4,668 research outputs found
The radial evolution of the solar wind, 1-10 AU
The interplanetary plasma and magnetic field observations from 1 to 10 AU are reviewed. Over this distance no clear reduction in average speed is seen. The range of wind speeds becomes smaller though high speed streams are still observed. The density, temperature and magnetic field profiles become dominated by the large values seen in the co-rotating interaction regions. The temperature falls more slowly than would be expected from a simple, adiabatic model. Co-rotating shocks appear beyond approximately 3 AU in Voyager data as opposed to beyond approximately 1.5 AU in the Pioneer data. Reverse shocks appear later than forward shocks; reverse shocks do not begin to appear until approximately 4 AU; reverse shocks appear to decay more rapidly than forward shocks. No clear effect due to interaction with the interstellar medium was seen in this radial range
Stream dynamics between 1 AU and 2 AU: A detailed comparison of observations and theory
A radial alignment of three solar wind stream structures observed by IMP-7 and -8 (at 1.0 AU) and Voyager 1 and 2 (in the range 1.4 to 1.8 AU) in late 1977 is presented. It is demonstrated that several important aspects of the observed dynamical evolution can be both qualitatively and quantitatively described with a single-fluid 2-D MHD numerical model of quasi-steady corotating flow, including accurate prediction of: (1) the formation of a corotating shock pair at 1.75 AU in the case of a simple, quasi-steady stream; (2) the coalescence of the thermodynamic and magnetic structures associated with the compression regions of two neighboring, interacting, corotating streams; and (3) the dynamical destruction of a small (i.e., low velocity-amplitude, short spatial-scale) stream by its overtaking of a slower moving, high-density region associated with a preceding transient flow. The evolution of these flow systems is discussed in terms of the concepts of filtering and entrainment
Ice Gouge Depth Determination Via an Efficient Stochastic Dynamics Technique
A simplified model of the motion of a grounding iceberg for determining the gouge depth into the seabed is proposed. Specifically, taking into account uncertainties relating to the soil strength, a nonlinear stochastic differential equation governing the evolution of the gouge length/depth in time is derived. Further, a recently developed Wiener path integral (WPI) based approach for solving approximately the nonlinear stochastic differential equation is employed; thus, circumventing computationally demanding Monte Carlo based simulations and rendering the approach potentially useful for preliminary design applications. The accuracy/reliability of the approach is demonstrated via comparisons with pertinent Monte Carlo simulation (MCS) data
Geographic classification of U.S. Washington State wines using elemental and water isotope composition
Wine fraud leaves wineries vulnerable to damage in reputation and potential lost revenue. To reduce this risk for wines from Washington State (WA), USA, advanced analytical instrumentation and statistical methods were employed to geographically classify 133 wines from 4 major wine producing regions, including 70 wines from WA. Analyses of 37 elements and 2 water isotopes were performed with Triple Quadrupole Inductively Coupled Plasma Mass Spectrometry and Cavity Ring-Down Spectroscopy, respectively. Linear discriminant analysis resulted in 96.2% discrimination, achieved with 11 parameters (Mn, Zn, Pb, Ni, As, D/H, La, Ce, Si, Zr and Sr) that were linearly combined into 3 functions. WA wines were uniquely distinguished in large part with low D/H ratios and Mn concentrations derived from the isotopically light precipitation and volcanic loess soils encountered in this region, respectively. This study is the first of its kind to focus on the authentication of WA wines
New Trends in Homeric Scholarship Homer’s Name, Underworld and Lyric Voice
This paper hosts three case-studies that are meant to be representative of paradigm-shifting trends in Homeric Studies and to cater to specialists and non-specialists alike. Boosted by new archaeological findings and by an increased awareness of Homer’s Near-Eastern entanglements, the “historicity” of the poems has regained centre stage. Against this backdrop, Andrea Debiasi develops a persuasive interpretation of Homer’s name, whose meaning points to the performative-agonistic dimension of Homeric poetry in the context of the clashes that characterized Euboia in the archaic age. By contrast, George Gazis focuses on the one aspect of the Homeric world that cannot possibly be mapped onto space and history, namely Hades. The underworld is unfathomable even for the gods, which accounts for its potential as a trigger of poetic invention. No less than Debiasi’s, this approach resonates with recent scholarship: a return to “history” is often complemented by an opposite, but fully compatible, “symbolic” trend, which has unraveled the systematic juxtaposition, in Homer’s world, between “history” and symbolic constructs. Finally, Cecilia Nobili shows that Homeric epics builds on pre-existing poetic genres such as elegy, although the earliest extant examples of the latter date to a later time. The claim that lyric poetry emerges though a confrontation with epics, then, is no less plausible than its opposite. One more important consequence of Nobili’s approach is that the “subjective” turn scholars have long recognized in Hellenistic and Roman epics is in fact firmly grounded in Homer himself.L’articolo presenta un saggio di alcune fra le tendenze che più hanno rinnovato gli studi omerici negli ultimi anni e che più possono interessare anche i non specialisti. Nel quadro del rinnovato interesse per la “storicità” dei poemi, favorita da nuove scoperte archeologiche e da una migliore conoscenza degli stretti rapporti fra epica greca e tradizioni