Mono‐ und biaxiale Spannungszustände in geokunststoffbewehrten Erdbauwerken und ihre Bemessungsrelevanz

Uni‐ and bi‐axial loading conditions in geosynthetic reinforced soil structures and their design relevance. Recent publications have focussed on the improved performance of certain geosynthetics under short‐ and long‐term biaxiale loading conditions. It was reported that the geosynthetic reinforcements act as a result of biaxial loading clearly stiffer as under uni‐axial loading. In the course of this publication the relevance of such material performance in the design of typical geosynthetic reinforced soil structures will be evaluated. Therefore the loading conditions of the reinforcements will be analysed. The evaluation will not only be based on the principles of geotechnical engineering but also on extensive numerical analyses as well as laboratory‐ and field‐tests. The analyses showed, that real biaxial loading conditions, as adapted for the laboratory tests, are to be observed only very limited and locally even assuming ideal boundary conditions. Therefore bi‐axial loading conditions do not have any design relevance.     

Electroluminescence from silicon nanoparticles fabricated from the gas phase

Electroluminescence from as-prepared silicon nanoparticles, fabricated by gas phase synthesis, is demonstrated. The particles are embedded between an n-doped GaAs substrate and a semitransparent indium tin oxide top electrode. The total electroluminescence intensity of the Si nanoparticles is more than a factor of three higher than the corresponding signal from the epitaxial III-V semiconductor. This, together with the low threshold voltage for electroluminescence, shows the good optical properties of these untreated particles and the efficient electrical injection into the device. Impact ionization by electrons emitted from the top electrode is identified as the origin of the electrically driven light emission.     

Chaotic analyses of weakly damped parametrically excited cross waves with surface tension

Summary. The Wiggins-Holmes extension of the Generalized Melnikov Method (GMM) to higher dimensions and the extension of the Generalized Herglotz Algorithm (GHA) to non-autonomous systems are applied to weakly damped parametrically excited cross waves with surface tension in a long rectangular wave channel in order to demonstrate that cross waves are chaotic. The Luke Lagrangian density function for surface gravity waves with surface tension and dissipation is expressed in three generalized coordinates (or, equivalently, three degrees of freedom) that are the time-dependent components of three velocity potentials that represent three standing waves. The generalized momenta are computed from the Lagrangian, and the Hamiltonian is computed from a Legendre transform of the Lagrangian. This Hamiltonian contains both autonomous and non-autonomous components that must be suspended by applying an extension of the Herglotz algorithm for non-autonomous transformations in order to apply the Kolmogorov-Arnold-Moser (KAM) averaging operation and the GMM. Three canonical transformations are applied to (i) eliminate cross product terms by a rotation of axes; (ii) to transform to action-angle canonical variables and to eliminate two degrees of freedom; and (iii) to suspend the non-autonomous terms and to apply the Hamilton-Jacobi transformation. The system of nonlinear non-autonomous evolution equations determined from Hamiltons equations of motion of the second kind must be averaged in order to obtain an autonomous system that may be analyzed by the GMM. Hyperbolic saddle points that are connected by heteroclinic separatrices are computed from the unperturbed autonomous system. The non-dissipative perturbed Hamiltonian system with surface tension satisfies the KAM non-degeneracy requirements, and the Melnikov integral is calculated to demonstrate that the motion is chaotic. For the perturbed dissipative system with surface tension, the only hyperbolic fixed point that survives the averaged equations is a fixed point of weak chaos that is not connected by a homoclinic separatrix; consequently, the Melnikov integral is identically zero. The chaotic motion for the perturbed dissipative system with surface tension is demonstrated by numerical computation of positive Liapunov characteristic exponents.     

Keywords in planning: what do we mean by ‘community resilience’?

In this paper, we critically explore the combination of a dynamic, multilayered understanding of community with an open-ended, ‘emergent’ understanding of resilience, and highlight the relevance for planners. We argue prevailing planning policies and practices on community resilience tend to work with rather simplistic, one-dimensional understandings of both ‘community’ and ‘resilience’. The multiple layers of meaning that are embedded in the word community are ignored when it is treated as an add-on intended to give underlying ideas about resilience planning greater public appeal. Apart and together the concepts of community and resilience bring into play a host of tensions between, for example, continuity and change, resistance and adaptation, inclusion and exclusion. This paper offers a framework for ensuring that these important considerations are openly negotiated within transparent normative frameworks of planning policy and practice.     

