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  • 1
    Electronic Resource
    Electronic Resource
    Study of the surface structure of tin dioxide layers for gas sensors by atomic-force microscopy (1998)
    Springer
    Semiconductors 32 (1998), S. 587-589 
    Details
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract This paper presents the results of a study by atomic-force microscopy of tin dioxide layers as a function of the conditions under which they are doped with iodine and tellurium during the production of the layers by thermal vacuum deposition of tin, followed by oxidation. Data concerning the atomic-force microscopy of layers fabricated in various processing regimes are presented and discussed. It is shown that introducing volatile impurities into the starting charge is an effective means of modifying the surface structure of the layers and of altering the character of its microsurface. The temperature dependence of the sensitivity of the layers to toluene vapor is studied and analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1187443
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  • 2
    Electronic Resource
    Electronic Resource
    Study of submicron deposits in polycrystalline materials using the internal-friction method (1997)
    Springer
    Semiconductors 31 (1997), S. 714-715 
    Details
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An internal friction method is proposed for investigating the kinetics of impurity deposits on grain surfaces in polycrystalline samples. The possibilities of the method have been tested on polycrystalline, gas-sensitive, tellurium-doped layers of tin dioxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1187074
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  • 3
    Electronic Resource
    Electronic Resource
    Equilibrium of native point defects in tin dioxide (1998)
    Springer
    Semiconductors 32 (1998), S. 1033-1035 
    Details
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A model of electrically active and neutral native point defects in SnO2 is developed. Thermodynamic analysis of the equilibrium of the native point defects makes it possible to construct the phase diagram $$P_{O_2 } - T - x$$ of lead dioxide. The contradiction between n-type monopolar conductivity and the two-sided homogeneity region of the SnO2 phase is resolved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1187560
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  • 4
    Electronic Resource
    Electronic Resource
    Computation of steady state characteristics of self-excited induction generators (1995)
    Springer
    Electrical engineering 78 (1995), S. 237-240 
    Details
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Übersicht In der vorliegenden Arbeit werden ein mathematisches Modell und ein Programm für die Berechnung des stationären Betriebs von autonomen Asynchrongeneratoren vorgestellt. Spannung und Strom, Frequenz, Laststrom und Leistung werden bei Änderung der Drehzahl, Last und Kapazität bestimmt. Untersuchungen wurden durchgeführt, um die theoretischen Ergebnisse zu überprüfen. Die gemessenen und berechneten Werte wurden miteinander verglichen und eine gute Übereinstimmung festgestellt.
    Notes: Contents In this paper a mathematical model and algorithm are presented to obtain the steady state characteristics of autonomous induction generators. The values of the stator voltage and current, frequency, load current and power are calculated for varying rotor speed, load and terminal capacitance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01240228
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic properties of exchange-coupled Fe/FeO bilayers : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5106-5108 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic, structural and microstructural properties of sputtered Fe thin films and Fe(backward-slash)Fe–O bilayers were studied as a function of the Fe layer thickness, the type of the Fe oxide and the substrate used. Two different ways to prepare the oxide layers were used; postdeposition oxidation and reactive sputtering. Postdeposition oxidation produced films with mixed Fe–oxides (FeO, Fe3O4, Fe2O3); however reactive sputtering led to bilayers with controlled stoichiometry, Fe(backward-slash)FeO, Fe(backward-slash)Fe3O4, and Fe(backward-slash)FE2O3, respectively. The coercivity of both the Fe films and fE(backward-slash)Fe–O bilayers, deposited on substrates with or without Cr buffer layer, was found to increase with decreasing Fe film thickness. The coercivity of the samples deposited on a Ag buffer layer was much lower and did not change substantially with the Fe film thickness. The presence of the Fe–oxide layer led to a large increase of coercivity. This is attributed to the higher anisotropy of the oxide and to exchange coupling of Fe–oxide with the softer Fe layer. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361316
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  • 6
    Electronic Resource
    Electronic Resource
    Microstructure and high temperature magnetic properties of Sm(Co, Cu, Fe, Zr)z (z=6.7–9.1) permanent magnets (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 2800-2804 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of ratio z on the high temperature magnetic properties of Sm(Co, Fe, Cu, Zr)z magnets have been examined in a range of ratio z values from 6.7 to 9.1. Reasonably high coercivity at room temperature has been achieved in all the magnets. It was found that the lower the ratio z, the smaller the temperature coefficient of coercivity. When the ratio z=7.0, a temperature coefficient of coercivity of −0.03%/°C can be achieved, which is more than eight times smaller than the magnet with z=8.5. A coercivity of more than 10 kOe has been obtained at 773 K for the newly developed magnets, which is believed to be the highest coercivity at 773 K ever reported. Transmission electron microscope studies showed that the cell size decreases with the decrease of the ratio z, while the density of lamella phase remains almost the same. This suggests that smaller cell size leads to a smaller temperature coefficient of intrinsic coercivity. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369597
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  • 7
    Electronic Resource
    Electronic Resource
