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Sample records for field ripple reduction

  1. Reduction of toroidal magnetic field ripple in the advanced material tokamak experiment on JFT-2M

    Sato, M.; Miura, Y.; Kimura, H.; Yamamoto, M.; Koike, T.; Nakayama, T.; Hasegawa, M.; Urata, K.

    1998-01-01

    In order to reduce fast ion losses due to the toroidal field ripple, the reduction of ripple amplitude (δ) by inserting ferritic steel is studied, taking its toroidal mode number into account. The guideline of the design for reduction is wider and thicker ferritic board (FB) is located at further position from VV. The δ depends on the toroidal magnetic field. The value of B r21 /B t in the case of displacement of few cm is about 1 x 10 -5 which is one order smaller than the critical value. The offsetting of FB is not a problem for locked mode. Preliminary experiments with insertion of one or two FB's indicate no adverse effect on global plasma parameters. (author)

  2. Reduction of toroidal magnetic field ripple in the advanced material tokamak experiment on JFT-2M

    Sato, M.; Miura, Y.; Kimura, H.; Yamamoto, M.; Koike, T. [Japan Atomic Energy Research Inst. (Japan); Nakayama, T. [Hitachi Ltd. (Japan); Hasegawa, M. [Mitsubishi Electric Corp. (Japan); Urata, K. [Mitsubishi Heavy Industries Ltd. (Japan)

    1998-07-01

    In order to reduce fast ion losses due to the toroidal field ripple, the reduction of ripple amplitude ({delta}) by inserting ferritic steel is studied, taking its toroidal mode number into account. The guideline of the design for reduction is wider and thicker ferritic board (FB) is located at further position from VV. The {delta} depends on the toroidal magnetic field. The value of B{sub r21} /B{sub t} in the case of displacement of few cm is about 1 x 10{sup -5} which is one order smaller than the critical value. The offsetting of FB is not a problem for locked mode. Preliminary experiments with insertion of one or two FB's indicate no adverse effect on global plasma parameters. (author)

  3. Ferritic insertion for reduction of toroidal magnetic field ripple on JT-60U

    Shinohara, K.; Sakurai, S.; Ishikawa, M.; Tsuzuki, K.; Suzuki, Y.; Masaki, K.; Naito, O.; Kurihara, K.; Suzuki, T.; Koide, Y.; Fujita, T.; Miura, Y.

    2007-01-01

    Ferritic steel tiles (FSTs) have been installed to improve the energetic ion confinement by reducing a toroidal magnetic field ripple. Aiming at cost-effective installation, orbit-following calculations of energetic ions were carried out for a design of the installation of ferritic steel on the JT-60U by using the fully three dimensional magnetic field orbit-following Monte-Carlo (F3D OFMC) code, which had been developed for ferritic insert experiments on the JFT-2M and can treat the complex magnetic field structure produced by ferritic inserts. The installed FSTs add a non-linear magnetic field on magnetic sensors for plasma control and an equilibrium calculation. The code for real-time control has been modified to take into account the magnetic field by the FSTs. The plasma operation was successfully resumed after usual conditioning processes and real-time plasma control was successfully carried out. The heat load measurement indicates the improved confinement of energetic ions. These results are important for practical application of the ferritic steel, which is a leading candidate of a structural material on a DEMO reactor

  4. Toroidal field ripple effects in large tokamaks

    Uckan, N.A.; Tsang, K.T.; Callen, J.D.

    1975-01-01

    In an experimental power reactor, the ripple produced by the finite number of toroidal field coils destroys the ideal axisymmetry of the configuration and is responsible for additional particle trapping, loss regions and plasma transport. The effects of toroidal field ripple on the plasma transport coefficient, the loss of alpha particles and energetic injection ions, and the relaxation of toroidal flows are investigated in a new and systematic way. The relevant results are applied to the ORNL-EPR reference design; the maximum ripple there of about 2.2 percent at the outer edge of the plasma column is found to be tolerable from plasma physics considerations

  5. CBA main magnet power supply ripple reduction

    Bagley, G.; Edwards, R.J.

    1983-01-01

    The preliminary results of a development program to minimize beam perturbation resulting from ripple current generated by the CBA Main Magnet Power Supply are presented. The assessment of the magnitude and causes of the ripple generated led to a modification of the SCR Gate Driver and the addition of a bandpass amplifier correction loop which gave significant improvement. A description of the changes made and the results obtained are included. A second design approach was developed in which the timing of the SCR gate pulses is directly determined by a VCO. The results reported with this VCO Loop indicate superior performance particularly at frequencies below 60 Hz. A shunt transistor regulator design is proposed to minimize higher SCR switching frequency harmonics

  6. Reduction of ripple voltage in a dynamitron

    Langsdorf, A. Jr.

    1982-01-01

    We determined that a precise neutralization of the RF ripple voltage on the high-voltage terminal of a Dynamitron has previously been prevented by a nonegligible phase shift of RF currents in the two halves of the approx. 100-kHz class C oscillator tank circuit, which is actually constituted of two slightly unequal high-Q coupled circuits because it has two ground points: the inescapable center-tap-ground in the capacitive legs and a center-tap-ground lead to the induction coil. The latter is needed to prevent damage by flashover transients; equivalent to its removal was the adjusting of RF ground return current to a null by aid of a current transformer on this lead and the suitable adjusting of trimmer capacitance. While the phase shift was thus held to a null, the actual ripple amplitude on the hv terminal was minimized by adjusting additional trimmer capacitances installed in the terminal of the machine. Then p/p 100-kHz ripple at 2-MV dc output was reduced to about 50V and RMS resolution by (p,#betta#) resonance threshold data near 1 MV was about 250 V. The limit to resolution has various causes including mechanical vibrations and unbalanced harmonics of the RF

  7. Output Current Ripple Reduction Algorithms for Home Energy Storage Systems

    Jin-Hyuk Park

    2013-10-01

    Full Text Available This paper proposes an output current ripple reduction algorithm using a proportional-integral (PI controller for an energy storage system (ESS. In single-phase systems, the DC/AC inverter has a second-order harmonic at twice the grid frequency of a DC-link voltage caused by pulsation of the DC-link voltage. The output current of a DC/DC converter has a ripple component because of the ripple of the DC-link voltage. The second-order harmonic adversely affects the battery lifetime. The proposed algorithm has an advantage of reducing the second-order harmonic of the output current in the variable frequency system. The proposed algorithm is verified from the PSIM simulation and experiment with the 3 kW ESS model.

  8. Effects of Resonant Helical Field on Toroidal Field Ripple in IR-T1 Tokamak

    Mahdavipour, B.; Salar Elahi, A.; Ghoranneviss, M.

    2018-02-01

    The toroidal magnetic field which is created by toroidal coils has the ripple in torus space. This magnetic field ripple has an importance in plasma equilibrium and stability studies in tokamak. In this paper, we present the investigation of the interaction between the toroidal magnetic field ripple and resonant helical field (RHF). We have estimated the amplitude of toroidal field ripples without and with RHF (with different q = m/n) ( m = 2, m = 3, m = 4, m = 5, m = 2 & 3, n = 1) using “Comsol Multiphysics” software. The simulations show that RHF has effects on the toroidal ripples.

  9. Torque ripple reduction in electric machines

    Reddy, Patel Bhageerath; Huh, Kum-Kang; El-Refaie, Ayman Mohamed Fawzi; Galioto, Steven Joseph

    2017-08-22

    An electric machine, such as an Internal Permanent magnet or Synchronous Reluctance machine, having X phases, that includes a stator assembly, having M slots, with a stator core and stator teeth, that is further configured with stator windings to generate a stator magnetic field when excited with alternating currents and extends along a longitudinal axis with an inner surface that defines a cavity; and a rotor assembly, having N poles, disposed within the cavity which is configured to rotate about the longitudinal axis, wherein the rotor assembly includes a shaft, a rotor core located circumferentially around the shaft. The machine is configured such that a value k=M/(X*N) wherein k is a non-integer greater than about 1.3. The electric machine may alternatively, or additionally, include a non-uniformed gap between the exterior surface of the rotor spokes and the interior stator surface of the stator.

  10. Edge pedestal characteristics in JET and JT-60U tokamaks under variable toroidal field ripple

    Urano, H.; Saibene, G.; Oyama, N.; Parail, V.; P. de Vries,; Sartori, R.; Kamada, Y.; Kamiya, K.; Loarte, A.; Lonnroth, J.; Sakamoto, Y.; Salmi, A.; Shinohara, K.; Takenaga, H.; Yoshida, M.

    2011-01-01

    The effects of toroidal field (TF) ripple on the edge pedestal characteristics were examined in the TF ripple scan experiments at the plasma current I(p) of 1.1 MA in JET and JT-60U. The TF ripple amplitude delta(R) was defined as a value averaged over the existing ripple wells at the separatrix on

  11. Radial electric field in JET advanced tokamak scenarios with toroidal field ripple

    Crombe, K.; Andrew, Y.; Biewer, T. M.; Blanco, E.; de Vries, P. C.; Giroud, C.; Hawkes, N. C.; Meigs, A.; Tala, T.; von Hellermann, M.; Zastrow, K. D.

    2009-01-01

    A dedicated campaign has been run on JET to study the effect of toroidal field (TF) ripple on plasma performance. Radial electric field measurements from experiments on a series of plasmas with internal transport barriers (ITBs) and different levels of ripple amplitude are presented. They have been

  12. Buck supplies output voltage ripple reduction using fuzzy control

    Nicu BIZON

    2007-12-01

    Full Text Available Using the PWM control for switching power supplies the peaks EMI noise appear at the switching frequency and its harmonics. Using randomize or chaotic PWM control techniques in these systems the power spectrum is spread out in all frequencies band spectral emissions, but with a bigger ripple in the output voltage. The proposed nonlinear feedback control method, which induces chaos, is based by fuzzy rules that minimize the output voltage ripple. The feasibility and effectiveness of this relative simple method is shown by simulation. A comparison with the previous control method is included, too.

  13. Emittance growth due to dipole ripple and sextupole

    Shih, H.J.; Ellison, J.A.; Syphers, M.J.; Newberger, B.S.

    1993-05-01

    Ripple in the power supplies for storage ring magnets can have adverse effects on the circulating beams: orbit distortion and emittance growth from dipole ripple, tune modulation and dynamic aperture reduction from quadrupole ripple, etc. In this paper, we study the effects of ripple in the horizontal bending field of the SSC in the presence of nonlinearity, in particular, the growth in beam emittance

  14. Effects of toroidal field ripple on suprathermal ions in tokamak plasmas

    Goldston, R.J.; Towner, H.H.

    1980-02-01

    Analytic calculations of three important effects of toroidal field ripple on suprathermal ions in tokamak plasmas are presented. In the first process, collisional ripple-trapping, beam ions become trapped in local magnetic wells near their banana tips due to pitch-angle scattering as they traverse the ripple on barely unripple-trapped orbits. In the second process, collisionless ripple-trapping, near-perpendicular untrapped ions are captured (again near a banana tip) due to their finite orbits, which carry them out into regions of higher ripple. In the third process, banana-drift diffusion, fast-ion banana orbits fail to close precisely, due to a ripple-induced variable lingering period near the banana tips. These three mechanisms lead to substantial radial transport of banana-trapped, neutral-beam-injected ions when the quantity α* identical with epsilon/sin theta/Nqdelta is of order unity or smaller

  15. Effects of toroidal field ripple on suprathermal ions in tokamak plasmas

    Goldston, R.J.; Towner, H.H.

    1981-01-01

    Analytic calculations of three important effects of toroidal field ripple on suprathermal ions in tokamak plasmas are presented. In the first process, collisional ripple-trapping, ions become trapped in local magnetic wells near their banana tips owing to pitch-angle scattering as they traverse the ripple on barely unripple-trapped orbits. In the second process, collisionless ripple-trapping, ions are captured (again near a banana tip) owing to their finite orbits, which carry them out into regions of higher ripple. In the third process, banana-drift diffusion, fast-ion banana orbits fail to close precisely, due to a ripple-induced 'variable lingering period' near the banana tips. These three mechanisms lead to substantial radial transport of banana-trapped, neutral-beam-injected ions when the quantity α* is identical with epsilonsinthetaNqdelta is of order unity or smaller. (author)

  16. Effects of toroidal field ripple on injected deuterons in the FED device

    Fowler, R.H.; Rome, J.A.

    1981-07-01

    A Monte Carlo beam deposition and thermalization code is used to assess the effects of toroidal field (TF) ripple on injected fast deuterons in the Fusion Engineering Device (FED). The code uses realistic geometry for the beam, plasma equilibrium, TF ripple, and vacuum chamber. For injection at an angle of 35 0 (co) from perpendicular, no particles were ripple trapped and less than 1% of the injected power went to the wall and the limiter. However, due to the large amounts of computer time required by these programs, only 100 particles were followed in the rippled case and the results must be regarded as preliminary

  17. Ripple reduction activities in the MG room at the Bevatron, August 1991 to August 1992

    Blasbalg, M.; Bennett, M.

    1992-08-01

    This report discusses the following topics: magnet - voltage dividers temperature ampersand voltage influence error calculation; magnet filters summarized data table; magnet transfer function measurement setup and connection diagrams; response of existing magnet system including ripple reduction filters - Dec 1991; magnet filters - mutual inductance problem; and damping the magnet filters

  18. Reduction of torque ripple in DTC induction motor drive with discrete voltage vectors

    Rosić Marko

    2014-01-01

    Full Text Available This paper presents а practical implementation of direct torque control (DTC of an induction machine on MSK2812 DSP platform, and the analysis of possibilities for reduction of torque ripple. Basic theoretical background relating the DTC was primarily set and the obtained experimental results have been given. It is shown that the torque ripple can be reduced by adjusting the intensity of voltage vectors and by modification of hysteresis comparator, while the simplicity of the basic DTC algorithm has been maintained. [Projekat Ministarstva nauke Republike Srbije, br. TR33016

  19. Torque ripple reduction of brushless DC motor based on adaptive input-output feedback linearization.

    Shirvani Boroujeni, M; Markadeh, G R Arab; Soltani, J

    2017-09-01

    Torque ripple reduction of Brushless DC Motors (BLDCs) is an interesting subject in variable speed AC drives. In this paper at first, a mathematical expression for torque ripple harmonics is obtained. Then for a non-ideal BLDC motor with known harmonic contents of back-EMF, calculation of desired reference current amplitudes, which are required to eliminate some selected harmonics of torque ripple, are reviewed. In order to inject the reference harmonic currents to the motor windings, an Adaptive Input-Output Feedback Linearization (AIOFBL) control is proposed, which generates the reference voltages for three phases voltage source inverter in stationary reference frame. Experimental results are presented to show the capability and validity of the proposed control method and are compared with the vector control in Multi-Reference Frame (MRF) and Pseudo-Vector Control (P-VC) method results. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  20. Computational studies of the effect of magnetic field ''ripple'' on neutral beam heating of ZEPHYR

    Lister, G.G.; Gruber, O.

    1981-01-01

    The results of computations to estimate the heating efficiency of neutral injection in the proposed ZEPHYR experiment are presented. A suitably modified version of the Monte-Carlo neutral deposition and orbit following code FREYA was used for these calculations, in which particular emphasis has been placed on the effects of toroidal field ripple. We find that the ripple associated with the preliminary design of the experiment (+-6%) would result in intolerable energy losses due to ''ripple trapping'' of the fast ions produced by the neutral beam and insufficient heating of the central plasma. The necessary conditions for ignition can be obtained with a total heating power of 25 MW provided the ripple can be reduced to +-1%, in which case energy losses could be kept below 30%. These results are compatible with those found from transport code calculations of the losses to be expected due to ripple enhanced thermal conduction in the plasma

  1. FLOC: Field Line and Orbit Code for the study of ripple beam injection into tokamaks

    Fowler, R. H.; Lee, D. K.; Gaffney, P. W.; Rome, J. A.

    1978-06-01

    The computer code described is used to study ripple beam injection into a tokamak plasma. The collisionless guiding center equations of motion are integrated to find the orbits of single particles in realistic magnetic fields for ripple injection. In order to determine if the ripple is detrimental to the plasma, the magnetic flux surfaces are constructed by integration of the field line equations. The numerical techniques are described, and use of the code is outlined. A program listing is provided, and the results of sample cases are presented.

  2. FLOC: Field Line and Orbit Code for the study of ripple beam injection into tokamaks

    Fowler, R.H.; Lee, D.K.; Gaffney, P.W.; Rome, J.A.

    1978-06-01

    The computer code described is used to study ripple beam injection into a tokamak plasma. The collisionless guiding center equations of motion are integrated to find the orbits of single particles in realistic magnetic fields for ripple injection. In order to determine if the ripple is detrimental to the plasma, the magnetic flux surfaces are constructed by integration of the field line equations. The numerical techniques are described, and use of the code is outlined. A program listing is provided, and the results of sample cases are presented

  3. A Method of Sky Ripple Residual Nonuniformity Reduction for a Cooled Infrared Imager and Hardware Implementation.

    Li, Yiyang; Jin, Weiqi; Li, Shuo; Zhang, Xu; Zhu, Jin

    2017-05-08

    Cooled infrared detector arrays always suffer from undesired ripple residual nonuniformity (RNU) in sky scene observations. The ripple residual nonuniformity seriously affects the imaging quality, especially for small target detection. It is difficult to eliminate it using the calibration-based techniques and the current scene-based nonuniformity algorithms. In this paper, we present a modified temporal high-pass nonuniformity correction algorithm using fuzzy scene classification. The fuzzy scene classification is designed to control the correction threshold so that the algorithm can remove ripple RNU without degrading the scene details. We test the algorithm on a real infrared sequence by comparing it to several well-established methods. The result shows that the algorithm has obvious advantages compared with the tested methods in terms of detail conservation and convergence speed for ripple RNU correction. Furthermore, we display our architecture with a prototype built on a Xilinx Virtex-5 XC5VLX50T field-programmable gate array (FPGA), which has two advantages: (1) low resources consumption; and (2) small hardware delay (less than 10 image rows). It has been successfully applied in an actual system.

  4. Radial electric field in JET advanced tokamak scenarios with toroidal field ripple

    Crombe, K [Postdoctoral Fellow of the Research Foundation - Flanders (FWO), Department of Applied Physics, Ghent University, Rozier 44, B-9000 Gent (Belgium); Andrew, Y; De Vries, P C; Giroud, C; Hawkes, N C; Meigs, A; Zastrow, K-D [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon, OX14 3DB (United Kingdom); Biewer, T M [Oak Ridge National Laboratory, Oak Ridge, TN 37831-6169, TN (United States); Blanco, E [Laboratorio Nacional de Fusion, Asociacion EURATOM-CIEMAT, Madrid (Spain); Tala, T [VTT Technical Research Centre of Finland, Association EURATOM-Tekes, PO Box 1000, FIN-02044 VTT (Finland); Von Hellermann, M [FOM Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, Trilateral Euregio Cluster, PO Box 1207, 3430 BE Nieuwegein (Netherlands)], E-mail: Kristel.Crombe@jet.uk

    2009-05-15

    A dedicated campaign has been run on JET to study the effect of toroidal field (TF) ripple on plasma performance. Radial electric field measurements from experiments on a series of plasmas with internal transport barriers (ITBs) and different levels of ripple amplitude are presented. They have been calculated from charge exchange measurements of impurity ion temperature, density and rotation velocity profiles, using the force balance equation. The ion temperature and the toroidal and poloidal rotation velocities are compared in plasmas with both reversed and optimized magnetic shear profiles. Poloidal rotation velocity (v{sub {theta}}) in the ITB region is measured to be of the order of a few tens of km s{sup -1}, significantly larger than the neoclassical predictions. Increasing levels of the TF ripple are found to decrease the ion temperature gradient in the ITB region, a measure for the quality of the ITB, and the maximum value of v{sub {theta}} is reduced. The poloidal rotation term dominates in the calculations of the total radial electric field (E{sub r}), with the largest gradient in E{sub r} measured in the radial region coinciding with the ITB.

  5. Implementation of vertically asymmetric toroidal-field ripple for beam heating of tokamak reactor plasmas

    Jassby, D.L.; Sheffield, G.V.; Towner, H.H.; Weissenburger, D.W.

    1976-10-01

    The neutral-beam energy required for adequate penetration of tokamak plasmas of high opacity can be reduced by a large factor if the beam is injected vertically into a region of large TF (toroidal-field) ripple. Energetic ions are trapped in local magnetic wells and drift vertically toward the midplane (z = 0). If the ripple is made very small on the opposite side of the midplane, drifting ions are detrapped and thermalized in the central plasma region. This paper discusses design considerations for establishing the required vertically asymmetric ripple. Examples are given of special TF-coil configurations, and of the use of auxiliary coil windings to create the prescribed ripple profiles

  6. Effect of toroidal field ripple on the formation of internal transport barriers

    Vries, P C de; Hawkes, N C; Challis, C D; Andrew, Y; Beurskens, M; Brix, M; Giroud, C; Zastrow, K-D [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Joffrin, E [EFDA-JET CSU, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB (United Kingdom); Litaudon, X [Association EURATOM-CEA, DSM/DFRC, CEA Cadarache, 13108, St Paul lez Durance (France); Brzozowski, J; Johnson, T [Association EURATOM-VR, Fusion Plasma Physics, EES, KTH, Stockholm (Sweden); Crombe, K [Department of Applied Physics, Ghent University, Ghent (Belgium); Hobirk, J [Max-Planck-Institut fuer Plasmaphysik, Euratom Association, 85748 Garching (Germany); Loennroth, J; Salmi, A [Association Euratom-Tekes, Helsinki University of Technology, PO Box 4100, 02015 TKK (Finland); Tala, T [Association Euratom-Tekes, VTT, PO Box 1000, 02044 VTT (Finland); Yavorskij, V [Institute for Theoretical Physics, Association EURATOM-OEAW, University of Innsbruck (Austria)], E-mail: Peter.de.Vries@jet.uk

    2008-06-15

    The effect of a toroidal field (TF) ripple on the formation and performance of internal transport barriers (ITBs) has been studied in JET. It was found that the TF ripple had a profound effect on the toroidal plasma rotation. An increased TF ripple up to {delta} = 1% led to a lower rotation and reduced the rotational shear in the region where the ITBs were formed. ITB triggering events were observed in all cases and it is thought that the rotational shear may be less important for this process than, for example, the q-profile. However, the increase in the pressure gradient following the ITB trigger was reduced in discharges with a larger TF ripple and consequently a lower rotational shear. This suggests that toroidal rotation and its shear play a role in the growth of the ITB once it has been triggered.

  7. An Analysis of Ripple and Error Fields Induced by a Blanket in the CFETR

    Yu, Guanying; Liu, Xufeng; Liu, Songlin

    2016-10-01

    The Chinese Fusion Engineering Tokamak Reactor (CFETR) is an important intermediate device between ITER and DEMO. The Water Cooled Ceramic Breeder (WCCB) blanket whose structural material is mainly made of Reduced Activation Ferritic/Martensitic (RAFM) steel, is one of the candidate conceptual blanket design. An analysis of ripple and error field induced by RAFM steel in WCCB is evaluated with the method of static magnetic analysis in the ANSYS code. Significant additional magnetic field is produced by blanket and it leads to an increased ripple field. Maximum ripple along the separatrix line reaches 0.53% which is higher than 0.5% of the acceptable design value. Simultaneously, one blanket module is taken out for heating purpose and the resulting error field is calculated to be seriously against the requirement. supported by National Natural Science Foundation of China (No. 11175207) and the National Magnetic Confinement Fusion Program of China (No. 2013GB108004)

  8. Use of field ripple for burn phase control in short-pulse tokamak reactors

    Davidson, J.N.; Stacey, W.M. Jr.

    1979-05-01

    The possible use of toroidal field ripple to control temperature excursions was investigated. In particular, the magnitude of the power savings necessary to control the ion temperature for about 120 seconds during the burn phase of an ETF tokamak was determined through the use of a global dynamics code. Then the amount of field ripple necessary to effect that control was calculated for each case. In the next section the basic properties of the simulation code are given and the various plasma cases investigated are described in some detail. There follows a discussion of the field ripple control mechanisms and their application to the problem at hand. Finally, the results of the study are presented along with the conclusions drawn from them

  9. Capacitor voltage ripple reduction and arm energy balancing in MMC-HVDC

    Parikh, Harsh; Martin-Loeches, Ruben Sánches; Tsolaridis, Georgios

    2016-01-01

    Modular Multilevel Converters are emerging and widely used in HVDC applications. However, the submodule capacitors are still large and the energy balancing under unbalanced conditions is a challenge. In this paper, an analytical model focusing on the energy stored in the capacitors and voltage...... variations is utilized in order to achieve better performance. By injecting a second order harmonic component into the circulating current, the energy variation and consequently the capacitor voltage ripple is reduced allowing for a capacitor size reduction. At the same time, an arm energy balancing...

  10. Hurricane Sandy's Fingerprint: Ripple Bedforms at an Inner Continental Shelf Sorted Bedform Field Site

    DuVal, C.; Trembanis, A. C.; Beaudoin, J. D.; Schmidt, V. E.; Mayer, L. A.

    2013-12-01

    The hydrodynamics and seabed morphodynamics on the inner continental shelf and near shore environments have increasing relevance with continued development of near shore structures, offshore energy technologies and artificial reef construction. Characterizing the stresses on and response of the seabed near and around seabed objects will inform best practices for structural design, seabed mine and unexploded ordnance detection, and archaeological and benthic habitat studies. As part of an ONR funded project, Delaware's Redbird Reef is being studied for object scour and sorted bedform morphodynamics (Trembanis et al., in press). Central to this study are the effects of large storm events, such as Hurricane Sandy, which have had significant impact on the seafloor. Previous studies of inner shelf bedform dynamics have typically focused on near bed currents and bed stressors (e.g. Trembanis et al., 2004), sorted bedforms (e.g. Green et al., 2004) and object scour (e.g. Quinn, 2006; Trembanis et al., 2007; Mayer et al., 2007), but our understanding of the direct effects of objects and object scour on bedform morphodynamics is still incomplete. With prominent sorted bedform ripple fields, the Delaware Redbird artificial reef site, composed of 997 former New York City subway cars, as well as various military vehicles, tugboats, barges and ballasted tires, has made an ideal study location (Raineault et al., 2013 and 2011). Acoustic mapping of the Redbird reef three days prior to Sandy and two days after the following nor'easter, captured the extensive effects of the storms to the site, while acoustic Doppler current profilers characterized both the waves and bottom currents generated by the storm events. Results of the post-Sandy survey support the theory of sorted bedform evolution proposed by Murray and Thieler (2004). Acoustic imagery analysis indicates a highly energized and mobile bed during the storms, leading to self-organization of bedforms and creation of large

  11. Grey Wolf based control for speed ripple reduction at low speed operation of PMSM drives.

    Djerioui, Ali; Houari, Azeddine; Ait-Ahmed, Mourad; Benkhoris, Mohamed-Fouad; Chouder, Aissa; Machmoum, Mohamed

    2018-03-01

    Speed ripple at low speed-high torque operation of Permanent Magnet Synchronous Machine (PMSM) drives is considered as one of the major issues to be treated. The presented work proposes an efficient PMSM speed controller based on Grey Wolf (GW) algorithm to ensure a high-performance control for speed ripple reduction at low speed operation. The main idea of the proposed control algorithm is to propose a specific objective function in order to incorporate the advantage of fast optimization process of the GW optimizer. The role of GW optimizer is to find the optimal input controls that satisfy the speed tracking requirements. The synthesis methodology of the proposed control algorithm is detailed and the feasibility and performances of the proposed speed controller is confirmed by simulation and experimental results. The GW algorithm is a model-free controller and the parameters of its objective function are easy to be tuned. The GW controller is compared to PI one on real test bench. Then, the superiority of the first algorithm is highlighted. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

  12. Torque ripple reduction of brushless DC motor with harmonic current injection based on integral terminal sliding mode control

    Boroujeni, Mojtaba Shirvani; Markadeh, Gholamreza Arab; Soltani, Jafar

    2018-01-01

    Brushless Harmonic current injection to the stator windings is one of the most effective methods for torque ripple reduction of brushless DC motors. Because of multi harmonic contents of the stator currents, the conventional methods based on rotational reference frame cannot be used to calculate...

  13. Stimulated Raman scattering by an intense relativistic electron beam in a long rippled magnetic field

    Efthimion, P.C.; Schlesinger, S.P.

    1977-01-01

    For the first time, the parametric coupling of the negative-energy cyclotron and space-charge modes to a fast coaxial waveguide structure is observed. The coaxial waveguide smooth center conductor is internally loaded to maintain a 5% ripple of 1.4-, 1.6-, or 2.0-cm periods on the background axial magnetic field throughout the interaction region of 70 cm. The parametric coupling may be considered a stimulated scattering process with the rippled magnetic field of zero frequency in the lab frame appearing as an electromagnetic pump wave in the beam frame, with 30-MW/cm 2 power density imparting to the electrons a quiver velocity V/sub os/ approx. = 0.1c. As predicted by theory, the frequency of the microwave radiation generated by the negative-energy cyclotron mode decreases with increasing magnetic field while remaining constant for the negative-energy space-charge mode. Power levels from 1 to 5 MW have been measured at mm and cm wavelengths. Radiation at frequencies of 2γ 2 V/L, where V and L are the beam velocity and ripple period, respectively, has been observed at high magnetic fields with an exponential-growth rate consistent with parametric coupling theory. This mechanism could be employed as a tunable generator of millimeter and submillimeter wavelength radiation

  14. Stimulated Raman scattering by an intense relativistic electron beam in a long rippled magnetic field

    Efthimion, P.C.

    1977-01-01

    For the first time, the parametric coupling of the negative energy cyclotron and space-charge modes to a fast coaxial waveguide structure is observed. The coaxial waveguide smooth center conductor is internally loaded to maintain a 5% ripple of 1.4, 1.6, or 2.0 cm periods on the background axial magnetic field throughout the interaction region of 70 cm. The parametric coupling may be considered a stimulated scattering process with the rippled magnetic field of zero frequency in the laboratory frame appearing as an electromagnetic pump wave in the beam frame, with 30 MW/cm 2 power density imparting to the electrons a quiver velocity V/sub os/ = 0.1 c. As predicted by theory, the frequency of the microwave radiation generated by the negative energy cyclotron mode decreases with increasing magnetic field while remaining constant for the negative energy space-charge mode. Power levels from 1 to 5 MW have been measured at mm and cm wavelengths. Radiation at frequencies 2γ 2 V/L, where V and L are the beam velocity and ripple period respectively, has been observed at high magnetic fields with an exponential growth rate consistent with parametric coupling theory. This mechanism could be employed as a tunable generator of submillimeter and infrared wavelength radiation

  15. Simulated near-field mapping of ripple pattern supported metal nanoparticles arrays for SERS optimization

    Arya, Mahima; Bhatnagar, Mukul; Ranjan, Mukesh; Mukherjee, Subroto; Nath, Rabinder; Mitra, Anirban

    2017-11-01

    An analytical model has been developed using a modified Yamaguchi model along with the wavelength dependent plasmon line-width correction. The model has been used to calculate the near-field response of random nanoparticles on the plane surface, elongated and spherical silver nanoparticle arrays supported on ion beam produced ripple patterned templates. The calculated near-field mapping for elongated nanoparticles arrays on the ripple patterned surface shows maximum number of hot-spots with a higher near-field enhancement (NFE) as compared to the spherical nanoparticle arrays and randomly distributed nanoparticles on the plane surface. The results from the simulations show a similar trend for the NFE when compared to the far field reflection spectra. The nature of the wavelength dependent NFE is also found to be in agreement with the observed experimental results from surface enhanced Raman spectroscopy (SERS). The calculated and the measured optical response unambiguously reveal the importance of interparticle gap and ordering, where a high intensity Raman signal is obtained for ordered elongated nanoparticles arrays case as against non-ordered and the aligned configuration of spherical nanoparticles on the rippled surface.

  16. Confinement of ripple-trapped slowing-down ions by a radial electric field

    Herrmann, W.

    1998-03-01

    Weakly collisional ions trapped in the toroidal field ripples at the outer plasma edge can be prevented to escape the plasma due to grad B-drift by a counteracting radial electric field. This leads to an increase in the density of ripple-trapped ions, which can be monitored by the analysis of charge exchange neutrals. The minimum radial electric field E r necessary to confine ions with energy E and charge q (q=-1: charge of the electron) is E r = -E/(q * R), where R is the major radius at the measuring point. Slowing-down ions from neutral injection are usually in the right energy range to be sufficiently collisionless in the plasma edge and show the confinement by radial electric fields in the range of tens of kV/m. The density of banana ions is almost unaffected by the radial electric field. Neither in L/H- nor in H/L-transitions does the density of ripple-trapped ions and, hence, the neutral particle fluxes, show jumps in times shorter than 1 ms. According to [1,2] the response time of the density and the fluxes to a sudden jump in the radial electric field is less than 200 μs, if the halfwidth of the electric field is larger or about 2 cm. This would exclude rapid jumps in the radial electric field at the transition. Whether the halfwidth of the electric field is that large during transition cannot be decided from the measurement of the fluxes alone. (orig.)

  17. Ripple Field AC Losses in 10-MW Wind Turbine Generators With a MgB2 Superconducting Field Winding

    Liu, Dong; Polinder, Henk; Magnusson, Niklas

    2016-01-01

    Superconducting (SC) synchronous generators are proposed as a promising candidate for 10-20-MW direct-drive wind turbines because they can have low weights and small sizes. A common way of designing an SC machine is to use SC wires with high current-carrying capability in the dc field winding...... and the ac armature winding is made with copper conductors. In such generators, the dc field winding is exposed to ac magnetic field ripples due to space harmonics from the armature. In generator design phases, the ac loss caused by these ripple fields needs to be evaluated to avoid local overheating...... and an excessive cooling budget. To determine the applicability of different design solutions in terms of ac losses, this paper estimates the ac loss level of 10-MW wind generator designs employing a MgB2 SC field winding. The effects on ac losses are compared between nonmagnetic and ferromagnetic teeth...

  18. Advanced RF-KO slow-extraction method for the reduction of spill ripple

    Noda, K; Shibuya, S; Uesugi, T; Muramatsu, M; Kanazawa, M; Takada, E; Yamada, S

    2002-01-01

    Two advanced RF-knockout (RF-KO) slow-extraction methods have been developed at HIMAC in order to reduce the spill ripple for accurate heavy-ion cancer therapy: the dual frequency modulation (FM) method and the separated function method. As a result of simulations and experiments, it was verified that the spill ripple could be considerably reduced using these advanced methods, compared with the ordinary RF-KO method. The dual FM method and the separated function method bring about a low spill ripple within standard deviations of around 25% and of 15% during beam extraction within around 2 s, respectively, which are in good agreement with the simulation results.

  19. Ripple transport in a modular Helias

    Beidler, C.D.

    1989-01-01

    Neoclassical transport rates are determined for Helical-Axis Advanced Stellarators (Helias). Special emphasis is given to Wendelstein VII-X candidates, for which the magnetic field is produced by a large number of discrete non-planar coils. The investigation is concentrated on the long-mean-free-path regime where particles trapped in local ripple wells of the magnetic field make the dominant contribution to transport. For Wendelstein VII-X, such particles fall into two classes; those localized in the helical ripple common to all stellarator-type devices and those very-localized particles which are trapped in the modular ripples existing between the individual coils. Using analytical techniques it is shown that helical-ripple transport rates are substantially reduced for all Wendelstein VII-X candidates relative to classical stellarator/torsatron configurations. This reduction is most pronounced in the 1/ν regime - equivalent helical ripples of less than 1% lead to reduction factors of more than an order of magnitude - but is significant throughout the entire long-mean-free-path regime. Modular ripple transport in Wendelstein VII-X is calculated by analytically solving the appropriate bounce-averaged kinetic equation. This solution assumes a general magnetic field model and fully accounts for the deformation of modular ripples due to the presence of the other magnetic-field harmonics. Results indicate that 12 coils per field period are necessary if modular-ripple losses are to remain smaller than helical-ripple losses over the entire plasma cross section. (orig.)

  20. Ripple artifact reduction using slice overlap in slice encoding for metal artifact correction.

    den Harder, J Chiel; van Yperen, Gert H; Blume, Ulrike A; Bos, Clemens

    2015-01-01

    Multispectral imaging (MSI) significantly reduces metal artifacts. Yet, especially in techniques that use gradient selection, such as slice encoding for metal artifact correction (SEMAC), a residual ripple artifact may be prominent. Here, an analysis is presented of the ripple artifact and of slice overlap as an approach to reduce the artifact. The ripple artifact was analyzed theoretically to clarify its cause. Slice overlap, conceptually similar to spectral bin overlap in multi-acquisition with variable resonances image combination (MAVRIC), was achieved by reducing the selection gradient and, thus, increasing the slice profile width. Time domain simulations and phantom experiments were performed to validate the analyses and proposed solution. Discontinuities between slices are aggravated by signal displacement in the frequency encoding direction in areas with deviating B0. Specifically, it was demonstrated that ripple artifacts appear only where B0 varies both in-plane and through-plane. Simulations and phantom studies of metal implants confirmed the efficacy of slice overlap to reduce the artifact. The ripple artifact is an important limitation of gradient selection based MSI techniques, and can be understood using the presented simulations. At a scan-time penalty, slice overlap effectively addressed the artifact, thereby improving image quality near metal implants. © 2014 Wiley Periodicals, Inc.

  1. High Ripples Reduction in DTC of Induction Motor by Using a New Reduced Switching Table

    Mokhtari, Bachir; Benkhoris, Mohamed F.

    2016-05-01

    The direct torque and flux control (DTC) of electrical motors is characterized by ripples of torque and flux. Among the many solutions proposed to reduce them is to use modified switching tables which is very advantageous; because its implementation is easy and requires no additional cost compared to other solutions. This paper proposes a new reduced switching table (RST) to improve the DTC by reducing harmful ripples of torque and flux. This new switching table is smaller than the conventional one (CST) and depends principally at the flux error. This solution is studied by simulation under Matlab/Simulink and experimentally validated on a testbed with DSPACE1103. The results obtained of a DTC with RST applied to a three-phase induction motor (IM) show a good improvement and an effectiveness of proposed solution, the torque ripple decreases about 47% and 3% for the stator flux compared with a basic DTC.

  2. A dual mode operated boost inverter and its control strategy for ripple current reduction in single-phase uninterruptible power supplies

    Tang, Y.; Yao, W.; Blaabjerg, Frede

    2015-01-01

    In single-phase uninterruptible power supply (UPS) applications, it is well known that the AC side instantaneous power is not constant by nature. The resulting input current from the DC source side will inevitably contain low frequency ripple components that may largely deteriorate the system...... as active power conversion, while its CM operation is controlled in such a way that the low frequency ripple current on the DC side can be maintained in a minimum level. The proposed ripple current reduction method may not only work with linear loads, but also nonlinear loads, where more sophisticated...

  3. Pre-compression volume on flow ripple reduction of a piston pump

    Xu, Bing; Song, Yuechao; Yang, Huayong

    2013-11-01

    Axial piston pump with pre-compression volume(PCV) has lower flow ripple in large scale of operating condition than the traditional one. However, there is lack of precise simulation model of the axial piston pump with PCV, so the parameters of PCV are difficult to be determined. A finite element simulation model for piston pump with PCV is built by considering the piston movement, the fluid characteristic(including fluid compressibility and viscosity) and the leakage flow rate. Then a test of the pump flow ripple called the secondary source method is implemented to validate the simulation model. Thirdly, by comparing results among the simulation results, test results and results from other publications at the same operating condition, the simulation model is validated and used in optimizing the axial piston pump with PCV. According to the pump flow ripples obtained by the simulation model with different PCV parameters, the flow ripple is the smallest when the PCV angle is 13°, the PCV volume is 1.3×10-4 m3 at such operating condition that the pump suction pressure is 2 MPa, the pump delivery pressure 15 MPa, the pump speed 1 000 r/min, the swash plate angle 13°. At the same time, the flow ripple can be reduced when the pump suction pressure is 2 MPa, the pump delivery pressure is 5 MPa,15 MPa, 22 MPa, pump speed is 400 r/min, 1 000 r/min, 1 500 r/min, the swash plate angle is 11°, 13°, 15° and 17°, respectively. The finite element simulation model proposed provides a method for optimizing the PCV structure and guiding for designing a quieter axial piston pump.

  4. Flow ripple reduction of an axial piston pump by a combination of cross-angle and pressure relief grooves: Analysis and optimization

    Xu, Bing; Ye, Shaogan; Zhang, Junhui; Zhang, Chunfeng

    2016-01-01

    This paper investigates the potential of flow ripple reduction of an axial piston pump by a combination of cross-angle and pressure relief grooves. A dynamic model is developed to analyze the pumping dynamics of the pump and validated by experimental results. The effects of cross-angle on the flow ripples in the outlet and inlet ports, and the piston chamber pressure are investigated. The effects of pressure relief grooves on the optimal solutions obtained by a multi-objective optimization method are identified. A sensitivity analysis is performed to investigate the sensitivity of cross-angle to different working conditions. The results reveal that the flow ripples from the optimal solutions are smaller using the cross-angle and pressure relief grooves than those using the cross-angle and ordinary precompression and decompression angles and the cross-angle can be smaller. In addition, when the optimal design is used, the outlet flow ripples sensitivity can be reduced significantly.

  5. Ripple Communication.

    Wilcox, R. Stimson

    1980-01-01

    Discusses how surface-dwelling animals use the water surface as a mode of communication by making ripple signals while they swim about. Provides information about surfaces and surface waves, ripple communication in water striders, ripple signal characteristics, sensing and orienting, other modes of communication, and evolution of ripple…

  6. Energy measurement of fast ions trapped in the toroidal field ripple of Tore Supra

    Basiuk, V.; Becoulet, A.; Hutter, T.; Martin, G.; Pecquet, A.L.; Saoutic, B.

    1993-09-01

    During additional heating in Tore Supra (ICRF or NBI) fast ion losses due to the toroidal field ripple were clearly measured by a set of graphite probes. This diagnostic collects the flow of fast ions entering a vertical port and usually shows a maximum flux for ions originating from the vicinity of surface δ * = 0. During the monster sawteeth regime, achieved with ICRF, a remarkable phenomenon was observed: the ejection of fast ions, not correlated with any measured MHD activity. The radial distribution of these ions is quite different from that usually observed exhibiting a peak located in the central section of the plasma. In order to measure the energy distribution of these ions, from 80 keV (energy of the neutral beam injected in Tore Supra) up to 1 MeV (expected during ICRF), a new diagnostic is under construction. The principle of the diagnostic is to discriminate the ions in energy using their Larmor radius (p = 1.3 cm for 100 keV → p = 3.6 cm for 700 keV, B = 4T). The detector is made of a hollow graphite cylinder with a small entrance slot, located in a vertical port on the ion drift side. An array of six metallic collectors placed inside the graphite cylinder intercepts the ions. The current on each collector was estimated at 10 → 100 nA, during ICRF heating. The energy resolution of this diagnostic is expected to be about 20 keV for the lowest energy range and 100 keV for the highest. This type of ruggedized detector might be extrapolated for the measurements of alpha particle losses in future DT experiments. It should also be suitable for the studies of stochastic ripple diffusion. (authors). 3 refs., 9 figs

  7. Magnet pole shape design for reduction of thrust ripple of slotless permanent magnet linear synchronous motor with arc-shaped magnets considering end-effect based on analytical method

    Kyung-Hun Shin

    2017-05-01

    Full Text Available The shape of the magnet is essential to the performance of a slotless permanent magnet linear synchronous machine (PMLSM because it is directly related to desirable machine performance. This paper presents a reduction in the thrust ripple of a PMLSM through the use of arc-shaped magnets based on electromagnetic field theory. The magnetic field solutions were obtained by considering end effect using a magnetic vector potential and two-dimensional Cartesian coordinate system. The analytical solution of each subdomain (PM, air-gap, coil, and end region is derived, and the field solution is obtained by applying the boundary and interface conditions between the subdomains. In particular, an analytical method was derived for the instantaneous thrust and thrust ripple reduction of a PMLSM with arc-shaped magnets. In order to demonstrate the validity of the analytical results, the back electromotive force results of a finite element analysis and experiment on the manufactured prototype model were compared. The optimal point for thrust ripple minimization is suggested.

  8. Pole-shape optimization of permanent-magnet linear synchronous motor for reduction of thrust ripple

    Tavana, Nariman Roshandel, E-mail: nroshandel@ee.iust.ac.i [Department of Electrical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114 (Iran, Islamic Republic of); Shoulaie, Abbas, E-mail: shoulaie@iust.ac.i [Department of Electrical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114 (Iran, Islamic Republic of)

    2011-01-15

    In this paper, we have used magnet arc shaping technique in order to improve the performance of permanent-magnet linear synchronous motor (PMLSM). At first, a detailed analytical modeling based on Maxwell equations is presented for the analysis and design of PMLSM with the arc-shaped magnetic poles (ASMPs). Then the accuracy of presented method is verified by finite-element method. Very close agreement between the analytical and finite-element results shows the effectiveness of the proposed method. Finally, a magnet shape design is carried out based on the analytical method to enhance the motor developed thrust. Pertinent evaluations on the optimal design performance demonstrate that shape optimization leads to a design with extra low thrust ripple.

  9. Pole-shape optimization of permanent-magnet linear synchronous motor for reduction of thrust ripple

    Tavana, Nariman Roshandel; Shoulaie, Abbas

    2011-01-01

    In this paper, we have used magnet arc shaping technique in order to improve the performance of permanent-magnet linear synchronous motor (PMLSM). At first, a detailed analytical modeling based on Maxwell equations is presented for the analysis and design of PMLSM with the arc-shaped magnetic poles (ASMPs). Then the accuracy of presented method is verified by finite-element method. Very close agreement between the analytical and finite-element results shows the effectiveness of the proposed method. Finally, a magnet shape design is carried out based on the analytical method to enhance the motor developed thrust. Pertinent evaluations on the optimal design performance demonstrate that shape optimization leads to a design with extra low thrust ripple.

  10. Measurements of the ripple effect and geometric distribution of switched gradient fields inside a magnetic resonance scanner.

    Sundström, Henrik; Mild, Kjell Hansson; Wilén, Jonna

    2015-02-01

    Knowledge of patient exposure during magnetic resonance imaging (MRI) procedures is limited, and the need for such knowledge has been demonstrated in recent in vitro and in vivo studies of the genotoxic effects of MRI. This study focuses on the dB/dt of the switched gradient field (SGF) and its geometric distribution. These values were characterized by measuring the peak dB/dt generated by a programmed gradient current of alternating triangles inside a 1.5T MR scanner. The maximum dB/dt exposure to the gradient field was 6-14 T/s, and this occurred at the edges of the field of view (FOV) 20-25 cm from the isocenter in the longitudinal direction. The dB/dt exposure dropped off to roughly half the maximum (3-7 T/s) at the edge of the bore. It was found that the dB/dt of the SGF was distorted by a 200 kHz ripple arising from the amplifier. The ripple is small in terms of B-field, but the high frequency content contributes to a peak dB/dt up to 18 times larger than that predicted by the slew rate (4 T/s m) and the distance from the isocenter. Measurements on a 3 T MRI scanner, however, revealed a much smaller filtered ripple of 100 kHz in dB/dt. These findings suggest that the gradient current to each coil together with information on the geometrical distribution of the gradient field and ripple effects could be used to assess the SGF exposure within an MRI bore. © 2014 Wiley Periodicals, Inc.

  11. Ripple structure in degenerate electron-gas-dominated stars with intense magnetic fields

    Wilkes, J.M.

    1988-01-01

    We investigate the implications of ripple structure, i.e., the appearance of oscillating and discontinuous slopes in the thermodynamic variables of a degenerate electron gas, for models of magnetic stars dominated by such a gas. We also examine the effects in these models of the recent discovery by R.L. Ingraham that strong magnetic fields can inhibit degeneracy in an electron gas. The thesis begins with the presentation of a theory of self-gravitating fluids based upon recent work in modern continuum mechanics and thermodynamics on electromagnetic interactions in continuous media. Our theory predicts as a general result the existence of an anisotropic pressure tensor in such a fluid, which is in agreement with the one known to occur in the special case of a free-electron gas in a magnetic field. Furthermore, the theory clarifies the relation between this pressure tensor and the scalar thermodynamic pressure, and provides an unambiguous prescription for the incorporation of these and other variables, such as the magnetization, in the fluid equations of motion. We next show that under suitable assumptions the usual thermodynamic equilibrium and stability conditions for such a fluid follow from the general theory. A definition of local thermodynamic equilibrium is then introduced, and used to develop a local equilibrium statistical mechanics of ideal gases. From this we derive the equations of state for an ideal free-electron gas in a magnetic field. Finally, these equations of state are used in a simplified system of structure equations for model stars in intense magnetic fields. We find the effects of degeneracy-inhibition to be small in these simple models

  12. The effect of toroidal field ripple on confined alphas in TFTR D-T plasmas

    Duong, H.H.; Medley, S.S.

    1996-05-01

    The Pellet Charge Exchange (PCX) diagnostic on the Tokamak Fusion Test Reactor (TFTR) presently measures trapped alpha distribution functions with very small pitch angle (v parallel /v ∼ 0.05) at the midplane. The measured PCX alpha signal exhibits a depletion region near the outboard region. Results of the alpha energy spectra and radial profile suggest stochastic ripple diffusion is the cause of the depletion. Comparison of the ripple stochastization boundary with Goldston-White-Boozer theory also shows the correct functional dependence on alpha energy and q-profile

  13. Rolling Ripple

    2006-01-01

    NASA's Mars Exploration Rover Opportunity continues to cut southward across a plain marked by large sand ripples and a pavement of outcrop rock. The ripple in the center of the image shows a distinct pattern of banding, which the science team hopes to investigate more closely during the trek through this terrain. The banding and other features have inspired a hypothesis that Meridiani ripples are old features that are currently being eroded, and not transported, by wind. This navigation camera image was taken on Opportunity's sol 795, April 19, 2006.

  14. Reducing Ripple In A Switching Voltage Regulator

    Paulkovich, John; Rodriguez, G. Ernest

    1994-01-01

    Ripple voltage in output of switching voltage regulator reduced substantially by simple additional circuitry adding little to overall weight and size of regulator. Heretofore, additional filtering circuitry needed to obtain comparable reductions in ripple typically as large and heavy as original regulator. Current opposing ripple current injected into filter capacitor.

  15. Torque Ripple Reduction of a Novel Modular Arc-Linear Flux-Switching Permanent-Magnet Motor with Rotor Step Skewing

    Xiangdong Liu

    2016-05-01

    Full Text Available A novel modular arc-linear flux-switching permanent-magnet motor (MAL-FSPM used for scanning system instead of reduction gearboxes and kinematic mechanisms is proposed and researched in this paper by the finite element method (FEM. The MAL-FSPM combines characteristics of flux-switching permanent-magnet motor and linear motor and can realize the direct driving and limited angular movement. Structure and operation principle of the MAL-FSPM are analyzed. Cogging torque model of the MAL-FSPM is established. The characteristics of cogging torque and torque ripple are investigated for: (1 distance (dend between left end of rotor and left end of stator is more than two rotor tooth pitch (τp; and (2 dend is less than two rotor tooth pitch. Cogging torque is an important component of torque ripple and the period ratio of the cogging torque to the back electromotive force (EMF equals one for the MAL-FSPM before optimization. In order to reduce the torque ripple as much as possible and affect the back EMF as little as possible, influence of period ratio of cogging torque to back EMF on rotor step skewing is investigated. Rotor tooth width and stator slot open width are optimized to increase the period ratio of cogging torque to back EMF. After the optimization, torque ripple is decreased by 79.8% for dend > τp and torque ripple is decreased by 49.7% for dend < τp. Finally, 3D FEM model is established to verify the 2D results.

  16. Dynamics of Neural Responses in Ferret Primary Auditory Cortex: I. Spectro-Temporal Response Field Characterization by Dynamic Ripple Spectra

    Depireux, Didier A; Simon, Jonathan Z; Klein, David J; Shamma, Shihab A

    1999-01-01

    .... It is calculated here from the responses to elementary 'ripples,' a family of sounds with drifting, sinusoidal, spectral envelopes - the complex spectrotemporal envelope of any broadband, dynamic...

  17. Ripple Belt

    2006-01-01

    16 July 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows windblown materials that have collected and been shaped into large ripples in a valley in the Auqakuh Vallis system in northeastern Arabia Terra, Mars. Location near: 29.1oN, 299.6oW Image width: 2 km (1.2 mi) Illumination from: lower left Season: Northern Winter

  18. Speed control with torque ripple reduction of switched reluctance motor by Hybrid Many Optimizing Liaison Gravitational Search technique

    Nutan Saha

    2017-06-01

    Full Text Available This paper presents a control scheme for simultaneous control of the speed of Switched Reluctance Motor (SRM and minimizing the torque ripple employing Hybrid Many Optimizing Liaison Gravitational Search Algorithm (Hybrid MOLGSA technique. The control mechanism includes two controlling loops, the outer loop is governed for speed control and a current controller for the inner loop, intelligent selection of turn on and turn off angle for a 60 KW, 3-phase 6/8 SRM. It is noticed that the torque ripple coefficient, ISE of speed & current are reduced by 12.81%, 38.60%, 16.74% respectively by Hybrid MOLGSA algorithm compared to Gravitational Search Algorithm (GSA algorithm. It is also observed that the settling times for the controller using the parameter values for obtaining best values of torque ripple, Integral square error of speed and current are reduced by 51.25%, 58.04% and 59.375% by proposed Hybrid MOLGSA algorithm compared to the GSA algorithm.

  19. Ripple Trap

    2006-01-01

    3 April 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the margin of a lava flow on a cratered plain in the Athabasca Vallis region of Mars. Remarkably, the cratered plain in this scene is essentially free of bright, windblown ripples. Conversely, the lava flow apparently acted as a trap for windblown materials, illustrated by the presence of the light-toned, wave-like texture over much of the flow. That the lava flow surface trapped windblown sand and granules better than the cratered plain indicates that the flow surface has a rougher texture at a scale too small to resolve in this image. Location near: 10.7oN, 204.5oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Winter

  20. Injection of electrons with predominantly perpendicular energy into an area of toroidal field ripple in a tokamak plasma to improve plasma confinement

    Ono, Masayuki; Furth, Harold

    1993-01-01

    An electron injection scheme for controlling transport in a tokamak plasma. Electrons with predominantly perpendicular energy are injected into a ripple field region created by a group of localized poloidal field bending magnets. The trapped electrons then grad-B drift vertically toward the plasma interior until they are detrapped, charging the plasma negative. Calculations indicate that the highly perpendicular velocity electrons can remain stable against kinetic instabilities in the regime of interest for tokamak experiments. The penetration distance can be controlled by controlling the "ripple mirror ratio", the energy of the injected electrons, and their v.sub..perp. /v.sub.51 ratio. In this scheme, the poloidal torque due to the injected radial current is taken by the magnets and not by the plasma. Injection is accomplished by the flat cathode containing an ECH cavity to pump electrons to high v.sub..perp..

  1. Energy measurement of fast ions trapped in the toroidal magnetic field ripple of Tore Supra during ICRF heating

    Basiuk, V.; Becoulet, A.; Grisolia, C.; Hutter, T.; Mayaux, G.; Martin, G.; Saoutic, B.; Vartanian, S.

    1995-01-01

    Direct losses of ions trapped in the toroidal field ripple of Tore Supra using two techniques were made. The first (DRIPPLE I) correlates the ion loss current measured by an electric probe with the ion loss power measured by a calorimeter. As the calorimeter integrates over all particle energies and time, it yields only the averaged lost ion energy. The second technique (DRIPPLE II), still under development, is a Faraday cup positioned and filtered so as to select ions by their Larmor radius. The currents measured are small (1-100 nA), and improvements in instrumentation are needed to take full advantage of the data, but the preliminary results are still useful. During ICRH (hydrogen minority regime, resonance on axis) a direct correlation between the lost ion mean energy and the density of hydrogen was seen. The energy increased when the hydrogen minority density decreased. Moreover, the line averaged density and the lower hybrid heating (LH) had also an effect on fast ion losses. (authors). 3 refs., 7 figs

  2. Time course and hemispheric lateralization effects of complex pitch processing: evoked magnetic fields in response to rippled noise stimuli.

    Hertrich, Ingo; Mathiak, Klaus; Lutzenberger, Werner; Ackermann, Hermann

    2004-01-01

    To delineate the time course and processing stages of pitch encoding at the level of the supratemporal plane, the present study recorded evoked magnetic fields in response to rippled noise (RN) stimuli. RN largely masks simple tonotopic representations and addresses pitch processing within the temporal domain (periodicity encoding). Four dichotic stimulus types (111 or 133 Hz RN at one ear, white noise to the other one) were applied in randomized order during either visual distraction or selective auditory attention. Strictly periodic signals, noise-like events, and mixtures of both signals served as control conditions. (1) Attention-dependent ear x hemisphere interactions were observed within the time domain of the M50 field, indicating early streaming of auditory information. (2) M100 responses to strictly periodic stimuli were found lateralized to the right hemisphere. Furthermore, the higher-pitched stimuli yielded enhanced activation as compared to the lower-pitch signals (pitch scaling), conceivably reflecting sensory memory operations. (3) Besides right-hemisphere pitch scaling, the relatively late M100 component in association with the RN condition (latency = 136 ms) showed significantly stronger field strengths over the left hemisphere. Control experiments revealed this lateralization effect to be related to noise rather than pitch processing. Furthermore, subtle noise variations interacted with signal periodicity. Obviously, thus, complex task demands such as RN encoding give rise to functional segregation of auditory processing across the two hemispheres (left hemisphere: noise, right hemisphere: periodicity representation). The observed noise/periodicity interactions, furthermore, might reflect pitch-synchronous spectral evaluation at the level of the left supratemporal plane, triggered by right-hemisphere representation of signal periodicity. Copyright 2004 Elsevier Ltd.

  3. Containerless Ripple Turbulence

    Putterman, Seth; Wright, William; Duval, Walter; Panzarella, Charles

    2002-11-01

    One of the longest standing unsolved problems in physics relates to the behavior of fluids that are driven far from equilibrium such as occurs when they become turbulent due to fast flow through a grid or tidal motions. In turbulent flows the distribution of vortex energy as a function of the inverse length scale [or wavenumber 'k'] of motion is proportional to 1/k5/3 which is the celebrated law of Kolmogorov. Although this law gives a good description of the average motion, fluctuations around the average are huge. This stands in contrast with thermally activated motion where large fluctuations around thermal equilibrium are highly unfavorable. The problem of turbulence is the problem of understanding why large fluctuations are so prevalent which is also called the problem of 'intermittency'. Turbulence is a remarkable problem in that its solution sits simultaneously at the forefront of physics, mathematics, engineering and computer science. A recent conference [March 2002] on 'Statistical Hydrodynamics' organized by the Los Alamos Laboratory Center for Nonlinear Studies brought together researchers in all of these fields. Although turbulence is generally thought to be described by the Navier-Stokes Equations of fluid mechanics the solution as well as its existence has eluded researchers for over 100 years. In fact proof of the existence of such a solution qualifies for a 1 M millennium prize. As part of our NASA funded research we have proposed building a bridge between vortex turbulence and wave turbulence. The latter occurs when high amplitude waves of various wavelengths are allowed to mutually interact in a fluid. In particular we have proposed measuring the interaction of ripples [capillary waves] that run around on the surface of a fluid sphere suspended in a microgravity environment. The problem of ripple turbulence poses similar mathematical challenges to the problem of vortex turbulence. The waves can have a high amplitude and a strong nonlinear

  4. Containerless Ripple Turbulence

    Putterman, Seth; Wright, William; Duval, Walter; Panzarella, Charles

    2002-01-01

    One of the longest standing unsolved problems in physics relates to the behavior of fluids that are driven far from equilibrium such as occurs when they become turbulent due to fast flow through a grid or tidal motions. In turbulent flows the distribution of vortex energy as a function of the inverse length scale [or wavenumber 'k'] of motion is proportional to 1/k(sup 5/3) which is the celebrated law of Kolmogorov. Although this law gives a good description of the average motion, fluctuations around the average are huge. This stands in contrast with thermally activated motion where large fluctuations around thermal equilibrium are highly unfavorable. The problem of turbulence is the problem of understanding why large fluctuations are so prevalent which is also called the problem of 'intermittency'. Turbulence is a remarkable problem in that its solution sits simultaneously at the forefront of physics, mathematics, engineering and computer science. A recent conference [March 2002] on 'Statistical Hydrodynamics' organized by the Los Alamos Laboratory Center for Nonlinear Studies brought together researchers in all of these fields. Although turbulence is generally thought to be described by the Navier-Stokes Equations of fluid mechanics the solution as well as its existence has eluded researchers for over 100 years. In fact proof of the existence of such a solution qualifies for a 1 M$ millennium prize. As part of our NASA funded research we have proposed building a bridge between vortex turbulence and wave turbulence. The latter occurs when high amplitude waves of various wavelengths are allowed to mutually interact in a fluid. In particular we have proposed measuring the interaction of ripples [capillary waves] that run around on the surface of a fluid sphere suspended in a microgravity environment. The problem of ripple turbulence poses similar mathematical challenges to the problem of vortex turbulence. The waves can have a high amplitude and a strong nonlinear

  5. Space Vector Modulation for DC-Link Current Ripple Reduction in Back-To-Back Current Source Converters for Microgrid Applications

    Guo, Xiaoqiang; Xu, David; Guerrero, Josep M.

    2015-01-01

    Back-to-back converters have been typically used to interconnect the microgrids. For a back-to-back current source converter, the dc-link current ripple is one of the important parameters. A large ripple will cause the electromagnetic interference, undesirable high-frequency losses, and system...... instability. Conventionally, with a given switching frequency and rated voltage, the current ripple can be reduced by increasing the dc-link inductor, but it leads to bulky size, high cost and slow dynamic response. In order to solve this problem, this paper reveals that the current ripple can...

  6. Ripple induced trapped particle loss in tokamaks

    White, R.B.

    1996-05-01

    The threshold for stochastic transport of high energy trapped particles in a tokamak due to toroidal field ripple is calculated by explicit construction of primary resonances, and a numerical examination of the route to chaos. Critical field ripple amplitude is determined for loss. The expression is given in magnetic coordinates and makes no assumptions regarding shape or up-down symmetry. An algorithm is developed including the effects of prompt axisymmetric orbit loss, ripple trapping, convective banana flow, and stochastic ripple loss, which gives accurate ripple loss predictions for representative Tokamak Fusion Test Reactor and International Thermonuclear Experimental Reactor equilibria. The algorithm is extended to include the effects of collisions and drag, allowing rapid estimation of alpha particle loss in tokamaks

  7. Toroidal ripple transport of beam ions in the mega-ampère spherical tokamak

    McClements, K. G.; Hole, M. J.

    2012-01-01

    The transport of injected beam ions due to toroidal magnetic field ripple in the mega-ampère spherical tokamak (MAST) is quantified using a full orbit particle tracking code, with collisional slowing-down and pitch-angle scattering by electrons and bulk ions taken into account. It is shown that the level of ripple losses is generally rather low, although it depends sensitively on the major radius of the outer midplane plasma edge; for typical values of this parameter in MAST plasmas, the reduction in beam heating power due specifically to ripple transport is less than 1%, and the ripple contribution to beam ion diffusivity is of the order of 0.1 m 2 s –1 or less. It is concluded that ripple effects make only a small contribution to anomalous transport rates that have been invoked to account for measured neutron rates and plasma stored energies in some MAST discharges. Delayed (non-prompt) losses are shown to occur close to the outer midplane, suggesting that banana-drift diffusion is the most likely cause of the ripple-induced losses.

  8. Generalized ripple-banana transport in a tokamak

    Yushmanov, P.N.

    1983-01-01

    The paper considers the transport of banana particles in a rippled magnetic field over the entire energy range. It is shown that all familiar regimes of ripple transport - ripple-plateau, banana-drift and stochastic - can be described in a unified manner. The general expression obtained for the rippled fluxes of banana particles describes, apart from the already familiar regimes, also the as yet unstudied energy region between the drift and stochastic regimes. A generalized ripple-banana thermal conductivity coefficient, chisub(i)sup(RB), is calculated. (author)

  9. Constrained ripple optimization of Tokamak bundle divertors

    Hively, L.M.; Rome, J.A.; Lynch, V.E.; Lyon, J.F.; Fowler, R.H.; Peng, Y-K.M.; Dory, R.A.

