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Sample records for stress fields existed

  1. Heat induced fracturing of rock in an existing uniaxial stress field

    International Nuclear Information System (INIS)

    Mathis, J.; Stephansson, O.; Bjarnason, B.; Hakami, H.; Herdocia, A.; Mattila, U.; Singh, U.

    1986-01-01

    This study was initiated under the premise that it may be possible to determine the state of stress in the earth's crust by heat induced fracturing of the rock surrounding a borehole. The theory involved is superficially simple, involving the superposition of the stress field around a borehole due to the existing virgin stresses and the uniform stress field of thermally loaded rock as induced by a heater. Since the heat stress field is uniform, varying only in magnitude and gradient as a function of heater input, fracturing should be controlled by the non-uniform virgin stress field. To determine if the method was, in fact, feasible, a series of laboratory test were conducted. These tests consisted of physically loading center drilled cubes of rock, 0.3 m on a side, uniaxially from 0 to 25 MPa. The blocks were then thermally loaded with a nominally rated 3.7 kW heater until failure occurred. Results from these laboratory tests were then compared to analytical studies of the problem, i.e., finite element and discrete theoretical analysis. Overall, results were such that the method is likely eliminated as a stress measurement technique. The immediate development of a thermal compressive zone on the borehole wall overlaps the tensile zone created by the uniaxial stress field, forcing the failure is thus controlled largely by the power input of the heater, being retarded by the small compressive stresses genrated by the uniaxial stress field. This small retardation effect is of such low magnitude that the retardation effect is of such low magnitude that the fracture time is relatively insensitive to the local virgin stress field. (authors)

  2. Evaluate existing radiation fields

    International Nuclear Information System (INIS)

    Aldrich, J.M.; Haggard, D.L.; Endres, G.W.R.; Fix, J.J.

    1981-01-01

    Knowledge of the spectrum of energies for beta, gamma, and neutron radiation experienced in the field is crucial to the proper interpretation of personnel dose. Calibration sources and techniques are determined on the basis of their relationship to field exposure. Selected techniques were used to obtain neutron, photon, and beta energy spectra data at several Hanford locations. Four neutron energy spectra and dose measurement methods were used: (1) multisphere spectrometer system; (2) tissue equivalent proportional counter (TEPC); (3) RASCAL (9'' to 3'' sphere ratios); and (4) helium-3 neutron spectrometer. Gamma spectroscopy was done using standard techniques. A specially designed TLD dosimeter was used to obtain beta spectrum measurements. The design and use of each of these instruments is described in the body of this report. Data collected and analyzed for each of the Hanford locations are included

  3. Analysis of field errors in existing undulators

    International Nuclear Information System (INIS)

    Kincaid, B.M.

    1990-01-01

    The Advanced Light Source (ALS) and other third generation synchrotron light sources have been designed for optimum performance with undulator insertion devices. The performance requirements for these new undulators are explored, with emphasis on the effects of errors on source spectral brightness. Analysis of magnetic field data for several existing hybrid undulators is presented, decomposing errors into systematic and random components. An attempts is made to identify the sources of these errors, and recommendations are made for designing future insertion devices. 12 refs., 16 figs

  4. Electric foot shock stress adaptation: Does it exist or not?

    Science.gov (United States)

    Bali, Anjana; Jaggi, Amteshwar Singh

    2015-06-01

    Stress adaptation is a protective phenomenon against repeated stress exposure and is characterized by a decreased responsiveness to a repeated stress stimulus. The adaptation is associated with a complex cascade of events, including the changes in behavior, neurotransmitter and gene expression levels. The non-adaptation or maladaptation to stress may underlie the affective disorders, such as anxiety, depression and post-traumatic stress disorder (PTSD). Electric foot shock is a complex stressor, which includes both physical and emotional components. Unlike immobilization, restraint and cold immersion stress, the phenomenon of stress adaptation is not very well defined in response to electric foot shock. A number of preclinical studies have reported the development of adaptation to electric foot shock stress. However, evidence also reveals the non-adaptive behavior in response to foot shocks. The distinct adaptive/non-adaptive responses may be possibly influenced by the type, intensity, and duration of the stress. The present review discusses the existence or non-existence of adaptation to electric foot shock stress along with possible mechanism. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Non-existence of limit cycles for planar vector fields

    Directory of Open Access Journals (Sweden)

    Jaume Gine

    2014-03-01

    Full Text Available This article presents sufficient conditions for the non-existence of limit cycles for planar vector fields. Classical methods for the nonexistence of limit cycles are connected with the theory developed here.

  6. CTCP temperature fields and stresses

    Directory of Open Access Journals (Sweden)

    Minjiang Zhang

    2017-11-01

    Full Text Available Cross-tensioned concrete pavements (CTCPs are used in the construction of continuous Portland cement concrete pavements. They eliminate the need for transverse joints and also restrict cracking of the pavement. A CTCP consists of three components, namely, the CTCP slab, the sand sliding layer (SSL, and the cement-stabilized macadam base, from top to down. The retard-bonded tendons (RBTs of the CTCP slab are arranged diagonally. In the present study, a detailed 3D finite element model was developed and used to examine the temperature fields and stresses of a CTCP by thermal-mechanical coupling analysis, and the results were compared with field measurements. The model investigations revealed that, under typical cloudless summer conditions, the temperature field of the CTCP varied nonlinearly with both time and depth. The resultant step-type temperature gradient of the CTCP represents a significant deviation from that of a conventional pavement and impacts the thermal contact resistance of the SSL. It was found that the SSL could effectively reduce the temperature stresses in the CTCP, and that the residual temperature stresses were effectively resisted by the staged cross-tensioned RBTs. The potential problem areas in the vicinity of the temperature stresses were also investigated by the finite element method and field tests. Keywords: Portland cement concrete pavement, Prestressed concrete pavement, Temperature stress, Temperature field, Finite element method, Retard-bonded tendon

  7. Four-dimensional boson field theory. II. Existence

    International Nuclear Information System (INIS)

    Baker, G.A. Jr.

    1986-01-01

    The existence of the continuum, quantum field theory found by Baker and Johnson [G. A. Baker, Jr. and J. D. Johnson, J. Phys. A 18, L261 (1985)] to be nontrivial is proved rigorously. It is proved to satisfy all usual requirements of such a field theory, except rotational invariance. Currently known information is consistent with rotational invariance however. Most of the usual properties of other known Euclidean boson quantum field theories hold here, in a somewhat weakened form. Summability of the sufficiently strongly ultraviolet cutoff bare coupling constant perturbation series is proved as well as a nonzero radius of convergence for high-temperature expansions of the corresponding continuous-spin Ising model. The description of the theory by these two series methods is shown to be equivalent. The field theory is probably not asymptotically free

  8. On the problem of existence of quantum field theory

    International Nuclear Information System (INIS)

    Chaichian, M.; Hayashi, M.; Nelipa, N.F.; Pukhov, E.A.

    1978-01-01

    Existence of quantum field theory is considered for the four-dimensional phi 3 -model. The mathematical tool of contraction mapping principle is used to investigate the question of existence of solution for the infinite system of coupled equations for the Green functions of the theory in the Euclidean region. Formulation of the problem for this model with one divergent part is interesting in itself and provides the first attempt towards the study of other renormalizable quantum field theory models with infinite number of divergent graphs. For sufficiently small values of coupling constant, the theory has a unique solution for the truncated system of equations for the Green functions. However, for the complete, infinite set of equations, the Banach fixed point theorem admits a solution only when the coupling constant tends to zero. Possible reasons for such a result are discussed. (author)

  9. Existence of longitudinal waves in pre-stressed anisotropic elastic ...

    Indian Academy of Sciences (India)

    waves is truly longitudinal. Longitudinal wave in an anisotropic elastic medium is defined as the wave motion in which the particle motion (i.e., the. Keywords. General anisotropy; elastic stiffness; pre-stress; group velocity; ray direction; longitudinal waves; polarization. J. Earth Syst. Sci. 118, No. 6, December 2009, pp. 677– ...

  10. The maximum possible stress intensity factor for a crack in an unknown residual stress field

    International Nuclear Information System (INIS)

    Coules, H.E.; Smith, D.J.

    2015-01-01

    Residual and thermal stress fields in engineering components can act on cracks and structural flaws, promoting or inhibiting fracture. However, these stresses are limited in magnitude by the ability of materials to sustain them elastically. As a consequence, the stress intensity factor which can be applied to a given defect by a self-equilibrating stress field is also limited. We propose a simple weight function method for determining the maximum stress intensity factor which can occur for a given crack or defect in a one-dimensional self-equilibrating stress field, i.e. an upper bound for the residual stress contribution to K I . This can be used for analysing structures containing defects and subject to residual stress without any information about the actual stress field which exists in the structure being analysed. A number of examples are given, including long radial cracks and fully-circumferential cracks in thick-walled hollow cylinders containing self-equilibrating stresses. - Highlights: • An upper limit to the contribution of residual stress to stress intensity factor. • The maximum K I for self-equilibrating stresses in several geometries is calculated. • A weight function method can determine this maximum for 1-dimensional stress fields. • Simple MATLAB scripts for calculating maximum K I provided as supplementary material.

  11. Stress field of a dislocating inclined fault

    Energy Technology Data Exchange (ETDEWEB)

    Huang, F.; Wang, T.

    1980-02-01

    Analytical expressions are derived for the stress field caused by a rectangular dislocating fault of an arbitrary dip in a semi-infinite elastic medium for the case of unequal Lame constants. The results of computations for the stress fields on the ground surface of an inclined strike-slip and an inclined dip-slip fault are represented by contour maps. The effects of Poisson Ratio of the medium, the dip angle, upper and lower boundaries of the faults on the stress field at surface have been discussed. As an application, the contour maps for shear stress and hydrostatic stress of near fields of the Tonghai (1970), Haicheng (1975) and Tangshan (1976) earthquakes have been calculated and compared with the spatial distributions of strong aftershocks of these earthquakes. It is found that most of the strong aftershocks are distributed in the regions of tensional stress, where the hydrostatic stress is positive.

  12. Stress field of a dislocating inclined fault

    Energy Technology Data Exchange (ETDEWEB)

    Huang, F.; Wang, T.

    1980-02-01

    In this paper, analytical expressions of the stress field given rise by a rectangular dislocating fault of an arbitrary dip in a semi-infinite elastic medium for the case of unequal Lame constants are derived. The results of computations for the stress fields on the ground surface of an inclined strike-slip and an inclined dip-slip fault are represented by contour maps. The effects of the Poisson Ratio of the medium, the dip angle, upper and lower boundaries of the faults on the stress field at the surface have been discussed. As an application, the contour maps for shear stress and hydrostatic stress of near fields of the Tonghai (1970), Haicheng, (1975) and Tangshan (1976) earthquakes have been calculated and compared with the spatial distributions of strong aftershocks of these earthquakes. It is found that most of the strong aftershocks are distributed in the regions of tensional stress where the hydrostatic stress is positive.

  13. Investigations of some rock stress measuring techniques and the stress field in Norway

    Energy Technology Data Exchange (ETDEWEB)

    Hanssen, Tor Harald

    1997-12-31

    Rock stresses are important to the safe construction and operation of all man-made structures in rock, whether In mining, civil or petroleum engineering. The crucial issue is their relative magnitude and orientation. This thesis develops equipment and methods for further rock stress assessment and reevaluates existing overcoring rock stress measurements, and relates this information to the present geological setting. Both laboratory work and field work are involved. In the field, rock stresses are measured by the overcoring and the hydraulic fracturing technique. An observation technique for assessing likely high stresses is developed. The field data refer to several hydropower projects and to some offshore hydrocarbon fields. The principal sections are: (1) Tectonic setting in the western Fennoscandia, (2) Triaxial rock stress measurements by overcoring using the NTH cell (a strain gauge cell developed at the Norwegian technical university in Trondheim and based on the CSIR cell of the South African Council for Scientific and Industrial Research), (3) Laboratory testing of the NTH cell, (4) Quality ranking of stresses measured by the NTH cell, (4) Recalculated rock stresses and implications to the regional stress field, (5) Hydraulic fracturing stress measurements. 113 refs., 98 figs., 62 tabs.

  14. Investigations of some rock stress measuring techniques and the stress field in Norway

    Energy Technology Data Exchange (ETDEWEB)

    Hanssen, Tor Harald

    1998-12-31

    Rock stresses are important to the safe construction and operation of all man-made structures in rock, whether In mining, civil or petroleum engineering. The crucial issue is their relative magnitude and orientation. This thesis develops equipment and methods for further rock stress assessment and reevaluates existing overcoring rock stress measurements, and relates this information to the present geological setting. Both laboratory work and field work are involved. In the field, rock stresses are measured by the overcoring and the hydraulic fracturing technique. An observation technique for assessing likely high stresses is developed. The field data refer to several hydropower projects and to some offshore hydrocarbon fields. The principal sections are: (1) Tectonic setting in the western Fennoscandia, (2) Triaxial rock stress measurements by overcoring using the NTH cell (a strain gauge cell developed at the Norwegian technical university in Trondheim and based on the CSIR cell of the South African Council for Scientific and Industrial Research), (3) Laboratory testing of the NTH cell, (4) Quality ranking of stresses measured by the NTH cell, (4) Recalculated rock stresses and implications to the regional stress field, (5) Hydraulic fracturing stress measurements. 113 refs., 98 figs., 62 tabs.

  15. Stress field models from Maxwell stress functions: southern California

    Science.gov (United States)

    Bird, Peter

    2017-08-01

    The lithospheric stress field is formally divided into three components: a standard pressure which is a function of elevation (only), a topographic stress anomaly (3-D tensor field) and a tectonic stress anomaly (3-D tensor field). The boundary between topographic and tectonic stress anomalies is somewhat arbitrary, and here is based on the modeling tools available. The topographic stress anomaly is computed by numerical convolution of density anomalies with three tensor Green's functions provided by Boussinesq, Cerruti and Mindlin. By assuming either a seismically estimated or isostatic Moho depth, and by using Poisson ratio of either 0.25 or 0.5, I obtain four alternative topographic stress models. The tectonic stress field, which satisfies the homogeneous quasi-static momentum equation, is obtained from particular second derivatives of Maxwell vector potential fields which are weighted sums of basis functions representing constant tectonic stress components, linearly varying tectonic stress components and tectonic stress components that vary harmonically in one, two and three dimensions. Boundary conditions include zero traction due to tectonic stress anomaly at sea level, and zero traction due to the total stress anomaly on model boundaries at depths within the asthenosphere. The total stress anomaly is fit by least squares to both World Stress Map data and to a previous faulted-lithosphere, realistic-rheology dynamic model of the region computed with finite-element program Shells. No conflict is seen between the two target data sets, and the best-fitting model (using an isostatic Moho and Poisson ratio 0.5) gives minimum directional misfits relative to both targets. Constraints of computer memory, execution time and ill-conditioning of the linear system (which requires damping) limit harmonically varying tectonic stress to no more than six cycles along each axis of the model. The primary limitation on close fitting is that the Shells model predicts very sharp

  16. Field Demonstraton of Existing Microhole Coiled Tubing Rig (MCTR) Technology

    Energy Technology Data Exchange (ETDEWEB)

    Kent Perry; Samih Batarseh; Sheriff Gowelly; Thomas Hayes

    2006-05-09

    The performance of an advanced Microhole Coiled Tubing Rig (MCTR) has been measured in the field during the drilling of 25 test wells in the Niobrara formation of Western Kansas and Eastern Colorado. The coiled tubing (CT) rig designed, built and operated by Advanced Drilling Technologies (ADT), was documented in its performance by GTI staff in the course of drilling wells ranging in depth from 500 to nearly 3,000 feet. Access to well sites in the Niobrara for documenting CT rig performance was provided by Rosewood Resources of Arlington, VA. The ADT CT rig was selected for field performance evaluation because it is one of the most advanced commercial CT rig designs that demonstrate a high degree of process integration and ease of set-up and operation. Employing an information collection protocol, data was collected from the ADT CT rig during 25 drilling events that encompassed a wide range of depths and drilling conditions in the Niobrara. Information collected included time-function data, selected parametric information indicating CT rig operational conditions, staffing levels, and field observations of the CT rig in each phase of operation, from rig up to rig down. The data obtained in this field evaluation indicates that the ADT CT rig exhibited excellent performance in the drilling and completion of more than 25 wells in the Niobrara under varied drilling depths and formation conditions. In the majority of the 25 project well drilling events, ROP values ranged between 300 and 620 feet per hour. For all but the lowest 2 wells, ROP values averaged approximately 400 feet per hour, representing an excellent drilling capability. Most wells of depths between 500 and 2,000 feet were drilled at a total functional rig time of less than 16 hours; for wells as deep at 2,500 to 3,000 feet, the total rig time for the CT unit is usually well under one day. About 40-55 percent of the functional rig time is divided evenly between drilling and casing/cementing. The balance of

  17. Global Geopotential Energy & Stress Field

    DEFF Research Database (Denmark)

    Schiffer, Christian; Nielsen, S.B.

    of the oceanic lithosphere. An entire modelling of the shallow Geopotential Energy is hereby approached, not taking into account possible deeper signals but all lithospheric signals for the subsequent stress calculation. Therefore a global lithospheric density model is necessary to calculate the corresponding...... response to Geopotential Energy and the Geoid. A linearized inverse method fits a lithospheric reference model to reproduce measured data sets, such as topography and surface heat flow, while assuming isostasy and solving the steady state heat equation. A FEM code solves the equations of equilibrium...

  18. Magnetic field aberration induced by cycle stress

    International Nuclear Information System (INIS)

    Yang En; Li Luming; Chen Xing

    2007-01-01

    Magneto-mechanical effect has been causing people's growing interest because of its relevance to several technology problems. One of them is the variation of surface magnetic field induced by stress concentration under the geomagnetic field. It can be used as an innovative, simple and convenient potential NDE method, called as magnetic memory method. However, whether and how this can be used as a quantitative measurement method, is still a virginal research field where nobody sets foot in. In this paper, circle tensile stress within the elastic region was applied to ferromagnetic sample under geomagnetic field. Experiment results on the relation between surface magnetic field and elastic stress were presented, and a simple model was derived. Simulation of the model was reconciled with the experimental results. This can be of great importance for it provides a brighter future for the promising Magnetic Memory NDE method-the potential possibility of quantitative measurement

  19. Osteomalacia and coxa vara. An unusual co-existence for femoral neck stress fracture

    Directory of Open Access Journals (Sweden)

    Kerim Sariyilmaz

    2015-01-01

    Conclusion: Joint and bone pain without any trauma should be investigated and bone metabolism disorders should be kept in mind. There might be co-existing factors related with stress fractures, and they must be treated simultaneously.

  20. Point defects dynamics in a stress field

    International Nuclear Information System (INIS)

    Smetniansky de De Grande, Nelida.

    1989-01-01

    The dependence of anisotropic defect diffusion on stress is studied for a hexagonal close packed (hcp) material under irradiation and uniaxially stressed. The diffusion is described as a discrete process of thermally activated jumps. It is shown that the presence of an external stress field enhances the intrinsic anisotropic diffusion, being this variation determined by the defect dipole tensors' symmetry in the equilibrium and saddle point configurations. Also, the point defect diffusion equations to sinks, like edge dislocations and spherical cavities, are solved and the sink strengths are calculated. The conclusion is that the dynamics of the interaction between defects and sinks is controlled by the changes in diffusivity induced by stress fields. (Author) [es

  1. The mutual influence of krypton implantation and pre-existing stress states in polycrystalline alpha titanium

    Energy Technology Data Exchange (ETDEWEB)

    Nsengiyumva, S. [Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa); Department of Physics, Kigali Institute of Education, P.O. Box 5039 Kigali (Rwanda)], E-mail: schadrack.nsengiyumva@uct.ac.za; Ntsoane, T.P. [Nuclear Energy Corporation of South Africa (NECSA), P.O. Box 582 (South Africa); Raji, A.T. [Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa); Topic, M. [iThemba LABS, Somerset West 7129 (South Africa); Kellermann, G. [Laboratorio Nacional de Luz Sincrotron (LNLS), Campinas (Brazil); Riviere, J.P. [Laboratoire de Physique des Materiaux UMR6630-CNRS, 86960 (France); Britton, D.T.; Haerting, M. [Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa)

    2009-08-15

    The stress profile in polycrystalline titanium implanted with krypton ions at different fluences has been determined using synchrotron radiation diffraction. For each fluence, the krypton profile has been measured using Rutherford backscattering geometry. The results were compared to model calculations obtained from the SRIM 2008 computer code. A strong stress relaxation was found for high fluence implantation, whereas for low fluence implantation an additional source of tensile stress was introduced in the near surface region. The projected range of the implanted krypton was significantly reduced compared to the expected range. A possible cause of this discrepancy is the drift of implanted ions under the influence of the pre-existing stress gradient.

  2. The mutual influence of krypton implantation and pre-existing stress states in polycrystalline alpha titanium

    International Nuclear Information System (INIS)

    Nsengiyumva, S.; Ntsoane, T.P.; Raji, A.T.; Topic, M.; Kellermann, G.; Riviere, J.P.; Britton, D.T.; Haerting, M.

    2009-01-01

    The stress profile in polycrystalline titanium implanted with krypton ions at different fluences has been determined using synchrotron radiation diffraction. For each fluence, the krypton profile has been measured using Rutherford backscattering geometry. The results were compared to model calculations obtained from the SRIM 2008 computer code. A strong stress relaxation was found for high fluence implantation, whereas for low fluence implantation an additional source of tensile stress was introduced in the near surface region. The projected range of the implanted krypton was significantly reduced compared to the expected range. A possible cause of this discrepancy is the drift of implanted ions under the influence of the pre-existing stress gradient.

  3. PDX toroidal field coils stress analysis

    International Nuclear Information System (INIS)

    Nikodem, Z.D.; Smith, R.A.

    1975-01-01

    A method used in the stress analysis of the PDX toroidal field coil is developed. A multilayer coil design of arbitrary dimensions in the shape of either a circle or an oval is considered. The analytical model of the coil and the supporting coil case with connections to the main support structure is analyzed using the finite element technique. The three dimensional magnetic fields and the non-uniform body forces which are a loading condition on a coil due to toroidal and poloidal fields are calculated. The method of analysis permits rapid and economic evaluations of design changes in coil geometry as well as in coil support structures. Some results pertinent to the design evolution and their comparison are discussed. The results of the detailed stress analysis of the final coil design due to toroidal field, poloidal field and temperature loads are presented

  4. On the existence of polynomial Lyapunov functions for rationally stable vector fields

    DEFF Research Database (Denmark)

    Leth, Tobias; Wisniewski, Rafal; Sloth, Christoffer

    2018-01-01

    This paper proves the existence of polynomial Lyapunov functions for rationally stable vector fields. For practical purposes the existence of polynomial Lyapunov functions plays a significant role since polynomial Lyapunov functions can be found algorithmically. The paper extents an existing result...... on exponentially stable vector fields to the case of rational stability. For asymptotically stable vector fields a known counter example is investigated to exhibit the mechanisms responsible for the inability to extend the result further....

  5. Stress field reconstruction in an active mudslide

    Science.gov (United States)

    Baroň, Ivo; Kernstocková, Markéta; Melichar, Rostislav

    2017-07-01

    Meso-scale structures from gravitational slope deformation observed in landslides and deep-seated gravitational slope failures are very similar to those of endogenous ones. Therefore we applied palaeostress analysis of fault-slip data for reconstructing the stress field of an active mudslide in Pechgraben, Austria. This complex compound landslide has developed in clayey colluvium and shale and was activated after a certain period of dormancy in June 2013. During the active motion on June 12, 2013, 73 fault-slip traces at 9 locations were measured within the landslide body. The heterogeneous fault-slip data were processed in term of palaeostresses, the reconstructed palaeostress tensor being characterized by the orientations of the three principal stress axes and the stress ratio (which provides the shape of the stress ellipsoid). The results of the palaeostress analysis were compared to airborne laser scan digital terrain models that revealed dynamics and superficial displacements of the moving mass prior and after our survey. The results were generally in good agreement with the observed landslide displacement pattern and with the anticipated stress regime according to Mohr-Coulomb failure criteria and Anderson's theory. The compressional regime was mostly registered at the toe in areas, where a compressional stress field is expected during previous mass-movement stages, or at margins loaded by subsequent landslide bodies from above. On the other hand, extension regimes were identified at the head scarps of secondary slides, subsequently on bulged ridges at the toe and in the zone of horst-and-graben structures in the lower central part of the main landslide body, where the basal slip surface probably had locally convex character. Strike-slip regimes, as well as oblique normal or oblique reverse regimes were observed at the lateral margins of the landslide bodies. The directions of principal stresses could be used as markers of landslide movement directions

  6. Electromagnetic field and mechanical stress analysis code

    International Nuclear Information System (INIS)

    1978-01-01

    Analysis TEXMAGST is a two stage linear finite element code for the analysis of static magnetic fields in three dimensional structures and associated mechanical stresses produced by the anti J x anti B forces within these structures. The electromagnetic problem is solved in terms of magnetic vector potential A for a given current density anti J as curl 1/μ curl anti A = anti J considering the magnetic permeability as constant. The Coulombian gauge (div anti A = o) was chosen and was implemented through the use of Lagrange multipliers. The second stage of the problem - the calculation of mechanical stresses in the same three dimensional structure is solved by using the same code with few modifications - through a restart card. Body forces anti J x anti B within each element are calculated from the solution of the first stage run and represent the input to the second stage run which will give the solution for the stress problem

  7. On the existence of pointlike localized fields in conformally invariant quantum physics

    International Nuclear Information System (INIS)

    Joerss, M.

    1992-11-01

    In quantum field theory the existence of pointlike localizable objects called 'fields' is a preassumption. Since charged fields are in general not observable this situation is unsatisfying from a quantum physics point of view. Indeed in any quantum theory the existence of fields should follow from deeper physical concepts and more natural first principles like stability, locality, causality and symmetry. In the framework of algebraic quantum field theory with Haag-Kastler nets of local observables this is presented for the case of conformal symmetry in 1+1 dimensions. Conformal fields are explicitly constructed as limits of observables localized in finite regions of space-time. These fields then allow to derive a geometric identification of modular operators, Haag duality in the vacuum sector, the PCT-theorem and an equivalence theorem for fields and algebras. (orig.)

  8. Existence of solutions for Hamiltonian field theories by the Hamilton-Jacobi technique

    International Nuclear Information System (INIS)

    Bruno, Danilo

    2011-01-01

    The paper is devoted to prove the existence of a local solution of the Hamilton-Jacobi equation in field theory, whence the general solution of the field equations can be obtained. The solution is adapted to the choice of the submanifold where the initial data of the field equations are assigned. Finally, a technique to obtain the general solution of the field equations, starting from the given initial manifold, is deduced.

  9. Conformal Haag-Kastler nets, pointlike localized fields and the existence of operator product expansions

    International Nuclear Information System (INIS)

    Fredenhagen, K.; Joerss, M.

    1994-10-01

    Starting from a chiral conformal Haag-Kastler net on 2 dimensional Minkowski space we construct associated pointlike localized fields. This amounts to a proof of the existence of operator product expansions. We derive the result in two ways. One is based on the geometrical identification of the modular structure, the other depends on a ''conformal cluster theorem'' of the conformal two-point-functions in algebraic quantum field theory. The existence of the fields then implies important structural properties of the theory, as PCT-invariance, the Bisognano-Wichmann identification of modular operators, Haag duality and additivity. (orig.)

  10. On the existence of classical solutions for stationary extended mean field games

    KAUST Repository

    Gomes, Diogo A.; Patrizi, Stefania; Voskanyan, Vardan

    2014-01-01

    In this paper we consider extended stationary mean-field games, that is mean-field games which depend on the velocity field of the players. We prove various a-priori estimates which generalize the results for quasi-variational mean-field games in Gomes et al. (2012). In addition we use adjoint method techniques to obtain higher regularity bounds. Then we establish the existence of smooth solutions under fairly general conditions by applying the continuity method. When applied to standard stationary mean-field games as in Lasry and Lions (2006), Gomes and Sanchez-Morgado (2011) or Gomes et al. (2012) this paper yields various new estimates and regularity properties not available previously. We discuss additionally several examples where the existence of classical solutions can be proved. © 2013 Elsevier Ltd. All rights reserved.

  11. On the existence of classical solutions for stationary extended mean field games

    KAUST Repository

    Gomes, Diogo A.

    2014-04-01

    In this paper we consider extended stationary mean-field games, that is mean-field games which depend on the velocity field of the players. We prove various a-priori estimates which generalize the results for quasi-variational mean-field games in Gomes et al. (2012). In addition we use adjoint method techniques to obtain higher regularity bounds. Then we establish the existence of smooth solutions under fairly general conditions by applying the continuity method. When applied to standard stationary mean-field games as in Lasry and Lions (2006), Gomes and Sanchez-Morgado (2011) or Gomes et al. (2012) this paper yields various new estimates and regularity properties not available previously. We discuss additionally several examples where the existence of classical solutions can be proved. © 2013 Elsevier Ltd. All rights reserved.

  12. Existence for stationary mean-field games with congestion and quadratic Hamiltonians

    KAUST Repository

    Gomes, Diogo A.

    2015-09-03

    Here, we investigate the existence of solutions to a stationary mean-field game model introduced by J.-M. Lasry and P.-L. Lions. This model features a quadratic Hamiltonian and congestion effects. The fundamental difficulty of potential singular behavior is caused by congestion. Thanks to a new class of a priori bounds, combined with the continuation method, we prove the existence of smooth solutions in arbitrary dimensions. © 2015 Springer Basel

  13. On the Existence of Solutions for Stationary Mean-Field Games with Congestion

    KAUST Repository

    Evangelista, David

    2017-09-11

    Mean-field games (MFGs) are models of large populations of rational agents who seek to optimize an objective function that takes into account their location and the distribution of the remaining agents. Here, we consider stationary MFGs with congestion and prove the existence of stationary solutions. Because moving in congested areas is difficult, agents prefer to move in non-congested areas. As a consequence, the model becomes singular near the zero density. The existence of stationary solutions was previously obtained for MFGs with quadratic Hamiltonians thanks to a very particular identity. Here, we develop robust estimates that give the existence of a solution for general subquadratic Hamiltonians.

  14. Existence of weak solutions to first-order stationary mean-field games with Dirichlet conditions

    KAUST Repository

    Ferreira, Rita; Gomes, Diogo A.; Tada, Teruo

    2018-01-01

    In this paper, we study first-order stationary monotone mean-field games (MFGs) with Dirichlet boundary conditions. While for Hamilton--Jacobi equations Dirichlet conditions may not be satisfied, here, we establish the existence of solutions of MFGs that satisfy those conditions. To construct these solutions, we introduce a monotone regularized problem. Applying Schaefer's fixed-point theorem and using the monotonicity of the MFG, we verify that there exists a unique weak solution to the regularized problem. Finally, we take the limit of the solutions of the regularized problem and using Minty's method, we show the existence of weak solutions to the original MFG.

  15. On the Existence of Solutions for Stationary Mean-Field Games with Congestion

    KAUST Repository

    Evangelista, David; Gomes, Diogo A.

    2017-01-01

    Mean-field games (MFGs) are models of large populations of rational agents who seek to optimize an objective function that takes into account their location and the distribution of the remaining agents. Here, we consider stationary MFGs with congestion and prove the existence of stationary solutions. Because moving in congested areas is difficult, agents prefer to move in non-congested areas. As a consequence, the model becomes singular near the zero density. The existence of stationary solutions was previously obtained for MFGs with quadratic Hamiltonians thanks to a very particular identity. Here, we develop robust estimates that give the existence of a solution for general subquadratic Hamiltonians.

  16. Existence of weak solutions to first-order stationary mean-field games with Dirichlet conditions

    KAUST Repository

    Ferreira, Rita

    2018-04-19

    In this paper, we study first-order stationary monotone mean-field games (MFGs) with Dirichlet boundary conditions. While for Hamilton--Jacobi equations Dirichlet conditions may not be satisfied, here, we establish the existence of solutions of MFGs that satisfy those conditions. To construct these solutions, we introduce a monotone regularized problem. Applying Schaefer\\'s fixed-point theorem and using the monotonicity of the MFG, we verify that there exists a unique weak solution to the regularized problem. Finally, we take the limit of the solutions of the regularized problem and using Minty\\'s method, we show the existence of weak solutions to the original MFG.

  17. Existence for stationary mean-field games with congestion and quadratic Hamiltonians

    KAUST Repository

    Gomes, Diogo A.; Mitake, Hiroyoshi

    2015-01-01

    Here, we investigate the existence of solutions to a stationary mean-field game model introduced by J.-M. Lasry and P.-L. Lions. This model features a quadratic Hamiltonian and congestion effects. The fundamental difficulty of potential singular

  18. Existence of 121 limit cycles in a perturbed planar polynomial Hamiltonian vector field of degree 11

    International Nuclear Information System (INIS)

    Wang, S.; Yu, P.

    2006-01-01

    In this article, a systematic procedure has been explored to studying general Z q -equivariant planar polynomial Hamiltonian vector fields for the maximal number of closed orbits and the maximal number of limit cycles after perturbation. Following the procedure by taking special consideration of Z 12 -equivariant vector fields of degree 11, the maximal of 99 closed orbits are obtained under a well-defined coefficient group. Consequently, perturbation parameter control in limit cycle computation leads to the existence of 121 limit cycles in the perturbed Hamiltonian vector field, which gives rise to the lower bound of Hilbert number of 11th-order systems as H(11) ≥ 11 2 . Two conjectures are proposed regarding the maximal number of closed orbits for equivariant polynomial Hamiltonian vector fields and the maximal number of limit cycles bifurcated from the well defined Hamiltonian vector fields after perturbation

  19. Macroscopic electrical field distribution and field-induced surface stresses of needle-shaped field emitters

    Energy Technology Data Exchange (ETDEWEB)

    Moy, Charles K.S., E-mail: charles.moy@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); ARC Centre of Excellence for Design in Light Metals, The University of Sydney, Sydney, NSW 2006 (Australia); School of Civil Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Ranzi, Gianluca [ARC Centre of Excellence for Design in Light Metals, The University of Sydney, Sydney, NSW 2006 (Australia); School of Civil Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Petersen, Timothy C. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); Ringer, Simon P. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); ARC Centre of Excellence for Design in Light Metals, The University of Sydney, Sydney, NSW 2006 (Australia)

    2011-05-15

    One major concern since the development of the field ion microscope is the mechanical strength of the specimens. The macroscopic shape of the imaging tip greatly influences field-induced stresses and there is merit in further study of this phenomenon from a classical perspective. Understanding the geometrical, as opposed to localized electronic, factors that affect the stress might improve the quality and success rate of atom probe experiments. This study uses macroscopic electrostatic principles and finite element modelling to investigate field-induced stresses in relation to the shape of the tip. Three two-dimensional idealized models are considered, namely hyperbolic, parabolic and sphere-on-orthogonal-cone; the shapes of which are compared to experimental tips prepared by electro-polishing. Three dimensional morphologies of both a nano-porous and single-crystal aluminium tip are measured using electron tomography to quantitatively test the assumption of cylindrical symmetry for electro-polished tips. The porous tip was prepared and studied to demonstrate a fragile specimen for which such finite element studies could determine potential mechanical failure, prior to any exhaustive atom probe investigation. -- Research highlights: {yields} We use electrostatic principles and finite element to model field-induced stresses. {yields} We study two-dimensional idealized needle-shaped field emitters. {yields} Stress distribution of hyperbolic, parabolic and sphere-on-orthogonal-cone tips mapped. {yields} Electron tomography to obtain the morphology of three-dimensional aluminium tips. {yields} Studies of the morphology of the porous tip demonstrate a fragile specimen.

  20. Short-time existence of solutions for mean-field games with congestion

    KAUST Repository

    Gomes, Diogo A.

    2015-11-20

    We consider time-dependent mean-field games with congestion that are given by a Hamilton–Jacobi equation coupled with a Fokker–Planck equation. These models are motivated by crowd dynamics in which agents have difficulty moving in high-density areas. The congestion effects make the Hamilton–Jacobi equation singular. The uniqueness of solutions for this problem is well understood; however, the existence of classical solutions was only known in very special cases, stationary problems with quadratic Hamiltonians and some time-dependent explicit examples. Here, we demonstrate the short-time existence of C∞ solutions for sub-quadratic Hamiltonians.

  1. Defining the Field of Existence of Shrouded Blades in High-Speed Gas Turbines

    Science.gov (United States)

    Belousov, Anatoliy I.; Nazdrachev, Sergeiy V.

    2018-01-01

    This work provides a method for determining the region of existence of banded blades of gas turbines for aircraft engines based on the analytical evaluation of tensile stresses in specific characteristic sections of the blade. This region is determined by the set of values of the parameter, which forms the law of distribution of the cross-sectional area of the cross-sections along the height of the airfoil. When seven independent parameters (gas-dynamic, structural and strength) are changed, the choice of the best option is proposed at the early design stage. As an example, the influence of the dimension of a turbine on the domain of the existence of banded blades is shown.

  2. Redesigning existing transcranial magnetic stimulation coils to reduce energy: application to low field magnetic stimulation

    Science.gov (United States)

    Wang, Boshuo; Shen, Michael R.; Deng, Zhi-De; Smith, J. Evan; Tharayil, Joseph J.; Gurrey, Clement J.; Gomez, Luis J.; Peterchev, Angel V.

    2018-06-01

    Objective. To present a systematic framework and exemplar for the development of a compact and energy-efficient coil that replicates the electric field (E-field) distribution induced by an existing transcranial magnetic stimulation coil. Approach. The E-field generated by a conventional low field magnetic stimulation (LFMS) coil was measured for a spherical head model and simulated in both spherical and realistic head models. Then, using a spherical head model and spatial harmonic decomposition, a spherical-shaped cap coil was synthesized such that its windings conformed to a spherical surface and replicated the E-field on the cortical surface while requiring less energy. A prototype coil was built and electrically characterized. The effect of constraining the windings to the upper half of the head was also explored via an alternative coil design. Main results. The LFMS E-field distribution resembled that of a large double-cone coil, with a peak field strength around 350 mV m‑1 in the cortex. The E-field distributions of the cap coil designs were validated against the original coil, with mean errors of 1%–3%. The cap coil required as little as 2% of the original coil energy and was significantly smaller in size. Significance. The redesigned LFMS coil is substantially smaller and more energy-efficient than the original, improving cost, power consumption, and portability. These improvements could facilitate deployment of LFMS in the clinic and potentially at home. This coil redesign approach can also be applied to other magnetic stimulation paradigms. Finally, the anatomically-accurate E-field simulation of LFMS can be used to interpret clinical LFMS data.

  3. The co-existence of depression, anxiety and post-traumatic stress symptoms in the perinatal period: A systematic review.

    Science.gov (United States)

    Agius, Andee; Xuereb, Rita Borg; Carrick-Sen, Debbie; Sultana, Roberta; Rankin, Judith

    2016-05-01

    to identify and appraise the current international evidence regarding the presence and prevalence of the co-existence of depression, anxiety and post-traumatic stress symptoms in the antenatal and post partum period. using a list of keywords, Medline, CINHAL, Cochrane Library, EMBASE, PsychINFO, Web of Science and the Index of Theses and Conference Proceedings (Jan 1960 - Jan 2015) were systematically searched. Experts in the field were contacted to locate papers that were in progress or in press. Reference lists from relevant review articles were searched. Inclusion criteria included full papers published in English reporting concurrent depression, anxiety and post-traumatic stress symptoms in pregnant and post partum women. A validated data extraction review tool was used. 3424 citations were identified. Three studies met the full inclusion criteria. All reported findings in the postnatal period. No antenatal studies were identified. The prevalence of triple co-morbidity was relatively low ranging from 2% to 3%. triple co-morbidity does occur, although the prevalence appears to be low. Due to the presentation of complex symptoms, women with triple co-morbidity are likely to be difficult to identify, diagnose and treat. Clinical staff should be aware of the potential of complex symptomatology. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. The stress field and transient stress generation at shallow depths in the Canadian shield

    International Nuclear Information System (INIS)

    Hasegawa, H.S.

    1984-01-01

    A prominent feature of the stress field in eastern Canada is the high horizontal stress at shallow depths. Possible causative factors to this shallow stress field are remanent stresses from a previous tectonic orogeny, plate tectonic stresses and glacial-related stresses (glacial drag and flexual stress). The inherent difficulty in differentiating residual from current stress is one of the reasons why the relative contributions to the stress field from the phenomena described above are not properly understood. Maximum stress-strain changes an underground vault is likely to encounter from natural phenomena should occur when the periphery of the advancing or retreating glacier is near the vault. Theoretical calculations indicate that lithospheric flexure, differential postglacial uplift and possibly glacial drag may be able to generate significant horizontal stresses around a vault. In order to calculate the earthquake potential of these induced stress changes, the ambient tectonic stress field should also be included and a suitable failure criterion (e.g. Coulomb-Mohr) used. For earthquakes to generate appreciable stress-strain concentrations near a vault; the seismic signal must contain appreciable energy at appropriate frequencies (wavelengths comparable to vault dimensions) and be of appreciable duration; the particle velocity must be high (> 10 cm/s), induced strain is a function of particle velocity; and, the hypocentre must be less than half a fault length from the vault for residual deformation (strain and tilt) to be significant. The most severe case is when the causative fault intersects the vault

  5. Evaluation of the residual stress field in a steam generator end tube after hydraulic expansion

    International Nuclear Information System (INIS)

    Thiel, F.; Kang, S.; Chabrerie, J.

    1994-01-01

    This paper presents a finite element elastoplastic model of a nuclear steam generator end tube, used to evaluate the residual stress field existing after hydraulic expansion of the tube into the tubesheet of the heat exchanger. This model has been tested against an experimental hydraulic expansion, carried out on full scale end tubes. The operation was monitored thanks to strain gages localized on the outer surface of the tubes, subjected to elastoplastic deformations. After a presentation of the expansion test and the description of the numerical model, the authors compare the stress fields issues from the gages and from the model. The comparison shows a good agreement. These results allow them to calculate the stress field resulting from normal operating conditions, while taking into account a correct initial state of stress. Therefore the authors can improve the understanding of the behavior of a steam generator end tube, with respect to stress corrosion cracking and crack growth

  6. Mean-Field Scenario for the Athermal Creep Dynamics of Yield-Stress Fluids

    Science.gov (United States)

    Liu, Chen; Martens, Kirsten; Barrat, Jean-Louis

    2018-01-01

    We develop a theoretical description based on an existent mean-field model for the transient dynamics prior to the steady flow of yielding materials. The mean-field model not only reproduces the experimentally observed nonlinear time dependence of the shear-rate response to an external stress, but also allows for the determination of the different physical processes involved in the onset of the reacceleration phase after the initial slowing down and a distinct fluidization phase. The fluidization time displays a power-law dependence on the distance of the applied stress to an age-dependent yield stress, which is not universal but strongly dependent on initial conditions.

  7. Superposition of Stress Fields in Diametrically Compressed Cylinders

    Directory of Open Access Journals (Sweden)

    João Augusto de Lima Rocha

    Full Text Available Abstract The theoretical analysis for the Brazilian test is a classical plane stress problem of elasticity theory, where a vertical force is applied to a horizontal plane, the boundary of a semi-infinite medium. Hypothesizing a normal radial stress field, the results of that model are correct. Nevertheless, the superposition of three stress fields, with two being based on prior results and the third based on a hydrostatic stress field, is incorrect. Indeed, this work shows that the Cauchy vectors (tractions are non-vanishing in the parallel planes in which the two opposing vertical forces are applied. The aim of this work is to detail the process used in the construction of the theoretical model for the three stress fields used, with the objective being to demonstrate the inconsistency often stated in the literature.

  8. Effect of co-existing plant specie on soil microbial activity under heavy metal stress

    International Nuclear Information System (INIS)

    Nwuche, C. O.; Ugoji, E. O.

    2010-01-01

    The influence of plant primary compounds on the activity of soil microbial communities under heavy metal stress was studied in a pot-culture field experiment conducted in a green house. Amaranthus spinosus was cultivated in an agricultural soil previously amended in the laboratory with solutions of different trace elements in two separate treatment modes: singly and in combination. Culture-independent metabolism based indices such as the rate of carbon and nitrogen mineralization, microbial biomass carbon and soil basal respiration were monitored fortnightly over a period of six weeks. Result shows that plant detritus have significant modifying effect on soil microbe-metal interactions. Data on microbial and biochemical processes in the respective mesocosms did not vary from control; not even in mesocosms containing very high concentrations of copper, zinc and nickel. The soil microbial biomass carbon and the rate of carbon and nitrogen cycling were not impeded by the respective metal treatment while the respiration responses increased as a result of increase in metabolic activity of the soil microbes. The plant based substrates enabled the soil microflora to resist high metal contamination because of its tendency to absorb large amounts of inorganic cations.

  9. Existence of charges and mass-spliting in relativistic quantum field theory

    International Nuclear Information System (INIS)

    Gal-Ezer, E.; Horwitz, L.P.

    1976-01-01

    The existence of charge operators associated with integrals of local densities in the (Wightman) framework of quantum field theory, in the presence of explicit symmetry breaking, can be demonstrated in certain cases. Their construction, in terms of null-plane integrals, is rather delicate. The possibility that a finite number of null-plane charges, which includes the Poincare generators, close on an algebra whose irreducible representations contain particles with different masses is considered; domain problems are shown to invalidate the basic hypotheses of the O'Raifeartaigh theorem. Null-plane Fourier transforms, which enter into the discussion of current algebra at infinite momentum, are also studied. It is shown that slns behavior is the maximal growth of high energy off mass shell amplitudes consistent with the existence of null-plane charges and null-plane Fourier transforms. Under the assumption that asymptotic states exist, these results also hold in the case of spontaneously broken chiral symmetry, with massless pseudoscalar Goldstone bosons

  10. Existence of a component corotating with the earth in high-latitude disturbance magnetic fields

    Science.gov (United States)

    Suzuki, A.; Kim, J. S.; Sugiura, M.

    1982-01-01

    A study of the data from the high-latitude North American IMS network of magnetic stations suggests that there is a component in substorm perturbations that corotates with the earth. It is as yet not certain whether the existence of this component stems from the corotation of a part of the magnetospheric plasma involved in the substorm mechanism or if it is a 'phase change' resulting from the control of the substorm manifestations by the earth's main magnetic field which is not axially symmetric. There are other geophysical phenomena showing a persistence of longitudinal variations corotating with the earth. These phenomena are of significance for a better understanding of ionosphere-magnetosphere coupling.

  11. On Definitions and Existence of Combinatorial Entropy of 2d Fields

    DEFF Research Database (Denmark)

    Forchhammer, Søren Otto; Shtarkov, Yuri; Justesen, Jørn

    1998-01-01

    Different definitions of combinatorial entropy is presented and conditions for their existence examined.......Different definitions of combinatorial entropy is presented and conditions for their existence examined....

  12. Pre-existing high glucocorticoid receptor number predicting development of posttraumatic stress symptoms after military deployment

    NARCIS (Netherlands)

    van Zuiden, Mirjam; Geuze, Elbert; Willemen, Hanneke L. D. M.; Vermetten, Eric; Maas, Mirjam; Heijnen, Cobi J.; Kavelaars, Annemieke

    2011-01-01

    The development of posttraumatic stress disorder (PTSD) is influenced by preexisting vulnerability factors. The authors aimed at identifying a preexisting biomarker representing a vulnerability factor for the development of PTSD. To that end, they determined whether the dexamethasone binding

  13. Stress Prediction for Distributed Structural Health Monitoring Using Existing Measurements and Pattern Recognition.

    Science.gov (United States)

    Lu, Wei; Teng, Jun; Zhou, Qiushi; Peng, Qiexin

    2018-02-01

    The stress in structural steel members is the most useful and directly measurable physical quantity to evaluate the structural safety in structural health monitoring, which is also an important index to evaluate the stress distribution and force condition of structures during structural construction and service phases. Thus, it is common to set stress as a measure in steel structural monitoring. Considering the economy and the importance of the structural members, there are only a limited number of sensors that can be placed, which means that it is impossible to obtain the stresses of all members directly using sensors. This study aims to develop a stress response prediction method for locations where there are insufficent sensors, using measurements from a limited number of sensors and pattern recognition. The detailed improved aspects are: (1) a distributed computing process is proposed, where the same pattern is recognized by several subsets of measurements; and (2) the pattern recognition using the subset of measurements is carried out by considering the optimal number of sensors and number of fusion patterns. The validity and feasibility of the proposed method are verified using two examples: the finite-element simulation of a single-layer shell-like steel structure, and the structural health monitoring of the space steel roof of Shenzhen Bay Stadium; for the latter, the anti-noise performance of this method is verified by the stress measurements from a real-world project.

  14. Modelling of the Global Geopotential Energy & Stress Field

    DEFF Research Database (Denmark)

    Schiffer, Christian; Nielsen, S.B.

    Lateral density and topography variations yield in and important contribution to the lithospheric stress field. The leading quantity is the Geopotential Energy, the integrated lithostatic pressure in a rock column. The horizontal gradient of this quantity is related to horizontal stresses through...... the Equations of equilibrium of stresses. The Geopotential Energy furthermore can be linearly related to the Geoid under assumption of local isostasy. Satellite Geoid measurements contain, however, also non-isostatic deeper mantle responses of long wavelength. Unfortunately, high-pass filtering of the Geoid...... flow in the presence of local isostasy and a steady state geotherm. Subsequently we use a FEM code to solve the Equations of equilibrium of stresses for a three dimensional elastic shell. The modelled results are shown and compared with the global stress field and other publications....

  15. Stress field modelling from digital geological map data

    Science.gov (United States)

    Albert, Gáspár; Barancsuk, Ádám; Szentpéteri, Krisztián

    2016-04-01

    To create a model for the lithospheric stress a functional geodatabase is required which contains spatial and geodynamic parameters. A digital structural-geological map is a geodatabase, which usually contains enough attributes to create a stress field model. Such a model is not accurate enough for engineering-geological purposes because simplifications are always present in a map, but in many cases maps are the only sources for a tectonic analysis. The here presented method is designed for field geologist, who are interested to see the possible realization of the stress field over the area, on which they are working. This study presents an application which can produce a map of 3D stress vectors from a kml-file. The core application logic is implemented on top of a spatially aware relational database management system. This allows rapid and geographically accurate analysis of the imported geological features, taking advantage of standardized spatial algorithms and indexing. After pre-processing the map features in a GIS, according to the Type-Property-Orientation naming system, which was described in a previous study (Albert et al. 2014), the first stage of the algorithm generates an irregularly spaced point cloud by emitting a pattern of points within a user-defined buffer zone around each feature. For each point generated, a component-wise approximation of the tensor field at the point's position is computed, derived from the original feature's geodynamic properties. In a second stage a weighted moving average method calculates the stress vectors in a regular grid. Results can be exported as geospatial data for further analysis or cartographic visualization. Computation of the tensor field's components is based on the implementation of the Mohr diagram of a compressional model, which uses a Coulomb fracture criterion. Using a general assumption that the main principal stress must be greater than the stress from the overburden, the differential stress is

  16. Full-field stress determination in photoelasticity with phase shifting technique

    Science.gov (United States)

    Guo, Enhai; Liu, Yonggang; Han, Yongsheng; Arola, Dwayne; Zhang, Dongsheng

    2018-04-01

    Photoelasticity is an effective method for evaluating the stress and its spatial variations within a stressed body. In the present study, a method to determine the stress distribution by means of phase shifting and a modified shear-difference is proposed. First, the orientation of the first principal stress and the retardation between the principal stresses are determined in the full-field through phase shifting. Then, through bicubic interpolation and derivation of a modified shear-difference method, the internal stress is calculated from the point with a free boundary along its normal direction. A method to reduce integration error in the shear difference scheme is proposed and compared to the existing methods; the integration error is reduced when using theoretical photoelastic parameters to calculate the stress component with the same points. Results show that when the value of Δx/Δy approaches one, the error is minimum, and although the interpolation error is inevitable, it has limited influence on the accuracy of the result. Finally, examples are presented for determining the stresses in a circular plate and ring subjected to diametric loading. Results show that the proposed approach provides a complete solution for determining the full-field stresses in photoelastic models.

  17. Field instrumentation for hydrofracturing stress measurements

    International Nuclear Information System (INIS)

    Bjarnason, Bjarni; Torikka, Arne.

    1989-08-01

    A recently developed system for rock stress measurements by the hydraulic fracturing method is documented in detail. The new equipment is intended for measurement in vertical or nearvertical boreholes, down to a maximum depth of 1000 m. The minimum borehole, diameter required is 56 mm. Downhole instrumentation comprises a straddle packer assembly for borehole fracturing, equipment for determination of fracture orientations and a pressure transducer. The downhole tools are operated by means of a multihose system, containing high pressure hydraulic tubings, signal cable and carrying wire into one hose unit. The surface components of the equipment include a system for generation and control of water pressures up to approximately 75 MPa, an hydraulically operated drum for the multihose and a data acquisition system. All surface instrumentation is permanently mounted on a truck, which also serves as power source for the instrumentation. In addition to the description of instrumentation, the theoretical fundament and the testing procedures associated with the hydraulic fracturing method are briefly outlined

  18. Determining the stress field in active volcanoes using focal mechanisms

    Directory of Open Access Journals (Sweden)

    Bruno Massa

    2016-11-01

    Full Text Available Stress inversion of seismological datasets became an essential tool to retrieve the stress field of active tectonics and volcanic areas. In particular, in volcanic areas, it is able to put constrains on volcano-tectonics and in general in a better understanding of the volcano dynamics. During the last decades, a wide range of stress inversion techniques has been proposed, some of them specifically conceived to manage seismological datasets. A modern technique of stress inversion, the BRTM, has been applied to seismological datasets available at three different regions of active volcanism: Mt. Somma-Vesuvius (197 Fault Plane Solutions, FPSs, Campi Flegrei (217 FPSs and Long Valley Caldera (38,000 FPSs. The key role of stress inversion techniques in the analysis of the volcano dynamics has been critically discussed. A particular emphasis was devoted to performances of the BRTM applied to volcanic areas.

  19. Numerical analysis of interacting cracks in biaxial stress field

    International Nuclear Information System (INIS)

    Kovac, M.; Cizelj, L.

    1999-01-01

    The stress corrosion cracks as seen for example in PWR steam generator tubing made of Inconel 600 usually produce highly irregular kinked and branched crack patterns. Crack initialization and propagation depends on stress state underlying the crack pattern. Numerical analysis (such as finite element method) of interacting kinked and branched cracks can provide accurate solutions. This paper discusses the use of general-purpose finite element code ABAQUS for evaluating stress fields at crack tips of interacting complex cracks. The results obtained showed reasonable agreement with the reference solutions and confirmed use of finite elements in such class of problems.(author)

  20. Field Guide for Testing Existing Photovoltaic Systems for Ground Faults and Installing Equipment to Mitigate Fire Hazards

    Energy Technology Data Exchange (ETDEWEB)

    Brooks, William [Brooks Engineering, Vacaville, CA (United States); Basso, Thomas [National Renewable Energy Lab. (NREL), Golden, CO (United States); Coddington, Michael [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-10-01

    Ground faults and arc faults are the two most common reasons for fires in photovoltaic (PV) arrays and methods exist that can mitigate the hazards. This report provides field procedures for testing PV arrays for ground faults, and for implementing high resolution ground fault and arc fault detectors in existing and new PV system designs.

  1. Investigations in thermal fields and stress fields induced by electron beam welding

    International Nuclear Information System (INIS)

    Basile, G.

    1979-12-01

    This document presents the thermal study of electron beam welding and identifies stresses and strains from welding: description of the operating principles of the electron gun and characterization of various welding parameters, examination of the temperature fields during electron beam welding development of various mathematic models and comparison with experimental results, measurement and calculation of stresses and strains in the medium plane of the welding assembly, residual stresses analysis [fr

  2. Existence of optimal controls for systems governed by mean-field ...

    African Journals Online (AJOL)

    In this paper, we study the existence of an optimal control for systems, governed by stochastic dierential equations of mean-eld type. For non linear systems, we prove the existence of an optimal relaxed control, by using tightness techniques and Skorokhod selection theorem. The optimal control is a measure valued process ...

  3. The use of high altitude remote sensing in determining existing vegetation and monitoring ecological stress

    Science.gov (United States)

    Foster, K.; Garcia, A.

    1972-01-01

    High altitude color and multispectral black and white photography was used to survey existing vegetation and soil conditions on the Empire Ranch where large scale development will soon begin. Utilizing stereo pairs of the high altitude color photography, four vegetation classifications were discernable as a function of topography and foliage characteristics. In contrast to the undeveloped Ranch, the same photography was used to detect environmental changes in the Tucson metropolitan area as a result of rapid urbanization. The most prevalent change related to development is the removal of vegetation in high density areas to allow for housing starts. Erosion then occurs where vegetation has been removed.

  4. Micromagnetic insight into a magnetoreceptor in birds: existence of magnetic field amplifiers in the beak

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Greiner, Walter

    2009-01-01

    The Earth's magnetic field provides an important source of directional information for many living organisms, especially birds, but the sensory receptor responsible for magnetic field detection still has to be identified. Recently, magnetic iron oxide particles were detected in dendritic endings...... of the ophthalmic nerves in the skin of the upper beak of homing pigeons and were shown to fulfill the special prerequisites of a biological receptor. Here we study the proposed receptor theoretically and formulate the criteria for which it becomes operational and can be used for registering the weak magnetic...... fields as, e.g., the geomagnetic field, by a bird....

  5. Recent tectonic stress field, active faults and geothermal fields (hot-water type) in China

    Science.gov (United States)

    Wan, Tianfeng

    1984-10-01

    It is quite probable that geothermal fields of the hot-water type in China do not develop in the absence of recently active faults. Such active faults are all controlled by tectonic stress fields. Using the data of earthquake fault-plane solutions, active faults, and surface thermal manifestations, a map showing the recent tectonic stress field, and the location of active faults and geothermal fields in China is presented. Data collected from 89 investigated prospects with geothermal manifestations indicate that the locations of geothermal fields are controlled by active faults and the recent tectonic stress field. About 68% of the prospects are controlled by tensional or tensional-shear faults. The angle between these faults and the direction of maximum compressive stress is less than 45°, and both tend to be parallel. About 15% of the prospects are controlled by conjugate faults. Another 14% are controlled by compressive-shear faults where the angle between these faults and the direction maximum compressive stress is greater than 45°.

  6. Study of the characteristics of crust stress field in East China by inversion of stress tensor

    International Nuclear Information System (INIS)

    Huilan, Z.; Rugang, D.

    1991-12-01

    This paper combines the search procedure with the optimization procedure to inverse the average stress tensor, and applies this method to study the crustal stress field using data of the solution of P wave first motion. By dealing with the data of Haicheng, Tangshan, Xingtai, Anyang, Liyang, Taiwan, Fujian and Guangdong areas, we obtain the characteristics of crust stress field of East China. The directions of the principal pressure stress always possess a small dip angle, but the azimuths vary from NEE (in north part of East China) to SEE (in the south part). This frame probably is related to the push-extrusive effects of the northwestern Pacific plate from NEE and the Philippine plate from SEE. (author). 5 refs, 8 figs, 4 tabs

  7. Photoelastic analyses of stresses in toroidal magnetic field coils

    International Nuclear Information System (INIS)

    Pih, H.

    1977-02-01

    Several two-dimensional photoelastic stress analyses were made on models of circular and oval toroidal magnetic field coils for fusion reactors. The circumferential variation of each coil's in-plane magnetic force was simulated by applying different pressures to 16 segmented regions of the inner surface of the models. One special loading fixture was used for the model of each shape and size. Birefringence and isoclinic angles were measured in a transmission polariscope at selected points on the loaded model. Boundary stresses in the cases of known boundary conditions were determined directly from the isochromatics. Separate principal stresses were calculated using the combination of photoelastic information and isopachic data obtained by the electrical analogy method from the solution of Laplace's equation. Comparisons were made between experimental results and those computed using the finite element method. The stress distribution between theoretical and experimental agrees very well, although the finite element method yielded slightly higher stresses than the photoelastic method; further work is needed to resolve this difference. In this investigation several variations of coil geometry and methods of support were evaluated. Based on experimental results, optimum structural designs of toroidal field coils were recommended

  8. Effect of oil-pipelines existed in HVTL corridor on the electric field distribution

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, H.M. [College of Technological Studies, Kuwait (Kuwait). Dept. of Electrical Engineering

    2007-07-01

    The overhead transmission of large amounts of electricity over long distances requires high transmission voltages which can generate high electric fields that may have harmful effects on both human and animals. Therefore, corridors or right-of-way are left on both sides along the route of transmission lines. Overhead power transmission lines need strips of land to be designated as rights-of-way. These strips of land can also support other uses such as pipelines, railroads and highways. The primary purpose for minimizing the field effects of high voltage AC lines is to reduce the electric field at ground level. This study investigated the effects of oil-pipelines running parallel to the lines in the rights-of-way corridors on the electric fields generated from high voltage electrical networks in Kuwait. In order to examine the impact of certain design parameters on the electric field distribution near the ground surface, this study varied the oil pipelines diameter, the proximity of the pipeline from the transmission line center and the number of pipelines. The objective was to determine if the amount of land which is required as right-of-way can be reduced. This study also examined the effect of two parallel oil pipelines on the field distribution. Both pipelines were separated by a given distance and ran parallel to the transmission line conductors. The charge simulation method (CSM) was used to simulate and model both the conductors of the transmission lines and the oil-pipelines. Graphs for the electric field distribution profiles at the ground surface, at transmission line conductors' surfaces and at the surfaces of the oil pipelines were presented and evaluated for each scenario. 10 refs., 12 figs.

  9. Existence of solutions for the anti-plane stress for a new class of “strain-limiting” elastic bodies

    KAUST Repository

    Bulí ček, Miroslav; Má lek, Josef; Rajagopal, K. R.; Walton, Jay R.

    2015-01-01

    © 2015, Springer-Verlag Berlin Heidelberg. The main purpose of this study is to establish the existence of a weak solution to the anti-plane stress problem on V-notch domains for a class of recently proposed new models that could describe elastic materials in which the stress can increase unboundedly while the strain yet remains small. We shall also investigate the qualitative properties of the solution that is established. Although the equations governing the deformation that are being considered share certain similarities with the minimal surface problem, the boundary conditions and the presence of an additional model parameter that appears in the equation and its specific range makes the problem, as well as the result, different from those associated with the minimal surface problem.

  10. Existence of solutions for the anti-plane stress for a new class of “strain-limiting” elastic bodies

    KAUST Repository

    Bulíček, Miroslav

    2015-04-21

    © 2015, Springer-Verlag Berlin Heidelberg. The main purpose of this study is to establish the existence of a weak solution to the anti-plane stress problem on V-notch domains for a class of recently proposed new models that could describe elastic materials in which the stress can increase unboundedly while the strain yet remains small. We shall also investigate the qualitative properties of the solution that is established. Although the equations governing the deformation that are being considered share certain similarities with the minimal surface problem, the boundary conditions and the presence of an additional model parameter that appears in the equation and its specific range makes the problem, as well as the result, different from those associated with the minimal surface problem.

  11. Does there exist a sensible quantum theory of an ''algebra-valued'' scalar field?

    International Nuclear Information System (INIS)

    Anco, S.C.; Wald, R.M.

    1989-01-01

    Consider a scalar field phi in Minkowski spacetime, but let phi be valued in an associative, commutative algebra openA rather than openR. One may view the resulting theory as describing a collection of coupled real scalar fields. At the classical level, theories of this type are completely well behaved and have a global symmetry group which is a nontrivial enlargement of the Poincare group. (They are analogs of the new class of gauge theories for massless spin-2 fields found recently by one of us, whose gauge group is a nontrivial enlargement of the usual diffeomorphism group.) We investigate the quantization of such scalar field theories here by studying the case of a λphi 4 field, with phi valued in the two-dimensional algebra generated by an identity element e and a nilpotent element v satisfying v 2 = 0. The Coleman-Mandula theorem, which states that the symmetry group of a nontrivial quantum field theory cannot be a nontrivial enlargement of the Poincare group, is evaded here because the finite ''extra'' symmetries of the classical theory fail to be implemented in the quantum theory by unitary operators and the infinitesimal symmetries (which can be represented in the quantum theory by quadratic forms) connect the one-particle Hilbert space to multiparticle states. Nevertheless, we find that the conventional Feynman rules for this theory lead to vacuum decay at the tree level and fail to yield a well-defined S matrix. Some alternative approaches are investigated, but these also appear to fail

  12. Short-time existence of solutions for mean-field games with congestion

    KAUST Repository

    Gomes, Diogo A.; Voskanyan, Vardan K.

    2015-01-01

    We consider time-dependent mean-field games with congestion that are given by a Hamilton–Jacobi equation coupled with a Fokker–Planck equation. These models are motivated by crowd dynamics in which agents have difficulty moving in high-density areas

  13. Internal Stresses in Wires for High Field Magnets

    International Nuclear Information System (INIS)

    Han, K.; Embury, J.D.; Lawson, A.C.; Von Dreele, R.B.; Wood, J.T.; Richardson, J.W. Jr.

    1998-01-01

    The codeformation of Cu-Ag or Cu-Nb composite wires used for high field magnets has a number of important microstructural consequences, including the production of very fine scale structures, the development of very high internal surface area to volume ratios during the drawing and the storage of defects at interphase interfaces. In addition, the fabrication and codeformation of phases which differ in crystal structure, thermal expansion, elastic modulus and lattice parameter lead to the development of short wavelength internal stresses. These internal stresses are measured by neutron diffraction and transmission electron microscopy as a function of the imposed drawing strain. The internal stresses lead to important changes in elastic plastic response which can be related to both magnet design and service life and these aspects will be described in detail

  14. Field Test and Evaluation of Engineered Biomineralization Technology for Sealing Existing Wells

    Energy Technology Data Exchange (ETDEWEB)

    Cunningham, Alfred [Montana State Univ., Bozeman, MT (United States)

    2015-12-21

    This research project addresses one of the goals of the U.S. Department of Energy (DOE) Carbon Storage Program (CSP) aimed at developing Advanced Wellbore Integrity Technologies to Ensure Permanent Geologic Carbon Storage. The technology field-tested in this research project is referred to as microbially induced calcite precipitation (MICP), which utilizes a biologically-based process to precipitate calcium carbonate. If properly controlled MICP can successfully seal fractures, high permeability zones, and compromised wellbore cement in the vicinity of wellbores and in nearby caprock, thereby improving the storage security of geologically-stored carbon dioxide. This report describes an MICP sealing field test performed on a 24.4 cm (9.625 inch) diameter well located on the Gorgas Steam Generation facility near Jasper, Alabama. The research was aimed at (1) developing methods for delivering MICP promoting fluids downhole using conventional oil field technologies and (2) assessing the ability of MICP to seal cement and formation fractures in the near wellbore region in a sandstone formation. Both objectives were accomplished successfully during a field test performed during the period April 1-11, 2014. The test resulted in complete biomineralization sealing of a horizontal fracture located 340.7 m (1118 feet) below ground surface. A total of 24 calcium injections and six microbial inoculation injections were required over a three day period in order to achieve complete sealing. The fractured region was considered completely sealed when it was no longer possible to inject fluids into the formation without exceeding the initial formation fracture pressure. The test was accomplished using conventional oil field technology including an 11.4 L (3.0 gallon) wireline dump bailer for injecting the biomineralization materials downhole. Metrics indicating successful MICP sealing included reduced injectivity during seal formation, reduction in pressure falloff, and

  15. Stress field determination in an alloy 600 stress corrosion crack specimen

    International Nuclear Information System (INIS)

    Rassineux, B.; Labbe, T.

    1995-05-01

    In the context of EDF studies on stress corrosion cracking rates in the Alloy 600 steam generators tubes, we studied the influence of strain hardened surface layers on the different stages of cracking for a tensile smooth specimen (TLT). The stress field was notably assessed to try and explain the slow/rapid-propagation change observed beyond the strain hardened layers. The main difficulty is to simulate in a finite element model the inner and outer surfaces of these strain hardened layers, produced by the final manufacturing stages of SG tubes which have not been heat treated. In the model, the strain hardening is introduced by simulating a multi-layer material. Residual stresses are simulated by an equivalent fictitious thermomechanical calculation, realigned with respect to X-ray measurements. The strain hardening introduction method was validated by an analytical calculation giving identical results. Stress field evolution induced by specimen tensile loading were studied using an elastoplastic 2D finite element calculations performed with the Aster Code. The stress profile obtained after load at 660 MPa shows no stress discontinuity at the boundary between the strain hardened layer and the rest of the tube. So we propose that a complementary calculation be performed, taking into account the multi-cracked state of the strain hardened zones by means of a damage variable. In fact, this state could induce stress redistribution in the un-cracked area, which would perhaps provide an explanation of the crack-ground rate change beyond the strain hardened zone. The calculations also evidence the harmful effects of plastic strains on a strain hardened layer due to the initial state of the tube (not heat-treated), to grit blasting or to shot peening. The initial compressive stress condition of this surface layer becomes, after plastic strain, a tensile stress condition. These results are confirmed by laboratory test. (author). 10 refs., 18 figs., 9 tabs., 2 appends

  16. High-energy quasi-monoenergetic neutron fields: existing facilities and future needs

    CERN Document Server

    Pomp, S; Mayer, S; Reitz, G; Rottger, S; Silari, M; Smit, F D; Vincke, H; Yasuda, H

    2014-01-01

    The argument that well-characterised quasi-monoenergetic neutron (QMN) sources reaching into the energy domain >20 MeV are needed is presented. A brief overview of the existing facilities is given, and a list of key factors that an ideal QMN source for dosimetry and spectrometry should offer is presented. The authors conclude that all of the six QMN facilities currently in existence worldwide operate in sub-optimal conditions for dosimetry. The only currently available QMN facility in Europe capable of operating at energies >40 MeV, TSL in Uppsala, Sweden, is threatened with shutdown in the immediate future. One facility, NFS at GANIL, France, is currently under construction. NFS could deliver QMN beams up to about 30 MeV. It is, however, so far not clear if and when NFS will be able to offer QMN beams or operate with only so-called white neutron beams. It is likely that by 2016, QMN beams with energies >40 MeV will be available only in South Africa and Japan, with none in Europe.

