WorldWideScience

Sample records for stress-assisted void growth

  1. Size-Effects in Void Growth

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof

    2005-01-01

    The size-effect on ductile void growth in metals is investigated. The analysis is based on unit cell models both of arrays of cylindrical voids under plane strain deformation, as well as arrays of spherical voids using an axisymmetric model. A recent finite strain generalization of two higher order...... strain gradient plasticity models is implemented in a finite element program, which is used to study void growth numerically. The results based on the two models are compared. It is shown how gradient effects suppress void growth on the micron scale when compared to predictions based on conventional...... models. This increased resistance to void growth, due to gradient hardening, is accompanied by an increase in the overall strength for the material. Furthermore, for increasing initial void volume fraction, it is shown that the effect of gradients becomes more important to the overall response but less...

  2. Void growth suppression by dislocation impurity atmospheres

    International Nuclear Information System (INIS)

    Weertman, J.; Green, W.V.

    1976-01-01

    A detailed calculation is given of the effect of an impurity atmosphere on void growth under irradiation damage conditions. Norris has proposed that such an atmosphere can suppress void growth. The hydrostatic stress field of a dislocation that is surrounded by an impurity atmosphere was found and used to calculate the change in the effective radius of a dislocation line as a sink for interstitials and vacancies. The calculation of the impurity concentration in a Cottrell cloud takes into account the change in hydrostatic pressure produced by the presence of the cloud itself. It is found that void growth is eliminated whenever dislocations are surrounded by a condensed atmosphere of either oversized substitutional impurity atoms or interstitial impurity atoms. A condensed atmosphere will form whenever the average impurity concentration is larger than a critical concentration

  3. Stress-assisted grain growth in nanocrystalline metals: Grain boundary mediated mechanisms and stabilization through alloying

    International Nuclear Information System (INIS)

    Zhang, Yang; Tucker, Garritt J.; Trelewicz, Jason R.

    2017-01-01

    The mechanisms of stress-assisted grain growth are explored using molecular dynamics simulations of nanoindentation in nanocrystalline Ni and Ni-1 at.% P as a function of grain size and deformation temperature. Grain coalescence is primarily confined to the high stress region beneath the simulated indentation zone in nanocrystalline Ni with a grain size of 3 nm. Grain orientation and atomic displacement vector mapping demonstrates that coalescence transpires through grain rotation and grain boundary migration, which are manifested in the grain interior and grain boundary components of the average microrotation. A doubling of the grain size to 6 nm and addition of 1 at.% P eliminates stress-assisted grain growth in Ni. In the absence of grain coalescence, deformation is accommodated by grain boundary-mediated dislocation plasticity and thermally activated in pure nanocrystalline Ni. By adding solute to the grain boundaries, the temperature-dependent deformation behavior observed in both the lattice and grain boundaries inverts, indicating that the individual processes of dislocation and grain boundary plasticity will exhibit different activity based on boundary chemistry and deformation temperature.

  4. Void growth and coalescence in metals deformed at elevated temperature

    DEFF Research Database (Denmark)

    Klöcker, H.; Tvergaard, Viggo

    2000-01-01

    For metals deformed at elevated temperatures the growth of voids to coalescence is studied numerically. The voids are assumed to be present from the beginning of deformation, and the rate of deformation considered is so high that void growth is dominated by power law creep of the material, without...... any noticeable effect of surface diffusion. Axisymmetric unit cell model computations are used to study void growth in a material containing a periodic array of voids, and the onset of the coalescence process is defined as the stage where plastic flow localizes in the ligaments between neighbouring...... voids. The focus of the study is on various relatively high stress triaxialties. In order to represent the results in terms of a porous ductile material model a set of constitutive relations are used, which have been proposed for void growth in a material undergoing power law creep....

  5. Nucleation and growth of voids by radiation. Pt. 2

    International Nuclear Information System (INIS)

    Mayer, R.M.; Brown, L.M.

    1980-01-01

    The original model of Brown, Kelly and Mayer [1] for the nucleation of interstitial loops has been extended to take into account the following: (i) mobility of the vacancies, (ii) generation and migration of gas atoms during irradiation, (iii) nucleation and growth of voids, and (iv) vacancy emission from voids and clusters at high temperatures. Using chemicalrate equations, additional expressions are formulated for the nucleation and growth of vacancy loops and voids. (orig.)

  6. Theory of void swelling, irradiation creep and growth

    International Nuclear Information System (INIS)

    Wood, M.H.; Bullough, R.; Hayns, M.R.

    Recent progress in our understanding of the fundamental mechanisms involved in swelling, creep and growth of materials subjected to irradiation is reviewed. The topics discussed are: the sink types and their strengths in the lossy continuum; swelling and void distribution analysis, including recent work on void nucleation; and, irradiation creep and growth of zirconium and zircaloy are taken as an example

  7. A sharp interface model for void growth in irradiated materials

    Science.gov (United States)

    Hochrainer, Thomas; El-Azab, Anter

    2015-03-01

    A thermodynamic formalism for the interaction of point defects with free surfaces in single-component solids has been developed and applied to the problem of void growth by absorption of point defects in irradiated metals. This formalism consists of two parts, a detailed description of the dynamics of defects within the non-equilibrium thermodynamic frame, and the application of the second law of thermodynamics to provide closure relations for all kinetic equations. Enforcing the principle of non-negative entropy production showed that the description of the problem of void evolution under irradiation must include a relationship between the normal fluxes of defects into the void surface and the driving thermodynamic forces for the void surface motion; these thermodynamic forces are identified for both vacancies and interstitials and the relationships between these forces and the normal point defect fluxes are established using the concepts of transition state theory. The latter theory implies that the defect accommodation into the surface is a thermally activated process. Numerical examples are given to illustrate void growth dynamics in this new formalism and to investigate the effect of the surface energy barriers on void growth. Consequences for phase field models of void growth are discussed.

  8. Theories of nucleation and growth of bubbles and voids

    International Nuclear Information System (INIS)

    Speight, M.V.

    1977-01-01

    The application of classical nucleation theory to the formation of voids from a supersaturated concentration of vacancies is reviewed. The effect of a dissolved concentration of barley soluble gas on the nucleation rate of voids is emphasized. Exposure to a damaging flux of irradiation is the most effective way of introducing a vacancy supersaturation, but interstitials are produced at an equal rate. The concentration of interstitials inhibits the nucleation of voids which can occur only in the presence of dislocations since they preferentially absorb interstitials. It is well known that a definite value of internal gas pressure is necessary to stabilize a bubble so that it shows no tendencies to either shrink or grow. The arguments are reviewed which conclude that this pressure is determined by the specific surface free energy of the solid rather than the surface tension. While the former property refers to the energy necessary to create new surface, the latter is a measure of the work done in elastically stretching a a given surface. The presence of an equilibrium gas bubble leaves the stresses in the surrounding solid unperturbed only when surface energy and surface tension are numerically equal. A bubble with internal pressure greater than the restraint offered by surface energy tends to grow to relieve the excess pressure. The mechanism of growth can involve the migration of vacancies from remote sources to the bubble surface or the plastic straining of the solid surrounding the bubble. The kinetics of both mechanisms are developed and compared. The theory of growth of grain-boundary voids by vacancy condensation under an applied stress is also considered. (author)

  9. Constitutive modeling of void-growth-based tensile ductile failures with stress triaxiality effects

    KAUST Repository

    Mora Cordova, Angel; Liu, Jinxing; El Sayed, Tamer S.

    2014-01-01

    In most metals and alloys, the evolution of voids has been generally recognized as the basic failure mechanism. Furthermore, stress triaxiality has been found to influence void growth dramatically. Besides strain intensity, it is understood

  10. Void growth to coalescence in a non-local material

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof

    2008-01-01

    of different material length parameters in a multi-parameter theory is studied, and it is shown that the important length parameter is the same as under purely hydrostatic loading. It is quantified how micron scale voids grow less rapidly than larger voids, and the implications of this in the overall strength...... of the material is emphasized. The size effect on the onset of coalescence is studied, and results for the void volume fraction and the strain at the onset of coalescence are presented. It is concluded that for cracked specimens not only the void volume fraction, but also the typical void size is of importance...... to the fracture strength of ductile materials....

  11. Three-dimensional investigation of grain orientation effects on void growth in commercially pure titanium

    International Nuclear Information System (INIS)

    Pushkareva, Marina; Adrien, Jérôme; Maire, Eric; Segurado, Javier; Llorca, Javier; Weck, Arnaud

    2016-01-01

    The fracture process of commercially pure titanium was visualized in model materials containing artificial holes. These model materials were fabricated using a femtosecond laser coupled with a diffusion bonding technique to obtain voids in the interior of titanium samples. Changes in void dimensions during in-situ straining were recorded in three dimensions using x-ray computed tomography. Void growth obtained experimentally was compared with the Rice and Tracey model which predicted well the average void growth. A large scatter in void growth data was explained by differences in grain orientation which was confirmed by crystal plasticity simulations. It was also shown that grain orientation has a stronger effect on void growth than intervoid spacing and material strength. Intervoid spacing, however, appears to control whether the intervoid ligament failure is ductile or brittle.

  12. Three-dimensional investigation of grain orientation effects on void growth in commercially pure titanium

    Energy Technology Data Exchange (ETDEWEB)

    Pushkareva, Marina [Department of Mechanical Engineering, University of Ottawa, 150 Louis Pasteur, Ottawa, ON, Canada K1N 6N5 (Canada); Adrien, Jérôme; Maire, Eric [Université de Lyon, INSA-Lyon, MATEIS CNRS UMR5510, 7 Avenue Jean Capelle, F-69621 Villeurbanne (France); Segurado, Javier; Llorca, Javier [IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Department of Materials Science, Polytechnic University of Madrid, E. T. S. de Ingenieros de Caminos, 28040 Madrid (Spain); Weck, Arnaud, E-mail: aweck@uottawa.ca [Department of Mechanical Engineering, University of Ottawa, 150 Louis Pasteur, Ottawa, ON, Canada K1N 6N5 (Canada); IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, ON, Canada K1N 6N5 (Canada); Centre for Research in Photonics at the University of Ottawa, 800 King Edward Ave., Ottawa, ON, Canada K1N 6N5 (Canada)

    2016-08-01

    The fracture process of commercially pure titanium was visualized in model materials containing artificial holes. These model materials were fabricated using a femtosecond laser coupled with a diffusion bonding technique to obtain voids in the interior of titanium samples. Changes in void dimensions during in-situ straining were recorded in three dimensions using x-ray computed tomography. Void growth obtained experimentally was compared with the Rice and Tracey model which predicted well the average void growth. A large scatter in void growth data was explained by differences in grain orientation which was confirmed by crystal plasticity simulations. It was also shown that grain orientation has a stronger effect on void growth than intervoid spacing and material strength. Intervoid spacing, however, appears to control whether the intervoid ligament failure is ductile or brittle.

  13. Dislocation mechanism of void growth at twin boundary of nanotwinned nickel based on molecular dynamics simulation

    International Nuclear Information System (INIS)

    Zhang, Yanqiu; Jiang, Shuyong; Zhu, Xiaoming; Zhao, Yanan

    2016-01-01

    Molecular dynamics simulation was performed to investigate dislocation mechanism of void growth at twin boundary (TB) of nanotwinned nickel. Simulation results show that the deformation of nanotwinned nickel containing a void at TB is dominated by the slip involving both leading and trailing partials, where the trailing partials are the dissociation products of stair-rod dislocations formed by the leading partials. The growth of a void at TB is attributed to the successive emission of the leading partials followed by trailing partials as well as the escape of these partial dislocations from the void surface. - Highlights: • Dislocation mechanism of void growth at TB of nanotwinned nickel is investigated. • Deformation of the nanotwinned nickel is dominated by leading and trailing partials. • Growth of void at TB is caused by successive emission and escape of these partials.

  14. Void growth to coalescence in a non-local material

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof

    of different material length parameters in a multi-parameter theory is studied, and it is shown that the important length parameter is the same as under purely hydrostatic loading. It is quantified how micron scale voids grow less rapidly than larger voids, and the implications of this in the overall strength...... of the material is emphasized. It is concluded that for cracked specimens not only the void volume fraction, but also the typical void size is of importance to the fracture strength of ductile materials....

  15. Molecular dynamics modeling and simulation of void growth in two dimensions

    Science.gov (United States)

    Chang, H.-J.; Segurado, J.; Rodríguez de la Fuente, O.; Pabón, B. M.; LLorca, J.

    2013-10-01

    The mechanisms of growth of a circular void by plastic deformation were studied by means of molecular dynamics in two dimensions (2D). While previous molecular dynamics (MD) simulations in three dimensions (3D) have been limited to small voids (up to ≈10 nm in radius), this strategy allows us to study the behavior of voids of up to 100 nm in radius. MD simulations showed that plastic deformation was triggered by the nucleation of dislocations at the atomic steps of the void surface in the whole range of void sizes studied. The yield stress, defined as stress necessary to nucleate stable dislocations, decreased with temperature, but the void growth rate was not very sensitive to this parameter. Simulations under uniaxial tension, uniaxial deformation and biaxial deformation showed that the void growth rate increased very rapidly with multiaxiality but it did not depend on the initial void radius. These results were compared with previous 3D MD and 2D dislocation dynamics simulations to establish a map of mechanisms and size effects for plastic void growth in crystalline solids.

  16. Molecular dynamics modeling and simulation of void growth in two dimensions

    International Nuclear Information System (INIS)

    Chang, H-J; Segurado, J; LLorca, J; Rodríguez de la Fuente, O; Pabón, B M

    2013-01-01

    The mechanisms of growth of a circular void by plastic deformation were studied by means of molecular dynamics in two dimensions (2D). While previous molecular dynamics (MD) simulations in three dimensions (3D) have been limited to small voids (up to ≈10 nm in radius), this strategy allows us to study the behavior of voids of up to 100 nm in radius. MD simulations showed that plastic deformation was triggered by the nucleation of dislocations at the atomic steps of the void surface in the whole range of void sizes studied. The yield stress, defined as stress necessary to nucleate stable dislocations, decreased with temperature, but the void growth rate was not very sensitive to this parameter. Simulations under uniaxial tension, uniaxial deformation and biaxial deformation showed that the void growth rate increased very rapidly with multiaxiality but it did not depend on the initial void radius. These results were compared with previous 3D MD and 2D dislocation dynamics simulations to establish a map of mechanisms and size effects for plastic void growth in crystalline solids. (paper)

  17. Numerical simulation of void growth under dynamic loading

    International Nuclear Information System (INIS)

    Iqbal, A.

    1996-01-01

    Following a brief general review of developments in material behavior under high strain rates, a cylindrical cell surrounding a spherical void in OFHC copper is numerically simulated by Zerri-Armstrong model. This simulation results show that the plastic deformation tends to be concentrated in the vicinity of voids either in the axial or transverse direction depending upon the stress state. This event is associated with the accelerated void through accompanying coalescence causing ductile fracture. A3-node triangular mesh generation code used as input for finite element code is developed by a 'Central Generation' technique. (author)

  18. Absence of saturation of void growth in rate theory with anisotropic diffusion

    CERN Document Server

    Hudson, T S; Sutton, A P

    2002-01-01

    We present a first attempt at solution the problem of the growth of a single void in the presence of anisotropically diffusing radiation induced self-interstitial atom (SIA) clusters. In order to treat a distribution of voids we perform ensemble averaging over the positions of centres of voids using a mean-field approximation. In this way we are able to model physical situations in between the Standard Rate Theory (SRT) treatment of swelling (isotropic diffusion), and the purely 1-dimensional diffusion of clusters in the Production Bias Model. The background absorption by dislocations is however treated isotropically, with a bias for interstitial cluster absorption assumed similar to that of individual SIAs. We find that for moderate anisotropy, unsaturated void growth is characteristic of this anisotropic diffusion of clusters. In addition we obtain a higher initial void swelling rate than predicted by SRT whenever the diffusion is anisotropic.

  19. Effects of void anisotropy on the ignition and growth rates of energetic materials

    Science.gov (United States)

    Rai, Nirmal Kumar; Sen, Oishik; Udaykumar, H. S.

    2017-06-01

    Initiation of heterogeneous energetic materials is thought to occur at hot spots; reaction fronts propagate from sites of such hot spots into the surrounding material resulting in complete consumption of the material. Heterogeneous materials, such as plastic bonded explosives (PBXs) and pressed materials contain numerous voids, defects and interfaces at which hot spots can occur. Amongst the various mechanisms of hot spot formation, void collapse is considered to be the predominant one in the high strain rate loading conditions. It is established in the past the shape of the voids has a significant effect on the initiation behavior of energetic materials. In particular, void aspect ratio and orientations play an important role in this regard. This work aims to quantify the effects of void aspect ratio and orientation on the ignition and growth rates of chemical reaction from the hot spot. A wide range of aspect ratio and orientations is considered to establish a correlation between the ignition and growth rates and the void morphology. The ignition and growth rates are obtained from high fidelity reactive meso-scale simulations. The energetic material considered in this work is HMX and Tarver McGuire HMX decomposition model is considered to capture the reaction mechanism of HMX. The meso-scale simulations are performed using a Cartesian grid based Eulerian solver SCIMITAR3D. The void morphology is shown to have a significant effect on the ignition and growth rates of HMX.

  20. Studies of void growth in a thin ductile layer between ceramics

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    1997-01-01

    The growth of voids in a thin ductile layer between ceramics is analysed numerically, using an axisymmetric cell model to represent an array of uniformly distributed spherical voids at the central plane of the layer. The purpose is to determine the full traction-separation law relevant to crack...... growth by a ductile mechanism along the thin layer. Plastic flow in the layer is highly constrained by the ceramics, so that a high. level of triaxial tension develops, leading in some cases to cavitation instabilities. The computations are continued to a state near the occurrence of void coalescence....

  1. On hydrogen-induced plastic flow localization during void growth and coalescence

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, D.C.; Sofronis, P. [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, IL 61801 (United States); Dodds, R.H. Jr. [Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 North Mathews Avenue, Urbana, IL 61801 (United States)

    2007-11-15

    Hydrogen-enhanced localized plasticity (HELP) is recognized as a viable mechanism of hydrogen embrittlement. A possible way by which the HELP mechanism can bring about macroscopic material failure is through hydrogen-induced accelerated void growth and coalescence. Assuming a periodic array of spherical voids loaded axisymmetrically, we investigate the hydrogen effect on the occurrence of plastic flow localization upon void growth and its dependence on macroscopic stress triaxiality. Under a macroscopic stress triaxiality equal to 1 and prior to void coalescence, the finite element calculation results obtained with material data relevant to A533B steel indicate that a hydrogen-induced localized shear band forms at an angle of about 45 {sup circle} from the axis of symmetry. At triaxiality equal to 3, void coalescence takes place by accelerated hydrogen-induced localization of plasticity mainly in the ligament between the voids. Lastly, we discuss the numerical results within the context of experimental observations on void growth and coalescence in the presence of hydrogen. (author)

  2. Constitutive modeling of void-growth-based tensile ductile failures with stress triaxiality effects

    KAUST Repository

    Mora Cordova, Angel

    2014-07-01

    In most metals and alloys, the evolution of voids has been generally recognized as the basic failure mechanism. Furthermore, stress triaxiality has been found to influence void growth dramatically. Besides strain intensity, it is understood to be the most important factor that controls the initiation of ductile fracture. We include sensitivity of stress triaxiality in a variational porous plasticity model, which was originally derived from hydrostatic expansion. Under loading conditions rather than hydrostatic deformation, we allow the critical pressure for voids to be exceeded so that the growth due to plasticity becomes dependent on the stress triaxiality. The limitations of the spherical void growth assumption are investigated. Our improved constitutive model is validated through good agreements with experimental data. Its capacity for reproducing realistic failure patterns is also indicated by a numerical simulation of a compact tensile (CT) test. © 2013 Elsevier Inc.

  3. Visualization by X-ray tomography of void growth and coalescence leading to fracture in model materials

    International Nuclear Information System (INIS)

    Weck, A.; Wilkinson, D.S.; Maire, E.; Toda, H.

    2008-01-01

    The literature contains many models for the process of void nucleation, growth and coalescence leading to ductile fracture. However, these models lack in-depth experimental validation, in part because void coalescence is difficult to capture experimentally. In this paper, an embedded array of holes is obtained by diffusion bonding a sheet filled with laser-drilled holes between two intact sheets. The experiments have been performed with both pure copper and Glidcop. Using X-ray computed tomography, we show that void growth and coalescence (or linkage) are well captured in both materials. The Brown and Embury model for void coalescence underestimates coalescence strains due to constraining effects. However, both the Rice and Tracey model for void growth and the Thomason model for void coalescence give good predictions for copper samples when stress triaxiality is considered. The Thomason model, however, fails to predict coalescence for the Glidcop samples; this is primarily due to secondary void nucleation

  4. Discrete modelling of ductile crack growth by void growth to coalescence

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2007-01-01

    of the ligaments between the crack-tip and a void or between voids involves the development of very large strains, which are included in the model by using remeshing at several stages of the plastic deformation. The material is here described by standard isotropic hardening Mises theory. For a very small void...

  5. Temperature sensitivity of void nucleation and growth parameters for single crystal copper: a molecular dynamics study

    International Nuclear Information System (INIS)

    Rawat, S; Chavan, V M; Warrier, M; Chaturvedi, S

    2011-01-01

    The effect of temperature on the void nucleation and growth is studied using the molecular dynamics (MD) code LAMMPS (Large-Scale Atomic/Molecular Massively Parallel Simulator). Single crystal copper is triaxially expanded at 5 × 10 9  s −1 strain rate keeping the temperature constant. It is shown that the nucleation and growth of voids at these atomistic scales follows a macroscopic nucleation and growth (NAG) model. As the temperature increases there is a steady decrease in the nucleation and growth thresholds. As the melting point of copper is approached, a double-dip in the pressure–time profile is observed. Analysis of this double-dip shows that the first minimum corresponds to the disappearance of the long-range order due to the creation of stacking faults and the system no longer has a FCC structure. There is no nucleation of voids at this juncture. The second minimum corresponds to the nucleation and incipient growth of voids. We present the sensitivity of NAG parameters to temperature and the analysis of double-dip in the pressure–time profile for single crystal copper at 1250 K

  6. One dimensional motion of interstitial clusters and void growth in Ni and Ni alloys

    Science.gov (United States)

    Yoshiie, T.; Ishizaki, T.; Xu, Q.; Satoh, Y.; Kiritani, M.

    2002-12-01

    One dimensional (1-D) motion of interstitial clusters is important for the microstructural evolution in metals. In this paper, the effect of 2 at.% alloying with elements Si (volume size factor to Ni: -5.81%), Cu (7.18%), Ge (14.76%) and Sn (74.08%) in Ni on 1-D motion of interstitial clusters and void growth was studied. In neutron irradiated pure Ni, Ni-Cu and Ni-Ge, well developed dislocation networks and voids in the matrix, and no defects near grain boundaries were observed at 573 K to a dose of 0.4 dpa by transmission electron microscopy. No voids were formed and only interstitial type dislocation loops were observed near grain boundaries in Ni-Si and Ni-Sn. The reaction kinetics analysis which included the point defect flow into planar sink revealed the existence of 1-D motion of interstitial clusters in Ni, Ni-Cu and Ni-Ge, and lack of such motion in Ni-Si and Ni-Sn. In Ni-Sn and Ni-Si, the alloying elements will trap interstitial clusters and thereby reduce the cluster mobility, which lead to the reduction in void growth.

  7. Void formation and growth in copper-nickel alloys during irradiation in the high voltage electron microscope

    International Nuclear Information System (INIS)

    Leffers, T.; Singh, B.N.; Barlow, P.

    1977-05-01

    The formation and growth of voids during irradiation in a high-voltage electron microscope were studied in copper and Cu-Ni alloys. For each composition, the range of irradiation temperatures from 250 deg C to 550 deg C was covered. The development of the irradiation-induced dislocation structure was also studied. At irradiation temperatures up to 450 deg C, the void swelling decreased rapidly with increasing Ni content and became practically zero for Cu-10%Ni. The decrease in swelling was produced mainly by decreased void growth (and not by decreased void number density). At 550 deg C the void swelling increased with increasing Ni content up to 5%, whereas for Cu-10%Ni the swelling became practically zero; again the changes in swelling with Ni content were mainly determined by changes in void growth. The reduction in void swelling and growth due to alloying is ascribed to vacancy or interstitial trapping at submicroscopic Ni precipitates, i.e. to the precipitates acting as recombination centres. The increase in void swelling and growth with increasing Ni content, on the other hand, is ascribed to dislocation climb sources that emit loops, and hence produce a fairly high dislocation density at a temperature where there are only few dislocations in pure copper or Cu-Ni with lower Ni content. (author)

  8. Taylor-plasticity-based analysis of length scale effects in void growth

    KAUST Repository

    Liu, Junxian

    2014-09-25

    We have studied the void growth problem by employing the Taylor-based strain gradient plasticity theories, from which we have chosen the following three, namely, the mechanism-based strain gradient (MSG) plasticity (Gao et al 1999 J. Mech. Phys. Solids 47 1239, Huang et al 2000 J. Mech. Phys. Solids 48 99-128), the Taylor-based nonlocal theory (TNT; 2001 Gao and Huang 2001 Int. J. Solids Struct. 38 2615) and the conventional theory of MSG (CMSG; Huang et al 2004 Int. J. Plast. 20 753). We have addressed the following three issues which occur when plastic deformation at the void surface is unconstrained. (1) Effects of elastic deformation. Elasticity is essential for cavitation instability. It is therefore important to guarantee that the gradient term entering the Taylor model is the effective plastic strain gradient instead of the total strain gradient. We propose a simple elastic-plastic decomposition method. When the void size approaches the minimum allowable initial void size related to the maximum allowable geometrically necessary dislocation density, overestimation of the flow stress due to the negligence of the elastic strain gradient is on the order of lεY/R0 near the void surface, where l, εY and R0 are, respectively, the intrinsic material length scale, the yield strain and the initial void radius. (2) MSG intrinsic inconsistency, which was initially mentioned in Gao et al (1999 J. Mech. Phys. Solids 47 1239) but has not been the topic of follow-up studies. We realize that MSG higher-order stress arises due to the linear-strain-field approximation within the mesoscale cell with a nonzero size, lε. Simple analysis shows that within an MSG mesoscale cell near the void surface, the difference between microscale and mesoscale strains is on the order of (lε/R0)2, indicating that when lε/R0 ∼ 1.0, the higher-order stress effect can make the MSG result considerably different from the TNT or CMSG results. (3) Critical condition for cavitation instability

  9. Effect of residual stresses on interface crack growth by void expansion mechanism

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2006-01-01

    Crack growth along an interface between two adjacent elastic-plastic materials in a layered solid is analysed, using special interface elements to represent the fracture process ahead of the crack-tip. These interface elements account for ductile failure by the nucleation and growth of voids to c....... The results show that the value of the T-stress component in the softer material adjacent to the interface crack plays the dominant role, such that a negative value of this stress component gives a significant increase of the interface fracture toughness.......Crack growth along an interface between two adjacent elastic-plastic materials in a layered solid is analysed, using special interface elements to represent the fracture process ahead of the crack-tip. These interface elements account for ductile failure by the nucleation and growth of voids...... to coalescence. In these elements the stress components normal to the interface and the shear stresses are given by equilibrium with the surrounding material, and the stress component tangential to the interface is determined by the requirement of compatibility with the surrounding material in the tangential...

  10. Stress redistribution and void growth in butt-welded canisters for spent nuclear fuel

    International Nuclear Information System (INIS)

    Josefson, B.L.; Karlsson, L.; Haeggblad, H.Aa.

    1993-02-01

    The stress-redistribution in Cu-Fe canisters for spent nuclear fuel during waiting for deposition and after final deposition is calculated numerically. The constitutive equation modelling creep deformation during this time period employs values on materials parameters determined within the SKB-project on 'mechanical integrity of canisters for spent nuclear fuel'. The welding residual stresses are redistributed without lowering maximum values during the waiting period, a very low amount of void growth is predicted for this type of copper during the deposition period. This leads to an estimated very large rupture time

  11. The VIMOS Public Extragalactic Redshift Survey. Measuring the growth rate of structure around cosmic voids

    Science.gov (United States)

    Hawken, A. J.; Granett, B. R.; Iovino, A.; Guzzo, L.; Peacock, J. A.; de la Torre, S.; Garilli, B.; Bolzonella, M.; Scodeggio, M.; Abbas, U.; Adami, C.; Bottini, D.; Cappi, A.; Cucciati, O.; Davidzon, I.; Fritz, A.; Franzetti, P.; Krywult, J.; Le Brun, V.; Le Fèvre, O.; Maccagni, D.; Małek, K.; Marulli, F.; Polletta, M.; Pollo, A.; Tasca, L. A. M.; Tojeiro, R.; Vergani, D.; Zanichelli, A.; Arnouts, S.; Bel, J.; Branchini, E.; De Lucia, G.; Ilbert, O.; Moscardini, L.; Percival, W. J.

    2017-11-01

    We aim to develop a novel methodology for measuring thegrowth rate of structure around cosmic voids. We identified voids in the completed VIMOS Public Extragalactic Redshift Survey (VIPERS), using an algorithm based on searching for empty spheres. We measured the cross-correlation between the centres of voids and the complete galaxy catalogue. The cross-correlation function exhibits a clear anisotropy in both VIPERS fields (W1 and W4), which is characteristic of linear redshift space distortions. By measuring the projected cross-correlation and then de-projecting it we are able to estimate the un-distorted cross-correlation function. We propose that given a sufficiently well-measured cross-correlation function one should be able to measure the linear growth rate of structure by applying a simple linear Gaussian streaming model for the redshift space distortions (RSD). Our study of voids in 306 mock galaxy catalogues mimicking the VIPERS fields suggests that VIPERS is capable of measuring β, the ratio of the linear growth rate to the bias, with an error of around 25%. Applying our method to the VIPERS data, we find a value for the redshift space distortion parameter, β = 0.423-0.108+0.104 which, given the bias of the galaxy population we use, gives a linear growth rate of f σ8 = 0.296-0.078+0.075 at z = 0.727. These results are consistent with values observed in parallel VIPERS analyses that use standard techniques. Based on observations collected at the European Southern Observatory, Cerro Paranal, Chile, using the Very Large Telescope under programs 182.A-0886 and partly 070.A-9007. Also based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in

  12. Effects of Grain Boundaries and Dislocation Cell Walls on Void Nucleation and Growth in Aluminium during Fast Neutron Irradiation

    DEFF Research Database (Denmark)

    Horsewell, Andy; Rahman, F. A.; Singh, Bachu Narain

    1983-01-01

    and growth occurs in a zone extending up to 10 mu m from grain boundaries in annealed material. In polygonized material, the presence of dislocation cell walls leads to cell size dependent void formation and growth; the swelling rate in the large cells is substantially higher than in the annealed material....

  13. Stress-Assisted Corrosion in Boiler Tubes

    Energy Technology Data Exchange (ETDEWEB)

    Preet M Singh; Steven J Pawel

    2006-05-27

    A number of industrial boilers, including in the pulp and paper industry, needed to replace their lower furnace tubes or decommission many recovery boilers due to stress-assisted corrosion (SAC) on the waterside of boiler tubes. More than half of the power and recovery boilers that have been inspected reveal SAC damage, which portends significant energy and economic impacts. The goal of this project was to clarify the mechanism of stress-assisted corrosion (SAC) of boiler tubes for the purpose of determining key parameters in its mitigation and control. To accomplish this in-situ strain measurements on boiler tubes were made. Boiler water environment was simulated in the laboratory and effects of water chemistry on SAC initiation and growth were evaluated in terms of industrial operations. Results from this project have shown that the dissolved oxygen is single most important factor in SAC initiation on carbon steel samples. Control of dissolved oxygen can be used to mitigate SAC in industrial boilers. Results have also shown that sharp corrosion fatigue and bulbous SAC cracks have similar mechanism but the morphology is different due to availability of oxygen during boiler shutdown conditions. Results are described in the final technical report.

  14. Kinetic aspects of the growth of platelets and voids in H implanted Si

    International Nuclear Information System (INIS)

    Grisolia, J.; Cristiano, F.; Ben Assayag, G.; Claverie, A.

    2001-01-01

    We have undertaken a systematic and quantitative study of the extended defects formed after high-dose proton implantation in silicon. This study is based on the transmission electron microscopy (TEM) and secondary ion mass spectroscopy (SIMS) experiments to 'follow' the thermal evolution of platelets and voids for a large variety of annealing conditions up to 900 deg. C. Up to about 500 deg. C, only platelets are observed and, as the anneal proceeds, they grow in size and reduce their density through the conservative exchange of hydrogen (H) atoms. On the contrary, above 500 deg. C, H starts to diffuse out of the defect-rich region and this out-diffusion can be completed after 700 deg. C anneals. Concurrently, platelets tend to disappear and voids appear. Above 700 deg. C anneals, hydrogen cannot be detected anymore in the layers and only voids remain. Upon time, they also grow in size and reduce their density. This is again attributed to the Ostwald ripening of voids which involves now vacancy diffusion from small voids to large ones. In summary, we have shown that platelets and voids both undergo quasi-conservative ripening upon annealing; at low-temperature (LT) platelets exchange the H atoms they are composed of while at high-temperature voids exchange vacancies

  15. Analysis of Void Growth and Coalescence in Porous Polymer Materials. Coalescence in Polymer Materials

    Directory of Open Access Journals (Sweden)

    S. A. Reffas

    2013-06-01

    Full Text Available The use of polymeric materials in engineering applications is growing more and more all over the world. This issue requests new methodologies of analysis in order to assess the material’s capability to withstand complex loads. The use of polyacetal in engineering applications has increased rapidly in the last decade. In order to evaluate the behavior, the damage and coalescence of this type of polymer, a numerical method based on damage which occurs following several stages (nucleation of cavities, their growth and coalescence in more advanced stages of deformation is proposed in this work. A particular attention is given on the stress-strain and the volumetric strain evolution under different triaxiality and for three initial void shapes. Its application to polyacetal allows approving this approach for technical polymers. Finally, this method allow us to compare the obtained results of basic calculations at different triaxiality and to discuss their possible influence on the initial size and the geometrical shape of the porosity on the material failure.

  16. Taylor-plasticity-based analysis of length scale effects in void growth

    KAUST Repository

    Liu, Junxian; Demiral, Murat; El Sayed, Tamer S.

    2014-01-01

    plasticity as the flow rule, the critical cavitation condition, appearing when the derivative of the externally imposed mean stress with respect to the current void radius becomes zero, is rewritten analytically according to the Leibniz relation and found

  17. Fast and interrupted expansion in cyclic void growth in dusty plasma

    International Nuclear Information System (INIS)

    Van de Wetering, F M J H; Brooimans, R J C; Nijdam, S; Beckers, J; Kroesen, G M W

    2015-01-01

    Low-pressure acetylene plasmas are able to spontaneously form dust particles. This will result in a dense cloud of solid particles that is levitated in the plasma. The formed particles can grow up to micrometers. We observed a spontaneous interruption in the expansion of the so-called dust void. A dust void is a macroscopic region in the plasma that is free of nanoparticles. The phenomenon is periodical and reproducible. We refer to the expansion interruption as ‘hiccup’. The expanding void is an environment in which a new cycle of dust particle formation can start. At a certain moment in time, this cycle reaches the (sudden) coagulation phase and as a result the void will temporarily shrink. To substantiate this reasoning, the electron density is determined non-intrusively using microwave cavity resonance spectroscopy. Moreover, video imaging of laser light scattering of the dust particles provides their spatial distribution. The emission intensity of a single argon transition is measured similarly. Our results support the aforementioned hypothesis for what happens during the void hiccup. The void dynamics preceding the hiccup are modeled using a simple analytical model for the two dominant forces (ion drag and electric) working on a nanoparticle in a plasma. The model results qualitatively reproduce the measurements. (paper)

  18. Separation of nucleation and growth of voids during tensile deformation of a dual phase steel using synchrotron microtomography

    Energy Technology Data Exchange (ETDEWEB)

    Requena, Guillermo, E-mail: guillermo.requena@tuwien.ac.at [INSA-Lyon, MATEIS CNRS UMR5510, F-69621 Villeurbanne (France); Maire, Eric; Leguen, Claire [INSA-Lyon, MATEIS CNRS UMR5510, F-69621 Villeurbanne (France); Thuillier, Sandrine [LIMATB, Université de Bretagne-Sud, rue de Saint Maudé, BP 92116, 56321 Lorient Cedex (France)

    2014-01-01

    The damage evolution in a DP980 dual phase steel is followed in situ by synchrotron microtomography during tensile deformation focusing on the effect that the triaxiality, induced by different sample geometries, exerts on damage formation and damage evolution. The growth of existing voids is separated from the voids nucleated between consecutive deformation steps using three-dimensional image analysis. The experimental results are correlated with those obtained by finite element analysis using a Gurson–Tvergaard–Needleman framework with a Chu and Needleman formulation to introduce the effect of nucleation of cavities. A relatively simple way to determine the nucleation parameters is proposed based on the volume of nucleated voids obtained from the tomographies. The evolution of the total volume fraction of cavities obtained from the calculations shows a good agreement with the experiments for the notched samples and reflects the effect of triaxiality on damage. Contrarily to experiments, the calculated accumulated volume fraction of nucleated voids does not reflect the effect of triaxiality suggesting the necessity to implement this parameter in the nucleation model.

  19. Examination and modeling of void growth kinetics in modern high strength dual phase steels during uniaxial tensile deformation

    Energy Technology Data Exchange (ETDEWEB)

    Saeidi, N., E-mail: navidsae@gmail.com [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Ashrafizadeh, F.; Niroumand, B. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Forouzan, M.R.; Mohseni mofidi, S. [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Barlat, F. [Materials Mechanics Laboratory (MML), Graduate Institute of Ferrous Technology (GIFT), Pohang University of Science and Technology - POSTECH, San 31 Hyoja-dong, Nam-gu, Pohang, Gyeongbuk 790-784 (Korea, Republic of)

    2016-04-01

    Ductile fracture mechanisms during uniaxial tensile testing of two different modern high strength dual phase steels, i.e. DP780 and DP980, were studied. Detailed microstructural characterization of the strained and sectioned samples was performed by scanning electron microscopy as well as EBSD examination. The results revealed that interface decohesion, especially at martensite particles located at ferrite grain boundaries, was the most probable mechanism for void nucleation. It was also revealed that the creation of cellular substructure can reduce stored strain energy and thereby, higher true fracture strain was obtained in DP980 than DP780 steel. Prediction of void growth behavior based on some previously proposed models showed unreliable results. Therefore, a modified model based on Rice-Tracey family models was proposed which showed a very lower prediction error compared with other models. - Highlights: • Damage mechanism in two modern high strength dual phase steels was studied. • Creation of cellular substructures can reduce the stored strain energy within the ferrite grains. • The experimental values were examined by Agrawal as well as RT family models. • A modified model was proposed for prediction of void growth behavior of DP steels.

  20. Direct observation of the growth of voids in multifilamentary superconducting materials via hot stage scanning electron microscopy

    International Nuclear Information System (INIS)

    Wang, J.L.F.; Holthuis, J.T.; Pickus, M.R.; Lindberg, R.W.

    1978-11-01

    The need for large high field magnetic devices has focused attention on multifilamentary superconductors based on A15 compounds such as Nb 3 Sn. The commercial bronze process for fabricating multifilamentary superconducting Nb 3 Sn wires was developed. A major problem is strain sensitivity when long reaction times are employed. An improved hot stage for the scanning electron microscope was constructed to study the formation of the A15 phase by solid state diffusion. The nucleation and growth of voids near the interface of the A15 phase (Nb 3 Sn) and matrix were observed, monitored, and recorded on video tape. Successive layers of material heated in the hot stage were subsequently removed and the new surfaces were re-examined, using SEM-EDX and optical microscopy, to confirm the fact that the observed porosity was indeed a bulk rather than a surface phenomenon. These voids are considered to be a primary cause for degrading the mechanical, thermal and superconducting properties

  1. Temperature controlled 'void' formation

    International Nuclear Information System (INIS)

    Dasgupta, P.; Sharma, B.D.

    1975-01-01

    The nucleation and growth of voids in structural materials during high temperature deformation or irradiation is essentially dependent upon the existence of 'vacancy supersaturation'. The role of temperature dependent diffusion processes in 'void' formation under varying conditions, and the mechanical property changes associated with this microstructure are briefly reviewed. (author)

  2. Void lattices

    International Nuclear Information System (INIS)

    Chadderton, L.T.; Johnson, E.; Wohlenberg, T.

    1976-01-01

    Void lattices in metals apparently owe their stability to elastically anisotropic interactions. An ordered array of voids on the anion sublattice in fluorite does not fit so neatly into this scheme of things. Crowdions may play a part in the formation of the void lattice, and stability may derive from other sources. (Auth.)

  3. Determination of the void nucleation rate from void size distributions

    International Nuclear Information System (INIS)

    Brailsford, A.D.

    1977-01-01

    A method of estimating the void nucleation rate from one void size distribution and from observation of the maximum void radius at prior times is proposed. Implicit in the method are the assumptions that both variations in the critical radius with dose and vacancy thermal emission processes during post-nucleation quasi-steady-state growth may be neglected. (Auth.)

  4. Void shape effects and voids starting from cracked inclusion

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2011-01-01

    Numerical, axisymmetric cell model analyses are used to study the growth of voids in ductile metals, until the mechanism of coalescence with neighbouring voids sets in. A special feature of the present analyses is that extremely small values of the initial void volume fraction are considered, dow...

  5. Effect of precipitate-matrix interface sinks on the growth of voids in the matrix

    International Nuclear Information System (INIS)

    Brailsford, A.D.; Mansur, L.K.

    1981-01-01

    A qualitative discussion of the differing roles played by coherent and incoherent precipitates as point defect sinks is presented. Rate theory is used to obtain semiquantitative estimates of the growth of cavities in the matrix when either type of precipitate is present. Methods for deriving the sink strengths of precipitates of arbitrary shape are developed. In three materials where available microstructural information allows an analysis, precipitates are found to cause only a small relative suppression of cavity growth via the mechanisms here considered

  6. Partial discharges in spheroidal voids: Void orientation

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1997-01-01

    Partial discharge transients can be described in terms of the charge induced on the detecting electrode. The influence of the void parameters upon the induced charge is examined and discussed for spheroidal voids. It is shown that a quantitative interpretation of the induced charge requires...

  7. Nonlocal plasticity effects on interaction of different size voids

    DEFF Research Database (Denmark)

    Tvergaard, Viggo; Niordson, Christian Frithiof

    2004-01-01

    A nonlocal elastic-plastic material model is used to show that the rate of void growth is significantly reduced when the voids are small enough to be comparable with a characteristic material length. For a very small void in the material between much larger voids the competition between...... dimensional array of spherical voids. It is shown that the high growth rate of very small voids predicted by conventional plasticity theory is not realistic when the effect of a characteristic length, dependent on the dislocation structure, is accounted for. (C) 2003 Elsevier Ltd. All rights reserved....

  8. Pediatric Voiding Cystourethrogram

    Science.gov (United States)

    Scan for mobile link. Children's (Pediatric) Voiding Cystourethrogram A children’s (pediatric) voiding cystourethrogram uses fluoroscopy – a form of real-time x-ray – to examine a child’s bladder ...

  9. Cosmic void clumps

    Science.gov (United States)

    Lares, M.; Luparello, H. E.; Garcia Lambas, D.; Ruiz, A. N.; Ceccarelli, L.; Paz, D.

    2017-10-01

    Cosmic voids are of great interest given their relation to the large scale distribution of mass and the way they trace cosmic flows shaping the cosmic web. Here we show that the distribution of voids has, in consonance with the distribution of mass, a characteristic scale at which void pairs are preferentially located. We identify clumps of voids with similar environments and use them to define second order underdensities. Also, we characterize its properties and analyze its impact on the cosmic microwave background.

  10. Dynamic void behavior in polymerizing polymethyl methacrylate cement.

    Science.gov (United States)

    Muller, Scott D; McCaskie, Andrew W

    2006-02-01

    Cement mantle voids remain controversial with respect to survival of total hip arthroplasty. Void evolution is poorly understood, and attempts at void manipulation can only be empirical. We induced voids in a cement model simulating the constraints of the proximal femur. Intravoid pressure and temperature were recorded throughout polymerization, and the initial and final void volumes were measured. Temperature-dependent peak intravoid pressures and void volume increases were observed. After solidification, subatmospheric intravoid pressures were observed. The magnitude of these observations could not be explained by the ideal gas law. Partial pressures of the void gas at peak pressures demonstrated a dominant effect of gaseous monomer, thereby suggesting that void growth is a pressure-driven phenomenon resulting from temperature-dependent evaporation of monomer into existing trapped air voids.

  11. On void nucleation

    International Nuclear Information System (INIS)

    Subbotin, A.V.

    1978-01-01

    Nucleation of viable voids in irradiated materials is considered. The mechanism of evaporation and absorption of interstitials and vacancies disregarding the possibility of void merging is laid down into the basis of the discussion. The effect of irradiated material structure on void nucleation is separated from the effect of the properties of supersaturated solutions of vacancies and interstitials. An analytical expression for the nucleation rate is obtained and analyzed in different cases. The interstitials are concluded to effect severely the nucleation rate of viable voids

  12. The sink strengths of voids and the expected swelling for both random and ordered void distributions

    International Nuclear Information System (INIS)

    Quigley, T.M.; Murphy, S.M.; Bullough, R.; Wood, M.H.

    1981-10-01

    The sink strength of a void has been obtained when the void is a member of a random or ordered distribution of voids. The former sink strength derivation has employed the embedding model and the latter the cellular model. In each case the spatially varying size-effect interaction between the intrinsic point defects and the voids has been included together with the presence of other sink types in addition to the voids. The results are compared with previously published sink strengths that have made use of an approximate representation for the size-effect interactions, and indicate the importance of using the exact form of the interaction. In particular the bias for interstitials compared with vacancies of small voids is now much reduced and contamination of the surfaces of such voids no longer appears essential to facilitate the nucleation and growth of the voids. These new sink strengths have been used, in conjunction with recently published dislocation sink strengths, to calculate the expected swelling of materials containing network dislocations and voids. Results are presented for both the random and the void lattice situations. (author)

  13. Void nucleation at heterogeneities

    International Nuclear Information System (INIS)

    Seyyedi, S.A.; Hadji-Mirzai, M.; Russell, K.C.

    The energetics and kinetics of void nucleation at dislocations and interfaces are analyzed. These are potential void nucleation sites only when they are not point defect sinks. Both kinds of site are found to be excellent catalysts in the presence of inert gas

  14. Void hierarchy and cosmic structure

    International Nuclear Information System (INIS)

    Weygaert, Rien van de; Ravi Sheth

    2004-01-01

    Within the context of hierarchical scenarios of gravitational structure formation we describe how an evolving hierarchy of voids evolves on the basis of two processes, the void-in-void process and the void-in-cloud process. The related analytical formulation in terms of a two-barrier excursion problem leads to a self-similarly evolving peaked void size distribution

  15. Constitutive modeling of rate dependence and microinertia effects in porous-plastic materials with multi-sized voids (MSVs)

    KAUST Repository

    Liu, Jinxing; El Sayed, Tamer S.

    2012-01-01

    Micro-voids of varying sizes exist in most metals and alloys. Both experiments and numerical studies have demonstrated the critical influence of initial void sizes on void growth. The classical Gurson-Tvergaard-Needleman model summarizes

  16. Air void clustering.

    Science.gov (United States)

    2015-06-01

    Air void clustering around coarse aggregate in concrete has been identified as a potential source of : low strengths in concrete mixes by several Departments of Transportation around the country. Research was : carried out to (1) develop a quantitati...

  17. Stress-assisted discontinuous precipitation during creep of Ti3Al-Nb alloys

    International Nuclear Information System (INIS)

    Rowe, R.G.; Hall, E.L.

    1991-01-01

    Stress-assisted discontinuous precipitation was observed during creep of Ti-25Al-12.5Nb at. pct and associated with microstructures in which large primary creep strains were observed earlier. It was found that a large shift between the equilibrium beta(0) (B2) phase composition at the heat treatment temperature and disordered beta (bcc) phase at the creep temperature provided a driving force for discontinuous precipitation of disordered beta phase. Applied stress accelerated the growth of discontinuous beta phase at grain boundaries perpendicular to the principal stress axis, but did not produce a significant shift in composition. The difference between beta and ordered beta phase boundaries in the Ti-Al-Nb system at 650 C and 1040 C suggests that discontinuous precipitation or related dissolution should occur in all Ti3Al-Nb alloys. 11 refs

  18. Positive void reactivity

    International Nuclear Information System (INIS)

    Diamond, D.J.

    1992-09-01

    This report is a review of some of the important aspects of the analysis of large loss-of-coolant accidents (LOCAs). One important aspect is the calculation of positive void reactivity. To study this subject the lattice physics codes used for void worth calculations and the coupled neutronic and thermal-hydraulic codes used for the transient analysis are reviewed. Also reviewed are the measurements used to help validate the codes. The application of these codes to large LOCAs is studied with attention focused on the uncertainty factor for the void worth used to bias the results. Another aspect of the subject dealt with in the report is the acceptance criteria that are applied. This includes the criterion for peak fuel enthalpy and the question of whether prompt criticality should also be a criterion. To study the former, fuel behavior measurements and calculations are reviewed. (Author) (49 refs., 2 figs., tab.)

  19. Void effects on BWR Doppler and void reactivity feedback

    International Nuclear Information System (INIS)

    Hsiang-Shou Cheng; Diamond, D.J.

    1978-01-01

    The significance of steam voids and control rods on the Doppler feedback in a gadolinia shimmed BWR is demonstrated. The importance of bypass voids when determining void feedback is also shown. Calculations were done using a point model, i.e., feedback was expressed in terms of reactivity coefficients which were determined for individual four-bundle configurations and then appropriately combined to yield reactor results. For overpower transients the inclusion of the void effect of control rods is to reduce Doppler feedback. For overpressurization transients the inclusion of the effect of bypass void wil increase the reactivity due to void collapse. (author)

  20. Dislocation and void segregation in copper during neutron irradiation

    DEFF Research Database (Denmark)

    Singh, Bachu Narain; Leffers, Torben; Horsewell, Andy

    1986-01-01

    ); the irradiation experiments were carried out at 250 degree C. The irradiated specimens were examined by transmission electron microscopy. At both doses, the irradiation-induced structure was found to be highly segregated; the dislocation loops and segments were present in the form of irregular walls and the voids...... density, the void swelling rate was very high (approximately 2. 5% per dpa). The implications of the segregated distribution of sinks for void formation and growth are briefly discussed....

  1. Size-effects at a crack-tip interacting with a number of voids

    DEFF Research Database (Denmark)

    Tvergaard, Viggo; Niordson, Christian Frithiof

    2008-01-01

    A strain gradient plasticity theory is used to analyse the growth of discretely represented voids in front of a blunting crack tip, in order to study the influence of size effects on two competing mechanisms of crack growth. For a very small void volume fraction the crack tip tends to interact...... of the characteristic material length relative to the initial void radius. For a case showing the multiple void mechanism, it is found that the effect of the material length can change the behaviour towards the void by void mechanism. A material model with three characteristic length scales is compared with a one...

  2. In-situ cyclic stress experiment at the Clinton P. Anderson Meson Physics Facility (LAMPF) for determining the effect of dislocation vibration on void growth in metals during irradiation

    International Nuclear Information System (INIS)

    Green, W.V.; Sommer, W.F.; Coulter, C.A.

    1979-01-01

    Experience is reported with the first in-situ cyclic-stress irradiation at LAMPF. A proton beam ion current of 3 to 6 μA of 800 MeV protons was utilized for 24 days irradiation. Radiation damage effects of 800 MeV protons incident on a 1-cm thick Cu target were calculated using the nucleon-meson transport code to determine the nuclear reactions produced by the protons, the theory of Lindhard to evaluate the resultant damage energy deposited in the target. These calculations have been extended to Al. Damage effects were nearly uniform through a 1-cm target thickness, and the results obtained can be expressed in cross section form. The calculation yielded a damage energy cross section of about 63 barn-keV, a nuclear transmutation cross section of 0.44 barns, and indicated copious hydrogen, helium, and neutron production. Analysis of the effect of dislocation vibration on the efficiency of a dislocation line as a sink for point defects predicted that dislocation vibration should suppress void growth. The effect results from the fact that the dislocation will sweep up vacancies, which diffuse less rapidly than interstitials. The growth rate of voids in Al under simultaneous proton irradiation and cyclic stressing are compared to that of samples irradiated at the same time but without any stressing. The samples are placed one behind the other along the proton path so that identical irradiation histories can be achieved. The temperature of the samples is controlled, known and uniform. The initial preirradiation state is a prestrained state of a few hundred stress cycles. The samples are irradiated without stress through the incubation period for void nucleation before the cyclic stress is applied

  3. A variational void coalescence model for ductile metals

    KAUST Repository

    Siddiq, Amir; Arciniega, Roman; El Sayed, Tamer

    2011-01-01

    We present a variational void coalescence model that includes all the essential ingredients of failure in ductile porous metals. The model is an extension of the variational void growth model by Weinberg et al. (Comput Mech 37:142-152, 2006

  4. Effect of helium on void formation in nickel

    International Nuclear Information System (INIS)

    Brimhall, J.L.; Simonen, E.P.

    1977-01-01

    This study examines the influence of helium on void formation in self-ion irradiated nickel. Helium was injected either simultaneously with, or prior to, the self-ion bombardment. The void microstructure was characterized as a function of helium deposition rate and the total heavy-ion dose. In particular, at 575 0 C and 5 X 10 -3 displacements per atom per second the void density is found to be proportional to the helium deposition rate. The dose dependence of swelling is initially dominated by helium driven nucleation. The void density rapidly saturates after which swelling continues with increasing dose only from void growth. It is concluded that helium promotes void nucleation in nickel with either helium implantation technique, pre-injection or simultaneous injection. Qualitative differences, however, are recognized. (Auth.)

  5. The Metallicity of Void Dwarf Galaxies

    Science.gov (United States)

    Kreckel, K.; Croxall, K.; Groves, B.; van de Weygaert, R.; Pogge, R. W.

    2015-01-01

    The current ΛCDM cosmological model predicts that galaxy evolution proceeds more slowly in lower density environments, suggesting that voids are a prime location to search for relatively pristine galaxies that are representative of the building blocks of early massive galaxies. To test the assumption that void galaxies are more pristine, we compare the evolutionary properties of a sample of dwarf galaxies selected specifically to lie in voids with a sample of similar isolated dwarf galaxies in average density environments. We measure gas-phase oxygen abundances and gas fractions for eight dwarf galaxies (Mr > -16.2), carefully selected to reside within the lowest density environments of seven voids, and apply the same calibrations to existing samples of isolated dwarf galaxies. We find no significant difference between these void dwarf galaxies and the isolated dwarf galaxies, suggesting that dwarf galaxy chemical evolution proceeds independent of the large-scale environment. While this sample is too small to draw strong conclusions, it suggests that external gas accretion is playing a limited role in the chemical evolution of these systems, and that this evolution is instead dominated mainly by the internal secular processes that are linking the simultaneous growth and enrichment of these galaxies.

  6. Void formation and its impact on Cu−Sn intermetallic compound formation

    International Nuclear Information System (INIS)

    Ross, Glenn; Vuorinen, Vesa; Paulasto-Kröckel, Mervi

    2016-01-01

    Void formation in the Cu−Sn system has been identified as a major reliability issue with small volume electronic interconnects. Voids form during the interdiffusion of electrochemically deposited Cu and Sn, with varying magnitude and density. Electroplating parameters include the electrolytic chemistry composition and the electroplating current density, all of which appear to effect the voiding characteristics of the Cu−Sn system. In addition, interfacial voiding affects the growth kinetics of the Cu_3Sn and Cu_6Sn_5 intermetallic compounds of the Cu−Sn system. The aim here is to present voiding data as a function of electroplating chemistry and current density over a duration (up to 72 h) of isothermal annealing at 423 K (150 °C). Voiding data includes the average interfacial void size and average void density. Voids sizes grew proportionally as a function of thermal annealing time, whereas the void density grew initially very quickly but tended to saturate at a fixed density. A morphological evolution analysis called the physicochemical approach is utilised to understand the processes that occur when a voided Cu/Cu_3Sn interface causes changes to the IMC phase growth. The method is used to simulate the intermetallic thickness growths' response to interfacial voiding. The Cu/Cu_3Sn interface acts as a Cu diffusion barrier disrupting the diffusion of Cu. This resulted in a reduction in the Cu_3Sn thickness and an accelerated growth rate of Cu_6Sn_5. - Highlights: • Average void size is proportional linearly to thermal annealing time. • Average void density grows initially very rapidly followed by saturation. • Voids located close to the Cu/Cu_3Sn interface affect IMC growth rates. • Voids act as a diffusion barrier inhibiting Cu diffusion towards Sn. • Voids located at the interface cause Cu_3Sn to be consumed by Cu_6Sn_5.

  7. Archaeology of Void Spaces

    Science.gov (United States)

    Look, Cory

    The overall goal of this research is to evaluate the efficacy of pXRF for the identification of ancient activity areas at Pre-Columbian sites in Antigua that range across time periods, geographic regions, site types with a variety of features, and various states of preservation. These findings have important implications for identifying and reconstructing places full of human activity but void of material remains. A synthesis for an archaeology of void spaces requires the construction of new ways of testing anthrosols, and identifying elemental patterns that can be used to connect people with their places and objects. This research begins with an exploration of rich middens in order to study void spaces. Midden archaeology has been a central focus in Caribbean research, and consists of an accumulation of discarded remnants from past human activities that can be tested against anthrosols. The archaeological collections visited for this research project involved creating new databases to generate a comprehensive inventory of sites, materials excavated, and assemblages available for study. Of the more than 129 Pre-Columbian sites documented in Antigua, few sites have been thoroughly surveyed or excavated. Twelve Pre-Columbian sites, consisting of thirty-six excavated units were selected for study; all of which contained complete assemblages for comparison and soil samples for testing. These excavations consisted almost entirely of midden excavations, requiring new archaeological investigations to be carried out in spaces primarily void of material remains but within the village context. Over the course of three seasons excavations, shovel test pits, and soil augers were used to obtain a variety of anthrosols and archaeological assemblages in order to generate new datasets to study Pre-Columbian activity areas. The selection of two primary case study sites were used for comparison: Indian Creek and Doigs. Findings from this research indicate that accounting for the

  8. Factors affecting stress assisted corrosion cracking of carbon steel under industrial boiler conditions

    Science.gov (United States)

    Yang, Dong

    Failure of carbon steel boiler tubes from waterside has been reported in the utility boilers and industrial boilers for a long time. In industrial boilers, most waterside tube cracks are found near heavy attachment welds on the outer surface and are typically blunt, with multiple bulbous features indicating a discontinuous growth. These types of tube failures are typically referred to as stress assisted corrosion (SAC). For recovery boilers in the pulp and paper industry, these failures are particularly important as any water leak inside the furnace can potentially lead to smelt-water explosion. Metal properties, environmental variables, and stress conditions are the major factors influencing SAC crack initation and propagation in carbon steel boiler tubes. Slow strain rate tests (SSRT) were conducted under boiler water conditions to study the effect of temperature, oxygen level, and stress conditions on crack initation and propagation on SA-210 carbon steel samples machined out of boiler tubes. Heat treatments were also performed to develop various grain size and carbon content on carbon steel samples, and SSRTs were conducted on these samples to examine the effect of microstructure features on SAC cracking. Mechanisms of SAC crack initation and propagation were proposed and validated based on interrupted slow strain tests (ISSRT). Water chemistry guidelines are provided to prevent SAC and fracture mechanics model is developed to predict SAC failure on industrial boiler tubes.

  9. Three-dimensional simulations of void collapse in energetic materials

    Science.gov (United States)

    Rai, Nirmal Kumar; Udaykumar, H. S.

    2018-03-01

    The collapse of voids in porous energetic materials leads to hot-spot formation and reaction initiation. This work advances the current knowledge of the dynamics of void collapse and hot-spot formation using 3D reactive void collapse simulations in HMX. Four different void shapes, i.e., sphere, cylinder, plate, and ellipsoid, are studied. For all four shapes, collapse generates complex three-dimensional (3D) baroclinic vortical structures. The hot spots are collocated with regions of intense vorticity. The differences in the vortical structures for the different void shapes are shown to significantly impact the relative sensitivity of the voids. Voids of high surface area generate hot spots of greater intensity; intricate, highly contorted vortical structures lead to hot spots of corresponding tortuosity and therefore enhanced growth rates of reaction fronts. In addition, all 3D voids are shown to be more sensitive than their two-dimensional (2D) counterparts. The results provide physical insights into hot-spot formation and growth and point to the limitations of 2D analyses of hot-spot formation.

  10. Displacive stability of a void in a void lattice

    International Nuclear Information System (INIS)

    Brailsford, A.D.

    1977-01-01

    It has recently been suggested that the stability of the void-lattice structure in irradiated metals may be attributed to the effect of the overlapping of the point-defect diffusion fields associated with each void. It is shown here, however, that the effect is much too weak. When one void is displaced from its lattice site, the displacement is shown to relax to zero as proposed, but a conservative estimate indicates that the characteristic time is equivalent to an irradiation dose of the order of 300 displacements per atom which is generally much greater than the dose necessary for void-lattice formation

  11. CTF Void Drift Validation Study

    Energy Technology Data Exchange (ETDEWEB)

    Salko, Robert K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gosdin, Chris [Pennsylvania State Univ., University Park, PA (United States); Avramova, Maria N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gergar, Marcus [Pennsylvania State Univ., University Park, PA (United States)

    2015-10-26

    This milestone report is a summary of work performed in support of expansion of the validation and verification (V&V) matrix for the thermal-hydraulic subchannel code, CTF. The focus of this study is on validating the void drift modeling capabilities of CTF and verifying the supporting models that impact the void drift phenomenon. CTF uses a simple turbulent-diffusion approximation to model lateral cross-flow due to turbulent mixing and void drift. The void drift component of the model is based on the Lahey and Moody model. The models are a function of two-phase mass, momentum, and energy distribution in the system; therefore, it is necessary to correctly model the ow distribution in rod bundle geometry as a first step to correctly calculating the void distribution due to void drift.

