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  • 1
    Electronic Resource
    Electronic Resource
    Low-order parabolic theory for 2D boundary-layer stability (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 1449-1458 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We formulate here a lowest order parabolic (LOP) theory for investigating the stability of two-dimensional spatially developing boundary layer flows. Adopting a transformation earlier proposed by the authors, and including terms of order R−2/3 where R is the local boundary-layer thickness Reynolds number, we derive a minimal composite equation that contains only those terms necessary to describe the dynamics of the disturbance velocity field in the bulk of the flow as well as in the critical and wall layers. This equation completes a hierarchy of three equations, with an ordinary differential equation correct to R−1/2 (similar to but different from the Orr–Sommerfeld) at one end, and a "full" nonparallel equation nominally correct to R−1 at the other (although the latter can legitimately claim higher accuracy only when the mean flow in the boundary layer is computed using higher order theory). The LOP equation is shown to give results close to the full nonparallel theory, and is the highest-order stability theory that is justifiable with the lowest-order mean velocity profiles for the boundary layer. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870008
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  • 2
    Electronic Resource
    Electronic Resource
    Microstructure of Molybdenum Disilicide-Silicon Carbide Nanocomposite Thin Films (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Composite thin films of molybdenum disilicide-silicon carbide (MoSi2-SiC) have been deposited via rf magnetron sputtering onto molybdenum substrates. An intermediate layer was deposited in the presence of nitrogen gas and evaluated as a potential diffusion barrier layer. The composite films have been characterized using X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, and Auger electron spectroscopy. The as-deposited films were amorphous but crystallized into nanometer-sized grains after annealing under vacuum at 1000°C for 30 min. There was a significant amount of interdiffusion between the film and substrate, which resulted in the formation of subsilicides such as Mo5Si3 and MoSi3, as well as Mo2C. The films that were deposited via reactive sputtering in a nitrogen ambient were amorphous in both the as-deposited and annealed conditions. Significantly fewer second phases were detected with the presence of the intermediate layer, which suggests the potential use of the nitrided (MoSixNyCz) layer as a high-temperature diffusion barrier layer for the silicon and carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02505.x
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  • 3
    Electronic Resource
    Electronic Resource
    Rate-optimal schedule for multi-rate DSP computations (1995)
    Springer
    The journal of VLSI signal processing systems for signal, image, and video technology 9 (1995), S. 211-232 
    Details
    ISSN: 1573-109X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper we present a novel framework ofmulti-rate scheduling of signal processing programs represented by regular stream flow graphs (RSFGs). The main contribution of this paper is translating the scheduling problem of RSFGs into an equivalent problem in the domain of Karp-Miller computation graphs. A distinct feature of our scheduling framework—called themulti-rate software pipelining—is to allow maximum overlapping of operations from successive iterations, subject only to precedence constraints caused by data dependences. p ]We demonstrate that the scheduling of regular stream flow graphs can be formulated as a mathematical problem by capturing data dependences between two actors as a precedence relation between the firing of these actors. Using linear schedules, the problem is further translated into a linear program formulation. An efficient solution for the linear programming problem is obtained by first constructing what is called theprecedence graph. A polynomial-time solution is obtained by observing that the optimal computation rate is theminimum cost-to-time ratio cycle (MCTRC) in the precedence graph and using the well-established solution methods for the MCTRC problem. Finally, to minimize the buffer requirement for the obtained rate-optimal schedule, a graph coloring method based on thecyclic interval graph representation has been proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407086
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  • 4
    Electronic Resource
    Electronic Resource
    An experimental study of the discharge coefficient of pipe perforations (1995)
    Springer
    Experiments in fluids 19 (1995), S. 348-352 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Experiments were conducted to study the variation of the pressure loss coefficient of pipe perforations with geometrical parameters of the perforations and a Reynolds number based on the hydraulic diameter of an orifice representing the perforations. The experimental data are used to develop an empirical relationship between the head loss across the perforations and the geometrical and hydraulic parameters related to the perforations which was seen to give better predictions when the perforations are not very closely spaced. The experimental results reported herein correspond to the pipes of small perforated length, with downstream end of the pipe closed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203420
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  • 5
    Electronic Resource
    Electronic Resource
    Thermal, spectral and magnetic studies on glycine complexes of cobalt(II), nickel(II) and zinc(II) with hydrazine (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 117-127 
    Details
    ISSN: 1572-8943
    Keywords: bis-hydrazine metal glycinates ; complexes ; hydrazinium metal glycinates ; metal powders ; thermal analyses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrazinium metal glycinates [(N2H5 2M(NH2CH2COO)4] and bis(hydrazine)metal glycinates, [M(NH2CH2COO)2(N2H4)2], whereM=Co, Ni or Zn have been prepared and characterized by chemical analyses, magnetic moments and vibrational and electronic spectra. The thermal behaviour of these compounds has been studied by thermogravimetry and differential thermal analyses. These complexes decompose with high exothermicity giving metal powder as the final residue. The X-ray powder data of each set of complexes show isomorphism among themselves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979952
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  • 6
    Electronic Resource
    Electronic Resource
    Acetate and malonate complexes of cobalt(II), nickel(II) and zinc(II) with hydrazinium cation (1997)
