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1.
2.
Birkett Huber Jörg Rambau Francisco Santos 《Journal of the European Mathematical Society》2000,2(2):179-198
In 1994, Sturmfels gave a polyhedral version of the Cayley Trick of elimination theory: he established an order-preserving
bijection between the posets of coherent mixed subdivisions of a Minkowski sum ?1+...+?
r
of point configurations and of coherent polyhedral subdivisions of the associated Cayley embedding ?(?1,...,?
r
). In this paper we extend this correspondence in a natural way to cover also non-coherent subdivisions. As an application, we show that the Cayley Trick combined with results of Santos on subdivisions of Lawrence
polytopes provides a new independent proof of the Bohne-Dress theorem on zonotopal tilings. This application uses a combinatorial
characterization of lifting subdivisions, also originally proved by Santos.
Received February 18, 1999 / final version received January 25, 2000?Published online May 22, 2000 相似文献
3.
Dipl.-Math. W. Wolf 《Mathematical Methods of Operations Research》1968,12(1):50-54
Zusammenfassung Mit Hilfe des Iterationsverfahrens vonHoward wird das optimale Anschaffungs-und Betriebsalter für ein deutsches PKW-Fabrikat bestimmt. Diese Zeiten liegen unterhalb der entsprechenden Werte, dieHoward auf Grund amerikanischer Daten erhalten hat.
Vorgel. v.: H.P.Künzi. 相似文献
Summary By aid of theHoward-Algorithm the optimal purchase- and operating age for a German automobile is determined. These time-spans are lying below the corresponding values which were received byHoward on account of American data.
Vorgel. v.: H.P.Künzi. 相似文献
4.
Dr. Werner Hildenbrand 《Mathematical Methods of Operations Research》1966,10(2):65-80
Zusammenfassung Das Ziel der vorliegenden Arbeit ist es, die Menge der effizienten Aktivitäten einer konvexen Technologie zu untersuchen. Es wird gezeigt, daß der Begriff der Facette aus der linearen Aktivitätsanalyse auch im Fall einer beliebigen konvexen Technologie definiert werden kann, und es werden für diesen allgemeinen Fall analoge Sätze über Facetten bewiesen. Die Beschreibung der Facetten einer Technologie durch geeignete Preis-(oder Bewertungs-)systeme kann in voller Allgemeinheit gegeben werden.
Der Autor hat über mathematische Grundlagen der linearen Aktivitätsanalyse, wie sie inKoopmans [3], chap. III entwickelt wurde, in einem von Prof.W. Wittmann geleiteten Kolloquium an der Universität Heidelberg im S. S. 1964 und W. S. 1964/65 vorgetragen.
Vorgel. v.:W. Wittmann. 相似文献
Summary The purpose of this paper is to study the set of efficient activities of a convex technology. It is shown that the concept of a facet, as it is used in linear activity analysis, can also be defined in the case of an arbitrary convex technology; for this general case analogous theorems on facets are proved. A characterization of the facets of a technology by suitable price (or valuation) systems can be given in full generality.
Der Autor hat über mathematische Grundlagen der linearen Aktivitätsanalyse, wie sie inKoopmans [3], chap. III entwickelt wurde, in einem von Prof.W. Wittmann geleiteten Kolloquium an der Universität Heidelberg im S. S. 1964 und W. S. 1964/65 vorgetragen.
Vorgel. v.:W. Wittmann. 相似文献
5.
Peter Maaß Sergei V. Pereverzev Ronny Ramlau Sergei G. Solodky 《Numerische Mathematik》2001,87(3):485-502
Summary. The aim of this paper is to describe an efficient adaptive strategy for discretizing ill-posed linear operator equations
of the first kind: we consider Tikhonov-Phillips regularization
with a finite dimensional approximation instead of A. We propose a sparse matrix structure which still leads to optimal convergences rates but requires substantially less scalar
products for computing compared with standard methods.
Received September 16, 1998 / Revised version received August 4, 1999 / Published online August 2, 2000 相似文献
6.
In this paper we give a characterization of the height of K3 surfaces in characteristic p>0. This enables us to calculate the cycle classes in families of K3 surfaces of the loci where the height is at least h. The formulas for such loci can be seen as generalizations of the famous formula of Deuring for the number of supersingular
elliptic curves in characteristic p. In order to describe the tangent spaces to these loci we study the first cohomology of higher closed forms.
Received October 14, 1999 / final version received February 22, 2000?Published online May 22, 2000 相似文献
7.
The radical R(T) of a planar ternary ring (PTR) T, which plays an important role in the theory of halforderings and orderings of PTRs, allows also to give an algebraic characterization ofJunkers' multiple-valued halforderings of projective planes. As an application we obtain some information on the group of projectivities in projective planes.
Herrn Professor G. Tallini zum 60. Geburtstag gewidmet 相似文献
Herrn Professor G. Tallini zum 60. Geburtstag gewidmet 相似文献
8.
