Science.gov

Sample records for swarms field experiment

  1. Swarm: ESA's Magnetic Field Mission

    NASA Astrophysics Data System (ADS)

    Haagmans, R.; Menard, Y.; Floberghagen, R.; Plank, G.; Drinkwater, M. R.

    2010-12-01

    Swarm is the fifth Earth Explorer mission in ESA’s Living Planet Programme. The objective of the Swarm mission is to provide the best ever survey of the geomagnetic field and its temporal evolution. The Mission shall deliver data that allow access to new insights into the Earth system by improving our understanding of the Earth’s interior and near-Earth electro-magnetic environment. After release from a single launcher, a side-by-side flying slowly decaying lower pair of satellites will be released at an initial altitude of about 490 km together with a third satellite that will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations that are required to separate and model various sources of the geomagnetic field and near-Earth current systems. The mission aims to provide a unique view into Earth core dynamics, mantle conductivity, crustal magnetisation, ionospheric and magnetospheric current systems and upper atmosphere dynamics - ranging from understanding the geodynamo to contributing to space weather. The scientific objectives and results from recent scientific studies will be presented. In addition the current status of the project, which is presently in the development phase, will be addressed. The mission is scheduled for launch in 2012.

  2. Swarm equatorial electric field chain: First results

    NASA Astrophysics Data System (ADS)

    Alken, P.; Maus, S.; Chulliat, A.; Vigneron, P.; Sirol, O.; Hulot, G.

    2015-02-01

    The eastward equatorial electric field (EEF) in the E region ionosphere drives many important phenomena at low latitudes. We developed a method of estimating the EEF from magnetometer measurements of near-polar orbiting satellites as they cross the magnetic equator, by recovering a clean signal of the equatorial electrojet current and modeling the observed current to determine the electric field present during the satellite pass. This algorithm is now implemented as an official Level-2 Swarm product. Here we present first results of EEF estimates from nearly a year of Swarm data. We find excellent agreement with independent measurements from the ground-based coherent scatter radar at Jicamarca, Peru, as well as horizontal field measurements from the West African Magnetometer Network magnetic observatory chain. We also calculate longitudinal gradients of EEF measurements made by the A and C lower satellite pair and find gradients up to about 0.05 mV/m/deg with significant longitudinal variability.

  3. Swarm Equatorial Electric Field Inversion Chain

    NASA Astrophysics Data System (ADS)

    Alken, Patrick; Maus, Stefan; Vigneron, Pierre; Sirol, Olivier; Hulot, Gauthier

    2014-05-01

    The day-time eastward equatorial electric field (EEF) in the ionospheric E-region plays a crucial role in equatorial ionospheric dynamics. It is responsible for driving the equatorial electrojet (EEJ) current system, equatorial vertical ion drifts, and the equatorial ionization anomaly (EIA). Due to its importance, there is much interest in accurately measuring and modeling the EEF for both climatological and near real-time studies. The Swarm satellite mission offers a unique opportunity to estimate the equatorial electric field from measurements of the geomagnetic field. Due to the near-polar orbits of each satellite, the on-board magnetometers record a full profile in latitude of the ionospheric current signatures at satellite altitude. These latitudinal magnetic profiles are then modeled using a first principles approach with empirical climatological inputs specifying the state of the ionosphere, in order to recover the EEF. We will present preliminary estimates of the EEF using the first Swarm geomagnetic field measurements, and compare them with independently measured electric fields from the JULIA ground-based radar in Peru.

  4. Gravity field models derived from Swarm GPS data

    NASA Astrophysics Data System (ADS)

    Teixeira da Encarnação, João; Arnold, Daniel; Bezděk, Aleš; Dahle, Christoph; Doornbos, Eelco; van den IJssel, Jose; Jäggi, Adrian; Mayer-Gürr, Torsten; Sebera, Josef; Visser, Pieter; Zehentner, Norbert

    2016-07-01

    It is of great interest to numerous geophysical studies that the time series of global gravity field models derived from Gravity Recovery and Climate Experiment (GRACE) data remains uninterrupted after the end of this mission. With this in mind, some institutes have been spending efforts to estimate gravity field models from alternative sources of gravimetric data. This study focuses on the gravity field solutions estimated from Swarm global positioning system (GPS) data, produced by the Astronomical Institute of the University of Bern, the Astronomical Institute (ASU, Czech Academy of Sciences) and Institute of Geodesy (IfG, Graz University of Technology). The three sets of solutions are based on different approaches, namely the celestial mechanics approach, the acceleration approach and the short-arc approach, respectively. We derive the maximum spatial resolution of the time-varying gravity signal in the Swarm gravity field models to be degree 12, in comparison with the more accurate models obtained from K-band ranging data of GRACE. We demonstrate that the combination of the GPS-driven models produced with the three different approaches improves the accuracy in all analysed monthly solutions, with respect to any of them. In other words, the combined gravity field model consistently benefits from the individual strengths of each separate solution. The improved accuracy of the combined model is expected to bring benefits to the geophysical studies during the period when no dedicated gravimetric mission is operational.

  5. Swarm field dynamics and functional morphogenesis

    SciTech Connect

    Millonas, M.M. |

    1993-02-01

    A class of models with application to swarm behavior as well as many other types of complex systems is studied with an emphasis on analytic techniques and results. Special attention is given to the role played by fluctuations in determining the behavior of such systems. In particular it is suggested that such fluctuations may play an active role, and not just the usual passive one, in the organization of structure in the vicinity of a non-equilibrium phase transition. One model, that of an ant swarm, is analyzed in more detail as an illustration of these ideas.

  6. Swarm field dynamics and functional morphogenesis

    SciTech Connect

    Millonas, M.M. Santa Fe Inst., NM )

    1993-01-01

    A class of models with application to swarm behavior as well as many other types of complex systems is studied with an emphasis on analytic techniques and results. Special attention is given to the role played by fluctuations in determining the behavior of such systems. In particular it is suggested that such fluctuations may play an active role, and not just the usual passive one, in the organization of structure in the vicinity of a non-equilibrium phase transition. One model, that of an ant swarm, is analyzed in more detail as an illustration of these ideas.

  7. Interaction field modeling of mini-UAV swarm

    NASA Astrophysics Data System (ADS)

    Liou, William W.; Ro, Kapseong; Szu, Harold

    2006-05-01

    A behavior-based, simple interaction model inspired by molecular interaction field depicted by the Lennard-Jones function is examined for the averaged interaction in swarming. The modeled kinematic equation of motion contains only one variable, instead of a multiple state variable dependence a more complete dynamics entails. The model assumes a spatial distribution of the potential associate with the swarm. The model has been applied to examine the formation of swarm and the results are reported. The modeling can be reflected in an equilibrium theory for the operation of a swarm of mini-UAVs pioneered by Szu, where every member serves the mission while exploiting other's loss, resulting in a zero-sum game among the team members.

  8. Swarm Measurements of Ionospheric Electric Field and Plasma

    NASA Astrophysics Data System (ADS)

    Burchill, J.; Knudsen, D.; Eriksson, A.

    2009-05-01

    Swarm is a three-spacecraft European Space Agency Earth Explorer mission that will include precision in-situ measurements of magnetic field, electric field, and plasma parameters at altitudes up to 530 km, twice per second for four years beginning in late 2010. Electric fields in the direction perpendicular to the local magnetic field will be measured by the Swarm Electric Field Instruments (EFI) using a technique based on measurements of ion drift. The Swarm EFI's represent a new generation of ion drift measurement in that they use an intensified CCD-based technique to generate 2-D images of low-energy ion distribution functions from which both ion drift velocity and temperature are derived. These measurements will be complemented by Langmuir-probe measurements of electron density, electron temperature and spacecraft potential. We present an overview of the mission and of the predicted performance characteristics of the EFI, and examine the benefits of the Swarm configuration for ionospheric research relative to previous precision magnetic field research missions such as Ørsted and CHAMP.

  9. A Swarm lithospheric magnetic field model to SH degree 80

    NASA Astrophysics Data System (ADS)

    Thébault, Erwan; Vigneron, Pierre; Langlais, Benoit; Hulot, Gauthier

    2016-07-01

    The Swarm constellation of satellites was launched in November 2013 and since then has delivered high-quality scalar and vector magnetic field measurements. A consortium of several research institutions was selected by the European Space Agency to provide a number of scientific products to be made available to the scientific community on a regular basis. In this study, we present the dedicated lithospheric field inversion model. It uses carefully selected magnetic field scalar and vector measurements from the three Swarm satellites between March 2014 and December 2015 and directly benefits from the explicit expression of the magnetic field gradients by the lower pair of Swarm satellites. The modeling scheme is a two-step one and relies first on a regional modeling approach that is very sensitive to small spatial scales and weak signals which we seek to describe. The final model is built from adjacent regional solutions and consists in a global spherical harmonics model expressed between degrees 16 and 80. The quality of the derived model is assessed through a comparison with independent models based on Swarm and the CHAMP satellites. This comparison emphasizes the high level of accuracy of the current model after only 2 years of measurements but also highlights the possible improvements which will be possible once the lowest two satellites reach lower altitudes.

  10. Gravity field models derived from Swarm GPS data

    NASA Astrophysics Data System (ADS)

    de Teixeira da Encarnação, João; Arnold, Daniel; Bezděk, Aleš; Dahle, Christoph; Doornbos, Eelco; van den IJssel, Jose; Jäggi, Adrian; Mayer-Gürr, Torsten; Sebera, Josef; Visser, Pieter; Zehentner, Norbert

    2016-04-01

    The GPS instruments on-board the three Earth's Magnetic Field and Environment Explorer (Swarm) satellites provide the opportunity to measure the gravity field model at basin-wide spatial scales. In spite of being a geo-magnetic satellite mission, Swarm's GPS receiver collects highly accurate hl-SST data (van den IJssel et al., 2015), which has been exploited to produce gravity field models at a number of institutes, namely at the Astronomical Institute (ASU) of the Czech Academy of Sciences (Bezděk et al., 2014), the Astronomical Institute of the University of Bern (AIUB, Jäggi et al., 2015) and the Institute of Geodesy (IfG) of the Graz University of Technology (Zehentner et al., 2015). With the help of GRACE gravity field models, which are derived from much more accurate ll-SST data, we investigate the best combination strategy for producing a superior model on the basis of the solutions produced by the three institutes, similarly to the approach taken by the European Gravity Service for Improved Emergency Management project (http://egsiem.eu). We demonstrate that the Swarm-derived gravity field models are able to resolve monthly solutions with 1666km spatial resolutions (roughly up to degree 12). We illustrate how these monthly solutions correlate with GRACE-derived monthly solutions, for the period of 2014 - 2015, as well as indicate which geographical areas are measured more or less accurately.

  11. Electron swarm experiments in dense rare gases: a review

    NASA Astrophysics Data System (ADS)

    Borghesani, A. Francesco

    2014-03-01

    Swarm techniques have largely been used to investigate electron transport in very dilute gases in order to shed light on the electron-atom (molecule) scattering cross section and, hence, on the interaction potential. The theoretical basis for the analysis of these experiments is classical Kinetic Theory. However, electron transport in dense media, either in gaseous- or condensed phase, is a physical phenomenon of fundamental and practical interest. Dense rare gases are model systems for disordered media. They are particularly well suited to investigate how the dynamics and energetics of quasifree electrons change as the environment density is gradually increased. A review on the electron swarm experiments in dense rare gases is presented here. Contribution to the Topical Issue "Electron and Positron Induced Processes", edited by Michael Brunger, Radu Campeanu, Masamitsu Hoshino, Oddur Ingólfsson, Paulo Limão-Vieira, Nigel Mason, Yasuyuki Nagashima and Hajime Tanuma.

  12. Swarm Observations of Field-Aligned Currents: Case Studies

    NASA Astrophysics Data System (ADS)

    Le, G.; Chi, P. J.; Gjerloev, J. W.; Stolle, C.; Luhr, H.; Park, J.; Rauberg, J.

    2014-12-01

    In this paper, we report the results of a few case studies of multi-point magnetic field measurements of field-aligned currents (FACs) from Swarm constellation mission to understand their temporal and spatial characteristics. During the commissioning phase, the three Swarm spacecraft were in an identical polar orbit with a string-of-pearl configuration with small separations. During the science operational phase (since April, 2014), the three spacecraft were placed in slightly different polar orbits: one spacecraft in a higher altitude orbit (507km x 512km) and two side-by-side in lower altitude orbits (459km x 462km). We analyze a few FAC events in both orbital phases and during periods of active geomagnetic conditions. The multi-point observations enable us to examine the FACs' temporal evolution and separate their temporal and spatial variations.

  13. Low-latitude field-aligned currents deduced by Swarm

    NASA Astrophysics Data System (ADS)

    Lühr, Hermann; Kervalishvili, Guram; Rauberg, Jan

    2015-04-01

    ESA's constellation mission Swarm was successfully launched on 22 November 2013. The three satellites are orbiting the Earth at 470 km and 520 km altitude. The lower pair Swarm-A and C is flying side-by-side separated by only 1.4° in latitude. Magnetic field readings of this pair are used to determine for the first time field-aligned currents (FAC) uniquely in the ionosphere. Of particular interest for this presentation are FACs at low and equatorial latitudes. Indications for several of such current systems have been deduced from CHAMP observations. Examples to be studied are meridional and vertical currents driven by the F-region dynamo. They are expected to show opposite polarities between noon and sunset. Likewise there are FACs expected to balance the electric potential differences between the foci of the Sq current vortices in the two hemispheres, which should be most prominent during solstice seasons. Another example is the FAC associated with equatorial plasma bubbles. They are expected to flow along the walls of the electron density depleted volume. Due to the limited amount of suitable Swarm data we will focus on June solstice and September equinox 2014 for this presentation.

  14. Probing the Earth's core with magnetic field observations from Swarm

    NASA Astrophysics Data System (ADS)

    Finlay, Christopher; Olsen, Nils; Kotsiaros, Stavros; Gillet, Nicolas; Tøffner-Clausen, Lars

    2016-07-01

    By far the largest part of the Earth's magnetic field is generated by motions taking place within our planet's liquid metal outer core. Variations of this core-generated field thus provide a unique means of probing the dynamics taking place in the deepest reaches of the Earth. In this contribution we present a new high resolution model of the core-generated magnetic field, and its recent time changes, derived from a dataset that includes more two years of observations from the Swarm mission. Resulting inferences regarding the underlying core flow, its dynamics, and the nature of the geodynamo process will be discussed. The CHAOS-6 geomagnetic field model, covering the interval 1999-2016, is derived from magnetic data collected by the three Swarm missions, as well as the earlier CHAMP and Oersted satellites, and monthly means data collected from 160 ground observatories. Advantage is taken of the constellation aspect of the Swarm mission by ingesting both scalar and vector field differences along-track and across track between the lower pair of Swarm satellites. The internal part of the model consists of a spherical harmonic (SH) expansion, time-dependent for degrees 20 and below. The model coefficients are estimated using a regularized, iteratively reweighted, least squares scheme involving Huber weights. At Earth's surface, CHAOS-6 shows evidence for positive acceleration of the field intensity in 2015 over a broad area around longitude 90deg E that is also seen at ground observatories such as Novosibirsk. At the core surface, we are able to map the secular variation (linear trend in the magnetic field) up to SH degree 16. The radial field acceleration at the core surface in 2015 is found be largest at low latitudes under the India-South East Asia region and under the region of northern South America, as well as at high northern latitudes under Alaska and Siberia. Surprisingly, there is also evidence for some acceleration in the central Pacific region, for example

  15. Electron Swarms

    NASA Astrophysics Data System (ADS)

    Crompton, Robert W.

    1998-10-01

    Swarm experiments provide an invaluable link between gaseous electronics and atomic physics, that is, between the collective behavior of electrons in gases in electric and magnetic fields and the collision processes that determine that behavior. Early swarm experiments were made to gain an understanding of the basic physics of electrical conduction in gases and electrical breakdown. Subsequent peaks of activity have been associated with attempts to explain quantitatively electromagnetic wave propagation in the ionosphere and in high temperature air, and with applied research in such diverse areas as gas lasers, health physics, gas insulation for high voltage transmission lines, plasma processing, and particle detectors . Through improved experimental techniques and the application of numerical techniques to unravel the complex connection between the individual electron-neutral collisions and the transport coefficients that characterize the properties of the swarm, swarm experiments now contribute accurate, and sometimes unique, cross section data for low-energy electron-atom/molecule collisions. Alternatively they can provide self-consistent sets of cross sections that enable reliable forecasts of the collective behaviour to be made. In the talk I shall aim to provide an understanding of the basic principles underlying swarm experiments, and the interpratation of the results from them, through a description of their development and application up to the present day.

  16. Determination of the Earth's lithospheric magnetic field using vector gradient data from the Swarm satellite constellation

    NASA Astrophysics Data System (ADS)

    Kotsiaros, Stavros; Finlay, Chris; Olsen, Nils

    2015-04-01

    One of the main goals of the Swarm three-satellite constellation mission is to determine the lithospheric field globally with the best possible resolution. To achieve that, explicit advantage of the constellation aspect of Swarm has to be taken by using gradient estimates. We derive lithospheric field models using more than one year of East-West and North-South magnetic gradient data, approximated by first differences of field vector data between the two lower Swarm satellites and along each satellite orbit, respectively. Despite the current relatively high altitude of 450 km of the Swarm satellites, the results are promising. We find that Swarm gradient data are less sensitive to large-scale external field fluctuations and enhance the resolution of the determined lithospheric field compared to only vector data. The derived models agree very well with previous models derived from CHAMP data, serving as an initial validation of the Swarm mission.

  17. Deriving a Core Magnetic Field Model from Swarm Satellite Data

    NASA Astrophysics Data System (ADS)

    Lesur, V.; Rother, M.; Wardinski, I.

    2014-12-01

    A model of the Earth's core magnetic field has been built using Swarm satellite mission data and observatory quasi-definitive data. The satellite data processing scheme, which was used to derive previous satellite field models (i.e. GRIMM series), has been modified to handle discrepancies between the satellite total intensity data derived from the vector fluxgate magnetometer and the absolute scalar instrument. Further, the Euler angles, i.e. the angles between the vector magnetometer and the satellite reference frame, have been recalculated on a series of 30-day windows to obtain an accurate model of the core field for 2014. Preliminary derivations of core magnetic field and SV models for 2014 present the same characteristics as during the CHAMP era. The acceleration (i.e. the field second time derivative) has shown a rapid evolution over the last few years, and is present in the current model, which confirms previous observations.

  18. Time-variable gravity fields derived from GPS tracking of Swarm

    NASA Astrophysics Data System (ADS)

    Bezděk, Aleš; Sebera, Josef; Teixeira da Encarnação, João; Klokočník, Jaroslav

    2016-06-01

    Since 2002 Gravity Recovery and Climate Experiment (GRACE) provides monthly gravity fields from K-band ranging (KBR) between two GRACE satellites. These KBR gravity monthlies have enabled the global observation of time-varying Earth mass signal at a regional scale (about 400 km resolution). Apart from KBR, monthly gravity solutions can be computed from onboard GPS data. The newly reprocessed GPS monthlies from 13 yr of GRACE data are shown to yield correct time-variable gravity signal (seasonality, trends, interannual variations) at a spatial resolution of 1300 km (harmonic degree 15). We show that GPS fields from new Swarm mission are of similar quality as GRACE GPS monthlies. Thus, Swarm GPS monthlies represent new and independent source of information on time-variable gravity, and, although with lower resolution and accuracy, they can be used for its monitoring, particularly if GRACE KBR/GPS data become unavailable before GRACE Follow-On is launched (2017 August).

  19. Time-variable gravity fields derived from GPS tracking of Swarm

    NASA Astrophysics Data System (ADS)

    Bezděk, Aleš; Sebera, Josef; da Encarnação, João Teixeira; Klokočník, Jaroslav

    2016-03-01

    Since 2002 Gravity Recovery and Climate Experiment (GRACE) provides monthly gravity fields from K-band ranging (KBR) between two GRACE satellites. These KBR gravity monthlies have enabled the global observation of time-varying Earth mass signal at a regional scale (about 400 km resolution). Apart from KBR, monthly gravity solutions can be computed from onboard GPS data. The newly reprocessed GPS monthlies from 13 years of GRACE data are shown to yield correct time-variable gravity signal (seasonality, trends, interannual variations) at a spatial resolution of 1300 km (harmonic degree 15). We show that GPS fields from new Swarm mission are of similar quality as GRACE GPS monthlies. Thus Swarm GPS monthlies represent new and independent source of information on time-variable gravity, and, although with lower resolution and accuracy, they can be used for its monitoring, particularly if GRACE KBR/GPS data becomes unavailable before GRACE Follow-On is launched (August 2017).

  20. Multi-point Magnetic Field Observations of Field-Aligned Currents from Swarm Constellation Mission

    NASA Astrophysics Data System (ADS)

    Le, Guan; Chi, Peter; Lühr, Hermann; Gjerloev, Jesper; Stolle, Claudia; Park, Jaeheung; Rauberg, Jan

    2015-04-01

    In this paper, we report the results of case studies of multi-point magnetic field measurements of field-aligned currents (FACs) from Swarm constellation mission to understand their temporal characteristics and hemispheric asymmetry. For science operations (since April, 2014), the three spacecraft were placed in slightly different polar orbits: Swarm B spacecraft in a higher altitude orbit (507km x 512km) and Swarm A and C side-by-side in lower altitude orbits (459km x 462km). In the beginning of the science operational phase, the longitudinal separations of the orbital planes were small, and Swarm A/C pair and Swarm B were nearly out of phase in the orbit. This unique orbit configuration provides opportunities to study some new features of FACs. Specifically, the Swarm satellites make multiple crossings of a FAC region within a few hours. Such data enable us to study temporal variations in several time scales, from 1 minute up to about 3 hours. Furthermore, the three satellites make nearly simultaneous observations of FACs in northern and southern hemispheres, which provide us an opportunity to study the hemispheric asymmetry.

  1. Management of Post-mining Large-scale Ground Failures: Blast Swarms Field Experiment for Calibration of Permanent Microseismic Early-warning Systems

    NASA Astrophysics Data System (ADS)

    Contrucci, I.; Klein, E.; Bigarré, P.; Lizeur, A.; Lomax, A.; Bennani, M.

    2010-02-01

    In France, decades of coal and iron-ore mining have left extensive underground cavities beneath or in the vicinity of urban areas. This poses an environmental challenge for society. To ensure post-mining risk management and public safety, wherever remediation is not possible, numerous real-time microseismic monitoring systems are being installed. The objective is to detect remote rock mass fracturing processes, precursory events and acceleration phases for appropriate and timely action. Although no consistent collapse has occurred in any of the monitored areas yet, single 3-D probes record many microseismic events of very low amplitude which create difficulties in the quantitative data analysis. The development of specific quantitative processing has therefore become a major issue in our research work. For that purpose, a field experiment was carried out on six of the instrumented sites. It consisted of sequences of small blasts in mine pillars which were accurately controlled in terms of the location, orientation and energy of the explosive source. The data analysis was used to calibrate parameters (velocity model, 3-D sensor orientation, etc.) for reliable 3-D localization and to develop an empirical law to estimate the source energy from the sensor energy. This work now enables us to analyze real microseismic events with a considerably better level of accuracy and to obtain enough information and confidence to discuss these data in terms of site stability.

  2. Scientific Highlights from the Swarm Electric Field Instruments

    NASA Astrophysics Data System (ADS)

    Knudsen, D. J.; Archer, W. E.; Burchill, J. K.; Buchert, S. C.; Donovan, E.; Fejer, B. G.; Jackel, B. J.; Patrick, M.; St-Maurice, J. P.; Stolle, C.

    2014-12-01

    The Swarm mission brings a new perspective to ionospheric observations by virtue of its precision, multi-point measurements of key plasma parameters that include plasma density, electron and ion temperature, and ion drift velocity, from which electric field estimates are derived. Ion measurements are made using an orthogonal pair of Thermal Ion Imager sensors which image 2-D (energy/angle) distributions of rammed ion populations, providing ion drift and temperature estimates in three directions. Ion flows are resolved to ~10 m/s at 2 samples/s. We show examples of ion upflow at high latitudes, as well as vertical drift variations of order 1 m/s resolved through averaging of slowly-varying drifts near the equator. We also report occurences of highly anisotropic ion temperature at high latitudes, in most cases with temperature perpendicular to B exceeding that parallel to B, though with some exceptions. During the first two months of operation, the Swarm satellites followed each other in a "pearls on a string" arrangement, providing a picture of the time evolution, on a one-minute time scale, of regions of enhanced energy dissipation as determined via the Poynting vector. Finally we show examples of highly structured plasma flows associated with auroral arcs observed by ground-based cameras.

  3. First results from the Swarm Dedicated Ionospheric Field Inversion chain

    NASA Astrophysics Data System (ADS)

    Chulliat, A.; Vigneron, P.; Hulot, G.

    2016-06-01

    Data-based modeling of the magnetic field originating in the Earth's ionosphere is challenging due to the multiple timescales involved and the small spatial scales of some of the current systems, especially the equatorial electrojet (EEJ) that flows along the magnetic dip equator. The Dedicated Ionospheric Field Inversion (DIFI) algorithm inverts a combination of Swarm satellite and ground observatory data at mid- to low latitudes and provides models of the solar-quiet (Sq) and EEJ magnetic fields on the ground and at satellite altitude. The basis functions of these models are spherical harmonics in quasi-dipole coordinates and Fourier series describing the 24-, 12-, 8- and 6-h periodicities, as well as the annual and semiannual variations. A 1-D conductivity model of the Earth and a 2-D conductivity model of the oceans and continents are used to separate the primary ionospheric field from its induced counterpart. First results from the DIFI algorithm confirm several well-known features of the seasonal variability and westward drift speed of the Sq current systems. They also reveal a peculiar seasonal variability of the Sq field in the Southern hemisphere and a longitudinal variability reminiscent of the EEJ wave-4 structure in the same hemisphere. These observations suggest that the Sq and EEJ currents might be electrically coupled, but only for some seasons and longitudes and more so in the Southern hemisphere than in the Northern hemisphere.

  4. The Swarm Initial Field Model - a Model of the Earth's Magnetic Field for 2014 Determined From One Year of Swarm Satellite Constellation Data

    NASA Astrophysics Data System (ADS)

    Olsen, N.; Hulot, G.; Lesur, V.; Finlay, C. C.; Beggan, C.; Chulliat, A.; Sabaka, T. J.

    2014-12-01

    Almost one year of data from ESA's Swarm constellation mission are used to derive a model of the Earth's magnetic field and its time variation (secular variation). The model describes contributions from the core and lithosphere as well as large-scale contributions from the magnetosphere (and its Earth-induced counterpart). We use data from geomagnetic quiet times (Kp less than 2o, time change of Dst-index less than 2 nT/hr) and dark regions (sun below horizon) and co-estimate the Euler angles describing the rotation between the vector magnetometer instrument frame and the North-East-Center (NEC) frame. In addition to the magnetic field observations provided by each of the three Swarm satellites we include the East-west magnetic gradient information provided by the lower Swarm satellite pair, thereby explicitly taking advantage of the constellation aspect of Swarm. We assess the spatial and temporal model resolution that can be obtained from one year of Swarm satellite data by comparison with other recent models that also include non-Swarm magnetic observations.

  5. NanoSWARM: A Nano-satellite Mission to Measure Particles and Fields Around the Moon

    NASA Astrophysics Data System (ADS)

    Garrick-Bethell, I.

    2015-12-01

    The NanoSWARM mission concept uses a fleet of cubesats around the Moon to address a number of open problems in planetary science: 1) The mechanisms of space weathering, 2) The origins of planetary magnetism, 3) The origins, distributions, and migration processes of surface water on airless bodies, and 4) The physics of small-scale magnetospheres. To accomplish these goals, NanoSWARM targets scientifically rich features on the Moon known as swirls. Swirls are high-albedo features correlated with strong magnetic fields and low surface-water. NanoSWARM cubesats will make the first near-surface (<1 km altitude) measurements of solar wind flux and magnetic fields at swirls. NanoSWARM cubesats will also perform low-altitude neutron measurements to provide key constraints on the distribution of polar hydrogen concentrations, which are important volatile sinks in the lunar water cycle. To release its cubesats, NanoSWARM uses a high-heritage mother ship in a low altitude, polar, circular orbit. NanoSWARM's results will have direct applications to the geophysics, volatile distribution, and plasma physics of numerous other bodies, in particular asteroids and the terrestrial planets. The technologies and methods used by NanoSWARM will enable many new cubesat missions in the next decade. NanoSWARM was proposed as a NASA Discovery mission in February 2015.

  6. NanoSWARM - A nano-satellite mission to measure particles and fields around the Moon

    NASA Astrophysics Data System (ADS)

    Garrick-Bethell, Ian; Russell, Christopher; Pieters, Carle; Weiss, Benjamin; Halekas, Jasper; Poppe, Andrew; Larson, Davin; Lawrence, David; Elphic, Richard; Hayne, Paul; Blakely, Richard; Kim, Khan-Hyuk; Choi, Young-Jun; Jin, Ho; Hemingway, Doug; Nayak, Michael; Puig-Suari, Jordi; Jaroux, Belgacem; Warwick, Steven

    2015-04-01

    The NanoSWARM mission concept uses a fleet of cubesats around the Moon to address a number of open problems in planetary science: 1) The mechanisms of space weathering, 2) The origins of planetary magnetism, 3) The origins, distributions, and migration processes of surface water on airless bodies, and 4) The physics of small-scale magnetospheres. To accomplish these goals, NanoSWARM targets scientifically rich features on the Moon known as swirls. Swirls are high-albedo features correlated with strong magnetic fields and low surface-water. NanoSWARM cubesats will make the first near-surface (<500 m altitude) measurements of solar wind flux and magnetic fields at swirls. NanoSWARM cubesats will also perform low-altitude neutron measurements to provide key constraints on the distribution of polar hydrogen concentrations, which are important volatile sinks in the lunar water cycle. To release its cubesats, NanoSWARM uses a high-heritage mother ship in a low altitude, polar, circular orbit. NanoSWARM's results will have direct applications to the geophysics, volatile distribution, and plasma physics of numerous other bodies, in particular asteroids and the terrestrial planets. The technologies and methods used by NanoSWARM will enable many new cubesat missions in the next decade, and expand the cubesat paradigm into deep space. NanoSWARM will be proposed as a NASA Discovery mission in early 2015.

  7. Reversible swarming and separation of self-propelled chemically powered nanomotors under acoustic fields.

    PubMed

    Xu, Tailin; Soto, Fernando; Gao, Wei; Dong, Renfeng; Garcia-Gradilla, Victor; Magaña, Ernesto; Zhang, Xueji; Wang, Joseph

    2015-02-18

    The collective behavior of biological systems has inspired efforts toward the controlled assembly of synthetic nanomotors. Here we demonstrate the use of acoustic fields to induce reversible assembly of catalytic nanomotors, controlled swarm movement, and separation of different nanomotors. The swarming mechanism relies on the interaction between individual nanomotors and the acoustic field, which triggers rapid migration and assembly around the nearest pressure node. Such on-demand assembly of catalytic nanomotors is extremely fast and reversible. Controlled movement of the resulting swarm is illustrated by changing the frequency of the acoustic field. Efficient separation of different types of nanomotors, which assemble in distinct swarming regions, is illustrated. The ability of acoustic fields to regulate the collective behavior of catalytic nanomotors holds considerable promise for a wide range of practical applications. PMID:25634724

  8. Swarm kinematic orbits and gravity fields from 18 months of GPS data

    NASA Astrophysics Data System (ADS)

    Jäggi, A.; Dahle, C.; Arnold, D.; Bock, H.; Meyer, U.; Beutler, G.; van den IJssel, J.

    2016-01-01

    The Swarm mission consists of three satellites orbiting the Earth at low orbital altitudes. The onboard GPS receivers, star cameras, and laser retro-reflectors make the Swarm mission an interesting candidate to explore the contribution of Swarm GPS data to the recovery of both the static and time-variable gravity fields. We use 1.5 years of Swarm GPS and attitude data to generate kinematic positions of high quality to perform gravity field determination using the Celestial Mechanics Approach. The generated gravity fields reveal severe systematic errors along the geomagnetic equator. Their size is correlated with the ionospheric density and thus strongly varying over the analyzed time period. Similar to the findings of the GOCE mission, the systematic errors are related to the Swarm GPS carrier phase data and may be reduced by rejecting GPS data affected by large ionospheric changes. Such a measure yields a strong reduction of the systematic errors along the geomagnetic equator in the gravity field recovery. Long wavelength signatures of the gravity field may then be recovered with a similar quality as achieved with GRACE GPS data, which makes the Swarm mission well suited to bridge a potential gap between the current GRACE and the future GRACE Follow-On mission.

  9. A model of Earth's magnetic field derived from 2 years of Swarm satellite constellation data

    NASA Astrophysics Data System (ADS)

    Olsen, Nils; Finlay, Christopher C.; Kotsiaros, Stavros; Tøffner-Clausen, Lars

    2016-07-01

    More than 2 years of magnetic field data taken by the three-satellite constellation mission Swarm are used to derive a model of Earth's magnetic field and its time variation. This model is called SIFMplus. In addition to the magnetic field observations provided by each of the three Swarm satellites, explicit advantage is taken of the constellation aspect of Swarm by including East-West magnetic intensity and vector field gradient information from the lower satellite pair. Along-track differences of the magnetic intensity as well as of the vector components provide further information concerning the North-South gradient. The SIFMplus model provides a description of the static lithospheric field that is very similar to models determined from CHAMP data, up to at least spherical harmonic degree n=75. Also the core field part of SIFMplus, with a quadratic time dependence for n ≤ 6 and a linear time dependence for n=7-15, demonstrates the possibility to determine high-quality field models from only 2 years of Swarm data, thanks to the unique constellation aspect of Swarm. To account for the magnetic signature caused by ionospheric electric currents at polar latitudes we co-estimate, together with the model of the core, lithospheric and large-scale magnetospheric fields, a magnetic potential that depends on quasi-dipole latitude and magnetic local time.

  10. Ring Current and Field Aligned Currents from Cluster-Swarm Observations

    NASA Astrophysics Data System (ADS)

    Yang, J.; Dunlop, M. W.; Yang, Y.; Xiong, C.; Shen, C.; Luhr, H.; Bogdanova, Y.; Olsen, N.; Zhang, Q. H.; Cao, J.; Ritter, P.; Masson, A.; Carr, C.; Haagmans, R.

    2015-12-01

    We explore the capability of Swarm-Cluster coordination for probing the behavior of the field aligned currents (FAC) adjacent to the ring current (RC) at medium and low orbits and show statistical analysis of the local time variation of R1/R2 FACs. The RC and connecting R2 FACs influence the geomagnetic field at low Earth orbit (LEO) and are sampled in situ by the four Cluster spacecraft. Coordination of the configuration of three Swarm spacecraft configurations with the constellation of the four Cluster spacecraft is possible; providing a set of distributed, multi-point measurements covering this region. Particular events showing close coordination of all spacecraft are considered during the start of the Swarm operations. We report here preliminary results of joint signatures of R1 and R2 FACs and demonstrate the use and application of new analysis techniques derived from the calculation of curl B and magnetic gradients to compare estimates of the current distributions. Multi-spacecraft analysis can access perpendicular currents associated with the FAC signatures at the Swam locations. We also show preliminary statistical results of FAC correlations between Swarm spacecraft to reveal local time behaviour. For context, we identify the associated auroral boundaries determine from FAC intensity gradients in order to help interpret and resolve the R1 and R2 FACs. We also show preliminary results of an extended survey of the ring current crossings for different years, using estimates of the local current density, field curvature and total current.

  11. Swarming and mating activity of Anopheles gambiae mosquitoes in semi-field enclosures.

    PubMed

    Achinko, D; Thailayil, J; Paton, D; Mireji, P O; Talesa, V; Masiga, D; Catteruccia, F

    2016-03-01

    Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) is the major Afro-tropical vector of malaria. Novel strategies proposed for the elimination and eradication of this mosquito vector are based on the use of genetic approaches, such as the sterile insect technique (SIT). These approaches rely on the ability of released males to mate with wild females, and depend on the application of effective protocols to assess the swarming and mating behaviours of laboratory-reared insects prior to their release. The present study evaluated whether large semi-field enclosures can be utilized to study the ability of males from a laboratory colony to respond to natural environmental stimuli and initiate normal mating behaviour. Laboratory-reared males exhibited spatiotemporally consistent swarming behaviour within the study enclosures. Swarm initiation, peak and termination time closely tracked sunset. Comparable insemination rates were observed in females captured in copula in the semi-field cages relative to females in small laboratory cages. Oviposition rates after blood feeding were also similar to those observed in laboratory settings. The data suggest that outdoor enclosures are suitable for studying swarming and mating in laboratory-bred males in field-like settings, providing an important reference for future studies aimed at assessing the comparative mating ability of strains for SIT and other vector control strategies. PMID:26508420

  12. Swarm - The European Space Agency's Constellation Mission: Mapping Earth's Magnetic and Electric Fields

    NASA Astrophysics Data System (ADS)

    Floberghagen, Rune

    2016-07-01

    Launched on 22 November 2013, the three-satellite Swarm constellation is about halfway into its four-year nominal mission. Embarking identical, high accuracy and high spatial as well as temporal resolution instrumentation on all satellites, the mission has ambitious goals reaching from the deep Earth interior (the liquid outer core) all the way out to the solar-terrestrial interaction in the magnetosphere. One may safely state that the mission addresses a diverse range of science issues, and therefore acts as a true discoverer in many fields. Measurements of the magnetic field (magnitude and vector components), the electric field (through ion drift velocity, ion density, ion temperature, electron density, electron temperature and spacecraft potential), the gas density and horizontal winds as well as precise positioning are supported by a range of derived products for the magnetic field, geophysics, aeronomy and space physics communities. Indeed, Swarm is at the forefront of cross-cutting science issues that involve significant parts of the space and earth physics community. In recent data exploitation and science projects we have also seen a high number of coupling studies emerging. This contribution details the status and achievements of the mission in the field of magnetic field, electric field and geospace research. It furthermore discusses the the Agency's further plans, beyond the currently foreseen nominal end of mission in spring 2018. The role of Swarm for space weather research will also be discussed.

  13. Swarm Observations of Field-aligned Currents Associated with Pulsating Auroral Patches

    NASA Astrophysics Data System (ADS)

    Gillies, D. M.; Knudsen, D. J.; Spanswick, E.; Donovan, E.; Burchill, J. K.; Patrick, M.

    2015-12-01

    Using the ground-based optical data from the THEMIS all-sky imager network in conjunction with magnetometers on board the Swarm satellites, we performed a study of in situ field-aligned currents located near the edges of regions of pulsating aurora. A total of nine traversals of Swarm over regions of pulsating aurora identified using THEMIS ASI were studied. We used a satellite-aligned keogram to identify when Swarm was within a patch of pulsating aurora. A downward current in the range of ~1-6 μA/m2 can be seen just poleward of the boundary. A weaker upward current of ~1-3 μA/m2 is observed throughout the interior of the patch. The existence of these currents has been reported before but their magnitudes have not been quantified. In this study we quantify the magnitudes, in some cases by using two satellites traversing the same pulsating regions. We also compared Swarm's two-satellite FAC product to the single-satellite results and determine that the data product can be compromised in regions of pulsating aurora, a phenomenon that occurs over widespread regions and tends to persist for hours. Acknowledgements: This research was supported by an ESA Living Planet Fellowship and various CSA grants.

  14. An algorithm for deriving core magnetic field models from the Swarm data set

    NASA Astrophysics Data System (ADS)

    Rother, Martin; Lesur, Vincent; Schachtschneider, Reyko

    2013-11-01

    In view of an optimal exploitation of the Swarm data set, we have prepared and tested software dedicated to the determination of accurate core magnetic field models and of the Euler angles between the magnetic sensors and the satellite reference frame. The dedicated core field model estimation is derived directly from the GFZ Reference Internal Magnetic Model (GRIMM) inversion and modeling family. The data selection techniques and the model parameterizations are similar to what were used for the derivation of the second (Lesur et al., 2010) and third versions of GRIMM, although the usage of observatory data is not planned in the framework of the application to Swarm. The regularization technique applied during the inversion process smoothes the magnetic field model in time. The algorithm to estimate the Euler angles is also derived from the CHAMP studies. The inversion scheme includes Euler angle determination with a quaternion representation for describing the rotations. It has been built to handle possible weak time variations of these angles. The modeling approach and software have been initially validated on a simple, noise-free, synthetic data set and on CHAMP vector magnetic field measurements. We present results of test runs applied to the synthetic Swarm test data set.

  15. Ring Current and Field Aligned Currents from Cluster-Swarm Observations

    NASA Astrophysics Data System (ADS)

    Dunlop, Malcolm; Yang, Junying; Yang, Yanyan; Xiong, Chao; Lühr, Hermann; Finlay, Christopher C.; Olsen, Nils; Shen, Chao; Bogdanova, Yulia. V.; Zhang, Qinghe; Cao, Jinbin; Ritter, Patricia; Masson, Arnaud; Carr, Chris; Haagmans, Roger

    2016-04-01

    We explore the capability of Swarm-Cluster coordination for probing the behavior of the field aligned currents (FAC) adjacent to the ring current (RC) at medium and low orbits and show statistical analysis of the local time variation of R1/R2 FACs. The RC and connecting R2 FACs influence the geomagnetic field at low Earth orbit (LEO) and are sampled in situ by the four Cluster spacecraft. Coordination of the configuration of three Swarm spacecraft configurations with the constellation of the four Cluster spacecraft is possible; providing a set of distributed, multi-point measurements covering this region. Particular events showing close coordination of all spacecraft are considered during the start of the Swarm operations. We report here preliminary results of joint signatures of R1 and R2 FACs and demonstrate the use and application of new analysis techniques derived from the calculation of curl B and magnetic gradients to compare estimates of the current distributions. Multi-spacecraft analysis can access perpendicular currents associated with the FAC signatures at the Swam locations. For context, we identify the associated auroral boundaries determine from FAC intensity gradients in order to help interpret and resolve the R1 and R2 FACs. We also show preliminary results of an extended survey of the ring current crossings for different years, using estimates of the local current density, field curvature and total current.

  16. Heating mechanisms for electron swarms in radio-frequency electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Dujko, S.; Bošnjaković, D.; White, R. D.; Petrović, Z. Lj

    2015-10-01

    Starting from analytical and numerical solutions of the equation for collisionless motion of a single electron in time-varying electric and magnetic fields, we investigate the possible mechanisms for power absorption of electron swarms in neutral gases. A multi term theory for solving the Boltzmann equation is used to investigate the power absorption of electrons in radio-frequency (rf) electric and magnetic fields in collision-dominated regime for Reid’s inelastic ramp model gas and molecular oxygen. It is found that the effect of resonant absorption of energy in oscillating rf electric and magnetic fields observed under conditions when collisions do not occur, carries directly over to the case where collisions control the swarm behavior. In particular, we have observed the periodic structures in the absorbed power versus amplitude of the applied rf magnetic field curve which have a physical origin similar to the oscillatory phenomena observed for collisionless electron motion. The variation of the absorbed power and other transport properties with the field frequency and field amplitudes in varying configurations of rf electric and magnetic fields is addressed using physical arguments.

  17. Do small swarms have an advantage when house hunting? The effect of swarm size on nest-site selection by Apis mellifera.

    PubMed

    Schaerf, T M; Makinson, J C; Myerscough, M R; Beekman, M

    2013-10-01

    Reproductive swarms of honeybees are faced with the problem of finding a good site to establish a new colony. We examined the potential effects of swarm size on the quality of nest-site choice through a combination of modelling and field experiments. We used an individual-based model to examine the effects of swarm size on decision accuracy under the assumption that the number of bees actively involved in the decision-making process (scouts) is an increasing function of swarm size. We found that the ability of a swarm to choose the best of two nest sites decreases as swarm size increases when there is some time-lag between discovering the sites, consistent with Janson & Beekman (Janson & Beekman 2007 Proceedings of European Conference on Complex Systems, pp. 204-211.). However, when simulated swarms were faced with a realistic problem of choosing between many nest sites discoverable at all times, larger swarms were more accurate in their decisions than smaller swarms owing to their ability to discover nest sites more rapidly. Our experimental fieldwork showed that large swarms invest a larger number of scouts into the decision-making process than smaller swarms. Preliminary analysis of waggle dances from experimental swarms also suggested that large swarms could indeed discover and advertise nest sites at a faster rate than small swarms. PMID:23904590

  18. Do small swarms have an advantage when house hunting? The effect of swarm size on nest-site selection by Apis mellifera

    PubMed Central

    Schaerf, T. M.; Makinson, J. C.; Myerscough, M. R.; Beekman, M.

    2013-01-01

    Reproductive swarms of honeybees are faced with the problem of finding a good site to establish a new colony. We examined the potential effects of swarm size on the quality of nest-site choice through a combination of modelling and field experiments. We used an individual-based model to examine the effects of swarm size on decision accuracy under the assumption that the number of bees actively involved in the decision-making process (scouts) is an increasing function of swarm size. We found that the ability of a swarm to choose the best of two nest sites decreases as swarm size increases when there is some time-lag between discovering the sites, consistent with Janson & Beekman (Janson & Beekman 2007 Proceedings of European Conference on Complex Systems, pp. 204–211.). However, when simulated swarms were faced with a realistic problem of choosing between many nest sites discoverable at all times, larger swarms were more accurate in their decisions than smaller swarms owing to their ability to discover nest sites more rapidly. Our experimental fieldwork showed that large swarms invest a larger number of scouts into the decision-making process than smaller swarms. Preliminary analysis of waggle dances from experimental swarms also suggested that large swarms could indeed discover and advertise nest sites at a faster rate than small swarms. PMID:23904590

  19. Boltzmann analyses of swarm experiments over the years

    NASA Astrophysics Data System (ADS)

    Pitchford, Leanne

    2013-09-01

    Art Phelps was one of the ``grand old men'' in field of gaseous electronics. He was a graduate student when the GEC got started and he attended almost all of the meetings over the years. During his remarkably long career, he produced a number of the classic papers in our field as a glance at Web of Science will show. Art was my mentor and friend, and I had the privilege of working with him for many years on various topics related mainly to electron scattering and transport in weakly ionized gases. In this talk, I will discuss the originality of some of his early work on these subjects in the context of their times, focusing in particular on his publications from the mid-1960's with his colleagues from Westinghouse Research Laboratories. These report the first numerical solutions of the Boltzmann equation for electrons, to my knowledge, and they inspired much subsequent work related to the extraction of quantitative information about low-energy electron scatting with simple gases from measurements of macroscopic parameters (mobility, diffusion,..). I will outline some of the work he and I did together in this topical area using more sophisticated numerical techniques. This and other work in the field eventually led to the establishment of the ongoing GEC Plasma Data Exchange Project which now involves a number of people (the LXCat team), as discussed in Tuesday's workshop. The LXCat team had completed work on noble gases and had just started working on evaluations of cross sections for simple molecules when Art died. We are fortunate to have had his involvement on these projects. Art had ideas for future work in these areas, and some are included in a long e-mail message from Art a couple of years ago that I will share because it includes some suggestions [to the community] for future work.

  20. Earthquake swarm activity highlights crustal faulting associated with the Waimangu-Rotomahana-Mt Tarawera geothermal field, Taupo Volcanic Zone

    NASA Astrophysics Data System (ADS)

    Bannister, Stephen; Sherburn, Steven; Bourguignon, Sandra

    2016-03-01

    The Waimangu-Rotomahana-Mt.Tarawera geothermal field (WRTGF) in the Taupo Volcanic Zone, New Zealand, experiences frequent but sporadic earthquake swarms with durations of less than 1 day. Here we examine detailed locations of the seismic activity using precise double-difference relative location techniques. We utilize a combination of cross-correlation-derived arrival times and catalogue-based arrival times from 582 earthquakes recorded in the area between 2004 and 2015 for the relocation analysis. The new earthquake locations highlight a ~ 6 km long NE-SW lineation, which we infer to represent a sub-surface fault that extends along the northern side of Waimangu geothermal system and the north-western end of Lake Rotomahana. We suggest that this structural feature acts as a permeable pathway for aqueous fluid and CO2 release up to the surface geothermal field and Lake Rotomahana, from a deeper magmatic source.

  1. Expansion of Swarm Experiments at JILA to Microplasma Research

    NASA Astrophysics Data System (ADS)

    Tachibana, Kunihide

    2013-09-01

    Strongly attracted by the Art's remarkable work on metastable atoms in the 50s, I joined JILA as a posdoc at his laboratory in 1978. The assigned machine for me was a drift tube, and the first work was to check the validity of previous results. In a sense, I was tested of my skills as an experimentalist, but soon later I was able to start an original work on the measurement of excitation coefficient of rare gas atoms using the machine. We applied the laser absorption spectroscopy for the measurement of the excited atoms. The argon-ion-laser excited dye-laser at the lab for the light source was awfully unstable, but I was so lucky to have a wonderful support from John Hall, a Novel prize winner in 2005, to stabilize the laser system. After I came back to Japan in 1980, I extended the work to the measurement of Xe metastable (1s5) and resonant (1s4) atoms in a micro discharge cell of a plasma display panel. Then, I have deeply got into the world of microplasmas, exploring the new world with sophisticated arrays of microplasmas to find unusual properties as metamaterials for electromagnetic waves. Throughout my whole research life, I would like to sincerely thank Art for the wonderful experiences with him at JILA.

  2. Swarm observations of field-aligned currents associated with pulsating auroral patches

    NASA Astrophysics Data System (ADS)

    Gillies, D. M.; Knudsen, D.; Spanswick, E.; Donovan, E.; Burchill, J.; Patrick, M.

    2015-11-01

    We have performed a superposed epoch study of in situ field-aligned currents located near the edges of regions of pulsating aurora observed simultaneously using ground-based optical data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imager (ASI) network and magnetometers on board the Swarm satellites. A total of nine traversals of Swarm over regions of pulsating aurora identified using THEMIS ASI were studied. We determined that in the cases where a clear boundary can be identified, strong downward currents are seen just poleward and equatorward of the pulsating patches. A downward current in the range of ~1-6 μA/m2 can be seen just poleward of the boundary. A weaker upward current of ~1-3 μA/m2 is observed throughout the interior of the patch. These observations indicate that currents carried by precipitating electrons within patches could close through horizontal currents and be returned at the edges, in agreement with Oguti and Hayashi (1984) and Hosokawa et al. (2010b). In addition to confirming these earlier results and adding to their statistical significance, the contribution of this study is to quantify the upward and downward current magnitudes, in some cases using two satellites traversing the same pulsating regions. Finally, we compare Swarm's two-satellite field-aligned current product to the single-satellite results and determine that the data product can be compromised in regions of pulsating aurora, a phenomenon that occurs over widespread regions and tends to persist for long periods of time. These results underscore the importance of electrical coupling between the ionosphere and magnetosphere in regions of patchy pulsating aurora.

  3. Monte Carlo simulation of electron swarms in nitrogen in uniform E times B fields

    SciTech Connect

    Raju, G.R.G.; Dincer, M.S. )

    1990-10-01

    The motion of electrons in nitrogen in uniform {ital E} {times} {ital B} fields is simulated using the Monte Carlo technique for 240 {le}= {ital E/N} {le} 600 Td (1 Td = 1 {times} 10{sup {minus}17} V cm{sup 2}) and 0 {le} {ital B/N} {le} 0.45 {times} 10{sup {minus}17} T cm{sup 3}. The electron-molecule collision cross sections adopted are the same cross sections as those used previously for the numerical solution of the Boltzmann equation. The swarm parameters obtained from the Monte Carlo simulation are compared with the Boltzmann solution and with the experimental data available in the literature. In relation to {ital E} {times} {ital B} fields, it is concluded that the Monte Carlo approach provides an independent method of substantiating the validity of the equivalent electric field approach.

  4. Spatially extensive uniform stress fields on Venus inferred from radial dike swarm geometries: The Aphrodite Terra example

    NASA Technical Reports Server (NTRS)

    Grosfils, Eric B.; Head, James W.

    1993-01-01

    The high resolution and near global coverage of Magellan radar images is facilitating attempts to systematically investigate the stresses that have deformed the venusian crust. Here we continue earlier efforts to utilize approximately 170 large, radially lineated structures interpreted as dike swarms to assess the orientation of the regional maximum horizontal compressive stress (MHCS) which existed in their vicinities during emplacement. Examination of swarms near the equator reveals a link to broad scale regional structures, such as Aphrodite Terra, across distances in excess of 1000 km, suggesting the existence of first order stress fields which affect areas of more than 10(exp 6) sq km in a uniform fashion. Focusing further upon the Aphrodite Terra region, the MHCS field in the surrounding lowlands inferred from radial swarms is oriented approximately normal to the slope of the highland topography. This stress configuration appears, at a simple level, to be incompatible with that expected during either upwelling or downwelling construction of the highlands. In addition, the relatively undeformed geometry of the radial structures within the highlands implies that these dike swarm features formed more recently than their highly deformed surroundings. We conclude that the differential stresses which existed during emplacement of the dike swarms within and adjacent to the Aphrodite Terra highlands are related to the gravitational relaxation of pre-existing topography.

  5. Spatially extensive uniform stress fields on Venus inferred from radial dike swarm geometries: The Aphrodite Terra example

    NASA Astrophysics Data System (ADS)

    Grosfils, Eric B.; Head, James W.

    1993-03-01

    The high resolution and near global coverage of Magellan radar images is facilitating attempts to systematically investigate the stresses that have deformed the venusian crust. Here we continue earlier efforts to utilize approximately 170 large, radially lineated structures interpreted as dike swarms to assess the orientation of the regional maximum horizontal compressive stress (MHCS) which existed in their vicinities during emplacement. Examination of swarms near the equator reveals a link to broad scale regional structures, such as Aphrodite Terra, across distances in excess of 1000 km, suggesting the existence of first order stress fields which affect areas of more than 106 sq km in a uniform fashion. Focusing further upon the Aphrodite Terra region, the MHCS field in the surrounding lowlands inferred from radial swarms is oriented approximately normal to the slope of the highland topography. This stress configuration appears, at a simple level, to be incompatible with that expected during either upwelling or downwelling construction of the highlands. In addition, the relatively undeformed geometry of the radial structures within the highlands implies that these dike swarm features formed more recently than their highly deformed surroundings. We conclude that the differential stresses which existed during emplacement of the dike swarms within and adjacent to the Aphrodite Terra highlands are related to the gravitational relaxation of pre-existing topography.

  6. Updating the CHAOS series of field models using Swarm data and resulting candidate models for IGRF-12

    NASA Astrophysics Data System (ADS)

    Finlay, C. C.; Olsen, N.; Tøffner-clausen, L.

    2014-12-01

    Ten months of data from ESA's Swarm mission, together with recent ground observatory monthly means, are used to update the CHAOS series of geomagnetic field models with a focus on time-changes of the core field. As for previous CHAOS field models quiet-time, night-side, data selection criteria are employed and the magnetic field data is used in the instrument frame with Euler angles for the rotation to the North-East-Center (NEC) frame co-estimated. The new model spans more than 15 years between 1999 and 2014, with the internal field being time-dependent up to spherical harmonic degree 20 using a 6th order spline representation with knot points spaced at 0.5 year intervals. The resulting field model is able to consistently fit data from six independent low Earth orbit satellites: Oersted, CHAMP, SAC-C and the three Swarm satellites. As an example, we present comparisons of the excellent model fit obtained to both the Swarm data and the CHAMP data. The new model also provides a good description of observatory secular variation, capturing rapid field evolution events during the past decade. Maps of the core surface field and its secular variation can already be extracted in the Swarm-era. We therefore conclude that Swarm data is suitable for building high-resolution models of the large-scale internal field, and proceed to extract IGRF-12 candidate models for the main field in epochs 2010 and 2015, as well as the predicted linear secular variarion for 2015-2020. The properties of these IGRF candidate models are briefly presented.

  7. Electron swarm transport coefficients in H2O - He mixtures: Experiment and calculations

    NASA Astrophysics Data System (ADS)

    de Urquijo, J.; Juárez, A. M.; Hernández-Ávila, J. L.; Basurto, E. E.; Ness, K. F.; Robson, R. E.; White, Ron; Brunger, M. J.

    2013-09-01

    In this presentation we report recent measurements of electron swarm transport coefficients using the pulsed-Townsend technique for mixtures of water and helium over the range of applied fields E/N from 0-200Td. Comparison is made with transport coefficients calculated using a multi-term Boltzmann equation solution and recently proposed electron-water cross-section sets. This represents a new and more discriminative test on the accuracy and consistency of such sets. Negative differential conductivity is observed for a small window of mixture ratios, even though the pure gases themselves do not demonstrate NDC. Similar interesting effects are observed in the ionization rates as a function of the mixture ratios. The origin of these behaviours will be discussed. Work supported by the Australian Research Council (DP and COE schemes) and by PAPIIT-UNAM IN 116111.

  8. Particle Swarm Optimization

    NASA Technical Reports Server (NTRS)

    Venter, Gerhard; Sobieszczanski-Sobieski Jaroslaw

    2002-01-01

    The purpose of this paper is to show how the search algorithm known as particle swarm optimization performs. Here, particle swarm optimization is applied to structural design problems, but the method has a much wider range of possible applications. The paper's new contributions are improvements to the particle swarm optimization algorithm and conclusions and recommendations as to the utility of the algorithm, Results of numerical experiments for both continuous and discrete applications are presented in the paper. The results indicate that the particle swarm optimization algorithm does locate the constrained minimum design in continuous applications with very good precision, albeit at a much higher computational cost than that of a typical gradient based optimizer. However, the true potential of particle swarm optimization is primarily in applications with discrete and/or discontinuous functions and variables. Additionally, particle swarm optimization has the potential of efficient computation with very large numbers of concurrently operating processors.

  9. Sustaining a biobank through a series of earthquake swarms: lessons learned from our New Zealand experience.

    PubMed

    Morrin, Helen R; Robinson, Bridget A

    2013-08-01

    In the early hours of September 4, 2010, the city of Christchurch in New Zealand was awakened by a major magnitude 7.1 earthquake event that was the start of a series of earthquake swarms. By January 2012, the city had sustained over 10,000 earthquakes and aftershocks, including 4 major events. New Zealand is positioned along the geological Pacific Rim of Fire and is subject to volcanic and seismic movements. However, this series of earthquakes arose from a previously undetected fault that had been dormant for over 10,000 years. The impact on the city, businesses, and people of Christchurch has been profound. Sustaining our cancer biobank through this period has been extremely challenging, as our city's infrastructure including utilities, telecommunication, and transport facilities were fractured, buildings collapsed, and a National State of Emergency was declared. What had not been anticipated was that this impact would continue to be felt up to the present time. After each major earthquake event, the immediate focus of our response was to ensure the safety of all personnel. The secondary response was to ensure the continued preservation of stored specimens. Our third response was to reestablish operational processes without endangering staff. Our responses have been reviewed and lessons formulated that can be incorporated into biobank emergency response plans. They include operational aspects of equipment restraint, cryostorage, staff trauma, specimen relocation, legislation, and management of the repair processes. Emergency response planning for a biobank is a "best practice" standard. Future-proofing a biobank from a significant natural disaster such as a series of earthquake swarms is limited. However, lessons learned from our experience may help to mitigate the impact of future events within our global community. PMID:24845587

  10. Intense field-aligned currents in the polar cap as evidenced from the Swarm satellite constellation

    NASA Astrophysics Data System (ADS)

    Luhr, H.; Kervalishvili, G.; Huang, T.

    2015-12-01

    Traditionally the polar cap has been considered as a region of low activity and reduced energy input. More recent observations, however, evidence more and more exceptions from that. For example, CHAMP and GRACE recorded significant mass density anomalies over the polar cap practically during every magnetic storm. The question is, which process provides enough Joule heating and/or particle precipitation along the open field lines. A promising mechanism is field-aligned currents (FACs). In the past it has been difficult to make reliable estimates of FACs in the polar cap from single satellite magnetic field measurements. An important assumption that the currents are organized in sheets is often not fulfilled in the polar cap. As a consequence current densities are largely underestimated. Only recently ESA's Swarm constellation mission offers reliable FAC estimates from dual-satellite measurements. Significant differences between single and dual-satellite estimates are found in the polar cap. We will show the relation between polar cap FAC patches and IMF orientation and solar wind conditions. Based on these results suggestions for possible current drivers are made.

  11. Recent geomagnetic secular variation from Swarm and ground observatories as estimated in the CHAOS-6 geomagnetic field model

    NASA Astrophysics Data System (ADS)

    Finlay, Christopher C.; Olsen, Nils; Kotsiaros, Stavros; Gillet, Nicolas; Tøffner-Clausen, Lars

    2016-07-01

    We use more than 2 years of magnetic data from the Swarm mission, and monthly means from 160 ground observatories as available in March 2016, to update the CHAOS time-dependent geomagnetic field model. The new model, CHAOS-6, provides information on time variations of the core-generated part of the Earth's magnetic field between 1999.0 and 2016.5. We present details of the secular variation (SV) and secular acceleration (SA) from CHAOS-6 at Earth's surface and downward continued to the core surface. At Earth's surface, we find evidence for positive acceleration of the field intensity in 2015 over a broad area around longitude 90°E that is also seen at ground observatories such as Novosibirsk. At the core surface, we are able to map the SV up to at least degree 16. The radial field SA at the core surface in 2015 is found to be largest at low latitudes under the India-South-East Asia region, under the region of northern South America, and at high northern latitudes under Alaska and Siberia. Surprisingly, there is also evidence for significant SA in the central Pacific region, for example near Hawaii where radial field SA is observed on either side of a jerk in 2014. On the other hand, little SV or SA has occurred over the past 17 years in the southern polar region. Inverting for a quasi-geostrophic core flow that accounts for this SV, we obtain a prominent planetary-scale, anti-cyclonic, gyre centred on the Atlantic hemisphere. We also find oscillations of non-axisymmetric, azimuthal, jets at low latitudes, for example close to 40°W, that may be responsible for localized SA oscillations. In addition to scalar data from Ørsted, CHAMP, SAC-C and Swarm, and vector data from Ørsted, CHAMP and Swarm, CHAOS-6 benefits from the inclusion of along-track differences of scalar and vector field data from both CHAMP and the three Swarm satellites, as well as east-west differences between the lower pair of Swarm satellites, Alpha and Charlie. Moreover, ground observatory SV

  12. Recent Advances In Studies Of Positron Swarms In Electric And Magnetic Fields In Gases

    NASA Astrophysics Data System (ADS)

    Bankovic, A.

    2010-07-01

    A Monte Carlo simulation technique has been used for the calculation of positron transport properties in neutral gases under the influence of electric and magnetic fields. The motivation for this work was twofold. First, positrons have applications in many research areas ranging from gamma-ray astronomy to biomedicine. Second motivating factor is associated with the recent development of positron traps, designed for the determination of low-energy cross sections for positron-matter interactions. Further improvements and optimization of these devices require a detailed knowledge of both collision and transport processes of positrons in gases in various configuration of electric and magnetic fields. The high magnitude of the cross section for positronium (Ps) formation process comparing to other collisional processes and its strong energy dependence are two major factors for the development of many interesting kinetic phenomena observed in the positron transport. One of the most striking phenomena is the existence of negative differential conductivity (NDC) in the bulk drift speed component and the absence of any sign of this phenomenon in the profile of the flux component. Along similar lines we have observed that the differences between the flux and bulk components of various transport coefficients, originating from the non-conservative nature of Ps formation, are much higher than those that have been ever observed for electrons. The influence of magnetic field in a crossed field configuration (E×B) is also investigated. Due to the presence of magnetic field the number of transport coefficients is increased. Since the longitudinal and transverse components of the drift velocity exhibit different sensitivities with respect to the magnetic field strength, it is found that the NDC effect in a crossed field configuration can be controlled by the magnetic field. The magnetic cooling effect has also been observed - the mean energy of the swarm is a decreasing function

  13. Field-aligned currents' scale analysis performed with the Swarm constellation

    NASA Astrophysics Data System (ADS)

    Lühr, Hermann; Park, Jaeheung; Gjerloev, Jesper W.; Rauberg, Jan; Michaelis, Ingo; Merayo, Jose M. G.; Brauer, Peter

    2015-01-01

    We present a statistical study of the temporal- and spatial-scale characteristics of different field-aligned current (FAC) types derived with the Swarm satellite formation. We divide FACs into two classes: small-scale, up to some 10 km, which are carried predominantly by kinetic Alfvén waves, and large-scale FACs with sizes of more than 150 km. For determining temporal variability we consider measurements at the same point, the orbital crossovers near the poles, but at different times. From correlation analysis we obtain a persistent period of small-scale FACs of order 10 s, while large-scale FACs can be regarded stationary for more than 60 s. For the first time we investigate the longitudinal scales. Large-scale FACs are different on dayside and nightside. On the nightside the longitudinal extension is on average 4 times the latitudinal width, while on the dayside, particularly in the cusp region, latitudinal and longitudinal scales are comparable.

  14. A nonequilibrium statistical field theory of swarms and other spatially extended complex systems

    SciTech Connect

    Millonas, M.M. Santa Fe Inst., NM )

    1993-01-01

    A class of models with applications to swarm behavior as well as many other types of spatially extended complex biological and physical systems is studied. Internal fluctuations can play an active role in the organization of the phase structure of such systems. Consequently, it is not possible to fully understand the behavior of these systems without explicitly incorporating the fluctuations. In particular, for the class of models studied here the effect of internal fluctuations due to finite size is a renormalized decrease in the temperature near the point of spontaneous symmetry breaking. We briefly outline how these models can be applied to the behavior of an ant swarm.

  15. A nonequilibrium statistical field theory of swarms and other spatially extended complex systems

    SciTech Connect

    Millonas, M.M. |

    1993-07-01

    A class of models with applications to swarm behavior as well as many other types of spatially extended complex biological and physical systems is studied. Internal fluctuations can play an active role in the organization of the phase structure of such systems. Consequently, it is not possible to fully understand the behavior of these systems without explicitly incorporating the fluctuations. In particular, for the class of models studied here the effect of internal fluctuations due to finite size is a renormalized decrease in the temperature near the point of spontaneous symmetry breaking. We briefly outline how these models can be applied to the behavior of an ant swarm.