  17. Study On Aftershock Triggering In Consideration Of Tectonic Stress Field

    Science.gov (United States)

    Hu, C.; Cai, Y.

    2007-12-01

    : The occurrence of earthquake is related to the strength of rock and tectonic stress field. The seismic risk factor (SRF),D=\\left|{τn }\\right|/(μσn ) is proposed to describe the dangerous status of aftershock triggering in this paper. Dearthquakes, velocity field from GPS as well as geological survey. As one order of approximation, the magnitudes of the regional tectonic stress field can be estimated by the Coulomb failure criterion. Finite element method (FEM) and the concept of the factor D are used to study the aftershock triggering of the 1976 Tangshan Ms=7.8 earthquake. The results show that: (1) Most of the aftershocks triggered by the Tangshan earthquake occurred in the two-leaf-shaped regions of D≥ 1 near the north-east end of the main-shock fault. The largest leaf is about 100km long and 40km wide. (2) The areas of aftershock triggering predicted by the seismic risk factorD and Δ CFS (the changes in the Coulomb failure stress) are almost the same near the fault. The difference between them is that the aftershock area predicted by Δ CFS≥ 0 is too large and the area predicted by the factor D≥ 1 is limited. The areas of aftershock triggering predicted by Δ CFS≥ 0.04 MPa are nearly the same as those of D≥ 1 obtained by the study. (3) Sometimes Δ CFS =0.01MPa is taken as a low threshold of aftershock triggering. However, Δ CFS≥ 0 only means the probability increase of the earthquake triggering, not means the earthquake will occur. The earthquake occurrence is not only related to Δ CFS, but also to the tectonic stress field before the main-shock.

  18. Do Capacity Coupled Electric Fields Accelerate Tibial Stress Fracture Healing

    Science.gov (United States)

    2006-12-01

    MRI confirmed a large coexisting haemangioma which may have confounded perception of stress fracture symptoms. Table 1 is a comprehensive subject...Johnson JR, Light KI, Yuan HA: A double-blind study of capacitively coupled electrical stimulation as an adjunct to lumbar spinal fusions. Spine 24...Simmons JW, Jr., Mooney V, Thacker I: Pseudarthrosis after lumbar spine fusion: nonoperative salvage with pulsed electromagnetic fields. Am J

  19. Stress field control during large caldera-forming eruptions

    Directory of Open Access Journals (Sweden)

    Antonio Costa

    2016-10-01

    Full Text Available Crustal stress field can have a significant influence on the way magma is channelled through the crust and erupted explosively at the surface. Large Caldera Forming Eruptions (LCFEs can erupt hundreds to thousands of cubic kilometres of magma in a relatively short time along fissures under the control of a far-field extensional stress. The associated eruption intensities are estimated in the range 109 - 1011 kg/s. We analyse syn-eruptive dynamics of LCFEs, by simulating numerically explosive flow of magma through a shallow dyke conduit connected to a magma chamber that in turn is fed by a deeper magma reservoir, both under the action of an extensional far-field stress. Results indicate that huge amounts of high viscosity silicic magma can be erupted over timescales of a few to several hours. Our study provides answers to outstanding questions relating to the intensity and duration of catastrophic volcanic eruptions in the past. In addition, it presents far-reaching implications for the understanding of dynamics and intensity of large-magnitude volcanic eruptions on Earth and to highlight the necessity of a future research to advance our knowledge of these rare catastrophic events.

  20. Temperature Field Prediction for Determining the Residual Stresses Under Heat Treatment of Aluminum Alloys

    Directory of Open Access Journals (Sweden)

    A. V. Livshits

    2014-01-01

    Full Text Available The article is devoted to non-stationary temperature field blanks from aluminum alloys during heat treatment. It consists of the introduction and two smaller paragraphs. In the introduction the author concerns the influence of residual stresses arising in the manufacturing process of details, on the strength of the whole aircraft construction and, consequently, on their technical and economic parameters, such as weight, reliability, efficiency, and cost. He also notes that the residual stresses appeared during the production of parts change their location, size and direction under the influence of the elastic deformations that occur during the exploitation of aircraft. Redistributed residual stresses may have a chaotic distribution that may cause overlap of these stresses on the stresses caused by the impact of workload of constructions and destruction or damage of aircraft components.The first paragraph is devoted to the existing methods and techniques for determining the residual stresses. The presented methods and techniques are analyzed to show the advantages and disadvantages of each of them. The conclusion is drawn that the method to determine the residual stresses is necessary, its cost is less than those of existing ones, and an error does not exceed 10%.In the second section, the author divides the problem of determining the residual stresses into two parts, and describes the solution methods of the first one. The first problem is to define the temperature field of the work piece. The author uses a Fourier equation with the definition of initial and boundary conditions to describe a mathematical model of the heat cycle of work piece cooling. He draws special attention here to the fact that it is complicated to determine the heat transfer coefficient, which characterizes the process of cooling the work piece during hardening because of its dependence on a number of factors, such as changing temperature-dependent material properties of

  1. Investigation on stresses of superconductors under pulsed magnetic fields based on multiphysics model

    International Nuclear Information System (INIS)

    Yang, Xiaobin; Li, Xiuhong; He, Yafeng; Wang, Xiaojun; Xu, Bo

    2017-01-01

    Highlights: • The differential equation including temperature and magnetic field was derived for a long cylindrical superconductor. • Thermal stress and electromagnetic stress were studied at the same time under pulse field magnetizing. • The distributions of the magnetic field, the temperature and stresses are studied and compared for two pulse fields of the different duration. • The Role thermal stress and electromagnetic stress play in the process of pulse field magnetizing is discussed. - Abstract: A multiphysics model for the numerical computation of stresses, trapped field and temperature distribution of a infinite long superconducting cylinder is proposed, based on which the stresses, including the thermal stresses and mechanical stresses due to Lorentz force, and trapped fields in the superconductor subjected to pulsed magnetic fields are analyzed. By comparing the results under pulsed magnetic fields with different pulse durations, it is found that the both the mechanical stress due to the electromagnetic force and the thermal stress due to temperature gradient contribute to the total stress level in the superconductor. For pulsed magnetic field with short durations, the thermal stress is the dominant contribution to the total stress, because the heat generated by AC-loss builds up significant temperature gradient in such short durations. However, for a pulsed field with a long duration the gradient of temperature and flux, as well as the maximal tensile stress, are much smaller. And the results of this paper is meaningful for the design and manufacture of superconducting permanent magnets.

  2. Investigation on stresses of superconductors under pulsed magnetic fields based on multiphysics model

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaobin, E-mail: yangxb@lzu.edu.cn; Li, Xiuhong; He, Yafeng; Wang, Xiaojun; Xu, Bo

    2017-04-15

    Highlights: • The differential equation including temperature and magnetic field was derived for a long cylindrical superconductor. • Thermal stress and electromagnetic stress were studied at the same time under pulse field magnetizing. • The distributions of the magnetic field, the temperature and stresses are studied and compared for two pulse fields of the different duration. • The Role thermal stress and electromagnetic stress play in the process of pulse field magnetizing is discussed. - Abstract: A multiphysics model for the numerical computation of stresses, trapped field and temperature distribution of a infinite long superconducting cylinder is proposed, based on which the stresses, including the thermal stresses and mechanical stresses due to Lorentz force, and trapped fields in the superconductor subjected to pulsed magnetic fields are analyzed. By comparing the results under pulsed magnetic fields with different pulse durations, it is found that the both the mechanical stress due to the electromagnetic force and the thermal stress due to temperature gradient contribute to the total stress level in the superconductor. For pulsed magnetic field with short durations, the thermal stress is the dominant contribution to the total stress, because the heat generated by AC-loss builds up significant temperature gradient in such short durations. However, for a pulsed field with a long duration the gradient of temperature and flux, as well as the maximal tensile stress, are much smaller. And the results of this paper is meaningful for the design and manufacture of superconducting permanent magnets.

  3. Green's Function and Stress Fields in Stochastic Heterogeneous Continua

    Science.gov (United States)

    Negi, Vineet

    Many engineering materials used today are heterogenous in composition e.g. Composites - Polymer Matrix Composites, Metal Matrix Composites. Even, conventional engineering materials - metals, plastics, alloys etc. - may develop heterogeneities, like inclusions and residual stresses, during the manufacturing process. Moreover, these materials may also have intrinsic heterogeneities at a nanoscale in the form of grain boundaries in metals, crystallinity in amorphous polymers etc. While, the homogenized constitutive models for these materials may be satisfactory at a macroscale, recent studies of phenomena like fatigue failure, void nucleation, size-dependent brittle-ductile transition in polymeric nanofibers reveal a major play of micro/nanoscale physics in these phenomena. At this scale, heterogeneities in a material may no longer be ignored. Thus, this demands a study into the effects of various material heterogeneities. In this work, spatial heterogeneities in two material properties - elastic modulus and yield stress - have been investigated separately. The heterogeneity in the elastic modulus is studied in the context of Green's function. The Stochastic Finite Element method is adopted to get the mean statistics of the Green's function defined on a stochastic heterogeneous 2D infinite space. A study of the elastic-plastic transition in a domain having stochastic heterogenous yield stress was done using Mont-Carlo methods. The statistics for various stress and strain fields during the transition were obtained. Further, the effects of size of the domain and the strain-hardening rate on the stress fields during the heterogeneous elastic-plastic transition were investigated. Finally, a case is made for the role of the heterogenous elastic-plastic transition in damage nucleation and growth.

  4. Elastic constants of stressed and unstressed materials in the phase-field crystal model

    Science.gov (United States)

    Wang, Zi-Le; Huang, Zhi-Feng; Liu, Zhirong

    2018-04-01

    A general procedure is developed to investigate the elastic response and calculate the elastic constants of stressed and unstressed materials through continuum field modeling, particularly the phase-field crystal (PFC) models. It is found that for a complete description of system response to elastic deformation, the variations of all the quantities of lattice wave vectors, their density amplitudes (including the corresponding anisotropic variation and degeneracy breaking), the average atomic density, and system volume should be incorporated. The quantitative and qualitative results of elastic constant calculations highly depend on the physical interpretation of the density field used in the model, and also importantly, on the intrinsic pressure that usually pre-exists in the model system. A formulation based on thermodynamics is constructed to account for the effects caused by constant pre-existing stress during the homogeneous elastic deformation, through the introducing of a generalized Gibbs free energy and an effective finite strain tensor used for determining the elastic constants. The elastic properties of both solid and liquid states can be well produced by this unified approach, as demonstrated by an analysis for the liquid state and numerical evaluations for the bcc solid phase. The numerical calculations of bcc elastic constants and Poisson's ratio through this method generate results that are consistent with experimental conditions, and better match the data of bcc Fe given by molecular dynamics simulations as compared to previous work. The general theory developed here is applicable to the study of different types of stressed or unstressed material systems under elastic deformation.

  5. Existence of vigorous lineages of crop-wild hybrids in Lettuce under field conditions.

    Science.gov (United States)

    Hooftman, Danny A P; Hartman, Yorike; Oostermeijer, J Gerard B; Den Nijs, Hans J C M

    2009-01-01

    Plant to plant gene flow is a route of environmental exposure for GM plants specifically since crosses with wild relatives could lead to the formation of more vigorous hybrids, which could increase the rate of introgression and the environmental impact. Here, we test the first step in the process of potential transgene introgression: whether hybrid vigor can be inherited to the next generation, which could lead to fixation of altered, i.e., elevated, quantitative traits. The potential for a permanent elevated fitness was tested using individual autogamous progeny lineages of hybrids between the crop Lactuca sativa (Lettuce) and the wild species Lactuca serriola (Prickly Lettuce). We compared progeny from motherplants grown under either greenhouse or field conditions. The survival of young plants depended strongly on maternal environment. Furthermore, we observed that offspring reproductive fitness components were correlated with maternal fitness. Our study demonstrates that post-zygotic genotypic sorting at the young plants stage reduces the number of genotypes non-randomly, leading to inheritance of high levels of reproductive traits in the surviving hybrid lineages, compared to the pure wild relatives. Consequently, directional selection could lead to displacement of the pure wild relative and fixation of more vigorous genome segments originating from crops, stabilizing plant traits at elevated levels. Such information can be used to indentify segments which are less likely to introgress into wild relative populations as a target for transgene insertion. © ISBR, EDP Sciences, 2010.

  6. Corrosion of metals exposed to 25% magnesium chloride solution and tensile stress: Field and laboratory studies

    Directory of Open Access Journals (Sweden)

    Xianming Shi

    2017-12-01

    Full Text Available The use of chemicals for snow and ice control operations is a common practice for improving the safety and mobility of roadways in cold climate, but brings significant concerns over their risks including the corrosive effects on transportation infrastructure and motor vehicles. The vast majority of existing studies and methods to test the deicer corrosivity have been restricted to laboratory environments and unstressed metals, which may not reliably simulate actual service conditions. As such, we report a case study in which stainless steel SS 304 (unstressed and externally tensile stressed, aluminum (Al 1100 and low carbon steel (C1010 coupons were exposed to 25% MgCl2 under field conditions for six weeks. A new corrosion test-bed was developed in Montana to accelerate the field exposure to this deicer. To further investigate the observed effect of tensile stress on the corrosion of stainless steel, SS 304 (unstressed and externally stressed coupons were exposed to 25% MgCl2 solution under the laboratory conditions. The C 1010 exhibited the highest percentage of rust area and suffered the most weight loss as a result of field exposure and MgCl2 sprays. In terms of ultimate tensile strength, the Al 1100 coupons saw the greatest reduction and the unstressed and externally stressed SS 304 coupons saw the least. The ability of MgCl2 to penetrate deep into the matrix of aluminum alloy poses great risk to such structural material. Tensile stressed SS 304 suffered more corrosion than unstressed SS 304 in both the field and laboratory conditions. Results from this case study may shed new light on the deicer corrosion issue and help develop improved field testing methods to evaluate the deicer corrosivity to metals in service.

  7. Utsu aftershock productivity law explained from geometric operations on the permanent static stress field of mainshocks

    Science.gov (United States)

    Mignan, Arnaud

    2018-03-01

    The aftershock productivity law is an exponential function of the form K ∝ exp(αM), with K being the number of aftershocks triggered by a given mainshock of magnitude M and α ≈ ln(10) being the productivity parameter. This law remains empirical in nature although it has also been retrieved in static stress simulations. Here, we parameterize this law using the solid seismicity postulate (SSP), the basis of a geometrical theory of seismicity where seismicity patterns are described by mathematical expressions obtained from geometric operations on a permanent static stress field. We first test the SSP that relates seismicity density to a static stress step function. We show that it yields a power exponent q = 1.96 ± 0.01 for the power-law spatial linear density distribution of aftershocks, once uniform noise is added to the static stress field, in agreement with observations. We then recover the exponential function of the productivity law with a break in scaling obtained between small and large M, with α = 1.5ln(10) and ln(10), respectively, in agreement with results from previous static stress simulations. Possible biases of aftershock selection, proven to exist in epidemic-type aftershock sequence (ETAS) simulations, may explain the lack of break in scaling observed in seismicity catalogues. The existence of the theoretical kink, however, remains to be proven. Finally, we describe how to estimate the solid seismicity parameters (activation density δ+, aftershock solid envelope r∗ and background stress amplitude range Δo∗) for large M values.

  8. Numerical analysis of stress fields generated by quenching process

    Directory of Open Access Journals (Sweden)

    A. Bokota

    2011-04-01

    Full Text Available In work the presented numerical models of tool steel hardening processes take into account mechanical phenomena generated by thermalphenomena and phase transformations. In the model of mechanical phenomena, apart from thermal, plastic and structural strain, alsotransformations plasticity was taken into account. The stress and strain fields are obtained using the solution of the Finite Elements Method of the equilibrium equation in rate form. The thermophysical constants occurring in constitutive relation depend on temperature and phase composite. For determination of plastic strain the Huber-Misses condition with isotropic strengthening was applied whereas fordetermination of transformation plasticity a modified Leblond model was used. In order to evaluate the quality and usefulness of thepresented models a numerical analysis of stresses and strains associated hardening process of a fang lathe of cone shaped made of tool steel was carried out.

  9. Effects of distance from center of a weld to fixed end on residual stress and stress intensity factor of a piping weld. Evaluation of SCC growth under residual stress field. Report 1

    International Nuclear Information System (INIS)

    Miyazaki, Katsumasa; Numata, Masanori; Saito, Koichi; Mochizuki, Masahito

    2006-01-01

    The fixed conditions of butt welds between straight pipe and valve or pump in the actual piping system are different from those of straight pipes. However, the effect of fixed condition on the residual stress and the stress intensity factor for evaluation of structural integrity of cracked piping was not clear. In this study, the finite element analyses were conducted by considering the differences in the distance from the center of weld to the fixed end L to clarify the effect of fixed condition on the residual stress and the stress intensity factor. For the 600 A piping, the axial residual stress distribution was not affected by the distance L. Furthermore, the stress intensity factor of circumferential crack under the residual stress field with fixed condition could be estimated by using the existing simplified solution for piping. (author)

  10. Magnetostriction of a sphere: stress development during magnetization and residual stresses due to the remanent field

    Science.gov (United States)

    Reich, Felix A.; Rickert, Wilhelm; Stahn, Oliver; Müller, Wolfgang H.

    2017-03-01

    Based on the principles of rational continuum mechanics and electrodynamics (see Truesdell and Toupin in Handbuch der Physik, Springer, Berlin, 1960 or Kovetz in Electromagnetic theory, Oxford University Press, Oxford, 2000), we present closed-form solutions for the mechanical displacements and stresses of two different magnets. Both magnets are initially of spherical shape. The first (hard) magnet is uniformly magnetized and deforms due to the field induced by the magnetization. In the second problem of a (soft) linear-magnetic sphere, the deformation is caused by an applied external field, giving rise to magnetization. Both problems can be used for modeling parts of general magnetization processes. We will address the similarities between both settings in context with the solutions for the stresses and displacements. In both problems, the volumetric Lorentz force density vanishes. However, a Lorentz surface traction is present. This traction is determined from the magnetic flux density. Since the obtained displacements and stresses are small in magnitude, we may use Hooke's law with a small-strain approximation, resulting in the Lamé- Navier equations of linear elasticity theory. If gravity is neglected and azimuthal symmetry is assumed, these equations can be solved in terms of a series. This has been done by Hiramatsu and Oka (Int J Rock Mech Min Sci Geomech Abstr 3(2):89-90, 1966) before. We make use of their series solution for the displacements and the stresses and expand the Lorentz tractions of the analyzed problems suitably in order to find the expansion coefficients. The resulting algebraic system yields finite numbers of nonvanishing coefficients. Finally, the resulting stresses, displacements, principal strains and the Lorentz tractions are illustrated and discussed.

  11. Wave fields in Weyl spaces and conditions for the existence of a preferred pseudo-Riemannian structure

    International Nuclear Information System (INIS)

    Audretsch, J.; Gaehler, F.; Straumann, N.

    1984-01-01

    Previous axiomatic approaches to general relativity which led to a Weylian structure of space-time are supplemented by a physical condition which implies the existence of a preferred pseudo-Riemannian structure. It is stipulated that the trajectories of the short wave limit of classical massive fields agree with the geodesics of the Weyl connection and it is shown that this is equivalent to the vanishing of the covariant derivative of a ''mass function'' of nontrivial Weyl type.This in turn is proven to be equivalent to the existence of a preferred metric of the conformal structure such that the Weyl connection is reducible to a connection of the bundle of orthonormal frames belonging to this distinguished metric. (orig.)

  12. No evidence for local adaptation to salt stress in the existing populations of invasive Solidago canadensis in China.

    Science.gov (United States)

    Li, Junmin; Liu, Haiyan; Yan, Ming; Du, Leshan

    2017-01-01

    Local adaptation is an important mechanism underlying the adaptation of plants to environmental heterogeneity, and the toxicity of salt results in strong selection pressure on salt tolerance in plants and different ecotypes. Solidago canadensis, which is invasive in China, has spread widely and has recently colonized alkali sandy loams with a significant salt content. A common greenhouse experiment was conducted to test the role of local adaptation in the successful invasion of S. canadensis into salty habitats. Salt treatment significantly decreased the growth of S. canadensis, including rates of increase in the number of leaves and plant height; the root, shoot, and total biomass. Furthermore, salt stress significantly reduced the net photosynthetic rate, stomatal conductance, transpiration rate and relative chlorophyll content but significantly increased peroxidase activity and the proline content of S. canadensis and the root/shoot ratio. Two-way analysis of variance showed that salt treatment had a significant effect on the physiological traits of S. canadensis, except for the intercellular CO2 concentration, whereas the population and the salt × population interaction had no significant effect on any physiological traits. Most of the variation in plasticity existed within and not among populations, excep for the root/shoot ratio. S. canadensis populations from soil with moderate/high salt levels grew similarly to S. canadensis populations from soils with low salt levels. No significant correlation between salt tolerance indices and soil salinity levels was observed. The plasticity of the proline content, intercellular CO2 concentration and chlorophyll content had significant correlations with the salt tolerance index. These findings indicate a lack of evidence for local adaption in the existing populations of invasive S. canadensis in China; instead, plasticity might be more important than local adaptation in influencing the physiological traits and salt

  13. No evidence for local adaptation to salt stress in the existing populations of invasive Solidago canadensis in China.

    Directory of Open Access Journals (Sweden)

    Junmin Li

    Full Text Available Local adaptation is an important mechanism underlying the adaptation of plants to environmental heterogeneity, and the toxicity of salt results in strong selection pressure on salt tolerance in plants and different ecotypes. Solidago canadensis, which is invasive in China, has spread widely and has recently colonized alkali sandy loams with a significant salt content. A common greenhouse experiment was conducted to test the role of local adaptation in the successful invasion of S. canadensis into salty habitats. Salt treatment significantly decreased the growth of S. canadensis, including rates of increase in the number of leaves and plant height; the root, shoot, and total biomass. Furthermore, salt stress significantly reduced the net photosynthetic rate, stomatal conductance, transpiration rate and relative chlorophyll content but significantly increased peroxidase activity and the proline content of S. canadensis and the root/shoot ratio. Two-way analysis of variance showed that salt treatment had a significant effect on the physiological traits of S. canadensis, except for the intercellular CO2 concentration, whereas the population and the salt × population interaction had no significant effect on any physiological traits. Most of the variation in plasticity existed within and not among populations, excep for the root/shoot ratio. S. canadensis populations from soil with moderate/high salt levels grew similarly to S. canadensis populations from soils with low salt levels. No significant correlation between salt tolerance indices and soil salinity levels was observed. The plasticity of the proline content, intercellular CO2 concentration and chlorophyll content had significant correlations with the salt tolerance index. These findings indicate a lack of evidence for local adaption in the existing populations of invasive S. canadensis in China; instead, plasticity might be more important than local adaptation in influencing the physiological

  14. Microearthquake Study of the Salton Sea Geothermal Field, California: Evidence of Stress Triggering

    International Nuclear Information System (INIS)

    Holland, Austin A.

    2002-01-01

    A digital network of 24 seismograph stations was operated from September 15, 1987 to September 30, 1988, by Lawrence Livermore National Laboratory and Unocal as part of the Salton Sea Scientific Drilling Project to study seismicity related to tectonics and geothermal activity near the drilling site. More than 2001 microearthquakes were relocated in this study in order to image any pervasive structures that may exist within the Salton Sea geothermal field. First, detailed velocity models were obtained through standard 1-D inversion techniques. These velocity models were then used to relocate events using both single event methods and Double-Differencing, a joint hypocenter location method. An anisotropic velocity model was built from anisotropy estimates obtained from well logs within the study area. During the study period, the Superstition Hills sequence occurred with two moderate earthquakes of MS 6.2 and MS 6.6. These moderate earthquakes caused a rotation of the stress field as observed from the inversion of first motion data from microearthquakes at the Salton Sea geothermal field. Coulomb failure analysis also indicates that microearthquakes occurring after the Superstition Hills sequence are located within a region of stress increase suggesting stress triggering caused by the moderate earthquakes

  15. Existence and regularity of solutions of a phase field model for solidification with convection of pure materials in two dimensions

    Directory of Open Access Journals (Sweden)

    Jose Luiz Boldrini

    2003-11-01

    Full Text Available We study the existence and regularity of weak solutions of a phase field type model for pure material solidification in presence of natural convection. We assume that the non-stationary solidification process occurs in a two dimensional bounded domain. The governing equations of the model are the phase field equation coupled with a nonlinear heat equation and a modified Navier-Stokes equation. These equations include buoyancy forces modelled by Boussinesq approximation and a Carman-Koseny term to model the flow in mushy regions. Since these modified Navier-Stokes equations only hold in the non-solid regions, which are not known a priori, we have a free boundary-value problem.

  16. Flavour fields in steady state: stress tensor and free energy

    International Nuclear Information System (INIS)

    Banerjee, Avik; Kundu, Arnab; Kundu, Sandipan

    2016-01-01

    The dynamics of a probe brane in a given gravitational background is governed by the Dirac-Born-Infeld action. The corresponding open string metric arises naturally in studying the fluctuations on the probe. In Gauge-String duality, it is known that in the presence of a constant electric field on the worldvolume of the probe, the open string metric acquires an event horizon and therefore the fluctuation modes on the probe experience an effective temperature. In this article, we bring together various properties of such a system to a formal definition and a subsequent narration of the effective thermodynamics and the stress tensor of the corresponding flavour fields, also including a non-vanishing chemical potential. In doing so, we point out a potentially infinitely-degenerate scheme-dependence of regularizing the free energy, which nevertheless yields a universal contribution in certain cases. This universal piece appears as the coefficient of a log-divergence in free energy when a space-filling probe brane is embedded in AdS d+1 -background, for d=2,4, and is related to conformal anomaly. For the special case of d=2, the universal factor has a striking resemblance to the well-known heat current formula in (1+1)-dimensional conformal field theory in steady-state, which endows a plausible physical interpretation to it. Interestingly, we observe a vanishing conformal anomaly in d=6.

  17. On the problem of the existence of the solutions of the nonlinear nonsingular equations of quantum field theory

    International Nuclear Information System (INIS)

    Nelipa, N.F.

    1978-01-01

    The existence of the solution of the nonlinear, singular equations of quantum field theory is discussed. By making use of the Banach's and Schauder's fixed point theorems, the condition of the existence of these equations is found. As some illustration, these methods were applied to the equations for the π-scattering on static nucleon. The investigations of the other equations of quantum field theory (Chew-Low, double dispersin relation, Green's function) lead to the similar result. The application of the Newton-Kantorovich method to the Chew-Low equations also gives the similar result. What are the causes of such situation[ The main suggestions which the author has used were that the Banach's, the Schauder's, and the Newton-Kantorovich methods were applied and the Hoelder space was choosen. It may be that the method are crude. It may be that the solutions do not belong to the Hoelder space. Now it is rather difficult to say which role each of these two suggestions plays. (Kobatake, H.)

  18. A Comparison between Deep and Shallow Stress Fields in Korea Using Earthquake Focal Mechanism Inversions and Hydraulic Fracturing Stress Measurements

    Science.gov (United States)

    Lee, Rayeon; Chang, Chandong; Hong, Tae-kyung; Lee, Junhyung; Bae, Seong-Ho; Park, Eui-Seob; Park, Chan

    2016-04-01

    We are characterizing stress fields in Korea using two types of stress data: earthquake focal mechanism inversions (FMF) and hydraulic fracturing stress measurements (HF). The earthquake focal mechanism inversion data represent stress conditions at 2-20 km depths, whereas the hydraulic fracturing stress measurements, mostly conducted for geotechnical purposes, have been carried out at depths shallower than 1 km. We classified individual stress data based on the World Stress Map quality ranking scheme. A total of 20 FMF data were classified into A-B quality, possibly representing tectonic stress fields. A total of 83 HF data out of compiled 226 data were classified into B-C quality, which we use for shallow stress field characterization. The tectonic stress, revealed from the FMF data, is characterized by a remarkable consistency in its maximum stress (σ1) directions in and around Korea (N79±2° E), indicating a quite uniform deep stress field throughout. On the other hand, the shallow stress field, represented by HF data, exhibits local variations in σ1 directions, possibly due to effects of topography and geologic structures such as faults. Nonetheless, there is a general similarity in σ1 directions between deep and shallow stress fields. To investigate the shallow stress field statistically, we follow 'the mean orientation and wavelength analysis' suggested by Reiter et al. (2014). After the stress pattern analysis, the resulting stress points distribute sporadically over the country, not covering the entire region evenly. In the western part of Korea, the shallow σ1directions are generally uniform with their search radius reaching 100 km, where the average stress direction agrees well with those of the deep tectonic stress. We note two noticeable differences between shallow and deep stresses in the eastern part of Korea. First, the shallow σ1 orientations are markedly non-uniform in the southeastern part of Korea with their search radius less than 25 km

  19. Field Phenotyping of Soybean Roots for Drought Stress Tolerance

    Directory of Open Access Journals (Sweden)

    Berhanu A. Fenta

    2014-08-01

    Full Text Available Root architecture was determined together with shoot parameters under well watered and drought conditions in the field in three soybean cultivars (A5409RG, Jackson and Prima 2000. Morphology parameters were used to classify the cultivars into different root phenotypes that could be important in conferring drought tolerance traits. A5409RG is a drought-sensitive cultivar with a shallow root phenotype and a root angle of <40°. In contrast, Jackson is a drought-escaping cultivar. It has a deep rooting phenotype with a root angle of >60°. Prima 2000 is an intermediate drought-tolerant cultivar with a root angle of 40°–60°. It has an intermediate root phenotype. Prima 2000 was the best performing cultivar under drought stress, having the greatest shoot biomass and grain yield under limited water availability. It had abundant root nodules even under drought conditions. A positive correlation was observed between nodule size, above-ground biomass and seed yield under well-watered and drought conditions. These findings demonstrate that root system phenotyping using markers that are easy-to-apply under field conditions can be used to determine genotypic differences in drought tolerance in soybean. The strong association between root and nodule parameters and whole plant productivity demonstrates the potential application of simple root phenotypic markers in screening for drought tolerance in soybean.

  20. Necessary and sufficient conditions for the existence of a lagrangian in field theory. III. Generalized analytic representations of tensorial field equations

    International Nuclear Information System (INIS)

    Santilli, R.M.

    1977-01-01

    In this paper we first study the equivalence transformations of class C 2 , regular, tensorial, quasi-linear systems of field which (a) preserve the continuity, regularity, and quasi-linear structure of the systems; and (b) occur within a fixed system of Minkowski coordinates and field components. We identify, among the transformations of this class, those which either induce or preserve a self-adjoint structure of the field equations and we term them genotopic and isotopic transformations, respectively. We then give the necessary and sufficient conditions for an equivalence transformation of the above type to be either genotopic or isotopic. By using this methodology, we then extend the theorem on the necessary and sufficient condition for the existence of ordered direct analytic representations introduced in the preceding paper to the case of ordered indirect analytic representations in terms of the conventional Lagrange equations; we introduce a method for the construction of a Lagrangian, when it exists, in this broader context; and we explore some implications of the underlying methodology for the problem of the structure of the Lagrangian capable of representing interactions within the framework of the indirect analytic representations. Some of the several aspects which demand an inspection prior to the use of this analytic approach in actual models are pointed out.In particular, we indicate a possible deep impact in the symmetries and conservation laws of the system generated by the use of the concept of indirect analytic representation

  1. The stress field and its sources in the North Atlantic Realm and Europe

    DEFF Research Database (Denmark)

    Nielsen, S.B.; Schiffer, Christian; Stephenson, Randell Alexander

    A number of sources contribute to the lithospheric stress field. Lithospheric density heterogeneities cause horizontal gradients of the vertically integrated lithostatic pressure, which give rise to gravitational/geopotential stresses. Variations of pressure, temperature and composition in the co...

  2. Stress distributions of coils for toroidal magnetic field

    International Nuclear Information System (INIS)

    Kajita, Tateo; Miyamoto, Kenro.

    1976-01-01

    The stress distributions of a D shaped coil and a circular coil are computed by the finite element method. The dependences of the stress distribution on the geometrical parameters of the stress distribution on the geometrical parameters of the coils and supporting methods are examined. The maximum amount of the stress in the D shaped coil is not much smaller than that of the circular one. However, the stress distribution of the D shaped coil becomes much more uniform. The supporting method has as much effect as the geometrical parameters of the coil on the stress distribution. (auth.)

  3. Nanoscale multiphase phase field approach for stress- and temperature-induced martensitic phase transformations with interfacial stresses at finite strains

    Science.gov (United States)

    Basak, Anup; Levitas, Valery I.

    2018-04-01

    A thermodynamically consistent, novel multiphase phase field approach for stress- and temperature-induced martensitic phase transformations at finite strains and with interfacial stresses has been developed. The model considers a single order parameter to describe the austenite↔martensitic transformations, and another N order parameters describing N variants and constrained to a plane in an N-dimensional order parameter space. In the free energy model coexistence of three or more phases at a single material point (multiphase junction), and deviation of each variant-variant transformation path from a straight line have been penalized. Some shortcomings of the existing models are resolved. Three different kinematic models (KMs) for the transformation deformation gradient tensors are assumed: (i) In KM-I the transformation deformation gradient tensor is a linear function of the Bain tensors for the variants. (ii) In KM-II the natural logarithms of the transformation deformation gradient is taken as a linear combination of the natural logarithm of the Bain tensors multiplied with the interpolation functions. (iii) In KM-III it is derived using the twinning equation from the crystallographic theory. The instability criteria for all the phase transformations have been derived for all the kinematic models, and their comparative study is presented. A large strain finite element procedure has been developed and used for studying the evolution of some complex microstructures in nanoscale samples under various loading conditions. Also, the stresses within variant-variant boundaries, the sample size effect, effect of penalizing the triple junctions, and twinned microstructures have been studied. The present approach can be extended for studying grain growth, solidifications, para↔ferro electric transformations, and diffusive phase transformations.

  4. Determining stress fields of shearer-loader picks

    Energy Technology Data Exchange (ETDEWEB)

    Luszczkiewicz, J; Sikora, W

    1987-06-01

    Analyzes factors which influence stress distribution in the NK-4 shearer-loader picks during coal cutting. The AFT optically active cover, 0.0015 mm thick, was used. The pick with the AFT cover was loaded using a force of 33 kN. Isoclinic lines showing stress distribution were photographed. Effects of pick design and its holder type on stress distribution were investigated. Investigations showed that distribution of normal stresses in a pick shaft has a non-linear character. The hole in a pick shaft increased stress concentration in that shaft section. Eliminating the hole reduced stress concentration. Reducing shaft length by about 20 mm did not increase stresses in that shaft zone. 15 refs.

  5. Surgical Stress Abrogates Pre-Existing Protective T Cell Mediated Anti-Tumor Immunity Leading to Postoperative Cancer Recurrence.

    Directory of Open Access Journals (Sweden)

    Abhirami A Ananth

    Full Text Available Anti-tumor CD8+ T cells are a key determinant for overall survival in patients following surgical resection for solid malignancies. Using a mouse model of cancer vaccination (adenovirus expressing melanoma tumor-associated antigen (TAA-dopachrome tautomerase (AdDCT and resection resulting in major surgical stress (abdominal nephrectomy, we demonstrate that surgical stress results in a reduction in the number of CD8+ T cell that produce cytokines (IFNγ, TNFα, Granzyme B in response to TAA. This effect is secondary to both reduced proliferation and impaired T cell function following antigen binding. In a prophylactic model, surgical stress completely abrogates tumor protection conferred by vaccination in the immediate postoperative period. In a clinically relevant surgical resection model, vaccinated mice undergoing a positive margin resection with surgical stress had decreased survival compared to mice with positive margin resection alone. Preoperative immunotherapy with IFNα significantly extends survival in surgically stressed mice. Importantly, myeloid derived suppressor cell (MDSC population numbers and functional impairment of TAA-specific CD8+ T cell were altered in surgically stressed mice. Our observations suggest that cancer progression may result from surgery-induced suppression of tumor-specific CD8+ T cells. Preoperative immunotherapies aimed at targeting the prometastatic effects of cancer surgery will reduce recurrence and improve survival in cancer surgery patients.

  6. Post-hoc pattern-oriented testing and tuning of an existing large model: lessons from the field vole.

    Directory of Open Access Journals (Sweden)

    Christopher J Topping

    Full Text Available Pattern-oriented modeling (POM is a general strategy for modeling complex systems. In POM, multiple patterns observed at different scales and hierarchical levels are used to optimize model structure, to test and select sub-models of key processes, and for calibration. So far, POM has been used for developing new models and for models of low to moderate complexity. It remains unclear, though, whether the basic idea of POM to utilize multiple patterns, could also be used to test and possibly develop existing and established models of high complexity. Here, we use POM to test, calibrate, and further develop an existing agent-based model of the field vole (Microtus agrestis, which was developed and tested within the ALMaSS framework. This framework is complex because it includes a high-resolution representation of the landscape and its dynamics, of the individual's behavior, and of the interaction between landscape and individual behavior. Results of fitting to the range of patterns chosen were generally very good, but the procedure required to achieve this was long and complicated. To obtain good correspondence between model and the real world it was often necessary to model the real world environment closely. We therefore conclude that post-hoc POM is a useful and viable way to test a highly complex simulation model, but also warn against the dangers of over-fitting to real world patterns that lack details in their explanatory driving factors. To overcome some of these obstacles we suggest the adoption of open-science and open-source approaches to ecological simulation modeling.

  7. Level of physical activity, well-being, stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain

    DEFF Research Database (Denmark)

    Krøll, Lotte Skytte; Hammarlund, Catharina Sjödahl; Westergaard, Maria Lurenda

    2017-01-01

    where questionnaires on physical activity, psychological well-being, perceived stress and self-rated health were completed by 148 persons with migraine and 100 healthy controls matched by sex and average age. Semi-structured interviews were conducted to assess characteristics of migraine, tension......-existing tension-type headache and neck pain in a clinic-based sample, b) the level of physical activity, psychological well-being, perceived stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain compared to healthy controls, c) the perceived ability of persons...... well-being, higher level of perceived stress and poorer self-rated health compared to healthy controls. They reported reduced ability to perform physical activity owing to migraine (high degree), tension-type headache (moderate degree) and neck pain (low degree). The most burdensome condition...

  8. Systematic Review of Uit Parameters on Residual Stresses of Sensitized AA5456 and Field Based Residual Stress Measurements for Predicting and Mitigating Stress Corrosion Cracking

    Science.gov (United States)

    2014-03-01

    University Press, 2009, pp. 820–824. [30] S. Kou, Welding Metallurgy , 2nd ed. Hoboken, NJ: John Wiley and Sons, Inc., 2003. [31] M. N.James et al...around welds in aluminum ship structures both in the laboratory and in the field. Tensile residual stresses are often generated during welding and, in...mitigate and even reverse these tensile residual stresses. This research uses x-ray diffraction to measure residual stresses around welds in AA5456 before

  9. Conditions of the existence of the exact symmetric representation for some algebra classes with involution of the fields of real and complex numbers

    International Nuclear Information System (INIS)

    Ivanov, V.P.

    1980-01-01

    Necessary and sufficient conditions for existence of the exact symmetric representation of algebras with involution called sometimes regular of the fields of real and complex numbers are formulated in the paper

  10. Magnetic memory signals variation induced by applied magnetic field and static tensile stress in ferromagnetic steel

    International Nuclear Information System (INIS)

    Huang, Haihong; Yang, Cheng; Qian, Zhengchun; Han, Gang; Liu, Zhifeng

    2016-01-01

    Stress can induce a spontaneous magnetic field in ferromagnetic steel under the excitation of geomagnetic field. In order to investigate the impact of applied magnetic field and tensile stress on variation of the residual magnetic signals on the surface of ferromagnetic materials, static tensile tests of Q235 structural steel were carried out, with the normal component of the residual magnetic signals, H p (y), induced by applied magnetic fields with different intensities measured through the tensile tests. The H p (y), its slope coefficient K S and maximum gradient K max changing with the applied magnetic field H and tensile stress were observed. Results show that the magnitude of H p (y) and its slope coefficient K S increase linearly with the increase of stress in the elastic deformation stage. Under yield stress, H p (y) and K S reach its maximum, and then decrease slightly with further increase of stress. Applied magnetic field affects the magnitude of H p (y) instead of changing the signal curve′s profile; and the magnitude of H p (y), K S , K max and the change rate of K S increase with the increase of applied magnetic field. The phenomenon is also discussed from the viewpoint of magnetic charge in ferromagnetic materials. - Highlights: • We investigated how applied magnetic field and tensile stress impact H p (y) signals. • Magnitude of H p (y), K S and K max increase with the increase of applied magnetic field. • Both applied magnetic field and tensile stress impact material magnetic permeability. • Applied magnetic field can help to evaluate the stress distribution of components.

  11. Magnetic memory signals variation induced by applied magnetic field and static tensile stress in ferromagnetic steel

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Haihong, E-mail: huanghaihong@hfut.edu.cn; Yang, Cheng; Qian, Zhengchun; Han, Gang; Liu, Zhifeng

    2016-10-15

    Stress can induce a spontaneous magnetic field in ferromagnetic steel under the excitation of geomagnetic field. In order to investigate the impact of applied magnetic field and tensile stress on variation of the residual magnetic signals on the surface of ferromagnetic materials, static tensile tests of Q235 structural steel were carried out, with the normal component of the residual magnetic signals, H{sub p}(y), induced by applied magnetic fields with different intensities measured through the tensile tests. The H{sub p}(y), its slope coefficient K{sub S} and maximum gradient K{sub max} changing with the applied magnetic field H and tensile stress were observed. Results show that the magnitude of H{sub p}(y) and its slope coefficient K{sub S} increase linearly with the increase of stress in the elastic deformation stage. Under yield stress, H{sub p}(y) and K{sub S} reach its maximum, and then decrease slightly with further increase of stress. Applied magnetic field affects the magnitude of H{sub p}(y) instead of changing the signal curve′s profile; and the magnitude of H{sub p}(y), K{sub S}, K{sub max} and the change rate of K{sub S} increase with the increase of applied magnetic field. The phenomenon is also discussed from the viewpoint of magnetic charge in ferromagnetic materials. - Highlights: • We investigated how applied magnetic field and tensile stress impact H{sub p}(y) signals. • Magnitude of H{sub p}(y), K{sub S} and K{sub max} increase with the increase of applied magnetic field. • Both applied magnetic field and tensile stress impact material magnetic permeability. • Applied magnetic field can help to evaluate the stress distribution of components.

  12. Do Capacitively Coupled Electric Fields Accelerate Tibial Stress Fracture Healing

    National Research Council Canada - National Science Library

    Hoffman, Andrew

    2002-01-01

    A convenience sample based on availability of tibial stress fracture cases at local Sports Medicine Clinics will be selected over 2-3 years until forty subjects (20 male, 20 female) have been treated...

  13. Do Capacity Coupled Electric Fields Accelerate Tibial Stress Fracture Healing?

    National Research Council Canada - National Science Library

    Hoffman, Andrew

    2004-01-01

    A convenience sample based on availability of tibial stress fracture cases a% local Sports Medicine Clinics will be selected over 4 years until forty subjects (20 male, 20 female) have been treated...

  14. Do Capacitively Coupled Electric Fields Accelerate Tibial Stress Fracture Healing

    National Research Council Canada - National Science Library

    Hoffman, Andrew

    2003-01-01

    A convenience sample based on availability of tibial stress fracture cases at local Sports Medicine Clinics will be selected over 2-3 years until forty subjects (20 male, 20 female) have been treated...

  15. End Late Paleozoic tectonic stress field in the southern edge of Junggar Basin

    Directory of Open Access Journals (Sweden)

    Wei Ju

    2012-09-01

    Full Text Available This paper presents the end Late Paleozoic tectonic stress field in the southern edge of Junggar Basin by interpreting stress-response structures (dykes, folds, faults with slickenside and conjugate joints. The direction of the maximum principal stress axes is interpreted to be NW–SE (about 325°, and the accommodated motion among plates is assigned as the driving force of this tectonic stress field. The average value of the stress index R′ is about 2.09, which indicates a variation from strike-slip to compressive tectonic stress regime in the study area during the end Late Paleozoic period. The reconstruction of the tectonic field in the southern edge of Junggar Basin provides insights into the tectonic deformation processes around the southern Junggar Basin and contributes to the further understanding of basin evolution and tectonic settings during the culmination of the Paleozoic.

  16. Prevention of brittle fracture of steel structures by controlling the local stress and strain fields

    Directory of Open Access Journals (Sweden)

    Moyseychik Evgeniy Alekseevich

    Full Text Available In the article the author offers a classification of the methods to increase the cold resistance of steel structural shapes with a focus on the regulation of local fields of internal stresses and strains to prevent brittle fracture of steel structures. The need of a computer thermography is highlighted not only for visualization of temperature fields on the surface, but also to control the fields of residual stresses and strains in a controlled element.

  17. Flow and Stress Field Analysis of Different Fluids and Blades for Fermentation Process

    OpenAIRE

    Cheng-Chi Wang; Po-Jen Cheng; Kuo-Chi Liu; Ming-Yi Tsai

    2014-01-01

    Fermentation techniques are applied for the biotechnology and are widely used for food manufacturing, materials processing, chemical reaction, and so forth. Different fluids and types of blades in the tank for fermentation cause distinct flow and stress field distributions on the surface between fluid and blade and various flow reactions in the tank appear. This paper is mainly focused on the analysis of flow field with different fluid viscosities and also studied the stress field acting on t...

  18. Plane-stress fields for sharp notches in pressure-sensitive materials

    International Nuclear Information System (INIS)

    Al-Abduljabbar, Abdulhamid

    2003-01-01

    The effect of pressure sensitive yield on materials toughness can be determined by investigating stress fields around cracks and notches. In this work, fully-developed plastic stress fields around sharp wedge-shaped notches of perfectly-plastic pressure-sensitive materials are investigated for plane-stress case and Mode 1 loading condition. The pressure-sensitive yielding behavior is represented using the Drucker-Prager criterion. Using equilibrium equations, boundary conditions, and the yield criterion, closed-form expressions for stress fields are derived. The analysis covers the gradual change in the notch angle and compares it with the limiting case of a pure horizontal crack. Effects of notch geometry and pressure sensitivity on stress fields are examined by considering different specimen geometries, as well as different levels of pressure sensitivity. Results indicate that while the stress values directly ahead of the notch-tip are not affected, the extent of stress sector at notch front is reduced, thereby causing increase in the radial stress value around the notch. As the pressure sensitivity increases the reduction of the stress sector directly ahead of the notch tip is more evident. Also, for high pressure sensitivity values, introduction of the notch angle reduces the variation of the stress levels. Results are useful for design of structural components. (author)

  19. Level of physical activity, well-being, stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain.

    Science.gov (United States)

    Krøll, Lotte Skytte; Hammarlund, Catharina Sjödahl; Westergaard, Maria Lurenda; Nielsen, Trine; Sloth, Louise Bönsdorff; Jensen, Rigmor Højland; Gard, Gunvor

    2017-12-01

    The prevalence of migraine with co-existing tension-type headache and neck pain is high in the general population. However, there is very little literature on the characteristics of these combined conditions. The aim of this study was to investigate a) the prevalence of migraine with co-existing tension-type headache and neck pain in a clinic-based sample, b) the level of physical activity, psychological well-being, perceived stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain compared to healthy controls, c) the perceived ability of persons with migraine and co-existing tension-type headache and neck pain to perform physical activity, and d) which among the three conditions (migraine, tension-type headache or neck pain) is rated as the most burdensome condition. The study was conducted at a tertiary referral specialised headache centre where questionnaires on physical activity, psychological well-being, perceived stress and self-rated health were completed by 148 persons with migraine and 100 healthy controls matched by sex and average age. Semi-structured interviews were conducted to assess characteristics of migraine, tension-type headache and neck pain. Out of 148 persons with migraine, 100 (67%) suffered from co-existing tension-type headache and neck pain. Only 11% suffered from migraine only. Persons with migraine and co-existing tension-type headache and neck pain had lower level of physical activity and psychological well-being, higher level of perceived stress and poorer self-rated health compared to healthy controls. They reported reduced ability to perform physical activity owing to migraine (high degree), tension-type headache (moderate degree) and neck pain (low degree). The most burdensome condition was migraine, followed by tension-type headache and neck pain. Migraine with co-existing tension-type headache and neck pain was highly prevalent in a clinic-based sample. Persons with migraine and co-existing

  20. Inter-Annual Variability of Soil Moisture Stress Function in the Wheat Field

    Science.gov (United States)

    Akuraju, V. R.; Ryu, D.; George, B.; Ryu, Y.; Dassanayake, K. B.

    2014-12-01

    Root-zone soil moisture content is a key variable that controls the exchange of water and energy fluxes between land and atmosphere. In the soil-vegetation-atmosphere transfer (SVAT) schemes, the influence of root-zone soil moisture on evapotranspiration (ET) is parameterized by the soil moisture stress function (SSF). Dependence of actual ET: potential ET (fPET) or evaporative fraction to the root-zone soil moisture via SSF can also be used inversely to estimate root-zone soil moisture when fPET is estimated by remotely sensed land surface states. In this work we present fPET versus available soil water (ASW) in the root zone observed in the experimental farm sites in Victoria, Australia in 2012-2013. In the wheat field site, fPET vs ASW exhibited distinct features for different soil depth, net radiation, and crop growth stages. Interestingly, SSF in the wheat field presented contrasting shapes for two cropping years of 2012 and 2013. We argue that different temporal patterns of rainfall (and resulting soil moisture) during the growing seasons in 2012 and 2013 are responsible for the distinctive SSFs. SSF of the wheat field was simulated by the Agricultural Production Systems sIMulator (APSIM). The APSIM was able to reproduce the observed fPET vs. ASW. We discuss implications of our findings for existing modeling and (inverse) remote sensing approaches relying on SSF and alternative growth-stage-dependent SSFs.

  1. Influence of plastic slip localization on grain boundary stress fields and microcrack nucleation

    International Nuclear Information System (INIS)

    Sauzay, Maxime; Vor, Kokleang

    2013-01-01

    Slip localization is widely observed in metallic polycrystals after tensile deformation, cyclic deformation (persistent slip bands) or pre-irradiation followed by tensile deformation (channels). Such strong deformation localized in thin slip bands induces local stress concentrations in the quasi-elastic matrix around, at the intersections between slip bands and grain boundaries where microcracks are often observed. Since the work of Stroh, such stress fields have been modeled using the dislocation pile-up theory which leads to stress singularities similar to the LEFM ones. The Griffith criterion has then been widely applied, leading usually to strong underestimations of the macroscopic stress for microcrack nucleation. In fact, slip band thickness is finite: 50-1000 nm depending on material, temperature and loading conditions. Then, many slip planes are plastically activated through the thickness. Stress fields have probably been overestimated using the pile-up theory which assumes that all dislocations are located on the same atomic plane. To evaluate more realistic stress fields, crystalline finite element (FE) computations are carried out using microstructure inputs (slip band aspect ratio and spacing). Slip bands (low critical resolved shear stress) are embedded in an elastic matrix. The following results are obtained concerning grain boundary normal stress fields: - strong influence of slip band thickness close to the slip band corner, which is not accounted for by the pile-up theory. But far away, the thickness has a negligible effect and the predicted stress fields are close to the one predicted by the pile-up theory, - analytical formulae are deduced from the numerous FE computation results which allows the prediction of surface/bulk slips as well as grain boundary stress fields. Slip band plasticity parameters, slip band length and thickness, Schmid factor and remote stress are taken into account. The dependence with respect to the various parameters can

  2. Estimating salinity stress in sugarcane fields with spaceborne hyperspectral vegetation indices

    Science.gov (United States)

    Hamzeh, S.; Naseri, A. A.; AlaviPanah, S. K.; Mojaradi, B.; Bartholomeus, H. M.; Clevers, J. G. P. W.; Behzad, M.

    2013-04-01

    The presence of salt in the soil profile negatively affects the growth and development of vegetation. As a result, the spectral reflectance of vegetation canopies varies for different salinity levels. This research was conducted to (1) investigate the capability of satellite-based hyperspectral vegetation indices (VIs) for estimating soil salinity in agricultural fields, (2) evaluate the performance of 21 existing VIs and (3) develop new VIs based on a combination of wavelengths sensitive for multiple stresses and find the best one for estimating soil salinity. For this purpose a Hyperion image of September 2, 2010, and data on soil salinity at 108 locations in sugarcane (Saccharum officina L.) fields were used. Results show that soil salinity could well be estimated by some of these VIs. Indices related to chlorophyll absorption bands or based on a combination of chlorophyll and water absorption bands had the highest correlation with soil salinity. In contrast, indices that are only based on water absorption bands had low to medium correlations, while indices that use only visible bands did not perform well. From the investigated indices the optimized soil-adjusted vegetation index (OSAVI) had the strongest relationship (R2 = 0.69) with soil salinity for the training data, but it did not perform well in the validation phase. The validation procedure showed that the new salinity and water stress indices (SWSI) implemented in this study (SWSI-1, SWSI-2, SWSI-3) and the Vogelmann red edge index yielded the best results for estimating soil salinity for independent fields with root mean square errors of 1.14, 1.15, 1.17 and 1.15 dS/m, respectively. Our results show that soil salinity could be estimated by satellite-based hyperspectral VIs, but validation of obtained models for independent data is essential for selecting the best model.

  3. Measurement and modeling of magnetic hysteresis under field and stress application in iron–gallium alloys

    International Nuclear Information System (INIS)

    Evans, Phillip G.; Dapino, Marcelo J.

    2013-01-01

    Measurements are performed to characterize the hysteresis in magnetomechanical coupling of iron–gallium (Galfenol) alloys. Magnetization and strain of production and research grade Galfenol are measured under applied stress at constant field, applied field at constant stress, and alternately applied field and stress. A high degree of reversibility in the magnetomechanical coupling is demonstrated by comparing a series of applied field at constant stress measurements with a single applied stress at constant field measurement. Accommodation is not evident and magnetic hysteresis for applied field and stress is shown to be coupled. A thermodynamic model is formulated for 3-D magnetization and strain. It employs a stress, field, and direction dependent hysteron that has an instantaneous loss mechanism, similar to Coulomb-friction or Preisach-type models. Stochastic homogenization is utilized to account for the smoothing effect that material inhomogeneities have on bulk processes. - Highlights: ► We conduct coupled experiments and develop nonlinear thermodynamic models for magnetostrictive iron–gallium (Galfenol) alloys. ► The measurements show unexpected kinematic reversibility in the magnetomechanical coupling. ► This is in contrast with the magnetomechanical coupling in steel which is both thermodynamically and kinematically irreversible. ► The model accurately describes the measurements and provides a framework for understanding hysteresis in ferromagnetic materials which exhibit kinematically reversible magnetomechanical coupling.

  4. No Time to Waste: Transcriptome Study Reveals that Drought Tolerance in Barley May Be Attributed to Stressed-Like Expression Patterns that Exist before the Occurrence of Stress.

    Science.gov (United States)

    Janiak, Agnieszka; Kwasniewski, Miroslaw; Sowa, Marta; Gajek, Katarzyna; Żmuda, Katarzyna; Kościelniak, Janusz; Szarejko, Iwona

    2017-01-01

    Plant survival in adverse environmental conditions requires a substantial change in the metabolism, which is reflected by the extensive transcriptome rebuilding upon the occurrence of the stress. Therefore, transcriptomic studies offer an insight into the mechanisms of plant stress responses. Here, we present the results of global gene expression profiling of roots and leaves of two barley genotypes with contrasting ability to cope with drought stress. Our analysis suggests that drought tolerance results from a certain level of transcription of stress-influenced genes that is present even before the onset of drought. Genes that predispose the plant to better drought survival play a role in the regulatory network of gene expression, including several transcription factors, translation regulators and structural components of ribosomes. An important group of genes is involved in signaling mechanisms, with significant contribution of hormone signaling pathways and an interplay between ABA, auxin, ethylene and brassinosteroid homeostasis. Signal transduction in a drought tolerant genotype may be more efficient through the expression of genes required for environmental sensing that are active already during normal water availability and are related to actin filaments and LIM domain proteins, which may function as osmotic biosensors. Better survival of drought may also be attributed to more effective processes of energy generation and more efficient chloroplasts biogenesis. Interestingly, our data suggest that several genes involved in a photosynthesis process are required for the establishment of effective drought response not only in leaves, but also in roots of barley. Thus, we propose a hypothesis that root plastids may turn into the anti-oxidative centers protecting root macromolecules from oxidative damage during drought stress. Specific genes and their potential role in building up a drought-tolerant barley phenotype is extensively discussed with special emphasis

  5. No Time to Waste: Transcriptome Study Reveals that Drought Tolerance in Barley May Be Attributed to Stressed-Like Expression Patterns that Exist before the Occurrence of Stress

    Directory of Open Access Journals (Sweden)

    Agnieszka Janiak

    2018-01-01

    Full Text Available Plant survival in adverse environmental conditions requires a substantial change in the metabolism, which is reflected by the extensive transcriptome rebuilding upon the occurrence of the stress. Therefore, transcriptomic studies offer an insight into the mechanisms of plant stress responses. Here, we present the results of global gene expression profiling of roots and leaves of two barley genotypes with contrasting ability to cope with drought stress. Our analysis suggests that drought tolerance results from a certain level of transcription of stress-influenced genes that is present even before the onset of drought. Genes that predispose the plant to better drought survival play a role in the regulatory network of gene expression, including several transcription factors, translation regulators and structural components of ribosomes. An important group of genes is involved in signaling mechanisms, with significant contribution of hormone signaling pathways and an interplay between ABA, auxin, ethylene and brassinosteroid homeostasis. Signal transduction in a drought tolerant genotype may be more efficient through the expression of genes required for environmental sensing that are active already during normal water availability and are related to actin filaments and LIM domain proteins, which may function as osmotic biosensors. Better survival of drought may also be attributed to more effective processes of energy generation and more efficient chloroplasts biogenesis. Interestingly, our data suggest that several genes involved in a photosynthesis process are required for the establishment of effective drought response not only in leaves, but also in roots of barley. Thus, we propose a hypothesis that root plastids may turn into the anti-oxidative centers protecting root macromolecules from oxidative damage during drought stress. Specific genes and their potential role in building up a drought-tolerant barley phenotype is extensively discussed

  6. THE FIELD OF RECENT TECTONIC STRESSES IN CENTRAL AND SOUTH-EASTERN ASIA

    Directory of Open Access Journals (Sweden)

    Yu. L. Rebetsky

    2014-01-01

    Full Text Available  The publication presents results of the study aimed at reconstruction of recent crustal stresses for Central and South-Eastern Asia with application of the method of cataclastic analysis of displacements caused by ruptures, which was proposed by Yu.L. Rebetsky. Two sources of seismic data were referred to: (1 the catalog comprising data from publications covering the period from 1904 to 1992, and (2 the Global Centroid Moment Tensor (CMT Database of earthquake mechanisms (http://earthquake.usgs.gov/eqarchives/sopor, which covers the period from 1978 to 2010. The method of cataclastic analysis in its earliest version was applied in 1996 and 1997 when seismic data from the first catalog were analyzed, and it yielded only parameters of stress ellipsoids; the reconstructions were published in a Russian-Chinese journal (it does not exist now. In this paper, these reconstructions are presented in new graphical formats of GIS. Data from the Global CMT Database were analyzed by the method of cataclastic analysis in the new revision with application of its stages 1 and 2. Based on the calculations, orientations of axes of principal stresses, types of ellipsoids, correlations between spherical and deviatoric components of stress tensors, and reduced stresses were determined. The two sets of reconstructions are compared in this paper. The catalog of earthquake focal mechanisms for the period from 1904 to 1992 consolidated information provided by different authors, and thus focal data for many seismic events were highly inconsistent; therefore, the reliability of reconstructions based on such data seems to be lower than that on the basis the Global CMT Database for the period from 1978 to 2010. Some of the reconstructed stress tensor parameters are mapped. For the areas which data are given in the Global CMT Database and considered as more reliable, mapping is based on stress parameters calculated from such data. For the areas that are not covered by the

  7. Analysis of fracture patterns and local stress field variations in fractured reservoirs

    Science.gov (United States)

    Deckert, Hagen; Drews, Michael; Fremgen, Dominik; Wellmann, J. Florian

    2010-05-01

    A meaningful qualitative evaluation of permeabilities in fractured reservoirs in geothermal or hydrocarbon industry requires the spatial description of the existing discontinuity pattern within the area of interest and an analysis how these fractures might behave under given stress fields. This combined information can then be used for better estimating preferred fluid pathway directions within the reservoir, which is of particular interest for defining potential drilling sites. A description of the spatial fracture pattern mainly includes the orientation of rock discontinuities, spacing relationships between single fractures and their lateral extent. We have examined and quantified fracture patterns in several outcrops of granite at the Costa Brava, Spain, and in the Black Forest, Germany, for describing reservoir characteristics. For our analysis of fracture patterns we have used photogrammetric methods to create high-resolution georeferenced digital 3D images of outcrop walls. The advantage of this approach, compared to conventional methods for fracture analysis, is that it provides a better 3D description of the fracture geometry as the entity of position, extent and orientation of single fractures with respect to their surrounding neighbors is conserved. Hence for instance, the method allows generating fracture density maps, which can be used for a better description of the spatial distribution of discontinuities in a given outcrop. Using photogrammetric techniques also has the advantage to acquire very large data sets providing statistically sound results. To assess whether the recorded discontinuities might act as fluid pathways information on the stress field is needed. A 3D model of the regional tectonic structure was created and the geometry of the faults was put into a mechanical 3D Boundary Element (BE) Model. The model takes into account the elastic material properties of the geological units and the orientation of single fault segments. The

  8. Inferences about the local stress field from focal mechanisms: Applications to earthquakes in the southern Great Basin of Nevada

    International Nuclear Information System (INIS)

    Harmsen, S.C.; Rogers, A.M.

    1986-01-01

    Focal mechanisms determined from regional-network earthquake data or aftershock field investigation often contain members ranging from strike slip to normal slip in extensional tectonic environments or from strike slip to thrust slip in compressional environments. Although the coexistence of normal and strike-slip faulting has suggested to some investigators that the maximum and intermediate principal stresses are of approximately equal magnitude, several have asserted that the directions of principle stresses can or must interchange to accommodate both types of mechanisms (Zoback and Zoback 1980b; Vetter and Ryall, 1983). A Coulomb-Navier criterion of slip is invoked to demonstrate that both types of mechanisms, as well as oblique members having preferred nodal-plane dips intermediate between those of the strike-slip and normal mechanisms, may be observed in a region where the stress field, resolved into principal components, is axially symmetric. The proximate coexistence of earthquakes having diverse focal mechanisms could be interpreted as evidence for an approximately axially symmetric stress field in a region where optimally oriented planes of weakness are known to exist in the host rock. 10 refs., 6 figs

  9. Spatial variations of current tectonic stress field and its relationship to the structure and rheology of lithosphere around the Bohai Sea, North China

    Science.gov (United States)

    Li, Xianrui; Wang, Jie; Zeng, Zuoxun; Dai, Qingqin

    2017-05-01

    The tectonic stress field in the middle-upper crust is closely related to the structure and rheology of the lithosphere. To determine the stress field in the deep crust, we inversed the focal mechanism solutions (FMSs) of 62 earthquakes that occurred between 2009 and 2015 in the Bohai Sea and its surrounding areas using broadband seismic waveforms collected from 140 stations. We then derived the tectonic stress field using the software SATSI (Spatial And Temporal Stress Inversion) based on the damped linear inversion method. The inversion results show that both the maximum (σ1) and minimum (σ3) principle stress axes throughout the entire region are nearly horizontal except in the Tangshan and Haicheng areas, suggesting that the study area is predominantly under a strike-slip faulting stress regime. The σ1 and σ3 axes are found to be oriented in the NEE-SWW or nearly E-W and NNW-SSE or nearly S-N directions, respectively. These results indicate that the stress field in the North China Craton is controlled by the combined effects of the Pacific Plate westward subduction and the India-Eurasia Plate collision. However, localized normal faulting stress regimes (where the vertical stress σv ≈ σ1) are observed in the Tangshan and Haicheng areas, where low viscosity bodies (LVBs) were identified using geophysical data. Based on the analysis of focal mechanism solutions, active faults and lithosphere rheology characteristics in the Tangshan and Haicheng areas, we speculate that the anomalous stress regime is caused by the local extension resulting from the movement of strike-slip faults under the action of the regional stress field. The existence of LVB may indicate weakness in the crust that favors the accumulation of tectonic stress and triggers large earthquakes.

  10. Hydraulic fracturing stress measurements at Yucca Mountain, Nevada, and relationship to the regional stress field

    International Nuclear Information System (INIS)

    Stock, J.M.; Healy, J.H.; Hickman, S.H.; Zoback, M.D.

    1985-01-01

    Hydraulic fracturing stress measurements and acoustic borehole televiewer logs were run in holes USW G-1 and USW G-2 at Yucca Mountain as part of the Nevada Nuclear Waste Storage Investigations for the U. S. Department of Energy. Eight tests in the saturated zone, at depths from 646 to 1288 m, yielded values of the least horizontal stress S/sub h/ that are considerably lower than the vertical principal stress S/sub v/. In tests for which the greatest horizontal principal stress S/sub H/ could be determined, it was found to be less than S/sub v/, indicating a normal faulting stress regime. The borehole televiewer logs showed the presence of long (in excess of 10 m), vertical, drilling-induced fractures in the first 300 m below the water table. These are believed to form by the propagation of small preexisting cracks under the excess downhole fluid pressures (up to 5.2 MPa) applied during drilling. The presence of these drilling-induced hydrofractures provides further confirmation of the low value of the least horizontal stresses. A least horizontal principal stress direction of N60 0 W--N65 0 W is indicated by the orientation of the drilling-induced hydrofractures (N25 0 E--N30 0 E), and the orientation of stress-induced well bore breakouts in the lower part of USW G-2 (N65 0 W). This direction is in good agreement with indicators of stress direction from elsewhere at the Nevada Test Site. The observed stress magnitudes and directions were examined for the possibility of slip on preexisting faults. Using these data, the Coulomb criterion for frictional sliding suggests that for coefficients of friction close to 0.6, movement on favorably oriented faults could be expected

  11. Use of Pulsing Electromagnetic Fields for the Treatment of Pelvic Stress Fractures Among Female Soldiers

    National Research Council Canada - National Science Library

    Jones, D

    1995-01-01

    .... Pulsing electromagnetic fields (PEMFs)have been shown to speed the healing of non-union fractures and we have used them successfully to treat stress fractures in the lower limbs. All women at Ft...

  12. Fracture mechanics and residual fatigue life analysis for complex stress fields. Technical report

    International Nuclear Information System (INIS)

    Besuner, P.M.

    1975-07-01

    This report reviews the development and application of an influence function method for calculating stress intensity factors and residual fatigue life for two- and three-dimensional structures with complex stress fields and geometries. Through elastic superposition, the method properly accounts for redistribution of stress as the crack grows through the structure. The analytical methods used and the computer programs necessary for computation and application of load independent influence functions are presented. A new exact solution is obtained for the buried elliptical crack, under an arbitrary Mode I stress field, for stress intensity factors at four positions around the crack front. The IF method is then applied to two fracture mechanics problems with complex stress fields and geometries. These problems are of current interest to the electric power generating industry and include (1) the fatigue analysis of a crack in a pipe weld under nominal and residual stresses and (2) fatigue analysis of a reactor pressure vessel nozzle corner crack under a complex bivariate stress field

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

    NARCIS (Netherlands)

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

    2012-01-01

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

  14. Numerical and experimental study of moisture-induced stress and strain field developments in timber logs

    DEFF Research Database (Denmark)

    Larsen, Finn; Ormarsson, Sigurdur

    2013-01-01

    shrinkage and the inhomogeneity of the material. To obtain a better understanding of how stresses develop during climatic variations, the field histories of stresses (and strains) in cross sections in their entirety need to be studied. The present paper reports on experiments and numerical simulations...

