With digital equipment becoming increasingly networked, either on wired or wireless networks, for personal and professional use alike, distributed software systems have become a crucial element in information and communications technologies. The study of these systems forms the core of the ARLES' work, which is specifically concerned with defining new system software architectures, based on the use of emerging networking technologies. In this context, we concentrate on the study of distributed systems which bring to life the vision of ubiquitous computing systems, also known as ambient intelligence.

반도체 공정 overview

http://szseminar.asu.edu/readings/EPSL_Schmidt_1998.pdf

Experimentally based water budgets for dehydrating slabs and consequences for arc magma generation

Fluids and melts liberated from subducting oceanic crust recycle lithophile elements back into the mantle wedge, facilitate melting and ultimately lead to prolific subduction-zone arc volcanism1,2 The nature and composition of the mobile phases generated in the subducting slab at high pressures have, however, remained largely unknown3,4,5,6,7 Here we report direct LA-ICPMS measurements of the composition of fluids and melts equilibrated with a basaltic eclogite at pressures equivalent to depths in the Earth of 120–180 km and temperatures of 700–1,200 °C The resultant liquid/mineral partition coefficients constrain the recycling rates of key elements The dichotomy of dehydration versus melting at 120 km depth is expressed through contrasting behaviour of many trace elements (U/Th, Sr, Ba, Be and the light rare-earth elements) At pressures equivalent to 180 km depth, however, a supercritical liquid with melt-like solubilities for the investigated trace elements is observed, even at low temperatures This mobilizes most of the key trace elements (except the heavy rare-earth elements, Y and Sc) and thus limits fluid-phase transfer of geochemical signatures in subduction zones to pressures less than 6 GPa

Trace element signature of subduction-zone fluids, melts and supercritical liquids at 120–180 km depth

The global range of subduction zone thermal models

This chapter has four main aims. Provide a comprehensive picture of the composition of volcanic rocks from subduction-related magmatic arcs. Review evidence in favor of the existence of andesitic, as well as basaltic primary magmas in arcs. Present new data on the composition of arc lower crust, based mainly on our work on the Talkeetna arc section in southcentral Alaska. Summarize evidence from arc lower crustal sections that a substantial proportion of the dense, lower crustal pyroxenites and garnet granulites produced by crystal fractionation are missing.

One View of the Geochemistry of Subduction-Related Magmatic Arcs, with an Emphasis on Primitive Andesite and Lower Crust

Results of fluid dynamical experiments on the behavior of subducted slabs are presented that address two important characteristics of subduction: slab penetration through the transition zone and horizontal slab migration. Cold, negatively buoyant molded slabs of concentrated sucrose solution, with viscosities of 3–5 × 106 P were introduced into a more dilute, two-layered sucrose solution representing the upper and lower mantle. The transition zone was modeled by a step increase in both density and viscosity. Ratios of slab thickness to upper layer depth, the relative viscosities in each layer, and the effective Rayleigh number were close to mantle values. The initial configuration consisted of two plates separated by a trench gap, with one plate attached to a dipping slab, simulating a developing subduction zone with an overriding plate. Two different boundary conditions were used at the trailing (ridge) end of the subducting plate: (1) fixed end, corresponding to zero ridge motion, and (2) free end, corresponding to zero ridge resistance. Based on results from 15 experiments with various combinations of upper layer, lower layer, and slab densities (ρU, ρL, ρS) and viscosities, we find that slab penetration depth is sensitive to both the normalized slab density anomaly R = (ρS - ρL)/(ρS - ρU) and the dip angle. Three penetration regimes are recognized: R ≳ 0.5, in which the slab sinks into the lower layer without distortion; −0.2 ≲ R ≲ 0.5, which permits limited penetration, the amount dependent on dip angle (in this regime the slab develops a thick root just beneath the transition zone); and R < −0.2, in which the slab is deflected by the transition, and little or no penetration occurs. Retrograde slab motion and trench migration occurred in nearly every case, with the overriding plate moving parallel to but faster than the trench, causing the gap between subducting and overriding plates to close with time. Prograde trench motion was never observed, and the trench remained stationary only in the extreme case (free ridge condition with equal upper and lower layer densities). These results suggest that the transient extension found in many back arc basins may be a direct consequence of the tendency for retrograde subduction and the amount of extension may be governed in part by the degree of slab penetration through the transition zone.

