Results 51 to 60 of about 5,647,728 (213)
Low-Rank Optimization on the Cone of Positive Semidefinite Matrices [PDF]
SIAM Journal on Optimization, 2010 We propose an algorithm for solving optimization problems defined on a subset of the cone of symmetric positive semidefinite matrices. This algorithm relies on the factorization $X=YY^T$, where the number of columns of Y fixes an upper bound on the rank of the positive semidefinite matrix X.
Journée, Michel +3 more
openaire +3 more sources
On Symmetries of Hyperbolic Lattices of Large Rank
Mathematische Nachrichten, EarlyView.ABSTRACT For an even, integral hyperbolic lattice L$L$, the symmetry group of L$L$ is the quotient of the group of positive isometries of L$L$ by the Weyl subgroup of (−2)$(-2)$‐reflections. Following Nikulin, the exceptional lattice of L$L$ is defined as the sublattice generated by elements that have finite orbit under the symmetry group of L$L$.
Torben Grabbel +4 more
wiley +1 more source
Data‐driven emulation of flow‐dependent background‐error variance in variational data assimilation
Quarterly Journal of the Royal Meteorological Society, EarlyView.A machine‐learning approach is developed to emulate flow‐dependent background‐error variance within a variational data assimilation framework. The method reproduces uncertainty information that would normally require a 50‐member ensemble using only five members, while maintaining comparable observation fit and forecast performance.
Wei Pan +3 more
wiley +1 more source
Heinz均值凸性的一个注记(A note on the convexity of the Heinz means)
Zhejiang Daxue xuebao. Lixue ban, 2013 Recently, KITTANEH obtained an improvement of the Heinz inequality for all unitarily invariant norms. In this note, we obtain a refinement of KITTANEH's result. We shall conclude this paper with some numerical examples.
ZOULi-min(邹黎敏)
doaj +1 more source
On a product of positive semidefinite matrices
Linear Algebra and its Applications, 1999 The matrix \(A\) is said to be positive semidefinite (psd) if there exists a matrix \(P\) such that \(PP^*=A\). If \(A\) and its conjugate transpose \(A^*\) have the same range space, then \(A\) is called EP. Necessary and sufficient conditions are given for the product of two positive semidefinite (psd) matrices to be EP. As a consequence, it is shown
Meenakshi, A.R., Rajian, C.
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Neural Network‐Based Runtime Monitoring and Control for Unknown Nonlinear Systems
International Journal of Robust and Nonlinear Control, EarlyView.ABSTRACT Real‐time system monitoring and stabilization become especially challenging when the system dynamics are unknown. This article introduces a novel design for monitoring and stabilizing unknown nonlinear systems with measurement noise. The design utilizes a generic modelling framework by decomposing the system into a known tunable linear ...
Jianglin Lan, Xianxian Zhao, Ron Patton
wiley +1 more source
Marginally Strictly Negative Imaginary Systems
International Journal of Robust and Nonlinear Control, EarlyView.ABSTRACT This article revisits a fundamental question in negative imaginary (NI) systems theory: what is the weakest viable notion of strictness that still preserves the classical feedback stability picture? To address this question, we introduce the notion of marginally strictly negative imaginary (MSNI) systems to accommodate simple nonzero imaginary‐
Tianzhe Zhang +3 more
wiley +1 more source
Matrices with positive semidefinite real part
, 2019 Matrices with the property that the real part is positive definite, have been studied for the past five decades or more. Many results in the form of inequalities have been obtained for matrices possessing this property.
Choudhury, Projesh Nath, Sivakumar, KC
core +1 more source
Orbital Stabilization of Hybrid Mechanical Systems—A Port‐Hamiltonian Approach
International Journal of Robust and Nonlinear Control, EarlyView.ABSTRACT In this article, we address the problem of stabilizing hybrid periodic orbits in mechanical systems characterized by both continuous and discrete dynamics. We introduce a total energy shaping controller, formulated in the port‐Hamiltonian framework, that guarantees asymptotic orbital stability of a prescribed hybrid periodic orbit.
Thomas O'Brien +2 more
wiley +1 more source
The role of identification in data‐driven policy iteration: A system theoretic study
International Journal of Robust and Nonlinear Control, EarlyView.Abstract The goal of this article is to study fundamental mechanisms behind so‐called indirect and direct data‐driven control for unknown systems. Specifically, we consider policy iteration applied to the linear quadratic regulator problem. Two iterative procedures, where data collected from the system are repeatedly used to compute new estimates of ...
Bowen Song, Andrea Iannelli
wiley +1 more source