Universität Rostock, Institut für Mathematik, 1993-2014
https://doi.org/10.18453/rosdok_id00005816
Schriftenreihe
Freier 
Zugang
Thomas Kalinowski
University of Rostock, Institute of Mathematics, 2003
https://doi.org/10.18453/rosdok_id00005912
Intensity maps are nonnegative matrices describing the intensity modulation of beams in radiotherapy. An important step in the planning process is to determine a segmentation, that is a representation of an intensity map as a positive combination of special matrices corresponding to fixed positions…
Workingpaper
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René Bartsch, Harry Poppe
University of Rostock, Institute of Mathematics, 2003
https://doi.org/10.18453/rosdok_id00005911
Based on some set-theoretical observations, compactness results are given for general hit-and-miss hyperspaces. Compactness here is sometimes viewed splitting into "k-Lindelöfness" and "kcompactness" for cardinals k. To focus only hit-and-miss structures, could look quite old-fashioned, but some…
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René Bartsch
University of Rostock, Institute of Mathematics, 2003
https://doi.org/10.18453/rosdok_id00005910
Besides some remarks on hit-and-miss hyperspaces and (relative) compactness of unions of (relative) compact sets, and using these together with a natural map from a function space between topological spaces into a function space between their Vietoris hyperspaces, we derive Ascoli-like theorems for…
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Konrad Engel
University of Rostock, Institute of Mathematics, 2003
https://doi.org/10.18453/rosdok_id00005909
We present a new efficient leaf sequencing algorithm for the generation of intensity maps by a nonnegative combination of segments. Intensity maps describe the intensity modulation of beams in radiotherapy. We only study the static case (stop and shoot) an optimize the total number of monitor units…
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Konrad Engel, Eckhard Tabbert
University of Rostock, Institute of Mathematics, 2003
https://doi.org/10.18453/rosdok_id00005908
We present a new fast radiotherapy planning algorithm which determines approximatively optimal gantry and table angles, kinds of wedges, leaf positions and intensities simultaneously in a global way. Other parameters are optimized only independently of each other. The algorithm uses an elaborate…
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Sven Hartmann, Uwe Leck
University of Rostock, Institute of Mathematics, 2003
https://doi.org/10.18453/rosdok_id00005907
We discuss the existence of matrix representations for generalized and minimum participation constraints which are frequently used in database design and conceptual modelling. Matrix representations, also known as Armstrong relations, have been studied in literature e.g. for functional dependencies…
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Thomas Kalinowski
University of Rostock, Institute of Mathematics, 2003
https://doi.org/10.18453/rosdok_id00005906
Multileaf collimators are widely used in radiotherapy to realize intensity modulated fields as superpositions of homogeneous fields, so called segments. One important step in the planning process is the decomposition of the modulated field into a small number of segments such that the total number…
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Hans Joachim Grüter, Helga Jepp, Hans-Peter Mangel, Christine Sikora, Hans-Dieter Sill
University of Rostock, Institut für Mathematik, 2003
https://doi.org/10.18453/rosdok_id00005904
Workingpaper
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Thomas Kalinowski
University of Rostock, Institute of Mathematics, 2004
https://doi.org/10.18453/rosdok_id00005903
Intensity maps are nonnegative matrices describing the intensity modulation of beams in radiotherapy. In order to use a multileaf collimator in the static mode for the realization of the intensity modulation one has to determine a segmentation, i.e. a representation of an intensity map as a positive…
Workingpaper
Freier Zugang
Thomas Kalinowski
University of Rostock, Institute of Mathematics, 2004
https://doi.org/10.18453/rosdok_id00005902
Multileaf collimators (MLCs) are the prevailing tool for the realization of radiation fields in intensity modulated radiation therapy (IMRT). One step in the treatment planning is to determine a set of leaf positions realizing a certain intensity modulated radiation field. In this paper we suggest…
Workingpaper
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Thomas Kalinowski
University of Rostock, Institute of Mathematics, 2004
https://doi.org/10.18453/rosdok_id00005901
We present an algorithm for optimal step-and-shoot intensity modulated radiation therapy without interleaf collision and with elimination of tongue-and-groove effects. Adapting the concepts of [6] we characterize the minimal number of monitor units as the maximal weight of a path in a properly…
Workingpaper
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Dalibor Froncek, Uwe Leck
