769 research outputs found
Stochastic Block Mirror Descent Methods for Nonsmooth and Stochastic Optimization
In this paper, we present a new stochastic algorithm, namely the stochastic
block mirror descent (SBMD) method for solving large-scale nonsmooth and
stochastic optimization problems. The basic idea of this algorithm is to
incorporate the block-coordinate decomposition and an incremental block
averaging scheme into the classic (stochastic) mirror-descent method, in order
to significantly reduce the cost per iteration of the latter algorithm. We
establish the rate of convergence of the SBMD method along with its associated
large-deviation results for solving general nonsmooth and stochastic
optimization problems. We also introduce different variants of this method and
establish their rate of convergence for solving strongly convex, smooth, and
composite optimization problems, as well as certain nonconvex optimization
problems. To the best of our knowledge, all these developments related to the
SBMD methods are new in the stochastic optimization literature. Moreover, some
of our results also seem to be new for block coordinate descent methods for
deterministic optimization
Linearly Convergent First-Order Algorithms for Semi-definite Programming
In this paper, we consider two formulations for Linear Matrix Inequalities
(LMIs) under Slater type constraint qualification assumption, namely, SDP
smooth and non-smooth formulations. We also propose two first-order linearly
convergent algorithms for solving these formulations. Moreover, we introduce a
bundle-level method which converges linearly uniformly for both smooth and
non-smooth problems and does not require any smoothness information. The
convergence properties of these algorithms are also discussed. Finally, we
consider a special case of LMIs, linear system of inequalities, and show that a
linearly convergent algorithm can be obtained under a weaker assumption
Constraints on the Dark Side of the Universe and Observational Hubble Parameter Data
This paper is a review on the observational Hubble parameter data that have
gained increasing attention in recent years for their illuminating power on the
dark side of the universe --- the dark matter, dark energy, and the dark age.
Currently, there are two major methods of independent observational H(z)
measurement, which we summarize as the "differential age method" and the
"radial BAO size method". Starting with fundamental cosmological notions such
as the spacetime coordinates in an expanding universe, we present the basic
principles behind the two methods. We further review the two methods in greater
detail, including the source of errors. We show how the observational H(z) data
presents itself as a useful tool in the study of cosmological models and
parameter constraint, and we also discuss several issues associated with their
applications. Finally, we point the reader to a future prospect of upcoming
observation programs that will lead to some major improvements in the quality
of observational H(z) data.Comment: 20 pages, 6 figures, and 1 table, uses REVTeX 4.1. Review article,
accepted by Advances in Astronom
Computation of transient viscous flows using indirect radial basis function networks
In this paper, an indirect/integrated radial-basis-function network (IRBFN) method is further developed to solve transient partial differential equations (PDEs) governing fluid flow problems. Spatial derivatives are discretized using one- and two-dimensional IRBFN
interpolation schemes, whereas temporal derivatives are
approximated using a method of lines and a finite-difference technique. In the case of moving interface problems, the IRBFN method is combined with the level set method to capture the evolution of the interface. The accuracy of the method is investigated by considering several benchmark test problems, including the classical lid-driven cavity flow. Very accurate results are achieved using relatively low numbers of data points
Implementation of UAV Coordination Based on a Hierarchical Multi-UAV Simulation Platform
In this paper, a hierarchical multi-UAV simulation platform,called XTDrone,
is designed for UAV swarms, which is completely open-source 4 . There are six
layers in XTDrone: communication, simulator,low-level control, high-level
control, coordination, and human interac-tion layers. XTDrone has three
advantages. Firstly, the simulation speedcan be adjusted to match the computer
performance, based on the lock-step mode. Thus, the simulations can be
conducted on a work stationor on a personal laptop, for different purposes.
Secondly, a simplifiedsimulator is also developed which enables quick algorithm
designing sothat the approximated behavior of UAV swarms can be observed
inadvance. Thirdly, XTDrone is based on ROS, Gazebo, and PX4, andhence the
codes in simulations can be easily transplanted to embeddedsystems. Note that
XTDrone can support various types of multi-UAVmissions, and we provide two
important demos in this paper: one is aground-station-based multi-UAV
cooperative search, and the other is adistributed UAV formation flight,
including consensus-based formationcontrol, task assignment, and obstacle
avoidance.Comment: 12 pages, 10 figures. And for the, see
https://gitee.com/robin_shaun/XTDron
Integrating Managerial Pattern and Competitive Advantages: The Moderation of Competitive Inertia
In dynamic competition, the competitive inertia is determined by components both inside and outside of company. This paper investigated that, after integration, how can firm appropriately alter their integrating managerial pattern, according to competitive inertia, in order to achieve better advantages cause from integration. Through 10-year data of the oligopoly enterprises in airconditioner industry in China, the analysis demonstrated that, improving flexibilities of integration managerial pattern helps to build differentiation advantages, while negative to cost advantages; while firm competitive inertia grew, systematicness of integration managerial pattern would have positive effects on differentiation advantages, while negative on cost advantages.Key words: Integrating managerial pattern; Competitive dynamics; Competitive inertia; Competitive advantage
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