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

    NARCIS (Netherlands)

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

    2012-01-01

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

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

    NARCIS (Netherlands)

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

    2012-01-01

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

  17. Effect of External Electric Field Stress on Gliadin Protein Conformation

    OpenAIRE

    Singh, Ashutosh; Munshi, Shirin; Raghavan, Vijaya

    2013-01-01

    A molecular dynamic (MD) modeling approach was applied to evaluate the effect of external electric field on gliadin protein structure and surface properties. Static electric field strengths of 0.001 V/nm and 0.002 V/nm induced conformational changes in the protein but had no significant effect on its surface properties. The study of hydrogen bond evolution during the course of simulation revealed that the root mean square deviation, radius of gyration and secondary structure formation, all de...

  18. Estimating the Reactivation Potential of Pre-Existing Fractures in Subsurface Granitoids from Outcrop Analogues and in-Situ Stress Modeling: Implications for EGS Reservoir Stimulation with an Example from Thuringia (Central Germany)

    Science.gov (United States)

    Kasch, N.; Ustaszewski, K. M.; Siegburg, M.; Navabpour, P.; Hesse, G.

    2014-12-01

    The Mid-German Crystalline Rise (MGCR) in Thuringia (central Germany) is part of the European Variscan orogen and hosts large extents of Visean granites (c. 350 Ma), locally overlain by up to 3 km of Early Permian to Mid-Triassic volcanic and sedimentary rocks. A geothermal gradient of 36°C km-1 suggests that such subsurface granites form an economically viable hot dry rock reservoir at > 4 km depth. In order to assess the likelihood of reactivating any pre-existing fractures during hydraulic reservoir stimulation, slip and dilation tendency analyses (Morris et al. 1996) were carried out. For this purpose, we determined orientations of pre-existing fractures in 14 granite exposures along the southern border fault of an MGCR basement high. Additionally, the strike of 192 Permian magmatic dikes affecting the granite was considered. This analysis revealed a prevalence of NW-SE-striking fractures (mainly joints, extension veins, dikes and subordinately brittle faults) with a maximum at 030/70 (dip azimuth/dip). Borehole data and earthquake focal mechanisms reveal a maximum horizontal stress SHmax trending N150°E and a strike-slip regime. Effective in-situ stress magnitudes at 4.5 km depth, assuming hydrostatic conditions and frictional equilibrium along pre-existing fractures with a friction coefficient of 0.85 yielded 230 and 110 MPa for SHmax and Shmin, respectively. In this stress field, fractures with the prevailing orientations show a high tendency of becoming reactivated as dextral strike-slip faults if stimulated hydraulically. To ensure that a stimulation well creates fluid connectivity on a reservoir volume as large as possible rather than dissipating fluids along existing fractures, it should follow a trajectory at the highest possible angle to the orientation of prevailing fractures, i.e. subhorizontal and NE-SW-oriented. References: Morris, A., D. A. Ferrill, and D. B. Henderson (1996), Slip-tendency analysis and fault reactivation, Geology, 24, 275-278.

  19. The measurement of internal stress fields in weldments and around cracks using high resolution neutron diffraction

    International Nuclear Information System (INIS)

    Allen, A.J.; Hutchings, M.T.; Windsor, C.G.

    1987-01-01

    The paper describes and illustrates the capability of neutron diffraction to measure the complete internal lattice macrostrain field, and hence the stress field, within steel components and weldments arising from their fabrication. A brief outline is given of the theory of the neutron method. The experimental considerations are discussed. The method is illustrated by its application to the measurement of the stress distribution in a:- uniaxially stressed mild steel rod, a double - V test weld, a tube-plate weld, and a cracked fatigue test specimen. (U.K.)

  20. Shielding Flowers Developing under Stress: Translating Theory to Field Application

    Directory of Open Access Journals (Sweden)

    Noam Chayut

    2014-07-01

    Full Text Available Developing reproductive organs within a flower are sensitive to environmental stress. A higher incidence of environmental stress during this stage of a crop plants’ developmental cycle will lead to major breaches in food security. Clearly, we need to understand this sensitivity and try and overcome it, by agricultural practices and/or the breeding of more tolerant cultivars. Although passion fruit vines initiate flowers all year round, flower primordia abort during warm summers. This restricts the season of fruit production in regions with warm summers. Previously, using controlled chambers, stages in flower development that are sensitive to heat were identified. Based on genetic analysis and physiological experiments in controlled environments, gibberellin activity appeared to be a possible point of horticultural intervention. Here, we aimed to shield flowers of a commercial cultivar from end of summer conditions, thus allowing fruit production in new seasons. We conducted experiments over three years in different settings, and our findings consistently show that a single application of an inhibitor of gibberellin biosynthesis to vines in mid-August can cause precocious flowering of ~2–4 weeks, leading to earlier fruit production of ~1 month. In this case, knowledge obtained on phenology, environmental constraints and genetic variation, allowed us to reach a practical solution.

  1. Implications of recent developments in the plastic fracture mechanics field to the PCI stress corrosion problem

    International Nuclear Information System (INIS)

    Smith, E.

    1980-01-01

    Fractographic observations on irradiated Zircaloy cladding stress corrosion fracture surfaces are considered against the background of recent developments in the plastic fracture mechanics field. Dimples have been observed on the fracture surfaces of failed cladding, even though the cracks in metallographic sections are tight, i.e., crack propagation is associated with a low crack tip opening angle. This result is interpreted as providing evidence for an environmentally assisted ductile mode of fracture. The presence of this fracture mode forms the basis of an argument, which adds further support for the view that power ramp stress corrosion cladding failures are caused by stress concentrations that produce stress gradients in the cladding. (orig.)

  2. Mechanical stress analysis for the poloidal field coils of TORE SUPRA

    International Nuclear Information System (INIS)

    Ane, J.M.; Perin, J.P.

    1985-01-01

    Hoop stresses, up to 100 MPa, in the poloidal field coils of TORE SUPRA have to be reacted back to the main body of the coil where a conductor ends or is twisted for an interturn or an interlayer transition. The load is taken by shear stress through the insulation. Carefully designed configurations, based on 1D, 2D and 3D analysis results, limit the shear stress levels to 15 MPa. A fatigue test of a conductor termination has shown that the experimental results are in good agreement with the calculated stresses

  3. Flow and Stress Field Analysis of Different Fluids and Blades for Fermentation Process

    Directory of Open Access Journals (Sweden)

    Cheng-Chi Wang

    2014-02-01

    Full Text Available Fermentation techniques are applied for the biotechnology and are widely used for food manufacturing, materials processing, chemical reaction, and so forth. Different fluids and types of blades in the tank for fermentation cause distinct flow and stress field distributions on the surface between fluid and blade and various flow reactions in the tank appear. This paper is mainly focused on the analysis of flow field with different fluid viscosities and also studied the stress field acting on the blades with different scales and shapes of them under specific rotational speed. The results show that the viscosity of fluid influences the flow field and stress distributions on the blades. The maximum stress that acts on the blade is increased with the increasing of viscosity. On the other hand, the ratio of blade length to width influences stress distributions on the blade. At the same time, the inclined angle of blade is also the key parameter for the consideration of design and appropriate inclined angle of blade will decrease the maximum stress. The results provide effective means of gaining insights into the flow and stress distribution of fermentation process.

  4. Stress fields around a crack lying parallel to a free surface

    International Nuclear Information System (INIS)

    Higashida, Yutaka; Kamada, K.

    1980-12-01

    A method of stress analysis for a two dimentional crack, which is subjected to internal gas pressure, and situated parallel to a free surface of a material, is presented. It is based on the concept of continuously distributed edge dislocations of two kinds, i.e. one with Burgers vector normal to the free surface and the other with parallel to it. Stress fields of individual dislocations are chosen so as to satisfy stress free boundary conditions at the free surface, by taking account of image dislocations. Distributions of the both kinds of dislocations in the crack are derived so as to give the internal gas pressure and, at the same time, to satisfy shear stress free boundary condition on the crack surface. Stress fields σsub(xx), σsub(yy) and σsub(xy) in the sub-surface layer are then determined from them. They have square root singularities at the crack-tip. (author)

  5. Stress Corrosion Cracking of Steel and Aluminum in Sodium Hydroxide: Field Failure and Laboratory Test

    Directory of Open Access Journals (Sweden)

    Y. Prawoto

    2012-01-01

    Full Text Available Through an investigation of the field failure analysis and laboratory experiment, a study on (stress corrosion cracking SCC behavior of steel and aluminum was performed. All samples were extracted from known operating conditions from the field failures. Similar but accelerated laboratory test was subsequently conducted in such a way as to mimic the field failures. The crack depth and behavior of the SCC were then analyzed after the laboratory test and the mechanism of stress corrosion cracking was studied. The results show that for the same given stress relative to ultimate tensile strength, the susceptibility to SCC is greatly influenced by heat treatment. Furthermore, it was also concluded that when expressed relative to the (ultimate tensile strength UTS, aluminum has similar level of SCC susceptibility to that of steel, although with respect to the same absolute value of applied stress, aluminum is more susceptible to SCC in sodium hydroxide environment than steel.

  6. Effects of upper mantle heterogeneities on the lithospheric stress field and dynamic topography

    Science.gov (United States)

    Osei Tutu, Anthony; Steinberger, Bernhard; Sobolev, Stephan V.; Rogozhina, Irina; Popov, Anton A.

    2018-05-01

    The orientation and tectonic regime of the observed crustal/lithospheric stress field contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. In this study, we analyze the influence of the thermal and density structure of the upper mantle on the lithospheric stress field and topography. We use a 3-D lithosphere-asthenosphere numerical model with power-law rheology, coupled to a spectral mantle flow code at 300 km depth. Our results are validated against the World Stress Map 2016 (WSM2016) and the observation-based residual topography. We derive the upper mantle thermal structure from either a heat flow model combined with a seafloor age model (TM1) or a global S-wave velocity model (TM2). We show that lateral density heterogeneities in the upper 300 km have a limited influence on the modeled horizontal stress field as opposed to the resulting dynamic topography that appears more sensitive to such heterogeneities. The modeled stress field directions, using only the mantle heterogeneities below 300 km, are not perturbed much when the effects of lithosphere and crust above 300 km are added. In contrast, modeled stress magnitudes and dynamic topography are to a greater extent controlled by the upper mantle density structure. After correction for the chemical depletion of continents, the TM2 model leads to a much better fit with the observed residual topography giving a good correlation of 0.51 in continents, but this correction leads to no significant improvement of the fit between the WSM2016 and the resulting lithosphere stresses. In continental regions with abundant heat flow data, TM1 results in relatively small angular misfits. For example, in western Europe the misfit between the modeled and observation-based stress is 18.3°. Our findings emphasize that the relative contributions coming from shallow and deep mantle dynamic forces are quite different for the lithospheric stress field and dynamic

  7. Displacement and stress fields around rock fractures opened by irregular overpressure variations

    Directory of Open Access Journals (Sweden)

    Shigekazu eKusumoto

    2014-05-01

    Full Text Available Many rock fractures are entirely driven open by fluids such as ground water, geothermal water, gas, oil, and magma. These are a subset of extension fractures (mode I cracks; e.g., dikes, mineral veins and joints referred to as hydrofractures. Field measurements show that many hydrofractures have great variations in aperture. However, most analytical solutions for fracture displacement and stress fields assume the loading to be either constant or with a linear variation. While these solutions have been widely used, it is clear that a fracture hosted by heterogeneous and anisotropic rock is normally subject to loading that is neither constant nor with a linear variation. Here we present new general solutions for the displacement and stress fields around hydrofractures, modelled as two-dimensional elastic cracks, opened by irregular overpressure variations given by the Fourier cosine series. Each solution has two terms. The first term gives the displacement and stress fields due to the average overpressure acting inside the crack; it is given by the initial term of the Fourier coefficients expressing the overpressure variation. The second term gives the displacement and stress fields caused by the overpressure variation; it is given by general terms of the Fourier coefficients and solved through numerical integration. Our numerical examples show that the crack aperture variation closely reflects the overpressure variation. Also, that the general displacement and stress fields close to the crack follow the overpressure variation but tend to be more uniform far from the crack. The present solutions can be used to estimate the displacement and stress fields around any fluid-driven crack, that is, any hydrofracture, as well as its aperture, provided the variation in overpressure can be described by Fourier series. The solutions add to our understanding of local stresses, displacements, and fluid transport associated with hydrofractures in the crust.

  8. On the stress calculation within phase-field approaches: a model for finite deformations

    Science.gov (United States)

    Schneider, Daniel; Schwab, Felix; Schoof, Ephraim; Reiter, Andreas; Herrmann, Christoph; Selzer, Michael; Böhlke, Thomas; Nestler, Britta

    2017-08-01

    Numerical simulations based on phase-field methods are indispensable in order to investigate interesting and important phenomena in the evolution of microstructures. Microscopic phase transitions are highly affected by mechanical driving forces and therefore the accurate calculation of the stresses in the transition region is essential. We present a method for stress calculations within the phase-field framework, which satisfies the mechanical jump conditions corresponding to sharp interfaces, although the sharp interface is represented as a volumetric region using the phase-field approach. This model is formulated for finite deformations, is independent of constitutive laws, and allows using any type of phase inherent inelastic strains.

  9. Coherent gradient sensing method for measuring thermal stress field of thermal barrier coating structures

    Directory of Open Access Journals (Sweden)

    Kang Ma

    2017-01-01

    Full Text Available Coherent gradient sensing (CGS method can be used to measure the slope of a reflective surface, and has the merits of full-field, non-contact, and real-time measurement. In this study, the thermal stress field of thermal barrier coating (TBC structures is measured by CGS method. Two kinds of powders were sprayed onto Ni-based alloy using a plasma spraying method to obtain two groups of film–substrate specimens. The specimens were then heated with an oxy-acetylene flame. The resulting thermal mismatch between the film and substrate led to out-of-plane deformation of the specimen. The deformation was measured by the reflective CGS method and the thermal stress field of the structure was obtained through calibration with the help of finite element analysis. Both the experiment and numerical results showed that the thermal stress field of TBC structures can be successfully measured by CGS method.

  10. [Effects of psychological stress on performances in open-field test of rats and tyrosine's modulation].

    Science.gov (United States)

    Chen, Wei-Qiang; Cheng, Yi-Yong; Li, Shu-Tian; Hong, Yan; Wang, Dong-Lan; Hou, Yue

    2009-02-01

    To explore the effects of different doses of tyrosine modulation on behavioral performances in open field test of psychological stress rats. The animal model of psychological stress was developed by restraint stress for 21 days. Wistar rats were randomly assigned to five groups (n = 10) as follows: control group (CT), stress control group (SCT), low, medium and high-doses of tyrosine modulation stress groups (SLT, SMT and SIT). The changes of behavioral performances were examined by open-field test. Serum levels of cortisol, norepinephrine and dopamine were also detected. The levels of serum cortisol were all increased obviously in the four stress groups, and their bodyweight gainings were diminished. The behavioral performances of SCT rats in open-field test were changed significantly in contrast to that of CT rats. However, The behavioral performances of SMT and SHT rats were not different from that of CT rats. In addition, the serum levels of norepinephrine and dopamine were downregulated obviously in SCT and SLT groups, and no differences were observed in other groups. Psychological stress can impair body behavioral performances, and moderate tyrosine modulation may improve these abnormal changes. The related mechanisms may be involved with the changes of norepinephrine and dopamine.

  11. Numerical modeling of tectonic stress field and fault activity in North China

    Directory of Open Access Journals (Sweden)

    Li Yan

    2012-02-01

    Full Text Available On the basis of a 3-dimension visco-elastic finite element model of lithosphere in North China, we numerically simulate the recent mutative figures of tectonic stress field. Annual change characteristics of stress field are; 1 Maximum principal tensile stress is about 3–9 kPaa−1 and its azimuth lie in NNW-SSE. 2 Maximum principal compressive stress is about 1–6 kPaa−1 and its azimuth lie in NEE-SWW. 3 Maximum principal tensile stress is higher both in the west region and Liaoning Province. 4 Variation of tectonic stress field benefits fault movement in the west part and northeast part of North China. 5 Annual accumulative rates of Coulomb fracture stress in Tanlu fault belt have segmentation patterns: Jiashan-Guangji segment is the highest (6 kPaa−1, Anshan-Liaodongwan segment is the second (5 kPaa−1, and others are relatively lower (3–4 kPaa−1.

  12. Physiologic response of rats to cold stress after exposure to 60-Hz electric fields

    International Nuclear Information System (INIS)

    Hilton, D.I.; Phillips, R.D.; Free, M.J.; Lang, L.L.; Chandon, J.H.; Kaune, W.T.

    1978-01-01

    In two experiments, the responses of the hypothalamo-pituitary-adrenal, thermoregulatory and cardiovascular systems were assessed in rats subjected to cold stress after exposure to uniform 60-Hz electric fields of 100 kV/m for one month. In the first experiment, plasma corticosterone levels were measured following exposure or sham exposure with the animals maintained at room temperature (∼23 deg). Corticosterone levels were also measured in rats subjected to cold stress (-13 deg. for one hour) immediately after the exposure period. Plasma corticosterone levels in the cold-stressed animals were significantly higher than in those kept at room temperature; however, there were no significant differences between exposed and sham-exposed animals for either the ambient or cold-stress situations. The second experiment followed the same field exposure and cold-stress protocol, only measurements of heart rate, deep colonic temperature and skin temperature were made before, during and after cold-stressing. The results for exposed and sham-exposed animals were essentially identical, failing to demonstrate any effect of electric field exposure on thermoregulatory and cardiovascular response to cold stress. (author)

  13. System level approaches for mainstreaming tobacco control into existing health programs in India: Perspectives from the field

    Directory of Open Access Journals (Sweden)

    Rajmohan Panda

    2015-01-01

    Full Text Available Introduction: India is the second largest consumer of tobacco in the world, and varieties of both smoked and smokeless tobacco products are widely available. The national program for tobacco control is run like a vertical stand-alone program. There is a lack of understanding of existing opportunities and barriers within the health programs that influence the integration of tobacco control messages into them. The present formative research identifies such opportunities and barriers. Methods: We conducted a multi-step, mixed methodological study of primary care personnel and policy-makers in two Indian states of Andhra Pradesh and Gujarat. The primary purpose of our study was to investigate health worker and policy-maker perceptions on the integration of tobacco control intervention. We systematically collected data in three steps: In Step I, we conducted in-depth interviews (IDIs and focus group discussions with primary care health personnel, Step II consists of a quantitative survey among health care providers (n = 1457 to test knowledge, attitudes and practices in tobacco control and Step III we conducted 75 IDIs with program heads and policy-makers to evaluate the relative congruence of their views on integration of the tobacco control program. Results: Majority of the health care providers recognized tobacco use as a major health problem. There was a general consensus for the need of training for effective dissemination of information from health care providers to patients. Almost 92% of the respondents opined that integration of tobacco control with other health programs will be highly effective to downscale the tobacco epidemic. Conclusions: Our findings suggest the need for integration of tobacco control program into existing health programs. Integration of tobacco control strategies into the health care system within primary and secondary care will be more effective and counseling for tobacco cessation should be available for population

  14. Cavitation microstreaming and stress fields created by microbubbles.

    Science.gov (United States)

    Collis, James; Manasseh, Richard; Liovic, Petar; Tho, Paul; Ooi, Andrew; Petkovic-Duran, Karolina; Zhu, Yonggang

    2010-02-01

    Cavitation microstreaming plays a role in the therapeutic action of microbubbles driven by ultrasound, such as the sonoporative and sonothrombolytic phenomena. Microscopic particle-image velocimetry experiments are presented. Results show that many different microstreaming patterns are possible around a microbubble when it is on a surface, albeit for microbubbles much larger than used in clinical practice. Each pattern is associated with a particular oscillation mode of the bubble, and changing between patterns is achieved by changing the sound frequency. Each microstreaming pattern also generates different shear stress and stretch/compression distributions in the vicinity of a bubble on a wall. Analysis of the micro-PIV results also shows that ultrasound-driven microstreaming flows around bubbles are feasible mechanisms for mixing therapeutic agents into the surrounding blood, as well as assisting sonoporative delivery of molecules across cell membranes. Patterns show significant variations around the bubble, suggesting sonoporation may be either enhanced or inhibited in different zones across a cellular surface. Thus, alternating the patterns may result in improved sonoporation and sonothrombolysis. The clear and reproducible delineation of microstreaming patterns based on driving frequency makes frequency-based pattern alternation a feasible alternative to the clinically less desirable practice of increasing sound pressure for equivalent sonoporative or sonothrombolytic effect. Surface divergence is proposed as a measure relevant to sonoporation.

  15. Pore Pressure and Field stress variation from Salt Water Injection; A case Study from Beaver Lodge Field in Williston Basin

    Science.gov (United States)

    Mohammed, R. A.; Khatibi, S.

    2017-12-01

    One of the major concerns in producing from oil and gas reservoirs in North American Basins is the disposal of high salinity salt water. It is a misconception that Hydro frack triggers Earthquakes, but due to the high salinity and density of water being pumped to the formation that has pore space of the rock already filled, which is not the case in Hydro-frack or Enhanced Oil Recovery in which fracturing fluid is pumped into empty pore space of rocks in depleted reservoirs. A review on the Bakken history showed that the concerns related to induce seismicity has increased over time due to variations in Pore pressure and In-situ stress that have shown steep changes in the region over the time. In this study, we focused on Pore pressure and field Stress variations in lower Cretaceous Inyan Kara and Mississippian Devonian Bakken, Inyan Kara is the major source for class-II salt-water disposal in the basin. Salt-water disposal is the major cause for induced seismicity. A full field study was done on Beaver Lodge Field, which has many salt-water disposal wells Adjacent to Oil and Gas Wells. We analyzed formation properties, stresses, pore-pressure, and fracture gradient profile in the field and. The constructed Mechanical Earth Model (MEM) revealed changes in pore pressure and stresses over time due to saltwater injection. Well drilled in the past were compared to recently drilled wells, which showed much stress variations. Safe mud weight Window of wells near proximity of injection wells was examined which showed many cases of wellbore instabilities. Results of this study will have tremendous impact in studying environmental issues and the future drilling and Fracking operations.

  16. Stress fields in the Antarctic plate inferred from focal mechanisms of intraplate earthquakes

    Directory of Open Access Journals (Sweden)

    Atsuki Kubo

    1999-03-01

    Full Text Available Typical directional features of intraplate stresses are extracted from focal mechanism solutions of earthquakes in the Antarctic plate. Typical directions of stresses are obtained in the following regions, 1 Bellingshausen Sea, 2 south of Juan-Fernandez microplate, 3 Balleny Island region and 4 Kerguelen region. P axes in regions 1 and 2 have been interpreted by ridge push force. However these interpretations are based on one focal mechanism for each event and on crude physical concept of ridge push. It is difficult to explain intraplate stress fields in these regions only by the local ridge push force. The stress direction in region 3 can be interpreted by both deformation near triple junction and deformation due to deglaciation. Earthquakes near region 4 appear to be normal fault event. Because normal fault events appear only in the younger ocean floor, the stress field may be affected by thermal features such as hot spots Quantitative modeling and superposition of various stress factors are required to discriminate among stress origins. It is difficult to discuss stress directions in and around Antarctic continent, because number of the earthquakes is not enough.

  17. Stress analyses of ITER toroidal field coils under fault conditions

    International Nuclear Information System (INIS)

    Jong, C.T.J.

    1990-02-01

    The International Thermonuclear Experimental Reactor (ITER) is intended as an experimental thermonuclear tokamak reactor for testing the basic physics, performance and technologies essential to future fusion reactors. The ITER design will be based on extensive new design work, supported by new physical and technological results, and on the great body of experience built up over several years from previous national and international reactor studies. Conversely, the ITER design process should provide the fusion community with valuable insights into what key areas need further development or clarification as we move forward towards practical fusion power. As part of the design process of the ITER toroidal field coils the mechanical behaviour of the magnetic system under fault conditions has to be analysed in more detail. This paper describes the work carried out to create a detailed finite element model of two toroidal field coils as well as some results of linear elastic analyses with fault conditions. The analyses have been performed with the finite element code ANSYS. (author). 5 refs.; 8 figs.; 2 tabs

  18. Existing of Vesicular Arbuscular Mycorrhizal on The Corn Field Subjected by Long-term Organic and Inorganic Fertilizers

    Directory of Open Access Journals (Sweden)

    Sri Yusnaini

    2009-09-01

    Full Text Available The existing of vesicular arbuscular mycorrhizal fungi was determined in continuously cropping systems which had applied by organic and/or inorganic fertilizers for a long term (4 years application of corn and upland rice rotation. The experiment was established at Taman Bogo, Probolinggo sub-district, East Lampung district. The experiment were: control (without fertilizer, 20 Mg ha-1 chicken manure (CK, 20 Mg ha-1 green manure Glyricidium sp. (GM, 100 % inorganic fertilizers (IF (urea 300 kg ha-1, SP 36 200 kg ha-1, and KCl 100 kg ha-1, 50% CK + 50% IF, 50% GM + 50% IF, 75% CK + 25% IF, and 75% GM + 25% IF. Soil samples were taken at the first corn growing season (2001 and the eight corn growing season (2004. VAM fungi spores were examined by wet sieving methods. The results showed that application of chicken manure or its combination with inorganic fertilizers had higher VAM fungi spore. The dominant species of VAM fungi at all treatment was Glomus constrictum.

  19. Development of the electromagnetic tomography system. Field test results using existing equipment; EM tomography system no kaihatsu. Kison sochi ni yoru test sokutei kekka

    Energy Technology Data Exchange (ETDEWEB)

    Kumekawa, Y; Miura, Y; Takasugi, S [Geothermal Energy Research and Development Co. Ltd., Tokyo (Japan); Arai, E [Metal Mining Agency of Japan, Tokyo (Japan)

    1996-05-01

    With the purpose of developing an electromagnetic tomography system, an observation was carried out with existing equipment combined, and the data was analyzed. The measuring equipment consisted of existing borehole vertical magnetic field sensors as the sensor part, MT method receivers as the receiving device, and existing CSMT method transmitters as the transmitting device. The measuring was performed at the Richmond Field Station which was abundant in existing data and which had a comparatively simple resistivity structure. The borehole vertical magnetic field sensors were lowered inside the borehole, and signal sources were arranged at 10m apart on the traverse line in the direction from northeast to southwest with the borehole as the center. The analysis of the data was made with the use of EM1D by three models, namely, 10 ohm{center_dot}m homogeneous earth model, 100 ohm{center_dot}m homogeneous earth model, and horizontal 7 layer model prepared on the basis of electric logging results; and a comparative examination was made against the measured data. As a result, it was demonstrated that the test measurement agreed very well with the model from the electric logging results and that it was the data reflecting a resistivity structure. 8 refs., 6 figs.

  20. Thermal Stress FE Analysis of Large-scale Gas Holder Under Sunshine Temperature Field

    Science.gov (United States)

    Li, Jingyu; Yang, Ranxia; Wang, Hehui

    2018-03-01

    The temperature field and thermal stress of Man type gas holder is simulated by using the theory of sunshine temperature field based on ASHRAE clear-sky model and the finite element method. The distribution of surface temperature and thermal stress of gas holder under the given sunshine condition is obtained. The results show that the thermal stress caused by sunshine can be identified as one of the important factors for the failure of local cracked oil leakage which happens on the sunny side before on the shady side. Therefore, it is of great importance to consider the sunshine thermal load in the stress analysis, design and operation of large-scale steel structures such as the gas holder.

  1. Mapping residual stress fields from Vickers hardness indents using Raman microprobe spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sparks, R.G.; Enloe, W.S.; Paesler, M.A.

    1988-12-01

    Micro-Raman spectroscopy is used to map the residual stress fields in the vicinity of Vickers hardness indents. Both 514.5 and 488.0 nm, light is used to excite the effect and the resulting shifted and broadened Raman peaks are analyzed using computer deconvolution. Half-wave plates are used to vary the orientation of the incident later light`s polarization state with respect to crystal orientation. The Raman scattered light is then analyzed for polarization dependences which are indicative of the various components of the Raman scattering tensor. Such studies can yield valuable information about the orientation of stress components in a well known stress field. The results can then be applied to the determination of stress components in machined semiconductor materials.

  2. Evaluation of properties and thermal stress field for thermal barrier coatings

    Institute of Scientific and Technical Information of China (English)

    王良; 齐红宇; 杨晓光; 李旭

    2008-01-01

    In order to get thermal stress field of the hot section with thermal barrier coating (TBCs), the thermal conductivity and elastic modulus of top-coat are the physical key properties. The porosity of top-coat was tested and evaluated under different high temperatures. The relationship between the microstructure (porosity of top-coat) and properties of TBCs were analyzed to predict the thermal properties of ceramic top-coat, such as thermal conductivity and elastic modulus. The temperature and stress field of the vane with TBCs were simulated using two sets of thermal conductivity data and elastic modulus, which are from literatures and this work, respectively. The results show that the temperature and stress distributions change with thermal conductivity and elastic modulus. The differences of maximum temperatures and stress are 6.5% and 8.0%, respectively.

  3. Extreme of random field over rectangle with application to concrete rupture stresses

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager

    2000-01-01

    to time consuming simulation procedures. This paperrevives a conceptually simple approach that gives surprisingly good results in particular for wide band typesof random processes and fields. The closed form formulas obtained for smooth Gaussian fieldsover rectangles contain size effects both with respect...... to the area of the rectangle and the side lengths of therectangle. Published rupture stress data for plain concrete beams illustrate the applicability of the derivedclosed form extreme value distributions as models for distributions of rupture stresses related to weakest linkmechanisms....

  4. THEORETICAL COMPUTATION OF A STRESS FIELD IN A CYLINDRICAL GLASS SPECIMEN

    Directory of Open Access Journals (Sweden)

    NORBERT KREČMER

    2011-03-01

    Full Text Available This work deals with the computation of the stress field generated in an infinitely high glass cylinder while cooling. The theory of structural relaxation is used in order to compute the heat capacity, the thermal expansion coefficient, and the viscosity. The relaxation of the stress components is solved in the frame of the Maxwell viscoelasticity model. The obtained results were verified by the sensitivity analysis and compared with some experimental data.

  5. Dynamics of Mount Somma-Vesuvius edifice: from stress field inversion to analogue and numerical modelling

    Science.gov (United States)

    De Matteo, Ada; Massa, Bruno; D'Auria, Luca; Castaldo, Raffaele

    2017-04-01

    Geological processes are generally very complex and too slow to be directly observed in their completeness; modelling procedures overcome this limit. The state of stress in the upper lithosphere is the main responsible for driving geodynamical processes; in order to retrieve the active stress field in a rock volume, stress inversion techniques can be applied on both seismological and structural datasets. This approach has been successfully applied to active tectonics as well as volcanic areas. In this context the best approach in managing heterogeneous datasets in volcanic environments consists in the analysis of spatial variations of the stress field by applying robust techniques of inversion. The study of volcanic seismicity is an efficient tool to retrieve spatial and temporal pattern of the pre-, syn- and inter-eruptive stress field: magma migration as well as dynamics of magma chamber and hydrothermal system are directly connected to the volcanic seismicity. Additionally, analysis of the temporal variations of stress field pattern in volcanoes could be a useful monitoring tool. Recently the stress field acting on several active volcanoes has been investigated by using stress inversion techniques on seismological datasets (Massa et al., 2016). The Bayesian Right Trihedra Method (BRTM; D'Auria and Massa, 2015) is able to successfully manage heterogeneous datasets allowing the identification of regional fields locally overcame by the stress field due to volcano specific dynamics. In particular, the analysis of seismicity and stress field inversion at the Somma-Vesuvius highlighted the presence of two superposed volumes characterized by different behaviour and stress field pattern: a top volume dominated by an extensional stress field, in accordance with a gravitational spreading-style of deformation, and a bottom volume related to a regional extensional stress field. In addition, in order to evaluate the dynamics of deformation, both analogue and numerical

  6. 2D mapping of plane stress crack-tip fields following an overload

    Directory of Open Access Journals (Sweden)

    P. J. Withers

    2015-07-01

    Full Text Available The evolution of crack-tip strain fields in a thin (plane stress compact tension sample following an overload (OL event has been studied using two different experimental techniques. Surface behaviour has been characterised by Digital Image Correlation (DIC, while the bulk behaviour has been characterised by means of synchrotron X-ray diffraction (XRD. The combination of both surface and bulk information allowed us to visualise the through-thickness evolution of the strain fields before the OL event, during the overload event, just after OL and at various stages after it. Unlike previous work, complete 2D maps of strains around the crack-tip were acquired at 60m spatial resolution by XRD. The DIC shows less crack opening after overload and the XRD a lower crack-tip peak stress after OL until the crack has grown past the compressive crack-tip residual stress introduced by the overload after which the behaviour returned to that for the baseline fatigue response. While the peak crack-tip stress is supressed by the compressive residual stress, the crack-tip stress field changes over each cycle are nevertheless the same for all Kmax cycles except at OL.

  7. Site characterization and validation - stress field in the SCV block and around the validation drift. Stage 3

    International Nuclear Information System (INIS)

    McKinnon, S.; Carr, P.

    1990-04-01

    The results of previous stress measurement and stress modelling programmes carried out in the vicinity of the SCV block have been reviewed. Collectively, the results show that the stress field is influenced by the presence of the old mine excavations, and the measurements can be divided into near-field and far-field locations. The near-field measurements denote the extent and magnitude of the mining induced stresses while the far-field measurements reflect virgin conditions. Because of large scatter in the previous data, additional stress measurements were carried out using the CSIRO hollow inclusion cell. Combining all measurements, an estimate of the virgin stress tensor was made. Three-dimensional stress modelling was carried out using the program BEFE to determine the state of stress in the SCV block, and around the validation drift. This modelling showed that most of the SCV block is in a virgin stress field. Stresses acting on the fracture zones in the SCV block will be due only to the virgin stress field and induced stresses from the validation drift. (orig.)

  8. Stress analysis in high-temperature superconductors under pulsed field magnetization

    Science.gov (United States)

    Wu, Haowei; Yong, Huadong; Zhou, Youhe

    2018-04-01

    Bulk high-temperature superconductors (HTSs) have a high critical current density and can trap a large magnetic field. When bulk superconductors are magnetized by the pulsed field magnetization (PFM) technique, they are also subjected to a large electromagnetic stress, and the resulting thermal stress may cause cracking of the superconductor due to the brittle nature of the sample. In this paper, based on the H-formulation and the law of heat transfer, we can obtain the distributions of electromagnetic field and temperature, which are in qualitative agreement with experiment. After that, based on the dynamic equilibrium equations, the mechanical response of the bulk superconductor is determined. During the PFM process, the change in temperature has a dramatic effect on the radial and hoop stresses, and the maximum radial and hoop stress are 24.2 {{MPa}} and 22.6 {{MPa}}, respectively. The mechanical responses of a superconductor for different cases are also studied, such as the peak value of the applied field and the size of bulk superconductors. Finally, the stresses are also presented for different magnetization methods.

  9. Life estimation of low-cycle fatigue of pipe elbows. Proposed criteria of low-cycle fatigue life under the multi-axial stress field

    International Nuclear Information System (INIS)

    Ando, Kotoji; Takahashi, Koji; Matsuo, Kazuya; Urabe, Yoshio

    2013-01-01

    Pipe elbows were important parts frequently used in the pipelines of nuclear power, thermal power and chemical plants, and their integrity needed to be assured under seismic loads and thermal stresses considering local wall thinning or complex stress distribution due to special configuration different from straight pipe. This article investigated in details elastic-plastic stress-strain state of pipe elbow using finite element analysis and clarified there existed high bi-axial stress field at side inner surface of pipe elbow axial cracks initiated. Bi-axial stress factor was around 0.6 for sound elbow and up to 0.95 for local wall thinning at crown. Fracture strain of 1.15 was reduced to around 0.15 for bi-axial stress factor from 0.6 to 0.9. Normalized fatigue life for bi-axial stress field (0.6 - 0.8) was largely reduced to around 15, 19 and 10% of fatigue life of uni-axial state dependent on material strength level. Proposed revised universal slopes taking account of multi-axial stress factor could explain qualitatively effects of strain range, internal pressure and ratchet strain (pre-strain) on low-cycle fatigue life of pipe elbow. (T. Tanaka)

  10. Anisotropy, magnetic field and stress influences on the phase transitions on spin-flop-type antiferromagnets

    International Nuclear Information System (INIS)

    Machado, S.F.; Espirito Santo Univ., Vitoria; Tsallis, C.

    1983-01-01

    Within a mean field approximation, the influences of anisotropy (in the spin space) and external uniaxial stress on the Heisenberg antiferromagnet in the presence of magnetic field are discussed. The phase diagram evolution (as function of anisotropy and stress) which is obtained, enables a satisfactory overall interpretation of recent experiments on Mn(Br sub(1-x) Cl sub(x)) 2 .4H 2 O, K 2 [FeCl 5 (H 2 O)], CoCl 2 .6H 2 O and (C 2 H 5 NH 3 ) 2 CuCl 4 . (Author) [pt

  11. 3D finite element analysis of stress distributions and strain energy release rates for adhesive bonded flat composite lap shear joints having pre-existing delaminations

    Energy Technology Data Exchange (ETDEWEB)

    Parida, S. K.; Pradhan, A. K. [Indian Institute of Technology, Bhubaneswar (India)

    2014-02-15

    The rate of propagation of embedded delamination in the strap adherend of lap shear joint (LSJ) made of carbon/epoxy composites has been evaluated employing three-dimensional non-linear finite elements. The delamination has been presumed to pre-exist in the thin resin layer between the first and second plies of the strap adherend. The inter-laminar peel and shear stress distributions have been studied in details and are seen to be predominantly three-dimensional in nature. The components of strain energy release rate (SERR) corresponding to the opening, sliding and cross sliding modes of delamination are significantly different at the two fronts of the embedded delamination. The sequential release of multi-point constraint (MPC) finite elements in the vicinity of the delamination fronts enables to simulate the growth of the delamination at either ends. This simulation procedure can be utilized effectively for evaluation of the status of the structural integrity of the bonded joints.

  12. Wall Shear Stress, Wall Pressure and Near Wall Velocity Field Relationships in a Whirling Annular Seal

    Science.gov (United States)

    Morrison, Gerald L.; Winslow, Robert B.; Thames, H. Davis, III

    1996-01-01

    The mean and phase averaged pressure and wall shear stress distributions were measured on the stator wall of a 50% eccentric annular seal which was whirling in a circular orbit at the same speed as the shaft rotation. The shear stresses were measured using flush mounted hot-film probes. Four different operating conditions were considered consisting of Reynolds numbers of 12,000 and 24,000 and Taylor numbers of 3,300 and 6,600. At each of the operating conditions the axial distribution (from Z/L = -0.2 to 1.2) of the mean pressure, shear stress magnitude, and shear stress direction on the stator wall were measured. Also measured were the phase averaged pressure and shear stress. These data were combined to calculate the force distributions along the seal length. Integration of the force distributions result in the net forces and moments generated by the pressure and shear stresses. The flow field inside the seal operating at a Reynolds number of 24,000 and a Taylor number of 6,600 has been measured using a 3-D laser Doppler anemometer system. Phase averaged wall pressure and wall shear stress are presented along with phase averaged mean velocity and turbulence kinetic energy distributions located 0.16c from the stator wall where c is the seal clearance. The relationships between the velocity, turbulence, wall pressure and wall shear stress are very complex and do not follow simple bulk flow predictions.

  13. The effects of a stress field and chemical diffusion on electronic behaviour in InAs/GaAs quantum dots

    International Nuclear Information System (INIS)

    Zhang Xu; Wang Chongyu

    2006-01-01

    The effects of a stress field and chemical diffusion on electronic behaviour in self-assembled InAs/GaAs quantum dots (QD) are investigated by using first-principle calculations. We find that a potential well appears in a QD without a lattice misfit and chemical diffusion, and both stress field and Ga chemical diffusion can induce the formation of a potential barrier, which strongly affects the electronic behaviour within the QD. The stress field can localize electrons to the base of the QD. And associated with Ga diffusion, the stress field will induce an inverted electronic alignment. The electronic behaviour in the QD without a stress field does not present the confined or localized characteristics caused by a lattice misfit, atomic size and Ga diffusion. This study provides useful information for modulating electronic behaviour by introducing a stress field and chemical diffusion

  14. Magnetopriming - an alternate strategy for crop stress management of field crops

    International Nuclear Information System (INIS)

    Anand, Anjali

    2014-01-01

    Abiotic stresses are major deterrent to sustainable crop production worldwide. Seed germination and early seedling growth are considered as the most critical stages of plant growth under stress conditions. Maximising stress tolerance of crop species by breeding is an integral part of development of strategies for improving sustainable food production under stressed environment but the unprecedented rate at which stress is increasing vis-a-vis the time taken for development of a tolerant variety, necessitates exploring alternate strategies of crop stress management. Seed priming has emerged as a promising crop stress management technique that increases the speed of germination thus ensuring synchronized field emergence of the crop. Magnetopriming (exposure of seeds to magnetic field) is a non invasive physical stimulant used for improving seedling vigour that helps in establishment of crop stand under stress. In our experiments on maize; chickpea and wheat under water deficit and salinity, respectively, improved seed water absorption characteristics resulted in faster hydration of enzymes (amylases, protease and dehydrogenase) leading to early germination and enhanced vigour of seedlings under stress. Increased levels of hydrogen peroxide in faster germinating - magnetoprimed seeds, under both the growing conditions, suggested its role in oxidative signaling during seed germination process. An 'oxidative window' for reactive oxygen species ensured that faster germination rate in magnetoprimed seeds led to vigourous seedlings. Improved root system integrated with higher photosynthetic efficiency and efficient partitioning of Na + increased yield from magnetoprimed seeds under salinity in controlled experiments. Magnetopriming can be effectively used as a pre-sowing treatment for mitigating adverse effects of water deficit and salinity at seed germination and early seedling growth. Unlike other conventional priming techniques it avoids seed hydration and

  15. Effect of the induced magnetic field on peristaltic flow of a couple stress fluid

    International Nuclear Information System (INIS)

    Mekheimer, Kh.S.

    2008-01-01

    We have analyzed the MHD flow of a conducting couple stress fluid in a slit channel with rhythmically contracting walls. In this analysis we are taking into account the induced magnetic field. Analytical expressions for the stream function, the magnetic force function, the axial pressure gradient, the axial induced magnetic field and the distribution of the current density across the channel are obtained using long wavelength approximation. The results for the pressure rise, the frictional force per wave length, the axial induced magnetic field and distribution of the current density across the channel have been computed numerically and the results were studied for various values of the physical parameters of interest, such as the couple stress parameter γ, the Hartmann number M, the magnetic Reynolds number R m and the time averaged mean flow rate θ. Contour plots for the stream and magnetic force functions are obtained and the trapping phenomena for the flow field is discussed

  16. Stress Response to High Magnetic Fields in Transgenic Arabidopsis thaliana Plants.

    Science.gov (United States)

    Morgan, A. N.; Watson, B. C.; Maloney, J. R.; Meisel, M. W.; Brooks, J. S.; Paul, A.-L.; Ferl, R. J.

    2000-03-01

    With increasingly greater strength magnetic fields becoming available in research and medicine, the response of living tissue exposed to high magnetic fields has come under investigation. In this experiment, genetically engineered arabidopsis plants were exposed to homogeneous magnetic fields of varying strengths using a superconducting NMR magnet (0 to 9 T) at UF and a resistive magnet (0 to 25 T) at the NHMFL. The engineered plants produce the enzyme β-glucaronidase (GUS) when under stressful environmental conditions. The level of GUS activity is determined through qualitative histochemical assays and quantitative fluorometric assays. The control group of plants experienced baseline levels of GUS activity, but some of the plants that were exposed to magnetic fields in excess of 9 T show increased stress response. Additional information is available at http://www.phys.ufl.edu/ ~meisel/maglev.htm.

  17. Analytical model of stress field in submerged arc welding butt joint with thorough penetration

    Directory of Open Access Journals (Sweden)

    Winczek Jerzy

    2018-01-01

    Full Text Available Analytical model of temporary and residual stresses for butt welding with thorough penetration was described assuming planar section hypothesis and using integral equations of stress equilibrium of the bar and simple Hooke’s law. In solution the effect of phase transformations (structure changes and structural strains has been taken into account. Phase transformations during heating are limited by temperature values at the beginning and at the end of austenitic transformation, depending on chemical composition of steel while the progress of phase transformations during cooling is determined on the basis of TTT-welding diagram. Temperature values at the beginning and at the end of transformation are conditioned by the speed of heating. Kinetics of diffusional transformation is described basing on Johnson-Mehl-Avrami-Kolmogorov equation, while martensitic transformation, basing on Koistinen-Marburger equation. Stresses in elasto-plastic state are determined by iteration, using elastic solutions method with changeable longitudinal modulus of elasticity, conditioned by stress-strain curve. Computations of stress field have been conducted for one-side butt welded of two steel flats made from S235 steel. It has enabled a clear interpretation of influence of temperature field and phase transformation on stresses caused by welding using Submerged Arc Welding (SAW method.

  18. Early field performance of drought-stressed scots pine (pinus sylvestris l.) seedlings

    International Nuclear Information System (INIS)

    Kulac, S.; Clcek, E.; Tasdemir, U.

    2015-01-01

    Scots pine (Pinus sylvestris) has a large natural distribution throughout the world, including semi-arid areas of Turkey, where it is being used for afforestation. Determining the drought resistance of Scots pine provenances can increase the success of afforestation efforts in semi-arid regions. In the first stage of this study, water-stress treatments were applied to ten provenances of one-year-old Scots pine seedlings in their second vegetation period (between April and November). The diameter and height of the seedlings were evaluated in the nursery in order to determine their morphology. The four drought-stress treatments consisted of once-weekly irrigation (IR1), twice-weekly irrigation (IR2-Control), biweekly irrigation (IR3) and open field conditions (IR4). Later, the water-stressed seedlings were planted in a semi-arid district in Bayburt, Turkey, and their survival and growth performances were evaluated over a five-year period. The nursery study showed that drought stress and provenance as well as the interaction of the two significantly affected the morphological characteristics of the seedlings. Under water-stress conditions, the best growth performance was found in the Dokurcun, Degirmendere and Dirgine provenance seedlings. Water-stress and provenance factors and their interaction also affected the open field performance of the seedlings, where the Degirmendere, Dirgine and Dokurcun provenances again exhibited the best performance. Consequently, these Scots pine provenances can be recommended for afforestation sites having conditions similar to those of the study site. (author)

  19. Modelling and experimental characterisation of a residual stress field in a ferritic compact tension specimen

    International Nuclear Information System (INIS)

    Wenman, M.R.; Price, A.J.; Steuwer, A.; Chard-Tuckey, P.R.; Crocombe, A.

    2009-01-01

    The aim of the work is to elucidate the influence of plasticity behaviour on the residual stress field in a ferritic reactor pressure vessel steel. To this end, we investigate two compressively pre-loaded compact tension (CT) specimens to generate a mechanical residual stress field. One specimen was subsequently pre-cracked by fatigue before both specimens were measured using high-energy synchrotron X-ray diffraction. A fine grain size microstructure (∼5-10 μm grain size) allowed a small X-ray beam slit size and therefore gauge volume. The results provide an excellent data set for validation of finite element (FE) modelling predictions against which they have been compared. The results of both mechanical testing and modelling suggest that the use of a combined hardening model is needed to accurately predict the residual stress field present in the specimen after pre-loading. Some discrepancy between the modelled crack tip stress values and those found by X-ray diffraction remain which can be partly explained by volume averaging effects in the presence of very high stress/strain gradients.

  20. Modelling and experimental characterisation of a residual stress field in a ferritic compact tension specimen

    Energy Technology Data Exchange (ETDEWEB)

    Wenman, M.R., E-mail: m.wenman@imperial.ac.u [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Price, A.J. [Faculty of Engineering and Physical Sciences (J5), University of Surrey, Guildford GU2 7XH (United Kingdom); Steuwer, A. [ESS Scandinavia, Stora Algatan 4, 22350 Lund (Sweden) and Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Chard-Tuckey, P.R. [Nuclear Department, Defence College of Management and Technology, HMS Sultan, Gosport, Hants PO12 3BY (United Kingdom); Crocombe, A. [Faculty of Engineering and Physical Sciences (J5), University of Surrey, Guildford GU2 7XH (United Kingdom)

    2009-12-15

    The aim of the work is to elucidate the influence of plasticity behaviour on the residual stress field in a ferritic reactor pressure vessel steel. To this end, we investigate two compressively pre-loaded compact tension (CT) specimens to generate a mechanical residual stress field. One specimen was subsequently pre-cracked by fatigue before both specimens were measured using high-energy synchrotron X-ray diffraction. A fine grain size microstructure (approx5-10 mum grain size) allowed a small X-ray beam slit size and therefore gauge volume. The results provide an excellent data set for validation of finite element (FE) modelling predictions against which they have been compared. The results of both mechanical testing and modelling suggest that the use of a combined hardening model is needed to accurately predict the residual stress field present in the specimen after pre-loading. Some discrepancy between the modelled crack tip stress values and those found by X-ray diffraction remain which can be partly explained by volume averaging effects in the presence of very high stress/strain gradients.

  1. Residual stress characterization of steel TIG welds by neutron diffraction and by residual magnetic stray field mappings

    Energy Technology Data Exchange (ETDEWEB)

    Stegemann, Robert, E-mail: Robert.Stegemann@bam.de [Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12200 Berlin (Germany); Cabeza, Sandra; Lyamkin, Viktor; Bruno, Giovanni; Pittner, Andreas [Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12200 Berlin (Germany); Wimpory, Robert; Boin, Mirko [HZB Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Kreutzbruck, Marc [Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12200 Berlin (Germany); IKT, University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart (Germany)

    2017-03-15

    The residual stress distribution of tungsten inert gas welded S235JRC+C plates was determined by means of neutron diffraction (ND). Large longitudinal residual stresses with maxima around 600 MPa were found. With these results as reference, the evaluation of residual stress with high spatial resolution GMR (giant magneto resistance) sensors was discussed. The experiments performed indicate a correlation between changes in residual stresses (ND) and the normal component of local residual magnetic stray fields (GMR). Spatial variations in the magnetic field strength perpendicular to the welds are in the order of the magnetic field of the earth. - Highlights: • Comparison of magnetic microstructure with neutron diffraction stress analysis. • High spatial resolution magnetic stray field images of hypereutectoid TIG welds. • Spatial variations of the stray fields are below the magnetic field of the earth. • GMR spin valve gradiometer arrays adapted for the evaluation of magnetic microstructures. • Magnetic stray fields are closely linked to microstructure of the material.

  2. Dynamic Response in Transient Stress-Field Behavior Induced by Hydraulic Fracturing

    Science.gov (United States)

    Jenkins, Andrew

    Hydraulic fracturing is a technique which is used to exploit geologic features and subsurface properties in an effort to increase production in low-permeability formations. The process of hydraulic fracturing provides a greater surface contact area between the producing formation and the wellbore and thus increases the amount of recoverable hydrocarbons from within the reservoir. The use of this stimulation technique has brought on massive applause from the industry due to its widespread success and effectiveness, however the dynamic processes that take part in the development of hydraulic fractures is a relatively new area of research with respect to the massive scale operations that are seen today. The process of hydraulic fracturing relies upon understanding and exploiting the in-situ stress distribution throughout the area of study. These in-situ stress conditions are responsible for directing fracture orientation and propagation paths throughout the period of injection. The relative magnitude of these principle stresses is key in developing a successful stimulation plan. In horizontal well plan development the interpretation of stress within the reservoir is required for determining the azimuth of the horizontal well path. These horizontal laterals are typically oriented in a manner such that the well path lies parallel to the minimum horizontal stress. This allows for vertical fractures to develop transversely to the wellbore, or normal to the least principle stress without the theoretical possibility of fractures overlapping, creating the most efficient use of the fluid energy during injection. The orientation and magnitude of these in-situ stress fields however can be dynamic, controlled by the subsequent fracture propagation and redistribution of the surrounding stresses. That is, that as the fracture propagates throughout the reservoir, the relative stress fields surrounding the fractures may see a shift and deviate from their original direction or

  3. Demountable low stress high field toroidal field magnet system for tokamak fusion reactors

    International Nuclear Information System (INIS)

    Powell, J.; Hsieh, D.; Lehner, J.; Suenaga, M.

    1978-01-01

    A new type of superconducting magnet system for large fusion reactors is described. Instead of winding large planar or multi-axis coils, as has been proposed in previous fusion reactor designs, the superconducting coils are made by joining together several prefabricated conductor sections. The joints can be unmade and sections removed if they fail. Conductor sections can be made at a factory and shipped to the reactor site for assembly. The conductor stress level in the assembled coil can be kept small by external support of the coil at a number of points along its perimeter, so that the magnetic forces are transmitted to an external warm reinforcement structure. This warm reinforcement structure can also be the primary containment for the fusion reactor, constructed similar to a PCRV (Prestressed Concrete Reactor Vessel) used in fission reactors. Low thermal conductivity, high strength supports are used to transfer the magnetic forces to the external reinforcement through a hydraulic system. The hydraulic supports are movable and can be programmed to accommodate thermal contraction and to minimize stress in the superconducting coil. (author)

  4. Demountable low stress high field toroidal field magnet system for tokamak fusion reactors

    International Nuclear Information System (INIS)

    Powell, J.; Hsieh, D.; Lehner, J.; Suenaga, M.

    1977-01-01

    A new type of superconducting magnet system for large fusion reactors is described in this report. Instead of winding large planar or multi-axis coils, as has been proposed in previous fusion reactor designs, the superconducting coils are made by joining together several prefabricated conductor sections. The joints can be unmade and sections removed if they fail. Conductor sections can be made at a factory and shipped to the reactor site for assembly. The conductor stress level in the assembled coil can be kept small by external support of the coil at a number of points along its perimeter, so that the magnetic forces are transmitted to an external warm reinforcement structure. This warm reinforcement structure can also be the primary containment for the fusion reactor, constructed similar to a PCRV (Prestressed Concrete Reactor Vessel) used in fission reactors. Low thermal conductivity, high strength supports are used to transfer the magnetic forces to the external reinforcement through a hydraulic system. The hydraulic supports are movable and can be programmed to accommodate thermal contraction and to minimize stress in the superconducting coil

  5. Quantifying the stress fields due to a delta-hydride precipitate in alpha-Zr matrix

    Energy Technology Data Exchange (ETDEWEB)

    Tummala, Hareesh [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Capolungo, Laurent [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tome, Carlos N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-10-19

    This report is a preliminary study on δ-hydride precipitate in zirconium alloy performed using 3D discrete dislocation dynamics simulations. The ability of dislocations in modifying the largely anisotropic stress fields developed by the hydride particle in a matrix phase is addressed for a specific dimension of the hydride. The influential role of probable dislocation nucleation at the hydride-matrix interface is reported. Dislocation nucleation around a hydride was found to decrease the shear stress (S13) and also increase the normal stresses inside the hydride. We derive conclusions on the formation of stacks of hydrides in zirconium alloys. The contribution of mechanical fields due to dislocations was found to have a non-negligible effect on such process.

  6. The University of California Institute of Environmental Stress Marathon Field Studies

    Science.gov (United States)

    Maron, Michael B.

    2014-01-01

    In 1973, the Institute of Environmental Stress of the University of California-Santa Barbara, under the direction of Steven M. Horvath, began a series of field and laboratory studies of marathon runners during competition. As one of Horvath's graduate students, many of these studies became part of my doctoral dissertation. The rationale for…

  7. Field performance of timber bridges. 11, Spearfish Creek stress-laminated box-beam bridge

    Science.gov (United States)

    J. P. Wacker; M. A. Ritter; K. Stanfill-McMillan

    The Spearfish Creek bridge was constructed in 1992 in Spearfish, South Dakota. It is a single-span, stress-laminated, box-beam superstructure. Performance of the bridge is being monitored for 5 years, beginning at installation. This report summarizes results for the first 3-1/2 years of monitoring and includes information on the design, construction, and field...

  8. Bias stress effect and recovery in organic field effect transistors : proton migration mechanism

    NARCIS (Netherlands)

    Sharma, A.; Mathijssen, S.G.J.; Kemerink, M.; Leeuw, de D.M.; Bobbert, P.A.; Bao, Z.; McCulloch, I.

    2010-01-01

    Organic field-effect transistors exhibit operational instabilities when a gate bias is applied. For a constant gate bias the threshold voltage shifts towards the applied gate bias voltage, an effect known as the bias-stress effect. We have performed a detailed experimental and theoretical study of

  9. Degradation of Au–Ti contacts of SiGe HBTs during electromagnetic field stress

    International Nuclear Information System (INIS)

    Alaeddine, A; Genevois, C; Cuvilly, F; Daoud, K; Kadi, M

    2011-01-01

    This paper addresses electromagnetic field stress effects on SiGe heterojunction bipolar transistors (HBTs)' reliability issues, focusing on the relationship between the stress-induced current and device structure degradations. The origin of leakage currents and electrical parameter shifts in failed transistors has been studied by complementary failure analysis techniques. Characterization of the structure before and after ageing was performed by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). For the stressed samples, interface deformations of the titanium (Ti) thin film around all gold (Au) contacts have been clearly detected. These degradations include localized interface reaction between Au and Ti layers as well as their lateral atomic migration causing a significant reduction of Ti thickness. EDS analysis of the disordered region which is near the Si 3 N 4 interface has shown significant signals from Au. These observations could be attributed to the coupling between high current densities induced by stress and thermal effects due to local heating effects

  10. The effect of a tectonic stress field on coal and gas outbursts.

    Science.gov (United States)

    An, Fenghua; Cheng, Yuanping

    2014-01-01

    Coal and gas outbursts have always been a serious threat to the safe and efficient mining of coal resources. Ground stress (especially the tectonic stress) has a notable effect on the occurrence and distribution of outbursts in the field practice. A numerical model considering the effect of coal gas was established to analyze the outburst danger from the perspective of stress conditions. To evaluate the outburst tendency, the potential energy of yielded coal mass accumulated during an outburst initiation was studied. The results showed that the gas pressure and the strength reduction from the adsorbed gas aggravated the coal mass failure and the ground stress altered by tectonics would affect the plastic zone distribution. To demonstrate the outburst tendency, the ratio of potential energy for the outburst initiation and the energy consumption was used. Increase of coal gas and tectonic stress could enhance the potential energy accumulation ratio, meaning larger outburst tendency. The component of potential energy for outburst initiation indicated that the proportion of elastic energy was increased due to tectonic stress. The elastic energy increase is deduced as the cause for a greater outburst danger in a tectonic area from the perspective of stress conditions.

  11. Identification of natural fractures and in situ stress at Rantau Dedap geothermal field

    Science.gov (United States)

    Artyanto, Andika; Sapiie, Benyamin; Idham Abdullah, Chalid; Permana Sidik, Ridwan

    2017-12-01

    Rantau Dedap Area is a geothermal field which is located in Great Sumatra Fault (GSF). The fault and fracture are main factor in the permeability of the geothermal system. However, not all faults and fractures have capability of to flow the fluids. Borehole image log is depiction of the borehole conditions, it is used to identify the natural fractures and drilling induced fracture. Both of them are used to identify the direction of the fracture, direction of maximum horizontal stress (SHmax), and geomechanics parameters. The natural fractures are the results of responses to stress on a rock and permeability which controlling factor in research area. Breakouts is found in this field as a trace of drilling induced fracture due to in situ stress work. Natural fractures are strongly clustered with true strike trending which first, second, and third major direction are N170°E - N180°E (N-S), N60°E - N70°E (NE-SW), and N310°E - N320°E (NW-SE), while the dominant dip is 80° -90°. Based on borehole breakout analysis, maximum horizontal stress orientation is identified in N162°E - N204°E (N-S) and N242°E (NE-SW) direction. It’s constantly similar with regional stress which is affected by GSF. Several parameters have been identified and analyzed are SHmax, SHmin, and Sy. It can be concluded that Rantau Dedap Geothermal Field is affected by strike-slip regime. The determination of in situ stress and natural fractures are important to study the pattern of permeability which is related to the fault in reservoir of this field.

  12. Monodimensional estimation of maximum Reynolds shear stress in the downstream flow field of bileaflet valves.

    Science.gov (United States)

    Grigioni, Mauro; Daniele, Carla; D'Avenio, Giuseppe; Barbaro, Vincenzo

    2002-05-01

    Turbulent flow generated by prosthetic devices at the bloodstream level may cause mechanical stress on blood particles. Measurement of the Reynolds stress tensor and/or some of its components is a mandatory step to evaluate the mechanical load on blood components exerted by fluid stresses, as well as possible consequent blood damage (hemolysis or platelet activation). Because of the three-dimensional nature of turbulence, in general, a three-component anemometer should be used to measure all components of the Reynolds stress tensor, but this is difficult, especially in vivo. The present study aimed to derive the maximum Reynolds shear stress (RSS) in three commercially available prosthetic heart valves (PHVs) of wide diffusion, starting with monodimensional data provided in vivo by echo Doppler. Accurate measurement of PHV flow field was made using laser Doppler anemometry; this provided the principal turbulence quantities (mean velocity, root-mean-square value of velocity fluctuations, average value of cross-product of velocity fluctuations in orthogonal directions) needed to quantify the maximum turbulence-related shear stress. The recorded data enabled determination of the relationship, the Reynolds stresses ratio (RSR) between maximum RSS and Reynolds normal stress in the main flow direction. The RSR was found to be dependent upon the local structure of the flow field. The reported RSR profiles, which permit a simple calculation of maximum RSS, may prove valuable during the post-implantation phase, when an assessment of valve function is made echocardiographically. Hence, the risk of damage to blood constituents associated with bileaflet valve implantation may be accurately quantified in vivo.

  13. Notes on the measurement of stress by resistance gauges in the presence of a magnetic field

    International Nuclear Information System (INIS)

    Armand, G.; Lapujoulade, J.

    1961-01-01

    The technique of stress measurement by resistance gauges is well known. Although it is not yet perfect it possesses many advantages and shows great possibilities. In the presence of a magnetic field the measurement is perturbed by certain phenomena, and we have undertaken to calculate their order of magnitude with a view to establishing the error involved in the measurement. Our problem was to measure the stresses on the various parts of the magnet in the synchrotron Saturne. It is known that the induction passes from a value of about nil to 15000 gauss in 0.8 second, and returns to zero in the same time interval; this cycle recurs every 3.2 seconds. In order to isolate the effects the problem of measurements in a static field will be examined first, after which the results obtained will be extended to the case of dynamic fields. (author) [fr

  14. Stress field during early magmatism in the Ali Sabieh Dome, Djibouti, SE Afar rift

    Science.gov (United States)

    Sue, Christian; Le Gall, Bernard; Daoud, Ahmed Mohamed

    2014-09-01

    The so-called Ali Sabieh range, SE Afar rift, exhibits an atypical antiform structure occurring in the overall extensional tectonic context of the Afar triple junction. We dynamically analyzed the brittle deformation of this specific structural high using four different methods in order to better constrain the tectonic evolution of this key-area in the Afar depression. Paleostress inversions appear highly consistent using the four methods, which a posteriori validates this approach. Computed paleostress fields document two major signals: an early E-W extensional field, and a later transcurrent field, kinematically consistent with the previous one. The Ali Sabieh range may have evolved continuously during Oligo-Miocene times from large-scale extensional to transcurrent tectonism, as the result of probable local stress permutation between σ1 and σ2 stress axes.

  15. Conservation laws and stress-energy-momentum tensors for systems with background fields

    Energy Technology Data Exchange (ETDEWEB)

    Gratus, Jonathan, E-mail: j.gratus@lancaster.ac.uk [Lancaster University, Lancaster LA1 4YB (United Kingdom); The Cockcroft Institute, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Obukhov, Yuri N., E-mail: yo@thp.uni-koeln.de [Institute for Theoretical Physics, University of Cologne, 50923 Koeln (Germany); Tucker, Robin W., E-mail: r.tucker@lancaster.ac.uk [Lancaster University, Lancaster LA1 4YB (United Kingdom); The Cockcroft Institute, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom)

    2012-10-15

    This article attempts to delineate the roles played by non-dynamical background structures and Killing symmetries in the construction of stress-energy-momentum tensors generated from a diffeomorphism invariant action density. An intrinsic coordinate independent approach puts into perspective a number of spurious arguments that have historically lead to the main contenders, viz the Belinfante-Rosenfeld stress-energy-momentum tensor derived from a Noether current and the Einstein-Hilbert stress-energy-momentum tensor derived in the context of Einstein's theory of general relativity. Emphasis is placed on the role played by non-dynamical background (phenomenological) structures that discriminate between properties of these tensors particularly in the context of electrodynamics in media. These tensors are used to construct conservation laws in the presence of Killing Lie-symmetric background fields. - Highlights: Black-Right-Pointing-Pointer The role of background fields in diffeomorphism invariant actions is demonstrated. Black-Right-Pointing-Pointer Interrelations between different stress-energy-momentum tensors are emphasised. Black-Right-Pointing-Pointer The Abraham and Minkowski electromagnetic tensors are discussed in this context. Black-Right-Pointing-Pointer Conservation laws in the presence of nondynamic background fields are formulated. Black-Right-Pointing-Pointer The discussion is facilitated by the development of a new variational calculus.

  16. The Effect of Magnetic Field and Initial Stress on Fractional Order Generalized Thermoelastic Half-Space

    Directory of Open Access Journals (Sweden)

    Sunita Deswal

    2013-01-01

    Full Text Available The aim of this paper is to study magneto-thermoelastic interactions in an initially stressed isotropic homogeneous half-space in the context of fractional order theory of generalized thermoelasticity. State space formulation with the Laplace transform technique is used to obtain the general solution, and the resulting formulation is applied to the ramp type increase in thermal load and zero stress. Solutions of the problem in the physical domain are obtained by using a numerical method of the Laplace inverse transform based on the Fourier expansion technique, and the expressions for the displacement, temperature, and stress inside the half-space are obtained. Numerical computations are carried out for a particular material for illustrating the results. Results obtained for the field variables are displayed graphically. Some comparisons have been shown in figures to present the effect of fractional parameter, ramp parameter, magnetic field, and initial stress on the field variables. Some particular cases of special interest have been deduced from the present investigation.

  17. Experimental Study on Wing Crack Behaviours in Dynamic-Static Superimposed Stress Field Using Caustics and High-Speed Photography

    Directory of Open Access Journals (Sweden)

    L.Y. Yang

    2014-07-01

    Full Text Available During the drill-and-blast progress in rock tunnel excavation of great deep mine, rock fracture is evaluated by both blasting load and pre-exiting earth stress (pre-compression. Many pre-existing flaws in the rock mass, like micro-crack, also seriously affect the rock fracture pattern. Under blasting load with pre-compression, micro-cracks initiate, propagate and grow to be wing cracks. With an autonomous design of static-dynamic loading system, dynamic and static loads were applied on some PMMA plate specimen with pre-existing crack, and the behaviour of the wing crack was tested by caustics corroding with a high-speed photography. Four programs with different static loading modes that generate different pre-compression fields were executed, and the length, velocity of the blasting wing crack and dynamic stress intensity factor (SIF at the wing crack tip were analyzed and discussed. It is found that the behaviour of blasting-induced wing crack is affected obviously by blasting and pre-compression. And pre-compression, which is vertical to the direction of the wing crack propagation, hinders the crack propagation. Furthermore, the boundary constraint condition plays an important role on the behaviour of blasting induced crack during the experiment.

  18. Mechanical stress calculations for toroidal field coils by the finite element method

    International Nuclear Information System (INIS)

    Soell, M.; Jandl, O.; Gorenflo, H.

    1976-09-01

    After discussing fundamental relationships of the finite element method, this report describes the calculation steps worked out for mechanical stress calculations in the case of magnetic forces and forces produced by thermal expansion or compression of toroidal field coils using the SOLID SAP IV computer program. The displacement and stress analysis are based on the 20-node isoparametric solid element. The calculation of the nodal forces produced by magnetic body forces are discussed in detail. The computer programs, which can be used generally for mesh generation and determination of the nodal forces, are published elsewhere. (orig.) [de

  19. Effective stresses and shear failure pressure from in situ Biot's coefficient, Hejre Field, North Sea

    DEFF Research Database (Denmark)

    Regel, Jeppe Bendix; Orozova-Bekkevold, Ivanka; Andreassen, Katrine Alling

    2017-01-01

    , is significantly different from 1. The log-derived Biot's coefficient is above 0.8 in the Shetland Chalk Group and in the Tyne Group, and 0.6-0.8 in the Heno Sandstone Formation. We show that the effective vertical and horizontal stresses obtained using the log-derived Biot's coefficient result in a drilling......We propose a combination of Biot's equations for effective stress and the expression for shear failure in a rock to obtain an expression for minimum pore pressure in a stable vertical well bore. We show that a Biot's coefficient calculated from logging data in the Hejre Field, North Sea...

