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  • Articles  (51)
  • Springer  (51)
  • American Society of Hematology
  • 1990-1994  (51)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (51)
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  • Articles  (51)
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  • 1
    ISSN: 1432-0630
    Keywords: 68.55 + b ; 62.20 Fe ; 78.65 Jd
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In-depth stress distribution GaAs layers grown by Molecular Beam Epitaxy (MBE) on Si (001) has been studied by X-ray diffraction, photoluminescence and Raman spectroscopy. In order to determine the stress state at different distances to the interface GaAs/Si, layers of different thickness were prepared by chemical etching of the grown samples. We observe a non-uniform residual strain distribution through the GaAs on Si epilayer. Residual strain of thermal origin is larger in the highly defective region (∼ 0.4 μm) near the GaAs/Si interface where we have found a non-elastic relation between measured in-plane (a ‖) and in growth direction (a ⊥) lattice parameters. However, thermal strain is partially relaxed by formation of 107 cm−2 dislocations in the region of better crystalline quality near the external surface.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The in vitro decay of Aextoxicon punctatum and Fagus sylvatica wood by the fungi Trametes versicolor, Ganoderma australe, Phlebia chrysocrea and Lentinus cyathiformis was studied by the agar-block method, and then the decayed woods were analyzed by chemical and spectroscopic techniques. The results demonstrated the strong resistance of the A. punctatum wood to the brown-rot fungus L. cyathiformis; the resistance might be related to the low S/G lignin ratio in this Austral hardwood. Wood decay by the Austral white-rot fungi G. australe and P. chrysocrea was rather limited, and preferential degradation of lignin was not produced although all the fungi studied increased wood digestibility. The most characteristic white and brown-rot decay patterns were observed during the in vitro decay with T. versicolor and L. cyathiformis, respectively. Trametes versicolor caused high weight losses and reduced the lignin content of the wood, whereas L. cyathiformis produced a preferential removal of xylan. No important changes in the solid-state 13C NMR spectra were observed after wood degradation by T. versicolor, but this technique evidenced an increase in aromatic carbon by L. cyathiformis. This increase was higher than that found in the Klason lignin content, suggesting the presence of altered lignin fractions in the brown-rotted wood.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of intelligent manufacturing 2 (1991), S. 253-260 
    ISSN: 1572-8145
    Keywords: Tabu search ; GRASP ; just-in-time ; scheduling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In recent years the Just-in-Time (JIT) production philosophy as been adopted by many companies around the world. This has motivated the study of scheduling models that embrace the essential components of JIT systems. In this paper, we present a search heurustic for the weighted earliness penalty problem with deadlines in parallel identical machines. Our approach combines elements of the solution methods known as greedy randomized adaptive search procedure (GRASP) and tabu search. It also uses a branch-and-bound post-processor to optimize individually the sequence of the jobs assigned to each machine.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of intelligent and robotic systems 6 (1992), S. 219-240 
    ISSN: 1573-0409
    Keywords: Force control ; slip-stick friction ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper explores two practical issues related to the force control of manipulators. The first issue examined is how system stability is effected by commonly occurring manipulator nonlinearities, such as sampled-data, control signal saturation and slip-stick friction. It is shown that discretely implemented force control algorithms can drive the feedback force controlled manipulator into a limit cycle, even for a very small sampling period that by far satisfies Shannon's sampling theorem. The bounds of stability are enhanced by the presence of control signal saturation and slip stick friction. The second issue investigated is the inclusion of a high gain inner position loop as a means to minimize the unpredictability in the steady state error due to slip-stick friction. In order to support the theoretical conclusions, experiments were performed with the PUMP 560 industrial robot testbed facility developed at Colorado State University.
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  • 5
    ISSN: 1432-0630
    Keywords: 68.55 ; 78.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of silicon-oxide thin films is presented. A complete set of experiments has been performed showing the influence of the concentration of the precursor gases, N2O and SiH4, and their influence on total and partial pressures on film growth and properties. In this paper we demonstrate the ability of this LCVD method to deposit silicon oxide films of different compositions and densities by appropriate control of gas composition and total pressure. Moreover, a material specific calibration plot comprising data obtained using different preparation techniques is presented, allowing determination of the stoichiometry of SiO x films by using FTIR spectroscopy independently of the deposition method. For the range of processing conditions examined, the experimental results suggest that chemical processes governing deposition take place mainly in the gas phase.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 237-271 
    ISSN: 1572-8986
    Keywords: High-power transferred arc ; air plasma ; turbulence ; radiative transfer ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A physical model of two zones (constricted arc and cathode jet) of a 1-MW transferred arc in air is presented. It is based on the solution al conservation equations by a finite-differenee method. Turbulence is treated with Prandtl's approximation, whereas radiative transfer is solved considering a nonhontogeneous medium, with the hypothesis of gray spectral bands. The in of radiative transfer on the temperature field is illustrated using two-band and four-band radiation models. We also show the influence of several parameters on plasma jet properties: current intensity between 500 and 1500 A; gas mass /low rate between 10 and 90g/s, vortex injection. The arc characteristics are analyzed in accordance with physical mechanisms such as heat conduction, radiation, turbulence, convection, and miring of cold gas.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 28 (1993), S. 3451-3456 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Phase relations below 1700°C in the ZrO2-rich region of the zirconia-ytterbia system have been established using thermal expansion, room-temperature X-ray diffraction, precision lattice parameter measurements and microscopic observations. The solubility limits of ytterbia in both monoclinic and tetragonal zirconia were determined. A eutectoid reaction, tetragonal zirconia solid solution→ monoclinic + cubic zirconia solid solutions at 400 ± 20°C and 2.4 mol % ytterbia was found. The left-hand boundary of the cubic zirconia solid-solution field was redetermined between room temperature and about 1700°C. Long-range ordering was present at 40 mol % ytterbia and the formation of an ordered phase, Zr3Yb4O12, isostructural with M7O12-type compounds was found. Its thermal stability was established between room temperature and 1630 ± 10°C, in which it decomposes into cubic zirconia solid solution by an order-disorder reaction.
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  • 8
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 33 (1990), S. 1-17 
    ISSN: 1573-4889
    Keywords: Ni-Cr-Al alloys ; alloy microstructure ; oxidation ; refractory-metal additions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior at 1023 and 1123 K in air has been followed for several Ni-Cr-Al ternary alloys and with small additions of refractory elements Nb, Mo, and Ta. Prior to testing, the alloys were characterized by microscopic and microanalytic methods. Microstructural observations have shown that the formation of oxide layers depends on the original microstructure. Discontinuous thermogravimetric tests were used to relate the behavior of different chromium, aluminum, and refractory-element additions, and eventually to service conditions in similar environments in which general oxidation takes place. The addition of refractory elements generally impaired the oxidation resistance.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 27 (1992), S. 747-749 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The optical constantsn(λ) and α(λ) have been determined for CdSxSe y films electrodeposited on to glass doped with SnO2. From a (αhv)2 versus photon energy plot, a value for the direct band gap of the electrodeposited polycrystalline semiconductor ofE g=1.83 eV was obtained, which indicates a low proportion of S2− in the thin films formed.
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