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1.
This paper considers a scheduling problem occurring in a specialized service system with parallel servers. In the system,
customers are divided into the “ordinary” and “special” categories according to their service needs. Ordinary customers can
be served by any server, while special customers can be served only by the flexible servers. We assume that the service time
for any ordinary customer is the same and all special customers have another common service time. We analyze three classes
of service policies used in practice, namely, policies with priority, policies without priority and mixed policies. The worst-case
performance ratios are obtained for all of these service policies. 相似文献
2.
M. Jonckheere 《Queueing Systems》2006,54(3):193-202
So-called Whittle networks have recently been shown to give tight approximations for the performance of non-locally balanced
networks with blocking, including practical routing policies such as joining the shortest queue. In the present paper, we
turn the attention to networks without blocking. To this end, we consider a set of “insensitive” dynamic load balancing schemes
preserving the structure of Whittle networks in the case of infinite buffers and examine their efficiency. Using Hausdorff’s
theorem, we prove that the optimal insensitive schemes are static in this case, i.e., routing decisions do not depend on the
current state of the queues. On the other hand, simulations show that the performance of static policies is generally much
worse than that of “non balanced” sensitive dynamic policies. This demonstrates that strict insensitivity and efficiency may
be incompatible objectives for networks with dynamic load balancing in case of infinite buffers.
AMS Subject Classifications 60K25 · 68M20 相似文献
3.
Various demands of different patients over both medical resource and time domains in health care systems raise requests of
strategies for balanced system capacity from an operations perspective. In this paper, a quantitative modeling technique with
both patient arrival and associated treatment process integrated are used to characterize health care system performance and
evaluate system efficiency. The patient arrival process is described as a dynamic random Poisson process and patient treatments
are characterized as consumption processes of various health care resources over time with a view of the “product line” used.
The waiting time of patients and usage of health care resources are proposed as system performance measures based on their
means, variances, and confidence intervals. A simulation considering patients with several various diseases is given to find
a mechanism of conflicting factors in decisions of balanced system capacity, and an operation scheme of “evenly balanced load
for bottlenecks” is obtained based on analysis of simulation outputs. Simul8 provides the software environment for the simulation. 相似文献
4.
The lexicographically-ordered CSP (“lexicographic CSP” or “LO-CSP” for short) combines a simple representation of preferences
with the feasibility constraints of ordinary CSPs. Preferences are defined by a total ordering across all assignments, such
that a change in assignment to a given variable is more important than any change in assignment to any less important variable.
In this paper, we show how this representation can be extended to handle conditional preferences in two ways. In the first,
for each conditional preference relation, the parents have higher priority than the children in the original lexicographic
ordering. In the second, the relation between parents and children need not correspond to the importance ordering of variables.
In this case, by obviating the “overwhelming advantage” effect with respect to the original variables and values, the representational
capacity is significantly enhanced. For problems of the first type, any of the algorithms originally devised for ordinary
LO-CSPs can also be used when some of the domain orderings are dependent on assignments to “parent” variables. For problems
of the second type, algorithms based on lexical orders can be used if the representation is augmented by variables and constraints
that link preference orders to assignments. In addition, the branch-and-bound algorithm originally devised for ordinary LO-CSPs
can be extended to handle CSPs with conditional domain orderings. 相似文献
5.
A. T. Filippov 《Theoretical and Mathematical Physics》2010,163(3):753-767
We propose new models of the “affine” theory of gravity in multidimensional space-times with symmetric connections. We use
and develop ideas of Weyl, Eddington, and Einstein, in particular, Einstein’s proposed method for obtaining the geometry using
the Hamilton principle. More specifically, the connection coefficients are determined using a “geometric” Lagrangian that
is an arbitrary function of the generalized (nonsymmetric) Ricci curvature tensor (and, possibly, other fundamental tensors)
expressed in terms of the connection coefficients regarded as independent variables. Such a theory supplements the standard
Einstein theory with dark energy (the cosmological constant, in the first approximation), a neutral massive (or tachyonic)
meson, and massive (or tachyonic) scalar fields. These fields couple only to gravity and can generate dark matter and/or inflation.
