THEORETICAL COMPUTATION OF A STRESS FIELD IN A CYLINDRICAL GLASS SPECIMEN

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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.

Self-generation of magnetic fields

International Nuclear Information System (INIS)

Dolan, T.J.

2000-01-01

The stars generate self-magnetic fields on large spatial scales and long time scales,and laser-produced plasmas generate intense self-magnetic fields on very short spatial and time scales. Two questions are posed : (1) Could a self-magnetic field be generated in a laboratory plasma with intermediate spatial and time scales? (2) If a self-magnetic field were generated,would it evolve towards a minimum energy state? If the answers turned out to be affirmative,then self-magnetic fields could possibly have interesting applications

Stress field of a dislocating inclined fault

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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.

Evaluation of stresses generated in steel finger joint of bridge by X-ray stress measurement

International Nuclear Information System (INIS)

Kohri, Ami; Kawano, Yutaka; Nishido, Takayuki

2017-01-01

In a steel bridge, the evaluation of the stress generated in the finger joint without a gap to absorb temperature change can be an index when evaluating the remaining life. This study chose as the object the finger joint of a diagonal bridge, where the generated stress state is considered to be more complicated, prepared a finger joint test specimen that simulated an actual part, and performed a load test. For judgment, FEM analysis, non-destructive X-ray stress measurement, and measurement of the generated stress using strain gauge were applied. Compared with the FEM analysis results, the difference in the stress value was generated due to the difference in the contact state, but the trends of the stress distribution were equivalent. In addition, the same measurement value as the strain gauge was obtained, and the validity of the X-ray stress measurement method was confirmed. As a result, it was found that the stress measurement method by X-ray is effective for measuring the generated stress including the residual stress of the finger joint without gap at a bridge. (A.O.)

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.

Inertial effects on the stress generation of active fluids

Science.gov (United States)

Takatori, S. C.; Brady, J. F.

2017-09-01

Suspensions of self-propelled bodies generate a unique mechanical stress owing to their motility that impacts their large-scale collective behavior. For microswimmers suspended in a fluid with negligible particle inertia, we have shown that the virial swim stress is a useful quantity to understand the rheology and nonequilibrium behaviors of active soft matter systems. For larger self-propelled organisms such as fish, it is unclear how particle inertia impacts their stress generation and collective movement. Here we analyze the effects of finite particle inertia on the mechanical pressure (or stress) generated by a suspension of self-propelled bodies. We find that swimmers of all scales generate a unique swim stress and Reynolds stress that impact their collective motion. We discover that particle inertia plays a similar role as confinement in overdamped active Brownian systems, where the reduced run length of the swimmers decreases the swim stress and affects the phase behavior. Although the swim and Reynolds stresses vary individually with the magnitude of particle inertia, the sum of the two contributions is independent of particle inertia. This points to an important concept when computing stresses in computer simulations of nonequilibrium systems: The Reynolds and the virial stresses must both be calculated to obtain the overall stress generated by a system.

Co-Rumination Exacerbates Stress Generation among Adolescents with Depressive Symptoms.

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Rose, Amanda J; Glick, Gary C; Smith, Rhiannon L; Schwartz-Mette, Rebecca A; Borowski, Sarah K

2017-07-01

Through stress generation, individuals' own thoughts and behaviors can actually lead to increases in their experience of stress. Unfortunately, stress generation is especially common among individuals who are already suffering from elevated depressive symptoms. However, despite the acknowledgement that some individuals with depressive symptoms generate greater stress than others, few studies have identified specific factors that could exacerbate stress generation among individuals with depressive symptoms. The present study examines co-rumination as a factor that might exacerbate stress generation among adolescents with depressive symptoms using a short-term longitudinal design. Considering these processes among adolescents was critical given that many youth experience increases in depressive symptoms at this developmental stage and that co-rumination also becomes more common at adolescence. Participants were 628 adolescents (326 girls; 302 boys) who reported on their depressive symptoms, experiences of stress, and co-rumination with a best friend. Interpersonal stressors (peer and family stress) and non-interpersonal stressors (school and sports stress) were assessed. Consistent with past research, adolescents with depressive symptoms experienced greater interpersonal and non-interpersonal stress over time. Importantly, co-rumination interacted with both depressive symptoms and gender in predicting increases in peer stress. Depressive symptoms predicted the generation of peer stress only for girls who reported high levels of co-rumination with friends. Implications for protecting youth with depressive symptoms against stress generation are discussed.