  20. Phase-Field Relaxation of Topology Optimization with Local Stress Constraints

    DEFF Research Database (Denmark)

    Stainko, Roman; Burger, Martin

    2006-01-01

    inequality constraints. We discretize the problem by finite elements and solve the arising finite-dimensional programming problems by a primal-dual interior point method. Numerical experiments for problems with local stress constraints based on different criteria indicate the success and robustness......We introduce a new relaxation scheme for structural topology optimization problems with local stress constraints based on a phase-field method. In the basic formulation we have a PDE-constrained optimization problem, where the finite element and design analysis are solved simultaneously...

  1. The presence of blogs in the field of Library and Information Sciences in Spain: Can we talk about the existence of a “Biblogsfera”?

    Directory of Open Access Journals (Sweden)

    Miguel Ángel Vera Baceta

    2014-03-01

    Full Text Available The blog phenomenon has meant a natural way of grouping and establishing communication amongst those who have similar concerns. This has happened the same way in the field of science, thus creating communities of special interest in a context in which blogs are consolidating as sources of information and extra tools for research. While the authors’ freedom to organise and offer their contents may be considered one of the main advantages and a trigger for the success of blogs, it is also one of their main drawbacks. The contents and communities of blogs are not easy to identify, classify and quantify, so that they constitute a vague concept under the name of “blogosphere”. This article is meant to identify the blogs related to the field of Library and Information Sciences in Spain, their authorship, their contents and their connections in order to clarify if we can really talk about the existence of a “Biblogsfera”.

  2. Quercitol and osmotic adaptation of field-grown Eucalyptus under seasonal drought stress.

    Science.gov (United States)

    Arndt, Stefan K; Livesley, Stephen J; Merchant, Andrew; Bleby, Timothy M; Grierson, Pauline F

    2008-07-01

    This study investigated the role of quercitol in osmotic adjustment in field-grown Eucalyptus astringens Maiden subject to seasonal drought stress over the course of 1 year. The trees grew in a native woodland and a farm plantation in the semi-arid wheatbelt region of south Western Australia. Plantation trees allocated relatively more biomass to leaves than woodland trees, but they suffered greater drought stress over summer, as indicated by lower water potentials, CO(2)assimilation rates and stomatal conductances. In contrast, woodland trees had relatively fewer leaves and suffered less drought stress. Plantation trees under drought stress engaged in osmotic adjustment, but woodland trees did not. Quercitol made a significant contribution to osmotic adjustment in drought-stressed trees (25% of total solutes), and substantially more quercitol was measured in the leaves of plantation trees (5% dry matter) than in the leaves of woodland trees (2% dry matter). We found no evidence that quercitol was used as a carbon storage compound while starch reserves were depleted under drought stress. Differences in stomatal conductance, biomass allocation and quercitol production clearly indicate that E. astringens is both morphologically and physiologically 'plastic' in response to growth environment, and that osmotic adjustment is only one part of a complex strategy employed by this species to tolerate drought.

  3. Residual stress characterization of steel TIG welds by neutron diffraction and by residual magnetic stray field mappings

    Science.gov (United States)

    Stegemann, Robert; Cabeza, Sandra; Lyamkin, Viktor; Bruno, Giovanni; Pittner, Andreas; Wimpory, Robert; Boin, Mirko; Kreutzbruck, Marc

    2017-03-01

    The residual stress distribution of tungsten inert gas welded S235JRC+C plates was determined by means of neutron diffraction (ND). Large longitudinal residual stresses with maxima around 600 MPa were found. With these results as reference, the evaluation of residual stress with high spatial resolution GMR (giant magneto resistance) sensors was discussed. The experiments performed indicate a correlation between changes in residual stresses (ND) and the normal component of local residual magnetic stray fields (GMR). Spatial variations in the magnetic field strength perpendicular to the welds are in the order of the magnetic field of the earth.

  4. Stress-free states of continuum dislocation fields : Rotations, grain boundaries, and the Nye dislocation density tensor

    NARCIS (Netherlands)

    Limkumnerd, Surachate; Sethna, James P.

    We derive general relations between grain boundaries, rotational deformations, and stress-free states for the mesoscale continuum Nye dislocation density tensor. Dislocations generally are associated with long-range stress fields. We provide the general form for dislocation density fields whose

  5. Geophysical Properties of Hard Rock for Investigation of Stress Fields in Deep Mines

    Science.gov (United States)

    Tibbo, M.; Young, R. P.; Schmitt, D. R.; Milkereit, B.

    2014-12-01

    A complication in geophysical monitoring of deep mines is the high-stress dependency of the physical properties of hard rocks. In-mine observations show anisotropic variability of the in situ P- and S-wave velocities and resistivity of the hard rocks that are likely related to stress field changes. As part of a comprehensive study in a deep, highly stressed mine located in Sudbury, Ontario, Canada, data from in situ monitoring of the seismicity, conductivity, stress, and stress dependent physical properties has been obtain. In-laboratory experiments are also being performed on borehole cores from the Sudbury mines. These experiments will measure the Norite borehole core's properties including elastic modulus, bulk modulus, P- and S-wave velocities, and density. Hydraulic fracturing has been successfully implemented in industries such as oil and gas and enhanced geothermal systems, and is currently being investigated as a potential method for preconditioning in mining. However, further research is required to quantify how hydraulic fractures propagate through hard, unfractured rock as well as naturally fractured rock typically found in mines. These in laboratory experiments will contribute to a hydraulic fracturing project evaluating the feasibility and effectiveness of hydraulic fracturing as a method of de-stressing hard rock mines. A tri-axial deformation cell equipped with 18 Acoustic Emission (AE) sensors will be used to bring the borehole cores to a tri-axial state of stress. The cores will then be injected with fluid until the the hydraulic fracture has propagated to the edge of the core, while AE waveforms will be digitized continuously at 10 MHz and 12-bit resolution for the duration of each experiment. These laboratory hydraulic fracture experiments will contribute to understanding how parameters including stress ratio, fluid injection rate, and viscosity, affect the fracturing process.

  6. Burrow characteristics of the co-existing sibling species Mus booduga and Mus terricolor and the genetic basis of adaptation to hypoxic/hypercapnic stress

    Directory of Open Access Journals (Sweden)

    Narayan Gopeshwar

    2009-04-01

    Full Text Available Abstract Background The co-existing, sibling species Mus booduga and Mus terricolor show a difference in site-preference for burrows. The former build them in flat portion of the fields while the latter make burrows in earthen mounds raised for holding water in cultivated fields. In northern India which experiences great variation in climatic condition between summer and winter, M. booduga burrows have an average depth of 41 cm, as against 30 cm in southern India with less climatic fluctuation. M. terricolor burrows are about 20 cm deep everywhere. The three chromosomal species M. terricolor I, II and III have identical burrows, including location of the nest which is situated at the highest position. In contrast, in M. booduga burrows, the nest is at the lowest position. Results The nest chamber of M. booduga is located at greater depth than the nest chamber of M. terricolor. Also, in the burrows of M. booduga the exchange of air takes place only from one side (top surface in contrast to the burrows of M. terricolor where air exchange is through three sides. Hence, M. booduga lives in relatively more hypoxic and hypercapnic conditions than M. terricolor. We observed the fixation of alternative alleles in M. booduga and M. terricolor at Superoxide dismutase-1 (Sod-1, Transferrin (Trf and Hemoglobin beta chain (Hbb loci. All the three are directly or indirectly dependent on oxygen concentration for function. In addition to these, there are differences in burrow patterns and site-preference for burrows suggesting difference in probable adaptive strategy in these co-existing sibling species. Conclusion The burrow structure and depth of nest of the chromosomal species M. terricolor I, II and III are same everywhere probably due to the recency of their evolutionary divergence. Moreover, there is lack of competition for the well-adapted 'microhabitats' since they are non-overlapping in distribution. However, the co-existing sibling species M. booduga

  7. Analysis of the stress field in a wedge using the fast expansions with pointwise determined coefficients

    Science.gov (United States)

    Chernyshov, A. D.; Goryainov, V. V.; Danshin, A. A.

    2018-03-01

    The stress problem for the elastic wedge-shaped cutter of finite dimensions with mixed boundary conditions is considered. The differential problem is reduced to the system of linear algebraic equations by applying twice the fast expansions with respect to the angular and radial coordinate. In order to determine the unknown coefficients of fast expansions, the pointwise method is utilized. The problem solution derived has explicit analytical form and it’s valid for the entire domain including its boundary. The computed profiles of the displacements and stresses in a cross-section of the cutter are provided. The stress field is investigated for various values of opening angle and cusp’s radius.

  8. Stress analysis of three-dimensional roadway layout of stagger arrangement with field observation

    Science.gov (United States)

    Cui, Zimo; Chanda, Emmanuel; Zhao, Jingli; Wang, Zhihe

    2018-01-01

    Longwall top-coal caving (LTCC) has been a popular, more productive and cost-effective method for extracting thick (> 5 m) to ultra-thick coal seams in recent years. However, low-level recovery ratio of coal resources and top-coal loss above the supports at both ends of working face are long-term problems. Geological factors, such as large dip angle, soft rock, mining depth further complicate the problems. This paper proposes addressing this issue by adopting three-dimensional roadway layout of stagger arrangement (3-D RLSA). In this study, the first step was to analyse the stress environment surrounding head entry in the replacing working face based on the stress distribution characteristics at the triangular coal-pillar side in gob and the stress slip line field theory. In the second step, filed observation was conducted. Finally, an economic evaluation of the 3-D RLSA for extracting thick to ultra-thick seams was conducted.

  9. Extension joints: a tool to infer the active stress field orientation (case study from southern Italy)

    Science.gov (United States)

    De Guidi, Giorgio; Caputo, Riccardo; Scudero, Salvatore; Perdicaro, Vincenzo

    2013-04-01

    An intense tectonic activity in eastern Sicily and southern Calabria is well documented by the differential uplift of Late Quaternary coastlines and by the record of the strong historical earthquakes. The extensional belt that crosses this area is dominated by a well established WNW-ESE-oriented extensional direction. However, this area is largely lacking of any structural analysis able to define the tectonics at a more local scale. In the attempt to fill this gap of knowledge, we carried out a systematic analysis of extension joint sets. In fact, the systematic field collection of these extensional features, coupled with an appropriate inversion technique, allows to determine the characteristic of the causative tectonic stress field. Joints are defined as outcrop-scale mechanical discontinuities showing no evidence of shear motion and being originated as purely extensional fractures. Such tectonic features are one of the most common deformational structures in every tectonic environment and particularly abundant in the study area. A particular arrangement of joints, called "fracture grid-lock system", and defined as an orthogonal joint system where mutual abutting and crosscutting relationships characterize two geologically coeval joint sets, allow to infer the direction and the magnitude of the tectonic stress field. We performed the analyses of joints only on Pleistocene deposits of Eastern Sicily and Southern Calabria. Moreover we investigated only calcarenite sediments and cemented deposits, avoiding claysh and loose matrix-supported clastic sediments where the deformation is generally accomodated in a distributed way through the relative motion between the single particles. In the selection of the sites, we also took into account the possibility to clearly observe the geometric relationships among the joints. For this reason we chose curvilinear road cuts or cliffs, wide coastal erosional surfaces and quarries. The numerical inversions show a similar stress

  10. Photoelastic and analytical investigation of stress in toroidal magnetic field coils

    International Nuclear Information System (INIS)

    Pih, H.; Gray, W.H.

    1975-01-01

    A series of two-dimensional photoelastic stress analyses on circular and oval toroidal magnetic field coils for fusion reactors were made. The circumferential variation of the coil's magnetic force was simulated by applying different pressures to sixteen segmented regions of the inner surface of the models. Isochromatics and isoclinics were measured at selected points on the loaded model in a transmission polariscope using a microphotometer. Separate principal stresses were obtained using the combination of photoelastic information and isopachic data measured from the solution of Laplace's equation by the electrical analog method. Analysis of the same coil geometries, loadings, and boundary conditions were made using the finite element method. General agreement between theory and experiment was realized. From this investigation several variations of coil geometry and methods of support were evaluated. Based upon this experiment, suggestions for optimum structural design of toroidal field coils are presented

  11. Developing Field Test Procedures for Chloride Stress Corrosion Cracking in the Arabian Gulf

    Directory of Open Access Journals (Sweden)

    Hanan Farhat

    2018-01-01

    Full Text Available Oil and gas production and petrochemical plants in the Arabian Gulf are exposed to severe environmental conditions of high temperature and humidity. This makes these plants susceptible to chloride-induced stress corrosion cracking (CSCC. The laboratory testing fails to provide the exact field environmental conditions. A cost efficient field test setup for CSCC was designed and developed for the Arabian Gulf. The setup included designing self-sustained loading devices, samples, and sample racks. The samples were exposed to a stress equivalent to 80% and 100% of their yield strength. This paper describes the developed test procedures to establish testing with high level of accuracy and repeatability. It also discusses the design aspects and the challenges that were met.

  12. GOLIA-RK, Structure Stress for Isotropic Materials with Creep and Temperature Fields

    International Nuclear Information System (INIS)

    Donea, J.; Giuliani, S.

    1976-01-01

    1 - Nature of the physical problem solved: Stress analysis of complex structures in presence of creep, dimensional changes and thermal field. Plane stress, plane strain, generalized plane strain and axisymmetric problems can be solved. The material is assumed to be either isotropic or transversely isotropic. Any laws of material behaviour can easily be incorporated by the user (see subroutines WIGNER and CLAW). 2 - Method of solution: Finite element method using triangular elements with linear local fields. The equations for the displacements are solved by Choleski's method. An algorithm is incorporated to calculate automatically the successive time steps in a creep problem. 3 - Restrictions on the complexity of the problem: Maximum number of elements is 700. Maximum number of nodal points is 400. The indexes of two adjacent nodes are not permitted to differ by more than 19

  13. Analytical Solution for Stress Field and Intensity Factor in CSTBD under Mixed Mode Conditions

    Directory of Open Access Journals (Sweden)

    Najaf Ali Ghavidel

    2014-06-01

    Full Text Available Considering the fact that rocks fail faster under tensile stress, rock tensile strength is of greatimportance in applications such as blasting, rock fragmentation, slope stability, hydraulic fracturing,caprock integrity, and geothermal energy extraction. There are two direct and indirect methods tomeasure tensile strength. Since direct methods always encompass difficulties in test setup, indirectmethods, specifically the Brazilian test, have often been employed for tensile strength measurement.Tensile failure is technically attributed to crack propagation in rock. Fracture mechanics hassignificant potential for the determination of crack behaviour as well as propagation pattern. To applyBrazilian tests, cracked disc geometry has been suggested by the International Society for RockMechanics ISRM. Accordingly, a comprehensive study is necessary to evaluate stress field and stressintensity factor (SIF around the crack in the centre of the specimen. In this paper, superpositionprinciple is employed to solve the problem of cracked straight-through Brazilian disc (CSTBD, usingtwo methods of dislocation and complex stress function. Stress field and SIF in the vicinity of thecrack tip are then calculated. With the proposed method, the magnitude of critical load for crackinitiation in structures can be predicted. This method is valid for any crack of any arbitrary length andangle. In addition, numerical modelling has been carried out for the Brazilian disc. Finally, theanalytical solution has been compared with numerical modelling results showing the same outcomefor both methods.

  14. Heat transfer and thermal stress analysis in fluid-structure coupled field

    International Nuclear Information System (INIS)

    Li, Ming-Jian; Pan, Jun-Hua; Ni, Ming-Jiu; Zhang, Nian-Mei

    2015-01-01

    In this work, three-dimensional simulation on conjugate heat transfer in a fluid-structure coupled field was carried out. The structure considered is from the dual-coolant lithium-lead (DCLL) blanket, which is the key technology of International Thermo-nuclear Experimental Reactor (ITER). The model was developed based on finite element-finite volume method and was employed to investigate mechanical behaviours of Flow Channel Insert (FCI) and heat transfer in the blanket under nuclear reaction. Temperature distribution, thermal deformation and thermal stresses were calculated in this work, and the effects of thermal conductivity, convection heat transfer coefficient and flow velocity were analyzed. Results show that temperature gradients and thermal stresses of FCI decrease when FCI has better heat conductivity. Higher convection heat transfer coefficient will result in lower temperature, thermal deformations and stresses in FCI. Analysis in this work could be a theoretical basis of blanket optimization. - Highlights: • We use FVM and FEM to investigate FCI structural safety considering heat transfer and FSI effects. • Higher convective heat transfer coefficient is beneficial for the FCI structural safety without much affect to bulk flow temperature. • Smaller FCI thermal conductivity can better prevent heat leakage into helium, yet will increase FCI temperature gradient and thermal stress. • Three-dimensional simulation on conjugate heat transfer in a fluid-structure coupled field was carried out

  15. Influence of the lithosphere-asthenosphere boundary on the stress field northwest of the Alps

    Science.gov (United States)

    Maury, J.; Cornet, F. H.; Cara, M.

    2014-11-01

    In 1356, a magnitude 6-7 earthquake occurred near Basel, in Switzerland. But recent compilations of GPS measurements reveal that measured horizontal deformation rates in northwestern continental Europe are smaller than error bars on the measurements, proving present tectonic activity, if any, is very small in this area. We propose to reconcile these apparently antinomic observations with a mechanical model of the lithosphere that takes into account the geometry of the lithosphere-asthenosphere boundary, assuming that the only loading mechanism is gravity. The lithosphere is considered to be an elastoplastic material satisfying a Von Mises plasticity criterion. The model, which is 400 km long, 360 km wide and 230 km thick, is centred near Belfort in eastern France, with its width oriented parallel to the N145°E direction. It also takes into account the real topography of both the ground surface and that of the Moho discontinuity. Not only does the model reproduce observed principal stress directions orientations, it also identifies a plastic zone that fits roughly the most seismically active domain of the region. Interestingly, a somewhat similar stress map may be produced by considering an elastic lithosphere and an ad-hoc horizontal `tectonic' stress field. However, for the latter model, examination of the plasticity criterion suggests that plastic deformation should have taken place. It is concluded that the present-day stress field in this region is likely controlled by gravity and rheology, rather than by active Alpine tectonics.

  16. Stress

    Science.gov (United States)

    ... can be life-saving. But chronic stress can cause both physical and mental harm. There are at least three different types of stress: Routine stress related to the pressures of work, family, and other daily responsibilities Stress brought about ...

  17. Nickel--chromium strain gages for cryogenic stress analysis of superconducting structures in high magnetic fields

    International Nuclear Information System (INIS)

    Freynik, H.S. Jr.; Roach, D.R.; Deis, D.W.; Hirzel, D.G.

    1977-01-01

    Evaluation and calibration measurements were performed on commercial nickel-chromium metal-foil strain gages in a high-magnetic-field (12 T), liquid-helium (4.2 K) environment. The purpose was to fully characterize strain gages for use at cryogenic temperatures in high magnetic fields. In this study, the magnetoresistance of a number of strain gages was measured in three orthogonal directions at mechanical strain levels to 8900 μm/m. As a result, a unique calibration curve was defined for magnetoresistance strain errors that is independent of strain level and field direction to 12 T at 4.2 K. A current strain-gage application is the measurement of superconductor mechanical properties. These gages will soon be used in the stress analysis of superconducting fusion magnets during cooldown from ambient temperatures and during operation at 4.2 K with magnetic fields to 12 T

  18. Impact of Brake Pad Structure on Temperature and Stress Fields of Brake Disc

    OpenAIRE

    Wang, Guoshun; Fu, Rong

    2013-01-01

    Utilizing ABAQUS finite element software, the study established the relationship between a brake pad structure and distributions of temperature and thermal stress on brake disc. By introducing radial structure factor and circular structure factor concepts, the research characterized the effect of friction block radial and circumferential arrangement on temperature field of the brake disc. A method was proposed for improving heat flow distribution of the brake disc through optimizing the posit...

  19. Generalized stress field in granular soils heap with Rayleigh–Ritz method

    Directory of Open Access Journals (Sweden)

    Gang Bi

    2017-02-01

    Full Text Available The stress field in granular soils heap (including piled coal will have a non-negligible impact on the settlement of the underlying soils. It is usually obtained by measurements and numerical simulations. Because the former method is not reliable as pressure cells instrumented on the interface between piled coal and the underlying soft soil do not work well, results from numerical methods alone are necessary to be doubly checked with one more method before they are extended to more complex cases. The generalized stress field in granular soils heap is analyzed with Rayleigh–Ritz method. The problem is divided into two cases: case A without horizontal constraint on the base and case B with horizontal constraint on the base. In both cases, the displacement functions u(x, y and v(x, y are assumed to be cubic polynomials with 12 undetermined parameters, which will satisfy the Cauchy's partial differential equations, generalized Hooke's law and boundary equations. A function is built with the Rayleigh–Ritz method according to the principle of minimum potential energy, and the problem is converted into solving two undetermined parameters through the variation of the function, while the other parameters are expressed in terms of these two parameters. By comparison of results from the Rayleigh–Ritz method and numerical simulations, it is demonstrated that the Rayleigh–Ritz method is feasible to study the generalized stress field in granular soils heap. Solutions from numerical methods are verified before being extended to more complicated cases.

  20. Model calculations of stresses and deformations in rock salt in the near field of heated borehols

    International Nuclear Information System (INIS)

    Pudewills, A.

    1984-08-01

    With the help of the finite element computer code ADINA thermally induced borehole closure and stress distribution in the salt were investigated by the example of the 'Temperature Test 3' performed in the Asse mine during which the temperature and the borehole closure were measured. The aim of the calculations has been the assessment of the capabilities of the ADINA code to solve complex thermomechanical problems and to verify the available thermomechanical material laws for rock salt. In these computations the modulus of elasticity and the creep law of salt were varied in order to assess the influence exerted by these material parameters. The computed borehole closures are in good agreement with the measured data. In second part the model computations of thermomechanical phenomena around a 300 m deep borehole are presented for a HLW repository with and without brine, respectively. The finite element investigations are carried out for a periodical and symmetrical disposal field configuration with an equivalent radius of 28 m of the cylindrical unit cell. The initial state of stress was assumed to be lithostatic. A hydrostatic fluid pressure of 12 MPa was chosen for the case of accidental flooding of the repository field shortly after emplacement of the waste canisters. The essential results of this thermomechanical analysis are the borehole closure and the stresses in rock salt in the near field of the repository borehole. (orig./HP) [de

  1. Flight performance of an advanced CZT imaging detector in a balloon-borne wide-field hard X-ray telescope-ProtoEXIST1

    Energy Technology Data Exchange (ETDEWEB)

    Hong, J., E-mail: jaesub@head.cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Allen, B.; Grindlay, J. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Barthelemy, S.; Baker, R. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Garson, A.; Krawczynski, H. [Washington University in St. Louis and the McDonnell Center for the Space Sciences, St. Louis, MO 63130 (United States); Apple, J.; Cleveland, W.H. [NASA Marshall Space Flight Center and Universities Space Research Association, Huntsville, AL 35812 (United States)

    2011-10-21

    We successfully carried out the first high-altitude balloon flight of a wide-field hard X-ray coded-aperture telescope ProtoEXIST1, which was launched from the Columbia Scientific Balloon Facility at Ft. Sumner, New Mexico on October 9, 2009. ProtoEXIST1 is the first implementation of an advanced CdZnTe (CZT) imaging detector in our ongoing program to establish the technology required for next generation wide-field hard X-ray telescopes such as the High Energy Telescope (HET) in the Energetic X-ray Imaging Survey Telescope (EXIST). The CZT detector plane in ProtoEXIST1 consists of an 8x8 array of closely tiled 2 cmx2 cmx0.5 cm thick pixellated CZT crystals, each with 8x8 pixels, mounted on a set of readout electronics boards and covering a 256 cm{sup 2} active area with 2.5 mm pixels. A tungsten mask, mounted at 90 cm above the detector provides shadowgrams of X-ray sources in the 30-600 keV band for imaging, allowing a fully coded field of view of 9{sup o}x9{sup o} (and 19{sup o}x19{sup o} for 50% coding fraction) with an angular resolution of 20'. In order to reduce the background radiation, the detector is surrounded by semi-graded (Pb/Sn/Cu) passive shields on the four sides all the way to the mask. On the back side, a 26 cmx26 cmx2 cm CsI(Na) active shield provides signals to tag charged particle induced events as well as {>=}100keV background photons from below. The flight duration was only about 7.5 h due to strong winds (60 knots) at float altitude (38-39 km). Throughout the flight, the CZT detector performed excellently. The telescope observed Cyg X-1, a bright black hole binary system, for {approx}1h at the end of the flight. Despite a few problems with the pointing and aspect systems that caused the telescope to track about 6.4{sup o} off the target, the analysis of the Cyg X-1 data revealed an X-ray source at 7.2{sigma} in the 30-100 keV energy band at the expected location from the optical images taken by the onboard daytime star camera. The

  2. Quantum fields interacting with colliding plane waves: the stress-energy tensor and backreaction

    International Nuclear Information System (INIS)

    Dorca, M.; Verdaguer, E.

    1997-01-01

    Following a previous work on the quantization of a massless scalar field in a space-time representing the head on collision of two plane waves which focus into a Killing-Cauchy horizon, we compute the renormalized expectation value of the stress-energy tensor of the quantum field near that horizon in the physical state which corresponds to the Minkowski vacuum before the collision of the waves. It is found that for minimally coupled and conformally coupled scalar fields the respective stress-energy tensors are unbounded in the horizon. The specific form of the divergences suggests that when the semiclassical Einstein equations describing the backreaction of the quantum fields on the space-time geometry are taken into account, the horizon will acquire a curvature singularity. Thus the Killing-Cauchy horizon which is known to be unstable under ''generic'' classical perturbations is also unstable by vacuum polarization. The calculation is done following the point-splitting regularization technique. The dynamical colliding wave space-time has four quite distinct space-time regions, namely, one flat region, two single plane wave regions, and one interaction region. Exact mode solutions of the quantum field equation cannot be found exactly, but the blueshift suffered by the initial modes in the plane wave and interaction regions makes the use of the WKB expansion a suitable method of solution. To ensure the correct regularization of the stress-energy tensor, the initial flat modes propagated into the interaction region must be given to a rather high adiabatic order of approximation. (orig.)

  3. Effects of chronic restraint stress and estradiol on open field activity, spatial memory, and monoaminergic neurotransmitters in ovariectomized rats.

    Science.gov (United States)

    Bowman, R E; Ferguson, D; Luine, V N

    2002-01-01

    Twenty-one days of chronic restraint stress impairs male rat performance on the radial arm maze [Luine et al. (1994) Brain Res. 639, 167-170], but enhances female rat performance [Bowman et al. (2001) Brain Res. 904, 279-289]. To assess possible ovarian hormone mechanisms underlying this sexually dimorphic response to stress, we examined chronic stress effects in ovariectomized rats. Ovariectomized rats received Silastic capsule implants containing cholesterol or estradiol and were assigned to a daily restraint stress (21 days, 6 h/day) or non-stress group. Following the stress period, subjects were tested for open field activity and radial arm maze performance. Stress and estradiol treatment affected open field activity. All stressed animals, with or without estradiol treatment, made fewer total outer sector crossings. In contrast, estradiol-treated animals, with or without stress, made more inner sector visits, an indication that estradiol decreased anxious behavior on the open field across time. As measured by the total number of visits required to complete the task, stress did not affect radial arm maze performance in ovariectomized rats, but estradiol-treated animals, with or without stress, performed better than non-treated animals on the radial arm maze. Stressed subjects receiving estradiol showed the best radial arm maze performance. Following killing, tissue samples were obtained from various brain regions known to contribute to learning and memory, and monoamine and metabolite levels were measured. Several changes were observed in response to both stress and estradiol. Most noteworthy, stress treatment decreased homovanillic acid levels in the prefrontal cortex, an effect not previously observed in stressed intact females. Estradiol treatment increased norepinephrine levels in CA3 region of the hippocampus, mitigating stress-dependent changes. Both stress and estradiol decreased dentate gyrus levels of 5-hydroxyindole acetic acid. In summary, the current

  4. Combined effect of electric field and residual stress on propagation of indentation cracks in a PZT-5H ferroelectric ceramic

    International Nuclear Information System (INIS)

    Huang, H.Y.; Chu, W.Y.; Su, Y.J.; Qiao, L.J.; Gao, K.W.

    2005-01-01

    The combined effect of electric field and residual stress on propagation of unloaded indentation cracks in a PZT-5 ceramic has been studied. The results show that residual stress itself is too small to induce delayed propagation of the indentation cracks in silicon oil. If applied constant electric field is larger than 0.2 kV/cm, the combined effect of electric field and residual stress can cause delayed propagation of the indentation crack after passing an incubation time in silicon oil, but the crack will arrest after propagating for 10-30 μm because of decrease of the resultant stress intensity factor induced by the field and residual stress with increasing the crack length. The threshold electric field for delayed propagation of the indentation crack in silicon oil is E DP = 0.2 kV/cm. If the applied electric field is larger than 5.25 kV/cm, combined effect of the electric field and residual stress can cause instant propagation of the indentation crack, and under sustained electric field, the crack which has propagated instantly can propagate continuously, until arrest at last. The critical electric field for instant propagation of the indentation crack is E P = 5.25 kV/cm. If the applied electric field is larger than 12.6 kV/cm, the microcracks induced by the electric field initiate everywhere, grow and connect in a smooth specimen, resulting in delayed failure, even without residual stress. The threshold electric field for delayed failure of a smooth specimen in silicon oil is E DF = 12.6 kV/cm and the critical electric field for instant failure is E F = 19.1 kV/cm

  5. Contemporary stress field in the area of the 2016 Amatrice seismic sequence (central Italy

    Directory of Open Access Journals (Sweden)

    Maria Teresa Mariucci

    2016-11-01

    Full Text Available We update the last present-day stress map for Italy relatively to the area of 2016 Amatrice seismic sequence (central Italy taking into account a large number of earthquakes occurred from August 24 to October 3, 2016. In particular in this paper, we discuss the new stress data from crustal earthquake focal mechanisms selecting those with Magnitude ≥ 4.0; at the same time, we revise the borehole data, analyze the stratigraphic profiles and the relative sonic logs in 4 deep wells located close to the Amatrice sequence along the Apennine belt and toward east along the Adriatic foredeep. From these data we consider the P-wave velocity trend with depth and estimate rock density following an empirical relationship. Then we calculate the overburden stress magnitude for each well. The new present-day stress indicators confirm the presence of prevalent normal faulting regime and better define the local stress field in the area, highlighting a slight rotation from NE-SW to ENE-WSW of extension. The analysis evidences that the lithostatic gradient gradually changes from ~26 MPa/km in the belt to less than 23 MPa/km along the Adriatic foredeep. Finally, at a depth of 5 km we estimate the vertical stress magnitude varying from 130 MPa to 114 moving from the Apennine belt to the Adriatic foredeep. Although the wells are very close each other they show different P wave velocities from the belt to the foredeep with values ~7km/s and ~4 km/s at 5 km depth, respectively.

  6. Beneficial effects of CO2 enrichment to field-grown soybeans under ozone stress

    International Nuclear Information System (INIS)

    Lee, E.H.; Mulchi, C.L.

    1991-01-01

    Damage from gaseous air pollution [e.g. ozone (O 3 ) and sulfur dioxide (SO 2 )] on crops in the US has been estimated to exceed several billion dollars annually. Atmospheric carbon dioxide (CO 2 ) concentrations have increased from about 290 ppm in the late 1800's to current levels of 350 ppm. The combined effects of increased CO 2 and O 3 stress have not been studied under field conditions. The present study was conducted to determine the interactive effects of CO 2 enrichment and O 3 stress on the growth and physiology of 'Clark' soybean, testing the hypothesis that elevated CO 2 will ameliorate the effects of O 3 stress. Experiments with soybeans in open-top field chambers showed that increasing CO 2 levels to 400 parts per million (ppm) negated current ambient ozone harmful effects on soybean yields. When ambient O 3 levels were doubled, it was necessary to increase the atmospheric CO 2 concentration to 500 ppm to negate O 3 damage. Rising CO 2 counteracts O 3 pollution. Reduced stomatal conductance and decreased photosynthesis appear to reverse the CO 2 stimulation

  7. The generalized fracture criteria based on the multi-parameter representation of the crack tip stress field

    Science.gov (United States)

    Stepanova, L. V.

    2017-12-01

    The paper is devoted to the multi-parameter asymptotic description of the stress field near the crack tip of a finite crack in an infinite isotropic elastic plane medium subject to 1) tensile stress; 2) in-plane shear; 3) mixed mode loading for a wide range of mode-mixity situations (Mode I and Mode II). The multi-parameter series expansion of stress tensor components containing higher-order terms is obtained. All the coefficients of the multiparameter series expansion of the stress field are given. The main focus is on the discussion of the influence of considering the higher-order terms of the Williams expansion. The analysis of the higher-order terms in the stress field is performed. It is shown that the larger the distance from the crack tip, the more terms it is necessary to keep in the asymptotic series expansion. Therefore, it can be concluded that several more higher-order terms of the Williams expansion should be used for the stress field description when the distance from the crack tip is not small enough. The crack propagation direction angle is calculated. Two fracture criteria, the maximum tangential stress criterion and the strain energy density criterion, are used. The multi-parameter form of the two commonly used fracture criteria is introduced and tested. Thirty and more terms of the Williams series expansion for the near-crack-tip stress field enable the angle to be calculated more precisely.

  8. Simultaneous wall-shear-stress and wide-field PIV measurements in a turbulent boundary layer

    Science.gov (United States)

    Gomit, Guillaume; Fourrie, Gregoire; de Kat, Roeland; Ganapathisubramani, Bharathram

    2015-11-01

    Simultaneous particle image velocimetry (PIV) and hot-film shear stress sensor measurements were performed to study the large-scale structures associated with shear stress events in a flat plate turbulent boundary layer at a high Reynolds number (Reτ ~ 4000). The PIV measurement was performed in a streamwise-wall normal plane using an array of six high resolution cameras (4 ×16MP and 2 ×29MP). The resulting field of view covers 8 δ (where δ is the boundary layer thickness) in the streamwise direction and captures the entire boundary layer in the wall-normal direction. The spatial resolution of the measurement is approximately is approximately 70 wall units (1.8 mm) and sampled each 35 wall units (0.9 mm). In association with the PIV setup, a spanwise array of 10 skin-friction sensors (spanning one δ) was used to capture the footprint of the large-scale structures. This combination of measurements allowed the analysis of the three-dimensional conditional structures in the boundary layer. Particularly, from conditional averages, the 3D organisation of the wall normal and streamwise velocity components (u and v) and the Reynolds shear stress (-u'v') related to a low and high shear stress events can be extracted. European Research Council Grant No-277472-WBT.

  9. Earthquake recurrence models fail when earthquakes fail to reset the stress field

    Science.gov (United States)

    Tormann, Thessa; Wiemer, Stefan; Hardebeck, Jeanne L.

    2012-01-01

    Parkfield's regularly occurring M6 mainshocks, about every 25 years, have over two decades stoked seismologists' hopes to successfully predict an earthquake of significant size. However, with the longest known inter-event time of 38 years, the latest M6 in the series (28 Sep 2004) did not conform to any of the applied forecast models, questioning once more the predictability of earthquakes in general. Our study investigates the spatial pattern of b-values along the Parkfield segment through the seismic cycle and documents a stably stressed structure. The forecasted rate of M6 earthquakes based on Parkfield's microseismicity b-values corresponds well to observed rates. We interpret the observed b-value stability in terms of the evolution of the stress field in that area: the M6 Parkfield earthquakes do not fully unload the stress on the fault, explaining why time recurrent models fail. We present the 1989 M6.9 Loma Prieta earthquake as counter example, which did release a significant portion of the stress along its fault segment and yields a substantial change in b-values.

  10. Engineering stress in thin films for the field of bistable MEMS

    International Nuclear Information System (INIS)

    Ratnayake, Dilan; Gowrishetty, Usha R; McNamara, Shamus P; Walsh, Kevin M; Martin, Michael D; Porter, Daniel A; Berfield, Thomas A

    2015-01-01

    While stress-free and tensile films are well-suited for released in-plane MEMS designs, compressive films are needed for released out-of-plane MEMS structures such as buckled beams and diaphragms. This study presents a characterization of stress on a variety of sputtered and plasma-enhanced chemical vapour deposition (PECVD)-deposited films, including titanium tungsten, invar, silicon nitride and amorphous silicon, appropriate for the field of bistable MEMS. Techniques and strategies are presented (including varying substrate bias, pressure, temperature, and frequency multiplexing) for tuning internal stress across the spectrum from highly compressive (−2300 MPa) to highly tensile (1500 MPa). Conditions for obtaining stress-free films are also presented in this work. Under certain conditions during the PECVD deposition of amorphous silicon, interesting ‘micro-bubbles’ formed within the deposited films. Strategies to mitigate their formation are presented, resulting in a dramatic improvement in surface roughness quality from 667 nm root mean square (RMS) to 16 nm RMS. All final deposited films successfully passed the traditional ‘tape test’ for adhesion. (paper)

  11. Impact of new traumatic or stressful life events on pre-existing PTSD in traumatized refugees: results of a longitudinal study

    Directory of Open Access Journals (Sweden)

    Katrin Schock

    2016-11-01

    Full Text Available Background: A significant proportion of trauma survivors experience an additional critical life event in the aftermath. These renewed experiences of traumatic and stressful life events may lead to an increase in trauma-related mental health symptoms.Method: In a longitudinal study, the effects of renewed experiences of a trauma or stressful life event were examined. For this purpose, refugees seeking asylum in Germany were assessed for posttraumatic stress symptoms (PTS, Posttraumatic Stress Diagnostic Scale (PDS, anxiety, and depression (Hopkins Symptom Checklist [HSCL-25] before treatment start as well as after 6 and 12 months during treatment (N=46. Stressful life events and traumatic events were recorded monthly. If a new event happened, PDS and HSCL were additionally assessed directly afterwards. Mann–Whitney U-tests were performed to calculate the differences between the group that experienced an additional critical event (stressful vs. trauma during treatment (n=23 and the group that did not (n=23, as well as differences within the critical event group between the stressful life event group (n=13 and the trauma group (n=10.Results: Refugees improved significantly during the 12-month period of our study, but remained severely distressed. In a comparison of refugees with a new stressful life event or trauma, significant increases in PTS, anxiety, and depressive symptoms were found directly after the experience, compared to the group without a renewed event during the 12 months of treatment. With regard to the different critical life events (stressful vs. trauma, no significant differences were found regarding overall PTS, anxiety, and depression symptoms. Only avoidance symptoms increased significantly in the group experiencing a stressful life event.Conclusion: Although all clinicians should be aware of possible PTS symptom reactivation, especially those working with refugees and asylum seekers, who often experience new critical life

  12. Impact of new traumatic or stressful life events on pre-existing PTSD in traumatized refugees: results of a longitudinal study.

    Science.gov (United States)

    Schock, Katrin; Böttche, Maria; Rosner, Rita; Wenk-Ansohn, Mechthild; Knaevelsrud, Christine

    2016-01-01

    A significant proportion of trauma survivors experience an additional critical life event in the aftermath. These renewed experiences of traumatic and stressful life events may lead to an increase in trauma-related mental health symptoms. In a longitudinal study, the effects of renewed experiences of a trauma or stressful life event were examined. For this purpose, refugees seeking asylum in Germany were assessed for posttraumatic stress symptoms (PTS), Posttraumatic Stress Diagnostic Scale (PDS), anxiety, and depression (Hopkins Symptom Checklist [HSCL-25]) before treatment start as well as after 6 and 12 months during treatment ( N =46). Stressful life events and traumatic events were recorded monthly. If a new event happened, PDS and HSCL were additionally assessed directly afterwards. Mann-Whitney U -tests were performed to calculate the differences between the group that experienced an additional critical event (stressful vs. trauma) during treatment ( n =23) and the group that did not ( n =23), as well as differences within the critical event group between the stressful life event group ( n =13) and the trauma group ( n =10). Refugees improved significantly during the 12-month period of our study, but remained severely distressed. In a comparison of refugees with a new stressful life event or trauma, significant increases in PTS, anxiety, and depressive symptoms were found directly after the experience, compared to the group without a renewed event during the 12 months of treatment. With regard to the different critical life events (stressful vs. trauma), no significant differences were found regarding overall PTS, anxiety, and depression symptoms. Only avoidance symptoms increased significantly in the group experiencing a stressful life event. Although all clinicians should be aware of possible PTS symptom reactivation, especially those working with refugees and asylum seekers, who often experience new critical life events, should understand symptom

  13. Stress-energy tensors for vector fields outside a static black hole

    International Nuclear Information System (INIS)

    Barrios, F.A.; Vaz, C.

    1989-01-01

    We obtain new, approximate stress-energy tensors to describe gauge fields in the neighborhood of a Schwarzschild black hole. We assume that the coefficient of ∇ 2 R in the trace anomaly is correctly given by ζ-function regularization. Our approximation differs from that of Page and of Brown and Ottewill and relies upon a new, improved ansatz for the form of the stress-energy tensor in the ultrastatic optical metric of the black hole. The Israel-Hartle-Hawking thermal tensor is constructed to be regular on the horizon and possess the correct asymptotic behavior. Our approximation of Unruh's tensor is likewise constructed to be regular on the future horizon and exhibit a luminosity which agrees with Page's numerically obtained value. Geometric expressions for the approximate tensors are given, and the approximate energy density of the thermal tensor on the horizon is compared with recent numerical estimates

  14. Vacuum stress tensor of a scalar field in a rectangular waveguide

    International Nuclear Information System (INIS)

    Rodrigues, R.B.; Svaiter, N.F.; Paola, R.D.M. de

    2001-11-01

    Using the heat Kernel method and the analytical continuation of the zeta function, we calculate the canonical and improved vacuum stress tensors, {T μν (vector x)} and {Θ μν (vector x)}, associated with a massless scalar field confined in the interior of an infinity long rectangular waveguide. The local depence of the renormalized energy for two special configurations when the total energy is positive and negative are presented using {T 00 (vector x)} and {Θ 00 (vector x)}. From the stress tensors we obtain the local casimir forces in all walls by introducing a particular external configuration. It is hown that this external configuration cannot give account of the edge divergences of the local forces. The local form of the forces is obtained for three special configurations. (author)

  15. Full-field fabric stress mapping by micro Raman spectroscopy in a yarn push-out test.

    Science.gov (United States)

    Lei, Z K; Qin, F Y; Fang, Q C; Bai, R X; Qiu, W; Chen, X

    2018-02-01

    The full-field stress distribution of a two-dimensional plain fabric was mapped using micro Raman spectroscopy (MRS) through a novel yarn push-out test, simulating a quasi-static projectile impact on the fabric. The stress-strain relationship for a single yarn was established using a digital image correlation method in a single-yarn tensile test. The relationship between Raman peak shift and aramid Kevlar 49 yarn stress was established using MRS in a single-yarn tensile test. An out-of-plane loading test was conducted on an aramid Kevlar 49 plain fabric, and the yarn stress was measured using MRS. From the full-field fabric stress distribution, it can be observed that there is a cross-shaped distribution of high yarn stress; this result would be helpful in further studies on load transfer on a fabric during a projectile impact.

  16. HPA axis response to social stress is attenuated in schizophrenia but normal in depression: evidence from a meta-analysis of existing studies.

    Science.gov (United States)

    Ciufolini, Simone; Dazzan, Paola; Kempton, Matthew J; Pariante, Carmine; Mondelli, Valeria

    2014-11-01

    We conducted a meta-analysis to investigate the HPA axis response to social stress in studies that used the Trier Social Stress Test (TSST), or comparable distressing paradigms, in individuals with either depression or schizophrenia. Sample size-adjusted effect sizes (Hedge's g statistic) were calculated to estimate the HPA axis stress response to social stress. We used a meta-regression model to take into account the moderating effect of the baseline cortisol level. Participants with depression show an activation pattern to social stress similar to that of healthy controls. Despite a normal cortisol production rate, individuals with schizophrenia have lower cortisol levels than controls both in anticipation and after exposure to social stress. Participants with depression and higher cortisol levels before the task have an increased cortisol production and reached higher cortisol levels during the task. This may be explained by the presence of an impaired negative feedback. The activation pattern present in schizophrenia may explain the reduced ability to appropriately contextualize past experiences shown by individuals with psychosis in social stressful situation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Osteoblastic differentiation and stress response of human mesenchymal stem cells exposed to alternating current electric fields

    Directory of Open Access Journals (Sweden)

    Kaplan David L

    2011-01-01

    Full Text Available Abstract Background Electric fields are integral to many biological events, from maintaining cellular homeostasis to embryonic development to healing. The application of electric fields offers substantial therapeutic potential, while optimal dosing regimens and the underlying mechanisms responsible for the positive clinical impact are poorly understood. Methods The purpose of this study was to track the differentiation profile and stress response of human bone marrow derived mesenchymal stem cells (hMSCs undergoing osteogenic differentiation during exposure to a 20 mV/cm, 60 kHz electric field. Morphological and biochemical changes were imaged using endogenous two-photon excited fluorescence (TPEF and quantitatively assessed through eccentricity calculations and extraction of the redox ratio from NADH, FAD and lipofuscin contributions. Real time reverse transcriptase-polymerase chain reactions (RT-PCR were used to track osteogenic differentiation markers, namely alkaline phosphatase (ALP and collagen type 1 (col1, and stress response markers, such as heat shock protein 27 (hsp27 and heat shock protein 70 (hsp70. Comparisons of collagen deposition between the stimulated hMSCs and controls were examined through second harmonic generation (SHG imaging. Results Quantitative differences in cell morphology, as described through an eccentricity ratio, were found on days 2 and days 5 (p Conclusions Electrical stimulation is a useful tool to improve hMSC osteogenic differentiation, while heat shock proteins may reveal underlying mechanisms, and optical non-invasive imaging may be used to monitor the induced morphological and biochemical changes.

  18. PSYCHOLOGICAL PROBLEMS AND STRESS FACED BY SOLDIERS WHO OPERATE IN ASYMMETRIC WARFARE ENVIRONMENTS: EXPERIENCES IN THE FIELD

    Directory of Open Access Journals (Sweden)

    Giuseppe CAFORIO

    2014-10-01

    Full Text Available This article deals with the problems of anxiety, stress and psychological discomfort that can affect soldiers sent on asymmetric warfare operations. It is based on secondary analysis of the data of two important field researches whose results have recently (2013 been published. Although the two researches adopted different methodologies, the testimonies are fully comparable and show that soldiers from different countries and cultures display common or similar reactions when they are placed in the stress conditions that the asymmetric environment involves. The approach of the paper is drawn up in such a way as to make the reader a participating observer of the reality of such missions. It is therefore centered on the personal testimonies of the soldiers interviewed in the two researches, testimonies reported just as they are, in their simplicity and, often, drama, with comments by the author kept to a minimum in order to give readers ample opportunity to evaluate and interpret the reported texts on their own. The research data, drawn from the declarations of those directly concerned, reveal the existence of a problem of psychological distress resulting from deployment in asymmetric warfare situations that is in part different in the causes of the problems resulting from deployment in traditional combat and affects percentages of participating soldiers that are not high but definitely significant. The highest incidence appears to be constituted by problems relating to reintegration into normal social and working life upon returning from the mission. This is followed in percentage terms by anxiety situations relating to life far from the family, due in large part to a sense of powerlessness for the scant possibility of managing family situations that may have cropped up or already existed beforehand.

  19. Active stress field and seismotectonic features in Intra-Carpathian region of Romania

    Science.gov (United States)

    Oros, Eugen; Popa, Mihaela; Diaconescu, Mihai; Radulian, Mircea

    2017-04-01

    The Romanian Intra-Carpathian Region is located on the eastern half of Tisa-Dacia geodynamic block from the Neogene Carpathian-Pannonian Basin. The distribution of seismicity displays clear clusters and narrower zones with seismogenic potential confirmed by the damaging earthquakes recoded in the region, e.g. July 01, 1829 (Mw=6.2), October 10, 1834 (Mw=5.6), January 26, 1916 (Mw=6.4), July 12, 1991 (Mw=5.7), December 2, 1991 (Mw=5.5). The state of recent stress and deformation appears to be controlled by the interaction of plate-boundary and intraplate forces, which include the counterclockwise rotation and N-NE-directed indentation of the Adria microplate and buoyancy forces associated with differential topography and lithospheric heterogeneities. The stress field and tectonic regime are investigated at regional and local scales by the formal inversion of focal mechamisms. There can be observed short-scale lateral changes of i) tectonic regimes from compressive (reverse and strike-slip faultings) to pure extensive (normal faultings) and ii) variation of stress directions (SHmax) from NE-SW to EW and WNW-ESE towards Southern Carpathians and NS within Easter Carpathians. The changes in stress directions occur over a distance that is comparable to or smaller than the thickness of the lithosphere. A comparative analysis of stress tensor with GPS velocity/displacememt vectors shows variations from paralellism to orthogonality, suggesting different mechanisms of crustal deformations.The major seismic activity (Mw≥5.0) appears to be generally concentrated along the faults systems bordering de Tisa-Dacia Block, intersections of faults of different ages, internal shear zones and with the border of the former structural terrains, old rifts and neostructures.

  20. Caffeine and sleep-deprivation mediated changes in open-field behaviours, stress response and antioxidant status in mice

    Directory of Open Access Journals (Sweden)

    J. Olakunle Onaolapo

    2016-07-01

    Conclusion: Repeated caffeine consumption and/or acute sleep-deprivation led to significant changes in pattern of open-field behaviour and stress/antioxidant response in mice. Responses seen in the study are probably due to modulatory effects of caffeine on the total body response to stressful stimuli.

  1. Reynolds and Maxwell stress measurements in the reversed field pinch experiment Extrap-T2R

    Science.gov (United States)

    Vianello, N.; Antoni, V.; Spada, E.; Spolaore, M.; Serianni, G.; Cavazzana, R.; Bergsåker, H.; Cecconello, M.; Drake, J. R.

    2005-08-01

    The complete Reynolds stress (RS) has been measured in the edge region of the Extrap-T2R reversed field pinch experiment. The RS exhibits a strong gradient in the region where a high E × B shear takes place. Experimental results show this gradient to be almost entirely due to the electrostatic contribution. This has been interpreted as experimental evidence of flow generation via turbulence mechanism. The scales involved in flow generation are deduced from the frequency decomposition of RS tensor. They are found related to magnetohydrodynamic activity but are different with respect to the scales responsible for turbulent transport.

  2. Reynolds and Maxwell stress measurements in the reversed field pinch experiment Extrap-T2R

    International Nuclear Information System (INIS)

    Vianello, N.; Antoni, V.; Spada, E.; Spolaore, M.; Serianni, G.; Cavazzana, R.; Bergsaaker, H.; Cecconello, M.; Drake, J.R.

    2005-01-01

    The complete Reynolds stress (RS) has been measured in the edge region of the Extrap-T2R reversed field pinch experiment. The RS exhibits a strong gradient in the region where a high E x B shear takes place. Experimental results show this gradient to be almost entirely due to the electrostatic contribution. This has been interpreted as experimental evidence of flow generation via turbulence mechanism. The scales involved in flow generation are deduced from the frequency decomposition of RS tensor. They are found related to magnetohydrodynamic activity but are different with respect to the scales responsible for turbulent transport

  3. Effects of 60 Hz electric fields on operant and social stress behaviors of nonhuman primates

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, W.R.; Coelho, A.M. Jr.; Easley, S.P.; Lucas, J.H.; Moore, G.T.; Orr, J.L.; Smith, H.D.; Taylor, L.L.; Tuttle, M.L.

    1987-10-24

    The objective of this program is to investigate, using the baboon as a nonhuman primate surrogate for the human, possible behavioral effects associated with exposure to high intensity 60 Hz electric fields. Results from this program, along with information from experiments conducted elsewhere, will be used by the Department of Energy (DOE) to estimate and evaluate the likelihood of deleterious consequences resulting from exposure of humans to the electric fields associated with power transmission over high voltage lines. This research program consists of four major research projects, all of which have been successfully completed. The first project evaluated the potentially aversive character of exposure to 60 Hz electric fields by determining the threshold intensity that produces escape or avoidance responses. The second project estimated the threshold intensity for detection threshold was 12 kV/m; the range of means was 6 to 16 kV/m. The third project assessed, in separate experiments conducted at 30 and 60 kV/m, effects of chronic exposure to electric fields on the performance of two operant conditioning tasks, fixed ratio (FR), and differential reinforcement of low rate (DRL). In the same two experiments, the fourth project investigated, using the systematic quantitative observational sampling methods of primatology, the possible stress-inducing effects of chronic exposure to 60 Hz electric fields on the behavior of baboons living in small social groups. 131 refs., 87 figs., 123 tabs.

  4. Stress Field Variation after the 2001 Skyros Earthquake, Greece, Derived from Seismicity Rate Changes

    Science.gov (United States)

    Leptokaropoulos, K.; Papadimitriou, E.; Orlecka-Sikora, B.; Karakostas, V.

    2012-04-01

    The spatial variation of the stress field (ΔCFF) after the 2001 strong (Mw=6.4) Skyros earthquake in North Aegean Sea, Greece, is investigated in association with the changes of earthquake production rates. A detailed slip model is considered in which the causative fault is consisted of several sub-faults with different coseismic slip onto each one of them. First the spatial distribution of aftershock productivity is compared with the static stress changes due to the coseismic slip. Calculations of ΔCFF are performed at different depths inside the seismogenic layer, defined from the vertical distribution of the aftershocks. Seismicity rates of the smaller magnitude events with M≥Mc for different time increments before and after the main shock are then derived from the application of a Probability Density Function (PDF). These rates are computed by spatially smoothing the seismicity and for this purpose a normal grid of rectangular cells is superimposed onto the area and the PDF determines seismicity rate values at the center of each cell. The differences between the earthquake occurrence rates before and after the main shock are compared and used as input data in a stress inversion algorithm based upon the Rate/State dependent friction concept in order to provide an independent estimation of stress changes. This model incorporates the physical properties of the fault zones (characteristic relaxation time, fault constitutive parameters, effective friction coefficient) with a probabilistic estimation of the spatial distribution of seismicity rates, derived from the application of the PDF. The stress patterns derived from the previously mentioned approaches are compared and the quantitative correlation between the respective results is accomplished by the evaluation of Pearson linear correlation coefficient and its confidence intervals to quantify their significance. Different assumptions and combinations of the physical and statistical parameters are tested for

  5. The stress energy tensor of a locally supersymmetric quantum field on a curved spacetime

    International Nuclear Information System (INIS)

    Koehler, M.

    1995-04-01

    For an analogon of the free Wess-Zumino model on Ricci flat spacetimes, the relation between a conserved 'supercurrent' and the point-separated improved energy momentum tensor is investigated and a similar relation as on Minkowski space is established. The expectation value of the latter in any globally Hadamard product state is found to be a priori finite in the coincidence limit if the theory is massive. On arbitrary globally hyperbolic spacetimes the 'supercurrent' is shown to be a well defined operator valued distribution on the GNS Hilbertspace of any globally Hadamard product state. Viewed as a new field, all n-point distributions exist, giving a new example for a Wightman field on that manifold. Moreover, it is shown that this field satisfies a new wave front set spectrum condition in a nontrivial way. (orig.)

  6. Modeling of stresses and electric fields in piezoelectric multilayer: Application to multi quantum wells

    Directory of Open Access Journals (Sweden)

    Dhaneshwar Mishra

    2017-07-01

    Full Text Available Exact closed-form expressions have been derived for the stresses and the electric fields induced in piezoelectric multilayers deposited on a substrate with lattice misfit and thermal expansion coefficient mismatch. The derived formulations can model any number of layers using recursive relations that minimize the computation time. A proper rotation matrix has been utilized to generalize the expressions so that they can be used for various growth orientations with each layer having hexagonal crystal symmetry. As an example, the influence of lattice misfit and thermal expansion coefficient mismatch on the state of electroelastic fields in different layers of GaN multi quantum wells has been examined. A comparison with the finite element analysis results showed very close agreement. The analytical expressions developed herein will be useful in designing optoelectronic devices as well as in predicting defect density in multi quantum wells.

  7. Effects of the stress field induced by a running tyre on the soil pore system

    DEFF Research Database (Denmark)

    Berisso, Feto Esimo; Schjønning, Per; Lamandé, Mathieu

    2013-01-01

    state in the soil profile beneath the harvester tyre was calculated using the SoilFlex model. Pore continuity index (N) and blocked air-filled porosity (εb) were estimated from the relationship between ka and air-filled porosity (εa) for a range of matric potentials. Calculated and measured stresses...... repeated wheelings were performed by a forage harvester (wheel load 6100 kg; tyre width 80 cm). Mean normal and horizontal stresses were measured with Bolling probes (at 10, 20 and 40 cm depth) and load cells (at 40, 50, 60 cm lateral distance from the centreline of the wheel rut at 10, 30 and 50 cm depth......), respectively. Intact soil cores of 100 cm3 sampled at 10, 30 and 50 cm depth in a soil transcet running from the centreline of the wheel rut to the unwheeled part of the field were used for measurements of water retention and air permeability (ka) at −30, −100 and −300 hPa matric potential. The complete stress...

  8. Temperature field and thermal stress analysis of the HT-7U vacuum vessel

    International Nuclear Information System (INIS)

    Song Yuntao; Yao Damao; Wu Songtao; Weng Peide

    2000-01-01

    The HT-7U vacuum vessel is an all-metal-welded double-wall interconnected with toroidal and poloidal stiffening ribs. The channels formed between the ribs and walls are filled with boride water as a nuclear shielding. On the vessel surface facing the plasma are installed cable-based Ohmic heaters. Prior to plasma operation the vessel is to be baked out and discharge cleaned at about 250 degree C. During baking out the non-uniformity of temperature distribution on the vacuum vessel will bring about serious thermal stress that can damage the vessel. In order to determine and optimize the design of the HT-7U vacuum vessel, a three-dimensional finite element model was performed to analyse its temperature field and thermal stress. the maximal thermal stress appeared on the round of lower vertical port and maximal deformation located just on the region between the upper vertical port and the horizontal port. The results show that the reinforced structure has a good capability of withstanding the thermal loads

  9. How plants cope with water stress in the field. Photosynthesis and growth.

    Science.gov (United States)

    Chaves, M M; Pereira, J S; Maroco, J; Rodrigues, M L; Ricardo, C P P; Osório, M L; Carvalho, I; Faria, T; Pinheiro, C

    2002-06-01

    Plants are often subjected to periods of soil and atmospheric water deficit during their life cycle. The frequency of such phenomena is likely to increase in the future even outside today's arid/semi-arid regions. Plant responses to water scarcity are complex, involving deleterious and/or adaptive changes, and under field conditions these responses can be synergistically or antagonistically modified by the superimposition of other stresses. This complexity is illustrated using examples of woody and herbaceous species mostly from Mediterranean-type ecosystems, with strategies ranging from drought-avoidance, as in winter/spring annuals or in deep-rooted perennials, to the stress resistance of sclerophylls. Differences among species that can be traced to different capacities for water acquisition, rather than to differences in metabolism at a given water status, are described. Changes in the root : shoot ratio or the temporary accumulation of reserves in the stem are accompanied by alterations in nitrogen and carbon metabolism, the fine regulation of which is still largely unknown. At the leaf level, the dissipation of excitation energy through processes other than photosynthetic C-metabolism is an important defence mechanism under conditions of water stress and is accompanied by down-regulation of photochemistry and, in the longer term, of carbon metabolism.

  10. Ferroelectric behavior of a lead titanate nanosphere due to depolarization fields and mechanical stresses

    Energy Technology Data Exchange (ETDEWEB)

    Andrade Landeta, J.; Lascano, I.

    2017-07-01

    A theorical model has been developed based on the theory of Ginzburg-Landau-Devonshire to study and predict the effects the decreasing of size particle in a nanosphere of PbTiO3 subjected to the action of depolarization fields and mechanical stress. It was considered that the nanosphere is surrounded by a layer of space charges on its surface, and containing 180° domains generated by minimizing free energy of depolarization. Energy density of depolarization, wall domain and electro-elastic energy have been incorporated into the free energy of the theory Ginzburg-Landau-Devonshire. Free energy minimization was performed to determine the spontaneous polarization and transition temperature system. These results show that the transition temperature for nanosphere is substantially smaller than the corresponding bulk material. Also, it has been obtained that the stability of the ferroelectric phase of nanosphere is favored for configurations with a large number of 180° domains, with the decreasing of thickness space charge layer, and the application of tensile stress and decreases with compressive stress. (Author)

  11. Focal mechanisms in the southern Aegean from temporary seismic networks - implications for the regional stress field and ongoing deformation processes

    Science.gov (United States)

    Friederich, W.; Brüstle, A.; Küperkoch, L.; Meier, T.; Lamara, S.; Egelados Working Group

    2014-05-01

    The lateral variation of the stress field in the southern Aegean plate and the subducting Hellenic slab is determined from recordings of seismicity obtained with the CYCNET and EGELADOS networks in the years from 2002 to 2007. First motions from 7000 well-located microearthquakes were analysed to produce 540 well-constrained focal mechanisms. They were complemented by another 140 derived by waveform matching of records from larger events. Most of these earthquakes fall into 16 distinct spatial clusters distributed over the southern Aegean region. For each cluster, a stress inversion could be carried out yielding consistent estimates of the stress field and its spatial variation. At crustal levels, the stress field is generally dominated by a steeply dipping compressional principal stress direction except in places where coupling of the subducting slab and overlying plate come into play. Tensional principal stresses are generally subhorizontal. Just behind the forearc, the crust is under arc-parallel tension whereas in the volcanic areas around Kos, Columbo and Astypalea tensional and intermediate stresses are nearly degenerate. Further west and north, in the Santorini-Amorgos graben and in the area of the islands of Mykonos, Andros and Tinos, tensional stresses are significant and point around the NW-SE direction. Very similar stress fields are observed in western Turkey with the tensional axis rotated to NNE-SSW. Intermediate-depth earthquakes below 100 km in the Nisyros region indicate that the Hellenic slab experiences slab-parallel tension at these depths. The direction of tension is close to east-west and thus deviates from the local NW-oriented slab dip presumably owing to the segmentation of the slab. Beneath the Cretan sea, at shallower levels, the slab is under NW-SE compression. Tensional principal stresses in the crust exhibit very good alignment with extensional strain rate principal axes derived from GPS velocities except in volcanic areas, where both

  12. Exploratory rearing: a context- and stress-sensitive behavior recorded in the open-field test.

    Science.gov (United States)

    Sturman, Oliver; Germain, Pierre-Luc; Bohacek, Johannes

    2018-02-16

    Stressful experiences are linked to anxiety disorders in humans. Similar effects are observed in rodent models, where anxiety is often measured in classic conflict tests such as the open-field test. Spontaneous rearing behavior, in which rodents stand on their hind legs to explore, can also be observed in this test yet is often ignored. We define two forms of rearing, supported rearing (in which the animal rears against the walls of the arena) and unsupported rearing (in which the animal rears without contacting the walls of the arena). Using an automated open-field test, we show that both rearing behaviors appear to be strongly context dependent and show clear sex differences, with females rearing less than males. We show that unsupported rearing is sensitive to acute stress, and is reduced under more averse testing conditions. Repeated testing and handling procedures lead to changes in several parameters over varying test sessions, yet unsupported rearing appears to be rather stable within a given animal. Rearing behaviors could therefore provide an additional measure of anxiety in rodents relevant for behavioral studies, as they appear to be highly sensitive to context and may be used in repeated testing designs.

  13. A procedure for temperature-stress fields calculation of WWER-1000 primary circuit in PTS event

    Energy Technology Data Exchange (ETDEWEB)

    Petkov, G [Technical Univ., Dept. Thermal and Nuclear Power Engineering, Sofia (Bulgaria); Groudev, P; Argirov, J [Bulgarian Academy of Science, Inst. for Nuclear Research and Nuclear Energy, Sofia (Bulgaria)

    1997-09-01

    The paper presents the procedure of an investigation of WWER-1000 primary circuit temperature-stress field by the use of thermohydraulic computation data for a pressurized thermal shock event ``Core overcooling``. The procedure is based on a model of the plane stress state with ideal contact between wall and medium for the calculation. The computation data are calculated on the base of WWER-1000 thermohydraulic model by the RELAP5/MOD3 codes. This model was developed jointly by the Bulgarian and BNL/USA staff to provide an analytical tool for performing safety analysis. As a result of calculations by codes the computation data for temperature field law (linear laws of a few distinguished parts) and pressure of coolant at points on inner surface of WWER-1000 primary circuit equipment are received. Such calculations can be used as a base for determination of all-important load-carrying sections of the primary circuit pipes and vessels, which need further consideration. (author). 7 refs, 2 figs, 2 tabs.

  14. Characterization of stress-induced suppression of long-term potentiation in the hippocampal CA1 field of freely moving rats.

    Science.gov (United States)

    Hirata, Riki; Togashi, Hiroko; Matsumoto, Machiko; Yamaguchi, Taku; Izumi, Takeshi; Yoshioka, Mitsuhiro

    2008-08-21

    Several lines of evidence have shown that exposure to stress impairs long-term potentiation (LTP) in the CA1 field of the hippocampus, but the detailed mechanisms for this effect remain to be clarified. The present study elucidated the synaptic mechanism of stress-induced LTP suppression in conscious, freely moving rats using electrophysiological approaches. Open field stress (i.e., novel environment stress) and elevated platform stress (i.e., uncontrollable stress) were employed. Basal synaptic transmission was significantly reduced during exposure to elevated platform stress but not during exposure to open field stress. LTP induction was blocked by elevated platform stress but not influenced by open field stress. Significant increases in serum corticosterone levels were observed in the elevated platform stress group compared with the open field stress group. Furthermore, LTP suppression induced by elevated platform stress was prevented by pretreatment with an anxiolytic drug diazepam (1 mg/kg, i.p.). These results suggest that stress-induced LTP suppression depends on the relative intensity of the stressor. The inhibitory synaptic response induced by an intense psychological stress, such as elevated platform stress, may be attributable to LTP impairment in the CA1 field of the hippocampus.

  15. Vitamin D deficiency, oxidative stress and antioxidant status: only weak association seen in the absence of advanced age, obesity or pre-existing disease.

    Science.gov (United States)

    Wang, Erica W; Siu, Parco M; Pang, Marco Y; Woo, Jean; Collins, Andrew R; Benzie, Iris F F

    2017-07-01

    Vitamin D deficiency (plasma 25-hydroxycholecalciferol (25(OH)D)70 % of participants were vitamin D deficient. No significant correlations and no biomarker differences across 25(OH)D quartiles or groups were seen except for total antioxidant status. A weak direct association (r 0·252, Pstress biomarkers in the absence of advanced age, obesity and disease, though some evidence of depleted antioxidant status in those with vitamin D deficiency was seen. Poor antioxidant status may pre-date increased oxidative stress. Study of effects of correction of deficiency on antioxidant status and oxidative stress in vitamin D-deficient but otherwise healthy subjects is needed.

  16. Stress field determination in an alloy 600 stress corrosion crack specimen; Determination du champ de contraintes dans une eprouvette de corrosion sous contrainte de l`alliage 600

    Energy Technology Data Exchange (ETDEWEB)

    Rassineux, B.; Labbe, T.

    1995-05-01

    In the context of EDF studies on stress corrosion cracking rates in the Alloy 600 steam generators tubes, we studied the influence of strain hardened surface layers on the different stages of cracking for a tensile smooth specimen (TLT). The stress field was notably assessed to try and explain the slow/rapid-propagation change observed beyond the strain hardened layers. The main difficulty is to simulate in a finite element model the inner and outer surfaces of these strain hardened layers, produced by the final manufacturing stages of SG tubes which have not been heat treated. In the model, the strain hardening is introduced by simulating a multi-layer material. Residual stresses are simulated by an equivalent fictitious thermomechanical calculation, realigned with respect to X-ray measurements. The strain hardening introduction method was validated by an analytical calculation giving identical results. Stress field evolution induced by specimen tensile loading were studied using an elastoplastic 2D finite element calculations performed with the Aster Code. The stress profile obtained after load at 660 MPa shows no stress discontinuity at the boundary between the strain hardened layer and the rest of the tube. So we propose that a complementary calculation be performed, taking into account the multi-cracked state of the strain hardened zones by means of a damage variable. In fact, this state could induce stress redistribution in the un-cracked area, which would perhaps provide an explanation of the crack-ground rate change beyond the strain hardened zone. The calculations also evidence the harmful effects of plastic strains on a strain hardened layer due to the initial state of the tube (not heat-treated), to grit blasting or to shot peening. The initial compressive stress condition of this surface layer becomes, after plastic strain, a tensile stress condition. These results are confirmed by laboratory test. (author). 10 refs., 18 figs., 9 tabs., 2 appends.

