The role of elasticity in slab bending

International audiencePrevious studies showed that plate rheology exerts a dominant control on the shape and velocity of subducting plates. Here, we perform a systematic investigation of the role of elasticity in slab bending, using fully dynamic 2-D models where an elastic, viscoelastic, or viscoelastoplastic plate subducts freely into a purely viscous mantle. We derive a scaling relationship between the bending radius of viscoelastic slabs and the Deborah number, De, which is the ratio of Maxwell time over deformation time. We show that De controls the ratio of elastically stored energy over viscously dissipated energy and find that at De>10-2, substantially less energy is required to bend a viscoelastic slab to the same shape as a purely viscous slab with the same intrinsic viscosity. Elastically stored energy at higher De favors retreating modes of subduction via unbending, while trench advance only occurs for some cases with De 1, where most zones have low De 0.1. Slabs with De<10-2 either have very low viscosities or they may be yielding, in which case our De estimates may be underestimated by up to an order of magnitude, potentially pointing towards a significant role of elasticity in ∼60% of the subduction zones. In support of such a role of elasticity in subduction, we find that increasing De correlates with increasing proportion of larger seismic events in both instrumental and historic catalogues

Multi-bit sigma-delta modulators with enhanced dynamic-range using non-linear DAC for hearing aids

15th IEEE International Conference on Electronics, Circuits and Systems, MaltaThis paper presents the possibility of employing nonlinear low-resolution DACs in the feedback paths of multi-bit second-order Sigma-Delta modulators. The proposed technique is particularly attractive in applications such as hearing aids, requiring a very large dynamic range and medium signal-tonoise-plus-distortion-ratio. As demonstrated through simulated results in which noise and mismatch effects are included, for the same over-sampling ratio, improvements in the order of 6-to-9 dB in the dynamic range can be achieved when comparing with the same topology employing linear-DACs

Low-power 6-bit 1-GS/s two-channel pipeline ADC with open-loop amplification using amplifiers with local-feedback

IEEE International Symposium on Circuits and Systems, pp. 2258 – 2261, Seattle, EUAA low-power 1.2 V 6-bit 1-GS/s time-interleaved pipeline ADC designed in 130 nm CMOS is described. It is based on a new 2-channel 1.5-bit MDAC that performs openloop residue amplification using a shared amplifier employing local-feedback. Time mismatches between channels are highly attenuated, simply by using two passive front-end Sample-and-Hold circuits, with dedicated switch-linearization control circuits, driven by a single clock phase. Simulated results of the ADC achieve 5.35-bit ENOB, with 20 mW and without requiring any gain control/calibration scheme

Digital-domain self-calibration technique for video-rate pipeline A/D converters using Gaussian white noise

Electronics Letters Vol.38, nº 19A digital-domain selfsalibmtion technique for video-rate pipeline AID converters based an a Gaussian white noise input signal is presented. The pmposed algorithm is simple and efficient. A design example is shown 10 illustrate that the overall linemiry of a pipeline ADC can be highly improved using this technique

Design of improved rail-to-rail low-distortion and low-stress switches in advanced CMOS technologies

This paper describes the efficient design of an improved and dedicated switched-capacitor (SC) circuit capable of linearizing CMOS switches to allow SC circuits to reach low distortion levels. The described circuit (SC linearization control circuit, SLC) has the advantage over conventional clock-bootstrapping circuits of exhibiting low-stress, since large gate voltages are avoided. This paper presents exhaustive corner simulation results of a SC sample-and-hold (S/H) circuit which employs the proposed and optimized circuits, together with the experimental evaluation of a complete 10-bit ADC utilizing the referred S/H circuit. These results show that the SLC circuits can reduce distortion and increase dynamic linearity above 12 bits for wide input signal bandwidths

A FRAMEWORK TO SUPPORT SERVICE-ORIENTED ARCHITECTURE INVESTMENT DECISION

Service-oriented architecture (SOA) is a system paradigm that structures business functions as loosely coupled services to enable business agility. SOA requires significant up-front investments, and in return, promises a vast array of benefits. Unfortunately, in contrast to the costs of the investment, monetary benefits associated with SOA are more difficult to measure. For one reason, benefits such as increased agility or improved flexibility are elusive in nature, making it harder to define metrics for their calculation. For another, SOA value is realized in long term under uncertainty, and traditional capital budgeting methods often fail to capture uncertainty when valuing investments. In this paper, we provide a decision framework to analyze the monetary impact of SOA investment in an organization. Combining traditional NPV analysis with option pricing models, our framework accounts for operational and strategic costs and benefits of SOA and proposes an extended investment value to support managerial investment decision

