WorldWideScience

Sample records for underlying velocity field

  1. Ultrasonic velocity and amplitude characterization of magnetorheological fluids under magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Lopez, J., E-mail: jaimerl@caend.upm-csic.es [Centro de Acustica Aplicada y Ensayos No Destructivos, UPM-CSIC, 28006 Madrid (Spain); Elvira Segura, L.; Montero de Espinosa Freijo, F. [Centro de Acustica Aplicada y Ensayos No Destructivos, UPM-CSIC, 28006 Madrid (Spain)

    2012-01-15

    Variations in velocity of sound and amplitude of the signal of a commercial magnetorheological fluid under different magnetic fields are studied experimentally. Different factors such as orientation, uniformity, geometry and intensity of the magnetic field are investigated. An increase in the change of MR fluid acoustical properties is obtained when the magnetic field intensity is risen. In addition, these properties show an opposite behavior when a magnetic field is applied parallel or perpendicular to the ultrasound propagation. Experiments using an electromagnet and permanent magnets as the source of magnetic field are also compared. Properties such as anisotropy in sound velocity and amplitude make these materials interesting regarding applications. - Highlights: > First sound attenuation measurements as function of the magnetic field in MR fluids. > Sound velocity and attenuation anisotropy due to the microstructure is detected. > Geometry, intensity and uniformity of the magnetic field affect sound propagation.

  2. Measurements of Dendritic Growth Velocities in Undercooled Melts of Pure Nickel Under Static Magnetic Fields

    Science.gov (United States)

    Gao, Jianrong; Zhang, Zongning; Zhang, Yingjie

    2012-01-01

    Dendritic growth velocities in undercooled melts of pure Ni have been intensively studied over the past fifty years. However, the literature data are at marked variance with the prediction of the widely accepted model for rapid dendritic growth both at small and at large undercoolings. In the present work, bulk melts of pure Ni samples of high purity were undercooled by glass fluxing treatment under a static magnetic field. The recalescence processes of the samples at different undercoolings were recorded using a high-speed camera, and were modeled using a software to determine the dendritic growth velocities. The present data confirmed the effect of melt flow on dendritic growth velocities at undercoolings below 100 K. A comparison of the present data with previous measurements on a lower purity material suggested an effect of impurities on dendritic growth velocities at undercoolings larger than 200 K as well.

  3. Response of Velocity Anisotropy of Shale Under Isotropic and Anisotropic Stress Fields

    Science.gov (United States)

    Li, Xiaying; Lei, Xinglin; Li, Qi

    2018-03-01

    We investigated the responses of P-wave velocity and associated anisotropy in terms of Thomsen's parameters to isotropic and anisotropic stress fields on Longmaxi shales cored along different directions. An array of piezoelectric ceramic transducers allows us to measure P-wave velocities along numerous different propagation directions. Anisotropic parameters, including the P-wave velocity α along a symmetry axis, Thomsen's parameters ɛ and δ, and the orientation of the symmetry axis, could then be extracted by fitting Thomsen's weak anisotropy model to the experimental data. The results indicate that Longmaxi shale displays weakly intrinsic velocity anisotropy with Thomsen's parameters ɛ and δ being approximately 0.05 and 0.15, respectively. The isotropic stress field has only a slight effect on velocity and associated anisotropy in terms of Thomsen's parameters. In contrast, both the magnitude and orientation of the anisotropic stress field with respect to the shale fabric are important in controlling the evolution of velocity and associated anisotropy in a changing stress field. For shale with bedding-parallel loading, velocity anisotropy is enhanced because velocities with smaller angles relative to the maximum stress increase significantly during the entire loading process, whereas those with larger angles increase slightly before the yield stress and afterwards decrease with the increasing differential stress. For shale with bedding-normal loading, anisotropy reversal is observed, and the anisotropy is progressively modified by the applied differential stress. Before reaching the yield stress, velocities with smaller angles relative to the maximum stress increase more significantly and even exceed the level of those with larger angles. After reaching the yield stress, velocities with larger angles decrease more significantly. Microstructural features such as the closure and generation of microcracks can explain the modification of the velocity anisotropy

  4. Effects of light illumination on electron velocity of AlGaN/GaN heterostructures under high electric field

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Lei; Yang, Xuelin, E-mail: xlyang@pku.edu.cn; Cheng, Jianpeng; Sang, Ling; Xu, Fujun; Tang, Ning [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Feng, Zhihong; Lv, Yuanjie [National Key Laboratory of Application Specific Integrated Circuit, Hebei Semiconductor Research Institute, Shijiazhuang 050051 (China); Wang, Xinqiang; Shen, B., E-mail: bshen@pku.edu.cn [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China); Ge, Weikun [Department of Physics, Tsinghua University, Beijing 100084 (China)

    2014-12-15

    We have investigated the variation of electron velocity in AlGaN/GaN heterostructures depending on illuminating light intensity and wavelength. It is shown that the electron velocity at high electric field increases under above-band light illumination. This electron velocity enhancement is found to be related to the photo-generated cold holes which interact with hot electrons and thus accelerate the energy relaxation at high electric field. The results suggest an alternative way to improve the electron energy relaxation rate and hence the electron velocity in GaN based heterostructures.

  5. Velocity and magnetic field measurements of Taylor plumes in SSX under different boundary conditions

    Science.gov (United States)

    Kaur, Manjit; Brown, M. R.; Han, J.; Shrock, J. E.; Schaffner, D. A.

    2016-10-01

    The SSX device has been modified by the addition of a 1 m long glass extension for accommodating pulsed theta pinch coils. The Taylor plumes are launched from a magnetized plasma gun and flow to an expansion volume downstream. The time of flight (TOF) measurements of these plumes are carried out using a linear array of Ḃ probes (separated by 10cm). TOF of the plasma plumes from one probe location to the next is determined by direct comparison of the magnetic field structures as well as by carrying out a cross-correlation analysis. With the glass boundary, the typical velocity of the Taylor plumes is found to be 25km /s , accompanied by a fast plasma (>= 50km /s) at the leading edge. Magnetic field embedded in the Taylor plumes is measured in the expansion chamber using a three-dimensional array of Ḃ probes and is found to be 700G . Some flux conservation of the Taylor plumes is provided by using a resistive (soak time 3 μs) and a mesh (soak time 170 μs > discharge time) liner around the glass tube for improving the downstream Taylor state velocity as well as the magnetic field. The results from these different boundary conditions will be presented. Work supported by DOE OFES and ARPA-E ALPHA programs.

  6. Three-dimensional simulation of the motion of a single particle under a simulated turbulent velocity field

    Science.gov (United States)

    Moreno-Casas, P. A.; Bombardelli, F. A.

    2015-12-01

    A 3D Lagrangian particle tracking model is coupled to a 3D channel velocity field to simulate the saltation motion of a single sediment particle moving in saltation mode. The turbulent field is a high-resolution three dimensional velocity field that reproduces a by-pass transition to turbulence on a flat plate due to free-stream turbulence passing above de plate. In order to reduce computational costs, a decoupled approached is used, i.e., the turbulent flow is simulated independently from the tracking model, and then used to feed the 3D Lagrangian particle model. The simulations are carried using the point-particle approach. The particle tracking model contains three sub-models, namely, particle free-flight, a post-collision velocity and bed representation sub-models. The free-flight sub-model considers the action of the following forces: submerged weight, non-linear drag, lift, virtual mass, Magnus and Basset forces. The model also includes the effect of particle angular velocity. The post-collision velocities are obtained by applying conservation of angular and linear momentum. The complete model was validated with experimental results from literature within the sand range. Results for particle velocity time series and distribution of particle turbulent intensities are presented.

  7. Neutron stars velocities and magnetic fields

    Science.gov (United States)

    Paret, Daryel Manreza; Martinez, A. Perez; Ayala, Alejandro.; Piccinelli, G.; Sanchez, A.

    2018-01-01

    We study a model that explain neutron stars velocities due to the anisotropic emission of neutrinos. Strong magnetic fields present in neutron stars are the source of the anisotropy in the system. To compute the velocity of the neutron star we model its core as composed by strange quark matter and analice the properties of a magnetized quark gas at finite temperature and density. Specifically we have obtained the electron polarization and the specific heat of magnetized fermions as a functions of the temperature, chemical potential and magnetic field which allow us to study the velocity of the neutron star as a function of these parameters.

  8. Temporal Changes of the Photospheric Velocity Fields

    Czech Academy of Sciences Publication Activity Database

    Klvaňa, Miroslav; Švanda, Michal; Bumba, Václav

    2005-01-01

    Roč. 29, č. 1 (2005), s. 89-98 ISSN 0351-2657. [Hvar astrophysical colloquium /7./: Solar activity cycle and global phenomena. Hvar, 20.09.2004-24.09.2004] R&D Projects: GA ČR GA205/04/2129 Institutional research plan: CEZ:AV0Z10030501 Keywords : Solar photosphere * velocity fields * tidal waves Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  9. Anomalous transport in correlated velocity fields.

    Science.gov (United States)

    Berkowitz, Brian; Scher, Harvey

    2010-01-01

    We examine different types of heterogeneous hydraulic conductivity fields to ascertain the basic structural features that dominate the transport behavior. We contrast two approaches to the analysis, within the framework of the continuous time random walk (CTRW), considering recent simulations of particle transport in two correlated flow fields to discern these key features. These flow fields are the steady-state solutions of Darcy flow in systems with correlated distributions, P(K(x)), of hydraulic conductivity values K(x). One approach uses the organizational structure of the Lagrangian velocities determined from simulations to derive correlated space-time distributions for particle tracking, which are used to fit simulated breakthrough curve (BTC) data. These fits emphasize the ability to account for both early arrival times and late-time long tailing. The other approach, in this paper, treats the simulated BTCs as "measurements" and uses a truncated power-law form of psi(t), the probability density function (pdf) of local transit times, in a partial differential equation form of CTRW. Excellent fits to both data sets are obtained with a single value of beta, the key parameter that characterizes the nature of the dispersive transport. The value of beta is derivable from the high xi behavior of the pdf histogram Phi(xi) (where xi is the inverse velocity) of the Darcy field, which determines the late-time tail within psi(t). The quality of the two fits obtained herein with a physically derived parameter set is a probe of how heterogeneous hydraulic conductivity fields with different types of correlation can affect the larger-scale transport behavior. The features that give rise to a power-law tail of local transition times and a limit of the time range for non-Fickian behavior dominate the transport. The correlation structures of the different P(K(x)) play a secondary role compared to the spectrum of less frequent events (e.g., low velocity regions) that have a

  10. Mechanoluminescence of nylon under high velocity impact

    Science.gov (United States)

    Bonora, N.; Ruggiero, A.; Iannitti, G.; Abbate, C.; Iannuzzo, F.; Busatto, G.

    2014-05-01

    The light emissions produced during deformation of solids induced by any mechanical action is called mechanoluminescence (ML). This phenomenon was reported mostly in hypervelocity impacts. Using high speed video-recording, the authors found evidence of ML for nylon at much lower impact velocity (of the order of 100 m/s). In order to understand the mechanism responsible for ML, Taylor impact experiments were planned and performed. Several impact configurations were investigated: Taylor anvil impact, Taylor impact on nylon anvil and rod-on-rod impact experiment. During the tests, the emitted light was measured using a wide-spectrum visible-to-infrared photodiode with response below 1 microsecond, and the signals were analyzed. The existence of a limiting impact velocity below which ML is no longer observed seems to be indicative of the fact that ML is controlled by the high pressure that is generated under uniaxial strain loading conditions. This result is consistent with the fact that, as soon as the compressive stress wave travels longitudinally in the Taylor sample and the pressure drops as a result of the arrival of the release waves, the ML no longer occurs. When tests were repeated in vacuum, no light emission in the visible range was observed. This finding seems to indicate that light emission occurs as a result of the oxidation of free radicals generated by the rupture of the polymer chains caused by the dynamic pressure wave.

  11. A stochastic differential equation framework for the turbulent velocity field

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler; Schmiegel, Jürgen

    We discuss a stochastic differential equation, as a modelling framework for the turbulent velocity field, that is capable of capturing basic stylized facts of the statistics of velocity increments. In particular, we focus on the evolution of the probability density of velocity increments...

  12. Velocity field measurement in micro-bubble emission boiling

    International Nuclear Information System (INIS)

    Ito, Daisuke; Saito, Yasushi; Natazuka, Jun

    2017-01-01

    Liquid inlet behavior to a heat surface in micro-bubble emission boiling (MEB) was investigated by flow measurement using particle image velocimetry (PIV). Subcooled pool boiling experiments under atmospheric pressure were carried out using a heat surface with a diameter of 10 mm. An upper end of a heater block made of copper was used as the heat surface. Working fluid was the deionized water and the subcooling was varied from 40 K to 70 K. Three K-type thermocouples were installed in the copper block to measure the temperature gradient, and the heat flux and wall superheat were estimated from these temperature data to make a boiling curve. The flow visualization around the heat surface was carried out using a high-speed video camera and a light sheet. The microbubbles generated in the MEB were used as tracer particles and the velocity field was obtained by PIV analysis of the acquired image sequence. As a result, the higher heat fluxes than the critical heat flux could be obtained in the MEB region. In addition, the distribution characteristics of the velocity in MEB region were studied using the PIV results and the location of the stagnation point in the velocity fields was discussed. (author)

  13. A new method for accurate estimation of velocity field statistics

    NARCIS (Netherlands)

    Bernardeau, F; vandeWeygaert, R

    1996-01-01

    We introduce two new methods to obtain reliable velocity field statistics from N-body simulations, or indeed from any general density and velocity fluctuation field sampled by discrete points, These methods, the Voronoi tessellation method and Delaunay tessellation method, are based on the use of

  14. Velocity field statistics and tessellation techniques : Unbiased estimators of Omega

    NARCIS (Netherlands)

    Van de Weygaert, R; Bernardeau, F; Muller,; Gottlober, S; Mucket, JP; Wambsganss, J

    1998-01-01

    We describe two new - stochastic-geometrical - methods to obtain reliable velocity field statistics from N-body simulations and from any general density and velocity fluctuation field sampled at a discrete set of locations. These methods, the Voronoi tessellation method and Delaunay tessellation

  15. Velocity Field Statistics and Tessellation Techniques : Unbiased Estimators of Omega

    NARCIS (Netherlands)

    Weygaert, R. van de; Bernardeau, F.

    1998-01-01

    Abstract: We describe two new, stochastic-geometrical, methods to obtain reliable velocity field statistics from N-body simulations and from any general density and velocity fluctuation field sampled at a discrete set of locations. These methods, the Voronoi tessellation method and Delaunay

  16. Universal Velocity-Field Characteristics for a Nanowire Arbitrary Degeneracy

    International Nuclear Information System (INIS)

    Chek, Desmond C. Y.; Hashim, Abdul Manaf; Tan, Michael Loong Peng; Arora, Vijay K.

    2011-01-01

    The effects of electric field on the carrier motion and drift velocity in nanowire (NW) are presented in this paper. When the electric field is applied in NW, the electron is expected to move in anti-parallel direction to the electric field. This is so-called randomness motion is transformed into streamlined motion in extremely high electric field. The normalized Fermi energy and relative electron population as a function of electric field are examined for various degeneracies. It was found that the electric field has lesser influence on the relative electron population with the increased degeneracy. The drift velocity in NW is shown to increase with electric field until it reaches the saturation velocity. Two approximations have been made to simplify the theoretical equation. It is also shown in this paper that when the quantum emission is taken into account, the drift and saturation velocity degrades.

  17. Magnetic and Velocity Field Variations in the Active Regions NOAA ...

    Indian Academy of Sciences (India)

    Abstract. We study the magnetic and velocity field evolution in the two magnetically complex active regions NOAA 10486 and NOAA 10488 observed during October–November 2003. We have used the available data to examine net flux and Doppler velocity time profiles to identify changes associated with evolutionary and ...

  18. Three-dimensional instantaneous velocity field measurement using ...

    Indian Academy of Sciences (India)

    2014-02-13

    Feb 13, 2014 ... set equal to 20 μl/min. The instantaneous 3D velocity field is obtained by correlating the particles obtained from the 3D numerical reconstruction of holograms using particle tracking velocimetry. (PTV). Keywords. Holography; velocity measurements; laminar flow in microchannel. PACS Nos 42.40.–i; 06.30.

  19. Reconstructing the velocity field beyond the local universe

    CSIR Research Space (South Africa)

    Johnston, R

    2014-10-01

    Full Text Available We present a maximum probability approach to reconstructing spatial maps of the peculiar velocity field at redshifts z ~ 0.1, where the velocities have been measured from distance indicators (DI) such as D(sub n) - s relations or Tully...

  20. Charge carrier velocity in graphene field-effect transistors

    Science.gov (United States)

    Bonmann, Marlene; Vorobiev, Andrei; Andersson, Michael A.; Stake, Jan

    2017-12-01

    To extend the frequency range of transistors into the terahertz domain, new transistor technologies, materials, and device concepts must be continuously developed. The quality of the interface between the involved materials is a highly critical factor. The presence of impurities can degrade device performance and reliability. In this paper, we present a method that allows the study of the charge carrier velocity in a field-effect transistor vs impurity levels. The charge carrier velocity is found using high-frequency scattering parameter measurements followed by delay time analysis. The limiting factors of the saturation velocity and the effect of impurities are then analysed by applying analytical models of the field-dependent and phonon-limited carrier velocity. As an example, this method is applied to a top-gated graphene field-effect transistor (GFET). We find that the extracted saturation velocity is ca. 1.4 ×107 cm/s and is mainly limited by silicon oxide substrate phonons. Within the considered range of residual charge carrier concentrations, charged impurities do not limit the saturation velocity directly by the phonon mechanism. Instead, the impurities act as traps that emit charge carriers at high fields, preventing the current from saturation and thus limiting power gain of the GFETs. The method described in this work helps to better understand the influence of impurities and clarifies methods of further transistor development. High quality interfaces are required to achieve current saturation via velocity saturation in GFETs.

  1. Velocity-Field Theory, Boltzmann's Transport Equation and Geometry

    Science.gov (United States)

    Ichinose, Shoichi

    Boltzmann equation describes the time development of the velocity distribution in the continuum fluid matter. We formulate the equation using the field theory where the velocity-field plays the central role. The matter (constituent particles) fields appear as the density and the viscosity. Fluctuation is examined, and is clearly discriminated from the quantum effect. The time variable is emergently introduced through the computational process step. The collision term, for the (velocity)**4 potential (4-body interaction), is explicitly obtained and the (statistical) fluctuation is closely explained. The present field theory model does not conserve energy and is an open-system model. (One dimensional) Navier-Stokes equation or Burger's equation, appears. In the latter part, we present a way to directly define the distribution function by use of the geometry, appearing in the mechanical dynamics, and Feynman's path-integral.

  2. Velocity Gradients as a Tracer for Magnetic Fields

    Science.gov (United States)

    González-Casanova, Diego F.; Lazarian, A.

    2017-01-01

    Strong Alfvénic turbulence develops eddy-like motions perpendicular to the local direction of magnetic fields. This local alignment induces velocity gradients perpendicular to the local direction of the magnetic field. We use this fact to propose a new technique of studying the direction of magnetic fields from observations, which we call the velocity gradient technique. We test our idea by employing the synthetic observations obtained via 3D magnetohydrodynamical (MHD) numerical simulations for different sonic and Alfvén Mach numbers. We calculate the velocity gradient, {\\boldsymbol{Ω }}, using the velocity centroids. We find that {\\boldsymbol{Ω }} traces the projected magnetic field best for the synthetic maps obtained with sub-Alfvénic simulations and provides good point-wise correspondence between the magnetic field direction and the direction of {\\boldsymbol{Ω }}. The reported alignment is much better than the alignment between the density gradients and the magnetic field, and we demonstrate that it can be used to find the magnetic field strength with an analog of the Chandrasekhar-Fermi method. This new technique does not require dust polarimetry, and our study opens up a new way of studying magnetic fields using spectroscopic data.

  3. Three-dimensional instantaneous velocity field measurement using ...

    Indian Academy of Sciences (India)

    2014-02-13

    Feb 13, 2014 ... ... Singh P K Panigrahi. Contributed Papers Volume 82 Issue 2 February 2014 pp 439-444 ... Abstract. In the present study, a digital holography microscope has been developed to study instantaneous 3D velocity field in a square channel of 1000 × 1000 2 cross-section. The flow field is seeded with ...

  4. Patch near field acoustic holography based on particle velocity measurements

    DEFF Research Database (Denmark)

    Zhang, Yong-Bin; Jacobsen, Finn; Bi, Chuan-Xing

    2009-01-01

    Patch near field acoustic holography (PNAH) based on sound pressure measurements makes it possible to reconstruct the source field near a source by measuring the sound pressure at positions on a surface. that is comparable in size to the source region of concern. Particle velocity is an alternative...

  5. Evolution of velocity and density fields around clusters of galaxies

    International Nuclear Information System (INIS)

    Lilje, P.B.; Lahav, O.

    1990-01-01

    The evolution of the averaged density and infall velocity profiles around clusters of galaxies in several cosmological scenarios based on gravitational instability is explored. The analysis is based on the statistics of peaks in random Gaussian fields and the spherical infall model. This method is shown to give accurate predictions for the cluster-galaxy cross-correlation function when compared with N-body simulations. The predictions for the average infall velocity as function of radius are not as accurate, but are still useful. The discrepancy is probably caused by shear in the velocity field. The predictions for the cluster-galaxy cross-correlation function on large scales are very different for models with little power on large scales (like the Cold Dark Matter and the Hot Dark Matter models) and models with much power on large scales (like the Primordial Isocurvature Baryon models). The ensemble average infall velocity as a function of radius, if it would be possible to measure it, provides a useful method of for distinguishing between models with different levels of biasing of the galaxy number density fluctuations relative to mass fluctuations. Observations of the density and velocity profiles in one supercluster (i.e., the Local Supercluster) are of limited value for setting constraints on models of structure formation in the Universe. However, the r -1 dependence of the velocity field in the Local Supercluster is in good agreement with the predictions of the Cold Dark Matter model, contrary to some claims. (orig.)

  6. POLARIZED LINE FORMATION IN NON-MONOTONIC VELOCITY FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Sampoorna, M.; Nagendra, K. N., E-mail: sampoorna@iiap.res.in, E-mail: knn@iiap.res.in [Indian Institute of Astrophysics, Koramangala, Bengaluru 560034 (India)

    2016-12-10

    For a correct interpretation of the observed spectro-polarimetric data from astrophysical objects such as the Sun, it is necessary to solve the polarized line transfer problems taking into account a realistic temperature structure, the dynamical state of the atmosphere, a realistic scattering mechanism (namely, the partial frequency redistribution—PRD), and the magnetic fields. In a recent paper, we studied the effects of monotonic vertical velocity fields on linearly polarized line profiles formed in isothermal atmospheres with and without magnetic fields. However, in general the velocity fields that prevail in dynamical atmospheres of astrophysical objects are non-monotonic. Stellar atmospheres with shocks, multi-component supernova atmospheres, and various kinds of wave motions in solar and stellar atmospheres are examples of non-monotonic velocity fields. Here we present studies on the effect of non-relativistic non-monotonic vertical velocity fields on the linearly polarized line profiles formed in semi-empirical atmospheres. We consider a two-level atom model and PRD scattering mechanism. We solve the polarized transfer equation in the comoving frame (CMF) of the fluid using a polarized accelerated lambda iteration method that has been appropriately modified for the problem at hand. We present numerical tests to validate the CMF method and also discuss the accuracy and numerical instabilities associated with it.

  7. Sound velocity variations and melting of vanadium under shock compression

    International Nuclear Information System (INIS)

    Dai Chengda; Jin Xiaogang; Zhou Xianming; Liu Jianjun; Hu Jinbiao

    2001-01-01

    The sound velocities of vanadium at shock pressure ranging from 154 to 250 GPa were determined using transparent-window optical analyser techniques. A discontinuity in sound velocities at about 225 GPa may mark the partial melting under shock compression. The comparison between the measured sound velocity data sets above ∼225 GPa and calculated values yields γ 0 ∼2.0 and the empirical expression γρ=γ 0 ρ 0 is basically tenable. Additionally, shock temperatures along the principal Hugoniot of vanadium were also determined from interfacial radiation intensities according to Grover's ideal interface model. Thus the temperature at this solid-liquid phase transition was constrained to be round about 7800(±800) K on the basis of the measured Hugoniot temperatures, melting temperatures, and high-pressure sound velocity variations with pressure. (author)

  8. Size-effect of explosive sensitivity under low velocity impact

    Science.gov (United States)

    Ma, Danzhu; Chen, Pengwan; Zhou, Qiang

    2013-06-01

    Low velocity impact may ignite the solid high explosives and cause undesired explosion incidents. The safety of high explosives under low velocity impact is one of the most important problems in handling, manufacture, storage, and transportation procedures. More and more evaluation tests have been developed for low velocity impact scenarios, including, but not limited to the drop hammer impact test, the Susan test, the Spigot test, and the Steven test, with a charge mass varying from tens of milligrams to several kilograms. The effects of specimen size on explosive sensitivity were found in our drop hammer impact test and Steven tests, including the threshold velocity/height and reaction violence. To further analyze the size effects on explosive sensitivity under low velocity impacts, we collected the impact sensitivity data of several PBX explosives in the drop hammer test, the Steven test, the Susan test and the Spigot test. The effective volume of explosive charge and the threshold specific mechanical energy were introduced to investigate the size-effect on the explosive ignition thresholds. The effective volumes of explosive charge in Steven test and Spigot test were obtained by numerical simulation, due to the localization of the impact. The threshold specific mechanical energy is closely related to the effective volume of explosive charge. The results show that, with the increase of effective volume, the specific mechanical energy needed for explosive ignition decreases and trends to reach a constant value. The mechanisms of size effects on explosive sensitivity are also discussed.

  9. Specimen size effect of explosive sensitivity under low velocity impact

    Science.gov (United States)

    Ma, Danzhu; Chen, Pengwan; Dai, Kaida; Zhou, Qiang

    2014-05-01

    Low velocity impact may ignite the solid high explosives and cause undesired explosion incidents. The safety of high explosives under low velocity impact is one of the most important issues in handling, manufacture, storage, and transportation procedures. Various evaluation tests have been developed for low velocity impact scenarios, including, but not limited to the drop hammer test, the Susan test, the Spigot test, and the Steven test, with a charge mass varying from tens of milligrams to several kilograms. The effects of specimen size on explosive sensitivity were found in some impact tests such as drop hammer test and Steven tests, including the threshold velocity/height and reaction violence. To analyse the specimen size effects on explosive sensitivity under low velocity impacts, we collected the impact sensitivity data of several PBX explosives in the drop hammer test, the Steven test, the Susan test and the Spigot test. The effective volume of explosive charge and the critical specific mechanical energy were introduced to investigate the size-effect on the explosive reaction thresholds. The effective volumes of explosive charge in Steven test and Spigot test were obtained by numerical simulation, due to the deformation localization of the impact loading. The critical specific mechanical energy is closely related to the effective volume of explosive charge. The results show that, with the increase of effective volume, the critical mechanical energy needed for explosive ignition decreases and tends to reach a constant value. The mechanisms of size effects on explosive sensitivity are also discussed.

  10. Channel flow analysis. [velocity distribution throughout blade flow field

    Science.gov (United States)

    Katsanis, T.

    1973-01-01

    The design of a proper blade profile requires calculation of the blade row flow field in order to determine the velocities on the blade surfaces. An analysis theory is presented for several methods used for this calculation and associated computer programs that were developed are discussed.

  11. Three-dimensional instantaneous velocity field measurement using ...

    Indian Academy of Sciences (India)

    2014-02-13

    Feb 13, 2014 ... In the present study, a digital holography microscope has been developed to study instantaneous 3D ... Rv. 1. Introduction. Digital holography is a nonintrusive optical technique having immense potential for 3D .... microscope (DHM) for 3D instantaneous velocity field measurements in microchannels.

  12. Thermocouple based method of temperature and velocity field mapping

    Czech Academy of Sciences Publication Activity Database

    Gregor, J.; Jakubová, I.; Mendl, T.; Šenk, J.; Kopecký, Vladimír

    2002-01-01

    Roč. 52, supplement D (2002), s. 596-600 ISSN 0011-4626. [Symposium on Plasma Physics and Technology/20th./. Prague, 10.06.2002-13.06.2002] Institutional research plan: CEZ:AV0Z2043910 Keywords : determination of temperature, velocity field Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.311, year: 2002

  13. Transformations Based on Continuous Piecewise-Affine Velocity Fields

    DEFF Research Database (Denmark)

    Freifeld, Oren; Hauberg, Søren; Batmanghelich, Kayhan

    2017-01-01

    We propose novel finite-dimensional spaces of well-behaved transformations. The latter are obtained by (fast and highly-accurate) integration of continuous piecewise-affine velocity fields. The proposed method is simple yet highly expressive, effortlessly handles optional constraints (e.g., volume...

  14. Results of verification and investigation of wind velocity field forecast. Verification of wind velocity field forecast model

    International Nuclear Information System (INIS)

    Ogawa, Takeshi; Kayano, Mitsunaga; Kikuchi, Hideo; Abe, Takeo; Saga, Kyoji

    1995-01-01

    In Environmental Radioactivity Research Institute, the verification and investigation of the wind velocity field forecast model 'EXPRESS-1' have been carried out since 1991. In fiscal year 1994, as the general analysis, the validity of weather observation data, the local features of wind field, and the validity of the positions of monitoring stations were investigated. The EXPRESS which adopted 500 m mesh so far was improved to 250 m mesh, and the heightening of forecast accuracy was examined, and the comparison with another wind velocity field forecast model 'SPEEDI' was carried out. As the results, there are the places where the correlation with other points of measurement is high and low, and it was found that for the forecast of wind velocity field, by excluding the data of the points with low correlation or installing simplified observation stations to take their data in, the forecast accuracy is improved. The outline of the investigation, the general analysis of weather observation data and the improvements of wind velocity field forecast model and forecast accuracy are reported. (K.I.)

  15. Near field acoustic holography with particle velocity transducers

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Liu, Yang

    2005-01-01

    Near field acoustic holography is usually based on measurement of the pressure. This paper describes an investigation of an alternative technique that involves measuring the normal component of the acoustic particle velocity. A simulation study shows that there is no appreciable difference between...... in a plane further away, high spatial frequency components are reduced by the reciprocal wave number ratio (k/kz). For the same reason holography based on the particle velocity is less sensitive to transducer mismatch than the conventional technique based on the pressure. These findings are confirmed...

  16. Sound field separation with sound pressure and particle velocity measurements

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Jacobsen, Finn; Leclère, Quentin

    2012-01-01

    separation techniques make it possible to distinguish between outgoing and incoming waves from the two sides, and thus NAH can be applied. In this paper, a separation method based on the measurement of the particle velocity in two layers and another method based on the measurement of the pressure...... and the velocity in a single layer are proposed. The two methods use an equivalent source formulation with separate transfer matrices for the outgoing and incoming waves, so that the sound from the two sides of the array can be modeled independently. A weighting scheme is proposed to account for the distance......In conventional near-field acoustic holography (NAH) it is not possible to distinguish between sound from the two sides of the array, thus, it is a requirement that all the sources are confined to only one side and radiate into a free field. When this requirement cannot be fulfilled, sound field...

  17. Strength calculation for fiber concrete slabs under high velocity impact

    Science.gov (United States)

    Artem, Ustinov; Kopanica, Dmitry; Belov, Nikolay; Jugov, Nikolay; Jugov, Alexey; Koshko, Bogdan; Kopanitsa, Georgy

    2017-01-01

    The paper presents results of the research on strength of concrete slabs reinforced with steel fiber and tested under a high velocity impact. Mathematical models are proposed to describe the behavior of continua with a complex structure with consideration of porosity, non-elastic effects, phase transformations and dynamic destructions of friable and plastic materials under shock wave impact. The models that describe the behavior of structural materials were designed in the RANET-3 CAD software system. This allowed solving the tasks of hit and explosion in the full three-dimensional statement using finite elements method modified for dynamic problems. The research results demonstrate the validity of the proposed mathematical model to calculate stress-strain state and fracture of layered fiber concrete structures under high velocity impact caused by blast wave.

  18. PIV measurements of velocities and accelerations under breaking waves on a slope

    DEFF Research Database (Denmark)

    Vested, Malene Hovgaard; Carstensen, Stefan; Christensen, Erik Damgaard

    2017-01-01

    waves. In this study, we have investigated the wave kinematics under steep and breaking waves on a laboratory beach with a slope of 1/25. The velocity field was measured by use of Particle Image Velocimetry (PIV) at a sample rate of 96Hz. The high sample rate allowed for the accelerations...... to be determined directly from the sampled velocities. It was found that both velocities and accelerations differ from the ones predicted from common wave theories such as streamfunction theory. This was especially evident at the top part of the wave close to the surface. This was not surprising, since...

  19. The Local Stellar Velocity Field via Vector Spherical Harmonics

    Science.gov (United States)

    Makarov, V. V.; Murphy, D. W.

    2007-01-01

    We analyze the local field of stellar tangential velocities for a sample of 42,339 nonbinary Hipparcos stars with accurate parallaxes, using a vector spherical harmonic formalism.We derive simple relations between the parameters of the classical linear model (Ogorodnikov-Milne) of the local systemic field and low-degree terms of the general vector harmonic decomposition. Taking advantage of these relationships, we determine the solar velocity with respect to the local stars of (V(sub X), V(sub Y), V(sub Z)) = (10.5, 18.5, 7.3) +/- 0.1 km s(exp -1) not for the asymmetric drift with respect to the local standard of rest. If only stars more distant than 100 pc are considered, the peculiar solar motion is (V(sub X), V(sub Y), V(sub Z)) = (9.9, 15.6, 6.9) +/- 0.2 km s(exp -1). The adverse effects of harmonic leakage, which occurs between the reflex solar motion represented by the three electric vector harmonics in the velocity space and higher degree harmonics in the proper-motion space, are eliminated in our analysis by direct subtraction of the reflex solar velocity in its tangential components for each star...

  20. Doppler velocity fields in magnetic structures and their surroundings

    Czech Academy of Sciences Publication Activity Database

    Klvaňa, Miroslav; Bumba, Václav; Švanda, Michal

    2006-01-01

    Roč. 30, č. 1 (2006), s. 21-30 ISSN 1845-8319. [Central European Solar Physics Meeting /2./. Bairisch Kölldorf, 19.05.2005-21.05.2005] R&D Projects: GA AV ČR IAA3003404; GA ČR GA205/04/2129 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar photosphere * velocity field * magnetic and non-magnetic regions Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  1. Correction factor to dye-measured flow velocity under varying water and sediment discharges

    Science.gov (United States)

    Dye-tracing technique was a widely used method to measure velocity of overland flow in soil erosion studies under both laboratory and field conditions. Few studies were performed to quantify the effects of sediment load on correction factor on steep slopes. The objective was to investigate the poten...

  2. The Local Stellar Velocity Field via Vector Spherical Harmonics

    Science.gov (United States)

    Markarov, V. V.; Murphy, D. W.

    2007-01-01

    We analyze the local field of stellar tangential velocities for a sample of 42,339 nonbinary Hipparcos stars with accurate parallaxes, using a vector spherical harmonic formalism. We derive simple relations between the parameters of the classical linear model (Ogorodnikov-Milne) of the local systemic field and low-degree terms of the general vector harmonic decomposition. Taking advantage of these relationships, we determine the solar velocity with respect to the local stars of (V(sub X), V(sub Y), V(sub Z)) (10.5, 18.5, 7.3) +/- 0.1 km s(exp -1) not corrected for the asymmetric drift with respect to the local standard of rest. If only stars more distant than 100 pc are considered, the peculiar solar motion is (V(sub X), V(sub Y), V(sub Z)) (9.9, 15.6, 6.9) +/- 0.2 km s(exp -1). The adverse effects of harmonic leakage, which occurs between the reflex solar motion represented by the three electric vector harmonics in the velocity space and higher degree harmonics in the proper-motion space, are eliminated in our analysis by direct subtraction of the reflex solar velocity in its tangential components for each star. The Oort parameters determined by a straightforward least-squares adjustment in vector spherical harmonics are A=14.0 +/- 1.4, B=13.1 +/- 1.2, K=1.1 +/- 1.8, and C=2.9 +/- 1.4 km s(exp -1) kpc(exp -1). The physical meaning and the implications of these parameters are discussed in the framework of a general linear model of the velocity field. We find a few statistically significant higher degree harmonic terms that do not correspond to any parameters in the classical linear model. One of them, a third-degree electric harmonic, is tentatively explained as the response to a negative linear gradient of rotation velocity with distance from the Galactic plane, which we estimate at approximately -20 km s(exp -1) kpc(exp -1). A similar vertical gradient of rotation velocity has been detected for more distant stars representing the thick disk (z greater than 1 kpc

  3. Shear velocity of the Rotokawa geothermal field using ambient noise

    Science.gov (United States)

    Civilini, F.; Savage, M. K.; Townend, J.

    2014-12-01

    Ambient noise correlation is an increasingly popular seismological technique that uses the ambient seismic noise recorded at two stations to construct an empirical Green's function. Applications of this technique include determining shear velocity structure and attenuation. An advantage of ambient noise is that it does not rely on external sources of seismic energy such as local or teleseismic earthquakes. This method has been used in the geothermal industry to determine the depths at which magmatic processes occur, to distinguish between production and non-production areas, and to observe seismic velocity perturbations associated with fluid extraction. We will present a velocity model for the Rotokawa geothermal field near Taupo, New Zealand, produced from ambient noise cross correlations. Production at Rotokawa is based on the "Rotokawa A" combined cycle power station established in 1997 and the "Nga Awa Purua" triple flash power plant established in 2010. Rotokawa Joint Venture, a partnership between Mighty River Power and Tauhara North No. 2 Trust currently operates 174 MW of generation at Rotokawa. An array of short period seismometers was installed in 2008 and occupies an area of roughly 5 square kilometers around the site. Although both cultural and natural noise sources are recorded at the stations, the instrument separation distance provides a unique challenge for analyzing cross correlations produced by both signal types. The inter-station spacing is on the order of a few kilometers, so waves from cultural sources generally are not coherent from one station to the other, while the wavelength produced by natural noise is greater than the station separation. Velocity models produced from these two source types will be compared to known geological models of the site. Depending on the amount of data needed to adequately construct cross-correlations, a time-dependent model of velocity will be established and compared with geothermal production processes.

  4. CONSTRAINING THE NFW POTENTIAL WITH OBSERVATIONS AND MODELING OF LOW SURFACE BRIGHTNESS GALAXY VELOCITY FIELDS

    International Nuclear Information System (INIS)

    Kuzio de Naray, Rachel; McGaugh, Stacy S.; Mihos, J. Christopher

    2009-01-01

    We model the Navarro-Frenk-White (NFW) potential to determine if, and under what conditions, the NFW halo appears consistent with the observed velocity fields of low surface brightness (LSB) galaxies. We present mock DensePak Integral Field Unit (IFU) velocity fields and rotation curves of axisymmetric and nonaxisymmetric potentials that are well matched to the spatial resolution and velocity range of our sample galaxies. We find that the DensePak IFU can accurately reconstruct the velocity field produced by an axisymmetric NFW potential and that a tilted-ring fitting program can successfully recover the corresponding NFW rotation curve. We also find that nonaxisymmetric potentials with fixed axis ratios change only the normalization of the mock velocity fields and rotation curves and not their shape. The shape of the modeled NFW rotation curves does not reproduce the data: these potentials are unable to simultaneously bring the mock data at both small and large radii into agreement with observations. Indeed, to match the slow rise of LSB galaxy rotation curves, a specific viewing angle of the nonaxisymmetric potential is required. For each of the simulated LSB galaxies, the observer's line of sight must be along the minor axis of the potential, an arrangement that is inconsistent with a random distribution of halo orientations on the sky.

  5. [OIII] Velocity Fields and Rotation Curves of MUSCEL Galaxies

    Science.gov (United States)

    Kuzio de Naray, Rachel

    2018-01-01

    The MUSCEL (MUltiwavelength observations of the Structure, Chemistry and Evolution of LSB galaxies) program is designed to study the spatially-resolved star formation histories and kinematics of low surface brightness galaxies to determine why they have followed a different evolutionary path than high surface brightness galaxies. Here we present the observed [OIII]5007 velocity fields and derived rotation curves of four MUSCEL targets using observations taken with the VIRUS-P IFU. We also fit cuspy and cored halo models to the data to examine the structure of their dark matter halos.

  6. Velocity fields in mixing-enhanced compressible shear layers

    Science.gov (United States)

    Watanabe, Shigeya; Mungal, M. G.

    2005-01-01

    Planar velocity fields of mixing-enhanced compressible planar shear layers are measured via particle image velocimetry (PIV) in order to investigate the mechanism of mixing enhancement by sub-boundary-layer triangular disturbances. The measurements are conducted at convective Mach numbers, M_{{c}}, of 0.62 and 0.24 to examine compressibility effects on effectiveness of the mixing enhancement technique. Instantaneous side- and plan-view vector maps of the shear layers are obtained, and turbulence statistical quantities are derived from the instantaneous velocity data. Schlieren and planar laser Mie scattering (PLMS) techniques are also used to measure the shear-layer thickness and growth rate as well as surveying the qualitative flow fields. The velocity fields for several disturbance configurations with different shape, size, or thickness are compared in terms of the shear-layer thickness and growth rate in order to investigate the effects of the configuration variation on the mixing enhancement strategy. Configuration parameters include thickness, the semi-vertex angle of the triangular disturbance, and the streamwise offset of the disturbance from the splitter tip. The measured transverse profile of the mean streamwise velocity shows a characteristic shape with triple inflection points for the effective mixing-enhanced cases at the two different compressibility conditions, while periodic inflection points are observed in the spanwise direction. A pair of stationary counter-rotating streamwise vortices introduced by the subboundary-layer disturbances are also observed, even in the fully developed region of the shear layers. At M_{{c}} {=} 0.62, it is found that in successfully enhanced cases, regardless of the disturbance configurations, the present mixing-enhancement strategy has the effect of increasing the turbulence intensity and Reynolds stress, and suppressing the turbulence anisotropy increase with increasing compressibility, i.e. alleviating the

  7. Velocity profiles and surface roughness under breaking waves

    Science.gov (United States)

    Craig, Peter D.

    1996-01-01

    Recent measurements under wave-breaking conditions in the ocean, lakes, and tanks reveal a layer immediately below the surface in which dissipation decays as depth to the power -2 to -4 and downwind velocities are approximately linear with depth. This behavior is consistent with predictions of a conventional, one-dimensional, level 2.5 turbulence closure model, in which the influence of breaking waves is parameterized as a surface source of turbulent kinetic energy. The model provides an analytic solution which describes the near-surface power law behavior and the deeper transition to the "law of the wall." The mixing length imposed in the model increases linearly away from a minimum value, the roughness length, at the surface. The surface roughness emerges as an important scaling factor in the wave-enhanced layer but is the major unknown in the formulation. Measurements in the wave-affected layer are still rare, but one exceptional set, both in terms of its accuracy and proximity to the surface, is that collected by Cheung and Street [1988] in the Stanford wind tunnel. Their velocity profiles first confirm the accuracy of the model, and, second, allow estimation, via a best fit procedure, of roughness lengths at five different wind speeds. Conclusions are tentative but indicate that the roughness length increases with wind speed and appears to take a value of approximately one sixth the dominant surface wavelength. A more traditional wall-layer model, which ignores the flux of turbulent kinetic energy, will also accurately reproduce the measured velocity profiles. In this case, enhanced surface turbulence is forced on the model by the assumption of a large surface roughness, three times that required by the full model. However, the wall-layer model cannot predict the enhanced dissipation near the surface.

  8. Velocity flow field and water level measurements in shoaling and breaking water waves

    CSIR Research Space (South Africa)

    Mukaro, R

    2010-01-01

    Full Text Available levels were measured using capacitive waves gauges, while the instantaneous velocity flow fields were measured using video techniques together with digital correlation techniques. The instantaneous velocity flow fields were further analyzed to yield...

  9. Field test and theoretical analysis of electromagnetic pulse propagation velocity on crossbonded cable systems

    DEFF Research Database (Denmark)

    Jensen, Christian Flytkjær; Bak, Claus Leth; Gudmundsdottir, Unnur Stella

    2014-01-01

    In this paper, the electromagnetic pulse propagation velocity on a three-phase cable system, consisting of three single core (SC) cables in flat formation with an earth continuity conductor is under study. The propagation velocity is an important parameter for most travelling wave off- and online...... fault location methods and needs to be exactly known for optimal performance of these algorithm types. Field measurements are carried out on a 6.9 km and a 31.4 km 245 kV crossbonded cable system, and the results are analysed using the modal decomposition theory. Several ways for determining...

  10. On the velocity fields in elliptical galaxies with dark matter

    International Nuclear Information System (INIS)

    Yoshii, Yuzuru

    1987-01-01

    The tensor virial theorem is used to investigate a dynamical state of an oblate system of luminous matter which is embedded in the more extended dark matter with reasonable density profiles. The relation between the ratio of rotation to random velocities and the ellipticity of a luminous system has been derived. If dark matter is distributed almost spherically, then the rotation velocity in the luminous system with isotropic velocity dispersions is larger than in the isolated system with the same ellipticity. Therefore, the anisotropy in velocity dispersions necessary to be consistent with the observed slow rotations of giant ellipticals should be larger than that for the isolated system without dark matter. (author)

  11. SULFENTRAZONE PHYTOREMEDIATION UNDER FIELD CONDITIONS

    Directory of Open Access Journals (Sweden)

    ALESSANDRA FERREIRA BELO

    2016-01-01

    Full Text Available Phytoremediation is a technique that has been used with increasing frequency to decontaminate soils treated with herbicides that have long - term residual effects, such as sulfentrazone. The goal was to assess phytoremediation of the herbicide sulfentrazone under field conditions by the species Canavalia ensiformis and Crotalaria juncea . The treatments consisted of combinations of the plant species C. ensiformis and C. juncea plus a control treatment (with manual weeding and four doses of the herbicide sulfentrazone. The experimental design used herein was a split - plot randomized block design with four replicates per subplot. The treatments were kept in the field for 75 days. After this period, the experimental area was again furrowed and fertilized, considering the requirements for Pennisetum glaucum , a plant used as an indicator of the presence of sulfentrazone. Thirty - four days after sowing pearl millet, the fresh and dry shoot masses of the plants were assessed. At the end of the cycle, the plant height, stem diameter, internode length, number of leaves, number of panicles, and fresh and dry panicle masses were determined. Previous cultivation of phytoremediation species C. ensiformis and C. juncea promotes sulfentrazone remediation. C. ensiformis is the most efficient species for the decontamination of the herbicide sulfentrazone under field conditions.

  12. Measuring Average Angular Velocity with a Smartphone Magnetic Field Sensor

    Science.gov (United States)

    Pili, Unofre; Violanda, Renante

    2018-01-01

    The angular velocity of a spinning object is, by standard, measured using a device called a tachometer. However, by directly using it in a classroom setting, the activity is likely to appear as less instructive and less engaging. Indeed, some alternative classroom-suitable methods for measuring angular velocity have been presented. In this paper,…

  13. Experimental investigation of the velocity field in buoyant diffusion flames using PIV and TPIV algorithm

    Science.gov (United States)

    L. Sun; X. Zhou; S.M. Mahalingam; D.R. Weise

    2005-01-01

    We investigated a simultaneous temporally and spatially resolved 2-D velocity field above a burning circular pan of alcohol using particle image velocimetry (PIV). The results obtained from PIV were used to assess a thermal particle image velocimetry (TPIV) algorithm previously developed to approximate the velocity field using the temperature field, simultaneously...

  14. 3C velocity field measurement in microscale using time resolved micro-PIV

    OpenAIRE

    N., Erkan; K., Okamoto; Dept. of Quantum Eng. and Sys. Science, The University of Tokyo; Inst. of Env. Studies, The University of Tokyo

    2007-01-01

    Measurement of the 3C velocity field in the microfluidic devices with the conventional techniques and conventional micro-PIV is still difficult due to the limited optical access to the microscale flow fields. Mainly micro PIV vector field realizations have been remained limited to 2C velocities. In this study, 3C velocity measurement in microscale using 2-dimentional time-resolved micro PIV images is proposed. The method is based on the PIV performs cross-correlation (CC) peak height tracking...

  15. Migration velocity analysis using pre-stack wave fields

    KAUST Repository

    Alkhalifah, Tariq Ali

    2016-08-25

    Using both image and data domains to perform velocity inversion can help us resolve the long and short wavelength components of the velocity model, usually in that order. This translates to integrating migration velocity analysis into full waveform inversion. The migration velocity analysis part of the inversion often requires computing extended images, which is expensive when using conventional methods. As a result, we use pre-stack wavefield (the double-square-root formulation) extrapolation, which includes the extended information (subsurface offsets) naturally, to make the process far more efficient and stable. The combination of the forward and adjoint pre-stack wavefields provides us with update options that can be easily conditioned to improve convergence. We specifically use a modified differential semblance operator to split the extended image into a residual part for classic differential semblance operator updates and the image (Born) modelling part, which provides reflections for higher resolution information. In our implementation, we invert for the velocity and the image simultaneously through a dual objective function. Applications to synthetic examples demonstrate the features of the approach.

  16. Velocity field and coherent structures in the near wake of a utility-scale wind turbine

    Science.gov (United States)

    Hong, Jiarong; Dasari, Teja; Wu, Yue; Liu, Yun

    2017-11-01

    Super-large-scale particle image velocity (SLPIV) and the associated flow visualization technique using natural snowfall have been shown as an effective tool to probe turbulent velocity field and coherent structures around utility-scale wind turbines (Hong et al. Nature Comm. 2014). Here we present a follow-up study using the data collected during multiple deployments from 2014 to 2016 around the 2.5 MW turbine at EOLOS field station. The data include SLPIV measurements in the near wake of the turbine in a field of view of 120 m (height) x 60 m (width), and the visualization of tip vortex behavior near the bottom blade tip over a broad range of turbine operational conditions. SLPIV results indicate a highly intermittent flow field in the near wake, consisting of both intense wake expansion and contraction events. Such intermittent states of the near wake are shown to be influenced by both the incoming wind conditions and the turbine operation. The visualization of tip vortex behavior demonstrates the presence of the state of consistent vortex formation as well as various types of disturbed vortex states. The occurrence of these states is statistically analyzed and is shown to be correlated with turbine operational and response parameters under different field conditions. National Science Foundation Fluid Dynamics Program.

  17. Proving diamonds under ultra-high pressure with sound velocity measurements

    Science.gov (United States)

    Shigemori, Keisuke; Shimizu, Katsuya; Asakura, Yasuhiro; Sakaiya, Tatsuhiro; Kondo, Tadashi; Hironaka, Yoichiro; Irifune, Tetsuo; Sumiya, Hitoshi; Kadono, Toshihiko; Azechi, Hiroshi

    2014-10-01

    Diamond under terapascal (TPa) regime is of great interest on its phase transition to a post diamond phase. Many experimental works have been done on the diamond at the TPa regime by measuring the shock parameters (shock velocity, particle velocity). We measured sound velocities of shock-compressed diamond under several pressures by means of x-ray backlighting technique. Experiments were done on GEKKO-HIPER laser irradiation facility at Institute of Laser Engineering, Osaka University. We obtained sound velocities at a pressure of 0.4 - 2.0 TPa by changing the laser intensity. The experimental sound velocity suggests that a clear discontinuity at around 0.7 TPa where the melting of the diamond starts. The sound velocity drops then slightly increases with increasing pressure. The slope of the sound velocity over 1 TPa is lower than that under 0.7 TPa, indicating the melting of the diamond.

  18. Magnetic field and temperature dependence of the critical vortex velocity in type-II superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Grimaldi, G; Leo, A; Cirillo, C; Attanasio, C; Nigro, A; Pace, S [CNR-INFM Laboratorio Regionale SuperMat, Via Salvador Allende, I-84081 Baronissi (Italy)], E-mail: grimaldi@sa.infn.it

    2009-06-24

    We study the vortex dynamics in the instability regime induced by high dissipative states well above the critical current in Nb superconducting strips. The magnetic field and temperature behavior of the critical vortex velocity corresponding to the observed dynamic instability is ascribed to intrinsic non-equilibrium phenomena. The Larkin-Ovchinnikov (LO) theory of electronic instability in high velocity vortex motion has been applied to interpret the temperature dependence of the critical vortex velocity. The magnetic field dependence of the vortex critical velocity shows new features in the low-field regime not predicted by LO.

  19. Integration of Dense Velocity Fields in the ITRF: Quantification and Mitigation of Inconsistencies Between Individual Solutions

    Science.gov (United States)

    Legrand, Juliette; Bruyninx, Carine; Saria, Elifuraha; Griffiths, Jake; Craymer, Michael; Dawson, John; Kenyeres, Ambrus; Santamaría-Gómez, Alvaro; Sanchez, Laura; Altamimi, Zuheir

    2013-04-01

    The objective of the IAG Working Group "Integration of Dense Velocity Fields in the ITRF" is to provide a GNSS-based dense, unified and reliable velocity field globally referenced in the ITRF (International Terrestrial Reference Frame) and useful for geodynamical and geophysical interpretations. The WG is embedded in IAG Sub-Commission 1.3 "Regional Reference Frames" where it coexists with the Regional Reference Frame Sub-Commissions AFREF (Africa), APREF (Asia & Pacific), EUREF (Europe), NAREF (North America), SCAR (Antarctica), SIRGAS (Latin America & Caribbean). These IAG Regional Reference Frame sub-commissions are responsible for providing GNSS-based densified weekly solutions for their region. In addition, the ULR consortium is also a contributor to the WG. To obtain such a densified velocity field, the WG will combine the individual weekly solutions from different contributors and then stack these weekly combined solutions in order to derive a cumulative position and velocity solution as well as the associated residual position time series. The preliminary weekly combinations include 8 individual solutions (AFREF, APREF, EUREF, NAREF (NGS, GSB), SIRGAS, IGS, ULR) and contain about two thousand stations in addition to the ITRF2008. The agreement between the solutions is promising and leads to weekly RMS ranging from 2 to 8 mm. However, this agreement is presently limited by inconsistencies at the modeling and meta data level: 1) the meta data need to be verified as systematic biases occur, probably due to wrong antenna eccentricities and 2) different antenna calibration models have been used by the contributors: some solutions use igs08.atx, while others use igs05.atx or even individual calibrations. In addition, an optimal rescaling of the covariance matrices during the weekly combination is still under investigation. This poster will focus on the quantification and, if possible, the mitigation of these inconsistencies and on the improvement of the

  20. The Velocity Field of the Globular Cluster System in NGC 5128 (Cen A)

    Science.gov (United States)

    Harris, William; Woodley, Kristin; Geisler, Doug; Gomez, Matias; Harris, Gretchen

    2007-02-01

    We propose to carry out a comprehensive new dynamical study of the globular cluster system of NGC 5128 (Centaurus A), the nearest giant E galaxy. A key component of our proposal is a completely new catalog of globular cluster candidates that we have generated from a wide-field (1.4 sq deg) R-band imaging survey of NGC 5128 taken April 2006 with Magellan/IMACS under remarkable 0.45" seeing. We have used this new imaging survey to isolate a list of GC candidates that is far more precise, complete, and contamination-free than in any previous work. As spectroscopic followup, we will use the CTIO 4m + Hydra to measure velocities for 800 new GC candidates, of which 400 or more should be bona fide clusters. Our new data will double the known NGC 5128 GC sample and will eliminate the spatial biases inherent in all previous studies of this unique system. More importantly, the large new velocity database will be the springboard for a superior dynamical analysis of the galaxy and the halo velocity field. This work will allow us to define later programs aimed at detailed abundance and age distribution profiles for the system, and systematic trends with metallicity, that will closely connect with galaxy formation models. In addition, our GC database will rank among the largest ever assembled for a single galaxy, not only enabling us to test galaxy formation models but also providing a benchmark dataset in globular cluster research.

  1. Axisymmetric electromagnetic field influence on the characteristic velocity of an arc-jet

    Science.gov (United States)

    Oggero, M.; Gennuso, D.

    1984-01-01

    Tests for determining the influence of an axisymmetric EM field on the characteristic velocity of an arc jet are presented. The experimental set up is briefly described. Tests were performed with rotation induced by the centrifugal and magnetic fields in the same sense. The fuels used were HE and N2 and the results are discussed. It is found that by variation of the induction, current, and arc jet strength, the behavior is determined essentially by the shape of the cathodic and anodic blobs on the electrodes together with their movement under the combined effect of the aerodynamic and magnetic fields. In view of the different characteristics of He and N2 in respect to the dissociation heat and ionization, it is expected that the regime of the arc jet when used with H2 fuel will be similar to that with He.

  2. Modeling delamination of FRP laminates under low velocity impact

    Science.gov (United States)

    Jiang, Z.; Wen, H. M.; Ren, S. L.

    2017-09-01

    Fiber reinforced plastic laminates (FRP) have been increasingly used in various engineering such as aeronautics, astronautics, transportation, naval architecture and their impact response and failure are a major concern in academic community. A new numerical model is suggested for fiber reinforced plastic composites. The model considers that FRP laminates has been constituted by unidirectional laminated plates with adhesive layers. A modified adhesive layer damage model that considering strain rate effects is incorporated into the ABAQUS / EXPLICIT finite element program by the user-defined material subroutine VUMAT. It transpires that the present model predicted delamination is in good agreement with the experimental results for low velocity impact.

  3. Update schemes of multi-velocity floor field cellular automaton for pedestrian dynamics

    Science.gov (United States)

    Luo, Lin; Fu, Zhijian; Cheng, Han; Yang, Lizhong

    2018-02-01

    Modeling pedestrian movement is an interesting problem both in statistical physics and in computational physics. Update schemes of cellular automaton (CA) models for pedestrian dynamics govern the schedule of pedestrian movement. Usually, different update schemes make the models behave in different ways, which should be carefully recalibrated. Thus, in this paper, we investigated the influence of four different update schemes, namely parallel/synchronous scheme, random scheme, order-sequential scheme and shuffled scheme, on pedestrian dynamics. The multi-velocity floor field cellular automaton (FFCA) considering the changes of pedestrians' moving properties along walking paths and heterogeneity of pedestrians' walking abilities was used. As for parallel scheme only, the collisions detection and resolution should be considered, resulting in a great difference from any other update schemes. For pedestrian evacuation, the evacuation time is enlarged, and the difference in pedestrians' walking abilities is better reflected, under parallel scheme. In face of a bottleneck, for example a exit, using a parallel scheme leads to a longer congestion period and a more dispersive density distribution. The exit flow and the space-time distribution of density and velocity have significant discrepancies under four different update schemes when we simulate pedestrian flow with high desired velocity. Update schemes may have no influence on pedestrians in simulation to create tendency to follow others, but sequential and shuffled update scheme may enhance the effect of pedestrians' familiarity with environments.

  4. GPS velocity field across the Ossetia region of the Great Caucasus

    Science.gov (United States)

    Milyukov, Vadim; Mironov, Alexey; Steblov, Grigory; Drobishev, Valery; Hubaev, Hariton; Kusraev, Anatoliy; Shevchenko, Vladimir

    2014-05-01

    The Ossetia part of the Great Caucasus is located within the Trans-Caucasian uplift. According to modern understanding this large structure is the northern ending of the planetary-scale structure - the East-African-Trans-Caucasus rift zone. This region, being one of the most tectonically active regions of the Caucasus, was not covered by satellite geodetic measurements made in the Caucasus and surrounding areas since the early 1990s. This work presents results of the development of the network of survey-mode sites and GPS velocity field of this region, which is also part of the international project under leadership of R. Reilinger (MIT) for studying geodynamics of the eastern Mediterranean and Caucasus. The network established during the campaigns of 2010-2013 crosses from north to south the main tectonic structures of the Ossetia part of the Great Caucasus: the northern and southern slopes of the Great Caucasus ridge, the Tibsky thrust fault, the Northern Caucasian step, the Orkhevsky thrust fault, the Georgian block. The main profile of the network is oriented from north-east to south-west. The other two profiles are transverse to the main one and are oriented from west to east. The first of them is located along the southern and northern borders of the Orkhevskii thrust fault, covering the area of the Racha 1991 earthquake, with release to the Gagra-Dzhava zone. The second of them passes along the northern slope of Great Caucasus Ridge. The GPS data included 25 sites were processed using the GAMIT/GLOBK software. Velocity uncertainties for many sites are less then 1 mm/year. GPS velocities are presented in two reference systems: ITRF08 and fixed Eurasia. In terrestrial system of coordinates ITRF08 the horizontal motions of Ossetia region are characterized by the steady north-east trend with velocities of 25-30 mm/year, that as a whole coincides with velocities estimation of modern movements of the North Caucasus. With respect to Eurasia one can note the

  5. Excess velocity of magnetic domain walls close to the depinning field

    Science.gov (United States)

    Caballero, Nirvana B.; Fernández Aguirre, Iván; Albornoz, Lucas J.; Kolton, Alejandro B.; Rojas-Sánchez, Juan Carlos; Collin, Sophie; George, Jean Marie; Diaz Pardo, Rebeca; Jeudy, Vincent; Bustingorry, Sebastian; Curiale, Javier

    2017-12-01

    Magnetic field driven domain wall velocities in [Co/Ni] based multilayers thin films have been measured using polar magneto-optic Kerr effect microscopy. The low field results are shown to be consistent with the universal creep regime of domain wall motion, characterized by a stretched exponential growth of the velocity with the inverse of the applied field. Approaching the depinning field from below results in an unexpected excess velocity with respect to the creep law. We analyze these results using scaling theory to show that this speeding up of domain wall motion can be interpreted as due to the increase of the size of the deterministic relaxation close to the depinning transition. We propose a phenomenological model to accurately fit the observed excess velocity and to obtain characteristic values for the depinning field Hd, the depinning temperature Td, and the characteristic velocity scale v0 for each sample.

  6. Global Neuromagnetic Cortical Fields Have Non-Zero Velocity.

    Directory of Open Access Journals (Sweden)

    David M Alexander

    Full Text Available Globally coherent patterns of phase can be obscured by analysis techniques that aggregate brain activity measures across-trials, whether prior to source localization or for estimating inter-areal coherence. We analyzed, at single-trial level, whole head MEG recorded during an observer-triggered apparent motion task. Episodes of globally coherent activity occurred in the delta, theta, alpha and beta bands of the signal in the form of large-scale waves, which propagated with a variety of velocities. Their mean speed at each frequency band was proportional to temporal frequency, giving a range of 0.06 to 4.0 m/s, from delta to beta. The wave peaks moved over the entire measurement array, during both ongoing activity and task-relevant intervals; direction of motion was more predictable during the latter. A large proportion of the cortical signal, measurable at the scalp, exists as large-scale coherent motion. We argue that the distribution of observable phase velocities in MEG is dominated by spatial filtering considerations in combination with group velocity of cortical activity. Traveling waves may index processes involved in global coordination of cortical activity.

  7. Global Neuromagnetic Cortical Fields Have Non-Zero Velocity.

    Science.gov (United States)

    Alexander, David M; Nikolaev, Andrey R; Jurica, Peter; Zvyagintsev, Mikhail; Mathiak, Klaus; van Leeuwen, Cees

    2016-01-01

    Globally coherent patterns of phase can be obscured by analysis techniques that aggregate brain activity measures across-trials, whether prior to source localization or for estimating inter-areal coherence. We analyzed, at single-trial level, whole head MEG recorded during an observer-triggered apparent motion task. Episodes of globally coherent activity occurred in the delta, theta, alpha and beta bands of the signal in the form of large-scale waves, which propagated with a variety of velocities. Their mean speed at each frequency band was proportional to temporal frequency, giving a range of 0.06 to 4.0 m/s, from delta to beta. The wave peaks moved over the entire measurement array, during both ongoing activity and task-relevant intervals; direction of motion was more predictable during the latter. A large proportion of the cortical signal, measurable at the scalp, exists as large-scale coherent motion. We argue that the distribution of observable phase velocities in MEG is dominated by spatial filtering considerations in combination with group velocity of cortical activity. Traveling waves may index processes involved in global coordination of cortical activity.

  8. Effects of local flow field on flow accelerated corrosion. Effect of flow velocity on corrosion rate

    International Nuclear Information System (INIS)

    Nagaya, Yukinori; Nakamura, Akira; Murase, Michio; Utanohara, Yoichi

    2010-01-01

    Flow accelerated corrosion (FAC) is one of important issues for aging of nuclear power plants. In this study, in order to evaluate the effects of flow field on corrosion rate due to FAC, corrosion rates downstream of an orifice were measured using an electric resistance method. In these experiments, a test loop under high temperature and high pressure conditions was used. The pipe inner diameter was 50 mm and the ratio of orifice diameter which was 24.3 mm to the pipe diameter was about 0.5. The water temperature was controlled at 150 within ± 1 degC. To evaluate the effect of flow velocity on FAC rate, we carried out two series of measurements. During each period of measurements, we changed the flow velocity from 1.4 to 5.0 m/s, or from 2.1 to 3.5 m/s. In these results, FAC rates downstream of the orifice increased remarkably by increasing the flow velocity, while the changes of FAC rates upstream were little. The results show a possibility that the effect of flow velocity on FAC rate in the upstream of the orifice is different from that in the downstream. It turned out that the maximum FAC rate downstream of the orifice is proportional to Re 0.82 in the range of Reynolds number, Re=3.5x10 5 - 1.3x10 6 . However these measurement results might be different on the little difference of water quality or the difference of initial conditions of sensor surface, therefore we have to evaluate these effects in the future. We confirmed that FAC rates downstream of the orifice can possibly be evaluated by the parameter based on the flow velocity. (author)

  9. Electric fields in plasmas under pulsed currents

    International Nuclear Information System (INIS)

    Tsigutkin, K.; Doron, R.; Stambulchik, E.; Bernshtam, V.; Maron, Y.; Fruchtman, A.; Commisso, R. J.

    2007-01-01

    Electric fields in a plasma that conducts a high-current pulse are measured as a function of time and space. The experiment is performed using a coaxial configuration, in which a current rising to 160 kA in 100 ns is conducted through a plasma that prefills the region between two coaxial electrodes. The electric field is determined using laser spectroscopy and line-shape analysis. Plasma doping allows for three-dimensional spatially resolved measurements. The measured peak magnitude and propagation velocity of the electric field is found to match those of the Hall electric field, inferred from the magnetic-field front propagation measured previously

  10. An experimental study of low concentration sludge settling velocity under turbulent condition.

    Science.gov (United States)

    Guo, Lisha; Zhang, Daijun; Xu, Danyu; Chen, Yuan

    2009-05-01

    Particle Image Velocimetry (PIV) was used to study the settling of activated sludge flocs under turbulent flow conditions. Experimental results showed that a larger particle diameter led to a higher settling velocity while the higher turbulence intensity led to lower settling velocity. Based on the measurements a mathematical relation has been derived which correlates the settling velocity for individual sludge flocs under turbulent conditions through a modified Vesilind equation. Settling velocity shows a power-type relation to sludge particle diameter and an exponential-type relation with turbulence intensity and sludge concentration.

  11. H0, q0 and the local velocity field. [Hubble and deceleration constants in Big Bang expansion

    Science.gov (United States)

    Sandage, A.; Tammann, G. A.

    1982-01-01

    An attempt is made to find a systematic deviation from linearity for distances that are under the control of the Virgo cluster, and to determine the value of the mean random motion about the systematic flow, in order to improve the measurement of the Hubble and the deceleration constants. The velocity-distance relation for large and intermediate distances is studied, and type I supernovae are calibrated relatively as distance indicators and absolutely to obtain a new value for the Hubble constant. Methods of determining the deceleration constant are assessed, including determination from direct measurement, mean luminosity density, virgocentric motion, and the time scale test. The very local velocity field is investigated, and a solution is preferred with a random peculiar radial velocity of very nearby field galaxies of 90-100 km/s, and a Virgocentric motion of the local group of 220 km/s, leading to an underlying expansion rate of 55, in satisfactory agreement with the global value.