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.

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.

Does the stress generation hypothesis apply to eating disorders?: an examination of stress generation in eating, depressive, and anxiety symptoms.

Science.gov (United States)

Bodell, Lindsay P; Hames, Jennifer L; Holm-Denoma, Jill M; Smith, April R; Gordon, Kathryn H; Joiner, Thomas E

2012-12-15

The stress generation hypothesis posits that individuals actively contribute to stress in their lives. Although stress generation has been studied frequently in the context of depression, few studies have examined whether this stress generation process is unique to depression or whether it occurs in other disorders. Although evidence suggests that stress contributes to the development of eating disorders, it is unclear whether eating disorders contribute to subsequent stress. A prospective design was used to examine the influence of eating disorder symptoms on negative life stressors. Two hundred and ninety female undergraduates completed questionnaires at two time points that examined eating disorder, depressive and anxiety symptoms and the presence of negative life events. Regression analyses found that while eating disorder symptoms (i.e. bulimic symptoms and drive for thinness) were independent, significant predictors of negative life events, they did not predict negative life events above and beyond symptoms of depression. Limitations include the use of self-report measures and a college-based sample, which may limit generalizability of the results. Findings suggest that if stress generation is present in individuals with symptoms of eating disorders, it is likely attributable to symptoms of depression. Thus, it may be important for clinicians to target depressive symptoms in order to reduce the frequency of negative life stressors among individuals with eating disorders. Copyright © 2012 Elsevier B.V. All rights reserved.

The residual stress evaluation for expansion process of steam generator tubes

International Nuclear Information System (INIS)

King, C.-S.; Lee, S.-C.; Shim, D.-N.

2004-01-01

The reliability of a nuclear power plant is affected by the reliability of steam generator tube and the reliability of steam generator tube is affected by stress corrosion cracking(SCC). Many steam generator tubes were experiencing stress corrosion cracking and stress corrosion cracking is affected material characteristics, corrosive environments and added stresses. The added stresses have the manufacturing stresses and operating stresses, the manufacturing stresses include the residual stresses generating in the tube manufacture and tube expanding procedure. We will investigate for influence which affected to residual stresses with tube plastic deformation method and measurement region. (author)

Negative life events and symptoms of depression and anxiety: stress causation and/or stress generation.

Science.gov (United States)

Phillips, Anna C; Carroll, Douglas; Der, Geoff

2015-01-01

Stressful life events are known to contribute to development of depression; however, it is possible this link is bidirectional. The present study examined whether such stress generation effects are greater than the effects of stressful life events on depression, and whether stress generation is also evident with anxiety. Participants were two large age cohorts (N = 732 aged 44 years; N = 705 aged 63 years) from the West of Scotland Twenty-07 study. Stressful life events, depression, and anxiety symptoms were measured twice five years apart. Cross-lagged panel analysis examined the mutual influences of stressful life events on depression and on anxiety over time. Life events predicted later depressive symptomatology (p = .01), but the depression predicting life events relationship was less strong (p = .06), whereas earlier anxiety predicted life events five years later (p = .001). There was evidence of sex differences in the extent to which life events predicted later anxiety. This study provides evidence of stress causation for depression and weaker evidence for stress generation. In contrast, there was strong evidence of stress generation for anxiety but weaker evidence for stress causation, and that differed for men and women.

