Monotonicity of saddle maps

We prove an analog of Schoen--Yau univalentness theorem for saddle maps between discs.Comment: 9 pages, 3 figure

Metric minimizing surfaces revisited

A surface which does not admit a length nonincreasing deformation is called metric minimizing. We show that metric minimizing surfaces in CAT(0) spaces are locally CAT(0) with respect to their intrinsic metric

Correlations and Counting Statistics of an Atom Laser

We demonstrate time-resolved counting of single atoms extracted from a weakly interacting Bose-Einstein condensate of $^{87}$Rb atoms. The atoms are detected with a high-finesse optical cavity and single atom transits are identified. An atom laser beam is formed by continuously output coupling atoms from the Bose-Einstein condensate. We investigate the full counting statistics of this beam and measure its second order correlation function $g^{(2)}(\tau)$ in a Hanbury Brown and Twiss type experiment. For the monoenergetic atom laser we observe a constant correlation function $g^{(2)}(\tau)=1.00\pm0.01$ and an atom number distribution close to a Poissonian statistics. A pseudo-thermal atomic beam shows a bunching behavior and a Bose distributed counting statistics

Numerical Optimization of Plate-Line Design for Enhanced Wake-Vortex Decay

The design of plate lines as a ground-mounted device for wake-vortex decay enhancement is investigated in this work. The most important design parameters, the aspect ratio and plate distance, are analyzed for the wake vortices generated by two aircraft: the A340 as well as the A380. Large-eddy-simulations are used to simulate the wake-vortex evolution in ground proximity for different parameter combinations. Fully rolled-up wake vortices are initialized using a Lamb–Oseen vortex model resembling the characteristics of the two aircraft. With the stochastic so-called kriging method, estimates of the performance and respective probabilistic envelopes are given for the design parameter region, spanned by the large-eddy-simulation. The vortex circulation averaged over the rapid decay phase is taken as the objective function. The large-eddy-simulation parameters are selected in the vicinity of the expected optimum. An optimal parameter combination can be localized in the A340 case, as well as in the A380 case. For both cases, statistical relevance is provided. Moreover, it can be deduced that the optimal parameters for the A380 are also well suited for smaller aircraft like an A340

Aircraft Wake-Vortex Decey in Ground Proximity - Physical Mechanisms and Artificial Enhancement.

Aircraft wake-vortex evolution in ground proximity is investigated numerically by means of large-eddy simulations. The simulations are performed either with a flat ground or with different modifications to the ground surface to trigger rapid vortex decay. The impact of environmental turbulence in terms of turbulent wind is taken into account, where wall-resolved and wall-modeled large-eddy simulation are performed for low- and high-Reynoldsnumber cases, respectively. To understand wake-vortex decay mechanisms in ground proximity, the interaction of primary and secondary vortices is carefully investigated. We find that vortex decay can be initiated at an earlier time and substantially accelerated with obstacles at the ground. We explain the fundamental vortex dynamics describing five characteristics of the phenomenon and quantify the decay. We demonstrate that similar effects can be achieved, employing relatively small plate lines as opposed to the original large block-shaped barriers. The obstacles trigger two kinds of so-called end effects: pressure disturbances propagating within the vortex cores and secondary vortex structures propagating along the outside of the vortex cores

SERVICE INNOVATION WITH INFORMATION MARKETS

Assessing innovation alternatives is a difficult task especially in newly upcoming forms of organization like Business Value Networks. This paper highlights the use of Information Markets and discusses state of the art Market Maker models. We designed a Market Maker mechanism in order to enhance liquidity, and hence, efficiency in the market. Therefore, an agent-based simulation as well as a field experiment was run to evaluate the usefulness and performance of Market Maker. It can be shown that the introduction of automated trading techniques increases market efficiency and thus the quality of the forecasting results for service innovation assessment

Wake vortices of landing aircraft

As a consequence of lift generation, flying aircraft generate a complex turbulent wake consisting of flow strkctures. The evolution of the aircraft's wake prior to and directly after touchdown still poses many open questions