2,199 research outputs found

    Pennsylvanian Rocks and Fusulinids of East Utah and Northwest Colorado Correlated with Kansas Section

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    Stratigraphic sections of Pennsylvanian rocks in the eastern Uinta Mountains of Utah and Colorado and of the lowermost Pennsylvanian in the eastern White River uplift area of northwestern Colorado are illustrated and discussed. Parts of the fusulinid faunas from these sections are described and illustrated. Largely on the basis of them, correlations are made with the stratigraphic section of the midcontinent region. The Belden shale of the White River uplift is described as the Belden formation and limestones and shales of the Uinta Mountains, formerly referred to the upper part of the Brazer formation, are referred to it. The Pennsylvanian rocks in the eastern Uinta Mountains are divided, in ascending order, into the Belden formation, Hell\u27s Canyon formation, Youghall formation, and Weber sandstone. Four species of Millerella are described and illustrated from the Belden formation and several others are identified. As this fauna is composed entirely of Millerella, the Belden formation is referred to the Zone of Millerella and is correlated with the type section of the Morrowan of Arkansas and the Kearny formation of Kansas. Species from the Hell\u27s Canyon formation belonging to Millerella, Pseudostaffella, Eoschubertella, and Fusulinella are identified, 5 of them being described and illustrated. The Hell\u27s Canyon formation is referred to the uppermost part of the Zone of Fusulinella. The Youghall formation contains an abundant fauna of Wedekindellina and Fusulina, 10 forms of which are described and illustrated. The Youghall formation is referred to the Zone of Fusulina and is correlated with the Cherokee of Kansas and Iowa. No fossils were found in the Weber sandstone. Its age was not determined

    Pennsylvanian Morrowan Rocks and Fusulinids of Kansas

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    Subsurface pre-Desmoinesian Pennsylvanian rocks of Kearny County, southwestern Kansas, are named the Kearny formation, and, mainly on the basis of their fusulinid faunas, they are referred to the Morrowan series. Four species and one variety of fusulinids from the type section of the Kearny formation are described and illustrated as Millerella marblensis Thompson, M. pressa, n. sp., M. pinguis, n. sp., M.? advena n. sp., and M.? advena var. ampla, n. var. Also, the fusulinid fauna from the type section of the Morrowan series at Morrow, Arkansas, is here described and illustrated for the first time. All four of the species of fusulinids, and possibly the variety, present in the Kearny formation in Kansas are also recognized in Morrowan rocks of Arkansas

    Solar Stereoscopy with STEREO/EUVI A and B spacecraft from small (6 deg) to large (170 deg) spacecraft separation angles

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    We performed for the first time stereoscopic triangulation of coronal loops in active regions over the entire range of spacecraft separation angles (αsep6,43,89,127\alpha_{sep}\approx 6^\circ, 43^\circ, 89^\circ, 127^\circ, and 170170^\circ). The accuracy of stereoscopic correlation depends mostly on the viewing angle with respect to the solar surface for each spacecraft, which affects the stereoscopic correspondence identification of loops in image pairs. From a simple theoretical model we predict an optimum range of αsep22125\alpha_{sep} \approx 22^\circ-125^\circ, which is also experimentally confirmed. The best accuracy is generally obtained when an active region passes the central meridian (viewed from Earth), which yields a symmetric view for both STEREO spacecraft and causes minimum horizontal foreshortening. For the extended angular range of αsep6127\alpha_{sep}\approx 6^\circ-127^{\circ} we find a mean 3D misalignment angle of μPF2139\mu_{PF} \approx 21^\circ-39^\circ of stereoscopically triangulated loops with magnetic potential field models, and μFFF1521\mu_{FFF} \approx 15^\circ-21^\circ for a force-free field model, which is partly caused by stereoscopic uncertainties μSE9\mu_{SE} \approx 9^\circ. We predict optimum conditions for solar stereoscopy during the time intervals of 2012--2014, 2016--2017, and 2021--2023.Comment: Solar Physics, (in press), 22 pages, 9 figure

    A two-armed bandit based scheme for accelerated decentralized learning

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    The two-armed bandit problem is a classical optimization problem where a decision maker sequentially pulls one of two arms attached to a gambling machine, with each pull resulting in a random reward. The reward distributions are unknown, and thus, one must balance between exploiting existing knowledge about the arms, and obtaining new information. Bandit problems are particularly fascinating because a large class of real world problems, including routing, QoS control, game playing, and resource allocation, can be solved in a decentralized manner when modeled as a system of interacting gambling machines. Although computationally intractable in many cases, Bayesian methods provide a standard for optimal decision making. This paper proposes a novel scheme for decentralized decision making based on the Goore Game in which each decision maker is inherently Bayesian in nature, yet avoids computational intractability by relying simply on updating the hyper parameters of sibling conjugate priors, and on random sampling from these posteriors. We further report theoretical results on the variance of the random rewards experienced by each individual decision maker. Based on these theoretical results, each decision maker is able to accelerate its own learning by taking advantage of the increasingly more reliable feedback that is obtained as exploration gradually turns into exploitation in bandit problem based learning. Extensive experiments demonstrate that the accelerated learning allows us to combine the benefits of conservative learning, which is high accuracy, with the benefits of hurried learning, which is fast convergence. In this manner, our scheme outperforms recently proposed Goore Game solution schemes, where one has to trade off accuracy with speed. We thus believe that our methodology opens avenues for improved performance in a number of applications of bandit based decentralized decision making