  12. Laser transit anemometer measurements of a JANNAF nozzle base velocity flow field

    Science.gov (United States)

    Hunter, William W., Jr.; Russ, C. E., Jr.; Clemmons, J. I., Jr.

    1990-01-01

    Velocity flow fields of a nozzle jet exhausting into a supersonic flow were surveyed. The measurements were obtained with a laser transit anemometer (LTA) system in the time domain with a correlation instrument. The LTA data is transformed into the velocity domain to remove the error that occurs when the data is analyzed in the time domain. The final data is shown in velocity vector plots for positions upstream, downstream, and in the exhaust plane of the jet nozzle.

  13. Group velocity measurement using spectral interference in near-field scanning optical microscopy

    International Nuclear Information System (INIS)

    Mills, John D.; Chaipiboonwong, Tipsuda; Brocklesby, William S.; Charlton, Martin D. B.; Netti, Caterina; Zoorob, Majd E.; Baumberg, Jeremy J.

    2006-01-01

    Near-field scanning optical microscopy provides a tool for studying the behavior of optical fields inside waveguides. In this experiment the authors measure directly the variation of group velocity between different modes of a planar slab waveguide as the modes propagate along the guide. The measurement is made using the spectral interference between pulses propagating inside the waveguide with different group velocities, collected using a near-field scanning optical microscope at different points down the guide and spectrally resolved. The results are compared to models of group velocities in simple guides

  14. Near-field acoustic holography with sound pressure and particle velocity measurements

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren

    of the particle velocity has notable potential in NAH, and furthermore, combined measurement of sound pressure and particle velocity opens a new range of possibilities that are examined in this study. On this basis, sound field separation methods have been studied, and a new measurement principle based on double...... layer measurements of the particle velocity has been proposed. Also, the relation between near-field and far-field radiation from sound sources has been examined using the concept of the supersonic intensity. The calculation of this quantity has been extended to other holographic methods, and studied...

  15. Experimental Investigation on the Influence of a Double-Walled Confined Width on the Velocity Field of a Submerged Waterjet

    Directory of Open Access Journals (Sweden)

    Xiaolong Ding

    2017-12-01

    Full Text Available The current research on confined submerged waterjets mainly focuses on the flow field of the impinging jet and wall jet. The double-sided wall vertically confined waterjet, which is widely used in many fields such as mining, cleaning and surface strengthening, has rarely been studied so far. In order to explore the influence of a double-sided wall confined width on the velocity field of submerged waterjet, an experiment was conducted with the application of 2D particle image velocimetry (PIV technology. The distribution of mean velocity and turbulent velocity in both horizontal and vertical planes was used to characterize the flow field under various confined widths. The results show that the vertical confinement has an obvious effect on the decay rate of the mean centerline velocity. When the confined width changes from 15 to 5, the velocity is reduced by 20%. In addition, with the decrease of the confined width, the jet has a tendency to spread horizontally. The vertically confined region induces a space hysteresis effect which changes the location of the transition region moving downstream. There are local negative pressure zones separating the fluid and the wall. This study of a double-walled confined jet provides some valuable information with respect to its mechanism and industrial application.

  16. Hα LINE PROFILE ASYMMETRIES AND THE CHROMOSPHERIC FLARE VELOCITY FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Kuridze, D.; Mathioudakis, M.; Kennedy, M.; Keenan, F. P. [Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast BT7 1NN (United Kingdom); Simões, P. J. A.; Voort, L. Rouppe van der; Fletcher, L. [SUPA School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Carlsson, M.; Jafarzadeh, S. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway); Allred, J. C.; Kowalski, A. F. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Graham, D. [INAF-Ossevatorio Astrofisico di Arcetri, I-50125 Firenze (Italy)

    2015-11-10

    The asymmetries observed in the line profiles of solar flares can provide important diagnostics of the properties and dynamics of the flaring atmosphere. In this paper the evolution of the Hα and Ca ii λ8542 lines are studied using high spatial, temporal, and spectral resolution ground-based observations of an M1.1 flare obtained with the Swedish 1 m Solar Telescope. The temporal evolution of the Hα line profiles from the flare kernel shows excess emission in the red wing (red asymmetry) before flare maximum and excess in the blue wing (blue asymmetry) after maximum. However, the Ca ii λ8542 line does not follow the same pattern, showing only a weak red asymmetry during the flare. RADYN simulations are used to synthesize spectral line profiles for the flaring atmosphere, and good agreement is found with the observations. We show that the red asymmetry observed in Hα is not necessarily associated with plasma downflows, and the blue asymmetry may not be related to plasma upflows. Indeed, we conclude that the steep velocity gradients in the flaring chromosphere modify the wavelength of the central reversal in the Hα line profile. The shift in the wavelength of maximum opacity to shorter and longer wavelengths generates the red and blue asymmetries, respectively.

  17. Numerical Study of Buoyancy Convection of Air under Permanent Magnetic Field and Comparison with That under Gravity Field

    Directory of Open Access Journals (Sweden)

    Kewei Song

    2014-01-01

    Full Text Available Magnetothermal free convection of air in a square enclosure under a nonuniform magnetic field provided by a permanent neodymium-iron-boron magnet is numerically studied. The natural convection under the gravity field alone is also studied for comparison. The physical fields of magnetizing force, velocity, and temperature as well as the local distribution characteristic of Nusselt number are all presented in this paper. The results show that the buoyancy convection of air in the square enclosure under magnetic field is quite different from that under the gravity field. The local value of Nusselt number under the magnetic field supplied by a permanent magnet with a residual magnetic flux density of about 4.5 Tesla can reach a high value of about three times larger than the maximum local value of Nusselt number under the gravity field. Relatively uniform distributions of temperature gradient and Nusselt number can be obtained along the cold wall of the enclosure under the magnetic field. A permanent magnet with high magnetic energy product with Br reaching to 3.5 Tesla can play a comparative role on the averaged Nusselt number compared with that under the gravity environment.

  18. Magnetic and velocity fields MHD flow of a stretched vertical ...

    African Journals Online (AJOL)

    Analytical solutions for heat and mass transfer by laminar flow of Newtonian, viscous, electrically conducting and heat generation/absorbing fluid on a continuously moving vertical permeable surface with buoyancy in the presence of a magnetic field and a first order chemical reaction are reported. The solutions for magnetic ...

  19. Image registration using stationary velocity fields parameterized by norm-minimizing Wendland kernel

    DEFF Research Database (Denmark)

    Pai, Akshay Sadananda Uppinakudru; Sommer, Stefan Horst; Sørensen, Lauge

    Interpolating kernels are crucial to solving a stationary velocity field (SVF) based image registration problem. This is because, velocity fields need to be computed in non-integer locations during integration. The regularity in the solution to the SVF registration problem is controlled by the re...... that Wendland SVF based measures separate (Alzheimer's disease v/s normal controls) better than both B-Spline SVFs (pamygdala) and B-Spline freeform deformation (pamygdala and cortical gray matter)....

  20. TAURUS observations of the emission-line velocity field of Centaurus A (NGC 5128)

    International Nuclear Information System (INIS)

    Taylor, K.; Atherton, P.D.

    1983-01-01

    Using TAURUS - an Imaging Fabry Perot system in conjunction with the IPCS on the AAT, the authors have studied the velocity field of the Hα emission line at a spatial resolution of 1.7'' over the dark lane structure of Centaurus A. The derived velocity field is quite symmetrical and strongly suggests that the emission line material is orbiting the elliptical component, as a warped disc. (orig.)

  1. Particle image velocimetry measurements of 2-dimensional velocity field around twisted tape

    Energy Technology Data Exchange (ETDEWEB)

    Song, Min Seop; Park, So Hyun; Kim, Eung Soo, E-mail: kes7741@snu.ac.kr

    2016-11-01

    Highlights: • Measurements of the flow field in a pipe with twisted tape were conducted by particle image velocimetry (PIV). • A novel matching index of refraction technique utilizing 3D printing and oil mixture was adopted to make the test section transparent. • Undistorted particle images were clearly captured in the presence of twisted tape. • 2D flow field in the pipe with twisted tape revealed the characteristic two-peak velocity profile. - Abstract: Twisted tape is a passive component used to enhance heat exchange in various devices. It induces swirl flow that increases the mixing of fluid. Thus, ITER selected the twisted tape as one of the candidates for turbulence promoting in the divertor cooling. Previous study was mainly focused on the thermohydraulic performance of the twisted tape. As detailed data on the velocity field around the twisted tape was insufficient, flow visualization study was performed to provide fundamental data on velocity field. To visualize the flow in a complex structure, novel matching index of refraction technique was used with 3-D printing and mixture of anise and mineral oil. This technique enables the camera to capture undistorted particle image for velocity field measurement. Velocity fields at Reynolds number 1370–9591 for 3 different measurement plane were obtained through particle image velocimetry. The 2-dimensional averaged velocity field data were obtained from 177 pair of instantaneous velocity fields. It reveals the characteristic two-peak flow motion in axial direction. In addition, the normalized velocity profiles were converged with increase of Reynolds numbers. Finally, the uncertainty of the result data was analyzed.

  2. Clear and Measurable Signature of Modified Gravity in the Galaxy Velocity Field

    Science.gov (United States)

    Hellwing, Wojciech A.; Barreira, Alexandre; Frenk, Carlos S.; Li, Baojiu; Cole, Shaun

    2014-06-01

    The velocity field of dark matter and galaxies reflects the continued action of gravity throughout cosmic history. We show that the low-order moments of the pairwise velocity distribution v12 are a powerful diagnostic of the laws of gravity on cosmological scales. In particular, the projected line-of-sight galaxy pairwise velocity dispersion σ12(r) is very sensitive to the presence of modified gravity. Using a set of high-resolution N-body simulations, we compute the pairwise velocity distribution and its projected line-of-sight dispersion for a class of modified gravity theories: the chameleon f(R) gravity and Galileon gravity (cubic and quartic). The velocities of dark matter halos with a wide range of masses would exhibit deviations from general relativity at the (5-10)σ level. We examine strategies for detecting these deviations in galaxy redshift and peculiar velocity surveys. If detected, this signature would be a "smoking gun" for modified gravity.

  3. 10kHz TRPIV near-field velocity and far-field noise: experimental results of a Mach 0.6 jet

    Science.gov (United States)

    Kan, Pinqing; Lewalle, Jacques

    2012-11-01

    Last year, we extracted footprints of sources from far-field pressure data of high speed jet. In this paper, we focus on processing 10kHz TR-PIV data in the near-field region. The velocity and pressure data were collected in the jet experiment of Kerwin Low, et al. in 2011. From the PIV snapshots, we extract kinematic indicators, construct their histories over the sequence of snapshots, and select the most promising diagnostics by cross-correlation with far-field pressure. For these indicators, including mass flux, we map out their fluctuations and their downstream propagation. In particular, the phase velocity of fluctuations is compared to the local convective speed. Events with large relative phase velocity are identified, and the corresponding velocity and vorticity fields are mapped out. Our goal is to correlate such events to the far-field footprints of sources. For more info and results related to the experiment, please refer to abstracts by Z.P. Berger and by M.G. Berry at this meeting. This work is supported by Glauser group of Syracuse University, Spectral Energies LLC under AFOSR SBIR grant, and by a Syracuse University Graduate Fellowship. Thanks for partial support from Spectral Energies LLC (under SBIR grant from AFOSR), Syracuse University and the LCS College.

  4. Radiography by selective detection of scatter field velocity components

    Science.gov (United States)

    Jacobs, Alan M. (Inventor); Dugan, Edward T. (Inventor); Shedlock, Daniel (Inventor)

    2007-01-01

    A reconfigurable collimated radiation detector, system and related method includes at least one collimated radiation detector. The detector has an adjustable collimator assembly including at least one feature, such as a fin, optically coupled thereto. Adjustments to the adjustable collimator selects particular directions of travel of scattered radiation emitted from an irradiated object which reach the detector. The collimated detector is preferably a collimated detector array, where the collimators are independently adjustable. The independent motion capability provides the capability to focus the image by selection of the desired scatter field components. When an array of reconfigurable collimated detectors is provided, separate image data can be obtained from each of the detectors and the respective images cross-correlated and combined to form an enhanced image.

  5. A simple measuring technique of surface flow velocity to analyze the behavior of velocity fields in hydraulic engineering applications.

    Science.gov (United States)

    Tellez, Jackson; Gomez, Manuel; Russo, Beniamino; Redondo, Jose M.

    2015-04-01

    An important achievement in hydraulic engineering is the proposal and development of new techniques for the measurement of field velocities in hydraulic problems. The technological advances in digital cameras with high resolution and high speed found in the market, and the advances in digital image processing techniques now provides a tremendous potential to measure and study the behavior of the water surface flows. This technique was applied at the Laboratory of Hydraulics at the Technical University of Catalonia - Barcelona Tech to study the 2D velocity fields in the vicinity of a grate inlet. We used a platform to test grate inlets capacity with dimensions of 5.5 m long and 4 m wide allowing a zone of useful study of 5.5m x 3m, where the width is similar of the urban road lane. The platform allows you to modify the longitudinal slopes from 0% to 10% and transversal slope from 0% to 4%. Flow rates can arrive to 200 l/s. In addition a high resolution camera with 1280 x 1024 pixels resolution with maximum speed of 488 frames per second was used. A novel technique using particle image velocimetry to measure surface flow velocities has been developed and validated with the experimental data from the grate inlets capacity. In this case, the proposed methodology can become a useful tools to understand the velocity fields of the flow approaching the inlet where the traditional measuring equipment have serious problems and limitations. References DigiFlow User Guide. (2012), (June). Russo, B., Gómez, M., & Tellez, J. (2013). Methodology to Estimate the Hydraulic Efficiency of Nontested Continuous Transverse Grates. Journal of Irrigation and Drainage Engineering, 139(10), 864-871. doi:10.1061/(ASCE)IR.1943-4774.0000625 Teresa Vila (1), Jackson Tellez (1), Jesus Maria Sanchez (2), Laura Sotillos (1), Margarita Diez (3, 1), and J., & (1), M. R. (2014). Diffusion in fractal wakes and convective thermoelectric flows. Geophysical Research Abstracts - EGU General Assembly 2014

  6. Comparison of velocity and temperature fields for two types of spacers in an annular channel

    Directory of Open Access Journals (Sweden)

    Lávička David

    2012-04-01

    Full Text Available The paper deals with measurement of flow field using a modern laser method (PIV in an annular channel of very small dimension - a fuel cell model. The velocity field was measured in several positions and plains around the spacer. The measurement was extended also to record temperatures by thermocouples soldered into stainless-steel tube wall. The measurement was focused on cooling process of the preheated fuel cell tube model, where the tube was very slowly flooded with water. Main result of the paper is comparison of two spacer's designs with respect to measured velocity and temperature fields.

  7. Diffusion with intrinsic trapping in 2-d incompressible stochastic velocity fields

    International Nuclear Information System (INIS)

    Vlad, M.; Spineanu, F.; Misguich, J.H.; Vlad, M.; Spineanu, F.; Balescu, R.

    1998-10-01

    A new statistical approach that applies to the high Kubo number regimes for particle diffusion in stochastic velocity fields is presented. This 2-dimensional model describes the partial trapping of the particles in the stochastic field. the results are close to the numerical simulations and also to the estimations based on percolation theory. (authors)

  8. Plasmon instability under four external fields

    International Nuclear Information System (INIS)

    Pereira, R.B.; Fonseca, A.L.A.; Nunes, O.A.C.

    1998-01-01

    The plasmon instability in a laboratory produced plasma in the presence of four external fields, namely two laser fields, one strong magnetic field and one static electric field, is discussed. The method of unitary transformations is used to transform the problem of electron motion under the four external fields to that of an electron in the presence only of crossed electric and magnetic fields. A kinetic equation for the plasmon population is derived from which the damping (amplification) rate is calculated. We found that the joint action of the four fields results in a relatively larger amplification rate for some values of the static electric field in contrast to the case where no electric field is present. It was also found that the plasmon growth rate favors plasmon wave vectors in an extremely narrow band i.e., the plasmon instability in four external fields is a very selective mechanism for plasmon excitation. (author)

  9. Temperature and velocity measurement fields of fluids using a schlieren system.

    Science.gov (United States)

    Martínez-González, Adrian; Guerrero-Viramontes, J A; Moreno-Hernández, David

    2012-06-01

    This paper proposes a combined method for two-dimensional temperature and velocity measurements in liquid and gas flow using a schlieren system. Temperature measurements are made by relating the intensity level of each pixel in a schlieren image to the corresponding knife-edge position measured at the exit focal plane of the schlieren system. The same schlieren images were also used to measure the velocity of the fluid flow. The measurement is made by using particle image velocimetry (PIV). The PIV software used in this work analyzes motion between consecutive schlieren frames to obtain velocity fields. The proposed technique was applied to measure the temperature and velocity fields in the natural convection of water provoked by a heated rectangular plate.

  10. Determining cardiac velocity fields and intraventricular pressure distribution from a sequence of ultrafast CT cardiac images.

    Science.gov (United States)

    Song, S M; Leahy, R M; Boyd, D P; Brundage, B H; Napel, S

    1994-01-01

    A method of computing the velocity field and pressure distribution from a sequence of ultrafast CT (UFCT) cardiac images is demonstrated. UFCT multi-slice cine imaging gives a series of tomographic slices covering the volume of the heart at a rate of 17 frames per second. The complete volume data set can be modeled using equations of continuum theory and through regularization, velocity vectors of both blood and tissue can be determined at each voxel in the volume. The authors present a technique to determine the pressure distribution throughout the volume of the left ventricle using the computed velocity field. A numerical algorithm is developed by discretizing the pressure Poisson equation (PPE), which Is based on the Navier-Stokes equation. The algorithm is evaluated using a mathematical phantom of known velocity and pressure-Couette flow. It is shown that the algorithm based on the PPE can reconstruct the pressure distribution using only the velocity data. Furthermore, the PPE is shown to be robust in the presence of noise. The velocity field and pressure distribution derived from a UFCT study of a patient are also presented.

  11. Two-Dimensional Far Field Source Locating Method with Nonprior Velocity

    Directory of Open Access Journals (Sweden)

    Qing Chen

    2016-01-01

    Full Text Available Relative position of seismic source and sensors has great influence on locating accuracy, particularly in far field conditions, and the accuracy will decrease seriously due to limited calculation precision and prior velocity error. In order to improve the locating accuracy of far field sources by isometric placed sensors in a straight line, a new locating method with nonprior velocity is proposed. After exhaustive research, this paper states that the hyperbola which is used for locating will be very close to its asymptote when seismic source locates in far field of sensors; therefore, the locating problem with prior velocity is equivalent to solving linear equations and the problem with nonprior velocity is equivalent to a nonlinear optimization problem with respect to the unknown velocity. And then, this paper proposed a new locating method based on a one-variable objective function with respect to the unknown velocity. Numerical experiments show that the proposed method has faster convergence speed, higher accuracy, and better stability.

  12. A Unified Geodetic Vertical Velocity Field (UGVVF), Version 1.0

    Science.gov (United States)

    Schmalzle, G.; Wdowinski, S.

    2014-12-01

    Tectonic motion, volcanic inflation or deflation, as well as oil, gas and water pumping can induce vertical motion. In southern California these signals are inter-mingled. In tectonics, properly identifying regions that are contaminated by other signals can be important when estimating fault slip rates. Until recently vertical deformation rates determined by high precision Global Positioning Systems (GPS) had large uncertainties compared to horizontal components and were rarely used to constrain tectonic models of fault motion. However, many continuously occupied GPS stations have been operating for ten or more years, often delivering uncertainties of ~1 mm/yr or less, providing better constraints for tectonic modeling. Various processing centers produced GPS time series and estimated vertical velocity fields, each with their own set of processing techniques and assumptions. We compare vertical velocity solutions estimated by seven data processing groups as well as two combined solutions (Figure 1). These groups include: Central Washington University (CWU) and New Mexico Institute of Technology (NMT), and their combined solution provided by the Plate Boundary Observatory (PBO) through the UNAVCO website. Also compared are the Jet Propulsion Laboratory (JPL) and Scripps Orbit and Permanent Array Center (SOPAC) and their combined solution provided as part of the NASA MEaSUREs project. Smaller velocity fields included are from Amos et al., 2014, processed at the Nevada Geodetic Laboratory, Shen et al., 2011, processed by UCLA and called the Crustal Motion Map 4.0 (CMM4) dataset, and a new velocity field provided by the University of Miami (UM). Our analysis includes estimating and correcting for systematic vertical velocity and uncertainty differences between groups. Our final product is a unified velocity field that contains the median values of the adjusted velocity fields and their uncertainties. This product will be periodically updated when new velocity fields

  13. Search for auroral belt Eparallel fields with high-velocity barium ion injections

    International Nuclear Information System (INIS)

    Heppner, J.P.; Ledley, B.G.; Miller, M.L.; Marionni, P.A.; Pongratz, M.B.; Slater, D.W.; Hallinan, T.J.; Rees, D.

    1989-01-01

    Four high-velocity shaped charge Ba + injections were conducted from two Black Brant-10 rockets at collision-free altitudes (770-975 km) over northern Alaska (L = 7.4-10.6) in April 1984 under active auroral and magnetic disturbance (Kp 4+ and 5) conditions. The motions of the Ba + pencil beams from these injections were accurately triangulated to altitudes ranging from 9,000 to 14,000 km from multistation image observations. Well-defined initial conditions and improved software for predicting the unperturbed. E = 0, trajectories in the presence of convection, E perpendicular , fields permitted an accurate detection of changes in the motion which could be attributed to E parallel fields. Large (> 1 keV) potential changes that might be anticipated from double-layer or V-, U- and S-shaped potential structures were not encountered even though the Ba + rays were clearly located on auroral arc flux tubes on at least several occasions and were at various times in close proximity to auroral flux tubes for many minutes. Abnormally intense E perpendicular fields that might also indicate that the above potential structures were also not observed. Transient accelerations and/or decelerations involving magnetic field-aligned energy changes ≤ 375 eV were, however, encountered by each of the seven principal Ba + rays tracked to high altitudes. Acceleration events were only slightly more frequent than deceleration events. Interpretation, taking into account limits on the duration of the events and simultaneous auroral conditions, favors explanation in terms of propagating waves, soliton trains, or other pulse forms provided that the propagation is primarily field-aligned

  14. Thermodynamical instabilities under strong magnetic fields

    Science.gov (United States)

    Chen, Y. J.

    2017-03-01

    The thermodynamical instabilities of low densities in the n p matter and n p e matter are studied within several relativistic nuclear models under some values of magnetic fields. The results are compared between each other and the effects of the symmetry energy slope at saturation density on the instability are investigated. The instability regions can exhibit bands due to the presence of Landau levels for very strong magnetic fields of the order of 1017 G, while for weaker magnetic fields, the bands are replaced by many diffused or scattered pieces. It also shows that the proton fraction in the inner crust of neutron stars may be complex under strong magnetic fields.

  15. A new state-of-the-art tool to investigate rock friction under extreme slip velocities and accelerations: SHIVA

    Science.gov (United States)

    Niemeijer, André; di Toro, Giulio; Nielsen, Stefan; Scarlato, Piergiorgio; Romeo, Gianni; di Stefano, Giuseppe; Smith, Steven; di Felice, Fabio; Mariano, Sofia

    2010-05-01

    Despite considerable effort over the past several decades, the mechanics of earthquakes rupture remain largely unknown. In order to complement fault drilling projects and field and seismological observations, recent friction experiments strive to reproduce as closely as possible in-situ (natural) conditions of slip velocity and acceleration on intact and fault rocks. In this contribution, we present a novel state-of-the-art experimental rotary shear apparatus (SHIVA or Slow to HIgh Velocity Apparatus) capable of shearing samples at sliding velocities up to 10 m/s, accelerations of ~ 40 m/s2 and normal stresses up to 50 MPa. In comparison with existing high speed friction machines, this apparatus extends the range of sliding velocities, normal stresses, sample size and, more importantly, accelerations. The apparatus consists of a pair of brushless electric motors (a low velocity motor, 10-6-10-3 m/s, power 5 kW, and a high velocity motor, 10-3 - 10 m/s, power 270 kW), that are connected by a gear system that allows a switch between motors without loss of velocity and force. The motors drive a rotary shaft which clamps ring-shaped samples (diameter 40- 50 mm). On the other side of the rotary shaft, a stationary shaft holds the other half of the sample assembly. The shaft is held stationary by a pair of stainless steel arms, one of which is attached to the side of the concrete-filled base where torque is measured by a tension cell. Axial force (maximum 37 kN) is applied on this side by a piston-cylinder couple with an arm to increase the force. The entire machine measures by 3.5 by 1.2 meters and weighs 3700 kg. We aim to perform experiments on rock samples of a variety of compositions using slip velocities and accelerations that simulate slip velocity functions that occur during earthquakes. In addition, we plan to develop a pore fluid system and a pressure vessel in order to perform experiments that include the physical-chemical processes that occur during slow

  16. A drift chamber with uniform electric field and measurements of the electron drift velocity

    International Nuclear Information System (INIS)

    Ma Chimao; Mao Zepu; Zhou Jie; Yan Jie

    1985-01-01

    The measurements of the electron drift velocity as a function of the electric field have been made in a small drift chamber with uniform electric field for Ar/CH 4 , Ar/i-C 4 H 10 , Ar/CO 2 and SQS gas mixtures. The values of the electric field range from about 0.3 to 2.5 kV/cm. The results of the measurements are discussed

  17. Drift chamber with uniform electric field and measurements of the electron drift velocity

    International Nuclear Information System (INIS)

    MA Chi-mao; MAO Ze-pu; ZHOU Jie; YAN Jie

    1985-01-01

    Measurements of the electron drift velocity as a function of the electric field have been made in a small drift chamber with uniform electric field for Ar/CH 4 , Ar/i-C 4 H 10 , Ar/CO 2 , and SQS gas mixtures. The value of the electric field ranges from about 0.3 to 2.5 kV/cm. The results of the measurements are discussed

  18. Visualization of velocity field and phase distribution in gas-liquid two-phase flow by NMR imaging

    International Nuclear Information System (INIS)

    Matsui, G.; Monji, H.; Obata, J.

    2004-01-01

    NMR imaging has been applied in the field of fluid mechanics, mainly single phase flow, to visualize the instantaneous flow velocity field. In the present study, NMR imaging was used to visualize simultaneously both the instantaneous phase structure and velocity field of gas-liquid two-phase flow. Two methods of NMR imaging were applied. One is useful to visualize both the one component of liquid velocity and the phase distribution. This method was applied to horizontal two-phase flow and a bubble rising in stagnant oil. It was successful in obtaining some pictures of velocity field and phase distribution on the cross section of the pipe. The other is used to visualize a two-dimensional velocity field. This method was applied to a bubble rising in a stagnant water. The velocity field was visualized after and before the passage of a bubble at the measuring cross section. Furthermore, the distribution of liquid velocity was obtained. (author)

  19. Real-Time Navigation of Nonholonomic Mobile Robots under Velocity Vector Control

    Directory of Open Access Journals (Sweden)

    Zi-Hui Zhang

    2012-09-01

    Full Text Available In this paper, linear navigation law is studied in depth and we suggest an efficient, practical and simple approach for nonholonomic mobile robot navigation under velocity vector control based on the linear navigation law. First of all, an obstacle is equivalent to a velocity vector when detected by a robot's sensory system according to the relative distant and relative direction between the robot and the obstacle. Then the vector sum of all obstacles' equivalent velocity vectors (OEVVs and the linear navigation velocity vector (LNVV derived from the linear navigation law drives the robot to reach the desired goal position without colliding with any obstacle in the robot's workspace. Furthermore, during the process of driving the mobile robot under the resultant velocity vector, a set of strategies for velocity and acceleration constraints (VAC is devised to make kinematic behaviours of the mobile robot more practical. Finally, to validate the effectiveness and superiority, extensive simulation results with no obstacles, a single obstacle and multiple obstacles are provided.

  20. Suppression of thermal noise in a non-Markovian random velocity field

    International Nuclear Information System (INIS)

    Ueda, Masahiko

    2016-01-01

    We study the diffusion of Brownian particles in a Gaussian random velocity field with short memory. By extending the derivation of an effective Fokker–Planck equation for the Lanvegin equation with weakly colored noise to a random velocity-field problem, we find that the effect of thermal noise on particles is suppressed by the existence of memory. We also find that the renormalization effect for the relative diffusion of two particles is stronger than that for single-particle diffusion. The results are compared with those of molecular dynamics simulations. (paper: classical statistical mechanics, equilibrium and non-equilibrium)

  1. Determine of velocity field with PIV and CFD during the flow around of bridge piers

    Directory of Open Access Journals (Sweden)

    Picka D.

    2013-04-01

    Full Text Available The article describes the processing of specific junior research FAST-J-11-51/1456 which dealt with physical and CFD of the velocity field during the flow around of bridge piers. Physical modelling has been carried out in Laboratory of water management research in Institute of Water Structures in Brno University of Technology – Faculty of Civil Engineering. To measure of the velocity field in profile of bridge piers were used laser measuring method PIV (Particle Image Velocimetry. The results of PIV served as a basis for comparing experimental data with CFD results of this type of flow in the commercial software ANSYS CFX.

  2. Velocity Regulation in Switched Reluctance Motors under Magnetic Flux Saturation Conditions

    Directory of Open Access Journals (Sweden)

    Victor M. Hernández-Guzmán

    2018-01-01

    Full Text Available We propose a controller for velocity regulation in switched reluctance motors under magnetic flux saturation conditions. Both hysteresis and proportional control are employed in the internal electric current loops. A classical PI velocity controller is employed in the external loop. Our control law is the simplest one proposed in the literature but provided with a formal stability proof. We prove that the state is bounded having an ultimate bound which can be rendered arbitrarily small by a suitable selection of controller gains. Furthermore, this result stands when starting from any initial condition within a radius which can be arbitrarily enlarged using suitable controller gains. We present a simulation study where even convergence to zero of velocity error is observed as well as a good performance when regulating velocity in the presence of unknown step changes in external torque disturbances.

  3. Group velocity effect on resonant, long-range wake-fields in slow wave structures

    CERN Document Server

    Smirnov, A V

    2002-01-01

    Synchronous wake-fields in a dispersive waveguide are derived in a general explicit form on the basis of a rigorous electro-dynamical approach using Fourier transformations. The fundamental role of group velocity in wake-field propagation, calculation of attenuation, amplitudes, form-factors and loss-factors is analyzed for single bunch radiation. Adiabatic tapering of the waveguide and bunch density variation is taken into account analytically for the time-domain fields. Effects of field 'compression/expansion' and group delays are demonstrated. The role of these effects is discussed for single bunch wake-fields, transient beam loading, BBU and HOMs. A novel waveguide structure with central rf coupling and both positive and negative velocities is proposed. It can be used effectively in both high-energy accelerators and single-section linacs.

  4. Particle size, magnetic field, and blood velocity effects on particle retention in magnetic drug targeting.

    Science.gov (United States)

    Cherry, Erica M; Maxim, Peter G; Eaton, John K

    2010-01-01

    A physics-based model of a general magnetic drug targeting (MDT) system was developed with the goal of realizing the practical limitations of MDT when electromagnets are the source of the magnetic field. The simulation tracks magnetic particles subject to gravity, drag force, magnetic force, and hydrodynamic lift in specified flow fields and external magnetic field distributions. A model problem was analyzed to determine the effect of drug particle size, blood flow velocity, and magnetic field gradient strength on efficiency in holding particles stationary in a laminar Poiseuille flow modeling blood flow in a medium-sized artery. It was found that particle retention rate increased with increasing particle diameter and magnetic field gradient strength and decreased with increasing bulk flow velocity. The results suggest that MDT systems with electromagnets are unsuitable for use in small arteries because it is difficult to control particles smaller than about 20 microm in diameter.

  5. Three-dimensional P velocity structure of the crust and upper mantle under Beijing region

    Energy Technology Data Exchange (ETDEWEB)

    Quan, A.; Liu, F.; Sun, Y.

    1980-04-01

    By use of the teleseismic P arrival times at 15 stations of the Beijing network for 120 events distributed over various azimuths, we studied the three-dimensional P velocity structure under the Beijing region. In calculating the theoretic travel time, we adopted the source parameters given in BISC, and used the J-B model as the standard model of earth. On inversion, we adopted singular value decomposition as a generalized inversion package, which can be used for solving very large over-determined systems of equations Gm = t without resorting to normal equations G/sup T/Gm = G/sup T/t. The results are that within the crust and upper mantle under the Beijing region there are clear lateral differences. In the results obtained by use of data from 1972 to 1975, it can be seen that there are three different zones of P-velocity. In the southeast Beijing region, P velocity is lower than that of the normal model by 10 to 14% within the crust, and by 8 to 9% within the upper mantle. The northwest Beijing region is a higher-velocity zone, within which the average P-velocity is faster than that of the normal model by about 9%. It disappears after entering into the upper mantle. The central part of this region is a normal zone. On the surface, the distribution of these P velocity variations corresponds approximately to the distribution of the over-burden. But in the deeper region, the distribution of velocity variation agrees with the distribution of seismicity. It is interesting to note that the hypocenters of several major earthquakes in this region, e.g., the Sanhe-Pinggu earthquake (1679, M = 8), the Shacheng earthquake (1730, M = 6-3/4) and the Tangshan earthquake (1976, M = 7.8), are all located very close to this boundary of these P-velocity variation zones.

  6. Numerical Investigation of Viscous Flow Velocity Field around a Marine Cavitating Propeller

    Directory of Open Access Journals (Sweden)

    Zhifeng Zhu

    2014-11-01

    Full Text Available Velocity field around a ship cavitating propeller is investigated based on the viscous multiphase flow theory. Using a hybrid grid, the unsteady Navier-stokes (N-S and the bubble dynamics equations are solved in this paper to predict the velocity in a propeller wake and the vapor volume fraction on the back side of propeller blade for a uniform inflow. Compared with experimental results, the numerical predictions of cavitation and axial velocity coincide with the measured data. The evolution of tip vortex is shown, and the interaction between the tip vortex of the current blade and the wake of the next one occurs in the far propeller wake. The frequency of velocity signals changes from shaft rate to blade rate. The phenomena reflect the instability of propeller wake.

  7. Measurement of velocity field in pipe with classic twisted tape using matching refractive index technique

    International Nuclear Information System (INIS)

    Song, Min Seop; Park, So Hyun; Kim, Eung Soo

    2014-01-01

    Many researchers conducted experiments and numerical simulations to measure or predict a Nusselt number or a friction factor in a pipe with a twisted tape while some other studies focused on the heat transfer performance enhancement using various twisted tape configurations. However, since the optical access to the inner space of a pipe with a twisted tape was limited, the detailed flow field data were not obtainable so far. Thus, researchers mainly relied on the numerical simulations to obtain the data of the flow field. In this study, a 3D printing technique was used to manufacture a transparent test section for optical access. And also, a noble refractive index matching technique was used to eliminate optical distortion. This two combined techniques enabled to measure the velocity profile with Particle Image Velocimetry (PIV). The measured velocity field data can be used either to understand the fundamental flow characteristics around a twisted tape or to validate turbulence models in Computational Fluid Dynamics (CFD). In this study, the flow field in the test-section was measured for various flow conditions and it was finally compared with numerically calculated data. Velocity fields in a pipe with a classic twisted tape was measured using a particle image velocimetry (PIV) system. To obtain undistorted particle images, a noble optical technique, refractive index matching, was used and it was proved that high-quality image can be obtained from this experimental equipment. The velocity data from the PIV was compared with the CFD simulations

  8. Experimental study on centerline velocities of a rectangular capture hood under realistic conditions.

    Science.gov (United States)

    He, Xinjian; Lewis, Braxton V; Guffey, Steven E

    2018-02-01

    Capture hoods are an important component of a local ventilation system designed to reduce exposures to airborne contaminants. The velocity at any point along the centerline of the hood (V x ) is currently estimated using one of many predictive equations developed since the 1930s. It is unproven that those predictive equations for V x are accurate, despite the prodigious number of studies concerning them. Among other issues, almost all experimental verifications were conducted for conditions that were either unrealistically ideal without competing air currents (e.g., zero cross draft) or were not described. This study measured values of V x along the midline using Particle Image Velocimetry (PIV) at distances of 1-14 inches in front of a rectangular capture hood. The experiments were conducted in a large wind tunnel (9' × 12' × 40', H × W × L) using a heated, breathing, anthropomorphically sized manikin. Three 0 degree draft velocities (V draft = 4, 14, and 50 ft/min) were tested, all directed toward the hood face and the back of the manikin (if present). For each value of V draft , the velocity fields were measured in a factorial design with and without the manikin, and with and without a worktable underneath the hood. An ideal condition was represented by a freestanding hood at the 4 fpm draft. Nonideal conditions included the presence of a worktable or manikin, and the combination of table and manikin. Each condition was tested at the three levels of V draft . The experimental results found significant effects (p < 0.001) for V draft , the presence of the manikin, the presence of the worktable, and all combinations of those factors. The effects of the independent variables were most pronounced at distances greater than 10 in (25.4 cm) from the hood face. It is concluded that none of the previously published models accurately predicted V x under the realistic conditions tested in this study. A satisfactory model will have to include terms for V draft and the

  9. Deformation at a Complex Strike-Slip Plate Boundary: Modeling the Southern California GPS Velocity Field

    Science.gov (United States)

    Thatcher, W. R.; Murray-Moraleda, J. R.

    2009-12-01

    Because of EarthScope and related deployments, Southern California has perhaps the highest Global Positioning System (GPS) station density of any of Earth’s seismically active regions. Here we provide an updated analysis of the Southern California velocity field to illustrate both the strengths of high station density and the inherent limitations of surface geodetic measurements for quantifying earthquake-related deformation processes. Modeling GPS velocity fields in seismically active regions worldwide indicates deformation can be efficiently and usefully described as relative motions among elastic, fault-bounded crustal blocks. However, subjective choices of block geometry are unavoidable and introduce significant uncertainties in model formulation and in the resultant GPS fault slip rate estimates. To facilitate comparison between GPS and geologic results in southern California we use the SCEC Community Fault Model (CFM) and geologic slip rates tabulated in the 2008 Uniform California Earthquake Rupture Forecast (UCERF2) report as starting points for identifying the most important faults and specifying the block geometry. We then apply this geometry in an inversion of the SCEC Crustal Motion Model (CMM4) GPS velocity field to estimate block motions and intra-block fault slip rates and compare our results with previous work. In most parts of southern California—for example, north of the San Andreas Big Bend and SE of Los Angeles--our block geometry closely resembles that assumed in previous studies (McCaffrey 2005 JGR; Meade & Hager 2005 JGR; Becker et al. 2005 GJI). In these regions GPS slip rates can be reliably estimated and values for individual faults generally agree from one study to another and are also consistent with geologic estimates. However, there is no consensus on block geometry in the Transverse Ranges, Los Angeles Basin and Central Mojave Desert, where CFM faults are densely distributed, UCERF2 slip rates on several faults are comparable, and

  10. The Crustal Velocity Field Mosaic of the Alpine Mediterranean Area: Insight from New Geodetic Data

    Science.gov (United States)

    Farolfi, G.; Del Ventisette, C.

    2016-08-01

    Geodetic techniques, such as Global Navigation Satellite System (GNSS), Synthetic Aperture Radar (SAR), satellite gravity missions, etc., have made significant contributions in monitoring temporal and spatial changes in Earth's lithosphere and atmosphere.A new crustal velocity field for the Alpine Mediterranean area (Farolfi & Del Ventisette, 2015) was determined by using a time series spanning 6.5 years of GNSS permanent stations. Thus, processing was performed by using state-of-the-art antenna phase center model, new recomputed satellite orbits and a new more accurate tropospheric model.The aim of this work is to calculate and analyze the spatial variations of continuous time series of GNSS permanent stations, to estimate crustal velocities in the Alpine Mediterranean area. The resulting velocity field gives a strong contribution in the framework of the contemporary geodynamics.

  11. VELOCITY FIELD OF COMPRESSIBLE MAGNETOHYDRODYNAMIC TURBULENCE: WAVELET DECOMPOSITION AND MODE SCALINGS

    International Nuclear Information System (INIS)

    Kowal, Grzegorz; Lazarian, A.

    2010-01-01

    We study compressible magnetohydrodynamic turbulence, which holds the key to many astrophysical processes, including star formation and cosmic-ray propagation. To account for the variations of the magnetic field in the strongly turbulent fluid, we use wavelet decomposition of the turbulent velocity field into Alfven, slow, and fast modes, which presents an extension of the Cho and Lazarian decomposition approach based on Fourier transforms. The wavelets allow us to follow the variations of the local direction of the magnetic field and therefore improve the quality of the decomposition compared to the Fourier transforms, which are done in the mean field reference frame. For each resulting component, we calculate the spectra and two-point statistics such as longitudinal and transverse structure functions as well as higher order intermittency statistics. In addition, we perform a Helmholtz- Hodge decomposition of the velocity field into incompressible and compressible parts and analyze these components. We find that the turbulence intermittency is different for different components, and we show that the intermittency statistics depend on whether the phenomenon was studied in the global reference frame related to the mean magnetic field or in the frame defined by the local magnetic field. The dependencies of the measures we obtained are different for different components of the velocity; for instance, we show that while the Alfven mode intermittency changes marginally with the Mach number, the intermittency of the fast mode is substantially affected by the change.

  12. Methodology to estimate the relative pressure field from noisy experimental velocity data

    International Nuclear Information System (INIS)

    Bolin, C D; Raguin, L G

    2008-01-01

    The determination of intravascular pressure fields is important to the characterization of cardiovascular pathology. We present a two-stage method that solves the inverse problem of estimating the relative pressure field from noisy velocity fields measured by phase contrast magnetic resonance imaging (PC-MRI) on an irregular domain with limited spatial resolution, and includes a filter for the experimental noise. For the pressure calculation, the Poisson pressure equation is solved by embedding the irregular flow domain into a regular domain. To lessen the propagation of the noise inherent to the velocity measurements, three filters - a median filter and two physics-based filters - are evaluated using a 2-D Couette flow. The two physics-based filters outperform the median filter for the estimation of the relative pressure field for realistic signal-to-noise ratios (SNR = 5 to 30). The most accurate pressure field results from a filter that applies in a least-squares sense three constraints simultaneously: consistency between measured and filtered velocity fields, divergence-free and additional smoothness conditions. This filter leads to a 5-fold gain in accuracy for the estimated relative pressure field compared to without noise filtering, in conditions consistent with PC-MRI of the carotid artery: SNR = 5, 20 x 20 discretized flow domain (25 X 25 computational domain).

  13. Filament formation in wind-cloud interactions- II. Clouds with turbulent density, velocity, and magnetic fields

    Science.gov (United States)

    Banda-Barragán, W. E.; Federrath, C.; Crocker, R. M.; Bicknell, G. V.

    2018-01-01

    We present a set of numerical experiments designed to systematically investigate how turbulence and magnetic fields influence the morphology, energetics, and dynamics of filaments produced in wind-cloud interactions. We cover 3D, magnetohydrodynamic systems of supersonic winds impacting clouds with turbulent density, velocity, and magnetic fields. We find that lognormal density distributions aid shock propagation through clouds, increasing their velocity dispersion and producing filaments with expanded cross-sections and highly magnetized knots and subfilaments. In self-consistently turbulent scenarios, the ratio of filament to initial cloud magnetic energy densities is ∼1. The effect of Gaussian velocity fields is bound to the turbulence Mach number: Supersonic velocities trigger a rapid cloud expansion; subsonic velocities only have a minor impact. The role of turbulent magnetic fields depends on their tension and is similar to the effect of radiative losses: the stronger the magnetic field or the softer the gas equation of state, the greater the magnetic shielding at wind-filament interfaces and the suppression of Kelvin-Helmholtz instabilities. Overall, we show that including turbulence and magnetic fields is crucial to understanding cold gas entrainment in multiphase winds. While cloud porosity and supersonic turbulence enhance the acceleration of clouds, magnetic shielding protects them from ablation and causes Rayleigh-Taylor-driven subfilamentation. Wind-swept clouds in turbulent models reach distances ∼15-20 times their core radius and acquire bulk speeds ∼0.3-0.4 of the wind speed in one cloud-crushing time, which are three times larger than in non-turbulent models. In all simulations, the ratio of turbulent magnetic to kinetic energy densities asymptotes at ∼0.1-0.4, and convergence of all relevant dynamical properties requires at least 64 cells per cloud radius.

  14. A sound field separation technique based on measurements with pressure-velocity probes

    DEFF Research Database (Denmark)

    Zhang, Yong-Bin; Chen, Xin-Zhao; Jacobsen, Finn

    2009-01-01

    It has recently been shown that statistically optimized near field acoustic holography based on measurement with an array of pressure-velocity transducers makes it possible to distinguish between sources on the two sides of the array and thus suppress the influence of a disturbing source [F...

  15. Wet and gassy zones in a municipal landfill from P- and S-wave velocity fields

    NARCIS (Netherlands)

    Konstantaki, L.A.; Ghose, R.; Draganov, D.S.; Heimovaara, T.J.

    2016-01-01

    The knowledge of the distribution of leachate and gas in a municipal landfill is of vital importance to the landfill operators performing improved landfill treatments and for environmental protection and efficient biogas extraction. We have explored the potential of using the velocity fields of

  16. Radial velocities of giants in two high-galactic-latitude fields

    Energy Technology Data Exchange (ETDEWEB)

    Friel, E.D.

    1988-06-01

    Radial velocities of small samples of G and K giants previously identified in high-galactic-latitude fields in SA 94 and Serpens are presented and analyzed for dependences on metallicity and galactocentric distances. In each field, the small samples of seven metal-poor stars with Fe/H less than -0.8 show mean radial velocities and high velocity dispersions expected for the halo population. For stars more metal rich than Fe/H = -0.8, there is no strong evidence in either field for a dependence of velocity dispersion on metallicity. In Serpens, the dispersion of 50 km/s for the 32 metal-rich stars is in good agreement with that expected for a thick-disk population. In SA 94, thirteen stars with Fe/H greater than -0.8 show a uniform dispersion of 29 km/s, in agreement with the expected old-disk kinematics. The contrast between results for the two fields is suggestive, but the small sizes of the samples prevent any strong conclusions from being drawn. 37 references.

  17. Three-Dimensional Velocity Field De-Noising using Modal Projection

    Science.gov (United States)

    Frank, Sarah; Ameli, Siavash; Szeri, Andrew; Shadden, Shawn

    2017-11-01

    PCMRI and Doppler ultrasound are common modalities for imaging velocity fields inside the body (e.g. blood, air, etc) and PCMRI is increasingly being used for other fluid mechanics applications where optical imaging is difficult. This type of imaging is typically applied to internal flows, which are strongly influenced by domain geometry. While these technologies are evolving, it remains that measured data is noisy and boundary layers are poorly resolved. We have developed a boundary modal analysis method to de-noise 3D velocity fields such that the resulting field is divergence-free and satisfies no-slip/no-penetration boundary conditions. First, two sets of divergence-free modes are computed based on domain geometry. The first set accounts for flow through ``truncation boundaries'', and the second set of modes has no-slip/no-penetration conditions imposed on all boundaries. The modes are calculated by minimizing the velocity gradient throughout the domain while enforcing a divergence-free condition. The measured velocity field is then projected onto these modes using a least squares algorithm. This method is demonstrated on CFD simulations with artificial noise. Different degrees of noise and different numbers of modes are tested to reveal the capabilities of the approach. American Heart Association Award 17PRE33660202.

  18. Velocity field measurements in an evaporating sessile droplet by means of micro-PIV technique

    Directory of Open Access Journals (Sweden)

    Yagodnitsyna Anna

    2016-01-01

    Full Text Available Velocity fields are measured in evaporating sessile droplets on two substrates with different contact angles and contact angle hysteresis using micro resolution particle image velocimetry technique. Different flow patterns are observed in different stages of droplet evaporation: a flow with vortices and a radial flow. Flow structure is found to be similar for droplets on different substrates.

  19. Near field acoustic holography based on the equivalent source method and pressure-velocity transducers

    DEFF Research Database (Denmark)

    Zhang, Y.-B.; Chen, X.-Z.; Jacobsen, Finn

    2009-01-01

    The advantage of using the normal component of the particle velocity rather than the sound pressure in the hologram plane as the input of conventional spatial Fourier transform based near field acoustic holography (NAH) and also as the input of the statistically optimized variant of NAH has...

  20. Magnetic Circuit Design and Multiphysics Analysis of a Novel MR Damper for Applications under High Velocity

    Directory of Open Access Journals (Sweden)

    Jiajia Zheng

    2014-02-01

    Full Text Available A novel magnetorheological (MR damper with a multistage piston and independent input currents is designed and analyzed. The equivalent magnetic circuit model is investigated along with the relation between magnetic induction density in the working gap and input currents of the electromagnetic coils. Finite element method (FEM is used to analyze the distribution of magnetic field through the MR fluid region. Considering the real situation, coupling equations are presented to analyze the electromagnetic-thermal-flow coupling problems. Software COMSOL is used to analyze the multiphysics, that is, electromagnetic, thermal dynamic, and fluid mechanic. A measurement index involving total damping force, dynamic range, and induction time needed for magnetic coil is put forward to evaluate the performance of the novel multistage MR damper. The simulation results show that it is promising for applications under high velocity and works better when more electromagnetic coils are applied with input currents separately. Besides, in order to reduce energy consumption, it is recommended to apply more electromagnetic coils with relative low currents based on the analysis of pressure drop along the annular gap.

  1. Depression storage and infiltration effects on overland flow depth-velocity-friction at desert conditions: field plot results and model

    Directory of Open Access Journals (Sweden)

    M. J. Rossi

    2012-09-01

    Full Text Available Water infiltration and overland flow are relevant in considering water partition among plant life forms, the sustainability of vegetation and the design of sustainable hydrological models and management. In arid and semi-arid regions, these processes present characteristic trends imposed by the prevailing physical conditions of the upper soil as evolved under water-limited climate. A set of plot-scale field experiments at the semi-arid Patagonian Monte (Argentina were performed in order to estimate the effect of depression storage areas and infiltration rates on depths, velocities and friction of overland flows. The micro-relief of undisturbed field plots was characterized at z-scale 1 mm through close-range stereo-photogrammetry and geo-statistical tools. The overland flow areas produced by controlled water inflows were video-recorded and the flow velocities were measured with image processing software. Antecedent and post-inflow moisture were measured, and texture, bulk density and physical properties of the upper soil were estimated based on soil core analyses. Field data were used to calibrate a physically-based, mass balanced, time explicit model of infiltration and overland flows. Modelling results reproduced the time series of observed flow areas, velocities and infiltration depths. Estimates of hydrodynamic parameters of overland flow (Reynolds-Froude numbers are informed. To our knowledge, the study here presented is novel in combining several aspects that previous studies do not address simultaneously: (1 overland flow and infiltration parameters were obtained in undisturbed field conditions; (2 field measurements of overland flow movement were coupled to a detailed analysis of soil microtopography at 1 mm depth scale; (3 the effect of depression storage areas in infiltration rates and depth-velocity friction of overland flows is addressed. Relevance of the results to other similar desert areas is justified by the accompanying

  2. Modification of Turbulent Pipe Flow Equations to Estimate the Vertical Velocity Profiles Under Woody Debris Jams

    Science.gov (United States)

    Cervania, A.; Knack, I. M. W.

    2017-12-01

    The presence of woody debris (WD) jams in rivers and streams increases the risk of backwater flooding and reduces the navigability of a channel, but adds fish and macroinvertebrate habitat to the stream. When designing river engineering projects engineers use hydraulic models to predict flow behavior around these obstructions. However, the complexities of flow through and beneath WD jams are still poorly understood. By increasing the ability to predict flow behavior around WD jams, landowners and engineers are empowered to develop sustainable practices regarding the removal or placement of WD in rivers and flood plains to balance the desirable and undesirable effects to society and the environment. The objective of this study is to address some of this knowledge gap by developing a method to estimate the vertical velocity profile of flow under WD jams. When flow passes under WD jams, it becomes affected by roughness elements on all sides, similar to turbulent flows in pipe systems. Therefore, the method was developed using equations that define the velocity profiles of turbulent pipe flows: the law of the wall, the logarithmic law, and the velocity defect law. Flume simulations of WD jams were conducted and the vertical velocity profiles were measured along the centerline. A calculated velocity profile was fit to the measured profile through the calibration of eight parameters. An optimal value or range of values have been determined for several of these parameters using cross-validation techniques. The results indicate there may be some promise to using this method in hydraulic models.

  3. Frictional melting of gabbro under extreme experimental conditions of normal stress, acceleration, and sliding velocity

    NARCIS (Netherlands)

    Niemeijer, A.; Di Toro, G.; Nielsen, S.; Di Felice, F.

    2011-01-01

    With the advent of high‐velocity shear apparatus, several experimental studies have been performed in recent years, improving our understanding of the evolution of fault strength during seismic slip. However, these experiments were conducted under relatively low normal stress (<20 MPa) and using

  4. Estimation of vector velocity

    DEFF Research Database (Denmark)

    2000-01-01

    Using a pulsed ultrasound field, the two-dimensional velocity vector can be determined with the invention. The method uses a transversally modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation. The new...

  5. The effect of spatially varying velocity field on the transport of radioactivity in a porous medium.

    Science.gov (United States)

    Sen, Soubhadra; Srinivas, C V; Baskaran, R; Venkatraman, B

    2016-10-01

    In the event of an accidental leak of the immobilized nuclear waste from an underground repository, it may come in contact of the flow of underground water and start migrating. Depending on the nature of the geological medium, the flow velocity of water may vary spatially. Here, we report a numerical study on the migration of radioactivity due to a space dependent flow field. For a detailed analysis, seven different types of velocity profiles are considered and the corresponding concentrations are compared. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. A new GPS velocity field in the south-western Balkans: insights for continental dynamics

    Science.gov (United States)

    D'Agostino, N.; Avallone, A.; Duni, L.; Ganas, A.; Georgiev, I.; Jouanne, F.; Koci, R.; Kuka, N.; Metois, M.

    2017-12-01

    The Balkans peninsula is an area of active distributed deformation located at the southern boundary of the Eurasian plate. Relatively low strain rates and logistical reasons have so far limited the characterization and definition of the active tectonics and crustal kinematics. The increasing number of GNSS stations belonging to national networks deployed for scientific and cadastral purposes, now provides the opportunity to improve the knowledge of the crustal kinematics in this area and to define a cross-national velocity field that illuminates the active tectonic deformation. In this work we homogeneously processed the data from the south western Balkans and neighbouring regions using available rinex files from scientific and cadastral networks (ALBPOS, EUREF, HemusNET, ITALPOS, KOPOS, MAKPOS, METRICA, NETGEO, RING, TGREF). In order to analyze and interpret station velocities relative to the Eurasia plate and to reduce the common mode signal, we updated the Eurasian terrestrial reference frame described in Métois et al. 2015. Starting from this dataset we present a new GPS velocity field covering the south western part of the Balkan Peninsula. Using this new velocity field, we derive the strain rate tensor to analyze the regional style of the deformation. Our results (1) improve the picture of the general southward flow of the crust characterizing the south western Balkans behind the contractional belt at the boundary with Adriatic and (2) provide new key elements for the understanding of continental dynamics in this part of the Eurasian plate boundary.

  7. Electric-field control of magnetic domain-wall velocity in ultrathin cobalt with perpendicular magnetization.

    Science.gov (United States)

    Chiba, D; Kawaguchi, M; Fukami, S; Ishiwata, N; Shimamura, K; Kobayashi, K; Ono, T

    2012-06-06

    Controlling the displacement of a magnetic domain wall is potentially useful for information processing in magnetic non-volatile memories and logic devices. A magnetic domain wall can be moved by applying an external magnetic field and/or electric current, and its velocity depends on their magnitudes. Here we show that the applying an electric field can change the velocity of a magnetic domain wall significantly. A field-effect device, consisting of a top-gate electrode, a dielectric insulator layer, and a wire-shaped ferromagnetic Co/Pt thin layer with perpendicular anisotropy, was used to observe it in a finite magnetic field. We found that the application of the electric fields in the range of ± 2-3 MV cm(-1) can change the magnetic domain wall velocity in its creep regime (10(6)-10(3) m s(-1)) by more than an order of magnitude. This significant change is due to electrical modulation of the energy barrier for the magnetic domain wall motion.

  8. Effective Transport in Lattice Fracture Networks with Uncorrelated and Correlated Velocity Field

    Science.gov (United States)

    Kang, P. K.; Dentz, M.; Juanes, R.

    2010-12-01

    We study stochastic transport through a lattice fracture network with quenched disorder, and evaluate the limits of predictability of the transport behavior across realizations of spatial heterogeneity. As shown in the figure, We consider a two-dimensional regular fracture network model characterized by a constant fracture length, fracture aperture and fracture angle. We assign independent and identically distributed random particle velocities to each link. This implies a random uncorrelated particle transport velocity field. Different values of particle velocity are assumed to be the result of microscale processes, such as different conductance or adsorption rate. Within a Lagrangian framework, we perform coarse graining, noise averaging, and ensemble averaging, to obtain an effective transport model for the average particle density and its fluctuations between realizations. We show that the average particle density is described exactly by a continuous time random walk (CTRW), and the particle density variance is quantified by a novel two-particle CTRW. An important question regarding predictability of transport is how the variance — especially, the variance where the particle density is maximum — evolves in time. Simulations using the two-particle CTRW can answer to this question. We generalize our model for the correlated velocity field. This second model assigns random transmissivities to the fractures and solves the Darcy equation for an incompressible fluid, enforcing mass conservation at fracture intersections. The latter yields a correlated random flow through the fracture system. To incorporate the impact of heterogeneity and the velocity correlation on effective transport, we study Lagrangian velocity transitions in space and time. We demonstrate that Lagrangian velocities are Markov process in space but not in time. Using the property of spatial Markov process, we derive a CTRW in phase space characterized by a correlated velocity increment. We

  9. Nonpremixed flame in a counterflow under electric fields

    KAUST Repository

    Park, Daegeun

    2016-05-08

    Electrically assisted combustion has been studied in order to control or improve flame characteristics, and emphasizing efficiency and emission regulation. Many phenomenological observations have been reported on the positive impact of electric fields on flame, however there is a lack of detailed physical mechanisms for interpreting these. To clarify the effects of electric fields on flame, I have investigated flame structure, soot formation, and flow field with ionic wind electrical current responses in nonpremixed counterflow flames. The effects of direct current (DC) electric field on flame movement and flow field was also demonstrated in premixed Bunsen flames. When a DC electric field was applied to a lower nozzle, the flames moved toward the cathode side due to Lorentz force action on the positive ions, soot particles simultaneously disappeared completely and laser diagnostics was used to identify the results from the soot particles. To understand the effects of an electric field on flames, flow visualization was performed by Mie scattering to check the ionic wind effect, which is considered to play an important role in electric field assisted combustion. Results showed a bidirectional ionic wind, with a double-stagnant flow configuration, which blew from the flame (ionic source) toward both the cathode and the anode. This implies that the electric field affects strain rate and the axial location of stoichiometry, important factors in maintaining nonpremixed counterflow flames; thus, soot formation of the counterflow flame can also be affected by the electric field. In a test of premixed Bunsen flames having parallel electrodes, flame movement toward the cathode and bidirectional ionic wind were observed. Using PIV measurement it was found that a created radial velocity caused by positive ions (i.e. toward a cathode), was much faster than the velocity toward the anode. Even in a study of alternating current (AC) electric fields, bidirectional ionic wind could

  10. Performance Investigation of Air Velocity Effects on PV Modules under Controlled Conditions

    Directory of Open Access Journals (Sweden)

    Muzaffar Ali

    2017-01-01

    Full Text Available Junction temperature of PV modules is one of the key parameters on which the performance of PV modules depends. In the present work, an experimental investigation was carried out to analyze the effects of air velocity on the performance of two PV modules, that is, monocrystalline silicon and polycrystalline silicon under the controlled conditions of a wind tunnel in the presence of an artificial solar simulator. The parameters investigated include the surface temperature variation, power output, and efficiency of PV modules under varying air velocity from near zero (indoor lab. conditions to 15 m/s. Additionally, the results were also determined at two different module angular positions: at 0° angle, that is, parallel to air direction and at 10° angle with the direction of coming air to consider the effects of tilt angles. Afterwards, the thermal analysis of the modules was performed using Ansys-Fluent in which junction temperature and heat flux of modules were determined by applying appropriate boundary conditions, such as air velocity, heat flux, and solar radiation. Finally, the numerical results are compared with the experiment in terms of junction temperatures of modules and good agreement was found. Additionally, the results showed that the maximum module temperature drops by 17.2°C and the module efficiency and power output increased from 10 to 12% with increasing air velocity.

  11. Velocity shear Kelvin-Helmholtz instability with inhomogeneous DC electric field in the magnetosphere of Saturn

    Science.gov (United States)

    Kandpal, Praveen; Kaur, Rajbir; Pandey, R. S.

    2018-01-01

    In this paper parallel flow velocity shear Kelvin-Helmholtz instability has been studied in two different extended regions of the inner magnetosphere of Saturn. The method of the characteristic solution and kinetic approach has been used in the mathematical calculation of dispersion relation and growth rate of K-H waves. Effect of magnetic field (B), inhomogeneity (P/a), velocity shear scale length (Ai), temperature anisotropy (T⊥ /T||), electric field (E), ratio of electron to ion temperature (Te /Ti), density gradient (εnρi) and angle of propagation (θ) on the dimensionless growth rate of K-H waves in the inner magnetosphere of Saturn has been observed with respect to k⊥ρi . Calculations of this theoretical analysis have been done taking the data from the Cassini in the inner magnetosphere of Saturn in the two extended regions of Rs ∼4.60-4.01 and Rs ∼4.82-5.0. In our study velocity shear, temperature anisotropy and magnitude of the electric field are observed to be the major sources of free energy for the K-H instability in both the regions considered. The inhomogeneity of electric field, electron-ion temperature ratio, and density gradient have been observed playing stabilizing effect on K-H instability. This study also indicates the effect of the vicinity of icy moon Enceladus on the growth of K-H instability.

  12. Velocity overshoot decay mechanisms in compound semiconductor field-effect transistors with a submicron characteristic length

    International Nuclear Information System (INIS)

    Jyegal, Jang

    2015-01-01

    Velocity overshoot is a critically important nonstationary effect utilized for the enhanced performance of submicron field-effect devices fabricated with high-electron-mobility compound semiconductors. However, the physical mechanisms of velocity overshoot decay dynamics in the devices are not known in detail. Therefore, a numerical analysis is conducted typically for a submicron GaAs metal-semiconductor field-effect transistor in order to elucidate the physical mechanisms. It is found that there exist three different mechanisms, depending on device bias conditions. Specifically, at large drain biases corresponding to the saturation drain current (dc) region, the velocity overshoot suddenly begins to drop very sensitively due to the onset of a rapid decrease of the momentum relaxation time, not the mobility, arising from the effect of velocity-randomizing intervalley scattering. It then continues to drop rapidly and decays completely by severe mobility reduction due to intervalley scattering. On the other hand, at small drain biases corresponding to the linear dc region, the velocity overshoot suddenly begins to drop very sensitively due to the onset of a rapid increase of thermal energy diffusion by electrons in the channel of the gate. It then continues to drop rapidly for a certain channel distance due to the increasing thermal energy diffusion effect, and later completely decays by a sharply decreasing electric field. Moreover, at drain biases close to a dc saturation voltage, the mechanism is a mixture of the above two bias conditions. It is suggested that a large secondary-valley energy separation is essential to increase the performance of submicron devices

  13. Measurement of electroosmotic and electrophoretic velocities using pulsed and sinusoidal electric fields.

    Science.gov (United States)

    Sadek, Samir H; Pimenta, Francisco; Pinho, Fernando T; Alves, Manuel A

    2017-04-01

    In this work, we explore two methods to simultaneously measure the electroosmotic mobility in microchannels and the electrophoretic mobility of micron-sized tracer particles. The first method is based on imposing a pulsed electric field, which allows to isolate electrophoresis and electroosmosis at the startup and shutdown of the pulse, respectively. In the second method, a sinusoidal electric field is generated and the mobilities are found by minimizing the difference between the measured velocity of tracer particles and the velocity computed from an analytical expression. Both methods produced consistent results using polydimethylsiloxane microchannels and polystyrene micro-particles, provided that the temporal resolution of the particle tracking velocimetry technique used to compute the velocity of the tracer particles is fast enough to resolve the diffusion time-scale based on the characteristic channel length scale. Additionally, we present results with the pulse method for viscoelastic fluids, which show a more complex transient response with significant velocity overshoots and undershoots after the start and the end of the applied electric pulse, respectively. © 2016 The Authors. Electrophoresis published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Velocity dependence of transient hyperfine field at Pt ions rapidly recoiling through magnetized Fe

    International Nuclear Information System (INIS)

    Stuchbery, A.E.; Ryan, C.G.; Bolotin, H.H.

    1981-01-01

    The velocity-dependence of the transient hyperfine magnetic field acting at nuclei of 196 Pt ions rapidly recoiling through thin magnetized Fe was investigated at a number of recoil velocities. The state of interest (2 1 + ) was populated by Coulomb excitation using beams of 80- and 120-MeV 32 S and 150- and 220-MeV 58 Ni ions. The 2 1 + →0 1 + γ-ray angular distribution precession measurements were carried out in coincidence with backscattered projectiles. From these results, the strength of the transient field acting on Pt ions recoiling through magnetized Fe with average velocities in the extended range 2.14<=v/vsub(o)<=4.82 (vsub(o) = c/137) was found to be consistent with a linear velocity dependence and to be incompatible with the specific vsup(0.45+-0.18) dependence which has been previously reported to account well for all ions in the mass range from oxygen through samarium. This seemingly singular behaviour for Pt and other ions in the Pt mass vicinity is discussed

  15. Experimental analysis of the velocity field in an anular channel with helicoidal wire

    International Nuclear Information System (INIS)

    Lemos, M.J.S. de.

    1979-06-01

    In general, nuclear reactor fuel elements are rod bundles with coolant flowing axially among them. LMFBR's (Liquid Metal Fast Breeder Reactor) have wire wrapped fuel rods, with the wire working as spacer and mixer. The present work consists in the experimental analysis of the velocity field created by a typical LMFBR fuel rod placed in a cylinder, yielding an annular channel with helicoidal wire. Using hot wire anemometry, the main and secondary velocity fields were measured. The range for Re was from 2.2x 10 4 to 6.1x 10 4 , for air. The aspect ratio, P/D, and the lead-to-diameter ratio, 1/D, were 1.2 and 15, respectively. (Author) [pt

  16. Velocity map imaging of scattering dynamics in orthogonal two-color fields

    Science.gov (United States)

    Würzler, D.; Eicke, N.; Möller, M.; Seipt, D.; Sayler, A. M.; Fritzsche, S.; Lein, M.; Paulus, G. G.

    2018-01-01

    In strong-field ionization processes, two-color laser fields are frequently used for controlling sub-cycle electron dynamics via the relative phase of the laser fields. Here we apply this technique to velocity map imaging spectroscopy using an unconventional orientation with the polarization of the ionizing laser field perpendicular to the detector surface and the steering field parallel to it. This geometry allows not only to image the phase-dependent photoelectron momentum distribution (PMD) of low-energy electrons that interact only weakly with the ion (direct electrons), but also to investigate the low yield of higher-energy rescattered electrons. Phase-dependent measurements of the PMD of neon and xenon demonstrate control over direct and rescattered electrons. The results are compared with semi-classical calculations in three dimensions including elastic scattering at different orders of return and with solutions of the three-dimensional time-dependent Schrödinger equation.

  17. Visualizing flow fields using acoustic Doppler current profilers and the Velocity Mapping Toolbox

    Science.gov (United States)

    Jackson, P. Ryan

    2013-01-01

    The purpose of this fact sheet is to provide examples of how the U.S. Geological Survey is using acoustic Doppler current profilers for much more than routine discharge measurements. These instruments are capable of mapping complex three-dimensional flow fields within rivers, lakes, and estuaries. Using the Velocity Mapping Toolbox to process the ADCP data allows detailed visualization of the data, providing valuable information for a range of studies and applications.