The new field masses (real or imaginary) have a geometric origin and must appear in any concrete model. The concrete choice
of the Lagrangian determines further details of the theory, for example, the nature of the fields that can describe massive
particles, tachyons, or even “phantoms.” In “natural” geometric theories, dark energy must also arise. The basic parameters
of the theory (cosmological constant, mass, possible dimensionless constants) are theoretically indeterminate, but in the
framework of modern “multiverse” ideas, this is more a virtue than a defect. We consider further extensions of the affine
models and in more detail discuss approximate effective (“physical”) Lagrangians that can be applied to the cosmology of the
early Universe. 相似文献
6.
We are interested in the maximum possible number of facets that Dirichlet stereohedra for three-dimensional crystallographic
groups can have. In two previous papers, D. Bochiş and the second author studied the problem for noncubic groups. This paper
deals with “full” cubic groups, while “quarter” cubic groups are left for a subsequent paper. Here, “full” and “quarter” refers
to the recent classification of three-dimensional crystallographic groups by Conway, Delgado-Friedrichs, Huson and Thurston.
This paper’s main result is that Dirichlet stereohedra for any of the 27 full groups cannot have more than 25 facets. We also
find stereohedra with 17 facets for one of these groups.
Research partially supported by the Spanish Ministry of Education and Science, grant number MTM2005-08618-C02-02. 相似文献
7.
We introduce in this paper the concept of “impulse evolutionary game”. Examples of evolutionary games are usual differential
games, differentiable games with history (path-dependent differential games), mutational differential games, etc. Impulse
evolutionary systems and games cover in particular “hybrid systems” as well as “qualitative systems”. The conditional viability
kernel of a constrained set (with a target) is the set of initial states such that for all strategies (regarded as continuous
feedbacks) played by the second player, there exists a strategy of the first player such that the associated run starting
from this initial state satisfies the constraints until it hits the target. This paper characterizes the concept of conditional
viability kernel for “qualitative games” and of conditional valuation function for “qualitative games” maximinimizing an intertemporal
criterion. The theorems obtained so far about viability/capturability issues for evolutionary systems, conditional viability
for differential games and about impulse and hybrid systems are used to provide characterizations of conditional viability
under impulse evolutionary games. 相似文献
8.
Dušan Teodorović Vijay Varadarajan Jovan Popović Mohan Raj Chinnaswamy Sharath Ramaraj 《Annals of Operations Research》2006,143(1):123-131
In this paper, an “intelligent” isolated intersection control system was developed. The developed “intelligent” system makes
“real time” decisions as to whether to extend (and how much) current green time. The model developed is based on the combination
of the dynamic programming and neural networks. Many tests show that the outcome (the extension of the green time) of the
proposed neural network is nearly equal to the best solution. Practically negligible CPU times were achieved, and were thus
absolutely acceptable for the “real time” application of the developed algorithm. 相似文献
9.
Microarrays offer unprecedented possibilities for the so-called omic, e.g., genomic and proteomic, research. However, they
are also quite challenging data to analyze. The aim of this paper is to provide a short tutorial on the most common approaches
used for pattern discovery and cluster analysis as they are currently used for microarrays, in the hope to bring the attention
of the Algorithmic Community on novel aspects of classification and data analysis that deserve attention and have potential
for high reward.
R. Giancarlo is partially supported by Italian MIUR grants PRIN “Metodi Combinatori ed Algoritmici per la Scoperta di Patterns
in Biosequenze” and FIRB “Bioinformatica per la Genomica e la Proteomica” and Italy-Israel FIRB Project “Pattern Discovery
Algorithms in Discrete Structures, with Applications to Bioinformatics”. D. Scaturro is supported by a MIUR Fellowship in
the Italy-Israel FIRB Project “Pattern Discovery Algorithms in Discrete Structures, with Applications to Bioinformatics”. 相似文献
10.
Summary A software system has been developed for the study of dynamic glyph visualizations in the context of Visual Data Mining in
Virtual Reality. The system uses parallel processing to calculate data visualizations in real-time, with real-time interaction
and dynamic changes to the view. The system allows morphing between different visualizations, the use of dynamic features
like “vibrations” and “rotations” of thousands of objects individually, and dynamic visualization, where the influence of
any variable of a dataset with a “reasonable” distribution, can be shown as a dynamic development. It appears that these facilities
for dynamic data visualization have a very promising potential, but their optimal use will depend on further developments
in the context of their individual practical application. 相似文献
11.