    1983-02-01

    Magnetic field ripple from a tokamak bundle divertor is localized to a small toroidal sector and must be treated differently from the usual (distributed) toroidal field (TF) coil ripple. Generally, in a tokamak with an unoptimized divertor design, all of the banana-trapped fast ions are quickly lost due to banana drift diffusion or to trapping between the 1/R variation in absolute value vector B ω B and local field maxima due to the divertor. A computer code has been written to optimize automatically on-axis ripple subject to these constraints, while varying up to nine design parameters. Optimum configurations have low on-axis ripple ( 0 ) are lost. However, because finite-sized TF coils have not been used in this study, the flux bundle is not expanded

  10. Mesopontine median raphe regulates hippocampal ripple oscillation and memory consolidation.

    Wang, Dong V; Yau, Hau-Jie; Broker, Carl J; Tsou, Jen-Hui; Bonci, Antonello; Ikemoto, Satoshi

    2015-05-01

    Sharp wave-associated field oscillations (∼200 Hz) of the hippocampus, referred to as ripples, are believed to be important for consolidation of explicit memory. Little is known about how ripples are regulated by other brain regions. We found that the median raphe region (MnR) is important for regulating hippocampal ripple activity and memory consolidation. We performed in vivo simultaneous recording in the MnR and hippocampus of mice and found that, when a group of MnR neurons was active, ripples were absent. Consistently, optogenetic stimulation of MnR neurons suppressed ripple activity and inhibition of these neurons increased ripple activity. Notably, using a fear conditioning procedure, we found that photostimulation of MnR neurons interfered with memory consolidation. Our results demonstrate a critical role of the MnR in regulating ripples and memory consolidation.

  11. New 30 kA power system at Fermilab and its use for measuring the effects of ripple current on the performance of superconducting high field magnets

    Carcagno, R.; Feher, S.; Garvey, J.; Jaskierny, W.; Lamm, M.; Makulski, A.; Orris, D.F.; Pfeffer, H.; Tartaglia, M.; Tompkins, J.; Wolff, D.; /Fermilab

    2004-12-01

    A new 30 kA, 30 V dc Power System was designed, built, and commissioned at Fermilab for testing Superconducting High Field Magnets. This system has been successfully supporting operations at the Fermilab Magnet Test Facility since April 2002. It is based on six commercial 150 kW Power Energy Industries power supply modules and the following in-house modules: six 720 Hz filters, two 15 kA/1kV dc solid-state dump switch, and a 3 MJ/30 kA/1 kV dc dump resistor. Additional inhouse electronic components were designed and built to provide precise current regulation and distribution of current and current rate of change. An industrial-type Programmable Logic Controller system was used to provide equipment interlocks and monitoring. This paper summarizes studies on the influence of characteristics of this new power system--such as ripple current--on the performance of High Field Superconducting magnets.

  12. A Stellar Ripple

    2006-01-01

    This false-color composite image shows the Cartwheel galaxy as seen by the Galaxy Evolution Explorer's far ultraviolet detector (blue); the Hubble Space Telescope's wide field and planetary camera 2 in B-band visible light (green); the Spitzer Space Telescope's infrared array camera at 8 microns (red); and the Chandra X-ray Observatory's advanced CCD imaging spectrometer-S array instrument (purple). Approximately 100 million years ago, a smaller galaxy plunged through the heart of Cartwheel galaxy, creating ripples of brief star formation. In this image, the first ripple appears as an ultraviolet-bright blue outer ring. The blue outer ring is so powerful in the Galaxy Evolution Explorer observations that it indicates the Cartwheel is one of the most powerful UV-emitting galaxies in the nearby universe. The blue color reveals to astronomers that associations of stars 5 to 20 times as massive as our sun are forming in this region. The clumps of pink along the outer blue ring are regions where both X-rays and ultraviolet radiation are superimposed in the image. These X-ray point sources are very likely collections of binary star systems containing a blackhole (called massive X-ray binary systems). The X-ray sources seem to cluster around optical/ultraviolet-bright supermassive star clusters. The yellow-orange inner ring and nucleus at the center of the galaxy result from the combination of visible and infrared light, which is stronger towards the center. This region of the galaxy represents the second ripple, or ring wave, created in the collision, but has much less star formation activity than the first (outer) ring wave. The wisps of red spread throughout the interior of the galaxy are organic molecules that have been illuminated by nearby low-level star formation. Meanwhile, the tints of green are less massive, older visible-light stars. Although astronomers have not identified exactly which galaxy collided with the Cartwheel, two of three candidate galaxies can be

  13. Electronic properties of rippled graphene

    Gui Gui; Ma Zhenqiang; Zhong Jianxin

    2012-01-01

    Short range periodic ripples in graphene have been modeled. The electronic properties of the rippled graphene have been investigated using first-principles calculations. Compared with flat graphene, there is a band gap opening in rippled graphene. Generally, the value of energy gaps increases as the height of ripples increase, but it decreases as the range of ripples enlarges. The maximum value of energy gaps in rippled graphene can reach several hundred meV, which turns rippled graphene into a good semiconductor. As a result, the magnitude of energy gaps can be tuned effectively by controlling the range and height of ripples in graphene.

  14. Comparisons of Unconsolidated Sediments Analyzed by APXS (MSL-Curiosity) within Gale Crater, Mars: Soils, Sands of the Barchan and Linear Dunes of the Active Bagnold Dune Field, and Ripple-field Sands.

    Thompson, L. M.; O'Connell-Cooper, C.; Spray, J. G.; Gellert, R.; Boyd, N. I.; Desouza, E.

    2017-12-01

    The MSL-APXS has analyzed a variety of unconsolidated sediments within the Gale impact crater, including soils, sands from barchan [High, Namib dunes], and linear dunes [Nathan Bridges, Mount Desert dunes], within the active Bagnold dune field, and sands from two smaller ripple fields ("mega-ripples"). The Gale "soils" (unsorted, unconsolidated sediments, ranging from fine-grained particles (including dust) to coarser "pebbly" material [>2 mm]), are, to a large degree, similar to Martian basaltic soils quantified by APXS, at Gusev crater (MER-A_Spirit) and Meridiani Planum (MER-B_Opportunity). Some local contributions are indicated by, for example, the enriched K levels (relative to a martian average basaltic soil [ABS]) within coarser Gale soil samples, and a Cr, Mn, Fe enrichment within finer-grained samples. Sands (grain size 62 µm to 2 mm) of the Bagnold dunes, generally, exhibit elevated Mg and Ni, indicating enrichment from olivine and pyroxene, but depleted S, Cl and Zn, indicating high activity levels and low dust. Compositional differences, related both to position within a dune (i.e., crest versus off-crest sand), and type of dune (linear versus barchan), are identified. Off-crest sands have Na, Al, Si, K, P contents similar to (or slightly depleted, relative to) the ABS, enrichment in Mg, and low dust content, whilst crest sands contain very high Mg and Ni (relative to the ABS), low felsic elemental concentrations and very low dust content. Cr is significantly enriched (and, to a lesser degree, Mn, Fe, Ti) in the off-crest sands of the linear dunes. In contrast, barchan dunes off-crest sands have Cr, Mn, Fe, and Ti abundances similar to those in the Gale soils. Additionally, Ni concentrations in barchan dunes off-crest sands are enriched relative to the linear dunes. Analyses from a small, isolated "mega-ripple" reveal a composition similar to that of the Gale soils, including a high dust content. The second mega-ripple, within a larger ripple field, is

  15. Ripple enhanced transport of suprathermal alpha particles

    Tani, K.; Takizuka, T.; Azumi, M.

    1986-01-01

    The ripple enhanced transport of suprathermal alpha particles has been studied by the newly developed Monte-Carlo code in which the motion of banana orbit in a toroidal field ripple is described by a mapping method. The existence of ripple-resonance diffusion has been confirmed numerically. We have developed another new code in which the radial displacement of banana orbit is given by the diffusion coefficients from the mapping code or the orbit following Monte-Carlo code. The ripple loss of α particles during slowing down has been estimated by the mapping model code as well as the diffusion model code. From the comparison of the results with those from the orbit-following Monte-Carlo code, it has been found that all of them agree very well. (author)

  16. Reduction theory for a rational function field

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Planck-Institut für Mathematik, Postfach 7280, D-53072 Bonn, Germany. MS received 9 September 2002; revised 16 October 2002. Abstract. Let G be a split reductive group over a finite field Fq . Let F = Fq (t) and let A denote the ad`eles of F. We ...

  17. Permeation through graphene ripples

    Liang, Tao; He, Guangyu; Wu, Xu; Ren, Jindong; Guo, Hongxuan; Kong, Yuhan; Iwai, Hideo; Fujita, Daisuke; Gao, Hongjun; Guo, Haiming; Liu, Yingchun; Xu, Mingsheng

    2017-06-01

    Real graphene sheets show limited anti-permeation performance deviating from the ideally flat honeycomb carbon lattice that is impermeable to gases. Ripples in graphene are prevalent and they could significantly influence carrier transport. However, little attention has been paid to the role of ripples in the permeation properties of graphene. Here, we report that gases can permeate through graphene ripples at room temperature. The feasibility of gas permeation through graphene ripples is determined by detecting the initial oxidation sites of Cu surface covered with isolated graphene domain. Nudged elastic band (NEB) calculations demonstrate that the oxygen atom permeation occurs via the formation of C-O-C bond, in which process the energy barrier through the rippled graphene lattice is much smaller than that through a flat graphene lattice, rendering permeation through ripples more favorable. Combining with the recent advances in atoms intercalation between graphene and metal substrate for transfer-free and electrically insulated graphene, this discovery provides new perspectives regarding graphene’s limited anti-permeation performance and evokes for rational design of graphene-based encapsulation for barrier and selective gas separation applications through ripple engineering.

  18. PathShuffle: Credit Mixing and Anonymous Payments for Ripple

    Moreno-Sanchez Pedro; Ruffing Tim; Kate Aniket

    2017-01-01

    The I owe you (IOU) credit network Ripple is one of the most prominent alternatives in the burgeoning field of decentralized payment systems. Ripple’s path-based transactions set it apart from cryptocurrencies such as Bitcoin. Its pseudonymous nature, while still maintaining some regulatory capabilities, has motivated several financial institutions across the world to use Ripple for processing their daily transactions. Nevertheless, with its public ledger, a credit network such as Ripple is n...

  19. Reduction of a Ship's Magnetic Field Signatures

    Holmes, John

    2008-01-01

    Decreasing the magnetic field signature of a naval vessel will reduce its susceptibility to detonating naval influence mines and the probability of a submarine being detected by underwater barriers and maritime patrol aircraft. Both passive and active techniques for reducing the magnetic signatures produced by a vessel's ferromagnetism, roll-induced eddy currents, corrosion-related sources, and stray fields are presented. Mathematical models of simple hull shapes are used to predict the levels of signature reduction that might be achieved through the use of alternate construction materials. Al

  20. Ripple losses during ICRF heating in Tore Supra

    Basiuk, V.; Eriksson, L.-G.; Bergeaud, V.; Chantant, M.; Martin, G.; Nguyen, F.; Reichle, R.; Vallet, J.C.; Delpeche, L.; Surle, F.

    2004-01-01

    The toroidal field coils in Tore Supra are supra-conducting, and their number is restricted to 18. As a result, the ripple is fairly large, about 7% at the plasma boundary. Tore Supra has consequently been equipped with dedicated ripple loss diagnostics, which has allowed ripple loss studies. This paper reports on the measurements made with these diagnostics and provides an analysis of the experimental results, comparing them with theoretical expectations whenever possible. Furthermore, the main heating source accelerating ions in Tore Supra is ion cyclotron resonance range of frequency (ICRF) heating, and the paper provides new information on the ripple losses of ICRF accelerated ions. (author)

  1. Automatic detection and visualisation of MEG ripple oscillations in epilepsy

    Nicole van Klink

    2017-01-01

    Full Text Available High frequency oscillations (HFOs, 80–500 Hz in invasive EEG are a biomarker for the epileptic focus. Ripples (80–250 Hz have also been identified in non-invasive MEG, yet detection is impeded by noise, their low occurrence rates, and the workload of visual analysis. We propose a method that identifies ripples in MEG through noise reduction, beamforming and automatic detection with minimal user effort. We analysed 15 min of presurgical resting-state interictal MEG data of 25 patients with epilepsy. The MEG signal-to-noise was improved by using a cross-validation signal space separation method, and by calculating ~2400 beamformer-based virtual sensors in the grey matter. Ripples in these sensors were automatically detected by an algorithm optimized for MEG. A small subset of the identified ripples was visually checked. Ripple locations were compared with MEG spike dipole locations and the resection area if available. Running the automatic detection algorithm resulted in on average 905 ripples per patient, of which on average 148 ripples were visually reviewed. Reviewing took approximately 5 min per patient, and identified ripples in 16 out of 25 patients. In 14 patients the ripple locations showed good or moderate concordance with the MEG spikes. For six out of eight patients who had surgery, the ripple locations showed concordance with the resection area: 4/5 with good outcome and 2/3 with poor outcome. Automatic ripple detection in beamformer-based virtual sensors is a feasible non-invasive tool for the identification of ripples in MEG. Our method requires minimal user effort and is easily applicable in a clinical setting.

  2. New 30 kA power system at Fermilab and its use for measuring the effects of ripple current on the performance of superconducting high field magnets

    Carcagno, R.; Feher, S.; Garvey, J.; Jaskierny, W.; Lamm, M.; Makulski, A.; Orris, D.F.; Pfeffer, H.; Tartaglia, M.; Tompkins, J.; Wolff, D.

    2004-01-01

    A new 30 kA, 30 V dc Power System was designed, built, and commissioned at Fermilab for testing Superconducting High Field Magnets. This system has been successfully supporting operations at the Fermilab Magnet Test Facility since April 2002. It is based on six commercial 150 kW Power Energy Industries power supply modules and the following in-house modules: six 720 Hz filters, two 15 kA/1kV dc solid-state dump switch, and a 3 MJ/30 kA/1 kV dc dump resistor. Additional in-house electronic components were designed and built to provide precise current regulation and distribution of current and current rate of change. An industrial-type Programmable Logic Controller system was used to provide equipment interlocks and monitoring. This paper summarizes studies on the influence of characteristics of this new power system--such as ripple current--on the performance of High Field Superconducting Magnets

  3. Rotation and neoclassical ripple transport in ITER

    Paul, E. J.; Landreman, M.; Poli, F. M.; Spong, D. A.; Smith, H. M.; Dorland, W.

    2017-11-01

    Neoclassical transport in the presence of non-axisymmetric magnetic fields causes a toroidal torque known as neoclassical toroidal viscosity (NTV). The toroidal symmetry of ITER will be broken by the finite number of toroidal field coils and by test blanket modules (TBMs). The addition of ferritic inserts (FIs) will decrease the magnitude of the toroidal field ripple. 3D magnetic equilibria in the presence of toroidal field ripple and ferromagnetic structures are calculated for an ITER steady-state scenario using the variational moments equilibrium code (VMEC). Neoclassical transport quantities in the presence of these error fields are calculated using the stellarator Fokker-Planck iterative neoclassical conservative solver (SFINCS). These calculations fully account for E r , flux surface shaping, multiple species, magnitude of ripple, and collisionality rather than applying approximate analytic NTV formulae. As NTV is a complicated nonlinear function of E r , we study its behavior over a plausible range of E r . We estimate the toroidal flow, and hence E r , using a semi-analytic turbulent intrinsic rotation model and NUBEAM calculations of neutral beam torque. The NTV from the \\vert{n}\\vert = 18 ripple dominates that from lower n perturbations of the TBMs. With the inclusion of FIs, the magnitude of NTV torque is reduced by about 75% near the edge. We present comparisons of several models of tangential magnetic drifts, finding appreciable differences only for superbanana-plateau transport at small E r . We find the scaling of calculated NTV torque with ripple magnitude to indicate that ripple-trapping may be a significant mechanism for NTV in ITER. The computed NTV torque without ferritic components is comparable in magnitude to the NBI and intrinsic turbulent torques and will likely damp rotation, but the NTV torque is significantly reduced by the planned ferritic inserts.

  4. Quantum Hamiltonian reduction and conformal field theories

    Bershadsky, M.

    1991-01-01

    It is proved that irreducible representation of the Virasoro algebra can be extracted from an irreducible representation space of the SL (2, R) current algebra by putting a constraint on the latter using the BRST formalism. Thus there is a SL(2, R) symmetry in the Virasoro algebra which is gauged and hidden. This construction of the Virasoro algebra is the quantum analog of the Hamiltonian reduction. The author then naturally leads to consider an SL(2, R) Wess-Zumino-Witten model. This system is related to the quantum field theory of the coadjoint orbit of the Virasoro group. Based on this result he presents the canonical derivation of the SL(2, R) current algebra in Polyakov's theory of two dimensional gravity; it is manifestation of the SL(2, R) symmetry in the conformal field theory hidden by the quantum Hamiltonian reduction. He discusses the quantum Hamiltonian reduction of the SL(n, R) current algebra for the general type of constraints labeled by index 1 ≤ l ≤ (n - 1) and claim that it leads to the new extended conformal algebras W n l . For l = 1 he recovers the well known W n algebra introduced by A. Zamolodchikov. For SL(3, R) Wess-Zumino-Witten model there are two different possibilities of constraining it. The first possibility gives the W 3 algebra, while the second leads to the new chiral algebra W 3 2 generated by the stress-energy tensor, two bosonic supercurrents with spins 3/2 and the U(1) current. He conjectures a Kac formula that describes the highly reducible representation for this algebra. He also makes some speculations concerning the structure of W gravity

  5. Uniting ripple-formation theory under water and winds: A universal scaling relation for the wavelength of fluid-drag ripples across fluids and planetary bodies

    Lapotre, M. G. A.; Lamb, M. P.; Ewing, R. C.; McElroy, B. J.

    2016-12-01

    Current ripples form on riverbeds and on the seafloor from viscous drag exerted by water flow over sand and are thought to be absent in subaerial systems, where ripple formation is dominated by a mechanism involving the impacting and splashing of sand grains. A fluid-drag mechanism, however, is not precluded in subaerial conditions and was originally hypothesized by R. A. Bagnold. Despite decades of observations in the field and in the laboratory, no universal scaling relation exists to predict the size of fluid-drag ripples. We combine dimensional analysis and a new extensive data compilation to develop a relationship and predict the equilibrium wavelength of current ripples. Our analysis shows that ripples are spaced farther apart when formed by more viscous fluids, smaller bed shear velocities, in coarser grains, or for smaller sediment specific gravity. Our scaling relation also highlights the abrupt transition between current ripples and subaqueous dunes, and thus allows for a process-based segregation of ripples from dunes. When adjusting for subaerial conditions, we predict the formation of decimeter-scale wind-drag ripples on Earth and meter-scale wind-drag ripples on Mars. The latter are ubiquitous on the Red Planet, and are found to co-exist with smaller decimeter-scale ripples, which we interpret as impact ripples. Because the predicted scale of terrestrial wind-drag ripples overlaps with that of impact ripples, it is possible that wind-drag ripples exist on Earth too, but are not recognized as such. When preserved in rocks, fluid-drag ripple stratification records flow directions and fluid properties that are crucial to constrain paleo-environments. Our new theory allows for predictions of ripple size, perhaps in both fluvial and eolian settings, and thus potentially represents a powerful tool for paleo-environmental reconstructions on different planetary bodies.

  6. Effects of complex magnetic ripple on fast ions in JFT-2M ferritic insert experiments

    Shinohara, Kouji; Kawashima, H.; Tsuzuki, K.

    2003-01-01

    In JFT-2M, the ferritic steel plates (FPs) were installed inside the vacuum vessel all over vacuum vessel, which is named Ferritic Inside Wall (FIW), as the third step of the Advanced Material Tokamak Experiment (AMTEX) program. A toroidal field ripple was reduced, however the magnetic field structure has become the complex ripple structure with a non-periodic feature in the toroidal direction because of the existence of other components and ports that limit the periodic installation of FPs. Under the complex magnetic ripple, we investigated its effect on the heat flux to the first wall due to the fast ion loss. The small heat flux was observed as the result of the reduced magnetic ripple by FIW. Additional FPs were also installed outside the vacuum vessel to produce the localized larger ripple. The small ripple trapped loss was observed when the shallow ripple well exist in the poloidal cross section, and the large ripple trapped loss was observed when the ripple well hollow out the plasma region deeply. The experimental results were almost consistent with the newly developed Fully three Dimensional magnetic field Orbit-Following Monte-Carlo (F3D OFMC) code including the three dimensional complex structure of the toroidal field ripple and the non-axisymmetric first wall geometry. By using F3D OFMC, we investigated the effect on the ripple trapped loss of the localized larger ripple produced by FPs in detail. The ripple well structure, e.g. the thickness of the ripple well, is important for ripple trapped loss in complex magnetic ripple rather than the value defined at one position in a poloidal cross section. (author)

  7. Electronic ripple indicator

    Davidson, J. K.; Houck, W. H.

    1971-01-01

    Electronic circuit for monitoring excessive ripple voltage on dc power lines senses voltage variations from few millivolts to maximum of 10 volts rms. Instrument is used wherever power supply fluctuations might endanger system operations or damage equipment. Device is inexpensive and easily packaged in small chassis.

  8. Angular tuning of the magnetic birefringence in rippled cobalt films

    Arranz, Miguel A., E-mail: MiguelAngel.Arranz@uclm.es [Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, Avda. Camilo J. Cela 10, 13071 Ciudad Real (Spain); Colino, José M. [Instituto de Nanociencia, Nanotecnología y Materiales Moleculares, Universidad de Castilla-La Mancha, Campus de la Fábrica de Armas, 45071 Toledo (Spain)

    2015-06-22

    We report the measurement of magnetically induced birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferromagnetic films were studied using Kerr magnetometry and magnetic birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the magnetic birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotation and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes.

  9. PathShuffle: Credit Mixing and Anonymous Payments for Ripple

    Moreno-Sanchez Pedro

    2017-07-01

    Full Text Available The I owe you (IOU credit network Ripple is one of the most prominent alternatives in the burgeoning field of decentralized payment systems. Ripple’s path-based transactions set it apart from cryptocurrencies such as Bitcoin. Its pseudonymous nature, while still maintaining some regulatory capabilities, has motivated several financial institutions across the world to use Ripple for processing their daily transactions. Nevertheless, with its public ledger, a credit network such as Ripple is no different from a cryptocurrency in terms of weak privacy; recent demonstrative deanonymization attacks raise important concerns regarding the privacy of the Ripple users and their transactions. However, unlike for cryptocurrencies, there is no known privacy solution compatible with the existing credit networks such as Ripple.

  10. Angular tuning of the magnetic birefringence in rippled cobalt films

    Arranz, Miguel A.; Colino, José M.

    2015-01-01

    We report the measurement of magnetically induced birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferromagnetic films were studied using Kerr magnetometry and magnetic birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the magnetic birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotation and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes

  11. Rippled beam free electron laser amplifier

    Carlsten, Bruce E.

    1999-01-01

    A free electron laser amplifier provides a scalloping annular electron beam that interacts with the axial electric field of a TM.sub.0n mode. A waveguide defines an axial centerline and, a solenoid arranged about the waveguide produces an axial constant magnetic field within the waveguide. An electron beam source outputs a annular electron beam that interacts with the axial magnetic field to have an equilibrium radius and a ripple radius component having a variable radius with a ripple period along the axial centerline. An rf source outputs an axial electric field that propagates within the waveguide coaxial with the electron beam and has a radial mode that interacts at the electron beam at the equilibrium radius component of the electron beam.

  12. Shape and Dimensions of Ripples

    Jacobsen, Niels Gjøl

    and the general conclusion is that sharp crested ripples is thought unlikely to become stable under oscillatory flow due to the large increase in bed shear stresses because of the rapid contraction of the flow around the crest. Further, a dynamically moving ripple crest is investigated. The key focus...... are the recirculation zone and its penetration into the main flow. This will be compared to the period averaged bed shear stress. An analysis of the bed load transport, both as a transport capacity in the phase resolved space and an analysis of possible stable ripples is conducted. This leads to some stable ripples...

  13. On single-time reduction in quantum field theory

    Arkhipov, A.A.

    1984-01-01

    It is shown, how the causality and spectrality properties in qUantum field theory may help one to carry out a single-time reduction of the Bethe-Salpeter wave fUnction. The single-time reduction technique is not based on any concrete model of the quantum field theory. Axiomatic formulations underline the quantum field theory

  14. Mechanics of wind ripple stratigraphy.

    Forrest, S B; Haff, P K

    1992-03-06

    Stratigraphic patterns preserved under translating surface undulations or ripples in a depositional eolian environment are computed on a grain by grain basis using physically based cellular automata models. The spontaneous appearance, growth, and motion of the simulated ripples correspond in many respects to the behavior of natural ripples. The simulations show that climbing strata can be produced by impact alone; direct action of fluid shear is unnecessary. The model provides a means for evaluating the connection between mechanical processes occurring in the paleoenvironment during deposition and the resulting stratigraphy preserved in the geologic column: vertical compression of small laminae above a planar surface indicates nascent ripple growth; supercritical laminae are associated with unusually intense deposition episodes; and a plane erosion surface separating sets of well-developed laminae is consistent with continued migration of mature ripples during a hiatus in deposition.

  15. Anisotropic Ripple Deformation in Phosphorene.

    Kou, Liangzhi; Ma, Yandong; Smith, Sean C; Chen, Changfeng

    2015-05-07

    Two-dimensional materials tend to become crumpled according to the Mermin-Wagner theorem, and the resulting ripple deformation may significantly influence electronic properties as observed in graphene and MoS2. Here, we unveil by first-principles calculations a new, highly anisotropic ripple pattern in phosphorene, a monolayer black phosphorus, where compression-induced ripple deformation occurs only along the zigzag direction in the strain range up to 10%, but not the armchair direction. This direction-selective ripple deformation mode in phosphorene stems from its puckered structure with coupled hinge-like bonding configurations and the resulting anisotropic Poisson ratio. We also construct an analytical model using classical elasticity theory for ripple deformation in phosphorene under arbitrary strain. The present results offer new insights into the mechanisms governing the structural and electronic properties of phosphorene crucial to its device applications.

  16. Runaway-ripple interaction in Tokamaks

    Laurent, L.; Rax, J.M.

    1989-08-01

    Two approaches of the interaction between runaway electrons and the ripple field, in tokamaks, are discussed. The first approach considers the resonance effect as an intense cyclotron heating of the electrons, by the ripple field, in the guiding center frame of the fast particles. In the second approach, an Hamiltonian formalism is used. A criterion for the onset of chaotic behavior and the results are given. A new universal instability of the runaway population in tokamak configuration is found. When combined with cyclotron losses one of its major consequence is to act as an effective slowing down mechanism preventing the free fall acceleration toward the synchrotron limit. This configuration allows the explanation of some experimental results of Tore Supra and Textor

  17. Minimization of torque ripple in ferrite-assisted synchronous reluctance motors by using asymmetric stator

    Xu, Meimei; Liu, Guohai; Zhao, Wenxiang; Aamir, Nazir

    2018-05-01

    Torque ripple is one of the important issues for ferrite assisted synchronous reluctance motors (FASRMs). In this paper, an asymmetrical stator is proposed for the FASRM to reduce its torque ripple. In the proposed FASRM, an asymmetrical stator is designed by appropriately choosing the angle of the slot-opening shift. Meanwhile, its analytical torque expressions are derived. The results show that the proposed FASRM has an effective reduction in the cogging torque, reluctance torque ripple and total torque ripple. Moreover, it is easy to implement while the average torque is not sacrificed.

  18. Gap junction networks can generate both ripple-like and fast ripple-like oscillations

    Simon, Anna; Traub, Roger D.; Vladimirov, Nikita; Jenkins, Alistair; Nicholson, Claire; Whittaker, Roger G.; Schofield, Ian; Clowry, Gavin J.; Cunningham, Mark O.; Whittington, Miles A.

    2014-01-01

    Fast ripples (FRs) are network oscillations, defined variously as having frequencies of > 150 to > 250 Hz, with a controversial mechanism. FRs appear to indicate a propensity of cortical tissue to originate seizures. Here, we demonstrate field oscillations, at up to 400 Hz, in spontaneously epileptic human cortical tissue in vitro, and present a network model that could explain FRs themselves, and their relation to ‘ordinary’ (slower) ripples. We performed network simulations with model pyramidal neurons, having axons electrically coupled. Ripples ( 250 Hz, were sustained or interrupted, and had little jitter in the firing of individual axons. The form of model FR was similar to spontaneously occurring FRs in excised human epileptic tissue. In vitro, FRs were suppressed by a gap junction blocker. Our data suggest that a given network can produce ripples, FRs, or both, via gap junctions, and that FRs are favored by clusters of axonal gap junctions. If axonal gap junctions indeed occur in epileptic tissue, and are mediated by connexin 26 (recently shown to mediate coupling between immature neocortical pyramidal cells), then this prediction is testable. PMID:24118191

  19. "Ripples" in an Aluminum Pool?

    Rohr, James; Wang, Si-Yin; Nesterenko, Vitali F.

    2018-05-01

    Our motivation for this article is for students to realize that opportunities for discovery are all around them. Discoveries that can still puzzle present day researchers. Here we explore an observation by a middle school student concerning the production of what appears to be water-like "ripples" produced in aluminum foil when placed between two colliding spheres. We both applaud and explore the student's reasoning that the ripples were formed in a melted aluminum pool.

  20. Learning-enhanced coupling between ripple oscillations in association cortices and hippocampus.

    Khodagholy, Dion; Gelinas, Jennifer N; Buzsáki, György

    2017-10-20

    Consolidation of declarative memories requires hippocampal-neocortical communication. Although experimental evidence supports the role of sharp-wave ripples in transferring hippocampal information to the neocortex, the exact cortical destinations and the physiological mechanisms of such transfer are not known. We used a conducting polymer-based conformable microelectrode array (NeuroGrid) to record local field potentials and neural spiking across the dorsal cortical surface of the rat brain, combined with silicon probe recordings in the hippocampus, to identify candidate physiological patterns. Parietal, midline, and prefrontal, but not primary cortical areas, displayed localized ripple (100 to 150 hertz) oscillations during sleep, concurrent with hippocampal ripples. Coupling between hippocampal and neocortical ripples was strengthened during sleep following learning. These findings suggest that ripple-ripple coupling supports hippocampal-association cortical transfer of memory traces. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  1. Hamiltonian reduction of SU(2) Yang-Mills field theory

    Khvedelidze, A.M.; Pavel, H.-P.

    1998-01-01

    The unconstrained system equivalent to SU (2) Yang-Mills field theory is obtained in the framework of the generalized Hamiltonian formalism using the method of Hamiltonian reduction. The reduced system is expressed in terms of fields with 'nonrelativistic' spin-0 and spin-2

  2. Euler-Poincare reduction for discrete field theories

    Vankerschaver, Joris

    2007-01-01

    In this note, we develop a theory of Euler-Poincare reduction for discrete Lagrangian field theories. We introduce the concept of Euler-Poincare equations for discrete field theories, as well as a natural extension of the Moser-Veselov scheme, and show that both are equivalent. The resulting discrete field equations are interpreted in terms of discrete differential geometry. An application to the theory of discrete harmonic mappings is also briefly discussed

  3. A low-ripple chargepump circuit for high voltage applications

    Berkhout, M.; Berkhout, M.; van Steenwijk, G.; van Steenwijk, Gijs; van Tuijl, Adrianus Johannes Maria

    1995-01-01

    The subject of this paper is a fully integrated chargepump circuit with a very low output voltage ripple. At a supply voltage of 30V the chargepump can source 1mA at an output voltage of 40V. Two simple modifications to the classical chargepump circuit give a substantial reduction of the output

  4. New possibility of magnetic ripple shielding for specific heat measurements in hybrid magnets

    Tarnawski, Z.; Meulen, der, H. van; Franse, J.J.M.; Kadowaki, K.; Veenhuizen, P.A.; Klaasse, J.

    1988-01-01

    A test of the new high Tc superconducting materials for magnetic ripple shielding has been carried out. It was found that magnetic ripples of 0.0009 T (peak-to-peak) in the frequency range below 20 kHz can be completely shielded in high static fields by a 2 mm thick Y-Ba-Cu-O screen.

  5. Ion peak narrowing by applying additional AC voltage (ripple voltage) to FAIMS extractor electrode.

    Pervukhin, Viktor V; Sheven, Dmitriy G

    2010-01-01

    The use of a non-uniform electric field in a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer increases sensitivity but decreases resolution. The application of an additional AC voltage to the extractor electrode ("ripple" voltage, U(ripple)) can overcome this effect, which decreases the FAIMS peak width. In this approach, the diffusion ion loss remains minimal in the non-uniform electric field in the cylindrical part of the device, and all ion losses under U(ripple) occur in a short portion of their path. Application of the ripple voltage to the extractor electrode is twice as efficient as the applying of U(ripple) along the total length of the device. 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

  6. Age Is Associated with Reduced Sharp-Wave Ripple Frequency and Altered Patterns of Neuronal Variability.

    Wiegand, Jean-Paul L; Gray, Daniel T; Schimanski, Lesley A; Lipa, Peter; Barnes, C A; Cowen, Stephen L

    2016-05-18

    Spatial and episodic memory performance declines with age, and the neural basis for this decline is not well understood. Sharp-wave ripples are brief (∼70 ms) high-frequency oscillatory events generated in the hippocampus and are associated with the consolidation of spatial memories. Given the connection between ripple oscillations and memory consolidation, we investigated whether the structure of ripple oscillations and ripple-triggered patterns of single-unit activity are altered in aged rats. Local field and single-unit activity surrounding sharp-wave ripple events were examined in the CA1 region of the hippocampus of old (n = 5) and young (n = 6) F344 rats during periods of rest preceding and following performance on a place-dependent eyeblink-conditioning task. Neural responses in aged rats differed from responses in young rats in several ways. First, compared with young rats, the rate of ripple occurrence (ripple density) is reduced in aged rats during postbehavior rest. Second, mean ripple frequency during prebehavior and postbehavior rest is lower in aged animals (aged: 132 Hz; young: 146 Hz). Third, single neurons in aged animals responded more consistently from ripple to ripple. Fourth, variability in interspike intervals was greater in aged rats. Finally, neurons were tuned to a narrower range of phases of the ripple oscillation relative to young animals. Together, these results suggest that the CA1 network in aged animals has a reduced "vocabulary" of available representational states. The hippocampus is a structure that is critical for the formation of episodic memories. Sharp-wave ripple events generated in the hippocampus have been implicated in memory consolidation processes critical to memory stabilization. We examine here whether these ripple oscillations are altered over the course of the life span, which could contribute to hippocampus-dependent memory deficits that occur during aging. This experiment used young and aged memory-impaired rats

  7. Spontaneous ripple formation in phosphorene: electronic properties and possible applications.

    Zhou, Yungang; Yang, Li; Zu, Xiaotao; Gao, Fei

    2016-06-09

    According to the Mermin-Wagner theorem and theory of elasticity, long-range order in two-dimensional (2D) crystals will be inevitably destroyed due to a thermal fluctuation. Thus, a 2D lattice prefers a corrugation meaning that a 2D crystal is easy to present a ripple. In this work, we, via employing ab initio molecular dynamics (AIMD) simulations, for the first time evidenced that the inherent dynamics of phosphorene would lead to a spontaneous formation of ripples at room temperature. The height of a ripple closely associates with the temperature and the width. Via density functional theory (DFT) calculations, we further demonstrated that the emergence of ripples would remarkably reduce the bandgap of phosphorene. Via the construction of the unique phosphorene structure, we finally found that such a rippled structure is expected to be used in the light-emitting field. These results give us further knowledge of phosphorene, which goes beyond the current scope of phosphorene limited to the flat lattice.

  8. Helical ripple transport in stellarators at low collision frequency

    Beidler, C.D.

    1987-12-01

    Numerical and analytical techniques have been developed to investigate the plasma transport which is due to particles trapping/detrapping in the local helical ripple wells of a stellarator's magnetic field. This process is of considerable importance as it provides the dominant transport mechanism in a stellarator plasma at ''low'' collision frequency: that is, when the frequency with which a particle is collisionally detrapped from a local ripple well is less than the bounce frequency of the particle in that well. A form of the longitudinal adiabatic invariant, J, is constructed and shown to describe accurately the orbits of ripple trapped particles. Unlike previous expressions for J, the form derived here correctly accounts for the local toroidal variation of the magnetic field. The expression for J is incorporated into a rapid ''hybrid'' Monte Carlo simulation of ripple transport in stellarators. The simulation is a hybrid in the sense that particle orbits in the narrow region of phase space on either side of the ripple trapping/detrapping boundary are followed using guiding center equations of motion while orbits in the remainder of phase space are described using adiabatic invariants. An analytical expression for the distribution function of ripple trapped particles in a stellarator - valid at all low collision frequencies - has been obtained by series solution of the bounce - averaged kinetic equation. This solution has been applied to both 'standard' and a class of 'transport optimized' stellarator magnetic fields. Analytical estimates of the diffusion coefficient obtained from the series solution show excellent agreement with the numerical results of the hybrid Monte Carlo code in all cases studied. 55 refs., 30 figs

  9. Asynchronous ripple oscillations between left and right hippocampi during slow-wave sleep.

    Villalobos, Claudio; Maldonado, Pedro E; Valdés, José L

    2017-01-01

    Spatial memory, among many other brain processes, shows hemispheric lateralization. Most of the published evidence suggests that the right hippocampus plays a leading role in the manipulation of spatial information. Concurrently in the hippocampus, memory consolidation during sleep periods is one of the key steps in the formation of newly acquired spatial memory traces. One of the most characteristic oscillatory patterns in the hippocampus are sharp-wave ripple (SWR) complexes. Within this complex, fast-field oscillations or ripples have been demonstrated to be instrumental in the memory consolidation process. Since these ripples are relevant for the consolidation of memory traces associated with spatial navigation, and this process appears to be lateralized, we hypothesize that ripple events between both hippocampi would exhibit different temporal dynamics. We tested this idea by using a modified "split-hyperdrive" that allows us to record simultaneous LFPs from both right and left hippocampi of Sprague-Dawley rats during sleep. We detected individual events and found that during sleep periods these ripples exhibited a different occurrence patterns between hemispheres. Most ripple events were synchronous between intra- rather than inter-hemispherical recordings, suggesting that ripples in the hippocampus are independently generated and locally propagated within a specific hemisphere. In this study, we propose the ripples' lack of synchrony between left and right hippocampi as the putative physiological mechanism underlying lateralization of spatial memory.

  10. Mechanisms of sharp wave initiation and ripple generation.

    Schlingloff, Dániel; Káli, Szabolcs; Freund, Tamás F; Hájos, Norbert; Gulyás, Attila I

    2014-08-20

    Replay of neuronal activity during hippocampal sharp wave-ripples (SWRs) is essential in memory formation. To understand the mechanisms underlying the initiation of irregularly occurring SWRs and the generation of periodic ripples, we selectively manipulated different components of the CA3 network in mouse hippocampal slices. We recorded EPSCs and IPSCs to examine the buildup of neuronal activity preceding SWRs and analyzed the distribution of time intervals between subsequent SWR events. Our results suggest that SWRs are initiated through a combined refractory and stochastic mechanism. SWRs initiate when firing in a set of spontaneously active pyramidal cells triggers a gradual, exponential buildup of activity in the recurrent CA3 network. We showed that this tonic excitatory envelope drives reciprocally connected parvalbumin-positive basket cells, which start ripple-frequency spiking that is phase-locked through reciprocal inhibition. The synchronized GABA(A) receptor-mediated currents give rise to a major component of the ripple-frequency oscillation in the local field potential and organize the phase-locked spiking of pyramidal cells. Optogenetic stimulation of parvalbumin-positive cells evoked full SWRs and EPSC sequences in pyramidal cells. Even with excitation blocked, tonic driving of parvalbumin-positive cells evoked ripple oscillations. Conversely, optogenetic silencing of parvalbumin-positive cells interrupted the SWRs or inhibited their occurrence. Local drug applications and modeling experiments confirmed that the activity of parvalbumin-positive perisomatic inhibitory neurons is both necessary and sufficient for ripple-frequency current and rhythm generation. These interneurons are thus essential in organizing pyramidal cell activity not only during gamma oscillation, but, in a different configuration, during SWRs. Copyright © 2014 the authors 0270-6474/14/3411385-14$15.00/0.

  11. Electromagnetic processes during phase commutation in field regulated reluctance machine

    Shishkov, A. N.; Sychev, D. A.; Zemlyansky, A. A.; Krupnova, M. N.; Funk, T. A.; Ishmet'eva, V. D.

    2018-03-01

    The processes of currents switching in stator windings have been explained by the existence of the electromagnetic torque ripples in the electric drive with the field-regulated reluctance machine. The maximum value of ripples in the open loop control system for the six-phase machine can reach 20 percent from the developed electromagnetic torque. This method allows one to make calculation of ripple spike towards average torque developed by the electromotor for the different number of phases. Application of a trapezoidal form of current at six phases became the solution. In case of a less number of phases than six, a ripple spike considerably increases, which is inadmissible. On the other hand, increasing the number of phases tends to the increase of the semiconductor inverter external dimensions based on the inconspicuous decreasing of a ripple spike. The creation and usage of high-speed control loops of current (HCLC) have been recommended for a reduction of the electromagnetic torque’s ripple level, as well as the appliance of positive current feedback in switching phase currents. This decision allowed one to receive a mean value of the torque more than 10%, compared to system without change, to reduce greatly ripple spike of the electromagnetic torque. The possibility of the electric drive effective operation with FRRM in emergency operation has been shown.

  12. A Simple Ripple Filter for FLUKA

    Bassler, Niels; Herrmann, Rochus

    In heavy ion radiotherapy, pristine C-12 beams are usually widened a few mm (FWHM) along the beam axis, before the actual spread out Bragg peak (SOBP) is build. The pristine beam widening is commonly performed with a ripple filter, known from the facility at GSI (Darmstadt) and at HIT (Heidelberg......). The ripple filter at GSI and HIT consists of several wedge like structures, which widens the Bragg-peak up to e.g. 3 mm. For Monte Carlo simulations of C-12 therapy, the exact setup, including the ripple filter needs to be simulated. In the Monte Carlo particle transport program FLUKA, the ripple filter can....... Since the ripple filter is a periodic geometry, one could use the LATTIC card with advantage, but here we shall take a Monte Carlo based approach istead. The advantage of this method is that our input file merely contains one body as the ripple filter, which can be a flat slab (or any other arbitrary...

  13. Numerical simulation of aeolian sand ripples

    Kang Liqiang; Guo Liejin

    2004-01-01

    With a new horizontal saltation displacement vector, a model is implemented to simulate the initiation and evolution of aeolian sand ripples. In the model, saltation distance considers the effects of surface height and slope. A linear stability analysis is also carried out for formation of sand ripples. The results show that, the model can be able to successfully reproduce sand ripples which can increase in scale by merging of small ripples. The linear stability analysis indicates that sand ripples appear when the relaxation rate parameter is below a threshold value and wind strength parameter is larger than a critical value. The results also verified that the formation of sand ripples is a self-organization process

  14. Two different mechanisms associated with ripple-like oscillations (100-250 Hz) in the human epileptic subiculum in vitro

    Alvarado-Rojas, C; Huberfeld, G; Baulac, M; Clemenceau, S; Charpier, S; Miles, R; Menendez de la Prida, L; Le Van Quyen, M

    2015-01-01

    Transient high-frequency oscillations (150-600 Hz) in local field potential generated by human hippocampal and parahippocampal areas have been related to both physiological and pathological processes. The cellular basis and effects of normal and abnormal forms of high-frequency oscillations (HFO) has been controversial. Here, we searched for HFOs in slices of the subiculum prepared from human hippocampal tissue resected for treatment of pharmacoresistant epilepsy. HFOs occurred spontaneously in extracellular field potentials during interictal discharges (IID) and also during pharmacologically induced preictal discharges (PID) preceding ictal-like events. While most of these events might be considered pathological since they invaded the fast ripple band (>250 Hz), others were spectrally similar to physiological ripples (150-250 Hz). Do similar cellular mechanisms underly IID-ripples and PID-ripples? Are ripple-like oscillations a valid proxy of epileptogenesis in human TLE? With combined intra- or juxta-cellular and extracellular recordings, we showed that, despite overlapping spectral components, ripple-like IID and PID oscillations were associated with different cellular and synaptic mechanisms. IID-ripples were associated with rhythmic GABAergic and glutamatergic synaptic potentials with moderate neuronal firing. In contrast, PID-ripples were associated with depolarizing synaptic inputs frequently reaching the threshold for bursting in most cells. Thus ripple-like oscillations (100-250 Hz) in the human epileptic hippocampus are associated with different mechanisms for synchrony reflecting distinct dynamic changes in inhibition and excitation during interictal and pre-ictal states. PMID:25448920

  15. Wave Driven Fluid-Sediment Interactions over Rippled Beds

    Foster, Diane; Nichols, Claire

    2008-11-01

    Empirical investigations relating vortex shedding over rippled beds to oscillatory flows date back to Darwin in 1883. Observations of the shedding induced by oscillating forcing over fixed beds have shown vortical structures to reach maximum strength at 90 degrees when the horizontal velocity is largest. The objective of this effort is to examine the vortex generation and ejection over movable rippled beds in a full-scale, free surface wave environment. Observations of the two-dimensional time-varying velocity field over a movable sediment bed were obtained with a submersible Particle Image Velocimetry (PIV) system in two wave flumes. One wave flume was full scale and had a natural sand bed and the other flume had an artificial sediment bed with a specific gravity of 1.6. Full scale observations over an irregularly rippled bed show that the vortices generated during offshore directed flow over the steeper bed form slope were regularly ejected into the water column and were consistent with conceptual models of the oscillatory flow over a backward facing step. The results also show that vortices remain coherent during ejection when the background flow stalls (i.e. both the velocity and acceleration temporarily approach zero). These results offer new insight into fluid sediment interaction over rippled beds.

  16. Magnetic ripple and the modeling of lower-hybrid current drive in tokamaks

    Peysson, Y.; Arslanbekov, R.; Basiuk, V.; Carrasco, J.; Litaudon, X.; Moreau, D.; Bizarro, J.P.

    1996-01-01

    Using ray-tracing, a detailed investigation of the lower hybrid (LH) wave propagation in presence of toroidal magnetic field ripple is presented. By coupling ray tracing with a one-dimensional relativistic Fokker-Planck code, simulations of LH experiments have been performed for the Tore Supra tokamak. Taking into account magnetic ripple in LH simulations, a better agreement is found between numerical predictions and experimental observations, such as non-thermal Bremsstrahlung emission, current profile, ripple-induced power losses in local magnetic mirrors, when plasma conditions correspond to the ' 'few passes' regime. (author)

  17. Extracellular calcium controls the expression of two different forms of ripple-like hippocampal oscillations.

    Aivar, Paloma; Valero, Manuel; Bellistri, Elisa; Menendez de la Prida, Liset

    2014-02-19

    Hippocampal high-frequency oscillations (HFOs) are prominent in physiological and pathological conditions. During physiological ripples (100-200 Hz), few pyramidal cells fire together coordinated by rhythmic inhibitory potentials. In the epileptic hippocampus, fast ripples (>200 Hz) reflect population spikes (PSs) from clusters of bursting cells, but HFOs in the ripple and the fast ripple range are vastly intermixed. What is the meaning of this frequency range? What determines the expression of different HFOs? Here, we used different concentrations of Ca(2+) in a physiological range (1-3 mM) to record local field potentials and single cells in hippocampal slices from normal rats. Surprisingly, we found that this sole manipulation results in the emergence of two forms of HFOs reminiscent of ripples and fast ripples recorded in vivo from normal and epileptic rats, respectively. We scrutinized the cellular correlates and mechanisms underlying the emergence of these two forms of HFOs by combining multisite, single-cell and paired-cell recordings in slices prepared from a rat reporter line that facilitates identification of GABAergic cells. We found a major effect of extracellular Ca(2+) in modulating intrinsic excitability and disynaptic inhibition, two critical factors shaping network dynamics. Moreover, locally modulating the extracellular Ca(2+) concentration in an in vivo environment had a similar effect on disynaptic inhibition, pyramidal cell excitability, and ripple dynamics. Therefore, the HFO frequency band reflects a range of firing dynamics of hippocampal networks.

  18. A High Power Density Single-Phase PWM Rectifier With Active Ripple Energy Storage

    Wang, Ruxi [Virginia Polytechnic Institute and State University (Virginia Tech); Wang, Fei [ORNL; Boroyevich, Dushan [Virginia Polytechnic Institute and State University (Virginia Tech); Burgos, Rolando [ABB; Lai, Rixin [General Electric; Ning, Puqi [ORNL; Rajashekara, Kaushik [Rolls Royce

    2011-01-01

    It is well known that single-phase pulse width modulation rectifiers have second-order harmonic currents and corresponding ripple voltages on the dc bus. The low-frequency harmonic current is normally filtered using a bulk capacitor in the bus, which results in low power density. However, pursuing high power density in converter design is a very important goal in the aerospace applications. This paper studies methods for reducing the energy storage capacitor for single-phase rectifiers. The minimum ripple energy storage requirement is derived independently of a specific topology. Based on theminimum ripple energy requirement, the feasibility of the active capacitor s reduction schemes is verified. Then, we propose a bidirectional buck boost converter as the ripple energy storage circuit, which can effectively reduce the energy storage capacitance. The analysis and design are validated by simulation and experimental results.

  19. On the formation of current ripples

    Bartholdy, Jesper; Ernstsen, Verner Brandbyge; Flemming, Burg W.

    2015-01-01

    such an explanation based on a virtual boundary layer concept, and present a model predicting ripple height on the basis of grain size, current velocity and water depth. The model contradicts the conventional view of current ripples as bedforms not scaling with flow depth. Furthermore, it confirms the dependence...

  20. Molecular structure of the lecithin ripple phase

    de Vries, AH; Yefimov, S; Mark, AE; Marrink, SJ

    2005-01-01

    Molecular dynamics simulations of lecithin lipid bilayers in water as they are cooled from the liquid crystalline phase show the spontaneous formation of rippled bilayers. The ripple consists of two domains of different length and orientation, connected by a kink. The organization of the lipids in

  1. Pattern formation - Instabilities in sand ripples

    Hansen, J. L.; v. Hecke, M.; Haaning, A.

    2001-01-01

    Sand ripples are seen below shallow wavy water and are formed whenever water oscillates over a bed of sand. Here we analyse the instabilities that can upset this perfect patterning when the ripples are subjected to large changes in driving amplitude or frequency, causing them to deform both...

  2. Surface magnetization and the role of pattern defects in various types of ripple patterned films

    Colino, Jose M; Arranz, Miguel A; Barbero, Antonio J; Bollero, A; Camarero, J

    2016-01-01

    We present a detailed study of the magnetic properties of cobalt films with wide-area nanoscale ripple patterns, either on their surface only, or on both the film surface and substrate interface. Angular dependence vectorial-resolved magnetometry measurements and magnetic force microscopy with in situ magnetic field have been used to determine the magnetization reversal processes to correlate them to the different patterned nanostructures. All the samples show well-defined uniaxial magnetic anisotropy with the anisotropy axis lying along the ripple direction. Atomic force microscopy of the different types of pattern reveals various pattern defects: height corrugation and breaks of continuity along the ripple direction, and overlapping ripples and Y-shaped defects (pattern dislocation) across the pattern. In spite of the existence of such customary defects of erosive-regime patterns, the type of low-amplitude, surface-patterned films remarkably behave as a macrospin over almost the whole in-plane angular range (340°), with negligible spread of anisotropy axis or energy. In turn, it is found that high-amplitude surface-patterned films develop an angular distribution of anisotropy axes, probably related to the large distribution of amplitudes in a pattern of short ripples, and a significant distribution of anisotropy fields ΔH k /H k up to 15%. On the other hand, films grow on pre-patterned silicon with a significantly longer mean ripple length, and develop a larger anisotropy energy with H k up to 110 mT, probably because of the double interface effect. The switching fields close to the magnetization easy axis of all types of ripple pattern are not well reproduced by the macrospin approximation, but the observed pattern defects seem to be not responsible for the domain wall pinning that occurs with the field applied along the ripple direction. (paper)

  3. Model of ripples in graphene

    Bonilla, L. L.; Carpio, A.

    2012-11-01

    We propose a model of ripples in suspended graphene sheets based on plate equations that are made discrete with the periodicity of the honeycomb lattice and then periodized. In addition, the equation for the displacements with respect to the planar configuration contains a double-well site potential, a nonlinear friction, and a multiplicative white-noise term satisfying the fluctuation-dissipation theorem. The nonlinear friction terms agree with those proposed by Eichler [Nature Nanotech.1748-338710.1038/nnano.2011.71 6, 339 (2011)] to explain their experiments with a graphene resonator. The site double-well potential indicates that the carbon atoms at each lattice point have equal probability to move upward or downward off plane. For the considered parameter values, the relaxation time due to friction is much larger than the periods of membrane vibrations and the noise is quite small. Then ripples with no preferred orientation appear as long-lived metastable states for any temperature. Numerical solutions confirm this picture.

  4. Parallelization of Reversible Ripple-carry Adders

    Thomsen, Michael Kirkedal; Axelsen, Holger Bock

    2009-01-01

    The design of fast arithmetic logic circuits is an important research topic for reversible and quantum computing. A special challenge in this setting is the computation of standard arithmetical functions without the generation of \\emph{garbage}. Here, we present a novel parallelization scheme...... wherein $m$ parallel $k$-bit reversible ripple-carry adders are combined to form a reversible $mk$-bit \\emph{ripple-block carry adder} with logic depth $\\mathcal{O}(m+k)$ for a \\emph{minimal} logic depth $\\mathcal{O}(\\sqrt{mk})$, thus improving on the $mk$-bit ripple-carry adder logic depth $\\mathcal...

  5. Higher-order paraxial theory of the propagation of ring rippled laser beam in plasma: Relativistic ponderomotive regime

    Purohit, Gunjan; Rawat, Priyanka; Chauhan, Prashant; Mahmoud, Saleh T.

    2015-01-01

    This article presents higher-order paraxial theory (non-paraxial theory) for the ring ripple formation on an intense Gaussian laser beam and its propagation in plasma, taking into account the relativistic-ponderomotive nonlinearity. The intensity dependent dielectric constant of the plasma has been determined for the main laser beam and ring ripple superimposed on the main laser beam. The dielectric constant of the plasma is modified due to the contribution of the electric field vector of ring ripple. Nonlinear differential equations have been formulated to examine the growth of ring ripple in plasma, self focusing of main laser beam, and ring rippled laser beam in plasma using higher-order paraxial theory. These equations have been solved numerically for different laser intensities and plasma frequencies. The well established experimental laser and plasma parameters are used in numerical calculation. It is observed that the focusing of the laser beams (main and ring rippled) becomes fast in the nonparaxial region by expanding the eikonal and other relevant quantities up to the fourth power of r. The splitted profile of laser beam in the plasma is observed due to uneven focusing/defocusing of the axial and off-axial rays. The growths of ring ripple increase when the laser beam intensity increases. Furthermore, the intensity profile of ring rippled laser beam gets modified due to the contribution of growth rate

  6. Listening to Whispers of Ripple: Linking Wallets and Deanonymizing Transactions in the Ripple Network

    Moreno-Sanchez Pedro; Zafar Muhammad Bilal; Kate Aniket

    2016-01-01

    The decentralized I owe you (IOU) transaction network Ripple is gaining prominence as a fast, low-cost and efficient method for performing same and cross-currency payments. Ripple keeps track of IOU credit its users have granted to their business partners or friends, and settles transactions between two connected Ripple wallets by appropriately changing credit values on the connecting paths. Similar to cryptocurrencies such as Bitcoin, while the ownership of the wallets is implicitly pseudony...

  7. Impact of Attitude: The Ripple Effect.

    Bullen, Robert

    1983-01-01

    Describes the potential ripple effect of a principal's mercurial personality and poor interpersonal skills on teachers, students, families, and the community. Suggests effective personnel selection methods to enhance the chances of employing desirable principals. (SB)

  8. Cryptocurrency market making in the Ripple network

    Brezigar, Jakob

    2016-01-01

    Market maker provides counterparty for buyers and sellers of financial instruments in transaction settlement. Market makers quote the bid price and the ask price at the same time. This price setting process is called market making. This thesis covers theoretical and practical basis for implementation of autonomous market making algorithm for a promising cryptocurrency market called Ripple. We summarize market making theory, how Ripple cryptocurrency protocol works and how price formation proc...

  9. Dune and ripple migration along Curiosity's traverse in Gale Crater on Mars

    Silvestro, S.; Vaz, D.; Ewing, R. C.; Fenton, L. K.; Michaels, T. I.; Ayoub, F.; Bridges, N. T.

    2013-12-01

    The NASA Mars Science Laboratory (MSL) rover, Curiosity, has safely landed near a 35-km-long dark dune field in Gale Crater on Mars. This dune field lies along Curiosity's traverse to Aeolis Mons (Mt. Sharp). Here we present new evidence of aeolian activity and further estimate wind directions within the dune field through analysis of ripple migration with the COSI-Corr technique, which provides precise measurements of ripple displacement at the sub-pixel scale.The area analyzed is located ~10 km southwest of rover Curiosity's current position and ~4 km SW of its selected path through Aeolis Mons (Mt. Sharp) (Fig. 1a). Here barchan dunes with elongated horns and seif dunes coexist with more typical barchan and dome dunes (Fig. 1a, b), with slopes sculpted by two intersecting ripple crestline orientations trending at 45° and 330°. The range of dune types and ripple orientations indicate the dune field morphology is influenced by at least two winds from the NW and the NE. The direction of migration is toward the SW, suggesting the most recent sand transporting winds were from the NE (Fig. 1c). These results match previous predictions and can be used to forecast the wind conditions close to the entry point to Mt. Sharp. Fig. 1: a-b) Study area c) Ripple migration direction computed using the COSI-Corr technique

  10. Rippled cosmological dark matter from a damped oscillating Newton constant

    Davidson, Aharon

    2005-01-01

    Let the reciprocal Newton 'constant' be an apparently non-dynamical Brans-Dicke scalar field damped oscillating towards its general relativistic VEV. We show, without introducing additional matter fields or dust, that the corresponding cosmological evolution averagely resembles, in the Jordan frame, the familiar dark radiation → dark matter → dark energy domination sequence. The fingerprints of our theory are fine ripples, hopefully testable, in the FRW scale factor; they die away at the general relativity limit. The possibility that the Brans-Dicke scalar also serves as the inflaton is favourably examined

  11. Listening to Whispers of Ripple: Linking Wallets and Deanonymizing Transactions in the Ripple Network

    Moreno-Sanchez Pedro

    2016-10-01

    Full Text Available The decentralized I owe you (IOU transaction network Ripple is gaining prominence as a fast, low-cost and efficient method for performing same and cross-currency payments. Ripple keeps track of IOU credit its users have granted to their business partners or friends, and settles transactions between two connected Ripple wallets by appropriately changing credit values on the connecting paths. Similar to cryptocurrencies such as Bitcoin, while the ownership of the wallets is implicitly pseudonymous in Ripple, IOU credit links and transaction flows between wallets are publicly available in an online ledger. In this paper, we present the first thorough study that analyzes this globally visible log and characterizes the privacy issues with the current Ripple network. In particular, we define two novel heuristics and perform heuristic clustering to group wallets based on observations on the Ripple network graph. We then propose reidentification mechanisms to deanonymize the operators of those clusters and show how to reconstruct the financial activities of deanonymized Ripple wallets. Our analysis motivates the need for better privacy-preserving payment mechanisms for Ripple and characterizes the privacy challenges faced by the emerging credit networks.

  12. Seabed ripple morphology and surficial sediment size at the SAX04 experiments near Fort Walton Beach, Florida, fall 2004

    Hanes, Daniel M.; Erikson, Li H.; Lescinski, Jamie M.R.; Harney, Jodi N.; Carter, Carissa L.; Hatcher, Gerry A.; Lacy, Jessica R.; Rubin, David M.

    2007-01-01

    Data presented in this report originates from measurements obtained off the Florida coast (fig. 1) as part of the Sediment Acoustics Experiment (SAX04) and Ripples Department Research Initiative (DRI) (Office of Naval Research (ONR), Critical Benthic Environmental Processes and Modeling, Long Range BAA 04-001, Sept. 10, 2003). The aim of this document is to present methods employed to extract data and the resulting measured ripple characteristics (ripple height, wavelength, and orientation) and seabed grain sizes. Application and analysis of the data with respect to hydro- and morphodynamics will be addressed in subsequent reports. Sediment transport in the coastal region is a complex process involving interactions between flow dynamics, sediments, and bedforms. Sediment type and bed geometry directly influence entrainment of sediments into suspension, and at sites where ripples occur (sand formations on the order of several cm high and less than two meter long wavelengths), the understanding of ripple dynamics is an essential component in improving sediment transport models. To gain a better understanding and ability to predict sediment transport, a field study was undertaken to investigate morphology, orientation, and dynamics of ripples on the seafloor. The data obtained from the field campaign also supports an on-going effort to study the effects of ripples on low grazing acoustic penetration into sandy marine sediments for the detection of objects, such as mines (Jackson and others, 2002).

  13. A particle model of rolling grain ripples under waves

    Andersen, Ken Haste

    2001-01-01

    A simple model for the formation of rolling grain ripples on a flat sand bed by the oscillatory flow generated by a surface wave is presented. An equation of motion is derived for the individual ripples, seen as "particles," on the otherwise flat bed. The model accounts for the initial appearance...... of the ripples, the subsequent coarsening of the ripples, and the final equilibrium state. The model is related to the physical parameters of the problem, and an analytical approximation for the equilibrium spacing of the ripples is developed. It is found that the spacing between the ripples scales...

  14. Evaluation of beam delivery and ripple filter design for non-isocentric proton and carbon ion therapy.

    Grevillot, L; Stock, M; Vatnitsky, S

    2015-10-21

    This study aims at selecting and evaluating a ripple filter design compatible with non-isocentric proton and carbon ion scanning beam treatment delivery for a compact nozzle. The use of non-isocentric treatments when the patient is shifted as close as possible towards the nozzle exit allows for a reduction in the air gap and thus an improvement in the quality of scanning proton beam treatment delivery. Reducing the air gap is less important for scanning carbon ions, but ripple filters are still necessary for scanning carbon ion beams to reduce the number of energy steps required to deliver homogeneous SOBP. The proper selection of ripple filters also allows a reduction in the possible transverse and depth-dose inhomogeneities that could appear in non-isocentric conditions in particular. A thorough review of existing ripple filter designs over the past 16 years is performed and a design for non-isocentric treatment delivery is presented. A unique ripple filter quality index (QIRiFi) independent of the particle type and energy and representative of the ratio between energy modulation and induced scattering is proposed. The Bragg peak width evaluated at the 80% dose level (BPW80) is proposed to relate the energy modulation of the delivered Bragg peaks and the energy layer step size allowing the production of homogeneous SOBP. Gate/Geant4 Monte Carlo simulations have been validated for carbon ion and ripple filter simulations based on measurements performed at CNAO and subsequently used for a detailed analysis of the proposed ripple filter design. A combination of two ripple filters in a series has been validated for non-isocentric delivery and did not show significant transverse and depth-dose inhomogeneities. Non-isocentric conditions allow a significant reduction in the spot size at the patient entrance (up to 350% and 200% for protons and carbon ions with range shifter, respectively), and therefore in the lateral penumbra in the patients.

  15. Torque ripple minimization in a doubly salient permanent magnet motors by skewing the rotor teeth

    Sheth, N.K.; Sekharbabu, A.R.C.; Rajagopal, K.R.

    2006-01-01

    This paper presents the effects of skewing the rotor teeth on the performance of an 8/6 doubly salient permanent magnet motor using a simple method, which utilizes the results obtained from the 2-D FE analysis. The optimum skewing angle is obtained as 12-15 o for the least ripple torque without much reduction in the back-emf

  16. Cochlear implant users' spectral ripple resolution.

    Jeon, Eun Kyung; Turner, Christopher W; Karsten, Sue A; Henry, Belinda A; Gantz, Bruce J

    2015-10-01

    This study revisits the issue of the spectral ripple resolution abilities of cochlear implant (CI) users. The spectral ripple resolution of recently implanted CI recipients (implanted during the last 10 years) were compared to those of CI recipients implanted 15 to 20 years ago, as well as those of normal-hearing and hearing-impaired listeners from previously published data from Henry, Turner, and Behrens [J. Acoust. Soc. Am. 118, 1111-1121 (2005)]. More recently, implanted CI recipients showed significantly better spectral ripple resolution. There is no significant difference in spectral ripple resolution for these recently implanted subjects compared to hearing-impaired (acoustic) listeners. The more recently implanted CI users had significantly better pre-operative speech perception than previously reported CI users. These better pre-operative speech perception scores in CI users from the current study may be related to better performance on the spectral ripple discrimination task; however, other possible factors such as improvements in internal and external devices cannot be excluded.

