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  • 1
    Electronic Resource
    Electronic Resource
    Effects of outflow boundary condition on convective heat transfer with strong recirculating flow (1994)
    Springer
    Heat and mass transfer 29 (1994), S. 463-470 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Es werden drei verschiedene Methoden herangezogen, um die Erfüllung der Ausflußbedingung bei der Berechnung des konvektiven Wärmeübergangs von einem zweidimensionalen Fluidstrahl an die Wände eines rechteckigen Hohlraumes zu erzwingen. Diese seien kurz bezeichnet als: (1) lokales Massenerhaltungsprinzip, (2) Einkomponentenprinzip, (3) Vollausbildung des Strömungsprofils. Unter Verwendung dieser drei Prinzipien ermittelte numerische Lösungen wurden mit experimentell (Naphtalin-Sublimationsmethode) gefundenen Ergebnissen verglichen. Es zeigte sich, daß Methode (3) ungeeignet ist, Methode (2) gute Ergebnisse für den Hohlraumboden liefert, aber an den Seitenwänden qualitativ von den Versuchsdaten abweicht und daß Methode (1) die beste Übereinstimmung bewirkt. Bei Problemen, welche starke Rezirkulationsströmungen am Austritt des zur Berechnung vorgegebenen Kontrollraumes erwarten lassen, sollte daher dieser Methode der Vorzug gegeben werden.
    Notes: Abstract Three practices of treating outflow boundary condition were adopted in computations for convective heat transfer of a two-dimensional jet impinging in a rectangular cavity. The three practices were local mass conservation method, local one-way method and fully developed assumption. The numerical solutions of the three methods were compared with test data obtained via, naphthalene sublimation technique. It was found that the fully developed assumption was inappropriate, and the local one-way method could provide reasonably good results for the cavity bottom, while for the lateral wall the results with this method qualitatively differed from the test data. The solution with the local mass conservation method was the best. It thus suggested that for a problem expected with a strong recirculating flow at the exit of the computation domain, the local mass conservation method be adopted to treat the outflow boundary condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01539498
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  • 2
    Electronic Resource
    Electronic Resource
    Process of formation of bone-like apatite layer on silica gel (1993)
    Springer
    Journal of materials science 4 (1993), S. 127-131 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: It has been proposed that a hydrated silica plays an important role in forming a biologically active apatite layer on the surfaces of bioactive glasses and glass-ceramics in the body. Recent experiments have shown that a silica hydrogel actually induces apatite formation on its surface in a simulated body fluid (SBF). In the present study the process of apatite formation on silica gel was investigated by means of thin-film X-ray diffraction, Fourier-transformed infrared reflection spectroscopy and scanning electron microscopic observation of the surface of the silica gel, as well as the measurement of changes in the ion concentration of the fluid. It was found that the induction period for the apatite nucleation on the surface of the silica gel was about 6 days. Once the apatite nuclei were formed they grew, taking a spherulitic form by consuming the calcium and phosphate ions from the surrounding fluid. Each spherulite consisted of a lot of flake that clustered into a petal-like morphology. The flake was carbonate-containing hydroxyapatite of small-crystallites and/or defective structure. The Ca/P ratio of the apatite was estimated as 1.5–1.6. Thus, the apatite formed was able to induce secondary nucleation of the apatite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120381
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of residual glassy phase in a bioactive glass-ceramic on the formation of its surface apatite layerin vitro (1992)
    Springer
    Journal of materials science 3 (1992), S. 452-456 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A bioactive glass containing (in wt%) SiO2 48, P2O5 9.5, Na2O 20 and CaO 22.5 was transformed into a glass-ceramic through a heat treatment. The apatite formation on the surface of this glass-ceramic was examined in a simulated physiological solution. The data from X-ray diffraction, infrared reflection spectroscopy, scanning electron microscopy together with energy-dispersive X-ray analysis and composition imaging of backscattered electrons showed that the formation of the surface apatite layer depends on the relative amount of residual glassy phase in the glass-ceramic. The apatite layer was found to formin vitro on its surface if the glass-ceramic contained a residual glassy phase in a relative proportion more than a limiting volume. It lay on a layer rich in silica. However, only, a silica-rich layer was developed within the surface region of the glass-ceramic during the interaction with solution if the glass was almost completely crystallized. It is proposed that the apatite formation on the surface of the glass-ceramic is mainly caused by its residual glass. The residual glass facilitating apatite formation is considered to provide a negatively charged surface developed during its corrosion in the surrounding solution. The negatively charged surface attracts calcium ions and creates a solution within the glass — solution interface that is highly supersaturated with respect to hydroxyapatite. This leads to the formation of apatite on the surface of the glass-ceramic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00701242
