A wide optical-input dynamic range is demonstrated for an inverted p-down InAlAs/InGaAs avalanche photodiode. The 3 dB down bandwidth maintains a value as high as 18 GHz for an input optical power ...level of up to + 2.5 dBm. Such high-power tolerance meets the requirements of various future optical fibre communications systems such as 100 Gbit/s Ethernet which has a serial baud rate of 25 Gbit/s. PUBLICATION ABSTRACT
Utilizando un conjunto experimental especialmente diseñado, hemos estudiado la llamada transición de flujo continuo a intermitente en pilas de arena confinadas en una celda de Hele-Shaw donde la ...altura de deposición de la arena puede ser controlada además del flujo de alimentación. A través de mediciones sistemáticas que varían la altura y el flujo de entrada, hemos establecido cómo el tamaño de la pila al que tiene lugar la transición depende de los dos parámetros estudiados. Los resultados obtenidos permiten explicar, al menos semi-cuantitativamente, las observaciones comúnmente reportadas en la literatura, realizadas en experimentos donde la altura de deposición no fue controlada. Using a specially designed experimental set up, we have studied the so-called continuous to intermittent flow transition in sand piles confined in a Hele-Shaw cell where the deposition height of the sand can be controlled in addition to the input flow. Through systematic measurements varying the height and the input flow, we have established how the size of the pile at which the transition takes place depends on the two parameters studied. The results obtained allows to explain, at least semi-quantitatively, the observations commonly reported in the literature, carried out in experiments where the deposition height is not controlled. PACS: Hele-Shaw flows, 47.15.gp; Avalanches (granular systems), 45.70.Ht; Avalanches, phase transitions in, 64.60.av; Granular systems, classical mechanics of, 45.70.-n
Abstract
The UIS characteristic of the device is a key parameter of the super-junction MOSFET, which represents the reliable performance of the device in the face of extreme conditions. The maximum ...avalanche energy (
E
AS
) that the device can withstand under a single pulse of the gate electrode or the maximum avalanche energy (
E
AR
) that the device can withstand under multiple pulses of the gate electrode is commonly used in the industry to characterize the UIS characteristic. To solve the avalanche energy problem of super-junction MOSFET, we propose a novel structure of super-junction MOSFET with a P-type diffused region on the top of the N-column drift region.
The Tamins rock avalanche lies adjacent to the Flims rock avalanche, the largest in the Alps. Its deposit forms a ridge across the Rhine Valley just downstream of the confluence of the Vorderrhein ...and Hinterrhein rivers. The deposit is dominated by a 1.6-km-long longitudinal ridge, Ils Aults, and two roughly 600-m-long transverse ridges. Several extensional scarps bear witness to spreading of the deposit. A breach through the deposit, where the Rhine River presently flows, reveals a carapace and intense fragmentation. Exposure dating using cosmogenic
36
Cl yields an age of 9420 ± 880 years. This suggests that the Tamins event occurred in a time frame similar to the Flims event but was slightly earlier than the Flims rock avalanche, as also required by stratigraphic relationships. 3D volume modeling reveals bulking of only 14%. The motion of the rock avalanche seems to have occurred first as a flexible block, which underwent fragmentation and simple shearing where the top moved faster than the bottom. The ensuing spreading led to the formation of extensional scarps. There is no identified weak layer along the sliding surface; nevertheless, modeling suggests a friction angle of 10°.
In mountainous areas, channelized rock avalanches swarm downslope leading to large impact forces on building structures in residential areas. Arrays of rock avalanche baffles are usually installed in ...front of rigid barriers to attenuate the flow energy of rock avalanches. However, previous studies have not sufficiently addressed the mechanisms of interaction between the rock avalanches and baffles. In addition, empirical design approaches such as debris flow (Tang et al., Quat Int 250:63–73,
2012
), rockfall (Spang and Rautenstrauch, 1237–1243,
1988
), snow avalanches (Favier et al., 14:3–15,
2012
), and rock avalanches (Manzella and Labiouse, Landslides 10:23–36,
2013
), which are applied in natural geo-disasters mitigation cannot met construction requirements. This study presents details of numerical modeling using the discrete element method (DEM) to investigate the effect of the configuration of baffles (number and spacing of baffle columns and rows) on the impact force that rock avalanches exert on baffles. The numerical modeling is firstly conducted to provide insights into the flow interaction between rock avalanches and an array of baffles. Then, a modeling analysis is made to investigate the change pattern of the impact force with respect to baffle configurations. The results demonstrate that three crucial influencing factors (baffle row numbers, baffle column spacing, and baffle row spacing) have close relationship with energy dissipation of baffles. Interestingly, it is found that capacity of energy dissipation of baffles increases with increasing baffle row numbers and baffle row spacing, while it decreases with increasing baffle column spacing. The results obtained from this study are useful for facilitating design of baffles against rock avalanches.