  18. Direct simultaneous measurement of intraglottal geometry and velocity fields in excised larynges.

    Science.gov (United States)

    Khosla, Sid; Oren, Liran; Ying, Jun; Gutmark, Ephraim

    2014-04-01

    Current theories regarding the mechanisms of phonation are based on assumptions about the aerodynamics between the vocal folds during the closing phase of vocal fold vibration. However, many of these fundamental assumptions have never been validated in a tissue model. In this study, the main objective was to determine the aerodynamics (velocity fields) and the geometry of the medial surface of the vocal folds during the closing phase of vibration. The main hypothesis is that intraglottal vortices are produced during vocal fold closing when the glottal duct has a divergent shape and that these vortices are associated with negative pressures. Experiments using seven excised canine larynges. The particle imaging velocimetry (PIV) method was used to determine the velocity fields at low, mid-, and high subglottal pressures for each larynx. Modifications were made to previously described PIV methodology to allow the measurement of both the intraglottal velocity fields and the position of the medial aspects of the vocal fold. At relatively low subglottal pressures, little to no intraglottal vortices were seen. At mid- and high subglottal pressures, the flow separation vortices occurred and produced maximum negative pressures, relative to atmospheric, of -2.6 to -14.6 cm H2 O. Possible physiological and surgical implications are discussed. Intraglottal vortices produce significant negative pressures at mid- and high subglottal pressures. These vortices may be important in increasing maximum flow declination rate and acoustic intensity. N/A. © 2014 The American Laryngological, Rhinological and Otological Society, Inc.

  19. Calculation of acoustic field based on laser-measured vibration velocities on ultrasonic transducer surface

    Science.gov (United States)

    Hu, Liang; Zhao, Nannan; Gao, Zhijian; Mao, Kai; Chen, Wenyu; Fu, Xin

    2018-05-01

    Determination of the distribution of a generated acoustic field is valuable for studying ultrasonic transducers, including providing the guidance for transducer design and the basis for analyzing their performance, etc. A method calculating the acoustic field based on laser-measured vibration velocities on the ultrasonic transducer surface is proposed in this paper. Without knowing the inner structure of the transducer, the acoustic field outside it can be calculated by solving the governing partial differential equation (PDE) of the field based on the specified boundary conditions (BCs). In our study, the BC on the transducer surface, i.e. the distribution of the vibration velocity on the surface, is accurately determined by laser scanning measurement of discrete points and follows a data fitting computation. In addition, to ensure the calculation accuracy for the whole field even in an inhomogeneous medium, a finite element method is used to solve the governing PDE based on the mixed BCs, including the discretely measured velocity data and other specified BCs. The method is firstly validated on numerical piezoelectric transducer models. The acoustic pressure distributions generated by a transducer operating in an homogeneous and inhomogeneous medium, respectively, are both calculated by the proposed method and compared with the results from other existing methods. Then, the method is further experimentally validated with two actual ultrasonic transducers used for flow measurement in our lab. The amplitude change of the output voltage signal from the receiver transducer due to changing the relative position of the two transducers is calculated by the proposed method and compared with the experimental data. This method can also provide the basis for complex multi-physical coupling computations where the effect of the acoustic field should be taken into account.

  20. Magnetic field-aligned plasma expansion in critical ionization velocity space experiments

    International Nuclear Information System (INIS)

    Singh, N.

    1989-01-01

    Motivated by the recent Critical Ionization Velocity (CIV) experiments in space, the temporal evolution of a plasma cloud released in an ambient plasma is studied. Time-dependent Vlasov equations for both electrons and ions, along with the Poisson equation for the self-consistent electric field parallel to the ambient magnetic field, are solved. The initial cloud is assumed to consist of cold, warm, and hot electrons with temperatures T/sub c/ ≅ 0.2 eV, T/sub w/ ≅ 2 eV, and T/sub h/ ≅ 10 eV, respectively. It is found that the minor hot electrons escape the cloud, and their velocity distribution function shows the typical time-of-flight dispersion feature - that is, the larger the distance from the cloud, the larger is the average drift velocity of the escaping electrons. The major warm electrons expand along the magnetic field line with the corresponding ion-acoustic speed. The combined effect of the escaping hot electrons and the expanding warm ones sets up an electric potential structure which accelerates the ambient electrons into the cloud. Thus, the energy loss due to the electron escape is partly replenished. The electric field distribution in the potential structure depends on the stage of the evolution; before the rarefaction waves propagating from the edges of the cloud reach its center, the electric fields point into the cloud. After this stage the cloud divides into two subclouds, with each having their own bipolar electric fields. Effects of collisions on the evolution of plasma clouds are also discussed. The relevance of the results seen from the calculations are discussed in the context of recent space experiments on CIV

  1. The effect of magnetic field configuration on particle pinch velocity in compact helical system (CHS)

    International Nuclear Information System (INIS)

    Iguchi, H.; Ida, K.; Yamada, H.

    1994-01-01

    Radial particle transport has been experimentally studied in the low-aspect-ratio heliotron/torsatron device CHS. A non-diffusive outward particle flow (inverse pinch) is observed in the magnetic configuration with the magnetic axis shifted outward, while an inward pinch, like in tokamaks, is observed with the magnetic axis shifted inward. This change in the direction of anomalous particle flow is not due to the reversal of temperature gradient nor the radial electric field. The observation suggests that the particle pinch velocity is sensitive to the magnetic field structure. (author)

  2. Velocity measurements in the near field of a diesel fuel injector by ultrafast imagery

    Science.gov (United States)

    Sedarsky, David; Idlahcen, Saïd; Rozé, Claude; Blaisot, Jean-Bernard

    2013-02-01

    This paper examines the velocity profile of fuel issuing from a high-pressure single-orifice diesel injector. Velocities of liquid structures were determined from time-resolved ultrafast shadow images, formed by an amplified two-pulse laser source coupled to a double-frame camera. A statistical analysis of the data over many injection events was undertaken to map velocities related to spray formation near the nozzle outlet as a function of time after start of injection. These results reveal a strong asymmetry in the liquid profile of the test injector, with distinct fast and slow regions on opposite sides of the orifice. Differences of ˜100 m/s can be observed between the `fast' and `slow' sides of the jet, resulting in different atomization conditions across the spray. On average, droplets are dispersed at a greater distance from the nozzle on the `fast' side of the flow, and distinct macrostructure can be observed under the asymmetric velocity conditions. The changes in structural velocity and atomization behavior resemble flow structures which are often observed in the presence of string cavitation produced under controlled conditions in scaled, transparent test nozzles. These observations suggest that widely used common-rail supply configurations and modern injectors can potentially generate asymmetric interior flows which strongly influence diesel spray morphology. The velocimetry measurements presented in this work represent an effective and relatively straightforward approach to identify deviant flow behavior in real diesel sprays, providing new spatially resolved information on fluid structure and flow characteristics within the shear layers on the jet periphery.

  3. Hybrid micro-/nano-particle image velocimetry for 3D3C multi-scale velocity field measurement in microfluidics

    International Nuclear Information System (INIS)

    Min, Young Uk; Kim, Kyung Chun

    2011-01-01

    The conventional two-dimensional (2D) micro-particle image velocimetry (micro-PIV) technique has inherent bias error due to the depth of focus along the optical axis to measure the velocity field near the wall of a microfluidics device. However, the far-field measurement of velocity vectors yields good accuracy for micro-scale flows. Nano-PIV using the evanescent wave of total internal reflection fluorescence microscopy can measure near-field velocity vectors within a distance of around 200 nm from the solid surface. A micro-/nano-hybrid PIV system is proposed to measure both near- and far-field velocity vectors simultaneously in microfluidics. A near-field particle image can be obtained by total internal reflection fluorescence microscopy using nanoparticles, and the far-field velocity vectors are measured by three-hole defocusing micro-particle tracking velocimetry (micro-PTV) using micro-particles. In order to identify near- and far-field particle images, lasers of different wavelengths are adopted and tested in a straight microchannel for acquiring the three-dimensional three-component velocity field. We found that the new technique gives superior accuracy for the velocity profile near the wall compared to that of conventional nano-PIV. This method has been successfully applied to precisely measure wall shear stress in 2D microscale Poiseulle flows

  4. Numerical simulation of velocity and temperature fields in natural circulation loop

    Science.gov (United States)

    Sukomel, L. A.; Kaban’kov, O. N.

    2017-11-01

    Low flow natural circulation regimes are realized in many practical applications and the existence of the reliable engineering and design calculation methods of flows driven exclusively by buoyancy forces is an actual problem. In particular it is important for the analysis of start up regimes of passive safety systems of nuclear power plants. In spite of a long year investigations of natural circulation loops no suitable predicting recommendations for heat transfer and friction for the above regimes have been proposed for engineering practice and correlations for forced flow are commonly used which considerably overpredicts the real flow velocities. The 2D numerical simulation of velocity and temperature fields in circular tubes for laminar flow natural circulation with reference to the laboratory experimental loop has been carried out. The results were compared with the 1D modified model and experimental data obtained on the above loop. The 1D modified model was still based on forced flow correlations, but in these correlations the physical properties variability and the existence of thermal and hydrodynamic entrance regions are taken into account. The comparison of 2D simulation, 1D model calculations and the experimental data showed that even subject to influence of liquid properties variability and entrance regions on heat transfer and friction the use of 1D model with forced flow correlations do not improve the accuracy of calculations. In general, according to 2D numerical simulation the wall shear stresses are mainly affected by the change of wall velocity gradient due to practically continuous velocity profiles deformation along the whole heated zone. The form of velocity profiles and the extent of their deformation in its turn depend upon the wall heat flux density and the hydraulic diameter.

  5. Updated velocity field for the Caribbean plate from COCONet GPS observations

    Science.gov (United States)

    Miller, J. A.; Mattioli, G. S.; Jansma, P. E.

    2013-05-01

    The currently accepted kinematic model of the Caribbean plate presented by DeMets et al., 2007, is based on velocities from 6 continuous and 14 campaign GPS sites. Our work attempts to refine the current plate model by evaluating data from the 60+ continuous GPS stations that comprise COCONet. COCONet (Continuously Operating Caribbean Observation Network) is an NSF-funded collaborative natural hazards research effort that has enhanced the geodetic infrastructure in the region surrounding the Caribbean plate. Data for this study was obtained from the open data archive at UNAVCO. GPS data have been processed with an absolute point positioning strategy using GIPSY-OASIS II, using the non-fiducial, final precise clock and orbit parameters provided by JPL. An updated velocity field for the Caribbean plate will be presented and co-seismic and post-seismic slip, recorded by network stations will be examined for earthquakes that have occurred within the COCONet footprint.

  6. Quasi-direct numerical simulation of a pebble bed configuration. Part I: Flow (velocity) field analysis

    International Nuclear Information System (INIS)

    Shams, A.; Roelofs, F.; Komen, E.M.J.; Baglietto, E.

    2013-01-01

    Highlights: ► Quasi direct numerical simulations (q-DNS) of a pebble bed configuration has been performed. ► This q-DNS database may serve as a reference for the validation of different turbulence modeling approaches. ► A wide range of qualitative and quantitative data throughout the computational domain has been generated. ► Results for mean, RMS and covariance of velocity field are extensively reported in this paper. -- Abstract: High temperature reactors (HTR) are being considered for deployment around the world because of their excellent safety features. The fuel is embedded in a graphite moderator and can sustain very high temperatures. However, the appearance of hot spots in the pebble bed cores of HTR's may affect the integrity of the pebbles. A good prediction of the flow and heat transport in such a pebble bed core is a challenge for available turbulence models and such models need to be validated. In the present article, quasi direct numerical simulations (q-DNS) of a pebble bed configuration are reported, which may serve as a reference for the validation of different turbulence modeling approaches. Such approaches can be used in order to perform calculations for a randomly arranged pebble bed. Simulations are performed at a Reynolds number of 3088, based on pebble diameter, with a porosity level of 0.42. Detailed flow analyses have shown complex physics flow behavior and make this case challenging for turbulence model validation. Hence, a wide range of qualitative and quantitative data for velocity and temperature field have been extracted for this benchmark. In the present article (part I), results related to the flow field (mean, RMS and covariance of velocity) are documented and discussed in detail. Moreover, the discussion regarding the temperature field will be published in a separate article

  7. Observing and Modeling Temporal Variations of Seismic Velocities at the Geysers Geothermal Field, California

    Science.gov (United States)

    Lai, V. H.; Tsai, V. C.; Taira, T.

    2016-12-01

    Perturbations in subsurface elastic parameters induce changes in seismic velocity. To understand the stress perturbations due to geothermal operation, we apply seismic noise interferometry to examine the temporal variations of seismic velocity (dv/v) at the Geysers Geothermal Field, California. Our observations show a strong positive correlation between dv/v and net production (steam production minus fluid injection), and a strong negative correlation between dv/v and fluid injection. Notably, there is little time lag (less than a month) between dv/v and fluid injection in the SE region of the field, suggesting a rapid response in elastic properties in this highly saturated region. The influx of fluid decreases the effective shear modulus, which in turn decreases the velocities. A number of hypotheses have been suggested to cause stress perturbations in the field, including poroelastic-induced stresses, direct elastic loading and thermoelastic-induced stresses. We perform a 1-D hydrological simulation to calculate the expected variations in dv/v due to different stresses by considering Murnaghan's theory of finite deformations and the third-order terms in the strain energy function. The synthetic dv/v measurements are spatially averaged based on computed sensitivity kernels, allowing for direct comparison with both the amplitude and phase of dv/v observations. We show the order-of-magnitude effect that each of the stresses have on the dv/v measurement, and explore the possibility of using dv/v to constrain important hydrological and elastic properties such as hydraulic conductivity in the field.

  8. Experimental investigation of acceleration and velocity fields in turbulent channel flow

    Science.gov (United States)

    Christensen, Kenneth Thor

    2001-12-01

    Time-resolved particle-image velocimetry measurements are made in the streamwise-wall-normal plane of turbulent channel flow at Reτ = 547, 1133, and 1734. These measurements are meant to complement efforts in the development of a new class of large-eddy simulation (LES) subgrid-scale models for the simulation of high-Reynolds-number wall turbulence. Optimal formulations of LES are based upon minimizing the mean-square error associated with estimating the short- term dynamics of the resolved scales of the turbulence. However, due to the empirical nature of optimal LES, extension of optimal formulations to higher Reynolds number requires experimental documentation of the statistical and structural behavior of both the velocity and the evolution of the flow at higher Reynolds numbers. It is found that coherent arrangements of hairpin-like vortices in the outer layer leave their imprint upon the statistics of the flow. Estimates of the conditionally- averaged velocity field associated with a spanwise vortex core consist of a series of swirling motions located along a line inclined away from the wall. This pattern is consistent with the observations of outer-layer turbulence in which groups of hairpin/hairpin-like vortices occur aligned in the streamwise direction. The velocity time derivatives are associated predominantly with small scales in both space and time. Examination of instantaneous and estimates of the conditionally averaged velocity time-derivative fields indicates that the smaller-scale vortices leave a convective imprint upon the time derivatives. Further, the streamwise spectra of the velocity time-derivative support the notion that convective effects dominate the smaller scales of the flow. Comparison between the bulk convective-derivative and time-derivative spectra illustrate this behavior. At low wavenumbers, the bulk convective-derivative and time-derivative spectra coincide with one another, implying that the larger scales are dominated by

  9. Heliospheric magnetic field polarity inversions driven by radial velocity field structures

    Czech Academy of Sciences Publication Activity Database

    Landi, S.; Hellinger, Petr; Velli, M.

    2006-01-01

    Roč. 33, č. 14 (2006), L14101/1-L14101/5 ISSN 0094-8276 Grant - others:European Commission(XE) HRPN-CT-2001-00310 Institutional research plan: CEZ:AV0Z30420517 Keywords : solar wind * magnetic field polarity inversions * microstreams * turbulence Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.602, year: 2006

  10. Doped spin ladders under magnetic field

    International Nuclear Information System (INIS)

    Roux, G.

    2007-07-01

    This thesis deals with the physics of doped two-leg ladders which are a quasi one-dimensional and unconventional superconductor. We particularly focus on the properties under magnetic field. Models for strongly correlated electrons on ladders are studied using exact diagonalization and density-matrix renormalization group (DMRG). Results are also enlightened by using the bosonization technique. Taking into account a ring exchange it highlights the relation between the pairing of holes and the spin gap. Its influence on the dynamics of the magnetic fluctuations is also tackled. Afterwards, these excitations are probed by the magnetic field by coupling it to the spin degree of freedom of the electrons through Zeeman effect. We show the existence of doping-dependent magnetization plateaus and also the presence of an inhomogeneous superconducting phase (FFLO phase) associated with an exceeding of the Pauli limit. When a flux passes through the ladder, the magnetic field couples to the charge degree of freedom of the electrons via orbital effect. The diamagnetic response of the doped ladder probes the commensurate phases of the t-J model at low J/t. Algebraic transverse current fluctuations are also found once the field is turned on. Lastly, we report numerical evidences of a molecular superfluid phase in the 3/2-spin attractive Hubbard model: at a density low enough, bound states of four fermions, called quartets, acquire dominant superfluid fluctuations. The observed competition between the superfluid and density fluctuations is connected to the physics of doped ladders. (author)

  11. A new car-following model for autonomous vehicles flow with mean expected velocity field

    Science.gov (United States)

    Wen-Xing, Zhu; Li-Dong, Zhang

    2018-02-01

    Due to the development of the modern scientific technology, autonomous vehicles may realize to connect with each other and share the information collected from each vehicle. An improved forward considering car-following model was proposed with mean expected velocity field to describe the autonomous vehicles flow behavior. The new model has three key parameters: adjustable sensitivity, strength factor and mean expected velocity field size. Two lemmas and one theorem were proven as criteria for judging the stability of homogeneousautonomous vehicles flow. Theoretical results show that the greater parameters means larger stability regions. A series of numerical simulations were carried out to check the stability and fundamental diagram of autonomous flow. From the numerical simulation results, the profiles, hysteresis loop and density waves of the autonomous vehicles flow were exhibited. The results show that with increased sensitivity, strength factor or field size the traffic jam was suppressed effectively which are well in accordance with the theoretical results. Moreover, the fundamental diagrams corresponding to three parameters respectively were obtained. It demonstrates that these parameters play almost the same role on traffic flux: i.e. before the critical density the bigger parameter is, the greater flux is and after the critical density, the opposite tendency is. In general, the three parameters have a great influence on the stability and jam state of the autonomous vehicles flow.

  12. The Seismo-Generated Electric Field Probed by the Ionospheric Ion Velocity

    Science.gov (United States)

    (Tiger) Liu, Jann-Yenq

    2017-04-01

    The ion density, ion temperature, and the ion velocity probed by IPEI (ionospheric Plasma and Electrodynamics Instrument) onboard ROCSAT (i.e. FORMOSAT-1), and the global ionospheric map (GIM) of the total electron content (TEC) derived from measurements of ground-based GPS receivers are employed to study seismo-ionospheric precursors (SIPs) of the 31 March 2002 M6.8 Earthquake in Taiwan. The GIM TEC and ROCSAT/IPEI ion density significantly decrease specifically over the epicenter area 1-5 days before the earthquake, which suggests that the associated SIPs have observed. The ROCSAT/IPEI ion temperature reveals no significant changes before and after the earthquake, while the latitude-time-TEC plots extracted from the GIMs along the Taiwan longitude illustrate that the equatorial ionization anomaly significantly weakens and moves equatorward, which indicates that the daily dynamo electric field has been disturbed and cancelled by possible seismo-generated electric field on 2 days before (29 March) the earthquake. Here, for the first time a vector parameter of ion velocity is employed to study SIPs. It is found that ROCSAT/IPEI ion velocity becomes significantly downward, which confirms that a westward electric field of about 0.91mV/m generated during the earthquake preparation period being essential 1-5 days before the earthquake. Liu, J. Y., and C. K. Chao (2016), An observing system simulation experiment for FORMOSAT-5/AIP detecting seismo-ionospheric precursors, Terrestrial Atmospheric and Oceanic Sciences, DOI: 10.3319/TAO.2016.07.18.01(EOF5).

  13. Capabilities of optical SIV technique in measurements of flow velocity vector field dynamics

    Science.gov (United States)

    Mikheev, N. I.; Dushin, N. S.; Saushin, I. I.

    2017-11-01

    The main difference between Smoke Image Velocimetry (SIV) technique and the conventional PIV is that higher concentration of tracer particles typical of smoke visualization techniques is used in SIV. Not separate particles but smoke structures with continuous pixel intensity are visible in the recorded images. Owing to better smoke reflectivity, higher spatial and temporal resolution is obtained in the case when relatively simple equipment (camera and laser) is used. It is simple enough to perform SIV measurements of velocity vector field dynamics at the frequency exceeding 15000 Hz, which offers new opportunities in unsteady flow examination. The paper describes fundamentals of SIV technique and gives some new results obtained using this method for the measurements that require high spatial and temporal resolution. The latter include frequency spectra of turbulent velocity fluctuations, turbulence dissipation profiles in the boundary layer and higher-order moments of velocity fluctuations. It has been shown that SIV technique considerably extends the potential of experimental studies of turbulence and flow structure in high-speed processes.

  14. The crustal velocity field mosaic of the Alpine Mediterranean area (Italy): Insights from new geodetic data

    Science.gov (United States)

    Farolfi, Gregorio; Del Ventisette, Chiara

    2016-04-01

    A new horizontal crustal velocity field of Alpine Mediterranean area was determined by continuous long time series (6.5 years) of 113 Global Navigation Satellite System (GNSS) permanent stations. The processing was performed using state-of-the-art absolute antenna phase center correction model and recomputed precise IGS orbits available since April 2014. Moreover, a new more accurate tropospheric mapping function for geodetic applications was adopted. Results provide a new detailed map of the kinematics throughout the entire study area. This area is characterized by a complex tectonic setting driven by the interaction of Eurasian and African plates. The eastern Alps, Corsica, Sardinia and the Tyrrhenian Sea (which is covered only by interpolation data) show small velocity residuals with respect to the Eurasian plate. The whole Apennines axis discriminates two different velocity patterns, the Adriatic and the Tyrrhenian area. The area around Messina Strait, which separates peninsular Italy and Sicily, represents a poorly understood region. Results identify an important boundary zone between two different domains, Calabria and Sicily, which are characterized by different crustal motions. The northeastern part of Sicily and Calabria move like Adriatic area, whilst the rest of Sicily, Malta and Lampedusa are dominated by African motion.

  15. Liquid methanol under a static electric field

    Science.gov (United States)

    Cassone, Giuseppe; Giaquinta, Paolo V.; Saija, Franz; Saitta, A. Marco

    2015-02-01

    We report on an ab initio molecular dynamics study of liquid methanol under the effect of a static electric field. We found that the hydrogen-bond structure of methanol is more robust and persistent for field intensities below the molecular dissociation threshold whose value (≈0.31 V/Å) turns out to be moderately larger than the corresponding estimate obtained for liquid water. A sustained ionic current, with ohmic current-voltage behavior, flows in this material for field intensities above 0.36 V/Å, as is also the case of water, but the resulting ionic conductivity (≈0.40 S cm-1) is at least one order of magnitude lower than that of water, a circumstance that evidences a lower efficiency of proton transfer processes. We surmise that this study may be relevant for the understanding of the properties and functioning of technological materials which exploit ionic conduction, such as direct-methanol fuel cells and Nafion membranes.

  16. Liquid methanol under a static electric field

    Energy Technology Data Exchange (ETDEWEB)

    Cassone, Giuseppe, E-mail: giuseppe.cassone@impmc.upmc.fr [Sorbonne Universités, UPMC Univ Paris 06, UMR 7590, IMPMC, F-75005 Paris (France); CNRS, UMR 7590, IMPMC, F-75005 Paris (France); Università degli Studi di Messina, Dipartimento di Fisica e di Scienze della Terra, Contrada Papardo, 98166 Messina (Italy); CNR-IPCF, Viale Ferdinando Stagno d’Alcontres 37, 98158 Messina (Italy); Giaquinta, Paolo V., E-mail: paolo.giaquinta@unime.it [Università degli Studi di Messina, Dipartimento di Fisica e di Scienze della Terra, Contrada Papardo, 98166 Messina (Italy); Saija, Franz, E-mail: saija@ipcf.cnr.it [CNR-IPCF, Viale Ferdinando Stagno d’Alcontres 37, 98158 Messina (Italy); Saitta, A. Marco, E-mail: marco.saitta@impmc.upmc.fr [Sorbonne Universités, UPMC Univ Paris 06, UMR 7590, IMPMC, F-75005 Paris (France); CNRS, UMR 7590, IMPMC, F-75005 Paris (France)

    2015-02-07

    We report on an ab initio molecular dynamics study of liquid methanol under the effect of a static electric field. We found that the hydrogen-bond structure of methanol is more robust and persistent for field intensities below the molecular dissociation threshold whose value (≈0.31 V/Å) turns out to be moderately larger than the corresponding estimate obtained for liquid water. A sustained ionic current, with ohmic current-voltage behavior, flows in this material for field intensities above 0.36 V/Å, as is also the case of water, but the resulting ionic conductivity (≈0.40 S cm{sup −1}) is at least one order of magnitude lower than that of water, a circumstance that evidences a lower efficiency of proton transfer processes. We surmise that this study may be relevant for the understanding of the properties and functioning of technological materials which exploit ionic conduction, such as direct-methanol fuel cells and Nafion membranes.

  17. Microscopic dynamics and velocity profiles of bacterial superfluids under oscillatory shear

    Science.gov (United States)

    Cheng, Xiang; Guo, Shuo; Samanta, Devranjan; Peng, Yi; Xu, Xinliang

    Bacterial suspensions a premier example of active fluids show an unusual response to shear stresses. Rather than increasing the viscosity of the suspending fluid, swimming bacteria can self-organize into collective flows under shear, turning the suspension into a ``superfluid'' with zero apparent viscosity. Although the existence of the bacterial superfluid has been demonstrated in bulk rheology measurements, little is known about the microscopic dynamics of such an exotic phase. Here, by combining sensitive rheology measurements with high-speed confocal microscopy, we study the detailed 3D dynamics of concentrated bacterial suspensions confined in narrow gaps under oscillatory shear. We find that sheared bacterial suspensions in the superfluidic phase exhibit velocity profiles with strong spatial heterogeneity, unexpected from the established hydrodynamic theory of active fluids. We quantitatively explain the observed velocity profiles by considering a balance of active stresses and shear stresses in an ensemble average. Our experiments reveal a profound influence of shear flows on bacterial locomotion and provide new insights to the origin of the unique flow behaviors of active fluids.

  18. Easy monitoring of velocity fields in microfluidic devices using spatiotemporal image correlation spectroscopy.

    Science.gov (United States)

    Travagliati, Marco; Girardo, Salvatore; Pisignano, Dario; Beltram, Fabio; Cecchini, Marco

    2013-09-03

    Spatiotemporal image correlation spectroscopy (STICS) is a simple and powerful technique, well established as a tool to probe protein dynamics in cells. Recently, its potential as a tool to map velocity fields in lab-on-a-chip systems was discussed. However, the lack of studies on its performance has prevented its use for microfluidics applications. Here, we systematically and quantitatively explore STICS microvelocimetry in microfluidic devices. We exploit a simple experimental setup, based on a standard bright-field inverted microscope (no fluorescence required) and a high-fps camera, and apply STICS to map liquid flow in polydimethylsiloxane (PDMS) microchannels. Our data demonstrates optimal 2D velocimetry up to 10 mm/s flow and spatial resolution down to 5 μm.

  19. Optimization of Transverse Oscillating Fields for Vector Velocity Estimation with Convex Arrays

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    2013-01-01

    A method for making Vector Flow Images using the transverse oscillation (TO) approach on a convex array is presented. The paper presents optimization schemes for TO fields for convex probes and evaluates their performance using Field II simulations and measurements using the SARUS experimental...... scanner. A 3 MHz 192 elements convex array probe (pitch 0.33 mm) is used in both simulations and measurements. An F-number of 5 is used in transmit and two 32 element wide peaks are used in receive separated by 96 elements between peaks. Parabolic velocity profiles are simulated at beam-to-flow angles......) at a depth of 40 mm. Measurements have been made using the SARUS experimental ultrasound scanner and a BK Medical 8820e convex array transducer. Sixty-four elements was used in transmit and 2 x 32 elements in receive for creating a color flow map image of a flow rig phantom with a laminar, parabolic flow...

  20. Constraining the optical depth of galaxies and velocity bias with cross-correlation between the kinetic Sunyaev-Zeldovich effect and the peculiar velocity field

    Science.gov (United States)

    Ma, Yin-Zhe; Gong, Guo-Dong; Sui, Ning; He, Ping

    2018-03-01

    We calculate the cross-correlation function between the kinetic Sunyaev-Zeldovich (kSZ) effect and the reconstructed peculiar velocity field using linear perturbation theory, with the aim of constraining the optical depth τ and peculiar velocity bias of central galaxies with Planck data. We vary the optical depth τ and the velocity bias function bv(k) = 1 + b(k/k0)n, and fit the model to the data, with and without varying the calibration parameter y0 that controls the vertical shift of the correlation function. By constructing a likelihood function and constraining the τ, b and n parameters, we find that the quadratic power-law model of velocity bias, bv(k) = 1 + b(k/k0)2, provides the best fit to the data. The best-fit values are τ = (1.18 ± 0.24) × 10-4, b=-0.84^{+0.16}_{-0.20} and y0=(12.39^{+3.65}_{-3.66})× 10^{-9} (68 per cent confidence level). The probability of b > 0 is only 3.12 × 10-8 for the parameter b, which clearly suggests a detection of scale-dependent velocity bias. The fitting results indicate that the large-scale (k ≤ 0.1 h Mpc-1) velocity bias is unity, while on small scales the bias tends to become negative. The value of τ is consistent with the stellar mass-halo mass and optical depth relationship proposed in the literature, and the negative velocity bias on small scales is consistent with the peak background split theory. Our method provides a direct tool for studying the gaseous and kinematic properties of galaxies.

  1. High-Velocity Impact Behaviour of Prestressed Composite Plates under Bird Strike Loading

    Directory of Open Access Journals (Sweden)

    Sebastian Heimbs

    2012-01-01

    Full Text Available An experimental and numerical analysis of the response of laminated composite plates under high-velocity impact loads of soft body gelatine projectiles (artificial birds is presented. The plates are exposed to tensile and compressive preloads before impact in order to cover realistic loading conditions of representative aeronautic structures under foreign object impact. The modelling methodology for the composite material, delamination interfaces, impact projectile, and preload using the commercial finite element code Abaqus are presented in detail. Finally, the influence of prestress and of different delamination modelling approaches on the impact response is discussed and a comparison to experimental test data is given. Tensile and compressive preloading was found to have an influence on the damage pattern. Although this general behaviour could be predicted well by the simulations, further numerical challenges for improved bird strike simulation accuracy are highlighted.

  2. Gyrokinetic full f analysis of electric field dynamics and poloidal velocity in the FT2-tokamak configuration

    International Nuclear Information System (INIS)

    Leerink, S.; Heikkinen, J. A.; Janhunen, S. J.; Kiviniemi, T. P.; Nora, M.; Ogando, F.

    2008-01-01

    The ELMFIRE gyrokinetic simulation code has been used to perform full f simulations of the FT-2 tokamak. The dynamics of the radial electric field and the creation of poloidal velocity in the presence of turbulence are presented.

  3. Sound field separation with a double layer velocity transducer array (L)

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Jacobsen, Finn

    2011-01-01

    of the array. The technique has been examined and compared with direct velocity based reconstruction, as well as with a technique based on the measurement of the sound pressure and particle velocity. The double layer velocity method circumvents some of the drawbacks of the pressure-velocity based...

  4. Seeing-limited radial velocity field mapping of extended emission line sources using a new imaging Fabry-Perot system

    International Nuclear Information System (INIS)

    Tayler, K.; Atherton, P.D.

    1980-01-01

    TAURUS, a new Fabry-Perot imaging device, designed to obtain complete seeing-limited radial velocity field maps of extended emission-line sources, is described. A servo-controlled Fabry-Perot is used with a focal reducer and a two-dimensional photon-counting (area detector) system, to obtain the velocity information. The system has been fully tested and the first observations of the highly complex velocity field of the irregular galaxy, M82, are used to illustrate the power of the instrument. (author)

  5. Experimental and Numeral Investigation on X-cor Sandwich Structure under Low-velocity Impact

    Directory of Open Access Journals (Sweden)

    ZHU Fei

    2017-04-01

    Full Text Available X-cor sandwich is a new kind of foam sandwich reinforced by Z-pin techniques. Under low velocity impact damage, failure mechanism of X-cor sandwich structure is complex. Failure behavior of X-cor sandwich structure at different energy stages was analyzed, and the effects of the volume fraction of Z-pin implant and the density of the foam core on the failure behavior were also discussed. Z-pin diameter of specimens in low speed impact test was 0.5 mm, and the implantation angle was 22°, and the type of foam and Z-pin implant volume fraction in the experiment was variable .The results show that under 6 J impact energy, the impact energy is mainly absorbed by the panel’s delamination. The sandwich contained Z-pin is beneficial to reduce the delamination area, while the delamination area of blank sample increases by 45.1%. The foam density has little effect on the delamination area. The Z-pin fails under 12 J impact energy. The residual compressive strength ratio increases first and then decreases with the increase of volume fraction of Z-pin. The sample has the highest residual compressive strength ratio when the volume fraction reaches 0.42%. As the foam density increases, the residual compressive strength ratio increases. When the energy reaches 18 J, shear crack appears in the foam core, and the crack absorbs most of the energy. The weaker the foam core, the larger the residual compressive strength ratio is, and the more the volume fraction of Z-pin implanted, the lower the residual compressive strength ratio is. The low velocity impact model is also established by numerical simulation, and the result of impact damage is directly transferred and applied to study the residual strength model; the result obtained is 25%~29% higher than the experimental value.

  6. Elasticity of cerium up to 4.4 GPa by sound velocity measurements under hydrostatic pressure

    International Nuclear Information System (INIS)

    Wang, Zhigang; Bi, Yan; Xu, Liang; Liu, Lei

    2014-01-01

    We report here the longitudinal and shear sound velocities on polycrystalline cerium under hydrostatic pressure across the iso-structural γ-α phase transition up to 4.4 GPa. Comparing with previous methods, the pressure-density relation of Ce has been calculated by integrating with the initial travel time and pressure without any fitting. The pressure correction of the Grüneisen parameter and linear expansion coefficient are taken into account during the integration process. The sound velocities, bulk modulus, shear modulus, Debye temperature, and vibrational entropy are achieved and have been compared with previous results. The bulk modulus of cerium in α phase agrees with the previous results determined by neutron and x-ray diffraction. The Debye temperature above and below the phase transition are θ D γ =130.9 K and θ D α =151.9 K, respectively. The difference of the Debye temperature from respective experiment is found and has been expounded. We consider that the vibrational entropy change per atom of 0.44 k B as the Kondo collapse of 17% volume change, and 0.70 k B as the total change from γ phase to complete α phase. (papers)

  7. Elasticity of cerium up to 4.4 GPa by sound velocity measurements under hydrostatic pressure

    Science.gov (United States)

    Wang, Zhigang; Bi, Yan; Xu, Liang; Liu, Lei

    2014-04-01

    We report here the longitudinal and shear sound velocities on polycrystalline cerium under hydrostatic pressure across the iso-structural γ-α phase transition up to 4.4 GPa. Comparing with previous methods, the pressure-density relation of Ce has been calculated by integrating with the initial travel time and pressure without any fitting. The pressure correction of the Grüneisen parameter and linear expansion coefficient are taken into account during the integration process. The sound velocities, bulk modulus, shear modulus, Debye temperature, and vibrational entropy are achieved and have been compared with previous results. The bulk modulus of cerium in α phase agrees with the previous results determined by neutron and x-ray diffraction. The Debye temperature above and below the phase transition are \\theta _{D}^{\\gamma }=130.9\\;{\\rm{K}} and \\theta _{D}^{\\alpha }=151.9\\;{\\rm{K}}, respectively. The difference of the Debye temperature from respective experiment is found and has been expounded. We consider that the vibrational entropy change per atom of 0.44 k B as the Kondo collapse of 17% volume change, and 0.70 k B as the total change from γ phase to complete α phase.

  8. Ultrasonic detection of spall damage nucleation under low-velocity repeated impact

    Directory of Open Access Journals (Sweden)

    Watanabe T.

    2012-08-01

    Full Text Available Repeated plate impact testing with impact stress well below the threshold spall-stress (2.6 GPa on medium carbon steel was carried out to the identical target plate by impacting the flyer plate. Occurrence of spall damage under low-velocity repeated impact was evaluated nondestructively with a low frequency scanning acoustic microscope. We observed the spall damage distribution by the B- and C-scan images. In order to initiate the spall damage (voids in a ductile material or cracks in a brittle one the particular value of threshold spall-stress should be exceeded what already belongs to a commonly accepted knowledge. Generally, the spall damage development is dependent on the amplitude and the duration of the stress pulse. If the stress is high and duration is long enough to create tensile failure of material, the voids or cracks nucleate along the spall plane, and consequently, they form macrocracks. Therefore, the spall damage does not create when the first impact stress is less than the threshold spall-stress. However, after the fifth low-velocity repeated impact test, the generation of the spall damage was detected, even if the impact stress (1.1–1.7 GPa was lower than the threshold spall-stress (2.6 GPa.

  9. Neotectonic Velocity Field of the Western United States: A new Maximum-likelihood Solution

    Science.gov (United States)

    Bird, P.

    2002-12-01

    New kinematic finite-element program NeoKinema solves for long-term-average velocity fields and fault slip rates in deforming lithosphere, based on three kinds of information: (1) geologic slip rates of an unlimited number of faults, with standard deviations (which may be large); (2) geodetic velocities of benchmarks, either in fixed or free-floating velocity reference frame, with covariance matrix; (3) stress-direction data. Faults need not be explicitly represented in the finite element grid. The geodetic data are corrected for local effects of temporary fault locking by an iterative procedure. The strain rates of non-faulting finite elements are determined by a balance between (a) minimization of viscous dissipation, and (b) conformity to principal strain rate directions interpolated from the stress-direction data. NeoKinema has been applied to model neotectonics of the western United States, from the Gorda "plate" on the west, to the Gulf of California on the south, Yellowstone on the east, and Victoria on the north. Data comes from 378 active or potentially-active faults, 298 benchmarks of the WUSC002 solution [Bennett et al., 1999], and 2080 stress directions from the World Stress Map 2000 [Mueller et al., 2000]. The F-E grid has 1813 nodes and 3468 triangular elements of 30-km and 60-km dimensions. Results of this first application are very plausible, and confirm the concept of a Sierra Nevada-Great Valley plate moving ~9 mm/a NW. After a few local artifacts are investigated and eliminated (primarily by better gridding), the model will be used to compute various measures of long-term seismic hazard. It is already apparent from the map of predicted strain rates that 20th-century seismicity levels in western Oregon, the Wasatch Front area of Utah, and the Las Vegas region have been less than their long-term-average expectations.

  10. Velocity field in the wake of a hydropower farm equipped with Achard turbines

    International Nuclear Information System (INIS)

    Georgescu, A-M; Cosoiu, C I; Alboiu, N; Hamzu, Al; Georgescu, S C

    2010-01-01

    The study consists of experimental and numerical investigations related to the water flow in the wake of a hydropower farm, equipped with three Achard turbines. The Achard turbine is a French concept of vertical axis cross-flow marine current turbine, with three vertical delta-blades, which operates irrespective of the water flow direction. A farm model built at 1:5 scale has been tested in a water channel. The Achard turbines run in stabilized current, so the flow can be assumed to be almost unchanged in horizontal planes along the vertical z-axis, thus allowing 2D numerical modelling, for different farm configurations: the computational domain is a cross-section of all turbines at a certain z-level. The two-dimensional numerical model of that farm has been used to depict the velocity field in the wake of the farm, with COMSOL Multiphysics and FLUENT software, to compute numerically the overall farm efficiency. The validation of the numerical models with experimental results is performed via the measurement of velocity distribution, by Acoustic Doppler Velocimetry, in the wake of the middle turbine within the farm. Three basic configurations were studied experimentally and numerically, namely: with all turbines aligned on a row across the upstream flow direction; with turbines in an isosceles triangular arrangement pointing downstream; with turbines in an isosceles triangular arrangement pointing upstream. As long as the numerical flow in the wake fits the experiments, the numerical results for the power coefficient (turbine efficiency) are trustworthy. The farm configuration with all turbines aligned on a same row leads to lower values of the experimental velocities than the numerical ones, while the farm configurations where the turbines are in isosceles triangular arrangement, pointing downstream or upstream, present a better match between numerical and experimental data.

  11. SAR-based Estimation of Glacial Extent and Velocity Fields on Isanotski Volcano, Aleutian Islands, Alaska

    Science.gov (United States)

    Sousa, D.; Lee, A.; Parker, O. P.; Pressler, Y.; Guo, S.; Osmanoglu, B.; Schmidt, C.

    2012-12-01

    Global studies show that Earth's glaciers are losing mass at increasing rates, creating a challenge for communities that rely on them as natural resources. Field observation of glacial environments is limited by cost and inaccessibility. Optical remote sensing is often precluded by cloud cover and seasonal darkness. Synthetic aperture radar (SAR) overcomes these obstacles by using microwave-frequency electromagnetic radiation to provide high resolution information on large spatial scales and in remote, atmospherically obscured environments. SAR is capable of penetrating clouds, operating in darkness, and discriminating between targets with ambiguous spectral signatures. This study evaluated the efficacy of two SAR Earth observation methods on small (Unimak Island, Aleutian Archipelago, USA. The local community on the island, the City of False Pass, relies on glacial melt for drinking water and hydropower. Two methods were used: (1) velocity field estimation based on Repeat Image Feature Tracking (RIFT) and (2) glacial boundary delineation based on interferometric coherence mapping. NASA Uninhabited Aerial Vehicle SAR (UAVSAR) single-polarized power images and JAXA Advanced Land Observing Satellite Phased Array type L-band SAR (ALOS PALSAR) single-look complex images were analyzed over the period 2008-2011. UAVSAR image pairs were coregistered to sub-pixel accuracy and processed with the Coregistration of Optically Sensed Images and Correlation (COSI-Corr) feature tracking module to derive glacial velocity field estimates. Maximum glacier velocities ranged from 28.9 meters/year to 58.3 meters/year. Glacial boundaries were determined from interferometric coherence of ALOS PALSAR data and subsequently refined with masking operations based on terrain slope and segment size. Accuracy was assessed against hand-digitized outlines from high resolution UAVSAR power images, yielding 83.0% producer's accuracy (errors of omission) and 86.1% user's accuracy (errors of

  12. Detailed experimental investigations on flow behaviors and velocity field properties of a supersonic mixing layer

    Science.gov (United States)

    Tan, Jianguo; Zhang, Dongdong; Li, Hao; Hou, Juwei

    2018-03-01

    The flow behaviors and mixing characteristics of a supersonic mixing layer with a convective Mach number of 0.2 have been experimentally investigated utilizing nanoparticle-based planar laser scattering and particle image velocimetry techniques. The full development and evolution process, including the formation of Kelvin-Helmholtz vortices, breakdown of large-scale structures and establishment of self-similar turbulence, is exhibited clearly in the experiments, which can give a qualitative graphically comparing for the DNS and LES results. The shocklets are first captured at this low convective Mach number, and their generation mechanisms are elaborated and analyzed. The convective velocity derived from two images with space-time correlations is well consistent with the theoretical result. The pairing and merging process of large-scale vortices in transition region is clearly revealed in the velocity vector field. The analysis of turbulent statistics indicates that in weakly compressible mixing layers, with the increase of convective Mach number, the peak values of streamwise turbulence intensity and Reynolds shear stress experience a sharp decrease, while the anisotropy ratio seems to keep quasi unchanged. The normalized growth rate of the present experiments shows a well agreement with former experimental and DNS data. The validation of present experimental results is important for that in the future the present work can be a reference for assessing the accuracy of numerical data.

  13. Simultaneous measurement of 3D zooplankton trajectories and surrounding fluid velocity field in complex flows.

    Science.gov (United States)

    Adhikari, Deepak; Gemmell, Brad J; Hallberg, Michael P; Longmire, Ellen K; Buskey, Edward J

    2015-11-01

    We describe an automated, volumetric particle image velocimetry (PIV) and tracking method that measures time-resolved, 3D zooplankton trajectories and surrounding volumetric fluid velocity fields simultaneously and non-intrusively. The method is demonstrated for groups of copepods flowing past a wall-mounted cylinder. We show that copepods execute escape responses when subjected to a strain rate threshold upstream of a cylinder, but the same threshold range elicits no escape responses in the turbulent wake downstream. The method was also used to document the instantaneous slip velocity of zooplankton and the resulting differences in trajectory between zooplankton and non-inertial fluid particles in the unsteady wake flow, showing the method's capability to quantify drift for both passive and motile organisms in turbulent environments. Applications of the method extend to any group of organisms interacting with the surrounding fluid environment, where organism location, larger-scale eddies and smaller-scale fluid deformation rates can all be tracked and analyzed. © 2015. Published by The Company of Biologists Ltd.

  14. A search for long-lived velocity fields at the solar poles

    Science.gov (United States)

    Durney, B. R.; Lytle, D. M.; Cram, L. E.; Guenther, D. B.; Keil, S. L.

    1985-01-01

    A search has been made in the polar regions of the sun for large-scale (50-200 Mm) velocity fields with lifetimes of the order of the solar rotation period (approximately equal to or greater than 30 days). The observations show that any such large-scale, long-lived velocity patterns in the polar regions must have an amplitude less than 5 m/s. Marginally significant detections (at the 2-3 sigma level) were made of two kinds of structures with amplitudes of order 3 m/s. One has a rotation period approximately 38 days (close to the polar rotation period at the sun's surface), and a scale approximately 150 Mm; the other has a period approximately 24 days and a scale approximately 100 Mm. Tentatively, the first structure is interpreted as being of supergranular origin. The second structure is interpreted as the overshooting of the dominant convective mode of the lower solar convection zone - the giant granulation.

  15. Comparison of pressure reconstruction approaches based on measured and simulated velocity fields

    Directory of Open Access Journals (Sweden)

    Manthey Samuel

    2017-09-01

    Full Text Available The pressure drop over a pathological vessel section can be used as an important diagnostic indicator. However, it cannot be measured non-invasively. Multiple approaches for pressure reconstruction based on velocity information are available. Regarding in-vivo data introducing uncertainty these approaches may not be robust and therefore validation is required. Within this study, three independent methods to calculate pressure losses from velocity fields were implemented and compared: A three dimensional and a one dimensional method based on the Pressure Poisson Equation (PPE as well as an approach based on the work-energy equation for incompressible fluids (WERP. In order to evaluate the different approaches, phantoms from pure Computational Fluid Dynamics (CFD simulations and in-vivo PC-MRI measurements were used. The comparison of all three methods reveals a good agreement with respect to the CFD pressure solutions for simple geometries. However, for more complex geometries all approaches lose accuracy. Hence, this study demonstrates the need for a careful selection of an appropriate pressure reconstruction algorithm.

  16. Experimental investigation of fibre reinforced plastics with hybrid layups under high-velocity impact loads

    Directory of Open Access Journals (Sweden)

    Marco Romano

    2014-07-01

    Full Text Available This paper deals with experimental investigations concerning energy dissipation capacity of different kinds of reinforcement fibres in monolithic and hybrid layups under high-velocity impact loads. The investigated kinds of fibres are carbon, glass and basalt fibres. Therefore test panels, using the same thermoset resin, were built up and cured by autoclave processing. The fibre volume content of the test panels has been determined. Furthermore the influence of a separating layer at selected positions in the hybrid stacked panels was investigated. The results show the influence and the energy dissipation capacity of each single kind of fibre and the enhanced properties for the hybrid layups by hybrid stacking sequences and the use of a separating core material.

  17. Image registration using stationary velocity fields parameterized by norm-minimizing Wendland kernel

    DEFF Research Database (Denmark)

    Pai, Akshay Sadananda Uppinakudru; Sommer, Stefan Horst; Sørensen, Lauge

    by the regularization term. In a variational formulation, this term is traditionally expressed as a squared norm which is a scalar inner product of the interpolating kernels parameterizing the velocity fields. The minimization of this term using the standard spline interpolation kernels (linear or cubic) is only...... approximative because of the lack of a compatible norm. In this paper, we propose to replace such interpolants with a norm-minimizing interpolant - the Wendland kernel which has the same computational simplicity like B-Splines. An application on the Alzheimer's disease neuroimaging initiative showed...... that Wendland SVF based measures separate (Alzheimer's disease v/s normal controls) better than both B-Spline SVFs (pSpline freeform deformation (p

  18. Tensor-based morphometry with mappings parameterized by stationary velocity fields in Alzheimer's disease neuroimaging initiative.

    Science.gov (United States)

    Bossa, Matías Nicolás; Zacur, Ernesto; Olmos, Salvador

    2009-01-01

    Tensor-based morphometry (TBM) is an analysis technique where anatomical information is characterized by means of the spatial transformations between a customized template and observed images. Therefore, accurate inter-subject non-rigid registration is an essential prerrequisite. Further statistical analysis of the spatial transformations is used to highlight some useful information, such as local statistical differences among populations. With the new advent of recent and powerful non-rigid registration algorithms based on the large deformation paradigm, TBM is being increasingly used. In this work we evaluate the statistical power of TBM using stationary velocity field diffeomorphic registration in a large population of subjects from Alzheimer's Disease Neuroimaging Initiative project. The proposed methodology provided atrophy maps with very detailed anatomical resolution and with a high significance compared with results published recently on the same data set.

  19. Technique for velocity vector field dynamics measurement on the basis of smoke visualization of flow

    Science.gov (United States)

    Mikheev, N. I.; Dushin, N. S.; Saushin, I. I.

    2017-09-01

    The main difference between Smoke Image Velocimetry (SIV) technique and traditional PIV is that the smoke with continuous intensity in the image is seeded into the flow instead of separate particles. Owing to better smoke reflectivity, relatively primitive equipment is enough to measure the dynamics of velocity vector fields with the frequency of 25 kHz and higher. The image processing algorithm is adapted to high tracer concentration and relatively large displacement of smoke patches between two consecutive frames. The results of SIV testing are presented, including the estimations of the most measurement noise sensitive characteristics of turbulence calculated from spatial derivatives of fluctuations of small-scale turbulence. The measurement results have been shown to agree well with the data obtained by other methods. Application of SIV technique opens new possibilities in the research of flow pattern and turbulence in unsteady and fast processes.

  20. PIC Simulations of Velocity-space Instabilities in a Decreasing Magnetic Field: Viscosity and Thermal Conduction

    Science.gov (United States)

    Riquelme, Mario; Quataert, Eliot; Verscharen, Daniel

    2018-02-01

    We use particle-in-cell (PIC) simulations of a collisionless, electron–ion plasma with a decreasing background magnetic field, {\\boldsymbol{B}}, to study the effect of velocity-space instabilities on the viscous heating and thermal conduction of the plasma. If | {\\boldsymbol{B}}| decreases, the adiabatic invariance of the magnetic moment gives rise to pressure anisotropies with {p}| | ,j> {p}\\perp ,j ({p}| | ,j and {p}\\perp ,j represent the pressure of species j (electron or ion) parallel and perpendicular to B ). Linear theory indicates that, for sufficiently large anisotropies, different velocity-space instabilities can be triggered. These instabilities in principle have the ability to pitch-angle scatter the particles, limiting the growth of the anisotropies. Our simulations focus on the nonlinear, saturated regime of the instabilities. This is done through the permanent decrease of | {\\boldsymbol{B}}| by an imposed plasma shear. We show that, in the regime 2≲ {β }j≲ 20 ({β }j\\equiv 8π {p}j/| {\\boldsymbol{B}}{| }2), the saturated ion and electron pressure anisotropies are controlled by the combined effect of the oblique ion firehose and the fast magnetosonic/whistler instabilities. These instabilities grow preferentially on the scale of the ion Larmor radius, and make {{Δ }}{p}e/{p}| | ,e≈ {{Δ }}{p}i/{p}| | ,i (where {{Δ }}{p}j={p}\\perp ,j-{p}| | ,j). We also quantify the thermal conduction of the plasma by directly calculating the mean free path of electrons, {λ }e, along the mean magnetic field, finding that {λ }e depends strongly on whether | {\\boldsymbol{B}}| decreases or increases. Our results can be applied in studies of low-collisionality plasmas such as the solar wind, the intracluster medium, and some accretion disks around black holes.

  1. On the Nature of Velocity Fields in High-z Galaxies

    Science.gov (United States)

    Prochaska, Jason X.; Chen, Hsiao-Wen; Wolfe, Arthur M.; Dessauges-Zavadsky, Miroslava; Bloom, Joshua S.

    2008-01-01

    We analyze the gas kinematics of damped Lyα systems (DLAs) hosting high-z gamma-ray bursts (GRBs) and those toward quasars (QSO-DLAs), focusing on three statistics: (1) Δv90, the velocity interval encompassing 90% of the integrated optical depth, and (2) W1526 and (3) W1548, the rest equivalent widths of the Si II 1526 and C IV 1548 transitions, respectively. The Δv90 distributions of the GRB-DLAs and QSO-DLAs are similar; each has median Δv90 ≈ 80 km s-1 and a significant tail, extending to several hundred km s-1. This suggests comparable galaxy masses for the parent populations of GRB-DLAs and QSO-DLAs, and we infer that the average dark matter halo mass of GRB galaxies is lesssim1012 M⊙. The unique configuration of GRB-DLA sight lines and the presence (and absence) of fine-structure absorption together give special insight into the nature of high-z protogalactic velocity fields. The data support a scenario in which the Δv90 statistic reflects dynamics in the interstellar medium (ISM) and W1526 traces motions outside the ISM (e.g., halo gas and galactic-scale winds). The W1526 statistic and gas metallicity [M/H] are tightly correlated, especially for the QSO-DLAs: [M/H] = a + blog(W1526/1Å) with a = -0.92 +/- 0.05 and b = 1.41 +/- 0.10. We argue that the W1526 statistic primarily tracks dynamical motions in the halos of high-z galaxies and interpret this correlation as a mass-metallicity relation with very similar slope to the trend observed in local, low-metallicity galaxies. Finally, the GRB-DLAs exhibit systematically larger W1526 values (>0.5 Å) than the QSO-DLAs (langleW1528rangle ≈ 0.5 Å), which may suggest that galactic-scale outflows contribute to the largest observed velocity fields.

  2. Indirect measurement of near-surface velocity and pressure fields based on measurement of moving free surface profiles

    International Nuclear Information System (INIS)

    Sibamoto, Yasuteru; Nakamura, Hideo

    2005-01-01

    A non-intrusive technique for measurement of the velocity and pressure fields adjacent to a moving fluid surface is developed. The technique is based on the measurement of fluid surface profile. The velocity and pressure fields are derived with use of the boundary element method (BEM) by seeking for an incompressible flow field that satisfies the kinematic boundary condition imposed by the time-dependent fluid surface profile. The proposed technique is tested by deriving the velocity and pressure fields inversely from the fluid surface profiles obtained by a forward BEM calculation of fluid surface response to externally-imposed pressure. The inverse calculation results show good agreement with the imposed pressure distribution in the forward calculation. (author)

  3. Burst Speed of Wild Fishes under High-Velocity Flow Conditions Using Stamina Tunnel with Natural Guidance System in River

    Science.gov (United States)

    Izumi, Mattashi; Yamamoto, Yasuyuki; Yataya, Kenichi; Kamiyama, Kohhei

    Swimming experiments were conducted on wild fishes in a natural guidance system stamina tunnel (cylindrical pipe) installed in a fishway of a local river under high-velocity flow conditions (tunnel flow velocity : 211 to 279 cm·s-1). In this study, the swimming characteristics of fishes were observed. The results show that (1) the swimming speeds of Tribolodon hakonensis (Japanese dace), Phoxinus lagowshi steindachneri (Japanese fat-minnow), Plecoglossus altivelis (Ayu), and Zacco platypus (Pale chub) were in proportion to their body length under identical water flow velocity conditions; (2) the maximum burst speed of Japanese dace and Japanese fat-minnow (measuring 4 to 6 cm in length) was 262 to 319 cm·s-1 under high flow velocity conditions (225 to 230 cm·s-1), while the maximum burst speed of Ayu and Pale chub (measuring 5 cm to 12 cm in length) was 308 to 355 cm·s-1 under high flow velocity conditions (264 to 273 cm·s-1) ; (3) the 50cm-maximum swimming speed of swimming fishes was 1.07 times faster than the pipe-swimming speed; (4) the faster the flow velocity, the shorter the swimming distance became.

  4. Remote Sensing Data in Wind Velocity Field Modelling: a Case Study from the Sudetes (SW Poland)

    Science.gov (United States)

    Jancewicz, Kacper

    2014-06-01

    The phenomena of wind-field deformation above complex (mountainous) terrain is a popular subject of research related to numerical modelling using GIS techniques. This type of modelling requires, as input data, information on terrain roughness and a digital terrain/elevation model. This information may be provided by remote sensing data. Consequently, its accuracy and spatial resolution may affect the results of modelling. This paper represents an attempt to conduct wind-field modelling in the area of the Śnieżnik Massif (Eastern Sudetes). The modelling process was conducted in WindStation 2.0.10 software (using the computable fluid dynamics solver Canyon). Two different elevation models were used: the Global Land Survey Digital Elevation Model (GLS DEM) and Digital Terrain Elevation Data (DTED) Level 2. The terrain roughness raster was generated on the basis of Corine Land Cover 2006 (CLC 2006) data. The output data were post-processed in ArcInfo 9.3.1 software to achieve a high-quality cartographic presentation. Experimental modelling was conducted for situations from 26 November 2011, 25 May 2012, and 26 May 2012, based on a limited number of field measurements and using parameters of the atmosphere boundary layer derived from the aerological surveys provided by the closest meteorological stations. The model was run in a 100-m and 250-m spatial resolution. In order to verify the model's performance, leave-one-out cross-validation was used. The calculated indices allowed for a comparison with results of former studies pertaining to WindStation's performance. The experiment demonstrated very subtle differences between results in using DTED or GLS DEM elevation data. Additionally, CLC 2006 roughness data provided more noticeable improvements in the model's performance, but only in the resolution corresponding to the original roughness data. The best input data configuration resulted in the following mean values of error measure: root mean squared error of velocity

  5. Evolution of Mass and Velocity Field in the Cosmic Web: Comparison between Baryonic and Dark Matter

    Science.gov (United States)

    Zhu, Weishan; Feng, Long-Long

    2017-03-01

    We investigate the evolution of the cosmic web since z = 5 in grid-based cosmological hydrodynamical simulations, focusing on the mass and velocity fields of both baryonic and cold dark matter. The tidal tensor of density is used as the main method for web identification, with λ th = 0.2-1.2. The evolution trends in baryonic and dark matter are similar, although moderate differences are observed. Sheets appear early, and their large-scale pattern may have been set up by z = 3. In terms of mass, filaments supersede sheets as the primary collapsing structures from z ˜ 2-3. Tenuous filaments assembled with each other to form prominent ones at z dark matter field, and is even moderately stronger between {\\boldsymbol{ω }} and {{\\boldsymbol{e}}}1, and ω and {{\\boldsymbol{e}}}3. Compared with dark matter, there is slightly less baryonic matter found residing in filaments and clusters, and its vorticity developed more significantly below 2-3 Mpc. These differences may be underestimated because of the limited resolution and lack of star formation in our simulation. The impact of the change of dominant structures in overdense regions at z ˜ 2-3 on galaxy formation and evolution is shortly discussed.

  6. A New Velocity Field from a Dense GPS Array in the Southernmost Longitudinal Valley, Southeastern Taiwan

    Directory of Open Access Journals (Sweden)

    Horng-Yue Chen

    2013-01-01

    Full Text Available In the southernmost Longitudinal Valley (LV, Taiwan, we analyzed a dense GPS array composed of 10 continuous stations and 86 campaign-mode stations. By removing the effects of the four major earthquakes (one regional and three local occurred during the 1992 - 2010 observation period, we derived a new horizontal velocity field in this area, which then allows better locating the surface traces of the major active faults, including the Longitudinal Valley Fault (LVF system and the Central Range Fault, and characterizing the slip behaviors along the faults. Note that LVF reveals two sub-parallel strands in the study area: the Luyeh Fault to the west and the Lichi Fault to the east. Based on the results of strain analyses, including dilatation and shear strain, and projected vectors of station velocities across the major faults, we came to the following geological interpretations. During the inter-seismic periods, the surface deformation of the southernmost LV is mainly accommodated by the faulting on the two branches of the LVF; there is very little surface deformation on the Central Range Fault. The Luyeh River appears to act as a boundary to divide the LVF to behave differently to its northern and southern sides. The Lichi Fault reveals a change of slip kinematics from an oblique shearing/thrusting in the north to a nearly pure shearing with minor extension to the south. Regarding the slip behavior of the Luyeh Fault, it exhibits a creeping behavior in the north and a partially near-surface-locked faulting behavior in the south. We interpret that the two strands of the LVF merge together in the northern Taitung alluvial plain and turns to E-W trend toward the offshore area.

  7. The impact of groundwater velocity fields on streamlines in an aquifer system with a discontinuous aquitard (Inner Mongolia, China)

    Science.gov (United States)

    Wu, Qiang; Zhao, Yingwang; Xu, Hua

    2018-04-01

    Many numerical methods that simulate groundwater flow, particularly the continuous Galerkin finite element method, do not produce velocity information directly. Many algorithms have been proposed to improve the accuracy of velocity fields computed from hydraulic potentials. The differences in the streamlines generated from velocity fields obtained using different algorithms are presented in this report. The superconvergence method employed by FEFLOW, a popular commercial code, and some dual-mesh methods proposed in recent years are selected for comparison. The applications to depict hydrogeologic conditions using streamlines are used, and errors in streamlines are shown to lead to notable errors in boundary conditions, the locations of material interfaces, fluxes and conductivities. Furthermore, the effects of the procedures used in these two types of methods, including velocity integration and local conservation, are analyzed. The method of interpolating velocities across edges using fluxes is shown to be able to eliminate errors associated with refraction points that are not located along material interfaces and streamline ends at no-flow boundaries. Local conservation is shown to be a crucial property of velocity fields and can result in more accurate streamline densities. A case study involving both three-dimensional and two-dimensional cross-sectional models of a coal mine in Inner Mongolia, China, are used to support the conclusions presented.

  8. Velocity field measurement in gas-liquid metal two-phase flow with use of PIV and neutron radiography techniques

    International Nuclear Information System (INIS)

    Saito, Y.; Mishima, K.; Tobita, Y.; Suzuki, T.; Matsubayashi, M.

    2001-01-01

    Neutron radiography and PIV (Particle Image Velocimetry) techniques were applied to measurements of velocity field in gas-liquid metal two-phase flow. Visualization and measurements of two-phase flow were conducted using molten lead bismuth and nitrogen gas as working fluids and particles made of gold-cadmium (AuCd 3 ) inter-metallic alloy were employed as the tracer. Discrimination method between bubble and tracer images in two-phase flow was developed based on the σ-scaling method. Time-averaged liquid velocity fields, gas velocity fields and void profile were calculated from discriminated images, respectively. From these measurements, the basic characteristics of gas-liquid metal two-phase mixture were clarified. (author)

  9. An experimental study of velocities under pressure for ancient oceanic rocks

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, K.V.L.N.S.

    Seismic velocities of Indus suture rock types from Dras-Sanko-Kargil, Kashmir Himalaya, as a function of pressure up to 10 kbar were studied. The high-pressure measurements on the rocks reflect the depthwise increase in velocity, and in general...

  10. The Dynamics of Oblate Drop Between Heterogeneous Plates Under Alternating Electric Field. Non-uniform Field

    Science.gov (United States)

    Kashina, M. A.; Alabuzhev, A. A.

    2018-02-01

    The dynamics of the incompressible fluid drop under the non-uniform electric field are considered. The drop is bounded axially by two parallel solid planes and the case of heterogeneous plates is investigated. The external electric field acts as an external force that causes motion of the contact line. We assume that the electric current is alternative current and the AC filed amplitude is a spatially non-uniform function. In equilibrium, the drop has the form of a circular cylinder. The equilibrium contact angle is 0.5 π. In order to describe this contact line motion the modified Hocking boundary condition is applied: the velocity of the contact line is proportional to the deviation of the contact angle and the speed of the fast relaxation processes, which frequency is proportional to twice the frequency of the electric field. The Hocking parameter depends on the polar angle, i.e. the coefficient of the interaction between the plate and the fluid (the contact line) is a function of the plane coordinates. This function is expanded in a series of the Laplace operator eigenfunctions.

  11. Clustering and relative velocity of heavy particles under gravitational settling in isotropic turbulent flows

    Science.gov (United States)

    Jin, Guodong; He, Guo-Wei

    2015-11-01

    Clustering and intermittency in radial relative velocity (RRV) of heavy particles of same size settling in turbulent flows can be remarkably changed due to gravity. Clustering is monotonically reduced at Stokes number less than 1 under gravity due to the disability of the centrifugal mechanism, however it is non-monotonically enhanced at Stokes number greater than 1 due to the multiplicative amplification in the case that the proposed effective Kubo number is less than 1. Although gravity causes monotonical reduction in the rms of RRV of particles at a given Stokes number with decreasing Froude number, the variation tendency in the tails of standardized PDF of RRV versus Froude number is obviously different: the tails become narrower at a small Stokes number, while they become broader at a large Stokes number. The mechanism of this variation stems from the compromise between the following two competing factors. The mitigation of correlation of particle positions and the regions of high strain rate which are more intermittent reduces the intermittency in RRV at small Stokes numbers, while the significant reduction in the backward-in-time relative separations will make particle pairs see small-scale structures, leading to a higher intermittency in RRV at large Stokes numbers. NSAF of China (grant number U1230126); NSFC (grant numbers 11072247 and 11232011).

  12. On the Behavior of Fiberglass Epoxy Composites under Low Velocity Impact Loading

    Directory of Open Access Journals (Sweden)

    Gautam S. Chandekar

    2010-01-01

    Full Text Available Response of fiberglass epoxy composite laminates under low velocity impact loading is investigated using LS-DYNA®, and the results are compared with experimental analysis performed using an instrumented impact test setup (Instron dynatup 8250. The composite laminates are manufactured using H-VARTM© process with basket weave E-Glass fabrics. Epon 862 is used as a resin system and Epicure-W as a hardening agent. Composite laminates, with 10 layers of fiberglass fabrics, are modeled using 3D solid elements in a mosaic fashion to represent basket weave pattern. Mechanical properties are calculated by using classical micromechanical theory and assigned to the elements using ORTHOTROPIC ELASTIC material model. The damage occurred since increasing impact energy is incorporated using ADVANCED COMPOSITE DAMAGE material model in LS-DYNA®. Good agreements are obtained with the failure damage results in LS-DYNA® and experimental results. Main considerations for comparison are given to the impact load carrying capacity and the amount of impact energy absorbed by the laminates.

  13. High-resolution Vertical Profiling of Ocean Velocity and Water Properties Under Hurricane Frances in September 2004

    Science.gov (United States)

    Sanford, T. B.; D'Asarp, E. A.; Girton, J. B.; Price, J. F.; Webb, D. C.

