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- ItemShort Communication: the Influence of Air-Abrasive Trimming on the Current Noise of Thick Film Resistors(London [u.a.] : Gordon & Breach, 1984) Wolf, M.[No abstract available]
- ItemOn Experimental Data of the Tcr of Tfrs and Their Relation to Theoretical Models of Conduction Mechanism(London [u.a.] : Gordon & Breach, 1985) Storbeck, I.; Wolf, M.Any theory of electrical conduction in TFRs encounters mainly two problems: (i) explanation of the dependence of R□ on properties of conducting component (volume fraction, grain size, resistivity), (ii) explanation of the temperature dependence of R□ taking into account (i). In order to achieve this one has to fit some microscopic parameters to experimental R□-and TCR-values, and to check if they are reasonable or not. The aim of the following discussion is to show, that such a fitting by means of experimental TCR-values is not correct. This is due to the fact that TCR-behaviour, as is well known, is determined also by the dependence of resistivity on strain. But any theoretical model neglects strains, also those who are induced by thermal strains. By means of published experiments concerning the strain dependence of resistance, the magnitude is estimated by which the TCR-values have to be corrected for the described fit.
- ItemMAGNUS - mehrstufige Analyse grosser Netzwerke und Systeme(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 1994) Borchardt, Jürgen; Grund, Friedrich; Horn, Dietmar; Uhle, Manfred[no abstract available]
- ItemStand des Altglasrecyclings - Verpackungsverordnung und Duales System(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Hoffmann, Werner[no abstract available]
- ItemBorosilicate glass matrix composites reinforced with short metal fibres(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Boccaccini, Aldo R.; Ondracek, Gerhard; Syhre, ClaudiaThe reinforcement of a borosihcate glass with Hastelloy X short fibres is discussed. A fabrication process consisting of wet mixing of the glass powder and the metallic fibres and hot pressing of the mixtures was developed. Composites containing 15 vol.% fibres homogeneously distributed in a near fully dense glass matrix were obtained. Both Young's modulus and fracture strength increased with increasing volume fraction of fibres. The experimental values for the Young's modulus are in agreement with theoretical predictions. No fibre pull-out during fracture was detected and there is a good interfacial bond. By means of a rule-of-mixture calculation for the fracture energy, a five-fold increase in fracture toughness for composites containing 15 vol.% fibres can be predicted.
- ItemMechanism of volatilization of fluorides from E-glass melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Pentzel, Constanze[no abstract available]
- ItemNew developments in NOₓ control - The Pilkington "3R" process(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Shulver, IanThere is increasing pressure from the regulatory authorities to reduce the emissions of the nitrogen oxides from glass plants by a significant amount. Exploiting its own technology, Pilkington originally developed the "3R" process for reducing these NOₓ emissions to below 500 mg/m³ waste gas (≈1.5 kg/t glass) from its float glass furnaces. This process has now been demonstrated to be apphcable to other types of regenerative furnaces. The capital costs incurred in installing 3R are less than 10% of alternative processes, with operating costs also significantly reduced. Unlike some o f the alternatives, the Pilkington process requires no fundamental changes in furnace design or operation and is the most effective technology to meet the most demanding NOₓ legislation
- ItemLarge end-fired furnaces with a melting area of 100 m^2 and more(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Pieper, Helmut[no abstract available]
- ItemIsolierglas ohne Reflexionsverzerrungen(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Küffner jr., Peter[no abstract available]
- ItemUltrasonic measurements and complex elastic moduli of silicate glass melts in the viscoelastic and viscous range(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Bornöft, Hansjörg; Brückner, RolfThe temperature- and frequency-dependence of the ultrasonic velocity and attenuation in glass melts is investigated up to a temperature of 1400 C by means of an equipment for measuring the longitudinal and transversal ultrasonic waves. The range of dispersion and the attenuation maxima are determined at frequencies 0.5 to 4 MHz completely for the DGG standard glass I and for the glass melts (composidons in mol%): 7 4 Si0₂ , 16Na₂O, 10CaO and 7 4 Si0₂ , 16 K₂O, 10CaO and partly for the glass melt 7 4 Si0₂ , 16CS₂O, 10CaO and for the B₂O₃ melt. The whole number of elastic constants follows from the ultrasonic velocities and from the density in the usual way The properties of these glass melts are compared along the temperature and viscosity. The transition from the elastic solid to the viscous fluid can be characterized by the elastic modul and interpreted as a viscoelasdc response of an unrelaxed to a relaxed dynamic network which depolymerizes reversibly with increasing and polymerizes with decreasing temperature. The internal frieden, Q⁻¹ characterizes the inelastic pordon during the periodical stress of the ultrasonic waves. The activation energy of Q⁻¹ obtained via frequencies and temperature of the maxima of is nearly twice the amount of the viscosity activation energy in the same temperature region.