    Memory effect and temperature behavior in spin valves with and without antiferromagnetic subsystems (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5692-5695 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature behavior and memory effect in standard spin valves (SV) and SVs with synthetic antiferromagnetic (Co/Ru/Co) (SV-SAF) subsystems have been studied. SV-SAFs show much better temperature stability. Memory effect refers to the phenomenon that the exchange bias can be altered at temperatures (TR's) much lower than the blocking temperature (TB), and these temperatures (TR's) are imprinted into SVs. The memory effect greatly deteriorates the magnetoresistance behaviors in SV. Our results suggest that the memory effect is caused by a distribution of local blocking temperatures (Tb's). The magnetization state in the pinned layer is critical in determining the temperature behavior of HE and magnetoresistance. By partially reversing the magnetization in the pinned ferromagnetic (FM) layers, we are able to separate the temperature dependencies of the local exchange bias (He) associated with regions consisting of different Tb's. Two features have been observed: (1) the local exchange bias (He) with a narrow Tb distribution has a weak temperature dependence; (2) the simple algebraic sum of local He's nearly reproduce the total HE with the difference between these two quantities representing the domain wall energy in the FM layer. On the other hand, SV-SAFs show strong resistance to memory effects because of two factors; the strong exchange coupling through the Ru layer, and the net magnetic moment of Co/Ru/Co layers in SV-SAF being close to zero. The former makes the two SV-SAF FM layers behave coherently, while the latter makes the interaction between the SV-SAF and the external field negligibly small. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371580
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  • 8
    Electronic Resource
    Electronic Resource
    Hydrogeology of the Upper Aquifer, Dobrich Region, Northeastern Bulgaria (1997)
    Springer
    Hydrogeology journal 5 (1997), S. 75-85 
    Details
    ISSN: 1435-0157
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé: L'aquifère supérieur de la Dobrogée (nord-est de la Bulgarie) est constitué par des calcaires, des calcarénites, des sables, et probablement des calcaires dolomitiques d'âge messinien, dont l'épaisseur totale varie de 40 à 200 m. Dans la plus grande partie de la zone il est recouvert par des matériaux détritiques à faible perméabilité (loess) et à perméabilitéélevée (sables et alluvions). Des marnes et des argiles d'âges différents, selon les secteurs, constituent le substratum imperméable. L'ensemble peut être considéré comme un aquifère à fonctionnement karstique très peu accusé, à cause probablement de sa forte porosité, d'après la faible variation des debits des sources contrôlées. La nature de la couverture quaternaire joue un rôle important sur 'hydrogéochimie. Les principales sources de contamination sont liées aux activités agricoles, aux stabulations et aux usées urbaines; la teneur élevée en nitrates des eaux de nombreux puits en témoigne. L'intrusion marine, en tant que processus polluant, semble commencer dans quelques secteurs du bord orienta.
    Abstract: Resumen: El acuífero superior de la región de Dobrich, al noreste de Bulgaria, está constituido por calizas, calcarenitas, arenas y probablemente calizas dolomíticas de edad Messiniense, con un espesor total que varía entre 40 y 200 m. En la mayor parte del área se encuentra recubierto por depósitos de materiales detríticos, desde escasamente permeables (loess), a muy permeables (arenas y aluviones). Es sustrato impermeable está constituido por margas y arcillas de distintas edades. En el conjunto del acuífero, los procesos kársticos son muy poco acusados, según se deduce de la escasa variación de los caudales en las surgencias controladas. Se pone de manifiesto la importancia que desempeña en la hidroquímica la naturaleza del recubrimiento cuaterario, al tiempo que se deduce que los principales focos de contaminación están relacionados con las actividades agrícolas, las estabulaciones ganaderas y las aguas residuales urbanas, tal y como indica el elevado contenido en nitratos de las aguas de numerosos pozos. Fenómenos de intrusión marina parecen haberse iniciado en algunos sectores del borde oriental.
    Notes: Abstract: The upper aquifer of the Dobrich region, northeastern Bulgaria, is composed of limestone, calcarenite, sand and probably dolomitic limestone, of Messinian age; total thickness is 40–200 m. Most of the area is underlain by surficial deposits that include slightly permeable loess and highly permeable sand and alluvium. The nearly impervious substratum comprises marl and clay of varying age. In the aquifer as a whole karstic processes are not very pronounced, based on observations of the small variations in the discharges of the springs that have been monitored. The lithology of the Quaternary-age surficial deposits strongly influences the hydrochemistry of groundwater in the aquifer. The main sources of pollution are related to agricultural activities, corralled livestock, and urban wastewater, as indicated by the high nitrate contents of the water in numerous wells. Seawater intrusion is occuring in some eastern parts of the region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100400050120
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  • 9
    Electronic Resource
    Electronic Resource
    Modeling of the properties of enzyme-containing dispersions (1998)
    Springer
    Fibre chemistry 30 (1998), S. 150-153 
    Details
    ISSN: 1573-8493
    Source: Springer Online Journal Archives 1860-2000
    Topics: Technology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An equation giving a mathematical description of the change in the viscosity of a dispersion for spinning fibre biocatalysts with incorporation of a different amount of disperse phase in solutions of cellulose triacetate in methylene chloride of varying concentration was obtained. The correspondence of the experimental and calculated values of the viscosity of the spinning dispersions was demonstrated. It was found that a change in the particle size and deformability of the disperse phase and formation of associates of particles of the enzyme solution are the basic causes of the change in the rheological properties of the dispersions when the viscosity of the dispersion medium and volume fraction of disperse phase change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02430476
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  • 10
    Electronic Resource
    Electronic Resource
    Ellipsometry as a rapid method of establishing a correlation between the porosity and the gas sensitivity of tin dioxide layers (1999)
    Springer
    Technical physics 44 (1999), S. 468-469 
    Details
    ISSN: 1090-6525
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is shown for the first time that reflection ellipsometry may be an effective method of establishing a correlation between the main parameters of gas-sensitive layers and their optical characteristics, suitable for rapid monitoring. This can advance the capability of predicting the properties of a material from its preparation conditions and consequently can reduce the optimization cycle time and thus lower the cost of a technology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1259325
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