    2006-12-01

    In ONR's CBLAST Hurricane research program observations were made of the upper ocean's response to Hurricane Frances. Three EM-APEX floats (velocity sensing versions of Webb Research APEX floats) and two Lagrangian floats were deployed north of Hispaniola from a C-130 aircraft ahead of Hurricane Frances in September 2004. The EM-APEX floats measured T, S and V over the upper 500 m starting about a day before the storm's arrival. The Lagrangian floats measured temperature and salinity while following the three- dimensional boundary layer turbulence in the upper 40 m. One EM-APEX float was directly under the track of the storm's eye, another EM-APEX and two Lagrangian floats went in about 50 km to the right of the track (where the surface winds are strongest) and the third float was about 100 km to the right. The EM-APEX floats profiled for 10 hours from the surface to 200 m, then continued profiling between 35 and 200 m with excursions to 500 m every half inertial period. After 5 days, the EM-APEX floats surfaced and transmitted the accumulated processed observations, then the floats profiled to 500 m every half inertial period until recovered early in October aided by GPS and Iridium. The float array sampled in unprecedented detail the upper-ocean turbulence, momentum, and salt and heat changes in response to the hurricane. The buildup of surface gravity waves in advance of the storm was also observed in the velocity profiles, with significant wave heights of up to 11 m. Rapid acceleration of inertial currents in the surface mixing layer (SML) to over 1 m/s stimulated vertical mixing by shear instability at the SML base, as indicated by low Richardson numbers and SML deepening from about 40 m to 120 m under the strongest wind forcing. Surface cooling of about 2.5 C was primarily due to the SML deepening and entrainment of colder water, with a small contribution from surface heat flux. Intense inertial pumping was observed under the eye, with vertical excursions of

  14. Comparison of vertical E × B drift velocities and ground-based magnetometer observations of DELTA H in the low latitude under geomagnetically disturbed conditions

    Science.gov (United States)

    Prabhu, M.; Unnikrishnan, K.

    2018-04-01

    In the present work, we analyzed the daytime vertical E × B drift velocities obtained from Jicamarca Unattended Long-term Ionosphere Atmosphere (JULIA) radar and ΔH component of geomagnetic field measured as the difference between the magnitudes of the horizontal (H) components between two magnetometers deployed at two different locations Jicamarca, and Piura in Peru for 22 geomagnetically disturbed events in which either SC has occurred or Dstmax linear, polynomial (order 2), and polynomial (order 3) regression analysis were considered. The regression parameters in all the three cases were calculated using the Least Square Method (LSM), using the daytime vertical E × B drift velocity and ΔH. A formula was developed which indicates the relationship between daytime vertical E × B drift velocity and ΔH, for the disturbed periods. The E × B drift velocity was then evaluated using the formulae thus found for the three regression analysis and validated for the 'disturbed periods' of 3 selected events. The E × B drift velocities estimated by the three regression analysis have a fairly good agreement with JULIA radar observed values under different seasons and solar activity conditions. Root Mean Square (RMS) errors calculated for each case suggest that polynomial (order 3) regression analysis provides a better agreement with the observations from among the three.

  15. A velocity probe-based method for continuous detonation and shock measurement in near-field underwater explosion

    Science.gov (United States)

    Li, Kebin; Li, Xiaojie; Yan, Honghao; Wang, Xiaohong; Miao, Yusong

    2017-12-01

    A new velocity probe which permits recording the time history of detonation and shock waves has been developed by improving the commercial on principle and structure. A method based on the probe is then designed to measure the detonation velocity and near-field shock parameters in a single underwater explosion, by which the oblique shock wave front of cylindrical charges and the peak pressure attenuation curve of spherical explosive are obtained. A further derivation of detonation pressure, adiabatic exponent, and other shock parameters is conducted. The present method offers a novel and reliable parameter determination for near-field underwater explosion.

  16. Nonlinear relaxation field in charged systems under high electric fields

    International Nuclear Information System (INIS)

    Morawetz, K.

    2000-01-01

    The influence of an external electric field on the current in charged systems is investigated. The results from the classical hierarchy of density matrices are compared with the results from the quantum kinetic theory. The kinetic theory yields a systematic treatment of the nonlinear current beyond linear response. To this end the dynamically screened and field-dependent Lenard-Balescu equation is integrated analytically and the nonlinear relaxation field is calculated. The classical linear response result known as Debye - On-Sager relaxation effect is only obtained if asymmetric screening is assumed. Considering the kinetic equation of one specie the other species have to be screened dynamically while the screening with the same specie itself has to be performed statically. Different other approximations are discussed and compared. (author)

  17. A Comparison of High Density Velocity Fields obtained from Isotropic and Anisotropic Prestack Depth Migration as a Constraint on Amplitude Inversion

    International Nuclear Information System (INIS)

    Ratcliffe, A.; Williams, G.; Fogg, A.; Hawkins, K.

    2002-01-01

    Anisotropic prestack depth migration has clear benefits for imaging purposes in many areas. An additional benefit of the anisotropic imaging is that the velocity field derived for migration ties closely to vertical well velocities. We find that this velocity field contains more accurate information than an isotropically derived field and consequently, gives better constraints on amplitude inversion of the seismic data.We illustrate these conclusions by presenting a case study from the Southern North Sea Anglo-Dutch Basin. The field is a typical Rotilegend reservoir comprising Horst and tilted fault blocks. Imaging in this area is made difficult by salt tectonics, causing structural complexity, and overburden consisting of complex lithologies containing large interval velocity contrasts.We start by comparing the initial isotropic and anisotropic prestack depth migration results. We then discuss the low and high-density velocity fields obtained from automatic seismic velocity analyses on both datasets and examine the geological consistency of these velocity fields. Finally, we use these low and high-density velocity fields to constraint seismic amplitude inversion and compare these acoustic impedance results with those obtained from an inversion constrained by well velocity information. We find that the inversion results obtained from the obtained from the isotropically derived velocity fields follow the well inversion better than those obtained from the isotropically derived velocity fields

  18. Measurements of the velocity fields by PIV method round about titling gate

    Science.gov (United States)

    Mistrová, Ivana; Zubík, Pavel

    2012-04-01

    The article deals with problems of using of measurement method Particle Image Velocimetry (PIV) to measure velocity fields in the flowing water in front, above and behind drowned titling weir gate. The aim was to obtain information about the distribution of speed in the area of interest for the verification or calibration of the numerical model. Experiments were carried out in inclinable channel connected to the hydraulic circuit with a pump and storage tank at the Water Management Research Laboratory (LVV) of Institute of Water Structures at the Faculty of Civil Engineering in Brno University of Technology. Hydraulic inclinable channel has cross-section with dimensions of 0.4×0.4m and length of 12.5m. The measured area has cross-section approximately 0.2m wide and 0.4m high and its length is 1m. The results of physical modelling allowed a comparison of experimental data with numerical simulation results of this type of flow in the commercial software ANSYS CFX-12.0.

  19. Temperature and velocity field of coolant at inlet to WWER-440 core - evaluation of experimental data

    International Nuclear Information System (INIS)

    Jirous, F.; Klik, F.; Janeba, B.; Daliba, J.; Delis, J.

    1989-01-01

    Experimentally determined were coolant temperature and velocity fields at the inlet of the WWER-440 reactor core. The accuracy estimate is presented of temperature measurements and the relation is given for determining the resulting measurement error. An estimate is also made of the accuracy of solution of the system of equations for determining coefficients B kn using the method of the least square fit. Coefficients B kn represent the relative contribution of the mass flow of the k-th fuel assembly from the n-th loop and allow the calculation of coolant temperatures at the inlet of the k-th fuel assembly, when coolant temperatures in loops at reactor inlet are known. A comparison is made of the results of measurements on a hydrodynamic model of a WWER-440 reactor with results of measurements made at unit 4 of the Dukovany nuclear power plant. Full agreement was found for 32 model measurements and 6 reactor measurements. It may be assumed that the results of other model measurements obtained for other operating variants will also apply for an actual reactor. Their applicability may, however, only be confirmed by repeating the experiment on other WWER-440 reactors. (Z.M.). 5 figs., 7 refs

  20. Finite Time Approach to Equilibrium in a Fractional Brownian Velocity Field

    Science.gov (United States)

    Horvai, Peter; Komorowski, Tomasz; Wehr, Jan

    2007-05-01

    We consider the solution of the equation r (t) = W(r(t)), r(0) = r 0 > 0 where W(ṡ) is a fractional Brownian motion (f.B.m.) with the Hurst exponent α∈ (0,1). We show that for almost all realizations of W(ṡ) the trajectory reaches in finite time the nearest equilibrium point (i.e. zero of the f.B.m.) either to the right or to the left of r 0, depending on whether W( r 0) is positive or not. After reaching the equilibrium the trajectory stays in it forever. The problem is motivated by studying the separation between two particles in a Gaussian velocity field which satisfies a local self-similarity hypothesis. In contrast to the case when the forcing term is a Brownian motion (then an analogous statement is a consequence of the Markov property of the process) we show our result using as the principal tools the properties of time reversibility of the law of the f.B.m., see Lemma 2.4 below, and the small ball estimate of Molchan, Commun. Math. Phys. 205 (1999) 97-111.

  1. Tensor-based morphometry with stationary velocity field diffeomorphic registration: application to ADNI.

    Science.gov (United States)

    Bossa, Matias; Zacur, Ernesto; Olmos, Salvador

    2010-07-01

    Tensor-based morphometry (TBM) is an analysis technique where anatomical information is characterized by means of the spatial transformations mapping a customized template with the observed images. Therefore, accurate inter-subject non-rigid registration is an essential prerequisite for both template estimation and image warping. Subsequent statistical analysis on the spatial transformations is performed to highlight voxel-wise differences. Most of previous TBM studies did not explore the influence of the registration parameters, such as the parameters defining the deformation and the regularization models. In this work performance evaluation of TBM using stationary velocity field (SVF) diffeomorphic registration was performed in a subset of subjects from Alzheimer's Disease Neuroimaging Initiative (ADNI) study. A wide range of values of the registration parameters that define the transformation smoothness and the balance between image matching and regularization were explored in the evaluation. The proposed methodology provided brain atrophy maps with very detailed anatomical resolution and with a high significance level compared with results recently published on the same data set using a non-linear elastic registration method. Copyright (c) 2010 Elsevier Inc. All rights reserved.

  2. Measurements of the velocity fields by PIV method round about titling gate

    Directory of Open Access Journals (Sweden)

    Mistrová Ivana

    2012-04-01

    Full Text Available The article deals with problems of using of measurement method Particle Image Velocimetry (PIV to measure velocity fields in the flowing water in front, above and behind drowned titling weir gate. The aim was to obtain information about the distribution of speed in the area of interest for the verification or calibration of the numerical model. Experiments were carried out in inclinable channel connected to the hydraulic circuit with a pump and storage tank at the Water Management Research Laboratory (LVV of Institute of Water Structures at the Faculty of Civil Engineering in Brno University of Technology. Hydraulic inclinable channel has cross-section with dimensions of 0.4×0.4m and length of 12.5m. The measured area has cross-section approximately 0.2m wide and 0.4m high and its length is 1m. The results of physical modelling allowed a comparison of experimental data with numerical simulation results of this type of flow in the commercial software ANSYS CFX-12.0.

  3. Effect of an external electric field on the propagation velocity of premixed flames

    KAUST Repository

    Sánchez-Sanz, Mario

    2015-01-01

    © 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. There have been many experimental investigations into the ability of electric fields to enhance combustion by acting upon ion species present in flames [1]. In this work, we examine this phenomenon using a one-dimensional model of a lean premixed flame under the influence of a longitudinal electric field. We expand upon prior two-step chain-branching reaction laminar models with reactions to model the creation and consumption of both a positively-charged radical species and free electrons. Also included are the electromotive force in the conservation equation for ion species and the electrostatic form of the Maxwell equations in order to resolve ion transport by externally applied and internally induced electric fields. The numerical solution of these equations allows us to compute changes in flame speed due to electric fields. Further, the variation of key kinetic and transport parameters modifies the electrical sensitivity of the flame. From changes in flame speed and reactant profiles we are able to gain novel, valuable insight into how and why combustion can be controlled by electric fields.

  4. Numerical simulation of bubble behavior in subcooled flow boiling under velocity and temperature gradient

    International Nuclear Information System (INIS)

    Bahreini, Mohammad; Ramiar, Abas; Ranjbar, Ali Akbar

    2015-01-01

    Highlights: • Condensing bubble is numerically investigated using VOF model in OpenFOAM package. • Bubble mass reduces as it goes through condensation and achieves higher velocities. • At a certain time the slope of changing bubble diameter with time, varies suddenly. • Larger bubbles experience more lateral migration to higher velocity regions. • Bubbles migrate back to a lower velocity region for higher liquid subcooling rates. - Abstract: In this paper, numerical simulation of the bubble condensation in the subcooled boiling flow is performed. The interface between two-phase is tracked via the volume of fluid (VOF) method with continuous surface force (CSF) model, implemented in the open source OpenFOAM CFD package. In order to simulate the condensing bubble with the OpenFOAM code, the original energy equation and mass transfer model for phase change have been modified and a new solver is developed. The Newtonian flow is solved using the finite volume scheme based on the pressure implicit with splitting of operators (PISO) algorithm. Comparison of the simulation results with previous experimental data revealed that the model predicted well the behavior of the actual condensing bubble. The bubble lifetime is almost proportional to bubble initial size and is prolonged by increasing the system pressure. In addition, the initial bubble size, subcooling of liquid and velocity gradient play an important role in the bubble deformation behavior. Velocity gradient makes the bubble move to the higher velocity region and the subcooling rate makes it to move back to the lower velocity region.

  5. Particle Agglomeration in Bipolar Barb Agglomerator Under AC Electric Field

    International Nuclear Information System (INIS)

    Huang Chao; Ma Xiuqin; Sun Youshan; Wang Meiyan; Zhang Changping; Lou Yueya

    2015-01-01

    The development of an efficient technology for removing fine particles in flue gas is essential as the haze is becoming more and more serious. To improve agglomeration effectiveness of fine particles, a dual zone electric agglomeration device consisting of a charging chamber and an agglomeration chamber with bipolar barb electrodes was developed. The bipolar barb electric agglomerator with a polar distance of 200 mm demonstrates good agglomeration effectiveness for particles with a size less than 8.0 μm under applied AC electric field. An optimal condition for achieving better agglomeration effectiveness was found to be as follows: flue gas flow velocity of 3.00 m/s, particle concentration of 2.00 g/m 3 , output voltage of 35 kV and length of the barb of 16 mm. In addition, 4.0–6.0 μm particles have the best effectiveness with the variation of particle volume occupancy of −3.2. (paper)

  6. Tribological Performance of Ni3Al Matrix Composites Synthesized by Laser Melt Deposition Under Different Scanning Velocities

    Science.gov (United States)

    Huang, Yuchun; Shi, Xiaoliang; Liu, Xiyao; Yan, Zhao; Deng, Xiaobin

    2018-02-01

    In order to study the effect of scanning velocity on the microstructure and tribological properties of Ni3Al matrix composites containing graphene nanoplatelets (NGs), a series of NG samples are successfully synthesized by laser melt deposition under the various scanning velocities from 300 to 500 mm s-1. The sliding friction tests of NG against GCr15 steel balls are carried out under 10 N and 0.2 m s-1 at room temperature. The microstructures, tribological properties and wear mechanisms of the NG samples are analyzed. The results show that the scanning velocity can be optimized to effectively control the surface hardness and relative density, as well as tribological performance of NG. The NG sample synthesized under scanning velocity of 450 mm s-1 has a dense and fine microstructure as well as excellent properties such as higher relative density (98.6%), lower friction coefficient (0.23) and wear rate (5.5 × 10-6 mm3 N-1 m-1). The lower substrate layer with dense and stable structure plays an important role in supporting the upper glaze layer with rich graphene and oxides, as well as nanocrystalline structure, which contributes to the excellent friction-reducing and wear resistance performances of NG. The research results could be used to guide the selection of suitable scanning velocity and study the wear mechanisms of NG for having excellent tribological performance.

  7. Exploiting LSPIV to assess debris-flow velocities in the field

    Science.gov (United States)

    Theule, Joshua I.; Crema, Stefano; Marchi, Lorenzo; Cavalli, Marco; Comiti, Francesco

    2018-01-01

    The assessment of flow velocity has a central role in quantitative analysis of debris flows, both for the characterization of the phenomenology of these processes and for the assessment of related hazards. Large-scale particle image velocimetry (LSPIV) can contribute to the assessment of surface velocity of debris flows, provided that the specific features of these processes (e.g. fast stage variations and particles up to boulder size on the flow surface) are taken into account. Three debris-flow events, each of them consisting of several surges featuring different sediment concentrations, flow stages, and velocities, have been analysed at the inlet of a sediment trap in a stream in the eastern Italian Alps (Gadria Creek). Free software has been employed for preliminary treatment (orthorectification and format conversion) of video-recorded images as well as for LSPIV application. Results show that LSPIV velocities are consistent with manual measurements of the orthorectified imagery and with front velocity measured from the hydrographs in a channel recorded approximately 70 m upstream of the sediment trap. Horizontal turbulence, computed as the standard deviation of the flow directions at a given cross section for a given surge, proved to be correlated with surface velocity and with visually estimated sediment concentration. The study demonstrates the effectiveness of LSPIV in the assessment of surface velocity of debris flows and permit the most crucial aspects to be identified in order to improve the accuracy of debris-flow velocity measurements.

  8. Velocity Fields and Galaxy Interaction in the Quartet of Galaxies ...

    Indian Academy of Sciences (India)

    2015-10-07

    Oct 7, 2015 ... Figure 3. Derived rotational curves of the galaxies. One pixel on the horizontal axis corre- sponds to 0.77 arcsec. For each plot, the radial velocity of the galaxy center, the angle and. PA of the sector used to obtain velocity data, as well as the inclination of galaxy used in the calculations are shown.

  9. Impact of velocity correlation and distribution on transport in fractured media: Field evidence and theoretical model

    Science.gov (United States)

    Kang, Peter K.; Le Borgne, Tanguy; Dentz, Marco; Bour, Olivier; Juanes, Ruben

    2015-02-01

    Flow and transport through fractured geologic media often leads to anomalous (non-Fickian) transport behavior, the origin of which remains a matter of debate: whether it arises from variability in fracture permeability (velocity distribution), connectedness in the flow paths through fractures (velocity correlation), or interaction between fractures and matrix. Here we show that this uncertainty of distribution- versus correlation-controlled transport can be resolved by combining convergent and push-pull tracer tests because flow reversibility is strongly dependent on velocity correlation, whereas late-time scaling of breakthrough curves is mainly controlled by velocity distribution. We build on this insight, and propose a Lagrangian statistical model that takes the form of a continuous time random walk (CTRW) with correlated particle velocities. In this framework, velocity distribution and velocity correlation are quantified by a Markov process of particle transition times that is characterized by a distribution function and a transition probability. Our transport model accurately captures the anomalous behavior in the breakthrough curves for both push-pull and convergent flow geometries, with the same set of parameters. Thus, the proposed correlated CTRW modeling approach provides a simple yet powerful framework for characterizing the impact of velocity distribution and correlation on transport in fractured media.

  10. Exploiting LSPIV to assess debris-flow velocities in the field

    Directory of Open Access Journals (Sweden)

    J. I. Theule

    2018-01-01

    Full Text Available The assessment of flow velocity has a central role in quantitative analysis of debris flows, both for the characterization of the phenomenology of these processes and for the assessment of related hazards. Large-scale particle image velocimetry (LSPIV can contribute to the assessment of surface velocity of debris flows, provided that the specific features of these processes (e.g. fast stage variations and particles up to boulder size on the flow surface are taken into account. Three debris-flow events, each of them consisting of several surges featuring different sediment concentrations, flow stages, and velocities, have been analysed at the inlet of a sediment trap in a stream in the eastern Italian Alps (Gadria Creek. Free software has been employed for preliminary treatment (orthorectification and format conversion of video-recorded images as well as for LSPIV application. Results show that LSPIV velocities are consistent with manual measurements of the orthorectified imagery and with front velocity measured from the hydrographs in a channel recorded approximately 70 m upstream of the sediment trap. Horizontal turbulence, computed as the standard deviation of the flow directions at a given cross section for a given surge, proved to be correlated with surface velocity and with visually estimated sediment concentration. The study demonstrates the effectiveness of LSPIV in the assessment of surface velocity of debris flows and permit the most crucial aspects to be identified in order to improve the accuracy of debris-flow velocity measurements.

  11. Dynamical system with plastic self-organized velocity field as an alternative conceptual model of a cognitive system.

    Science.gov (United States)

    Janson, Natalia B; Marsden, Christopher J

    2017-12-05

    It is well known that architecturally the brain is a neural network, i.e. a collection of many relatively simple units coupled flexibly. However, it has been unclear how the possession of this architecture enables higher-level cognitive functions, which are unique to the brain. Here, we consider the brain from the viewpoint of dynamical systems theory and hypothesize that the unique feature of the brain, the self-organized plasticity of its architecture, could represent the means of enabling the self-organized plasticity of its velocity vector field. We propose that, conceptually, the principle of cognition could amount to the existence of appropriate rules governing self-organization of the velocity field of a dynamical system with an appropriate account of stimuli. To support this hypothesis, we propose a simple non-neuromorphic mathematical model with a plastic self-organized velocity field, which has no prototype in physical world. This system is shown to be capable of basic cognition, which is illustrated numerically and with musical data. Our conceptual model could provide an additional insight into the working principles of the brain. Moreover, hardware implementations of plastic velocity fields self-organizing according to various rules could pave the way to creating artificial intelligence of a novel type.

  12. Measuring aortic pulse wave velocity using high-field cardiovascular magnetic resonance: comparison of techniques

    Directory of Open Access Journals (Sweden)

    Shaffer Jean M

    2010-05-01

    Full Text Available Abstract Background The assessment of arterial stiffness is increasingly used for evaluating patients with different cardiovascular diseases as the mechanical properties of major arteries are often altered. Aortic stiffness can be noninvasively estimated by measuring pulse wave velocity (PWV. Several methods have been proposed for measuring PWV using velocity-encoded cardiovascular magnetic resonance (CMR, including transit-time (TT, flow-area (QA, and cross-correlation (XC methods. However, assessment and comparison of these techniques at high field strength has not yet been performed. In this work, the TT, QA, and XC techniques were clinically tested at 3 Tesla and compared to each other. Methods Fifty cardiovascular patients and six volunteers were scanned to acquire the necessary images. The six volunteer scans were performed twice to test inter-scan reproducibility. Patient images were analyzed using the TT, XC, and QA methods to determine PWV. Two observers analyzed the images to determine inter-observer and intra-observer variabilities. The PWV measurements by the three methods were compared to each other to test inter-method variability. To illustrate the importance of PWV using CMR, the degree of aortic stiffness was assessed using PWV and related to LV dysfunction in five patients with diastolic heart failure patients and five matched volunteers. Results The inter-observer and intra-observer variability results showed no bias between the different techniques. The TT and XC results were more reproducible than the QA; the mean (SD inter-observer/intra-observer PWV differences were -0.12(1.3/-0.04(0.4 for TT, 0.2(1.3/0.09(0.9 for XC, and 0.6(1.6/0.2(1.4 m/s for QA methods, respectively. The correlation coefficients (r for the inter-observer/intra-observer comparisons were 0.94/0.99, 0.88/0.94, and 0.83/0.92 for the TT, XC, and QA methods, respectively. The inter-scan reproducibility results showed low variability between the repeated

  13. Faraday diamagnetism under slowly oscillating magnetic fields

    Science.gov (United States)

    Kimura, Tsunehisa; Kimura, Fumiko; Kimura, Yosuke

    2018-04-01

    Diamagnetism is a universal phenomenon of materials arising from the orbital motion of electrons bound to atoms, which is commonly known as Langevin diamagnetism. The orbital motion also occurs according to the Faraday's law of induction when the applied magnetic field is oscillating. However, the influence of this dynamic effect on the magnetism of materials has seldom been studied. Here, we propose a new type diamagnetism coined Faraday diamagnetism. The magnitude of this diamagnetism evaluated by an atomic electric circuit model was as large as that of Langevin diamagnetism. The predicted scale of Faraday diamagnetism was supported by experiments.

  14. Magnetohydrodynamic flow of generalized Maxwell fluids in a rectangular micropump under an AC electric field

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Guangpu [School of Mathematical Science, Inner Mongolia University, Hohhot, Inner Mongolia 010021 (China); Jian, Yongjun, E-mail: jianyj@imu.edu.cn [School of Mathematical Science, Inner Mongolia University, Hohhot, Inner Mongolia 010021 (China); Chang, Long [School of Mathematics and Statistics, Inner Mongolia University of Finance and Economics, Hohhot, Inner Mongolia 010051 (China); Buren, Mandula [School of Mathematical Science, Inner Mongolia University, Hohhot, Inner Mongolia 010021 (China)

    2015-08-01

    By using the method of separation of variables, an analytical solution for the magnetohydrodynamic (MHD) flow of the generalized Maxwell fluids under AC electric field through a two-dimensional rectangular micropump is reduced. By the numerical computation, the variations of velocity profiles with the electrical oscillating Reynolds number Re, the Hartmann number Ha, the dimensionless relaxation time De are studied graphically. Further, the comparison with available experimental data and relevant researches is presented. - Highlights: • MHD flow of the generalized Maxwell fluids under AC electric field is analyzed. • The MHD flow is confined to a two-dimensional rectangular micropump. • Analytical solution is obtained by using the method of separation of variables. • The influences of related parameters on the MHD velocity are discussed.

  15. Magnetohydrodynamic flow of generalized Maxwell fluids in a rectangular micropump under an AC electric field

    International Nuclear Information System (INIS)

    Zhao, Guangpu; Jian, Yongjun; Chang, Long; Buren, Mandula

    2015-01-01

    By using the method of separation of variables, an analytical solution for the magnetohydrodynamic (MHD) flow of the generalized Maxwell fluids under AC electric field through a two-dimensional rectangular micropump is reduced. By the numerical computation, the variations of velocity profiles with the electrical oscillating Reynolds number Re, the Hartmann number Ha, the dimensionless relaxation time De are studied graphically. Further, the comparison with available experimental data and relevant researches is presented. - Highlights: • MHD flow of the generalized Maxwell fluids under AC electric field is analyzed. • The MHD flow is confined to a two-dimensional rectangular micropump. • Analytical solution is obtained by using the method of separation of variables. • The influences of related parameters on the MHD velocity are discussed

  16. Global positioning system data analysis: velocity ranges and a new definition of sprinting for field sport athletes.

    Science.gov (United States)

    Dwyer, Dan B; Gabbett, Tim J

    2012-03-01

    Global positioning system (GPS) technology has improved the speed, accuracy, and ease of time-motion analyses of field sport athletes. The large volume of numerical data generated by GPS technology is usually summarized by reporting the distance traveled and time spent in various locomotor categories (e.g., walking, jogging, and running). There are a variety of definitions used in the literature to represent these categories, which makes it nearly impossible to compare findings among studies. The purpose of this work was to propose standard definitions (velocity ranges) that were determined by an objective analysis of time-motion data. In addition, we discuss the limitations of the existing definition of a sprint and present a new definition of sprinting for field sport athletes. Twenty-five GPS data files collected from 5 different sports (men's and women's field hockey, men's and women's soccer, and Australian Rules Football) were analyzed to identify the average velocity distribution. A curve fitting process was then used to determine the optimal placement of 4 Gaussian curves representing the typical locomotor categories. Based on the findings of these analyses, we make recommendations about sport-specific velocity ranges to be used in future time-motion studies of field sport athletes. We also suggest that a sprint be defined as any movement that reaches or exceeds the sprint threshold velocity for at least 1 second and any movement with an acceleration that occurs within the highest 5% of accelerations found in the corresponding velocity range. From a practical perspective, these analyses provide conditioning coaches with information on the high-intensity sprinting demands of field sport athletes, while also providing a novel method of capturing maximal effort, short-duration sprints.

  17. Behavior of impurity ion velocities during the pulsed poloidal current drive in the Madison symmetric torus reversed-field pinch

    International Nuclear Information System (INIS)

    Sakakita, Hajime; Craig, Darren; Anderson, Jay K.; Chapman, Brett E.; Den-Hartog, Daniel J.; Prager, Stewart C.; Biewer, Ted M.; Terry, Stephen D.

    2003-01-01

    We report on passive measurements of impurity ion velocities during the pulsed poloidal current drive (PPCD) in the Madison Symmetric Torus reversed-field pinch. During PPCD, the electron temperature increased and a sudden reduction of magnetic fluctuations was observed. For this change, we have studied whether plasma velocity is affected. Plasma rotation is observed to decrease during PPCD. From measurements of line intensities for several impurities at 10 poloidal chords, it is found that the impurity line emission shifts outward. The ion temperature of impurities is reasonably connected to that measured by charge exchange recombination spectroscopy from core to edge. (author)

  18. On magnetic field strength effect on velocity and turbulence characterization using Phase-Contrast Magnetic Resonance Imaging (PC-MRI)

    Science.gov (United States)

    van de Moortele, Pierre-Francois; Amili, Omid; Coletti, Filippo; Toloui, Mostafa

    2017-11-01

    Cardiovascular flows are predominantly laminar. Nevertheless, transient and even turbulent flows have been observed in the vicinity of the heart (e.g. valves, ascending aorta, valvular/vascular stenosis). Effective in-vivo hemodynamic-based diagnostics in these sites require both high-resolution velocity measurements (especially in the near-vessel wall regions) and accurate evaluation of blood flow turbulence level (e.g. in terms of TKE). In addition to phase contrast (PC), appropriately designed PC-MRI sequences provide intravoxel incoherent motion encoding, a unique tool for simultaneous, non-invasive evaluation of velocity 3D vector fields and Reynolds stresses in cardiovascular flows in vivo. However, limited spatial and temporal resolution of PC-MRI result in inaccuracies in the estimation of hemodynamics (e.g. WSS) and of flow turbulence characteristics. This study aims to assess whether SNR gains at higher magnetic field could overcome these limits, providing more accurate velocity and turbulence characterization at higher spatial resolution. Experiments are conducted on MR Scanners at 3 and 7 Tesla with a U-bent pipe flow shaped phantom. 3D velocity fields, Reynolds stresses and TKE are analyzed and compared to a reference PIV experiments.

  19. Water droplet deformation under the motion in gas area with subsonic velocities

    Directory of Open Access Journals (Sweden)

    Kuibin Pavel A.

    2015-01-01

    Full Text Available The experimental investigation of water droplet deformation (characteristic dimensions 3 ÷ 6 mm when moving through the gas area (air with 1÷ 5 m/s velocities was carried out. The high-speed (delay time between the frames is less than 100 ns tools of cross-correlation videorecording were used. A cyclic change nature of the droplet shapes (from close to spherical to conditionally ellipsoidal was found. The characteristic times of “deformation cycles” and the maximal deviations of droplet dimensions relative to initial dimensions were determined. The influence of droplet velocities and its dimensions on the deformation characteristics was determined.

  20. Flow velocities and bed shear stresses in a stone cover under an oscillatory flow

    DEFF Research Database (Denmark)

    Stenanato, F.; Nielsen, Anders Wedel; Sumer, B. Mutlu

    2010-01-01

    layers of stones. The flow velocities in the pores of the stones were measured using LDA (Laser Doppler Anemometer). In addition to the velocity measurements, the bed shear stresses were also measured using a hotfilm (Constant Temperature Anemometry). It is found that the boundary layer of the outer flow...... current boundary layer without any externally generated turbulence. The bd shear stress is found to be very low, more than ten times smaller than in the case of a smooth base bottom without stone cover....

  1. Balance velocities of the Greenland ice sheet

    DEFF Research Database (Denmark)

    Joughin, I.; Fahnestock, M.; Ekholm, Simon

    1997-01-01

    We present a map of balance velocities for the Greenland ice sheet. The resolution of the underlying DEM, which was derived primarily from radar altimetery data, yields far greater detail than earlier balance velocity estimates for Greenland. The velocity contours reveal in striking detail......, the balance map is useful for ice-sheet modelling, mass balance studies, and field planning....

  2. Effect of Gas Velocity on the Dust Sediment Layer in the Coupled Field of Corona Plasma and Cyclone

    International Nuclear Information System (INIS)

    Wei Mingshan; Ma Chaochen; Li Minghua; Danish, S N

    2006-01-01

    A dust sediment layer was found on the outer tube wall when the ESCP (electrostatic centrifugal precipitator) trapped diesel particulates or ganister sand. The Compton back scatter method was used to measure the sediment thickness during the experiment. The effect of the inlet gas velocity on the dust sediment layer was investigated. PIV (Particle Image Velocimetry) was used to measure the velocity field between the inner barb tube wall and the outer tube wall. Experiments showed that the thickness of the sediment increased with time, and the sediment layer at the lower end was much thicker than that at the upper end. The agglomeration on the outer tube wall could be removed when the inlet gas velocity was increased to a certain value

  3. Surface wave waveform inversions for local shear-wave velocities under eastern Australia

    NARCIS (Netherlands)

    Passier, M.L.; Hilst, R.D. van der; Snieder, R.K.

    1997-01-01

    The waveform inversion method developed by Kushnir et al. [1989] and expanded by Passier and Snieder [1995b] yields estimates of structure along short interstation paths and of average velocity gradients. In contrast, 3D tomographic inversions yield local estimates of the earth structure by

  4. Crustal Deformation in the Northern Andes - New GPS Velocity Field and "Broken Indentor" Model

    Science.gov (United States)

    Kellogg, J. N.; Mora-Páez, H.; Freymueller, J. T.

    2017-12-01

    We present a new precise velocity field for northwestern South America and the southwest Caribbean based on GPS CORS (Continuously Operating Reference Stations) in Panama (ACP and COCONet) and Colombia (GeoRED) with a minimum of 2.5 years of observations. This paper presents the first comprehensive model of North Andean block (NAB) motion. We estimate that the NAB is moving to the northeast at a rate of 8.6 mm/yr. The NAB vector can be resolved into a margin-parallel (035°) component of 8.1 mm/yr rigid "escape" and a margin-normal (125°) component of 4.3 mm/yr. The margin-normal shortening of only 4.3 mm/yr in the Eastern Cordillera of Colombia is surprising in view of paleobotanical, fission-track, and seismic reflection data that suggest rapid uplift (7 km) and shortening (120 km) in the last 10 Ma. We present a "broken indenter" model for the Panama-Choco arc, in which the Choco arc has been recently accreted to the NAB, resulting in a rapid decrease in shortening in the Eastern Cordillera. The Panama arc is colliding eastward with the NAB at approximately 16-17 mm/yr, and the Panama-Choco collision may have been responsible for much of the uplift of the Eastern Cordillera. The present on-going collision poses a major earthquake hazard from the Panama-Colombia border to Medellin, Colombia. Since the northeastward margin-parallel "escape" rate is now greater than the rate of shortening in the Eastern Cordillera, northeast trending right-lateral strike-slip faulting is the primary seismic hazard for the 8 million inhabitants of the city of Bogota. There continues to be a high risk of a great mega-subduction zone earthquake in southern Colombia from the Ecuador-Colombia trench. Trench earthquakes have only released a fraction of the energy accumulated in the trench since the great 1906 earthquake, and interseismic strain is accumulating rapidly as far north as Tumaco.

  5. Shape, size, velocity and field-aligned currents of dayside plasma injections: a multi-altitude study

    Directory of Open Access Journals (Sweden)

    A. Marchaudon

    2009-03-01

    Full Text Available On 20 February 2005, Cluster in the outer magnetosphere and Double Star-2 (TC-2 at mid-altitude are situated in the vicinity of the northern cusp/mantle, with Cluster moving sunward and TC-2 anti-sunward. Their magnetic footprints come very close together at about 15:28 UT, over the common field-of-view of SuperDARN radars. Thanks to this conjunction, we determine the velocity, the transverse sizes, perpendicular and parallel to this velocity, and the shape of three magnetic flux tubes of magnetosheath plasma injection. The velocity of the structures determined from the Cluster four-spacecraft timing analysis is almost purely antisunward, in contrast with the antisunward and duskward convection velocity inside the flux tubes. The transverse sizes are defined from the Cluster-TC-2 separation perpendicular to the magnetic field, and from the time spent by a Cluster spacecraft in one structure; they are comprised between 0.6 and 2 RE in agreement with previous studies. Finally, using a comparison between the eigenvectors deduced from a variance analysis of the magnetic perturbation at the four Cluster and at TC-2, we show that the upstream side of the injection flux tubes is magnetically well defined, with even a concave front for the third one giving a bean-like shape, whereas the downstream side is far more turbulent. We also realise the first quantitative comparison between field-aligned currents at Cluster calculated with the curlometer technique and with the single-spacecraft method, assuming infinite parallel current sheets and taking into account the velocity of the injection flux tubes. The results agree nicely, confirming the validity of both methods. Finally, we compare the field-aligned current distribution of the three injection flux tubes at the altitudes of Cluster and TC-2. Both profiles are fairly similar, with mainly a pair of opposite field-aligned currents, upward at low-latitude and downward at high-latitude. In terms of

  6. Effects of Vegetation Morphology on Mean Velocity and Turbulence Intensity under Oscillatory Flows and Their Implications for Sediment Transport in Benthic Zone

    Science.gov (United States)

    San Juan Blanco, J. E.; Veliz, G.; Tinoco, R. O.

    2016-12-01

    Aquatic vegetation modifies the flow by generating coherent structures and imposing resistance. Flow-vegetation interaction becomes function of individual plant morphology (stem and leaf shape and dimensions), canopy density, and spatial distribution of vegetation. We investigate the effect of plant morphology on turbulence intensity under oscillatory flows. By using a state-of-the-art 3D volumetric Particle Image Velocimetry system (3D-PIV), we characterize the mean velocity and turbulence statistics near and around submerged vegetation within an oscillatory tunnel. The U-shape oscillatory tunnel allows us to reproduce well-defined waves over a wide range of periods and amplitudes, whereas the 3D-PIV system allows us to obtain instantaneous velocity fields with high temporal frequency and spatial resolution in the vicinity of several types of vegetation. Our study of the three-dimensional velocity field provides further insight into the near-bed flow conditions and its interactions with the observed leaf-, stem- and canopy-scale flow structures, which in turn control resuspension and deposition of sediment within and around patches of vegetation. Since vegetation-induced turbulence drives essential transport mechanisms for ecosystem development, such as gas exchange, nutrient transport, bed and suspended sediment transport, among others, characterization of its dependence on plant morphology and flow conditions will improve our understanding of their role in aquatic environments and the impacts caused by human activities on coastal and tidal vegetated areas.

  7. Experimental study and theoretical interpretation of saturation effect on ultrasonic velocity in tight sandstones under different pressure conditions

    Science.gov (United States)

    Li, Dongqing; Wei, Jianxin; Di, Bangrang; Ding, Pinbo; Huang, Shiqi; Shuai, Da

    2018-03-01

    Understanding the influence of lithology, porosity, permeability, pore structure, fluid content and fluid distribution on the elastic wave properties of porous rocks is of great significance for seismic exploration. However, unlike conventional sandstones, the petrophysical characteristics of tight sandstones are more complex and less understood. To address this problem, we measured ultrasonic velocity in partially saturated tight sandstones under different effective pressures. A new model is proposed, combining the Mavko-Jizba-Gurevich relations and the White model. The proposed model can satisfactorily simulate and explain the saturation dependence and pressure dependence of velocity in tight sandstones. Under low effective pressure, the relationship of P-wave velocity to saturation is pre-dominantly attributed to local (pore scale) fluid flow and inhomogeneous pore-fluid distribution (large scale). At higher effective pressure, local fluid flow gradually decreases, and P-wave velocity gradually shifts from uniform saturation towards patchy saturation. We also find that shear modulus is more sensitive to saturation at low effective pressures. The new model includes wetting ratio, an adjustable parameter that is closely related to the relationship between shear modulus and saturation.

  8. DNA Concentration Due To Migration Under Parallel Fields

    Science.gov (United States)

    Montes, Ryan; Ladd, Anthony; Butler, Jason

    2017-11-01

    Pressure driven flow of DNA solutions through a microchannel (100-400 micron) in the presence of an opposing electric field, generates a net migration of DNA towards the walls. Over time a strongly inhomogeneous distribution of DNA develops in the channel with almost all the DNA localized within 10 micron of the walls. Near the walls the electrophoretic velocity drives a return flux of DNA towards the inlet. Thus despite an average fluid velocity that is at least 10 times the electrophoretic velocity, almost all the DNA remains trapped within the device. Experimental observations have provided unambiguous evidence that DNA migration occurs as outlined above, and that the migration is necessary for trapping. The mechanism inducing this DNA migration has been attributed to hydrodynamic interactions induced by the electric field. Migration due to viscoelasticity is another possibility, but a series of experiments systematically varying the ionic strength of the buffer solution verify that the electrically-induced flow, not the viscoelasticity, is the cause of the migration. This migration mechanism can be used to purify and concentrate DNA within micro-TAS devices.

  9. Temperature and velocity fields in natural convection by PIV and LIF

    DEFF Research Database (Denmark)

    Meyer, Knud Erik; Larsen, Poul Scheel; Westergaard, C. H.

    2002-01-01

    plate and cooled walls is 1.4×10^10. The flow is turbulent and is similar to some indoor room flows. Combined Particle Image Velocimetry (PIV) and Planar Light Induced Fluorescence (LIF) are used to measure local velocities and temperatures. Data measured in a symmetry plane parallel to a sidewall...

  10. Development of two-dimensional velocity field measurement using particle tracking velocimetry on neutron radiography

    International Nuclear Information System (INIS)

    Saito, Y.; Mishima, K.; Suzuki, T.; Matsubayashi, M.

    2003-01-01

    The structures of liquid metal two-phase flow are investigated for analyzing the core meltdown accident of fast reactor. The experiments of high-density ratio two-phase flow for lead-bismuth molten metal and nitrogen gases are conducted to understand in detail. The liquid phase velocity distributions of lead-bismuth molten metal are measured by neutron radiography using Au-Cd tracer particles. The liquid phase velocity distributions are obtained usually by using particle image velocimetry (PIV) on the neutron radiography. The PIV, however is difficult to get the velocity vector distribution quantitatively. An image of neutron radiography is divided into two images of the bubbles and the tracer particles each in particle tracking velocimetry (PTV), which distinguishes tracer contents in the bubble from them in the liquid phase. The locations of tracer particles in the liquid phase are possible to determine by particle mask correlation method, in which the bubble images are separated from the tracer images by Σ-scaling method. The particle tracking velocimetry give a full detail of the velocity vector distributions of the liquid phase in two-phase flow, in comparison with the PIV method. (M. Suetake)

  11. Child Mortality as Predicted by Nutritional Status and Recent Weight Velocity in Children under Two in Rural Africa.

    LENUS (Irish Health Repository)

    2012-01-31

    WHO has released prescriptive child growth standards for, among others, BMI-for-age (BMI-FA), mid-upper arm circumference-for-age, and weight velocity. The ability of these indices to predict child mortality remains understudied, although growth velocity prognostic value underlies current growth monitoring programs. The study aims were first to assess, in children under 2, the independent and combined ability of these indices and of stunting to predict all-cause mortality within 3 mo, and second, the comparative abilities of weight-for-length (WFL) and BMI-FA to predict short-term (<3 mo) mortality. We used anthropometry and survival data from 2402 children aged between 0 and 24 mo in a rural area of the Democratic Republic of Congo with high malnutrition and mortality rates and limited nutritional rehabilitation. Analyses used Cox proportional hazard models and receiver operating characteristic curves. Univariate analysis and age-adjusted analysis showed predictive ability of all indices. Multivariate analysis without age adjustment showed that only very low weight velocity [HR = 3.82 (95%CI = 1.91, 7.63); P < 0.001] was independently predictive. With age adjustment, very low weight velocity [HR = 3.61 (95%CI = 1.80, 7.25); P < 0.001] was again solely retained as an independent predictor. There was no evidence for a difference in predictive ability between WFL and BMI-FA. This paper shows the value of attained BMI-FA, a marker of wasting status, and recent weight velocity, a marker of the wasting process, in predicting child death using the WHO child growth standards. WFL and BMI-FA appear equivalent as predictors.

  12. The 3-D strain patterns in Turkey using geodetic velocity fields from the RTK-CORS (TR) network

    Science.gov (United States)

    Kutoglu, Hakan Senol; Toker, Mustafa; Mekik, Cetin

    2016-03-01

    This study presents our use of GPS data to obtain and quantify the full continuous strain tensor using a 3-D velocity field in Turkey. In this study, GPS velocities improve the estimation of short-term strain tensor fields for determining the seismic hazard of Turkey. The tensorial analysis presents different aspects of deformation, such as the normal and shear strains, including their directions, the compressional and extensional strains. This analysis is appropriate for the characterizing the state of the current seismic deformation. GPS velocity data from continuous measurements (2009-2012) to estimate deformations were processed using the GAMIT/GLOBK software. Using high-rate GPS data from permanent 146 GNSS stations (RTK-CORS-TR network), the strain distribution was determined and interpolated using a biharmonic spline technique. We show the strain field patterns within axial and plane form at several critical locations, and discuss these results within the context of the seismic and tectonic deformation of Turkey. We conclude that the knowledge of the crustal strain patterns provides important information on the location of the main faults and strain accumulation for the hazard assessment. The results show an agreement between the seismic and tectonic strains confirming that there are active crustal deformations in Turkey.

  13. Application of Multi-Plane Particle Shadow Velocimetry to Obtain Velocity Fields Through an Optically Clear Object

    Science.gov (United States)

    Hinkle, Steven; Truong, Christine; Sinding, Kyle; Jefferies, Rhett; Harris, Jeff; Krane, Michael

    2016-11-01

    Particle Shadow Velocimetry (PSV) is performed using an LED array to illuminate a volume of fluid rather than individual two-dimensional laser sheets as is done in Particle Image Velocimetry (PIV). Multi-plane PSV is a technique that is able to take advantage of the volumetric illumination of PSV to simultaneously take velocity field measurements in two different planes along the same optical axis within the fluid flow. This technique can be further extended to resolve flow fields around and through clear objects to obtain measurements along the optical axis both in front of and behind the object. A proof of concept application of taking images both in front of and behind cylindrical rods is presented. The rods, one made of clear acrylic and the other borosilicate glass, were chosen to have an index of refraction close to that of the surrounding fluid. Two different calibration targets are arranged on either side of the cylinder and simultaneous images are taken to show that velocity measurements in front of and behind the rod are possible to obtain utilizing multi-plane PSV. This methodology will be implemented in future measurements to obtain velocity fields for an airfoil on both the suction and pressure sides simultaneously in fully developed turbulent flow. Penn State ARL.

  14. Velocity map imaging of attosecond and femtosecond dynamics in atoms and small molecules in strong laser fields

    International Nuclear Information System (INIS)

    Kling, M.F.; Ni, Yongfeng; Lepine, F.; Khan, J.I.; Vrakking, M.J.J.; Johnsson, P.; Remetter, T.; Varju, K.; Gustafsson, E.; L'Huillier, A.; Lopez-Martens, R.; Boutu, W.

    2005-01-01

    Full text: In the past decade, the dynamics of atomic and small molecular systems in strong laser fields has received enormous attention, but was mainly studied with femtosecond laser fields. We report on first applications of attosecond extreme ultraviolet (XUV) pulse trains (APTs) from high-order harmonic generation (HHG) for the study of atomic and molecular electron and ion dynamics in strong laser fields utilizing the Velocity Map Imaging Technique. The APTs were generated in argon from harmonics 13 to 35 of a 35 fs Ti:sapphire laser, and spatially and temporally overlapped with an intense IR laser field (up to 5x10 13 W/cm 2 ) in the interaction region of a Velocity Map Imaging (VMI) machine. In the VMI setup, electrons and ions that were created at the crossing point of the laser fields and an atomic or molecular beam were accelerated in a dc-electric field towards a two-dimensional position-sensitive detector, allowing to reconstruct the full initial three-dimensional velocity distribution. The poster will focus on results that were obtained for argon atoms. We recorded the velocity distribution of electron wave packets that were strongly driven in the IR laser field after their generation in Ar via single-photon ionization by attosecond XUV pulses. The 3D evolution of the electron wave packets was observed on an attosecond timescale. In addition to earlier experiments with APTs using a magnetic bottle electron time-of-flight spectrometers and with single attosecond pulses, the angular dependence of the electrons kinetic energies can give further insight into the details of the dynamics. Initial results that were obtained for molecular systems like H 2 , D 2 , N 2 , and CO 2 using the same powerful approach will be highlighted as well. We will show, that detailed insight into the dynamics of these systems in strong laser fields can be obtained (e.g. on the alignment, above-threshold ionization, direct vs. sequential two-photon ionization, dissociation, and

  15. The transition of dynamic rupture styles in elastic media under velocity-weakening friction

    KAUST Repository

    Gabriel, A.-A.

    2012-09-01

    Although kinematic earthquake source inversions show dominantly pulse-like subshear rupture behavior, seismological observations, laboratory experiments and theoretical models indicate that earthquakes can operate with different rupture styles: either as pulses or cracks, that propagate at subshear or supershear speeds. The determination of rupture style and speed has important implications for ground motions and may inform about the state of stress and strength of active fault zones. We conduct 2D in-plane dynamic rupture simulations with a spectral element method to investigate the diversity of rupture styles on faults governed by velocity-and-state-dependent friction with dramatic velocity-weakening at high slip rate. Our rupture models are governed by uniform initial stresses, and are artificially initiated. We identify the conditions that lead to different rupture styles by investigating the transitions between decaying, steady state and growing pulses, cracks, sub-shear and super-shear ruptures as a function of background stress, nucleation size and characteristic velocity at the onset of severe weakening. Our models show that small changes of background stress or nucleation size may lead to dramatic changes of rupture style. We characterize the asymptotic properties of steady state and self-similar pulses as a function of background stress. We show that an earthquake may not be restricted to a single rupture style, but that complex rupture patterns may emerge that consist of multiple rupture fronts, possibly involving different styles and back-propagating fronts. We also demonstrate the possibility of a super-shear transition for pulse-like ruptures. Finally, we draw connections between our findings and recent seismological observations.

  16. Coefficient of Friction Measurements for Thermoplastics and Fiber Composites under Low Sliding Velocity and High Pressure

    DEFF Research Database (Denmark)

    Poulios, Konstantinos; Svendsen, G.; Hiller, Jochen

    2012-01-01

    materials which are untypical for brake applications, like thermoplastics and fiber composites, can offer superior performance in terms of braking torque, wear resistance and cost than typical brake linings. In this paper coefficient of friction measurements for various thermoplastic and fiber composite......Friction materials for typical brake applications are normally designed considering thermal stability as the major performance criterion. There are however brake applications with very limited sliding velocities, where the generated heat is insignificant. In such cases it is possible that friction...

  17. Coefficient of Friction Measurements for Thermoplastics and Fibre Composites Under Low Sliding Velocity and High Pressure

    DEFF Research Database (Denmark)

    Poulios, Konstantinos; Svendsen, Gustav Winther; Hiller, Jochen

    2013-01-01

    that friction materials which are untypical for brake applications, like thermoplastics and fibre composites, can offer superior performance in terms of braking torque, wear resistance and cost than typical brake linings. In this paper coefficient of friction measurements for various thermoplastic and fibre......Friction materials for typical brake applications are normally designed considering thermal stability as the major performance criterion. There are, however, brake applications with very limited sliding velocities, where the generated heat is insignificant. In such cases it is possible...... in order to interpret the changes of friction observed during the running-in phase....

  18. Heat transfer simulation of motorcycle fins under varying velocity using CFD method

    Science.gov (United States)

    Shahril, K.; Mohd Kasim, Nurhayati Binti; Sabri, M.

    2013-12-01

    Motorcycle engine releases heat to the atmosphere through the mode of force convection. To solve this, fins are provided on the outer of the cylinder. The heat transfer rate is defined depending on the velocity of vehicle, fin geometry and the ambient temperature. Increasing the temperature difference between the object and the environment, increasing the convection heat transfer coefficient, or increasing the surface area of the object increases the heat transfer. Many experimental methods are available in literature to analyze the effect of these factors on the heat transfer rate. However, CFD analysis will be use to simulate the heat transfer of the engine block. ANSYS software is selected to run the simulation.

  19. In-cylinder velocity field measurements in a motored diesel engine

    Energy Technology Data Exchange (ETDEWEB)

    Cipolla, G.; Puglisi, A.; Vafidis, C.

    1987-01-01

    Measurements of three velocity components and of the corresponding turbulent fluctuations are reported obtained by laser Doppler anemometry in the cylinder of a FIAT-IVECO 8140 DI Diesel engine motored at 1000 rpm with a 16:1 compression ratio. The results show that the air swirl velocities at inlet valve closure are axially stratified while the intake-generated axial flow structures persist, although decaying, up to 70/sup 0/ BTDC when the squish effect transforms the in-cylinder flow structure. The presence of a flow towards the piston crevice is detected at 20/sup 0/ BTDC while at TDC of compression the formation of, at least, one toroidal vortex in the axial plane inside the piston bowl is detected. The findings of this investigation are compared with similar measurements in simplified engine configurations and reveal a satisfactory qualitative as well as quantitative agreement.

  20. Statistically optimized near field acoustic holography using an array of pressure-velocity probes

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Jaud, Virginie

    2007-01-01

    of a measurement aperture that extends well beyond the source can be relaxed. Both NAH and SONAH are based on the assumption that all sources are on one side of the measurement plane whereas the other side is source free. An extension of the SONAH procedure based on measurement with a double layer array...... of pressure microphones has been suggested. The double layer technique makes it possible to distinguish between sources on the two sides of the array and thus suppress the influence of extraneous noise coming from the “wrong” side. It has also recently been demonstrated that there are significant advantages...... in NAH based on an array of acoustic particle velocity transducers (in a single layer) compared with NAH based on an array of pressure microphones. This investigation combines the two ideas and examines SONAH based on an array of pressure-velocity intensity probes through computer simulations as well...

  1. Influence of initial velocity on trajectories of a charged particle in uniform crossed electric and magnetic fields

    International Nuclear Information System (INIS)

    Khotimah, Siti Nurul; Viridi, Sparisoma; Widayani

    2017-01-01

    Magnetic and electric fields can cause a charged particle to form interesting trajectories. In general, each trajectory is discussed separately in university physics textbooks for undergraduate students. In this work, a solution of a charged particle moving in a uniform electric field at right angles to a uniform magnetic field (uniform crossed electric and magnetic fields) is reported; it is limited to particle motion in a plane. Specific solutions and their trajectories are obtained only by varying the initial particle velocity. The result shows five basic trajectory patterns, i.e., straight line, sinusoid-like, cycloid, cycloid-like with oscillation, and circle-like. The region of each trajectory is also mapped in the initial velocity space of the particle. This paper is intended for undergraduate students and describes further the trajectories of a charged particle through the regions of electric and magnetic fields influenced by initial condition of the particle, where electromagnetic radiation of an accelerated particle is not considered. (paper)

  2. Studying the instantaneous velocity field in gas-sheared liquid films in a horizontal duct

    Science.gov (United States)

    Vasques, Joao; Tokarev, Mikhail; Cherdantsev, Andrey; Hann, David; Hewakandamby, Buddhika; Azzopardi, Barry

    2016-11-01

    In annular flow, the experimental validation of the basic assumptions on the liquid velocity profile is vital for developing theoretical models of the flow. However, the study of local velocity of liquid in gas-sheared films has proven to be a challenging task due to the highly curved and disturbed moving interface of the phases, small scale of the area of interrogation, high velocity gradients and irregular character of the flow. This study reports on different optical configurations and interface-tracking methods employed in a horizontal duct in order to obtain high-resolution particle image velocimetry (PIV) data in such types of complex flows. The experimental envelope includes successful measurements in 2D and 3D waves regimes, up to the disturbance wave regime. Preliminary data show the presence of complex structures in the liquid phase, which includes re-circulation areas below the liquid interface due to the gas-shearing action, together with non-uniform transverse movements of the liquid phase close to the wall due to the presence of 3D waves at the interface. With the aid of the moving interface-tracking, PIV, time-resolved particle-tracking velocimetry and vorticity measurements were performed.

  3. Stresses of PTT, Giesekus, and Oldroyd-B fluids in a Newtonian velocity field near the stick-slip singularity

    Science.gov (United States)

    Evans, J. D.; Palhares Junior, I. L.; Oishi, C. M.

    2017-12-01

    We characterise the stress singularity of the Oldroyd-B, Phan-Thien-Tanner (PTT), and Giesekus viscoelastic models in steady planar stick-slip flows. For both PTT and Giesekus models in the presence of a solvent viscosity, the asymptotics show that the velocity field is Newtonian dominated near to the singularity at the join of the stick and slip surfaces. Polymer stress boundary layers are present at both the stick and slip surfaces. By integrating along streamlines, we verify the polymer stress behavior of r-4/11 for PTT and r-5/16 for Giesekus, where r is the radial distance from the singularity. These asymptotic results for PTT and Giesekus do not hold in the limit of vanishing quadratic stress terms for Oldroyd-B. However, we can consider the Oldroyd-B model in the fixed kinematics of a prescribed Newtonian velocity field. In contrast to PTT and Giesekus, this is not the correct balance for the momentum equation but does allow insight into the behavior of the Oldroyd-B equations near the singularity. A three-region asymptotic structure is again apparent with now a polymer stress singularity of r-4/5. The high Weissenberg boundary layer equations are found to manifest themselves at the stick surface and are of thickness r3/2. At the slip surface, dominant balance between the upper convected stress and rate-of-strain terms gives a slip boundary layer of thickness r2. The solution of the slip boundary layer shows that the polymer stress is now singular along the slip surface. These results are supported through numerical integration along streamlines of the Oldroyd-B equations in a Newtonian velocity field. The Oldroyd-B model thus extends the point singularity at the join of the stick and slip surfaces to the whole of slip surface. As such, it does not have a physically meaningful solution in a Newtonian velocity field. We would expect a similar stress behavior for this model in the true viscoelastic velocity field.

  4. Solution-gated graphene field effect transistors integrated in microfluidic systems and used for flow velocity detection.

    Science.gov (United States)

    He, Rong Xiang; Lin, Peng; Liu, Zhi Ke; Zhu, Hong Wei; Zhao, Xing Zhong; Chan, Helen L W; Yan, Feng

    2012-03-14

    Solution-gated graphene field effect transistors (SGGT) were integrated in microfluidic systems. The transfer characteristics of a SGGT with an Ag/AgCl gate electrode shifted horizontally with the change of the ionic concentration of KCl solution in the microchannel and the relationship can be fitted with the Nernst equation, which was attributed to the change of the potential drop at the Ag/AgCl electrode. Therefore the gate electrode is one important factor for the ion sensitive property of the SGGT. Then SGGTs were used as flow velocity sensors, which were based on measuring the streaming potentials in microfluidic channels. A linear relationship between the shift of the transfer curve of the SGGT and the flow velocity was obtained, indicating that the SGGT is a promising transducer for measuring flow velocity in a microchip. Since the streaming potential is influenced by the three physical quantities, including the flow velocity, the ionic strength of the fluid and the zeta potential of the substrate, the device can be used for sensing any one of the three quantities when the other two were known. It is noteworthy that SGGTs have been used for various types of chemical and biological sensors. Array of the devices integrated in multichannel microchips are expected to find many important applications in the lab-on-a-chip systems in the future. © 2012 American Chemical Society

  5. Numerical Simulation of Pre-heated Confined PBX Charge Under Low Velocity

    Science.gov (United States)

    Hu, Cai; Wu, Yanqing; Huang, Fenglei; Liu, Yan; Explosion; damage Team

    2017-06-01

    Impact sensitivity and thermal safety are very important for explosive safety usage.To investigate the effect of thermal softening on impact sensitivity of HMX-based PBX, a finite element model aiming at pre-heated confined PBX charge sbujected to bullets impact has been established. The predicted ignition starting area of the explosive charge was evaluated based on volume strain and equivalent strain contours. It showed that the ignition starting area moves towards the center of the explosives from the surface with increase of heating temperature. The threshold velocity does not increase monotonically with the pre-heating temperature increases. Instead, the threshold velocity rises till 360 m/s when the cook-off temperature is lower than 75°, then decreases the increased temperature. The results imply that our PBX has the lowest impact sensitivity at about 75°. These numerical results agree very well with the corresponding experiment results conducted by Dai et al. The influence of thermal softening on the impact sensitivity has been analyzed. As the strength decreases, more impact energy will be absorbed. At the same time, shear resistance ability will be weaken and volume compression work may play a more important role to ignition. China National Nature Science Foundation (11572045), ``Science Challenging Program'' (JCKY2016212A501), opening fund from Safety ammunition research and Development Center (RMC2015B03).

  6. Ballistic Resistance of Honeycomb Sandwich Panels under In-Plane High-Velocity Impact

    Science.gov (United States)

    Yang, Shu; Wang, Dong; Yang, Li-Jun

    2013-01-01

    The dynamic responses of honeycomb sandwich panels (HSPs) subjected to in-plane projectile impact were studied by means of explicit nonlinear finite element simulations using LS-DYNA. The HSPs consisted of two identical aluminum alloy face-sheets and an aluminum honeycomb core featuring three types of unit cell configurations (regular, rectangular-shaped, and reentrant hexagons). The ballistic resistances of HSPs with the three core configurations were first analyzed. It was found that the HSP with the reentrant auxetic honeycomb core has the best ballistic resistance, due to the negative Poisson's ratio effect of the core. Parametric studies were then carried out to clarify the influences of both macroscopic (face-sheet and core thicknesses, core relative density) and mesoscopic (unit cell angle and size) parameters on the ballistic responses of the auxetic HSPs. Numerical results show that the perforation resistant capabilities of the auxetic HSPs increase as the values of the macroscopic parameters increase. However, the mesoscopic parameters show nonmonotonic effects on the panels' ballistic capacities. The empirical equations for projectile residual velocities were formulated in terms of impact velocity and the structural parameters. It was also found that the blunter projectiles result in higher ballistic limits of the auxetic HSPs. PMID:24187526

  7. Mean Velocity Prediction Information Feedback Strategy in Two-Route Systems under ATIS

    Directory of Open Access Journals (Sweden)

    Jianqiang Wang

    2015-02-01

    Full Text Available Feedback contents of previous information feedback strategies in advanced traveler information systems are almost real-time traffic information. Compared with real-time information, prediction traffic information obtained by a reliable and effective prediction algorithm has many undisputable advantages. In prediction information environment, a traveler is prone to making a more rational route-choice. For these considerations, a mean velocity prediction information feedback strategy (MVPFS is presented. The approach adopts the autoregressive-integrated moving average model (ARIMA to forecast short-term traffic flow. Furthermore, prediction results of mean velocity are taken as feedback contents and displayed on a variable message sign to guide travelers' route-choice. Meanwhile, discrete choice model (Logit model is selected to imitate more appropriately travelers' route-choice behavior. In order to investigate the performance of MVPFS, a cellular automaton model with ARIMA is adopted to simulate a two-route scenario. The simulation shows that such innovative prediction feedback strategy is feasible and efficient. Even more importantly, this study demonstrates the excellence of prediction feedback ideology.

  8. A new velocity field for Africa from combined GPS and DORIS space geodetic Solutions: Contribution to the definition of the African reference frame (AFREF)

    Science.gov (United States)

    Saria, E.; Calais, E.; Altamimi, Z.; Willis, P.; Farah, H.

    2013-04-01

    We analyzed 16 years of GPS and 17 years of Doppler orbitography and radiopositioning integrated by satellite (DORIS) data at continuously operating geodetic sites in Africa and surroundings to describe the present-day kinematics of the Nubian and Somalian plates and constrain relative motions across the East African Rift. The resulting velocity field describes horizontal and vertical motion at 133 GPS sites and 9 DORIS sites. Horizontal velocities at sites located on stable Nubia fit a single plate model with a weighted root mean square residual of 0.6 mm/yr (maximum residual 1 mm/yr), an upper bound for plate-wide motions and for regional-scale deformation in the seismically active southern Africa and Cameroon volcanic line. We confirm significant southward motion ( ˜ 1.5 mm/yr) in Morocco with respect to Nubia, consistent with earlier findings. We propose an updated angular velocity for the divergence between Nubia and Somalia, which provides the kinematic boundary conditions to rifting in East Africa. We update a plate motion model for the East African Rift and revise the counterclockwise rotation of the Victoria plate and clockwise rotation of the Rovuma plate with respect to Nubia. Vertical velocities range from - 2 to +2 mm/yr, close to their uncertainties, with no clear geographic pattern. This study provides the first continent-wide position/velocity solution for Africa, expressed in International Terrestrial Reference Frame (ITRF2008), a contribution to the upcoming African Reference Frame (AFREF). Except for a few regions, the African continent remains largely under-sampled by continuous space geodetic data. Efforts are needed to augment the geodetic infrastructure and openly share existing data sets so that the objectives of AFREF can be fully reached.

  9. The superluminal velocities as the consequence of non-classical states of electromagnetic field

    Science.gov (United States)

    Veklenko, B. A.

    2017-06-01

    It was shown within the framework of conventional quantum electrodynamics, and without using perturbation theory, the presence of superluminal signals, transferring the information, while investigating the scattering of quantum electromagnetic field by excited atom. The superluminal signals are impossible in the theory of free fields, but their existence is predicted by the theory of interacting fields.

  10. Influence of anisotropy on anomalous scaling of a passive scalar advected by the Navier-Stokes velocity field.

    Science.gov (United States)

    Jurcisinová, E; Jurcisin, M; Remecký, R

    2009-10-01

    The influence of weak uniaxial small-scale anisotropy on the stability of the scaling regime and on the anomalous scaling of the single-time structure functions of a passive scalar advected by the velocity field governed by the stochastic Navier-Stokes equation is investigated by the field theoretic renormalization group and operator-product expansion within one-loop approximation of a perturbation theory. The explicit analytical expressions for coordinates of the corresponding fixed point of the renormalization-group equations as functions of anisotropy parameters are found, the stability of the three-dimensional Kolmogorov-like scaling regime is demonstrated, and the dependence of the borderline dimension d(c) is an element of (2,3] between stable and unstable scaling regimes is found as a function of the anisotropy parameters. The dependence of the turbulent Prandtl number on the anisotropy parameters is also briefly discussed. The influence of weak small-scale anisotropy on the anomalous scaling of the structure functions of a passive scalar field is studied by the operator-product expansion and their explicit dependence on the anisotropy parameters is present. It is shown that the anomalous dimensions of the structure functions, which are the same (universal) for the Kraichnan model, for the model with finite time correlations of the velocity field, and for the model with the advection by the velocity field driven by the stochastic Navier-Stokes equation in the isotropic case, can be distinguished by the assumption of the presence of the small-scale anisotropy in the systems even within one-loop approximation. The corresponding comparison of the anisotropic anomalous dimensions for the present model with that obtained within the Kraichnan rapid-change model is done.

  11. Slip velocity has major impact on the frictional strength and microstructure of quartz-muscovite gouges under hydrothermal conditions

    Science.gov (United States)

    Niemeijer, Andre R.

    2015-04-01

    Previous friction experiments on rock analogue experiments of mixtures of salt and phyllosilicates, demonstrated the possibility of producing mylonitic fault rocks through the simultaneous operation of pressure solution and frictional sliding. This frictional-viscous flow process produces a strong velocity-dependence of friction, with friction values dropping from 0.8 to ~0.2-0.3 over just one order of magnitude decrease in sliding velocity. Here, we present the results of rotary shear experiments on simulated fault gouges of 80 wt% quartz and 20 wt% muscovite. Sliding experiments using a four orders of magnitude range of constant velocities (0.03 - 300 μm/s) to a displacement of 30 mm were done at 500 ° C, 120 MPa effective normal stress and 80 MPa fluid pressure to verify the mechanism at hydrothermal conditions and to link the produced microstructure to the observed strength. At the lowest sliding velocity tested, final friction reached a value of ~0.3, which is lower than that of pure muscovite under similar conditions. With increasing sliding velocity, friction increases, reaching a maximum of ~0.9 at 3 μm/s after which it decreases mildly to ~0.8 at 300 μm/s. The bulk microstructure of the sample sheared at 0.03 μm/s shows an anastomosing foliation of muscovite grain intervened by asymmetrical quartz clasts, with an average grain size of about 20 μm, slightly lower than the median starting size (~49 μm). In contrast, the grains of the sample deformed at 300 micron/s are very small, many of them smaller than distinguishable in the light microscope (i.e. orientations, possibly indicating a Crystallographic Preferred Orientation. These zones of uniform extinction can be found in all samples and their thickness decreases monotonically with decreasing sliding velocity. The microstructure observed at low velocity, in the frictional-viscous regime, is similar to numerous examples from natural fault rocks (e.g. the Median Tectonic Line and the Zuccale Fault

  12. Superconductors for fusion magnets tested under pulsed field in SULTAN

    International Nuclear Information System (INIS)

    Bruzzone, P.; Bottura, L.; Katheder, H.; Blau, B.; Rohleder, I.; Vecsey, G.