Indexing the Trajectories of Moving Objects in Networks*

The management of moving objects has been intensively studied in recent years. A wide and increasing range of database applications has to deal with spatial objects whose position changes continuously over time, called moving objects. The main interest of these applications is to efficiently store and query the positions of these continuously moving objects. To achieve this goal, index structures are required. The main proposals of index structures for moving objects deal with unconstrained 2-dimensional movement. Constrained movement is a special and a very important case of object movement. For example, cars move in roads and trains in railroads. In this paper we propose a new index structure for moving objects on networks, the MON-Tree. We describe two network models that can be indexed by the MON-Tree. The first model is edge oriented, i.e., the network consists of nodes and edges and there is a polyline associated to each edge. The second one is more suitable for transportation networks and is route oriented, i.e., the network consists of routes and junctions. In this model, a polyline also serves as a representation of the routes. We propose the index in terms of the basic algorithms for insertion and querying. We test our proposal in an extensive experimental evaluation with generated data sets using as underlying networks the roads of Germany. In our tests, the MON-Tree shows good scalabiliy and outperforms the competing index structures in updating (index creation) as well as in querying.*This work was partially supported by a grant Gu 293/8–l from the Deutsche Forschungsgemeinschaft (DFG), project Datenbanken für bewegte Objekte (Databases for Moving Objects).     

Extending the postpartum anovulatory period in dairy cattle with estradiol cypionate

Estradiol cypionate (ECP), a long-acting estrogen, has been used therapeutically in early postpartum (PP) dairy cows. In experiment 1, effects of ECP on circulating reproductive hormones, cyclicity, and ovarian function in early PP dairy cows were investigated. Lactating Holsteins received 10 mg of ECP (ECP; n = 17) or placebo (CON; n = 16) on d 7 PP. Serum and ultrasound data were acquired from 5 to 90 d of lactation. Compared to CON, ECP cows had greater serum estradiol for 10 d and lower serum FSH for 15 d posttreatment. After ECP, the appearance of follicles > or = 10 mm and time to first ovulation were delayed. Nevertheless, by 90 d PP, normal estrous cycles were found in only 50% of CON versus 88% of ECP cows. Primiparous, but not multiparous, cows receiving ECP had higher milk yields. Experiment 2 investigated effects of ECP on reproduction and milk production on a commercial dairy. Cows were blocked by parity and randomized to three treatments: 0 (n = 85), 4 (n = 85), or 10 (n = 86) mg of ECP on d 5 to 8 PP. Data included cycling status (two ultrasound examinations at 30 to 33 d PP and 7 d later), individual reproduction records, and daily milk yields from 10 to 90 d PP. In primiparous cows, ECP had no significant effects on ovulatory status or milk yields. By 40 d PP, a greater percentage of multiparous cows receiving 10 mg of ECP remained anovulatory compared with those receiving 0 or 4 mg. Milk yields were highest for multiparous cows receiving 4 mg of ECP, intermediate for the 10-mg dose, and lowest for controls. Lower conception was observed in multiparous cows receiving 4 mg of ECP. In summary, ECP delayed time to first ovulation particularly in multiparous cows, an effect associated with observed inhibition of circulating FSH. Milk yield responses to ECP were inconsistent within parity groups across the two experiments.     

Fluid dynamics of pulsed sieve plate extraction columns

The presented contribution reports on comprehensive hydrodynamic investigations in two pulsed sieve-plate extraction columns (PSE) on a pilot scale. The experiments were conducted with three different sieve plate geometries employing test systems recommended by EFCE, under varying pulsation conditions and throughputs. The results of the investigation add to the existing knowledge of relationships between hydrodynamic parameters, drop size, hold-up, flooding throughput and mixing and operating parameters. They also provide useful information for scale up, selection of sieve-plate geometry, most favorable operating range, and constructive design of equipment. On the basis of measurements, analytical methods are recommended for prediction of PSE hydrodynamics.