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  • 1
    Electronic Resource
    Electronic Resource
    Lasers for materials processing: specifications and trends (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 1089-1102 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An overview is given of the types of lasers dominating the field of laser materials processing. The most prominent lasers in this field are the CO2 and the Nd: YAG laser. The domain of CO2 lasers is applications which demand high laser powers (up to 30 kW are available at present), whereas the domain of Nd:YAG lasers is micro-machining applications. In the kilowatt range of laser output power, the two types of lasers are in competition. New diffusion-cooled CO2 laser systems are capable of output laser powers of several kilowatts, with good beam qualities, while still being quite compact. The output power and beam quality of Nd:YAG lasers has been improved in recent years, so that Nd:YAG lasers are now an alternative to CO2 lasers even in the kilowatt range. This is especially true for applications that demand optical fibre transmission of the laser beam, which is possible with Nd:YAG laser light but not with the longerwavelength light emitted by CO2 lasers. The main problem in solid-state lasers such as Nd:YAG is the thermal lensing effect and damage due to thermal stresses. In order to reduce thermal loading, cooling has to be enhanced. Several alternative geometries have been proposed to reduce thermal loading and, by this, thermal lensing effects. There are now slab and tube geometries which allow much higher output powers than the conventionally used laser rods. A very new scheme proposes a thin slab whose cooled side is also used as one of the laser mirrors, so that thermal gradients occur mainly in the direction of the beam propagation and not perpendicular to it, as is the case in the other geometries. As well as CO2 and Nd:YAG lasers, semiconductor laser diodes are very promising for direct use of the emitted light or as pump sources for Nd:YAG and other solid-state lasers. When packaging together thousands of single laser diodes, output powers of several kilowatts can be realized. Major problems are collimation of the highly divergent laser beams and cooling of the laser diode bars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326469
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  • 2
    Electronic Resource
    Electronic Resource
    Channelled substrate window twin stripe GaAs/GaAIAs visible lasers: fabrication and steady-state analysis (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 141-154 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract GaAs/GaAIAs high-power window stripe lasers have been developed with a uniform active layer in the region adjacent to the device facets and with a curved active layer in the central region. A single-step liquid-phase epitaxy growth is used in the fabrication process to form two internal lateral current paths, so allowing for a very simple fabrication process. The optical coupling between the two stimulation emission regions reduces the beam divergence. The steady-state analysis of such a laser structure, including heating effects, agrees well with experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00563219
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation and characterization of WO3/SiO2 catalysts (1995)
    Springer
    Catalysis letters 33 (1995), S. 209-215 
    Details
    ISSN: 1572-879X
    Keywords: tungsten oxide ; silica ; Raman spectroscopy ; surface structure ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two sets of WO3/SiO2 catalysts were prepared from (NH4 6H2W12O40 (aqueous method) and W(η3-C3H5)4 (non-aqueous method). The molecular structures and dispersions of the surface tungsten oxide species for the WO3/SiO2 catalysts under ambient and in situ dehydrated conditions were investigated by Raman spectroscopy. The samples prepared from (NH4)6H2W12O40 (aqueous method) exhibit very strong Raman features due to the presence of crystalline WO3 and the samples prepared from W(η3-C3H5)4 (non-aqueous method) do not possess crystalline WO3. These results suggest that the preparation method exerts an influence on the dispersion of the surface tungsten oxide species on SiO2. The surface tungsten oxide species under ambient conditions possess polytungstate clusters, W12O 42 12− , on the silica support. Upon dehydration at elevated temperatures, the hydrated polytungstate clusters decompose and interact with the silica support via the formation of isolated, octahedrally coordinated tungsten oxide species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00814225
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  • 4
    Electronic Resource
    Electronic Resource
    Norm inequalities of positive operator matrices (1995)
    Springer
    Integral equations and operator theory 22 (1995), S. 281-294 
    Details
    ISSN: 1420-8989
    Keywords: 47A30 ; 47A10 ; 47B25 ; 15A48
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01378777
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  • 5
    Electronic Resource
    Electronic Resource
    A three-dimensional machine-vision approach for automatic robot programming (1995)
    Springer
    Journal of intelligent and robotic systems 12 (1995), S. 23-48 
    Details
    ISSN: 1573-0409
    Keywords: Robot programming ; automatic programming ; machine vision ; 3D hand-motion analysis