    1995-01-01

    The SULTAN III test facility has been upgraded with a pair of pulsed field coils to carry out AC losses and stability experiments under full operating loads on large size, fusion conductors for ITER. A fast data aquisition system records the conductor behaviour under fast field transient. The commissioning results of the pulsed coils and instrumentation are critically discussed and the test capability of the set up is assessed. (orig.)

  13. Spatial heterogeneity of biofouling under different cross-flow velocities in reverse osmosis membrane systems

    KAUST Repository

    Farhat, Nadia

    2016-09-06

    The spatially heterogeneous distribution of biofouling in spiral wound membrane systems restricts (i) the water distribution over the membrane surface and therefore (ii) the membrane-based water treatment. The objective of the study was to assess the spatial heterogeneity of biofilm development over the membrane fouling simulator (MFS) length (inlet and outlet part) at three different cross-flow velocities (0.08, 0.12 and 0.16 m/s). The MFS contained sheets of membrane and feed spacer and simulated the first 0.20 m of spiral-wound membrane modules where biofouling accumulates the most in practice. In-situ non-destructive oxygen imaging using planar optodes was applied to determine the biofilm spatially resolved activity and heterogeneity.

  14. Expressions to Rayleigh circumferential phase velocity and dispersion relation for a cylindrical surface under mechanical pressure

    Science.gov (United States)

    Sebold, Jean Eduardo; de Lacerda, Luiz Alkimin

    2018-04-01

    This paper describes a substantiated mathematical theory for Rayleigh waves propagated on some types of metal cylinders. More specifically, it presents not only a new way to express the dispersion relation of Rayleigh waves propagated on the cylindrical surface, but also how it can be used to construct a mathematical equation showing that the applied static mechanical pressure affects the shear modulus of the metal cylinder. All steps, required to conclude the process, consider the equation of motion as a function of radial and circumferential coordinates only, while the axial component can be overlooked without causing any problems. Some numerical experiments are done to illustrate the changes in the Rayleigh circumferential phase velocity in a metal cylindrical section due to static mechanical pressure around its external surface.

  15. Stereoscopy of dust density waves under microgravity: Velocity distributions and phase-resolved single-particle analysis

    Energy Technology Data Exchange (ETDEWEB)

    Himpel, Michael, E-mail: himpel@physik.uni-greifswald.de; Killer, Carsten; Melzer, André [Institute of Physics, Ernst-Moritz-Arndt-University, 17489 Greifswald (Germany); Bockwoldt, Tim; Piel, Alexander [IEAP, Christian-Albrechts-Universität Kiel, D-24098 Kiel (Germany); Ole Menzel, Kristoffer [ABB Switzerland Ltd, Corporate Research Center, 5405 Dättwil (Switzerland)

    2014-03-15

    Experiments on dust-density waves have been performed in dusty plasmas under the microgravity conditions of parabolic flights. Three-dimensional measurements of a dust density wave on a single particle level are presented. The dust particles have been tracked for many oscillation periods. A Hilbert analysis is applied to obtain trajectory parameters such as oscillation amplitude and three-dimensional velocity amplitude. While the transverse motion is found to be thermal, the velocity distribution in wave propagation direction can be explained by harmonic oscillations with added Gaussian (thermal) noise. Additionally, it is shown that the wave properties can be reconstructed by means of a pseudo-stroboscopic approach. Finally, the energy dissipation mechanism from the kinetic oscillation energy to thermal motion is discussed and presented using phase-resolved analysis.

  16. The Effect of "Pumping" and "Nonpumping" Techniques on Velocity Production and Muscle Activity During Field-Based BMX Cycling.

    Science.gov (United States)

    Rylands, Lee P; Hurst, Howard T; Roberts, Simon J; Graydon, Robert W

    2017-02-01

    Rylands, LP, Hurst, HT, Roberts, SJ, and Graydon, RW. The effect of "pumping" and "nonpumping" techniques on velocity production and muscle activity during field-based BMX cycling. J Strength Cond Res 31(2): 445-450, 2017-The aim of the current study was to determine if a technique called "pumping" had a significant effect on velocity production in Bicycle Motocross (BMX) cycling. Ten National standard male BMX riders fitted with surface electromyography (sEMG) sensors completed a timed lap of an indoor BMX track using the technique of pumping, and a lap without pumping. The lap times were recorded for both trials and their surface sEMG was recorded to ascertain any variation in muscle activation of the biceps brachii, triceps brachii, vastus lateralis, and medial gastrocnemius. The findings revealed no significant differences between any of muscle groups (p > 0.05). However, significant differences (p < 0.001) were observed between the pumping and nonpumping trials for both mean lap velocity (42 ± 1.8 km·h, 33 ± 2.9 km·h, respectively) and lap times (43.3 ± 3.1 seconds, 34.7 ± 1.49 seconds, respectively). The lap times recorded for the pumping trials were 19.50 ± 4.25% lower than the nonpumping, whereas velocity production was 21.81 ± 5.31% greater in the pumping trial compared with the nonpumping trial. The technique of pumping contributed significantly to velocity production, although not at the cost of additional muscle activity. From a physiological and technical perspective, coaches and riders should prioritize this technique when devising training regimes.

  17. Comparison of field and laboratory seismic velocity anisotropy measurement (scaling factor)

    Czech Academy of Sciences Publication Activity Database

    Vilhelm, J.; Rudajev, Vladimír; Živor, Roman; Lokajíček, Tomáš; Pros, Zdeněk

    2008-01-01

    Roč. 5, č. 2 (2008), s. 161-169 ISSN 1214-9705. [Czech-Polish-Slovak Symposium on Mining and Environmental Geophysics. Janov nad Nisou, 24.09.2007-27.09.2007] R&D Projects: GA ČR GA205/06/0906 Institutional research plan: CEZ:AV0Z30130516 Keywords : ultrasound sounding * seismic velocity * anisotropy * shallow seismic refraction Subject RIV: DC - Siesmology, Volcanology, Earth Structure http://www.irsm.cas.cz/?Lang=ENG&Menu=25,29,0,0;&File=Obsah/AGG/Contents/AGGC5_2(150)08.htm

  18. Flow field velocity measurements for non-isothermal systems. [of chemically reactive flow inside fused silica CVD reactor vessels

    Science.gov (United States)

    Johnson, E. J.; Hyer, P. V.; Culotta, P. W.; Clark, I. O.

    1991-01-01

    Experimental techniques which can be potentially utilized to measure the gas velocity fields in nonisothermal CVD systems both in ground-based and space-based investigations are considered. The advantages and disadvantages of a three-component laser velocimetry (LV) system that was adapted specifically for quantitative determination of the mixed convective flows in a chamber for crystal growth and film formation by CVD are discussed. Data from a horizontal research CVD reactor indicate that current models for the effects of thermophoretic force are not adequate to predict the thermophoretic bias in arbitrary flow configurations. It is concluded that LV techniques are capable of characterizing the fluid dynamics of a CVD reactor at typical growth temperatures. Thermal effects are shown to dominate and stabilize the fluid dynamics of the reactor. Heating of the susceptor increases the gas velocities parallel to the face of a slanted susceptor by up to a factor of five.

  19. The Effect of Non-Steady Overlying Water Velocity on Oxygen Consumption Under Losing and Gaining Flow Conditions

    Science.gov (United States)

    Galloway, J. A.; Wu, L.; Lewandowski, J.; Arnon, S.

    2017-12-01

    Wastewater treatment plants which discharge treated effluent into river systems can drastically alter downstream flow regime from steady flow velocities to water velocities which fluctuate on a diurnal cycle. The impacts of flow variations are expected to have complex and non-linear impacts on the temporal and spatial redox dynamics within the hyporheic zone. The objective of the current study was to qualitatively describe the effect of non-steady flow on oxygen consumption under losing and gaining conditions. A novel system which allowed for precise control and modulation of pore water velocities was deployed in a specially designed, 260 cm-long by 29 cm-wide flume. Experiments were carried out under various vertical fluxes. Oxygen dynamics were investigated by using planar optodes to measure oxygen concentrations in the hyporheic zone at a high temporal and spatial resolution. These empirical measurements were then used as inputs for a reactive transport model allowing for the calculation of oxygen consumption rates. A complex interplay between direction and magnitude of surface water velocity changes as well as antecedent flow conditions was discovered and quantitatively described. The development and calibration of the model allowed us to explore the relationships discovered in a variety of scenarios. Overall, unsteady flow conditions lead to up to a 2-fold increase in the delivery of dissolved oxygen to the hyporheic zone and lead to a higher rate of oxygen consumption than would have been predicted by a comparable steady surface flow. Vertical fluxes reduce the magnitude of the effect of surface water perturbations. The results of the current study provide an insight into how anthropogenic changes to discharge regimes in river systems can impact the biogeochemistry of the hyporheic zone.

  20. Towards 3C-3D digital holographic fluid velocity vector field measurement—tomographic digital holographic PIV (Tomo-HPIV)

    International Nuclear Information System (INIS)

    Soria, J; Atkinson, C

    2008-01-01

    Most unsteady and/or turbulent flows of geophysical and engineering interest have a highly three-dimensional (3D) complex topology and their experimental investigation is in pressing need of quantitative velocity measurement methods that are robust and can provide instantaneous 3C-3D velocity field data over a significant volumetric domain of the flow. This paper introduces and demonstrates a new method that uses multiple digital CCD array cameras to record in-line digital holograms of the same volume of seed particles from multiple orientations. This technique uses the same basic equipment as Tomo-PIV minus the camera lenses, it overcomes the depth-of-field problem of digital in-line holography and does not require the complex optical calibration of Tomo-PIV. The digital sensors can be oriented in an optimal manner to overcome the depth-of-field limitation of in-line holograms recorded using digital CCD or CMOS array cameras, resulting in a 3D reconstruction of the seed particles within the volume of interest, which can subsequently be analysed using 3D cross-correlation PIV analysis to yield a 3C-3D velocity field. A demonstration experiment of Tomo-HPIV using uniform translation with nominally 11 µm diameter seed particles shows that the 3D displacement derived from 3D cross-correlation Tomo-HPIV analysis can be measured within 5% of the imposed uniform translation, where the imposed uniform translation has an estimated standard uncertainty of 4.3%. So this paper proposes a multi-camera digital holographic imaging 3C-3D PIV method, which is identified as tomographic digital holographic PIV or Tomo-HPIV

  1. Galvanotactic behavior of Tetrahymena pyriformis under electric fields

    International Nuclear Information System (INIS)

    Kim, Dal Hyung; Kim, Paul Seung Soo; Kim, Min Jun; Lee, Kyoungwoo; Kim, JinSeok

    2013-01-01

    Tetrahymena pyriformis, a eukaryotic ciliate, swims toward a cathode in straight or cross-shaped microchannels under an applied electric field, a behavioral response called cathodal galvanotaxis. In straight channel experiments, a one-dimensional electric field was applied, and the galvanotactic swimming behavior of Tetrahymena pyriformis was observed and described in detail while the polarity of this field is switched. In most individual cases, the cell would immediately switch its direction toward the cathode; however, exceptional cases have been observed where cells exhibit a turning delay or do not turn after a polarity switch. In cross-channel experiments, feedback control using vision-based tracking was used to steer a cell in the microchannel intersection using a two-dimensional electric field generated by four electrodes placed at four ends of the cross channel. The motivation for this work is to study the swimming behavior of Tetrahymena pyriformis as a microrobot under the control of electric fields. (paper)

  2. Measurement of the magnetic moment of the 21+ state of 72Zn via extension of the high-velocity transient-field method

    International Nuclear Information System (INIS)

    Fiori, E.

    2010-12-01

    Magnetic moments can provide deep insight for nuclear structure and of the wave function composition, particularly when the single particle character of the nucleus is dominating. For this reason, the magnetic moment of the first excited state of the radioactive neutron-rich 72 Zn was measured at the GANIL facility (Caen, France). The result of the experiment confirmed the trend predicted by the shell model calculations, even if the error on the measurement did not allow for a rigorous constraint of the theories. The measurement was performed using the transient field (TF) technique and the nuclei of interest were produced in a fragmentation reaction. Before this experiment, the high-velocity TF (HVTF) technique had been used only with projectile up to Z = 24. It was the first time that a magnetic moment of an heavy ion with Z > 24 was measured in the high velocity regime. To further develop the technique and to gather information about the hyperfine interaction between the polarized electrons and the nucleons, two experiments were performed at LNS (Catania, Italy). In this thesis the development of the high-velocity TF technique for the experiments on g(2 + ; 72 Zn) and field strength B TF (Kr, Ge) is presented. The analysis of the results and their interpretation is then discussed. It was demonstrated that the HVTF technique, combined with Coulomb excitation, can be used for the measurement of g-factors of very short-lived states, with lifetimes of the order of tens of ps and lower, of heavy ions (A ∼ 80) traveling with intermediate relativistic speeds, β ∼ 0.25. The standard TF technique at low velocities (a few percent of the speed of light) has been used for a long time to provide the strong magnetic field necessary for the measurement of g-factors of very short-lived states. The breakthrough of the present development is the different velocity regime of the higher mass projectile under which the experiment is carried out

  3. Quantitative Velocity Field Measurements in Reduced-Gravity Combustion Science and Fluid Physics Experiments

    Science.gov (United States)

    Greenberg, Paul S.; Wernet, Mark P.

    1999-01-01

    Systems have been developed and demonstrated for performing quantitative velocity measurements in reduced gravity combustion science and fluid physics investigations. The unique constraints and operational environments inherent to reduced-gravity experimental facilities pose special challenges to the development of hardware and software systems. Both point and planar velocimetric capabilities are described, with particular attention being given to the development of systems to support the International Space Station laboratory. Emphasis has been placed on optical methods, primarily arising from the sensitivity of the phenomena of interest to intrusive probes. Limitations on available power, volume, data storage, and attendant expertise have motivated the use of solid-state sources and detectors, as well as efficient analysis capabilities emphasizing interactive data display and parameter control.

  4. Experimental Study of Damage Development in Salt Rock under Uniaxial Stress Using Ultrasonic Velocity and Acoustic Emissions

    Directory of Open Access Journals (Sweden)

    Haoran Li

    2018-04-01

    Full Text Available Ultrasonic waves and acoustic emissions (AE are important technologies to reveal rock damage. However, few studies have simultaneously monitored both types of data in the same experiment because of limitations on the experimental apparatus. In this study, an integrated ultrasonic wave and AE testing device was developed to investigate the deformation characteristics and damage development of salt rock. Fracture experiments under uniaxial compression were carried out on three samples from the Jintan Salt Mine, Jiangsu Province, China. The deformation process can be divided into five stages. In the compression fissure and linear deformation stages, P- and S-waves rose slightly to stability, and acoustic emission activity was weak (0.04% and 2.66%, respectively. Subsequently, S-wave velocity slowly declined and AE events become more active, with about 13.8% of the total in the stabilized-growth cracks stage. When the salt rock entered the accelerated-growth cracks stage, AE events increased to 75.27%; with features of an earthquake swarm, the velocities of P- and S-waves began to fall significantly. After the peak stress, salt rock produced only a small number of AE events. The beginning stress of rock damage and dilatancy were about 42–50% and 62–67% of the uniaxial compressive strength, respectively. The ultrasonic wave velocity ratio, Ib-value, and r-value effectively predicted rock failure, but the r-value was superior owing to its sensitivity and ease of measurement.

  5. Using micro-seismicity and seismic velocities to map subsurface geologic and hydrologic structure within the Coso geothermal field, California

    Science.gov (United States)

    Kaven, Joern Ole; Hickman, Stephen H.; Davatzes, Nicholas C.

    2012-01-01

    Geothermal reservoirs derive their capacity for fluid and heat transport in large part from faults and fractures. Micro-seismicity generated on such faults and fractures can be used to map larger fault structures as well as secondary fractures that add access to hot rock, fluid storage and recharge capacity necessary to have a sustainable geothermal resource. Additionally, inversion of seismic velocities from micro-seismicity permits imaging of regions subject to the combined effects of fracture density, fluid pressure and steam content, among other factors. We relocate 14 years of seismicity (1996-2009) in the Coso geothermal field using differential travel times and simultaneously invert for seismic velocities to improve our knowledge of the subsurface geologic and hydrologic structure. We utilize over 60,000 micro-seismic events using waveform cross-correlation to augment to expansive catalog of P- and S-wave differential travel times recorded at Coso. We further carry out rigorous uncertainty estimation and find that our results are precise to within 10s of meters of relative location error. We find that relocated micro-seismicity outlines prominent, through-going faults in the reservoir in some cases. We also find that a significant portion of seismicity remains diffuse and does not cluster into more sharply defined major structures. The seismic velocity structure reveals heterogeneous distributions of compressional (Vp) and shear (Vs) wave speed, with Vp generally lower in the main field when compared to the east flank and Vs varying more significantly in the shallow portions of the reservoir. The Vp/Vs ratio appears to outline the two main compartments of the reservoir at depths of -0.5 to 1.5 km (relative to sea-level), with a ridge of relatively high Vp/Vs separating the main field from the east flank. In the deeper portion of the reservoir this ridge is less prominent. Our results indicate that high-precision relocations of micro-seismicity can provide

  6. Numerical Simulation of the Field Velocities and Local Disturbances of a Long Gravity Wave Passing above an Immersed Vertical Barrier

    Directory of Open Access Journals (Sweden)

    Laouar Abdelhamid

    2008-01-01

    Full Text Available This work is interested in the study of the passage of a long gravity wave above an immersed vertical barrier. The latter is placed at a right angle in the middle of the occupied fluid domain which is limited vertically by both a free surface and an impermeable horizontal bottom. We want to determine the field velocity and the local disturbances in the vicinity of the barrier. For this, we use the generalized theory of shallow water and complex variables method. For illustration, we consider a solitary wave as an emitted long wave.

  7. Scale-dependent complementarity of climatic velocity and environmental diversity for identifying priority areas for conservation under climate change.

    Science.gov (United States)

    Carroll, Carlos; Roberts, David R; Michalak, Julia L; Lawler, Joshua J; Nielsen, Scott E; Stralberg, Diana; Hamann, Andreas; Mcrae, Brad H; Wang, Tongli

    2017-11-01

    As most regions of the earth transition to altered climatic conditions, new methods are needed to identify refugia and other areas whose conservation would facilitate persistence of biodiversity under climate change. We compared several common approaches to conservation planning focused on climate resilience over a broad range of ecological settings across North America and evaluated how commonalities in the priority areas identified by different methods varied with regional context and spatial scale. Our results indicate that priority areas based on different environmental diversity metrics differed substantially from each other and from priorities based on spatiotemporal metrics such as climatic velocity. Refugia identified by diversity or velocity metrics were not strongly associated with the current protected area system, suggesting the need for additional conservation measures including protection of refugia. Despite the inherent uncertainties in predicting future climate, we found that variation among climatic velocities derived from different general circulation models and emissions pathways was less than the variation among the suite of environmental diversity metrics. To address uncertainty created by this variation, planners can combine priorities identified by alternative metrics at a single resolution and downweight areas of high variation between metrics. Alternately, coarse-resolution velocity metrics can be combined with fine-resolution diversity metrics in order to leverage the respective strengths of the two groups of metrics as tools for identification of potential macro- and microrefugia that in combination maximize both transient and long-term resilience to climate change. Planners should compare and integrate approaches that span a range of model complexity and spatial scale to match the range of ecological and physical processes influencing persistence of biodiversity and identify a conservation network resilient to threats operating at

  8. Magnetization reversal of ferromagnetic nanoparticles under inhomogeneous magnetic field

    International Nuclear Information System (INIS)

    Chang, Joonyeon; Yi, Hyunjung; Cheol Koo, Hyun; Mironov, V.L.; Gribkov, B.A.; Fraerman, A.A.; Gusev, S.A.; Vdovichev, S.N.

    2007-01-01

    We investigated remagnetization processes in ferromagnetic nanoparticles under inhomogeneous magnetic field induced by the tip of magnetic force microscope (MFM) in both theoretical and empirical ways. Systematic MFM observations were carried out on arrays of submicron-sized elliptical ferromagnetic particles of Co and FeCr with different sizes and periods. It clearly reveals the distribution of remanent magnetization and processes of local remagnetization of individual ferromagnetic particles. Modeling of remagnetization processes in ferromagnetic nanoparticles under magnetic field induced by MFM probe was performed on the base of Landau-Lifshitz-Gilbert equation for magnetization. MFM-induced inhomogeneous magnetic field is very effective to control the magnetic state of individual ferromagnetic nanoparticles as well as to create different distribution of magnetic field in array of ferromagnetic nanoparticles

  9. Application of a simplified calculation for full-wave microtremor H/ V spectral ratio based on the diffuse field approximation to identify underground velocity structures

    Science.gov (United States)

    Wu, Hao; Masaki, Kazuaki; Irikura, Kojiro; Sánchez-Sesma, Francisco José

    2017-12-01

    Under the diffuse field approximation, the full-wave (FW) microtremor H/ V spectral ratio ( H/ V) is modeled as the square root of the ratio of the sum of imaginary parts of the Green's function of the horizontal components to that of the vertical one. For a given layered medium, the FW H/ V can be well approximated with only surface waves (SW) H/ V of the "cap-layered" medium which consists of the given layered medium and a new larger velocity half-space (cap layer) at large depth. Because the contribution of surface waves can be simply obtained by the residue theorem, the computation of SW H/ V of cap-layered medium is faster than that of FW H/ V evaluated by discrete wavenumber method and contour integration method. The simplified computation of SW H/ V was then applied to identify the underground velocity structures at six KiK-net strong-motion stations. The inverted underground velocity structures were used to evaluate FW H/ Vs which were consistent with the SW H/ Vs of corresponding cap-layered media. The previous study on surface waves H/ Vs proposed with the distributed surface sources assumption and a fixed Rayleigh-to-Love waves amplitude ratio for horizontal motions showed a good agreement with the SW H/ Vs of our study. The consistency between observed and theoretical spectral ratios, such as the earthquake motions of H/ V spectral ratio and spectral ratio of horizontal motions between surface and bottom of borehole, indicated that the underground velocity structures identified from SW H/ V of cap-layered medium were well resolved by the new method.[Figure not available: see fulltext.

  10. Two different approaches for creating a prescribed opposed-flow velocity field for flame spread experiments

    Directory of Open Access Journals (Sweden)

    Carmignani Luca

    2015-01-01

    Full Text Available Opposed-flow flame spread over solid fuels is a fundamental area of research in fire science. Typically combustion wind tunnels are used to generate the opposing flow of oxidizer against which a laminar flame spread occurs along the fuel samples. The spreading flame is generally embedded in a laminar boundary layer, which interacts with the strong buoyancy-induced flow to affect the mechanism of flame spread. In this work, two different approaches for creating the opposed-flow are compared. In the first approach, a vertical combustion tunnel is used where a thin fuel sample, thin acrylic or ashless filter paper, is held vertically along the axis of the test-section with the airflow controlled by controlling the duty cycles of four fans. As the sample is ignited, a flame spreads downward in a steady manner along a developing boundary layer. In the second approach, the sample is held in a movable cart placed in an eight-meter tall vertical chamber filled with air. As the sample is ignited, the cart is moved downward (through a remote-controlled mechanism at a prescribed velocity. The results from the two approaches are compared to establish the boundary layer effect on flame spread over thin fuels.

  11. Modification of the quantum mechanical flux formula for electron-hydrogen ionization through Bohm's velocity field

    Science.gov (United States)

    Randazzo, J. M.; Ancarani, L. U.

    2015-12-01

    For the single differential cross section (SDCS) for hydrogen ionization by electron impact (e -H problem), we propose a correction to the flux formula given by R. Peterkop [Theory of Ionization of Atoms by Electron Impact (Colorado Associated University Press, Boulder, 1977)]. The modification is based on an alternative way of defining the kinetic energy fraction, using Bohm's definition of velocities instead of the usual asymptotic kinematical, or geometrical, approximation. It turns out that the solution-dependent, modified energy fraction is equally related to the components of the probability flux. Compared to what is usually observed, the correction yields a finite and well-behaved SDCS value in the asymmetrical situation where one of the continuum electrons carries all the energy while the other has zero energy. We also discuss, within the S -wave model of the e -H ionization process, the continuity of the SDCS derivative at the equal energy sharing point, a property not so clearly observed in published benchmark results obtained with integral and S -matrix formulas with unequal final states.

  12. Velocity and concentration fields in turbulent buoyant mixing in tilted tubes

    Science.gov (United States)

    Znaien, J.; Moisy, F.; Hulin, J. P.; Salin, D.; Hinch, E. J.

    2008-11-01

    2D PIV and LIF measurements have been performed on buoyancy driven flows of two miscible fluids of the same viscosity in a tube tilted at different angles θ from vertical and at different density contrasts (characterized by the Atwood number At). As θ increases and At decreases, the flow regime evolves, behind the front, from a turbulent shear flow towards a laminar counter flow with 3 layers of different concentrations. Time variations of the structure function show that both intermittent and developed turbulence occur in intermediate conditions. In the turbulent regime (Reλ˜60) the magnitudes of the longitudinal u'^2 and transverse v'^2 velocity fluctuations and of the component u'v' of the Reynolds stress tensor are shown to be largest on the tube axis while viscous stresses is only important close to the walls. The analyzis of the momentum transfer in the flow with buoyancy forces estimated from the concentration gradients demonstrates that 3D effects are required to achieve the momentum balance. These results are discussed in the framework of classical turbulence models.

  13. Two different approaches for creating a prescribed opposed-flow velocity field for flame spread experiments

    Science.gov (United States)

    Carmignani, Luca; Celniker, Greg; Bussett, Kyle; Paolini, Christopher; Bhattacharjee, Subrata

    2015-05-01

    Opposed-flow flame spread over solid fuels is a fundamental area of research in fire science. Typically combustion wind tunnels are used to generate the opposing flow of oxidizer against which a laminar flame spread occurs along the fuel samples. The spreading flame is generally embedded in a laminar boundary layer, which interacts with the strong buoyancy-induced flow to affect the mechanism of flame spread. In this work, two different approaches for creating the opposed-flow are compared. In the first approach, a vertical combustion tunnel is used where a thin fuel sample, thin acrylic or ashless filter paper, is held vertically along the axis of the test-section with the airflow controlled by controlling the duty cycles of four fans. As the sample is ignited, a flame spreads downward in a steady manner along a developing boundary layer. In the second approach, the sample is held in a movable cart placed in an eight-meter tall vertical chamber filled with air. As the sample is ignited, the cart is moved downward (through a remote-controlled mechanism) at a prescribed velocity. The results from the two approaches are compared to establish the boundary layer effect on flame spread over thin fuels.

  14. Numerical simulation of transverse jet flow field under supersonic inflow

    Directory of Open Access Journals (Sweden)

    Qian Li

    2017-01-01

    Full Text Available Transverse jet flow field under supersonic inflow is simulated numerically for studying the characteristic of fuel transverse jet and fuel mixing in scramjet combustion chamber. Comparison is performed between simulated results and the results of references and experiments. Results indicate that the CFD code in this paper is applicable for simulation of transverse jut flow field under supersonic inflow, but in order to providing more effective numerical predictive method, CFD code should be modified through increasing mesh density and adding LES module.

  15. Two tests of electric fields, second-order in source-velocity terms of closed, steady currents: (1) an electron beam; (2) a superconducting coil

    International Nuclear Information System (INIS)

    Kenyon, C.S.

    1980-01-01

    One particular prediction of Maxwell's theory that has been previously neglected is that the motion of charges traveling in closed loops produces no constant electric fields. This study presents and analyzes the results of two new experiments designed to test for second-order, source-velocity electric fields from steady, closed currents and analyzes another experiment in light of these fields. The first experiment employed an electron beam. The second used a niobium-titanium coil designed so that the voltage measurement configuration could be easily switched from a Faraday to a non-faraday configuration between sets of runs. The implications of the observation of a null charge on magnetically suspended superconducting spheres vis-a-vis the second-order, source-velocity fields were discussed as the third case. The observation of a null potential corresponding to a null effective charge from a hypothetical velocity-squared field in both the beam and the coil experiment placed the upper bound on a field term at 0.02 with respect a Coulomb term. An observed null charge on the suspended spheres reduced this bound to 0.001. Such an upper bound is strong evidence against alternative theories predicting a relative contribution of the order of unity for a simple velocity-squared term. A simple velocity-squared electric field would be indistinguishable from a velocity-squared charge variation. The latter test limits such a charge variation to 0.001 of the total charge. The suspended-spheres test allowed the previously neglected issue of a general second-order, source-velocity electric field to be addressed. The observed null charge in this test contradicts and thus eliminates a hypothesized, general, electric field expression containing three second-order, source-velocity terms

  16. Time-depth and velocity trend analysis of the Wasagu field ...

    African Journals Online (AJOL)

    It is known in the North Sea basin that depths to major reflectors as determined from surface seismic data are often larger than the well depths. From this study of data sets from Wasagu field in the Niger Delta, it has been found that this statement might not hold in an area where rapid lateral variations in the subsurface ...

  17. Tangential discontinuities in the solar wind: Correlated field and velocity changes in the Kelvin-Helmholtz Instability

    International Nuclear Information System (INIS)

    Neugebauer, M.; Alexander, C.J.; Schwenn, R.; Richter, A.K.

    1986-01-01

    Three-dimensional Helios plasma and field data are used to investigate the relative changes in direction of the velocity and magnetic field vectors across tangential discontinuities, (TDs) in the solar wind at solar distances of 0.29--0.50 AU. It is found for tangential discontinuities with both Δv and ΔB/B large that Δv and ΔB are closely aligned with each other, in agreement with the unexpected results of previous studies of tangential discontinuities observed at 1 AU and beyond. It is shown that this effect probably results from the destruction by the Kelvin-Helmholtz instability of TDs for which Δv and ΔB are not aligned. The observed decrease in the number of interplanetary discontinuities with increasing solar distance may be associated with the growth of the Kelvin-Helmholtz instability with decreasing Alfven speed

  18. Experimental investigation of the effect of air velocity on a unit cooler under frosting condition: a case study

    Science.gov (United States)

    Bayrak, Ergin; Çağlayan, Akın; Konukman, Alp Er S.

    2017-10-01

    Finned tube evaporators are used in a wide range of applications such as commercial and industrial cold/freezed storage rooms with high traffic loading under frosting conditions. In this case study, an evaporator with an integrated fan was manufactured and tested under frosting conditions by only changing the air flow rate in an ambient balanced type test laboratory compared to testing in a wind tunnel with a more uniform flow distribution in order to detect the effect of air flow rate on frosting. During the test, operation was performed separately based on three different air flow rates. The parameters concerning test operation such as the changes of air temperature, air relative humidity, surface temperature, air-side pressure drop and refrigerant side capacity etc. were followed in detail for each air flow rate. At the same time, digital images were captured in front of the evaporator; thus, frost thicknesses and blockage ratios at the course of fan stall were determined by using an image-processing technique. Consequently, the test and visual results showed that the trendline of air-side pressure drop increased slowly at the first stage of test operations, then increased linearly up to a top point and then the linearity was disrupted instantly. This point speculated the beginning of defrost operation for each case. In addition, despite detecting a velocity that needs to be avoided, a test applied at minimum air velocity is superior to providing minimum capacity in terms of loss of capacity during test operations.

  19. Dark Matter Profiles in Dwarf Galaxies: A Statistical Sample Using High-Resolution Hα Velocity Fields from PCWI

    Science.gov (United States)

    Relatores, Nicole C.; Newman, Andrew B.; Simon, Joshua D.; Ellis, Richard; Truong, Phuongmai N.; Blitz, Leo

    2018-01-01

    We present high quality Hα velocity fields for a sample of nearby dwarf galaxies (log M/M⊙ = 8.4-9.8) obtained as part of the Dark Matter in Dwarf Galaxies survey. The purpose of the survey is to investigate the cusp-core discrepancy by quantifying the variation of the inner slope of the dark matter distributions of 26 dwarf galaxies, which were selected as likely to have regular kinematics. The data were obtained with the Palomar Cosmic Web Imager, located on the Hale 5m telescope. We extract rotation curves from the velocity fields and use optical and infrared photometry to model the stellar mass distribution. We model the total mass distribution as the sum of a generalized Navarro-Frenk-White dark matter halo along with the stellar and gaseous components. We present the distribution of inner dark matter density profile slopes derived from this analysis. For a subset of galaxies, we compare our results to an independent analysis based on CO observations. In future work, we will compare the scatter in inner density slopes, as well as their correlations with galaxy properties, to theoretical predictions for dark matter core creation via supernovae feedback.

  20. Time evolution of propagating nonpremixed flames in a counterflow, annular slot burner under AC electric fields

    KAUST Repository

    Tran, Vu Manh

    2016-06-19

    The mechanism behind improved flame propagation speeds under electric fields is not yet fully understood. Although evidence supports that ion movements cause ionic wind, how this wind affects flame propagation has not been addressed. Here, we apply alternating current electric fields to a gap between the upper and lower parts of a counterflow, annular slot burner and present the characteristics of the propagating nonpremixed edge-flames produced. Contrary to many other previous studies, flame displacement speed decreased with applied AC voltage, and, depending on the applied AC frequency, the trailing flame body took on an oscillatory wavy motion. When flame displacement speeds were corrected using measured unburned flow velocities, we found no significant difference in flame propagation speeds, indicating no thermal or chemical effects by electric fields on the burning velocity. Thus, we conclude that the generation of bidirectional ionic wind is responsible for the impact of electric fields on flames and that an interaction between this bidirectional ionic wind and the flame parameters creates visible and/or measurable phenomenological effects. We also explain that the presence of trailing flame bodies is a dynamic response to an electric body force on a reaction zone, an area that can be considered to have a net positively charged volume. In addition, we characterize the wavy motion of the transient flame as a relaxation time independent of mixture strength, strain rate, and Lewis number.

  1. GIRAFFE multiple integral field units at VLT: a unique tool to recover velocity fields of distant galaxies

    OpenAIRE

    Flores, H.; Puech, M.; Hammer, F.; Garrido, O.; Hernandez, O.

    2004-01-01

    The GIRAFFE spectrograph is unique in providing the integral field spectroscopy of fifteen distant galaxies at the same time. It has been successfully implemented at the second VLT unit within the FLAMES facility. We present GIRAFFE observations acquired during the Guaranteed Time Observation of the Paris Observatory, using total exposure times ranging from 6 to 12 hours. The reduced 3D cube of each galaxy has been deconvolved using our new package DisGal3D. This software has been written usi...

  2. Sound velocity profile from velocimeter cast by NOAA Navigation Response Team-4 for Cleveland field examination survey in Lake Erie on 17 October 2007 (NODC Accession 0036139)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Physical oceanographic data were collected by NOAA Navigation Response Team-4 for Cleveland field examination survey in Lake Erie on 17 October 2007. Sound velocity...

  3. Velocity Fields Measurement of Natural Circulation Flow inside a Pool Using PIV Technique

    International Nuclear Information System (INIS)

    Kim, Seok; Kim, Dong Eok; Youn, Young Jung; Euh, Dong Jin; Song, Chul Hwa

    2012-01-01

    Thermal stratification is encountered in large pool of water increasingly being used as heat sink in new generation of advanced reactors. These large pools at near atmospheric pressure provide a heat sink for heat removal from the reactor or steam generator, and the containment by natural circulation as well as a source of water for core cooling. For examples, the PAFS (passive auxiliary feedwater system) is one of the advanced safety features adopted in the APR+ (Advanced Power Reactor Plus), which is intended to completely replace the conventional active auxiliary feedwater system. The PAFS cools down the steam generator secondary side and eventually removes the decay heat from the reactor core by adopting a natural convection mechanism. In a pool, the heat transfer from the PCHX (passive condensation heat exchanger) contributed to increase the pool temperature up to the saturation condition and induce the natural circulation flow of the PCCT (passive condensate cooling tank) pool water. When a heat rod is placed horizontally in a pool of water, the fluid adjacent to the heat rod gets heated up. In the process, its density reduces and by virtue of the buoyancy force, the fluid in this region moves up. After reaching the top free surface, the heated water moves towards the other side wall of the pool along the free surface. Since this heated water is cooling, it goes downward along the wall at the other side wall. Above heater rod, a natural circulation flow is formed. However, there is no flow below heater rod until pool water temperature increases to saturation temperature. In this study, velocity measurement was conducted to reveal a natural circulation flow structure in a small pool using PIV (particle image velocimetry) measurement technique

  4. Acoustic Emission Characteristics of Sedimentary Rocks Under High-Velocity Waterjet Impingement

    Science.gov (United States)

    Tian, Shouceng; Sheng, Mao; Li, Zhaokun; Ge, Hongkui; Li, Gensheng

    2017-10-01

    The success of waterjet drilling technology requires further insight into the rock failure mechanisms under waterjet impingement. By combining acoustic emission (AE) sensing and underwater sound recording techniques, an online system for monitoring submerged waterjet drilling has been developed. For four types of sedimentary rocks, their AE characteristics and correlations to the drilling performance have been obtained through time-frequency spectrum analysis. The area under the power spectrum density curve has been used as the indicator of AE energy. The results show that AE signals from the fluid dynamics and the rock failure are in different ranges of signal frequency. The main frequencies of the rock failure are within the higher range of 100-200 kHz, while the frequencies of the fluid dynamics are below 50 kHz. Further, there is a linear relationship between the AE energy and the drilling depth irrespective of rock type. The slope of the linear relationship is proportional to the rock strength and debris size. Furthermore, the AE-specific energy is a good indicator of the critical depth drilled by the waterjet. In conclusion, the AE characteristics on the power density and dominant frequency are capable of identifying the waterjet drilling performance on the rock materials and are correlated with the rock properties, i.e., rock strength and cutting size.

  5. Stimuli-Responsive Polymer-Clay Nanocomposites under Electric Fields

    OpenAIRE

    Piao, Shang Hao; Kwon, Seung Hyuk; Choi, Hyoung Jin

    2016-01-01

    This short Feature Article reviews electric stimuli-responsive polymer/clay nanocomposites with respect to their fabrication, physical characteristics and electrorheological (ER) behaviors under applied electric fields when dispersed in oil. Their structural characteristics, morphological features and thermal degradation behavior were examined by X-ray diffraction pattern, scanning electron microscopy and transmission electron microscopy, and thermogravimetric analysis, respectively. Particul...

  6. Evaporation studies on Themeda triandra under field conditions: a ...

    African Journals Online (AJOL)

    In the semi-arid regions of South Africa, the efficiency of water use by natural grazing plants is important and can be used to evaluate the production potentially of comparative grasses. Hydraulic non-floating lysimeters were designed and tested under field conditions and indicated that with accurate calibration for ...

  7. Nodulation potential of four Trifolium repens cultivars under field ...

    African Journals Online (AJOL)

    Four Trifolium repens (white clover) cultivars were evaluated under field conditions to determine the potential of these cultivars to sucessfully develop Rhizobium-associated root nodules. Nodulation of T. repens is often poor, because of suboptimal environmental conditions or absence of host-specific rhizobia. The cultivars ...

  8. Respiratory variation in peak aortic velocity accurately predicts fluid responsiveness in children undergoing neurosurgery under general anesthesia.

    Science.gov (United States)

    Morparia, Kavita G; Reddy, Srijaya K; Olivieri, Laura J; Spaeder, Michael C; Schuette, Jennifer J

    2018-04-01

    The determination of fluid responsiveness in the critically ill child is of vital importance, more so as fluid overload becomes increasingly associated with worse outcomes. Dynamic markers of volume responsiveness have shown some promise in the pediatric population, but more research is needed before they can be adopted for widespread use. Our aim was to investigate effectiveness of respiratory variation in peak aortic velocity and pulse pressure variation to predict fluid responsiveness, and determine their optimal cutoff values. We performed a prospective, observational study at a single tertiary care pediatric center. Twenty-one children with normal cardiorespiratory status undergoing general anesthesia for neurosurgery were enrolled. Respiratory variation in peak aortic velocity (ΔVpeak ao) was measured both before and after volume expansion using a bedside ultrasound device. Pulse pressure variation (PPV) value was obtained from the bedside monitor. All patients received a 10 ml/kg fluid bolus as volume expansion, and were qualified as responders if stroke volume increased >15% as a result. Utility of ΔVpeak ao and PPV and to predict responsiveness to volume expansion was investigated. A baseline ΔVpeak ao value of greater than or equal to 12.3% best predicted a positive response to volume expansion, with a sensitivity of 77%, specificity of 89% and area under receiver operating characteristic curve of 0.90. PPV failed to demonstrate utility in this patient population. Respiratory variation in peak aortic velocity is a promising marker for optimization of perioperative fluid therapy in the pediatric population and can be accurately measured using bedside ultrasonography. More research is needed to evaluate the lack of effectiveness of pulse pressure variation for this purpose.

  9. Influence of a forest canopy on velocity and temperature profiles under synoptic conditions

    Science.gov (United States)

    Pattantyus, A.; Hocut, C. M.; Wang, Y.; Creegan, E.; Krishnamurthy, R.; Otarola-Bust, S.; Leo, L. S.; Fernando, H. J. S.

    2017-12-01

    Numerous field campaigns have found the importance of surface conditions on boundary layer evolution. Specifically, soil properties were found to control surface fluxes of heat, moisture, and momentum that significantly modulated the atmospheric boundary layer (ABL) over flat and sparsely vegetated surfaces. There have been increasing numbers of studies related to canopy impacts on the boundary layer, such as CHATS, however few canopy studies over complex terrain have been performed with limited instrumentation. The recent Perdigão campaign greatly augmented the previous datasets available by instrumenting a unique, parallel ridge mountain in Perdigão, Portugal in unprecedented spatial and temporal resolution using traditional mast mounted sensors, instrumented aerial platforms, and remote sensing instrumentation. To aid the canopy studies, the Army Research Laboratory deployed sonic anemometers within the canopy transecting the ridges perpendicularly and placed five additional heavily instrumented meteorological masts on the northeast facing slope to investigate detailed slope flows. At each of these towers, there was an average of six levels of temperature, relative humidity, and wind sensors located above & below the canopy height which allowed a detailed study of the sub-canopy layer. In addition to the towers, two scanning Doppler LiDARs were oriented such that they performed synchronized dual Doppler virtual tower scans, extending from the canopy interface to several hundred meters above. Synoptically forced periods were analyzed to examine: the ABL structure of temperature, moisture, wind, and turbulent kinetic energy. Of particular interest are the shear layer at the canopy interface, recirculation events, as well as ejection and sweep events within the canopy and how these modify surface fluxes along the slopes.

  10. Comparative study of the microstructure of 5052 aluminum alloy sheets under quasi-static and high-velocity tension

    Energy Technology Data Exchange (ETDEWEB)

    Liu, D.H., E-mail: liudahai.hit@gmail.com [School of Aeronautical Manufacturing Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Yu, H.P.; Li, C.F. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer Dislocation slip mechanism works during both quasi-static and dynamic deformation. Black-Right-Pointing-Pointer Dynamic deformation induces denser dislocations and more cross-slip tendency. Black-Right-Pointing-Pointer Existed prestrain has an accommodating effect on dislocation generation and motion. - Abstract: In order to reveal the high-velocity deformation mechanisms of 5052 aluminum alloy sheets, this work compares the dynamic plastic deformation behavior and the microstructure evolutions with those of the quasi-static case by scanning electron microscopy (SEM) observations, electron back scattering diffraction (EBSD) analysis, and transmission electron microscopy (TEM) studies. Results show that the dynamic process exhibits a very different macro fracture shape and a much similar micro deformation pattern as compared with the quasi-static case, and under both conditions, the dislocation-slip mechanism works during deformation. For the shock effect of high-velocity deformation, much denser dislocations are generated and the tendency of cross-slip of dislocations increases. The dislocation bands are more narrow and denser than those shown in the quasi-static case, and a much more uniform dislocation configuration is also exhibited after dynamic loadings. In addition, under dynamic conditions, the existing of pre-strain will introduce an accommodated effect on the dynamically induced dislocations, a slight reduction of density combining with a higher movement tendency. The characteristics of multi-slips and homogenization effect of dislocations under dynamic conditions will result in much higher plasticity and strength of materials over the quasi-static ones.

  11. Monolayer phosphorene under time-dependent magnetic field

    Science.gov (United States)

    Nascimento, J. P. G.; Aguiar, V.; Guedes, I.

    2018-02-01

    We obtain the exact wave function of a monolayer phosphorene under a low-intensity time-dependent magnetic field using the dynamical invariant method. We calculate the quantum-mechanical energy expectation value and the transition probability for a constant and an oscillatory magnetic field. For the former we observe that the Landau level energy varies linearly with the quantum numbers n and m and the magnetic field intensity B0. No transition takes place. For the latter, we observe that the energy oscillates in time, increasing linearly with the Landau level n and m and nonlinearly with the magnetic field. The (k , l) →(n , m) transitions take place only for l = m. We investigate the (0,0) →(n , 0) and (1 , l) and (2 , l) probability transitions.

  12. Smearing model and restoration of star image under conditions of variable angular velocity and long exposure time.

    Science.gov (United States)

    Sun, Ting; Xing, Fei; You, Zheng; Wang, Xiaochu; Li, Bin

    2014-03-10

    The star tracker is one of the most promising attitude measurement devices widely used in spacecraft for its high accuracy. High dynamic performance is becoming its major restriction, and requires immediate focus and promotion. A star image restoration approach based on the motion degradation model of variable angular velocity is proposed in this paper. This method can overcome the problem of energy dispersion and signal to noise ratio (SNR) decrease resulting from the smearing of the star spot, thus preventing failed extraction and decreased star centroid accuracy. Simulations and laboratory experiments are conducted to verify the proposed methods. The restoration results demonstrate that the described method can recover the star spot from a long motion trail to the shape of Gaussian distribution under the conditions of variable angular velocity and long exposure time. The energy of the star spot can be concentrated to ensure high SNR and high position accuracy. These features are crucial to the subsequent star extraction and the whole performance of the star tracker.

  13. Photodegradation of clothianidin under simulated California rice field conditions.

    Science.gov (United States)

    Mulligan, Rebecca A; Redman, Zachary C; Keener, Megan R; Ball, David B; Tjeerdema, Ronald S

    2016-07-01

    Photodegradation can be a major route of dissipation for pesticides applied to shallow rice field water, leading to diminished persistence and reducing the risk of offsite transport. The objective of this study was to characterize the aqueous-phase photodegradation of clothianidin under simulated California rice field conditions. Photodegradation of clothianidin was characterized in deionized, Sacramento River and rice field water samples. Pseudo-first-order rate constants and DT50 values in rice field water (mean k = 0.0158 min(-1) ; mean DT50 = 18.0 equivalent days) were significantly slower than in deionized water (k = 0.0167 min(-1) ; DT50 = 14.7 equivalent days) and river water (k = 0.0146 min(-1) ; DT50 = 16.6 equivalent days) samples. Quantum yield ϕc values demonstrate that approximately 1 and 0.5% of the light energy absorbed results in photochemical transformation in pure and field water respectively. Concentrations of the photodegradation product thiazolymethylurea in aqueous photolysis samples were determined using liquid chromatography-tandem mass spectrometry and accounted for ≤17% in deionized water and ≤8% in natural water. Photodegradation rates of clothianidin in flooded rice fields will be controlled by turbidity and light attenuation. Aqueous-phase photodegradation may reduce the risk of offsite transport of clothianidin from flooded rice fields (via drainage) and mitigate exposure to non-target organisms. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

  14. High-resolution measurement of the unsteady velocity field to evaluate blood damage induced by a mechanical heart valve.

    Science.gov (United States)

    Bellofiore, Alessandro; Quinlan, Nathan J

    2011-09-01

    We investigate the potential of prosthetic heart valves to generate abnormal flow and stress patterns, which can contribute to platelet activation and lysis according to blood damage accumulation mechanisms. High-resolution velocity measurements of the unsteady flow field, obtained with a standard particle image velocimetry system and a scaled-up model valve, are used to estimate the shear stresses arising downstream of the valve, accounting for flow features at scales less than one order of magnitude larger than blood cells. Velocity data at effective spatial and temporal resolution of 60 μm and 1.75 kHz, respectively, enabled accurate extraction of Lagrangian trajectories and loading histories experienced by blood cells. Non-physiological stresses up to 10 Pa were detected, while the development of vortex flow in the wake of the valve was observed to significantly increase the exposure time, favouring platelet activation. The loading histories, combined with empirical models for blood damage, reveal that platelet activation and lysis are promoted at different stages of the heart cycle. Shear stress and blood damage estimates are shown to be sensitive to measurement resolution.

  15. Eighteen years of GPS surveys in the Aeolian Islands (southern Italy: open data archive and velocity field

    Directory of Open Access Journals (Sweden)

    Alessandra Esposito

    2015-10-01

    Full Text Available Since the early 1970s, geodetic networks became a most important tool to monitor the present day deformations of the volcanic arc of the Aeolian Islands. The first benchmarks were installed in this region at Lipari and Vulcano Islands and the number of GPS benchmarks increased in time since the early ’90s. These networks were periodically surveyed in the frame of national and international geodynamic projects and for Civil Protection programs devoted to the mitigation of the volcanic hazard. The Istituto Nazionale di Geofisica e Vulcanologia (INGV played a fundamental role in the realization and periodical reoccupation of these networks, with the goal to investigate the tectonic and volcanic processes, still active in this crucial area of the central Mediterranean. An updated GPS velocity map for this region, both for the horizontal and vertical component of land motion, with details for Lipari, Vulcano and Panarea Islands, is provided in this paper. The presented GPS velocity field also includes a set of additional discrete stations located in northern Sicily and Calabria together with data from the available CGPS networks active in southern Italy. Here we show the results from eighteen years of repeated GPS surveys performed in this region in the time span 1995-2013 and the open access AINET-GPS data archive, now freely available for the scientific community. Data will support scientific research and hopefully improve the assessment of volcanic and seismic hazard in this region.

  16. Negative Differential Velocity in Artificial Crystals Probed by High Magnetic Fields

    Science.gov (United States)

    Patanè, A.

    Progress in the synthesis and engineering of semiconductor materials has led to improved device performances and functionalities. In particular, in the last decade, there has been considerable interest in the physics and applications of highly-mismatched alloys in which small and highly-electronegative isovalent N-atoms are incorporated onto the anion sublattice of a III-V compound semiconductor.1 The most studied material is the GaAs1-xNx alloy. Our magnetotunnelling studies have shown that a small percentage of N (x alloy composition observed in other semiconductor compounds, such as InyGa1-yAs. The incorporation of N in GaAs gives rise to a qualitatively different type of alloy phenomenon: N-impurities and N-clusters tend to localize the extended Bloch states of GaAs at resonant energies in the conduction band (CB), thus fragmenting the energy-wavevector dispersion relations. The possibility of tailoring the electronic properties of III-V compounds by N-incorporation has stimulated proposals for innovative devices in optoelectronics and high frequency (terahertz, THz) electronics.7 However, to date, the implementation of dilute nitrides in these technologies presents several challenges, including a degradation of the electron mobility. Also, despite a rapidly expanding body of work on the electronic properties of GaAs1-xNx, the range of N-concentrations over which this alloy behaves as a good conductor is not yet well established. Our magnetotransport experiments have revealed how the incorporation of N in GaAs affects the electrical conductivity. Our studies in n-type GaAs1-xNx epilayers revealed a large increase of the resistivity, ρ, for x > 0.2%, which we have attributed to the emergence of defect states with deep (~ 0.3 eV) energy levels. Electron trapping onto these states was not observed at low x (x = 0.2%). In this ultra-dilute alloy regime and at low electric fields (F 1 kV/cm), electrons gain sufficient energy to approach the energy of the resonant N

  17. What Do the Hitomi Observations Tell Us About the Turbulent Velocities in the Perseus Cluster? Probing the Velocity Field with Mock Observations

    Science.gov (United States)

    ZuHone, J. A.; Miller, E. D.; Bulbul, E.; Zhuravleva, I.

    2018-02-01

    Hitomi made the first direct measurements of galaxy cluster gas motions in the Perseus cluster, which implied that its core is fairly “quiescent,” with velocities less than ∼200 km s‑1, despite the presence of an active galactic nucleus and sloshing cold fronts. Building on previous work, we use synthetic Hitomi/X-ray Spectrometer (SXS) observations of the hot plasma of a simulated cluster with sloshing gas motions and varying viscosity to analyze its velocity structure in a similar fashion. We find that sloshing motions can produce line shifts and widths similar to those measured by Hitomi. We find these measurements are unaffected by the value of the gas viscosity, since its effects are only manifested clearly on angular scales smaller than the SXS ∼1‧ PSF. The PSF biases the line shift of regions near the core as much as ∼40–50 km s‑1, so it is crucial to model this effect carefully. We also infer that if sloshing motions dominate the observed velocity gradient, Perseus must be observed from a line of sight that is somewhat inclined from the plane of these motions, but one that still allows the spiral pattern to be visible. Finally, we find that assuming isotropy of motions can underestimate the total velocity and kinetic energy of the core in our simulation by as much as ∼60%. However, the total kinetic energy in our simulated cluster core is still less than 10% of the thermal energy in the core, in agreement with the Hitomi observations.

  18. Response of Magnetic Force Microscopy Probes under AC Magnetic Field

    Science.gov (United States)

    Sungthong, A.; Ruksasakchai, P.; Saengkaew, K.; Cheowanish, I.; Damrongsak, B.

    2017-09-01

    In this paper, magnetic force microscopy (MFM) probes with different coating materials were characterized under AC magnetic field. A perpendicular magnetic write head similar to those used in hard disk drives was employed as the AC magnetic field generator. In order to measure a response of MFM probes to AC magnetic field, a MFM probe under test was scanned, at a scan height of 10 nm, across the surface of the magnetic write head. During MFM imaging, the write head was biased by a sufficient magnitude of AC current, approximately 30 mA. A spectral analysis for a frequency sweep from 1 kHz to 100 MHz was extracted from post-processing MFM images. As expected, a MFM probe coated with hard magnetic alloys, i.e. FePt, has the lowest response to AC magnetic fields. MFM probes coated with soft magnetic alloys, i.e. NiFe and NiCoCr, have a relatively high and flat response across the frequency range. Ni coated MFM probe has the highest response to AC magnetic fields. In addition, CoCr and NiCo coated MFM probes show lower response than NiFe and NiCoCr probes at low frequencies; however, theirs response to AC magnetic field increase for the AC magnetic field with a frequency above 50 kHz. This can be implied that those MFM probes are a good candidate for being used to study the high-frequency performance of perpendicular magnetic write heads. Noting that response of all MFM probes significantly decreased when driven frequencies above 1 MHz due to the limitation of the hardware, i.e. response of quadrant photodiode and op-amp in a pre-amplifier.

  19. Dynamical properties for the problem of a particle in an electric field of wave packet: Low velocity and relativistic approach

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Diego F.M., E-mail: diegofregolente@gmail.com [Institute for Multiscale Simulations, Friedrich-Alexander Universität, D-91052, Erlangen (Germany); Leonel, Edson D., E-mail: edleonel@rc.unesp.br [Departamento de Estatística, Matemática Aplicada e Computação, UNESP, Univ. Estadual Paulista, Av. 24A, 1515, Bela Vista, 13506-900, Rio Claro, SP (Brazil); Departamento de Física, UNESP, Univ. Estadual Paulista, Av. 24A, 1515, 13506-900, Rio Claro, SP (Brazil)

    2012-11-01

    We study some dynamical properties for the problem of a charged particle in an electric field considering both the low velocity and relativistic cases. The dynamics for both approaches is described in terms of a two-dimensional and nonlinear mapping. The structure of the phase spaces is mixed and we introduce a hole in the chaotic sea to let the particles to escape. By changing the size of the hole we show that the survival probability decays exponentially for both cases. Additionally, we show for the relativistic dynamics, that the introduction of dissipation changes the mixed phase space and attractors appear. We study the parameter space by using the Lyapunov exponent and the average energy over the orbit and show that the system has a very rich structure with infinite family of self-similar shrimp shaped embedded in a chaotic region.

  20. A single dumbbell falling under gravity in a cellular flow field

    CERN Document Server

    Piva, M F

    2003-01-01

    We study the motion of a single polymer chain settling under gravity in an ensemble of periodic, cellular flow fields, which are steady in time. The molecule is an elastic dumbbell composed of two beads connected by a nonbendable Hookean spring. Each bead is subject to a Stokes drag and a Brownian force from the flow. In the absence of particle inertia, the molecule settles out at a rate which depends on three parameters: the particle velocity in a fluid at rest, V sub g , the spring constant, B, and the diffusion coefficient, D. We investigate the dependence of the molecule settling velocity on B, for fixed V sub g and D. It is found that this velocity strongly depends on B and it has a minimum value less than V sub g. We also find that the molecule is temporarily trapped at fixed points for certain values of the parameters. We analyse one fixed point in detail and conclude that its stability is the main factor which contributes to slowing down the settling process.

  1. Dynamical anisotropic response of black phosphorus under magnetic field

    Science.gov (United States)

    Liu, Xuefeng; Lu, Wei; Zhou, Xiaoying; Zhou, Yang; Zhang, Chenglong; Lai, Jiawei; Ge, Shaofeng; Sekhar, M. Chandra; Jia, Shuang; Chang, Kai; Sun, Dong

    2018-04-01

    Black phosphorus (BP) has emerged as a promising material candidate for next generation electronic and optoelectronic devices due to its high mobility, tunable band gap and highly anisotropic properties. In this work, polarization resolved ultrafast mid-infrared transient reflection spectroscopy measurements are performed to study the dynamical anisotropic optical properties of BP under magnetic fields up to 9 T. The relaxation dynamics of photoexcited carrier is found to be insensitive to the applied magnetic field due to the broadening of the Landau levels and large effective mass of carriers. While the anisotropic optical response of BP decreases with increasing magnetic field, its enhancement due to the excitation of hot carriers is similar to that without magnetic field. These experimental results can be well interpreted by the magneto-optical conductivity of the Landau levels of BP thin film, based on an effective k · p Hamiltonian and linear response theory. These findings suggest attractive possibilities of multi-dimensional control of anisotropic response (AR) of BP with light, electric and magnetic field, which further introduces BP to the fantastic magnetic field sensitive applications.

  2. Response of Ferroelectric Molecules in Liquid Crystal Display under an Applied Electric Field

    Science.gov (United States)

    Takei, Misaki; Shirochi, Hideki; Yamashita, Masafumi

    2007-09-01

    The dynamic changes of ferroelectric liquid crystal (FLC) molecular alignments under the applied electric field were examined by observing the formation of conoscopic figures with a time resolution of 0.1 ms, which reflect the temporal and spatial dependences of the LC molecular alignments on the azimuthal angle. By a detailed comparison of the experimental conoscopic figures with simulated figures, the molecules began to shift from the central portion of the helix to the outer ends within 0.1 ms following application of the electric field. The positions of molecular layers having the fastest moving velocity (Δφ/Δ t) corresponded to the positions with the azimuthal angles of π/2 and 3π/2rad.

  3. Dynamics of Deformable Active Particles under External Flow Field

    Science.gov (United States)

    Tarama, Mitsusuke

    2017-10-01

    In most practical situations, active particles are affected by their environment, for example, by a chemical concentration gradient, light intensity, gravity, or confinement. In particular, the effect of an external flow field is important for particles swimming in a solvent fluid. For deformable active particles such as self-propelled liquid droplets and active vesicles, as well as microorganisms such as euglenas and neutrophils, a general description has been developed by focusing on shape deformation. In this review, we present our recent studies concerning the dynamics of a single active deformable particle under an external flow field. First, a set of model equations of active deformable particles including the effect of a general external flow is introduced. Then, the dynamics under two specific flow profiles is discussed: a linear shear flow, as the simplest example, and a swirl flow. In the latter case, the scattering dynamics of the active deformable particles by the swirl flow is also considered.

  4. Central and eastern Anatolian crustal deformation rate and velocity fields derived from GPS and earthquake data

    Science.gov (United States)

    Simão, N. M.; Nalbant, S. S.; Sunbul, F.; Komec Mutlu, A.

    2016-01-01

    We present a new strain-rate and associated kinematic model for the eastern and central parts of Turkey. In the east, a quasi N-S compressional tectonic regime dominates the deformation field and is partitioned through the two major structural elements of the region, which are the conjugate dextral strike-slip North Anatolian Fault Zone (NAFZ) and the sinistral strike slip East Anatolian Fault Zone (EAFZ). The observed surface deformation is similar to that inferred by anisotropy studies which sampled the region of the mantle closer to the crust (i.e. the lithospheric mantle and the Moho), and is dependent on the presence or absence of a lithospheric mantle, and of the level of coupling between it and the overlaying crust. The areas of the central and eastern parts of Turkey which are deforming at elevated rates are situated above areas with strong gradients in crustal thickness. This seems to indicate that these transition zones, situated between thinner and thicker crusts, promote more deformation at the surface. The regions that reveal elevated strain-rate values are 1) the Elaziğ-Bingol segment of the EAFZ, 2) the region around the Karlıova triple-junction including the Yedisu segment and the Varto fault, 3) the section of the NAFZ that extends from the Erzincan province up to the NAFZ-Ezinepazarı fault junction, and 4) sections of the Tuz Gölü Fault Zone. Other regions like the Adana basin, a significant part of the Central Anatolian Fault Zone (CAFZ), the Aksaray and the Ankara provinces, are deforming at smaller but still considerable rates and therefore should be considered as areas well capable of producing damaging earthquakes (between M6 and 7). This study also reveals that the central part of Turkey is moving at a faster rate towards the west than the eastern part Turkey, and that the wedge region between the NAFZ and the EAFZ accounts for the majority of the counter clockwise rotation between the eastern and the central parts of Turkey. This

  5. Separation of radiated sound field components from waves scattered by a source under non-anechoic conditions

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Jacobsen, Finn

    2010-01-01

    A method of estimating the sound field radiated by a source under non-anechoic conditions has been examined. The method uses near field acoustic holography based on a combination of pressure and particle velocity measurements in a plane near the source for separating outgoing and ingoing wave...... components. The outgoing part of the sound field is composed of both radiated and scattered waves. The method compensates for the scattered components of the outgoing field on the basis of the boundary condition of the problem, exploiting the fact that the sound field is reconstructed very close...... to the source. Thus the radiated free-field component is estimated simultaneously with solving the inverse problem of reconstructing the sound field near the source. The method is particularly suited to cases in which the overall contribution of reflected sound in the measurement plane is significant....

  6. Experimental results showing the internal three-component velocity field and outlet temperature contours for a model gas turbine combustor

    CSIR Research Space (South Africa)

    Meyers, BC

    2011-09-01

    Full Text Available A three-component flow field inside a can-type, forward flow experimental combustor was measured under non-reacting conditions. The combustor was run at atmospheric conditions with the air flow supplied from a fan and the outlet was straight...

  7. A new estimator for vector velocity estimation [medical ultrasonics

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    2001-01-01

    A new estimator for determining the two-dimensional velocity vector using a pulsed ultrasound field is derived. The estimator uses a transversely modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation....... The new estimator automatically compensates for the axial velocity when determining the transverse velocity. The estimation is optimized by using a lag different from one in the estimation process, and noise artifacts are reduced by averaging RF samples. Further, compensation for the axial velocity can...... be introduced, and the velocity estimation is done at a fixed depth in tissue to reduce the influence of a spatial velocity spread. Examples for different velocity vectors and field conditions are shown using both simple and more complex field simulations. A relative accuracy of 10.1% is obtained...

  8. Continuous control of light group velocity from subluminal to superluminal propagation with a standing-wave coupling field in a Rb vapor cell

    International Nuclear Information System (INIS)

    Bae, In-Ho; Moon, Han Seb

    2011-01-01

    We present the continuous control of the light group velocity from subluminal to superluminal propagation with an on-resonant standing-wave coupling field in the 5S 1/2 -5P 1/2 transition of the Λ-type system of 87 Rb atoms. When a coupling field was changed from a traveling-wave to a standing-wave field by adjusting the power of a counterpropagating coupling field, the probe pulse propagation continuously transformed from subluminal propagation, due to electromagnetically induced transparency with the traveling-wave coupling field, to superluminal propagation, due to narrow enhanced absorption with the standing-wave coupling field. The group velocity of the probe pulse was measured to be approximately 0.004c to -0.002c as a function of the disparity between the powers of the copropagating and the counterpropagating coupling fields.

  9. Particle Production under External Fields and Its Applications

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Hojin [Univ. of Wisconsin, Madison, WI (United States)

    2014-01-01

    The thesis presents studies of vacuum pair productions and its applications in early universe cosmology and high energy astrophysics. Vacuum often becomes unstable and spontaneously decays into pairs of particles in rapidly expanding universes or under strong external electromagnetic fields. Theoretically, spontaneous pair productions due to such non-trivial backgrounds of spacetimes or electromagnetic fields are well-understood. However, the effect of particle productions has not been observed so far because of experiemtal difficulties in obtaining large curvatures of space-times or strong electric fields. Although it may be impossible to observe the pair productions directly via laboratory experiments, there are still powerful sources of space-time curvatures or electric fields in cosmology and astrophysics, which result in observations. In Part I, we explore the inflationary models in early universe utilizing pair productions through gravity. We study observable signatures on the cosmic microwave background, such as isocurvature perturbations and non-Gaussianities, generated from the particle production of WIMPzillas and axions during or after inflation. In Part II, we investigate the electron-positron pair production in the magnetosphere of pulsars whose electromagnetic fields are expected to close to or even greater than the pair production threshold. In particular, we demonstrate that the pair production may be responsible for giant pulses from the Crab pulsar.

  10. Accurate Hugoniots and sound velocities of bismuth under shock compression in the 38-100 GPa range

    Directory of Open Access Journals (Sweden)

    Feng Xi

    2018-01-01

    Full Text Available Dynamic compression experiments of bismuth (Bi in a shock pressure range of 38-100 GPa were conducted using an explosive drive. The time-resolved particle velocity profiles at the Bi/LiF (lithium fluoride interface and the impact velocities were recorded with a displacement interferometer system for any reflector (DISAR. Shock velocities of Bi were measured based on the shorted-pin technique. Sound velocities of Bi were obtained from the peak state time duration measurements with the overtake method. Uncertainties in the measured Hugoniots and sound velocities were analyzed carefully. The new Hugoniot relation, Us = (1.666 ± 0.057 km/s + (1.596 ± 0.037Up (1.13 km/s ≤Up≤2.05 km/s, was determined by fitting the measured shock velocity and particle velocity to a line. The relation between the Grüneisen coefficient and the density, γρ=const., is found to be a good approximation to describe the sound velocities of Bi above the shock-induced melting pressure, by carefully analysis of the sound velocity data.

  11. Crop improvement using life cycle datasets acquired under field conditions

    Directory of Open Access Journals (Sweden)

    Keiichi eMochida

    2015-09-01

    Full Text Available Crops are exposed to various environmental stresses in the field throughout their life cycle. Modern plant science has provided remarkable insights into the molecular networks of plant stress responses in laboratory conditions, but the responses of different crops to environmental stresses in the field need to be elucidated. Recent advances in omics analytical techniques and information technology have enabled us to integrate data from a spectrum of physiological metrics of field crops. The interdisciplinary efforts of plant science and data science enable us to explore factors that affect crop productivity and identify stress tolerance-related genes and alleles. Here, we describe recent advances in technologies that are key components for data driven crop design, such as population genomics, chronological omics analyses, and computer-aided molecular network prediction. Integration of the outcomes from these technologies will accelerate our understanding of crop phenology under practical field situations and identify key characteristics to represent crop stress status. These elements would help us to genetically engineer designed crops to prevent yield shortfalls because of environmental fluctuations due to future climate change.