  12. Stability of void lattices under irradiation: a kinetic model

    International Nuclear Information System (INIS)

    Benoist, P.; Martin, G.

    1975-01-01

    Voids are imbedded in a homogeneous medium where point defects are uniformly created and annihilated. As shown by a perturbation calculation, the proportion of the defects which are lost on the cavities goes through a maximum, when the voids are arranged on a translation lattice. If a void is displaced from its lattice site, its growth rate becomes anisotropic and is larger in the direction of the vacant site. The relative efficiency of BCC versus FCC void lattices for the capture of point defects is shown to depend on the relaxation length of the point defects in the surrounding medium. It is shown that the rate of energy dissipation in the crystal under irradiation is maximum when the voids are ordered on the appropriate lattice

  13. Stability of void lattices under irradiation: a kinetic model

    International Nuclear Information System (INIS)

    Benoist, P.; Martin, G.

    1975-01-01

    Voids are imbedded in a homogeneous medium where point defects are uniformly created and annihilated. As shown by a perturbation calculation, the proportion of the defects which are lost on the cavities goes through a maximum, when the voids are arranged on a translation lattice. If a void is displaced from its lattice site, its growth the rate becomes anisotropic and is larger in the direction of the vacant site. The relative efficiency of BCC versus FCC void lattices for the capture of point defects is shown to depend on the relaxation length of the point defects in the surrounding medium. It is shown that the rate of energy dissipation in the crystal under irradiation is maximum when the voids are ordered on the appropriate lattice [fr

  14. On the formation of voids in internal tin Nb$_{3}$Sn superconductors

    CERN Document Server

    Scheuerlein, C; Haibel, A

    2007-01-01

    In this article we describe three void growth mechanisms in Nb$_{3}$Sn strands of the internal tin design on the basis of combined synchrotron micro-tomography and x-ray diffraction measurements during in-situ heating cycles. Initially void growth is driven by a reduction of void surface area by void agglomeration. The main void volume increase is caused by density changes during the formation of Cu3Sn in the strand. Subsequent transformation of Cu-Sn intermetallics into the lower density a-bronze reduces the void volume again. Long lasting temperature ramps and isothermal holding steps can neither reduce the void volume nor improve the chemical strand homogeneity prior to the superconducting A15 phase nucleation and growth.

  15. Role of stress-assisted martensite in the design of strong ultrafine-grained duplex steels

    International Nuclear Information System (INIS)

    Yen, Hung-Wei; Ooi, Steve Woei; Eizadjou, Mehdi; Breen, Andrew; Huang, Ching-Yuan; Bhadeshia, H.K.D.H.; Ringer, Simon P.

    2015-01-01

    This work explains the occurrence of transformation-induced plasticity via stress-assisted martensite, when designing ultrafine-grained duplex steels. It is found that, when the austenite is reduced to a fine scale of about 300 nm, the initial deformation-induced microstructure can be dominated by parallel lamellae of ε martensite or mechanical twinning, which cannot efficiently provide nucleation sites for strain-induced martensite. Hence, α′ martensite nucleation occurs independently by a stress-assisted process that enhances transformation-induced plasticity in ultrafine-grained austenite. This metallurgical principle was validated experimentally by using a combination of transmission Kikuchi diffraction mapping, transmission electron microscopy and atom probe microscopy, and demonstrated theoretically by the thermodynamics model of stress-assisted martensite

  16. Radiation-induced void swelling in metals and alloys

    International Nuclear Information System (INIS)

    Zelinskij, V.F.; Neklyudov, I.M.; Ozhigov, L.S.; Reznichenko, Eh.A.; Rozhkov, V.V.; Chernyaeva, T.T.

    1979-01-01

    Main regularities in the development of radiation-induced void swelling are considered. Special attention is paid to consideration of a possibility to obtain information on material behaviour under conditions of reactor irradiation proceeding from the data of simulation experiments and to methods of rate control, for the processes which occur in material during irradiation and further annealing by the way of rationalized alloying, of thermomechanical treatment and programmed change of irradiation conditions under operation. Problems of initiation and growth of voids in irradiated materials are discussed as well as the ways to decrease the rate of radiation-induced void swelling

  17. A variational void coalescence model for ductile metals

    KAUST Repository

    Siddiq, Amir

    2011-08-17

    We present a variational void coalescence model that includes all the essential ingredients of failure in ductile porous metals. The model is an extension of the variational void growth model by Weinberg et al. (Comput Mech 37:142-152, 2006). The extended model contains all the deformation phases in ductile porous materials, i.e. elastic deformation, plastic deformation including deviatoric and volumetric (void growth) plasticity followed by damage initiation and evolution due to void coalescence. Parametric studies have been performed to assess the model\\'s dependence on the different input parameters. The model is then validated against uniaxial loading experiments for different materials. We finally show the model\\'s ability to predict the damage mechanisms and fracture surface profile of a notched round bar under tension as observed in experiments. © Springer-Verlag 2011.

  18. PRECISION COSMOGRAPHY WITH STACKED VOIDS

    International Nuclear Information System (INIS)

    Lavaux, Guilhem; Wandelt, Benjamin D.

    2012-01-01

    We present a purely geometrical method for probing the expansion history of the universe from the observation of the shape of stacked voids in spectroscopic redshift surveys. Our method is an Alcock-Paczyński (AP) test based on the average sphericity of voids posited on the local isotropy of the universe. It works by comparing the temporal extent of cosmic voids along the line of sight with their angular, spatial extent. We describe the algorithm that we use to detect and stack voids in redshift shells on the light cone and test it on mock light cones produced from N-body simulations. We establish a robust statistical model for estimating the average stretching of voids in redshift space and quantify the contamination by peculiar velocities. Finally, assuming that the void statistics that we derive from N-body simulations is preserved when considering galaxy surveys, we assess the capability of this approach to constrain dark energy parameters. We report this assessment in terms of the figure of merit (FoM) of the dark energy task force and in particular of the proposed Euclid mission which is particularly suited for this technique since it is a spectroscopic survey. The FoM due to stacked voids from the Euclid wide survey may double that of all other dark energy probes derived from Euclid data alone (combined with Planck priors). In particular, voids seem to outperform baryon acoustic oscillations by an order of magnitude. This result is consistent with simple estimates based on mode counting. The AP test based on stacked voids may be a significant addition to the portfolio of major dark energy probes and its potentialities must be studied in detail.

  19. Air void clustering : [technical summary].

    Science.gov (United States)

    2015-06-01

    Air void clustering around coarse aggregate in concrete has been : identified as a potential source of low strengths in concrete mixes by : several Departments of Transportation around the country. Research : was carried out to (1) develop a quantita...

  20. Constitutive modeling of rate dependence and microinertia effects in porous-plastic materials with multi-sized voids (MSVs)

    KAUST Repository

    Liu, Jinxing

    2012-11-27

    Micro-voids of varying sizes exist in most metals and alloys. Both experiments and numerical studies have demonstrated the critical influence of initial void sizes on void growth. The classical Gurson-Tvergaard-Needleman model summarizes the influence of voids with a single parameter, namely the void-volume fraction, excluding any possible effects of the void-size distribution. We extend our newly proposed model including the multi-sized void (MSV) effect and the void-interaction effect for the capability of working for both moderate and high loading rate cases, where either rate dependence or microinertia becomes considerable or even dominant. Parametric studies show that the MSV-related competitive mechanism among void growth leads to the dependence of the void growth rate on void size, which directly influences the void\\'s contribution to the total energy composition. We finally show that the stress-strain constitutive behavior is also affected by this MSV-related competitive mechanism. The stabilizing effect due to rate sensitivity and microinertia is emphasized. © 2013 IOP Publishing Ltd.

  1. Nucleation from a cluster of inclusions, leading to void coalescense

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2017-01-01

    A cell model analysis is used to study the nucleation and subsequent growth of voids from a non-uniform distribution of inclusions in a ductile material. Nucleation is modeled as either stress controlled or strain controlled. The special clusters considered consist of a number of uniformly spaced...... inclusions located along a plane perpendicular to the maximum principal tensile stress. A plane strain approximation is used, where the inclusions are parallel cylinders perpendicular to the plane. Clusters with different numbers of inclusions are compared with the nucleation and growth from a single...... inclusion, such that the total initial volume of the inclusions is the same for the clusters and the single inclusion. After nucleation, local void coalescence inside the clusters is accounted for, since this makes it possible to compare the rate of growth of the single larger void that results from...

  2. Alignment of voids in the cosmic web

    NARCIS (Netherlands)

    Platen, Erwin; van de Weygaert, Rien; Jones, Bernard J. T.

    2008-01-01

    We investigate the shapes and mutual alignment of voids in the large-scale matter distribution of a Lambda cold dark matter (Lambda CDM) cosmology simulation. The voids are identified using the novel watershed void finder (WVF) technique. The identified voids are quite non-spherical and slightly

  3. On cavitation instabilities with interacting voids

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2012-01-01

    voids so far apart that the radius of the plastic zone around each void is less than 1% of the current spacing between the voids, can still affect each others at the occurrence of a cavitation instability such that one void stops growing while the other grows in an unstable manner. On the other hand...

  4. Use of Raman Spectroscopy and Delta Volume Growth from Void Collapse to Assess Overwrap Stress Gradients Compromising the Reliability of Large Kevlar/Epoxy COPVs

    Science.gov (United States)

    Kezirian, Michael T.; Phoenix, S. Leigh; Eldridge, Jeffrey I.

    2009-01-01

    Composite Overwrapped Pressure Vessels (COPVs) are frequently used for storing pressurized gases aboard spacecraft and aircraft when weight saving is desirable compared to all-metal versions. Failure mechanisms in fibrous COPVs and variability in lifetime can be very different from their metallic counterparts; in the former, catastrophic stress-rupture can occur with virtually no warning, whereas in latter, a leak before burst design philosophy can be implemented. Qualification and certification typically requires only one burst test on a production sample (possibly after several pressure cycles) and the vessel need only meet a design burst strength (the maximum operating pressure divided by a knockdown factor). Typically there is no requirement to assess variability in burst strength or lifetime, much less determine production and materials processing parameters important to control of such variability. Characterizing such variability and its source is crucial to models for calculating required reliability over a given lifetime (e.g. R = 0.9999 for 15 years). In this paper we present a case study of how lack of control of certain process parameters in COPV manufacturing can result in variations among vessels and between production runs that can greatly increase uncertainty and reduce reliability. The vessels considered are 40-inch ( NASA Glenn Research center, Cleveland, OH, 44135 29,500 in3 ) spherical COPVs with a 0.74 in. thick Kevlar49/epoxy overwrap and with a titanium liner of which 34 were originally produced. Two burst tests were eventually performed that unexpectedly differed by almost 5%, and were 10% lower than anticipated from burst tests on 26-inch sister vessels similar in every detail. A major observation from measurements made during proof testing (autofrettage) of the 40-inch vessels was that permanent volume growth from liner yielding varied by a factor of more than two (150 in3 to 360 in3 ), which suggests large differences in the residual

  5. Cluster-void degeneracy breaking: Modified gravity in the balance

    Science.gov (United States)

    Sahlén, Martin; Silk, Joseph

    2018-05-01

    Combining galaxy cluster and void abundances is a novel, powerful way to constrain deviations from general relativity and the Λ CDM model. For a flat w CDM model with growth of large-scale structure parametrized by the redshift-dependent growth index γ (z )=γ0+γ1z /(1 +z ) of linear matter perturbations, combining void and cluster abundances in future surveys with Euclid and the four-meter multiobject spectroscopic telescope could improve the figure of merit for (w ,γ0,γ1) by a factor of 20 compared to individual abundances. In an ideal case, improvement on current cosmological data is a figure of merit factor 600 or more.

  6. Void formation and its impact on Cu−Sn intermetallic compound formation

    Energy Technology Data Exchange (ETDEWEB)

    Ross, Glenn, E-mail: Glenn.Ross@aalto.fi; Vuorinen, Vesa; Paulasto-Kröckel, Mervi

    2016-08-25

    Void formation in the Cu−Sn system has been identified as a major reliability issue with small volume electronic interconnects. Voids form during the interdiffusion of electrochemically deposited Cu and Sn, with varying magnitude and density. Electroplating parameters include the electrolytic chemistry composition and the electroplating current density, all of which appear to effect the voiding characteristics of the Cu−Sn system. In addition, interfacial voiding affects the growth kinetics of the Cu{sub 3}Sn and Cu{sub 6}Sn{sub 5} intermetallic compounds of the Cu−Sn system. The aim here is to present voiding data as a function of electroplating chemistry and current density over a duration (up to 72 h) of isothermal annealing at 423 K (150 °C). Voiding data includes the average interfacial void size and average void density. Voids sizes grew proportionally as a function of thermal annealing time, whereas the void density grew initially very quickly but tended to saturate at a fixed density. A morphological evolution analysis called the physicochemical approach is utilised to understand the processes that occur when a voided Cu/Cu{sub 3}Sn interface causes changes to the IMC phase growth. The method is used to simulate the intermetallic thickness growths' response to interfacial voiding. The Cu/Cu{sub 3}Sn interface acts as a Cu diffusion barrier disrupting the diffusion of Cu. This resulted in a reduction in the Cu{sub 3}Sn thickness and an accelerated growth rate of Cu{sub 6}Sn{sub 5}. - Highlights: • Average void size is proportional linearly to thermal annealing time. • Average void density grows initially very rapidly followed by saturation. • Voids located close to the Cu/Cu{sub 3}Sn interface affect IMC growth rates. • Voids act as a diffusion barrier inhibiting Cu diffusion towards Sn. • Voids located at the interface cause Cu{sub 3}Sn to be consumed by Cu{sub 6}Sn{sub 5}.

  7. Into the void

    Energy Technology Data Exchange (ETDEWEB)

    Ross, Elsie

    2011-05-15

    Wormholes are formed in cold heavy oil production with sand (CHOPS) operations and can lead to serious degradation of oil production. In order to better understand this phenomena BP is working on the development of a model to predict wormhole formation, this model could help for reserve estimates or operations guidance. They designed a two component model to represent wormhole network: the first one, the BP CHOPS model, uses the reservoir simulation and the wellbore network; the second one, models interaction of advanced fluid structure. This model is a good framework for wormhole modeling but it needs to be improved with more physics. A collaboration with Los Alamos National Laboratory to apply its tool to simulate the wormhole's growth showed that its development is asymmetrical.

  8. Air void structure and frost resistance

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange

    2014-01-01

    ). This observation is interesting as the parameter of total surface area of air voids normally is not included in air void analysis. The following reason for the finding is suggested: In the air voids conditions are favourable for ice nucleation. When a capillary pore is connected to an air void, ice formation...... on that capillary pores are connected to air voids. The chance that a capillary pore is connected to an air void depends on the total surface area of air voids in the system, not the spacing factor.......This article compiles results from 4 independent laboratory studies. In each study, the same type of concrete is tested at least 10 times, the air void structure being the only variable. For each concrete mix both air void analysis of the hardened concrete and a salt frost scaling test...

  9. Void Nucleation and Growth in Nonlinear Solids

    National Research Council Canada - National Science Library

    Horgan, Cornelius

    1998-01-01

    .... Our research has been concerned with load diffusion in such structures. An understanding of the fundamental mechanisms of load diffusion in composite subcomponents is essential in developing primary composite structures...

  10. Finding Brazing Voids by Holography

    Science.gov (United States)

    Galluccio, R.

    1986-01-01

    Vibration-induced interference fringes reveal locations of defects. Holographic apparatus used to view object while vibrated ultrasonically. Interference fringes in hologram reveal brazing defects. Holographic technique locates small voids in large brazed joints. Identifies unbrazed regions 1 in. to second power (6 cm to the second power) or less in area.

  11. On the role of initial void geometry in plastic deformation of metallic thin films: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Su, Yanqing [School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332-0340 (United States); Xu, Shuozhi, E-mail: shuozhixu@gatech.edu [GWW School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405 (United States)

    2016-12-15

    Void growth is usually considered one of the most critical phases leading to dynamic fracture of ductile materials. Investigating the detailed process of void growth at the nanoscale aids in understanding the damage mechanism of metals. While most atomistic simulations by far assume circular or spherical voids for simplicity, recent studies highlight the significance of the initial void ellipticity in mechanical response of voided metals. In this work, we perform large scale molecular dynamics simulations with millions of atoms to investigate the void growth in plastic deformation of thin films in face-centered cubic Cu. It is found that the initial ellipticity and the initial orientation angle of the void have substantial impacts on the dislocation nucleation, the void evolution, and the stress-strain response. In particular, the initial dislocation emission sites and the sequence of slip plane activation vary with the initial void geometry. For the void size evolution, three regimes are identified: (I) the porosity increases relatively slowly in the absence of dislocations, (II) the porosity grows much more rapidly after dislocations start to glide on different slip planes, and (III) the rate of porosity variation becomes much more slowly when dislocations are saturated in the model, and the void surface becomes irregular, non-smooth. In terms of the stress-strain response, the effects of the initial orientation angle are more pronounced when the initial void ellipticity is large; the influence of the initial void ellipticity is different for different initial orientation angles. The effects of the temperature, the strain rate, the loading direction, and the initial porosity in the void growth are also explored. Our results reveal the underlying mechanisms of initial void geometry-dependent plastic deformation of metallic thin films and shed light on informing more accurate theoretical models.

  12. On the role of initial void geometry in plastic deformation of metallic thin films: A molecular dynamics study

    International Nuclear Information System (INIS)

    Su, Yanqing; Xu, Shuozhi

    2016-01-01

    Void growth is usually considered one of the most critical phases leading to dynamic fracture of ductile materials. Investigating the detailed process of void growth at the nanoscale aids in understanding the damage mechanism of metals. While most atomistic simulations by far assume circular or spherical voids for simplicity, recent studies highlight the significance of the initial void ellipticity in mechanical response of voided metals. In this work, we perform large scale molecular dynamics simulations with millions of atoms to investigate the void growth in plastic deformation of thin films in face-centered cubic Cu. It is found that the initial ellipticity and the initial orientation angle of the void have substantial impacts on the dislocation nucleation, the void evolution, and the stress-strain response. In particular, the initial dislocation emission sites and the sequence of slip plane activation vary with the initial void geometry. For the void size evolution, three regimes are identified: (I) the porosity increases relatively slowly in the absence of dislocations, (II) the porosity grows much more rapidly after dislocations start to glide on different slip planes, and (III) the rate of porosity variation becomes much more slowly when dislocations are saturated in the model, and the void surface becomes irregular, non-smooth. In terms of the stress-strain response, the effects of the initial orientation angle are more pronounced when the initial void ellipticity is large; the influence of the initial void ellipticity is different for different initial orientation angles. The effects of the temperature, the strain rate, the loading direction, and the initial porosity in the void growth are also explored. Our results reveal the underlying mechanisms of initial void geometry-dependent plastic deformation of metallic thin films and shed light on informing more accurate theoretical models.

  13. Role of material properties and mechanical constraint on stress-assisted diffusion in plate electrodes of lithium ion batteries

    International Nuclear Information System (INIS)

    Song Yicheng; Zhang Junqian; Shao Xianjun; Guo Zhansheng

    2013-01-01

    This work investigates the stress-assisted diffusion of lithium ions in layered electrodes of Li-ion batteries. Decoupled diffusion governing equations are obtained. Material properties, which are characterized by a single dimensionless parameter, and mechanical constraint between a current collector and an active layer, which is characterized by the elastic modulus ratio and thickness ratio between the layers, are identified as key factors that govern the stress-assisted diffusion. For a symmetric plate electrode, stress is induced by the Li-ion concentration gradient, and stress-assisted diffusion therefore depends only on the material properties. For an asymmetric bilayer electrode, mechanical constraint plays a very important role in the diffusion via generation of bending stress. Diffusion may be facilitated, or inversely impeded, according to the constraint. By summarizing the coupling factors of common active materials and investigating the concentration variation induced by stress-assisted diffusion in various electrodes, this work provides insights on stress-assisted diffusion in a layered electrode, as well as suggestions for relevant modelling works on whether the stress-assisted diffusion should be taken into account according to the selection of material and structure. (paper)

  14. CT measurements of SAP voids in concrete

    DEFF Research Database (Denmark)

    Laustsen, Sara; Bentz, Dale P.; Hasholt, Marianne Tange

    2010-01-01

    X-ray computed tomography (CT) scanning is used to determine the SAP void distribution in hardened concrete. Three different approaches are used to analyse a binary data set created from CT measurement. One approach classifies a cluster of connected, empty voxels (volumetric pixel of a 3D image......) as one void, whereas the other two approaches are able to classify a cluster of connected, empty voxels as a number of individual voids. Superabsorbent polymers (SAP) have been used to incorporate air into concrete. An advantage of using SAP is that it enables control of the amount and size...... of the created air voids. The results indicate the presence of void clusters. To identify the individual voids, special computational approaches are needed. The addition of SAP results in a dominant peak in two of the three air void distributions. Based on the position (void diameter) of the peak, it is possible...

  15. Analysis on void reactivity of DCA lattice

    International Nuclear Information System (INIS)

    Min, B. J.; Noh, K. H.; Choi, H. B.; Yang, M. K.

    2001-01-01

    In case of loss of coolant accident, the void reactivity of CANDU fuel provides the positive reactivity and increases the reactor power rapidly. Therefore, it is required to secure credibility of the void reactivity for the design and analysis of reactor, which motivated a study to assess the measurement data of void reactivity. The assessment of lattice code was performed with the experimental data of void reactivity at 30, 70, 87 and 100% of void fractions. The infinite multiplication factors increased in four types of fuels as the void fractions of them grow. The infinite multiplication factors of uranium fuels are almost within 1%, but those of Pu fuels are over 10% by the results of WIMS-AECL and MCNP-4B codes. Moreover, coolant void reactivity of the core loaded with plutonium fuel is more negative compared with that with uranium fuel because of spectrum hardening resulting from large void fraction

  16. Void migration in fusion materials

    International Nuclear Information System (INIS)

    Cottrell, G.A.

    2002-01-01

    Neutron irradiation in a fusion power plant will cause helium bubbles and voids to form in the armour and blanket structural materials. If sufficiently large densities of such defects accumulate on the grain boundaries of the materials, the strength and the lifetimes of the metals will be reduced by helium embrittlement and grain boundary failure. This Letter discusses void migration in metals, both by random Brownian motion and by biassed flow in temperature gradients. In the assumed five-year blanket replacement time of a fusion power plant, approximate calculations show that the metals most resilient to failure are tungsten and molybdenum, and marginally vanadium. Helium embrittlement and grain boundary failure is expected to be more severe in steel and beryllium

  17. Void migration in fusion materials

    Science.gov (United States)

    Cottrell, G. A.

    2002-04-01

    Neutron irradiation in a fusion power plant will cause helium bubbles and voids to form in the armour and blanket structural materials. If sufficiently large densities of such defects accumulate on the grain boundaries of the materials, the strength and the lifetimes of the metals will be reduced by helium embrittlement and grain boundary failure. This Letter discusses void migration in metals, both by random Brownian motion and by biassed flow in temperature gradients. In the assumed five-year blanket replacement time of a fusion power plant, approximate calculations show that the metals most resilient to failure are tungsten and molybdenum, and marginally vanadium. Helium embrittlement and grain boundary failure is expected to be more severe in steel and beryllium.

  18. Sodium voiding analysis in Kalimer

    International Nuclear Information System (INIS)

    Chang, Won-Pyo; Jeong, Kwan-Seong; Hahn, Dohee

    2001-01-01

    A sodium boiling model has been developed for calculations of the void reactivity feedback as well as the fuel and cladding temperatures in the KALIMER core after onset of sodium boiling. The sodium boiling in liquid metal reactors using sodium as coolant should be modeled because of phenomenon difference observed from that in light water reactor systems. The developed model is a multiple -bubble slug ejection model. It allows a finite number of bubbles in a channel at any time. Voiding is assumed to result from formation of bubbles that fill the whole cross section of the coolant channel except for liquid film left on the cladding surface. The vapor pressure, currently, is assumed to be uniform within a bubble. The present study is focused on not only demonstration of the sodium voiding behavior predicted by the developed model, but also confirmation on qualitative acceptance for the model. In results, the model catches important phenomena for sodium boiling, while further effort should be made for the complete analysis. (author)

  19. Effect of voids-controlled vacancy supersaturations on B diffusion

    International Nuclear Information System (INIS)

    Marcelot, O.; Claverie, A.; Cristiano, F.; Cayrel, F.; Alquier, D.; Lerch, W.; Paul, S.; Rubin, L.; Jaouen, H.; Armand, C.

    2007-01-01

    We present here preliminary results on boron diffusion in presence of pre-formed voids of different characteristics. The voids were fabricated by helium implantation followed by annealing allowing the desorption of He prior to boron implantation. We show that under such conditions boron diffusion is always largely reduced and can even be suppressed in some cases. Boron diffusion suppression can be observed in samples not containing nanovoids in the boron-rich region. It is suggested that direct trapping of Si(int)s by the voids is not the mechanism responsible for the reduction of boron diffusion in such layers. Alternatively, our experimental results suggest that this reduction of diffusivity is more probably due to the competition between two Ostwald ripening phenomena taking place at the same time: in the boron-rich region, the competitive growth of extrinsic defects at the origin of TED and, in the void region, the Ostwald ripening of the voids which involves large supersaturations of Vs

  20. Effect of voids-controlled vacancy supersaturations on B diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Marcelot, O. [CEMES/CNRS, 29 rue Jeanne Marvig, 31055 Toulouse (France)]. E-mail: marcelot@cemes.fr; Claverie, A. [CEMES/CNRS, 29 rue Jeanne Marvig, 31055 Toulouse (France); Cristiano, F. [LAAS/CNRS, 7 av. du Col. Roche, 31077 Toulouse (France); Cayrel, F. [LMP, Universite de Tours, 16 rue Pierre et Marie Curie, BP 7155, 37071 Tours (France); Alquier, D. [LMP, Universite de Tours, 16 rue Pierre et Marie Curie, BP 7155, 37071 Tours (France); Lerch, W. [Mattson Thermal Products GmbH, Daimlerstr. 10, D-89160 Dornstadt (Germany); Paul, S. [Mattson Thermal Products GmbH, Daimlerstr. 10, D-89160 Dornstadt (Germany); Rubin, L. [Axcelis Technologies, 108 Cherry Hill Drive, Beverly MA 01915 (United States); Jaouen, H. [STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles (France); Armand, C. [LNMO/INSA, Service analyseur ionique, 135 av. de Rangueil, 31077 Toulouse (France)

    2007-04-15

    We present here preliminary results on boron diffusion in presence of pre-formed voids of different characteristics. The voids were fabricated by helium implantation followed by annealing allowing the desorption of He prior to boron implantation. We show that under such conditions boron diffusion is always largely reduced and can even be suppressed in some cases. Boron diffusion suppression can be observed in samples not containing nanovoids in the boron-rich region. It is suggested that direct trapping of Si(int)s by the voids is not the mechanism responsible for the reduction of boron diffusion in such layers. Alternatively, our experimental results suggest that this reduction of diffusivity is more probably due to the competition between two Ostwald ripening phenomena taking place at the same time: in the boron-rich region, the competitive growth of extrinsic defects at the origin of TED and, in the void region, the Ostwald ripening of the voids which involves large supersaturations of Vs.

  1. Critical Void Volume Fraction fc at Void Coalescence for S235JR Steel at Low Initial Stress Triaxiality

    Science.gov (United States)

    Grzegorz Kossakowski, Paweł; Wciślik, Wiktor

    2017-10-01

    The paper is concerned with the nucleation, growth and coalescence of microdefects in the form of voids in S235JR steel. The material is known to be one of the basic steel grades commonly used in the construction industry. The theory and methods of damage mechanics were applied to determine and describe the failure mechanisms that occur when the material undergoes deformation. Until now, engineers have generally employed the Gurson-Tvergaard- Needleman model. This material model based on damage mechanics is well suited to define and analyze failure processes taking place in the microstructure of S235JR steel. It is particularly important to determine the critical void volume fraction fc , which is one of the basic parameters of the Gurson-Tvergaard-Needleman material model. As the critical void volume fraction fc refers to the failure stage, it is determined from the data collected for the void coalescence phase. A case of multi-axial stresses is considered taking into account the effects of spatial stress state. In this study, the parameter of stress triaxiality η was used to describe the failure phenomena. Cylindrical tensile specimens with a circumferential notch were analysed to obtain low values of initial stress triaxiality (η = 0.556 of the range) in order to determine the critical void volume fraction fc . It is essential to emphasize how unique the method applied is and how different it is from the other more common methods involving parameter calibration, i.e. curve-fitting methods. The critical void volume fraction fc at void coalescence was established through digital image analysis of surfaces of S235JR steel, which involved studying real, physical results obtained directly from the material tested.

  2. Influences of triple junctions on stress-assisted grain boundary motion in nanocrystalline materials

    International Nuclear Information System (INIS)

    Aramfard, Mohammad; Deng, Chuang

    2014-01-01

    Stress-assisted grain boundary motion is among the most studied modes of microstructural evolution in crystalline materials. In this study, molecular dynamics simulations were used to systematically investigate the influences of triple junctions on the stress-assisted motion of symmetric tilt grain boundaries in Cu by considering a honeycomb nanocrystalline model. It was found that the grain boundary motion in nanocrystalline models was highly sensitive to the loading mode, and a strong coupling effect which was prevalent in bicrystal models was only observed when simple shear was applied. In addition, the coupling factor extracted from the honeycomb model was found to be larger and more sensitive to temperature change than that from bicrystal models for the same type of grain boundary under the same loading conditions. Furthermore, the triple junctions seemed to exhibit unusual asymmetric pinning effects to the migrating grain boundary and the constraints by the triple junctions and neighboring grains led to remarkable non-linear grain boundary motion in directions both parallel and normal to the applied shear, which was in stark contrast to that observed in bicrystal models. In addition, dislocation nucleation and propagation, which were absent in the bicrystal model, were found to play an important role on shear-induced grain boundary motion when triple junctions were present. In the end, a generalized model for shear-assisted grain boundary motion was proposed based on the findings from this research. (paper)

  3. Nocturia: The circadian voiding disorder

    Directory of Open Access Journals (Sweden)

    Jin Wook Kim

    2016-05-01

    Full Text Available Nocturia is a prevalent condition of waking to void during the night. The concept of nocturia has evolved from being a symptomatic aspect of disease associated with the prostate or bladder to a form of lower urinary tract disorder. However, recent advances in circadian biology and sleep science suggest that it might be important to consider nocturia as a form of circadian dysfunction. In the current review, nocturia is reexamined with an introduction to sleep disorders and recent findings in circadian biology in an attempt to highlight the importance of rediscovering nocturia as a problem of chronobiology.

  4. The dark matter of galaxy voids

    Science.gov (United States)

    Sutter, P. M.; Lavaux, Guilhem; Wandelt, Benjamin D.; Weinberg, David H.; Warren, Michael S.

    2014-03-01

    How do observed voids relate to the underlying dark matter distribution? To examine the spatial distribution of dark matter contained within voids identified in galaxy surveys, we apply Halo Occupation Distribution models representing sparsely and densely sampled galaxy surveys to a high-resolution N-body simulation. We compare these galaxy voids to voids found in the halo distribution, low-resolution dark matter and high-resolution dark matter. We find that voids at all scales in densely sampled surveys - and medium- to large-scale voids in sparse surveys - trace the same underdensities as dark matter, but they are larger in radius by ˜20 per cent, they have somewhat shallower density profiles and they have centres offset by ˜ 0.4Rv rms. However, in void-to-void comparison we find that shape estimators are less robust to sampling, and the largest voids in sparsely sampled surveys suffer fragmentation at their edges. We find that voids in galaxy surveys always correspond to underdensities in the dark matter, though the centres may be offset. When this offset is taken into account, we recover almost identical radial density profiles between galaxies and dark matter. All mock catalogues used in this work are available at http://www.cosmicvoids.net.

  5. The Beckoning Void in Moravagine

    Directory of Open Access Journals (Sweden)

    Stephen K. Bellstrom

    1979-01-01

    Full Text Available The Chapter «Mascha,» lying at the heart of Cendrars's Moravagine , contains within it a variety of images and themes suggestive of emptiness. The philosophy of nihilism is exemplified in the motivations and actions of the group of terrorists seeking to plunge Russia into revolutionary chaos. Mascha's anatomical orifice, symbolizing both a biological and a psychological fault, and the abortion of her child, paralleled by the abortion of the revolutionary ideal among her comrades, are also emblematic of the chapter's central void. Moreover, Cendrars builds the theme of hollowness by describing Moravagine with images of omission, such as «empan» (space or span, «absent,» and «étranger.» Moravagine's presence, in fact, characteristically causes an undercurrent of doubt and uncertainty about the nature of reality to become overt. It is this parodoxical presence which seems to cause the narrator (and consequently the narrative to «lose» a day at the most critical moment of the story. By plunging the reader into the narrator's lapsus memoriae , Cendrars aims at creating a feeling of the kind of mental and cosmic disorder for which Moravagine is the strategist and apologist. This technique of insufficiency is an active technique, even though it relies on the passive idea of removing explanation and connecting details. The reader is invited, or lured, into the central void of the novel and, faced with unresolvable dilemmas, becomes involved in the same disorder that was initially produced.

  6. Elastic wave scattering from multiple voids (porosity)

    International Nuclear Information System (INIS)

    Thompson, D.O.; Rose, J.H.; Thompson, R.B.; Wormley, S.J.

    1983-01-01

    This paper describes the development of an ultrasonic backscatter measurement technique which provides a convenient way to determine certain characteristics of a distribution of voids (porosity) in materials. A typical ultrasonic sample prepared by placing the ''frit'' in a crucible in an RF induction heater is shown. The results of the measurements were Fourier transformed into an amplitude-frequency description, and were then deconvolved with the transducer response function. Several properties needed to characterize a void distribution are obtained from the experimental results, including average void size, the spatial extent of the voids region, the average void separation, and the volume fraction of material contained in the void distribution. A detailed comparison of values obtained from the ultrasonic measurements with visually determined results is also given

  7. Cosmology with void-galaxy correlations.

    Science.gov (United States)

    Hamaus, Nico; Wandelt, Benjamin D; Sutter, P M; Lavaux, Guilhem; Warren, Michael S

    2014-01-31

    Galaxy bias, the unknown relationship between the clustering of galaxies and the underlying dark matter density field is a major hurdle for cosmological inference from large-scale structure. While traditional analyses focus on the absolute clustering amplitude of high-density regions mapped out by galaxy surveys, we propose a relative measurement that compares those to the underdense regions, cosmic voids. On the basis of realistic mock catalogs we demonstrate that cross correlating galaxies and voids opens up the possibility to calibrate galaxy bias and to define a static ruler thanks to the observable geometric nature of voids. We illustrate how the clustering of voids is related to mass compensation and show that volume-exclusion significantly reduces the degree of stochasticity in their spatial distribution. Extracting the spherically averaged distribution of galaxies inside voids from their cross correlations reveals a remarkable concordance with the mass-density profile of voids.

  8. Stress assisted selective ablation of ITO thin film by picosecond laser

    Science.gov (United States)

    Farid, Nazar; Chan, Helios; Milne, David; Brunton, Adam; M. O'Connor, Gerard

    2018-01-01

    Fast selective pattering with high precession on 175 nm ITO thin film with IR ps lasers is investigated. Ablation parameters are optimized with detailed studies on the scribed depth, topography, and particle generation using AFM and SEM. A comparison of 10 and 150 ps laser revealed that the shorter pulse (10 ps) laser is more appropriate in selective and partial ablation; up to 20 nm resolution for controlled depth with multipulses having energy below the damage threshold is demonstrated. The experimental results are interpreted to involve stress assisted ablation mechanism for the 10 ps laser while thermal ablation along with intense melting occurs for 150 ps laser. The transition between these regimes is estimated to occur at approximately 30 ps.

  9. Development of the impedance void meter

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Moon Ki; Song, Chul Hwa; Won, Soon Yeon; Kim, Bok Deuk [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1994-06-01

    An impedance void meter is developed to measure the area-averaged void fraction. Its basic principle is based on the difference in the electrical conductivity between phases. Several methods of measuring void fraction are briefly reviewed and the reason why this type of void meter is chosen to develop is discussed. Basic principle of the measurement is thoroughly described and several design parameters to affect the overall function are discussed in detail. As example of applications is given for vertical air-water flow. It is shown that the current design has good dynamic response as well as very fine spatial resolution. (Author) 47 refs., 37 figs.

  10. Effect of grain size on void swelling in irradiated materials: A phase-field approach

    International Nuclear Information System (INIS)

    Chang, Kunok; Lee, Gyeonggeun; Kwon, Junhyun

    2014-01-01

    The progress of swelling is retarded as the average grain diameter increases in a pure copper case. Within the framework of the production bias model (PBM), their experimental results were quantitatively explained. The phase-field method has already been used to investigate the void/bubble behavior in the irradiated materials. In particular, Millett et al. already incorporated the interaction between the point defect and the grain boundary in their study. Therefore, they described the void denuded zones and void peaked zones adjacent to the grain boundaries, which are already observed in the experimental investigations. We performed the phase-field simulation in order to verify the role of the grain diameter on the void swelling in the cascade damage condition. In addition, our results will be compared with the experimental observations or the theoretical works, such as PBM. Two-dimensional phase-field simulations were performed to investigate the void swelling process in the irradiated materials. We clearly observed the void denuded and void peaked zones, which were already observed in formal experimental and computational approaches. We also found that the progress of swelling was retarded as the average grain diameter increased. The triple junctions, which are believed to be a critical factor t affecting the fracture, are the main cites for the void nucleation and growth in our simulations

  11. Studies of void formation in pure metals

    International Nuclear Information System (INIS)

    Lanore, J.M.; Glowinski, L.; Risbet, A.; Regnier, P.; Flament, J.L.; Levy, V.; Adda, Y.

    1975-01-01

    Recent experiments on the effect of gases on the final configuration of vacancy clustering (void or loop), and on the local effects at dislocations are described. The contribution of this data to a general knowledge of void formation will be discussed, and Monte Carlo calculations of swelling induced by irradiation with different particles presented [fr

  12. Void Fraction Instrument operation and maintenance manual

    International Nuclear Information System (INIS)

    Borgonovi, G.; Stokes, T.I.; Pearce, K.L.; Martin, J.D.; Gimera, M.; Graves, D.B.

    1994-09-01

    This Operations and Maintenance Manual (O ampersand MM) addresses riser installation, equipment and personnel hazards, operating instructions, calibration, maintenance, removal, and other pertinent information necessary to safely operate and store the Void Fraction Instrument. Final decontamination and decommissioning of the Void Fraction Instrument are not covered in this document

  13. Studies of void formation in pure metals

    International Nuclear Information System (INIS)

    Lanore, J.M.; Glowinski, L.; Risbet, A.; Regnier, P.; Flament, J.L.

    1975-01-01

    Recent experiments on the effect of gases on the final configuration of vacancy clustering (void or loop), and on the local effects at dislocations are described. The contribution of this data to our general knowledge of void formation will be discussed, and Monte Carlo calculations of swelling induced by irradiation with different particles presented

  14. Statistics and geometry of cosmic voids

    International Nuclear Information System (INIS)

    Gaite, José

    2009-01-01

    We introduce new statistical methods for the study of cosmic voids, focusing on the statistics of largest size voids. We distinguish three different types of distributions of voids, namely, Poisson-like, lognormal-like and Pareto-like distributions. The last two distributions are connected with two types of fractal geometry of the matter distribution. Scaling voids with Pareto distribution appear in fractal distributions with box-counting dimension smaller than three (its maximum value), whereas the lognormal void distribution corresponds to multifractals with box-counting dimension equal to three. Moreover, voids of the former type persist in the continuum limit, namely, as the number density of observable objects grows, giving rise to lacunar fractals, whereas voids of the latter type disappear in the continuum limit, giving rise to non-lacunar (multi)fractals. We propose both lacunar and non-lacunar multifractal models of the cosmic web structure of the Universe. A non-lacunar multifractal model is supported by current galaxy surveys as well as cosmological N-body simulations. This model suggests, in particular, that small dark matter halos and, arguably, faint galaxies are present in cosmic voids

  15. Void formation in irradiated binary nickel alloys

    International Nuclear Information System (INIS)

    Shaikh, M.A.; Ahmed, M.; Akhter, J.I.

    1994-01-01

    In this work a computer program has been used to compute void radius, void density and swelling parameter for nickel and binary nickel-carbon alloys irradiated with nickel ions of 100 keV. The aim is to compare the computed results with experimental results already reported

  16. Void Measurement by the ({gamma}, n) Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Rouhani, S Zia

    1962-09-15

    It is proposed to use the ({gamma}, n) reaction for the measurement of the integrated void volume fraction in two phase flow of D{sub 2}O inside a duct. This method is applicable to different channel geometries, and it is shown to be insensitive to the pattern of void distribution over the cross-sectional area of the channels The method has been tested on mock-ups of voids in a round duct of 6 mm inside diameter. About 40 m.c. {sup 24}Na was used as a source of gamma-rays. The test results show that the maximum measured error in this arrangement is less than 2.5 % (net void) for a range of 2.7 % to 44.44 % actual void volume fractions.

  17. Void Measurement by the (γ, n) Reaction

    International Nuclear Information System (INIS)

    Rouhani, S. Zia

    1962-09-01

    It is proposed to use the (γ, n) reaction for the measurement of the integrated void volume fraction in two phase flow of D 2 O inside a duct. This method is applicable to different channel geometries, and it is shown to be insensitive to the pattern of void distribution over the cross-sectional area of the channels The method has been tested on mock-ups of voids in a round duct of 6 mm inside diameter. About 40 m.c. 24 Na was used as a source of gamma-rays. The test results show that the maximum measured error in this arrangement is less than 2.5 % (net void) for a range of 2.7 % to 44.44 % actual void volume fractions

  18. Pores and Void in Asclepiades’ Physical Theory

    Science.gov (United States)

    Leith, David

    2012-01-01

    This paper examines a fundamental, though relatively understudied, aspect of the physical theory of the physician Asclepiades of Bithynia, namely his doctrine of pores. My principal thesis is that this doctrine is dependent on a conception of void taken directly from Epicurean physics. The paper falls into two parts: the first half addresses the evidence for the presence of void in Asclepiades’ theory, and concludes that his conception of void was basically that of Epicurus; the second half focuses on the precise nature of Asclepiadean pores, and seeks to show that they represent void interstices between the primary particles of matter which are the constituents of the human body, and are thus exactly analogous to the void interstices between atoms within solid objects in Epicurus’ theory. PMID:22984299

  19. On localization and void coalescence as a precursor to ductile fracture.

    Science.gov (United States)

    Tekoğlu, C; Hutchinson, J W; Pardoen, T

    2015-03-28

    Two modes of plastic flow localization commonly occur in the ductile fracture of structural metals undergoing damage and failure by the mechanism involving void nucleation, growth and coalescence. The first mode consists of a macroscopic localization, usually linked to the softening effect of void nucleation and growth, in either a normal band or a shear band where the thickness of the band is comparable to void spacing. The second mode is coalescence with plastic strain localizing to the ligaments between voids by an internal necking process. The ductility of a material is tied to the strain at macroscopic localization, as this marks the limit of uniform straining at the macroscopic scale. The question addressed is whether macroscopic localization occurs prior to void coalescence or whether the two occur simultaneously. The relation between these two modes of localization is studied quantitatively in this paper using a three-dimensional elastic-plastic computational model representing a doubly periodic array of voids within a band confined between two semi-infinite outer blocks of the same material but without voids. At sufficiently high stress triaxiality, a clear separation exists between the two modes of localization. At lower stress triaxialities, the model predicts that the onset of macroscopic localization and coalescence occur simultaneously. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  20. Constraints on Cosmology and Gravity from the Dynamics of Voids.

    Science.gov (United States)

    Hamaus, Nico; Pisani, Alice; Sutter, P M; Lavaux, Guilhem; Escoffier, Stéphanie; Wandelt, Benjamin D; Weller, Jochen

    2016-08-26

    The Universe is mostly composed of large and relatively empty domains known as cosmic voids, whereas its matter content is predominantly distributed along their boundaries. The remaining material inside them, either dark or luminous matter, is attracted to these boundaries and causes voids to expand faster and to grow emptier over time. Using the distribution of galaxies centered on voids identified in the Sloan Digital Sky Survey and adopting minimal assumptions on the statistical motion of these galaxies, we constrain the average matter content Ω_{m}=0.281±0.031 in the Universe today, as well as the linear growth rate of structure f/b=0.417±0.089 at median redshift z[over ¯]=0.57, where b is the galaxy bias (68% C.L.). These values originate from a percent-level measurement of the anisotropic distortion in the void-galaxy cross-correlation function, ϵ=1.003±0.012, and are robust to consistency tests with bootstraps of the data and simulated mock catalogs within an additional systematic uncertainty of half that size. They surpass (and are complementary to) existing constraints by unlocking cosmological information on smaller scales through an accurate model of nonlinear clustering and dynamics in void environments. As such, our analysis furnishes a powerful probe of deviations from Einstein's general relativity in the low-density regime which has largely remained untested so far. We find no evidence for such deviations in the data at hand.

  1. On the abundance of extreme voids II: a survey of void mass functions

    International Nuclear Information System (INIS)

    Chongchitnan, Siri; Hunt, Matthew

    2017-01-01

    The abundance of cosmic voids can be described by an analogue of halo mass functions for galaxy clusters. In this work, we explore a number of void mass functions: from those based on excursion-set theory to new mass functions obtained by modifying halo mass functions. We show how different void mass functions vary in their predictions for the largest void expected in an observational volume, and compare those predictions to observational data. Our extreme-value formalism is shown to be a new practical tool for testing void theories against simulation and observation.

  2. Void formation by annealing of neutron-irradiated plastically deformed molybdenum

    International Nuclear Information System (INIS)

    Petersen, K.; Nielsen, B.; Thrane, N.

    1976-01-01

    The positron annihilation technique has been used in order to study the influence of plastic deformation on the formation and growth of voids in neutron irradiated molybdenum single crystals treated by isochronal annealing. Samples were prepared in three ways: deformed 12-19% before irradiation, deformed 12-19% after irradiation, and - for reference purposes -non-deformed. In addition a polycrystalline sample was prepared in order to study the influence of the grain boundaries. All samples were irradiated at 60 0 C with a flux of 2.5 x 10 18 fast neutrons/cm 2 . After irradiation the samples were subjected to isochronal annealing. It was found that deformation before irradiation probably enhanced the formation of voids slightly. Deformation after irradiation strongly reduced the void formation. The presence of grain boundaries in the polycrystalline sample had a reducing influence on the growth of voids. (author)

  3. VIDE: The Void IDentification and Examination toolkit

    Science.gov (United States)

    Sutter, P. M.; Lavaux, G.; Hamaus, N.; Pisani, A.; Wandelt, B. D.; Warren, M.; Villaescusa-Navarro, F.; Zivick, P.; Mao, Q.; Thompson, B. B.

    2015-03-01

    We present VIDE, the Void IDentification and Examination toolkit, an open-source Python/C++ code for finding cosmic voids in galaxy redshift surveys and N-body simulations, characterizing their properties, and providing a platform for more detailed analysis. At its core, VIDE uses a substantially enhanced version of ZOBOV (Neyinck 2008) to calculate a Voronoi tessellation for estimating the density field and performing a watershed transform to construct voids. Additionally, VIDE provides significant functionality for both pre- and post-processing: for example, VIDE can work with volume- or magnitude-limited galaxy samples with arbitrary survey geometries, or dark matter particles or halo catalogs in a variety of common formats. It can also randomly subsample inputs and includes a Halo Occupation Distribution model for constructing mock galaxy populations. VIDE uses the watershed levels to place voids in a hierarchical tree, outputs a summary of void properties in plain ASCII, and provides a Python API to perform many analysis tasks, such as loading and manipulating void catalogs and particle members, filtering, plotting, computing clustering statistics, stacking, comparing catalogs, and fitting density profiles. While centered around ZOBOV, the toolkit is designed to be as modular as possible and accommodate other void finders. VIDE has been in development for several years and has already been used to produce a wealth of results, which we summarize in this work to highlight the capabilities of the toolkit. VIDE is publicly available at http://bitbucket.org/cosmicvoids/vide_public and http://www.cosmicvoids.net.

  4. A variational constitutive model for the distribution and interactions of multi-sized voids

    KAUST Repository

    Liu, Jinxing

    2013-07-29

    The evolution of defects or voids, generally recognized as the basic failure mechanism in most metals and alloys, has been intensively studied. Most investigations have been limited to spatially periodic cases with non-random distributions of the radii of the voids. In this study, we use a new form of the incompressibility of the matrix to propose the formula for the volumetric plastic energy of a void inside a porous medium. As a consequence, we are able to account for the weakening effect of the surrounding voids and to propose a general model for the distribution and interactions of multi-sized voids. We found that the single parameter in classical Gurson-type models, namely void volume fraction is not sufficient for the model. The relative growth rates of voids of different sizes, which can in principle be obtained through physical or numerical experiments, are required. To demonstrate the feasibility of the model, we analyze two cases. The first case represents exactly the same assumption hidden in the classical Gurson\\'s model, while the second embodies the competitive mechanism due to void size differences despite in a much simpler manner than the general case. Coalescence is implemented by allowing an accelerated void growth after an empirical critical porosity in a way that is the same as the Gurson-Tvergaard-Needleman model. The constitutive model presented here is validated through good agreements with experimental data. Its capacity for reproducing realistic failure patterns is shown by simulating a tensile test on a notched round bar. © 2013 The Author(s).

  5. Reliability of Single Crystal Silver Nanowire-Based Systems: Stress Assisted Instabilities.

    Science.gov (United States)

    Ramachandramoorthy, Rajaprakash; Wang, Yanming; Aghaei, Amin; Richter, Gunther; Cai, Wei; Espinosa, Horacio D

    2017-05-23

    Time-dependent mechanical characterization of nanowires is critical to understand their long-term reliability in applications, such as flexible-electronics and touch screens. It is also of great importance to develop a theoretical framework for experimentation and analysis on the mechanics of nanowires under time-dependent loading conditions, such as stress-relaxation and fatigue. Here, we combine in situ scanning electron microscope (SEM)/transmission electron microscope (TEM) tests with atomistic and phase-field simulations to understand the deformation mechanisms of single crystal silver nanowires held under constant strain. We observe that the nanowires initially undergo stress-relaxation, where the stress reduces with time and saturates after some time period. The stress-relaxation process occurs due to the formation of few dislocations and stacking faults. Remarkably, after a few hours the nanowires rupture suddenly. The reason for this abrupt failure of the nanowire was identified as stress-assisted diffusion, using phase-field simulations. Under a large applied strain, diffusion leads to the amplification of nanowire surface perturbation at long wavelengths and the nanowire fails at the stress-concentrated thin cross-sectional regions. An analytical analysis on the competition between the elastic energy and the surface energy predicts a longer time to failure for thicker nanowires than thinner ones, consistent with our experimental observations. The measured time to failure of nanowires under cyclic loading conditions can also be explained in terms of this mechanism.

  6. The correlation of local deformation and stress-assisted local phase transformations in MMC foams

    Energy Technology Data Exchange (ETDEWEB)

    Berek, H., E-mail: harry.berek@ikgb.tu-freiberg.de [TU Bergakademie Freiberg, Agricolastraße 17, D-09599 Freiberg (Germany); Ballaschk, U.; Aneziris, C.G. [TU Bergakademie Freiberg, Agricolastraße 17, D-09599 Freiberg (Germany); Losch, K.; Schladitz, K. [Fraunhofer ITWM, Fraunhoferplatz 1, D-67663 Kaiserslautern (Germany)

    2015-09-15

    Cellular structures are of growing interest for industry, and are of particular importance for lightweight applications. In this paper, a special case of metal matrix composite foams (MMCs) is investigated. The investigated foams are composed of austenitic steel exhibiting transformation induced plasticity (TRIP) and magnesia partially stabilized zirconia (Mg-PSZ). Both components exhibit martensitic phase transformation during deformation, thus generating the potential for improved mechanical properties such as strength, ductility, and energy absorption capability. The aim of these investigations was to show that stress-assisted phase transformations within the ceramic reinforcement correspond to strong local deformation, and to determine whether they can trigger martensitic phase transformations in the steel matrix. To this end, in situ interrupted compression experiments were performed in an X-ray computed tomography device (XCT). By using a recently developed registration algorithm, local deformation could be calculated and regions of interest could be defined. Corresponding cross sections were prepared and used to analyze the local phase composition by electron backscatter diffraction (EBSD). The results show a strong correlation between local deformation and phase transformation. - Graphical abstract: Display Omitted - Highlights: • In situ compressive deformation on MMC foams was performed in an XCT. • Local deformation fields and their gradient amplitudes were estimated. • Cross sections were manufactured containing defined regions of interest. • Local EBSD phase analysis was performed. • Local deformation and local phase transformation are correlated.

  7. The correlation of local deformation and stress-assisted local phase transformations in MMC foams

    International Nuclear Information System (INIS)

    Berek, H.; Ballaschk, U.; Aneziris, C.G.; Losch, K.; Schladitz, K.

    2015-01-01

    Cellular structures are of growing interest for industry, and are of particular importance for lightweight applications. In this paper, a special case of metal matrix composite foams (MMCs) is investigated. The investigated foams are composed of austenitic steel exhibiting transformation induced plasticity (TRIP) and magnesia partially stabilized zirconia (Mg-PSZ). Both components exhibit martensitic phase transformation during deformation, thus generating the potential for improved mechanical properties such as strength, ductility, and energy absorption capability. The aim of these investigations was to show that stress-assisted phase transformations within the ceramic reinforcement correspond to strong local deformation, and to determine whether they can trigger martensitic phase transformations in the steel matrix. To this end, in situ interrupted compression experiments were performed in an X-ray computed tomography device (XCT). By using a recently developed registration algorithm, local deformation could be calculated and regions of interest could be defined. Corresponding cross sections were prepared and used to analyze the local phase composition by electron backscatter diffraction (EBSD). The results show a strong correlation between local deformation and phase transformation. - Graphical abstract: Display Omitted - Highlights: • In situ compressive deformation on MMC foams was performed in an XCT. • Local deformation fields and their gradient amplitudes were estimated. • Cross sections were manufactured containing defined regions of interest. • Local EBSD phase analysis was performed. • Local deformation and local phase transformation are correlated

  8. Evaluation of the Air Void Analyzer

    Science.gov (United States)

    2013-07-01

    concrete using image analysis: Petrography of cementitious materials. ASTM STP 1215. S.M. DeHayes and D. Stark, eds. Philadelphia, PA: American...Administration (FHWA). 2006. Priority, market -ready technologies and innovations: Air Void Analyzer. Washington D.C. PDF file. Germann Instruments (GI). 2011...tests and properties of concrete and concrete-making materials. STP 169D. West Conshohocken, PA: ASTM International. Magura, D.D. 1996. Air void

  9. Using voids to unscreen modified gravity

    Science.gov (United States)

    Falck, Bridget; Koyama, Kazuya; Zhao, Gong-Bo; Cautun, Marius

    2018-04-01

    The Vainshtein mechanism, present in many models of gravity, is very effective at screening dark matter haloes such that the fifth force is negligible and general relativity is recovered within their Vainshtein radii. Vainshtein screening is independent of halo mass and environment, in contrast to e.g. chameleon screening, making it difficult to test. However, our previous studies have found that the dark matter particles in filaments, walls, and voids are not screened by the Vainshtein mechanism. We therefore investigate whether cosmic voids, identified as local density minima using a watershed technique, can be used to test models of gravity that exhibit Vainshtein screening. We measure density, velocity, and screening profiles of stacked voids in cosmological N-body simulations using both dark matter particles and dark matter haloes as tracers of the density field. We find that the voids are completely unscreened, and the tangential velocity and velocity dispersion profiles of stacked voids show a clear deviation from Λ cold dark matter at all radii. Voids have the potential to provide a powerful test of gravity on cosmological scales.

  10. Simulation of dust voids in complex plasmas

    Science.gov (United States)

    Goedheer, W. J.; Land, V.

    2008-12-01

    In dusty radio-frequency (RF) discharges under micro-gravity conditions often a void is observed, a dust free region in the discharge center. This void is generated by the drag of the positive ions pulled out of the discharge by the electric field. We have developed a hydrodynamic model for dusty RF discharges in argon to study the behaviour of the void and the interaction between the dust and the plasma background. The model is based on a recently developed theory for the ion drag force and the charging of the dust. With this model, we studied the plasma inside the void and obtained an understanding of the way it is sustained by heat generated in the surrounding dust cloud. When this heating mechanism is suppressed by lowering the RF power, the plasma density inside the void decreases, even below the level where the void collapses, as was recently shown in experiments on board the International Space Station. In this paper we present results of simulations of this collapse. At reduced power levels the collapsed central cloud behaves as an electronegative plasma with corresponding low time-averaged electric fields. This enables the creation of relatively homogeneous Yukawa balls, containing more than 100 000 particles. On earth, thermophoresis can be used to balance gravity and obtain similar dust distributions.

  11. Multipole analysis of redshift-space distortions around cosmic voids

    Energy Technology Data Exchange (ETDEWEB)

    Hamaus, Nico; Weller, Jochen [Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians Universität, Scheinerstr. 1, D-81679 München (Germany); Cousinou, Marie-Claude; Pisani, Alice; Aubert, Marie; Escoffier, Stéphanie, E-mail: hamaus@usm.lmu.de, E-mail: cousinou@cppm.in2p3.fr, E-mail: pisani@cppm.in2p3.fr, E-mail: maubert@cppm.in2p3.fr, E-mail: escoffier@cppm.in2p3.fr, E-mail: jochen.weller@usm.lmu.de [Aix Marseille Univ., CNRS/IN2P3, CPPM, 163 avenue de Luminy, F-13288, Marseille (France)

    2017-07-01

    We perform a comprehensive redshift-space distortion analysis based on cosmic voids in the large-scale distribution of galaxies observed with the Sloan Digital Sky Survey. To this end, we measure multipoles of the void-galaxy cross-correlation function and compare them with standard model predictions in cosmology. Merely considering linear-order theory allows us to accurately describe the data on the entire available range of scales and to probe void-centric distances down to about 2 h {sup −1}Mpc. Common systematics, such as the Fingers-of-God effect, scale-dependent galaxy bias, and nonlinear clustering do not seem to play a significant role in our analysis. We constrain the growth rate of structure via the redshift-space distortion parameter β at two median redshifts, β( z-bar =0.32)=0.599{sup +0.134}{sub −0.124} and β( z-bar =0.54)=0.457{sup +0.056}{sub −0.054}, with a precision that is competitive with state-of-the-art galaxy-clustering results. While the high-redshift constraint perfectly agrees with model expectations, we observe a mild 2σ deviation at z-bar =0.32, which increases to 3σ when the data is restricted to the lowest available redshift range of 0.15< z <0.33.

  12. Multipole analysis of redshift-space distortions around cosmic voids

    Science.gov (United States)

    Hamaus, Nico; Cousinou, Marie-Claude; Pisani, Alice; Aubert, Marie; Escoffier, Stéphanie; Weller, Jochen

    2017-07-01

    We perform a comprehensive redshift-space distortion analysis based on cosmic voids in the large-scale distribution of galaxies observed with the Sloan Digital Sky Survey. To this end, we measure multipoles of the void-galaxy cross-correlation function and compare them with standard model predictions in cosmology. Merely considering linear-order theory allows us to accurately describe the data on the entire available range of scales and to probe void-centric distances down to about 2 h-1Mpc. Common systematics, such as the Fingers-of-God effect, scale-dependent galaxy bias, and nonlinear clustering do not seem to play a significant role in our analysis. We constrain the growth rate of structure via the redshift-space distortion parameter β at two median redshifts, β(bar z=0.32)=0.599+0.134-0.124 and β(bar z=0.54)=0.457+0.056-0.054, with a precision that is competitive with state-of-the-art galaxy-clustering results. While the high-redshift constraint perfectly agrees with model expectations, we observe a mild 2σ deviation at bar z=0.32, which increases to 3σ when the data is restricted to the lowest available redshift range of 0.15

  13. Multipole analysis of redshift-space distortions around cosmic voids

    International Nuclear Information System (INIS)

    Hamaus, Nico; Weller, Jochen; Cousinou, Marie-Claude; Pisani, Alice; Aubert, Marie; Escoffier, Stéphanie

    2017-01-01

    We perform a comprehensive redshift-space distortion analysis based on cosmic voids in the large-scale distribution of galaxies observed with the Sloan Digital Sky Survey. To this end, we measure multipoles of the void-galaxy cross-correlation function and compare them with standard model predictions in cosmology. Merely considering linear-order theory allows us to accurately describe the data on the entire available range of scales and to probe void-centric distances down to about 2 h −1 Mpc. Common systematics, such as the Fingers-of-God effect, scale-dependent galaxy bias, and nonlinear clustering do not seem to play a significant role in our analysis. We constrain the growth rate of structure via the redshift-space distortion parameter β at two median redshifts, β( z-bar =0.32)=0.599 +0.134 −0.124 and β( z-bar =0.54)=0.457 +0.056 −0.054 , with a precision that is competitive with state-of-the-art galaxy-clustering results. While the high-redshift constraint perfectly agrees with model expectations, we observe a mild 2σ deviation at z-bar =0.32, which increases to 3σ when the data is restricted to the lowest available redshift range of 0.15< z <0.33.