    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 research investigates a novel robot-programming approach that applies machine-vision techniques to generate a robot program automatically. The hand motions of a demonstrator are initially recorded as a long sequence of images using two CCD cameras. Machine-vision techniques are then used to recognize the hand motions in three-dimensional space including open, closed, grasp, release and move. The individual hand feature and its corresponding hand position in each sample image is translated to robot's manipulator-level instructions. Finally a robot plays back the task using the automatically generated program. A robot can imitate the hand motions demonstrated by a human master using the proposed machine-vision approach. Compared with the traditional leadthrough and structural programming-language methods, the robot's user will not have to physically move the robot arm through the desired motion sequence and learn complicated robot-programming languages. The approach is currently focused on the classification of hand features and motions of a human arm and, therefore, is restricted to simple pick-and-place applications. Only one arm of the human master can be presented in the image scene, and the master must not wear long-sleeved clothes during demonstration to prevent false identification. Analysis and classification of hand motions in a long sequence of images are time-consuming. The automatic robot programming currently developed is performed off-line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01258306
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  • 6
    Electronic Resource
    Electronic Resource
    On greedy heuristics for steiner minimum trees (1995)
    Springer
    Algorithmica 13 (1995), S. 381-386 
    Details
    ISSN: 1432-0541
    Keywords: Steiner trees ; Greed heuristic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We disprove a conjecture of Shor and Smith on a greedy heuristic for the Steiner minimum tree by showing that the length ratio between the Steiner minimum tree and the greedy tree constructed by their method for the same set of points can be arbitrarily close to√3/2. We also propose a new conjecture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01293486
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  • 7
    Electronic Resource
    Electronic Resource
    Electronic properties of silicon-nitride films deposited by low-energy ion-beam bombardment (1995)
    Springer
    Applied physics 61 (1995), S. 643-644 
    Details
    ISSN: 1432-0630
    Keywords: 73.61.Ng ; 41.75 ; 68.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Ultrathin silicon-nitride films have been synthesized on silicon substrates by low-energy nitrogen-ionbeam bombardment. The thicknesses of the obtained films are found to increase slightly with the duration of bombardment. Capacitance-voltage and current-voltage characteristics of silicon-nitride films prepared at different bombarding times show that the density of damages, charges in the films and interface states, the capacitance of the obtained ultrathin silicon-nitride films, the flat-band capacitance and the flat-band voltage increase with the duration of the bombarding process. The results of these analyses suggest a short bombarding processing for such a silicon-nitridation technique proposed here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01542876
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  • 8
    Electronic Resource
    Electronic Resource
    Photoacoustic phase spectrum of a layered sample (1995)
    Springer
    Applied physics 60 (1995), S. 419-423 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 78.20.Hp; 82.80.Kq; 87.50.Hj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Based on the Rosencwaig-Gersho theory (RG), we have studied the PhotoAcoustic Phase Spectrum (PAPS) of a two-layer sample. The theoretical results are mainly verified by an experiment, in which an intact plant leaf is used as the sample. The ratio of the optical absorption coefficient to the thermal diffusion coefficient for the subsurface layer can be obtained from the theoretical formula using measured phase values. The spectrum formed by the ratios at different wavelengths is in a good agreement with those experimentally obtained by phaseresolved photoacoustic spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538344
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  • 9
    Electronic Resource
    Electronic Resource
    Electronic properties of silicon-nitride films deposited by low-energy ion-beam bombardment (1995)
    Springer
    Applied physics 61 (1995), S. 643-644 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 73.61.Ng; 41.75; 68.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Ultrathin silicon-nitride films have been synthesized on silicon substrates by low-energy nitrogen-ion-beam bombardment. The thicknesses of the obtained films are found to increase slightly with the duration of bombardment. Capacitance–voltage and current–voltage characteristics of silicon-nitride films prepared at different bombarding times show that the density of damages, charges in the films and interface states, the capacitance of the obtained ultrathin silicon-nitride films, the flat-band capacitance and the flat-band voltage increase with the duration of the bombarding process. The results of these analyses suggest a short bombarding processing for such a silicon-nitridation technique proposed here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01542876
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  • 10
    Electronic Resource
    Electronic Resource
    Photoacoustic phase spectrum of a layered sample (1995)
    Springer
    Applied physics 60 (1995), S. 419-423 
    Details
    ISSN: 1432-0630
    Keywords: 78.20.Hp ; 82.80.Kq ; 87.50.Hj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Based on the Rosencwaig-Gersho theory (RG), we have studied the PhotoAcoustic Phase Spectrum (PAPS) of a two-layer sample. The theoretical results are mainly verified by an experiment, in which an intact plant leaf is used as the sample. The ratio of the optical absorption coefficient to the thermal diffusion coefficient for the subsurface layer can be obtained from the theoretical formula using measured phase values. The spectrum formed by the ratios at different wavelengths is in a good agreement with those experimentally obtained by phaseresolved photoacoustic spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538344
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