  12. Stimuli-Responsive Polymer-Clay Nanocomposites under Electric Fields

    Science.gov (United States)

    Piao, Shang Hao; Kwon, Seung Hyuk; Choi, Hyoung Jin

    2016-01-01

    This short Feature Article reviews electric stimuli-responsive polymer/clay nanocomposites with respect to their fabrication, physical characteristics and electrorheological (ER) behaviors under applied electric fields when dispersed in oil. Their structural characteristics, morphological features and thermal degradation behavior were examined by X-ray diffraction pattern, scanning electron microscopy and transmission electron microscopy, and thermogravimetric analysis, respectively. Particular focus is given to the electro-responsive ER characteristics of the polymer/clay nanocomposites in terms of the yield stress and viscoelastic properties along with their applications. PMID:28787852

  13. Stimuli-Responsive Polymer-Clay Nanocomposites under Electric Fields

    Directory of Open Access Journals (Sweden)

    Shang Hao Piao

    2016-01-01

    Full Text Available This short Feature Article reviews electric stimuli-responsive polymer/clay nanocomposites with respect to their fabrication, physical characteristics and electrorheological (ER behaviors under applied electric fields when dispersed in oil. Their structural characteristics, morphological features and thermal degradation behavior were examined by X-ray diffraction pattern, scanning electron microscopy and transmission electron microscopy, and thermogravimetric analysis, respectively. Particular focus is given to the electro-responsive ER characteristics of the polymer/clay nanocomposites in terms of the yield stress and viscoelastic properties along with their applications.

  14. Electron transport in bulk GaN under ultrashort high-electric field transient

    Science.gov (United States)

    Korotyeyev, V. V.; Kochelap, V. A.; Kim, K. W.

    2011-10-01

    We have investigated nonlinear electron transport in GaN induced by high-electric field transients by analyzing the temporal dependence of the electron drift velocity and temperature. For picosecond transients, our calculations have established that the electron dynamics retain almost all the features of the steady-state velocity-field characteristics including the portion with negative differential conductivity. It was also found that transient currents in GaN samples give rise to the THz re-emission effect—radiation of electromagnetic field, temporal and spectral properties of which directly relate to the velocity-field characteristics of the sample. The results clearly indicate that existing methods for the generation of high-electric field transients and subpicosecond signal measurements can be applied to the characterization of hot electron transport at ultrahigh fields while avoiding Joule self-heating, hot phonon accumulation and other undesirable effects.

  15. Field stabilization in superconducting cavities under pulsed operating

    International Nuclear Information System (INIS)

    Tessier, J.M.

    1996-01-01

    Within the framework of Tesla linear accelerator project, superconducting cavity battery is used to accelerate electrons and positrons. These cavities require pulsed running and must reach very high accelerating gradients. Under the action of the Lorentz force, the resonance frequency shifts and leaves the band-pass width, which hinders the field from taking its maximal value inside the cavity. The setting of an auto-oscillating loop allows to bring the generator frequency under the control of the cavity frequency. A feedback system is needed to reduce the energy dispersion inside the particle packets. The effects of the mechanical vibrations that disturb the accelerating voltage phase between two impulses are also compensated by a feedback loop. This thesis describes all these phenomena and computes their effects on the energy dispersion of the beam in both cases of relativistic and non-relativistic particles. (A.C.)

  16. The salt tolerance of Quinoa measured under field conditions

    DEFF Research Database (Denmark)

    Razzaghi, Fatemeh; Ahmadi, Seyed Hamid; Jensen, Christian Richardt

    Plant growth and economic yield decreases when high salt concentrations build-up in the root zone. Quinoa is a facultative halophyte crop, which can withstand saline conditions. There is no documentation of the threshold soil electrical conductivity that cause yield reduction in quinoa under field...... conditions. In this study the threshold electrical conductivity of soil saturation extract (ECe) and maximum ECe corresponding to no economic yield of quinoa (cv. Titicaca) were determined. The experimental factors were five levels of saline solution (0, 10, 20, 30 and 40 dS m-1) imposed during flowering...... and the minimum relative yield was 47% observed at 40 dS m-1 saline solution (FI40). The results showed that quinoa can grow under highly saline conditions although the seed yield decreases with increased ECe. The threshold ECe of quinoa was estimated to be between 3-6 dS m-1. There was 50% reduction in seed...

  17. Crustal deformation characteristics of Sichuan-Yunnan region in China on the constraint of multi-periods of GPS velocity fields

    Science.gov (United States)

    Yue, Caiya; Dang, Yamin; Dai, Huayang; Yang, Qiang; Wang, Xiankai

    2018-04-01

    In order to obtain deformation parameters in each block of Sichuan-Yunnan Region (SYG) in China by stages and establish a dynamic model about the variation of the strain rate fields and the surface expansion in this area, we taken the Global Positioning System (GPS) sites velocity in the region as constrained condition and taken advantage of the block strain calculation model based on spherical surface. We also analyzed the deformation of the active blocks in the whole SYG before and after the Wenchuan earthquake, and analyzed the deformation of active blocks near the epicenter of the Wenchuan earthquake in detail. The results show that, (1) Under the effects of the carving from India plate and the crimping from the potential energy of Tibetan Plateau for a long time, there is a certain periodicity in crustal deformation in SYG. And the period change and the earthquake occurrence have a good agreement. (2) The differences in GPS velocity fields relative Eurasian reference frame shows that the Wenchuan earthquake and the Ya'an earthquake mainly affect the crustal movement in the central and southern part of SYG, and the average velocity difference is about 4-8 mm/a for the Wenchuan earthquake and 2-4 mm/a for the Ya'an earthquake. (3) For the Wenchuan earthquake, the average strain changed from 10 to 20 nanostrian/a before earthquake to 40-50 nanostrian/a after the earthquake, but before and after the Ya'an earthquake, the strain value increased from about 15 nanostrian/a to about 30 nanostrian/a. (4) The Wenchuan earthquake has changed the strain parameter of each active block more or less. Especially, the Longmen block and Chengdu block near the epicenter. The research provides fundamental material for the study of the dynamic mechanism of the push extrusion from the north-east of the India plate and the crimp from Qinghai Tibet Plateau, and it also provides support for the study of crustal stress variation and earthquake prediction in Sichuan Yunnan region.

  18. Analysis of indirect rotor field oriented control-based induction machine performance under inaccurate field-oriented condition

    DEFF Research Database (Denmark)

    Liu, Yang; Tao, Geng; Wang, Huai

    2017-01-01

    Indirect rotor field oriented control (IRFOC) plays an important role in the high performance induction machine drives. In the indirect rotor field oriented control — based induction machine adjustable speed control system, the rotor field angle is usually obtained by the rotor angular velocity...... used in the indirect rotor field oriented control may have considerable error. In the paper, the angle error caused by rotor resistance variation is analyzed and the impact on the output torque and the rotor field intensity of the induction machine is studied. Simulations and experimental verification...

  19. Velocity-intermittency structure for wake flow of the pitched single wind turbine under different inflow conditions

    Science.gov (United States)

    Crist, Ryan; Cal, Raul Bayoan; Ali, Naseem; Rockel, Stanislav; Peinke, Joachim; Hoelling, Michael

    2017-11-01

    The velocity-intermittency quadrant method is used to characterize the flow structure of the wake flow in the boundary layer of a wind turbine array. Multifractal framework presents the intermittency as a pointwise Hölder exponent. A 3×3 wind turbine array tested experimentally provided a velocity signal at a 21×9 downstream location, measured via hot-wire anemometry. The results show a negative correlation between the velocity and the intermittency at the hub height and bottom tip, whereas the top tip regions show a positive correlation. Sweep and ejection based on the velocity and intermittency are dominant downstream from the rotor. The pointwise results reflect large-scale organization of the flow and velocity-intermittency events corresponding to a foreshortened recirculation region near the hub height and the bottom tip.

  20. Ensemble control of the Hardhof well field under constraints

    Science.gov (United States)

    Marti, Beatrice; McLaughlin, Dennis; Kinzelbach, Wolfgang; Kaiser, Hans-Peter

    2013-04-01

    Practical control of flow in aquifers has been based on deterministic models, not including stochastic information in the optimization (Bauser et al., 2010 or Marti et al., 2012). Only recently robust ensemble control of aquatic systems has been analyzed in linear and synthetic problems (Lin, B., 2012). We propose a control under constraints, which takes into account the stochastic information contained in an ensemble of realizations of a groundwater flow model with uncertain parameters, boundary and initial conditions. This control is applied to a real life problem setting (the Hardhof well field in Zurich) and analyzed with regard to efficiency of the control compared to a similar control based on a deterministic model. The Hardhof well field, which lies in the city of Zurich, Switzerland, provides roughly 15% of the town's drinking water demand from the Limmat valley aquifer. Groundwater and river filtrate are withdrawn in four large horizontal wells, each with a capacity of up to 48'000 m3 per day. The well field is threatened by potential pollution from leachate of a nearby land fill, possible accidents on the adjacent rail and road lines, and by diffuse pollution from former industrial sites and sewers located upstream of the well field. A line of recharge wells and basins forms a hydraulic barrier against the potentially contaminated water and increases the capacity of the well field. The amount and distribution of the artificial recharge to 3 infiltration basins and 12 infiltration wells has to be controlled on a daily basis to guarantee the effectiveness of the hydraulic barrier in the highly dynamic flow field. The Hardhof well field is simulated with a 2D-real-time groundwater flow model. The model is coupled to a controller, minimizing the inflow of potentially contaminated groundwater to the drinking water wells under various constraints (i.e. keeping the groundwater level between given thresholds, guaranteeing production of the drinking water demand

  1. 3D velocity field characterization of prosthetic heart valve with two different valve testers by means of stereo-PIV.

    Science.gov (United States)

    D'Avenio, Giuseppe; Grigioni, Mauro; Daniele, Carla; Morbiducci, Umberto; Hamilton, Kathrin

    2015-01-01

    Prosthetic heart valves can be associated to mechanical loading of blood, potentially linked to complications (hemolysis and thrombogenicity) which can be clinically relevant. In order to test such devices in pulsatile mode, pulse duplicators (PDs) have been designed and built according to different concepts. This study was carried out to compare anemometric measurements made on the same prosthetic device, with two widely used PDs. The valve (a 27-mm bileaflet valve) was mounted in the aortic section of the PD. The Sheffield University PD and the RWTH Aachen PD were selected as physical models of the circulation. These two PDs differ mainly in the vertical vs horizontal realization, and in the ventricular section, which in the RWTH PD allows for storage of potential energy in the elastic walls of the ventricle. A glassblown aorta, realized according to the geometric data of the same anatomical district in healthy individuals, was positioned downstream of the valve, obtaining 1:1 geometric similarity conditions. A NaI-glycerol-water solution of suitable kinematic viscosity and, at the same time, the proper refractive index, was selected. The flow field downstream of the valve was measured by means of the stereo-PIV (Particle Image Velocimetry) technique, capable of providing the complete 3D velocity field as well as the entire Reynolds stress tensor. The measurements were carried out at the plane intersecting the valve axis. A three-jet profile was clearly found in the plane crossing the leaflets, with both PDs. The extent of the typical recirculation zone in the Valsalva sinus was much larger in the RWTH PD, on account of the different duration of the swirling motion in the ventricular chamber, caused by the elasticity of the ventricle and its geometry. The comparison of the hemodynamical behaviour of the same bileaflet valve tested in two PDs demonstrated the role of the mock loop in affecting the valve performance.

  2. Electrohydrodynamic instability of premixed flames under manipulations of dc electric fields

    Science.gov (United States)

    Ren, Yihua; Cui, Wei; Li, Shuiqing

    2018-01-01

    We report an electrohydrodynamic instability in a premixed stagnation flame under manipulations of a dc electric field. This instability occurs when the electric field strength is at a certain value below the breakdown threshold, which is 0.75 kV/cm in the experimental setup. Above this value the flame front suddenly transits from a substrate-stabilized near-flat shape to a nozzle-stabilized conical surface, accompanied by a jump in the electric current through the flame field. At the transition moment, the flame spontaneously propagates upstream to the nozzle while the flow velocity at the upstream of the flame front decreases to zero, as revealed by high-speed photographs and PIV measurements. These phenomena indicate a transient balance between the fluid inertia and the electric body force around the instability threshold. A quantitative model suggests that the flame instability can be explained by a positive feedback loop, where the electric field applies a nonuniform electric body force, pulling the flame front upstream, and the pulled flame front in turn enhances the local electric body force. The electrohydrodynamic instability occurs when the electric pulling is strong enough and both the growth rates and the magnitudes of the electric body force on flame exceed those of the fluid dynamic pressure.

  3. The propagation of the nerve impulse under the effect of a magnetic field

    International Nuclear Information System (INIS)

    Chela-Flores, J.; El-Sayed, E.M.; Wang, X.Y.

    1988-09-01

    The recent significant advance in superconductivity at high temperatures has raised an important problem in biophysics, in view of the underlying interest that has arisen in experiments in which very high magnetic fields are needed (in the multi-tesla range). This is occurring against a theoretical background in which there is no reliable way of estimating the effect of magnetic fields on the central nervous system. This has led us to discuss the problem of the coupling of magnetic fields with the coherent propagation of the polarization of the plasma membrane along the axon. Our work lies within the context of the phenomenological model of nerve impulse propagation due to Hodgkin and Huxley. Using the concept of gauge invariance we find that the magnetic field has a non negligible effect on the velocity of propagation of the action potential in the limit of the Fitzhugh-Nagumo equation without recovery, but more realistic cases do not change the main conclusions of this work. (author). 26 refs

  4. Propagating nonpremixed edge-flames in a counterflow, annular slot burner under DC electric fields

    KAUST Repository

    Tran, Vu Manh

    2016-09-11

    Characteristics of propagating nonpremixed edge-flames were investigated in a counterflow, annular slot burner. A high-voltage direct current (DC) was applied to the lower part of the burner and the upper part was grounded, creating electric field lines perpendicular to the direction of edge-flame propagation. Upon application of an electric field, an ionic wind is caused by the migration of positive and negative ions to lower and higher electrical potential sides of a flame, respectively. Under an applied DC, we found a significant decrease in edge-flame displacement speeds unlike several previous studies, which showed an increase in displacement speed. Within a moderate range of field intensity, we found effects on flame propagation speeds to be negligible after correcting the flame displacement speed with respect to the unburned flow velocity ahead of the flame edge. This indicates that the displacement speed of an edge-flame strongly depends on ionic wind and that an electric field has little or no impact on propagation speed. The ionic wind also influenced the location of the stoichiometric contour in front of the propagating edge in a given configuration such that a propagating edge was relocated to the higher potential side due to an imbalance between ionic winds originating from positive and negative ions. In addition, we observed a steadily wrinkled flame following transient propagation of the edge-flame, a topic for future research. © 2016 The Combustion Institute

  5. Domain wall dynamics in ultrathin Pt/Co/AlOx microstrips under large combined magnetic fields

    Science.gov (United States)

    Jué, E.; Thiaville, A.; Pizzini, S.; Miltat, J.; Sampaio, J.; Buda-Prejbeanu, L. D.; Rohart, S.; Vogel, J.; Bonfim, M.; Boulle, O.; Auffret, S.; Miron, I. M.; Gaudin, G.

    2016-01-01

    The dynamics of magnetic domain walls in ultrathin strip-patterned Pt/Co/AlOx samples with perpendicular easy axis has been studied experimentally under an easy-axis field, superposed to a hard-axis field oriented along the strip. The easy-axis field is large so that the domain walls move well beyond the creep regime. A chiral effect is observed where the domain wall velocity shows a monotonous and surprisingly large variation with an in-plane field. A micromagnetic analysis, combining analytic, one-dimensional, and two-dimensional simulations with structural disorder, shows that this behavior can be reproduced with a Dzyaloshinskii-Moriya interaction of the interfacial type, with due consideration of the dynamics of the tilt degree of freedom of the domain wall. The estimated effective value of this interaction (D ≈-2.2 mJ /m2 for a 0.6 nm Co thickness) is consistent with values obtained by other techniques. It is also shown, by micromagnetic analysis, that several modes and characteristic times occur in the dynamics of the tilt of such domain walls.

  6. Abiotic partitioning of clothianidin under simulated rice field conditions.

    Science.gov (United States)

    Mulligan, Rebecca A; Parikh, Sanjai J; Tjeerdema, Ronald S

    2015-10-01

    Clothianidin is registered for pre- and post-flood application in Californian rice fields for control of the rice seed midge, Cricotopus sylvestris, and the rice water weevil, Lissorhoptrus oryzophilus. The objective was to characterize air-water and soil-water partitioning of clothianidin under simulated Californian rice field conditions. Clothianidin was confirmed to be non-volatile (from water) via the gas purge method, as no loss from the aqueous phase was observed at 22 and 37 °C; an upper-limit KH value was calculated at 2.9 × 10(-11) Pa m(3) mol(-1) (20 °C). Soil-water partitioning was determined by the batch equilibrium method using four soils collected from rice fields in the Sacramento Valley, and sorption affinity (Kd ), sorbent capacity, desorption and organic-carbon-normalized distribution (Koc ) were determined. Values for pH, cation exchange capacity and organic matter content ranged from 4.5 to 6.6, from 5.9 to 37.9 and from 1.25 to 1.97% respectively. The log Koc values (22 and 37 °C) ranged from 2.6 to 2.7, while sorption capacity was low at 22 °C and decreased further at 37 °C. Hysteresis was observed in soils at both temperatures, suggesting that bound residues do not readily desorb. Soil-water and air-water partitioning will not significantly reduce offsite transport of clothianidin from flooded rice fields via drainage. © 2014 Society of Chemical Industry.

  7. Hygrothermal wave propagation in viscoelastic graphene under in-plane magnetic field based on nonlocal strain gradient theory

    Science.gov (United States)

    Karami, Behrouz; Shahsavari, Davood; Li, Li

    2018-03-01

    A size-dependent model is developed for the hygrothermal wave propagation analysis of an embedded viscoelastic single layer graphene sheet (SLGS) under the influence of in-plane magnetic field. The bi-Helmholtz nonlocal strain gradient theory involving three small scale parameters is introduced to account for the size-dependent effects. The size-dependent model is deduced based on Hamilton's principle. The closed-form solution of eigenfrequency relation between wave number and phase velocity is achieved. By studying the size-dependent effects on the flexural wave of SLGS, the dispersion relation predicted by the developed size-dependent model can show a good match with experimental data. The influence of in-plane magnetic field, temperature and moisture of environs, structural damping, damped substrate, lower and higher order nonlocal parameters and the material characteristic parameter on the phase velocity of SLGS is explored.

  8. On whistler-mode group velocity

    International Nuclear Information System (INIS)

    Sazhin, S.S.

    1986-01-01

    An analytical of the group velocity of whistler-mode waves propagating parallel to the magnetic field in a hot anisotropic plasma is presented. Some simple approximate formulae, which can be used for the magnetospheric applications, are derived. These formulae can predict some properties of this group velocity which were not previously recognized or were obtained by numerical methods. In particular, it is pointed out that the anisotropy tends to compensate for the influence of the electron temperature on the value of the group velocity when the wave frequency is well below the electron gyrofrequency. It is predicted, that under conditions at frequencies near the electron gyrofrequency, this velocity tends towards zero

  9. Seismic microzonation and velocity models of El Ejido area (SE Spain) from the diffuse-field H/V method

    Science.gov (United States)

    García-Jerez, Antonio; Seivane, Helena; Navarro, Manuel; Piña-Flores, José; Luzón, Francisco; Vidal, Francisco; Posadas, Antonio M.; Aranda, Carolina

    2016-04-01

    El Ejido town is located in the Campo de Dalías coastal plain (Almería province, SE Spain), emplaced in one of the most seismically active regions of Spain. The municipality has 84000 inhabitants and presented a high growth rate during the last twenty years. The most recent intense seismic activity occurred close to this town was in 1993 and 1994, with events of Mb = 4.9 and Mb = 5.0, respectively. To provide a basis for site-specific hazard analysis, we first carried out a seismic microzonation of this town in terms of predominant periods and geotechnical properties. The predominant periods map was obtained from ambient noise observations on a grid of 250 x 250 m in the main urban area, and sparser measurements on the outskirts. These broad-band records, of about 20 minutes long each, were analyzed by using the horizontal-to-vertical spectral ratio technique (H/V). Dispersion curves obtained from two array measurements of ambient noise and borehole data provided additional geophysical information. All the surveyed points in the town were found to have relatively long predominant periods ranging from 0.8 to 2.3 s and growing towards the SE. Secondary high-frequency (> 2Hz) peaks were found at about the 10% of the points only. On the other hand, Vs30 values of 550 - 650 m/s were estimated from the array records, corresponding to cemented sediments and medium-hard rocks. The local S-wave velocity structure has been inverted from the H/V curves for a subset of the measurement sites. We used an innovative full-wavefield method based on the diffuse-wavefield approximation (Sánchez-Sesma et al., 2011) combined with the simulated annealing algorithm. Shallow seismic velocities and deep boreholes data were used as constraints. The results show that the low-frequency resonances are related with the impedance contrast between several hundred meters of medium-hard sedimentary rocks (marls and calcarenites) with the stiffer basement of the basin, which dips to the SE. These

  10. Enhancement and Suppression in the Visual Field under Perceptual Load

    Directory of Open Access Journals (Sweden)

    Nathan A Parks

    2013-05-01

    Full Text Available The perceptual load theory of attention proposes that the degree to which visual distractors are processed is a function of the attentional demands of a task – greater demands increase filtering of irrelevant distractors. The spatial configuration of such filtering is unknown. Here, we used steady-state visual evoked potentials (SSVEPs in conjunction with time-domain event-related potentials (ERPs to investigate the distribution of load-induced distractor suppression and task-relevant enhancement in the visual field. Electroencephalogram (EEG was recorded while subjects performed a foveal go/no-go task that varied in perceptual load. Load-dependent distractor suppression was assessed by presenting a contrast reversing ring at one of three eccentricities (2°, 6°, or 11° during performance of the go/no-go task. Rings contrast reversed at 8.3 Hz, allowing load-dependent changes in distractor processing to be tracked in the frequency-domain. ERPs were calculated to the onset of stimuli in the load task to examine load-dependent modulation of task-relevant processing. Results showed that the amplitude of the distractor SSVEP (8.3Hz was attenuated under high perceptual load (relative to low load at the most proximal (2° eccentricity but not at more eccentric locations (6˚ or 11˚. Task-relevant ERPs revealed a significant increase in N1 amplitude under high load. These results are consistent with a center-surround configuration of load-induced enhancement and suppression in the visual field.

  11. Enhancement and suppression in the visual field under perceptual load

    Science.gov (United States)

    Parks, Nathan A.; Beck, Diane M.; Kramer, Arthur F.

    2013-01-01

    The perceptual load theory of attention proposes that the degree to which visual distractors are processed is a function of the attentional demands of a task—greater demands increase filtering of irrelevant distractors. The spatial configuration of such filtering is unknown. Here, we used steady-state visual evoked potentials (SSVEPs) in conjunction with time-domain event-related potentials (ERPs) to investigate the distribution of load-induced distractor suppression and task-relevant enhancement in the visual field. Electroencephalogram (EEG) was recorded while subjects performed a foveal go/no-go task that varied in perceptual load. Load-dependent distractor suppression was assessed by presenting a contrast reversing ring at one of three eccentricities (2, 6, or 11°) during performance of the go/no-go task. Rings contrast reversed at 8.3 Hz, allowing load-dependent changes in distractor processing to be tracked in the frequency-domain. ERPs were calculated to the onset of stimuli in the load task to examine load-dependent modulation of task-relevant processing. Results showed that the amplitude of the distractor SSVEP (8.3 Hz) was attenuated under high perceptual load (relative to low load) at the most proximal (2°) eccentricity but not at more eccentric locations (6 or 11°). Task-relevant ERPs revealed a significant increase in N1 amplitude under high load. These results are consistent with a center-surround configuration of load-induced enhancement and suppression in the visual field. PMID:23734135

  12. IN-SYNC VI. Identification and Radial Velocity Extraction for 100+ Double-Lined Spectroscopic Binaries in the APOGEE/IN-SYNC Fields

    Science.gov (United States)

    Fernandez, M. A.; Covey, Kevin R.; De Lee, Nathan; Chojnowski, S. Drew; Nidever, David; Ballantyne, Richard; Cottaar, Michiel; Da Rio, Nicola; Foster, Jonathan B.; Majewski, Steven R.; Meyer, Michael R.; Reyna, A. M.; Roberts, G. W.; Skinner, Jacob; Stassun, Keivan; Tan, Jonathan C.; Troup, Nicholas; Zasowski, Gail

    2017-08-01

    We present radial velocity measurements for 70 high confidence, and 34 potential binary systems in fields containing the Perseus Molecular Cloud, Pleiades, NGC 2264, and the Orion A star-forming region. Eighteen of these systems have been previously identified as binaries in the literature. Candidate double-lined spectroscopic binaries (SB2s) are identified by analyzing the cross-correlation functions (CCFs) computed during the reduction of each APOGEE spectrum. We identify sources whose CCFs are well fit as the sum of two Lorentzians as likely binaries, and provide an initial characterization of the system based on the radial velocities indicated by that dual fit. For systems observed over several epochs, we present mass ratios and systemic velocities; for two systems with observations on eight or more epochs, and which meet our criteria for robust orbital coverage, we derive initial orbital parameters. The distribution of mass ratios for multi-epoch sources in our sample peaks at q = 1, but with a significant tail toward lower q values. Tables reporting radial velocities, systemic velocities, and mass ratios are provided online. We discuss future improvements to the radial velocity extraction method we employ, as well as limitations imposed by the number of epochs currently available in the APOGEE database. The Appendix contains brief notes from the literature on each system in the sample, and more extensive notes for select sources of interest.

  13. Visualisation of the velocity field in a scaled water model for validation of numerical calculations for a powder fuelled boiler

    Energy Technology Data Exchange (ETDEWEB)

    Dumortier, Laurent [Luleaa Univ. of Technology (Sweden)

    2001-01-01

    Validation of numerical predictions of the flow field in a powder fired industry boiler by flow visualisation in a water model has been studied. The bark powder fired boiler at AssiDomaen Kraftliner in Piteaa has been used as a case study. A literature study covering modelling of combusting flows by water models and different flow visualisation techniques has been carried out. The main conclusion as regards the use of water models is that only qualitative information can be expected. As far as turbulent flow is assured in the model as well as the real furnace, the same Reynolds number is not required. Geometrical similarity is important but modelling of burner jets requires adaptation of the jet diameters in the model. Guidelines for this are available and are presented in the report. The review of visualisation techniques shows that a number of methods have been used successfully for validation of flow field predictions. The conclusion is that the Particle Image Velocimetry and Particle Tracking Velocimetry methods could be very suitable for validation purposes provided that optical access is possible. The numerical predictions include flow fields in a 1130 scale model of the AssiDomaen furnace with water flow as well as flow and temperature fields in the actual furnace. Two burner arrangements were considered both for the model and the actual furnace, namely the present configuration with four front burners and a proposed modification where an additional burner is positioned at a side wall below the other burners. There are many similarities between the predicted flow fields in the model and the full scale furnace but there are also some differences, in particular in the region above the burners and the effects of the low region re-circulation on the lower burner jets. The experiments with the water model have only included the arrangement with four front burners. There were problems determining the velocities in the jets and the comparisons with predictions are

  14. Oscillations of oblate drop between heterogeneous plates under uniform electric field

    Science.gov (United States)

    Kashina, M. A.; Alabuzhev, A. A.

    2018-01-01

    The forced oscillations of the incompressible fluid drop under the action of the uniform electric field are considered. In equilibrium, the drop has the form of a circular cylinder bounded axially by the parallel solid planes; the contact angle is right. An incompressible fluid of different density surrounds the drop. The external electric field acts as an external force that causes motion of the contact line. In order to describe this contact line motion, the modified Hocking boundary condition is applied: the velocity of the contact line is proportional to the deviation of the contact angle and the speed of the fast relaxation processes, whose frequency is proportional to twice the frequency of the electric field. The case of heterogeneous plates is investigated. We assume that the Hocking parameter depends on the polar angle in this case. The function describing the change in the coefficient of the interaction between the plate and the fluid (the contact line) is expanded in a series of the Laplace operator eigenfunctions.

  15. Characterization of velocity and temperature fields in a 217 pin wire wrapped fuel bundle of sodium cooled fast reactor

    International Nuclear Information System (INIS)

    Naveen Raj, M.; Velusamy, K.

    2016-01-01

    Highlights: • We simulate flow and temperature fields in fuel subassembly of fast reactor. • We perform high fidelity computations for 217 pin bundle of 7 axial pitch lengths. • We investigate transverse and axial flows in different types of subchannels. • Correlations are proposed for transverse flow, which form input for subchannel analysis. • Periodic variations of large magnitude are observed in subchannel flow rates. - Abstract: RANS based computational fluid dynamic (CFD) simulation of flow and temperature fields in a fast reactor fuel subassembly has been carried out. The sodium cooled prototype subassembly consists of 217 pins with helical wire spacers. An axial length of seven helical wire pitches has been considered for the study adopting a structured mesh having 36 million points and 84 processors in parallel. The computational model has been validated against in-house and published experimental data for friction factor and Nusselt number. Also, the transverse flow in the central subchannel and swirl flow in the peripheral subchannel are compared against reported experimental data and those computed by subchannel models. The focus of the study is investigation of transverse and axial flows in different types of subchannels. Based on the 3-dimensional CFD study, correlations have been proposed for calculation of transverse flow, which forms an important input for development of subchannel analysis codes. Periodic variations have been observed in the subchannel axial flow rates. For the subchannels located in the central region, the peak to peak variation in the axial flow rate is ∼21% and it is found to be contributed by the changes in the flow area and hydraulic resistance due to frequent passage of helical wires through the subchannel. For the subchannels located in the periphery, this variation is as high as 50%. The transverse flow in the central subchannels follows a cosine profile, for all the faces. However, there is a phase lag of 120

  16. Plasma screening effects on the energies of hydrogen atom under the influence of velocity-dependent potential

    International Nuclear Information System (INIS)

    Bahar, M. K.

    2014-01-01

    In order to examine the plasma screening and velocity-dependent potential effects on the hydrogen atom, the Schrödinger equation including a more general exponential cosine screened Coulomb and velocity-dependent potential is solved numerically in the framework asymptotic iteration method. The more general exponential cosine screened Coulomb potential is used to model Debye and quantum plasma for the specific values of the parameters in its structure. However, in order to examine effects of velocity-dependent potential on energy values of hydrogen atom in Debye and quantum plasma, the isotropic form factor of velocity-dependent potential is given as harmonic oscillator type, ρ(r)=ρ o r 2 . Then, the energies of s and p states are calculated numerically without any approximation. In order to investigate thoroughly plasma screening effects and contribution of velocity-dependent potential on energy values of hydrogen atom, the corresponding calculations are carried out by using different values of parameters of more general exponential cosine screened Coulomb potential and isotropic dependence, results of which are discussed

  17. Measurement of sliding velocity and induction time of a single micro-bubble under an inclined collector surface

    Energy Technology Data Exchange (ETDEWEB)

    Najafi, A.S.; Xu, Z.; Masliyah, J. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical and Materials Engineering

    2008-12-15

    Flotation is a major process by which bitumens are recovered from oil sands slurries, and air bubble-bitumen attachment is necessary for the effective separation of aerated bitumen. This study investigated the interactions between a gas bubble and a solid, flat surface. Various physical and chemical conditions were studied in order to determine their impact on the sliding velocity and induction times of the micro-bubble as it slid underneath an inclined solid surface. The bubble's trajectory was monitored by a high-speed video imaging system. Tests were conducted using de-aerated process water in order to study the effect of dissolved gases on bubble sliding velocity. Simulated process water was also used to study the role of the natural surfactants contained in recycle process water. The study showed that terminal and sliding velocities of the bubbles were functions of temperature. Sliding velocities increased with increases in liquid temperature. Increases in liquid temperature also reduced the induction time used to quantify bubble-solid attachment. Induction times were also reduced with increases in surface hydrophobicity. Induction times measured for CO{sub 2} bubbles were shorter than those observed with air, oxygen, and hydrogen bubbles. It was concluded that the use of natural surface active agents in process water reduced bubble terminal rising velocity and increased the induction times of bubble-solid attachment. 36 refs., 2 tabs., 15 figs.

  18. TRAJ - a FORTRAN 77 computer program for the calculation of trajectories on the basis of space and time varying velocity fields

    International Nuclear Information System (INIS)

    Zimmer, J.

    1986-09-01

    The computation of three dimensional trajectories is described in this report. Since measurements of the position and velocity of individual fluid parcels are difficult to be carried out and analytic solutions applicable to the trajectory problem are not available, trajectories have to be calculated by successive observations of the corresponding velocity fields using a method of successive approximation. The application is restricted to cartesian grid coordinate system with equidistant grid points. This model was developed for meteorological purposes (transport of pollutants) but can also be used for other fluids and scales. (orig./PW) [de

  19. Field Test of Driven Pile Group under Lateral Loading

    Science.gov (United States)

    Gorska, Karolina; Rybak, Jaroslaw; Wyjadlowski, Marek

    2017-12-01

    All the geotechnical works need to be tested because the diversity of soil parameters is much higher than in other fields of construction. Horizontal load tests are necessary to determine the lateral capacity of driven piles subject to lateral load. Various load tests were carried out altogether on the test field in Kutno (Poland). While selecting the piles for load tests, different load combinations were taken into account. The piles with diverse length were chosen, on the basis of the previous tests of their length and integrity. The subsoil around the piles consisted of mineral soils: clays and medium compacted sands with the density index ID>0.50. The pile heads were free. The points of support of the “base” to which the dial gauges (displacement sensors) were fastened were located at the distance of 0.7 m from the side surface of the pile loaded laterally. In order to assure the independence of measurement, additional control (verifying) geodetic survey of the displacement of the piles subject to the load tests was carried out (by means of the alignment method). The trial load was imposed in stages by means of a hydraulic jack. The oil pressure in the actuator was corrected by means of a manual pump in order to ensure the constant value of the load in the on-going process of the displacement of the pile under test. On the basis of the obtained results it is possible to verify the numerical simulations of the behaviour of piles loaded by a lateral force.

  20. Accumulation of mercury in Typha domingensis under field conditions.

    Science.gov (United States)

    Lominchar, M A; Sierra, M J; Millán, R

    2015-01-01

    Typha species is a common wetland plant used in the treatment of urban and industrial effluents. But, despite their widespread implementation, there are not many studies based on the behaviour of this plant growing in an areas affected by mercury. The present work investigates the ability of Typha domingensis to accumulate mercury under field conditions. The study area was along the Valdeazogues river which flows through the Almadén mining district (Ciudad Real, Spain) that is considered the largest mercury reservoir in the world. The mercury concentration in different plant fractions was measured as well as the available and total concentration in the bottom sediments. The results showed that the highest mercury concentrations were found in the belowground organs. T. domingensis had a high efficiency to accumulate mercury in their organs although available metal concentrations in the environment did not exceed 0.16 mg kg(-1). Bioaccumulation factors (BAF) ranged between 121 and 3168 in roots. Furthermore, significant correlations were found between mercury concentration in all plant organs and Hg in sediments (both total and available). These results demonstrated that T. domingensis could be used as a biomonitor as well as in phytoextraction technology in areas affected by mercury. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Postseismic velocity changes following the 2010 Mw 7.1 Darfield earthquake, New Zealand, revealed by ambient seismic field analysis

    Science.gov (United States)

    Heckels, R. E. G.; Savage, M. K.; Townend, J.

    2018-01-01

    Quantifying seismic velocity changes following large earthquakes can provide insights into fault healing and reloading processes. This study presents temporal velocity changes detected following the September 2010 Mw 7.1 Darfield event in Canterbury, New Zealand. We use continuous waveform data from several temporary seismic networks lying on and surrounding the Greendale Fault, with a maximum inter-station distance of 156 km. Nine-component, day-long Green's functions were computed for frequencies between 0.1 and 1.0 Hz for continuous seismic records from immediately after the 4 September 2010 earthquake until 10 January 2011. Using the moving-window cross-spectral method seismic velocity changes were calculated. Over the study period, an increase in seismic velocity of 0.14 % ± 0.04 % was determined near the Greendale Fault, providing a new constraint on postseismic relaxation rates in the region. A depth analysis further showed that velocity changes were confined to the uppermost 5 km of the subsurface. We attribute the observed changes to postseismic relaxation via crack-healing of the Greendale Fault and throughout the surrounding region.

  2. Marine traffic model based on cellular automaton: Considering the change of the ship's velocity under the influence of the weather and sea

    Science.gov (United States)

    Qi, Le; Zheng, Zhongyi; Gang, Longhui

    2017-10-01

    It was found that the ships' velocity change, which is impacted by the weather and sea, e.g., wind, sea wave, sea current, tide, etc., is significant and must be considered in the marine traffic model. Therefore, a new marine traffic model based on cellular automaton (CA) was proposed in this paper. The characteristics of the ship's velocity change are taken into account in the model. First, the acceleration of a ship was divided into two components: regular component and random component. Second, the mathematical functions and statistical distribution parameters of the two components were confirmed by spectral analysis, curve fitting and auto-correlation analysis methods. Third, by combining the two components, the acceleration was regenerated in the update rules for ships' movement. To test the performance of the model, the ship traffic flows in the Dover Strait, the Changshan Channel and the Qiongzhou Strait were studied and simulated. The results show that the characteristics of ships' velocities in the simulations are consistent with the measured data by Automatic Identification System (AIS). Although the characteristics of the traffic flow in different areas are different, the velocities of ships can be simulated correctly. It proves that the velocities of ships under the influence of weather and sea can be simulated successfully using the proposed model.

  3. Experimental study of the possibility of reducing the resistance and unevenness of output field of velocities in flat diffuser channels with large opening angles

    Science.gov (United States)

    Dmitriev, S. S.; Vasil'ev, K. E.; Mokhamed, S. M. S. O.; Gusev, A. A.; Barbashin, A. V.

    2017-11-01

    In modern combined cycle gas turbines (CCGT), when designing the reducers from the output diffuser of a gas turbine to a boiler-utilizer, wide-angle diffusers are used, in which practically from the input a flow separation and transition to jet stream regime occurs. In such channels, the energy loss in the field of velocities sharply rise and the field of velocities in the output from them is characterized by considerable unevenness that worsens the heat transfer process in the first by motion tube bundles of the boiler-utilizer. The results of experimental research of the method for reducing the energy loss and alignment of the field of velocities at the output from a flat asymmetrical diffuser channel with one deflecting wall with the opening angle of 40° by means of placing inside the channel the flat plate parallel to the deflecting wall are presented in the paper. It is revealed that, at this placement of the plate in the channel, it has a chance to reduce the energy loss by 20%, considerably align the output field of velocities, and decrease the dynamic loads on the walls in the output cross-section. The studied method of resistance reduction and alignment of the fields of velocities in the flat diffuser channels was used for optimization of the reducer from the output diffuser of the gas turbine to the boiler-utilizer of CCGT of PGU-450T type of Kaliningrad Thermal Power Plant-2. The obtained results are evidence that the configuration of the reducer installed in the PGU-450T of Kaliningrad Thermal Power Plant-2 is not optimal. It follows also from the obtained data that working-off the reducer should be necessarily conducted by the test results of the channel consisting of the model of reducer with the model of boiler-utilizer installed behind it. Application of the method of alignment of output field of velocities and reducing the resistance in the wide-angle diffusers investigated in the work made it possible—when using the known model of diffusion

  4. Three-dimensional morphologies of inclined equiaxed dendrites growing under forced convection by phase-field-lattice Boltzmann method

    Science.gov (United States)

    Sakane, Shinji; Takaki, Tomohiro; Ohno, Munekazu; Shibuta, Yasushi; Shimokawabe, Takashi; Aoki, Takayuki

    2018-02-01

    Three-dimensional growth morphologies of equiaxed dendrites growing under forced convection, with their preferred growth direction inclined from the flow direction, were investigated by performing large-scale phase-field lattice Boltzmann simulations on a graphical-processing-unit supercomputer. The tip velocities of the dendrite arms with their preferred growth directions inclined toward the upstream and downstream directions increased and decreased, respectively, as a result of forced convection. In addition, the tip velocities decreased monotonically as the angle between the preferred growth direction and the upstream direction increased. Here, the degree of acceleration of the upstream tips was larger than the degree of deceleration of the downstream tips. The angles between the actual tip growth directions and the preferred growth direction of the dendrite arms exhibited a characteristic change with two local maxima and two local minima.

  5. Seismic detection of fault zone hydrocarbon conduit-seal potential using velocity, frequency, and Q analysis: La Concepcion Field, Lake Maracaibo Venezuela example

    Science.gov (United States)

    Alahdal, Ahmed Omar

    The 3-D Post-Stack Time Migrated Seismic Data of La Concepcion Field, Maracaibo Basin, Venezuela cover an existing field with known oil and gas pay zones. The thesis problem is how to use this seismic data in an interpretation of leaky faults that occur in the exploration area of interest. A solution to the problem was obtained using an integrated geophysical approach that included published seismic attribute methods (Variance Cube, Geoframe IESX). Specific developments in this thesis to solve the interpretation problem of leaky faults in the region include (1) an image ray perturbation approach for updating the interval velocity in a faulted domain (2) a peak frequency approach to attenuation estimation within intervals and (3) a scaled interpretation of the velocity measurements at sonic, checkshot and surface seismic reflection data. The first development refines the interval velocities within fracture zones. The second development identifies anomalous attenuation most likely due to the presence of gas. The combined effects of low interval velocity and high attenuation are interpreted to be signs of leaking faults.

  6. Measurement of flow velocity fields in small vessel-mimic phantoms and vessels of small animals using micro ultrasonic particle image velocimetry (micro-EPIV).

    Science.gov (United States)

    Qian, Ming; Niu, Lili; Wang, Yanping; Jiang, Bo; Jin, Qiaofeng; Jiang, Chunxiang; Zheng, Hairong

    2010-10-21

    Determining a multidimensional velocity field within microscale opaque fluid flows is needed in areas such as microfluidic devices, biofluid mechanics and hemodynamics research in animal studies. The ultrasonic particle image velocimetry (EchoPIV) technique is appropriate for measuring opaque flows by taking advantage of PIV and B-mode ultrasound contrast imaging. However, the use of clinical ultrasound systems for imaging flows in small structures or animals has limitations associated with spatial resolution. This paper reports on the development of a high-resolution EchoPIV technique (termed as micro-EPIV) and its application in measuring flows in small vessel-mimic phantoms and vessels of small animals. Phantom experiments demonstrate the validity of the technique, providing velocity estimates within 4.1% of the analytically derived values with regard to the flows in a small straight vessel-mimic phantom, and velocity estimates within 5.9% of the computationally simulated values with regard to the flows in a small stenotic vessel-mimic phantom. Animal studies concerning arterial and venous flows of living rats and rabbits show that the micro-EPIV-measured peak velocities within several cardiac cycles are about 25% below the values measured by the ultrasonic spectral Doppler technique. The micro-EPIV technique is able to effectively measure the flow fields within microscale opaque fluid flows.

  7. Propulsion Physics Under the Changing Density Field Model

    Science.gov (United States)

    Robertson, Glen A.

    2011-01-01

    To grow as a space faring race, future spaceflight systems will requires new propulsion physics. Specifically a propulsion physics model that does not require mass ejection without limiting the high thrust necessary to accelerate within or beyond our solar system and return within a normal work period or lifetime. In 2004 Khoury and Weltman produced a density dependent cosmology theory they called Chameleon Cosmology, as at its nature, it is hidden within known physics. This theory represents a scalar field within and about an object, even in the vacuum. Whereby, these scalar fields can be viewed as vacuum energy fields with definable densities that permeate all matter; having implications to dark matter/energy with universe acceleration properties; implying a new force mechanism for propulsion physics. Using Chameleon Cosmology, the author has developed a new propulsion physics model, called the Changing Density Field (CDF) Model. This model relates to density changes in these density fields, where the density field density changes are related to the acceleration of matter within an object. These density changes in turn change how an object couples to the surrounding density fields. Whereby, thrust is achieved by causing a differential in the coupling to these density fields about an object. Since the model indicates that the density of the density field in an object can be changed by internal mass acceleration, even without exhausting mass, the CDF model implies a new propellant-less propulsion physics model

  8. Investigation of the flow field around a propeller-rudder configuration: on-surface pressure measurements and velocity-pressure-phase-locked correlations

    OpenAIRE

    Felli, Mario; Falchi, Massimo; Pereira, Francisco

    2011-01-01

    The present paper deals with the problem of the propeller induced perturbation on the rudder . The study aims at providing insights on the key mechanisms governing the complex interaction between the propeller wake structures and the rudder. In this regard, a wide experimental activity that concerned PIV and LDV velocity measurements and wall-pressure-measurements on the two faces of the rudder was performed in a cavitation tunnel. The major flow features that distinguish the flow field aroun...

  9. BVOC emission pattern from Quercus robur under field conditions

    Science.gov (United States)

    Pokorska, O.; Dewulf, J.; Joó; Šimpraga, M.; Steppe, K.; Amelynck, C.; Schoon, N.; Muller, J. J.; van Langenhove, H.

    2010-12-01

    Over the past decades biogenic volatile organic compounds (BVOC) have been widely studied not only for better understanding their functions, biosynthesis and regulation, but also because they have great impact on regional and global air quality [1]. Since all BVOCs react with hydroxyl radicals (OH●) and may also react with nitrate radicals (NO3●) and ozone (O3), they contribute to the formation of ozone and secondary organic aerosols. In this study we focus on Quercus robur which is a widely spread tree species in Europe and known as a strong isoprene emitter. We aimed to investigate seasonal patterns of BVOC emissions from Quercus robur under field conditions and to explore the intra-species variations within Quercus robur trees as both are of great importance for accurate modeling and regional inventories. Measurements were performed during a period from May till October 2009 at the campus of Ghent University (Belgium) using a dynamic branch enclosure system. Experiments were conducted on four potted Quercus robur trees with a varying 1-1.5 m height. Samples were collected on Tenax TA-Carbotrap adsorbent tubes and analyzed by TD-GC-MS. Isoprene was the predominant compound released by Quercus robur (QR1) with a pronounced seasonal emission. The normalized emission rates for isoprene calculated according to Guenther’s algorithm (standard conditions of temperature 30°C and PAR 1000 µmol m-2 s-1) varied from 29.89 µg h-1 g(DW)-1 in Spring (May) to 28.62 µg h-1 g(DW)-1 in Fall (October) reaching peak of 105.51 µg h-1 g(DW)-1 in August. Apart from isoprene, through the whole measurement period trans-β-ocimene and β-caryophyllene were the only BVOC emitted in detectable range (sum of the emissions varied between 0.15 µg h-1 g(DW)-1 in July and 0.24 µg h-1 g(DW)-1 in October). No clear seasonal pattern was observed for those compounds. In May when acorns where developing on enclosed branch, emissions of limonene and β-farnesene were also observed. The

  10. Influence of crack distribution of rocks on P-wave velocity anisotropy - a laboratory and field scale study

    Czech Academy of Sciences Publication Activity Database

    Vilhelm, J.; Rudajev, Vladimír; Živor, Roman; Lokajíček, Tomáš; Pros, Zdeněk

    2010-01-01

    Roč. 58, č. 6 (2010), s. 1099-1110 ISSN 0016-8025 R&D Projects: GA ČR GA205/06/0906; GA AV ČR IAA300130906 Institutional research plan: CEZ:AV0Z30130516 Keywords : anisotropy * fracture * stiffness * seismic velocity * shallow seismic refraction method * ultrasound radiation Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.493, year: 2010

  11. A new GPS velocity field for the Pacific Plate - Part 1: constraints on plate motion, intraplate deformation, and the viscosity of Pacific basin asthenosphere

    Science.gov (United States)

    DeMets, C.; Márquez-Azúa, Bertha; Cabral-Cano, Enrique

    2014-12-01

    We combine new, well-determined GPS velocities from Clarion, Guadalupe and Socorro islands on young seafloor in the eastern Pacific basin with newly estimated velocities for 26 GPS sites from older seafloor in the central, western and southern parts of the Pacific Plate to test for deformation within the interior of the Pacific Plate and estimate the viscosity of the asthenosphere below the plate. Relative to a Pacific Plate reference frame defined from the velocities of the 26 GPS sites in other areas of the Pacific Plate, GPS sites on Clarion and Guadalupe islands in the eastern Pacific move 1.2 ± 0.6 mm yr-1 (1σ) towards S09°W ± 38° and 1.9 ± 0.3 mm yr-1 towards S19°E ± 10°, respectively. The two velocities, which are consistent within their 95 per cent uncertainties, both differ significantly from Pacific Plate motion. Transient volcanic deformation related to a 1993-1996 eruption of the Socorro Island shield volcano renders our GPS velocity from that island unreliable for the tectonic analysis although its motion is also southward like those of Clarion and Guadalupe islands. We test but reject the possibilities that drift of Earth's origin in ITRF2008 or unmodelled elastic offsets due to large-magnitude earthquakes around the Pacific rim since 1993 can be invoked to explain the apparent slow southward motions of Clarion and Guadalupe islands. Similarly, corrections to the Pacific Plate GPS velocity field for possible viscoelastic deformation triggered by large-magnitude earthquakes since 1950 also fail to explain the southward motions of the two islands. Viscoelastic models with prescribed asthenospheric viscosities lower than 1 × 1019 Pa s instead introduce statistically significant inconsistencies into the Pacific Plate velocity field, suggesting that the viscosity of the asthenosphere below the plate is higher than 1 × 1019 Pa s. Elastic deformation from locked Pacific-North America Plate boundary faults is also too small to explain the southward

  12. Temporal velocity variations beneath the Coso geothermal field observed using seismic double difference tomography of compressional and shear wave arrival times

    Science.gov (United States)

    Seher, T.; Zhang, H.; Fehler, M. C.; Newman, G. A.

    2011-12-01

    Microseismic imaging can be an important tool for characterizing geothermal reservoirs. Since microseismic sources occur more or less continuously due to the operations of a geothermal plant and the naturally occurring background seismicity, passive seismic monitoring is well suited for quantifying the temporal variations in reservoir properties that occur within the geothermal reservoir during production. In this study we will use microseismic data recorded between 1996 and 2008 to investigate the temporal variations in seismic velocity below the Coso geothermal field in California. In this study we will apply the double difference tomography method to simultaneously locate a suite of microseismic events and determine the compressional and shear wave velocity as well as their ratio. The double-difference method uses both absolute and relative arrival times of earthquakes measured at the same station, which allows a more precise determination of the relative locations of earthquakes. In particular, we apply a cross-correlation technique to improve the measurement of relative traveltimes. The large number of microearthquakes observed between 1996 and 2008 allows us to characterize subsurface velocity and to investigate changes in velocity that accompany production from the geothermal reservoir.

  13. Properties of a Bound Polaron under a Perpendicular Magnetic Field

    International Nuclear Information System (INIS)

    Liu Jia; Chen Ziyu; Xiao Jinglin; Huo Shufen

    2007-01-01

    We investigate the influence of a perpendicular magnetic field on a bound polaron near the interface of a polar-polar semiconductor with Rashba effect. The external magnetic field strongly changes the ground state binding energy of the polaron and the Rashba spin-orbit (SO) interaction originating from the inversion asymmetry in the heterostructure splits the ground state binding energy of the bound polaron. In this paper, we have shown how the ground state binding energy will be with the change of the external magnetic field, the location of a single impurity, the wave vector of the electron and the electron areal density, taking into account the SO coupling. Due to the presence of the phonons, whose energy gives negative contribution to the polaron's, the spin-splitting states of the bound polaron are more stable, and we find that in the condition of week magnetic field, the Zeeaman effect can be neglected.

  14. Solitons in a Dielectric Medium under an External Magnetic Field

    OpenAIRE

    Isamu, NAKATA; Hiroaki, ONO; Mitito, YOSIDA; College of Integrated Arts and Sciences, University of Osaka Prefecture; Department of Mathematics and Physics, Faculty of Engineering, Setunan University; Nippondenso Co., Ltd.

    1993-01-01

    Solitons in a dielectric medium propagating along an external magnetic field is investigated. By means of a nonlinear perturbation method, the derivative nonlinear Schrodinger equation is derived and the possibility of propagation of the spiky and algebraic solitons is shown.

  15. Losses in superconducting multifilament composites under alternating changing fields

    International Nuclear Information System (INIS)

    Turck, B.

    1979-03-01

    The first part of this report presents a brief review of the losses in superconducting composites in a changing external field. The losses are expressed for a single triangular shaped pulse and for a field varying exponentially with time. The losses are calculated as a function of two important time constants. The first is due to the coupling currents between the filaments, the second is due to the eddy currents induced in the matrix. In the second part of the report, the case of an oscillating sinusoidal field is considered. In particular, in a rapidly varying field, several layers of filaments can be saturated by returning currents. Complete expressions of the losses are provided together with simplified expressions which enable one to calculate the losses in most cases. In the third part, a comparison between several kinds of conductors shows that in some cases the losses are reduced by increasing the twist pitch of the conductor

  16. The role of wind field induced flow velocities in destratification and hypoxia reduction at Meiling Bay of large shallow Lake Taihu, China.

    Science.gov (United States)

    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

  17. Numerical simulations of mechanical and ignition-deflagration responses for PBXs under low-to-medium-level velocity impact loading.

    Science.gov (United States)

    Yang, Kun; Wu, Yanqing; Huang, Fenglei; Li, Ming

    2017-09-05

    An effective computational model is required to accurately predict the dynamic responses in accidental initiations of explosives. The present work uses a series of two-dimensional mechanical-chemical simulations performed via a hydrodynamic-code, DREXH-2D, to efficiently describe the mechanical and ignition-deflagration responses of cased cylindrical polymer-bonded explosives (PBXs) undergoing a low-to-medium-level impact (70-350m/s) in longitudinal direction. The ignition response was predicted based on an ignition criterion of effective plastic work. Slow burning and its growth to deflagration were described through a pressure-dependent reaction rate equation. The extreme value of effective plastic work was found to be useful to determine the ignition threshold velocity for PBXs. For low-level velocity impact, the incident stress wave reflection from lateral surfaces contributed to the formation of ignition regions. After the ignition, the deflagration was induced in the medium-level impact, and its violence was related to the shock strength. However, the low-strength stress wave only induced reaction at local regions, and sequent burning was no longer sensitive to the strength of incident wave. The predicted pressure and temperature results of PBXs were consistent with the medium-level impact tests performed by China Academy of Engineering Physics. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Balance Velocities of the Greenland Ice Sheet

    Science.gov (United States)

    Joughin, Ian; Fahnestock, Mark; Ekholm, Simon; Kwok, Ron

    1997-01-01

    We present a map of balance velocities for the Greenland ice sheet. The resolution of the underlying DEM, which was derived primarily from radar altimetry data, yields far greater detail than earlier balance velocity estimates for Greenland. The velocity contours reveal in striking detail the location of an ice stream in northeastern Greenland, which was only recently discovered using satellite imagery. Enhanced flow associated with all of the major outlets is clearly visible, although small errors in the source data result in less accurate estimates of the absolute flow speeds. Nevertheless, the balance map is useful for ice-sheet modelling, mass balance studies, and field planning.

  19. Kinetics of diuron under aerobic condition and residue analysis in sugarcane under subtropical field conditions.

    Science.gov (United States)

    Tandon, Shishir; Pant, Ravi

    2017-10-10

    The phenylureas group includes persistent herbicides which are major pollutants to soil and water. Dissipation kinetics of diuron in different soils under sugarcane field conditions was investigated. Diuron was extracted with acetone and florisil solid phase extraction clean-up and characterized by high-performance liquid chromatography-UV. Diuron persisted for more than 100 days and dissipation followed monophasic first-order kinetics. Persistence was more in sandy loam compared to silty clay loam soil. Half-life of diuron in silty clay loam soil was 22.57 and 32.37 days and in sandy loam was 28.35 and 43.93 days at 2 and 4 kg ha-1applications, respectively. Average recovery in soil, bagasse, leaf-straw and juice ranged from 75.95% to 84.20%, 80.15% to 89.35%, 77.46% to 86.19% and 81.88% to 92.68%, respectively. The quantitation limits for soil, bagasse, leaf-straw and juice were 0.01, 0.03, 0.04 μg g -1 and 0.008 μg mL -1 , respectively. Application of diuron inhibited growth of soil microbes initially but they recovered later. At harvest, diuron residues were below maximum residue limits in all samples. The study revealed that under subtropical conditions, diuron is safe for use in weed management and would not pose any residual/environmental problem and that sugarcane crop could be used safe for human/animal consumption.

  20. Vector velocity estimation using directional beam forming and cross-correlation

    DEFF Research Database (Denmark)

    2000-01-01

    The two-dimensional velocity vector using a pulsed ultrasound field can be determined with the invention. The method uses a focused ultrasound field along the velocity direction for probing the moving medium under investigation. Several pulses are emitted and the focused received fields along...

  1. Operation in the turbulent jet field of a linear array of multiple rectangular jets using a two-dimensional jet (Variation of mean velocity field

    Directory of Open Access Journals (Sweden)

    Fujita Shigetaka

    2016-01-01

    Full Text Available The mean flowfield of a linear array of multiple rectangular jets run through transversely with a two-dimensional jet, has been investigated, experimentally. The object of this experiment is to operate both the velocity scale and the length scale of the multiple rectangular jets using a two-dimensional jet. The reason of the adoption of this nozzle exit shape was caused by the reports of authors in which the cruciform nozzle promoted the inward secondary flows strongly on both the two jet axes. Aspect ratio of the rectangular nozzle used in this experiment was 12.5. Reynolds number based on the nozzle width d and the exit mean velocity Ue (≅ 39 m / s was kept constant 25000. Longitudinal mean velocity was measured using an X-array Hot-Wire Probe (lh = 3.1 μm in diameter, dh = 0.6 mm effective length : dh / lh = 194 operated by the linearized constant temperature anemometers (DANTEC, and the spanwise and the lateral mean velocities were measured using a yaw meter. The signals from the anemometers were passed through the low-pass filters and sampled using A.D. converter. The processing of the signals was made by a personal computer. Acquisition time of the signals was usually 60 seconds. From this experiment, it was revealed that the magnitude of the inward secondary flows on both the y and z axes in the upstream region of the present jet was promoted by a two-dimensional jet which run through transversely perpendicular to the multiple rectangular jets, therefore the potential core length on the x axis of the present jet extended 2.3 times longer than that of the multiple rectangular jets, and the half-velocity width on the rectangular jet axis of the present jet was suppressed 41% shorter compared with that of the multiple rectangular jets.

  2. Coherent scattering of an atom in the field of a standing wave under conditions of initial quantum correlation of subsystems

    Energy Technology Data Exchange (ETDEWEB)

    Trubilko, A. I., E-mail: trubilko.andrey@gmail.com [St. Petersburg University of State Fire Service of the Russian Ministry of Emergency Situations (Russian Federation)

    2016-10-15

    Coherent scattering of a two-level atom in the field of a quantized standing wave of a micromaser is considered under conditions of initial quantum correlation between the atom and the field. Such a correlation can be produced by a broadband parametric source. The interaction leading to scattering of the atom from the nonuniform field occurs in the dispersion limit or in the wing of the absorption line of the atom. Apart from the quantized field, the atom simultaneously interacts with two classical counterpropagating waves with different frequencies, which are acting in the plane perpendicular to the atom’s propagation velocity and to the wavevector of the standing wave. Joint action of the quantized field and two classical waves induces effective two-photon and Raman resonance interaction on the working transition. The effective Hamiltonian of the interaction is derived using the unitary transformation method developed for a moving atom. A strong effect is detected, which makes it possible to distinguish the correlated initial state of the atom and the field in the scattering of atom from the state of independent systems. For all three waves, scattering is not observed when systems with quantum correlation are prepared using a high-intensity parametric source. Conversely, when the atom interacts only with the nonuniform field of the standing wave, scattering is not observed in the case of the initial factorized state.

  3. Flickering characteristics and temperature field of premixed methane/air flame under the influence of co-flow

    International Nuclear Information System (INIS)

    Fujisawa, Nobuyuki; Abe, Takao; Yamagata, Takayuki; Tomidokoro, Hirofumi

    2014-01-01

    Highlights: • Flickering characteristics and temperature field of premixed methane/air flame are studied in co-flow. • The temperature is measured by improved flame reaction technique by correcting the number density of metal atoms. • The temperature calibration is conducted by sodium D-line reversal method. • The oscillation amplitude of flame decreases and the frequency increases with co-flow velocity. • The oscillation amplitude increases with equivalence ratio. - Abstract: The flickering characteristics and the temperature field of an axisymmetric premixed methane/air flame under the influence of co-flow are studied experimentally using the image analysis and the flame reaction technique. The premixed flame is visualized by the alkali metal solution of sodium (Na) for characterizing the flickering characteristics. The temperature measurement of the flame is carried out using the flame reaction technique combined with the relationship between the local intensity of the flame and the temperature from the sodium D-line reversal method, and the influence of the number density distribution of Na on the measured temperature field is corrected by the measurement integrated analysis of the flame with the iterative procedure. This technique is validated by the local temperature measurement in the steady flame under the influence of co-flow using the thermocouple calibrated by the sodium D-line reversal method. The flame visualization and temperature measurement in the flickering flame of the premixed methane/air flame indicates that the flame contour and the temperature field oscillate periodically with the flickering frequency due to the Kelvin–Helmholtz instability of the flame. The oscillation amplitude decreases and the frequency increases gradually with the co-flow velocity increases similar to the observation in the diffusion flame in literature, while the oscillation amplitude grows with the equivalence ratio increases. These changes in the flickering

  4. Autonomous Observations of the Upper Ocean Stratification and Velocity Field about the Seasonally-Retreating Marginal Ice Zone

    Science.gov (United States)

    2016-12-30

    CLASSIFICATION OF: a. REPORT b. ABST~ CT c. TH.IS PAGE u u u 17. LIMITATION OF 18. NUMBER ABSTRACT OF PAGES uu 8 19a. NAME OF RESPONSIBLE PERSON John M...edu Mary-Louise Timmermans Ill Kline Geology Laboratory, Yale University PO Box 208109, New Haven CT 06520-8109 phone: (203) 432-3167 fax: (203...the MlZ DRl in vo lved deployment ofice-Tethered Profile rs with Velocity (ITP-V) to sample the ocean and return those observations to the Pis in near

  5. Simulation of prepackaged grout bleed under field conditions : [summary].

    Science.gov (United States)

    2014-04-01

    Post-tensioning (PT) is a method of compensating : for concretes weakness under tension by adding : steel. Tubes (ducts) are cast into concrete : components; after the concrete sets, high-strength steel cables (tendons or strand) are run : through...

  6. Alignment of the hydrogen molecule under intense laser fields.

    Science.gov (United States)

    Lopez, Gary V; Fournier, Martin; Jankunas, Justin; Spiliotis, Alexandros K; Rakitzis, T Peter; Chandler, David W

    2017-07-07

    Alignment of the electronically excited E,F state of the H 2 molecule is studied using the velocity mapping imaging technique. Photofragment images of H + due to the dissociation mechanism that follows the 2-photon excitation into the (E,F; ν = 0, J = 0) electronic state show a strong dependence on laser intensity, which is attributed to the high polarizability anisotropy of the H 2 (E,F) state. We observe a marked structure in the angular distribution, which we explain as the interference between the prepared J = 0 and Stark-mixed J = 2 rovibrational states of H 2 , as the laser intensity increases. Quantification of these effects allows us to extract the polarizability anisotropy of the H 2 (E,F J = 0) state yielding a value of 312 ± 82 a.u. (46 Å 3 ). By comparison, CS 2 has 10 Å 3 , I 2 has 7 Å 3 , and hydrochlorothiazide (C 7 H 8 ClN 3 O 4 S 2 ) has about 25 Å 3 meaning that we have created the most easily aligned molecule ever measured, by creating a mixed superposition state that is highly anisotropic in its polarizability.

  7. Alignment of the hydrogen molecule under intense laser fields

    Science.gov (United States)

    Lopez, Gary V.; Fournier, Martin; Jankunas, Justin; Spiliotis, Alexandros K.; Rakitzis, T. Peter; Chandler, David W.

    2017-07-01

    Alignment of the electronically excited E,F state of the H2 molecule is studied using the velocity mapping imaging technique. Photofragment images of H+ due to the dissociation mechanism that follows the 2-photon excitation into the (E,F; ν = 0, J = 0) electronic state show a strong dependence on laser intensity, which is attributed to the high polarizability anisotropy of the H2 (E,F) state. We observe a marked structure in the angular distribution, which we explain as the interference between the prepared J = 0 and Stark-mixed J = 2 rovibrational states of H2, as the laser intensity increases. Quantification of these effects allows us to extract the polarizability anisotropy of the H2 (E,F J = 0) state yielding a value of 312 ± 82 a.u. (46 Å3). By comparison, CS2 has 10 Å3, I2 has 7 Å3, and hydrochlorothiazide (C7H8ClN3O4S2) has about 25 Å3 meaning that we have created the most easily aligned molecule ever measured, by creating a mixed superposition state that is highly anisotropic in its polarizability.

  8. Effects of Ph on Calcium Carbonate Precipitation Under Magnetic Field

    Directory of Open Access Journals (Sweden)

    Nelson Saksono

    2010-10-01

    Full Text Available Magnetic field effect on CaCO3 precipitation is the key parameter in evaluating the effectiveness of Anti-scale Magnetic Treatment (AMT. The purpose of this study was to investigate magnetic fields influence on CaCO3 precipitation in high and low super-saturated CaCO3 solution by varied pH CaCO3 solution using circulation flow fluid system. The observation results in the high super saturated solution (pH 8.5 showed the increase of precipited CaCO3 in magnetized solutions compared to those in non-magnetic solution during circulation process. In the low super-saturated CaCO3 solution (pH 6.4 it was found that magnetic treatment increased CaCO3 precipitation after circulation process. In high super-saturated solution, magnetic field strengthens ion interactions, which reduce precipitation during circulation process. However, in low super-saturated CaCO3 solution, magnetic field weakens hydrate ion interaction which indicated by decreasing of the conductivity of solution. It increases the precipitation of CaCO3 after the circulation of magnetization process has completed.

  9. Comparative Analysis Of Empowerment Under Farmer Field School ...

    African Journals Online (AJOL)

    Based on the findings of the study the following recommendations were made: That agricultural extension should change from information –driven approach of introducing technology, to a participatory approach of learning-by-doing. That in the course of regular field trainings and experimentations the farmer will easily learn ...

  10. Mesoscale Modelling of Block Copolymers under External Fields.

    NARCIS (Netherlands)

    Lyakhova, Kateryna S.

    2005-01-01

    A remarkable feature of block copolymer systems is their ability to self-assemble into a variety of ordered structures with domain sizes in the mesoscale range. One of the open questions is the dynamics of structure formation, which can be highly dependent on external fields often present in

  11. Computed leaching of pesticides from soil under field conditions

    NARCIS (Netherlands)

    Leistra, M.; Dekkers, W.A.

    1976-01-01

    With a computer model, pesticide behavior in soil after spring application to a sandy loam field with a potato crop, was simulated. Special attention was paid to the risk of leaching through the upper meter of soil in catchment areas. Unsaturated water flow resulting from rainfall was modeled in

  12. Numerical simulation of electro-magnetic and flow fields of TiAl melt under electric field

    Directory of Open Access Journals (Sweden)

    Zhang Yong

    2010-08-01

    Full Text Available This article aims at building an electromagnetic and fluid model, based on the Maxwell equations and Navier-Stokes equations, in TiAl melt under two electric fields. FEM (Finite Element Method and APDL (ANSYS Parametric Design Language were employed to perform the simulation, model setup, loading and problem solving. The melt in molds of same cross section area with different flakiness ratio (i.e. width/depth under the load of sinusoidal current or pulse current was analyzed to obtain the distribution of electromagnetic field and flow field. The results show that the induced magnetic field occupies sufficiently the domain of the melt in the mold with a flakiness ratio of 5:1. The melt is driven bipolarly from the center in each electric field. It is also found that the pulse electric field actuates the TiAl melt to flow stronger than what the sinusoidal electric field does.

