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  • Springer  (66)
  • 2000-2004  (66)
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  • 1
    Electronic Resource
    Electronic Resource
    Binary Searching with Nonuniform Costs and Its Application to Text Retrieval (2000)
    Springer
    Algorithmica 27 (2000), S. 145-169 
    Details
    ISSN: 1432-0541
    Keywords: Key words. Optimized binary search, Nonuniform costs, Text retrieval, Secondary memory.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. We study the problem of minimizing the expected cost of binary searching for data where the access cost is not fixed and depends on the last accessed element, such as data stored in magnetic or optical disk. We present an optimal algorithm for this problem that finds the optimal search strategy in O(n 3 ) time, which is the same time complexity of the simpler classical problem of fixed costs. Next, we present two practical linear expected time algorithms, under the assumption that the access cost of an element is independent of its physical position. Both practical algorithms are online, that is, they find the next element to access as the search proceeds. The first one is an approximate algorithm which minimizes the access cost disregarding the goodness of the problem partitioning. The second one is a heuristic algorithm, whose quality depends on its ability to estimate the final search cost, and therefore it can be tuned by recording statistics of previous runs. We present an application for our algorithms related to text retrieval. When a text collection is large it demands specialized indexing techniques for efficient access. One important type of index is the suffix array, where data access is provided through an indirect binary search on the text stored in magnetic disk or optical disk. Under this cost model we prove that the optimal algorithm cannot perform better than Ω(1/ log n) times the standard binary search. We also prove that the approximate strategy cannot, on average, perform worse than 39% over the optimal one. We confirm the analytical results with simulations, showing improvements between 34% (optimal) and 60% (online) over standard binary search for both magnetic and optical disks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004530010010
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  • 2
    Electronic Resource
    Electronic Resource
    Optimal design of beam reinforced composite structures under elasto-plastic loading conditions (2000)
    Springer
    Structural and multidisciplinary optimization 19 (2000), S. 50-63 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A design optimization process for elasto-plastic material behaviour of laminate composite structures, made of thermoplastic resins, is described. The approach considers two optimization levels. At the first level the geometric linear behaviour under elasto-plastic loading conditions is adopted in order to obtain the optimal solution as a function of ply angles of the plate or shallow shells. At this stage the objective is to recover the plastic zones using only the anisotropic material properties. At the second level the ply thickness of the plates or shallow shells and the height and width of the reinforcement beams are changed to structure weight minimization, under the constraints of maximum allowed displacement or maximum strain-stress level related with amount of plastic zone, without structural plastic collapse or geometric instability in plastic loading conditions. It is expected that contradictory objectives, as minimum elasto-plastic energy and structural weight, are satisfied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001580050085
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  • 3
    Electronic Resource
    Electronic Resource
    Sharing Resources at Nonuniform Access Rates (2000)
    Springer
    Theory of computing systems 34 (2000), S. 13-26 
    Details
    ISSN: 1433-0490
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. We introduce DPPr (for ``Dining Philosophers Problem with rates'') as a generalization of the heavy-load case of the Dining Philosophers Problem (DPP). In DPPr, processes are required to be scheduled to access shared resources with prespecified relative frequencies. DPPr is an abstraction of resource-sharing problems to which the synchronization of some distributed algorithms for neural-network models and the generation of timing signals in asynchronous digital circuits are related. Two fully distributed, synchronous solutions are given for DPPr in this paper. The first solution employs a reduction to heavy-load DPP and after that a distributed scheduling mechanism that has been used to solve this problem with optimal concurrency. The second solution tackles the DPPr instance directly by operating on a multigraph based on that instance. We conclude by indicating how the two synchronous solutions carry over to the asynchronous case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002240010008
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  • 4
    Electronic Resource
    Electronic Resource
    An analytical approach to neuronal connectivity (2004)
    Springer
    The European physical journal 42 (2004), S. 573-580 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. This paper describes how to analytically characterize the connectivity of neuromorphic networks taking into account the morphology of their elements. By assuming that all neurons have the same shape and are regularly distributed along a two-dimensional orthogonal lattice with parameter Δ, we obtain the exact number of connections and cycles of any length by applying convolutions and the respective spectral density derived from the adjacency matrix. It is shown that neuronal shape plays an important role in defining the spatial distribution of synapses in neuronal networks. In addition, we observe that neuromorphic networks typically present an interesting property where the pattern of connections is progressively shifted along the spatial domain for increasing connection lengths. This arises from the fact that the axon reference point usually does not coincide with the cell center of mass of neurons. Morphological measurements for characterization of the spatial distribution of connections, including the adjacency matrix spectral density and the lacunarity of the connections, are suggested and illustrated. We also show that Hopfield networks with connectivity defined by different neuronal morphologies, which are quantified by the analytical approach proposed herein, lead to distinct performances for associative recall, as measured by the overlap index. The potential of our approach is illustrated for digital images of real neuronal cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00017-7
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  • 5
    Electronic Resource