  14. Conclusive evidence of abrupt coagulation inside the void during cyclic nanoparticle formation in reactive plasma

    International Nuclear Information System (INIS)

    Wetering, F. M. J. H. van de; Nijdam, S.; Beckers, J.

    2016-01-01

    In this letter, we present scanning electron microscopy (SEM) results that confirm in a direct way our earlier explanation of an abrupt coagulation event as the cause for the void hiccup. In a recent paper, we reported on the fast and interrupted expansion of voids in a reactive dusty argon–acetylene plasma. The voids appeared one after the other, each showing a peculiar, though reproducible, behavior of successive periods of fast expansion, abrupt contraction, and continued expansion. The abrupt contraction was termed “hiccup” and was related to collective coagulation of a new generation of nanoparticles growing in the void using relatively indirect methods: electron density measurements and optical emission spectroscopy. In this letter, we present conclusive evidence using SEM of particles collected at different moments in time spanning several growth cycles, which enables us to follow the nanoparticle formation process in great detail.

  15. Coolant Void Reactivity Analysis of CANDU Lattice

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin Su; Lee, Hyun Suk; Tak, Tae Woo; Lee, Deok Jung [UNIST, Ulsan (Korea, Republic of)

    2016-05-15

    Models of CANDU-6 and ACR-700 fuel lattices were constructed for a single bundle and 2 by 2 checkerboard to understand the physics related to CVR. Also, a familiar four factor formula was used to predict the specific contributions to reactivity change in order to achieve an understanding of the physics issues related to the CVR. At the same time, because the situation of coolant voiding should bring about a change of neutron behavior, the spectral changes and neutron current were also analyzed. The models of the CANDU- 6 and ACR-700 fuel lattices were constructed using the Monte Carlo code MCNP6 using the ENDF/B-VII.0 continuous energy cross section library based on the specification from AECL. The CANDU fuel lattice was searched through sensitivity studies of each design parameter such as fuel enrichment, fuel pitch, and types of burnable absorber for obtaining better behavior in terms of CVR. Unlike the single channel coolant voiding, the ACR-700 bundle has a positive reactivity change upon 2x2 checkerboard coolant voiding. Because of the new path for neutron moderation, the neutrons from the voided channel move to the no-void channel where they lose energy and come back to the voided channel as thermal neutrons. This phenomenon causes the positive CVR when checkerboard voiding occurs. The sensitivity study revealed the effects of the moderator to fuel volume ratio, fuel enrichment, and burnable absorber on the CVR. A fuel bundle with low moderator to fuel volume ratio and high fuel enrichment can help achieve negative CVR.

  16. 38 CFR 3.207 - Void or annulled marriage.

    Science.gov (United States)

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Void or annulled marriage... Void or annulled marriage. Proof that a marriage was void or has been annulled should consist of: (a... marriage void, together with such other evidence as may be required for a determination. (b) Annulled. A...

  17. Software quality assurance plan for void fraction instrument

    International Nuclear Information System (INIS)

    Gimera, M.

    1994-01-01

    Waste Tank SY-101 has been the focus of extensive characterization work over the past few years. The waste continually generates gases, most notably hydrogen, which are periodically released from the waste. Gas can be trapped in tank waste in three forms: as void gas (bubbles), dissolved gas, or absorbed gas. Void fraction is the volume percentage of a given sample that is comprised of void gas. The void fraction instrument (VFI) acquires the data necessary to calculate void fraction. This document covers the product, Void Fraction Data Acquisition Software. The void fraction software being developed will have the ability to control the void fraction instrument hardware and acquire data necessary to calculate the void fraction in samples. This document provides the software quality assurance plan, verification and validation plan, and configuration management plan for developing the software for the instrumentation that will be used to obtain void fraction data from Tank SY-101

  18. Post-void residual urine under 150 ml does not exclude voiding dysfunction in women

    DEFF Research Database (Denmark)

    Khayyami, Yasmine; Klarskov, Niels; Lose, Gunnar

    2016-01-01

    INTRODUCTION AND HYPOTHESIS: It has been claimed that post-void residual urine (PVR) below 150 ml rules out voiding dysfunction in women with stress urinary incontinence (SUI) and provides license to perform sling surgery. The cut-off of 150 ml seems arbitrary, not evidence-based, and so we sough...

  19. Nucleation of voids - the impurity effect

    International Nuclear Information System (INIS)

    Chen, I-W; Taiwo, A.

    1984-01-01

    Nucleation of voids under irradiation in multicomponent alloys remains an unsolved theoretical problem. Of particular interest are the effects of nonequilibrium solute segregation phenomena on the critical nucleus and the nucleation rate. The resolution of the multicomponent nucleation in a dissipative system also has broader implication to the field of irreversible thermodynamics. The present paper describes a recent study of solute segregation effects in void nucleation. We begin with a thermodynamic model for a nonequilibrium void with interfacial segregation. The thermodynamic model is coupled with kinetic considerations of solute/solvent diffusion under a bias, which is itself related to segregation by the coating effect, to assess the stability of void embryos. To determine nucleation rate, we develop a novel technique by extending the most probable path method in statistical mechanics for nonequilibrium steady state to simulate large fluctuation with nonlinear dissipation. The path of nucleation is determined by solving an analogous problem on particle trajectory in classical dynamics. The results of both the stability analysis and the fluctuation analysis establish the paramount significance of the impurity effect via the mechanism of nonequilibrium segregation. We conclude that over-segregation is probably the most general cause for the apparently low nucleation barriers that are responsible for nearly ubiquitous occurrence of void swelling in common metals

  20. Failure by void coalescence in metallic materials containing primary and secondary voids subject to intense shearing

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau; Tvergaard, Viggo

    2011-01-01

    Failure under intense shearing at close to zero stress triaxiality is widely observed for ductile metallic materials, and is identified in experiments as smeared-out dimples on the fracture surface. Numerical cell-model studies of equal sized voids have revealed that the mechanism governing...... this shear failure mode boils down to the interaction between primary voids which rotate and elongate until coalescence occurs under severe plastic deformation of the internal ligaments. The objective of this paper is to analyze this failure mechanism of primary voids and to study the effect of smaller...... secondary damage that co-exists with or nucleation in the ligaments between larger voids that coalesce during intense shearing. A numerical cell-model study is carried out to gain a parametric understanding of the overall material response for different initial conditions of the two void populations...

  1. Comparative study of void fraction models

    International Nuclear Information System (INIS)

    Borges, R.C.; Freitas, R.L.

    1985-01-01

    Some models for the calculation of void fraction in water in sub-cooled boiling and saturated vertical upward flow with forced convection have been selected and compared with experimental results in the pressure range of 1 to 150 bar. In order to know the void fraction axial distribution it is necessary to determine the net generation of vapour and the fluid temperature distribution in the slightly sub-cooled boiling region. It was verified that the net generation of vapour was well represented by the Saha-Zuber model. The selected models for the void fraction calculation present adequate results but with a tendency to super-estimate the experimental results, in particular the homogeneous models. The drift flux model is recommended, followed by the Armand and Smith models. (F.E.) [pt

  2. From Voids to Yukawaballs And Back

    International Nuclear Information System (INIS)

    Land, V.; Goedheer, W. J.

    2008-01-01

    When dust particles are introduced in a radio-frequency discharge under micro-gravity conditions, usually a dust free void is formed due to the ion drag force pushing the particles away from the center. Experiments have shown that it is possible to close the void by reducing the power supplied to the discharge. This reduces the ion density and with that the ratio between the ion drag force and the opposing electric force. We have studied the behavior of a discharge with a large amount of dust particles (radius 3.4 micron) with our hydrodynamic model, and simulated the closure of the void for conditions similar to the experiment. We also approached the formation of a Yukawa ball from the other side, starting with a discharge at low power and injecting batches of dust, while increasing the power to prevent extinction of the discharge. Eventually the same situation could be reached.

  3. Partial discharges in ellipsoidal and spheroidal voids

    DEFF Research Database (Denmark)

    Crichton, George C; Karlsson, P. W.; Pedersen, Aage

    1989-01-01

    Transients associated with partial discharges in voids can be described in terms of the charges induced on the terminal electrodes of the system. The relationship between the induced charge and the properties which are usually measured is discussed. The method is illustrated by applying it to a s......Transients associated with partial discharges in voids can be described in terms of the charges induced on the terminal electrodes of the system. The relationship between the induced charge and the properties which are usually measured is discussed. The method is illustrated by applying...

  4. Voids and overdensities of coupled Dark Energy

    International Nuclear Information System (INIS)

    Mainini, Roberto

    2009-01-01

    We investigate the clustering properties of dynamical Dark Energy even in association of a possible coupling between Dark Energy and Dark Matter. We find that within matter inhomogeneities, Dark Energy migth form voids as well as overdensity depending on how its background energy density evolves. Consequently and contrarily to what expected, Dark Energy fluctuations are found to be slightly suppressed if a coupling with Dark Matter is permitted. When considering density contrasts and scales typical of superclusters, voids and supervoids, perturbations amplitudes range from |δ φ | ∼ O(10 −6 ) to |δ φ | ∼ O(10 −4 ) indicating an almost homogeneous Dark Energy component

  5. Radar application in void and bar detection

    International Nuclear Information System (INIS)

    Amry Amin Abas; Mohamad Pauzi Ismail; Suhairy Sani

    2003-01-01

    Radar is one of the new non-destructive testing techniques for concrete and structures inspection. Radar is a non-ionizing electromagnetic wave that can penetrate deep into concrete or soil in about several tenths of meters. Method of inspection using radar enables us to perform high resolution detection, imaging and mapping of subsurface concrete and soil condition. This paper will discuss the use of radar for void and bar detection and sizing. The samples used in this paper are custom made samples and comparison will be made to validate the use of radar in detecting, locating and also size determination of voids and bars. (Author)

  6. Measurement of void fractions by nuclear techniques

    International Nuclear Information System (INIS)

    Hernandez G, A.; Vazquez G, J.; Diaz H, C.; Salinas R, G.A.

    1997-01-01

    In this work it is done a general analysis of those techniques used to determine void fractions and it is chosen a nuclear technique to be used in the heat transfer circuit of the Physics Department of the Basic Sciences Management. The used methods for the determination of void fractions are: radioactive absorption, acoustic techniques, average velocity measurement, electromagnetic flow measurement, optical methods, oscillating absorption, nuclear magnetic resonance, relation between pressure and flow oscillation, infrared absorption methods, sound neutron analysis. For the case of this work it will be treated about the radioactive absorption method which is based in the gamma rays absorption. (Author)

  7. Partial discharge patterns related to surface deterioration in voids in epoxy

    DEFF Research Database (Denmark)

    Holbøll, Joachim; Henriksen, Mogens

    1990-01-01

    Results are presented from an investigation of the relationship between changes in partial discharge patterns and the surface deterioration process taking place in small naturally formed spherical voids in epoxy plastic. The voids were exposed to a moderate electric stress above inception level......, where partial discharges were present for more than 1500 h. Two types of electrical tree growth were found, the bush like tree and a single channel-like tree, which led to very different partial discharge patterns. It is concluded that the formation of crystals on a void surface leads to an immediate...... and easy-to-detect increase in the partial discharge activity with subsequent severe surface deterioration (deep pit formations) in the vicinity of the crystal. However, the partial discharge signal from a specimen with a black channel-like tree structure did not give any indication of channel growth...

  8. Void nucleation by the helium atoms during lifetime of reactor pressure vessel

    International Nuclear Information System (INIS)

    Rahman, F.A.

    1984-01-01

    Void formation and growth has a great influence on the reactor pressure vessel steels during its lifetime and during post-irradiation annealing to increase its life. The present investigation aimed at the fact that if one can prevent void nucleation, accordingly one would not wary about void formation and growth. From that concept a model for helium production by transmutation reaction and corresponding swelling under irradiation conditions for several number of steels have been developed. This was done for recommending a steel type that can oppose such a phenomena. In the same time the present investigation gives a procedure utilizing such phenomena for checking the validity of pressure vessel steel used in the NPP

  9. The evolution of voids in the adhesion approximation

    Science.gov (United States)

    Sahni, Varun; Sathyaprakah, B. S.; Shandarin, Sergei F.

    1994-08-01

    We apply the adhesion approximation to study the formation and evolution of voids in the universe. Our simulations-carried out using 1283 particles in a cubical box with side 128 Mpc-indicate that the void spectrum evolves with time and that the mean void size in the standard Cosmic Background Explorer Satellite (COBE)-normalized cold dark matter (CDM) model with H50 = 1 scals approximately as bar D(z) = bar Dzero/(1+2)1/2, where bar Dzero approximately = 10.5 Mpc. Interestingly, we find a strong correlation between the sizes of voids and the value of the primordial gravitational potential at void centers. This observation could in principle, pave the way toward reconstructing the form of the primordial potential from a knowledge of the observed void spectrum. Studying the void spectrum at different cosmological epochs, for spectra with a built in k-space cutoff we find that the number of voids in a representative volume evolves with time. The mean number of voids first increases until a maximum value is reached (indicating that the formation of cellular structure is complete), and then begins to decrease as clumps and filaments erge leading to hierarchical clustering and the subsequent elimination of small voids. The cosmological epoch characterizing the completion of cellular structure occurs when the length scale going nonlinear approaches the mean distance between peaks of the gravitaional potential. A central result of this paper is that voids can be populated by substructure such as mini-sheets and filaments, which run through voids. The number of such mini-pancakes that pass through a given void can be measured by the genus characteristic of an individual void which is an indicator of the topology of a given void in intial (Lagrangian) space. Large voids have on an average a larger measure than smaller voids indicating more substructure within larger voids relative to smaller ones. We find that the topology of individual voids is strongly epoch dependent

  10. Friction stir welding process to repair voids in aluminum alloys

    Science.gov (United States)

    Rosen, Charles D. (Inventor); Litwinski, Edward (Inventor); Valdez, Juan M. (Inventor)

    1999-01-01

    The present invention provides an in-process method to repair voids in an aluminum alloy, particularly a friction stir weld in an aluminum alloy. For repairing a circular void or an in-process exit hole in a weld, the method includes the steps of fabricating filler material of the same composition or compatible with the parent material into a plug form to be fitted into the void, positioning the plug in the void, and friction stir welding over and through the plug. For repairing a longitudinal void (30), the method includes machining the void area to provide a trough (34) that subsumes the void, fabricating filler metal into a strip form (36) to be fitted into the trough, positioning the strip in the trough, and rewelding the void area by traversing a friction stir welding tool longitudinally through the strip. The method is also applicable for repairing welds made by a fusing welding process or voids in aluminum alloy workpieces themselves.

  11. The Metallicity of Void Dwarf Galaxies

    NARCIS (Netherlands)

    Kreckel, K.; Croxall, K.; Groves, B.; van de Weygaert, R.; Pogge, R. W.

    The current ΛCDM cosmological model predicts that galaxy evolution proceeds more slowly in lower density environments, suggesting that voids are a prime location to search for relatively pristine galaxies that are representative of the building blocks of early massive galaxies. To test the

  12. "Dark energy" in the Local Void

    Science.gov (United States)

    Villata, M.

    2012-05-01

    The unexpected discovery of the accelerated cosmic expansion in 1998 has filled the Universe with the embarrassing presence of an unidentified "dark energy", or cosmological constant, devoid of any physical meaning. While this standard cosmology seems to work well at the global level, improved knowledge of the kinematics and other properties of our extragalactic neighborhood indicates the need for a better theory. We investigate whether the recently suggested repulsive-gravity scenario can account for some of the features that are unexplained by the standard model. Through simple dynamical considerations, we find that the Local Void could host an amount of antimatter (˜5×1015 M ⊙) roughly equivalent to the mass of a typical supercluster, thus restoring the matter-antimatter symmetry. The antigravity field produced by this "dark repulsor" can explain the anomalous motion of the Local Sheet away from the Local Void, as well as several other properties of nearby galaxies that seem to require void evacuation and structure formation much faster than expected from the standard model. At the global cosmological level, gravitational repulsion from antimatter hidden in voids can provide more than enough potential energy to drive both the cosmic expansion and its acceleration, with no need for an initial "explosion" and dark energy. Moreover, the discrete distribution of these dark repulsors, in contrast to the uniformly permeating dark energy, can also explain dark flows and other recently observed excessive inhomogeneities and anisotropies of the Universe.

  13. Void porosity measurements in coastal structures

    NARCIS (Netherlands)

    Bosma, C.; Verhagen, H.J.; D'Angremond, K.; Sint Nicolaas, W.

    2002-01-01

    The paper describes the use of two fundamental design parameters, the void porosity and layer thickness in rock armour constructions. These design parameters are very sensible for factors such as the boundary definition of a rock layer, rock production properties, intrinsic properties and

  14. Void Structures in Regularly Patterned ZnO Nanorods Grown with the Hydrothermal Method

    Directory of Open Access Journals (Sweden)

    Yu-Feng Yao

    2014-01-01

    Full Text Available The void structures and related optical properties after thermal annealing with ambient oxygen in regularly patterned ZnO nanrorod (NR arrays grown with the hydrothermal method are studied. In increasing the thermal annealing temperature, void distribution starts from the bottom and extends to the top of an NR in the vertical (c-axis growth region. When the annealing temperature is higher than 400°C, void distribution spreads into the lateral (m-axis growth region. Photoluminescence measurement shows that the ZnO band-edge emission, in contrast to defect emission in the yellow-red range, is the strongest under the n-ZnO NR process conditions of 0.003 M in Ga-doping concentration and 300°C in thermal annealing temperature with ambient oxygen. Energy dispersive X-ray spectroscopy data indicate that the concentration of hydroxyl groups in the vertical growth region is significantly higher than that in the lateral growth region. During thermal annealing, hydroxyl groups are desorbed from the NR leaving anion vacancies for reacting with cation vacancies to form voids.

  15. Void fraction prediction in saturated flow boiling

    International Nuclear Information System (INIS)

    Francisco J Collado

    2005-01-01

    Full text of publication follows: An essential element in thermal-hydraulics is the accurate prediction of the vapor void fraction, or fraction of the flow cross-sectional area occupied by steam. Recently, the author has suggested to calculate void fraction working exclusively with thermodynamic properties. It is well known that the usual 'flow' quality, merely a mass flow rate ratio, is not at all a thermodynamic property because its expression in function of thermodynamic properties includes the slip ratio, which is a parameter of the process not a function of state. By the other hand, in the classic and well known expression of the void fraction - in function of the true mass fraction of vapor (also called 'static' quality), and the vapor and liquid densities - does not appear the slip ratio. Of course, this would suggest a direct procedure for calculating the void fraction, provided we had an accurate value of the true mass fraction of vapor, clearly from the heat balance. However the classic heat balance is usually stated in function of the 'flow' quality, what sounds really contradictory because this parameter, as we have noted above, is not at all a thermodynamic property. Then we should check against real data the actual relationship between the thermodynamic properties and the applied heat. For saturated flow boiling just from the inlet of the heated tube, and not having into account the kinetic and potential terms, the uniform applied heat per unit mass of inlet water and per unit length (in short, specific linear heat) should be closely related to a (constant) slope of the mixture enthalpy. In this work, we have checked the relation between the specific linear heat and the thermodynamic enthalpy of the liquid-vapor mixture using the actual mass fraction. This true mass fraction is calculated using the accurate measurements of the outlet void fraction taken during the Cambridge project by Knights and Thom in the sixties for vertical and horizontal

  16. Tank SY-101 void fraction instrument functional design criteria

    International Nuclear Information System (INIS)

    McWethy, L.M.

    1994-01-01

    This document presents the functional design criteria for design, analysis, fabrication, testing, and installation of a void fraction instrument for Tank SY-101. This instrument will measure the void fraction in the waste in Tank SY-101 at various elevations

  17. Risk management of low air void asphalt concrete mixtures.

    Science.gov (United States)

    2013-07-01

    Various forms of asphalt pavement distress, such as rutting, shoving and bleeding, can be attributed, in many cases, to low air voids in : the mixtures during production and placement. The occurrence of low air void contents during plant production m...

  18. Void formation in ODS EUROFER produced by hot isostatic pressing

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, Y.; Monge, M.A.; Munoz, A.; Leguey, T.; Pareja, R. [Madrid Univ. Carlos-3, Dept. de Fisica (Spain); Castro, V. de [Oxford Univ., Dept. of Materials (United Kingdom)

    2007-07-01

    for positrons trapped in voids. Unmilled EUROFER and the EUROFER plate did not show this behavior attributed to the formation of voids induced by annealing. The results indicate that the milling damage retained in the HIPed material has the capability to cluster into voids and growth by heating. These voids appear to be stable upon annealing 1323 K. (authors)

  19. Plasticity size effects in voided crystals

    DEFF Research Database (Denmark)

    Hussein, M. I.; Borg, Ulrik; Niordson, Christian Frithiof

    singularities in an elastic material. The lattice resistance to dislocation motion, dislocation nucleation, dislocation interaction with obstacles and annihilation are incorporated through a set of constitutive rules. Over the range of length scales investigated, both the discrete dislocation and strain......The shear and equi-biaxial straining responses of periodic voided single crystals are analysed using discrete dislocation plasticity and a continuum strain gradient crystal plasticity theory. In the discrete dislocation formulation the dislocations are all of edge character and are modelled as line...... predictions of the two formulations for all crystal types and void volume fractions considered when the material length scale in the non-local plasticity model chosen to be $0.325\\mu m$ (around ten times the slip plane spacing in the discrete dislocation models)....

  20. Plasticity size effects in voided crystals

    DEFF Research Database (Denmark)

    Hussein, M.I.; Borg, Ulrik; Niordson, Christian Frithiof

    2008-01-01

    as line singularities in an elastic material. The lattice resistance to dislocation motion, dislocation nucleation, dislocation interaction with obstacles and annihilation are incorporated through a set of constitutive rules. Over the range of length scales investigated, both the discrete dislocation......The shear and equi-biaxial straining responses of periodic voided single crystals are analysed using discrete dislocation plasticity and a continuum strain gradient crystal plasticity theory. In the discrete dislocation formulation, the dislocations are all of edge character and are modelled...... between predictions of the two formulations for all crystal types and void volume fractions considered when the material length scale in the non-local plasticity model is chosen to be 0.325 mu m (about 10 times the slip plane spacing in the discrete dislocation models)....

  1. Effect of void cluster on ductile failure evolution

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2016-01-01

    The behavior of a non-uniform void distribution in a ductile material is investigated by using a cell model analysis to study a material with a periodic pattern of void clusters. The special clusters considered consist of a number of uniformly spaced voids located along a plane perpendicular...

  2. Void probability scaling in hadron nucleus interactions

    International Nuclear Information System (INIS)

    Ghosh, Dipak; Deb, Argha; Bhattacharyya, Swarnapratim; Ghosh, Jayita; Bandyopadhyay, Prabhat; Das, Rupa; Mukherjee, Sima

    2002-01-01

    Heygi while investigating with the rapidity gap probability (that measures the chance of finding no particle in the pseudo-rapidity interval Δη) found that a scaling behavior in the rapidity gap probability has a close correspondence with the scaling of a void probability in galaxy correlation study. The main aim in this paper is to study the scaling behavior of the rapidity gap probability

  3. Neutron gauging to detect voids in polyurethane

    International Nuclear Information System (INIS)

    Tsang, F.Y.; Alger, D.M.; Brugger, R.M.

    1978-01-01

    Thermal-neutron radiography and fast-neutron gauging measurements were made to evaluate the feasibility of detecting voids in a polyurethane block placed between steel plates. This sandwich of polyurethane and steel simulates the walls of a canister being designed to hold explosive devices. The polyurethane would act as a shock absorber in the canister. A large fabrication cost saving would result by casting the polyurethane, but a nondestructive testing (NDT) method is needed to determine the uniformity of the polyurethane fill. The radiography measurements used a beam of thermal neutrons, while the gauging used filtered beams of 24 keV and fission spectrum neutrons. For the 83-mm-thick polyurethane and 130-mm-thick steel matrix, the thermal-neutron radiography was able to detect only those voids equal to about one-half the polyurethane thickness. The gauging detected voids in the path of the neutron beam of a few millimetres thickness in seconds to minutes. The gauging is feasible as an NDT method for the canister application

  4. Transcutaneous sacral neurostimulation for irritative voiding dysfunction.

    Science.gov (United States)

    Walsh, I K; Johnston, R S; Keane, P F

    1999-01-01

    Patients with irritative voiding dysfunction are often unresponsive to standard clinical treatment. We evaluated the response of such individuals to transcutaneous electrical stimulation of the third sacral nerve. 32 patients with refractory irritative voiding dysfunction (31 female and 1 male; mean age 47 years) were recruited to the study. Ambulatory transcutaneous electrical neurostimulation was applied bilaterally to the third sacral dermatomes for 1 week. Symptoms of frequency, nocturia, urgency, and bladder pain were scored by each patient throughout and up to 6 months following treatment. The mean daytime frequency was reduced from 11.3 to 7.96 (p = 0.01). Nocturia episodes were reduced from a mean of 2.6 to 1.8 (p = 0.01). Urgency and bladder pain mean symptom scores were reduced from 5.97 to 4.89 and from 1.48 to 0.64, respectively. After stopping therapy, symptoms returned to pretreatment levels within 2 weeks in 40% of the patients and within 6 months in 100%. Three patients who continued with neurostimulation remained satisfied with this treatment modality at 6 months. Transcutaneous third sacral nerve stimulation may be an effective and noninvasive ambulatory technique for the treatment of patients with refractory irritative voiding dysfunction. Following an initial response, patients may successfully apply this treatment themselves to ensure long-term relief.

  5. Void fraction measurements using neutron radiography

    International Nuclear Information System (INIS)

    Glickstein, S.S.; Vance, W.H.; Joo, H.

    1992-01-01

    Real-time neutron radiography is being evaluated for studying the dynamic behavior of two phase flow and for measuring void fraction in vertical and inclined water ducts. This technique provides a unique means of visualizing the behavior of fluid flow inside thick metal enclosures. To simulate vapor conditions encountered in a fluid flow duct, an air-water flow system was constructed. Air was injected into the bottom of the duct at flow rates up to 0.47 I/s (1 cfm). The water flow rate was varied between 0--3.78 I/m (0--1 gpm). The experiments were performed at the Pennsylvania State University nuclear reactor facility using a real-time neutron radiography camera. With a thermal neutron flux on the order of 10 6 n/cm 2 /s directed through the thin duct dimension, the dynamic behavior of the air bubbles was clearly visible through 5 cm (2 in.) thick aluminum support plates placed on both sides of the duct wall. Image analysis techniques were employed to extract void fractions from the data which was recorded on videotape. This consisted of time averaging 256 video frames and measuring the gray level distribution throughout the region. The distribution of the measured void fraction across the duct was determined for various air/water mixtures. Details of the results of experiments for a variety of air and water flow conditions are presented

  6. Vesicoureteral reflux in children: comparison of contrast - enhanced voiding ultrasonography with radiographic voiding cystourethrography - preliminary report

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Chong Hyun; Kim, Hyun Joo; Goo, Hyun Woo; Kim, Hungy; Lee, Jung Joo; Kim, Ellen Ai-Rhan; Kim, Ki Soo; Park, Young Seo; Pi, Soo Young [Ulsan Univ. College of Medicine, Seoul (Korea, Republic of)

    2001-01-01

    To compared the usefullness of contrst-enhanced voiding ultrasonogrphy (US) with that of radiogrphic voiding cystourethrography (VCUG) for the diagnosis of vesicoureteral reflux (VUR) in children. Ninety-five kidney-ureter units of 47 patients referred for investigation of VUR underwent contrast -enhanced voiding US followed by radiographic VCUG. After baseline US examination of the urinaru tract, residual urine in the bladder was drained through an inserted Foley catheter and the bladder was gravityfilled at a height of 1 m with normal saline. A galactose-based, microbubble-containning echo-enhancing agent (Lvovist; Dchering, Berlin, Germany) was then administered. The amount of this was approximately 10% of bldder capacity, and VUR was diagnosed when microbubbles appeared in the ureter or pelvocalyceal system. Using radiographic VCUG as a reference point, the accuracy with which contrst-enhanced voiding US detected VUR was calcilated. In 87 of 95 kidney-ureter units (91.6%), the two methods showed similiar results regarding the diagnosis or exclusion of VUR, which was detected by both in 12 units, but by neither in 75. VUR was shown to occcur in a total of 20 units, but in eight of these by one method only. In two units, VUR detected by contrast-enhanced voiding US was was not demostarted by radiographic VCUG; in six units, the resverse was true. In the detection of VUR, contrast-enhanced voiding us showed a sensitivity of 66.7%, a sprcificity of 97.4%, a positive predictive value of 85.7%, and a negative predictive value of 92.6%. Contrst-enhanced voiding US is highly specific and has high positive and nagative predictive values; its sensitivity, however, is not sufficiently high. The modality appears to be a useful diagnostic tool for the detection of VUR without exposure to ionizing radiation, though to be certain of its value, more experience of its use its first required.

  7. Vesicoureteral reflux in children: comparison of contrast - enhanced voiding ultrasonography with radiographic voiding cystourethrography - preliminary report

    International Nuclear Information System (INIS)

    Yoon, Chong Hyun; Kim, Hyun Joo; Goo, Hyun Woo; Kim, Hungy; Lee, Jung Joo; Kim, Ellen Ai-Rhan; Kim, Ki Soo; Park, Young Seo; Pi, Soo Young

    2001-01-01

    To compared the usefullness of contrst-enhanced voiding ultrasonogrphy (US) with that of radiogrphic voiding cystourethrography (VCUG) for the diagnosis of vesicoureteral reflux (VUR) in children. Ninety-five kidney-ureter units of 47 patients referred for investigation of VUR underwent contrast -enhanced voiding US followed by radiographic VCUG. After baseline US examination of the urinaru tract, residual urine in the bladder was drained through an inserted Foley catheter and the bladder was gravityfilled at a height of 1 m with normal saline. A galactose-based, microbubble-containning echo-enhancing agent (Lvovist; Dchering, Berlin, Germany) was then administered. The amount of this was approximately 10% of bldder capacity, and VUR was diagnosed when microbubbles appeared in the ureter or pelvocalyceal system. Using radiographic VCUG as a reference point, the accuracy with which contrst-enhanced voiding US detected VUR was calcilated. In 87 of 95 kidney-ureter units (91.6%), the two methods showed similiar results regarding the diagnosis or exclusion of VUR, which was detected by both in 12 units, but by neither in 75. VUR was shown to occcur in a total of 20 units, but in eight of these by one method only. In two units, VUR detected by contrast-enhanced voiding US was was not demostarted by radiographic VCUG; in six units, the resverse was true. In the detection of VUR, contrast-enhanced voiding us showed a sensitivity of 66.7%, a sprcificity of 97.4%, a positive predictive value of 85.7%, and a negative predictive value of 92.6%. Contrst-enhanced voiding US is highly specific and has high positive and nagative predictive values; its sensitivity, however, is not sufficiently high. The modality appears to be a useful diagnostic tool for the detection of VUR without exposure to ionizing radiation, though to be certain of its value, more experience of its use its first required

  8. Measurements of void fraction by an improved multi-channel conductance void meter

    International Nuclear Information System (INIS)

    Song, Chul-Hwa; Chung, Moon Ki; No, Hee Cheon

    1998-01-01

    An improved multi-channel Conductance Void Meter (CVM) was developed to measure a void fraction. Its measuring principle is basically based upon the differences of electrical conductance of a two-phase mixture due to the variation of void fraction around a sensor. The sensor is designed to be flush-mounted to the inner wall of the test section to avoid the flow disturbances. The signal processor with three channels is specially designed so as to minimize the inherent error due to the phase difference between channels. It is emphasized that the guard electrodes are electrically shielded in order not to affect the measurements of two-phase mixture conductance, but to make the electric fields evenly distributed in a measuring volume. Void fraction is measured for bubbly and slug flow regimes in a vertical air-water loop, and statistical signal processing techniques are applied to show that CVM has a good dynamic resolution which is required to investigate the structural developments of bubbly flow and the propagation of void waves in a flow channel. (author)

  9. Voiding dysfunction in children aged five to 15 years

    Directory of Open Access Journals (Sweden)

    Karaklajić Dragana

    2004-01-01

    Full Text Available Voiding dysfunction in children was analyzed in 91 patients in a period from January 1st to October 1st 1998. Most of the patients had functional voiding disorder (92.31%, and only 7.69% manifested monosymptomatic night enuresis. The number of girls was bigger in the group of patients with voiding dysfunction while the boys were predominant in the group with mono-symptomatic nocturnal enuresis. More than a half of children with functional voiding disorder had repeated urinal infections (58.23%, incontinence (93.49%, need for urgent voiding (68.13%, and vesicoureteral reflux (47.61%. The most common type of voiding dysfunction was urge syndrome/urge incontinence. The incidence of dysfunctional voiding disorder was more often in children with scaring changes of kidney which were diagnosed by static scintigraphy.

  10. On the observability of coupled dark energy with cosmic voids

    Science.gov (United States)

    Sutter, P. M.; Carlesi, Edoardo; Wandelt, Benjamin D.; Knebe, Alexander

    2015-01-01

    Taking N-body simulations with volumes and particle densities tuned to match the sloan digital sky survey DR7 spectroscopic main sample, we assess the ability of current void catalogues to distinguish a model of coupled dark matter-dark energy from Λ cold dark matter cosmology using properties of cosmic voids. Identifying voids with the VIDE toolkit, we find no statistically significant differences in the ellipticities, but find that coupling produces a population of significantly larger voids, possibly explaining the recent result of Tavasoli et al. In addition, we use the universal density profile of Hamaus et al. to quantify the relationship between coupling and density profile shape, finding that the coupling produces broader, shallower, undercompensated profiles for large voids by thinning the walls between adjacent medium-scale voids. We find that these differences are potentially measurable with existing void catalogues once effects from survey geometries and peculiar velocities are taken into account.

  11. Mechanistic model for void distribution in flashing flow

    International Nuclear Information System (INIS)

    Riznic, J.; Ishii, M.; Afgan, N.

    1987-01-01

    A problem of discharging of an initially subcooled liquid from a high pressure condition into a low pressure environment is quite important in several industrial systems such as nuclear reactors and chemical reactors. A new model for the flashing process is proposed here based on the wall nucleation theory, bubble growth model and drift-flux bubble transport model. In order to calculate the bubble number density, the bubble number transport equation with a distributed source from the wall nucleation sites is used. The model predictions in terms of the void fraction are compared to Moby Dick and BNL experimental data. It shows that satisfactory agreements could be obtained from the present model without any floating parameter to be adjusted with data. This result indicates that, at least for the experimental conditions considered here, the mechanistic prediction of the flashing phenomenon is possible based on the present wall nucleation based model. 43 refs., 4 figs

  12. Water tests for determining post voiding behavior in the LMFBR

    International Nuclear Information System (INIS)

    Hinkle, W.D.

    1976-06-01

    The most serious of the postulated accidents considered in the design of the Liquid Metal Cooled Fast Breeder Reactor (LMFBR) is the Loss of Pipe Integrity (LOPI) accident. Analysis models used to calculate the consequences of this accident assume that once boiling is initiated film dryout occurs in the hot assembly as a result of rapid vapor bubble growth and consequent flow stoppage or reversal. However, this assumption has not been put to any real test. Once boiling is initiated in the hot assembly during an LMFBR LOPI accident, a substantial gravity pressure difference would exist between this assembly and other colder assemblies in the core. This condition would give rise to natural circulation flow boiling accompanied by pressure and flow oscillations. It is possible that such oscillations could prevent or delay dryout and provide substantial post-voiding heat removal. The tests described were conceived with the objective of obtaining basic information and data relating to this possibility

  13. Dependence of hotspot initiation on void distribution in high explosive crystals simulated with molecular dynamics

    Science.gov (United States)

    Herring, Stuart Davis

    Microscopic defects may dramatically affect the susceptibility of high explosives to shock initiation. Such defects redirect the shock's energy and become hotspots (concentrations of stress and heat) that can initiate chemical reactions. Sufficiently large or numerous defects may produce a self-sustaining deflagration or even detonation from a shock notably too weak to detonate defect-free samples. The effects of circular or spherical voids on the shock sensitivity of a model (two- or three-dimensional) high explosive crystal are considered. We simulate a piston impact using molecular dynamics with a Reactive Empirical Bond Order (REBO) model potential for a sub-micron, sub-ns exothermic reaction in a diatomic molecular solid. In both dimensionalities, the probability of initiating chemical reactions rises more suddenly with increasing piston velocity for larger voids that collapse more deterministically. A void of even 10 nm radius (˜39 interatomic spacings) reduces the minimum initiating velocity by a factor of 4 (8 in 3D). The transition at larger velocities to detonation is studied in micron-long samples with a single void (and its periodic images). Reactions during the shock traversal increase rapidly with velocity, then become a reliable detonation. In 2D, a void of radius 2.5 nm reduces the critical velocity by 10% from the perfect crystal; a Pop plot of the detonation delays at higher velocities shows a characteristic pressure dependence. 3D samples are more likely to react but less to detonate. In square lattices of voids, reducing the (common) void radius or increasing the porosity without changing the other parameter causes the hotspots to consume the material faster and detonation to occur sooner and at lower velocities. Early behavior is seen to follow a very simple ignition and growth model; the pressure exponents are more realistic than with single voids. The hotspots collectively develop a broad pressure wave (a sonic, diffuse deflagration front

  14. Effects of alloying elements on defect structures in the incubation period for void swelling in austenitic stainless steels

    International Nuclear Information System (INIS)

    Horiki, M.; Yoshiie, T.; Huang, S.S.; Sato, K.; Cao, X.Z.; Xu, Q.; Troev, T.D.

    2013-01-01

    Positron lifetime measurements were used to study the effects of alloying elements on the defect structure during the incubation period for void swelling in several fcc model alloys. Pure Ni, four model alloys (Fe–Cr–Ni, Fe–Cr–Ni–Mo–Mn, Fe–Cr–Ni–Mo–Mn–Si and Fe–Cr–Ni–Mo–Mn–Si–Ti), and four commercial alloys (SUS316LSS, SUS316SS, SUS304SS and Ti added modified SUS316SS) were irradiated with electrons and neutrons. Even at 363 and 573 K to a dose of 0.2 dpa, an effect of alloying elements was observed. At 363 K irradiation, voids were formed only in Ni and Fe–Cr–Ni. At 573 K irradiation, voids were formed in Ni and all model alloys, though the concentration depended on the alloying elements. In commercial alloys, precipitates were formed instead of vacancy clusters, which prevented void growth

  15. IAEA sodium void reactivity benchmark calculations

    International Nuclear Information System (INIS)

    Hill, R.N.; Finck, P.J.

    1992-01-01

    In this paper, the IAEA-1 992 ''Benchmark Calculation of Sodium Void Reactivity Effect in Fast Reactor Core'' problem is evaluated. The proposed design is a large axially heterogeneous oxide-fueled fast reactor as described in Section 2; the core utilizes a sodium plenum above the core to enhance leakage effects. The calculation methods used in this benchmark evaluation are described in Section 3. In Section 4, the calculated core performance results for the benchmark reactor model are presented; and in Section 5, the influence of steel and interstitial sodium heterogeneity effects is estimated

  16. Patient dose reduction during voiding cystourethrography

    International Nuclear Information System (INIS)

    Ward, Valerie L.

    2006-01-01

    Voiding cystourethrography (VCUG) is a commonly performed examination in a pediatric uroradiology practice. This article contains suggestions on how the radiation dose to a child from VCUG can be made ''as low as reasonably achievable'' (ALARA). The pediatric radiologist should consider the appropriateness of the clinical indication before performing VCUG and utilize radiation exposure techniques and parameters during VCUG to reduce radiation exposure to a child. The medical physicist and fluoroscope manufacturer can also work together to optimize a pulsed-fluoroscopy unit and further reduce the radiation exposure. Laboratory and clinical research is necessary to investigate methods that reduce radiation exposures during VCUG, and current research is presented here. (orig.)

  17. Morphological Segregation in the Surroundings of Cosmic Voids

    Energy Technology Data Exchange (ETDEWEB)

    Ricciardelli, Elena; Tamone, Amelie [Laboratoire d’Astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), 1290 Sauverny (Switzerland); Cava, Antonio [Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix (Switzerland); Varela, Jesus, E-mail: elena.ricciardelli@epfl.ch [Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza San Juan 1, E-44001 Teruel (Spain)

    2017-09-01

    We explore the morphology of galaxies living in the proximity of cosmic voids, using a sample of voids identified in the Sloan Digital Sky Survey Data Release 7. At all stellar masses, void galaxies exhibit morphologies of a later type than galaxies in a control sample, which represent galaxies in an average density environment. We interpret this trend as a pure environmental effect, independent of the mass bias, due to a slower galaxy build-up in the rarefied regions of voids. We confirm previous findings about a clear segregation in galaxy morphology, with galaxies of a later type being found at smaller void-centric distances with respect to the early-type galaxies. We also show, for the first time, that the radius of the void has an impact on the evolutionary history of the galaxies that live within it or in its surroundings. In fact, an enhanced fraction of late-type galaxies is found in the proximity of voids larger than the median void radius. Likewise, an excess of early-type galaxies is observed within or around voids of a smaller size. A significant difference in galaxy properties in voids of different sizes is observed up to 2 R {sub void}, which we define as the region of influence of voids. The significance of this difference is greater than 3 σ for all the volume-complete samples considered here. The fraction of star-forming galaxies shows the same behavior as the late-type galaxies, but no significant difference in stellar mass is observed in the proximity of voids of different sizes.

  18. A NEW STATISTICAL PERSPECTIVE TO THE COSMIC VOID DISTRIBUTION

    International Nuclear Information System (INIS)

    Pycke, J-R; Russell, E.

    2016-01-01

    In this study, we obtain the size distribution of voids as a three-parameter redshift-independent log-normal void probability function (VPF) directly from the Cosmic Void Catalog (CVC). Although many statistical models of void distributions are based on the counts in randomly placed cells, the log-normal VPF that we obtain here is independent of the shape of the voids due to the parameter-free void finder of the CVC. We use three void populations drawn from the CVC generated by the Halo Occupation Distribution (HOD) Mocks, which are tuned to three mock SDSS samples to investigate the void distribution statistically and to investigate the effects of the environments on the size distribution. As a result, it is shown that void size distributions obtained from the HOD Mock samples are satisfied by the three-parameter log-normal distribution. In addition, we find that there may be a relation between the hierarchical formation, skewness, and kurtosis of the log-normal distribution for each catalog. We also show that the shape of the three-parameter distribution from the samples is strikingly similar to the galaxy log-normal mass distribution obtained from numerical studies. This similarity between void size and galaxy mass distributions may possibly indicate evidence of nonlinear mechanisms affecting both voids and galaxies, such as large-scale accretion and tidal effects. Considering the fact that in this study, all voids are generated by galaxy mocks and show hierarchical structures in different levels, it may be possible that the same nonlinear mechanisms of mass distribution affect the void size distribution.

  19. Relationship between voided volume and the urge to void among patients with lower urinary tract symptoms.

    Science.gov (United States)

    Blaivas, Jerry G; Tsui, Johnson F; Amirian, Michael; Ranasinghe, Buddima; Weiss, Jeffrey P; Haukka, Jari; Tikkinen, Kari A O

    2014-12-01

    The aim of this study was to explore the relationship between voided volume (VV) and urge to void among patients with lower urinary tract symptoms. Consecutive adult patients (aged 23-90 years) were enrolled, and completed a 24 h bladder diary and the Urgency Perception Scale (UPS). Patients were categorized as urgency or non-urgency based on the Overactive Bladder Symptom Score. The relationship between UPS and VV (based on the bladder diary) was analyzed by Spearman's rho and proportional odds model. In total, 1265 micturitions were evaluated in 117 individuals (41 men, 76 women; 56 individuals in the urgency and 61 in the non-urgency group). The mean (± SD) VV and UPS were 192 ± 127 ml and 2.4 ± 1.2 ml in the urgency group and 173 ± 124 ml and 1.7 ± 1.1 ml in the non-urgency group, respectively. Spearman's rho (between UPS and VV) was 0.21 [95% confidence interval (CI) 0.13-029, p < 0.001] for the urgency group, 0.32 (95% CI 0.25-0.39, p < 0.001) for the non-urgency group, and 0.28 (95% CI 0.23-0.33, p < 0.001) for the total cohort. Urgency patients had higher UPS [odds ratio (OR) 3.1, 95% CI 2.5-3.8]. Overall, each additional 50 ml VV increased the odds of having a higher UPS with OR 1.2 (95% CI 1.2-1.3). The relationship between VV and UPS score was similar in both groups (p = 0.548 for interaction). Although urgency patients void with a higher UPS score, among both urgency and non-urgency patients there is only a weak correlation between VV and the urge to void. This suggests that there are factors other than VV that cause the urge to void.

  20. Void migration, coalescence and swelling in fusion materials

    International Nuclear Information System (INIS)

    Cottrell, G.A.

    2003-01-01

    A recent analysis of the migration of voids and bubbles, produced in neutron irradiated fusion materials, is outlined. The migration, brought about by thermal hopping of atoms on the surface of a void, is normally a random Brownian motion but, in a temperature gradient, can be slightly biassed up the gradient. Two effects of such migrations are the transport of voids and trapped transmutation helium atoms to grain boundaries, where embrittlement may result; and the coalescence of migrating voids, which reduces the number of non-dislocation sites available for the capture of knock-on point defects and thereby enables the dislocation bias process to maintain void swelling. A selection of candidate fusion power plant armour and structural metals have been analysed. The metals most resistant to void migration and its effects are tungsten and molybdenum. Steel and beryllium are least so and vanadium is intermediate

  1. Dependence of calculated void reactivity on film-boiling representation

    International Nuclear Information System (INIS)

    Whitlock, J.; Garland, W.

    1992-01-01

    Partial voiding of a fuel channel can lead to complicated neutronic analysis, because of highly nonuniform spatial distributions. An investigation of the distribution dependence of void reactivity in a Canada deuterium uranium (CANDU) lattice, specifically in the regime of film boiling, was done. Although the core is not expected to be critical at the time of sheath dryout, this study augments current knowledge of void reactivity in this type of lattice

  2. Anticavitation and Differential Growth in Elastic Shells

    KAUST Repository

    Moulton, Derek E.; Goriely, Alain

    2010-01-01

    infinite growth or resorption is imposed at the inner surface of the shell. However, void collapse can occur in a limiting sense when radial and circumferential growth are properly balanced. Growth functions which diverge or vanish at a point arise

  3. Void shrinkage in stainless steel during high energy electron irradiation

    International Nuclear Information System (INIS)

    Singh, B.N.; Foreman, A.J.E.

    1976-03-01

    During irradiation of thin foils of an austenitic stainless steel in a high voltage electron microscope, steadily growing voids have been observed to suddenly shrink and disappear at the irradiation temperature of 650 0 Cthe phenomenon has been observed in specimens both with and withoutimplanted helium. Possible mechanisms for void shrinkage during irradiation are considered. It is suggested that the dislocation-pipe-diffusion of vacancies from or of self-interstitial atoms to the voids can explain the shrinkage behaviour of voids observed during our experiments. (author)

  4. Void fraction instrument acceptance test procedure

    International Nuclear Information System (INIS)

    Stokes, T.I.; Pearce, K.L.

    1994-01-01

    This document presents the results of the acceptance test for the mechanical and electrical features (not specifically addressed by the software ATP) of the void fraction instrument (VFI). Acceptance testing of the VFI, control console, and decontamination spray assembly was conducted in the 306E building high bay and area adjacent to the facility. The VFI was tested in the horizontal position supported in multiple locations on rolling tables. The control console was located next to the VFI pneumatic control assembly. The VFI system was operated exactly as is expected in the tank farm, with the following exceptions: power was provided from a building outlet and the VFI was horizontal. The testing described in this document verifies that the mechanical and electrical features are operating as designed and that the unit is ready for field service

  5. How to perform the perfect voiding cystourethrogram

    International Nuclear Information System (INIS)

    Agrawalla, Seema; Pearce, Rowena; Goodman, T.Robin

    2004-01-01

    The voiding cystourethrogram (VCUG) examination is a difficult investigation to perform and is a stressful experience for patients and their parents, as well as for the radiologists, technicians and paediatric radiology nurses involved in the examination. Despite the VCUG being one of the most commonly performed fluoroscopic procedures in paediatric radiology practice, there is no general consensus as to the best way to perform this investigation. This is particularly concerning when one considers the potentially high gonadal radiation dose children may receive. Because of this, we have undertaken a comprehensive literature review of various aspects of the test in order to determine the best way to perform the VCUG in modern paediatric radiology practice. (orig.)

  6. Dynamics of core voiding during boiloff experiments

    International Nuclear Information System (INIS)

    Analytis, G.T.; Aksan, S.N.; Stierli, F.; Yadigaroglu, G.

    1987-01-01

    A series of boiloff experiments were conducted at the EIR NEPTUN test facility with a bundle consisting of 37 PWR fuel rod simulators. The test section was filled with subcooled coolant and the power was turned on. After an initial heatup phase, coolant was expelled from the test section due to rapid vapor generation near the mid-plane where the power generation was highest. Gradual boiloff of the remaining water followed. It was found that the ''collapsed liquid level'' (CLL) and the rod temperature histories could be predicted well, provided the initial expulsion of the coolant was calculated correctly. The axial void fraction and enthalpy profiles calculated with TRAC-BD/MOD1 provided the information needed for understanding the importance of heat transfer to the coolant before the inception of vapor generation, and the sensitivity of the results to the interfacial friction correlation used

  7. Effect of metallurgical variables on void swelling

    International Nuclear Information System (INIS)

    Johnston, W.G.; Lauritzen, T.; Rosolowski, J.H.; Turkalo, A.M.

    1976-01-01

    The mechanism of void swelling is reviewed briefly and the anticipated effects of metallurgical variables are described. Experimental results showing the effects of metallurgical variables are reviewed, most of the work being done by simulation methods employing charged particle bombardments to simulate reactor damage. Although the early emphasis was on structural variables such as grain size, cold work and precipitates to control swelling, it now seems that the practical reduction of swelling will be achieved by modifying alloy composition. Void swelling is strongly influenced by the relative amounts of Fe, Cr, and Ni in an alloy; the amount of swelling can be varied by three orders of magnitude by changing the relative amounts of the three elements in an austenitic ternary alloy. The effect of composition on swelling of a simple ferritic alloy will also be described. The swelling of a simple austenitic alloy of Fe, Cr, and Ni can be reduced by certain minor element additions. The most effective swelling inhibitors are Si, Ti, Zr, and Nb, and combinations of Si and Ti are synergetic. Swelling reductions of two orders of magnitude have been achieved with combined additions. Predictions of swelling in commercial solid solution alloys are made on the basis of the present knowledge of the effects of major composition and minor element additions. The predictions agree with experimental results. For more complex commercial alloys, predictions are made for the effects on swelling of heat treatments that cause changes in matrix composition. In some cases, heat treatment is expected to change the peak swelling by more than a factor of ten, and to shift the peak swelling temperature by almost 100 0 C. Sensitivity of swelling to detailed matrix composition places emphasis on the need for developing understanding of the stability of structure and local composition in an irradiation environment

  8. Post Operative Voiding Efficacy after Anterior Colporrhaphy

    Directory of Open Access Journals (Sweden)

    Behnoosh Miladpoor

    2010-02-01

    Full Text Available The aim of this study was to determine the most effective and suitable time to remove the urinary catheter (Foley after anterior and posterior colporrhaphy surgery. Patients who experience anterior Colporrhaphy operation for genuine stress incontinency or pelvic organ prolapsed will have post operative voiding dysfunction. These patients need postoperative drainage. One of the methods preferred for this purpose is to apply Foley Catheter, but there is no particular regimen available for the exact time of catheter removal in these patients. We have tried to find out the best time to remove Foley catheter after which the repeated Foley catheter is not required or minimized. One hundred and eighty nine patients who have been undergone Colporrhaphy have been selected randomly and divided into three groups' as 1, 2 and 4 days of catheter removal. The number of patients in each group was 62, 63 and 64 respectively. In all three groups, before removing urinary catheter, it was clamped every 4 hrs, for 3 times. After removing of Foley, the patients were guided for urination; the voiding and residual volume was measured. In the patients with an increase of residual volume, the  repeated Foley requirement was increased. However,  5.6 % of the patients with residual volume of ≤ 33 percent and 23.9% of the patients with residual volume between 33 to 68 percent, and finally  64.8% of the patients with residual volume of ≥ 68% had repeated Foley insertion. When considering the number of days, 85, 65 and 35.7 percent of the patients needed repeated Foley after 1, 2, and 4 days of catheter removal respectively. Interestingly, in the third group ( 4 days of the catheter removal with residual volume of ≤ 33% the repeated Foley requirement was nil, with no increase risk of urinary infection. We suggest that the best time to remove the urinary Foley catheter after anterior and posterior Colporrhaphy is the day four.

  9. Generalized Rate Theory for Void and Bubble Swelling and its Application to Plutonium Metal Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Allen, P. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wolfer, W. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-10-16

    In the classical rate theory for void swelling, vacancies and self-interstitials are produced by radiation in equal numbers, and in addition, thermal vacancies are also generated at the sinks, primarily at edge dislocations, at voids, and at grain boundaries. In contrast, due to the high formation energy of self-interstitials for normal metals and alloys, their thermal generation is negligible, as pointed out by Bullough and Perrin. However, recent DFT calculations of the formation energy of self-interstitial atoms in bcc metals have revealed that the sum of formation and migration energies for self-interstitials atoms (SIA) is of the same order of magnitude as for vacancies. The ratio of the activation energies for thermal generation of SIA and vacancies is presented. For fcc metals, this ratio is around three, but for bcc metals it is around 1.5. Reviewing theoretical predictions of point defect properties in δ-Pu, this ratio could possibly be less than one. As a result, thermal generation of SIA in bcc metals and in plutonium must be taken into considerations when modeling the growth of voids and of helium bubbles, and the classical rate theory (CRT) for void and bubble swelling must be extended to a generalized rate theory (GRT).

  10. Shock loading and reactive flow modeling studies of void induced AP/AL/HTPB propellant

    Science.gov (United States)

    Miller, P. J.; Lindfors, A. J.

    1998-07-01

    The unreactive Hugoniot of a class 1.3 propellant has been investigated by shock compression experiments. The results are analyzed in terms of an ignition and growth reactive flow model using the DYNA2D hydrocode. The calculated shock ignition parameters of the model show a linear dependence on measured void volume which appears to reproduce the observed gauge records well. Shock waves were generated by impact in a 75 mm single stage powder gun. Manganin and PVDF pressure gauges provided pressure-time histories to 140 kbar. The propellants were of similar formulation differing only in AP particle size and the addition of a burn rate modifer (Fe2O3) from that of previous investigations. Results show neglible effect of AP particle size on shock response in contrast to the addition of Fe2O3 which appears to `stiffen' the unreactive Hugoniot and enhances significantly the reactive rates under shock. The unreactive Hugoniot, within experimental error, compares favorably to the solid AP Hugoniot. Shock experiments were performed on propellant samples strained to induce insitu voids. The material state was quantified by uniaxial tension dialatometry. The experimental records show a direct correlation between void volume (0 to 1.7%) and chemical reactivity behind the shock front. These results are discussed in terms of `hot spot' ignition resulting from the shock collapse of the voids.

  11. Void worths in subcritical cores cooled by lead-bismuth

    International Nuclear Information System (INIS)

    Wallenius, Janne; Tucek, Kamil; Gudowski, Waclaw

    2001-01-01

    The introduction lead-bismuth coolant in accelerator driven transmutation systems (ADS) was: good neutron economy (higher source efficiency); natural circulation possible (decay heat removal); synergy with spallation target (simplified coolant management); high temperature of boiling (larger overpower margin); smaller void worths (operation at higher k-values). This paper deals with different aspects of the void worths in JAERI ADS

  12. Voids and the Cosmic Web: cosmic depression & spatial complexity

    NARCIS (Netherlands)

    van de Weygaert, Rien; Shandarin, S.; Saar, E.; Einasto, J.

    2016-01-01

    Voids form a prominent aspect of the Megaparsec distribution of galaxies and matter. Not only do theyrepresent a key constituent of the Cosmic Web, they also are one of the cleanest probesand measures of global cosmological parameters. The shape and evolution of voids are highly sensitive tothe

  13. Void nucleation in spheroidized steels during tensile deformation

    International Nuclear Information System (INIS)

    Fisher, J.R. Jr.

    1980-04-01

    An investigation was conducted to determine the effects of various mechanical and material parameters on void formation at cementite particles in axisymmetric tensile specimens of spheroidized plain carbon steels. Desired microstructures for each of three steel types were obtained. Observations of void morphology with respect to various microstructural features were made using optical and scanning electron microscopy

  14. Alignment of galaxy spins in the vicinity of voids

    International Nuclear Information System (INIS)

    Slosar, Anže; White, Martin

    2009-01-01

    We provide limits on the alignment of galaxy orientations with the direction to the void center for galaxies lying near the edges of voids. We locate spherical voids in volume limited samples of galaxies from the Sloan Digital Sky Survey using the HB inspired void finder and investigate the orientation of (color selected) spiral galaxies that are nearly edge-on or face-on. In contrast with previous literature, we find no statistical evidence for departure from random orientations. Expressed in terms of the parameter c, introduced by Lee and Pen to describe the strength of such an alignment, we find that c0.11(0.13) at 95% (99.7%) confidence limit within a context of a toy model that assumes a perfectly spherical voids with sharp boundaries

  15. Structural control of void formation in dual phase steels

    DEFF Research Database (Denmark)

    Azuma, Masafumi

    The objective of this study is to explore the void formation mechanisms and to clarify the influence of the hardness and structural parameters (volume fraction, size and morphology) of martensite particles on the void formation and mechanical properties in dual phase steels composed of ferrite...... and (iii) strain localization. The critical strain for void formation depends on hardness of the martensite, but is independent of the volume fraction, shape, size and distribution of the martensite. The strain partitioning between the martensite and ferrite depends on the volume fraction and hardness...... of the martensite accelerates the void formation in the martensite by enlarging the size of voids both in the martensite and ferrite. It is suggested that controlling the hardness and structural parameters associated with the martensite particles such as morphology, size and volume fraction are the essential...

  16. KETAHANAN HIDUP BEBERAPA JENIS TUMBUHAN DI KAWASAN VOID BEKAS TAMBANG BATUBARA

    Directory of Open Access Journals (Sweden)

    Kissinger Kissinger

    2018-04-01

    Full Text Available The selection of plant species for phytoremediation activities is very important in the conservation of soil, water, plant, and animal life to create a conducive environment within a community or ecosystem. Plant survival is one indication for the selection of phytoremediation plants. This study aims to determine the survival of some plants in void areas of coal mining. Types of plants used are surface water plants species and the edge of void plant species. The plants of surface water area consisting of Kiambang (Salvinia sp., Enceng gondok (Eichornia crassipes, Genjer (Limnocharis flava, and Kangkung (Ipomoea aquatica. The plants which planted on edge of void were purun tikus (Eleocharis dulcis and Bamban (Donax canniformis. Time of observation time was 6 months. Data were analyzed using a tabular matrix that contained the percentage of plant life/period time. The growth of the plant is specifically defined according to the color visibility and the development of plant form. The results of the study found that the highest surface survival species were Kiambang (Salvinia sp. and Kangkung (Ipomoea aquatica. Both of them still survive for 6 months of observation. The growth percentage of these two plants at the end of the observations are 36% and 20% respectively. Enceng gondok (Eichhornia crassipes has a survival for 4 months. Whole water plant growth was depressed by indications of death, tendencies to yellowish-brownish or blackish, and smaller body parts. Purun tikus (Eleocharis dulcis and Bamban (Donax canniformis grown on the edge of voids have a high survival. Both of them showed ≥95% survival at the end of observation time.

  17. Growth

    Science.gov (United States)

    John R. Jones; George A. Schier

    1985-01-01

    This chapter considers aspen growth as a process, and discusses some characteristics of the growth and development of trees and stands. For the most part, factors affecting growth are discussed elsewhere, particularly in the GENETICS AND VARIATION chapter and in chapters in PART 11. ECOLOGY. Aspen growth as it relates to wood production is examined in the WOOD RESOURCE...

  18. RELAXATION OF BLAZAR-INDUCED PAIR BEAMS IN COSMIC VOIDS

    Energy Technology Data Exchange (ETDEWEB)

    Miniati, Francesco [Physics Department, Wolfgang-Pauli-Strasse 27, ETH-Zuerich, CH-8093 Zuerich (Switzerland); Elyiv, Andrii, E-mail: fm@phys.ethz.ch [Institut d' Astrophysique et de Geophysique, Universite de Liege, B-4000 Liege (Belgium)

    2013-06-10

    The stability properties of a low-density ultrarelativistic pair beam produced in the intergalactic medium (IGM) by multi-TeV gamma-ray photons from blazars are analyzed. The problem is relevant for probes of magnetic field in cosmic voids through gamma-ray observations. In addition, dissipation of such beams could considerably affect the thermal history of the IGM and structure formation. We use a Monte Carlo method to quantify the properties of the blazar-induced electromagnetic shower, in particular the bulk Lorentz factor and the angular spread of the pair beam generated by the shower, as a function of distance from the blazar itself. We then use linear and nonlinear kinetic theory to study the stability of the pair beam against the growth of electrostatic plasma waves, employing the Monte Carlo results for our quantitative estimates. We find that the fastest growing mode, like any perturbation mode with even a very modest component perpendicular to the beam direction, cannot be described in the reactive regime. Due to the effect of nonlinear Landau damping, which suppresses the growth of plasma oscillations, the beam relaxation timescale is found to be significantly longer than the inverse Compton loss time. Finally, density inhomogeneities associated with cosmic structure induce loss of resonance between the beam particles and plasma oscillations, strongly inhibiting their growth. We conclude that relativistic pair beams produced by blazars in the IGM are stable on timescales that are long compared with the electromagnetic cascades. There appears to be little or no effect of pair beams on the IGM.