  16. Field-aligned Currents' Scale Analysis Performed by the Swarm Constellation

    NASA Astrophysics Data System (ADS)

    Luhr, H.; Park, J.; Gjerloev, J. W.; Rauberg, J.; Michaelis, I.; Le, G.; Merayo, J. M. G.; Brauer, P.

    2014-12-01

    We present a statistical study of the temporal and spatial scale characteristics of different field-aligned current (FAC) types. Very suitable for this purpose is the closely spaced Swarm satellite formation, which existed shortly after launch during the commissioning phase. As dataset we use the standard Level 2 product, Single Satellite FAC, which comes at a data rate of 1 Hz, corresponding to an along-track distance of 7.5 km. FACs are known to cover a wide range of scales from 1km to several hundred kilometres, the smaller the scale the larger the amplitude. We like to divide the FACs into two classes. Those of intermediate scale, some tens of kilometres, which are carried predominantly by kinetic Alfvén waves, while the large-scale FACs are assumed to be stationary current structures on the timescales of a satellite crossing. For distinguishing between the two we first look how the temporal variability changes with scale. For that we consider subsequent measurements at the same point, the orbital cross-over near the geographic poles, and interpret the temporal current changes. Here we focus on observations in the southern hemisphere at locations where the geographic pole lies within the auroral region. In a next step the latitudinal and longitudinal scales of the larger-scale FAC structures are investigated. FACs related to Alfvén waves cannot be studied in this way because we have no simultaneous measurements at the same latitude and longitude. The results from this analysis are different for dayside and nightside. Implications for the FAC characteristics resulting from these observations are interpreted in the end.

  17. Swarm Verification

    NASA Technical Reports Server (NTRS)

    Holzmann, Gerard J.; Joshi, Rajeev; Groce, Alex

    2008-01-01

    Reportedly, supercomputer designer Seymour Cray once said that he would sooner use two strong oxen to plow a field than a thousand chickens. Although this is undoubtedly wise when it comes to plowing a field, it is not so clear for other types of tasks. Model checking problems are of the proverbial "search the needle in a haystack" type. Such problems can often be parallelized easily. Alas, none of the usual divide and conquer methods can be used to parallelize the working of a model checker. Given that it has become easier than ever to gain access to large numbers of computers to perform even routine tasks it is becoming more and more attractive to find alternate ways to use these resources to speed up model checking tasks. This paper describes one such method, called swarm verification.

  18. Daphnia swarms: from single agent dynamics to collective vortex formation

    NASA Astrophysics Data System (ADS)

    Ordemann, Anke; Balazsi, Gabor; Caspari, Elizabeth; Moss, Frank

    2003-05-01

    Swarm theories have become fashionable in theoretical physics over the last decade. They span the range of interactions from individual agents moving in a mean field to coherent collective motions of large agent populations, such as vortex-swarming. But controlled laboratory tests of these theories using real biological agents have been problematic due primarily to poorly known agent-agent interactions (in the case of e.g. bacteria and slime molds) or the large swarm size (e.g. for flocks of birds and schools of fish). Moreover, the entire range of behaviors from single agent interactions to collective vortex motions of the swarm have here-to-fore not been observed with a single animal. We present the results of well defined experiments with the zooplankton Daphnia in light fields showing this range of behaviors. We interpret our results with a theory of the motions of self-propelled agents in a field.

  19. Swarm and ESR observations of the ionospheric response to a field-aligned current system in the high-latitude midnight sector

    NASA Astrophysics Data System (ADS)

    Pitout, F.; Marchaudon, A.; Blelly, P.-L.; Bai, X.; Forme, F.; Buchert, S. C.; Lorentzen, D. A.

    2015-06-01

    We present a conjunction between the Swarm fleet and the European Incoherent Scatter Svalbard Radar (ESR) on 9 January 2014. The Swarm orbit in the early phase of the mission gives us the unique opportunity of sequencing the temporal evolution of the observed field-aligned current system in the nightside, near magnetic local midnight. These field-aligned currents are seen to move poleward through the radar field of view and to affect the observed ionosphere. The upward field-aligned current (FAC) is responsible, at least in part, for the heating of the ionospheric electrons. It is less clear whether the downward FAC cools the ionosphere. We use the TRANSCAR model of the ionosphere to quantify the thermoelectric effect that comes into play. Finally, we compare the plasma parameters measured by the Langmuir probe on board Swarm and the ESR and conclude on an agreement within the errors.

  20. Potential impact of Swarm electric field data on global 2D convection mapping in combination with SuperDARN radar data

    NASA Astrophysics Data System (ADS)

    Fiori, R. A. D.; Boteler, D. H.; Knudsen, D.; Burchill, J.; Koustov, A. V.; Cousins, E. D. P.; Blais, C.

    2013-02-01

    The Electric Field Instrument (EFI) onboard the Swarm satellites will make continuous measurements of the three-dimensional ion drift in the topside F region providing a convenient data set for mapping the ionospheric convection pattern. In this study, a spherical cap harmonic analysis (SCHA) algorithm has been developed to generate maps of the high-latitude convection pattern in the narrow region surrounding the footprints of the Swarm satellite tracks where the solution will be constrained by measurements. This technique has been tested using input velocity values generated from a statistical model at simulated coordinates of Swarm EFI measurements. To obtain a global context from the Swarm ion drift measurements, the Swarm data set is merged with values of the E × B plasma drift determined using a statistical model at typical locations of measurements for the Super Dual Auroral Radar Network (SuperDARN) radars in the northern hemisphere. It is shown that the addition of Swarm ion drifts to a SuperDARN data set increased the proportion of the calculated convection pattern that is constrained by measurement, by a relative increase of as much as 12% for a period of good SuperDARN coverage and 30% for a period of poor SuperDARN coverage. For a data set comprising two years of past SuperDARN operation and 4 years of future satellite operation, it is shown that a distribution of the relative increase peaks at 12.5%. The magnitude of the improvement depends on the size of the SuperDARN data set, the number of satellites contributing to the Swarm data set, and the extent of the overlap between instruments. Contributions from a Swarm data set also allows for the determination of convection features and properties, such as the location of convection vortices or the value of the cross polar cap potential, that could not be calculated by SuperDARN data alone due to a limited data set.

  1. Robot Swarms

    NASA Technical Reports Server (NTRS)

    Morring, Frank, Jr.

    2005-01-01

    Engineers and interns at this NASA field center are building the prototype of a robotic rover that could go where no wheeled rover has gone before-into the dark cold craters at the lunar poles and across the Moon s rugged highlands-like a walking tetrahedron. With NASA pushing to meet President Bush's new exploration objectives, the robots taking shape here today could be on the Moon in a decade. In the longer term, the concept could lead to shape-shifting robot swarms designed to explore distant planetary surfaces in advance of humans. "If you look at all of NASA s projections of the future, anyone s projections of the space program, they re all rigid-body architecture," says Steven Curtis, principal investigator on the effort. "This is not rigid-body. The whole key here is flexibility and reconfigurability with a capital R."

  2. Collective motion patterns of swarms with delay coupling: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Szwaykowska, Klementyna; Schwartz, Ira B.; Mier-y-Teran Romero, Luis; Heckman, Christoffer R.; Mox, Dan; Hsieh, M. Ani

    2016-03-01

    The formation of coherent patterns in swarms of interacting self-propelled autonomous agents is a subject of great interest in a wide range of application areas, ranging from engineering and physics to biology. In this paper, we model and experimentally realize a mixed-reality large-scale swarm of delay-coupled agents. The coupling term is modeled as a delayed communication relay of position. Our analyses, assuming agents communicating over an Erdös-Renyi network, demonstrate the existence of stable coherent patterns that can be achieved only with delay coupling and that are robust to decreasing network connectivity and heterogeneity in agent dynamics. We also show how the bifurcation structure for emergence of different patterns changes with heterogeneity in agent acceleration capabilities and limited connectivity in the network as a function of coupling strength and delay. Our results are verified through simulation as well as preliminary experimental results of delay-induced pattern formation in a mixed-reality swarm.

  3. Collective motion patterns of swarms with delay coupling: Theory and experiment.

    PubMed

    Szwaykowska, Klementyna; Schwartz, Ira B; Mier-Y-Teran Romero, Luis; Heckman, Christoffer R; Mox, Dan; Hsieh, M Ani

    2016-03-01

    The formation of coherent patterns in swarms of interacting self-propelled autonomous agents is a subject of great interest in a wide range of application areas, ranging from engineering and physics to biology. In this paper, we model and experimentally realize a mixed-reality large-scale swarm of delay-coupled agents. The coupling term is modeled as a delayed communication relay of position. Our analyses, assuming agents communicating over an Erdös-Renyi network, demonstrate the existence of stable coherent patterns that can be achieved only with delay coupling and that are robust to decreasing network connectivity and heterogeneity in agent dynamics. We also show how the bifurcation structure for emergence of different patterns changes with heterogeneity in agent acceleration capabilities and limited connectivity in the network as a function of coupling strength and delay. Our results are verified through simulation as well as preliminary experimental results of delay-induced pattern formation in a mixed-reality swarm. PMID:27078366

  4. Swarm and ESR observations of the ionospheric response to a field-aligned current system in the high-latitude midnight sector

    NASA Astrophysics Data System (ADS)

    Pitout, F.; Marchaudon, A.; Blelly, P. L.; Bai, X.; Forme, F.; Buchert, S. C.; Lorentzen, D. A.

    2015-12-01

    We present a conjunction between the Swarm fleet and the EISCAT Svalbard Radar (ESR) on 9 January 2014. The Swarm orbit in the early phase of the mission gives us the unique opportunity of sequencing the temporal evolution of the observed field-aligned current system in the nightside, near magnetic local midnight. These field-aligned currents are seen to move poleward through the radar field of view and to affect the observed ionosphere. The upward FAC is responsible, at least in part, for the heating of the ionospheric electrons. It is less clear whether the downward FAC cools the ionosphere. We use the TRANSCAR model of the ionosphere to quantify the thermoelectric effect that comes into play. Finally, we compare the plasma parameters measured by the Langmuir probe on board Swarm and the ESR, and conclude on an agreement within the errors

  5. Benchmark calculations of nonconservative charged-particle swarms in dc electric and magnetic fields crossed at arbitrary angles.

    PubMed

    Dujko, S; White, R D; Petrović, Z Lj; Robson, R E

    2010-04-01

    A multiterm solution of the Boltzmann equation has been developed and used to calculate transport coefficients of charged-particle swarms in gases under the influence of electric and magnetic fields crossed at arbitrary angles when nonconservative collisions are present. The hierarchy resulting from a spherical-harmonic decomposition of the Boltzmann equation in the hydrodynamic regime is solved numerically by representing the speed dependence of the phase-space distribution function in terms of an expansion in Sonine polynomials about a Maxwellian velocity distribution at an internally determined temperature. Results are given for electron swarms in certain collisional models for ionization and attachment over a range of angles between the fields and field strengths. The implicit and explicit effects of ionization and attachment on the electron-transport coefficients are considered using physical arguments. It is found that the difference between the two sets of transport coefficients, bulk and flux, resulting from the explicit effects of nonconservative collisions, can be controlled either by the variation in the magnetic field strengths or by the angles between the fields. In addition, it is shown that the phenomena of ionization cooling and/or attachment cooling/heating previously reported for dc electric fields carry over directly to the crossed electric and magnetic fields. The results of the Boltzmann equation analysis are compared with those obtained by a Monte Carlo simulation technique. The comparison confirms the theoretical basis and numerical integrity of the moment method for solving the Boltzmann equation and gives a set of well-established data that can be used to test future codes and plasma models. PMID:20481843

  6. Polar Magnetic Field Experiment

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1999-01-01

    This grant covers the initial data reduction and analysis of the magnetic field measurements of the Polar spacecraft. At this writing data for the first three years of the mission have been processed and deposited in the key parameter database. These data are also available in a variety of time resolutions and coordinate systems via a webserver at UCLA that provides both plots and digital data. The flight software has twice been reprogrammed: once to remove a glitch in the data where there were rare collisions between commands in the central processing unit and once to provide burst mode data at 100 samples per second on a regular basis. The instrument continues to function as described in the instrument paper (1.1 in the bibliography attached below). The early observations were compared with observations on the same field lines at lower altitude. The polar magnetic measurements also proved to be most useful for testing the accuracy of MHD models. WE also made important contributions to study of waves and turbulence.

  7. ArcGIS studies and field relationships of Paleoproterozoic mafic dyke swarms from the south of Devarakonda area, Eastern Dharwar Craton, southern India: Implications for their relative ages

    NASA Astrophysics Data System (ADS)

    Samal, Amiya K.; Srivastava, Rajesh K.; Sinha, Lokesh K.

    2015-07-01

    Google Earth Image and cross-cutting field relationships of distinct Paleoproterozoic mafic dykes from south of Devarakonda area in the Eastern Dharwar Craton has been studied to establish relative emplacement ages. The Devarakonda, covering an area of ˜700 km2, shows spectacular cross-cutting field relationships between different generations of mafic dykes, and is therefore selected for the present study. Although some recent radiometric age data are available for distinct Paleoproterozoic mafic dykes from the Eastern Dharwar Craton, there is no analogous age data available for the study area. Therefore, relative age relationships of distinct mafic dykes have been established for the study area using cross-cutting field relationships and GIS techniques, which shows slightly different picture than other parts of the Eastern Dharwar Craton. It is suggested that NE-SW trending mafic dykes are youngest in age (probably belong to ˜1.89 Ga dyke swarm), whereas NNW-SSE trending mafic dykes have oldest emplacement age. Further, the NNW-SSE mafic dykes are older to the other two identified mafic dyke swarms, i.e., WNW-ESE (˜2.18 Ga) and N-S trending (˜2.21 Ga) mafic dyke swarms, as dykes of these two swarms cross-cut a NNW-SSE dyke. It provides an evidence for existence of a new set of mafic dykes that is older to the ˜2.21 Ga and probably younger to the ˜2.37 Ga swarm. Present study also supports existence of two mafic dyke swarms having similar trend (ENE-WSW to NE-SW) but emplaced in two different ages (one is ˜2.37 Ga and other ˜1.89 Ga).

  8. Lower crustal earthquake swarms beneath Mammoth Mountain, California - evidence for the magmatic roots to the Mammoth Mountain mafic volcanic field?

    NASA Astrophysics Data System (ADS)

    Hill, D. P.; Shelly, D. R.

    2010-12-01

    Mammoth Mountain is a cluster of dacitic domes erupted ~ 68 ka. It stands on the SW topographic rim of Long Valley caldera in eastern CA. Structurally, it is outboard of the caldera ring-fracture system and its magmatic system is genetically distinct from that of the caldera. It resides within a field of mafic (basaltic) vents that erupted between 190 - 8 ka. A series of phreatic explosions from the north flank of the mountain some 700 ybp attest to the infusion of heat to shallow depths shortly prior to the 600 ybp eruptions of the Inyo Domes 6 to 12 km north of the Mountain. Unrest beneath Mammoth Mountain since 1980 has included 1) swarms of brittle-failure earthquakes in the upper 10 km of the crust that define concentric elliptical ring-like patterns centered beneath the summit, 2) mid-crustal (depths 10 to 20 km) long-period volcanic earthquakes, 3) the onset of diffuse CO2 degassing in 1990 following an 11-month-long swarm of shallow (<10 km), brittle-failure earthquakes in 1989, 4) occasional very-long-period earthquakes at depths of ~ 3 km, and 5) brief swarms of lower-crustal, brittle-failure earthquakes at depths of 20 to 30 km, including sizable episodes June 16-17, 2006 and September 29-30, 2009. Seismic waveform correlation analysis at multiple stations reveals that these lower-crustal, brittle-failure swarms consist of tens to hundreds of repeated similar events and also serves to identify many events not included in the Northern California Seismic Network (NCSN) catalog. In the case of the 2009 episode, an evolution in waveform is clearly discernible over the sequence, suggesting a corresponding evolution in source location or mechanism. Work is ongoing to take advantage of the waveform similarity to estimate precise hypocentral locations of these events in order to distinguish between these possibilities.We suggest that the brittle-failure earthquakes at depths of 20 to 30 km are occurring within the more mafic mid- to lower-crust, which can remain

  9. Small-scale field-aligned currents caused by tropical cyclones as observed by the SWARM satellites above the ionosphere

    NASA Astrophysics Data System (ADS)

    Aoyama, T.; Iyemori, T.; Nakanishi, K.

    2014-12-01

    We present case studies of small-scale magnetic fluctuations above typhoons, hurricanes and cyclones as observed by the swarm constellation. It is reported lately that AGWs(atmospheric gravity waves) generated by meteorological phenomena in the troposphere such as typhoons and tornadoes, large earthquakes and volcanic eruptions propagate to the mesosphere and thermosphere. We observe them in various forms(e.g. airglows, ionospheric disturbances and TEC variations). We are proposing the following model. AGWs caused by atmospheric disturbances in the troposphere propagate to the ionospheric E-layer, drive dynamo action and generate field-aligned currents. The satellites observe magnetic fluctuations above the ionosphere. In this presentation, we focus on cases of tropical cyclone(hurricanes in North America, typhoons in North-West Pacific).

  10. Long Swarms and Short Swarms

    NASA Astrophysics Data System (ADS)

    McNutt, S. R.

    2011-12-01

    Many earthquake swarms at volcanoes last several months, then have a sharp uptick in rate in the hours before eruption. Examples include 2006 Augustine, 8.5 months then 10 hours; 1992 Spurr, 10 months then 4 hours; 1994 Rabaul, ~1 year then 27 hours; 2008 Kasatochi, 6 weeks then 2 days; and 2011 Puyuehue Cordon Caulle, 5 weeks then 2 days. For the well studied Augustine case, broadband data showed that very long period (VLP) energy accompanied 221 of 722 located earthquakes in the 10 hours before the first explosive eruption on 11 January 2006. This was revealed by low-pass filtering and the period of the VLP signal was 50 sec. The Augustine broadband stations were campaign instruments at distances of 2-3 km from the vent. No similar VLP energy has been found in events during the 8.5 month long swarm. Okmok volcano had a short swarm only lasting 5 hours prior to its 12 July 2008 eruption. Low-pass filtering of data from broadband station OKSO, 10 km from the vent, showed that 23 of 42 located events had VLP energy with a period of 30-40 sec. Events from Kasatochi volcano were scanned on station ATKA. Here the broadband station is much farther away at 88 km but the earthquakes in the short swarm 7 August 2008 were much larger with many M>3 events. The station suffered data gaps so only a few hours of data were scanned but numerous events were observed with VLP energy starting just after the P phase. Low-pass filtering showed VLP energy with a period of 10-12 sec. No VLP energy has been found in events of the preceding 6 week long swarm. These observations at three different volcanoes suggest that the short swarms represent a different process than the long swarms. The long swarms likely reflect pressure increases in the surrounding country rock caused by increasing magma pressure. The short swarms in contrast, appear to represent discrete pulses of magma injection at shallow depths. For all three volcanoes the earthquakes looked like typical volcano-tectonic (VT

  11. Observations of high-latitude geomagnetic field fluctuations during St. Patrick's Day storm: Swarm and SuperDARN measurements

    NASA Astrophysics Data System (ADS)

    De Michelis, Paola; Consolini, Giuseppe; Tozzi, Roberta; Marcucci, Maria Federica

    2016-06-01

    The aim of this work is to study the properties of the magnetic field's fluctuations produced by ionospheric and magnetospheric electric currents during the St. Patrick's Day geomagnetic storm (17 March 2015). We analyse the scaling features of the external contribution to the horizontal geomagnetic field recorded simultaneously by the three satellites of the Swarm constellation during a period of 13 days (13-25 March 2015). We examine the different latitudinal structure of the geomagnetic field fluctuations and analyse the dynamical changes in the magnetic field scaling features during the development of the geomagnetic storm. Analysis reveals consistent patterns in the scaling properties of magnetic fluctuations and striking changes between the situation before the storm, during the main phase and recovery phase. We discuss these dynamical changes in relation to those of the overall ionospheric polar convection and potential structures as reconstructed using SuperDARN data. Our findings suggest that distinct turbulent regimes characterised the mesoscale magnetic field's fluctuations and that some factors, which are known to influence large-scale fluctuations, have also an influence on mesoscale fluctuations. The obtained results are an example of the capability of geomagnetic field fluctuations data to provide new insights about ionospheric dynamics and ionosphere-magnetosphere coupling. At the same time, these results could open doors for development of new applications where the dynamical changes in the scaling features of the magnetic fluctuations are used as local indicators of magnetospheric conditions.

  12. Family Oriented Geographic Field Experience.

    ERIC Educational Resources Information Center

    Williams, Karen Ann Lalk

    This paper describes a program of geographic education through field experience trips for family groups. Developed at Delta College in Michigan, the approach is unique because it emphasizes learning experiences for families rather than for individual students. The family is interpreted to include nuclear families, single-parent families with…

  13. Turbulence of swarming sperm.

    PubMed

    Creppy, Adama; Praud, Olivier; Druart, Xavier; Kohnke, Philippa L; Plouraboué, Franck

    2015-09-01

    Collective motion of self-sustained swarming flows has recently provided examples of small-scale turbulence arising where viscous effects are dominant. We report the first observation of universal enstrophy cascade in concentrated swarming sperm consistent with a body of evidence built from various independent measurements. We found a well-defined k^{-3} power-law decay of a velocity field power spectrum and relative dispersion of small beads consistent with theoretical predictions in 2D turbulence. Concentrated living sperm displays long-range, correlated whirlpool structures of a size that provides an integral scale of turbulence. We propose a consistent explanation for this quasi-2D turbulence based on self-structured laminated flow forced by steric interactions and alignment, a state of active matter that we call "swarming liquid crystal." We develop scaling arguments consistent with this interpretation. PMID:26465513

  14. Turbulence of swarming sperm

    NASA Astrophysics Data System (ADS)

    Creppy, Adama; Praud, Olivier; Druart, Xavier; Kohnke, Philippa L.; Plouraboué, Franck

    2015-09-01

    Collective motion of self-sustained swarming flows has recently provided examples of small-scale turbulence arising where viscous effects are dominant. We report the first observation of universal enstrophy cascade in concentrated swarming sperm consistent with a body of evidence built from various independent measurements. We found a well-defined k-3 power-law decay of a velocity field power spectrum and relative dispersion of small beads consistent with theoretical predictions in 2D turbulence. Concentrated living sperm displays long-range, correlated whirlpool structures of a size that provides an integral scale of turbulence. We propose a consistent explanation for this quasi-2D turbulence based on self-structured laminated flow forced by steric interactions and alignment, a state of active matter that we call "swarming liquid crystal." We develop scaling arguments consistent with this interpretation.

  15. Main field and secular variation candidate models for the 12th IGRF generation after 10 months of Swarm measurements

    NASA Astrophysics Data System (ADS)

    Saturnino, Diana; Langlais, Benoit; Civet, François; Thébault, Erwan; Mandea, Mioara

    2015-06-01

    We describe the main field and secular variation candidate models for the 12th generation of the International Geomagnetic Reference Field model. These two models are derived from the same parent model, in which the main field is extrapolated to epoch 2015.0 using its associated secular variation. The parent model is exclusively based on measurements acquired by the European Space Agency Swarm mission between its launch on 11/22/2013 and 09/18/2014. It is computed up to spherical harmonic degree and order 25 for the main field, 13 for the secular variation, and 2 for the external field. A selection on local time rather than on true illumination of the spacecraft was chosen in order to keep more measurements. Data selection based on geomagnetic indices was used to minimize the external field contributions. Measurements were screened and outliers were carefully removed. The model uses magnetic field intensity measurements at all latitudes and magnetic field vector measurements equatorward of 50° absolute quasi-dipole magnetic latitude. A second model using only the vertical component of the measured magnetic field and the total intensity was computed. This companion model offers a slightly better fit to the measurements. These two models are compared and discussed.We discuss in particular the quality of the model which does not use the full vector measurements and underline that this approach may be used when only partial directional information is known. The candidate models and their associated companion models are retrospectively compared to the adopted IGRF which allows us to criticize our own choices.

  16. CM5, a Pre-Swarm Comprehensive Geomagnetic Field Model Derived from Over 12 Yr of CHAMP, Orsted, SAC-C and Observatory Data

    NASA Technical Reports Server (NTRS)

    Sabaka, Terence J.; Olsen, Nils; Tyler, Robert H.; Kuvshinov, Alexey

    2014-01-01

    A comprehensive magnetic field model named CM5 has been derived from CHAMP, Ørsted and SAC-C satellite and observatory hourly-means data from 2000 August to 2013 January using the Swarm Level-2 Comprehensive Inversion (CI) algorithm. Swarm is a recently launched constellation of three satellites to map the Earth's magnetic field. The CI technique includes several interesting features such as the bias mitigation scheme known as Selective Infinite Variance Weighting (SIVW), a new treatment for attitude error in satellite vector measurements, and the inclusion of 3-D conductivity for ionospheric induction. SIVW has allowed for a much improved lithospheric field recovery over CM4 by exploiting CHAMP along-track difference data yielding resolution levels up to spherical harmonic degree 107, and has allowed for the successful extraction of the oceanic M2 tidal magnetic field from quiet, nightside data. The 3-D induction now captures anomalous Solar-quiet features in coastal observatory daily records. CM5 provides a satisfactory, continuous description of the major magnetic fields in the near-Earth region over this time span, and its lithospheric, ionospheric and oceanic M2 tidal constituents may be used as validation tools for future Swarm Level-2 products coming from the CI algorithm and other dedicated product algorithms.

  17. Self-Guided Field Experience.

    ERIC Educational Resources Information Center

    Mehrotra, Chandra M. N.

    A field experience program in which all undergraduate psychology students at the College of St. Scholastica spend about 10 weeks away from campus in an applied setting of their choice is presented. Components of the program are described in terms of: (1) selection of sites made by students in consultation with faculty advisors; (2) proposals…

  18. Field Experience, Practicums, and Internships.

    ERIC Educational Resources Information Center

    Witucke, Virginia

    1986-01-01

    A field experience program balances great potential for learning against a major expenditure of resources and requires vision, commitment, flexibility, and persistence to implement. It enhances academic learning through use of the outside world's resources and provides a link to the world in which students prepare to live. (MSE)

  19. Velocity correlations in laboratory insect swarms

    NASA Astrophysics Data System (ADS)

    Ni, R.; Ouellette, N. T.

    2015-12-01

    In contrast to animal groups such as bird flocks or migratory herds that display net, directed motion, insect swarms do not possess global order. Without such order, it is difficult to define and characterize the transition to collective behavior in swarms; nevertheless, visual observation of swarms strongly suggests that swarming insects do behave collectively. It has recently been suggested that correlation rather than order is the hallmark of emergent collective behavior. Here, we report measurements of spatial velocity correlation functions in laboratory mating swarms of the non-biting midge Chironomus riparius. Although we find some correlation at short distances, our swarms are in general only weakly correlated, in contrast to what has been observed in field studies. Our results hint at the potentially important role of environmental conditions on collective behavior, and suggest that general indicators of the collective nature of swarming are still needed.

  20. Mojave remote sensing field experiment

    NASA Technical Reports Server (NTRS)

    Arvidson, Raymond E.; Petroy, S. B.; Plaut, J. J.; Shepard, Michael K.; Evans, D.; Farr, T.; Greeley, Ronald; Gaddis, L.; Lancaster, N.

    1991-01-01

    The Mojave Remote Sensing Field Experiment (MFE), conducted in June 1988, involved acquisition of Thermal Infrared Multispectral Scanner (TIMS); C, L, and P-band polarimetric radar (AIRSAR) data; and simultaneous field observations at the Pisgah and Cima volcanic fields, and Lavic and Silver Lake Playas, Mojave Desert, California. A LANDSAT Thematic Mapper (TM) scene is also included in the MFE archive. TM-based reflectance and TIMS-based emissivity surface spectra were extracted for selected surfaces. Radiative transfer procedures were used to model the atmosphere and surface simultaneously, with the constraint that the spectra must be consistent with field-based spectral observations. AIRSAR data were calibrated to backscatter cross sections using corner reflectors deployed at target sites. Analyses of MFE data focus on extraction of reflectance, emissivity, and cross section for lava flows of various ages and degradation states. Results have relevance for the evolution of volcanic plains on Venus and Mars.

  1. Nuclide-migration field experiments

    SciTech Connect

    Erdal, B.R.; Wolfsberg, K.; Johnstone, J.K.; Erickson, K.L.; Friedman, A.M.; Fried, S.; Hines, J.J.

    1981-03-01

    When considering groundwater flow and radionuclide retention in the complex flow systems that can occur in geologic formations, one has a serious problem in determining if laboratory studies are being performed under conditions appropriate to natural systems. This document is the project plan for a program designed to begin to address these problems. The project is being carried out jointly by the Los Alamos National Laboratory, Sandia National Laboratories, and Argonne National Laboratory. The work has three principal objectives: (1) to develop the experimental, instrumental, and safety techniques necessary to conduct controlled, small-scale radionuclide migration field experiments, including those involving actinides; (2) to use these techniques to define radionuclide migration through rock by performing generic, at-depth experiments under closely monitored conditions; and (3) to determine whether available lithologic, geochemical, and hydrologic properties together with existing or developing transport models are sufficient and appropriate to describe real field conditions.

  2. A 2015 International Geomagnetic Reference Field (IGRF) candidate model based on Swarm's experimental absolute magnetometer vector mode data

    NASA Astrophysics Data System (ADS)

    Vigneron, Pierre; Hulot, Gauthier; Olsen, Nils; Léger, Jean-Michel; Jager, Thomas; Brocco, Laura; Sirol, Olivier; Coïsson, Pierdavide; Lalanne, Xavier; Chulliat, Arnaud; Bertrand, François; Boness, Axel; Fratter, Isabelle

    2015-06-01

    Each of the three satellites of the European Space Agency Swarm mission carries an absolute scalar magnetometer (ASM) that provides the nominal 1-Hz scalar data of the mission for both science and calibration purposes. These ASM instruments, however, also deliver autonomous 1-Hz experimental vector data. Here, we report on how ASM-only scalar and vector data from the Alpha and Bravo satellites between November 29, 2013 (a week after launch) and September 25, 2014 (for on-time delivery of the model on October 1, 2014) could be used to build a very valuable candidate model for the 2015.0 International Geomagnetic Reference Field (IGRF). A parent model was first computed, describing the geomagnetic field of internal origin up to degree and order 40 in a spherical harmonic representation and including a constant secular variation up to degree and order 8. This model was next simply forwarded to epoch 2015.0 and truncated at degree and order 13. The resulting ASM-only 2015.0 IGRF candidate model is compared to analogous models derived from the mission's nominal data and to the now-published final 2015.0 IGRF model. Differences among models mainly highlight uncertainties enhanced by the limited geographical distribution of the selected data set (essentially due to a lack of availability of data at high northern latitude satisfying nighttime conditions at the end of the time period considered). These appear to be comparable to differences classically observed among IGRF candidate models. These positive results led the ASM-only 2015.0 IGRF candidate model to contribute to the construction of the final 2015.0 IGRF model.

  3. Verification of Emergent Behaviors in Swarm-based Systems

    NASA Technical Reports Server (NTRS)

    Rouff, Christopher; Vanderbilt, Amy; Hinchey, Mike; Truszkowski, Walt; Rash, James

    2004-01-01

    The emergent properties of swarms make swarm-based missions powerful, but at the same time more difficult to design and to assure that the proper behaviors will emerge. We are currently investigating formal methods and techniques for verification and validation of swarm-based missions. The Autonomous Nano-Technology Swarm (ANTS) mission is being used as an example and case study for swarm-based missions to experiment and test current formal methods with intelligent swarms. Using the ANTS mission, we have evaluated multiple formal methods to determine their effectiveness in modeling and assuring swarm behavior. This paper introduces how intelligent swarm technology is being proposed for NASA missions, and gives the results of a comparison of several formal methods and approaches for specifying intelligent swarm-based systems and their effectiveness for predicting emergent behavior.

  4. Ethiopian Tertiary dike swarms

    NASA Technical Reports Server (NTRS)

    Mohr, P. A.

    1971-01-01

    Mapping of the Ethiopian rift and Afar margins revealed the existence of Tertiary dike swarms. The structural relations of these swarms and the fed lava pile to monoclinal warping of the margins partly reflect a style of continental margin tectonics found in other parts of the world. In Ethiopia, however, conjugate dike trends appear to be unusually strongly developed. Relation of dikes to subsequent margin faulting is ambiguous, and there are instances where the two phenomena are spatially separate and of differing trends. There is no evidence for lateral migration with time of dike injection toward the rift zone. No separate impingement of Red Sea, Gulf of Aden, and African rift system stress fields on the Ethiopian region can be demonstrated from the Tertiary dike swarms. Rather, a single, regional paleostress field existed, suggestive of a focus beneath the central Ethiopian plateau. This stress field was dominated by tension: there is no cogent evidence for shearing along the rift margins. A gentle compression along the rift floor is indicated. A peculiar sympathy of dike hade directions at given localities is evident.

  5. Electron swarm coefficients and the limiting field strength of SF6-N2O mixtures

    NASA Astrophysics Data System (ADS)

    Basurto, E.; Hernández-Ávila, J. L.; Juárez, A. M.; de Urquijo, J.

    2013-09-01

    The electron drift velocities and the effective ionization coefficients have been measured with a pulsed Townsend apparatus for the SF6-N2O mixtures (1-75% SF6) over the combined density-normalized electric field strength, E/N, from 130 to 420 Td (1 Townsend = 10-17 V cm2). Strong electron detachment effects have been observed for gas pressure mixtures above 1 Torr due mostly to NO-, arising as a dissociation product of N2O. In contrast, the influence of detachment due to the negative ions from SF6 is shown to be very small. It has been found that the limiting electric field strength, E/Nlim, of the SF6-N2O mixture is slightly superior (25-5%) to that of SF6-N2 for SF6 amounts of 0-50%, respectively.

  6. Time-delayed autosynchronous swarm control.

    PubMed

    Biggs, James D; Bennet, Derek J; Dadzie, S Kokou

    2012-01-01

    In this paper a general Morse potential model of self-propelling particles is considered in the presence of a time-delayed term and a spring potential. It is shown that the emergent swarm behavior is dependent on the delay term and weights of the time-delayed function, which can be set to induce a stationary swarm, a rotating swarm with uniform translation, and a rotating swarm with a stationary center of mass. An analysis of the mean field equations shows that without a spring potential the motion of the center of mass is determined explicitly by a multivalued function. For a nonzero spring potential the swarm converges to a vortex formation about a stationary center of mass, except at discrete bifurcation points where the center of mass will periodically trace an ellipse. The analytical results defining the behavior of the center of mass are shown to correspond with the numerical swarm simulations. PMID:22400623

  7. Time-delayed autosynchronous swarm control

    NASA Astrophysics Data System (ADS)

    Biggs, James D.; Bennet, Derek J.; Dadzie, S. Kokou

    2012-01-01

    In this paper a general Morse potential model of self-propelling particles is considered in the presence of a time-delayed term and a spring potential. It is shown that the emergent swarm behavior is dependent on the delay term and weights of the time-delayed function, which can be set to induce a stationary swarm, a rotating swarm with uniform translation, and a rotating swarm with a stationary center of mass. An analysis of the mean field equations shows that without a spring potential the motion of the center of mass is determined explicitly by a multivalued function. For a nonzero spring potential the swarm converges to a vortex formation about a stationary center of mass, except at discrete bifurcation points where the center of mass will periodically trace an ellipse. The analytical results defining the behavior of the center of mass are shown to correspond with the numerical swarm simulations.

  8. Swarm Economics

    NASA Astrophysics Data System (ADS)

    Kazadi, Sanza; Lee, John

    The Hamiltonian Method of Swarm Design is applied to the design of an agent based economic system. The method allows the design of a system from the global behaviors to the agent behaviors, with a guarantee that once certain derived agent-level conditions are satisfied, the system behavior becomes the desired behavior. Conditions which must be satisfied by consumer agents in order to bring forth the `invisible hand of the market' are derived and demonstrated in simulation. A discussion of how this method might be extended to other economic systems and non-economic systems is presented.

  9. Flagellar flows around bacterial swarms

    NASA Astrophysics Data System (ADS)

    Dauparas, Justas; Lauga, Eric

    2016-08-01

    Flagellated bacteria on nutrient-rich substrates can differentiate into a swarming state and move in dense swarms across surfaces. A recent experiment measured the flow in the fluid around an Escherichia coli swarm [Wu, Hosu, and Berg, Proc. Natl. Acad. Sci. USA 108, 4147 (2011)], 10.1073/pnas.1016693108. A systematic chiral flow was observed in the clockwise direction (when viewed from above) ahead of the swarm with flow speeds of about 10 μ m /s , about 3 times greater than the radial velocity at the edge of the swarm. The working hypothesis is that this flow is due to the action of cells stalled at the edge of a colony that extend their flagellar filaments outward, moving fluid over the virgin agar. In this work we quantitatively test this hypothesis. We first build an analytical model of the flow induced by a single flagellum in a thin film and then use the model, and its extension to multiple flagella, to compare with experimental measurements. The results we obtain are in agreement with the flagellar hypothesis. The model provides further quantitative insight into the flagella orientations and their spatial distributions as well as the tangential speed profile. In particular, the model suggests that flagella are on average pointing radially out of the swarm and are not wrapped tangentially.

  10. Prompt penetration electric fields and the extreme topside ionospheric response to the June 22-23, 2015 geomagnetic storm as seen by the Swarm constellation

    NASA Astrophysics Data System (ADS)

    Astafyeva, Elvira; Zakharenkova, Irina; Alken, Patrick

    2016-09-01

    Using data from the three Swarm satellites, we study the ionospheric response to the intense geomagnetic storm of June 22-23, 2015. With the minimum SYM-H excursion of -207 nT, this storm is so far the second strongest geomagnetic storm in the current 24th solar cycle. A specific configuration of the Swarm satellites allowed investigation of the evolution of the storm-time ionospheric alterations on the day- and the nightside quasi-simultaneously. With the development of the main phase of the storm, a significant dayside increase of the vertical total electron content (VTEC) and electron density Ne was first observed at low latitudes on the dayside. From ~22 UT of 22 June to ~1 UT of 23 June, the dayside experienced a strong negative ionospheric storm, while on the nightside an extreme enhancement of the topside VTEC occurred at mid-latitudes of the northern hemisphere. Our analysis of the equatorial electrojet variations obtained from the magnetic Swarm data indicates that the storm-time penetration electric fields were, most likely, the main driver of the observed ionospheric effects at the initial phase of the storm and at the beginning of the main phase. The dayside ionosphere first responded to the occurrence of the strong eastward equatorial electric fields. Further, penetration of westward electric fields led to gradual but strong decrease of the plasma density on the dayside in the topside ionosphere. At this stage, the disturbance dynamo could have contributed as well. On the nightside, the observed extreme enhancement of the Ne and VTEC in the northern hemisphere (i.e., the summer hemisphere) in the topside ionosphere was most likely due to the combination of the prompt penetration electric fields, disturbance dynamo and the storm-time thermospheric circulation. From ~2.8 UT, the ionospheric measurements from the three Swarm satellites detected the beginning of the second positive storm on the dayside, which was not clearly associated with electrojet

  11. Particle Swarm Transport in Fracture Networks

    NASA Astrophysics Data System (ADS)

    Pyrak-Nolte, L. J.; Mackin, T.; Boomsma, E.

    2012-12-01

    intersections were larger in width than the individual fractures, enabling the swarm to expand freely because of less confinement from the fracture walls. When swarms were released in a fracture network supporting an ambient flow rate, the ability to transport cohesive swarms through the fracture network was a function of the flow rate and swarm volume. For low ambient flow rates (< 4 μl/min), the gravitational force on the swarm dominated, and swarm transport followed a path similar to that for a quiescent fluid. For flow rates > 4 μl/min, large swarms (30 μl) remained cohesive (i.e. low loss of particles) as swarms were driven through the network both in the direction of and opposite to the direction of gravity. These experiments demonstrate conditions under which colloidal-size contaminants can be driven through a fracture network. High-speed transport of cohesive swarms depends on the volume of the swarm and the ambient flow rates that provide a balance of forces that prevents significant loss of particle from the swarm or deposition of particles along the flow path. Swarms that are transported cohesively travel along a highly localized path through a fracture network. Acknowledgment: The authors wish to acknowledge support of this work by the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy (DE-FG02-09ER16022) and NSF REU program in the Physics Department at Purdue University.

  12. ANALYSIS OF DIFFUSION FIELD EXPERIMENTS

    EPA Science Inventory

    The report describes general theoretical frameworks for the ordering of diffusion field data in terms of meteorological measurements. The three methods described are surface-layer (Monin-Obukhov) similarity, convective scaling, and statistical theory using wind fluctuations. Earl...

  13. Field Experiments in Litter Control

    ERIC Educational Resources Information Center

    Finnie, William C.

    1973-01-01

    A series of urban and highway litter experiments in Richmond (Virginia), St. Louis, and Philadelphia indicated well-designed litter cans reduced littering about 15 percent along city streets and nearly 30 percent along highways. Also, the propensity to litter is critically affected by the characteristics of the individual and environmental…

  14. Family Oriented Field Experience in Geography.

    ERIC Educational Resources Information Center

    Williams, Karen A.

    A family-oriented geography field course about the southwestern United States was conducted in 1978 by a community college in Michigan (Delta College). Course activities took place in Colorado. The major purpose of the field experience was to offer learning experiences to family groups rather than to individual students. For purposes of the field…

  15. Field experiences with intelligent pigs

    SciTech Connect

    Smith, S.N.; Duvivier, J.P.; Lefevre, D.E.; Robb, G.A.

    1996-08-01

    Oil and gas production operations use intelligent pigs for corrosion inspection of gathering systems and pipelines worldwide. The authors have been involved with intelligent pig inspections which have been conducted on over 155 different pipelines owned by one international corporation. A variety of intelligent pig vendors have been used with tools ranging from standard first generation magnetic flux leakage (MFL) to high-resolution MFL to standard and custom made ultrasonic (UT) tools. Experiences encountered during these inspections are discussed and resolutions to many of the problems are described.

  16. How to Thrive during Your Field Experiences

    ERIC Educational Resources Information Center

    Schaffer, Connie; Welsh, Kelly

    2014-01-01

    Field experiences, also referred to as practicums or clinical experiences, are part of every accredited teacher preparation program. These pre-student teaching experiences place future teachers in a preK-12 classroom where they have the opportunity not just to observe, but also to learn about teaching by interacting with teachers and students. The…

  17. Field Experiments of Family Planning Incentives.

    ERIC Educational Resources Information Center

    Rogers, Everett M.

    A review of four quasi-experiments on family planning incentives in three Asian nations is presented, and a multi-national comparative field experiment on family planning incentives is proposed. Experiments include: (1) The Ernakulam vasectomy campaigns, (2) Indian Tea Estates retirement bond incentive program, (3) Taiwan educational bond…

  18. TOPICAL REVIEW: Kinetic phenomena in charged particle transport in gases, swarm parameters and cross section data

    NASA Astrophysics Data System (ADS)

    Petrovic, Z. Lj; Suvakov, M.; Nikitovic, Z.; Dujko, S.; Sasic, O.; Jovanovic, J.; Malovic, G.; Stojanovic, V.

    2007-02-01

    In this review we discuss the current status of the physics of charged particle swarms, mainly electrons. The whole field is analysed mainly through its relationship to plasma modelling and illustrated by some recent examples developed mainly by our group. The measurements of the swarm coefficients and the availability of the data are briefly discussed. More time is devoted to the development of complete electron molecule cross section sets along with recent examples such as NO, CF4 and HBr. We extend the discussion to the availability of ion and fast neutral data and how swarm experiments may serve to provide new data. As a point where new insight into the kinetics of charge particle transport is provided, the role of kinetic phenomena is discussed and recent examples are listed. We focus here on giving two examples on how non-conservative processes make dramatic effects in transport, the negative absolute mobility and the negative differential conductivity for positrons in argon. Finally we discuss the applicability of swarm data in plasma modelling and the relationship to other fields where swarm experiments and analysis make significant contributions. Based on the general invited lecture presented by the first author at ESCAMPIG 2006 at Lecce in Italy.

  19. From theory to field experiments

    NASA Astrophysics Data System (ADS)

    de Vos, Bram

    2016-04-01

    Peter Raats' achievements in Haren (NL) 1986-1997 were based on a solid theoretical insight in hydrology and transport process in soil. However, Peter was also the driving force behind many experimental studies and applied research. This will be illustrated by a broad range of examples ranging from the dynamics of composting processes of organic material; modelling and monitoring nutrient leaching at field-scale; wind erosion; water and nutrient dynamics in horticultural production systems; oxygen diffusion in soils; and processes of water and nutrient uptake by plant roots. Peter's leadership led to may new approaches and the introduction of innovative measurement techniques in Dutch research; ranging from TDR to nutrient concentration measurements in closed fertigation systems. This presentation will give a brief overview how Peter's theoretical and mathematical insights accelerated this applied research.

  20. Velocity Structure in the West Bohemia Seismic Zone: Velocity Models Retrieved from different Earthquake Swarms

    NASA Astrophysics Data System (ADS)

    Alexandrakis, C.; Löberich, E.; Kieslich, A.; Calo, M.; Vavrycuk, V.; Buske, S.

    2015-12-01

    Earthquake swarms, fluid migration and gas springs are indications of the ongoing geodynamic processes within the West Bohemia seismic zone located at the Czech-German border. The possible relationship between the fluids, gas and seismicity is of particular interest and has motivated numerous past, ongoing and future studies, including a multidisciplinary monitoring proposal through the International Continental Scientific Drilling Program (ICDP). The most seismically active area within the West Bohemia seismic zone is located at the Czech town Nový Kostel. The Nový Kostel zone experiences frequent swarms of several hundreds to thousands of earthquakes over a period of weeks to several months. The seismicity is always located in the same area and depth range (~5-15 km), however the activated fault segments and planes differ. For example, the 2008 swarm activated faults along the southern end of the seismic zone, the 2011 swarm activated the northern segment, and the recent 2014 swarm activated the middle of the seismic zone. This indicates changes to the local stress field, and may relate to fluid migration and/or the complicated tectonic situation. The West Bohemia Seismic Network (WEBNET) is ideally located for studying the Nový Kostel swarm area and provides good azimuthal coverage. Here, we use the high quality P- and S-wave arrival picks recorded by WEBNET to calculate swarm-dependent velocity models for the 2008 and 2011 swarms, and an averaged (swarm independent) model using earthquakes recorded between 1991 and 2011. To this end, we use double-difference tomography to calculate P- and S-wave velocity models. The models are compared and examined in terms of swarm-dependent velocities and structures. Since the P-to-S velocity ratio is particularly sensitive to the presence of pore fluids, we derive ratio models directly from the inverted P- and S-wave models in order to investigate the potential influence of fluids on the seismicity. Finally, clustering

  1. Indirect Reciprocity; A Field Experiment

    PubMed Central

    van Apeldoorn, Jacobien; Schram, Arthur

    2016-01-01

    Indirect reciprocity involves cooperative acts towards strangers, either in response to their kindness to third parties (downstream) or after receiving kindness from others oneself (upstream). It is considered to be important for the evolution of cooperative behavior amongst humans. Though it has been widely studied theoretically, the empirical evidence of indirect reciprocity has thus far been limited and based solely on behavior in laboratory experiments. We provide evidence from an online environment where members can repeatedly ask and offer services to each other, free of charge. For the purpose of this study we created several new member profiles, which differ only in terms of their serving history. We then sent out a large number of service requests to different members from all over the world. We observe that a service request is more likely to be rewarded for those with a profile history of offering the service (to third parties) in the past. This provides clear evidence of (downstream) indirect reciprocity. We find no support for upstream indirect reciprocity (in this case, rewarding the service request after having previously received the service from third parties), however. Our evidence of downstream indirect reciprocity cannot be attributed to reputational effects concerning one’s trustworthiness as a service user. PMID:27043712

  2. Swarming rings of bacteria.

    NASA Astrophysics Data System (ADS)

    Brenner, M. P.; Levitov, L. S.

    1996-03-01

    The behavior of bacterii controlled by chemotaxis can lead to a complicated spatial organization, producing swarming rings, and steady or moving aggregates( E. O. Budrene, and H. C. Berg, Complex patterns formed by motile cells of Escherichia coli. Nature 349, 630-633 (1991). ). We present a simple theory that explains the experimentally observed structures, by solving analytically two coupled differential equations, for the densities of bacterii and of chemoattractant. The equations have an interesting relation to the exactly solvable Burgers equation, and admit soliton-like solutions, that can be steady or moving. In addition, we find that there are singular solutions to the equations in which the bacterial density diverges. The theory agrees very well with the experiment: the solitons correspond to the observed travelling rings, the singularities describe formation of aggregates. In particular, the theory explains why the velocity of swarming rings decreases with the increase of the food concentration, the fact apparently not accounted by other existing approaches( L. Tsimring et. al., Phys. Rev. Lett., 75, 1859 (1995); Woodward, et al, Biophysical Journal, 68, 2181-2189 (1995). ).

  3. Swarm formation control utilizing elliptical surfaces and limiting functions.

    PubMed

    Barnes, Laura E; Fields, Mary Anne; Valavanis, Kimon P

    2009-12-01

    In this paper, we present a strategy for organizing swarms of unmanned vehicles into a formation by utilizing artificial potential fields that were generated from normal and sigmoid functions. These functions construct the surface on which swarm members travel, controlling the overall swarm geometry and the individual member spacing. Nonlinear limiting functions are defined to provide tighter swarm control by modifying and adjusting a set of control variables that force the swarm to behave according to set constraints, formation, and member spacing. The artificial potential functions and limiting functions are combined to control swarm formation, orientation, and swarm movement as a whole. Parameters are chosen based on desired formation and user-defined constraints. This approach is computationally efficient and scales well to different swarm sizes, to heterogeneous systems, and to both centralized and decentralized swarm models. Simulation results are presented for a swarm of 10 and 40 robots that follow circle, ellipse, and wedge formations. Experimental results are included to demonstrate the applicability of the approach on a swarm of four custom-built unmanned ground vehicles (UGVs). PMID:19447722

  4. Natural or Induced: Identifying Natural and Induced Swarms from Pre-production and Co-production Microseismic Catalogs at the Coso Geothermal Field

    USGS Publications Warehouse

    Schoenball, Martin; Kaven, Joern; Glen, Jonathan M.; Davatzes, Nicholas C.

    2015-01-01

    Increased levels of seismicity coinciding with injection of reservoir fluids have prompted interest in methods to distinguish induced from natural seismicity. Discrimination between induced and natural seismicity is especially difficult in areas that have high levels of natural seismicity, such as the geothermal fields at the Salton Sea and Coso, both in California. Both areas show swarm-like sequences that could be related to natural, deep fluid migration as part of the natural hydrothermal system. Therefore, swarms often have spatio-temporal patterns that resemble fluid-induced seismicity, and might possibly share other characteristics. The Coso Geothermal Field and its surroundings is one of the most seismically active areas in California with a large proportion of its activity occurring as seismic swarms. Here we analyze clustered seismicity in and surrounding the currently produced reservoir comparatively for pre-production and co-production periods. We perform a cluster analysis, based on the inter-event distance in a space-time-energy domain to identify notable earthquake sequences. For each event j, the closest previous event i is identified and their relationship categorized. If this nearest neighbor’s distance is below a threshold based on the local minimum of the bimodal distribution of nearest neighbor distances, then the event j is included in the cluster as a child to this parent event i. If it is above the threshold, event j begins a new cluster. This process identifies subsets of events whose nearest neighbor distances and relative timing qualify as a cluster as well as a characterizing the parent-child relationships among events in the cluster. We apply this method to three different catalogs: (1) a two-year microseismic survey of the Coso geothermal area that was acquired before exploration drilling in the area began; (2) the HYS_catalog_2013 that contains 52,000 double-difference relocated events and covers the years 1981 to 2013; and (3) a

  5. ESA Swarm Mission - Level 1b Products

    NASA Astrophysics Data System (ADS)

    Tøffner-Clausen, Lars; Floberghagen, Rune; Mecozzi, Riccardo; Menard, Yvon

    2014-05-01

    Swarm, a three-satellite constellation to study the dynamics of the Earth's magnetic field and its interactions with the Earth system, has been launched in November 2013. The objective of the Swarm mission is to provide the best ever survey of the geomagnetic field and its temporal evolution, which will bring new insights into the Earth system by improving our understanding of the Earth's interior and environment. The Level 1b Products of the Swarm mission contain time-series of the quality screened, calibrated, corrected, and fully geo-localized measurements of the magnetic field intensity, the magnetic field vector (provided in both instrument and Earth-fixed frames), the plasma density, temperature, and velocity. Additionally, quality screened and pre-calibrated measurements of the nongravitational accelerations are provided. Geo-localization is performed by 24- channel GPS receivers and by means of unique, three head Advanced Stellar Compasses for high-precision satellite attitude information. The Swarm Level 1b data will be provided in daily products separately for each of the three Swarm spacecrafts. This poster will present detailed lists of the contents of the Swarm Level 1b Products and brief descriptions of the processing algorithms used in the generation of these data.

  6. Ground and CHAMP observations of field-aligned current circuits generated by lower atmospheric disturbances and expectations to the SWARM to clarify their three dimensional structure

    NASA Astrophysics Data System (ADS)

    Iyemori, Toshihiko; Nakanishi, Kunihito; Aoyama, Tadashi; Lühr, Hermann

    2014-05-01

    Acoustic gravity waves propagated to the ionosphere cause dynamo currents in the ionosphere. They divert along geomagnetic field lines of force to another hemisphere accompanying electric field and then flow in the ionosphere of another hemisphere by the electric field forming closed current circuits. The oscillating current circuits with the period of acoustic waves generate magnetic variations on the ground, and they are observed as long period geomagnetic pulsations. This effect has been detected during big earthquakes, strong typhoons, tornados etc. On a low-altitude satellite orbit, the spatial distribution (i.e., structure) of the current circuits along the satellite orbit should be detected as temporal magnetic oscillations, and the effect is confirmed by a CHAMP data analysis. On the spatial structure, in particular, in the longitudinal direction, it has been difficult to examine by a single satellite or from ground magnetic observations. The SWARM satellites will provide an unique opportunity to clarify the three dimensional structure of the field-aligned current circuits.

  7. Overview of Field Experience - Degradation Rates & Lifetimes

    SciTech Connect

    Jordan, Dirk; Kurtz, Sarah

    2015-09-14

    The way a PV module fails may depend not only on its design and the materials used in its construction, but also on the weather it experiences, the way it is mounted, and the quality control during its manufacture. This presentation gives an overview of Field Experience - what degradation rates and what lifetimes are being observed in various regions.

  8. Parameter estimation for chaotic systems with a Drift Particle Swarm Optimization method

    NASA Astrophysics Data System (ADS)

    Sun, Jun; Zhao, Ji; Wu, Xiaojun; Fang, Wei; Cai, Yujie; Xu, Wenbo

    2010-06-01

    Inspired by the motion of electrons in metal conductors in an electric field, we propose a variant of Particle Swarm Optimization (PSO), called Drift Particle Swarm Optimization (DPSO) algorithm, and apply it in estimating the unknown parameters of chaotic dynamic systems. The principle and procedure of DPSO are presented, and the algorithm is used to identify Lorenz system and Chen system. The experiment results show that for the given parameter configurations, DPSO can identify the parameters of the systems accurately and effectively, and it may be a promising tool for chaotic system identification as well as other numerical optimization problems in physics.

  9. Earthquake swarms in Greenland

    NASA Astrophysics Data System (ADS)

    Larsen, Tine B.; Voss, Peter H.; Dahl-Jensen, Trine

    2014-05-01

    Earthquake swarms occur primarily near active volcanoes and in areas with frequent tectonic activity. However, intraplate earthquake swarms are not an unknown phenomenon. They are located near zones of weakness, e.g. in regions with geological contrasts, where dynamic processes are active. An earthquake swarm is defined as a period of increased seismicity, in the form of a cluster of earthquakes of similar magnitude, occurring in the same general area, during a limited time period. There is no obvious main shock among the earthquakes in a swarm. Earthquake swarms occur in Greenland, which is a tectonically stable, intraplate environment. The first earthquake swarms in Greenland were detected more than 30 years ago in Northern and North-Eastern Greenland. However, detection of these low-magnitude events is challenging due to the enormous distances and the relatively sparse network of seismographs. The seismograph coverage of Greenland has vastly improved since the international GLISN-project was initiated in 2008. Greenland is currently coved by an open network of 19 BB seismographs, most of them transmitting data in real-time. Additionally, earthquake activity in Greenland is monitored by seismographs in Canada, Iceland, on Jan Mayen, and on Svalbard. The time-series of data from the GLISN network is still short, with the latest station been added in NW Greenland in 2013. However, the network has already proven useful in detecting several earthquake swarms. In this study we will focus on two swarms: one occurring near/on the East Greenland coast in 2008, and another swarm occurring in the Disko-area near the west coast of Greenland in 2010. Both swarms consist of earthquakes with local magnitudes between 1.9 and 3.2. The areas, where the swarms are located, are regularly active with small earthquakes. The earthquake swarms are analyzed in the context of the general seismicity and the possible relationship to the local geological conditions.

  10. Transport of Particle Swarms Through Fractures

    NASA Astrophysics Data System (ADS)

    Boomsma, E.; Pyrak-Nolte, L. J.

    2011-12-01

    The transport of engineered micro- and nano-scale particles through fractured rock is often assumed to occur as dispersions or emulsions. Another potential transport mechanism is the release of particle swarms from natural or industrial processes where small liquid drops, containing thousands to millions of colloidal-size particles, are released over time from seepage or leaks. Swarms have higher velocities than any individual colloid because the interactions among the particles maintain the cohesiveness of the swarm as it falls under gravity. Thus particle swarms give rise to the possibility that engineered particles may be transported farther and faster in fractures than predicted by traditional dispersion models. In this study, the effect of fractures on colloidal swarm cohesiveness and evolution was studied as a swarm falls under gravity and interacts with fracture walls. Transparent acrylic was used to fabricate synthetic fracture samples with either (1) a uniform aperture or (2) a converging aperture followed by a uniform aperture (funnel-shaped). The samples consisted of two blocks that measured 100 x 100 x 50 mm. The separation between these blocks determined the aperture (0.5 mm to 50 mm). During experiments, a fracture was fully submerged in water and swarms were released into it. The swarms consisted of dilute suspensions of either 25 micron soda-lime glass beads (2% by mass) or 3 micron polystyrene fluorescent beads (1% by mass) with an initial volume of 5μL. The swarms were illuminated with a green (525 nm) LED array and imaged optically with a CCD camera. In the uniform aperture fracture, the speed of the swarm prior to bifurcation increased with aperture up to a maximum at a fracture width of approximately 10 mm. For apertures greater than ~15 mm, the velocity was essentially constant with fracture width (but less than at 10 mm). This peak suggests that two competing mechanisms affect swarm velocity in fractures. The wall provides both drag, which

  11. Swarm Intelligence in Text Document Clustering

    SciTech Connect

    Cui, Xiaohui; Potok, Thomas E

    2008-01-01

    Social animals or insects in nature often exhibit a form of emergent collective behavior. The research field that attempts to design algorithms or distributed problem-solving devices inspired by the collective behavior of social insect colonies is called Swarm Intelligence. Compared to the traditional algorithms, the swarm algorithms are usually flexible, robust, decentralized and self-organized. These characters make the swarm algorithms suitable for solving complex problems, such as document collection clustering. The major challenge of today's information society is being overwhelmed with information on any topic they are searching for. Fast and high-quality document clustering algorithms play an important role in helping users to effectively navigate, summarize, and organize the overwhelmed information. In this chapter, we introduce three nature inspired swarm intelligence clustering approaches for document clustering analysis. These clustering algorithms use stochastic and heuristic principles discovered from observing bird flocks, fish schools and ant food forage.

  12. Bifurcating Particle Swarms in Smooth-Walled Fractures

    NASA Astrophysics Data System (ADS)

    Pyrak-Nolte, L. J.; Sun, H.

    2010-12-01

    Particle swarms can occur naturally or from industrial processes where small liquid drops containing thousands to millions of micron-size to colloidal-size particles are released over time from seepage or leaks into fractured rock. The behavior of these particle swarms as they fall under gravity are affected by particle interactions as well as interactions with the walls of the fractures. In this paper, we present experimental results on the effect of fractures on the cohesiveness of the swarm and the formation of bifurcation structures as they fall under gravity and interact with the fracture walls. A transparent cubic sample (100 mm x 100 mm x 100 mm) containing a synthetic fracture with uniform aperture distributions was optically imaged to quantify the effect of confinement within fractures on particle swarm formation, swarm velocity, and swarm geometry. A fracture with a uniform aperture distribution was fabricated from two polished rectangular prisms of acrylic. A series of experiments were performed to determine how swarm movement and geometry are affected as the walls of the fracture are brought closer together from 50 mm to 1 mm. During the experiments, the fracture was fully saturated with water. We created the swarms using two different particle sizes in dilute suspension (~ 1.0% by mass). The particles were 3 micron diameter fluorescent polymer beads and 25 micron diameter soda-lime glass beads. Experiments were performed using swarms that ranged in size from 5 µl to 60 µl. The swarm behavior was imaged using an optical fluorescent imaging system composed of a CCD camera illuminated by a 100 mW diode-pumped doubled YAG laser. As a swarm falls in an open-tank of water, it forms a torroidal shape that is stable as long as no ambient or background currents exist in the water tank. When a swarm is released into a fracture with an aperture less than 5 mm, the swarm forms the torroidal shape but it is distorted because of the presence of the walls. The

  13. Monte Carlo simulation of electron swarm parameters in O2

    NASA Astrophysics Data System (ADS)

    Settaouti, A.; Settaouti, L.

    2007-03-01

    Oxygen plasmas have found numerous applications in plasma processing, such as reactive sputtering, dry etching of polymers, oxidation, and resist removal of semiconductors. Swarm and transport coefficients are essential for better understanding and modelling of these gas discharge processes. The electron swarms in a gas under the influence of an electric field can be simulated with the help of a Monte Carlo method. The swarm parameters evaluated are compared with experimental results.

  14. Multispacecraft current estimates at swarm

    NASA Astrophysics Data System (ADS)

    Dunlop, M. W.; Yang, Y.-Y.; Yang, J.-Y.; Lühr, H.; Shen, C.; Olsen, N.; Ritter, P.; Zhang, Q.-H.; Cao, J.-B.; Fu, H.-S.; Haagmans, R.

    2015-10-01

    During the first several months of the three-spacecraft Swarm mission all three spacecraft came repeatedly into close alignment, providing an ideal opportunity for validating the proposed dual-spacecraft method for estimating current density from the Swarm magnetic field data. Two of the Swarm spacecraft regularly fly side-by-side in closely similar orbits, while the third at times approaches the other two. This provides a data set which under certain assumptions of stationarity of the magnetic field can produce 2, 3, 4, 5 (or more) point measurements, which can be cross compared. We find that at low Earth orbit the use of time-shifted positions allow stable estimates of current density to be made and can verify temporal effects as well as validating the interpretation of the current components as arising predominantly from field-aligned currents. In the case of four-spacecraft configurations we can resolve the full vector current and therefore can check the perpendicular as well as parallel current density components directly, together with the quality factor for the estimates directly (for the first time in situ at low Earth orbit).

  15. [Experiences with varroatosis control (field cases)].

    PubMed

    Sabolic, M; Liebig, G

    1989-01-01

    The prevalence of Varroa jacobsoni in 20 bee-farms with an average of 371 swarms in the administrative districts of Tübingen and Stuttgart was investigated between 1983 and 1987. In summer as well as after each treatment the debris was examined regularly. On 19 bee-farms the population dynamics of the mites showed a similar pattern. During the first year after the varroatosis diagnosis we found an average of 30-50 mites after autumn treatment. This number increased to 300-600 varroa mites during the second and to several thousand during the third and fourth year. Evidently, the late autumn/early winter treatment of the more heavily infected swarms (during the third or fourth year after diagnosis) with Perizin or Folbex-VA-neu was usually insufficient to prevent damage or even a complete breakdown. In such swarms formic acid in form of the Illertisser mite plate must be applied as early as August or at the latest in September (after the end of the honey season). On one of the 20 bee-farms the development of the varroa mite infection differed from the other 19 farms. In this case the mite infection developed very slowly. The husbandry and environmental conditions could not explain this phenomenon. We think that this warrants further investigations. PMID:2617530

  16. The role of rotational mechanisms in electron swarm parameters at low reduced electric field in N2, O2 and H2

    NASA Astrophysics Data System (ADS)

    Ridenti, M. A.; Alves, L. L.; Guerra, V.; Amorim, J.

    2015-06-01

    The homogeneous Boltzmann equation for electrons in N2, O2 and H2 is solved under the classical two-term approximation, for reduced electric fields in the interval 10  -  4  -10 Td where the electron-neutral encounters are limited to elastic, rotational and vibrational collisions. Rotational excitations/de-excitations are described using the following three different approaches: the discrete inelastic/superelastic collisional operator, written for a number of rotational levels that depends on the molecular gas and the specific rotational cross sections considered the continuous approximation for rotations; a modified version of the continuous approximation for rotations, including a Chapman-Cowling corrective term proportional to the gas temperature. The expression of the rotational collision operator for this latter approach is deduced here and the results show that it bridges the gap between the discrete and the continuous descriptions at low/intermediate reduced electric fields. The calculations are compared with the measurements for the available swarm parameters to assess the validity of the different approaches and cross sections adopted to describe the rotational mechanisms.