  17. Ripple transport in helical-axis advanced stellarators - a comparison with classical stellarator/torsatrons

    Beidler, C.D.; Hitchon, W.N.G.

    1993-08-01

    Calculations of the neoclassical transport rates due to particles trapped in the helical ripples of a stellarator's magnetic field are carried out, based on solutions of the bounce-averaged kinetic equation. These calculations employ a model for the magnetic field strength, B, which is an accurate approximation to the actual B for a wide variety of stellarator-type devices, among which are Helical-Axis Advanced Stellarators (Helias) as well as conventional stellarators and torsatrons. Comparisons are carried out in which it is shown that the Helias concept leads to significant reductions in neoclassical transport rates throughout the entire long-mean-free-path regime, with the reduction being particularly dramatic in the ν -1 regime. These findings are confirmed by numerical simulations. Further, it is shown that the behavior of deeply trapped particles in Helias can be fundamentally different from that in classical stellarator/torsatrons; as a consequence, the beneficial effects of a radial electric field on the transport make themselves felt at lower collision frequency than is usual. (orig.)

  18. Beamforming applied to surface EEG improves ripple visibility.

    van Klink, Nicole; Mol, Arjen; Ferrier, Cyrille; Hillebrand, Arjan; Huiskamp, Geertjan; Zijlmans, Maeike

    2018-01-01

    Surface EEG can show epileptiform ripples in people with focal epilepsy, but identification is impeded by the low signal-to-noise ratio of the electrode recordings. We used beamformer-based virtual electrodes to improve ripple identification. We analyzed ten minutes of interictal EEG of nine patients with refractory focal epilepsy. EEGs with more than 60 channels and 20 spikes were included. We computed ∼79 virtual electrodes using a scalar beamformer and marked ripples (80-250 Hz) co-occurring with spikes in physical and virtual electrodes. Ripple numbers in physical and virtual electrodes were compared, and sensitivity and specificity of ripples for the region of interest (ROI; based on clinical information) were determined. Five patients had ripples in the physical electrodes and eight in the virtual electrodes, with more ripples in virtual than in physical electrodes (101 vs. 57, p = .007). Ripples in virtual electrodes predicted the ROI better than physical electrodes (AUC 0.65 vs. 0.56, p = .03). Beamforming increased ripple visibility in surface EEG. Virtual ripples predicted the ROI better than physical ripples, although sensitivity was still poor. Beamforming can facilitate ripple identification in EEG. Ripple localization needs to be improved to enable its use for presurgical evaluation in people with epilepsy. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

  19. Field Study of Infiltration Capacity Reduction of Porous Mixture Surfaces

    Luis A. Sañudo-Fontaneda

    2014-03-01

    Full Text Available Porous surfaces have been used all over the world in source control techniques to minimize flooding problems in car parks. Several studies highlighted the reduction in the infiltration capacity of porous mixture surfaces after several years of use. Therefore, it is necessary to design and develop a new methodology to quantify this reduction and to identify the hypothetical differences in permeability between zones within the same car park bay due to the influence of static loads in the parked vehicles. With this aim, nine different zones were selected in order to check this hypothesis (four points under the wheels of a standard vehicle and five points between wheels. This article presents the infiltration capacity reduction results, using the LCS permeameter, of Polymer-Modified Porous Concrete (9 bays and Porous Asphalt (9 bays surfaces in the University of Cantabria Campus parking area (Spain 5 years after their construction. Statistical analysis methodology was proposed for assessing the results. Significant differences were observed in permeability and reduction in infiltration capacity in the case of porous concrete surfaces, while no differences were found for porous asphalt depending on the measurement zone.

  20. Electric and magnetic field reduction by alternative transmission line options

    Stewart, J.R. (Power Technologies, Inc., Schenectady, NY (United States)); Dale, S.J. (Oak Ridge National Lab., TN (United States)); Klein, K.W. (Energetics, Inc., Columbia, MD (United States))

    1991-01-01

    Ground level electric, and more recently magnetic, fields from overhead power transmission lines are increasingly important considerations in right of way specification, with states setting or planning to set edge of right of way limits. Research has been conducted in high phase order power transmission wherein six of twelve phases are used to transmit power in less physical space and with reduced electrical environmental effects than conventional designs. The first magnetic field testing, as reported in this paper, has verified predictive methods for determination of magnetic fields from high phase order lines. Based on these analytical methods, field profiles have been determined for lines of different phase order of comparable power capacity. Potential advantages of high phase order as a means of field mitigation are discussed. 10 refs., 12 figs., 3 tabs.

  1. Mathematical Relationship Between Particle Reynolds Number and Ripple Factor using Tapi River Data, India.

    S. M. Yadav

    2011-02-01

    Full Text Available The computation of bed load allows for the fact that only part of the shear stress is used for transport of sediments and some of the shear stress is wasted in overcoming the resistance due to bed forms therefore the total shear stress developed in the open channel requires correction in the form of correction factor called ripple factor. Different methods have been followed for correcting the actual shear stress in order to compute the sediment load. Correction factors are based on particular characteristics grain size of particle. In the present paper the ripple factor has been obtained for non uniform bed material considering the various variables like discharge, hydraulic mean depth, flow velocity, bed slope, average diameter of particle etc. by collecting the field data of Tapi river for 15 years for a particular gauging station. The ripple factor is obtained using Meyer Peter and Muller formula, Einstein Formula, Kalinske’s formula, Du Boy’s formula, Shield’s formula, Bagnold’s formula, average of six formulae and multiple regression analysis. The variation of ripple factor with particle Reynolds Number is studied. The ripple factor obtained by different approaches are further analyzed using Origin software and carrying out multiple regression on the 15 years of data with more than 10 parameters, ripple factor by multiple regression has been obtained. These values are further analysed and giving statistical mean to the parameters a relationship of power form has been developed. The ripple factor increases with the increase in the value of Particle Reynolds number. The large deviation is observed in case of Kalinske’s approach when compare with other approaches

  2. Molecular structure of the lecithin ripple phase

    de Vries, Alex H.; Yefimov, Serge; Mark, Alan E.; Marrink, Siewert J.

    2005-04-01

    Molecular dynamics simulations of lecithin lipid bilayers in water as they are cooled from the liquid crystalline phase show the spontaneous formation of rippled bilayers. The ripple consists of two domains of different length and orientation, connected by a kink. The organization of the lipids in one domain of the ripple is found to be that of a splayed gel; in the other domain the lipids are gel-like and fully interdigitated. In the concave part of the kink region between the domains the lipids are disordered. The results are consistent with the experimental information available and provide an atomic-level model that may be tested by further experiments. molecular dynamics simulation | structural model

  3. Comparison of Output Current Ripple in Single and Dual Three-Phase Inverters for Electric Vehicle Motor Drives

    Jelena Loncarski

    2015-04-01

    Full Text Available The standard solution for the traction system in battery powered electric vehicles (EVs is a two-level (2L inverter feeding a three-phase motor. A simple and effective way to achieve a three-level (3L inverter in battery-supplied electric vehicles consists of using two standard three-phase 2L inverters with the open-end winding connection of standard three-phase ac motors. The 3L inverter solution can be usefully adopted in EVs since it combines several benefits such as current ripple reduction, increment of phase motor voltage with limited voltage ratings of the two battery banks, improvement in system reliability, etc. The reduction in current ripple amplitude is particularly relevant since it is a source of electromagnetic interference and audio noise from the inverter-motor power connection cables and from the motor itself. By increasing the inverter switching frequency the ripple amplitude is reduced, but the drive efficiency decreases due to the proportionally increased switching losses. In this paper the peak-to-peak ripple amplitude of the dual-2L inverter is evaluated and compared with the corresponding ripple of the single-2L inverter, considering the same voltage and power motor ratings. The ripple analysis is carried out as a function of the modulation index to cover the whole modulation range of the inverter, and the theoretical results are verified with experimental tests carried out by an inverter-motor drive prototype.

  4. Rippling and drift instabilities in the straight cylinder tokamak

    Rogister, A.

    1984-01-01

    It is shown that the electron and ion diamagnetic drifts stabilize the rippling mode in the straigth cylindrical tokamak model. Parallel electron heat conduction is further stabilizing if the parameter etasub(e) = dlnTsub(e)/dlnN is positive. This has a consequence that the mode does not survive at temperatures exceeding, typically, 50 eV for standard values of magnetic field and density. The collisional drift wave is found to be always stable even when the effect of the tokamak current is included in the calculation. (orig.)

  5. Dimensional reduction in field theory and hidden symmetries in extended supergravity

    Kremmer, E.

    1985-01-01

    Dimensional reduction in field theories is discussed both in theories which do not include gravity and in gravity theories. In particular, 11-dimensional supergravity and its reduction to 4 dimensions is considered. Hidden symmetries of supergravity with N=8 in 4 dimensions, global E 7 and local SU(8)-invariances in particular are detected. The hidden symmmetries permit to interpret geometrically the scalar fields

  6. Origin of the two scales of wind ripples on Mars

    Lapotre, M. G. A.; Ewing, R. C.; Lamb, M. P.; Fischer, W. W.; Grotzinger, J. P.; Rubin, D. M.; Lewis, K. W.; Ballard, M.; Day, M. D.; Gupta, S.; Banham, S.; Bridges, N.; Des Marais, D. J.; Fraeman, A. A.; Grant, J. A., III; Ming, D. W.; Mischna, M.; Rice, M. S.; Sumner, D. Y.; Vasavada, A. R.; Yingst, R. A.

    2016-12-01

    Earth's sandy deserts host two main types of bedforms - decimeter-scale ripples and larger dunes. Years of orbital observations on Mars also confirmed the existence of two modes of active eolian bedforms - meter-scale ripples, and dunes. By analogy to terrestrial ripples, which are thought to form from a grain mechanism, it was hypothesized that large martian ripples also formed from grain impacts, but spaced further apart due to elongated saltation trajectories from the lower martian gravity and different atmospheric properties. However, the Curiosity rover recently documented the coexistence of three scales of bedforms in Gale crater. Because a grain impact mechanism cannot readily explain two distinct and coeval ripple modes in similar sand sizes, a new mechanism seems to be required to explain one of the scales of ripples. Small ripples are most similar to Earth's impact ripples, with straight crests and subdued profiles. In contrast, large martian ripples are sinuous and asymmetric, with lee slopes dominated by grain flows and grainfall deposits. Thus, large martian ripples resemble current ripples formed underwater on Earth, suggesting that they may form from a fluid-drag mechanism. To test this hypothesis, we develop a scaling relation to predict the spacing of fluid-drag ripples from an extensive flume data compilation. The size of large martian ripples is predicted by our scaling relation when adjusted for martian atmospheric properties. Specifically, we propose that the wavelength of martian wind-drag ripples arises from the high kinematic viscosity of the low-density atmosphere. Because fluid density controls drag-ripple size, our scaling relation can help constrain paleoatmospheric density from wind-drag ripple stratification.

  7. Beam-ripple monitor with secondary electrons

    Sato, Shinji; Kanazawa, Mitsutaka; Noda, Koji; Takada, Eiichi; Komiyama, Akihito; Ichinohe, Ken-ichi; Sano, Yoshinobu

    1997-01-01

    To replace the scintillation-ripple monitor, we have developed a new monitor with a smaller destructive effect on the beam. In this monitor, we use secondary electrons emitted from an aluminum foil with a thickness of 2 μm. The signals of secondary electrons are amplified by an electron multiplier having a maximum gain of 10 6 . By using the new monitor, we could clearly observe the beam ripple with a beam intensity of 3.6x10 8 pps (particle per second). This monitor can also be used as an intensity monitor in the range of 10 4 - 10 9 pps. (author)

  8. Ripple Ring Basins on Ganymede and Callisto

    Croft, S. K.

    1985-01-01

    The unusual morphology of the Valhalla multiple or ripple-ring basin in Callisto was totally unexpected in light of the morphologies of large impact structures on the terrestrial planets. Two other ripple-ring basins (RRB's), Asgard and a smaller structure near the crater Adlinda are also described. Several additional RRB's were found on Callisto, an example of which is shown. A previously unrecognized RRB on Ganymede was also found. An image and geologic sketch map of this RRB are shown. Morphometric and positional data for all known RRB's are given.

  9. Minimal Representations and Reductive Dual Pairs in Conformal Field Theory

    Todorov, Ivan

    2010-01-01

    A minimal representation of a simple non-compact Lie group is obtained by 'quantizing' the minimal nilpotent coadjoint orbit of its Lie algebra. It provides context for Roger Howe's notion of a reductive dual pair encountered recently in the description of global gauge symmetry of a (4-dimensional) conformal observable algebra. We give a pedagogical introduction to these notions and point out that physicists have been using both minimal representations and dual pairs without naming them and hence stand a chance to understand their theory and to profit from it.

  10. Optimum geometry for torque ripple minimization of switched reluctance motors

    Sahin, F.; Ertan, H.B.; Leblebicioglu, K.

    2000-01-01

    For switched reluctance motors, one of the major problems is torque ripple which causes increased undesirable acoustic noise and possibly speed ripple. This paper describes an approach to determine optimum magnetic circuit parameters to minimize low speed torque ripple for such motors. The

  11. Dynamical models for sand ripples beneath surface waves

    Andersen, Ken Haste; Chabanol, M.-L.; v. Hecke, M.

    2001-01-01

    We introduce order parameter models for describing the dynamics of sand ripple patterns under oscillatory flow. A crucial ingredient of these models is the mass transport between adjacent ripples, which we obtain from detailed numerical simulations for a range of ripple sizes. Using this mass tra...

  12. Hippocampal sharp wave/ripples during sleep for consolidation of associative memory.

    Wiâm Ramadan

    Full Text Available The beneficial effect of sleep on memory has been well-established by extensive research on humans, but the neurophysiological mechanisms remain a matter of speculation. This study addresses the hypothesis that the fast oscillations known as ripples recorded in the CA1 region of the hippocampus during slow wave sleep (SWS may provide a physiological substrate for long term memory consolidation. We trained rats in a spatial discrimination task to retrieve palatable reward in three fixed locations. Hippocampal local field potentials and cortical EEG were recorded for 2 h after each daily training session. There was an increase in ripple density during SWS after early training sessions, in both trained rats and in rats randomly rewarded for exploring the maze. In rats learning the place -reward association, there was a striking further significant increase in ripple density correlated with subsequent improvements in behavioral performance as the rat learned the spatial discrimination aspect of the task. The results corroborate others showing an experience-dependent increase in ripple activity and associated ensemble replay after exploratory activity, but in addition, for the first time, reveal a clear further increase in ripple activity related to associative learning based on spatial discrimination.

  13. Diversity of sharp-wave–ripple LFP signatures reveals differentiated brain-wide dynamical events

    Ramirez-Villegas, Juan F.; Logothetis, Nikos K.; Besserve, Michel

    2015-01-01

    Sharp-wave–ripple (SPW-R) complexes are believed to mediate memory reactivation, transfer, and consolidation. However, their underlying neuronal dynamics at multiple scales remains poorly understood. Using concurrent hippocampal local field potential (LFP) recordings and functional MRI (fMRI), we study local changes in neuronal activity during SPW-R episodes and their brain-wide correlates. Analysis of the temporal alignment between SPW and ripple components reveals well-differentiated SPW-R subtypes in the CA1 LFP. SPW-R–triggered fMRI maps show that ripples aligned to the positive peak of their SPWs have enhanced neocortical metabolic up-regulation. In contrast, ripples occurring at the trough of their SPWs relate to weaker neocortical up-regulation and absent subcortical down-regulation, indicating differentiated involvement of neuromodulatory pathways in the ripple phenomenon mediated by long-range interactions. To our knowledge, this study provides the first evidence for the existence of SPW-R subtypes with differentiated CA1 activity and metabolic correlates in related brain areas, possibly serving different memory functions. PMID:26540729

  14. Diversity of sharp-wave-ripple LFP signatures reveals differentiated brain-wide dynamical events.

    Ramirez-Villegas, Juan F; Logothetis, Nikos K; Besserve, Michel

    2015-11-17

    Sharp-wave-ripple (SPW-R) complexes are believed to mediate memory reactivation, transfer, and consolidation. However, their underlying neuronal dynamics at multiple scales remains poorly understood. Using concurrent hippocampal local field potential (LFP) recordings and functional MRI (fMRI), we study local changes in neuronal activity during SPW-R episodes and their brain-wide correlates. Analysis of the temporal alignment between SPW and ripple components reveals well-differentiated SPW-R subtypes in the CA1 LFP. SPW-R-triggered fMRI maps show that ripples aligned to the positive peak of their SPWs have enhanced neocortical metabolic up-regulation. In contrast, ripples occurring at the trough of their SPWs relate to weaker neocortical up-regulation and absent subcortical down-regulation, indicating differentiated involvement of neuromodulatory pathways in the ripple phenomenon mediated by long-range interactions. To our knowledge, this study provides the first evidence for the existence of SPW-R subtypes with differentiated CA1 activity and metabolic correlates in related brain areas, possibly serving different memory functions.

  15. Ion flow ripples in the Earth's plasma sheet

    De Spiegeleer, Alexandre; Hamrin, Maria; Pitkänen, Timo; Norqvist, Patrik; Mann, Ingrid

    2016-04-01

    For a long time, magnetotail flows were considered rather smooth and laminar, and primarily dominated by a simple convection flow pattern. However, in the early 90's, high speed bursty bulk flows (BBFs) were discovered and found to commonly perturb the underlying convection flows. In addition, there are other disturbances complicating the magnetotail flow pattern. Instabilities such as the Kelvin-Helmholz instability and the kink instability can cause different types of magnetic field oscillations, such as field line resonances. It is expected that ions will follow these oscillations if the typical time and length scales are larger than the gyroperiod and gyroradius of the ions. Though low-velocity sloshing and ripple disturbances of the average magnetotail convection flows have been observed, their connection with magnetic field oscillations is not fully understood. Furthermore, when studying BFFs, these "Ion Flow Ripples" (IFRs) are often neglected, dismissed as noise or can even erroneously be identified as BBFs. It is therefore of utter importance to find out and understand the role of IFRs in magnetotail dynamics. In a statistical investigation, we use several years of Cluster plasma sheet data to study the low-speed flows in the magnetotail. We investigate different types of IFRs, study their occurrence, and discuss their possible causes.

  16. Field error reduction experiment on the REPUTE-1 RFP device

    Toyama, H.; Shinohara, S.; Yamagishi, K.

    1989-01-01

    The vacuum chamber of the RFP device REPUTE-1 is a welded structure using 18 sets of 1 mm thick Inconel bellows (inner minor radius 22 cm) and 2.4 mm thick port segments arranged in toroidal geometry as shown in Fig. 1. The vacuum chamber is surrounded by 5 mm thick stainless steel shells. The time constant of the shell is 1 ms for vertical field penetration. The pulse length in REPUTE-1 is so far 3.2 ms (about 3 times longer than shell skin time). The port bypass plates have been attached as shown in Fig. 2 to reduce field errors so that the pulse length becomes longer and the loop voltage becomes lower. (author) 5 refs., 4 figs

  17. A Biatrial Myxoma with Triple Ripples.

    Barik, Ramachandra

    2018-01-01

    Cardiac myxoma is a benign tumor, but it is known for its space-occupying effect at the site of origin and frequent systemic embolization. This case report highlights a biatrial myxoma of interatrial septum who presented with significant tricuspid valve regurgitation, atrial fibrillation, and cardioembolic stroke of the left parietal lobe, i.e., a biatrial myxoma with triple ripples.

  18. The Ripple Tank: Management and Observation

    Auty, Geoff

    2017-01-01

    This overview is intended to help colleagues achieve successful and satisfying observations using a ripple tank. There are many observations to consider that can effectively illustrate reflection, refraction, interference and diffraction, but the most important consideration is to make every effort to enable students to see the effects we want…

  19. Recording Images Observed Using Ripple Tanks

    Auty, Geoff

    2018-01-01

    Diagrams and photographs (or computer simulations) should not replace effective observations of the wave properties that can be illustrated using a ripple tank, but they can provide support when discussing and revising what has been observed. This article explains and illustrates a route towards successful photography, which is much easier with…

  20. Measuring Social Capital Change Using Ripple Mapping

    Baker, Barbara; Johannes, Elaine M.

    2013-01-01

    This article provides a detailed description of how to implement a ripple mapping activity to assess youth program effects on community capital and concludes with examples from Maine and Kansas. The maps lead to group reflection on project outcomes and further research and evaluation questions for group members. The results from five Maine…

  1. Modulations of anisotropic optical transmission on alumina-doped zinc oxide surface by femtosecond laser induced ripples

    Lu, Yanhui; Jiang, Lan; Sun, Jingya; Cao, Qiang; Wang, Qingsong; Han, Weina; Lu, Yongfeng

    2018-04-01

    This study demonstrated that femtosecond-laser-induced ripples on an alumina-doped zinc oxide (AZO) film with space intervals of approximately 340 and 660 nm exhibit modulations of anisotropic optical transmission. At low laser fluence, ripples can not affect the original absorption peak of AZO film, but at higher laser fluence, the absorption peak of AZO film is disappeared due to the modulation by femtosecond laser induced ripples. Moreover, the relationship between the anisotropic optical transmission and the features of nanostructures is discussed. Ripples with a space interval of approximately 660 nm have a higher ability to block light than nanostructures with a space interval of approximately 340 nm. These observations indicate that anisotropic optical transmission has potential applications in the field of optoelectronics.

  2. Observations of plan-view sand ripple behavior and spectral wave climate on the inner shelf of San Pedro Bay, California

    Xu, J. P.

    2005-01-01

    Concurrent video images of sand ripples and current meter measurements of directional wave spectra are analyzed to study the relations between waves and wave-generated sand ripples. The data were collected on the inner shelf off Huntington Beach, California, at 15 m water depth, where the sea floor is comprised of well-sorted very fine sands (D50=92 ??m), during the winter of 2002. The wave climate, which was controlled by southerly swells (12-18 s period) and westerly wind waves (5-10 s period), included three wave types: (A) uni-modal, swells only; (B) bi-modal, swells dominant; and (C) bi-modal, wind-wave dominant. Each wave type has distinct relations with the plan-view shapes of ripples that are classified into five types: (1) sharp-crested, two-dimensional (2-D) ripples; (2) sharp-crested, brick-pattern, 3-D ripples; (3) bifurcated, 3-D ripples; (4) round-crested, shallow, 3-D ripples; and (5) flat bed. The ripple spacing is very small and varies between 4.5 and 7.5 cm. These ripples are anorbital as ripples in many field studies. Ripple orientation is only correlated with wave directions during strong storms (wave type C). In a poly-modal, multi-directional spectral wave environment, the use of the peak parameters (frequency, direction), a common practice when spectral wave measurements are unavailable, may lead to significant errors in boundary layer and sediment transport calculations. ?? 2004 Elsevier Ltd. All rights reserved.

  3. Current-ripple effect on superconductive dc critical current measurements

    Goodrich, L.F.; Bray, S.L.; Clark, A.F.

    1988-01-01

    The effect of sample-current power-supply ripple on dc critical current measurement in multifilamentary NbTi superconductors was evaluated. In general the ripple in a current supply became more significant above 500 A because effective filtering was hard to achieve. Ripple also caused noise at the input of the voltmeter used for the measurements. The quantitative effect of current ripple was studied using a battery current supply modified to allow the creation of ripple current with variable frequency and amplitude. Problems common to all large-conductor critical current measurements are discussed

  4. Space-frequency analysis and reduction of potential field ambiguity

    A. Rapolla

    1997-06-01

    Full Text Available Ambiguity of depth estimation of magnetic sources via spectral analysis can be reduced representing its field via a set of space-frequency atoms. This is obtained throughout a continuous wavelet transform using a Morlet analyzing wavelet. In the phase-plane representation even a weak contribution related to deep-seated sources is clearly distinguished with respect a more intense effect of a shallow source, also in the presence of a strong noise. Furthermore, a new concept of local power spectrum allows the depth to both the sources to be correctly interpreted. Neither result can be provided by standard Fourier analysis. Another method is proposed to reduce ambiguity by inversion of potential field data lying along the vertical axis. This method allows a depth resolution to gravity or the magnetic methods and below some conditions helps to reduce their inherent ambiguity. Unlike the case of monopoles, inversion of a vertical profile of gravity data above a cubic source gives correct results for the cube side and density.

  5. Spatial variability of the wave bottom boundary layer over movable rippled beds

    Rodriguez-Abudo, S.; Foster, D.L.; Henriquez, M.

    2013-01-01

    Observations of the spatially dependent velocity field over movable bed forms subjected to slightly skewed and asymmetric regular wave forcing were collected. The dynamics between the ripple elements is dominated by coherent vortices, characterized by the swirling strength, and evidenced in the

  6. Permanent magnet working point ripple in synchronous generators

    Stefan Sjökvist

    2017-04-01

    Full Text Available Permanent magnets (PMs are today widely used in electrical machines of all sorts. With their increase in popularity, the amount of research has increased as well. In this study, the magnetic flux density ripple of the working point of the PMs in a 100 kW PM synchronous generator has been investigated for three different load cases: no load, AC load, and DC load. The PMs will be subjected to a shift in working point as a consequence of the characteristics of the electrical loading. This study is based on finite element method simulations where the ripple of the magnetic flux density in the PMs was recorded at three positions within a PM. The slot harmonic of 7.5 times the electrical frequency (f(el was present in the results for all load cases, but mainly at the surface of the PM, as expected. Results showed an unexpected harmonic of 1.5 f(el, assumed to be an undertone of the slot harmonics. The 6f(el harmonic for the DC load case was significantly higher than for the AC load case and is caused by the current fluctuation during passive rectification. For the studied machine, the added harmonics in the magnetic field due to passive rectification are less than the slot-related harmonics.

  7. Spectral Ripple Discrimination in Normal Hearing Infants

    Horn, David L.; Won, Jong Ho; Rubinstein, Jay T.; Werner, Lynne A.

    2016-01-01

    Objectives Spectral resolution is a correlate of open-set speech understanding in post-lingually deaf adults as well as pre-lingually deaf children who use cochlear implants (CIs). In order to apply measures of spectral resolution to assess device efficacy in younger CI users, it is necessary to understand how spectral resolution develops in NH children. In this study, spectral ripple discrimination (SRD) was used to measure listeners’ sensitivity to a shift in phase of the spectral envelope of a broadband noise. Both resolution of peak to peak location (frequency resolution) and peak to trough intensity (across-channel intensity resolution) are required for SRD. Design SRD was measured as the highest ripple density (in ripples per octave) for which a listener could discriminate a 90 degree shift in phase of the sinusoidally-modulated amplitude spectrum. A 2X3 between subjects design was used to assess the effects of age (7-month-old infants versus adults) and ripple peak/trough “depth” (10, 13, and 20 dB) on SRD in normal hearing listeners (Experiment 1). In Experiment 2, SRD thresholds in the same age groups were compared using a task in which ripple starting phases were randomized across trials to obscure within-channel intensity cues. In Experiment 3, the randomized starting phase method was used to measure SRD as a function of age (3-month-old infants, 7-month-old infants, and young adults) and ripple depth (10 and 20 dB in repeated measures design). Results In Experiment 1, there was a significant interaction between age and ripple depth. The Infant SRDs were significantly poorer than the adult SRDs at 10 and 13 dB ripple depths but adult-like at 20 dB depth. This result is consistent with immature across-channel intensity resolution. In contrast, the trajectory of SRD as a function of depth was steeper for infants than adults suggesting that frequency resolution was better in infants than adults. However, in Experiment 2 infant performance was

  8. Rippled plasma wall accelerating structures

    Cavenago, M.

    1992-01-01

    A concept to form a hot, pulsed, inhomogeneous plasma and to use it as a linac structure is presented. The plasma spatial distribution is controlled by an external magnetic field and by the location of thermionic emitters; microwave ECR heating at frequency ω 1 favours plasma build up and reduces plasma resistivity. A shorter microwave pulse with frequency ω 2 ≠ ω 1 excites a longitudinal mode. An expression for the maximum attainable accelerating field is found. A linearized theory of accelerating modes is given. (Author) 6 refs., 3 figs

  9. Comparing the force ripple during asynchronous and conventional stimulation.

    Downey, Ryan J; Tate, Mark; Kawai, Hiroyuki; Dixon, Warren E

    2014-10-01

    Asynchronous stimulation has been shown to reduce fatigue during electrical stimulation; however, it may also exhibit a force ripple. We quantified the ripple during asynchronous and conventional single-channel transcutaneous stimulation across a range of stimulation frequencies. The ripple was measured during 5 asynchronous stimulation protocols, 2 conventional stimulation protocols, and 3 volitional contractions in 12 healthy individuals. Conventional 40 Hz and asynchronous 16 Hz stimulation were found to induce contractions that were as smooth as volitional contractions. Asynchronous 8, 10, and 12 Hz stimulation induced contractions with significant ripple. Lower stimulation frequencies can reduce fatigue; however, they may also lead to increased ripple. Future efforts should study the relationship between force ripple and the smoothness of the evoked movements in addition to the relationship between stimulation frequency and NMES-induced fatigue to elucidate an optimal stimulation frequency for asynchronous stimulation. © 2014 Wiley Periodicals, Inc.

  10. Supersymmetry for gauged double field theory and generalised Scherk–Schwarz reductions

    Berman, David S.; Lee, Kanghoon

    2014-01-01

    Previous constructions of supersymmetry for double field theory have relied on the so-called strong constraint. In this paper, the strong constraint is relaxed and the theory is shown to possess supersymmetry once the generalised Scherk–Schwarz reduction is imposed. The equivalence between the generalised Scherk–Schwarz reduced theory and the gauged double field theory is then examined in detail for the supersymmetric theory. As a biproduct we write the generalised Killing spinor equations for the supersymmetric double field theory

  11. On the limits of uniaxial magnetic anisotropy tuning by a ripple surface pattern

    Arranz, Miguel A. [Facultad de Ciencias Químicas, Universidad de Castilla-La Mancha, Avda. Camilo J. Cela 10, 13071 Ciudad Real (Spain); Colino, Jose M., E-mail: josemiguel.colino@uclm.es [Instituto de Nanociencia, Nanotecnología y Materiales Moleculares, Universidad de Castilla-La Mancha, Campus de la Fábrica de Armas, 45071 Toledo (Spain); Palomares, Francisco J. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, c/ Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain)

    2014-05-14

    Ion beam patterning of a nanoscale ripple surface has emerged as a versatile method of imprinting uniaxial magnetic anisotropy (UMA) on a desired in-plane direction in magnetic films. In the case of ripple patterned thick films, dipolar interactions around the top and/or bottom interfaces are generally assumed to drive this effect following Schlömann's calculations for demagnetizing fields of an ideally sinusoidal surface [E. Schlömann, J. Appl. Phys. 41, 1617 (1970)]. We have explored the validity of his predictions and the limits of ion beam sputtering to induce UMA in a ferromagnetic system where other relevant sources of magnetic anisotropy are neglected: ripple films not displaying any evidence of volume uniaxial anisotropy and where magnetocrystalline contributions average out in a fine grain polycrystal structure. To this purpose, the surface of 100 nm cobalt films grown on flat substrates has been irradiated at fixed ion energy, fixed ion fluency but different ion densities to make the ripple pattern at the top surface with wavelength Λ and selected, large amplitudes (ω) up to 20 nm so that stray dipolar fields are enhanced, while the residual film thickness t = 35–50 nm is sufficiently large to preserve the continuous morphology in most cases. The film-substrate interface has been studied with X-ray photoemission spectroscopy depth profiles and is found that there is a graded silicon-rich cobalt silicide, presumably formed during the film growth. This graded interface is of uncertain small thickness but the range of compositions clearly makes it a magnetically dead layer. On the other hand, the ripple surface rules both the magnetic coercivity and the uniaxial anisotropy as these are found to correlate with the pattern dimensions. Remarkably, the saturation fields in the hard axis of uniaxial continuous films are measured up to values as high as 0.80 kG and obey a linear dependence on the parameter ω{sup 2}/Λ/t in quantitative

  12. The development of a modified spectral ripple test.

    Aronoff, Justin M; Landsberger, David M

    2013-08-01

    Poor spectral resolution can be a limiting factor for hearing impaired listeners, particularly for complex listening tasks such as speech understanding in noise. Spectral ripple tests are commonly used to measure spectral resolution, but these tests contain a number of potential confounds that can make interpretation of the results difficult. To measure spectral resolution while avoiding those confounds, a modified spectral ripple test with dynamically changing ripples was created, referred to as the spectral-temporally modulated ripple test (SMRT). This paper describes the SMRT and provides evidence that it is sensitive to changes in spectral resolution.

  13. Disrupting neural activity related to awake-state sharp wave-ripple complexes prevents hippocampal learning.

    Nokia, Miriam S; Mikkonen, Jarno E; Penttonen, Markku; Wikgren, Jan

    2012-01-01

    Oscillations in hippocampal local-field potentials (LFPs) reflect the crucial involvement of the hippocampus in memory trace formation: theta (4-8 Hz) oscillations and ripples (~200 Hz) occurring during sharp waves are thought to mediate encoding and consolidation, respectively. During sharp wave-ripple complexes (SPW-Rs), hippocampal cell firing closely follows the pattern that took place during the initial experience, most likely reflecting replay of that event. Disrupting hippocampal ripples using electrical stimulation either during training in awake animals or during sleep after training retards spatial learning. Here, adult rabbits were trained in trace eyeblink conditioning, a hippocampus-dependent associative learning task. A bright light was presented to the animals during the inter-trial interval (ITI), when awake, either during SPW-Rs or irrespective of their neural state. Learning was particularly poor when the light was presented following SPW-Rs. While the light did not disrupt the ripple itself, it elicited a theta-band oscillation, a state that does not usually coincide with SPW-Rs. Thus, it seems that consolidation depends on neuronal activity within and beyond the hippocampus taking place immediately after, but by no means limited to, hippocampal SPW-Rs.

  14. Relationship between channel interaction and spectral-ripple discrimination in cochlear implant users.

    Jones, Gary L; Won, Jong Ho; Drennan, Ward R; Rubinstein, Jay T

    2013-01-01

    Cochlear implant (CI) users can achieve remarkable speech understanding, but there is great variability in outcomes that is only partially accounted for by age, residual hearing, and duration of deafness. Results might be improved with the use of psychophysical tests to predict which sound processing strategies offer the best potential outcomes. In particular, the spectral-ripple discrimination test offers a time-efficient, nonlinguistic measure that is correlated with perception of both speech and music by CI users. Features that make this "one-point" test time-efficient, and thus potentially clinically useful, are also connected to controversy within the CI field about what the test measures. The current work examined the relationship between thresholds in the one-point spectral-ripple test, in which stimuli are presented acoustically, and interaction indices measured under the controlled conditions afforded by direct stimulation with a research processor. Results of these studies include the following: (1) within individual subjects there were large variations in the interaction index along the electrode array, (2) interaction indices generally decreased with increasing electrode separation, and (3) spectral-ripple discrimination improved with decreasing mean interaction index at electrode separations of one, three, and five electrodes. These results indicate that spectral-ripple discrimination thresholds can provide a useful metric of the spectral resolution of CI users.

  15. Lamina-specific contribution of glutamatergic and GABAergic potentials to hippocampal sharp wave-ripple complexes.

    Schönberger, Jan; Draguhn, Andreas; Both, Martin

    2014-01-01

    The mammalian hippocampus expresses highly organized patterns of neuronal activity which form a neuronal correlate of spatial memories. These memory-encoding neuronal ensembles form on top of different network oscillations which entrain neurons in a state- and experience-dependent manner. The mechanisms underlying activation, timing and selection of participating neurons are incompletely understood. Here we studied the synaptic mechanisms underlying one prominent network pattern called sharp wave-ripple complexes (SPW-R) which are involved in memory consolidation during sleep. We recorded SPW-R with extracellular electrodes along the different layers of area CA1 in mouse hippocampal slices. Contribution of glutamatergic excitation and GABAergic inhibition, respectively, was probed by local application of receptor antagonists into s. radiatum, pyramidale and oriens. Laminar profiles of field potentials show that GABAergic potentials contribute substantially to sharp waves and superimposed ripple oscillations in s. pyramidale. Inhibitory inputs to s. pyramidale and s. oriens are crucial for action potential timing by ripple oscillations, as revealed by multiunit-recordings in the pyramidal cell layer. Glutamatergic afferents, on the other hand, contribute to sharp waves in s. radiatum where they also evoke a fast oscillation at ~200 Hz. Surprisingly, field ripples in s. radiatum are slightly slower than ripples in s. pyramidale, resulting in a systematic shift between dendritic and somatic oscillations. This complex interplay between dendritic excitation and perisomatic inhibition may be responsible for the precise timing of discharge probability during the time course of SPW-R. Together, our data illustrate a complementary role of spatially confined excitatory and inhibitory transmission during highly ordered network patterns in the hippocampus.

  16. Ripple-Triggered Stimulation of the Locus Coeruleus during Post-Learning Sleep Disrupts Ripple/Spindle Coupling and Impairs Memory Consolidation

    Novitskaya, Yulia; Sara, Susan J.; Logothetis, Nikos K.; Eschenko, Oxana

    2016-01-01

    Experience-induced replay of neuronal ensembles occurs during hippocampal high-frequency oscillations, or ripples. Post-learning increase in ripple rate is predictive of memory recall, while ripple disruption impairs learning. Ripples may thus present a fundamental component of a neurophysiological mechanism of memory consolidation. In addition to…

  17. Effect of double-shell structure on reduction of field errors in the STP-3(M) reversed-field pinch

    Yamada, S.; Masamune, S.; Nagata, A.; Arimoto, H.; Oshiyama, H.; Sato, K.I.

    1988-08-01

    Reversed-field pinch (RFP) operation on STP-3 (M) proved that the adition of a quasistational vertical field B sub(perpendicular) together with large reduction of irregular magnetic field at the shell gap could remarkably improve properties of the plasma confinement. Here, the gaps of a thick shell is wholely covered with the single primary coil having a shell shape. The measured field error at the gap is as small as 7.5 % of the poloidal field. The application of B sub(perpendicular) sets the plasma at a more perfect equilibrium. In this operation, the plasma resistivety much decreased by a factor 2 and the electron temperature rose up to 0.8 keV. (author)

  18. Smooth horizons and quantum ripples

    Golovnev, Alexey

    2015-01-01

    Black holes are unique objects which allow for meaningful theoretical studies of strong gravity and even quantum gravity effects. An infalling and a distant observer would have very different views on the structure of the world. However, a careful analysis has shown that it entails no genuine contradictions for physics, and the paradigm of observer complementarity has been coined. Recently this picture was put into doubt. In particular, it was argued that in old black holes a firewall must form in order to protect the basic principles of quantum mechanics. This AMPS paradox has already been discussed in a vast number of papers with different attitudes and conclusions. Here we want to argue that a possible source of confusion is the neglect of quantum gravity effects. Contrary to widespread perception, it does not necessarily mean that effective field theory is inapplicable in rather smooth neighbourhoods of large black hole horizons. The real offender might be an attempt to consistently use it over the huge distances from the near-horizon zone of old black holes to the early radiation. We give simple estimates to support this viewpoint and show how the Page time and (somewhat more speculative) scrambling time do appear. (orig.)

  19. Smooth horizons and quantum ripples

    Golovnev, Alexey [Saint Petersburg State University, High Energy Physics Department, Saint-Petersburg (Russian Federation)

    2015-05-15

    Black holes are unique objects which allow for meaningful theoretical studies of strong gravity and even quantum gravity effects. An infalling and a distant observer would have very different views on the structure of the world. However, a careful analysis has shown that it entails no genuine contradictions for physics, and the paradigm of observer complementarity has been coined. Recently this picture was put into doubt. In particular, it was argued that in old black holes a firewall must form in order to protect the basic principles of quantum mechanics. This AMPS paradox has already been discussed in a vast number of papers with different attitudes and conclusions. Here we want to argue that a possible source of confusion is the neglect of quantum gravity effects. Contrary to widespread perception, it does not necessarily mean that effective field theory is inapplicable in rather smooth neighbourhoods of large black hole horizons. The real offender might be an attempt to consistently use it over the huge distances from the near-horizon zone of old black holes to the early radiation. We give simple estimates to support this viewpoint and show how the Page time and (somewhat more speculative) scrambling time do appear. (orig.)

  20. Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

    Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal, E-mail: zainabh@petronas.com.my [Centre of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

    2014-03-24

    Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

  1. Effects of spectral smearing on performance of the spectral ripple and spectro-temporal ripple tests.

    Narne, Vijaya Kumar; Sharma, Mridula; Van Dun, Bram; Bansal, Shalini; Prabhu, Latika; Moore, Brian C J

    2016-12-01

    The main aim of this study was to use spectral smearing to evaluate the efficacy of a spectral ripple test (SRt) using stationary sounds and a recent variant with gliding ripples called the spectro-temporal ripple test (STRt) in measuring reduced spectral resolution. In experiment 1 the highest detectable ripple density was measured using four amounts of spectral smearing (unsmeared, mild, moderate, and severe). The thresholds worsened with increasing smearing and were similar for the SRt and the STRt across the three conditions with smearing. For unsmeared stimuli, thresholds were significantly higher (better) for the STRt than for the SRt. An amplitude fluctuation at the outputs of simulated (gammatone) auditory filters centered above 6400 Hz was identified as providing a potential detection cue for the STRt stimuli. Experiment 2 used notched noise with energy below and above the passband of the SRt and STRt stimuli to reduce confounding cues in the STRt. Thresholds were almost identical for the STRt and SRt for both unsmeared and smeared stimuli, indicating that the confounding cue for the STRt was eliminated by the notched noise. Thresholds obtained with notched noise present could be predicted reasonably accurately using an excitation-pattern model.

  2. A Prospective Study of Ripple Mapping the Post-Infarct Ventricular Scar to Guide Substrate Ablation for Ventricular Tachycardia.

    Luther, Vishal; Linton, Nick W F; Jamil-Copley, Shahnaz; Koa-Wing, Michael; Lim, Phang Boon; Qureshi, Norman; Ng, Fu Siong; Hayat, Sajad; Whinnett, Zachary; Davies, D Wyn; Peters, Nicholas S; Kanagaratnam, Prapa

    2016-06-01

    Post-infarct ventricular tachycardia is associated with channels of surviving myocardium within scar characterized by fractionated and low-amplitude signals usually occurring late during sinus rhythm. Conventional automated algorithms for 3-dimensional electro-anatomic mapping cannot differentiate the delayed local signal of conduction within the scar from the initial far-field signal generated by surrounding healthy tissue. Ripple mapping displays every deflection of an electrogram, thereby providing fully informative activation sequences. We prospectively used CARTO-based ripple maps to identify conducting channels as a target for ablation. High-density bipolar left ventricular endocardial electrograms were collected using CARTO3v4 in sinus rhythm or ventricular pacing and reviewed for ripple mapping conducting channel identification. Fifteen consecutive patients (median age 68 years, left ventricular ejection fraction 30%) were studied (6 month preprocedural implantable cardioverter defibrillator therapies: median 19 ATP events [Q1-Q3=4-93] and 1 shock [Q1-Q3=0-3]). Scar (ripple mapping conducting channels were seen within each scar (length 60 mm; initial component 0.44 mV; delayed component 0.20 mV; conduction 55 cm/s). Ablation was performed along all identified ripple mapping conducting channels (median 18 lesions) and any presumed interconnected late-activating sites (median 6 lesions; Q1-Q3=2-12). The diastolic isthmus in ventricular tachycardia was mapped in 3 patients and colocated within the ripple mapping conducting channels identified. Ventricular tachycardia was noninducible in 85% of patients post ablation, and 71% remain free of ventricular tachycardia recurrence at 6-month median follow-up. Ripple mapping can be used to identify conduction channels within scar to guide functional substrate ablation. © 2016 American Heart Association, Inc.

  3. Analysis and Speed Ripple Mitigation of a Space Vector Pulse Width Modulation-Based Permanent Magnet Synchronous Motor with a Particle Swarm Optimization Algorithm

    Xing Liu

    2016-11-01

    Full Text Available A method is proposed for reducing speed ripple of permanent magnet synchronous motors (PMSMs controlled by space vector pulse width modulation (SVPWM. A flux graph and mathematics are used to analyze the speed ripple characteristics of the PMSM. Analysis indicates that the 6P (P refers to pole pairs of the PMSM time harmonic of rotor mechanical speed is the main harmonic component in the SVPWM control PMSM system. To reduce PMSM speed ripple, harmonics are superposed on a SVPWM reference signal. A particle swarm optimization (PSO algorithm is proposed to determine the optimal phase and multiplier coefficient of the superposed harmonics. The results of a Fourier decomposition and an optimized simulation model verified the accuracy of the analysis as well as the effectiveness of the speed ripple reduction methods, respectively.

  4. Restoration of dimensional reduction in the random-field Ising model at five dimensions

    Fytas, Nikolaos G.; Martín-Mayor, Víctor; Picco, Marco; Sourlas, Nicolas

    2017-04-01

    The random-field Ising model is one of the few disordered systems where the perturbative renormalization group can be carried out to all orders of perturbation theory. This analysis predicts dimensional reduction, i.e., that the critical properties of the random-field Ising model in D dimensions are identical to those of the pure Ising ferromagnet in D -2 dimensions. It is well known that dimensional reduction is not true in three dimensions, thus invalidating the perturbative renormalization group prediction. Here, we report high-precision numerical simulations of the 5D random-field Ising model at zero temperature. We illustrate universality by comparing different probability distributions for the random fields. We compute all the relevant critical exponents (including the critical slowing down exponent for the ground-state finding algorithm), as well as several other renormalization-group invariants. The estimated values of the critical exponents of the 5D random-field Ising model are statistically compatible to those of the pure 3D Ising ferromagnet. These results support the restoration of dimensional reduction at D =5 . We thus conclude that the failure of the perturbative renormalization group is a low-dimensional phenomenon. We close our contribution by comparing universal quantities for the random-field problem at dimensions 3 ≤D equality at all studied dimensions.

  5. Structure of the ripple phase of phospholipid multibilayers

    Sengupta, Kheya; Raghunathan, V.A.; Katsaras, John

    2003-01-01

    We present electron density maps (EDMs) of the ripple phase formed by phosphorylcholine lipids such as dimyristoyl phosphatidylcholine (DMPC), palmitoyl-oleoyl phosphatidylcholine (POPC), dihexadecyl phosphatidylcholine, and dilauroyl phosphatidylcholine (DLPC). With the exception of DLPC, the rippled bilayers have a sawtooth shape in all the systems, with one arm being almost twice as long as the other. For DMPC and POPC bilayers, EDMs have been obtained at different temperatures at a fixed relative humidity, and the overall shape of the ripples and the ratio of the lengths of the two arms are found to be insensitive to temperature. EDMs of all the systems with saturated hydrocarbon chains suggest the existence of a mean chain tilt along the ripple wave vector. In the literature it is generally assumed that the asymmetry of the rippled bilayers (absence of a mirror plane normal to the ripple wave vector) arises from a sawtoothlike height profile. However, in the case of DLPC, the height profile is found to be almost symmetric and the asymmetry results mainly from different bilayer thicknesses in the two arms of the ripple. We also present EDMs of the metastable ripple phase of dipalmitoyl phosphatidylcholine, formed on cooling from the L α phase

  6. Vibrational resonances of nonrigid vehicles: Polygonization and ripple patterns

    Dekker, H.

    2009-01-01

    The well-known phenomenon of ripples on roads has its modern counterpart in ripple patterns on railroads and polygonization of wheels on state-of-the-art lightrail streetcars. Here we study an idealized mechanical suspension model for the vibrational frequency response of a buggy with a nonrigid

  7. Automatic Detection of Sand Ripple Features in Sidescan Sonar Imagery

    2014-07-09

    Among the features used in forensic scientific fingerprint analysis are terminations or bifurcations of print ridges. Sidescan sonar imagery of ripple...always be pathological cases. The size of the blocks of pixels used in determining the ripple wavelength is evident in the output images on the right in

  8. DFR Perturbative Quantum Field Theory on Quantum Space Time, and Wick Reduction

    Piacitelli, Gherardo

    We discuss the perturbative approach à la Dyson to a quantum field theory with nonlocal self-interaction :φ⋆···⋆φ, according to Doplicher, Fredenhagen and Roberts (DFR). In particular, we show that the Wick reduction of nonlocally time-ordered products of Wick monomials can be performed as usual, and we discuss a very simple Dyson diagram.

  9. Large wind ripples on Mars: A record of atmospheric evolution

    Lapotre, M. G. A.; Ewing, R. C.; Lamb, M. P.; Fischer, W. W.; Grotzinger, J. P.; Rubin, D. M.; Lewis, K. W.; Ballard, M. J.; Day, M.; Gupta, S.; Banham, S. G.; Bridges, N. T.; Des Marais, D. J.; Fraeman, A. A.; Grant, J. A.; Herkenhoff, K. E.; Ming, D. W.; Mischna, M. A.; Rice, M. S.; Sumner, D. A.; Vasavada, A. R.; Yingst, R. A.

    2016-07-01

    Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter- to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them unlike terrestrial wind ripples. Rather, these structures resemble fluid-drag ripples, which on Earth include water-worked current ripples, but on Mars instead form by wind because of the higher kinematic viscosity of the low-density atmosphere. A reevaluation of the wind-deposited strata in the Burns formation (about 3.7 billion years old or younger) identifies potential wind-drag ripple stratification formed under a thin atmosphere.

  10. Large wind ripples on Mars: A record of atmospheric evolution

    Lapotre, M G; Ewing, R C; Lamb, M P; Fischer, W W; Grotzinger, J P; Rubin, D M; Lewis, K W; Ballard, M; Day, Mitch D.; Gupta, S.; Banham, S G; Bridges, N T; Des Marais, D J; Fraeman, A A; Grant, J A; Herkenhoff, Kenneth E.; Ming, D W; Mischna, M A; Rice, M S; Sumner, D A; Vasavada, A R; Yingst, R A

    2016-01-01

    Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter– to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them unlike terrestrial wind ripples. Rather, these structures resemble fluid-drag ripples, which on Earth include water-worked current ripples, but on Mars instead form by wind because of the higher kinematic viscosity of the low-density atmosphere. A reevaluation of the wind-deposited strata in the Burns formation (about 3.7 billion years old or younger) identifies potential wind-drag ripple stratification formed under a thin atmosphere.

  11. Pyramidal cell-interneuron interactions underlie hippocampal ripple oscillations.

    Stark, Eran; Roux, Lisa; Eichler, Ronny; Senzai, Yuta; Royer, Sebastien; Buzsáki, György

    2014-07-16

    High-frequency ripple oscillations, observed most prominently in the hippocampal CA1 pyramidal layer, are associated with memory consolidation. The cellular and network mechanisms underlying the generation, frequency control, and spatial coherence of the rhythm are poorly understood. Using multisite optogenetic manipulations in freely behaving rodents, we found that depolarization of a small group of nearby pyramidal cells was sufficient to induce high-frequency oscillations, whereas closed-loop silencing of pyramidal cells or activation of parvalbumin- (PV) or somatostatin-immunoreactive interneurons aborted spontaneously occurring ripples. Focal pharmacological blockade of GABAA receptors abolished ripples. Localized PV interneuron activation paced ensemble spiking, and simultaneous induction of high-frequency oscillations at multiple locations resulted in a temporally coherent pattern mediated by phase-locked interneuron spiking. These results constrain competing models of ripple generation and indicate that temporally precise local interactions between excitatory and inhibitory neurons support ripple generation in the intact hippocampus. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Ripple/Carcinoid pattern sebaceoma with apocrine differentiation.

    Misago, Noriyuki; Narisawa, Yutaka

    2011-02-01

    Sebaceoma is a benign sebaceous neoplasm, which has been reported to show characteristic growth patterns, such as, ripple, labyrinthine/sinusoidal, and carcinoid-like patterns. Another recent finding regarding in sebaceoma is the observation of apocrine differentiation within the sebaceoma lesion. This report describes a case of carcinoid (a partial ripple and labyrinthine) pattern sebaceoma with apocrine differentiation with a literature review and immunohistochemical studies. The various characteristic growth patterns in sebaceoma were suggested to simply be variations of the same growth pattern arranged in cords, namely, a unified term "ripple/carcinoid pattern." The primitive sebaceous germinative cells in sebaceoma may still have the ability to undergo apocrine differentiation. Most of the reports so far on sebaceoma with apocrine differentiation, including the present case, describe a ripple/carcinoid pattern, thus suggesting that ripple/carcinoid pattern sebaceoma is composed of more primitive sebaceous germinative cells than conventional sebaceoma.

  13. Highly sensitive detection of a current ripple

    Aoki, Takashi; Gushiken, Tutomu; Nishikigouri, Kazutaka; Kumada, Masayuki.

    1996-01-01

    In the HIMAC, there are six thyristor-controlled power sources for driving two synchrotrons. These power sources are the three-output terminal power sources which are equipped with positive output, negative output and neutral point for the common mode countermeasures. As electromagnet circuits are connected to the three-output terminal power sources, those are three-line type. In the inside of the power source circuits controlled by thyristors, there is the oscillation peculiar to the power sources, and the variation of voltage induces current spikes. This time, in order to assess the results of the common mode countermeasures in the power source and electromagnet circuits, as one method of cross-check, it is considered that since electromagnet current flows being divided to the bridging resistance and the coil, if attention is paid to the current on bridging resistance side, the ripple components of common mode and normal mode can be detected with high sensitivity, and this was verified. The present state of heightening the performance of synchrotron power sources is explained. The cross-check of the method of assessing the performance of electromagnet power sources is reported. The method of measuring ripple current and the results of the measurement are reported. (K.I.)

  14. Quantum and classical ripples in graphene

    Hašík, Juraj; Tosatti, Erio; MartoÅák, Roman

    2018-04-01

    Thermal ripples of graphene are well understood at room temperature, but their quantum counterparts at low temperatures are in need of a realistic quantitative description. Here we present atomistic path-integral Monte Carlo simulations of freestanding graphene, which show upon cooling a striking classical-quantum evolution of height and angular fluctuations. The crossover takes place at ever-decreasing temperatures for ever-increasing wavelengths so that a completely quantum regime is never attained. Zero-temperature quantum graphene is flatter and smoother than classical graphene at large scales yet rougher at short scales. The angular fluctuation distribution of the normals can be quantitatively described by coexistence of two Gaussians, one classical strongly T -dependent and one quantum about 2° wide, of zero-point character. The quantum evolution of ripple-induced height and angular spread should be observable in electron diffraction in graphene and other two-dimensional materials, such as MoS2, bilayer graphene, boron nitride, etc.

  15. Defining Constellation Suit Helmet Field of View Requirements Employing a Mission Segment Based Reduction Process

    McFarland, Shane

    2009-01-01

    Field of view has always been a design feature paramount to helmets, and in particular space suits, where the helmet must provide an adequate field of view for a large range of activities, environments, and body positions. For Project Constellation, a different approach to helmet requirement maturation was utilized; one that was less a direct function of body position and suit pressure and more a function of the mission segment in which the field of view will be required. Through taxonimization of various parameters that affect suited field of view, as well as consideration for possible nominal and contingency operations during that mission segment, a reduction process was employed to condense the large number of possible outcomes to only six unique field of view angle requirements that still captured all necessary variables while sacrificing minimal fidelity.

  16. Are phantoms useful for predicting the potential of dose reduction in full-field digital mammography?

    Gennaro, Gisella; Katz, Luc; Souchay, Henri; Alberelli, Claudio; Maggio, Cosimo di

    2005-01-01

    A phantom study was performed in full-field digital mammography to investigate the opportunity and the magnitude of a possible dose reduction that would leave the image quality above the accepted thresholds associated with some classical phantoms. This preliminary work is intended to lay the groundwork for a future clinical study on the impact of dose reduction on clinical results. Three different mammography phantoms (ACR RMI 156, CIRS 11A and CDMAM 3.4) were imaged by a full-field digital mammography unit (GE Senographe 2000D) at different dose levels. Images were rated by three observers with softcopy reading and scoring methods specific to each phantom. Different types of data analysis were applied to the ACR (American College of Radiology) and the other two phantoms, respectively. With reference to the minimum acceptance score in screen/film accreditation programmes, the ACR phantom showed that about 45% dose reduction could be applied, while keeping the phantom scores above that threshold. A relative comparison was done for CIRS and CDMAM, for which no threshold is defined. CIRS scoring remained close to the reference level down to 40% dose reduction, the inter- and intra-observer variability being the main source of uncertainty. Contrast-detail curves provided by CDMAM overlapped down to 50% dose reduction, at least for object contrast values ranging between 30% and 3%. This multi-phantom study shows the potential of further reducing the dose in full-field digital mammography beyond the current values. A common dose reduction factor around 50% seems acceptable for all phantoms. However, caution is required before extrapolating the results for clinical use, given the limitations of these widely used phantoms, mainly related to their limited dynamic range and uniform background

  17. Real time implementation of viable torque and flux controllers and torque ripple minimization algorithm for induction motor drive

    Vasudevan, M.; Arumugam, R.; Paramasivam, S.

    2006-01-01

    Field oriented control (FOC) and direct torque control (DTC) are becoming the industrial standards for induction motors torque and flux control. This paper aims to give a contribution for a detailed comparison between these two control techniques, emphasizing their advantages and disadvantages. The performance of these two control schemes is evaluated in terms of torque and flux ripple and their transient response to step variations of the torque command. Moreover, a new torque and flux ripple minimization technique is also proposed to improve the performance of the DTC drive. Based on the experimental results, the analysis has been presented

  18. Ripples and ripples: from sandy deserts to ion-sputtered surfaces

    Aste, T; Valbusa, U

    2005-01-01

    We study the morphological evolution of surfaces during ion sputtering and we compare their dynamical corrugation with aeolian ripple formation in sandy deserts. We show that, although the two phenomena are physically different, they must obey similar geometrical constraints and therefore they can be described within the same theoretical framework. The present theory distinguishes between atoms that stay bounded in the bulk and others that are mobile on the surface. We describe the excavation mechanisms, the adsorption and the surface mobility by means of a continuous equation derived from the study of dune formation on sand. We explore the spontaneous development of ordered nanostructures and explain the different dynamical behaviours experimentally observed in metals or in semiconductors or in amorphous systems. We also show that this novel approach can describe the occurrence of rotation in the ripple direction and the formation of other kinds of self-organized patterns induced by changes in the sputtering incidence angle

  19. The molecular dynamics simulation of ion-induced ripple growth

    Suele, P.; Heinig, K.-H.

    2009-01-01

    The wavelength-dependence of ion-sputtering induced growth of repetitive nanostructures, such as ripples has been studied by molecular dynamics (MD) simulations in Si. The early stage of the ion erosion driven development of ripples has been simulated on prepatterned Si stripes with a wavy surface. The time evolution of the height function and amplitude of the sinusoidal surface profile has been followed by simulated ion-sputtering. According to Bradley-Harper (BH) theory, we expect correlation between the wavelength of ripples and the stability of them. However, we find that in the small ripple wavelength (λ) regime BH theory fails to reproduce the results obtained by molecular dynamics. We find that at short wavelengths (λ 35 nm is stabilized in accordance with the available experimental results. According to the simulations, few hundreds of ion impacts in λ long and few nanometers wide Si ripples are sufficient for reaching saturation in surface growth for for λ>35 nm ripples. In another words, ripples in the long wavelength limit seems to be stable against ion-sputtering. A qualitative comparison of our simulation results with recent experimental data on nanopatterning under irradiation is attempted.

  20. Facile characterization of ripple domains on exfoliated graphene.

    Choi, Jin Sik; Kim, Jin-Soo; Byun, Ik-Su; Lee, Duk Hyun; Hwang, In Rok; Park, Bae Ho; Choi, Taekjib; Park, Jeong Young; Salmeron, Miquel

    2012-07-01

    Ripples in graphene monolayers deposited on SiO(2)/Si wafer substrates were recently shown to give rise to friction anisotropy. High friction appears when the AFM tip slides in a direction perpendicular to the ripple crests and low friction when parallel. The direction of the ripple crest is, however, hard to determine as it is not visible in topographic images and requires elaborate measurements of friction as a function of angle. Here we report a simple method to characterize ripple crests by measuring the cantilever torsion signal while scanning in the non-conventional longitudinal direction (i.e., along the cantilever axis, as opposed to the usual friction measurement). The longitudinal torsion signal provides a much clearer ripple domain contrast than the conventional friction signal, while both signals show respective rotation angle dependences that can be explained using the torsion component of the normal reaction force exerted by the graphene ripples. We can also determine the ripple direction by comparing the contrast in torsion images obtained in longitudinal and lateral scans without sample rotation or complicated normalization.

  1. Strategy of restraining ripple error on surface for optical fabrication.

    Wang, Tan; Cheng, Haobo; Feng, Yunpeng; Tam, Honyuen

    2014-09-10

    The influence from the ripple error to the high imaging quality is effectively reduced by restraining the ripple height. A method based on the process parameters and the surface error distribution is designed to suppress the ripple height in this paper. The generating mechanism of the ripple error is analyzed by polishing theory with uniform removal character. The relation between the processing parameters (removal functions, pitch of path, and dwell time) and the ripple error is discussed through simulations. With these, the strategy for diminishing the error is presented. A final process is designed and demonstrated on K9 work-pieces using the optimizing strategy with magnetorheological jet polishing. The form error on the surface is decreased from 0.216λ PV (λ=632.8  nm) and 0.039λ RMS to 0.03λ PV and 0.004λ RMS. And the ripple error is restrained well at the same time, because the ripple height is less than 6 nm on the final surface. Results indicate that these strategies are suitable for high-precision optical manufacturing.

  2. Ripple characteristic of the main ring magnet power supply for the KEK 12 GeV PS

    Sato, Hikaru; Sueno, Tuyosi; Mikawa, Katsuhiko

    1995-01-01

    First of all, general description of the main ring magnet power supply for the KEK 12 GeV PS will be described. The main power supply consists of thyristor rectifiers, DC filters, reactive power compensators, AC harmonic filters and control systems. Devices and control systems for suppressing ripple component of magnet field will be described. (author)

  3. Thermal ripples in model molybdenum disulfide monolayers

    Remsing, Richard C.; Klein, Michael L. [Institute for Computational Molecular Science, Center for the Computational, Design of Functional Layered Materials, and Department of Chemistry, Temple University, 1925 N. 12th St., 19122, Philadelphia, PA (United States); Waghmare, Umesh V. [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, 560 064, Jakkur, Bangalore (India)

    2017-01-15

    Molybdenum disulfide (MoS{sub 2}) monolayers have the potential to revolutionize nanotechnology. To reach this potential, it will be necessary to understand the behavior of this two-dimensional (2D) material on large length scales and under thermal conditions. Herein, we use molecular dynamics (MD) simulations to investigate the nature of the rippling induced by thermal fluctuations in monolayers of the 2H and 1T phases of MoS{sub 2}. The 1T phase is found to be more rigid than the 2H phase. Both monolayer phases are predicted to follow long wavelength scaling behavior typical of systems with anharmonic coupling between vibrational modes as predicted by classic theories of membrane-like systems. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Martian Dune Ripples as Indicators of Recent Surface Wind Patterns

    Johnson, M.; Zimbelman, J. R.

    2015-12-01

    Sand dunes have been shown to preserve the most recent wind patterns in their ripple formations. This investigation continues the manual documentation of ripples on Martian dunes in order to assess surface wind flow. Study sites investigated must have clear HiRISE frames and be able to represent diverse locations across the surface, decided primarily by their spread of latitude and longitude values. Additionally, frames with stereo pairs are preferred because of their ability to create digital terrain models. This will assist in efforts to relate dune slopes and obstacles to ripple patterns. The search and analysis period resulted in 40 study sites with mapped ripples. Lines were drawn perpendicular to ripple crests across three adjacent ripples in order to document both ripple wavelength from line length and inferred wind direction from azimuth. It is not possible to infer a unique wind direction from ripple orientation alone and therefore these inferred directions have a 180 degree ambiguity. Initial results from all study sites support previous observations that the Martian surface has many dune types in areas with adequate sand supply. The complexity of ripple patterns varies greatly across sites as well as within individual sites. Some areas of uniform directionality for hundreds of kilometers suggest a unimodal wind regime while overlapping patterns suggest multiple dominant winds or seasonally varying winds. In most areas, form flow related to dune shape seems to have a large effect on orientation and must be considered along with the dune type. As long as the few steep slip faces on these small dunes are avoided, form flow can be considered the dominant cause of deviation from the regional wind direction. Regional results, wind roses, and comparisons to previous work will be presented for individual sites.