  19. Radionuclide voiding cystography in intrarenal reflux detection

    International Nuclear Information System (INIS)

    Rizzoni, G.; Perale, R.; Bui, F.; Pitter, M.; Pavanello, L.; Boscolo, R.; Passerini Glazel, G.; Macri, C.

    1986-01-01

    In order to evaluate the possibility of detecting intra-renal reflux (IRR) with a more sensitive procedure, 48 children with recurrent urinary tract infections underwent intravenous urography (IVU) and voiding cystourethrogram (VCU) using a solution containing contrast medium and sup(99m)Tc-sulfur colloid particles which are known to persist in the renal parenchyma for a long time. Scintigraphic images were taken at 5 and 20 hours after VCU. 18 children had no vesico-ureteral reflux, 11 showed unilateral and 19 bilateral VUR, which was therefore present in 49 renal units. Among the 49 renal refluxing units (RRUs) IRR was detected radiologically in 8; of these isotopic activity in the renal area was present in all 6 RRUs who were examined at 20 hours. Of the remaining 41 RRUs with no radiologically detectable IRR 24 were evaluated at 20 hours and 5 (21%) showed renal radioactivity. Renal scars were significantly more frequent in kidneys with radioisotopic activity at 20 hours. The results of this study indicate that radionuclide cystography using sup(99m)Tc-sulfur colloid is a reliable procedure for demonstrating IRR, and to this end is more sensitive than X-ray VCU. Radionuclide cystography with sulfur colloid particles should therefore be considered a simple and useful complementary procedure, which is more sensitive than X-ray VCU in the diagnosis and follow-up of IRR

  20. Kirkendall void formation in reverse step graded Si1-xGex/Ge/Si(001) virtual substrates

    Science.gov (United States)

    Sivadasan, Vineet; Rhead, Stephen; Leadley, David; Myronov, Maksym

    2018-02-01

    Formation of Kirkendall voids is demonstrated in the Ge underlayer of reverse step graded Si1-xGex/Ge buffer layers grown on Si(001) using reduced pressure chemical vapour deposition (RP-CVD). This phenomenon is seen when the constant composition Si1-xGex layer is grown at high temperatures and for x ≤ 0.7. The density and size of the spherical voids can be tuned by changing Ge content in the Si1-xGex and other growth parameters.

  1. Partial discharges within two spherical voids in an epoxy resin

    International Nuclear Information System (INIS)

    Illias, H A; Mokhlis, H; Tunio, M A; Chen, G; Bakar, A H A

    2013-01-01

    A void in a dielectric insulation material may exist due to imperfection in the insulation manufacturing or long term stressing. Voids have been identified as one of the common sources of partial discharge (PD) activity within an insulation system, such as in cable insulation and power transformers. Therefore, it is important to study PD phenomenon within void cavities in insulation. In this work, a model of PD activity within two spherical voids in a homogeneous dielectric material has been developed using finite element analysis software to study the parameters affecting PD behaviour. The parameters that have been taken into account are the void surface conductivity, electron generation rate and the inception and extinction fields. Measurements of PD activity within two spherical voids in an epoxy resin under ac sinusoidal applied voltage have also been performed. The simulation results have been compared with the measurement data to validate the model and to identify the parameters affecting PD behaviour. Comparison between measurements of PD activity within single and two voids in a dielectric material have also been made to observe the difference of the results under both conditions. (paper)

  2. The association of age of toilet training and dysfunctional voiding

    Directory of Open Access Journals (Sweden)

    Hodges SJ

    2014-10-01

    Full Text Available Steve J Hodges, Kyle A Richards, Ilya Gorbachinsky, L Spencer KraneDepartment of Urology, Wake Forest University, Winston-Salem, NC, USAObjective: To determine whether age of toilet training is associated with dysfunctional voiding in children.Materials and methods: We compared patients referred to the urologic clinics for voiding dysfunction with age-matched controls without urinary complaints. Characteristics including age and reason for toilet training, method of training, and encopresis or constipation were compared between both groups.Results: Initiation of toilet training prior to 24 months and later than 36 months of age were associated with dysfunctional voiding. However, dysfunctional voiding due to late toilet training was also associated with constipation.Conclusion: Dysfunctional voiding may be due to delayed emptying of the bowel and bladder by children. The symptoms of dysfunctional voiding are more common when toilet training early, as immature children may be less likely to empty in a timely manner, or when training late due to (or in association with constipation.Keywords: voiding dysfunction, constipation

  3. Local, zero-power void coefficient measurements in the ACPR

    Energy Technology Data Exchange (ETDEWEB)

    Rivard, J B; Thome, F V [Sandia Laboratories (United States)

    1974-07-01

    Changes in reactivity may be stimulated in the ACPR by the local introduction of voids into the reactor coolant. The local void coefficients of reactivity which describe this effect are of interest from a reactor safety point-of-view, and their determination is the subject of this presentation. Bottled nitrogen gas was used to produce the voids. The gas was forced out of a small diameter tube which was positioned vertically in the core lattice with its open end below the fuel. The gas was passed through a pressure regulator, a valve, and a flowmeter to establish a steady flow condition, following which a delayed-critical (zero-power) reactor state was established. Correlation of the average volume of core void created by the nitrogen flow with the reactivity worth of the delayed-critical control-rod bank position produced the values of the zero-power void coefficients of reactivity. The void coefficients were determined at various core positions from {approx}6 mm to 142 mm beyond the central irradiation space and for three different flow rates. For the range of void fractions investigated, these coefficients are negative, with values ranging between -$0.02 and -$0.12. Tabular and graphical results of the measurements are presented, and details of the coefficient determination are explained. (author)

  4. On nonlinear excitation of voids in dusty plasmas

    International Nuclear Information System (INIS)

    Nebbat, E.; Annou, R.; Bharuthram, R.

    2007-01-01

    The void, which is a dust-free region inside the dust cloud in the plasma, results from a balance of the electrostatic force and the ion-drag force on a dust particulate that has numerous forms, some of which are based on models whereas others are driven from first principles. To explain the generation of voids, K. Avinash, A. Bhattacharjee, and S. Hu [Phys. Rev. Lett. 90, 075001 (2003)] proposed a time-dependent nonlinear model that describes the void as a result of an instability. We augment this model by incorporating the grain drift and reintroducing the velocity convective term as well as by replacing the modeled ion-drag force by a more accurate one. The analysis is conducted in a spherical configuration. It is revealed that the void formation is a threshold phenomenon, i.e., it depends on the grain size. Furthermore, the void possesses a sharp boundary beyond which the dust density decreases and may present a corrugated aspect. For big size grains, the use of both ion-drag forces leads to voids of the same dimension, though for grains of small sizes, the Avinash force drives voids of a higher dimension. The model shows good agreement with the experiment

  5. Void nucleation at elevated temperatures under cascade-damage irradiation

    International Nuclear Information System (INIS)

    Semenov, A.A.; Woo, C.H.

    2002-01-01

    The effects on void nucleation of fluctuations respectively due to the randomness of point-defect migratory jumps, the random generation of free point defects in discrete packages, and the fluctuating rate of vacancy emission from voids are considered. It was found that effects of the cascade-induced fluctuations are significant only at sufficiently high total sink strength. At lower sink strengths and elevated temperatures, the fluctuation in the rate of vacancy emission is the dominant factor. Application of the present theory to the void nucleation in annealed pure copper neutron-irradiated at elevated temperatures with doses of 10 -4 -10 -2 NRT dpa showed reasonable agreement between theory and experiment. This application also predicts correctly the temporal development of large-scale spatial heterogeneous microstructure during the void nucleation stage. Comparison between calculated and experimental void nucleation rates in neutron-irradiated molybdenum at temperatures where vacancy emission from voids is negligible showed reasonable agreement as well. It was clearly demonstrated that the athermal shrinkage of relatively large voids experimentally observable in molybdenum at such temperatures may be easily explained in the framework of the present theory

  6. Local, zero-power void coefficient measurements in the ACPR

    International Nuclear Information System (INIS)

    Rivard, J.B.; Thome, F.V.

    1974-01-01

    Changes in reactivity may be stimulated in the ACPR by the local introduction of voids into the reactor coolant. The local void coefficients of reactivity which describe this effect are of interest from a reactor safety point-of-view, and their determination is the subject of this presentation. Bottled nitrogen gas was used to produce the voids. The gas was forced out of a small diameter tube which was positioned vertically in the core lattice with its open end below the fuel. The gas was passed through a pressure regulator, a valve, and a flowmeter to establish a steady flow condition, following which a delayed-critical (zero-power) reactor state was established. Correlation of the average volume of core void created by the nitrogen flow with the reactivity worth of the delayed-critical control-rod bank position produced the values of the zero-power void coefficients of reactivity. The void coefficients were determined at various core positions from ∼6 mm to 142 mm beyond the central irradiation space and for three different flow rates. For the range of void fractions investigated, these coefficients are negative, with values ranging between -$0.02 and -$0.12. Tabular and graphical results of the measurements are presented, and details of the coefficient determination are explained. (author)

  7. Lecture background notes on transient sodium boiling and voiding in fast reactors

    International Nuclear Information System (INIS)

    Okrent, D.; Fauske, H.K.

    1972-01-01

    This set of lecture background notes includes the following: (1) Introductory remarks on fast reactor safety, which are intended to provide some perspective on the role played by sodium boiling. (2) A discussion of superheat which reviews the experimental data and nucleation models with emphasis on the pressure-temperature history effect on radius of active cavity sites, including the role played by inert gas. (3) A discussion of the growth and collapse of spherical bubbles. (4) A historical description of the development of computer codes to describe voiding and a detailed description of the analytical formulation of typical models for calculating voiding due to boiling, fission gas release, and molten fuel-coolant interaction. (U.S.)

  8. Acoustics and voiding dynamics during SLSF simulations of LMFBR undercooling transients

    International Nuclear Information System (INIS)

    Anderson, T.T.; Kuzay, T.M.; Marr, W.W.; Miles, K.J.; Pedersen, D.R.; Thompson, D.H.; Wilson, R.E.

    1978-01-01

    The SLSF is the largest U.S. in-reactor test vehicle for steady-state and transient experiments in an environment typical of a LMFBR core. The SLSF experiment program, sponsored by the Department of Energy, contributes to the LMFBR safety assurance program by providing data on key phenomena that occur during postulated reactor accidents. This paper describes completed SLSF experiments, in-core instrumentation used, and methods of data interpretation to determine sodium boiling and voiding dynamics. Boiling inception is shown to be identifiable from several types of in-core instruments. Location of the boiling front and void growth derived from experimental data are compared with analytical predictions. These and other data form the basis to improve understanding of accidents and to validate or guide the development of accident analysis methods

  9. Magnetic resonance voiding cystography in the diagnosis of vesicoureteral reflux: comparative study with voiding cystourethrography.

    Science.gov (United States)

    Lee, Sang Kwon; Chang, Yongmin; Park, Noh Hyuck; Kim, Young Hwan; Woo, Seongku

    2005-04-01

    To evaluate the feasibility of magnetic resonance voiding cystography (MRVC) compared with voiding cystourethrography (VCUG) for detecting and grading vesicoureteral reflux (VUR). MRVC was performed upon 20 children referred for investigation of reflux. Either coronal T1-weighted spin-echo (SE) or gradient-echo (GE) (fast multiplanar spoiled gradient-echo (FMPSPGR) or turbo fast low-angle-shot (FLASH)) images were obtained before and after transurethral administration of gadolinium solution, and immediately after voiding. The findings of MRVC were compared with those of VCUG and technetium-99m ((99m)Tc) dimercaptosuccinic acid (DMSA) single-photon emission computed tomography (SPECT) performed within 6 months of MRVC. VUR was detected in 23 ureterorenal units (16 VURs by both methods, 5 VURs by VCUG, and 2 VURs by MRVC). With VCUG as the standard of reference, the sensitivity of MRVC was 76.2%; the specificity, 90.0%; the positive predictive value, 88.9%; and the negative predictive value, 78.3%. There was concordance between two methods regarding the grade of reflux in all 16 ureterorenal units with VUR detected by both methods. Of 40 kidneys, MRVC detected findings of renal damage or reflux nephropathy in 13 kidneys, and (99m)Tc DMSA renal SPECT detected findings of reflux nephropathy in 17 kidneys. Although MRVC is shown to have less sensitivity for VUR than VCUG, MRVC may represent a method of choice offering a safer nonradiation test that can additionally evaluate the kidneys for changes related to reflux nephropathy. Copyright 2005 Wiley-Liss, Inc.

  10. A void fraction model for annular two-phase flow

    Energy Technology Data Exchange (ETDEWEB)

    Tandon, T.N.; Gupta, C.P.; Varma, H.K.

    1985-01-01

    An analytical model has been developed for predicting void fraction in two-phase annular flow. In the analysis, the Lockhart-Martinelli method has been used to calculate two-phase frictional pressure drop and von Karman's universal velocity profile is used to represent the velocity distribution in the annular liquid film. Void fractions predicted by the proposed model are generally in good agreement with a available experimental data. This model appears to be as good as Smith's correlation and better than the Wallis and Zivi correlations for computing void fraction.

  11. Local void and slip model used in BODYFIT-2PE

    International Nuclear Information System (INIS)

    Chen, B.C.J.; Chien, T.H.; Kim, J.H.; Lellouche, G.S.

    1983-01-01

    A local void and slip model has been proposed for a two-phase flow without the need of fitting any empirical parameters. This model is based on the assumption that all bubbles have reached their terminal rise velocities in the two-phase region. This simple model seems to provide reasonable calculational results when compared with the experimental data and other void and slip models. It provides a means to account for the void and slip of a two-phase flow on a local basis. This is particularly suitable for a fine mesh thermal-hydraulic computer program such as BODYFIT-2PE

  12. Estimation of air void and aggregate spatial distributions in concrete under uniaxial compression using computer tomography scanning

    International Nuclear Information System (INIS)

    Wong, R.C.K.; Chau, K.T.

    2005-01-01

    Normal- and high-strength concrete cylinders (designed compressive strengths of 30 and 90 MPa at 28 days) were loaded uniaxially. Computer tomography (CT) scanning technique was used to examine the evolution of air voids inside the specimens at various loading states up to 85% of the ultimate compressive strength. The normal-strength concrete yielded a very different behaviour in changes of internal microstructure as compared to the high-strength concrete. There were significant instances of nucleation and growth in air voids in the normal-strength concrete specimen, while the increase in air voids in the high-strength concrete specimen was insignificant. In addition, CT images were used for mapping the aggregate spatial distributions within the specimens. No intrinsic anisotropy was detected from the fabric analysis

  13. Void consolidation during open-die forging for ultralarge rotor shafts. (1. Formulation of void-closing behavior)

    International Nuclear Information System (INIS)

    Ono, Shin-ichi; Minami, Katsuyuki; Ochiai, Tomoyuki; Iwadate, Tadao; Nakata, Shin-ichi.

    1995-01-01

    Open-die forging experiments using different die geometries under hot isothermal conditions and three-dimensional simulations using rigid-plastic finite-element method were performed to formulate a void-closing behavior using only two factors; the integral of hydrostatic stress and the equivalent strain. First, upsetting, side-upsetting and V-shape die cogging of several cylinders with a spherical void at the center are carried out and the information on the void volume reduction is obtained. Seconds, the same forgings, but without voids is treated numerically and the development of stress and strain at the location of voids is investigated. Then, by combining these results, and using regression analysis, it is found that the void volume reduction is expressed as a polynomial function of the two factors. When the polynomial function is used, various forging methods can be evaluated quantitatively in terms of void-closing behavior. Therefore it is beneficial to optimize the forging process for a large rotor shaft. (author)

  14. Air-void embedded GaN-based light-emitting diodes grown on laser drilling patterned sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hao; Li, Yufeng; Wang, Shuai; Feng, Lungang; Xiong, Han; Yun, Feng, E-mail: fyun2010@mail.xjtu.edu.cn [Key Laboratory of Physical Electronics and Devices of Ministry of Education and Shaanxi Provincial Key Laboratory of Photonics and Information Technology, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Solid-State Lighting Engineering Research Center, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Su, Xilin [Shaanxi Supernova Lighting Technology Co., Ltd., Xi’an, Shaanxi 710075 (China)

    2016-07-15

    Air-void structure was introduced in GaN-based blue light-emitting diodes (LED) with one-step growth on periodic laser drilling patterned sapphire substrate, which free of any photolithography or wet/dry etching process. The influence of filling factors (FF) of air-void on crystal quality and optical performance were investigate. Transmission electron microscopy images and micro-Raman spectroscopy indicated that the dislocation was bended and the partially compressed strain was released. When FF was 55.43%, compared with the LED structure grown on flat sapphire substrate, the incorporation of air-void was observed to reduce the compressed stress of ∼20% and the luminance intensity has improved by 128%. Together with the simulated reflection intensity enhancement by finite difference time-domain (FDTD) method, we attribute the enhanced optical performance to the combined contribution of strong back-side light reflection of air-void and better GaN epitaxial quality. This approach provides a simple replacement to the conventional air-void embedded LED process.

  15. Void formation in ODS EUROFER produced by hot isostatic pressing

    International Nuclear Information System (INIS)

    Ortega, Y.; Monge, M.A.; Castro, V. de; Munoz, A.; Leguey, T.; Pareja, R.

    2009-01-01

    Positron annihilation experiments were performed on oxide dispersion strengthened (ODS) and non-ODS EUROFER prepared by mechanical alloying and hot isostatic pressing. The results revealed the presence of small voids in these materials in the as-HIPed conditions. Their evolution under isochronal annealing experiments was investigated. The coincidence Doppler broadening spectra of ODS EUROFER exhibited a characteristic signature attributed to positron annihilation in Ar-decorated voids at the oxide particle/matrix interfaces. The variation of the positron annihilation parameters with the annealing temperature showed three stages: up to 623 K, between 823 and 1323 K, and above 1323 K. In the temperature range 823-1323 K void coarsening had effect. Above 1323 K some voids annealed out, but others, associated to oxide particles and small precipitates, survived to annealing at 1523 K. Transmission electron microscopy observations were also performed to verify the characteristics of the surviving defects after annealing at 1523 K.

  16. Void formation in ODS EUROFER produced by hot isostatic pressing

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, Y. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain)], E-mail: yanicet@fis.ucm.es; Monge, M.A. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Castro, V. de [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Munoz, A.; Leguey, T.; Pareja, R. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain)

    2009-04-30

    Positron annihilation experiments were performed on oxide dispersion strengthened (ODS) and non-ODS EUROFER prepared by mechanical alloying and hot isostatic pressing. The results revealed the presence of small voids in these materials in the as-HIPed conditions. Their evolution under isochronal annealing experiments was investigated. The coincidence Doppler broadening spectra of ODS EUROFER exhibited a characteristic signature attributed to positron annihilation in Ar-decorated voids at the oxide particle/matrix interfaces. The variation of the positron annihilation parameters with the annealing temperature showed three stages: up to 623 K, between 823 and 1323 K, and above 1323 K. In the temperature range 823-1323 K void coarsening had effect. Above 1323 K some voids annealed out, but others, associated to oxide particles and small precipitates, survived to annealing at 1523 K. Transmission electron microscopy observations were also performed to verify the characteristics of the surviving defects after annealing at 1523 K.

  17. Comment on theories for helium-assisted void nucleation

    International Nuclear Information System (INIS)

    Russell, K.C.

    1976-01-01

    Voids form by agglomeration of irradiation-induced vacancies which remain after preferential absorption of self interstitials at dislocation lines. Helium which is formed by (n,α) transmutations and, in simulation studies, may be ion-implanted, often plays an important, but puzzling role. In some materials, very few voids form in the absence of helium, even after intense irradiation. In many other materials , voids form readily under a variety of irradiation conditions, even in the absence of helium. Why some materials require helium - typically in the 10 -6 apa (atom per atom) range - and others do not, and the reason for that particular level are by no means clear. The physics of void nucleation, particularly the role of helium, have been the subject of several theoretical papers. This note presents a critique of these theories, and then briefly outlines a new analysis which is not subject to their limitations. (Auth.)

  18. (100) faceted anion voids in electron irradiated fluorite

    International Nuclear Information System (INIS)

    Johnson, E.

    1979-01-01

    High fluence electron irradiation of fluorite crystals in the temperature range 150 to 320 K results in formation of a simple cubic anion void superlattice. Above 320 K the damage structure changes to a random distribution of large [001] faceted anion voids. This voidage behaviour, similar to that observed in a range of irradiated metals, is discussed in terms points defect rather than conventional colour centre terminology. (Auth.)

  19. Uroflowmetry in neurologically normal children with voiding disorders

    DEFF Research Database (Denmark)

    Jensen, K M; Nielsen, K.K.; Kristensen, E S

    1985-01-01

    of neurological deficits underwent a complete diagnostic program including intravenous urography, voiding cystography and cystoscopy as well as spontaneous uroflowmetry, cystometry-emg and pressure-flow-emg study. The incidence of dyssynergia was 22%. However, neither the flow curve pattern nor single flow...... variables were able to identify children with dyssynergia. Consequently uroflowmetry seems inefficient in the screening for dyssynergia in neurological normal children with voiding disorders in the absence of anatomical bladder outlet obstruction....

  20. Effect of Dark Energy Perturbation on Cosmic Voids Formation

    Science.gov (United States)

    Endo, Takao; Nishizawa, Atsushi J.; Ichiki, Kiyotomo

    2018-05-01

    In this paper, we present the effects of dark energy perturbation on the formation and abundance of cosmic voids. We consider dark energy to be a fluid with a negative pressure characterised by a constant equation of state w and speed of sound c_s^2. By solving fluid equations for two components, namely, dark matter and dark energy fluids, we quantify the effects of dark energy perturbation on the sizes of top-hat voids. We also explore the effects on the size distribution of voids based on the excursion set theory. We confirm that dark energy perturbation negligibly affects the size evolution of voids; c_s^2=0 varies the size only by 0.1% as compared to the homogeneous dark energy model. We also confirm that dark energy perturbation suppresses the void size when w -1 (Basse et al. 2011). In contrast to the negligible impact on the size, we find that the size distribution function on scales larger than 10 Mpc/h highly depends on dark energy perturbation; compared to the homogeneous dark energy model, the number of large voids of radius 30Mpc is 25% larger for the model with w = -0.9 and c_s^2=0 while they are 20% less abundant for the model with w = -1.3 and c_s^2=0.

  1. Measurement of local void fraction in a ribbed annulus

    International Nuclear Information System (INIS)

    Steimke, J.L.

    1992-01-01

    The computer code FLOWTRAN-TF is used to analyze hypothetical hydraulic accidents for the nuclear reactor at the Savannah River Site. During a hypothetical Large Break Loss-of-Coolant Accident (LOCA), reactor assemblies would contain a two-phase mixture of air and water which flows downward. Reactor assemblies consist of nested, ribbed annuli. Longitudinal ribs divide each annulus into four subchannels. For accident conditions, air and water can flow past ribs from one subchannel to another. For FLOWTRAN-TF to compute the size of those flows, it is necessary to know the local void fraction in the region of the rib. Measurements have previously been made of length-average void fraction in a ribbed annulus. However, no direct measurements were available of local void fraction. Due to the lack of data, a test was designed to measure local void fraction at the rib. One question addressed by the test was whether void fraction at the rib is solely a function of azimuthal-average void fraction or a function of additional variables such as pressure boundary conditions. This report provides a discussion of this test

  2. Influence of the void fraction in the linear reactivity model

    International Nuclear Information System (INIS)

    Castillo, J.A.; Ramirez, J.R.; Alonso, G.

    2003-01-01

    The linear reactivity model allows the multicycle analysis in pressurized water reactors in a simple and quick way. In the case of the Boiling water reactors the void fraction it varies axially from 0% of voids in the inferior part of the fuel assemblies until approximately 70% of voids to the exit of the same ones. Due to this it is very important the determination of the average void fraction during different stages of the reactor operation to predict the burnt one appropriately of the same ones to inclination of the pattern of linear reactivity. In this work a pursuit is made of the profile of power for different steps of burnt of a typical operation cycle of a Boiling water reactor. Starting from these profiles it builds an algorithm that allows to determine the voids profile and this way to obtain the average value of the same one. The results are compared against those reported by the CM-PRESTO code that uses another method to carry out this calculation. Finally, the range in which is the average value of the void fraction during a typical cycle is determined and an estimate of the impact that it would have the use of this value in the prediction of the reactivity produced by the fuel assemblies is made. (Author)

  3. Continuous in-situ measurements of fission fragment irradiation induced void swelling in Ni

    International Nuclear Information System (INIS)

    Lefakis, H.

    1980-01-01

    A novel simulation technique has been developed to study the early stages of irradiation induced void formation in metals. The technique makes use of fission fragment irradiation produced by doping with 235 U and irradiating in a thermal neutron flux under highly controlled irradiation-environmental conditions. Employment of a computer and a high temperature radiation resistant LVDT resulted in a high volumetric sensitivity and the production of continuous, in-situ void swelling data for bulk specimens. Results for Ni, used as a test-metal served to corroborate the technique in a number of ways including comparisons with (a) reactor data, (b) direct post-irradiation specimen length measurements and (c) TEM examinations of irradiated samples. The technique has several unique advantages and, in conjunction with other conventional methods, it offers the possibility of detailed evaluation of void nucleation and growth theories. In view of the present results no definitive answer may be given on the issue of the incubation period while checks with two theoretical models have yielded an order-of-magnitude agreement

  4. Comprehensive Characterization of Voids and Microstructure in TATB-based Explosives from 10 nm to 1 cm: Effects of Temperature Cycling and Compressive Creep

    Energy Technology Data Exchange (ETDEWEB)

    Willey, T M; Lauderbach, L; Gagliardi, F; Cunningham, B; Lorenz, K T; Lee, J I; van Buuren, T; Call, R; Landt, L; Overturf, G

    2010-02-26

    This paper outlines the characterization of voids and Microstructure in TATB-based Explosives over several orders of magnitude, from sizes on the order of 10 nm to about 1 cm. This is accomplished using ultra small angle x-ray scattering to investigate voids from a few nm to a few microns, ultra small angle neutron scattering for voids from 100 nm to 10 microns, and x-ray computed microtomography to investigate microstructure from a few microns to a few centimeters. The void distributions of LX-17 are outlined, and the microstructure of LX-17 is presented. Temperature cycling and compressive creep cause drastically different damage to the microstructure. Temperature cycling leads to a volume expansion (ratchet growth) in TATB-based explosives, and x-ray scattering techniques that are sensitive to sizes up to a few microns indicated changes to the void volume distribution that had previously accounted for most, but not all of the change in density. This paper presents the microstructural damage larger than a few microns caused by ratchet growth. Temperature cycling leads to void creation in the binder poor regions associated with the interior portion of formulated prills. Conversely, compressive creep causes characteristically different changes to microstructure; fissures form at binder-rich prill boundaries prior to mechanical failure.

  5. Urinary tract infection after voiding cystourethrogram.

    Science.gov (United States)

    Johnson, E K; Malhotra, N R; Shannon, R; Jacobson, D L; Green, J; Rigsby, C K; Holl, J L; Cheng, E Y

    2017-08-01

    Reported rates of post-procedural urinary tract infection (ppUTI) after voiding cystourethrogram (VCUG) are highly variable (0-42%). This study aimed to determine the risk of ppUTI after cystogram, and evaluate predictors of ppUTI. A retrospective cohort study of children undergoing VCUG or radionuclide cystogram (henceforth 'cystogram') was conducted. Children with neurogenic bladder who underwent cystogram in the operating room and without follow-up at the study institution were excluded. Incidence of symptomatic ppUTI within 7 days after cystogram was recorded. Predictors of ppUTI were evaluated using univariate statistics. A total of 1108 children (54% female, median age 1.1 years) underwent 1203 cystograms: 51% were on periprocedural antibiotics, 75% had a pre-existing urologic diagnosis (i.e., vesicoureteral reflux (VUR) or hydronephrosis; not UTI alone), and 18% had a clinical UTI within 30 days before cystogram. Of the cystograms, 41% had an abnormal cystogram and findings included VUR (82%), ureterocele (6%), and diverticula (6%). Twelve children had a ppUTI (1.0%; four girls, five uncircumcised boys, three circumcised boys; median age 0.9 years). Factors significantly associated with diagnosis of a ppUTI (Summary fig.) included: pre-existing urologic diagnosis prior to cystogram (12/12, 100% of patients with ppUTI), abnormal cystogram results (11/12, 92%), and use of periprocedural antibiotics (11/12, 92%). All 11 children with an abnormal cystogram had VUR ≥ Grade III. However, among all children with VUR ≥ Grade III, 4% (11/254) had a ppUTI. This is the largest study to date that has examined incidence and risk factors for ppUTI after cystogram. The retrospective nature of the study limited capture of some clinical details. This study demonstrated that the risk of ppUTI after a cystogram is very low (1.0% in this cohort). Having a pre-existing urologic diagnosis such as VUR or hydronephrosis was associated with ppUTI; therefore, children with

  6. Reliability Impact of Stockpile Aging: Stress Voiding; TOPICAL

    International Nuclear Information System (INIS)

    ROBINSON, DAVID G.

    1999-01-01

    The objective of this research is to statistically characterize the aging of integrated circuit interconnects. This report supersedes the stress void aging characterization presented in SAND99-0975, ''Reliability Degradation Due to Stockpile Aging,'' by the same author. The physics of the stress voiding, before and after wafer processing have been recently characterized by F. G. Yost in SAND99-0601, ''Stress Voiding during Wafer Processing''. The current effort extends this research to account for uncertainties in grain size, storage temperature, void spacing and initial residual stress and their impact on interconnect failure after wafer processing. The sensitivity of the life estimates to these uncertainties is also investigated. Various methods for characterizing the probability of failure of a conductor line were investigated including: Latin hypercube sampling (LHS), quasi-Monte Carlo sampling (qMC), as well as various analytical methods such as the advanced mean value (Ah/IV) method. The comparison was aided by the use of the Cassandra uncertainty analysis library. It was found that the only viable uncertainty analysis methods were those based on either LHS or quasi-Monte Carlo sampling. Analytical methods such as AMV could not be applied due to the nature of the stress voiding problem. The qMC method was chosen since it provided smaller estimation error for a given number of samples. The preliminary results indicate that the reliability of integrated circuits due to stress voiding is very sensitive to the underlying uncertainties associated with grain size and void spacing. In particular, accurate characterization of IC reliability depends heavily on not only the frost and second moments of the uncertainty distribution, but more specifically the unique form of the underlying distribution

  7. Breaking the vicious circle: Onabotulinum toxin A in children with therapy-refractory dysfunctional voiding

    NARCIS (Netherlands)

    L.A. 't Hoen (Lisette); J. van den Hoek (Joop); K.P. Wolffenbuttel (Katja); F. van der Toorn; J.R. Scheepe (Jeroen)

    2015-01-01

    textabstractIntroduction An increased activity of the external urethral sphincter or pelvic floor muscles during voluntary voiding leads to dysfunctional voiding. Frequently reported symptoms are urinary incontinence, urinary tract infections and high post-void residuals. Dysfunctional voiding is a

  8. Automated air-void system characterization of hardened concrete: Helping computers to count air-voids like people count air-voids---Methods for flatbed scanner calibration

    Science.gov (United States)

    Peterson, Karl

    Since the discovery in the late 1930s that air entrainment can improve the durability of concrete, it has been important for people to know the quantity, spacial distribution, and size distribution of the air-voids in their concrete mixes in order to ensure a durable final product. The task of air-void system characterization has fallen on the microscopist, who, according to a standard test method laid forth by the American Society of Testing and Materials, must meticulously count or measure about a thousand air-voids per sample as exposed on a cut and polished cross-section of concrete. The equipment used to perform this task has traditionally included a stereomicroscope, a mechanical stage, and a tally counter. Over the past 30 years, with the availability of computers and digital imaging, automated methods have been introduced to perform the same task, but using the same basic equipment. The method described here replaces the microscope and mechanical stage with an ordinary flatbed desktop scanner, and replaces the microscopist and tally counter with a personal computer; two pieces of equipment much more readily available than a microscope with a mechanical stage, and certainly easier to find than a person willing to sit for extended periods of time counting air-voids. Most laboratories that perform air-void system characterization typically have cabinets full of prepared samples with corresponding results from manual operators. Proponents of automated methods often take advantage of this fact by analyzing the same samples and comparing the results. A similar iterative approach is described here where scanned images collected from a significant number of samples are analyzed, the results compared to those of the manual operator, and the settings optimized to best approximate the results of the manual operator. The results of this calibration procedure are compared to an alternative calibration procedure based on the more rigorous digital image accuracy

  9. ON THE STAR FORMATION PROPERTIES OF VOID GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Moorman, Crystal M.; Moreno, Jackeline; White, Amanda; Vogeley, Michael S. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Hoyle, Fiona [Pontifica Universidad Catolica de Ecuador, 12 de Octubre 1076 y Roca, Quito (Ecuador); Giovanelli, Riccardo; Haynes, Martha P., E-mail: crystal.m.moorman@drexel.edu [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University Ithaca, NY 14853 (United States)

    2016-11-10

    We measure the star formation properties of two large samples of galaxies from the SDSS in large-scale cosmic voids on timescales of 10 and 100 Myr, using H α emission line strengths and GALEX FUV fluxes, respectively. The first sample consists of 109,818 optically selected galaxies. We find that void galaxies in this sample have higher specific star formation rates (SSFRs; star formation rates per unit stellar mass) than similar stellar mass galaxies in denser regions. The second sample is a subset of the optically selected sample containing 8070 galaxies with reliable H i detections from ALFALFA. For the full H i detected sample, SSFRs do not vary systematically with large-scale environment. However, investigating only the H i detected dwarf galaxies reveals a trend toward higher SSFRs in voids. Furthermore, we estimate the star formation rate per unit H i mass (known as the star formation efficiency; SFE) of a galaxy, as a function of environment. For the overall H i detected population, we notice no environmental dependence. Limiting the sample to dwarf galaxies still does not reveal a statistically significant difference between SFEs in voids versus walls. These results suggest that void environments, on average, provide a nurturing environment for dwarf galaxy evolution allowing for higher specific star formation rates while forming stars with similar efficiencies to those in walls.

  10. Electromigration of intergranular voids in metal films for microelectronic interconnects

    CERN Document Server

    Averbuch, A; Ravve, I

    2003-01-01

    Voids and cracks often occur in the interconnect lines of microelectronic devices. They increase the resistance of the circuits and may even lead to a fatal failure. Voids may occur inside a single grain, but often they appear on the boundary between two grains. In this work, we model and analyze numerically the migration and evolution of an intergranular void subjected to surface diffusion forces and external voltage applied to the interconnect. The grain-void interface is considered one-dimensional, and the physical formulation of the electromigration and diffusion model results in two coupled fourth-order one-dimensional time-dependent PDEs. The boundary conditions are specified at the triple points, which are common to both neighboring grains and the void. The solution of these equations uses a finite difference scheme in space and a Runge-Kutta integration scheme in time, and is also coupled to the solution of a static Laplace equation describing the voltage distribution throughout the grain. Since the v...

  11. How institutional voids influence Brazilian foreign direct investment in Angola

    Directory of Open Access Journals (Sweden)

    Renato Virches

    2017-04-01

    Full Text Available How do institutional voids influence emerging market multinationals (EMNEs foreign direct investment (FDI in developing countries? In this article we respond to this question by examining Brazilian FDI in Angola as our analytical setting. We focus on the host country’s institutions and its institutional voids as essential factors that attract the FDI of EMNES to developing countries. The research indicates that Brazilian companies fill in much of these voids within the market intermediaries, often creating a point of competitive advantage, and also creating advantages in relation to FDI from other economies that invest in Angola. The scarce literature on FDI in Africa has been largely dedicated to the analysis of Chinese investment in the region. We aim to complement recent research on the influence of the host country’s institutions on the behavior of FDI in developing countries, explaining how some EMNEs are able to use the institutional voids of developing countries as market opportunities. Our findings should provide also implications for EMNEs managers from other emerging markets by providing a better understanding of how Brazilian multinationals expand their business in less developed countries, handle institutional voids and manage relationships with local and foreign institutions in the host country.

  12. Understanding void fraction in steady state and dynamic environments

    International Nuclear Information System (INIS)

    Chexal, B.; Maulbetsch, J.; Harrison, J.; Petersen, C.; Jensen, P.; Horowitz, J.

    1997-01-01

    Understanding void fraction behavior in steady-state and dynamic environments is important to accurately predict the thermal-hydraulic behavior of two-phase or two-component systems. The Chexal-Lellouche (C-L) void fraction mode described herein covers the full range of pressures, flows, void fractions, and fluid types (steam-water, air-water, and refrigerants). A drift flux model formulation is used which covers the complete range of concurrent and countercurrent flows. The (1996) model revises the earlier C-L void fraction correlation, improves the capability of the model in countercurrent flow based on the incorporation of additional data, and improves the characteristics of the correlation that are important in transient programs. The model has been qualified with data from a number of steady state two-phase and two-component tests, and has been incorporated into the transient analysis code RELAP5 and RETRAN-3D and evaluated with a variety of transient and steady state tests. A 'plug-in' module for the void fraction correlation has been developed and implemented in RELAP5 and RETRAN-3D. The module is available as source code for inclusion into other thermal-hydraulic programs and can be used in any program that utilizes the same interface variables

  13. Controlling Interfacial Separation in Porous Structures by Void Patterning

    Science.gov (United States)

    Ghareeb, Ahmed; Elbanna, Ahmed

    Manipulating interfacial response for enhanced adhesion or fracture resistance is a problem of great interest to scientists and engineers. In many natural materials and engineering applications, an interface exists between a porous structure and a substrate. A question that arises is how the void distribution in the bulk may affect the interfacial response and whether it is possible to alter the interfacial toughness without changing the surface physical chemistry. In this paper, we address this question by studying the effect of patterning voids on the interfacial-to-the overall response of an elastic plate glued to a rigid substrate by bilinear cohesive material. Different patterning categories are investigated; uniform, graded, and binary voids. Each case is subjected to upward displacement at the upper edge of the plate. We show that the peak force and maximum elongation at failure depend on the voids design and by changing the void size, alignment or gradation we may control these performance measures. We relate these changes in the measured force displacement response to energy release rate as a measure of interfacial toughness. We discuss the implications of our results on design of bulk heterogeneities for enhanced interfacial behavior.

  14. STM-Induced Void Formation at the Al{sub 2}O{sub 3}/Ni{sub 3}Al(111) Interface

    Energy Technology Data Exchange (ETDEWEB)

    Magtoto, N.P.; Niu, C.; Anzaldura, M.; Kelber, J.A.; Jennison, D.R.

    2000-09-21

    Under UHV conditions at 300 K, the applied electric field and/or resulting current from an STM tip creates nanoscale voids at the interface between an epitaxial, 7.0 {angstrom} thick Al{sub 2}O{sub 3} film and a Ni{sub 3}Al(111) substrate. This phenomenon is independent of tip polarity. Constant current (1 nA) images obtained at +0.1 V bias and +2.0 bias voltage (sample positive) reveal that voids are within the metal at the interface and, when small, are capped by the oxide film. Void size increases with time of exposure. The rate of void growth increases with applied bias/field and tunneling current, and increases significantly for field strengths >5 MV/cm, well below the dielectric breakdown threshold of 12 {+-} 1 MV/cm. Slower rates of void growth are, however, observed at lower applied field strengths. Continued growth of voids, to {approximately}30 {angstrom} deep and {approximately}500 {angstrom} wide, leads to the eventual failure of the oxide overlayer. Density Functional Theory calculations suggest a reduction-oxidation (REDOX) mechanism: interracial metal atoms are oxidized via transport into the oxide, while oxide surface Al cations are reduced to admetal species which rapidly diffuse away. This is found to be exothermic in model calculations, regardless of the details of the oxide film structure; thus, the barriers to void formation are kinetic rather than thermodynamic. We discuss our results in terms of mechanisms for the localized pitting corrosion of aluminum, as our results suggest nanovoid formation requires just electric field and current, which are ubiquitous in environmental conditions.

  15. The relationship between temperament, gender, and childhood dysfunctional voiding.

    Science.gov (United States)

    Colaco, Marc; Dobkin, Roseanne D; Sterling, Matthew; Schneider, Dona; Barone, Joseph

    2013-08-01

    Dysfunctional voiding (DV) is an extremely common pediatric complaint. The goal of this study was to examine the relationship between DV and childhood temperament. Information about the voiding behaviors and temperaments of 50 children was examined using a case-control model. Caregivers were asked to fill out the Children's Behavior Questionnaire in order to rate their child on the dimensions of surgency, negative affect, and effortful control. The relationship between DV and these dimensions was then evaluated. Males with DV were found to have lower effortful control than males with normal voiding habits. Females with DV did not demonstrate a difference in effortful control, but did demonstrate a higher rate of surgency. The results suggest that temperament does have an association with DV. These findings are in line with temperamental associations with other externalizing trouble behaviors and may inform potential treatment strategies for DV.

  16. Prediction of pool void fraction by new drift flux correlation

    International Nuclear Information System (INIS)

    Kataoka, I.; Ishii, M.

    1986-06-01

    A void fraction for a bubbling or boiling pool system is one of the important parameters in analyzing heat and mass transfer processes. Using the drift flux formulation, correlations for the pool void fraction have been developed in collaboration with a large number of experimental data. It has been found that the drift velocity in a pool system depends upon vessel diameter, system pressure, gas flux and fluid physical properties. The results show that the relative velocity and void fraction can be quite different from those predicted by conventional correlations. In terms of the rise velocity, four different regimes are identified. These are bubbly, churn-turbulent, slug and cap bubble regimes. The present correlations are shown to agree with the experimental data over wide ranges of parameters such as vessel diameter, system pressure, gas flux and physical properties. 39 refs., 41 figs

  17. Internal Nano Voids in Yttria-Stabilised Zirconia (YSZ Powder

    Directory of Open Access Journals (Sweden)

    Chen Barad

    2017-12-01

    Full Text Available Porous yttria-stabilised zirconia ceramics have been gaining popularity throughout the years in various fields, such as energy, environment, medicine, etc. Although yttria-stabilised zirconia is a well-studied material, voided yttria-stabilised zirconia powder particles have not been demonstrated yet, and might play an important role in future technology developments. A sol-gel synthesis accompanied by a freeze-drying process is currently being proposed as a method of obtaining sponge-like nano morphology of embedded faceted voids inside yttria-stabilised zirconia particles. The results rely on a freeze-drying stage as an effective and simple method for generating nano-voided yttria-stabilised zirconia particles without the use of template-assisted additives.

  18. Multiple void formation in plasmas containing multispecies charged grains

    International Nuclear Information System (INIS)

    Liu, Y. H.; Chen, Z. Y.; Bogaerts, A.; Yu, M. Y.

    2006-01-01

    Self-organized separation of charged-dust species in two-dimensional dusty plasmas is studied by means of molecular-dynamics simulation. The multispecies dust grains, interacting through a screened Coulomb potential with a long-range attractive component, are confined by an external quadratic potential and subjected to a radially outward ion drag force. It is found that, in general, the species are spatially separated by bandlike dust-free (or void) regions, and grains of the same species tend to populate a common shell. At large ion drag and/or large plasma screening, a central disklike void as well as concentric bandlike voids separating the different species appear. Because of the outward drag and the attractive component of the dust-dust interaction forces, highly asymmetrical states consisting of species-separated dust clumps can also exist despite the fact that all the forces are either radial or central

  19. A DRAGON-MCNP comparison of void reactivity calculations

    Energy Technology Data Exchange (ETDEWEB)

    Marleau, G [Ecole Polytechnique, Montreal, PQ (Canada). Inst. de Genie Nucleaire; Milgram, M S [Atomic Energy of Canada Ltd., Chalk River, ON (Canada)

    1996-12-31

    The determination of the reactivity coefficients associated with coolant voiding in a CANDU reactor is a subject which has attracted a large amount of interest in the last few years both from the theoretical and experimental point of view. One expects that deterministic codes such as DRAGON and WIMS-AECL or the MCNP4 Monte Carlo code should be able to adequately simulate the cell behaviour upon coolant voiding. However, the absence of an experimental database at equilibrium and discharge burnups has not permitted the full validation of any of these lattice codes, although a partial validation through comparison of two different computer codes has been considered. Here we present a comparison between DRAGON and MCNP4 of the void reactivity evaluation for fresh fuel. (author). 16 refs., 5 tabs.

  20. Void distributions in liquid BiBr{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Maruyama, K [Faculty of Science, Niigata University, Niigata 950-2181 (Japan); Endo, H [Faculty of Science, Kyoto University, Kyoto 606-8224 (Japan); Hoshino, H [Faculty of Education, Hirosaki University, Hirosaki 036-8560 (Japan); Kawakita, Y [Faculty of Sciences, Kyushu University, Fukuoka 810-8560 (Japan); Kohara, S; Itou, M [Japan Synchrotron Radiation Research Institute(JASRI), Sayo-cho 679-5198 (Japan)

    2008-02-15

    The X-ray diffraction experiments and the reverse Monte Carlo analysis for liquid BiBr{sub 3} have been performed to clarify the distribution of Bi and Br ions around voids, comparing with previous results derived in the neutron diffraction experiments. The hexagonal cages involving voids are formed by the corner-sharing of the trigonal pyramidal BiBr{sub 3} blocks. The neighboring cages are linked together in highly correlated fashion. The observed pre-peak in S(Q) at 1.3A{sup -1} is related to the pre-peak of the void-based S'{sub CC} (Q) due to an intermediate chemical order in the structure. The pre-peak intensity increases with increasing temperature. This characteristic change for the pre-peak intensity is discussed by considering the modifications of the topology and stacking in the hexagonal cages.

  1. A DRAGON-MCNP comparison of void reactivity calculations

    International Nuclear Information System (INIS)

    Marleau, G.

    1995-01-01

    The determination of the reactivity coefficients associated with coolant voiding in a CANDU reactor is a subject which has attracted a large amount of interest in the last few years both from the theoretical and experimental point of view. One expects that deterministic codes such as DRAGON and WIMS-AECL or the MCNP4 Monte Carlo code should be able to adequately simulate the cell behaviour upon coolant voiding. However, the absence of an experimental database at equilibrium and discharge burnups has not permitted the full validation of any of these lattice codes, although a partial validation through comparison of two different computer codes has been considered. Here we present a comparison between DRAGON and MCNP4 of the void reactivity evaluation for fresh fuel. (author). 16 refs., 5 tabs

  2. Two-dimensional void reconstruction by neutron transmission

    International Nuclear Information System (INIS)

    Zakaib, G.D.; Harms, A.A.; Vlachopoulos, J.

    1978-01-01

    Contemporary algebraic reconstruction methods are utilized in investigating the two-dimensional void distribution in a water analog from neutron transmission measurements. It is sought to ultimately apply these techniques to the determination of time-averaged void distribution in two-phase flow systems as well as for potential usage in neutron radiography. Initially, projection data were obtained from a digitized model of a hypothetical two-phase representation and later from neutron beam traverses across a voided methacrylate plastic model. From 10 to 15 views were incorporated, and decoupling of overlapped measurements was utilized to afford greater resolution. In general, the additive Algebraic Reconstruction Technique yielded the best reconstructions, with others showing promise for noisy data. Results indicate the need for some further development of the method in interpreting real data

  3. Voiding patterns in men evaluated by a questionnaire survey

    DEFF Research Database (Denmark)

    Sommer, P; Nielsen, K K; Bauer, T

    1990-01-01

    A questionnaire on obstructive and irritative voiding symptoms was sent to 572 men aged between 20 and 79 years, selected at random from the National Register; 337 questionnaires were completed. None of the responders had consulted a doctor because of voiding symptoms. There was a significant...... voiding symptoms in men aged 60 to 79 years without subjective prostatism was the same as in patients admitted with prostatism, although most of the men had milder symptoms. Only nocturia and urge incontinence were more prevalent in patients admitted with prostatism. About 20% of men in the oldest decades...... had symptoms equal in severity to those found in men undergoing prostatectomy; 29% and 11% of men in the eighth decade [corrected] had nocturia twice and 3 times or more respectively; 19% complained of urge incontinence. More information on possible treatment is needed....

  4. Noninvasive Medical Tools for Evaluating Voiding Pattern in Real Life

    Directory of Open Access Journals (Sweden)

    Kwonsoo Chun

    2017-04-01

    Full Text Available Voiding dysfunction is a common disease that contributes to a lower quality of life and has an increased prevalence in the elderly population. Noninvasive and objective methods such as uroflowmetry (UFM and voiding diaries (VDs are essential for exact diagnosis and effective treatment of this condition because patients with different causes of voiding dysfunction can complain of the same lower urinary tract symptoms. Further, different treatment options can be determined based on the diagnosis made from these symptoms. In order to improve the quality of UFM and VDs and to provide a convenient testing environment, several advances have been made by previous investigators. In this study, we investigate the history and technological mechanisms of UFM and VDs. We also aim to review UFM from the viewpoint of clinical and at-home uses, including the recently proposed toilet-shaped UFM and electronic VDs.

  5. Loss of urinary voiding sensation due to herpes zoster.

    Science.gov (United States)

    Hiraga, Akiyuki; Nagumo, Kiyomi; Sakakibara, Ryuji; Kojima, Shigeyuki; Fujinawa, Naoto; Hashimoto, Tasuku

    2003-01-01

    A case of sacral herpes zoster infection in a 56-year-old man with the complication of loss of urinary voiding sensation is presented. He had typical herpes zoster eruption on the left S2 dermatome, hypalgesia of the S1-S4 dermatomes, and absence of urinary voiding sensation. There was no other urinary symptom at the first medical examination. Urinary complications associated with herpes zoster are uncommon, but two types, acute cystitis and acute retention, have been recognized. No cases of loss of urinary voiding sensation due to herpes zoster have been reported. In this case, hypalgesia of the sacral dermatomes was mild compared to the marked loss of urethral sensation. This inconsistency is explained by the hypothesis that the number of urethral fibers is very small as compared to that of cutaneous fibers, therefore, urethral sensation would be more severely disturbed than cutaneous sensation. Copyright 2003 Wiley-Liss, Inc.

  6. Interface failure by cavity growth to coalescence

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2000-01-01

    For a thin metal layer between ceramics ductile failure by the growth of voids along one of the interfaces is studied numerically. An axisymmetric cell model is used to represent an array of uniformly distributed hemispherical interface voids. The bonding to the ceramics gives rise to highly cons...

  7. Effects of two-phase mixing and void drift models on subchannel void fraction predictions in vertical bundles

    Energy Technology Data Exchange (ETDEWEB)

    Leung, K.H. [McMaster Univ., Hamilton, Ontario (Canada)], E-mail: leungk4@mcmaster.ca

    2009-07-01

    The evaluation of the subchannel code ASSERT against the OECD/NEA BFBT benchmark data demonstrated that at low pressures, the void fraction in the corner and side subchannels of a vertical bundle was over-predicted. Preliminary results suggest that this was due to the use of Carlucci's empirical correlation for void drift beyond its applicable range of pressure. Further examination indicates that the choice of the mixing and void drift models has a negligible effect on the error of the subchannel void fraction predictions. A single, isolated subchannel was simulated and results suggest that the root cause behind the over-prediction is inadequate mixing at the sides and corners of the bundle. Increasing the magnitude of the void drift coefficients in Carlucci's model at low pressure was found to improve the overall accuracy of the predictions. A simple correlation relating {omega} to the outlet pressure was found to increase the number of points falling within experimental error by 1.0%. (author)

  8. Effects of two-phase mixing and void drift models on subchannel void fraction predictions in vertical bundles

    International Nuclear Information System (INIS)

    Leung, K.H.

    2009-01-01

    The evaluation of the subchannel code ASSERT against the OECD/NEA BFBT benchmark data demonstrated that at low pressures, the void fraction in the corner and side subchannels of a vertical bundle was over-predicted. Preliminary results suggest that this was due to the use of Carlucci's empirical correlation for void drift beyond its applicable range of pressure. Further examination indicates that the choice of the mixing and void drift models has a negligible effect on the error of the subchannel void fraction predictions. A single, isolated subchannel was simulated and results suggest that the root cause behind the over-prediction is inadequate mixing at the sides and corners of the bundle. Increasing the magnitude of the void drift coefficients in Carlucci's model at low pressure was found to improve the overall accuracy of the predictions. A simple correlation relating Ω to the outlet pressure was found to increase the number of points falling within experimental error by 1.0%. (author)

  9. Effects of Void Uncertainties on Pin Power Distributions and the Void Reactivity Coefficient for a 10X10 BWR Assembly

    International Nuclear Information System (INIS)

    Jatuff, F.; Krouthen, J.; Helmersson, S.; Chawla, R.

    2004-01-01

    A significant source of uncertainty in Boiling Water Reactor physics is associated with the precise characterisation of the axially-dependent neutron moderation properties of the coolant inside the fuel assembly channel, and the corresponding effects on reactor physics parameters such as the lattice neutron multiplication, the neutron migration length, and the pin-by-pin power distribution. In this paper, the effects of particularly relevant void fraction uncertainties on reactor physics parameters have been studied for a BWR assembly of type Westinghouse SVEA-96 using the CASMO-4, HELIOS/PRESTO-2 and MCNP4C codes. The SVEA-96 geometry is characterised by the sub-division of the assembly into four different sub-bundles by means of an inner bypass with a cruciform shape. The study has covered the following issues: (a) the effects of different cross-section data libraries on the void coefficient of reactivity, for a wide range of void fractions; (b) the effects due to a heterogeneous vs. homogeneous void distribution inside the sub-bundles; and (c) the consequences of partly inserted absorber blades producing different void fractions in different sub-bundles. (author)

  10. Effects contributing to positive coolant void reactivity in CANDU

    International Nuclear Information System (INIS)

    Whitlock, J.J.; Garland, W.J.; Milgram, M.S.

    1995-01-01

    The lattice cell code WIMS-AECL (Ref. 3) is used to model a typical CANDU lattice cell, using nominal geometric bucklings, the PIJ option, and 69-group Winfrith library. The effect of cell voiding is modeled as a 100% instantaneous removal of coolant from the lattice. This is conservative because of the neglect of time dependence and partial core voiding, considered more plausible in CANDU. Results are grouped into three spectral groups: fast neutrons (0.821 to 10 MeV), epithermal neutrons (0.625 eV to 0.821 MeV), and thermal neutrons (<0.625 eV)

  11. Supernovae observations in a 'meatball' universe with a local void

    International Nuclear Information System (INIS)

    Kainulainen, Kimmo; Marra, Valerio

    2009-01-01

    We study the impact of cosmic inhomogeneities on the interpretation of observations. We build an inhomogeneous universe model without dark energy that can confront supernova data and yet is reasonably well compatible with the Copernican principle. Our model combines a relatively small local void, that gives apparent acceleration at low redshifts, with a meatball model that gives sizable lensing (dimming) at high redshifts. Together these two elements, which focus on different effects of voids on the data, allow the model to mimic the concordance model.

  12. Supernovae observations in a 'meatball' universe with a local void

    Energy Technology Data Exchange (ETDEWEB)

    Kainulainen, Kimmo; Marra, Valerio [Department of Physics, University of Jyvaeskylae, PL 35 (YFL), FIN-40014 Jyvaeskylae, Finland and Helsinki Institute of Physics, University of Helsinki, PL 64, FIN-00014 Helsinki (Finland)

    2009-12-15

    We study the impact of cosmic inhomogeneities on the interpretation of observations. We build an inhomogeneous universe model without dark energy that can confront supernova data and yet is reasonably well compatible with the Copernican principle. Our model combines a relatively small local void, that gives apparent acceleration at low redshifts, with a meatball model that gives sizable lensing (dimming) at high redshifts. Together these two elements, which focus on different effects of voids on the data, allow the model to mimic the concordance model.

  13. Supernovae observations in a ``meatball'' universe with a local void

    Science.gov (United States)

    Kainulainen, Kimmo; Marra, Valerio

    2009-12-01

    We study the impact of cosmic inhomogeneities on the interpretation of observations. We build an inhomogeneous universe model without dark energy that can confront supernova data and yet is reasonably well compatible with the Copernican principle. Our model combines a relatively small local void, that gives apparent acceleration at low redshifts, with a meatball model that gives sizable lensing (dimming) at high redshifts. Together these two elements, which focus on different effects of voids on the data, allow the model to mimic the concordance model.

  14. Void redistribution in sand under post-earthquake loading

    International Nuclear Information System (INIS)

    Boulanger, R.W.; Truman, S.P.

    1996-01-01

    A mechanism for void redistribution in an infinite slope under post-earthquake loading conditions is described by consideration of the in situ loading paths that can occur under post-earthquake conditions and the results of triaxial tests designed to represent specific in situ post-earthquake loading paths. The mechanism is illustrated by application to an example problem. Void redistribution is shown to be a phenomena that may be more pronounced at the field scale than at the laboratory scale. (author). 12 refs., 4 figs

  15. Influence of void on image quality of industrial SPECT

    International Nuclear Information System (INIS)

    Park, J G; Jung, S H; Kim, J B; Moon, J; Kim, C H

    2013-01-01

    Industrial single photon emission computed tomography (SPECT) is a promising technique to determine the dynamic behavior of industrial process media and has been developed in the Korea Atomic Energy Research Institute. The present study evaluated the influence of a void, which is presence in multiphase reactors of industrial process, on the image quality of an industrial SPECT. The results are very encouraging; that is, the performance of the industrial SPECT system is little influenced by the presence of a void, which means that industrial SPECT is an appropriate tool to estimate the dynamic characteristics of the process media in a water-air phase bubble column with a static gas sparger

  16. Transient void fraction measurements in rod bundle geometries

    International Nuclear Information System (INIS)

    Chan, A.M.C.

    1998-01-01

    A new gamma densitometer with a Ba-133 source and a Nal(TI) scintillator operated in the count mode has been designed for transient void fraction measurements in the RD-14M heated channels containing a seven-element heater bundle. The device was calibrated dynamically in the laboratory using an air-water flow loop. The void fraction measured was found to compare well with values obtained using the trapped-water method. The device was also found to follow very well the passage of air slugs in pulsating flow with slug passing frequencies of up to about 1.5 hz. (author)

  17. Void swelling behaviour of austenitic stainless steel during electron irradiation

    International Nuclear Information System (INIS)

    Sheng Zhongqi; Xiao Hong; Peng Feng; Ti Zhongxin

    1994-04-01

    The irradiation swelling behaviour of 00Cr17Ni14Mo2 austenitic stainless steel (AISI 316L) was investigated by means of high voltage electron microscope. Results showed that in solution annealed condition almost no swelling incubation period existed, and the swelling shifted from the transition period to the steady-state one when the displacement damage was around 40 dpa. In cold rolled condition there was evidently incubation period, and when the displacement damage was up to 84 dpa the swelling still remained in the transition period. The average size and density of voids in both conditions were measured, and the factors, which influenced the void swelling, were discussed. (3 figs.)

  18. Effect of the critical size of initial voids on stress-induced migration

    International Nuclear Information System (INIS)

    Aoyagi, Minoru

    2004-01-01

    The stress-induced migration phenomenon is one of the problems related to the reliability of metal interconnections in semiconductor devices. This phenomenon causes voids and fractures in interconnections. The basic feature of this phenomenon is vacancy migration to minute initial voids. Expanding initial voids grow into larger voids and fractures. The purpose of this work is to theoretically clarify the effects of residual thermal stress and void surface stress on the behavior of the initial voids which exist immediately after a passivation process. Using a spherical metal sample with a spherical void under external stress, vacancy absorption or emission was investigated between the void surface and the sample surface. The behavior of vacancies and atoms was also investigated in interconnections under residual thermal stress. We show that the void or sample surface becomes a vacancy sink or source, depending on the mutual relationship between the surface stress due to the surface-free energy and the residual thermal stress. We also reveal that the initial voids, which exist immediately after a passivation process, grow into larger voids and fractures when the size of the initial voids exceeds the critical size. If the size of the initial void can be controlled to below the critical size, voids and fractures do not occur

  19. Behavior of aluminum oxide, intermetallics and voids in Cu-Al wire bonds

    International Nuclear Information System (INIS)

    Xu, H.; Liu, C.; Silberschmidt, V.V.; Pramana, S.S.; White, T.J.; Chen, Z.; Acoff, V.L.

    2011-01-01

    Nanoscale interfacial evolution in Cu-Al wire bonds during isothermal annealing from 175 deg. C to 250 deg. C was investigated by high resolution transmission electron microscopy (HRTEM). The native aluminum oxide film (∼5 nm thick) of the Al pad migrates towards the Cu ball during annealing. The formation of intermetallic compounds (IMC) is controlled by Cu diffusion, where the kinetics obey a parabolic growth law until complete consumption of the Al pad. The activation energies to initiate crystallization of CuAl 2 and Cu 9 Al 4 are 60.66 kJ mol -1 and 75.61 kJ mol -1 , respectively. During IMC development, Cu 9 Al 4 emerges as a second layer and grows together with the initial CuAl 2 . When Al is completely consumed, CuAl 2 transforms to Cu 9 Al 4 , which is the terminal product. Unlike the excessive void growth in Au-Al bonds, only a few voids nucleate in Cu-Al bonds after long-term annealing at high temperatures (e.g., 250 o C for 25 h), and their diameters are usually in the range of tens of nanometers. This is due to the lower oxidation rate and volumetric shrinkage of Cu-Al IMC compared with Au-Al IMC.