Landau–Ginzburg theory of cortex dynamics di Santo, Serena; Villegas, Pablo; Burioni, Raffaella ...
Proceedings of the National Academy of Sciences - PNAS,
02/2018, Volume:
115, Issue:
7
Journal Article
Peer reviewed
Open access
Understanding the origin, nature, and functional significance of complex patterns of neural activity, as recorded by diverse electrophysiological and neuroimaging techniques, is a central challenge ...in neuroscience. Such patterns include collective oscillations emerging out of neural synchronization as well as highly heterogeneous outbursts of activity interspersed by periods of quiescence, called “neuronal avalanches.” Much debate has been generated about the possible scale invariance or criticality of such avalanches and its relevance for brain function. Aimed at shedding light onto this, here we analyze the large-scale collective properties of the cortex by using a mesoscopic approach following the principle of parsimony of Landau–Ginzburg. Our model is similar to that of Wilson–Cowan for neural dynamics but crucially, includes stochasticity and space; synaptic plasticity and inhibition are considered as possible regulatory mechanisms. Detailed analyses uncover a phase diagram including down-state, synchronous, asynchronous, and up-state phases and reveal that empirical findings for neuronal avalanches are consistently reproduced by tuning our model to the edge of synchronization. This reveals that the putative criticality of cortical dynamics does not correspond to a quiescent-to-active phase transition as usually assumed in theoretical approaches but to a synchronization phase transition, at which incipient oscillations and scale-free avalanches coexist. Furthermore, our model also accounts for up and down states as they occur (e.g., during deep sleep). This approach constitutes a framework to rationalize the possible collective phases and phase transitions of cortical networks in simple terms, thus helping to shed light on basic aspects of brain functioning from a very broad perspective.
Abstract
The work considers methods for the prediction of the avalanche danger. It shown that for the local forecasts the most efficient way is to simulate snow mass by the particles dynamics ...technique. Basin on this model it is possible to predict the critical parameters for the avalanche sliding, the character of motion of snow mass, the force and energy of its impact on the movable and immovable obstacles with different shape and, hence, a destructive avalanche ability.
Criticality between Cortical States Fontenele, Antonio J; de Vasconcelos, Nivaldo A P; Feliciano, Thaís ...
Physical review letters,
2019-May-24, Volume:
122, Issue:
20
Journal Article
Peer reviewed
Open access
Since the first measurements of neuronal avalanches, the critical brain hypothesis has gained traction. However, if the brain is critical, what is the phase transition? For several decades, it has ...been known that the cerebral cortex operates in a diversity of regimes, ranging from highly synchronous states (with higher spiking variability) to desynchronized states (with lower spiking variability). Here, using both new and publicly available data, we test independent signatures of criticality and show that a phase transition occurs in an intermediate value of spiking variability, in both anesthetized and freely moving animals. The critical exponents point to a universality class different from mean-field directed percolation. Importantly, as the cortex hovers around this critical point, the avalanche exponents follow a linear relation that encompasses previous experimental results from different setups and is reproduced by a model.
Continuum numerical modeling of dynamic crack propagation has been a great challenge over the past decade. This is particularly the case for anticracks in porous materials, as reported in sedimentary ...rocks, deep earthquakes, landslides, and snow avalanches, as material inter-penetration further complicates the problem. Here, on the basis of a new elastoplasticity model for porous cohesive materials and a large strain hybrid Eulerian-Lagrangian numerical method, we accurately reproduced the onset and propagation dynamics of anticracks observed in snow fracture experiments. The key ingredient consists of a modified strain-softening plastic flow rule that captures the complexity of porous materials under mixed-mode loading accounting for the interplay between cohesion loss and volumetric collapse. Our unified model represents a significant step forward as it simulates solid-fluid phase transitions in geomaterials which is of paramount importance to mitigate and forecast gravitational hazards.
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