vicino-orientali, Andrea Debiasi propone una convincente interpretazione del nome di Omero, che indica in lui il “performer-agonista” per eccellenza e ne proietta la biografia fantastica sullo sfondo delle guerre che segnarono l’Eubea in età arcaica. Quello che in Omero è chiaramente fuori dalla carta geografica e dal tempo storico è invece oggetto dello studio di George Gazis, dedicato all’Ade: un mondo invisibile agli stessi dèi, sottratto al tempo allo spazio e quindi luogo di incubazione per la consapevole invenzione, anche poetica – negli studi recenti, il ritorno della “storia” è andato di pari passo con la tendenza opposta ma perfettamente compatibile di ritrovare nei poemi una giustapposi-zione continua e sistematica fra realia e rappresentazioni simboliche. Infine, Cecilia Nobili mostra che l’epica omerica presuppone l’esistenza di generi poetici, come l’elegia, che sono attestati solo in epiche più tarde: dire che la lirica nasce da un confronto oppositivo con l’epica si rivela quindi non più vero del suo contrario, e la svolta “soggettiva” spesso attribuita all’epica ellenistica e poi romana ha in realtà un saldo ancoraggio nello stesso Omero
Traffic Network Optimum Principle - Minimum Probability of Congestion Occurrence
We introduce an optimum principle for a vehicular traffic network with road
bottlenecks. This network breakdown minimization (BM) principle states that the
network optimum is reached, when link flow rates are assigned in the network in
such a way that the probability for spontaneous occurrence of traffic breakdown
at one of the network bottlenecks during a given observation time reaches the
minimum possible value. Based on numerical simulations with a stochastic
three-phase traffic flow model, we show that in comparison to the well-known
Wardrop's principles the application of the BM principle permits considerably
greater network inflow rates at which no traffic breakdown occurs and,
therefore, free flow remains in the whole network.Comment: 22 pages, 6 figure
Coupled-Map Modeling of One-Dimensional Traffic Flow
We propose a new model of one-dimensional traffic flow using a coupled map
lattice. In the model, each vehicle is assigned a map and changes its velocity
according to it. A single map is designed so as to represent the motion of a
vehicle properly, and the maps are coupled to each other through the headway
distance. By simulating the model, we obtain a plot of the flow against the
concentration similar to the observed data in real traffic flows. Realistic
traffic jam regions are observed in space-time trajectories.Comment: 5 postscript figures available upon reques
Performances of Anode-resistive Micromegas for HL-LHC
Micromegas technology is a promising candidate to replace Atlas forward muon
chambers -tracking and trigger- for future HL-LHC upgrade of the experiment.
The increase on background and pile-up event probability requires detector
performances which are currently under studies in intensive RD activities.
We studied performances of four different resistive Micromegas detectors with
different read-out strip pitches. These chambers were tested using \sim120 GeV
momentum pions, at H6 CERN-SPS beam line in autumn 2010. For a strip pitch 500
micrometers we measure a resolution of \sim90 micrometers and a efficiency of
~98%. The track angle effect on the efficiency was also studied. Our results
show that resistive techniques induce no degradation on the efficiency or
resolution, with respect to the standard Micromegas. In some configuration the
resistive coating is able to reduce the discharge currents at least by a factor
of 100.Micromegas technology is a promising candidate to replace Atlas forward
muon chambers -tracking and trigger- for future HL-LHC upgrade of the
experiment. The increase on background and pile-up event probability requires
detector performances which are currently under studies in intensive RD
activities. We studied performances of four different resistive Micromegas
detectors with different read-out strip pitches. These chambers were tested
using \sim120 GeV momentum pions, at H6 CERN-SPS beam line in autumn 2010. For
a strip pitch 500 micrometers we measure a resolution of \sim90 micrometers and
a efficiency of \sim98%. The track angle effect on the efficiency was also
studied. Our results show that resistive techniques induce no degradation on
the efficiency or resolution, with respect to the standard Micromegas. In some
configuration the resistive coating is able to reduce the discharge currents at
least by a factor of 100.Comment: "Presented at the 2011 Hadron Collider Physics symposium (HCP-2011),
Paris, France, November 14-18 2011, 3 pages, 6 figures.
The Effects of the Intense Solar Activity of March/June 1991 Observed in the Outer Heliosphere
The properties of the large scale Global Merged Interaction Region(GMIR)generated by the intense solar events of March and June 1991 with their marked south-north assymetry are studied using the available solar wind, interplanetary
magnetic field and energetic particle data from the observing network of Pioneer 10 and Voyager 1 and 2 in the outer heliosphere
Multi-Bunch Solutions of Differential-Difference Equation for Traffic Flow
Newell-Whitham type car-following model with hyperbolic tangent optimal
velocity function in a one-lane circuit has a finite set of the exact solutions
for steady traveling wave, which expressed by elliptic theta function. Each
solution of the set describes a density wave with definite number of
car-bunches in the circuit. By the numerical simulation, we observe a
transition process from a uniform flow to the one-bunch analytic solution,
which seems to be an attractor of the system. In the process, the system shows
a series of cascade transitions visiting the configurations closely similar to
the higher multi-bunch solutions in the set.Comment: revtex, 7 pages, 5 figure
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