  5. Fluctuation reduction and enhanced confinement in the MST reversed-field pinch

    Chapman, B.E.

    1997-10-01

    Plasmas with a factor of ≥3 improvement in energy confinement have been achieved in the MST reversed-field pinch (RFP). These plasmas occur spontaneously, following sawtooth crashes, subject to constraints on, eg, toroidal magnetic field reversal and wall conditioning. Possible contributors to the improved confinement include a reduction of core-resonant, global magnetic fluctuations and a reduction of electrostatic fluctuations over the entire plasma edge. One feature of these plasmas is a region of strong ExB flow shear in the edge. Never before observed in conjunction with enhanced confinement in the RFP, such shear is common in enhanced confinement discharges in tokamaks and stellarators. Another feature of these plasmas is a new type of discrete dynamo event. Like sawtooth crashes, a common form of discrete dynamo, these events correspond to bursts of edge parallel current. The reduction of electrostatic fluctuations in these plasmas occurs within and beyond the region of strong ExB flow shear, similar to what is observed in tokamaks and stellarators. However, the reductions in the MST include fluctuations whose correlation lengths are larger than the width of the shear region. The reduction of the global magnetic fluctuations is most likely due to flattening of the μ=μ 0 rvec J· rvec B/B 2 profile. Flattening can occur, eg, due to the new type of discrete dynamo event and reduced edge resistivity. Enhanced confinement plasmas are also achieved in the MST when auxiliary current is applied to flatten the μ profile and reduce magnetic fluctuations. Unexpectedly, these plasmas also exhibit a region (broader than in the case above) of strong ExB flow shear in the edge, an edge-wide reduction of electrostatic fluctuations, and the new type of discrete dynamo event. Auxiliary current drive has historically been viewed as the principal route to fusion reactor viability for the RFP

  6. Enhanced electrocatalytic CO2 reduction via field-induced reagent concentration

    Liu, Min; Pang, Yuanjie; Zhang, Bo; de Luna, Phil; Voznyy, Oleksandr; Xu, Jixian; Zheng, Xueli; Dinh, Cao Thang; Fan, Fengjia; Cao, Changhong; de Arquer, F. Pelayo García; Safaei, Tina Saberi; Mepham, Adam; Klinkova, Anna; Kumacheva, Eugenia; Filleter, Tobin; Sinton, David; Kelley, Shana O.; Sargent, Edward H.

    2016-09-01

    Electrochemical reduction of carbon dioxide (CO2) to carbon monoxide (CO) is the first step in the synthesis of more complex carbon-based fuels and feedstocks using renewable electricity. Unfortunately, the reaction suffers from slow kinetics owing to the low local concentration of CO2 surrounding typical CO2 reduction reaction catalysts. Alkali metal cations are known to overcome this limitation through non-covalent interactions with adsorbed reagent species, but the effect is restricted by the solubility of relevant salts. Large applied electrode potentials can also enhance CO2 adsorption, but this comes at the cost of increased hydrogen (H2) evolution. Here we report that nanostructured electrodes produce, at low applied overpotentials, local high electric fields that concentrate electrolyte cations, which in turn leads to a high local concentration of CO2 close to the active CO2 reduction reaction surface. Simulations reveal tenfold higher electric fields associated with metallic nanometre-sized tips compared to quasi-planar electrode regions, and measurements using gold nanoneedles confirm a field-induced reagent concentration that enables the CO2 reduction reaction to proceed with a geometric current density for CO of 22 milliamperes per square centimetre at -0.35 volts (overpotential of 0.24 volts). This performance surpasses by an order of magnitude the performance of the best gold nanorods, nanoparticles and oxide-derived noble metal catalysts. Similarly designed palladium nanoneedle electrocatalysts produce formate with a Faradaic efficiency of more than 90 per cent and an unprecedented geometric current density for formate of 10 milliamperes per square centimetre at -0.2 volts, demonstrating the wider applicability of the field-induced reagent concentration concept.

  7. Raman scattering in a nearly resonant density ripple

    Barr, H.C.; Chen, F.F.

    1987-01-01

    Stimulated Raman scattering of light waves by an underdense plasma is affected by the presence of a density ripple caused by a simultaneously occurring stimulated Brillouin instability. The problem is treated kinetically for the particularly interesting case where the ripple has nearly the same wavelength as the plasma wave. The ripple is found to reduce the growth rate of the usual Raman instability but allows other decay modes to occur. Numerical results for the frequencies, growth rates, and k spectra of these modes are obtained. A physical explanation is given for a baffling result of the calculation. The physical picture is also of interest to particle acceleration by plasma waves

  8. Immune-mediated rippling muscle disease and myasthenia gravis.

    Bettini, Mariela; Gonorazky, Hernan; Chaves, Marcelo; Fulgenzi, Ernesto; Figueredo, Alejandra; Christiansen, Silvia; Cristiano, Edgardo; Bertini, Enrico S; Rugiero, Marcelo

    2016-10-15

    Cases of acquired rippling muscle disease in association with myasthenia gravis have been reported. We present three patients with iRMD (immune-mediated rippling muscle disease) and AChR-antibody positive myasthenia gravis. None of them had thymus pathology. They presented exercise-induced muscle rippling combined with generalized myasthenia gravis. One of them had muscle biopsy showing a myopathic pattern and a patchy immunostaining with caveolin antibodies. They were successfully treated steroids and azathioprine. The immune nature of this association is supported by the response to immunotherapies and the positivity of AChR-antibodies. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Analysis of Input and Output Ripples of PWM AC Choppers

    Pekik Argo Dahono

    2008-11-01

    Full Text Available This paper presents an analysis of input and output ripples of PWM AC choppers. Expressions of input and output current and voltage ripples of single-phase PWM AC choppers are first derived. The derived expressions are then extended to three-phase PWM AC choppers. As input current and output voltage ripples specification alone cannot be used to determine the unique values of inductance and capacitance of the LC filters, an additional criterion based on the minimum reactive power is proposed. Experimental results are included in this paper to show the validity of the proposed analysis method.

  10. Analisis Ripple Masukan Dan Keluaran PWM AC Chopper 3-Fasa Pada Beban Motor Induksi 3-Fasa

    Luthfi, Muhamad; Dachlan, Harry Soekotjo; Wijono, Wijono

    2013-01-01

    Penggunaan chopper dalam sistem kelistrikan akan menimbulkan ripple pada tegangan keluarannya. Kebanyakan ripple difahami terbangkit pada sisi output. Pada penelitian ini ripple pada sisi input juga dianalisis. Disamping ripple, penggunaan chopper akan membangkitkan harmonisa yang akan menimbulkan rugirugi. Untuk memperkecil rugi-rugi tersebut, pada sisi input maupun output perlu dipasang filter LC. Penentuan nilai komponen filter ini dipengaruhi oleh ripple yang timbul. Dengan mengetahui m...

  11. Climbing ripple structure and associated storm-lamination from a ...

    Pranhita–Godavari Valley, south India, displays well developed climbing ripple lamination and ... sedimentary environments, such as river flood .... Sediment, sequence and facies ..... tic Archaean Witwatersrand Supergroup, South Africa;.

  12. Oscillatory ripples, evaluation of ancient wave climates and ...

    Oscillatory ripples, evaluation of ancient wave climates and epierogeny in the Anambra ... conditions, epierogenic patterns and paleogeographic history of the basins. ... shallow and marked by low to moderate hydrodynamic energy conditions.

  13. Real time algorithms for sharp wave ripple detection.

    Sethi, Ankit; Kemere, Caleb

    2014-01-01

    Neural activity during sharp wave ripples (SWR), short bursts of co-ordinated oscillatory activity in the CA1 region of the rodent hippocampus, is implicated in a variety of memory functions from consolidation to recall. Detection of these events in an algorithmic framework, has thus far relied on simple thresholding techniques with heuristically derived parameters. This study is an investigation into testing and improving the current methods for detection of SWR events in neural recordings. We propose and profile methods to reduce latency in ripple detection. Proposed algorithms are tested on simulated ripple data. The findings show that simple realtime algorithms can improve upon existing power thresholding methods and can detect ripple activity with latencies in the range of 10-20 ms.

  14. Design and Analysis of LT Codes with Decreasing Ripple Size

    Sørensen, Jesper Hemming; Popovski, Petar; Østergaard, Jan

    2012-01-01

    In this paper we propose a new design of LT codes, which decreases the amount of necessary overhead in comparison to existing designs. The design focuses on a parameter of the LT decoding process called the ripple size. This parameter was also a key element in the design proposed in the original...... work by Luby. Specifically, Luby argued that an LT code should provide a constant ripple size during decoding. In this work we show that the ripple size should decrease during decoding, in order to reduce the necessary overhead. Initially we motivate this claim by analytical results related...... to the redundancy within an LT code. We then propose a new design procedure, which can provide any desired achievable decreasing ripple size. The new design procedure is evaluated and compared to the current state of the art through simulations. This reveals a significant increase in performance with respect...

  15. Correlation between the ripple phase and stripe domains in membranes.

    Bernchou, Uffe; Midtiby, Henrik; Ipsen, John Hjort; Simonsen, Adam Cohen

    2011-12-01

    We investigate the relationship between stripe domains and the ripple phase in membranes. These have previously been observed separately without being linked explicitly. Past results have demonstrated that solid and ripple phases exhibit rich textural patterns related to the orientational order of tilted lipids and the orientation of ripple corrugations. Here we reveal a highly complex network pattern of ripple and solid domains in DLPC, DPPC bilayers with structures covering length scales from 10 nm to 100 μm. Using spincoated double supported membranes we investigate domains by correlated AFM and fluorescence microscopy. Cooling experiments demonstrate the mode of nucleation and growth of stripe domains enriched in the fluorescent probe. Concurrent AFM imaging reveals that these stripe domains have a one-to-one correspondence with a rippled morphology running parallel to the stripe direction. Both thin and thick stripe domains are observed having ripple periods of 13.5±0.2 nm and 27.4±0.6 nm respectively. These are equivalent to previously observed asymmetric/equilibrium and symmetric/metastable ripple phases, respectively. Thin stripes grow from small solid domains and grow predominantly in length with a speed of ~3 times that of the thick stripes. Thick stripes grow by templating on the sides of thinner stripes or can emerge directly from the fluid phase. Bending and branching angles of stripes are in accordance with an underlying six fold lattice. We discuss mechanisms for the nucleation and growth of ripples and discuss a generic phase diagram that may partly rationalize the coexistence of metastable and stable phases. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. MD 1691: Active halo control using tune ripple at injection

    Garcia Morales, Hector; Bruce, Roderik; Redaelli, Stefano; Fitterer, Miriam; Fiascaris, Maria; Nisbet, David; Thiesen, Hugues; Valentino, Gianluca; Xu, Chen; CERN. Geneva. ATS Department

    2017-01-01

    In this MD we performed halo excitation through tune ripple. This consists in an excitation that introduces new resonance sidebands around the existing resonance lines. In presence of sufficient detuning with amplitude, these sidebands can in principle affect only the dynamics of the halo particles at large amplitudes. Tune ripple was induced through a current modulation of the warm trim quadrupoles in IR7. This is the first time this method is experimentally tested at the LHC.

  17. Soot reduction under DC electric fields in counterflow non-premixed laminar ethylene flames

    Park, Daegeun

    2014-04-23

    The effects of DC electric fields on non-premixed ethylene flames in a counterflow burner were studied experimentally with a focus on the reduction of soot particles. The experiment was conducted by connecting a high voltage terminal and a ground terminal to a lower (fuel) and upper (oxidizer) nozzle, respectively. We applied direct current (DC) potentials in a range of -5 kV < Vdc < 5 kV. Uniform electric fields were then generated in the gap between the two nozzles. The experimental conditions were selected to cover both soot formation (SF) and soot formation oxidation (SFO) flames. The flames subjected to the negative electric fields moved toward the fuel nozzle because of an ionic wind due to the Lorentz force acting on the positive ions in the flames. In addition, the yellow luminosity significantly decreased, indicating changes in the sooting characteristics. To analyze the sooting characteristics under the electric fields, planar laser induced incandescence (PLII) and fluorescence (PLIF) techniques were used to visualize the soot, polycyclic aromatic hydrocarbons (PAHs), and OH radicals. The sooting limits in terms of the fuel and oxygen mole fractions were measured. No substantial soot formation due to the effects of the DC electric fields for the tested range of voltages and reactant mole fractions could be identified. The detailed flame behaviors and sooting characteristics under the DC electric fields are discussed. Copyright © Taylor & Francis Group, LLC.

  18. Magnetic analysis of the magnetic field reduction system of the ITER neutral beam injector

    Barrera, Germán, E-mail: german.barrera@ciemat.es [CIEMAT, Laboratorio Nacional de Fusión, Avda. Complutense 22, 28040 Madrid (Spain); Ahedo, Begoña; Alonso, Javier; Ríos, Luis [CIEMAT, Laboratorio Nacional de Fusión, Avda. Complutense 22, 28040 Madrid (Spain); Chareyre, Julien; El-Ouazzani, Anass [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France); Agarici, Gilbert [Fusion for Energy, Josep Pla 2, Torres Diagonal Litoral B3, 07/08, 08019 Barcelona (Spain)

    2015-10-15

    The neutral beam system for ITER consists of two heating and current drive neutral beam injectors (HNB) and a diagnostic neutral beam (DNB) injector. The proposed physical plant layout allows a possible third HNB injector to be installed later. For the correct operation of the beam, the ion source and the ion path until it is neutralized must operate under a very low magnetic field environment. To prevent the stray ITER field from penetrating inside those mentioned critical areas, a magnetic field reduction system (MFRS) will envelop the beam vessels and the high voltage transmission lines to ion source. This system comprises the passive magnetic shield (PMS), a box like assembly of thick low carbon steel plates, and the Active Correction and Compensation Coils (ACCC), a set of coils carrying a current which depends on the tokamak stray field. This paper describes the magnetic model and analysis results presented at the PMS and ACCC preliminary design review held in ITER organization in April 2013. The paper focuses on the magnetic model description and on the description of the analysis results. The iterative process for obtaining optimized currents in the coils is presented. The set of coils currents chosen among the many possible solutions, the magnetic field results in the interest regions and the fulfillment of the magnetic field requirements are described.

  19. Deterministic ripple-spreading model for complex networks.

    Hu, Xiao-Bing; Wang, Ming; Leeson, Mark S; Hines, Evor L; Di Paolo, Ezequiel

    2011-04-01

    This paper proposes a deterministic complex network model, which is inspired by the natural ripple-spreading phenomenon. The motivations and main advantages of the model are the following: (i) The establishment of many real-world networks is a dynamic process, where it is often observed that the influence of a few local events spreads out through nodes, and then largely determines the final network topology. Obviously, this dynamic process involves many spatial and temporal factors. By simulating the natural ripple-spreading process, this paper reports a very natural way to set up a spatial and temporal model for such complex networks. (ii) Existing relevant network models are all stochastic models, i.e., with a given input, they cannot output a unique topology. Differently, the proposed ripple-spreading model can uniquely determine the final network topology, and at the same time, the stochastic feature of complex networks is captured by randomly initializing ripple-spreading related parameters. (iii) The proposed model can use an easily manageable number of ripple-spreading related parameters to precisely describe a network topology, which is more memory efficient when compared with traditional adjacency matrix or similar memory-expensive data structures. (iv) The ripple-spreading model has a very good potential for both extensions and applications.

  20. The ripple electromagnetic calculation: accuracy demand and possible responses

    Cocilovo, V.; Ramogida, G.; Formisano, A.; Martone, R.; Portone, A.; Roccella, M.; Roccella, R.

    2006-01-01

    Due to a number of causes (the finite number of toroidal field coils or the presence of concentrate blocks of magnetic materials, as the neutral beam shielding) the actual magnetic configuration in a Tokamak differs from the desired one. For example, a ripple is added to the ideal axisymmetric toroidal field, impacting the equilibrium and stability of the plasma column; as a further example the magnetic field out of plasma affects the operation of a number of critical components, included the diagnostic system and the neutral beam. Therefore the actual magnetic field has to be suitably calculated and his shape controlled within the required limits. Due to the complexity of its design, the problem is quite critical for the ITER project. In this paper the problem is discussed both from mathematical and numerical point of view. In particular, a complete formulation is proposed, taking into account both the presence of the non linear magnetic materials and the fully 3D geometry. Then the quality level requirements are discussed, included the accuracy of calculations and the spatial resolution. As a consequence, the numerical tools able to fulfil the quality needs while requiring reasonable computer burden are considered. In particular possible tools based on numerical FEM scheme are considered; in addition, in spite of the presence of non linear materials, the practical possibility to use Biot-Savart based approaches, as cross check tools, is also discussed. The paper also analyses the possible geometrical simplifications of the geometry able to make possible the actual calculation while guarantying the required accuracy. Finally the characteristics required for a correction system able to effectively counteract the magnetic field degradation are presented. Of course a number of examples will be also reported and commented. (author)

  1. Ripple FPN reduced algorithm based on temporal high-pass filter and hardware implementation

    Li, Yiyang; Li, Shuo; Zhang, Zhipeng; Jin, Weiqi; Wu, Lei; Jin, Minglei

    2016-11-01

    Cooled infrared detector arrays always suffer from undesired Ripple Fixed-Pattern Noise (FPN) when observe the scene of sky. The Ripple Fixed-Pattern Noise seriously affect the imaging quality of thermal imager, especially for small target detection and tracking. It is hard to eliminate the FPN by the Calibration based techniques and the current scene-based nonuniformity algorithms. In this paper, we present a modified space low-pass and temporal high-pass nonuniformity correction algorithm using adaptive time domain threshold (THP&GM). The threshold is designed to significantly reduce ghosting artifacts. We test the algorithm on real infrared in comparison to several previously published methods. This algorithm not only can effectively correct common FPN such as Stripe, but also has obviously advantage compared with the current methods in terms of detail protection and convergence speed, especially for Ripple FPN correction. Furthermore, we display our architecture with a prototype built on a Xilinx Virtex-5 XC5VLX50T field-programmable gate array (FPGA). The hardware implementation of the algorithm based on FPGA has two advantages: (1) low resources consumption, and (2) small hardware delay (less than 20 lines). The hardware has been successfully applied in actual system.

  2. Robust low frequency current ripple elimination algorithm for grid-connected fuel cell systems with power balancing technique

    Kim, Jong-Soo; Choe, Gyu-Yeong; Lee, Byoung-Kuk [School of Information and Communication Engineering, Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Kang, Hyun-Soo [R and D Center, Advanced Drive Technology (ADT) Company, 689-26 Geumjeong-dong, Gunpo-si, Gyeonggi-do 435-862 (Korea, Republic of)

    2011-05-15

    The low frequency current ripple in grid-connected fuel cell systems is generated from dc-ac inverter operation, which generates 60 Hz fundamental component, and gives harmful effects on fuel cell stack itself, such as making cathode surface responses slower, causing an increase of more than 10% in the fuel consumption, creating oxygen starvation, causing a reduction in the operating lifetime, and incurring a nuisance tripping such as overload situation. With these reasons, low frequency current ripple makes fuel cell system unstable and lifetime of fuel cell stack itself short. This paper presents a fast and robust control algorithm to eliminate low frequency current ripple in grid-connected fuel cell systems. Compared with the conventional methods, in the proposed control algorithm, dc link voltage controller is shifted from dc-dc converter to dc-ac inverter, resulting that dc-ac inverter handles dc link voltage control and output current control simultaneously with help of power balancing technique. The results indicate that the proposed algorithm can not only completely eliminate current ripple but also significantly reduce the overshoot or undershoot during transient states without any extra hardware. The validity of the proposed algorithm is verified by computer simulations and also by experiments with a 1 kW laboratory prototype. (author)

  3. Electric and Magnetic Fields (EMF) RAPID Program Engineering Project 8: FINAL REPORT, Evaluation of Field Reduction Technologies, Volume 1 (Report) and Volume 2 (Appendices)

    Commonwealth Associates, Inc.; IIT Research Institute

    1997-08-01

    This draft report consists of two volumes. Volume 1, the main body, contains an introducto~ sectionj an overview of magnetic fields sectio~ and field reduction technology evaluation section. Magnetic field reduction methods are evalpated for transmission lines, distribution Iines,sulxtations, building wiring applkmd machinery, and transportation systems. The evaluation considers effectiveness, co% and other ftiors. Volume 2 contains five appendices, Append~ A presents magnetic field shielding information. Appendices B and C present design assumptions and magnetic field plots for transmission and distribution lines, respectively. Appendices D and E present cost estimate details for transmission and distribution limes, respectively.

  4. Reduction of field emission in superconducting cavities with high power pulsed RF

    Graber, J.; Crawford, C.; Kirchgessner, J.; Padamsee, H.; Rubin, D.; Schmueser, P.

    1994-01-01

    A systematic study is presented of the effects of pulsed high power RF processing (HPP) as a method of reducing field emission (FE) in superconducting radio frequency (SRF) cavities to reach higher accelerating gradients for future particle accelerators. The processing apparatus was built to provide up to 150 kW peak RF power to 3 GHz cavities, for pulse lengths from 200 μs to 1 ms. Single-cell and nine-cell cavities were tested extensively. The thermal conductivity of the niobium for these cavities was made as high as possible to ensure stability against thermal breakdown of superconductivity. HPP proves to be a highly successful method of reducing FE loading in nine-cell SRF cavities. Attainable continuous wave (CW) fields increase by as much as 80% from their pre-HPP limits. The CW accelerating field achieved with nine-cell cavities improved from 8-15 MV/m with HPP to 14-20 MV/m. The benefits are stable with subsequent exposure to dust-free air. More importantly, HPP also proves effective against new field emission subsequently introduced by cold and warm vacuum ''accidents'' which admitted ''dirty'' air into the cavities. Clear correlations are obtained linking FE reduction with the maximum surface electric field attained during processing. In single cells the maximums reached were E peak =72 MV/m and H peak =1660 Oe. Thermal breakdown, initiated by accompanying high surface magnetic fields is the dominant limitation on the attainable fields for pulsed processing, as well as for final CW and long pulse operation. To prove that the surface magnetic field rather than the surface electric fields is the limitation to HPP effectiveness, a special two-cell cavity with a reduced magnetic to electric field ratio is successfully tested. During HPP, pulsed fields reach E peak =113 MV/m (H peak =1600 Oe) and subsequent CW low power measurement reached E peak =100 MV/m, the highest CW field ever measured in a superconducting accelerator cavity. ((orig.))

  5. Electric and magnetic field reduction and research: A report to the Washington State Legislature

    Geissinger, L.G.; Waller, P.; Chartier, V.L.; Olsen, R.G.

    1993-01-01

    Increasingly, citizens of Washington State are expressing their concerns about possible adverse health effects of electric and magnetic fields (EMF) from electric utility power systems. A number of legislative proposals over the past several years have prompted governmental officials to evaluate available options for reducing electric and magnetic field strengths surrounding these systems (with a concentration on magnetic fields) or otherwise manage public exposure to power lines by increasing land use controls and setbacks for new development. Unsuccessful proposals brought before the Washington Legislature include 2 mG magnetic field limits for new transmission lines at the right-of-way edge; a temporary moratorium on transmission construction; requirements for providing public information on EMF; and expansion of the role of state governmental agencies in transmission siting and design. A successful Whatcom County initiative limits the voltage of new transmission to 115 kV in all but industrial land use zones, an action likely to have an unintended outcome of increasing magnetic fields in some areas. It is clear that better communication is needed about possible options for EMF management, costs and consequences, despite the fact scientific evidence on the existence of human health effects is inconclusive. This paper describes the work that Washington State undertook in 1990-92 in response to Engrossed Substitute Senate Bill 6771 establishing the Electric Transmission Research Needs Task Force. The Task Force was directed to report to the Legislature on possible exposure reduction methods; recommending engineering research that could lead to more effective approaches in the future

  6. Characterization of electromagnetic fields in the aSPECT spectrometer and reduction of systematic errors

    Ayala Guardia, Fidel

    2011-10-15

    The aSPECT spectrometer has been designed to measure, with high precision, the recoil proton spectrum of the free neutron decay. From this spectrum, the electron antineutrino angular correlation coefficient a can be extracted with high accuracy. The goal of the experiment is to determine the coefficient a with a total relative error smaller than 0.3%, well below the current literature value of 5%. First measurements with the aSPECT spectrometer were performed in the Forschungs-Neutronenquelle Heinz Maier-Leibnitz in Munich. However, time-dependent background instabilities prevented us from reporting a new value of a. The contents of this thesis are based on the latest measurements performed with the aSPECT spectrometer at the Institut Laue-Langevin (ILL) in Grenoble, France. In these measurements, background instabilities were considerably reduced. Furthermore, diverse modifications intended to minimize systematic errors and to achieve a more reliable setup were successfully performed. Unfortunately, saturation effects of the detector electronics turned out to be too high to determine a meaningful result. However, this and other systematics were identified and decreased, or even eliminated, for future aSPECT beamtimes. The central part of this work is focused on the analysis and improvement of systematic errors related to the aSPECT electromagnetic fields. This work yielded in many improvements, particularly in the reduction of the systematic effects due to electric fields. The systematics related to the aSPECT magnetic field were also minimized and determined down to a level which permits to improve the present literature value of a. Furthermore, a custom NMR-magnetometer was developed and improved during this thesis, which will lead to reduction of magnetic field-related uncertainties down to a negligible level to determine a with a total relative error of at least 0.3%.

  7. Characterization of electromagnetic fields in the αSPECTspectrometer and reduction of systematic errors

    Ayala Guardia, Fidel

    2011-10-01

    The aSPECT spectrometer has been designed to measure, with high precision, the recoil proton spectrum of the free neutron decay. From this spectrum, the electron antineutrino angular correlation coefficient a can be extracted with high accuracy. The goal of the experiment is to determine the coefficient a with a total relative error smaller than 0.3%, well below the current literature value of 5%. First measurements with the aSPECT spectrometer were performed in the Forschungs-Neutronenquelle Heinz Maier-Leibnitz in Munich. However, time-dependent background instabilities prevented us from reporting a new value of a. The contents of this thesis are based on the latest measurements performed with the aSPECT spectrometer at the Institut Laue-Langevin (ILL) in Grenoble, France. In these measurements, background instabilities were considerably reduced. Furthermore, diverse modifications intended to minimize systematic errors and to achieve a more reliable setup were successfully performed. Unfortunately, saturation effects of the detector electronics turned out to be too high to determine a meaningful result. However, this and other systematics were identified and decreased, or even eliminated, for future aSPECT beamtimes. The central part of this work is focused on the analysis and improvement of systematic errors related to the aSPECT electromagnetic fields. This work yielded in many improvements, particularly in the reduction of the systematic effects due to electric fields. The systematics related to the aSPECT magnetic field were also minimized and determined down to a level which permits to improve the present literature value of a. Furthermore, a custom NMR-magnetometer was developed and improved during this thesis, which will lead to reduction of magnetic field-related uncertainties down to a negligible level to determine a with a total relative error of at least 0.3%.

  8. Reduction of truncation errors in planar near-field aperture antenna measurements using the method of alternating orthogonal projections

    Martini, Enrica; Breinbjerg, Olav; Maci, Stefano

    2006-01-01

    A simple and effective procedure for the reduction of truncation error in planar near-field to far-field transformations is presented. The starting point is the consideration that the actual scan plane truncation implies a reliability of the reconstructed plane wave spectrum of the field radiated...

  9. Magnetized Reverse Shock: Density-fluctuation-induced Field Distortion, Polarization Degree Reduction, and Application to GRBs

    Deng Wei; Zhang Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States); Li Hui [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Stone, James M., E-mail: deng@physics.unlv.edu, E-mail: zhang@physics.unlv.edu, E-mail: hli@lanl.gov, E-mail: jstone@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544-1001 (United States)

    2017-08-10

    The early optical afterglow emission of several gamma-ray bursts (GRBs) shows a high linear polarization degree (PD) of tens of percent, suggesting an ordered magnetic field in the emission region. The light curves are consistent with being of a reverse shock (RS) origin. However, the magnetization parameter, σ , of the outflow is unknown. If σ is too small, an ordered field in the RS may be quickly randomized due to turbulence driven by various perturbations so that the PD may not be as high as observed. Here we use the “Athena++” relativistic MHD code to simulate a relativistic jet with an ordered magnetic field propagating into a clumpy ambient medium, with a focus on how density fluctuations may distort the ordered magnetic field and reduce PD in the RS emission for different σ values. For a given density fluctuation, we discover a clear power-law relationship between the relative PD reduction and the σ value of the outflow. Such a relation may be applied to estimate σ of the GRB outflows using the polarization data of early afterglows.

  10. Analysis of active and passive magnetic field reduction systems (MFRS) of the ITER NBI

    Roccella, M.; Lucca, F.; Roccella, R.; Pizzuto, A.; Ramogida, G.; Portone, A.; Tanga, A.; Formisano, A.; Martone, R.

    2007-01-01

    In ITER two heating (HNBI) and one diagnostic neutral beam injectors (DNBI) are foreseen. Inside these components there are very stringent limits on the magnetic field (the flux density must be below some G along the ion path and below 20 G in the neutralizing regions). To achieve these performances in an environment with high stray field due to the plasma and the poloidal field coils (PFC), both passive and active shielding systems have been foreseen. The present design of the magnetic field reduction systems (MFRS) is made of seven active coils and of a box surrounding the NBI region, consisting of ferromagnetic plates. The electromagnetic analyses of the effectiveness of these shields have been performed by a 3D FEM model using ANSYS code for the HNBI. The ANSYS models of the ferromagnetic box and of the active coils are fully parametric, thus any size change of the ferromagnetic box and coils (linear dimension or thickness) preserving the overall box shape could be easily reproduced by simply changing some parameter in the model

  11. Analysis of active and passive magnetic field reduction systems (MFRS) of the ITER NBI

    Roccella, M. [L.T. Calcoli S.a.S., Piazza Prinetti 26/B, Merate (Lecco) (Italy)], E-mail: roccella@ltcalcoli.it; Lucca, F.; Roccella, R. [L.T. Calcoli S.a.S., Piazza Prinetti 26/B, Merate (Lecco) (Italy); Pizzuto, A.; Ramogida, G. [Associazione EURATOM sulla Fusione - ENEA Frascati (Italy); Portone, A.; Tanga, A. [ITER EFDA (Italy); Formisano, A.; Martone, R. [CREATE Napoli (Italy)

    2007-10-15

    In ITER two heating (HNBI) and one diagnostic neutral beam injectors (DNBI) are foreseen. Inside these components there are very stringent limits on the magnetic field (the flux density must be below some G along the ion path and below 20 G in the neutralizing regions). To achieve these performances in an environment with high stray field due to the plasma and the poloidal field coils (PFC), both passive and active shielding systems have been foreseen. The present design of the magnetic field reduction systems (MFRS) is made of seven active coils and of a box surrounding the NBI region, consisting of ferromagnetic plates. The electromagnetic analyses of the effectiveness of these shields have been performed by a 3D FEM model using ANSYS code for the HNBI. The ANSYS models of the ferromagnetic box and of the active coils are fully parametric, thus any size change of the ferromagnetic box and coils (linear dimension or thickness) preserving the overall box shape could be easily reproduced by simply changing some parameter in the model.

  12. Source of spill ripple in the RF-KO slow-extraction method with FM and AM

    Noda, K.; Furukawa, T.; Shibuya, S.; Muramatsu, M.; Uesugi, T.; Kanazawa, M.; Torikoshi, M.; Takada, E.; Yamada, S.

    2002-01-01

    The RF-knockout (RF-KO) slow-extraction method with frequency modulation (FM) and amplitude modulation (AM) has brought high-accuracy irradiation to the treatment of a cancer tumor moving with respiration, because of a quick response to beam start/stop. However, a beam spill extracted from a synchrotron ring through RF-KO slow-extraction has a huge ripple with a frequency of around 1 kHz related to the FM. The spill ripple will disturb the lateral dose distribution in the beam scanning methods. Thus, the source of the spill ripple has been investigated through experiments and simulations. There are two tune regions for the extraction process through the RF-KO method: the extraction region and the diffusion region. The particles in the extraction region can be extracted due to amplitude growth through the transverse RF field, only when its frequency matches with the tune in the extraction region. For a large chromaticity, however, the particles in the extraction region can be extracted through the synchrotron oscillation, even when the frequency does not match with the tune in the extraction region. Thus, the spill structure during one period of the FM strongly depends on the horizontal chromaticity. They are repeated with the repetition frequency of the FM, which is the very source of the spill ripple in the RF-KO method

  13. Thermal dynamics of silver clusters grown on rippled silica surfaces

    Bhatnagar, Mukul, E-mail: mkbh10@gmail.com [FCIPT, Institute for Plasma Research, Gandhinagar, Gujarat (India); Nirma University, Ahmedabad, Gujarat (India); Ranjan, Mukesh [FCIPT, Institute for Plasma Research, Gandhinagar, Gujarat (India); Nirma University, Ahmedabad, Gujarat (India); Jolley, Kenny; Lloyd, Adam; Smith, Roger [Dept. of Mathematical Sciences, Loughborough University, Leicestershire LE11 3TU (United Kingdom); Mukherjee, Subroto [FCIPT, Institute for Plasma Research, Gandhinagar, Gujarat (India); Nirma University, Ahmedabad, Gujarat (India)

    2017-02-15

    Highlights: • Low energy oblique angle ion bombardment forms ripple pattern on silicon surface. • The ripple patterns have wavelengths between 20 and 45 nm and correspondingly low height. • Silver nanoparticles have been deposited at an angle of 70° on patterned silicon templates. • The as-deposited np are annealed in vacuo at temperature of 573 K for a time duration of 1 h. • MD simulation is used to model the process and compare the results to the experiment. • Results show that silver clusters grow preferentially along parallel to the rippled surface. • Mobility of silver atoms depends on the site to which they are bonded on this amorphous surface. • MD simulations show contour ordered coalescence which is dependent on ripple periodicity. - Abstract: Silver nanoparticles have been deposited on silicon rippled patterned templates at an angle of incidence of 70° to the surface normal. The templates are produced by oblique incidence argon ion bombardment and as the fluence increases, the periods and heights of the structures increase. Structures with periods of 20 nm, 35 nm and 45 nm have been produced. Moderate temperature vacuum annealing shows the phenomenon of cluster coalescence following the contour of the more exposed faces of the ripple for the case of 35 nm and 45 nm but not at 20 nm where the silver aggregates into larger randomly distributed clusters. In order to understand this effect, the morphological changes of silver nanoparticles deposited on an asymmetric rippled silica surface are investigated through the use of molecular dynamics simulations for different deposition angles of incidence between 0° and 70° and annealing temperatures between 500 K and 900 K. Near to normal incidence, clusters are observed to migrate over the entire surface but for deposition at 70°, a similar patterning is observed as in the experiment. The random distribution of clusters for the periodicity ≈ of 20 nm is linked to the geometry of the silica

  14. VHTR Construction Ripple Effect using Inter-Industry Analysis

    Lee, T. H.; Lee, K. Y.; Shin, Y. J.

    2015-01-01

    As a part of a VHTR economic analysis, we have studied the VHTR construction cost and operation and maintenance cost. However, it is somewhat difficult to expect the exact cost due to insufficient reference data and experience. As a result, we propose quantitative analysis techniques for ripple effects such as the production inducement effect, added value inducement effect, and employment inducement effect for VHTR 600MWt x 4 module construction and operation ripple effect based on NOAK. This paper presents a new method for the ripple effect and preliminary ripple effect consequence. We proposed a ripple effect analysis method using a time series and inter-industry table. As a result, we can predict that a 600MWth x 4 module VHTR reactor construction will bring about a 43771 employment effect, 24160 billion KRW production effect, and 4472 billion added value effect for 22 years. It is necessary to use the sub-account values of an inter-industry table to obtain a more precise effect result. However, the methodology can be applied with minor modification to another reactor type.

  15. VHTR Construction Ripple Effect using Inter-Industry Analysis

    Lee, T. H.; Lee, K. Y.; Shin, Y. J. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    As a part of a VHTR economic analysis, we have studied the VHTR construction cost and operation and maintenance cost. However, it is somewhat difficult to expect the exact cost due to insufficient reference data and experience. As a result, we propose quantitative analysis techniques for ripple effects such as the production inducement effect, added value inducement effect, and employment inducement effect for VHTR 600MWt x 4 module construction and operation ripple effect based on NOAK. This paper presents a new method for the ripple effect and preliminary ripple effect consequence. We proposed a ripple effect analysis method using a time series and inter-industry table. As a result, we can predict that a 600MWth x 4 module VHTR reactor construction will bring about a 43771 employment effect, 24160 billion KRW production effect, and 4472 billion added value effect for 22 years. It is necessary to use the sub-account values of an inter-industry table to obtain a more precise effect result. However, the methodology can be applied with minor modification to another reactor type.

  16. Wave plus current over a ripple-covered bed

    Fredsøe, Jørgen; Andersen, Ken Haste; Sumer, B. Mutlu

    1999-01-01

    This paper concerns the combined wave and current boundary layer flow over a ripple-covered bed, The study comprises experiments as well as a numerical modelling study: the experimental part comprises laser Doppler anemometry (LDA) velocity and turbulence measurements, and a flow-visualization st......This paper concerns the combined wave and current boundary layer flow over a ripple-covered bed, The study comprises experiments as well as a numerical modelling study: the experimental part comprises laser Doppler anemometry (LDA) velocity and turbulence measurements, and a flow......-visualization study in the laboratory with ripples, 22 cm in length, and 3.5 cm in height. One wave-alone, three current-alone, and three combined waves and current tests were conducted. The wave-velocity-to-current-velocity ratio ranges from 1 to 2.4. The orbiral-amplitude-ro-ripple-length ratio (at the bed) is 0.......41. The effect of superimposing waves on a current is to displace the velocity profile to higher elevations. The velocity profiles exhibit two "logarithmic layers", one associated with the actual roughness of the bed (the actual ripple roughness), and the other with the apparent roughness induced by the waves...

  17. Field experience on Zn injection on PWR plants with a view to dose rate reduction

    Roumiguiere, F.

    2005-01-01

    Operating experience acquired at PWR plants shows that zinc injection in the primary coolant at low concentration (∼5 ppb) is a very effective tool to achieve a reduction of the dose rate build-up. The beneficial effect of zinc consists on improving the protective layer characteristics of the reactor coolant system surfaces, which results in a lower pickup of activated products (Co-60, Co-58), and consequently a reduction of the associated dose rates. Zinc injection was introduced at the Unit B of the Biblis Power Station in September 1996 and at the Obrigheim Nuclear Power Station in February 1998, as a measure for reduction of radiation fields. The effectiveness of the method and its compatibility with the overall plant was examined in a rather comprehensive surveillance program at these plants. The already published data show that zinc injection did not lead to any operating restrictions or other negative effects on plants systems and components. Zinc injection is still being implemented today at these plants. Zinc injection is considered today as a mature technique and is now being successfully applied at a number of PWRs in Germany, Brazil, USA and Japan, with the support of Framatome-ANP. Several PWRs in Europe and Asia are preparing for zinc chemistry in the near future. The method is inexpensive and easy to apply. Its implementation is highly advisable in terms of the cost/benefit criterion following the ALARA principle. This paper gives an overview of the experience gathered with the method. The main subject addressed by the paper is the evolution of dose rates at the primary system and work-related doses since introduction of the method. In German PWRs with Incoloy 800 steam generator tubing material (Ni-content ∼32%), the observed reductions correspond to a decrease in dose rates of around 10 to 15% per year following, as predicted, the half-life time of 60 Co. Overall reductions in high radiation areas are now in the range of 50% after 5 years of

  18. Reduction of ambipolar characteristics of vertical channel tunneling field-effect transistor by using dielectric sidewall

    Park, Chun Woong; Cho, Il Hwan; Choi, Woo Young; Lee, Jong-Ho

    2013-01-01

    Ambipolar characteristics of tunneling FETs have been improved by introducing a novel structure which contains dielectric sidewall in the gate region. In the ambipolar operation mode, gate field effect on intrinsic-drain junction region can be reduced with dielectric sidewall. As a result, ambipolar state tunneling probability is decreased at the intrinsic-drain junction. Since the sidewall region is located near the drain region, tunneling probability of source-intrinsic region is not affected by dielectric sidewall. This asymmetric characteristics means only ambipolar current of tunneling FETs can be prohibited by dielectric sidewall. Reduction of ambipolar characteristic of proposed structure has been evaluated with dimension and location of dielectric sidewall. Quantitative analysis of ambipolar characteristics is also investigated with tunneling. (paper)

  19. Mechanisms for Selective Single-Cell Reactivation during Offline Sharp-Wave Ripples and Their Distortion by Fast Ripples.

    Valero, Manuel; Averkin, Robert G; Fernandez-Lamo, Ivan; Aguilar, Juan; Lopez-Pigozzi, Diego; Brotons-Mas, Jorge R; Cid, Elena; Tamas, Gabor; Menendez de la Prida, Liset

    2017-06-21

    Memory traces are reactivated selectively during sharp-wave ripples. The mechanisms of selective reactivation, and how degraded reactivation affects memory, are poorly understood. We evaluated hippocampal single-cell activity during physiological and pathological sharp-wave ripples using juxtacellular and intracellular recordings in normal and epileptic rats with different memory abilities. CA1 pyramidal cells participate selectively during physiological events but fired together during epileptic fast ripples. We found that firing selectivity was dominated by an event- and cell-specific synaptic drive, modulated in single cells by changes in the excitatory/inhibitory ratio measured intracellularly. This mechanism collapses during pathological fast ripples to exacerbate and randomize neuronal firing. Acute administration of a use- and cell-type-dependent sodium channel blocker reduced neuronal collapse and randomness and improved recall in epileptic rats. We propose that cell-specific synaptic inputs govern firing selectivity of CA1 pyramidal cells during sharp-wave ripples. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Rippling modes in the edge of a tokamak plasma

    Carreras, B.A.; Callen, J.D.; Gaffney, P.W.; Hicks, H.R.

    1982-02-01

    A promising resistive magnetohydrodynamic candidate for the underlying cause of turbulence in the edge of a tokamak plasma is the rippling instability. In this paper we develop a computational model for these modes in the cylindrical tokamak approximation and explore the linear growth and single-helicity quasi-linear saturation phases of the rippling modes for parameters appropriate to the edge of a tokamak plasma. Large parallel heat conduction does not stabilize these modes; it only reduces their growth rate by a factor scaling as k/sub parallel//sup -4/3/. Nonlinearly, individual rippling modes are found to saturate by quasi-linear flattening of the resistivity profile. The saturated amplitude of the modes scales as m/sup -1/, and the radial extent of these modes grows linearly with time due to radial Vector E x Vector B 0 convection. This evolution is found to be terminated by parallel heat conduction

  1. Rippling modes in the edge of a tokamak plasma

    Carreras, B.A.; Gaffney, P.W.; Hicks, H.R.; Callan, J.D.

    1982-01-01

    A promising resistive magnetohydrodynamic candidate for the underlying cause of turbulence in the edge of a tokamak plasma is the rippling instability. In this paper a computational model for these modes in the cylindrical tokamak approximation was developed and the linear growth and single-helicity quasi-linear saturation phases of the rippling modes for parameters appropriate to the edge of a tokamak plasma were explored. Large parallel heat conduction does not stabilize these modes; it only reduces their growth rate by a factor sacling as K/sup -4/3//sub parallel/. Nonlinearly, individual rippling modes are found to saturate by quasi-linear flattening of the resistivity profile. The saturated amplitude of the modes scales as m -1 , and the radial extent of these modes grows linearly with time due to radial E x B 0 convection. This evolution is found to be terminated by parallel heat conduction

  2. Evolution of a Rippled Membrane during Phospholipase A2 Hydrolysis Studied by Time-Resolved AFM

    Leidy, Chad; Mouritsen, Ole G.; Jørgensen, Kent

    2004-01-01

    The sensitivity of phospholipase A2 (PLA2) for lipid membrane curvature is explored by monitoring, through time-resolved atomic force microscopy, the hydrolysis of supported double bilayers in the ripple phase. The ripple phase presents a corrugated morphology. PLA2 is shown to have higher activity...... toward the ripple phase compared to the gel phase in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes, indicating its preference for this highly curved membrane morphology. Hydrolysis of the stable and metastable ripple structures is monitored for equimolar DMPC/1,2-distearoyl- sn-glycero-3....... This is reflected in an increase in ripple spacing, followed by a sudden flattening of the lipid membrane during hydrolysis. Hydrolysis of the ripple phase results in anisotropic holes running parallel to the ripples, suggesting that the ripple phase has strip regions of higher sensitivity to enzymatic attack. Bulk...

  3. Ion bombardment induced ripple topography on amorphous solids

    Carter, G.; Nobes, M.J.; Paton, F.; Williams, J.S.

    1977-01-01

    Earlier studies of the ion bombardment induced ripple morphology on the surfaces of amorphous solids when compared with geomorphological effects are shown to possess many similar features. The present study, with 40 keV Ar + ion bombarded Si suggests that analogies are incomplete, however, and that greater similarities with the process of macroscopic sandblasting (corrosion) exist. It is shown that the genesis of wave like structures on Si is from isolated features, which have the appearance of ripple trains, which are faceted. It is suggested that these features result from particle flux enhancement processes near surface dimples generated by stress induced surface lifting. (author)

  4. Gravitational-Like Lens Based on Graphene Ripple.

    Liu, Daqing; Chen, Shuyue; Ma, Ning; Zhao, Xiang; Xu, Zhuo

    2015-10-01

    We conducted a semiclassical study on carrier movement in curved graphene. A previous attempt was made to show that curved graphene is a readily available and cheap laboratory material used to study general relativity effects, especially if the electron energies satisfy 4μeV ≪ |E| ≪ 3eV. Furthermore, a gravitational-like lens can be constructed based on a special graphene ripple; this lens has neither chromatic nor cometic aberration. One can design an ideal electron lens using a graphene ripple.

  5. Reduction of Truncation Errors in Planar Near-Field Aperture Antenna Measurements Using the Gerchberg-Papoulis Algorithm

    Martini, Enrica; Breinbjerg, Olav; Maci, Stefano

    2008-01-01

    A simple and effective procedure for the reduction of truncation errors in planar near-field measurements of aperture antennas is presented. The procedure relies on the consideration that, due to the scan plane truncation, the calculated plane wave spectrum of the field radiated by the antenna is...

  6. The H-mode pedestal, ELMs and TF ripple effects in JT-60U/JET dimensionless identity experiments

    Saibene, G.; Oyama, N.; Loennroth, J.; Andrew, Y.; Luna, E. de la; Giroud, C.; Huysmans, G.T.A.; Kamada, Y.; Kempenaars, M.A.H.; Loarte, A.; Donald, D. Mc; Nave, M.M.F.; Meiggs, A.; Parail, V.; Sartori, R.; Sharapov, S.; Stober, J.; Suzuki, T.; Takechi, M.; Toi, K.; Urano, H.

    2007-01-01

    This paper summarizes results of dimensionless identity experiments in JT-60U and JET, aimed at the comparison of the H-mode pedestal and ELM behaviour in the two devices. Given their similar size, dimensionless matched plasmas are also similar in their dimensional parameters (in particular, the plasma minor radius a is the same in JET and JT-60U). Power and density scans were carried out at two values of I p , providing a q scan (q 95 = 3.1 and 5.1) with fixed (and matched) toroidal field. Contrary to initial expectations, a dimensionless match between the two devices was quite difficult to achieve. In general, p ped in JT-60U is lower than in JET and, at low q, the pedestal pressure of JT-60U with a Type I ELMy edge is matched in JET only in the Type III ELM regime. At q 95 = 5.1, a dimensionless match in ρ*, ν* and β p,ped is obtained with Type I ELMs, but only with low power JET H-modes. These results motivated a closer investigation of experimental conditions in the two devices, to identify possible 'hidden' physics that prevents obtaining a good match of pedestal values over a large range of plasmas parameters. Ripple-induced ion losses of the medium bore plasma used in JT-60U for the similarity experiments are identified as the main difference with JET. The magnitude of the JT-60U ripple losses is sufficient to induce counter-toroidal rotation in co-injected plasma. The influence of ripple losses was demonstrated at q 95 = 5.1: reducing ripple losses by ∼2 (from 4.3 to 1.9 MW) by replacing positive with negative neutral beam injection at approximately constant P in resulted in an increased p ped in JT-60U, providing a good match to full power JET H-modes. At the same time, the counter-toroidal rotation decreased. Physics mechanisms relating ripple losses to pedestal performance are not yet identified, and the possible role of velocity shear in the pedestal stability, as well as the possible influence of ripple on thermal ion transport are briefly

  7. Radon reduction techniques for suspended timber floors and pressure field extension assessment of hardcore specifications

    Gregory, T.J.; Stephen, R.K.

    1994-01-01

    This paper comprises two case studies. The first describes a series of mitigation measures carried out in a small primary school fitted with a suspended timber floor. Radon levels had been successfully reduced but the floor subsequently collapsed due to an outbreak of dry-rot. The floor was replaced with a ground-bearing concrete slab fitted with a typical example of one of 200 or so sump-and-fan systems fitted by Cornwall County Council (CCC). Following consultation with the Building Research Establishment (BRE) a network of small bore pipes was fitted below the floor during construction to record variations in radon levels and pressures. The second case study describes the floor replacement at a second, similar school but with a permeable layer of material under the concrete slab and more pressure measurement points. The pressure measurements and their subsequent analysis are described and the performance of the two installations compared. Using BRE and CCC expertise, this technique is now being applied to a number of other replacement floors in order to assess pressure field extension in a variety of hardcore and blinding materials. It is hoped that by careful selection of hardcore and blinding specifications the increased pressure field extension obtained could result in a new-build properties requiring fewer underfloor suction points and/or a reduction in fan power consumption with a greater degree of confidence of success than at present. The selection and design of suction systems to date has been on a very pragmatic basis. (author)

  8. Preliminary ripple effect analysis for HTR 350MWt 4 modules construction

    Lee, T. H.; Lee, K. Y.; Shin, Y. J. [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    We propose quantitative analysis techniques for ripple effects such as the production inducement effect and employment inducement effect for HTR 350MWt x 4 module construction and operation ripple effect based on NOAK. It is known that APR1400 reactors export ripple effect is about 8,500 billion KRW. As a result, HTR construction has more effective effect than that of APR1400.

  9. Influence of phosphate and copper on reductive dechlorination of thiobencarb in California rice field soils.

    Gunasekara, Amrith S; Tenbrook, Patti L; Palumbo, Amanda J; Johnson, Catherine S; Tjeerdema, Ronald S

    2005-12-28

    The potential for reductive dechlorination of the herbicide thiobencarb (TB) by microbes and its prevention in saturated anaerobic rice field soils was examined in laboratory microcosms. TB is effective in controlling both annual grasses and broadleaf weeds. In anoxic microcosms, TB was effectively degraded within 30 days to its dechlorinated product, deschlorothiobencarb (DTB), in two Sacramento Valley rice field soils. TB dechlorination, and subsequent degradation, followed pseudo-zero- (lag phase) and first-order (degradation phase) kinetics. Logistic regression analysis (r2 > 0.841) produced a half-life (t(1/2)) in nonsterile soils ranging from 10 to 15 days, which was also observed when microcosms were amended with low concentrations (copper (Cu2+; as the fungicides Cu(OH)2 and CuSO4.5H2O). High Cu2+ concentrations (>40 mg L(-1)) were added to the microcosms to determine if copper toxicity to dechlorinating microbes is concentration dependent within the range used. After 30 days, the low-copper-amended soils closely resembled the nonsterile experiments to which no Cu2+ was added while the high-copper-amended microcosms were similar to the sterile experiment. Microcosms were also separately amended with 5.7 g L(-1) phosphate (PO4(2-); as KH2PO4), a nutrient regularly applied to rice fields. Phosphate-amended experiments also showed TB degradation, but no DTB formation, indicating the phosphate played a role, possibly as a microbial inhibitor or an alternative electron acceptor, in limiting the dechlorination of TB. In summary, TB dechlorination was inhibited at high Cu(OH)2, CuSO4.5H2O, and KH2PO4 concentrations.

  10. Turbulence and sediment transport over sand dunes and ripples

    Bennis, A.; Le Bot, S.; lafite, R.; Bonneton, P.; Ardhuin, F.

    2013-12-01

    Several bedforms are present near to the surfzone of natural beaches. Dunes and ripples are frequently observed. Understanding the turbulence over these forms is essential for the sediment transport. The turbulent flow and the suspended sand particles interact with each other. At the moment, the modelling strategy for turbulence is still a challenge. According to the spatial scales, some different methods to model the turbulence are employed, in particular the RANS (Reynolds Averaged Navier-Stokes) and the LES (Large Eddy Simulation). A hybrid method combining both RANS and LES is set up here. We have adapted this method, initially developed for atmospheric flow, to the oceanic flow. This new method is implemented inside the 3D hydrodynamic model, MARS 3D, which is forced by waves. LES is currently the best way to simulate turbulent flow but its higher cost prevents it from being used for large scale applications. So, here we use RANS near the bottom while LES is set elsewhere. It allows us minimize the computational cost and ensure a better accuracy of the results than with a fully RANS model. In the case of megaripples, the validation step was performed with two sets of field data (Sandy Duck'97 and Forsoms'13) but also with the data from Dune2D model which uses only RANS for turbulence. The main findings are: a) the vertical profiles of the velocity are similar throughout the data b) the turbulent kinetic energy, which was underestimated by Dune2D, is in line with the observations c) the concentration of the suspended sediment is simulated with a better accuracy than with Dune2D but this remains lower than the observations.

  11. Field-scale modeling of acidity production and remediation efficiency during in situ reductive dechlorination

    Brovelli, A.; Robinson, C. E.; Barry, D. A.; Gerhard, J.

    2009-12-01

    Enhanced reductive dechlorination is a viable technology for in situ remediation of chlorinated solvent DNAPL source areas. Although in recent years increased understanding of this technology has led to more rapid dechlorination rates, complete dechlorination can be hindered by unfavorable conditions. Hydrochloric acid produced from dechlorination and organic acids generated from electron donor fermentation can lead to significant groundwater acidification. Adverse pH conditions can inhibit the activity of dehalogenating microorganisms and thus slow or stall the remediation process. The extent of acidification likely to occur at a contaminated site depends on a number of factors including (1) the extent of dechlorination, (2) the pH-sensitivity of dechlorinating bacteria, and (3) the geochemical composition of the soil and water, in particular the soil’s natural buffering capacity. The substantial mass of solvents available for dechlorination when treating DNAPL source zones means that these applications are particularly susceptible to acidification. In this study a reactive transport biogeochemical model was developed to investigate the chemical and physical parameters that control the build-up of acidity and subsequent remediation efficiency. The model accounts for the site water chemistry, mineral precipitation and dissolution kinetics, electron donor fermentation, gas phase formation, competing electron-accepting processes (e.g., sulfate and iron reduction) and the sensitivity of microbial processes to pH. Confidence in the model was achieved by simulating a well-documented field study, for which the 2-D field scale model was able to reproduce long-term variations of pH, and the concurrent build up of reaction products. Sensitivity analyses indicated the groundwater flow velocity is able to reduce acidity build-up when the rate of advection is comparable or larger than the rate of dechlorination. The extent of pH change is highly dependent on the presence of

  12. Plasma-filled rippled wall rectangular backward wave oscillator

    Performance of the backward wave oscillator (BWO) is greatly enhanced with the introduction of plasma. Linear theory of the dispersion relation and the growth rate have been derived and analysed numerically for plasma-filled rippled wall rectangular waveguide driven by sheet electron beam. To see the effect of plasma ...

  13. Analysis of ripple formation in single crystal spot welds

    Rappaz, M. [Ecole Polytechnique Federale de Lausanne (Switzerland). Lab de Metallurgie Physique; Corrigan, D.; Boatner, L.A. [Oak Ridge National Lab., TN (United States). Solid State Div.

    1997-10-01

    Stationary spot welds have been made at the (001) surface of Fe-l5%Ni-15%Cr single crystals using a Gas Tungsten Arc (GTA). On the top surface of the spot welds, very regular and concentric ripples were observed after solidification by differential interference color microscopy. Their height (typically 1--5 {micro}m) and spacing (typically {approximately} 60 {micro}m) decreased with the radius of the pool. These ripples were successfully accounted for in terms of capillary-wave theory using the fundamental mode frequency f{sub 0} given by the first zero of the zero-order Bessel function. The spacing d between the ripples was then equated to v{sub s}/f{sub 0}, where v{sub s} is the solidification rate. From the measured ripple spacing, the velocity of the pool was deduced as a function of the radius, and this velocity was in good agreement with the results of a heat-flow simulation.

  14. Ripple distribution for nonlinear fiber-optic channels.

    Sorokina, Mariia; Sygletos, Stylianos; Turitsyn, Sergei

    2017-02-06

    We demonstrate data rates above the threshold imposed by nonlinearity on conventional optical signals by applying novel probability distribution, which we call ripple distribution, adapted to the properties of the fiber channel. Our results offer a new direction for signal coding, modulation and practical nonlinear distortions compensation algorithms.

  15. Uncovering Transdisciplinary Team Project Outcomes through Ripple Effect Mapping

    Daniels, Catherine H.; Chalker-Scott, Linda; Martini, Nicole

    2016-01-01

    The Garden Team at Washington State University is a transdisciplinary, geographically dispersed group of faculty and staff. As with many such teams, member retention requires effort, as busy individuals may not see the overall benefits of active team membership. Ripple effect mapping is a strategy that can illustrate the tangible and often…

  16. The WEBSIM FISHBANKS Simulation Laboratory: Analysis of Its Ripple Effects

    Arantes do Amaral, João Alberto; Hess, Aurélio

    2018-01-01

    In this article, we discuss the ripple effects of the WEBSIM FISHBANKS Simulation Laboratory held at Federal University of Sao Paulo (UNIFESP) in 2014, held as a result of a partnership between the Sloan School of Management of the Massachusetts Institute of Technology, the UNIFESP, and the Brazilian Chapter of the System Dynamics Society of…

  17. Ripple design of LT codes for AWGN channel

    Sørensen, Jesper Hemming; Koike-Akino, Toshiaki; Orlik, Philip

    2012-01-01

    In this paper, we present an analytical framework for designing LT codes in additive white Gaussian noise (AWGN) channels. We show that some of analytical results from binary erasure channels (BEC) also hold in AWGN channels with slight modifications. This enables us to apply a ripple-based design...

  18. Ripple Design of LT Codes for BIAWGN Channels

    Sørensen, Jesper Hemming; Koike-Akino, Toshiaki; Orlik, Philip

    2014-01-01

    This paper presents a novel framework, which enables a design of rateless codes for binary input additive white Gaussian noise (BIAWGN) channels, using the ripple-based approach known from the works for the binary erasure channel (BEC). We reveal that several aspects of the analytical results from...

  19. Delayed ripple counter simplifies square-root computation

    Cliff, R.

    1965-01-01

    Ripple subtract technique simplifies the logic circuitry required in a binary computing device to derive the square root of a number. Successively higher numbers are subtracted from a register containing the number out of which the square root is to be extracted. The last number subtracted will be the closest integer to the square root of the number.

  20. Ripple Effect Mapping: A "Radiant" Way to Capture Program Impacts

    Kollock, Debra Hansen; Flage, Lynette; Chazdon, Scott; Paine, Nathan; Higgins, Lorie

    2012-01-01

    Learn more about a promising follow-up, participatory group process designed to document the results of Extension educational efforts within complex, real-life settings. The method, known as Ripple Effect Mapping, uses elements of Appreciative Inquiry, mind mapping, and qualitative data analysis to engage program participants and other community…

  1. Ripple coarsening on ion beam-eroded surfaces.

    Teichmann, Marc; Lorbeer, Jan; Frost, Frank; Rauschenbach, Bernd

    2014-01-01

    The temporal evolution of ripple pattern on Ge, Si, Al 2 O 3, and SiO 2 by low-energy ion beam erosion with Xe (+) ions is studied. The experiments focus on the ripple dynamics in a fluence range from 1.1 × 10(17) cm(-2) to 1.3 × 10(19) cm(-2) at ion incidence angles of 65° and 75° and ion energies of 600 and 1,200 eV. At low fluences a short-wavelength ripple structure emerges on the surface that is superimposed and later on dominated by long wavelength structures for increasing fluences. The coarsening of short wavelength ripples depends on the material system and angle of incidence. These observations are associated with the influence of reflected primary ions and gradient-dependent sputtering. The investigations reveal that coarsening of the pattern is a universal behavior for all investigated materials, just at the earliest accessible stage of surface evolution.

  2. Relationship between behavioral and physiological spectral-ripple discrimination.

    Won, Jong Ho; Clinard, Christopher G; Kwon, Seeyoun; Dasika, Vasant K; Nie, Kaibao; Drennan, Ward R; Tremblay, Kelly L; Rubinstein, Jay T

    2011-06-01

    Previous studies have found a significant correlation between spectral-ripple discrimination and speech and music perception in cochlear implant (CI) users. This relationship could be of use to clinicians and scientists who are interested in using spectral-ripple stimuli in the assessment and habilitation of CI users. However, previous psychoacoustic tasks used to assess spectral discrimination are not suitable for all populations, and it would be beneficial to develop methods that could be used to test all age ranges, including pediatric implant users. Additionally, it is important to understand how ripple stimuli are processed in the central auditory system and how their neural representation contributes to behavioral performance. For this reason, we developed a single-interval, yes/no paradigm that could potentially be used both behaviorally and electrophysiologically to estimate spectral-ripple threshold. In experiment 1, behavioral thresholds obtained using the single-interval method were compared to thresholds obtained using a previously established three-alternative forced-choice method. A significant correlation was found (r = 0.84, p = 0.0002) in 14 adult CI users. The spectral-ripple threshold obtained using the new method also correlated with speech perception in quiet and noise. In experiment 2, the effect of the number of vocoder-processing channels on the behavioral and physiological threshold in normal-hearing listeners was determined. Behavioral thresholds, using the new single-interval method, as well as cortical P1-N1-P2 responses changed as a function of the number of channels. Better behavioral and physiological performance (i.e., better discrimination ability at higher ripple densities) was observed as more channels added. In experiment 3, the relationship between behavioral and physiological data was examined. Amplitudes of the P1-N1-P2 "change" responses were significantly correlated with d' values from the single-interval behavioral

  3. The effect of the adsorbate layer on the work function reduction of gold substrates under external electric fields

    He, Xiang; Cheng, Feng; Chen, Zhao-Xu

    2017-12-01

    The interface interaction between the dimethyl sulfide (DMS) molecule and the gold substrate under external electric fields is investigated by density functional theory method. The polarized DMS adsorbate reduces the work function of the gold substrate while the induced substrate dipole upon the adsorption slightly increases the work function. The DMS layer partially shields the Au(111) substrate from the electric fields and the vacuum level of DMS/Au(111) shifts less than of Au(111) in consequence. Under electric fields pointing outward from the Au(111) surface, both the reduction of work function and the adsorption of DMS molecule are enhanced on the surface. We also suggest the possible application of the field-effect transistor (FET) sensor with gold gate for detecting DMS molecule by utilizing the reduction of substrate work function upon adsorption. The effects of coverage and electric field on the theoretical sensitivity of the sensor are also discussed.

  4. Ripple formation in unilamellar-supported lipid bilayer revealed by FRAPP.

    Harb, Frédéric; Simon, Anne; Tinland, Bernard

    2013-12-01

    The mechanisms of formation and conditions of the existence of the ripple phase are fundamental thermodynamic questions with practical implications for medicine and pharmaceuticals. We reveal a new case of ripple formation occurring in unilamellar-supported bilayers in water, which results solely from the bilayer/support interaction, without using lipid mixtures or specific ions. This ripple phase is detected by FRAPP using diffusion coefficient measurements as a function of temperature: a diffusivity plateau is observed. It occurs in the same temperature range where ripple phase existence has been observed using other methods. When AFM experiments are performed in the appropriate temperature range the ripple phase is confirmed.