  17. Emergent motion patterns of delay-coupled swarms

    NASA Astrophysics Data System (ADS)

    Szwaykowska, Klementyna; Mier-Y-Teran-Romero, Luis; Schwartz, Ira

    Emergent pattern-forming behaviours of aggregates of interacting autonomous agents are a topic of great interest in complex systems research, with applications including biology, environmental monitoring, and defence. We model, and experimentally verify, pattern formation in a swarm of delay-coupled agents, using a simple but general model of agent interactions. Using mean-field dynamics, we perform a thorough analytical study of the bifurcation structure as a function of network connectivity and delay to describe the emergence of pattern formation. We show that swarm motion patterns observed for a homogeneous swarm with all-to-all communication are robust to decreasing network connectivity and to heterogeneity in the parameters governing individual agent behaviours. We perform systematic numerical studies to show where the mean-field theory deviates from simulation and experiment. This research is funded by the Office of Naval Research (ONR) (Contract No. N0001412WX20083 and NRL Base Funding Contract No. N0001414WX00023). KS holds a NRC Research Associateship Award. LMR is a post-doctoral fellow at JHU, supported by NIH.

  18. Teacher Knowledge Development in Early Field Experiences

    ERIC Educational Resources Information Center

    Ingersoll, Casey; Jenkins, Jayne M.; Lux, Karen

    2014-01-01

    Investigation of physical education preservice teacher knowledge development has been primarily limited to study of a single semester of early field experience (EFE), with findings from these investigations driving EFE design. The purpose of this research was to investigate what types of knowledge develop and how knowledge evolves and interacts to…

  19. Laboratory and Field Experiments in Motor Learning.

    ERIC Educational Resources Information Center

    Singer, Robert N.; And Others

    This manual for research in motor learning was written for scientifically based physical educators, experimental psychologists, and others interested in the investigation of learning and performance phenomena associated with skill acquisition. Laboratory and field experiments are presented that can be run with or without the presence of a formal…

  20. Engaging Sacred Space: Experiments in the Field

    ERIC Educational Resources Information Center

    della Dora, Veronica

    2011-01-01

    This article reflects on the experience of theorizing sacred space through field practice as part of a fieldtrip to Barcelona. In particular, it focuses on the critical analysis of different approaches to sacred space as applied to various sites in the city. The article opens with a brief review of three mainstream approaches to sacred space: the…

  1. Memorable Experiences of a Science Field Trip.

    ERIC Educational Resources Information Center

    Knapp, Doug

    2000-01-01

    Attempts to learn more about memorable experiences associated with science field trips by conducting a 1-month and an 18-month evaluation of elementary school students who had participated in an environmental science program at a community park in a Midwestern city. Concludes that students' memories were nonspecific and disassociated from…

  2. PAINT COATINGS: CONTROLLED FIELD AND CHAMBER EXPERIMENTS

    EPA Science Inventory

    To determine the impact of pollution levels on the weathering rates of coatings, laboratory chamber experiments and controlled field exposures at North Carolina and Ohio sites were conducted in such a manner to separate the contributions due to dry deposition, wet deposition, pre...

  3. Adaptive Remote-Sensing Techniques Implementing Swarms of Mobile Agents

    SciTech Connect

    Cameron, S.M.; Loubriel, G.M.; Rbinett, R.D. III; Stantz, K.M.; Trahan, M.W.; Wagner, J.S.

    1999-04-01

    This paper focuses on our recent work at Sandia National Laboratories toward engineering a physics-based swarm of mobile vehicles for distributed sensing applications. Our goal is to coordinate a sensor array that optimizes sensor coverage and multivariate signal analysis by implementing artificial intelligence and evolutionary computational techniques. These intelligent control systems integrate both globally operating decision-making systems and locally cooperative information-sharing modes using genetically-trained neural networks. Once trained, neural networks have the ability to enhance real-time operational responses to dynamical environments, such as obstacle avoidance, responding to prevailing wind patterns, and overcoming other natural obscurants or interferences (jammers). The swarm realizes a collective set of sensor neurons with simple properties incorporating interactions based on basic community rules (potential fields) and complex interconnecting functions based on various neural network architectures, Therefore, the swarm is capable of redundant heterogeneous measurements which furnishes an additional degree of robustness and fault tolerance not afforded by conventional systems, while accomplishing such cognitive tasks as generalization, error correction, pattern recognition, and sensor fission. The robotic platforms could be equipped with specialized sensor devices including transmit/receive dipole antennas, chemical or biological sniffers in combination with recognition analysis tools, communication modulators, and laser diodes. Our group has been studying the collective behavior of an autonomous, multi-agent system applied to emerging threat applications. To accomplish such tasks, research in the fields of robotics, sensor technology, and swarms are being conducted within an integrated program. Mission scenarios under consideration include ground penetrating impulse radar (GPR) for detection of under-ground structures, airborne systems, and plume

  4. Emergency preparedness activities during an ongoing seismic swarm: the experience of the 2011-2012 Pollino (Southern Italy) sequence

    NASA Astrophysics Data System (ADS)

    Masi, A.; Mucciarelli, M.; Chiauzzi, L.; De Costanzo, G.; Loperte, G.

    2012-04-01

    Facing natural disasters effects can be a very difficult task lacking suitable activities and tools to preventively prepare the involved community (people, authorities, professionals, …) to the expected events. Therefore, a suite of preventive actions should be carried out to mitigate natural risks, in particular working to reduce the territorial vulnerability with respect to the specific natural hazard at hand, and to increase people response capacity. In fact, building social capacity helps to increase the risk perception and the people capacity to adapt to and cope with natural hazards. Since October 2011 a seismic swarm is affecting the Pollino mountain range, Southern Italy. At present the sequence is still ongoing, with more than 500 events with M>1, at least 40 well perceived by the population and a maximum magnitude at 3.6. The area mainly affected by the seismic sequence includes 12 villages, with a total population of about 50.000 inhabitants and, according to the current seismic hazard map it has high seismicity level. Such area was hit by a magnitude Ml=5.7 event in 1998 that produced macroseismic intensity not higher that VII-VIII degree of MCS scale and caused one dead, some injured and widespread damage in at least six municipalities. During the sequence, the National Department of Civil Protection (DPC) and the Civil Protection of Basilicata Region decided to put in action some measures aimed at verifying and enhancing emergency preparedness. These actions have been carried out with a constant and fruitful collaboration among the main stakeholders involved (scientific community, local and national governmental agencies, civil protection volunteers, etc) trough the following main activities: 1. collaboration between scientific community and the local and national offices of Civil Protection especially in the relationship with local authorities (e.g. mayors, which are civil protection authorities in their municipality); 2. interaction between DPC

  5. Spatial and temporal evolution of a microseismic swarm induced by water injection in the Arkema-Vauvert salt field (southern France)

    NASA Astrophysics Data System (ADS)

    Godano, Maxime; Bardainne, Thomas; Regnier, Marc; Deschamps, Anne; Valette, Marc

    2012-01-01

    This study investigates a microseismic swarm induced by injection operations in the Arkema-Vauvert salt field. The seismic activity in this field is monitored only by two permanent 3-component stations deployed in two wells. This study focuses on a period of 21 months (2004 January-2005 September) during which 1214 seismic events are located. The seismic activity is divided into three periods correlating with the water injection operations, highlighting a migration of the seismicity toward a thrust fault connecting the injection well and the production well. A waveform analysis reveals S-wave anisotropy, and focal mechanisms are computed using P, Sv and Sh amplitudes manually measured on anisotropy-corrected seismograms. First, synthetic resolution tests assess the reliability of the focal mechanisms determination from the two 3-component stations deployed in the field. Synthetic data are generated for 1056 earthquakes with various focal mechanisms and are perturbed with noise. The results indicate that the type of focal mechanism is correctly retrieved for 74 per cent of the synthetic earthquakes, but the uncertainties of the strike and rake are significant (from 15 to 45?). Next, the focal mechanisms are computed for 532 real earthquakes. The solutions primarily correspond to a dip-slip/thrust fault type with subvertical NE-SW and subhorizontal N-S to NW-SE nodal planes. Correlations between the focal mechanisms and the spatio-temporal distribution of the seismic activity are noteworthy. The study shows it is possible to reliably retrieve double-couple focal mechanisms for some faulting geometries with two 3-component seismological stations. However, the reliability of the focal mechanism retrieval depends on the station configuration. Therefore, the addition of further stations would improve the results.

  6. Guidance and control of swarms of spacecraft

    NASA Astrophysics Data System (ADS)

    Morgan, Daniel James

    control uses a finite horizon to apply the most up-to-date control sequence while simultaneously calculating a new assignment and trajectory based on updated state information. Using a finite horizon allows collisions to only be considered between spacecraft that are near each other at the current time. This relaxes the all-to-all communication assumption so that only neighboring agents need to communicate. Experimental validation is done using the formation flying testbed. The swarm-reconfiguration algorithms are tested using multiple quadrotors. Experiments have been performed using sequential convex programming for offline trajectory planning, model predictive control and sequential convex programming for real-time trajectory generation, and the variable-swarm, distributed auction algorithm for optimal assignment. These experiments show that the swarm-reconfiguration algorithms can be implemented in real time using actual hardware. In general, this dissertation presents guidance and control algorithms that maintain and reconfigure swarms of spacecraft while maintaining the shape of the swarm, preventing collisions between the spacecraft, and minimizing the amount of propellant used.

  7. From hybrid swarms to swarms of hybrids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The introgression of modern humans (Homo sapiens) with Neanderthals 40,000 YBP after a half-million years of separation, may have led to the best example of a hybrid swarm on earth. Modern trade and transportation in support of the human hybrids has continued to introduce additional species, genotyp...

  8. The Geologic Remote Sensing Field Experiment (GRSFE)

    NASA Technical Reports Server (NTRS)

    Dale-Bannister, Mary A.; Arvidson, Raymond E.; Guinness, Edward E.; Slavney, Susan H.; Stein, Thomas C.

    1991-01-01

    Field measurements for the Geologic Remote Sensing Field Experiment (GRSFE) were concentrated in the Lunar Lake area of Nevada. The GRSFE data are meant to be used in a variety of investigations, including tests of multispectral radiative transfer models for scattering and emission from planetary surfaces in support of the Earth Observing System (EOS), Mars Observer, and Magellan Missions. Studies will also be pursued to establish the neotectonic and paleoclimatic history of the arid southwestern United States. The data will also be used to support Mars Rover Sample Return (MRSR) simulation studies.

  9. Periodic reversal of direction allows Myxobacteria to swarm

    PubMed Central

    Wu, Yilin; Kaiser, A. Dale; Jiang, Yi; Alber, Mark S.

    2009-01-01

    Many bacteria can rapidly traverse surfaces from which they are extracting nutrient for growth. They generate flat, spreading colonies, called swarms because they resemble swarms of insects. We seek to understand how members of any dense swarm spread efficiently while being able to perceive and interfere minimally with the motion of others. To this end, we investigate swarms of the myxobacterium, Myxococcus xanthus. Individual M. xanthus cells are elongated; they always move in the direction of their long axis; and they are in constant motion, repeatedly touching each other. Remarkably, they regularly reverse their gliding directions. We have constructed a detailed cell- and behavior-based computational model of M. xanthus swarming that allows the organization of cells to be computed. By using the model, we are able to show that reversals of gliding direction are essential for swarming and that reversals increase the outflow of cells across the edge of the swarm. Cells at the swarm edge gain maximum exposure to nutrient and oxygen. We also find that the reversal period predicted to maximize the outflow of cells is the same (within the errors of measurement) as the period observed in experiments with normal M. xanthus cells. This coincidence suggests that the circuit regulating reversals evolved to its current sensitivity under selection for growth achieved by swarming. Finally, we observe that, with time, reversals increase the cell alignment, and generate clusters of parallel cells. PMID:19164578

  10. Utilizing Urban Environments for Effective Field Experiences

    NASA Astrophysics Data System (ADS)

    MacAvoy, S. E.; Knee, K.

    2014-12-01

    Research surveys suggest that students are demanding more applied field experiences from their undergraduate environmental science programs. For geoscience educators at liberal arts colleges without field camps, university vehicles, or even geology departments, getting students into the field is especially rewarding - and especially challenging. Here, we present strategies that we have used in courses ranging from introductory environmental science for non-majors, to upper level environmental methods and geology classes. Urban locations provide an opportunity for a different type of local "field-work" than would otherwise be available. In the upper-level undergraduate Environmental Methods class, we relied on a National Park area located a 10-minute walk from campus for most field exercises. Activities included soil analysis, measuring stream flow and water quality parameters, dendrochronology, and aquatic microbe metabolism. In the non-majors class, we make use of our urban location to contrast water quality in parks and highly channelized urban streams. Here we share detailed lesson plans and budgets for field activities that can be completed during a class period of 2.5 hours with a $75 course fee, show how these activities help students gain quantitative competency, and provide student feedback about the classes and activities.

  11. Shelter in a Swarm.

    PubMed

    Harshey, Rasika M; Partridge, Jonathan D

    2015-11-20

    Flagella propel bacteria during both swimming and swarming, dispersing them widely. However, while swimming bacteria use chemotaxis to find nutrients and avoid toxic environments, swarming bacteria appear to suppress chemotaxis and to use the dynamics of their collective motion to continuously expand and acquire new territory, barrel through lethal chemicals in their path, carry along bacterial and fungal cargo that assists in exploration of new niches, and engage in group warfare for niche dominance. Here, we focus on two aspects of swarming, which, if understood, hold the promise of revealing new insights into microbial signaling and behavior, with ramifications beyond bacterial swarming. These are as follows: how bacteria sense they are on a surface and turn on programs that promote movement and how they override scarcity and adversity as dense packs. PMID:26277623

  12. Autonomous and Autonomic Swarms

    NASA Technical Reports Server (NTRS)

    Hinchey, Michael G.; Rash, James L.; Truszkowski, Walter F.; Rouff, Christopher A.; Sterritt, Roy

    2005-01-01

    A watershed in systems engineering is represented by the advent of swarm-based systems that accomplish missions through cooperative action by a (large) group of autonomous individuals each having simple capabilities and no global knowledge of the group s objective. Such systems, with individuals capable of surviving in hostile environments, pose unprecedented challenges to system developers. Design and testing and verification at much higher levels will be required, together with the corresponding tools, to bring such systems to fruition. Concepts for possible future NASA space exploration missions include autonomous, autonomic swarms. Engineering swarm-based missions begins with understanding autonomy and autonomicity and how to design, test, and verify systems that have those properties and, simultaneously, the capability to accomplish prescribed mission goals. Formal methods-based technologies, both projected and in development, are described in terms of their potential utility to swarm-based system developers.

  13. The FIELDS experiment for Solar Probe Plus

    NASA Astrophysics Data System (ADS)

    Bale, S.; Spp/Fields Team

    2010-12-01

    Many of our basic ideas on the plasma physics of acceleration, energy flow, and dissipation, and structure of the solar wind have never been rigorously confronted by direct experimental measurements in the region where these processes are actually occurring. Although Alfven waves, shocks, and magnetic reconnection are often invoked as heating mechanisms, there have never been any direct measurements of Alfvenic waves nor the associated Poynting flux nor any measurements of ion or electron kinetic energy flux in the region from 10 R_s to 30 R_s where the final stages of wind acceleration are believed to occur. The radial profiles of both slow and fast solar wind acceleration are based on remote-sensing measurements and have been obtained for only a few selected events. Thus, the spatial radial and perpendicular scales of the acceleration process have been averaged by line-of-sight effects and the possibility of intense localized acceleration cannot be ruled out. The Solar Probe Plus (SPP) mission calls for the high quality fields and particles measurements required to solve the coronal heating and wind acceleration problem. The SPP 'FIELDS' experiment measures the electric and magnetic fields fundamental to the plasma physics of the structured and turbulent solar wind, flux ropes, collisionless shocks, and magnetic reconnection. FIELDS will make the first-ever measurements of the DC/Low-Frequency electric field inside of 1 AU allowing for in situ, high cadence measurements of the Poynting vector, the Elsasser variables, and E/B diagnostics of the wave spectrum to fce in the solar wind. SPP/FIELDS measures the radio wave (type III and II) signatures of microflares, energized electrons, and CME propagation. SPP/ FIELDS measures the plasma electron density to ~2% accuracy and the core electron temperature to ~5-10% accuracy more than 90% of the time at perihelion. FIELDS will also measure the in situ density fluctuation spectrum and structures at a very high cadence (

  14. Swarms: Optimum aggregations of spacecraft

    NASA Technical Reports Server (NTRS)

    Mayer, H. L.

    1980-01-01

    Swarms are aggregations of spacecraft or elements of a space system which are cooperative in function, but physically isolated or only loosely connected. For some missions the swarm configuration may be optimum compared to a group of completely independent spacecraft or a complex rigidly integrated spacecraft or space platform. General features of swarms are induced by considering an ensemble of 26 swarms, examples ranging from Earth centered swarms for commercial application to swarms for exploring minor planets. A concept for a low altitude swarm as a substitute for a space platform is proposed and a preliminary design studied. The salient design feature is the web of tethers holding the 30 km swarm in a rigid two dimensional array in the orbital plane. A mathematical discussion and tutorial in tether technology and in some aspects of the distribution of services (mass, energy, and information to swarm elements) are included.

  15. The Fate of Colloidal Swarms in Fractures

    NASA Astrophysics Data System (ADS)

    Pyrak-Nolte, L. J.; Olander, M. K.

    2009-12-01

    In the next 10-20 years, nano- and micro-sensor engineering will advance to the stage where sensor swarms could be deployed in the subsurface to probe rock formations and the fluids contained in them. Sensor swarms are groups of nano- or micro- sensors that are maintained as a coherent group to enable either sensor-to-sensor communication and/or coherent transmission of information as a group. The ability to maintain a swarm of sensors depends on the complexity of the flow paths in the rock, on the size and shape of the sensors and on the chemical interaction among the sensors, fluids, and rock surfaces. In this study, we investigate the effect of fracture aperture and fluid currents on the formation, evolution and break-up of colloidal swarms under gravity. Transparent cubic samples (100 mm x 100 mm x 100 mm) containing synthetic fractures with uniform and non-uniform aperture distributions were used to quantify the effect of aperture on swarm formation, swarm velocity, and swarm geometry using optical imaging. A fracture with a uniform aperture distribution was fabricated from two polished rectangular prisms of acrylic. A fracture with a non-uniform aperture distribution was created with a polished rectangular acrylic prism and an acrylic replica of an induced fracture surface from a carbonate rock. A series of experiments were performed to determine how swarm movement and geometry are affected as the walls of the fracture are brought closer together from 50 mm to 1 mm. During the experiments, the fracture was fully saturated with water. We created the swarms using two different particle sizes in dilute suspension (~ 1.0% by mass) . The particles were 3 micron diameter fluorescent polymer beads and 25 micron diameter soda-lime glass beads. The swarm behavior was imaged using an optical fluorescent imaging system composed of a CCD camera illuminated by a 100 mW diode-pumped doubled YAG laser. A swam was created when approximately 0.01 g drop of the suspension was

  16. Limiting field strength and electron swarm coefficients of the CF3I-SF6 gas mixture

    NASA Astrophysics Data System (ADS)

    de Urquijo, J.; Mitrani, A.; Ruíz-Vargas, G.; Basurto, E.

    2011-08-01

    We have measured the electron drift velocity, longitudinal diffusion, and the effective ionization coefficients in the gaseous mixture of CF3I-SF6 over the density-normalized electric field intensity E/N, from 375 to 500 Td (1 Td = 10-17 V cm2). A pulsed Townsend technique was used. Overall, the gas mixture compositions were varied from 50 to 90% CF3I. We have found that the limiting field strength E/Nlim of the CF3I-SF6 mixture is superior to that of CF3I-N2, and always higher than that of SF6. Moreover, over the whole mixture range, the range of the limiting field strength for the CF3I-SF6 mixture is 360-437 Td, these limits corresponding for pure SF6 and CF3I, respectively.

  17. Dynamics of Bacterial Swarming

    PubMed Central

    Darnton, Nicholas C.; Turner, Linda; Rojevsky, Svetlana; Berg, Howard C.

    2010-01-01

    Abstract When vegetative bacteria that can swim are grown in a rich medium on an agar surface, they become multinucleate, elongate, synthesize large numbers of flagella, produce wetting agents, and move across the surface in coordinated packs: they swarm. We examined the motion of swarming Escherichia coli, comparing the motion of individual cells to their motion during swimming. Swarming cells' speeds are comparable to bulk swimming speeds, but very broadly distributed. Their speeds and orientations are correlated over a short distance (several cell lengths), but this correlation is not isotropic. We observe the swirling that is conspicuous in many swarming systems, probably due to increasingly long-lived correlations among cells that associate into groups. The normal run-tumble behavior seen in swimming chemotaxis is largely suppressed, instead, cells are continually reoriented by random jostling by their neighbors, randomizing their directions in a few tenths of a second. At the edge of the swarm, cells often pause, then swim back toward the center of the swarm or along its edge. Local alignment among cells, a necessary condition of many flocking theories, is accomplished by cell body collisions and/or short-range hydrodynamic interactions. PMID:20483315

  18. Electron swarm transport coefficients in mixtures of H2O with He and Ar: Experiment and Boltzmann equation calculations

    NASA Astrophysics Data System (ADS)

    de Urquijo, Jaime; Basurto, E.; Juarez, A. M.; Ness, Kevin; Robson, Robert; Brunger, Michael; White, Ron

    2014-10-01

    The drift velocity of electrons in mixtures of gaseous water with helium and argon are measured over the range of reduced electric fields from 0--300 Td using a pulsed-Townsend technique. Small admixtures of water to both helium and argon are found to produce negative differential conductivity (NDC), despite NDC being absent from the pure gases. Comparison of the measured drift velocities with those calculated from a multi-term solution of Boltzmann's equation provides a further discriminative assessment on the accuracy and completeness of electron water vapour cross-sections. Funding acknowledgements: ARC, Mexican govt (PAPIIT IN 111014).

  19. Rotating wall compression of positron swarm in a harmonic potential: a Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Marjanovic, Srdjan; Bankovic, Ana; Suvakov, Milovan; Aled Isaac, C.; van der Werf, Dirk Peter; Charlton, Michael; Petrovic, Zoran Lj.

    2012-06-01

    Several experiments have demonstrated successful application of rotating wall technique for compressing positron beams in a single particle regime. While the basic mechanism of compression is understood, the role of the cooling gases which have to be used is poorly explained. Thus, we have simulated behavior of a swarm of particles (electrons or positrons) in an antisymmetric dipole rotating field inside a buffer gas trap. We have used our existing Monte Carlo code for the simulation, as the single particle conditions are inherently assumed. Varying mixtures of CF4 and N2 are used as the buffer gas in order to mimic the operating conditions of Surko trap, and to pinpoint the collisions responsible for compression. For a given parameter range, the simulation shows significant compression and axialization of positron swarm. We have investigated the change of swarm behavior by varying the applied rotating wall potential and frequency, strength of axial magnetic field, and background gas composition and pressure. The results show fast initial heating of the swarm, and subsequent cooling to the thermal temperature, as the radius of the cloud compresses, demonstrating that it is possible to compress the beam of charged particles in a single particle regime.

  20. The AMPTE CCE Magnetic Field Experiment

    NASA Technical Reports Server (NTRS)

    Potemra, T. A.; Zanetti, L. J.; Acuna, M. H.

    1985-01-01

    The Magnetic Field Experiment on the Active Magnetosheric Particle Tracer Explorer (AMPTE) Charge Composition Explorer (CCE) spacecraft consists of a triaxial fluxgate-magnetometer system containing sensors mounted on a 2.3-m two-link collapsible boom. It is pointed out that this instrument is similar to those flown on Voyager 1 and 2, and those scheduled to flight on the Giotto and Viking spacecraft. A description is provided of the sensor system and the analog electronics, and some preliminary data are presented.

  1. Determination of transport and reaction swarm coefficients from the analysis of complex transient pulses from the pulsed Townsend experiment

    NASA Astrophysics Data System (ADS)

    Bekstein, A.; de Urquijo, J.; Ducasse, O.; Rodríguez-Luna, J. C.; Juárez, A. M.

    2012-06-01

    We present in this paper the interpretation and analysis of transient pulses from a pulsed Townsend experiment by solving the continuity equations of the charged carriers (electrons and ions) involved in the avalanche. The set of second order partial differential equations is solved by SIMAV, a simulator designed specifically for the pulsed Townsend avalanche. Complex situations involving processes such as electron detachment, ion-molecule reactions, Penning ionization and secondary electron emission from ion impact at the cathode, virtually impossible to solve analytically, are discussed here to illustrate the capability of the simulator to help explain the various reaction processes involved in the avalanche, and also to derive some of the transport and reaction coefficients.

  2. Calculation of Electron Swarm Parameters of SF6/N2 in a Uniform Field Using an Improved Monte Carlo Collision Simulation Method

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Pfeiffer, W.; Kouzichine, N.; Qiu, Yuchang; Kuffel, E.; Li, Kenli

    2008-02-01

    The electron swarm parameters of SF6/N2 are calculated in the present study using an improved Monte Carlo collision simulation method (MCS). And some improved sampling techniques are also adopted. The simulation results show that the improved simulation method can provide more accurate results.

  3. Scale analysis of equatorial plasma irregularities derived from Swarm constellation

    NASA Astrophysics Data System (ADS)

    Xiong, Chao; Stolle, Claudia; Lühr, Hermann; Park, Jaeheung; Fejer, Bela G.; Kervalishvili, Guram N.

    2016-07-01

    In this study, we investigated the scale sizes of equatorial plasma irregularities (EPIs) using measurements from the Swarm satellites during its early mission and final constellation phases. We found that with longitudinal separation between Swarm satellites larger than 0.4°, no significant correlation was found any more. This result suggests that EPI structures include plasma density scale sizes less than 44 km in the zonal direction. During the Swarm earlier mission phase, clearly better EPI correlations are obtained in the northern hemisphere, implying more fragmented irregularities in the southern hemisphere where the ambient magnetic field is low. The previously reported inverted-C shell structure of EPIs is generally confirmed by the Swarm observations in the northern hemisphere, but with various tilt angles. From the Swarm spacecrafts with zonal separations of about 150 km, we conclude that larger zonal scale sizes of irregularities exist during the early evening hours (around 1900 LT).

  4. Hybrid dynamics in delay-coupled swarms with ``mothership'' networks

    NASA Astrophysics Data System (ADS)

    Hindes, Jason; Schwartz, Ira

    Swarming behavior continues to be a subject of immense interest because of its centrality in many naturally occurring systems in biology and physics. Moreover, the development of autonomous mobile agents that can mimic the behavior of swarms and can be engineered to perform complex tasks without constant intervention is a very active field of practical research. Here we examine the effects on delay-coupled swarm pattern formation from the inclusion of a small fraction of highly connected nodes, ``motherships'', in the swarm interaction network. We find a variety of new behaviors and bifurcations, including new hybrid motions of previously analyzed patterns. Both numerical and analytic techniques are used to classify the dynamics and construct the phase diagram. The implications for swarm control and robustness from topological heterogeneity are also discussed. This research was funded by the office of Naval Research (ONR), and was performed while JH held a National Research Council Research Associateship Award.

  5. Magnetic Field Experiment Data Analysis System

    NASA Technical Reports Server (NTRS)

    Holland, D. B.; Zanetti, L. J.; Suther, L. L.; Potemra, T. A.; Anderson, B. J.

    1995-01-01

    The Johns Hopkins University Applied Physics Laboratory (JHU/APL) Magnetic Field Experiment Data Analysis System (MFEDAS) has been developed to process and analyze satellite magnetic field experiment data from the TRIAD, MAGSAT, AMPTE/CCE, Viking, Polar BEAR, DMSP, HILAT, UARS, and Freja satellites. The MFEDAS provides extensive data management and analysis capabilities. The system is based on standard data structures and a standard user interface. The MFEDAS has two major elements: (1) a set of satellite unique telemetry processing programs for uniform and rapid conversion of the raw data to a standard format and (2) the program Magplot which has file handling, data analysis, and data display sections. This system is an example of software reuse, allowing new data sets and software extensions to be added in a cost effective and timely manner. Future additions to the system will include the addition of standard format file import routines, modification of the display routines to use a commercial graphics package based on X-Window protocols, and a generic utility for telemetry data access and conversion.

  6. Technology-Focused Early Field Experiences in Preservice Teacher Education

    ERIC Educational Resources Information Center

    Lux, Nicholas J.

    2013-01-01

    Although a broad body of research exists on field experiences in teacher education, one specific area of inquiry lacking substantial current research is that of technology-focused early field experiences, or field experiences that occur prior to student teaching and more formal clinical experiences. To address this gap, I conducted this…

  7. Swarming: flexible roaming plans.

    PubMed

    Partridge, Jonathan D; Harshey, Rasika M

    2013-03-01

    Movement over an agar surface via swarming motility is subject to formidable challenges not encountered during swimming. Bacteria display a great deal of flexibility in coping with these challenges, which include attracting water to the surface, overcoming frictional forces, and reducing surface tension. Bacteria that swarm on "hard" agar surfaces (robust swarmers) display a hyperflagellated and hyperelongated morphology. Bacteria requiring a "softer" agar surface (temperate swarmers) do not exhibit such a dramatic morphology. For polarly flagellated robust swarmers, there is good evidence that restriction of flagellar rotation somehow signals the induction of a large number of lateral flagella, but this scenario is apparently not relevant to temperate swarmers. Swarming bacteria can be further subdivided by their requirement for multiple stators (Mot proteins) or a stator-associated protein (FliL), secretion of essential polysaccharides, cell density-dependent gene regulation including surfactant synthesis, a functional chemotaxis signaling pathway, appropriate cyclic (c)-di-GMP levels, induction of virulence determinants, and various nutritional requirements such as iron limitation or nitrate availability. Swarming strategies are as diverse as the bacteria that utilize them. The strength of these numerous designs stems from the vantage point they offer for understanding mechanisms for effective colonization of surface niches, acquisition of pathogenic potential, and identification of environmental signals that regulate swarming. The signature swirling and streaming motion within a swarm is an interesting phenomenon in and of itself, an emergent behavior with properties similar to flocking behavior in diverse systems, including birds and fish, providing a convenient new avenue for modeling such behavior. PMID:23264580

  8. Particle Swarm Optimization Toolbox

    NASA Technical Reports Server (NTRS)

    Grant, Michael J.

    2010-01-01

    The Particle Swarm Optimization Toolbox is a library of evolutionary optimization tools developed in the MATLAB environment. The algorithms contained in the library include a genetic algorithm (GA), a single-objective particle swarm optimizer (SOPSO), and a multi-objective particle swarm optimizer (MOPSO). Development focused on both the SOPSO and MOPSO. A GA was included mainly for comparison purposes, and the particle swarm optimizers appeared to perform better for a wide variety of optimization problems. All algorithms are capable of performing unconstrained and constrained optimization. The particle swarm optimizers are capable of performing single and multi-objective optimization. The SOPSO and MOPSO algorithms are based on swarming theory and bird-flocking patterns to search the trade space for the optimal solution or optimal trade in competing objectives. The MOPSO generates Pareto fronts for objectives that are in competition. A GA, based on Darwin evolutionary theory, is also included in the library. The GA consists of individuals that form a population in the design space. The population mates to form offspring at new locations in the design space. These offspring contain traits from both of the parents. The algorithm is based on this combination of traits from parents to hopefully provide an improved solution than either of the original parents. As the algorithm progresses, individuals that hold these optimal traits will emerge as the optimal solutions. Due to the generic design of all optimization algorithms, each algorithm interfaces with a user-supplied objective function. This function serves as a "black-box" to the optimizers in which the only purpose of this function is to evaluate solutions provided by the optimizers. Hence, the user-supplied function can be numerical simulations, analytical functions, etc., since the specific detail of this function is of no concern to the optimizer. These algorithms were originally developed to support entry

  9. Swarming: Flexible Roaming Plans

    PubMed Central

    Partridge, Jonathan D.

    2013-01-01

    Movement over an agar surface via swarming motility is subject to formidable challenges not encountered during swimming. Bacteria display a great deal of flexibility in coping with these challenges, which include attracting water to the surface, overcoming frictional forces, and reducing surface tension. Bacteria that swarm on “hard” agar surfaces (robust swarmers) display a hyperflagellated and hyperelongated morphology. Bacteria requiring a “softer” agar surface (temperate swarmers) do not exhibit such a dramatic morphology. For polarly flagellated robust swarmers, there is good evidence that restriction of flagellar rotation somehow signals the induction of a large number of lateral flagella, but this scenario is apparently not relevant to temperate swarmers. Swarming bacteria can be further subdivided by their requirement for multiple stators (Mot proteins) or a stator-associated protein (FliL), secretion of essential polysaccharides, cell density-dependent gene regulation including surfactant synthesis, a functional chemotaxis signaling pathway, appropriate cyclic (c)-di-GMP levels, induction of virulence determinants, and various nutritional requirements such as iron limitation or nitrate availability. Swarming strategies are as diverse as the bacteria that utilize them. The strength of these numerous designs stems from the vantage point they offer for understanding mechanisms for effective colonization of surface niches, acquisition of pathogenic potential, and identification of environmental signals that regulate swarming. The signature swirling and streaming motion within a swarm is an interesting phenomenon in and of itself, an emergent behavior with properties similar to flocking behavior in diverse systems, including birds and fish, providing a convenient new avenue for modeling such behavior. PMID:23264580

  10. The MOSO field experiment - Overview of findings

    NASA Astrophysics Data System (ADS)

    Ólafsson, Haraldur; Jonassen, Marius O.; Ágústsson, Hálfdán; Rögnvaldsson, Ólafur; Hjarðar, Bjarni G. Þ.; Rasol, Dubravka; Reuder, Joachim; Jónsson, Sigurður; Líf Kristinsdóttir, Birta

    2013-04-01

    In 2009 and 2011, the MOSO I and MOSO II meteorological field experiments took place in SW-Iceland. The main objectives were to describe the low level atmospheric coastal flows in the vicinity of mountains. The observations for the MOSO dataset were made using a large number of automatic weather stations, microbarographs, radiosoundings and a remotely piloted aircraft. The highlights of the findings include a four-dimensional description of the sea-breeze in Iceland, weak downslope acceleration, summer- and winter-time mountain wake flow, transition between wake flow and sea-breeze. The orographic drag force is explored and shown to be not so high most of the time in the predicted high-drag state. The observations from the remotely piloted aircraft have been used successfully to nudge simulations of the flow and are shown to be promising for operational use in numerical prediction of mesoscale coastal and orographic flows.

  11. FIFE, First ISLSCP Field Experiment - Results overview

    NASA Technical Reports Server (NTRS)

    Hall, F. G.; Markham, B. J.; Wang, J. R.; Huemmerich, F.; Sellers, P. J.; Strebel, D. E.; Kanemasu, E. T.; Kelly, Robert D.; Blad, Blaine L.

    1990-01-01

    Results of the analyses of the First International Satellite Land-Surface Climatology Project Field Experiment (FIFE) are described which relate to the mass and energy flux of a particular area. The extensive satellite and ground data are used to analyze the energy balance over the FIFE site, monitor the energy-budget components, study atmospheric effects on remote sensing, examine cloud cover, and investigate fluxes in the atmospheric boundary layer. The results verify existing theories relating energy-balance components with surface biology and remote sensing, and satellites can be used to estimate surface-energy budgets. Some analyses provide data that contradict present theories regarding thermodynamic and biophysical methodologies for estimating surface-heat fluxes.

  12. Complexity and Fly Swarms

    NASA Astrophysics Data System (ADS)

    Cates, Grant; Murray, Joelle

    Complexity is the study of phenomena that emerge from a collection of interacting objects and arises in many systems throughout physics, biology, finance, economics and more. Certain kinds of complex systems can be described by self-organized criticality (SOC). An SOC system is one that is internally driven towards some critical state. Recent experimental work suggests scaling behavior of fly swarms-one of the hallmarks of an SOC system. Our goal is to look for SOC behavior in computational models of fly swarms.

  13. Radiofrequency electron swarm transport in reactive gases and plasmas

    NASA Astrophysics Data System (ADS)

    Maeda, K.; Makabe, T.

    1994-01-01

    This paper gives a historical review of the development of radiofrequency (RF) electron swarm from a theoretical point of view. Also the recent progress of the direct numerical procedure (DNP) for solving the Boltzmann equation will be discussed with some typical examples of the temporally modulated velocity distribution in Ar and HCl in an RF field. The significance of DNP will be demonstrated for an RF swarm in the frequency range from MHz to GHz at strong fields.

  14. Magnetospheric ULF wave studies in the frame of Swarm mission: new advanced tools for automated detection of pulsations in magnetic and electric field observations

    NASA Astrophysics Data System (ADS)

    Balasis, Georgios; Daglis, Ioannis A.; Papadimitriou, Constantinos; Georgiou, Marina; Giamini, Sigiava A.; Sandberg, Ingmar; Haagmans, Roger

    2014-05-01

    The rekindling of the interest in space science in the last 15 years has led to many successful satellite missions in the Earth's magnetosphere and topside ionosphere, which were able to provide the scientific community with high-quality data on the magnetic and electric fields surrounding our planet. This data pool will be further enriched by the measurements of ESA's Swarm mission, a constellation of three satellites in different polar orbits, flying at altitudes from 400 to 550 km, which was launched on the 22nd of November 2013. Aiming at the best scientific exploitation of this corpus of accumulated data, we have developed a set of analysis tools that can cope with measurements of various spacecraft, at various regions of the magnetosphere and in the topside ionosphere. Our algorithms are based on a combination of wavelet spectral methods and artificial neural network techniques and are suited for the detection of waves and wave-like disturbances as well as the extraction of several physical parameters. Our recent work demonstrates the applicability of our developed analysis tools, both for individual case studies and statistical analysis of ultra low frequency (ULF) waves. We provide evidence for a rare simultaneous observation of a ULF wave event in the Earth's magnetosphere, topside ionosphere and surface: we have found a specific time interval during the Halloween 2003 magnetic storm, when the Cluster and CHAMP spacecraft were in good local time (LT) conjunction, and have examined the ULF wave activity in the Pc3 (22-100 mHz), Pc4 (7-22 mHz) and Pc5 (1-7 mHz) bands using data from the Geotail, Cluster and CHAMP missions, as well as the CARISMA, GIMA and IMAGE magnetometer networks. Our study shows that the same wave event, characterized by increased activity in the high end of the Pc3 band, was simultaneously observed by all three satellite missions and by certain stations of ground networks. This observation provides a strong argument in favour of the

  15. Magnetic field experiment on the Freja Satellite

    NASA Astrophysics Data System (ADS)

    Freja Magnetic Field Experiment Team

    1994-11-01

    Freja is a Swedish scientific satellite mission to study fine scale auroral processes. Launch was October 6, 1992, piggyback on a Chinese Long March 2C, to the present 600×1750 km, 63° inclination orbit. The JHU/APL provided the Magnetic Field Experiment (MFE), which includes a custom APL-designed Forth, language microprocessor. This approach has led to a truly generic and flexible design with adaptability to differing mission requirements and has resulted in the transfer of significant ground analysis to on-board processing. Special attention has been paid to the analog electronic and digital processing design in an effort to lower system noise levels, verified by inflight data showing unprecedented system noise levels for near-Earth magnetic field measurements, approaching the fluxgate sensor levels. The full dynamic range measurements are of the 3-axis Earth's magnetic field taken at 128 vector samples s-1 and digitized to 16 bit, resolution, primarily used to evaluate currents and the main magnetic field of the Earth. Additional 3-axis ‘AC’ channels are bandpass filtered from 1.5 to 128 Hz to remove the main field spin signal, the range is±650 nT. These vector measurements cover Pc waves to ion gyrofrequency magnetic wave signals up to the oxygen gyrofrequency (˜40 Hz). A separate, seventh channel samples the spin axis sensor with a bandpass filter of 1.5 to 256 Hz, the signal of which is fed to a software FFT. This on-board FFT processing covers the local helium gyrofrequencies (˜160 Hz) and is plotted in the Freja Summary Plots (FSPs) along with disturbance fields. First data were received in the U.S. October 16 from Kiruna, Sweden via the Internet and SPAN e-mail networks, and were from an orbit a few hours earlier over Greenland and Sweden. Data files and data products, e.g., FSPs generated at the Kiruna ground station, are communicated in a similar manner through an automatic mail distribution system in Stockholm to PIs and various users

  16. Space Weather opportunity from Swarm products in near real time

    NASA Astrophysics Data System (ADS)

    Stolle, C.; Floberghagen, R.; Luhr, H.; Maus, S.; Knudsen, D. J.; Alken, P.; Doornbos, E.; Hamilton, B.; Thomson, A. W.; Visser, P. N.

    2012-12-01

    The Swarm constellation mission will provide multipoint measurements of neutral and plasma parameters describing the properties of the upper atmosphere, the ionosphere and magnetosphere and their coupling processes. Several quantities derived from Swarm observations, such as the Total Electron Content, radial and field-aligned currents, equatorial electric fields, a low-latitude plasma irregularity indicator, thermospheric density, and magnetic field signatures from magnetospheric currents, will be distributed by ESA as so-called Level-2 products. The Swarm payloads, however, provide even further opportunities for scientific investigations and services for near-Earth space exploration. This talk will present certain Swarm data products that can be offered for dedicated activities in space situational awareness and near real-time application. Examples are warning systems for critical events or assimilation models for now- and forecasting the state of the near-Earth space. Associated requirements concerning product specification and product delay will be discussed.

  17. Swarm magnetic gradients for lithospheric modelling (SLIM)

    NASA Astrophysics Data System (ADS)

    Bouman, Johannes; Ebbing, Jörg; Kotsiaros, Stavros; Brönner, Marco; Haagmans, Roger; Fuchs, Martin; Holzrichter, Nils; Olsen, Nils; Baykiev, Eldar

    2016-04-01

    We present first results of a feasibility study to use magnetic gradient information derived from Swarm data for crustal field modelling. The study is part of ESA's Support To Science Element (STSE) Swarm+ Innovations. In a first step, magnetic gradients have been derived from the observations taken by the three Swarm satellites, with emphasis on the two side-by-side flying spacecraft. Next, these gradients are used to compute magnetic gradient grids at 450 km altitude (the present mean altitude of the lower Swarm satellites) for one example region, North-West Europe. The suggested area comprise both exposed basement geology in southern Sweden and Norway with crustal scale magnetic anomalies and the Sorgenfrei-Tornquist Zone, a well-studied large scale tectonic fault system. With sensitivity analysis we studied the added benefit of the information from the gradient grids for lithospheric magnetic field modelling. A wealth of aeromagnetic data and additional constraining information for the example area allows us to validate our modelling results in great detail.

  18. Transport of Particle Swarms Through Variable Aperture Fractures

    NASA Astrophysics Data System (ADS)

    Boomsma, E.; Pyrak-Nolte, L. J.

    2012-12-01

    Particle transport through fractured rock is a key concern with the increased use of micro- and nano-size particles in consumer products as well as from other activities in the sub- and near surface (e.g. mining, industrial waste, hydraulic fracturing, etc.). While particle transport is often studied as the transport of emulsions or dispersions, particles may also enter the subsurface from leaks or seepage that lead to particle swarms. Swarms are drop-like collections of millions of colloidal-sized particles that exhibit a number of unique characteristics when compared to dispersions and emulsions. Any contaminant or engineered particle that forms a swarm can be transported farther, faster, and more cohesively in fractures than would be expected from a traditional dispersion model. In this study, the effects of several variable aperture fractures on colloidal swarm cohesiveness and evolution were studied as a swarm fell under gravity and interacted with the fracture walls. Transparent acrylic was used to fabricate synthetic fracture samples with (1) a uniform aperture, (2) a converging region followed by a uniform region (funnel shaped), (3) a uniform region followed by a diverging region (inverted funnel), and (4) a cast of a an induced fracture from a carbonate rock. All of the samples consisted of two blocks that measured 100 x 100 x 50 mm. The minimum separation between these blocks determined the nominal aperture (0.5 mm to 20 mm). During experiments a fracture was fully submerged in water and swarms were released into it. The swarms consisted of a dilute suspension of 3 micron polystyrene fluorescent beads (1% by mass) with an initial volume of 5μL. The swarms were illuminated with a green (525 nm) LED array and imaged optically with a CCD camera. The variation in fracture aperture controlled swarm behavior. Diverging apertures caused a sudden loss of confinement that resulted in a rapid change in the swarm's shape as well as a sharp increase in its velocity

  19. Experiments with Low Voltage Field Emission EPMA

    NASA Astrophysics Data System (ADS)

    Fournelle, J.; Cathey, H. E.

    2014-12-01

    We report results from 5-7 keV Field Emission EPMA experiments on selected natural minerals and synthetic materials to illustrate some strengths -- and pitfalls --of low keV FE-EPMA. In a silicate mineral in pseudotachylite from South Mountain, AZ (Goodwin, 1999), the spatial resolution (equation of Merlet & Llovet, 2012, with an 80 nm diameter beam) at 7 keV for Si Ka is calculated to be 588 nm, 391 nm for Ca Ka and 641 nm for Fe La. This pseudotachylite contains abundant 5-10 um sieve-textured crystals full of inclusions with low BSE intensity. Previous 15 keV work suggested the sieve phase was amphibole. At 7 keV, it is possible to identify the compositions of the submicron inclusions as SiO2 and a K-rich alumino-silicate phase; the host composition is epidote. The enhanced resolution of FE-EPMA reveals problems with some microanalytical standards. Vicenzi and Rose (2008) showed submicron inclusions in the Smithsonian Kakanui hornblende standard. Our 7 keV experiments show the ~400 nm inclusions consist of a silicate phase (glass?), Fe-Ti oxide and possibly a gas bubble, concentrated along planes or grain boundaries. SEM imaging of an inclusion analyzed with a focused FE beam shows radiating trails of debris on the hornblende host, consistent with residue from a popped vapor bubble in the inclusion. How should FE-EPMA handle standards that may have inclusions? Use a focused beam avoiding inclusions? Sometimes, perhaps. However, we used a defocused beam to "average" the phases. The results show little or no deviation from the published wet chemical analysis. Operation at reduced keV may require use of non-traditional X-ray lines (e.g. Gopon et al, 2013 for Fe Ll vs Fe La). Experiments at 5 keV were also performed upon a synthetic material enriched in Nd (Nd-Mg-Zn). Fischer & Baun (1967) demonstrated problems with the Ma/Mb lines of REE; we find that use of the Nd Mz line is necessary in order to achieve reasonable results in this material (98 wt% total, Nd 36 wt

  20. Habit versus planned behaviour: a field experiment.

    PubMed

    Verplanken, B; Aarts, H; van Knippenberg, A; Moonen, A

    1998-03-01

    A field experiment investigated the prediction and change in repeated behaviour in the domain of travel mode choices. Car use during seven days was predicted from habit strength (measured by self-reported frequency of past behaviour, as well as by a more covert measure based on personal scripts incorporating the behaviour), and antecedents of behaviour as conceptualized in the theory of planned behaviour (attitude, subjective norm, perceived behavioural control and behavioural intention). Both habit measures predicted behaviour in addition to intention and perceived control. Significant habit x intention interactions indicated that intentions were only significantly related to behaviour when habit was weak, whereas no intention-behaviour relation existed when habit was strong. During the seven-day registration of behaviour, half of the respondents were asked to think about the circumstances under which the behaviour was executed. Compared to control participants, the behaviour of experimental participants was more strongly related to their previously expressed intentions. However, the habit-behaviour relation was unaffected. The results demonstrate that, although external incentives may increase the enactment of intentions, habits set boundary conditions for the applicability of the theory of planned behaviour. PMID:9554090

  1. Extraterrestrial Virtual Field Experience: Water at Meridiani

    NASA Astrophysics Data System (ADS)

    Duggan-Haas, D.; Million, C.; Sullivan, R. J., Jr.; Hayes, A. G., Jr.; Ross, R. M.; St Clair, M.

    2014-12-01

    The Spacecraft Planetary Imaging Facility (SPIF) at Cornell University, in collaboration with Million Concepts and the Paleontological Research Institute (PRI), has developed the Extraterrestrial Virtual Field Experience (EVFE), a web-based, game-like and inquiry-driven classroom activity targeted to middle school through undergraduate introductory Earth science classrooms. Students play the role of mission scientists for a NASA rover mission, tasked with targeting the rover's scientific instruments to investigate a specific scientific question about the landing site. As with the real mission, the student operators must optimize the efficient use of limited resources and time against the need to make observations to address working hypotheses. The activity uses only real--not artificial or simulated--mission data, and students are guided throughout by a "Mission Manager" who provides hints and advice about the scientific meaning of observations within the broader context of the mission objectives. The MER Opportunity EVFE is a pilot effort, the first of five EVFE modules planned a rate of one per year that will feature different NASA missions and scientific topics. The MER Opportunity EVFE has already been developed and focuses on the investigation of the history of water on Mars at the Meridiani landing site of the Opportunity rover. The module includes a teacher guide and is currently available to educators through the SPIF website.

  2. Technology Supported Cognitive Apprenticeship Transforms the Student Teaching Field Experience: Improving the Student Teaching Field Experience for All Triad Members

    ERIC Educational Resources Information Center

    Alger, Christianna; Kopcha, Theodore J.

    2011-01-01

    Despite issues of fragmentation, isolation, and disconnection from the university associated with the student teaching field experience, the field experience plays a critical role in teacher education. In this article, the authors provide an overview of eSupervision, a technology-based innovation to improve the student teaching field experience by…

  3. Particle Swarms in Fractures: Open Versus Partially Closed Systems

    NASA Astrophysics Data System (ADS)

    Boomsma, E.; Pyrak-Nolte, L. J.

    2014-12-01

    In the field, fractures may be isolated or connected to fluid reservoirs anywhere along the perimeter of a fracture. These boundaries affect fluid circulation, flow paths and communication with external reservoirs. The transport of drop like collections of colloidal-sized particles (particle swarms) in open and partially closed systems was studied. A uniform aperture synthetic fracture was constructed using two blocks (100 x 100 x 50 mm) of transparent acrylic placed parallel to each other. The fracture was fully submerged a tank filled with 100cSt silicone oil. Fracture apertures were varied from 5-80 mm. Partially closed systems were created by sealing the sides of the fracture with plastic film. The four boundary conditions study were: (Case 1) open, (Case 2) closed on the sides, (Case 3) closed on the bottom, and (Case 4) closed on both the sides and bottom of the fracture. A 15 μL dilute suspension of soda-lime glass particles in oil (2% by mass) were released into the fracture. Particle swarms were illuminated using a green (525 nm) LED array and imaged with a CCD camera. The presence of the additional boundaries modified the speed of the particle swarms (see figure). In Case 1, enhanced swarm transport was observed for a range of apertures, traveling faster than either very small or very large apertures. In Case 2, swarm velocities were enhanced over a larger range of fracture apertures than in any of the other cases. Case 3 shifted the enhanced transport regime to lower apertures and also reduced swarm speed when compared to Case 2. Finally, Case 4 eliminated the enhanced transport regime entirely. Communication between the fluid in the fracture and an external fluid reservoir resulted in enhanced swarm transport in Cases 1-3. The non-rigid nature of a swarm enables drag from the fracture walls to modify the swarm geometry. The particles composing a swarm reorganize in response to the fracture, elongating the swarm and maintaining its density. Unlike a

  4. [Study on whorl swarming growth phenomenon of Proteus mirabilis].

    PubMed

    He, Xianyuan; Liao, Sixiang; Liu, Junkang; Li, Kun; Liu, Yanxia; Yu, Lurong

    2015-02-01

    The present paper is aimed to explore the origins of Proteus mirabilis (PM) whorl swarming growth phenomenon. The whorl swarming growth phenomenon of PM was observed by changed bacterial culture inoculation time, humidity, vaccination practices, cultured flat placement, magnetic field, pH and other factors. Bacterial ring spiral direction of rotation is counterclockwise and the volatile growth process of PM was whorl swarming growth phenomenon. Spiro fluctuation phenomenon was of high frequency in the sealing tanks by cultured anytime inoculation, wherever inoculation technique applied or not, the presence or absence of the magnetic field, and wherever the dish position was. The experimental results showed that the whorl swarming growth phenomenon of PM requires specific pH environment, in which the facts may be relative to its genetic characteristics and the Earths rotation. PMID:25997280

  5. Selectively-informed particle swarm optimization.

    PubMed

    Gao, Yang; Du, Wenbo; Yan, Gang

    2015-01-01

    Particle swarm optimization (PSO) is a nature-inspired algorithm that has shown outstanding performance in solving many realistic problems. In the original PSO and most of its variants all particles are treated equally, overlooking the impact of structural heterogeneity on individual behavior. Here we employ complex networks to represent the population structure of swarms and propose a selectively-informed PSO (SIPSO), in which the particles choose different learning strategies based on their connections: a densely-connected hub particle gets full information from all of its neighbors while a non-hub particle with few connections can only follow a single yet best-performed neighbor. Extensive numerical experiments on widely-used benchmark functions show that our SIPSO algorithm remarkably outperforms the PSO and its existing variants in success rate, solution quality, and convergence speed. We also explore the evolution process from a microscopic point of view, leading to the discovery of different roles that the particles play in optimization. The hub particles guide the optimization process towards correct directions while the non-hub particles maintain the necessary population diversity, resulting in the optimum overall performance of SIPSO. These findings deepen our understanding of swarm intelligence and may shed light on the underlying mechanism of information exchange in natural swarm and flocking behaviors. PMID:25787315

  6. Selectively-informed particle swarm optimization

    PubMed Central

    Gao, Yang; Du, Wenbo; Yan, Gang

    2015-01-01

    Particle swarm optimization (PSO) is a nature-inspired algorithm that has shown outstanding performance in solving many realistic problems. In the original PSO and most of its variants all particles are treated equally, overlooking the impact of structural heterogeneity on individual behavior. Here we employ complex networks to represent the population structure of swarms and propose a selectively-informed PSO (SIPSO), in which the particles choose different learning strategies based on their connections: a densely-connected hub particle gets full information from all of its neighbors while a non-hub particle with few connections can only follow a single yet best-performed neighbor. Extensive numerical experiments on widely-used benchmark functions show that our SIPSO algorithm remarkably outperforms the PSO and its existing variants in success rate, solution quality, and convergence speed. We also explore the evolution process from a microscopic point of view, leading to the discovery of different roles that the particles play in optimization. The hub particles guide the optimization process towards correct directions while the non-hub particles maintain the necessary population diversity, resulting in the optimum overall performance of SIPSO. These findings deepen our understanding of swarm intelligence and may shed light on the underlying mechanism of information exchange in natural swarm and flocking behaviors. PMID:25787315

  7. Selectively-informed particle swarm optimization

    NASA Astrophysics Data System (ADS)

    Gao, Yang; Du, Wenbo; Yan, Gang

    2015-03-01

    Particle swarm optimization (PSO) is a nature-inspired algorithm that has shown outstanding performance in solving many realistic problems. In the original PSO and most of its variants all particles are treated equally, overlooking the impact of structural heterogeneity on individual behavior. Here we employ complex networks to represent the population structure of swarms and propose a selectively-informed PSO (SIPSO), in which the particles choose different learning strategies based on their connections: a densely-connected hub particle gets full information from all of its neighbors while a non-hub particle with few connections can only follow a single yet best-performed neighbor. Extensive numerical experiments on widely-used benchmark functions show that our SIPSO algorithm remarkably outperforms the PSO and its existing variants in success rate, solution quality, and convergence speed. We also explore the evolution process from a microscopic point of view, leading to the discovery of different roles that the particles play in optimization. The hub particles guide the optimization process towards correct directions while the non-hub particles maintain the necessary population diversity, resulting in the optimum overall performance of SIPSO. These findings deepen our understanding of swarm intelligence and may shed light on the underlying mechanism of information exchange in natural swarm and flocking behaviors.

  8. Particle Swarm Transport through Immiscible Fluid Layers in a Fracture

    NASA Astrophysics Data System (ADS)

    Teasdale, N. D.; Boomsma, E.; Pyrak-Nolte, L. J.

    2011-12-01

    Immiscible fluids occur either naturally (e.g. oil & water) or from anthropogenic processes (e.g. liquid CO2 & water) in the subsurface and complicate the transport of natural or engineered micro- or nano-scale particles. In this study, we examined the effect of immiscible fluids on the formation and evolution of particle swarms in a fracture. A particle swarm is a collection of colloidal-size particles in a dilute suspension that exhibits cohesive behavior. Swarms fall under gravity with a velocity that is greater than the settling velocity of a single particle. Thus a particle swarm of colloidal contaminants can potentially travel farther and faster in a fracture than expected for a dispersion or emulsion of colloidal particles. We investigated the formation, evolution, and break-up of colloidal swarms under gravity in a uniform aperture fracture as hydrophobic/hydrophyllic particle swarms move across an oil-water interface. A uniform aperture fracture was fabricated from two transparent acrylic rectangular prisms (100 mm x 50 mm x 100 mm) that are separated by 1, 2.5, 5, 10 or 50 mm. The fracture was placed, vertically, inside a glass tank containing a layer of pure silicone oil (polydimethylsiloxane) on distilled water. Along the length of the fracture, 30 mm was filled with oil and 70 mm with water. Experiments were conducted using silicone oils with viscosities of 5, 10, 100, or 1000 cSt. Particle swarms (5 μl) were comprised of a 1% concentration (by mass) of 25 micron glass beads (hydrophilic) suspended in a water drop, or a 1% concentration (by mass) of 3 micron polystyrene fluorescent beads (hydrophobic) suspended in a water drop. The swarm behavior was imaged using an optical fluorescent imaging system composed of a CCD camera and by green (525 nm) LED arrays for illumination. Swarms were spherical and remained coherent as they fell through the oil because of the immiscibility of oil and water. However, as a swarm approached the oil-water interface, it

  9. Precise science orbits for the Swarm satellite constellation

    NASA Astrophysics Data System (ADS)

    van den IJssel, Jose; Encarnação, João; Doornbos, Eelco; Visser, Pieter

    2015-09-01

    The European Space Agency (ESA) Swarm mission was launched on 22 November 2013 to study the dynamics of the Earth's magnetic field and its interaction with the Earth system. The mission consists of three identical satellites, flying in carefully selected near polar orbits. Two satellites fly almost side-by-side at an initial altitude of about 480 km, and will descend due to drag to around 300 km during the mission lifetime. The third satellite was placed in a higher orbit of about 530 km altitude, and therefore descends much more slowly. To geolocate the Swarm observations, each satellite is equipped with an 8-channel, dual-frequency GPS receiver for Precise Orbit Determination (POD). Onboard laser retroreflectors provide the opportunity to validate the orbits computed from the GPS observations using Satellite Laser Ranging (SLR) data. Precise Science Orbits (PSOs) for the Swarm satellites are computed by the Faculty of Aerospace Engineering at Delft University of Technology in the framework of the Swarm Satellite Constellation Application and Research Facility (SCARF). The PSO product consists of both a reduced-dynamic and a kinematic orbit solution. After a short description of the Swarm GPS data characteristics, the adopted POD strategy for both orbit types is explained and first PSO results from more than one year of Swarm GPS data are presented. Independent SLR validation shows that the reduced-dynamic Swarm PSOs have an accuracy of better than 2 cm, while the kinematic orbits have a slightly reduced accuracy of about 4-5 cm. Orbit comparisons indicate that the consistency between the reduced-dynamic and kinematic Swarm PSO for most parts of the Earth is at the 4-5 cm level. Close to the geomagnetic poles and along the geomagnetic equator, however, the kinematic orbits show larger errors, which are probably due to ionospheric scintillations that affect the Swarm GPS receivers over these areas.

  10. Field experiences in science teacher preparation programs of Missouri

    NASA Astrophysics Data System (ADS)

    Rhea, Marilyn Sue Alvis

    The purpose of this study was to collect and analyze data pertinent to identifying the differences and similarities in the design and implementation of field experiences for pre-service science teachers in institutions of higher education in the State of Missouri. Directors of field experience from 25 Institutions of Higher Education (IHE) that prepare both elementary and secondary science teachers and 5 additional IHE that prepare only elementary teachers were surveyed using a 48-item Likert scale instrument designed for this study. Data were collected on the hours of field experience in relation to science and other methods classes, distribution of field experience hours across the program, and total hours of field experience required. Comparisons were made between elementary and secondary science teacher preparation programs. Five areas of field experience were surveyed: design of early field experience, design of student teaching, support provided by IHE for cooperating schools, field experience assessment practices, and relationships between pre-service teachers, cooperating teachers and IHE educators. Analyses of the responses indicate statistically significant differences in the number of field experience hours between IRE programs for both early field experience (p < .05) and student teaching (p < .01). Differences in number of field experience hours by level of certification were not significant. Correlation of scores was significant between the elementary and secondary levels for both early field experience design (r = .97) and student teaching design (r = .75). No other significant correlation was found. This study found highly heterogeneous practices regarding field experience exist in Missouri IHE programs. When reported practices are compared to standards set in the professional literature, as a group Missouri IHE science teacher preparation programs could be described as traditional apprenticeships or quasi-professional development school programs.

  11. Exploring Group Cohesion in a Higher Education Field Experience

    ERIC Educational Resources Information Center

    Malcarne, Brian Keith

    2012-01-01

    The purpose of this study was to gain understanding into the experience of group cohesion for university students participating in an academic field experience. A mixed methods approach was used following a two-phase, sequential research design to help provide a more complete explanation of how group cohesion was impacted by the field experience.…

  12. Swarm robotics and minimalism

    NASA Astrophysics Data System (ADS)

    Sharkey, Amanda J. C.

    2007-09-01

    Swarm Robotics (SR) is closely related to Swarm Intelligence, and both were initially inspired by studies of social insects. Their guiding principles are based on their biological inspiration and take the form of an emphasis on decentralized local control and communication. Earlier studies went a step further in emphasizing the use of simple reactive robots that only communicate indirectly through the environment. More recently SR studies have moved beyond these constraints to explore the use of non-reactive robots that communicate directly, and that can learn and represent their environment. There is no clear agreement in the literature about how far such extensions of the original principles could go. Should there be any limitations on the individual abilities of the robots used in SR studies? Should knowledge of the capabilities of social insects lead to constraints on the capabilities of individual robots in SR studies? There is a lack of explicit discussion of such questions, and researchers have adopted a variety of constraints for a variety of reasons. A simple taxonomy of swarm robotics is presented here with the aim of addressing and clarifying these questions. The taxonomy distinguishes subareas of SR based on the emphases and justifications for minimalism and individual simplicity.

  13. An improved cockroach swarm optimization.

    PubMed

    Obagbuwa, I C; Adewumi, A O

    2014-01-01

    Hunger component is introduced to the existing cockroach swarm optimization (CSO) algorithm to improve its searching ability and population diversity. The original CSO was modelled with three components: chase-swarming, dispersion, and ruthless; additional hunger component which is modelled using partial differential equation (PDE) method is included in this paper. An improved cockroach swarm optimization (ICSO) is proposed in this paper. The performance of the proposed algorithm is tested on well known benchmarks and compared with the existing CSO, modified cockroach swarm optimization (MCSO), roach infestation optimization RIO, and hungry roach infestation optimization (HRIO). The comparison results show clearly that the proposed algorithm outperforms the existing algorithms. PMID:24959611

  14. Argonne plasma wake-field acceleration experiments

    SciTech Connect

    Rosenzweig, J.B.; Cole, B.; Gai, W.; Konecny, R.; Norem, J.; Schoessow, P.; Simpson, J.

    1989-03-14

    Four years after the initial proposal of the Plasma Wake-field Accelerator (PWFA), it continues to be the object of much investigation, due to the promise of the ultra-high accelerating gradients that can exist in relativistic plasma waves driven in the wake of charged particle beams. These wake-fields are of interest both in the laboratory, for acceleration and focusing of electrons and positrons in future linear colliders, and in nature as a possible cosmic ray acceleration mechanism. The purpose of the present work is to review the recent experimental advances made in PWFA research at Argonne National Laboratory. Some of the topics discussed are: the Argonne Advanced Accelerator Test Facility; linear plasma wake-field theory; measurement of linear plasma wake-fields; review of nonlinear plasma wave theory; and experimental measurement of nonlinear plasma wake-fields. 25 refs., 11 figs.

  15. Features of Bacillus cereus swarm cells.

    PubMed

    Senesi, Sonia; Salvetti, Sara; Celandroni, Francesco; Ghelardi, Emilia

    2010-11-01

    When propagated on solid surfaces, Bacillus cereus can produce differentiated swarm cells under a wide range of growth conditions. This behavioural versatility is ecologically relevant, since it allows this bacterium to adapt swarming to environmental changes. Swarming by B. cereus is medically important: swarm cells are more virulent and particularly prone to invade host tissues. Characterisation of swarming-deficient mutants highlights that flagellar genes as well as genes governing different metabolic pathways are involved in swarm-cell differentiation. In this review, the environmental and genetic requirements for swarming and the role played by swarm cells in the virulence this pathogen exerts will be outlined. PMID:21035546

  16. Coordinated circling behavior of Daphnia swarming around an optical marker

    NASA Astrophysics Data System (ADS)

    Ordemann, Anke; Russell, David F.; Moss, Frank

    2002-03-01

    The common fresh water zooplankton Daphnia, as well as many other zooplankton species, are known to form swarms as a predator confusing behavior. In rare events in the field as well as in laboratory environments a swarm of Daphnia has been observed to perform a vortex like motion, similar to a flock of birds circling before coming to rest. To shed more light on this coordinated behavior we study experimentally the motion of Daphnia inside a swarm in respect to the motion of single Daphnia. Daphnia can be induced to swarm by an optical marker such as a vertical shaft of light in the visual range, to which they are attracted. Following the tracks of several Daphnia and characterizing their paths by a variety of measures we observe the development of a circular motion around the optical marker.

  17. Delay induced instabilities in self-propelling swarming particles

    NASA Astrophysics Data System (ADS)

    Forgoston, Eric; Schwartz, Ira

    2008-03-01

    We consider a general model of self-propelling biological or artificial individuals interacting through a pairwise attractive force in a two-dimensional system in the presence of noise and communication time delay. Previous work has shown that a large enough noise intensity will cause a translating swarm of individuals to transition to a rotating swarm with a stationary center of mass. In this work, we use numerical simulations to show that with the addition of a time delay, the model possesses a transition that depends on the size of the coupling parameter. This transition is independent of the swarm state (traveling or rotating) and is characterized by the alignment of all of the individuals along with a swarm oscillation. By considering the mean field equations without noise, we show that the time delay induced transition is associated with a Hopf bifurcation. The analytical result yields good agreement with numerical computations of the value of the coupling parameter at the Hopf point.

