1,692 research outputs found
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><sub>g</sub>355) 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><sub>g</sub>355, m<sup>−1</sup>) and DOC concentrations (μM)
were highest in the inner shelf (0.342 ± 0.11 m<sup>−1</sup>,
92.67 ± 14.60 μM) and lower in the middle
(0.226 ± 0.05 m<sup>−1</sup>, 78.38 ± 10.64 μM) and outer
(0.185 ± 0.05 m<sup>−1</sup>, 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<sup>−1</sup>) especially in the surface waters
(26.87 ± 2.39 μm<sup>−1</sup>) 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><sub>g</sub>355
(mean 66.99 ± 7.94 μM; 0.182 ± 0.05 m<sup>−1</sup>) and a
high <i>S</i> (mean 25.95 ± 1.58 μm<sup>−1</sup>) 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><sub>g</sub>355 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><sup>2</sup> = 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
A multiplying-by-two CMOS amplifier for high-speed ADCs based on parametric amplification
15th International Conference on Mixed Design of Integrated Circuits and Systems, pp. 177 – 180, Poznan, PolóniaIn this paper a new structure for a multiplying-by-two amplifier is proposed. It is implemented by
switching MOS capacitors with floating sources from inversion into depletion dropping the capacitance values in the
amplification phase. Low-power is achieved since no operational amplifiers are required but, instead, simple sourcefollowers
are used to provide the required isolation. Simulation results show that linearity levels better than 60dB and
gain accuracies of better than 1.6% are achieved making this circuit well suited to be used in ultra low-power highspeed
6-to-8 bits pipeline or multi-stage algorithmic ADCs
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