Normal personality traits, rumination and stress generation among early adolescent girls

Science.gov (United States)

Stroud, Catherine B.; Sosoo, Effua E.; Wilson, Sylia

2017-01-01

This study examined associations between personality and stress generation. Expanding upon prior work, we examined (a) the role of Positive Emotionality (PE), Negative Emotionality (NE), and Constraint (CON), and their lower-order facets, as predictors of acute and chronic interpersonal stress generation; (b) whether personality moderated effects of rumination on stress generation; and (c) whether personality increased exposure to independent (uncontrollable) stress. These questions were examined in a one-year study of 126 adolescent girls (M age = 12.39 years) using contextual stress interviews. NE predicted increases in acute and chronic interpersonal stress generation, but not independent stress. NE, CON and affiliative PE each moderated the effect of rumination on chronic interpersonal stress generation. These effects were driven by particular lower-order traits. PMID:28845067

Laser-induced generation of pure tensile stresses

International Nuclear Information System (INIS)

Niemz, M.H.; Lin, C.P.; Pitsillides, C.; Cui, J.; Doukas, A.G.; Deutsch, T.F.

1997-01-01

While short compressive stresses can readily be produced by laser ablation, the generation of pure tensile stresses is more difficult. We demonstrate that a 90 degree prism made of polyethylene can serve to produce short and pure tensile stresses. A compressive wave is generated by ablating a thin layer of strongly absorbing ink on one surface of the prism with a Q-switched frequency-doubled Nd:YAG laser. The compressive wave driven into the prism is reflected as a tensile wave by the polyethylene-air interface at its long surface. The low acoustic impedance of polyethylene makes it ideal for coupling tensile stresses into liquids. In water, tensile stresses up to -200bars with a rise time of the order of 20 ns and a duration of 100 ns are achieved. The tensile strength of water is determined for pure tensile stresses lasting for 100 ns only. The technique has potential application in studying the initiation of cavitation in liquids and in comparing the effect of compressive and tensile stress transients on biological media. copyright 1997 American Institute of Physics

DC Motor control using motor-generator set with controlled generator field

Science.gov (United States)

Belsterling, Charles A.; Stone, John

1982-01-01

A d.c. generator is connected in series opposed to the polarity of a d.c. power source supplying a d.c. drive motor. The generator is part of a motor-generator set, the motor of which is supplied from the power source connected to the motor. A generator field control means varies the field produced by at least one of the generator windings in order to change the effective voltage output. When the generator voltage is exactly equal to the d.c. voltage supply, no voltage is applied across the drive motor. As the field of the generator is reduced, the drive motor is supplied greater voltage until the full voltage of the d.c. power source is supplied when the generator has zero field applied. Additional voltage may be applied across the drive motor by reversing and increasing the reversed field on the generator. The drive motor may be reversed in direction from standstill by increasing the generator field so that a reverse voltage is applied across the d.c. motor.

Apparatuses and methods for generating electric fields

Science.gov (United States)

Scott, Jill R; McJunkin, Timothy R; Tremblay, Paul L

2013-08-06

Apparatuses and methods relating to generating an electric field are disclosed. An electric field generator may include a semiconductive material configured in a physical shape substantially different from a shape of an electric field to be generated thereby. The electric field is generated when a voltage drop exists across the semiconductive material. A method for generating an electric field may include applying a voltage to a shaped semiconductive material to generate a complex, substantially nonlinear electric field. The shape of the complex, substantially nonlinear electric field may be configured for directing charged particles to a desired location. Other apparatuses and methods are disclosed.

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.

Transient thermal stresses in composite hollow circular cylinder due to partial heat generation

International Nuclear Information System (INIS)

Goshima, Takahito; Miyao, Kaju

1979-01-01

Clad materials are adopted for the machines and structures used in contact with high temperature, corrosive atmosphere in view of their strength and economy. Large thermal stress sometimes arises in clad cylinders due to uneaven temperature field and the difference in linear thermal expansion. Vessels are often heated uneavenly, and shearing stress occurs, which is not observed in uniform heating. In this study, infinitely long, concentric cylinders of two layers were analyzed, when the internal heat changing in stepped state is generated in cylindrical form. The unsteady thermal stress occurred was determined, using thermo-elastic potential and stress functions, and assuming the thermal properties and elastic modulus of materials as constant regardless of the temperature. Laplace transformation was used, and the basic equations for thermo-elastic displacement were employed as the basis of calculation. The analysis of the temperature distribution and stress is explained. Numerical calculation was carried out on the example of an internal cylinder of SUS 304 stainless steel and an external cylinder of mild steel. The maximum shearing stress occurred in the direction of 40 deg from the heat source, and was affected largely by the position of heat generation. The effect became remarkable as time elapsed. (Kako, I.)