  5. Computational analysis of network activity and spatial reach of sharp wave-ripples.

    Sadullah Canakci

    Full Text Available Network oscillations of different frequencies, durations and amplitudes are hypothesized to coordinate information processing and transfer across brain areas. Among these oscillations, hippocampal sharp wave-ripple complexes (SPW-Rs are one of the most prominent. SPW-Rs occurring in the hippocampus are suggested to play essential roles in memory consolidation as well as information transfer to the neocortex. To-date, most of the knowledge about SPW-Rs comes from experimental studies averaging responses from neuronal populations monitored by conventional microelectrodes. In this work, we investigate spatiotemporal characteristics of SPW-Rs and how microelectrode size and distance influence SPW-R recordings using a biophysical model of hippocampus. We also explore contributions from neuronal spikes and synaptic potentials to SPW-Rs based on two different types of network activity. Our study suggests that neuronal spikes from pyramidal cells contribute significantly to ripples while high amplitude sharp waves mainly arise from synaptic activity. Our simulations on spatial reach of SPW-Rs show that the amplitudes of sharp waves and ripples exhibit a steep decrease with distance from the network and this effect is more prominent for smaller area electrodes. Furthermore, the amplitude of the signal decreases strongly with increasing electrode surface area as a result of averaging. The relative decrease is more pronounced when the recording electrode is closer to the source of the activity. Through simulations of field potentials across a high-density microelectrode array, we demonstrate the importance of finding the ideal spatial resolution for capturing SPW-Rs with great sensitivity. Our work provides insights on contributions from spikes and synaptic potentials to SPW-Rs and describes the effect of measurement configuration on LFPs to guide experimental studies towards improved SPW-R recordings.

  6. Synergies across the natural resources management fields in Southern Africa: Disaster Risk Reduction and One Health

    Clara Bocchino

    2013-02-01

    Full Text Available For various reasons, Southern Africa may be considered the playground as well as the thinking tank for many theories and practices in the natural resources management field. History has contributed to reshape conservation practices through colonial times, and recent wars have led to the relocation of people from their homelands and the appropriation by people of previously protected areas due to socio-economic pressures. Contemporary practices stemming from sustainable development have not yielded the expected results in resolving critical socio-economic stresses that impact on environmental health. Furthermore, human health has deteriorated in remote rural areas due to the failures of governance systems and the perpetration of non-participatory models for natural resources management, especially conservation. This paper seeks to explore how two relatively new approaches, Disaster Risk Reduction and One Health, can together tap into the theoretical and practical gaps left by previous paradigms in order to instill a sustainable development approach that can benefit both people and natural resources in remote and poor rural areas.

  7. Drift Reduction in Pedestrian Navigation System by Exploiting Motion Constraints and Magnetic Field

    Muhammad Ilyas

    2016-09-01

    Full Text Available Pedestrian navigation systems (PNS using foot-mounted MEMS inertial sensors use zero-velocity updates (ZUPTs to reduce drift in navigation solutions and estimate inertial sensor errors. However, it is well known that ZUPTs cannot reduce all errors, especially as heading error is not observable. Hence, the position estimates tend to drift and even cyclic ZUPTs are applied in updated steps of the Extended Kalman Filter (EKF. This urges the use of other motion constraints for pedestrian gait and any other valuable heading reduction information that is available. In this paper, we exploit two more motion constraints scenarios of pedestrian gait: (1 walking along straight paths; (2 standing still for a long time. It is observed that these motion constraints (called “virtual sensor”, though considerably reducing drift in PNS, still need an absolute heading reference. One common absolute heading estimation sensor is the magnetometer, which senses the Earth’s magnetic field and, hence, the true heading angle can be calculated. However, magnetometers are susceptible to magnetic distortions, especially in indoor environments. In this work, an algorithm, called magnetic anomaly detection (MAD and compensation is designed by incorporating only healthy magnetometer data in the EKF updating step, to reduce drift in zero-velocity updated INS. Experiments are conducted in GPS-denied and magnetically distorted environments to validate the proposed algorithms.

  8. Spatial patterns of cyanobacterial mat growth on sand ripples

    Mariotti, G.; Klepac-Ceraj, V.; Perron, J. T.; Bosak, T.

    2016-02-01

    Photosynthetic microbial mats produce organic matter, cycle nutrients, bind pollutants and stabilize sediment in sandy marine environments. Here, we investigate the influence of bedforms and wave motion on the growth rate, composition and spatial variability of microbial mats by growing cyanobacterial mats on a rippled bed of carbonate sand in a wave tank. The tank was forced with an oscillatory flow with velocities below the threshold for sediment motion yet able to induce a porewater flow within the sediment. Different spatial patterns developed in mats depending on the initial biochemistry of the water medium. When growing in a medium rich in nitrogen, phosphorous and micronutrients, mats grew faster on ripple troughs than on ripple crests. After two months, mats covered the bed surface uniformly, and the microbial communities on the crests and in the troughs had similar compositions. Differences in bed shear stress and nutrient availability between crests and troughs were not able to explain the faster growth in the troughs. We hypothesize that this growth pattern is due to a "strainer" effect, i.e. the suspended bacteria from the inoculum were preferentially delivered to troughs by the wave-induced porewater flow. In the experiments initiated in a medium previously used up by a microbial mat and thus depleted in nutrients, mats grew preferentially on the ripple crests. This spatial pattern persisted for nearly two years, and the microbial composition on troughs and crests was different. We attribute this pattern to the upwelling of porewater in the crests, which increased the delivery of nutrients from sediment to the cyanobacteria on the bed surface. Thus, the macroscopic patterns formed by photosynthetic microbial mats on sand ripples may be used to infer whether mats are nutrient-limited and whether they are recently colonized or older than a month.

  9. Neutron scattering studies of crude oil viscosity reduction with electric field

    Du, Enpeng

    topic. Dr. Tao with his group at Temple University, using his electro or magnetic rheological viscosity theory has developed a new technology, which utilizes electric or magnetic fields to change the rheology of complex fluids to reduce the viscosity, while keeping the temperature unchanged. After we successfully reduced the viscosity of crude oil with field and investigated the microstructure changing in various crude oil samples with SANS, we have continued to reduce the viscosity of heavy crude oil, bunker diesel, ultra low sulfur diesel, bio-diesel and crude oil and ultra low temperature with electric field treatment. Our research group developed the viscosity electrorheology theory and investigated flow rate with laboratory and field pipeline. But we never visualize this aggregation. The small angle neutron scattering experiment has confirmed the theoretical prediction that a strong electric field induces the suspended nano-particles inside crude oil to aggregate into short chains along the field direction. This aggregation breaks the symmetry, making the viscosity anisotropic: along the field direction, the viscosity is significantly reduced. The experiment enables us to determine the induced chain size and shape, verifies that the electric field works for all kinds of crude oils, paraffin-based, asphalt-based, and mix-based. The basic physics of such field induced viscosity reduction is applicable to all kinds of suspensions.

  10. The effect of biological cohesion on current ripple development

    Malarkey, Jonathan; Baas, Jaco H.; Hope, Julie

    2014-05-01

    Results are presented from laboratory experiments examining the role of biological cohesion, associated with Extra Polymeric Substances, on the development of current ripples. The results demonstrate the importance of biological cohesion compared to the effect of physical cohesion associated with clays in an otherwise sandy bed. FURTHER INFORMATION In fluvial and marine environments sediment transport is mainly dependent on the nature of the bed surface (rippled or flat) and the nature of cohesion in the bed. Cohesion can be either physical, as a result of the presence of clays, or biological as a result of the presence of organisms. In the case of the latter, biological cohesion occurs as a result of the presence of Extra Polymeric Substances (EPS) secreted by microorganisms. While it is known that EPS can dramatically increase the threshold of motion (Grant and Gust, 1987), comparatively little is known about the effect of EPS on ripple formation and development. The experiments described here seek to fill this gap. They also allow the effect of biological cohesion to be compared with that of physical cohesion from previous experiments (Baas et al., 2013). The experiments, which were conducted in a 10m flume at Bangor University, involved a current over a bed made of fine sand, with a median diameter of 0.148mm, and various amounts of xanthan gum, a proxy for naturally occurring EPS (Vardy et al., 2007). The hydrodynamic experimental conditions were matched very closely to those of Baas et al. (2013). The ripple dimensions were recorded through the glass side wall of the tank using time lapse photography. In the physical cohesion experiments of Baas et al. (2013) for clay contents up to 12%, the clay was very quickly winnowed out of the bed, leaving essentially clay-free ripples that developed at more or less the same rate as clean sand ripples. The resulting equilibrium ripples were essentially the same length as the clean sand ripples but reduced in height. By

  11. IMAGE ENHANCEMENT AND SPECKLE REDUCTION OF FULL POLARIMETRIC SAR DATA BY GAUSSIAN MARKOV RANDOM FIELD

    M. Mahdian

    2013-09-01

    Full Text Available In recent years, the use of Polarimetric Synthetic Aperture Radar (PolSAR data in different applications dramatically has been increased. In SAR imagery an interference phenomenon with random behavior exists which is called speckle noise. The interpretation of data encounters some troubles due to the presence of speckle which can be considered as a multiplicative noise affecting all coherent imaging systems. Indeed, speckle degrade radiometric resolution of PolSAR images, therefore it is needful to perform speckle filtering on the SAR data type. Markov Random Field (MRF has proven to be a powerful method for drawing out eliciting contextual information from remotely sensed images. In the present paper, a probability density function (PDF, which is fitted well with the PolSAR data based on the goodness-of-fit test, is first obtained for the pixel-wise analysis. Then the contextual smoothing is achieved with the MRF method. This novel speckle reduction method combines an advanced statistical distribution with spatial contextual information for PolSAR data. These two parts of information are combined based on weighted summation of pixel-wise and contextual models. This approach not only preserves edge information in the images, but also improves signal-to-noise ratio of the results. The method maintains the mean value of original signal in the homogenous areas and preserves the edges of features in the heterogeneous regions. Experiments on real medium resolution ALOS data from Tehran, and also high resolution full polarimetric SAR data over the Oberpfaffenhofen test-site in Germany, demonstrate the effectiveness of the algorithm compared with well-known despeckling methods.

  12. Economic feasibility of surface flow constructed (SFCW) wetlands for reduction of water pollution from agricultural fields in Denmark

    Gachango, Florence Gathoni; Pedersen, Søren Marcus; Kjaergaard, Charlotte

    2014-01-01

    Constructed wetlands have been proposed as cost effective and more targeted technologies in the reduction of nitrogen and phosphorous water pollution in drainage losses from agricultural fields in Denmark. Using two pig farms and one dairy farm situated in a pumped lowland catchment as study cases...

  13. Reduction of static field equation of Faddeev model to first order PDE

    Hirayama, Minoru; Shi Changguang

    2007-01-01

    A method to solve the static field equation of the Faddeev model is presented. For a special combination of the concerned field, we adopt a form which is compatible with the field equation and involves two arbitrary complex functions. As a result, the static field equation is reduced to a set of first order partial differential equations

  14. Intrinsic rippling enhances static non-reciprocity in a graphene metamaterial.

    Ho, Duc Tam; Park, Harold S; Kim, Sung Youb

    2018-01-18

    In mechanical systems, Maxwell-Betti reciprocity means that the displacement at point B in response to a force at point A is the same as the displacement at point A in response to the same force applied at point B. Because the notion of reciprocity is general, fundamental, and is operant for other physical systems like electromagnetics, acoustics, and optics, there is significant interest in understanding systems that are not reciprocal, or exhibit non-reciprocity. However, most studies on non-reciprocity have occurred in bulk-scale structures for dynamic problems involving time reversal symmetry. As a result, little is known about the mechanisms governing static non-reciprocal responses, particularly in atomically-thin two-dimensional materials like graphene. Here, we use classical atomistic simulations to demonstrate that out-of-plane ripples, which are intrinsic to graphene, enable significant, multiple orders of magnitude enhancements in the statically non-reciprocal response of graphene metamaterials. Specifically, we find that a striking interplay between the ripples and the stress fields that are induced in the metamaterials due to their geometry impacts the displacements that are transmitted by the metamaterial, thus leading to a significantly enhanced static non-reciprocal response. This study thus demonstrates the potential of two-dimensional mechanical metamaterials for symmetry-breaking applications.

  15. Factors Controlling In Situ Uranium and Technetium Bio-Reduction and Reoxidation at the NABIR Field Research Center

    Istok, Jonathan; Krumholz, L; McKinley, J.; Gu, B.

    2004-01-01

    Summary of Recent Field Testing: Extensive in situ (in ground) field testing using the push-pull method has demonstrated that indigenous microorganisms in the shallow ( ∼ 20 mM. Field data and laboratory studies suggest that U(IV) is likely oxidized by Fe(III) minerals produced by enzymatic Fe(II) oxidation or by Fe(II) oxidation by nitrite. U(IV) reoxidation rates (10-3 to 10-2 uM/hr) were somewhat larger than U(VI) reduction rates indicating that sustained nitrate removal will be necessary to maintain the stability of U(IV) in this environment

  16. Spectral Ripple Discrimination in Normal-Hearing Infants.

    Horn, David L; Won, Jong Ho; Rubinstein, Jay T; Werner, Lynne A

    Spectral resolution is a correlate of open-set speech understanding in postlingually deaf adults and prelingually deaf children who use cochlear implants (CIs). To apply measures of spectral resolution to assess device efficacy in younger CI users, it is necessary to understand how spectral resolution develops in normal-hearing children. In this study, spectral ripple discrimination (SRD) was used to measure listeners' sensitivity to a shift in phase of the spectral envelope of a broadband noise. Both resolution of peak to peak location (frequency resolution) and peak to trough intensity (across-channel intensity resolution) are required for SRD. SRD was measured as the highest ripple density (in ripples per octave) for which a listener could discriminate a 90° shift in phase of the sinusoidally-modulated amplitude spectrum. A 2 × 3 between-subjects design was used to assess the effects of age (7-month-old infants versus adults) and ripple peak/trough "depth" (10, 13, and 20 dB) on SRD in normal-hearing listeners (experiment 1). In experiment 2, SRD thresholds in the same age groups were compared using a task in which ripple starting phases were randomized across trials to obscure within-channel intensity cues. In experiment 3, the randomized starting phase method was used to measure SRD as a function of age (3-month-old infants, 7-month-old infants, and young adults) and ripple depth (10 and 20 dB in repeated measures design). In experiment 1, there was a significant interaction between age and ripple depth. The infant SRDs were significantly poorer than the adult SRDs at 10 and 13 dB ripple depths but adult-like at 20 dB depth. This result is consistent with immature across-channel intensity resolution. In contrast, the trajectory of SRD as a function of depth was steeper for infants than adults suggesting that frequency resolution was better in infants than adults. However, in experiment 2 infant performance was significantly poorer than adults at 20 d

  17. Source of spill ripple in the RF-KO slow-extraction method with FM and AM

    Noda, K; Shibuya, S; Muramatsu, M; Uesugi, T; Kanazawa, M; Torikoshi, M; Takada, E; Yamada, S

    2002-01-01

    The RF-knockout (RF-KO) slow-extraction method with frequency modulation (FM) and amplitude modulation (AM) has brought high-accuracy irradiation to the treatment of a cancer tumor moving with respiration, because of a quick response to beam start/stop. However, a beam spill extracted from a synchrotron ring through RF-KO slow-extraction has a huge ripple with a frequency of around 1 kHz related to the FM. The spill ripple will disturb the lateral dose distribution in the beam scanning methods. Thus, the source of the spill ripple has been investigated through experiments and simulations. There are two tune regions for the extraction process through the RF-KO method: the extraction region and the diffusion region. The particles in the extraction region can be extracted due to amplitude growth through the transverse RF field, only when its frequency matches with the tune in the extraction region. For a large chromaticity, however, the particles in the extraction region can be extracted through the synchrotron ...

  18. Theory of the rippling instability in toroidal devices

    Rogister, A.

    1985-04-01

    The theory of the rippling instability is developed for axisymmetric toroidal plasmas including ion viscosity and parallel electron heat conduction, but assuming that the growth rate is small compared to the wave angular frequency. Parallel electron heat conduction is stabilizing but ion viscosity broadens the instability domain. Under certain conditions, an important top-bottom asymmetry of the density fluctuation spectrum may arise. (orig./GG)

  19. Periodic sediment shift in migrating ripples influences benthic microbial activity

    Zlatanović, Sanja; Fabian, Jenny; Mendoza-Lera, Clara; Woodward, K. Benjamin; Premke, Katrin; Mutz, Michael

    2017-06-01

    Migrating bedforms have high levels of particulate organic matter and high rates of pore water exchange, causing them to be proposed as hot spots of carbon turnover in rivers. Yet, the shifting of sediments and associated mechanical disturbance within migrating bedforms, such as ripples, may stress and abrade microbial communities, reducing their activity. In a microcosm experiment, we replicated the mechanical disturbances caused by the periodic sediment shift within ripples under oligotrophic conditions. We assessed the effects on fungal and bacterial biomass ratio (F:B), microbial community respiration (CR), and bacterial production (BCP) and compared with stable undisturbed sediments. Interactions between periodic mechanical disturbance and sediment-associated particulate organic matter (POM) were tested by enriching sediments collected from migrating ripples with different qualities of POM (fish feces, leaf litter fragments and no addition treatments). F:B and BCP were affected by an interaction between mechanical disturbance and POM quality. Fish feces enriched sediments showed increased F:B and BCP compared to sediments with lower POM quality and responded with a decrease of F:B and BCP to sediment disturbance. In the other POM treatments F:B and BCP were not affected by disturbance. Microbial respiration was however reduced by mechanical disturbance to similar low activity levels regardless of POM qualities added, whereas fish feces enriched sediment showed short temporary boost of CR. With the worldwide proliferation of migrating sand ripples due to massive catchment erosion, suppressed mineralization of POM will increasingly affect stream metabolism, downstream transport of POM and carbon cycling from reach to catchment scale.

  20. Large wind ripples on Mars: A record of atmospheric evolution

    Lapotre, M. G. A.; Ewing, R. C.; Lamb, M. P.; Fischer, W. W.; Grotzinger, J. P.; Rubin, D. M.; Lewis, K. W.; Ballard, M. J.; Daybell, M.; Gupta, S.; Banham, S. G.; Bridges, N. T.; Des Marais, D. J.; Fraeman, A. A.; Grant, J. A.

    2016-01-01

    Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter– to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them ...

  1. Ripple compensation for a class-D amplifier

    Cox, Stephen M.; du Toit Mouton, Hendrik

    2015-01-01

    This paper presents the first detailed mathematical analysis of the ripple compensation technique for reducing audio distortion in a class-D amplifier with negative feedback. The amplifier converts a relatively low-frequency audio signal to a high-frequency train of rectangular pulses whose widths are slowly modulated according to the audio signal (pulse-width modulation, PWM). Distortion manifests itself through unwanted audio-frequency harmonics that arise in the output due to nonlinearitie...

  2. Oscillon dynamics and rogue wave generation in Faraday surface ripples.

    Xia, H; Maimbourg, T; Punzmann, H; Shats, M

    2012-09-14

    We report new experimental results which suggest that the generation of extreme wave events in the Faraday surface ripples is related to the increase in the horizontal mobility of oscillating solitons (oscillons). The analysis of the oscillon trajectories in a horizontal plane shows that at higher vertical acceleration, oscillons move chaotically, merge and form enclosed areas on the water surface. The probability of the formation of such craters, which precede large wave events, increases with the increase in horizontal mobility.

  3. A PIPO Boost Converter with Low Ripple and Medium Current Application

    Bandri, S.; Sofian, A.; Ismail, F.

    2018-04-01

    This paper presents a Parallel Input Parallel Output (PIPO) boost converter is proposed to gain power ability of converter, and reduce current inductors. The proposed technique will distribute current for n-parallel inductor and switching component. Four parallel boost converters implement on input voltage 20.5Vdc to generate output voltage 28.8Vdc. The PIPO boost converter applied phase shift pulse width modulation which will compare with conventional PIPO boost converters by using a similar pulse for every switching component. The current ripple reduction shows an advantage PIPO boost converter then conventional boost converter. Varies loads and duty cycle will be simulated and analyzed to verify the performance of PIPO boost converter. Finally, the unbalance of current inductor is able to be verified on four area of duty cycle in less than 0.6.

  4. Particle size reduction in debris flows: Laboratory experiments compared with field data from Inyo Creek, California

    Arabnia, O.; Sklar, L. S.; Mclaughlin, M. K.

    2014-12-01

    Rock particles in debris flows are reduced in size through abrasion and fracture. Wear of coarse sediments results in production of finer particles, which alter the bulk material rheology and influence flow dynamics and runout distance. Particle wear also affects the size distribution of coarse particles, transforming the initial sediment size distribution produced on hillslopes into that delivered to the fluvial channel network. A better understanding of the controls on particle wear in debris flows would aid in the inferring flow conditions from debris flow deposits, in estimating the initial size of sediments entrained in the flow, and in modeling debris flow dynamics and mapping hazards. The rate of particle size reduction with distance traveled should depend on the intensity of particle interactions with other particles and the flow boundary, and on rock resistance to wear. We seek a geomorphic transport law to predict rate of particle wear with debris flow travel distance as a function of particle size distribution, flow depth, channel slope, fluid composition and rock strength. Here we use four rotating drums to create laboratory debris flows across a range of scales. Drum diameters range from 0.2 to 4.0 m, with the largest drum able to accommodate up to 2 Mg of material, including boulders. Each drum has vanes along the boundary to prevent sliding. Initial experiments use angular clasts of durable granodiorite; later experiments will use less resistant rock types. Shear rate is varied by changing drum rotational velocity. We begin experiments with well-sorted coarse particle size distributions, which are allowed to evolve through particle wear. The fluid is initially clear water, which rapidly acquires fine-grained wear products. After each travel increment all coarse particles (mass > 0.4 g) are weighed individually. We quantify particle wear rates using statistics of size and mass distributions, and by fitting various comminution functions to the data

  5. Reducing torque ripples in permanent magnet synchronous motor

    Rihab Abdelmoula

    2017-09-01

    Full Text Available Permanent magnet synchronous motors (PMSMs are exceptionally promising thanks to their many advantages compared with other types of electrical machines. Indeed, PMSMs are characterized by their important torque density, light weight, high air gap flux density, high acceleration, high efficiency and strong power-to-weight ratio. A surface-mounted PMSM (SPMSM is used in this work. The SPMSM is built using a 2D finite element method (FEM. Cogging torque, torque ripples and back-EMF are examined during the design process in order to obtain sinusoidal back-EMF and to minimise torque ripples which are one of the major problems with PMSMs. Two procedures are used to reduce the cogging torque of SPMSM: the effect of slot opening and the influence of skewing the stator laminations. Cogging torque factor tc and the torque ripples factor tr have been calculated to compare the two configurations (open slots and closed slots. Then, the configuration with closed slots is utilised with skewing the stator laminations for different angle 0°, 10° and 15°.

  6. Ripple-Spreading Network Model Optimization by Genetic Algorithm

    Xiao-Bing Hu

    2013-01-01

    Full Text Available Small-world and scale-free properties are widely acknowledged in many real-world complex network systems, and many network models have been developed to capture these network properties. The ripple-spreading network model (RSNM is a newly reported complex network model, which is inspired by the natural ripple-spreading phenomenon on clam water surface. The RSNM exhibits good potential for describing both spatial and temporal features in the development of many real-world networks where the influence of a few local events spreads out through nodes and then largely determines the final network topology. However, the relationships between ripple-spreading related parameters (RSRPs of RSNM and small-world and scale-free topologies are not as obvious or straightforward as in many other network models. This paper attempts to apply genetic algorithm (GA to tune the values of RSRPs, so that the RSNM may generate these two most important network topologies. The study demonstrates that, once RSRPs are properly tuned by GA, the RSNM is capable of generating both network topologies and therefore has a great flexibility to study many real-world complex network systems.

  7. Reduction of interior sound fields in flexible cylinders by active vibration control

    Jones, J. D.; Fuller, C. R.

    1988-01-01

    The mechanisms of interior sound reduction through active control of a thin flexible shell's vibrational response are presently evaluated in view of an analytical model. The noise source is a single exterior acoustic monopole. The active control model is evaluated for harmonic excitation; the results obtained indicate spatially-averaged noise reductions in excess of 20 dB over the source plane, for acoustic resonant conditions inside the cavity.

  8. Validation of a clinical assessment of spectral-ripple resolution for cochlear implant users.

    Drennan, Ward R; Anderson, Elizabeth S; Won, Jong Ho; Rubinstein, Jay T

    2014-01-01

    Nonspeech psychophysical tests of spectral resolution, such as the spectral-ripple discrimination task, have been shown to correlate with speech-recognition performance in cochlear implant (CI) users. However, these tests are best suited for use in the research laboratory setting and are impractical for clinical use. A test of spectral resolution that is quicker and could more easily be implemented in the clinical setting has been developed. The objectives of this study were (1) To determine whether this new clinical ripple test would yield individual results equivalent to the longer, adaptive version of the ripple-discrimination test; (2) To evaluate test-retest reliability for the clinical ripple measure; and (3) To examine the relationship between clinical ripple performance and monosyllabic word recognition in quiet for a group of CI listeners. Twenty-eight CI recipients participated in the study. Each subject was tested on both the adaptive and the clinical versions of spectral ripple discrimination, as well as consonant-nucleus-consonant word recognition in quiet. The adaptive version of spectral ripple used a two-up, one-down procedure for determining spectral ripple discrimination threshold. The clinical ripple test used a method of constant stimuli, with trials for each of 12 fixed ripple densities occurring six times in random order. Results from the clinical ripple test (proportion correct) were then compared with ripple-discrimination thresholds (in ripples per octave) from the adaptive test. The clinical ripple test showed strong concurrent validity, evidenced by a good correlation between clinical ripple and adaptive ripple results (r = 0.79), as well as a correlation with word recognition (r = 0.7). Excellent test-retest reliability was also demonstrated with a high test-retest correlation (r = 0.9). The clinical ripple test is a reliable nonlinguistic measure of spectral resolution, optimized for use with CI users in a clinical setting. The test

  9. VALIDATION OF A CLINICAL ASSESSMENT OF SPECTRAL RIPPLE RESOLUTION FOR COCHLEAR-IMPLANT USERS

    Drennan, Ward. R.; Anderson, Elizabeth S.; Won, Jong Ho; Rubinstein, Jay T.

    2013-01-01

    Objectives Non-speech psychophysical tests of spectral resolution, such as the spectral-ripple discrimination task, have been shown to correlate with speech recognition performance in cochlear implant (CI) users (Henry et al., 2005; Won et al. 2007, 2011; Drennan et al. 2008; Anderson et al. 2011). However, these tests are best suited for use in the research laboratory setting and are impractical for clinical use. A test of spectral resolution that is quicker and could more easily be implemented in the clinical setting has been developed. The objectives of this study were 1) To determine if this new clinical ripple test would yield individual results equivalent to the longer, adaptive version of the ripple discrimination test; 2) To evaluate test-retest reliability for the clinical ripple measure; and 3) To examine the relationship between clinical ripple performance and monosyllabic word recognition in quiet for a group of CI listeners. Design Twenty-eight CI recipients participated in the study. Each subject was tested on both the adaptive and the clinical versions of spectral ripple discrimination, as well as CNC word recognition in quiet. The adaptive version of spectral ripple employed a 2-up, 1-down procedure for determining spectral ripple discrimination threshold. The clinical ripple test used a method of constant stimuli, with trials for each of 12 fixed ripple densities occurring six times in random order. Results from the clinical ripple test (proportion correct) were then compared to ripple discrimination thresholds (in ripples per octave) from the adaptive test. Results The clinical ripple test showed strong concurrent validity, evidenced by a good correlation between clinical ripple and adaptive ripple results (r=0.79), as well as a correlation with word recognition (r = 0.7). Excellent test-retest reliability was also demonstrated with a high test-retest correlation (r = 0.9). Conclusions The clinical ripple test is a reliable non-linguistic measure

  10. Capturing the complex behavior of hydraulic fracture stimulation through multi-physics modeling, field-based constraints, and model reduction

    Johnson, S.; Chiaramonte, L.; Cruz, L.; Izadi, G.

    2016-12-01

    Advances in the accuracy and fidelity of numerical methods have significantly improved our understanding of coupled processes in unconventional reservoirs. However, such multi-physics models are typically characterized by many parameters and require exceptional computational resources to evaluate systems of practical importance, making these models difficult to use for field analyses or uncertainty quantification. One approach to remove these limitations is through targeted complexity reduction and field data constrained parameterization. For the latter, a variety of field data streams may be available to engineers and asset teams, including micro-seismicity from proximate sites, well logs, and 3D surveys, which can constrain possible states of the reservoir as well as the distributions of parameters. We describe one such workflow, using the Argos multi-physics code and requisite geomechanical analysis to parameterize the underlying models. We illustrate with a field study involving a constraint analysis of various field data and details of the numerical optimizations and model reduction to demonstrate how complex models can be applied to operation design in hydraulic fracturing operations, including selection of controllable completion and fluid injection design properties. The implication of this work is that numerical methods are mature and computationally tractable enough to enable complex engineering analysis and deterministic field estimates and to advance research into stochastic analyses for uncertainty quantification and value of information applications.

  11. Reduction of radiation fields in the cooling water circuits of PWRs: a one-step or a multistep process

    Lassau, R.T.; Cherepakhov, G.; Smee, J.L.; Berger, J.

    1988-01-01

    A basic problem for nuclear power plants is the formation or radioactive corrosion products in crud particles and oxide films found mainly in the primary side of the reactor cooling water circuits. The activated corrosion products produce radiation fields, which are the major source of exposure for personnel during maintenance and operation of the system. As a health safeguard for personnel, and for the considerable economic benefit to a plant that can be realized by the reduction of radiation fields, the nuclear industry implements physical and chemical decontamination methods to dissolve oxide films and to assist in the removal of crud during plant shutdowns. These procedures impact on the scheduling of activities that must be accomplished before the reactor can be returned to full operation and are therefore carefully planned to minimize the time for decontamination while maximizing the radioactive field reductions. Of considerable importance to the industry, therefore, are procedures that might be implemented during normal reactor operation and as a reactor approaches shutdown that would assist in the removal of radioactive material while controlling the recontamination during reactor operation. A study program was therefore undertaken to compare radioactive field reductions and corrosion rates obtained from a dilute multistep chemical decontamination with data obtained from a single-step parametric cycling experiment on PWR materials

  12. Limitations on current ripple of the power supplies for the SSC bending magnets

    Lebedev, V.A.

    1993-01-01

    Noise and ripple in the bending magnets of large proton collider cause the beam emittance growth and the luminosity degradation. The emittance growth due to voltage ripple of the bending magnets power supplies is studied. The role of the collider transverse feedback system is shown to be very important to facilitate the requirements to value of ripple. The longitudinal emittance growth due to slow variations of power supply current is studied as well. 9 refs.; 15 figs

  13. Detailed Analysis of Torque Ripple in High Frequency Signal Injection based Sensor less PMSM Drives

    Ravikumar Setty A.

    2017-01-01

    Full Text Available High Frequency Signal Injection based techniques are robust and well proven to estimate the rotor position from stand still to low speed. However, Injected high frequency signal introduces, high frequency harmonics in the motor phase currents and results in significant Output Torque ripple. There is no detailed analysis exist in the literature, to study the effect of injected signal frequency on Torque ripple. Objective of this work is to study the Torque Ripple resulting from High Frequency signal injection in PMSM motor drives. Detailed MATLAB/Simulink simulations are carried to quantify the Torque ripple at different Signal frequencies.

  14. Nonlocal theory of electromagnetic wave decay into two electromagnetic waves in a rippled density plasma channel

    Sati, Priti; Tripathi, V. K.

    2012-01-01

    Parametric decay of a large amplitude electromagnetic wave into two electromagnetic modes in a rippled density plasma channel is investigated. The channel is taken to possess step density profile besides a density ripple of axial wave vector. The density ripple accounts for the momentum mismatch between the interacting waves and facilitates nonlinear coupling. For a given pump wave frequency, the requisite ripple wave number varies only a little w.r.t. the frequency of the low frequency decay wave. The radial localization of electromagnetic wave reduces the growth rate of the parametric instability. The growth rate decreases with the frequency of low frequency electromagnetic wave.

  15. Diffraction analysis of sidelobe characteristics of optical elements with ripple error

    Zhao, Lei; Luo, Yupeng; Bai, Jian; Zhou, Xiangdong; Du, Juan; Liu, Qun; Luo, Yujie

    2018-03-01

    The ripple errors of the lens lead to optical damage in high energy laser system. The analysis of sidelobe on the focal plane, caused by ripple error, provides a reference to evaluate the error and the imaging quality. In this paper, we analyze the diffraction characteristics of sidelobe of optical elements with ripple errors. First, we analyze the characteristics of ripple error and build relationship between ripple error and sidelobe. The sidelobe results from the diffraction of ripple errors. The ripple error tends to be periodic due to fabrication method on the optical surface. The simulated experiments are carried out based on angular spectrum method by characterizing ripple error as rotationally symmetric periodic structures. The influence of two major parameter of ripple including spatial frequency and peak-to-valley value to sidelobe is discussed. The results indicate that spatial frequency and peak-to-valley value both impact sidelobe at the image plane. The peak-tovalley value is the major factor to affect the energy proportion of the sidelobe. The spatial frequency is the major factor to affect the distribution of the sidelobe at the image plane.

  16. Differentiation of specific ripple patterns helps to identify epileptogenic areas for surgical procedures.

    Kerber, Karolin; Dümpelmann, Matthias; Schelter, Björn; Le Van, Pierre; Korinthenberg, Rudolf; Schulze-Bonhage, Andreas; Jacobs, Julia

    2014-07-01

    High frequency oscillations (HFOs) at 80-500 Hz are promising markers of epileptic areas. Several retrospective studies reported that surgical removal of areas generating HFOs was associated with a good seizure outcome. Recent reports suggested that ripple (80-200 Hz) HFO patterns co-existed with different background EEG activities. We hypothesized that the coexisting background EEG pattern may distinguish physiological from epileptic ripples. Rates of HFOs were analyzed in intracranial EEG recordings of 22 patients. Additionally, ripple patterns were classified for each channel depending either as coexisting with a flat or oscillatory background activity. A multi-variate analysis was performed to determine whether removal of areas showing the above EEG markers correlated with seizure outcome. Removal of areas generating high rates of 'fast ripples (>200 Hz)' and 'ripples on a flat background activity' showed a significant correlation with a seizure-free outcome. In contrast, removal of high rates of 'ripples' or 'ripple patterns in a continuously oscillating background' was not significantly associated with seizure outcome. Ripples occurring in an oscillatory background activity may be suggestive of physiological activity, while those on a flat background reflect epileptic activity. Consideration of coexisting background patterns may improve the delineation of the epileptogenic areas using ripple oscillations. Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  17. Observations of the Hubble Deep Field with the Infrared Space Observatory .1. Data reduction, maps and sky coverage

    Serjeant, S.B.G.; Eaton, N.; Oliver, S.J.

    1997-01-01

    We present deep imaging at 6.7 and 15 mu m from the CAM instrument on the Infrared Space Observatory (ISO), centred on the Hubble Deep Field (HDF). These are the deepest integrations published to date at these wavelengths in any region of sky. We discuss the observational strategy and the data...... reduction. The observed source density appears to approach the CAM confusion limit at 15 mu m, and fluctuations in the 6.7-mu m sky background may be identifiable with similar spatial fluctuations in the HDF galaxy counts. ISO appears to be detecting comparable field galaxy populations to the HDF, and our...

  18. Reduction of truncation errors in planar, cylindrical, and partial spherical near-field antenna measurements

    Cano-Fácila, Francisco José; Pivnenko, Sergey; Sierra-Castaner, Manuel

    2012-01-01

    spectrum (PWS) is reliable only within a known region. The second domain is the field distribution over the antenna under test (AUT) plane in which the desired field is assumed to be concentrated on the antenna aperture. The method can be applied to any scanning geometry, but in this paper, only the planar...

  19. Green functions and dimensional reduction of quantum fields on product manifolds

    Haba, Z

    2008-01-01

    We discuss Euclidean Green functions on product manifolds P=N x M. We show that if M is compact and N is not compact then the Euclidean field on P can be approximated by its zero mode which is a Euclidean field on N. We estimate the remainder of this approximation. We show that for large distances on N the remainder is small. If P=R D-1 x S β , where S β is a circle of radius β, then the result reduces to the well-known approximation of the D-dimensional finite temperature quantum field theory by (D - 1)-dimensional one in the high-temperature limit. Analytic continuation of Euclidean fields is discussed briefly

  20. Reduction of momentum transfer rates by parallel electric fields: A two-fluid demonstration

    Delamere, P.A.; Stenbaek-Nielsen, H.C.; Otto, A.

    2002-01-01

    Momentum transfer between an ionized gas cloud moving relative to an ambient magnetized plasma is a general problem in space plasma physics. Obvious examples include the Io-Jupiter interaction, comets, and coronal mass ejections. Active plasma experiments have demonstrated that momentum transfer rates associated with Alfven wave propagation are poorly understood. Barium injection experiments from the Combined Release and Radiation Effects Satellite (CRRES) have shown that dense ionized clouds are capable of ExB drifting over large distances perpendicular to the magnetic field. The CRRES 'skidding' distances were much larger than predicted by magnetohydrodynamic theory and it has been proposed that parallel electric fields were a key component in the skidding phenomenon. A two-fluid code was used to demonstrate the role of parallel electric fields in reducing momentum transfer between two distinct plasma populations. In this study, a dense plasma was initialized moving relative to an ambient plasma and perpendicular to B. Parallel electric fields were introduced via a friction term in the electron momentum equation and the collision frequency was scaled in proportion to the field-aligned current density. The simulation results showed that parallel electric fields decreased the decelerating magnetic tension force on the plasma cloud through a magnetic diffusion/reconnection process

  1. On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

    V. V. Lobzin

    2008-09-01

    Full Text Available A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 fBiBi, where fBi is the proton gyrofrequency upstream of the shock, and shows that the probability to observe such a nonstationarity increases with Mach number. The profiles observed aboard different spacecraft and the dominating frequencies of the periodicities are usually different. Hence nonstationarity and/or rippling seem to be rather irregular both in space and time rather than resembling a quasiregular wave propagating on the shock surface.

  2. On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

    V. V. Lobzin

    2008-09-01

    Full Text Available A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 fBirippling seem to be rather irregular both in space and time rather than resembling a quasiregular wave propagating on the shock surface.

  3. Enhanced THz radiation generation by photo-mixing of tophat lasers in rippled density plasma with a planar magnetostatic wiggler and s-parameter

    Abedi-Varaki, M.

    2018-02-01

    In this paper, the effects of planar magnetostatic wiggler and s-parameter on the terahertz (THz) radiation generation through rippled plasma have been investigated. Efficient THz radiation generation by photo-mixing of tophat lasers for rippled density plasma in the presence of the wiggler field has been presented. Fundamental equations for the analysis of the non-linear current density and THz radiation generation by wiggler magnetostatic field have been derived. It is shown that for the higher order of the tophat lasers, the values of THz amplitude are greater. In fact, the higher order of the tophat lasers has a sharp gradient in the intensity of lasers, which leads to a stronger nonlinear ponderomotive force and, consequently, a stronger current density. In addition, it is seen that by increasing s-parameter, the normalized transverse profile becomes more focused near the axis of y. Furthermore, it is observed that the normalized laser efficiency has a decreasing trend with increasing normalized THz frequency for different values of the wiggler field. Also, it is shown that by employing a greater order of the tophat lasers and a stronger wiggler field, the efficiency of order of 30% can be achieved. Moreover, it is found that we can control focus and intensity of THz radiation emitted in rippled plasma by choosing the appropriate order of the tophat lasers and tuning of the wiggler field.

  4. Rippled shock front solutions for testing hydrodynamic stability simulations

    Munro, D.H.

    1989-01-01

    The response of a shock front to arbitrary small perturbations can be calculated analytically. Such rippled shock front solutions are useful for determining the accuracy of hydrodynamic simulation codes such as LASNEX [Comments Plasma Phys. Controlled Fusion 2, 51 (1977)], which are used to compute perturbation growth in inertial fusion targets. The LASNEX fractional errors are of order κ 2 L 2 , where κ is the transverse wavenumber of the perturbation, and L is the largest zone dimension. Numerical errors are about 25% for a calculation using 26 zones per transverse wavelength

  5. Reduction of the Earth's magnetic field inhibits growth rates of model cancer cell lines.

    Martino, Carlos F; Portelli, Lucas; McCabe, Kevin; Hernandez, Mark; Barnes, Frank

    2010-12-01

    Small alterations in static magnetic fields have been shown to affect certain chemical reaction rates ex vivo. In this manuscript, we present data demonstrating that similar small changes in static magnetic fields between individual cell culture incubators results in significantly altered cell cycle rates for multiple cancer-derived cell lines. This change as assessed by cell number is not a result of apoptosis, necrosis, or cell cycle alterations. While the underlying mechanism is unclear, the implications for all cell culture experiments are clear; static magnetic field conditions within incubators must be considered and/or controlled just as one does for temperature, humidity, and carbon dioxide concentration. Copyright © 2010 Wiley-Liss, Inc.

  6. Reduction of Marine Magnetic Data for Modeling the Main Field of the Earth

    Baldwin, R. T.; Ridgway, J. R.; Davis, W. M.

    1992-01-01

    The marine data set archived at the National Geophysical Data Center (NGDC) consists of shipborne surveys conducted by various institutes worldwide. This data set spans four decades (1953, 1958, 1960-1987), and contains almost 13 million total intensity observations. These are often less than 1 km apart. These typically measure seafloor spreading anomalies with amplitudes of several hundred nanotesla (nT) which, since they originate in the crust, interfere with main field modeling. The source for these short wavelength features are confined within the magnetic crust (i.e., sources above the Curie isotherm). The main field, on the other hand, is of much longer wavelengths and originates within the earth's core. It is desirable to extract the long wavelength information from the marine data set for use in modeling the main field. This can be accomplished by averaging the data along the track. In addition, those data which are measured during periods of magnetic disturbance can be identified and eliminated. Thus, it should be possible to create a data set which has worldwide data distribution, spans several decades, is not contaminated with short wavelengths of the crustal field or with magnetic storm noise, and which is limited enough in size to be manageable for the main field modeling. The along track filtering described above has proved to be an effective means of condensing large numbers of shipborne magnetic data into a manageable and meaningful data set for main field modeling. Its simplicity and ability to adequately handle varying spatial and sampling constraints has outweighed consideration of more sophisticated approaches. This filtering technique also provides the benefits of smoothing out short wavelength crustal anomalies, discarding data recorded during magnetically noisy periods, and assigning reasonable error estimates to be used in the least square modeling. A useful data set now exists which spans 1953-1987.

  7. Dimensional reduction of the Standard Model coupled to a new singlet scalar field

    Brauner, Tomáš [Faculty of Science and Technology, University of Stavanger,N-4036 Stavanger (Norway); Tenkanen, Tuomas V.I. [Department of Physics and Helsinki Institute of Physics,P.O. Box 64, FI-00014 University of Helsinki (Finland); Tranberg, Anders [Faculty of Science and Technology, University of Stavanger,N-4036 Stavanger (Norway); Vuorinen, Aleksi [Department of Physics and Helsinki Institute of Physics,P.O. Box 64, FI-00014 University of Helsinki (Finland); Weir, David J. [Faculty of Science and Technology, University of Stavanger,N-4036 Stavanger (Norway); Department of Physics and Helsinki Institute of Physics,P.O. Box 64, FI-00014 University of Helsinki (Finland)

    2017-03-01

    We derive an effective dimensionally reduced theory for the Standard Model augmented by a real singlet scalar. We treat the singlet as a superheavy field and integrate it out, leaving an effective theory involving only the Higgs and SU(2){sub L}×U(1){sub Y} gauge fields, identical to the one studied previously for the Standard Model. This opens up the possibility of efficiently computing the order and strength of the electroweak phase transition, numerically and nonperturbatively, in this extension of the Standard Model. Understanding the phase diagram is crucial for models of electroweak baryogenesis and for studying the production of gravitational waves at thermal phase transitions.

  8. Temperature-controlled structure and kinetics of ripple phases in one- and two-component supported lipid bilayers

    Kaasgaard, Thomas; Leidy, Chad; Crowe, J.H.

    2003-01-01

    Temperature-controlled atomic force microscopy (AFM) has been used to visualize and study the structure and kinetics of ripple phases in one-component dipalmitoylphosphaticlylcholine (DPPC) and two-component dimyristoylphosphatidylcholine-distearoylphosphatidylcholine (DMPC-DSPC) lipid bilayers....... The lipid bilayers are mica-supported double bilayers in which ripple-phase formation occurs in the top bilayer. In one-component DPPC lipid bilayers, the stable and metastable ripple phases were observed. In addition, a third ripple structure with approximately twice the wavelength of the metastable...... ripples was seen. From height profiles of the AFM images, estimates of the amplitudes of the different ripple phases are reported. To elucidate the processes of ripple formation and disappearance, a ripple-phase DPPC lipid bilayer was taken through the pretransition in the cooling and the heating...

  9. The bad public decisions’ ripple – setting the education off balance. Marketing simulation – education design decisions

    Ioana Teodora DINU

    2012-08-01

    Full Text Available The research goes in-depth of a highly debated public decision on education due to its topicality and suddenly enforced changes. The analysis argues that the perceptions of the groups which are mostly impacted by the changes contradict the effects targeted by the Law. These perceptions are tested in a split focus group (in three target subgroups – teaching staff, students and secretarial staff and both the initial observations and the ones filtered through the field literature prove a strong burden on the higher education system, which will only multiply like ripples in the context of the current economic situation.

  10. Biofeedback for stress reduction: towards a brigth future for a revitalized field

    Van den Broek, E.L.; Westerink, J.H.D.

    2012-01-01

    Stress has recently been baptized as the black death of the 21st century, which illustrates its threat to current health standards. Thisarticle proposes biofeedback systems as a means to reduce stress. Aconcise state-ofthe-art introduction on biofeedback systems is given. The field of mental health

  11. Soot reduction under DC electric fields in counterflow non-premixed laminar ethylene flames

    Park, Daegeun; Choi, Byungchul; Cha, Min; Chung, Suk-Ho

    2014-01-01

    terminal to a lower (fuel) and upper (oxidizer) nozzle, respectively. We applied direct current (DC) potentials in a range of -5 kV < Vdc < 5 kV. Uniform electric fields were then generated in the gap between the two nozzles. The experimental

  12. Biofeedback systems for stress reduction: Towards a Bright Future for a Revitalized Field

    van den Broek, Egon; Westerink, Joyce H.D.M.; Conchon, E.; Correia, C.; Fred, A.; Gamboa, H.

    2012-01-01

    Stress has recently been baptized as the black death of the 21st century, which illustrates its threat to current health standards. This article proposes biofeedback systems as a means to reduce stress. A concise state-ofthe-art introduction on biofeedback systems is given. The field of mental

  13. Biofeedback systems for stress reduction : Towards a bright future for a revitalized field

    Broek, E.L. van den; Westerink, J.H.D.M.

    2012-01-01

    Stress has recently been baptized as the black death of the 21st century, which illustrates its threat to current health standards. This article proposes biofeedback systems as a means to reduce stress. A concise state-of-the-art introduction on biofeedback systems is given. The field of mental

  14. Resonant Mode Reduction in Radiofrequency Volume Coils for Ultrahigh Field Magnetic Resonance Imaging

    Xiaoliang Zhang

    2011-07-01

    Full Text Available In a multimodal volume coil, only one mode can generate homogeneous Radiofrequency (RF field for Magnetic Resonance Imaging. The existence of other modes may increase the volume coil design difficulties and potentially decreases coil performance. In this study, we introduce common-mode resonator technique to high and ultrahigh field volume coil designs to reduce the resonant mode while maintain the homogeneity of the RF field. To investigate the design method, the common-mode resonator was realized by using a microstrip line which was split along the central to become a pair of parallel transmission lines within which common-mode currents exist. Eight common-mode resonators were placed equidistantly along the circumference of a low loss dielectric cylinder to form a volume coil. Theoretical analysis and comparison between the 16-strut common-mode volume coil and a conventional 16-strut volume coil in terms of RF field homogeneity and efficiency was performed using Finite-Difference Time-Domain (FDTD method at 298.2 MHz. MR imaging experiments were performed by using a prototype of the common-mode volume coil on a whole body 7 Tesla scanner. FDTD simulation results showed the reduced number of resonant modes of the common-mode volume coil over the conventional volume coil, while the RF field homogeneity of the two type volume coils was kept at the same level. MR imaging of a water phantom and a kiwi fruit showing the feasibility of the proposed method for simplifying the volume coil design is also presented.

  15. Missing lynx and trophic cascades in food webs: A reply to Ripple et al.

    John R. Squires; Nicholas J. DeCesare; Mark Hebblewhite; Joel Berger

    2012-01-01

    Ripple et al. (2011) proposed a hypothesis that the recovery of gray wolves (Canis lupus) may positively affect the viability of threatened Canada lynx (Lynx canadensis) populations in the contiguous United States through indirect species interactions. Ripple et al. (2011) proposed 2 key trophic linkages connecting wolf restoration with lynx recovery. First, recovering...

  16. Reynolds Number Effect on Spatial Development of Viscous Flow Induced by Wave Propagation Over Bed Ripples

    Dimas, Athanassios A.; Kolokythas, Gerasimos A.

    Numerical simulations of the free-surface flow, developing by the propagation of nonlinear water waves over a rippled bottom, are performed assuming that the corresponding flow is two-dimensional, incompressible and viscous. The simulations are based on the numerical solution of the Navier-Stokes equations subject to the fully-nonlinear free-surface boundary conditions and appropriate bottom, inflow and outflow boundary conditions. The equations are properly transformed so that the computational domain becomes time-independent. For the spatial discretization, a hybrid scheme is used where central finite-differences, in the horizontal direction, and a pseudo-spectral approximation method with Chebyshev polynomials, in the vertical direction, are applied. A fractional time-step scheme is used for the temporal discretization. Over the rippled bed, the wave boundary layer thickness increases significantly, in comparison to the one over flat bed, due to flow separation at the ripple crests, which generates alternating circulation regions. The amplitude of the wall shear stress over the ripples increases with increasing ripple height or decreasing Reynolds number, while the corresponding friction force is insensitive to the ripple height change. The amplitude of the form drag forces due to dynamic and hydrostatic pressures increase with increasing ripple height but is insensitive to the Reynolds number change, therefore, the percentage of friction in the total drag force decreases with increasing ripple height or increasing Reynolds number.

  17. Evidence of across-channel processing for spectral-ripple discrimination in cochlear implant listeners a

    Ho Won, Jong; Jones, Gary L.; Drennan, Ward R.; Jameyson, Elyse M.; Rubinstein, Jay T.

    2011-01-01

    Spectral-ripple discrimination has been used widely for psychoacoustical studies in normal-hearing, hearing-impaired, and cochlear implant listeners. The present study investigated the perceptual mechanism for spectral-ripple discrimination in cochlear implant listeners. The main goal of this study was to determine whether cochlear implant listeners use a local intensity cue or global spectral shape for spectral-ripple discrimination. The effect of electrode separation on spectral-ripple discrimination was also evaluated. Results showed that it is highly unlikely that cochlear implant listeners depend on a local intensity cue for spectral-ripple discrimination. A phenomenological model of spectral-ripple discrimination, as an “ideal observer,” showed that a perceptual mechanism based on discrimination of a single intensity difference cannot account for performance of cochlear implant listeners. Spectral modulation depth and electrode separation were found to significantly affect spectral-ripple discrimination. The evidence supports the hypothesis that spectral-ripple discrimination involves integrating information from multiple channels. PMID:21973363

  18. Effect of buck driver ripple on BER performance in visible light communication using LED

    Deng, X.; Linnartz, J.P.M.G.; Arulandu, K.; Zhou, G.; Wu, Y.

    2015-01-01

    This paper analyses the communication performance for visible light communication (VLC) with Manchester encoded amplitude modulation. In particular, it considers the ripple generated by the LED driver as an important noise contribution for VLC. The ripple depends on the oscillation frequency of the

  19. Evidence of across-channel processing for spectral-ripple discrimination in cochlear implant listeners.

    Won, Jong Ho; Jones, Gary L; Drennan, Ward R; Jameyson, Elyse M; Rubinstein, Jay T

    2011-10-01

    Spectral-ripple discrimination has been used widely for psychoacoustical studies in normal-hearing, hearing-impaired, and cochlear implant listeners. The present study investigated the perceptual mechanism for spectral-ripple discrimination in cochlear implant listeners. The main goal of this study was to determine whether cochlear implant listeners use a local intensity cue or global spectral shape for spectral-ripple discrimination. The effect of electrode separation on spectral-ripple discrimination was also evaluated. Results showed that it is highly unlikely that cochlear implant listeners depend on a local intensity cue for spectral-ripple discrimination. A phenomenological model of spectral-ripple discrimination, as an "ideal observer," showed that a perceptual mechanism based on discrimination of a single intensity difference cannot account for performance of cochlear implant listeners. Spectral modulation depth and electrode separation were found to significantly affect spectral-ripple discrimination. The evidence supports the hypothesis that spectral-ripple discrimination involves integrating information from multiple channels. © 2011 Acoustical Society of America

  20. Reaction-Based Transport Modeling of Iron Reduction and Uranium Immobilization at Area 2 of the NABIR Field Research Center

    Yeh, Gour-Tsyh

    2006-01-01

    This research project (started Fall 2004) was funded by a grant to The Pennsylvania State University, University of Central Florida, and The University of Alabama in the Integrative Studies Element of the NABIR Program (DE-FG04-ER63914/63915/63196). Dr. Eric Roden, formerly at The University of Alabama, is now at the University of Wisconsin - Madison. Our project focuses on the development of a mechanistic understanding and quantitative models of coupled Fe(III)/U(VI) reduction in FRC Area 2 sediments. This work builds on our previous studies of microbial Fe(III) and U(VI) reduction, and is directly aligned with the Scheibe et al. NABIR FRC Field Project at Area 2

  1. External Magnetic Field Reduction Techniques for the Advanced Stirling Radioisotope Generator

    Niedra, Janis M.; Geng, Steven M.

    2013-01-01

    Linear alternators coupled to high efficiency Stirling engines are strong candidates for thermal-to-electric power conversion in space. However, the magnetic field emissions, both AC and DC, of these permanent magnet excited alternators can interfere with sensitive instrumentation onboard a spacecraft. Effective methods to mitigate the AC and DC electromagnetic interference (EMI) from solenoidal type linear alternators (like that used in the Advanced Stirling Convertor) have been developed for potential use in the Advanced Stirling Radioisotope Generator. The methods developed avoid the complexity and extra mass inherent in data extraction from multiple sensors or the use of shielding. This paper discusses these methods, and also provides experimental data obtained during breadboard testing of both AC and DC external magnetic field devices.

  2. Real-time observation of FIB-created dots and ripples on GaAs

    Rose, F; Fujita, H; Kawakatsu, H

    2008-01-01

    We report a phenomenological study of Ga dots and ripples created by a focused ion beam (FIB) on the GaAs(001) surface. Real-time observation of dot diffusion and ripple formation was made possible by recording FIB movies. In the case of FIB irradiation with a 40 nA current of Ga + ions accelerated under 40 kV with an incidence angle of θ = 30 0 , increasing ion dose gives rise to three different regimes. In Regime 1, dots with lateral sizes in the range 50-460 nm are formed. Dots diffuse under continuous sputtering. In Regime 2, dots self-assemble into Bradley and Harper (BH) type ripples with a pseudo-period of λ = 1150 ± 25 nm. In Regime 3, ripples are eroded and the surface topology evolves into microplanes. In the case of normal incidence, FIB sputtering leads only to the formation of dots, without surface rippling

  3. Mean field approximation for the kinetics of the selective catalytic reduction of NO by ammonia

    Santos, M.; Bodanese, J.P. [Centro de Ensino Sao Jose, Universidade do Vale do Itajai (Brazil); S. Grandi, B.C. da [Departamento de Fisica, Universidade Federal de Santa Catarina, Florianopolis (Brazil)

    2007-04-15

    In this work we study a catalytic reaction model among three monomers in order to understand the chemical kinetics of the selective catalytic reduction of nitrogen oxide by ammonia (4NO+4NH{sub 3}+O{sub 2}{yields}4N{sub 2}+6H{sub 2}O). Our model takes into account the formation of the intermediate species in the global scheme of the reaction. In order to determine the dynamical behaviour of the model we used single site approximation method. In this approach we have observed that, depending on the values of the control parameters, the model presents an active or an inactive phase. In fact, the dynamical phase diagram of the model exhibits a first order line separating these two phases. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Trends in the Reduction of Inequalities in the Field of Education: Empirical Investigation from African Data

    Amaghouss JABRANE

    2015-12-01

    Full Text Available This paper attaches particular attention to the unequal dimension of education in Africa using several indicators. To account for the dynamics of the reduction of inequalities, we estimated the validity of the Kuznets curve of education. The results suggest that the shape of the Kuznets curve depends on the measure used to approximate inequality. Indeed, the assumption of the Kuznets curve is checked if the standard deviation of schooling is used. For its part, the Gini index maintains a significant negative relationship with the average number of years of study. The results also applies to all African countries and for each group of countries with a significant advance in reducing inequalities initiated by English speaking countries.

  5. High speed non-latching squid binary ripple counter

    Silver, A.H.; Phillips, R.R.; Sandell, R.D.

    1985-01-01

    High speed, single flux quantum (SFQ) binary scalers are important components in superconducting analog-to-digital converters (ADC). This paper reviews the concept for a SQUID ADC and the design of an SFQ binary ripple counter, and reports the simulation of key components, and fabrication and performance of non-latching SQUID scalers and SFQ binary ripple counters. The SQUIDs were fabricated with Nb/Nb 2 O 5 /PbIn junctions and interconnected by monolithic superconducting transmission lines and isolation resistors. Each SQUID functioned as a bistable flip-flop with the input connected to the center of the device and the output across one junction. All junctions were critically damped to optimize the pulse response. Operation was verified by observing the dc I-V curves of successive SQUIDs driven by a cw pulse train generated on the same chip. Each SQUID exhibited constant-voltage current steps at 1/2 the voltage of the preceding device as expected from the Josephson voltage-to-frequency relation. Steps were observed only for the same voltage polarity of successive devices and for proper phase bias of the SQUID. Binary frequency division was recorded up to 40GHz for devices designed to operate to 28GHz

  6. Reduction of thermal expansion in Z-pinches by electron beam assisted magnetic field generation

    Heikkinen, J.A.; Karttunen, S.J.

    1989-01-01

    Weak radial expansion of a Z-pinch plasma column during its strong initial ohmic heating phase is expected when the generation of a confining magnetic field is assisted by a correctly formed electron beam pulse. Appropriate one-dimensional magnetohydrodynamic equations are numerically solved, and the observed increase of plasma radius as a function of time for various discharge parameters is compared to a normal Z-pinch discharge initiation. (author)

  7. Reduction of the Poincare gauge field equations by means of a duality rotation

    Mielke, E.W.

    1981-10-01

    A rather general procedure is developed in order to reduce the two field equations of the Poincare gauge theory of gravity by a modified ansatz for the curvature tensor involving double duality. In the case of quasi-linear Lagrangians of the Yang-Mills type it is shown that non-trivial torsion solutions with duality properties necessarily ''live'' on an Einstein space as metrical background. (author)

  8. Biological reduction of uranium-From the laboratory to the field

    Dullies, Frank; Lutze, Werner; Gong, Weiliang; Nuttall, H. Eric

    2010-01-01

    The chemical and biological processes underlying in situ bioremediation of uranium-contaminated groundwater have been studied in the laboratory and in the field. This article focuses on the long-term stability of uraninite (UO 2 ) in the underground. A large tailings pond, 'Daenkritz 1' in Germany, was selected for this investigation. A single-pass flow-through experiment was run in a 100-liter column: bioremediation for 1 year followed by infiltration of tap water (2.5 years) saturated with oxygen, sufficient to oxidize the precipitated uraninite in two months. Instead, only 1 wt.% uraninite was released over 2.4 years at concentrations typically less than 20 μg/L. Uraninite was protected against oxidation by the mineral mackinawite (FeS 0.9 ), a considerable amount of which had formed, together with uraninite. A confined field test was conducted adjacent to the tailings pond, which after bio-stimulation showed similarly encouraging results as in the laboratory. Taking Daenkritz 1 as an example we show that in situ bioremediation can be a viable option for long-term site remediation, if the process is designed based on sufficient laboratory and field data. The boundary conditions for the site in Germany are discussed.

  9. Reduction of protease activity in milk by continuous flow high-intensity pulsed electric field treatments.

    Bendicho, S; Barbosa-Cánovas, G V; Martín, O

    2003-03-01

    High-intensity pulsed electric field (HIPEF) is a non-thermal food processing technology that is currently being investigated to inactivate microorganisms and certain enzymes, involving a limited increase of food temperature. Promising results have been obtained on the inactivation of microbial enzymes in milk when suspended in simulated milk ultrafiltrate. The aim of this study was to evaluate the effectiveness of continuous HIPEF equipment on inactivating a protease from Bacillus subtilis inoculated in milk. Samples were subjected to HIPEF treatments of up to 866 micros of squared wave pulses at field strengths from 19.7 to 35.5 kV/cm, using a treatment chamber that consisted of eight colinear chambers connected in series. Moreover, the effects of different parameters such as pulse width (4 and 7 micros), pulse repetition rates (67, 89, and 111 Hz), and milk composition (skim and whole milk) were tested. Protease activity decreased with increased treatment time or field strength and pulse repetition rate. Regarding pulse width, no differences were observed between 4 and 7 micros pulses when total treatment time was considered. On the other hand, it was observed that milk composition affected the results since higher inactivation levels were reached in skim than in whole milk. The maximum inactivation (81%) was attained in skim milk after an 866-micros treatment at 35.5 kV/cm and 111 Hz.

  10. Wave-induced ripple development in mixed clay-sand substrates

    Wu, Xuxu; Parsons, Daniel; Baas, Jaco H.; Mouazé, Dominique; McLelland, Stuart; Amoudry, Laurent; Eggenhuisen, Jorris; Cartigny, Matthieu; Ruessink, Gerben

    2016-04-01

    This paper reports on a series of experiments that aim to provide a fuller understanding of ripple development within clay-sand mixture substrates under oscillatory flow conditions. The work was conducted in the Total Environment Simulator at the University of Hull and constituted 6 separate runs, in which 5 runs were conducted under identical sets of regular waves (an additional run was conducted under irregular waves, but is not discussed in present paper). The bed content was systematically varied in its composition ranging from a pure sand bed through to a bed comprising 7.4% clay. A series of state-of-the-art measurements were employed to quantify interactions of near-bed hydrodynamics, sediment transport, and turbulence over rippled beds formed by wave action, during and after, each run. The experimental results demonstrate the significant influence of the amount of cohesive clay materials in the substrate on ripple evolution under waves. Most importantly, addition of clay in the bed dramatically slowed down the rate of ripple development and evolution. The equilibrium time of each run increased exponentially from 30 minutes under the control conditions of a pure sand bed, rising to ~350 minutes for the bed with the highest fraction of clay. The paper discusses the slower ripple growth rates with higher cohesive fractions, via an influence on critical shear, but highlights that the end equilibrium size of ripples is found to be independent of increasing substrate clay fraction. The suspended particles mass (SPM) concentration indicates that clay particles were suspended and winnowed by wave action. Additionally, laser granulometry of the final substrates verified that ripple crests were composed of pure sand layers that were absent at ripple troughs, reflecting a relatively higher winnowing efficiency at wave ripples crest. The winnowing process and its efficiency is inexorably linked to wave ripple development and evolution. The implications of the results

  11. Dose reduction through gridless technique in digital full-field mammography

    Diekmann, F.; Diekmann, S.; Berzeg, S.; Blick, U.; Fischer, T.; Hamm, B.

