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  • Articles  (55)
  • 1995-1999  (33)
  • 1985-1989  (22)
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  • 1
    Electronic Resource
    Electronic Resource
    Structural, optical, and electrical properties of Pb1−xYbxTe films (0〈x〈0.25) (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4843-4845 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the structural, optical, and electrical properties of Pb1−xYbxTe films (0〈x〈0.25) obtained by coevaporation onto Vycor, NaCl, and BaF2 substrates. They crystallize in the NaCl-type structure. The lattice parameter decreases slowly as x increases, not obeying the Vegard's law. Our data seem to indicate the stability of Yb2+ for 0〈x〈0.25. The optical band gap increases linearly with x. The resistivity of the films (n type) increases slowly whereas the mobility (135 cm2/V s for x=0.008) decreases faster as x increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343800
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  • 2
    Electronic Resource
    Electronic Resource
    Occurrence of krypton and xenon in the Bakreswar thermal spring gases (1989)
    Springer
    Naturwissenschaften 76 (1989), S. 520-521 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374125
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  • 3
    Electronic Resource
    Electronic Resource
    Second law analysis of a cyclic regenerator in presence of longitudinal heat conduction in matrix (1999)
    Springer
    Heat and mass transfer 34 (1999), S. 395-403 
    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
    Notes: Abstract The present analysis gives an account of exergy destruction in regenerative heat exchangers used in cryogenic applications from the view point of Second Law of Thermodynamics. Unlike the previous studies, the present work considers the solid storage matrix with temperature variation along both spatial and temporal co-ordinates. The present analysis also considers the effect of matrix longitudinal heat conduction on the Second Law behaviour. Finite longitudinal conductivity, which results from the distribution of temperature in the matrix, acts as a major non-ideality associated with the analyses done so far. The present analysis shows that the introduction of longitudinal conduction ensures the optimization of charging period for the regenerator. This makes it possible to optimize the regenerator performance globally to produce optimum combination of N tu and charging time. It is also observed that a decrease in longitudinal conductivity reduces the optimum charging time. Thus the non-existence of thermodynamic optima at the absence of longitudinal conduction is explained adequately.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002310050275
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  • 4
    Electronic Resource
    Electronic Resource
    Transient response of a parallel flow shell-and-tube heat exchanger and its control (1996)
    Springer
    Heat and mass transfer 31 (1996), S. 231-235 
    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  Rohrbündelapparate sind die am häufigsten verwendeten Wärmeübertrager. Während main in der Literatur zahlreiche Arbeiten über ihr stationäres thermisches Verhalten findet, liegen nur vergleichsweise wenige Arbeiten über ihr instationäres Verhalten vor. In der vorliegenden Arbeit wird das instationäre Verhalten eines Rohrbündelwärmeübertragers mit einem Durchgang unter Vernachlässigung der Wärmekapazität der Rohrwand untersucht. Zur Modellbildung wird ein Ansatz mit verteilten Parametern verwendet. Anders als bei einigen neueren Arbeiten inder Literatur erfolgt die Lösung nicht numerisch sondern analytisch unter Verwendung der Laplacetransformation. Dies liefert eine eindeutige Darstellung der Antwortfunktion und erleichtert damit die Auswahl geeigneter Regelstrategien. Für das Gleichstrommodell wird eine Regelstrategie unter Verwendung eines PID-Reglers formuliert.
    Notes: Abstract  The shell and tube heat exchangers constitute the single largest component of the heat exchanger family. Though a vast number of literature is available for their steady state analyses, the number of works on transient analysis are comparatively fewer. The present paper brings out the transient response of a single pass shell and tube heat exchanger neglecting wall heat capacitance. The model is constructed with a distributed parameter approach. Unlike a number of recent analyses the numerical technique is avoided and the path of double Laplace transform has been chosen instead. This gives a scope for a unique functional representation of the response which is useful for deciding the control strategies to be adopted. This strategy has been formulated for the parallel flow model using PID controllers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002310050050
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  • 5
    Electronic Resource
    Electronic Resource
    Transient response of a parallel flow shell-and-tube heat exchanger and its control (1996)
    Springer
    Heat and mass transfer 31 (1996), S. 231-235 
    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 Rohrbündelapparate sind die am häufigsten verwendeten Wärmeübertrager. Während main in der Literatur zahlreiche Arbeiten über ihr stationäres thermisches Verhalten findet, liegen nur vergleichsweise wenige Arbeiten über ihr instationäres Verhalten vor. In der vorliegenden Arbeit wird das instationäre Verhalten eines Rohrbündelwärmeübertragers mit einem Durchgang unter Vernachlässigung der Wärmekapazität der Rohrwand untersucht. Zur Modellbildung wird ein Ansatz mit verteilten Parametern verwendet. Anders als bei einigen neueren Arbeiten inder Literatur erfolgt die Lösung nicht numerisch sondern analytisch unter Verwendung der Laplacetransformation. Dies liefert eine eindeutige Darstellung der Antwortfunktion und erleichtert damit die Auswahl geeigneter Regelstrategien. Für das Gleichstrommodell wird eine Regelstrategie unter Verwendung eines PID-Reglers formuliert.
