Results 61 to 70 of about 290 (150)

Undecidable relativizations of algebras of relations. [PDF]

, 1999
In this paper we show that relativized versions of relation set algebras and cylindric set algebras have undecidable equational theories if we include coordinatewise versions of the counting operations into the similarity type.
Marx, M.J., Marx, M., Mikulas, Szabolcs, Mikulas, S.   +3 more
core   +1 more source

Analytical and Numerical Soliton Solutions of the Shynaray II‐A Equation Using the G′G,1G$$ \left(\frac{G^{\prime }}{G},\frac{1}{G}\right) $$‐Expansion Method and Regularization‐Based Neural Networks

Mathematical Methods in the Applied Sciences, Volume 49, Issue 9, Page 9814-9831, June 2026.
ABSTRACT Nonlinear differential equations play a fundamental role in modeling complex physical phenomena across solid‐state physics, hydrodynamics, plasma physics, nonlinear optics, and biological systems. This study focuses on the Shynaray II‐A equation, a relatively less‐explored parametric nonlinear partial differential equation that describes ...
Aamir Farooq, H. W. A. Riaz, Sadique Rehman, M. Mamun Miah, Wen Xiu Ma   +4 more
wiley   +1 more source

In Vivo Imaging With a Low‐Cost MRI Scanner and Cloud Data Processing in Low‐Resource Settings

NMR in Biomedicine, Volume 39, Issue 6, June 2026.
This study presented the system evolution at MUST: (a) Scanner after the initial assembly in 2023. (b) First reconstructed image (bell pepper). Front (c), rear (d), and global (e) views of the MUST scanner in the 2025 configuration, highlighting the improved electronics setup, RF coils, and mechanical integration.
Teresa Guallart‐Naval, Robert Asiimwe, Patricia Tusiime, Mary A. Nassejje, Leo Kinyera, Lemi Robin, Maureen Nayebare, Luiz G. C. Santos, Marina Fernández‐García, Lucas Swistunow, José M. Algarín, John Stairs, Michael Hansen, Ronald Amodoi, Andrew Webb, Joshua Harper, Steven J. Schiff, Johnes Obungoloch, Joseba Alonso   +18 more
wiley   +1 more source

Relation algebras from cylindric algebras

, 1999
We characterise the class SRaCAn of subalgebras of relation algebra reducts of n-dimensional cylindric algebras (for finite n ≥ 5) by the notion of a ‘hyper-basis’, analo-gous to the cylindric basis of Maddux, and by relativised representations.
Ian Hodkinson, Robin Hirsch
core  

Cylindric structures and dependencies in relational databases

, 2001
In this paper, we explore the precise connection between dependencies in relational databases and variants of cylindric algebras, and apply recent algebraic results to problems of axiomatising dependencies.
Düntsch, Ivo, Duntsch, I., Ivo Düntsch, Mikulás, Szabolcs, Szabolcs Mikulás   +4 more
core   +1 more source

Optimal Control‐Based Generic Framework for Radiofrequency Pulse Design in MRI

NMR in Biomedicine, Volume 39, Issue 6, June 2026.
This paper presents an open‐source Python‐based optimal control RF design framework, which can tackle various problems (short‐T2 selective excitation or B1‐robust excitation/inversion). It features three main methodological contributions: a specific cost is introduced to reduce pulse peak amplitude; consistent integration of various hard constraints on
Emilio Molina, Hélène Ratiney, Eric Van Reeth   +2 more
wiley   +1 more source

An Augmented Lagrangian Preconditioner for Navier–Stokes Equations With Runge–Kutta in Time

Numerical Linear Algebra with Applications, Volume 33, Issue 3, June 2026.
ABSTRACT We consider an implicit Runge–Kutta method for the numerical time integration of the nonstationary incompressible Navier–Stokes equations. This yields a sequence of nonlinear problems to be solved for the stages of the Runge–Kutta method. The resulting nonlinear system of differential equations is discretized using a finite element method.
Santolo Leveque, Yunhui He, Maxim Olshanskii   +2 more
wiley   +1 more source

The neat embedding problem for algebras other than cylindric algebras and for infinite dimensions [PDF]

, 2014
Hirsch and Hodkinson proved, for $3\leq ...
Hirsch, R, Sayed Ahmed, T
core  

Multi‐Goal‐Oriented Anisotropic Error Control and Mesh Adaptivity for Time‐Dependent Convection‐Dominated Problems

Proceedings in Applied Mathematics and Mechanics, Volume 26, Issue 2, June 2026.
ABSTRACT In this work, we present an anisotropic multi‐goal error control based on the dual weighted residual (DWR) method for time‐dependent convection–diffusion–reaction (CDR) equations. Motivated by former work, we combine multiple goals to single error functionals with weights chosen as algorithmic parameters.
Markus Bause, Marius Paul Bruchhäuser, Bernhard Endtmayer, Nils Margenberg, Ioannis Toulopoulos, Thomas Wick   +5 more
wiley   +1 more source

Decidability of cylindric set algebras of dimension two and first-order logic with two variables

, 1999
The aim of this paper is to give a new proof for the decidability and finite model property of first-order logic with two variables (without function symbols), using a combinatorial theorem due to Herwig.
Marx, M., Mikulas, Szabolcs
core   +1 more source