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  • 4
    Electronic Resource
    Electronic Resource
    Preferred shapes and modes of internal motion in a four-boson system (1990)
    Springer
    Few body systems 9 (1990), S. 11-23 
    Details
    ISSN: 1432-5411
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A four-body quantum-mechanical system is studied and through suitable manipulations of its wave functions, dominant shapes and modes of internal motion are ascribed to a number of its low-lying 0+ states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01077670
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of inorganic salts on the micellar behaviour of ethylene oxide-propylene oxide block copolymers in aqueous solution (1993)
    Springer
    Colloid & polymer science 271 (1993), S. 657-667 
    Details
    ISSN: 1435-1536
    Keywords: Micelles ; Ethylene oxide-propylene oxide block copolymers ; Aggregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The aggregation behaviour of two ethylene oxide-propylene oxide block copolymers (PEO-PPO-PEO) in aqueous solution has been investigated in the presence of added salts (KCNS, KI, KBr, KCl and KF) by viscosity, cloud point, light scattering, pulse gradient spin echo NMR, and solubilization measurements. The salts have a strong effect on the cloud points of the pluronics. Both P-85 and L-64 form micelles which increase in size and change into elongated shapes when the cloud point is approached. The changes of size and shape of the micelles, revealed by the intrinsic viscosity and rheological properties, seem to occur at the same temperature relative to the cloud point, independent of the nature of the salt. The onset of micelle formation is also shifted in the same direction as the cloud point by the salts, but by a much smaller amount.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652828
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  • 6
    Electronic Resource
    Electronic Resource
    Plant growth response to olestra as related to beneficial use of municipal sludge (1994)
    Springer
    Archives of environmental contamination and toxicology 26 (1994), S. 408-414 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Consumer food ingredients may enter the terrestrial environment as constituents of municipal sludge which is used as a beneficial fertilizer source in land application. Evaluation of the plant/soil response to specific organic constituents, in the presence and absence of municipal sludge, is thus an important scientific component. Olestra is a consumer ingredient used in savory snacks to eliminate fat content and reduce calories in these foods. The fat substitute olestra is a mixture of hexa, hepta, and octaesters of sucrose with medium and long-chain fatty acids. Experiments were conducted of plant response in olestra mixtures with soil or municipal sludge/soil over a range from 0–1,000 mg olestra/kg dry soil. The plants grown from seed were corn, fescue, wheat, and soybean, with the latter two continued to seed production maturity. The comparison of effects rationale used in this study requires some consistent response to be measured and removes emphasis from singular, statistically significant response. The investment in multiple measures of plant response, separate periods of time, and appropriate multiple controls are necessary to place emphasis on consistent trends for a comparison rationale. For olestra, the notion of consistent effects permits the conclusion that more highly saturated solid olestra did not impact plant growth at concentrations of 0–1,000 mg olestra/kg dry soil in soil alone or in sludge/soil mixtures. The absence of effects occurred with germination, height, and biomass parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203571
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  • 7
    Electronic Resource
    Electronic Resource
    Depressurization of natural gas hydrates in berea sandstone cores (1990)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 8 (1990), S. 71-88 
    Details
    ISSN: 1573-1111