- ItemIndustrial experience with oxygen-fired glass furnaces(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Lauwers, Eddy; Strohberg, HorstAmong the leading industrial gases suppliers, Praxair has developed a leadership position in oxygen combustion technology and in on-site oxygen supply technology with its Vacuum Pressure Swing Adsorption process. A tailor-made solution with regard to oxygen burner technology and to oxygen supply method is provided to meet customer requirements. The latest developments show a reduction in particulate emission o f up to 30 % and in NOx emission of up to 90 % compared to air/fuel-fired operations. These results are confirmed in industrial use. Due to specific requirements in applicadon technology, different burner concepts have been developed. These concepts can be classified in two groups: Conventional burners with direct oxygen-fuel mixing create high flame temperatures and NOx formadon; recirculating burners create low flame temperatures and NOx formation due to controlled fluid dynamics to entrain furnace atmosphere into the main oxygen stream before the now diluted oxygen reacts with the fuel.
- ItemComposition of titania coatings deposited by different techniques(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Laube, Michael; Wagner, Wolfgang; Rauch, Friedrich; Ottermann, Clemens; Bange, Klaus; Niederwald, HansjörgQuantitative dement concentrations in titania films produced by different deposition techniques (evaporation, sputtering, ion-assisted deposition, ion plating and dip coating) have been determined by means of Rutherford Backscattering Spectrometry and Nuclear Reaction Analysis with the reaction ¹H(¹⁵N, αγ)¹²C. Large differences of the hydrogen content are found for the various production techniques and the related deposition parameters, which correlate with the refractive index of the respective film. In dependence on the deposition conditions the oxygen/titanium ratio of the investigated titania films varies between 1.95 and 2.09. The impurities detected in the films (tantalum, molybdenum, silicon, argon, carbon, sodium) can be related to specific deposition conditions. Three multilayer interference systems containing TiO₂ and SiO₂ show large variations in hydrogen content resembling those found for single TiO₂ films.
- ItemModeling of the bubble population in glass melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Roi, Torsten; Seidel, Olaf; Nölle, Günther; Höhne, DiethardPrevious studies of refining models have mostly dealt with the mathematical description of the behavior of individual bubbles in glass melts. A further step was the modeling of the ascent and growth of groups of bubbles, including restrictions with respect to the spatial distribution of the individual bubbles. Even though no algorithm was derived in this stage which described the total bubble balance during refining, these investigations have produced important results in the field of bubble growth and ascent. In this study, a general and comprehensive mathematical description of the bubble population during refining shall be given, on the basis of the population balance equation used in chemical engineering. The general balance equation for bubbles during refining is presented together with the corresponding computer model. Several experimental investigations into bubble size distribution are described, together with an analysis of the reduction of the bubble concentration in the pot. The obtained values were used as initial parameters and estimates in computer simulations. Some special results of modeling are shown and discussed.
