Three dimensional simulations of a swimmer's hand using an immersed boundary method

The force coefficients of the hand (and forearm) of a human swimmer have been determined in several experimental studies and direct numerical simulations (DNS) before. In present study the flow around a swimmer's hand and forearm is simulated at different velocities and angles of attack using an immersed boundary code. The force coefficients were calculated and compared with previous research.In advance of the study of the swimmer's hand, simulations of the flow around a sphere were performed to validate the code. The drag coefficient fitted the expected curve pretty well, except for a certain area where the boundary layer should have become turbulent. In addition the distinguished flow regimes behind the sphere were consistent with previous results.Under steady flow conditions the drag- and lift coefficient of the hand were constant throughout the range of swimming speeds tested (Cd = 1.128 ± 0.001 and Cl = 0.081 ± 0.001), the results were consistent with previous research.The propulsive force (Cd = 1.127 ± 0.011) peaked at an angle of attack of ?0, this is when the orientation of the hand palm is facing the flow. The trend of both the drag- and lift coefficients as a function of angle of attack was consistent with the expectations. However, the amplitude of the lift coefficient was smaller than expected. The force coefficients of the hand (and forearm) of a human swimmer have been determined in several experimental studies and direct numerical simulations (DNS) before. In present study the flow around a swimmer's hand and forearm is simulated at different velocities and angles of attack using an immersed boundary code. The force coefficients were calculated and compared with previous research.In advance of the study of the swimmer's hand, simulations of the flow around a sphere were performed to validate the code. The drag coefficient fitted the expected curve pretty well, except for a certain area where the boundary layer should have become turbulent. In addition the distinguished flow regimes behind the sphere were consistent with previous results.Under steady flow conditions the drag- and lift coefficient of the hand were constant throughout the range of swimming speeds tested (Cd = 1.128 ± 0.001 and Cl = 0.081 ± 0.001), the results were consistent with previous research.The propulsive force (Cd = 1.127 ± 0.011) peaked at an angle of attack of ?0, this is when the orientation of the hand palm is facing the flow. The trend of both the drag- and lift coefficients as a function of angle of attack was consistent with the expectations. However, the amplitude of the lift coefficient was smaller than expected

Experimental Quantum Teleportation with a 3-Bell-state Analyzer

We present a Bell-state analyzer for time-bin qubits allowing the detection of three out of four Bell-states with linear optics, two detectors and no auxiliary photons. The theoretical success rate of this scheme is 50%. A teleportation experiment was performed to demonstrate its functionality. We also present a teleportation experiment with a Fidelity larger than the cloning limit of F=5/6.Comment: 11 pages, 14 figure

Lagere stikstofbemesting drukt melkproductie

Verlaging van de stikstofgift gaat echter ten koste van de grasproductie. Daardoor kunnen minder koeien per hectare worden gehouden

The morphology of solid-liquid contacting efficiency in trickle-bed reactors

Trickle-flow is traditionally modeled by means of hydrodynamic parameters such as liquid holdup, two-phase pressure drop and wetting efficiency. Several studies showed that these parameters are not only a function of flow conditions and bed properties, but also of the flow history and morphology of flow. These can have a major influence on the distribution in the bed. The effect of flow morphology on liquid holdup and pressure drop is widely discussed in literature, but little attention is paid to its effect on wetting efficiency. Trickle-bed reactor models suggest that not a only bed-averaged but also the distribution of wetting efficiency may be of importance for reactor performance. Both the average wetting efficiency and the distribution of wetting are probably a function flow history and morphology. The distribution of wetting efficiency for different flow morphologies were investigated by means of a colorometric method that was developed for this purpose. Representative wetting distributions could be obtained. Flow morphologies and liquid distributions were manipulated by means of the pre-wetting procedure that was performed prior to flow. Pulse and Levec pre-wetted beds were investigated. These distributions were explained in detail in terms of flow morphology. It was found that the average wetting efficiency in pulse pre-wetted beds are much higher than in Levec pre-wetted beds. All particles in the pulse pre-wetted beds at all investigated flow conditions were contacted by the flowing liquid. This was not the case for the Levec pre-wetted beds. It was found that the flow in Levec pre-wetted beds become similar to that in pulse pre-wetted beds at high liquid flow rates. It was investigated how these distributions can affect reactor modeling, based on popular particle-scale models that relate reactor efficiency to wetting efficiency. According to these models, the wetting efficiency distribution in pulse pre-wetted beds can be characterised by means of only its average value. This is not the case for Levec pre-wetted beds. These results are however a strong function of the models that were employed. Finally, some recommendations are made in terms of the preferred pre-wetting method or flow morphology for different types of reactions. These recommendations are also based on models and have not been verified with experiments.Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2007.Chemical Engineeringunrestricte

Quantum Teleportation with a 3-Bell-state Analyzer

We present a novel Bell-state analyzer for time-bin qubits allowing the detection of three out of four Bell-states with linear optics, only two detectors and no auxiliary photons. The theoretical success rate of this scheme is 50%. A teleportation experiment was performed to demonstrate its functionality. We also present a teleportation experiment with a fidelity larger than the cloning limit.Comment: 4 pages, 6 figure

Long distance entanglement swapping with photons from separated sources

We report the first experimental realization of entanglement swapping over large distances in optical fibers. Two photons separated by more than two km of optical fibers are entangled, although they never directly interacted. We use two pairs of time-bin entangled qubits created in spatially separated sources and carried by photons at telecommunication wavelengths. A partial Bell state measurement is performed with one photon from each pair which projects the two remaining photons, formerly independent onto an entangled state. A visibility high enough to violate a Bell inequality is reported, after both photons have each travelled through 1.1 km of optical fiber.Comment: 4 pages, 3 figures, submitte

Kroos verwijderen verbetert waterkwaliteit; uitrijden op grasland geen bezwaar

Door het kroos af te voeren kan de waterkwaliteit op korte termijn worden verbeterd

Demonstratiebedrijven Veehouderij en Natuur

In het onderstaande wordt een korte beschrijving van de drie bedrijven gegeven en wordt aangegeven hoe deze bedrijven agrarisch natuurbeheer in hun bedrijfsvoering inpassen

Quantum teleportation over the Swisscom telecommunication network

We present a quantum teleportation experiment in the quantum relay configuration using the installed telecommunication network of Swisscom. In this experiment, the Bell state measurement occurs well after the entanglement has been distributed, at a point where the photon upon which data is teleported is already far away, and the entangled qubits are photons created from a different crystal and laser pulse than the teleported qubit. A raw fidelity of 0.93+/-0.04 has been achieved using a heralded single-photon source.Comment: 6 pages, 7 figures, updated references on May 3rd. To be published in Journal of the Optical Society of America B, Feature issue "Optical Quantum-Information Science", February 200