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991.
By a totally regular parallelism of the real projective 3-space
P3:=PG(3, \mathbb R){\Pi_3:={{\rm PG}}(3, \mathbb {R})} we mean a family T of regular spreads such that each line of Π
3 is contained in exactly one spread of T. For the investigation of totally regular parallelisms the authors mainly employ Klein’s correspondence λ of line geometry and the polarity π
5 associated with the Klein quadric H
5 (for details see Chaps. 1 and 3). The λ-image of a totally regular parallelism T is a hyperflock of H
5, i.e., a family H of elliptic subquadrics of H
5 such that each point of H
5 is on exactly one subquadric of H. Moreover, {p5(span l(X))|X ? T}=:HT{\{\pi_5({{\rm span}} \,\lambda(\mathcal {X}))\vert\mathcal {X}\in\bf{T}\}=:\mathcal {H}_{\bf{T}}} is a hyperflock determining line set, i.e., a set Z{\mathcal {Z}} of 0-secants of H
5 such that each tangential hyperplane of H
5 contains exactly one line of Z{\mathcal {Z}} . We say that dim(span HT)=:dT{{{\rm dim}}({{\rm span}}\,\mathcal {H}_{\bf{T}})=:d_{\bf{T}}} is the dimension of
T and that T is a d
T
- parallelism. Clifford parallelisms and 2-parallelisms coincide. The examples of non-Clifford parallelisms exhibited in Betten
and Riesinger [Result Math 47:226–241, 2004; Adv Geom 8:11–32, 2008; J Geom (to appear)] are totally regular and of dimension
3. If G{\mathcal{G}} is a hyperflock determining line set, then {l-1 (p5(X) ?H5) | X ? G}{\{\lambda^{-1}\,{\rm (}\pi_5(X){\,\cap H_5)\,|\, X\in\mathcal{G}\}}} is a totally regular parallelism. In the present paper the authors construct examples of topological (see Definition 1.1)
4- and 5-parallelisms via hyperflock determining line sets. 相似文献
992.
Thermophoresis moves molecules along temperature gradients, typically from hot to cold. We superpose fluid flow with thermophoretic molecule flow under well-defined microfluidic conditions, imaged by fluorescence microscopy. DNA is trapped and accumulated 16-fold in regions where both flows oppose each other. Strong 800-fold accumulation is expected, however, with slow trapping kinetics. The experiment is equally described by a three-dimensional and one-dimensional analytical model. As an application, we show how a radially converging temperature field confines short DNA into a 10 microm small spot. 相似文献
993.
Banchio AJ Gapinski J Patkowski A Häussler W Fluerasu A Sacanna S Holmqvist P Meier G Lettinga MP Nägele G 《Physical review letters》2006,96(13):138303
In this joint experimental-theoretical work we study hydrodynamic interaction effects in dense suspensions of charged colloidal spheres. Using x-ray photon correlation spectroscopy we have determined the hydrodynamic function H(q), for a varying range of electrosteric repulsion. We show that H(q) can be quantitatively described by means of a novel Stokesian dynamics simulation method for charged Brownian spheres, and by a modification of a many-body theory developed originally by Beenakker and Mazur. Very importantly, we can explain the behavior of H(q) for strongly correlated particles without resorting to the controversial concept of hydrodynamic screening, as was attempted in earlier work by Riese [Phys. Rev. Lett. 85, 5460 (2000)]. 相似文献
994.
Magnetic-resonance force microscopy is combined with cross-polarization and spin-decoupling NMR techniques to obtain double-resonance NMR signals of micrometer-scaled objects. The effective one-dimensional spatial resolution obtained in our experiments performed on a KPF6 single crystal sample is approximately 0.5 microm. The spectral linewidth of 900 Hz is sample limited. The described double-resonance techniques can introduce new chemical specificity to the magnetic-force sensor. 相似文献
995.
Andreas Grtner Dieter Schuh Jrg P. Kotthaus 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):195
A novel method to experimentally study the dynamics of long-living excitons in coupled quantum well semiconductor heterostructures is presented. Lithographically defined top gate electrodes imprint in-plane artificial potential landscapes for excitons via the quantum confined Stark effect. Excitons are shuttled laterally in a time-dependent potential landscape defined by an interdigitated gate structure. Long-range drift exceeding a distance of at an exciton drift velocity is observed in a gradient potential formed by a resistive gate stripe. 相似文献
996.
