Einsatz von gekeimtem Getreide in der Geflügelfütterung

Ab August 2005 muss die Bio-Geflügelfütterung laut EU-Bio-Verordnung (1804/1999/EG) zu 100 % mit ökologisch erzeugten Komponenten erfolgen. Für die Rationsgestaltung fallen hochwertige, konventionell erzeugte Eiweißträger weg. Es wurde geprüft, inwieweit gekeimter Weizen in 100 % Bio-Rationen zur Proteinversorgung von Küken, Jung- und Legehennen beitragen kann und ob diese Rationen bedarfsgerecht sind. In zehn Bodenhaltungs-Stallabteilen ohne Außenauslauf wurden jeweils 19 Hennen und ein Hahn zweier Herkünfte (Lohmann Tradition –LT-, ISA Brown) vom Schlupf bis zur 40. Lebenswoche (LW) bei einer Besatzdichte von 5 Tieren/qm (ab der 5. LW) gehalten. Acht Versuchsgruppen wurden kombiniert mit 100 % Bio-Ergänzer und Weizenkeimen (4 Gruppen) oder -körnern (4 Gruppen) gefüttert, zwei Kontrollgruppen mit Alleinfutter mit bis zu 15 % konventionellen Komponenten. Die 48-stündige Keimung des Weizens führte zu keinen Änderungen in den Gehalten der Rohnährstoffe, außer Stärke und Zucker, und damit auch zu keiner Verbesserung der Proteinversorgung der Tiere. Einige Vitamingehalte (B1, B2, K, C) und der Gehalt der essentiellen Linolensäure stiegen an. Es gab keine signifikanten Unterschiede zwischen den Futtergruppen (Keim-, Körner und Alleinfütterung) und Herkünften in der Legeleistung, verschiedenen Eiqualitätsparametern und im Gefiederzustand, außer einer Tendenz zu höheren Eigewichten in der Keimfütterungsgruppe und höheren Lebendgewichten der LT-Hennen in der 14. und 21. LW. Unter den gegebenen Bedingungen gewährleistete die 100 % Bio-Fütterung einen sehr guten Gesundheits- und Gefiederzustand der Tiere bei zufrieden stellenden Leistungen. Biophotonenmessungen ergaben signifikant höhere Dotter-Lumineszenz-Werte als bei zugekauften Eiern aus konventioneller Boden- und Käfighaltung. Lediglich die nochmals höheren Werte bei den Eiern der Kontrollgruppe deuteten möglicherweise darauf hin, dass die 100 % Bio-Fütterung weniger bedarfsgerecht war als die Fütterung mit Alleinfutter. Zudem bestanden beim 100 % Bio-Ergänzer ein hoher Futterverbrauch und eine höhere Futtervergeudung. Weitere Untersuchung zur Bestimmung des Nährstoffbedarfs von Jung- und Legehennen unter ökologischen Haltungsbedingungen sowie zur Entwicklung bedarfsgerechter ökologischer Futterrationen sind notwendig

Magnetic Field Effects on Plasma Plumes

Here, we will discuss our numerical studies of plasma jets and loops, of basic interest for plasma propulsion and plasma astrophysics. Space plasma propulsion systems require strong guiding magnetic fields known as magnetic nozzles to control plasma flow and produce thrust. Propulsion methods currently being developed that require magnetic nozzles include the VAriable Specific Impulse Magnetoplasma Rocket (VASIMR) [1] and magnetoplasmadynamic thrusters. Magnetic nozzles are functionally similar to de Laval nozzles, but are inherently more complex due to electromagnetic field interactions. The two crucial physical phenomenon are thrust production and plasma detachment. Thrust production encompasses the energy conversion within the nozzle and momentum transfer to a spacecraft. Plasma detachment through magnetic reconnection addresses the problem of the fluid separating efficiently from the magnetic field lines to produce maximum thrust. Plasma jets similar to those of VASIMR will be studied with particular interest in dual jet configurations, which begin as a plasma loops between two nozzles. This research strives to fulfill a need for computational study of these systems and should culminate with a greater understanding of the crucial physics of magnetic nozzles with dual jet plasma thrusters, as well as astrophysics problems such as magnetic reconnection and dynamics of coronal loops.[2] To study this problem a novel, hybrid kinetic theory and single fluid magnetohydrodynamic (MHD) solver known as the Magneto-Gas Kinetic Method is used.[3] The solver is comprised of a "hydrodynamic" portion based on the Gas Kinetic Method and a "magnetic" portion that accounts for the electromagnetic behaviour of the fluid through source terms based on the resistive MHD equations. This method is being further developed to include additional physics such as the Hall effect. Here, we will discuss the current level of code development, as well as numerical simulation result

Effects of segmented electrode in Hall current plasma thrusters

Segmented electrodes placed along a ceramic channel in a Hall thruster are shown to influence significantly the plasma potential distribution. Both the radial potential and the axial acceleration region are sensitive to the location of the segmented electrodes. The measured and theoretical potential profiles appear to be affected in detail by the electrode material (graphite) having lower secondary electron emission than the ceramic channel walls. The measured plasma potential profile is shown as well to correlate with the observed and desirable narrowing of the plasma plume emanating from the thruster. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70788/2/JAPIAU-92-9-4906-1.pd

Plasma Characterization of Hall Thruster with Active and Passive Segmented Electrodes

