1,579 research outputs found
Spiking Chemical Sensor (SCS): A new platform for neuro-chemical sensing
No full textPublished versio
Towards a Reconfigurable Sense-and-Stimulate Neural Interface Generating Biphasic Interleaved Stimulus
No full textPublished versio
Non-destructive evaluation of cement-based materials from pressure-stimulated electrical emission - Preliminary results
No full textThis is the post-print version of the final paper published in Construction and Building Materials. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2010 Elsevier B.V.This paper introduces the possibility of in situ assessment of loading and remaining strength in concrete structures by means of measuring discharge of electric current from loaded specimens.
The paper demonstrates that the techniques have been applied to other rock-like materials, but that for the first time they are applied to cement-based materials and a theoretical model is proposed in relation to the appearance of electrical signals during sample loading and up to fracture.
A series of laboratory experiments on cement mortar specimens in simple uniaxial compression, and subsequently in bending – hence displaying both tension and compression – are described and show clear correlations between resulting strains and currents measured. Under uniaxial loading there is a well-defined relationship between the pressure-stimulated current (PSC) as a result of a monotonic mechanical loading regime. Similar results are observed in the three-point bending tests where a range of loading regimes is studied, including stepped changes in loading.
While currents can be measured at low strains, best results seem to be obtained when strains approach and exceed yield stress values.
This technique clearly has immense potential for structural health monitoring of cement-based structures. Both intermittent and continuous monitoring becomes possible, and given an ongoing campaign of monitoring, remaining strength can be estimated
Numerical predictions of the fatigue life of aluminium welded joints
No full textThe fatigue life of arc welded joints made of aluminium alloy has been investigated by means of the implicit gradient method. This approach is suitable for estimating the fatigue life of welded joints characterised by different opening angles of the fillet weld and different thicknesses. The main fatigue data are related to cruciform joints, rectangular hollow section T-joints and bead removed joints. Using the principal stress as the local equivalent stress and a notch tip of the weld toe radius equal to zero, the paper analyses about two hundred experimental data taken from the literature and proposes a universal scatter band in the range of 104 to 5·106 cycles. This scatter band has an inverse slope around 4 and, at high cycle fatigue, the strength is about half that of steel joints. However, the scatter band is similar to welded joints made of steel previously analyse
Correlation of pressure stimulated currents in rocks with the damage parameter
No full textPressure Stimulated Current (PSC) experiments were conducted on marble samples to correlate PSC with the
damage parameter, D. The phenomena and procedures taking place in the vicinity of the fracture limit were observed
and analytically described. PSC recordings were conducted by application of uniaxial compressional
stress, both at a constant stress rate and at a constant deformation rate. A linear relationship was shown to exist
between the emitted PSC and the damage parameter which quantifies the deviation from linear elasticity and the
concentration of microcracks.JCR Journalope
Incentives vs. Control: An Analysis of U.S. Dual-Class Companies
No full textDual-class common stock allows for the separation of voting rights and cash flow rights across the different classes of equity. We construct a large sample of dual-class firms in the United States and analyze the relationships of insider's cash flow rights and voting rights with firm value, performance, and investment behavior. We find that relationship of firm value to cash flow rights is positive and concave and the relationship to voting rights is negative and convex. Identical quadratic relationships are found for the respective ownership variables with sales growth, capital expenditures, and the combination of R&D and advertising. Our evidence is consistent with an entrenchment effect of voting control that leads managers to underinvest and an incentive effect of cash flow ownership that induces managers to pursue more aggressive strategies.