  17. Analysis of stress fields and elastic energies in the vicinity of nanograin boundaries using the disclination approach

    Science.gov (United States)

    Sukhanov, Ivan I.; Ditenberg, Ivan A.

    2017-12-01

    The paper provides a theoretical analysis of elastic stresses and elastic energy distribution in nanostructured metal materials in the vicinity of nanograin boundaries with a high partial disclination density. The analysis demonstrates the stress field distribution in disclination grain boundary configurations as a function of nanograin size, taking into account the superposition of these stresses in screening the disclination pile-ups. It is found that the principal stress tensor components reach maximum values only in disclination planes P ≈ E/25 and that the stress gradients peak at nodal points ∂P/∂x ≈ 0.08E nm-1. The shear stress components are localized within the physical grain size, and the specific elastic energy distribution for such configurations reveals characteristic local maxima which can be the cause for physical broadening of nanograin boundaries.

  18. Multi-parameter approximation of stress field in a cracked specimen using purpose-built Java applications

    Czech Academy of Sciences Publication Activity Database

    Veselý, V.; Sopek, J.; Tesař, D.; Frantík, P.; Pail, T.; Seitl, Stanislav

    2015-01-01

    Roč. 9, č. 33 (2015), s. 120-133 ISSN 1971-8993 Institutional support: RVO:68081723 Keywords : Cracked specimen * Near-crack-tip fields * Williams expansion * Higher order terms * Stress field reconstruction * Finite element analysis * Java application Subject RIV: JL - Materials Fatigue, Friction Mechanics

  19. Unraveling the nature of electric field- and stress- induced structural transformations in soft PZT by a new powder poling technique.

    Science.gov (United States)

    Kalyani, Ajay Kumar; V, Lalitha K; James, Ajit R; Fitch, Andy; Ranjan, Rajeev

    2015-02-25

    A 'powder-poling' technique was developed to study electric field induced structural transformations in ferroelectrics exhibiting a morphotropic phase boundary (MPB). The technique was employed on soft PZT exhibiting a large longitudinal piezoelectric response (d(33) ∼ 650 pC N(-1)). It was found that electric poling brings about a considerable degree of irreversible tetragonal to monoclinic transformation. The same transformation was achieved after subjecting the specimen to mechanical stress, which suggests an equivalence of stress and electric field with regard to the structural mechanism in MPB compositions. The electric field induced structural transformation was also found to be accompanied by a decrease in the spatial coherence of polarization.

  20. Stress

    Science.gov (United States)

    ... taking care of an aging parent. With mental stress, the body pumps out hormones to no avail. Neither fighting ... with type 1 diabetes. This difference makes sense. Stress blocks the body from releasing insulin in people with type 2 ...

  1. Stress field of a near-surface basal screw dislocation in elastically anisotropic hexagonal crystals

    Directory of Open Access Journals (Sweden)

    Valeri S. Harutyunyan

    2017-11-01

    Full Text Available In this study, we derive and analyze the analytical expressions for stress components of the dislocation elastic field induced by a near-surface basal screw dislocation in a semi-infinite elastically anisotropic material with hexagonal crystal lattice. The variation of above stress components depending on “free surface–dislocation” distance (i.e., free surface effect is studied by means of plotting the stress distribution maps for elastically anisotropic crystals of GaN and TiB2 that exhibit different degrees of elastic anisotropy. The dependence both of the image force on a screw dislocation and the force of interaction between two neighboring basal screw dislocations on the “free surface–dislocation” distance is analyzed as well. The influence of elastic anisotropy on the latter force is numerically analyzed for GaN and TiB2 and also for crystals of such highly elastically-anisotropic materials as Ti, Zn, Cd, and graphite. The comparatively stronger effect of the elastic anisotropy on dislocation-induced stress distribution quantified for TiB2 is attributed to the higher degree of elastic anisotropy of this compound in comparison to that of the GaN. For GaN and TiB2, the dislocation stress distribution maps are highly influenced by the free surface effect at “free surface–dislocation” distances roughly smaller than ≈15 and ≈50 nm, respectively. It is found that, for above indicated materials, the relative decrease of the force of interaction between near-surface screw dislocations due to free surface effect is in the order Ti > GaN > TiB2 > Zn > Cd > Graphite that results from increase of the specific shear anisotropy parameter in the reverse order Ti < GaN < TiB2 < Zn < Cd < Graphite. The results obtained in this study are also applicable to the case when a screw dislocation is situated in the “thin film–substrate” system at a (0001 basal interface between the film and substrate provided that the elastic constants

  2. Neuronal cellular responses to extremely low frequency electromagnetic field exposure: implications regarding oxidative stress and neurodegeneration.

    Directory of Open Access Journals (Sweden)

    Marcella Reale

    Full Text Available Neurodegenerative diseases comprise both hereditary and sporadic conditions characterized by an identifying progressive nervous system dysfunction and distinctive neuopathophysiology. The majority are of non-familial etiology and hence environmental factors and lifestyle play key roles in their pathogenesis. The extensive use of and ever increasing worldwide demand for electricity has stimulated societal and scientific interest on the environmental exposure to low frequency electromagnetic fields (EMFs on human health. Epidemiological studies suggest a positive association between 50/60-Hz power transmission fields and leukemia or lymphoma development. Consequent to the association between EMFs and induction of oxidative stress, concerns relating to development of neurodegenerative diseases, such as Alzheimer disease (AD, have been voiced as the brain consumes the greatest fraction of oxygen and is particularly vulnerable to oxidative stress. Exposure to extremely low frequency (ELF-EMFs are reported to alter animal behavior and modulate biological variables, including gene expression, regulation of cell survival, promotion of cellular differentiation, and changes in cerebral blood flow in aged AD transgenic mice. Alterations in inflammatory responses have also been reported, but how these actions impact human health remains unknown. We hence evaluated the effects of an electromagnetic wave (magnetic field intensity 1 mT; frequency, 50-Hz on a well-characterized immortalized neuronal cell model, human SH-SY5Y cells. ELF-EMF exposure elevated the expession of NOS and O2(-, which were countered by compensatory changes in antioxidant catylase (CAT activity and enzymatic kinetic parameters related to CYP-450 and CAT activity. Actions of ELF-EMFs on cytokine gene expression were additionally evaluated and found rapidly modified. Confronted with co-exposure to H2O2-induced oxidative stress, ELF-EMF proved not as well counteracted and resulted in a

  3. A stress field in the vortex lattice in the type-II superconductor

    Directory of Open Access Journals (Sweden)

    Maruszewski, Bogdan

    2008-02-01

    Full Text Available Magnetic flux can penetrate a type-II superconductor in the form of Abrikosov vortices (also called flux lines, flux tubes, or fluxons, each carrying a quantum of magnetic flux. These tiny vortices of supercurrent tend to arrange themselves in a triangular and/or quadratic flux-line lattice, which is more or less perturbed by material inhomogeneities that pin the flux lines. Pinning is caused by imperfections of the crystal lattice, such as dislocations, point defects, grain boundaries, etc. Hence, a honeycomb-like pattern of the vortex array presents some mechanical properties. If the Lorentz force of interactions between the vortices is much bigger than the pinning force, the vortex lattice behaves elastically. So we assume that the pinning force is negligible in the sequel and we deal with soft vortices. The vortex motion in the vortex lattice and/or creep of the vortices in the vortex fluid is accompanied by energy dissipation. Hence, except for the elastic properties, the vortex field is also of a viscous character. The main aim of the paper is a formulation of a thermoviscoelastic stress - strain constitutive law consisted of coexistence of the ordered and disordered states of the vortex field. Its form describes an auxetic-like thermomechanical (anomalous property of the vortex field.

  4. Vortex configuration in the presence of local magnetic field and locally applied stress

    International Nuclear Information System (INIS)

    Wissberg, Shai; Kremen, Anna; Shperber, Yishai; Kalisky, Beena

    2017-01-01

    Highlights: • We discuss different ways to determine vortex configuration using a scanning SQUID. • We determined the vortex configuration by approaching the sample during cooling. • We observed an accumulation of vortices when contact was made with the sample. • We show how we can manipulate local vortex configuration using contact. - Abstract: Vortex configuration is determined by the repulsive interaction, which becomes dominant with increasing vortex density, by the pinning potential, and by other considerations such as the local magnetic fields, currents flowing in the sample, or as we showed recently, by local stress applied on the sample. In this work we describe different ways to control vortex configuration using scanning SQUID microscopy.

  5. Vortex configuration in the presence of local magnetic field and locally applied stress

    Energy Technology Data Exchange (ETDEWEB)

    Wissberg, Shai; Kremen, Anna; Shperber, Yishai; Kalisky, Beena, E-mail: beena@biu.ac.il

    2017-02-15

    Highlights: • We discuss different ways to determine vortex configuration using a scanning SQUID. • We determined the vortex configuration by approaching the sample during cooling. • We observed an accumulation of vortices when contact was made with the sample. • We show how we can manipulate local vortex configuration using contact. - Abstract: Vortex configuration is determined by the repulsive interaction, which becomes dominant with increasing vortex density, by the pinning potential, and by other considerations such as the local magnetic fields, currents flowing in the sample, or as we showed recently, by local stress applied on the sample. In this work we describe different ways to control vortex configuration using scanning SQUID microscopy.

  6. Simulations of stress-induced twinning and de-twinning: A phase field model

    International Nuclear Information System (INIS)

    Hu Shenyang; Henager, Chuck H.; Chen Longqing

    2010-01-01

    Twinning in certain metals or under certain conditions is a major plastic deformation mode. Here we present a phase field model to describe twin formation and evolution in a polycrystalline fcc metal under loading and unloading. The model assumes that twin nucleation, growth and de-twinning is a process of partial dislocation nucleation and slip on successive habit planes. Stacking fault energies, energy pathways (γ surfaces), critical shear stresses for the formation of stacking faults and dislocation core energies are used to construct the thermodynamic model. The simulation results demonstrate that the model is able to predict the nucleation of twins and partial dislocations, as well as the morphology of the twin nuclei, and to reasonably describe twin growth and interaction. The twin microstructures at grain boundaries are in agreement with experimental observation. It was found that de-twinning occurs during unloading in the simulations, however, a strong dependence of twin structure evolution on loading history was observed.

  7. Irregular focal mechanisms observed at Salton Sea Geothermal Field: Possible influences of anthropogenic stress perturbations

    Science.gov (United States)

    Crandall-Bear, Aren; Barbour, Andrew J.; Schoenball, Martin; Schoenball, Martin

    2018-01-01

    At the Salton Sea Geothermal Field (SSGF), strain accumulation is released through seismic slip and aseismic deformation. Earthquake activity at the SSGF often occurs in swarm-like clusters, some with clear migration patterns. We have identified an earthquake sequence composed entirely of focal mechanisms representing an ambiguous style of faulting, where strikes are similar but deformation occurs due to steeply-dipping normal faults with varied stress states. In order to more accurately determine the style of faulting for these events, we revisit the original waveforms and refine estimates of P and S wave arrival times and displacement amplitudes. We calculate the acceptable focal plane solutions using P-wave polarities and S/P amplitude ratios, and determine the preferred fault plane. Without constraints on local variations in stress, found by inverting the full earthquake catalog, it is difficult to explain the occurrence of such events using standard fault-mechanics and friction. Comparing these variations with the expected poroelastic effects from local production and injection of geothermal fluids suggests that anthropogenic activity could affect the style of faulting.

  8. A method of fundamental solutions in poroelasticity to model the stress field in geothermal reservoirs

    CERN Document Server

    Augustin, Matthias Albert

    2015-01-01

    This monograph focuses on the numerical methods needed in the context of developing a reliable simulation tool to promote the use of renewable energy. One very promising source of energy is the heat stored in the Earth’s crust, which is harnessed by so-called geothermal facilities. Scientists from fields like geology, geo-engineering, geophysics and especially geomathematics are called upon to help make geothermics a reliable and safe energy production method. One of the challenges they face involves modeling the mechanical stresses at work in a reservoir. The aim of this thesis is to develop a numerical solution scheme by means of which the fluid pressure and rock stresses in a geothermal reservoir can be determined prior to well drilling and during production. For this purpose, the method should (i) include poroelastic effects, (ii) provide a means of including thermoelastic effects, (iii) be inexpensive in terms of memory and computational power, and (iv) be flexible with regard to the locations of data ...

  9. Remote Field Eddy Current Probes for the Detection of Stress Corrosion in Transmission Pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Plamen Alexandroz [Iowa State Univ., Ames, IA (United States)

    2002-01-01

    Magnetic flux leakage (MFL) is a technique used widely in non-destructive testing (NDT) of natural gas and petroleum transmission pipelines. This inspection method relies on magnetizing the pipe-wall in axial direction. The MFL inspection tool is equipped with an array of Hall sensors located around the circumference of the pipe, which registers the flux leakage caused by any defects present in the pipe-wall. Currently, the tool magnetizes the pipewall in axial direction making it largely insensitive to axially oriented defects. One type of defect, which is of a growing concern in the gas and petroleum industry is the stress corrosion crack (SCC). The SCCs are a result of aging, corrosion, fatigue and thermal stresses. SCCs are predominantly axially oriented and are extremely tight, which makes them impossible to be detected using current inspection technology. A possible solution to this problem is to utilize the remote field eddy current (RFEC) effect to detect axially oriented defects. The RFEC method has been widely used in industry in the inspection of tubular products. The method uses a pair of excitation and pick-up coils. The pick-up coil located in the remote field region, usually two, three pipe-diameters away from the excitation coil. With RFEC the presence of defects is detected by the disturbance in the phase of the signal measured by the pick-up coil relative to that of the excitation coil. Unlike conventional eddy current testing the RFEC method is sensitive to defects on the exterior of the inspected product, which makes it a good candidate for the development of in-line inspection technology. This work focuses on the development of non-destructive testing technique, which uses remote field eddy currents induced by rotating magnetic field (RMF). A major advantage of the RMF is that it makes possible to not only detect a defect but also localize its position in circumferential direction. Also, it could potentially allow detection of defects

  10. Field Performance of Five Soybean Mutants Under Drought Stress Conditions and Molecular Analysis Using SSR Markers

    Directory of Open Access Journals (Sweden)

    Y Yuliasti

    2017-08-01

    Full Text Available The objectives of this research wereto evaluate (1 the performance of soybean mutant lines under drought stress conditions, and(2 the genetic diversity and relationship among the mutant lines using SSR markers.The field evaluation was conducted during the dry season of 2011 and 2012 at the experimental Farm of Mataram University, West Nusa Tenggara, Indonesia. The field experiment was set up in a randomized block design. Ten mutant lines and two control varieties were evaluated in four replications. Genetic distance among evaluated lines were determined based on allelic diversity analysis using 40 simple sequence repeat (SSR loci. Under drought stress conditions, two mutant lines, Kdl3 and Kdl8,showed a better performance compared to the other ones. The high yielding mutant lines were Kdl3and Kdl8, which yielded 1.75 t ha-1and 1.69 t ha-1, respectively, compared to the parent and national control, Panderman 1.43 t ha-1 and Muria 1.32 t ha-1. These mutant linesrequired 30.75 to 32days to flower and 79.75 to 83.75 day to harvest with relatively short plant height 28.25 and 23.35 cmrespectively. Those mutant characters were better than those of the other three mutants, the original parents, and the control soybean species. Since the evaluated soybean mutant lines yielded more under drought stress conditions than the standard varieties, they can be used and registered as drought-tolerant soybean mutants. Moreover, the evaluated soybean accessions showed a wide genetic distance. The accessions were clustered into two groups according to their genetic background, namelygroup I (the Panderman with three mutant lines and group II (the Muria with two mutant lines. Twenty-three out of 40 evaluated SSR loci, including AW31, BE806, CMAC7L, S080, S126, S57, S171, S224, S285, S294, S393, S294, S383, S511, S511, S520, S540, S547, S551, S571, S577, and S578, provided polymorphic alleles between the parents and their mutants and could be used to differentiate

  11. Analysis of Stress and Strain Fields in and around Inclusions of Various Shapes in a Cylindrical Specimen Loaded in Tension

    Directory of Open Access Journals (Sweden)

    Neimitz A.

    2016-06-01

    Full Text Available A numerical analysis is performed of the stress field in and around inclusions of various shapes. Inclusions both stiffer and more compliant than the metal matrix are analysed. The critical stresses required for inclusion fracture are estimated after observation of cavities and inclusions by scanning electron microscopy. Real inclusions were observed after performing uniaxial loading to different amounts of overall strain. The material tested was Hardox-400 steel.

  12. On the link between stress field and small-scale hydraulic fracture growth in anisotropic rock derived from microseismicity

    Science.gov (United States)

    Gischig, Valentin Samuel; Doetsch, Joseph; Maurer, Hansruedi; Krietsch, Hannes; Amann, Florian; Evans, Keith Frederick; Nejati, Morteza; Jalali, Mohammadreza; Valley, Benoît; Obermann, Anne Christine; Wiemer, Stefan; Giardini, Domenico

    2018-01-01

    To characterize the stress field at the Grimsel Test Site (GTS) underground rock laboratory, a series of hydrofracturing and overcoring tests were performed. Hydrofracturing was accompanied by seismic monitoring using a network of highly sensitive piezosensors and accelerometers that were able to record small seismic events associated with metre-sized fractures. Due to potential discrepancies between the hydrofracture orientation and stress field estimates from overcoring, it was essential to obtain high-precision hypocentre locations that reliably illuminate fracture growth. Absolute locations were improved using a transverse isotropic P-wave velocity model and by applying joint hypocentre determination that allowed for the computation of station corrections. We further exploited the high degree of waveform similarity of events by applying cluster analysis and relative relocation. Resulting clouds of absolute and relative located seismicity showed a consistent east-west strike and 70° dip for all hydrofractures. The fracture growth direction from microseismicity is consistent with the principal stress orientations from the overcoring stress tests, provided that an anisotropic elastic model for the rock mass is used in the data inversions. The σ1 stress is significantly larger than the other two principal stresses and has a reasonably well-defined orientation that is subparallel to the fracture plane; σ2 and σ3 are almost equal in magnitude and thus lie on a circle defined by the standard errors of the solutions. The poles of the microseismicity planes also lie on this circle towards the north. Analysis of P-wave polarizations suggested double-couple focal mechanisms with both thrust and normal faulting mechanisms present, whereas strike-slip and thrust mechanisms would be expected from the overcoring-derived stress solution. The reasons for these discrepancies can be explained by pressure leak-off, but possibly may also involve stress field rotation around the

  13. Utilization of ultrasonic tomography for the mapping of residual stress fields in thick metal sections. Final report

    International Nuclear Information System (INIS)

    Hildebrand, B.P.; Hufferd, D.E.

    1977-01-01

    It is well known that the velocity of sound propagation through a solid is altered when a stress is applied. The velocity change is small, and dependent upon the type of wave being propagated as well as the magnitude of the stress. Sensitivity is greatest to shear wave sound with the polarization vector parallel to the direction of stress. In this case, velocity changes as great as 0.6 percent were measured. Preliminary work is described aimed at evaluating computerized reconstruction of velocity fields from velocity profiles to map residual stress concentrations in thick metal sections. Experimental results with liquid and solid models are described. One could image velocity anomalies of 0.2 percent and estimate that 0.05 percent is technically feasible. It is concluded that this technique has great potential for finding and mapping residual stress in thick metal sections

  14. Influence of static magnetic fields in phototaxis and osmotic stress in Gymnodinium catenatum (Dinophyceae).

    Science.gov (United States)

    Vale, Paulo

    2017-07-01

    Phototaxis response of the toxic microalgae Gymnodinium catenatum was studied in vitro. The percentage of cells remaining at mid-depth 20 min after stirring increased with solar radio, X-ray and solar flares output. It also increased with geomagnetic activity and temperature, and was dependent on culture time. Increase in the local static magnetic field with a permanent magnet did not influence the positive phototaxis response. However, survival and growth to a provoked hypo-osmotic shock in an altered static magnetic field was dependent on culture time and geomagnetic activity at a threshold below 22 nT. The results from phototaxis and hypo-osmotic shock experiments were in line with the previous hypothesis for the existence of two separate deleterious mechanisms conditioning the natural blooms of G. catenatum: one that is dependent on solar radiation and the other that is related to geomagnetic activity. Variations in electromagnetic fields caused by tectonic activity were also capable of influencing G. catenatum phototaxis and growth response in vitro.

  15. A linear least squares approach for evaluation of crack tip stress field parameters using DIC

    Science.gov (United States)

    Harilal, R.; Vyasarayani, C. P.; Ramji, M.

    2015-12-01

    In the present work, an experimental study is carried out to estimate the mixed-mode stress intensity factors (SIF) for different cracked specimen configurations using digital image correlation (DIC) technique. For the estimation of mixed-mode SIF's using DIC, a new algorithm is proposed for the extraction of crack tip location and coefficients in the multi-parameter displacement field equations. From those estimated coefficients, SIF could be extracted. The required displacement data surrounding the crack tip has been obtained using 2D-DIC technique. An open source 2D DIC software Ncorr is used for the displacement field extraction. The presented methodology has been used to extract mixed-mode SIF's for specimen configurations like single edge notch (SEN) specimen and centre slant crack (CSC) specimens made out of Al 2014-T6 alloy. The experimental results have been compared with the analytical values and they are found to be in good agreement, thereby confirming the accuracy of the algorithm being proposed.

  16. Casimir effects for a flat plasma sheet: II. Fields and stresses

    International Nuclear Information System (INIS)

    Barton, G

    2005-01-01

    We study the self-stresses experienced by the single plasma sheet modelled in the preceding paper, and determine the exact mean-squared Maxwell fields in vacuum around it. These are effects that probe the physics of such systems further than do the ground-state eigenvalues responsible for the cohesive energy β; in particular, unlike β they depend not only on the collective properties but also on the self-fields of the charge carriers. The classical part of the interaction between the sheet and a slowly moving charged particle follows as a byproduct. The main object is to illustrate, in simple closed or almost closed form, the consequences of imperfect (dispersive) reflectivity. The largely artificial limit of perfect reflection reduces all the results to those long familiar outside a half-space taken to reflect perfectly from the outset; but a careful examination of the approach to this limit is needed in order to resolve paradoxes associated with the surface energy, and with the mechanism which, in the limit, disjoins the two flanking half-spaces both electromagnetically and quantally

  17. Determinations of directions of the mean stress field in Sichuan-Yunnan region from a number of focal mechanism solutions

    Science.gov (United States)

    Zhong, Ji-Mao; Cheng, Wan-Zheng

    2006-07-01

    Based on the spatial orientation and slip direction of the fault plane solutions, we present the expression of corresponding mechanical axis tensor in geographic coordinate system, and then put forward a method for calculating average mechanical axis tensor and its eigenvalues, which involves solving the corresponding eigenequation. The method for deducing mean stress field from T, B, and P axes parameters of a number of focal mechanism solutions has been verified by inverting data of mean stress fields in Fuyun region and in Tangshan region with fitting method of slip direction, and both results are consistent. To study regional average stress field, we need to choose a population of focal mechanism solutions of earthquakes in the massifs where there are significant tectonic structures. According to the focal mechanism solutions of 256 moderate-strong earthquakes occurred in 13 seismic zones of Sichuan-Yunnan region, the quantitative analysis results of stress tensor in each seismic zone have been given. The algorithm of such method is simple and convenient, which makes the method for analyzing tectonic stress field with large amount of focal mechanism solution data become quantified.

  18. A comparison of ionizing radiation and high field stress effects in n-channel power vertical double-diffused metal-oxide-semiconductor field-effect transistors

    International Nuclear Information System (INIS)

    Park, Mun-Soo; Na, Inmook; Wie, Chu R.

    2005-01-01

    n-channel power vertical double-diffused metal-oxide-semiconductor field-effect-transistor (VDMOSFET) devices were subjected to a high electric field stress or to a x-ray radiation. The current-voltage and capacitance-voltage measurements show that the channel-side interface and the drain-side interface are affected differently in the case of high electric field stress, whereas the interfaces are nearly uniformly affected in the case of x-ray radiation. This paper also shows that for the gated diode structure of VDMOSFET, the direct-current current-voltage technique measures only the drain-side interface; the subthreshold current-voltage technique measures only the channel-side interface; and the capacitance-voltage technique measures both interfaces simultaneously and clearly distinguishes the two interfaces. The capacitance-voltage technique is suggested to be a good quantitative method to examine both interface regions by a single measurement

  19. Genetic variation of drought tolerance in Pinus pinaster at three hierarchical levels: a comparison of induced osmotic stress and field testing.

    Science.gov (United States)

    Gaspar, Maria João; Velasco, Tania; Feito, Isabel; Alía, Ricardo; Majada, Juan

    2013-01-01

    Understanding the survival capacity of forest trees to periods of severe water stress could improve knowledge of the adaptive potential of different species under future climatic scenarios. In long lived organisms, like forest trees, the combination of induced osmotic stress treatments and field testing can elucidate the role of drought tolerance during the early stages of establishment, the most critical in the life of the species. We performed a Polyethylene glycol-osmotic induced stress experiment and evaluated two common garden experiments (xeric and mesic sites) to test for survival and growth of a wide range clonal collection of Maritime pine. This study demonstrates the importance of additive vs non additive effects for drought tolerance traits in Pinus pinaster, and shows differences in parameters determining the adaptive trajectories of populations and family and clones within populations. The results show that osmotic adjustment plays an important role in population variation, while biomass allocation and hydric content greatly influence survival at population level. Survival in the induced osmotic stress experiment presented significant correlations with survival in the xeric site, and height growth at the mesic site, at population level, indicating constraints of adaptation for those traits, while at the within population level no significant correlation existed. These results demonstrate that population differentiation and within population genetic variation for drought tolerance follow different patterns.

  20. Genetic variation of drought tolerance in Pinus pinaster at three hierarchical levels: a comparison of induced osmotic stress and field testing.

    Directory of Open Access Journals (Sweden)

    Maria João Gaspar

    Full Text Available Understanding the survival capacity of forest trees to periods of severe water stress could improve knowledge of the adaptive potential of different species under future climatic scenarios. In long lived organisms, like forest trees, the combination of induced osmotic stress treatments and field testing can elucidate the role of drought tolerance during the early stages of establishment, the most critical in the life of the species. We performed a Polyethylene glycol-osmotic induced stress experiment and evaluated two common garden experiments (xeric and mesic sites to test for survival and growth of a wide range clonal collection of Maritime pine. This study demonstrates the importance of additive vs non additive effects for drought tolerance traits in Pinus pinaster, and shows differences in parameters determining the adaptive trajectories of populations and family and clones within populations. The results show that osmotic adjustment plays an important role in population variation, while biomass allocation and hydric content greatly influence survival at population level. Survival in the induced osmotic stress experiment presented significant correlations with survival in the xeric site, and height growth at the mesic site, at population level, indicating constraints of adaptation for those traits, while at the within population level no significant correlation existed. These results demonstrate that population differentiation and within population genetic variation for drought tolerance follow different patterns.

  1. Anisotropy migration of self-point defects in dislocation stress fields in BCC Fe and FCC Cu

    International Nuclear Information System (INIS)

    Sivak, A.B.; Chernov, V.M.; Dubasova, N.A.; Romanov, V.A.

    2007-01-01

    Spatial dependence of the interaction energies of self-point defects (vacancies and self interstitial atoms in stable, metastable and saddle point configurations) with edge dislocations in slip systems {1 1 0} and {1 0 0} in BCC Fe and {1 1 1} in FCC Cu was calculated using the anisotropic theory of elasticity and molecular statics (hybrid method). The migration pathways of vacancies and SIA ( dumbbell in Fe and dumbbell in Cu) along which the migration of the defects with the lowest energy barriers were defined in the presence of the dislocation stress fields. These pathways are significantly different in the stress fields of dislocations

  2. Strong Associations Exist among Oxidative Stress and Antioxidant Biomarkers in the Circulating, Cellular and Urinary Anatomical Compartments in Guatemalan Children from the Western Highlands.

    Directory of Open Access Journals (Sweden)

    María J Soto-Méndez

    Full Text Available A series of antioxidant enzymes and non-enzymatic compounds act to protect cells from uncontrolled propagation of free radicals. It is poorly understood, though, to what extent and how their interaction is harmonized.To explore associative interactions among a battery of urinary and blood biomarkers of oxidative stress and enzymatic and non-enzymatic markers of the antioxidant defense system in children from low income households.For this cross-sectional descriptive study, urine, red cells, and plasma were sampled in 82 preschool children attending three daycare centers in Quetzaltenango Guatemala. The urinary oxidative stress biomarkers studied were F2-isoprostanes and 8-hydroxy-deoxy-guanosine. Red cell enzyme activities measured were: catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase. Circulating non-enzymatic antioxidants selected were: retinol, tocopherols, β-carotene and coenzymes Q9 and Q10.In a Spearman rank-order correlation hemi-matrix, of 55 paired combinations of the 11 biomarkers, 28 (51% were significantly correlated among each other (p ≤ 0.05, with the strongest association being retinol and tocopherols (r = 0.697, p 0.5 to ≤ 0.10. F2-isoprostanes showed the greatest number of cross-associations, having significant interactions with 8 of the 10 remaining biomarkers. Goodness-of-fit modeling improved or maintained the r value for 24 of the significant interactions and for one of the 5 borderline associations. Multiple regression backward stepwise analysis indicated that plasma retinol, β-carotene and coenzyme Q10 were independent predictors of urinary F2-isoprostanes.Numerous significant associations resulted among biomarkers of oxidation and responders to oxidation. Interesting findings were the apparent patterns of harmonious interactions among the elements of the oxidation-antioxidation systems in this population.

  3. Effect of stress-state and spacing on voids in a shear-field

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2012-01-01

    in the overall average stress state can be prescribed. This also allows for studies of the effect of different initial void spacing in the two in-plane coordinate directions. The stress states considered are essentially simple shear, with various levels of tensile stresses or compressive stresses superposed, i.......e. low positive stress triaxiality or even negative stress triaxiality. For high aspect ratio unit cells a clear localization band is found inside the cell, which actually represents several parallel bands, due to periodicity. In the materials represented by a low aspect ratio unit cell localization...

  4. Static magnetic field treatment of seeds improves carbon and nitrogen metabolism under salinity stress in soybean.

    Science.gov (United States)

    Baghel, Lokesh; Kataria, Sunita; Guruprasad, Kadur Narayan

    2016-10-01

    The effectiveness of magnetopriming was assessed for alleviation of salt-induced adverse effects on soybean growth. Soybean seeds were pre-treated with static magnetic field (SMF) of 200 mT for 1 h to evaluate the effect of magnetopriming on growth, carbon and nitrogen metabolism, and yield of soybean plants under different salinity levels (0, 25, and 50 mM NaCl). The adverse effect of NaCl-induced salt stress was found on growth, yield, and various physiological attributes of soybeans. Results indicate that SMF pre-treatment significantly increased plant growth attributes, number of root nodules, nodules, fresh weight, biomass accumulation, and photosynthetic performance under both non-saline and saline conditions as compared to untreated seeds. Polyphasic chlorophyll a fluorescence (OJIP) transients from magnetically treated plants gave a higher fluorescence yield at J-I-P phase. Nitrate reductase activity, PIABS , photosynthetic pigments, and net rate of photosynthesis were also higher in plants that emerged from SMF pre-treated seeds as compared to untreated seeds. Leghemoglobin content and hemechrome content in root nodules were also increased by SMF pre-treatment. Thus pre-sowing exposure of seeds to SMF enhanced carbon and nitrogen metabolism and improved the yield of soybeans in terms of number of pods, number of seeds, and seed weight under saline as well as non-saline conditions. Consequently, SMF pre-treatment effectively mitigated adverse effects of NaCl on soybeans. It indicates that magnetopriming of dry soybean seeds can be effectively used as a pre-sowing treatment for alleviating salinity stress. Bioelectromagnetics. 37:455-470, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  5. Elastic crack-tip stress field in a semi-strip

    Directory of Open Access Journals (Sweden)

    Victor Reut

    2018-04-01

    Full Text Available In this article the plain elasticity problem for a semi-strip with a transverse crack is investigated in the different cases of the boundary conditions at the semi-strips end. Unlike many works dedicated to this subject, the fixed singularities in the singular integral equation�s kernel are considered. The integral transformations� method is applied by the generalized scheme to reduce the initial problem to a one-dimensional problem. The one-dimensional problem is formulated as the vector boundary value problem which is solved with the help of matrix differential calculations and Green�s matrix apparatus. The solution of the problem is reduced to the solving of the system of three singular integral equations. Depending on the conditions given on the short edge of the semi-strip, the constructed singular integral equation can have one, or two fixed singularities. A special method is applied to solve this equation in regard of the singularities existence. Hence the system of the singular integral equations (SSIE is solved with the help of the generalized method. The stress intensity factors (SIF are investigated for different lengths of crack. The novelty of this work is in the application of new approach allowing the consideration of the fixed singularities in the problem about a transverse crack in the elastic semi-strip. The comparison of the numerical results� accuracy during the usage of the different approaches to the solving of SSIE is worked out

  6. Effect of interleukin-1beta on the behavior of rats during mild stress in the open-field test.

    Science.gov (United States)

    Pertsov, S S; Koplik, E V; Simbirtsev, A S; Kalinichenko, L S

    2009-11-01

    We studied the effect of interleukin-1beta on the behavior of rats with different individual typological characteristics during mild stress in the open-field test. Intraperitoneal injection of interleukin-1beta (5 microg/kg, 108 U/mg) was followed by a decrease in orientation and exploratory activity of passive and, particularly, of active animals in the open field. As differentiated from rats receiving physiological saline, the initial differences in behavioral characteristics of active and passive animals were not revealed in the repeated test after injection of interleukin-1beta. We conclude that interleukin-1beta abolishes the behavioral differences between active and passive specimens in the open field. These data suggest that administration of interleukin-1beta to rats leads to reorganization of the mechanisms for emotional evaluation of adverse emotiogenic factors under conditions of mild stress in the open-field test.

  7. Field validation of Tasmania's aquaculture industry bounce-diving schedules using Doppler analysis of decompression stress.

    Science.gov (United States)

    Smart, David R; Van den Broek, Cory; Nishi, Ron; Cooper, P David; Eastman, David

    2014-09-01

    Tasmania's aquaculture industry produces over 40,000 tonnes of fish annually, valued at over AUD500M. Aquaculture divers perform repetitive, short-duration bounce dives in fish pens to depths up to 21 metres' sea water (msw). Past high levels of decompression illness (DCI) may have resulted from these 'yo-yo' dives. This study aimed to assess working divers, using Doppler ultrasonic bubble detection, to determine if yo-yo diving was a risk factor for DCI, determine dive profiles with acceptable risk and investigate productivity improvement. Field data were collected from working divers during bounce diving at marine farms near Hobart, Australia. Ascent rates were less than 18 m·min⁻¹, with routine safety stops (3 min at 3 msw) during the final ascent. The Kisman-Masurel method was used to grade bubbling post dive as a means of assessing decompression stress. In accordance with Defence Research and Development Canada Toronto practice, dives were rejected as excessive risk if more than 50% of scores were over Grade 2. From 2002 to 2008, Doppler data were collected from 150 bounce-dive series (55 divers, 1,110 bounces). Three series of bounce profiles, characterized by in-water times, were validated: 13-15 msw, 10 bounces inside 75 min; 16-18 msw, six bounces inside 50 min; and 19-21 msw, four bounces inside 35 min. All had median bubble grades of 0. Further evaluation validated two successive series of bounces. Bubble grades were consistent with low-stress dive profiles. Bubble grades did not correlate with the number of bounces, but did correlate with ascent rate and in-water time. These data suggest bounce diving was not a major factor causing DCI in Tasmanian aquaculture divers. Analysis of field data has improved industry productivity by increasing the permissible number of bounces, compared to earlier empirically-derived tables, without compromising safety. The recommended Tasmanian Bounce Diving Tables provide guidance for bounce diving to a depth of 21 msw

  8. The extended algebra of observables for Dirac fields and the trace anomaly of their stress-energy tensor

    Energy Technology Data Exchange (ETDEWEB)

    Dappiagi, Claudio; Hack, Thomas-Paul; Pinamonti, Nicola [Hamburg Univ. (Germany). II. Inst. fuer Theoretische Physik

    2009-03-15

    We discuss from scratch the classical structure of Dirac spinors on an arbitrary globally hyperbolic, Lorentzian spacetime, their formulation as a locally covariant quantum field theory, and the associated notion of a Hadamard state. Eventually, we develop the notion of Wick polynomials for spinor fields, and we employ the latter to construct a covariantly conserved stress-energy tensor suited for back-reaction computations. We explicitly calculate its trace anomaly in particular. (orig.)

  9. The extended algebra of observables for Dirac fields and the trace anomaly of their stress-energy tensor

    International Nuclear Information System (INIS)

    Dappiagi, Claudio; Hack, Thomas-Paul; Pinamonti, Nicola

    2009-03-01

    We discuss from scratch the classical structure of Dirac spinors on an arbitrary globally hyperbolic, Lorentzian spacetime, their formulation as a locally covariant quantum field theory, and the associated notion of a Hadamard state. Eventually, we develop the notion of Wick polynomials for spinor fields, and we employ the latter to construct a covariantly conserved stress-energy tensor suited for back-reaction computations. We explicitly calculate its trace anomaly in particular. (orig.)

  10. Seasonal variation of the impact of a stressful procedure on open field behaviour and blood corticosterone in laboratory mice.

    Science.gov (United States)

    Meyer, L; Caston, J; Mensah-Nyagan, A G

    2006-02-28

    Behavioural and hormonal seasonal changes are well documented in various vertebrate species living in their natural environment but circannual variations that may occur in laboratory animals reared in standard conditions are poorly investigated. This study shows that, in laboratory mice, the effects of stress on behavioural inhibition, investigatory behaviour and blood concentration of corticosterone are seasonally dependent. No consistency was observed between the reactivity of biological structures controlling the hormonal response to stress and the behavioural activities investigated at every period of the year. During the spring time, stress, which elicited a decrease of investigatory behaviour (estimated by the walking time in an open field), increased behavioural inhibition (estimated by the percentage of walking in the central area of the open field) as well as the blood corticosterone concentration in laboratory mice. In autumn, stress had no significant effect on behaviour despite the great hormonal concentration increase. The results reveal that, at certain period of the year, a stressful procedure is unable to affect behavioural parameters in laboratory mice which were maintained in constant 12-h dark/12-h light cycle. The report constitutes a novel piece of information suggesting a potential role of the endogenous biological clock in the modulation of stress response in mammals.

  11. Effects of pulsed magnetic field treatment of soybean seeds on calli growth, cell damage, and biochemical changes under salt stress.

    Science.gov (United States)

    Radhakrishnan, Ramalingam; Leelapriya, Thasari; Kumari, Bollipo Diana Ranjitha

    2012-12-01

    The effects of magnetic field (MF) treatments of soybean seeds on calli growth, cell damage, and biochemical changes under salt stress were investigated under controlled conditions. Soybean seeds were exposed to a 1.0 Hz sinusoidal uniform pulsed magnetic field (PMF) of 1.5 µT for 5 h/day for 20 days. Non-treated seeds were considered as controls. For callus regeneration, the embryonic axis explants were taken from seeds and inoculated in a saline medium with a concentration of 10 mM NaCl for calli growth analysis and biochemical changes. The combined treatment of MF and salt stress was found to significantly increase calli fresh weight, total soluble sugar, total protein, and total phenol contents, but it decreased the ascorbic acid, lipid peroxidation, and catalase activity of calli from magnetically exposed seeds compared to the control calli. PMF treatment significantly improved calli tolerance to salt stress in terms of an increase in flavonoid, flavone, flavonole, alkaloid, saponin, total polyphenol, genistein, and daidzein contents under salt stress. The results suggest that PMF treatment of soybean seeds has the potential to counteract the adverse effects of salt stress on calli growth by improving primary and secondary metabolites under salt stress conditions. Copyright © 2012 Wiley Periodicals, Inc.

  12. Stress- and Magnetic Field-Induced Martensitic Transformation at Cryogenic Temperatures in Fe-Mn-Al-Ni Shape Memory Alloys

    Science.gov (United States)

    Xia, Ji; Xu, Xiao; Miyake, Atsushi; Kimura, Yuta; Omori, Toshihiro; Tokunaga, Masashi; Kainuma, Ryosuke

    2017-12-01

    Stress-induced and magnetic-field-induced martensitic transformation behaviors at low temperatures were investigated for Fe-Mn-Al-Ni alloys. The magnetic-field-induced reverse martensitic transformation was directly observed by in situ optical microscopy. Magnetization measurements under pulsed magnetic fields up to 50 T were carried out at temperatures between 4.2 and 125 K on a single-crystal sample; full magnetic-field-induced reverse martensitic transformation was confirmed at all tested temperatures. Compression tests from 10 to 100 K were conducted on a single-crystal sample; full shape recovery was obtained at all tested temperatures. It was found that the temperature dependence of both the critical stress and critical magnetic field is small and that the transformation hysteresis is less sensitive to temperature even at cryogenic temperatures. The temperature dependence of entropy change during martensitic transformation up to 100 K was then derived using the Clausius-Clapeyron relation with critical stresses and magnetic fields.

  13. Horizontal rotation of the local stress field in response to magmatic activity: Evidence from case studies and modeling

    Science.gov (United States)

    Roman, D. C.

    2003-12-01

    A complete understanding of the initiation, evolution, and termination of volcanic eruptions requires reliable monitoring techniques to detect changes in the conduit system during periods of activity, as well as corresponding knowledge of conduit structure and of magma physical properties. Case studies of stress field orientation prior to, during, and after magmatic activity can be used to relate changes in stress field orientation to the state of the magmatic conduit system. These relationships may be tested through modeling of induced stresses. Here I present evidence from case studies and modeling that horizontal rotation of the axis of maximum compressive stress at an active volcano indicates pressurization of a magmatic conduit, and that this rotation, when observed, may also be indicative of the physical properties of the ascending magma. Changes in the local stress field orientation during the 1992 eruption sequence at Crater Peak (Mt. Spurr), Alaska were analyzed by calculating and inverting subsets of over 150 fault-plane solutions. Local stress tensors for four time periods, corresponding approximately to changes in activity at the volcano, were calculated based on the misfit of individual fault-plane solutions to a regional stress tensor. Results indicate that for nine months prior to the eruption, local maximum compressive stress was oriented perpendicular to regional maximum compressive stress. A similar horizontal rotation was observed beginning in November of 1992, coincident with an episode of elevated earthquake and tremor activity indicating intrusion of magma into the conduit. During periods of quiescence the local stress field was similar to the regional stress field. Similar horizontal rotations have been observed at Mt. Ruapehu, New Zealand (Miller and Savage 2001, Gerst 2003), Usu Volcano, Japan (Fukuyama et al. 2001), Unzen Volcano, Japan (Umakoshi et al. 2001), and Mt. St. Helens Volcano, USA (Moran 1994) in conjunction with eruptive

  14. Geodynamics of the East African Rift System ∼30 Ma ago: A stress field model

    Science.gov (United States)

    Min, Ge; Hou, Guiting

    2018-06-01

    The East African Rift System (EARS) is thought to be an intra-continental ridge that meets the Red Sea and the Gulf of Aden at the Ethiopian Afar as the failed arm of the Afar triple junction. The geodynamics of EARS is still unclear even though several models have been proposed. One model proposes that the EARS developed in a local tensile stress field derived from far-field loads because of the pushing of oceanic ridges. Alternatively, some scientists suggest that the formation of the EARS can be explained by upwelling mantle plumes beneath the lithospheric weak zone (e.g., the Pan-African suture zone). In our study, a shell model is established to consider the Earth's spherical curvature, the lithospheric heterogeneity of the African continent, and the coupling between the mantle plumes and the mid-ocean ridge. The results are calculated via the finite element method using ANSYS software and fit the geological evidence well. To discuss the effects of the different rock mechanical parameters and the boundary conditions, four comparative models are established with different parameters or boundary conditions. Model I ignores the heterogeneity of the African continent, Model II ignores mid-ocean spreading, Model III ignores the upwelling mantle plumes, and Model IV ignores both the heterogeneity of the African continent and the upwelling mantle plumes. Compared to these models is the original model that shows the best-fit results; this model indicates that the coupling of the upwelling mantle plumes and the mid-ocean ridge spreading causes the initial lithospheric breakup in Afar and East Africa. The extension direction and the separation of the EARS around the Tanzanian craton are attributed to the heterogeneity of the East African basement.

  15. Laser cutting of triangular geometry into 2024 aluminum alloy: Influence of triangle size on thermal stress field

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, Bekir Sami; Akhtar, Syed Sohail [King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Keles, Omer; Boran, Kurtulus [Gazi University, Ankara (Turkmenistan)

    2015-08-15

    Laser cutting of a triangular geometry into aluminum 2024 alloy is carried out. Thermal stress field in the cutting section is predicted using the finite element code ABAQUS. Surface temperature predictions are validated through the thermocouple data. Morphological changes in the cut section are examined incorporating optical and electron scanning microscopes. The effects of the size of the triangular geometry on thermal stress field are also examined. It is found that surface temperature predictions agree well with thermocouple data. von Mises stress remains high in the region close to the corners of the triangular geometry, which is more pronounced for the small size triangle. This behavior is associated with the occurrence of the high cooling rates in this region. Laser cut edges are free from large scale sideways burning and large size burr attachments. However, some locally scattered dross attachments are observed at the kerf exit.

  16. Experimental evidence of stress-field-induced selection of variants in Ni-Mn-Ga ferromagnetic shape-memory alloys

    International Nuclear Information System (INIS)

    Wang, Y. D.; Brown, D. W.; Choo, H.; Liaw, P. K.; Benson, M. L.; Cong, D. Y.; Zuo, L.

    2007-01-01

    The in situ time-of-flight neutron-diffraction measurements captured well the martensitic transformation behavior of the Ni-Mn-Ga ferromagnetic shape-memory alloys under uniaxial stress fields. We found that a small uniaxial stress applied during phase transformation dramatically disturbed the distribution of variants in the product phase. The observed changes in the distributions of variants may be explained by considering the role of the minimum distortion energy of the Bain transformation in the effective partition among the variants belonging to the same orientation of parent phase. It was also found that transformation kinetics under various stress fields follows the scale law. The present investigations provide the fundamental approach for scaling the evolution of microstructures in martensitic transitions, which is of general interest to the condensed matter community

  17. Mindfulness Training and Reductions in Teacher Stress and Burnout: Results from Two Randomized, Waitlist-Control Field Trials

    Science.gov (United States)

    Roeser, Robert W.; Schonert-Reichl, Kimberly A.; Jha, Amishi; Cullen, Margaret; Wallace, Linda; Wilensky, Rona; Oberle, Eva; Thomson, Kimberly; Taylor, Cynthia; Harrison, Jessica

    2013-01-01

    The effects of randomization to mindfulness training (MT) or to a waitlist-control condition on psychological and physiological indicators of teachers' occupational stress and burnout were examined in 2 field trials. The sample included 113 elementary and secondary school teachers (89% female) from Canada and the United States. Measures were…

  18. Assessing the accuracy of hyperspectral and multispectral satellite imagery for categorical and quantitative mapping of salinity stress in sugarcane fields

    NARCIS (Netherlands)

    Hamzeh, Saied; Naseri, Abd Ali; Alavipanah, Seyed Kazem; Bartholomeus, Harm; Herold, Martin

    2016-01-01

    This study evaluates the feasibility of hyperspectral and multispectral satellite imagery for categorical and quantitative mapping of salinity stress in sugarcane fields located in the southwest of Iran. For this purpose a Hyperion image acquired on September 2, 2010 and a Landsat7 ETM+ image

  19. Anisotropic stress in narrow sGe fin field-effect transistor channels measured using nano-focused Raman spectroscopy

    Science.gov (United States)

    Nuytten, T.; Bogdanowicz, J.; Witters, L.; Eneman, G.; Hantschel, T.; Schulze, A.; Favia, P.; Bender, H.; De Wolf, I.; Vandervorst, W.

    2018-05-01

    The continued importance of strain engineering in semiconductor technology demands fast and reliable stress metrology that is non-destructive and process line-compatible. Raman spectroscopy meets these requirements but the diffraction limit prevents its application in current and future technology nodes. We show that nano-focused Raman scattering overcomes these limitations and can be combined with oil-immersion to obtain quantitative anisotropic stress measurements. We demonstrate accurate stress characterization in strained Ge fin field-effect transistor channels without sample preparation or advanced microscopy. The detailed analysis of the enhanced Raman response from a periodic array of 20 nm-wide Ge fins provides direct access to the stress levels inside the nanoscale channel, and the results are validated using nano-beam diffraction measurements.

  20. Field performance of maize (Zea mays L. cultivars under drought stress

    Directory of Open Access Journals (Sweden)

    Kazem GHASSEMI-GOLEZANI

    2018-04-01

    Full Text Available This research was carried out in 2014 at the Research Farm of the University of Tabriz, Iran. The experiment was arranged as split plot on the basis of randomized complete block with three replicates to assess the effects of four irrigation intervals (irrigations after 60, 80, 100 and 120 mm evaporation on physiological and agronomical traits of three cultivars of maize (Zea mays L.; ‘SC704’, ‘NS640’, ‘DC303’: late, mid and early maturing, respectively. Irrigation intervals and maize cultivars were assigned to the main and sub-plots, respectively. Leaf temperature of all maize cultivars significantly increased, but chlorophyll content index, maximum efficiency of photosystem II, number of grains per plant, 1000 grain mass, plant biomass, grain yield and harvest index significantly decreased with increasing irrigation intervals. Late maturing cultivar (‘SC704’ was superior in all studied traits, followed by mid (‘NS640’ and early (‘DC303’ maturing cultivars. It was concluded that water limitation can potentially reduce performance of maize cultivars in the field, but the extent of this reduction depends on genotype and severity of stress.

  1. Effects of Starvation and Thermal Stress on the Thermal Tolerance of Silkworm, Bombyx mori: Existence of Trade-offs and Cross-Tolerances.

    Science.gov (United States)

    Mir, A H; Qamar, A

    2017-09-27

    Organisms, in nature, are often subjected to multiple stressors, both biotic and abiotic. Temperature and starvation are among the main stressors experienced by organisms in their developmental cycle and the responses to these stressors may share signaling pathways, which affects the way these responses are manifested. Temperature is a major factor governing the performance of ectothermic organisms in ecosystems worldwide and, therefore, the thermal tolerance is a central issue in the thermobiology of these organisms. Here, we investigated the effects of starvation as well as mild heat and cold shocks on the thermal tolerance of the larvae of silkworm, Bombyx mori (Linnaeus). Starvation acted as a meaningful or positive stressor as it improved cold tolerance, measured as chill coma recovery time (CCRT), but, at the same time, it acted as a negative stressor and impaired the heat tolerance, measured as heat knockdown time (HKT). In the case of heat tolerance, starvation negated the positive effects of both mild cold as well as mild heat shocks and thus indicated the existence of trade-off between these stressors. Both mild heat and cold shocks improved the thermal tolerance, but the effects were more prominent when the indices were measured in response to a stressor of same type, i.e., a mild cold shock improved the cold tolerance more than the heat tolerance and vice versa. This improvement in thermal tolerance by both mild heat as well as cold shocks indicated the possibility of cross-tolerance between these stressors.

  2. Stress

    DEFF Research Database (Denmark)

    Keller, Hanne Dauer

    2015-01-01

    Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....

  3. Stress !!!

    OpenAIRE

    Fledderus, M.

    2012-01-01

    Twee op de vijf UT-studenten hebben last van ernstige studiestress, zo erg zelfs dat het ze in hun privéleven belemmert. Die cijfers komen overeen met het landelijk beeld van stress onder studenten. Samen met 14 andere universiteits- en hogeschoolbladen enquêteerde UT Nieuws bijna 5500 studenten. Opvallend is dat mannelijke studenten uit Twente zich veel minder druk lijken te maken over hun studie. Onder vrouwen ligt de stress juist erg hoog ten opzichte van het landelijk gemiddelde.

  4. Residual stress evaluation by Barkhausen signals with a magnetic field sensor for high efficiency electrical motors

    Science.gov (United States)

    Tsuchida, Yuji; Enokizono, Masato

    2018-04-01

    The iron loss of industrial motors increases by residual stress during manufacturing processes. It is very important to make clear the distribution of the residual stress in the motor cores to reduce the iron loss in the motors. Barkhausen signals which occur on electrical steel sheets can be used for the evaluation of the residual stress because they are very sensitive to the material properties. Generally, a B-sensor is used to measure Barkhausen signals, however, we developed a new H-sensor to measure them and applied it into the stress evaluation. It is supposed that the Barkhausen signals by using a H-sensor can be much effective to the residual stress on the electrical steel sheets by referring our results regarding to the stress evaluations. We evaluated the tensile stress of the electrical steel sheets by measuring Barkhausen signals by using our developed H-sensor for high efficiency electrical motors.

  5. Full-Field Stress Determination Around Circular Discontinuity in a Tensile-Loaded Plate using x-displacements Only

    Science.gov (United States)

    Baek, Tae Hyun; Chung, Tae Jin; Panganiban, Henry

    The significant effects of stress raisers demand well-defined evaluation techniques to accurately determine the stress along the geometric boundary. A simple and accurate method for the determination of stress concentration around circular geometric discontinuity in a tensile-loaded plate is illustrated. The method is based on the least-squares technique, mapping functions, and a complex power series representation (Laurent series) of the stress functions for the calculation of tangential stress around the hole. Traction-free conditions were satisfied at the geometric discontinuity using conformal mapping and analytic continuation. In this study, we use only a relatively small amount of x-component displacement data of points away from the discontinuity of concern with their respective coordinates. Having this information we can easily obtain full-field stresses at the edge of the geometric discontinuity. Excellent results were obtained when the number of terms of the power series expansions, m=1. The maximum stress concentration calculation results using the present method and FEM using ANSYS agree well by less than one per cent difference. Experimental advantage of the method underscores the use of relatively small amount of data which are conveniently determined being away from the edge. Moreover, the small amount of measured input data needed affords the approach suitable for applications such as the multi-parameter concept used to obtain stress intensity factors from measured data. The use of laser speckle interferometry and moiré interferometry are also potential future related fields since the optical system for one-directional measurement is much simple.

  6. The feature of the focal mechanism solutions and tectonic stress field around the focus of Zaduo earthquake (Ms 6.3) in eastern Tibet

    Science.gov (United States)

    Yang, Y.; Zeng, Z.; Shuang, X.; Li, X.

    2017-12-01

    On 17th October, 2016, an earthquake of Ms6.3 occurred in Zaduo County, Qinghai Province (32.9°N, 95.0°E), 159 km away from the epicenter of Yushu Ms7.3 earthquake in 2011. The earthquake is located in the eastern Tibet Plateau and the north region of Eastern Himalayan Syntaxis. Using the broadband seismic waveform data form regional networks, we determined the focal mechanism solutions (FMSs) of 83 earthquakes (M>3.5) occurred in Zaduo and its adjacent areas from 2009 to 2017. We also collected another 63 published FMSs and then inversed the current tectonic stress field in study region using the damped linear inversion method. The results show that the Zaduo earthquake is a normal oblique earthquake. The FMSs in our study region are mainly in strike-slip and normal fault patterns. The strike-slip earthquakes are mainly distributed in Yushu-Ganzi, Zaduo and Yanshiping fault zones, and the normal faulting events occurred in Nu Jiang fault zone and Nierong County and its vicinity, the south and southwest of the study areas. The tectonic stress field results indicate that the stress distribution in the north and east of the study region changes homogeneously and slowly. From west to east, the σ1 gradually changes from NNE to NE direction, and the σ3 varies from NWW to NW direction. Both the maximum (σ1) and minimum (σ3) principal stress axes in the study area are nearly horizontal, except in the Nu Jiang fault zone and its vicinity, the south of the study area, which is in a normal faulting stress regime (σ1 is vertical and σ3 is horizontal). The localized normal faulting stress field in the south area, which is almost limited in a semicircle, indicates that a high pressure and low viscosity body with low S-wave velocity and high conductivity might exists beneath the anomaly area. And there may be another semicircle abnormal area beyond the south of the study region. Waveform data for this study are provided by Data Management Centre of China National Seismic

  7. The influence of occupational heat exposure on cognitive performance and blood level of stress hormones: a field study report.

    Science.gov (United States)

    Mazlomi, Adel; Golbabaei, Farideh; Farhang Dehghan, Somayeh; Abbasinia, Marzieh; Mahmoud Khani, Somayeh; Ansari, Mohammad; Hosseini, Mostafa

    2017-09-01

    This article aimed to investigate the effect of heat stress on cognitive performance and the blood concentration of stress hormones among workers of a foundry plant. Seventy workers within the exposed (35 people) and unexposed (35 people) groups were studied. The wet bulb globe temperature (WBGT) index was measured for heat stress assessment. The cognitive performance tests were conducted using the Stroop color word test (SCWT) before and during working hours. For the assessment of the serum level of cortisol and the plasma level of adrenaline and noradrenaline, blood samples were taken during working hours from both groups. Only for SCWT III was there a significant relationship between heat stress and test duration, error rate and reaction time. The laboratory test results revealed significantly higher concentrations of cortisol, adrenaline and noradrenaline in the exposed subjects than in the unexposed group. There existed a positive correlation between cortisol, adrenaline, noradrenaline and WBGT index and also test duration and reaction time of SCWT III, and number of errors of SCWT I, SCWT II and SCWT III during work. Heat stress can lead to an increase in the blood level of stress hormones, resulting in cognitive performance impairment.

  8. Field performance of timber bridges. 9, Big Erick`s stress-laminated deck bridge

    Science.gov (United States)

    J. A. Kainz; J. P. Wacker; M. Nelson

    The Big Erickas bridge was constructed during September 1992 in Baraga County, Michigan. The bridge is 72 ft long, 16 ft wide, and consists of three simple spans: two stress-laminated deck approach spans and a stress-laminated box center span. The bridge is unique in that it is one of the first known stress-laminated timber bridge applications to use Eastern Hemlock...

  9. Field performance of stress-laminated timber bridges on low-volume roads

    Science.gov (United States)

    M. A. Ritter; J. P. Wacker; S. R. Duwadi

    1995-01-01

    Stress-laminated timber bridges were first introduced in the United States in the late 1980s. Since that time, the concept of stress-laminating has received a great deal of attention and hundreds of bridges have been built. Most of these bridges are located on rural low-volume roads. To evaluate the performance of stress-laminated bridges, the United States Department...

  10. Stress-related endocrinological and psychopathological effects of short- and long-term 50Hz electromagnetic field exposure in rats.

    Science.gov (United States)

    Szemerszky, Renáta; Zelena, Dóra; Barna, István; Bárdos, György

    2010-01-15

    It is believed that different electromagnetic fields do have beneficial and harmful biological effects. The aim of the present work was to study the long-term consequences of 50 Hz electromagnetic field (ELF-EMF) exposure with special focus on the development of chronic stress and stress-induced psychopathology. Adult male Sprague-Dawley rats were exposed to ELF-EMF (50 Hz, 0.5 mT) for 5 days, 8h daily (short) or for 4-6 weeks, 24h daily (long). Anxiety was studied in elevated plus maze test, whereas depression-like behavior of the long-treated group was examined in the forced swim test. Some days after behavioral examination, the animals were decapitated among resting conditions and organ weights, blood hormone levels as well as proopiomelanocortin mRNA level from the anterior lobe of the pituitary gland were measured. Both treatments were ineffective on somatic parameters, namely none of the changes characteristic to chronic stress (body weight reduction, thymus involution and adrenal gland hypertrophy) were present. An enhanced blood glucose level was found after prolonged ELF-EMF exposure (p=0.013). The hormonal stress reaction was similar in control and short-term exposed rats, but significant proopiomelanocortin elevation (pfloating time; p=0.006) were found following long-term ELF-EMF exposure. Taken together, long and continuous exposure to relatively high intensity electromagnetic field may count as a mild stress situation and could be a factor in the development of depressive state or metabolic disturbances. Although we should stress that the average intensity of the human exposure is normally much smaller than in the present experiment.

  11. Soil mechanical stresses in high wheel load agricultural field traffic: a case study

    DEFF Research Database (Denmark)

    Lamandé, Mathieu; Schjønning, Per

    2017-01-01

    highly skewed. Across tyres, the maximum stress in the contact area correlated linearly with, but was much higher than, the mean ground pressure. For each of the three soil depths, the maximum stresses under the tyres were significantly correlated with the wheel load, but not with other loading......Subsoil compaction is a serious long-term threat to soil functions. Only a few studies have quantified the mechanical stresses reaching deep subsoil layers for modern high wheel load machinery. In the present study we measured the vertical stresses in the tyre–soil contact area and at 0.3, 0...

  12. Three dimensional viscoelastic simulation on dynamic evolution of stress field in North China induced by the 1966 Xingtai earthquake

    Science.gov (United States)

    Chen, Lian-Wang; Lu, Yuan-Zhong; Liu, Jie; Guo, Ruo-Mei

    2001-09-01

    Using three dimensional (3D) viscoelastic finite element method (FEM) we study the dynamic evolution pattern of the coseismic change of Coulomb failure stress and postseismic change, on time scale of hundreds years, of rheological effect induced by the M S=7.2 Xingtai earthquake on March 22, 1966. Then, we simulate the coseismic disturbance in stress field in North China and dynamic change rate on one-year scale caused by the Xingtai earthquake and Tangshan earthquake during 15 years from 1966 to 1980. Finally, we discuss the triggering of a strong earthquake to another future strong earthquake.

  13. Temporal changes of static stress drop as a proxy for poroelastic effects at The Geysers geothermal field, California

    Science.gov (United States)

    Staszek, Monika; Orlecka-Sikora, Beata; Lasocki, Stanislaw; Kwiatek, Grzegorz; Leptokaropoulos, Konstantinos; Martinez-Garzon, Patricia

    2017-04-01

    One of the major environmental impacts of shale gas exploitation is triggered and induced seismicity. Due to the similarity of fluid injection process data from geothermal fields can be used as a proxy for shale gas exploitation associated seismicity. Therefore, in this paper we utilize 'The Geysers' dataset compiled within SHale gas Exploration and Exploitation induced Risks (SHEER) project. The dependence of earthquake static stress drops on pore pressure in the medium was previously suggested by Goertz-Allmann et al. (2011), who observed an increase of the static stress drop with the distance from injection well during reservoir stimulation at Deep Heat Mining project in Basel, Switzerland. Similar observation has been done by Kwiatek et al. (2014) in Berlín geothermal field, El Salvador. In this study, we use a high-quality data from The Geysers geothermal field to determine whether the static stress drops and the stress drop distributions change statistically significantly in time or not, and how such changes are correlated with the values of hypocenter depth, water injection rate, and distance from injection well. For the analyses we use a group of 354 earthquakes, which occurred in the proximity of Prati-9 and Prati-29 injection wells. Spectral parameters of these earthquakes were determined using mesh spectral ratio technique. Our results indicate that: (1) the static stress drop variation in time is statistically significant, (2) median static stress drop is inversely related to median injection rate. Therefore, it is highly expected that static stress drop is influenced by pore pressure in underground fluid injection conditions. References: Goertz-Allmann B., Goertz A., Wiemer S. (2011), Stress drop variations of induced earthquakes at the Basel geothermal site. Geophysical Research Letters, 38, L09308, doi:10.1029/2011GL047498. Kwiatek G., Bulut F., Bohnhoff M., Dresen G. (2014), High-resolution analysis of seismicity induced at Berlin geothermal field

  14. Thermoelastic Stress Field Investigation of GaN Material for Laser Lift-off Technique based on Finite Element Method

    International Nuclear Information System (INIS)

    Ting, Wang; Zhan-Zhong, Cui; Li-Xin, Xu

    2009-01-01

    The transient thermoelastic stress fields of GaN films is analyzed by the finite element method for the laser lift-off (LLO) technique. Stress distributions in GaN films irradiated by pulse laser with different energy densities as functions of time and depth are simulated. The results show that the high thermoelastic stress distributions in GaN films localize within about 1 μm below the GaN/Al 2 O 3 interface using proper laser parameters. It is also found that GaN films can avoid the thermal deformation because the maximum thermoelastic stress 4.28 GPa is much smaller than the yield strength of GaN 15GPa. The effects of laser beam dimension and the thickness of GaN films on stress distribution are also analyzed. The variation range of laser beam dimension as a function of the thickness of GaN films is simulated to keep the GaN films free of thermal deformation. LLO experiments are also carried out. GaN-based light-emitting diodes (LEDs) are separated from sapphire substrates using the parameters obtained from the simulation. Compared with devices before LLO, P–I–V measurements of GaN-based LEDs after LLO show that the electrical and optical characteristics improve greatly, indicating that no stress damage is brought to GaN films using proper parameters obtained by calculation during LLO

  15. [Open-field behavioral study in rat hyperlipidemia combined with chronic unpredictable mild stress model].

    Science.gov (United States)

    Hu, Hua; Zhang, Yingchun; Xu, Yeqing; Liu, Chunfeng; Wang, Liwei

    2015-06-16

    To investigate behavioral changes in a rat hyperlipidemia model induced by high lipid feed combined with depression by Chronic Unpredictable Mild Stress (CUMS). A total of 40 rats were randomly divided into control (CON), control feed for 9 weeks followed by CUMS for 4 weeks (CON + CUMS), high fat diet (HFD) and high lipid feed for 9 weeks followed by CUMS for 4 weeks (HFD + CUMS) (n = 10 each). Open-field test was individually measured at baseline, week 9 and week 13. (1) Serum lipids: total cholesterol [(2.67 ± 0.04) mmol/L, (2.68 ± 0.02) mmol/L] and low density lipoprotein [(1.08 ± 0.03) mmol/L, (1.06 ± 0.01) mmol/L] of HFD and HFD + CUMS were both significantly higher than those of CON and CON + CUMS [(1.78 ± 0.12) mmol/L, (0.79 ± 0.04) mmol/L; (1.76 ± 0.09) mmol/L, (0.76 ± 0.06) mmol/L, all P Open-field test: at week 13, compared to CON rats, CON + CUMS rats exhibited enhanced locomotor activity during the first minute, reduced activity in the center squares and rearing, and increased the number of grooming and defecation (all P < 0.05). In comparison to the CON rats, a decrease in total squares in 5 min, central squares and peripheral squares was observed in HFD rats at week 13 (all P < 0.05). However, compared with HFD, CON, CON + CUMS rats, when high lipid feed for 9 weeks combined with depression, significant decrease activities in total squares in 5 min, central squares and peripheral squares were observed in HFD + CUMS rats at week 13. Besides these, the number of rearing was reduced, however, locomotor activity during the first minute and the number of grooming and defecation was significantly increased (all P < 0.001). Under uncontrolled hyperlipidemia, severe depressive symptoms will present more early once exposure to a series of chronic stressors followed by significant autonomic nervous dysfunctional symptoms.

  16. Preliminary investigation of the structural influence of entry-entry intersections and inhomogeneous initial-stress fields on repository disposal rooms

    International Nuclear Information System (INIS)

    Loken, M.C.

    1983-07-01

    The structural influence of entry-entry intersections and inhomogeneous initial stress fields on a repository configuration has been investigated. The out-of-plane stress increases rapidly into the pillar from the rib of the connecting corridor to the plane strain value within one pillar width of the intersection, indicating that a two-dimensional analysis is valid over a major portion of the disposal room and pillar. Inhomogeneous initial stress fields do not significantly alter the trends of the resulting post-excavation stress fields. However, the magnitude of the vertical stress and the effective stress is slightly greater near the corner at the intersection. Further nonlinear analyses are required to assess the stability of the pillar at the intersection because of the high deviatoric stresses occurring in that region. 6 references

  17. Integrability conditions for the existence of a Lagrangian in Newtonian mechanics and field theory. Annual progress report, March 1, 1978-May 31, 1979

    International Nuclear Information System (INIS)

    Sternberg, S.; Santilli, R.M.

