6,960 research outputs found
Polymer multimode waveguide optical and electronic PCB manufacturing
No full textThe paper describes the research in the £1.3 million IeMRC Integrated Optical and Electronic Interconnect PCB Manufacturing (OPCB) Flagship Project in which 8 companies and 3 universities carry out collaborative research and which was formed and is technically led by the author. The consortium’s research is aimed at investigating a range of fabrication techniques, some established and some novel, for fabricating polymer multimode waveguides from several polymers, some formulations of which are being developed within the project. The challenge is to develop low cost waveguide manufacturing techniques compatible with commercial PCB manufacturing and to reduce their alignment cost. The project aims to take the first steps in making this hybrid optical waveguide and electrical copper track printed circuit board disruptive technology widely available by establishing and incorporating waveguide design rules into commercial PCB layout software and transferring the technology for fabricating such boards to a commercial PCB manufacturer. To focus the research the project is designing an optical waveguide backplane to tight realistic constraints, using commercial layout software with the new optical design rules, for a demonstrator into which 4 daughter cards are plugged, each carrying an aggregate of 80 Gb/s data so that each waveguide carries 10 Gb/s
The spectrum of Volterra operators on weighted spaces of entire functions
No full textWe investigate the spectrum of the Volterra operator Vg with symbol an entire
function g, when it acts on weighted Banach spaces H∞
v
(C) of entire functions with
sup-norms and when it acts on Hörmander algebras Ap or A0
pThis research was partially supported by MINECO Project MTM2013-43540-P and by GV Project Prometeo II/2013/013.Bonet Solves, JA. (2015). The spectrum of Volterra operators on weighted spaces of entire functions. Quarterly Journal of Mathematics. 66:799-807. https://doi.org/10.1093/qmath/hav019S7998076
Solving the measurement problem: de Broglie-Bohm loses out to Everett
No full textThe quantum theory of de Broglie and Bohm solves the measurement problem, but the hypothetical corpuscles play no role in the argument. The solution finds a more natural home in the Everett interpretation
Statistical language learning
No full textTheoretical arguments based on the "poverty of the stimulus" have denied a
priori the possibility that abstract linguistic representations can be learned
inductively from exposure to the environment, given that the linguistic input
available to the child is both underdetermined and degenerate. I reassess such
learnability arguments by exploring a) the type and amount of statistical
information implicitly available in the input in the form of distributional and
phonological cues; b) psychologically plausible inductive mechanisms for
constraining the search space; c) the nature of linguistic representations,
algebraic or statistical. To do so I use three methodologies: experimental
procedures, linguistic analyses based on large corpora of naturally occurring
speech and text, and computational models implemented in computer
simulations.
In Chapters 1,2, and 5, I argue that long-distance structural dependencies
- traditionally hard to explain with simple distributional analyses based on ngram
statistics - can indeed be learned associatively provided the amount of
intervening material is highly variable or invariant (the Variability effect). In
Chapter 3, I show that simple associative mechanisms instantiated in Simple
Recurrent Networks can replicate the experimental findings under the same
conditions of variability. Chapter 4 presents successes and limits of such results
across perceptual modalities (visual vs. auditory) and perceptual presentation
(temporal vs. sequential), as well as the impact of long and short training
procedures. In Chapter 5, I show that generalisation to abstract categories from
stimuli framed in non-adjacent dependencies is also modulated by the Variability
effect. In Chapter 6, I show that the putative separation of algebraic and
statistical styles of computation based on successful speech segmentation versus
unsuccessful generalisation experiments (as published in a recent Science paper)
is premature and is the effect of a preference for phonological properties of the
input. In chapter 7 computer simulations of learning irregular constructions
suggest that it is possible to learn from positive evidence alone, despite Gold's
celebrated arguments on the unlearnability of natural languages. Evolutionary
simulations in Chapter 8 show that irregularities in natural languages can emerge
from full regularity and remain stable across generations of simulated agents. In
Chapter 9 I conclude that the brain may endowed with a powerful statistical
device for detecting structure, generalising, segmenting speech, and recovering
from overgeneralisations. The experimental and computational evidence gathered
