564 research outputs found
Iris Codes Classification Using Discriminant and Witness Directions
The main topic discussed in this paper is how to use intelligence for
biometric decision defuzzification. A neural training model is proposed and
tested here as a possible solution for dealing with natural fuzzification that
appears between the intra- and inter-class distribution of scores computed
during iris recognition tests. It is shown here that the use of proposed neural
network support leads to an improvement in the artificial perception of the
separation between the intra- and inter-class score distributions by moving
them away from each other.Comment: 6 pages, 5 figures, Proc. 5th IEEE Int. Symp. on Computational
Intelligence and Intelligent Informatics (Floriana, Malta, September 15-17),
ISBN: 978-1-4577-1861-8 (electronic), 978-1-4577-1860-1 (print
Facets for Art Gallery Problems
The Art Gallery Problem (AGP) asks for placing a minimum number of stationary
guards in a polygonal region P, such that all points in P are guarded. The
problem is known to be NP-hard, and its inherent continuous structure (with
both the set of points that need to be guarded and the set of points that can
be used for guarding being uncountably infinite) makes it difficult to apply a
straightforward formulation as an Integer Linear Program. We use an iterative
primal-dual relaxation approach for solving AGP instances to optimality. At
each stage, a pair of LP relaxations for a finite candidate subset of primal
covering and dual packing constraints and variables is considered; these
correspond to possible guard positions and points that are to be guarded.
Particularly useful are cutting planes for eliminating fractional solutions.
We identify two classes of facets, based on Edge Cover and Set Cover (SC)
inequalities. Solving the separation problem for the latter is NP-complete, but
exploiting the underlying geometric structure, we show that large subclasses of
fractional SC solutions cannot occur for the AGP. This allows us to separate
the relevant subset of facets in polynomial time. We also characterize all
facets for finite AGP relaxations with coefficients in {0, 1, 2}.
Finally, we demonstrate the practical usefulness of our approach. Our cutting
plane technique yields a significant improvement in terms of speed and solution
quality due to considerably reduced integrality gaps as compared to the
approach by Kr\"oller et al.Comment: 29 pages, 18 figures, 1 tabl
Integrating Systems Health Management with Adaptive Controls for a Utility-Scale Wind Turbine
Increasing turbine up-time and reducing maintenance costs are key technology drivers for wind turbine operators. Components within wind turbines are subject to considerable stresses due to unpredictable environmental conditions resulting from rapidly changing local dynamics. Systems health management has the aim to assess the state-of-health of components within a wind turbine, to estimate remaining life, and to aid in autonomous decision-making to minimize damage. Advanced adaptive controls can provide the mechanism to enable optimized operations that also provide the enabling technology for Systems Health Management goals. The work reported herein explores the integration of condition monitoring of wind turbine blades with contingency management and adaptive controls. Results are demonstrated using a high fidelity simulator of a utility-scale wind turbine
Identification of the De-synchronization, Synchronization and Forced Oscillation Phenomenon of a Nonlinear System
Abstract-The phenomena of de-synchronization, synchronization, and forced oscillation has been investigation using describing function theory for a two input and two output nonlinear system containing saturation-type nonlinearities and subjected to high-frequency deterministic signal for the purpose of limit cycle quenching. The analytical results have been compared with the results of digital simulation Matlab-Simulink for a typical example varying the nonlinear element
Scheduling divisible loads with time and cost constraints
In distributed computing, divisible load theory provides an important system model for allocation of data-intensive computations to processing units working in parallel. The main task is to define how a computation job should be split into parts, to which processors those parts should be allocated and in which sequence. The model is characterized by multiple parameters describing processor availability in time, transfer times of job parts to processors, their computation times and processor usage costs. The main criteria are usually the schedule length and cost minimization. In this paper, we provide the generalized formulation of the problem, combining key features of divisible load models studied in the literature, and prove its NP-hardness even for unrestricted processor availability windows. We formulate a linear program for the version of the problem with a fixed number of processors. For the case with an arbitrary number of processors, we close the gaps in the study of special cases, developing efficient algorithms for single criterion and bicriteria versions of the problem, when transfer times are negligible
EFFICIENT MODULAR IMPLEMENTATION OF BRANCH-AND-BOUND ALGORITHMS *
This paper demonstrates how branch-and-bound algorithms can be modularized to obtain implementation efficiencies. For the manager, this advantage can be used to obtain faster implementation of algorithm results; for the scientist, it allows efficiencies in the construction of similar algorithms with different search and addressing structures for the purpose of testing to find a preferred algorithm. The demonstration in part is achieved by showing how the computer code of a central module of logic can be transported between different algorithms that have the same search strategy. Modularizations of three common searches (the best-bound search and two variants of the last-in-first-out search) with two addressing methods are detailed and contrasted. Using four assembly line balancing algorithms as examples, modularization is demonstrated and the search and addressing methods are contrasted. The application potential of modularization is broad and includes linear programming-based integer programming. Benefits and disadvantages of modularization are discussed. Computational results demonstrate the viability of the method.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75538/1/j.1540-5915.1988.tb00251.x.pd
Extended formulations from communication protocols in output-efficient time
Deterministic protocols are well-known tools to obtain extended formulations,
with many applications to polytopes arising in combinatorial optimization.
Although constructive, those tools are not output-efficient, since the time
needed to produce the extended formulation also depends on the number of rows
of the slack matrix (hence, on the exact description in the original space). We
give general sufficient conditions under which those tools can be implemented
as to be output-efficient, showing applications to e.g.~Yannakakis' extended
formulation for the stable set polytope of perfect graphs, for which, to the
best of our knowledge, an efficient construction was previously not known. For
specific classes of polytopes, we give also a direct, efficient construction of
extended formulations arising from protocols. Finally, we deal with extended
formulations coming from unambiguous non-deterministic protocols
Engineering Art Galleries
The Art Gallery Problem is one of the most well-known problems in
Computational Geometry, with a rich history in the study of algorithms,
complexity, and variants. Recently there has been a surge in experimental work
on the problem. In this survey, we describe this work, show the chronology of
developments, and compare current algorithms, including two unpublished
versions, in an exhaustive experiment. Furthermore, we show what core
algorithmic ingredients have led to recent successes
Consistency for 0-1 Programming
Concepts of consistency have long played a key role in constraint programming
but never developed in integer programming (IP). Consistency nonetheless plays
a role in IP as well. For example, cutting planes can reduce backtracking by
achieving various forms of consistency as well as by tightening the linear
programming (LP) relaxation. We introduce a type of consistency that is
particularly suited for 0-1 programming and develop the associated theory. We
define a 0-1 constraint set as LP-consistent when any partial assignment that
is consistent with its linear programming relaxation is consistent with the
original 0-1 constraint set. We prove basic properties of LP-consistency,
including its relationship with Chvatal-Gomory cuts and the integer hull. We
show that a weak form of LP-consistency can reduce or eliminate backtracking in
a way analogous to k-consistency but is easier to achieve. In so doing, we
identify a class of valid inequalities that can be more effective than
traditional cutting planes at cutting off infeasible 0-1 partial assignments
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