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.

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.

Stress analysis of steam generator row-1 tubes

International Nuclear Information System (INIS)

Kim, Woo Gon; Ryu, Woo Seog; Lee, Ho Jin; Kim, Sung Chung

2000-01-01

Residual stresses induced in U-bending and tube-to-tubesheet joining processes of PWR's steam generator row-1 tube were measured by X-ray method and Hole-Drilling Method(HDM). The stresses resulting from the internal pressure and the temperature gradient in the steam generator were also estimated theoretically. In U-bent regions, the residual stresses at extrados were induced with compressive stress(-), and its maximum value reached -319 Mpa in axial direction at ψ=0 .deg. in position. Maximum tensile residual stress of 170 MPa was found to be at the flank side at position of ψ=90 deg., i.e., at apex region. In tube-to-tubesheet joining methods, the residual stresses induced by the explosive joint method were found to be lower than that by the mechanical roll method. The gradient of residual stress along the expanded tube was highest at the transition region, and the residual stress in circumferential direction was found to be higher than the residual stress in axial direction. Hoop stress due to an internal pressure between primary and secondary side was analyzed to be 76 MPa and thermal stress was 45 MPa

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.

Residual stresses generated in F-522 steel by different machining processes

International Nuclear Information System (INIS)

Gracia-Navas, V.; Ferreres, I.; Maranon, J. A.; Garcia-Rosales, C.; Gil-Sevillano, J.

2005-01-01

Machining operations induce plastic deformation and heat generation in the near surface area of the machined part, giving rise to residual stresses. Depending on their magnitude and sign, these stresses can be detrimental or beneficial to the service life of the part. The final stress state depends on the machining process applied, as well as on the machining parameters. Therefore, the establishment of adequate machining guidelines requires the measurement of the residual stresses generated both at the surface and inside the material. in this work, the residual stresses generated in F-522 steel by two hard turning (conventional and laser assisted) and two grinding (production and finishing) processes were measured by X-ray diffraction. Additionally, depth profiles of the volume fraction of retained austenite, microstructure and nano hardness were obtained in order to correlate those results with the residual stress state obtained for each machining process. It has been observed that turning generates tensile stresses in the surface while grinding causes compressive stresses. Below the surface grinding generates weak tensile or nearly null stresses whereas turning generates strong compressive stresses. These results show that the optimum mechanising process (disregarding economical considerations) implies the combination of turning plus elimination of a small thickness by final grinding. (Author) 19 refs

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.

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.

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°.

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

Stress generation by myosin minifilaments in actin bundles

International Nuclear Information System (INIS)

Dasanayake, Nilushi L; Carlsson, Anders E

2013-01-01

Forces and stresses generated by the action of myosin minifilaments are analyzed in idealized computer-generated actin bundles, and compared to results for isotropic actin networks. The bundles are generated as random collections of actin filaments in two dimensions with constrained orientations, crosslinked and attached to two fixed walls. Myosin minifilaments are placed on actin filament pairs and allowed to move and deform the network so that it exerts forces on the walls. The vast majority of simulation runs end with contractile minifilament stress, because minifilaments rotate into energetically stable contractile configurations. This process is aided by the bending and stretching of actin filaments, which accomodate minifilament rotation. Stresses for bundles are greater than those for isotropic networks, and antiparallel filaments generate more tension than parallel filaments. The forces transmitted by the actin network to the walls of the simulation cell often exceed the tension in the minifilament itself. (paper)

Negative life events and symptoms of depression and anxiety: stress causation and/or stress generation

OpenAIRE

Phillips, Anna C.; Carroll, Douglas; Der, Geoffrey

2015-01-01

Background and Objectives: Stressful life events are known to contribute to development of depression, however, it is possible this link is bi-directional. The present study examined whether such stress generation effects are greater than the effects of stressful life events on depression, and whether stress generation is also evident with anxiety. Design: Participants were two large age cohorts (N = 732 aged 44 years; N = 705 aged 63 years) from the West of Scotland Twenty-07 study. Methods:...