Dieter Claeys Koenraad Laevens Joris Walraevens Herwig Bruneel 《Mathematical Methods of Operations Research》2010,72(1):1-23
Whereas the buffer content of batch-service queueing systems has been studied extensively, the customer delay has only occasionally
been studied. The few papers concerning the customer delay share the common feature that only the moments are calculated explicitly.
In addition, none of these surveys consider models including the combination of batch arrivals and a server operating under
the full-batch service policy (the server waits to initiate service until he can serve at full capacity). In this paper, we
aim for a complete characterisation—i.e., moments and tail probabilities - of the customer delay in a discrete-time queueing
system with batch arrivals and a batch server adopting the full-batch service policy. In addition, we demonstrate that the
distribution of the number of customer arrivals in an arbitrary slot has a significant impact on the moments and the tail
probabilities of the customer delay. 相似文献
997.
This work focuses on the calculation of shakedown load-factors of structures by using the lower-bound theorem of shakedown analysis. The resultant optimization problem is solved by an interior-point algorithm. In general, the application of shakedown analysis to practical problems leads to large-scale problems with large numbers of unknowns and constraints. Thus the solution turns out to be computationally intensive. For this reason it is important to reduce the dimension of the considered problem. Therefore, the major improvement of the presented algorithm consists of a problem-oriented reformulation of the problem reducing the size of the system to be solved. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
998.
Dieter Claeys Joris Walraevens Koenraad Laevens Herwig Bruneel 《4OR: A Quarterly Journal of Operations Research》2010,8(3):255-269
In this paper, we compute the probability generating functions (PGF’s) of the customer delay for two batch-service queueing
models with batch arrivals. In the first model, the available server starts a new service whenever the system is not empty
(without waiting to fill the capacity), while the server waits until he can serve at full capacity in the second model. Moments
can then be obtained from these PGF’s, through which we study and compare both systems. We pay special attention to the influence
of the distribution of the arrival batch sizes. The main observation is that the difference between the two policies depends
highly on this distribution. Another conclusion is that the results are considerably different as compared to Bernoulli (single)
arrivals, which are frequently considered in the literature. This demonstrates the necessity of modeling the arrivals as batches. 相似文献
999.
Anne Seebach Severine Dietz Dieter Lessmann Kay Knoeller 《Isotopes in environmental and health studies》2013,49(1):99-110
Abstract A method is presented to assess lake water–groundwater interactions by modelling isotope signatures of lake water using meteorological parameters and field data. The modelling of δ18O and δD variations offers information about the groundwater influx into a meromictic Lusatian mining lake. Therefore, a water balance model is combined with an isotope water balance model to estimate analogies between simulated and measured isotope signatures within the lake water body. The model is operated with different evaporation rates to predict δ18O and δD values in a lake that is only controlled by weather conditions with neither groundwater inflow nor outflow. Comparisons between modelled and measured isotope values show whether the lake is fed by the groundwater or not. Furthermore, our investigations show that an adaptation of the Craig and Gordon model [H. Craig, L.I. Gordon. Deuterium and oxygen-18 variations in the ocean and the marine atmosphere. In Stable Isotopes in Oceanographic Studies and Paleotemperature, Spoleto, E. Tongiorgi (Ed.), pp. 9–130, Consiglio Nazionale delle Ricerche, Laboratorio di Geologia Nucleare, Pisa (1965).] to specific conditions in temperate regions seems necessary. 相似文献
1000.
In this paper we describe some fluorescent plant and mushroom dyes. This part of natural product chemistry was of little interest for most natural scientists until today. Most of these substances are published in scientific papers, but there are only rare hints for eventually fluorescence‐phenomenones. Equipped with an UV‐lamp, test tubes and some common solvents, natural products can easily be tested to show fluorescence. In the context of this publication the authors discovered a new Hypericin sensibilized Peroxyoxalate‐Chemoluminescence (strong orangered emission). 相似文献