    1979-01-01

    Studies of general covariance and its application to particle motion and continuum mechanics were continued. Also developed was a new method in microlocal analysis which has applications to integral geometry, geometrical quantization and the fine structure of certain types of spectra. The classical aspect of a program was studied by a comprehensive analysis of the integrability conditions for the existence of a Lagrangian or, independently, of a Hamiltonian for the representation of given Newtonian systems with forces nonderivable from a potential, as well as the methods for the computation of these functions from the equations of motion. The study of a classical, complementary, methodological approach to the same class of systems was also initiated. It consists of the representation of systems with forces nonderivable from a potential via a generalization of Hamilton's equations posessing a Lie-admissible algebraic structure. The problem of the quantization of forces nonderivable from a potential was then studied via the use of these complementary methods. The use of the integrability conditions for the existence of a Hamiltonian representation (the inverse problem) yielded, under certain restrictions, the conventional Heisenberg's equations, but expressed in terms of a generalized Hamiltonian structure. The use of the Lie-admissible formulations yielded a generalization of Heisenberg's equations possessing a generalized (Lie-admissible) algebraic structure, but expressed in terms of a conventional Hamiltonian structure. These preliminary studies were then applied to the investigation of the old idea that the strong interactions are of the type considered, local and nonderivable from a potential, as an approximation of expected nonlocal settings. The experimental verification of Pauli's exclusion principle and other basic physical laws for the nuclear and the hadronic structure was proposed. A list of publications is included

  18. Assessment of occupational health problems and physiological stress among the brick field workers of West Bengal, India

    Directory of Open Access Journals (Sweden)

    Banibrata Das

    2014-08-01

    Full Text Available Objectives: The brick field industry is one of the oldest industries in India, which employs a large number of workers of poor socioeconomic status. The main aim of the present investigation is i to determine the prevalence of musculoskeletal disorders among brick field workers, ii to determine the prevalence of respiratory disorders and physiological stress among brick field workers compared to control workers. Material and Methods: For this study, a total of 220 brick field workers and 130 control subjects were selected randomly. The control subjects were mainly involved in hand-intensive jobs. The Modified Nordic Questionnaire was applied to assess the discomfort felt among both groups of workers. Thermal stress was also assessed by measuring the WBGT index. The pulmonary functions were checked using the spirometry. Physiological assessment of the workload was carried out by recording the heart rate and blood pressure of the workers prior to work and just after work in the field. Results: Brick field workers suffered from pain especially in the lower back (98%, hands (93%, knees (86%, wrists (85%, shoulders (76% and neck (65%. Among the brick-making activities, brick field workers felt discomfort during spading for mud collection (98%, carrying bricks (95% and molding (87%. The results showed a significantly lower p value < 0.001 in FVC, FEV1, FEV1/FVC ratio and PEFR in brick field workers compared to the control group. The post-activity heart rate of the brick field workers was 148.6 beats/min, whereas the systolic and diastolic blood pressure results were 152.8 and 78.5 mm/Hg, respectively. Conclusions: This study concludes that health of the brick field workers was highly affected due to working in unhealthy working conditions for a long period of time.

  19. Stress !!!

    NARCIS (Netherlands)

    Fledderus, M.

    2012-01-01

    Twee op de vijf UT-studenten hebben last van ernstige studiestress, zo erg zelfs dat het ze in hun privéleven belemmert. Die cijfers komen overeen met het landelijk beeld van stress onder studenten. Samen met 14 andere universiteits- en hogeschoolbladen enquêteerde UT Nieuws bijna 5500 studenten.

  20. Field performance of timber bridges. 5, Little Salmon Creek stress-laminated deck bridge

    Science.gov (United States)

    M. A. Ritter; J. A. Kainz; G. J. Porter

    The Little Salmon Creek bridge was constructed in November 1988 on the Allegheny National Forest in Pennsylvania. The bridge is a simple span, single-lane, stress-laminated deck superstructure that is approximately 26-ft long and 16-ft wide. The bridge is unique in that it is the first known stress-laminated timber bridge to be constructed of hardwood lumber. The...

  1. Field performance of timber bridges. 7, Connell Lake stress-laminated deck bridge

    Science.gov (United States)

    L. E. Hislop; M. A. Ritter

    The Connell Lake bridge was constructed in early 1991 on the Tongass National Forest, Alaska, as a demonstration bridge under the Timber Bridge Initiative. The bridge is a stress-laminated deck structure with an approximate 36-ft length and 18-ft width and is the first known stress-laminated timber bridge constructed in Alaska. Performance of the bridge was monitored...

  2. Field performance of timber bridges. 6, Hoffman Run stress-laminated deck bridge

    Science.gov (United States)

    M. A. Ritter; P. D. Hilbrich Lee; G. J. Porter

    The Hoffman Run bridge, located just outside Dahoga, Pennsylvania, was constructed in October 1990. The bridge is a simple-span, single-lane, stress-laminated deck superstructure that is approximately 26 ft long and 16 ft wide. It is the second stress-laminated timber bridge to be constructed of hardwood lumber in Pennsylvania. The performance of the bridge was...

  3. Effects of transverse temperature field nonuniformity on stress in silicon sheet growth

    Science.gov (United States)

    Mataga, P. A.; Hutchinson, J. W.; Chalmers, B.; Bell, R. O.; Kalejs, J. P.

    1987-01-01

    Stress and strain rate distributions are calculated using finite element analysis for steady-state growth of thin silicon sheet temperature nonuniformities imposed in the transverse (sheet width) dimension. Significant reductions in residual stress are predicted to occur for the case where the sheet edge is cooled relative to its center provided plastic deformation with high creep rates is present.

  4. Physiological and transcriptomic responses in the seed coat of field-grown soybean (Glycine max L. Merr.) to abiotic stress.

    Science.gov (United States)

    Leisner, Courtney P; Yendrek, Craig R; Ainsworth, Elizabeth A

    2017-12-12

    Understanding how intensification of abiotic stress due to global climate change affects crop yields is important for continued agricultural productivity. Coupling genomic technologies with physiological crop responses in a dynamic field environment is an effective approach to dissect the mechanisms underpinning crop responses to abiotic stress. Soybean (Glycine max L. Merr. cv. Pioneer 93B15) was grown in natural production environments with projected changes to environmental conditions predicted for the end of the century, including decreased precipitation, increased tropospheric ozone concentrations ([O 3 ]), or increased temperature. All three environmental stresses significantly decreased leaf-level photosynthesis and stomatal conductance, leading to significant losses in seed yield. This was driven by a significant decrease in the number of pods per node for all abiotic stress treatments. To understand the underlying transcriptomic response involved in the yield response to environmental stress, RNA-Sequencing analysis was performed on the soybean seed coat, a tissue that plays an essential role in regulating carbon and nitrogen transport to developing seeds. Gene expression analysis revealed 49, 148 and 1,576 differentially expressed genes in the soybean seed coat in response to drought, elevated [O 3 ] and elevated temperature, respectively. Elevated [O 3 ] and drought did not elicit substantive transcriptional changes in the soybean seed coat. However, this may be due to the timing of sampling and does not preclude impacts of those stresses on different tissues or different stages in seed coat development. Expression of genes involved in DNA replication and metabolic processes were enriched in the seed coat under high temperate stress, suggesting that the timing of events that are important for cell division and proper seed development were altered in a stressful growth environment.

  5. Site response variation due to the existence of near-field cracks based on strong motion records in the Shi-Wen river valley, southern Taiwan

    Science.gov (United States)

    Wu, Chi-Shin; Yu, Teng-To; Peng, Wen-Fei; Yeh, Yeoin-Tein; Lin, Sih-Siao

    2014-10-01

    Site effect analysis has been applied to investigate soil classification, alluvium depth, and fracture detection, although the majority of previous studies have typically focused only on the response of large-scale single structures. In contrast, we investigated the site effect for small-scale cracks using a case study in southern Taiwan to provide a means of monitoring slope stability or foundation integrity in situ using only an accelerometer. We adopted both the reference site and horizontal-to-vertical spectral ratio methods. We obtained seismographs associated with the typhoon-related development of a crack set (52 m long, 5 m deep) in a steep slope and compared the resonance frequency between two conditions (with and without cracks). Moreover, we divided the seismic waves into P, S, and coda waves and examined the seismic source effect. Our results demonstrate that frequencies of 14.5-17.5 Hz are most sensitive to these cracks, particularly for the E-W component of the P-waves, which coincides with the crack’s strike. Peak ground acceleration, which is controlled by seismic moment and attenuated distance, is another important factor determining the resonance results. Our results demonstrate that the ratio of temporal seismic waves can be used to detect the existence of nearby subsurface cracks.

  6. Site response variation due to the existence of near-field cracks based on strong motion records in the Shi-Wen river valley, southern Taiwan

    International Nuclear Information System (INIS)

    Wu, Chi-Shin; Yu, Teng-To; Peng, Wen-Fei; Yeh, Yeoin-Tein; Lin, Sih-Siao

    2014-01-01

    Site effect analysis has been applied to investigate soil classification, alluvium depth, and fracture detection, although the majority of previous studies have typically focused only on the response of large-scale single structures. In contrast, we investigated the site effect for small-scale cracks using a case study in southern Taiwan to provide a means of monitoring slope stability or foundation integrity in situ using only an accelerometer. We adopted both the reference site and horizontal-to-vertical spectral ratio methods. We obtained seismographs associated with the typhoon-related development of a crack set (52 m long, 5 m deep) in a steep slope and compared the resonance frequency between two conditions (with and without cracks). Moreover, we divided the seismic waves into P, S, and coda waves and examined the seismic source effect. Our results demonstrate that frequencies of 14.5−17.5 Hz are most sensitive to these cracks, particularly for the E−W component of the P-waves, which coincides with the crack’s strike. Peak ground acceleration, which is controlled by seismic moment and attenuated distance, is another important factor determining the resonance results. Our results demonstrate that the ratio of temporal seismic waves can be used to detect the existence of nearby subsurface cracks. (paper)

  7. Assessment of occupational health problems and physiological stress among the brick field workers of West Bengal, India.

    Science.gov (United States)

    Das, Banibrata

    2014-06-01

    The brick field industry is one of the oldest industries in India, which employs a large number of workers of poor socioeconomic status. The main aim of the present investigation is i) to determine the prevalence of musculoskeletal disorders among brick field workers, ii) to determine the prevalence of respiratory disorders and physiological stress among brick field workers compared to control workers. For this study, a total of 220 brick field workers and 130 control subjects were selected randomly. The control subjects were mainly involved in hand-intensive jobs. The Modified Nordic Questionnaire was applied to assess the discomfort felt among both groups of workers. Thermal stress was also assessed by measuring the WBGT index. The pulmonary functions were checked using the spirometry. Physiological assessment of the workload was carried out by recording the heart rate and blood pressure of the workers prior to work and just after work in the field. Brick field workers suffered from pain especially in the lower back (98%), hands (93%), knees (86%), wrists (85%), shoulders (76%) and neck (65%). Among the brick-making activities, brick field workers felt discomfort during spading for mud collection (98%), carrying bricks (95%) and molding (87%). The results showed a significantly lower p value workers compared to the control group. The post-activity heart rate of the brick field workers was 148.6 beats/min, whereas the systolic and diastolic blood pressure results were 152.8 and 78.5 mm/Hg, respectively. This study concludes that health of the brick field workers was highly affected due to working in unhealthy working conditions for a long period of time.

  8. Stress field sensitivity analysis within Mesozoic successions in the Swiss Alpine foreland using 3-D-geomechanical-numerical models

    Science.gov (United States)

    Reiter, Karsten; Hergert, Tobias; Heidbach, Oliver

    2016-04-01

    impact of fault geometry and frictional properties is observed within a distance of impact on the stress state is caused by the variability of the geomechanical stratigraphy. The stress anisotropy increases when tectonic shortening is applied to the models. Stress magnitudes and anisotropy are largest within the stiff formations such as limestone. These stiff formations carry the load due to far field tectonic forces, whereas weak formations, like the argillaceous target horizon for the waste disposal, exhibits smaller stress magnitudes. Using the fracture potential as a more unambiguous indicator, the stiff overburden rocks are closer to failure than the target horizon for the repository, whereas stiff formations below the target rocks are far from failure.

  9. Stress-induced metallic behavior under magnetic field in Pr1-xCaxMnO3 (x=0.5 and 0.4) thin films (invited)

    International Nuclear Information System (INIS)

    Prellier, W.; Simon, Ch.; Mercey, B.; Hervieu, M.; Haghiri-Gosnet, A. M.; Saurel, D.; Lecoeur, Ph.; Raveau, B.

    2001-01-01

    We have investigated the role of the stress induced by the presence of the substrate in thin films of colossal magnetoresistive manganites on structural, resistive, and magnetic properties. Because of the strong coupling between the small structural distortions related to the charge ordering (CO) and the resistive properties, the presence of the substrate prevents the full development of the charge ordering in Pr 0.5 Ca 0.5 MnO 3 , especially in the very thin films. For thicker films, the CO state exists, but is not fully developed. Correlatively, the magnetic field which is necessary to suppress the CO is decreased drastically from 25 T to about 5 T on SrTiO 3 substrates. We have also investigated the influence of the doping level by studying the case of Pr 0.6 Ca 0.4 MnO 3 . [copyright] 2001 American Institute of Physics

  10. Naloxone effects on behavior of inbred mice with different response to emotional stress in open field test.

    Science.gov (United States)

    Nadorova, A V; Kozlovskaja, M M; Seredenin, S B

    2009-10-01

    Effects of nonspecific opiate receptor antagonist naloxone in doses of 0.1, 0.5, 1.0, 5.0, 10.0 mg/kg on open field behavior and spontaneous motor activity were studied in male BALB/c and C57Bl/6 mice. Differently directed effects of naloxone on behavioral parameters of emotional-stress reaction in BALB/c and C57Bl/6 mice were observed. Naloxone increased motor activity in the open field test in BALB/c mice, but decreased it in C57Bl/6 mice. In the absence of stress, naloxone in the studied dose range did not affect spontaneous motor activity in C57Bl/6 mice, and significantly reduced activity in BALB/c mice in doses 0.5 and 1.0 mg/kg.

  11. Bias-stress characterization of solution-processed organic field-effect transistor based on highly ordered liquid crystals

    Science.gov (United States)

    Kunii, M.; Iino, H.; Hanna, J.

    2017-06-01

    Bias-stress effects in solution-processed, 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10) field effect transistors (FETs) are studied under negative and positive direct current bias. The bottom gate, bottom contact polycrystalline Ph-BTBT-10 FET with a hybrid gate dielectric of polystyrene and SiO2 shows high field effect mobility as well as a steep subthreshold slope when fabricated with a highly ordered smectic E liquid crystalline (SmE) film as a precursor. Negative gate bias-stress causes negative threshold voltage shift (ΔVth) for Ph-BTBT-10 FET in ambient air, but ΔVth rapidly decreases as the gate bias decreases and approaches to near zero when the gate bias goes down to 9 V in amplitude. In contrast, positive gate bias-stress causes negligible ΔVth even with a relatively high bias voltage. These results conclude that Ph-BTBT-10 FET has excellent bias-stress stability in ambient air in the range of low to moderate operating voltages.

  12. Effect of an absorbent overlay on the residual stress field induced by laser shock processing on aluminum samples

    International Nuclear Information System (INIS)

    Rubio-Gonzalez, C.; Gomez-Rosas, G.; Ocana, J.L.; Molpeceres, C.; Banderas, A.; Porro, J.; Morales, M.

    2006-01-01

    Laser shock processing (LSP) or laser shock peening is a new technique for strengthening metals. This process induces a compressive residual stress field, which increases fatigue crack initiation life and reduces fatigue crack growth rate. Specimens of 6061-T6 aluminum alloy are used in this investigation. A convergent lens is used to deliver 2.5 J, 8 ns laser pulses by a Q-switch Nd:YAG laser, operating at 10 Hz. The pulses are focused to a diameter of 1.5 mm onto aluminum samples. Density of 2500 pulses/cm 2 with infrared (1064 nm) radiation was used. The effect of an absorbent overlay on the residual stress field using this LSP setup and this energy level is evaluated. Residual stress distribution as a function of depth is assessed by the hole drilling method. It is observed that the overlay makes the compressive residual stress profile move to the surface. This effect is explained on the basis of the vaporization of the coat layer suppressing thermal effects on the metallic substrate. The effect of coating the specimen surface before LSP treatment may have advantages on improving wear and contact fatigue properties of this aluminum alloy

  13. Caffeine and sleep-deprivation mediated changes in open-field behaviours, stress response and antioxidant status in mice

    OpenAIRE

    Onaolapo, J. Olakunle; Onaolapo, Y. Adejoke; Akanmu, A. Moses; Olayiwola, Gbola

    2016-01-01

    Objectives: Effects of daily caffeine consumption on open-field behaviours, serum corticosterone and brain antioxidant levels were investigated after six hours of total sleep-deprivation in prepubertal mice. We tested the hypothesis that daily caffeine consumption may significantly alter behaviour, stress and antioxidative response of prepubertal mice to an acute episode of total sleep-deprivation. Methods: Prepubertal Swiss mice of both sexes were assigned to two main groups of 120 each (...

  14. INTEREST OF FINITE ELEMENT ANALYSIS TO DETERMINE STRESS FIELDS AT THE SUMMIT OF A VY FLAP ABOUT ONE CLINICAL CASE

    OpenAIRE

    Pauchot , Julien; Remache , Djamel; Chambert , Jérôme; Elkhyat , Ahmed; Jacquet , Emmanuelle

    2013-01-01

    International audience; After performing a V-Y advancement flap, we observed an unusually shaped necrosis, resembling a keyhole at the apex of the flap. As high closing tensions are an accepted cause of skin necrosis, we developed a mathematical model based on the finite element analysis in order to determine the stress field by simulating the mechanical behavior of human skin during suture and to explain this particular shape of necrosis. For the modeling, a planar nonlinear two-dimensional ...

  15. Characterizing the potential for fault reactivation related to CO2 injection through subsurface structural mapping and stress field analysis, Wellington Field, Sumner County, KS

    Science.gov (United States)

    Schwab, D.; Bidgoli, T.; Taylor, M. H.

    2015-12-01

    South-central Kansas has experienced an unprecedented increase in seismic activity since 2013. The spatial and temporal relationship of the seismicity with brine disposal operations has renewed interest in the role of fluids in fault reactivation. This study focuses on determining the suitability of CO2 injection into a Cambro-Ordovician reservoir for long-term storage and a Mississippian reservoir for enhanced oil recovery in Wellington Field, Sumner County, Kansas. Our approach for determining the potential for induced seismicity has been to (1) map subsurface faults and estimate in-situ stresses, (2) perform slip and dilation tendency analysis to identify optimally-oriented faults relative to the estimated stress field, and (3) monitor surface deformation through cGPS data and InSAR imaging. Through the use of 3D seismic reflection data, 60 near vertical, NNE-striking faults have been identified. The faults range in length from 140-410 m and have vertical separations of 3-32m. A number of faults appear to be restricted to shallow intervals, while others clearly cut the top basement reflector. Drilling-induced tensile fractures (N=78) identified from image logs and inversion of earthquake focal mechanism solutions (N=54) are consistent with the maximum horizontal stress (SHmax) oriented ~E-W. Both strike-slip and normal-slip fault plane solutions for earthquakes near the study area suggest that SHmax and Sv may be similar in magnitude. Estimates of stress magnitudes using step rate tests (Shmin = 2666 psi), density logs (Sv = 5308 psi), and calculations from wells with drilling induced tensile fractures (SHmax = 4547-6655 psi) are determined at the gauge depth of 4869ft. Preliminary slip and dilation tendency analysis indicates that faults striking 0°-20° are stable, whereas faults striking 26°-44° may have a moderate risk for reactivation with increasing pore-fluid pressure.

  16. Field performance of timber bridges. 8, Lynches Woods Park stress-laminated deck bridge

    Science.gov (United States)

    J. P. Wacker; M. A. Ritter; D. Conger

    The Lynches Woods Park bridge was constructed during the summer of 1990 in Newberry, South Carolina. It is a single-span, single-lane, stress-laminated deck superstructure that measures approximately 30 ft long, 16 ft wide, and 14 in. deep. The bridge is unique in that is one of the first known stress-laminated deck bridges to be constructed of Southern Pine lumber...

  17. Field performance of timber bridges. 4, Graves Crossing stress-laminated deck bridge

    Science.gov (United States)

    J. P. Wacker; M. A. Ritter

    The Graves Crossing bridge was constructed October 1991 in Antrim County, Michigan, as part of the demonstration timber bridge program sponsored by the USDA Forest Service. The bridge is a two-span continuous, stress-laminated deck superstructure and it is 36-ft long and 26-ft wide. The bridge is one of the first stress-laminated deck bridges to be built of sawn lumber...

  18. Local versus regional active stress field in 5900m San Gregorio Magno 1 well (southern Apennines, Italy).

    Science.gov (United States)

    Pierdominici, S.; Montone, P.; Mariucci, M. T.

    2009-04-01

    The aim of this work is to characterize the local stress field in a peculiar sector of the southern Apennines by analyzing borehole breakouts, fractures and logging data along the San Gregorio Magno 1 deep well, and to compare the achieved stress field with the regional one. The study area is characterized by diffuse low-Magnitude seismicity, although in historical times it has been repeatedly struck by moderate to large earthquakes. We have analyzed in detail the 5900m San Gregorio Magno 1 well drilled in 1996-97 by ENI S.p.A. and located very close (1.3 km away) to the Irpinia Fault. This fault was responsible of the strongest earthquake happened in this area, the 23rd November 1980 M6.9 earthquake that produced the first unequivocal historical surface faulting ever documented in Italy. The mainshock enucleated on a fault 38 km-long with a strike of 308° and 60-70° northeast-dipping, consistent with a NE-SW T-axis and a normal faulting tectonic regime. Borehole breakouts, active faults and focal mechanism solutions have allowed to define the present-day stress along and around the San Gregorio Magno 1 well and other analysis (logging data) to discriminate the presence of fracture zones and/or faults at depth. We have considered data from 1200m to the bottom of San Gregorio Magno 1 well. Our analysis of stress-induced wellbore breakouts shows an inhomogeneous direction of minimum horizontal stress (N359+-31°) orientation along the well. This direction is moderately consistent with the Shmin-trend determined from breakouts in other wells in this region and also with the regional active stress field inferred from active faults and earthquake focal plane solutions (N44 Shmin oriented). For this reason we have computed for each breakout zone the difference between the local trend and the regional one; comparing these breakout rotations with the spikes or changing trend of logs we have identified possible fractures or faults at different depths. We have correlated

  19. Nickel--chromium strain gages for cryogenic stress analysis of superconducting structures in high magnetic fields

    International Nuclear Information System (INIS)

    Anon.

    1977-01-01

    Magnetoresistance measurements of strain gages were made. The magnitude and variation of the magnetoresistance of a large number of strain gages were measured for the following conditions: (1) dc magnetic fields up to 12 T, (2) three orthogonal field directions, (3) increasing and decreasing fields, (4) a wide range of strain levels, and (5) liquid helium temperature

  20. Stress.

    Science.gov (United States)

    Chambers, David W

    2008-01-01

    We all experience stress as a regular, and sometimes damaging and sometimes useful, part of our daily lives. In our normal ups and downs, we have our share of exhaustion, despondency, and outrage--matched with their corresponding positive moods. But burnout and workaholism are different. They are chronic, dysfunctional, self-reinforcing, life-shortening habits. Dentists, nurses, teachers, ministers, social workers, and entertainers are especially susceptible to burnout; not because they are hard-working professionals (they tend to be), but because they are caring perfectionists who share control for the success of what they do with others and perform under the scrutiny of their colleagues (they tend to). Workaholics are also trapped in self-sealing cycles, but the elements are ever-receding visions of control and using constant activity as a barrier against facing reality. This essay explores the symptoms, mechanisms, causes, and successful coping strategies for burnout and workaholism. It also takes a look at the general stress response on the physiological level and at some of the damage American society inflicts on itself.

  1. EXIST Perspective for SFXTs

    Science.gov (United States)

    Ubertini, Pietro; Sidoli, L.; Sguera, V.; Bazzano, A.

    2009-12-01

    Supergiant Fast X-ray Transients (SFXTs) are one of the most interesting (and unexpected) results of the INTEGRAL mission. They are a new class of HMXBs displaying short hard X-ray outbursts (duration less tha a day) characterized by fast flares (few hours timescale) and large dinamic range (10E3-10E4). The physical mechanism driving their peculiar behaviour is still unclear and highly debated: some models involve the structure of the supergiant companion donor wind (likely clumpy, in a spherical or non spherical geometry) and the orbital properties (wide separation with eccentric or circular orbit), while others involve the properties of the neutron star compact object and invoke very low magnetic field values (B 1E14 G, magnetars). The picture is still highly unclear from the observational point of view as well: no cyclotron lines have been detected in the spectra, thus the strength of the neutron star magnetic field is unknown. Orbital periods have been measured in only 4 systems, spanning from 3.3 days to 165 days. Even the duty cycle seems to be quite different from source to source. The Energetic X-ray Imaging Survey Telescope (EXIST), with its hard X-ray all-sky survey and large improved limiting sensitivity, will allow us to get a clearer picture of SFXTs. A complete census of their number is essential to enlarge the sample. A long term and continuous as possible X-ray monitoring is crucial to -(1) obtain the duty cycle, -(2 )investigate their unknown orbital properties (separation, orbital period, eccentricity),- (3) to completely cover the whole outburst activity, (4)-to search for cyclotron lines in the high energy spectra. EXIST observations will provide crucial informations to test the different models and shed light on the peculiar behaviour of SFXTs.

  2. Timing effects of heat-stress on plant physiological characteristics and growth: a field study with prairie vegetation

    Directory of Open Access Journals (Sweden)

    Dan Wang

    2016-11-01

    Full Text Available More intense, more frequent, and longer heat-waves are expected in the future due to global warming, which could have dramatic agricultural, economic and ecological impacts. This field study examined how plant responded to heat-stress (HS treatment at different timing in naturally-occurring vegetation. HS treatment (5 days at 40.5 ºC were applied to 12 1m2 plots in restored prairie vegetation dominated by Andropogon gerardii (warm-season C4 grass and Solidago canadensis (warm-season C3 forb at different growing stages. During and after HS, air, canopy, and soil temperature were monitored; net CO2 assimilation (Pn, quantum yield of photosystem II (ФPSII, stomatal conductance (gs, and internal CO2 level (Ci of the dominant species were measured. One week after the last HS treatment, all plots were harvested and the biomass of above-ground tissue and flower weight of the two dominant species was determined. HS decreased physiological performance and growth for both species, with S. canadensis being affected more than A. gerardii, indicated by negative heat stress effect on both physiological and growth responses. There were significant timing effect of heat stress on the two species, with greater reductions in the photosynthesis and productivity occurred when heat stress was applied at later-growing season. The reduction in aboveground productivity in S. canadensis but not A. gerardii could have important implications for plant community structure by increasing the competitive advantage of A. gerardii in this grassland. The present experiment showed that heat stress, though ephemeral, may promote long-term effects on plant community structure, vegetation dynamics, biodiversity, and ecosystem functioning of terrestrial biomes when more frequent and severe heat stress occur in the future.

  3. The Effect of the Free Surface on the Singular Stress Field at the Fatigue Crack Front

    Directory of Open Access Journals (Sweden)

    Oplt Tomáš

    2017-11-01

    Full Text Available Description of stress singularity in the vicinity of a free surface is presented. Its presence causes the retardation of the fatigue crack growth in that region and fatigue crack is being curved. Numerical model is used to study dependence of the stress singularity exponent on Poisson’s ratio. Estimated values are compared to those already published. Experimentally measured angles of fatigue crack on SENB specimens confirm the relation between Poisson’s ratio and the angle between crack front and free surface.

  4. Stress relaxation technique of high magnetic field superconducting magnet for the nuclear fusion

    International Nuclear Information System (INIS)

    Kamimoto, Masayuki; Tateishi, Hiroshi; Agatsuma, Ko; Arai, Kazuaki; Umeda, Masaichi

    1999-01-01

    Here were attempted not only to prove effectiveness of a stress self-supporting type wire material for magnet constituting technique, but also to develop a fiber reinforcing type superconducting wire material used by materials with excellent strain resistance to expand usable range of the stress self-supporting type with material. In 1997 fiscal year, superconductive features of the wire material produced by using composite processing method were evaluated, actual applicability for superconducting wire material was inspected, and investigation on manufacturing parameter of NbN thin films on trial production at present apparatus was conducted. (G.K.)

  5. Frequency- and axial-field-dependent circular magnetization reversal in a stress-annealed Fe-based nanocrystalline wire

    International Nuclear Information System (INIS)

    Li, Y.F.; Vazquez, M.; Yin, S.Z.

    2009-01-01

    Absract: After suitable annealing under a tensile stress, Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 amorphous wire becomes the nano-structured material together with a transverse anisotropy field H k =-3.2 kA/m. Its circular permeability, μ=μ'-jμ'', was determined from the measurements of the impedance, as a function of the frequency (f=333-33,333 Hz) and amplitude (I AC =0.1-100 mA) of AC current and the axially applied DC field (H=0-89 kA/m). We found that the circular technical magnetization of this sample carried out by the spontaneous domain nucleation process. The influences of the AC current frequency and the axial DC field on the circular magnetization have been studied

  6. Application of H-matrices method to the calculation of the stress field in a viscoelastic medium

    Science.gov (United States)

    Ohtani, M.; Hirahara, K.

    2017-12-01

    In SW Japan, the Philippine Sea plate subducts from the south and the large earthquakes around M (Magnitude) 8 repeatedly occur at the plate boundary along the Nankai Trough, called as Nankai/Tonankai earthquakes. Near the rupture area of these earthquakes, the active volcanoes lines in the Kyushu region SW Japan, such as Sakurajima volcano. There are also distributed in the Tokai-Kanto region SE Japan, such as Mt. Fuji. The eruption of Mt. Fuji in 1707, called as Hoei eruption, have occurred 49 days after the one of the series of Nankai/Tonankai earthquakes, 1707 Hoei earthquake (M8.4). It suggests that the stress field due to the earthquake sometimes helps the volcanoes to erupt. When we consider the stress change due to the earthquake, the effect of viscoelastic deformation of the crust will be important. FEM is always used for modeling such inelastic effect. However, it requires the high computational cost of O(N3), where N is the number of discretized cells of the inelastic medium. Recently, a new method based on BIEM is proposed by Barbot and Fialko (2010). In their method, calculation of the stress field due to the inelastic strain is replaced to solve the inhomogeneous Navier's equation with equivalent body forces of the inelastic strain. Then, using the stress-strain greenfunction in an elastic medium, we can take into account the inelastic effect. In this study, we employ their method to evaluate the stress change at the active volcanoes around the Nankai/Tonankai earthquakes. Their method requires the computational cost and memory storage of O(N2). We try to reduce the computational amount and the memory by applying the fast computation method of H-matrices method. With H-matrices method, a dense matrix is divided into hierarchical structure of submatrices, and each submatrix is approximated to be low rank. When we divide the viscoelastic medium into N = 8,640 or 69,120 uniform cuboid cells and apply the H-matrices method, the required storage memory for

  7. Characterizing the Potential for Injection-Induced Fault Reactivation Through Subsurface Structural Mapping and Stress Field Analysis, Wellington Field, Sumner County, Kansas

    Science.gov (United States)

    Schwab, Drew R.; Bidgoli, Tandis S.; Taylor, Michael H.

    2017-12-01

    Kansas, like other parts of the central U.S., has experienced a recent increase in seismicity. Correlation of these events with brine disposal operations suggests pore fluid pressure increases are reactivating preexisting faults, but rigorous evaluation at injection sites is lacking. Here we determine the suitability of CO2 injection into the Cambrian-Ordovician Arbuckle Group for long-term storage and into a Mississippian reservoir for enhanced oil recovery in Wellington Field, Sumner County, Kansas. To determine the potential for injection-induced earthquakes, we map subsurface faults and estimate in situ stresses, perform slip and dilation tendency analyses to identify well-oriented faults relative to the estimated stress field, and determine the pressure changes required to induce slip at reservoir and basement depths. Three-dimensional seismic reflection data reveal 12 near-vertical faults, mostly striking NNE, consistent with nodal planes from moment tensor solutions from recent earthquakes in the region. Most of the faults cut both reservoirs and several clearly penetrate the Precambrian basement. Drilling-induced fractures (N = 40) identified from image logs and inversion of earthquake moment tensor solutions (N = 65) indicate that the maximum horizontal stress is approximately EW. Slip tendency analysis indicates that faults striking <020° are stable under current reservoir conditions, whereas faults striking 020°-049° may be prone to reactivation with increasing pore fluid pressure. Although the proposed injection volume (40,000 t) is unlikely to reactive faults at reservoir depths, high-rate injection operations could reach pressures beyond the critical threshold for slip within the basement, as demonstrated by the large number of injection-induced earthquakes west of the study area.

  8. Environmental stresses of field growth allow cinnamyl alcohol dehydrogenase-deficient Nicotiana attenuata plants to compensate for their structural deficiencies.

    Science.gov (United States)

    Kaur, Harleen; Shaker, Kamel; Heinzel, Nicolas; Ralph, John; Gális, Ivan; Baldwin, Ian T

    2012-08-01

    The organized lignocellulosic assemblies of cell walls provide the structural integrity required for the large statures of terrestrial plants. Silencing two CINNAMYL ALCOHOL DEHYDROGENASE (CAD) genes in Nicotiana attenuata produced plants (ir-CAD) with thin, red-pigmented stems, low CAD and sinapyl alcohol dehydrogenase activity, low lignin contents, and rubbery, structurally unstable stems when grown in the glasshouse (GH). However, when planted into their native desert habitat, ir-CAD plants produced robust stems that survived wind storms as well as the wild-type plants. Despite efficient silencing of NaCAD transcripts and enzymatic activity, field-grown ir-CAD plants had delayed and restricted spread of red stem pigmentation, a color change reflecting blocked lignification by CAD silencing, and attained wild-type-comparable total lignin contents. The rubbery GH phenotype was largely restored when field-grown ir-CAD plants were protected from wind, herbivore attack, and ultraviolet B exposure and grown in restricted rooting volumes; conversely, it was lost when ir-CAD plants were experimentally exposed to wind, ultraviolet B, and grown in large pots in growth chambers. Transcript and liquid chromatography-electrospray ionization-time-of-flight analysis revealed that these environmental stresses enhanced the accumulation of various phenylpropanoids in stems of field-grown plants; gas chromatography-mass spectrometry and nuclear magnetic resonance analysis revealed that the lignin of field-grown ir-CAD plants had GH-grown comparable levels of sinapaldehyde and syringaldehyde cross-linked into their lignins. Additionally, field-grown ir-CAD plants had short, thick stems with normal xylem element traits, which collectively enabled field-grown ir-CAD plants to compensate for the structural deficiencies associated with CAD silencing. Environmental stresses play an essential role in regulating lignin biosynthesis in lignin-deficient plants.

  9. Calculation of the residual stress field created by quenching and grinding in a cast duplex stainless steel pipe

    International Nuclear Information System (INIS)

    Dupas, P.; Le Delliou, P.

    1997-01-01

    We calculate with a finite element program the residual stresses generated by quenching and grinding a cast duplex stainless steel pipe. These calculations are performed with Code Aster (developed by EDF/R and D D). They are preliminary to a 3D study concerning an elbow made of the same material. Quenching is simulated by an axisymmetric thermomechanical calculation. Grinding are simulated either by lowering mechanical properties in ground parts of the pipe, either by the releasing the nodes. Stresses due to quenching are in high compression in the skin and tensile in the middle. After grinding (the first concerning both internal and external skins, the second concerning only the internal skin), stresses become tensile on the skin. These results are compared to those obtained in a similar study by CEA and also to the measurement. Some important differences appear in the thermal results between the two FE programs, due to a too coarse time step in the CASTEM 2000 calculation. However, the effect on the residual stress field is not very important. Two complementary studies have shown a negligible influence of mesh size, as well as an equivalence of the two numerical methods used for simulating grinding (lowering the Young modulus and releasing the nodes), according the values given at the notes of the skin by the first method are corrected. (authors)

  10. Measurement of residual stress fields in FHPP welding: a comparison between DSPI combined with hole-drilling and neutron diffraction

    Science.gov (United States)

    Viotti, Matias R.; Albertazzi, Armando; Staron, Peter; Pisa, Marcelo

    2013-04-01

    This paper shows a portable device to measure mainly residual stress fields outside the optical bench. This system combines the traditional hole drilling technique with Digital Speckle Pattern Interferometry. The novel feature of this device is the high degree of compaction since only one base supports simultaneously the measurement module and the hole-drilling device. The portable device allows the measurement of non-uniform residual stresses in accordance with the ASTM standard. In oil and gas offshore industries, alternative welding procedures among them, the friction hydro pillar processing (FHPP) is highlighted and nowadays is an important maintenance tool since it has the capability to produce structure repairs without risk of explosions. In this process a hole is drilled and filled with a consumable rod of the same material. The rod, which could be cylindrical or conical, is rotated and pressed against the hole, leading to frictional heating. In order to assess features about the residual stress distribution generated by the weld into the rod as well as into the base material around the rod, welded samples were evaluated by neutron diffraction and by the hole drilling technique having a comparison between them. For the hole drilling technique some layers were removed by using electrical discharge machining (EDM) after diffraction measurements in order to assess the bulk stress distribution. Results have shown a good agreement between techniques.

  11. Differential metabolome analysis of field-grown maize kernels in response to drought stress

    Science.gov (United States)

    Drought stress constrains maize kernel development and can exacerbate aflatoxin contamination. In order to identify drought responsive metabolites and explore pathways involved in kernel responses, a metabolomics analysis was conducted on kernels from a drought tolerant line, Lo964, and a sensitive ...

  12. A new theoretical model of the quasistatic single-fiber pullout problem: Analysis of stress field

    DEFF Research Database (Denmark)

    Qing, Hai

    2013-01-01

    with respect to the axial direction is neglected for shear stress-strain relationship. The general solutions of the axial and radial displacements in both fibre and matrix are obtained in explicit forms. In the debonded region, a modified Coulomb's friction law, in which the frictional coefficient...

  13. Field performance of timber bridges. 15, Pueblo County, Colorado, stress-laminated deck bridge

    Science.gov (United States)

    L. E. Hislop

    The Pueblo County 204B bridge was constructed in March 1990 in Pueblo, Colorado, as a demonstration bridge under the USDA Forest Service Timber Bridge Initiative. The stress-laminated deck superstructure is approximately 10 m long, 9 m wide, and 406 mm deep, with a skew of 10 degrees. Performance monitoring was conducted for 3 years, beginning at...

  14. On the diffusion process of irradiation-induced point defects in the stress field of a moving dislocation

    International Nuclear Information System (INIS)

    Steinbach, E.

    1987-01-01

    The cellular model of a dislocation is used for an investigation of the time-dependent diffusion process of irradiation-induced point defects interacting with the stress field of a moving dislocation. An analytic solution is given taking into account the elastic interaction due to the first-order size effect and the stress-induced interaction, the kinematic interaction due to the dislocation motion as well as the presence of secondary neutral sinks. The results for the space and time-dependent point defect concentration, represented in terms of Mathieu-Bessel and Mathieu-Hankel functions, emphasize the influence of the parameters which have been taken into consideration. Proceeding from these solutions, formulae for the diffusion flux reaching unit length of the dislocation, which plays an important role with regard to void swelling and irradiation-induced creep, are derived

  15. Performance of organic field effect transistors with high-k gate oxide after application of consecutive bias stress

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sunwoo; Choi, Changhwan; Lee, Kilbock [Department of Materials Science and Engineering, Hanyang University, Seoul, 133-791 (Korea, Republic of); Cho, Joong Hwee [Department of Embedded Systems Engineering,University of Incheon, Incheon 406-722 (Korea, Republic of); Ko, Ki-Young [Korea Institute of Patent Information, Seoul, 146-8 (Korea, Republic of); Ahn, Jinho, E-mail: jhahn@hanyang.ac.kr [Department of Materials Science and Engineering, Hanyang University, Seoul, 133-791 (Korea, Republic of)

    2012-10-30

    We report the effect of consecutive electrical stress on the performance of organic field effect transistors (OFETs). Sputtered aluminum oxide (Al{sub 2}O{sub 3}) and hafnium oxide (HfO{sub 2}) were used as gate oxide layers. After the electrical stress, the threshold voltage, which strongly depends on bulk defects, was remarkably shifted to the negative direction, while the other performance characteristics of OFETs such as on-current, transconductance and mobility, which are sensitive to interface defects, were slightly decreased. This result implies that the defects in the bulk layer are significantly affected compared to the defects in the interface layer. Thus, it is important to control the defects in the pentacene bulk layer in order to maintain the good reliabilities of pentacene devices. Those defects in HfO{sub 2} gate oxide devices were larger compared to those in Al{sub 2}O{sub 3} gate oxide devices.

  16. Field testing existence values for riparian ecosystems

    Science.gov (United States)

    John W. Duffield; Chris J. Neher; David A. Patterson; Patricia A. Champ

    2007-01-01

    This paper presents preliminary findings on a cash and contingent valuation (cv) experiment. The study replicates major elements of an earlier (1990) experiment, which solicited hypothetical and actual donations to benefit instream flows for Montana fisheries. Extensions of the earlier work include: repeat contacts to increase response rate, follow-up of the contingent...

  17. Extremes of random fields over arbitrary domains with application to concrete rupture stresses

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager

    2004-01-01

    function class is studied for Gaussian processes in earlier works by the author and it has been obtained explicitly for Gaussian fields on rectangular domains in the plane. Simulation studies show that rather good predictions are obtained for sufficiently smooth wide band Gaussian processes and fields...

  18. Distributed deformation structures in shallow water carbonates subsiding through a simple stress field (Jandaira Formation, NE Brazil)

    Science.gov (United States)

    Bertotti, Giovanni; Bisdom, Kevin; Bezerra, Hilario; Reijmer, John; Cazarin, Carol

    2016-04-01

    Despite the scarcity of major deformation structures such as folds and faults, the flat-lying, post-rift shallow water carbonates of the Jandaira Formation (Potiguar Basin, NE Brazil) display well-organized fracture systems distributed of tens of km2. Structures observed in the outcropping carbonates are sub-vertical, generally N-S trending mode I and hybrid veins and barren fractures, sub-vertical roughly E-W trending stylolites and sub-horizontal stylolites. These features developed during subsidence in a simple and constant stress field characterized by, beside gravity, a significant horizontal stress probably of tectonic origin. The corresponding depth curves have different origin and slopes and, therefore, cross each other resulting in position of the principal stresses which change with depth. As a result, the type and amount of fractures affecting subsiding rocks change despite the fact that the far-field stresses remain constant. Following early diagenesis and porosity elimination in the first 100-200m depth, Jandaira carbonates experienced wholesale fracturing at depths of 400-800m resulting in a network of NNW-NE trending fractures partly organized in conjugate sets with a low interfault angle and a sub-vertical intersection, and sub-vertical stylolites roughly perpendicular to the fractures. Intense fluid circulation was activated as a consequence through the carbonates. With increasing subsidence, sub-horizontal stylolites formed providing calcite which precipitated in the open fractures transforming them in veins. The Jandaira formation lost thereby the permeability it had reached during the previous stage. Because of the lack of major deformation, the outcrops of the Jandaira Formation is an excellent analog for carbonate reservoirs in the Middle East, South Atlantic and elsewhere.

  19. Effect of magnetic field and silver nanoparticles on yield and water use efficiency of Carum copticum under water stress conditions

    Directory of Open Access Journals (Sweden)

    Seghatoleslami Mohammadjavad

    2015-03-01

    Full Text Available Normally the productivity of cropping systems in arid and semi- arid regions is very low. The sustainable agricultural systems try to find out environmental friendly technologies based on physical and biological treatments to increase crop production. In this study two irrigation treatments (control and water stress and six methods of fertilizer treatment (control, NPK-F, using magnetic band- M, using silver nano particles- N, M+N and M+N+50% F on performance of ajowan were compared. Results showed that treatments with magnetic field or base fertilizer had more yield compared to the control and silver nanoparticles (N treatments. Application of silver nanoparticles had no positive effect on yield. The highest seed and biomass WUE achieved in base fertilizer or magnetic field treatments. Under water stress treatment, seed WUE significantly increased. In conclusion magnetic field exposure, probably by encourage nutrient uptake efficiency could be applied to reduce fertilizer requirement. On the other hand the cultivation of plants under low MF could be an alternative way of WUE improving.

  20. Numerical modeling to assess possible influence of the mine openings on far-field in-situ stress measurements at Stripa

    International Nuclear Information System (INIS)

    Chan, T.; Guvanasen, V.; Littlestone, N.

    1981-03-01

    Finite element analyses were carried out to assess the possible effects of the Stripa mine openings on the in-situ stress measured in a 400-m-deep borehole drilled from the surface. For this assessment, four 2-dimensional cases were modeled. These cases variously included two horizontal sections, and two separate, idealized vertical sections. An iron ore body in the mine was assumed to be completely extracted, thereby providing conservative estimates of stress concentration effects. Since no in-situ stress measurements were made before mining, overburden weight and horizontal stresses measured by hyrodfracturing were assumed to be the pre-mining state of stress. The stress state resulting from excavation of the mine was calculated by the finite element model. In the cases using horizontal sections, the model predicted a stress concentration factor at the borehole of approximately 1.15, which is negligible considering the difficulty of obtaining accurate stress measurements. For the vertical sections the model predicted higher stress concentration factors at depths less than 200 m. This was expected because the vertical sections chosen brought the borehole unrealistically close to the mine openings, thereby leading to overly conservative estimates. In general, deviations in the magnitudes and orientations of the calculated redistributed principal stresses from the assumed pre-mining state of stress were found to be comparable to the scatter of overcoring data. It is, therefore, recommended that, for near-field stress calculations, the vertical stress due to overburden weight and the horizontal stresses measured by hydrofracturing at the borehole be considered the unperturbed far-field in situ state of stress

  1. Changes in permeability caused by transient stresses: field observations, experiments, and mechanisms

    Science.gov (United States)

    Manga, Michael; Beresnev, Igor; Brodsky, Emily E.; Elkhoury, Jean E.; Elsworth, Derek; Ingebritsen, Steve E.; Mays, David C.; Wang, Chi-Yuen

    2012-01-01

    Oscillations in stress, such as those created by earthquakes, can increase permeability and fluid mobility in geologic media. In natural systems, strain amplitudes as small as 10–6 can increase discharge in streams and springs, change the water level in wells, and enhance production from petroleum reservoirs. Enhanced permeability typically recovers to prestimulated values over a period of months to years. Mechanisms that can change permeability at such small stresses include unblocking pores, either by breaking up permeability-limiting colloidal deposits or by mobilizing droplets and bubbles trapped in pores by capillary forces. The recovery time over which permeability returns to the prestimulated value is governed by the time to reblock pores, or for geochemical processes to seal pores. Monitoring permeability in geothermal systems where there is abundant seismicity, and the response of flow to local and regional earthquakes, would help test some of the proposed mechanisms and identify controls on permeability and its evolution.

  2. GEODYNAMIC ACTIVITY OF MODERN STRUCTURES AND TECTONIC STRESS FIELDS IN NORTHEAST ASIA

    Directory of Open Access Journals (Sweden)

    L. P. Imaeva

    2017-01-01

    Full Text Available Based on the analysis of changes in the stress-strain state of the crust at the boundary of the Eurasian and North American tectonic plates, we develop a dynamic model of the main seismogenerating structures inNortheast Asia. We have established a regularity in changes of geodynamic regimes within the interplate boundary between the Kolyma-Chukotka crustal plate and the Eurasian, North American and Pacific tectonic plates: spreading in the Gakkel Ridge area; rifting in the Laptev Sea shelf; a mixture of tectonic stress types in the Kharaulakh segment; transpression in the Chersky seismotectonic zone, in the segment from the Komandor to the Aleutian Islands, and in the Koryak segment; and crustal stretching in the Chukotka segment.

  3. Numerical Simulation of Temperature Field and Residual Stress Distribution for Laser Cladding Remanufacturing

    Directory of Open Access Journals (Sweden)

    Liang Hua

    2014-05-01

    Full Text Available A three-dimensional finite element model was employed to simulate the cladding process of Ni-Cr-B-Si coatings on 16MnR steel under different parameters of laser power, scanning speed, and spot diameter. The temperature and residual stress distribution, the depth of the heat affected zone (HAZ, and the optimized parameters for laser cladding remanufacturing technology were obtained. The orthogonal experiment and intuitive analysis on the depth of the HAZ were performed to study the influence of different cladding parameters. A new criterion based on the ratio of the maximum tensile residual stress and fracture strength of the substrate was proposed for optimization of the remanufacturing parameters. The result showed well agreement with that of the HAZ analysis.

  4. HKT transporters mediate salt stress resistance in plants: from structure and function to the field.

    Science.gov (United States)

    Hamamoto, Shin; Horie, Tomoaki; Hauser, Felix; Deinlein, Ulrich; Schroeder, Julian I; Uozumi, Nobuyuki

    2015-04-01

    Plant cells are sensitive to salinity stress and do not require sodium as an essential element for their growth and development. Saline soils reduce crop yields and limit available land. Research shows that HKT transporters provide a potent mechanism for mediating salt tolerance in plants. Knowledge of the molecular ion transport and regulation mechanisms and the control of HKT gene expression are crucial for understanding the mechanisms by which HKT transporters enhance crop performance under salinity stress. This review focuses on HKT transporters in monocot plants and in Arabidopsis as a dicot plant, as a guide to efforts toward improving salt tolerance of plants for increasing the production of crops and bioenergy feedstocks. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Caffeine and sleep-deprivation mediated changes in open-field behaviours, stress response and antioxidant status in mice.

    Science.gov (United States)

    Onaolapo, J Olakunle; Onaolapo, Y Adejoke; Akanmu, A Moses; Olayiwola, Gbola

    2016-01-01

    Effects of daily caffeine consumption on open-field behaviours, serum corticosterone and brain antioxidant levels were investigated after six hours of total sleep-deprivation in prepubertal mice. We tested the hypothesis that daily caffeine consumption may significantly alter behaviour, stress and antioxidative response of prepubertal mice to an acute episode of total sleep-deprivation. Prepubertal Swiss mice of both sexes were assigned to two main groups of 120 each (subdivided into 6 groups of 10 each, based on sex), and administered vehicle or graded oral doses of caffeine (10, 20, 40, 80 and 120 mg/kg/day) for 14 days. On day 14, a main group was subjected to 6 h of total sleep-deprivation by 'gentle-handling'. Open-field behaviours were then assessed in both groups, after which animals were euthanized, and levels of corticosterone, superoxide dismutase and glutathione peroxidase assayed. Horizontal locomotion, rearing and grooming increased significantly, compared to control, with sleep-deprived (SD) mice showing stronger caffeine-driven responses at higher doses; and SD female mice showing sustained response to caffeine, compared to respective males. Plasma corticosterone increased with increasing doses of caffeine in both non sleep-deprived (NSD) and SD mice; although SD mice had higher corticosterone levels. Sleep-deprivation and/or higher doses of caffeine were associated with derangements in brain antioxidant levels. Repeated caffeine consumption and/or acute sleep-deprivation led to significant changes in pattern of open-field behaviour and stress/antioxidant response in mice. Responses seen in the study are probably due to modulatory effects of caffeine on the total body response to stressful stimuli.

  6. Field performance of timber bridges. 16, North Siwell Road stress-laminated bridge

    Science.gov (United States)

    J. A. Kainz

    The North Siwell Road bridge was constructed during December 1994 in Hinds County, Mississippi. The bridge is a single-span, stress-laminated T-beam structure that measures 9.1 m (30 ft) long and 8.7 m (28.5 ft) wide. Performance of the bridge was monitored for 24 months, beginning at the time of installation. Monitoring involved gathering and evaluating data relative...

  7. Field performance of timber bridges. 13, Mohawk Canal stress-laminated bridge

    Science.gov (United States)

    P. D. Hilbrich Lee; X. Lauderdale

    The Mohawk Canal bridge was constructed in August 1994, just outside Roll, Arizona. It is a simple-span, double-lane, stress-laminated deck superstructure, approximately 6.4 m (21 ft) long and 10.4 m (34 ft) wide and constructed with Combination 16F-V3 Douglas Fir glued-laminated timber beam laminations. The performance of the bridge was monitored continuously for 2...

  8. Field performance of timber bridges. 17, Ciphers stress-laminated deck bridge

    Science.gov (United States)

    James P. Wacker; James A. Kainz; Michael A. Ritter

    In September 1989, the Ciphers bridge was constructed within the Beltrami Island State Forest in Roseau County, Minnesota. The bridge superstructure is a two-span continuous stress-laminated deck that is approximately 12.19 m long, 5.49 m wide, and 305 mm deep (40 ft long, 18 ft wide, and 12 in. deep). The bridge is one of the first to utilize red pine sawn lumber for...

  9. Field performance of timber bridges. 10, Sanborn Brook stress-laminated deck bridge

    Science.gov (United States)

    P. D. Hilbrich Lee; J. P. Wacker; M. A. Ritter

    The Sanborn Brook bridge was constructed in August 1991, 10 miles northeast of Concord, New Hampshire, as part of the demonstration timber bridge program of the USDA Forest Service. The bridge is a simple-span, double-lane, stress-laminated deck superstructure constructed from Southern Pine lumber and is approximately 25 ft long and 28 ft wide with a skew of 14 degrees...

  10. Field performance of timber bridges. 12, Christian Hollow stress-laminated box-beam bridge

    Science.gov (United States)

    J. P. Wacker; S. C. Catherman; R. G. Winnett

    In January 1992, the Christian Hollow bridge was constructed in Steuben County, New York. The bridge is a single-span, stress-laminated box-beam superstructure that is 9.1 m long, 9.8 m wide, and 502 mm deep (30 ft long, 32 ft wide, and 19-3/4 in. deep). The performance of the bridge was continuously monitored for 28 months, beginning shortly after installation....

  11. Exploring and reducing stress in young restaurant workers: results of a randomized field trial.

    Science.gov (United States)

    Petree, Robyn D; Broome, Kirk M; Bennett, Joel B

    2012-01-01

    Young adult restaurant workers face the dual stressors of work adjustment and managing personal responsibilities. We assessed a new psychosocial/health promotion training designed to reduce these stressors in the context of restaurant work. DESIGN . A cluster-randomized trial of a training program, with surveys administered approximately 2 weeks before training and both 6 and 12 months after training. A national restaurant chain. A total of 947 restaurant workers in 28 restaurants. Personal stress, exposure to problem coworkers, and personal and job characteristics. Team Resilience (TR) is an interactive program for stress management, teamwork, and work-life balance. TR focuses on "five Cs" of resilience: compassion, commitment, centering, community, and confidence. ANALYSIS . Mixed-model (multilevel) analysis of covariances. Compared with workers in control stores, workers in TR-trained stores showed significant reductions over time in exposure to problem coworkers (F[2, 80.60]  =  4.48; p  =  .01) and in personal stress (F[2, 75.28]  =  6.12; p  =  .003). The TR program may help young workers who face the challenges of emerging adulthood and work-life balance.

  12. Experimental and calculating study on the stressed state of superconducting coils of toroidal field in the T-15 tokamak

    International Nuclear Information System (INIS)

    Vaulina, I.G.; Gusev, S.V.; Sivkova, G.N.

    1987-01-01

    Results of calculational and experimental atudy of stress-deformed state of superconducting coils of the T-15 tokamak toroidal field are presented. The calculations are made using the method of finite elements and refined theory of cores. Experimental studies were carried out using elastic tensometric model of polymer materials. Test results are compared with the calculational results. Divergence between calculational and experimental values of displacement of characteristic points in the unit does not exceed 20 %. Results of model studies confirm the expediency of the calculational model used for designing SOTP unit for the T-15 tokamak

  13. USE OF AUTODESK SIMULATION MULTIPHYSICS FOR RESEARCH OF TEMPERATURE FIELDS, STRESS AND DEFOMATION IN THE CONSTRUCTION OF GEAR PUMP

    Directory of Open Access Journals (Sweden)

    A. V. Puzanov

    2016-01-01

    Full Text Available Gear pumps are the most common type of hydraulic machines. They are used in various industries: oil and gas processing industry, in machine tools, mobile military, road-building and agricultural machinery. The need to ensure efficiency of hydraulic mobile applications in a wide climatic range requires increasing the accuracy of the calculation methods for the design of their elements. The results of temperature field modeling and caused them stress and strain. The results obtained allowed to justify the design and technological solutions, providing an increase of hydraulic performance at critical ambient temperatures.

  14. The effect of guide-field and boundary conditions on collisionless magnetic reconnection in a stressed X-point collapse

    Energy Technology Data Exchange (ETDEWEB)

    Graf von der Pahlen, J.; Tsiklauri, D. [School of Physics and Astronomy, Queen Mary University of London, London E1 4NS (United Kingdom)

    2014-01-15

    Works of Tsiklauri and Haruki [Phys. Plasmas 15, 102902 (2008); 14, 112905 (2007)] are extended by inclusion of the out-of-plane magnetic (guide) field. In particular, magnetic reconnection during collisionless, stressed X-point collapse for varying out-of-plane guide-fields is studied using a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code. For zero guide-field, cases for both open and closed boundary conditions are investigated, where magnetic flux and particles are lost and conserved, respectively. It is found that reconnection rates, out-of-plane currents and density in the X-point increase more rapidly and peak sooner in the closed boundary case, but higher values are reached in the open boundary case. The normalized reconnection rate is fast: 0.10-0.25. In the open boundary case it is shown that an increase of guide-field yields later onsets in the reconnection peak rates, while in the closed boundary case initial peak rates occur sooner but are suppressed. The reconnection current changes similarly with increasing guide-field; however for low guide-fields the reconnection current increases, giving an optimal value for the guide-field between 0.1 and 0.2 times the in-plane field in both cases. Also, in the open boundary case, it is found that for guide-fields of the order of the in-plane magnetic field, the generation of electron vortices occurs. Possible causes of the vortex generation, based on the flow of decoupled particles in the diffusion region and localized plasma heating, are discussed. Before peak reconnection onset, oscillations in the out-of-plane electric field at the X-point are found, ranging in frequency from approximately 1 to 2 ω{sub pe} and coinciding with oscillatory reconnection. These oscillations are found to be part of a larger wave pattern in the simulation domain. Mapping the out-of-plane electric field along the central lines of the domain over time and applying a 2D Fourier transform reveal that

  15. Characteristics of Superjunction Lateral-Double-Diffusion Metal Oxide Semiconductor Field Effect Transistor and Degradation after Electrical Stress

    Science.gov (United States)

    Lin, Jyh‑Ling; Lin, Ming‑Jang; Lin, Li‑Jheng

    2006-04-01

    The superjunction lateral double diffusion metal oxide semiconductor field effect has recently received considerable attention. Introducing heavily doped p-type strips to the n-type drift region increases the horizontal depletion capability. Consequently, the doping concentration of the drift region is higher and the conduction resistance is lower than those of conventional lateral-double-diffusion metal oxide semiconductor field effect transistors (LDMOSFETs). These characteristics may increase breakdown voltage (\\mathit{BV}) and reduce specific on-resistance (Ron,sp). In this study, we focus on the electrical characteristics of conventional LDMOSFETs on silicon bulk, silicon-on-insulator (SOI) LDMOSFETs and superjunction LDMOSFETs after bias stress. Additionally, the \\mathit{BV} and Ron,sp of superjunction LDMOSFETs with different N/P drift region widths and different dosages are discussed. Simulation tools, including two-dimensional (2-D) TSPREM-4/MEDICI and three-dimensional (3-D) DAVINCI, were employed to determine the device characteristics.

  16. Seismic anisotropy and its relation with crust structure and stress field in the Reggio Emilia Region (Northern Italy)

    Science.gov (United States)

    Margheriti, L.; Ferulano, M. F.; Di Bona, M.

    2006-11-01

    Shear wave splitting is measured at 14 seismic stations in the Reggio Emilia region above local background seismicity and two sequences of seismic events. The good quality of the waveforms together with the favourable distribution of earthquake foci allows us to place strong constraints on the geometry and the depth of the anisotropic volume. It is about 60 km2 wide and located between 6 and 11 km depth, inside Mesozoic age carbonate rocks. The splitting results suggest also the presence of a shallower anisotropic layer about 1 km thick and few km wide in the Pliocene-Quaternary alluvium above the Mesozoic layer. The fast polarization directions (N30°E) are approximately parallel to the maximum horizontal stress (σ1 is SSW-NNE) in the region and also parallel to the strike of the main structural features in the Reggio Emilia area. The size of the delay times suggests about 4.5 per cent shear wave velocity anisotropy. These parameters agree with an interpretation of seismic anisotropy in terms of the extensive-dilatancy anisotropy model which considers the rock volume to be pervaded by fluid-saturated microcracks aligned by the active stress field. We cannot completely rule out the contribution of aligned macroscopic fractures as the cause of the shear wave anisotropy even if the parallel shear wave polarizations we found are diagnostic of transverse isotropy with a horizontal axis of symmetry. This symmetry is commonly explained by parallel stress-aligned microcracks.

  17. Identification of Dynamic Flow Stress Curves Using the Virtual Fields Methods: Theoretical Feasibility Analysis

    Science.gov (United States)

    Leem, Dohyun; Kim, Jin-Hwan; Barlat, Frédéric; Song, Jung Han; Lee, Myoung-Gyu

    2018-03-01

    An inverse approach based on the virtual fields method (VFM) is presented to identify the material hardening parameters under dynamic deformation. This dynamic-VFM (D-VFM) method does not require load information for the parameter identification. Instead, it utilizes acceleration fields in a specimen's gage region. To investigate the feasibility of the proposed inverse approach for dynamic deformation, the virtual experiments using dynamic finite element simulations were conducted. The simulation could provide all the necessary data for the identification such as displacement, strain, and acceleration fields. The accuracy of the identification results was evaluated by changing several parameters such as specimen geometry, velocity, and traction boundary conditions. The analysis clearly shows that the D-VFM which utilizes acceleration fields can be a good alternative to the conventional identification procedure that uses load information. Also, it was found that proper deformation conditions are required for generating sufficient acceleration fields during dynamic deformation to enhance the identification accuracy with the D-VFM.

  18. Focal mechanisms in the southern Aegean from temporary seismic networks – implications for the regional stress field and ongoing deformation processes

    Directory of Open Access Journals (Sweden)

    W. Friederich

    2014-05-01

    Full Text Available The lateral variation of the stress field in the southern Aegean plate and the subducting Hellenic slab is determined from recordings of seismicity obtained with the CYCNET and EGELADOS networks in the years from 2002 to 2007. First motions from 7000 well-located microearthquakes were analysed to produce 540 well-constrained focal mechanisms. They were complemented by another 140 derived by waveform matching of records from larger events. Most of these earthquakes fall into 16 distinct spatial clusters distributed over the southern Aegean region. For each cluster, a stress inversion could be carried out yielding consistent estimates of the stress field and its spatial variation. At crustal levels, the stress field is generally dominated by a steeply dipping compressional principal stress direction except in places where coupling of the subducting slab and overlying plate come into play. Tensional principal stresses are generally subhorizontal. Just behind the forearc, the crust is under arc-parallel tension whereas in the volcanic areas around Kos, Columbo and Astypalea tensional and intermediate stresses are nearly degenerate. Further west and north, in the Santorini–Amorgos graben and in the area of the islands of Mykonos, Andros and Tinos, tensional stresses are significant and point around the NW–SE direction. Very similar stress fields are observed in western Turkey with the tensional axis rotated to NNE–SSW. Intermediate-depth earthquakes below 100 km in the Nisyros region indicate that the Hellenic slab experiences slab-parallel tension at these depths. The direction of tension is close to east–west and thus deviates from the local NW-oriented slab dip presumably owing to the segmentation of the slab. Beneath the Cretan sea, at shallower levels, the slab is under NW–SE compression. Tensional principal stresses in the crust exhibit very good alignment with extensional strain rate principal axes derived from GPS velocities except

  19. Near-field thermal transient and thermomechanical stress analysis of a disposal vault in crystalline hard rock

    International Nuclear Information System (INIS)

    Tsui, K.K.; Tsai, A.; Lee, C.F.

    1981-01-01

    The Canadian Nuclear Fuel Waste Management Program currently focuses on the development of a disposal vault in crystalline hard rock at a reference depth of 1 km below the surface in a suitable pluton in the Canadian Shield. As part of Ontario Hydro's technical assistance to the Atomic Energy of Canada Limited in this program, studies are being carried out to determine the effects of radiogenic heat on the near-field behaviour of a disposal vault. This paper presents the study results obtained to date. Temperature and stress fields were computed and cross-checked by several finite element codes. A comparison between vertical and horizontal borehole emplacement concepts is made. The effects of material non-linearity (temperature dependence) and three-dimensionality on the thermomechanical response are evaluated. Case histories of thermal spalling or fracturing in rock were summarized and discussed to illustrate the possible mechanisms and processes involved in thermal fracturing. An assessment of the thermomechanical stability of the rock mass around a disposal vault under a state of high horizontal in-situ stress is also presented

  20. A multiscale coupled finite-element and phase-field framework to modeling stressed grain growth in polycrystalline thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jamshidian, M., E-mail: jamshidian@cc.iut.ac.ir [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Institute of Structural Mechanics, Bauhaus-University Weimar, Marienstrasse 15, 99423 Weimar (Germany); Thamburaja, P., E-mail: prakash.thamburaja@gmail.com [Department of Mechanical & Materials Engineering, Universiti Kebangsaan Malaysia (UKM), Bangi 43600 (Malaysia); Rabczuk, T., E-mail: timon.rabczuk@tdt.edu.vn [Division of Computational Mechanics, Ton Duc Thang University, Ho Chi Minh City (Viet Nam); Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City (Viet Nam)

    2016-12-15

    A previously-developed finite-deformation- and crystal-elasticity-based constitutive theory for stressed grain growth in cubic polycrystalline bodies has been augmented to include a description of excess surface energy and grain-growth stagnation mechanisms through the use of surface effect state variables in a thermodynamically-consistent manner. The constitutive theory was also implemented into a multiscale coupled finite-element and phase-field computational framework. With the material parameters in the constitutive theory suitably calibrated, our three-dimensional numerical simulations show that the constitutive model is able to accurately predict the experimentally-determined evolution of crystallographic texture and grain size statistics in polycrystalline copper thin films deposited on polyimide substrate and annealed at high-homologous temperatures. In particular, our numerical analyses show that the broad texture transition observed in the annealing experiments of polycrystalline thin films is caused by grain growth stagnation mechanisms. - Graphical abstract: - Highlights: • Developing a theory for stressed grain growth in polycrystalline thin films. • Implementation into a multiscale coupled finite-element and phase-field framework. • Quantitative reproduction of the experimental grain growth data by simulations. • Revealing the cause of texture transition to be due to the stagnation mechanisms.

  1. Octupolar out-of-plane magnetic field structure generation during collisionless magnetic reconnection in a stressed X-point collapse

    Energy Technology Data Exchange (ETDEWEB)

    Graf von der Pahlen, J.; Tsiklauri, D. [School of Physics and Astronomy, Queen Mary University of London, London E1 4NS (United Kingdom)

    2014-06-15

    The out-of-plane magnetic field, generated by fast magnetic reconnection, during collisionless, stressed X-point collapse, was studied with a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code, using both closed (flux conserving) and open boundary conditions on a square grid. It was discovered that the well known quadrupolar structure in the out-of-plane magnetic field gains four additional regions of opposite magnetic polarity, emerging near the corners of the simulation box, moving towards the X-point. The emerging, outer, magnetic field structure has opposite polarity to the inner quadrupolar structure, leading to an overall octupolar structure. Using Ampere's law and integrating electron and ion currents, defined at grid cells, over the simulation domain, contributions to the out-of-plane magnetic field from electron and ion currents were determined. The emerging regions of opposite magnetic polarity were shown to be the result of ion currents. Magnetic octupolar structure is found to be a signature of X-point collapse, rather than tearing mode, and factors relating to potential discoveries in experimental scenarios or space-craft observations are discussed.

  2. Effects of 60 Hz electric fields on operant and social stress behaviors of nonhuman primates: Projects 3 and 4

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, W.R.; Coelho, A.M. Jr.; Easley, S.P.; Orr, J.L.; Smith, H.D.; Taylor, L.L.; Tuttle, M.L.

    1987-01-01

    The objective of this program is to investigate, using the baboon as a nonhuman primate surrogate for the human, possible hehavioral effects associated with exposure to high intensity 60 Hz electric fields. Results from this program, along with information from experiments conducted elsewhere, will be used by the Department of Energy (DOE) to estimate and evaluate the likelihood of deleterious consequences resulting from exposure of humans to the electric fields associated with power transmission over high voltage lines. This research program consists of four major research projects, all of which have been successfully completed. The third project assessed, in separate experiments conducted at 30 and 60 kV/m, effects of chronic exposure to electric fields on the performance of two operant conditioning tasks, fixed ratio (FR), and differential reinforcement of low rate (DRL). In the same two experiments, the fourth project investigated, using the systematic quantitative observational sampling methods of primatology, the possible stress-inducing effects of chronic exposure to 60 Hz electric fields on the behavior of baboons living in small social groups. This volume contains only appendices for projects 3 and 4. 81 figs., 67 tabs.

  3. Requirements for existing buildings

    DEFF Research Database (Denmark)

    Thomsen, Kirsten Engelund; Wittchen, Kim Bjarne

    This report collects energy performance requirements for existing buildings in European member states by June 2012.......This report collects energy performance requirements for existing buildings in European member states by June 2012....

  4. Greening Existing Tribal Buildings

    Science.gov (United States)

    Guidance about improving sustainability in existing tribal casinos and manufactured homes. Many steps can be taken to make existing buildings greener and healthier. They may also reduce utility and medical costs.