Normal personality traits, rumination and stress generation among early adolescent girls

OpenAIRE

Stroud, Catherine B.; Sosoo, Effua E.; Wilson, Sylia

2015-01-01

This study examined associations between personality and stress generation. Expanding upon prior work, we examined (a) the role of Positive Emotionality (PE), Negative Emotionality (NE), and Constraint (CON), and their lower-order facets, as predictors of acute and chronic interpersonal stress generation; (b) whether personality moderated effects of rumination on stress generation; and (c) whether personality increased exposure to independent (uncontrollable) stress. These questions were exam...

Idea Generation in Highly Institutionalized Fields

DEFF Research Database (Denmark)

Agoguè, Marine; Boxenbaum, Eva

innovation. An important question facing innovation research is thus how actors can generate ideas that break with the field frame in highly institutionalized fields? To answer this question, we draw on insights into dual process modeling from cognitive sciences. Dual process modeling emphasizes...... the different nature of the conscious (deliberate) and subconscious (implicit) systems involved in ideation. We further elaborate on how these two systems relate to four streams of research that management scholars evoke to model microprocesses of generating new ideas, namely metaphors, conceptual blending......The early phase of innovation processes in highly institutionalized fields relies on the capabilities of actors to generate new ideas that break with the field frame. Informed by a dominant logic, a field frame shapes collective cognition and can thus prevent the generation of new ideas and block...

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

A longitudinal examination of stress generation in depressive and anxiety disorders.

Science.gov (United States)

Uliaszek, Amanda A; Zinbarg, Richard E; Mineka, Susan; Craske, Michelle G; Griffith, James W; Sutton, Jonathan M; Epstein, Alyssa; Hammen, Constance

2012-02-01

The current study compared two competing theories of the stress generation model of depression (stress causation vs. stress continuation) using interview-based measures of episodic life stress, as well as interpersonal and noninterpersonal chronic life stress. We also expanded on past research by examining anxiety disorders as well as depressive disorders. In addition, we examined the role of neuroticism and extraversion in these relationships. Participants were 627 adolescents enrolled in a two-site, longitudinal study of risk factors for depressive and anxiety disorders. Baseline and follow-up assessments were approximately one year apart. Results supported the stress causation theory for episodic stress generation for anxiety disorders, with neuroticism partially accounting for this relationship. The stress causation theory was also supported for depression, but only for more moderate to severe stressors; neuroticism partially accounted for this relationship as well. Finally, we found evidence for interpersonal and noninterpersonal chronic life stress continuation in both depressive and anxiety disorders. The present findings have implications regarding the specificity of the stress generation model to depressive disorders, as well as variables involved in the stress generation process. PsycINFO Database Record (c) 2012 APA, all rights reserved.

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

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

Reynolds stress and shear flow generation

DEFF Research Database (Denmark)

Korsholm, Søren Bang; Michelsen, Poul; Naulin, V.

2001-01-01

The so-called Reynolds stress may give a measure of the self-consistent flow generation in turbulent fluids and plasmas by the small-scale turbulent fluctuations. A measurement of the Reynolds stress can thus help to predict flows, e.g. shear flows in plasmas. This may assist the understanding...... of improved confinement scenarios such as H-mode confinement regimes. However, the determination of the Reynolds stress requires measurements of the plasma potential, a task that is difficult in general and nearly impossible in hot plasmas in large devices. In this work we investigate an alternative method......, based on density measurements, to estimate the Reynolds stress, and demonstrate the validity range of this quantity, which we term the pseudo-Reynolds stress. The advantage of such a quantity is that accurate measurements of density fluctuations are much easier to obtain experimentally. Prior...

