66,799 research outputs found

    Economical processing of fiber-reinforced components with thermal expansion molding

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    The concept of economical fabrication of fiber-reinforced structural components is illustrated with an example of a typical control surface (aileron). The concept provides for fabricating struts, ribs, and a cover plate as an integral structure in a hardening device and then joining the closure cover plate mechanically. Fabrication of the integral structure is achieved by the 'thermal expansion molding' technique. The hardening pressure is produced by silicone rubber cores which expand under the influence of temperature. Test results are presented for several rubber materials as well as for various structural pieces. The technique is demonstrated extensively for an aileron, consisting of five ribs, struts, and a cover plate. Economically, for a large scale technical production of an aileron, cost savings of twenty-five percent can be realized compared to those for a sheet metal structure

    Electron-phonon interaction for adiabatic anharmonic phonons

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    A model with Holstein-like electron-phonon coupling is studied in the limit of adiabatic phonons. The phonon distribution is anharmonic with two degenerate maxima. This model can be related to fermions in a correlated binary alloy and describes microscopic phase separation. We discuss the weak and strong electron-phonon coupling limit and present a qualitative phase diagram. In terms of the phononic displacements it consists of a homogeneous, an alternating, and a disordered phase. There is a first order phase transition between the homogeneous and the alternating phase, and second order phase transition between the alternating and the disordered phase. The opening of a gap inside the disordered phase is treated by a dynamical mean-field theory.Comment: 11 pages, 3 figures, revised and published versio

    Non-equilibrium radiation nuclear reactor

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    An externally moderated thermal nuclear reactor is disclosed which is designed to provide output power in the form of electromagnetic radiation. The reactor is a gaseous fueled nuclear cavity reactor device which can operate over wide ranges of temperature and pressure, and which includes the capability of processing and recycling waste products such as long-lived transuranium actinides. The primary output of the device may be in the form of coherent radiation, so that the reactor may be utilized as a self-critical nuclear pumped laser

    Possibilities and limitations of protein supply in organic poultry and pig production

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    It is one of the general recommendations in animal nutrition that the diet should be formulated according to the specific requirements of animals at the various stages of their development. To which degree the farmer can adapt the nutrient supply to the specific requirements of the animals depends primarily on the production goal and on the availability of nutrient resources. This report gives a general introduction to the present situation for dietary protein supply to poultry and pig production in relation to the principles for organic agriculture and husbandry production. Furthermore it includes partly literature based on research from conventional animal production, as the requirements on the level of the animals are not different in both systems. Moreover, there only few research projects of organic production systems available. This report is primarily focussing on the question whether a nutrient supply of 100% organic feed can and should be realised. In this context, it is not possible to cover all aspects in detail as the report cannot replace a textbook. The main emphasis is laid on a coherent argumentation based on the leading ideas of organic agriculture. Concerning further relevant aspects it is referred to the report ”Supply and demand for concentrated organic feed in the EU in 2002 and 2003” by Susanne Padel as part of the same EU-project: ‘Research to support the EU-regulation on Organic Agriculture’ (www.organic-revision.org) and to the project “Availability of organically reared livestock” (S. Gomez, JRC, Institute for Prospective Technological Studies, this study is expected to be completed in November 2005). In conventional animal production, a nutrient supply that is closely related to the requirements is an important tool in the performance-oriented production (FLACHOWSKY, 1998). The objective of animal nutrition is to adapt the nutrient supply as accurately as possible to the requirements resulting from maintenance and performance need. Soybean meal, due to the high protein content and high protein quality, has developed into the most important protein source in the nutrition of monogastric animals. Additionally, synthetic amino acids (DL-methionine) and industrial amino acids (produced from microbial fermentation, L-amino acids) are used to balance the supply of essential amino acids. While the use of soybean meal and synthetic amino acids is normal practice in conventional animal production, the Council-Regulation No. 2092/91, amended by Council Regulation No. 1804/99 on organic livestock production bans the use of chemically extracted soybean meal and synthetic amino acids on organic farms as livestock must be fed primarily on organically produced feedstuffs (Annex 1, paragraph 4.2). By way of a derogation from paragraph 4.2, for a transitional period expiring on 24 August 2005, the use of a limited proportion of non-organic feedstuffs is authorised where farmers can show to the satisfaction of the inspection body that they are unable to obtain feed exclusively from organic production (paragraph 4.8). The derogation, although with a declining percentage of non-organic feedstuffs over the next years, has been prolonged in July 2005. The preferable use of home-grown feedstuffs and limitations in the choice of boughtin feedstuffs can be the cause of considerable variation in the composition of the diets, and considerably restrict the possibilities for the adaptation of the feed ration to the specific requirements. Due to the limited availability of essential amino acids in particular, there is concern that nutritional imbalances encountered in practice might lead to deteriorating animal health and welfare. On the other hand, there is also the concern that allowing conventional feedstuffs to be fed in organic livestock production will result in intensification of production. The intensification might cause the same problems in organic production as conventional production already shows (animal health problems, risk of residues and GM contamination etc.). Thus, the use of non-organic feedstuffs may have a damaging effect on consumer confidence in organic products of animal origin. In the following the nutritional-physiological effects of a variation in protein supply with respect to growth performance and protein accretion in broilers, turkeys, laying hens, and pigs are examined by means of a literature review. Additionally, the potential effects of the protein content in the diet on product quality, animal health and environmental damage are addressed. It is the aim of the report to provide an overview of the many different aspects of the protein supply in organic poultry and pig production. Many different aspects are taken into account to elaborate possibilities to handle the use of organic and non-organic feedstuffs with respect to the objectives and framework conditions of organic livestock production. However, due to the complex interactions not all aspects can be covered. There is room and need for explanation and for further research

    A Lower Estimate for the Modified Steiner Functional

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    We prove inequality (1) for the modified Steiner functional A(M), which extends the notion of the integral of mean curvature for convex surfaces.We also establish an exression for A(M) in terms of an integral over all hyperplanes intersecting the polyhedralral surface M.Comment: 6 pages, Late

    A Note on Asymptotic Freedom at High Temperatures

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    This short note considers, within the external field approach outlined in hep-ph/0202026, the role of the lowest lying gluon Landau mode in QCD in the high temperature limit. Its influence on a temperature- and field-dependent running coupling constant is examined. The thermal imaginary part of the mode is temperature-independent in our approach and exactly cancels the well-known zero temperature imaginary part, thus rendering the Savvidy vacuum stable. Combining the real part of the mode with the contributions from the higher lying Landau modes and the vacuum contribution, a field-independent coupling alpha_s(T) is obtained. It can be interpreted as the ordinary zero temperature running coupling constant with average thermal momenta \approx 2pi T for gluons and \approx pi T for quarks.Comment: 4 pages; minor changes, version to appear in Phys. Rev.
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