  18. Delay-induced instabilities in self-propelling swarms.

    PubMed

    Forgoston, Eric; Schwartz, Ira B

    2008-03-01

    We consider a general model of self-propelling particles interacting through a pairwise attractive force in the presence of noise and communication time delay. Previous work by Erdmann [Phys. Rev. E 71, 051904 (2005)] has shown that a large enough noise intensity will cause a translating swarm of individuals to transition to a rotating swarm with a stationary center of mass. We show that with the addition of a time delay, the model possesses a transition that depends on the size of the coupling amplitude. This transition is independent of the initial swarm state (traveling or rotating) and is characterized by the alignment of all of the individuals along with a swarm oscillation. By considering the mean field equations without noise, we show that the time-delay-induced transition is associated with a Hopf bifurcation. The analytical result yields good agreement with numerical computations of the value of the coupling parameter at the Hopf point. PMID:18517450

  19. Delay-induced instabilities in self-propelling swarms

    NASA Astrophysics Data System (ADS)

    Forgoston, Eric; Schwartz, Ira B.

    2008-03-01

    We consider a general model of self-propelling particles interacting through a pairwise attractive force in the presence of noise and communication time delay. Previous work by Erdmann [Phys. Rev. E 71, 051904 (2005)] has shown that a large enough noise intensity will cause a translating swarm of individuals to transition to a rotating swarm with a stationary center of mass. We show that with the addition of a time delay, the model possesses a transition that depends on the size of the coupling amplitude. This transition is independent of the initial swarm state (traveling or rotating) and is characterized by the alignment of all of the individuals along with a swarm oscillation. By considering the mean field equations without noise, we show that the time-delay-induced transition is associated with a Hopf bifurcation. The analytical result yields good agreement with numerical computations of the value of the coupling parameter at the Hopf point.

  20. Delay-induced instabilities in self-propelling swarms

    PubMed Central

    Forgoston, Eric; Schwartz, Ira B.

    2013-01-01

    We consider a general model of self-propelling particles interacting through a pairwise attractive force in the presence of noise and communication time delay. Previous work by Erdmann et al. [Phys. Rev. E 71, 051904 (2005)] has shown that a large enough noise intensity will cause a translating swarm of individuals to transition to a rotating swarm with a stationary center of mass. We show that with the addition of a time delay, the model possesses a transition that depends on the size of the coupling amplitude. This transition is independent of the initial swarm state (traveling or rotating) and is characterized by the alignment of all of the individuals along with a swarm oscillation. By considering the mean field equations without noise, we show that the time-delay-induced transition is associated with a Hopf bifurcation. The analytical result yields good agreement with numerical computations of the value of the coupling parameter at the Hopf point. PMID:18517450

  1. Formation control of robotic swarm using bounded artificial forces.

    PubMed

    Qin, Long; Zha, Yabing; Yin, Quanjun; Peng, Yong

    2013-01-01

    Formation control of multirobot systems has drawn significant attention in the recent years. This paper presents a potential field control algorithm, navigating a swarm of robots into a predefined 2D shape while avoiding intermember collisions. The algorithm applies in both stationary and moving targets formation. We define the bounded artificial forces in the form of exponential functions, so that the behavior of the swarm drove by the forces can be adjusted via selecting proper control parameters. The theoretical analysis of the swarm behavior proves the stability and convergence properties of the algorithm. We further make certain modifications upon the forces to improve the robustness of the swarm behavior in the presence of realistic implementation considerations. The considerations include obstacle avoidance, local minima, and deformation of the shape. Finally, detailed simulation results validate the efficiency of the proposed algorithm, and the direction of possible futrue work is discussed in the conclusions. PMID:24453809

  2. Formation Control of Robotic Swarm Using Bounded Artificial Forces

    PubMed Central

    Zha, Yabing; Peng, Yong

    2013-01-01

    Formation control of multirobot systems has drawn significant attention in the recent years. This paper presents a potential field control algorithm, navigating a swarm of robots into a predefined 2D shape while avoiding intermember collisions. The algorithm applies in both stationary and moving targets formation. We define the bounded artificial forces in the form of exponential functions, so that the behavior of the swarm drove by the forces can be adjusted via selecting proper control parameters. The theoretical analysis of the swarm behavior proves the stability and convergence properties of the algorithm. We further make certain modifications upon the forces to improve the robustness of the swarm behavior in the presence of realistic implementation considerations. The considerations include obstacle avoidance, local minima, and deformation of the shape. Finally, detailed simulation results validate the efficiency of the proposed algorithm, and the direction of possible futrue work is discussed in the conclusions. PMID:24453809

  3. Analysis of image thresholding segmentation algorithms based on swarm intelligence

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Lu, Kai; Gao, Yinghui; Yang, Bo

    2013-03-01

    Swarm intelligence-based image thresholding segmentation algorithms are playing an important role in the research field of image segmentation. In this paper, we briefly introduce the theories of four existing image segmentation algorithms based on swarm intelligence including fish swarm algorithm, artificial bee colony, bacteria foraging algorithm and particle swarm optimization. Then some image benchmarks are tested in order to show the differences of the segmentation accuracy, time consumption, convergence and robustness for Salt & Pepper noise and Gaussian noise of these four algorithms. Through these comparisons, this paper gives qualitative analyses for the performance variance of the four algorithms. The conclusions in this paper would give a significant guide for the actual image segmentation.

  4. Giant radiating dyke swarms on Earth and Venus

    NASA Technical Reports Server (NTRS)

    Ernst, Richard E.; Head, James W.; Parfitt, Elisabeth; Wilson, Lionel; Grosfils, Eric

    1993-01-01

    On Earth, giant radiating dyke swarms are usually preserved as fan-shaped fragments which have been dismembered from their original configuration by subsequent plate tectonic rifting events. Analysis of the largest fragments and consideration of their original configuration has led to the idea that many swarms are plume related, and that dyke swarms radiate away from plume centers. Magellan radar data reveal abundant intact giant radiating swarms on Venus which are similar in scale and pattern to those on Earth. The absence of intense weathering and plate tectonic processes on Venus accounts for the preservation of the primary radiating patterns. It is characteristic of both Earth and Venus that giant radiating dikes are emplaced laterally for distances of at least 2000 km away from plume centers. At distances beyond the influence of the plume on both Earth and Venus, the radiating dyke pattern is often swept into a linear pattern aligned with the regional stress field. There is tremendous potential synergism between the characterization and analysis of terrestrial dyke swarms (where significant erosion has revealed their structure and emplacement directions at depth) and the giant swarms of Venus (where the complete circumferential structure is preserved, and the surface fracture systems above near surface dikes and the nature of the central source regions are revealed). In this study, we report on the characteristics of radial dyke swarms on Earth and Venus and draw some preliminary comparisons from the two perspectives. In summary, on both planets there is evidence for plume-related magmatic centers associated with vertical and lateral injection of magma over considerable distances (up to at least 2000 km). The abundance of very broadly radiating swarms on Venus supports the notion that the swarms on Earth were radiating over broad sectors at the time of intrusion but were dissected by later events. The Venus data show that a swarm can change from radiating

  5. A mathematical model for flight guidance in honeybee swarms.

    PubMed

    Fetecau, R C; Guo, A

    2012-11-01

    When a colony of honeybees relocates to a new nest site, less than 5 % of the bees (the scout bees) know the location of the new nest. Nevertheless, the small minority of informed bees manages to provide guidance to the rest and the entire swarm is able to fly to the new nest intact. The streaker bee hypothesis, one of the several theories proposed to explain the guidance mechanism in bee swarms, seems to be supported by recent experimental observations. The theory suggests that the informed bees make high-speed flights through the swarm in the direction of the new nest, hence conspicuously pointing to the desired direction of travel. This work presents a mathematical model of flight guidance in bee swarms based on the streaker bee hypothesis. Numerical experiments, parameter studies, and comparison with experimental data are presented. PMID:22890574

  6. FINAL RESULTS OF THE CONDORS CONVECTIVE DIFFUSION FIELD EXPERIMENT

    EPA Science Inventory

    The Convective Diffusion Observed by Remote Sensors (CONDORS) field experiment conducted at the Boulder Atmospheric Observatory used innovative techniques to obtain three dimensional mappings of plume concentration fields of oil fog detected by lidar and "chaff" detected by Doppl...

  7. Field Trips as Valuable Learning Experiences in Geography Courses

    ERIC Educational Resources Information Center

    Krakowka, Amy Richmond

    2012-01-01

    Field trips have been acknowledged as valuable learning experiences in geography. This article uses Kolb's (1984) experiential learning model to discuss how students learn and how field trips can help enhance learning. Using Kolb's experiential learning theory as a guide in the design of field trips helps ensure that field trips contribute to…

  8. From hybrid swarms to swarms of hybrids

    USGS Publications Warehouse

    Stohlgren, Thomas J.; Szalanski, Allen L; Gaskin, John F.; Young, Nicholas E.; West, Amanda; Jarnevich, Catherine S.; Tripodi, Amber

    2015-01-01

    Science has shown that the introgression or hybridization of modern humans (Homo sapiens) with Neanderthals up to 40,000 YBP may have led to the swarm of modern humans on earth. However, there is little doubt that modern trade and transportation in support of the humans has continued to introduce additional species, genotypes, and hybrids to every country on the globe. We assessed the utility of species distributions modeling of genotypes to assess the risk of current and future invaders. We evaluated 93 locations of the genus Tamarix for which genetic data were available. Maxent models of habitat suitability showed that the hybrid, T. ramosissima x T. chinensis, was slightly greater than the parent taxa (AUCs > 0.83). General linear models of Africanized honey bees, a hybrid cross of Tanzanian Apis mellifera scutellata and a variety of European honey bee including A. m. ligustica, showed that the Africanized bees (AUC = 0.81) may be displacing European honey bees (AUC > 0.76) over large areas of the southwestern U.S. More important, Maxent modeling of sub-populations (A1 and A26 mitotypes based on mDNA) could be accurately modeled (AUC > 0.9), and they responded differently to environmental drivers. This suggests that rapid evolutionary change may be underway in the Africanized bees, allowing the bees to spread into new areas and extending their total range. Protecting native species and ecosystems may benefit from risk maps of harmful invasive species, hybrids, and genotypes.

  9. The JPL MSAT mobile laboratory and the pilot field experiments

    NASA Technical Reports Server (NTRS)

    Berner, Jeff B.; Emerson, Richard F.

    1988-01-01

    A Mobile Laboratory/Propagation Measurement Van (PMV) was developed to support the field experiments of the Mobile Satellite Experiment (MSAT-X) Project. This van was designed to provide flexibility, self-sufficiency and data acquisition to allow for both measurement of equipment performance and the mobile environment. The design philosophy and implementation of the PMV are described. The Pilot Field Experiments and an overall description of the three experiments in which the PMV was used are described.

  10. Binary Particle Swarm Optimization based Biclustering of Web Usage Data

    NASA Astrophysics Data System (ADS)

    Rathipriya, R.; Thangavel, K.; Bagyamani, J.

    2011-07-01

    Web mining is the nontrivial process to discover valid, novel, potentially useful knowledge from web data using the data mining techniques or methods. It may give information that is useful for improving the services offered by web portals and information access and retrieval tools. With the rapid development of biclustering, more researchers have applied the biclustering technique to different fields in recent years. When biclustering approach is applied to the web usage data it automatically captures the hidden browsing patterns from it in the form of biclusters. In this work, swarm intelligent technique is combined with biclustering approach to propose an algorithm called Binary Particle Swarm Optimization (BPSO) based Biclustering for Web Usage Data. The main objective of this algorithm is to retrieve the global optimal bicluster from the web usage data. These biclusters contain relationships between web users and web pages which are useful for the E-Commerce applications like web advertising and marketing. Experiments are conducted on real dataset to prove the efficiency of the proposed algorithms.

  11. Bell Experiment with Classical Optical Fields

    NASA Astrophysics Data System (ADS)

    Little, Bethany; Qian, Xiao-Feng; Howell, John; Eberly, J. H.

    We theoretically and experimentally explore the implications of entanglement in statistically classical optical fields. The description of these fields in terms of polarization and amplitude degrees of freedom can take a non-separable form which employs a mathematical description of entanglement often associated with quantum phenomena. By subjecting these optical fields to a Bell analysis, we examine the role of entanglement in marking the quantum-classical boundary. We report a value of the Bell parameter greater than calB = 2 . 54 , many standard deviations outside the limit calB = 2 established by the Clauser-Horne-Shimony-Holt Bell inequality. This suggests that Bell violation has less to do with quantum theory than previously thought, but everything to do with entanglement. University of Rochester Research Award, NSF PHY-1203931, NSF PHY-1505189, and NSF/INSPIRE PHY-1539859.

  12. Minimizing magnetic fields for precision experiments

    SciTech Connect

    Altarev, I.; Fierlinger, P.; Lins, T.; Marino, M. G.; Nießen, B.; Petzoldt, G.; Reisner, M.; Stuiber, S. Sturm, M.; Taggart Singh, J.; Taubenheim, B.; Rohrer, H. K.; Schläpfer, U.

    2015-06-21

    An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here, we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a 40% improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.

  13. Thought Field Therapy: A Former Insider's Experience

    ERIC Educational Resources Information Center

    Pignotti, Monica

    2007-01-01

    Thought Field Therapy (TFT) is a novel therapy that employs finger tapping on purported acupressure points. Over the past decade, TFT, promoted on the Internet and through testimonials of fast cures, has gained popularity with therapists, including clinical social workers. Although TFT claims to cure a wide variety of psychological and physical…

  14. Isolated particle swarm optimization with particle migration and global best adoption

    NASA Astrophysics Data System (ADS)

    Tsai, Hsing-Chih; Tyan, Yaw-Yauan; Wu, Yun-Wu; Lin, Yong-Huang

    2012-12-01

    Isolated particle swarm optimization (IPSO) segregates particles into several sub-swarms in order to improve the ability of the global optimization. In this study, particle migration and global best adoption (gbest adoption) are used to improve IPSO. Particle migration allows particles to travel among sub-swarms, based on the fitness of the sub-swarms. The use of gbest adoption allows sub-swarms to peep at the gbest proportionally or probably after a certain number of iterations, i.e. gbest replacing, and gbest sharing, respectively. Three well-known benchmark functions are utilized to determine the parameter settings of the IPSO. Then, 13 benchmark functions are used to study the performance of the designed IPSO. Computational experience demonstrates that the designed IPSO is superior to the original version of particle swarm optimization (PSO) in terms of the accuracy and stability of the results, when isolation phenomenon, particle migration and gbest sharing are involved.

  15. Characteristics of a Model Industrial Technology Education Field Experience.

    ERIC Educational Resources Information Center

    Foster, Phillip R.; Kozak, Michael R.

    1986-01-01

    This report contains selected findings from a research project that investigated field experiences in industrial technology education. Funded by the Texas Education Agency, the project addressed the identification of characteristics of a model field experience in industrial technology education. This was accomplished using the Delphi technique.…

  16. Technology's Role in Field Experiences for Preservice Teacher Training

    ERIC Educational Resources Information Center

    Hixon, Emily; So, Hyo-Jeong

    2009-01-01

    The purpose of this paper is to provide a comprehensive review of how technology has been used to enhance or replace field experiences in preservice teacher preparation programs, and discuss the benefits and limitations of traditional and technology-enhanced/virtual field experience approaches. In this paper, three types of technology-enhanced…

  17. Assisting Your Preservice Teacher to Be Successful during Field Experiences

    ERIC Educational Resources Information Center

    Brett, Christine

    2006-01-01

    Field experience (junior practicum and student teaching) is considered by many to be the most influential part of a teacher preparation program (Cruickshank & Aramalin, 1986; Tannehill & Zakrajsek, 1988). During field experiences, preservice teachers (hereafter referred to as PSTs) are guided by a cooperating teacher (hereafter referred to as a…

  18. Preparing Middle School Teachers: Using Collaborative Middle School Field Experiences.

    ERIC Educational Resources Information Center

    Ramey, Linda K.

    Wright State University, Ohio, has developed an undergraduate degree in Middle Childhood Education with extensive content preparation and initial field experiences. Participants complete an undergraduate program in two specialized areas accompanied by 15 hours of teacher education professional coursework and field experiences in urban and suburban…

  19. Concerns of Teacher Candidates in an Early Field Experience

    ERIC Educational Resources Information Center

    Chang, Sau Hou

    2009-01-01

    The present study examined the concerns of teacher candidates in an early field experience. Thirty-five teacher candidates completed the Teacher Concerns Checklist (TCC, Fuller & Borich, 2000) at the beginning, middle and end of their early field experiences. Results showed that teacher candidates ranked impact as the highest concern, self as the…

  20. Volcanic earthquake swarms at Mt. Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    Kaminuma, Katsutada; Ueki, Sadato; Juergen, Kienle

    1985-04-01

    Mount Erebus is an active volcano in Antarctica located on Ross Island. A convecting lava lake occupies the summit crater of Mt. Erebus. Since December 1980 the seismic activity of Mt. Erebus has been continuously monitored using a radio-telemetered network of six seismic stations. The seismic activity observed by the Ross Island network during the 1982-1983 field season shows that: (1)Strombolian eruptions occur frequently at the Erebus summit lava lake at rates of 2-5 per day; (2)centrally located earthquakes map out a nearly vertical, narrow conduit system beneath the lava lake; (3)there are other source regions of seismicity on Ross Island, well removed from Mt. Erebus proper. An intense earthquake swarm recorded in October 1982 near Abbott Peak, 10 km northwest of the summit of Mt. Erebus, and volcanic tremor accompanying the swarm, may have been associated with new dike emplacement at depth.

  1. Coherent Pattern Prediction in Swarms of Delay-Coupled Agents

    NASA Astrophysics Data System (ADS)

    Mier-Y-Teran-Romero, Luis; Forgoston, Eric; Scwartz, Ira

    2013-03-01

    We consider a general swarm model of self-propelling particles interacting through a pairwise potential in the presence of a fixed communication time delay. Previous work has shown that swarms with communication time delays and noise may display pattern transitions that depend on the size of the coupling amplitude. We extend these results by completely unfolding the bifurcation structure of the mean field approximation. Our analysis reveals a direct correspondence between the different dynamical behaviors found in different regions of the coupling-time delay plane with the different classes of simulated coherent swarm patterns. We derive the spatio-temporal scales of the swarm structures, and also demonstrate how the complicated interplay of coupling strength, time delay, noise intensity, and choice of initial conditions can affect the swarm. In addition, when adding noise to the system, we find that for sufficiently large values of the coupling strength and/or the time delay, there is a noise intensity threshold that forces a transition of the swarm from a misaligned state into an aligned state. We show that this alignment transition exhibits hysteresis when the noise intensity is taken to be time dependent. Office of Naval Research, NIH (LMR and IBS) and NRL (EF)

  2. Coherent Pattern Prediction in Swarms of Delay-Coupled Agents

    PubMed Central

    Mier-y-Teran-Romero, Luis; Forgoston, Eric; Schwartz, Ira B.

    2013-01-01

    We consider a general swarm model of self-propelling agents interacting through a pairwise potential in the presence of noise and communication time delay. Previous work has shown that a communication time delay in the swarm induces a pattern bifurcation that depends on the size of the coupling amplitude. We extend these results by completely unfolding the bifurcation structure of the mean field approximation. Our analysis reveals a direct correspondence between the different dynamical behaviors found in different regions of the coupling-time delay plane with the different classes of simulated coherent swarm patterns. We derive the spatiotemporal scales of the swarm structures, as well as demonstrate how the complicated interplay of coupling strength, time delay, noise intensity, and choice of initial conditions can affect the swarm. In particular, our studies show that for sufficiently large values of the coupling strength and/or the time delay, there is a noise intensity threshold that forces a transition of the swarm from a misaligned state into an aligned state. We show that this alignment transition exhibits hysteresis when the noise intensity is taken to be time dependent. PMID:24255625

  3. Coherent Pattern Prediction in Swarms of Delay-Coupled Agents.

    PubMed

    Mier-Y-Teran-Romero, Luis; Forgoston, Eric; Schwartz, Ira B

    2012-10-01

    We consider a general swarm model of self-propelling agents interacting through a pairwise potential in the presence of noise and communication time delay. Previous work has shown that a communication time delay in the swarm induces a pattern bifurcation that depends on the size of the coupling amplitude. We extend these results by completely unfolding the bifurcation structure of the mean field approximation. Our analysis reveals a direct correspondence between the different dynamical behaviors found in different regions of the coupling-time delay plane with the different classes of simulated coherent swarm patterns. We derive the spatiotemporal scales of the swarm structures, as well as demonstrate how the complicated interplay of coupling strength, time delay, noise intensity, and choice of initial conditions can affect the swarm. In particular, our studies show that for sufficiently large values of the coupling strength and/or the time delay, there is a noise intensity threshold that forces a transition of the swarm from a misaligned state into an aligned state. We show that this alignment transition exhibits hysteresis when the noise intensity is taken to be time dependent. PMID:24255625

  4. Swarm-based algorithm for phase unwrapping.

    PubMed

    da Silva Maciel, Lucas; Albertazzi, Armando G

    2014-08-20

    A novel algorithm for phase unwrapping based on swarm intelligence is proposed. The algorithm was designed based on three main goals: maximum coverage of reliable information, focused effort for better efficiency, and reliable unwrapping. Experiments were performed, and a new agent was designed to follow a simple set of five rules in order to collectively achieve these goals. These rules consist of random walking for unwrapping and searching, ambiguity evaluation by comparing unwrapped regions, and a replication behavior responsible for the good distribution of agents throughout the image. The results were comparable with the results from established methods. The swarm-based algorithm was able to suppress ambiguities better than the flood-fill algorithm without relying on lengthy processing times. In addition, future developments such as parallel processing and better-quality evaluation present great potential for the proposed method. PMID:25321125

  5. A comprehensive review of swarm optimization algorithms.

    PubMed

    Ab Wahab, Mohd Nadhir; Nefti-Meziani, Samia; Atyabi, Adham

    2015-01-01

    Many swarm optimization algorithms have been introduced since the early 60's, Evolutionary Programming to the most recent, Grey Wolf Optimization. All of these algorithms have demonstrated their potential to solve many optimization problems. This paper provides an in-depth survey of well-known optimization algorithms. Selected algorithms are briefly explained and compared with each other comprehensively through experiments conducted using thirty well-known benchmark functions. Their advantages and disadvantages are also discussed. A number of statistical tests are then carried out to determine the significant performances. The results indicate the overall advantage of Differential Evolution (DE) and is closely followed by Particle Swarm Optimization (PSO), compared with other considered approaches. PMID:25992655

  6. A Comprehensive Review of Swarm Optimization Algorithms

    PubMed Central

    2015-01-01

    Many swarm optimization algorithms have been introduced since the early 60’s, Evolutionary Programming to the most recent, Grey Wolf Optimization. All of these algorithms have demonstrated their potential to solve many optimization problems. This paper provides an in-depth survey of well-known optimization algorithms. Selected algorithms are briefly explained and compared with each other comprehensively through experiments conducted using thirty well-known benchmark functions. Their advantages and disadvantages are also discussed. A number of statistical tests are then carried out to determine the significant performances. The results indicate the overall advantage of Differential Evolution (DE) and is closely followed by Particle Swarm Optimization (PSO), compared with other considered approaches. PMID:25992655

  7. Frog Swarms: Earthquake Precursors or False Alarms?

    PubMed Central

    Grant, Rachel A.; Conlan, Hilary

    2013-01-01

    juvenile animals migrating away from their breeding pond, after a fruitful reproductive season. As amphibian populations undergo large fluctuations in numbers from year to year, this phenomenon will not occur on a yearly basis but will depend on successful reproduction, which is related to numerous climatic and geophysical factors. Hence, most large swarms of amphibians, particularly those involving very small frogs and occurring in late spring or summer, are not unusual and should not be considered earthquake precursors. In addition, it is likely that reports of several mass migration of small toads prior to the Great Sichuan Earthquake in 2008 were not linked to the subsequent M = 7.9 event (some occurred at a great distance from the epicentre), and were probably co-incidence. Statistical analysis of the data indicated frog swarms are unlikely to be connected with earthquakes. Reports of unusual behaviour giving rise to earthquake fears should be interpreted with caution, and consultation with experts in the field of earthquake biology is advised. PMID:26479746

  8. Magnetic field experiment for Voyagers 1 and 2

    NASA Technical Reports Server (NTRS)

    Behannon, K. W.; Acuna, M. H.; Burlaga, L. F.; Lepping, R. P.; Ness, N. F.; Neubauer, F. M.

    1977-01-01

    The magnetic field experiments of the Voyager program involve studies of the planetary fields of Jupiter, Saturn, possibly Uranus, and several satellites; the solar wind and satellite interactions with the planetary fields, as well as large- and micro-scale features of the interplanetary magnetic field will also be investigated. Dual low field and high field magnetometer systems with dynamic ranges of + or - 0.5 G and + or - 20 G respectively provide high reliability for the missions and permit the separation of the spacecraft and ambient fields. Quantization uncertainty, rms noise levels and data compaction schemes of the magnetometer systems are also mentioned.

  9. Components of Swarm Intelligence

    SciTech Connect

    David Bruemmer; Donald Dudenhoeffer; Matthew Anderson; Mark McKay

    2004-03-01

    This paper discusses the successes and failures over the past three years as efforts at the Idaho National Engineering and Environmental Laboratory (INEEL) have developed and evaluated robot behaviors that promote the emergence of swarm intelligence. Using a team of 12 small robots with the ability to respond to light and sound, the INEEL has investigated the fundamental advantages of swarm behavior as well as the limitations of this approach. The paper discusses the ways in which biology has inspired this work and the ways in which adherence to the biological model has proven to be both a benefit and hindrance to developing a fieldable system. The paper outlines how a hierarchical command and control structure can be imposed in order to permit human control at a level of group abstraction and discusses experimental results that show how group performance scales as different numbers of robots are utilized. Lastly, the paper outlines the applications for which the resulting capabilities have been applied and demonstrated.

  10. Classroom and Field Experiments for Florida's Environmental Resources.

    ERIC Educational Resources Information Center

    Lewis, Jim

    This booklet is intended to help teachers in Florida manage the growing interest in environmental education. Fourteen experiments are grouped into the environmental areas of the water cycle, groundwater, water pollution, waste and water treatment, air pollution, and field experiments. Experiments include demonstrations of the water cycle, the…

  11. Markerless Human Motion Tracking Using Hierarchical Multi-Swarm Cooperative Particle Swarm Optimization

    PubMed Central

    Saini, Sanjay; Zakaria, Nordin; Rambli, Dayang Rohaya Awang; Sulaiman, Suziah

    2015-01-01

    The high-dimensional search space involved in markerless full-body articulated human motion tracking from multiple-views video sequences has led to a number of solutions based on metaheuristics, the most recent form of which is Particle Swarm Optimization (PSO). However, the classical PSO suffers from premature convergence and it is trapped easily into local optima, significantly affecting the tracking accuracy. To overcome these drawbacks, we have developed a method for the problem based on Hierarchical Multi-Swarm Cooperative Particle Swarm Optimization (H-MCPSO). The tracking problem is formulated as a non-linear 34-dimensional function optimization problem where the fitness function quantifies the difference between the observed image and a projection of the model configuration. Both the silhouette and edge likelihoods are used in the fitness function. Experiments using Brown and HumanEva-II dataset demonstrated that H-MCPSO performance is better than two leading alternative approaches—Annealed Particle Filter (APF) and Hierarchical Particle Swarm Optimization (HPSO). Further, the proposed tracking method is capable of automatic initialization and self-recovery from temporary tracking failures. Comprehensive experimental results are presented to support the claims. PMID:25978493

  12. Markerless human motion tracking using hierarchical multi-swarm cooperative particle swarm optimization.

    PubMed

    Saini, Sanjay; Zakaria, Nordin; Rambli, Dayang Rohaya Awang; Sulaiman, Suziah

    2015-01-01

    The high-dimensional search space involved in markerless full-body articulated human motion tracking from multiple-views video sequences has led to a number of solutions based on metaheuristics, the most recent form of which is Particle Swarm Optimization (PSO). However, the classical PSO suffers from premature convergence and it is trapped easily into local optima, significantly affecting the tracking accuracy. To overcome these drawbacks, we have developed a method for the problem based on Hierarchical Multi-Swarm Cooperative Particle Swarm Optimization (H-MCPSO). The tracking problem is formulated as a non-linear 34-dimensional function optimization problem where the fitness function quantifies the difference between the observed image and a projection of the model configuration. Both the silhouette and edge likelihoods are used in the fitness function. Experiments using Brown and HumanEva-II dataset demonstrated that H-MCPSO performance is better than two leading alternative approaches-Annealed Particle Filter (APF) and Hierarchical Particle Swarm Optimization (HPSO). Further, the proposed tracking method is capable of automatic initialization and self-recovery from temporary tracking failures. Comprehensive experimental results are presented to support the claims. PMID:25978493

  13. Field-reversed configuration (FRC) experiments

    NASA Astrophysics Data System (ADS)

    Siemon, R. E.; Chrien, R. E.; Hugrass, W. N.; Okada, S.; Rej, D. J.; Taggart, D. P.; Tuszewski, M.; Webster, R. B.; Wright, B. L.; Slough, J. T.

    FRCs with equilibrium separatrix radii up to 0.18 m have been formed and studied in FRX-C/LSM. For best formation conditions at low fill pressure, the particle confinement exceeds the predictions of LHD transport calculations by up to a factor of two; however, the inferred flux confinement is more anomalous than in smaller FRCs. Higher bias field produces axial shocks and degradation in confinement, while higher fill pressure results in gross fluting during formation. FRCs have been formed in TRX with s from 2 to 6. These relatively collisional FRCs exhibit flux lifetimes of 10 yields 20 kinetic growth times for the internal tilt mode. The coaxial slow source has produced annular FRCs in a coaxial coil geometry on slow time scales using low voltages.

  14. The Ecology of Field Experience: Toward an Understanding of the Role of Field Experiences in Teacher Development.

    ERIC Educational Resources Information Center

    Zeichner, Kenneth M.

    There continues to be a great deal of debate about the role that field experiences play in teacher development and about the relative contribution of various individual and institutional factors to the socialization process. Field experiences in teacher education entail a complex set of interactions among program features, settings, and people…

  15. Multiscale Model of Swarming Bacteria

    NASA Astrophysics Data System (ADS)

    Alber, Mark

    2011-03-01

    Many bacteria can rapidly traverse surfaces from which they are extracting nutrient for growth. They generate flat, spreading colonies, called swarms because they resemble swarms of insects. In the beginning of the talk, swarms of the M. xanthus will be described in detail. Individual M. xanthus cells are elongated; they always move in the direction of their long axis; and they are in constant motion, repeatedly touching each other. As a cell glides, the slime capsule of a cell interacts with the bare agar surface, non-oriented slime which arises from the surface contact with the slime capsule, or oriented slime trails. Remarkably, cells regularly reverse their gliding directions. In this talk a detailed cell- and behavior-based computational model of M. xanthus swarming will be used to demonstrate that reversals of gliding direction and cell bending are essential for swarming and that specific reversal frequencies result in optimal swarming rate of the whole population. This suggests that the circuit regulating reversals evolved to its current sensitivity under selection for growth achieved by swarming.

  16. Mod-2 wind turbine field operations experiment

    NASA Technical Reports Server (NTRS)

    Gordon, L. H.

    1985-01-01

    The three-machine, 7.5 MW Goodnoe Hills located near Goldendale, Washington and is now in a research/experimental operations phase that offers a unique opportunity to study the effects of single and multiple wind turbines interacting with each other, the power grid; and the environment. Following a brief description of the turbine and project history, this paper addresses major problem areas and research and development test results. Field operations, both routine and nonroutine, are discussed. Routine operation to date has produced over 13,379,000 KWh of electrical energy during 11,064 hr of rotation. Nonroutine operation includes suspended activities caused by a crack in the low speed shaft that necessitated a redesign and reinstallation of this assembly on all three turbines. With the world's largest cluster back in full operation, two of the turbines will be operated over the next years to determine their value as energy producer. The third unit will be used primarily for conducting research tests requiring configuration changes to better understand the wind turbine technology. Technical areas summarized pertain to system performance and enhancements. Specific research tests relating to acoustics, TV interference, and wake effects conclude the paper.

  17. A Gravitational Experiment Involving Inhomogeneous Electric Fields

    SciTech Connect

    Datta, T.; Yin Ming; Vargas, Jose

    2004-02-04

    Unification of gravitation with other forms of interactions, particularly with electromagnetism, will have tremendous impacts on technology and our understanding of nature. The economic impact of such an achievement will also be unprecedented and far more extensive than the impact experienced in the past century due to the unification of electricity with magnetism and optics. Theoretical unification of gravitation with electromagnetism using classical differential geometry has been pursued since the late nineteen twenties, when Einstein and Cartan used teleparallelism for the task. Recently, Vargas and Torr have followed the same line of research with more powerful mathematics in a more general geometric framework, which allows for the presence of other interactions. Their approach also uses Kaehler generalization of Cartan's exterior calculus, which constitutes a language appropriate for both classical and quantum physics. Given the compelling nature of teleparallelism (path-independent equality of vectors at a distance) and the problems still existing with energy-momentum in general relativity, it is important to seek experimental evidence for such expectations. Such experimental programs are likely to provide quantitative guidance to the further development of current and future theories. We too, have undertaken an experimental search for potential electrically induced gravitational (EIG) effects. This presentation describes some of the practical concerns that relates to our investigation of electrical influences on laboratory size test masses. Preliminary results, appear to indicate a correlation between the application of a spatially inhomogeneous electric field and the appearance of an additional force on the test mass. If confirmed, the presence of such a force will be consistent with the predictions of Vargas-Torr. More importantly, proven results will shed new light and clearer understanding of the interactions between gravitational and electromagnetic

  18. Inverse turbulent cascade in swarming sperm

    NASA Astrophysics Data System (ADS)

    Creppy, Adama; Praud, Olivier; Druart, Xavier; Kohnke, Philippa; Plouraboue, Franck; Inra, Cnrs, Umr, F-37380 Nouzilly, France Team; Université de Toulouse, Inpt, Ups, Imft, Umr 5502, France Team

    2014-11-01

    Collective motion of self-sustained swarming flows has recently provided examples of small scale turbulence arising where viscosity effects are dominant. We report the first observation of an universal inverse enstrophy cascade in concentrated swarming sperm consistent with a body of evidence built from various independent measurements. We found a well-defined k-3 power-law decay of velocity field power-spectrum and relative dispersion of small beads consistent with theoretical predictions in two-dimensional turbulence. Concentrated living sperm displays long-range, correlated whirlpool structures the size of which provides turbulence's integral scale. We propose a consistent explanation for this quasi-two-dimensional turbulence based on self-structured laminated flow forced by steric interaction and alignment, a state of active matter that we call ``swarming liquid crystal.'' We develop scaling arguments consistent with this interpretation. The implication of multi-scale collective dynamics of sperm's collective motility for fertility assessment is discussed. This work has been supported by the French Agence Nationale pour la Recherche (ANR) in the frame of the Contract MOTIMO (ANR-11-MONU-009-01). We thank Pierre Degond, Eric Climent, Laurent Lacaze and Frédéric Moulin for interesting discussions.

  19. FIELD EXPERIMENTS AND MODELING AT CDG AIRPORTS

    NASA Astrophysics Data System (ADS)

    Ramaroson, R.

    2009-12-01

    Richard Ramaroson1,4, Klaus Schaefer2, Stefan Emeis2, Carsten Jahn2, Gregor Schürmann2, Maria Hoffmann2, Mikhael Zatevakhin3, Alexandre Ignatyev3. 1ONERA, Châtillon, France; 4SEAS, Harvard University, Cambridge, USA; 2FZK, Garmisch, Germany; (3)FSUE SPbAEP, St Petersburg, Russia. 2-month field campaigns have been organized at CDG airports in autumn 2004 and summer 2005. Air quality and ground air traffic emissions have been monitored continuously at terminals and taxi-runways, along with meteorological parameters onboard trucks and with a SODAR. This paper analyses the commercial engine emissions characteristics at airports and their effects on gas pollutants and airborne particles coupled to meteorology. LES model results for PM dispersion coupled to microphysics in the PBL are compared to measurements. Winds and temperature at the surface and their vertical profiles have been stored with turbulence. SODAR observations show the time-development of the mixing layer depth and turbulent mixing in summer up to 800m. Active low level jets and their regional extent have been observed and analyzed. PM number and mass size distribution, morphology and chemical contents are investigated. Formation of new ultra fine volatile (UFV) particles in the ambient plume downstream of running engines is observed. Soot particles are mostly observed at significant level at high power thrusts at take-off (TO) and on touch-down whereas at lower thrusts at taxi and aprons ultra the UFV PM emissions become higher. Ambient airborne PM1/2.5 is closely correlated to air traffic volume and shows a maximum beside runways. PM number distribution at airports is composed mainly by volatile UF PM abundant at apron. Ambient PM mass in autumn is higher than in summer. The expected differences between TO and taxi emissions are confirmed for NO, NO2, speciated VOC and CO. NO/NO2 emissions are larger at runways due to higher power. Reactive VOC and CO are more produced at low powers during idling at

  20. First results of a scientific validation of Swarm ASM data

    NASA Astrophysics Data System (ADS)

    Chulliat, Arnaud; Alken, Patrick; Hulot, Gauthier

    2014-05-01

    The Absolute Scalar Magnetometer (ASM) is an optically pumped helium-4 magnetometer providing scalar measurements of the Earth's magnetic field onboard each of the three Swarm satellites. Its performance (accuracy, noise level, data cleanliness) is expected to be unprecedented among satellite scalar magnetometers. The main function of the ASMs during the Swarm mission will be to calibrate the vector field magnetometers. As part of the commissioning of the ASM instrument, we will compare preliminary ASM data with predictions from various recent geomagnetic models. Special focus will be placed on the DMSP-MAG-1 model, which relies on geomagnetic data from the Defense Meteorological Satellite Program (DMSP) until 2013.

  1. Cluster operations in support of SWARM and first results

    NASA Astrophysics Data System (ADS)

    Masson, Arnaud; Escoubet, Philippe; Laakso, Harri

    2015-04-01

    The measure of the Earth's magnetic field is perturbed by the external electric currents flowing in the magnetosphere and the ionosphere. One of the SWARM prime scientific objectives is to investigate the influence of these currents, including the ring current and field aligned currents (FAC). To help disentangle their effects, special operations have been designed and coordinated with the ESA Cluster mission. This unique constellation of four satellites enable the measure of these currents at higher altitudes better than any previous mission. The complementarity of these two missions was foreseen at the beginning of the SWARM mission design, about 10 years ago. The 2014 special operations in support of SWARM is in other words a forward-looking idea becoming reality. We will first briefly recall a few scientific highlights of the Cluster mission, related to the first measure of currents in space by a constellation of four satellites. We will then talk about the 2014 special operations designed and executed in support of SWARM. We will then present future special operations that are planned to be executed by Cluster up to 2018 in support of SWARM. Preliminary results already obtained will be also evoked.

  2. Multidisciplinary Field Training in Undergraduate Physical Geography: Russian Experience

    ERIC Educational Resources Information Center

    Kasimov, Nikolay S.; Chalov, Sergey R.; Panin, Andrey V.

    2013-01-01

    Field training is seen as a central component of the discipline of Physical Geography and an essential part of the undergraduate curriculum. This paper explores the structure and relationships between fieldwork and theoretical courses and the abundant experiences of field training in the undergraduate curriculum of 37 Russian universities. It…

  3. Pre-Service Teachers' Reflections during Field Experience

    ERIC Educational Resources Information Center

    Al-Hassan, Omayya; Al-Barakat, Ali; Al-Hassan, Yazid

    2012-01-01

    This research study investigates pre-service teachers' perceptions of their field experience in kindergartens and schools in Jordan. A total of 57 pre-service early years teachers wrote weekly reflective journals describing and commenting on their experiences during placement in kindergartens and elementary schools. Three major themes emerged from…

  4. EXPERIMENTAL DESIGN AND INSTRUMENTATION FOR A FIELD EXPERIMENT

    EPA Science Inventory

    This report concerns the design of a field experiment for a military setting in which the effects of carbon monoxide on neurobehavioral variables are to be studied. ield experiment is distinguished from a survey by the fact that independent variables are manipulated, just as in t...

  5. CONVECTIVE DIFFUSION FIELD MEASUREMENTS COMPARED WITH LABORATORY AND NUMERICAL EXPERIMENTS

    EPA Science Inventory

    Some of the more fundamental diffusion parameters measured in the CONDORS convective diffusion field experiment are compared with laboratory experiment and numerical modeling results by means of nondimensionalizations using convective scaling (i.e., mixing depth, z sub i, for len...

  6. An innovative, interdisciplinary educational experience in field research.

    PubMed

    Smith, M; Barton, J; Baxter, J

    1996-01-01

    Although interdisciplinary practice is necessary to meet the complex health needs of populations, there are few planned interdisciplinary learning experiences within educational programs for the health professions. The authors describe an interdisciplinary learning experience in field research for students and faculty members from schools of nursing and medicine. PMID:8700424

  7. On the design of experiments to study extreme field limits

    SciTech Connect

    Bulanov, S. S.; Chen, M.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.; Bulanov, S. V.; Esirkepov, T. Zh.; Kando, M.; Koga, J. K.; Zhidkov, A. G.; Chen, P.; Mur, V. D.; Narozhny, N. B.; Popov, V. S.; Thomas, A. G. R.; Korn, G.

    2012-12-21

    We propose experiments on the collision of high intensity electromagnetic pulses with electron bunches and on the collision of multiple electromagnetic pulses for studying extreme field limits in the nonlinear interaction of electromagnetic waves. The effects of nonlinear QED will be revealed in these laser plasma experiments.

  8. The Impact of an International Field Experience on Preservice Teachers

    ERIC Educational Resources Information Center

    Pence, Holly M.; Macgillivray, Ian K.

    2008-01-01

    This study addresses the question, "What is the impact of an international field experience on preservice teachers?" and corroborates many of the findings of a similar study by Willard-Holt [(2001). "The impact of a short-term international experience for preservice teachers." "Teaching and Teacher Education, 17," 505-517]. In May 2005, 15 teacher…

  9. Electric Dipole Moment Experiment Systematic from Electric Field Discharge Current

    NASA Astrophysics Data System (ADS)

    Feinberg, B.; Gould, Harvey

    2014-09-01

    A magnetic field, in the direction of the electric field and synchronous with the electric field reversal, will mimic an EDM signal. One might expect a discharge across the electric field plates to produce magnetic fields with only small or vanishing components parallel to the electric field, minimizing its systematic effect. Our experimental model, using simulated discharge currents, found otherwise: the discharge current may be at an angle to the normal, and thus generate a normal magnetic field. Comparison of data from the experimental model with the results from calculations will be presented, along with estimates of the time-averaged normal magnetic field seen by atoms in an electron EDM experiment using a fountain of laser-cooled francium, as a function of discharge current.

  10. TPE-1R (M) reversed field pinch experiment

    SciTech Connect

    Shimada, T.; Hirano, Y.; Maejima, Y.; Ogawa, K.

    1981-01-01

    This report describes the engineering aspects of the design, tests, and performances of the toroidal device TPE-1RM with which plasma physics researches on ''Reversed Field Pinch''configurations are carried out and this is an intermediate scale like HBTX-1A, ZT-40M, and ETA-BETA II. In TPE-1RM experiments are being performed in order to obtain an optimum reversed field configurations for MHD stability. The main description in this report is devoted to the metal vacuum vessel and specially contrived electrical circuit for field programming control techniques. The experiments with this device have been successful both from the technical and physcial points of view.

  11. A sensor fusion field experiment in forest ecosystem dynamics

    NASA Technical Reports Server (NTRS)

    Smith, James A.; Ranson, K. Jon; Williams, Darrel L.; Levine, Elissa R.; Goltz, Stewart M.

    1990-01-01

    The background of the Forest Ecosystem Dynamics field campaign is presented, a progress report on the analysis of the collected data and related modeling activities is provided, and plans for future experiments at different points in the phenological cycle are outlined. The ecological overview of the study site is presented, and attention is focused on forest stands, needles, and atmospheric measurements. Sensor deployment and thermal and microwave observations are discussed, along with two examples of the optical radiation measurements obtained during the experiment in support of radiative transfer modeling. Future activities pertaining to an archival system, synthetic aperture radar, carbon acquisition modeling, and upcoming field experiments are considered.

  12. Frog Swarms: Earthquake Precursors or False Alarms?

    PubMed

    Grant, Rachel A; Conlan, Hilary

    2013-01-01

    -incidence. Statistical analysis of the data indicated frog swarms are unlikely to be connected with earthquakes. Reports of unusual behaviour giving rise to earthquake fears should be interpreted with caution, and consultation with experts in the field of earthquake biology is advised. PMID:26479746

  13. Modeling HEDLA magnetic field generation experiments on laser facilities

    NASA Astrophysics Data System (ADS)

    Fatenejad, M.; Bell, A. R.; Benuzzi-Mounaix, A.; Crowston, R.; Drake, R. P.; Flocke, N.; Gregori, G.; Koenig, M.; Krauland, C.; Lamb, D.; Lee, D.; Marques, J. R.; Meinecke, J.; Miniati, F.; Murphy, C. D.; Park, H.-S.; Pelka, A.; Ravasio, A.; Remington, B.; Reville, B.; Scopatz, A.; Tzeferacos, P.; Weide, K.; Woolsey, N.; Young, R.; Yurchak, R.

    2013-03-01

    The Flash Center is engaged in a collaboration to simulate laser driven experiments aimed at understanding the generation and amplification of cosmological magnetic fields using the FLASH code. In these experiments a laser illuminates a solid plastic or graphite target launching an asymmetric blast wave into a chamber which contains either Helium or Argon at millibar pressures. Induction coils placed several centimeters away from the target detect large scale magnetic fields on the order of tens to hundreds of Gauss. The time dependence of the magnetic field is consistent with generation via the Biermann battery mechanism near the blast wave. Attempts to perform simulations of these experiments using the FLASH code have uncovered previously unreported numerical difficulties in modeling the Biermann battery mechanism near shock waves which can lead to the production of large non-physical magnetic fields. We report on these difficulties and offer a potential solution.

  14. Pattern Formation and Functionality in Swarm Models

    NASA Astrophysics Data System (ADS)

    Rauch, Erik; Millonas, Mark; Chialvo, Dante

    1996-03-01

    We explore a simplified class of models we call swarms, which are inspired by the collective behavior of social insects. We perform a mean-field type stability analysis and numerical simulations of the model. Several interesting types of functional behavior appear in the vicinity of a second order phase transition, including the formation of stable lines of traffic flow, memory consolidation, and bootstrapping. In addition to providing an understanding of certain classes of biological behavior, these models bear a generic resemblence to a number of pattern formation processes in the physical sciences.

  15. Collective motion in Proteus mirabilis swarms

    NASA Astrophysics Data System (ADS)

    Haoran, Xu

    Proteus mirabilisis a Gram-negative, rod-shaped bacterium. It is widely distributed in soil and water, and it is well known for exhibiting swarming motility on nutrient agar surfaces. In our study, we focused on the collective motility of P. mirabilis and uncovered a range of interesting phenomena. Here we will present our efforts to understand these phenomena through experiments and simulation. Mailing address: Room 306 Science Centre North Block, The Chinese University of Hong Kong, Shatin, N.T. Hong Kong SAR. Phone: +852-3943-6354. Fax: +852-2603-5204. E-mail:xhrphx@gmail.com.

  16. Swarming of self-propelled camphor boats

    NASA Astrophysics Data System (ADS)

    Heisler, Eric; Suematsu, Nobuhiko J.; Awazu, Akinori; Nishimori, Hiraku

    2012-05-01

    When an ensemble of self-propelled camphor boats move in a one-dimensional channel, they exhibit a variety of collective behaviors. Under certain conditions, the boats tend to cluster together and move in a relatively tight formation. This type of behavior, referred to as clustering or swarming here, is one of three types recently observed in experiment. Similar clustering behavior is also reproduced in simulations based on a simple theoretical model. Here we examine this model to determine the clustering mechanism and the conditions under which clustering occurs. We also propose a method of quantifying the behavior that may be used in future experimental work.

  17. Influencing attitudes toward science through field experiences in biology

    NASA Astrophysics Data System (ADS)

    Carpenter, Deborah Mcintyre

    The purpose of this study was to determine how student attitudes toward science are influenced by field experiences in undergraduate biology courses. The study was conducted using two institutions of higher education including a 2-year lower-level and a 2-year upper-level institution. Data were collected through interviews with student participants, focus group discussions, students' journal entries, and field notes recorded by the researcher during the field activities. Photographs and video recordings were also used as documentation sources. Data were collected over a period of 34 weeks. Themes that emerged from the qualitative data included students' beliefs that field experiences (a) positively influence student motivation to learn, (b) increase student ability to learn the concepts being taught, and (c) provide opportunities for building relationships and for personal growth. The findings of the study reinforce the importance of offering field-study programs at the undergraduate level to allow undergraduate students the opportunity to experience science activities in a field setting. The research study was framed by the behavioral and developmental theories of attitude and experience including the Theory of Planned Behavior (Ajzen, 1991) and the Theory of Experiential Learning (Kolb, 1984).

  18. Magnetic field experiment for Voyagers 1 and 2

    NASA Technical Reports Server (NTRS)

    Behannon, K. W.; Aluna, M. H.; Burlaga, L. F.; Lepping, R. P.; Ness, N. F.; Neubauer, F. M.

    1977-01-01

    The magnetic field experiment to be carried on the Voyager 1 and 2 missions consists of dual low field (LFM) and high field magnetometer (HFM) systems. The dual systems provide greater reliability and, in the case of the LFM's, permit the separation of spacecraft magnetic fields from the ambient fields. Additional reliability is achieved through electronics redundancy. The wide dynamic ranges of plus or minus 0.5G for the LFM's and plus or minus 20G for the HFM's, low quantization uncertainty of plus or minus 0.002 gamma in the most sensitive (plus or minus 8 gamma) LFM range, low sensor RMS noise level of 0.006 gamma, and use of data compaction schemes to optimize the experiment information rate all combine to permit the study of a broad spectrum of phenomena during the mission. Planetary fields at Jupiter, Saturn, and possibly Uranus; satellites of these planets; solar wind and satellite interactions with the planetary fields; and the large-scale structure and microscale characteristics of the interplanetary magnetic field are studied. The interstellar field may also be measured.

  19. Cell-Division Behavior in a Heterogeneous Swarm Environment.

    PubMed

    Erskine, Adam; Herrmann, J Michael

    2015-01-01

    We present a system of virtual particles that interact using simple kinetic rules. It is known that heterogeneous mixtures of particles can produce particularly interesting behaviors. Here we present a two-species three-dimensional swarm in which a behavior emerges that resembles cell division. We show that the dividing behavior exists across a narrow but finite band of parameters and for a wide range of population sizes. When executed in a two-dimensional environment the swarm's characteristics and dynamism manifest differently. In further experiments we show that repeated divisions can occur if the system is extended by a biased equilibrium process to control the split of populations. We propose that this repeated division behavior provides a simple model for cell-division mechanisms and is of interest for the formation of morphological structure and to swarm robotics. PMID:26545164

  20. Composite Particle Swarm Optimizer With Historical Memory for Function Optimization.

    PubMed

    Li, Jie; Zhang, JunQi; Jiang, ChangJun; Zhou, MengChu

    2015-10-01

    Particle swarm optimization (PSO) algorithm is a population-based stochastic optimization technique. It is characterized by the collaborative search in which each particle is attracted toward the global best position (gbest) in the swarm and its own best position (pbest). However, all of particles' historical promising pbests in PSO are lost except their current pbests. In order to solve this problem, this paper proposes a novel composite PSO algorithm, called historical memory-based PSO (HMPSO), which uses an estimation of distribution algorithm to estimate and preserve the distribution information of particles' historical promising pbests. Each particle has three candidate positions, which are generated from the historical memory, particles' current pbests, and the swarm's gbest. Then the best candidate position is adopted. Experiments on 28 CEC2013 benchmark functions demonstrate the superiority of HMPSO over other algorithms. PMID:26390177

  1. SCARF - The Swarm Satellite Constellation Application and Research Facility

    NASA Astrophysics Data System (ADS)

    Olsen, N.; Alken, P.; Beggan, C.; Chulliat, A.; Doornbos, E.; Floberghagen, R.; Friis-Christensen, E. A.; Hamilton, B.; Hulot, G.; van den IJssel, J.; Kuvshinov, A. V.; Lesur, V.; Luhr, H.; Macmillan, S.; Maus, S.; Olsen, P. H.; Park, J.; Plank, G.; Ritter, P.; Rother, M.; Sabaka, T. J.; Stolle, C.; Thebault, E.; Thomson, A. W.; Tøffner-Clausen, L.; Velimsky, J.; Visser, P. N.

    2011-12-01

    In order to take advantage of the unique constellation aspect of the Swarm mission, considerably advanced data analysis tools will need to be developed. Scientific use of data from the Swarm mission will also benefit significantly from derived products, the so-called Level-2 products, that take into account the features of the constellation. For this reason ESA has established a "Satellite Constellation Application and Research Facility" (SCARF), in the form of a consortium of several research institutions. A number of Level-2 data products will be offered by this consortium, including various models of the core and lithospheric field, as well as of the ionospheric and magnetospheric field. In addition, derived parameters like mantle conductivity, thermospheric mass density and winds, field-aligned currents, an ionospheric plasma bubble index, the ionospheric total electron content and the dayside equatorial zonal electrical field will be calculated. Following the end of the currently running 30-month development phase, this service is expected to be operational for a period of 5 years after the launch of the Swarm Mission, which is scheduled for summer 2012. All of the derived products will be available through the Swarm Payload Data Ground Segment (PDGS), located at ESRIN, the ESA Centre for Earth Observation in Frascati, Italy.

  2. FLASH magnetohydrodynamic simulations of shock-generated magnetic field experiments

    NASA Astrophysics Data System (ADS)

    Tzeferacos, P.; Fatenejad, M.; Flocke, N.; Gregori, G.; Lamb, D. Q.; Lee, D.; Meinecke, J.; Scopatz, A.; Weide, K.

    2012-12-01

    We report the results of benchmark FLASH magnetohydrodynamic (MHD) simulations of experiments conducted by the University of Oxford High Energy Density Laboratory Astrophysics group and its collaborators at the Laboratoire pour l'Utilisation des Lasers Intenses (LULI). In these experiments, a long-pulse laser illuminates a target in a chamber filled with Argon gas, producing shock waves that generate magnetic fields via the Biermann battery mechanism. We first outline the implementation of 2D cylindrical geometry in the unsplit MHD solver in FLASH and present results of verification tests. We then describe the results of benchmark 2D cylindrical MHD simulations of the LULI experiments using FLASH that explore the impact of external fields along with the possibility of magnetic field amplification by turbulence that is associated with the shock waves and that is induced by a grid placed in the gas-filled chamber.

  3. Visualization of Biosurfactant Film Flow in a Bacillus subtilis Swarm Colony on an Agar Plate

    PubMed Central

    Kim, Kyunghoon; Kim, Jung Kyung

    2015-01-01

    Collective bacterial dynamics plays a crucial role in colony development. Although many research groups have studied the behavior of fluidic swarm colonies, the detailed mechanics of its motion remains elusive. Here, we developed a visualization method using submicron fluorescent beads for investigating the flow field in a thin layer of fluid that covers a Bacillus subtilis swarm colony growing on an agar plate. The beads were initially embedded in the agar plate and subsequently distributed spontaneously at the upper surface of the expanding colony. We conducted long-term live cell imaging of the B. subtilis colony using the fluorescent tracers, and obtained high-resolution velocity maps of microscale vortices in the swarm colony using particle image velocimetry. A distinct periodic fluctuation in the average speed and vorticity of flow in swarm colony was observed at the inner region of the colony, and correlated with the switch between bacterial swarming and growth phases. At the advancing edge of the colony, both the magnitudes of velocity and vorticity of flow in swarm colony were inversely correlated with the spreading speed of the swarm edge. The advanced imaging tool developed in this study would facilitate further understanding of the effect of micro vortices in swarm colony on the collective dynamics of bacteria. PMID:26343634

  4. Visualization of Biosurfactant Film Flow in a Bacillus subtilis Swarm Colony on an Agar Plate.

    PubMed

    Kim, Kyunghoon; Kim, Jung Kyung

    2015-01-01

    Collective bacterial dynamics plays a crucial role in colony development. Although many research groups have studied the behavior of fluidic swarm colonies, the detailed mechanics of its motion remains elusive. Here, we developed a visualization method using submicron fluorescent beads for investigating the flow field in a thin layer of fluid that covers a Bacillus subtilis swarm colony growing on an agar plate. The beads were initially embedded in the agar plate and subsequently distributed spontaneously at the upper surface of the expanding colony. We conducted long-term live cell imaging of the B. subtilis colony using the fluorescent tracers, and obtained high-resolution velocity maps of microscale vortices in the swarm colony using particle image velocimetry. A distinct periodic fluctuation in the average speed and vorticity of flow in swarm colony was observed at the inner region of the colony, and correlated with the switch between bacterial swarming and growth phases. At the advancing edge of the colony, both the magnitudes of velocity and vorticity of flow in swarm colony were inversely correlated with the spreading speed of the swarm edge. The advanced imaging tool developed in this study would facilitate further understanding of the effect of micro vortices in swarm colony on the collective dynamics of bacteria. PMID:26343634

  5. Evolution of Collective Behaviors for a Real Swarm of Aquatic Surface Robots

    PubMed Central

    Duarte, Miguel; Costa, Vasco; Gomes, Jorge; Rodrigues, Tiago; Silva, Fernando; Oliveira, Sancho Moura; Christensen, Anders Lyhne

    2016-01-01

    Swarm robotics is a promising approach for the coordination of large numbers of robots. While previous studies have shown that evolutionary robotics techniques can be applied to obtain robust and efficient self-organized behaviors for robot swarms, most studies have been conducted in simulation, and the few that have been conducted on real robots have been confined to laboratory environments. In this paper, we demonstrate for the first time a swarm robotics system with evolved control successfully operating in a real and uncontrolled environment. We evolve neural network-based controllers in simulation for canonical swarm robotics tasks, namely homing, dispersion, clustering, and monitoring. We then assess the performance of the controllers on a real swarm of up to ten aquatic surface robots. Our results show that the evolved controllers transfer successfully to real robots and achieve a performance similar to the performance obtained in simulation. We validate that the evolved controllers display key properties of swarm intelligence-based control, namely scalability, flexibility, and robustness on the real swarm. We conclude with a proof-of-concept experiment in which the swarm performs a complete environmental monitoring task by combining multiple evolved controllers. PMID:26999614

  6. Evolution of Collective Behaviors for a Real Swarm of Aquatic Surface Robots.

    PubMed

    Duarte, Miguel; Costa, Vasco; Gomes, Jorge; Rodrigues, Tiago; Silva, Fernando; Oliveira, Sancho Moura; Christensen, Anders Lyhne

    2016-01-01

    Swarm robotics is a promising approach for the coordination of large numbers of robots. While previous studies have shown that evolutionary robotics techniques can be applied to obtain robust and efficient self-organized behaviors for robot swarms, most studies have been conducted in simulation, and the few that have been conducted on real robots have been confined to laboratory environments. In this paper, we demonstrate for the first time a swarm robotics system with evolved control successfully operating in a real and uncontrolled environment. We evolve neural network-based controllers in simulation for canonical swarm robotics tasks, namely homing, dispersion, clustering, and monitoring. We then assess the performance of the controllers on a real swarm of up to ten aquatic surface robots. Our results show that the evolved controllers transfer successfully to real robots and achieve a performance similar to the performance obtained in simulation. We validate that the evolved controllers display key properties of swarm intelligence-based control, namely scalability, flexibility, and robustness on the real swarm. We conclude with a proof-of-concept experiment in which the swarm performs a complete environmental monitoring task by combining multiple evolved controllers. PMID:26999614

  7. Swarm intelligence in bioinformatics: methods and implementations for discovering patterns of multiple sequences.

    PubMed

    Cui, Zhihua; Zhang, Yi

    2014-02-01

    As a promising and innovative research field, bioinformatics has attracted increasing attention recently. Beneath the enormous number of open problems in this field, one fundamental issue is about the accurate and efficient computational methodology that can deal with tremendous amounts of data. In this paper, we survey some applications of swarm intelligence to discover patterns of multiple sequences. To provide a deep insight, ant colony optimization, particle swarm optimization, artificial bee colony and artificial fish swarm algorithm are selected, and their applications to multiple sequence alignment and motif detecting problem are discussed. PMID:24749453

  8. SCARF - The Swarm Satellite Constellation Application and Research Facility

    NASA Astrophysics Data System (ADS)

    Olsen, Nils

    2014-05-01

    Swarm, a three-satellite constellation to study the dynamics of the Earth's magnetic field and its interactions with the Earth system, has been launched in November 2013. The objective of the Swarm mission is to provide the best ever survey of the geomagnetic field and its temporal evolution, which will bring new insights into the Earth system by improving our understanding of the Earth's interior and environment. In order to take advantage of the unique constellation aspect of Swarm, considerably advanced data analysis tools have been developed. Scientific users will also benefit significantly from derived products, the so-called Level-2 products, that take into account the features of the constellation. The Swarm SCARF (Satellite Constellation Application and Research Facility), a consortium of several research institutions, has been established with the goal of deriving Level-2 products by combination of data from the three satellites, and of the various instruments. A number of Level-2 data products will be offered by this consortium, including various models of the core and lithospheric field, as well as of the ionospheric and magnetospheric field. In addition, derived parameters like mantle conductivity, thermospheric mass density and winds, field-aligned currents, an ionospheric plasma bubble index, the ionospheric total electron content and the dayside equatorial zonal electrical field will be calculated. This service is expected to be operational for a period of at least 5 years. The present paper describes the Swarm input data products (Level-1b and auxiliary data) used by SCARF, the various processing chains of SCARF, and the Level-2 output data products determined by SCARF.

  9. NATO TG-25 joint field experiment in distributed sensor networks

    NASA Astrophysics Data System (ADS)

    Mays, Brian; Vu, Hao; Srour, Nino

    2003-09-01

    NATO's Task Group (TG-25) on acoustic and seismic sensing is responsible for assessing the potential technologies that can be cooperatively developed and shared within NATO's countries to provide effective, robust and low-cost battlefield sensor systems. The primary applications will be detection and/or classification of ground troops, ground vehicles, airborne vehicles, artillery and sniper. TG-25 has 3 main objectives: (1) to establish acoustic and seismic standards and data exchange procedures, (2) to compare, analyze, exchange, and develop analytical techniques, computational models and signal processing algorithms, and (3) to plan and conduct joint field experiments. In this paper, we discuss participation in the joint NATO field experiment conducted in France in October 2002. The experiment's goal is to demonstrate interoperability of unattended ground sensors from various participating nations. Results of the experiments will be briefed and discussed. Keywords: TG-25, unattended ground sensor, vehicle tracking

  10. Natural attenuation of xenobiotic compounds: Anaerobic field injection experiment

    SciTech Connect

    Ruegge, K.; Bjerg, P.L.; Mosbaek, H.; Christensen, T.H.

    1995-12-31

    Currently, a continuous field injection experiment is being performed in the anaerobic part of a pollution plume downgradient of the Grindsted Landfill in Denmark. This natural gradient experiment includes an injection of 18 different xenobiotic compounds with bromide as a tracer. The injection is taking place under methanogenic/sulfate-reducing conditions and the compounds will, as they migrate with the groundwater, pass through a zone where the redox conditions have been determined as iron-reducing.

  11. Particle Swarm Optimization with Double Learning Patterns

    PubMed Central

    Shen, Yuanxia; Wei, Linna; Zeng, Chuanhua; Chen, Jian

    2016-01-01

    Particle Swarm Optimization (PSO) is an effective tool in solving optimization problems. However, PSO usually suffers from the premature convergence due to the quick losing of the swarm diversity. In this paper, we first analyze the motion behavior of the swarm based on the probability characteristic of learning parameters. Then a PSO with double learning patterns (PSO-DLP) is developed, which employs the master swarm and the slave swarm with different learning patterns to achieve a trade-off between the convergence speed and the swarm diversity. The particles in the master swarm and the slave swarm are encouraged to explore search for keeping the swarm diversity and to learn from the global best particle for refining a promising solution, respectively. When the evolutionary states of two swarms interact, an interaction mechanism is enabled. This mechanism can help the slave swarm in jumping out of the local optima and improve the convergence precision of the master swarm. The proposed PSO-DLP is evaluated on 20 benchmark functions, including rotated multimodal and complex shifted problems. The simulation results and statistical analysis show that PSO-DLP obtains a promising performance and outperforms eight PSO variants. PMID:26858747

  12. Particle Swarm Optimization with Double Learning Patterns.

    PubMed

    Shen, Yuanxia; Wei, Linna; Zeng, Chuanhua; Chen, Jian

    2016-01-01

    Particle Swarm Optimization (PSO) is an effective tool in solving optimization problems. However, PSO usually suffers from the premature convergence due to the quick losing of the swarm diversity. In this paper, we first analyze the motion behavior of the swarm based on the probability characteristic of learning parameters. Then a PSO with double learning patterns (PSO-DLP) is developed, which employs the master swarm and the slave swarm with different learning patterns to achieve a trade-off between the convergence speed and the swarm diversity. The particles in the master swarm and the slave swarm are encouraged to explore search for keeping the swarm diversity and to learn from the global best particle for refining a promising solution, respectively. When the evolutionary states of two swarms interact, an interaction mechanism is enabled. This mechanism can help the slave swarm in jumping out of the local optima and improve the convergence precision of the master swarm. The proposed PSO-DLP is evaluated on 20 benchmark functions, including rotated multimodal and complex shifted problems. The simulation results and statistical analysis show that PSO-DLP obtains a promising performance and outperforms eight PSO variants. PMID:26858747

  13. Multicomponent reactive transport modeling of uranium bioremediation field experiments

    SciTech Connect

    Fang, Yilin; Yabusaki, Steven B.; Morrison, Stan J.; Amonette, James E.; Long, Philip E.