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 1401-1413 
    Details
    ISSN: 1572-8943
    Keywords: complexes ; metal oxides ; thermal analysis ; XRD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrazinium(1+) metal acetates and malonate dihydrates of the molecular formula [(N2H5)2M(CH3COO)4] and (N2H5)2[M(OOCCH2COO)2(H2O)2] respectively, whereM=Co, Ni or Zn, have been prepared and characterized by chemical analyses, conductance, magnetic, spectral, thermal and X-ray powder diffraction studies. The magnetic moments and electronic spectra indicate that these complexes are of high-spin octahedral variety. The infrared spectra show that the hydrazinium ions are coordinated in the case of acetate complexes, whereas in the malonate complexes the hydrazinium ions are out side the coordination sphere. These complexes undergo exothermic decomposition in the temperature range 150–450°C to give the respective metal oxide as the final residue. The X-ray powder diffraction patterns of the malonate complexes indicate isomorphism among them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01983451
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  • 7
    Electronic Resource
    Electronic Resource
    Covariantising the Beltrami equation in W-gravity (1996)
    Springer
    Letters in mathematical physics 37 (1996), S. 375-383 
    Details
    ISSN: 1573-0530
    Keywords: Primary: 81T40 ; secondary: 35Q53 ; 32G05 ; string theory ; W-geometry ; Beltrami equation ; uniformisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract Recently, certain higher-dimensional complex manifolds were obtained by S. Govindarajan [1] by associating a higher dimensional uniformisation to the generalised Teichmüller spaces of Hitchin. The extra dimensions are provided by the ‘times’ of the generalised KdV hierarchy. In this Letter, we complete the proof that these manifolds provide the analog of superspace for W-gravity and that W-symmetry linearises on these spaces. This is done by explicitly constructing the relationship between the Beltrami differentials which naturally occur in the higher-dimensional manifolds and the Beltrami differentials which occur in W-gravity. This also resolves an old puzzle regarding the relationship between KdV flow. and W-diffeomorphisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312669
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  • 8
    Electronic Resource
    Electronic Resource
    Pb-induced alterations in tyrosine hydroxylase activity in rat brain (1997)
    Springer
    Molecular and cellular biochemistry 175 (1997), S. 137-141 
    Details
    ISSN: 1573-4919
    Keywords: Pb ; dopamine biosynthesis ; tyrosine hydroxylase ; brain ; SDS-PAGE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Our previous studies have shown that exposure to low levels of Pb results in significant reductions in dopamine (DA) and its metabolites (3,4-dihyroxyphenylacetic acid, DOPAC and homovanillic acid, HVA) in nucleus acumbens (NA). This area of brain receives dopaminergic projections from the ventral tegmentum and is considered vital in manifestation of many behavioral responses. Similarly, basal and K+-induced release of DA was found significantly reduced in the Pb-exposed rats as compared to the controls in this brain region. Additional studies indicated that acute infusion of Pb in nucleus acumbens caused significant release of DA. Based on these observations it was postulated that the reductions in DA contents and in the basal and stimulus-induced release of DA in NA were manifestations of attenuated dopaminergic activity in this brain region. However, the mechanism of this attenuation is not yet clear. Studies reported here were designed to evaluate the role of a key regulatory enzy me in biosynthesis of DA, i.e. tyrosine hydroxylase (TH) in Pb-induced reductions in dopaminergic activity. The results of these studies indicated that 50 and 500 ppm Pb produced 22.8 and 56% inhibition of TH activity in vitro respectively, and that the enzyme activity was reduced to 43% in rats exposed to 50 ppm lead for 30 days as compared to the controls. The alterations in TH activity in Pb-exposed animals were further confirmed by Western blot analysis. Collectively, these results suggest that Pb-induced inhibition of TH activity in rat brain may contribute to the reductions in dopaminergic activity observed in Pb-exposed animals. (Mol Cell Biochem 175: 137–141, 1997)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006891830182
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  • 9
    Electronic Resource
    Electronic Resource
    Region - specific alterations in tyrosine hydroxylase activity in rats exposed to lead (1998)
    Springer
    Molecular and cellular biochemistry 189 (1998), S. 19-24 
    Details
    ISSN: 1573-4919
    Keywords: brain ; pb ; tyrosine hydroxylase ; SDS-PAGE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Previous studies from our laboratory showed that subchronic exposure to low levels of Pb resulted in significant decrease in dopamine (DA) content, attenuation of stimulus-induced release of DA in the dopaminergic projection area of nucleus accumbens (NA), and alterations in tyrosine hydroxylase (TH) activity in rat whole brain homogenates. The present study reported here was conducted to assess the functional integrity of DA synthesis in different brain regions of rats subchronically (90-days) exposed to 50 ppm Pb by measuring the activity of the rate limiting enzyme, tyrosine hydroxylase, in seven brain regions. In Pb-exposed rats, TH activity was reduced in two of the seven brain regions investigated, i.e., nucleus accumbens (42% reduction) and frontal cortex (61% reduction) when compared to controls. In contrast, Pb exposure did not affect the TH activity in cerebellum, brainstem, hippocampus, hypothalamus and striatum. The changes in TH activity in nucleus accumbens (NA) and frontal cortex (FC) in Pb-exposed rats were further confirmed by Western blot analysis using TH polyclonal antibody. Collectively, these results indicate that low level subchronic Pb exposure may affect TH protein in these brain regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006896111280
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  • 10
    Electronic Resource
    Electronic Resource
    Pressure-dependent plasticity models: Loading-unloading criteria and the consistent linearization of an integration algorithm (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 339-345 
    Details
    ISSN: 1069-8299
    Keywords: numerical integration ; plasticity ; pressure-dependent plasticity ; porous metals ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A general methodology for the numerical integration of pressure-dependent plasticity models is developed, and the corresponding ‘linearization moduli’ are derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640110407
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