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  • Springer  (257)
  • Cambridge University Press  (5)
  • 1990-1994  (262)
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  • 1
    Electronic Resource
    Electronic Resource
    Positive temperature coefficient of resistance effect in hot-pressed cristobalite-silicon carbide composites (1994)
    Springer
    Journal of materials science 29 (1994), S. 1097-1100 
    Details
    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 Conductive silicon carbide particles were incorporated into an insulating cristobalite ceramic matrix to produce composite materials with a sizeable positive temperature coefficient (PTC) effect. A large drop in resistivity with silicon carbide content at room temperature, or percolation behaviour, was observed. The PTC effect of the composites, which resulted from the thermal expansion of the cristobalite ceramic matrix, was a maximum with five orders of magnitude for the specimen with 25 vol% silicon carbide. The PTC transition temperature of the composites was at 260 °C, which coincided exactly the reversible high-low phase inversion temperature of the cristobalite ceramic matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351437
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  • 2
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    Positive temperature coefficient of resistance effect in hot-pressed cristobalite-silicon carbide composites (1994)
    Springer
    Details
    Publication Date: 1994-02-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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    PAPER CURRENT
  • 3
    Electronic Resource
    Electronic Resource
    The Far Right in Current South African Politics (1991)
    Cambridge : Cambridge University Press
    The @journal of modern African studies 29 (1991), S. 627-667 
    Details
    ISSN: 0022-278X
    Source: Cambridge Journals Digital Archives
    Topics: Ethnic Sciences , History , Political Science , Economics
    Notes: Afrikaner consciousness and identification have a tradition of very clear ethnic roots. Derived from a common ancestral stock that gives biological, historical, and linguistic characteristics to their identity, Afrikaners also share a Protestant religion tradition, with a major theme of Calvinistic predestination and being in South Africa due to divine providence. While opposing parties may vie for their support, the sentiment of favouring Afrikaners and whites – in that order – is shared by all.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1017/S0022278X00005693
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  • 4
    Electronic Resource
    Electronic Resource
    Protest Marches in South Africa (1990)
    Cambridge : Cambridge University Press
    The @journal of modern African studies 28 (1990), S. 573-602 
    Details
    ISSN: 0022-278X
    Source: Cambridge Journals Digital Archives
    Topics: Ethnic Sciences , History , Political Science , Economics
    Notes: The year 1989 will in future generations be known as the annus mirabilis, not only as far as developments in Eastern Europe are concerned, but also within the context of South African politics. The September general elections for the tricameral Parliament marked a turning point in the direction of governmental policies. Nowhere has the changing mood been more clearly demonstrated than in the streets of the cities and towns. A countrywide spate of protest marches has occurred since the historic first government-approved peaceful anti-apartheid march in Cape Town on 13 September 1989, and these have become the most visible symptom of the advance to the so-called ‘new South Africa’.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1017/S0022278X00054744
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  • 5
    Electronic Resource
    Electronic Resource
    February, Vernon: The Afrikaners of South Africa : London and New York, Kegan Paul International, 1991 (1992)
    Cambridge : Cambridge University Press
    The @journal of modern African studies 30 (1992), S. 534-536 
    Details
    ISSN: 0022-278X
    Source: Cambridge Journals Digital Archives
    Topics: Ethnic Sciences , History , Political Science , Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1017/S0022278X00010995
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of plant genotype on the transformation of cultivated alfalfa (Medicago sativa) by Agrobacterium tumefaciens (1994)
    Springer
    Plant cell reports 13 (1994), S. 330-334 
    Details
    ISSN: 1432-203X
    Keywords: Medicago sativa ; Alfalfa ; Transformation ; Agrobacterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The trait for somatic embryogenesis is being introduced sexually into alfalfa (Medicago sativa) breeding populations to facilitate genetic transformation of this crop. Cocultivation experiments were conducted with an agronomically-improved embryogenic clone from one such population as well as with two other embryogenic clones, one of which was the source of the embryogenic trait in the breeding populations. Transgenic plants were produced from the agronomically-improved clone whereas none were produced from the other two clones. Among the 16 transgenic plants analyzed there was a range in both copy number and number of integration sites for the NPT-II gene; those plants regenerated after a prolonged selection phase in vitro generally had the highest numbers in both respects. There was no evidence of sectoral chimerism of the transgene in a subsample of transgenic plants analyzed by PCR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232631
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  • 7
    Electronic Resource
    Electronic Resource
    Ramp edges, Mach bands, and the functional significance of the simple cell assembly (1994)
    Springer
    Biological cybernetics 70 (1994), S. 449-461 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. The responses of “complex” simple cells to sharp and blurred ramp edges were studied. These responses are quite similar to those in the case of lines, which implies that phase information cannot be used to discriminate between ramp edges and lines. Furthermore, if the maximum of the modulus is used as a position estimate, a systematic bias toward the ramp side results, and this bias increases with edge blur. In contrast, a local extremum in the real part of the cell responses provides a precise position estimate, even for strongly blurred edges. Possible multiscale detection strategies are discussed in the context of a syntactical visual reconstruction. This is illustrated by an explanation of Mach bands as perceived at trapezoidal edges, including Ratliff’s Mach-band cancellation stimulus, and criteria for local probability summation in the prediction of Mach-band detection thresholds are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004220050048
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  • 8
    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
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  • 9
    Electronic Resource
    Electronic Resource
    A proof of the Gilbert-Pollak conjecture on the Steiner ratio (1992)
    Springer
    Algorithmica 7 (1992), S. 121-135 
    Details
    ISSN: 1432-0541
    Keywords: Steiner trees ; Spanning trees ; Steiner ratio ; Convexity ; Hexagonal trees
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract LetP be a set ofn points on the euclidean plane. LetL s(P) andL m (P) denote the lengths of the Steiner minimum tree and the minimum spanning tree onP, respectively. In 1968, Gilbert and Pollak conjectured that for anyP,L s (P)≥(√3/2)L m (P). We provide a proof for their conjecture in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01758755
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  • 10
    Electronic Resource
    Electronic Resource
    On Steiner minimal trees withL p distance (1992)
    Springer
    Algorithmica 7 (1992), S. 179-191 
    Details
    ISSN: 1432-0541
    Keywords: Steiner trees ; Spanning trees ; Steiner ratio ; L p distance ; Bounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract LetL p be the plane with the distanced p (A 1 ,A 2 ) = (¦x 1 −x 2¦ p + ¦y1 −y 2¦p)/1p wherex i andy i are the cartesian coordinates of the pointA i . LetP be a finite set of points inL p . We consider Steiner minimal trees onP. It is proved that, for 1 〈p 〈 ∞, each Steiner point is of degree exactly three. Define the Steiner ratio ϱ p to be inf{L s (P)/L m (P)¦P⊂L p } whereL s (P) andL m (P) are lengths of the Steiner minimal tree and the minimal spanning tree onP, respectively. Hwang showed ϱ1 = 2/3. Chung and Graham proved ϱ2 〉 0.842. We prove in this paper that ϱ{∞} = 2/3 and √(√2/2)ϱ1ϱ2 ≤ ϱp ≤ √3/2 for anyp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01758757
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