    2003-01-01

    Purpose: To determine the role of the scatter grid in digital full-field mammography with respect to image quality and dose and to compare the experimental results with initial clinical experience. Materials and Methods: A phantom consisting of 205 fields that enclose gold dots of different thickness and size (CD-Mam phantom, Medical Department, Nijmegen, Netherlands) was used for digital full-field mammography with the conventional grid module and a special gridless module. Four different breast thicknesses were simulated using Plexiglas as scatter material. First, the phantom was exposed at the parameter and dose settings automatically selected in each experimental setup (with and without grid). Subsequently, the phantom was exposed at the different simulated breast thicknesses using the gridless module in combination with the parameters automatically selected for the grid module. This was followed by a series of phantom mammograms obtained with the experimental setup reversed. The 16 mammograms were evaluated by 3 readers and the results compared considering breast thickness, radiation dose, and quality. The gridless module was used for preoperative labeling in 16 patients for comparison of mammograms obtained with and without a grid. Results: For the same entrance dose used in routine mammography, digital mammography without grid is superior to digital mammography with grid when performed on simulated thin breasts (Plexiglas less than 3 cm), with no difference found when performed on simulated large breasts. The advantages of gridless mammography are more pronounced at a markedly reduced entrance dose (identical parenchymal dose without and with grid using the dose automatically selected for the gridless module). This tendency is confirmed by the initial clinical comparison. (orig.) [de

  12. Evaluation of the potential for reduction in well spacing of the Bakken sand pool, Court Field

    Majcher, M.B.; Estrada, C.A. [Society of Petroleum Engineers, Richardson, TX (United States)]|[Nexen Inc., Calgary, AB (Canada); Archer, J.C. [Nexen Inc., Calgary, AB (Canada)

    2005-11-01

    For the past 15 years, the Court field has produced hydrocarbons from the Mississippian/Devonian middle Bakken sandstone reservoir. The formation is located in west central Saskatchewan and was deposited in a marine shelf environment and later reworked into tidally influenced sand ridges. Vertical wells and a waterflood recovery scheme have been used to produce heavy crude with an API gravity of 17. A better understanding of the reservoir behaviour is required in order to advance field development and maintain successful waterflood management. Three-dimensional seismic and well logs were used to map the structural complexity of the sand ridge. This study examined the feasibility of using production and seismic data to update and substantiate a simulation model which was used to evaluate downspace potential. Stratigraphic disparities were taken into account as discontinuous interbedded siltstones may be flow barriers that create anisotropy in the permeability zone. Grid orientation was altered to align axially with the permeability trends of the main sand ridge. This study also reviewed an earlier field simulation and generated an updated model. The potential to reduce well spacing was then identified and waterflood optimization of the middle Bakken reservoir was evaluated. It was concluded that the edges of the sand ridge and areas isolated from existing injectors have the greatest potential for infill drilling and additional water injection because of the high sinkhole density. It was noted that drilling edge regions with high oil saturations have a risk of low permeability zones, resulting in low production rates and the possibility of an ineffective waterflood scheme. Therefore, a successful waterflood in the edge zones would require injector-producer pairs in the equivalent sand facies. 4 refs., 36 figs.

  13. Reduction of diazinon and dimethoate in apple juice by pulsed electric field treatment.

    Zhang, Yuanyuan; Hou, Yaxi; Zhang, Yan; Chen, Jie; Chen, Fang; Liao, Xiaojun; Hu, Xiaosong

    2012-03-15

    Organophosphorus pesticides (OPPs) are widely used in agricultural production in China, and residues of OPPs in agro-products and foods have become a public health concern. Chronic exposure to OPPs can result in potential immunosuppressive effects, cytotoxicity and mutagenicity. Pulsed electric fields (PEFs) have the potential to be used as an alternative to conventional techniques of food production. The aim of the present study was to investigate the influence of PEFs on the degradation of diazinon and dimethoate added to apple juice. PEF treatment significantly promoted the degradation of both pesticides (P apple juice and in mitigating sample toxicity. Copyright © 2011 Society of Chemical Industry.

  14. Background field removal technique using regularization enabled sophisticated harmonic artifact reduction for phase data with varying kernel sizes.

    Kan, Hirohito; Kasai, Harumasa; Arai, Nobuyuki; Kunitomo, Hiroshi; Hirose, Yasujiro; Shibamoto, Yuta

    2016-09-01

    An effective background field removal technique is desired for more accurate quantitative susceptibility mapping (QSM) prior to dipole inversion. The aim of this study was to evaluate the accuracy of regularization enabled sophisticated harmonic artifact reduction for phase data with varying spherical kernel sizes (REV-SHARP) method using a three-dimensional head phantom and human brain data. The proposed REV-SHARP method used the spherical mean value operation and Tikhonov regularization in the deconvolution process, with varying 2-14mm kernel sizes. The kernel sizes were gradually reduced, similar to the SHARP with varying spherical kernel (VSHARP) method. We determined the relative errors and relationships between the true local field and estimated local field in REV-SHARP, VSHARP, projection onto dipole fields (PDF), and regularization enabled SHARP (RESHARP). Human experiment was also conducted using REV-SHARP, VSHARP, PDF, and RESHARP. The relative errors in the numerical phantom study were 0.386, 0.448, 0.838, and 0.452 for REV-SHARP, VSHARP, PDF, and RESHARP. REV-SHARP result exhibited the highest correlation between the true local field and estimated local field. The linear regression slopes were 1.005, 1.124, 0.988, and 0.536 for REV-SHARP, VSHARP, PDF, and RESHARP in regions of interest on the three-dimensional head phantom. In human experiments, no obvious errors due to artifacts were present in REV-SHARP. The proposed REV-SHARP is a new method combined with variable spherical kernel size and Tikhonov regularization. This technique might make it possible to be more accurate backgroud field removal and help to achive better accuracy of QSM. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Comparing auditory filter bandwidths, spectral ripple modulation detection, spectral ripple discrimination, and speech recognition: Normal and impaired hearing.

    Davies-Venn, Evelyn; Nelson, Peggy; Souza, Pamela

    2015-07-01

    Some listeners with hearing loss show poor speech recognition scores in spite of using amplification that optimizes audibility. Beyond audibility, studies have suggested that suprathreshold abilities such as spectral and temporal processing may explain differences in amplified speech recognition scores. A variety of different methods has been used to measure spectral processing. However, the relationship between spectral processing and speech recognition is still inconclusive. This study evaluated the relationship between spectral processing and speech recognition in listeners with normal hearing and with hearing loss. Narrowband spectral resolution was assessed using auditory filter bandwidths estimated from simultaneous notched-noise masking. Broadband spectral processing was measured using the spectral ripple discrimination (SRD) task and the spectral ripple depth detection (SMD) task. Three different measures were used to assess unamplified and amplified speech recognition in quiet and noise. Stepwise multiple linear regression revealed that SMD at 2.0 cycles per octave (cpo) significantly predicted speech scores for amplified and unamplified speech in quiet and noise. Commonality analyses revealed that SMD at 2.0 cpo combined with SRD and equivalent rectangular bandwidth measures to explain most of the variance captured by the regression model. Results suggest that SMD and SRD may be promising clinical tools for diagnostic evaluation and predicting amplification outcomes.

  16. Comparing auditory filter bandwidths, spectral ripple modulation detection, spectral ripple discrimination, and speech recognition: Normal and impaired hearinga)

    Davies-Venn, Evelyn; Nelson, Peggy; Souza, Pamela

    2015-01-01

    Some listeners with hearing loss show poor speech recognition scores in spite of using amplification that optimizes audibility. Beyond audibility, studies have suggested that suprathreshold abilities such as spectral and temporal processing may explain differences in amplified speech recognition scores. A variety of different methods has been used to measure spectral processing. However, the relationship between spectral processing and speech recognition is still inconclusive. This study evaluated the relationship between spectral processing and speech recognition in listeners with normal hearing and with hearing loss. Narrowband spectral resolution was assessed using auditory filter bandwidths estimated from simultaneous notched-noise masking. Broadband spectral processing was measured using the spectral ripple discrimination (SRD) task and the spectral ripple depth detection (SMD) task. Three different measures were used to assess unamplified and amplified speech recognition in quiet and noise. Stepwise multiple linear regression revealed that SMD at 2.0 cycles per octave (cpo) significantly predicted speech scores for amplified and unamplified speech in quiet and noise. Commonality analyses revealed that SMD at 2.0 cpo combined with SRD and equivalent rectangular bandwidth measures to explain most of the variance captured by the regression model. Results suggest that SMD and SRD may be promising clinical tools for diagnostic evaluation and predicting amplification outcomes. PMID:26233047

  17. Reduction of ballistic spin scattering in a spin-FET using stray electric fields

    Nemnes, G A; Manolescu, A; Gudmundsson, V

    2012-01-01

    The quasi-bound states which appear as a consequence of the Rashba spin-orbit (SO) coupling, introduce a strongly irregular behavior of the spin-FET conductance at large Rashba parameter. Moreover, the presence of the bulk inversion asymmetry, i.e. the Dresselhaus SO coupling, may compromise the spin-valve effect even at small values of the Rashba parameter. However, by introducing stray electric fields in addition to the SO couplings, we show that the effect of the SO induced quasi-bound states can be tuned. The oscillations of the spin-resolved conductance become smoother and the control of the spin-FET characteristics becomes possible. For the calculations we employ a multi-channel scattering formalism, based on the R-matrix method extended to spin transport, in the presence of Rashba and Dresselhaus SO couplings.

  18. Reduction of the scatter dose to the testicle outside the radiation treatment fields

    Kubo, H.; Shipley, W.U.

    1982-01-01

    A technique is described to reduce the dose to the contralateral testicle of patients with testis tumors during retroperitoneal therapy with 10 MV X-rays. When a conventional clam-shell shielding device was used, the dose to the testis from the photons scattered by the patient and the collimator jaws was found to be about 1.6% of the prescribed midplane dose. A more substantial gonadal shield made of low melting Ostalloy, that reduced further the dose from internal scattered X rays, was therefore designed. A 10 cm thick lead scrotal block above the scrotum immediately outside the field is shown to reduce the external scattered radiation to negligible levels. Using the shield and the block, it is possible to reduce the dose to the testicle to one-tenth of one percent of the prescribed midplane dose

  19. Reduction of the scatter dose to the testicle outside the radiation treatment fields

    Kubo, H.; Shipley, W.U.

    1982-01-01

    A technique is described to reduce the dose to the contralateral testicle of patients with testis tumors during retroperitoneal therapy with 10 MV X rays. When a conventional clam-shell shielding device was used, the dose to the testis from the photons scattered by the patient and collimator jaws was found to be about 1.6% of the prescribed midplane dose. A more substantial gonadal shield made of low melting point Ostalloy, that reduced further the dose from internal scattered X rays, was therefore designed. A 10 cm thick lead scrotal block above the scrotum immediately outside the field is shown to reduce the external scattering radiation to negligible levels. Using the shield and the block, it is possible to reduce the dose to the testicle to one-tenth of one percent of the prescribed midplane dose

  20. The Tianjin geothermal field (north-eastern China): Water chemistry and possible reservoir permeability reduction phenomena

    Minissale, Angelo; Montegrossi, Giordano; Orlando, Andrea [Institute of Geosciences and Earth Resources, National Research Council of Italy (CNR), Via G. La Pira 4, 50121 Florence (Italy); Borrini, Daniele; Tassi, Franco [Department of Earth Sciences, University of Florence, Via G. La Pira 4, 50121 Florence (Italy); Vaselli, Orlando [Institute of Geosciences and Earth Resources, National Research Council of Italy (CNR), Via G. La Pira 4, 50121 Florence (Italy); Department of Earth Sciences, University of Florence, Via G. La Pira 4, 50121 Florence (Italy); Huertas, Antonio Delgado [Estacion Experimental de Zaidin (CSIC), Prof. Albareda 1, 18008 Granada (Spain); Yang, Jincheng; Cheng, Wanquing [Aode Renewable Energy Research Institute, 90 Weijin South Road, Nankai District, 300381 Tianjin (China); Tedesco, Dario [Department of Environmental Sciences, Second University of Naples, Via Vivaldi 43, Caserta 81100 (Italy); Institute of Environmental Geology and Geo Engineering (CNR), Piazzale A. Moro 5, Roma 00100 (Italy); Poreda, Robert [Department of Earth and Environmental Sciences, University of Rochester, 227 Hutchison Hall, Rochester, NY 14627 (United States)

    2008-08-15

    Injection of spent (cooled) thermal fluids began in the Tianjin geothermal district, north-eastern China, at the end of the 1990s. Well injectivities declined after 3-4 years because of self-sealing processes that reduced reservoir permeability. The study focuses on the factors that may have caused the observed decrease in permeability, using chemical and isotopic data on fluids (water and gas) and mineral phases collected from production and injection wells. The results of data processing and interpretation indicate that (1) it is very unlikely that calcite and silica precipitation is taking place in the reservoir; (2) the Fe- and Zn-rich mineral phases (e.g. sulfides, hydroxides and silicates) show positive saturation indexes; (3) SEM and XRD analyses of filtered material reveal that the latter mineral phases are common; (4) visual observation of casings and surface installations, and of corrosion products, suggests that a poor quality steel was used in their manufacture; (5) significant quantities of solids (e.g. quartz and feldspar crystals) are carried by the geothermal fluid; (6) seasonal changes in fluid composition lead to a reduction in casing corrosion during the summer. It was concluded that the decrease in injectivity in the Tianjin wells is caused only in part by the oxidation of casings, downhole pumps, and surface installations, triggered by free oxygen in the injected fluids; the utilization of better quality steels should drastically reduce this type of corrosion. Self-sealing of pores and fractures by reservoir formation solids and by the Fe-corrosion products suspended in the injected fluids seems to be a more important phenomenon, whose effect could be greatly reduced by installing filtering devices at all sites. (author)

  1. Back-flow ripples in troughs downstream of unit bars: Formation, preservation and value for interpreting flow conditions

    Herbert, Christopher; Alexander, Jan; Martinez De Alvaro, Maria

    2015-01-01

    Back-flow ripples are bedforms created within the lee-side eddy of a larger bedform with migration directions opposed or oblique to that of the host bedform. In the flume experiments described in this article, back-flow ripples formed in the trough downstream of a unit bar and changed with mean flow velocity; varying from small incipient back-flow ripples at low velocities, to well-formed back-flow ripples with greater velocity, to rapidly migrating transient back-flow ripples formed at the g...

  2. Emission spectra from super-critical rippled plasma density profiles illuminated by intense laser pulses

    Ondarza R, R.; Boyd, T.J.M.

    2000-01-01

    High-order harmonic emission from the interaction of intense femtosecond laser pulses with super-critical plasmas characterized by a rippled density profile at the vacuum-plasma interface has been observed from particle-in-cell (PIC) simulations. A plasma simulation box several laser wavelengths in extent was prepared with a rippled density of a fraction of a laser wavelength. Emission spectra at the very initial stage of the interaction were recorded with spectral characteristics dissimilar to those previously reported in the literature. The reflected light spectra were characterized by a strong emission at the plasma line and by a series of harmonics at multiples of the ripple frequency. Harmonic spectra were obtained for different values of the plasma ripple frequency. In all cases the harmonics were emitted at the precise multiple harmonic number of the ripple frequency. Another important feature apparent from the simulations was that the emission peaks appeared to havea complex structure as compared with those for unrippled plasmas. For the cases when the plasma was rippled the peaks that corresponded to the multiples of the rippled density typically showed a double peak for the first few harmonics. The reflected emission plots for the main laser pulse showed strong emission at the plasma frequency and at multiples of that frequency as reported by the authors in the literature. (Author)

  3. Effect of ripple loads on sustained-load cracking in titanium alloys

    Pao, P.S.; Meyn, D.A.; Bayles, R.A.; Feng, C.R.; Yoder, G.R.

    1995-01-01

    In the present paper, the authors have extended their study on the effect of the ripple loads on the sustained-load cracking (SLC) behavior of two titanium alloys, Ti-6Al-4V (an α-β alloy) and Ti-15V-3Cr-3Al-3Sn (a β-α alloy), in an ambient air environment. The methodology which has been used successfully to treat ripple effects on stress-corrosion cracking (SCC) is employed again to address the influence of ripple loads on sustained-load cracking. Ripple loads can significantly reduce the apparent sustained load cracking resistance of titanium alloys in a relatively benign environment such as ambient air. For a ripple-load amplitude equal to 5% of the sustained load, the ripple-load cracking thresholds (K IRLC ) of beta-annealed Ti-6Al-4V and Ti-15V-3Cr-3al-3Sn are less than half of the respective sustained-load cracking thresholds (K ISLC ). The extent of ripple-load degradation for these alloys in ambient air -- relative to K ISLC , were found comparable to those observed in a much more aggressive 3.5% NaCl aqueous solution

  4. Seasonal and local time variability of ripples from airglow imager observations in US and Japan

    J. Yue

    2010-07-01

    Full Text Available Ripples as seen in airglow imagers are small wavy structures with short horizontal wavelengths (<15 km. Ripples are thought to form as the result of local instabilities, which are believed to occur when the amplitude of gravity waves becomes large enough. We have investigated ripple formation based on years of airglow imager observations located at Fort Collins, Colorado (41° N, 105° W and Misato Observatory, Japan (34° N, 135° E/Shigaraki MU Observatory (35° N, 136° E. Na temperature-wind lidar observations are employed to detect convective and dynamic instabilities in the mesosphere and lower thermosphere (MLT region over Fort Collins, Colorado. Seasonal variation of the ripple occurrence in Colorado is compared to that of the lidar-measured instability. The occurrence frequency of ripples varies semiannually, with maxima occurring during solstices and minima during equinoxes in both Colorado and Japan. However, the probability of convective and dynamic instabilities varies annually with a peak in Colorado winter. The seasonal variation of the occurrence frequency of ripples correlates with that of the gravity wave variances in the MLT. Ripple occurrence over Colorado also shows strong local time dependence, but it bears little resemblance to the local time dependence of instability probability.

  5. Comparing spatial tuning curves, spectral ripple resolution, and speech perception in cochlear implant users.

    Anderson, Elizabeth S; Nelson, David A; Kreft, Heather; Nelson, Peggy B; Oxenham, Andrew J

    2011-07-01

    Spectral ripple discrimination thresholds were measured in 15 cochlear-implant users with broadband (350-5600 Hz) and octave-band noise stimuli. The results were compared with spatial tuning curve (STC) bandwidths previously obtained from the same subjects. Spatial tuning curve bandwidths did not correlate significantly with broadband spectral ripple discrimination thresholds but did correlate significantly with ripple discrimination thresholds when the rippled noise was confined to an octave-wide passband, centered on the STC's probe electrode frequency allocation. Ripple discrimination thresholds were also measured for octave-band stimuli in four contiguous octaves, with center frequencies from 500 Hz to 4000 Hz. Substantial variations in thresholds with center frequency were found in individuals, but no general trends of increasing or decreasing resolution from apex to base were observed in the pooled data. Neither ripple nor STC measures correlated consistently with speech measures in noise and quiet in the sample of subjects in this study. Overall, the results suggest that spectral ripple discrimination measures provide a reasonable measure of spectral resolution that correlates well with more direct, but more time-consuming, measures of spectral resolution, but that such measures do not always provide a clear and robust predictor of performance in speech perception tasks. © 2011 Acoustical Society of America

  6. The Ripple Effect: Citation Chain Reactions of a Nobel Prize

    Faber Frandsen, Tove; Nicolaisen, Jeppe

    2013-01-01

    This paper explores the possible citation chain reactions of a Nobel Prize using the mathematician Robert J. Aumann as a case example. The results show that the award of the Nobel Prize in 2005 affected not only the citations to his work, but also affected the citations to the references in his s...... citation network. The effect is discussed using innovation decision process theory as a point of departure to identify the factors that created a bandwagon effect leading to the reported observations....... scientific oeuvre. The results indicate that the spillover effect is almost as powerful as the effect itself. We are consequently able to document a ripple effect in which the awarding of the Nobel Prize ignites a citation chain reaction to Aumann's scientific ouvre and to the references in its nearest...

  7. The Ripple Pond: Enabling Spiking Networks to See

    Saeed eAfshar

    2013-11-01

    Full Text Available We present the biologically inspired Ripple Pond Network (RPN, a simply connected spiking neural network which performs a transformation converting two dimensional images to one dimensional temporal patterns suitable for recognition by temporal coding learning and memory networks. The RPN has been developed as a hardware solution linking previously implemented neuromorphic vision and memory structures such as frameless vision sensors and neuromorphic temporal coding spiking neural networks. Working together such systems are potentially capable of delivering end-to-end high-speed, low-power and low-resolution recognition for mobile and autonomous applications where slow, highly sophisticated and power hungry signal processing solutions are ineffective. Key aspects in the proposed approach include utilising the spatial properties of physically embedded neural networks and propagating waves of activity therein for information processing, using dimensional collapse of imagery information into amenable temporal patterns and the use of asynchronous frames for information binding.

  8. The ripple pond: enabling spiking networks to see.

    Afshar, Saeed; Cohen, Gregory K; Wang, Runchun M; Van Schaik, André; Tapson, Jonathan; Lehmann, Torsten; Hamilton, Tara J

    2013-01-01

    We present the biologically inspired Ripple Pond Network (RPN), a simply connected spiking neural network which performs a transformation converting two dimensional images to one dimensional temporal patterns (TP) suitable for recognition by temporal coding learning and memory networks. The RPN has been developed as a hardware solution linking previously implemented neuromorphic vision and memory structures such as frameless vision sensors and neuromorphic temporal coding spiking neural networks. Working together such systems are potentially capable of delivering end-to-end high-speed, low-power and low-resolution recognition for mobile and autonomous applications where slow, highly sophisticated and power hungry signal processing solutions are ineffective. Key aspects in the proposed approach include utilizing the spatial properties of physically embedded neural networks and propagating waves of activity therein for information processing, using dimensional collapse of imagery information into amenable TP and the use of asynchronous frames for information binding.

  9. Emulating porphyrins with a rippled multivacancy graphene system

    Mombrú, Dominique; Faccio, Ricardo; Mombrú, Alvaro W.

    2018-04-01

    The interaction between a complex porphyrin-like system formed by an iron atom and multivacant graphene layer and O2, CO and CO2 molecules is studied, using Density Functional Theory (DFT) calculations. The multivacancy graphene system used for this study, consists in the removal of a 1,4-dimethybenzene-like moiety, in a 6 × 6 supercell. This removal and the structural optimization subsequently performed, yield to a biaxial vacancy, where the location of an iron atom embedded in it, lead to a system with resemblance to iron-porphyrin systems. This similar structure could be used to form complexes where gas molecules are allowed to interact with these iron-octavacant graphene systems. The study focuses on the structure of the system and the net magnetic moment for different gas molecules: O2, CO2 and CO. Rippling in the vacant graphene is enhanced through this interaction.

  10. Direct measurements of mean Reynolds stress and ripple roughness in the presence of energetic forcing by surface waves

    Scully, Malcolm; Trowbridge, John; Sherwood, Christopher R.; Jones, Katie R.; Traykovski, Peter A.

    2018-01-01

    Direct covariance observations of the mean flow Reynolds stress and sonar images of the seafloor collected on a wave‐exposed inner continental shelf demonstrate that the drag exerted by the seabed on the overlying flow is consistent with boundary layer models for wave‐current interaction, provided that the orientation and anisotropy of the bed roughness are appropriately quantified. Large spatial and temporal variations in drag result from nonequilibrium ripple dynamics, ripple anisotropy, and the orientation of the ripples relative to the current. At a location in coarse sand characterized by large two‐dimensional orbital ripples, the observed drag shows a strong dependence on the relative orientation of the mean current to the ripple crests. At a contrasting location in fine sand, where more isotropic sub‐orbital ripples are observed, the sensitivity of the current to the orientation of the ripples is reduced. Further, at the coarse site under conditions when the currents are parallel to the ripple crests and the wave orbital diameter is smaller than the wavelength of the relic orbital ripples, the flow becomes hydraulically smooth. This transition is not observed at the fine site, where the observed wave orbital diameter is always greater than the wavelength of the observed sub‐orbital ripples. Paradoxically, the dominant along‐shelf flows often experience lower drag at the coarse site than at the fine site, despite the larger ripples, highlighting the complex dynamics controlling drag in wave‐exposed environments with heterogeneous roughness.

  11. Ripples on spikes show increased phase-amplitude coupling in mesial temporal lobe epilepsy seizure onset zones

    Weiss, Shennan A; Orosz, Iren; Salamon, Noriko; Moy, Stephanie; Wei, Linqing; Van ’t Klooster, Maryse A; Knight, Robert T; Harper, Ronald M; Bragin, Anatol; Fried, Itzhak; Engel, Jerome; Staba, Richard J

    2016-01-01

    Objective Ripples (80–150 Hz) recorded from clinical macroelectrodes have been shown to be an accurate biomarker of epileptogenic brain tissue. We investigated coupling between epileptiform spike phase and ripple amplitude to better understand the mechanisms that generate this type of pathological ripple (pRipple) event. Methods We quantified phase amplitude coupling (PAC) between epileptiform EEG spike phase and ripple amplitude recorded from intracranial depth macroelectrodes during episodes of sleep in 12 patients with mesial temporal lobe epilepsy. PAC was determined by 1) a phasor transform that corresponds to the strength and rate of ripples coupled with spikes, and a 2) ripple-triggered average to measure the strength, morphology, and spectral frequency of the modulating and modulated signals. Coupling strength was evaluated in relation to recording sites within and outside the seizure onset zone (SOZ). Results Both the phasor transform and ripple-triggered averaging methods showed ripple amplitude was often robustly coupled with epileptiform EEG spike phase. Coupling was more regularly found inside than outside the SOZ, and coupling strength correlated with the likelihood a macroelectrode’s location was within the SOZ (pripples coupled with EEG spikes inside the SOZ to rates of coupled ripples in non-SOZ was greater than the ratio of rates of ripples on spikes detected irrespective of coupling (pripple amplitude (pripple spectral frequency (pripple amplitude. The changes in excitability reflected as epileptiform spikes may also cause clusters of pathologically interconnected bursting neurons to grow and synchronize into aberrantly large neuronal assemblies. PMID:27723936

  12. Area/latency optimized early output asynchronous full adders and relative-timed ripple carry adders.

    Balasubramanian, P; Yamashita, S

    2016-01-01

    This article presents two area/latency optimized gate level asynchronous full adder designs which correspond to early output logic. The proposed full adders are constructed using the delay-insensitive dual-rail code and adhere to the four-phase return-to-zero handshaking. For an asynchronous ripple carry adder (RCA) constructed using the proposed early output full adders, the relative-timing assumption becomes necessary and the inherent advantages of the relative-timed RCA are: (1) computation with valid inputs, i.e., forward latency is data-dependent, and (2) computation with spacer inputs involves a bare minimum constant reverse latency of just one full adder delay, thus resulting in the optimal cycle time. With respect to different 32-bit RCA implementations, and in comparison with the optimized strong-indication, weak-indication, and early output full adder designs, one of the proposed early output full adders achieves respective reductions in latency by 67.8, 12.3 and 6.1 %, while the other proposed early output full adder achieves corresponding reductions in area by 32.6, 24.6 and 6.9 %, with practically no power penalty. Further, the proposed early output full adders based asynchronous RCAs enable minimum reductions in cycle time by 83.4, 15, and 8.8 % when considering carry-propagation over the entire RCA width of 32-bits, and maximum reductions in cycle time by 97.5, 27.4, and 22.4 % for the consideration of a typical carry chain length of 4 full adder stages, when compared to the least of the cycle time estimates of various strong-indication, weak-indication, and early output asynchronous RCAs of similar size. All the asynchronous full adders and RCAs were realized using standard cells in a semi-custom design fashion based on a 32/28 nm CMOS process technology.

  13. Surface ripple evolution by argon ion irradiation in polymers

    Goyal, Meetika; Aggarwal, Sanjeev; Sharma, Annu

    2016-01-01

    In this report, an attempt has been made to investigate the morphological evolution of nanoscale surface ripples on aliphatic (polypropylene, PP) and aromatic (polyethylene terephthalate, PET) polymeric substrates irradiated with 50 keV Ar"+ ions. The specimens were sputtered at off normal incidence of 30° with 5 × 10"1"6 Ar"+ cm"−"2. The topographical features and structural behavior of the specimens were studied using Atomic Force Microscopy (AFM) and UV-Visible spectroscopy techniques, respectively. The Stopping and Range of Ions in Matter simulations were performed to calculate sputtering yield of irradiated PP and PET polymers. Sputtering yield of carbon atoms has been found to be smaller for PP (0.40) as compared to PET (0.73), which is attributed to the different structures of two polymers. AFM analysis demonstrates the evolution of ripple like features with amplitude (2.50 nm) and wavelength (690 nm) on PET while that of lower amplitude (1.50 nm) and higher wavelength (980 nm) on PP specimen. The disorder parameter (Urbach energy) has been found to increase significantly from 0.30 eV to 1.67 eV in case of PP as compared to a lesser increase from 0.35 eV to 0.72 eV in case of PET as revealed by UV-Visible characterization. A mutual correlation between ion beam sputtering induced topographical variations with that of enhancement in the disorder parameter of the specimens has been discussed.

  14. Adaptive feedforward of estimated ripple improves the closed loop system performance significantly

    Kwon, S.; Regan, A.; Wang, Y.M.; Rohlev, A.S.

    1998-01-01

    The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for the low energy section of Acceleration Production of Tritium (APT) accelerator. This paper addresses the problem of LLRF control system for LEDA. The authors propose an estimator of the ripple and its time derivative and a control law which is based on PID control and adaptive feedforward of estimated ripple. The control law reduces the effect of the deterministic cathode ripple that is due to high voltage power supply and achieves tracking of desired set points

  15. Online high voltage power supply ripple estimation and feedforward in LEDA

    Kwon, S.; Regan, A.; Wang, Y.M.; Rohlev, T.

    1999-01-01

    The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for the low energy section of Acceleration Production of Tritium (APT) accelerator. This paper addresses the problem of LLRF control system for LEDA. They propose an estimator of the ripple and its time derivative and a control law which is based on PID control and adaptive feedforward of estimated ripple. The control law reduces the effect of the deterministic cathode ripple that is due to high voltage power supply and achieves tracking of desired set points

  16. Final Report: Mechanisms of sputter ripple formation: coupling among energetic ions, surface kinetics, stress and composition

    Chason, Eric; Shenoy, Vivek

    2013-01-22

    Self-organized pattern formation enables the creation of nanoscale surface structures over large areas based on fundamental physical processes rather than an applied template. Low energy ion bombardment is one such method that induces the spontaneous formation of a wide variety of interesting morphological features (e.g., sputter ripples and/or quantum dots). This program focused on the processes controlling sputter ripple formation and the kinetics controlling the evolution of surfaces and nanostructures in high flux environments. This was done by using systematic, quantitative experiments to measure ripple formation under a variety of processing conditions coupled with modeling to interpret the results.

  17. A New Switched Reluctance Motor Design to Reduce Torque Ripple using Finite Element Fuzzy Optimization

    S. R. Mousavi-Aghdam

    2012-03-01

    Full Text Available This paper presents a new design to reduce torque ripple in Switched Reluctance Motors (SRM. Although SRM possesses many advantages in terms of motor structure, it suffers from large torque ripple that causes problems such as vibration and acoustic noise. The paper describes new rotor and stator pole shapes with a non-uniform air gap profile to reduce torque ripple while retaining its average value. An optimization using fuzzy strategy is successfully performed after sensitivity analysis. The two dimensional (2-D finite element method (FEM results, have demonstrated validity of the proposed new design.

  18. The wave plus current flow over vortex ripples at an arbitrary angle

    Andersen, Ken Haste; Faraci, C

    2003-01-01

    This work concerns the wave plus current flow over a sand bed covered by vortex ripples, with the current and the waves coming from different angles. Experiments were performed in a basin, where current and waves were perpendicular, in order to determine the conditions (current strength) leading...... to a regular ripple pattern formation. Numerical simulations were conducted changing the direction between the waves and the current from 0degrees to 90degrees and the ratio between the current strength and the wave orbital velocity from 0.2 to 1.5. Close to the bed, the current aligns parallel to the ripple...

  19. Pattern dynamics of vortex ripples in sand: Nonlinear modeling and experimental validation

    Andersen, Ken Haste; Abel, M.; Krug, J.

    2002-01-01

    Vortex ripples in sand are studied experimentally in a one-dimensional setup with periodic boundary conditions. The nonlinear evolution, far from the onset of instability, is analyzed in the framework of a simple model developed for homogeneous patterns. The interaction function describing the mass...... transport between neighboring ripples is extracted from experimental runs using a recently proposed method for data analysis, and the predictions of the model are compared to the experiment. An analytic explanation of the wavelength selection mechanism in the model is provided, and the width of the stable...... band of ripples is measured....

  20. Development of FEMAG. Calculation code of magnetic field generated by ferritic plates in the tokamak devices

    Urata, Kazuhiro [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

    2003-03-01

    In design of the future fusion devises in which low activation ferritic steel is planned to use as the plasma facing material and/or the inserts for ripple reduction, the appreciation of the error field effect against the plasma as well as the optimization of ferritic plate arrangement to reduce the toroidal field ripple require calculation of magnetic field generated by ferritic steel. However iterative calculations concerning the non-linearity in B-H curve of ferritic steel disturbs high-speed calculation required as the design tool. In the strong toroidal magnetic field that is characteristic in the tokamak fusion devices, fully magnetic saturation of ferritic steel occurs. Hence a distribution of magnetic charges as magnetic field source is determined straightforward and any iteration calculation are unnecessary. Additionally objective ferritic steel geometry is limited to the thin plate and ferritic plates are installed along the toroidal magnetic field. Taking these special conditions into account, high-speed calculation code ''FEMAG'' has been developed. In this report, the formalization of 'FEMAG' code, how to use 'FEMAG', and the validity check of 'FEMAG' in comparison with a 3D FEM code, with the measurements of the magnetic field in JFT-2M are described. The presented examples are numerical results of design studies for JT-60 modification. (author)

  1. Edge plasma physics modifications due to magnetic ripple in RFX-mod

    Scarin, P.; Agostini, M.; Carraro, L.; Cavazzana, R.; Ciaccio, G.; De Masi, G.; Spizzo, G.; Spolaore, M.; Vianello, N.

    2015-01-01

    The edge of the RFX-mod (R = 2 m, a = 0.46 m) Reversed Field Pinch is characterized by weak magnetic chaos affecting ion and electron diffusion. Edge particle transport is strongly influenced by a toroidal asymmetry caused by magnetic islands. An ambipolar radial electric field ensures local neutrality and possesses the same symmetry as the parent magnetic ripple: the result is the modulation of the perpendicular flow, with a slowing-down at the island X-point. In this paper we present a complete statistical analysis, over a large database of RFX-mod discharges, of the edge properties as they are modified by the magnetic topology: the plasma wall footprint follows the helical shape of the dominant central mode (m/n = 1/7), with an increase of H α emission and electron density corresponding to the O-point of the inner magnetic island. Edge turbulence is modified by the magnetic topology, being generated in the O-point region and damped near the X-point

  2. Control of surface ripple amplitude in ion beam sputtered polycrystalline cobalt films

    Colino, Jose M., E-mail: josemiguel.colino@uclm.es [Institute of Nanoscience, Nanotechnology and Molecular Materials, University of Castilla-La Mancha, Campus de la Fabrica de Armas, Toledo 45071 (Spain); Arranz, Miguel A. [Facultad de Ciencias Quimicas, University of Castilla-La Mancha, Ciudad Real 13071 (Spain)

    2011-02-15

    We have grown both polycrystalline and partially textured cobalt films by magnetron sputter deposition in the range of thickness (50-200 nm). Kinetic roughening of the growing film leads to a controlled rms surface roughness values (1-6 nm) increasing with the as-grown film thickness. Ion erosion of a low energy 1 keV Ar+ beam at glancing incidence (80{sup o}) on the cobalt film changes the surface morphology to a ripple pattern of nanometric wavelength. The wavelength evolution at relatively low fluency is strongly dependent on the initial surface topography (a wavelength selection mechanism hereby confirmed in polycrystalline rough surfaces and based on the shadowing instability). At sufficiently large fluency, the ripple wavelength steadily increases on a coarsening regime and does not recall the virgin surface morphology. Remarkably, the use of a rough virgin surface makes the ripple amplitude in the final pattern can be controllably increased without affecting the ripple wavelength.

  3. Plasma waves generated by rippled magnetically focused electron beams surrounded by tenuous plasmas

    Cuperman, S.; Petran, F.

    1982-01-01

    This chapter investigates the electrostatic instability and the corresponding unstable wave spectrum of magnetically focused neutralized rippled electron beams under spacelike conditions. Topics considered include general equations and equilibrium, the derivation of the dispersion relation, and the solution of the dispersion relation (long wavelength perturbations, short wavelength perturbations, the rippled beam). The results indicate that in the long wavelength limit two types of instability (extending over different frequency ranges) exist. An instability of the beam-plasma type occurs due to the interaction between the beam electrons and the surrounding plasm electrons at the beam-plasma interface. A parametric type instability is produced by the coupling of a fast forward wave and a fast backward wave due to the rippling (modulation) of the beam. It is demonstrated that in the short wavelength limit, surface waves which are stable for the laminar beam may become unstable in the rippled beam case

  4. Roles of effective helical ripple rates in nonlinear stability of externally induced magnetic islands

    Nishimura, Seiya, E-mail: n-seiya@kobe-kosen.ac.jp [Kobe City College of Technology, Kobe, Hyogo 651-2194 (Japan)

    2015-02-15

    Magnetic islands are externally produced by resonant magnetic perturbations (RMPs) in toroidal plasmas. Spontaneous annihilation of RMP-induced magnetic islands called self-healing has been observed in helical systems. A possible mechanism of the self-healing is shielding of RMP penetration by helical ripple-induced neoclassical flows, which give rise to neoclassical viscous torques. In this study, effective helical ripple rates in multi-helicity helical systems are revisited, and a multi-helicity effect on the self-healing is investigated, based on a theoretical model of rotating magnetic islands. It is confirmed that effective helical ripple rates are sensitive to magnetic axis positions. It is newly found that self-healing thresholds also strongly depend on magnetic axis positions, which is due to dependence of neoclassical viscous torques on effective helical ripple rates.

  5. Self-Assembled Gold Nano-Ripple Formation by Gas Cluster Ion Beam Bombardment.

    Tilakaratne, Buddhi P; Chen, Quark Y; Chu, Wei-Kan

    2017-09-08

    In this study, we used a 30 keV argon cluster ion beam bombardment to investigate the dynamic processes during nano-ripple formation on gold surfaces. Atomic force microscope analysis shows that the gold surface has maximum roughness at an incident angle of 60° from the surface normal; moreover, at this angle, and for an applied fluence of 3 × 10 16 clusters/cm², the aspect ratio of the nano-ripple pattern is in the range of ~50%. Rutherford backscattering spectrometry analysis reveals a formation of a surface gradient due to prolonged gas cluster ion bombardment, although the surface roughness remains consistent throughout the bombarded surface area. As a result, significant mass redistribution is triggered by gas cluster ion beam bombardment at room temperature. Where mass redistribution is responsible for nano-ripple formation, the surface erosion process refines the formed nano-ripple structures.

  6. A high voltage ratio and low ripple interleaved DC-DC converter for fuel cell applications.

    Chang, Long-Yi; Chao, Kuei-Hsiang; Chang, Tsang-Chih

    2012-01-01

    This paper proposes a high voltage ratio and low ripple interleaved boost DC-DC converter, which can be used to reduce the output voltage ripple. This converter transfers the low DC voltage of fuel cell to high DC voltage in DC link. The structure of the converter is parallel with two voltage-doubler boost converters by interleaving their output voltages to reduce the voltage ripple ratio. Besides, it can lower the current stress for the switches and inductors in the system. First, the PSIM software was used to establish a proton exchange membrane fuel cell and a converter circuit model. The simulated and measured results of the fuel cell output characteristic curve are made to verify the correctness of the established simulation model. In addition, some experimental results are made to validate the effectiveness in improving output voltage ripple of the proposed high voltage ratio interleaved boost DC-DC converters.

  7. A third-order class-D amplifier with and without ripple compensation

    Cox, Stephen M.; du Toit Mouton, H.

    2018-06-01

    We analyse the nonlinear behaviour of a third-order class-D amplifier, and demonstrate the remarkable effectiveness of the recently introduced ripple compensation (RC) technique in reducing the audio distortion of the device. The amplifier converts an input audio signal to a high-frequency train of rectangular pulses, whose widths are modulated according to the input signal (pulse-width modulation) and employs negative feedback. After determining the steady-state operating point for constant input and calculating its stability, we derive a small-signal model (SSM), which yields in closed form the transfer function relating (infinitesimal) input and output disturbances. This SSM shows how the RC technique is able to linearise the small-signal response of the device. We extend this SSM through a fully nonlinear perturbation calculation of the dynamics of the amplifier, based on the disparity in time scales between the pulse train and the audio signal. We obtain the nonlinear response of the amplifier to a general audio signal, avoiding the linearisation inherent in the SSM; we thereby more precisely quantify the reduction in distortion achieved through RC. Finally, simulations corroborate our theoretical predictions and illustrate the dramatic deterioration in performance that occurs when the amplifier is operated in an unstable regime. The perturbation calculation is rather general, and may be adapted to quantify the way in which other nonlinear negative-feedback pulse-modulated devices track a time-varying input signal that slowly modulates the system parameters.

  8. Reduction in life span on normal human fibroblasts exposed to low-dose radiation in heavy-ion radiation field

    Suzuki, Masao; Yamaguchi, Chizuru; Yasuda, Hiroshi; Uchihori, Yukio; Fujitaka, Kazunobu

    2003-01-01

    We studied the effect of in vitro life span in normal human fibroblasts exposed to chronically low-dose radiation in heavy-ion radiation field. Cells were cultured in a CO 2 incubator, which was set in the irradiation room for biological study of heavy ions in the Heavy Ion Medical Accelerator in Chiba (HIMAC) at National Institute of Radiological Sciences (NIRS), and exposed to scattered radiations produced with heavy-ion beams throughout the life span of the cell population. Absorbed dose, which was measured using a thermoluminescence dosimeter(TLD) and a Si-semiconductor detector, was to be 1.4 mGy per day when operating the HIMAC machine for biological experiments. The total population doubling number of the exposed cells reduced to 79-93% of non-exposed control cells in the three independent experiments. There is evidence that the exposure of chronically low-dose radiation in heavy-ion radiation field promotes the life-span reduction in cellular level. (author)

  9. Studies of suprathermal electron loss in the magnetic ripple of Tore Supra

    Basiuk, V.; Lipa, M.; Martin, G.; Chantant, M.; Guilhem, D.; Imbeaux, F.; Mitteau, R.; Peysson, Y.; Surle, F.

    2000-01-01

    A new prototype of protection against fast electron trapped in the magnetic ripple was installed on Tore-Supra in 1998. It was designed to support the high flux of fast electron generated by lower hybrid in the CIEL project (up to 6 MW/m 2 ) during steady state experiments. So it is actively cooled and allows a direct measurement of the energy lost in the ripple. (author)

  10. Simulation of Alpha Particles in Rotating Plasma Interacting with a Stationary Ripple

    Fetterman, Abraham J.; Fisch, Nathaniel J.

    2011-01-01

    Superthermal ExB rotation can provide magnetohydrodynamic (MHD) stability and enhanced confinement to axisymmetric mirrors. However, the rotation speed has been limited by phenomena at end electrodes. A new prediction is that rotation might instead be produced using a magnetic ripple and alpha particle kinetic energy, in an extension of the alpha channeling concept. The interaction of alpha particles with the ripple results in visually interesting and practically useful orbits.

  11. Temperature-Controlled High-Speed AFM: Real-Time Observation of Ripple Phase Transitions.

    Takahashi, Hirohide; Miyagi, Atsushi; Redondo-Morata, Lorena; Scheuring, Simon

    2016-11-01

    With nanometer lateral and Angstrom vertical resolution, atomic force microscopy (AFM) has contributed unique data improving the understanding of lipid bilayers. Lipid bilayers are found in several different temperature-dependent states, termed phases; the main phases are solid and fluid phases. The transition temperature between solid and fluid phases is lipid composition specific. Under certain conditions some lipid bilayers adopt a so-called ripple phase, a structure where solid and fluid phase domains alternate with constant periodicity. Because of its narrow regime of existence and heterogeneity ripple phase and its transition dynamics remain poorly understood. Here, a temperature control device to high-speed atomic force microscopy (HS-AFM) to observe dynamics of phase transition from ripple phase to fluid phase reversibly in real time is developed and integrated. Based on HS-AFM imaging, the phase transition processes from ripple phase to fluid phase and from ripple phase to metastable ripple phase to fluid phase could be reversibly, phenomenologically, and quantitatively studied. The results here show phase transition hysteresis in fast cooling and heating processes, while both melting and condensation occur at 24.15 °C in quasi-steady state situation. A second metastable ripple phase with larger periodicity is formed at the ripple phase to fluid phase transition when the buffer contains Ca 2+ . The presented temperature-controlled HS-AFM is a new unique experimental system to observe dynamics of temperature-sensitive processes at the nanoscopic level. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Assessing the role of spectral and intensity cues in spectral ripple detection and discrimination in cochlear-implant users.

    Anderson, Elizabeth S; Oxenham, Andrew J; Nelson, Peggy B; Nelson, David A

    2012-12-01

    Measures of spectral ripple resolution have become widely used psychophysical tools for assessing spectral resolution in cochlear-implant (CI) listeners. The objective of this study was to compare spectral ripple discrimination and detection in the same group of CI listeners. Ripple detection thresholds were measured over a range of ripple frequencies and were compared to spectral ripple discrimination thresholds previously obtained from the same CI listeners. The data showed that performance on the two measures was correlated, but that individual subjects' thresholds (at a constant spectral modulation depth) for the two tasks were not equivalent. In addition, spectral ripple detection was often found to be possible at higher rates than expected based on the available spectral cues, making it likely that temporal-envelope cues played a role at higher ripple rates. Finally, spectral ripple detection thresholds were compared to previously obtained speech-perception measures. Results confirmed earlier reports of a robust relationship between detection of widely spaced ripples and measures of speech recognition. In contrast, intensity difference limens for broadband noise did not correlate with spectral ripple detection measures, suggesting a dissociation between the ability to detect small changes in intensity across frequency and across time.

  13. Selective Reduction of AMPA Currents onto Hippocampal Interneurons Impairs Network Oscillatory Activity

    Le Magueresse, Corentin; Monyer, Hannah

    2012-01-01

    Reduction of excitatory currents onto GABAergic interneurons in the forebrain results in impaired spatial working memory and altered oscillatory network patterns in the hippocampus. Whether this phenotype is caused by an alteration in hippocampal interneurons is not known because most studies employed genetic manipulations affecting several brain regions. Here we performed viral injections in genetically modified mice to ablate the GluA4 subunit of the AMPA receptor in the hippocampus (GluA4HC−/− mice), thereby selectively reducing AMPA receptor-mediated currents onto a subgroup of hippocampal interneurons expressing GluA4. This regionally selective manipulation led to a strong spatial working memory deficit while leaving reference memory unaffected. Ripples (125–250 Hz) in the CA1 region of GluA4HC−/− mice had larger amplitude, slower frequency and reduced rate of occurrence. These changes were associated with an increased firing rate of pyramidal cells during ripples. The spatial selectivity of hippocampal pyramidal cells was comparable to that of controls in many respects when assessed during open field exploration and zigzag maze running. However, GluA4 ablation caused altered modulation of firing rate by theta oscillations in both interneurons and pyramidal cells. Moreover, the correlation between the theta firing phase of pyramidal cells and position was weaker in GluA4HC−/− mice. These results establish the involvement of AMPA receptor-mediated currents onto hippocampal interneurons for ripples and theta oscillations, and highlight potential cellular and network alterations that could account for the altered working memory performance. PMID:22675480

  14. A High Power Density Integrated Charger for Electric Vehicles with Active Ripple Compensation

    Liwen Pan

    2015-01-01

    Full Text Available This paper suggests a high power density on-board integrated charger with active ripple compensation circuit for electric vehicles. To obtain a high power density and high efficiency, silicon carbide devices are reported to meet the requirement of high-switching-frequency operation. An integrated bidirectional converter is proposed to function as AC/DC battery charger and to transfer energy between battery pack and motor drive of the traction system. In addition, the conventional H-bridge circuit suffers from ripple power pulsating at second-order line frequency, and a scheme of active ripple compensation circuit has been explored to solve this second-order ripple problem, in which a pair of power switches shared traction mode, a ripple energy storage capacitor, and an energy transfer inductor. Simulation results in MATLAB/Simulink validated the eligibility of the proposed topology. The integrated charger can work as a 70 kW motor drive circuit or a converter with an active ripple compensation circuit for 3 kW charging the battery. The impact of the proposed topology and control strategy on the integrated charger power losses, efficiency, power density, and thermal performance has also been analysed and simulated.

  15. In the field of energy cost reduction, what is the potential?; En matiere de reduction des depenses d`energie: quel est le gisement?

    Millet, B. [Departement Industrie, CEREN (France)

    1996-12-31

    Through a segmentation of the fuel and electric power consumptions in the various industrial sectors and energy consumption process types in France in 1990, the energy conservation potential in the French metalworking and mechanical industry is analyzed and its evolution up to 2005 is assessed. It is shown that the reduction potential amounts to 450 kTep or 20 percent of the metalworking and metallic construction industry energy consumption, with an important part for the out-of-process sector (space heating, compressed air production, lighting). In the process sector, important reductions could be realized in thermal treatments and metal heating prior forming

  16. Dune field pattern formation and recent transporting winds in the Olympia Undae Dune Field, north polar region of Mars

    Ewing, Ryan C.; Peyret, Aymeric-Pierre B.; Kocurek, Gary; Bourke, Mary

    2010-01-01

    High-Resolution Imaging Science Experiment (HiRISE) imagery of the central Olympia Undae Dune Field in the north polar region of Mars shows a reticulate dune pattern consisting of two sets of nearly orthogonal dune crestlines, with apparent slipfaces on the primary crests, ubiquitous wind ripples, areas of coarse-grained wind ripples, and deflated interdune areas. Geomorphic evidence and dune field pattern analysis of dune crest length, spacing, defect density, and orientation indicates that ...

  17. [Bio-electrochemical effect on hydrogenotrophic sulfate reduction stimulated by electrical field in the presence of H2 under atmospheric pressure].

    Xu, Hui-Wei; Zhang, Xu; Yang, Shan-Shan; Li, Guang-He

    2009-07-15

    Microbial sulfate reduction rate is limited with H2 as electron donor. In order to improve hydrogenotrophic sulfate reduction under normal atmospheric H2 pressure, a bio-electrochemical system with direct current was designed and performed in this study. Results indicates that sulfate reduction rate (SRR) increases with the augment of current intensity under lower current intensity (I electric or magnetic field stimulates the proliferation of sulfate-reducing bacteria (SRB) and the activity of the enzymes. When I is higher than 1.50 mA, the activity of SRB is inhibited, resulting in lower reduction rate compared with that at lower current. If controlling the cathode potential lower than -0.69 V and H2 partial pressure 1.01 x 10(5) Pa, electro-catalytic sulfate reduction process takes place with H2 as reductant in this bio-electrochemical system. However, the overall reduction rate is still lower than that when I = 1.50 mA is applied, and additionally the energy consumption is much higher. Therefore, electric field of low intensity can enhance hydrogenotrophic sulfate reduction in the presence of H2 under atmospheric pressure.

  18. IDENTIFIKASI PENYAKIT PADA TERUMBU KARANG MENGGUNAKAN RIPPLE DOWN RULES

    Agus Cahyo Nugroho

    2018-01-01

    Full Text Available Along with the development of technology, people developed a system that capable of adopting processes and human thinking as an expert system that contains specific knowledge so that everyone can use it to solve a specific problem, namely the diagnosis of coral reef disease. The purpose of this study is to develop an expert system for diagnosing coral reef disease  in the form of websites using PHP with a MySQL database. Expert system for diagnosing coral reef disease problem is using Ripple Down Rules (RDR method has a goal to discover symptoms that appear in the form of questions that can diagnose the coral reef disease based on website. Web based expert system is able to recognize types of coral reef disease after consultation by answering a few questions that are displayed by the application of expert systems and can infer some types of coral  reef disease. Data coral reef disease that already known adapt to rules which are made for matching the symptoms of coral reef disease.

  19. Screening conditions in a magnetized plasma with electron beam, with application to ripple trapped electron losses

    Faudot, E.; Heuraux, S. [Nancy-1 Univ. Henri Poincare, LPMIA, UMR CNRS 7040, 54 (France); Colas, L.; Saint-Laurent, F.; Martin, G.; Basiuk, V. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee

    2004-07-01

    In Tore Supra, electrons are accelerated by lower hybrid waves in the direction parallel to the confinement magnetic field, in order to drive non-inductive current. But electrons have also on increase of their perpendicular velocity, then 10% of the most energetic electrons get trapped in the magnetic ripple between 2 adjacent toroidal coils, thus forming a beam. The electron beam follows a banana trajectory, the 20 mm wide protection represented by a cooled copper tube is assumed to protect the VP entrance from this energetic flux. Nevertheless, this beam is able to go beyond the copper tube and creates a hot spot on the steel panel edge able to melt the metal. Heat fluxes deposition on the vertical port (VP) can be understood with a beam+sheath theory including the fact that the sheaths can be obstructed when their length becomes greater than flux tube length. By this way, we identify 4 deposition regimes: 2 free sheath regimes and 2 obstructed sheath regimes. Beam flux deposits either at the entrance of the VP along first 2 cm behind the copper tube or until the end of the VP when beam flux is high and for free sheath. Obstructed sheaths make the repulsive, potential for electrons decrease and so accelerate the flux deposition. (authors)

  20. Reducing plant radiation fields by source term reduction - tracking cobalt and antimony to their sources at Gentilly-2

    Gauthier, P.; Guzonas, D.A.

    2006-01-01

    the same specifications at Gentilly-2 as at other CANDU 6 plants. Consequently, the task group revisited operating and maintenance practices, going back through station operating history to identify operational practices that could have lead to increased 59 Co release and/or 60 Co production. The focus rapidly moved to the fuel handling system, as it had long been suspected, but never proven, that the Stellite ram balls were a major source of 59 Co; the fuelling machines provide a direct route for the introduction of corrosion or wear products into the reactor core. Data on the gamma fields measured in the fuelling machine D 2 O supply room from 1995 to the present were reviewed. Water samples were taken and chemically analysed. The results confirmed the presence of 59 Co, probably generated by the wear and corrosion of the Stellite ram balls, and also confirmed the presence of antimony in the system. As part of the task group program, γ-spectrometry was performed in the course of a refuelling cycle. The results showed that variations in the general radiation fields observed in the fuelling machine D 2 O supply room resulted from variations of the 122 Sb and 124 Sb concentrations in the process water. The presence of 122 Sb (t 1/2 3.2 d) suggested that the antimony was recently released from the reactor core. 60 Co was also detected but the level was constant; 59 Co from the ram balls is invisible to γ-spectrometry before it is activated to 60 Co. Remedial actions were implemented in mid-July, 2004. Shortly after, a significant reduction in the radiation fields in the Gentilly-2 fuelling machine D2 O supply room was confirmed. During an unplanned outage in December 2004, a decrease in fields, in particular those due to 60 Co and radioantimony, was found at the reactor face. Activity monitoring scheduled for the 2005 annual outage should confirm if the source of the abnormally high fields has finally been identified. This presentation will describe the task force

  1. Data reduction pipeline for the CHARIS integral-field spectrograph I: detector readout calibration and data cube extraction

    Brandt, Timothy D.; Rizzo, Maxime; Groff, Tyler; Chilcote, Jeffrey; Greco, Johnny P.; Kasdin, N. Jeremy; Limbach, Mary Anne; Galvin, Michael; Loomis, Craig; Knapp, Gillian; McElwain, Michael W.; Jovanovic, Nemanja; Currie, Thayne; Mede, Kyle; Tamura, Motohide; Takato, Naruhisa; Hayashi, Masahiko

    2017-10-01

    We present the data reduction pipeline for CHARIS, a high-contrast integral-field spectrograph for the Subaru Telescope. The pipeline constructs a ramp from the raw reads using the measured nonlinear pixel response and reconstructs the data cube using one of three extraction algorithms: aperture photometry, optimal extraction, or χ2 fitting. We measure and apply both a detector flatfield and a lenslet flatfield and reconstruct the wavelength- and position-dependent lenslet point-spread function (PSF) from images taken with a tunable laser. We use these measured PSFs to implement a χ2-based extraction of the data cube, with typical residuals of ˜5% due to imperfect models of the undersampled lenslet PSFs. The full two-dimensional residual of the χ2 extraction allows us to model and remove correlated read noise, dramatically improving CHARIS's performance. The χ2 extraction produces a data cube that has been deconvolved with the line-spread function and never performs any interpolations of either the data or the individual lenslet spectra. The extracted data cube also includes uncertainties for each spatial and spectral measurement. CHARIS's software is parallelized, written in Python and Cython, and freely available on github with a separate documentation page. Astrometric and spectrophotometric calibrations of the data cubes and PSF subtraction will be treated in a forthcoming paper.

  2. Assessment of Estimation Methods ForStage-Discharge Rating Curve in Rippled Bed Rivers

    P. Maleki

    2016-02-01

    Full Text Available Introduction: Interactionbetweenwater flow characteristics andthe bed erodibilityplays an important role in sediment transport process. In order to reach stability, rivers with deposition or bottom erosion make a different bed form in the riverbed. One way to identify thebehavior of therivers is to study the structure and formation of bed forms within them. Ripples are the smallest of the bed forms. The longitudinal cross section of ripples are usually not symmetrical. The upstream face is long and has a gentle slope, and the downstream face is short and steep. The height of ripples is usually between 0.5 cm and 2 cm; the height ripple is not more than 5 cm. The wave lengths normally do not exceed 30cm, and they are usually within the range of 1 cm to 15 cm. Their occurrence is the result of the unstable viscous layer near the boundary. They can form in both shallow and deep water.With an increase of the flow velocity, the plan form of the ripples gradually develops form straight line to curves and then to a pattern like fish scales, symmetrical or unsymmetrical, as shown in Fig 1. Figure1-The patterndevelopment oftheripple Raudkivi (1966 was the first person that, the flow structure over ripples was investigated experimentally.Hethenestablishseveraldifferent conditionsonthemovingsandbedinanlaboratorychannelconsisted of a rectangular cross-section with base width of 70cm, wasable toform arow ofripples , he wassucceed toform arow ofripples.JafariMianaei and Keshavarzi(2008,studied the turbulentflow betweentwoartificialripples for investigate the change of kinetic energyandshearstress on overripples. The stage- discharge rating curve is one of the most important tools in the hydraulic studies. In alluvial rivers,bed rippled are formed and significantly affect the stage- discharge rating curve. In this research, the effects of two different type of ripples (parallel and flakeshape onthe hydraulic characteristicsof flow were experimentally studied

  3. Nike Experiment to Observe Strong Areal Mass Oscillations in a Rippled Target Hit by a Short Laser Pulse

    Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J. L.; Kessler, T. J.; Schmitt, A. J.; Obenschain, S. P.; Metzler, N.; Oh, J.

    2010-11-01

    When a short (sub-ns) laser pulse deposits finite energy in a target, the shock wave launched into it is immediately followed by a rarefaction wave. If the irradiated surface is rippled, theory and simulations predict strong oscillations of the areal mass perturbation amplitude in the target [A. L. Velikovich et al., Phys. Plasmas 10, 3270 (2003).] The first experiment designed to observe this effect has become possible by adding short-driving-pulse capability to the Nike laser, and has been scheduled for the fall of 2010. Simulations show that while the driving pulse of 0.3 ns is on, the areal mass perturbation amplitude grows by a factor ˜2 due to ablative Richtmyer-Meshkov instability. It then decreases, reverses phase, and reaches another maximum, also about twice its initial value, shortly after the shock breakout at the rear target surface. This signature behavior is observable with the monochromatic x-ray imaging diagnostics fielded on Nike.

  4. Dynamic and photometric evolutionary models of tidal tails and ripples

    Wallin, J.F.

    1989-01-01

    An investigation into the causes of star formation in tidal tails has been conducted using a restricted three-body dynamical model in conjunction with a broad-band photometric evolutionary code. In these models, regions of compression form inside the disk and along the tidal tail and tidal bridge. The effects these density changes have on the colors of the tidal features are examined with a broad-band photometric evolutionary code. A spiral galaxy population is synthesized and the effects of modest changes in the star formation rate are explored. Limits on the density changes needed to make detectable changes in the colors are calculated using a Schmidt (1959) law. These models suggest that the blue colors and knotty features observed in the tidal features of some galaxies result from increased rates of star formation induced by tidally produced density increases. Limitations of this model are discussed along with photometric evolutionary models based on the density evolution in the tails. The Lynds and Toomre (1976) interpretation of ring galaxies as the natural result of a nearly head-on collision between a disk galaxy and a companion galaxy has become widely accepted. Similarly, Quinn's (1984) interpretation of the shells in elliptical galaxies as the aftermath of the cannibalization of a low-mass companion has been quite successful in accounting for the observations. Restricted three-body calculations of high inclination, low impact parameter encounters demonstrate that the shell-like ripples observed in a number of disk galaxies can also be produced as collisional artifacts from internal oscillations much as in ring galaxies

  5. Serotonin dependent masking of hippocampal sharp wave ripples.

    ul Haq, Rizwan; Anderson, Marlene L; Hollnagel, Jan-Oliver; Worschech, Franziska; Sherkheli, Muhammad Azahr; Behrens, Christoph J; Heinemann, Uwe

    2016-02-01

    Sharp wave ripples (SPW-Rs) are thought to play an important role in memory consolidation. By rapid replay of previously stored information during slow wave sleep and consummatory behavior, they result from the formation of neural ensembles during a learning period. Serotonin (5-HT), suggested to be able to modify SPW-Rs, can affect many neurons simultaneously by volume transmission and alter network functions in an orchestrated fashion. In acute slices from dorsal hippocampus, SPW-Rs can be induced by repeated high frequency stimulation that induces long-lasting LTP. We used this model to study SPW-R appearance and modulation by 5-HT. Although stimulation in presence of 5-HT permitted LTP induction, SPW-Rs were "masked"--but appeared after 5-HT wash-out. This SPW-R masking was dose dependent with 100 nM 5-HT being sufficient--if the 5-HT re-uptake inhibitor citalopram was present. Fenfluramine, a serotonin releaser, could also mask SPW-Rs. Masking was due to 5-HT1A and 5-HT2A/C receptor activation. Neither membrane potential nor membrane conductance changes in pyramidal cells caused SPW-R blockade since both remained unaffected by combining 5-HT and citalopram. Moreover, 10 and 30 μM 5-HT mediated SPW-R masking preceded neuronal hyperpolarization and involved reduced presynaptic transmitter release. 5-HT, as well as a 5-HT1A agonist, augmented paired pulse facilitation and affected the coefficient of variance. Spontaneous SPW-Rs in mice hippocampal slices were also masked by 5-HT and fenfluramine. While neuronal ensembles can acquire long lasting LTP during higher 5-HT levels, lower 5-HT levels enable neural ensembles to replay previously stored information and thereby permit memory consolidation memory. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Effect of ripple-induced transport on H-mode performance in tokamaks

    Parail, V.; Vries, P. de; Lonnroth, J.; Kiviniemi, T.; Johnson, T.; Loarte, A.; Saibene, G.; Hatae, T.; Kamada, Y.; Konovalov, S.; Oyama, N.; Shinohara, K.; Tobita, K.; Urano, H.

    2005-01-01

    A number of experiments have shown that ripple-induced transport influences performance of ELMy H-modes in the tokamak. A noticeable difference in confinement, ELM frequency and amplitude was found between JET (with ripple amplitude δ∼0.1%) and JT-60U (with δ∼1%) in otherwise identical discharges. It was previously shown in JET experiments with enhanced ripple that a gradual increase in the ripple amplitude first leads to a modest improvement in plasma confinement, which is followed by the degradation of edge pedestal and further transition to the L-mode regime if δ increases further. The DIII-D team recently reported a marginal increase in confinement in experiments with an edge transport enhanced by the externally driven resonant magnetic perturbation. Numerical predictive modelling of the dynamics of ELMy H-mode JET plasma relevant to a JET/JT-60U similarity experiment has been conducted taking into account ripple-induced ion transport, which was computed using the orbit following code ASCOT. This predictive modelling reveals that, depending on plasma parameters, ripple amplitude and localisation (the latter depending on the toroidal coil design), this additional transport can either improve global plasma confinement or reduce it. These controlled ripple losses might be used as an effective tool for ELM mitigation and may provide an explanation for the difference between JET and JT-60U observed in the similarity experiments. A detailed comparison between ripple- induced transport and the alternative method of ELM mitigation by an externally driven edge magnetic perturbation is discussed. The fact that ripple losses mainly increase ion transport, while a stochastic magnetic layer increases electron transport indicates that it might be beneficial to use a combination of both methods in future experiments. This work was funded partly by the United Kingdom Engineering and Physical Sciences Research Council and by the European Communities under the contract of

  7. The role of wind field induced flow velocities in destratification and hypoxia reduction at Meiling Bay of large shallow Lake Taihu, China.