    Shear yielding of amorphous glassy solids: Effect of temperature and strain rate

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    We study shear yielding and steady state flow of glassy materials with molecular dynamics simulations of two standard models: amorphous polymers and bidisperse Lennard-Jones glasses. For a fixed strain rate, the maximum shear yield stress and the steady state flow stress in simple shear both drop linearly with increasing temperature. The dependence on strain rate can be described by a either a logarithm or a power-law added to a constant. In marked contrast to predictions of traditional thermal activation models, the rate dependence is nearly independent of temperature. The relation to more recent models of plastic deformation and glassy rheology is discussed, and the dynamics of particles and stress in small regions is examined in light of these findings

    Adsorption-desorption kinetics in nanoscopically confined oligomer films under shear

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    The method of molecular dynamics computer simulations is employed to study oligomer melts confined in ultra-thin films and subjected to shear. The focus is on the self-diffusion of oligomers near attractive surfaces and on their desorption, together with the effects of increasing energy of adsorption and shear. It is found that the mobility of the oligomers near an attractive surface is strongly decreased. Moreover, although shearing the system forces the chains to stretch parallel to the surfaces and thus increase the energy of adsorption per chain, flow also promotes desorption. The study of chain desorption kinetics reveals the molecular processes responsible for the enhancement of desorption under shear. They involve sequences of conformations starting with a desorbed tail and proceeding in a very fast, correlated, segment-by-segment manner to the desorption of the oligomers from the surfaces.

    Deflection and Rotation of CMEs from Active Region 11158

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    Between the 13 and 16 of February 2011 a series of coronal mass ejections (CMEs) erupted from multiple polarity inversion lines within active region 11158. For seven of these CMEs we use the Graduated Cylindrical Shell (GCS) flux rope model to determine the CME trajectory using both Solar Terrestrial Relations Observatory (STEREO) extreme ultraviolet (EUV) and coronagraph images. We then use the Forecasting a CME's Altered Trajectory (ForeCAT) model for nonradial CME dynamics driven by magnetic forces, to simulate the deflection and rotation of the seven CMEs. We find good agreement between the ForeCAT results and the reconstructed CME positions and orientations. The CME deflections range in magnitude between 10 degrees and 30 degrees. All CMEs deflect to the north but we find variations in the direction of the longitudinal deflection. The rotations range between 5\mydeg and 50\mydeg with both clockwise and counterclockwise rotations occurring. Three of the CMEs begin with initial positions within 2 degrees of one another. These three CMEs all deflect primarily northward, with some minor eastward deflection, and rotate counterclockwise. Their final positions and orientations, however, respectively differ by 20 degrees and 30 degrees. This variation in deflection and rotation results from differences in the CME expansion and radial propagation close to the Sun, as well as the CME mass. Ultimately, only one of these seven CMEs yielded discernible in situ signatures near Earth, despite the active region facing near Earth throughout the eruptions. We suggest that the differences in the deflection and rotation of the CMEs can explain whether each CME impacted or missed the Earth.Comment: 18 pages, 6 figures, accepted in Solar Physic

    Coronal Shock Waves, EUV Waves, and Their Relation to CMEs. III. Shock-Associated CME/EUV Wave in an Event with a Two-Component EUV Transient

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    On 17 January 2010, STEREO-B observed in extreme ultraviolet (EUV) and white light a large-scale dome-shaped expanding coronal transient with perfectly connected off-limb and on-disk signatures. Veronig et al. (2010, ApJL 716, 57) concluded that the dome was formed by a weak shock wave. We have revealed two EUV components, one of which corresponded to this transient. All of its properties found from EUV, white light, and a metric type II burst match expectations for a freely expanding coronal shock wave including correspondence to the fast-mode speed distribution, while the transient sweeping over the solar surface had a speed typical of EUV waves. The shock wave was presumably excited by an abrupt filament eruption. Both a weak shock approximation and a power-law fit match kinematics of the transient near the Sun. Moreover, the power-law fit matches expansion of the CME leading edge up to 24 solar radii. The second, quasi-stationary EUV component near the dimming was presumably associated with a stretched CME structure; no indications of opening magnetic fields have been detected far from the eruption region.Comment: 18 pages, 10 figures. Solar Physics, published online. The final publication is available at http://www.springerlink.co
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