An experimental study of subduction and slab migration

We present results from two-dimensional (2-D) numerical experiments on the thermal and dynamical evolution of the subducting slab and of the overlying mantle wedge for a range in subduction parameters. These include subduction rate and the age and rheology of both subducting and overriding plates. Experiments also consider the influence of slab forcing conditions (from purely kinematic to purely dynamic) on the evolution of both the slab and mantle wedge. One goal is to determine how different parameters control thermal evolution of the slab-wedge interface, from just after subduction initiation up through roughly 500–600 km of subduction, where temperatures are approaching steady state. An additional goal is to define optimal conditions for the melting of slab sediments and crust. Results show slab surface temperatures (SSTs) depend strongly on subduction velocity, plate thermal structure, and upper mantle (or wedge) viscosity structure. Fast subduction beneath a thick (>70 km) overriding plate results in the coolest SSTs. Maximum SSTs are recorded as an early transient event for cases of slow subduction ( 100 km) which deflects the zone of maximum shear away from slab-wedge interface.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/96JB03553

Thermal and dynamical evolution of the upper mantle in subduction zones

The subduction of oceanic lithosphere plays a key role in plate tectonics, the thermal evolution of the mantle and recycling processes between Earth's interior and surface. Information on mantle flow, thermal conditions and chemical transport in subduction zones come from the geochemistry of arc volcanoes1,2,3, seismic images4,5 and geodynamic models6,7,8,9,10. The majority of this work considers subduction as a two-dimensional process, assuming limited variability in the direction parallel to the trench. In contrast, observationally based models increasingly appeal to three-dimensional flow associated with trench migration and the sinking of oceanic plates with a translational component of motion11 (rollback). Here we report results from laboratory experiments that reveal fundamental differences in three-dimensional mantle circulation and temperature structure in response to subduction with and without a rollback component. Without rollback motion, flow in the mantle wedge is sluggish, there is no mass flux around the plate and plate edges heat up faster than plate centres. In contrast, during rollback subduction flow is driven around and beneath the sinking plate, velocities increase within the mantle wedge and are focused towards the centre of the plate, and the surface of the plate heats more along the centreline.

Laboratory models of the thermal evolution of the mantle during rollback subduction

Recent geochemical studies of uranium-thorium series disequilibrium in rocks from subduction zones require magmas to be transported through the mantle from just above the subducting slab to the surface in as little as ∼30,000 years. We present a series of laboratory experiments that investigate the characteristic time scales and flow patterns of the diapiric upwelling model of subduction zone magmatism. Results indicate that the interaction between buoyantly upwelling diapirs and subduction-induced flow in the mantle creates a network of low-density, low-viscosity conduits through which buoyant flow is rapid, yielding transport times commensurate with those indicated by uranium-thorium studies.

https://science.sciencemag.org/content/sci/292/5526/2472.full.pdf

Diapiric Flow at Subduction Zones: A Recipe for Rapid Transport

Accumulation and survival of compositional heterogeneity at the base of the convecting mantle is investigated using laboratory experiments with temperature dependent viscous fluids. Two models of heterogeneity in the D” layer are considered: (1) a reservoir of dense material above the core-mantle boundary and (2) continuous recharge of the D” layer by subduction of cold, negatively buoyant high viscosity slabs of oceanic lithosphere. Survival of a dense reservoir depends on Rp, the ratio of stabilizing compositional buoyancy to destabilizing thermal buoyancy. Rapid mixing occurs for Rp ≤ 1; for Rp ≥ 1, mixing occurs by slow entrainment only. The reservoir model predicts D” layer heterogeneity is concentrated beneath lower mantle upwellings. Differentiation of composite slabs, consisting of dense crustal and light depleted components, occurs in a hot thermal boundary layer. Composite slabs pile up in the basal thermal boundary layer, and upon heating the light component is ejected by Rayleigh-Taylor instabilities. The dense component accumulates in the boundary layer, arrayed in a pattern of interconnected spokes, and is slowly entrained into thermal plumes. According to these experiments the time required for conversion of slabs to plumes in D” is 1–2 Gyr. The correlation between lateral variations in D” layer thickness and lateral variations in lower mantle seismic velocity suggests that D″ may consist of dense material, perhaps former oceanic lithosphere, which has sunk through the lower mantle.

Chris Kincaid

Papers

An experimental study of subduction and slab migration

Thermal and dynamical evolution of the upper mantle in subduction zones

Laboratory models of the thermal evolution of the mantle during rollback subduction

Diapiric Flow at Subduction Zones: A Recipe for Rapid Transport

Experiments on the interaction of thermal convection and compositional layering at the base of the mantle