    Jalil, Abdul; Li, Yiping; Du, Wei; Wang, Wencai; Wang, Jianwei; Gao, Xiaomeng; Khan, Hafiz Osama Sarwar; Pan, Baozhu; Acharya, Kumud

    2018-01-01

    Wind induced flow velocity patterns and associated thermal destratification can drive to hypoxia reduction in large shallow lakes. The effects of wind induced hydrodynamic changes on destratification and hypoxia reduction were investigated at the Meiling bay (N 31° 22' 56.4″, E 120° 9' 38.3″) of Lake Taihu, China. Vertical flow velocity profile analysis showed surface flow velocities consistency with the wind field and lower flow velocity profiles were also consistent (but with delay response time) when the wind speed was higher than 6.2 m/s. Wind field and temperature found the control parameters for hypoxia reduction and for water quality conditions at the surface and bottom profiles of lake. The critical temperature for hypoxia reduction at the surface and the bottom profile was ≤24.1C° (below which hypoxic conditions were found reduced). Strong prevailing wind field (onshore wind directions ESE, SE, SSE and E, wind speed ranges of 2.4-9.1 m/s) reduced the temperature (22C° to 24.1C°) caused reduction of hypoxia at the near surface with a rise in water levels whereas, low to medium prevailing wind field did not supported destratification which increased temperature resulting in increased hypoxia. Non-prevailing wind directions (offshore) were not found supportive for the reduction of hypoxia in study area due to less variable wind field. Daytime wind field found more variable (as compared to night time) which increased the thermal destratification during daytime and found supportive for destratification and hypoxia reduction. The second order exponential correlation found between surface temperature and Chlorophyll-a (R 2 : 0.2858, Adjusted R-square: 0.2144 RMSE: 4.395), Dissolved Oxygen (R 2 : 0.596, Adjusted R-square: 0.5942, RMSE: 0.3042) concentrations. The findings of the present study reveal the driving mechanism of wind induced thermal destratification and hypoxic conditions, which may further help to evaluate the wind role in eutrophication

  8. Energy-separated sequential irradiation for ripple pattern tailoring on silicon surfaces

    Kumar, Tanuj [Department of Physics, Central University of Haryana, Jant-Pali, Mahendergarh 1123029 (India); Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Kumar, Manish, E-mail: manishbharadwaj@gmail.com [Department of Physics, Central University of Rajasthan, Kishangarh 305801 (India); Panchal, Vandana [Department of Physics, National Institute of Technology, Kurukshetra 136119 (India); Sahoo, P.K. [School of Physical Sciences, National Institute of Science Education and Research, Bhubaneswar 751005 (India); Kanjilal, D. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2015-12-01

    Highlights: • A new process for controlling the near-surface amorphization of ripples on Si surfaces. • Ripples generation by 100 KeV Ar{sup +} and amorphization control by 60 KeV Ar{sup +} irradiation. • Advantage of energy-separated irradiation demonstrated by detailed RBS and AFM studies. • Relevant mechanism is presented on the basis of DAMAGE and SIMNRA simulations. • Key role of solid flow towards the amorphous/crystalline interface is demonstrated. - Abstract: Nanoscale ripples on semiconductor surfaces have potential application in biosensing and optoelectronics, but suffer from uncontrolled surface-amorphization when prepared by conventional ion-irradiation methods. A two-step, energy-separated sequential-irradiation enables simultaneous control of surface-amorphization and ripple-dimensions on Si(1 0 0). The evolution of ripples using 100 keV Ar{sup +} bombardment and further tuning of the patterns using a sequential-irradiation by 60 keV Ar{sup +} at different fluences are demonstrated. The advantage of this approach as opposed to increased fluence at the same energy is clarified by atomic force microscopy and Rutherford backscattering spectroscopy investigations. The explanation of our findings is presented through DAMAGE simulation.

  9. Adhesion modification of neural stem cells induced by nanoscale ripple patterns

    Pedraz, P; Casado, S; Rodriguez, V; Ayuso-Sacido, A; Gnecco, E; Giordano, M C; Mongeot, F Buatier de

    2016-01-01

    We have studied the influence of anisotropic nanopatterns (ripples) on the adhesion and morphology of mouse neural stem cells (C17.2) on glass substrates using cell viability assay, optical microscopy and atomic force microscopy. The ripples were produced by defocused ion beam sputtering with inert Ar ions, which physically remove atoms from the surface at the energy of 800 eV. The ripple periodicity (∼200 nm) is comparable to the thickness of the cytoplasmatic microspikes (filopodia) which link the stem cells to the substrate. All methods show that the cell adhesion is significantly lowered compared to the same type of cells on flat glass surfaces. Furthermore, the AFM analysis reveals that the filopodia tend to be trapped parallel or perpendicular to the ripples, which limits the spreading of the stem cell on the rippled substrate. This opens the perspective of controlling the micro-adhesion of stem cells and the orientation of their filopodia by tuning the anisotropic substrate morphology without chemical reactions occurring at the surface. (paper)

  10. Hierarchical thermoplastic rippled nanostructures regulate Schwann cell adhesion, morphology and spatial organization.

    Masciullo, Cecilia; Dell'Anna, Rossana; Tonazzini, Ilaria; Böettger, Roman; Pepponi, Giancarlo; Cecchini, Marco

    2017-10-12

    Periodic ripples are a variety of anisotropic nanostructures that can be realized by ion beam irradiation on a wide range of solid surfaces. Only a few authors have investigated these surfaces for tuning the response of biological systems, probably because it is challenging to directly produce them in materials that well sustain long-term cellular cultures. Here, hierarchical rippled nanotopographies with a lateral periodicity of ∼300 nm are produced from a gold-irradiated germanium mold in polyethylene terephthalate (PET), a biocompatible polymer approved by the US Food and Drug Administration for clinical applications, by a novel three-step embossing process. The effects of nano-ripples on Schwann Cells (SCs) are studied in view of their possible use for nerve-repair applications. The data demonstrate that nano-ripples can enhance short-term SC adhesion and proliferation (3-24 h after seeding), drive their actin cytoskeleton spatial organization and sustain long-term cell growth. Notably, SCs are oriented perpendicularly with respect to the nanopattern lines. These results provide information about the possible use of hierarchical nano-rippled elements for nerve-regeneration protocols.

  11. Direct imaging of atomic-scale ripples in few-layer graphene.

    Wang, Wei L; Bhandari, Sagar; Yi, Wei; Bell, David C; Westervelt, Robert; Kaxiras, Efthimios

    2012-05-09

    Graphene has been touted as the prototypical two-dimensional solid of extraordinary stability and strength. However, its very existence relies on out-of-plane ripples as predicted by theory and confirmed by experiments. Evidence of the intrinsic ripples has been reported in the form of broadened diffraction spots in reciprocal space, in which all spatial information is lost. Here we show direct real-space images of the ripples in a few-layer graphene (FLG) membrane resolved at the atomic scale using monochromated aberration-corrected transmission electron microscopy (TEM). The thickness of FLG amplifies the weak local effects of the ripples, resulting in spatially varying TEM contrast that is unique up to inversion symmetry. We compare the characteristic TEM contrast with simulated images based on accurate first-principles calculations of the scattering potential. Our results characterize the ripples in real space and suggest that such features are likely common in ultrathin materials, even in the nanometer-thickness range.

  12. A ripple-spreading genetic algorithm for the aircraft sequencing problem.

    Hu, Xiao-Bing; Di Paolo, Ezequiel A

    2011-01-01

    When genetic algorithms (GAs) are applied to combinatorial problems, permutation representations are usually adopted. As a result, such GAs are often confronted with feasibility and memory-efficiency problems. With the aircraft sequencing problem (ASP) as a study case, this paper reports on a novel binary-representation-based GA scheme for combinatorial problems. Unlike existing GAs for the ASP, which typically use permutation representations based on aircraft landing order, the new GA introduces a novel ripple-spreading model which transforms the original landing-order-based ASP solutions into value-based ones. In the new scheme, arriving aircraft are projected as points into an artificial space. A deterministic method inspired by the natural phenomenon of ripple-spreading on liquid surfaces is developed, which uses a few parameters as input to connect points on this space to form a landing sequence. A traditional GA, free of feasibility and memory-efficiency problems, can then be used to evolve the ripple-spreading related parameters in order to find an optimal sequence. Since the ripple-spreading model is the centerpiece of the new algorithm, it is called the ripple-spreading GA (RSGA). The advantages of the proposed RSGA are illustrated by extensive comparative studies for the case of the ASP.

  13. Deciphering the role of CA1 inhibitory circuits in sharp wave-ripple complexes.

    Cutsuridis, Vassilis; Taxidis, Jiannis

    2013-01-01

    Sharp wave-ripples (SWRs) are population oscillatory patterns in hippocampal LFPs during deep sleep and immobility, involved in the replay of memories acquired during wakefulness. SWRs have been extensively studied, but their exact generation mechanism is still unknown. A computational model has suggested that fast perisomatic inhibition may generate the high frequency ripples (~200 Hz). Another model showed how replay of memories can be controlled by various classes of inhibitory interneurons targeting specific parts of pyramidal cells (PC) and firing at particular SWR phases. Optogenetic studies revealed new roles for interneuronal classes and rich dynamic interplays between them, shedding new light in their potential role in SWRs. Here, we integrate these findings in a conceptual model of how dendritic and somatic inhibition may collectively contribute to the SWR generation. We suggest that sharp wave excitation and basket cell (BC) recurrent inhibition synchronises BC spiking in ripple frequencies. This rhythm is imposed on bistratified cells which prevent pyramidal bursting. Axo-axonic and stratum lacunosum/moleculare interneurons are silenced by inhibitory inputs originating in the medial septum. PCs receiving rippling inhibition in both dendritic and perisomatic areas and excitation in their apical dendrites, exhibit sparse ripple phase-locked spiking.

  14. Cost-Effectiveness Analysis of Surface Flow Constructed Wetlands (SFCW) for Nutrient Reduction in Drainage Discharge from Agricultural Fields in Denmark.

    Gachango, F G; Pedersen, S M; Kjaergaard, C

    2015-12-01

    Constructed wetlands have been proposed as cost-effective and more targeted technologies in the reduction of nitrogen and phosphorous water pollution in drainage losses from agricultural fields in Denmark. Using two pig farms and one dairy farm situated in a pumped lowland catchment as case studies, this paper explores the feasibility of implementing surface flow constructed wetlands (SFCW) based on their cost effectiveness. Sensitivity analysis is conducted by varying the cost elements of the wetlands in order to establish the most cost-effective scenario and a comparison with the existing nutrients reduction measures carried out. The analyses show that the cost effectiveness of the SFCW is higher in the drainage catchments with higher nutrient loads. The range of the cost effectiveness ratio on nitrogen reduction differs distinctively with that of catch crop measure. The study concludes that SFCW could be a better optimal nutrients reduction measure in drainage catchments characterized with higher nutrient loads.

  15. Computational study of ammonia adsorption on the perfect and rippled graphene sheet

    Seyed-Talebi, Seyedeh Mozhgan; Beheshtian, Javad

    2013-01-01

    Adsorption of an ammonia molecule onto perfect and rippled graphene is studied using molecular mechanics calculations. The most stable orientation of an ammonia molecule and equilibrium distance of this molecule over graphene surface (motivated by the recent realization of graphene sensors to detect individual gas molecules) is determined using DFT calculation. This result is in agreement with the predicted molecular mechanics calculation result. It also has been found that (i) the ammonia molecule is weakly adsorbed onto the graphene sheet; (ii) the periodic nature of the potential energy stored between ammonia and perfect graphene is altered due to the sinusoidal ripples; and (iii) the effect of amplitude and wavelength of the one-dimensional created ripple on different energy modes is reported

  16. Low cost concepts to reduce the voltage ripple of the DC power supply

    Cheng, Y.; Liu, K.B.

    1993-01-01

    If the gain of current feedback is low, the short term stability of magnet power supply will be affected by a soft power line. Typically, the step-charge and the imbalance of the three phase power line cause the most serious voltage ripple. Usually, the voltage feedback with a coupling transformer is considered to reduce the voltage ripple. However, for the high current power supply, the space and cooling problem of the coupling transformer become inconvenient. In this paper, the authors suggest to use the toroidal core with the compensation winding, working like a DCCT, as the coupling transformer. Then, a high speed detector of the AC line level is developed. It restricts the voltage ripple passing to the coupling transformer. These methods have the advantage of small size, low power consumption and low cost

  17. Computational study of ammonia adsorption on the perfect and rippled graphene sheet

    Seyed-Talebi, Seyedeh Mozhgan [Department of Physics, Shahid Rajaee Teacher Training University, Tehran (Iran, Islamic Republic of); Beheshtian, Javad, E-mail: J.Beheshtian@Srttu.edu [Department of Chemistry, Shahid Rajaee Teacher Training University, Tehran (Iran, Islamic Republic of)

    2013-11-15

    Adsorption of an ammonia molecule onto perfect and rippled graphene is studied using molecular mechanics calculations. The most stable orientation of an ammonia molecule and equilibrium distance of this molecule over graphene surface (motivated by the recent realization of graphene sensors to detect individual gas molecules) is determined using DFT calculation. This result is in agreement with the predicted molecular mechanics calculation result. It also has been found that (i) the ammonia molecule is weakly adsorbed onto the graphene sheet; (ii) the periodic nature of the potential energy stored between ammonia and perfect graphene is altered due to the sinusoidal ripples; and (iii) the effect of amplitude and wavelength of the one-dimensional created ripple on different energy modes is reported.

  18. Reducing Torque Ripples of the Axial Flux PM Motors by Magnet Stepping and Shifting

    E. Cetin

    2018-02-01

    Full Text Available Higher efficiency on electric machines is the research goal of many studies. An example is the axial flux permanent magnet machines. These machines have some advantages like their watt/kg efficiency and torque density. This study aims to develop the performance characteristics of the axial flux permanent magnet machines. A new rotor magnet poles design in axial flux machines is suggested to mitigate the torque ripples. The method of stepping and shifting of the magnets is used. Two different designs are compared to verify the proposed approach. 3D finite element analysis is used for simulations. Torque ripple and back electromotive force waveforms are obtained from computer analysis. As a conclusion, the suggested method is found to be useable and mitigates the torque ripples. In addition to that, back EMF waveforms are turned to sinusoidal by the suggested design.

  19. Xe ion beam induced rippled structures on differently oriented single-crystalline Si surfaces

    Hanisch, Antje; Grenzer, Joerg; Facsko, Stefan [Forschungszentrum Dresden-Rossendorf, Institut fuer Ionenstrahlphysik und Materialforschung, PO Box 510119, 01314 Dresden (Germany); Biermanns, Andreas; Pietsch, Ullrich, E-mail: A.Hanisch@fzd.d [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany)

    2010-03-24

    We report on Xe{sup +} induced ripple formation at medium energy on single-crystalline silicon surfaces of different orientations using substrates with an intentional miscut from the [0 0 1] direction and a [1 1 1] oriented wafer. The ion beam incidence angle with respect to the surface normal was kept fixed at 65{sup 0} and the ion beam projection was parallel or perpendicular to the [1 1 0] direction. By a combination of atomic force microscopy, x-ray diffraction and high-resolution transmission electron microscopy we found that the features of the surface and subsurface rippled structures such as ripple wavelength and amplitude and the degree of order do not depend on the surface orientation as assumed in recent models of pattern formation for semiconductor surfaces. (fast track communication)

  20. Ripple structures on surfaces and underlying crystalline layers in ion beam irradiated Si wafers

    Grenzer, J.; Muecklich, A. [Forschungszentrum Rossendorf, Institut fuer Ionenstrahlphysik und Materialforschung, Dresden (Germany); Biermanns, A.; Grigorian, S.A.; Pietsch, U. [Institute of Physics, University of Siegen (Germany)

    2009-08-15

    We report on the formation of ion beam induced ripples in Si(001) wafers when bombarded with Ar+ ions at an energy of 60 keV. A set of samples varying incidence and azimuthal angles of the ion beam with respect to the crystalline surface orientation was studied by two complementary near surface sensitive techniques, namely atomic force microscopy and depth-resolved X-ray grazing incidence diffraction (GID). Additionally, cross-section TEM investigations were carried out. The ripple-like structures are formed at the sample surface as well as at the buried amorphous-crystalline interface. Best quality of the ripple pattern was found when the irradiating ion beam was aligned parallel to the (111) planes. The quality decreases rapidly if the direction of the ion beam deviates from (111). (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  1. Effect of impurities and ripple upon power regulation in self-sustained tokamaks

    Bromberg, L.; Cohn, D.R.

    1981-01-01

    Tokamak power reactors will likely operate in a self sustained heating mode where additional power losses are introduced to permit higher levels of alpha particle heating (and thus higher levels of total fusion power) at thermal equilibrium. Illustrative 0-dimensional calculations are made to assess requirements for power regulation of self sustained tokamak plasmas by the use of impurity radiation. Effects of impurities upon allowable fuel density and thermal stability are determined. Requirements are calculated for passive thermal stability control by temperature driven radial motion in the presence of ripple transport losses; it appears that stability might be attained over a relatively wide temperature range with a small amount of ripple transport loss. Requirements for power regulation by the use of ripple transport are also determined

  2. Temperature dependence of rippled corrugations induced on the Rh(1 1 0) surface via ion sputtering

    Molle, Alessandro; Buatier de Mongeot, F.; Granone, F.; Buzio, R.; Firpo, G.; Boragno, C.; Valbusa, U.

    2005-01-01

    Metal surfaces can be easily nanopatterned via ion sputtering: mounds or ripples can be created depending on the surface symmetry and temperature. However, in many cases these structures are unstable at room temperature and above, due to the adatom fast diffusion. This fact prevents the use of such systems as substrate or nanostamps for a technological implementation. In this paper we present a spot profile analysis low energy electron diffraction (SPA-LEED) study on the nanopatterning of a Rh(1 1 0) single crystal. Like the other (1 1 0) metal surfaces, previously investigated, also Rh(1 1 0) shows for increasing temperatures a transition between different rippled morphologies. The main advantage of this system is its stability at room temperature. From SPA-LEED data we can measure the structural features (average periodicity and local faceting) of the observed rippled structures

  3. Lacosamide and Levetiracetam Have No Effect on Sharp-Wave Ripple Rate.

    Kudlacek, Jan; Chvojka, Jan; Posusta, Antonin; Kovacova, Lubica; Hong, Seung Bong; Weiss, Shennan; Volna, Kamila; Marusic, Petr; Otahal, Jakub; Jiruska, Premysl

    2017-01-01

    Pathological high-frequency oscillations are a novel marker used to improve the delineation of epileptogenic tissue and, hence, the outcome of epilepsy surgery. Their practical clinical utilization is curtailed by the inability to discriminate them from physiological oscillations due to frequency overlap. Although it is well documented that pathological HFOs are suppressed by antiepileptic drugs (AEDs), the effect of AEDs on normal HFOs is not well known. In this experimental study, we have explored whether physiological HFOs (sharp-wave ripples) of hippocampal origin respond to AED treatment. The results show that application of a single dose of levetiracetam or lacosamide does not reduce the rate of sharp-wave ripples. In addition, it seems that these new generation drugs do not negatively affect the cellular and network mechanisms involved in sharp-wave ripple generation, which may provide a plausible explanation for the absence of significant negative effects on cognitive functions of these drugs, particularly on memory.

  4. A Zero Input Current Ripple ZVS/ZCS Boost Converter with Boundary-Mode Control

    Ching-Ming Lai

    2014-10-01

    Full Text Available In this paper, in order to achieve zero ripple conditions, the use of a ripple mirror (RM circuit for the boost converter is proposed. The operation modes are studied and steady-state analyses performed to show the merits of the proposed converter. It is found that the proposed RM circuit technique can provide much better flexibility than the two-phase interleaved boost converter for locating the zero ripple operating point in the design stage. In addition, the choice of using a boundary-mode control is mainly based on the consideration of achieving both ZVS (zero voltage switching/ZCS (zero current switching soft-switching and constant on-time control for the converter. To verify the performance of the proposed converter, a 48 V input and 200 W/200 V output prototype is constructed. Experimental results verify the effectiveness of the proposed converter.

  5. Utilization of reduced fuelling ripple set in ROP detector layout optimization

    Kastanya, Doddy

    2012-01-01

    Highlights: ► ADORE is an ROP detect layout optimization algorithm in CANDU reactors. ► The effect of using reduced set of fuelling ripples in ADORE is assessed. ► Significant speedup can be realized by adopting this approach. ► The quality of the results is comparable to results from full set of ripples. - Abstract: The ADORE (Alternative Detector layout Optimization for REgional overpower protection system) algorithm for performing the optimization of regional overpower protection (ROP) for CANDU® reactors has been recently developed. This algorithm utilizes the simulated annealing (SA) stochastic optimization technique to come up with an optimized detector layout for the ROP systems. For each history in the SA iteration where a particular detector layout is evaluated, the goodness of this detector layout is measured in terms of its trip set point value which is obtained by performing a probabilistic trip set point calculation using the ROVER-F code. Since during each optimization execution thousands of candidate detector layouts are evaluated, the overall optimization process is time consuming. Since for each ROVER-F evaluation the number of fuelling ripples controls the execution time, reducing the number of fuelling ripples will reduce the overall execution time. This approach has been investigated and the results are presented in this paper. The challenge is to construct a set of representative fuelling ripples which will significantly speedup the optimization process while guaranteeing that the resulting detector layout has similar quality to the ones produced when the complete set of fuelling ripples is employed.

  6. A unifying model for planform straightness of ripples and dunes in air and water

    Rubin, David M.

    2012-01-01

    Geologists, physicists, and mathematicians have studied ripples and dunes for more than a century, but despite considerable effort, no general model has been proposed to explain perhaps the most fundamental property of their morphology: why are some bedforms straight, continuous, parallel, and uniform in planform geometry (i.e. two-dimensional) whereas others are irregular (three-dimensional)? Here we argue that physical coupling along the crest of a bedform is required to produce straight crests and that along-crest flow and sand transport provide effective physical mechanisms for that coupling. Ripples and dunes with the straightest and most continuous crests include longitudinal and oblique dunes in unidirectional flows, wave ripples, dunes in reversing flows, wind ripples, and ripples migrating along a slope. At first glance, these bedforms appear quite different (ripples and dunes; air and water; transverse, oblique, and longitudinal orientations relative to the net sand-transport direction), but they all have one property in common: a process that increases the amount of along-crest sand transport (that lengthens and straightens their crests) relative to the across-crest transport (that makes them migrate and take the more typical and more three-dimensional planform geometry). In unidirectional flows that produce straight bedforms, along-crest transport of sand is caused by along-crest flow (non-transverse bedform orientation), gravitational transport along an inclined crest, or ballistic splash in air. Bedforms in reversing flows tend to be straighter than their unidirectional counterparts, because reverse transport across the bedform crest reduces the net across-crest transport (that causes the more typical irregular geometry) relative to the along-crest transport (that smoothes and straightens planform geometry).

  7. Intelligent measurement and compensation of linear motor force ripple: a projection-based learning approach in the presence of noise

    Liu, Yang; Song, Fazhi; Yang, Xiaofeng; Dong, Yue; Tan, Jiubin

    2018-06-01

    Due to their structural simplicity, linear motors are increasingly receiving attention for use in high velocity and high precision applications. The force ripple, as a space-periodic disturbance, however, would deteriorate the achievable dynamic performance. Conventional force ripple measurement approaches are time-consuming and have high requirements on the experimental conditions. In this paper, a novel learning identification algorithm is proposed for force ripple intelligent measurement and compensation. Existing identification schemes always use all the error signals to update the parameters in the force ripple. However, the error induced by noise is non-effective for force ripple identification, and even deteriorates the identification process. In this paper only the most pertinent information in the error signal is utilized for force ripple identification. Firstly, the effective error signals caused by the reference trajectory and the force ripple are extracted by projecting the overall error signals onto a subspace spanned by the physical model of the linear motor as well as the sinusoidal model of the force ripple. The time delay in the linear motor is compensated in the basis functions. Then, a data-driven approach is proposed to design the learning gain. It balances the trade-off between convergence speed and robustness against noise. Simulation and experimental results validate the proposed method and confirm its effectiveness and superiority.

  8. A comprehensive study and analysis of second order harmonic ripple in DC microgrid feeding single phase PWM inverter loads

    Gautam, Aditya R.; Fulwani, Deepak; Guerrero, Josep M.

    2016-01-01

    The paper presents a detailed analysis of second order harmonic ripple in a DC microgrid. A boost converter feeding PWM inverter load is considered and equivalent circuit is proposed. The effect of the size of input capacitor, output capacitor and inductor of boost converter, on this ripple has...

  9. In-field evaluation of clinoptilolite feeding efficacy on the reduction of milk aflatoxin M1 concentration in dairy cattle

    Panagiotis D. Katsoulos

    2016-06-01

    Full Text Available Abstract Background Clinoptilolite is a natural zeolite with high adsorption capacity for polar mycotoxins such as aflatoxins. The efficacy of clinoptilolite in ameliorating the toxic effects of aflatoxicosis has been proven in monogastric animals, but there is no such evidence for ruminants. The aim of this study was to evaluate, under field conditions, whether the dietary administration of clinoptilolite in dairy cows could reduce the concentration of aflatoxin M1 (AFM1 in bulk-tank milk, in farms with higher than or close to 0.05 μg/kg of milk (European maximum allowed residual level. An objective of the present study was also to investigate the effect of particle size of clinoptilolite on aflatoxin binding. Methods Fifteen commercial Greek dairy herds with AFM1 concentrations in bulk tank milk ≥0.05 μg/kg were selected. Bulk tank milk AFM1 was determined prior to the onset and on day 7 of the experiment. Clinoptilolite was added in the total mixed rations of all farms at the rate of 200 g per animal per day, throughout this period. Two different particle sizes of clinoptilolite were used; less than 0.15 mm in 9 farms (LC group and less than 0.8 mm in 6 farms (HC group. Results Clinoptilolite administration significantly reduced AFM1 concentrations in milk in all farms tested at an average rate of 56.2 % (SD: 15.11. The mean milk AFM1 concentration recorded on Day 7 was significantly (P < 0.001 lower compared to that of Day 0 (0.036 ± 0.0061 vs. 0.078 ± 0.0074 μg/kg. In LC group farms the reduction of milk AFM1 concentration was significantly higher than HC group farms (0.046 ± 0.0074 vs. 0.036 ± 0.0061 μg/kg, P = 0.002. As indicated by the Pearson correlation, there was a significant and strong linear correlation among the milk AFM1 concentrations on Days 0 and 7 (R = 0.95, P < 0.001. Conclusions Dietary administration of clinoptilolite, especially of smallest particle size, at the rate of

  10. Ripples and the formation of anisotropic lipid domains: Imaging two-component double bilayers by atomic force microscopy_copy_03

    Leidy, C.; Kaasgaard, Thomas; Crowe, J.H.

    2002-01-01

    by atomic force microscopy, we investigated the origin of these anisotropic lipid domain patterns, and found that ripple phase formation is directly responsible for the anisotropic nature of these domains. The nucleation and growth of fluid-phase domains are found to be directed by the presence of ripples....... In particular, the fluid-phase domains elongate parallel to the ripples. The results show that ripple phase formation may have implications for domain formation in biological systems....

  11. Tuning the shape and damage in ion-beam induced ripples on silicon

    Biermanns, Andreas; Pietsch, Ullrich [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany); Hanisch, Antje; Grenzer, Joerg [Helmholtz-Zentrum Dresden-Rossendorf, Institut fuer Ionenstrahlphysik und Materialforschung, P.O. Box 510119, 01314 Dresden (Germany); Metzger, Till Hartmut [ESRF, 6 rue Jules Horowitz, BP220, 38043 Grenoble Cedex (France)

    2011-11-15

    We investigate the influence of ion beam parameters on the ripple formation on Si(001) surfaces after bombardment with Xe{sup +} ions of 25 keV kinetic energy using a scanning ion beam system. By combining grazing incidence X-ray diffraction, small angle scattering and X-ray reflectivity, we show that during ion irradiation with 70 off-normal angle of incidence, changing the size of the irradiated area leads to an increased number of defects at the interface towards crystalline material. At 65 angle of incidence, the ripple amplitude grows. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. On ripples and rafts: Curvature induced nanoscale structures in lipid membranes

    Schmid, Friederike; Dolezel, Stefan; Meinhardt, Sebastian; Lenz, Olaf

    2014-01-01

    We develop an elastic theory that predicts the spontaneous formation of nanoscale structures in lipid bilayers which locally phase separate between two phases with different spontaneous monolayer curvature. The theory rationalizes in a unified manner the observation of a variety of nanoscale structures in lipid membranes: Rippled states in one-component membranes, lipid rafts in multicomponent membranes. Furthermore, we report on recent observations of rippled states and rafts in simulations of a simple coarse-grained model for lipid bilayers, which are compatible with experimental observations and with our elastic model

  13. Impacts of Ripple Current to the Loading and Lifetime of Power Semiconductor Device

    Ma, Ke; Choi, Uimin; Blaabjerg, Frede

    2017-01-01

    The thermal loading of power electronics devices is determined by many factors and has being a crucial design consideration because it is closely related to the reliability and cost of the converter system. In this paper the impacts of the ripple current to the loss and thermal loading, as well...... as reliability performances of power devices are comprehensively investigated and tested. It is concluded that the amplitude of ripple current may modify the loss and thermal loading of the power devices, especially under the conditions of converter with low power output, and thus the lifetime of devices could...

  14. Observing trans-Planckian ripples in the primordial power spectrum with future large scale structure probes

    Hamann, Jan; Hannestad, Steen; Sloth, Martin Snoager

    2008-01-01

    We revisit the issue of ripples in the primordial power spectra caused by trans-Planckian physics, and the potential for their detection by future cosmological probes. We find that for reasonably large values of the first slow-roll parameter epsilon (> 0.001), a positive detection of trans......-Planckian ripples can be made even if the amplitude is as low as 10^-4. Data from the Large Synoptic Survey Telescope (LSST) and the proposed future 21 cm survey with the Fast Fourier Transform Telescope (FFTT) will be particularly useful in this regard. If the scale of inflation is close to its present upper bound...

  15. Hippocampal Ripple Oscillations and Inhibition-First Network Models: Frequency Dynamics and Response to GABA Modulators.

    Donoso, José R; Schmitz, Dietmar; Maier, Nikolaus; Kempter, Richard

    2018-03-21

    Hippocampal ripples are involved in memory consolidation, but the mechanisms underlying their generation remain unclear. Models relying on interneuron networks in the CA1 region disagree on the predominant source of excitation to interneurons: either "direct," via the Schaffer collaterals that provide feedforward input from CA3 to CA1, or "indirect," via the local pyramidal cells in CA1, which are embedded in a recurrent excitatory-inhibitory network. Here, we used physiologically constrained computational models of basket-cell networks to investigate how they respond to different conditions of transient, noisy excitation. We found that direct excitation of interneurons could evoke ripples (140-220 Hz) that exhibited intraripple frequency accommodation and were frequency-insensitive to GABA modulators, as previously shown in in vitro experiments. In addition, the indirect excitation of the basket-cell network enabled the expression of intraripple frequency accommodation in the fast-gamma range (90-140 Hz), as in vivo In our model, intraripple frequency accommodation results from a hysteresis phenomenon in which the frequency responds differentially to the rising and descending phases of the transient excitation. Such a phenomenon predicts a maximum oscillation frequency occurring several milliseconds before the peak of excitation. We confirmed this prediction for ripples in brain slices from male mice. These results suggest that ripple and fast-gamma episodes are produced by the same interneuron network that is recruited via different excitatory input pathways, which could be supported by the previously reported intralaminar connectivity bias between basket cells and functionally distinct subpopulations of pyramidal cells in CA1. Together, our findings unify competing inhibition-first models of rhythm generation in the hippocampus. SIGNIFICANCE STATEMENT The hippocampus is a part of the brain of humans and other mammals that is critical for the acquisition and

  16. Vzdrževanje likvidnosti kriptovalutnega trga v omrežju Ripple

    BREZIGAR, JAKOB

    2017-01-01

    Vzdrževalec likvidnosti zagotavlja prodajalcem in kupcem finančnih inštrumentov nasprotno stranko pri sklepanju transakcij. Izvajanju nakupnega in prodajnega naročila hkrati pravimo vzdrževanje likvidnosti. Diplomsko delo obsega teoretično in praktično osnovo za izdelavo algoritma za samodejno vzdrževanje likvidnosti na enem izmed perspektivnih kriptovalutnih trgov Ripple. V diplomskem delu povzamemo teoretične osnove vzdrževanja likvidnosti, delovanje kriptovalutnega protokola Ripple in proc...

  17. A comparison of mantle versus involved-field radiotherapy for Hodgkin's lymphoma: reduction in normal tissue dose and second cancer risk

    Koh, Eng-Siew; Paul, Narinder; Hodgson, David C; Tran, Tu Huan; Heydarian, Mostafa; Sachs, Rainer K; Tsang, Richard W; Brenner, David J; Pintilie, Melania; Xu, Tony; Chung, June

    2007-01-01

    Hodgkin's lymphoma (HL) survivors who undergo radiotherapy experience increased risks of second cancers (SC) and cardiac sequelae. To reduce such risks, extended-field radiotherapy (RT) for HL has largely been replaced by involved field radiotherapy (IFRT). While it has generally been assumed that IFRT will reduce SC risks, there are few data that quantify the reduction in dose to normal tissues associated with modern RT practice for patients with mediastinal HL, and no estimates of the expected reduction in SC risk. Organ-specific dose-volume histograms (DVH) were generated for 41 patients receiving 35 Gy mantle RT, 35 Gy IFRT, or 20 Gy IFRT, and integrated organ mean doses were compared for the three protocols. Organ-specific SC risk estimates were estimated using a dosimetric risk-modeling approach, analyzing DVH data with quantitative, mechanistic models of radiation-induced cancer. Dose reductions resulted in corresponding reductions in predicted excess relative risks (ERR) for SC induction. Moving from 35 Gy mantle RT to 35 Gy IFRT reduces predicted ERR for female breast and lung cancer by approximately 65%, and for male lung cancer by approximately 35%; moving from 35 Gy IFRT to 20 Gy IFRT reduces predicted ERRs approximately 40% more. The median reduction in integral dose to the whole heart with the transition to 35 Gy IFRT was 35%, with a smaller (2%) reduction in dose to proximal coronary arteries. There was no significant reduction in thyroid dose. The significant decreases estimated for radiation-induced SC risks associated with modern IFRT provide strong support for the use of IFRT to reduce the late effects of treatment. The approach employed here can provide new insight into the risks associated with contemporary IFRT for HL, and may facilitate the counseling of patients regarding the risks associated with this treatment

  18. Young Investigator Award and Swash Zone Morphology: Field Manipulation and Simulation

    Werner, Brad

    1998-01-01

    .... Self organization models for subaerial and subaqueous ripples, bedforms and beach cusps were developed and a field experiment was conducted to test the model for beach cusp formation against a standing wave model...

  19. Utilization of independent component analysis for accurate pathological ripple detection in intracranial EEG recordings recorded extra- and intra-operatively.

    Shimamoto, Shoichi; Waldman, Zachary J; Orosz, Iren; Song, Inkyung; Bragin, Anatol; Fried, Itzhak; Engel, Jerome; Staba, Richard; Sharan, Ashwini; Wu, Chengyuan; Sperling, Michael R; Weiss, Shennan A

    2018-01-01

    To develop and validate a detector that identifies ripple (80-200 Hz) events in intracranial EEG (iEEG) recordings in a referential montage and utilizes independent component analysis (ICA) to eliminate or reduce high-frequency artifact contamination. Also, investigate the correspondence of detected ripples and the seizure onset zone (SOZ). iEEG recordings from 16 patients were first band-pass filtered (80-600 Hz) and Infomax ICA was next applied to derive the first independent component (IC1). IC1 was subsequently pruned, and an artifact index was derived to reduce the identification of high-frequency events introduced by the reference electrode signal. A Hilbert detector identified ripple events in the processed iEEG recordings using amplitude and duration criteria. The identified ripple events were further classified and characterized as true or false ripple on spikes, or ripples on oscillations by utilizing a topographical analysis to their time-frequency plot, and confirmed by visual inspection. The signal to noise ratio was improved by pruning IC1. The precision of the detector for ripple events was 91.27 ± 4.3%, and the sensitivity of the detector was 79.4 ± 3.0% (N = 16 patients, 5842 ripple events). The sensitivity and precision of the detector was equivalent in iEEG recordings obtained during sleep or intra-operatively. Across all the patients, true ripple on spike rates and also the rates of false ripple on spikes, that were generated due to filter ringing, classified the seizure onset zone (SOZ) with an area under the receiver operating curve (AUROC) of >76%. The magnitude and spectral content of true ripple on spikes generated in the SOZ was distinct as compared with the ripples generated in the NSOZ (p ripple rates and properties defined using this approach may accurately delineate the seizure onset zone. Strategies to improve the spatial resolution of intracranial EEG and reduce artifact can help improve the clinical utility of

  20. Achieving high field-effect mobility in amorphous indium-gallium-zinc oxide by capping a strong reduction layer.

    Zan, Hsiao-Wen; Yeh, Chun-Cheng; Meng, Hsin-Fei; Tsai, Chuang-Chuang; Chen, Liang-Hao

    2012-07-10

    An effective approach to reduce defects and increase electron mobility in a-IGZO thin-film transistors (a-IGZO TFTs) is introduced. A strong reduction layer, calcium, is capped onto the back interface of a-IGZO TFT. After calcium capping, the effective electron mobility of a-IGZO TFT increases from 12 cm(2) V(-1) s(-1) to 160 cm(2) V(-1) s(-1). This high mobility is a new record, which implies that the proposed defect reduction effect is key to improve electron transport in oxide semiconductor materials. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Cost-effectiveness analysis of surface flow constructed wetlands (SFCW) for nutrient reduction in drainage discharge from agricultural fields in Denmark

    Gachango, Florence Gathoni; Pedersen, Søren Marcus; Kjærgaard, Charlotte

    2015-01-01

    Constructed wetlands have been proposed as cost-effective and more targeted technologies in the reduction of nitrogen and phosphorous water pollution in drainage losses from agricultural fields in Denmark. Using two pig farms and one dairy farm situated in a pumped lowland catchment as case studies......, this paper explores the feasibility of implementing surface flow constructed wetlands (SFCW) based on their cost effectiveness. Sensitivity analysis is conducted by varying the cost elements of the wetlands in order to establish the most cost-effective scenario and a comparison with the existing nutrients...... reduction measures carried out. The analyses show that the cost effectiveness of the SFCW is higher in the drainage catchments with higher nutrient loads. The range of the cost effectiveness ratio on nitrogen reduction differs distinctively with that of catch crop measure. The study concludes that SFCW...

  2. Density ripples in expanding low-dimensional gases as a probe of correlations

    Imambekov, A.; Mazets, I. E.; Petrov, D. S.

    2009-01-01

    fluctuations. For the case of free ballistic expansion relevant to current experiments, we present simple analytical relations between the spectrum of "density ripples" and the correlation functions of the original confined systems. We analyze several physical regimes, including weakly and strongly interacting...

  3. A non-unity torque sharing function for torque ripple minimization of switched reluctance generators

    Park, Kiwoo; Liu, Xiao; Chen, Zhe

    2013-01-01

    This paper presents a new torque ripple minimization technique for a Switched Reluctance Generator (SRG). Although the SRG has many advantageous characteristics as a generator, it has not been widely employed in the industry. One of the most notorious disadvantages of the SRG is its high torque...

  4. Relation Between Observed Micromagnetic Ripple and FMR Width in Ultrasoft Magnetic Films

    Chechenin, N.G.; Craus, C.B.; Chezan, A.R.; Vystavel, T.; Boerma, D.O.; Hosson, J.Th.M. De; Niesen, L.

    2002-01-01

    Using Lorentz transmission electron microscopy, the micromagnetic structure was observed and the periodicity and angular spread of the in-plane magnetization were estimated for Fe–Zr–N films sputter-deposited on different substrates. The influence of the micromagnetic ripple on the ferromagnetic

  5. Directional excitation of Rg due to ripple-fired explosions: 2-Dimensional finite-difference simulations

    Jih, Rong-Song

    1993-01-01

    A major issue for the Non-Proliferation Treaty is the discrimination of large chemical explosions from possible clandestine or small nuclear tests. Unless discrimination is possible, the numerous mining blasts could give ample opportunity for concealing clandestine tests. Ripple-fired explosions are commonly used to fragment rocks during quarry and open-pit mining. The periodicity inherent in the ripple firing could produce a seismic reinforcement at the frequency of the delay between shots or rows. It has been suggested that the convolution of a single explosion with a comb function of variable spacing and variable amplitude can be used to model the distinctive signature of ripple firing. Baumgardt and Ziegler (1988) delicately demonstrated that the incoherent array-stack spectra can be used to identify some multiple shots recorded at NORSAR. By superpositioning the waveform due to a single shot with proper time delay, they were able to model the source multiplicity under the assumption that the spatial spreading of the shots is negligible with respect to the distance to the receiver. The work by Stump et al. successfully characterized the major features of the wavefield due to ripple firings at near-source ranges

  6. Formation of two ripple modes on Si by ion erosion with simultaneous Fe incorporation

    Cornejo, Marina; Ziberi, Bashkim; Meinecke, Christoph; Frost, Frank

    2011-01-01

    This report focuses on the self organized nanostructure formation on Si (0 0 1) by erosion with low energy Kr + ions with simultaneous incorporation of metallic atoms, in particular Fe. The incorporation of Fe is thought to play an important role in the formation of some features. In the experimental set-up used here the Fe atoms come from the sputtering of a cylindrical stainless steel target situated between the source and the sample holder. It is demonstrated how the Fe flux can be regulated by operational parameters of the ion source. It is shown that two different ripple modes, one perpendicular to the ion beam projection on the surface and the other parallel, were formed at near normal incidence (α = 20 o ) with ion energy between 300 eV and 2000 eV and a fluence of 6.7 x 10 18 cm -2 . The perpendicular mode ripples dominated the topography when E ion = 2000 eV, while the parallel mode ripples were the main features observed when E ion = 300 eV. The correlation of Fe concentration with ion sources parameters and resulting topography is analyzed. It is demonstrated that a certain Fe concentration is necessary for the formation of ripples that are oriented perpendicular to the ion beam and that the Fe concentration alone does not determine the evolving topography.

  7. Direct writing of sub-wavelength ripples on silicon using femtosecond laser at high repetition rate

    Xie, Changxin; Li, Xiaohong; Liu, Kaijun; Zhu, Min; Qiu, Rong; Zhou, Qiang

    2016-01-01

    Graphical abstract: - Highlights: • The NSRs and DSRs are obtained on silicon surface. • With increasing direct writing speed, the NSRs suddenly changes and becomes the DSRs. • We develop a Sipe–Drude interference theory by considering the thermal excitation. - Abstract: The near sub-wavelength and deep sub-wavelength ripples on monocrystalline silicon were formed in air by using linearly polarized and high repetition rate femtosecond laser pulses (f = 76 MHz, λ = 800 nm, τ = 50 fs). The effects of laser pulse energy, direct writing speed and laser polarization on silicon surface morphology are studied. When the laser pulse energy is 2 nJ/pulse and the direct writing speed varies from 10 to 25 mm/s, the near sub-wavelength ripples (NSRs) with orientation perpendicular to the laser polarization are generated. While the direct writing speed reaches 30 mm/s, the direction of the obtained deep sub-wavelength ripples (DSRs) suddenly changes and becomes parallel to the laser polarization, rarely reported so far for femtosecond laser irradiation of silicon. Meanwhile, we extend the Sipe–Drude interference theory by considering the thermal excitation, and numerically calculate the efficacy factor for silicon irradiated by femtosecond laser pulses. The revised Sipe–Drude interference theoretical results show good agreement with the periods and orientations of sub-wavelength ripples.

  8. High energy Xe{sup +} ion beam induced ripple structures on silicon

    Hanisch, Antje; Grenzer, Joerg; Facsko, Stefan; Winkler, Ingolf [Forschungszentrum Dresden-Rossendorf, Institute for Ion Beam Physics and Materials Research, Dresden (Germany); Biermanns, Andreas; Grigorian, Souren; Pietsch, Ullrich [University of Siegen (Germany). Institute of Physics

    2008-07-01

    Ion beam bombardment on semiconductor surfaces leads to well-defined morphological structures in the nanoscale range. Due to the impact of ions a self-organized wave-like surface structure develops. Ion bombardment causes an amorphization of a surface-adjacent layer of several nanometers and creates a periodical structure on the surface as well as at the amorphous-crystalline interface. We investigate the dependence of the periodicity on the crystallography of (100) silicon bombarded with Xe{sup +} ions, the ion beam incidence and the azimutal angle of the sample surface. So far we found that the ripple wavelength scales with the ion energy in a range of 5 to 70 keV. In order to understand the initiation of the ripple formation we also ask the question which role the initial surface structure plays. Therefore we investigate the formation of ripples on pre-structured and rough surfaces such as wafers with an intentional miscut. Therefore, we not only introduce a certain initial roughness but also vary the orientation of the (100) lattice plane in respect to the surface. We distinguish between ion beam induced surface effects (sputter erosion) and the influence of the crystalline Si lattice (strain) on the ripple formation.

  9. Highly-stabilized power supply for synchrotron accelerators. High speed, low ripple power supply

    Sato, Kenji [Osaka Univ., Ibaraki (Japan). Research Center for Nuclear Physics; Kumada, Masayuki; Fukami, Kenji; Koseki, Shoichiro; Kubo, Hiroshi; Kanazawa, Toru

    1997-02-01

    In synchrotron accelerators, in order to utilize high energy beam effectively, those are operated by repeating acceleration and taking-out at short period. In order to accelerate by maintaining beam track stable, the tracking performance with the error less than 10{sup -3} in the follow-up of current is required for the power supply. Further, in order to maintain the intensity and uniformity of beam when it is taken out, very low ripple is required for output current. The power supply having such characteristics has been developed, and applied to the HIMAC and the SPring-8. As the examples of the application of synchrotrons, the accelerators for medical treatment and the generation of synchrotron radiation are described. As to the power supply for the deflection magnets and quadrupole magnets of synchrotron accelerators, the specifications of the main power supply, the method of reducing ripple, the method of improving tracking, and active filter control are reported. As to the test results, the measurement of current ripple and tracking error is shown. The lowering of ripple was enabled by common mode filter and the symmetrical connection of electromagnets, and high speed response was realized by the compensation for delay with active filter. (K.I.)

  10. Analysis of dc-Link Voltage Switching Ripple in Three-Phase PWM Inverters

    Marija Vujacic

    2018-02-01

    Full Text Available The three-phase voltage source inverter (VSI is de facto standard in power conversion systems. To realize high power density systems, one of the items to be correctly addressed is the design and selection of the dc-link capacitor in relation to the voltage switching ripple. In this paper, effective formulas for designing the dc-link capacitor as a function of the switching voltage ripple amplitude are obtained, considering the operating conditions such as the modulation index and the output current amplitude. The calculations are obtained considering the requirements and restrictions referring to the high (switching-frequency dc-link voltage ripple component. Analyses have been performed considering the dc source impedance (non-ideal dc voltage source at the switching frequency and a balanced load. Analytical expressions are derived for the dc-link voltage switching ripple amplitude and its maximum value over the fundamental period. Different values of modulation index and output phase angle have been considered and different diagrams are presented. Analytical results were validated both by simulations and comprehensive experimental tests.

  11. Modelling and measurements of sand transport processes over full-scale ripples in oscillatory flow

    van der Werf, Jebbe J.; Ribberink, Jan S.; O'Donoghue, Tom; Doucette, Jeffrey C.

    2006-01-01

    A new series of laboratory experiments was performed in the Aberdeen Oscillatory Flow Tunnel (AOFT) and the Large Oscillating Water Tunnel (LOWT) to investigate time-averaged suspended sand concentrations and transport rates over rippled beds in regular and irregular oscillatory flow. The

  12. Restrictions on TWT Helix Voltage Ripple for Acceptable Notch Filter Performance

    Hyslop, B.

    1984-12-01

    An ac ripple on the helix voltage of the 1-2 GHz TWT's creates FM sidebands that cause amplitude and phase modulation of the microwave TWT output signal. A limit of 16 volts peak-to-peak is required for acceptable superconducting notch filter performance.

  13. Amplitude equation and long-range interactions in underwater sand ripples in one dimension

    Schnipper, Teis; Mertens, Keith; Ellegaard, Clive

    2008-01-01

    We present an amplitude equation for sand ripples under oscillatory flow in a situation where the sand is moving in a narrow channel and the height profile is practically one dimensional. The equation has the form h(t)=epsilon-(h-(h) over bar) + ((h(x))(2)-1)h(xx)-h(xxxx) + delta((h(x))(2))(xx...

  14. Analysis and minimization of Torque Ripple for variable Flux reluctance machines

    Bao, J.; Gysen, B.L.J.; Boynov, K.; Paulides, J.J.H.; Lomonova, E.A.

    2017-01-01

    Variable flux reluctance machines (VFRMs) are permanent-magnet-free three-phase machines and are promising candidates for applications requiring low cost and robustness. This paper studies the torque ripple and minimization methods for 12-stator VFRMs. Starting with the analysis of harmonics in the

  15. Analysis of transient state in HTS tapes under ripple DC load current

    Stepien, M.; Grzesik, B.

    2014-05-01

    The paper concerns the analysis of transient state (quench transition) in HTS tapes loaded with the current having DC component together with a ripple component. Two shapes of the ripple were taken into account: sinusoidal and triangular. Very often HTS tape connected to a power electronic current supply (i.e. superconducting coil for SMES) that delivers DC current with ripples and it needs to be examined under such conditions. Additionally, measurements of electrical (and thermal) parameters under such ripple excitation is useful to tape characterization in broad range of load currents. The results presented in the paper were obtained using test bench which contains programmable DC supply and National Instruments data acquisition system. Voltage drops and load currents were measured vs. time. Analysis of measured parameters as a function of the current was used to tape description with quench dynamics taken into account. Results of measurements were also used to comparison with the results of numerical modelling based on FEM. Presented provisional results show possibility to use results of measurements in transient state to prepare inverse models of superconductors and their detailed numerical modelling.

  16. Ripple Effects: Budgets Grow Modestly, but Energy Costs Cloud the Horizon

    Oder, Norman

    2006-01-01

    In this article, the author reports the ripple effects of the energy squeeze due to Hurricane Katrina and other factors that sent energy costs skyrocketing. Energy costs are a good part of why budget growth, which has been steady over the past five years, has been slowing down. The projected change from FY2005 to FY2006 is only 3.3%, compared to…

  17. Correlation between micrometer-scale ripple alignment and atomic-scale crystallographic orientation of monolayer graphene.

    Choi, Jin Sik; Chang, Young Jun; Woo, Sungjong; Son, Young-Woo; Park, Yeonggu; Lee, Mi Jung; Byun, Ik-Su; Kim, Jin-Soo; Choi, Choon-Gi; Bostwick, Aaron; Rotenberg, Eli; Park, Bae Ho

    2014-12-01

    Deformation normal to the surface is intrinsic in two-dimensional materials due to phononic thermal fluctuations at finite temperatures. Graphene's negative thermal expansion coefficient is generally explained by such an intrinsic property. Recently, friction measurements on graphene exfoliated on a silicon oxide surface revealed an anomalous anisotropy whose origin was believed to be the formation of ripple domains. Here, we uncover the atomistic origin of the observed friction domains using a cantilever torsion microscopy in conjunction with angle-resolved photoemission spectroscopy. We experimentally demonstrate that ripples on graphene are formed along the zigzag direction of the hexagonal lattice. The formation of zigzag directional ripple is consistent with our theoretical model that takes account of the atomic-scale bending stiffness of carbon-carbon bonds and the interaction of graphene with the substrate. The correlation between micrometer-scale ripple alignment and atomic-scale arrangement of exfoliated monolayer graphene is first discovered and suggests a practical tool for measuring lattice orientation of graphene.

  18. Synchrony, waves and ripple in spatially coupled Kuramoto oscillators with Mexican hat connectivity.

    Heitmann, Stewart; Ermentrout, G Bard

    2015-06-01

    Spatiotemporal waves of synchronized activity are known to arise in oscillatory neural networks with lateral inhibitory coupling. How such patterns respond to dynamic changes in coupling strength is largely unexplored. The present study uses analysis and simulation to investigate the evolution of wave patterns when the strength of lateral inhibition is varied dynamically. Neural synchronization was modeled by a spatial ring of Kuramoto oscillators with Mexican hat lateral coupling. Broad bands of coexisting stable wave solutions were observed at all levels of inhibition. The stability of these waves was formally analyzed in both the infinite ring and the finite ring. The broad range of multi-stability predicted hysteresis in transitions between neighboring wave solutions when inhibition is slowly varied. Numerical simulation confirmed the predicted transitions when inhibition was ramped down from a high initial value. However, non-wave solutions emerged from the uniform solution when inhibition was ramped upward from zero. These solutions correspond to spatially periodic deviations of phase that we call ripple states. Numerical continuation showed that stable ripple states emerge from synchrony via a supercritical pitchfork bifurcation. The normal form of this bifurcation was derived analytically, and its predictions compared against the numerical results. Ripple states were also found to bifurcate from wave solutions, but these were locally unstable. Simulation also confirmed the existence of hysteresis and ripple states in two spatial dimensions. Our findings show that spatial synchronization patterns can remain structurally stable despite substantial changes in network connectivity.

  19. New Experiments on Wave Physics with a Simply Modified Ripple Tank

    Logiurato, Fabrizio

    2014-01-01

    The ripple tank is one of the physics education devices most appreciated by teachers and students. It allows one to visualize various phenomena related to wave physics in an effective and enthralling way. Usually this apparatus consists of a tank with a transparent bottom that is filled with a thin layer of water. A source of light illuminates the…

  20. Numerical investigation of the efficiency of emission reduction and heat extraction in a sedimentary geothermal reservoir: a case study of the Daming geothermal field in China.

    Guo, Xuyang; Song, Hongqing; Killough, John; Du, Li; Sun, Pengguang

    2018-02-01

    The utilization of geothermal energy is clean and has great potential worldwide, and it is important to utilize geothermal energy in a sustainable manner. Mathematical modeling studies of geothermal reservoirs are important as they evaluate and quantify the complex multi-physical effects in geothermal reservoirs. However, previous modeling efforts lack the study focusing on the emission reduction efficiency and the deformation at geothermal wellbores caused by geothermal water extraction/circulation. Emission efficiency is rather relevant in geothermal projects introduced in areas characterized by elevated air pollution where the utilization of geothermal energy is as an alternative to burning fossil fuels. Deformation at geothermal wellbores is also relevant as significant deformation caused by water extraction can lead to geothermal wellbore instability and can consequently decrease the effectiveness of the heat extraction process in geothermal wells. In this study, the efficiency of emission reduction and heat extraction in a sedimentary geothermal reservoir in Daming County, China, are numerically investigated based on a coupled multi-physical model. Relationships between the efficiency of emission reduction and heat extraction, deformation at geothermal well locations, and geothermal field parameters including well spacing, heat production rate, re-injection temperature, rock stiffness, and geothermal well placement patterns are analyzed. Results show that, although large heat production rates and low re-injection temperatures can lead to decreased heat production in the last 8 years of heat extraction, they still improve the overall heat production capacity and emission reduction capacity. Also, the emission reduction capacity is positively correlated with the heat production capacity. Deformation at geothermal wellbore locations is alleviated by smaller well spacing, lower heat production rates, and smaller numbers of injectors in the well pattern, and by

  1. Effect of ripple taper on band-gap overlap in a coaxial Bragg structure operating at terahertz frequency

    Ding Xueyong; Li Hongfan; Lv Zhensu

    2012-01-01

    Based on the mode-coupling method, numerical analysis is presented to demonstrate the influence of ripple taper on band-gap overlap in a coaxial Bragg structure operating at terahertz frequency. Results show that the interval between the band-gaps of the competing mode and the desired working mode is narrowed by use of positive-taper ripples, but is expanded if negative-taper ripples are employed, and the influence of the negative-taper ripples is obviously more advantageous than the positive-taper ripples; the band-gap overlap of modes can be efficiently separated by use of negative-taper ripples. The residual side-lobes of the frequency response in a coaxial Bragg structure with ripple taper also can be effectively suppressed by employing the windowing-function technique. These peculiarities provide potential advantage in constructing a coaxial Bragg cavity with high quality factor for single higher-order-mode operation of a high-power free-electron maser in the terahertz frequency range.

  2. A simple overlap angle control strategy for reducing commutation torque ripple in a brushless DC motor drive

    Chetan K. Lad

    2017-08-01

    Full Text Available A commutation torque ripple is generated in a brushless DC motor due to a finite time taken for current transfer between outgoing phase and incoming phase due to the phase inductance. The effect of commutation ripple will be more severe for low voltage high current BLDC drives used for automotive applications. Direct Torque Control (DTC techniques are used to reduce the torque ripple. Two phase conduction with six voltage space vectors and three phase conduction with twelve voltage space vectors with DTC are used to reduce the torque ripple. Twelve Step DTC (TSDTC is capable of reducing torque ripple considerably but at the cost of increased inverter and winding losses. In Six Step DTC (SSDTC the torque ripple is higher than that of TSDTC but with reduced winding and inverter losses. In this paper an attempt has been made to strike a balance between torque ripple and losses. A novel Direct Torque Control with twelve voltage space vector with overlap angle control has been proposed. The proposed method is validated through simulation and experimental results.

  3. [SPECIFIC DIAGNOSTIC SIGNIFICANCE OF "RIPPLE SIGN" OF MEDIAL FEMORAL CONDYLE UNDER ARTHROSCOPE IN MEDIAL LONGITUDINAL MENISCAL TEARS].

    Ren Shiyou; Sun, Limang; Chen, Guofei; Jiang, Changqing; Zhang, Xintao; Zhang Wentao

    2015-01-01

    To investigate the reliability of the "ripple sign" on the upper surface of the medial femoral condyle in the diagnosis of medial longitudinal meniscal tears under arthroscope. Between June 2013 and June 2014, 56 patients with knee injuries were included. There were 35 males and 21 females with an average age of 22.2 years (range, 12-38 years). The causes of injury were sports in 40 cases, falling in 10 cases, and traffic accident in 6 cases. The injury was located at the left knee in 22 cases and at the right knee in 34 cases. The disease duration was 10-40 days (mean, 20.2 days). Of 56 patients, 15 cases had simple medial meniscal injury; 41 cases had combined injuries, including anterior cruciate ligament injury in 38 cases, posterior cruciate ligament injury in 2 cases, and patellar dislocation in 1 case. The "ripple sign" was observed under arthroscope before operation. Repair of medial meniscal injury and reconstruction of cruciate ligament were performed. The positive "ripple sign" was seen under arthroscope in all patients, who were diagnosed to have longitudinal meniscal tears, including 23 cases of mild "ripple sign" , 28 cases of moderate "ripple sign", and 5 cases of severe "ripple sign". The "ripple sign" on the upper surface of the medial femoral condyle is a reliable diagnostic evidence of medial longitudinal meniscal tears.

  4. Analysis and Minimization of Output Current Ripple for Discontinuous Pulse-Width Modulation Techniques in Three-Phase Inverters

    Gabriele Grandi

    2016-05-01

    Full Text Available This paper gives the complete analysis of the output current ripple in three-phase voltage source inverters considering the different discontinuous pulse-width modulation (DPWM strategies. In particular, peak-to-peak current ripple amplitude is analytically evaluated over the fundamental period and compared among the most used DPWMs, including positive and negative clamped (DPWM+ and DPWM−, and the four possible combinations between them, usually named as DPWM0, DPWM1, DPWM2, and DPWM3. The maximum and the average values of peak-to-peak current ripple are estimated, and a simple method to correlate the ripple envelope with the ripple rms is proposed and verified. Furthermore, all the results obtained by DPWMs are compared to the centered pulse-width modulation (CPWM, equivalent to the space vector modulation to identify the optimal pulse-width modulation (PWM strategy as a function of the modulation index, taking into account the different average switching frequency. In this way, the PWM technique providing for the minimum output current ripple is identified over the whole modulation range. The analytical developments and the main results are experimentally verified by current ripple measurements with a three-phase PWM inverter prototype supplying an induction motor load.

  5. High frequency vibration characteristics of electric wheel system under in-wheel motor torque ripple

    Mao, Yu; Zuo, Shuguang; Wu, Xudong; Duan, Xianglei

    2017-07-01

    With the introduction of in-wheel motor, the electric wheel system encounters new vibration problems brought by motor torque ripple excitation. In order to analyze new vibration characteristics of electric wheel system, torque ripple of in-wheel motor based on motor module and vector control system is primarily analyzed, and frequency/order features of the torque ripple are discussed. Then quarter vehicle-electric wheel system (QV-EWS) dynamics model based on the rigid ring tire assumption is established and the main parameters of the model are identified according to tire free modal test. Modal characteristics of the model are further analyzed. The analysis indicates that torque excitation of in-wheel motor is prone to arouse horizontal vibration, in which in-phase rotational, anti-phase rotational and horizontal translational modes of electric wheel system mainly participate. Based on the model, vibration responses of the QV-EWS under torque ripple are simulated. The results show that unlike vertical low frequency (lower than 20 Hz) vibration excited by road roughness, broadband torque ripple will arouse horizontal high frequency (50-100 Hz) vibration of electric wheel system due to participation of the three aforementioned modes. To verify the theoretical analysis, the bench experiment of electric wheel system is conducted and vibration responses are acquired. The experiment demonstrates the high frequency vibration phenomenon of electric wheel system and the measured order features as well as main resonant frequencies agree with simulation results. Through theoretical modeling, analysis and experiments this paper reveals and explains the high frequency vibration characteristics of electric wheel system, providing references for the dynamic analysis, optimal design of QV-EWS.

  6. Final Technical Report. Factors Controlling In Situ Uranium and Technetium Bio-Reduction and Reoxidation at the NABIR Field Research Center

    Dr. Jonathan D. Istok , Oregon State University; Dr. Lee Krumholz, University of Oklahoma; Dr. James McKinley, Pacific Northwest National Laboratory; Dr. Baohua Gu, Oak Ridge National Laboratory

    2006-01-01

    The overall goal of this project was to better understand factors and processes controlling microbially-mediated reduction and reoxidation of U and Tc in the unconsolidated residuum overlying the Nolichucky shale at the Field Research Center (FRC) at Oak Ridge National Laboratory. Project activities were designed to test the following hypotheses: (1) The small rates of denitrification and U bio-reduction observed in laboratory incubations of sediments from FRC Area 1 at low pH (< 5) are due to the presence of high concentrations of toxic metals (especially Al and Ni). Rates of Tc reduction will also be small at low pH in the presence of high concentrations of toxic metals. (2) In situ rates of U and perhaps Tc bio-reduction can be increased by increasing system pH and thus precipitating toxic metals from solution. (3) In situ rates of U and Tc bio-reduction can be increased by the addition of humic substances, which complex toxic metals such as Al and Ni, buffer pH, and serve as electron shuttles to facilitate U and Tc reduction. (4) Microbially-reduced U and Tc are rapidly oxidized in the presence of high concentrations of NO3- and the denitrification intermediates NO2-, N2O, and NO. (5) An electron-donor-addition strategy (type and form of donor, with or without pH adjustment and with or without the co-addition of humic substances) can be devised to reduce U and Tc concentrations for an extended period of time in low pH groundwater in the presence of high concentrations of NO3-, Al, and Ni. This strategy operates by removing or complexing these components of FRC groundwater to allow the subsequent reduction of U(VI) and Tc(VII)

  7. Efficacy of patient skin dose reduction by a compensating filter through of irradiation field overlaps on the area during percutaneous coronary intervention

    Yamasaki, Hiroyuki; Yamaguchi, Sadao; Yamamoto, Naomi; Miyagawa, Takashi; Hirose, Etsuko; Takenaka, Tatsuaki; Nakahara, Makoto

    2011-01-01

    Our study was involved with entrance surface dose reduction and irradiation field by the filter use of PCI, and insertion in place of an effective compensating filter to maximize entrance surface dose reduction, which we verified. The radiation dosimetry put a 6 cc ion chamber on the back side of the thorax phantom, and changed the filter of the four corners (a: upper left, b: upper right, c: lower right, d: lower left) of the monitor confirmed with fluoroscopy [(0) no filter, (1) one filter, (2) two filters]. The angle of C arm was assumed to be eight directions and 0 degrees adopted by this hospital. It was compared with a corrective rate of which one was no filter. Next, the presence of filter and irradiation field overlaps on the area in monitor in the angle of C arm was verified by this hospital's classic example. As for corrective rate, (1) becomes 0.41 and (2) become 0.25 at fluoroscopy, (1) becomes 0.26 and (2) become 0.16 at exposure. Irradiation field overlaps on the area (+) compensating filter (-) was many with d of right anterior oblique (RAO)/cranial (CAU), a of RAO and c of CAU at left coronary angiography (CAG), c of left anterior oblique (LAO) at right CAG, b of LAO/cranial (CRA) (left CAG), b of CRA (right CAG) and a and d of RAO (right CAG) at both CAG. Irradiation field overlaps on the area (+) compensating filter (+) was many with b of CRA at left CAG, a of LAO/CRA at right CAG, b of CRA (left CAG) and b of RAO (right CAG) at both CAG. When the compensating filter is used the entrance surface dose reduction effect was great. If automatic exposure control protects the part of irradiation field overlaps on the area in the range without operating excessively, the radiological risk can be reduced, and it is conceivable as useful clinical setting. (author)

  8. Reduction of Polarization Field Strength in Fully Strained c-Plane InGaN/(In)GaN Multiple Quantum Wells Grown by MOCVD.