Oxidatively generated DNA/RNA damage in psychological stress states

DEFF Research Database (Denmark)

Jørgensen, Anders

2013-01-01

age-related somatic disorders. The overall aim of the PhD project was to investigate the relation between psychopathology, psychological stress, stress hormone secretion and oxidatively generated DNA and RNA damage, as measured by the urinary excretion of markers of whole-body DNA/RNA oxidation (8...... between the 24 h urinary cortisol excretion and the excretion of 8-oxodG/8-oxoGuo, determined in the same samples. Collectively, the studies could not confirm an association between psychological stress and oxidative stress on nucleic acids. Systemic oxidatively generated DNA/RNA damage was increased......Both non-pathological psychological stress states and mental disorders are associated with molecular, cellular and epidemiological signs of accelerated aging. Oxidative stress on nucleic acids is a critical component of cellular and organismal aging, and a suggested pathogenic mechanism in several...

Strong and superstrong pulsed magnetic fields generation

CERN Document Server

Shneerson, German A; Krivosheev, Sergey I

2014-01-01

Strong pulsed magnetic fields are important for several fields in physics and engineering, such as power generation and accelerator facilities. Basic aspects of the generation of strong and superstrong pulsed magnetic fields technique are given, including the physics and hydrodynamics of the conductors interacting with the field as well as an account of the significant progress in generation of strong magnetic fields using the magnetic accumulation technique. Results of computer simulations as well as a survey of available field technology are completing the volume.

Quasi-Static Electric Field Generator

Science.gov (United States)

Generazio, Edward R. (Inventor)

2017-01-01

A generator for producing an electric field for with an inspection technology system is provided. The generator provides the required variable magnitude quasi-static electric fields for the "illumination" of objects, areas and volumes to be inspected by the system, and produces human-safe electric fields that are only visible to the system. The generator includes a casing, a driven, non-conducting and triboelectrically neutral rotation shaft mounted therein, an ungrounded electrostatic dipole element which works in the quasi-static range, and a non-conducting support for mounting the dipole element to the shaft. The dipole element has a wireless motor system and a charging system which are wholly contained within the dipole element and the support that uses an electrostatic approach to charge the dipole element.

Magnetic field generation device for magnetohydrodynamic electric power generation

International Nuclear Information System (INIS)

Kuriyama, Yoshihiko.

1993-01-01

An existent magnetic field generation device for magnetohydrodynamic electric power generation comprises at least a pair of permanent magnets disposed to an inner circumferential surface of a yoke having such a cross sectional area that two pairs of parallel sides are present, in which different magnetic poles are opposed while interposing a flow channel for a conductive fluid therebetween. Then, first permanent magnets which generate main magnetic fields are disposed each at a gap sandwiching a plane surface including a center axis of a flow channel for the conductive fluid. Second permanent magnets which generate auxiliary magnetic fields are disposed to an inner circumferential surface of a yoke intersecting the yoke to which the first permanent magnets are disposed. The magnetic poles on the side of the flow channel for the second permanent magnets have identical polarity with that of the magnetic poles of the adjacent first permanent magnets. As a result, a magnetic flux density in the flow channel for the conductive fluid can be kept homogeneous and at a high level from a position of the axial line of the flow channel to the outer circumference, thereby enabling to remarkably improve a power generation efficiency. (N.H.)

Interphase and intergranular stress generation in carbon steels

International Nuclear Information System (INIS)

Oliver, E.C.; Daymond, M.R.; Withers, P.J.

2004-01-01

Neutron diffraction spectra have been acquired during tensile straining of high and low carbon steels, in order to compare the evolution of internal stress in ferritic steel with and without a reinforcing phase. In low carbon steel, the generation of intergranular stresses predominates, while in high carbon steel similar intergranular stresses among ferrite grain families are superposed upon a large redistribution of stress between phases. Comparison is made to calculations using elastoplastic self-consistent and finite element methods

Vulnerability-specific stress generation: An examination of negative cognitive and interpersonal styles

Science.gov (United States)

Liu, Richard T.; Alloy, Lauren B.; Mastin, Becky M.; Choi, Jimmy Y.; Boland, Elaine M.; Jenkins, Abby L.

