ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    A novel structure of visible semiconductor lasers (1990)
    Springer
    Optical and quantum electronics 22 (1990), S. 385-389 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Terraced substrate inner current stripe lasers emitting in the range of 750–780 nm are developed with very simple fabrication processes. The lasers have good performance of cw room temperature, linear light-current output over 30 mW per facet and maintain stable fundamental transverse and longitudinal mode of 2–4 times current threshold. The current threshold of 25 mA under cw room temperature operation has been achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02189221
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    On Rosen's gradient projection methods (1990)
    Springer
    Annals of operations research 24 (1990), S. 9-28 
    Details
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract This paper is a survey of Rosen's projection methods in nonlinear programming. Through the discussion of previous works, we propose some interesting questions for further research, and also present some new results about the questions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02216813
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    A kinematic shakedown theorem considering external loading and temperature variation (1990)
    Springer
    Acta mechanica solida Sinica 3 (1990), S. 143-153 
    Details
    ISSN: 0894-9166
    Keywords: cyclic plasticity ; kinematic shakedown
    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 kinematic shakedown theorem including the external loading and temperature variation is derived based on the concept of an assumed yield surface. An example is given to show the efficiency of the theorem obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02207573
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    On heuristics for minimum length rectilinear partitions (1990)
    Springer
    Algorithmica 5 (1990), S. 111-128 
    Details
    ISSN: 1432-0541
    Keywords: Rectilinear figure ; Rectilinear partition ; Monotonic histogram ; Dynamic programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The problem of partitioning a rectilinear figure into rectangles with minimum length is NP-hard and has bounded heuristics. In this paper we study a related problem,Elimination Problem (EP), in which a rectilinear figure is partitioned into a set of rectilinear figures containing no concave vertices of a fixed direction with minimum length. We show that a heuristic for EP within a factor of 4 from optimal can be computed in timeO(n 2), wheren is the number of vertices of the input figure, and a variant of this heuristic, within a factor of 6 from optimal, can be computed in timeO(n logn). As an application, we give a bounded heuristic for the problem of partitioning a rectilinear figure into histograms of a fixed direction with minimum length. An auxiliary result is that an optimal rectangular partition of a monotonic histogram can be computed in timeO(n 2), using a known speed-up technique in dynamic programming.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01840380
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...