    Notes: Abstract The shell and tube heat exchangers constitute the single largest component of the heat exchanger family. Though a vast number of literature is available for their steady state analyses, the number of works on transient analysis are comparatively fewer. The present paper brings out the transient response of a single pass shell and tube heat exchanger neglecting wall heat capacitance. The model is constructed with a distributed parameter approach. Unlike a number of recent analyses the numerical technique is avoided and the path of double Laplace transform has been chosen instead. This gives a scope for a unique functional representation of the response which is useful for deciding the control strategies to be adopted. This strategy has been formulated for the parallel flow model using PID controllers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02328613
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  • 6
    Electronic Resource
    Electronic Resource
    Parallelization of the Volterra algorithm for linear optimal open loop control (1989)
    Springer
    Computational mechanics 5 (1989), S. 305-320 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract If and when the time variation of optimal controls of a linear system subject to known forces is required, they can be obtained by the computationally advantageous open loop Volterra formulation (as opposed to the costlier Riccati formulation). For the computation, the Volterra equation is discretized in the time domain via such schemes as trapezoidal integration or SIMPSON's rule and the resulting linear system is solved to obtain the control vector values at discrete time points within the control timeT. In the case of very large order systems (degrees of freedom ∼ 5000) a parallel technique is absolutely neccessary, and this paper enunciates an efficient parallel stratagem with efficiencies in the range of 80% and 100%. The algorithm uses ‘s + 1’ processors, ‘s’ being the number of intervals within the control timeT, and typically each processor characterizes one time point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01046948
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal analysis of hydrated calcium aluminates (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 765-774 
    Details
    ISSN: 1572-8943
    Keywords: calcium aluminates ; cement ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Differential scanning calorimeter (DSC) has been used to study the dehydration characteristics of hydrated calcium aluminates such as CA, CA2 and C12A7 where C and A stand for CaO and Al2O3 respectively. Dehydration of CAH10 and C2AH8 (whereH=H2O) occur ∼ at 160–180°C and 200–280°C respectively. These two phases are unstable and ultimately get transformed to AH3 and C3AH6. Dehydration of AH3 and C3AH6 occur between 290 and 350°C and overlap at lower scanning rate. The activation energy for dehydration of the stable AH3 and C2AH6 phases has been found to be 107.16 and 35.58 kJ mol−1 respectively. The compressive strength of the hydrated calcium aluminates has been determined. The result shows that in the case of CA, almost 90% of ultimate strength has been attained in 1 day whereas in CA2, ultimate strength has been attained in 14 days and in C12A7 in 1 day. DSC results have been correlated with the rate of strength developments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01981812
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  • 8
    Electronic Resource
    Electronic Resource
    Thickness dependence of Curie temperature of MnBi thin films (1985)
    Springer
    Journal of materials science 4 (1985), S. 1203-1207 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00723459
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  • 9
    Electronic Resource
    Electronic Resource
    Axially symmetrical jet mixing of an incompressible dusty fluid (1985)
    Springer
    Acta mechanica 55 (1985), S. 111-122 
    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 Incompressible laminar jet mixing of a dustry fluid issuing from a circular jet has been considered by using Saffman's model for dusty fluid. Assuming the velocity and temperature in the jet to differ only slightly from that of the surrounding stream, a perturbation method has been employed to linearize the basic equations. The linearized equations have been solved by using Hankel transform, technique. Numerical computations have been made to discuss the veoocity and temperature profiles. It is observed that the particles move faster than the fluid in the down stream direction and the particles temperature is lower than the fluid temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01267984
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  • 10
    Electronic Resource
    Electronic Resource
    Heat transfer response of free convection flow from a vertical heated plate to an oscillating surface heat flux (1998)
    Springer
    Acta mechanica 126 (1998), S. 101-113 
    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 An investigation is undertaken of the unsteady response of two-dimensional laminar free convection boundary layer flow of a viscous incompressible fluid along a semi-infinite vertical heated plate where the mean surface heat flux oscillates with a small amplitude about a steady profile. The buoyancy forces are favourable, resulting from a positive flux of heat from the surface of the plate into the fluid. The interaction of the time-periodic heat flux with the usual boundary-layer flow is examined by using a linearized theory. Solutions are obtained using three distinct methods, namely an extended series expansion method for low frequencies, an asymptotic series expansion method for high frequencies and a fully numerical finite difference method for general frequencies. Calculations have been carried out for a wide range of parameters to examine the solutions in terms of the amplitude and phase angle of the fluctuating parts of the surface shear stress and the surface temperature. It has been found that the amplitude and phase angle of both the shear stress and the surface temperature predicted by these three methods are in very good agreement in their respective ranges of validity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01172801
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