here suggests that statistical language learning is more powerful than heretofore
acknowledged by the current literature
New computer program solves wide variety of heat flow problems
No full textBoeing Engineering Thermal Analyzer /BETA/ computer program uses numerical methods to provide accurate heat transfer solutions to a wide variety of heat flow problems. The program solves steady-state and transient problems in almost any situation that can be represented by a resistance-capacitance network
Inexact Subdomain Solves Using Deflated GMRES for Helmholtz Problems
No full textIn recent years, domain decomposition based preconditioners have become popular tools to solve the Helmholtz equation. Notorious for causing a variety of convergence issues, the Helmholtz equation remains a challenging PDE to solve numerically. Even for simple model problems, the resulting linear system after discretisation becomes indefinite and tailored iterative solvers are required to obtain the numerical solution efficiently. At the same time, the mesh must be kept fine enough in order to prevent numerical dispersion ‘polluting’ the solution [4]. This leads to very large linear systems, further amplifying the need to develop economical solver methodologies.Numerical Analysi
DNS of turbulent mixing layers with variable density
No full textWe present some preliminary results of direct numerical simulations of three-dimensional, temporal, plane mixing layers with variable density. The simulations are run with a parallel in-house code that solves the Navier-Stokes equations in the Low-Mach number approximation, using a novel algorithm based on an extended version of the velocity-vorticity formulation used by Kim, Moin & Moser (1987) for incompressible flows. The simulations are run with Pr=0.7 and achieve Re_lambda=90-110 during the self-similar evolution of the mixing layer. Four cases with density ratios s=1,2,4 and 8 are presented. Our results show good agreement with previous experimental and numerical studies, and allow us to characterize the scales in the temperature spectra
Factorization of weakly compact operators between Banach spaces and Fréchet or (LB)-spaces
No full text[EN] In this note we show that weakly compact operators from a Banach space X into
a complete (LB)-space E need not factorize through a reflexive Banach space. If E is a Fréchet space, then weakly compact operators from a Banach space X into E factorize through a reflexive Banach space. The factorization of operators from a Fréchet or a complete (LB)-space into a Banach space mapping bounded sets into relatively weakly compact sets is also investigated.The research of the first author was partially supported by MEC and FEDER Project MTM2010-15200 and by GV Project Prometeo/2008/101. The support of the University of Aberdeen and the Universidad Polit´ecnica of Valencia is gratefully acknowledged.Bonet Solves, JA.; Wright, JM. (2012). Factorization of weakly compact operators between Banach spaces and Fréchet or (LB)-spaces. Matematicki Vesnik. 64(4):330-335. https://riunet.upv.es/handle/10251/58753S33033564
Microstructural evolution of Ti–6Al–4V during the sintering of microspheres of Ti for orthopedic implants
No full text[EN] There are also important complementary stabilization treatments of the microstructure by means of controlled cooling at high speeds it avoids the formation of beta phases in grain boundaries, at the same time that avoid the broken-up of the Widmanstaetten structure, developing in an increase in mechanical resistance and fatigue resistance of the prosthesis. (C) 2003 Elsevier Science B.V. All rights reserved.Amigó, V.; Salvador Moya, MD.; Romero, F.; Solves-Camallonga, C.; Moreno, J. (2003). Microstructural evolution of Ti-6Al-4V during the sintering of microspheres of Ti for orthopedic implants. Journal of Materials Processing Technology. 141(1):117-122. https://doi.org/10.1016/S0924-0136(03)00243-7S117122141
A note about Volterra operators on weighted Banach spaces of entire functions
No full textWe characterize boundedness, compactness and weak compactness of Volterra operators Vg acting between
different weighted Banach spaces H∞
v (C) of entire functions with sup-norms in terms of the symbol g; thus
we complement recent work by Bassallote, Contreras, Hernandez-Mancera, Martín and Paul [3] for spaces of
holomorphic functions on the disc and by Constantin and Peláez [16] for reflexive weighted Fock spaces.
C 2015 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimThe research of J. Bonet was partially supported by MEC and FEDER Project MTM2010-15200 and by GV Project Prometeo II/2013/013. The research of J. Taskinen was partially supported by the Vaisala Foundation of the Finnish Academy of Sciences and Letters.Bonet Solves, JA.; Taskinen, J. (2015). A note about Volterra operators on weighted Banach spaces of entire functions. Mathematical News / Mathematische Nachrichten. 288(11-12):1216-1225. https://doi.org/10.1002/mana.201400099S1216122528811-1
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