    2009-10-15

    Biostimulation field experiments with acetate amendment are being performed at a former uranium mill tailings site in Rifle, Colorado, to investigate subsurface processes controlling in situ bioremediation of uranium-contaminated groundwater. An important part of the research is identifying and quantifying field-scale models of the principal terminal electron-accepting processes (TEAPs) during biostimulation and the consequent biogeochemical impacts to the subsurface receiving environment. Integrating abiotic chemistry with the microbially mediated TEAPs in the reaction network brings into play geochemical observations (e.g., pH, alkalinity, redox potential, major ions, and secondary minerals) that the reactive transport model must recognize. These additional constraints provide for a more systematic and mechanistic interpretation of the field behaviors during biostimulation. The reaction network specification developed for the 2002 biostimulation field experiment was successfully applied without additional calibration to the 2003 and 2007 field experiments. The robustness of the model specification is significant in that 1) the 2003 biostimulation field experiment was performed with 3 times higher acetate concentrations than the previous biostimulation in the same field plot (i.e., the 2002 experiment), and 2) the 2007 field experiment was performed in a new unperturbed plot on the same site. The biogeochemical reactive transport simulations accounted for four TEAPs, two distinct functional microbial populations, two pools of bioavailable Fe(III) minerals (iron oxides and phyllosilicate iron), uranium aqueous and surface complexation, mineral precipitation, and dissolution. The conceptual model for bioavailable iron reflects recent laboratory studies with sediments from the Old Rifle Uranium Mill Tailings Remedial Action (UMTRA) site that demonstrated that the bulk (~90%) of Fe(III) bioreduction is associated with the phyllosilicates rather than the iron oxides

  14. Estimating storm areal average rainfall intensity in field experiments

    NASA Astrophysics Data System (ADS)

    Peters-Lidard, Christa D.; Wood, Eric F.

    1994-07-01

    Estimates of areal mean precipitation intensity derived from rain gages are commonly used to assess the performance of rainfall radars and satellite rainfall retrieval algorithms. Areal mean precipitation time series collected during short-duration climate field studies are also used as inputs to water and energy balance models which simulate land-atmosphere interactions during the experiments. In two recent field experiments (1987 First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) and the Multisensor Airborne Campaign for Hydrology 1990 (MAC-HYDRO '90)) designed to investigate the climatic signatures of land-surface forcings and to test airborne sensors, rain gages were placed over the watersheds of interest. These gages provide the sole means for estimating storm precipitation over these areas, and the gage densities present during these experiments indicate that there is a large uncertainty in estimating areal mean precipitation intensity for single storm events. Using a theoretical model of time- and area-averaged space- time rainfall and a model rainfall generator, the error structure of areal mean precipitation intensity is studied for storms statistically similar to those observed in the FIFE and MAC-HYDRO field experiments. Comparisons of the error versus gage density trade-off curves to those calculated using the storm observations show that the rainfall simulator can provide good estimates of the expected measurement error given only the expected intensity, coefficient of variation, and rain cell diameter or correlation length scale, and that these errors can quickly become very large (in excess of 20%) for certain storms measured with a network whose size is below a "critical" gage density. Because the mean storm rainfall error is particularly sensitive to the correlation length, it is important that future field experiments include radar and/or dense rain gage networks capable of accurately characterizing the

  15. Magnetic field uniformity for the nEDM experiment

    NASA Astrophysics Data System (ADS)

    Slutsky, Simon; nEDM Collaboration

    2014-09-01

    The nEDM experiment at the Spallation Neutron Source (SNS) will search for a neutron electric dipole moment (EDM) with a sensitivity of <5*10-28 e-cm. Neutrons will precess in a constant magnetic field and variable electric field, and non-zero neutron EDM will appear as a variation in the precession frequency correlated with the changing electric field. Geometric phase and neutron polarization lifetime effects constrain the allowed magnetic field gradient to below 0.1 uG/cm. Gradients nearly satisfying this requirement have been achieved using a cos(θ) coil inside an open-ended superconducting lead shield operated at cryogenic temperatures and using the design electric fields. I will describe efforts to further improve the magnet design using a superconducting endcap.

  16. Dynamic field-frequency lock for tracking magnetic field fluctuations in electron spin resonance experiments

    NASA Astrophysics Data System (ADS)

    Asfaw, Abraham; Tyryshkin, Alexei; Lyon, Stephen

    Global magnetic field fluctuations present significant challenges to pulsed electron spin resonance experiments on systems with long spin coherence times. We will discuss results from experiments in which we follow instantaneous changes in magnetic field by locking to the free induction decay of a proton NMR signal using a phase-locked loop. We extend conventional field-frequency locking techniques used in NMR to follow slow magnetic field drifts by using a modified Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence in which the phase of the pi-pulses follows the phase of the proton spins at all times. Hence, we retain the ability of the CPMG pulse sequence to refocus local magnetic field inhomogeneities without refocusing global magnetic field fluctuations. In contrast with conventional field-frequency locking techniques, our experiments demonstrate the potential of this method to dynamically track global magnetic field fluctuations on timescales of about 2 seconds and with rates faster than a kHz. This frequency range covers the dominant noise frequencies in our electron spin resonance experiments as previously reported.

  17. Enhancing Preservice Teacher Development: Field Experiences with Gifted Students

    ERIC Educational Resources Information Center

    Chamberlin, Michelle T.; Chamberlin, Scott A.

    2010-01-01

    During 3 field experience visits, 23 elementary preservice teachers implemented mathematical problem-solving tasks with grade 3-6 gifted students. Researchers investigated what the teachers learned about gifted students regarding student characteristics, mathematical problem-solving tasks, and pedagogy. Each teacher completed a pre- and…

  18. An Experiment In Field-Based Elementary Teacher Education.

    ERIC Educational Resources Information Center

    Swann, Margaret H.

    The Experimental Program in Elementary Education (EXEL) at Shepherd College in West Virginia began in 1973 with authorization by the West Virginia State Department of Education. The program was developed with the hope of producing more confident and competent teachers. EXEL provides continuous field experience from the second semester of the…

  19. Creating Dissonance in Pre-Service Teachers' Field Experiences

    ERIC Educational Resources Information Center

    Eisenhardt, Sara; Besnoy, Kevin; Steele, Emily

    2012-01-01

    The study is practical in nature and addresses the call for investigating effective aspects of field experiences in teacher preparation. The authors designed a framework of assignments requiring the pre-service teachers to collect data about two diverse elementary students in their assigned elementary classroom during the twelve weeks of their…

  20. Infusing Outdoor Field Experiences into the Secondary Biology Curriculum.

    ERIC Educational Resources Information Center

    Owens, Ginny

    1984-01-01

    To offer students biological field experiences, teachers should use their own basic skills, be enthusiastic motivators, participate in community programs/courses/workshops to acquire additional skills/knowledge for outdoor biological education, plan outdoor excursions with safety considerations in mind, and use available resources for classroom…

  1. The spherical probe electric field and wave experiment. [Cluster mission

    NASA Technical Reports Server (NTRS)

    Gustafsson, G.; Aggson, T.; Bostrom, R.; Block, L. P.; Cattell, C.; Decreau, P. M. E.; Egeland, A.; Falthammar, C.-G.; Grard, R. J. L.; Gurnett, D. A.

    1988-01-01

    The experiment is designed to measure the electric field and density fluctuations with sampling rates up to 40,000 samples/sec. The description includes Langmuir sweeps that can be made to determine the electron density and temperature, the study of nonlinear processes that result in acceleration of plasma, and the analysis of large scale phenomena where all four spacecraft are needed.

  2. Field-Based Research Experience in Earth Science Teacher Education.

    ERIC Educational Resources Information Center

    O'Neal, Michael L.

    2003-01-01

    Describes the pilot of a field-based research experience in earth science teacher education designed to produce well-prepared, scientifically and technologically literate earth science teachers through a teaching- and research-oriented partnership between in-service teachers and a university scientist-educator. Indicates that the pilot program was…

  3. Nonphysical Results with the Electric-Field Mapping Experiment.

    ERIC Educational Resources Information Center

    Ayars, Eric

    1996-01-01

    Discusses the behavior of the current near the end of the paper in the electric-field mapping experiment and approaches to solving problems associated with this behavior. Presents programs that can be used to model the boundary condition computationally. (JRH)

  4. Rational Ignorance in Education: A Field Experiment in Student Plagiarism

    ERIC Educational Resources Information Center

    Dee, Thomas S.; Jacob, Brian A.

    2012-01-01

    Plagiarism appears to be a common problem among college students, yet there is little evidence on the effectiveness of interventions designed to minimize plagiarism. This study presents the results of a field experiment that evaluated the effects of a web-based educational tutorial in reducing plagiarism. We found that assignment to the treatment…

  5. A Model for a Rural School Field Experience.

    ERIC Educational Resources Information Center

    Hull, Ray; Hegtvedt, Kathryn

    Fifteen University of Oregon undergraduate education majors participated in a successful 3-day program of total immersion in rural community living and teaching in Condon, Oregon. The field experience model had unique elements: (1) the course was offered as an alternative to a required course in teaching strategies and student teachers were…

  6. Field experiments on an intelligent towed vehicle ``Flying Fish``

    SciTech Connect

    Koterayama, W.; Yamaguchi, S.; Nakamura, M.

    1995-12-31

    A depth, pitch and roll controllable towed vehicle, ``Flying Fish`` is being developed to measure the ocean current, temperature, salinity, dissolved oxygen, pH, turbidity, chlorophyll and total inorganic hydrocarbon. The first field experiments on its performance were carried out in the Japan sea last summer. The motion data of the ``Flying Fish`` are compared with those of numerical simulations.

  7. Conceptualizing Developmentally Responsive Teaching in Early Field Experiences

    ERIC Educational Resources Information Center

    Howell, Penny B.

    2012-01-01

    The purpose of this descriptive qualitative study was to examine case study as a pedagogical tool used to scaffold the conceptualization of developmentally responsive pedagogy for middle level preservice teachers in early field experiences. Child study projects (CSP) completed by middle level preservice candidates were analyzed to determine if…

  8. Experiments to investigate particulate materials in reduced gravity fields

    NASA Technical Reports Server (NTRS)

    Bowden, M.; Eden, H. F.; Felsenthal, P.; Glaser, P. E.; Wechsler, A. E.

    1967-01-01

    Study investigates agglomeration and macroscopic behavior in reduced gravity fields of particles of known properties by measuring and correlating thermal and acoustical properties of particulate materials. Experiment evaluations provide a basis for a particle behavior theory and measure bulk properties of particulate materials in reduced gravity.

  9. Magnetic field uniformity for the nEDM experiment

    NASA Astrophysics Data System (ADS)

    Slutsky, Simon; nEDM Collaboration

    2013-10-01

    The nEDM experiment at the Spallation Neutron Source (SNS) will search for a neutron electric dipole moment (EDM) with a sensitivity of < 5 .10-28 e-cm. Neutrons will precess in a constant magnetic field and variable electric field, and non-zero neutron EDM will appear as a variation in the precession frequency. Gradients in the magnetic field lead to spurious EDM signals through a geometric phase effect. The volume averaged magnetic gradient must be below 0.1 μG/cm to reach the desired sensitivity. In this talk, we describe an effort to produce such a uniform magnetic field in a laboratory using a cos (θ) coil operated at cryogenic temperatures inside a superconducting lead shield.

  10. The Ecology of Field Experience: Toward an Understanding of the Role of Field Experiences in Teacher Development.

    ERIC Educational Resources Information Center

    Zeichner, Kenneth M.

    1985-01-01

    This paper focuses on conceptual and methodological limitations which have been identified in relation to research on field experiences. A point of view is offered as to how research in this area can begin to provide the kinds of empirical data which will be more useful for policy decisions. (CB)

  11. NATO SET-093 joint field experiment at Bourges, France

    NASA Astrophysics Data System (ADS)

    Marty, C.; Bruel, F.; Prieur, D.; Naz, P.; Miller, L. S.

    2009-05-01

    This paper describes the NATO Task Group SET-093/RTG53/MSE (referred to as TG-53 in this report) Acoustic Detection of Weapons Firing Joint Field Experiment II conducted at the Etablissement Technique de Bourges (ETBS), Bourges, France, during 16 to 27 June 2008. This field experiment is a follow-on to the NATO TG-53 Acoustic Detection of Weapons Firing Joint Field Experiment I conducted at the Yuma Proving Grounds (YPG), Yuma, Arizona, USA, during 31 October to 4 November 2005 [1]. The objectives of the joint experiment were: (i) to collect acoustic signatures of direct and indirect firings from weapons' such as small arms, mortars, artillery, rockets, and C4 explosives, (ii) to analyze the propagation effects of grassy, wooded, and urban terrains, (iii) to share signatures collected from a variety of acoustic sensors, on the ground and in the air, distributed over a wide area, and (iv) to demonstrate the interoperability of disparate sensors developed by the various nations involved. The participating NATO countries , including France, the Netherlands, the United Kingdom, Canada, and the United States of America, and Israel as well as part of the Mediterranean dialogue countries, deployed nearly 90 sensors and sensor systems over the test range area.

  12. The Swarm Level 2-CAT2 data products

    NASA Astrophysics Data System (ADS)

    Lühr, Hermann

    2014-05-01

    ESA's Earth Observation mission Swarm was successfully launched on 22 November 2013. The constellation of three satellites is expected to provide unique information about the geomagnetic field and the ionosphere-thermosphere system. Due to the complexity of information provided by the constellation, ESA has decided to implement dedicated processors developed by experts in the field. These will provide the community with user-friendly high-level data products for a variety of key ionospheric and geomagnetic physical parameters. These Swarm Level2 CAT-2 data products will be distributed freely to the scientific community. They comprise estimates of field-aligned currents (FAC), an indicator for ionospheric irregularities (Equatorial Plasma Bubble), product name (IBI), topside total electron content (TEC), and the equatorial electric field at E-region altitude (EEF). All of these four quantities will be provided as time series sampled along the orbits. We will present first examples of the products and quantify their accuracy.

  13. Intermittent magnetic field excitations in the Madison Dynamo Experiment

    NASA Astrophysics Data System (ADS)

    Nornberg, M. D.; Spence, E. J.; Jacobson, C. M.; Parada, C. A.; Kendrick, R. D.; Forest, C. B.

    2006-10-01

    Determining the onset conditions for magnetic field growth in magnetohydrodynamics is fundamental to understanding how astrophysical dynamos such as the Earth, the Sun, and the galaxy self-generate magnetic fields. The role of turbulence in modifying these onset conditions is studied in the Madison Dynamo Experiment. A turbulent flow of liquid sodium, composed primarily of two counter-rotating helical vortices, is generated by impellers. Laser Doppler velocimetry measurements of the flow in an identical-scale water experiment demonstrate that the turbulence is isotropic, though not homogeneous, with particularly long-lived eddies in the shear layer between the two flow cells. The magnetic field induced when an axial field is applied shows intermittent periods of growth and has a spatial structure consistent with the fastest growing magnetic eigenmode predicted by a laminar kinematic dynamo model of the mean flow. Turbulent fluctuations of the velocity field change the flow geometry such that the eigenmode growth rate is temporarily positive, thus generating the magnetic bursts. It is found from ensemble averaging that the bursts gain strength and frequency with increased impeller rotation rate, though they become shorter so that each burst remains a rare, random event. Nornberg et al., Phys. Rev. Lett., in press (2006), physics/0606239.

  14. In-flight scalar calibration and characterisation of the Swarm magnetometry package

    NASA Astrophysics Data System (ADS)

    Tøffner-Clausen, Lars; Lesur, Vincent; Olsen, Nils; Finlay, Christopher C.

    2016-07-01

    We present the in-flight scalar calibration and characterisation of the Swarm magnetometry package consisting of the absolute scalar magnetometer, the vector magnetometer, and the spacecraft structure supporting the instruments. A significant improvement in the scalar residuals between the pairs of magnetometers is demonstrated, confirming the high performance of these instruments. The results presented here, including the characterisation of a Sun-driven disturbance field, form the basis of the correction of the magnetic vector measurements from Swarm which is applied to the Swarm Level 1b magnetic data.[Figure not available: see fulltext.

  15. Using a Field Experience to Build Understanding of Planetary Geology

    NASA Astrophysics Data System (ADS)

    Higbie, M.; Treiman, A.; Kiefer, W.; Shipp, S.

    2004-12-01

    In the summer of 2004, the Lunar and Planetary Institute hosted 25 middle- and high-school teachers on a week-long field experience in Idaho and Montana. This workshop mixed field work with classroom experiences and provided educators and scientists the opportunity to interact. The educators investigated deposits associated with Glacial Lake Missoula floods and lava flows in the Craters of the Moon National Monument and Preserve. The participants applied what they learned about Earth-based processes to develop understanding of processes operating on Mars and the most recent results from NASA's missions to Mars. This was the most recent of five field-based experiences that used Earth-planet comparisons as a basis for experiential learning. These field experiences all are designed to strengthen content knowledge of geologic processes and planetary sciences. Learning geology through fieldwork enables participants to take ownership of the content through real-life experience; in essence, the teacher becomes the student. Establishing deeper knowledge of the content increases their confidence in facilitating inquiry-based science in their own classrooms. In addition to content, the educators are immersed in the process of science. Participants make observations, compile notes and illustrations, debate interpretations, draw conclusions, and communicate findings. Care was taken to separate observations and interpretations to help build an understanding of scientific reasoning. Discussions often involved questions without solutions, or with multiple solutions. While some participants expressed discomfort with these aspects of the nature of science, most were more comfortable with open-ended, inquiry based exploration by the close of the workshop. The field work is coupled with discussion and activities in the classroom. Participants reflected on the field sites and placed them in the context of the geologic history of the region. Observations and interpretations at

  16. Active experiments in the ionosphere and geomagnetic field variations

    NASA Astrophysics Data System (ADS)

    Sivokon, V. P.; Cherneva, N. V.; Khomutov, S. Y.; Serovetnikov, A. S.

    2014-11-01

    Variations of ionospheric-magnetospheric relation energy, as one of the possible outer climatology factors, may be traced on the basis of analysis of natural geophysical phenomena such as ionosphere artificial radio radiation and magnetic storms. Experiments on active impact on the ionosphere have been carried out for quite a long time in Russia as well. The most modern heating stand is located in Alaska; it has been used within the HAARP Program. The possibility of this stand to affect geophysical fields, in particular, the geomagnetic field is of interest.

  17. Particle Swarm Imaging (PSIM) - Innovative Gamma-Ray Assay - 13497

    SciTech Connect

    Parvin, Daniel; Clarke, Sean; Humes, Sarah J.

    2013-07-01

    Particle Swarm Imaging is an innovative technique used to perform quantitative gamma-ray assay. The innovation overcomes some of the difficulties associated with the accurate measurement and declaration of measurement uncertainties of radionuclide inventories within waste items when the distribution of activity is unknown. Implementation requires minimal equipment, with field measurements and results obtained using only a single electrically cooled HRGS gamma-ray detector. Examples of its application in the field are given in this paper. (authors)

  18. ITER Test Blanket Module Error Field Simulation Experiments

    NASA Astrophysics Data System (ADS)

    Schaffer, M. J.

    2010-11-01

    Recent experiments at DIII-D used an active-coil mock-up to investigate effects of magnetic error fields similar to those expected from two ferromagnetic Test Blanket Modules (TBMs) in one ITER equatorial port. The largest and most prevalent observed effect was plasma toroidal rotation slowing across the entire radial profile, up to 60% in H-mode when the mock-up local ripple at the plasma was ˜4 times the local ripple expected in front of ITER TBMs. Analysis showed the slowing to be consistent with non-resonant braking by the mock-up field. There was no evidence of strong electromagnetic braking by resonant harmonics. These results are consistent with the near absence of resonant helical harmonics in the TBM field. Global particle and energy confinement in H-mode decreased by <20% for the maximum mock-up ripple, but <5% at the local ripple expected in ITER. These confinement reductions may be linked with the large velocity reductions. TBM field effects were small in L-mode but increased with plasma beta. The L-H power threshold was unaffected within error bars. The mock-up field increased plasma sensitivity to mode locking by a known n=1 test field (n = toroidal harmonic number). In H-mode the increased locking sensitivity was from TBM torque slowing plasma rotation. At low beta, locked mode tolerance was fully recovered by re-optimizing the conventional DIII-D ``I-coils'' empirical compensation of n=1 errors in the presence of the TBM mock-up field. Empirical error compensation in H-mode should be addressed in future experiments. Global loss of injected neutral beam fast ions was within error bars, but 1 MeV fusion triton loss may have increased. The many DIII-D mock-up results provide important benchmarks for models needed to predict effects of TBMs in ITER.

  19. Swarm's Absolute Scalar Magnetometer metrological performances

    NASA Astrophysics Data System (ADS)

    Leger, J.; Fratter, I.; Bertrand, F.; Jager, T.; Morales, S.

    2012-12-01

    The Absolute Scalar Magnetometer (ASM) has been developed for the ESA Earth Observation Swarm mission, planned for launch in November 2012. As its Overhauser magnetometers forerunners flown on Oersted and Champ satellites, it will deliver high resolution scalar measurements for the in-flight calibration of the Vector Field Magnetometer manufactured by the Danish Technical University. Latest results of the ground tests carried out to fully characterize all parameters that may affect its accuracy, both at instrument and satellite level, will be presented. In addition to its baseline function, the ASM can be operated either at a much higher sampling rate (burst mode at 250 Hz) or in a dual mode where it also delivers vector field measurements as a by-product. The calibration procedure and the relevant vector performances will be discussed.

  20. Tuning the mass of chameleon fields in Casimir force experiments.

    PubMed

    Brax, Ph; van de Bruck, C; Davis, A C; Shaw, D J; Iannuzzi, D

    2010-06-18

    We have calculated the chameleon pressure between two parallel plates in the presence of an intervening medium that affects the mass of the chameleon field. As intuitively expected, the gas in the gap weakens the chameleon interaction mechanism with a screening effect that increases with the plate separation and with the density of the intervening medium. This phenomenon might open up new directions in the search of chameleon particles with future long-range Casimir force experiments. PMID:20867290

  1. Vacuum magnetic field mapping experiments for validated determination of the helical field coil location in stellarators

    SciTech Connect

    Peterson, J.; Hanson, J.; Hartwell, G.; Knowlton, S.

    2010-03-15

    Understanding the behavior of plasmas in magnetic confinement fusion devices typically requires accurate knowledge of the magnetic field structure. In stellarator-type confinement devices, the helical magnetic field is produced by currents in external coils and may be traced experimentally in the absence of plasma through the experimental technique of vacuum magnetic field mapping. Field mapping experiments, such as these, were performed on the recently constructed compact toroidal hybrid to verify the range of accessible magnetic configurations, compare the actual magnetic configuration with the design configuration, and identify any vacuum field errors that lead to perturbations of the vacuum magnetic flux surfaces. Furthermore, through the use of a new coil optimization routine, modifications are made to the simulation coil model such that better agreement exists between the experimental and simulation results. An outline of the optimization procedure is discussed in conjunction with the results of one such optimization process performed on the helical field coil.

  2. Optimizing Field-Reversed Configuration Plasmas for Plasma Compression Experiments

    NASA Astrophysics Data System (ADS)

    Grabowski, C.; Degnan, J. H.; Amdahl, D. J.; Domonkos, M.; Ruden, E. L.; White, W.; Wurden, G. A.; Frese, M. H.; Frese, S. D.; Camacho, J. F.; Coffey, S. K.; Kostora, M.; McCullough, J.; Sommars, W.; Kiuttu, G. F.; Lynn, A. G.; Yates, K.; Bauer, B. S.; Fuelling, S.; Pahl, R.

    2013-10-01

    The Field-Reversed Configuration Heating Experiment (FRCHX) is a collaborative experiment between the Air Force Research Laboratory (AFRL) and Los Alamos National Laboratory (LANL) to study high energy density plasmas and various associated phenomena. With FRCHX, a field-reversed configuration (FRC) plasma is formed via reversed-field theta pinch and then translated a short distance into a cylindrical aluminum shell (solid liner), where it is either compressed by the magnetically-driven implosion of the shell or diagnosed in preparation for such compression tests. The lifetime of the trapped magnetic flux within the FRC is an important parameter affecting the confinement of plasma during the compression and ultimately the final density, temperature, and yield of neutrons from the plasma. Processes occurring during formation, initial plasma temperature, and instabilities in turn all affect the trapped-flux lifetime and the integrity of the FRC. A discussion of FRC parameters measured on FRCHX and efforts that have been made to improve these parameters and the FRC stability will be presented in connection with results from recent FRCHX experiments. This work is supported by DOE-OFES.

  3. Acoustic experience shapes female mate choice in field crickets

    PubMed Central

    Bailey, Nathan W; Zuk, Marlene

    2008-01-01

    Female choice can drive the evolution of extravagant male traits. In invertebrates, the influence of prior social experience on female choice has only recently been considered. To better understand the evolutionary implications of experience-mediated plasticity in female choice, we investigated the effect of acoustic experience during rearing on female responsiveness to male song in the field cricket Teleogryllus oceanicus. Acoustic experience has unique biological relevance in this species: a morphological mutation has rendered over 90 per cent of males on the Hawaiian island of Kauai silent in fewer than 20 generations, impeding females' abilities to locate potential mates. Females reared in silent conditions mimicking Kauai were less discriminating of male calling song and more responsive to playbacks, compared with females that experienced song during rearing. Our results to our knowledge, are the first demonstration of long-term effects of acoustic experience in an arthropod, and suggest that female T. oceanicus may be able to compensate for the reduced availability of long-range male sexual signals by increasing their responsiveness to the few remaining signallers. Understanding the adaptive significance of experience-mediated plasticity in female choice provides insight into processes that facilitate rapid evolutionary change and shape sexual selection pressure in natural populations. PMID:18700205

  4. Acoustic experience shapes female mate choice in field crickets.

    PubMed

    Bailey, Nathan W; Zuk, Marlene

    2008-11-22

    Female choice can drive the evolution of extravagant male traits. In invertebrates, the influence of prior social experience on female choice has only recently been considered. To better understand the evolutionary implications of experience-mediated plasticity in female choice, we investigated the effect of acoustic experience during rearing on female responsiveness to male song in the field cricket Teleogryllus oceanicus. Acoustic experience has unique biological relevance in this species: a morphological mutation has rendered over 90 per cent of males on the Hawaiian island of Kauai silent in fewer than 20 generations, impeding females' abilities to locate potential mates. Females reared in silent conditions mimicking Kauai were less discriminating of male calling song and more responsive to playbacks, compared with females that experienced song during rearing. Our results to our knowledge, are the first demonstration of long-term effects of acoustic experience in an arthropod, and suggest that female T. oceanicus may be able to compensate for the reduced availability of long-range male sexual signals by increasing their responsiveness to the few remaining signallers. Understanding the adaptive significance of experience-mediated plasticity in female choice provides insight into processes that facilitate rapid evolutionary change and shape sexual selection pressure in natural populations. PMID:18700205

  5. A scanning drift tube apparatus for spatiotemporal mapping of electron swarms

    NASA Astrophysics Data System (ADS)

    Korolov, I.; Vass, M.; Bastykova, N. Kh.; Donkó, Z.

    2016-06-01

    A "scanning" drift tube apparatus, capable of mapping of the spatiotemporal evolution of electron swarms, developing between two plane electrodes under the effect of a homogeneous electric field, is presented. The electron swarms are initiated by photoelectron pulses and the temporal distributions of the electron flux are recorded while the electrode gap length (at a fixed electric field strength) is varied. Operation of the system is tested and verified with argon gas; the measured data are used for the evaluation of the electron bulk drift velocity. The experimental results for the space-time maps of the electron swarms — presented here for the first time — also allow clear observation of deviations from hydrodynamic transport. The swarm maps are also reproduced by particle simulations.

  6. A scanning drift tube apparatus for spatiotemporal mapping of electron swarms.

    PubMed

    Korolov, I; Vass, M; Bastykova, N Kh; Donkó, Z

    2016-06-01

    A "scanning" drift tube apparatus, capable of mapping of the spatiotemporal evolution of electron swarms, developing between two plane electrodes under the effect of a homogeneous electric field, is presented. The electron swarms are initiated by photoelectron pulses and the temporal distributions of the electron flux are recorded while the electrode gap length (at a fixed electric field strength) is varied. Operation of the system is tested and verified with argon gas; the measured data are used for the evaluation of the electron bulk drift velocity. The experimental results for the space-time maps of the electron swarms - presented here for the first time - also allow clear observation of deviations from hydrodynamic transport. The swarm maps are also reproduced by particle simulations. PMID:27370421

  7. Magnetic Field Stabilization for 129Xe EDM Search Experiment

    NASA Astrophysics Data System (ADS)

    Furukawa, Takeshi; Inoue, Takeshi; Nanao, Tsubasa; Yoshimi, Akihiro; Tsuchiya, Masato; Hayashi, Hironori; Uchida, Makoto; Asahi, Koichiro

    2011-09-01

    Magnetic field stabilization is a crucial condition parameter for many kinds of ultra-high precision measurements such as a search for an electric dipole moment (EDM). The instability of magnetic field strength often arises from the drift of current flow in a solenoid coil to generate the magnetic field. For our EDM search experiment with maser oscillating diamagnetic 129Xe atoms, we have developed a new stabilized current source based on a feedback system which is devised to correct the amount of current flow measured precisely with high-precision digital multimeter and standard resistor. Using this new current source, we have successfully reduced the drifts of coil current by at least a factor of 100 compared to commercially available current sources.

  8. An Integral, Multidisciplinary and Global Geophysical Field Experience for Undergraduates

    NASA Astrophysics Data System (ADS)

    Vázquez, O.; Carrillo, D. J.; Pérez-Campos, X.

    2007-05-01

    The udergraduate program of Geophysical Engineering at the School of Engineering, of the Univesidad Nacional Autónoma de México (UNAM), went through an update process that concluded in 2006. As part of the program, the student takes three geophysical prospecting courses (gravity and magnetics, electric, electromagnetics, and seismic methods). The older program required a three-week field experience for each course in order to gradute. The new program considers only one extended field experience. This work stresses the importance of international academic exchange, where undergraduate students could participate, such as the Summer of Applied Geophysical Experience (SAGE), and interaction with research programs, such as the MesoAmerican Subduction Experiment (MASE). Also, we propose a scheeme for this activity based on those examples; both of them have in common real geophysical problems, from which students could benefit. Our proposal covers academic and logistic aspects to be taken into account, enhancing the relevance of interaction between other academic institutions, industry, and UNAM, in order to obtain a broader view of geophysics.

  9. Dark matter effective field theory scattering in direct detection experiments

    DOE PAGESBeta

    Schneck, K.; Cabrera, B.; Cerdeño, D. G.; Mandic, V.; Rogers, H. E.; Agnese, R.; Anderson, A. J.; Asai, M.; Balakishiyeva, D.; Barker, D.; et al

    2015-05-18

    We examine the consequences of the effective field theory (EFT) of dark matter-nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. Here. we demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. In conclusion, we discussmore » the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.« less

  10. Dark matter effective field theory scattering in direct detection experiments

    DOE PAGESBeta

    Schneck, K.

    2015-05-01

    We examine the consequences of the effective field theory (EFT) of dark matter–nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. We demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. We also discuss the implicationsmore » of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.« less

  11. Dark matter effective field theory scattering in direct detection experiments

    SciTech Connect

    Schneck, K.

    2015-05-01

    We examine the consequences of the effective field theory (EFT) of dark matter–nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. We demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. We also discuss the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.

  12. Dark matter effective field theory scattering in direct detection experiments

    SciTech Connect

    Schneck, K.; Cabrera, B.; Cerdeño, D. G.; Mandic, V.; Rogers, H. E.; Agnese, R.; Anderson, A. J.; Asai, M.; Balakishiyeva, D.; Barker, D.; Basu Thakur, R.; Bauer, D. A.; Billard, J.; Borgland, A.; Brandt, D.; Brink, P. L.; Bunker, R.; Caldwell, D. O.; Calkins, R.; Chagani, H.; Chen, Y.; Cooley, J.; Cornell, B.; Crewdson, C. H.; Cushman, P.; Daal, M.; Di Stefano, P. C. F.; Doughty, T.; Esteban, L.; Fallows, S.; Figueroa-Feliciano, E.; Godfrey, G. L.; Golwala, S. R.; Hall, J.; Harris, H. R.; Hofer, T.; Holmgren, D.; Hsu, L.; Huber, M. E.; Jardin, D. M.; Jastram, A.; Kamaev, O.; Kara, B.; Kelsey, M. H.; Kennedy, A.; Leder, A.; Loer, B.; Lopez Asamar, E.; Lukens, P.; Mahapatra, R.; McCarthy, K. A.; Mirabolfathi, N.; Moffatt, R. A.; Morales Mendoza, J. D.; Oser, S. M.; Page, K.; Page, W. A.; Partridge, R.; Pepin, M.; Phipps, A.; Prasad, K.; Pyle, M.; Qiu, H.; Rau, W.; Redl, P.; Reisetter, A.; Ricci, Y.; Roberts, A.; Saab, T.; Sadoulet, B.; Sander, J.; Schnee, R. W.; Scorza, S.; Serfass, B.; Shank, B.; Speller, D.; Toback, D.; Upadhyayula, S.; Villano, A. N.; Welliver, B.; Wilson, J. S.; Wright, D. H.; Yang, X.; Yellin, S.; Yen, J. J.; Young, B. A.; Zhang, J.

    2015-05-18

    We examine the consequences of the effective field theory (EFT) of dark matter-nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. Here. we demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. In conclusion, we discuss the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.

  13. Inverse Simulation of Field Infiltration Experiment Counting Preferential Flow

    NASA Astrophysics Data System (ADS)

    Zumr, David; Snehota, Michal; Nemcova, Renata; Dohnal, Michal; Cislerova, Milena

    2010-05-01

    The field tension and ponded infiltration experiments were conducted to monitor and describe irregularities of moisture propagation and to estimate the soil hydraulic properties (Distric Cambisol, Korkusova Hut, Sumava). On these soils the preferential pathways have been observed in several scales with the use of dye tracers, MRI and CT imaging. Preferential behavior was detected also during laboratory infiltration experiments. The flow irregularities are credited to variable air entrapment at the beginning of infiltrations. The field infiltration experiment was carried out in a shallow pit for a period of one day. The upper boundary condition was controlled by the tension disk infiltrometer, the propagation of a water front was monitored by two tensiometers installed in two depths below the infiltration disk. The propagation of saline solution front during ponded infiltration was visualized with high resolution electrical resistivity tomography (ERT). Infiltration experiments were monitored with TDR probes, tensiometers and ERT. Zones of preferential flow were determined through analyses of photographs taken during laboratory dye tracer infiltration experiments performed on undisturbed soil samples. Connectivity, volumetric ratio and spatial development of preferential pathways were evaluated as the necessary information for numerical simulations of flow using dual-permeability approach. 2D axisymetric numerical simulations were conducted to evaluate the results of the experiment. The parameter estimator PEST coupled with the simulation code S2D_DUAL (Vogel et al., 2000) were employed. Two different approaches were used: 1. Single-domain approach based on Richards' equation. 2. Dual-permeability approach based on two interacting water flow domains (matrix and preferential domains), each governed by one Richards' equation. Concerning the existence of preferential flow on investigated soil, the dual-permeability model gives a better picture of the flow regime. The

  14. Swarm GPS Receiver Performance under the Influence of Ionospheric Scintillation

    NASA Astrophysics Data System (ADS)

    Ren, Le; Schön, Steffen

    2016-04-01

    The Swarm mission launched on 22 November 2013 is ESA's first constellation of satellites to study the dynamics of the Earth's magnetic field and its interaction with the Earth system. This mission consists of three identical satellites in near-polar orbits , two flying almost side-by-side at an initial altitude of 460 km, the third flying in a higher orbit of about 530 km. Each satellite is equipped with a high precision 8-channels dual-frequency receiver for the precise orbit determination, which is also the essential fundament in order to take full advantage of the data information provided by this constellation, e.g. for the recovery of gravity field. The quality of the final orbit determination depends on the observation data from the receivers. In this contribution, we will analyze the performance of the Swarm on-board receivers, especially under the influence of ionospheric scintillation caused by ionospheric irregularities. This is a prerequisite for high quality satellite positioning as well as a sound study of the ionosphere. Ionospheric scintillation can lead to the phase disturbances, cycle slips or even loss of signal tracking. The RINEX observation data from Swarm Level 1b products are used to analyze the Swarm receiver performance. We will demonstrate the signal strength, code and phase noise, different linear combinations (geometry free, ionosphere free), as well as GDOP values for the 3 Swarm satellites. The first results show that the observation data are severely disturbed and the signals could be lost around the geomagnetic equator and geomagnetic poles where the ionosphere is active. The results also show that the receivers are more stable in those areas after the update in October 2015.

  15. Collective Behaviour without Collective Order in Wild Swarms of Midges

    PubMed Central

    Attanasi, Alessandro; Cavagna, Andrea; Del Castello, Lorenzo; Giardina, Irene; Melillo, Stefania; Parisi, Leonardo; Pohl, Oliver; Rossaro, Bruno; Shen, Edward; Silvestri, Edmondo; Viale, Massimiliano

    2014-01-01

    Collective behaviour is a widespread phenomenon in biology, cutting through a huge span of scales, from cell colonies up to bird flocks and fish schools. The most prominent trait of collective behaviour is the emergence of global order: individuals synchronize their states, giving the stunning impression that the group behaves as one. In many biological systems, though, it is unclear whether global order is present. A paradigmatic case is that of insect swarms, whose erratic movements seem to suggest that group formation is a mere epiphenomenon of the independent interaction of each individual with an external landmark. In these cases, whether or not the group behaves truly collectively is debated. Here, we experimentally study swarms of midges in the field and measure how much the change of direction of one midge affects that of other individuals. We discover that, despite the lack of collective order, swarms display very strong correlations, totally incompatible with models of non-interacting particles. We find that correlation increases sharply with the swarm's density, indicating that the interaction between midges is based on a metric perception mechanism. By means of numerical simulations we demonstrate that such growing correlation is typical of a system close to an ordering transition. Our findings suggest that correlation, rather than order, is the true hallmark of collective behaviour in biological systems. PMID:25057853

  16. Obtaining precise electron swarm parameters from a pulsed Townsend setup

    NASA Astrophysics Data System (ADS)

    Dahl, Dominik A.; Teich, Timm H.; Franck, Christian M.

    2012-12-01

    A swarm parameter experiment is introduced, which implements the pulsed Townsend (PT) electrical method with a high degree of automatization. The experimental setup and measurement procedures are described in detail, and a comprehensive definition of the swarm model is given and used for signal analysis. The intrinsic parameters of electron drift currents in the PT method are identified, and novel regression methods are presented for obtaining electron swarm parameters from PT measurements. The setup and methods are verified with measurements in Ar, N2 and CO2, which are focused on the (E/N)-range between dominating electron attachment and weakly dominating ionization. The present data are compared with experimental reference data, and to electron transport coefficients calculated by a Boltzmann solver and simulated by a Monte Carlo method. Excellent agreement was found between the present data and the Monte Carlo results, but there are significant discrepancies to widely used recommended swarm parameters of N2 and CO2. Finally, it is proposed to revise some hitherto recommended values of electron transport coefficients.

  17. An immune-inspired swarm aggregation algorithm for self-healing swarm robotic systems.

    PubMed

    Timmis, J; Ismail, A R; Bjerknes, J D; Winfield, A F T

    2016-08-01

    Swarm robotics is concerned with the decentralised coordination of multiple robots having only limited communication and interaction abilities. Although fault tolerance and robustness to individual robot failures have often been used to justify the use of swarm robotic systems, recent studies have shown that swarm robotic systems are susceptible to certain types of failure. In this paper we propose an approach to self-healing swarm robotic systems and take inspiration from the process of granuloma formation, a process of containment and repair found in the immune system. We use a case study of a swarm performing team work where previous works have demonstrated that partially failed robots have the most detrimental effect on overall swarm behaviour. We have developed an immune inspired approach that permits the recovery from certain failure modes during operation of the swarm, overcoming issues that effect swarm behaviour associated with partially failed robots. PMID:27178784

  18. Swarm: from Earth to Magnetosphere One Year after Launch

    NASA Astrophysics Data System (ADS)

    Haagmans, R.; Floberghagen, R.

    2014-12-01

    The ESA Earth Observation Swarm satellite mission, a constellation of three satellites to measure the Earth's magnetic and electric fields as well as the neutral environment, was launched on November 22, 2013. The mission delivers observations that provide new insight into the Earth system by improving our understanding of the Earth's interior as well as the near Earth electro-magnetic environment. The unprecedented high-accuracy and high spatial resolution measurements of the strength, direction and time variations of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, provide the required observations to model the various sources of the geomagnetic field. The three satellites fly in a constellation. Swarm Alpha and Charlie are orbiting almost next to each other at a distance of about 150 km at the equator and Charlie is approximately 10 seconds delayed relative to Alpha. At the start of the science phase they were injected at an altitude of 462 km and an inclination of 87.35°, in naturally decaying orbits. Swarm Bravo started in a higher orbit at 510 km with an inclination of 87.75°. This causes a relative drift between Alpha/Charlie and Bravo resulting in a local time difference of about 6 hours in the third year of the mission. Different objectives of the mission may benefit more during different phases of the constellation. This presentation will include the mission status a year after launch and focus on the products, studies and results related to the external fields.

  19. On the tensile strength of insect swarms.

    PubMed

    Ni, Rui; Ouellette, Nicholas T

    2016-01-01

    Collective animal groups are often described by the macroscopic patterns they form. Such global patterns, however, convey limited information about the nature of the aggregation as a whole. Here, we take a different approach, drawing on ideas from materials testing to probe the macroscopic mechanical properties of mating swarms of the non-biting midge Chironomus riparius. By manipulating ground-based visual features that tend to position the swarms in space, we apply an effective tensile load to the swarms, and show that we can quasi-statically pull single swarms apart into multiple daughter swarms. Our results suggest that swarms surprisingly have macroscopic mechanical properties similar to solids, including a finite Young's modulus and yield strength, and that they do not flow like viscous fluids. PMID:27559838

  20. Male motion coordination in anopheline mating swarms

    NASA Astrophysics Data System (ADS)

    Shishika, Daigo; Manoukis, Nicholas C.; Butail, Sachit; Paley, Derek A.

    2014-09-01

    The Anopheles gambiae species complex comprises the primary vectors of malaria in much of sub-Saharan Africa. Most of the mating in these species occurs in swarms composed almost entirely of males. Intermittent, organized patterns in such swarms have been observed, but a detailed description of male-male interactions has not previously been available. We identify frequent, time-varying interactions characterized by periods of parallel flight in data from 8 swarms of Anopheles gambiae and 3 swarms of Anopheles coluzzii filmed in 2010 and 2011 in the village of Donéguébogou, Mali. We use the cross correlation of flight direction to quantify these interactions and to induce interaction graphs, which show that males form synchronized subgroups whose size and membership change rapidly. A swarming model with damped springs between each male and the swarm centroid shows good agreement with the correlation data, provided that local interactions represented by damping of relative velocity between males are included.

  1. Capture of planetesimals into a circumterrestrial swarm

    SciTech Connect

    Weidenschilling, S.J.

    1984-01-01

    The lunar origin model considered involves processing of protolunar material through a circumterrestrial swarm of particles. Once such a swarm has formed, it can gain mass by capturing infalling planetesimals and ejecta from giant impacts on the Earth, although the angular momentum supply from these sources remains a problem. Examined is the first stage of formation of a geocentric swarm by capture of planetesimals from initialy heliocentric orbits. The only plausible capture mechanism that is not dependent on very low approach velocities is the mutual collision of planetesimals passing within Earth's sphere of influence. This capture scenario was tested directly by many body numerical integration of planetesimal orbits in near Earth space. Results agree that the systematic contribution of angular momentum is insufficient to maintain an orbiting swarm under heavy bombardment. Thus, a circumterrestrial swarm can be formed rather easily, but is hard to sustain because the mean net angular momentum of a many body swarm is small.

  2. Massless scalar field and solar-system experiments

    SciTech Connect

    Formiga, J. B.

    2011-04-15

    The solution of Einstein's field equations with the energy-momentum tensor of a massless scalar field is known as the Fisher solution. It is well known that this solution has a naked singularity due to the ''charge''{Sigma} of the massless scalar field. Here I obtain the radial null geodesic of the Fisher solution and use it to confirm that there is no black hole. In addition, I use the parametrized post-Newtonian formalism to show that the Fisher spacetime predicts the same effects on solar-system experiments as the Schwarzschild one does, as long as we impose a limit on {Sigma}. I show that this limit is not a strong constraint and we can even take values of {Sigma} bigger than M. By using the exact formula of the redshift and some assumptions, I evaluate this limit for the experiment of Pound and Snider [Phys. Rev. 140, B788 (1965)]. It turns out that this limit is {Sigma}<5.8x10{sup 3} m.

  3. Magnetic Diagnostics and Field Structure in the Madison Dynamo Experiment

    NASA Astrophysics Data System (ADS)

    Rasmus, A. M.; Clark, M.; Kaplan, E. J.; Kendrick, R. D.; Nornberg, M. D.; Rahbarnia, K.; Taylor, N. Z.; Forest, C. B.

    2010-11-01

    The Madison Dynamo Experiment(MDE) is expected to spontaneously self-generate a magnetic field in a two vortex flow geometry driven by counter rotating impellers in a 1 m diameter sphere filled with liquid sodium. This poster will focus on the spatial structure of the magnetic field associated with the dynamo eigenmodes and the turbulent fluctuations. A new internal array of Hall probes will increase the number of probe locations from 60 to 100 (in addition to 74 existing surface probes), including 40 spanning the center of the experiment. Three orthogonal measurements of the magnetic field are taken at each internal location, whereas previous internal probes took one directional data (2 directional after probe rotation on a different run). This will allow resolution of harmonic modes up to a poloidal order of l=7 and a toroidal order of m=5. Cross correlation analysis between the surface probes and internal probes will be used to determine the internal structure associated with each l and m. This work is supported by the NSF/DOE partnership in plasma physics.

  4. Development of Micro UAV Swarms

    NASA Astrophysics Data System (ADS)

    Bürkle, Axel; Leuchter, Sandro

    Some complex application scenarios for micro UAVs (Unmanned Aerial Vehicles) call for the formation of swarms of multiple drones. In this paper a platform for the creation of such swarms is presented. It consists of modified commercial quadrocopters and a self-made ground control station software architecture. Autonomy of individual drones is generated through a micro controller equipped video camera. Currently it is possible to fly basic maneuvers autonomously, such as take-off, fly to position, and landing. In the future the camera's image processing capabilities will be used to generate additional control information. Different co-operation strategies for teams of UAVs are currently evaluated with an agent based simulation tool. Finally complex application scenarios for multiple micro UAVs are presented.

  5. Organic Computing and Swarm Intelligence

    NASA Astrophysics Data System (ADS)

    Merkle, Daniel; Middendorf, Martin; Scheidler, Alexander

    The relations between swarm intelligence and organic computing are discussed in this chapter. The aim of organic computing is to design and study computing systems that consist of many autonomous components and show forms of collective behavior. Such organic computing systems (OC systems) should possess self-x properties (e.g., self-healing, self-managing, self-optimizing), have a decentralized control, and be adaptive to changing requirements of their user. Examples of OC systems are described in this chapter and two case studies are presented that show in detail that OC systems share important properties with social insect colonies and how methods of swarm intelligence can be used to solve problems in organic computing.

  6. Electron swarm parameters in water vapour

    NASA Astrophysics Data System (ADS)

    Hasegawa, H.; Date, H.; Shimozuma, M.

    2007-04-01

    Electron swarm parameters, such as the drift velocity and the ionization coefficient, in water vapour have been measured for relatively wide ranges in reduced electric fields (E/N) at room temperature. The drift velocity (Wm) was obtained based upon the arrival-time spectra of electrons by using a double-shutter drift tube for the E/N from 60 to 1000 Td, while the first and second ionization coefficients (α and γ) were determined by the steady-state Townsend method from 50 to 3000 Td. A comparison between the results and other data in the literature shows that our results for both the drift velocity and the effective ionization coefficient are lower than those of the other data in the above ranges.

  7. Acoustic network event classification using swarm optimization

    NASA Astrophysics Data System (ADS)

    Burman, Jerry

    2013-05-01

    Classifying acoustic signals detected by distributed sensor networks is a difficult problem due to the wide variations that can occur in the transmission of terrestrial, subterranean, seismic and aerial events. An acoustic event classifier was developed that uses particle swarm optimization to perform a flexible time correlation of a sensed acoustic signature to reference data. In order to mitigate the effects from interference such as multipath, the classifier fuses signatures from multiple sensors to form a composite sensed acoustic signature and then automatically matches the composite signature with reference data. The approach can classify all types of acoustic events but is particularly well suited to explosive events such as gun shots, mortar blasts and improvised explosive devices that produce an acoustic signature having a shock wave component that is aperiodic and non-linear. The classifier was applied to field data and yielded excellent results in terms of reconstructing degraded acoustic signatures from multiple sensors and in classifying disparate acoustic events.

  8. Equilibrium evolution in oscillating-field current-drive experiments

    SciTech Connect

    McCollam, K. J.; Anderson, J. K.; Blair, A. P.; Craig, D.; Den Hartog, D. J.; Ebrahimi, F.; O'Connell, R.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Stone, D. R.; Brower, D. L.; Deng, B. H.; Ding, W. X.

    2010-08-15

    Oscillating-field current drive (OFCD) is a proposed method of steady-state toroidal plasma sustainment in which ac poloidal and toroidal loop voltages are applied to produce a dc plasma current. OFCD is added to standard, inductively sustained reversed-field pinch plasmas in the Madison Symmetric Torus [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. Equilibrium profiles and fluctuations during a single cycle are measured and analyzed for different relative phases between the two OFCD voltages and for OFCD off. For OFCD phases leading to the most added plasma current, the measured energy confinement is slightly better than that for OFCD off. By contrast, the phase of the maximum OFCD helicity-injection rate also has the maximum decay rate, which is ascribed to transport losses during discrete magnetic-fluctuation events induced by OFCD. Resistive-magnetohydrodynamic simulations of the experiments reproduce the observed phase dependence of the added current.

  9. Large scale meteorological influence during the Geysers 1979 field experiment

    SciTech Connect

    Barr, S.

    1980-01-01

    A series of meteorological field measurements conducted during July 1979 near Cobb Mountain in Northern California reveals evidence of several scales of atmospheric circulation consistent with the climatic pattern of the area. The scales of influence are reflected in the structure of wind and temperature in vertically stratified layers at a given observation site. Large scale synoptic gradient flow dominates the wind field above about twice the height of the topographic ridge. Below that there is a mixture of effects with evidence of a diurnal sea breeze influence and a sublayer of katabatic winds. The July observations demonstrate that weak migratory circulations in the large scale synoptic meteorological pattern have a significant influence on the day-to-day gradient winds and must be accounted for in planning meteorological programs including tracer experiments.

  10. Equilibrium evolution in oscillating-field current-drive experiments

    NASA Astrophysics Data System (ADS)

    McCollam, K. J.; Anderson, J. K.; Blair, A. P.; Craig, D.; Den Hartog, D. J.; Ebrahimi, F.; O'Connell, R.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Stone, D. R.; Brower, D. L.; Deng, B. H.; Ding, W. X.

    2010-08-01

    Oscillating-field current drive (OFCD) is a proposed method of steady-state toroidal plasma sustainment in which ac poloidal and toroidal loop voltages are applied to produce a dc plasma current. OFCD is added to standard, inductively sustained reversed-field pinch plasmas in the Madison Symmetric Torus [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. Equilibrium profiles and fluctuations during a single cycle are measured and analyzed for different relative phases between the two OFCD voltages and for OFCD off. For OFCD phases leading to the most added plasma current, the measured energy confinement is slightly better than that for OFCD off. By contrast, the phase of the maximum OFCD helicity-injection rate also has the maximum decay rate, which is ascribed to transport losses during discrete magnetic-fluctuation events induced by OFCD. Resistive-magnetohydrodynamic simulations of the experiments reproduce the observed phase dependence of the added current.

  11. SRNL RADIONUCLIDE FIELD LYSIMETER EXPERIMENT: BASELINE CONSTRUCTION AND IMPLEMENTATION

    SciTech Connect

    Roberts, K.; Kaplan, D.; Bagwell, L.; Powell, B.; Almond, P.; Emerson, H.; Hixon, A.; Jablonski, J.; Buchanan, C.; Waterhouse, T.

    2012-10-17

    The purpose of this document is to compile information regarding experimental design, facility design, construction, radionuclide source preparation, and path forward for the ten year Savannah River National Laboratory (SRNL) Radionuclide Field Lysimeter Experiment at the Savannah River Site (SRS). This is a collaborative effort by researchers at SRNL and Clemson University. The scientific objectives of this study are to: Study long-term radionuclide transport under conditions more representative of vadose zone conditions than laboratory experiments; Provide more realistic quantification of radionuclide transport and geochemistry in the vadose zone, providing better information pertinent to radioactive waste storage solutions than presently exists; Reduce uncertainty and improve justification for geochemical models such as those used in performance assessments and composite analyses.

  12. Experiments of cylindrical isentropic compression by ultrahigh magnetic field

    NASA Astrophysics Data System (ADS)

    Gu, Zhuowei; Zhou, Zhongyu; Zhang, Chunbo; Tang, Xiaosong; Tong, Yanjin; Zhao, Jianheng; Sun, Chengwei

    2015-09-01

    The high Explosive Magnetic Flux Implosion Compression Generator (EMFICG) is a kind of unique high energy density dynamic technique with characters like ultrahigh pressure and low temperature rising and could be suitable as a tool of cylindrical isentropic compression. The Institute of Fluid Physics, Chinese Academy of Engineering Physics (IFP, CAEP) have developed EMFICG technique and realized cylindrical isentropic compression. In the experiments, a seed magnetic field of 5-6 Tesla were built first and compressed by a stainless steel liner which is driven by high explosive. The inner free surface velocity of sample was measured by PDV. The isentropic compression of a copper sample was verified and the isentropic pressure is over 100 GPa. The cylindrical isentropic compression process has been numerical simulated by 1D MHD code and the simulation results were compared with the experiments. Compared with the transitional X-ray flash radiograph measurement, this method will probably promote the data accuracy.

  13. EFEDA - European field experiment in a desertification-threatened area

    NASA Technical Reports Server (NTRS)

    Bolle, H.-J.; Andre, J.-C.; Arrue, J. L.; Barth, H. K.; Bessemoulin, P.; Brasa, A.; De Bruin, H. A. R.; Cruces, J.; Dugdale, G.; Engman, E. T.

    1993-01-01

    During June 1991 more than 30 scientific teams worked in Castilla-La Mancha, Spain, studying the energy and water transfer processes between soil, vegetation, and the atmosphere in semiarid conditions within the coordinated European research project EFEDA (European Field Experiment in Desertification-threatened Areas). Measurements were made from the microscale (e.g., measurements on single plants) up to a scale compatible with the grid size of global models. For this purpose three sites were selected 70 km apart and heavily instrumented at a scale in the order of 30 sq km. Aircraft missions, satellite data, and movable equipment were deployed to provide a bridge to the larger scale. This paper gives a description of the experimental design along with some of the preliminary results of this successful experiment.

  14. ASCOT 91 field experiment : PNL airsonde data summary.

    SciTech Connect

    JM Hubbe and KJ Allwine

    1991-07-01

    Pacific Northwest Laboratory (PNL) participated in the Winter 1991 Atmospheric Studies in Complex Terrain (ASCOT) field experiment conducted in the vicinity of the Rocky Flats Plant between Boulder and Denver, Colorado. This report contains a summary of operations and data associated with free-release-ball oon-borne atmospheric soundings made by PNL between January 29 and February 8, 1991. Given here are descriptions of the site and instrumentation, a brief summary of the soundings, and a description of the data post processing. The appendices contain a detailed summary of all soundings and ASCOT plots of completed soundings.

  15. Does canvassing increase voter turnout? A field experiment.

    PubMed

    Gerber, A S; Green, D P

    1999-09-14

    This paper reports the results of a randomized field experiment involving registered voters in the city of New Haven. Nonpartisan get-out-the-vote messages were delivered through personal canvassing shortly before the November 1998 election. We find that personal canvassing increased voter turnout by approximately 6. The effect of personal contact seems to be slightly smaller for voters registered with a major political party and higher for unaffiliated voters, although the hypothesis that all voters are equally affected could not be rejected. Study of several alternative political messages provided equivocal evidence suggesting the superiority of a canvassing appeal that emphasizes the closeness of the election. PMID:10485930

  16. Lagrange Interpolation Learning Particle Swarm Optimization

    PubMed Central

    2016-01-01

    In recent years, comprehensive learning particle swarm optimization (CLPSO) has attracted the attention of many scholars for using in solving multimodal problems, as it is excellent in preserving the particles’ diversity and thus preventing premature convergence. However, CLPSO exhibits low solution accuracy. Aiming to address this issue, we proposed a novel algorithm called LILPSO. First, this algorithm introduced a Lagrange interpolation method to perform a local search for the global best point (gbest). Second, to gain a better exemplar, one gbest, another two particle’s historical best points (pbest) are chosen to perform Lagrange interpolation, then to gain a new exemplar, which replaces the CLPSO’s comparison method. The numerical experiments conducted on various functions demonstrate the superiority of this algorithm, and the two methods are proven to be efficient for accelerating the convergence without leading the particle to premature convergence. PMID:27123982

  17. Lagrange Interpolation Learning Particle Swarm Optimization.

    PubMed

    Kai, Zhang; Jinchun, Song; Ke, Ni; Song, Li

    2016-01-01

    In recent years, comprehensive learning particle swarm optimization (CLPSO) has attracted the attention of many scholars for using in solving multimodal problems, as it is excellent in preserving the particles' diversity and thus preventing premature convergence. However, CLPSO exhibits low solution accuracy. Aiming to address this issue, we proposed a novel algorithm called LILPSO. First, this algorithm introduced a Lagrange interpolation method to perform a local search for the global best point (gbest). Second, to gain a better exemplar, one gbest, another two particle's historical best points (pbest) are chosen to perform Lagrange interpolation, then to gain a new exemplar, which replaces the CLPSO's comparison method. The numerical experiments conducted on various functions demonstrate the superiority of this algorithm, and the two methods are proven to be efficient for accelerating the convergence without leading the particle to premature convergence. PMID:27123982

  18. Collective control of spacecraft swarms for space exploration

    NASA Astrophysics Data System (ADS)

    Sabatini, Marco; Palmerini, Giovanni B.

    2009-11-01

    Swarms are characterized in nature by a dynamic behaviour which is quite appealing for researchers involved in numerous fields of study, like robotics, computer science, pure mathematics and space sciences. Global group organization acquired in absence of centralized control is the feature of natural swarms which is most interesting to reproduce. This study proposes to make use of some evolutionary robotics findings in order to obtain the autonomous group organization in the framework of a deeper knowledge of the astrodynamics. The main task which will be accomplished is the implementation of the control laws for the single satellite. A careful tuning of the parameters at member level is necessary in order to gain an autonomously evolving global behaviour in a number of space missions of immediate interest. In remote sensing missions, for example, trains of a small number of satellites are already orbiting and integrating their collected data: in near future entire swarms of agents could accomplish this task, and should be controlled in order to acquire and maintain the desired leader-follower configuration. Another example can be seen in deep space exploration of unknown celestial bodies, where the migration of the entire swarm from a reference orbit to a (previously unknown) targeted one is an issue; the same group migration is of interest in Earth orbit, when transferring from parking to operational orbit. Finally, self-assembly of rigid-like virtual structures is also simulated. This paper shows that all these cases are autonomously performed by the swarm by correctly implementing four simple rules at individual level, which assess the primal needs for any satellite: avoid collision, remain grouped, align to the neighbor, reach a goal.

  19. Radio frequency wave experiments on the MST reversed field pinch

    SciTech Connect

    Forest, C.B.; Chattopadhyay, P.K.; Nornberg, M.D.; Prager, S.C.; Thomas, M.A.; Uchimoto, E.; Smirnov, A.P.; Harvey, R.W.; Ram, A.K.

    1999-04-01

    Experiments, simulations, and theory all indicate that the magnetic fluctuations responsible for the poor confinement in the reversed field pinch (RFP) can be controlled by altering the radial profile of the current density. The magnetic fluctuations in the RFP are due to resistive MHD instabilities caused by current profile peaking; thus confinement in the RFP is ultimately the result of a misalignment between inductively driven current profiles and the stable current profiles characteristic of the Taylor state. If a technique such as rf current drive can be developed to non-inductively sustain a Taylor state (a current profile linearly stable to all tearing modes), the confinement of the RFP and its potential as a reactor concept are likely to increase. Whether there is a self-consistent path from poor confinement to greatly improved confinement through current profile modification is an issue for future experiments to address if and only if near term experiments can demonstrate: (1) coupling to and the propagation of rf waves in RFP plasmas, (2) efficient current drive, and (3) control of the power deposition which will make it possible to control the current profile. In this paper, modeling results and experimental plans are presented for two rf experiments which have the potential of satisfying these three goals: high-n{sub {parallel}} lower hybrid (LH) waves and electron Bernstein waves (EBWs).

  20. The South Carolina Coastal Erosion Study: Nearshore Hydrodynamics Field Experiment

    NASA Astrophysics Data System (ADS)

    Haas, K. A.; Voulgaris, G.; Demir, H.; Work, P. A.; Hanes, D. M.

    2004-12-01

    As part of the South Carolina Coastal Erosion Study (SCCES) a nearshore field experiment was carried out for five days in December 2003 just north of Myrtle Beach, South Carolina, providing measurements of the waves, currents and morphological evolution. This experiment occurred concurrently with an extensive field campaign several kilometers offshore which included measurements of the waves and currents on and near a significant sand shoal. The purpose of the nearshore experiment was to aid in the identification of the effect of the offshore shoal on the nearshore processes. The resulting dataset will be used for verification of numerical models being used to investigate the hydrodynamics of the region. The experiment was carried out from December 10 to December 15 and consisted of measurements of the waves and currents, extensive surveys of the bathymetry every day, grab samples of the sediments, and video imagery. The hydrodynamics were measured using two Sontek Triton downward-looking Acoustic Doppler Velocimeters and two Nortek AquaDopp profilers arranged in a cross-shore line from inside the swash to several surf zone widths past the breakers. The bathymetric surveying was accomplished using both a differential GPS system and a total station. Surveying was performed each day in order to capture the morphological changes. On the last day, seven sediment samples were taken along a single cross-section to determine the sediment characteristics across the beach. Additionally, a video camera was located on a balcony of the top floor of a nearby hotel providing an excellent field of view of the entire experimental area. Digital video was captured directly onto a computer during all daylight hours and many control points were surveyed in each day to facilitate rectification of the imagery. A variety of conditions were encountered during the experiment, including two storm fronts which passed through, generating wind speeds up to 15 m/s. The first storm generated

  1. Investigating the auroral electrojets using Swarm

    NASA Astrophysics Data System (ADS)

    Smith, Ashley; Macmillan, Susan; Beggan, Ciaran; Whaler, Kathy

    2016-04-01

    The auroral electrojets are large horizontal currents that flow within the ionosphere in ovals around the polar regions. They are an important aspect of space weather and their position and intensity vary with solar wind conditions and geomagnetic activity. The electrojet positions are also governed by the Earth's main magnetic field. During more active periods, the auroral electrojets typically move equatorward and become more intense. This causes a range of effects on Earth and in space, including geomagnetically induced currents in power transmission networks, disturbance to radio communications and increased drag on satellites due to expansion of the atmosphere. They are also indicative of where the aurora are visible. Monitoring of the auroral electrojets in the pre-satellite era was limited to the network of ground-based magnetic observatories, from which the traditional AE activity indices are produced. These suffer in particular from the stations' poor distribution in position and so this motivates the use of satellite-based measurements. With polar low-Earth orbit satellites carrying magnetometers, all latitudes can be sampled with excellent resolution. This poster presents an investigation using Swarm's magnetometer data to detect the electrojets as the spacecraft move above them. We compare and contrast two approaches, one which uses vector data and the other which uses scalar data (Hamilton and Macmillan 2013, Vennerstrom and Moretto, 2013). Using ideas from both approaches we determine the oval positions and intensities from Swarm and earlier satellites. The variation in latitude and intensity with solar wind conditions, geomagnetic activity and secular variation of the main field is investigated. We aim to elucidate the relative importance of these factors. Hamilton, B. and Macmillan, S., 2013. Investigation of decadal scale changes in the auroral oval positions using Magsat and CHAMP data. Poster at IAGA 12th Scientific Assembly, 2013. http

  2. Multiscale Modelling and Analysis of Collective Decision Making in Swarm Robotics

    PubMed Central

    Vigelius, Matthias; Meyer, Bernd; Pascoe, Geoffrey

    2014-01-01

    We present a unified approach to describing certain types of collective decision making in swarm robotics that bridges from a microscopic individual-based description to aggregate properties. Our approach encompasses robot swarm experiments, microscopic and probabilistic macroscopic-discrete simulations as well as an analytic mathematical model. Following up on previous work, we identify the symmetry parameter, a measure of the progress of the swarm towards a decision, as a fundamental integrated swarm property and formulate its time evolution as a continuous-time Markov process. Contrary to previous work, which justified this approach only empirically and a posteriori, we justify it from first principles and derive hard limits on the parameter regime in which it is applicable. PMID:25369026

  3. The k -Unanimity Rule for Self-Organized Decision-Making in Swarms of Robots.

    PubMed

    Scheidler, Alexander; Brutschy, Arne; Ferrante, Eliseo; Dorigo, Marco

    2016-05-01

    In this paper, we propose a collective decision-making method for swarms of robots. The method enables a robot swarm to select, from a set of possible actions, the one that has the fastest mean execution time. By means of positive feedback the method achieves consensus on the fastest action. The novelty of our method is that it allows robots to collectively find consensus on the fastest action without measuring explicitly the execution times of all available actions. We study two analytical models of the decision-making method in order to understand the dynamics of the consensus formation process. Moreover, we verify the applicability of the method in a real swarm robotics scenario. To this end, we conduct three sets of experiments that show that a robotic swarm can collectively select the shortest of two paths. Finally, we use a Monte Carlo simulation model to study and predict the influence of different parameters on the method. PMID:27093717

  4. Multiscale modelling and analysis of collective decision making in swarm robotics.

    PubMed

    Vigelius, Matthias; Meyer, Bernd; Pascoe, Geoffrey

    2014-01-01

    We present a unified approach to describing certain types of collective decision making in swarm robotics that bridges from a microscopic individual-based description to aggregate properties. Our approach encompasses robot swarm experiments, microscopic and probabilistic macroscopic-discrete simulations as well as an analytic mathematical model. Following up on previous work, we identify the symmetry parameter, a measure of the progress of the swarm towards a decision, as a fundamental integrated swarm property and formulate its time evolution as a continuous-time Markov process. Contrary to previous work, which justified this approach only empirically and a posteriori, we justify it from first principles and derive hard limits on the parameter regime in which it is applicable. PMID:25369026

  5. Electromagnetic induction tomography field experiment at Lost Hills, CA

    SciTech Connect

    Buettner, H. M.; Berryman, J. G.