Injonctions métropolitaines: grands projets de transformation urbaine et jeux institutionnels
No full textIl capitolo analizza la governance delle metropoli dell'Europa meridionale attraverso continuità e rotture e il modo in cui queste città stanno rispondendo agli sconvolgimenti - sia contingenti che sistemici - emersi in seguito alla crisi dei mutui subprime. Queste forze sembrano favorire intensi processi di metropolizzazione e regionalizzazione dell'urbano, che influenzano la rete tra gli attori istituzionali a diversi livelli e il campo dei meccanismi di trasformazione spaziale metropolitana. L'attenzione si concentra sui grandi progetti di sviluppo, perché rivelano una dinamica complessa e controversa. Gli esempi esplorati ad Atene, Madrid, Milano e Roma evidenziano una complessa interazione tra attori globali e locali e l'affermazione di un approccio neoliberale alla pianificazione e alle politiche urbane. Ciò sta portando alla privatizzazione di beni e servizi e, allo stesso tempo, alla finanziarizzazione del territorio urbano.The chapter considers some elements of continuity and rupture in the governance of the metropolis of Southern Europe, trying to understand how they are responding to the various contingent or systemic ‘upheavals’ that have occurred since the 2008 subprime crisis. These forces seem to foster intense processes of metropolisation and regionalisation of the urban, which affect the network between institutional actors at different levels and the field of the mechanisms of metropolitan spatial transformation. The focus is on large-scale urban development projects because they reveal a complex and contested dynamic that has affected the cities of Southern Europe in different ways. Indeed, the cases explored in Athens, Madrid, Milan and Rome highlight the involvement of a complex array of global and local actors and the emergence of a neo-liberal approach to urban planning and policy, which has led to the privatisation of goods and services – and, in the process, to the financialisation of urban land.Le chapitre analyse la gouvernance des métropoles d’Europe du Sud à travers leurs continuités et leurs ruptures et comment ces villes répondent aux bouleversements – contingents ou systémiques – apparus après la crise des « subprimes ».Des processus intenses de métropolisation et de régionalisation de l’urbain investissent aussi bien les réseaux d’acteurs institutionnels à différents niveaux que les mécanismes du changement spatial. L’accent est ici porté sur les grands projets de développement car ils sont révélateurs d’une dynamique complexe et controversée. En effet, les exemples explorés à Athènes, Madrid, Milan et Rome mettent en évidence un jeu complexe d’acteurs globaux et locaux et l’affirmation d’une approche néolibérale de la planification et des politiques urbaines. Celle-ci conduit à la privatisation des biens et des services et, dans le même temps, à la financiarisation du sol urbain
Educational software bundle for studying magnetotelluric theory and specific geoelectric structure models
No full textITC measurements on sodium fluoride doped with Mg+2
No full textIonic thermocurrent measurements ITC were carried out on NaF doped with 50 ppm Mg+2. The ITC spectrum of a preheated crystal consists of two bands with maximum at 236 and 251 K. The analysis of these bands leads to a migration enthalpy hm of 0.78 and 0.83 eV and to a migration entropy sm of 2.1 and 2.6 K respectively. The value of the ratio sm/hm is comparable to the results of other processes (formation and migration) and is comparable to theoretical expectations.On a mesuré le courant thermoionique (ITC) d'un monocristal de NaF, dopé avec 50 ppm de Mg+ 2 et préchauffé. Le spectre ITC de ce cristal a été décomposé en deux bandes, avec les maximums à 236 K et 251 K; elles correspondent à des enthalpies de migration hm de 0,78 et 0,83 eV et à des entropies sm de migration de 2,1 K et 2,6 K. Le rapport sm/hm est comparable à celui d'autres processus (de formation ou de migration de défauts) et à une estimation théorique
High-power CMOS current driver with accurate transconductance for electrical impedance tomography
No full textCurrent drivers are fundamental circuits in bioimpedance measurements including electrical impedance tomography (EIT). In the case of EIT, the current driver is required to have a large output impedance to guarantee high current accuracy over a wide range of load impedance values. This paper presents an integrated current driver which meets these requirements and is capable of delivering large sinusoidal currents to the load. The current driver employs a differential architecture and negative feedback, the latter allowing the output current to be accurately set by the ratio of the input voltage to a resistor value. The circuit was fabricated in a 0.6- μm high-voltage CMOS process technology and its core occupies a silicon area of 0.64 mm (2) . It operates from a ± 9 V power supply and can deliver output currents up to 5 mA p-p. The accuracy of the maximum output current is within 0.41% up to 500 kHz, reducing to 0.47% at 1 MHz with a total harmonic distortion of 0.69%. The output impedance is 665 k Ω at 100 kHz and 372 k Ω at 500 kHz
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