  13. Effect of liquid film velocity and thickness on thinning rate of flow accelerated corrosion under water-steam two-phase flow

    International Nuclear Information System (INIS)

    Satake, Masaaki; Yoneda, Kimitoshi; Morita, Ryo; Fujiwara, Kazutoshi; Inada, Fumio

    2014-01-01

    Pipe wall thinning phenomena are serious problems for the operation and management of nuclear power plants. Flow accelerated corrosion (FAC) is one of the pipe wall thinning phenomena. Its mechanism under water single-phase flow is generally revealed and the prediction equation of thinning rate is constructed with practical accuracy. Under water-steam two-phase flow, it is considered that FAC is occurred in annular flow and its mechanism is almost the same as that under water single-phase flow. However, the detail of its mechanism is not revealed. In this study, FAC experiments under water-steam two-phase flow are performed by changing the liquid film velocity and thickness. The flow pattern is vertical upward annular flow. From these experiments, the thinning rate increases when the liquid film velocity becomes higher. However, the liquid film thickness does not influence the thinning rate so much. The oxide layer of test piece surface is mainly magnetite. The thickness of oxide layer where FAC occurs is less than 1 μm. On the other hand, the thickness of oxide layer where FAC does not occur is about 1.5 μm and there are porous scales on the oxide layer. It is assumed that one of the reasons why FAC does not occur is that concentration of iron in liquid film is saturated. (author)

  14. A broadband waveguide for protein crystallography under intense microwave fields

    Science.gov (United States)

    Weissenborn, R.; Reinhardt, T.; Hansen, V.; Maret, G.; Gisler, T.

    2004-12-01

    We present a slab-line waveguide whose geometry is optimized for wide-angle x-ray diffraction (XRD) experiments on protein crystals during irradiation with intense microwave fields. Characterization of the waveguide transmission and reflectivity (using time-domain reflectometry) and of the electric field distribution inside the waveguide (using finite-difference time-domain calculations) shows that the present device has a broad bandwidth from below 0.5 to 18 GHz, allowing one to perform frequency-dependent XRD studies with a well-defined transverse mode structure and negligible reflection losses. As shown with a specific example, our device provides a simple way to couple microwave irradiation experiments with high-resolution x-ray diffraction measurements from millimeter-size crystalline samples. The present design might prove useful for systematic studies of microwave effects on protein structure and dynamics.

  15. Cigar-shaped quarkonia under strong magnetic field

    Science.gov (United States)

    Suzuki, Kei; Yoshida, Tetsuya

    2016-03-01

    Heavy quarkonia in a homogeneous magnetic field are analyzed by using a potential model with constituent quarks. To obtain anisotropic wave functions and corresponding eigenvalues, the cylindrical Gaussian expansion method is applied, where the anisotropic wave functions are expanded by a Gaussian basis in the cylindrical coordinates. Deformation of the wave functions and the mass shifts of the S-wave heavy quarkonia (ηc, J /ψ , ηc(2 S ), ψ (2 S ) and bottomonia) are examined for the wide range of external magnetic field. The spatial structure of the wave functions changes drastically as adjacent energy levels cross each other. Possible observables in heavy-ion collision experiments and future lattice QCD simulations are also discussed.

  16. Thermal convection driven by acoustic field under microgravity

    OpenAIRE

    Tanabe, Mitsuaki; 田辺 光昭

    2007-01-01

    Natural convection is suppressed in space environment due to the weightlessness. Only centrifugal force is utilized currently to drive gas-phase thermal convection in space. This paper presents an alternative way to drive thermal convection. From the investigation of combustion oscillation in rocket motors, a new thermal convection had been found in stationary acoustic fields. Analyzing the phenomena, acoustic radiation force is found to be the candidate driving force. With a simplified syste...

  17. Electrohydrodynamics of a compound vesicle under an AC electric field

    Science.gov (United States)

    Priti Sinha, Kumari; Thaokar, Rochish M.

    2017-07-01

    Compound vesicles are relevant as simplified models for biological cells as well as in technological applications such as drug delivery. Characterization of these compound vesicles, especially the inner vesicle, remains a challenge. Similarly their response to electric field assumes importance in light of biomedical applications such as electroporation. Fields lower than that required for electroporation cause electrodeformation in vesicles and can be used to characterize their mechanical and electrical properties. A theoretical analysis of the electrohydrodynamics of a compound vesicle with outer vesicle of radius R o and an inner vesicle of radius λ {{R}o} , is presented. A phase diagram for the compound vesicle is presented and elucidated using detailed plots of electric fields, free charges and electric stresses. The electrohydrodynamics of the outer vesicle in a compound vesicle shows a prolate-sphere and prolate-oblate-sphere shape transitions when the conductivity of the annular fluid is greater than the outer fluid, and vice-versa respectively, akin to single vesicle electrohydrodynamics reported in the literature. The inner vesicle in contrast shows sphere-prolate-sphere and sphere-prolate-oblate-sphere transitions when the inner fluid conductivity is greater and smaller than the annular fluid, respectively. Equations and methodology are provided to determine the bending modulus and capacitance of the outer as well as the inner membrane, thereby providing an easy way to characterize compound vesicles and possibly biological cells.

  18. Predictive value of ventilatory inflection points determined under field conditions.

    Science.gov (United States)

    Heyde, Christian; Mahler, Hubert; Roecker, Kai; Gollhofer, Albert

    2016-01-01

    The aim of this study was to evaluate the predictive potential provided by two ventilatory inflection points (VIP1 and VIP2) examined in field without using gas analysis systems and uncomfortable facemasks. A calibrated respiratory inductance plethysmograph (RIP) and a computerised routine were utilised, respectively, to derive ventilation and to detect VIP1 and VIP2 during a standardised field ramp test on a 400 m running track on 81 participants. In addition, average running speed of a competitive 1000 m run (S1k) was observed as criterion. The predictive value of running speed at VIP1 (SVIP1) and the speed range between VIP1 and VIP2 in relation to VIP2 (VIPSPAN) was analysed via regression analysis. VIPSPAN rather than running speed at VIP2 (SVIP2) was operationalised as a predictor to consider the covariance between SVIP1 and SVIP2. SVIP1 and VIPSPAN, respectively, provided 58.9% and 22.9% of explained variance in regard to S1k. Considering covariance, the timing of two ventilatory inflection points provides predictive value in regard to a competitive 1000 m run. This is the first study to apply computerised detection of ventilatory inflection points in a field setting independent on measurements of the respiratory gas exchange and without using any facemasks.

  19. Premixed combustion under electric field in a constant volume chamber

    KAUST Repository

    Cha, Min Suk

    2012-12-01

    The effects of electric fields on outwardly propagating premixed flames in a constant volume chamber were experimentally investigated. An electric plug, subjected to high electrical voltages, was used to generate electric fields inside the chamber. To minimize directional ionic wind effects, alternating current with frequency of 1 kHz was employed. Lean and rich fuel/air mixtures for both methane and propane were tested to investigate various preferential diffusion conditions. As a result, electrically induced instability showing cracked structure on the flame surface could be observed. This cracked structure enhanced flame propagation speed for the initial period of combustion and led to reduction in flame initiation and overall combustion duration times. However, by analyzing pressure data, it was found that overall burning rates are not much affected from the electric field for the pressurized combustion period. The reduction of overall combustion time is less sensitive to equivalence ratio for methane/air mixtures, whereas the results demonstrate pronounced effects on a lean mixture for propane. The improvement of combustion characteristics in lean mixtures will be beneficial to the design of lean burn engines. Two hypothetical mechanisms to explain the electrically induced instability were proposed: 1) ionic wind initiated hydrodynamic instability and 2) thermodiffusive instability through the modification of transport property such as mass diffusivity. © 2012 IEEE.

  20. Convection patterns in a liquid metal under an imposed horizontal magnetic field.

    Science.gov (United States)

    Yanagisawa, Takatoshi; Hamano, Yozo; Miyagoshi, Takehiro; Yamagishi, Yasuko; Tasaka, Yuji; Takeda, Yasushi

    2013-12-01

    We performed laboratory experiments of Rayleigh-Bénard convection with liquid gallium under various intensities of a uniform imposed horizontal magnetic field. An ultrasonic velocity profiling method was used to visualize the spatiotemporal structure of the flows with simultaneous monitoring of the temperature fluctuations in the liquid gallium layer. The explored Rayleigh numbers Ra range from the critical value for onset of convection to 10(5); the Chandrasekhar number Q covers values up to 1100. A regime diagram of the convection patterns was established in relation to the Ra and Q values for a square vessel with aspect ratio 5. We identified five flow regimes: (I) a fluctuating large-scale pattern without rolls, (II) weakly constrained rolls with fluctuations, (III) a continuous oscillation of rolls, (IV) repeated roll number transitions with random reversals of the flow direction, and (V) steady two-dimensional (2D) rolls. These flow regimes are classified by the Ra/Q values, the ratio of the buoyancy to the Lorentz force. Power spectra from the temperature time series indicate that regimes I and II have the features of developed turbulence, while the other regimes do not. The region of steady 2D rolls (Busse balloon) extends to high Ra values in the present setting by a horizontal magnetic field and regime V is located inside the Busse balloon. Concerning the instabilities of the steady 2D rolls, regime III is the traveling wave convection developed from the oscillatory instability. Regime IV can be regarded as a state of phase turbulence, which is induced by intermittent occurrences of the skewed-varicose instability.

  1. Anomalous scaling of passive scalar fields advected by the Navier-Stokes velocity ensemble: effects of strong compressibility and large-scale anisotropy.

    Science.gov (United States)

    Antonov, N V; Kostenko, M M

    2014-12-01

    The field theoretic renormalization group and the operator product expansion are applied to two models of passive scalar quantities (the density and the tracer fields) advected by a random turbulent velocity field. The latter is governed by the Navier-Stokes equation for compressible fluid, subject to external random force with the covariance ∝δ(t-t')k(4-d-y), where d is the dimension of space and y is an arbitrary exponent. The original stochastic problems are reformulated as multiplicatively renormalizable field theoretic models; the corresponding renormalization group equations possess infrared attractive fixed points. It is shown that various correlation functions of the scalar field, its powers and gradients, demonstrate anomalous scaling behavior in the inertial-convective range already for small values of y. The corresponding anomalous exponents, identified with scaling (critical) dimensions of certain composite fields ("operators" in the quantum-field terminology), can be systematically calculated as series in y. The practical calculation is performed in the leading one-loop approximation, including exponents in anisotropic contributions. It should be emphasized that, in contrast to Gaussian ensembles with finite correlation time, the model and the perturbation theory presented here are manifestly Galilean covariant. The validity of the one-loop approximation and comparison with Gaussian models are briefly discussed.

  2. Seed ageing and field performance of maize under water stress ...

    African Journals Online (AJOL)

    As a result, plant biomass and grain yield per unit area for plants from aged seeds were considerably lower than those from non-aged seeds. No significant interaction of irrigation × seed ageing was observed for grain yield, suggesting that aged seeds had low yield under both well and limited irrigation conditions. Therefore ...

  3. Seed ageing and field performance of maize under water stress

    African Journals Online (AJOL)

    use

    2011-12-14

    Dec 14, 2011 ... As a result, plant biomass and grain yield per unit area for plants from aged seeds were considerably lower than those from non-aged seeds. No significant interaction of irrigation × seed ageing was observed for grain yield, suggesting that aged seeds had low yield under both well and limited irrigation ...

  4. field performance of cowpea genotypes grown under virus pressure ...

    African Journals Online (AJOL)

    journal

    viral diseases, particularly Cucumber mosaic virus (CMV) and Blackeye cowpea mosaic virus (BlCMV), can be a limiting factor in cowpea production. We evaluated under virus pressure the performance of four PI's (441917,. 441919, 612607, 180014) and a commercial cultivar (Coronet), in Puerto Rico during 2007-2008.

  5. field performance of cowpea genotypes grown under virus pressure ...

    African Journals Online (AJOL)

    journal

    Cowpea [Vigna unguiculata (L.) Walp] is an important grain legume in many regions of the tropics. However, viral diseases, particularly Cucumber mosaic virus (CMV) and Blackeye cowpea mosaic virus (BlCMV), can be a limiting factor in cowpea production. We evaluated under virus pressure the performance of four PI's ...

  6. Anisotropic transport properties of quasiballistic InAs nanowires under high magnetic field

    Science.gov (United States)

    Vigneau, Florian; Zeng, Zaiping; Escoffier, Walter; Caroff, Philippe; Leturcq, Renaud; Niquet, Yann-Michel; Raquet, Bertrand; Goiran, Michel

    2018-03-01

    The magnetoconductance of a long channel InAs nanowire based field effect transistor in the quasiballistic regime under large magnetic field is investigated. The quasi-1D nanowire is fully characterized by a bias voltage spectroscopy and measurements under magnetic field up to 50 T applied either perpendicular or parallel to the nanowire axis lifting the spin and orbital degeneracies of the subbands. Under normal magnetic field, the conductance shows quantized steps due to the backscattering reduction and a decrease due to depopulation of the 1D modes. Under axial magnetic field, a quasioscillatory behavior is evidenced due to the coupling of the magnetic field with the angular momentum of the wave function. In addition the formation of cyclotron orbits is highlighted under high magnetic field. The experimental results are compared with theoretical calculation of the 1D band structure and related parameters.

  7. Cooper Pair Breakup in YBCO under Strong Terahertz Fields

    OpenAIRE

    Glossner, Andreas; Zhang, Caihong; Kikuta, Shinya; Kawayama, Iwao; Murakami, Hironaru; Müller, Paul; Tonouchi, Masayoshi

    2012-01-01

    We show that strong electric fields of ~ 30 kV cm^(-1) at terahertz frequencies can significantly weaken the superconducting characteristics of cuprate superconductors. High-power terahertz time-domain spectroscopy (THz-TDS) was used to investigate the in-plane conductivity of YBa2Cu3O7-delta (YBCO) with highly intense single-cycle terahertz pulses. Even though the terahertz photon energy (~ 1.5 meV) was significantly smaller than the energy gap in YBCO (~ 20-30 meV), the optical conductivity...

  8. The fluid flow of Czochralski melt under the electromagnetic field

    OpenAIRE

    加藤, 拓哉; 二條久保, 裕; 岩本, 光生; 齋藤, 晋一; 赤松, 正人; 尾添, 紘之; Takuya, Katoh; Yuu, Nijoukubo; Mitsuo, Iwamoto; Shinichi, Saitoh; Masato, Akamatsu; Hiroyuki, Ozoe; 大分大院; 大分大工; 大分大工

    2009-01-01

    The silicon single crystal is use for the semiconductor device and it is mainly manufactured by the Czochralski crystal growing method. Under the Cz method, the forced convection and natural convection caused by the crystal rotation and the temperature difference between the crystal and crucible. In traditional system, the melt convection is controlled by the heater power, the crystal and crucible rotation. We apply Lorentz force to control the melt convection in this study, the Lorentz force...

  9. The effect of divalent ions on the elasticity and pore collapse of chalk evaluated from compressional wave velocity and low-field Nuclear Magnetic Resonance (NMR)

    DEFF Research Database (Denmark)

    Katika, Konstantina; Addassi, Mouadh; Alam, Mohammad Monzurul

    2015-01-01

    density and ultrasonic velocities measured on core plugs. Low-field NMR spectroscopy was used in addition to the mechanical testing to prove any changes observed after the saturation related to the surface-to-volume ratio of the pore space in each of the samples or to surface relaxivity. Backscatter...... rich in magnesium and calcium ions softens the contact among the mineral grains. Pore collapse strength is deteriorating after the saturation of chalk with water rich in divalent ions. The presence of calcium and sulfate ions in the saturating fluid results in pore collapse at lower stresses than...

  10. Hyperthermic effect of magnetic nanoparticles under electromagnetic field

    Directory of Open Access Journals (Sweden)

    Giovanni Baldi

    2009-06-01

    Full Text Available Magnetic nanoparticles have attracted increasingly attention due to their potential applications in many industrial fields, even extending their use in biomedical applications. In the latter contest the main features of magnetic nanoparticles are the possibility to be driven by external magnetic fields, the ability to pass through capillaries without occluding them and to absorb and convert electromagnetic radiation in to heat (Magnetic Fluid Hyperthermia. The main challenges of the current works on hyperthermia deal with the achievement of highly efficiency magnetic nanoparticles, the surface grafting with ligands able to facilitate their specific internalisation in tumour cells and the design of stealth nanocomposites able to circulate in the blood compartment for a long time. This article presents the synthesis of cobalt ferrite nanoparticles dispersed in diethylene glycol via the so called polyol strategy and the crystal size control through successive synthesis steps. Preliminary heat dissipation evaluations on the prepared samples were carried out and the question of how particles sizes affect their magnetic and hyperthermic properties was addressed as well. Furthermore we will present how surface chemistry can be modified in order to change the dispersity of the product without affecting magnetic and hyperthermic properties.

  11. Pressure drop and heat transfer of lithium single-phase flow under transverse magnetic field

    International Nuclear Information System (INIS)

    Takahashi, Minoru; Aritomi, Masanori; Inoue, Akira; Matsuzaki, Mitsuo

    1996-01-01

    Pressure drop and heat transfer characteristics of a lithium single-phase flow in a rectangular channel was investigated experimentally in the presence of a magnetic field. Friction loss coefficient under non-magnetic field and skin friction coefficient under magnetic field agreed well with the Blasius formula and a simple analytical expression, respectively. Nusselt number under non-magnetic field was slightly lower than the correlation by Hartnett and Irvine. Heat transfer was enhanced by increasing magnetic field above the Hartmann number of about 200. (author)

  12. Superposed epoch analysis of vertical ion velocity, electron temperature, field-aligned current, and thermospheric wind in the dayside auroral region as observed by DMSP and CHAMP

    Science.gov (United States)

    Kervalishvili, G.; Lühr, H.

    2016-12-01

    This study reports on the results obtained by a superposed epoch analysis (SEA) method applied to the electron temperature, vertical ion velocity, field-aligned current (FAC), and thermospheric zonal wind velocity at high-latitudes in the Northern Hemisphere. The SEA study is performed in a magnetic latitude versus magnetic local time (MLat-MLT) frame. The obtained results are based on observations collected during the years 2001-2005 by the CHAMP and DMSP (F13 and F15) satellites. The dependence on interplanetary magnetic field (IMF) orientations is also investigated using data from the NASA/GSFC's OMNI database. Further, the obtained results are subdivided into three Lloyd seasons of 130 days each, which are defined as follows: local winter (1 January ± 65 days), combined equinoxes (1 April and 1 October ± 32days), and local summer (1 July ± 65 days). A period of 130 days is needed by the CHAMP satellite to pass through all local times. The time and location of the electron temperature peaks from CHAMP measurements near the cusp region are used as the reference parameter for the SEA method to investigate the relationship between the electron temperature and other ionospheric quantities. The SEA derived MLat profiles of the electron temperature show a seasonal dependence, increasing from winter to summer, as expected. But, the temperature rise (difference between the reference temperature peak and the background electron temperature) strongly decreases towards local summer. The SEA derived MLat profiles of the ion vertical velocity at DMSP altitude show the same seasonal behaviour as the electron temperature rice. There exists a clear linear relation between these two variables with a quiet large correlation coefficient value, >0.9. The SEA derived MLat profiles of both, thermospheric zonal wind velocity and FAC, show a clear IMF By orientation dependence for all local seasons. The zonal wind velocity is prominently directed towards west in the MLat-MLT frame

  13. Relativistic Killingbeck energy states under external magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Eshghi, M. [Islamic Azad University, Researchers and Elite Club, Central Tehran Branch, Tehran (Iran, Islamic Republic of); Mehraban, H. [Semnan University, Faculty of Physics, Semnan (Iran, Islamic Republic of); Ikhdair, S.M. [An-Najah National University, Department of Physics, Faculty of Science, Nablus, West Bank, Palestine (Country Unknown); Near East University, Department of Electrical Engineering, Nicosia, Northern Cyprus (Turkey)

    2016-07-15

    We address the behavior of the Dirac equation with the Killingbeck radial potential including the external magnetic and Aharonov-Bohm (AB) flux fields. The spin and pseudo-spin symmetries are considered. The correct bound state spectra and their corresponding wave functions are obtained. We seek such a solution using the biconfluent Heun's differential equation method. Further, we give some of our results at the end of this study. Our final results can be reduced to their non-relativistic forms by simply using some appropriate transformations. The spectra, in the spin and pseudo-spin symmetries, are very similar with a slight difference in energy spacing between different states. (orig.)

  14. Relativistic Killingbeck energy states under external magnetic fields

    International Nuclear Information System (INIS)

    Eshghi, M.; Mehraban, H.; Ikhdair, S.M.

    2016-01-01

    We address the behavior of the Dirac equation with the Killingbeck radial potential including the external magnetic and Aharonov-Bohm (AB) flux fields. The spin and pseudo-spin symmetries are considered. The correct bound state spectra and their corresponding wave functions are obtained. We seek such a solution using the biconfluent Heun's differential equation method. Further, we give some of our results at the end of this study. Our final results can be reduced to their non-relativistic forms by simply using some appropriate transformations. The spectra, in the spin and pseudo-spin symmetries, are very similar with a slight difference in energy spacing between different states. (orig.)

  15. Viscoelastoplastic bodies under cyclic loading in thermal-radiation fields

    OpenAIRE

    Atwa D. Zeyad

    2017-01-01

    Deformation of viscoelastoplastic bodies in the neutron and thermal fluxes under a one-time loading has been studied previously in [1–3]. A mathematical model has been set forth in [4] for a cyclic deformation of elastoplastic bodies in a neutron flux. In the paper [5,6] ferrofluid flow and heat transfer in a semi annulus enclosure is investigated considering thermal radiation. This article [7] explores the effect of thermal radiation on Al2O3–water nanofluid flow and heat transfer in an encl...

  16. Multiparameter full waveform inversion of multicomponent ocean-bottom-cable data from the Valhall field. Part 2: imaging compressive-wave and shear-wave velocities

    Science.gov (United States)

    Prieux, Vincent; Brossier, Romain; Operto, Stéphane; Virieux, Jean

    2013-09-01

    Multiparameter elastic full waveform inversion (FWI) is a promising technology that allows inferences to be made on rock and fluid properties, which thus narrows the gap between seismic imaging and reservoir characterization. Here, we assess the feasibility of 2-D vertical transverse isotropic visco-elastic FWI of wide-aperture multicomponent ocean-bottom-cable data from the Valhall oil field. A key issue is to design a suitable hierarchical data-driven and model-driven FWI workflow, the aim of which is to reduce the nonlinearity of the FWI. This nonlinearity partly arises because the shear (S) wavespeed can have a limited influence on seismic data in marine environments. In a preliminary stage, visco-acoustic FWI of the hydrophone component is performed to build a compressional (P)-wave velocity model, a density model and a quality-factor model, which provide the necessary background models for the subsequent elastic inversion. During the elastic FWI, the P and S wavespeeds are jointly updated in two steps. First, the hydrophone data are inverted to mainly update the long-to-intermediate wavelengths of the S wavespeeds from the amplitude-versus-offset variations of the P-P reflections. This S-wave velocity model is used as an improved starting model for the subsequent inversion of the better-resolving data recorded by the geophones. During these two steps, the P-wave velocity model is marginally updated, which supports the relevance of the visco-acoustic FWI results. Through seismic modelling, we show that the resulting visco-elastic model allows several P-to-S converted phases recorded on the horizontal-geophone component to be matched. Several elastic quantities, such as the Poisson ratio, and the ratio and product between the P and S wavespeeds, are inferred from the P-wave and S-wave velocity models. These attributes provide hints for the interpretation of an accumulation of gas below lithological barriers.

  17. Surface field in an ensemble of superconducting spheres under external magnetic field

    CERN Document Server

    Peñaranda, A; Ramírez-Piscina, L

    1999-01-01

    We perform calculations of the magnetic field on the surface of an ensemble of superconducting spheres when placed into an external magnetic field, which is the configuration employed in superheated superconducting granule detectors. The Laplace equation is numerically solved with appropriate boundary conditions by means of an iterative procedure and a multipole expansion.

  18. The solution of the laminar-boundary-layer equation for the flat plate for velocity and temperature fields for variable physical properties and for the diffusion field at high concentration

    Science.gov (United States)

    Schuh, H

    1950-01-01

    In connection with Pohlhausen's solution for the temperature field on the flat plate, a series of formulas were indicated by means of which the velocity and temperature field for variable physical characteristics can be computed by an integral equation and an iteration method based on it. With it, the following cases were solved: On the assumption that the viscosity simply varies with the temperature while the other fluid properties remain constant, the velocity and temperature field on the heated and cooled plate, respectively, was computed at the Prandtl numbers 12.5 and 100 (viscous fluids). A closer study of these two cases resulted in general relations: The calculations for a gas of Pr number 0.7 (air) were conducted on the assumption that all fluid properties vary with the temperature, and the velocities are low enough for the heat of friction to be discounted. The result was a thickening of the boundary layers, but no appreciable modification in shearing stress or heat-transfer coefficient.

  19. Development of site class and site coefficient maps of Semarang, Indonesia using field shear wave velocity data

    Directory of Open Access Journals (Sweden)

    Partono Windu

    2017-01-01

    Full Text Available The new Indonesian National Code for seismic resistance design (SNI-03-1726-2012 issued recently utilizes seismic response spectra for the whole area of the country. Site class and site coefficient are two parameters needed for designing response spectra. Site class can be estimated using average standard penetration test (N-SPT, average shear wave velocity (Vs and average un-drained shear strength (Su of top 30 meter soil deposit. Site coefficients can be predicted using probabilistic seismic hazard analysis (PSHA by implementing total probability theorem. To perform PSHA, Vs30 is a parameter needed for calculating ground motion at bedrock elevation. This paper presents the results of PSHA and site class analysis using Vs30 values estimated based on N-SPT results collected from 265 boring locations in Semarang. Seismic data in a radius of 500 km from Semarang were collected for PSHA. Site class and site coefficient maps are then developed for the whole study area.

  20. New GPS velocity field in the northern Andes (Ecuador - Colombia) : partial locking along the subduction and northeastward escape of the Northern Andean Block

    Science.gov (United States)

    Nocquet, Jean-Mathieu; Mothes, Patricia; Mohamed, Chlieh; Jarrin, Paul; Martin, Vallee; Rui, Gorki; Regnier, Marc

    2010-05-01

    Rapid subduction of the Nazca plate beneath the Ecuador-Colombia margin (~58 mm/yr) results in two different processes: (1) elastic stress is accumulating along the Nazca/South America plate interface which is responsible of one of the largest megathrust earthquake sequence during the last century (1906, Mw = 8.8, 1942 Mw = 7.8, 1958 Mw = 7.7, and 1979 Mw = 8.2) (2) the Northern Andean Block (NAB) moves northeastward with respect to Stable South America. However, kinematics of the NAB and its level of internal deformation has yet to be quantified. We present a new GPS velocity field covering the northern Andes from south of the Gulf of Guyaquil to the Carribean plate. Our velocity field includes new continuously-recording GPS stations installed along the Ecuadorian coast, together with campaign sites observed since 1994. The observed velocity field confirms that the current surface deformation results from the superimposition of a NNE motion the crustal North Andean Block occurring at ~8 mm/yr and the elastic deformation induced by partial locking of the subduction interface. We first estimate the long-term kinematics of the North Andean block in a joint inversion including GPS data, earthquake slip vectors and quaternary slip rates on major faults. The inversion provides an Euler pole located at long. -107.8°E, lat. 36.2°N, 0.091°/Ma and indicates little internal deformation of the North Andean Block (wrms of residual velcoties is 1.3 mm/yr). As a consequence, 30% of the obliquity of the Nazca/South America motion is accommodated by transcurrent deformation along the eastern boundary of the NAB. Residual velocities with respect to the North Andean Block are then modelled in terms of elastic locking along the subduction interface. Models indicate that the subduction interface is partially locked (50%) up to a depth of 40 km over the area of rupture of the 1906 earthquake. Further south, coupling decreases with latitude, with no coupling detected at the latitude

  1. Flow of a Bingham fluid in a porous bed under the action of a magnetic field: Application to magneto-hemorheology

    Directory of Open Access Journals (Sweden)

    J.C. Misra

    2017-06-01

    Full Text Available The study deals with an investigation of the flow of a Bingham plastic fluid in a porous bed under the action of an external magnetic field. Porosity of the bed has been described by considering Brinkman model. Both steady and pulsatile motion of this non-Newtonian fluid have been analysed. The governing equations are solved numerically by developing a suitable finite difference scheme. As an application of the theory in the field of magneto-hemorheology, the said physical variables have been computed by considering the values of the involved parameters for blood flow in a pathological state, when the system is under the action of an external magnetic field. The pathological state corresponds to a situation, where the lumen of an arterial segment has turned into a porous structure due to formation of blood clots. Numerical estimates are obtained for the velocity profile and volumetric flow rate of blood, as well as for the shear stress, in the case of blood flow in a diseased artery, both the velocity and volumetric flow rate diminish, as the strength of the external magnetic field is enhanced. The study further shows that blood velocity is maximum in the plug (core region. It decreases monotonically as the particles of blood travel towards the wall. The study also bears the potential of providing numerical estimates for many industrial fluids that follow Bingham plastic model, when the values of different parameters are chosen appropriately.

  2. Cholinergic transmission underlies modulation of frustration by open field exposure.

    Science.gov (United States)

    Psyrdellis, Mariana; Pautassi, Ricardo Marcos; Mustaca, Alba; Justel, Nadia

    2016-01-01

    Frustration can be defined as an emotional state generated by the omission or devaluation in the quantity or quality of an expected appetitive reward. Thus, reactivity to a reward is affected by prior experience with the different reinforcer values of that reward. This phenomenon is known as incentive relativity, and can be studied by different paradigms. Although methodologically simple, the exploration of a novel open field (OF) is a complex situation that involves several behavioral processes, including stress induction and novelty detection. OF exposure can enhance or block the acquisition of associative and non-associative memories. These experiments evaluated the effect of OF exploration on frustration and the role played by the cholinergic system in this phenomenon. OF exploration before first or second trial of incentive downshift modulated the expression of frustration. This effect of OF was blocked by the administration of scopolamine either before or after OF exploration. These results indicate that the cholinergic system is involved in the acquisition and consolidation of OF information.

  3. Broccoli (Brassica oleracea var. italica head initiation under field conditions

    Directory of Open Access Journals (Sweden)

    Alina Kałużewicz

    2012-12-01

    Full Text Available A two–year study on the influence of temperature on broccoli head initiation was carried out at the ''Marcelin'' experimental station of the Poznań University of Life Sciences. In each year of the study, plants were planted in the field at four dates. The evaluation of the developmental phase of the broccoli shoot apex was based on the analysis of microscope slides. The date of head initiation was assumed as the day on which the first of the examined apices were found to be at the early generative phase. The plant characteristics (number of leaves, leaf area and stem diameter on the date of initiation were also determined. Variation in length of the period from planting to head initiation was found both between dates of planting and between experimental years. The shortest period from planting to initiation was when the plants were planted in April and June (17-18 days in the first year and the longest one for planting in April in the first year of the study (29 days. The length of the period from planting to head initiation depended on mean daily air temperature. The higher the temperature was, the shorter was the period.

  4. Supplementary Eye Field Encodes Confidence in Decisions Under Risk.

    Science.gov (United States)

    So, NaYoung; Stuphorn, Veit

    2016-02-01

    Choices are made with varying degrees of confidence, a cognitive signal representing the subjective belief in the optimality of the choice. Confidence has been mostly studied in the context of perceptual judgments, in which choice accuracy can be measured using objective criteria. Here, we study confidence in subjective value-based decisions. We recorded in the supplementary eye field (SEF) of monkeys performing a gambling task, where they had to use subjective criteria for placing bets. We found neural signals in the SEF that explicitly represent choice confidence independent from reward expectation. This confidence signal appeared after the choice and diminished before the choice outcome. Most of this neuronal activity was negatively correlated with confidence, and was strongest in trials on which the monkey spontaneously withdrew his choice. Such confidence-related activity indicates that the SEF not only guides saccade selection, but also evaluates the likelihood that the choice was optimal. This internal evaluation influences decisions concerning the willingness to bear later costs that follow from the choice or to avoid them. More generally, our findings indicate that choice confidence is an integral component of all forms of decision-making, whether they are based on perceptual evidence or on value estimations. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  5. Analysis of large-scale horizontal velocities and the magnetic field on the sun during fast reorganization periods

    Czech Academy of Sciences Publication Activity Database

    Molodykh, S.I.; Ambrož, Pavel; Kovalenko, V.A.

    2009-01-01

    Roč. 49, č. 7 (2009), s. 860-865 ISSN 0016-7932 R&D Projects: GA AV ČR IAA300030808 Institutional research plan: CEZ:AV0Z10030501 Keywords : Sun * solar magnetic field * solar activity Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.947, year: 2007

  6. LDV measurements of the velocity field on the inlet section of a pumped storage equipped with a symmetrical suction elbow for variable discharge values

    International Nuclear Information System (INIS)

    Drǎghici, I; Bosioc, A I; Anton, L E; Muntean, S

    2014-01-01

    The storage pumps are equipped with various types of inlet casings. The flow nonuniformity is generated by the suction elbows being ingested by the impeller leading to unsteady phenomena and worse cavitational behaviour. A symmetrical suction elbow model corresponding to the double flux storage pump was manufactured and installed on the test rig in order to assess the flow field at the pump inlet. The experimental investigations are performed for 9 discharge values from 0.5 to 1.3 of nominal discharge. LDV measurements are performed on the annular section of the pump inlet in order to quantify the flow non-uniformity generated by the symmetrical suction elbow. Both axial and circumferential velocity components are simultaneously measured on the half plane (180°) of the annular inlet section along to 19 survey axis with 62 points on each. The flow field on the next half plane is determined tacking into account the symmetry. As a result, the flow map on the pump inlet annular section is reconstructed revealing a significant variation of the circumferential velocity component. The absolute flow angle is computed showing a significant variation of ±38°

  7. Monosize magnetic hydrophobic beads for lysozyme purification under magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Altintas, Evrim Banu [Department of Chemistry, Hacettepe University, Beytepe, Ankara (Turkey); Denizli, Adil, E-mail: denizli@hacettepe.edu.tr [Department of Chemistry, Hacettepe University, Beytepe, Ankara (Turkey)

    2009-06-01

    Monosize and magnetic poly(glycidyl methacrylate-N-methacryloyl-(L)-tryptophan) [mPGMATrp] beads (1.6 {mu}m in diameter) were used for hydrophobic affinity capture of lysozyme from chicken egg-white. N-methacryloyl-(L)-tryptophan (MATrp), which gives hydrophobicity to the resulting polymer, was synthesized by reacting methacryloyl chloride and L-tryptophan methyl ester then characterized by Nuclear Magnetic Resonance (NMR). mPGMATrp beads were produced by dispersion polymerization in the presence of magnetite nano-powder. mPGMATrp beads were characterized by means of swelling studies, elemental analysis, Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). Lysozyme adsorption experiments were performed under different experimental conditions (i.e., lysozyme concentration, temperature, and ionic strength) in magnetically stabilized fluidized bed system, (MSFB). Maximum adsorption capacity was 263.9 mg/g. It was observed that mPGMATrp beads can be used without significant loss in lysozyme adsorption capacity after 25 adsorption-elution cycle.

  8. Monosize magnetic hydrophobic beads for lysozyme purification under magnetic field

    International Nuclear Information System (INIS)

    Altintas, Evrim Banu; Denizli, Adil

    2009-01-01

    Monosize and magnetic poly(glycidyl methacrylate-N-methacryloyl-(L)-tryptophan) [mPGMATrp] beads (1.6 μm in diameter) were used for hydrophobic affinity capture of lysozyme from chicken egg-white. N-methacryloyl-(L)-tryptophan (MATrp), which gives hydrophobicity to the resulting polymer, was synthesized by reacting methacryloyl chloride and L-tryptophan methyl ester then characterized by Nuclear Magnetic Resonance (NMR). mPGMATrp beads were produced by dispersion polymerization in the presence of magnetite nano-powder. mPGMATrp beads were characterized by means of swelling studies, elemental analysis, Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). Lysozyme adsorption experiments were performed under different experimental conditions (i.e., lysozyme concentration, temperature, and ionic strength) in magnetically stabilized fluidized bed system, (MSFB). Maximum adsorption capacity was 263.9 mg/g. It was observed that mPGMATrp beads can be used without significant loss in lysozyme adsorption capacity after 25 adsorption-elution cycle.

  9. On guided circumferential waves in soft electroactive tubes under radially inhomogeneous biasing fields

    Science.gov (United States)

    Wu, Bin; Su, Yipin; Chen, Weiqiu; Zhang, Chuanzeng

    2017-02-01

    Soft electroactive (EA) tube actuators and many other cylindrical devices have been proposed recently in literature, which show great advantages over those made from conventional hard solid materials. However, their practical applications may be limited because these soft EA devices are prone to various failure modes. In this paper, we present an analysis of the guided circumferential elastic waves in soft EA tube actuators, which has potential applications in the in-situ nondestructive evaluation (NDE) or online structural health monitoring (SHM) to detect structural defects or fatigue cracks in soft EA tube actuators and in the self-sensing of soft EA tube actuators based on the concept of guided circumferential elastic waves. Both circumferential SH and Lamb-type waves in an incompressible soft EA cylindrical tube under inhomogeneous biasing fields are considered. The biasing fields, induced by the application of an electric voltage difference to the electrodes on the inner and outer cylindrical surfaces of the EA tube in addition to an axial pre-stretch, are inhomogeneous in the radial direction. Dorfmann and Ogden's theory of nonlinear electroelasticity and the associated linear theory for small incremental motion constitute the basis of our analysis. By means of the state-space formalism for the incremental wave motion along with the approximate laminate technique, dispersion relations are derived in a particularly efficient way. For a neo-Hookean ideal dielectric model, the proposed approach is first validated numerically. Numerical examples are then given to show that the guided circumferential wave propagation characteristics are significantly affected by the inhomogeneous biasing fields and the geometrical parameters. Some particular phenomena such as the frequency veering and the nonlinear dependence of the phase velocity on the radial electric voltage are discussed. Our numerical findings demonstrate that it is feasible to use guided circumferential

  10. Stem breakage of salt marsh vegetation under wave forcing: A field and model study

    Science.gov (United States)

    Vuik, Vincent; Suh Heo, Hannah Y.; Zhu, Zhenchang; Borsje, Bas W.; Jonkman, Sebastiaan N.

    2018-01-01

    One of the services provided by coastal ecosystems is wave attenuation by vegetation, and subsequent reduction of wave loads on flood defense structures. Therefore, stability of vegetation under wave forcing is an important factor to consider. This paper presents a model which determines the wave load that plant stems can withstand before they break or fold. This occurs when wave-induced bending stresses exceed the flexural strength of stems. Flexural strength was determined by means of three-point-bending tests, which were carried out for two common salt marsh species: Spartina anglica (common cord-grass) and Scirpus maritimus (sea club-rush), at different stages in the seasonal cycle. Plant stability is expressed in terms of a critical orbital velocity, which combines factors that contribute to stability: high flexural strength, large stem diameter, low vegetation height, high flexibility and a low drag coefficient. In order to include stem breakage in the computation of wave attenuation by vegetation, the stem breakage model was implemented in a wave energy balance. A model parameter was calibrated so that the predicted stem breakage corresponded with the wave-induced loss of biomass that occurred in the field. The stability of Spartina is significantly higher than that of Scirpus, because of its higher strength, shorter stems, and greater flexibility. The model is validated by applying wave flume tests of Elymus athericus (sea couch), which produced reasonable results with regards to the threshold of folding and overall stem breakage percentage, despite the high flexibility of this species. Application of the stem breakage model will lead to a more realistic assessment of the role of vegetation for coastal protection.

  11. Absorption measurement s in InSe single crystal under an applied electric field

    International Nuclear Information System (INIS)

    Ates, A.; Guerbulak, B.; Guer, E.; Yildirim, T.; Yildirim, M.

    2002-01-01

    InSe single crystal was grown by Bridgman-Stockberger method. Electric field effect on the absorption measurements have been investigated as a function of temperature in InSe single crystal. The absorption edge shifted towards longer wavelengths and decreased of intensity in absorption spectra under an electric field. Using absorption measurements, Urbach energy was calculated under an electric field. Applied electric field caused a increasing in the Urbach energy. At 10 K and 320 K, the first exciton energies were calculated as 1.350 and 1.311 eV for zero voltage and 1.334 and 1.301 eV for electric field respectively

  12. Measurement of velocity and velocity derivatives based on pattern tracking in 3D LIF images

    Energy Technology Data Exchange (ETDEWEB)

    Deusch, S.; Merava, H.; Rys, P. [Swiss Federal Inst. of Technol., Zurich (Switzerland). Dept. of Chem. Eng.; Dracos, T. [Swiss Federal Institute of Technology, Untergasse 14, 8126 Zumikon (Switzerland)

    2000-10-01

    Pattern tracking in consecutive 3D LIF images based on least squares matching (LSM) of grey levels has been developed recently for velocity and velocity gradient measurements. The shortcomings of this method are clearly shown. The present article presents an improvement on this method by introducing a local multi-patch (LMP) technique through the LSM approach. The method is validated using the flow field of a turbulent channel flow obtained by direct numerical simulation (DNS) and a synthetic image with grey-level patterns. The results show that LMP matching allows the determination of the velocity and the velocity gradient fields with high accuracy including the second derivatives. Measurements of a round non-buoyant jet are presented which demonstrate the good performance of the method when applied under laboratory conditions. This method can also be applied on two-dimensional images provided that the flow is strictly two-dimensional. (orig.)

  13. Measurement of velocity and velocity derivatives based on pattern tracking in 3D LIF images

    Science.gov (United States)

    Deusch, S.; Merava, H.; Dracos, T.; Rys, P.

    Pattern tracking in consecutive 3D LIF images based on least squares matching (LSM) of grey levels has been developed recently for velocity and velocity gradient measurements. The shortcomings of this method are clearly shown. The present article presents an improvement on this method by introducing a local multi-patch (LMP) technique through the LSM approach. The method is validated using the flow field of a turbulent channel flow obtained by direct numerical simulation (DNS) and a synthetic image with grey-level patterns. The results show that LMP matching allows the determination of the velocity and the velocity gradient fields with high accuracy including the second derivatives. Measurements of a round non-buoyant jet are presented which demonstrate the good performance of the method when applied under laboratory conditions. This method can also be applied on two-dimensional images provided that the flow is strictly two-dimensional.

  14. Daytime, low latitude, vertical ExB drift velocities, inferred from ground-based magnetometer observations in the Peruvian, Philippine and Indian longitude sectors under quiet and disturbed conditions

    CERN Document Server

    Anderson, D; Chau, J; Yumoto, K; Bhattacharya, A; Alex, S

    2006-01-01

    Daytime, low latitude, vertical ExB drift velocities, inferred from ground-based magnetometer observations in the Peruvian, Philippine and Indian longitude sectors under quiet and disturbed conditions

  15. Difference of horizontal-to-vertical spectral ratios of observed earthquakes and microtremors and its application to S-wave velocity inversion based on the diffuse field concept

    Science.gov (United States)

    Kawase, Hiroshi; Mori, Yuta; Nagashima, Fumiaki

    2018-01-01

    We have been discussing the validity of using the horizontal-to-vertical spectral ratios (HVRs) as a substitute for S-wave amplifications after Nakamura first proposed the idea in 1989. So far a formula for HVRs had not been derived that fully utilized their physical characteristics until a recent proposal based on the diffuse field concept. There is another source of confusion that comes from the mixed use of HVRs from earthquake and microtremors, although their wave fields are hardly the same. In this study, we compared HVRs from observed microtremors (MHVR) and those from observed earthquake motions (EHVR) at one hundred K-NET and KiK-net stations. We found that MHVR and EHVR share similarities, especially until their first peak frequency, but have significant differences in the higher frequency range. This is because microtremors mainly consist of surface waves so that peaks associated with higher modes would not be prominent, while seismic motions mainly consist of upwardly propagating plain body waves so that higher mode resonances can be seen in high frequency. We defined here the spectral amplitude ratio between them as EMR and calculated their average. We categorize all the sites into five bins by their fundamental peak frequencies in MHVR. Once we obtained EMRs for five categories, we back-calculated EHVRs from MHVRs, which we call pseudo-EHVRs (pEHVR). We found that pEHVR is much closer to EHVR than MHVR. Then we use our inversion code to invert the one-dimensional S-wave velocity structures from EHVRs based on the diffuse field concept. We also applied the same code to pEHVRs and MHVRs for comparison. We found that pEHVRs yield velocity structures much closer to those by EHVRs than those by MHVRs. This is natural since what we have done up to here is circular except for the average operation in EMRs. Finally, we showed independent examples of data not used in the EMR calculation, where better ground structures were successfully identified from p

  16. Monitoring of the spatio-temporal change in the interplate coupling at northeastern Japan subduction zone based on the spatial gradients of surface velocity field

    Science.gov (United States)

    Iinuma, Takeshi

    2018-04-01

    A monitoring method to grasp the spatio-temporal change in the interplate coupling in a subduction zone based on the spatial gradients of surface displacement rate fields is proposed. I estimated the spatio-temporal change in the interplate coupling along the plate boundary in northeastern (NE) Japan by applying the proposed method to the surface displacement rates based on global positioning system observations. The gradient of the surface velocities is calculated in each swath configured along the direction normal to the Japan Trench for time windows such as 0.5, 1, 2, 3 and 5 yr being shifted by one week during the period of 1997-2016. The gradient of the horizontal velocities is negative and has a large magnitude when the interplate coupling at the shallow part (less than approximately 50 km in depth) beneath the profile is strong, and the sign of the gradient of the vertical velocity is sensitive to the existence of the coupling at the deep part (greater than approximately 50 km in depth). The trench-parallel variation of the spatial gradients of a displacement rate field clearly corresponds to the trench-parallel variation of the amplitude of the interplate coupling on the plate interface, as well as the rupture areas of previous interplate earthquakes. Temporal changes in the trench-parallel variation of the spatial gradient of the displacement rate correspond to the strengthening or weakening of the interplate coupling. We can monitor the temporal change in the interplate coupling state by calculating the spatial gradients of the surface displacement rate field to some extent without performing inversion analyses with applying certain constraint conditions that sometimes cause over- and/or underestimation at areas of limited spatial resolution far from the observation network. The results of the calculation confirm known interplate events in the NE Japan subduction zone, such as the post-seismic slip of the 2003 M8.0 Tokachi-oki and 2005 M7.2 Miyagi

  17. An application of liquid sublayer dryout mechanism to the prediction of critical heat flux under low pressure and low velocity conditions in round tubes

    International Nuclear Information System (INIS)

    Lee, Kwang-Won; Yang, Jae-Young; Baik, Se-Jin

    1997-01-01

    Based on several experimental evidences for nucleate boiling in annular film and the existence of residual liquid film flow rate at the critical heat flux (CHF) location, the liquid sublayer dryout (LSD) mechanism under annular film is firstly introduced to evaluate the CHF data at low pressure and low velocity (LPLV) conditions, which would not be predicted by a normal annular film dryout (AFD) model. In this study, the CHF occurrence due to annular film separation or breaking down is phenomenologically modelled by applying the LSD mechanism to this situation. In this LSD mechanism, the liquid sublayer thickness, the incoming liquid velocity to the liquid sublayer, and the axial distance from the onset of annular flow to the CHF location are used as the phenomena-controlling parameters. From the model validation on the 1406 CHF data points ranging over P = 0.1 - 2 MPa, G = 4 - 499 kg/m 2 s, L/D = 4 - 402, most of CHF data (more than 1000 points) are predicted within ±30% error bounds by the LSD mechanism. However, some calculation results that critical qualities are less than 0.4 are considerably overestimated by this mechanism. These overpredictions seem to be caused by inadequate CHF mechanism classification criteria and an insufficient consideration of the flow instability effect on CHF. Further studies for a new classification criterion screening the CHF data affected by flow instabilities and a new bubble detachment model for LPLV conditions are needed to improve the model accuracy. (author)

  18. The SCEC Unified Community Velocity Model (UCVM) Software Framework for Distributing and Querying Seismic Velocity Models

    Science.gov (United States)

    Maechling, P. J.; Taborda, R.; Callaghan, S.; Shaw, J. H.; Plesch, A.; Olsen, K. B.; Jordan, T. H.; Goulet, C. A.

    2017-12-01

    Crustal seismic velocity models and datasets play a key role in regional three-dimensional numerical earthquake ground-motion simulation, full waveform tomography, modern physics-based probabilistic earthquake hazard analysis, as well as in other related fields including geophysics, seismology, and earthquake engineering. The standard material properties provided by a seismic velocity model are P- and S-wave velocities and density for any arbitrary point within the geographic volume for which the model is defined. Many seismic velocity models and datasets are constructed by synthesizing information from multiple sources and the resulting models are delivered to users in multiple file formats, such as text files, binary files, HDF-5 files, structured and unstructured grids, and through computer applications that allow for interactive querying of material properties. The Southern California Earthquake Center (SCEC) has developed the Unified Community Velocity Model (UCVM) software framework to facilitate the registration and distribution of existing and future seismic velocity models to the SCEC community. The UCVM software framework is designed to provide a standard query interface to multiple, alternative velocity models, even if the underlying velocity models are defined in different formats or use different geographic projections. The UCVM framework provides a comprehensive set of open-source tools for querying seismic velocity model properties, combining regional 3D models and 1D background models, visualizing 3D models, and generating computational models in the form of regular grids or unstructured meshes that can be used as inputs for ground-motion simulations. The UCVM framework helps researchers compare seismic velocity models and build equivalent simulation meshes from alternative velocity models. These capabilities enable researchers to evaluate the impact of alternative velocity models in ground-motion simulations and seismic hazard analysis applications

  19. Dynamic Phase Transitions In The Spin-2 Ising System Under An Oscillating Magnetic Field Within The Effective-Field Theory

    International Nuclear Information System (INIS)

    Ertas, Mehmet; Keskin, Mustafa; Deviren, Bayram

    2010-01-01

    The dynamic phase transitions are studied in the spin-2 Ising model under a time-dependent oscillating magnetic field by using the effective-field theory with correlations. The effective-field dynamic equation is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first- or second-order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic order parameter and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are presented in (T/zJ, h/zJ) plane.

  20. Phase-Field simulation of phase decomposition in Fe-Cr-Co alloy under an external magnetic field

    Science.gov (United States)

    Koyama, Toshiyuki; Onodera, Hidehiro

    2004-07-01

    Phase decomposition during isothermal aging of a Fe-Cr-Co ternary alloy under an external magnetic field is simulated based on the phase-field method. In this simulation, since the Gibbs energy available from the thermodynamic CALPHAD database of the equilibrium phase diagram is employed as a chemical free energy, the present calculation provides the quantitative microstructure changes directly linked to the phase diagram. The simulated microstructure evolution demonstrates that the lamella like microstructure elongated along the external magnetic field is evolved with the progress of aging. The morphological and temporal developments of the simulated microstructures are in good agreement with experimental results that have been obtained for this alloy system.

  1. The magnetostriction in a superconductor-magnet system under non-uniform magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xueyi; Jiang, Lang; Wu, Hao [Key Laboratory of Mechanics on Disaster and Environment in Western China attached to the Ministry of Education of China, Lanzhou University, Lanzhou, Gansu 730000 (China); Gao, Zhiwen, E-mail: gaozhw@lzu.edu.cn [Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)

    2017-03-15

    Highlights: • We studied firstly magnetostriction in HTS under non-uniform magnetic field. • The superconductors may be homogeneous and nonhomogeneous. • The magnetostrictions response of the HTS is sensitive to the critical current density and amplitude of the applied magnetic field. • The magnetostriction of nonhomogeneous HTS is larger than that of homogeneous HTS. - Abstract: This paper describes a numerical model to examine the magnetostriction of bulk high-temperature superconductor (HTS) under non-uniform magnetic field in conjunction with finite element analysis. Through this model, the magnetostriction of homogeneous and nonhomogeneous HTS can be implemented under non-uniform magnetic field. Further, the effects of critical current density, applied field frequency and amplitude are also considered. The computational study can provide a fundamental mechanistic understanding the effects of non-uniform magnetic field on magnetostriction of HTS.

  2. ‘Postage-stamp PIV’: small velocity fields at 400 kHz for turbulence spectra measurements

    Science.gov (United States)

    Beresh, Steven J.; Henfling, John F.; Spillers, Russell W.; Spitzer, Seth M.

    2018-03-01

    Time-resolved particle image velocimetry recently has been demonstrated in high-speed flows using a pulse-burst laser at repetition rates reaching 50 kHz. Turbulent behavior can be measured at still higher frequencies if the field of view is greatly reduced and lower laser pulse energy is accepted. Current technology allows image acquisition at 400 kHz for sequences exceeding 4000 frames but for an array of only 128  ×  120 pixels, giving the moniker of ‘postage-stamp PIV’. The technique has been tested far downstream of a supersonic jet exhausting into a transonic crossflow. Two-component measurements appear valid until 120 kHz, at which point a noise floor emerges whose magnitude is dependent on the reduction of peak locking. Stereoscopic measurement offers three-component data for turbulent kinetic energy spectra, but exhibits a reduced signal bandwidth and higher noise in the out-of-plane component due to the oblique camera images. The resulting spectra reveal two regions exhibiting power-law dependence describing the turbulent decay. The frequency response of the present measurement configuration exceeds nearly all previous velocimetry measurements in high speed flow.

  3. Simultaneous three-dimensional temperature and velocity field measurements using astigmatic imaging of non-encapsulated thermo-liquid crystal (TLC) particles.

    Science.gov (United States)

    Segura, Rodrigo; Rossi, Massimiliano; Cierpka, Christian; Kähler, Christian J

    2015-02-07

    A combination of cutting edge developments is presented to characterize three-dimensional (3D) temperature and velocity fields in microscopic flows. An emulsion of non-encapsulated thermo-liquid crystal (TLC) micro spheres, with a narrow size distribution is used to track the flow's motion and temperature distribution. A state-of-the-art light engine, which combines the spectrum of six light pipes, provides a balanced illumination which allows for strong and detectable color patterns across the TLC's temperature response range. Lastly, the ability of the TLC material to reflect select wavelength bands with an unchanging and independent circular polarization chirality is exploited by a filter that blocks background noise, while exclusively transmitting the color signal of the TLC particles. This approach takes advantage of the peculiar physical properties of TLCs to allow the estimation of individual TLC particle's 3D position, for the first time, using Astigmatism Particle Tracking Velocimetry (APTV).

  4. Moessbauer study of epsilon-Fe under an external magnetic field

    CERN Document Server

    Nasu, S; Kawakami, T; Tsutsui, T; Endo, S

    2002-01-01

    Using a diamond anvil cell, sup 5 sup 7 Fe Moessbauer measurements of the high-pressure phase of iron, epsilon-Fe at 20 GPa, have been performed at 4.5 K under external magnetic fields up to 7 T. The magnitudes of the hyperfine magnetic fields depend linearly on the external magnetic fields, H sub e sub x sub t. This implies that there is no induced hyperfine field due to the local magnetic moment and epsilon-Fe under 20 GPa at 4.5 K is determined as a Pauli paramagnet.

  5. Redshift of A 1(longitudinal optical) mode for GaN crystals under strong electric field

    Science.gov (United States)

    Gu, Hong; Wu, Kaijie; Zheng, Shunan; Shi, Lin; Zhang, Min; Liu, Zhenghui; Liu, Xinke; Wang, Jianfeng; Zhou, Taofei; Xu, Ke

    2018-01-01

    We investigated the property of GaN crystals under a strong electric field. The Raman spectra of GaN were measured using an ultraviolet laser, and a remarkable redshift of the A 1(LO) mode was observed. The role of the surface depletion layer was discussed, and the interrelation between the electric field and phonons was revealed. First-principles calculations indicated that, in particular, the phonons that vibrate along the [0001] direction are strongly influenced by the electric field. This effect was confirmed by a surface photovoltage experiment. The results revealed the origin of the redshift and presented the phonon property of GaN under a strong electric field.

  6. Space charge field effect on light emitting from tetracene field-effect transistor under AC electric field

    Energy Technology Data Exchange (ETDEWEB)

    Ohshima, Yuki; Kohn, Hideki; Manaka, Takaaki [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo, 152-8552 (Japan); Iwamoto, Mitsumasa, E-mail: iwamoto@pe.titech.ac.j [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo, 152-8552 (Japan)

    2009-11-30

    By applying square wave AC voltage to the Au source electrode of tetracene based field-effect transistor (FET), electroluminescence (EL) was obtained. The results suggest that electrons and holes were injected alternately from the source electrode and recombined each other, and lead to the EL. This type of EL was localized at the interface between the source electrode and tetracene, and enhanced periodically with two relaxation times in accordance with the applied AC voltage cycle. We modeled the carrier behavior in the FET and explained the decay of EL, taking into account the space charge field contribution. Finally, using an AC voltage superposed on DC bias voltage, it was shown that electron injection was prompted only by space charge field.

  7. A free software for pore-scale modelling: solving Stokes equation for velocity fields and permeability values in 3D pore geometries

    KAUST Repository

    Gerke, Kirill

    2015-04-01

    In this contribution we introduce a novel free software which solves the Stokes equation to obtain velocity fields for low Reynolds-number flows within externally generated 3D pore geometries. Provided with velocity fields, one can calculate permeability for known pressure gradient boundary conditions via Darcy\\'s equation. Finite-difference schemes of 2nd and 4th order of accuracy are used together with an artificial compressibility method to iteratively converge to a steady-state solution of Stokes\\' equation. This numerical approach is much faster and less computationally demanding than the majority of open-source or commercial softwares employing other algorithms (finite elements/volumes, lattice Boltzmann, etc.) The software consists of two parts: 1) a pre and post-processing graphical interface, and 2) a solver. The latter is efficiently parallelized to use any number of available cores (the speedup on 16 threads was up to 10-12 depending on hardware). Due to parallelization and memory optimization our software can be used to obtain solutions for 300x300x300 voxels geometries on modern desktop PCs. The software was successfully verified by testing it against lattice Boltzmann simulations and analytical solutions. To illustrate the software\\'s applicability for numerous problems in Earth Sciences, a number of case studies have been developed: 1) identifying the representative elementary volume for permeability determination within a sandstone sample, 2) derivation of permeability/hydraulic conductivity values for rock and soil samples and comparing those with experimentally obtained values, 3) revealing the influence of the amount of fine-textured material such as clay on filtration properties of sandy soil. This work was partially supported by RSF grant 14-17-00658 (pore-scale modelling) and RFBR grants 13-04-00409-a and 13-05-01176-a.

  8. Magnetohydrodynamic flow in a rectangular duct under a uniform transverse magnetic field at high Hartmann number

    International Nuclear Information System (INIS)

    Temperley, D.J.

    1976-01-01

    In this paper we consider fully developed, laminar, unidirectional flow of uniformly conducting, incompressible fluid through a rectangular duct of uniform cross-section. An externally applied magnetic field acts parallel to one pair of opposite walls and induced velocity and magnetic fields are generated in a direction parallel to the axis of the duct. The governing equations and boundary conditions for the latter fields are introduced and study is then concentrated on the special case of a duct having all walls non-conducting. For values of the Hartmann number M>>1, classical asymptotic analysis reveals the leading terms in the expansions of the induced fields in all key regions, with the exception of certain boundary layers near the corners of the duct. The order of magnitude of the affect of the latter layers on the flow-rate is discussed and closed-form solutions are obtained for the induced fields near the corners of the duct. Attempts were made to formulate a concise Principle of Minimum Singularity to enable the correct choice of eigen functions for the various field components in the boundary layers on the walls parallel to the applied field. It was found, however, that these components are best found by taking the outer expansion of the closed-form solution in those boundary-layers near the corners of the duct where classical asymptotic analysis is not applicable. (author)

  9. Design, fabrication and testing of an apparatus for in-situ investigation of free dendritic growth under an applied electric field

    Science.gov (United States)

    Nasresfahani, Mohamad Reza; Niroumand, Behzad; Kermanpur, Ahmad

    2015-04-01

    Modification of dendritic growth of primary phase during solidification has been a continuous quest for materials researchers during last decades. Use of electric current during solidification has been recently proposed as a suitable tool for refinement and modification of dendritic microstructures. Mechanisms by which an electric field could affect a dendritic morphology are not entirely clear as it is difficult to study the solidification phenomena during cooling. This paper reports the design, fabrication and testing of an instrument for in-situ study of the dendritic growth of transparent model materials in the presence of an applied electric field. The system consists of an isothermal bath, a growth chamber and an optical and imaging system. The structure of the growth chamber is designed to allow the growth of only a single dendrite under the applied electric field. In contrast to some previously made instruments which use two orthogonally placed cameras to take care of dendrite tilting or rotation errors, in this research a mathematical approach for calculating the actual dimensions and growth velocity of the dendrite using only one camera was suggested. This greatly simplifies the structure of the instrument. Solidification of a transparent model material, i.e. a succinonitrile alloy, was investigated as a case study under different applied electric fields using the instrument. The results of the study showed a reduction in the dendrite tip velocity in the presence of the electric field.

  10. Orbital velocity

    OpenAIRE

    Modestino, Giuseppina

    2016-01-01

    The trajectory and the orbital velocity are determined for an object moving in a gravitational system, in terms of fundamental and independent variables. In particular, considering a path on equipotential line, the elliptical orbit is naturally traced, verifying evidently the keplerian laws. The case of the planets of the solar system is presented.

  11. Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocity

    Directory of Open Access Journals (Sweden)

    M. L. Parkinson

    2006-03-01

    Full Text Available Akasofu's solar wind ε parameter describes the coupling of solar wind energy to the magnetosphere and ionosphere. Analysis of fluctuations in ε using model independent scaling techniques including the peaks of probability density functions (PDFs and generalised structure function (GSF analysis show the fluctuations were self-affine (mono-fractal, single exponent scaling over 9 octaves of time scale from ~46 s to ~9.1 h. However, the peak scaling exponent α0 was a function of the fluctuation bin size, so caution is required when comparing the exponents for different data sets sampled in different ways. The same generic scaling techniques revealed the organisation and functional form of concurrent fluctuations in azimuthal magnetospheric electric fields implied by SuperDARN HF radar measurements of line-of-sight Doppler velocity, vLOS, made in the high-latitude austral ionosphere. The PDFs of vLOS fluctuation were calculated for time scales between 1 min and 256 min, and were sorted into noon sector results obtained with the Halley radar, and midnight sector results obtained with the TIGER radar. The PDFs were further sorted according to the orientation of the interplanetary magnetic field, as well as ionospheric regions of high and low Doppler spectral width. High spectral widths tend to occur at higher latitude, mostly on open field lines but also on closed field lines just equatorward of the open-closed boundary, whereas low spectral widths are concentrated on closed field lines deeper inside the magnetosphere. The vLOS fluctuations were most self-affine (i.e. like the solar wind ε parameter on the high spectral width field lines in the noon sector ionosphere (i.e. the greater cusp, but suggested multi-fractal behaviour on closed field lines in the midnight sector (i.e. the central plasma sheet. Long tails in the PDFs imply that "microbursts" in ionospheric convection occur far more frequently, especially on open field lines, than can be

  12. Electrically Injected Polariton Lasing from a GaAs-Based Microcavity under Magnetic Field

    KAUST Repository

    Bhattacharya, Pallab

    2012-01-01

    Suppression of relaxation bottleneck and subsequent polariton lasing is observed in a GaAs-based microcavity under the application of a magnetic field. The threshold injection current density is 0.32 A/cm2 at 7 Tesla.

  13. Influence factor analysis of atmospheric electric field monitoring near ground under different weather conditions

    International Nuclear Information System (INIS)

    Wan, Haojiang; Wei, Guanghui; Cui, Yaozhong; Chen, Yazhou

    2013-01-01

    Monitoring of atmospheric electric field near ground plays a critical role in atmospheric environment detecting and lightning warning. Different environmental conditions (e.g. buildings, plants, weather, etc.) have different influences on the data's coherence in an atmospheric electric field detection network. In order to study the main influence factors of atmospheric electric field monitoring under different weather conditions, with the combination of theoretical analysis and experiments, the electric field monitoring data on the ground and on the top of a building are compared in fair weather and thunderstorm weather respectively in this paper. The results show that: In fair weather, the field distortion due to the buildings is the main influence factor on the electric field monitoring. In thunderstorm weather, the corona ions produced from the ground, besides the field distortion due to the buildings, can also influence the electric field monitoring results.

  14. Introduction to vector velocity imaging

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Udesen, Jesper; Hansen, Kristoffer Lindskov

    it virtually impossible to compensate for the factor and obtain correct velocity estimates for either CFM or spectral velocity estimation. This talk will describe methods for finding the correct velocity by estimating both the axial and lateral component of the velocity vector. The transverse oscillation...... method introduces an ultrasound field that oscillation not only along the ultrasound beam both also transverse to it to estimate both the lateral and axial velocity for the full velocity vector. The correct velocity magnitude can be found from this as well as the instantaneous angle. This can be obtained...... over the full region of interest and a real time image at a frame rate of 20 Hz can be displayed. Real time videos have been obtained from both our research systems and from commercial BK Medical scanners. The vector velocity images reveal the full complexity of the human blood flow. It is easy to see...

  15. Fretting friction and wear characteristics of magnetorheological fluid under different magnetic field strengths

    International Nuclear Information System (INIS)

    Zhang, P.; Lee, K.H.; Lee, C.H.

    2017-01-01

    A magnetorheological fluid (MRF) performs differently under different magnetic field strength. This study examined the fretting friction and wear characteristics of MRFs under a range of magnetic field strengths and oscillation frequencies. The fretting friction and wear behaviors of MRF are investigated using a fretting friction and wear tester. The surfaces of specimen are examined by optical microscopy and 3D surface profilometer before and after the tests and wear surface profiles, the wear volume loss and wear coefficient for each magnetic field strength are evaluated. The results show that the friction and wear properties of MRF change according to the magnetic field strength and oscillation frequency. - Highlights: • Fretting friction and wear characteristics of MRF is examined. • The friction coefficients increased with increasing magnetic field strength. • The coefficient of friction decreased with increasing oscillation frequency. • Wear volume and coefficient become worse with increasing magnetic field strength.

  16. Electrical insulation characteristics of liquid helium under high speed rotating field

    International Nuclear Information System (INIS)

    Ishii, I.; Fuchino, S.; Okano, M.; Tamada, N.

    1996-01-01

    Electrical breakdown behavior of liquid helium was investigated under high speed rotating field. In the development of superconducting turbine generator it is essential to get the knowledge of electrical insulation characteristics of liquid helium under high speed rotating field. When the current of the field magnet of a superconducting generator is changed, changing magnetic field generates heat in the conductor and it causes bubbles in the liquid helium around the conductor. The behavior of the bubbles is affected largely by the buoyancy which is generated by the centrifugal force. Electrical breakdown behavior of the liquid helium is strongly dependent on the gas bubbles in the liquid. Electrical breakdown voltage between electrodes was measured in a rotating cryostat with and without heater input for bubble formation. Decrease of the breakdown voltage by the heater power was smaller in the rotating field than that in the non rotating field

  17. Investigation on stresses of superconductors under pulsed magnetic fields based on multiphysics model

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaobin, E-mail: yangxb@lzu.edu.cn; Li, Xiuhong; He, Yafeng; Wang, Xiaojun; Xu, Bo

    2017-04-15

    Highlights: • The differential equation including temperature and magnetic field was derived for a long cylindrical superconductor. • Thermal stress and electromagnetic stress were studied at the same time under pulse field magnetizing. • The distributions of the magnetic field, the temperature and stresses are studied and compared for two pulse fields of the different duration. • The Role thermal stress and electromagnetic stress play in the process of pulse field magnetizing is discussed. - Abstract: A multiphysics model for the numerical computation of stresses, trapped field and temperature distribution of a infinite long superconducting cylinder is proposed, based on which the stresses, including the thermal stresses and mechanical stresses due to Lorentz force, and trapped fields in the superconductor subjected to pulsed magnetic fields are analyzed. By comparing the results under pulsed magnetic fields with different pulse durations, it is found that the both the mechanical stress due to the electromagnetic force and the thermal stress due to temperature gradient contribute to the total stress level in the superconductor. For pulsed magnetic field with short durations, the thermal stress is the dominant contribution to the total stress, because the heat generated by AC-loss builds up significant temperature gradient in such short durations. However, for a pulsed field with a long duration the gradient of temperature and flux, as well as the maximal tensile stress, are much smaller. And the results of this paper is meaningful for the design and manufacture of superconducting permanent magnets.