Rade T. Živaljević 《Discrete and Computational Geometry》2009,41(1):135-161
This paper lays the foundation for a theory of combinatorial groupoids that allows us to use concepts like “holonomy”, “parallel transport”, “bundles”, “combinatorial curvature”, etc. in the context
of simplicial (polyhedral) complexes, posets, graphs, polytopes and other combinatorial objects. We introduce a new, holonomy-type
invariant for cubical complexes, leading to a combinatorial “Theorema Egregium” for cubical complexes that are non-embeddable
into cubical lattices. Parallel transport of Hom-complexes and maps is used as a tool to extend Babson–Kozlov–Lovász graph coloring results to more general statements about
nondegenerate maps (colorings) of simplicial complexes and graphs.
The author was supported by grants 144014 and 144026 of the Serbian Ministry of Science and Technology. 相似文献
12.
The various features of any product are differentially appealing to the various portions of the consumer population and have
differential costs of production and marketing. This paper considers the problem of “overall product optimization”, or more
specifically, “optimal product configuration”. Product price is, of course, a part of this configuration. 相似文献
13.
E. D. Livshits 《Proceedings of the Steklov Institute of Mathematics》2011,272(1):107-118
We discuss new models of an “affine” theory of gravity in multidimensional space-times with symmetric connections. We use and develop ideas of Weyl, Eddington, and Einstein, in particular, Einstein’s proposal to specify the space-time
geometry by the use of the Hamilton principle. More specifically, the connection coefficients are determined using a “geometric”
Lagrangian that is an arbitrary function of the generalized (nonsymmetric) Ricci curvature tensor (and, possibly, of other
fundamental tensors) expressed in terms of the connection coefficients regarded as independent variables. Such a theory supplements
the standard Einstein gravity with dark energy (the cosmological constant, in the first approximation), a neutral massive
(or tachyonic) vector field (vecton), and massive (or tachyonic) scalar fields. These fields couple only to gravity and can generate dark matter and/or inflation.
The new field masses (real or imaginary) have a geometric origin and must appear in any concrete model. The concrete choice
of the geometric Lagrangian determines further details of the theory, for example, the nature of the vector and scalar fields
that can describe massive particles, tachyons, or even “phantoms.” In “natural” geometric theories, which are discussed here,
dark energy must also arise. We mainly focus on intricate relations between geometry and dynamics while only very briefly
considering approximate cosmological models inspired by the geometric approach. 相似文献
14.
Vector and Hermite subdivision schemes both act on vector data, but since the latter one interprets the vectors as function
values and consecutive derivatives they differ by the “renormalization” of the Hermite scheme in any step. In this paper we
give an algebraic factorization method in one and several variables to relate any Hermite subdivision scheme that satisfies
the so–called spectral condition to a vector subdivision scheme. These factorizations are natural extensions of the “zero
at π” condition known for the masks of refinable functions. Moreover, we show how this factorization can be used to investigate
different forms of convergence of the Hermite scheme and why the multivariate situation is conceptionally more intricate than
the univariate one. Finally, we give some examples of such factorizations. 相似文献
15.
Alan Dow 《Israel Journal of Mathematics》1987,59(3):353-376
Recently Frank Tall has introduced the notion of a poset being “endowed” which is used in a forcing and reflection type proof
to show that certain properties are preserved by forcing with such a poset. Subsequently Bill Fleissner introduced the property
of a boolean algebra having a “lynx” and used this in an “Axiom and combinatorics” type proof of the same result. The two
notions are basically the same thing. In this paper we prove that some of the usual Cohen algebras have lynxes, that it is
consistent that nearly all of them have lynxes and investigate more generally the notion of lynxes.
Research supported by NSERC of Canada. 相似文献
16.