2014-01-01

Although there is substantial evidence documenting the stress generation effect in depression (i.e., the tendency for depression-prone individuals to experience higher rates of life stress to which they contribute), additional research is required to advance current understanding of the specific types of dependent stress (i.e., events influenced by characteristics and attendant behaviors of the individual) relevant to this effect. The present study tested an extension of the stress generation hypothesis, in which the content of dependent stress that is produced by depression-prone individuals is contingent upon, and matches, the nature of their particular vulnerabilities. This extension was tested within the context of two cognitive models (i.e., hopelessness theory [Abramson, Metalsky, & Alloy, 1989] and Cole’s [1990, 1991] competency-based model) and two interpersonal models (i.e., Swann’s [1987] self-verification theory and Coyne’s [1976] interpersonal theory) of depression. Overall, support was obtained for vulnerability-specific stress generation. Specifically, in analyses across vulnerability domains, evidence of stress-generation specificity was found for all domain-specific cognitive vulnerabilities except self-perceived social competence. The within-domain analyses for cognitive vulnerabilities produced more mixed results, but were largely supportive. Additionally, excessive reassurance-seeking was specifically predictive of dependent stress in the social domain, and moderated, but did not mediate, the relation between negative inferential styles overall and in the interpersonal domain and their corresponding generated stress. Finally, no evidence was found for a stress generation effect with negative feedback-seeking. PMID:24679143

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)

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....

A multifunctional energy-saving magnetic field generator

Science.gov (United States)

Xiong, Hui; Sun, Wanpeng; Liu, Jinzhen; Shi, Jinhua

2018-03-01

To improve the energy utilization of magnetic field generators for biological applications, a multifunctional energy-saving magnetic field generator (ESMFG) is presented. It is capable of producing both an alternating magnetic field (AMF) and a bipolar pulse magnetic field (BPMF) with high energy-saving and energy-reuse rates. Based on a theoretical analysis of an RLC second-order circuit, the energy-saving and energy-reuse rates of both types of magnetic fields can be calculated and are found to have acceptable values. The results of an experimental study using the proposed generator show that for the BPMF, the peak current reaches 130 A and the intensity reaches 70.3 mT. For the AMF, the intensity is 11.0 mT and the RMS current is 20 A. The energy-saving and energy-reuse rates for the AMF generator are 61.3% and 63.5%, respectively, while for the BPMF generator, the energy-saving rate is 33.6%. Thus, the proposed ESMFG has excellent potential for use in biomedical applications.

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)

Spontaneous generation and reversals of mean flows in a convectively-generated internal gravity wave field

Science.gov (United States)

Couston, Louis-Alexandre; Lecoanet, Daniel; Favier, Benjamin; Le Bars, Michael

2017-11-01

We investigate via direct numerical simulations the spontaneous generation and reversals of mean zonal flows in a stably-stratified fluid layer lying above a turbulent convective fluid. Contrary to the leading idealized theories of mean flow generation by self-interacting internal waves, the emergence of a mean flow in a convectively-generated internal gravity wave field is not always possible because nonlinear interactions of waves of different frequencies can disrupt the mean flow generation mechanism. Strong mean flows thus emerge when the divergence of the Reynolds stress resulting from the nonlinear interactions of internal waves produces a strong enough anti-diffusive acceleration for the mean flow, which, as we will demonstrate, is the case when the Prandtl number is sufficiently low, or when the energy input into the internal wavefield by the convection and density stratification are sufficiently large. Implications for mean zonal flow production as observed in the equatorial stratospheres of the Earth, Saturn and Jupiter, and possibly occurring in other geophysical systems such as planetary and stellar interiors will be briefly discussed. Funding provided by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program through Grant Agreement No. 681835-FLUDYCO-ERC-2015-CoG.

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

Blue light irradiation-induced oxidative stress in vivo via ROS generation in rat gingival tissue.

Science.gov (United States)

Yoshida, Ayaka; Shiotsu-Ogura, Yukako; Wada-Takahashi, Satoko; Takahashi, Shun-suke; Toyama, Toshizo; Yoshino, Fumihiko