  20. THE PREDICTION OF VOID VOLUME IN SUBCOOLED NUCLEATE POOL BOILING

    Energy Technology Data Exchange (ETDEWEB)

    Duke, E. E. [General Dynamics, San Diego, CA (United States)

    1963-11-15

    A three- step equation was developed that adequately describes the average volume of vapor occurring on a horizontal surface due to nucleate pool boiling of subcooled water. Since extensive bubble frequency data are lacking, the data of others were combined with experimental observations to make predictions of void volume at ambient pressure with various degrees of subcooling. (auth)

  1. Nucleation of voids and other irradiation-produced defect aggregates

    International Nuclear Information System (INIS)

    Wiedersich, H.; Katz, J.L.

    1976-01-01

    The nucleation of defect clusters in crystalline solids from radiation-produced defects is different from the usual nucleation processes in one important aspect: the condensing defects, interstitial atoms and vacancies, can mutually annihilate and are thus similar to matter and antimatter. The nucleation process is described as the simultaneous reaction of vacancies and interstitials (and gas atoms if present) with embryos of all sizes. The reaction rates for acquisition of point defects (and gas atoms) are calculated from their respective jump frequencies and concentrations in the supersaturated system. The reaction rates for emission of point defects are derived from the free energies of the defect clusters in the thermodynamic equilibrium system, i.e., the system without excess point defects. This procedure differs from that used in conventional nucleation theory and permits the inclusion of the ''antimatter'' defect into the set of reaction-rate equations in a straightforward manner. The method is applied to steady-state nucleation, during irradiation, of both dislocation loops and voids in the absence and in the presence of immobile and mobile gas. The predictions of the nucleation theory are shown to be in qualitative agreement with experimental observations, e.g., void densities increase with increasing displacement rates; gases such as helium enhance void nucleation; at low displacement rates and at high temperatures the presence of gas is essential to void formation. For quantitative predictions, the theory must be extended to include the termination of nucleation

  2. Predictive efficacy of radioisotope voiding cystography for renal outcome

    International Nuclear Information System (INIS)

    Kim, Seok Ki; Lee, Dong Soo; Kim, Kwang Myeung; Choi, Whang; Chung, June Key; Lee, Myung Chul

    2000-01-01

    As vesicoureteral reflux (VUR) could lead to renal functional deterioration when combined with urinary tract infection, we need to decide whether operative anti-reflux treatment should be performed at the time of diagnosis of VUR. Predictive value of radioisotope voiding cystography (RIVCG) for renal outcome was tested. In 35 children (18 males, 17 females), radiologic voiding cystoure-thrography (VCU), RIVCG and DMSA scan were performed. Change in renal function was evaluated using the follow-up DMSA scan, ultrasonography, and clinical information. Discriminant analysis was performed using individual or integrated variables such as reflux amount and extent at each phase of voiding on RIVCG, in addition to age, gender and cortical defect on DMSA scan at the time of diagnosis. Discriminant function was composed and its performance was examined. Reflux extent at the filling phase and reflux amount and extent at postvoiding phase had a significant prognostic value. Total reflux amount was a composite variable to predict prognosis. Discriminant function composed of reflux extent at the filling phase and reflux amount and extent at postvoiding phase showed better positive predictive value and specificity than conventional reflux grading. RIVCG could predict renal outcome by disclosing characteristic reflux pattern during various voiding phases.=20

  3. Decay of charge deposited on the wall of gaseous void

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1992-01-01

    sustained in the void. However, the absolute value of this field is reduced with an increase in bulk permittivity. It is concluded that the present choice of a point charge to simulate the wall charge has the disadvantage that such a source is associated with a field singularity, and thus it is not possible...

  4. Electric field theory and the fallacy of void capacitance

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1991-01-01

    The concept of the capacitance of a gaseous void is discussed as applied to electrical insulation science. The most pertinent aspect of the capacitance definition is that of reference to a single-valued potential difference between surfaces. This implies that these surfaces must be surfaces...

  5. Effect of main stream void distribution on cavitating hydrofoil

    International Nuclear Information System (INIS)

    Ito, J.

    1993-01-01

    For the safety analysis of a loss of coolant accident in a pressurized water reactor, it is important to establish an analytical method which predicts the pump performance under gas-liquid two-phase flow condition. J.H. Kim briefly reviewed several major two-phase flow pump models, and discussed the parameters that could significantly affect two-phase pump behavior. The parameter pointed out to be of the most importance is void distribution at the pump inlet. This says that the pipe bend near the pump inlet makes the void distribution at the pump inlet nonuniform, and this matter can have a significant effect on the impeller blade performance. This paper proposes an analytical method of solution for a partially cavitating hydrofoil placed in the main stream of incompressible homogeneous bubbly two-phase flow conditions whose void fraction is exponentially distributed normal to chordline. The paper clarifies the effect of main stream void distribution parameter on the partially cavitating hydrofoil characteristics

  6. The cosmic web in CosmoGrid void regions

    NARCIS (Netherlands)

    Rieder, Steven; van de Weygaert, Rien; Cautun, Marius; Beygu, Burcu; Portegies Zwart, Simon

    2016-01-01

    We study the formation and evolution of the cosmic web, using the high-resolution CosmoGrid ΛCDM simulation. In particular, we investigate the evolution of the large-scale structure around void halo groups, and compare this to observations of the VGS-31 galaxy group, which consists of three

  7. Monte Carlo validation of self shielding and void effect calculations

    International Nuclear Information System (INIS)

    Tellier, H.; Coste, M.; Raepsaet, C.; Soldevila, M.; Van der Gucht, C.

    1995-01-01

    The self shielding validation and the void effect are studied with Monte Carlo method. The satisfactory comparison obtained between the APOLLO 2 results of the self shielding effect and the TRIPOLI and MCNP results allows us to be confident in the multigroup transport code. (K.A.)

  8. Extrapolation of ZPR sodium void measurements to the power reactor

    International Nuclear Information System (INIS)

    Beck, C.L.; Collins, P.J.; Lineberry, M.J.; Grasseschi, G.L.

    1976-01-01

    Sodium-voiding measurements of ZPPR assemblies 2 and 5 are analyzed with ENDF/B Version IV data. Computations include directional diffusion coefficients to account for streaming effects resulting from the plate structure of the critical assembly. Bias factors for extrapolating critical assembly data to the CRBR design are derived from the results of this analysis

  9. Detection of Vesico-Ureteric Reflux Using Voiding Hippuran Ureterograms

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, J. B.; Palser, R. [Section of Nuclear Medicine, Manitoba Cancer Treatment and Research Foundation, Winnipeg General Hospital, Winnipeg (Canada); Macpherson, R. I. [Children' s Hospital of Winnipeg, Winnipeg (Canada)

    1971-02-15

    Initial results of a technique for the demonstration of vesico-ureteric reflux in children are described. Hippuran-{sup 131}I (15 {mu}Ci) (ortho-iodohippurate) is injected intravenously. A standard renogram is obtained. Additional collimation is added to the recording probes and they are positioned to record the radioactivity from the mid-ureteric region. Recordings of normal and abnormal peristaltic activity during per-ora hydration of the patient are thus obtained. When the child is willing to void, he is placed upright on a bed pan, the probes positioned to record over the lower ureteric region and recordings are made while the child voids. All data are recorded on a 512-channel analyser operated in the multi-scaler node. Data are punched out on paper tape and, after an 11 point computer smoothing program, are displayed graphically. These recordings show different patterns in normal children and those with vesico-ureteric reflux. There are several advantages to this technique over the standard radiological and other radionuclide voiding cystoureterograms. The results are compared with contrast voiding cystourethrograms in both normal children and those with vesico-ureteric reflux. (author)

  10. 3D optical tomography in the presence of void regions

    Science.gov (United States)

    Riley, J.; Dehghani, Hamid; Schweiger, Martin; Arridge, Simon R.; Ripoll, Jorge; Nieto-Vesperinas, Manuel

    2000-12-01

    We present an investigation of the effect of a 3D non-scattering gap region on image reconstruction in diffuse optical tomography. The void gap is modelled by the Radiosity-Diffusion method and the inverse problem is solved using the adjoint field method. The case of a sphere with concentric spherical gap is used as an example.

  11. Experimental facility and void fraction calibration methods for impedance probes

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Fernando L. de; Rocha, Marcelo S., E-mail: floliveira@ipen.br, E-mail: msrocha@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    An experimental facility was designed and constructed with aims of to calibrate a capacitance probe for gas-liquid flow void fraction measurements. The facility is composed of a metallic hack with a vertical 2,300 mm high glass tube with 38 mm ID with stagnant water and compressed air bubbling system simulating the gas phase (vapor). At the lower part, a mixing section with a porous media element releases the air bubbles into the water, and the compressed air flow is measured by two calibrated rotameters. At the upper part a stagnant water tank separates the liquid and gas. Two pressure taps are located near the lower and upper sides of the glass tube for pressure difference measurement. The pressure difference is used for low void fraction values (0-15%) calibration methods, as described in the work. Two electrically controlled quick closing valves are installed between the porous media element and the upward separation tank for high void fraction values measurement (15-50%) used to calibrate the capacitance probe. The experimental facility design, construction, capacitance probe calibration methods and results, as well as flow pattern visualization, are presented. Finally, the capacitance probe will be installed on a natural circulation circuit mounted at the Nuclear Engineering Center (CEN/IPEN/CNEN-SP) for measurement of the instantaneous bulk void. Instantaneous signals generated by the capacitance probe will allow the determination of natural circulation loop global energy balance. (author)

  12. Influence of ageing, inclusions and voids on ductile fracture ...

    Indian Academy of Sciences (India)

    Unknown

    The strain hardening capacity has a marked effect on void size, and is an indicator of fracture .... a model of ductile failure based on the concept that the critical step in the .... Ashby M F, Gandhi C and Taplin D M R 1979 Acta Metal. 27. 699.

  13. Experimental facility and void fraction calibration methods for impedance probes

    International Nuclear Information System (INIS)

    Oliveira, Fernando L. de; Rocha, Marcelo S.

    2013-01-01

    An experimental facility was designed and constructed with aims of to calibrate a capacitance probe for gas-liquid flow void fraction measurements. The facility is composed of a metallic hack with a vertical 2,300 mm high glass tube with 38 mm ID with stagnant water and compressed air bubbling system simulating the gas phase (vapor). At the lower part, a mixing section with a porous media element releases the air bubbles into the water, and the compressed air flow is measured by two calibrated rotameters. At the upper part a stagnant water tank separates the liquid and gas. Two pressure taps are located near the lower and upper sides of the glass tube for pressure difference measurement. The pressure difference is used for low void fraction values (0-15%) calibration methods, as described in the work. Two electrically controlled quick closing valves are installed between the porous media element and the upward separation tank for high void fraction values measurement (15-50%) used to calibrate the capacitance probe. The experimental facility design, construction, capacitance probe calibration methods and results, as well as flow pattern visualization, are presented. Finally, the capacitance probe will be installed on a natural circulation circuit mounted at the Nuclear Engineering Center (CEN/IPEN/CNEN-SP) for measurement of the instantaneous bulk void. Instantaneous signals generated by the capacitance probe will allow the determination of natural circulation loop global energy balance. (author)

  14. Calculation of Void in the Fort Saint Vrain Material

    Energy Technology Data Exchange (ETDEWEB)

    Potter, David Charles [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Taylor, Craig Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Coons, James Elmer [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-05-11

    The percent void of the Fort Saint Vrain (FSV) material is estimated to be 21.1% based on the volume of the gap at the top of the drums, the volume of the coolant channels in the FSV fuel element, and the volume of the fuel handling channel in the FSV fuel element.

  15. Nucleation of voids in materials supersaturated with mobile interstitials, vacancies and divacancies

    International Nuclear Information System (INIS)

    Wolfer, W.G.; Si-Ahmed, A.

    1982-01-01

    In previous void nucleation theories, the void size has been allowed to change only by one atomic volume through vacancy or interstitial absorption or through vacancy emission. To include the absorption of divacancies, the classical nucleation theory is here extended to include double-step transitions between clusters. The new nucleation theory is applied to study the effect of divacancies on void formation. It is found that the steady-state void nucleation rate is enhanced by several orders of magnitude as compared to results with previous void nucleation theories. However, to obtain void nucleation rates comparable to measured ones, the effect of impurities, segregation and insoluble gases must still be invoked. (author)

  16. Influence of second phase dispersion on void formation during irradiation

    International Nuclear Information System (INIS)

    Sundararaman, M.; Banerjee, S.; Krishnan, R.

    Irradiation-induced void formation in alloys has been found to be strongly influenced by the microstructure, the important microstructural parameters being the dislocation density and the nature, density and distribution of second-phase precipitates. The effects of various types of precipitates on void swelling have been examined using the generally-accepted model of void formation : void embryos are assumed to grow in a situation where equal numbers of vacancies and interstitials are continuously generated by the incident irradiation, the interstitials being somewhat perferentially absorbed in some sinks present in the material. The mechanism of the trapping of defects by a distribution of precipitates has been discussed and the available experimental results on the suppression of void formation in materials containing coherent precipitates have been reviewed. Experimental results on the microstructure developed in a nickel-base alloys, Inconel-718 (considered to be a candidate material for structural applications in fast reactors), have been presented. The method of determination of the coherency strain associated with the precipitates has been illustrated with the help of certain observations made on this alloy. The major difficulty in using a two-phase alloy in an irradiation environment is associated with the irradiation-induced instability of the precipitates. Several processes such as precipitate dislocation (in which the incident radiation removes the outer layer of precipitates by recoil), enhanced diffusion disordering, fragmentation of precipitates, etc. are responsible for bringinq about a significant change in the structure of a two-phase material during irradiation. The effect of these processes on the continued performance of a two-phase alloy subjected to irradiation at an elevated temperature has been discussed. (auth.)

  17. Is abdominal wall contraction important for normal voiding in the female rat?

    Directory of Open Access Journals (Sweden)

    Boone Timothy B

    2007-03-01

    Full Text Available Abstract Background Normal voiding behavior in urethane-anesthetized rats includes contraction of the abdominal wall striated muscle, similar to the visceromotor response (VMR to noxious bladder distension. Normal rat voiding requires pulsatile release of urine from a pressurized bladder. The abdominal wall contraction accompanying urine flow may provide a necessary pressure increment for normal efficient pulsatile voiding. This study aimed to evaluate the occurrence and necessity of the voiding-associated abdominal wall activity in urethane-anesthetized female rats Methods A free-voiding model was designed to allow assessment of abdominal wall activity during voiding resulting from physiologic bladder filling, in the absence of bladder or urethral instrumentation. Physiologic diuresis was promoted by rapid intravascular hydration. Intercontraction interval (ICI, voided volumes and EMG activity of the rectus abdominis were quantified. The contribution of abdominal wall contraction to voiding was eliminated in a second group of rats by injecting botulinum-A (BTX, 5 U into each rectus abdominis to induce local paralysis. Uroflow parameters were compared between intact free-voiding and BTX-prepared animals. Results Abdominal wall response is present in free voiding. BTX preparation eliminated the voiding-associated EMG activity. Average per-void volume decreased from 1.8 ml to 1.1 ml (p Conclusion The voiding-associated abdominal wall response is a necessary component of normal voiding in urethane anesthetized female rats. As the proximal urethra may be the origin of the afferent signaling which results in the abdominal wall response, the importance of the bladder pressure increment due to this response may be in maintaining a normal duration intermittent pulsatile high frequency oscillatory (IPHFO/flow phase and thus efficient voiding. We propose the term Voiding-associated Abdominal Response (VAR for the physiologic voiding-associated EMG

  18. Voids and superstructures: correlations and induced large-scale velocity flows

    Science.gov (United States)

    Lares, Marcelo; Luparello, Heliana E.; Maldonado, Victoria; Ruiz, Andrés N.; Paz, Dante J.; Ceccarelli, Laura; Garcia Lambas, Diego

    2017-09-01

    The expanding complex pattern of filaments, walls and voids build the evolving cosmic web with material flowing from underdense on to high density regions. Here, we explore the dynamical behaviour of voids and galaxies in void shells relative to neighbouring overdense superstructures, using the Millenium simulation and the main galaxy catalogue in Sloan Digital Sky Survey data. We define a correlation measure to estimate the tendency of voids to be located at a given distance from a superstructure. We find voids-in-clouds (S-types) preferentially located closer to superstructures than voids-in-voids (R-types) although we obtain that voids within ˜40 h-1 Mpc of superstructures are infalling in a similar fashion independently of void type. Galaxies residing in void shells show infall towards the closest superstructure, along with the void global motion, with a differential velocity component depending on their relative position in the shell with respect to the direction to the superstructure. This effect is produced by void expansion and therefore is stronger for R-types. We also find that galaxies in void shells facing the superstructure flow towards the overdensities faster than galaxies elsewhere at the same relative distance to the superstructure. The results obtained for the simulation are also reproduced for the Sky Survey Data Release data with a linearized velocity field implementation.

  19. Three-dimensional core analysis on a super fast reactor with negative local void reactivity

    International Nuclear Information System (INIS)

    Cao Liangzhi; Oka, Yoshiaki; Ishiwatari, Yuki; Ikejiri, Satoshi

    2009-01-01

    Keeping negative void reactivity throughout the cycle life is one of the most important requirements for the design of a supercritical water-cooled fast reactor (super fast reactor). Previous conceptual design has negative overall void reactivity. But the local void reactivity, which is defined as the reactivity change when the coolant of one fuel assembly disappears, also needs to be kept negative throughout the cycle life because the super fast reactor is designed with closed fuel assemblies. The mechanism of the local void reactivity is theoretically analyzed from the neutrons balance point of view. Three-dimensional neutronics/thermal-hydraulic coupling calculation is employed to analyze the characteristics of the super fast reactor including the local void reactivity. Some configurations of the core are optimized to decrease the local void reactivity. A reference core is successfully designed with keeping both overall and local void reactivity negative. The maximum local void reactivity is less than -30 pcm

  20. Mechanism of Void Prediction in Flip Chip Packages with Molded Underfill

    Science.gov (United States)

    Wu, Kuo-Tsai; Hwang, Sheng-Jye; Lee, Huei-Huang

    2017-08-01

    Voids have always been present using the molded underfill (MUF) package process, which is a problem that needs further investigation. In this study, the process was studied using the Moldex3D numerical analysis software. The effects of gas (air vent effect) on the overall melt front were also considered. In this isothermal process containing two fluids, the gas and melt colloid interact in the mold cavity. Simulation enabled an appropriate understanding of the actual situation to be gained, and, through analysis, the void region and exact location of voids were predicted. First, the global flow end area was observed to predict the void movement trend, and then the local flow ends were observed to predict the location and size of voids. In the MUF 518 case study, simulations predicted the void region as well as the location and size of the voids. The void phenomenon in a flip chip ball grid array underfill is discussed as part of the study.

  1. Void swelling in fast reactor irradiated high purity binary iron-chromium alloys

    International Nuclear Information System (INIS)

    Little, E.A.; Stow, D.A.

    The void swelling characteristics of a series of high purity binary iron-chromium alloys containing 0 - 615 0 C. The void swelling behaviour can be qualitatively rationalized in terms of point defect trapping and precipitation processes involving chromium atoms

  2. Effect of scale size, orientation type and dispensing method on void ...

    Indian Academy of Sciences (India)

    AIZAT ABAS

    2018-04-13

    Apr 13, 2018 ... reduce the formation of void during encapsulation process. Keywords. Ball grid ... Additionally, the usage of LBM to study of void in CUF was again conducted by ... models are fabricated using clear Perspex and plastics beads.

  3. Parallel Void Thread in Long-Reach Ethernet Passive Optical Networks

    KAUST Repository

    Elrasad, Amr; Shihada, Basem

    2015-01-01

    This work investigates void filling (idle periods) in long-reach Ethernet passive optical networks. We focus on reducing grant delays and hence reducing the average packet delay. We introduce a novel approach called parallel void thread (PVT), which

  4. Void fraction instrument software, Version 1,2, Acceptance test report

    International Nuclear Information System (INIS)

    Gimera, M.

    1995-01-01

    This provides the report for the void fraction instrument acceptance test software Version 1.2. The void fraction will collect data that will be used to calculate the quantity of gas trapped in waste tanks

  5. Voids, nanochannels and formation of nanotubes with mobile Sn fillings in Sn doped ZnO nanorods

    International Nuclear Information System (INIS)

    Ortega, Y; Dieker, Ch; Jaeger, W; Piqueras, J; Fernandez, P

    2010-01-01

    ZnO nanorods containing different hollow structures have been grown by a thermal evaporation-deposition method with a mixture of ZnS and SnO 2 powders as precursor. Transmission electron microscopy shows rods with rows of voids as well as rods with empty channels along the growth axis. The presence of Sn nanoprecipitates associated with the empty regions indicates, in addition, that these are generated by diffusion processes during growth, probably due to an inhomogeneous distribution of Sn. The mechanism of forming voids and precipitates appears to be based on diffusion processes similar to the Kirkendall effect, which can lead to void formation at interfaces of bulk materials or in core-shell nanostructures. In some cases the nanorods are ZnO tubes partially filled with Sn that has been found to melt and expand by heating the nanotubes under the microscope electron beam. Such metal-semiconductor nanostructures have potential applications as thermal nanosensors or as electrical nanocomponents.

  6. Void initiation from interfacial debonding of spherical silicon particles inside a silicon-copper nanocomposite: a molecular dynamics study

    Science.gov (United States)

    Cui, Yi; Chen, Zengtao

    2017-02-01

    Silicon particles with diameters from 1.9 nm to 30 nm are embedded in a face-centered-cubic copper matrix to form nanocomposite specimens for simulation. The interfacial debonding of silicon particles from the copper matrix and the subsequent growth of nucleated voids are studied via molecular dynamics (MD). The MD results are examined from several different perspectives. The overall mechanical performance is monitored by the average stress-strain response and the accumulated porosity. The ‘relatively farthest-traveled’ atoms are identified to characterize the onset of interfacial debonding. The relative displacement field is plotted to illustrate both subsequent interfacial debonding and the growth of a nucleated void facilitated by a dislocation network. Our results indicate that the initiation of interfacial debonding is due to the accumulated surface stress if the matrix is initially dislocation-free. However, pre-existing dislocations can make a considerable difference. In either case, the dislocation emission also contributes to the subsequent debonding process. As for the size effect, the debonding of relatively larger particles causes a drop in the stress-strain curve. The volume fraction of second-phase particles is found to be more influential than the size of the simulation box on the onset of interfacial debonding. The volume fraction of second-phase particles also affects the shape of the nucleated void and, therefore, influences the stress response of the composite.

  7. Void swelling and segregation in dilute nickel alloys

    International Nuclear Information System (INIS)

    Potter, D.I.; Rehn, L.E.; Okamoto, P.R.; Wiedersich, H.

    1977-01-01

    Five binary alloys containing 1 at.% of Al, Ti, Mo, Si and Be in nickel were irradiated at temperatures from 525 to 675 0 C with 3.5-MeV 58 Ni + ions. The resultant microstructures were examined by TEM, and void diameters, number densities and swelling are presented for each alloy over the temperature interval investigated. A systematic relation between solute misfit (size factor) and void swelling is established for these alloys. Solute concentration profiles near the irradiated surface were determined and these also exhibited a systematic behavior--undersize solutes segregated to the surface, whereas oversize solutes were depleted. The results are consistent with calculations based on strong interstitial-solute trapping by undersize solutes and vacancy-solute trapping by oversize solutes that are weak interstitial traps

  8. Generalized Rate Theory for Void and Bubble Swelling and its Application to Delta-Plutonium

    Energy Technology Data Exchange (ETDEWEB)

    Allen, P. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wall, M. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wolfer, W. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-10-04

    A rate theory for void and bubble swelling is derived that allows both vacancies and self-interstitial atoms to be generated by thermal activation at all sinks. In addition, they can also be produced by displacement damage from external and internal radiation. This generalized rate theory (GRT) is applied to swelling of gallium-stabilized δ-plutonium in which α-decay causes the displacement damage. Since the helium atoms produced also become trapped in vacancies, a distinction is made between empty and occupied vacancies. The growth of helium bubbles observed by transmission electron microscopy (TEM) in weapons-grade and in material enriched with Pu238 is analyzed, using different values for the formation energy of self-interstitial atoms (SIA) and two different sets of relaxation volumes for the vacancy and for the SIA. One set allows preferential capture of SIA at dislocations, while the other set gives equal preference to both vacancy and SIA. It is found that the helium bubble diameters observed are in better agreement with GRT predictions if no preferential capture occurs at dislocations. Therefore, helium bubbles in δ-plutonium will not evolve into voids. The helium density within the bubbles remains sufficiently high to cause thermal emission of SIA. Based on a helium density between two to three helium atoms per vacant site, the sum of formation and migration energies must be around 2.0 eV for SIA in δ-plutonium.

  9. 40 CFR 1065.525 - Engine starting, restarting, shutdown, and optional repeating of void discrete modes.

    Science.gov (United States)

    2010-07-01

    ..., and optional repeating of void discrete modes. 1065.525 Section 1065.525 Protection of Environment... repeating of void discrete modes. (a) Start the engine using one of the following methods: (1) Start the... during one of the modes of a discrete-mode test, you may void the results only for that individual mode...

  10. Void coalescence mechanism for combined tension and large amplitude cyclic shearing

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau; Andersen, Rasmus Grau; Tvergaard, Viggo

    2017-01-01

    Void coalescence at severe shear deformation has been studied intensively under monotonic loading conditions, and the sequence of micro-mechanisms that governs failure has been demonstrated to involve collapse, rotation, and elongation of existing voids. Under intense shearing, the voids are flat...

  11. Void structure of concrete with superabsorbent polymers and its relation to frost resistance of concrete

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange; Jensen, Ole Mejlhede; Laustsen, Sara

    2013-01-01

    the difference between poor and satisfactory frost-resistance. Furthermore, the results indicate that voids created directly by SAP protect concrete against frost deterioration just like other air voids; if the concrete contains enough SAP voids, these alone can provide sufficient frost resistance. © 2013 RILEM....

  12. A theoretical derivation of the transients related to partial discharges in ellipsoidal voids

    DEFF Research Database (Denmark)

    Crichton, George C; Karlsson, A.; Pedersen, Aage

    1988-01-01

    be drawn about the effects of the gas within the void as well as the size, shape, and location of voids. The method is illustrated by applying it to a spheroidal void in a simple disk-type gas-insulated-substation (GIS) spacer. It is found that the nonattaching gas generates an induced charge...

  13. Laboratory and exterior decay of wood plastic composite boards: voids analysis and computed tomography

    Science.gov (United States)

    Grace Sun; Rebecca E. Ibach; Meghan Faillace; Marek Gnatowski; Jessie A. Glaeser; John Haight

    2016-01-01

    After exposure in the field and laboratory soil block culture testing, the void content of wood–plastic composite (WPC) decking boards was compared to unexposed samples. A void volume analysis was conducted based on calculations of sample density and from micro-computed tomography (microCT) data. It was found that reference WPC contains voids of different sizes from...

  14. Influence of void ratio on thermal performance of heat pipe receiver

    International Nuclear Information System (INIS)

    Gui Xiaohong; Tang Dawei; Liang Shiqiang; Lin Bin; Yuan Xiugan

    2012-01-01

    Highlights: ► The temperature gradient increases significantly and the utility ratio of PCM decreases obviously as void ratio increases. ► Void cavity influences the process of phase change greatly. ► PCM melts slowly during sunlight periods and freezes slowly during eclipse periods as void ratio increases. ► The temperature gradient of PCM zone is very significant with the effect of void cavity. - Abstract: In this paper, influence of void ratio on thermal performance of heat pipe receiver under microgravity is numerically simulated. Accordingly, mathematical model is set up. Numerical method is offered. The temperature field of Phase Change Material (PCM) canister is shown. Numerical results are compared with numerical ones of National Aeronautics and Space Administration (NASA). Numerical results show that the temperature gradient increases significantly and the utility ratio of PCM decreases obviously as void ratio increases. Void cavity influences the process of phase change greatly. PCM melts slowly during sunlight periods and freezes slowly during eclipse periods as void ratio increases. The thermal resistance of void cavity is much bigger than that of PCM canister wall. Void cavity prevents the heat transfer between PCM zone and canister wall. The temperature gradient of PCM zone is very significant with the effect of void cavity. So the thermal stress of heat pipe receiver may increase, and the lifetime may decrease as void ratio increases.

  15. Void Formation during Diffusion - Two-Dimensional Approach

    Science.gov (United States)

    Wierzba, Bartek

    2016-06-01

    The final set of equations defining the interdiffusion process in solid state is presented. The model is supplemented by vacancy evolution equation. The competition between the Kirkendall shift, backstress effect and vacancy migration is considered. The proper diffusion flux based on the Nernst-Planck formula is proposed. As a result, the comparison of the experimental and calculated evolution of the void formation in the Fe-Pd diffusion couple is shown.

  16. Effect of helium on void swelling in vanadium

    International Nuclear Information System (INIS)

    Brimhall, J.L.; Simonen, E.P.

    1975-01-01

    Little difference in void microstructural swelling of vanadium is observed when helium is injected simultaneously with a 46- or 5-MeV nickel beam as compared to no helium injection, at least at high dose rates. At lower dose rates, a strong helium effect is seen when the helium is injected prior to heavy ion bombardment. The effect of the helium is shown to be a strong function of the overall displacement damage rate

  17. Influence of silicon on void nucleation in irradiated alloys

    International Nuclear Information System (INIS)

    Esmailzadeh, B.; Kumar, A.; Garner, F.A.

    1984-01-01

    The addition of silicon to pure nickel, Ni-Cr alloys and Fe-Ni-Cr alloys raises the diffusivity of each of the alloy components. The resultant increase in the effective vacancy diffusion coefficient causes large reductions in the nucleation rate of voids during irradiation. This extends the transient regime of swelling, which is controlled not only by the amount of silicon in solution but also by the precipitation kinetics of precipitates rich in nickel and silicon

  18. A FACSIMILE code for calculating void swelling, version VS1

    International Nuclear Information System (INIS)

    Windsor, M.; Bullough, R.; Wood, M.H.

    1979-11-01

    VS1 is the first of a series of FACSIMILE codes that are being made available to predict the swelling of materials under irradiation at different temperatures, using chemical rate equations for the point defect losses to voids, interstitial loops, dislocation network, grain boundaries and foil surfaces. In this report the rate equations used in the program are given together with a detailed description of the code and directions for its use. (author)

  19. Validation uncertainty of MATRA code for subchannel void distributions

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Dae-Hyun; Kim, S. J.; Kwon, H.; Seo, K. W. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    To extend code capability to the whole core subchannel analysis, pre-conditioned Krylov matrix solvers such as BiCGSTAB and GMRES are implemented in MATRA code as well as parallel computing algorithms using MPI and OPENMP. It is coded by fortran 90, and has some user friendly features such as graphic user interface. MATRA code was approved by Korean regulation body for design calculation of integral-type PWR named SMART. The major role subchannel code is to evaluate core thermal margin through the hot channel analysis and uncertainty evaluation for CHF predictions. In addition, it is potentially used for the best estimation of core thermal hydraulic field by incorporating into multiphysics and/or multi-scale code systems. In this study we examined a validation process for the subchannel code MATRA specifically in the prediction of subchannel void distributions. The primary objective of validation is to estimate a range within which the simulation modeling error lies. The experimental data for subchannel void distributions at steady state and transient conditions was provided on the framework of OECD/NEA UAM benchmark program. The validation uncertainty of MATRA code was evaluated for a specific experimental condition by comparing the simulation result and experimental data. A validation process should be preceded by code and solution verification. However, quantification of verification uncertainty was not addressed in this study. The validation uncertainty of the MATRA code for predicting subchannel void distribution was evaluated for a single data point of void fraction measurement at a 5x5 PWR test bundle on the framework of OECD UAM benchmark program. The validation standard uncertainties were evaluated as 4.2%, 3.9%, and 2.8% with the Monte-Carlo approach at the axial levels of 2216 mm, 2669 mm, and 3177 mm, respectively. The sensitivity coefficient approach revealed similar results of uncertainties but did not account for the nonlinear effects on the

  20. Void coefficient of reactivity calculation for AP-600 core

    International Nuclear Information System (INIS)

    Suparlina, L.; Budiono, T.A.; Mardha, A.; Tukiran

    1998-01-01

    Void coefficient of reactivity as one of reactor kinetics parameters has been carried out. The calculation was done into two steps which is cell calculation using WIMSD/4 and core calculation using Batan-2DIFF code programs with the condition of beginning of cycle with all fresh fuels elements and all control rods withdrawn. The one dimension transport program in four neutron energy groups is used to calculate the cell generation of various core materials cell has been calculated in 1/4 fuel element with cluster model and square pitch arrange. Moderator density have been reduced until 20% for the void coefficient of reactivity calculation. Macroscopic cross-section as the out put of WIMSD/4 is being used as the input at the diffusion neutron program for core calculation. The void coefficient of reactivity of the AP-600 core can be determined with regular neutron flux and adjoint in four energy groups and X-Y geometry. The results is shown that the K eff calculation value is different 5.2% from the design data

  1. Pelvic floor spasm as a cause of voiding dysfunction.

    Science.gov (United States)

    Kuo, Tricia L C; Ng, L G; Chapple, Christopher R

    2015-07-01

    Pelvic floor disorders can present with lower urinary tract symptoms, bowel, sexual dysfunction, and/or pain. Symptoms of pelvic muscle spasm (nonrelaxing pelvic floor or hypertonicity) vary and can be difficult to recognize. This makes diagnosis and management of these disorders challenging. In this article, we review the current evidence on pelvic floor spasm and its association with voiding dysfunction. To distinguish between the different causes of voiding dysfunction, a video urodynamics study and/or electromyography is often required. Conservative measures include patient education, behavioral modifications, lifestyle changes, and pelvic floor rehabilitation/physical therapy. Disease-specific pelvic pain and pain from pelvic floor spasm needs to be differentiated and treated specifically. Trigger point massage and injections relieves pain in some patients. Botulinum toxin A, sacral neuromodulation, and acupuncture has been reported in the management of patients with refractory symptoms. Pelvic floor spasm and associated voiding problems are heterogeneous in their pathogenesis and are therefore often underrecognized and undertreated; it is therefore essential that a therapeutic strategy needs to be personalized to the individual patient's requirements. Therefore, careful evaluation and assessment of individuals using a multidisciplinary team approach including a trained physical therapist/nurse clinician is essential in the management of these patients.

  2. Nebular metallicities in two isolated local void dwarf galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Nicholls, David C.; Jerjen, Helmut; Dopita, Michael A. [Research School of Astronomy and Astrophysics, Australian National University, Cotter Rd., Weston ACT 2611 (Australia); Basurah, Hassan, E-mail: David.Nicholls@anu.edu.au [Astronomy Department, King Abdulaziz University, P.O. Box 80203, Jeddah (Saudi Arabia)

    2014-01-01

    Isolated dwarf galaxies, especially those situated in voids, may provide insight into primordial conditions in the universe and the physical processes that govern star formation in undisturbed stellar systems. The metallicity of H II regions in such galaxies is key to investigating this possibility. From the SIGRID sample of isolated dwarf galaxies, we have identified two exceptionally isolated objects, the Local Void galaxy [KK98]246 (ESO 461-G036) and another somewhat larger dwarf irregular on the edge of the Local Void, MCG-01-41-006 (HIPASS J1609-04). We report our measurements of the nebular metallicities in these objects. The first object has a single low luminosity H II region, while the second is in a more vigorous star forming phase with several bright H II regions. We find that the metallicities in both galaxies are typical for galaxies of this size, and do not indicate the presence of any primordial gas, despite (for [KK98]246) the known surrounding large reservoir of neutral hydrogen.

  3. Enthalpy and void distributions in subchannels of PHWR fuel bundles

    Energy Technology Data Exchange (ETDEWEB)

    Park, J W; Choi, H; Rhee, B W [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1999-12-31

    Two different types of the CANDU fuel bundles have been modeled for the ASSERT-IV code subchannel analysis. From calculated values of mixture enthalpy and void fraction distribution in the fuel bundles, it is found that net buoyancy effect is pronounced in the central region of the DUPIC fuel bundle when compared with the standard CANDU fuel bundle. It is also found that the central region of the DUPIC fuel bundle can be cooled more efficiently than that of the standard fuel bundle. From the calculated mixture enthalpy distribution at the exit of the fuel channel, it is found that the mixture enthalpy and void fraction can be highest in the peripheral region of the DUPIC fuel bundle. On the other hand, the enthalpy and the void fraction were found to be highest in the central region of the standard CANDU fuel bundle at the exit of the fuel channel. This study shows that the subchannel analysis is very useful in assessing thermal behavior of the fuel bundle that could be used in CANDU reactors. 10 refs., 4 figs., 2 tabs. (Author)

  4. Tomography of integrated circuit interconnect with an electromigration void

    Energy Technology Data Exchange (ETDEWEB)

    Levine, Zachary H. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8410 (United States); Rensselaer Polytechnic Institute, Troy, New York 12180-3590 (United States); Kalukin, Andrew R. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8410 (United States); Kuhn, Markus [Intel Corporation RA1-329, 5200 Northeast Elam Young Parkway, Hillsboro, Oregon 74124 (United States); Frigo, Sean P. [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); McNulty, Ian [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Retsch, Cornelia C. [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Wang, Yuxin [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Arp, Uwe [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8410 (United States); Lucatorto, Thomas B. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8410 (United States); Ravel, Bruce D. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8410 (United States)] (and others)

    2000-05-01

    An integrated circuit interconnect was subject to accelerated-life test conditions to induce an electromigration void. The silicon substrate was removed, leaving only the interconnect test structure encased in silica. We imaged the sample with 1750 eV photons using the 2-ID-B scanning transmission x-ray microscope at the Advanced Photon Source, a third-generation synchrotron facility. Fourteen views through the sample were obtained over a 170 degree sign range of angles (with a 40 degree sign gap) about a single rotation axis. Two sampled regions were selected for three-dimensional reconstruction: one of the ragged end of a wire depleted by the void, the other of the adjacent interlevel connection (or ''via''). We applied two reconstruction techniques: the simultaneous iterative reconstruction technique and a Bayesian reconstruction technique, the generalized Gaussian Markov random field method. The stated uncertainties are total, with one standard deviation, which resolved the sample to 200{+-}70 and 140{+-}30 nm, respectively. The tungsten via is distinguished from the aluminum wire by higher absorption. Within the void, the aluminum is entirely depleted from under the tungsten via. The reconstructed data show the applicability of this technique to three-dimensional imaging of buried defects in submicrometer structures relevant to the microelectronics industry. (c) 2000 American Institute of Physics.

  5. Enthalpy and void distributions in subchannels of PHWR fuel bundles

    Energy Technology Data Exchange (ETDEWEB)

    Park, J. W.; Choi, H.; Rhee, B. W. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1998-12-31

    Two different types of the CANDU fuel bundles have been modeled for the ASSERT-IV code subchannel analysis. From calculated values of mixture enthalpy and void fraction distribution in the fuel bundles, it is found that net buoyancy effect is pronounced in the central region of the DUPIC fuel bundle when compared with the standard CANDU fuel bundle. It is also found that the central region of the DUPIC fuel bundle can be cooled more efficiently than that of the standard fuel bundle. From the calculated mixture enthalpy distribution at the exit of the fuel channel, it is found that the mixture enthalpy and void fraction can be highest in the peripheral region of the DUPIC fuel bundle. On the other hand, the enthalpy and the void fraction were found to be highest in the central region of the standard CANDU fuel bundle at the exit of the fuel channel. This study shows that the subchannel analysis is very useful in assessing thermal behavior of the fuel bundle that could be used in CANDU reactors. 10 refs., 4 figs., 2 tabs. (Author)

  6. Nebular Metallicities in Two Isolated Local Void Dwarf Galaxies

    Science.gov (United States)

    Nicholls, David C.; Jerjen, Helmut; Dopita, Michael A.; Basurah, Hassan

    2014-01-01

    Isolated dwarf galaxies, especially those situated in voids, may provide insight into primordial conditions in the universe and the physical processes that govern star formation in undisturbed stellar systems. The metallicity of H II regions in such galaxies is key to investigating this possibility. From the SIGRID sample of isolated dwarf galaxies, we have identified two exceptionally isolated objects, the Local Void galaxy [KK98]246 (ESO 461-G036) and another somewhat larger dwarf irregular on the edge of the Local Void, MCG-01-41-006 (HIPASS J1609-04). We report our measurements of the nebular metallicities in these objects. The first object has a single low luminosity H II region, while the second is in a more vigorous star forming phase with several bright H II regions. We find that the metallicities in both galaxies are typical for galaxies of this size, and do not indicate the presence of any primordial gas, despite (for [KK98]246) the known surrounding large reservoir of neutral hydrogen.

  7. Void-free epoxy castings for cryogenic insulators and seals

    International Nuclear Information System (INIS)

    Quirk, J.F.

    1983-01-01

    The design of the Westinghouse Magnet for the Oak Ridge National Laboratory's Large Coil Program (LCP) incorporates a main lead bushing which transmits heat-leak loads by conduction to the supercritical helium stream. The bushing, which consists of epoxy resin cast about a copper conductor, must be electrically insulated, vacuum tight and be capable of withstanding the stresses encountered in cryognic service. The seal design of the bushing is especially important; leakage from either the helium system or the external environment into the vacuum will cause the magnet to quench. Additionally, the epoxy-resin casting must resist mechanical loads caused by the weight of leads attached to the bushing and thermal stresses transmitted to the epoxy via the conductor. The epoxy resin is cast about the conductor in such a way as to provide the required vacuum tight seal. The technique by which this is accomplished is reviewed. Equally important is the elimination of voids in the epoxy which will act as stress-concentrating discontinuities during cooling to or warming from 4K. The types of voids that could be expected and their causes are described. The paper reviews techniques employed to eliminate voids within the cast-resin portion of the bushing

  8. Herpes zoster-associated voiding dysfunction in hematopoietic malignancy patients.

    Science.gov (United States)

    Imafuku, Shinichi; Takahara, Masakazu; Uenotsuchi, Takeshi; Iwato, Koji; Furue, Masutaka

    2008-01-01

    Voiding dysfunction is a rare but important complication of lumbo-sacral herpes zoster. Although the symptoms are transient, the clinical impact on immunocompromised patients cannot be overlooked. To clarify the time course of voiding dysfunction in herpes zoster, 13 herpes zoster patients with voiding dysfunction were retrospectively analyzed. Of 13 patients, 12 had background disease, and six of these were hematopoietic malignancies; four of these patients were hematopoietic stem cell transplant (HSCT) recipients. Ten patients had sacral lesions, two had lumbar, and one had thoracic lesions. Interestingly, patients with severe rash, or with hematopoietic malignancy had later onset of urinary retention than did patients with mild skin symptoms (Mann-Whitney U analysis, P = 0.053) or with other background disease (P = 0.0082). Patients with severe skin rash also had longer durations (P = 0.035). In one case, acute urinary retention occurred as late as 19 days after the onset of skin rash. In immune compromised subjects, attention should be paid to patients with herpes zoster in the lumbo-sacral area for late onset of acute urinary retention even after the resolution of skin symptoms.

  9. Kinetic Monte Carlo simulation of three-dimensional shape evolution with void formation using Solid-by-Solid model: Application to via and trench filling

    International Nuclear Information System (INIS)

    Kaneko, Yutaka; Hiwatari, Yasuaki; Ohara, Katsuhiko; Asa, Fujio

    2013-01-01

    In this paper we present the Kinetic Monte Carlo simulation system for the simulation of three-dimensional shape evolution with void formation as a model for electrodeposition. The basic system is the Solid-by-Solid model which is an extension of the conventional Solid-on-Solid model for crystal growth to include void formation. The advantage of the Solid-by-Solid model is that complex three-dimensional shape evolution accompanying void formation (from point defects to macro voids) can be simulated without the difficulty of treating moving boundaries. This model has been extended to include the solution part in which the migration of ions is simulated by the coarse-grained random walk. A multi-scale method is employed to generate the concentration gradient in the diffusion layer. The extended model is applied to the simulation of via and trench fillings by copper electrodeposition. Three kinds of additives are included: suppressors, accelerators and chloride ions. The mechanism of void formation, effects of additives and their influence on the bottom-up filling are discussed within the framework of this model

  10. A general treatment of one- to three-dimensional diffusion reaction kinetics of interstitial clusters: Implications for the evolution of voids

    International Nuclear Information System (INIS)

    Trinkaus, H.; Singh, B.N.; Golubov, S.I.

    2008-05-01

    In recent years, it has been shown that a number of striking features in the microstructural evolution occurring in metals under cascade damage generating irradiation (e.g. enhanced swelling near grain boundaries, decoration of dislocations with SIA loops, saturation of void growth and void lattice formation) can be rationalised in terms of intra-cascade clustering of vacancies and self-interstitial atoms (SIAs), differences in the thermal stability and mobility of the resulting clusters and one-dimensional (1D) glide diffusion of SIA clusters ('production bias model'). The 1D diffusion of SIA clusters is generally disturbed by changes between equivalent 1D diffusion paths and by transversal diffusion by self-climb, resulting in diffusion reaction kinetics between the 1D and 3D limiting cases. In this paper, a general treatment of such kinetics operating in systems containing random distributions of sinks is presented. The complicated partial sink strengths of different components of the system for the annihilation of SIA clusters are expressed by those for the simple 1D and 3D limiting cases. The effects of direction changes and transversal diffusion are first considered separately and are then combined. The significance of the present treatment for damage accumulation under cascade damage conditions is illustrated by applying it to the discussion of void growth characteristics, particularly of the conditions for saturation of void growth. (au)

  11. A general treatment of one- to three-dimensional diffusion reaction kinetics of interstitial clusters: Implications for the evolution of voids

    Energy Technology Data Exchange (ETDEWEB)

    Trinkaus, H. (Inst. Festkoerperforschung, Forschungszentrum Juelich (Germany)); Singh, B.N. (Risoe DTU, Roskilde (Denmark)); Golubov, S.I. (Oak Ridge National Lab., Materials Science and Technology Div., TN (United States))

    2008-05-15

    In recent years, it has been shown that a number of striking features in the microstructural evolution occurring in metals under cascade damage generating irradiation (e.g. enhanced swelling near grain boundaries, decoration of dislocations with SIA loops, saturation of void growth and void lattice formation) can be rationalised in terms of intra-cascade clustering of vacancies and self-interstitial atoms (SIAs), differences in the thermal stability and mobility of the resulting clusters and one-dimensional (1D) glide diffusion of SIA clusters ('production bias model'). The 1D diffusion of SIA clusters is generally disturbed by changes between equivalent 1D diffusion paths and by transversal diffusion by self-climb, resulting in diffusion reaction kinetics between the 1D and 3D limiting cases. In this paper, a general treatment of such kinetics operating in systems containing random distributions of sinks is presented. The complicated partial sink strengths of different components of the system for the annihilation of SIA clusters are expressed by those for the simple 1D and 3D limiting cases. The effects of direction changes and transversal diffusion are first considered separately and are then combined. The significance of the present treatment for damage accumulation under cascade damage conditions is illustrated by applying it to the discussion of void growth characteristics, particularly of the conditions for saturation of void growth. (au)

  12. Learning from errors: analysis of medication order voiding in CPOE systems.

    Science.gov (United States)

    Kannampallil, Thomas G; Abraham, Joanna; Solotskaya, Anna; Philip, Sneha G; Lambert, Bruce L; Schiff, Gordon D; Wright, Adam; Galanter, William L

    2017-07-01

    Medication order voiding allows clinicians to indicate that an existing order was placed in error. We explored whether the order voiding function could be used to record and study medication ordering errors. We examined medication orders from an academic medical center for a 6-year period (2006-2011; n  = 5 804 150). We categorized orders based on status (void, not void) and clinician-provided reasons for voiding. We used multivariable logistic regression to investigate the association between order voiding and clinician, patient, and order characteristics. We conducted chart reviews on a random sample of voided orders ( n  = 198) to investigate the rate of medication ordering errors among voided orders, and the accuracy of clinician-provided reasons for voiding. We found that 0.49% of all orders were voided. Order voiding was associated with clinician type (physician, pharmacist, nurse, student, other) and order type (inpatient, prescription, home medications by history). An estimated 70 ± 10% of voided orders were due to medication ordering errors. Clinician-provided reasons for voiding were reasonably predictive of the actual cause of error for duplicate orders (72%), but not for other reasons. Medication safety initiatives require availability of error data to create repositories for learning and training. The voiding function is available in several electronic health record systems, so order voiding could provide a low-effort mechanism for self-reporting of medication ordering errors. Additional clinician training could help increase the quality of such reporting. © The Author 2017. Published by Oxford University Press on behalf of the American Medical Informatics Association. All rights reserved. For Permissions, please email: journals.permissions@oup.com

  13. Is the far border of the Local Void expanding?

    Science.gov (United States)

    Iwata, I.; Chamaraux, P.

    2011-07-01

    Context. According to models of evolution in the hierarchical structure formation scenarios, voids of galaxies are expected to expand. The Local Void (LV) is the closest large void, and it provides a unique opportunity to test observationally such an expansion. It has been found that the Local Group, which is on the border of the LV, is running away from the void center at ~260 km s-1. Aims: In this study we investigate the motion of the galaxies at the far-side border of the LV to examine the presence of a possible expansion. Methods: We selected late-type, edge-on spiral galaxies with radial velocities between 3000 km s-1 and 5000 km s-1, and carried out HI 21 cm line and H-band imaging observations. The near-infrared Tully-Fisher relation was calibrated with a large sample of galaxies and carefully corrected for Malmquist bias. It was used to compute the distances and the peculiar velocities of the LV sample galaxies. Among the 36 sample LV galaxies with good quality HI line width measurements, only 15 galaxies were selected for measuring their distances and peculiar velocities, in order to avoid the effect of Malmquist bias. Results: The average peculiar velocity of these 15 galaxies is found to be -419+208-251 km s-1, which is not significantly different from zero. Conclusions: Due to the intrinsically large scatter of Tully-Fisher relation, we cannot conclude whether there is a systematic motion against the center of the LV for the galaxies at the far-side boundary of the void. However, our result is consistent with the hypothesis that those galaxies at the far-side boundary have an average velocity of ~260 km s-1 equivalent to what is found at the position of the Local Group. Based on data taken at Nançay radiotelescope operated by Observatoire de Paris, CNRS and Université d'Orléans, Infrared Survey Facility (IRSF) which is operated by Nagoya university under the cooperation of South African Astronomical Observatory, Kyoto University, and National

  14. Effect of initial void shape on ductile failure in a shear field

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2015-01-01

    For voids in a shear field unit cell model analyses have been used to show that ductile failure is predicted even though the stress triaxiality is low or perhaps negative, so that the void volume fraction does not grow during deformation. Here, the effect of the void shape is studied by analyzing...... with circular cross-section, i.e. the voids in shear flatten out to micro-cracks, which rotate and elongate until interaction with neighboring micro-cracks gives coalescence. Even though the mechanism of ductile failure is the same, the load carrying capacity predicted, for the same initial void volume fraction...

  15. Sensitivity analysis of an impedance void meter to the void distribution in annular flow: A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Lemonnier, H.; Nakach, R.; Favreau, C.; Selmer-Olsen, S. (CEA Centre d' Etudes Nucleaires de Grenoble, 38 (France). Service d' Etudes Thermohydrauliques)

    1991-04-01

    Impedance void meters are frequently used to measure the are-averaged void fraction in pipes. This is primarily for two reasons: firstly, this method is non-instrusive since the measurement can be made by electrodes flush mounted in the walls, and secondly, the signal processing equipment is simple. Impedance probes may be calibrated by using a pressure drop measurement or a quick closing valve system. In general, little attention is paid to void distribution effects. It can be proved that in annular flow, the departure from radial symmetry has a strong influence on the measured mean film thickness. This can be easily demonstrated by solving the Laplace equation for the electrical potential by simple analytical methods. When some spatial symmetry conditions are encountered, it is possible to calculate directly the conductance of the two-phase medium without a complete calculation of the potential. A solution of this problem by using the separation of variables technique is also presented. The main difficulty with this technique is the mixed nature of the boundary conditions: the boundary condition is both of Neumann and of Drichlet type on the same coordinate curve. This formulation leads to a non-separable problem, which is solved by truncating an infinite algebraic set of linear equations. The results, although strictly valid in annular flow, may give the correct trends when applied to bubbly flow. Finally, the theory provides an error estimate and a design criterion to improve the probe reliability. (orig.).

  16. Sensitivity analysis of an impedance void meter to the void distribution in annular flow: A theoretical study

    International Nuclear Information System (INIS)

    Lemonnier, H.; Nakach, R.; Favreau, C.; Selmer-Olsen, S.

    1991-01-01

    Impedance void meters are frequently used to measure the are-averaged void fraction in pipes. This is primarily for two reasons: firstly, this method is non-instrusive since the measurement can be made by electrodes flush mounted in the walls, and secondly, the signal processing equipment is simple. Impedance probes may be calibrated by using a pressure drop measurement or a quick closing valve system. In general, little attention is paid to void distribution effects. It can be proved that in annular flow, the departure from radial symmetry has a strong influence on the measured mean film thickness. This can be easily demonstrated by solving the Laplace equation for the electrical potential by simple analytical methods. When some spatial symmetry conditions are encountered, it is possible to calculate directly the conductance of the two-phase medium without a complete calculation of the potential. A solution of this problem by using the separation of variables technique is also presented. The main difficulty with this technique is the mixed nature of the boundary conditions: the boundary condition is both of Neumann and of Drichlet type on the same coordinate curve. This formulation leads to a non-separable problem, which is solved by truncating an infinite algebraic set of linear equations. The results, although strictly valid in annular flow, may give the correct trends when applied to bubbly flow. Finally, the theory provides an error estimate and a design criterion to improve the probe reliability. (orig.)

  17. Physics study of Canada deuterium uranium lattice with coolant void reactivity analysis

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin Su; Lee, Hyun Suk; Tak, Tae Woo; Lee, Deok Jung [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of); Shin, Ho Cheol [Korea Hydro and Nuclear Power Central Research Institute (KHNP-CRI), Daejeon (Korea, Republic of)

    2017-02-15

    This study presents a coolant void reactivity analysis of Canada Deuterium Uranium (CANDU)-6 and Advanced Canada Deuterium Uranium Reactor-700 (ACR-700) fuel lattices using a Monte Carlo code. The reactivity changes when the coolant was voided were assessed in terms of the contributions of four factors and spectrum shifts. In the case of single bundle coolant voiding, the contribution of each of the four factors in the ACR-700 lattice is large in magnitude with opposite signs, and their summation becomes a negative reactivity effect in contrast to that of the CANDU-6 lattice. Unlike the coolant voiding in a single fuel bundle, the 2 x 2 checkerboard coolant voiding in the ACR-700 lattice shows a positive reactivity effect. The neutron current between the no-void and voided bundles, and the four factors of each bundle were analyzed to figure out the mechanism of the positive coolant void reactivity of the checkerboard voiding case. Through a sensitivity study of fuel enrichment, type of burnable absorber, and moderator to fuel volume ratio, a design strategy for the CANDU reactor was suggested in order to achieve a negative coolant void reactivity even for the checkerboard voiding case.

  18. Effective void fraction for a BWR assembly with boiling in the bypass region

    International Nuclear Information System (INIS)

    Galperin, A.; Segev, M.; Knoglinger, E.

    1991-09-01

    Average BWR assembly cross-sections for nominal conditions, namely for zero bypass void, can be utilised in the analysis of transient conditions with boiling in the bypass. A model is developed to yield an effective channel void for such conditions. The use of this void in conjunction with the 'nominal conditions' cross section library approximately preserves the assembly K-infinity corresponding to the true channel and bypass voids. The effective void is an augmentation of the actual channel void. The augment is proportional to the bypass-to-channel volume ratio, to the bypass void, and to a weight W which is introduced to quantify the fact that a water molecule in the bypass has a different assembly criticality worth than one in the channel. The formula developed is superior to the practice of choosing W=1, namely a simple, non-weighted, transfer of water from channel to bypass. The use of this approximate effective channel void reproduces actual K-infinity values of assemblies to better than 5 mk, whereas the use of a simple model sometimes misspredicts the assembly K-infinity by 40 mK. The effective void model cannot handle cases in which both channel and bypass void value are high, simply because then the effective void α ch eff becomes meaningless. A method to treat the α eff >1 domain is developed by which corrections to cross sections are provided. Such corrections are synthesised as functions of the assembly parameters. (author) figs., tabs., refs

  19. Direct evidence of void passivation in Cu(InGa)(SSe)2 absorber layers

    International Nuclear Information System (INIS)

    Lee, Dongho; Kim, Young-Su; Mo, Chan B.; Huh, Kwangsoo; Yang, JungYup; Nam, Junggyu; Baek, Dohyun; Park, Sungchan; Kim, ByoungJune; Kim, Dongseop; Lee, Jaehan; Heo, Sung; Park, Jong-Bong; Kang, Yoonmook

    2015-01-01

    We have investigated the charge collection condition around voids in copper indium gallium sulfur selenide (CIGSSe) solar cells fabricated by sputter and a sequential process of selenization/sulfurization. In this study, we found direct evidence of void passivation by using the junction electron beam induced current method, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The high sulfur concentration at the void surface plays an important role in the performance enhancement of the device. The recombination around voids is effectively suppressed by field-assisted void passivation. Hence, the generated carriers are easily collected by the electrodes. Therefore, when the S/(S + Se) ratio at the void surface is over 8% at room temperature, the device performance degradation caused by the recombination at the voids is negligible at the CIGSSe layer

  20. Direct evidence of void passivation in Cu(InGa)(SSe){sub 2} absorber layers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dongho; Kim, Young-Su; Mo, Chan B.; Huh, Kwangsoo; Yang, JungYup, E-mail: jungyupyang@gmail.com, E-mail: ddang@korea.ac.kr; Nam, Junggyu; Baek, Dohyun; Park, Sungchan; Kim, ByoungJune; Kim, Dongseop [PV Development Team, Energy Solution Business Division, Samsung SDI, 467 Beonyeong-ro, Seobuk-gu, Cheonan-si, Chungcheongnam-do 331-330 (Korea, Republic of); Lee, Jaehan [Core Technology Laboratory, Battery Research Center, Samsung SDI, 130 Samsung-ro, Yeongtong-gu Suwon-si, Gyeonggi-do 443-803 (Korea, Republic of); Heo, Sung; Park, Jong-Bong [Analytical Engineering Group, Samsung Advanced Institute of Technology, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-803 (Korea, Republic of); Kang, Yoonmook, E-mail: jungyupyang@gmail.com, E-mail: ddang@korea.ac.kr [KUKIST Green School, Graduate School of Energy and Environment, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 136-701 (Korea, Republic of)

    2015-02-23

    We have investigated the charge collection condition around voids in copper indium gallium sulfur selenide (CIGSSe) solar cells fabricated by sputter and a sequential process of selenization/sulfurization. In this study, we found direct evidence of void passivation by using the junction electron beam induced current method, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The high sulfur concentration at the void surface plays an important role in the performance enhancement of the device. The recombination around voids is effectively suppressed by field-assisted void passivation. Hence, the generated carriers are easily collected by the electrodes. Therefore, when the S/(S + Se) ratio at the void surface is over 8% at room temperature, the device performance degradation caused by the recombination at the voids is negligible at the CIGSSe layer.

  1. Systematic Study on the Self-Assembled Hexagonal Au Voids, Nano-Clusters and Nanoparticles on GaN (0001.

    Directory of Open Access Journals (Sweden)

    Puran Pandey

    Full Text Available Au nano-clusters and nanoparticles (NPs have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001 by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600°C, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800°C based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots.

  2. Void Shapes Controlled by Using Interruption-Free Epitaxial Lateral Overgrowth of GaN Films on Patterned SiO2 AlN/Sapphire Template

    Directory of Open Access Journals (Sweden)

    Yu-An Chen

    2014-01-01

    Full Text Available GaN epitaxial layers with embedded air voids grown on patterned SiO2 AlN/sapphire templates were proposed. Using interruption-free epitaxial lateral overgrowth technology, we realized uninterrupted growth and controlled the shape of embedded air voids. These layers showed improved crystal quality using X-ray diffraction and measurement of etching pits density. Compared with conventional undoped-GaN film, the full width at half-maximum of the GaN (0 0 2 and (1 0 2 peaks decreased from 485 arcsec to 376 arcsec and from 600 arcsec to 322 arcsec, respectively. Transmission electron microscopy results showed that the coalesced GaN growth led to bending threading dislocation. We also proposed a growth model based on results of scanning electron microscopy.

  3. Emission-line galaxies toward the booetes void

    International Nuclear Information System (INIS)

    Moody, J.W.

    1986-01-01

    Galaxies with strong emission are potentially useful as probes of the large-scale galaxian distribution. However, to serve as probes, their relative frequency and clustering properties must be known. This dissertation presents a study of these properties for field galaxies having [OIII] λ5007 emission equivalent widths greater than 10 A and reports on a search for galaxies with [OIII] λ5007 emission in the direction of the Booetes void, a volume located at α = 4/sup h/48/sup m/, δ = 47 0 , and cz = 15,000 km/sec that has been demonstrated to be under-abundant in galaxies by a factor of at least four. The study of field emission-line galaxies was done in two magnitude limited surveys consisting of 341 galaxies from both the north and south galactic caps having previously published redshifts and photometry. The galaxy spectra used for redshifts were examined and supplemented by new observations for 56 objects, primarily those with confirmed or suspected emission. Emission-line galaxies were found to comprise 8.8% of galaxies in a Illa-J selected sample or 6.6% of galaxies in a Illa-F selected sample. A search for emission-line galaxies towards the Booetes void was undertaken using the Burrell Schmidt telescope and an objective prism giving a reciprocal dispersion of 900 A/mm at Hβ. Three galaxies were found to lie within it, a result consistent with distributions through the void ranging from uniform to under-abundant by a factor of three

  4. Stress-assisted, microbial-induced corrosion of stainless steel primary piping and other aging issues at the Omega West Reactor

    International Nuclear Information System (INIS)

    Andrade, A.

