Status of a five-centimeter-diameter ion thruster technology program

Prototype auxiliary propulsion subsystem with isolated single tank propellant feed system and 5-cm-diameter ion thruste

Numerical Analysis of a New Mixed Formulation for Eigenvalue Convection-Diffusion Problems

A mixed formulation is proposed and analyzed mathematically for coupled convection-diffusion in heterogeneous medias. Transfer in solid parts driven by pure diffusion is coupled with convection-diffusion transfer in fluid parts. This study is carried out for translation-invariant geometries (general infinite cylinders) and unidirectional flows. This formulation brings to the fore a new convection-diffusion operator, the properties of which are mathematically studied: its symmetry is first shown using a suitable scalar product. It is proved to be self-adjoint with compact resolvent on a simple Hilbert space. Its spectrum is characterized as being composed of a double set of eigenvalues: one converging towards −∞ and the other towards +∞, thus resulting in a nonsectorial operator. The decomposition of the convection-diffusion problem into a generalized eigenvalue problem permits the reduction of the original three-dimensional problem into a two-dimensional one. Despite the operator being nonsectorial, a complete solution on the infinite cylinder, associated to a step change of the wall temperature at the origin, is exhibited with the help of the operator’s two sets of eigenvalues/eigenfunctions. On the computational point of view, a mixed variational formulation is naturally associated to the eigenvalue problem. Numerical illustrations are provided for axisymmetrical situations, the convergence of which is found to be consistent with the numerical discretization

Wie viel Arbeit macht die Aufzucht von Ökologischen Junghennen? Arbeitwirtschaftlicher Vergleich der konventionellen und ökologischen Aufzucht von Legehennen

Organic pullets are reared with daylight and are not beak-trimmed. Therefore, certain provisions are needed in order to prevent feather-pecking and cannibalism. Respec-tive guidelines are set by the German Organic Associations. It was the goal of this study to investigate whether the higher rearing standards are associated with an increased labour demand compared to conventional rearing systems. Using a ques-tionnaire, data from 32 hen-houses (10 conventional and 6 organic barn systems, 10 conventional and 6 organic aviary systems) about duration and number of working procedures were collected and exemplary models calculated. Total labour demand was between 2.36 and 7.37 worker`s hours/100 pullets. It did not differ between or-ganic and conventional rearing when comparing similar flock sizes, but were partly differently allocated to the different working procedures. On average, organic farms had smaller flocks, and there was a large influence of flock size on labour demand with small houses requiring most labour per hen. Also aviaries were more labour demanding than barn systems, but were usually associated with higher flock sizes. Our results indicate that improved pullet rearing that allows the birds to perform their natural behaviour more completely, does not necessarily cause higher labour re-quirements

Junghennen - Arbeitszeitvergleich praxisüblicher Haltungsverfahren

Dieses KTBL-Heft informiert über den Arbeitszeitbedarf in der Junghennenhaltung. In Abhängigkeit vom Haltungssverfahren, der Bestandgröße und der Vermarktungsform für konventionell und ökologisch wirtschaftenden Betriebe wurden Arbeitszeitwerte in der Praxis erfasst und daraus auf der Basis von Modellrechnungen Arbeitszeitbedarfswerte abgeleitet. Die ermittelten Arbeitszeitbedarfswerte liefern Junghennenhaltern für Neu- und Umbaumaßnahmen Vergleichswerte und ermöglichen ihnen eine fundierte PLanung ihrer Arbeitskapazitäten

Lectures on F-theory compactifications and model building

These lecture notes are devoted to formal and phenomenological aspects of F-theory. We begin with a pedagogical introduction to the general concepts of F-theory, covering classic topics such as the connection to Type IIB orientifolds, the geometry of elliptic fibrations and the emergence of gauge groups, matter and Yukawa couplings. As a suitable framework for the construction of compact F-theory vacua we describe a special class of Weierstrass models called Tate models, whose local properties are captured by the spectral cover construction. Armed with this technology we proceed with a survey of F-theory GUT models, aiming at an overview of basic conceptual and phenomenological aspects, in particular in connection with GUT breaking via hypercharge flux.Comment: Invited contribution to the proceedings of the CERN Winter School on Supergravity, Strings and Gauge Theory 2010, to appear in Classical and Quantum Gravity; 63 pages; v2: references added, typos correcte

Настройка моделей при создании систем поддержки принятия стратегических решений

Показана актуальность разработки платформы (программной среды), позволяющей на её основе создавать системы стратегического управления организациями, используя сквозные технологии поддержки принятия решений и универсальные инструментальные средства. Статья посвящена решению одной из задач, возникающей при разработке такой платформы - настройке универсальных моделей поддержки принятия решений под условия принятия решений и особенности предметной области стратегического управления. Разработан механизм настройки моделей, выявлены и представлены параметры настройки

On Flux Quantization in F-Theory II: Unitary and Symplectic Gauge Groups

We study the quantization of the M-theory G-flux on elliptically fibered Calabi-Yau fourfolds with singularities giving rise to unitary and symplectic gauge groups. We seek and find its relation to the Freed-Witten quantization of worldvolume fluxes on 7-branes in type IIB orientifold compactifications on Calabi-Yau threefolds. By explicitly constructing the appropriate four-cycles on which to calculate the periods of the second Chern class of the fourfolds, we find that there is a half-integral shift in the quantization of G-flux whenever the corresponding dual 7-brane is wrapped on a non-spin submanifold. This correspondence of quantizations holds for all unitary and symplectic gauge groups, except for SU(3), which behaves mysteriously. We also perform our analysis in the case where, in addition to the aforementioned gauge groups, there is also a 'flavor' U(1)-gauge group.Comment: 33 pages, 4 figure

Chemisorption of NTCDA on Ag(1 1 1): a NIXSW study including non-dipolar and electron-stimulated effects

Abstract The adsorption of one monolayer of 1,4,5,8-naphthalene-tetracarboxylicacid-dianhydride (NTCDA) on the Ag(1 1 1)-surface was studied using the normal incidence X-ray standing waves (XSW) technique. Results regarding two key-issues are presented: Most prominent, the precise adsorbate-substrate bonding distance could be evaluated to 3.02 ± 0.02 Å (for the ''relaxed monolayer''-structure). This value is significantly smaller than a van der Waals bonding distance and clearly indicates the chemisorptive bonding character. Concordant results were obtained from both O 1s photo-and O KLL Auger electron emission. This was enabled by the development of a data analysis procedure--the second issue addressed--which takes into account non-dipolar contributions to the photoemission as well as electronstimulated Auger excitations. The latter effect adds a fraction to the total Auger yield being as high as 50% and hence may be important for any XSW study using Auger signals