  5. Correlation between the local stress and the grain misorientation in the polycrystalline Al2O3 measured by near-field luminescence spectroscopy

    Science.gov (United States)

    Tomimatsu, Toru; Takigawa, Ryo

    2018-06-01

    Owing to its high spatial resolution, near-field spectroscopy is a useful method for sensing the stress in a narrow region of submicron order. Here, on the basis of the highly resolved images obtained by near-field luminescence spectroscopy, we propose a statistical method of analyzing grain anisotropy-induced stress in polycrystalline Al2O3. We focus on two characteristics of a spectra: the intensity ratio and peak shift of luminescence of two lines (R1 and R2) from Al2O3 to discuss crystal orientation and stress, respectively. By incorporating the concept of the crystal misorientation parameter using intensity ratio, an apparent correlation between the magnitude of stress and the misorientation is found. This correlation analysis provides an important insight for the investigation of local thermal stress in Al2O3.

  6. Simultaneous measurement of temperature, stress, and electric field in GaN HEMTs with micro-Raman spectroscopy.

    Science.gov (United States)

    Bagnall, Kevin R; Moore, Elizabeth A; Badescu, Stefan C; Zhang, Lenan; Wang, Evelyn N

    2017-11-01

    As semiconductor devices based on silicon reach their intrinsic material limits, compound semiconductors, such as gallium nitride (GaN), are gaining increasing interest for high performance, solid-state transistor applications. Unfortunately, higher voltage, current, and/or power levels in GaN high electron mobility transistors (HEMTs) often result in elevated device temperatures, degraded performance, and shorter lifetimes. Although micro-Raman spectroscopy has become one of the most popular techniques for measuring localized temperature rise in GaN HEMTs for reliability assessment, decoupling the effects of temperature, mechanical stress, and electric field on the optical phonon frequencies measured by micro-Raman spectroscopy is challenging. In this work, we demonstrate the simultaneous measurement of temperature rise, inverse piezoelectric stress, thermoelastic stress, and vertical electric field via micro-Raman spectroscopy from the shifts of the E 2 (high), A 1 longitudinal optical (LO), and E 2 (low) optical phonon frequencies in wurtzite GaN. We also validate experimentally that the pinched OFF state as the unpowered reference accurately measures the temperature rise by removing the effect of the vertical electric field on the Raman spectrum and that the vertical electric field is approximately the same whether the channel is open or closed. Our experimental results are in good quantitative agreement with a 3D electro-thermo-mechanical model of the HEMT we tested and indicate that the GaN buffer acts as a semi-insulating, p-type material due to the presence of deep acceptors in the lower half of the bandgap. This implementation of micro-Raman spectroscopy offers an exciting opportunity to simultaneously probe thermal, mechanical, and electrical phenomena in semiconductor devices under bias, providing unique insight into the complex physics that describes device behavior and reliability. Although GaN HEMTs have been specifically used in this study to

  7. Simultaneous measurement of temperature, stress, and electric field in GaN HEMTs with micro-Raman spectroscopy

    Science.gov (United States)

    Bagnall, Kevin R.; Moore, Elizabeth A.; Badescu, Stefan C.; Zhang, Lenan; Wang, Evelyn N.

    2017-11-01

    As semiconductor devices based on silicon reach their intrinsic material limits, compound semiconductors, such as gallium nitride (GaN), are gaining increasing interest for high performance, solid-state transistor applications. Unfortunately, higher voltage, current, and/or power levels in GaN high electron mobility transistors (HEMTs) often result in elevated device temperatures, degraded performance, and shorter lifetimes. Although micro-Raman spectroscopy has become one of the most popular techniques for measuring localized temperature rise in GaN HEMTs for reliability assessment, decoupling the effects of temperature, mechanical stress, and electric field on the optical phonon frequencies measured by micro-Raman spectroscopy is challenging. In this work, we demonstrate the simultaneous measurement of temperature rise, inverse piezoelectric stress, thermoelastic stress, and vertical electric field via micro-Raman spectroscopy from the shifts of the E2 (high), A1 longitudinal optical (LO), and E2 (low) optical phonon frequencies in wurtzite GaN. We also validate experimentally that the pinched OFF state as the unpowered reference accurately measures the temperature rise by removing the effect of the vertical electric field on the Raman spectrum and that the vertical electric field is approximately the same whether the channel is open or closed. Our experimental results are in good quantitative agreement with a 3D electro-thermo-mechanical model of the HEMT we tested and indicate that the GaN buffer acts as a semi-insulating, p-type material due to the presence of deep acceptors in the lower half of the bandgap. This implementation of micro-Raman spectroscopy offers an exciting opportunity to simultaneously probe thermal, mechanical, and electrical phenomena in semiconductor devices under bias, providing unique insight into the complex physics that describes device behavior and reliability. Although GaN HEMTs have been specifically used in this study to

  8. Effects of electric field and Coriolis force on electrohydrodynamic stability of poorly conducting couple stress parallel fluid flow in a channel

    International Nuclear Information System (INIS)

    Shankar, B.M.; Rudraiah, N.

    2013-01-01

    The linear stability of electrohydrodynamic poorly conducting couple stress viscous parallel fluid flow in a channel is studied in the presence of a non-uniform transverse electric field and Coriolis force using energy method and supplemented with Galerkin Technique. The sufficient condition for stability is obtained for sufficiently small values of the Reynolds number, R e . From this condition we show that strengthening or weakening of the stability criterion is dictated by the values of the strength of electric field, the coefficient of couple stress fluid and independent of Taylor number. In particular, it is shown that the interaction of electric field with couple stress is more effective in stabilizing the poorly conducting couple stress fluid compared to that in an ordinary Newtonian viscous fluid. (author)

  9. Effects of microstructure and local mechanical fields on intergranular stress corrosion cracking of a friction stir welded aluminum–copper–lithium 2050 nugget

    International Nuclear Information System (INIS)

    Dhondt, Matthieu; Aubert, Isabelle; Saintier, Nicolas; Olive, Jean Marc

    2014-01-01

    Highlights: • Applied stress changes the corrosion mode from pitting to intergranular cracking. • Residual stresses are sufficient to induce intergranular stress corrosion cracking. • Effect of crystallographic texture on the development of IGSCC evidenced by EBSD. • Cubic elasticity drives the local orientation of the intergranular cracking. • Tomography observations show the 3D nature of the corrosion development. - Abstract: The effects of the microstructure and mechanical fields on intergranular stress corrosion cracking (IGSCC) of the nugget zone of heat treated welds obtained by friction stir welding in the AA2050 aluminum alloy have been investigated at different scales. At low strain rate, in 1.0 NaCl aqueous solution, IGSCC develops in the microstructure, whereas only pitting corrosion is observed without any mechanical stress. Based on surface observations, EBSD analysis and X-ray tomography, the key role of sub-millimetric textured bands (induced by the welding process) on the IGSCC is demonstrated. Analyses at a more local scale show the grain boundary (low angle boundary, special coincident site lattice boundary or high angle boundary) do not have a significant effect on crack initiation. Crystal plasticity finite element calculations show that the threshold normal stress at grain boundaries for IGSCC development is about 80% of the macroscopic stress. It is also highlighted by crystal plasticity calculations that there is a drastic effect of the local stress field on the shape of cracks. Finally, it is shown that plasticity induced residual stresses are sufficient for the formation of IGSCC

  10. Field measurements, simulation modeling and development of analysis for moisture stressed corn and soybeans, 1982 studies

    Science.gov (United States)

    Blad, B. L.; Norman, J. M.; Gardner, B. R.

    1983-01-01

    The experimental design, data acquisition and analysis procedures for agronomic and reflectance data acquired over corn and soybeans at the Sandhills Agricultural Laboratory of the University of Nebraska are described. The following conclusions were reached: (1) predictive leaf area estimation models can be defined which appear valid over a wide range of soils; (2) relative grain yield estimates over moisture stressed corn were improved by combining reflectance and thermal data; (3) corn phenology estimates using the model of Badhwar and Henderson (1981) exhibited systematic bias but were reasonably accurate; (4) canopy reflectance can be modelled to within approximately 10% of measured values; and (5) soybean pubescence significantly affects canopy reflectance, energy balance and water use relationships.

  11. Influence of the tilt angle of Percutaneous Aortic Prosthesis on Velocity and Shear Stress Fields

    Directory of Open Access Journals (Sweden)

    Bruno Alvares de Azevedo Gomes

    Full Text Available Abstract Background: Due to the nature of the percutaneous prosthesis deployment process, a variation in its final position is expected. Prosthetic valve placement will define the spatial location of its effective orifice in relation to the aortic annulus. The blood flow pattern in the ascending aorta is related to the aortic remodeling process, and depends on the spatial location of the effective orifice. The hemodynamic effect of small variations in the angle of inclination of the effective orifice has not been studied in detail. Objective: To implement an in vitro simulation to characterize the hydrodynamic blood flow pattern associated with small variations in the effective orifice inclination. Methods: A three-dimensional aortic phantom was constructed, reproducing the anatomy of one patient submitted to percutaneous aortic valve implantation. Flow analysis was performed by use of the Particle Image Velocimetry technique. The flow pattern in the ascending aorta was characterized for six flow rate levels. In addition, six angles of inclination of the effective orifice were assessed. Results: The effective orifice at the -4° and -2° angles directed the main flow towards the anterior wall of the aortic model, inducing asymmetric and high shear stress in that region. However, the effective orifice at the +3° and +5° angles mimics the physiological pattern, centralizing the main flow and promoting a symmetric distribution of shear stress. Conclusion: The measurements performed suggest that small changes in the angle of inclination of the percutaneous prosthesis aid in the generation of a physiological hemodynamic pattern, and can contribute to reduce aortic remodeling.

  12. Evaluation of the evolving stress field of the Yellowstone volcanic plateau, 1988 to 2010, from earthquake first-motion inversions

    Science.gov (United States)

    Russo, E.; Waite, G. P.; Tibaldi, A.

    2017-03-01

    Although the last rhyolite eruption occurred around 70 ka ago, the silicic Yellowstone volcanic field is still considered active due to high hydrothermal and seismic activity and possible recent magma intrusions. Geodetic measurements document complex deformation patterns in crustal strain and seismic activity likewise reveal spatial and temporal variations in the stress field. We use earthquake data recorded between 1988 and 2010 to investigate these variations and their possible causes in more detail. Earthquake relocations and a set of 369 well-constrained, double-couple, focal mechanism solutions were computed. Events were grouped according to location and time to investigate trends in faulting. The majority of the events have normal-faulting solutions, subordinate strike-slip kinematics, and very rarely, reverse motions. The dominant direction of extension throughout the 0.64 Ma Yellowstone caldera is nearly ENE, consistent with the perpendicular direction of alignments of volcanic vents within the caldera, but our study also reveals spatial and temporal variations. Stress-field solutions for different areas and time periods were calculated from earthquake focal mechanism inversion. A well-resolved rotation of σ3 was found, from NNE-SSW near the Hebgen Lake fault zone, to ENE-WSW near Norris Junction. In particular, the σ3 direction changed throughout the years around Norris Geyser Basin, from being ENE-WSW, as calculated in the study by Waite and Smith (2004), to NNE-SSW, while the other σ3 directions are mostly unchanged over time. The presence of ;chocolate tablet; structures, with two sets of nearly perpendicular normal faults, was identified in many stages of the deformation history both in the Norris Geyser Basin area and inside the caldera.

  13. High-Field Nb3Sn Cos-theta Dipole with Stress Management

    Energy Technology Data Exchange (ETDEWEB)

    Novitski, Igor [Fermilab; Carmichael, Justin [Fermilab; Kashikhin, Vadim V. [Fermilab; Zlobin, Alexander V. [Fermilab

    2017-01-01

    Cost-effective superconducting dipole magnets with operating fields up to 16 T are being considered for the LHC en-ergy upgrade (HE-LHC) and a Future Circular Collider (FCC). To demonstrate feasibility of 15 T accelerator quality dipole mag-nets, FNAL as a part of the US-MDP is developing a single-aper-ture Nb3Sn dipole demonstrator based on a 4-layer graded cos-theta coil with 60 mm aperture and cold iron yoke. In parallel, to explore the limit of the Nb3Sn accelerator magnet technology, op-timize magnet design and performance parameters, and reduce magnet cost, magnet design studies are also being performed to push the nominal bore field to 16 T in a 60-mm aperture cos-theta dipole. Results of these studies are reported and discussed in this paper.

  14. High-electric-field-stress-induced degradation of SiN passivated AlGaN/GaN high electron mobility transistors

    International Nuclear Information System (INIS)

    Wen-Ping, Gu; Huan-Tao, Duan; Jin-Yu, Ni; Yue, Hao; Jin-Cheng, Zhang; Qian, Feng; Xiao-Hua, Ma

    2009-01-01

    AlGaN/GaN high electron mobility transistors (HEMTs) are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degradation has been found, consisting of the decrease of saturation drain current I Dsat , maximal transconductance g m , and the positive shift of threshold voltage V TH at high drain-source voltage V DS . The high-electric-field stress degrades the electric characteristics of AlGaN/GaN HEMTs because the high field increases the electron trapping at the surface and in AlGaN barrier layer. The SiN passivation of AlGaN/GaN HEMTs decreases the surface trapping and 2DEG depletion a little during the high-electric-field stress. After the hot carrier stress with V DS = 20 V and V GS = 0 V applied to the device for 10 4 sec, the SiN passivation decreases the stress-induced degradation of I Dsat from 36% to 30%. Both on-state and pulse-state stresses produce comparative decrease of I Dsat , which shows that although the passivation is effective in suppressing electron trapping in surface states, it does not protect the device from high-electric-field degradation in nature. So passivation in conjunction with other technological solutions like cap layer, prepassivation surface treatments, or field-plate gate to weaken high-electric-field degradation should be adopted. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  15. Field monoterpene emission of Mediterranean oak (Quercus ilex) in the central Iberian Peninsula measured by enclosure and micrometeorological techniques: Observation of drought stress effect

    Science.gov (United States)

    Plaza, J.; NúñEz, L.; Pujadas, M.; PéRez-Pastor, R.; Bermejo, V.; GarcíA-Alonso, S.; Elvira, S.

    2005-02-01

    An experimental characterization of biogenic emission from Quercus ilex ssp. rotundifolia in a forest near Madrid, Spain, was carried out in the early autumn of the years 2000-2003. A dynamic branch enclosure technique was implemented to determine the monoterpene emission rates of this evergreen oak species during the 2000 and 2001 campaigns. Major compounds emitted during both measurement periods were limonene, α-pinene, β-pinene, sabinene, and myrcene. In the 2000 field campaign the light- and temperature-dependent model of [1993] did not fit the data due to drastic reductions of emission rates (and leaf gas exchange related parameters) observed at high air temperature and low air humidity (high water vapor pressure deficit). This plant physiological activity depletion and the subsequent emission reduction were attributed to severe water soil deficit conditions, as precipitation was very scarce during the growing season. In contrast, during the 2001 field campaign, neither emission nor physiological activity showed strong decreases in hot days. A good fit of experimental data to Guenther model was achieved in this field campaign (r2 = 0.90), and linear regression gave a standard emission factor (ES) of 14.0 μg gdw-1 h-1 (gdw is grams dry weight). Soil moisture was presumably higher than during the 2000 campaign due to recent rain events. With the purpose of documenting the drought stress effect at canopy level, monoterpene oak fluxes were measured by the modified Bowen ratio micrometeorological technique throughout the 2001 field campaign and in the late summer of 2002 and 2003. The measured emission by both techniques showed a reasonably good correlation, although micrometeorological fluxes were, in general, lower than upscaled branch emission rates. According to Guenther's parameterization, standard emission fluxes (FS) of 0.30 μg m-2 s-1 (r2 = 0.61) and 0.28 μg m-2 s-1 (r2 = 0.67) were derived for the 2001 and 2002 field campaigns, respectively. However

  16. Stress fields and energy of disclination-type defects in zones of localized elastic distortions

    Science.gov (United States)

    Sukhanov, Ivan I.; Tyumentsev, Alexander N.; Ditenberg, Ivan A.

    2016-11-01

    This paper studies theoretically the elastically deformed state and analyzes deformation mechanisms in nanocrystals in the zones of localized elastic distortions and related disclination-type defects, such as dipole, quadrupole and multipole of partial disclinations. Significant differences in the energies of quadrupole and multipole configurations in comparison with nanodipole are revealed. The mechanism of deformation localization in the field of elastic distortions is proposed, which is a quasi-periodic sequence of formation and relaxation of various disclination ensembles with a periodic change in the energy of the defect.

  17. Effects of lead exposure on oxidative stress biomarkers and plasma biochemistry in waterbirds in the field.

    Science.gov (United States)

    Martinez-Haro, Monica; Green, Andy J; Mateo, Rafael

    2011-05-01

    Medina lagoon in Andalusia has one of the highest densities of spent lead (Pb) shot in Europe. Blood samples from waterbirds were collected in 2006-2008 to measure Pb concentration (PbB), δ-aminolevulinic acid dehydratase (ALAD), oxidative stress biomarkers and plasma biochemistry. PbB above background levels (>20 μg/dl) was observed in 19% (n=59) of mallards (Anas platyrhynchos) and in all common pochards (Aythya ferina) (n=4), but common coots (Fulica atra) (n=37) and moorhens (Gallinula chloropus) (n=12) were all 6 μg/dl. In mallards, an inhibition of glutathione peroxidase (GPx) and an increased level of oxidized glutathione (oxGSH) in red blood cells (RBC) were associated with PbB levels >20 μg/dl. In coots, PbB levels were negatively related to vitamin A and carotenoid levels in plasma, and total glutathione in RBCs; and positively related with higher superoxide dismutase and GPx activities and % oxGSH in RBCs. Overall, the results indicate that previously assumed background levels of PbB for birds need to be revised. Copyright © 2011 Elsevier Inc. All rights reserved.

  18. Effect of modulated ultrahigh frequency field on behavior and hormone level in female rats under emotional stress

    Energy Technology Data Exchange (ETDEWEB)

    Rasulov, M.M.

    The effect of a modulated electromagnetic field (MEMF) (field frequency of 40 MHz and modulated frequency of 50 Hz, 1 h exposure daily for 30 days) on behavior and level of sexual hormones, determined from the length of the estrous cycle and of its separate phases, was studied in female Wistar rats subjected to sexual deprivation. The ratio of frequency of running to number of vertical positions (R:V) was used as an index. Activity of rats declined during the 1-h exposure to MEMF; this may indicate the direct effect of MEMF on the central nervous system. Analysis of behavior after MEMF treatments ceased showed that the R:V ratio increased from 3.2:1 to 3:1 in month 3 and reached 2:1 in month 5. The relative significance of sexual behavior (lordosis, licking of perineum) more than double in comparison with the initial level. The findings support the existence of individual differences in sensitivity to a UHF field. The data on the estrous cycle indicate the tranquilizing effect of a UHF field on the neuroendocrine system and the greater resistance of individual animals exposed to MEMF to the development of sexual neurosis. 12 references, 2 figures.

  19. Multi-parameter approximation of the stress field in a cracked body in the more distant surroundings of the crack tip

    Czech Academy of Sciences Publication Activity Database

    Veselý, V.; Sobek, J.; Frantík, P.; Seitl, Stanislav

    2016-01-01

    Roč. 89, AUG (2016), s. 20-35 ISSN 0142-1123. [International Conference on Characterisation of Crack Tip Fields /3./. Urbino, 20.04.2015-22.04.2015] Institutional support: RVO:68081723 Keywords : Crack-tip fields * Williams power series * Higher order terms * Stress field reconstruction * Multi-parameter approximation accuracy Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.899, year: 2016

  20. 19 mm sized bileaflet valve prostheses' flow field investigated by bidimensional laser Doppler anemometry (part II: maximum turbulent shear stresses)

    Science.gov (United States)

    Barbaro, V; Grigioni, M; Daniele, C; D'Avenio, G; Boccanera, G

    1997-11-01

    The investigation of the flow field generated by cardiac valve prostheses is a necessary task to gain knowledge on the possible relationship between turbulence-derived stresses and the hemolytic and thrombogenic complications in patients after valve replacement. The study of turbulence flows downstream of cardiac prostheses, in literature, especially concerns large-sized prostheses with a variable flow regime from very low up to 6 L/min. The Food and Drug Administration draft guidance requires the study of the minimum prosthetic size at a high cardiac output to reach the maximum Reynolds number conditions. Within the framework of a national research project regarding the characterization of cardiovascular endoprostheses, an in-depth study of turbulence generated downstream of bileaflet cardiac valves is currently under way at the Laboratory of Biomedical Engineering of the Istituto Superiore di Sanita. Four models of 19 mm bileaflet valve prostheses were used: St Jude Medical HP, Edwards Tekna, Sorin Bicarbon, and CarboMedics. The prostheses were selected for the nominal Tissue Annulus Diameter as reported by manufacturers without any assessment of valve sizing method, and were mounted in aortic position. The aortic geometry was scaled for 19 mm prostheses using angiographic data. The turbulence-derived shear stresses were investigated very close to the valve (0.35 D0), using a bidimensional Laser Doppler anemometry system and applying the Principal Stress Analysis. Results concern typical turbulence quantities during a 50 ms window at peak flow in the systolic phase. Conclusions are drawn regarding the turbulence associated to valve design features, as well as the possible damage to blood constituents.

  1. THE TECTONICS STRESS AND STRAIN FIELD MODELING ADJUSTED FOR EVOLUTION OF GEOLOGICAL STRUCTURES (SAILAG INTRUSION, EASTERN SAYAN

    Directory of Open Access Journals (Sweden)

    V. N. Voytenko

    2013-01-01

    Full Text Available The article describes a tectonophysical model showing evolution of structures in the Sailag granodiorite massif in relation to its gold-bearing capacity. The model takes into account the load patterns according to geological data, accumulated deformation, and gravity stresses. This model provides for updating the structural-geological model showing development of the intrusion body and the ore field. Forecasted are destruction patterns in the apical and above-dome parts of the massif  in the intrusion and contraction phase, formation of the long-term shear zone at the steeply dipping slope of the intrusion body, and subvertical fractures associated with the long-term shear zone and vertical mechanical ‘layering’ of the intrusive body.  

  2. Mean field diffusion models for precipitation in crystalline GaAs including surface tension and bulk stresses

    Energy Technology Data Exchange (ETDEWEB)

    Dreyer, Wolfgang [Weierstrass-Institut fuer Angewandte Analysis und Stochastik (WIAS) im Forschungsverbund Berlin e.V. (Germany); Kimmerle, Sven-Joachim [Humboldt-Univ. Berlin (Germany). Dept. of Mathematics

    2009-07-01

    Based on a thermodynamically consistent model for precipitation in gallium arsenide crystals including surface tension and bulk stresses by Dreyer and Duderstadt, we propose different mathematical models to describe the size evolution of liquid droplets in a crystalline solid. The first class of models treats the diffusion-controlled regime of interface motion, while the second class is concerned with the interface-controlled regime of interface motion. Our models take care of conservation of mass and substance. We consider homogenised models, where different length scales of the experimental situation have been exploited in order to simplify the equations. These homogenised models generalise the well-known Lifshitz-Slyozov-Wagner model for Ostwald ripening. Mean field models capture the main properties of our system and are well adapted for numerics and further analysis. Numerical evidence suggests in which case which one of the two regimes might be appropriate to the experimental situation. (orig.)

  3. Recent developments in multi-parametric three-dimensional stress field representation in plates weakened by cracks and notches

    Directory of Open Access Journals (Sweden)

    P. Lazzarin

    2013-07-01

    Full Text Available The paper deals with the three-dimensional nature and the multi-parametric representation of the stress field ahead of cracks and notches of different shape. Finite thickness plates are considered, under different loading conditions. Under certain hypotheses, the three-dimensional governing equations of elasticity can be reduced to a system where a bi-harmonic equation and a harmonic equation have to be simultaneously satisfied. The former provides the solution of the corresponding plane notch problem, the latter provides the solution of the corresponding out-of-plane shear notch problem. The analytical frame is applied to some notched and cracked geometries and its degree of accuracy is discussed comparing theoretical results and numerical data from 3D FE models.

  4. Theoretical and numerical studies of crack initiation and propagation in rock masses under freezing pressure and far-field stress

    Directory of Open Access Journals (Sweden)

    Yongshui Kang

    2014-10-01

    Full Text Available Water-bearing rocks exposed to freezing temperature can be subjected to freeze–thaw cycles leading to crack initiation and propagation, which are the main causes of frost damage to rocks. Based on the Griffith theory of brittle fracture mechanics, the crack initiation criterion, propagation direction, and crack length under freezing pressure and far-field stress are analyzed. Furthermore, a calculation method is proposed for the stress intensity factor (SIF of the crack tip under non-uniformly distributed freezing pressure. The formulae for the crack/fracture propagation direction and length of the wing crack under freezing pressure are obtained, and the mechanism for coalescence of adjacent cracks is investigated. In addition, the necessary conditions for different coalescence modes of cracks are studied. Using the topology theory, a new algorithm for frost crack propagation is proposed, which has the capability to define the crack growth path and identify and update the cracked elements. A model that incorporates multiple cracks is built by ANSYS and then imported into FLAC3D. The SIFs are then calculated using a FISH procedure, and the growth path of the freezing cracks after several calculation steps is demonstrated using the new algorithm. The proposed method can be applied to rocks containing fillings such as detritus and slurry.

  5. Strained Si channel NMOSFETs using a stress field with Si1-yC y source and drain stressors

    International Nuclear Information System (INIS)

    Chang, S.T.; Tasi, H.-S.; Kung, C.Y.

    2006-01-01

    The strain field in the silicon channel of a metal-oxide-semiconductor transistor with silicon-carbon alloy source and drain stressors was evaluated using the commercial process simulator FLOOPS-ISE TM . The physical origin of the strain components in the transistor channel region was explained. The magnitude and distribution of the strain components, and their dependence on device design parameters such as the spacing L G between the silicon-carbon alloy stressors, the carbon mole fraction in the stressors and stressor depth were investigated. Reducing the stressor spacing L G or increasing the carbon mole fraction in the stressors and stressor depth increases the magnitude of the vertical compressive stress and the lateral tensile stress in the portion of the N channel region where the inversion charge resides. This is beneficial for improving the electron mobility in n-channel metal-oxide-semiconductor transistors. A simple guiding principle for an optimum combination of the above-mentioned device design parameters in terms of mobility enhancement, drain current enhancement and the tradeoff consideration for junction leakage current degradation

  6. Water-use strategies of six co-existing Mediterranean woody species during a summer drought

    NARCIS (Netherlands)

    Quero, J.L.; Sterck, F.J.; Martínez-Vilalta, J.; Villar, R.

    2011-01-01

    Drought stress is known to limit plant performance in Mediterranean-type ecosystems. We have investigated the dynamics of the hydraulics, gas exchange and morphology of six co-existing Mediterranean woody species growing under natural field conditions during a drought that continued during the

  7. The interaction of fatigue cracks with a residual stress field using thermoelastic stress analysis and synchrotron X-ray diffraction experiments

    Science.gov (United States)

    Amjad, Khurram; Asquith, David; Sebastian, Christopher M.; Wang, Wei-Chung

    2017-01-01

    This article presents an experimental study on the fatigue behaviour of cracks emanating from cold-expanded holes utilizing thermoelastic stress analysis (TSA) and synchrotron X-ray diffraction (SXRD) techniques with the aim of resolving the long-standing ambiguity in the literature regarding potential relaxation, or modification, of beneficial compressive residual stresses as a result of fatigue crack propagation. The crack growth rates are found to be substantially lower as the crack tip moved through the residual stress zone induced by cold expansion. The TSA results demonstrated that the crack tip plastic zones were reduced in size by the presence of the residual compressive stresses induced by cold expansion. The crack tip plastic zones were found to be insignificant in size in comparison to the residual stress zone resulting from cold expansion, which implied that they were unlikely to have had a notable impact on the surrounding residual stresses induced by cold expansion. The residual stress distributions measured along the direction of crack growth, using SXRD, showed no signs of any significant stress relaxation or redistribution, which validates the conclusions drawn from the TSA data. Fractographic analysis qualitatively confirmed the influence on crack initiation of the residual stresses induced by the cold expansion. It was found that the application of single compressive overload caused a relaxation, or reduction in the residual stresses, which has wider implications for improving the fatigue life. PMID:29291095

  8. Fast algorithms for evaluating the stress field of dislocation lines in anisotropic elastic media

    Science.gov (United States)

    Chen, C.; Aubry, S.; Oppelstrup, T.; Arsenlis, A.; Darve, E.

    2018-06-01

    In dislocation dynamics (DD) simulations, the most computationally intensive step is the evaluation of the elastic interaction forces among dislocation ensembles. Because the pair-wise interaction between dislocations is long-range, this force calculation step can be significantly accelerated by the fast multipole method (FMM). We implemented and compared four different methods in isotropic and anisotropic elastic media: one based on the Taylor series expansion (Taylor FMM), one based on the spherical harmonics expansion (Spherical FMM), one kernel-independent method based on the Chebyshev interpolation (Chebyshev FMM), and a new kernel-independent method that we call the Lagrange FMM. The Taylor FMM is an existing method, used in ParaDiS, one of the most popular DD simulation softwares. The Spherical FMM employs a more compact multipole representation than the Taylor FMM does and is thus more efficient. However, both the Taylor FMM and the Spherical FMM are difficult to derive in anisotropic elastic media because the interaction force is complex and has no closed analytical formula. The Chebyshev FMM requires only being able to evaluate the interaction between dislocations and thus can be applied easily in anisotropic elastic media. But it has a relatively large memory footprint, which limits its usage. The Lagrange FMM was designed to be a memory-efficient black-box method. Various numerical experiments are presented to demonstrate the convergence and the scalability of the four methods.

  9. Measuring the stress field around an evolving crack in tensile deformed Mg AZ31 using three-dimensional X-ray diffraction

    DEFF Research Database (Denmark)

    Oddershede, Jette; Camin, Bettina; Schmidt, Søren

    2012-01-01

    The stress field around a notch in a coarse grained Mg AZ31 sample has been measured under tensile load using the individual grains as probes in an in situ high energy synchrotron diffraction experiment. The experimental set-up, a variant of three-dimensional X-ray diffraction microscopy, allows...... the position, orientation and full stress tensor of each illuminated grain to be determined and, hence, enables the study of evolving stress fields in coarse grained materials with a spatial resolution equal to the grain size. Grain resolved information like this is vital for understanding what happens when...... the traditional continuum mechanics approach breaks down and fracture is governed by local heterogeneities (e.g. phase or stress differences) between grains. As a first approximation the results obtained were averaged through the thickness of the sample and compared with an elastic–plastic continuum finite...

  10. Rotating shallow water modeling of planetary,astrophysical and plasma vortical structures (plasma transport across a magnetic field,model of the jupiter's GRS, prediction of existence of giant vortices in spiral galaxies

    Directory of Open Access Journals (Sweden)

    M. V. Nezlin

    1999-01-01

    Full Text Available Three kinds of results have been described in this paper. Firstly, an experimental study of the Rossby vortex meridional drift on the rotating shallow water has been carried out. Owing to the stringent physical analogy between the Rossby vortices and drift vortices in the magnetized plasma, the results obtained have allowed one to make a conclusion that the transport rate of the plasma, trapped by the drift vortices, across the magnetic field is equivalent to the “gyro-Bohm” diffusion coefficient. Secondly, a model of big vortices of the type of the Great Red Spot of Jupiter, dominating in the atmospheres of the outer planets, has been produced. Thirdly, the rotating shallow water modeling has been carried out of the hydrodynamical generation mechanism of spiral structures in galaxies. Trailing spiral waves of various azimuthal modes, generated by a shear flow between fast rotating “nucleus” and slow rotating periphery, were produced. The spirals are similar to those existing in the real galaxies. The hydrodynamical concept of the spiral structure formation in galaxies has been substantiated. Strong anticyclonic vortices between the spiral arms of the structures under study have been discovered for the first time. The existence of analogous vortices in real galaxies has been predicted. (This prediction has been reliably confirmed recently in special astronomical observations, carried out on the basis of the mentioned laboratory modeling and the prediction made – see the paper by A. Fridman et al. (Astrophysics and Space Science, 1997, 252, 115.

  11. Stress and strain field singularities, micro-cracks, and their role in failure initiation at the composite laminate free-edge

    Science.gov (United States)

    Dustin, Joshua S.

    A state-of-the-art multi-scale analysis was performed to predict failure initiation at the free-edge of an angle-ply laminate using the Strain Invariant Failure Theory (SIFT), and multiple improvements to this analysis methodology were proposed and implemented. Application of this analysis and theory led to the conclusion that point-wise failure criteria which ignore the singular stress and strain fields from a homogenized analysis and the presence of free-edge damage in the form of micro-cracking, may do so at the expense of failure prediction capability. The main contributions of this work then are made in the study of the laminate free-edge singularity and in the effects of micro-cracking at the composite laminate free-edge. Study of both classical elasticity and finite element solutions of the laminate free-edge stress field based upon the assumption of homogenized lamina properties reveal that the order of the free-edge singularity is sufficiently small such that the domain of dominance of this term away from the laminate free-edge is much smaller than the relevant dimensions of the microstructure. In comparison to a crack-tip field, these free-edge singularities generate stress and strain fields which are half as intense as those at the crack-tip, leading to the conclusion that existing flaws at the free-edge in the form of micro-cracks would be more prone to the initiation of free-edge failure than the existence of a singularity in the free-edge elasticity solutions. A methodical experiment was performed on a family of [±25°/90°] s laminates made of IM7/8552 carbon/epoxy composite, to both characterize micro-cracks present at the laminate free-edge and to study their behavior under the application of a uniform extensional load. The majority of these micro-cracks were of length on the order of a few fiber diameters, though larger micro-cracks as long as 100 fiber diameters were observed in thicker laminates. A strong correlation between the application of

  12. Artificial intelligence analysis of hyperspectral remote sensing data for management of water, weed, and nitrogen stresses in corn fields

    Science.gov (United States)

    Waheed, Tahir

    This study investigated the possibility of using ground-based remotely sensed hyperspectral observations with a special emphasis on detection of water, weed and nitrogen stresses contributing towards in-season decision support for precision crop management (PCM). A three factor split-split-plot experiment, with four randomized blocks as replicates, was established during the growing seasons of 2003 and 2004. Corn (Zea mays L.) hybrid DKC42-22 was grown because this hybrid is a good performer on light soils in Quebec. There were twelve 12 x 12m plots in a block (one replication per treatment per block) and the total number of plots was 48. Water stress was the main factor in the experiment. A drip irrigation system was laid out and each block was split into irrigated and non-irrigated halves. The second main factor of the experiment was weeds with two levels i.e. full weed control and no weed control. Weed treatments were assigned randomly by further splitting the irrigated and non-irrigated sub-blocks into two halves. Each of the weed treatments was furthermore split into three equal sub-sub-plots for nitrogen treatments (third factor of the experiment). Nitrogen was applied at three levels i.e. 50, 150 and 250 kg N ha-1 (Quebec norm is between 120-160 kg N ha-1). The hyperspectral data were recorded (spectral resolution = 1 nm) mid-day (between 1000 and 1400 hours) with a FieldSpec FR spectroradiometer over a spectral range of 400-2500 run at three growth stages namely: early growth, tasseling and full maturity, in each of the growing season. There are two major original contributions in this thesis: First is the development of a hyperspectral data analysis procedure for separating visible (400-700 nm), near-infrared (700-1300 nm) and mid-infrared (1300-2500 nm) regions of the spectrum for use in discriminant analysis procedure. In addition, of all the spectral band-widths analyzed, seven waveband-aggregates were identified using STEPDISC procedure, which were the

  13. fields

    Directory of Open Access Journals (Sweden)

    Brad J. Arnold

    2014-07-01

    Full Text Available Surface irrigation, such as flood or furrow, is the predominant form of irrigation in California for agronomic crops. Compared to other irrigation methods, however, it is inefficient in terms of water use; large quantities of water, instead of being used for crop production, are lost to excess deep percolation and tail runoff. In surface-irrigated fields, irrigators commonly cut off the inflow of water when the water advance reaches a familiar or convenient location downfield, but this experience-based strategy has not been very successful in reducing the tail runoff water. Our study compared conventional cutoff practices to a retroactively applied model-based cutoff method in four commercially producing alfalfa fields in Northern California, and evaluated the model using a simple sensor system for practical application in typical alfalfa fields. These field tests illustrated that the model can be used to reduce tail runoff in typical surface-irrigated fields, and using it with a wireless sensor system saves time and labor as well as water.

  14. Simulation of three-dimensional tectonic stress fields and quantitative prediction of tectonic fracture within the Damintun Depression, Liaohe Basin, northeast China

    Science.gov (United States)

    Guo, Peng; Yao, Leihua; Ren, Desheng

    2016-05-01

    Tectonic fractures are important factors that influence oil and natural gas migration and accumulation within "buried hill" reservoirs. To obtain a quantitative forecast of the development and distribution of reservoir fractures in the Damintun Depression, we analyzed the characteristics of regional structural evolution and paleotectonic stress field setting. A reasonable geological model of the research area was built based on an interpretation of the geological structure, a test for rock mechanics, and experiment on acoustic emission. Thereafter, a three-dimensional paleotectonic stress field during the Yanshan movement was simulated by the finite element method. Rock failure criterion and comprehensive evaluation coefficient of fractures were used to determine the quantitative development of fractures and predict zones that are prone to fracture development. Under an intense Yanshan movement, high stress strength is distributed in the south and northeast parts of the study area, where stress is extremely high. The fracture development zones are mainly controlled by the tectonic stress field and typically located in the same areas as those of high maximum principal and shear stresses. The predicted areas with developed fractures are consistent with the wells with high fracture linear density and in locations with high-producing oil and gas wells.

  15. Stress Characterization of 4H-SiC Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) using Raman Spectroscopy and the Finite Element Method.

    Science.gov (United States)

    Yoshikawa, Masanobu; Kosaka, Kenichi; Seki, Hirohumi; Kimoto, Tsunenobu

    2016-07-01

    We measured the depolarized and polarized Raman spectra of a 4H-SiC metal-oxide-semiconductor field-effect transistor (MOSFET) and found that compressive stress of approximately 20 MPa occurs under the source and gate electrodes and tensile stress of approximately 10 MPa occurs between the source and gate electrodes. The experimental result was in close agreement with the result obtained by calculation using the finite element method (FEM). A combination of Raman spectroscopy and FEM provides much data on the stresses in 4H-SiC MOSFET. © The Author(s) 2016.

  16. Total antioxidant capacity, total oxidant status and oxidative stress index in the men exposed to 1.5 T static magnetic field.

    Science.gov (United States)

    Sirmatel, O; Sert, C; Sirmatel, F; Selek, S; Yokus, B

    2007-06-01

    The aim of this study was to investigate the effects of a high-strength magnetic field produced by a magnetic resonance imaging (MRI) apparatus on oxidative stress. The effects of a 1.5 T static magnetic field on the total antioxidant capacity (TAC), total oxidant status (TOS) and oxidative stress index (OSI) in male subjects were investigated. In this study, 33 male volunteers were exposed to a 1.5 T static magnetic field for a short time and the TAC, TOS and OSI of each subject were determined. Magnetic field exposure was provided using a magnetic resonance apparatus; radiofrequency was not applied. Blood samples were taken from subjects and TAC, TOS and OSI values were measured using the methods of Erel. TAC showed a significant increase in post-exposures compared to pre-exposures to the magnetic field (p < 0.05). OSI and TOS showed a significant decrease in post-exposures compared to pre-exposures to a 1.5 T magnetic field (for each of two, p < 0.01). The 1.5 T static magnetic field used in the MRI apparatus did not yield a negative effect; on the contrary, it produced the positive effect of decreasing oxidative stress in men following short-term exposure.

  17. Spatial learning, monoamines and oxidative stress in rats exposed to 900 MHz electromagnetic field in combination with iron overload.

    Science.gov (United States)

    Maaroufi, Karima; Had-Aissouni, Laurence; Melon, Christophe; Sakly, Mohsen; Abdelmelek, Hafedh; Poucet, Bruno; Save, Etienne

    2014-01-01

    The increasing use of mobile phone technology over the last decade raises concerns about the impact of high frequency electromagnetic fields (EMF) on health. More recently, a link between EMF, iron overload in the brain and neurodegenerative disorders including Parkinson's and Alzheimer's diseases has been suggested. Co-exposure to EMF and brain iron overload may have a greater impact on brain tissues and cognitive processes than each treatment by itself. To examine this hypothesis, Long-Evans rats submitted to 900 MHz exposure or combined 900 MHz EMF and iron overload treatments were tested in various spatial learning tasks (navigation task in the Morris water maze, working memory task in the radial-arm maze, and object exploration task involving spatial and non spatial processing). Biogenic monoamines and metabolites (dopamine, serotonin) and oxidative stress were measured. Rats exposed to EMF were impaired in the object exploration task but not in the navigation and working memory tasks. They also showed alterations of monoamine content in several brain areas but mainly in the hippocampus. Rats that received combined treatment did not show greater behavioral and neurochemical deficits than EMF-exposed rats. None of the two treatments produced global oxidative stress. These results show that there is an impact of EMF on the brain and cognitive processes but this impact is revealed only in a task exploiting spontaneous exploratory activity. In contrast, there are no synergistic effects between EMF and a high content of iron in the brain. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Performance enhancement in uniaxially tensile stressed GeSn n-channel fin tunneling field-effect transistor: Impact of stress direction

    Science.gov (United States)

    Wang, Hongjuan; Han, Genquan; Jiang, Xiangwei; Liu, Yan; Zhang, Chunfu; Zhang, Jincheng; Hao, Yue

    2017-04-01

    In this work, the boosting effect on the performance of GeSn n-channel fin tunneling FET (nFinTFET) enabled by uniaxial tensile stress is investigated theoretically. As the fin rotates within the (001) plane, the uniaxial tensile stress is always along its direction. The electrical characteristics of tensile-stressed GeSn nFinTFETs with point and line tunneling modes are computed utilizing the technology computer aided design (TCAD) simulator in which the dynamic nonlocal band-to-band tunneling (BTBT) algorithm is employed. In comparison with the relaxed devices, tensile-stressed GeSn nFinTFETs achieve a substantial enhancement in band-to-band tunneling generation rate (G BTBT) and on-state current I ON owing to the reduced bandgap E G induced by the tensile stress. Performance improvement of GeSn nFinTFETs induced by tensile stress demonstrates a strong dependence on channel direction and tunneling modes. Under the same magnitude of stress, line-nFinTFETs obtain a more pronounced I ON enhancement over the transistors with point tunneling mode.

  19. Satellite-based mapping of field-scale stress indicators for crop yield forecasting: an application over Mead, NE

    Science.gov (United States)

    Yang, Y.; Anderson, M. C.; Gao, F.; Wardlow, B.; Hain, C.; Otkin, J.; Sun, L.; Dulaney, W.

    2017-12-01

    In agricultural regions, water is one of the most widely limiting factors of crop performance and production. Evapotranspiration (ET) describes crop water use through transpiration and water lost through direct soil evaporation, which makes it a good indicator of soil moisture availability and vegetation health and thus has been an integral part of many yield estimation efforts. The Evaporative Stress Index (ESI) describes temporal anomalies in a normalized evapotranspiration metric (fRET) as derived from satellite remote sensing and has demonstrated capacity to explain regional yield variability in water limited crop growing regions. However, its performance in some regions where the vegetation cycle is intensively managed appears to be degraded. In this study we generated maps of ET, fRET, and ESI at high spatiotemporal resolution (30-m pixels, daily timesteps) using a multi-sensor data fusion method, integrating information from satellite platforms with good temporal coverage and other platforms that provide field-scale spatial detail. The study was conducted over the period 2010-2014, covering a region around Mead, Nebraska that includes both rainfed and irrigated crops. Correlations between ESI and measurements of corn yield are investigated at both the field and county level to assess the value of ESI as a yield forecasting tool. To examine the role of phenology in ESI-yield correlations, annual input fRET timeseries were aligned by both calendar day and by biophysically relevant dates (e.g. days since planting or emergence). Results demonstrate that mapping of fRET and ESI at 30-m has the advantage of being able to resolve different crop types with varying phenology. The study also suggests that incorporating phenological information significantly improves yield-correlations by accounting for effects of phenology such as variable planting date and emergence date. The yield-ESI relationship in this study well captures the inter-annual variability of yields

  20. Possible relationship between the stress-induced synaptic response and metaplasticity in the hippocampal CA1 field of freely moving rats.

    Science.gov (United States)

    Hirata, Riki; Matsumoto, Machiko; Judo, Chika; Yamaguchi, Taku; Izumi, Takeshi; Yoshioka, Mitsuhiro; Togashi, Hiroko

    2009-07-01

    Hippocampal long-term potentiation (LTP) is suppressed not only by stress paradigms but also by low frequency stimulation (LFS) prior to LTP-inducing high frequency stimulation (HFS; tetanus), termed metaplasticity. These synaptic responses are dependent on N-methyl-D-aspartate receptors, leading to speculations about the possible relationship between metaplasticity and stress-induced LTP impairment. However, the functional significance of metaplasticity has been unclear. The present study elucidated the electrophysiological and neurochemical profiles of metaplasticity in the hippocampal CA1 field, with a focus on the synaptic response induced by the emotional stress, contextual fear conditioning (CFC). The population spike amplitude in the CA1 field was decreased during exposure to CFC, and LTP induction was suppressed after CFC in conscious rats. The synaptic response induced by CFC was mimicked by LFS, i.e., LFS impaired the synaptic transmission and subsequent LTP. Plasma corticosterone levels were increased by both CFC and LFS. Extracellular levels of gamma-aminobutyric acid (GABA), but not glutamate, in the hippocampus increased during exposure to CFC or LFS. Furthermore, electrical stimulation of the medial prefrontal cortex (mPFC), which caused decreases in freezing behavior during exposure to CFC, counteracted the LTP impairment induced by LFS. These findings suggest that metaplasticity in the rat hippocampal CA1 field is related to the neural basis of stress experience-dependent fear memory, and that hippocampal synaptic response associated stress-related processes is under mPFC regulation.

  1. A new method of fully three dimensional analysis of stress field in the soil layer of a soil-mantled hillslope

    Science.gov (United States)

    Wu, Y. H.; Nakakita, E.

    2017-12-01

    Hillslope stability is highly related to stress equilibrium near the top surface of soil-mantled hillslopes. Stress field in a hillslope can also be significantly altered by variable groundwater motion under the rainfall influence as well as by different vegetation above and below the slope. The topographic irregularity, biological effects from vegetation and variable rainfall patterns couple with others to make the prediction of shallow landslide complicated and difficult. In an increasing tendency of extreme rainfall, the mountainous area in Japan has suffered more and more shallow landslides. To better assess shallow landslide hazards, we would like to develop a new mechanically-based method to estimate the fully three-dimensional stress field in hillslopes. The surface soil-layer of hillslope is modelled as a poroelastic medium, and the tree surcharge on the slope surface is considered as a boundary input of stress forcing. The modelling of groundwater motion is involved to alter effective stress state in the soil layer, and the tree root-reinforcement estimated by allometric equations is taken into account for influencing the soil strength. The Mohr-Coulomb failure theory is then used for locating possible yielding surfaces, or says for identifying failure zones. This model is implemented by using the finite element method. Finally, we performed a case study of the real event of massive shallow landslides occurred in Hiroshima in August, 2014. The result shows good agreement with the field condition.

  2. A new procedure for investigating three-dimensional stress fields in a thin plate with a through-the-thickness crack

    Science.gov (United States)

    Yi, Dake; Wang, TzuChiang

    2018-06-01

    In the paper, a new procedure is proposed to investigate three-dimensional fracture problems of a thin elastic plate with a long through-the-thickness crack under remote uniform tensile loading. The new procedure includes a new analytical method and high accurate finite element simulations. In the part of theoretical analysis, three-dimensional Maxwell stress functions are employed in order to derive three-dimensional crack tip fields. Based on the theoretical analysis, an equation which can describe the relationship among the three-dimensional J-integral J( z), the stress intensity factor K( z) and the tri-axial stress constraint level T z ( z) is derived first. In the part of finite element simulations, a fine mesh including 153360 elements is constructed to compute the stress field near the crack front, J( z) and T z ( z). Numerical results show that in the plane very close to the free surface, the K field solution is still valid for in-plane stresses. Comparison with the numerical results shows that the analytical results are valid.

  3. Deformation correlations, stress field switches and evolution of an orogenic intersection: The Pan-African Kaoko-Damara orogenic junction, Namibia

    Directory of Open Access Journals (Sweden)

    Ben Goscombe

    2017-11-01

    Full Text Available Age calibrated deformation histories established by detailed mapping and dating of key magmatic time markers are correlated across all tectono-metamorphic provinces in the Damara Orogenic System. Correlations across structural belts result in an internally consistent deformation framework with evidence of stress field rotations with similar timing, and switches between different deformation events. Horizontal principle compressive stress rotated clockwise ∼180° in total during Kaoko Belt evolution, and ∼135° during Damara Belt evolution. At most stages, stress field variation is progressive and can be attributed to events within the Damara Orogenic System, caused by changes in relative trajectories of the interacting Rio De La Plata, Congo, and Kalahari Cratons. Kaokoan orogenesis occurred earliest and evolved from collision and obduction at ∼590 Ma, involving E–W directed shortening, progressing through different transpressional states with ∼45° rotation of the stress field to strike-slip shear under NW–SE shortening at ∼550–530 Ma. Damaran orogenesis evolved from collision at ∼555–550 Ma with NW–SE directed shortening in common with the Kaoko Belt, and subsequently evolved through ∼90° rotation of the stress field to NE–SW shortening at ∼512–508 Ma. Both Kaoko and Damara orogenic fronts were operating at the same time, with all three cratons being coaxially convergent during the 550–530 Ma period; Rio De La Plata directed SE against the Congo Craton margin, and both together over-riding the Kalahari Craton margin also towards the SE. Progressive stress field rotation was punctuated by rapid and significant switches at ∼530–525 Ma, ∼508 Ma and ∼505 Ma. These three events included: (1 Culmination of main phase orogenesis in the Damara Belt, coinciding with maximum burial and peak metamorphism at 530–525 Ma. This occurred at the same time as termination of transpression and initiation of

  4. Magnetic small-angle scattering of subthermal neutrons by internal stress fields in work-hardened nickel single crystals oriented for multiple glide

    International Nuclear Information System (INIS)

    Vorbrugg, W.; Schaerpf, O.

    1975-01-01

    The small-angle scattering of Ni single crystals with (111) and (100) axis orientation is measured by a photographic method in the work-hardened state after tensile deformation. Parameters are the external magnetic field H parallel to the axis (600 2 ]<=8,8), and the elastic stress tausub(el)(0<=tausub(el)<=tausub(pl)) applied to the deformed crystals during the experiments. The scattering is found to be anisotropic and characteristic for the chosen orientation. The quantitative photometric analysis shows that the parameters mentioned above only influence the intensity but not the distribution of the scattered neutrons. The scattering increases with the elastic stress and decreases with the magnetic field. In particular, in the unloaded state there is a linear relation between the scattered intensity and the plastic shear stress. (author)

  5. Does the low hole transport mass in and Si nanowires lead to mobility enhancements at high field and stress: A self-consistent tight-binding study

    Science.gov (United States)

    Kotlyar, R.; Linton, T. D.; Rios, R.; Giles, M. D.; Cea, S. M.; Kuhn, K. J.; Povolotskyi, Michael; Kubis, Tillmann; Klimeck, Gerhard

    2012-06-01

    The hole surface roughness and phonon limited mobility in the silicon , , and square nanowires under the technologically important conditions of applied gate bias and stress are studied with the self-consistent Poisson-sp3d5s*-SO tight-binding bandstructure method. Under an applied gate field, the hole carriers in a wire undergo a volume to surface inversion transition diminishing the positive effects of the high and valence band nonparabolicities, which are known to lead to the large gains of the phonon limited mobility at a zero field in narrow wires. Nonetheless, the hole mobility in the unstressed wires down to the 5 nm size remains competitive or shows an enhancement at high gate field over the large wire limit. Down to the studied 3 nm sizes, the hole mobility is degraded by strong surface roughness scattering in and wires. The channels are shown to experience less surface scattering degradation. The physics of the surface roughness scattering dependence on wafer and channel orientations in a wire is discussed. The calculated uniaxial compressive channel stress gains of the hole mobility are found to reduce in the narrow wires and at the high field. This exacerbates the stressed mobility degradation with size. Nonetheless, stress gains of a factor of 2 are obtained for wires down to 3 nm size at a 5×1012 cm-2 hole inversion density per gate area.

  6. Field and polarity dependence of time-to-resistance increase in Fe-O films studied by constant voltage stress method

    International Nuclear Information System (INIS)

    Eriguchi, Koji; Ohta, Hiroaki; Ono, Kouichi; Wei Zhiqiang; Takagi, Takeshi

    2009-01-01

    Constant voltage stress (CVS) was applied to Fe-O films prepared by a sputtering process to investigate a stress-induced resistance increase leading to a fundamental mechanism for switching behaviors. Under the CVS, an abrupt resistance increase was found for both stress polarities. A conduction mechanism after the resistance increase exhibited non-Ohmic transport. The time-to-resistance increase (t r ) under the CVS was revealed to strongly depend on stress voltage as well as the polarity. From a polarity-dependent resistance increase determined by a time-zero measurement, the voltage and polarity-dependent t r were discussed on the basis of field- and structure-enhanced thermochemical reaction mechanisms

  7. The exponential rise of induced seismicity with increasing stress levels in the Groningen gas field and its implications for controlling seismic risk

    Science.gov (United States)

    Bourne, S. J.; Oates, S. J.; van Elk, J.

    2018-06-01

    Induced seismicity typically arises from the progressive activation of recently inactive geological faults by anthropogenic activity. Faults are mechanically and geometrically heterogeneous, so their extremes of stress and strength govern the initial evolution of induced seismicity. We derive a statistical model of Coulomb stress failures and associated aftershocks within the tail of the distribution of fault stress and strength variations to show initial induced seismicity rates will increase as an exponential function of induced stress. Our model provides operational forecasts consistent with the observed space-time-magnitude distribution of earthquakes induced by gas production from the Groningen field in the Netherlands. These probabilistic forecasts also match the observed changes in seismicity following a significant and sustained decrease in gas production rates designed to reduce seismic hazard and risk. This forecast capability allows reliable assessment of alternative control options to better inform future induced seismic risk management decisions.

  8. A new solution of Einstein's vacuum field equations

    Indian Academy of Sciences (India)

    The motivation for the new solution ensues ... terms of singularity, does not seem to work universally as there also exist other solutions of eq. ..... the field equations and not necessarily a contribution to the energy–stress tensor, rather just.

  9. Fabrication of artificial arteriovenous fistula and analysis of flow field and shear stress by using μ-PIV technology

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sun Cheol; Kim, Hyun Kyu [Div. of Vascular Surgery, Dept. of Surgery, College of Medicine, The Catholic University of Korea, Seoul (Korea, Republic of); Song, Ryun Geun; Kim, Sun Ho; Lee, Jin Kee [School of Mechanical Engineering, Sungkyunkwan University, Suwon (Korea, Republic of); Kim, Seung Hyun [School of Engineering, Brown University, Providence (United States)

    2016-12-15

    Radio-cephalic arteriovenous fistula (RC-AVF) is an operation performed to achieve vascular access for hemodialysis. Although RC-AVF is a reliable and well-known method, this technique presents high rates of early failure depending on the vessel condition. These failures are due to blood shear stress around the anastomosis site and the vascular access failure caused by thrombosis secondary to stenosis formation, as well as vascular access reocclusion after percutaneous interventions. In this work, we fabricate in vitro 3D RC-AVF by using polydimethylsiloxane and 3D printing technology to understand the underlying mechanism and predict AVF failure. Micro- Particle image velocimetry (μ-PIV) focusing on the cardiac pulse cycle is used to measure the velocity field within the artificial blood vessel. Results are confirmed by numerical simulation. Accordingly, the in vitro AVF model agrees well with the simulations. Overall, this research would provide the future possibility of using the proposed method to reduce in vivo AVF failure for various conditions.

  10. Effect of perphenazine enanthate on open-field test behaviour and stress-induced hyperthermia in domestic sheep.

    Science.gov (United States)

    Pedernera-Romano, Cecilia; Ruiz de la Torre, José L; Badiella, Llorenç; Manteca, Xavier

    2010-01-01

    The open-field test (OFT) and stress-induced hyperthermia (SIH) have been used to measure individual differences in fear. The present study has been designed as a pharmacological validation of OFT and SIH as indicators of fear in sheep using perphenazine enanthate (PPZ), a long-acting neuroleptic. Twenty four ewes of two breeds, Lacaune and Ripollesa, were tested in an arena measuring 5mx2.5m. Treatment group received one dose of 1.5mg/kg of PPZ and control group received sterile sesame oil. All animals were tested for 10min and behaviours were recorded. Rectal temperature was measured at the beginning (T1) and at the end (T2) of the test. SIH was defined as the difference between T2 and T1. Sheep were tested on days 1, 2, 3, 4, 7 and 9 after PPZ injection. Variables were analysed using a mixed model. PPZ decreased bleats on days 2, 3, 4 and the SIH response on days 2 and 3. Breed differences were observed. Treated animals showed positive correlations between SIH and bleats; squares entered; attempts to escape and negative correlation between SIH and visits to the food bucket. Our results suggest that behaviour and SIH on the OFT are useful measures of fear in sheep.

  11. Universal model of bias-stress-induced instability in inkjet-printed carbon nanotube networks field-effect transistors

    Science.gov (United States)

    Jung, Haesun; Choi, Sungju; Jang, Jun Tae; Yoon, Jinsu; Lee, Juhee; Lee, Yongwoo; Rhee, Jihyun; Ahn, Geumho; Yu, Hye Ri; Kim, Dong Myong; Choi, Sung-Jin; Kim, Dae Hwan

    2018-02-01

    We propose a universal model for bias-stress (BS)-induced instability in the inkjet-printed carbon nanotube (CNT) networks used in field-effect transistors (FETs). By combining two experimental methods, i.e., a comparison between air and vacuum BS tests and interface trap extraction, BS instability is explained regardless of either the BS polarity or ambient condition, using a single platform constituted by four key factors: OH- adsorption/desorption followed by a change in carrier concentration, electron concentration in CNT channel corroborated with H2O/O2 molecules in ambient, charge trapping/detrapping, and interface trap generation. Under negative BS (NBS), the negative threshold voltage shift (ΔVT) is dominated by OH- desorption, which is followed by hole trapping in the interface and/or gate insulator. Under positive BS (PBS), the positive ΔVT is dominated by OH- adsorption, which is followed by electron trapping in the interface and/or gate insulator. This instability is compensated by interface trap extraction; PBS instability is slightly more complicated than NBS instability. Furthermore, our model is verified using device simulation, which gives insights on how much each mechanism contributes to BS instability. Our result is potentially useful for the design of highly stable CNT-based flexible circuits in the Internet of Things wearable healthcare era.

  12. Measuring the stress field around an evolving crack in tensile deformed Mg AZ31 using three-dimensional X-ray diffraction

    International Nuclear Information System (INIS)

    Oddershede, Jette; Camin, Bettina; Schmidt, Søren; Mikkelsen, Lars P.; Sørensen, Henning Osholm; Lienert, Ulrich; Poulsen, Henning Friis; Reimers, Walter

    2012-01-01

    The stress field around a notch in a coarse grained Mg AZ31 sample has been measured under tensile load using the individual grains as probes in an in situ high energy synchrotron diffraction experiment. The experimental set-up, a variant of three-dimensional X-ray diffraction microscopy, allows the position, orientation and full stress tensor of each illuminated grain to be determined and, hence, enables the study of evolving stress fields in coarse grained materials with a spatial resolution equal to the grain size. Grain resolved information like this is vital for understanding what happens when the traditional continuum mechanics approach breaks down and fracture is governed by local heterogeneities (e.g. phase or stress differences) between grains. As a first approximation the results obtained were averaged through the thickness of the sample and compared with an elastic–plastic continuum finite element simulation. It was found that a full three-dimensional simulation was required to account for the measured transition from the overall plane stress case away from the notch to the essentially plane strain case observed near the notch tip. The measured and simulated stress contours were shown to be in good agreement except at the highest applied load, at which stress relaxation at the notch tip was observed in the experimental data. This stress relaxation is attributed to the initiation and propagation of a crack. Finally, it was demonstrated that the measured lattice rotations could be used as a qualitative measure of the shape and extent of the plastic deformation zone.

  13. A full-field residual stress estimation scheme for fitness-for-service assessment of pipe girth welds: Part II – A shell theory based implementation

    International Nuclear Information System (INIS)

    Song, Shaopin; Dong, Pingsha; Pei, Xianjun

    2015-01-01

    With the two key controlling parameters identified and their effectiveness demonstrated in Part I of this study series for constructing a continuous residual stress profile at weld region, a classical shell theory based model is proposed in this paper (Part II) for describing through-thickness residual stress distributions of both axial and hoop components at any axial location beyond weld region. The shell theory based model is analytically constructed through an assembly of two parts: One represents weld region and the other represents the remaining component section away from weld. The final assembly of the two parts leads to a closed form solution to both axial and hoop residual stress components as a function of axial distance from weld toe position. The effectiveness of the full-field residual stress estimation scheme is demonstrated by comparing with a series of finite element modeling results over a broad range of pipe weld geometries and welding conditions. The present development should provide a consistent and effective means for estimating through-thickness residual stress profile as a continuous function of pipe geometry, welding heat input, as well as material characteristics. - Highlights: • A shell theory based two-part assembly model is developed for generalizing residual stress distributions. • A full-field estimation of through-thickness residual stress profiles can be achieved. • The proposed estimation scheme offers both consistency and mechanics basis in residual stress profile generation. • An estimation scheme for welding-induced plastic zone size is proposed and validated. • The shell theory based estimation scheme can also provide a reasonable estimate on distortion in radial direction

  14. Effects of 60 Hz electric fields on operant and social stress behavior of nonhuman primates. Quarterly technical progress report No. 20, September 28-December 20, 1985

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, W.R.

    1986-01-03

    This research program will evaluate the aversive character of exposure to 60 Hz electric fields by determining the threshold intensity which produces avoidance or escape responses, will estimate the threshold intensity for detection of 60 Hz electric fields, will assess effects of chronic exposure to 60 Hz electric fields on the performance of two operant conditioning tasks, fixed ratio and differential reinforcement of low rate responding, will investigate, using the systematic quantitative observational sampling methods of primatology, the possible stress-inducing effects of chronic exposure to 60 Hz electric fields on the behavior of baboons living in small social groups. In all experiments, the electric fields will be described, characterized, and controlled to account for recognized artifacts associated with high intensity 60 Hz electric fields and the health of all subjects will be described using the methods of primate veterinary medicine.

  15. Why preeclampsia still exists?

    Science.gov (United States)

    Chelbi, Sonia T; Veitia, Reiner A; Vaiman, Daniel

    2013-08-01

    Preeclampsia (PE) is a deadly gestational disease affecting up to 10% of women and specific of the human species. Preeclampsia is clearly multifactorial, but the existence of a genetic basis for this disease is now clearly established by the existence of familial cases, epidemiological studies and known predisposing gene polymorphisms. PE is very common despite the fact that Darwinian pressure should have rapidly eliminated or strongly minimized the frequency of predisposing alleles. Consecutive pregnancies with the same partner decrease the risk and severity of PE. Here, we show that, due to this peculiar feature, preeclampsia predisposing-alleles can be differentially maintained according to the familial structure. Thus, we suggest that an optimal frequency of PE-predisposing alleles in human populations can be achieved as a result of a trade-off between benefits of exogamy, importance for maintaining genetic diversity and increase of the fitness owing to a stable paternal investment. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Existence of Projective Planes

    OpenAIRE

    Perrott, Xander

    2016-01-01

    This report gives an overview of the history of finite projective planes and their properties before going on to outline the proof that no projective plane of order 10 exists. The report also investigates the search carried out by MacWilliams, Sloane and Thompson in 1970 [12] and confirms their result by providing independent verification that there is no vector of weight 15 in the code generated by the projective plane of order 10.

  17. Does bioethics exist?

    Science.gov (United States)

    Turner, L

    2009-12-01

    Bioethicists disagree over methods, theories, decision-making guides, case analyses and public policies. Thirty years ago, the thinking of many scholars coalesced around a principlist approach to bioethics. That mid-level mode of moral reasoning is now one of many approaches to moral deliberation. Significant variation in contemporary approaches to the study of ethical issues related to medicine, biotechnology and health care raises the question of whether bioethics exists as widely shared method, theory, normative framework or mode of moral reasoning.

  18. Coercivity and induced magnetic anisotropy by stress and/or field annealing in Fe- and Co- based (Finemet-type) amorphous alloys

    International Nuclear Information System (INIS)

    Miguel, C.; Zhukov, A.; Val, J.J. del; Gonzalez, J.

    2005-01-01

    Uniaxial magnetic anisotropy has been induced in amorphous Fe 73.5 Cu 1 Nb 3 Si 15.5 B 7 (Fe-rich) and (Co 77 Si 13.5 B 9.5 ) 90 Fe 7 Nb 3 (Co-rich) ferromagnetic alloys by annealing under stress and/or magnetic field. Such anisotropy plays a crucial role on the magnetization process and, consequently, determine the future applications of these materials. The mechanisms involved on the origin of such induced magnetic anisotropy showed significant differences between Fe-rich and Co-rich amorphous alloys. This work provides a comparative study of the coercive field and induced magnetic anisotropy in Fe-rich and Co-rich (Finemet) amorphous alloys treated by stress and/or field

  19. Finite Element Optimised Back Analysis of In Situ Stress Field and Stability Analysis of Shaft Wall in the Underground Gas Storage

    Directory of Open Access Journals (Sweden)

    Yifei Yan

    2016-01-01

    Full Text Available A novel optimised back analysis method is proposed in this paper. The in situ stress field of an underground gas storage (UGS reservoir in a Turkey salt cavern is analysed by the basic theory of elastic mechanics. A finite element method is implemented to optimise and approximate the objective function by systematically adjusting boundary loads. Optimising calculation is performed based on a novel method to reduce the error between measurement and calculation as much as possible. Compared with common back analysis methods such as regression method, the method proposed can further improve the calculation precision. By constructing a large circular geometric model, the effect of stress concentration is eliminated and a minimum difference between computed and measured stress can be guaranteed in the rectangular objective region. The efficiency of the proposed method is investigated and confirmed by its capability on restoring in situ stress field, which agrees well with experimental results. The characteristics of stress distribution of chosen UGS wells are obtained based on the back analysis results and by applying the corresponding fracture criterion, the shaft walls are proven safe.

  20. In-situ studies of stress- and magnetic-field-induced phase transformation in a polymer-bonded Ni-Co-Mn-In composite

    International Nuclear Information System (INIS)

    Liu, D.M.; Nie, Z.H.; Wang, G.; Wang, Y.D.; Brown, D.E.; Pearson, J.; Liaw, P.K.; Ren, Y.

    2010-01-01

    A polymer-bonded Ni 45 Co 5 Mn 36.6 In 13.4 ferromagnetic shape-memory composite was fabricated, having magnetic-field-driven shape recovery properties. The thermo-magnetization curves of the composite suggested that the magnetic-field-induced reverse martensitic transformation occurs in the composite. The effects of temperature, stress, and magnetic-field on the phase transformation properties were systematically investigated using an in-situ high-energy X-ray diffraction technique. A temperature-induced reversible martensitic phase transformation was confirmed within the composite, showing a broad phase transformation interval. Stress-induced highly textured martensite was observed in the composite during uniaxial compressive loading, with a residual strain after unloading. The origin of the textured martensite can be explained by the grain-orientation-dependent Bain distortion energy. A recovery strain of ∼1.76% along the compression direction was evidenced in the pre-strained composite with an applied magnetic-field of 5 T. This recovery was caused by the magnetic-field-induced reverse martensitic phase transformation. The phase transformation properties of the ferromagnetic shape-memory composite, different from its bulk alloys, can be well explained by the Clausius-Clapeyron relation. The large magnetic-field-induced strain, together with good ductility and low cost, make the polymer-bonded Ni-Co-Mn-In composites potential candidates for magnetic-field-driven actuators.

  1. Some of the people, some of the time: field evidence for associations and dissociations between stress and drug use.

    Science.gov (United States)

    Furnari, Melody; Epstein, David H; Phillips, Karran A; Jobes, Michelle L; Kowalczyk, William J; Vahabzadeh, Massoud; Lin, Jia-Ling; Preston, Kenzie L

    2015-10-01

    Stress's role in drug use is supported by retrospective interview and laboratory studies, but prospective data confirming the association in daily life are sparse. This study aims to assess the relationship between drug use and stress in real time with ambulatory monitoring. For up to 16 weeks, 133 outpatients on opiate agonist treatment used smartphones to report each time they used drugs or felt more stressed than usual. They rated stress-event severity on a 10-point scale and as a hassle, day spoiler, or more than a day spoiler. For analysis, stress reports made within 72 h before a reported use of cocaine or opioid were binned into 24-h periods. Of 52 participants who reported stress events in the 72-h timeframe, 41 reported stress before cocaine use and 26 before opioid use. For cocaine use, the severity of stressors, rated numerically (r effect = 0.42, CL95 0.17-0.62, p = 0.00061) and percent rated as "more than a day spoiler" (r effect = 0.34, CL95 0.07-0.56, p = 0.0292)], increased linearly across the three days preceding use. The number of stressors did not predict cocaine use, and no measure of stress predicted opioid use. In ecological momentary assessment (EMA) from the whole sample of 133, stress and drug use occurred independently and there was no overall relationship. EMA did not support the idea that stress is a necessary or sufficient trigger for cocaine or heroin use after accounting for the base rates of stress and use. But EMA did show that stressful events can increase in severity in the days preceding cocaine use.