    1995-01-01

    After the discovery of cooling system leak of about 284 liters per twenty-four (24) hour period, an investigation determined that the 76.2-cm diameter, 33.5-m long stainless-steel (304) OWR delay line was losing water at the same nominal rate. An excavation effort revealed that a circumferential crack, approximately 0.0025 cm in width, extended around the bottom half of the delay line. In addition, other evidence of what appeared to be microcracking and pitting that originated at random nucleated sites around the pipe were also found. Results of destructive analysis and nondestructive testing allowed Los Alamos staff to conclude that the direct cause for the main crack and other pitting resulted from stress-assisted, microbial-induced corrosion of the stainless steel primary piping. The results also indicated that microbial action from bacteria that are normally present in earth can be extremely harmful to stainless- steel piping under certain conditions. Other potential problems that could have also eventually led to a permanent shutdown of the OWR were discussed. These problems, although never encountered nor associated with the current shutdown, were identified in aging studies and are associated with: (1) the water-cooled, bismuth gamma-ray shield and, (2) the aluminum thermal column head seal that prevents reactor vessel water from entering into the graphite-filled thermal column

  5. Void coalescence and fracture behavior of notched and un-notched tensile tested specimens in fine grain dual phase steel

    Energy Technology Data Exchange (ETDEWEB)

    Saeidi, N., E-mail: navidsae@gmail.com [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Ashrafizadeh, F.; Niroumand, B. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Forouzan, M.R.; Mohseni mofidi, S. [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Barlat, F. [Materials Mechanics Laboratory (MML), Graduate Institute of Ferrous Technology (GIFT), Pohang University of Science and Technology POSTECH, San 31 Hyoja-dong, Nam-gu, Pohang, Gyeongbuk 790-784 (Korea, Republic of)

    2015-09-17

    Due to growing global concern about the environmental issues, steel developers have been forced by automobile makers to produce more efficient steel grades with high strength to weight ratios along with high crashworthiness performance. In order to find deficiencies of the existing steels and develop superior steel products, detailed understanding of deformation and damage behavior in the existing steels is needed. In the present research, deformation and damage evolution during room temperature uniaxial tensile test of a modern high strength Dual Phase Steel, i.e. DP780, were studied. Detailed scanning electron microscopy (SEM) examination of the microstructures of notched and un-notched tensile fractured specimens revealed that in notched specimen, plastic deformation was concentrated more within the notched region. Therefore, much higher reduction in thickness with a high reduction gradient occurred in this region, In the un-notched specimen, however, plastic deformation was more uniformly distributed in larger parts of the gauge length, and therefore, thickness reduction happened with a lower gradient. Although geometric notch on the specimen did not change the void nucleation and growth mechanisms, the kinetics of these phenomena was influenced. On the other hand, voids linkage mechanism tended to change from void coalescence in the un-notched specimen to void sheeting in the notched specimen. Moreover, three different models developed by Brown & Embury (BM), Thomason and Pardoen were employed to predict the final fracture strain. It was revealed that, BM model showed much more accurate predictions for the studied DP steel in comparison with those of Thomason and Pardoens’ models.

  6. Void coalescence and fracture behavior of notched and un-notched tensile tested specimens in fine grain dual phase steel

    International Nuclear Information System (INIS)

    Saeidi, N.; Ashrafizadeh, F.; Niroumand, B.; Forouzan, M.R.; Mohseni mofidi, S.; Barlat, F.

    2015-01-01

    Due to growing global concern about the environmental issues, steel developers have been forced by automobile makers to produce more efficient steel grades with high strength to weight ratios along with high crashworthiness performance. In order to find deficiencies of the existing steels and develop superior steel products, detailed understanding of deformation and damage behavior in the existing steels is needed. In the present research, deformation and damage evolution during room temperature uniaxial tensile test of a modern high strength Dual Phase Steel, i.e. DP780, were studied. Detailed scanning electron microscopy (SEM) examination of the microstructures of notched and un-notched tensile fractured specimens revealed that in notched specimen, plastic deformation was concentrated more within the notched region. Therefore, much higher reduction in thickness with a high reduction gradient occurred in this region, In the un-notched specimen, however, plastic deformation was more uniformly distributed in larger parts of the gauge length, and therefore, thickness reduction happened with a lower gradient. Although geometric notch on the specimen did not change the void nucleation and growth mechanisms, the kinetics of these phenomena was influenced. On the other hand, voids linkage mechanism tended to change from void coalescence in the un-notched specimen to void sheeting in the notched specimen. Moreover, three different models developed by Brown & Embury (BM), Thomason and Pardoen were employed to predict the final fracture strain. It was revealed that, BM model showed much more accurate predictions for the studied DP steel in comparison with those of Thomason and Pardoens’ models

  7. Prediction of void fraction in subcooled flow boiling

    International Nuclear Information System (INIS)

    Petelin, S.; Koncar, B.

    1998-01-01

    The information on heat transfer and especially on the void fraction in the reactor core under subcooled conditions is very important for the water-cooled nuclear reactors, because of its influence upon the reactivity of the systems. This paper gives a short overview of subcooled boiling phenomenon and indicates the simplifications made by the RELAP5 model of subcooled boiling. RELAP5/MOD3.2 calculations were compared with simple one-dimensional models and with high-pressure Bartolomey experiments.(author)

  8. Urethane foam void filling. Innovative technology summary report

    International Nuclear Information System (INIS)

    1998-12-01

    Under the decontamination and decommissioning (D and D) Implementation Plan of the United States Department of Energy's (DOE's) Fernald Environmental Management Project (FEMP), non-recyclable process components and debris that are removed from buildings undergoing D and D are disposed of in an on-site disposal facility (OSDF). Critical to the design and operation of the FEMP's OSDF are provisions to protect against subsidence of the OSDF's cap. Subsidence of the cap could occur if void spaces within the OSDF were to collapse under the overburden of debris and the OSDF cap. Subsidence may create depressions in the OSDF's cap in which rainwater could collect and eventually seep into the OSDF. To minimize voids in the FEMP's OSDF, large metallic components are cut into smaller segments that can be arranged more compactly when placed in the OSDF. Component segmentation using an oxy-acetylene torch was the baseline approach used by the FEMP's D and D contractor on Plant 1, B and W Services, Inc., for the dismantlement and size-reduction of large metal components. Although this technology has performed satisfactorily, it is time-consuming, labor-intensive and costly. Use of the oxy-acetylene torch exposes workers to health and safety hazards including the risk of burns, carbon monoxide, and airborne contamination of residual lead-based paints and other contaminants on the surface of the components being segmented. In addition, solvents used to remove paint from the components before segmenting them emit flammable, noxious fumes. This demonstration investigated the feasibility of placing large vessels intact in the OSDF without segmenting them. To prevent the walls of the vessels from collapsing under the overburden or from degradation, an innovative approach was employed which involved filling the voids in the vessels with a fluid material that hardened on standing. The hardened filling would support the walls of the vessels, and prevent them from collapsing. This report

  9. Method for detecting cement voids or borehole washouts

    International Nuclear Information System (INIS)

    Smith, M.P.

    1980-01-01

    This invention, rather than relying on a measure of the thermal neutron population, uses a measurement of the epithermal neutron population by means of two spaced neutron detectors longitudinally spaced from a neutron source with a relatively high intensity neutron flux. Special detectors discriminate against the detection of thermal neutrons. By comparing the compensated porosity measurement using the dual speed detectors with an uncompensated porosity measured by using only one detector the location of borehole washouts or cement voids can be found. Full details are given. (U.K.)

  10. Method for detecting cement voids or borehole washouts

    International Nuclear Information System (INIS)

    Smith, M.P.

    1978-01-01

    A fast neutron source is used to irradiate earth formations in the vicinity of a well borehole. Dual spaced epithermal neutron detectors are used to sample the epithermal neutron population at two different spaced distances from the source. A compensated formation porosity is obtained from the ratio of counting rates at the dual spaced detectors. An uncompensated porosity value is obtained from the count rate at the short spaced detector. Borehole washout or cement void regions are located by comparing the compensated and uncompensated values of formation porosity obtained in this manner

  11. Dependence on supernovae light-curve processing in void models

    Energy Technology Data Exchange (ETDEWEB)

    Bengochea, Gabriel R., E-mail: gabriel@iafe.uba.ar [Instituto de Astronomía y Física del Espacio (IAFE), UBA-CONICET, CC 67, Suc. 28, 1428 Buenos Aires (Argentina); De Rossi, Maria E., E-mail: derossi@iafe.uba.ar [Instituto de Astronomía y Física del Espacio (IAFE), UBA-CONICET, CC 67, Suc. 28, 1428 Buenos Aires (Argentina); Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina)

    2014-06-02

    In this work, we show that when supernova Ia (SN Ia) data sets are used to put constraints on the free parameters of inhomogeneous models, certain extra information regarding the light-curve fitter used in the supernovae Ia luminosity fluxes processing should be taken into account. We found that the size of the void as well as other parameters of these models might be suffering extra degenerations or additional systematic errors due to the fitter. A recent proposal to relieve the tension between the results from Planck satellite and SNe Ia is re-analyzed in the framework of these subjects.

  12. Burnup dependence of coolant void reactivity for ACR-1000 cell

    International Nuclear Information System (INIS)

    Le Tellier, R.; Marleau, G.; Hebert, A.; Roubstov, D.; Altiparmakov, D.; Irish, D.

    2008-01-01

    The Advanced Candu Reactor (ACR-1000) is light water cooled, fueled with enriched uranium and has a smaller lattice pitch than the Candu-6. As a result, the neutronic behavior of the ACR-1000 cell is expected to be somewhat different from that of the Candu-6 leading to a negative coolant void reactivity (CVR). Here we evaluate the CVR for the ACR-1000 cell using the lattice code DRAGON and compare our results with those obtained using the code WIMS-AECL. The differences observed between these two codes for the burnup dependence of the CVR is mainly explained in terms of the specific cell leakage model used by both codes. (authors)

  13. Void fraction calculation in a channel containing boiling coolant

    International Nuclear Information System (INIS)

    Norelli, F.

    1978-01-01

    The problem of void fraction calculation was studied for a channel containing boiling coolant, when a slip ratio correlation is used. Use of fitting (e.g. polinomial or rational algebraic) for slip ratio correlation and the characteristic method are proposed in this work. In this way we are reduced to some elementary quadrature problem. Another problem discussed in the present work concerns what we must consider as ''initial condition'' in any initial value problem, in order to take into account different error distributions in steady state and in successive time-dependent calculations

  14. Topology and dark energy: testing gravity in voids.

    Science.gov (United States)

    Spolyar, Douglas; Sahlén, Martin; Silk, Joe

    2013-12-13

    Modified gravity has garnered interest as a backstop against dark matter and dark energy (DE). As one possible modification, the graviton can become massive, which introduces a new scalar field--here with a Galileon-type symmetry. The field can lead to a nontrivial equation of state of DE which is density and scale dependent. Tension between type Ia supernovae and Planck could be reduced. In voids, the scalar field dramatically alters the equation of state of DE, induces a soon-observable gravitational slip between the two metric potentials, and develops a topological defect (domain wall) due to a nontrivial vacuum structure for the field.

  15. Void fraction measurement system for high temperature flows

    Energy Technology Data Exchange (ETDEWEB)

    Teyssedou, A; Aube, F; Champagne, P [Montreal Univ., PQ (Canada). Institut de Genie Energetique

    1992-05-01

    A {gamma}-ray absorption technique has been developed for measuring the axial distribution of the void fraction for high-temperature and high-pressure two-phase flows. The system is mounted on a moving platform driven by a high-power stepping motor. A personal computer (IBM AT) connected to a data acquisition system is used to control the displacement of the {gamma} source and detector, and to read the response of the detector. All the measurement procedures are carried out automatically by dedicated software developed for this purpose. (Author).

  16. Closure behavior of spherical void in slab during hot rolling process

    Science.gov (United States)

    Cheng, Rong; Zhang, Jiongming; Wang, Bo

    2018-04-01

    The mechanical properties of steels are heavily deteriorated by voids. The influence of voids on the product quality should be eliminated through rolling processes. The study on the void closure during hot rolling processes is necessary. In present work, the closure behavior of voids at the center of a slab at 800 °C during hot rolling processes has been simulated with a 3D finite element model. The shape of the void and the plastic strain distribution of the slab are obtained by this model. The void decreases along the slab thickness direction and spreads along the rolling direction but hardly changes along the strip width direction. The relationship between closure behavior of voids and the plastic strain at the center of the slab is analyzed. The effects of rolling reduction, slab thickness and roller diameter on the closure behavior of voids are discussed. The larger reduction, thinner slab and larger roller diameter all improve the closure of voids during hot rolling processes. Experimental results of the closure behavior of a void in the slab during hot rolling process mostly agree with the simulation results..

  17. One-Group Perturbation Theory Applied to Measurements with Void

    International Nuclear Information System (INIS)

    Persson, Rolf

    1966-09-01

    Formulas suitable for evaluating progressive as well as single rod substitution measurements are derived by means of one-group perturbation theory. The diffusion coefficient may depend on direction and position. By using the buckling concept one can derive expressions which are quite simple and the perturbed flux can be taken into account in a comparatively simple way. By using an unconventional definition of cells a transition region is introduced quite logically. Experiments with voids around metal rods, diam. 3.05 cm, have been analysed. The agreement between extrapolated and directly measured buckling values is excellent, the buckling difference between lattices with water-filled and voided shrouds being 0. 263 ± 0.015/m 2 and 0.267 ± 0.005/m 2 resp. From single-rod experiments differences between diffusion coefficients are determined to δD r /D = 0.083 ± 0.004 and δD z /D = 0.120 ± 0.018. With air-filled shrouds there is consequently anisotropy in the neutron diffusion and we have (D z /D r ) air = 1.034 ± 0.020

  18. One-Group Perturbation Theory Applied to Measurements with Void

    Energy Technology Data Exchange (ETDEWEB)

    Persson, Rolf

    1966-09-15

    Formulas suitable for evaluating progressive as well as single rod substitution measurements are derived by means of one-group perturbation theory. The diffusion coefficient may depend on direction and position. By using the buckling concept one can derive expressions which are quite simple and the perturbed flux can be taken into account in a comparatively simple way. By using an unconventional definition of cells a transition region is introduced quite logically. Experiments with voids around metal rods, diam. 3.05 cm, have been analysed. The agreement between extrapolated and directly measured buckling values is excellent, the buckling difference between lattices with water-filled and voided shrouds being 0. 263 {+-} 0.015/m{sup 2} and 0.267 {+-} 0.005/m{sup 2} resp. From single-rod experiments differences between diffusion coefficients are determined to {delta}D{sub r}/D = 0.083 {+-} 0.004 and {delta}D{sub z}/D = 0.120 {+-} 0.018. With air-filled shrouds there is consequently anisotropy in the neutron diffusion and we have (D{sub z}/D{sub r}){sub air} = 1.034 {+-} 0.020.

  19. Monitoring Detrusor Oxygenation and Hemodynamics Noninvasively during Dysfunctional Voiding

    Science.gov (United States)

    Macnab, Andrew J.; Stothers, Lynn S.; Shadgan, Babak

    2012-01-01

    The current literature indicates that lower urinary tract symptoms (LUTSs) related to benign prostatic hyperplasia (BPH) have a heterogeneous pathophysiology. Pressure flow studies (UDSs) remain the gold standard evaluation methodology for such patients. However, as the function of the detrusor muscle depends on its vasculature and perfusion, the underlying causes of LUTS likely include abnormalities of detrusor oxygenation and hemodynamics, and available treatment options include agents thought to act on the detrusor smooth muscle and/or vasculature. Hence, near infrared spectroscopy (NIRS), an established optical methodology for monitoring changes in tissue oxygenation and hemodynamics, has relevance as a means of expanding knowledge related to the pathophysiology of BPH and potential treatment options. This methodological report describes how to conduct simultaneous NIRS monitoring of detrusor oxygenation and hemodynamics during UDS, outlines the clinical implications and practical applications of NIRS, explains the principles of physiologic interpretation of NIRS voiding data, and proposes an exploratory hypothesis that the pathophysiological causes underlying LUTS include detrusor dysfunction due to an abnormal hemodynamic response or the onset of oxygen debt during voiding. PMID:23019422

  20. Monitoring Detrusor Oxygenation and Hemodynamics Noninvasively during Dysfunctional Voiding

    Directory of Open Access Journals (Sweden)

    Andrew J. Macnab

    2012-01-01

    Full Text Available The current literature indicates that lower urinary tract symptoms (LUTSs related to benign prostatic hyperplasia (BPH have a heterogeneous pathophysiology. Pressure flow studies (UDSs remain the gold standard evaluation methodology for such patients. However, as the function of the detrusor muscle depends on its vasculature and perfusion, the underlying causes of LUTS likely include abnormalities of detrusor oxygenation and hemodynamics, and available treatment options include agents thought to act on the detrusor smooth muscle and/or vasculature. Hence, near infrared spectroscopy (NIRS, an established optical methodology for monitoring changes in tissue oxygenation and hemodynamics, has relevance as a means of expanding knowledge related to the pathophysiology of BPH and potential treatment options. This methodological report describes how to conduct simultaneous NIRS monitoring of detrusor oxygenation and hemodynamics during UDS, outlines the clinical implications and practical applications of NIRS, explains the principles of physiologic interpretation of NIRS voiding data, and proposes an exploratory hypothesis that the pathophysiological causes underlying LUTS include detrusor dysfunction due to an abnormal hemodynamic response or the onset of oxygen debt during voiding.

  1. The urodynamic evaluation of neuromodulation in patients with voiding dysfunction.

    Science.gov (United States)

    Everaert, K; Plancke, H; Lefevere, F; Oosterlinck, W

    1997-05-01

    To determine which patients with voiding dysfunction might be suitable for treatment with neuromodulation, using urodynamics to obtain an objective measure of improvement and to illustrate the effect of neuromodulation on voiding dysfunction. Patients were selected for implantation of a neuroprosthesis using a urodynamic evaluation before and during subchronic stimulation; 27 such patients (four men and 23 women, mean age 33 years, SD 15) were evaluated. Of the 27 patients, the 17 who responded well to neuromodulation all had hypocontractile detrusors and sphincter hypertonicity; sphincter relaxation during micturition was impaired. The urodynamic evaluation showed that these patients were not obstructed. Of 10 patients with spastic pelvic floor syndrome, nine responded well to the treatment. Those not responding to neuromodulation had mainly acontractile detrusors. The ideal candidates for neuromodulation are those patients with a spastic pelvic floor syndrome or with a hypocontractile detrusor, in combination with sphincter instability, and impaired sphincter relaxation. An increase of bladder contractility, enhancement of sphincter relaxation and decrease in bladder capacity and residual urine are the most important features of the response.

  2. Are we living near the center of a local void?

    Energy Technology Data Exchange (ETDEWEB)

    Cusin, Giulia [Département de Physique Théorique and Center for Astroparticle Physics, Université de Genève, 24 quai Ansermet, CH-1211 Genève 4 (Switzerland); Pitrou, Cyril; Uzan, Jean-Philippe, E-mail: giulia.cusin@unige.ch, E-mail: pitrou@iap.fr, E-mail: uzan@iap.fr [Institut d' Astrophysique de Paris, Université Pierre and Marie Curie—Paris V, CNRS-UMR 7095, 98 bis, Bd Arago, 75014 Paris (France)

    2017-03-01

    The properties of the cosmic microwave background (CMB) temperature and polarisation anisotropies measured by a static, off-centered observer located in a local spherically symmetric void, are described. In particular in this paper we compute, together with the standard 2-point angular correlation functions, the off-diagonal correlators, which are no more vanishing by symmetry. While the energy shift induced by the off-centered position of the observer can be suppressed by a proper choice of the observer velocity, a lensing-like effect on the CMB emission point remains. This latter effect is genuinely geometrical (e.g. non-degenerate with a boost) and reflects in the structure of the off-diagonal correlators. At lowest order in this effect, the temperature and polarisation correlation matrices have non-vanishing diagonal elements, as usual, and all the off-diagonal terms are excited. This particular signature of a local void model allows one, in principle, to disentangle geometrical effects from local kinematical ones in CMB observations.

  3. Modeling multiscale evolution of numerous voids in shocked brittle material.

    Science.gov (United States)

    Yu, Yin; Wang, Wenqiang; He, Hongliang; Lu, Tiecheng

    2014-04-01

    The influence of the evolution of numerous voids on macroscopic properties of materials is a multiscale problem that challenges computational research. A shock-wave compression model for brittle material, which can obtain both microscopic evolution and macroscopic shock properties, was developed using discrete element methods (lattice model). Using a model interaction-parameter-mapping procedure, qualitative features, as well as trends in the calculated shock-wave profiles, are shown to agree with experimental results. The shock wave splits into an elastic wave and a deformation wave in porous brittle materials, indicating significant shock plasticity. Void collapses in the deformation wave were the natural reason for volume shrinkage and deformation. However, media slippage and rotation deformations indicated by complex vortex patterns composed of relative velocity vectors were also confirmed as an important source of shock plasticity. With increasing pressure, the contribution from slippage deformation to the final plastic strain increased. Porosity was found to determine the amplitude of the elastic wave; porosity and shock stress together determine propagation speed of the deformation wave, as well as stress and strain on the final equilibrium state. Thus, shock behaviors of porous brittle material can be systematically designed for specific applications.

  4. The use of graphite for the reduction of void reactivity in CANDU reactors

    International Nuclear Information System (INIS)

    Min, B.J.; Kim, B.G.; Sim, K-S.

    1995-01-01

    Coolant void reactivity can be reduced by using burnable poison in CANDU reactors. The use of graphite in the fuel bundle is introduced to reduce coolant void reactivity by adding an appropriate amount of burnable poison in the central rod. This study shows that sufficiently low void reactivity which in controllable by Reactor Regulating System (RRS) can be achieved by using graphite used fuel with slightly enriched uranium. Zero void reactivity can be also obtained by using graphite used fuel with a large central rod. A new fuel bundle with graphite rods can substantially reduce the void reactivity with less burnup penalty compared to previously proposed low void reactivity fuel with depleted uranium. (author)

  5. The metallurgical approach on the solder voids behaviour in surface mount devices

    International Nuclear Information System (INIS)

    Mohabattul Zaman Bukhari

    1996-01-01

    Solder voids are believed to cause poor heat dissiption in the Surface Mount devices and reduce the reliability of the devices at higher operating services. There are a lot of factors involved in creating voids such as gas/flux entrapment, wettability, outgasseous, air bubbles in the solder paste, inconsistency of solder coverage and improper metal scheme selection. This study was done to observe the behaviour of the solder voids in term of flux entrapmentt and wettability. It is believed that flux entrapment and wettability are verify this hypothesis. Two types of metal scheme were chosen which are Nickel (Ni) plated and Tin (Sn) plated heatsink. X-ray techniques such as Radiographic Inspection Analysis and EDAX were used to detect the minute solder voids. The solder voids observed on the heatsinks and Copper shims after the reflow process are believed to be a non contact voids that resulted from some portion of the surface not wetting properly

  6. Method of simulating spherical voids for use as a radiographic standard

    International Nuclear Information System (INIS)

    Foster, B.E.

    1977-01-01

    A method of simulating small spherical voids in metal is provided. The method entails drilling or etching a hemispherical depression of the desired diameter in each of two sections of metal, the sections being flat plates or different diameter cylinders. A carbon bead is placed in one of the hemispherical voids and is used as a guide to align the second hemispherical void with that in the other plate. The plates are then bonded together with epoxy, tape or similar material and the two aligned hemispheres form a sphere within the material; thus a void of a known size has been created. This type of void can be used to simulate a pore in the development of radiographic techniques of actual voids (porosity) in welds and serve as a radiographic standard

  7. Measurements of void fraction in a heated tube in the rewetting conditions

    International Nuclear Information System (INIS)

    Freitas, R.L.

    1983-01-01

    The methods of void fraction measurements by transmission and diffusion of cold, thermal and epithermal neutrons were studied with cylindrical alluminium pieces simulating the steam. A great set of void fraction found in a wet zone was examined and a particulsar attention was given to the sensitivity effects of the method, mainly for high void fraction. Several aspects of the measurement techniques were analyzed, such as the effect of the phase radial distribution, neutron energy, water tempeture, effect of the void axial gradient. The technique of thermal neutron diffusion measurement was used to measure the axial profile of void fraction in a steady two-phase flow, where the pressure, mass velocity and heat flux are representative of the wet conditions. Experimental results are presented and compared with different void fraction models. (E.G.) [pt

  8. Shock-induced hotspot formation and chemical reaction initiation in PETN containing a spherical void

    International Nuclear Information System (INIS)

    Shan, Tzu-Ray; Thompson, Aidan P

    2014-01-01

    We present results of reactive molecular dynamics simulations of hotspot formation and chemical reaction initiation in shock-induced compression of pentaerythritol tetranitrate (PETN) with the ReaxFF reactive force field. A supported shockwave is driven through a PETN crystal containing a 20 nm spherical void at a sub-threshold impact velocity of 2 km/s. Formation of a hotspot due to shock-induced void collapse is observed. During void collapse, NO 2 is the dominant species ejected from the upstream void surface. Once the ejecta collide with the downstream void surface and the hotspot develops, formation of final products such as N 2 and H 2 O is observed. The simulation provides a detailed picture of how void collapse and hotspot formation leads to initiation at sub-threshold impact velocities.

  9. Structure-dependent behavior of stress-induced voiding in Cu interconnects

    International Nuclear Information System (INIS)

    Wu Zhenyu; Yang Yintang; Chai Changchun; Li Yuejin; Wang Jiayou; Li Bin; Liu Jing

    2010-01-01

    Stress modeling and cross-section failure analysis by focused-ion-beam have been used to investigate stress-induced voiding phenomena in Cu interconnects. The voiding mechanism and the effect of the interconnect structure on the stress migration have been studied. The results show that the most concentrated tensile stress appears and voids form at corners of vias on top surfaces of Cu M1 lines. A simple model of stress induced voiding in which vacancies arise due to the increase of the chemical potential under tensile stress and diffuse under the force of stress gradient along the main diffusing path indicates that stress gradient rather than stress itself determines the voiding rate. Cu interconnects with larger vias show less resistance to stress-induced voiding due to larger stress gradient at corners of vias.

  10. Modelling the void deformation and closure by hot forging of ingot castings

    DEFF Research Database (Denmark)

    Christiansen, Peter; Hattel, Jesper Henri; Kotas, Petr

    2012-01-01

    by mechanical deformation. The aim of this paper is to analyze numerically if and to what degree the voids areclosed by the forging. Using the commercial simulation software ABAQUS, both simplified model ingots and physically manufactured ingots containing prescribed void distributions are deformed and analyzed....... The analysis concernsboth the void density change and the location of the voids in the part after deformation. The latter can be important for the subsequent reliability of the parts, for instance regarding fatigue properties. The analysis incorporates the Gurson yield criterion for metals containing voids...... and focuses on how the voids deform depending on their size and distribution in the ingot as well ashow the forging forces are applied....

  11. The effect of voids on the hardening of body-centered cubic Fe

    Energy Technology Data Exchange (ETDEWEB)

    Nakai, Ryosuke, E-mail: ryosuke.nakai@jupiter.qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Yabuuchi, Kiyohiro, E-mail: k-yabuuchi@iae.kyoto-u.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 (Japan); Nogami, Shuhei, E-mail: shuhei.nogami@qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Hasegawa, Akira, E-mail: akira.hasegawa@qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan)

    2016-04-01

    The mechanical properties of metals are affected by various types of defects. Hardening is usually described through the interaction between dislocations and obstacles, in the so-called line tension theory. The strength factor in the line tension theory represents the resistance of a defect against the dislocation motion. In order to understand hardening from the viewpoint of the microstructure, an accurate determination of the strength factor of different types of defects is essential. In the present study, the strength factor of voids in body-centered cubic (BCC) Fe was investigated by two different approaches: one based on the Orowan equation to link the measured hardness with the average size and density of voids, and the other involving direct observation of the interaction between dislocations and voids by transmission electron microscope (TEM). The strength factor of voids induced by ion irradiation estimated by the Orowan equation was 0.6, whereas the strength factor estimated by the direct TEM approach was 0.8. The difference in the strength factors measured by the two approaches is due to the positional relationship between dislocations and voids: the central region of a void is stronger than the tip. Moreover, the gliding plane and the direction of dislocation may also affect the strength factor of voids. This study determined the strength factor of voids in BCC Fe accurately, and suggested that the contribution of voids to the irradiation hardening is larger than that of dislocation loops and Cu-rich precipitates. - Highlights: • The strength factor of voids in BCC Fe was experimentally investigated. • The strength factor of voids estimated by the line tension theory was 0.6. • The strength factor of voids estimated by the bowing angle of dislocations was 0.8. • The different strength factors are due to the positional relationship.

  12. Fuzzy Reasoning to More Accurately Determine Void Areas on Optical Micrographs of Composite Structures

    Science.gov (United States)

    Dominquez, Jesus A.; Tate, Lanetra C.; Wright, M. Clara; Caraccio, Anne

    2013-01-01

    Accomplishing the best-performing composite matrix (resin) requires that not only the processing method but also the cure cycle generate low-void-content structures. If voids are present, the performance of the composite matrix will be significantly reduced. This is usually noticed by significant reductions in matrix-dominated properties, such as compression and shear strength. Voids in composite materials are areas that are absent of the composite components: matrix and fibers. The characteristics of the voids and their accurate estimation are critical to determine for high performance composite structures. One widely used method of performing void analysis on a composite structure sample is acquiring optical micrographs or Scanning Electron Microscope (SEM) images of lateral sides of the sample and retrieving the void areas within the micrographs/images using an image analysis technique. Segmentation for the retrieval and subsequent computation of void areas within the micrographs/images is challenging as the gray-scaled values of the void areas are close to the gray-scaled values of the matrix leading to the need of manually performing the segmentation based on the histogram of the micrographs/images to retrieve the void areas. The use of an algorithm developed by NASA and based on Fuzzy Reasoning (FR) proved to overcome the difficulty of suitably differentiate void and matrix image areas with similar gray-scaled values leading not only to a more accurate estimation of void areas on composite matrix micrographs but also to a faster void analysis process as the algorithm is fully autonomous.

  13. A New Kind of Void Soap-free P(MMA-EA-MAA) Latex Particles

    Institute of Scientific and Technical Information of China (English)

    Kai KANG; Cheng You KAN; Yi DU; Yu Zhong LI; De Shan LIU

    2005-01-01

    Soap-free P(MMA-EA-MAA) particles with narrow size distribution were synthesized by seeded emulsion polymerization of methyl methacrylate (MMA), ethyl acrylate (EA) and methacrylic acid (MAA), and large voids inside the particles were generated by alkali posttreatment in the presence of 2-butanone. Results indicated that the size of void and the particle volume were related with the amount of 2-butanone. The generation mechanism of voids was proposed.

  14. Dependence of calculated void reactivity on film boiling representation in a CANDU lattice

    Energy Technology Data Exchange (ETDEWEB)

    Whitlock, J [McMaster Univ., Hamilton, ON (Canada). Dept. of Engineering Physics

    1994-12-31

    The distribution dependence of void reactivity in a CANDU (CANada Deuterium Uranium) lattice is studied, specifically in the regime of film boiling. A heterogeneous model of this phenomenon predicts a 4% increase in void reactivity over a homogeneous model for fresh fuel, and 11% at discharge. An explanation for this difference is offered, with regard to differing changes in neutron mean free path upon voiding. (author). 9 refs., 4 tabs., 6 figs.

  15. Characteristics of dust voids in a strongly coupled laboratory dusty plasma

    Science.gov (United States)

    Bailung, Yoshiko; Deka, T.; Boruah, A.; Sharma, S. K.; Pal, A. R.; Chutia, Joyanti; Bailung, H.

    2018-05-01

    A void is produced in a strongly coupled dusty plasma by inserting a cylindrical pin (˜0.1 mm diameter) into a radiofrequency discharge argon plasma. The pin is biased externally below the plasma potential to generate the dust void. The Debye sheath model is used to obtain the sheath potential profile and hence to estimate the electric field around the pin. The electric field force and the ion drag force on the dust particles are estimated and their balance accounts well for the maintenance of the size of the void. The effects of neutral density as well as dust density on the void size are studied.

  16. Convex-based void filling method for CAD-based Monte Carlo geometry modeling

    International Nuclear Information System (INIS)

    Yu, Shengpeng; Cheng, Mengyun; Song, Jing; Long, Pengcheng; Hu, Liqin

    2015-01-01

    Highlights: • We present a new void filling method named CVF for CAD based MC geometry modeling. • We describe convex based void description based and quality-based space subdivision. • The results showed improvements provided by CVF for both modeling and MC calculation efficiency. - Abstract: CAD based automatic geometry modeling tools have been widely applied to generate Monte Carlo (MC) calculation geometry for complex systems according to CAD models. Automatic void filling is one of the main functions in the CAD based MC geometry modeling tools, because the void space between parts in CAD models is traditionally not modeled while MC codes such as MCNP need all the problem space to be described. A dedicated void filling method, named Convex-based Void Filling (CVF), is proposed in this study for efficient void filling and concise void descriptions. The method subdivides all the problem space into disjointed regions using Quality based Subdivision (QS) and describes the void space in each region with complementary descriptions of the convex volumes intersecting with that region. It has been implemented in SuperMC/MCAM, the Multiple-Physics Coupling Analysis Modeling Program, and tested on International Thermonuclear Experimental Reactor (ITER) Alite model. The results showed that the new method reduced both automatic modeling time and MC calculation time

  17. An experimental and theoretical analysis of void fraction dynamics in a boiling channel

    International Nuclear Information System (INIS)

    Romberg, T.M.

    1977-01-01

    This paper describes an experimental and theoretical investigation of the void fraction dynamics at the exit of a test boiling channel which is operated near the 'instability threshold power' (the power level at which coolant flow instabilities occur). Dynamic measurements of the perturbations in channel inlet flow-rate, power input and exit void fraction are analysed using multivariate spectral analysis. The resulting experimental cross-spectral density functions between flow-rate/exit void fraction and power input/exit void fraction agree favourably with those calculated by a linearised hydrodynamic model in the frequency domain. (Author)

  18. Atomistic simulations of void migration under thermal gradient in UO2

    International Nuclear Information System (INIS)

    Desai, Tapan G.; Millett, Paul; Tonks, Michael; Wolf, Dieter

    2010-01-01

    It is well known that within a few hours after startup of a nuclear reactor, the temperature gradient within a fuel element causes migration of voids/bubbles radially inwards to form a central hole. To understand the atomic processes that control this migration of voids, we performed molecular dynamics (MD) simulations on single crystal UO 2 with voids of diameter 2.2 nm. An external temperature gradient was applied across the simulation cell. At the end of the simulation run, it was observed that the voids had moved towards the hot end of the simulation cell. The void migration velocity obtained from the simulations was compared with the available phenomenological equations for void migration due to different transport mechanisms. Surface diffusion of the slowest moving specie, i.e. uranium, was found to be the dominant mechanism for void migration. The contribution from lattice diffusion and the thermal stress gradient to the void migration was analyzed and found to be negligible. By extrapolation, a crossover from the surface-diffusion-controlled mechanism to the lattice-diffusion-controlled mechanism was found to occur for voids with sizes in the μm range.

  19. Irradiation-induced void evolution in iron: A phase-field approach with atomistic derived parameters

    International Nuclear Information System (INIS)

    Wang Yuan-Yuan; Ding Jian-Hua; Huang Shao-Song; Zhao Ji-Jun; Liu Wen-Bo; Ke Xiao-Qin; Wang Yun-Zhi; Zhang Chi

    2017-01-01

    A series of material parameters are derived from atomistic simulations and implemented into a phase field (PF) model to simulate void evolution in body-centered cubic (bcc) iron subjected to different irradiation doses at different temperatures. The simulation results show good agreement with experimental observations — the porosity as a function of temperature varies in a bell-shaped manner and the void density monotonically decreases with increasing temperatures; both porosity and void density increase with increasing irradiation dose at the same temperature. Analysis reveals that the evolution of void number and size is determined by the interplay among the production, diffusion and recombination of vacancy and interstitial. (paper)

  20. Experimental study of average void fraction in low-flow subcooled boiling

    International Nuclear Information System (INIS)

    Sun Qi; Wang Xiaojun; Xi Zhao; Zhao Hua; Yang Ruichang

    2005-01-01

    Low-flow subcooled void fraction in medium pressure was investigated using high-temperature high-pressure single-sensor optical probe in this paper. And then average void fraction was obtained through the integral calculation of local void fraction in the cross-section. The experimental data were compared with the void fraction model proposed in advance. The results show that the predictions of this model agree with the data quite well. The comparisons of Saha and Levy models with low-flow subcooled data show that Saha model overestimates the experimental data distinctively, and Levy model also gets relatively higher predictions although it is better than Saha model. (author)

  1. Void Fraction Measurement in Subcooled-Boiling Flow Using High-Frame-Rate Neutron Radiography

    International Nuclear Information System (INIS)

    Kureta, Masatoshi; Akimoto, Hajime; Hibiki, Takashi; Mishima, Kaichiro

    2001-01-01

    A high-frame-rate neutron radiography (NR) technique was applied to measure the void fraction distribution in forced-convective subcooled-boiling flow. The focus was experimental technique and error estimation of the high-frame-rate NR. The results of void fraction measurement in the boiling flow were described. Measurement errors on instantaneous and time-averaged void fractions were evaluated experimentally and analytically. Measurement errors were within 18 and 2% for instantaneous void fraction (measurement time is 0.89 ms), and time-averaged void fraction, respectively. The void fraction distribution of subcooled boiling was measured using atmospheric-pressure water in rectangular channels with channel width 30 mm, heated length 100 mm, channel gap 3 and 5 mm, inlet water subcooling from 10 to 30 K, and mass velocity ranging from 240 to 2000 kg/(m 2 .s). One side of the channel was heated homogeneously. Instantaneous void fraction and time-averaged void fraction distribution were measured parametrically. The effects of flow parameters on void fraction were investigated

  2. The dipole moment of a wall-charged void in a bulk dielectric

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1993-01-01

    The dipole moment of a wall-charged void is examined with reference to the spatial extent of the surface charge density σ and the distribution of this charge. The salient factors influencing the void dipole moment are also examined. From a study of spherical voids, it is shown that, although the σ......-distribution influences the dipole moment, the spatial extent of σ has a greater influence. This behavior is not unexpected. For a void of fixed dimensions, the smaller the charged surface area, the greater is the charges, and thus the greater the dipole moment...

  3. Measurement of local void fraction at elevated temperature and pressure

    International Nuclear Information System (INIS)

    Duncan, D.; Trabold, T.A.

    1993-03-01

    Significant advances have recently been made in analytical and computational methods for the prediction of local thermal-hydraulic conditions in gas/liquid two-phase flows. There is, however, a need for extensive experimental data, for the dual purposes of constitutive relation development and code qualification. There is especially true of systems involving complicated geometries and/or extreme flow conditions for which little, if any, applicable information exists in the open literature. For the tests described in the present paper, a novel electrical probe has been applied to measure the void fraction in atmospheric pressure air/water flows, and steam/water mixtures at high temperature and pressure. The data acquired in the latter experiments are compared with the results of a one-dimensional two-fluid computational analysis

  4. Partial discharge characteristics and mechanism in voids at impulse voltages

    International Nuclear Information System (INIS)

    Zhao, X F; Guo, Z F; Wang, Y Y; Li, J H; Li, Y M; Yao, X

    2011-01-01

    Partial discharge (PD) characteristics and mechanism in artificial cavities in an epoxy plate have been investigated for different void dimensions and impulse voltage waveforms. A differential measurement system was developed in order to detect PD current pulses effectively. Experimental results showed that the 50% probability PD inception voltage (PDIV 50 ) increases initially as the cavity diameter decreases at constant depth for double exponential impulses as well as oscillating impulses, but after aging, it becomes independent of the cavity diameter. Moreover, some distinctive characteristics of PD (e.g. main discharge and reverse discharge during the rise and fall phases of the applied voltage) were also investigated. The differences of the PD propagation and the mechanism between double exponential impulses and oscillating impulse were discussed

  5. Is voiding cystourethrogram necessary in all cases of antenatal hydronephrosis?

    Directory of Open Access Journals (Sweden)

    M S Ansari

    2009-01-01

    Full Text Available Hydronephrosis is the most common genitourinary anomaly as detected on obstetric ultrasonography and the incidence of associated vesicoureteral reflux is around 10-12%. There is inconsistency in the literature regarding which child should under go a voiding cystourethrogram (VCUG in cases of antenatal hydronephrosis (AHN. Besides, there is a scarcity of prospective studies to demonstrate the risk of varying degree of AHN, associated reflux and their long-term impact on the kidneys. The present analysis suggests that children with AHN should undergo an ultrasound within the first month of life and further course of action should be decided on the basis of the individual case. Children with persistent moderate to severe AHN should undergo a VCUG and a functional study.

  6. Dynamical 3-Space: Cosmic Filaments, Sheets and Voids

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2011-04-01

    Full Text Available Observations of weak gravitational lensing combined with statistical tomographic techniques have revealed that galaxies have formed along filaments, essentially one- dimensional lines or strings, which form sheets and voids. These have, in the main, been interpreted as “dark matter” effects. To the contrary here we report the discovery that the dynamical 3-space theory possesses such filamentary solutions. These solutions are purely space self-interaction effects, and are attractive to matter, and as well gener- ate electromagnetic lensing. This theory of space has explained bore hole anomalies, supermassive black hole masses in spherical galaxies and globular clusters, flat rota- tion curves of spiral galaxies, and other gravitational anomalies. The theory has two constants, G and , where the bore hole experiments show that 1 = 137 is the fine structure constant.

  7. Dynamical 3-Space: Cosmic Filaments, Sheets and Voids

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2011-04-01

    Full Text Available Observations of weak gravitational lensing combined with statistical tomographic techniques have revealed that galaxies have formed along filaments, essentially one-dimensional lines or strings, which form sheets and voids. These have, in the main, been interpreted as "dark matter" effects. To the contrary here we report the discovery that the dynamical 3-space theory possesses such filamentary solutions. These solutions are purely space self-interaction effects, and are attractive to matter, and as well generate electromagnetic lensing. This theory of space has explained bore hole anomalies, supermassive black hole masses in spherical galaxies and globular clusters, flat rotation curves of spiral galaxies, and other gravitational anomalies. The theory has two constants, $G$ and $alpha$, where the bore hole experiments show that $alpha approx 1/137$ is the fine structure constant.

  8. Results and applications in thermoelasticity of materials with voids

    Directory of Open Access Journals (Sweden)

    Michele Ciarletta

    1991-05-01

    Full Text Available We consider the linear theory of a thermoelastic porous solid in which the skeletal or matrix is a thermoelastic material and the interstices are void of material. We assume that the initial body is free from stresses. The concept of a distributed body asserts that the mass density at time t has the decomposition γν, where γ is the density of the matrix material and ν (0 In the first part, in order to derive some applications of the reciprocity theorem, we recall some results established by same authors in [3]. Then we obtain integral representations of the solution and prove that the solving of the boundary-initial value problem can be reduced to the solving of an associated uncoupled problem and to an integral equation for the volume fraction field.

  9. Void fraction prediction of NUPEC PSBT tests by CATHARE code

    International Nuclear Information System (INIS)

    Del Nevo, A.; Michelotti, L.; Moretti, F.; Rozzia, D.; D'Auria, F.

    2011-01-01

    The current generation of thermal-hydraulic system codes benefits of about sixty years of experiments and forty years of development and are considered mature tools to provide best estimate description of phenomena and detailed reactor system representations. However, there are continuous needs for checking the code capabilities in representing nuclear system, for drawing attention to their weak points, for identifying models which need to be refined for best-estimate calculations. Prediction of void fraction and Departure from Nucleate Boiling (DNB) in system thermal-hydraulics is currently based on empirical approaches. The database carried out by Nuclear Power Engineering Corporation (NUPEC), Japan addresses these issues. It is suitable for supporting the development of new computational tools based on more mechanistic approaches (i.e. three-field codes, two-phase CFD, etc.) as well as for validating current generation of thermal-hydraulic system codes. Selected experiments belonging to this database are used for the OECD/NRC PSBT benchmark. The paper reviews the activity carried out by CATHARE2 code on the basis of the subchannel (four test sections) and presents rod bundle (different axial power profile and test sections) experiments available in the database in steady state and transient conditions. The results demonstrate the accuracy of the code in predicting the void fraction in different thermal-hydraulic conditions. The tests are performed varying the pressure, coolant temperature, mass flow and power. Sensitivity analyses are carried out addressing nodalization effect and the influence of the initial and boundary conditions of the tests. (author)

  10. Detection of coolant void in lead-cooled fast reactors

    International Nuclear Information System (INIS)

    Wolniewicz, Peter; Håkansson, Ane; Jansson, Peter

    2015-01-01

    Highlights: • We model the ALFRED LFR using different Monte-Carlo codes. • We study the impact on coolant void on the fission cross section in fission chambers. • We develop a methodology to detect coolant void. • We study the impact of detector fissile coating burn-up. • We conclude that the developed methodology may be an attractive complement to LFR monitoring. - Abstract: Previous work (Wolniewicz et al., 2013) has indicated that using fission chambers coated with 242 Pu and 235 U, respectively, can provide the means of detecting changes in the neutron flux that are connected to coolant density changes in a small lead-cooled fast reactor. Such density changes may be due to leakages of gas into the coolant, which, over time, may coalesce to large bubbles implying a high risk of causing severe damage of the core. By using the ratio of the information provided by the two types of detectors a quantity is obtained that is sensitive to these density changes and, to the first order approximation, independent of the power level of the reactor. In this work we continue the investigation of this proposed methodology by applying it to the Advanced LFR European Demonstrator (ALFRED) and using realistic modelling of the neutron detectors. The results show that the methodology may be used to detect density changes indicating the initial stages of a coalescence process that may result in a large bubble. Also, it is shown that under certain circumstances, large bubbles passing through the core could be detected with this methodology

  11. Coolant voiding analysis following SGTR for an HLMC reactor

    International Nuclear Information System (INIS)

    Farmer, M.T.; Spencer, B.W.; Sienicki, J.J.

    2000-01-01

    Concepts are under development at Argonne National Laboratory for a small, modular, proliferation-resistant nuclear power steam supply system. Of primary interest here is the simplified system design, featuring steam generators that are directly immersed in the lead-bismuth eutectic (LBE) coolant of the primary system. To support the safety case for this design approach, model development and analysis of transient coolant voiding during a postulated guillotine-type steam generator tube rupture event has been carried out. For the current design, the blowdown will occur from the steam generator shell into the ruptured 12.7-mm-inside-diameter tube through which the LBE coolant passes. The steam will expand biaxially in the tube, with a portion of the flow vented upward to eventually expand into the cover-gas region, while the balance of the flow is vented downward as a jet into the surrounding downward-flowing LBE. Coolant freezing is not an issue in this case because of high feedwater temperature in relation to the freezing point of the LBE. The specific objectives of the current work are to (a) determine the penetration behavior of the steam jet into the lower cold-leg region, (b) characterize the resultant void behavior in terms of coherent bubble versus breakup into a size distribution of small bubbles, and (c) characterize the motion of the bubbles with regard to rise to the cover-gas region (via the liner-to-coolant vessel gap) versus downward transport with the flowing LBE and subsequent upflow through the core to the cover-gas region

  12. Development of quick-response area-averaged void fraction meter

    International Nuclear Information System (INIS)

    Watanabe, Hironori; Iguchi, Tadashi; Kimura, Mamoru; Anoda, Yoshinari

    2000-11-01

    Authors are performing experiments to investigate BWR thermal-hydraulic instability under coupling of neutronics and thermal-hydraulics. To perform the experiment, it is necessary to measure instantaneously area-averaged void fraction in rod bundle under high temperature/high pressure gas-liquid two-phase flow condition. Since there were no void fraction meters suitable for these requirements, we newly developed a practical void fraction meter. The principle of the meter is based on the electrical conductance changing with void fraction in gas-liquid two-phase flow. In this meter, metal flow channel wall is used as one electrode and a L-shaped line electrode installed at the center of flow channel is used as the other electrode. This electrode arrangement makes possible instantaneous measurement of area-averaged void fraction even under the metal flow channel. We performed experiments with air/water two-phase flow to clarify the void fraction meter performance. Experimental results indicated that void fraction was approximated by α=1-I/I o , where α and I are void fraction and current (I o is current at α=0). This relation holds in the wide range of void fraction of 0∼70%. The difference between α and 1-I/I o was approximately 10% at maximum. The major reasons of the difference are a void distribution over measurement area and an electrical insulation of the center electrode by bubbles. The principle and structure of this void fraction meter are very basic and simple. Therefore, the meter can be applied to various fields on gas-liquid two-phase flow studies. (author)

  13. LOG-NORMAL DISTRIBUTION OF COSMIC VOIDS IN SIMULATIONS AND MOCKS

    Energy Technology Data Exchange (ETDEWEB)

    Russell, E.; Pycke, J.-R., E-mail: er111@nyu.edu, E-mail: jrp15@nyu.edu [Division of Science and Mathematics, New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi (United Arab Emirates)

    2017-01-20

    Following up on previous studies, we complete here a full analysis of the void size distributions of the Cosmic Void Catalog based on three different simulation and mock catalogs: dark matter (DM), haloes, and galaxies. Based on this analysis, we attempt to answer two questions: Is a three-parameter log-normal distribution a good candidate to satisfy the void size distributions obtained from different types of environments? Is there a direct relation between the shape parameters of the void size distribution and the environmental effects? In an attempt to answer these questions, we find here that all void size distributions of these data samples satisfy the three-parameter log-normal distribution whether the environment is dominated by DM, haloes, or galaxies. In addition, the shape parameters of the three-parameter log-normal void size distribution seem highly affected by environment, particularly existing substructures. Therefore, we show two quantitative relations given by linear equations between the skewness and the maximum tree depth, and between the variance of the void size distribution and the maximum tree depth, directly from the simulated data. In addition to this, we find that the percentage of voids with nonzero central density in the data sets has a critical importance. If the number of voids with nonzero central density reaches ≥3.84% in a simulation/mock sample, then a second population is observed in the void size distributions. This second population emerges as a second peak in the log-normal void size distribution at larger radius.

  14. Severe Embrittlement of Neutron Irradiated Austenitic Steels Arising from High Void Swelling

    International Nuclear Information System (INIS)

    Neustroev, V.S.; Garner, F.

    2007-01-01

    Full text of publication follows: Data are presented from BOR-60 irradiations showing that significant radiation-induced swelling causes severe embrittlement in austenitic stainless steels, reducing the service life of structural components. Similar loss of ductility is expected when swelling arises in fusion and light water reactor environments. Above 7-16% swelling there is complete loss of ductility, with the onset of ductility loss beginning at lower swelling in ring-pull tensile tests than for flat tensile specimens. For steels that develop extensive precipitation during irradiation, the critical swelling level is even lower. A model is presented to demonstrate the effect of voids acting alone to produce the embrittlement. Although voids are not very effective hardeners, they are very effective to generate stress concentrations between voids. The stress concentration ratio increases strongly when the void diameter exceeds ∼40% of the void-to-void separation distance. When the volume fraction of voids is rather high (about 16 % and higher), a geometric situation develops where it is possible to create an intense field of deformation glide planes residing at an angle of 45 deg. to the void-to-void axis. Significant localized flow then proceeds on these planes for specimen stress levels that are significantly lower than the yield stress. Voids also segregate nickel to their surfaces such that flow localization occurs in the low-nickel inter-void regions to produce strain-induced martensite, which is further accelerated by stress concentrations at the advancing crack tip, leading to catastrophic failure. (authors)

  15. Modification of redshift and luminosity by voids in the expanding universe

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Humitaka

    1985-03-01

    Propagation of light in a clumpy universe is examined for redshift and luminosity. Taking a spherical void model and Swiss Chesse model, the modification is found to be the third order of (Hrsub(b)/c) for the redshift and the first order of it for the luminosity, rsub(b) being the radius of a void or a Swiss Cheese hole.

  16. 21 CFR 1305.19 - Cancellation and voiding of DEA Forms 222.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Cancellation and voiding of DEA Forms 222. 1305.19... I AND II CONTROLLED SUBSTANCES DEA Form 222 § 1305.19 Cancellation and voiding of DEA Forms 222. (a) A purchaser may cancel part or all of an order on a DEA Form 222 by notifying the supplier in...

  17. Determination of gas pressure in voids in epoxy casting using an ultrasonic measuring technique

    DEFF Research Database (Denmark)

    Larsen, Esben; Petersen, C. Bak; Henriksen, Mogens

    1990-01-01

    Results of measurements performed on a large open void, where pressure can be controlled from the outside, are compared to the theory of ultrasound transmission. The results verify the theory that the attenuation of transmitted ultrasonic signals through a void depends on the gas pressure inside ...

  18. Computer simulation of void formation in residual gas atom free metals by dual beam irradiation experiments

    International Nuclear Information System (INIS)

    Shimomura, Y.; Nishiguchi, R.; La Rubia, T.D. de; Guinan, M.W.

    1992-01-01

    In our recent experiments (1), we found that voids nucleate at vacancy clusters which trap gas atoms such as hydrogen and helium in ion- and neutron-irradiated copper. A molecular dynamics computer simulation, which implements an empirical embedded atom method to calculate forces that act on atoms in metals, suggests that a void nucleation occurs in pure copper at six and seven vacancy clusters. The structure of six and seven vacancy clusters in copper fluctuates between a stacking fault tetrahedron and a void. When a hydrogen is trapped at voids of six and seven vacancy, a void can keep their structure for appreciably long time; that is, the void do not relax to a stacking fault tetrahedron and grows to a large void. In order to explore the detailed atomics of void formation, it is emphasized that dual-beam irradiation experiments that utilize beams of gas atoms and self-ions should be carried out with residual gas atom free metal specimens. (author)

  19. A variational constitutive model for the distribution and interactions of multi-sized voids

    KAUST Repository

    Liu, Jinxing; El Sayed, Tamer S.

    2013-01-01

    of the radii of the voids. In this study, we use a new form of the incompressibility of the matrix to propose the formula for the volumetric plastic energy of a void inside a porous medium. As a consequence, we are able to account for the weakening effect

  20. The Effects of Void on Natural Ventilation Performance in Multi-Storey Housing

    Directory of Open Access Journals (Sweden)

    Fakhriah Muhsin

    2016-08-01

    Full Text Available Enhancing natural ventilation performance in multi-storey housing is very important for the living environment in terms of health and thermal comfort purposes. One of the most important design strategies to enhance natural ventilation in multi-storey housing is through the provision of voids. A void is a passive architectural feature, which is located in the middle of deep plan buildings. It is very crucial to consider the configurations of voids in the buildings for enhancing natural ventilation, especially for multi-storey housing. In this study, Malaysian Medium Cost Multi-Storey Housing (MMCMSH, which is an example of multi-storey housing located in a suburban area, has been selected in this study. This study aims to investigate the potential of void for enhancing natural ventilation performance in multi-storey housing by the comparison of two different void configurations. Field measurement of MMCMSH has been conducted to validate Computational Fluid Dynamic (CFD model and Atmospheric Boundary Layer (ABL is an important parameter for setting up the CFD Model’s domain. Ventilation rate (Q, which is necessary for comfort and health reasons, is an important parameter for the comparison of the different void configurations. This study revealed that the provision of void can enhance natural ventilation performance in multi-storey housing with an increase in the value of Q, from 3.44% to 40.07%, by enlarging the void’s width by 50% compared to the existing void.

  1. A model for void-induced back reaction between radiolytic products in NaCl

    NARCIS (Netherlands)

    Turkin, A.A.; Dubinko, V.I.; Vainshtein, D.I.; Hartog, H.W. den

    A kinetic model is formulated for the chemical reaction between radiolytic sodium colloids and gas bubbles, which are brought into contact with each other during the exposure to ionising radiation by the growing voids. The reaction starts with the evaporation of Na atoms into the void due to the

  2. Void fraction distribution in a heated rod bundle under flow stagnation conditions

    Energy Technology Data Exchange (ETDEWEB)

    Herrero, V.A.; Guido-Lavalle, G.; Clausse, A. [Centro Atomico Bariloche and Instituto Balseiro, Bariloche (Argentina)

    1995-09-01

    An experimental study was performed to determine the axial void fraction distribution along a heated rod bundle under flow stagnation conditions. The development of the flow pattern was investigated for different heat flow rates. It was found that in general the void fraction is overestimated by the Zuber & Findlay model while the Chexal-Lellouche correlation produces a better prediction.

  3. Fluid intake and voiding; habits and health knowledge in a young, healthy population.

    Science.gov (United States)

    Das, Rebekah N; Grimmer-Somers, Karen A

    2012-01-01

    Health professionals commonly advise patients with incontinence and other lower urinary tract symptoms about modifiable contributing factors such as drinking and voiding habits. Poor drinking and voiding habits may begin early in life, before symptoms emerge. However, little is known about the habits and knowledge young people have regarding healthy drinking and voiding behaviors. This research aimed to assess the habits and health knowledge of young people regarding fluid intake and voiding. A questionnaire was used to assess the drinking and voiding behaviors of first year university students and their knowledge about healthy fluid intake and voiding. The average daily fluid intake was >2 L/day for both genders. Poor drinking and voiding habits (such as high consumption of caffeinated drinks and alcohol, or nocturia) were common. Widely reported myths about the benefits of a high fluid intake were commonly believed. More informed public education regarding healthy fluid intake, and drinking and voiding habits, is required as part of the effort to reduce the development of lower urinary tract symptoms, including incontinence.

  4. Microscopic Void Detection for Predicting Remaining Life in Electric Cable Insulation

    International Nuclear Information System (INIS)

    Horvath, David A.; Avila, Steven M.

    2003-01-01

    A reliable method of testing for remaining life in electric cable insulation has continued to elude the nuclear industry as it seeks to extend the life and license of its nuclear stations. Until recently, a trendable, measurable electrical property has not been found, and unexpected cable failures continue to be reported. Most reliable approaches to date rely on monitoring mechanical properties, which are assumed to degrade faster than the insulation's electrical properties. This paper introduces a promising technique based on void characterization, which is dependent on an electrical property related to dielectric strength. A relationship between insulation void characteristics (size and density) and the onset of partial discharge is known to exist. A similar relationship can be shown between void characteristics and unacceptable leakage currents (another typical cable failure criterion). For low-voltage cables, it is believed void content can be correlated to mechanical property degradation.This paper will report on an approach for using void information, research results showing the existence of trendable void characteristics in commonly used electric insulation materials, and techniques for detecting the voids (both laboratory- and field-based techniques). Acoustical microscopy was found to be potentially more suitable than conventional ultrasound for nondestructive in situ detection and monitoring of void characteristics in jacketed multiconductor insulation while ignoring the jacket. Also, optical and scanning electron microscope techniques will play an essential role in establishing the database necessary for continued development and implementation of this promising technique

  5. PD-related stresses in the bulk dielectric for ellipsoidal voids

    DEFF Research Database (Denmark)

    Pedersen, Aage; Crichton, George C; McAllister, Iain Wilson

    1994-01-01

    In a previous study, the existence of a field enhancement in the solid dielectric in the vicinity of void undergoing PD activity was established. That study was undertaken with reference to a spherical void. In this paper, a more general investigation of this phenomenon of field enhancement...

  6. Radiation-induced segregation and void formation in C+ ion-irradiated vanadium-carbon alloys

    International Nuclear Information System (INIS)

    Takeyama, T.; Ohnuki, S.; Takahashi, H.; Sato, Y.; Mochizuki, S.

    1982-01-01

    To clarify the effect of interstitial elements on radiation-induced segregation and void formation in V and V-C alloys irradiated by 200 keV C + ions to a dose of 48 dpa at 973 K, the microstructural observation and the measurement of C segregation to the surfaces were carried out by TEM and XPS. Voids, dislocations and precipitates were produced in all of the specimens during irradiation. The addition of C in V led to a reduction of void size and to increase in void number density, consequently the void swelling was suppressed strongly. Radiation-induced segregation of C was observed clearly on and near the irradiated surfaces of V-C alloys and as a result of the enrichment of C atoms, carbides precipitated on the surfaces. It is the first evidence of the radiation-induced segregation of interstitial elements on the surfaces. Also, quasi-carbides were observed on the (210) habit plaints near large voids and dislocations in V. The phenomena show that C atoms, which was insolved and/or implanted, interact strongly with vacancies rather than self-interstitial atoms and migrate with vacancies toward defect sinks, such as surfaces, voids, and dislocations. The segregated zones of C reduced the sink efficiency of the defects, and showed the effect of the suppression on void in V-C alloys. (author)

  7. On grain size dependent void swelling in pure copper irradiated with fission neutrons

    International Nuclear Information System (INIS)

    Singh, B.N.; Eldrup, M.; Golubov, S.I.; Zinkle, S.J.