Non-emissive electrodes and ceramic spacers placed along the Hall thruster channel are shown to affect the plasma potential distribution and the thruster operation. These effects are associated with physical properties of the electrode material and depend on the electrode configuration, geometry and the magnetic field distribution. An emissive segmented electrode was able to maintain thruster operation by supplying an additional electron flux to sustain the plasma discharge between the anode and cathode neutralizer. These results indicate the possibility of new configurations for segmented electrode Hall thruster

Investigations of Probe Induced Perturbations in a Hall Thruster

An electrostatic probe used to measure spatial plasma parameters in a Hall thruster generates perturbations of the plasma. These perturbations are examined by varying the probe material, penetration distance, residence time, and the nominal thruster conditions. The study leads us to recommendations for probe design and thruster operating conditions to reduce discharge perturbations, including metal shielding of the probe insulator and operation of the thruster at lower densities

Measurements of Plasma Potential Distribution in Segmented Electrode Hall Thruster

Use of a segmented electrode placed at the Hall thruster exit can substantially reduce the voltage potential drop in the fringing magnetic field outside the thruster channel. In this paper, we investigate the dependence of this effect on thruster operating conditions and segmented electrode configuration. A fast movable emissive probe is used to measure plasma potential in a 1 kW laboratory Hall thruster with semented electrodes made of a graphite material. Relatively small probe-induced perturbations of the thruster discharge in the vicinity of the thruster exit allow a reasonable comparison of the measured results for different thruster configurations. It is shown that the plasma potential distribution is almost not sensitive to changes of the electrode potential, but depends on the magnetic field distribution and the electrode placement

Electrostatic Probe with Shielded Probe Insulator Tube for Low Disturbing Plasma Measurements in Hall Thrusters

Electrostatic probes are widely used to measure spatial plasma parameters of the quasi-neutral plasma in Hall thrusters and similar ExB electric discharge devices. Significant perturbations of the plasma, induced by such probes, can mask the actual physics involved in operation of these devices. In Hall thrusters, probe-induced perturbations can produce changes in the discharge current and plasma parameters on the order of their steady state values. These perturbations are explored by varying the material, penetration distance, and residence time of various probe designs. A possible cause of these perturbations appears to be the secondary electron emission, induced by energetic plasma electrons, from insulator ceramic tubes in which the probe wire is inserted. A new probe in which a low secondary electron emission material, such as metal, shields the probe ceramic tube, is shown to function without producing such large perturbations. A segmentation of this shield further prevents probe -induced perturbations, by not shortening the plasma through the conductive shield. In a set of experiments with a segmented shield probe, the thruster was operated in the input power range of 500-2.5 kW and discharge voltages of 200-500 V, while the probe-induced perturbations of the discharge current were below 4% of its steady state value in the region in which 90% of the voltage drop takes place

Verbindung von schulischer Ausbildung im Lernfeld und Zusatzqualifikationen

In der Ausbildung des Personals in technisch orientierten Handwerks- und Industrieberufen sticht seit Beginn der Einführung gesonderter Lernorte die Frage nach dem Verhältnis zwischen Betrieb und Schule, von Konkretem und Allgemeinen und nach der Rolle der Lernerinnen bzw. Arbeiterinnen im Lern- und Arbeitsprozess heraus: Was soll wie und an welchem Ort, was kann und sollte an diesem Lernort und wie tiefgehend sollte es dort gelernt werden? Welche Entwicklungsziele werden den Lernerinnen - vor dem Hintergrund sich ständig verändernder Strukturen und der besonderen Interessen der Unternehmen - gesetzt? Diese Fragen sind je nach Beruf und Situation unterschiedlich zu beantworten. Deshalb sei die Frage aufgeworfen, ob die konkreten Ziele und Inhalte allgemein (im Lehrplan) festgelegt werden oder ob nur Richtungen aufgezeigt werden sollen? Mit den Mitte bzw. Ende der 1990er Jahre eingeführten, nach Lernfeldern strukturierten Lehrplänen werden diese offener. Es werden nur in geringerem Maße besondere Inhalte festgelegt, vielmehr steht die Kompetenzentwicklung im Vordergrund. Das ermöglicht eine Anpassung der Inhalte nach den Interessen der Lernerinnen und nach regionalen Aspekten (vorrangig ansässige Unternehmen mit ihrem Tätigkeitsspektrum)

Electron-wall interaction in Hall thrusters

Electron-wall interaction effects in Hall thrusters are studied through measurements of the plasma response to variations of the thruster channel width and the discharge voltage. The discharge voltage threshold is shown to separate two thruster regimes. Below this threshold, the electron energy gain is constant in the acceleration region and therefore, secondary electron emission (SEE) from the channel walls is insufficient to enhance electron energy losses at the channel walls. Above this voltage threshold, the maximum electron temperature saturates. This result seemingly agrees with predictions of the temperature saturation, which recent Hall thruster models explain as a transition to space-charge saturated regime of the near-wall sheath. However, in the experiment, the maximum saturation temperature exceeds by almost three times the critical value estimated under the assumption of a Maxwellian electron energy distribution function. The channel narrowing, which should also enhance electron-wall collisions, causes unexpectedly larger changes of the plasma potential distribution than does the increase of the electron temperature with the discharge voltage. An enhanced anomalous crossed-field mobility (near wall or Bohm-type) is suggested by a hydrodynamic model as an explanation to the reduced electric field measured inside a narrow channel. We found, however, no experimental evidence of a coupling between the maximum electron temperature and the location of the accelerating voltage drop, which might have been expected due to the SEE-induced near-wall conductivity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87763/2/057104_1.pd