- ItemModelling of sand grain dissolution in industrial glass melting tanks(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Beerkens, Ruud G. C.; Muijsenberg, Hendricus P. H.; van der Heijden, TomA combinadon of two models, deseribing dissoludon of sand grains in bateh blankets or in the molten glass, is presented: a microscale and a macroscale model. The macroscale model is based on a 3-dimensional calculation procedure to determine the temperature distributions and the flows in industrial glass melting tanks. By means of microscale models, using mass transfer relations for diffusional transport, the dissolution rate of single sand grains can be calculated. The dissolution of the sand is determined by following a large number of single grains during their trajectories through the batch blanket and the molten glass in the glass melting tanks. The dissolution rate of a sand grain is calculated for the temperatures and flow conditions i n every volume element in the tank through which the grain proceeds. The dissolution rate in the batch blanket depends strongly on temperature and the stage of the dissolution process. Initially the very fast shrinkage rate of the grains as temperatures exceed 1200°C results within 10 min in the dissolution of more than 50 % of the sand in the blanket. Forced and free convection in the glass melt leads to increases in the dissolution rate, up to a factor 5 compared to motion-free conditions. Forced bubbling for instance results locally in extremely high mass transfer rates and often improves the melting performance of industrial glass furnaces.
- ItemThe mixed alkali effect revisited - A new look at an old problem(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Ingramm, Malcom D.Progress is reported in resolving the long-standing problem of the mixed alkali effect. Previously theories have failed to encompass all aspects of this phenomenon which involves both a loosening up of glass structure and the reduction of ionic diffusivities. The recently proposed "dynamic structural model", however, reconciles the electrical and structural anomalies by recoupling ion hopping processes to localized site relaxations in glass. The appearance of a mismatch energy and site memory effects leads to successful prediction of the diffusivity "crossover". This could be the first step towards establishing a consensus on the mixed alkah effect which is reflected in several recent publications on this subject.
- ItemBewertung von Altglasscherben und Konsequenzen für den Glasschmelzprozeß(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Enneking, Carolus Q. M.[no abstract available]
- ItemSpectroscopic investigations of glasses with semiconductor microcrystals at higher temperatures(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Kritz, Antje; Müller, MatthiasGlasses containing microcrystals of CuBr or CuCl show two characteristic absorption peaks caused by excitonic transitions. If temperature is increased the peaks become wider and flatter, whereas the complete disappearance o f the excitonic peaks takes place in a narrow temperature range of 30 to 50 K. Absorption intensity in the UV region (at about 30 000 cm⁻¹) increases simultaneously. The reason for these reversible changes is the melting of the microcrystals about 200 K below the melting point of the corresponding bulk crystals. The melting point depends on size and composition of the microcrystals.
- ItemBI-HESTRAL - Wärmeverfestigtes oder teilvorgespanntes Glas(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Bischoff, Gerd[no abstract available]
- ItemModelling of time strength behaviour of soda-lime-silica glass in moist environments(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Höhne, Lutz; Ullner, ChristianThe time strength behaviour of alkali silicate glasses depends on the environmental media and external stresses during aging as well as on the type of initial crack (kind of damage). An extended crack growth model based on the competing processes of crack growth and its retardation due to stress-enhanced alkali leaching in moist media has been implemented on a computer. Considering residual contact stresses, this model is able to simulate crack arrest, strength increase (or decrease, respectively) during aging under load, static and dynamic fadgue including strength distribudons of various soda-lime-silica glass applicadons. Lifetime predicdon of static fatigue can be improved up to about 10 years.
- ItemGlass-ceramic with preferred orientation of Li2Si205 crystals produced by extrusion below crystallization temperature and subsequent heat treatment(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Durschang, Bernward R.; Carl, Gunter; Rüssel, Christian; Marchetti, Kurt; Roeder, ErwinGlass-ceramics with oriented crystals have been produced from a lithium disilicate glass system by extruding the nucleated glass below the crystallization temperature, and subsequent heat treatment to achieve high-crystalline glass-ceramics. The extruded glass was found to possess a small amount of ahgned, elongated lithium disilicate crystallites and anisotropic stresses. The resulting glassceramic shows a high orientation of the needle-shaped Li₂Si₂O₅ crystals with their c-axis parallel to the extrusion direction. The degree of crystallographic orientation was found to be decreased for samples with an additional heat treatment slightly above Tg, placed between the extrusion process and the crystallization. The crystal alignment of specimens extruded below crystallization temperature is significantly higher than the alignment o f extruded glass-ceramic.