    Electronic Resource
    Characterizing neuromorphologic alterations with additive shape functionals (2003)
    Springer
    The European physical journal 37 (2003), S. 109-115 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The complexity of a neuronal cell shape is known to be related to its function. Specifically, among other indicators, a decreased complexity in the dendritic trees of cortical pyramidal neurons has been associated with mental retardation. In this paper we develop a procedure to address the characterization of morphological changes induced in cultured neurons by over-expressing a gene involved in mental retardation. Measures associated with the multiscale connectivity, an additive image functional, are found to give a reasonable separation criterion between two categories of cells. One category consists of a control group and two transfected groups of neurons, and the other, a class of cat ganglionary cells. The reported framework also identified a trend towards lower complexity in one of the transfected groups. Such results establish the suggested measures as an effective descriptors of cell shape.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2004-00035-y
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  • 6
    Electronic Resource
    Electronic Resource
    Replication timing of homologous α-satellite DNA in Roberts syndrome (2000)
    Springer
    Chromosome research 8 (2000), S. 645-650 
    Details
    ISSN: 1573-6849
    Keywords: homologous centromere replication ; Roberts syndrome ; sister chromatids cohesion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Roberts syndrome (RS) is associated with a characteristic constitutive heterochromatin anomaly, namely, at metaphase the centromeres and heterochromatic segments appear split. In addition to this cytogenetic phenomenon, known as the RS effect, several other cytological features, especially affecting mitotic chromosome disjunction, are also observed. Applying FISH to interphase nuclei, we investigated the replication patterns of homologous alphoid centromeric DNA of chromosomes 9, 11, 16 and 17 in three patients showing the RS effect and in four normal individuals. A tendency for homologous centromeres to replicate asynchronously was observed in RS patients. This tendency was more evident in chromosomes 9 and 16, with large heterochromatic blocks and particularly subject to RS effect. This asynchrony could reflect a more generalized alteration in repetitive DNA replication timing that, in turn, would prevent the establishment of proper cohesion between sister chromatid heterochromatin, leading to the RS effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009246327122
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  • 7
    Electronic Resource
    Electronic Resource
    Enlarged Geometries of Gauge Bundles (2000)
    Springer
    International journal of theoretical physics 39 (2000), S. 2779-2796 
    Details
    ISSN: 1572-9575
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The geometrical picture of gauge theories must be enlarged when a gauge potentialceases to behave like a connection, as it does in electroweak interactions. Whenthe gauge group has dimension four, the vector space isomorphism betweenspacetime and the gauge algebra is realized by a tetrad-like field. The objectmeasuring the deviation from a strict bundle structure has the formal behaviorof a spacetime connection, of which the deformed gauge field strength is thetorsion. A generalized derivative emerges in terms of which the two Bianchiidentities are formally recovered. Effects of gravitational type turn up. Thedynamical equations obtained correspond to a broken gauge model on acurved spacetime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026461115713
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  • 8
    Electronic Resource
    Electronic Resource
    Yang-Mills Fields as Optical Media (2000)
    Springer
    International journal of theoretical physics 39 (2000), S. 1085-1099 
    Details
    ISSN: 1572-9575
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A geometrization of the Yang-Mills field, by which an SU(2) gauge theorybecomes equivalent to a 3-space geometry—or optical system—is examined. Ina first step, ambient space remains Euclidean and current problems on flat spacecan be looked at from a new point of view. The Wu-Yang ambiguity, for example,appears related to the multiple possible torsions of distinct metric-preservingconnections. In a second step, the ambient space also becomes curved. In thegeneric case, the strictly Riemannian metric sector plays the role of an arbitraryhost space, with the gauge potential represented by a contorsion. For some fieldconfigurations, however, it is possible to obtain a purely metric representation.In those cases, if the space is symmetric homogeneous, the Christoffel connectionsare automatically solutions of the Yang-Mills equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003658625955
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  • 9
    Electronic Resource
    Electronic Resource
    Mixing Angle and Glashow Algebra (2000)
    Springer
    International journal of theoretical physics 39 (2000), S. 1985-1998 
    Details
    ISSN: 1572-9575
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Considering transformations in the basis of fundamental fields on a principalfiber bundle, without modification in the space-time sector, we construct analgebra GA, which we call Glashow algebra. The structure constants of thisalgebra depend on a mixing angle. The Lagrangian of the gauge theory ofelectroweak interactions without masses is obtained using a representation of GAwhich is the transformed of the adjoint representation of SU(2)⊗ U(1), anddoes not coincide with the adjoint representation of GA. The mixing angle isautomatically present in the theory if GA is used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003601502586
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  • 10
    Electronic Resource
    Electronic Resource
    Frequency Selective Surfaces with Anisotropic Dielectric Superstrates (2000)
    Springer
    International journal of infrared and millimeter waves 21 (2000), S. 461-475 
    Details
    ISSN: 1572-9559
    Keywords: frequency selective surfaces ; FSS ; dielectric anisotropy ; anisotropic superstrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A full wave analysis is developed for frequency selective surfaces composed of rectangular patches mounted on a dielectric anisotropic substrate and covered with a uniaxial anisotropic superstrate. The moment method is used in combination with the spectral domain immittance approach to determine the FSS structure reflection and transmission coefficients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006615316368
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