Rüdiger Schmidt 《Monatshefte für Mathematik》1979,88(3):253-263
Starting from problem 4 ofK. Wagner [2],H. Fleischner andP. D. Vestergaard [1] introduce the notion of a value-true walk in a finite, connected graph, the edges of which are valuated with nonnegative integers. Their main theorem states that the existence of such a walk is equivalent to the existence of an orientation of the edges with the following property: For every vertex the sum of the valuations of the incoming edges equals the sum of the valuations of the outgoing edges. Let us call such an orientation a cyclic one. In the present paper we study finite, valuated graphs that admit a cyclic orientation. First, we give two necessary conditions for a valuated graphG to admit a cyclic orientation concerning the stars and the bonds ofG, respectively. (The starS (v) of a vertexv is the set of all edges ofG incident withv.) Then, as the main part of the paper we give a characterization of those graphs for which the star- and the bond-condition is sufficient, respectively (for any valuation of the graph). These characterizations are in terms of constructability from trees andK
3, respectively, as well as in terms of forbidden subgraphs.
Mit 2 Abbildungen 相似文献
Mit 2 Abbildungen 相似文献
9.
In the context of stochastic resource-constrained project scheduling we introduce a novel class of scheduling policies, the
linear preselective policies. They combine the benefits of preselective policies and priority policies; two classes that are well known from both deterministic and stochastic scheduling. We study several properties of this new
class of policies which indicate its usefulness for computational purposes. Based on a new representation of preselective
policies as and/or
precedence constraints we derive efficient algorithms for computing earliest job start times and state a necessary and sufficient dominance criterion
for preselective policies.
A computational experiment based on 480 instances empirically validates the theoretical findings. 相似文献
10.
Marcos Salvai 《Monatshefte für Mathematik》2006,147(2):173-177
The Fréchet manifold
of all embeddings (up to orientation preserving reparametrizations) of the circle in S
3 has a canonical weak Riemannian metric. We use the characterization obtained by H. Gluck and F. Warner of the oriented great
circle fibrations of S
3 to prove that among all such fibrations π:S
3→B, the manifold B consisting of the oriented fibers is totally geodesic in
, or has minimum volume or diameter with the induced metric, exactly when π is a Hopf fibration.
Partially supported by foncyt, Antorchas, ciem (conicet) and secyt (unc). 相似文献
11.
C [0,1], α > 0 in (0,1) and α(1), we consider the second order differential operator on C[0,1] defined by Au: = αu″ + βu′, where D(A) may include Wentzell boundary conditions. Under integrability conditions involving √α and β/√α, we prove the
analyticity of the semigroup generated by (A,D(A)) on Co[0,1], Cπ[0,1] and on C[0,1], where Co[0,1]: {u∈ C[0,1]|u (1)} and Cπ[0,1]: = {u∈ C[0,1]| u (0) = u (1)}. We also prove different characterizations of D(A) related to some results in [1], where β≡ 0, exhibiting peculiarities
of Wentzell boundary conditions. Applications can be derived for the case αx = x
k (1 - x )kγ(x )(k≥j/2, x∈ [0,1], γ∈ C{0,1}). 相似文献
12.
Hubert Kiechle 《Journal of Geometry》1991,41(1-2):79-93
Lüneburg's generalization of a construction ofAndre is used to describe all countable, locally finite André-systems and the locally finite André-nearfields. The last section gives a characterization of those countable, locally finite André-planes which have locally finite groups of affine projectivites.
Herrn Professor Dr. Walter Benz zum 60. Geburtstag 相似文献
Herrn Professor Dr. Walter Benz zum 60. Geburtstag 相似文献
13.
14.
A graph is a strict-quasi parity (SQP) graph if every induced subgraph that is not a clique contains a pair of vertices with
no odd chordless path between them (an “even pair”). We present an O(n
3) algorithm for recognizing planar strict quasi-parity graphs, based on Wen-Lian Hsu's decomposition of planar (perfect) graphs
and on the (non-algorithmic) characterization of planar minimal non-SQP graphs given in [9].
Received: September 21, 1998 Final version received: May 9, 2000 相似文献
15.
16.
Alejandro Balbás José Garrido Silvia Mayoral 《Methodology and Computing in Applied Probability》2009,11(3):385-399
The current literature does not reach a consensus on which risk measures should be used in practice. Our objective is to give
at least a partial solution to this problem. We study properties that a risk measure must satisfy to avoid inadequate portfolio
selections. The properties that we propose for risk measures can help avoid the problems observed with popular measures, like
Value at Risk (VaR
α
) or Conditional VaR
α
(CVaR
α
). This leads to the definition of two new families: complete and adapted risk measures. Our focus is on risk measures generated by distortion functions. Two new properties are put forward for these:
completeness, ensuring that the distortion risk measure uses all the information of the loss distribution, and adaptability,
forcing the measure to use this information adequately.