  2. NW transverse fault system in Southern Bogota, Colombia: New seismologic and structural evidences derived from focal mechanisms and stress field determination

    Science.gov (United States)

    Angel Amaya, J.; Fierro Morales, J.; Ordoñez Potes, M.; Blanco, M.

    2012-12-01

    We present new seismological, morphotectonic and structural data of the Southern Bogota area. The goals of the study were to characterize the NW transverse fault system and to evaluate its effect on seismic wave's generation and propagation. The data set included epicenters of the RSNC (Red Sismologica Nacional de Colombia) catalog over the period 1993-2012, historical description of seismic events (period 1644-1921), structural field data (scale 1:100000) and remote sensors interpretation. The methodology included the structural analysis of over 476 faults having a known sense of offset by using a least squares iterative inversion outlined by Angelier (1984) to determinate the mean deviatoric principal stress tensor. Preliminary conclusions showed that both propagation medium and direction are determined by the structural and mechanic conditions of the Southern Bogota Shear Zone (SBSZ) defined by Fierro & Angel, (2008) as a NW-SE oblique-slip fault zone within sinistral and normal regimes. Based on both data sources (focal mechanism and field structural data) we attempted to reconstruct the stress field starting with a strike slip faulting stress regime (S2 vertical), the solution yielded a ENE-WSW orientation for horizontal principal stress (S1). It is hypothesized that the NW oblique-slip fault zone may generate and/or propagate seismic waves, as a local source, implying local hazard to Bogota the capital city of Colombia with over 8 million habitants.

  3. Magnetic property variation in carbon steel and chrome-molybdenum steel as a function of uniaxial stress noncoaxial with the magnetic field (abstract)

    International Nuclear Information System (INIS)

    Sablik, M.J.; Kaminski, D.A.; Jiles, D.C.; Biner, S.B.

    1993-01-01

    Magnescope 1 magnetic measurements were made on carbon steel specimens ranging from 0.1--0.8 wt %C and on chrome-molybdenum steel specimens cut from electric power plant pipes previously in service. The carbon steel specimens were heat-treated using three procedures: (1) spheroidization, (2) quenching, and (3) quench and tempering. The specimens were subjected to uniaxial tension up to 40 ksi. The inspection head was aligned so that the magnetic field was oriented at different angles with respect to the stress axis. Magnetic properties (such as coercivity and maximum differential permeability) were extracted from digitized magnetic hysteresis loop measurements. Magnetic properties were studied as a function of stress at each angle of stress-field orientation. To our knowledge, such a comprehensive study of noncoaxial stress and field effects has never been accomplished before for such a wide variety of steel specimens. Results for the various materials are presented for different orientation angles and compared to numerical results from the noncoaxial magnetomechanical hysteresis model of Sablik et al. 2

  4. Stress concentrations at structural discontinuities in active fault zones in the western United States: Implications for permeability and fluid flow in geothermal fields

    Science.gov (United States)

    Siler, Drew; Hinz, Nicholas H.; Faulds, James E.

    2018-01-01

    Slip can induce concentration of stresses at discontinuities along fault systems. These structural discontinuities, i.e., fault terminations, fault step-overs, intersections, bends, and other fault interaction areas, are known to host fluid flow in ore deposition systems, oil and gas reservoirs, and geothermal systems. We modeled stress transfer associated with slip on faults with Holocene-to-historic slip histories at the Salt Wells and Bradys geothermal systems in western Nevada, United States. Results show discrete locations of stress perturbation within discontinuities along these fault systems. Well field data, surface geothermal manifestations, and subsurface temperature data, each a proxy for modern fluid circulation in the fields, indicate that geothermal fluid flow is focused in these same areas where stresses are most highly perturbed. These results suggest that submeter- to meter-scale slip on these fault systems generates stress perturbations that are sufficiently large to promote slip on an array of secondary structures spanning the footprint of the modern geothermal activity. Slip on these secondary faults and fractures generates permeability through kinematic deformation and allows for transmission of fluids. Still, mineralization is expected to seal permeability along faults and fractures over time scales that are generally shorter than either earthquake recurrence intervals or the estimated life span of geothermal fields. This suggests that though stress perturbations resulting from fault slip are broadly important for defining the location and spatial extent of enhanced permeability at structural discontinuities, continual generation and maintenance of flow conduits throughout these areas are probably dependent on the deformation mechanism(s) affecting individual structures.

  5. Effects of combined exposure to pyridostigmine bromide and shaker stress on acoustic startle response, pre-pulse inhibition and open field behavior in mice.

    Science.gov (United States)

    Dubovicky, M; Paton, S; Morris, M; Mach, M; Lucot, J B

    2007-01-01

    The present study investigated the effect of combined exposure of pyridostigmine bromide (PB) and chronic shaker stress on acoustic startle responses (ASR), pre-pulse inhibition (PPI) and open field behavior of adult C57BL/6J mice. PB (10 mg kg(-1) day(-1) for 7 days) or saline was administered subcutaneously using osmotic Alzet minipumps implanted under the skin on the back of the mice. At the same time, the mice were exposed to 7 days of intermittent shaker stress. They were tested for ASR (100 dB and 120 dB stimuli) and PPI (70 dB + 100 dB and 70 dB + 120 dB) in the acoustic startle monitor system. The mice were assessed during the shaker stress on days 2 and 7 and 7, 14, 21 and 28 days after discontinuation of treatment. Separate groups of mice were tested in the open field in 15 min sessions on days 1, 3 and 6 during shaker stress and PB treatment. Exposure of mice to PB resulted in an exaggerated ASR, reduced PPI and non-significant decrease in locomotor activity. These behavioral changes were apparent only during exposure to PB. Repeated shaker stress did not have any effect on sensorimotor functions or open field behavior of mice. There was no prolonged or delayed effect of PB and/or stress on individual behavioral variables. The study found C57BL/6J mice to be behaviorally sensitive to PB treatment. (c) 2007 John Wiley & Sons, Ltd.

  6. Rate of fatigue crack growth in residual stress fields of welded titanium joints with different contents of embrittling impurities

    International Nuclear Information System (INIS)

    Troshchenko, V.T.; Pokrovskij, V.V.; Yarusevich, V.L.; Mikhajlov, V.I.; Sher, V.A.

    1990-01-01

    Resistance to fatigue crack growth (FCG) has been studied in welded joints of structural titanium alloys contaminated by embrittling impurities. Besides, effect of crack closing has been taken into account what makes it possible to determine the effective coefficient of the stress intensity. The rate of fatigue crack growth is proved to considerably depend on the value and direction of residual stresses. The rate dependence of FCG in welded joints of structural titanium alloys on the swing of effective coefficient of stress intensity is invariant to the value and direction of weld residual stresses

  7. On the measurement of the crack tip stress field as a means of determining Delta K(sub eff) under conditions of fatigue crack closure

    Science.gov (United States)

    Wallhead, Ian R.; Edwards, Lyndon; Poole, Peter

    1994-01-01

    The optical method of caustics has been successfully extended to enable stress intensity factors as low as 1MPa square root of m to be determined accurately for central fatigue cracks in 2024-T3 aluminium alloy test panels. The feasibility of using this technique to study crack closure, and to determine the effective stress intensity factor range, Delta K(sub eff), has been investigated. Comparisons have been made between the measured values of stress intensity factor, K(sub caus), and corresponding theoretical values, K(sub theo), for a range of fatigue cracks grown under different loading conditions. The values of K(sub caus) and K(sub theo) were in good agreement at maximum stress, where the cracks are fully open, while K(sub caus) exceeded K(sub theo) at minimum stress, due to crack closure. However, the levels of crack closure and values of Delta K(sub eff) obtained could not account for the variations of crack growth rate with loading conditions. It is concluded that the values of Delta K(sub eff), based on caustic measurements in a 1/square root of r stress field well outside the plastic zone, do not fully reflect local conditions which control crack tip behavior.

  8. Characterize the hydrogeological properties and probe the stress field in Salt Lake Valley, Utah using SAR imagery

    Science.gov (United States)

    Hu, X.; Lu, Z.; Barbot, S.; Wang, T.

    2017-12-01

    Aquifer skeletons deform actively in response to the groundwater redistribution and hydraulic head changes with varied time scales of delay and sensitivity, that can also, in some instances, trigger earthquakes. However, determining the key hydrogeological properties and understanding the interactions between aquifer and seismicity generally requires the analysis of dense water level data combined with expensive drilling data (borehole breakouts). Here we investigate the spatiotemporal correlation among ground motions, hydrological changes, earthquakes, and faults in Salt Lake Valley, Utah, based on InSAR observations from ENVISAT ASAR (2004-2010) and Sentinel-1A (2015-2016). InSAR results show a clear seasonal and long-term correlation between surface uplift/subsidence and groundwater recharge/discharge, with evidence for an average net uplift of 15 mm/yr for a period of 7 years. The long-term uplift, remarkably bounded by faults, reflects a net increase in pore pressure associated with prolonged water recharge probably decades ago. InSAR-derived ground deformation and its correlation with head variations allow us to quantify hydrogeological properties - decay coefficient, storage coefficient, and bulk compressibility. We also model the long-term deformation using a shallow vertical shearing reservoir to constrain its thickness and strain rate. InSAR-derived deformation help reveal the coupled hydrological and tectonic processes in Salt Lake Valley: the embedded faults disrupt the groundwater flow and partition the hydrological units, and the pore pressure changes rearrange the aquifer skeleton and modulate the stress field, which may affect the basin-wide seismicity.

  9. Improvement of thermophysiological stress in participants wearing protective clothing for spraying pesticide, and its application in the field.

    Science.gov (United States)

    Hayashi, C; Tokura, H

    2000-04-01

    Thermoregulatory responses were compared under two experimental conditions, in the laboratory (Experiment I), and in the field (Experiment II), between two kinds of protective clothing for spraying pesticides. One was currently being used (Type A), and was composed of ready made Gore-Tex clothing, mask, polyurethane gloves and rubber boots. The other one was newly designed (Type B), and was composed of pesticide-proof clothing (100% cotton with water repellent finish), mask, Gore-Tex gloves, and special boots consisting of rubber for the feet and ankle and Gore-Tex around the legs. In addition, the head and chest were cooled by frozen gel strips fixed in the cap and undershirt. In Experiment I, five female adults took part, in a climate-chamber controlled at an ambient temperature of 28 degrees C and a relative humidity of 60%. In Experiment II, five farmers (one male and four female) were tested in an apple orchard in July, August and September. The main results are summarized as follows: (1) change of rectal temperature was inhibited more effectively in Type B in Experiment I, (2) change of heart rate tended to be lower in Type B than in Type A in both experiments, (3) salivary lactic acid concentration at the end of the first exercise was significantly higher in Type A than in Type B in Experiment I, (4) the number of contractions in the handgrip exercise which was performed immediately after the third exercise, was significantly smaller in Type A than in Type B in Experiment I, (5) subjective comfort sensation was significantly improved in Type B in Experiments I and II. Thus, it was concluded that the newly designed protective clothing could reduce thermal stress during the spraying of pesticides in an apple orchard in summer.

  10. Estimation of toroidal field coil stresses from magnetic loads in FER and NET using analytic methods and improved computer subroutine for TFC stress estimation in TRESCODE

    International Nuclear Information System (INIS)

    Riemer, B.W.; Miki, Nobuharu; Hashizume, Takashi.

    1988-06-01

    This report describes the comparison of TF coil stresses in NET and FER. The analyses focus on the straight part of the inner legs, since it is this part of the coil which most directly influences the radial build of the machine. NET's TF coils are wedged together and the centering force on each of the coils is reacted by toroidal compression of the inner legs. The forces that act out of the plane of each coil are reacted by friction between adjacent inner legs such that the set of legs behave much like a cylinder under torsion. In contrast, the FER device employs a bucking cylinder to react the centering load, which incurs a penalty in radial thickness, and the out of plane forces are reacted by the use of shear keys between adjacent inner legs. Analytic techniques or ''hand methods'' have been used to estimate and compare the strains and stresses at the inner leg mid-plane section resulting from both in-plane and out-of-plane magnetic forces. Such techniques forced a more thorough understanding of the structural behavior of the coils. The amount of effort in analyzing the NET coil is greater than for FER as the reaction of centering load in its wedged design is more complex, and because it was found that friction plays a very important part in determining the coil stresses. The FER coil is simpler in this regard, and a ''hand estimation'' of its coil stresses was straightfoward. In this report, the program written to perform these analyses is also described. It was desired to provide new capabilities to the original TF stress subroutine in TRESCODE and to review and improve it where possible. This has been accomplished, and subroutines are now available for use in JAERI's system code, TRESCODE. It is hoped that the inner leg radial thickness can be better optimized by using the program. (author)

  11. O Ponto G Existe?

    Directory of Open Access Journals (Sweden)

    Carlos Alexandre Molina Noccioli

    2016-07-01

    Full Text Available Este trabalho busca analisar o tratamento linguístico-discursivo das informações acerca de um tópicotemático tradicionalmente visto como tabu, relacionado a questões sexuais, na notícia O ponto G existe?, publicada em 2008, na revista brasileira Superinteressante, destacando-se como o conhecimento em questão é representado socialmente ao se considerar a linha editorial da revista. A notícia caracteriza-se como um campo fértil para a análise das estratégias divulgativas, já que atrai, inclusive pelas escolhas temáticas, a curiosidade dos leitores. Imbuído de um tema excêntrico, o texto consegue angariar um público jovem interessado em discussões polêmicas relacionadas ao seu universo.

  12. Lebesgue Sets Immeasurable Existence

    Directory of Open Access Journals (Sweden)

    Diana Marginean Petrovai

    2012-12-01

    Full Text Available It is well known that the notion of measure and integral were released early enough in close connection with practical problems of measuring of geometric figures. Notion of measure was outlined in the early 20th century through H. Lebesgue’s research, founder of the modern theory of measure and integral. It was developed concurrently a technique of integration of functions. Gradually it was formed a specific area todaycalled the measure and integral theory. Essential contributions to building this theory was made by a large number of mathematicians: C. Carathodory, J. Radon, O. Nikodym, S. Bochner, J. Pettis, P. Halmos and many others. In the following we present several abstract sets, classes of sets. There exists the sets which are not Lebesgue measurable and the sets which are Lebesgue measurable but are not Borel measurable. Hence B ⊂ L ⊂ P(X.

  13. Method for evaluationo of the 3D residual stress field from X-ray diffraction measurements on heavy weldments

    International Nuclear Information System (INIS)

    Larsson, L.E.; Sandstroem, R.

    1982-03-01

    A method for evaluation of the three dimensional residual 30 stress distribution in heavy weldmwents has been developed. The evaluation is based on measured stress data at a number of depth levels below the plate surface. The method has been applied to two measurements on heavy weldments of A 553 B steel. Comparison to a previous evaluation shows good agreement. (Authors)

  14. Do `negative' temperatures exist?

    Science.gov (United States)

    Lavenda, B. H.

    1999-06-01

    A modification of the second law is required for a system with a bounded density of states and not the introduction of a `negative' temperature scale. The ascending and descending branches of the entropy versus energy curve describe particle and hole states, having thermal equations of state that are given by the Fermi and logistic distributions, respectively. Conservation of energy requires isentropic states to be isothermal. The effect of adiabatically reversing the field is entirely mechanical because the only difference between the two states is their energies. The laws of large and small numbers, leading to the normal and Poisson approximations, characterize statistically the states of infinite and zero temperatures, respectively. Since the heat capacity also vanishes in the state of maximum disorder, the third law can be generalized in systems with a bounded density of states: the entropy tends to a constant as the temperature tends to either zero or infinity.

  15. Hydraulics and gas exchange recover more rapidly from severe drought stress in small pot-grown grapevines than in field-grown plants.

    Science.gov (United States)

    Romero, Pascual; Botía, Pablo; Keller, Markus

    2017-09-01

    Modifications of plant hydraulics and shoot resistances (R shoot ) induced by water withholding followed by rewatering, and their relationships with plant water status, leaf gas exchange and water use efficiency at the leaf level, were investigated in pot-grown and field-grown, own-rooted Syrah grapevines in an arid climate. Water stress induced anisohydric behavior, gradually reducing stomatal conductance (g s ) and leaf photosynthesis (A) in response to decreasing midday stem water potential (Ψ s ). Water stress also rapidly increased intrinsic water-use efficiency (A/g s ); this effect persisted for many days after rewatering. Whole-plant (K plant ), canopy (K canopy ), shoot (K shoot ) and leaf (K leaf ) hydraulic conductances decreased during water stress, in tune with the gradual decrease in Ψ s , leaf gas exchange and whole plant water use. Water-stressed vines also had a lower Ψ gradient between stem and leaf (ΔΨ l ), which was correlated with lower leaf transpiration rate (E). E and ΔΨ l increased with increasing vapour pressure deficit (VPD) in non-stressed control vines but not in stressed vines. Perfusion of xylem-mobile dye showed that water flow to petioles and leaves was substantially reduced or even stopped under moderate and severe drought stress. Leaf blade hydraulic resistance accounted for most of the total shoot resistance. However, hydraulic conductance of the whole root system (K root ) was not significantly reduced until water stress became very severe in pot-grown vines. Significant correlations between K plant , K canopy and Ψ s , K canopy and leaf gas exchange, K leaf and Ψ s , and K leaf and A support a link between water supply, leaf water status and gas exchange. Upon re-watering, Ψ s recovered faster than gas exchange and leaf-shoot hydraulics. A gradual recovery of hydraulic functionality of plant organs was also observed, the leaves being the last to recover after rewatering. In pot-grown vines, K canopy recovered rather

  16. Effects of deglaciation on the crustal stress field and implications for endglacial faulting: A parametric study of simple Earth and ice models

    International Nuclear Information System (INIS)

    Lund, Bjoern

    2005-03-01

    The large faults of northern Scandinavia, hundreds of kilometres long and with offsets of more than 10 m, are inferred to be the result of major earthquakes triggered by the retreating ice sheet some 9,000 years ago. In this report we have studied a number of parameters involved in quantitative modelling of glacial isostatic adjustment (GIA) in order to illustrate how they affect stress, displacement and fault stability during deglaciation. Using a variety of reference models, we have verified that our modelling approach, a finite element analysis scheme with proper adjustments for the requirements of GIA modelling, performs satisfactory. The size of the model and the density of the grid have been investigated in order to be able to perform high resolution modelling in reasonable time. This report includes studies of both the ice and earth models. We have seen that the steeper the ice edge is, the more concentrated is the deformation around the edge and consequently shear stress localizes with high magnitudes around the ice edge. The temporal evolution of height and basal extent of the ice is very important for the response of the earth model, and we have shown that the last stages of ice retreat can cause fault instability over a large lateral region. The effect on shear stress and vertical displacement by variations in Earth model parameters such as stiffness, viscosity, density, compressibility and layer thickness was investigated. More complicated geometries, such as multiple layers and lateral layer thickness variations, were also studied. We generally find that these variations have more effect on the shear stress distributions than on the vertical displacement distributions. We also note that shear stress magnitude is affected more than the spatial shape of the shear stress distribution. Fault stability during glaciation/deglaciation was investigated by two different variations on the Mohr-Coulomb failure criterion. The stability of a fault in a stress field

  17. Effects of deglaciation on the crustal stress field and implications for endglacial faulting: A parametric study of simple Earth and ice models

    Energy Technology Data Exchange (ETDEWEB)

    Lund, Bjoern [Uppsala Univ. (Sweden). Dept. of Earth Sciences

    2005-03-01

    The large faults of northern Scandinavia, hundreds of kilometres long and with offsets of more than 10 m, are inferred to be the result of major earthquakes triggered by the retreating ice sheet some 9,000 years ago. In this report we have studied a number of parameters involved in quantitative modelling of glacial isostatic adjustment (GIA) in order to illustrate how they affect stress, displacement and fault stability during deglaciation. Using a variety of reference models, we have verified that our modelling approach, a finite element analysis scheme with proper adjustments for the requirements of GIA modelling, performs satisfactory. The size of the model and the density of the grid have been investigated in order to be able to perform high resolution modelling in reasonable time. This report includes studies of both the ice and earth models. We have seen that the steeper the ice edge is, the more concentrated is the deformation around the edge and consequently shear stress localizes with high magnitudes around the ice edge. The temporal evolution of height and basal extent of the ice is very important for the response of the earth model, and we have shown that the last stages of ice retreat can cause fault instability over a large lateral region. The effect on shear stress and vertical displacement by variations in Earth model parameters such as stiffness, viscosity, density, compressibility and layer thickness was investigated. More complicated geometries, such as multiple layers and lateral layer thickness variations, were also studied. We generally find that these variations have more effect on the shear stress distributions than on the vertical displacement distributions. We also note that shear stress magnitude is affected more than the spatial shape of the shear stress distribution. Fault stability during glaciation/deglaciation was investigated by two different variations on the Mohr-Coulomb failure criterion. The stability of a fault in a stress field

  18. Photoelastic method to quantitatively visualise the evolution of whole-field stress in 3D printed models subject to continuous loading processes

    Science.gov (United States)

    Ju, Yang; Ren, Zhangyu; Wang, Li; Mao, Lingtao; Chiang, Fu-Pen

    2018-01-01

    The combination of three-dimensional (3D) printing techniques and photoelastic testing is a promising way to quantitatively determine the continuous whole-field stress distributions in solids that are characterized by complex structures. However, photoelastic testing produces wrapped isoclinic and isochromatic phase maps, and unwrapping these maps has always been a significant challenge. To realize the visualization and transparentization of the stress fields in complex structures, we report a new approach to quantify the continuous evolution of the whole-field stress in photosensitive material that is applicable to the fabrication of complex structures using 3D printing technology. The stress fringe orders are determined by analyzing a series of continuous frames extracted from a video recording of the fringe changes over the entire loading process. The integer portion of the fringe orders at a specific point on the model can be determined by counting the valleys of the light intensity change curve over the whole loading process, and the fractional portion can be calculated based on the cosine function between the light intensity and retardation. This method allows the fringe orders to be determined from the video itself, which significantly improves characterization accuracy and simplifies the experimental operation over the entire processes. To validate the proposed method, we compare the results of the theoretical calculations to those of experiments based on the diametric compression of a circular disc prepared by a 3D printer with photosensitive resin. The results indicate that the method can accurately determine the stress fringe order, except for points where the deformation is too large to differentiate the fringes pertaining to photoplasticity.

  19. Evolution of the stress fields in the Zagros Foreland Folded Belt using focal mechanisms and kinematic analyses: the case of the Fars salient, Iran

    Science.gov (United States)

    Sarkarinejad, Khalil; Zafarmand, Bahareh; Oveisi, Behnam

    2018-03-01

    The NW-SE trending Zagros orogenic belt was initiated during the convergence of the Afro-Arabian continent and the Iranian microcontinent in the Late Cretaceous. Ongoing convergence is confirmed by intense seismicity related to compressional stresses collision-related in the Zagros orogenic belt by reactivation of an early extensional faulting to latter compressional segmented strike-slip and dip-slip faulting. These activities are strongly related either to the deep-seated basement fault activities (deep-seated earthquakes) underlies the sedimentary cover or gently dipping shallow-seated décollement horizon of the rheological weak rocks of the infra-Cambrian Hormuz salt. The compressional stress regimes in the different units play an important role in controlling the stress conditions between the different units within the sedimentary cover and basement. A significant set of nearly N-S trending right-lateral strike-slip faults exists throughout the study area in the Fars area in the Zagros Foreland Folded Belt. Fault-slip and focal mechanism data were analyzed using the stress inversion method to reconstruct the paleo and recent stress conditions. The results suggest that the current direction of maximum principal stress averages N19°E, with N38°E that for the past from Cretaceous to Tertiary (although a few sites on the Kar-e-Bass fault yield a different direction). The results are consistent with the collision of the Afro-Arabian continent and the Iranian microcontinent. The difference between the current and paleo-stress directions indicates an anticlockwise rotation in the maximum principle stress direction over time. This difference resulted from changes in the continental convergence path, but was also influenced by the local structural evolution, including the lateral propagation of folds and the presence of several local décollement horizons that facilitated decoupling of the deformation between the basement and the sedimentary cover. The obliquity of

  20. Exploring the Individual Contributory Personality Factors of Stress: A Survey of Washington State Elementary Teachers

    Science.gov (United States)

    Dean, Effie J.

    2010-01-01

    Prolonged stress is shown to lead to low productivity, which is one of the leading causes of poor performance, and high absenteeism/turnover in occupational fields (Norton, 2002). The field of education is a prime example of low productivity resulting from prolonged stress (Norton, 2002). Currently, there are many existing studies on environmental…

  1. Effect of geometry, material and pressure variability on strain and stress fields in dented pipelines under static and cyclic pressure loading using probability analysis

    Energy Technology Data Exchange (ETDEWEB)

    Al-Muslim, Husain Mohammed; Arif, Abul Fazal M. [King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia)

    2010-07-01

    Mechanical damage in transportation pipelines is an issue of extreme importance to pipeline operators and many others. Appropriate procedures for severity assessment are necessary. This paper mainly studies the effect of geometry, material and pressure variability on strain and stress fields in dented pipelines subjected to static and cyclic pressure. Finite element analysis (FEA) has often been used to overcome the limitations of a full-scale test, but it is still impossible to run FEA for all possible combinations of parameters. Probabilistic analysis offers an excellent alternative method to determine the sensitivity of the strain and stress fields to each of those input parameters. A hundred cases were randomly generated with Monte Carlo simulations and analyzed, a general formula was proposed to relate the output variables in terms of practically measured variables, and regression analysis was performed to confirm the appropriateness of the general formula.

  2. Focal mechanisms in the southern Aegean from temporary seismic networks – implications for the regional stress field and ongoing deformation processes

    OpenAIRE

    Friederich, W.; Brüstle, A.; Küperkoch, L.; Meier, T.; Lamara, S.; Working Group, Egelados

    2014-01-01

    The lateral variation of the stress field in the southern Aegean plate and the subducting Hellenic slab is determined from recordings of seismicity obtained with the CYCNET and EGELADOS networks in the years from 2002 to 2007. First motions from 7000 well-located microearthquakes were analysed to produce 540 well-constrained focal mechanisms. They were complemented by another 140 derived by waveform matching of records from larger events. Most of these earth...

  3. Measurement of the internal stress and electric field in a resonating piezoelectric transformer for high-voltage applications using the electro-optic and photoelastic effects.

    Science.gov (United States)

    VanGordon, James A; Kovaleski, Scott D; Norgard, Peter; Gall, Brady B; Dale, Gregory E

    2014-02-01

    The high output voltages from piezoelectric transformers are currently being used to accelerate charged particle beams for x-ray and neutron production. Traditional methods of characterizing piezoelectric transformers (PTs) using electrical probes can decrease the voltage transformation ratio of the device due to the introduction of load impedances on the order of hundreds of kiloohms to hundreds of megaohms. Consequently, an optical diagnostic was developed that used the photoelastic and electro-optic effects present in piezoelectric materials that are transparent to a given optical wavelength to determine the internal stress and electric field. The combined effects of the piezoelectric, photoelastic, and electro-optic effects result in a time-dependent change the refractive indices of the material and produce an artificially induced, time-dependent birefringence in the piezoelectric material. This induced time-dependent birefringence results in a change in the relative phase difference between the ordinary and extraordinary wave components of a helium-neon laser beam. The change in phase difference between the wave components was measured using a set of linear polarizers. The measured change in phase difference was used to calculate the stress and electric field based on the nonlinear optical properties, the piezoelectric constitutive equations, and the boundary conditions of the PT. Maximum stresses of approximately 10 MPa and electric fields of as high as 6 kV/cm were measured with the optical diagnostic. Measured results were compared to results from both a simple one-dimensional (1D) model of the piezoelectric transformer and a three-dimensional (3D) finite element model. Measured stresses and electric fields along the length of an operating length-extensional PT for two different electrical loads were within at least 50 % of 3D finite element simulated results. Additionally, the 3D finite element results were more accurate than the results from the 1D model

  4. Measurement of the internal stress and electric field in a resonating piezoelectric transformer for high-voltage applications using the electro-optic and photoelastic effects

    Energy Technology Data Exchange (ETDEWEB)

    VanGordon, James A.; Kovaleski, Scott D., E-mail: kovaleskis@missouri.edu; Norgard, Peter; Gall, Brady B. [Department of Electrical and Computer Engineering, University of Missouri, Columbia, Missouri 65211 (United States); Dale, Gregory E. [High Power Electrodynamics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2014-02-15

    The high output voltages from piezoelectric transformers are currently being used to accelerate charged particle beams for x-ray and neutron production. Traditional methods of characterizing piezoelectric transformers (PTs) using electrical probes can decrease the voltage transformation ratio of the device due to the introduction of load impedances on the order of hundreds of kiloohms to hundreds of megaohms. Consequently, an optical diagnostic was developed that used the photoelastic and electro-optic effects present in piezoelectric materials that are transparent to a given optical wavelength to determine the internal stress and electric field. The combined effects of the piezoelectric, photoelastic, and electro-optic effects result in a time-dependent change the refractive indices of the material and produce an artificially induced, time-dependent birefringence in the piezoelectric material. This induced time-dependent birefringence results in a change in the relative phase difference between the ordinary and extraordinary wave components of a helium-neon laser beam. The change in phase difference between the wave components was measured using a set of linear polarizers. The measured change in phase difference was used to calculate the stress and electric field based on the nonlinear optical properties, the piezoelectric constitutive equations, and the boundary conditions of the PT. Maximum stresses of approximately 10 MPa and electric fields of as high as 6 kV/cm were measured with the optical diagnostic. Measured results were compared to results from both a simple one-dimensional (1D) model of the piezoelectric transformer and a three-dimensional (3D) finite element model. Measured stresses and electric fields along the length of an operating length-extensional PT for two different electrical loads were within at least 50 % of 3D finite element simulated results. Additionally, the 3D finite element results were more accurate than the results from the 1D model

  5. Vacuum expectation value of the stress-energy tensor of a 2D-gravity field and loop amplitudes for strings of noncritical dimensions

    International Nuclear Information System (INIS)

    Danilov, G.S.

    1995-01-01

    It is shown that, in the theory of free noncritical strings, there are no modular-invariant partition functions on surfaces of higher genus. This is due to the fact that the vacuum expectation value of the stress-energy tensor is singular in the fundamental region on the complex plane in which Riemann surfaces are mapped. The above singularity is associated with a nonzero vacuum expectation value of the 2D-gravity field. 15 refs

  6. Effects of electric field and Coriolis force on electrohydrodynamic stability of poorly conducting couple stress parallel fluid flow in a channel

    International Nuclear Information System (INIS)

    Shankar, B.M.; Rudraiah, N.

    2013-01-01

    The effective functioning of microfluidic devices in chemical, electrical and mechanical engineering involving fluidics particularly those having vibrations and petroleum products containing organic, inorganic and other microfluidics require understanding and control of stability of poorly conducting parallel fluid flows. The electrical conductivity, σ, of a poorly conducting fluidics, increases with the temperature and the concentration of freely suspended particles like RBC, WBC and so on in the blood, the hylauronic acid (HA) and nutrients of synovial fluid in synovial joints will spin producing microrotation, forming micropolar fluid of Eringen. The presence of Deuterium - Tritium (DT) in inertial fusion target (IFT) may also be modeled using micropolar fluid theory of Eringen. A particular case of micropolar fluid theory when microrotation balances with the natural vorticity of a poorly conducting fluidics in the presence of an electric field is called ‘electrohydrodynamic couple stress fluid’ (EHDCF). These EHDCFs exhibit a variation of electrical conductivity, ∇ σ, increasing with temperature and concentration of freely suspended particles, releases the charges from the nuclei forming distribution of charge density, ρ e . These charges induce an electric field, 1 E i . If need be, we can apply an electric field, 1 E a , by embedding electrodes of different potentials at the boundaries. The total electric field, 1 E = 1 E i + 1 E a , produces a current density, 1 J = ρ σ 1 E, according to Ohm’s law and also produces an electric force, 1 F σ = σ 1 E. This current 1 J acts as sensing and the force, 1 F σ acts as actuation. These two properties make the poorly conducting couple stress fluid to act as a smart material. The objective of this paper is to show that EHDCV in presence of coriolis force plays a significant role in controlling the stability of parallel flows which is essential for an effective functioning of machineries that occur in

  7. 3D geomechanical modeling and numerical simulation of in-situ stress fields in shale reservoirs: A case study of the lower Cambrian Niutitang formation in the Cen'gong block, South China

    Science.gov (United States)

    Liu, Jingshou; Ding, Wenlong; Yang, Haimeng; Wang, Ruyue; Yin, Shuai; Li, Ang; Fu, Fuquan

    2017-08-01

    An analysis of the in-situ state of stress in a shale reservoir was performed based on comprehensive information about the subsurface properties from wellbores established during the development of an oil and gas field. Industrial-level shale gas production has occurred in the Niutitang formation of the lower Cambrian Cen'gong block, South China. In this study, data obtained from hydraulic fracturing, drilling-induced fractures, borehole breakout, global positioning system (GPS), and well deviation statistics have been used to determine the orientation of the maximum horizontal principal stress. Additionally, hydraulic fracturing and multi-pole array acoustic logging (XMAC) were used to determine the vertical variations in the in-situ stress magnitude. Based on logging interpretation and mechanical experiments, the spatial distributions of mechanical parameters were obtained by seismic inversion, and a 3D heterogeneous geomechanical model was established using a finite element stress analysis approach to simulate the in-situ stress fields. The effects of depth, faults, rock mechanics, and layer variations on the principal stresses, horizontal stress difference (Δσ), horizontal stress difference coefficient (Kh), and stress type coefficient (Sp) were determined. The results show that the direction of the maximum principal stress is ESE 120°. Additionally, the development zones of natural fractures appear to correlate with regions with high principal stress differences. At depths shallower than 375 m, the stress type is mainly a thrust faulting stress regime. At depths ranging from 375 to 950 m, the stress type is mainly a strike-slip faulting stress regime. When the depth is > 950 m, the stress type is mainly a normal faulting stress regime. Depth, fault orientation, and rock mechanics all affect the type of stress. The knowledge regarding the Cen'gong block is reliable and can improve borehole stability, casing set point determination, well deployment

  8. Two-parameter fracture mechanical analysis of a near-crack-tip stress field in wedge splitting test specimens

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Veselý, V.; Řoutil, L.

    2011-01-01

    Roč. 89, 21-22 (2011), s. 1852-1858 ISSN 0045-7949. [International Conference on Civil, Structural and Enviromental Engineering Computing /12./. Funchal, Madeira, 01.09.2009-04.09.2009] Institutional research plan: CEZ:AV0Z20410507 Keywords : Wedge splitting test * Stress intensity factor * T-stress * Numerical simulation * Direct method Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.874, year: 2011

  9. The EXIST Mission Concept Study

    Science.gov (United States)

    Fishman, Gerald J.; Grindlay, J.; Hong, J.

    2008-01-01

    EXIST is a mission designed to find and study black holes (BHs) over a wide range of environments and masses, including: 1) BHs accreting from binary companions or dense molecular clouds throughout our Galaxy and the Local Group, 2) supermassive black holes (SMBHs) lying dormant in galaxies that reveal their existence by disrupting passing stars, and 3) SMBHs that are hidden from our view at lower energies due to obscuration by the gas that they accrete. 4) the birth of stellar mass BHs which is accompanied by long cosmic gamma-ray bursts (GRBs) which are seen several times a day and may be associated with the earliest stars to form in the Universe. EXIST will provide an order of magnitude increase in sensitivity and angular resolution as well as greater spectral resolution and bandwidth compared with earlier hard X-ray survey telescopes. With an onboard optical-infra red (IR) telescope, EXIST will measure the spectra and redshifts of GRBs and their utility as cosmological probes of the highest z universe and epoch of reionization. The mission would retain its primary goal of being the Black Hole Finder Probe in the Beyond Einstein Program. However, the new design for EXIST proposed to be studied here represents a significant advance from its previous incarnation as presented to BEPAC. The mission is now less than half the total mass, would be launched on the smallest EELV available (Atlas V-401) for a Medium Class mission, and most importantly includes a two-telescope complement that is ideally suited for the study of both obscured and very distant BHs. EXIST retains its very wide field hard X-ray imaging High Energy Telescope (HET) as the primary instrument, now with improved angular and spectral resolution, and in a more compact payload that allows occasional rapid slews for immediate optical/IR imaging and spectra of GRBs and AGN as well as enhanced hard X-ray spectra and timing with pointed observations. The mission would conduct a 2 year full sky survey in

  10. Reconstruction of orientation of stresses acting in infinity within the Kovdor ore body based on field determinations

    Directory of Open Access Journals (Sweden)

    Rybin V. V.

    2017-03-01

    Full Text Available Mining Institute KSC RAS has conducted research which aim is to study the possibilities of increasing the tilt angles of pit walls in massifs of solid rock. One of the problems the solution of which will contribute to achieving this goal is to determine the direction of the maximum component of principal stresses in intact massif on the "infinity" necessary to work out mathematical models of rock massif including quarry recess. To solve this problem it has been proposed to use the results of parameters' measurement of stress state by the unloading method in near-wall rock massif. The basic research of near-wall rock massif has been conducted on mine quarry "Zhelezny" (JSC "Kovdor ore processing plant". The measurements have been performed by the discharge method in option of end measurements directly from the quarry ledges on special observation stations using horizontal wells. The direction of maximum compression acting in sub-meridional course in the Kovdor apatiteshtafelyte-baddeleite deposit (the Kovdor ore cluster has been determined by the conformal mapping method on the basis of experimental estimations of stress parameters in the rock massif. The results obtained are of great importance for assessing a level of stresses acting directly in a near open-pit zone. They are applied to set boundary conditions when modeling stress-strain state of near-wall rock massif and assess slope stability.

  11. Proteome analysis reveals distinct uranium stress response in two strains of Cyanobacteria native to Indian paddy fields

    International Nuclear Information System (INIS)

    Panda, Bandita; Basu, Bhakti; Acharya, Celin; Rajaram, Hema; Apte, Shree Kumar

    2017-01-01

    Uranium present in phosphate fertilizer contaminates agricultural land. Uranium exerts chemical toxicity to the resident biota as it induces oxidative stress by generating free radicals. Two strains of nitrogen fixing cyanobacteria viz., Anabaena PCC 7120 and L-31 native to Indian paddy, regularly experience oxidative stress induced by different stresses and heavy metals. The present study investigated their response to uranium exposure at proteomic level. LD_5_0 dose for Anabaena 7120 and Anabaena L-31 was determined to be 75 μM and 200 μM uranyl carbonate exposure for 3 h. A total of 79 proteins from Anabaena 7120 and 64 proteins from Anabaena L-31 were identified by MALDI mass spectrometry, of which levels of 45 and 27 proteins respectively were found to be differentially modulated in the two strains in response to uranium exposure. The differentially expressed proteins belonged to the major functional categories of photosynthesis, carbon metabolism and oxidative stress alleviation, commensurate with their uranium tolerance. Better oxidative stress management, and maintenance of metabolic and energy homeostasis lead to superior uranium tolerance in Anabaena L-31 as compared to Anabaena PCC 7120

  12. Effect of glacial-interglacial sea-level changes on the displacement and stress field in the forearc and along the plate interface of subduction zones

    Directory of Open Access Journals (Sweden)

    T. Li

    2012-02-01

    Full Text Available Combined seismological, space-geodetic and numerical studies have shown that the seismicity at subduction zones may be modulated by tides and glacier fluctuations on timescales of 1–100 a, because these changes in loads on Earth's surface are able to alter the stress field in the upper plate and along the plate interface. Here we use a two-dimensional finite-element model of a subduction zone to investigate how glacial-interglacial sea-level changes affect the forearc region and the plate interface. The model results show that a sea-level fall by 125 m over 100 ka causes up to 0.7 m of vertical displacement, with the maximum uplift occurring between the trench and the coast. The uplift signal induced by the sea-level fall decreases to zero ~20 km landward of the coastline. A subsequent sea-level rise by 125 m over 20 ka causes subsidence, which is again most pronounced in the submarine part of the forearc. The sea-level changes cause horizontal displacements of up to 0.12 m, which are directed seaward during sea-level fall and landward during sea-level rise. With respect to the stress field, the sea-level changes lead to variations in the vertical stress and the shear stress of up to 1.23 MPa and 0.4 MPa, respectively. The shear stress variations are highest beneath the coast, i.e. in the area where the sea-level changes cause the strongest flexure. The resulting Coulomb stress changes on the plate interface are of the order of 0.2–0.5 MPa and indicate that earthquakes are promoted during sea-level fall and delayed during sea-level rise. Our findings imply that eustatic sea-level changes during glacial-interglacial periods may have induced displacements and stress changes that were large enough to affect the seismic cycle of subduction thrusts.

  13. Transcriptional and biochemical markers in transplanted Perca flavescens to characterize cadmium- and copper-induced oxidative stress in the field

    International Nuclear Information System (INIS)

    Defo, Michel A.; Bernatchez, Louis; Campbell, Peter G.C.; Couture, Patrice

    2015-01-01

    Highlights: • Four-weeks exposure is sufficient to increase kidney metal levels in wild perch. • Cd and Cu affected indicators of retinoid metabolism and oxidative stress in fish. • Multi-level biological approaches are needed when assessing fish metal toxicology. • Changes at molecular level do not always mean changes at the functional level. • Wild juvenile perch may partly adjust to metal contamination by plastic responses. - Abstract: Despite recent progress achieved in elucidating the mechanisms underlying local adaptation to pollution, little is known about the evolutionary change that may be occurring at the molecular level. The goal of this study was to examine patterns of gene transcription and biochemical responses induced by metal accumulation in clean yellow perch (Perca flavescens) and metal depuration in contaminated fish in a mining and smelting region of Canada. Fish were collected from a reference lake (lake Opasatica) and a Cd, Cu and Zn contaminated lake (lake Dufault) located in the Rouyn-Noranda region (Qc, Canada) and caged for one or four weeks in their own lake or transplanted in the other lake. Free-ranging fish from the same lakes were also collected. Kidney Cd and Cu concentrations in clean fish caged in the contaminated lake increased with the time of exposure, but metal depuration did not occur in contaminated fish caged in the clean lake. After 4 weeks, the major retinoid metabolites analysed, the percentage of free dehydroretinol (dROH) and the retinol dehydrogenase-2 (rdh-2) transcription level in liver decreased in clean fish transplanted into the metal-contaminated lake, suggesting that metal exposure negatively impacted retinoid metabolism. However, we observed an increase in almost all of the retinoid parameters analysed in fish from the metal-impacted lake caged in the same lake, which we interpret as an adaptation response to higher ambient metal concentration. In support of this hypothesis, liver transcription levels

  14. Transcriptional and biochemical markers in transplanted Perca flavescens to characterize cadmium- and copper-induced oxidative stress in the field

    Energy Technology Data Exchange (ETDEWEB)

    Defo, Michel A. [Institut National De La Recherche Scientifique (INRS), Centre Eau Terre Environnement, 490 De La Couronne, Québec, QC G1K 9A9 (Canada); Bernatchez, Louis [Institut De Biologie Intégrative Et Des Systèmes (IBIS), Université Laval, Québec, QC G1V 0A6 (Canada); Campbell, Peter G.C.; Couture, Patrice [Institut National De La Recherche Scientifique (INRS), Centre Eau Terre Environnement, 490 De La Couronne, Québec, QC G1K 9A9 (Canada)

    2015-05-15

    Highlights: • Four-weeks exposure is sufficient to increase kidney metal levels in wild perch. • Cd and Cu affected indicators of retinoid metabolism and oxidative stress in fish. • Multi-level biological approaches are needed when assessing fish metal toxicology. • Changes at molecular level do not always mean changes at the functional level. • Wild juvenile perch may partly adjust to metal contamination by plastic responses. - Abstract: Despite recent progress achieved in elucidating the mechanisms underlying local adaptation to pollution, little is known about the evolutionary change that may be occurring at the molecular level. The goal of this study was to examine patterns of gene transcription and biochemical responses induced by metal accumulation in clean yellow perch (Perca flavescens) and metal depuration in contaminated fish in a mining and smelting region of Canada. Fish were collected from a reference lake (lake Opasatica) and a Cd, Cu and Zn contaminated lake (lake Dufault) located in the Rouyn-Noranda region (Qc, Canada) and caged for one or four weeks in their own lake or transplanted in the other lake. Free-ranging fish from the same lakes were also collected. Kidney Cd and Cu concentrations in clean fish caged in the contaminated lake increased with the time of exposure, but metal depuration did not occur in contaminated fish caged in the clean lake. After 4 weeks, the major retinoid metabolites analysed, the percentage of free dehydroretinol (dROH) and the retinol dehydrogenase-2 (rdh-2) transcription level in liver decreased in clean fish transplanted into the metal-contaminated lake, suggesting that metal exposure negatively impacted retinoid metabolism. However, we observed an increase in almost all of the retinoid parameters analysed in fish from the metal-impacted lake caged in the same lake, which we interpret as an adaptation response to higher ambient metal concentration. In support of this hypothesis, liver transcription levels

  15. Improved stress tolerance and productivity in transgenic rice plants constitutively expressing the Oryza sativa glutathione synthetase OsGS under paddy field conditions.

    Science.gov (United States)

    Park, Seong-Im; Kim, Young-Saeng; Kim, Jin-Ju; Mok, Ji-Eun; Kim, Yul-Ho; Park, Hyang-Mi; Kim, Il-Sup; Yoon, Ho-Sung

    2017-08-01

    Reactive oxygen species, which increase under various environmental stresses, have deleterious effects on plants. An important antioxidant, glutathione, is used to detoxify reactive oxygen species in plant cells and is mainly produced by two enzymes: gamma-glutamylcysteine synthetase (γ-ECS) and glutathione synthetase (GS). To evaluate the functional roles of the glutathione synthetase gene (OsGS) in rice, we generated four independent transgenic rice plants (TG1-TG4) that overexpressed OsGS under the control of the constitutively expressed OsCc1 promoter. When grown under natural paddy field conditions, the TG rice plants exhibited greater growth development, higher chlorophyll content, and higher GSH/GSSH ratios than control wild-type (WT) rice plants. Subsequently, the TG rice plants enhanced redox homeostasis by preventing hydroperoxide-mediated membrane damage, which improved their adaptation to environmental stresses. As a result, TG rice plants improved rice grain yield and total biomass following increases in panicle number and number of spikelets per panicle, despite differences in climate during the cultivation periods of 2014 and 2015. Overall, our results indicate that OsGS overexpression improved redox homeostasis by enhancing the glutathione pool, which resulted in greater tolerance to environmental stresses in the paddy fields. Copyright © 2017. Published by Elsevier GmbH.

  16. Pre-sowing static magnetic field treatment for improving water and radiation use efficiency in chickpea (Cicer arietinum L.) under soil moisture stress.

    Science.gov (United States)

    Mridha, Nilimesh; Chattaraj, Sudipta; Chakraborty, Debashis; Anand, Anjali; Aggarwal, Pramila; Nagarajan, Shantha

    2016-09-01

    Soil moisture stress during pod filling is a major constraint in production of chickpea (Cicer arietinum L.), a fundamentally dry land crop. We investigated effect of pre-sowing seed priming with static magnetic field (SMF) on alleviation of stress through improvement in radiation and water use efficiencies. Experiments were conducted under greenhouse and open field conditions with desi and kabuli genotypes. Seeds exposed to SMF (strength: 100 mT, exposure: 1 h) led to increase in root volume and surface area by 70% and 65%, respectively. This enabled the crop to utilize 60% higher moisture during the active growth period (78-118 days after sowing), when soil moisture became limiting. Both genotypes from treated seeds had better water utilization, biomass, and radiation use efficiencies (17%, 40%, and 26% over control). Seed pre-treatment with SMF could, therefore, be a viable option for chickpea to alleviate soil moisture stress in arid and semi-arid regions, helping in augmenting its production. It could be a viable option to improve growth and yield of chickpea under deficit soil moisture condition, as the selection and breeding program takes a decade before a tolerant variety is released. Bioelectromagnetics. 37:400-408, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  17. Tolerance of transgenic canola plants (Brassica napus) amended with plant growth-promoting bacteria to flooding stress at a metal-contaminated field site

    International Nuclear Information System (INIS)

    Farwell, Andrea J.; Vesely, Susanne; Nero, Vincent; Rodriguez, Hilda; McCormack, Kimberley; Shah, Saleh; Dixon, D. George; Glick, Bernard R.

    2007-01-01

    The growth of transgenic canola (Brassica napus) expressing a gene for the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase was compared to non-transformed canola exposed to flooding and elevated soil Ni concentration, in situ. In addition, the ability of the plant growth-promoting bacterium Pseudomonas putida UW4, which also expresses ACC deaminase, to facilitate the growth of non-transformed and transgenic canola under the above mentioned conditions was examined. Transgenic canola and/or canola treated with P. putida UW4 had greater shoot biomass compared to non-transformed canola under low flood-stress conditions. Under high flood-stress conditions, shoot biomass was reduced and Ni accumulation was increased in all instances relative to low flood-stress conditions. This is the first field study to document the increase in plant tolerance utilizing transgenic plants and plant growth-promoting bacteria exposed to multiple stressors. - Using transgenic plants and plant growth-promoting bacteria as phytoremediation methods increased plant tolerance at a metal-contaminated field site under low flood conditions

  18. Effect of electric field configuration on streamer and partial discharge phenomena in a hydrocarbon insulating liquid under AC stress

    International Nuclear Information System (INIS)

    Liu, Z; Liu, Q; Wang, Z D

    2016-01-01

    This paper concerns pre-breakdown phenomena, including streamer characteristics from a fundamental perspective and partial discharge (PD) measurements from an industrial perspective, in a hydrocarbon insulating liquid. The aim was to investigate the possible changes of the liquid’s streamer and PD characteristics and their correlations when the uniformity of the AC electric field varies. In the experiments, a plane-to-plane electrode system incorporating a needle protrusion was used in addition to a needle-to-plane electrode system. When the applied electric field became more uniform, fewer radial branches occurred and streamer propagation towards the ground electrode was enhanced. The transition from streamer propagation dominated breakdown in divergent fields to streamer initiation dominated breakdown in uniform fields was evidenced. Relationships between streamer and PD characteristics were established, which were found to be electric field dependent. PD of the same apparent charge would indicate longer streamers if the electric field is more uniform. (paper)

  19. Environmental Stresses of Field Growth Allow Cinnamyl Alcohol Dehydrogenase-Deficient Nicotiana attenuata Plants to Compensate for their Structural Deficiencies1[C][W][OA

    Science.gov (United States)

    Kaur, Harleen; Shaker, Kamel; Heinzel, Nicolas; Ralph, John; Gális, Ivan; Baldwin, Ian T.

    2012-01-01

    The organized lignocellulosic assemblies of cell walls provide the structural integrity required for the large statures of terrestrial plants. Silencing two CINNAMYL ALCOHOL DEHYDROGENASE (CAD) genes in Nicotiana attenuata produced plants (ir-CAD) with thin, red-pigmented stems, low CAD and sinapyl alcohol dehydrogenase activity, low lignin contents, and rubbery, structurally unstable stems when grown in the glasshouse (GH). However, when planted into their native desert habitat, ir-CAD plants produced robust stems that survived wind storms as well as the wild-type plants. Despite efficient silencing of NaCAD transcripts and enzymatic activity, field-grown ir-CAD plants had delayed and restricted spread of red stem pigmentation, a color change reflecting blocked lignification by CAD silencing, and attained wild-type-comparable total lignin contents. The rubbery GH phenotype was largely restored when field-grown ir-CAD plants were protected from wind, herbivore attack, and ultraviolet B exposure and grown in restricted rooting volumes; conversely, it was lost when ir-CAD plants were experimentally exposed to wind, ultraviolet B, and grown in large pots in growth chambers. Transcript and liquid chromatography-electrospray ionization-time-of-flight analysis revealed that these environmental stresses enhanced the accumulation of various phenylpropanoids in stems of field-grown plants; gas chromatography-mass spectrometry and nuclear magnetic resonance analysis revealed that the lignin of field-grown ir-CAD plants had GH-grown comparable levels of sinapaldehyde and syringaldehyde cross-linked into their lignins. Additionally, field-grown ir-CAD plants had short, thick stems with normal xylem element traits, which collectively enabled field-grown ir-CAD plants to compensate for the structural deficiencies associated with CAD silencing. Environmental stresses play an essential role in regulating lignin biosynthesis in lignin-deficient plants. PMID:22645069

  20. EFFECTS OF HEAT STRESS ON BLOOD ACID-BASE BALANCE AND MINERAL CONTENT IN GUINEA FOWLS WHEN DRINKING WATER TREATED WITH MAGNETIC FIELD WAS USED

    Directory of Open Access Journals (Sweden)

    Beata GŁOWIŃSKA

    2011-01-01

    Full Text Available The purpose of the study was to examine the effect of 24-hour heat stress on blood acid-base balance parameters and mineral content in guinea fowls when drinking water treated with magnetic field was used. The maximum environmental temperature at the end of the present experiment was 32oC. The relative humidity was maintained at 55% (±2. Blood samples were collected from birds three times: in the 1st, 12th and 24th hour of stress. Exposure to heat stress significantly increased blood bicarbonate ion concentration (HCO3 -, content of buffer alkali (BB and decreased shortage of alkali (BE but only in the 12th hour of stress. In the level of oxygen pressure (pO2 and percentage of oxygen content (O2sat in the 12th and 24th hour of the experiment statistically high significant decrease occurred. In consequence of high environmental temperature the statistically significant decrease of sodium was found. No changes in the level of potassium and chlorine ions in guinea fowls watered magnetized water occurred.

  1. Stress analysis of the conceptual design configurations of constant tension D-shaped superconducting toroidal field coils for TNS

    International Nuclear Information System (INIS)

    Fernades, R.; Smith, R.A.

    1977-01-01

    Conceptual design configurations of D-shaped toroidal field coils applicable to the TNS program are studied under the action of the toroidal field loading condition and the vertical field loading condition, but not the fault condition. Although the analysis is specific to an 8 Tesla design using a niobium titanium superconductor, the results can be extended to a coil with a different conductor material and subjected to a field of different magnitude provided the condition of linear elasticity is not violated. The analysis technique used is the finite element method, with three dimensional finite elements defined in the ANSYS computer code, and supplemented by closed form analytical solutions

  2. A Structural Finite Element Model for Lamellar Unit of Aortic Media Indicates Heterogeneous Stress Field After Collagen Recruitment

    Science.gov (United States)

    Thunes, James R.; Pal, Siladitya; Fortunato, Ronald N.; Phillippi, Julie A.; Gleason, Thomas G.; Vorp, David A.; Maiti, Spandan

    2016-01-01

    Incorporation of collagen structural information into the study of biomechanical behavior of ascending thoracic aortic (ATA) wall tissue should provide better insight into the pathophysiology of ATA. Structurally motivated constitutive models that include fiber dispersion and recruitment can successfully capture overall mechanical response of the arterial wall tissue. However, these models cannot examine local microarchitectural features of the collagen network, such as the effect of fiber disruptions and interaction between fibrous and non-fibrous components, which may influence emergent biomechanical properties of the tissue. Motivated by this need, we developed a finite element based three-dimensional structural model of the lamellar units of the ATA media that directly incorporates the collagen fiber microarchitecture. The fiber architecture was computer generated utilizing network features, namely fiber orientation distribution, intersection density and areal concentration, obtained from image analysis of multiphoton microscopy images taken from human aneurysmal ascending thoracic aortic media specimens with bicuspid aortic valve (BAV) phenotype. Our model reproduces the typical J-shaped constitutive response of the aortic wall tissue. We found that the stress state in the non-fibrous matrix was homogeneous until the collagen fibers were recruited, but became highly heterogeneous after that event. The degree of heterogeneity was dependent upon local network architecture with high stresses observed near disrupted fibers. The magnitude of non-fibrous matrix stress at higher stretch levels was negatively correlated with local fiber density. The localized stress concentrations, elucidated by this model, may be a factor in the degenerative changes in aneurysmal ATA tissue. PMID:27113538

  3. Investigation of Lattice and Thermal Stress in GaN/A1GaN Field-Effect Transistors

    National Research Council Canada - National Science Library

    Boutros, Karim

    2006-01-01

    ...) for the period 7/1/06 - 9/30/06. Our overall goal is to understand the role and contribution of residual stress and junction temperature on the degradation of AlGaN/GaN HEMT electrical device characteristics...

  4. Coping, Stress, and Job Satisfaction as Predictors of Advanced Placement Statistics Teachers' Intention to Leave the Field

    Science.gov (United States)

    McCarthy, Christopher J.; Lambert, Richard G.; Crowe, Elizabeth W.; McCarthy, Colleen J.

    2010-01-01

    This study examined the relationship of teachers' perceptions of coping resources and demands to job satisfaction factors. Participants were 158 Advanced Placement Statistics high school teachers who completed measures of personal resources for stress prevention, classroom demands and resources, job satisfaction, and intention to leave the field…

  5. The global existence problem in general relativity

    CERN Document Server

    Andersson, L

    2000-01-01

    We survey some known facts and open questions concerning the global properties of 3+1 dimensional space--times containing a compact Cauchy surface. We consider space--times with an $\\ell$--dimensional Lie algebra of space--like Killing fields. For each $\\ell \\leq 3$, we give some basic results and conjectures on global existence and cosmic censorship. For the case of the 3+1 dimensional Einstein equations without symmetries, a new small data global existence result is announced.

  6. Stress shadows - a controversial topic

    Science.gov (United States)

    Lasocki, Stanislaw; Karakostas, Vassilis G.; Papadimitriou, Eletheria E.; Orlecka-Sikora, Beata

    2010-05-01

    the sign of the change though distinctly more in areas of positive than of negative change. In the case of seismicity accompanying underground mining exploitation the coseismic stress changes expressed in terms of the Coulomb failure function are at least of one order smaller than those for earthquakes. Furthermore, they are only a small component of the total stress field variations in mining rockmass, which are mainly controlled by the mining process. Nevertheless, our studies of the induced seismicity in the Rudna mine in the Legnica-Głogow Copper District in Poland showed that the influence of the Coulomb stress changes on locations of subsequent events was statistically significant. We analyzed series of seismic events quantifying the triggering and inhibiting effect by the proportion of events in the series whose locations were consistent with the stress increased and stress decreased zones, respectively. It was found out that more than 60 per-cent of the analyzed seismic events occurred in areas where stress was enhanced due to the occurrence of previous events. The significance of this result was determined by comparing it with 2000 results of the same analysis carried out on the random permutations of the original series of events. The test indicated that the locations in positive stress changes areas were preferred statistically significantly when the stress changes exceeded 0.05 bar. However, no statistically significant inhibiting effect of negative static stress changes, within the considered range of these changes, was ascertained. Here we present details of these two studies and discuss possible reasons behind the negative conclusions on the existence of stress shadows.

  7. Residual stresses

    International Nuclear Information System (INIS)

    Macherauch, E.

    1978-01-01

    Residual stresses are stresses which exist in a material without the influence of external powers and moments. They come into existence when the volume of a material constantly changes its form as a consequence of mechanical, thermal, and/or chemical processes and is hindered by neighbouring volumes. Bodies with residual stress are in mechanical balance. These residual stresses can be manifested by means of all mechanical interventions disturbing this balance. Acoustical, optical, radiological, and magnetical methods involving material changes caused by residual stress can also serve for determining residual stress. Residual stresses have an ambivalent character. In technical practice, they are feared and liked at the same time. They cause trouble because they can be the cause for unexpected behaviour of construction elements. They are feared since they can cause failure, in the worst case with catastrophical consequences. They are appreciated, on the other hand, because, in many cases, they can contribute to improvements of the material behaviour under certain circumstances. But they are especially liked for their giving convenient and (this is most important) mostly uncontrollable explanations. For only in very few cases we have enough knowledge and possibilities for the objective evaluation of residual stresses. (orig.) [de

  8. Essential features of residual stress determination in thin-walled plane structures in a base of whole field interferometric measurements

    Science.gov (United States)

    Pisarev, Vladimir S.; Odintsev, I.; Balalov, V.; Apalkov, A.

    2003-05-01

    Sophisticated technique for reliable quantitative deriving residual stress values from initial experimental data, which are inherent in combined implementing the hole drilling method with both holographic and speckle interferometry, is described in detail. The approach developed includes both possible ways of obtaining initial experimental information. The first of them consists of recording a set of required interference fringe patterns, which are resulted from residual stress energy release after through hole drilling, in two orthogonal directions that coincide with principal strain directions. The second way is obtaining a series of interrelated fringe patterns when a direction of either observation in reflection hologram interferometry or dual-beam illumination in speckle interferometry lies arbitrary with respect to definite principal strain direction. A set of the most typical both actual and analogous reference fringe patterns, which are related to both reflection hologram and dual-beam speckle interferometry, are presented.

  9. Metabolic syndrome biomarkers and early breast cancer in Saudi women: evidence for the presence of a systemic stress response and/or a pre-existing metabolic syndrome-related neoplasia risk?

    International Nuclear Information System (INIS)

    Alokail, Majed S; Al-Daghri, Nasser; Abdulkareem, Amal; Draz, Hossam M; Yakout, Sobhy M; Alnaami, Abdullah M; Sabico, Shaun; Alenad, Amal M; Chrousos, George P

    2013-01-01

    Obesity has been linked to many adverse health consequences, including breast cancer. This study aims to determine adipocytokine and other biological changes in recently diagnosed breast cancer patients before therapy is started. A total of 109 female Saudi subjects [56 newly diagnosed, treatment-naïve, histologically-confirmed breast cancer cases and 53 age- and BMI-matched controls] were enrolled in this study. Anthropometric data were collected. Serum insulin, adipocytokines and plasminogen activator inhibitor-1 (PAI-1) concentrations were measured using a customized multiplex Luminex assay. Hypersensitive C-Reactive Protein (CRP), tumor necrosis factor-alpha (TNF-α), and angiotensin II (ANG II) were measured using ELISA. A few days in the diagnosis, breast cancer subjects had significantly higher systolic blood pressure (p = 0.03), glucose (p = 0.01), triglycerides (p = 0.001), leptin (p = 0.044), resistin (p = 0.04), ANG II (p = 0.02), TNF-α (p = 0.045), and CRP (p = 0.04) than the controls. On the other hand, HDL (p = 0.01) and adiponectin (p = 0.02) were significantly lower in cancer subjects than controls. A significant association was found between elevated triglycerides (TG) and breast cancer [OR (95% CI), 6.1(1.8, 15.6), p = 0.004], as well as elevated ANG II [OR (95% CI), 5.2(1.2, 14.3), p = 0.03]. On the other hand, aPAI and HDL correlated negatively with breast cancer [OR (95% CI), 0.076(0.01, 0.34), p = 0.001; 0.30(0.09, 0.95), p 0.04, respectively]. Circulating ANGII and triglycerides were positively associated with early breast cancer. In contrast, HDL-cholesterol correlated negatively with ANG II and aPAI in these patients. This suggests that patients with recently diagnosed breast cancer have biochemical changes consistent with an activated stress response and/or that patients with metabolic syndrome manifestations have a higher risk of developing this disease

  10. Field Measurement of Dynamic Compressive Stress Response of Pavement-Subgrade Induced by Moving Heavy-Duty Trucks

    Directory of Open Access Journals (Sweden)

    Lingshi An

    2018-01-01

    Full Text Available This paper presents the dynamic compressive stress response of pavement-subgrade induced by moving heavy-duty trucks. In order to study the distribution characteristic of dynamic pressure of pavement-subgrade in more detail, truck loadings, truck speeds, and dynamic pressure distributions at different depths were monitored under twenty-five working conditions on the section of Qiqihar-Nenjiang Highway in Heilongjiang Province, China. The effects of truck loading, truck speed, and depth on dynamic compressive stress response can be concluded as follows: (1 increasing truck loading will increase the dynamic pressure amplitude of subgrade-pavement and dominant frequencies are close to the characteristic frequencies caused by heavy-duty trucks at the speed of 70 km/h; (2 as truck speed increases, the dynamic pressure amplitudes of measuring points have an increasing tendency; the dynamic pressure spectrums are also significantly influenced by truck speed: the higher the truck speed, the wider the spectrum and the higher the dominant frequencies; (3 as depth increases, the dynamic pressure amplitudes of measuring points decrease rapidly. The influence of the front axle decreases gradually until disappearing and the compressive stress superposition phenomenon caused by rear double axles can be found with increasing depth.

  11. Stable symbiotic nitrogen fixation under water-deficit field conditions by a stress-tolerant alfalfa microsymbiont and its complete genome sequence.

    Science.gov (United States)

    Jozefkowicz, Cintia; Brambilla, Silvina; Frare, Romina; Stritzler, Margarita; Piccinetti, Carlos; Puente, Mariana; Berini, Carolina Andrea; Pérez, Pedro Reyes; Soto, Gabriela; Ayub, Nicolás

    2017-12-10

    We here characterized the stress-tolerant alfalfa microsymbiont Sinorhizobium meliloti B401. B401-treated plants showed high nitrogen fixation rates under humid and semiarid environments. The production of glycine betaine in isolated bacteroids positively correlated with low precipitation levels, suggesting that this compound acts as a critical osmoprotectant under field conditions. Genome analysis revealed that strain B401 contains alternative pathways for the biosynthesis and uptake of glycine betaine and its precursors. Such genomic information will offer substantial insight into the environmental physiology of this biotechnologically valuable nitrogen-fixing bacterium. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Residual stresses around Vickers indents

    International Nuclear Information System (INIS)

    Pajares, A.; Guiberteau, F.; Steinbrech, R.W.

    1995-01-01

    The residual stresses generated by Vickers indentation in brittle materials and their changes due to annealing and surface removal were studied in 4 mol% yttria partially stabilized zirconia (4Y-PSZ). Three experimental methods to gain information about the residual stress field were applied: (i) crack profile measurements based on serial sectioning, (ii) controlled crack propagation in post indentation bending tests and (iii) double indentation tests with smaller secondary indents located around a larger primary impression. Three zones of different residual stress behavior are deduced from the experiments. Beneath the impression a crack free spherical zone of high hydrostatic stresses exists. This core zone is followed by a transition regime where indentation cracks develop but still experience hydrostatic stresses. Finally, in an outward third zone, the crack contour is entirely governed by the tensile residual stress intensity (elastically deformed region). Annealing and surface removal reduce this crack driving stress intensity. The specific changes of the residual stresses due to the post indentation treatments are described and discussed in detail for the three zones

  13. Acute and chronic effects of exposure to a 1-mT magnetic field on the cytoskeleton, stress proteins, and proliferation of astroglial cells in culture

    International Nuclear Information System (INIS)

    Bodega, G.; Forcada, I.; Suarez, I.; Fernandez, B.

    2005-01-01

    This paper reports the effects of exposure to static, sinusoidal (50 Hz), and combined static/sinusoidal magnetic fields on cultured astroglial cells. Confluent primary cultures of astroglial cells were exposed to a 1-mT sinusoidal, static, or combined magnetic field for 1 h. In another experiment, cells were exposed to the combined magnetic field for 1, 2, and 4 h. The hsp25, hsp60, hsp70, actin, and glial fibrillary acidic protein contents of the astroglial cells were determined by immunoblotting 24 h after exposure. No significant differences were seen between control and exposed cells with respect to their contents of these proteins, neither were any changes in cell morphology observed. In a third experiment to determine the effect of a chronic (11-day) exposure to a combined 1-mT static/sinusoidal magnetic field on the proliferation of cultured astroglial cells, no significant differences were seen between control, sham-exposed, or exposed cells. These results suggest that exposure to 1-mT sinusoidal, static, or combined magnetic fields has no significant effects on the stress, cytoskeletal protein levels in, or proliferation of cultured astroglial cells

  14. Structural and numerical modeling of fluid flow and evolving stress fields at a transtensional stepover: A Miocene Andean porphyry copper system as a case study.

    Science.gov (United States)

    Nuñez, R. C.; Griffith, W. A.; Mitchell, T. M.; Marquardt, C.; Iturrieta, P. C.; Cembrano, J. M.

    2017-12-01

    Obliquely convergent subduction orogens show both margin-parallel and margin-oblique fault systems that are spatially and temporally associated with ore deposits and geothermal systems within the volcanic arc. Fault orientation and mechanical interaction among different fault systems influence the stress field in these arrangements, thus playing a first order