    Keywords: Depressurization ; dissociation ; gas hydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract D. W. Davidsonet al. [7] were among the first to recognize significant deposits of natural gas clathrate hydrates in the Western Hemisphere. This work discusses the recovery of gas from such deposits, through laboratory measurement and modeling of a depressurization scheme. The work provides a determination of the volume of gas produced and the position of the hydrate interface, as a function of time when a hydrate-containing core is depressurized. A moving boundary model is shown to provide a satisfactory fit to hydrate dissociation measurements. Qualitative information is provided concerning hydrate formation in Berea Sandstone cores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01131289
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  • 8
    Electronic Resource
    Electronic Resource
    Invariance of asymptotic stability of perturbed linear systems on Hilbert space (1991)
    Springer
    Journal of optimization theory and applications 68 (1991), S. 75-93 
    Details
    ISSN: 1573-2878
    Keywords: Infinite-dimensional systems ; distributed control problem ; stabilizability ; controllability ; semigroups ; perturbations ; feedback control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The questions of stabilizability of structurally perturbed or uncertain linear systems in Hilbert space of the form $$\dot x = (A + P(r))x + Bu$$ are considered. The operatorA is assumed to be the infinitesimal generator of aC 0-semigroup of contractionsT(t),t≥0, in a Hilbert spaceX;B is a bounded linear operator from another Hilbert spaceU toX; and {P(r),r ∈ Ω} is a family of bounded or unbounded perturbations ofA inX, where Ω is an arbitrary set, not necessarily carrying any topology. Sufficient conditions are presented that guarantee controllability and stabilizability of the perturbed system, given that the unperturbed system $$\dot x = Ax + Bu$$ has similar properties. In particular, it is shown that, for certain classes of perturbations, weak and strong stabilizability properties are preserved for the same state feedback operator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00939936
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  • 9
    Electronic Resource
    Electronic Resource
    Periodic transonic flow without and with condensation in a 2-D plane channel (1993)
    Springer
    Acta mechanica 100 (1993), S. 1-12 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Steady 2-D adiabatic viscous flow and diabatic inviscid flow with energy supply by homogeneous condensation in a channel with a wavy wall have been numerically simulated. The methods used are an analytical-numerical combination procedure for the shock/boundary layer interaction and a diabatic finite volume method to solve the time dependent Euler equations, being linked with the classical nucleation theory and a droplet growth law. The influences of viscous effects and heat addition on the flow field with more than one local supersonic region as well as the choking state have been investigated. The aim is to achieve an adiabatic periodic flow field with imbedded shock waves and a diabatic periodical one including condensation and evaporation phenomena. In the case of adiabatic flow the calculated velocity distribution is compared with experimental and analytical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01176859
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  • 10
    Electronic Resource
    Electronic Resource
    In vitro uptake and autoradiographic localization of tritiated gossypol inTaenia taeniaeformis metacestodes (1993)
    Springer
    Parasitology research 79 (1993), S. 279-285 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Gossypol, a natural polyphenolic compound, induces growth-inhibitory and antiparasitic effects inTaenia taeniaeformis metacestodes in vivo and in vitro. We investigated the uptake and localization of [3H]-gossypol in this parasite. Metacestodes were incubated in 10−5 M [3H]-gossypol at 37°C. Parasites steadily took up tritium activity over the first 3 h of incubation, after which a plateau was maintained for the duration of the experiment. Tissue: medium radioactivity ratios revealed that intralarval tritium activity matched extralarval activity within 30 min of incubation and continued to increase with time. Reverse-phase high-performance liquid chromatographic (HPLC) analysis confirmed tissue incorporation of tritium activity that manifested as a single radioactive species. Autoradiography localized [3H]-gossypol to the tegument, calcareous corpuscles, and parenchyma over the first 2 h of incubation. By 6 h, parenchymal radioactivity had disappeared.T. taeniaeformis metacestodes rapidly take up and accumulate [3H]-gossypol in vitro. This accumulation is apparently selective for specific sites, which may have implications for gossypol's metacestocidal action.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00932182
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