Results 31 to 40 of about 9,238,134 (300)

Systems of quadratic forms.

Journal für die reine und angewandte Mathematik (Crelles Journal), 1984
Let \(u_ F(r)\) be the smallest integer such that every system of r quadratic forms in n variables, defined over a field F, has a nontrivial common zero if \(n>u_ F(r)\). Let \(u_ F(r)=\infty\) if no such integer exists. Then \(u_ F(r)\leq frac{1}{2}(r^ 2+r)u_ F(1)\) and there exist fields for which this bound is best possible when \(r=1,2,3\). If F is
openaire   +2 more sources

Rigid Polynomial Differential Systems with Homogeneous Nonlinearities

Mathematics
Planar differential systems whose angular velocity is constant are called rigid or uniform differential systems. The first rigid system goes back to the pendulum clock of Christiaan Huygens in 1656; since then, the interest for the rigid systems has been
Jaume Llibre
doaj   +1 more source

Set simulations for quadratic systems

IEEE Transactions on Automatic Control, 2003
In this paper, we study the problem of propagating in time a bounding set for the state of a class of nonlinear quadratic systems. The sequence of bounding sets is called the set simulation of the system, and conveys useful information about the stability and qualitative behavior of the possible time responses of the system.
openaire   +2 more sources

Preimages of quadratic dynamical systems [PDF]

Involve, a Journal of Mathematics, 2011
For a quadratic endomorphism of the affine line defined over the rationals we consider the problem of bounding the number of rational points that eventually land at a given constant after iteration, called pre-images of the constant. In the article "Uniform Bounds on Pre-Images Under Quadratic Dynamical Systems," it was shown that the number of ...
Hutz, Benjamin, Hyde, Trevor, Krause, Benjamin   +2 more
openaire   +3 more sources

Phase portraits of separable quadratic systems and a bibliographical survey on quadratic systems

Expositiones Mathematicae, 2021
Although planar quadratic differential systems and their applications have been studied in more than one thousand papers, we still have no complete understanding of these systems. In this paper we have two objectives. First we provide a brief bibliographical survey on the main results about quadratic systems. Here we do not consider the applications of
Tao Li, Jaume Llibre
openaire   +4 more sources

Discordance Between Patient and Physician Global Assessments in Early Systemic Sclerosis

Arthritis Care &Research, EarlyView.
Objective This study aims to identify factors associated with patient global assessment (PtGA) and physician global assessment (PhGA) and discordance between them in systemic sclerosis (SSc). Methods Data from adults with early SSc (<5 years) from the Collaborative National Quality and Efficacy Registry were included.
Ellen Romich, Alexis Ogdie, Alisa Stephens Shields, Peter A. Merkel, Shervin Assassi, Elana J. Bernstein, Andreea Bujor, Flavia V. Castelino, Lorinda Chung, Luke B. Evnin, Tracy M. Frech, Jessica K. Gordon, Melissa Griffith, Faye N. Hant, Monica L. Harding, Laura K. Hummers, Dinesh Khanna, Kimberly S. Lakin, Dorota J. Lebiedz‐Odrobina, Yiming Luo, Ashima Makol, Maureen D. Mayes, Zsuzsanna H. McMahan, Jerry Molitor, Duncan F. Moore, Julie Paik, Carrie Richardson, Brian Skaug, Ami A. Shah, Ankoor Shah, Virginia Steen, John M. VanBuren, Elizabeth R. Volkmann, Carleigh Zahn, Nora Sandorfi, for the CONQUER Investigators   +35 more
wiley   +1 more source

Quadratic systems with two invariant real straight lines and an invariant parabola

Electronic Journal of Qualitative Theory of Differential Equations
After the linear differential systems in the plane the easiest ones are the quadratic polynomial differential systems. Due to their nonlinearity and also to their many applications these systems have been studied by many authors. Let QS denote the set of
Jaume Llibre, Huaxin Ou
doaj   +1 more source

Discordance Between Systemic Lupus Erythematosus Disease Activity Index Domain Weights and Their Association With Organ Damage Accrual

Arthritis Care &Research, EarlyView.
Objective Studies of damage accrual in patients with systemic lupus erythematosus (SLE) show associations with disease activity measured by the SLE Disease Activity Index 2000 (SLEDAI‐2K), but these associations are imperfect. SLEDAI scores are powerfully influenced by weightings (1–8) assigned to each domain.
Kevin Zhang, Eric F. Morand, Sarah E. Boyd, François Petitjean, Alberta Hoi, Rachel Koelmeyer, Iolanda Miceli, Julie A. Monk, Hieu T. Nim   +8 more
wiley   +1 more source

A Q‐Learning Algorithm to Solve the Two‐Player Zero‐Sum Game Problem for Nonlinear Systems

International Journal of Adaptive Control and Signal Processing, Volume 39, Issue 3, Page 566-581, March 2025.
A Q‐learning algorithm to solve the two‐player zero‐sum game problem for nonlinear systems. ABSTRACT This paper deals with the two‐player zero‐sum game problem, which is a bounded L2$$ {L}_2 $$‐gain robust control problem. Finding an analytical solution to the complex Hamilton‐Jacobi‐Issacs (HJI) equation is a challenging task.
Afreen Islam, Anthony Siming Chen, Guido Herrmann   +2 more
wiley   +1 more source

Quadratic engel curves and consumer demand [PDF]

, 1997
This paper presents a model of consumer demand that is consistent with the observed expenditure patterns of individual consumers in a long time series of expenditure surveys and is also able to provide a detailed welfare analysis of shifts in relative ...
Blundell, Richard, Richard Blundell, Lewbel, Arthur, Banks, J, Banks, James; id_orcid, James Banks, Lewbel, A, Arthur Lewbel, Blundell, R   +8 more
core   +1 more source