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005900
An orthogonal double cover (ODC) of the complete graph Kn by some graph G is a collection of n spanning subgraphs of Kn, all isomorphic to G, such that any two of the subgraphs share exactly one edge and every Edge of Kn is contained in exactly two of the subgraphs. A necessary condition for such an…
Workingpaper
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Gennian Ge, Martin Grüttmüller, Sven Hartmann, Rolf S. Rees
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005899
A mandatory representation design MRD(K;v) is a pairwise balanced design on v Points with block sizes from the set K in which for each k ∈ K there is at least one block in the design of size k. In this paper, we Show that the necessery criteria for an MRD(K;v) to exist are asymptotically sufficient…
Workingpaper
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Martin Grüttmüller, Thomas Kalinowski, Uwe Leck, Sven Hartmann, Ian T. Roberts
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005898
We study maximal families A of subsets of [n] = {1; 2; : : : ; n} such that A contains only pairs and triples and A /⊆ B for all {A,B} ⊆ A, i.e. A is an antichain. For any n, all such families A of minimum size are determined. This is equivalent to finding all graphs G = (V,E) with |V| = n and with…
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Martin Grüttmüller, Rolf S. Rees, Nabil Shalaby
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005896
In this paper we investigate exhaustively the cyclically indecomposable triple systems TSλ(v) for λ = 2, v ≤ 33 and λ = 3, v ≤ 21 and we identify the decomposable ones. We also construct, by using Skolem-type and Rosa-type sequences, cyclically indecomposable two-fold triple systems TS2(v) for all…
Workingpaper
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Konrad Engel, Thomas Kalinowski, Roger Labahn, Frank Sill, Dirk Timmermann
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005895
In this paper, we consider an optimization problem on directed acyclic graphs which is motivated by a standard task in low power VLSI design. With each vertex v of a directed acyclic graph, we associate two delay values d0(v) ≤ d1(v) and two leakage values c0(v) ≥ c1(v). The objective is to choose…
Workingpaper
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M. Greig, Martin Grüttmüller, Sven Hartmann
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005894
In this paper, we investigate the PBD-closure of sets K with {7, 13} ⊆ K ⊆ {7, 13, 19, 25, 31, 37, 43}. In particular, we show that v ≡ 1 mod 6, v ≥ 98689 implies v ∈ B({7,13}). As a preliminary result, many new 13-GDDs of type 13^q and resolvable BIBD with block size 6 or 12 are also constructed.…
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Ian T. Roberts, Sue D’Arcy, Judith Egan, Martin Grüttmüller
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005893
The cardinality of the minimal pairwise balanced designs on v elements with largest block size k is denoted by g(k)(v). It is known that 31 <= g(4)(18) <= 33. In this paper we show that g(4)(18) =/ 31.
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Reinhard Knörr
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005892
A k-transitive group of degree n > k is gen-erated by all the the elements fixing precisely i points if i <= k - 3. The cases i = k - 2, i = k - 1 and i = k are also considered.
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Reinhard Knörr
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005891
A class of natural linear characters for the centralizers of elements in the symmetric group is introduced. The character values of the corresponding monomial characters are calculated. They have a surprising combinatorial interpretation.
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Reinhard Knörr
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005890
We present a version of the orthogonality relations for group characters which appears to be new - at least in this generality. The proof given uses only Maschke's theorem and Schur's lemma. Among other consequences, Burnside's result on the existence of zeros for non-linear irreducible characters…
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Reinhard Knörr
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005888
A 'partial' inner product with respect to a given subset of Irr (G) is introduced and its basic properties are studied. As applications, a weak second orthogonality is shown in a Clifford setting and a version of the Burnside-Brauer theorem is given.
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Reinhard Knörr
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005887
Tensor inducing a Frobenius induced character leads to a sum of characters where each summand is given by first Tensor induction, then Frobenius induction. This qualitative statement is made precise. As an example, tensor induction of monomial characters is considered.
