112,115 research outputs found
Combinatorial methods in Dehn surgery
This is an expository paper, in which we give a summary of some of the joint
work of John Luecke and the author on Dehn surgery. We consider the situation
where we have two Dehn fillings and on a given
3-manifold , each containing a surface that is either essential or a
Heegaard surface. We show how a combinatorial analysis of the graphs of
intersection of the two corresponding punctured surfaces in enables one to
find faces of these graphs which give useful topological information about
and , and hence, in certain cases, good upper bounds on
the intersection number of the two filling slopes
Regularization and Kernelization of the Maximin Correlation Approach
Robust classification becomes challenging when each class consists of
multiple subclasses. Examples include multi-font optical character recognition
and automated protein function prediction. In correlation-based
nearest-neighbor classification, the maximin correlation approach (MCA)
provides the worst-case optimal solution by minimizing the maximum
misclassification risk through an iterative procedure. Despite the optimality,
the original MCA has drawbacks that have limited its wide applicability in
practice. That is, the MCA tends to be sensitive to outliers, cannot
effectively handle nonlinearities in datasets, and suffers from having high
computational complexity. To address these limitations, we propose an improved
solution, named regularized maximin correlation approach (R-MCA). We first
reformulate MCA as a quadratically constrained linear programming (QCLP)
problem, incorporate regularization by introducing slack variables in the
primal problem of the QCLP, and derive the corresponding Lagrangian dual. The
dual formulation enables us to apply the kernel trick to R-MCA so that it can
better handle nonlinearities. Our experimental results demonstrate that the
regularization and kernelization make the proposed R-MCA more robust and
accurate for various classification tasks than the original MCA. Furthermore,
when the data size or dimensionality grows, R-MCA runs substantially faster by
solving either the primal or dual (whichever has a smaller variable dimension)
of the QCLP.Comment: Submitted to IEEE Acces
Organic farming and multicriteria decisions: An economic survey
Organic food production is a sphere where decision making is multi-facetted and complex. This applies to producers, political decision makers and consumers alike. This paper provides an overview of the economic methods that can aid such multi criteria decision making. We first provide an outline of the many different Multi-Criteria Analysis (MCA) techniques available and their relative advantages and disadvantages. In addition, theoretical and practical problems related to the use of Cost-Benefit Analysis (CBA) and MCA respectively are briefly discussed. We then review the MCA literature on case studies on organic farming. Based on this review we provide directional markers for future research where MCA may possibly be applied and adapted in order to provide useful knowledge and support for decision makers in the context of organic farming
Magnetocrystalline anisotropy of Fe and Co slabs and clusters on SrTiO by first-principles
In this work, we present a detailed theoretical investigation of the
electronic and magnetic properties of ferromagnetic slabs and clusters
deposited on SrTiO via first-principles, with a particular emphasis on the
magneto-crystalline anisotropy (MCA). We found that in the case of Fe films
deposited on SrTiO the effect of the interface is to quench the MCA
whereas for Cobalt we observe a change of sign of the MCA from in-plane to
out-of-plane as compared to the free surface. We also find a strong enhancement
of MCA for small clusters upon deposition on a SrTiO substrate. The
hybridization between the substrate and the -orbitals of the cluster
extending in-plane for Fe and out-of-plane for Co is at the origin of this
enhancement of MCA. As a consequence, we predict that the Fe nanocrystals (even
rather small) should be magnetically stable and are thus good potential
candidates for magnetic storage devices.Comment: Physical ReviewB, 201
An Alloy Verification Model for Consensus-Based Auction Protocols
Max Consensus-based Auction (MCA) protocols are an elegant approach to
establish conflict-free distributed allocations in a wide range of network
utility maximization problems. A set of agents independently bid on a set of
items, and exchange their bids with their first hop-neighbors for a distributed
(max-consensus) winner determination. The use of MCA protocols was proposed,
, to solve the task allocation problem for a fleet of unmanned aerial
vehicles, in smart grids, or in distributed virtual network management
applications. Misconfigured or malicious agents participating in a MCA, or an
incorrect instantiation of policies can lead to oscillations of the protocol,
causing, , Service Level Agreement (SLA) violations.
In this paper, we propose a formal, machine-readable, Max-Consensus Auction
model, encoded in the Alloy lightweight modeling language. The model consists
of a network of agents applying the MCA mechanisms, instantiated with
potentially different policies, and a set of predicates to analyze its
convergence properties. We were able to verify that MCA is not resilient
against rebidding attacks, and that the protocol fails (to achieve a
conflict-free resource allocation) for some specific combinations of policies.
Our model can be used to verify, with a "push-button" analysis, the convergence
of the MCA mechanism to a conflict-free allocation of a wide range of policy
instantiations
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