    1998-11-03

    We have collected borehole to surface electromagnetic induction field data for a shallow steam injection that is underway at Mobil Oil' s Lost Hills-3 field in San Joaquin Valley. Earlier work had been done at the same site by Wilt et al. (1996). This site is an interesting test for techniques under development for environmental engineering, because it can be viewed as an excellent analog of a shallow environmental remediation using steam injection. Surface magnetic field data (vertical and radial fields, magnitude and phase) were collected using 18 receiver stations along two profiles which ran radially from the EM transmitter well from 5 m to 120 m. The data at each surface station were collected while the EM transmitter was raised slowly from a depth of 120 m to a final depth of 20 m. As part of this experiment, a calibration of the EM transmitter was also performed. Magnetic field data from Lost Hills were successfully collected, including both vertical and horizontal (surface radial) magnitude and phase data along a northerly profile and along a westerly profile. We have observed that the radial receiver data appear to be better behaved than the vertical receiver data, suggesting that these data may be less sensitive to environmental clutter (numerous metallic pipes crisscrossing the site at the surface) than are the vertical data. Some simple 1-D modeling has been done to confirm that the expected conductivity change in the steam zone should produce an observable anomaly in the measured data when comparing the pre-steam to the post-steam conditions. Results of this test were positive. Further analyses of these data making use of a new code developed in a companion paper are in progress and will presented separately.

  6. A Survey of Formal Methods for Intelligent Swarms

    NASA Technical Reports Server (NTRS)

    Truszkowski, Walt; Rash, James; Hinchey, Mike; Rouff, Chrustopher A.

    2004-01-01

    Swarms of intelligent autonomous spacecraft, involving complex behaviors and interactions, are being proposed for future space exploration missions. Such missions provide greater flexibility and offer the possibility of gathering more science data than traditional single spacecraft missions. The emergent properties of swarms make these missions powerful, but simultaneously far more difficult to design, and to assure that the proper behaviors will emerge. These missions are also considerably more complex than previous types of missions, and NASA, like other organizations, has little experience in developing or in verifying and validating these types of missions. A significant challenge when verifying and validating swarms of intelligent interacting agents is how to determine that the possible exponential interactions and emergent behaviors are producing the desired results. Assuring correct behavior and interactions of swarms will be critical to mission success. The Autonomous Nano Technology Swarm (ANTS) mission is an example of one of the swarm types of missions NASA is considering. The ANTS mission will use a swarm of picospacecraft that will fly from Earth orbit to the Asteroid Belt. Using an insect colony analogy, ANTS will be composed of specialized workers for asteroid exploration. Exploration would consist of cataloguing the mass, density, morphology, and chemical composition of the asteroids, including any anomalous concentrations of specific minerals. To perform this task, ANTS would carry miniaturized instruments, such as imagers, spectrometers, and detectors. Since ANTS and other similar missions are going to consist of autonomous spacecraft that may be out of contact with the earth for extended periods of time, and have low bandwidths due to weight constraints, it will be difficult to observe improper behavior and to correct any errors after launch. Providing V&V (verification and validation) for this type of mission is new to NASA, and represents the

  7. Identifying Discrimination at Work: The Use of Field Experiments

    PubMed Central

    Pager, Devah; Western, Bruce

    2013-01-01

    Antidiscrimination law offers protection to workers who have been treated unfairly on the basis of their race, gender, religion, or national origin. In order for these protections to be invoked, however, potential plaintiffs must be aware of and able to document discriminatory treatment. Given the subtlety of contemporary forms of discrimination, it is often difficult to identify discrimination when it has taken place. The methodology of field experiments offers one approach to measuring and detecting hiring discrimination, providing direct observation of discrimination in real-world settings. In this article, we discuss the findings of two recent field experiments measuring racial discrimination in low wage labor markets. This research provides several relevant findings for researchers and those interested in civil rights enforcement: (1) it produces estimates of the rate of discrimination at the point of hire; (2) it yields evidence about the interactions associated with discrimination (many of which reveal the subtlety with which contemporary discrimination is practiced); and (3) it provides a vehicle for both research on and enforcement of antidiscrimination law. PMID:24163481

  8. Field Experiment Data Support at the Goddard DAAC

    NASA Astrophysics Data System (ADS)

    Hrubiak, P. L.; Yang, R.; Ahmad, S.; Chiu, L.; Teng, W.; Liu, Z.; Serafino, G.; Rui, H.; Bonk, J.; Pollack, N.

    2001-12-01

    Historically, field experiment data support at the data center level has been sketchy, but in the last decade, because of rapid growth of electronic capabilities throughout the science community, the data center has become the resolution of choice to the problems of campaign data distribution and archival. Even so, field campaign data, being inherently non-uniform, require significant adaptation on the part of the archive. The participant complement for a campaign ranges widely-from one to three dozen investigators. Each has his/her own instrument, organizational affiliation, and funding. Many are academics with class schedules to consider, an office staff composed of graduate students and a correspondingly high turnover rate. Some are operating with very limited resources and lack the programming staff to tailor their data to archive specifications. Data delivery schedules, formatting and documentation are all driven by these factors. Planning for data volume also requires flexibility. Campaign data acquisition is sensitive to weather and a variety of logistical problems. Planning for campaign data volume is therefore a matter of determining thresholds. Since most campaign data sets tend to be small by data center standards, distribution is mainly from anonymous ftp sites front-ended by web sites. The Goddard DAAC opened its campaign archive in 1994 with data from the TRMM oriented TOGA-COARE campaign of 1992-93, and has most recently archived the TRMM global validation campaigns, designed to evaluate the physical assumptions made by TRMM rainfall algorithms, initialize and validate the cloud resolving models, test latent heating retrievals from TRMM measurements, and evaluate methods to estimate rainfall and latent heating from ground based radars. Launched by the TRMM Office in 1998, the TRMM campaigns were designed as a group so that specific measurements could be compared between experiments in order to gain insight into the regional dependence of any findings

  9. [Runoff Pollution Experiments of Paddy Fields Under Different Irrigation Patterns].

    PubMed

    Zhou, Jing-wen; Su, Bao-lin; Huang, Ning-bo; Guan, Yu-tang; Zhao, Kun

    2016-03-15

    To study runoff and non-point source pollution of paddy fields and to provide a scientific basis for agricultural water management of paddy fields, paddy plots in the Jintan City and the Liyang City were chosen for experiments on non-point source pollution, and flood irrigation and intermittent irrigation patterns were adopted in this research. The surface water level and rainfall were observed during the growing season of paddies, and the runoff amount from paddy plots and loads of total nitrogen (TN) and total phosphorus (TP) were calculated by different methods. The results showed that only five rain events of totally 27 rainfalls and one artificially drainage formed non-point source pollution from flood irrigated paddy plot, which resulted in a TN export coefficient of 49.4 kg · hm⁻² and a TP export coefficient of 1.0 kg · hm⁻². No any runoff event occurred from the paddy plot with intermittent irrigation even in the case of maximum rainfall of 95.1 mm. Runoff from paddy fields was affected by water demands of paddies and irrigation or drainage management, which was directly correlated to surface water level, rainfall amount and the lowest ridge height of outlets. Compared with the flood irrigation, intermittent irrigation could significantly reduce non-point source pollution caused by rainfall or artificial drainage. PMID:27337888

  10. Modelling of Ocean Induced Magnetic Signals in Swarm Satellite Data

    NASA Astrophysics Data System (ADS)

    Einspigel, D.; Velimsky, J.; Martinec, Z.; Sachl, L.

    2015-12-01

    It is well known that the motion of sea water in the Earth's main magnetic field induces the secondary magnetic field which can be measured by satellite, land-based or sea surface magnetic measurements, despite being rather weak, reaching intensities of up to a few nT. We focus on the extraction of ocean induced signals from Swarm satellite data and their interpretation by a comparison with synthetic signals. Results of our modeling and data processing efforts will be presented. We use two ocean circulation models: 1) DEBOT, a barotropic model of ocean tide flow and 2) LSOMG, a baroclinic model of global ocean circulation; and two different approaches for modelling the secondary magnetic field: 1) a single-layer approximation model and 2) a three-dimensional time-domain electromagnetic induction model. Swarm data are analyzed along night-time tracks of the satellites. Only a small amount of the data can be used for the analysis of ocean-induced signals because of permanently present strong signals from the magnetosphere and disruptive effects of polar electrojets. Nevertheless, the extracted signals from selected Swarm data tracks show a relatively good coincidence with predicted signals.

  11. Data management for interdisciplinary field experiments: OTTER project support

    NASA Technical Reports Server (NTRS)

    Angelici, Gary; Popovici, Lidia; Skiles, J. W.

    1993-01-01

    The ability of investigators of an interdisciplinary science project to properly manage the data that are collected during the experiment is critical to the effective conduct of science. When the project becomes large, possibly including several scenes of large-format remotely sensed imagery shared by many investigators requiring several services, the data management effort can involve extensive staff and computerized data inventories. The OTTER (Oregon Transect Ecosystem Research) project was supported by the PLDS (Pilot Land Data System) with several data management services, such as data inventory, certification, and publication. After a brief description of these services, experiences in providing them are compared with earlier data management efforts and some conclusions regarding data management in support of interdisciplinary science are discussed. In addition to providing these services, a major goal of this data management capability was to adopt characteristics of a pro-active attitude, such as flexibility and responsiveness, believed to be crucial for the effective conduct of active, interdisciplinary science. These are also itemized and compared with previous data management support activities. Identifying and improving these services and characteristics can lead to the design and implementation of optimal data management support capabilities, which can result in higher quality science and data products from future interdisciplinary field experiments.

  12. Field experiments using SPEAR: a speech control system for UGVs

    NASA Astrophysics Data System (ADS)

    Chhatpar, Siddharth R.; Blanco, Chris; Czerniak, Jeffrey; Hoffman, Orin; Juneja, Amit; Pruthi, Tarun; Liu, Dongqing; Karlsen, Robert; Brown, Jonathan

    2009-05-01

    This paper reports on a Field Experiment carried out by the Human Research and Engineering Directorate at Ft. Benning to evaluate the efficacy of using speech to control an Unmanned Ground Vehicle (UGV) concurrently with a handcontroller. The SPEAR system, developed by Think-A-Move, provides speech-control of UGVs. The system picks up user-speech in the ear canal with an in-ear microphone. This property allows it to work efficiently in high-noise environments, where traditional speech systems, employing external microphones, fail. It has been integrated with an iRobot PackBot 510 with EOD kit. The integrated system allows the hand-controller to be supplemented with speech for concurrent control. At Ft. Benning, the integrated system was tested by soldiers from the Officer Candidate School. The Experiment had dual focus: 1) Quantitative measurement of the time taken to complete each station and the cognitive load on users; 2) Qualitative evaluation of ease-of-use and ergonomics through soldier-feedback. Also of significant benefit to Think-A-Move was soldier-feedback on the speech-command vocabulary employed: What spoken commands are intuitive, and how the commands should be executed, e.g., limited-motion vs. unlimited-motion commands. Overall results from the Experiment are reported in the paper.

  13. Glass buildings on river banks as "polarized light traps" for mass-swarming polarotactic caddis flies.

    PubMed

    Kriska, György; Malik, Péter; Szivák, Ildikó; Horváth, Gábor

    2008-05-01

    The caddis flies Hydropsyche pellucidula emerge at dusk from the river Danube and swarm around trees and bushes on the river bank. We document here that these aquatic insects can also be attracted en masse to the vertical glass surfaces of buildings on the river bank. The individuals lured to dark, vertical glass panes land, copulate, and remain on the glass for hours. Many of them are trapped by the partly open, tiltable windows. In laboratory choice experiments, we showed that ovipositing H. pellucidula are attracted to highly and horizontally polarized light stimulating their ventral eye region and, thus, have positive polarotaxis. In the field, we documented that highly polarizing vertical black glass surfaces are significantly more attractive to both female and male H. pellucidula than weakly polarizing white ones. Using video polarimetry, we measured the reflection-polarization characteristics of vertical glass surfaces of buildings where caddis flies swarmed. We propose that after its emergence from the river, H. pellucidula is attracted to buildings by their dark silhouettes and the glass-reflected, horizontally polarized light. After sunset, this attraction may be strengthened by positive phototaxis elicited by the buildings' lights. The novelty of this visual-ecological phenomenon is that the attraction of caddis flies to vertical glass surfaces has not been expected because vertical glass panes do not resemble the horizontal surface of waters from which these insects emerge and to which they must return to oviposit. PMID:18253711

  14. Glass buildings on river banks as ``polarized light traps'' for mass-swarming polarotactic caddis flies

    NASA Astrophysics Data System (ADS)

    Kriska, György; Malik, Péter; Szivák, Ildikó; Horváth, Gábor

    2008-05-01

    The caddis flies Hydropsyche pellucidula emerge at dusk from the river Danube and swarm around trees and bushes on the river bank. We document here that these aquatic insects can also be attracted en masse to the vertical glass surfaces of buildings on the river bank. The individuals lured to dark, vertical glass panes land, copulate, and remain on the glass for hours. Many of them are trapped by the partly open, tiltable windows. In laboratory choice experiments, we showed that ovipositing H. pellucidula are attracted to highly and horizontally polarized light stimulating their ventral eye region and, thus, have positive polarotaxis. In the field, we documented that highly polarizing vertical black glass surfaces are significantly more attractive to both female and male H. pellucidula than weakly polarizing white ones. Using video polarimetry, we measured the reflection-polarization characteristics of vertical glass surfaces of buildings where caddis flies swarmed. We propose that after its emergence from the river, H. pellucidula is attracted to buildings by their dark silhouettes and the glass-reflected, horizontally polarized light. After sunset, this attraction may be strengthened by positive phototaxis elicited by the buildings’ lights. The novelty of this visual ecological phenomenon is that the attraction of caddis flies to vertical glass surfaces has not been expected because vertical glass panes do not resemble the horizontal surface of waters from which these insects emerge and to which they must return to oviposit.

  15. Swarm Absolute Scalar Magnetometers first in-orbit results

    NASA Astrophysics Data System (ADS)

    Fratter, Isabelle; Léger, Jean-Michel; Bertrand, François; Jager, Thomas; Hulot, Gauthier; Brocco, Laura; Vigneron, Pierre

    2016-04-01

    The ESA Swarm mission will provide the best ever survey of the Earth's magnetic field and its temporal evolution. This will be achieved by a constellation of three identical satellites, launched together on the 22nd of November 2013. In order to observe the magnetic field thoroughly, each satellite carries two magnetometers: a Vector Field Magnetometer (VFM) coupled with a star tracker camera, to measure the direction of the magnetic field in space, and an Absolute Scalar Magnetometer (ASM), to measure its intensity. The ASM is the French contribution to the Swarm mission. This new generation instrument was designed by CEA-Leti and developed in close partnership with CNES, with scientific support from IPGP. Its operating principle is based on the atomic spectroscopy of the helium 4 metastable state. It makes use of the Zeeman's effect to transduce the magnetic field into a frequency, the signal being amplified by optical pumping. The primary role of the ASM is to provide absolute measurements of the magnetic field's strength at 1 Hz, for the in-flight calibration of the VFM. As the Swarm magnetic reference, the ASM scalar performance is crucial for the mission's success. Thanks to its innovative design, the ASM offers the best precision, resolution and absolute accuracy ever attained in space, with similar performance all along the orbit. In addition, thanks to an original architecture, the ASM implements on an experimental basis a capacity for providing simultaneously vector measurements at 1 Hz. This new feature makes it the first instrument capable of delivering both scalar and vector measurements simultaneously at the same point. Swarm offers a unique opportunity to validate the ASM vector data in orbit by comparison with the VFM's. Furthermore, the ASM can provide scalar data at a much higher sampling rate, when run in "burst" mode at 250 Hz, with a 100 Hz measurement bandwidth. An analysis of the spectral content of the magnetic field above 1 Hz becomes thus

  16. The Value of Field Experience in Education for Health Care Administration.

    ERIC Educational Resources Information Center

    Hiller, Marc D.

    A sample of 54 health administration education programs were examined to identify and analyze current practices in field experience programs. The six primary areas investigated include: (1) the prevalence of field experience requirements; (2) the objectives and characteristics of field experience components; (3) the experiences encountered in…

  17. Enhancing comprehensive inversions using the Swarm constellation

    NASA Astrophysics Data System (ADS)

    Sabaka, T. J.; Olsen, N.

    2006-04-01

    This paper reports on the findings of a simulation study designed to test various satellite configurations sug-gested for the upcoming Swarm magnetic mapping mission. The test is to see whether the mission objectives of recovering small-scale core secular variation (SV) and lithospheric magnetic signals, as well as information about mantle conductivity structure, can be met. The recovery method used in this paper is known as com-prehensive inversion (CI) and involves the parameterization of all major fields followed by a co-estimation of these parameters in a least-squares sense in order to achieve proper signal separation. The advantage of co-estimation over serial estimation of parameters is demonstrated by example. Synthetic data were calculated for a pool of six Swarm satellites from a model based heavily on the CM4 comprehensive model, but which has more small-scale lithospheric structure, a more complicated magnetospheric field, and an induced field reflecting a 3-D conductivity model. These data also included realistic magnetic noise from spacecraft and payload. Though the parameterization for the CI is based upon that of CM4, modifications have been made to accommodate these new magnetospheric and induced fields, in particular with orthogonality constraints defined so as to avoid covariance between slowly varying induced fields and SV. The use of these constraints is made feasible through an efficient numerical implementation. Constellations of 4, 3, 2, and 1 satellites were considered; that with 3 was able to meet the mission objectives, consistently resolving the SV to about spherical harmonic (SH) degree n = 15 and the lithosphere to a limited n < 90 due to external field leakage, while those with 2 and 1 were not; 4 was an improvement over 3, but was much less than the improvement from 2 to 3. The resolution of the magnetospheric and induced SH time-series from the 3 satellite configuration was sufficient enough to allow the detection of 3-D mantle

  18. Electric Field Double Probe Measurements for Ionospheric Space Plasma Experiments

    NASA Technical Reports Server (NTRS)

    Pfaff, R.

    1999-01-01

    Double probes represent a well-proven technique for gathering high quality DC and AC electric field measurements in a variety of space plasma regimes including the magnetosphere, ionosphere, and mesosphere. Such experiments have been successfully flown on a variety of spacecraft including sounding rockets and satellites. Typical instrument designs involve a series of trades, depending on the science objectives, type of platform (e.g., spinning or 3-axis stabilized), expected plasma regime where the measurements will be made, available telemetry, budget, etc. In general, ionospheric DC electric field instruments that achieve accuracies of 0.1 mV/m or better, place spherical sensors at large distances (10m or more) from the spacecraft body in order to extend well beyond the spacecraft wake and sheath and to achieve large signal-to-noise ratios for DC and long wavelength measurements. Additional sets of sensors inboard of the primary, outermost sensors provide useful additional information, both for diagnostics of the plasma contact potentials, which particularly enhance the DC electric field measurements on non-spinning spacecraft, and for wavelength and phase velocity measurements that use the spaced receiver or "interferometer" technique. Accurate attitude knowledge enables B times V contributions to be subtracted from the measured potentials, and permits the measured components to be rotated into meaningful geophysical reference frames. We review the measurement technique for both DC and wave electric field measurements in the ionosphere discussing recent advances involving high resolution burst memories, multiple baseline double probes, new sensor surface materials, biasing techniques, and other considerations.

  19. Osmotic pressure in a bacterial swarm.

    PubMed

    Ping, Liyan; Wu, Yilin; Hosu, Basarab G; Tang, Jay X; Berg, Howard C

    2014-08-19

    Using Escherichia coli as a model organism, we studied how water is recruited by a bacterial swarm. A previous analysis of trajectories of small air bubbles revealed a stream of fluid flowing in a clockwise direction ahead of the swarm. A companion study suggested that water moves out of the agar into the swarm in a narrow region centered ∼ 30 μm from the leading edge of the swarm and then back into the agar (at a smaller rate) in a region centered ∼ 120 μm back from the leading edge. Presumably, these flows are driven by changes in osmolarity. Here, we utilized green/red fluorescent liposomes as reporters of osmolarity to verify this hypothesis. The stream of fluid that flows in front of the swarm contains osmolytes. Two distinct regions are observed inside the swarm near its leading edge: an outer high-osmolarity band (∼ 30 mOsm higher than the agar baseline) and an inner low-osmolarity band (isotonic or slightly hypotonic to the agar baseline). This profile supports the fluid-flow model derived from the drift of air bubbles and provides new (to our knowledge) insights into water maintenance in bacterial swarms. High osmotic pressure at the leading edge of the swarm extracts water from the underlying agar and promotes motility. The osmolyte is of high molecular weight and probably is lipopolysaccharide. PMID:25140422

  20. Microwave Remote Sensing and the Cold Land Processes Field Experiment

    NASA Technical Reports Server (NTRS)

    Kim, Edward J.; Cline, Don; Davis, Bert; Hildebrand, Peter H. (Technical Monitor)

    2001-01-01

    The Cold Land Processes Field Experiment (CLPX) has been designed to advance our understanding of the terrestrial cryosphere. Developing a more complete understanding of fluxes, storage, and transformations of water and energy in cold land areas is a critical focus of the NASA Earth Science Enterprise Research Strategy, the NASA Global Water and Energy Cycle (GWEC) Initiative, the Global Energy and Water Cycle Experiment (GEWEX), and the GEWEX Americas Prediction Project (GAPP). The movement of water and energy through cold regions in turn plays a large role in ecological activity and biogeochemical cycles. Quantitative understanding of cold land processes over large areas will require synergistic advancements in 1) understanding how cold land processes, most comprehensively understood at local or hillslope scales, extend to larger scales, 2) improved representation of cold land processes in coupled and uncoupled land-surface models, and 3) a breakthrough in large-scale observation of hydrologic properties, including snow characteristics, soil moisture, the extent of frozen soils, and the transition between frozen and thawed soil conditions. The CLPX Plan has been developed through the efforts of over 60 interested scientists that have participated in the NASA Cold Land Processes Working Group (CLPWG). This group is charged with the task of assessing, planning and implementing the required background science, technology, and application infrastructure to support successful land surface hydrology remote sensing space missions. A major product of the experiment will be a comprehensive, legacy data set that will energize many aspects of cold land processes research. The CLPX will focus on developing the quantitative understanding, models, and measurements necessary to extend our local-scale understanding of water fluxes, storage, and transformations to regional and global scales. The experiment will particularly emphasize developing a strong synergism between process

  1. Soil response to chemicals used in a field experiment

    NASA Astrophysics Data System (ADS)

    Jezierska-Tys, S.; Rutkowska, A.

    2013-03-01

    The effect of chemicals (Reglone 200 SL and Elastiq 550 EC) on soil microorganisms and their enzymatic activity was estimated. The study was conducted in a field experiment which was set up in the split-block design and comprised three treatments. Soil samples were taken six times, twice in each year of study. The results showed that the application of chemicals generally had no negative effect on the number of soil microorganisms. The application of Reglone 200 SL caused an increase of proteolytic and ureolytic activity and affected the activity of dehydrogenases, acid and alkaline phosphatases in the soil. The soil subjected of Elastiq 550 EC was characterized by lower activity of dehydrogenases, protease, urease and alkaline phosphatase.

  2. Prosocial Behavior and Subjective Insecurity in Violent Contexts: Field Experiments

    PubMed Central

    Vélez, María Alejandra; Trujillo, Carlos Andres; Moros, Lina; Forero, Clemente

    2016-01-01

    Subjective insecurity is a key determinant of different forms of prosocial behavior. In Study 1, we used field experiments with farmers in Colombian villages exposed to different levels of violence to investigate how individual perceptions of insecurity affect cooperation, trust, reciprocity and altruism. To do so, we developed a cognitive-affective measure of subjective insecurity. We found that subjective insecurity has a negative effect on cooperation but influences trust and altruism positively. In Study 2, carried out three years after Study 1, we repeated the initial design with additional measures of victimization. Our goal was to relate subjective insecurity with actual victimization. The findings of Study 2 support the initial results, and are robust and consistent for cooperative behavior and trust when including victimization as a mediator. Different indicators of victimization are positively correlated with subjective insecurity and an aggregate index of victimization has a negative effect on cooperation but exerts a positive influence on trust. PMID:27472437

  3. Prosocial Behavior and Subjective Insecurity in Violent Contexts: Field Experiments.

    PubMed

    Vélez, María Alejandra; Trujillo, Carlos Andres; Moros, Lina; Forero, Clemente

    2016-01-01

    Subjective insecurity is a key determinant of different forms of prosocial behavior. In Study 1, we used field experiments with farmers in Colombian villages exposed to different levels of violence to investigate how individual perceptions of insecurity affect cooperation, trust, reciprocity and altruism. To do so, we developed a cognitive-affective measure of subjective insecurity. We found that subjective insecurity has a negative effect on cooperation but influences trust and altruism positively. In Study 2, carried out three years after Study 1, we repeated the initial design with additional measures of victimization. Our goal was to relate subjective insecurity with actual victimization. The findings of Study 2 support the initial results, and are robust and consistent for cooperative behavior and trust when including victimization as a mediator. Different indicators of victimization are positively correlated with subjective insecurity and an aggregate index of victimization has a negative effect on cooperation but exerts a positive influence on trust. PMID:27472437

  4. How Many Insects Does It Take to Make a Swarm?

    NASA Astrophysics Data System (ADS)

    Ouellette, Nicholas

    2014-03-01

    Aggregations of social animals, such as flocks of birds, schools of fish, or swarms of insects, are beautiful, natural examples of self-organized behavior far from equilibrium. They tend to display a range of emergent properties, from enhanced sensing to the rapid propagation of information throughout the aggregate. Many classes of models have been proposed to describe these systems, including agent-based models that specify explicit social forces between individuals and continuum models that abstract the interactions between individuals into some smooth advecting velocity field. Assessing these various modeling approaches requires comparison with empirical data. We will discuss measurements of laboratory mating swarms of the non-biting midge Chironomus riparius in the context of model assessment. In particular, we focus on the question of the small-number limit: how large must the population be before collective properties emerge?

  5. Preliminary Results from the Field Experiment of OPACC

    NASA Astrophysics Data System (ADS)

    Zhao, Kun; Xue, Ming

    2015-04-01

    The project for the Observation, Prediction and Analysis of severe Convection of China (OPACC) is a 5-year project funded by the Chinese Ministry of Science and Technology Foundational Research (973) Program from January 2013, and it focuses on studying convective weather systems characteristic of the China region. Field observation is the key component of OPACC, which aims to obtain detailed observations of the internal structures, dynamics and microphysics and their evolution of typical convective systems during summer monsoon period in China, as well as their mesoscale environment. An observational experiment was conducted from June 1 to July 31, 2014 in the Changjiang-Huaihe River basin region that included 11 intensive observing periods (IOPs). During the IOPs, 6-hourly soundings were launched in order to catch the environment of convection. Special research instruments deployed include three C-band polarimetric radars, an S-band polarimetric radar and disdrometers. Observations from the operational networks, including those from rather dense operational S-band Doppler radars in the region, and from automated surface weather stations at up to 1-minute intervals, were collected. In the presentation, a brief summary of the field program will be given. The dynamical and microphysical structures of isolated convection, embedded convection and organized convection observed by polarimetric radars will be presented and compared to other studies of tropical and midlatitude convection.

  6. Magnetic Field Structure in the Madison Dynamo Experiment

    NASA Astrophysics Data System (ADS)

    Rasmus, A. M.; Clark, M.; Kaplan, E. J.; Nornberg, M. D.; Rahbarnia, K.; Taylor, N. Z.; Forest, C. B.

    2011-10-01

    The Madison Dynamo Experiment(MDE) is expected to spontaneously self-generate a magnetic field in a two vortex flow geometry driven by counter rotating impellers in a 1 m diameter sphere filled with liquid sodium. Prevoiusly an equatorial baffle was installed and has been demonstrated to reduce the largest scale turbulent-eddies. An additonal set of six rotatable baffles have been installed to optimize the helicity of the flow, lowering the critical magnetic Reynolds number. This poster will focus on the spatial structure of the magnetic field associated with the dynamo eigenmodes and the turbulent fluctuations. Singular value decomposition (SVD) and cross correlation analysis between the surface harmonics and internal probes will be used to determine the internal structure associated with each spherical harmonic. Spherical harmonic decomposition is of limited utility when analysing the equatorial array of internal probes as there is a limited angular spread (only one theta value and two phi values), whereas cross correlation and SVD allow the use of time domain data to infer internal modes excited via three-wave couplings. This work is supported by the NSF/DOE partnership in plasma physics.

  7. Frac-and-pack stimulation: Application, design, and field experience

    SciTech Connect

    Roodhart, L.P.; Fokker, P.A.; Davies, D.R.; Shlyapobersky, J.; Wong, G.K.

    1994-03-01

    This paper discusses the criteria for selecting wells to be frac-and-packed. The authors show how systematic study of the inflow performance can be used to assess the potential of frac-and-packed wells, to identify the controlling factors, and to optimize design parameters. They also show that fracture conductivity is often the key to successful treatment. This conductivity depends largely on proppant size; formation permeability damage around the created fracture has less effect. Appropriate allowance needs to be made for flow restrictions caused by the presence of the perforations, partial penetration, and non-Darcy effects. They describe the application of the overpressure-calibrated hydraulic fracture model in frac-and-pack treatment design, and discuss some operational considerations with reference to field examples. The full potential of this promising new completion method can be achieved only if the design is tailored to the individual well. This demands high-quality input data, which can be obtained only from a calibration test. This paper presents their strategy for frac-and-pack design, drawing on examples from field experience. They also point out several areas that the industry needs to address, such as the sizing of proppant in soft formations and the interaction between fracturing fluids and resin in resin-coated proppant.

  8. A field experiment: reducing interpersonal discrimination toward pregnant job applicants.

    PubMed

    Morgan, Whitney Botsford; Walker, Sarah Singletary; Hebl, Michelle Mikki R; King, Eden B

    2013-09-01

    The current research targets 4 potential stereotypes driving hostile attitudes and discriminatory behaviors toward pregnant women: incompetence, lack of commitment, inflexibility, and need for accommodation. We tested the relative efficacy of reducing concerns related to each of the stereotypes in a field experiment in which female confederates who sometimes wore pregnancy prostheses applied for jobs in a retail setting. As expected, ratings from 3 perspectives (applicants, observers, and independent coders) converged to show that pregnant applicants received more interpersonal hostility than did nonpregnant applicants. However, when hiring managers received (vs. did not receive) counterstereotypic information about certain pregnancy-related stereotypes (particularly lack of commitment and inflexibility), managers displayed significantly less interpersonal discrimination. Explicit comparisons of counterstereotypic information shed light on the fact that certain information may be more effective in reducing discrimination than others. We conclude by discussing how the current research makes novel theoretical contributions and describe some practical organizational implications for understanding and improving the experiences of pregnant workers. PMID:23957687

  9. Geothermal well stimulation - program summary and the Beowawe field experiment

    SciTech Connect

    Verity, R.V.

    1983-12-01

    Republic Geothermal, Inc. and its subcontractors have planned and executed laboratory studies and eight well stimulation field experiments under the Geothermal Reservoir Well Stimulation Program (GRWSP). The program, begun in February 1979, has concentrated on extending petroleum industry stimulation technology for use by the geothermal industry. The most recent experiment was in a naturally fractured Chevron well at Beowawe and involved an acid stimulation of a damaged interval which yielded a 2.3-fold increase in injectivity. Overall results to date have shown that stimulation is viable where adequate reservoirs are penetrated by wells encountering formation damage or locally tight formations. However, wells in marginal naturally fractured reservoirs have not been saved by the types of well stimulation jobs performed thus far. A recent discovery is that many wells can possibly be made outstanding producers by widening and propping compliant natural fractures. Confirmation of this constitutes unfinished business of the GRWSP, adn offers one of the greatest potential opportunities for enhancing the economics of geothermal power production.

  10. The field experiments on the HTO washout from the atmosphere

    SciTech Connect

    Golubev, A.V.; Mavrin, S.V.; Golubeva, V.N.; Stengach, A.V.; Balashov, Y.S.; Kovalenko, V.P.; Solomatin, I.I.

    2015-03-15

    HTO (tritiated water) wash-out from the atmosphere is one of the key processes governing the HTO transport from the atmosphere into soil and plants. Experimental studies of the HTO interaction with water drops were carried out both in laboratories and in the field. In the course of experiments, the following rain characteristics were recorded: rain intensity, size distribution of drops, and falling velocities and their dependence on drop diameter. A laser optical device was designed and used to measure the distribution of the drop radius and velocities during the period of experiment. The tritium source was placed at a height of 30 m. Rainwater samples were collected in plastic bottles and their HTO activity was determined by liquid scintillation techniques. The data obtained for the experimental values of the scavenging rate are within the range from 4.12*10{sup -5} to 1.57*10{sup -4} s{sup -1} and correspond to the precipitation intensity from 0.3 to 1.26 mm/hour. These results are in sufficiently good agreement with the results of earlier papers.

  11. Macroalgal mats and species abundance: a field experiment

    NASA Astrophysics Data System (ADS)

    Hull, S. C.

    1987-11-01

    A field experiment was carried out whereby the density of macroalgae ( Enteromorpha spp.) was manipulated and the resultant changes in sediment infaunal density were monitored. Four densities of Enteromorpha spp. were used: 0,0·3, 1, and 3 kg FW m -2, corresponding to control, low-, medium-, and high-density plots. The experiment ran from May to October 1985 and was sampled on three occasions. By July, the density of Corophium volutator was reduced at all weed levels when compared to control plots, whereas densities of Hydrobia ulvae, Macoma balthica, Nereis diversicolor, and Capitella capitata, all increased. Samples taken in October when the weed mats were buried in the sediment showed fewer differences than in July. Macoma, Nereis, and Capitella were still significantly more abundant at medium and high weed densities. Corophium showed no significant treatment effect. There was, however, a highly significant difference in population size structure for Corophium. Measurements of sediment redox potential and silt content under medium- and high-density plots revealed rapid anoxia with a significant increase in siltation.

  12. Coordinated Coverage of FACs with Cluster and Swarm

    NASA Astrophysics Data System (ADS)

    Dunlop, Malcolm; Yang, Junying; Yang, Yanyan; Bogdanova, Yulia; Xiong, Chao; Shen, Chao; Luehr, Hermann; Olsen, Nils; Zhang, Qinghe; Cao, Jinbin; Ritter, Patricia; Masson, Arnaud; Haagmans, Roger

    2015-04-01

    We explore the capability of Swarm-Cluster coordination for probing the behaviour of the field aligned currents (FAC) adjacent to the ring current (RC) at medium and low orbits. The RC and connecting R2 FACs influence the geomagnetic field at low Earth orbit (LEO) and are sampled in situ by the four Cluster spacecraft every perigee pass. Coordination of the configuration of three Swarm spacecraft configurations with the constellation of the four Cluster spacecraft has been achieved through joint operations; providing a set of distributed, multi-point measurements covering this region. A particularly close coordination of all spacecraft is considered during the start of the Swarm operations. We report here preliminary results of joint signatures of R1 and R2 FACs, and the use and application of new analysis techniques derived from the calculation of curl B and magnetic gradients to compare estimates of the current distributions. Hall currents associated with the FAC signatures at the Swam locations are shown to be directly obtainable from the three spacecraft configurations. For context, we identify the associated auroral boundaries through application of a method to determine the FAC intensity gradients in order to interpret and resolve the R1 and R2 FACs.

  13. The equatorial electrojet current modelling from SWARM satellite data

    NASA Astrophysics Data System (ADS)

    Benaissa, Mahfoud

    2016-07-01

    Equatorial ElectroJet (EEJ) is an intense eastward electric current circulating in the ionospheric magnetic equator band between 100 and 130 km of altitude in E region. These currents vary by day, by season, by solar activity, and also with the main magnetic field of internal origin. The irregularity of the ionosphere has a major impact on the performance of communication systems and navigation (GPS), industry.... Then it becomes necessary study the characteristics of EEJ. In this paper, we present a study of the equatorial electrojet (EEJ) phenomenon along one year (2014) period. In addition, the satellite data used in this study are obtained with SWARM satellite scalar magnetometer data respecting magnetically quiet days with KP < 2. In this paper, we process to separate and extract the electrojet intensity signal from other recorded signal-sources interfering with the main signal and reduce considerably the signal to noise ratio during the SWARM measurements. This pre-processing step allows removing all external contributions in regard to EEJ intensity value. Key words: Ionosphere (Equatorial ionosphere; Electric fields and currents; Equatorial electrojet (EEJ)); SWARM.

  14. Analysis of swarm behaviors based on an inversion of the fluctuation theorem.

    PubMed

    Hamann, Heiko; Schmickl, Thomas; Crailsheim, Karl

    2014-01-01

    A grand challenge in the field of artificial life is to find a general theory of emergent self-organizing systems. In swarm systems most of the observed complexity is based on motion of simple entities. Similarly, statistical mechanics focuses on collective properties induced by the motion of many interacting particles. In this article we apply methods from statistical mechanics to swarm systems. We try to explain the emergent behavior of a simulated swarm by applying methods based on the fluctuation theorem. Empirical results indicate that swarms are able to produce negative entropy within an isolated subsystem due to frozen accidents. Individuals of a swarm are able to locally detect fluctuations of the global entropy measure and store them, if they are negative entropy productions. By accumulating these stored fluctuations over time the swarm as a whole is producing negative entropy and the system ends up in an ordered state. We claim that this indicates the existence of an inverted fluctuation theorem for emergent self-organizing dissipative systems. This approach bears the potential of general applicability. PMID:23373981

  15. Magnetic Field Experiment on Yinghuo-1 at Mars

    NASA Astrophysics Data System (ADS)

    Zhao, Hua

    Magnetic Field Experiment on Yinghuo-1 at Mars Hua Zhao, G. W. Zhu, J. D. Wang, M. F. Yu, L. Li, Y. Q. Sun, S. W. Chen, H. Z. Liao, and B. Zhou Center for Space Science and Applied Research (CSSAR), Chinese Academy of Sciences, Beijing, China Abstract: A micro-satellite, Yinghuo-1, would be launched with Phobos-Grunt in October, 2009 to investigate the space environment around Mars. YH-1 and Phobos-Grunt forms a twopoint measurement configuration in the Martian space environment, and equipped with similar magnetic field and plasma detecting payload on two spacecraft would give some coordinated exploration around Mars. YH-1 would orbit Mars with periapsis of 800 km above the Martian surface, and apoapsis about 80000 km to the center of Mars. The orbit inclination is in the range of 0—7o to the Martian equator. A flux-gate type magnetometer, with two sensors, is developed for YH-1 spacecraft. Two sensors are mounted on one-side of the deployable solar panel with a radial separation about 45 cm to function as a gradiometer to minimize the affects of platform remanence. The dynamic range of √ magnetometer is with a 16-bit ADC converter, and the the noise level is better than 0.01 nT/ Hz, to measure three-component magnetic field from DC to 10Hz. Flux-gate magnetometer would work together with the Plasma Package onboard of YH-1 to investigate the Martian bow shock, magnetosheath, magnetic pileup region (MPR). A detail description of the flux-gate magnetometer is presented in this paper, with some test and calibration results.

  16. Type IV pili interactions promote intercellular association and moderate swarming of Pseudomonas aeruginosa.

    PubMed

    Anyan, Morgen E; Amiri, Aboutaleb; Harvey, Cameron W; Tierra, Giordano; Morales-Soto, Nydia; Driscoll, Callan M; Alber, Mark S; Shrout, Joshua D

    2014-12-16

    Pseudomonas aeruginosa is a ubiquitous bacterium that survives in many environments, including as an acute and chronic pathogen in humans. Substantial evidence shows that P. aeruginosa behavior is affected by its motility, and appendages known as flagella and type IV pili (TFP) are known to confer such motility. The role these appendages play when not facilitating motility or attachment, however, is unclear. Here we discern a passive intercellular role of TFP during flagellar-mediated swarming of P. aeruginosa that does not require TFP extension or retraction. We studied swarming at the cellular level using a combination of laboratory experiments and computational simulations to explain the resultant patterns of cells imaged from in vitro swarms. Namely, we used a computational model to simulate swarming and to probe for individual cell behavior that cannot currently be otherwise measured. Our simulations showed that TFP of swarming P. aeruginosa should be distributed all over the cell and that TFP-TFP interactions between cells should be a dominant mechanism that promotes cell-cell interaction, limits lone cell movement, and slows swarm expansion. This predicted physical mechanism involving TFP was confirmed in vitro using pairwise mixtures of strains with and without TFP where cells without TFP separate from cells with TFP. While TFP slow swarm expansion, we show in vitro that TFP help alter collective motion to avoid toxic compounds such as the antibiotic carbenicillin. Thus, TFP physically affect P. aeruginosa swarming by actively promoting cell-cell association and directional collective motion within motile groups to aid their survival. PMID:25468980

  17. Type IV pili interactions promote intercellular association and moderate swarming of Pseudomonas aeruginosa

    PubMed Central

    Anyan, Morgen E.; Amiri, Aboutaleb; Harvey, Cameron W.; Tierra, Giordano; Morales-Soto, Nydia; Driscoll, Callan M.; Alber, Mark S.; Shrout, Joshua D.

    2014-01-01

    Pseudomonas aeruginosa is a ubiquitous bacterium that survives in many environments, including as an acute and chronic pathogen in humans. Substantial evidence shows that P. aeruginosa behavior is affected by its motility, and appendages known as flagella and type IV pili (TFP) are known to confer such motility. The role these appendages play when not facilitating motility or attachment, however, is unclear. Here we discern a passive intercellular role of TFP during flagellar-mediated swarming of P. aeruginosa that does not require TFP extension or retraction. We studied swarming at the cellular level using a combination of laboratory experiments and computational simulations to explain the resultant patterns of cells imaged from in vitro swarms. Namely, we used a computational model to simulate swarming and to probe for individual cell behavior that cannot currently be otherwise measured. Our simulations showed that TFP of swarming P. aeruginosa should be distributed all over the cell and that TFP−TFP interactions between cells should be a dominant mechanism that promotes cell−cell interaction, limits lone cell movement, and slows swarm expansion. This predicted physical mechanism involving TFP was confirmed in vitro using pairwise mixtures of strains with and without TFP where cells without TFP separate from cells with TFP. While TFP slow swarm expansion, we show in vitro that TFP help alter collective motion to avoid toxic compounds such as the antibiotic carbenicillin. Thus, TFP physically affect P. aeruginosa swarming by actively promoting cell−cell association and directional collective motion within motile groups to aid their survival. PMID:25468980

  18. REVIEW ARTICLE: Measurement and interpretation of swarm parameters and their application in plasma modelling

    NASA Astrophysics Data System (ADS)

    Petrović, Z. Lj; Dujko, S.; Marić, D.; Malović, G.; Nikitović, Ž.; Šašić, O.; Jovanović, J.; Stojanović, V.; Radmilović-Rađenović, M.

    2009-10-01

    In this review paper, we discuss the current status of the physics of charged particle swarms, mainly electrons, having plasma modelling in mind. The measurements of the swarm coefficients and the availability of the data are briefly discussed. We try to give a summary of the past ten years and cite the main reviews and databases, which store the majority of the earlier work. The need for reinitiating the swarm experiments and where and how those would be useful is pointed out. We also add some guidance on how to find information on ions and fast neutrals. Most space is devoted to interpretation of transport data, analysis of kinetic phenomena, and accuracy of calculation and proper use of transport data in plasma models. We have tried to show which aspects of kinetic theory developed for swarm physics and which segments of data would be important for further improvement of plasma models. Finally, several examples are given where actual models are mostly based on the physics of swarms and those include Townsend discharges, afterglows, breakdown and some atmospheric phenomena. Finally we stress that, while complex, some of the results from the kinetic theory of swarms and the related phenomenology must be used either to test the plasma models or even to bring in new physics or higher accuracy and reliability to the models.

  19. Comparisons of sets of electron-neutral scattering cross sections and calculated swarm parameters in Ar

    NASA Astrophysics Data System (ADS)

    Biagi, S. F.; Alves, L. L.; Ferreira, C. M.; Bordage, M. C.; Hagelaar, G. J. M.; Pitchford, L. C.; Morgan, W. L.; Phelps, A. V.; Zatsarinny, O.; Bartschat, K.

    2011-10-01

    Extensive data are available in the literature for cross sections for electron-neutral scattering from argon and for swarm parameters in argon and argon-containing gas mixtures. Seven independently compiled sets of cross sections in argon are presently available on the LXCat website, including one set of data derived from theory. The recent theoretical elastic momentum transfer cross section is in excellent agreement with recent results from a swarm analysis. The purpose of this communication is to show intercomparisons of swarm parameters calculated using these different sets. For the most part and within the accuracy required for plasma modeling, calculated swarm parameters using the different cross section sets agree with experiement and among themselves. Swarm parameters calculated using classic 2-term Boltzmann solvers are in good agreement with those from Monte Carlo simulations except for the diffusion coefficients, where the 2-term approximation overestimates the values by about 30% in the 5 to 100 Td range. The cross section sets and measured swarm parameters used in this work are available on-line at www.lxcat.laplace.univ-tlse.fr.

  20. Swarms, swarming and entanglements of fungal hyphae and of plant roots

    PubMed Central

    Barlow, Peter W.; Fisahn, Joachim

    2013-01-01

    There has been recent interest in the possibility that plant roots can show oriented collective motion, or swarming behavior. We examine the evidence supportive of root swarming and we also present new observations on this topic. Seven criteria are proposed for the definition of a swarm, whose application can help identify putative swarming behavior in plants. Examples where these criteria are fulfilled, at many levels of organization, are presented in relation to plant roots and root systems, as well as to the root-like mycelial cords (rhizomorphs) of fungi. The ideas of both an “active” swarming, directed by a signal which imposes a common vector on swarm element aggregation, and a “passive” swarming, where aggregation results from external constraint, are introduced. Active swarming is a pattern of cooperative behavior peculiar to the sporophyte generation of vascular plants and is the antithesis of the competitive behavior shown by the gametophyte generation of such plants, where passive swarming may be found. Fungal mycelial cords could serve as a model example of swarming in a multi-cellular, non-animal system. PMID:24255743

  1. A seismic swarm and regional hydrothermal and hydrologic perturbations: The northern Endeavour segment, February 2005

    NASA Astrophysics Data System (ADS)

    Hooft, Emilie E. E.; Patel, Hemalinee; Wilcock, William; Becker, Keir; Butterfield, David; Davis, Earl; Dziak, Robert; Inderbitzen, Katherine; Lilley, Marvin; McGill, Paul; Toomey, Douglas; Stakes, Debra

    2010-12-01

    The February 2005 swarm at the overlapping spreading center (OSC) on the northern end of the Endeavour segment is the first swarm on the Juan de Fuca Ridge recorded on a local seafloor seismic network. The swarm included several larger earthquakes and caused triggered seismicity and a hydrothermal response in the Endeavour vent fields as well as regional-scale hydrologic pressure perturbations. The spatial and temporal pattern of over 6000 earthquakes recorded during this seismic sequence is complex. Small-magnitude events dominate, and seismicity rates wax and wane, indicating a magmatic process. The main swarm initiates at the northern end of the Endeavour ridge. However, most of the moment release, including six strike-slip events, occurs in the southwest Endeavour Valley, where the swarm epicenters generally migrate south. The main swarm is contemporaneous with a hydrologic pressure response at four sealed seafloor boreholes, ˜25-105 km away. We infer that the seismic sequence is driven by a largely aseismic magma intrusion at the northern Endeavour axis. Resulting stress changes trigger slip on tectonic faults and possibly dike propagation at the opposing limb of the Endeavour OSC in the southwest Endeavour Valley, consistent with the eventual decapitation of the Endeavour by the West Valley segment. Furthermore, 2.5 days after the start of the main swarm, seismicity is triggered beneath the Endeavour vent fields, and temperature increases at a diffuse vent in the Mothra field. We infer that this delayed response is due to a hydrologic pressure pulse that diffuses away from the main magma intrusion.

  2. Obtaining electron attachment cross sections by means of linear inversion of swarm parameters

    NASA Astrophysics Data System (ADS)

    Rabie, M.; Haefliger, P.; Chachereau, A.; Franck, C. M.

    2015-02-01

    We investigate electron attachment to strongly attaching gases as a function of the electron energy. The total electron attachment cross section of this electronegative sample gas is determined from the effective ionization rate constant νeff/N measured in a swarm experiment using the buffer gases N2 and CO2 with minor proportions (≲0.8%) of the sample gas SF6, and C3F8 respectively. The measured rate constants νeff/N for varying reduced electric field strengths E/N are unfolded from the electron energy distribution of the buffer gases. Different unfolding routines for so-called ill-posed problems are tested to find robust solutions for the attachment cross section. Finally, we propose Tikhonov regularization, which is a well defined algorithm for discrete linear inversion problems, as most efficient. Our method gives rise to an approximate and clearly defined solution for the attachment cross section, and it is described in detail.

  3. Impact of Swarm GPS receiver updates on POD performance

    NASA Astrophysics Data System (ADS)

    van den IJssel, Jose; Forte, Biagio; Montenbruck, Oliver

    2016-05-01

    The Swarm satellites are equipped with state-of-the-art Global Positioning System (GPS) receivers, which are used for the precise geolocation of the magnetic and electric field instruments, as well as for the determination of the Earth's gravity field, the total electron content and low-frequency thermospheric neutral densities. The onboard GPS receivers deliver high-quality data with an almost continuous data rate. However, the receivers show a slightly degraded performance when flying over the geomagnetic poles and the geomagnetic equator, due to ionospheric scintillation. Furthermore, with only eight channels available for dual-frequency tracking, the amount of collected GPS tracking data is relatively low compared with various other missions. Therefore, several modifications have been implemented to the Swarm GPS receivers. To optimise the amount of collected GPS data, the GPS antenna elevation mask has slowly been reduced from 10° to 2°. To improve the robustness against ionospheric scintillation, the bandwidths of the GPS receiver tracking loops have been widened. Because these modifications were first implemented on Swarm-C, their impact can be assessed by a comparison with the close flying Swarm-A satellite. This shows that both modifications have a positive impact on the GPS receiver performance. The reduced elevation mask increases the amount of GPS tracking data by more than 3 %, while the updated tracking loops lead to around 1.3 % more observations and a significant reduction in tracking losses due to severe equatorial scintillation. The additional observations at low elevation angles increase the average noise of the carrier phase observations, but nonetheless slightly improve the resulting reduced-dynamic and kinematic orbit accuracy as shown by independent satellite laser ranging (SLR) validation. The more robust tracking loops significantly reduce the large carrier phase observation errors at the geomagnetic poles and along the geomagnetic

  4. A Swarm of Ancient Stars

    NASA Astrophysics Data System (ADS)

    2010-12-01

    We know of about 150 of the rich collections of old stars called globular clusters that orbit our galaxy, the Milky Way. This sharp new image of Messier 107, captured by the Wide Field Imager on the 2.2-metre telescope at ESO's La Silla Observatory in Chile, displays the structure of one such globular cluster in exquisite detail. Studying these stellar swarms has revealed much about the history of our galaxy and how stars evolve. The globular cluster Messier 107, also known as NGC 6171, is a compact and ancient family of stars that lies about 21 000 light-years away. Messier 107 is a bustling metropolis: thousands of stars in globular clusters like this one are concentrated into a space that is only about twenty times the distance between our Sun and its nearest stellar neighbour, Alpha Centauri, across. A significant number of these stars have already evolved into red giants, one of the last stages of a star's life, and have a yellowish colour in this image. Globular clusters are among the oldest objects in the Universe. And since the stars within a globular cluster formed from the same cloud of interstellar matter at roughly the same time - typically over 10 billion years ago - they are all low-mass stars, as lightweights burn their hydrogen fuel supply much more slowly than stellar behemoths. Globular clusters formed during the earliest stages in the formation of their host galaxies and therefore studying these objects can give significant insights into how galaxies, and their component stars, evolve. Messier 107 has undergone intensive observations, being one of the 160 stellar fields that was selected for the Pre-FLAMES Survey - a preliminary survey conducted between 1999 and 2002 using the 2.2-metre telescope at ESO's La Silla Observatory in Chile, to find suitable stars for follow-up observations with the VLT's spectroscopic instrument FLAMES [1]. Using FLAMES, it is possible to observe up to 130 targets at the same time, making it particularly well suited

  5. A Swarm of Ancient Stars

    NASA Astrophysics Data System (ADS)

    2010-12-01

    We know of about 150 of the rich collections of old stars called globular clusters that orbit our galaxy, the Milky Way. This sharp new image of Messier 107, captured by the Wide Field Imager on the 2.2-metre telescope at ESO's La Silla Observatory in Chile, displays the structure of one such globular cluster in exquisite detail. Studying these stellar swarms has revealed much about the history of our galaxy and how stars evolve. The globular cluster Messier 107, also known as NGC 6171, is a compact and ancient family of stars that lies about 21 000 light-years away. Messier 107 is a bustling metropolis: thousands of stars in globular clusters like this one are concentrated into a space that is only about twenty times the distance between our Sun and its nearest stellar neighbour, Alpha Centauri, across. A significant number of these stars have already evolved into red giants, one of the last stages of a star's life, and have a yellowish colour in this image. Globular clusters are among the oldest objects in the Universe. And since the stars within a globular cluster formed from the same cloud of interstellar matter at roughly the same time - typically over 10 billion years ago - they are all low-mass stars, as lightweights burn their hydrogen fuel supply much more slowly than stellar behemoths. Globular clusters formed during the earliest stages in the formation of their host galaxies and therefore studying these objects can give significant insights into how galaxies, and their component stars, evolve. Messier 107 has undergone intensive observations, being one of the 160 stellar fields that was selected for the Pre-FLAMES Survey - a preliminary survey conducted between 1999 and 2002 using the 2.2-metre telescope at ESO's La Silla Observatory in Chile, to find suitable stars for follow-up observations with the VLT's spectroscopic instrument FLAMES [1]. Using FLAMES, it is possible to observe up to 130 targets at the same time, making it particularly well suited

  6. An Oceanographic Decision Support System for Scientific Field Experiments

    NASA Astrophysics Data System (ADS)

    Maughan, T.; Das, J.; McCann, M. P.; Rajan, K.

    2011-12-01

    Thom Maughan, Jnaneshwar Das, Mike McCann, Danelle Cline, Mike Godin, Fred Bahr, Kevin Gomes, Tom O'Reilly, Frederic Py, Monique Messie, John Ryan, Francisco Chavez, Jim Bellingham, Maria Fox, Kanna Rajan Monterey Bay Aquarium Research Institute Moss Lading, California, United States Many of the coastal ocean processes we wish to observe in order to characterize marine ecosystems have large spatial extant (tens of square km) and are dynamic moving kilometers in a day with biological processes spanning anywhere from minutes to days. Some like harmful algal blooms generate toxins which can significantly impact human health and coastal economies. In order to obtain a viable understanding of the biogeochemical processes which define their dynamics and ecology, it is necessary to persistently observe, track and sample within and near the dynamic fields using augmented methods of observation such as autonomous platforms like AUVs, gliders and surface craft. Field experiments to plan, execute and manage such multitude of assets are challenging. To alleviate this problem the autonomous systems group with its collaborators at MBARI and USC designed, built and fielded a prototype Oceanographic Decision Support System (ODSS) that provides situational awareness and a single portal to visualize and plan deployments for the large scale October 2010 CANON field program as well as a series of 2 week field programs in 2011. The field programs were conducted in Monterey Bay, a known 'red tide' incubator, and varied from as many as twenty autonomous platforms, four ships and 2 manned airplanes to coordinated AUV operations, drifters and a single ship. The ODSS web-based portal was used to assimilate information from a collection of sources at sea, including AUVs, moorings, radar data as well as remote sensing products generated by partner organizations to provide a synthesis of views useful to predict the movement of a chlorophyll patch in the confines of the northern Monterey Bay

  7. Scouts behave as streakers in honeybee swarms.

    PubMed

    Greggers, Uwe; Schöning, Caspar; Degen, Jacqueline; Menzel, Randolf

    2013-08-01

    Harmonic radar tracking was used to record the flights of scout bees during takeoff and initial flight path of two honeybee swarms. One swarm remained intact and performed a full flight to a destination beyond the range of the harmonic radar, while a second swarm disintegrated within the range of the radar and most of the bees returned to the queen. The initial stretch of the full flight is characterized by accelerating speed, whereas the disintegrating swarm flew steadily at low speed. The two scouts in the swarm displaying full flight performed characteristic flight maneuvers. They flew at high speed when traveling in the direction of their destination and slowed down or returned over short stretches at low speed. Scouts in the disintegrating swarm did not exhibit the same kind of characteristic flight performance. Our data support the streaker bee hypothesis proposing that scout bees guide the swarm by traveling at high speed in the direction of the new nest site for short stretches of flight and slowing down when reversing flight direction. PMID:23812604

  8. Scouts behave as streakers in honeybee swarms

    NASA Astrophysics Data System (ADS)

    Greggers, Uwe; Schöning, Caspar; Degen, Jacqueline; Menzel, Randolf

    2013-08-01

    Harmonic radar tracking was used to record the flights of scout bees during takeoff and initial flight path of two honeybee swarms. One swarm remained intact and performed a full flight to a destination beyond the range of the harmonic radar, while a second swarm disintegrated within the range of the radar and most of the bees returned to the queen. The initial stretch of the full flight is characterized by accelerating speed, whereas the disintegrating swarm flew steadily at low speed. The two scouts in the swarm displaying full flight performed characteristic flight maneuvers. They flew at high speed when traveling in the direction of their destination and slowed down or returned over short stretches at low speed. Scouts in the disintegrating swarm did not exhibit the same kind of characteristic flight performance. Our data support the streaker bee hypothesis proposing that scout bees guide the swarm by traveling at high speed in the direction of the new nest site for short stretches of flight and slowing down when reversing flight direction.

  9. Field experiments of nonlocal sediment transport on a steep hillslope

    NASA Astrophysics Data System (ADS)

    DiBiase, R.; Booth, A. M.; Ganti, V.; Scheingross, J. S.; Lamb, M. P.

    2014-12-01

    Steep rocky hillslopes dominate the areal extent of rapidly uplifting mountain ranges, and pose a significant hazard to encroaching population centers. Existing models for hillslope sediment transport developed for soil-mantled landscapes are poorly suited to explain the evolution of steep hillslopes characterized by: (1) intermittent or patchy soil cover, (2) slopes that exceed the angle of repose, and (3) transport events that often involve long travel distances. Recently, nonlocal formulations of hillslope sediment transport laws that account for long travel distances have been proposed to overcome the limitations of traditional continuum-based models. However, their application to natural landscapes has been limited owing to few field constraints on key parameters, and computational difficulties expanding the framework to two-dimensions. To address this knowledge gap, we performed a series of field experiments on natural hillslopes to inform a simple particle-based model of hillslope sediment transport. We compiled the distribution of average velocity and transport distance for over 300 stones ranging in diameter from 2-10 cm using a video camera and laser range-finder. To characterize surface roughness, we used a tripod-based laser scanner to generate a 1 cm-resolution digital elevation model of each 30 m long hillslope. We find that hillslope travel distance follows a heavy-tailed distribution that varies systematically with the ratio of particle diameter to roughness height, in general agreement to published laboratory experiments. Mean particle velocity ranges from 1-3 m/s and scales weakly with distance traveled. Our modeling exercise reveals three key effects that should be included in any treatment of steep hillslope evolution: (1) there is a strong grain-size and surface roughness dependence on sediment transport distance, (2) sediment storage on slopes steeper than the angle of repose is possible due to vegetation or topographic roughness, and (3

  10. The Deep Convective Clouds and Chemistry (DC3) Field Experiment

    NASA Astrophysics Data System (ADS)

    Barth, M. C.; Brune, W. H.; Cantrell, C. A.; Rutledge, S. A.; Crawford, J. H.; Huntrieser, H.; Homeyer, C. R.; Nault, B.; Cohen, R. C.; Pan, L.; Ziemba, L. D.

    2014-12-01

    The Deep Convective Clouds and Chemistry (DC3) field experiment took place in the central U.S. in May and June 2012 and had the objectives of characterizing the effect of thunderstorms on the chemical composition of the lower atmosphere and determining the chemical aging of upper troposphere (UT) convective outflow plumes. DC3 employed ground-based radars, lightning mapping arrays, and weather balloon soundings in conjunction with aircraft measurements sampling the composition of the inflow and outflow of a variety of thunderstorms in northeast Colorado, West Texas to central Oklahoma, and northern Alabama. A unique aspect of the DC3 strategy was to locate and sample the convective outflow a day after active convection in order to measure the chemical transformations within the UT convective plume. The DC3 data are being analyzed to investigate transport and dynamics of the storms, scavenging of soluble trace gases and aerosols, production of nitrogen oxides by lightning, relationships between lightning flash rates and storm parameters, and chemistry in the UT that is affected by the convection. In this presentation, we give an overview of the DC3 field campaign and highlight results from the campaign that are relevant to the upper troposphere and lower stratosphere region. These highlights include stratosphere-troposphere exchange in connection with thunderstorms, the 0-12 hour chemical aging and new particle formation in the UT outflow of a dissipating mesoscale convective system observed on June 21, 2012, and UT chemical aging in convective outflow as sampled the day after convection occurred and modeled in the Weather Research and Forecasting coupled with Chemistry model.

  11. Swarm Intelligence Optimization and Its Applications

    NASA Astrophysics Data System (ADS)

    Ding, Caichang; Lu, Lu; Liu, Yuanchao; Peng, Wenxiu

    Swarm Intelligence is a computational and behavioral metaphor for solving distributed problems inspired from biological examples provided by social insects such as ants, termites, bees, and wasps and by swarm, herd, flock, and shoal phenomena in vertebrates such as fish shoals and bird flocks. An example of successful research direction in Swarm Intelligence is ant colony optimization (ACO), which focuses on combinatorial optimization problems. Ant algorithms can be viewed as multi-agent systems (ant colony), where agents (individual ants) solve required tasks through cooperation in the same way that ants create complex social behavior from the combined efforts of individuals.

  12. Test plan for FY-94 digface characterization field experiments

    SciTech Connect

    Josten, N.E.; Roybal, L.G.

    1994-08-01

    The digface characterization concept has been under development at the Idaho National Engineering Laboratory (INEL) since fiscal year (FY) 1992 through the support of the Buried Waste Integrated Demonstration Program. A digface characterization system conducts continuous subsurface characterization simultaneously with retrieval of hazardous and radioactive waste from buried waste sites. The system deploys multiple sensors at the retrieval operation digface and collects data that provide a basis for detecting, locating, and classifying buried materials and hazardous conditions before they are disturbed by the retrieval equipment. This test plan describes ongoing efforts to test the digface characterization concept at the INEL`s Cold Test Pit using a simplified prototype deployment apparatus and off-the-shelf sensors. FY-94 field experiments will explore problems in object detection and classification. Detection and classification of objects are fundamental to three of the four primary functions of digface characterization during overburden removal. This test plan establishes procedures for collecting and validating the digface characterization data sets. Analysis of these data will focus on testing and further developing analysis methods for object detection and classification during overburden removal.

  13. A measurement system applicable for landslide experiments in the field.

    PubMed

    Guo, Wen-Zhao; Xu, Xiang-Zhou; Wang, Wen-Long; Yang, Ji-Shan; Liu, Ya-Kun; Xu, Fei-Long

    2016-04-01

    Observation of gravity erosion in the field with strong sunshine and wind poses a challenge. Here, a novel topography meter together with a movable tent addresses the challenge. With the topography meter, a 3D geometric shape of the target surface can be digitally reconstructed. Before the commencement of a test, the laser generator position and the camera sightline should be adjusted with a sight calibrator. Typically, the topography meter can measure the gravity erosion on the slope with a gradient of 30°-70°. Two methods can be used to obtain a relatively clear video, despite the extreme steepness of the slopes. One method is to rotate the laser source away from the slope to ensure that the camera sightline remains perpendicular to the laser plane. Another way is to move the camera farther away from the slope in which the measured volume of the slope needs to be corrected; this method will reduce distortion of the image. In addition, installation of tent poles with concrete columns helps to surmount the altitude difference on steep slopes. Results observed by the topography meter in real landslide experiments are rational and reliable. PMID:27131688

  14. Geothermal injection treatment: process chemistry, field experiences, and design options

    SciTech Connect

    Kindle, C.H.; Mercer, B.W.; Elmore, R.P.; Blair, S.C.; Myers, D.A.