Workingpaper
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Martin Grüttmüller, Ian T. Roberts, Sue D’Arcy, Judith Egan
University of Rostock, Institute of Mathematics, 2005
https://doi.org/10.18453/rosdok_id00005834
The minimum number of blocks having maximum size precisely four that are required to cover, exactly λ times, all pairs of elements from a set of cardinality v is denoted by gλ(4)(v) are known except for λ = 1 andv = 17 or 18. It is known that 30<= g(4)(17) <= 31 and 32 <= g(4)(18) <= 33. In this…
Workingpaper
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Ju Hyon Hui
University of Rostock, Institute of Mathematics, 2006
https://doi.org/10.18453/rosdok_id00005833
In this paper we study criteria of chaos for discrete dynamical Systems governed by noninvertible maps and apply them to the anti-control of chaos. We get some criteria of chaos for discrete dynamical systems governed by noninvertible maps using the subshift in the space of one-side symbolic…
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Hans-Dietrich Gronau, Markus Schmidmeier
University of Rostock, Institute of Mathematics, 2007
https://doi.org/10.18453/rosdok_id00005832
Let K be the complete oriented graph on the finite set of vertices A. A family G = {Ga : a ∈ A} of spanning subgraphs of K is an orthogonal cover provided every arrow of K occurs in exactly one Ga and for every two elements a, b ∈ A, the graphs Ga and Gopb have exactly one arrow in common. Gronau,…
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Christian Reiher
University of Rostock, Institute of Mathematics, 2008
https://doi.org/10.18453/rosdok_id00005831
In this brief note, we give a positive answer to a question that has recently been asked by L. Addario-Berry et al. in this journal, namely: Given a graph G = (V,E) and for every vertex v ∈ V a list Dv ⋸ {0,1,...,d(v)} satisfying |Dv| >= D(v)/2 + 1, does there necessarily exist a spanning subgraph H…
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Friedrich Liese, Bing Liu
University of Rostock, Institute of Mathematics, 2009
https://doi.org/10.18453/rosdok_id00005830
Goodness of fi t tests based on the empirical distribution function fail to be asymptotically distribution free if parameters are estimated. Asymptotically, the empirical process with estimated parameters is a centered Gaussian process with a covariance that di¤ers from the covariance function of…
Workingpaper
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Harry Poppe, René Bartsch
University of Rostock, Institute of Mathematics, 2009
https://doi.org/10.18453/rosdok_id00005829
Workingpaper
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Harry Poppe, René Bartsch
University of Rostock, Institute of Mathematics, 2009
https://doi.org/10.18453/rosdok_id00005828
Workingpaper
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Christian Reiher
University of Rostock, Institute of Mathematics, 2010
https://doi.org/10.18453/rosdok_id00005826
In the present thesis, we prove a conjecture belonging to a subbranch of additive combinatorics that is called combinatorial zero-sum theory. Denoting by p an arbitrary prime number, it has been known for about forty years that every sequence (P1, P2,..., P2p-1) consisting of 2p-1points from the…
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Wolfgang Engel
Universität Rostock, Institut für Mathematik, 2010
https://doi.org/10.18453/rosdok_id00005825
Workingpaper
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Ian T. Roberts, Sue D'Arcy, Hans-Dietrich Gronau
University of Rostock, Institute of Mathematics, 2011
https://doi.org/10.18453/rosdok_id00005824
R(n, k) denotes the minimum possible size of a completely separating system C on [n] with |A| = k for each A ϵ C. Values of R(n, k) are determined for (k-1/2)=
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Tobias Strauß, Welf Wustlich, Roger Labahn
University of Rostock, Institute of Mathematics, 2012
https://doi.org/10.18453/rosdok_id00005823
This article develops approaches to generate dynamical reservoirs of ESNs with desired properties reducing the amount of randomness. It is possible to create weight matrices with a predefined singular value spectrum. The procedure guarantees stability (Echo State property) and minimizes the Impact…
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Günter Mayer
University of Rostock, Institute of Mathematics, 2012
https://doi.org/10.18453/rosdok_id00005822
We give a survey on the symmetric solution set of linear systems of equations with perturbed input data starting with a description of its form and presenting several algorithms whose resulting interval vector encloses it. In particular, we derive the describing inequalities in a new way and…
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Tobias Strauß, Roger Labahn, Gundram Leifert, Welf Wustlich
University of Rostock, Institute of Mathematics, 2012
https://doi.org/10.18453/rosdok_id00005820
We review two decoding methods for recurrent neural networks – based on the well known weighted Levenshtein distance and the connectionist temporal classification (CTC) – and we introduce a new method – the dynamic Levenstein distance (DynWL). We compare these three methods analytically in terms of…
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Gundram Leifert, Tobias Strauß, Roger Labahn, Welf Wustlich
University of Rostock, Institute of Mathematics, 2012
https://doi.org/10.18453/rosdok_id00005819
A recent approach for offline handwriting recognition is to use multidimensional recurrent neural networks (MDRNN) with connectionist temporal classification which has shown to yield very good results on several datasets. MDRNNs contain special units – multidimensional Long Short-Term Memory…
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Gundram Leifert, Tobias Grüning, Tobias Strauß, Roger Labahn
University of Rostock, Institute of Mathematics, 2014
https://doi.org/10.18453/rosdok_id00005818
We describe CITlab’s recognition system for the ANWRESH-2014 Competition attached to the 14. International Conference on Frontiers in Handwriting Recognition, ICFHR 2014. The task comprises word recognition from segmented historical documents. The core components of our system are based on…
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Tobias Strauß, Tobias Grüning, Gundram Leifert, Roger Labahn
University of Rostock, Institute of Mathematics, 2014
https://doi.org/10.18453/rosdok_id00005817
We describe CITlab’s recognition system for the HTRtS competition attached to the 14. International Conference on Frontiers in Handwriting Recognition, ICFHR 2014. The task comprises the recognition of historical handwritten documents. The core algorithms of our system are based on multidimensional…
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