Absorption and fluorescence properties of chromophoric dissolved organic matter of the eastern Bering Sea in the summer with special reference to the influence of a cold pool

The absorption and fluorescence properties of chromophoric dissolved organic matter (CDOM) are reported for the inner shelf, slope waters and outer shelf regions of the eastern Bering Sea during the summer of 2008, when a warm, thermally stratified surface mixed layer lay over a cold pool (< 2 °C) that occupied the entire middle shelf. CDOM absorption at 355 nm (<i>a</i>_g355) and its spectral slope (<i>S</i>) in conjunction with excitation–emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC) revealed large variability in the characteristics of CDOM in different regions of the Bering Sea. PARAFAC analysis aided in the identification of three humic-like (components one, two and five) and two protein-like (a tyrosine-like component three, and a tryptophan-like component four) components. In the extensive shelf region, average absorption coefficients at 355 nm (<i>a</i>_g355, m⁻¹) and DOC concentrations (μM) were highest in the inner shelf (0.342 ± 0.11 m⁻¹, 92.67 ± 14.60 μM) and lower in the middle (0.226 ± 0.05 m⁻¹, 78.38 ± 10.64 μM) and outer (0.185 ± 0.05 m⁻¹, 79.24 ± 18.01 μM) shelves, respectively. DOC concentrations, however were not significantly different, suggesting CDOM sources and sinks to be uncoupled from DOC. Mean spectral slopes <i>S</i> were elevated in the middle shelf (24.38 ± 2.25 μm⁻¹) especially in the surface waters (26.87 ± 2.39 μm⁻¹) indicating high rates of photodegradation in the highly stratified surface mixed layer, which intensified northwards in the northern middle shelf likely contributing to greater light penetration and to phytoplankton blooms at deeper depths. The fluorescent humic-like components one, two, and five were most elevated in the inner shelf most likely from riverine inputs. Along the productive "green belt" in the outer shelf/slope region, absorption and fluorescence properties indicated the presence of fresh and degraded autochthonous DOM. Near the Unimak Pass region of the Aleutian Islands, low DOC and <i>a</i>_g355 (mean 66.99 ± 7.94 μM; 0.182 ± 0.05 m⁻¹) and a high <i>S</i> (mean 25.95 ± 1.58 μm⁻¹) suggested substantial photobleaching of the Alaska Coastal Water, but high intensities of humic-like and protein-like fluorescence suggested sources of fluorescent DOM from coastal runoff and glacier meltwaters during the summer. The spectral slope <i>S</i> vs. <i>a</i>_g355 relationship revealed terrestrial and oceanic end members along with intermediate water masses that were modeled using nonlinear regression equations that could allow water mass differentiation based on CDOM optical properties. Spectral slope <i>S</i> was negatively correlated (<i>r</i>² = 0.79) with apparent oxygen utilization (AOU) for waters extending from the middle shelf into the deep Bering Sea indicating increasing microbial alteration of CDOM with depth. Although our data show that the CDOM photochemical environment of the Bering Sea is complex, our current information on its optical properties will aid in better understanding of the biogeochemical role of CDOM in carbon budgets in relation to the annual sea ice and phytoplankton dynamics, and to improved algorithms of ocean color remote sensing for this region

Controlo por fase única de conversores A/D de baixa tensão

Este trabalho apresenta a aplicação de um controlo de fase única a um conversor concorrencial de baixa tensão. Com vista à validação da análise e conclusão teóricas, um conversor concorrencial de 10-bit 4 MS/s foi projectado e simulado. Foi primeiramente simulado com um controlo clássico de 6 fases, e posteriormente com um esquema de fase única. Os resultados de simulação mostram que as características globais são mantidas, apontando para que o uso de esquemas de fase única em conversores de baixa tensão seja uma solução que reduz a complexidade dos sistemas clássicos não sobrepostos.info:eu-repo/semantics/publishedVersio