    1984-09-01

    The successful development of geothermal reservoirs to generate electric power will require the injection disposal of approximately 700,000 gal/h (2.6 x 10/sup 6/ 1/h) of heat-depleted brine for every 50,000 kW of generating capacity. To maintain injectability, the spent brine must be compatible with the receiving formation. The factors that influence this brine/formation compatibility and tests to quantify them are discussed in this report. Some form of treatment will be necessary prior to injection for most situations; the process chemistry involved to avoid and/or accelerate the formation of precipitate particles is also discussed. The treatment processes, either avoidance or controlled precipitation approaches, are described in terms of their principles and demonstrated applications in the geothermal field and, when such experience is limited, in other industrial use. Monitoring techniques for tracking particulate growth, the effect of process parameters on corrosion and well injectability are presented. Examples of brine injection, preinjection treatment, and recovery from injectivity loss are examined and related to the aspects listed above.

  15. A measurement system applicable for landslide experiments in the field

    NASA Astrophysics Data System (ADS)

    Guo, Wen-Zhao; Xu, Xiang-Zhou; Wang, Wen-Long; Yang, Ji-Shan; Liu, Ya-Kun; Xu, Fei-Long

    2016-04-01

    Observation of gravity erosion in the field with strong sunshine and wind poses a challenge. Here, a novel topography meter together with a movable tent addresses the challenge. With the topography meter, a 3D geometric shape of the target surface can be digitally reconstructed. Before the commencement of a test, the laser generator position and the camera sightline should be adjusted with a sight calibrator. Typically, the topography meter can measure the gravity erosion on the slope with a gradient of 30°-70°. Two methods can be used to obtain a relatively clear video, despite the extreme steepness of the slopes. One method is to rotate the laser source away from the slope to ensure that the camera sightline remains perpendicular to the laser plane. Another way is to move the camera farther away from the slope in which the measured volume of the slope needs to be corrected; this method will reduce distortion of the image. In addition, installation of tent poles with concrete columns helps to surmount the altitude difference on steep slopes. Results observed by the topography meter in real landslide experiments are rational and reliable.

  16. Idaho field experiment 1981. Volume 2: measurement data

    SciTech Connect

    Start, G E; Sagendorf, J F; Ackermann, G R; Cate, J H; Hukari, N F; Dickson, C R

    1984-04-01

    The 1981 Idaho Field Experiment was conducted in southeastern Idaho over the upper Snake River Plain. Nine test-day case studies were conducted between July 15 and 30, 1981. Releases of SF/sub 6/ gaseous tracer were made for 8-hour periods from 46m above ground. Tracer was sampled hourly, for 12 sequential hours, at about 100 locations within an area 24km square. Also, a single total integrated sample of about 30 hours duration was collected at approximately 100 sites within an area 48 by 72km square (using 6km spacings). Extensive tower profiles of meteorology at the release point were collected. RAWINSONDES, RABALS and PIBALS were collected at 3 to 5 sites. Horizontal, low-altitude winds were monitored using the INEL MESONET. SF/sub 6/ tracer plume releases were marked with co-located oil fog releases and bi-hourly sequential launches of tetroon pairs. Aerial LIDAR observations of the oil fog plume and airborne samples of SF/sub 6/ were collected. High altitude aerial photographs of daytime plumes were collected. Volume II lists the data in tabular form or cites the special supplemental reports by other participating contractors. While the primary user file and the data archive are maintained on 9 track/1600 cpi magnetic tapes, listings of the individual values are provided for the user who either cannot utilize the tapes or wishes to preview the data. The accuracies and quality of these data are described.

  17. Field performance of the Walker Branch throughfall displacement experiment

    SciTech Connect

    Hanson, P.J.; Todd, D.E.; Edwards, N.T.; Huston, M.A.

    1994-10-06

    The authors are conducting a large-scale manipulative field experiments in an upland oak forest on the Walker Branch Watershed in eastern Tennessee USA to identify important ecosystem responses that might result from future precipitation changes. The manipulation of soil moisture is being implemented by a gravity-driven transfer of throughfall precipitation from one treatment plot to another. Throughfall is intercepted in {approx} 2,000 subcanopy troughs (0.3 x 5 m) suspended above the forest floor of the dry plots ({approx} 33% of the ground area is covered) and transferred by gravity flow across an ambient plot for subsequent distribution onto the wet treatment plot. Percent soil water is being monitored with time domain reflectometers at 310 sampling locations across the site. The experimental system is able to produce statistically significant differences in soil water content in years having both extremely dry and extremely wet conditions. Furthermore, comparisons of pre- and post-installation soil temperature measurements have documented the ability of the experimental design to produce these changes without changing the microclimate of the forest understory.

  18. Beam extraction experiment with field-emission arrays

    SciTech Connect

    Ishizuka, H.; Watanabe, A.; Shiho, M.

    1995-12-31

    An experimental project aimed to develop FEL drivers using a field-emission array is under way. The subject covers design and fabrication of novel micro-emitters, operation of FEAs, beam formation and emittance diagnostics. So far the generation of a focused beam has been demonstrated with an array of double-gated microemitters. Active control of FEAs has greatly improved the stability of the emission current. Large FEAs with an emitting area of up to 2 x 2 cm{sup 2} have been fabricated for the production of high-current beams. DC beams (1 - 5 keV < 100 {mu}A) extracted from Spindt cathodes were propagated over 1 m and projected on a fluorescent screen. Separate images of FEA tips were observed and emittance measurement has been carried out. The cathode is going to be replaced by a double-gated FEA to improve the beam quality. Pulsed extraction of high currents will also be tested, employing a non-gated FEA as the cathode of a 1 MV induction linac. Results of these experiments will be presented and perspectives concerning the FEA gun will be discussed.

  19. Micro-scale hydrological field experiments in Romania

    NASA Astrophysics Data System (ADS)

    Minea, Gabriel; Moroşanu, Gabriela A.

    2016-02-01

    The paper (communication) presents an overview of hydrologic field experiments at micro-scale in Romania. In order to experimentally investigate micro (plot)-scale hydrological impact of soil erosion, the National Institute of Hydrology and Water Management founded Voineşti Experimental Basin (VES) in 1964 and the Aldeni Experimental Basins (AEB) in 1984. AEB and VES are located in the Curvature Subcarpathians. Experimental plots are organized in a double systems and have an area of 80 m2 (runoff plots) at AEB and 300 m2 (water balance plots) at VES. Land use of plot: first plot "grass-land" is covered with perennial grass and second plot (control) consists in "bare soil". Over the latter one, the soil is hoeing, which results in a greater development of infiltration than in the first plot. Experimental investigations at micro-scale are aimed towards determining the parameters of the water balance equation, during natural and artificial rainfalls, researching of flows and soil erosion processes on experimental plots, extrapolating relations involving runoff coefficients from a small scale to medium scale. Nowadays, the latest evolutions in data acquisition and transmission equipment are represented by sensors (such as: sensors to determinate the soil moisture content). Exploitation and dissemination of hydrologic data is accomplished by research themes/projects, year-books of basic data and papers.

  20. A solution quality assessment method for swarm intelligence optimization algorithms.

    PubMed

    Zhang, Zhaojun; Wang, Gai-Ge; Zou, Kuansheng; Zhang, Jianhua

    2014-01-01

    Nowadays, swarm intelligence optimization has become an important optimization tool and wildly used in many fields of application. In contrast to many successful applications, the theoretical foundation is rather weak. Therefore, there are still many problems to be solved. One problem is how to quantify the performance of algorithm in finite time, that is, how to evaluate the solution quality got by algorithm for practical problems. It greatly limits the application in practical problems. A solution quality assessment method for intelligent optimization is proposed in this paper. It is an experimental analysis method based on the analysis of search space and characteristic of algorithm itself. Instead of "value performance," the "ordinal performance" is used as evaluation criteria in this method. The feasible solutions were clustered according to distance to divide solution samples into several parts. Then, solution space and "good enough" set can be decomposed based on the clustering results. Last, using relative knowledge of statistics, the evaluation result can be got. To validate the proposed method, some intelligent algorithms such as ant colony optimization (ACO), particle swarm optimization (PSO), and artificial fish swarm algorithm (AFS) were taken to solve traveling salesman problem. Computational results indicate the feasibility of proposed method. PMID:25013845

  1. Electrochemical 'bubble swarm' enhancement of ultrasonic surface cleaning.

    PubMed

    Birkin, P R; Offin, D G; Vian, C J B; Leighton, T G

    2015-09-01

    An investigation of surface cleaning using a swarm of gas bubbles within an acoustically activated stream is presented. Electrolysis of water at Pt microwires (100 μm diameter) to produce both hydrogen and oxygen bubbles is shown to enhance the extent of ultrasonic surface cleaning in a free flowing water stream containing an electrolyte (0.1 M Na2SO4) and low surfactant concentration (2 mM SDS). The surfactant was employed to allow control of the average size of the bubble population within the swarm. The electrochemical bubble swarm (EBS) is shown to perturb acoustic transmission through the stream. To optimise the cleaning process both the ultrasonic field and the electrochemical current are pulsed and synchronized but with different duty cycles. Cleaning action is demonstrated on structured surfaces (porcine skin and finger mimics) loaded with fluorescent particles. This action is shown to be significantly enhanced compared to that found with an inherent bubble population produced by the flow and acoustic regime alone under the same conditions. PMID:26234563

  2. Controlled in vivo swimming of a swarm of bacteria-like microrobotic flagella.

    PubMed

    Servant, Ania; Qiu, Famin; Mazza, Mariarosa; Kostarelos, Kostas; Nelson, Bradley J

    2015-05-20

    In vivo imaging and actuation of a swarm of magnetic helical microswimmers by external magnetic fields (less than 10 mT) in deep tissue is demonstrated for the first time. This constitutes a major milestone in the field, yielding a generation of micrometer-scale transporters with numerous applications in biomedicine including synthetic biology, assisted fertilization, and drug/gene delivery. PMID:25850420

  3. Does swarming cause honey bees to update their solar ephemerides?

    PubMed

    Towne, William F; Baer, Christopher M; Fabiny, Sarah J; Shinn, Lisa M

    2005-11-01

    Spatial orientation in the social insects offers several examples of specialized learning mechanisms that underlie complex learning tasks. Here we study one of these systems: the processes by which honey bees update, or fail to update, their memories of the sun's daily pattern of movement (the solar ephemeris function) in relation to the landscape. Specifically, we ask whether bees that have initially learned the solar ephemeris function relative to a conspicuous treeline at their natal site can later realign the ephemeris to a differently oriented treeline. We first confirm and clarify an earlier finding that bees transplanted passively (by being carried) do not re-learn the solar ephemeris in relation to the new treeline. When they cannot detect the sun directly, as on overcast days, these transplanted bees use a solar ephemeris function appropriate for their natal site, despite days or weeks of experience at the new site. We then ask whether bees put through a swarming process as they are transplanted are induced to re-learn the solar ephemeris function at the new site, as swarming is a natural process wherein bees transplant themselves. Most of the swarmed bees failed to re-learn, even though they did extensive learning flights (in comparison with those of non-swarmed controls) as they first emerged from the hive at the new site. We hypothesize that the bees' representation of the solar ephemeris function is stored in an encapsulated cognitive module in which the ephemeris is inextricably linked to the reference landscape in which it was learned. PMID:16244164

  4. Particle swarm optimization with recombination and dynamic linkage discovery.

    PubMed

    Chen, Ying-Ping; Peng, Wen-Chih; Jian, Ming-Chung

    2007-12-01

    In this paper, we try to improve the performance of the particle swarm optimizer by incorporating the linkage concept, which is an essential mechanism in genetic algorithms, and design a new linkage identification technique called dynamic linkage discovery to address the linkage problem in real-parameter optimization problems. Dynamic linkage discovery is a costless and effective linkage recognition technique that adapts the linkage configuration by employing only the selection operator without extra judging criteria irrelevant to the objective function. Moreover, a recombination operator that utilizes the discovered linkage configuration to promote the cooperation of particle swarm optimizer and dynamic linkage discovery is accordingly developed. By integrating the particle swarm optimizer, dynamic linkage discovery, and recombination operator, we propose a new hybridization of optimization methodologies called particle swarm optimization with recombination and dynamic linkage discovery (PSO-RDL). In order to study the capability of PSO-RDL, numerical experiments were conducted on a set of benchmark functions as well as on an important real-world application. The benchmark functions used in this paper were proposed in the 2005 Institute of Electrical and Electronics Engineers Congress on Evolutionary Computation. The experimental results on the benchmark functions indicate that PSO-RDL can provide a level of performance comparable to that given by other advanced optimization techniques. In addition to the benchmark, PSO-RDL was also used to solve the economic dispatch (ED) problem for power systems, which is a real-world problem and highly constrained. The results indicate that PSO-RDL can successfully solve the ED problem for the three-unit power system and obtain the currently known best solution for the 40-unit system. PMID:18179066

  5. Flash Expansion Threshold in Whirligig Swarms

    PubMed Central

    Romey, William L.; Lamb, Alicia R.

    2015-01-01

    In the selfish herd hypothesis, prey animals move toward each other to avoid the likelihood of being selected by a predator. However, many grouped animals move away from each other the moment before a predator attacks. Very little is known about this phenomenon, called flash expansion, such as whether it is triggered by one individual or a threshold and how information is transferred between group members. We performed a controlled experiment with whirligig beetles in which the ratio of sighted to unsighted individuals was systematically varied and emergent flash expansion was measured. Specifically, we examined: the percentage of individuals in a group that startled, the resulting group area, and the longevity of the flash expansion. We found that one or two sighted beetles in a group of 24 was not enough to cause a flash expansion after a predator stimulus, but four sighted beetles usually initiated a flash expansion. Also, the more beetles that were sighted the larger the resulting group area and the longer duration of the flash expansion. We conclude that flash expansion is best described as a threshold event whose adaptive value is to prevent energetically costly false alarms while quickly mobilizing an emergent predator avoidance response. This is one of the first controlled experiments of flash expansion, an important emergent property that has applications to understanding collective motion in swarms, schools, flocks, and human crowds. Also, our study is a convincing demonstration of social contagion, how the actions of one individual can pass through a group. PMID:26301958

  6. A Tale of Two Seismic Swarms: Implications for different forcing mechanisms (Invited)

    NASA Astrophysics Data System (ADS)

    Thelen, W. A.; Gomberg, J. S.; Bodin, P.; Hartog, R.; Wright, A.; Rohay, A.

    2009-12-01

    Within the compressional tectonic regime of the Columbia Basin, swarms are the dominant source of seismicity. Not all swarms, however, are created equal. Two recent swarms, the 2007-2008 swarm near Maupin, Oregon and the 2009 Wooded Island earthquake sequence near Richland, Washington, displayed very different behavior despite being within the same tectonic regime. The Maupin earthquake swarm lasted 20 months with strike-slip earthquakes with magnitudes as large as M3.8. The swarm was 18 km deep. Nearly all of the earthquakes within the Maupin swarm were highly similar with maximum p-wave lags of about 0.05 seconds. This seismic evidence therefore suggests a single, repeatable, and very energetic source with dimensions of less than 750 m at mid-crustal levels. Swarms, apparently collocated, also occurred in 1987 and 1976. However the waveforms from these swarms are not similar to the 2007-2008 sequence, suggesting that the source geometry or orientation of the source has changed from 1976 to 1987 and 2007. In contrast, the 2009 Wooded Island earthquake sequence is currently (as of September 3) only 8 months in duration, but has already had nearly five times the number earthquakes as the Maupin swarm, with a maximum magnitude of 3. The total energy released in the Wooded Island earthquake sequence was less than in the Maupin earthquake sequence. The earthquakes in the Wooded Island sequence were shallow, with focal depths of less than 2 km, which made focal mechanisms unreliable. However, the earthquakes were associated with a deformation anomaly detected from InSAR. Based on the correlations between waveforms, earthquakes that comprise this swarm can be classified into many different families, suggesting slip along a network of distributed shallow faults and/or a heterogeneous stress field. Precise relocations show a dipping structure, consistent with a fault geometry that matches well with source models of the InSAR deformation anomaly. Swarms have been attributed

  7. The Evolution of the South Atlantic Anomaly by Swarm Data

    NASA Astrophysics Data System (ADS)

    Pavón-Carrasco, F. J.; De Santis, A.; Qamili, E.

    2015-12-01

    The South Atlantic Anomaly (SAA) is a large depression of the Earth's magnetic field strength characterized by values of geomagnetic field intensity around 30% lower than expected for those latitudes and covers a large area in the South Atlantic Ocean and South America. This peculiar feature of the present geomagnetic field has an internal origin in a prominent patch of reversed polarity flux in the Earth's outer core. The study of the SAA is an important challenge nowadays, not only for the geomagnetic and paleomagnetic community, but also for other areas focused on the Earth Observation because of the reducing protective role of the geomagnetic field against the charged particles coming from the Sun and forming the solar wind. The SAA has showed to be a persistent feature of the geomagnetic field since its extent at the Earth's surface has increased during the last four centuries and even accelerated more recently. In this context, the ESA Swarm satellite mission is providing detailed measurements of the intensity and directional elements of the geomagnetic field with high-precision and resolution never reached in the former space missions. This work aims to analyze in detail in space and time the SAA from the core-mantle boundary up to satellite altitudes using the dataset provided by the Swarm satellites and all the available ground-based data.

  8. A Swarm of Ancient Stars

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This stellar swarm is M80 (NGC 6093), one of the densest of the 147 known globular star clusters in the Milky Way galaxy. Located about 28,000 light-years from Earth, M80 contains hundreds of thousands of stars, all held together by their mutual gravitational attraction. Globular clusters are particularly useful for studying stellar evolution, since all of the stars in the cluster have the same age (about 15 billion years), but cover a range of stellar masses. Every star visible in this image is either more highly evolved than, or in a few rare cases more massive than, our own Sun. Especially obvious are the bright red giants, which are stars similar to the Sun in mass that are nearing the ends of their lives.

  9. Scalar transport by planktonic swarms

    NASA Astrophysics Data System (ADS)

    Martinez-Ortiz, Monica; Dabiri, John O.

    2012-11-01

    Nutrient and energy transport in the ocean is primarily governed by the action of physical phenomena. In previous studies it has been suggested that aquatic fauna may significantly contribute to this process through the action of the induced drift mechanism. In this investigation, the role of planktonic swarms as ecosystem engineers is assessed through the analysis of scalar transport within a stratified water column. The vertical migration of Artemia salina is controlled via luminescent signals on the top and bottom of the column. The scalar transport of fluorescent dye is visualized and quantified through planar laser induced fluorescence (PLIF). Preliminary results show that the vertical movement of these organisms enhances scalar transport relative to control cases in which only buoyancy forces and diffusion are present. Funded by the BSF program (2011553).

  10. The NASA Cold Land Processes Field Experiment (CLPX)

    NASA Astrophysics Data System (ADS)

    Cline, D.; Elder, K.; Davis, B.; Hardy, J.; Liston, G.; Parsons, M.

    2002-12-01

    The Cold Land Processes Field Experiment (CLPX) is a multi-year effort to develop the quantitative understanding, models, and measurements necessary to extend our local-scale understanding of cold-region water fluxes, storage, and transformations to regional and global scales. Particularly emphasized is the development of a strong synergism between process-oriented understanding, land surface models and microwave remote sensing within a broad range of physiographic regimes. Objectives of the CLPX include evaluation and improvement of algorithms for retrieving snow and frozen soil information from active and passive microwave sensors, evaluating the effects of sensor spatial resolution on retrieval skill, coupling forward microwave radiative transfer schemes to distributed snow/soil models to improve assimilation of microwave remote sensing data, and development of sensor specifications for a new space-flight mission to measure cold land hydrologic processes. The experimental design is a multi-sensor, multi-scale approach to providing the comprehensive data set necessary to address these objectives. A series of nested study areas, at five scales ranging from 1-ha to 160,000 km2, provides the framework needed to address objectives concerning the scale and scaling of processes, measurements, and models. The largest of these, the Large Regional Study Area (160,000 km2), is located in north central Colorado and southern Wyoming. Within it is the Small Regional Study Area (37,000 km2). These two areas are the focus of satellite remote sensing data collection (MODIS, Landsat, Hyperion, SSM/I, AMSR, Radarsat, and others), and archival of mesoscale atmospheric model data sets (RUC2, LAPS, and RAMS). Nested within these are three 25-km x 25-km Meso-Cell Study Areas (MSA), that are the focus of airborne remote sensing data collection, including AIRSAR, POLSCAT, PSR-A, GAMMA, and AVIRIS. Within each of the three MSA are three 1-km x 1-km Intensive Study Areas (ISA), where

  11. Anomalous transport in fracture networks: field scale experiments and modelling

    NASA Astrophysics Data System (ADS)

    Kang, P. K.; Le Borgne, T.; Bour, O.; Dentz, M.; Juanes, R.

    2012-12-01

    Anomalous transport is widely observed in different settings and scales of transport through porous and fractured geologic media. A common signature of anomalous transport is the late-time power law tailing in breakthrough curves (BTCs) during tracer tests. Various conceptual models of anomalous transport have been proposed, including multirate mass transfer, continuous time random walk, and stream tube models. Since different conceptual models can produce equally good fits to a single BTC, tracer test interpretation has been plagued with ambiguity. Here, we propose to resolve such ambiguity by analyzing BTCs obtained from both convergent and push-pull flow configurations at two different fracture planes. We conducted field tracer tests in a fractured granite formation close to Ploemeur, France. We observe that BTC tailing depends on the flow configuration and the injection fracture. Specifically the tailing disappears under push-pull geometry, and when we injected at a fracture with high flux (Figure 1). This indicates that for this fractured granite, BTC tailing is controlled by heterogeneous advection and not by matrix diffusion. To explain the change in tailing behavior for different flow configurations, we employ a simple lattice network model with heterogeneous conductivity distribution. The model assigns random conductivities to the fractures and solves the Darcy equation for an incompressible fluid, enforcing mass conservation at fracture intersections. The mass conservation constraint yields a correlated random flow through the fracture system. We investigate whether BTC tailing can be explained by the spatial distribution of preferential flow paths and stagnation zones, which is controlled by the conductivity variance and correlation length. By combining the results from the field tests and numerical modeling, we show that the reversibility of spreading is a key mechanism that needs to be captured. We also demonstrate the dominant role of the injection

  12. Ozone process insights from field experiments - part I: overview

    NASA Astrophysics Data System (ADS)

    Hidy, G. M.

    This paper gives an overview of selected approaches recently adopted to analyze observations from field experiments that characterize the tropospheric physics and chemistry of ozone and related oxidation products. Analysis of ambient oxidant and precursor concentration measurements, combined with meteorological observations, has provided important information about tropospheric processes. Projection of the response of tropospheric ozone concentrations to changes in precursor emissions is achieved through emissions based air quality models (AQMs). These models integrate several "process" elements from source emissions to meteorological and chemical phenomena. Through field campaigns, new knowledge has become available which has enabled workers to better understand the strengths and weaknesses of AQMs and their components. Examples of insightful results include: (a) reconciliation of ambient concentrations of speciated volatile organic compounds (VOCs) with estimates from emissions models, and inventories, (b) verification of chemical mechanisms for ozone formation from its precursors using approximations applicable in different chemical regimes, (c) inference of regimes of sensitivity in ozone concentration to changes in VOC and NO x precursors from ozone management practices, (d) conceptualization of important air mass transport and mixing processes on different spatial and temporal scales that affect ozone and precursor concentrations distributions, and (e) application of the analysis of spatial and temporal variance to infer the origins of chemical product transport, and precursor distributions. Studies from the first category have been used to improve emissions models substantially over previous forms. The remainder of the analyses has yielded valuable insight into the chemical and meteorological mechanisms at work on different spatial and temporal scales. The methods have provided an observationally based framework for effective choices to improve ozone

  13. Experiments of Flow Field Influenced by Vegetation Distribution on Floodplain

    NASA Astrophysics Data System (ADS)

    Li, Jin-Fu; Wang, Shun-Chang; Chen, Su-Chin

    2015-04-01

    The vegetation on floodplain can block river flow, raise flood level, and scour riverbed downstream the vegetation region. However, it can also protect the dike, reduce flood velocity, and increase the stability of channel. This experiment analyzed the relationship between vegetation distribution and flow field. We designed three vegetation arrangement pattern of unilateral vegetation, unilateral interval vegetation and no vegetation, respectively. The unilateral vegetation was defined as a 4.9 m length and 0.5 m width with vegetative area in one side of the experiment flume. The unilateral interval vegetation was defined as the same dimension of vegetative area but inserted 2 gaps with 1 m interval, and the vegetative area was separated into 3 blocks. The model of a single plant was assembled with stem and frond. The stem was a woody cylinder with 10 cm height and 2.2 cm in diameter. The other part was plastic frond with 10 cm in height. The flume was 20 m length, 1 m width and 0.7 m height with 2 kinds of bed slopes in 0.001 and 0.002, and 3 different discharges in 0.2 m3/s, 0.145 m3/s and 0.0855 m3/s. The velocity was measured by 2-D electromagnetic velocimeter (ACM2-R2). In addition, water depth was measured by Vernier calipers. The velocity distribution showed that the current were divided into two parts. In the part of inside vegetation area, water level uplifted when flow entering the vegetation area, and it declined until the current leaving vegetation area. Compared with the current in the other half part of flume, the magnitudes of uplift were about 50% in both case of unilateral vegetation and unilateral interval vegetation. Downstream the vegetation area edge, the water level dropped immediately and violently. The water depth was shallower than that in the other half non-vegetation part, and the decline magnitude were 48% and 39% in cases of unilateral vegetation and unilateral interval vegetation, respectively. To explain this phenomenon, we measured

  14. High Magnetic field generation for laser-plasma experiments

    SciTech Connect

    Pollock, B B; Froula, D H; Davis, P F; Ross, J S; Fulkerson, S; Bower, J; Satariano, J; Price, D; Glenzer, S H

    2006-05-01

    An electromagnetic solenoid was developed to study the effect of magnetic fields on electron thermal transport in laser plasmas. The solenoid, which is driven by a pulsed power system suppling 30 kJ, achieves magnetic fields of 13 T. The field strength was measured on the solenoid axis with a magnetic probe and optical Zeeman splitting. The measurements agree well with analytical estimates. A method for optimizing the solenoid design to achieve magnetic fields exceeding 20 T is presented.

  15. Gene expression in Pseudomonas aeruginosa swarming motility

    PubMed Central

    2010-01-01

    Background The bacterium Pseudomonas aeruginosa is capable of three types of motilities: swimming, twitching and swarming. The latter is characterized by a fast and coordinated group movement over a semi-solid surface resulting from intercellular interactions and morphological differentiation. A striking feature of swarming motility is the complex fractal-like patterns displayed by migrating bacteria while they move away from their inoculation point. This type of group behaviour is still poorly understood and its characterization provides important information on bacterial structured communities such as biofilms. Using GeneChip® Affymetrix microarrays, we obtained the transcriptomic profiles of both bacterial populations located at the tip of migrating tendrils and swarm center of swarming colonies and compared these profiles to that of a bacterial control population grown on the same media but solidified to not allow swarming motility. Results Microarray raw data were corrected for background noise with the RMA algorithm and quantile normalized. Differentially expressed genes between the three conditions were selected using a threshold of 1.5 log2-fold, which gave a total of 378 selected genes (6.3% of the predicted open reading frames of strain PA14). Major shifts in gene expression patterns are observed in each growth conditions, highlighting the presence of distinct bacterial subpopulations within a swarming colony (tendril tips vs. swarm center). Unexpectedly, microarrays expression data reveal that a minority of genes are up-regulated in tendril tip populations. Among them, we found energy metabolism, ribosomal protein and transport of small molecules related genes. On the other hand, many well-known virulence factors genes were globally repressed in tendril tip cells. Swarm center cells are distinct and appear to be under oxidative and copper stress responses. Conclusions Results reported in this study show that, as opposed to swarm center cells, tendril

  16. Genetic Particle Swarm Optimization-Based Feature Selection for Very-High-Resolution Remotely Sensed Imagery Object Change Detection.

    PubMed

    Chen, Qiang; Chen, Yunhao; Jiang, Weiguo

    2016-01-01

    In the field of multiple features Object-Based Change Detection (OBCD) for very-high-resolution remotely sensed images, image objects have abundant features and feature selection affects the precision and efficiency of OBCD. Through object-based image analysis, this paper proposes a Genetic Particle Swarm Optimization (GPSO)-based feature selection algorithm to solve the optimization problem of feature selection in multiple features OBCD. We select the Ratio of Mean to Variance (RMV) as the fitness function of GPSO, and apply the proposed algorithm to the object-based hybrid multivariate alternative detection model. Two experiment cases on Worldview-2/3 images confirm that GPSO can significantly improve the speed of convergence, and effectively avoid the problem of premature convergence, relative to other feature selection algorithms. According to the accuracy evaluation of OBCD, GPSO is superior at overall accuracy (84.17% and 83.59%) and Kappa coefficient (0.6771 and 0.6314) than other algorithms. Moreover, the sensitivity analysis results show that the proposed algorithm is not easily influenced by the initial parameters, but the number of features to be selected and the size of the particle swarm would affect the algorithm. The comparison experiment results reveal that RMV is more suitable than other functions as the fitness function of GPSO-based feature selection algorithm. PMID:27483285

  17. Emergent behavioural phenotypes of swarming models revealed by mimicking a frustrated anti-ferromagnet

    PubMed Central

    Pearce, D. J. G.; Turner, M. S.

    2015-01-01

    Self-propelled particle (SPP) models are often compared with animal swarms. However, the collective animal behaviour observed in experiments often leaves considerable unconstrained freedom in the structure of a proposed model. Essentially, multiple models can describe the observed behaviour of animal swarms in simple environments. To tackle this degeneracy, we study swarms of SPPs in non-trivial environments as a new approach to distinguish between candidate models. We restrict swarms of SPPs to circular (periodic) channels where they polarize in one of two directions (like spins) and permit information to pass through windows between neighbouring channels. Co-alignment between particles then couples the channels (anti-ferromagnetically) so that they tend to counter-rotate. We study channels arranged to mimic a geometrically frustrated anti-ferromagnet and show how the effects of this frustration allow us to better distinguish between SPP models. Similar experiments could therefore improve our understanding of collective motion in animals. Finally, we discuss how the spin analogy can be exploited to construct universal logic gates, and therefore swarming systems that can function as Turing machines. PMID:26423438

  18. Emergent behavioural phenotypes of swarming models revealed by mimicking a frustrated anti-ferromagnet.

    PubMed

    Pearce, D J G; Turner, M S

    2015-10-01

    Self-propelled particle (SPP) models are often compared with animal swarms. However, the collective animal behaviour observed in experiments often leaves considerable unconstrained freedom in the structure of a proposed model. Essentially, multiple models can describe the observed behaviour of animal swarms in simple environments. To tackle this degeneracy, we study swarms of SPPs in non-trivial environments as a new approach to distinguish between candidate models. We restrict swarms of SPPs to circular (periodic) channels where they polarize in one of two directions (like spins) and permit information to pass through windows between neighbouring channels. Co-alignment between particles then couples the channels (anti-ferromagnetically) so that they tend to counter-rotate. We study channels arranged to mimic a geometrically frustrated anti-ferromagnet and show how the effects of this frustration allow us to better distinguish between SPP models. Similar experiments could therefore improve our understanding of collective motion in animals. Finally, we discuss how the spin analogy can be exploited to construct universal logic gates, and therefore swarming systems that can function as Turing machines. PMID:26423438

  19. Collective navigation of cargo-carrying swarms

    PubMed Central

    Shklarsh, Adi; Finkelshtein, Alin; Ariel, Gil; Kalisman, Oren; Ingham, Colin; Ben-Jacob, Eshel

    2012-01-01

    Much effort has been devoted to the study of swarming and collective navigation of micro-organisms, insects, fish, birds and other organisms, as well as multi-agent simulations and to the study of real robots. It is well known that insect swarms can carry cargo. The studies here are motivated by a less well-known phenomenon: cargo transport by bacteria swarms. We begin with a concise review of how bacteria swarms carry natural, micrometre-scale objects larger than the bacteria (e.g. fungal spores) as well as man-made beads and capsules (for drug delivery). A comparison of the trajectories of virtual beads in simulations (using different putative coupling between the virtual beads and the bacteria) with the observed trajectories of transported fungal spores implies the existence of adaptable coupling. Motivated by these observations, we devised new, multi-agent-based studies of cargo transport by agent swarms. As a first step, we extended previous modelling of collective navigation of simple bacteria-inspired agents in complex terrain, using three putative models of agent–cargo coupling. We found that cargo-carrying swarms can navigate efficiently in a complex landscape. We further investigated how the stability, elasticity and other features of agent–cargo bonds influence the collective motion and the transport of the cargo, and found sharp phase shifts and dual successful strategies for cargo delivery. Further understanding of such mechanisms may provide valuable clues to understand cargo-transport by smart swarms of other organisms as well as by man-made swarming robots. PMID:24312731

  20. Investigating the Origin of Seismic Swarms

    NASA Astrophysics Data System (ADS)

    Govoni, Aladino; Passarelli, Luigi; Braun, Thomas; Maccaferri, Francesco; Moretti, Milena; Lucente, Francesco Pio; Rivalta, Eleonora; Cesca, Simone; Hainzl, Sebastian; Woith, Heiko; De Gori, Pasquale; Dahm, Torsten; Chiarabba, Claudio; Margheriti, Lucia

    2013-10-01

    According to the U.S. Geological Survey's Earthquake Hazards Program, a seismic swarm is "a localized surge of earthquakes, with no one shock being conspicuously larger than all other shocks of the swarm. They might occur in a variety of geologic environments and are not known to be indicative of any change in the long-term seismic risk of the region in which they occur" (http://vulcan.wr.usgs.gov/Glossary/Seismicity/description_earthquakes.html).

  1. Calculations of transient fields in the Felix experiments at Argonne using null field integrated techniques

    NASA Astrophysics Data System (ADS)

    Han, H. C.; Davey, K. R.; Turner, L.

    1985-08-01

    The transient eddy current problem is characteristically computationally intensive. The motivation for this research was to realize an efficient, accurate, solution technique involving small matrices via an eigenvalue approach. Such a technique is indeed realized and tested using the null field integral technique. Using smart (i.e., efficient, global) basis functions to represent unknowns in terms of a minimum number of unknowns, homogeneous eigenvectors and eigenvalues are first determined. The general excitatory response is then represented in terms of these eigenvalues/eigenvectors. Excellent results are obtained for the Argonne Felix cylinder experiments using a 4 x 4 matrix. Extension to the 3-D problem (short cylinder) is set up in terms of an 8 x 8 matrix.

  2. Male motion coordination in anopheline mating swarms.

    PubMed

    Shishika, Daigo; Manoukis, Nicholas C; Butail, Sachit; Paley, Derek A

    2014-01-01

    The Anopheles gambiae species complex comprises the primary vectors of malaria in much of sub-Saharan Africa. Most of the mating in these species occurs in swarms composed almost entirely of males. Intermittent, organized patterns in such swarms have been observed, but a detailed description of male-male interactions has not previously been available. We identify frequent, time-varying interactions characterized by periods of parallel flight in data from 8 swarms of Anopheles gambiae and 3 swarms of Anopheles coluzzii filmed in 2010 and 2011 in the village of Donéguébogou, Mali. We use the cross correlation of flight direction to quantify these interactions and to induce interaction graphs, which show that males form synchronized subgroups whose size and membership change rapidly. A swarming model with damped springs between each male and the swarm centroid shows good agreement with the correlation data, provided that local interactions represented by damping of relative velocity between males are included. PMID:25212874

  3. Male motion coordination in anopheline mating swarms

    PubMed Central

    Shishika, Daigo; Manoukis, Nicholas C.; Butail, Sachit; Paley, Derek A.

    2014-01-01

    The Anopheles gambiae species complex comprises the primary vectors of malaria in much of sub-Saharan Africa. Most of the mating in these species occurs in swarms composed almost entirely of males. Intermittent, organized patterns in such swarms have been observed, but a detailed description of male-male interactions has not previously been available. We identify frequent, time-varying interactions characterized by periods of parallel flight in data from 8 swarms of Anopheles gambiae and 3 swarms of Anopheles coluzzii filmed in 2010 and 2011 in the village of Donéguébogou, Mali. We use the cross correlation of flight direction to quantify these interactions and to induce interaction graphs, which show that males form synchronized subgroups whose size and membership change rapidly. A swarming model with damped springs between each male and the swarm centroid shows good agreement with the correlation data, provided that local interactions represented by damping of relative velocity between males are included. PMID:25212874

  4. Spatial distribution and male mating success of Anopheles gambiae swarms

    PubMed Central

    2011-01-01

    Background Anopheles gambiae mates in flight at particular mating sites over specific landmarks known as swarm markers. The swarms are composed of males; females typically approach a swarm, and leave in copula. This mating aggregation looks like a lek, but appears to lack the component of female choice. To investigate the possible mechanisms promoting the evolution of swarming in this mosquito species, we looked at the variation in mating success between swarms and discussed the factors that structure it in light of the three major lekking models, known as the female preference model, the hotspot model, and the hotshot model. Results We found substantial variation in swarm size and in mating success between swarms. A strong correlation between swarm size and mating success was observed, and consistent with the hotspot model of lek formation, the per capita mating success of individual males did not increase with swarm size. For the spatial distribution of swarms, our results revealed that some display sites were more attractive to both males and females and that females were more attracted to large swarms. While the swarm markers we recognize help us in localizing swarms, they did not account for the variation in swarm size or in the swarm mating success, suggesting that mosquitoes probably are attracted to these markers, but also perceive and respond to other aspects of the swarming site. Conclusions Characterizing the mating system of a species helps understand how this species has evolved and how selective pressures operate on male and female traits. The current study looked at male mating success of An. gambiae and discussed possible factors that account for its variation. We found that swarms of An. gambiae conform to the hotspot model of lek formation. But because swarms may lack the female choice component, we propose that the An. gambiae mating system is a lek-like system that incorporates characteristics pertaining to other mating systems such as scramble

  5. Seismic Swarms at Paricutin Volcano Area. Magmatic Intrusion or Tectonic Seismicity?

    NASA Astrophysics Data System (ADS)

    Pinzon, J. I.; Nunez-Cornu, F. J.; Escudero, C. R.; Rowe, C. A.

    2014-12-01

    We relocate a seismic swarm with more than 700 earthquakes that took place between May and June 2006 in the Paricutin volcano area, Mexico inside of the Michoacan monogenetic volcanic field. This seismic swarm was recorded by the project "Mapping the Riviera Subduction Zone" (MARS), a temporary seismic network that was installed in the states of Jalisco, Colima and Michoacán between January 2006 and June 2007. Previously seismic swarms in the area were reported in the years of 1997, 1999 and 2000. For one that took place in the year of 1997 the Servicio Sismologico Nacional deployed a local network in the area, they conclude that the source of the seismicity was tectonic with depths between 18 and 12 km. The episodes of 1999 and 2000 were reported as similar to the 1997 swarm. A previous analysis of the 2006 swarm concludes that the depth of seismicity migrates from 9 to 5 km and was originated by a magmatic intrusion. We did a relocation of this swarm reading all the events and using Hypo71 and the P-wave velocity model used by the Jalisco Seismic and Acelerometric Network; a waveform analysis using cross-correlation method was also carried out. We obtained 15 earthquakes families with a correlation factor equal or greater than 0.79 and composed focal mechanism for each family. These families present a migration in depth beginning at 16 km and ended at 9 km. Our results agrees with a magmatic intrusion, but not so shallow as the previous study of the 2006 swarm.

  6. Determination of equilibrium electron temperature and times using an electron swarm model with BOLSIG+ calculated collision frequencies and rate coefficients

    DOE PAGESBeta

    Pusateri, Elise N.; Morris, Heidi E.; Nelson, Eric M.; Ji, Wei

    2015-08-04

    Electromagnetic pulse (EMP) events produce low-energy conduction electrons from Compton electron or photoelectron ionizations with air. It is important to understand how conduction electrons interact with air in order to accurately predict EMP evolution and propagation. An electron swarm model can be used to monitor the time evolution of conduction electrons in an environment characterized by electric field and pressure. Here a swarm model is developed that is based on the coupled ordinary differential equations (ODEs) described by Higgins et al. (1973), hereinafter HLO. The ODEs characterize the swarm electric field, electron temperature, electron number density, and drift velocity. Importantmore » swarm parameters, the momentum transfer collision frequency, energy transfer collision frequency, and ionization rate, are calculated and compared to the previously reported fitted functions given in HLO. These swarm parameters are found using BOLSIG+, a two term Boltzmann solver developed by Hagelaar and Pitchford (2005), which utilizes updated cross sections from the LXcat website created by Pancheshnyi et al. (2012). We validate the swarm model by comparing to experimental effective ionization coefficient data in Dutton (1975) and drift velocity data in Ruiz-Vargas et al. (2010). In addition, we report on electron equilibrium temperatures and times for a uniform electric field of 1 StatV/cm for atmospheric heights from 0 to 40 km. We show that the equilibrium temperature and time are sensitive to the modifications in the collision frequencies and ionization rate based on the updated electron interaction cross sections.« less

  7. Determination of equilibrium electron temperature and times using an electron swarm model with BOLSIG+ calculated collision frequencies and rate coefficients

    NASA Astrophysics Data System (ADS)

    Pusateri, Elise N.; Morris, Heidi E.; Nelson, Eric M.; Ji, Wei

    2015-08-01

    Electromagnetic pulse (EMP) events produce low-energy conduction electrons from Compton electron or photoelectron ionizations with air. It is important to understand how conduction electrons interact with air in order to accurately predict EMP evolution and propagation. An electron swarm model can be used to monitor the time evolution of conduction electrons in an environment characterized by electric field and pressure. Here a swarm model is developed that is based on the coupled ordinary differential equations (ODEs) described by Higgins et al. (1973), hereinafter HLO. The ODEs characterize the swarm electric field, electron temperature, electron number density, and drift velocity. Important swarm parameters, the momentum transfer collision frequency, energy transfer collision frequency, and ionization rate, are calculated and compared to the previously reported fitted functions given in HLO. These swarm parameters are found using BOLSIG+, a two term Boltzmann solver developed by Hagelaar and Pitchford (2005), which utilizes updated cross sections from the LXcat website created by Pancheshnyi et al. (2012). We validate the swarm model by comparing to experimental effective ionization coefficient data in Dutton (1975) and drift velocity data in Ruiz-Vargas et al. (2010). In addition, we report on electron equilibrium temperatures and times for a uniform electric field of 1 StatV/cm for atmospheric heights from 0 to 40 km. It is shown that the equilibrium temperature and time are sensitive to the modifications in the collision frequencies and ionization rate based on the updated electron interaction cross sections.

  8. Determination of equilibrium electron temperature and times using an electron swarm model with BOLSIG+ calculated collision frequencies and rate coefficients

    SciTech Connect

    Pusateri, Elise N.; Morris, Heidi E.; Nelson, Eric M.; Ji, Wei

    2015-08-04

    Electromagnetic pulse (EMP) events produce low-energy conduction electrons from Compton electron or photoelectron ionizations with air. It is important to understand how conduction electrons interact with air in order to accurately predict EMP evolution and propagation. An electron swarm model can be used to monitor the time evolution of conduction electrons in an environment characterized by electric field and pressure. Here a swarm model is developed that is based on the coupled ordinary differential equations (ODEs) described by Higgins et al. (1973), hereinafter HLO. The ODEs characterize the swarm electric field, electron temperature, electron number density, and drift velocity. Important swarm parameters, the momentum transfer collision frequency, energy transfer collision frequency, and ionization rate, are calculated and compared to the previously reported fitted functions given in HLO. These swarm parameters are found using BOLSIG+, a two term Boltzmann solver developed by Hagelaar and Pitchford (2005), which utilizes updated cross sections from the LXcat website created by Pancheshnyi et al. (2012). We validate the swarm model by comparing to experimental effective ionization coefficient data in Dutton (1975) and drift velocity data in Ruiz-Vargas et al. (2010). In addition, we report on electron equilibrium temperatures and times for a uniform electric field of 1 StatV/cm for atmospheric heights from 0 to 40 km. We show that the equilibrium temperature and time are sensitive to the modifications in the collision frequencies and ionization rate based on the updated electron interaction cross sections.

  9. SUPERVISED FIELD EXPERIENCE AND INTERNSHIP PROGRAMS IN EDUCATIONAL ADMINISTRATION AND SUPERVISION IN THE CALIFORNIA STATE COLLEGES.

    ERIC Educational Resources Information Center

    JOHNS, W. LLOYD

    A SURVEY OF EXISTING FIELD EXPERIENCE PROGRAMS IN THE 18 CALIFORNIA STATE COLLEGES WAS CONDUCTED TO IDENTIFY THE CHARACTERISTICS OF A HIGH-QUALITY SUPERVISED FIELD-EXPERIENCE PROGRAM IN EDUCATIONAL ADMINISTRATION AND SUPERVISION. DATA FOR MAJOR FINDINGS WERE COLLECTED FROM (1) A REVIEW OF THE LITERATURE, (2) AN EXAMINATION OF FIELD-EXPERIENCE…

  10. Field Experiments Aimed To The Analysis of Flood Generation Processes

    NASA Astrophysics Data System (ADS)

    Carriero, D.; Iacobellis, V.; Oliveto, G.; Romano, N.; Telesca, V.; Fiorentino, M.

    The study of the soil moisture dynamics and of the climate-soil-vegetation interac- tion is essential for the comprehension of possible climatic change phenomena, as well as for the analysis of occurrence of extreme hydrological events. In this trend the theoretically-based distribution of floods recently derived by Fiorentino and Ia- cobellis, [ŞNew insights about the climatic and geologic control on the probability distribution of floodsT, Water Resources Research, 2001, 37: 721-730] demonstrated, by an application in some Southern Italy basins, that processes at the hillslope scale strongly influence the basin response by means of the different mechanisms of runoff generation produced by various distributions of partial area contributing. This area is considered as a stochastic variable whose pdf position parameter showed strong de- pendence on the climate as it can seen in the studied basins behavior: in dry zones, where there is the prevalence of the infiltration excess (Horton) mechanism, the basin water loss parameter decreases as basin area increases and the flood peak source area depends on the permeability of soils; in humid zones, with the prevalence of satu- ration excess (Dunne) process, the loss parameter seems independent from the basin area and very sensitive to simple climatic index while only small portion of the area invested by the storm contributes to floods. The purpose of this work is to investigate the consistency of those interpretations by means of field experiments at the hillslope scale to establish a parameterization accounting for soil physical and hydraulic prop- erties, vegetation characteristics and land-use. The research site is the catchment of River Fiumarella di Corleto, which is located in Basilicata Region, Italy, and has a drainage area of approximately 32 km2. The environment has a rather dynamic geo- morphology and very interesting features from the soil-landscape modeling viewpoint [Santini A., A. Coppola, N. Romano, and

  11. Stochastic pattern transitions in large scale swarms

    NASA Astrophysics Data System (ADS)

    Schwartz, Ira; Lindley, Brandon; Mier-Y-Teran, Luis

    2013-03-01

    We study the effects of time dependent noise and discrete, randomly distributed time delays on the dynamics of a large coupled system of self-propelling particles. Bifurcation analysis on a mean field approximation of the system reveals that the system possesses patterns with certain universal characteristics that depend on distinguished moments of the time delay distribution. We show both theoretically and numerically that although bifurcations of simple patterns, such as translations, change stability only as a function of the first moment of the time delay distribution, more complex bifurcating patterns depend on all of the moments of the delay distribution. In addition, we show that for sufficiently large values of the coupling strength and/or the mean time delay, there is a noise intensity threshold, dependent on the delay distribution width, that forces a transition of the swarm from a misaligned state into an aligned state. We show that this alignment transition exhibits hysteresis when the noise intensity is taken to be time dependent. Research supported by the Office of Naval Research

  12. Exploring the Role of Field Experience Context in Preservice Teachers' Development as Mathematics Educators

    ERIC Educational Resources Information Center

    Cooper, Sandi; Nesmith, Suzanne

    2013-01-01

    Although the importance of field experience is supported and attended to by teacher education programs across the United States, there have been numerous national reports and research findings stressing the need for major improvements in the preparation of teachers with an emphasis on more authentic experiences. Quality field experiences have the…

  13. School's IN for Summer: An Alternative Field Experience for Elementary Science Methods Students

    ERIC Educational Resources Information Center

    Hanuscin, Deborah L.; Musikul, Kusalin

    2007-01-01

    Field experiences are critical to teacher learning and enhance the effectiveness of methods courses; however, when methods courses are offered in the summer, traditional school-based field experiences are not possible. This article describes an alternative campus-based experience created as part of an elementary science methods course. The Summer…

  14. The Examination of a Mentoring Relationship during a Metadiscrete Physical Education Field Experience

    ERIC Educational Resources Information Center

    Bower, Glenna G.; Bonnett, Stephanie

    2009-01-01

    Universities strive to graduate well-rounded individuals with opportunities to gain knowledge in the classroom and experience in the "real world". Therefore, many colleges focus their attention to offering discrete field experiences. However, few universities offer metadiscrete field experiences, with students majoring in exercise science or…

  15. A Field Trip to Gettysburg: A Model Experience.

    ERIC Educational Resources Information Center

    Olcott, Mark S.

    1987-01-01

    Using Gettysburg as an example, the author addresses the major components of a successful field trip, such as pre-teaching, memorizing, and the study of primary sources. Includes information on student participation and other factors of a successful field trip. (GEA)

  16. What have we Learned after a Decade of Experiments and Monitoring at the NEES@UCSB Permanently Instrumented Field Sites?

    NASA Astrophysics Data System (ADS)

    Steidl, J. H.; Civilini, F.; Seale, S. H.; Hegarty, P.

    2013-12-01

    The Wildlife Liquefaction Array (WLA) and Garner Valley Downhole Array (GVDA) located in southern California are facilities that for the last decade have been supported under the National Science Foundations George E. Brown, Jr., Network for Earthquake Engineering Simulation (NEES) program. These densely instrumented geotechnical and structural engineering field sites continuously record both acceleration and pore pressure, with accelerometers located on the surface and at various depths below the surface, and pore pressure transducers installed at depth within the liquefiable layers. Permanently instrumented structures for examining soil-foundation-structure interaction and a permanent cross-hole array at the sites have transformed these sites into multi-disciplinary earthquake engineering research facilities. Over the last decade, local and regional seismic activity, including multiple extremely active earthquake swarms, have produced a valuable new data set providing a unique opportunity to observe site response and the evolution of pore pressure generation with time throughout the liquefiable layer at an unprecedented level of detail. In addition to the earthquakes provided by nature, active testing experiments using the mobile shakers from NEES@UTexas and NEES@UCLA have produced an equally valuable data set on both site characterization studies and soil-foundation-structure interaction. The new observations of pore pressure and acceleration with depth are providing in situ empirical evidence documenting the range of ground motion levels at which the onset of nonlinear behavior and excess pore pressure begins, augmenting previous case history data, and laboratory data from cyclic tri-axial and centrifuge testing. The largest static pore pressure increases observed in the 'NEES' decade of monitoring were generated by four events at the WLA site, ranging in magnitude from 4.6 to 5.4 and all at distances less than 10km from the site. The largest peak horizontal

  17. Triggered Swarms and Induced Aftershock Sequences in Geothermal Systems

    NASA Astrophysics Data System (ADS)

    Shcherbakov, R.; Turcotte, D. L.; Yikilmaz, M. B.; Kellogg, L. H.; Rundle, J. B.

    2015-12-01

    Natural geothermal systems, which are used for energy generation, are usually associated with high seismic activity. This can be related to the large-scale injection and extraction of fluids to enhance geothermal recovery. This results in the changes of the pore pressure and pore-elastic stress field and can stimulate the occurrence of earthquakes. These systems are also prone to triggering of seismicity by the passage of seismic waves generated by large distant main shocks. In this study, we analyze clustering and triggering of seismicity at several geothermal fields in California. Particularly, we consider the seismicity at the Geysers, Coso, and Salton Sea geothermal fields. We analyze aftershock sequences generated by local large events with magnitudes greater than 4.0 and earthquake swarms generated by several significant long distant main shocks. We show that the rate of the aftershock sequences generated by the local large events in the two days before and two days after the reference event can be modelled reasonably well by the time dependent Epidemic Type Aftershock Sequence (ETAS) model. On the other hand, the swarms of activity triggered by large distant earthquakes cannot be described by the ETAS model. To model the increase in the rate of seismicity associated with triggering by large distant main shocks we introduce an additional time-dependent triggering mechanism into the ETAS model. In almost all cases the frequency-magnitude statistics of triggered sequences follow Gutenberg-Richter scaling to a good approximation. The analysis indicates that the seismicity triggered by relatively large local events can initiate sequences similar to regular aftershock sequences. In contrast, the distant main shocks trigger swarm like activity with faster decaying rates.

  18. Psychologists and the Incarcerated: New Trainees' Experience in the Field

    ERIC Educational Resources Information Center

    Edwards, Daniel J.

    2010-01-01

    The purpose of this study was to explore clinical psychologist trainees' perceptions of incarcerated individuals after a practicum experience at a local jail. A qualitative methodology, Interpretive Phenomenological Analysis, was utilized to explore subjective experiences and determine if participants' attitudes and beliefs were challenged with…

  19. Near-field spillover from a subreflector: Theory and experiment

    NASA Technical Reports Server (NTRS)

    Lee, S. W.; Acosta, R.; Cherrette, A. R.; Lam, P. T.

    1986-01-01

    In a dual reflector antenna, the spillover from the subreflector is important in determining the accuracy of near-field measurements. This is especially so when some of the feed elements are placed far away from the focus. In this paper, we present a high-frequency GTD analysis of the spillover field over a plane just behind the subreflector. Special attention is given to the field near the incident shadow boundary and the role played by the slope diffraction term. Our computations are in excellent agreement with experimental results.

  20. Hybridization Hotspots at Bat Swarming Sites

    PubMed Central

    Bogdanowicz, Wiesław; Piksa, Krzysztof; Tereba, Anna

    2012-01-01

    During late summer and early autumn in temperate zones of the Northern Hemisphere, thousands of bats gather at caves, mainly for the purpose of mating. We demonstrated that this swarming behavior most probably leads not only to breeding among bats of the same species but also interbreeding between different species. Using 14 nuclear microsatellites and three different methods (the Bayesian assignment approaches of STRUCTURE and NEWHYBRIDS and a principal coordinate analysis of pairwise genetic distances), we analyzed 375 individuals belonging to three species of whiskered bats (genus Myotis) at swarming sites across their sympatric range in southern Poland. The overall hybridization rate varied from 3.2 to 7.2%. At the species level, depending on the method used, these values ranged from 2.1–4.6% in M. mystacinus and 3.0–3.7% in M. brandtii to 6.5–30.4% in M. alcathoe. Hybrids occurred in about half of the caves we studied. In all three species, the sex ratio of hybrids was biased towards males but the observed differences did not differ statistically from those noted at the population level. In our opinion, factors leading to the formation of these admixed individuals and their relatively high frequency are: i) swarming behaviour at swarming sites, where high numbers of bats belonging to several species meet; ii) male-biased sex ratio during the swarming period; iii) the fact that all these bats are generally polygynous. The highly different population sizes of different species at swarming sites may also play some role. Swarming sites may represent unique hybrid hotspots, which, as there are at least 2,000 caves in the Polish Carpathians alone, may occur on a massive scale not previously observed for any group of mammal species in the wild. Evidently, these sites should be treated as focal points for the conservation of biodiversity and evolutionary processes. PMID:23300912

  1. Electron swarm parameters of the hydrofluoroolefine HFO1234ze

    NASA Astrophysics Data System (ADS)

    Chachereau, A.; Rabie, M.; Franck, C. M.

    2016-08-01

    In this contribution, the electron swarm parameters of the hydrofluoroolefine HFO1234ze (systematic name trans-1,3,3,3-tetrafluoro-1-propene) are experimentally investigated. The analysis of the electron avalanche current measured in a pulsed Townsend experiment yields the effective ionization rate coefficient, the electron drift velocity and the longitudinal electron diffusion coefficient. The subsequent ion current is analyzed as well, to obtain separately the ionization and attachment rate coefficients. Measurements in pure HFO1234ze at different pressures show that the effective ionization rate is strongly influenced by three-body attachment and the three-body attachment rate coefficient is derived.

  2. The Role of Neighbours Selection on Cohesion and Order of Swarms

    PubMed Central

    Calvão, Angelo M.; Brigatti, Edgardo

    2014-01-01

    We introduce a multi-agent model for exploring how selection of neighbours determines some aspects of order and cohesion in swarms. The model algorithm states that every agents' motion seeks for an optimal distance from the nearest topological neighbour encompassed in a limited attention field. Despite the great simplicity of the implementation, varying the amplitude of the attention landscape, swarms pass from cohesive and regular structures towards fragmented and irregular configurations. Interestingly, this movement rule is an ideal candidate for implementing the selfish herd hypothesis which explains aggregation of alarmed group of social animals. PMID:24809718

  3. A Winner Determination Algorithm for Combinatorial Auctions Based on Hybrid Artificial Fish Swarm Algorithm

    NASA Astrophysics Data System (ADS)

    Zheng, Genrang; Lin, ZhengChun

    The problem of winner determination in combinatorial auctions is a hotspot electronic business, and a NP hard problem. A Hybrid Artificial Fish Swarm Algorithm(HAFSA), which is combined with First Suite Heuristic Algorithm (FSHA) and Artificial Fish Swarm Algorithm (AFSA), is proposed to solve the problem after probing it base on the theories of AFSA. Experiment results show that the HAFSA is a rapidly and efficient algorithm for The problem of winner determining. Compared with Ant colony Optimization Algorithm, it has a good performance with broad and prosperous application.

  4. A Regular Tetrahedron Formation Strategy for Swarm Robots in Three-Dimensional Environment

    NASA Astrophysics Data System (ADS)

    Ercan, M. Fikret; Li, Xiang; Liang, Ximing

    A decentralized control method, namely Regular Tetrahedron Formation (RTF), is presented for a swarm of simple robots operating in three-dimensional space. It is based on virtual spring mechanism and enables four neighboring robots to autonomously form a Regular Tetrahedron (RT) regardless of their initial positions. RTF method is applied to various sizes of swarms through a dynamic neighbor selection procedure. Each robot's behavior depends only on position of three dynamically selected neighbors. An obstacle avoidance model is also introduced. Final, algorithm is studied with computational experiments which demonstrated that it is effective.

  5. Long-range Acoustic Interactions in Insect Swarms: An Adaptive Gravity Model

    NASA Astrophysics Data System (ADS)

    Gorbonos, Dan; Ianconescu, Reuven; Puckett, James G.; Ni, Rui; Ouellette, Nicholas T.; Gov, Nir S.

    The collective motion of groups of animals emerges from the net effect of the interactions between individual members of the group. In many cases, such as birds, fish, or ungulates, these interactions are mediated by sensory stimuli that predominantly arise from nearby neighbors. But not all stimuli in animal groups are short range. Here, we consider mating swarms of midges, which interact primarily via long-range acoustic stimuli. We exploit the similarity in form between the decay of acoustic and gravitational sources to build a model for swarm behavior. By accounting for the adaptive nature of the midges' acoustic sensing, we show that our ``adaptive gravity'' model makes mean-field predictions that agree well with experimental observations of laboratory swarms. Our results highlight the role of sensory mechanisms and interaction range in collective animal behavior. The adaptive interactions that we present here open a new class of equations of motion, which may appear in other biological contexts.

  6. An Approach to Self-Assembling Swarm Robots Using Multitree Genetic Programming

    PubMed Central

    An, Jinung

    2013-01-01

    In recent days, self-assembling swarm robots have been studied by a number of researchers due to their advantages such as high efficiency, stability, and scalability. However, there are still critical issues in applying them to practical problems in the real world. The main objective of this study is to develop a novel self-assembling swarm robot algorithm that overcomes the limitations of existing approaches. To this end, multitree genetic programming is newly designed to efficiently discover a set of patterns necessary to carry out the mission of the self-assembling swarm robots. The obtained patterns are then incorporated into their corresponding robot modules. The computational experiments prove the effectiveness of the proposed approach. PMID:23861655

  7. An approach to self-assembling swarm robots using multitree genetic programming.

    PubMed

    Lee, Jong-Hyun; Ahn, Chang Wook; An, Jinung

    2013-01-01

    In recent days, self-assembling swarm robots have been studied by a number of researchers due to their advantages such as high efficiency, stability, and scalability. However, there are still critical issues in applying them to practical problems in the real world. The main objective of this study is to develop a novel self-assembling swarm robot algorithm that overcomes the limitations of existing approaches. To this end, multitree genetic programming is newly designed to efficiently discover a set of patterns necessary to carry out the mission of the self-assembling swarm robots. The obtained patterns are then incorporated into their corresponding robot modules. The computational experiments prove the effectiveness of the proposed approach. PMID:23861655

  8. Self-organized sorting limits behavioral variability in swarms

    PubMed Central

    Copenhagen, Katherine; Quint, David A.; Gopinathan, Ajay

    2016-01-01

    Swarming is a phenomenon where collective motion arises from simple local interactions between typically identical individuals. Here, we investigate the effects of variability in behavior among the agents in finite swarms with both alignment and cohesive interactions. We show that swarming is abolished above a critical fraction of non-aligners who do not participate in alignment. In certain regimes, however, swarms above the critical threshold can dynamically reorganize and sort out excess non-aligners to maintain the average fraction close to the critical value. This persists even in swarms with a distribution of alignment interactions, suggesting a simple, robust and efficient mechanism that allows heterogeneously mixed populations to naturally regulate their composition and remain in a collective swarming state or even differentiate among behavioral phenotypes. We show that, for evolving swarms, this self-organized sorting behavior can couple to the evolutionary dynamics leading to new evolutionarily stable equilibrium populations set by the physical swarm parameters. PMID:27550316

  9. Self-organized sorting limits behavioral variability in swarms.

    PubMed

    Copenhagen, Katherine; Quint, David A; Gopinathan, Ajay

    2016-01-01

    Swarming is a phenomenon where collective motion arises from simple local interactions between typically identical individuals. Here, we investigate the effects of variability in behavior among the agents in finite swarms with both alignment and cohesive interactions. We show that swarming is abolished above a critical fraction of non-aligners who do not participate in alignment. In certain regimes, however, swarms above the critical threshold can dynamically reorganize and sort out excess non-aligners to maintain the average fraction close to the critical value. This persists even in swarms with a distribution of alignment interactions, suggesting a simple, robust and efficient mechanism that allows heterogeneously mixed populations to naturally regulate their composition and remain in a collective swarming state or even differentiate among behavioral phenotypes. We show that, for evolving swarms, this self-organized sorting behavior can couple to the evolutionary dynamics leading to new evolutionarily stable equilibrium populations set by the physical swarm parameters. PMID:27550316

  10. Structural Preconditions of West Bohemia Earthquake Swarms

    NASA Astrophysics Data System (ADS)

    Novotný, M.; Špičák, A.; Weinlich, F. H.

    2013-07-01

    The West Bohemia and adjacent Vogtland are well known for quasi-periodical earthquake swarms persisting for centuries. The seismogenic area near Nový Kostel involved about 90 % of overall earthquake activity clustered here in space and time. The latest major earthquake swarm took place in August-September 2011. In 1994 and 1997, two minor earthquake swarms appeared in another location, near Lazy. Recently, the depth-recursive tomography yielded a velocity image with an improved resolution along the CEL09 refraction profile passing between these swarm areas. The resolution, achieved in the velocity image and its agreement with the inverse gravity modeling along the collateral 9HR reflection profile, enabled us to reveal the key structural background of these West Bohemia earthquake swarms. The CEL09 velocity image detected two deeply rooted high-velocity bodies adjacent to the Nový Kostel and Lazy focal zones. They correspond to two Variscan mafic intrusions influenced by the SE inclined slab of Saxothuringian crust that subducted beneath the Teplá-Barrandian terrane in the Devonian era. In their uppermost SE inclined parts, they roof both focal zones. The high P-wave velocities of 6,100-6,200 m/s, detected in both roofing caps, indicate their relative compactness and impermeability. The focal domains themselves are located in the almost gradient-free zones with the swarm foci spread near the axial planes of profound velocity depressions. The lower velocities of 5,950-6,050 m/s, observed in the upper parts of focal zones, are indicative of less compact rock complexes corrugated and tectonically disturbed by the SE bordering magma ascents. The high-velocity/high-density caps obviously seal the swarm focal domains because almost no magmatic fluids of mantle origin occur in the Nový Kostel and Lazy seismogenic areas of the West Bohemia/Vogtland territory, otherwise rich in the mantle-derived fluids. This supports the hypothesis of the fluid triggering of earthquake

  11. Missile launch detection electric field perturbation experiment. Final report

    SciTech Connect

    Kane, R.J.; Rynne, T.M.

    1993-04-28

    The Lawrence Livermore National Laboratory and SARA Inc. participated in the ATMD missile launch activities that occurred at WSMR during January 1993. LLNL and SARA deployed sensors for monitoring of basic phenomena. An attempt was made to measure perturbations of the earth geo-potential during the launch of a Lance missile. The occurrence of the perturbation is expected from the conducting body of the missile and the exhaust plume. A set of voltage-probe antennas were used to monitor the local electric field perturbation from the launch at ranges of approximately 1 km. Examination of the data acquired during the launch period failed to show identifiable correlation of the field variations with the launch event. Three reasons are ascribed to this lack of event data: (1) The electric field potential variations have a limited spatial correlation length - the fields measured in one region have little correlation to measurements made at distances of a kilometer away. The potential variations are related to localized atmospheric disturbances and are generally unpredictable. A value for the spatial correlation length is also not known. (2) The conductivity of the plume and missile body are not adequate to produce a field perturbation of adequate magnitude. Phenomena related to the exhaust plume and missile may exist and be outside of the collection range of the equipment employed for these measurements. (3) The presence of 60 Hz power line noise was of sufficient magnitude to irreversibly contaminate measurements.

  12. It is an Experience, Not a Lesson: The Nature of High School Students' Experiences at a Biological Field Station

    NASA Astrophysics Data System (ADS)

    Behrendt, Marc E.

