstein–Cartan Lagrangian with suitable kinetic terms quadratic in the gravitational gauge field strengths (torsion and curvature) gives rise to new, massive propagating gravitational degrees of freedom. This is to be seen in close analogy to Fermi’s effective four-fermion interaction and its emergent W and Z bosons. 相似文献
85.
Karsten Gröger Max Kaiser Friedrich Dinkelacker 《Proceedings of the Combustion Institute》2019,37(3):3271-3278
For diesel sprays, the primary breakup processes are only rarely understood due to the high optical density and the resulting difficulties to measure them with extremely high spatial and sufficient temporal resolution. The Optical Connectivity Method (OCM) has been proposed in the last years to allow the determination of the breakup length of the connected liquid core, thus giving a measurement quantity of the primary breakup. In this work, an improved optical setup of the OCM is applied to a three-hole test injector nozzle where several measurement techniques are compared currently under well-defined conditions up to 100?MPa injection pressure. In this work, the direct comparison with X-Ray measurements done at the Advanced Photon Source of the Argonne National Laboratory will be described. This allows an evaluation of the OCM technique and a comparison of the different measurement quantities in the first 500?µm range of the spray. The structure of the spray is measured by X-Ray phase contrast imaging and the fuel mass distribution is measured by X-Ray absorption imaging. A detailed comparison of the two X-Ray techniques and the OCM technique has been possible for the first time. It is found that the measurement data of the spray near field are very congruent with all three methods. Due to this comparison, the measurement of the non-perturbed length, which describes the distance from the nozzle orifice up to the point where the formation of surface disturbances is starting, by the OCM is validated for the first time. Within this non-perturbed length of the spray, the OCM signal is weak before it starts to illuminate from the scattering of the perturbed surface. Thus, the OCM technique can deliver two characteristic length scales, the non-perturbed length and the breakup length, characterizing the primary spray breakup. 相似文献
86.
87.
The coupling of the electromagnetic field to gravity is discussed. In the premetric axiomatic approach based on the experimentally
well established conservation laws of electric charge and magnetic flux, the Maxwell equations are the same irrespective of
the presence or absence of gravity. In this sense, one can say that the charge “substratum” and the flux “substratum” are
not influenced by the gravitational field directly. However, the interrelation between these fundamental substrata, formalized
as the spacetime relation
H = H(F) between the 2-forms of the electromagnetic excitation H and the electromagnetic field strength F, is affected by gravity. Thus the validity of the equivalence principle for electromagnetism depends on the form of the spacetime
relation. We discuss the nonlocal and local linear constitutive relations and demonstrate that the spacetime metric can be
accompanied also by skewon, dilaton, and axion fields. All these premetric companions of the metric may eventually lead to
a violation of the equivalence principle. 相似文献
88.
89.
Several properties are calculated for A2Πu of —the majority for the first time—including electric and magnetic moments, and fine/hyperfine structure (fs/hfs) parameters. The new results are compared with our previous ones for X2 and B2 of [P.J. Bruna, F. Grein, J. Mol. Spectrosc. 227 (2004) 67–80]. The electric quadrupole Θ and hexadecapole Φ moments, polarizability α, and hfs constants a, b, c, d, eQq0, eQq2 are evaluated at the density functional theory (DFT) level [B3LYP/aug-cc-pVQZ]. The fs constants (spin–orbit coupling AΠ, Λ-doubling p, q, spin-rotation γΠ), and magnetic moments (g-factors) are obtained via 2nd-order sum-over-states expansions, using wavefunctions and matrix elements obtained with a multireference configuration interaction (MRDCI) method, and the Breit–Pauli Hamiltonian. At equilibrium, 2nd-order properties of A2Πu are dominated by its coupling with B2. For the A state, two independent components are reported for traceless tensor properties (multipoles Θ and Φ; hfs parameters c/d and q0/q2) and three for traced properties (polarizability α and g-factors), i.e., one more component than for axially symmetric Σ states. The currently available experimental data on — limited to AΠ, p, and q—are well reproduced by our theoretical results. 相似文献
90.
Mike Friedrich Revaz Nozadze Sandra de Keijzer Ralf Steinmeyer Vladimir Ermolayev Gregory S. Harms 《Journal of fluorescence》2018,28(1):29-39
Single molecule detection and tracking provides at times the only possible method to observe the interactions of low numbers of biomolecules, inlcuding DNA, receptors and signal mediating proteins in living systems. However, most existing imaging methods do not enable both high sensitivity and non-invasive imaging of large specimens. In this study we report a new setup for selective plane illumination microscopy (SPIM), which enables fast imaging and single molecule tracking with the resolution of confocal microscopy and the optical penetration beyond 300 μm. We detect and report our instrumental figures of merit, control values of fluorescence properties of single nano crystals in comparison to both standard widefield configurations, and also values of nanocrystals in multicellular “fruiting bodies” of Dictyostelium, an excellent control as a model developmental system. In the Dictyostelium , we also report some of our first tracking of single nanocrystals with SPIM. The new SPIM setup represents a new technique, which enables fast single molecule imaging and tracking in living systems. 相似文献