This research was partially funded by
1,3
Welzia Management, SGIIC SA, RD Sistemas SA, Comunidad Autónoma de Madrid Grant s-0505/tic/000230, and MEyC Grant BEC2000-1388-C04-03 and by
2
the Natural Sciences and Engineering Research Council of Canada (NSERC) Grant 36860-06. 相似文献
17.
Dr. rer. nat. B. Korte Dr. rer. nat. W. Oberhofer 《Mathematical Methods of Operations Research》1968,12(1):217-231
Zusammenfassung Bei der Ordnung von Input-Output-Matrizen treten Kriterien auf, die wesentlich komplexer sind als die Ordnungsbedingungen bei klassischen Reihenfolgeproblemen (z. B.Traveling-Salesman-Problem). Ausgehend von den Arbeiten vonHelmstädter werden im folgenden die mathematische Formulierung eines solchen Reihenfolgeproblems sowie zwei Algorithmen zu dessen Lösung angegeben. Ein Verfahren ist ein lexikographischer Suchalgorithmus, das andere eine Modifikation des bekanntenJacobi-Verfahrens zur Berechnung von EigenwertenHermitescher Matrizen.
Ein Teil dieser Arbeit wurde als Referat auf der Jahrestagung der Deutschen Gesellschaft für Unternehmensforschung (DGU) am 23. September 1968 in Dortmund vorgetragen.
Vorgel. v.:W. Krelle. 相似文献
Summary On the ordering of input-output matrices we use some criteria which are more complex than the order conditions of classical sequencing problems (e. g.Traveling-Salesman-Problem). Basing on the papers ofHelmstädter we will give a mathematical formulation of this sequencing problem and two algorithms solving them. One procedure is a lexicographic searching algorithm, the other one a modification of the well knownJacobi-method which calculates the eigenvalues ofHermiteian matrices.
Ein Teil dieser Arbeit wurde als Referat auf der Jahrestagung der Deutschen Gesellschaft für Unternehmensforschung (DGU) am 23. September 1968 in Dortmund vorgetragen.
Vorgel. v.:W. Krelle. 相似文献
18.
In a recent paper, the authors have proved results characterizing convexity-preserving maps defined on a subset of a not-necessarily
finite dimensional real vector space as projective maps. The purpose of this note is three-fold. First, we state a theorem
characterizing continuous, injective, convexity-preserving maps from a relatively open, connected subset of an affine subspace
of ℝ
m
into ℝ
n
as projective maps. This result follows from the more general results stated and proved in a coordinate-free manner in the
above paper, and is intended to be more accessible to researchers interested in optimization algorithms. Second, based on
that characterization theorem, we offer a characterization theorem for collinear scalings first introduced by Davidon in 1977
for deriving certain algorithms for nonlinear optimization, and a characterization theorem for projective transformations
used by Karmarkar in 1984 in his linear programming algorithm. These latter two theorems indicate that Davidon’s collinear
scalings and Karmarkar’s projective transformations are the only continuous, injective, convexity-preserving maps possessing
certain features that Davidon and Karmarkar respectively desired in the derivation of their algorithms. The proofs of these
latter two theorems utilize our characterization of continuous, injective, convexity-preserving maps in a way that has implications
to the choice of scalings and transformations in the derivation of optimization algorithms in general. The third purpose of
this note is to point this out.
Received: January 2000 / Accepted: November 2000?Published online January 17, 2001 相似文献
19.
Olaf Steinbach 《Numerische Mathematik》2001,88(2):367-379
Summary. In this paper we prove the stability of the projection onto the finite element trial space of piecewise polynomial, in particular, piecewise linear basis functions in
for . We formulate explicit and computable local mesh conditions to be satisfied which depend on the Sobolev index s. In conclusion we prove a stability condition needed in the numerical analysis of mixed and hybrid boundary element methods
as well as in the construction of efficient preconditioners in adaptive boundary and finite element methods.
Received October 14, 1999 / Revised version received March 24, 2000 / Published online October 16, 2000 相似文献
20.
Liming Cai Jianer Chen Rodney G. Downey Michael R. Fellows 《Archive for Mathematical Logic》1997,36(4-5):321-337
A completeness theory for parameterized computational complexity has been studied in a series of recent papers, and has been
shown to have many applications in diverse problem domains including familiar graph-theoretic problems, VLSI layout, games,
computational biology, cryptography, and computational learning [ADF,BDHW,BFH, DEF,DF1-7,FHW,FK]. We here study the parameterized
complexity of two kinds of problems: (1) problems concerning parameterized computations of Turing machines, such as determining
whether a nondeterministic machine can reach an accept state in steps (the Short TM Computation Problem), and (2) problems concerning derivations and factorizations, such as determining whether a word can be derived in a grammar in steps, or whether a permutation has a factorization of length over a given set of generators. We show hardness and completeness for these problems for various levels of the hierarchy. In particular, we show that Short TM Computation is complete for . This gives a new and useful characterization of the most important of the apparently intractable parameterized complexity
classes.
Received August 1, 1994 相似文献