Vergleichsbetrachtungen zu Seitenkanal-, Labyrinth- und Strahlpumpen

Zusammenfassung Für die drei Pumpenarten werden die Berechnungsgrundlagen aufgestellt und gezeigt, da? in bezug auf die Str?mungsvorg?nge eine Vereinheitlichung der fluidmechanischen Ans?tze zur Charakterisierung des Kennlinienverhaltens m?glich ist. Da bei den drei Wirkprinzipien die Impulsaustauscheffekte für die Energieübertragung zwischen den Fluiden und den Energieübertragungs-elementen die Basis bilden, ist eine derartige einheitliche Darstellungsweise gegeben. In diesem Zusammenhang wird das erweiterte Cordier-Diagramm für Fluidenergiemaschinen herangezogen und gezeigt, da? diese Maschinenarten übersichtlich in das Kennfeld eingefügt werden k?nnen und somit eine umfassende Aussage bezüglich der σ^*-σ^*-Charakteristik gew?hrleistet ist.     

Möglichkeiten und Grenzen Elektronischer Datenverarbeitung bei der Erforschung der Geschichte des Mittelalters

Research supported by computers in the field of medieval history, although developed in several areas, still produces controversial discussions. An attempt is made here to determine the possibilities and limits of the use of electronic data processing, with a critical eye of the various areas of application. The operation of electric calculators, which require a restriction to specific categories of questions, doubtless leads to new and different utilization of historical materials and data. From the point of view of how these materials are used, projects that have been developed to date can be divided into three categories of analysis: historical texts, personal history data, and economic-historical data. Of these, machine text analysis has, so far, not gotten beyond the development of indices, word-frequency studies and similar matters. For historical documents which contain names, several examples demonstrate how efficiently machine searches, comparisons, and sorting operations advance the exploration of the materials. Problems arise, however, in connection with a phenomenon that is typically medieval, namely, that names in the sources cannot be safely attributed to specific persons. In the field of economic-historical data, we find successful examples of statistical research supported by computers. The use of electronic data processing appears to be always successful in medieval studies when the materials used contain a large number of comparable data which can be formalized and categorized.      

The effect of pressure on carbon-black/elastomer powders. Part I: Density measurements on haf-black/sbr-powders at pressures up to 19 kbar

Carbon-black/elastomer powders were prepared by spray-drying mixtures of aqueous dispersions of high abrasion furnace (HAF) black with styrene-butadiene rubber (SBR) latex. The HAF/SBR ratio was varied in the range 100/0, 95/5, 75/25, 67/33, 50/50, 33/67 and 0/100 parts by weight. The powders were subjected to pressures up to 19 kbar in a piston-cylinder apparatus. The density of the powders was measured at different pressures and it was found that an interaction between carbon-black and polymer occurs which results in the formation of coherent samples. They exhibit a pressure dependent degree of porosity the magnitude of which was calculated from their density and compared to the porosity determined experimentally from the methanol uptake of the samples. At higher carbon-black loadings the specimen become increasingly porous with a corresponding decrease in density. Density measurements on the three-phase system (HAF/SBR/pores) permitted to determine the density of the HAF-black at 19 kbar as 1.97 g/cm³. Density and porosity at 0 kbar of the pressed specimen are a function of the pressure at which they were prepared. The density increases with increasing pressure whereas the porosity decreases due to stronger interaction between carbon-black and elastomer.     

Haptics in telerobotics

For telerobotic systems the ultimate goal is transparency, meaning the human operator cannot distinguish between operating in a local or a distant environment. To achieve this, the human operator is coupled with the telerobotic system with all necessary senses: visual, auditory and haptic modality. For the haptic modality this implies research in the following fields: robotic hardware, both handcontroller and teleoperators, and control aspects with time delay. The latter include both supervisory and bilateral control. In this paper the current and future aspects of haptics in telerobotics are shown focusing on the control research. With the evolving technology in these research areas telerobotic systems can now be found in a variety of different application fields, e.g. microassembly, surgery or space.     

Platinum migration out of zeolites onto iron oxide: an alternative to H spillover

TPR shows that the reduction of Fe₂O₃ to Fe₃O₄ is strongly enhanced in mixtures with platinumcontaining mordenite. However, no hydrogen spillover takes place from Pt⁰ particles along the walls of the zeolite pores. Only migration of platinum out of the zeolite onto the Fe₂O₃ leads to enhanced reduction of Fe₂O₃. TEM and EDX prove unambiguously that Pt clusters decorate Fe₂O₃ particles after an oxidative pretreatment of intimate mixtures, followed by reduction. Two paths exist for this migration of oxidized platinum: as Pt²⁺ ions and as PtO or PtO₂ clusters. The rate for both transport mechanisms increases with temperature. Pretreatment with H₂O vapor results in hydrated ions which have higher mobility and lead to more homogeneous distribution of the platinum over iron oxide particles. Reduction in wet hydrogen is slower than in dry hydrogen; no reduction to Fe ⁰ occurs in wet hydrogen.     

NETMAN: The design of a collaborative wearable computer system

This paper presents a wearable groupware system designed to enhance the communication and cooperation of highly mobile network technicians. It provides technicians in the field with the capabilities for realtime audioconferencing, transmission of video images back to the office, and contextsensitive access to a shared notebook. An infrared locationtracking device allows for the automatic retrieval of notebook entries depending on the user's current location.