The Generalized Riemann Problem (GRP) for a nonlinear hyperbolic system of m balance laws (or alternatively “quasi-conservative” laws) in one space dimension is now well-known and can be formulated
as follows: Given initial-data which are analytic on two sides of a discontinuity, determine the time evolution of the solution
at the discontinuity. In particular, the GRP numerical scheme (second-order high resolution) is based on an analytical evaluation
of the first time derivative. It turns out that this derivative depends only on the first-order spatial derivatives, hence
the initial data can be taken as piecewise linear. The analytical solution is readily obtained for a single equation (m = 1) and, more generally, if the system is endowed with a complete (coordinate) set of Riemann invariants. In this case it
can be “diagonalized” and reduced to the scalar case. However, most systems with m > 2 do not admit such a set of Riemann invariants. This paper introduces a generalization of this concept: weakly coupled
systems (WCS). Such systems have only “partial set” of Riemann invariants, but these sets are weakly coupled in a way which
enables a “diagonalized” treatment of the GRP. An important example of a WCS is the Euler system of compressible, nonisentropic
fluid flow (m = 3). The solution of the GRP discussed here is based on a careful analysis of rarefaction waves. A “propagation of singularities”
argument is applied to appropriate Riemann invariants across the rarefaction fan. It serves to “rotate” initial spatial slopes
into “time derivative”. In particular, the case of a “sonic point” is incorporated easily into the general treatment. A GRP
scheme based on this solution is derived, and several numerical examples are presented. Special attention is given to the
“acoustic approximation” of the analytical solution. It can be viewed as a proper linearization (different from the approach
of Roe) of the nonlinear system. The resulting numerical scheme is the simplest (second-order, high-resolution) generalization
of the Godunov scheme. 相似文献
17.
David L. Russell 《Journal of Global Optimization》2008,40(4):575-588
The background for this article is the question of modification of the geometric configuration of an elastic structure by
means of “volume” type actuation. In this actuation mode stresses are applied to the elastic body by injection/extraction
of a fluid into, or from, a large number of vacuoles in the elastic “matrix” material. Previous articles by the author, and
others, have examined this process and studied its effectiveness in the context of a “naive” continuous model. The present
paper continues along these lines, exploring “normal boundary component controllability” criterion for determining achievable
configurations for the controlled system in the two-dimensional case. Connections with conformal mapping lead to affirmative
results for approximate controllability in this sense and Fourier series techniques provide exact controllability results
for the case wherein the domain of the uncontrolled system is a two-dimensional disk.
相似文献
18.
Jean-Paul Gauthier Bastien Berret Frédéric Jean 《Proceedings of the Steklov Institute of Mathematics》2010,268(1):93-116
This paper develops the mathematical side of a theory of inactivations in human biomechanics. This theory has been validated
by practical experiments, including zero-gravity experiments. The theory mostly relies on Pontryagin’s maximum principle on
the one side and on transversality theory on the other side. It turns out that the periods of silence in the activation of
muscles that are observed in practice during the motions of the arm can appear only if “something like the energy expenditure”
is minimized. Conversely, minimization of a criterion taking into account the “energy expenditure” guaranties the presence
of these periods of silence, for sufficiently short movements. 相似文献
19.
A new quantitative definition of the “power index” is proposed for a voter in weighted voting systems (WV-schemes), where
the voters a priori do not have equal rights. The proposed “power index” is generated in a self-consistent manner from information
about the number of times that a voter enters any winning coalition in the WV-scheme. Explicit formulas are derived for computing
the “power index”. The discussion is illustrated with prototype examples.
__________
Translated from Prikladnaya Matematika i Informatika, No. 25, pp. 81–98, 2007. 相似文献
20.
Andrzej Herdegen 《Annales Henri Poincare》2006,7(2):253-301
Casimir effect in most general terms may be understood as a backreaction of a quantum system causing an adiabatic change of
the external conditions under which it is placed. This paper is the second installment of a work scrutinizing this effect
with the use of algebraic methods in quantum theory. The general scheme worked out in the first part is applied here to the
discussion of particular models. We consider models of the quantum scalar field subject to external interaction with “softened”
Dirichlet or Neumann boundary conditions on two parallel planes. We show that the case of electromagnetic field with softened
perfect conductor conditions on the planes may be reduced to the other two. The “softening” is implemented on the level of
the dynamics, and is not imposed ad hoc, as is usual in most treatments, on the level of observables. We calculate formulas for the backreaction energy in these
models. We find that the common belief that for electromagnetic field the backreaction force tends to the strict Casimir formula
in the limit of “removed cutoff” is not confirmed by our strict analysis. The formula is model dependent and the Casimir value
is merely a term in the asymptotic expansion of the formula in inverse powers of the distance of the planes. Typical behaviour
of the energy for large separation of the plates in the class of models considered is a quadratic fall-of. Depending on the
details of the “softening” of the boundary conditions the backreaction force may become repulsive for large separations.
Communicated by Klaus Fredenhagen
submitted 9/09/04, accepted 1/07/05 相似文献