    The purpose of this case study was to describe the nature of high school students' experiences in the immersive four-day field experience at Stone Laboratory Biological Field Station including excursions to Kelley's Island and South Bass Island. Six tenth, eleventh, and twelfth grade students participated through interviews, photovoice, observations, and a survey. Pretrip semi-structured interviews were conducted to understand each participant student's relationship with science. Participants were given cameras to record their field trip experiences to relate what they found interesting, important, and exciting. Back at school after the field trip, the participants were asked to choose their five most meaningful photographs, and write a short essay to describe the significance of each image. A posttrip semi-structured interview explored each participant's experiences during the field trip. An unstructured interview was conducted to discuss each participant's full photograph gallery from the field trip. Interview transcripts were member checked with one minor wording change. Analysis consisted of open coding using apriori codes derived from the ecological framework and emergent codes derived from the data. Coding was duplicated through multiple readers. Significant findings included: 1) Prior experience, prior knowledge, and funds of knowledge added relevance and value to an experience, facilitating interest development; 2) Experiences appeared to be more meaningful when all the senses were stimulated; 3) Friends and peers were an essential part of a quality experience; 4) Quality experiences included a wow factor, or sudden awareness; 5) Teachers needed to be within the experience, not the focus of the experience, and needed to be available to answer questions, be enthusiastic when a discovery was made, and promote student reflection concerning their perceptions and discoveries; 6) A quality informal learning situation incorporated the cognitive/affective, physical

  13. Taking Them into the Field: Mathematics Teacher Candidate Learning about Equity-Oriented Teaching Practices in a Mediated Field Experience

    ERIC Educational Resources Information Center

    Campbell, Sara Sunshine

    2012-01-01

    Teacher education programs have been criticized as too theoretical with university courses disconnected from the practical realities of classrooms. This single case study investigates a model of teacher education that worked to bridge the coursework-fieldwork gap in teacher education. The Mediated Field Experience (MFE) is a field experience…

  14. Periodic Reversals in Paenibacillus dendritiformis Swarming

    PubMed Central

    Strain, Shinji K.; Hernández, Roberto A.; Ben-Jacob, Eshel; Florin, E.-L.

    2013-01-01

    Bacterial swarming is a type of motility characterized by a rapid and collective migration of bacteria on surfaces. Most swarming species form densely packed dynamic clusters in the form of whirls and jets, in which hundreds of rod-shaped rigid cells move in circular and straight patterns, respectively. Recent studies have suggested that short-range steric interactions may dominate hydrodynamic interactions and that geometrical factors, such as a cell's aspect ratio, play an important role in bacterial swarming. Typically, the aspect ratio for most swarming species is only up to 5, and a detailed understanding of the role of much larger aspect ratios remains an open challenge. Here we study the dynamics of Paenibacillus dendritiformis C morphotype, a very long, hyperflagellated, straight (rigid), rod-shaped bacterium with an aspect ratio of ∼20. We find that instead of swarming in whirls and jets as observed in most species, including the shorter T morphotype of P. dendritiformis, the C morphotype moves in densely packed straight but thin long lines. Within these lines, all bacteria show periodic reversals, with a typical reversal time of 20 s, which is independent of their neighbors, the initial nutrient level, agar rigidity, surfactant addition, humidity level, temperature, nutrient chemotaxis, oxygen level, illumination intensity or gradient, and cell length. The evolutionary advantage of this unique back-and-forth surface translocation remains unclear. PMID:23603739

  15. Earthquake swarms on Mount Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    Kaminuma, Katsutada; Baba, Megumi; Ueki, Sadato

    1986-12-01

    Mount Erebus (3794 m), located on Ross Island in McMurdo Sound, is one of the few active volcanoes in Antartica. A high-sensitivity seismic network has been operated by Japanese and US parties on and around the Volcano since December, 1980. The results of these observations show two kinds of seismic activity on Ross Island: activity concentrated near the summit of Mount Erebus associated with Strombolian eruptions, and micro-earthquake activity spread through Mount Erebus and the surrounding area. Seismicity on Mount Erebus has been quite high, usually exceeding 20 volcanic earthquakes per day. They frequently occur in swarms with daily counts exceeding 100 events. Sixteen earthquake swarms with more than 250 events per day were recorded by the seismic network during the three year period 1982-1984, and three notable earthquake swarms out of the sixteen were recognized, in October, 1982 (named 82-C), March-April, 1984 (84-B) and July, 1984 (84-F). Swarms 84-B and 84-F have a large total number of earthquakes and large Ishimoto-Iida's "m"; hence these two swarms are presumed to constitute on one of the precursor phenomena to the new eruption, which took place on 13 September, 1984, and lasted a few months.

  16. Field experience with volume traps for assessing retrospective radon exposures.

    PubMed

    Paridaens, J; Vanmarcke, H; Zunic, Z S; McLaughlin, J P

    2001-05-14

    Approximately 200 volume traps were retrieved from dwellings in various radon prone areas in Europe. They were analysed for the purpose of retrospective radon assessment. Emphasis is put on specific problems encountered when using field samples as opposed to laboratory exposed samples. It was seen that in very dusty circumstances, direct penetration of radon decay products from the outside to the centre of the volume traps calls for extra caution. Rinsing the samples is proposed as a solution and was tested in field and laboratory conditions, showing good results. An attempt was made to give an assessment of the achievable accuracy of the method. Where possible, the volume trap retrospective results were compared with contemporary measurements or to retrospective results from surface traps. The overall impression is that although volume traps are sometimes hard to find in the field, the high reliability of the results makes it well worth the effort. PMID:11379924

  17. Near-field radiative thermal transport: From theory to experiment

    SciTech Connect

    Song, Bai Fiorino, Anthony; Meyhofer, Edgar; Reddy, Pramod

    2015-05-15

    Radiative thermal transport via the fluctuating electromagnetic near-field has recently attracted increasing attention due to its fundamental importance and its impact on a range of applications from data storage to thermal management and energy conversion. After a brief historical account of radiative thermal transport, we summarize the basics of fluctuational electrodynamics, a theoretical framework for the study of radiative heat transfer in terms of thermally excited propagating and evanescent electromagnetic waves. Various approaches to modeling near-field thermal transport are briefly discussed, together with key results and proposals for manipulation and utilization of radiative heat flow. Subsequently, we review the experimental advances in the characterization of both near-field heat flow and energy density. We conclude with remarks on the opportunities and challenges for future explorations of radiative heat transfer at the nanoscale.

  18. Radio frequency wave experiments on the MST reversed field pinch

    SciTech Connect

    Forest, C. B.; Chattopadhyay, P. K.; Nornberg, M. D.; Prager, S. C.; Thomas, M. A.; Uchimoto, E.; Smirnov, A. P.; Harvey, R. W.; Ram, A. K.

    1999-09-20

    Whether there is a self-consistent path from poor confinement to greatly improved confinement through current profile modification is an issue for future experiments to address if and only if near term experiments can demonstrate: (1) coupling to and the propagation of rf waves in RFP plasmas, (2) efficient current drive, and (3) control of the power deposition which will make it possible to control the current profile. In this paper, modeling results and experimental plans are presented for two rf experiments which have the potential of satisfying these three goals: high-n{sub (parallel} {sub sign)} lower hybrid (LH) waves and electron Bernstein waves (EBWs). (c) 1999 American Institute of Physics.

  19. Dark matter effective field theory scattering in direct detection experiments

    SciTech Connect

    Schneck, K.; Cabrera, B.; Cerdeno, D. G.; Mandic, V.; Rogers, H. E.; Agnese, R.; Anderson, A. J.; Asai, M.; Balakishiyeva, D.; Barker, D.; Basu Thakur, R.; Bauer, D. A.; Billard, J.; Borgland, A.; Brandt, D.; Brink, P. L.; Bunker, R.; Caldwell, D. O.; Calkins, R.; Chagani, H.; Chen, Y.; Cooley, J.; Cornell, B.; Crewdson, C. H.; Cushman, Priscilla B.; Daal, M.; Di Stefano, P. C.; Doughty, T.; Esteban, L.; Fallows, S.; Figueroa-Feliciano, E.; Godfrey, G. L.; Golwala, S. R.; Hall, Jeter C.; Harris, H. R.; Hofer, T.; Holmgren, D.; Hsu, L.; Huber, M. E.; Jardin, D. M.; Jastram, A.; Kamaev, O.; Kara, B.; Kelsey, M. H.; Kennedy, A.; Leder, A.; Loer, B.; Lopez Asamar, E.; Lukens, W.; Mahapatra, R.; McCarthy, K. A.; Mirabolfathi, N.; Moffatt, R. A.; Morales Mendoza, J. D.; Oser, S. M.; Page, K.; Page, W. A.; Partridge, R.; Pepin, M.; Phipps, A.; Prasad, K.; Pyle, M.; Qiu, H.; Rau, W.; Redl, P.; Reisetter, A.; Ricci, Y.; Roberts, A.; Saab, T.; Sadoulet, B.; Sander, J.; Schnee, R. W.; Scorza, S.; Serfass, B.; Shank, B.; Speller, D.; Toback, D.; Upadhyayula, S.; Villano, A. N.; Welliver, B.; Wilson, J. S.; Wright, D. H.; Yang, X.; Yellin, S.; Yen, J. J.; Young, B. A.; Zhang, J.

    2015-05-01

    We examine the consequences of the effective eld theory (EFT) of dark matter-nucleon scattering or current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. We demonstrate that spectral di*erences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. We also discuss the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.

  20. Low latitude geomagnetic field line resonance: Experiment and modeling

    SciTech Connect

    Waters, C.L.; Menk, F.W.; Fraser, B.J.

    1994-09-01

    The authors describe work to detect field line resonances, or the observation of Pc 3-5 geomagnetic pulsation events, at low latitude sites. These signals are extracted from ground based magnetometer arrays. The authors found one field line resonance structure in 5 weeks of data at L=1.8. At L=2.8 they were able to observe up to 4 harmonics concurrently. They compare these frequency spectra with the results of two different models of the plasma density in the lower ionosphere.

  1. Global meteorological data facility for real-time field experiments support and guidance

    NASA Technical Reports Server (NTRS)

    Shipham, Mark C.; Shipley, Scott T.; Trepte, Charles R.

    1988-01-01

    A Global Meteorological Data Facility (GMDF) has been constructed to provide economical real-time meteorological support to atmospheric field experiments. After collection and analysis of meteorological data sets at a central station, tailored meteorological products are transmitted to experiment field sites using conventional ground link or satellite communication techniques. The GMDF supported the Global Tropospheric Experiment Amazon Boundary Layer Experiment (GTE-ABLE II) based in Manaus, Brazil, during July and August 1985; an arctic airborne lidar survey mission for the Polar Stratospheric Clouds (PSC) experiment during January 1986; and the Genesis of Atlantic Lows Experiment (GALE) during January, February and March 1986. GMDF structure is similar to the UNIDATA concept, including meteorological data from the Zephyr Weather Transmission Service, a mode AAA GOES downlink, and dedicated processors for image manipulation, transmission and display. The GMDF improved field experiment operations in general, with the greatest benefits arising from the ability to communicate with field personnel in real time.

  2. Focus on Geography--Team Themes and Field Experiences.

    ERIC Educational Resources Information Center

    Daly, John L.

    1990-01-01

    Describes an approach used by the Wayland, Massachusetts, middle school to organizing students into instructional teams. Explains that each instructional team is organized into a "house" named after a significant individual around whom the curriculum and theme for field trips is designed. Highlights the Rachel Carson House activities of learning…

  3. Soil Science as a Field Discipline - Experiences in Iowa, USA

    NASA Astrophysics Data System (ADS)

    Burras, C. Lee

    2015-04-01

    Effective field understanding of soils is crucial. This is true everywhere but especially so in Iowa, a 15 million hectare state in the central USA's "corn belt." Iowa is intensely farmed and almost exclusively privately owned. Many regions of Iowa have had over 90% of their land area in row crops for the past 60 years. In these regions two very common land management strategies are tile drainage (1.5 million km total) and high rates of fertilization (e.g., 200 kg N/ha-yr for cropland) Iowa also has problematic environmental issues including high rates of erosion, excessive sediment and nutrient pollution in water bodies and episodic catastrophic floods. Given the preceding the Agronomy, Environmental Science and Sustainable Agriculture programs at Iowa State University (ISU) offer a strong suite of soil science classes - undergraduate through graduate. The objective of this presentation is to review selected field based soil science courses offered by those programs. This review includes contrasting and comparing campus-based and immersion classes. Immersion classes include ones offered at Iowa Lakeside Laboratory, as "soil judging" and internationally. Findings over the past 20 years are consistent. Students at all levels gain soil science knowledge, competency and confidence proportional to the amount of time spent in field activities. Furthermore their professional skepticism is sharpened. They are also preferentially hired even in career postings that do not require fieldwork. In other words, field learning results in better soil science professionals who have highly functional and sought after knowledge.

  4. Early Field Experience in Career and Technical Education

    ERIC Educational Resources Information Center

    Smalley, Scott Walter

    2011-01-01

    The purpose of the three studies in this dissertation was to enhance career and technical education in the area of agriculture, business, and family and consumer sciences. This dissertation contains three papers: (1) a Delphi study identifying the purpose, expected outcomes, and methods of documenting preservice teacher early field experience…

  5. Pioneer 10 and 11 (Jupiter and Saturn) magnetic field experiments

    NASA Technical Reports Server (NTRS)

    Jones, D. E.

    1986-01-01

    Magnet field data obtained by the vector helium magnetometer (VHM) during the encounters of Jupiter (Pioneer 10 and 11) and Saturn (Pioneer 11) was analyzed and interpreted. The puzzling characteristics of the Jovian and Saturnian magnetospheric magnetic fields were studied. An apparent substorm (including thinning of the dayside tail current sheet) was observed at Jupiter, as well as evidence suggesting that at the magnetopause the cusp is at an abnormally low latitude. The characteristics of Saturn's ring current as observed by Pioneer 11 were dramatically different from those suggested by the Voyager observations. Most importantly, very strong perturbations in the azimuthal ring current magnetic field suggest that the plane of the ring was not in the dipole equatorial plane, being tilted 5 to 10 deg. relative to the dipole and undergoing significant changes during the encounter. When these changing currents were corrected for, an improved planetary field determination was obtained. In addition, the ring and azimuthal currents at Saturn displayed significantly different time dependences.

  6. Rotating field antenna experiments in Phaedrus-B

    NASA Astrophysics Data System (ADS)

    Yasaka, Y.; Majeski, R.; Browning, J.; Hershkowitz, N.; Roberts, D.

    1987-09-01

    The rotating field antenna installed in the central cell of the Phaedrus-B tandem mirror consists of two close-spaced dual half-turn ICRF antennas. The symmetry axes of the antennas are rotated 90° with respect to each other. Each antenna is driven by a separate rf amplifier, with ≳200 KW power output. The polarization of the resultant antenna near fields is selected by the relative phasing of the antenna currents. In particular, the antenna set can produce nearly pure left or right circularly polarized fields. We find an increase in ion heating as the field polarization is varied from right circularly polarized through linear polarization to left circular polarization, for plasma densities up to 3-4×1012 cm-3, when the antenna set is driven at ω˜ωci (midplane). Ion temperature is diagnosed by a time of flight neutral energy analyzer. Results are compared to the predictions of the ICRF code ANTENA of Brian McVey.

  7. The Field Trip Book: Study Travel Experiences in Social Studies

    ERIC Educational Resources Information Center

    Morris, Ronald V.

    2010-01-01

    Looking for social studies adventures to help students find connections to democratic citizenship? Look no further! This book provides just the answer teachers need for engaging students in field trips as researching learners with emphasis on interdisciplinary social studies plus skills in collecting and reporting data gathered from field…

  8. Mechanisms of nitrogen retention in forest ecosystems - A field experiment

    NASA Technical Reports Server (NTRS)

    Vitousek, P. M.; Matson, P. A.

    1984-01-01

    Intensive forest management led to elevated losses of nitrogen from a recently harvested loblolly pine plantation in North Carolina. Measurements of nitrogen-15 retention in the field demonstrated that microbial uptake of nitrogen during the decomposition of residual organic material was the most important process retaining nitrogen. Management practices that remove this material cause increased losses of nitrogen to aquatic ecosystems and the atmosphere.

  9. Validation of microwave vegetation indices using field experiment data sets

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetation indices are valuable in many fields of geosciences. Conventional, visible-near infrared, indices are often limited by the effects of atmosphere, background soil conditions, and saturation at high levels of vegetation. A recent study established the theoretical basis for a new type of inde...

  10. Well-planning programs give students field-like experience

    SciTech Connect

    Sifferman, T.R.; Chapman, L.

    1983-01-01

    The University of Tulsa recently was given a package of computer well planning and drilling programs that will enable petroleum engineering students to gain valuable experience in designing well programs while still in school. Comprehensive homework assignments are now given in areas of drilling fluids programing, hydraulics, directional wells and surveying. Additional programs are scheduled for next semester.

  11. International Field Experiences Promote Professional Development for Sustainability Leaders

    ERIC Educational Resources Information Center

    Hull, R. Bruce; Kimmel, Courtney; Robertson, David P.; Mortimer, Michael

    2016-01-01

    Purpose: This paper aims to describe, explain and evaluate a graduate education program that provides international project experiences and builds competencies related to collaborative problem-solving, cultural capacity to work globally and sustainable development. Design/methodology/approach: Qualitative analysis of survey data from 28 students…

  12. Field Experience in Postsecondary Education: A Guidebook for Action.

    ERIC Educational Resources Information Center

    Schuttenberg, Ernest M.; Poppenhagen, Brent W.

    Four main areas are addressed in this guide for learners and mentors in internship experiences in postsecondary education: (1) career orientation and planning; (2) experiential learning theory; (3) individual learning and development; and (4) program implementation and evaluation. Part One of the text identifies the structure of work in…

  13. Presence of Russian honey bee genotypes in swarms in Louisiana.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Swarm traps were placed in an area around USDA, ARS apiaries near Baton Rouge, Louisiana, which had contained ARS Russian and other honey bees for several years. Eighty swarms were sampled and analyzed for their genotype (Russian, hybrid or non-Russian) and mite infestation percentages. Ten swarms...

  14. Husar-8 Rover Swarm Collective Activity Around Hunveyor-8: Planetary Robotics at the Kecskemét College, GAMF Faculty, Hungary

    NASA Astrophysics Data System (ADS)

    Pasztor, A.; Simon, T.; Nagy, Sz.; Bérczi, Sz.

    2009-03-01

    By constructing the HUSAR-8 model the GAMF Faculty at Kecskemét College began student robotics program with swarm strategy for navigation on the field trip in order to develop teaching programming and trigger student personal activity.

  15. Rocky 7 prototype Mars rover field geology experiments 1. Lavic Lake and sunshine volcanic field, California

    USGS Publications Warehouse

    Arvidson, R. E.; Acton, C.; Blaney, D.; Bowman, J.; Kim, S.; Klingelhofer, G.; Marshall, J.; Niebur, C.; Plescia, J.; Saunders, R.S.; Ulmer, C.T.

    1998-01-01

    Experiments with the Rocky 7 rover were performed in the Mojave Desert to better understand how to conduct rover-based, long-distance (kilometers) geological traverses on Mars. The rover was equipped with stereo imaging systems for remote sensing science and hazard avoidance and 57Fe Mo??ssbauer and nuclear magnetic resonance spectrometers for in situ determination of mineralogy of unprepared rock and soil surfaces. Laboratory data were also obtained using the spectrometers and an X ray diffraction (XRD)/XRF instrument for unprepared samples collected from the rover sites. Simulated orbital and descent image data assembled for the test sites were found to be critical for assessing the geologic setting, formulating hypotheses to be tested with rover observations, planning traverses, locating the rover, and providing a regional context for interpretation of rover-based observations. Analyses of remote sensing and in situ observations acquired by the rover confirmed inferences made from orbital and simulated descent images that the Sunshine Volcanic Field is composed of basalt flows. Rover data confirmed the idea that Lavic Lake is a recharge playa and that an alluvial fan composed of sediments with felsic compositions has prograded onto the playa. Rover-based discoveries include the inference that the basalt flows are mantled with aeolian sediment and covered with a dense pavement of varnished basalt cobbles. Results demonstrate that the combination of rover remote sensing and in situ analytical observations will significantly increase our understanding of Mars and provide key connecting links between orbital and descent data and analyses of returned samples. Copyright 1998 by the American Geophysical Union.

  16. Emergent dynamics of laboratory insect swarms

    NASA Astrophysics Data System (ADS)

    Kelley, Douglas H.; Ouellette, Nicholas T.

    2013-01-01

    Collective animal behaviour occurs at nearly every biological size scale, from single-celled organisms to the largest animals on earth. It has long been known that models with simple interaction rules can reproduce qualitative features of this complex behaviour. But determining whether these models accurately capture the biology requires data from real animals, which has historically been difficult to obtain. Here, we report three-dimensional, time-resolved measurements of the positions, velocities, and accelerations of individual insects in laboratory swarms of the midge Chironomus riparius. Even though the swarms do not show an overall polarisation, we find statistical evidence for local clusters of correlated motion. We also show that the swarms display an effective large-scale potential that keeps individuals bound together, and we characterize the shape of this potential. Our results provide quantitative data against which the emergent characteristics of animal aggregation models can be benchmarked.

  17. Field experiments of success-breeds-success dynamics.

    PubMed

    van de Rijt, Arnout; Kang, Soong Moon; Restivo, Michael; Patil, Akshay

    2014-05-13

    Seemingly similar individuals often experience drastically different success trajectories, with some repeatedly failing and others consistently succeeding. One explanation is preexisting variability along unobserved fitness dimensions that is revealed gradually through differential achievement. Alternatively, positive feedback operating on arbitrary initial advantages may increasingly set apart winners from losers, producing runaway inequality. To identify social feedback in human reward systems, we conducted randomized experiments by intervening in live social environments across the domains of funding, status, endorsement, and reputation. In each system we consistently found that early success bestowed upon arbitrarily selected recipients produced significant improvements in subsequent rates of success compared with the control group of nonrecipients. However, success exhibited decreasing marginal returns, with larger initial advantages failing to produce much further differentiation. These findings suggest a lesser degree of vulnerability of reward systems to incidental or fabricated advantages and a more modest role for cumulative advantage in the explanation of social inequality than previously thought. PMID:24778230

  18. Field experiments of success-breeds-success dynamics

    PubMed Central

    van de Rijt, Arnout; Kang, Soong Moon; Restivo, Michael; Patil, Akshay

    2014-01-01

    Seemingly similar individuals often experience drastically different success trajectories, with some repeatedly failing and others consistently succeeding. One explanation is preexisting variability along unobserved fitness dimensions that is revealed gradually through differential achievement. Alternatively, positive feedback operating on arbitrary initial advantages may increasingly set apart winners from losers, producing runaway inequality. To identify social feedback in human reward systems, we conducted randomized experiments by intervening in live social environments across the domains of funding, status, endorsement, and reputation. In each system we consistently found that early success bestowed upon arbitrarily selected recipients produced significant improvements in subsequent rates of success compared with the control group of nonrecipients. However, success exhibited decreasing marginal returns, with larger initial advantages failing to produce much further differentiation. These findings suggest a lesser degree of vulnerability of reward systems to incidental or fabricated advantages and a more modest role for cumulative advantage in the explanation of social inequality than previously thought. PMID:24778230

  19. Overview of results from the MST reversed field pinch experiment

    NASA Astrophysics Data System (ADS)

    Sarff, J. S.; Almagri, A. F.; Anderson, J. K.; Borchardt, M.; Cappechi, W.; Carmody, D.; Caspary, K.; Chapman, B. E.; Den Hartog, D. J.; Duff, J.; Eilerman, S.; Falkowski, A.; Forest, C. B.; Galante, M.; Goetz, J. A.; Holly, D. J.; Koliner, J.; Kumar, S.; Lee, J. D.; Liu, D.; McCollam, K. J.; McGarry, M.; Mirnov, V. V.; Morton, L.; Munaretto, S.; Nornberg, M. D.; Nonn, P. D.; Oliva, S. P.; Parke, E.; Pueschel, M. J.; Reusch, J. A.; Sauppe, J.; Seltzman, A.; Sovinec, C. R.; Stone, D.; Theucks, D.; Thomas, M.; Triana, J.; Terry, P. W.; Waksman, J.; Whelan, G. C.; Brower, D. L.; Ding, W. X.; Lin, L.; Demers, D. R.; Fimognari, P.; Titus, J.; Auriemma, F.; Cappello, S.; Franz, P.; Innocente, P.; Lorenzini, R.; Martines, E.; Momo, B.; Piovesan, P.; Puiatti, M.; Spolaore, M.; Terranova, D.; Zanca, P.; Davydenko, V. I.; Deichuli, P.; Ivanov, A. A.; Polosatkin, S.; Stupishin, N. V.; Spong, D.; Craig, D.; Stephens, H.; Harvey, R. W.; Cianciosa, M.; Hanson, J. D.; Breizman, B. N.; Li, M.; Zheng, L. J.

    2015-10-01

    An overview of recent results from the MST reversed field pinch programme is presented. With neutral beam injection, bursty energetic particle (EP) modes are observed. The profiles of the magnetic and density fluctuations associated with these EP modes are measured using a far infrared interferometer-polarimeter. Equilibrium reconstructions of the quasi-single-helicity 3D helical state are provided by the V3FIT code that now incorporates several of MST's advanced diagnostics. The orientation of the helical structure is controlled using a new resonant magnetic perturbation technique. Gyrokinetic simulations based on experimental equilibria predict unstable trapped-electron modes (TEMs), and small-scale density fluctuations are detected in improved-confinement plasmas with TEM-like features. Upgraded pellet injection permits study of density and beta limits over MST's full range of operation, and an MST-record line-average density of 0.9 × 1020 m3 (n/nG = 1.4) has been obtained. Impurity ion temperature measurements reveal a charge-to-mass-ratio dependence in the rapid heating that occurs during a sawtooth crash. Runaway of NBI-born fast ions during the impulsive sawtooth event agrees with test-particle theory. Magnetic self-organization studies include measurements of the dynamo emf with an applied ac inductive electric field using oscillating field current drive.

  20. Vegetation and soils field research data base: Experiment summaries

    NASA Technical Reports Server (NTRS)

    Biehl, L. L.; Daughtry, C. S. T.; Bauer, M. E.

    1984-01-01

    Understanding of the relationships between the optical, spectral characteristics and important biological-physical parameters of earth-surface features can best be obtained by carefully controlled studies over fields and plots where complete data describing the condition of targets are attainable and where frequent, timely spectral measurement can be obtained. Development of a vegetation and soils field research data base was initiated in 1972 at Purdue University's Laboratory for Applications of Remote Sensing and expanded in the fall of 1974 by NASA as part of LACIE. Since then, over 250,000 truck-mounted and helicopter-borne spectrometer/multiband radiometer observations have been obtained of more than 50 soil series and 20 species of crops, grasses, and trees. These data are supplemented by an extensive set of biophysical and meteorological data acquired during each mission. The field research data form one of the most complete and best-documented data sets acquired for agricultural remote sensing research. Thus, they are well-suited to serve as a data base for research to: (1) quantiatively determine the relationships of spectral and biophysical characteristics of vegetation, (2) define future sensor systems, and (3) develop advanced data analysis techniques.

  1. Which Field Experiences Best Prepare Future School Leaders? An Analysis of Kentucky's Principal Preparation Program

    ERIC Educational Resources Information Center

    Dodson, Richard L.

    2014-01-01

    This paper examines the effectiveness of field experiences in preparing school principals for the exigencies of the job. Current school principals throughout Kentucky were surveyed regarding their perceptions of the utility and comparative effectiveness of field experiences in the principal preparation program (PPP) each attended. Surveys were…

  2. Life on the Reservation: Cross-Cultural Field Experiences and Student Learning

    ERIC Educational Resources Information Center

    Richardson, Belinda Conrad; Dinkins, Elizabeth G.

    2014-01-01

    Twenty-first century classrooms are filled with increasingly diverse student populations. Effective teacher preparation programs must include explicit course work in culturally responsive pedagogies and field experiences that place educators in new sociocultural contexts. Field experiences in cross-cultural, place-based settings have the potential…

  3. The Influence of Technology-Rich Early Childhood Field Experiences on Preservice Teachers

    ERIC Educational Resources Information Center

    Lux, Nicholas; Lux, Christine

    2015-01-01

    Despite a comprehensive body of research on field experiences in teacher education, technology-rich early field experiences in early childhood environments is one particular area of inquiry lacking substantive current research. Therefore, this study was conducted to better understand how preservice teachers' perceptions of global concepts related…

  4. The Dilemma of Field Experience Assessment: Enhancing Professional Development or Fulfilling a Gate-Keeping Function?

    ERIC Educational Resources Information Center

    Cheng, May May-hung; Tang, Sylvia Yee-fan

    2008-01-01

    The field experience component in a teacher education programme serves both a gate-keeping function and a formative purpose that supports student teacher development. The authors were members of a research team which took care of the re-design of the assessment instrument for the field experience component of a teacher education programme, as well…

  5. Using Field Experiments to Change the Template of How We Teach Economics

    ERIC Educational Resources Information Center

    List, John A.

    2014-01-01

    In this article, the author explains why field experiments can improve what we teach and how we teach economics. Economists no longer operate as passive observers of economic phenomena. Instead, they participate actively in the research process by collecting data from field experiments to investigate the economics of everyday life. This change can…

  6. Developing a Performance Base for Field Experiences: A Grass Roots Approach.

    ERIC Educational Resources Information Center

    Merritt, Daniel L.

    Following a brief investigation of the need for performance objectives specifying teacher behavior, this report develops a performance base for field experience. The purpose of performance objectives in field experiences and the relationship of these objectives to the student teacher, cooperating teacher, and university supervisor are discussed in…

  7. The Effects of Primary Sources and Field Trip Experience on the Knowledge Retention of Multicultural Content

    ERIC Educational Resources Information Center

    Farmer, James; Knapp, Doug; Benton, Gregory M.

    2007-01-01

    Although small in scope, this study attempted to analyze the impacts of primary sources and field trip experiences on multicultural education through first-hand narrative interviews, one year after the experience. In particular, it assessed the recollections of students who participated in a one-half-day field trip to George Washington Carver…

  8. Examining the Content of Preservice Teachers' Reflections of Early Field Experiences

    ERIC Educational Resources Information Center

    Subramaniam, Karthigeyan

    2013-01-01

    This paper describes an exploratory study that examined the content of preservice elementary teachers' reflections of their documented early field experiences of science teaching in authentic contexts. The study used an early field experience model that was focused on the objective of profiling an elementary science teacher as the practical…

  9. The Impact of Technology Use in Special Education Field Experience on Preservice Teachers' Perceived Technology Expertise.

    ERIC Educational Resources Information Center

    Anderson, Cindy L.; Petch-Hogan, Beverly

    2001-01-01

    Eight preservice special education teachers participated in a technology-rich field experience with students with disabilities. Preservice teachers felt as a result of their field experience that their knowledge of computers increased, they were better able to evaluate effective software, and that they could use technology to facilitate…

  10. Issues in Field Experience Assessment in Teacher Education in a Standards-Based Context

    ERIC Educational Resources Information Center

    Tang, Sylvia Yee Fan

    2008-01-01

    This paper presents a study that shows the use of professional standards in field experience assessment in initial teacher education. A Professional Development Progress Map was developed in field experience assessment in a teacher education institution in Hong Kong. The study enriches our understanding of the holistic nature of assessing…

  11. Sites for Student Field Experiences in Refugee Mental Health. Task VI--Training.

    ERIC Educational Resources Information Center

    Hoshino, George; And Others

    This report on sites for student field experiences in refugee mental health has been prepared by the University of Minnesota's Mental Health Technical Assistance Center for the state refugee assistance programs. After a brief introduction describing the mission of the Technical Assistance Center, the characteristics of field experience in mental…

  12. ETIPS: Using Cases with Virtual Schools to Prepare for, Extend, and Deepen Preservice Teachers' Field Experiences

    ERIC Educational Resources Information Center

    Dexter, Sara L.; Riedel, Eric; Scharber, Cassandra

    2008-01-01

    Field experiences are identified as an important component in the preparation of new teachers. As such, methods to supplement field experiences with pre- and post-activities that ready preservice teachers to effectively learn from them warrant further examination. This paper presents one tool that has been used successfully to improve preservice…

  13. Focusing, Situating, and Grounding Micro-Level Evaluation Field Experiences: An Instructional Tool

    ERIC Educational Resources Information Center

    Skolits, Gary J.; Woodard, Thelma; Morrow, Jennifer Ann; Kaesbauer, Susanne

    2012-01-01

    Evaluator training field experiences seek to reinforce applicable content knowledge and promote applied skills. For students, even a small-scale field experience focusing on limited components of a larger evaluation process can seem particularly challenging. Students often do not recognize the relevance of established evaluation resources capable…

  14. Bacterial Swarming: social behaviour or hydrodynamics?

    NASA Astrophysics Data System (ADS)

    Vermant, Jan

    2010-03-01

    Bacterial swarming of colonies is typically described as a social phenomenon between bacteria, whereby groups of bacteria collectively move atop solid surfaces. This multicellular behavior, during which the organized bacterial populations are embedded in an extracellular slime layer, is connected to important features such as biofilm formation and virulence. Despite the possible intricate quorum sensing mechanisms that regulate swarming, several physico-chemical phenomena may play a role in the dynamics of swarming and biofilm formation. Especially the striking fingering patterns formed by some swarmer colonies on relatively soft sub phases have attracted the attention as they could be the signatures of an instability. Recently, a parallel has been drawn between the swarming patterns and the spreading of viscous drops under the influence of a surfactant, which lead to similar patterns [1]. Starting from the observation that several of the molecules, essential in swarming systems, are strong biosurfactants, the possibility of flows driven by gradients in surface tension, has been proposed. This Marangoni flows are known to lead to these characteristic patterns. For Rhizobium etli not only the pattern formation, but also the experimentally observed spreading speed has been shown to be consistent with the one expected for Marangoni flows for the surface pressures, thickness, and viscosities that have been observed [2]. We will present an experimental study of swarming colonies of the bacteria Pseudomonas aeruginosa, the pattern formation, the surfactant gradients and height profiles in comparison with predictions of a thin film hydrodynamic model.[4pt] [1] Matar O.K. and Troian S., Phys. Fluids 11 : 3232 (1999)[0pt] [2] Daniels, R et al., PNAS, 103 (40): 14965-14970 (2006)

  15. Distributed Sensing and Cooperating Control for Swarms of Robotic vehicles

    SciTech Connect

    Dohrmann, C.R.; Goldsmith, S.Y.; Hurtado, J.E.; Robinett, R.D.

    1998-10-09

    each agent sampling and sharing his information with others. Co- operative control is accomplished by each agent using its neighbors information to determine a control (or TECHNICAL DEVELOPMENT In this section we highlight the technical development of our distributed sensing and cooperative control ap- proach to effectively control a large swarm of au- tonomous, robotic vehicles. Recall that the agents are tasked with locating the chemical plume source within a chemical plume field. In our simulations, we assume that the agents are outfitted with a GPS sensor, which provides their cur- rent location, and a chemical "sniffer," which allows them to detect the strength of the chemical plume at their current location. Furthermore, we assume that the robots have onboard processing capability, and are able to communicate with one another via RF modems together with bit packing and error correction tech- niques, like those discussed by Lewis et al [4]. Thus, each agent is able to communicate and share informa- tion with all others (i.e., there is global communica- tion). In this mode, at a particular instant in time, the agents sample the chemical plume field and post this information and their current location for the oth- ers. The agents then assemble the information and de- termine a projected target of where they believe the chemical source is located. The position update for each agent is then based upon its current position and the position of the projected target.

  16. Design of a swarm of autonomous ground vehicles for use in remote sensing applications

    NASA Astrophysics Data System (ADS)

    Benavidez, Patrick J.

    As current technological trends are leading towards relatively small, cheap and powerful computational platforms that can support a multitude of sensors, systems of multiple smaller robots are becoming more cost effective than use of a single larger robot. Small, cheap and powerful are three key ingredients in enabling the development and deployment of larger swarms of robots. This thesis explores the concepts required for developing and deploying a swarm of autonomous ground vehicle (AGV) robots. The concepts investigated are communication, obstacle avoidance, navigation, path planning, formation planning, autonomous control, and task allocation. Each swarm robot concept is explored through comparison in the use of different instruments and methods to reach the end goal in creation and use of the system component. Verification of the need for these concepts in a multi-robot system is performed through simulation and experiments. Results from simulations and experiments provide a promising outlook for deployment of the robotic swarm on current wireless networks for long range experiments. Products of this thesis are the set of concepts that can be used to create and deploy an expandable system of heterogeneous robots for use in remote sensing applications, and software created to control two coordinator robots that were used to test the concepts.

  17. The Viking satellite program - Preliminary results from the APL Magnetic Field Experiment

    NASA Technical Reports Server (NTRS)

    Potemra, Thomas A.; Zanetti, Lawrence J.; Erlandson, Robert E.; Gustafsson, Georg; Acuna, Mario H.

    1986-01-01

    Sweden's Viking satellite, launched in February 1986, has been conducting plasma process observations in the earth magnetosphere and auroral regions; the U.S.-supplied APL Magnetic Field Experiment aboard Viking is used to determine field-aligned Birkeland current characteristics in previously unsampled regions of near-earth space. The Magnetic Field Experiment has an equivalent spatial resolution of 12 m in the auroral ionosphere when making measurements near apogee. The purposes of Viking's other instruments and their relationship to the Magnetic Field Experiment are discussed.

  18. Viking satellite program - preliminary results from the APL Magnetic Field Experiment

    SciTech Connect

    Potemra, T.A.; Zanetti, L.J.; Erlandson, R.E.; Gustafsson, G.; Acuna, M.H.

    1986-12-01

    Sweden's Viking satellite, launched in February 1986, has been conducting plasma process observations in the earth magnetosphere and auroral regions; the U.S.-supplied APL Magnetic Field Experiment aboard Viking is used to determine field-aligned Birkeland current characteristics in previously unsampled regions of near-earth space. The Magnetic Field Experiment has an equivalent spatial resolution of 12 m in the auroral ionosphere when making measurements near apogee. The purposes of Viking's other instruments and their relationship to the Magnetic Field Experiment are discussed.

  19. First experiments probing the collision of parallel magnetic fields using laser-produced plasmas

    SciTech Connect

    Rosenberg, M. J. Li, C. K.; Séguin, F. H.; Frenje, J. A.; Petrasso, R. D.; Fox, W.; Igumenshchev, I.; Stoeckl, C.; Glebov, V.; Town, R. P. J.

    2015-04-15

    Novel experiments to study the strongly-driven collision of parallel magnetic fields in β ∼ 10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell simulations predict a stronger flux compression and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.

  20. First experiments probing the collision of parallel magnetic fields using laser-produced plasmas

    SciTech Connect

    Rosenberg, M. J.; Li, C. K.; Fox, W.; Igumenshchev, I.; Seguin, F. H.; Town, R. P.; Frenje, J. A.; Stoeckl, C.; Glebov, V.; Petrasso, R. D.

    2015-04-08

    Novel experiments to study the strongly-driven collision of parallel magnetic fields in β~10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell (PIC) simulations predict a stronger flux compression and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.

  1. Swarms of UAVs and fighter aircraft

    SciTech Connect

    Trahan, M.W.; Wagner, J.S.; Stantz, K.M.; Gray, P.C.; Robinett, R.

    1998-11-01

    This paper describes a method of modeling swarms of UAVs and/or fighter aircraft using particle simulation concepts. Recent investigations into the use of genetic algorithms to design neural networks for the control of autonomous vehicles (i.e., robots) led to the examination of methods of simulating large collections of robots. This paper describes the successful implementation of a model of swarm dynamics using particle simulation concepts. Several examples of the complex behaviors achieved in a target/interceptor scenario are presented.

  2. Software Engineering and Swarm-Based Systems

    NASA Technical Reports Server (NTRS)

    Hinchey, Michael G.; Sterritt, Roy; Pena, Joaquin; Rouff, Christopher A.

    2006-01-01

    We discuss two software engineering aspects in the development of complex swarm-based systems. NASA researchers have been investigating various possible concept missions that would greatly advance future space exploration capabilities. The concept mission that we have focused on exploits the principles of autonomic computing as well as being based on the use of intelligent swarms, whereby a (potentially large) number of similar spacecraft collaborate to achieve mission goals. The intent is that such systems not only can be sent to explore remote and harsh environments but also are endowed with greater degrees of protection and longevity to achieve mission goals.

  3. FAC variety observed by Cluster, Champ and Swarm

    NASA Astrophysics Data System (ADS)

    Yang, Junying; Dunlop, Malcolm; Yang, Yanyan; Xiong, Chao; Lühr, Hermann; Bogdanova, Yulia; Zhang, Qinghe; Cao, Jinbin; Li, Liuyuan; Ma, Yuduan; Liu, Wenlong; Fu, Huishan; Wei, Xinhua; Lyu, Haoyu; Wang, Tieyan; Shen, Chao; Olsen, Nils; Ritter, Patricia

    2015-04-01

    Both large- and small-scale field-aligned currents (FAC) have been observed in the auroral zone. Small-scale systems are often observed with latitudinal thicknesses of several tens of kilometers. As to large-scale systems, these can extend over several degrees of magnetic latitude, and can be described in terms of R1 and R2 FAC systems. A detailed analysis of phenomenon in the auroral area has been done, using Cluster four satellites constellation, one low orbit satellite Champ and examples from the three satellites of Swarm. In particular, we focus on coordinated events between Cluster and Champ in order to classify the FAC signatures seen at both medium and low orbit. The FAC system exhibits both long and short term periodic variety. There is a good correspondence of FACs observed by high altitude Cluster constellation and the low altitude Champ and Swarm satellites. These signatures also associate with ground magnetic field data. Further work will investigate the relationship of FACs with sub-storm occurrence and changes in the IMF.

  4. Magnetic signals generated by ocean flow in Swarm satellite data: prediction and observation

    NASA Astrophysics Data System (ADS)

    Einspigel, David; Velimsky, Jakub; Martinec, Zdenek; Sachl, Libor

    2015-04-01

    Motion of sea water in the Earth's main magnetic field generates the secondary induced field which can be decomposed into its poloidal and toroidal components. While the toroidal component is not directly observable outside the oceans, the poloidal magnetic field have been already validated by CHAMP satellite magnetic observations, land-based magnetic measurements and sea surface magnetic field measurements, despite the poloidal field being rather weak, reaching an intensity of up to a few nT. New possibilities of observations of the ocean-induced magnetic field came with the launching of ESA's Swarm mission satellites which have provided a valuable amount of high-precision and high-resolution measurements of the Earth's magnetic field. For a detection of weak ocean-induced signals and their interpretation, numerical modelling is crucial. We present results of modelling of the secondary magnetic field generated by ocean flow. Two ocean flow models are incorporated: 1) DEBOT, a barotropic model of ocean tide flow and 2) LSOMG, a baroclinic model of global ocean circulation. The secondary magnetic field is modelled by two different approaches: 1) a single-layer approximation model and 2) a three-dimensional time-domain electromagnetic induction model. A preliminary comparison of predicted signals and observed signals extracted from Swarm satellite data will be shown. The future aim is to assimilate magnetic data provided by Swarm mission into the models.

  5. Swarm intelligence for detecting interesting events in crowded environments.

    PubMed

    Kaltsa, Vagia; Briassouli, Alexia; Kompatsiaris, Ioannis; Hadjileontiadis, Leontios J; Strintzis, Michael Gerasimos

    2015-07-01

    This paper focuses on detecting and localizing anomalous events in videos of crowded scenes, i.e., divergences from a dominant pattern. Both motion and appearance information are considered, so as to robustly distinguish different kinds of anomalies, for a wide range of scenarios. A newly introduced concept based on swarm theory, histograms of oriented swarms (HOS), is applied to capture the dynamics of crowded environments. HOS, together with the well-known histograms of oriented gradients, are combined to build a descriptor that effectively characterizes each scene. These appearance and motion features are only extracted within spatiotemporal volumes of moving pixels to ensure robustness to local noise, increase accuracy in the detection of local, nondominant anomalies, and achieve a lower computational cost. Experiments on benchmark data sets containing various situations with human crowds, as well as on traffic data, led to results that surpassed the current state of the art (SoA), confirming the method's efficacy and generality. Finally, the experiments show that our approach achieves significantly higher accuracy, especially for pixel-level event detection compared to SoA methods, at a low computational cost. PMID:25769154

  6. Stochastic analysis of a field-scale unsaturated transport experiment

    NASA Astrophysics Data System (ADS)

    Severino, G.; Comegna, A.; Coppola, A.; Sommella, A.; Santini, A.

    2010-10-01

    Modelling of field-scale transport of chemicals is of deep interest to public as well as private sectors, and it represents an area of active theoretical research in many environmentally-based disciplines. However, the experimental data needed to validate field-scale transport models are very limited due to the numerous logistic difficulties that one faces out. In the present paper, the migration of a tracer (Cl -) was monitored during its movement in the unsaturated zone beneath the surface of 8 m × 50 m sandy soil. Under flux-controlled, steady-state water flow ( Jw = 10 mm/day) was achieved by bidaily sprinkler irrigation. A pulse of 105 g/m 2 KCl was applied uniformly to the surface, and subsequently leached downward by the same (chloride-free) flux Jw over the successive two months. Chloride concentration monitoring was carried out in seven measurement campaigns (each one corresponding to a given time) along seven (parallel) transects. The mass recovery was near 100%, therefore underlining the very good-quality of the concentration data-set. The chloride concentrations are used to test two field-scale models of unsaturated transport: (i) the Advection-Dispersion Equation (ADE), which models transport far from the zone of solute entry, and (ii) the Stochastic- Convective Log- normal (CLT) transfer function model, which instead accounts for transport near the release zone. Both the models provided an excellent representation of the solute spreading at z > 0.45 m (being z = 0.45 m the calibration depth). As a consequence, by the depth z ≈ 50 cm one can regard transport as Fickian. The ADE model dramatically underestimates solute spreading at shallow depths. This is due to the boundary effects which are not captured by the ADE. The CLT model appears to be a more robust tool to mimic transport at every depth.

  7. What is Particle Swarm optimization? Application to hydrogeophysics (Invited)

    NASA Astrophysics Data System (ADS)

    Fernández Martïnez, J.; García Gonzalo, E.; Mukerji, T.

    2009-12-01

    Inverse problems are generally ill-posed. This yields lack of uniqueness and/or numerical instabilities. These features cause local optimization methods without prior information to provide unpredictable results, not being able to discriminate among the multiple models consistent with the end criteria. Stochastic approaches to inverse problems consist in shifting attention to the probability of existence of certain interesting subsurface structures instead of "looking for a unique model". Some well-known stochastic methods include genetic algorithms and simulated annealing. A more recent method, Particle Swarm Optimization, is a global optimization technique that has been successfully applied to solve inverse problems in many engineering fields, although its use in geosciences is still limited. Like all stochastic methods, PSO requires reasonably fast forward modeling. The basic idea behind PSO is that each model searches the model space according to its misfit history and the misfit of the other models of the swarm. PSO algorithm can be physically interpreted as a damped spring-mass system. This physical analogy was used to define a whole family of PSO optimizers and to establish criteria, based on the stability of particle swarm trajectories, to tune the PSO parameters: inertia, local and global accelerations. In this contribution we show application to different low-cost hydrogeophysical inverse problems: 1) a salt water intrusion problem using Vertical Electrical Soundings, 2) the inversion of Spontaneous Potential data for groundwater modeling, 3) the identification of Cole-Cole parameters for Induced Polarization data. We show that with this stochastic approach we are able to answer questions related to risk analysis, such as what is the depth of the salt intrusion with a certain probability, or giving probabilistic bounds for the water table depth. Moreover, these measures of uncertainty are obtained with small computational cost and time, allowing us a very

  8. A full field, 3-D velocimeter for microgravity crystallization experiments

    NASA Technical Reports Server (NTRS)

    Brodkey, Robert S.; Russ, Keith M.

    1991-01-01

    The programming and algorithms needed for implementing a full-field, 3-D velocimeter for laminar flow systems and the appropriate hardware to fully implement this ultimate system are discussed. It appears that imaging using a synched pair of video cameras and digitizer boards with synched rails for camera motion will provide a viable solution to the laminar tracking problem. The algorithms given here are simple, which should speed processing. On a heavily loaded VAXstation 3100 the particle identification can take 15 to 30 seconds, with the tracking taking less than one second. It seeems reasonable to assume that four image pairs can thus be acquired and analyzed in under one minute.

  9. Seismic swarm associated with the 2008 eruption of Kasatochi Volcano, Alaska: earthquake locations and source parameters

    USGS Publications Warehouse

    Ruppert, Natalia G.; Prejean, Stephanie G.; Hansen, Roger A.

    2011-01-01

    An energetic seismic swarm accompanied an eruption of Kasatochi Volcano in the central Aleutian volcanic arc in August of 2008. In retrospect, the first earthquakes in the swarm were detected about 1 month prior to the eruption onset. Activity in the swarm quickly intensified less than 48 h prior to the first large explosion and subsequently subsided with decline of eruptive activity. The largest earthquake measured as moment magnitude 5.8, and a dozen additional earthquakes were larger than magnitude 4. The swarm exhibited both tectonic and volcanic characteristics. Its shear failure earthquake features were b value = 0.9, most earthquakes with impulsive P and S arrivals and higher-frequency content, and earthquake faulting parameters consistent with regional tectonic stresses. Its volcanic or fluid-influenced seismicity features were volcanic tremor, large CLVD components in moment tensor solutions, and increasing magnitudes with time. Earthquake location tests suggest that the earthquakes occurred in a distributed volume elongated in the NS direction either directly under the volcano or within 5-10 km south of it. Following the MW 5.8 event, earthquakes occurred in a new crustal volume slightly east and north of the previous earthquakes. The central Aleutian Arc is a tectonically active region with seismicity occurring in the crusts of the Pacific and North American plates in addition to interplate events. We postulate that the Kasatochi seismic swarm was a manifestation of the complex interaction of tectonic and magmatic processes in the Earth's crust. Although magmatic intrusion triggered the earthquakes in the swarm, the earthquakes failed in context of the regional stress field.

  10. Seismic swarm associated with the 2008 eruption of Kasatochi Volcano, Alaska: Earthquake locations and source parameters

    USGS Publications Warehouse

    Ruppert, N.A.; Prejean, S.; Hansen, R.A.

    2011-01-01

    An energetic seismic swarm accompanied an eruption of Kasatochi Volcano in the central Aleutian volcanic arc in August of 2008. In retrospect, the first earthquakes in the swarm were detected about 1 month prior to the eruption onset. Activity in the swarm quickly intensified less than 48 h prior to the first large explosion and subsequently subsided with decline of eruptive activity. The largest earthquake measured as moment magnitude 5.8, and a dozen additional earthquakes were larger than magnitude 4. The swarm exhibited both tectonic and volcanic characteristics. Its shear failure earthquake features were b value = 0.9, most earthquakes with impulsive P and S arrivals and higher-frequency content, and earthquake faulting parameters consistent with regional tectonic stresses. Its volcanic or fluid-influenced seismicity features were volcanic tremor, large CLVD components in moment tensor solutions, and increasing magnitudes with time. Earthquake location tests suggest that the earthquakes occurred in a distributed volume elongated in the NS direction either directly under the volcano or within 5-10 km south of it. Following the MW 5.8 event, earthquakes occurred in a new crustal volume slightly east and north of the previous earthquakes. The central Aleutian Arc is a tectonically active region with seismicity occurring in the crusts of the Pacific and North American plates in addition to interplate events. We postulate that the Kasatochi seismic swarm was a manifestation of the complex interaction of tectonic and magmatic processes in the Earth's crust. Although magmatic intrusion triggered the earthquakes in the swarm, the earthquakes failed in context of the regional stress field. Copyright ?? 2011 by the American Geophysical Union.

  11. The 1987 Federal field exercise: The DOE experience

    SciTech Connect

    Adler, M.V.; Gant, K.S.

    1989-06-01

    The second full-scale field exercise of the Federal Radiological Emergency Response Plan (FRERP) was held at the Zion Nuclear Power Station, Zion, Illinois, in June 1987. The exercise incorporated the annual compliance exercise for the Zion plant and involved the operating utility, Commonwealth Edison Company, the states of Illinois and Wisconsin, local governments, volunteer groups, and representatives from 12 federal agencies. The 3-day exercise was played from many locations in the Zion area; Springfield, Illinois; Madison, Wisconsin; and Washington, DC. Approximately 1000 people participated in the exercise, which used a scenario in which an accident at the plant resulted in the release of radioactive material outside the plant boundary. The US Department of Energy (DOE) had major responsibilities during the planning, playing, and critiquing of the exercise; these functions are outlined in the report. This document describes the DOE participation in the planning and response during the exercise. During a radiological emergency, the FRERP gives DOE the responsibility for coordinating the federal radiological monitoring and assessment activities in support of the states and the cognizant federal agency. At Zion, a self-sufficient Federal Radiological Monitoring and Assessment Center was established by DOE at a nearby fairground in which over 200 people from DOE, the two states, and other federal agencies participated. Before the field exercise, a tabletop exercise and a dry run were held for training purposes. 5 refs., 6 figs.

  12. Overview of results in the MST reversed field pinch experiment

    SciTech Connect

    Prager, S. C.; Adney, J.; Almagri, A.; Anderson, J.; Blair, A.; Brower, D. L.; Cengher, M.; Chapman, B. E.; Choi, S.; Craig, D.; Combs, S.; Demers, D. R.; Hartog, D. J. Den; Deng, B.; Ding, W. X.; Ebrahimi, F.; Ennis, D.; Fiksel, G.; Fitzpatrick, R.; Foust, C.; Forest, C. B.; Franz, P.; Frassinetti, L.; Goetz, J.; Holly, D.; Hudson, B.; Kaufman, M.; Lovell, T.; Marrelli, L.; Martin, P.; McCollam, K.; Mirnov, V. V.; Nonn, P.; O'Connell, R.; Oliva, S.; Piovesan, P.; Predebon, I.; Sarff, J. S.; Spizzo, G.; Svidzinski, V.; Thomas, M.; Uchimoto, E.; White, R.; Wyman, M.

    2005-10-01

    Confinement in the reversed field pinch (RFP) has been shown to increase strongly with current profile control. The MST RFP can operate in two regimes: the standard regime with a naturally occurring current density profile, robust reconnection and dynamo activity; and the improved confinement regime with strong reduction in reconnection, dynamo and transport. New results in standard plasmas include the observation of a strong two-fluid Hall effect in reconnection and dynamo, the determination that the m = 0 edge resonant mode is nonlinearly driven, and the determination that tearing modes can lock to the wall via eddy currents in the shell. New results in improved confinement plasmas include observations that such plasmas are essentially dynamo-free, contain several isolated magnetic islands (as opposed to a stochastic field) and contain reduced high frequency turbulence. Auxiliary current drive and heating is now critical to RFP research. In MST, a programme to apply auxiliary systems to the RFP is underway and progress has accrued in several techniques, including lower hybrid and electron Bernstein wave injection, ac helicity injection current drive, pellet injection and neutral beam injection.

  13. Two-Channel Rectangular Dielectric Wake Field Accelerator Structure Experiment

    SciTech Connect

    Sotnikov, G. V.; Marshall, T. C.; Shchelkunov, S. V.; Didenko, A.; Hirshfield, J. L.

    2009-01-22

    A design is presented for a two-channel 30-GHz rectangular dielectric wake field accelerator structure being built for experimental tests at Argonne National Laboratory (ANL). This structure allows for a transformer ratio T much greater than two, and permits continuous coupling of energy from drive bunches to accelerated bunches. It consists of three planar slabs of cordierite ceramic ({epsilon} = 4.7) supported within a rectangular copper block, forming a drive channel 12 mmx6 mm, and an accelerator channel 2 mmx6 mm. When driven by a 50 nC, 14 MeV single bunch available at ANL, theory predicts an acceleration field of 6 MeV/m, and T = 12.6. Inherent transverse wake forces introduce deflections and some distortion of bunch profiles during transit through the structure that are estimated to be tolerable. Additionally, a cylindrical two-channel DWFA is introduced which shares many advantages of the rectangular structure including high T, and the added virtue of axisymmetry that eliminates lowest-order transverse deflecting forces.

  14. Field experience with a mobile tomographic nondestructive assay system

    SciTech Connect

    Prettyman, T.H.; Betts, S.E.; Taggart, D.P.; Estep, R.J.; Nicholas, N.J.; Lucas, M.C.; Harlan, R.A.

    1995-12-01

    A mobile tomographic gamma-ray scanner (TGS) developed by Los Alamos National Laboratory was recently demonstrated at the Rocky Flats Environmental Technology Site and is currently in use at Los Alamos waste storage areas. The scanner was developed to assay radionuclides in low-level, transuranic, and mixed waste in containers ranging in size from 2 ft{sup 3} boxes to 83-gallon overpacks. The tomographic imaging capability provides a complete correction for source distribution and matrix attenuation effects, enabling accurate assays of Pu-239 and other gamma-ray emitting isotopes. In addition, the system can reliably detect self-absorbing material such as plutonium metal shot, and can correct for bias caused by self-absorption. The system can be quickly configured to execute far-field scans, segmented gamma-ray scans, and a host of intermediate scanning protocols, enabling higher throughput (up to 20 drums per 8-hour shift). In this paper, we will report on the results of field trials of the mobile system at Rocky Flats and Los Alamos. Assay accuracy is confirmed for cases in which TGS assays can be compared with assays (e.g. with calorimetry) of individual packages within the drums. The mobile tomographic technology is expected to considerably reduce characterization costs at DOE production and environmental technology sites.

  15. Pesticide uptake in potatoes: model and field experiments.

    PubMed

    Juraske, Ronnie; Vivas, Carmen S Mosquera; Velásquez, Alexander Erazo; Santos, Glenda García; Moreno, Mónica B Berdugo; Gomez, Jaime Diaz; Binder, Claudia R; Hellweg, Stefanie; Dallos, Jairo A Guerrero

    2011-01-15

    A dynamic model for uptake of pesticides in potatoes is presented and evaluated with measurements performed within a field trial in the region of Boyacá, Colombia. The model takes into account the time between pesticide applications and harvest, the time between harvest and consumption, the amount of spray deposition on soil surface, mobility and degradation of pesticide in soil, diffusive uptake and persistence due to crop growth and metabolism in plant material, and loss due to food processing. Food processing steps included were cleaning, washing, storing, and cooking. Pesticide concentrations were measured periodically in soil and potato samples from the beginning of tuber formation until harvest. The model was able to predict the magnitude and temporal profile of the experimentally derived pesticide concentrations well, with all measurements falling within the 90% confidence interval. The fraction of chlorpyrifos applied on the field during plant cultivation that eventually is ingested by the consumer is on average 10(-4)-10(-7), depending on the time between pesticide application and ingestion and the processing step considered. PMID:21141816

  16. Overview of results from the MST reversed field pinch experiment

    NASA Astrophysics Data System (ADS)

    Sarff, J. S.; Almagri, A. F.; Anderson, J. K.; Borchardt, M.; Carmody, D.; Caspary, K.; Chapman, B. E.; Den Hartog, D. J.; Duff, J.; Eilerman, S.; Falkowski, A.; Forest, C. B.; Goetz, J. A.; Holly, D. J.; Kim, J.-H.; King, J.; Ko, J.; Koliner, J.; Kumar, S.; Lee, J. D.; Liu, D.; Magee, R.; McCollam, K. J.; McGarry, M.; Mirnov, V. V.; Nornberg, M. D.; Nonn, P. D.; Oliva, S. P.; Parke, E.; Reusch, J. A.; Sauppe, J. P.; Seltzman, A.; Sovinec, C. R.; Stephens, H.; Stone, D.; Theucks, D.; Thomas, M.; Triana, J.; Terry, P. W.; Waksman, J.; Bergerson, W. F.; Brower, D. L.; Ding, W. X.; Lin, L.; Demers, D. R.; Fimognari, P.; Titus, J.; Auriemma, F.; Cappello, S.; Franz, P.; Innocente, P.; Lorenzini, R.; Martines, E.; Momo, B.; Piovesan, P.; Puiatti, M.; Spolaore, M.; Terranova, D.; Zanca, P.; Belykh, V.; Davydenko, V. I.; Deichuli, P.; Ivanov, A. A.; Polosatkin, S.; Stupishin, N. V.; Spong, D.; Craig, D.; Harvey, R. W.; Cianciosa, M.; Hanson, J. D.

    2013-10-01

    An overview of recent results from the MST programme on physics important for the advancement of the reversed field pinch (RFP) as well as for improved understanding of toroidal magnetic confinement more generally is reported. Evidence for the classical confinement of ions in the RFP is provided by analysis of impurity ions and energetic ions created by 1 MW neutral beam injection (NBI). The first appearance of energetic-particle-driven modes by NBI in a RFP plasma is described. MST plasmas robustly access the quasi-single-helicity state that has commonalities to the stellarator and ‘snake’ formation in tokamaks. In MST the dominant mode grows to 8% of the axisymmetric field strength, while the remaining modes are reduced. Predictive capability for tearing mode behaviour has been improved through nonlinear, 3D, resistive magnetohydrodynamic computation using the measured resistivity profile and Lundquist number, which reproduces the sawtooth cycle dynamics. Experimental evidence and computational analysis indicates two-fluid effects, e.g., Hall physics and gyro-viscosity, are needed to understand the coupling of parallel momentum transport and current profile relaxation. Large Reynolds and Maxwell stresses, plus separately measured kinetic stress, indicate an intricate momentum balance and a possible origin for MST's intrinsic plasma rotation. Gyrokinetic analysis indicates that micro-tearing modes can be unstable at high beta, with a critical gradient for the electron temperature that is larger than for tokamak plasmas by roughly the aspect ratio.

  17. Tools and Setups for Experiments with AC and Rotating Magnetic Fields

    ERIC Educational Resources Information Center

    Ponikvar, D.

    2010-01-01

    A rotating magnetic field is the basis for the transformation of electrical energy to mechanical energy. School experiments on the rotating magnetic field are rare since they require the use of specially prepared mechanical setups and/or relatively large, three-phase power supplies to achieve strong magnetic fields. This paper proposes several…

  18. The Swarm Absolute Scalar Magnetometers now operating in orbit

    NASA Astrophysics Data System (ADS)

    Fratter, Isabelle; Leger, Jean-Michel; Bertrand, François; Jager, Thomas; Hulot, Gauthier

    2014-05-01

    Swarm is one of the Earth Explorer Missions run by the European Space Agency. Its principal goal is to make the best ever survey of the Earth's magnetic field and ionosphere and to study how they vary over space and time. This will be achieved by a constellation of three identical satellites, launched on the 22nd of November 2013. In order to observe the magnetic field thoroughly, each satellite carries two magnetometers: a Vector Field Magnetometer coupled with a star tracker camera, to measure the direction of the magnetic field in space, and an Absolute Scalar Magnetometer (ASM), to measure its intensity. The ASM is the French contribution to the Swarm mission. This new generation instrument, based on the atomic spectroscopy of the helium 4 metastable state, was developed by CEA-Leti (1) in Grenoble with technical assistance and financing from CNES (2) and scientific support from IPGP (3). As the Swarm magnetic reference, the ASM scalar performances are crucial for the mission's success. Thanks to a new dedicated design, the ASM offers the best precision and absolute accuracy ever attained in space, with similar performances all along the orbit. The ASM will thus deliver high resolution scalar measurements at 1 Hz for the in-flight calibration of the vector field data over the 4 year mission. It can also be operated at a much higher sampling rate ("burst" mode at 250 Hz). In addition, on an experimental basis, this instrument also takes vector field measurements, which are being validated jointly by CEA-Leti and IPGP, with support from CNES. This poster presents the capabilities and working principle of this instrument as well as the results of the in-flight verifications carried out during the 3 first months in orbit, including the performances, the last status and future prospects. 1 CEA-Leti : French Atomic Energy and Alternative Energies Commission - Electronics and Information Technology Laboratory 2 CNES : Centre National d'Etudes Spatiales - French Space

  19. A preliminary assessment of field transport experiments using encapsulated cells

    SciTech Connect

    Petrich, C.R.; Knaebel, D.B.; Ralston, D.R.; Crawford, R.L.; Stormo, K.E.

    1995-12-31

    Microencapsulation of nonindigenous degradative organisms is a technique that enhances microorganism survival. An intermediate-scale field tracer test was conducted to evaluate the transport of encapsulated-cell microbeads and other particles in a shallow, confined, heterogeneous aquifer consisting of unconsolidated silts, sands, and gravels under induced-gradient, uniform flow conditions. Tracers included bromide; 2-, 5-, and 15-{micro}m-diameter polystyrene microspheres; and encapsulated Flavobacterium microbeads ranging in diameter from approximately 2 to 80 {micro}m. Results suggest that aquifer heterogeneity was a dominant factor in bromide- and particle-transport patterns. Encapsulated-cell migration appeared to be retarded with respect to the bromide and microsphere tracers. Results of this study also indicate that encapsulated-cell particle sizes and encapsulation material characteristics may be important factors affecting the transport of encapsulated cells in a subsurface environment.

  20. Overview of C-2 Field Reversed Configuration Experiments

    NASA Astrophysics Data System (ADS)

    Guo, Houyang; TAE Team

    2013-10-01

    The C-2 compact toroid merging (CT) facility was built to form and sustain high temperature Field Reversed Configurations (FRC) with extremely high beta (i.e., with the ratio of confined plasma to external total magnetic pressure approaching 100%). Significant progress has been made in C-2 on both technology and physics fronts, achieving stable plasmas up to 5 ms with a dramatic improvement in confinement, far beyond the prediction from the conventional FRC scaling. The key approaches to these exciting achievements are (1) dynamic FRC formation by collisional merging of super-Alfvénic CTs, (2) effective control of stability and transport by plasma guns and neutral beam injection, and (3) active wall conditioning. The emerging confinement scaling for this new plasma regime shows a strong dependence on temperature in contrast to the usually observed Bohm or gyro-Bohm scaling in other magnetic confinement systems. This presentation highlights these recent advances.