    Zhang, Feng; Ikeda, Masao; Zhang, Shu-Ming; Liu, Jian-Ping; Tian, Ai-Qin; Wen, Peng-Yan; Cheng, Yang; Yang, Hui

    2016-12-01

    The polarization fields in c-plane InGaN/(In)GaN multiple quantum well (MQW) structures grown on sapphire substrate by metal-organic chemical vapor deposition are investigated in this paper. The indium composition in the quantum wells varies from 14.8 to 26.5% for different samples. The photoluminescence wavelengths are calculated theoretically by fully considering the related effects and compared with the measured wavelengths. It is found that when the indium content is lower than 17.3%, the measured wavelengths agree well with the theoretical values. However, when the indium content is higher than 17.3%, the measured ones are much shorter than the calculation results. This discrepancy is attributed to the reduced polarization field in the MQWs. For the MQWs with lower indium content, 100% theoretical polarization can be maintained, while, when the indium content is higher, the polarization field decreases significantly. The polarization field can be weakened down to 23% of the theoretical value when the indium content is 26.5%. Strain relaxation is excluded as the origin of the polarization reduction because there is no sign of lattice relaxation in the structures, judging by the X-ray diffraction reciprocal space mapping. The possible causes of the polarization reduction are discussed.

  9. Effect of pH and pulsed electric field process parameters on the aflatoxin reduction in model system using response surface methodology: Effect of pH and PEF on Aflatoxin Reduction.

    Vijayalakshmi, Subramanian; Nadanasabhapathi, Shanmugam; Kumar, Ranganathan; Sunny Kumar, S

    2018-03-01

    The presence of aflatoxin, a carcinogenic and toxigenic secondary metabolite produced by Aspergillus species, in food matrix has been a major worldwide problem for years now. Food processing methods such as roasting, extrusion, etc. have been employed for effective destruction of aflatoxins, which are known for their thermo-stable nature. The high temperature treatment, adversely affects the nutritive and other quality attributes of the food, leading to the necessity of application of non-thermal processing techniques such as ultrasonication, gamma irradiation, high pressure processing, pulsed electric field (PEF), etc. The present study was focused on analysing the efficacy of the PEF process in the reduction of the toxin content, which was subsequently quantified using HPLC. The process parameters of different pH model system (potato dextrose agar) artificially spiked with aflatoxin mix standard was optimized using the response surface methodology. The optimization of PEF process effects on the responses aflatoxin B1 and total aflatoxin reduction (%) by pH (4-10), pulse width (10-26 µs) and output voltage (20-65%), fitted 2FI model and quadratic model respectively. The response surface plots obtained for the processes were of saddle point type, with the absence of minimum or maximum response at the centre point. The implemented numerical optimization showed that the predicted and actual values were similar, proving the adequacy of the fitted models and also proved the possible application of PEF in toxin reduction.

  10. Plasma-filled rippled wall rectangular backward wave oscillator ...

    and (iv) the beam is free from any kind of macroscopic instabilities. We choose transverse magnetic modes (TM) because their axial electric field compo- nent drives the axial bunching of the electron beam. In mathematical terms we express the propagation field equation as exp{−i[knz − ωt]}, following the Floquet's theorem.

  11. Reduction of Averaging Time for Evaluation of Human Exposure to Radiofrequency Electromagnetic Fields from Cellular Base Stations

    Kim, Byung Chan; Park, Seong-Ook

    In order to determine exposure compliance with the electromagnetic fields from a base station's antenna in the far-field region, we should calculate the spatially averaged field value in a defined space. This value is calculated based on the measured value obtained at several points within the restricted space. According to the ICNIRP guidelines, at each point in the space, the reference levels are averaged over any 6min (from 100kHz to 10GHz) for the general public. Therefore, the more points we use, the longer the measurement time becomes. For practical application, it is very advantageous to spend less time for measurement. In this paper, we analyzed the difference of average values between 6min and lesser periods and compared it with the standard uncertainty for measurement drift. Based on the standard deviation from the 6min averaging value, the proposed minimum averaging time is 1min.

  12. Reaction-Based Reactive Transport Modeling of Iron Reduction and Uranium Immobilization at Area 2 of the NABIR Field Research Center

    Burgos, W.D.

    2009-09-02

    This report summarizes research conducted in conjunction with a project entitled “Reaction-Based Reactive Transport Modeling of Iron Reduction and Uranium Immobilization at Area 2 of the NABIR Field Research Center”, which was funded through the Integrative Studies Element of the former NABIR Program (now the Environmental Remediation Sciences Program) within the Office of Biological and Environmental Research. Dr. William Burgos (The Pennsylvania State University) was the overall PI/PD for the project, which included Brian Dempsey (Penn State), Gour-Tsyh (George) Yeh (Central Florida University), and Eric Roden (formerly at The University of Alabama, now at the University of Wisconsin) as separately-funded co-PIs. The project focused on development of a mechanistic understanding and quantitative models of coupled Fe(III)/U(VI) reduction in FRC Area 2 sediments. The work builds on our previous studies of microbial Fe(III) and U(VI) reduction, and was directly aligned with the Scheibe et al. ORNL FRC Field Project at Area 2.

  13. Mindfulness Training and Reductions in Teacher Stress and Burnout: Results from Two Randomized, Waitlist-Control Field Trials

    Roeser, Robert W.; Schonert-Reichl, Kimberly A.; Jha, Amishi; Cullen, Margaret; Wallace, Linda; Wilensky, Rona; Oberle, Eva; Thomson, Kimberly; Taylor, Cynthia; Harrison, Jessica

    2013-01-01

    The effects of randomization to mindfulness training (MT) or to a waitlist-control condition on psychological and physiological indicators of teachers' occupational stress and burnout were examined in 2 field trials. The sample included 113 elementary and secondary school teachers (89% female) from Canada and the United States. Measures were…

  14. Investigation research on improvement of safe handling techniques of radiation in medical fields; Reduction of exposure to medical radiation

    Tanaka, Minoru; Watabe, Makoto; Oono, Kuniko [Tokyo Metropolitan Isotope Research Center (Japan)

    1990-01-01

    Today, it is generally recognized that radiation exposure regardless of its use should be limited to the required minimum. The form of radiation utilization for medical treatment is extremely diverse, and to clarify the actual state of dose that doctors, radiation technicians, nurses and subjects as patients receive by the diagnosis and treatment accompanied by radiation exposure is not only indispensable for evaluating the risk they receive, but also to give the important data for pursuing the reduction of radiation exposure dose of those engaging in medical treatment and patients-subjects. In this investigation research, the actual state of radiation exposure in doctors, radiation technicians, nurses and patients or subjects was investigated, and the radiation exposure dose was measured, in this way the reduction of radiation exposure dose was attempted. The radiation exposure dose in one month was 10.8{+-}3.0 mrem in doctors, 10.4{+-}2.5 mrem in radiation technicians, and 6.3{+-}2.5 mrem in nurses. The risk coefficient in a specific medical university was 1155 men-rem. Also the case of nuclear medical diagnosis administering Ga-67 was measured. (K.I.).

  15. Ultradeep Near-Infrared ISAAC Observations of the Hubble Deep Field South: Observations, Reduction, Multicolor Catalog, and Photometric Redshifts

    Labbé, Ivo; Franx, Marijn; Rudnick, Gregory; Schreiber, Natascha M. Förster; Rix, Hans-Walter; Moorwood, Alan; van Dokkum, Pieter G.; van der Werf, Paul; Röttgering, Huub; van Starkenburg, Lottie; van der Wel, Arjen; Kuijken, Konrad; Daddi, Emanuele

    2003-03-01

    We present deep near-infrared (NIR) Js-, H-, and Ks-band ISAAC imaging of the Wide Field Planetary Camera 2 (WFPC2) field of the Hubble Deep Field South (HDF-S). The 2.5‧×2.5‧ high Galactic latitude field was observed with the Very Large Telescope under the best seeing conditions, with integration times amounting to 33.6 hr in Js, 32.3 hr in H, and 35.6 hr in Ks. We reach total AB magnitudes for point sources of 26.8, 26.2, and 26.2, respectively (3 σ), which make it the deepest ground-based NIR observation to date and the deepest Ks-band data in any field. The effective seeing of the co-added images is ~0.45" in Js, ~0.48" in H, and ~0.46" in Ks. Using published WFPC2 optical data, we constructed a Ks-limited multicolor catalog containing 833 sources down to Ktots,AB2.3 (in Johnson magnitudes). Because they are extremely faint in the observed optical, they would be missed by ultraviolet-optical selection techniques, such as the U-dropout method. Based on service mode observations collected at the European Southern Observatory, Paranal, Chile (ESO Program 164.O-0612). Also based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555.

  16. Field Test Evaluation of Conservation Retrofits of Low-Income, Single-Family Buildings in Wisconsin: Blower-Door-Directed Infiltration Reduction Procedure, Field Test Implementation and Results; TOPICAL

    Gettings, M.B.

    2001-01-01

    A blower-door-directed infiltration retrofit procedure was field tested on 18 homes in south central Wisconsin. The procedure, developed by the Wisconsin Energy Conservation Corporation, includes recommended retrofit techniques as well as criteria for estimating the amount of cost-effective work to be performed on a house. A recommended expenditure level and target air leakage reduction, in air changes per hour at 50 Pascal (ACH50), are determined from the initial leakage rate measured. The procedure produced an average 16% reduction in air leakage rate. For the 7 houses recommended for retrofit, 89% of the targeted reductions were accomplished with 76% of the recommended expenditures. The average cost of retrofits per house was reduced by a factor of four compared with previous programs. The average payback period for recommended retrofits was 4.4 years, based on predicted energy savings computed from achieved air leakage reductions. Although exceptions occurred, the procedure's 8 ACH50 minimum initial leakage rate for advising retrofits to be performed appeared a good choice, based on cost-effective air leakage reduction. Houses with initial rates of 7 ACH50 or below consistently required substantially higher costs to achieve significant air leakage reductions. No statistically significant average annual energy savings was detected as a result of the infiltration retrofits. Average measured savings were -27 therm per year, indicating an increase in energy use, with a 90% confidence interval of 36 therm. Measured savings for individual houses varied widely in both positive and negative directions, indicating that factors not considered affected the results. Large individual confidence intervals indicate a need to increase the accuracy of such measurements as well as understand the factors which may cause such disparity. Recommendations for the procedure include more extensive training of retrofit crews, checks for minimum air exchange rates to insure air quality

  17. Persistence at low temperature of the P beta' ripple in dipalmitoylphosphatidylcholine multilamellar vesicles containing either glycosphingolipids or cholesterol.

    Rock, P; Thompson, T E; Tillack, T W

    1989-03-13

    The disappearance and reappearance of the P beta' ripple in multilamellar liposomes of dipalmitoylphosphatidylcholine (DPPC) has been examined by freeze-etch electron microscopy. The presence of less than 10 mol% of various glycosphingolipids or cholesterol in the liposomes markedly increases the time required for ripple disappearance when the vesicles are cooled from 38 degrees C to 30 degrees C, as compared to the pure phospholipid. Once the ripples have begun to disappear in the two-component vesicles, they do not uniformly reappear until the system is heated above the main transition of DPPC and allowed to cool into the pretransition region. These results suggest that the long time for ripple disappearance in the two-component systems reflects a slow molecular reorganization process which occurs when the systems are forced to change from the P beta' gel to the L beta' gel by a temperature downshift.

  18. Equalization of FBG-induced group-delay ripples penalties using a coherent receiver and digital signal processing

    Veljanovski, V.; Al Fiad, M.S.A.S.; Borne, van den D.; Jansen, S.L.; Wuth, T.

    2009-01-01

    We show the mitigation of fiber Bragg gratings induced group delay ripple penalties through the use of coherent detection and electronic equalizer. For 111-Gb/s POLMUX-RZDQPSK only a negligible penalty is observed after 10 cascaded FBGs.

  19. Comparison of an assay for Dehalococcoides DNA and a microcosm study in predicting reductive dechlorination of chlorinated ethenes in the field

    Lu Xiaoxia; Wilson, John T.; Kampbell, Donald H.

    2009-01-01

    The study aims to compare the detection of 16S rRNA gene of Dehalococcoides species and the microcosm study for biotransformation in predicting reductive dechlorination of chlorinated ethenes in ground water at hazardous waste sites. A total of 72 ground water samples were collected from 12 PCE or TCE contaminated sites in the United States. The samples were analyzed and used to construct microcosms in the laboratory. The results showed that the presence of Dehalococcoides DNA was well associated with dechlorination to ethene in the field. Nearly half of the wells where Dehalococcoides DNA was detected had ethene as a dechlorination end product. In comparison, for ground water samples of 16 wells where ethene was detected, ethene was produced in 11 of the corresponding microcosms. For most microcosms, during two years of incubation, dechlorination was less extensive than that observed in the field. - Positive results of the assay for Dehalococcoides DNA and the microcosm study may suggest that reductive dechlorination is occurring in the field

  20. Effect of repeated pesticide applications on soil properties in cotton fields: I. Impact on microbes, iron reduction capacity and respiration

    Vig, K.; Singh, D.K.; Agarwal, H.C.; Dhawan, A.K.; Dureja, P.

    2001-01-01

    Soil microorganisms have a primary catabolic role in the environment through degradation of plant and animal residues. The activities of microorganisms in soil are thus, essential to the global cycling of nutrients. As these pesticides are designed to be biologically active, their continuous use might affect soil microflora either by changing their properties or their numbers, which may lead to impairment in soil fertility. Soil was analyzed for microbial numbers, iron reduction capacity and respiration. Stimulatory, inhibitory or no effects of insecticide treatments were observed on microbes and microbial activities. The insecticides used had only temporary effects on microbes and their activities which disappeared either before the next insecticide treatment was carried out or at the end of experimental period. (author)

  1. Field-scale evaluation of biological uranium reduction and reoxidation in the near-source zone at the NABIR Field Research Center in Oak Ridge, TN

    Craig S. Criddle; Peter Kitanidis; Scott Fendorf; Weimin Wu; Philip M. Jardine; Jizhong Zhou; Baohua Gu

    2006-01-01

    The primary objective of the project is to advance the understanding and predictive capability of coupled hydrological, geochemical, and microbiological processes that control the in situ transport and bioremediation radionuclides and co-contaminants at multiple scales. Specific objectives include: (1) Investigate the feasibility of in situ bioremediation of uranium in a highly contaminated region within the subsurface of Area 3 of the DoE ERSP FRC (2) Using a variety of tracer strategies, develop and model a system that establishes hydraulic control of the target region for biostimulation (3) Perform long term in situ biostimulation studies that create a microbial communities capable of reducing residual nitrate to N2 and mobile U(VI) to sparingly soluble U(IV) (4) Use a variety of solid and solution phase interrogation techniques to quantify the extent of in situ reduction and immobilization of U(VI). (5) Investigate a variety of geochemical factors that influence the stability and possible reoxidation of reduced uranium

  2. First row transition metal atoms embedded in multivacancies in a rippled graphene system

    Mombrú, Dominique; Faccio, Ricardo; Mombrú, Alvaro W.

    2018-03-01

    Ab-initio calculations based on density functional theory (DFT) have been performed to study systems where a first row transition metal atom is embedded in a rippled graphene due to the existence of an 8-order multivacancy. In addition to these cases, also the inclusion of a zinc atom, with a 3d10 electron configuration, was also studied. Structural distortions and magnetic response for each system were studied. A correlation was found for the magnitude of the rippling and the distortion in the vacancy. Variation in the trends was found for Cu and Zn cases, which were explained on the basis of the filling of the 3dx2-y2 orbital. All the systems exhibit lower magnetic moment in comparison to the metal-less system. The quenching of the magnetic moment due to the carbon atoms in the vacancy is observed for Sc and Cu.

  3. The resonance between runaway electrons and magnetic ripple in HT-7 Tokamak

    Zhou Ruijie; Hu Liqun; Lu Hongwei; Lin Shiyao; Zhong Guoqiang; Xu Ping; Zhang Jizong

    2011-01-01

    For suppressing the energy of runaway electrons in tokamak plasma, we analyzed the X-ray energy spectra by runaway electrons in different discharges of the HT-7 tokamak experiment performed in the autumn of 2009. The resonant phenomenon between runaway electrons and magnetic ripple was found. Although, the energy of runaway electrons in the plasma core can be as high as several tens of MeV, but when they are transported to the edge, the electron energy are limited to a certain range by resonance with the magnetic ripple of different harmonic numbers. The runaway electrons under high loop voltage resonate with low step magnetic perturbations, with high energy gain; whereas the runaway electrons under low loop voltage resonate with high level magnetic perturbations, with low energy gain. Using this mechanism, the energy of runaway electrons can be restricted to a low level, and this will significantly mitigate the damage effect on the equipment caused by runaway electrons. (authors)

  4. Harmonic Analysis on Torque Ripple of Brushless DC Motor Based on Advanced Commutation Control

    Yanpeng Ji

    2018-01-01

    Full Text Available This paper investigates the relationship between current, back electromotive force (back-EMF, and torque for permanent-magnet brushless DC (PM BLDC motors under advanced commutation control from the perspective of harmonics. Considering that the phase current is the influencing factor of both torque and torque ripple, this paper firstly analyzes the effects of advanced commutation on phase current and current harmonics. And then, based on the harmonics of the phase current and back-EMF, the torque harmonic expressions are deduced. The expressions reveal the relationship of harmonic order between the torque, phase current, and back-EMF and highlight the different contribution of individual torque harmonic to the total torque ripple. Finally, the proposed harmonic analysis method is verified by the experiments with different speed and load conditions.

  5. Spectral-Temporal Modulated Ripple Discrimination by Children With Cochlear Implants.

    Landsberger, David M; Padilla, Monica; Martinez, Amy S; Eisenberg, Laurie S

    A postlingually implanted adult typically develops hearing with an intact auditory system, followed by periods of deafness (or near deafness) and adaptation to the implant. For an early implanted child whose brain is highly plastic, the auditory system matures with consistent input from a cochlear implant. It is likely that the auditory system of early implanted cochlear implant users is fundamentally different than postlingually implanted adults. The purpose of this study is to compare the basic psychophysical capabilities and limitations of these two populations on a spectral resolution task to determine potential effects of early deprivation and plasticity. Performance on a spectral resolution task (Spectral-temporally Modulated Ripple Test [SMRT]) was measured for 20 bilaterally implanted, prelingually deafened children (between 5 and 13 years of age) and 20 hearing children within the same age range. Additionally, 15 bilaterally implanted, postlingually deafened adults, and 10 hearing adults were tested on the same task. Cochlear implant users (adults and children) were tested bilaterally, and with each ear alone. Hearing listeners (adults and children) were tested with the unprocessed SMRT and with a vocoded version that simulates an 8-channel cochlear implant. For children with normal hearing, a positive correlation was found between age and SMRT score for both the unprocessed and vocoded versions. Older hearing children performed similarly to hearing adults in both the unprocessed and vocoded test conditions. However, for children with cochlear implants, no significant relationship was found between SMRT score and chronological age, age at implantation, or years of implant experience. Performance by children with cochlear implants was poorer than performance by cochlear implanted adults. It was also found that children implanted sequentially tended to have better scores with the first implant compared with the second implant. This difference was not

  6. Reduction of ion thermal diffusivity associated with the transition of the radial electric field in neutral-beam-heated plasmas in the large helical device.

    Ida, K; Funaba, H; Kado, S; Narihara, K; Tanaka, K; Takeiri, Y; Nakamura, Y; Ohyabu, N; Yamazaki, K; Yokoyama, M; Murakami, S; Ashikawa, N; deVries, P C; Emoto, M; Goto, M; Idei, H; Ikeda, K; Inagaki, S; Inoue, N; Isobe, M; Itoh, K; Kaneko, O; Kawahata, K; Khlopenkov, K; Komori, A; Kubo, S; Kumazawa, R; Liang, Y; Masuzaki, S; Minami, T; Miyazawa, J; Morisaki, T; Morita, S; Mutoh, T; Muto, S; Nagayama, Y; Nakanishi, H; Nishimura, K; Noda, N; Notake, T; Kobuchi, T; Ohdachi, S; Ohkubo, K; Oka, Y; Osakabe, M; Ozaki, T; Pavlichenko, R O; Peterson, B J; Sagara, A; Saito, K; Sakakibara, S; Sakamoto, R; Sanuki, H; Sasao, H; Sasao, M; Sato, K; Sato, M; Seki, T; Shimozuma, T; Shoji, M; Suzuki, H; Sudo, S; Tamura, N; Toi, K; Tokuzawa, T; Torii, Y; Tsumori, K; Yamamoto, T; Yamada, H; Yamada, I; Yamaguchi, S; Yamamoto, S; Yoshimura, Y; Watanabe, K Y; Watari, T; Hamada, Y; Motojima, O; Fujiwara, M

    2001-06-04

    Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduction of ion thermal diffusivity was observed after the mode transition from ion root to electron root as predicted by neoclassical theory when the neoclassical ion loss is more dominant than the anomalous ion loss.

  7. Configuration of ripple domains and their topological defects formed under local mechanical stress on hexagonal monolayer graphene.

    Park, Yeonggu; Choi, Jin Sik; Choi, Taekjib; Lee, Mi Jung; Jia, Quanxi; Park, Minwoo; Lee, Hoonkyung; Park, Bae Ho

    2015-03-24

    Ripples in graphene are extensively investigated because they ensure the mechanical stability of two-dimensional graphene and affect its electronic properties. They arise from spontaneous symmetry breaking and are usually manifested in the form of domains with long-range order. It is expected that topological defects accompany a material exhibiting long-range order, whose functionality depends on characteristics of domains and topological defects. However, there remains a lack of understanding regarding ripple domains and their topological defects formed on monolayer graphene. Here we explore configuration of ripple domains and their topological defects in exfoliated monolayer graphenes on SiO2/Si substrates using transverse shear microscope. We observe three-color domains with three different ripple directions, which meet at a core. Furthermore, the closed domain is surrounded by an even number of cores connected together by domain boundaries, similar to topological vortex and anti-vortex pairs. In addition, we have found that axisymmetric three-color domains can be induced around nanoparticles underneath the graphene. This fascinating configuration of ripple domains may result from the intrinsic hexagonal symmetry of two-dimensional graphene, which is supported by theoretical simulation using molecular dynamics. Our findings are expected to play a key role in understanding of ripple physics in graphene and other two-dimensional materials.

  8. Objective assessment of spectral ripple discrimination in cochlear implant listeners using cortical evoked responses to an oddball paradigm.

    Lopez Valdes, Alejandro; Mc Laughlin, Myles; Viani, Laura; Walshe, Peter; Smith, Jaclyn; Zeng, Fan-Gang; Reilly, Richard B

    2014-01-01

    Cochlear implants (CIs) can partially restore functional hearing in deaf individuals. However, multiple factors affect CI listener's speech perception, resulting in large performance differences. Non-speech based tests, such as spectral ripple discrimination, measure acoustic processing capabilities that are highly correlated with speech perception. Currently spectral ripple discrimination is measured using standard psychoacoustic methods, which require attentive listening and active response that can be difficult or even impossible in special patient populations. Here, a completely objective cortical evoked potential based method is developed and validated to assess spectral ripple discrimination in CI listeners. In 19 CI listeners, using an oddball paradigm, cortical evoked potential responses to standard and inverted spectrally rippled stimuli were measured. In the same subjects, psychoacoustic spectral ripple discrimination thresholds were also measured. A neural discrimination threshold was determined by systematically increasing the number of ripples per octave and determining the point at which there was no longer a significant difference between the evoked potential response to the standard and inverted stimuli. A correlation was found between the neural and the psychoacoustic discrimination thresholds (R2=0.60, p<0.01). This method can objectively assess CI spectral resolution performance, providing a potential tool for the evaluation and follow-up of CI listeners who have difficulty performing psychoacoustic tests, such as pediatric or new users.

  9. Laterally structured ripple and square phases with one and two dimensional thickness modulations in a model bilayer system.

    Debnath, Ananya; Thakkar, Foram M; Maiti, Prabal K; Kumaran, V; Ayappa, K G

    2014-10-14

    Molecular dynamics simulations of bilayers in a surfactant/co-surfactant/water system with explicit solvent molecules show formation of topologically distinct gel phases depending upon the bilayer composition. At low temperatures, the bilayers transform from the tilted gel phase, Lβ', to the one dimensional (1D) rippled, Pβ' phase as the surfactant concentration is increased. More interestingly, we observe a two dimensional (2D) square phase at higher surfactant concentration which, upon heating, transforms to the gel Lβ' phase. The thickness modulations in the 1D rippled and square phases are asymmetric in two surfactant leaflets and the bilayer thickness varies by a factor of ∼2 between maximum and minimum. The 1D ripple consists of a thinner interdigitated region of smaller extent alternating with a thicker non-interdigitated region. The 2D ripple phase is made up of two superimposed square lattices of maximum and minimum thicknesses with molecules of high tilt forming a square lattice translated from the lattice formed with the thickness minima. Using Voronoi diagrams we analyze the intricate interplay between the area-per-head-group, height modulations and chain tilt for the different ripple symmetries. Our simulations indicate that composition plays an important role in controlling the formation of low temperature gel phase symmetries and rippling accommodates the increased area-per-head-group of the surfactant molecules.

  10. A Minimization of Speed Ripple of Sensorless DTC for controlled Induction Motors used in Electric Vehicles

    Khoucha , Farid; Marouani , Khoudir; Kheloui , Abdelaziz; Benbouzid , Mohamed

    2006-01-01

    International audience; The main theme of this paper is to present different switching techniques in DTC induction motor drives for electric vehicle applications, witch insert zero-voltage vector and/or more non zero-voltage vectors to the conventional switching table associated to full adaptive flux and speed observer. Those techniques are quite effective in reducing the torque pulsation and the speed ripples of the motors, as demonstrated in experimental results.

  11. Removal of Direct Current Link Harmonic Ripple in Single Phase Voltage Source Inverter Systems Using Supercapacitors

    2016-09-01

    Khaligh, “Optimization of sizing and battery cycle life in battery/ultracapacitor hybrid energy storage systems for electric vehicle applications...depth cycling operation in photovoltaic system ,” in 22nd International Conference “Mixed Design of Integrated Circuits and Systems ,” Toruń, Poland...CURRENT LINK HARMONIC RIPPLE IN SINGLE-PHASE VOLTAGE SOURCE INVERTER SYSTEMS USING SUPERCAPACITORS by Gabriel D. Hernandez September 2016

  12. Impact of cognitive stimulation on ripples within human epileptic and non-epileptic hippocampus

    Brázdil, M.; Cimbálník, J.; Roman, R.; Shaw, D. J.; Stead, M.; Daniel, P.; Jurák, Pavel; Halámek, Josef

    2015-01-01

    Roč. 16, JULY 25 (2015), 47:1-9 ISSN 1471-2202 R&D Projects: GA ČR GAP103/11/0933; GA MŠk ED0017/01/01; GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : high-frequency oscillations * hippocampal ripples * epilepsy * human cognition Subject RIV: FH - Neurology Impact factor: 2.304, year: 2015

  13. A High Power Density Integrated Charger for Electric Vehicles with Active Ripple Compensation

    Pan, Liwen; Zhang, Chengning

    2015-01-01

    This paper suggests a high power density on-board integrated charger with active ripple compensation circuit for electric vehicles. To obtain a high power density and high efficiency, silicon carbide devices are reported to meet the requirement of high-switching-frequency operation. An integrated bidirectional converter is proposed to function as AC/DC battery charger and to transfer energy between battery pack and motor drive of the traction system. In addition, the conventional H-bridge cir...

  14. The active filter voltage ripple correction system of the Brookhaven AGS main magnet power supply

    Marneris, I.; Bonati, R.; Geller, J.; Sandberg, J.N.; Soukas, A.

    1995-01-01

    This paper, and a companion paper, describe the improvements to the Main Magnet Power Supply (MMPS) so that it enables a more flexible operation of the AGS, enhances its reliability, and also improves the MMPS's ultimate performance specifications. One of the major areas for the latter is the fixed target program operating off the AGS slow extracted beam lines. The active filter, by improving the MMPS output ripple, is instrumental in the improvement of the ultimate duty factor of the extraction beam spill

  15. Assessing spectral and temporal processing in children and adults using temporal modulation transfer function (TMTF), Iterated Ripple Noise (IRN) perception, and spectral ripple discrimination (SRD).

    Peter, Varghese; Wong, Kogo; Narne, Vijaya Kumar; Sharma, Mridula; Purdy, Suzanne C; McMahon, Catherine

    2014-02-01

    There are many clinically available tests for the assessment of auditory processing skills in children and adults. However, there is limited data available on the maturational effects on the performance on these tests. The current study investigated maturational effects on auditory processing abilities using three psychophysical measures: temporal modulation transfer function (TMTF), iterated ripple noise (IRN) perception, and spectral ripple discrimination (SRD). A cross-sectional study. Three groups of subjects were tested: 10 adults (18-30 yr), 10 older children (12-18 yr), and 10 young children (8-11 yr) Temporal envelope processing was measured by obtaining thresholds for amplitude modulation detection as a function of modulation frequency (TMTF; 4, 8, 16, 32, 64, and 128 Hz). Temporal fine structure processing was measured using IRN, and spectral processing was measured using SRD. The results showed that young children had significantly higher modulation thresholds at 4 Hz (TMTF) compared to the other two groups and poorer SRD scores compared to adults. The results on IRN did not differ across groups. The results suggest that different aspects of auditory processing mature at different age periods and these maturational effects need to be considered while assessing auditory processing in children. American Academy of Audiology.

  16. Assessing the reduction of the hydrological connectivity of gully systems through vegetation restoration: field experiments and numerical modelling

    A. Molina

    2009-10-01

    Full Text Available Restoration of degraded land in the Southern Ecuadorian Andes has led to alterations in the functioning of degraded catchments. Recovery of vegetation on areas affected by overgrazing, as well as the reforestation or afforestation of gully areas have given rise to modifications of hydrological connectivity within the catchments. Recent research has highlighted the ability of gully channels to trap sediment eroded from steep slopes, especially if vegetation is established along the gully bed. However, vegetation cover not only induces sediment deposition in the gully bed, but may also have a potential to reduce runoff water volume. The performance of gully beds in reducing the transfer of runoff was investigated by conducting controlled concentrated flow experiments in the field. Experimental field data for nine gullies were derived by pouring concentrated inflow into the upstream end and measuring the outflow at the downstream end of the channel. Two consecutive flow experiments per gully were carried out, so that data for dry and wet soil conditions were collected. The hydrological response to concentrated flow was estimated for each experiment by calculating its cumulative infiltration coefficient, IC (%. The results showed a great difference in IC between dry and wet soil conditions. The IC for wet soil conditions was on average 24%, whereas it was 60% for dry conditions. Gullies with more than 50% surface vegetation cover exhibit the highest cumulative infiltration coefficients (81% for dry runs, and 34% for wet runs, but runoff transmission losses were not as clearly related to vegetation cover as sediment storage as shown in Molina et al. (2009. The experimental field data of 16 experiments were used to calibrate a hydrological model developed by Fiener and Auerswald (2005 in order to simulate the transfer of concentrated flow along the gully beds. The calibrated model was able to simulate the transfer of runoff water

  17. Sterile Acellular Dermal Collagen as a Treatment for Rippling Deformity of Breast

    Brittany Busse

    2014-01-01

    Full Text Available Prosthetic implants are frequently used for breast augmentation and breast reconstruction following mastectomy. Unfortunately, long-term aesthetic results of prosthetic breast restoration may be hindered by complications such as rippling, capsular contracture, and implant malposition. The advent of use of acellular dermal matrices has greatly improved the outcomes of prosthetic breast reconstruction. We describe a case of rippling deformity of breast that was treated using an acellular dermal matrix product, AlloMax. The patient presented with visible rippling of bilateral prosthetic breast implants as well as significant asymmetry of the breasts after multiple excisional biopsies for right breast ductal carcinoma in situ. A 6×10 cm piece of AlloMax was placed on the medial aspect of each breast between the implant and the skin flap. Follow-up was performed at 1 week, 3 months, and 1 year following the procedure. The patient recovered well from the surgery and there were no complications. At her first postoperative follow-up the patient was extremely satisfied with the result. At her 3-month and 1-year follow-up she had no recurrence of her previous deformity and no new deformity.

  18. Ripple-modulated electronic structure of a 3D topological insulator.

    Okada, Yoshinori; Zhou, Wenwen; Walkup, D; Dhital, Chetan; Wilson, Stephen D; Madhavan, V

    2012-01-01

    Three-dimensional topological insulators host linearly dispersing states with unique properties and a strong potential for applications. An important ingredient in realizing some of the more exotic states in topological insulators is the ability to manipulate local electronic properties. Direct analogy to the Dirac material graphene suggests that a possible avenue for controlling local properties is via a controlled structural deformation such as the formation of ripples. However, the influence of such ripples on topological insulators is yet to be explored. Here we use scanning tunnelling microscopy to determine the effects of one-dimensional buckling on the electronic properties of Bi(2)Te(3.) By tracking spatial variations of the interference patterns generated by the Dirac electrons we show that buckling imposes a periodic potential, which locally modulates the surface-state dispersion. This suggests that forming one- and two-dimensional ripples is a viable method for creating nanoscale potential landscapes that can be used to control the properties of Dirac electrons in topological insulators.

  19. Ripple formation on Si surfaces during plasma etching in Cl2

    Nakazaki, Nobuya; Matsumoto, Haruka; Sonobe, Soma; Hatsuse, Takumi; Tsuda, Hirotaka; Takao, Yoshinori; Eriguchi, Koji; Ono, Kouichi

    2018-05-01

    Nanoscale surface roughening and ripple formation in response to ion incidence angle has been investigated during inductively coupled plasma etching of Si in Cl2, using sheath control plates to achieve the off-normal ion incidence on blank substrate surfaces. The sheath control plate consisted of an array of inclined trenches, being set into place on the rf-biased electrode, where their widths and depths were chosen in such a way that the sheath edge was pushed out of the trenches. The distortion of potential distributions and the consequent deflection of ion trajectories above and in the trenches were then analyzed based on electrostatic particle-in-cell simulations of the plasma sheath, to evaluate the angular distributions of ion fluxes incident on substrates pasted on sidewalls and/or at the bottom of the trenches. Experiments showed well-defined periodic sawtooth-like ripples with their wave vector oriented parallel to the direction of ion incidence at intermediate off-normal angles, while relatively weak corrugations or ripplelike structures with the wave vector perpendicular to it at high off-normal angles. Possible mechanisms for the formation of surface ripples during plasma etching are discussed with the help of Monte Carlo simulations of plasma-surface interactions and feature profile evolution. The results indicate the possibility of providing an alternative to ion beam sputtering for self-organized formation of ordered surface nanostructures.

  20. Wave Tank Studies of Strong Modulation of Wind Ripples Due To Long Waves

    Ermakov, S.; Sergievskaya, I.; Shchegolkov, Yu.

    Modulation of wind capillary-gravity ripples due to long waves has been studied in wave tank experiment at low wind speeds using Ka-band radar. The experiments were carried out both for clean water and the water surface covered with surfactant films. It is obtained that the modulation of radar signals is quite strong and can increase with surfactant concentration and fetch. It is shown that the hydrodynamic Modulation Transfer Function (MTF) calculated for free wind ripples and taking into account the kinematic (straining) effect, variations of the wind stress and variations of surfactant concentration strongly underestimates experimental MTF-values. The effect of strong modulation is assumed to be connected with nonlinear harmonics of longer dm-cm- scale waves - bound waves ("parasitic ripples"). The intensity of bound waves depends strongly on the amplitude of decimetre-scale waves, therefore even weak modulation of the dm-scale waves due to long waves results to strong ("cascade") modulation of bound waves. Modulation of the system of "free/bound waves" is estimated using results of wave tank studies of bound waves generation and is shown to be in quali- tative agreement with experiment. This work was supported by MOD, UK via DERA Winfrith (Project ISTC 1774P) and by RFBR (Project 02-05-65102).

  1. Ripple scalings in geothermal facilities, a key to understand the scaling process

    Köhl, Bernhard; Grundy, James; Baumann, Thomas

    2017-04-01

    Scalings are a widespread problem among geothermal plants which exploit the Malm Aquifer in the Bavarian Molasse Zone. They effect the technical and economic efficiency of geothermal plants. The majority of the scalings observed at geothermal facilities exploring the Malm aquifer in the Bavarian Molasse Basin are carbonates. They are formed due to a disruption of the lime-carbonic-acid equilibrium during production caused by degassing of CO2. These scalings are found in the production pipes, at the pumps and at filters and can nicely be described using existing hydrogeochemical models. This study proposes a second mechanism for the formation of scalings in ground-level facilities. We investigated scalings which accumulated at the inlet to the heat exchanger. Interestingly, the scalings were recovered after the ground level facilities had been cleaned. The scalings showed distinct ripple structures, which is likely a result of solid particle deposition. From the ripple features the the flow conditions during their formation were calculated based on empirical equations (Soulsby, 2012). The calculations suggest that the deposits were formed during maintenance works. Thin section images of the sediments indicate a two-step process: deposition of sediment grains, followed by stabilization with a calcite layer. The latter likely occured during maintenance. To prevent this type of scalings blocking the heat exchangers, the maintenance procedure has to be revised. References: Soulsby, R. L.; Whitehouse, R. J. S.; Marten, K. V.: Prediction of time-evolving sand ripples in shelf seas. Continental Shelf Research 2012, 38, 47-62

  2. Oriented gold ripple-like structures on poly-L-lactic acid

    Juřík, Petr, E-mail: petr.jurik@gmail.com [Department of Solid State Engineering, Institute of Chemical Technology, Prague (Czech Republic); Slepička, Petr [Department of Solid State Engineering, Institute of Chemical Technology, Prague (Czech Republic); Mistrík, Jan; Janíček, Petr [Department of Applied Physics and Mathematics, University of Pardubice (Czech Republic); Rimpelová, Silvie [Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague (Czech Republic); Kolská, Zdeňka [Faculty of Science, University of J. E. Purkyně, Ústí nad Labem (Czech Republic); Švorčík, Václav [Department of Solid State Engineering, Institute of Chemical Technology, Prague (Czech Republic)

    2014-12-01

    Highlights: • We prepared oriented ripple-like structures on polymer surface with thin gold layer. • These structures show preferential orientation over large areas which is unusual for heat induced wrinkling. • Significant electrical and optical anisotropy was observed. • Zeta-potential, XPS, goniometry and ellipsometry suggest formation of gold lines separated by polymer gaps. • Increase in cell growth in comparison with poly-styrene mock was observed. - Abstract: In this paper chemical, morphological, electrical and biological properties of poly-L-lactic acid thin films with gold nanolayers were studied. These samples were examined as-sputtered and annealed at glass transition temperature. Morphological changes of poly-L-lactic films introduced by annealing were studied by means of atomic force microscopy. This method showed formation of oriented ripple-like structures on the surface of the film. X-ray photoelectron spectroscopy, goniometry, ellipsometry, sheet resistance measurement and electrokinetic analysis were used to determine distribution of gold on the surface. Combined data suggests that these ripple-like structures were formed by gold lines with insulating polymer gaps in between. These lines show preferential orientation over large areas and under proper conditions offer simple way to form electrically anisotropic material on large scale. Also cytocompatibility was studied showing increased cell adhesion and proliferation of mouse embryonic fibroblasts offering another use for these easily formed structures.

  3. Suppression of Gain Ripples in Superconducting Traveling-Wave Kinetic Inductance Amplifiers

    Bal, Mustafa; Erickson, Robert P.; Ku, Hsiang Sheng; Wu, Xian; Pappas, David P.

    Superconducting traveling-wave kinetic inductance (KIT) amplifiers demonstrated gain over a wide bandwidth with high dynamic range and low noise. However, the gain curve exhibits ripples. Impedance mismatch at the input and output ports of the KIT amplifier as wells as split ground planes of the coplanar waveguide (CPW) geometry are potential contributors to the ripple in the gain curve. Here we study the origin of these ripples in KIT amplifiers configured in CPW geometry using approximately 20 nm thick NbTiN films grown by reactive co-sputtering of NbN and TiN. Our NbTiN films have non-linear kinetic inductance as a function of current, described by L =L0 (1 +(I /I*) 2) , where I* = 15 . 96 +/- 0 . 11 mA measured by time domain reflectometry. We report the results of implementing an impedance taper that takes into account a significantly reduced phase velocity as it narrows, adding Au onto the CPW split grounds, as well as employing different designs of dispersion engineering. Qubit Measurements using KIT amplifiers will also be reported.

  4. X-ray scattering and diffraction from Xe-induced ripples in crystalline silicon

    Biermanns, Andreas; Pietsch, Ullrich; Grigorian, Souren [Universitaet Siegen (Germany); Grenzer, Joerg; Facsko, Stefan; Hanisch, Antje [Foschungszentrum Dresden-Rossendorf (Germany); Carbone, Dina; Metzger, Hartmut [ID Beamline, ESRF (France)

    2008-07-01

    The formation of surface-nanostructures with a characteristic size ranging from several nanometer up to microns has attracted significant interest in the last decades in the context of fabrication of novel opto-electronic and storage devices. One kind of those nanostructures are wave-like patterns (ripples) produced by an interplay between a roughening process caused by ion beam erosion (sputtering) of the surface and smoothening processes caused by surface diffusion. In this contribution we report on investigations of patterned Si(001) surfaces after irradiation with Xe{sup +}-ions using ion-energies up to 40 keV. During the sputtering, an amorphous surface-layer is formed followed by a rather sharp interface towards crystalline material, showing the same morphology as the surface. The structures of the amorphous layer and the amorphous-crystalline interface were studied by means of grazing-incidence-small angle scattering (GISAXS) and diffraction (GID) using synchrotron-radiation. We found that the crystal structure at the interface is expanded along the ripples, caused by the creation of defects inside the surface region, whereas this expansion is strongly reduced across the ripples. This different relaxation may play a driving role in pattern formation at the interface.

  5. Xe{sup +} ion beam induced rippled structures on Si miscut wafers

    Hanisch, Antje; Grenzer, Joerg [Forschungszentrum Dresden-Rossendorf, Dresden (Germany); Biermanns, Andreas; Pietsch, Ullrich [Institute of Physics, University of Siegen (Germany)

    2009-07-01

    We report on the influence of the initial roughness and crystallography of the substrate on the formation of self-organized ripple structures on semiconductors surfaces by noble gas ion bombardment. The Bradley-Harper theory predicts that an initial roughness is most important for starting the sputtering process which in the ends leads to the evolution of regular patterns. We produced periodic structures with intermediate Xe{sup +} ion energies (5-70 keV) at different incidence and azimuthal angles which lead to the assumption that also crystallography plays a role at the beginning of ripple evolution. Most of the previous investigations started from the original roughness of a polished silicon wafer. We used (001) silicon wafers with a miscut angle of 1 , 5 and 10 towards[110]. We studied the ripple formation keeping the ion beam parallel to the[111],[-1-11] or[-111] direction, i.e. parallel, antiparallel or perpendicular to the miscut direction[110]. The parallel and antiparallel case implies a variation of the incidence angle with increased roughness over the surface step terraces. The perpendicular orientation means almost no roughness. The results were compared to normal Si(001) and Si(111) wafers.

  6. Oriented gold ripple-like structures on poly-L-lactic acid

    Juřík, Petr; Slepička, Petr; Mistrík, Jan; Janíček, Petr; Rimpelová, Silvie; Kolská, Zdeňka; Švorčík, Václav

    2014-01-01

    Highlights: • We prepared oriented ripple-like structures on polymer surface with thin gold layer. • These structures show preferential orientation over large areas which is unusual for heat induced wrinkling. • Significant electrical and optical anisotropy was observed. • Zeta-potential, XPS, goniometry and ellipsometry suggest formation of gold lines separated by polymer gaps. • Increase in cell growth in comparison with poly-styrene mock was observed. - Abstract: In this paper chemical, morphological, electrical and biological properties of poly-L-lactic acid thin films with gold nanolayers were studied. These samples were examined as-sputtered and annealed at glass transition temperature. Morphological changes of poly-L-lactic films introduced by annealing were studied by means of atomic force microscopy. This method showed formation of oriented ripple-like structures on the surface of the film. X-ray photoelectron spectroscopy, goniometry, ellipsometry, sheet resistance measurement and electrokinetic analysis were used to determine distribution of gold on the surface. Combined data suggests that these ripple-like structures were formed by gold lines with insulating polymer gaps in between. These lines show preferential orientation over large areas and under proper conditions offer simple way to form electrically anisotropic material on large scale. Also cytocompatibility was studied showing increased cell adhesion and proliferation of mouse embryonic fibroblasts offering another use for these easily formed structures

  7. Torque Ripple Minimization and Performance Investigation of an In-Wheel Permanent Magnet Motor

    A. Mansouri

    2016-06-01

    Full Text Available Recently, electric vehicle motoring has become a topic of interest, due to the several problems caused by thermal engines such as pollution and high oil prices. Thus, electric motors are increasingly applied in vehicle’ applications and relevant research about these motors and their applications has been performed. Of particular interest are the improvements regarding torque production capability, the minimization of torque ripple and iron losses. The present work deals with the optimum design and the performance investigation of an outer rotor permanent magnet motor for in-wheel electric vehicle application. At first, and in order to find the optimum motor design, a new based particle-swarm multi-objective optimization procedure is applied. Three objective functions are used: efficiency maximization, weight and ripple torque minimization. Secondly, the effects of the permanent magnets segmentation, the stator slots opening, and the separation of adjacent magnets by air are outlined. The aim of the paper is the design of a topology with smooth output torque, low ripple torque, low iron losses and mechanical robustness.

  8. A diagnostic algorithm to optimize data collection and interpretation of Ripple Maps in atrial tachycardias.

    Koa-Wing, Michael; Nakagawa, Hiroshi; Luther, Vishal; Jamil-Copley, Shahnaz; Linton, Nick; Sandler, Belinda; Qureshi, Norman; Peters, Nicholas S; Davies, D Wyn; Francis, Darrel P; Jackman, Warren; Kanagaratnam, Prapa

    2015-11-15

    Ripple Mapping (RM) is designed to overcome the limitations of existing isochronal 3D mapping systems by representing the intracardiac electrogram as a dynamic bar on a surface bipolar voltage map that changes in height according to the electrogram voltage-time relationship, relative to a fiduciary point. We tested the hypothesis that standard approaches to atrial tachycardia CARTO™ activation maps were inadequate for RM creation and interpretation. From the results, we aimed to develop an algorithm to optimize RMs for future prospective testing on a clinical RM platform. CARTO-XP™ activation maps from atrial tachycardia ablations were reviewed by two blinded assessors on an off-line RM workstation. Ripple Maps were graded according to a diagnostic confidence scale (Grade I - high confidence with clear pattern of activation through to Grade IV - non-diagnostic). The RM-based diagnoses were corroborated against the clinical diagnoses. 43 RMs from 14 patients were classified as Grade I (5 [11.5%]); Grade II (17 [39.5%]); Grade III (9 [21%]) and Grade IV (12 [28%]). Causes of low gradings/errors included the following: insufficient chamber point density; window-of-interestRipple Maps in atrial tachycardias. This algorithm requires prospective testing on a real-time clinical platform. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  9. Interaction of rippled shock wave with flat fast-slow interface

    Zhai, Zhigang; Liang, Yu; Liu, Lili; Ding, Juchun; Luo, Xisheng; Zou, Liyong

    2018-04-01

    The evolution of a flat air/sulfur-hexafluoride interface subjected to a rippled shock wave is investigated. Experimentally, the rippled shock wave is produced by diffracting a planar shock wave around solid cylinder(s), and the effects of the cylinder number and the spacing between cylinders on the interface evolution are considered. The flat interface is created by a soap film technique. The postshock flow and the evolution of the shocked interface are captured by a schlieren technique combined with a high-speed video camera. Numerical simulations are performed to provide more details of flows. The wave patterns of a planar shock wave diffracting around one cylinder or two cylinders are studied. The shock stability problem is analytically discussed, and the effects of the spacing between cylinders on shock stability are highlighted. The relationship between the amplitudes of the rippled shock wave and the shocked interface is determined in the single cylinder case. Subsequently, the interface morphologies and growth rates under different cases are obtained. The results show that the shock-shock interactions caused by multiple cylinders have significant influence on the interface evolution. Finally, a modified impulsive theory is proposed to predict the perturbation growth when multiple solid cylinders are present.

  10. Hippocampal sharp wave‐ripple: A cognitive biomarker for episodic memory and planning

    2015-01-01

    ABSTRACT Sharp wave ripples (SPW‐Rs) represent the most synchronous population pattern in the mammalian brain. Their excitatory output affects a wide area of the cortex and several subcortical nuclei. SPW‐Rs occur during “off‐line” states of the brain, associated with consummatory behaviors and non‐REM sleep, and are influenced by numerous neurotransmitters and neuromodulators. They arise from the excitatory recurrent system of the CA3 region and the SPW‐induced excitation brings about a fast network oscillation (ripple) in CA1. The spike content of SPW‐Rs is temporally and spatially coordinated by a consortium of interneurons to replay fragments of waking neuronal sequences in a compressed format. SPW‐Rs assist in transferring this compressed hippocampal representation to distributed circuits to support memory consolidation; selective disruption of SPW‐Rs interferes with memory. Recently acquired and pre‐existing information are combined during SPW‐R replay to influence decisions, plan actions and, potentially, allow for creative thoughts. In addition to the widely studied contribution to memory, SPW‐Rs may also affect endocrine function via activation of hypothalamic circuits. Alteration of the physiological mechanisms supporting SPW‐Rs leads to their pathological conversion, “p‐ripples,” which are a marker of epileptogenic tissue and can be observed in rodent models of schizophrenia and Alzheimer's Disease. Mechanisms for SPW‐R genesis and function are discussed in this review. © 2015 The Authors Hippocampus Published by Wiley Periodicals, Inc. PMID:26135716

  11. Voluntary agreements in the field of energy efficiency and emission reduction: Review and analysis of experiences in the European Union

    Rezessy, Silvia; Bertoldi, Paolo

    2011-01-01

    A number of Member States of the EU have introduced voluntary agreements (VAs) that aim to deliver energy savings and emission reductions via increased energy efficiency in different end-use sectors, mainly targeting industry. Where there is a successful track record of cooperation between public authorities and the private sector, VAs can offer advantages to public authorities in comparison to legislation, most importantly better flexibility when introduced or updated, greater acceptance by industry, possibility for tailor-made solutions e.g. at the level of industrial sectors and opportunity to overcome the information asymmetry between public authorities and private actors. Nevertheless, VAs have been criticized for lack of specific obligations and lenient targets, as well as for deficiencies in compliance monitoring and self-reporting and difficulty in establishing the policy additionality of VA activity. This paper analyses the design of existing VAs in terms of general framework, targets and sectors, obligations and commitments, motivation to join, reporting and monitoring provisions, and results of existing VAs as reported by national authorities. The paper summarizes the key characteristics of voluntary agreements and gives recommendations for the successful application of this policy tool. - Highlights: → Analyze the design of voluntary agreements (VAs) for energy efficiency. → Study national-level VAs in the European Union. → Analyze their general framework and results delivered. → Summarize the key characteristics of VAs. → Give recommendations for the successful application of this policy tool.

  12. Intermittent 20-HZ-photic stimulation leads to a uniform reduction of alpha-global field power in healthy volunteers.

    Rau, R; Raschka, C; Koch, H J

    2001-01-01

    19-channel-EEGs were recorded from scalp surface of 30 healthy subjects (16m, 14f, mean age: 34 ys, SD: 11.7 ys) at rest and under IPS (Intermittent Photic Stimulation) at rates of 5, 10 and 20 Hertz (Hz). Digitalized data underwent spectral analysis with fast fourier transfomation (FFT) yielding the basis for the computation of global field power (GFP). For quantification GFP values in the frequency ranges of 5, 10 and 20 Hz at rest were divided by the corresponding data gained under IPS. While ratios from PDE data showed no stable parameter due to high interindividual variability, ratios of alpha-power turned out to be uniform in all subjects: IPS at 20 Hz always led to a suppression of alpha-power. Dividing alpha-GFP at rest by alpha-GFP under 20-Hz IPS thus resulted in a ratio paradigma.

  13. High-Resolution Mineralogical Characterization and Biogeochemical Modeling of Uranium Reduction Pathways at the NABIR Field-Research Center

    David R. Veblen; Chen Zhu; Lee Krumholz; Claudine Stirling; Emma-Kate Potter; Alex N. Halliday

    2004-01-01

    The effectiveness and feasibility of bioremediation at the field scale cannot be fully assessed until the mechanisms of immobilization and U speciation in the solid matrix are resolved. However, characterization of the immobilized U and its valence states is extremely difficult, because microbially mediated mineral precipitates are generally nanometer (nm)-sized, poorly crystalline, or amorphous. We are developing combined field emission gun--scanning electron microscopy (FEG-SEM, at Indiana University) and FEG transmission electron microscopy (TEM, at Hopkins) to detect and isolate uranium containing phases; (1) method developments for TEM sample preparations and parallel electron energy loss spectroscopy (EELS) determination of uranium valence; and (2) to determine the speciation, fate, reactivity, valence states of immobilized uranium, using the state-of-the-art 300-kV, FEG-TEM. We have obtained preliminary results on contaminated sediments from Area 3 at the Oak Ridge Field Research Center (FRC). TEM results show that the sediments contain numerous minerals, including quartz, mica/clay (muscovite and/or illite), rutile, ilmenite, zircon, and an Al-Sr-Ce-Ca phosphate mineral, none of which contain uranium above the EDS detection limit. Substantial U (up to ∼2 wt.%) is, however, clearly associated with two materials: (1) the Fe oxyhydroxide and (2) clots of a chemically complex material that is likely a mixture of several nm-scale phases. The Fe oxyhydroxide was identified as goethite from its polycrystalline SAED pattern and EDS analysis showing it to be very Fe-rich; the aggregate also displays one of several morphologies that are common for goethite. U is strongly sorbed to goethite in the FRC sediment, and the ubiquitous association with phosphorous suggests that complexes containing both U and P may play an important role in that sorption. Results from bulk analysis and SEM had previously demonstrated the association of U with Fe and thus suggested that U

  14. Reduction of radiation-induced xerostomia in nasopharyngeal carcinoma using CT simulation with laser patient marking and three-field irradiation technique

    Nishioka, Takeshi; Shirato, Hiroki; Arimoto, Takuro; Kaneko, Masanori; Kitahara, Toshihiro; Oomori, Keiichi; Yasuda, Motoyuki; Fukuda, Satoshi; Inuyama, Yukio; Miyasaka, Kazuo

    1997-01-01

    Purpose: Tumor control and reduction of postirradiation xerostomia in patients with nasopharyngeal carcinoma (NPC) using the three-field irradiation technique based on the CT-based simulation with laser patient marking was investigated. Methods and Materials: Seventy-eight patients with NPC were consecutively treated between 1983 and 1993. In 33 patients treated before 1987, target volume was determined using a conventional x-ray simulator with a reference of CT images, and the primary site was treated by the conventional parallel-opposed two-field technique (Group I). In 45 patients treated from 1987, target volume was determined using a CT simulator slice by slice, the treatment field was projected onto the patient's skin by a laser beam projector mounted on a C-arm, and the primary site was irradiated by a three-fields (anterior and bilateral) technique (Group II). In Group II, the shape of each field was determined using a beam's eye view to reduce the dose to the bilateral parotid glands. The three-field technique reduced the dose to the superficial lobe of parotid gland to about two-thirds of the dose given by the two-field technique. Radiation-induced xerostomia was evaluated by clinical symptoms and radio-isotope sialography. Results: The 5-year survival rate and disease-free survival rate were 46.6 and 31.2% in Group I, and 46.8 and 46.5% in Group II. A large variation in the volume of parotid glands were demonstrated, ranging from 9 cm 3 to 61 cm 3 among patients treated with CT simulation. Forty percent of the patients in Group II showed no or mild xerostomia, whereas all of the patients in Group I showed moderate to severe xerostomia (p < 0.01). The radioisotope sialography study showed that the mean secretion ratio by acid stimulation was improved from 3.8% in the Group I to 15.2% in the Group II (p < 0.01). Conclusions: CT simulation was useful to determine the size and shape of each field to reduce the dose to the parotid gland, of which size varies

  15. Reduction of soil erosion and mercury losses in agroforestry systems compared to forests and cultivated fields in the Brazilian Amazon.

    Béliveau, Annie; Lucotte, Marc; Davidson, Robert; Paquet, Serge; Mertens, Frédéric; Passos, Carlos J; Romana, Christine A

    2017-12-01

    In addition to causing physical degradation and nutrient depletion, erosion of cultivated soils in the Amazon affects aquatic ecosystems through the release of natural soil mercury (Hg) towards lakes and rivers. While traditional agriculture is generally cited as being among the main causes of soil erosion, agroforestry practices are increasingly appreciated for soil conservation. This study was carried out in family farms of the rural Tapajós region (Brazil) and aimed at evaluating soil erosion and associated Hg release for three land uses. Soils, runoff water and eroded sediments were collected at three sites representing a land cover gradient: a recently burnt short-cycle cropping system (SCC), a 2-year-old agroforestry system (AFS) and a mature forest (F). At each site, two PVC soil erosion plots (each composed of three 2 × 5 m isolated subplots) were implemented on steep and moderate slopes respectively. Sampling was done after each of the 20 rain events that occurred during a 1-month study period, in the peak of the 2011 rain season. Runoff volume and rate, as well as eroded soil particles with their Hg and cation concentrations were determined. Total Hg and cation losses were then calculated for each subplot. Erosion processes were dominated by land use type over rainfall or soil slope. Eroded soil particles, as well as the amount of Hg and cations (CaMgK) mobilized at the AFS site were similar to those at the F site, but significantly lower than those at the SCC site (p agroforestry systems, even in their early stages of implementation, are characterized by low erosion levels resembling those of local forest environments, thus contributing to the maintenance of soil integrity and to the reduction of Hg and nutrient mobility. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Reduction of fields between co-axial cylinders by means of interposed screens; L'abaissement des champs entre cylindres coaxiaux au moyen d'ecrans intercales

    Bernard, J; Bruck, H; Prevot, F

    1950-05-01

    The dielectric rigidity of the space between two coaxial cylinders at a given potential can be increased by interposing coaxial cylindrical screens (the method of C. M. Turner, Thesis, Univ. of Wisconsin, 1943). The combination of screens reducing the maximum value of a simple field between two cylinders is calculated as a function of number of screens, their radius, and their potential, and, for a given number of screens, the optimum radii and potentials for maximum field reduction are determined. [French] La rigidite dielectrique de l'espace compris entre deux cylindres coaxiaux, portes a des potentiels donnes, peut etre augmentee en intercalant des ecrans cylindriques coaxiaux (methode de C.M. Turner). En fonction de leur nombre, de leur rayon et de leur potentiel, on calcule de combien ces ecrans permettent de reduire la valeur du champ regnant primitivement entre les deux cylindres, et, pour un nombre d'ecrans donne, on determine les valeurs optima de leur rayon et potentiel, correspondant a la reduction maximum des champs. (auteur)

  17. fields

    Brad J. Arnold

    2014-07-01

    Full Text Available Surface irrigation, such as flood or furrow, is the predominant form of irrigation in California for agronomic crops. Compared to other irrigation methods, however, it is inefficient in terms of water use; large quantities of water, instead of being used for crop production, are lost to excess deep percolation and tail runoff. In surface-irrigated fields, irrigators commonly cut off the inflow of water when the water advance reaches a familiar or convenient location downfield, but this experience-based strategy has not been very successful in reducing the tail runoff water. Our study compared conventional cutoff practices to a retroactively applied model-based cutoff method in four commercially producing alfalfa fields in Northern California, and evaluated the model using a simple sensor system for practical application in typical alfalfa fields. These field tests illustrated that the model can be used to reduce tail runoff in typical surface-irrigated fields, and using it with a wireless sensor system saves time and labor as well as water.

  18. Optogenetic activation of septal cholinergic neurons suppresses sharp wave ripples and enhances theta oscillations in the hippocampus.

    Vandecasteele, Marie; Varga, Viktor; Berényi, Antal; Papp, Edit; Barthó, Péter; Venance, Laurent; Freund, Tamás F; Buzsáki, György

    2014-09-16

    Theta oscillations in the limbic system depend on the integrity of the medial septum. The different populations of medial septal neurons (cholinergic and GABAergic) are assumed to affect different aspects of theta oscillations. Using optogenetic stimulation of cholinergic neurons in ChAT-Cre mice, we investigated their effects on hippocampal local field potentials in both anesthetized and behaving mice. Cholinergic stimulation completely blocked sharp wave ripples and strongly suppressed the power of both slow oscillations (0.5-2 Hz in anesthetized, 0.5-4 Hz in behaving animals) and supratheta (6-10 Hz in anesthetized, 10-25 Hz in behaving animals) bands. The same stimulation robustly increased both the power and coherence of theta oscillations (2-6 Hz) in urethane-anesthetized mice. In behaving mice, cholinergic stimulation was less effective in the theta (4-10 Hz) band yet it also increased the ratio of theta/slow oscillation and theta coherence. The effects on gamma oscillations largely mirrored those of theta. These findings show that medial septal cholinergic activation can both enhance theta rhythm and suppress peri-theta frequency bands, allowing theta oscillations to dominate.

  19. Development of a Data Reduction Algorithm for Optical Wide Field Patrol (OWL) II: Improving Measurement of Lengths of Detected Streaks

    Park, Sun-Youp; Choi, Jin; Roh, Dong-Goo; Park, Maru; Jo, Jung Hyun; Yim, Hong-Suh; Park, Young-Sik; Bae, Young-Ho; Park, Jang-Hyun; Moon, Hong-Kyu; Choi, Young-Jun; Cho, Sungki; Choi, Eun-Jung

    2016-09-01

    As described in the previous paper (Park et al. 2013), the detector subsystem of optical wide-field patrol (OWL) provides many observational data points of a single artificial satellite or space debris in the form of small streaks, using a chopper system and a time tagger. The position and the corresponding time data are matched assuming that the length of a streak on the CCD frame is proportional to the time duration of the exposure during which the chopper blades do not obscure the CCD window. In the previous study, however, the length was measured using the diagonal of the rectangle of the image area containing the streak; the results were quite ambiguous and inaccurate, allowing possible matching error of positions and time data. Furthermore, because only one (position, time) data point is created from one streak, the efficiency of the observation decreases. To define the length of a streak correctly, it is important to locate the endpoints of a streak. In this paper, a method using a differential convolution mask pattern is tested. This method can be used to obtain the positions where the pixel values are changed sharply. These endpoints can be regarded as directly detected positional data, and the number of data points is doubled by this result.

  20. Shrink, twist, ripple and melt: Studies of frustrated liquid crystals

    Fernsler, Jonathan G.

    Complex structures can arise out of a simple system with more than one competing influence on its behavior. The protypical example of this is the two-dimensional triangular lattice Ising model. The ferromagnetic model has two simple degenerate ground states of all spins up or down, but the antiferromagnetic model is a frustrated system. Its geometry does not allow satisfaction of the antiferro condition everywhere, which produces complex ordered structures with dimerization of the spins [1]. Without frustration, the complex structures and phase behavior are lost. All of the topics discussed in this thesis concern smectic liquid crystals. Liquid crystals are perhaps uniquely adept at manifesting frustrated phases. Their combination of periodicity in one or more dimensions allows ordered structures, yet their fluid nature in remaining dimensions allows creation of defects and extraordinarily complex structures in ways that a normal crystal could not tolerate. Liquid crystals contain a huge menagerie of frustrated phases and effects including the polarization modulated [2], vortex lattice [3], twist grain boundary [4], and blue [5] phases, as well as frustrated structures such as cholesteric or SmC* helix unwinding [6], defect lattices in thin films [7], and bend melted grain boundary defects [8], arising from boundary conditions and field effects. In this thesis, we study four liquid crystal systems that show unusual phase behavior or complex structures, deriving from the effects of frustration. Frustration, despite some human prejudices against the word, leaves nature all the more interesting and beautiful.