Minimal set of generators of controllability space for singular linear dynamical systems

Due to the significant role played by singular systems in the form E ¿ x ( t ) = Ax ( t ) , on mathematical modeling of science and engineering problems; in the last years recent years its interest in the descriptive analysis of its structural and dynamic properties. However, much less effort has been devoted to studying the exact con- trollability by measuring the minimum set of controls needed to direct the entire system E ¿ x ( t ) = Ax ( t ) to any desired state. In this work, we focus the study on obtaining the set of all matrices B with a minimal number of columns, by making the singular system E ¿ x ( t ) = Ax ( t ) + Bu ( t ) controllable.Postprint (author's final draft

Bilinear softening parameters and equivalent LEFM R-curve in quasibrittle failure

For composites and adhesive joints, the determination of the cohesive zone parameters from Double Cantilever Beam specimens loaded with pure moments is now well established and documented. However, for quasibrittle materials used in Civil Engineering such as concrete or wood, the difficulty to apply a pure bending moment lies inappropriated the method used for composites. Nevertheless, the one-to-one correspondence which exists between the R-curve and the softening curve is here revisited and adapted for any kind of specimen geometry and for the bilinear approximation of the softening function, well-known to successfully describe the failure of a wide group of quasibrittle materials. It is shown that even though the connections between the cohesive parameters and the ‘equivalent LEFM’ R-curve are geometry and material dependent, their trends are preserved whatever the specimen geometry and the material are. The outline of a general estimation procedure of the cohesive zone parameters funded on the equivalent LEFM R-curve is proposed

POSTER: SPiDRE: accelerating sparse memory access patterns

Development in process technology has led to an exponential increase in processor speed and memory capacity. However, memory latencies have not improved as dramatically and represent a well-known problem in computer architecture. Cache memories provide more bandwidth with lower latencies than main memories but they are capacity limited. Locality-friendly applications benefit from a large and deep cache hierarchy. Nevertheless, this is a limited solution for applications suffering from sparse and irregular memory access patterns, such as data analytics. In order to accelerate them, we should maximize usable bandwidth, reduce latency and maximize moved data reuse. In this work we explore the Sparse Data Rearrange Engine (SPiDRE), a novel hardware approach to accelerate these applications through near-memory data reorganization.This work has been supported by the Spanish Ministry of Science and Innovation (contract TIN2015-65316-P, Ramon y Cajal fellowship number RYC-2016-21104 and FPI fellowship number BES-2017-080635), and by the Arm-BSC Centre of Excellence initiative.Peer ReviewedPostprint (author's final draft

Seahorse aquaculture, biology and conservation: knowledge gaps and research opportunities

11 páginas, 6 figuras, 1 tablaSeahorses are currently experiencing an unprecedented level of anthropogenic pressure promoted by habitat destruction and increasing fishing effort to supply premium markets. This study provides an overview of the scientific literature on seahorses in the 21st century and critically discusses five major knowledge gaps and research opportunities to advance the state of the art on this research field. The average number of publications per year increased from 10 (2001–2002) to ∼40 (2001–2015), the majority addressing issues on seahorse ecology, biology, and aquaculture, with the most studied species being Hippocampus kuda, H. guttulatus, H. reidi, H. abdominalis, H. erectus, H. hippocampus, and H. trimaculatus. This study explores the opportunity of using seahorses as flagship species to foster mangrove conservation and decrease trawling fisheries. It also suggests that further scientific studies are needed to better understand and manage the populations of the most heavily traded seahorse species, as well as the need to monitor their vulnerability to emerging pollutants and climate change. Sustainable seahorse aquaculture can play an important role in seahorse conservation, as well as in the development of reliable traceability tools to fight the illegal trade of these highly priced organismsWe thank the São Paulo Research Foundation–FAPESP (grants nos. 2013/22260-6 and 2015/18050-0) and The National Council for Scientific and Technological Development–CNPq (grant nos. 441356/2014-1) for the financial support provided. Thanks also to FCT/MEC through national funds, and the cofunding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020 for the financial support to CESAM (UID/AMB/50017/2013)Peer reviewe

Limits of the Stokes and Navier-Stokes equations in a punctured periodic domain

We treat three problems on a two-dimensional “punctured periodic domain”: we take Ωr=(−L,L)2∖rK, where r>0 and K is the closure of an open connected set that is star-shaped with respect to 0 and has a C1 boundary. We impose periodic boundary conditions on the boundary of Ω=(−L,L)2, and Dirichlet boundary conditions on ∂(rK). In this setting we consider the Poisson equation, the Stokes equations, and the time-dependent Navier–Stokes equations, all with a fixed forcing function f, and examine the behavior of solutions as r→0. In all three cases we show convergence of the solutions to those of the limiting problem, i.e. the problem posed on all of Ω with periodic boundary conditions

Functional output-controllability of time-invariant singular linear systems

In the space of finite-dimensional singular linear continuous-time-invariant systems described in the form \begin{equation}\label{eq1}\left . \begin{array}{rl} E \dot x(t)&= Ax(t)+Bu(t)\\ y(t)&=Cx(t)\end{array}{\kern-1mm}\right \}\end{equation} where $E,A\in M=M_{n}(\mathbb{C})$, $B\in M_{n\times m}(\mathbb{C})$, $C\in M_{p\times n}(\mathbb{C})$, functional output-controllability character is considered. A simple test based in the computation of the rank of a certain constant matrix that can be associated to the system is presentedPeer ReviewedPostprint (published version