    2001-03-01

    The effect of grain size on void swelling has its origin in the intrinsic property of grain boundaries as neutral and unsaturable sinks for both vacancies and self-interstitial atoms (SIAs). The phenomenon was investigated already in the 1970s and it was demonstrated that the grain size dependent void swelling measured under irradiation producing only Frenkel pairs could be satisfactorily explained in terms of the standard rate theory (SRT) and dislocation bias. Experimental results reported in the 1980s demonstrated, on the other hand, that the effect of grain boundaries on void swelling under cascade damage conditions was radically different and could not be explained in terms of the SRT. In an effort to understand the source of this significant difference, the effect of grain size on void swelling under cascade damage conditions has been investigated both experimentally and theoretically in pure copper irradiated with fission neutrons at 623K to a dose level of ∼0.3 dpa (displacement per atom). The post-irradiation defect microstructure including voids was investigated using transmission electron microscopy and positron annihilation spectroscopy. The evolution of void swelling was calculated within the framework of the production bias model (PBM) and the SRT. The grain size dependent void swelling measured experimentally is in good accord with the theoretical results obtained using PMB. Implications of these results on modeling of void swelling under cascade damage conditions are discussed. (au)

  8. Void reactivity decomposition for the Sodium-cooled Fast Reactor in equilibrium fuel cycle

    Energy Technology Data Exchange (ETDEWEB)

    Sun Kaichao, E-mail: kaichao.sun@psi.ch [Paul Scherrer Institut (PSI), 5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne (Switzerland); Krepel, Jiri; Mikityuk, Konstantin; Pelloni, Sandro [Paul Scherrer Institut (PSI), 5232 Villigen PSI (Switzerland); Chawla, Rakesh [Paul Scherrer Institut (PSI), 5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne (Switzerland)

    2011-07-15

    Highlights: > We analyze the void reactivity effect for three ESFR core fuel cycle states. > The void reactivity effect is decomposed by neutron balance method. > Novelly, the normalization to the integral flux in the active core is applied. > The decomposition is compared with the perturbation theory based results. > The mechanism and the differences of the void reactivity effect are explained. - Abstract: The Sodium-cooled Fast Reactor (SFR) is one of the most promising Generation IV systems with many advantages, but has one dominating neutronic drawback - a positive sodium void reactivity. The aim of this study is to develop and apply a methodology, which should help better understand the causes and consequences of the sodium void effect. It focuses not only on the beginning-of-life (BOL) state of the core, but also on the beginning of open and closed equilibrium (BOC and BEC, respectively) fuel cycle conditions. The deeper understanding of the principal phenomena involved may subsequently lead to appropriate optimization studies. Various voiding scenarios, corresponding to different spatial zones, e.g. node or assembly, have been analyzed, and the most conservative case - the voiding of both inner and outer fuel zones - has been selected as the reference scenario. On the basis of the neutron balance method, the corresponding SFR void reactivity has been decomposed reaction-, isotope-, and energy-group-wise. Complementary results, based on generalized perturbation theory and sensitivity analysis, are also presented. The numerical analysis for both neutron balance and perturbation theory methods has been carried out using appropriate modules of the ERANOS code system. A strong correlation between the flux worth, i.e. the product of flux and adjoint flux, and the void reactivity importance distributions has been found for the node- and assembly-wise voiding scenarios. The neutron balance based decomposition has shown that the void effect is caused mainly by the

  9. Void reactivity decomposition for the Sodium-cooled Fast Reactor in equilibrium fuel cycle

    International Nuclear Information System (INIS)

    Sun Kaichao; Krepel, Jiri; Mikityuk, Konstantin; Pelloni, Sandro; Chawla, Rakesh

    2011-01-01

    Highlights: → We analyze the void reactivity effect for three ESFR core fuel cycle states. → The void reactivity effect is decomposed by neutron balance method. → Novelly, the normalization to the integral flux in the active core is applied. → The decomposition is compared with the perturbation theory based results. → The mechanism and the differences of the void reactivity effect are explained. - Abstract: The Sodium-cooled Fast Reactor (SFR) is one of the most promising Generation IV systems with many advantages, but has one dominating neutronic drawback - a positive sodium void reactivity. The aim of this study is to develop and apply a methodology, which should help better understand the causes and consequences of the sodium void effect. It focuses not only on the beginning-of-life (BOL) state of the core, but also on the beginning of open and closed equilibrium (BOC and BEC, respectively) fuel cycle conditions. The deeper understanding of the principal phenomena involved may subsequently lead to appropriate optimization studies. Various voiding scenarios, corresponding to different spatial zones, e.g. node or assembly, have been analyzed, and the most conservative case - the voiding of both inner and outer fuel zones - has been selected as the reference scenario. On the basis of the neutron balance method, the corresponding SFR void reactivity has been decomposed reaction-, isotope-, and energy-group-wise. Complementary results, based on generalized perturbation theory and sensitivity analysis, are also presented. The numerical analysis for both neutron balance and perturbation theory methods has been carried out using appropriate modules of the ERANOS code system. A strong correlation between the flux worth, i.e. the product of flux and adjoint flux, and the void reactivity importance distributions has been found for the node- and assembly-wise voiding scenarios. The neutron balance based decomposition has shown that the void effect is caused mainly

  10. Blind void filling in LR-EPONs: How efficient it can be?

    KAUST Repository

    Elrasad, Amr; Shihada, Basem

    2015-01-01

    This work proposes a novel blind void (idle periods) filling in Long-Reach Ethernet Passive Optical Networks (LR-EPONs) namely Size Controlled Batch Void Filling (SCBVF). We emphasize on reducing grant delays and hence reducing the average packet delay. SCBVF delay reduction is achieved by early flushing data during the idle time periods (voids) between allocated grants. The proposed approach can be integrated with almost all of the previously reported dynamic bandwidth allocation schemes. SCBVF is less sensitive to differential distance between ONUs and can work well in case of small differential distances compared to previously reported void filling schemes. We support our work by extensive simulation study considering bursty traffic with long range dependency. Numerical results show a delay reduction up to 35% compared to non-void filling scheme outperforming its main competitors that can achieve up to 7% delay reduction.

  11. Collapse and coalescence of spherical voids subject to intense shearing: studied in full 3D

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau; Dahl, Jonas; Tvergaard, Viggo

    2012-01-01

    the numerical analysis, which is also reflected in published literature. Rather than moving towards very low triaxiality shearing, work has focused on extracting wide-ranging results for moderate stress triaxiality (T ~ 1), in order to achieve sufficient understanding of the influence of initial porosity, void...... significant straining of the matrix material located on the axis of rotation. In particular, the void surface material is severely deformed during shearing and void surface contact is established early in the deformation process. This 3D effect intensifies with decreasing stress triaxiality and complicates...... shape, void orientation etc. The objective of this work is to expand the range of stress triaxiality usually faced in 3D cell model studies, such that intense shearing is covered, and to bring forward details on the porosity and void shape evolution. The overall material response is presented...

  12. Core concepts for ''zero-sodium-void-worth core'' in metal fuelled fast reactor

    International Nuclear Information System (INIS)

    Chang, Y.I.; Hill, R.N.; Fujita, E.K.; Wade, D.C.; Kumaoka, Y.; Suzuki, M.; Kawashima, M.; Nakagawa, H.

    1991-01-01

    Core design options to reduce the sodium void worth in metal fueled LMRs are investigated. Two core designs which achieve a zero sodium void worth are analyzed in detail. The first design is a ''pancaked'' and annular core with enhanced transuranic burning capabilities; the high leakage in this design yields a low breeding ratio and small void worth. The second design is an axially multilayered annular core which is fissile self-sufficient; in this design, the upper and lower core regions are neutronically decoupled for reduced void worth while fissile self-sufficiency is achieved using internal axial blankets plus external radial and axial blanket zones. The neutronic performance characteristics of these low void worth designs are assessed here; their passive safety properties are discussed in a companion paper. 16 refs., 2 figs., 3 tabs

  13. Active infrared thermography for visualizing subsurface micro voids in an epoxy molding compound

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ji Yeol [Test and Package Center, Samsung Electronics, Asan(Korea, Republic of); Hwang, Soon Kyu; Choi, Jae Mook; Sohn, Hoon [Dept. of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2017-04-15

    This paper presents an automated subsurface micro void detection technique based on pulsed infrared thermography for inspecting epoxy molding compounds (EMC) used in electronic device packaging. Subsurface micro voids are first detected and visualized by extracting a lock-in amplitude image from raw thermal images. Binary imaging follows to achieve better visualization of subsurface micro voids. A median filter is then applied for removing sparse noise components. The performance of the proposed technique is tested using 36 EMC samples, which have subsurface (below 150 μm ~ 300 μm from the inspection surface) micro voids (150 μm ~ 300 μm in diameter). The experimental results show that the subsurface micro voids can be successfully detected without causing any damage to the EMC samples, making it suitable for automated online inspection.

  14. LMR design concepts for transuranic management in low sodium void worth cores

    International Nuclear Information System (INIS)

    Hill, R.N.

    1991-01-01

    The fuel cycle processing techniques and hard neutron spectrum of the integral Fast Reactor (IFR) metal fuel cycle have favorable characteristics for the management of transuranics; and the wide range of breeding characteristics available in metal fuelled cores provides for flexibility in transuranic management strategy. Previous studies indicate that most design options which decrease the breeding ratio also allow a decrease in sodium void worth; therefore, low void worths are achievable in transuranic burning (low breeding ratio) core designs. This paper describes numerous trade studies assessing various design options for a low void worth transuranic burner core. A flat annular core design appears to be a promising concept; the high leakage geometry yields a low breeding ratio and small sodium void worth. To allow flexibility in breeding characteristics, alternate design options which achieve fissile self-sufficiency are also evaluated. A self-sufficient core design which is interchangeable with the burner core and maintains a low sodium void worth is developed. (author)

  15. Measurement of void fraction distribution in two-phase flow by impedance CT with neural network

    International Nuclear Information System (INIS)

    Hayashi, Hideaki; Sumida, Isao; Sakai, Sinji; Wakai, Kazunori

    1996-01-01

    This paper describes a new method for measurement of void distribution using impedance CT with a hierarchical neural network. The present method consists of four processes. First, output electric currents are calculated by simulation of various distributions of void fraction. The relationship between distribution of void fraction and electric current is called 'teaching data'. Second, the neural network learns the teaching data by the back propagation method. Third, output electric currents are measured about actual two-phase flow. Finally, distribution of void fraction is calculated by the taught neural network using the measured electric currents. In this paper, measurement and learning parameters are adjusted, experimental results obtained using the impedance CT method are compared with data obtained by the impedance probe method. The results show that our method is effective for measurement of void fraction distribution. (author)

  16. Influence investigation of a void region on modeling light propagation in a heterogeneous medium.

    Science.gov (United States)

    Yang, Defu; Chen, Xueli; Ren, Shenghan; Qu, Xiaochao; Tian, Jie; Liang, Jimin

    2013-01-20

    A void region exists in some biological tissues, and previous studies have shown that inaccurate images would be obtained if it were not processed. A hybrid radiosity-diffusion method (HRDM) that couples the radiosity theory and the diffusion equation has been proposed to deal with the void problem and has been well demonstrated in two-dimensional and three-dimensional (3D) simple models. However, the extent of the impact of the void region on the accuracy of modeling light propagation has not been investigated. In this paper, we first implemented and verified the HRDM in 3D models, including both the regular geometries and a digital mouse model, and then investigated the influences of the void region on modeling light propagation in a heterogeneous medium. Our investigation results show that the influence of the region can be neglected when the size of the void is less than a certain range, and other cases must be taken into account.

  17. Effect of hardness of martensite and ferrite on void formation in dual phase steel

    DEFF Research Database (Denmark)

    Azuma, M.; Goutianos, Stergios; Hansen, Niels

    2012-01-01

    The influence of the hardness of martensite and ferrite phases in dual phase steel on void formation has been investigated by in situ tensile loading in a scanning electron microscope. Microstructural observations have shown that most voids form in martensite by evolving four steps: plastic...... deformation of martensite, crack initiation at the martensite/ferrite interface, crack propagation leading to fracture of martensite particles and void formation by separation of particle fragments. It has been identified that the hardness effect is associated with the following aspects: strain partitioning...... between martensite and ferrite, strain localisation and critical strain required for void formation. Reducing the hardness difference between martensite and ferrite phases by tempering has been shown to be an effective approach to retard the void formation in martensite and thereby is expected to improve...

  18. Void fraction fluctuations in two-phase gas-liquid flow

    International Nuclear Information System (INIS)

    Ulbrich, R.

    1987-01-01

    Designs of the apparatus in which two-phase gas-liquid flow occurs are usually based on the mean value of parameters such as pressure drop and void fraction. The flow of two-phase mixtures generally presents a very complicated flow structure, both in terms of the unsteady formation on the interfacial area and in terms of the fluctuations of the velocity, pressure and other variables within the flow. When the gas void fraction is near 0 or 1 / bubble or dispersed flow regimes / then oscillations of void fraction are very small. The intermittent flow such as plug and slug/ froth is characterized by alternately flow portions of liquid and gas. It influences the change of void fractions in time. The results of experimental research of gas void fraction fluctuations in two-phase adiabatic gas-liquid flow in a vertical pipe are presented

  19. Blind void filling in LR-EPONs: How efficient it can be?

    KAUST Repository

    Elrasad, Amr

    2015-07-01

    This work proposes a novel blind void (idle periods) filling in Long-Reach Ethernet Passive Optical Networks (LR-EPONs) namely Size Controlled Batch Void Filling (SCBVF). We emphasize on reducing grant delays and hence reducing the average packet delay. SCBVF delay reduction is achieved by early flushing data during the idle time periods (voids) between allocated grants. The proposed approach can be integrated with almost all of the previously reported dynamic bandwidth allocation schemes. SCBVF is less sensitive to differential distance between ONUs and can work well in case of small differential distances compared to previously reported void filling schemes. We support our work by extensive simulation study considering bursty traffic with long range dependency. Numerical results show a delay reduction up to 35% compared to non-void filling scheme outperforming its main competitors that can achieve up to 7% delay reduction.

  20. Force field inside the void in complex plasmas under microgravity conditions

    International Nuclear Information System (INIS)

    Kretschmer, M.; Khrapak, S.A.; Zhdanov, S.K.; Thomas, H.M.; Morfill, G.E.; Fortov, V.E.; Lipaev, A.M.; Molotkov, V.I.; Ivanov, A.I.; Turin, M.V.

    2005-01-01

    Observations of complex plasmas under microgravity conditions onboard the International Space Station performed with the Plasma-Kristall experiment-Nefedov facility are reported. A weak instability of the boundary between the central void (region free of microparticles) and the microparticle cloud is observed at low gas pressures. The instability leads to periodic injections of a relatively small number of particles into the void region (by analogy this effect is called the 'trampoline effect'). The trajectories of injected particles are analyzed providing information on the force field inside the void. The experimental results are compared with theory which assumes that the most important forces inside the void are the electric and the ion drag forces. Good agreement is found clearly indicating that under conditions investigated the void formation is caused by the ion drag force

  1. Core concepts for 'zero-sodium-void-worth core' in metal fuelled fast reactor

    International Nuclear Information System (INIS)

    Chang, Y.I.; Hill, R.N.; Fujita, E.K.; Wade, D.C.; Kumaoka, Y.; Suzuki, M.; Kawashima, M.; Nakagawa, H.

    1991-01-01

    Core design options to reduce the sodium void worth in metal fuelled LMRs are investigated. Two core designs which achieve a zero sodium void worth are analyzed in detail. The first design is a 'pancaked' and annular core with enhanced transuranic burning capabilities; the high leakage in this design yields a low breeding ratio and small void worth. The second design is an axially multilayered annular core which is fissile self-sufficient; in this design, the upper and lower core regions are neutronically decoupled for reduced void worth while fissile self-sufficiency is achieved using internal axial blankets plus external radial and axial blanket-zones. The neutronic performance characteristics of these low void worth designs are assessed here; their passive safety properties are discussed in a companion paper. (author)

  2. Add-on Therapy With the α-Blockers Tamsulosin and Naftopidil Improves Voiding Function by Enhancing Neuronal Activity in Prostatic Hyperplasia Rats.

    Science.gov (United States)

    Ko, Il-Gyu; Hwang, Lakkyong; Jin, Jun-Jang; Kim, Sang-Hoon; Han, Jin Hee; Jeon, Jung Won; Cho, Sung Tae

    2018-03-01

    Benign prostatic hyperplasia (BPH) impacts quality of life in men by causing lower urinary tract symptoms. α1-Adrenoceptor (α1-AR) blockers improve lower urinary tract symptoms. We investigated the efficacy of add-on therapy with α1-AR blockers on BPH rats. Rats in the drug-treated groups were orally administered each drug once a day for 30 days after orchiectomy. To induce BPH, rats were castrated and testosterone (20 mg/kg) was injected subcutaneously once per day for 30 days. Cystometry was conducted to measure voiding contraction pressure and the interval contraction time, immunohistochemistry was performed to measure c-Fos and nerve growth factor (NGF) expression in the neuronal voiding centers, and nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry was used to measure nitric oxide synthase (NOS) expression. Orchiectomy and testosterone injection decreased voiding contraction pressure and the interval contraction time, suggesting BPH symptoms. Voiding contraction pressure and the interval contraction time were greater in the group that received the combination treatment (tamsulosin with naftopidil) than in the tamsulosin monotherapy or naftopidil monotherapy groups. c-Fos, NGF, and NOS expression in the neuronal voiding centers was enhanced by BPH induction. c-Fos, NGF, and NOS expression was suppressed by the combination treatment (tamsulosin with naftopidil) to a greater extent than was the case for tamsulosin monotherapy or naftopidil monotherapy. Combination therapy of tamsulosin and naftopidil showed greater efficacy for the treatment of BPH than tamsulosin monotherapy or naftopidil monotherapy; therefore, combination therapy can be considered as a novel therapeutic method for BPH.

  3. The Santiago-Harvard-Edinburgh-Durham void comparison - I. SHEDding light on chameleon gravity tests

    Science.gov (United States)

    Cautun, Marius; Paillas, Enrique; Cai, Yan-Chuan; Bose, Sownak; Armijo, Joaquin; Li, Baojiu; Padilla, Nelson

    2018-05-01

    We present a systematic comparison of several existing and new void-finding algorithms, focusing on their potential power to test a particular class of modified gravity models - chameleon f(R) gravity. These models deviate from standard general relativity (GR) more strongly in low-density regions and thus voids are a promising venue to test them. We use halo occupation distribution (HOD) prescriptions to populate haloes with galaxies, and tune the HOD parameters such that the galaxy two-point correlation functions are the same in both f(R) and GR models. We identify both three-dimensional (3D) voids and two-dimensional (2D) underdensities in the plane of the sky to find the same void abundance and void galaxy number density profiles across all models, which suggests that they do not contain much information beyond galaxy clustering. However, the underlying void dark matter density profiles are significantly different, with f(R) voids being more underdense than GR ones, which leads to f(R) voids having a larger tangential shear signal than their GR analogues. We investigate the potential of each void finder to test f(R) models with near-future lensing surveys such as EUCLID and LSST. The 2D voids have the largest power to probe f(R) gravity, with an LSST analysis of tunnel (which is a new type of 2D underdensity introduced here) lensing distinguishing at 80 and 11σ (statistical error) f(R) models with parameters, |fR0| = 10-5 and 10-6, from GR.

  4. Development of quick-response area-averaged void fraction meter. Application to BWR condition

    Energy Technology Data Exchange (ETDEWEB)

    Iguchi, Tadashi; Watanabe, Hironori; Kimura, Mamoru; Anoda, Yoshinari [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2001-05-01

    Authors have been developed a practical conductance-type void fraction meter to measure instantaneously area-averaged void fraction in rod bundle. The principle of the meter is based on the fact that the electrical conductance changes with the change of void fraction in gas-liquid two-phase flow. According to air/water two-phase flow experiment, the void fraction was approximated by {alpha}=1-I/I{sub 0}, where {alpha} and I are void fraction and current (I{sub 0} is current at {alpha}=0). Authors investigated the performance of the void fraction meter under high temperature/high pressure conditions (BWR condition; 290degC, 7MPa). The results indicated that the void fraction was approximated by {alpha}=1-I/I{sub 0} even under high temperature/high pressure condition of stem/water flow. However, it is necessary to take account of temperature dependency of water specific conductance. Therefore, authors derived a correction equation for temperature dependency. Further, for applying the void fraction meter to a large-scale facility, it was found to be necessary to reduce the capacitance of the circuit. Then, authors developed the method to reduce the capacitance effect. Finally, authors succeeded to measure the void fraction in 2 x 2 bundle flow path at the range of 0% - 70% in the error of 10% under high temperature/high pressure and mass flux of less than 133 kg/m{sup 2}s. Developed void fraction meter is theoretically not affected by flow rate. Therefore, it can be applied to the condition of oscillating flow. (author)

  5. Hyperuniformity, quasi-long-range correlations, and void-space constraints in maximally random jammed particle packings. I. Polydisperse spheres.

    Science.gov (United States)

    Zachary, Chase E; Jiao, Yang; Torquato, Salvatore

    2011-05-01

    Hyperuniform many-particle distributions possess a local number variance that grows more slowly than the volume of an observation window, implying that the local density is effectively homogeneous beyond a few characteristic length scales. Previous work on maximally random strictly jammed sphere packings in three dimensions has shown that these systems are hyperuniform and possess unusual quasi-long-range pair correlations decaying as r(-4), resulting in anomalous logarithmic growth in the number variance. However, recent work on maximally random jammed sphere packings with a size distribution has suggested that such quasi-long-range correlations and hyperuniformity are not universal among jammed hard-particle systems. In this paper, we show that such systems are indeed hyperuniform with signature quasi-long-range correlations by characterizing the more general local-volume-fraction fluctuations. We argue that the regularity of the void space induced by the constraints of saturation and strict jamming overcomes the local inhomogeneity of the disk centers to induce hyperuniformity in the medium with a linear small-wave-number nonanalytic behavior in the spectral density, resulting in quasi-long-range spatial correlations scaling with r(-(d+1)) in d Euclidean space dimensions. A numerical and analytical analysis of the pore-size distribution for a binary maximally random jammed system in addition to a local characterization of the n-particle loops governing the void space surrounding the inclusions is presented in support of our argument. This paper is the first part of a series of two papers considering the relationships among hyperuniformity, jamming, and regularity of the void space in hard-particle packings.

  6. Brane surgery: energy conditions, traversable wormholes, and voids

    International Nuclear Information System (INIS)

    Barcelo, Carlos; Visser, Matt

    2000-01-01

    Branes are ubiquitous elements of any low-energy limit of string theory. We point out that negative tension branes violate all the standard energy conditions of the higher-dimensional spacetime they are embedded in; this opens the door to very peculiar solutions of the higher-dimensional Einstein equations. Building upon the (3+1)-dimensional implementation of fundamental string theory, we illustrate the possibilities by considering a toy model consisting of a (2+1)-dimensional brane propagating through our observable (3+1)-dimensional universe. Developing a notion of 'brane surgery', based on the Israel-Lanczos-Sen 'thin shell' formalism of general relativity, we analyze the dynamics and find traversable wormholes, closed baby universes, voids (holes in the spacetime manifold), and an evasion (not a violation) of both the singularity theorems and the positive mass theorem. These features appear generic to any brane model that permits negative tension branes: This includes the Randall-Sundrum models and their variants

  7. Experimental Study on Voided Reinforced Concrete Beams with Polythene Balls

    Science.gov (United States)

    Sivaneshan, P.; Harishankar, S.

    2017-07-01

    The primary component in any structure is concrete, that exist in buildings and bridges. In present situation, a serious problems faced by construction industry is exhaustive use of raw materials. Recent times, various methods are being adopted to limit the use of concrete. In structural elements like beams, polythene balls can be induced to reduce the usage of concrete. A simply supported reinforced concrete beam has two zones, one above neutral axis and other below neutral axis. The region below neutral axis is in tension and above neutral axis is in compression. As concrete is weak in tension, steel reinforcements are provided in tension zone. The concrete below the neutral axis acts as a stress transfer medium between the compression zone and tension zone. The concrete above the neutral axis takes minimum stress so that we could partially replace the concrete above neutral axis by creating air voids using recycled polythene balls. Polythene balls of varying diameters of 75 mm, 65 mm and 35 mm were partially replaced in compression zone. Hence the usage of concrete in beams and self-weight of the beams got reduced considerably. The Load carrying capacity, Deflection of beams and crack patterns were studied and compared with conventional reinforced concrete beams.

  8. Voiding dysfunction: another etiology of vulvovaginitis in young girls.

    Science.gov (United States)

    Romero, P; Rodríguez, E; Muñoz, M; Delucchi, A; Guerrero, J L; Lillo, A M; Cano, F; Matilde Osses, Sra; Romero, M I; Gonzalez Roca, C

    2011-08-01

    To determine the prevalence of voiding dysfunction (VD) in patients with persistent vulvovaginitis (PVV), and to evaluate the clinical response of PVV in the treatment of VD. Girls four years or older who consulted for PVV for at least one month and who did not respond to general measures. A physical examination was performed with visual inspection and colposcopy; vaginal samples for culture and vaginoscopy were carried out. On every patient urodynamic studies were performed. Girls who were diagnosed with VD were treated. A pediatric gynecologist did the follow-up; a successful response was considered when inflammatory symptoms and vaginal discharge ceased. Twenty patients were included, mean age 8.6 years (range: 4.6-14 years); 75% prepubertal symptoms lasted for 1.8 years; 19 (95%) had urodynamia, 10 (52.6%) had an overactive bladder, 8 (42.1%) external bladder sphincter dyssynergia, 1 (5.2%) hypotonic bladder, and 13 (65%) showed improvement. VD is an important cause when considering the etiology of PVV. 2011 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.

  9. Development of measurement method of void fraction distribution on subcooled flow boiling using neutron radiography

    International Nuclear Information System (INIS)

    Kureta, Masatoshi; Matsubayashi, Masahito; Akimoto, Hajime

    1999-03-01

    In relation to the development of a solid target of high intensity neutron source, plasma-facing components of fusion reactor and so forth, it is indispensable to estimate the void fraction for high-heat-load subcooled flow boiling of water. Since the existing prediction method of void fraction is based on the database for tubes, it is necessary to investigate extendibility of the existing prediction method to narrow-gap rectangular channels that is used in the high-heat-load devices. However, measurement method of void fraction in the narrow-gap rectangular channel has not been established yet because of the difficulty of measurement. The objectives of this investigation are development of a new system for bubble visualization and void fraction measurement on subcooled flow boiling in narrow-gap rectangular channels using the neutron radiography, and establishment of void fraction database by using this measurement system. This report describes the void fraction measurement method by the neutron radiography technique, and summarizes the measured void fraction data in one-side heated narrow-gap rectangular channels at subcooled boiling condition. (author)

  10. Interfacial area, velocity and void fraction in two-phase slug flow

    International Nuclear Information System (INIS)

    Kojasoy, G.; Riznic, J.R.

    1997-01-01

    The internal flow structure of air-water plug/slug flow in a 50.3 mm dia transparent pipeline has been experimentally investigated by using a four-sensor resistivity probe. Liquid and gas volumetric superficial velocities ranged from 0.55 to 2.20 m/s and 0.27 to 2.20 m/s, respectively, and area-averaged void fractions ranged from about 10 to 70%. The local distributions of void fractions, interfacial area concentration and interface velocity were measured. Contributions from small spherical bubbles and large elongated slug bubbles toward the total void fraction and interfacial area concentration were differentiated. It was observed that the small bubble void contribution to the overall void fraction was small indicating that the large slug bubble void fraction was a dominant factor in determining the total void fraction. However, the small bubble interfacial area contribution was significant in the lower and upper portions of the pipe cross sections

  11. submitter Thermal stability of interface voids in Cu grain boundaries with molecular dynamic simulations

    CERN Document Server

    Xydou, A; Aicheler, M; Djurabekova, F

    2016-01-01

    By means of molecular dynamic simulations, the stability of cylindrical voids is examined with respect to the diffusion bonding procedure. To do this, the effect of grain boundaries between the grains of different crystallographic orientations on the void closing time was studied at high temperatures from 0.7 up to 0.94 of the bulk melting temperature $(T_m)$. The diameter of the voids varied from 3.5 to 6.5 nm. A thermal instability occurring at high temperatures at the surface of the void placed in a grain boundary triggered the eventual closure of the void at all examined temperatures. The closing time has an exponential dependence on the examined temperature values. A model based on the defect diffusion theory is developed to predict the closing time for voids of macroscopic size. The diffusion coefficient within the grain boundaries is found to be overall higher than the diffusion coefficient in the region around the void surface. The activation energy for the diffusion in the grain boundary is calculate...

  12. Microstructural characterization of XLPE electrical insulation in power cables: determination of void size distributions using TEM

    International Nuclear Information System (INIS)

    Markey, L; Stevens, G C

    2003-01-01

    In an effort to progress in our understanding of the ageing mechanisms of high voltage cables submitted to electrical and thermal stresses, we present a quantitative study of voids, the defects which are considered to be partly responsible for cable failure. We propose a method based on large data sets of transmission electron microscopy (TEM) observations of replicated samples allowing for the determination of void concentration distribution as a function of void size in the mesoscopic to microscopic range at any point in the cable insulation. A theory is also developed to calculate the effect of etching on the apparent size of the voids observed. We present the first results of this sort ever obtained on two industrial cables, one of which was aged in an AC field. Results clearly indicate that a much larger concentration of voids occur near the inner semiconductor compared to the bulk of the insulation, independently of ageing. An effect of ageing can also be seen near the inner semiconductor, resulting in an increase in the total void internal surface area and a slight shift of the concentration curve towards larger voids, with the peak moving from about 40 nm to about 50 nm

  13. Stress Voiding in IC Interconnects - Rules of Evidence for Failure Analysts

    Energy Technology Data Exchange (ETDEWEB)

    FILTER, WILLIAM F.

    1999-09-17

    Mention the words ''stress voiding'', and everyone from technology engineer to manager to customer is likely to cringe. This IC failure mechanism elicits fear because it is insidious, capricious, and difficult to identify and arrest. There are reasons to believe that a damascene-copper future might be void-free. Nevertheless, engineers who continue to produce ICs with Al-alloy interconnects, or who assess the reliability of legacy ICs with long service life, need up-to-date insights and techniques to deal with stress voiding problems. Stress voiding need not be fearful. Not always predictable, neither is it inevitable. On the contrary, stress voids are caused by specific, avoidable processing errors. Analytical work, though often painful, can identify these errors when stress voiding occurs, and vigilance in monitoring the improved process can keep it from recurring. In this article, they show that a methodical, forensics approach to failure analysis can solve suspected cases of stress voiding. This approach uses new techniques, and patiently applies familiar ones, to develop evidence meeting strict standards of proof.

  14. Effects of wall roughness and entry length on void profile in vertical bubbly flow

    International Nuclear Information System (INIS)

    Takamasa, Tomoji

    1988-01-01

    An experimental study of upward air-water bubbly two-phase flow in an entry region was performed with various rough wall test tubes. The objective of the work is to clarify the effects of wall roughness and entry length on void profile. The fluid flows in the vertical circular test tube of 25 mm I.D. under nearly atmospheric pressure, at room temperature. The void profile changes from a pattern similar in appearance to the saddle shape which has local void peaks near the wall, into the power law shape whose curve is approximated by a power law formula, with increasing wall roughness and/or entry length. That is, wall roughness and entry length have a similar effect upon void profile. There are two patterns in the power law shape, a pattern with sharp center peak and a pattern with obtuse center peak. As wall roughness and/or entry length increase, the void profile changes from the former pattern to the latter pattern. At enough long entry length (L/D ≅ 150), every void profile has almost the same power law shape independent of wall roughness. Some void profiles are asymmetric to the axis. (author)

  15. Void fraction prediction in two-phase flows independent of the liquid phase density changes

    International Nuclear Information System (INIS)

    Nazemi, E.; Feghhi, S.A.H.; Roshani, G.H.

    2014-01-01

    Gamma-ray densitometry is a frequently used non-invasive method to determine void fraction in two-phase gas liquid pipe flows. Performance of flow meters using gamma-ray attenuation depends strongly on the fluid properties. Variations of the fluid properties such as density in situations where temperature and pressure fluctuate would cause significant errors in determination of the void fraction in two-phase flows. A conventional solution overcoming such an obstacle is periodical recalibration which is a difficult task. This paper presents a method based on dual modality densitometry using Artificial Neural Network (ANN), which offers the advantage of measuring the void fraction independent of the liquid phase changes. An experimental setup was implemented to generate the required input data for training the network. ANNs were trained on the registered counts of the transmission and scattering detectors in different liquid phase densities and void fractions. Void fractions were predicted by ANNs with mean relative error of less than 0.45% in density variations range of 0.735 up to 0.98 gcm −3 . Applying this method would improve the performance of two-phase flow meters and eliminates the necessity of periodical recalibration. - Highlights: • Void fraction was predicted independent of density changes. • Recorded counts of detectors/void fraction were used as inputs/output of ANN. • ANN eliminated necessity of recalibration in changeable density of two-phase flows

  16. Estimation of the Void Fraction in the moderator cell of the Cold Neutron Source

    International Nuclear Information System (INIS)

    Choi, Jungwoon; Kim, Young-ki

    2015-01-01

    To estimate the average void fraction in the liquid hydrogen, the Kazimi and Chen correlation is used with its modified method suggested by R.E. Williams in NBSR. Since the multiplying number can be changed along the operation condition and working fluid, the different figure is applied to estimate the average void fraction in the different moderator cell shape. This approach is checked with the void fraction measurement results from the HANARO-CNS mock-up test. Owing to national research demands on cold neutron beam utilization, the Cold Neutron Research Facility had been and operated for neuron scientists all over the world. In HANARO, the CNS facility has been operated since 2009. The actual void fraction, which is the one of dominant factors affecting the cold neutron flux, is difficult to know without the real measurement performed at the cryogenic temperature using the same moderator medium. Accordingly, the two-phase mock-up test in the CNS-IPA (In-pool assembly) had been performed using the liquid hydrogen in terms of the fluidity check, void fraction measurement, operation procedure set-up, and so on for the development of the HANARO-CNS. This paper presents the estimated void fraction in the different operating conditions and geometrical shape in the comparison with the measurement data of the void fraction in the full-scale mockup test based on the Kazimi and Chen correlation. This approach is applied to estimate the average void fraction in the newly designed moderator cell using the liquid hydrogen as a working fluid in the two-phase thermosiphon. From this calculation result, the estimated average void fraction will be used to design the optimized cold neutron source to produce the maximum cold neutron flux within the desired wavelength

  17. Estimation of the Void Fraction in the moderator cell of the Cold Neutron Source

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jungwoon; Kim, Young-ki [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    To estimate the average void fraction in the liquid hydrogen, the Kazimi and Chen correlation is used with its modified method suggested by R.E. Williams in NBSR. Since the multiplying number can be changed along the operation condition and working fluid, the different figure is applied to estimate the average void fraction in the different moderator cell shape. This approach is checked with the void fraction measurement results from the HANARO-CNS mock-up test. Owing to national research demands on cold neutron beam utilization, the Cold Neutron Research Facility had been and operated for neuron scientists all over the world. In HANARO, the CNS facility has been operated since 2009. The actual void fraction, which is the one of dominant factors affecting the cold neutron flux, is difficult to know without the real measurement performed at the cryogenic temperature using the same moderator medium. Accordingly, the two-phase mock-up test in the CNS-IPA (In-pool assembly) had been performed using the liquid hydrogen in terms of the fluidity check, void fraction measurement, operation procedure set-up, and so on for the development of the HANARO-CNS. This paper presents the estimated void fraction in the different operating conditions and geometrical shape in the comparison with the measurement data of the void fraction in the full-scale mockup test based on the Kazimi and Chen correlation. This approach is applied to estimate the average void fraction in the newly designed moderator cell using the liquid hydrogen as a working fluid in the two-phase thermosiphon. From this calculation result, the estimated average void fraction will be used to design the optimized cold neutron source to produce the maximum cold neutron flux within the desired wavelength.

  18. An approach of SFR safety study through the most penalizing sodium void reactivity - 105

    International Nuclear Information System (INIS)

    Tiberi, V.; Ivanov, E.; Pignet, S.

    2010-01-01

    Sodium void reactivity effects can affect the plant safety significantly during accidental transients. Accordingly, they have to be accurately investigated for any new sodium cooled fast reactor concept, even if a fuel with a melting point lower than the sodium boiling temperature is adopted. Thus all new reactor concepts should be compared to each - others adopting the value of the maximal possible sodium void reactivity as a discrimination parameter. However, taking into account that the sodium void worth is spatially depended, it is not evident which volume could be voided in order to obtain the maximal reactivity increase. Typically the complete active core voiding (zones initially loaded with 235 U or 239 Pu) is taken into account. This paper summarizes the extensive work carried-out in the IRSN to investigate the sodium-void reactivity spatial profiles of a fast sodium-cooled reactor core in the aim of defining a methodology to search for the area where the void contribution to the reactivity is strictly positive. Perturbation theory design approach available in the ERANOS 2.1 code has been adopted to evaluate the 'area of positive void worth'. To do that, the code has been previously validated against experimental based benchmarks (IRPhEP) and reference calculations. The evaluation of the absolute values of reactivity profiles can be improved later-on adopting more sophisticated methodologies to perform more accurate calculations of the sample with the voided area determined adopting the rough procedure described here. It has been demonstrated that even the non-reference way of ERANOS calculations could be used to provide the basis for different core concepts inter-comparison. (authors)

  19. The influence of different loads on the remodeling process of a bone and bioresorbable material mixture with voids

    Science.gov (United States)

    Giorgio, Ivan; Andreaus, Ugo; Madeo, Angela

    2016-03-01

    A model of a mixture of bone tissue and bioresorbable material with voids was used to numerically analyze the physiological balance between the processes of bone growth and resorption and artificial material resorption in a plate-like sample. The adopted model was derived from a theory for the behavior of porous solids in which the matrix material is linearly elastic and the interstices are void of material. The specimen—constituted by a region of bone living tissue and one of bioresorbable material—was acted by different in-plane loading conditions, namely pure bending and shear. Ranges of load magnitudes were identified within which physiological states become possible. Furthermore, the consequences of applying different loading conditions are examined at the end of the remodeling process. In particular, maximum value of bone and material mass densities, and extensions of the zones where bone is reconstructed were identified and compared in the two different load conditions. From the practical view point, during surgery planning and later rehabilitation, some choice of the following parameters is given: porosity of the graft, material characteristics of the graft, and adjustment of initial mixture tissue/bioresorbable material and later, during healing and remodeling, optimal loading conditions.

  20. Effect of void fraction correlations on two-phase pressure drop during flow boiling in narrow rectangular channel

    International Nuclear Information System (INIS)

    Huang, Dong; Gao, Puzhen; Chen, Chong; Lan, Shu

    2013-01-01

    Highlights: • Most of the slip ratio models and the Lockhart–Martinelli parameter based models give similar results. • The drift flux void fraction models give relatively small values. • The effect of void fraction correlations on two-phase friction pressure drop is inconspicuous. • The effect of void fraction correlations on two-phase acceleration pressure drop is significant. - Abstract: The void fraction of water during flow boiling in vertical narrow rectangular channel is experimentally investigated. The void fraction is indirectly determined using the present experimental data with various void fraction correlations or models published in the open literature. The effects of mass flux, mass quality, system pressure and inlet subcooling on the void fraction and pressure drop are discussed in detail. In addition, comparison and discussion among the numerous void fraction correlations are carried out. The effect of void fraction correlations on two-phase pressure drop is presented as well. The results reveal that most of the slip ratio correlations and the Lockhart–Martinelli parameter based void fraction correlations have results close to each other at mass quality higher than 0.2. The drift flux void fraction correlations give small values which are incompatible with other models making it inapplicable for narrow rectangular channel. The alteration of void fraction correlations has an inconspicuous effect on two-phase frictional pressure drop, while an obvious effect on two-phase accelerational pressure drop during flow boiling in narrow rectangular channel

  1. Calculation of the void reactivity of CANDU lattices using the SCALE code system

    Energy Technology Data Exchange (ETDEWEB)

    Valko, J. [Technische Univ. Delft (Netherlands). Interfacultair Reactor Inst.; Feher, S. [Technische Univ. Delft (Netherlands). Interfacultair Reactor Inst.; Hoogenboom, J.E. [Technische Univ. Delft (Netherlands). Interfacultair Reactor Inst.; Slobben, J. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands)

    1995-11-01

    The reactivity effect of coolant voiding in CANDU-type fuel lattices has been calculated with different methods using the SCALE code system. The known positive void reactivity coefficient of the original lattice was correctly obtained. A modified fuel bundle containing dysprosium and slightly enriched uranium to eliminate the positive reactivity effect was also calculated. Owing to the increased heterogeneity of this modified fuel the one-dimensional cylindrical calculation with XSDRN proved to be inadequate. Code options allowing bundle geometry were successfully used for the calculation of the strongly space dependent flux and spectrum changes which determine the void reactivity. (orig.).

  2. Accurate reactivity void coefficient calculation for the fast spectrum reactor FBR-IME

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Fabiano P.C.; Vellozo, Sergio de O.; Velozo, Marta J., E-mail: fabianopetruceli@outlook.com, E-mail: vellozo@cbpf.br, E-mail: martajann@gmail.com [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Secao de Engenharia Militar

    2017-07-01

    This paper aims to present an accurate calculation of the void reactivity coefficient for the FBR-IME, a fast spectrum reactor in development at the Engineering Military Institute (IME). The main design peculiarity lies in using mixed oxide [MOX - PuO{sub 2} + U(natural uranium)O{sub 2}] as fuel core. For this task, SCALE system was used to calculate the reactivity for several voids distributions generated by bubbles in the sodium beyond its boiling point. The results show that although the void reactivity coefficient is positive and location dependent, they are offset by other feedback effects, resulting in a negative overall coefficient. (author)

  3. The Influence of the Presence of Multiple Voids on the Discharge Patterns in Solid Epoxy Insulation

    DEFF Research Database (Denmark)

    Holbøll, Joachim T.; Henriksen, Mogens; Larsen, Esben

    1996-01-01

    In this paper, partial discharge test results from initial long term testing on samples which contain more voids, when exposed to a high electric stress will be presented. The influence on the discharge patterns, phase- and height-analyses, of such parameter as the number of voids and the void...... diameters will be given. A first evaluation/opinion of the impact this could have on the estimation of the insulation condition of electrical equipment, based on the identification of PD-patterns, will also be given....

  4. Comparative sodium void effects for different advanced liquid metal reactor fuel and core designs

    International Nuclear Information System (INIS)

    Dobbin, K.D.; Kessler, S.F.; Nelson, J.V.; Gedeon, S.R.; Omberg, R.P.

    1991-01-01

    An analysis of metal-, oxide-, and nitride-fueled advanced liquid metal reactor cores was performed to investigate the calculated differences in sodium void reactivity, and to determine the relationship between sodium void reactivity and burnup reactivity swing using the three fuel types. The results of this analysis indicate that nitride fuel has the least positive sodium void reactivity for any given burnup reactivity swing. Thus, it appears that a good design compromise between transient overpower and loss of flow response is obtained using nitride fuel. Additional studies were made to understand these and other nitride advantages. (author)

  5. Analysis of sodium-void experiments in ZPPR-3 modified Phase 3 core

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, T.

    1978-08-01

    An analysis is presented of a series of sodium-void reactivity measurements performed in assembly 3 of Zero Power Plutonium Reactor (ZPPR-3), a mockup of the US Demoplant. In this series, large-zone sodium-void effects were studied in detail in the presence of many singularities, namely, control rods (CRs) and control rod positions (CRPs). The Karlsruhe data-and-method have been applied to an analysis of these experiments, and the results are presented. The work is aimed at complementing the sodium-void reactivity analysis based on the SNEAK experiments, where it was difficult to simulate a large plutonium-core of a prototype fast breeder reactor.

  6. Impedance void-meter and neural networks for vertical two-phase flows

    International Nuclear Information System (INIS)

    Mi, Y.; Li, M.; Xiao, Z.; Tsoukalas, L.H.; Ishii, M.

    1998-01-01

    Most two-phase flow measurements, including void fraction measurements, depend on correct flow regime identification. There are two steps towards successful identification of flow regimes: one is to develop a non-intrusive instrument to demonstrate area-averaged void fluctuations, the other to develop a non-linear mapping approach to perform objective identification of flow regimes. A non-intrusive impedance void-meter provides input signals to a neural mapping approach used to identify flow regimes. After training, both supervised and self-organizing neural network learning paradigms performed flow regime identification successfully. The methodology presented holds considerable promise for multiphase flow diagnostic and measurement applications. (author)

  7. Evaluation of void fraction measurements from DADINE experience using RELAP4/MOD5 code

    International Nuclear Information System (INIS)

    Borges, R.C.; Freitas, R.L.

    1989-01-01

    The DADINE experiment measures the axial evolution of the void fraction by neutronic diffusion in two-phase flow in the wet regions of a pressurized water reactor in accident conditions. Since the theoretical/experimental confrontation is important for code evaluation, this paper presents the simulation with the RELAP4/MOD5 Code of the void fractions results obtained in the DADINE Experiment, that showed some deviation probably associated with the existing models in Code, special attention in the way of stablishing the two-phase flow and the no characterization of the differents flow regimes related with the void fractions. (author) [pt

  8. Comparison of void strengthening in fcc and bcc metals: Large-scale atomic-level modelling

    International Nuclear Information System (INIS)

    Osetsky, Yu.N.; Bacon, D.J.

    2005-01-01

    Strengthening due to voids can be a significant radiation effect in metals. Treatment of this by elasticity theory of dislocations is difficult when atomic structure of the obstacle and dislocation is influential. In this paper, we report results of large-scale atomic-level modelling of edge dislocation-void interaction in fcc (copper) and bcc (iron) metals. Voids of up to 5 nm diameter were studied over the temperature range from 0 to 600 K. We demonstrate that atomistic modelling is able to reveal important effects, which are beyond the continuum approach. Some arise from features of the dislocation core and crystal structure, others involve dislocation climb and temperature effects

  9. On grain-size-dependent void swelling in pure copper irradiated with fission neutrons

    DEFF Research Database (Denmark)

    Singh, Bachu Narain; Eldrup, Morten Mostgaard; Zinkle, S.J.

    2002-01-01

    The effect of grain size on void swelling has its origin in the intrinsic property of grain boundaries as neutral and unsaturable sinks for both vacancies and self-interstitial atoms. The phenomenon had already been investigated in the 1970s and it was demonstrated that the grain......-size-dependent void swelling measured under irradiation producing only Frenkel pairs could be satisfactorily explained in terms of the standard rate theory (SRT) and dislocation bias. Experimental results reported in the 1980s demonstrated, on the other hand, that the effect of grain boundaries on void swelling under...

  10. Effect of Contact Conditions on Void Coalescence at Low Stress Triaxiality Shearing

    DEFF Research Database (Denmark)

    Dahl, Jonas; Nielsen, Kim Lau; Tvergaard, Viggo

    2012-01-01

    , the deformed voids develop into shapes that closely resemble micro-cracks. It is found that the predictions using the frictionless pseudo-contact approach are in rather good agreement with corresponding simulations that fully account for frictionless contact. In particular, good agreement is found at close...... to zero stress triaxiality. Furthermore, it is shown that accounting for friction at the void surface strongly postpones the onset of coalescence, hence, increasing the overall material ductility. The changes in overall material behavior are here presented for a wide range of initial material and loading...... conditions, such as various stress triaxialities, void sizes, and friction coefficients....

  11. Two-phase flow void fraction measurement using gamma ray attenuation technique

    International Nuclear Information System (INIS)

    Silva, R.D. da.

    1985-01-01

    The present work deals with experimental void fraction measurements in two-phase water-nitrogen flow, by using a gamma ray attenuation technique. Several upward two-phase flow regimes in a vertical tube were simulated. The water flow was varied from 0.13 to 0.44 m 3 /h while the nitrogen flow was varied between 0.01 and 0.1 m 3 /h. The mean volumetric void fraction was determined based on the measured linear void fraction for each flow condition. The results were compared with other authors data and showed a good agreement. (author) [pt

  12. Optical tomography in the presence of void regions

    Science.gov (United States)

    Dehghani; Arridge; Schweiger; Delpy

    2000-09-01

    There is a growing interest in the use of near-infrared spectroscopy for the noninvasive determination of the oxygenation level within biological tissue. Stemming from this application, there has been further research in the use of this technique for obtaining tomographic images of the neonatal head, with the view of determining the levels of oxygenated and deoxygenated blood within the brain. Owing to computational complexity, methods used for numerical modeling of photon transfer within tissue have usually been limited to the diffusion approximation of the Boltzmann transport equation. The diffusion approximation, however, is not valid in regions of low scatter, such as the cerebrospinal fluid. Methods have been proposed for dealing with nonscattering regions within diffusing materials through the use of a radiosity-diffusion model. Currently, this new model assumes prior knowledge of the void region location; therefore it is instructive to examine the errors introduced in applying a simple diffusion-based reconstruction scheme in cases in which there exists a nonscattering region. We present reconstructed images of objects that contain a nonscattering region within a diffusive material. Here the forward data is calculated with the radiosity-diffusion model, and the inverse problem is solved with either the radiosity-diffusion model or the diffusion-only model. The reconstructed images show that even in the presence of only a thin nonscattering layer, a diffusion-only reconstruction will fail. When a radiosity-diffusion model is used for image reconstruction, together with a priori information about the position of the nonscattering region, the quality of the reconstructed image is considerably improved. The accuracy of the reconstructed images depends largely on the position of the anomaly with respect to the nonscattering region as well as the thickness of the nonscattering region.

  13. Production bias: A proposed modification of the driving force for void swelling under cascade damage conditions

    International Nuclear Information System (INIS)

    Woo, C.H.; Garner, F.A.

    1991-11-01

    A new concept of point-defect production as the main driving force for void swelling under cascade damage conditions is proposed. This concept takes into account the recombination and formation of immobile clusters and loops of vacancies and interstitials in the cascade region. The life times of the clusters and loops due to desolution are strong functions of the temperature, as well as their vacancy and interstitial nature. The resulting biased production of free point defects from the internal sources is shown to be a strong driving force for void swelling. The characteristics of void swelling due to production bias are described and compared with experimental results. We conclude that the production bias concept provides a good description of void swelling under cascade damage conditions

  14. Equations for calculating interfacial drag and shear from void fraction correlations

    International Nuclear Information System (INIS)

    Putney, J.M.

    1988-12-01

    Equations are developed for calculating interfacial drag and shear coefficients for dispersed vapour flows from void fraction correlations. The equations have a sound physical basis and lead to physically correct coefficients in all flow situations. (author)

  15. Production bias: A proposed modification of the driving force for void swelling under cascade damage conditions

    International Nuclear Information System (INIS)

    Woo, C.H.; Singh, B.N.; Garner, F.A.

    1992-01-01

    A new concept of point defect production as the main driving force for void swelling under cascade damage conditions is proposed. This concept takes into account the recombination and formation of immobile clusters and loops of vacancies and interstitials in the cascade region. The lifetimes of the clusters and loops due to desolution are strong functions of the temperature, as well as their vacancy and interstitial nature. The resulting biased production of free point defects from the internal sources is shown to be a strong driving force for void swelling. The characteristics of void swelling due to production bias are described and compared with experimental results. We conclude that the production bias concept provides a good description of void swelling under cascade damage conditions. (orig.)

  16. Void analysis of target residues at SPS energy -evidence of correlation with fractal behaviour

    International Nuclear Information System (INIS)

    Ghosh, Dipak; Deb, Argha; Das, Rupa . E-mail : dipakghosh_in@yahoo.com

    2007-01-01

    This paper presents an analysis of the target residues in 32 S -AgBr and 16 0 -AgBr interactions at 200 AGeV and 60AGeV respectively in terms of fractal moment by Takagi method and void probability scaling. The study reveals an interesting feature of the production process. In 16 O- AgBr interactions multifractal behaviour is present in both hemispheres and void probability does not show a scaling behaviour, but at high energy the situation changes. In 32 S -AgBr interactions for both hemisphere monofractal behaviour is indicated by that data and void probability also shows good scaling behaviour. This suggests that a possible correlation of void probability with fractal behaviour of target residues. (author)

  17. Measurement of the thermal Sunyaev-Zel'dovich effect around cosmic voids

    Science.gov (United States)

    Alonso, David; Hill, J. Colin; Hložek, Renée; Spergel, David N.

    2018-03-01

    We stack maps of the thermal Sunyaev-Zel'dovich effect produced by the Planck Collaboration around the centers of cosmic voids defined by the distribution of galaxies in the CMASS sample of the Baryon Oscillation Spectroscopic Survey, scaled by the void effective radii. We report a first detection of the associated cross-correlation at the 3.4 σ level: voids are under-pressured relative to the cosmic mean. We compare the measured Compton-y profile around voids with a model based solely on the spatial modulation of halo abundance with environmental density. The amplitude of the detected signal is marginally lower than predicted by an overall amplitude αv=0.67 ±0.2 . We discuss the possible interpretations of this measurement in terms of modeling uncertainties, excess pressure in low-mass halos, or nonlocal heating mechanisms.

  18. Capacitance sensor for void fraction measurement in a natural circulation refrigeration circuit

    International Nuclear Information System (INIS)

    Rocha, Marcelo S.; Cabral, Eduardo L.L.; Simoes-Moreira, Jose R.

    2009-01-01

    Natural circulation is widely used in nuclear reactors for residual heat refrigeration. In this work, a conductance probe is designed and constructed to measure the instantaneous bulk void fraction in a vertical tube section. This probe is installed in a natural circulation refrigeration loop designed to simulate a nuclear reactor primary refrigeration circuit. During the operation of the natural circulation loop several gas-liquid flow patterns are observed, including oscillatory flow. The instantaneous signal generated by the capacitance probe allows the calculation of the two-phase flow void fraction. The void fraction obtained by the probe will be compared with the theoretical void fraction calculated by the computational program RELAP5/MOD3.2.2 gamma. The probe design and electronics, as well as the previous results obtained are presented and discussed. (author)

  19. Forensic investigation of two voided slab bridges in the Virginia Department of Transportation's Richmond District.

    Science.gov (United States)

    2017-06-01

    The precast prestressed concrete voided slab structure is a popular bridge design because of its rapid construction and cost : savings in terms of eliminating formwork at the jobsite. However, the longitudinal shear transfer mechanism often fails, le...

  20. Three-Dimensional Computed Tomography as a Method for Finding Die Attach Voids in Diodes

    Science.gov (United States)

    Brahm, E. N.; Rolin, T. D.

    2010-01-01

    NASA analyzes electrical, electronic, and electromechanical (EEE) parts used in space vehicles to understand failure modes of these components. The diode is an EEE part critical to NASA missions that can fail due to excessive voiding in the die attach. Metallography, one established method for studying the die attach, is a time-intensive, destructive, and equivocal process whereby mechanical grinding of the diodes is performed to reveal voiding in the die attach. Problems such as die attach pull-out tend to complicate results and can lead to erroneous conclusions. The objective of this study is to determine if three-dimensional computed tomography (3DCT), a nondestructive technique, is a viable alternative to metallography for detecting die attach voiding. The die attach voiding in two- dimensional planes created from 3DCT scans was compared to several physical cross sections of the same diode to determine if the 3DCT scan accurately recreates die attach volumetric variability

  1. Analysis of void reactivity measurements in full MOX BWR physics experiments

    International Nuclear Information System (INIS)

    Ando, Yoshihira; Yamamoto, Toru; Umano, Takuya

    2008-01-01

    In the full MOX BWR physics experiments, FUBILA, four 9x9 test assemblies simulating BWR full MOX assemblies were located in the center of the core. Changing the in-channel moderator condition of the four assemblies from 0% void to 40% and 70% void mock-up, void reactivity was measured using Amplified Source Method (ASM) technique in the subcritical cores, in which three fission chambers were located. ASM correction factors necessary to express the consistency of the detector efficiency between measured core configurations were calculated using collision probability cell calculation and 3D-transport core calculation with the nuclear data library, JENDL-3.3. Measured reactivity worth with ASM correction factor was compared with the calculated results obtained through a diffusion, transport and continuous energy Monte Carlo calculation respectively. It was confirmed that the measured void reactivity worth was reproduced well by calculations. (author)

  2. Geotechnical reduction of void ratio in low-level radioactive waste burial sites: treatment alternatives

    International Nuclear Information System (INIS)

    Phillips, S.J.; Carlson, R.A.; McGuire, H.E.

    1981-01-01

    A substantial quantity of low-level radioactive and hazardous wastes has been interred in shallow land burial structures throughout the United States. Many of these structures (trenches, pits, and landfills) have proven to be unstable. Some surface feature manifestations such as large cracks, basins, and cave-ins are caused by voids filling and physico-chemical degradation and solubilization of the buried wastes which could result in the release of contamination. The surface features represent a potential for increased contamination transport to the biosphere via water, air, biologic, and direct pathways. Engineering alternatives for the reduction of buried waste and matrix materials voids are identified and discussed. As a guideline, a reduction of the voids within the waste to 80% or more of maximum relative dry density (a measure of in situ voids within the waste) is proposed. The advantages, disadvantages, and costs of each alternative are evaluated. Falling mass and pile driving engineering alternatives were selected for further development

  3. Analysis of sodium-void experiments in ZPPR-3 modified phase 3 core

    International Nuclear Information System (INIS)

    Yoshida, T.

    1978-08-01

    In this work, large-zone sodium-void effects are studied in detail in the presence of many singularities, namely, control rods (CRs) and control rod positions (CRPs). The results of measurements and calculations are compared by CIE (calculation/experiment) values, which are 1.07 when the voided core region is free of singularities. When the void region includes CPRs, which are concurrently voided, the CIE value deteriorates and varies from 0.35 to 1.58. The agreement can be improved considerably by correcting the reactivity worth of the sodium contained in the CRPs with the aid of experimental data (CIE = 1.00 +- 0.15). The heterogeneity correction for the fuel elements was performed by the plate-cell vollision probability code KAPPER. (GL) [de

  4. Idiopathic detrusor sphincter dyssynergia in neurologically normal patients with voiding abnormalities

    DEFF Research Database (Denmark)

    Jørgensen, T M; Djurhuus, J C; Schrøder, H D

    1982-01-01

    Symptomatology and clinical manifestations of detrusor sphincter dyssynergia are described in 23 patients without neurological disease. Their cardinal symptoms were recurrent cystitis, enuresis, frequent voiding, back pain during voiding and anal discomfort. The major objective finding was vesico......Symptomatology and clinical manifestations of detrusor sphincter dyssynergia are described in 23 patients without neurological disease. Their cardinal symptoms were recurrent cystitis, enuresis, frequent voiding, back pain during voiding and anal discomfort. The major objective finding...... was vesicoureteral reflux in 11 cases with kidney scarring in 10. Bladder trabeculation was found in 13 patients, bladder hyperreflexia in 8, and significant residual urine in 16 patients. The etiology of detrusor sphincter dyssynergia in non-neurological patients is discussed. By means of exclusion it is most...

  5. Shallow Reflection Method for Water-Filled Void Detection and Characterization

    Science.gov (United States)

    Zahari, M. N. H.; Madun, A.; Dahlan, S. H.; Joret, A.; Hazreek, Z. A. M.; Mohammad, A. H.; Izzaty, R. A.

    2018-04-01

    Shallow investigation is crucial in enhancing the characteristics of subsurface void commonly encountered in civil engineering, and one such technique commonly used is seismic-reflection technique. An assessment of the effectiveness of such an approach is critical to determine whether the quality of the works meets the prescribed requirements. Conventional quality testing suffers limitations including: limited coverage (both area and depth) and problems with resolution quality. Traditionally quality assurance measurements use laboratory and in-situ invasive and destructive tests. However geophysical approaches, which are typically non-invasive and non-destructive, offer a method by which improvement of detection can be measured in a cost-effective way. Of this seismic reflection have proved useful to assess void characteristic, this paper evaluates the application of shallow seismic-reflection method in characterizing the water-filled void properties at 0.34 m depth, specifically for detection and characterization of void measurement using 2-dimensional tomography.

  6. Quantifying voids effecting delamination in carbon/epoxy composites: static and fatigue fracture behavior

    Science.gov (United States)

    Hakim, I.; May, D.; Abo Ras, M.; Meyendorf, N.; Donaldson, S.

    2016-04-01

    On the present work, samples of carbon fiber/epoxy composites with different void levels were fabricated using hand layup vacuum bagging process by varying the pressure. Thermal nondestructive methods: thermal conductivity measurement, pulse thermography, pulse phase thermography and lock-in-thermography, and mechanical testing: modes I and II interlaminar fracture toughness were conducted. Comparing the parameters resulted from the thermal nondestructive testing revealed that voids lead to reductions in thermal properties in all directions of composites. The results of mode I and mode II interlaminar fracture toughness showed that voids lead to reductions in interlaminar fracture toughness. The parameters resulted from thermal nondestructive testing were correlated to the results of mode I and mode II interlaminar fracture toughness and voids were quantified.

  7. The effect of form pressure on the air void structure of SCC

    DEFF Research Database (Denmark)

    Jensen, Mikkel Vibæk; Hasholt, Marianne Tange; Geiker, Mette Rica

    2005-01-01

    The high workability of self-compacting concrete (SCC) invites to high casting rates. However, casting walls at high rate may result in large pressure at the bottom of the form and subsequently compression of the air voids. This paper deals with the influence of hydrostatic pressure during setting...... on the air void structure of hardened, air entrained SCC. The subject was examined through laboratory investigations of SCC with two different amounts of air entrainment. The condition in the form was simulated by using containers making it possible to cure concrete under various pressures corresponding...... to the bottom of castings of 0, 2, 4, and 6 meters height. The laboratory investigations were supplemented with data from two full-scale wall castings. The air void structure of the hardened concretes was determined on plane sections. The results indicate that the pressure related changes of the air void...

  8. Determination of void fraction from source range monitor and mass flow rate data

    International Nuclear Information System (INIS)

    McCormick, R.D.

    1986-09-01

    This is a report on the calculation of the TMI-2 primary coolant system local void fraction from source range neutron flux monitor data and from hot leg mass flowrate meter data during the first 100 minutes of the accident. The methods of calculation of void fraction from the two data sources is explained and the results are compared. It is indicated that the void fraction determined using the mass flowrate data contained an error of unknown magnitude due to the assumption of constant homogeneous volumetric flowrate used in the calculation and required further work. Void fraction determined from the source range monitor data is felt to be usable although an uncertainty analysis has not been performed

  9. Thermal analysis of the ZrH reactor 4 Pi and void backed reflector assemblies

    International Nuclear Information System (INIS)

    Larson, E.M.