  18. Investigation of the Decelerating Field of an Electron Multiplier under Negative Ion Impact

    DEFF Research Database (Denmark)

    Larsen, Elfinn; Kjeldgaard, K.

    1973-01-01

    The effect of the decelerating field of an electron multiplier towards negative ions was investigated under standard mass spectrometric conditions. Diminishing of this decelerating field by changing of the potential of the electron multiplier increased the overall sensitivity to negative ions...

  19. New grafted ferrite particles/liquid crystal composite under magnetic field

    Science.gov (United States)

    Manaila Maximean, D.

    2018-04-01

    A new colloidal composite formed by specially synthesized dimethylphenyl ferrite particles and a nematic liquid crystal (LC) is presented. By applying a small magnetic field during polarizing optical microscopy observations, it was found that the magnetic moment of the synthesized ferrite is perpendicular to the director of the LC. The optical transmission of laser light across the ferronematic was investigated under magnetic field. The critical magnetic field corresponding to the Freedericksz transition was obtained and discussed according to the Burylov and Raikher theory.

  20. Hyperfine Level Interactions of Diamond Nitrogen Vacancy Ensembles Under Transverse Magnetic Fields

    Science.gov (United States)

    2015-10-06

    transverse mag- netic bias field (B|| or B⊥) lifts this degeneracy, ener- getically separating the spin states and increasing sensi- tivity to magnetic or...light-trapping diamond waveguide geometry [19]. We lift the ms = ±1 degeneracy by ap- plying a static magnetic field and tune the microwave ex- citation...Hyperfine level interactions of diamond nitrogen vacancy ensembles under transverse magnetic fields Hannah Clevenson,1, 2, ∗ Edward H. Chen,1, 2

  1. Study on the effect of the side secondary air velocity on the aerodynamic field in a tangentially fired furnace with HBC-SSA Burner

    Science.gov (United States)

    Zhu, Tong; Sun, Shaozeng; Wu, Shaohua; Qin, Yukun

    1999-12-01

    The present paper has compared a group of furnace aerodynamic fields at different velocities of side secondary air (SSA) in a test model of 420t/h utility boiler, applying Horizontal Bias Combustion Pulverized Coal Burner with Side Secondary Air (HBC-SSA Burner). Experimental results show that, when the ram pressure ratio of side secondary air (SSA) to primary air (PA) (ρ2sv 2s /2 /ρ1v 1 2 ) is between 1.0 2.4, the furnace aerodynamic field only varies slightly. The relative rotational diameters (φ/L) in the burner domain are moderate and the furnace is in good fullness. When ρ2sv 2s /2 /ρ1v 1 2 is beyond 4, φ/L is so large that the stream sweeps water-cooled wall and rotates strongly in the furnace. Therefore, slagging and high temperature corrosion of tube metal will be formed on the water-cooled wall in actual operation. This investigation provides the basis for the application of this new type burner. In addition, numerical simulations are conducted, and some defects in the numerical simulation are also pointed out and analyzed in this paper.

  2. Ferrofluid lubrication of circular squeeze film bearings controlled by variable magnetic field with rotations of the discs, porosity and slip velocity

    Science.gov (United States)

    Shah, Rajesh C.; Shah, Rajiv B.

    2017-12-01

    Based on the Shliomis ferrofluid flow model (SFFM) and continuity equation for the film as well as porous region, modified Reynolds equation for lubrication of circular squeeze film bearings is derived by considering the effects of oblique radially variable magnetic field (VMF), slip velocity at the film-porous interface and rotations of both the discs. The squeeze film bearings are made up of circular porous upper disc of different shapes (exponential, secant, mirror image of secant and parallel) and circular impermeable flat lower disc. The validity of Darcy's Law is assumed in the porous region. The SFFM is important because it includes the effects of rotations of the carrier liquid as well as magnetic particles. The VMF is used because of its advantage of generating maximum field at the required active contact area of the bearing design system. Also, the effect of porosity is included because of its advantageous property of self-lubrication. Using Reynolds equation, general form of pressure equation is derived and expression for dimensionless load-carrying capacity is obtained. Using this expression, results for different bearing design systems (due to different shapes of the upper disc) are computed and compared for variation of different parameters.

  3. Study of Impact Damage in PVA-ECC Beam under Low-Velocity Impact Loading Using Piezoceramic Transducers and PVDF Thin-Film Transducers.

    Science.gov (United States)

    Qi, Baoxin; Kong, Qingzhao; Qian, Hui; Patil, Devendra; Lim, Ing; Li, Mo; Liu, Dong; Song, Gangbing

    2018-02-24

    Compared to conventional concrete, polyvinyl alcohol fiber reinforced engineering cementitious composite (PVA-ECC) offers high-strength, ductility, formability, and excellent fatigue resistance. However, impact-induced structural damage is a major concern and has not been previously characterized in PVA-ECC structures. We investigate the damage of PVA-ECC beams under low-velocity impact loading. A series of ball-drop impact tests were performed at different drop weights and heights to simulate various impact energies. The impact results of PVA-ECC beams were compared with mortar beams. A combination of polyvinylidene fluoride (PVDF) thin-film sensors and piezoceramic-based smart aggregate were used for impact monitoring, which included impact initiation and crack evolution. Short-time Fourier transform (STFT) of the signal received by PVDF thin-film sensors was performed to identify impact events, while active-sensing approach was utilized to detect impact-induced crack evolution by the attenuation of a propagated guided wave. Wavelet packet-based energy analysis was performed to quantify failure development under repeated impact tests.

  4. The critical ionization velocity

    International Nuclear Information System (INIS)

    Raadu, M.A.

    1980-06-01

    The critical ionization velocity effect was first proposed in the context of space plasmas. This effect occurs for a neutral gas moving through a magnetized plasma and leads to rapid ionization and braking of the relative motion when a marginal velocity, 'the critical velocity', is exceeded. Laboratory experiments have clearly established the significance of the critical velocity and have provided evidence for an underlying mechanism which relies on the combined action of electron impact ionization and a collective plasma interaction heating electrons. There is experimental support for such a mechanism based on the heating of electrons by the modified two-stream instability as part of a feedback process. Several applications to space plasmas have been proposed and the possibility of space experiments has been discussed. (author)

  5. InSAR velocity field across the North Anatolian Fault (eastern Turkey): Implications for the loading and release of interseismic strain accumulation

    KAUST Repository

    Cakir, Ziyadin

    2014-10-01

    We use the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique with the European Space Agency\\'s Envisat and ERS SAR data acquired on three neighboring descending tracks (T350, T078, and T307) to map the interseismic strain accumulation along a ~225 km long, NW-SE trending section of the North Anatolian Fault that ruptured during the 1939, 1942, and 1943 earthquakes in eastern Turkey. We derive a line-of-sight velocity map of the region with a high spatial resolution and accuracy which, together with the maps of earthquake surface ruptures, shed light on the style of continental deformation and the relationships between the loading and release of interseismic strain along segmented continental strike-slip faults. In contrast with the geometric complexities at the ground surface that appear to control rupture propagation of the 1939 event, modeling of the high-resolution PS-InSAR velocity field reveals a fairly linear and narrow throughgoing shear zone with an overall 20 ± 3 mm/yr slip rate above an unexpectedly shallow 7 ± 2 km locking depth. Such a shallow locking depth may result from the postseismic effects following recent earthquakes or from a simplified model that assumes a uniform degree of locking with depth on the fault. A narrow throughgoing shear zone supports the thick lithosphere model in which continental strike-slip faults are thought to extend as discrete shear zones through the entire crust. Fault segmentation previously reported from coseismic surface ruptures is thus likely inherited from heterogeneities in the upper crust that either preexist and/or develop during coseismic rupture propagation. The geometrical complexities that apparently persist for long periods may guide the dynamic rupture propagation surviving thousands of earthquake cycles.

  6. Determinants of under-five mortality in Gilgel Gibe Field Research ...

    African Journals Online (AJOL)

    2004-08-27

    The objective of this study was to investigate causes of death and its determinants in under-five children in Gilgel Gibe Field Research Center. Methods: A case-control study was conducted from December 12 to 27, 2005. Cases of under-five children who died between August 27, 2004 and September 22, 2005 and controls ...

  7. Studies on the survival of Ascaris suum eggs under laboratory and simulated field conditions

    NARCIS (Netherlands)

    Gaasenbeek, C.P.H.; Borgsteede, F.H.M.

    1998-01-01

    A series of four experiments was carried out to study the survival of Ascaris suum eggs: in a pig slurry unit on a farm, in the laboratory under anaerobic conditions and different relative humidities (rH), and under simulated field conditions. Survival of eggs in the pig slurry unit was 20% after

  8. Aphid wing induction and ecological costs of alarm pheromone emission under field conditions.

    Directory of Open Access Journals (Sweden)

    Eduardo Hatano

    2010-06-01

    Full Text Available The pea aphid, Acyrthosiphon pisum Harris, (Homoptera: Aphididae releases the volatile sesquiterpene (E-beta-farnesene (EBF when attacked by a predator, triggering escape responses in the aphid colony. Recently, it was shown that this alarm pheromone also mediates the production of the winged dispersal morph under laboratory conditions. The present work tested the wing-inducing effect of EBF under field conditions. Aphid colonies were exposed to two treatments (control and EBF and tested in two different environmental conditions (field and laboratory. As in previous experiments aphids produced higher proportion of winged morphs among their offspring when exposed to EBF in the laboratory but even under field conditions the proportion of winged offspring was higher after EBF application (6.84+/-0.98% compared to the hexane control (1.54+/-0.25%. In the field, the proportion of adult aphids found on the plant at the end of the experiment was lower in the EBF treatment (58.1+/-5.5% than in the control (66.9+/-4.6%, in contrast to the climate chamber test where the numbers of adult aphids found on the plant at the end of the experiment were, in both treatments, similar to the numbers put on the plant initially. Our results show that the role of EBF in aphid wing induction is also apparent under field conditions and they may indicate a potential cost of EBF emission. They also emphasize the importance of investigating the ecological role of induced defences under field conditions.

  9. Dynamic behaviors of ferroelectric liquid crystal molecules under an applied electric field

    Science.gov (United States)

    Kawaguchi, Masato; Takei, Misaki; Yamashita, Masafumi

    2009-03-01

    The dynamic changes in ferroelectric liquid crystal (FLC) molecular alignments under an applied electric field are examined by observing the formation of conoscopic figures with a time resolution of 0.1 ms. Close agreements between observed and simulated conoscopic figures under low voltage (30 V) were obtained. Under high voltage (120 V), however, the observed conoscopic figures became blurred between 0.8 ms and 1.1 ms after reversal of the electric field. The light scattering producing the blurriness occurred due to the development of fast transient molecular alignments during the switching transition above the applied voltage 70 V.

  10. Silver doped hydroxyapatite coatings by sacrificial anode deposition under magnetic field.

    Science.gov (United States)

    Swain, S; Rautray, T R

    2017-09-13

    Uniform distribution of silver (Ag) in the hydroxyapatite (HA) coated Ti surface has been a concern for which an attempt has been made to dope Ag in HA coating with and without magnetic field. Cathodic deposition technique was employed to coat Ag incorporated hydroxyapatite coating using a sacrificial silver anode method by using NdFeB bar magnets producing 12 Tesla magnetic field. While uniform deposition of Ag was observed in the coatings under magnetic field, dense coating was evident in the coating without magnetic field conditions. Uniformly distributed Ag incorporated HA in the present study has potential to fight microorganism while providing osseoconduction properties of the composite coating.

  11. Quantum Phase Shift of a Moving Dipole under a Magnetic Field at a Distance

    Science.gov (United States)

    Lee, Kang-Ho; Kim, Young-Wan; Kang, Kicheon

    2018-03-01

    We predict a quantum phase shift of a moving electric dipole in the presence of an external magnetic field at a distance. On the basis of the Lorentz-covariant field interaction approach, we show that a phase shift appears in the internal dipole state under the condition that the dipole is moving in the field-free region, which is distinct from the topological He-McKellar-Wilkens phase generated by a direct overlap of the dipole and the field. We discuss the experimental feasibility of detecting this phase with atomic interferometry and argue that detection of this phase will resolve the question of the locality in quantum electromagnetic interaction.

  12. Theoretical investigation of magnetic property in paramagnetic neodymium gallium garnet under high magnetic field

    International Nuclear Information System (INIS)

    Wang Wei; Liu Gongqiang; Wang Jinhui

    2006-01-01

    The magnetic property in neodymium gallium garnet (NdGaG) is studied by the quantum theory. The ground configuration split states are calculated taking into account the spin-orbit interaction and crystal field effect. Taking account of the Nd-Nd exchange interaction, a good agreement between experimental and theoretical values can be obtained for the variation of the magnetic moment with the external magnetic field under 'extreme' conditions (low temperature and high magnetic field). Moreover, the temperature dependence of magnetic moment and the magnetic susceptibility χ is also discussed. Above 30 K, the magnetization (M) shows a linear field (H e ) dependence

  13. Study of electric field distorted by space charges under positive lightning impulse voltage

    Science.gov (United States)

    Wang, Zezhong; Geng, Yinan

    2018-03-01

    Actually, many insulation problems are related to electric fields. And measuring electric fields is an important research topic of high-voltage engineering. In particular, the electric field distortion caused by space charge is the basis of streamer theory, and thus quantitatively measuring the Poisson electric field caused by space charge is significant to researching the mechanism of air gap discharge. In this paper, we used our photoelectric integrated sensor to measure the electric field distribution in a 1-m rod-plane gap under positive lightning impulse voltage. To verify the reliability of this quantitative measurement, we compared the measured results with calculated results from a numerical simulation. The electric-field time domain waveforms on the axis of the 1-m rod-plane out of the space charge zone were measured with various electrodes. The Poisson electric fields generated by space charge were separated from the Laplace electric field generated by applied voltages, and the amplitudes and variations were measured for various applied voltages and at various locations. This work also supplies the feasible basis for directly measuring strong electric field under high voltage.

  14. Motion of a point charge in electromagnetic fields under consideration of radiation damping

    International Nuclear Information System (INIS)

    Stoeckel, H.

    1976-01-01

    The 'new equation' of Mo and Papas for the description of a point charge in an electromagnetic field under consideration of radiation damping, published in 1971, doesn't show the known disadvantages of the Lorentz-Dirac equation, taken as a basis up to now. Different forms of the Mo-Papas equation are derived and the resulting force- and power-balances are discussed. Exact and approximated solutions are derived for simple given fields, for instance for a homogeneous magnetic field, a homogeneous electric field and for the field of a resting point charge. The scattering angles are calculated for the scattering of a point charge by a homogeneous magnetic resp. electric field of finite extension. The results agree well with approximation formulas of other authors. (author)

  15. Nanoconfined water under electric field at constant chemical potential undergoes electrostriction

    Science.gov (United States)

    Vanzo, Davide; Bratko, D.; Luzar, Alenka

    2014-02-01

    Electric control of nanopore permeation by water and solutions enables gating in membrane ion channels and can be exploited for transient surface tuning of rugged substrates, to regulate capillary permeability in nanofluidics, and to facilitate energy absorption in porous hydrophobic media. Studies of capillary effects, enhanced by miniaturization, present experimental challenges in the nanoscale regime thus making molecular simulations an important complement to direct measurement. In a molecular dynamics (MD) simulation, exchange of water between the pores and environment requires modeling of coexisting confined and bulk phases, with confined water under the field maintaining equilibrium with the unperturbed environment. In the present article, we discuss viable methodologies for MD sampling in the above class of systems, subject to size-constraints and uncertainties of the barostat function under confinement and nonuniform-field effects. Smooth electric field variation is shown to avoid the inconsistencies of MD integration under abruptly varied field and related ambiguities of conventional barostatting in a strongly nonuniform interfacial system. When using a proper representation of the field at the border region of the confined water, we demonstrate a consistent increase in electrostriction as a function of the field strength inside the pore open to a field-free aqueous environment.

  16. Recent developments in Liquid Phase Electroepitaxial growth of bulk crystals under magnetic field

    Science.gov (United States)

    Dost, Sadik; Lent, Brian; Sheibani, Hamdi; Liu, Yongcai

    2004-05-01

    This review article presents recent developments in Liquid Phase Electroepitaxial (LPEE) growth of bulk single crystals of alloy semiconductors under an applied static magnetic field. The growth rate in LPEE is proportional to the applied electric current. However, at higher electric current levels the growth becomes unstable due to the strong convection occurring in the liquid zone. In order to address this problem, a significant body of research has been performed in recent years to suppress and control the natural convection for the purpose of prolonging the growth process to grow larger crystals. LPEE growth experiments show that the growth rate under an applied static magnetic field is also proportional and increases with the field intensity level. The modeling of LPEE growth under magnetic field was also the subject of interest. Two-dimensional mathematical models developed for the LPEE growth process predicted that the natural convection in the liquid zone would be suppressed almost completely with increasing the magnetic field level. However, experiments and also three-dimensional models have shown that there is an optimum magnetic field level below which the growth process is stable and the convection in the liquid zone is suppressed, but above such a field level the convective flow becomes very strong and leads to unstable growth with unstable interfaces. To cite this article: S. Dost et al., C. R. Mecanique 332 (2004).

  17. Time course of changes in cerebral blood flow velocity after tourniquet deflation in patients with diabetes mellitus or previous stroke under sevoflurane anesthesia.

    Science.gov (United States)

    Hinohara, Hiroshi; Kadoi, Yuji; Takahashi, Kenichiro; Saito, Shigeru; Kawauchi, Chikara; Mizutani, Akio

    2011-06-01

    We observed an increase in mean middle cerebral artery blood flow velocity (V(mca)) after tourniquet deflation during orthopedic surgery under sevoflurane anesthesia in patients with diabetes mellitus or previous stroke. Eight controls, seven insulin-treated diabetic patients, and eight previous stroke patients were studied. Arterial blood pressure, heart rate, V(mca), arterial blood gases, and plasma lactate levels were measured every minute for 10 min after tourniquet release in all patients. V(mca) was measured using a transcranial Doppler probe. V(mca) in all three groups increased after tourniquet deflation, the increase lasting for 4 or 5 min. However, the degree of increase in V(mca) in the diabetic patients was smaller than that in the other two groups after tourniquet deflation (at 2 min after tourniquet deflation: control 58.5 ± 3.3, previous stroke 58.4 ± 4.6, diabetes 51.7 ± 2.3; P < 0.05 compared with the other two groups). In conclusion, the degree of increase in V (mca) in diabetic patients is smaller than that in controls and patients with previous stroke.

  18. Constraining galaxy cluster velocity field with the thermal Sunyaev-Zel'dovich and kinematic Sunyaev-Zel'dovich cross-bispectrum

    Science.gov (United States)

    Hurier, G.

    2017-08-01

    The Sunyaev-Zel'dovich (SZ) effects are produced by the interaction of cosmic microwave background (CMB) photons with the ionized and diffuse gas of electrons inside galaxy clusters integrated along the line of sight. The two main effects are the thermal SZ (tSZ) produced by thermal pressure inside galaxy clusters and the kinematic SZ (kSZ) produced by peculiar motion of galaxy clusters compared to CMB rest-frame. The kSZ effect is particularly challenging to measure as it follows the same spectral behavior as the CMB, and consequently cannot be separated from the CMB using spectral considerations. In this paper, we explore the feasibility of detecting the kSZ through the computation of the tSZ-CMB-CMB cross-correlation bispectrum for current and future CMB experiments. We conclude that the next generation of CMB experiments will offer the possibility to detect the tSZ-kSZ-kSZ bispectrum at high signal-to-noise ration (S/N). This measurement will constraints the intra-cluster dynamics and the velocity field of galaxy cluster that is extremely sensitive to the growth rate of structures and thus to dark energy properties. Additionally, we also demonstrate that the tSZ-kSZ-kSZ bispectrum can be used to break the degeneracies between the mass-observable relation and the cosmological parameters to set tight constraints, up to 4%, on the Y - M relation calibration.

  19. Experimental study of directionally solidified ferromagnetic shape memory alloy under multi-field coupling

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Yuping, E-mail: zhuyuping@126.com [Institute of Geophysics, China Earthquake Administration, Beijing 100081 (China); Chen, Tao; Teng, Yao [Faculty of Civil Engineering and Mechanics, Jiangsu University, Zhenjiang 212013 (China); Liu, Bingfei [Airport College, Civil Aviation University of China, Tianjin 300300 (China); Xue, Lijun [Tianjin Key Laboratory of the Design and Intelligent Control of the Advanced Mechatronical System, School of Mechanical Engineering, Tianjin University of Technology, Tianjin 300384 (China)

    2016-11-01

    Directionally solidified, polycrystalline Ni–Mn–Ga is studied in this paper. The polycrystalline Ni–Mn–Ga samples were cut at different angles to solidification direction. The magnetic field induced strain under constant stress and the temperature-induced strain under constant magnetic field during the loading–unloading cycle were measured. The experimental results show that the mechanical behavior during the loading–unloading cycle of the material is nonlinear and anisotropic. Based on the experimental results, the effects of multi-field coupling factors, such as stress, magnetic field, temperature and cutting angle on the mechanical behaviors were analyzed. Some useful conclusions were obtained, which will provide guidance for practical applications. - Highlights: • The magnetic-induced strains in different directions are tested. • The temperature-induced strains in different directions are tested. • The effects of coupling factors on directional solidification samples are studied.

  20. Experimental study of directionally solidified ferromagnetic shape memory alloy under multi-field coupling

    Science.gov (United States)

    Zhu, Yuping; Chen, Tao; Teng, Yao; Liu, Bingfei; Xue, Lijun

    2016-11-01

    Directionally solidified, polycrystalline Ni-Mn-Ga is studied in this paper. The polycrystalline Ni-Mn-Ga samples were cut at different angles to solidification direction. The magnetic field induced strain under constant stress and the temperature-induced strain under constant magnetic field during the loading-unloading cycle were measured. The experimental results show that the mechanical behavior during the loading-unloading cycle of the material is nonlinear and anisotropic. Based on the experimental results, the effects of multi-field coupling factors, such as stress, magnetic field, temperature and cutting angle on the mechanical behaviors were analyzed. Some useful conclusions were obtained, which will provide guidance for practical applications.

  1. Experimental study of directionally solidified ferromagnetic shape memory alloy under multi-field coupling

    International Nuclear Information System (INIS)

    Zhu, Yuping; Chen, Tao; Teng, Yao; Liu, Bingfei; Xue, Lijun

    2016-01-01

    Directionally solidified, polycrystalline Ni–Mn–Ga is studied in this paper. The polycrystalline Ni–Mn–Ga samples were cut at different angles to solidification direction. The magnetic field induced strain under constant stress and the temperature-induced strain under constant magnetic field during the loading–unloading cycle were measured. The experimental results show that the mechanical behavior during the loading–unloading cycle of the material is nonlinear and anisotropic. Based on the experimental results, the effects of multi-field coupling factors, such as stress, magnetic field, temperature and cutting angle on the mechanical behaviors were analyzed. Some useful conclusions were obtained, which will provide guidance for practical applications. - Highlights: • The magnetic-induced strains in different directions are tested. • The temperature-induced strains in different directions are tested. • The effects of coupling factors on directional solidification samples are studied.

  2. Thermal pulse measurements of space charge distributions under an applied electric field in thin films

    International Nuclear Information System (INIS)

    Zheng, Feihu; An, Zhenlian; Zhang, Yewen; Liu, Chuandong; Lin, Chen; Lei, Qingquan

    2013-01-01

    The thermal pulse method is a powerful method to measure space charge and polarization distributions in thin dielectric films, but a complicated calibration procedure is necessary to obtain the real distribution. In addition, charge dynamic behaviour under an applied electric field cannot be observed by the classical thermal pulse method. In this work, an improved thermal pulse measuring system with a supplemental circuit for applying high voltage is proposed to realize the mapping of charge distribution in thin dielectric films under an applied field. The influence of the modified measuring system on the amplitude and phase of the thermal pulse response current are evaluated. Based on the new measuring system, an easy calibration approach is presented with some practical examples. The newly developed system can observe space charge evolution under an applied field, which would be very helpful in understanding space charge behaviour in thin films. (paper)

  3. Numerical Study on Deformation and Interior Flow of a Droplet Suspended in Viscous Liquid under Steady Electric Fields

    Directory of Open Access Journals (Sweden)

    Zhentao Wang

    2014-07-01

    Full Text Available A model based on the volume of fluid (VOF method and leaky dielectric theory is established to predict the deformation and internal flow of the droplet suspended in another vicious fluid under the influence of the electric field. Through coupling with hydrodynamics and electrostatics, the rate of deformation and internal flow of the single droplet are simulated and obtained under the different operating parameters. The calculated results show that the direction of deformation and internal flow depends on the physical properties of fluids. The numerical results are compared with Taylor's theory and experimental results by Torza et al. When the rate of deformation is small, the numerical results are consistent with theory and experimental results, and when the rate is large the numerical results are consistent with experimental results but are different from Taylor's theory. In addition, fluid viscosity hardly affects the deformation rate and mainly dominates the deformation velocity. For high viscosity droplet spends more time to attain the steady state. The conductivity ratio and permittivity ratio of two different liquids affect the direction of deformation. When fluid electric properties change, the charge distribution at the interface is various, which leads to the droplet different deformation shapes.

  4. Seed vigour tests for predicting field emergence of maize under severe conditions

    OpenAIRE

    García de Yzaguirre, Álvaro; Lasa Dolhagaray, José Manuel

    1989-01-01

    [EN] With 40 to 50 different seed vigour tests available, appropiate procedures for choosing the best single test or combination the best predictors of seedling emergence of maize (Zea Mays L.) under severe conditions. Thirteen vigour tests and various field emergence trials were performed on six inbred lines and two commercial hybrids. The best single predictors of field emergence were identified by calculating simple correlation coefficients. The calculation of the geometric mean of the res...

  5. Effect of mycorrhizas application on plant growth and nutrient uptake in cucumber production under field conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ortas, I.

    2010-07-01

    Mycorrhizas application in horticultural production in the Eastern Mediterranean region of Turkey has been studied under field conditions for several years. The effects of different arbuscular mycorrhizal fungi (AMF) have been evaluated under field conditions for cucumber production. The parameters measured were seedling survival, plant growth and yield, and root colonization. In 1998 and 1999, Glomus mosseae and Glomus etunicatum inoculated cucumber seedlings were treated with and without P (100 kg P2O5 ha-1) application. A second experiment was set up to evaluate the response of cucumber to the inoculation with a consortia of indigenous mycorrhizae, G. mosseae, G. etunicatum, Glomus clarum, Glomus caledonium and a mixture of these four species. Inoculated and control non inoculated cucumber seedlings were established under field conditions in 1998, 2001, 2002 and 2004. Seedling quality, seedling survival under field conditions and yield response to mycorrhiza were tested. Fruits were harvested periodically; at blossom, plant leaves and root samples were taken for nutrient content and mycorrhizal colonization analysis respectively. The field experiment results showed that mycorrhiza inoculation significantly increased cucumber seedling survival, fruit yield, P and Zn shoot concentrations. Indigenous mycorrhiza inoculum was successful in colonizing plant roots and resulted in better plant growth and yield. The relative effectiveness of each of the inocula tested was not consistent in the different experiments, although inoculated plants always grew better than control no inoculated. The most relevant result for growers was the increased survival of seedlings. (Author) 20 refs.

  6. Frequency dependence of dielectric characteristics of seawater ionic solution under static magnetic field

    Science.gov (United States)

    Guo, Shaoshuai; Peng, Yufeng; Han, Xueyun; Li, Jiangting

    2017-09-01

    In order to study the electromagnetic wave transmission characteristics in seawater under external physical effects, we present a study of seawater ionic solution and perform a theoretical basis of magnetic field on water molecules and ionic motion to investigate the variation of dielectric properties with frequency under static magnetic field (0.38 T). Seawater is a naturally multi-component electrolyte solution, the main ingredients in seawater are inorganic salts, such as NaCl, MgSO4, MgCl2, CaCl2, KCl, NaHCO3, etc. The dielectric properties of these electrolyte solutions with different salinity values (0.01-5%) were measured in frequencies ranging from 40 to 5 MHz at 12∘C. The results show that the dielectric constant decreases with increasing frequencies no matter with magnetic field or without it. Frequency dependence of the dielectric constant of NaCl solution increases under magnetic field at measure concentrations. In a solution of MgCl2 ṡ 6H2O, KCl and NaHCO3 are consistent with NaCl solution, while CaCl2 ṡ 2H2O solution is in contrast with it. We also find that dielectric loss plays a major role in complex permittivity. With the effect of magnetic field, the proportion of dielectric loss is reducing in complex permittivity. On this basis it was concluded that the magnetic field influences the orientation of dipoles and the variation is different in salt aqueous solution.

  7. Electro-migration effect of titanium structure under high magnetic field

    International Nuclear Information System (INIS)

    Sakaida, Y; Iwai, K; Asai, S

    2009-01-01

    It is well known topic that electro-migration accompanies the transport of atoms, ions and holes in a material. Then we can say that both electro-migration and strong magnetic field have potential to control crystal alignment. In this study, an electric current and/or a static magnetic field were applied to a titanium sample parallel to each other to investigate the effects of the electric current and the static magnetic field on crystal alignment in the titanium. Using XRD analysis, it was understood that titanium crystals having a c-axis perpendicular to the electric current direction increased under the imposition of only the electric current and under the simultaneous imposition of the electric current and the magnetic field. On the other hand, titanium crystals having a c-axis parallel to the magnetic field direction increased under the imposition of only the magnetic field. The aligned result can be explained from the viewpoint of anisotropy of the Joule loss and the magnetization energy.

  8. Ferrofluid aggregation in chains under the influence of a magnetic field

    International Nuclear Information System (INIS)

    Ivanov, Alexey O.; Kantorovich, Sofia S.; Mendelev, Valentin S.; Pyanzina, Elena S.

    2006-01-01

    The paper is devoted to the basic problem of chain aggregate formation in magnetic fluids under the influence of an external magnetic field. Chain distribution in dynamic equilibrium is obtained on the basis of free energy minimization method under the condition when the interparticle dipole-dipole interaction between the nearest neighboring ferroparticles in each chain is taken into account. The modified mean field approach is used for considering the dipole-dipole interaction between all particles in a ferrofluid. The model describes well the molecular dynamics simulations of magnetostatic properties for monodisperse ferrofluids containing chain aggregates

  9. Influence of Direct Current Electric Field on Corrosion Behavior of Tin Under a Thin Electrolyte Layer

    Science.gov (United States)

    Huang, H. L.; Bu, F. R.; Tian, J.; Liu, D.

    2017-12-01

    The influence of a direct current electric field (DCEF) on corrosion behavior of tin under a thin electrolyte layer was investigated based on an array electrode technology by polarization, electrochemical impedance spectroscopy and surface analysis. The experimental results indicate that the corrosion rate of tin near the positive plate of DCEF increases with increased electric field intensity, which could be attributed to the acceleration of the migration of ions, the removal of corrosion products under DCEF and the damage of tin surface oxide film. Furthermore, tin at different positions in a DCEF exhibits different corrosion behavior, which could be ascribed to the difference of the local corrosion environment caused by the DCEF.

  10. Three-dimensional seismic velocity models, high-precision earthquake locations and their implications for seismic, tectonic and magmatic settings in the Coso Geothermal Field, California

    Science.gov (United States)

    Zhang, Q.; Lin, G.

    2012-12-01

    The Coso Geothermal Field (CGF) lies at the east of Sierra Nevada and is situated in tectonically active area with the presence of hot spring, rhyolite domes at the surface, strike-slip and normal faulting and frequent seismic activity. In this study, we present our comprehensive analysis of three-dimensional velocity structure, high-precision earthquake relocation and in situ Vp/Vs estimates. We select 1,893 master events among 177,000 events between 1981 and 2011 recorded by the Southern California Seismic Network stations. High-resolution three-dimensional (3-D) Vp and Vp/Vs models in Coso are inverted from the master events with 52,160 P- and 23,688 S-wave first arrivals by using the SIMUL2000 algorithm. The tomographic model reveals slightly high Vp and Vp/Vs in most regions of Coso near the surface compared to the layers at depth of 6 and 12 km, which is consistent with the fact that the Coso area is filled with diorite and minor basalt. The feature of low Vp, low Vs and low Vp/Vs between 6 and 12 km depths underneath the CGF can be related to the porous, gas-filled rock or volatile-rich magma. The low Vp, low Vs and low Vp/Vs structure from the surface to 3 km depth beneath the Indian Wells Valley is consistent with the existence of the 2 km deep sediment strata revealed by the borehole data. The resulting new 3-D velocity model is used to improve the absolute event location accuracy. We then apply waveform cross-correlation, similar event cluster analysis and differential time relocation methods to improve relative event location accuracy with the horizontal and vertical location uncertainties in tens of meters. The relocated seismicity indicates that the brittle-ductile transition depth is as shallow as 5 km underneath the CGF. We also estimate in situ near-source Vp/Vs ratio within each event cluster using differential times from cross-correlation to complement the Vp/Vs model from tomographic inversions, which will help to estimate the volume fraction of

  11. Light bending by nonlinear electrodynamics under strong electric and magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Young; Lee, Taekoon, E-mail: jykim@kunsan.ac.kr, E-mail: tlee@kunsan.ac.kr [Department of Physics, Kunsan National University, Daihakro 558, Kunsan 573-701 (Korea, Republic of)

    2011-11-01

    We calculate the bending angles of light under the strong electric and magnetic fields by a charged black hole and a magnetized neutron star according to the nonlinear electrodynamics of Euler-Heisenberg interaction. The bending angle of light by the electric field of charged black hole is computed from geometric optics and a general formula is derived for light bending valid for any orientation of the magnetic dipole. The astronomical significance of the light bending by magnetic field of a neutron star is discussed.

  12. Investigation of the role of thermal boundary layer processes in initiating convection under the NASA SPACE Field Program

    Science.gov (United States)

    Mcnider, Richard T.; Song, Aaron; Casey, Dan; Crosson, William; Wetzel, Peter

    1993-01-01

    The current NWS ground based network is not sufficient to capture the dynamic or thermodynamic structure leading to the initiation and organization of air mass moist convective events. Under this investigation we intend to use boundary layer mesoscale models (McNider and Pielke, 1981) to examine the dynamic triggering of convection due to topography and surface thermal contrasts. VAS and MAN's estimates of moisture will be coupled with the dynamic solution to provide an estimate of the total convective potential. Visible GOES images will be used to specify incoming insolation which may lead to surface thermal contrasts and JR skin temperatures will be used to estimate surface moisture (via the surface thermal inertia) (Weizel and Chang, 1988) which can also induce surface thermal contrasts. We will use the SPACE-COHMEX data base to evaluate the ability of the joint mesoscale model satellite products to show skill in predicting the development of air mass convection. We will develop images of model vertical velocity and satellite thermodynamic measures to derive images of predicted convective potential. We will then after suitable geographic registration carry out a pixel by pixel correlation between the model/satellite convective potential and the 'truth' which are the visible images. During the first half of the first year of this investigation we have concentrated on two aspects of the project. The first has been in generating vertical velocity fields from the model for COHMEX case days. We have taken June 19 as the first case and have run the mesoscale model at several different grid resolutions. We are currently developing the composite model/satellite convective image. The second aspect has been the attempted calibration of the surface energy budget to provide the proper horizontal thermal contrasts for convective initiation. We have made extensive progress on this aspect using the FIFE data as a test data set. The calibration technique looks very promising.

  13. Imaging axial and radial electric field components in dielectric targets under plasma exposure

    Science.gov (United States)

    Slikboer, Elmar; Sobota, Ana; Guaitella, Olivier; Garcia-Caurel, Enric

    2018-03-01

    This work presents new ways to investigate the individual electric field components in a dielectric target induced by a non thermal atmospheric pressure plasma jet. Mueller polarimetry is applied to investigate electro-optic crystals under exposure of guided ionization waves produced by a plasma jet. Three different cases are examined to visualize the different electric field components induced in the crystals by charges deposited on the surface by impact of the ionization waves. Investigating a Bi12 SiO20 (BSO) crystal at normal incidence allows measurement and visualization of the axial field, while if the crystal is examined at 45° both radial and axial electric field components are combined. For the first time, a Fe:LiNbO3 (Felinbo) crystal is examined using Mueller polarimetry under influence of a plasma jet. In this case, exclusively the patterns and local values of the radial field are obtained and not the axial field. These unique imaging options in the target for the individual electric field components allow a new and more complete investigation of the dynamics of surface discharges on dielectric materials.

  14. Communication: Polarizable polymer chain under external electric field in a dilute polymer solution

    International Nuclear Information System (INIS)

    Budkov, Yu. A.; Kolesnikov, A. L.; Kiselev, M. G.

    2015-01-01

    We study the conformational behavior of polarizable polymer chain under an external homogeneous electric field within the Flory type self-consistent field theory. We consider the influence of electric field on the polymer coil as well as on the polymer globule. We show that when the polymer chain conformation is a coil, application of external electric field leads to its additional swelling. However, when the polymer conformation is a globule, a sufficiently strong field can induce a globule-coil transition. We show that such “field-induced” globule-coil transition at the sufficiently small monomer polarizabilities goes quite smoothly. On the contrary, when the monomer polarizability exceeds a certain threshold value, the globule-coil transition occurs as a dramatic expansion in the regime of first-order phase transition. The developed theoretical model can be applied to predicting polymer globule density change under external electric field in order to provide more efficient processes of polymer functionalization, such as sorption, dyeing, and chemical modification

  15. Partitioning of Cotton Field Evapotranspiration under Mulched Drip Irrigation Based on a Dual Crop Coefficient Model

    Directory of Open Access Journals (Sweden)

    Fuqiang Tian

    2016-02-01

    Full Text Available Estimation of field crop evapotranspiration (ETc and its partitioning into evaporation and transpiration, are of great importance in hydrological modeling and agricultural water management. In this study, we used a dual crop coefficient model SIMDualKc to estimate the actual crop evapotranspiration (ETc act and the basal crop coefficients over a cotton field in Northwestern China. A two-year field experiment was implemented in the cotton field under mulched drip irrigation. The simulated ETc act is consistent with observed ETc act as derived based on the eddy covariance system in the field. Basal crop coefficients of cotton for the initial, mid-season, and end-season are 0.20, 0.90, and 0.50, respectively. The transpiration components of ETc  act are 96% (77% and 94% (74% in 2012 and 2013 with (without plastic mulch, respectively. The impact of plastic mulch cover on soil evaporation is significant during drip irrigation ranging from crop development stage to mid-season stage. The extent of the impact depends on the variation of soil moisture, available energy of the soil surface, and the growth of the cotton leaves. Our results show that the SIMDualKc is capable of providing accurate estimation of ETc act for cotton field under mulched drip irrigation, and could be used as a valuable tool to establish irrigation schedule for cotton fields in arid regions as Northwestern China.

  16. Resonant energy transfer under the influence of the evanescent field from the metal

    Science.gov (United States)

    Poudel, Amrit; Chen, Xin; Ratner, Mark A.

    2017-06-01

    We present a quantum framework based on a density matrix of a dimer system to investigate the quantum dynamics of excitation energy transfer (EET) in the presence of the evanescent field from the metal and the phonon bath. Due to the spatial correlation of the electric field in the vicinity of the metal, the spectral density of the evanescent field is similar to that of a shared phonon bath. However, the EET dynamics under the influence of the evanescent field is an open and a new problem. Here we use a thin metallic film to investigate the effect of the evanescent field on the excitation energy transfer in a dimer system based on a density matrix approach. Our results indicate that a thin metallic film enhances the energy transfer rate at the expense of absorbing energy during the process. Since the spectral density of the evanescent field is affected by the geometry of the medium and the distance of a dimer system from the medium, our results demonstrate the possibility to tune EET based on material geometry and distances. Our model also serves as an expansion to quantum heat engine models and provides a framework to investigate the EET in light harvesting molecular networks under the influence of the evanescent field.

  17. Dynamical pattern formation in a low-concentration magnetorheological fluid under two orthogonal sinusoidal fields

    International Nuclear Information System (INIS)

    Yépez, L.D.; Carrillo, J.L.; Donado, F.; Sausedo-Solorio, J.M.; Miranda-Romagnoli, P.

    2016-01-01

    The dynamical pattern formation of clusters of magnetic particles in a low-concentration magnetorheological fluid, under the influence of a superposition of two perpendicular sinusoidal fields, is studied experimentally. By varying the frequency and phase shift of the perpendicular fields, this configuration enables us to experimentally analyze a wide range of field configurations, including the case of a pure rotating field and the case of an oscillating unidirectional field. The fields are applied parallel to the horizontal plane where the fluid lies or in the vertical plane. For fields applied in the horizontal plane, we observed that, when the ratio of the frequencies increases, the average cluster size exhibits a kind of periodic resonances. When the phase shift between the fields is varied, the average chain length reaches maximal values for the cases of the rotating field and the unidirectional case. We analyze and discuss these results in terms of a weighted average of the time-dependent Mason number. In the case of a rotating field on the vertical plane, we also observe that the competition between the magnetic and the viscous forces determines the average cluster size. We show that this configuration generates a series of physically meaningful self-organization of clusters and transport phenomena. - Highlights: • A weighted average of the time-dependent Mason number is proposed. • The self-propelling clusters appear when a vertical rotating magnetic field is applied. • The largest average chain lengths are reached when frequencies are multiples one another. • Rotating and unidirectional alternating fields produce the largest average chain length values.

  18. Dynamical pattern formation in a low-concentration magnetorheological fluid under two orthogonal sinusoidal fields

    Energy Technology Data Exchange (ETDEWEB)

    Yépez, L.D.; Carrillo, J.L. [Instituto de Física de la Universidad Autónoma de Puebla, Ciudad Universitaria, Edif. 110 A, Puebla 72570 (Mexico); Donado, F.; Sausedo-Solorio, J.M.; Miranda-Romagnoli, P. [Instituto de Ciencias Básicas e Ingeniería Universidad Autónoma del Estado de Hidalgo, Pachuca 42090, Pachuca (Mexico)

    2016-06-15

    The dynamical pattern formation of clusters of magnetic particles in a low-concentration magnetorheological fluid, under the influence of a superposition of two perpendicular sinusoidal fields, is studied experimentally. By varying the frequency and phase shift of the perpendicular fields, this configuration enables us to experimentally analyze a wide range of field configurations, including the case of a pure rotating field and the case of an oscillating unidirectional field. The fields are applied parallel to the horizontal plane where the fluid lies or in the vertical plane. For fields applied in the horizontal plane, we observed that, when the ratio of the frequencies increases, the average cluster size exhibits a kind of periodic resonances. When the phase shift between the fields is varied, the average chain length reaches maximal values for the cases of the rotating field and the unidirectional case. We analyze and discuss these results in terms of a weighted average of the time-dependent Mason number. In the case of a rotating field on the vertical plane, we also observe that the competition between the magnetic and the viscous forces determines the average cluster size. We show that this configuration generates a series of physically meaningful self-organization of clusters and transport phenomena. - Highlights: • A weighted average of the time-dependent Mason number is proposed. • The self-propelling clusters appear when a vertical rotating magnetic field is applied. • The largest average chain lengths are reached when frequencies are multiples one another. • Rotating and unidirectional alternating fields produce the largest average chain length values.

  19. Determining the group velocity dispersion by field analysis for the LP0X, LP1X, and LP2X mode groups independently of the fiber length: applications to step-index fibers

    DEFF Research Database (Denmark)

    Israelsen, Stine Møller; Usuga Castaneda, Mario A.; Rottwitt, Karsten

    2017-01-01

    By knowing the electric field distribution of a guided mode in an optical fiber, we are able to evaluate the group velocity dispersion in a weakly guiding step-index fiber for a pure mode in the LP0X, LP1X, and LP2X mode groups independently of the fiber length. We demonstrate the method...

  20. An utilization of liquid sublayer dryout mechanism in predicting critical heat flux under low pressure and low velocity conditions in round tubes

    International Nuclear Information System (INIS)

    Lee, Kwang-Won; Baik, Se-Jin; Ro, Tae-Sun

    2000-01-01

    From a theoretical assessment of extensive critical heat flux (CHF) data under low pressure and low velocity (LPLV) conditions, it was found out that lots of CHF data would not be well predicted by a normal annular film dryout (AFD) mechanism, although their flow patterns were identified as annular-mist flow. To predict these CHF data, a liquid sublayer dryout (LSD) mechanism has been newly utilized in developing the mechanistic CHF model based on each identified CHF mechanism. This mechanism postulates that the CHF occurrence is caused by dryout of the thin liquid sublayer resulting from the annular film separation or breaking down due to nucleate boiling in annular film or hydrodynamic fluctuation. In principle, this mechanism well supports the experimental evidence of residual film flow rate at the CHF location, which can not be explained by the AFD mechanism. For a comparative assessment of each mechanism, the CHF model based on the LSD mechanism is developed together with that based on the AFD mechanism. The validation of these models is performed on the 1406 CHF data points ranging over P=0.1-2 MPa, G=4-499 kg m -2 s -1 , L/D=4-402. This model validation shows that 1055 and 231 CHF data are predicted within ±30 error bound by the LSD mechanism and the AFD mechanism, respectively. However, some CHF data whose critical qualities are <0.4 or whose tube length-to-diameter ratios are <70 are considerably overestimated by the CHF model based on the LSD mechanism. These overestimations seem to be caused by an inadequate CHF mechanism classification and an insufficient consideration of the flow instability effect on CHF. Further studies for a new classification criterion screening the CHF data affected by flow instabilities as well as a new bubble detachment model for LPLV conditions, are needed to improve the model accuracy.

  1. Magnetic properties in BaFe12O19 nanoparticles prepared under a magnetic field

    International Nuclear Information System (INIS)

    Wang Jun; Chen Qianwang; Che Shan

    2004-01-01

    It was observed that the nanocrystallites of BaFe 12 O 19 formed at 140 deg. C under a 0.25 T magnetic field exhibited a higher saturation magnetization (6.1 emu/g at room temperature) than that of the sample (1.1 emu/g) obtained under zero magnetic field. Both of the two approaches yielded plain-like particles with an average particle size of 12 nm. However, the Curie temperature (T c ), a direct measuring of the strength of superexchange interaction of Fe 3+ -O 2- -Fe 3+ , increased from 410 deg. C for the nanoparticles prepared without an external field applied to 452 deg. C for the particles formed under a 0.25 T magnetic field, which indicates that external magnetic fields can improve the occupancy of magnetic ions and then increase the superexchange interaction. This was confirmed by electron paramagnetic resonance and Moessbauer spectrum analysis. The results present in this paper suggest that in addition to oxygen defects, surface non-magnetic layer and a fraction of finer particles in the superparamagnetic range, cation vacancies should be responsible for the decreasing of saturation magnetization in magnetic nanoparticles

  2. Intercropping reduces nitrate leaching from under field crops without loss of yield: A modelling study

    NARCIS (Netherlands)

    Whitmore, A.P.; Schröder, J.J.

    2007-01-01

    A model of soil nitrogen dynamics under competing intercrops is described and used to interpret two sets of experimental field data from the literature. In one series of experiments, maize received slurry and mineral nitrogen (N) fertiliser or mineral N alone and was grown either alone or

  3. A general circuit model for spintronic devices under electric and magnetic fields

    KAUST Repository

    Alawein, Meshal

    2017-10-25

    In this work, we present a circuit model of diffusive spintronic devices capable of capturing the effects of both electric and magnetic fields. Starting from a modified version of the well-established drift-diffusion equations, we derive general equivalent circuit models of semiconducting/metallic nonmagnets and metallic ferromagnets. In contrast to other models that are based on steady-state transport equations which might also neglect certain effects such as thermal fluctuations, spin dissipation in the ferromagnets, and spin precession under magnetic fields, our model incorporates most of the important physics and is based on a time-dependent formulation. An application of our model is shown through simulations of a nonlocal spin-valve under the presence of a magnetic field, where we reproduce experimental results of electrical measurements that demonstrate the phenomena of spin precession and dephasing (“Hanle effect”).

  4. Predicting performance of polymer-bonded Terfenol-D composites under different magnetic fields

    International Nuclear Information System (INIS)

    Guan Xinchun; Dong Xufeng; Ou Jinping

    2009-01-01

    Considering demagnetization effect, the model used to calculate the magnetostriction of the single particle under the applied field is first created. Based on Eshelby equivalent inclusion and Mori-Tanaka method, the approach to calculate the average magnetostriction of the composites under any applied field, as well as the saturation, is studied by treating the magnetostriction particulate as an eigenstrain. The results calculated by the approach indicate that saturation magnetostriction of magnetostrictive composites increases with an increase of particle aspect and particle volume fraction, and a decrease of Young's modulus of the matrix. The influence of an applied field on magnetostriction of the composites becomes more significant with larger particle volume fraction or particle aspect. Experiments were done to verify the effectiveness of the model, the results of which indicate that the model only can provide approximate results.

  5. GEOFLOW: simulation of convection in a spherical shell under central force field

    Directory of Open Access Journals (Sweden)

    P. Beltrame

    2006-01-01

    Full Text Available Time-dependent dynamical simulations related to convective motion in a spherical gap under a central force field due to the dielectrophoretic effect are discussed. This work is part of the preparation of the GEOFLOW-experiment which is planned to run in a microgravity environment. The goal of this experiment is the simulation of large-scale convective motion in a geophysical or astrophysical framework. This problem is new because of, on the one hand, the nature of the force field (dielectrophoretic effect and, on another hand, the high degree of symmetries of the system, e.g. the top-bottom reflection. Thus, the validation of this simulation with well-known results is not possible. The questions concerning the influence of the dielectrophoretic force and the possibility to reproduce the theoretically expected motions in the astrophysical framework, are open. In the first part, we study the system in terrestrial conditions: the unidirectional Earth's force is superimposed on the central dielectrophoretic force field to compare with the laboratory experiments during the development of the equipment. In the second part, the GEOFLOW-experiment simulations in weightless conditions are compared with theoretical studies in the astrophysical framework's, in the first instance a fluid under a self-gravitating force field. We present complex time-dependent dynamics, where the dielectrophoretic force field causes significant differences in the flow compared to the case that does not involve this force field.

  6. Excitons and trions in single and vertically coupled quantum dots under an electric field

    Science.gov (United States)

    Zhai, Li-Xue; Wang, Yan; An, Zhong

    2017-08-01

    We present a theoretical study of the exciton (X0), the positive and negative trions (X+ and X-) in single and vertically coupled configurations of self-assembled InGaAs quantum dots under an electric field. The quantum states of X0, X+ and X- have been investigated using a quasi-one-dimensional (Q1D) model within the effective-mass approximation. For the single quantum dots, the electric-field dependent energy levels and the average inter-particle distances for the exciton and trions have been calculated. For the coupled quantum dots, the ground and the excited states for X0, X+ and X- have also been calculated and discussed. It is found that either the hole or the electron can be tuned into resonance states by the electric field and that the transition energy spectra for both trions consequently show crossing and anticrossing patterns. The recombination probabilities of the exciton and trion optical transitions are also calculated. The theoretical results have been compared with previously reported photoluminescence data and qualitative agreement is obtained. The trion conditional wave functions are also plotted under different electric field intensities, and it is found that a molecular orbital can be formed at a critical electric field intensity. The evolution of the energy levels of the trions in coupled quantum dots can be explained by the interplay of particle transfer and the electric field.

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

    KAUST Repository

    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.

  8. GigaGauss solenoidal magnetic field inside bubbles excited in under-dense plasma

    Science.gov (United States)

    Lécz, Zs.; Konoplev, I. V.; Seryi, A.; Andreev, A.

    2016-10-01

    This paper proposes a novel and effective method for generating GigaGauss level, solenoidal quasi-static magnetic fields in under-dense plasma using screw-shaped high intensity laser pulses. This method produces large solenoidal fields that move with the driving laser pulse and are collinear with the accelerated electrons. This is in contrast with already known techniques which rely on interactions with over-dense or solid targets and generates radial or toroidal magnetic field localized at the stationary target. The solenoidal field is quasi-stationary in the reference frame of the laser pulse and can be used for guiding electron beams. It can also provide synchrotron radiation beam emittance cooling for laser-plasma accelerated electron and positron beams, opening up novel opportunities for designs of the light sources, free electron lasers, and high energy colliders based on laser plasma acceleration.

  9. Analysis of Magnetic Field Intensity and Induced Current under Live Working Based on Charge Simulation Method

    Directory of Open Access Journals (Sweden)

    Luo Yuanxiang

    2015-01-01

    Full Text Available To the problem that safety distance is insufficient for 500 kV substation live working, a magnetic field analysis method for overhead line bus is given based on the charge simulation method. In the method, charge is calculated firstly, and the space field intensity distribution calculation is completed by overlying charge. The space field intensity distribution rule is carried out based on the appropriate analysis, and space field intensity distribution rule of substation is obtained. Then according to the calculation formula of inducing current, the human body induction current under a substation busbar is simulated based on MATLAB. The simulation results have a certain guidance function for actual live working.

  10. Unsteady flow of two-phase fluid in circular pipes under applied external magnetic and electrical fields

    Energy Technology Data Exchange (ETDEWEB)

    Gedik, Engin; Recebli, Ziyaddin [Faculty of Technology, Karabuk University, TR-78050, Karabuk (Turkey); Kurt, Hueseyin [Faculty of Engineering, Karabuk University, TR-78050, Karabuk (Turkey); Kecebas, Ali [Faculty of Technology, Afyon Kocatepe University, TR-03200, Afyon (Turkey)

    2012-03-15

    The unsteady viscous incompressible and electrically conducting of two-phase fluid flow in circular pipes with external magnetic and electrical field is considered in this present study. Effects of both uniform transverse external magnetic and electrical fields applied perpendicular to the fluid and each other on the two-phase (solid/liquid) unsteady flow is investigated numerically. While iron powders are being used as the first phase of two-phase fluid, pure water was used as the second phase. The system of the derived governing equations, which are based on the Navier-Stokes equations including Maxwell equations, are solved numerically by using Pdex4 function on the Matlab for both phases. The originality of this study is that, in addition to magnetic field, the effect of electrical field on two-phase unsteady fluids is being examined. The magnetic field which is applied on flow decreases the velocity of both phases, whereas the electrical field applied along with magnetic field acted to increase and decrease the velocity values depending on the direction of electrical field. Electrical field alone did not display any impact on two-phase flow. On the other hand, analytical and numerical results are compared and favorable agreements have been obtained. (authors)

  11. Impact of solar wind depression on the dayside magnetosphere under northward interplanetary magnetic field

    Directory of Open Access Journals (Sweden)

    S. Baraka

    2011-01-01

    Full Text Available We present a follow up study of the sensitivity of the Earth's magnetosphere to solar wind activity using a particles-in-cell model (Baraka and Ben Jaffel, 2007, but here during northward Interplanetary Magnetic Field (IMF. The formation of the magnetospheric cavity and its elongation around the planet is obtained with the classical structure of a magnetosphere with parallel lobes. An impulsive disturbance is then applied to the system by changing the bulk velocity of the solar wind to simulate a decrease in the solar wind dynamic pressure followed by its recovery. In response to the imposed drop in the solar wind velocity, a gap (abrupt depression in the incoming solar wind plasma appears moving toward the Earth. The gap's size is a ~15 RE and is comparable to the sizes previously obtained for both Bz<0 and Bz=0. During the initial phase of the disturbance along the x-axis, the dayside magnetopause (MP expands slower than the previous cases of IMF orientations as a result of the abrupt depression. The size of the MP expands nonlinearly due to strengthening of its outer boundary by the northward IMF. Also, during the initial 100 Δt, the MP shrank down from 13.3 RE to ~9.2 RE before it started expanding, a phenomenon that was also observed for southern IMF conditions but not during the no IMF case. As soon as they felt the solar wind depression, cusps widened at high altitude while dragged in an upright position. For the field's topology, the reconnection between magnetospheric and magnetosheath fields is clearly observed in both the northward and southward cusps areas. Also, the tail region in the northward IMF condition is more confined, in contrast to the fishtail-shape obtained in the southward IMF case. An X-point is formed in the tail at ~110 RE compared to ~103 RE and ~80 RE for Bz=0 and Bz<0, respectively. Our findings are consistent with existing reports from many space observatories (Cluster, Geotail, Themis, etc. for which predictions

  12. Male Mating Competitiveness of a Wolbachia-Introgressed Aedes polynesiensis Strain under Semi-Field Conditions

    Science.gov (United States)

    Bossin, Hervé; Dobson, Stephen L.

    2011-01-01

    Background Lymphatic filariasis (LF), a global public health problem affecting approximately 120 million people worldwide, is a leading cause of disability in the developing world including the South Pacific. Despite decades of ongoing mass drug administration (MDA) in the region, some island nations have not yet achieved the threshold levels of microfilaremia established by the World Health Organization for eliminating transmission. Previously, the generation of a novel Aedes polynesiensis strain (CP) infected with an exogenous type of Wolbachia has been described. The CP mosquito is cytoplasmically incompatible (i.e., effectively sterile) when mated with wildtype mosquitoes, and a strategy was proposed for the control of A. polynesiensis populations by repeated, inundative releases of CP males to disrupt fertility of wild females. Such a strategy could lead to suppression of the vector population and subsequently lead to a reduction in the transmission of filarial worms. Methodology/Principal Findings CP males and F1 male offspring from wild-caught A. polynesiensis females exhibit near equal mating competitiveness with F1 females under semi-field conditions. Conclusions/Significance While laboratory experiments are important, prior projects have demonstrated the need for additional testing under semi-field conditions in order to recognize problems before field implementation. The results reported here from semi-field experiments encourage forward progression toward small-scale field releases. PMID:21829750

  13. Experimental Study of Entropy Production in Cells under Alternating Electric Field

    Science.gov (United States)

    Ding, Chang-Jiang; Luo, Liao-Fu

    2012-08-01

    We put forward a new method for measuring the entropy production in the living cell. It involves heating the sample by alternating the electric field and recording the outward heat flow. The entropy production in a normal cell MCF10A and a cancerous cell MDA-MB-231 were measured and compared. The results show that the method is effective for the entropy measurement of a living organism. The scaled electro-induced entropy production rate (SEEP) of MDA-MB-231 monotonically increases with the electric field strength at 5-40 V/cm. While that of MCF10A changes non-monotonically and there exists a peak at 5-30 V/cm. The electro-induced entropy production ratio (EEPR) is smaller than 1 in a large range of field strengths, from 5 to 25 V/cm, which reveals that under 5-25 V/cm electric field exposure, the direction of the entropy flow may be changed from normal tissue to cancerous cells. We present a facile and effective strategy for experimentally investigating the thermodynamic properties of the cell and give a deeper insight into the physical difference between normal and cancerous cells under electric field exposure.

  14. Energy consumption of SO2 removal from humid air under electron beam and electric field influence

    International Nuclear Information System (INIS)

    Nichipor, H.; Radjuk, E.; Chmielewski, A.G.; Zimek, Z.

    1998-01-01

    The kinetic of SO 2 oxidation in humid air under influence of electron beam and electrical field was investigated by computer simulation method in steady state and pulse mode. SO 2 oxidation process was stimulated by radical and ion reactions. The calculation model has included 46 different particles and 160 chemical reactions. Gas mixture containing 1000 ppm of SO 2 concentration was investigated at temperature T=67 deg. C and pressure p=1 at. Water content was within the range 2-12%. Electron beam parameters were as follows: average beam current density 0.0032-3,2 mA/cm 2 , pulse duration 400 μs, repetition rate 50 Hz. Electrical field density was E/n =10 -15 Vcm 2 . Electrical pulse duration was changed within the range 5 x10 -7 -10 -5 s. The influence of the parameters of synchronized electron beam and electrical field pulses on energy deposition was under consideration. Energy cost of SO 2 removal on 90% level was estimated in steady state and pulse modes. It was found that total electron beam and electrical field energy losses in pulse mode are 6 times lower to compare with steady state conditions. The optimum of electrical field pulse duration from point of view minimum energy cost of SO 2 removal was found for different electron beam pulse current levels

  15. Genetically modified corn on fall armyworm and earwig populations under field conditions

    Directory of Open Access Journals (Sweden)

    Marina Regina Frizzas

    2014-02-01

    Full Text Available The effects of corn MON810 on the Spodoptera frugiperda (J.E. Smith and the earwig Doru luteipes (Scudder were tested under field conditions in Brazil. Results from MON810 corn fields were compared with those fields of conventional corn with and without the application of insecticides in four harvests in the region of Barretos, SP. It was assessed the damage to S. frugiperda via direct counts of the number of fall armyworms and adults and nymphs of the predator D. luteipes on corn plants. The rate of S. frugiperda damage and the average numbers of larvae (large and small were lower in the MON810 corn field relative to the control plot. There were no differences (P>0.05 between treatments regarding the predator abundance in corn plants. The second crop season ("safrinha" showed the greatest extent of S. frugiperda damage and the lowest average abundance of earwigs. MON810 was effective in controlling S. frugiperda and abundance of predator D. luteipes was similar in the three treatments under field conditions.

  16. Time-dependent scattering of incident light of various wavelengths in ferrofluids under external magnetic field

    Science.gov (United States)

    Jin, Jingyu; Song, Dongxing; Geng, Jiafeng; Jing, Dengwei

    2018-02-01

    Ferrofluids can exhibit the anisotropic thermodynamic properties under magnetic fields. The dynamic optical properties of ferrofluids in the presence of magnetic fields are of particular interest due to their potential application as various optical devices. Although time-dependent light scattering by ferrofluids have been extensively studied, the effect of wavelength of incident light have been rarely considered. Here, for the first time, we investigated both the time- and wavelength-dependent light scattering in water based ferrofluids containing Fe3O4 nanoparticles under an external magnetic field. The field-induced response behavior of the prepared ferrofluid samples was determined and verified first by thermal conductivity measurement and numerical simulation. Double-beam UV-Vis spectrophotometer was employed to record the temporal evolution of transmitted intensity of incident light of various wavelengths passing through the ferrofluid sample and propagating parallel to the applied field. As expected, the light intensity decreases to a certain value right after the field is turned on due to the thermal fluctuation induced disorder inside the flexible particle chains. Then the light intensity further decreases with time until the appearance of a minimum at time τ0 followed by an inversed increase before finally reaches equilibrium at a particular time. More importantly, the characteristic inversion time τ0 was found to follow a power law increase with the wavelength of incident light (τ0 ∼ λα, where α = 2.07). A quantitative explanation for the wavelength dependence of characteristic time was proposed based on the finite-difference time-domain (FDTD) method. The simulation results are in good agreement with our experimental observations. The time-dependent light scattering in ferrofluids under different incident wavelengths was rationalized by considering both the coarsening process of the particle chains and the occurrence of resonance within the

  17. A model explaining synchronization of neuron bioelectric frequency under weak alternating low frequency magnetic field

    International Nuclear Information System (INIS)

    Moral, A. del; Azanza, María J.

    2015-01-01

    A biomagnetic-electrical model is presented that explains rather well the experimentally observed synchronization of the bioelectric potential firing rate (“frequency”), f, of single unit neurons of Helix aspersa mollusc under the application of extremely low frequency (ELF) weak alternating (AC) magnetic fields (MF). The proposed model incorporates to our widely experimentally tested model of superdiamagnetism (SD) and Ca 2+ Coulomb explosion (CE) from lipid (LP) bilayer membrane (SD–CE model), the electrical quadrupolar long range interaction between the bilayer LP membranes of synchronized neuron pairs, not considered before. The quadrupolar interaction is capable of explaining well the observed synchronization. Actual extension of our SD–CE-model shows that the neuron firing frequency field, B, dependence becomes not modified, but the bioelectric frequency is decreased and its spontaneous temperature, T, dependence is modified. A comparison of the model with synchronization experimental results of pair of neurons under weak (B 0 ≅0.2–15 mT) AC-MF of frequency f M =50 Hz is reported. From the deduced size of synchronized LP clusters under B, is suggested the formation of small neuron networks via the membrane lipid correlation. - Highlights: • Neuron pair synchronization under low frequency alternating (AC) magnetic field (MF). • Superdiamagnetism and Ca 2+ Coulomb explosion for AC MF effect in synchronized frequency. • Membrane lipid electrical quadrupolar pair interaction as synchronization mechamism. • Good agreement of model with electrophysiological experiments on mollusc Helix neurons

  18. A model explaining synchronization of neuron bioelectric frequency under weak alternating low frequency magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Moral, A. del, E-mail: delmoral@unizar.es [Laboratorio de Magnetismo, Departamento de Física de Materia Condensada and Instituto de Ciencia de Materiales, Universidad de Zaragoza and Consejo Superior de Investigaciones Científicas, 50009 Zaragoza (Spain); Laboratorio de Magnetobiología, Departamento de Anatomía e Histología, Facultad de Medicina, Universidad de Zaragoza, 50009 Zaragoza (Spain); Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, 28223 Madrid (Spain); Azanza, María J., E-mail: mjazanza@unizar.es [Laboratorio de Magnetobiología, Departamento de Anatomía e Histología, Facultad de Medicina, Universidad de Zaragoza, 50009 Zaragoza (Spain); Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, 28223 Madrid (Spain)

    2015-03-01

    A biomagnetic-electrical model is presented that explains rather well the experimentally observed synchronization of the bioelectric potential firing rate (“frequency”), f, of single unit neurons of Helix aspersa mollusc under the application of extremely low frequency (ELF) weak alternating (AC) magnetic fields (MF). The proposed model incorporates to our widely experimentally tested model of superdiamagnetism (SD) and Ca{sup 2+} Coulomb explosion (CE) from lipid (LP) bilayer membrane (SD–CE model), the electrical quadrupolar long range interaction between the bilayer LP membranes of synchronized neuron pairs, not considered before. The quadrupolar interaction is capable of explaining well the observed synchronization. Actual extension of our SD–CE-model shows that the neuron firing frequency field, B, dependence becomes not modified, but the bioelectric frequency is decreased and its spontaneous temperature, T, dependence is modified. A comparison of the model with synchronization experimental results of pair of neurons under weak (B{sub 0}≅0.2–15 mT) AC-MF of frequency f{sub M}=50 Hz is reported. From the deduced size of synchronized LP clusters under B, is suggested the formation of small neuron networks via the membrane lipid correlation. - Highlights: • Neuron pair synchronization under low frequency alternating (AC) magnetic field (MF). • Superdiamagnetism and Ca{sup 2+} Coulomb explosion for AC MF effect in synchronized frequency. • Membrane lipid electrical quadrupolar pair interaction as synchronization mechamism. • Good agreement of model with electrophysiological experiments on mollusc Helix neurons.

  19. Equilibrium state analysis of a nonneutral plasma under a uniform magnetic field

    International Nuclear Information System (INIS)

    Fernandez, J.E.; Molinari, V.G.; Sumini, M.A.

    1990-01-01

    By recourse to the Boltzmann H-theorem, the existence of a thermodynamic equilibrium state has been proved for a nonneutral plasma under an external magnetic field. The equation describing the density profile of ions or electrons has been found. The density equation has been numerically solved for a generic magnetic field and plasma frequency, giving a parametric limit for the confinement region. An appropriate change of variable allows to approximate the density equation whose analytical solution has been found. The approximated density closely fits the numerical solution of the original equation. (Author)

  20. Thermal convection in square porous cavity under transverse oscillatory micro gravity field

    Science.gov (United States)

    Ghosh, Pradyumna; Ghosh, M. K.

    2007-12-01

    Two-dimensional thermal convection in saturated square porous cavity under transverse sinusoidal micro-gravity field, has been analyzed by solving mass and transient momentum and energy balance equations, using Darcy's law and Boussinesq's approximation. Isothermal boundary conditions are considered at the two vertical walls but at different temperatures and other two horizontal walls are adiabatic. Average Nusselt numbers are presented as a function of Darcy-Rayleigh number (Ramod) and dimensionless time. Thermally convective, transient nature of the flow field has also been presented for different Darcy-Rayleigh number (Ramod).