    1971-01-01

    A steady state thermal analysis is presented for: a BeO-TalOW-B 4 C poison back drum, and a Be void back drum. TAP listings and a results summary are presented for both drums. The results indicate the poison back drum may be used with an 1150 0 F cold wall and the void back drum may be used with a 1000 0 F cold wall. (14 references) (U.S.)

  10. Spatial dependence of void coefficient in the University of Arizona TRIGA research reactor

    International Nuclear Information System (INIS)

    Spriggs, Gregory D.; Doane, Harry; Wells, Robert

    1980-01-01

    The spatial dependence of the moderator void coefficient of reactivity in the axial direction was experimentally measured in the A-ring using a hollow, air-filled aluminum cylinder. It was found that the void coefficient was positive in the central region of the fuel section reaching a maximum value of approximately + .045 cents/cm 3 and was negative towards the outer edges of the fuel section reaching a maximum of - .09 cents/cm 3 . (author)

  11. A subchannel and CFD analysis of void distribution for the BWR fuel bundle test benchmark

    International Nuclear Information System (INIS)

    In, Wang-Kee; Hwang, Dae-Hyun; Jeong, Jae Jun

    2013-01-01

    Highlights: ► We analyzed subchannel void distributions using subchannel, system and CFD codes. ► The mean error and standard deviation at steady states were compared. ► The deviation of the CFD simulation was greater than those of the others. ► The large deviation of the CFD prediction is due to interface model uncertainties. -- Abstract: The subchannel grade and microscopic void distributions in the NUPEC (Nuclear Power Engineering Corporation) BFBT (BWR Full-Size Fine-Mesh Bundle Tests) facility have been evaluated with a subchannel analysis code MATRA, a system code MARS and a CFD code CFX-10. Sixteen test series from five different test bundles were selected for the analysis of the steady-state subchannel void distributions. Four test cases for a high burn-up 8 × 8 fuel bundle with a single water rod were simulated using CFX-10 for the microscopic void distribution benchmark. Two transient cases, a turbine trip without a bypass as a typical power transient and a re-circulation pump trip as a flow transient, were also chosen for this analysis. It was found that the steady-state void distributions calculated by both the MATRA and MARS codes coincided well with the measured data in the range of thermodynamic qualities from 5 to 25%. The results of the transient calculations were also similar to each other and very reasonable. The CFD simulation reproduced the overall radial void distribution trend which produces less vapor in the central part of the bundle and more vapor in the periphery. However, the predicted variation of the void distribution inside the subchannels is small, while the measured one is large showing a very high concentration in the center of the subchannels. The variations of the void distribution between the center of the subchannels and the subchannel gap are estimated to be about 5–10% for the CFD prediction and more than 20% for the experiment

  12. Video Voiding Device for Diagnosing Lower Urinary Tract Dysfunction in Men.

    Science.gov (United States)

    Shokoueinejad, Mehdi; Alkashgari, Rayan; Mosli, Hisham A; Alothmany, Nazeeh; Levin, Jacob M; Webster, John G

    2017-01-01

    We introduce a novel diagnostic Visual Voiding Device (VVD), which has the ability to visually document urinary voiding events and calculate key voiding parameters such as instantaneous flow rate. The observation of the urinary voiding process along with the instantaneous flow rate can be used to diagnose symptoms of Lower Urinary Tract Dysfunction (LUTD) and improve evaluation of LUTD treatments by providing subsequent follow-up documentations of voiding events after treatments. The VVD enables a patient to have a urinary voiding event in privacy while a urologist monitors, processes, and documents the event from a distance. The VVD consists of two orthogonal cameras which are used to visualize urine leakage from the urethral meatus, urine stream trajectory, and its break-up into droplets. A third, lower back camera monitors a funnel topped cylinder where urine accumulates that contains a floater for accurate readings regardless of the urine color. Software then processes the change in level of accumulating urine in the cylinder and the visual flow properties to calculate urological parameters. Video playback allows for reexamination of the voiding process. The proposed device was tested by integrating a mass flowmeter into the setup and simultaneously measuring the instantaneous flow rate of a predetermined voided volume in order to verify the accuracy of VVD compared to the mass flowmeter. The VVD and mass flowmeter were found to have an accuracy of ±2 and ±3% relative to full scale, respectively. A VVD clinical trial was conducted on 16 healthy male volunteers ages 23-65.

  13. Self-organized voids revisited: Experimental verification of the formation mechanism

    International Nuclear Information System (INIS)

    Song Juan; Jiang Yan; Ye Jun-Yi; Qian Meng-Di; Lin Xian; Bian Hua-Dong; Dai Ye; Ma Guo-Hong; Luo Fang-Fang; Chen Qing-Xi; Zhao Quan-Zhong; Qiu Jian-Rong

    2014-01-01

    We conduct several experiments to further clarify the formation mechanism of a self-organized void array induced by a single laser beam, including energy-related experiments, refractive-index-contrast-related experiments, depth-related experiments, and effective-numerical-aperture experiment. These experiments indicate that the interface spherical aberration is indeed responsible for the formation of void arrays. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  14. Effect of endocrine treatment on voiding and prostate size in men with prostate cancer

    DEFF Research Database (Denmark)

    Klarskov, Louise L; Klarskov, Peter; Mommsen, Søren

    2012-01-01

    The aim of this study was to assess and quantify changes in voiding parameters and prostate size in men with prostate cancer from before the start of endocrine treatment and during long-term follow-up.......The aim of this study was to assess and quantify changes in voiding parameters and prostate size in men with prostate cancer from before the start of endocrine treatment and during long-term follow-up....

  15. X-ray Computed Tomography Assessment of Air Void Distribution in Concrete

    Science.gov (United States)

    Lu, Haizhu

    Air void size and spatial distribution have long been regarded as critical parameters in the frost resistance of concrete. In cement-based materials, entrained air void systems play an important role in performance as related to durability, permeability, and heat transfer. Many efforts have been made to measure air void parameters in a more efficient and reliable manner in the past several decades. Standardized measurement techniques based on optical microscopy and stereology on flat cut and polished surfaces are widely used in research as well as in quality assurance and quality control applications. Other more automated methods using image processing have also been utilized, but still starting from flat cut and polished surfaces. The emergence of X-ray computed tomography (CT) techniques provides the capability of capturing the inner microstructure of materials at the micrometer and nanometer scale. X-ray CT's less demanding sample preparation and capability to measure 3D distributions of air voids directly provide ample prospects for its wider use in air void characterization in cement-based materials. However, due to the huge number of air voids that can exist within a limited volume, errors can easily arise in the absence of a formalized data processing procedure. In this study, air void parameters in selected types of cement-based materials (lightweight concrete, structural concrete elements, pavements, and laboratory mortars) have been measured using micro X-ray CT. The focus of this study is to propose a unified procedure for processing the data and to provide solutions to deal with common problems that arise when measuring air void parameters: primarily the reliable segmentation of objects of interest, uncertainty estimation of measured parameters, and the comparison of competing segmentation parameters.

  16. Determining the void fraction in draught sections of a boiling water cooled reactor

    International Nuclear Information System (INIS)

    Fedulin, V.N.; Barolomej, G.G.; Solodkij, V.A.; Shmelev, V.E.

    1987-01-01

    Consideration is being given to the problem of improving methods for calculation of the void fraction in large channels of cooling system of the boiling water cooled reactor during two-phase unsteady flow. Investigation of the structure of two-phase flow was conducted in draught section of the VK-50 reactor (diameter D=2 m, height H=3). The method for calculation of the void fraction in channels with H/D ratio close to 1 is suggested

  17. Radiation Dose from Voiding Cystourethrography (VCUG) Examination in Children

    International Nuclear Information System (INIS)

    Siriwiladluk, T.; Krisanachinda, A.

    2012-01-01

    Introduction: The purpose of this study is to determine entrance skin dose (ESD) from fluoroscopy and radiography procedures in voiding cystourethrography (VCUG) studies of pediatric patients by dose-area product (DAP) recording. Methods: Radiation doses received by 70 patients underwent VCUG procedures were determined by the DAP Meter, Wellh?fer Dosimetrie GmbH, Germany) directly coupled to the x-ray tube window (Philips Omni Diagnost Eleva) and an electrometer connected to a computer for data collection. The study revealed the radiation dose for VCUG and the baseline data on the entrance skin dose, ESD, dose area-product (DAP) and the effective dose, E, to establish local reference dose levels for VCUG in pediatric patients. Results: The mean(minimum-maximum) ESD, DAP and the effective dose of pediatric patients in 4 age ranges were 3.41(1-9) mGy, 46.58 (21.90-158.90) cGycm 2 and 0.10(0.05-0.33) mSv for 0- 1 years, 6.80(2-16) mGy, 115.55 (20.70-258.70)cGycm 2 and 0.24(0.04-0.54) mSv for >1-5 years, 11.76 (3-23) mGy, 292.28 (88.90-593.50)cGycm 2 and 0.61(0.19-1.25) mSv for >5-10 years, and 20.50(10-42) mGy, 575.98(255.60-1247.80) cGycm 2 and 1.12(0.54-2.62) mSv for >10-15 years respectively. Discussion: The dose levels for VCUG as recommended by the national reference doses (NRDs) of UK are classified at patient age of 0-1 years, 90 cGy.cm 2 , >1-5 years, 110 cGy.cm 2 , >5-10 years, 210 cGy.cm 2 and >10-15 years, 470 cGy.cm 2 respectively. Conclusions: The mean DAP of pediatric patients were higher than the dose level as recommended by NRD at the age range >1-5, >5-10 and >10-15 years. The limitation in this study was the non uniform in the number of patients at the higher age. Attempts could be made to lower the radiation dose to avoid the higher risk of developing radiation-induced cancer in children. (author)

  18. Relation Between Bitumen Content and Percentage Air Voids in Semi Dense Bituminous Concrete

    Science.gov (United States)

    Panda, R. P.; Das, Sudhanshu Sekhar; Sahoo, P. K.

    2018-06-01

    Hot mix asphalt (HMA) is a heterogeneous mix of aggregate, mineral filler, bitumen, additives and air voids. Researchers have indicated that the durability of the HMA is sensitive on the actual bitumen content and percentage air void. This paper aims at establishing the relationship between the bitumen content and the percentage air voids in Semi Dense Bituminous Concrete (SDBC) using Viscosity Grade-30 (VG-30) bitumen. Total 54 samples have been collected, for formulation and validation of relationship and observed that the percentage air voids increases with decrease in actual bitumen content and vice versa. A minor increase in percentage air voids beyond practice of designed air voids in Marshall Method of design is required for better performance, indicating a need for reducing the codal provision of minimum bitumen content for SDBC as specified in Specification for Road & Bridges (Fourth Revision) published by Indian Road Congress, 2001. The study shows a possibility of reducing designed minimum bitumen content from codal provision for SDBC by 0.2% of weight with VG-30 grade of Bitumen.

  19. Voiding dysfunction after abdominal radical hysterectomy. Comparison between patients with and without adjuvant irradiation therapy

    International Nuclear Information System (INIS)

    Ueda, Tomohiro; Yamauchi, Tamio; Kageyama, Susumu; Tsuzuki, Masahiro; Kawakami, Satoru; Yonese, Junji; Kawai, Tsuneo

    1994-01-01

    We evaluated 59 patients with voiding dysfunction after abdominal radical hysterectomy for uterine cancer. Of 59 patients, 45 underwent the surgery alone, and the other 14 underwent surgery and postoperative radiotherapy. Irradiation (mean dose, 60 Gy) was performed in bilateral commoni iliac regions excluding the bladder. In principle, the indwelling urethral catheter was removed 4 days after operation. All patients were followed up at the gynecologocal department until the onset of the voiding dysfunction. The mean interval between operation and the onset of voiding dysfunction was significantly longer (P<0.01) in the group treated by surgery alone (7.9 years) than in the group treated by surgery in combination with radiotherapy (3.8 year). Voiding dysfunction developed earlier as the age at the time of operation was higher. No differences were observed in the volume of residual urine, the detrusor function, or the incidence of urinary tract infection between the two groups. These results suggest that aged patients develop voiding dysfunction earlier after radical hysterectomy than young patients, and postoperative radiotherapy shortens the interval between operation and the onset of postoperative voiding dysfunction. (author)

  20. M-CHOLINOLYTICS IN RHEABILITATION OF CHILDREN WITH VOIDING DISFUNCTION AND URNARY BLADDER HYPERACTIVITY

    Directory of Open Access Journals (Sweden)

    I.V. Kazanskaya

    2006-01-01

    Full Text Available Voiding dysfunction is a common problem in pediatrics. Hyperactive urinary bladder is the most frequent cause of voiding dysfunction. Macholinolytic drugs are the first choice treatment for urinary bladder hyperactivity. The «urination pathology» center has investigated the efficacy of an macholinolytic, oxybutynin. The study included 25 children (aged 6–14 with different causes of voiding dysfunction and bladder hyperactivity. Oxybutynin was administered with a dosage of 5 mg twice a day, the follow up period was 8 weeks. The control evaluation of urodynamics (voiding rhythm, uroflowmetry, residual urine volume was performed at 4–8 weeks. Symptoms of bladder hyperactivity have been eliminated in 50% of patients, the bladder capacity has increased in 70% of cases, the frequency of night and day incontinence has diminished. The report demonstrates that oxybutynin has been most effective in patients with urinary bladder volume between 80 and 100 ml. the side effects, as dryness of mucous membranes and voiding difficulties, have been rarely observed. These side effects could be avoided by individual dose titration.Key words: voiding dysfunction, urinary bladder hyperactivity, oxybutynin, children.

  1. Finite Element Analysis of Transverse Compressive Loads on Superconducting Nb3Sn Wires Containing Voids

    Science.gov (United States)

    D'Hauthuille, Luc; Zhai, Yuhu; Princeton Plasma Physics Lab Collaboration; University of Geneva Collaboration

    2015-11-01

    High field superconductors play an important role in many large-scale physics experiments, particularly particle colliders and fusion devices such as the LHC and ITER. The two most common superconductors used are NbTi and Nb3Sn. Nb3Sn wires are favored because of their significantly higher Jc, allowing them to produce much higher magnetic fields. The main disadvantage is that the superconducting performance of Nb3Sn is highly strain-sensitive and it is very brittle. The strain-sensitivity is strongly influenced by two factors: plasticity and cracked filaments. Cracks are induced by large stress concentrators due to the presence of voids. We will attempt to understand the correlation between Nb3Sn's irreversible strain limit and the void-induced stress concentrations around the voids. We will develop accurate 2D and 3D finite element models containing detailed filaments and possible distributions of voids in a bronze-route Nb3Sn wire. We will apply a compressive transverse load for the various cases to simulate the stress response of a Nb3Sn wire from the Lorentz force. Doing this will further improve our understanding of the effect voids have on the wire's mechanical properties, and thus, the connection between the shape & distribution of voids and performance degradation.

  2. Wire-Mesh Tomography Measurements of Void Fraction in Rectangular Bubble Columns

    International Nuclear Information System (INIS)

    Reddy Vanga, B.N.; Lopez de Bertodano, M.A.; Zaruba, A.; Prasser, H.M.; Krepper, E.

    2004-01-01

    Bubble Columns are widely used in the process industry and their scale-up from laboratory scale units to industrial units have been a subject of extensive study. The void fraction distribution in the bubble column is affected by the column size, superficial velocity of the dispersed phase, height of the liquid column, size of the gas bubbles, flow regime, sparger design and geometry of the bubble column. The void fraction distribution in turn affects the interfacial momentum transfer in the bubble column. The void fraction distribution in a rectangular bubble column 10 cm wide and 2 cm deep has been measured using Wire-Mesh Tomography. Experiments were performed in an air-water system with the column operating in the dispersed bubbly flow regime. The experiments also serve the purpose of studying the performance of wire-mesh sensors in batch flows. A 'wall peak' has been observed in the measured void fraction profiles, for the higher gas flow rates. This 'wall peak' seems to be unique, as this distribution has not been previously reported in bubble column literature. Low gas flow rates yielded the conventional 'center peak' void profile. The effect of column height and superficial gas velocity on the void distribution has been investigated. Wire-mesh Tomography also facilitates the measurement of bubble size distribution in the column. This paper presents the measurement principle and the experimental results for a wide range of superficial gas velocities. (authors)

  3. Analysis of sodium-void-worths in ZPPR-3 modified phase 3 core

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, T.; Arai, K.; Otake, I. [Osaka Univ. (JP)

    1980-09-15

    The sodium-void-worths in the ZPPR-3 modified phase 3 core, in which singularities such as control-rods and sodium-followers were voided, have been analyzed using a unified diffusion coefficient. The unified diffusion coefficient is obtained by applying the Benoist formula to a super-cell consisting of different drawers, and is applicable not only to fuel drawers but also to control-rod drawers or sodium-followers. Using the coefficient the interference effect of neutron streaming between different drawers can be taken into account. The applicability of the unified diffusion coefficient to sodium-void-worth calculations has been checked in a slab model and a RZ model. The sodium-void-worths in the ZPPR-3 modified phase 3 core have been analyzed by carrying out 16-group three-dimensional diffusion calculations using the unified diffusion coefficient and the results have been compared with experimental data. The comparison indicates that the unified diffusion coefficient is useful in calculating the sodium-void-worth in a region including sodium-voided singularities.

  4. Use of electrical resistivity to detect underground mine voids in Ohio

    Science.gov (United States)

    Sheets, Rodney A.

    2002-01-01

    Electrical resistivity surveys were completed at two sites along State Route 32 in Jackson and Vinton Counties, Ohio. The surveys were done to determine whether the electrical resistivity method could identify areas where coal was mined, leaving air- or water-filled voids. These voids can be local sources of potable water or acid mine drainage. They could also result in potentially dangerous collapse of roads or buildings that overlie the voids. The resistivity response of air- or water-filled voids compared to the surrounding bedrock may allow electrical resistivity surveys to delineate areas underlain by such voids. Surface deformation along State Route 32 in Jackson County led to a site investigation, which included electrical resistivity surveys. Several highly resistive areas were identified using axial dipole-dipole and Wenner resistivity surveys. Subsequent drilling and excavation led to the discovery of several air-filled abandoned underground mine tunnels. A site along State Route 32 in Vinton County, Ohio, was drilled as part of a mining permit application process. A mine void under the highway was instrumented with a pressure transducer to monitor water levels. During a period of high water level, electrical resistivity surveys were completed. The electrical response was dominated by a thin, low-resistivity layer of iron ore above where the coal was mined out. Nearby overhead powerlines also affected the results.

  5. Two Hop Adaptive Vector Based Quality Forwarding for Void Hole Avoidance in Underwater WSNs.

    Science.gov (United States)

    Javaid, Nadeem; Ahmed, Farwa; Wadud, Zahid; Alrajeh, Nabil; Alabed, Mohamad Souheil; Ilahi, Manzoor

    2017-08-01

    Underwater wireless sensor networks (UWSNs) facilitate a wide range of aquatic applications in various domains. However, the harsh underwater environment poses challenges like low bandwidth, long propagation delay, high bit error rate, high deployment cost, irregular topological structure, etc. Node mobility and the uneven distribution of sensor nodes create void holes in UWSNs. Void hole creation has become a critical issue in UWSNs, as it severely affects the network performance. Avoiding void hole creation benefits better coverage over an area, less energy consumption in the network and high throughput. For this purpose, minimization of void hole probability particularly in local sparse regions is focused on in this paper. The two-hop adaptive hop by hop vector-based forwarding (2hop-AHH-VBF) protocol aims to avoid the void hole with the help of two-hop neighbor node information. The other protocol, quality forwarding adaptive hop by hop vector-based forwarding (QF-AHH-VBF), selects an optimal forwarder based on the composite priority function. QF-AHH-VBF improves network good-put because of optimal forwarder selection. QF-AHH-VBF aims to reduce void hole probability by optimally selecting next hop forwarders. To attain better network performance, mathematical problem formulation based on linear programming is performed. Simulation results show that by opting these mechanisms, significant reduction in end-to-end delay and better throughput are achieved in the network.

  6. An analytical approach to the positive reactivity void coefficient of TRIGA Mark-II reactor

    International Nuclear Information System (INIS)

    Edgue, Erdinc; Yarman, Tolga

    1988-01-01

    Previous calculations of reactivity void coefficient of I.T.U. TRIGA Mark-II Reactor was done by the second author et al. The theoretical predictions were afterwards, checked in this reactor experimentally. In this work an analytical approach is developed to evaluate rather quickly the reactivity void coefficient of I.T.U. TRIGA Mark-II, versus the size of the void inserted into the reactor. It is thus assumed that the reactor is a cylindrical, bare nuclear system. Next a belt of water of 2πrΔrH is introduced axially at a distance r from the center line of the system. r here, is the thickness of the belt, and H is the height of the reactor. The void is described by decreasing the water density in the belt region. A two group diffusion theory is adopted to determine the criticality of our configuration. The space dependency of the group fluxes are, thereby, assumed to be J 0 (2.405 r / R) cos (π Z / H), the same as that associated with the original bare reactor uniformly loaded prior to the change. A perturbation type of approach, thence, furnishes the effect of introducing a void in the belt region. The reactivity void coefficient can, rather surprisingly, be indeed positive. To our knowledge, this fact had not been established, by the supplier. The agreement of our predictions with the experimental results is good. (author)

  7. Modeling and Simulation of Voids in Composite Tape Winding Process Based on Domain Superposition Technique

    Science.gov (United States)

    Deng, Bo; Shi, Yaoyao

    2017-11-01

    The tape winding technology is an effective way to fabricate rotationally composite materials. Nevertheless, some inevitable defects will seriously influence the performance of winding products. One of the crucial ways to identify the quality of fiber-reinforced composite material products is examining its void content. Significant improvement in products' mechanical properties can be achieved by minimizing the void defect. Two methods were applied in this study, finite element analysis and experimental testing, respectively, to investigate the mechanism of how void forming in composite tape winding processing. Based on the theories of interlayer intimate contact and Domain Superposition Technique (DST), a three-dimensional model of prepreg tape void with SolidWorks has been modeled in this paper. Whereafter, ABAQUS simulation software was used to simulate the void content change with pressure and temperature. Finally, a series of experiments were performed to determine the accuracy of the model-based predictions. The results showed that the model is effective for predicting the void content in the composite tape winding process.

  8. Voids in the Cosmic Web as a probe of dark energy

    Directory of Open Access Journals (Sweden)

    B. Novosyadlyj

    2017-03-01

    Full Text Available The formation of large voids in the Cosmic Web from the initial adiabatic cosmological perturbations of space-time metric, density and velocity of matter is investigated in cosmological model with the dynamical dark energy accelerating expansion of the Universe. It is shown that the negative density perturbations with the initial radius of about 50 Mpc in comoving to the cosmological background coordinates and the amplitude corresponding to the r.m.s. temperature fluctuations of the cosmic microwave background lead to the formation of voids with the density contrast up to -0.9, maximal peculiar velocity about 400 km/s and the radius close to the initial one. An important feature of voids formation from the analyzed initial amplitudes and profiles is establishing the surrounding overdensity shell. We have shown that the ratio of the peculiar velocity in units of the Hubble flow to the density contrast in the central part of a void does not depend or weakly depends on the distance from the center of the void. It is also shown that this ratio is sensitive to the values of dark energy parameters and can be used to find them based on the observational data on mass density and peculiar velocities of galaxies in the voids.

  9. Dislocation creation and void nucleation in FCC ductile metals under tensile loading: a general microscopic picture.

    Science.gov (United States)

    Pang, Wei-Wei; Zhang, Ping; Zhang, Guang-Cai; Xu, Ai-Guo; Zhao, Xian-Geng

    2014-11-10

    Numerous theoretical and experimental efforts have been paid to describe and understand the dislocation and void nucleation processes that are fundamental for dynamic fracture modeling of strained metals. To date an essential physical picture on the self-organized atomic collective motions during dislocation creation, as well as the essential mechanisms for the void nucleation obscured by the extreme diversity in structural configurations around the void nucleation core, is still severely lacking in literature. Here, we depict the origin of dislocation creation and void nucleation during uniaxial high strain rate tensile processes in face-centered-cubic (FCC) ductile metals. We find that the dislocations are created through three distinguished stages: (i) Flattened octahedral structures (FOSs) are randomly activated by thermal fluctuations; (ii) The double-layer defect clusters are formed by self-organized stacking of FOSs on the close-packed plane; (iii) The stacking faults are formed and the Shockley partial dislocations are created from the double-layer defect clusters. Whereas, the void nucleation is shown to follow a two-stage description. We demonstrate that our findings on the origin of dislocation creation and void nucleation are universal for a variety of FCC ductile metals with low stacking fault energies.

  10. Relation Between Bitumen Content and Percentage Air Voids in Semi Dense Bituminous Concrete

    Science.gov (United States)

    Panda, R. P.; Das, Sudhanshu Sekhar; Sahoo, P. K.

    2018-02-01

    Hot mix asphalt (HMA) is a heterogeneous mix of aggregate, mineral filler, bitumen, additives and air voids. Researchers have indicated that the durability of the HMA is sensitive on the actual bitumen content and percentage air void. This paper aims at establishing the relationship between the bitumen content and the percentage air voids in Semi Dense Bituminous Concrete (SDBC) using Viscosity Grade-30 (VG-30) bitumen. Total 54 samples have been collected, for formulation and validation of relationship and observed that the percentage air voids increases with decrease in actual bitumen content and vice versa. A minor increase in percentage air voids beyond practice of designed air voids in Marshall Method of design is required for better performance, indicating a need for reducing the codal provision of minimum bitumen content for SDBC as specified in Specification for Road & Bridges (Fourth Revision) published by Indian Road Congress, 2001. The study shows a possibility of reducing designed minimum bitumen content from codal provision for SDBC by 0.2% of weight with VG-30 grade of Bitumen.

  11. New insight on bubble-void transition effects in irradiated materials

    International Nuclear Information System (INIS)

    Dubinko, V.I.

    1993-01-01

    An account of elastic interaction between cavities and point defects is shown to result in new critical quantities for bubblevoid transition effects in irradiated cubic crystals. In contrast to previous theories, the present one gives not only critical quantities which determine the onset of bias-driven void swelling but the maximum stationary number density and the corresponding mean radius of voids as well as the duration of the bimodal regime. The void density and swelling rate are shown to be independent from the gas level. In the region of low temperatures/high dose rates, the void density appears to be independent from irradiation parameters as well. The relationships among material constants are found at which the stabilization of gas bubbles occurs via the dislocation loop punching mechanism resulting in a drastic change in the cavity behaviour under irradiation such as the saturation (or even suppression) of void swelling and void lattice formation. The theoretical results are compared with experimental data and further experimental tests are proposed. (author). 38 refs., 1 tab., 11 figs

  12. Electron microscopy observations of helium bubble-void transition effects in nimonic PE16 alloys

    International Nuclear Information System (INIS)

    Mazey, D.J.; Nelson, R.S.

    1980-01-01

    High-nickel alloys based on the Nimonic PE16 composition have been injected at temperatures of 525 0 C and 625 0 C with 1000 ppm helium to produce a high gas-bubble concentration and subsequently irradiated with 36 MeV nickel ions. Extensive heterogeneous nucleation of bubbles is observed on faulted interstitial loops and dislocations. Evidence is found in standard PE16 alloy for bimodal bubble plus void distributions which persist during nickel-ion irradiation to 30 and 60 dpa at 625 0 C and result in a low void volume swelling of approximately 1%. The observations can be correlated with the critical bubble/void transition radius which is calculated from theory to be approximately 4.4 nm. Pre-injection of helium into a 'matrix' PE16 (low Si, Ti and Al) alloy produced an initial bubble population whose average size was above the calculated transition radius such that all bubbles eventually grew as voids during subsequent nickel-ion irradiation up to 60 dpa at 625 0 C where the void volume swelling reached approximately 12%. The observations are discussed briefly and related to theoretical predictions of the bubble/void transition radius. (author)

  13. Galaxy evolution in extreme environments: Molecular gas content star formation and AGN in isolated void galaxies

    Science.gov (United States)

    Das, Mousumi; Iono, Daisuke; Saito, Toshiki; Subramanian, Smitha

    Since the early redshift surveys of the large scale structure of our universe, it has become clear that galaxies cluster along walls, sheet and filaments leaving large, empty regions called voids between them. Although voids represent the most under dense parts of our universe, they do contain a sparse but significant population of isolated galaxies that are generally low luminosity, late type disk galaxies. Recent studies show that most void galaxies have ongoing star formation and are in an early stage of evolution. We present radio, optical studies of the molecular gas content and star formation in a sample of void galaxies. Using SDSS data, we find that AGN are rare in these systems and are found only in the Bootes void; their black hole masses and radio properties are similar to bright spirals galaxies. Our studies suggest that close galaxy interactions and gas accretion are the main drivers of galaxy evolution in these systems despite their location in the underdense environment of the voids.

  14. Anticavitation and Differential Growth in Elastic Shells

    KAUST Repository

    Moulton, Derek E.

    2010-07-22

    Elastic anticavitation is the phenomenon of a void in an elastic solid collapsing on itself. Under the action of mechanical loading alone typical materials do not admit anticavitation. We study the possibility of anticavitation as a consequence of an imposed differential growth. Working in the geometry of a spherical shell, we seek radial growth functions which cause the shell to deform to a solid sphere. It is shown, surprisingly, that most material models do not admit full anticavitation, even when infinite growth or resorption is imposed at the inner surface of the shell. However, void collapse can occur in a limiting sense when radial and circumferential growth are properly balanced. Growth functions which diverge or vanish at a point arise naturally in a cumulative growth process. © 2010 Springer Science+Business Media B.V.

  15. Quantifying the distribution of paste-void spacing of hardened cement paste using X-ray computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Tae Sup, E-mail: taesup@yonsei.ac.kr [School of Civil and Environmental Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of); Kim, Kwang Yeom, E-mail: kimky@kict.re.kr [Korea Institute of Construction Technology, 283 Goyangdae-ro, Ilsanseo-gu, Goyang, 411-712 (Korea, Republic of); Choo, Jinhyun, E-mail: jinhyun@stanford.edu [Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305 (United States); Kang, Dong Hun, E-mail: timeriver@naver.com [School of Civil and Environmental Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of)

    2012-11-15

    The distribution of paste-void spacing in cement-based materials is an important feature related to the freeze-thaw durability of these materials, but its reliable estimation remains an unresolved problem. Herein, we evaluate the capability of X-ray computed tomography (CT) for reliable quantification of the distribution of paste-void spacing. Using X-ray CT images of three mortar specimens having different air-entrainment characteristics, we calculate the distributions of paste-void spacing of the specimens by applying previously suggested methods for deriving the exact spacing of air-void systems. This methodology is assessed by comparing the 95th percentile of the cumulative distribution function of the paste-void spacing with spacing factors computed by applying the linear-traverse method to 3D air-void system and reconstructing equivalent air-void distribution in 3D. Results show that the distributions of equivalent void diameter and paste-void spacing follow lognormal and normal distributions, respectively, and the ratios between the 95th percentile paste-void spacing value and the spacing factors reside within the ranges reported by previous numerical studies. This experimental finding indicates that the distribution of paste-void spacing quantified using X-ray CT has the potential to be the basis for a statistical assessment of the freeze-thaw durability of cement-based materials. - Highlights: Black-Right-Pointing-Pointer The paste-void spacing in 3D can be quantified by X-ray CT. Black-Right-Pointing-Pointer The distribution of the paste-void spacing follows normal distribution. Black-Right-Pointing-Pointer The spacing factor and 95th percentile of CDF of paste-void spacing are correlated.

  16. Uncertainty Margin of Void Packet Determination for Ultrasonic Test in NPP

    International Nuclear Information System (INIS)

    Lee, Seungchan; Sung, Jejung; Lee, Jongchan; Kim, Jonguk

    2014-01-01

    In this study, the uncertainty of the void packet determination is estimated and the conservatism is reviewed by comparing with realistic uncertainty of Heckle's uncertainty. The methodology of ISO GUM is fully applied to calculate uncertainty, combined uncertainty and effective degree of freedom. Here some results are achieved as below: Combined uncertainty(UT) : 4.98%, Combined uncertainty(Heckle) : 1.44%, Degree of freedom: 5 ∼ 15, Effective degree of freedom(UT): 24.11, Effective degree of freedom(Heckle): 28.54, K value of t-distribution(UT): 2.042, K value of t-distribution(Heckle): 2.04, The uncertainty of this study using UT is enough in the case of achieving conservatism when the void packet determination of the safety related system is determined. As result of this study, UT uncertainty is more conservative than the Heckle's realistic uncertainty. From these results, it is shown that UT method has the great safety margin in determining the void packet. In comparing UT uncertainty with realistic uncertainty, this study (UT) has the conservatism of more than 3.4 times. UT method is good method to determine the void packet of ECCS pipe and to achieve the safety margin. In a safety related system, a void packet determination is issued by US NRC through the Generic Letter 2008-01. In case of the safety function, ECCS, CSS, and RHR systems are affected by the void packet. The related study has been being carried out by KHNP since 2012. In this study, the void packet determination using a ultra sonic test method has been carried out in some sites. This paper shows the uncertainty of the method using the ultra sonic test. The key parameters are introduced and estimated. Specially, the measurement conservatism for NPP is introduced to show the uncertainty margin

  17. Uncertainty Margin of Void Packet Determination for Ultrasonic Test in NPP

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seungchan; Sung, Jejung [Korea Hydro Nuclear Power Electricity Co., Daejeon (Korea, Republic of); Lee, Jongchan; Kim, Jonguk [FNC Technology Co., LTD., Yongin (Korea, Republic of)

    2014-05-15

    In this study, the uncertainty of the void packet determination is estimated and the conservatism is reviewed by comparing with realistic uncertainty of Heckle's uncertainty. The methodology of ISO GUM is fully applied to calculate uncertainty, combined uncertainty and effective degree of freedom. Here some results are achieved as below: Combined uncertainty(UT) : 4.98%, Combined uncertainty(Heckle) : 1.44%, Degree of freedom: 5 ∼ 15, Effective degree of freedom(UT): 24.11, Effective degree of freedom(Heckle): 28.54, K value of t-distribution(UT): 2.042, K value of t-distribution(Heckle): 2.04, The uncertainty of this study using UT is enough in the case of achieving conservatism when the void packet determination of the safety related system is determined. As result of this study, UT uncertainty is more conservative than the Heckle's realistic uncertainty. From these results, it is shown that UT method has the great safety margin in determining the void packet. In comparing UT uncertainty with realistic uncertainty, this study (UT) has the conservatism of more than 3.4 times. UT method is good method to determine the void packet of ECCS pipe and to achieve the safety margin. In a safety related system, a void packet determination is issued by US NRC through the Generic Letter 2008-01. In case of the safety function, ECCS, CSS, and RHR systems are affected by the void packet. The related study has been being carried out by KHNP since 2012. In this study, the void packet determination using a ultra sonic test method has been carried out in some sites. This paper shows the uncertainty of the method using the ultra sonic test. The key parameters are introduced and estimated. Specially, the measurement conservatism for NPP is introduced to show the uncertainty margin.

  18. Trampoline effect and the force field inside the void in complex plasma under microgravity conditions

    International Nuclear Information System (INIS)

    Khrapak, S. A.; Kretschmer, M.; Zhdanov, S. K.; Thomas, H. M.; MOrfill, G. e.; Fortov, V. E.; Lipaev, A. M.; Molotkov, V. I.; Ivanov, A. I.; Turin, M. V.

    2005-01-01

    The PKE-Nefedov facility onboard the International Space Station (ISS),operational since March, 2'001, has enabled the study of complex (dusty) plasmas under microgravity conditions. A complex plasma is generated by introducing micron sized grains in a capacitively coupled rf discharge. The grains form a cloud inside the bulk of the discharge and can be easily visualized with the help of standard tools-laser illumination and video cameras. In most of the experiments under microgravity conditions the central region of the discharge is free of grains a so called void is formed. Due to recent theoretical advances, showing that the ion drag force can be more than a factor of ten larger than had traditionally been believed, void formation is now through to be a consequence of this (enhanced) interaction. The way this process works is the following: the ions drifting from the central region of a discharge to its walls and electrodes transfer their momentum to the grains pushing them out of the center. However, no direct experimental results on the origin of the void formation were reported so far. In this paper we report new results on the observation of a weak instability of the void-complex plasma interface observed at a relatively low gas pressure (p=12Pa). The instability leads to periodic injections of a relatively small number of particles into the void region (by analogy this effect is called trampoline effect), The trajectories of injected particles are analyzed providing information on the force field and potential energy distribution inside the void. For the relatively low neutral gas pressure used in the experiment a direct comparison with theory involving a model of the ion drag force in the collisionless regime is possible. Such a comparison yields good agreement, implying that we have observed the first experimental confirmation of the ion drag mechanism as being responsible for the void formation. (Author)

  19. Trampoline effect and the force field inside the void in complex plasma under microgravity conditions

    Energy Technology Data Exchange (ETDEWEB)

    Khrapak, S. A.; Kretschmer, M.; Zhdanov, S. K.; Thomas, H. M.; MOrfill, G. e.; Fortov, V. E.; Lipaev, A. M.; Molotkov, V. I.; Ivanov, A. I.; Turin, M. V.

    2005-07-01

    The PKE-Nefedov facility onboard the International Space Station (ISS),operational since March, 2'001, has enabled the study of complex (dusty) plasmas under microgravity conditions. A complex plasma is generated by introducing micron sized grains in a capacitively coupled rf discharge. The grains form a cloud inside the bulk of the discharge and can be easily visualized with the help of standard tools-laser illumination and video cameras. In most of the experiments under microgravity conditions the central region of the discharge is free of grains a so called void is formed. Due to recent theoretical advances, showing that the ion drag force can be more than a factor of ten larger than had traditionally been believed, void formation is now through to be a consequence of this (enhanced) interaction. The way this process works is the following: the ions drifting from the central region of a discharge to its walls and electrodes transfer their momentum to the grains pushing them out of the center. However, no direct experimental results on the origin of the void formation were reported so far. In this paper we report new results on the observation of a weak instability of the void-complex plasma interface observed at a relatively low gas pressure (p=12Pa). The instability leads to periodic injections of a relatively small number of particles into the void region (by analogy this effect is called trampoline effect), The trajectories of injected particles are analyzed providing information on the force field and potential energy distribution inside the void. For the relatively low neutral gas pressure used in the experiment a direct comparison with theory involving a model of the ion drag force in the collisionless regime is possible. Such a comparison yields good agreement, implying that we have observed the first experimental confirmation of the ion drag mechanism as being responsible for the void formation. (Author)

  20. Effect of laser and/or electron beam irradiation on void swelling in SUS316L austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Subing [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Yang, Zhanbing, E-mail: yangzhanbing@ustb.edu.cn [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083 (China); Wang, Hui [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Watanabe, Seiichi; Shibayama, Tamaki [Center for Advanced Research of Energy and Materials, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628 (Japan)

    2017-05-15

    Large amounts of void swelling still limit the application of austenitic stainless steels in nuclear reactors due to radiation-induced lattice point defects. In this study, laser and/or beam irradiation was conducted in a temperature range of 573–773 K to explore the suppression of void swelling. The results show that during sequential laser-electron beam irradiation, the void nucleation is enhanced because of the vacancy clusters and void nuclei formed under pre-laser irradiation, causing greater void swelling than single electron beam irradiation. However, simultaneous laser-electron dual-beam irradiation exhibits an obvious suppression effect on void swelling due to the enhanced recombination between interstitials and vacancies in the temperature range of 573–773 K; especially at 723 K, the swelling under simultaneous dual-beam irradiation is 0.031% which is only 22% of the swelling under electron beam irradiation (0.137%). These results provide new insight into the suppression of void swelling during irradiation. - Highlights: •The temperature dependence of void swelling under simultaneous laser-electron dual-beam irradiation has been investigated. •Pre-laser irradiation enhances void nucleation at temperatures from 573 K to 773 K. •Simultaneous laser-electron dual-beam irradiation suppresses void swelling in the temperature range of 573–773 K.

  1. Study on influence of flow rates on voids in waxy crude oil subjected to dynamic and static cooling

    Directory of Open Access Journals (Sweden)

    Girma T. Chala

    2015-12-01

    Full Text Available The assumption of constant yield stress in the conventional restart pressure equation neglects the effects of thermal shrinkage and gas voids formation, which in turn resulted in an over-designed production piping systems. This paper presents a study on the effects of flow rates on the formation of voids in gelled waxy crude oil. A flow loop rig simulating offshore waxy crude oil transportation was used to produce a gel. A Magnetic Resonance Imaging (MRI was used to scan the gelled crude oil over the three planes. Waxy crude oil underwent both dynamic and static cooling to observe the effects of volume flow rates on the voids formed in wax-oil gel. Volume flow rate was found to have different influences on the intra-gel voids in the pipeline. A volume flow rate of 5 L/min resulted in a maximum total voids volume of 6.98% while 20 L/min produced a minimum total voids volume of 5.67% in the entire pipe. Slow flow rates resulted in a larger voids volume near the pipe wall. In contrast, faster flow rates produced insignificantly higher voids volume around pipe core. Generally, slower flow rates favoured the formation of higher total voids volume following sufficient steady time of wax crystal formation, producing larger voids areas in gelled waxy crude oil.

  2. Generation of nano-voids inside polylactide using femtosecond laser radiation

    Science.gov (United States)

    Viertel, Tina; Pabst, Linda; Olbrich, Markus; Ebert, Robby; Horn, Alexander; Exner, Horst

    2017-12-01

    The arrangement of nanometer-sized voids, induced by focusing intense laser radiation within transparent material can allow the generation of transparent components with dimensions in the micrometer to nanometre range due to internal contour cut and thus satisfy the progressive miniaturization of products in micro-optics and medical technologies. For further improvements in the precision of those components, a deep understanding of the involved processes during the interaction of laser radiation within the material is necessary. In this work, voids inside bulk polylactide (PLA), a bioabsorbable polymer, were generated using a femtosecond laser ( λ = 1030 nm, τH = 180 fs) with single and multiple pulse irradiation. The dependence of the spot size was examined by the use of four microscope objectives with focus radii of 4.9, 3.3, 2 and 1.2 µm. For the experiments, the pulse energy and focusing depth into the material were varied. The dimensions of the voids were experimentally determined as function of the intensity. Differences in the lateral and axial extents of the voids were obtained for different focus radii and focusing depths at same intensities. Furthermore, the intensity distribution of the laser radiation inside the material for the different focus radii and focusing depths, and their dependence on the lateral and axial sizes of the voids was simulated and compared with the experimental results.

  3. Study of pressure drop, void fraction and relative permeabilities of two phase flow through porous media

    International Nuclear Information System (INIS)

    Chu, W.; Dhir, V.K.; Marshall, J.

    1983-01-01

    An experimental investigation of two phase flow through porous layers formed of non-heated glass particles (nominal diameter 1 to 6 mm) has been made. Particulate bed depths of 30 cm and 70 cm were used. The effect of particle size, particle size distribution and bed porosity on void fraction and pressure drop through a particulate bed formed in a cylindrical test section has been investigated. The superficial velocity of liquid (water) is varied from 1.83 to 18.3 mm/s while the superficial velocity of gas (air) is varied from 0 to 68.4 mm/s. These superficial velocities were chosen so that pressure drop and void fraction measurement could be made for the porous layer in fixed and fluidized states. A model based on drift flux approach has been developed for the void fraction. Using the two phase friction pressure drop data, the relative permeabilities of the two phases have been concluded with void fraction. The void fraction and two phase friction pressure gradient in beds composed of mixtures of spherical particles as well as sharps of different nominal sizes have also been examined. It is found that the models for single size particles are also applicable to mixtures of particles if a mean particle diameter for the mixture is defined

  4. LMR design concepts for transuranic management in low sodium void worth cores

    International Nuclear Information System (INIS)

    Hill, R.N.

    1991-01-01

    The fuel cycle processing techniques and hard neuron spectrum of the Integral Fast Reactor (IFR) metal fuel cycle have favorable characteristics for the management of transuranics; and the wide range of breeding characteristics available in metal fuelled cores provides for flexibility in transuranic management strategy. Previous studies indicate that most design options which decrease the breeding ratio also show a decrease in sodium void worth; therefore, low void worths are achievable in transuranic burning (low breeding ratio) core designs. This paper describes numerous trade studies assessing various design options for a low void worth transuranic burner core. A flat annular core design appears to be a promising concept; the high leakage geometry yields a low breeding ratio and small sodium void worth. To allow flexibility in breeding characteristics, alternate design options which achieve fissile self-sufficiency are also evaluated. A self-sufficient core design which is interchangeable with the burner core and maintains a low sodium void worth is developed. 13 refs., 1 fig., 4 tabs

  5. Implementation of drift-flux model in artist and assessment to thetis void distribution

    International Nuclear Information System (INIS)

    Kim, H. C.; Yun, B. J.; Moon, S. K.; Jeong, J. J.; Lee, W. J.

    1998-01-01

    A system transient analysis code, ARTIST, based on the drift-flux model is being developed to enhance capability of predicting two-phase flow void distribution at low pressure and low flow conditions. The governing equations of the ARTIST code consist of three continuity equations (mixture, liquid, and noncondensibles), two energy equations (gas and mixture) and one mixture momentum euqation constituted with the drift-flux model. Area averaged one-dimensional conservation equations are established using the flow quality expressed in terms of the relative velocity. The relative velocity is obtained from the drift flux relationship. The Chexal-Lellouche void fraction correlation is used to provide the drift velocity and the concentration parameter. The implicit one-step method and the block elimination technique are employed as numerical solution scheme for the node-flowpath thermal-hydraulic network. In order to validate the ARIST code, the steady state void distributions of the THETIS boil-off tests are simulated. The axial void distributions calculated by the Chexal-Lellouche fraction correlation at low pressure and low flow are better than those of both the two-fluid model of RELAP5/MOD3 code and the homogeneous model. The drift-flux model of the ARTIST code is an efficient tool in predicting the void distribution of two-phase flow at low pressure and low flow condtions

  6. Newtonian self-gravitating system in a relativistic huge void universe model

    Energy Technology Data Exchange (ETDEWEB)

    Nishikawa, Ryusuke; Nakao, Ken-ichi [Department of Mathematics and Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka 558-8585 (Japan); Yoo, Chul-Moon, E-mail: ryusuke@sci.osaka-cu.ac.jp, E-mail: knakao@sci.osaka-cu.ac.jp, E-mail: yoo@gravity.phys.nagoya-u.ac.jp [Division of Particle and Astrophysical Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan)

    2016-12-01

    We consider a test of the Copernican Principle through observations of the large-scale structures, and for this purpose we study the self-gravitating system in a relativistic huge void universe model which does not invoke the Copernican Principle. If we focus on the the weakly self-gravitating and slowly evolving system whose spatial extent is much smaller than the scale of the cosmological horizon in the homogeneous and isotropic background universe model, the cosmological Newtonian approximation is available. Also in the huge void universe model, the same kind of approximation as the cosmological Newtonian approximation is available for the analysis of the perturbations contained in a region whose spatial size is much smaller than the scale of the huge void: the effects of the huge void are taken into account in a perturbative manner by using the Fermi-normal coordinates. By using this approximation, we derive the equations of motion for the weakly self-gravitating perturbations whose elements have relative velocities much smaller than the speed of light, and show the derived equations can be significantly different from those in the homogeneous and isotropic universe model, due to the anisotropic volume expansion in the huge void. We linearize the derived equations of motion and solve them. The solutions show that the behaviors of linear density perturbations are very different from those in the homogeneous and isotropic universe model.

  7. Measurement of the local void fraction at high pressures in a heating channel

    International Nuclear Information System (INIS)

    Martin, R.

    1969-01-01

    Void fraction measurements were made in two phase flow boiling systems at high pressures in a uniformly heated, rectangular channel with a high aspect ratio. The local void fraction values were calculated from measurements of the absorption of a thin collimated X-ray beam (2 mm x 0.05 mm). The mean void fraction in a horizontal section results from integration of the local values across the section. At a fixed measuring station the quality and- void fraction were varied by changing the heat flux, flow rate and pressure systematically. Two channels were used differing in length and thickness (150.8 cm x 5.3 cm x 0.2 cm and the significant features of this study are: -1) The void fraction measurements are among the first obtained at such high pressure (80 to 140 kg/cm 2 ); -2) In the experimental region under consideration the measurements are systematic and numerous enough to allow accurate interpolations: mass velocity from 50 to 220 g/cm 2 .s, heat flux from 40 to 170 W/cm 2 and calculated steam quality from -0.2 to 0.2; -3) Many tests were performed under local boiling conditions with the mean temperature of the fluid below the saturation temperature; and -4) These results were compared to the predictions of certain models presented in the literature and simple empirical formulae were developed to fit the experimental results. (author) [fr

  8. Near‐surface void detection using a seismic landstreamer and horizontal velocity and attenuation tomography

    Science.gov (United States)

    Buckley, Sean F.; Lane, John W.

    2012-01-01

    The detection and characterization of subsurface voids plays an important role in the study of karst formations and clandestine tunnels. Horizontal velocity and attenuation tomography (HVAT) using offset‐fan shooting and a towed seismic land streamer is a simple, rapid, minimally invasive method that shows promise for detecting near‐surface voids and providing information on the orientation of linear voids. HVAT surveys were conducted over a known subsurface steam tunnel on the University of Connecticut Depot Campus, Storrs, Connecticut. First‐arrival travel‐time and amplitude data were used to produce two‐dimensional (2D) horizontal (map view) velocity and attenuation tomograms. In addition, attenuation tomograms were produced based on normalized total trace energy (TTE). Both the velocity and TTE attenuation tomograms depict an anomaly consistent with the location and orientation of the known tunnel; the TTE method, however, requires significantly less processing time, and therefore may provide a path forward to semi‐automated, near real‐time detection of near‐surface voids. Further study is needed to assess the utility of the HVAT method to detect deeper voids and the effects of a more complex geology on HVAT results.

  9. Investigation of CTF void fraction prediction by ENTEK BM experiment data

    International Nuclear Information System (INIS)

    Hoang Minh Giang; Hoang Tan Hung; Nguyen Phu Khanh

    2015-01-01

    Recently, CTF, a version of COBRA-TF code is reviewed to validate its simulation models by several experiments such as Castellana 4x4 rod bundle, EPRI 5x5 bundle tests, PSBT bundle tests and TPTF experiment. These above experiments provide enthalpy, mass flux (Castellana), temperature (EPRI) and void fraction (PSBT, TPTF) at exit channel only. In order to simulate PWR rod bundle flow behavior, it is necessary to review CTF with more experiment in high pressure condition and it is found that the ENTEK BM facility is suitable for this purpose. The ENTEK BM facility is used to simulate Russia RBMK and VVER rod bundle two phase flow with pressure at 3 and 7 MPa and it gives measured void fraction distribution along the channel. This study focus on two points: (a) accuracy assessment between CTF void fraction distribution predictions versus experiment void fraction distributions and (b) investigation of void fraction prediction uncertainty from propagation of input deviations caused by measured accuracy. (author)

  10. Development of subchannel void measurement sensor and multidimensional two-phase flow dynamics in rod bundle

    International Nuclear Information System (INIS)

    Arai, T.; Furuya, M.; Kanai, T.; Shirakawa, K.

    2011-01-01

    An accurate subchannel database is crucial for modeling the multidimensional two-phase flow in a rod bundle and for validating subchannel analysis codes. Based on available reference, it can be said that a point-measurement sensor for acquiring void fractions and bubble velocity distributions do not infer interactions of the subchannel flow dynamics, such as a cross flow and flow distribution, etc. In order to acquire multidimensional two-phase flow in a 10×10 rod bundle with an o.d. of 10 mm and 3110 mm length, a new sensor consisting of 11-wire by 11-wire and 10-rod by 10-rod electrodes was developed. Electric potential in the proximity region between two wires creates a void fraction in the center subchannel region, like a so-called wire mesh sensor. A unique aspect of the devised sensor is that the void fraction near the rod surface can be estimated from the electric potential in the proximity region between one wire and one rod. The additional 400 points of void fraction and phasic velocity in 10×10 bundle can therefore be acquired. The devised sensor exhibits the quasi three-dimensional flow structures, i.e. void fraction, phasic velocity and bubble chord length distributions. These quasi three-dimensional structures exhibit the complexity of two-phase flow dynamics, such as coalescence and the breakup of bubbles in transient phasic velocity distributions. (author)

  11. Critical velocities for deflagration and detonation triggered by voids in a REBO high explosive

    Energy Technology Data Exchange (ETDEWEB)

    Herring, Stuart Davis [Los Alamos National Laboratory; Germann, Timothy C [Los Alamos National Laboratory; Jensen, Niels G [Los Alamos National Laboratory

    2010-01-01

    The effects of circular voids on the shock sensitivity of a two-dimensional model high explosive crystal are considered. We simulate a piston impact using molecular dynamics simulations with a Reactive Empirical Bond Order (REBO) model potential for a sub-micron, sub-ns exothermic reaction in a diatomic molecular solid. The probability of initiating chemical reactions is found to rise more suddenly with increasing piston velocity for larger voids that collapse more deterministically. A void with radius as small as 10 nm reduces the minimum initiating velocity by a factor of 4. The transition at larger velocities to detonation is studied in a micron-long sample with a single void (and its periodic images). The reaction yield during the shock traversal increases rapidly with velocity, then becomes a prompt, reliable detonation. A void of radius 2.5 nm reduces the critical velocity by 10% from the perfect crystal. A Pop plot of the time-to-detonation at higher velocities shows a characteristic pressure dependence.

  12. Calculational benchmark comparisons for a low sodium void worth actinide burner core design

    International Nuclear Information System (INIS)

    Hill, R.N.; Kawashima, M.; Arie, K.; Suzuki, M.

    1992-01-01

    Recently, a number of low void worth core designs with non-conventional core geometries have been proposed. Since these designs lack a good experimental and computational database, benchmark calculations are useful for the identification of possible biases in performance characteristics predictions. In this paper, a simplified benchmark model of a metal fueled, low void worth actinide burner design is detailed; and two independent neutronic performance evaluations are compared. Calculated performance characteristics are evaluated for three spatially uniform compositions (fresh uranium/plutonium, batch-averaged uranium/transuranic, and batch-averaged uranium/transuranic with fission products) and a regional depleted distribution obtained from a benchmark depletion calculation. For each core composition, the flooded and voided multiplication factor, power peaking factor, sodium void worth (and its components), flooded Doppler coefficient and control rod worth predictions are compared. In addition, the burnup swing, average discharge burnup, peak linear power, and fresh fuel enrichment are calculated for the depletion case. In general, remarkably good agreement is observed between the evaluations. The most significant difference is predicted performance characteristics is a 0.3--0.5% Δk/(kk) bias in the sodium void worth. Significant differences in the transmutation rate of higher actinides are also observed; however, these differences do not cause discrepancies in the performing predictions

  13. Experimental investigation of the effect of injected interstitials on void formation

    International Nuclear Information System (INIS)

    Badger, B. Jr.; Plumton, D.L.; Zinkle, S.J.; Sindelar, R.L.; Kulcinski, G.L.; Dodd, R.A.; Wolfer, W.G.

    1984-01-01

    Pure nickel, a pure 316-type stainless steel (P7) and two high strength copper alloys have been irradiated with either 14-MeV nickel or copper ions to a peak damage level of 50 dpa (K = 0.8) at homologous temperatures ranging from 0.4 to 0.6 Tm. The irradiated foils have been examined in cross section in an electron microscope. The injected interstitial effect on the suppression of the measured void densities in Ni and P7 was found to increase with decreasing temperature. The comparison of these results with nucleation theory shows good qualitative agreement. Quantitative discrepancies are attributed to diffusional spreading of point defects and to the presence of impurity atoms in the matrix. A copper alloy irradiated at 300 0 C showed a small heterogeneous void density characteristic of the high temperature end of the void swelling regime, while no voids formed in the alloys irradiated > 400 0 C. This result is in excellent agreement with nucleation theory which indicates the void swelling regime in ion-irradiated, low impurity copper should be less than 300 0 C (0.42 Tm)

  14. Materials characterization of free volume and void properties by two-dimensional positron annihilation lifetime spectroscopy

    Science.gov (United States)

    Chen, Hongmin; Van Horn, J. David; Jean, Y. C.; Hung, Wei-Song; Lee, Kueir-Rarn

    2013-04-01

    Positron annihilation lifetime spectroscopy (PALS) has been widely used to determine the free volume and void properties in polymeric materials. Recently, a two dimensional positron annihilation lifetime spectroscopy (2DPALS) system has been developed for membrane applications. The system measures the coincident signals between the lifetime and the energy which could separate the 2γ and 3γ annihilations and improve the accuracy in the determination of the free volume and void properties. When 2D-PALS is used in coupling with a variable mono-energy slow positron beam, it could be applied to a variety of material characterization. Results of free volumes and voids properties in a multi-layer polymer membrane characterized using 2D-PALS are presented.

  15. Definition of the large-scale extinction - A new solution of the central void phenomenon

    Science.gov (United States)

    Grabinska, T.

    1989-11-01

    The Estonian School results (Joeveer et al., 1977) concerning the galaxy cell structure were partly interpreted in the spirit of Zwicky's idea on intergalactic dust, although it remained a speculation. The same view was proposed also by Rudnicki to explain the evident deficit of galaxies in the central region (central void) of the Jagellonian field. Zieba (1974) tried to explain the effect of the central void in terms of an interstellar obscuration. This explanation of the central void (CV) in terms of a possible intergalactic dust was opened up again in 1984 and 1985; and its merits considered by Rudnicki et al. (1989). Now a new solution of the problem of the CV mystery is presented.

  16. Design aspects of gamma densitometers for void fraction measurements in small scale two-phase flows

    International Nuclear Information System (INIS)

    Chan, A.M.C.; Banerjee, S.

    1981-01-01

    Design procedure for a single-beam gamma densitometer operated in the count mode is described. The design is simple, compact and is particularly suited for small scale two-phase flow experiments with thin-metal walled or non-metallic test sections. The choice of gamma sources, scintillators and signal processing systems is discussed. The procedure has been applied by the authors in the design of densitometers for two transient experiments: refilling and rewetting experiments and flow boiling experiments. Good average void measurements were obtained for relatively fast transients. It has also been shown that some useful flow parameters other than void fractions can be obtained if two or more densitometers are used, eg, the average rewetting and entrained liquid velocities in the refilling and rewetting experiments, and the average void velocity in the flow boiling experiments. (orig.)

  17. Experimental investigation of void coalescence in a dual phase steel using X-ray tomography

    International Nuclear Information System (INIS)

    Landron, C.; Bouaziz, O.; Maire, E.; Adrien, J.

    2013-01-01

    In situ tensile tests were carried out during X-ray microtomography imaging of a smooth and a notched specimen of dual phase steel. The void coalescence was first qualitatively observed and quantitative data concerning this damage step was then acquired. The void coalescence criteria of Brown and Embury and of Thomason were then tested against the experimental data at both the macroscopic and local levels. Although macroscopic implementation of the criteria gave acceptable results, the local approach was probably closest to the real nature of void coalescence, because it takes into account local coalescence events observed experimentally before final fracture. The correlation between actual coalescing couples of cavities and local implementation of the two criteria showed that the Thomason criterion is probably the best adapted to predict the local coalescence events in the case of the material studied

  18. The discrete cones methods for two-dimensional neutral particle transport problems with voids

    International Nuclear Information System (INIS)

    Watanabe, Y.; Maynard, C.W.

    1983-01-01

    One of the most widely applied deterministic methods for time-independent, two-dimensional neutron transport calculations is the discrete ordinates method (DSN). The DSN solution, however, fails to be accurate in a void due to the ray effect. In order to circumvent this drawback, the authors have been developing a novel approximation: the discrete cones method (DCN), where a group of particles in a cone are simultaneously traced instead of particles in discrete directions for the DSN method. Programs, which apply to the DSN method in a non-vacuum region and the DCN method in a void, have been written for transport calculations in X-Y coordinates. The solutions for test problems demonstrate mitigation of the ray effect in voids without loosing the computational efficiency of the DSN method

  19. Average void fraction measurement in a two-phase vertical flow

    International Nuclear Information System (INIS)

    Mello, R.E.F. de; Behar, M.R.; Martines, E.W.

    1975-01-01

    The utilization of the radioactive tracer technique to measure the void fraction in a two phase flow air-water is presented. The radioactive tracer used was a salt of Br-82. The water flow rate varied between 0,4 and 2,0 m 3 /h, and the air flow rate between 0,2 and 1,0 m 3 /h. The resulting measured void fraction were between 0,05 and 0,32. These void fraction values were compared with those ones calculated with the measured flow rates and by use of empirical formulas, using different methods. After a convenient choice of the radioactive isotope, the measurements didn't present any special problem. The results have shown a good accordance with the values calculated by the formulas of R. Roumy, but was not possible yet to conclude, about the convenience of application and the grade of confidence of this method

  20. Self-organization of voids, gas bubbles and dislocation patterns under irradiation

    International Nuclear Information System (INIS)

    Dubinko, V.I.; Turkin, A.A.

    1993-01-01

    In the present paper three examples of self-organization in solids under irradiation are considered on the basis of original mechanisms, namely, the ordering of voids in void lattices under high temperature irradiation, the alignment of gas bubbles in bubble lattices under low-temperature gas atom implantation, and the formation of superdislocations (one-dimensional pile-ups of dislocation loops) and other dislocation patterns in the regimes of medium and high temperature irradiation. The ordering of cavities (i.e.voids or gas bubbles) is shown to arise due to a dissipative interaction between cavities induced by the interstitial dislocation loop absorption and punching, respectively, which represent anisotropic mechanisms of atomic transport. The dislocation patterning is shown to be driven by the dependence of dislocation bias for absorption of self-interstitial atoms on the dislocation arrangement. (author). 57 refs., 1 tab., 12 figs