2015-10-01

It has been reported that oxidative stress with reactive oxygen species (ROS) generation is induced by blue light irradiation to a living body. Only limited research has been reported in dental field on the dangers of blue light, mostly focusing on cytotoxicity associated with heat injury of dental pulp. We thus performed an in vivo study on oral tissue exposed to blue light. ROS generated upon blue light irradiation of flavin adenine dinucleotide were measured by electron spin resonance spectroscopy. After blue light irradiation, the palatal gingiva of Wistar rats were isolated. Collected samples were subjected to biochemical analysis of lipid peroxidation and glutathione. Singlet oxygen was generated by blue light irradiation, but was significantly quenched in an N-acetyl-L-cysteine (NAC) concentration-dependent manner. Blue light significantly accelerated oxidative stress and increased the oxidized glutathione levels in gingival tissue. These effects were also inhibited by NAC pre-administration. The results suggest that blue light irradiation at clinical levels of tooth bleaching treatment may enhance lipid peroxidation by the induction of oxidative stress and the consumption of a significant amount of intracellular glutathione. In addition, NAC might be an effective supplement for the protection of oral tissues against blue light irradiation-induced oxidative damage. Copyright © 2015 Elsevier B.V. All rights reserved.

Vulnerability-specific stress generation: An examination of negative cognitive and interpersonal styles

OpenAIRE

Liu, Richard T.; Alloy, Lauren B.; Mastin, Becky M.; Choi, Jimmy Y.; Boland, Elaine M.; Jenkins, Abby L.

2014-01-01

Although there is substantial evidence documenting the stress generation effect in depression (i.e., the tendency for depression-prone individuals to experience higher rates of life stress to which they contribute), additional research is required to advance current understanding of the specific types of dependent stress (i.e., events influenced by characteristics and attendant behaviors of the individual) relevant to this effect. The present study tested an extension of the stress generation...

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.

Generation of large-scale vorticity in rotating stratified turbulence with inhomogeneous helicity: mean-field theory

Science.gov (United States)

Kleeorin, N.

2018-06-01

We discuss a mean-field theory of the generation of large-scale vorticity in a rotating density stratified developed turbulence with inhomogeneous kinetic helicity. We show that the large-scale non-uniform flow is produced due to either a combined action of a density stratified rotating turbulence and uniform kinetic helicity or a combined effect of a rotating incompressible turbulence and inhomogeneous kinetic helicity. These effects result in the formation of a large-scale shear, and in turn its interaction with the small-scale turbulence causes an excitation of the large-scale instability (known as a vorticity dynamo) due to a combined effect of the large-scale shear and Reynolds stress-induced generation of the mean vorticity. The latter is due to the effect of large-scale shear on the Reynolds stress. A fast rotation suppresses this large-scale instability.

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.

Z a Fast Pulsed Power Generator for Ultra-High Magnetic Field Generation

Science.gov (United States)

Spielman, R. B.; Stygar, W. A.; Struve, K. W.; Asay, J. R.; Hall, C. A.; Bernard, M. A.; Bailey, J. E.; McDaniel, D. H.

2004-11-01

Advances in fast, pulsed-power technologies have resulted in the development of very high current drivers that have current rise times ~100 ns. The largest such pulsed power driver today is the new Z accelerator located at Sandia National Laboratories in Albuquerque, New Mexico. Z can deliver more than 20 MA with a time-to-peak of 105 ns to low inductance (~1 nH) loads. Such large drivers are capable of directly generating magnetic fields approaching 3 kT in small, 1 cm3 volumes. In addition to direct field generation, Z can be used to compress an applied, axial seed field with a plasma. Flux compression schemes are not new and are, in fact, the basis of all explosive flux-compression generators, but we propose the use of plasma armatures rather than solid, conducting armatures. We present experimental results from the Z accelerator in which magnetic fields of ~2 kT are generated and measured with several diagnostics. Issues such as energy loss in solid conductors and dynamic response of current-carrying conductors to very large magnetic fields are reviewed in context with Z experiments. We describe planned flux-compression experiments that are expected to create the highest-magnitude uniform-field volumes yet attained in the laboratory.

Estimation of a stress field in the earth`s crust using drilling-induced tensile fractures observed at well WD-1 in the Kakkonda geothermal field; Kakkonda WD-1 sei de kansokusareta drilling induced tensile fracture ni yoru chikaku oryokuba no suitei

Energy Technology Data Exchange (ETDEWEB)

Okabe, T. [GERD Geothermal Energy Research and Development Co. Ltd., Tokyo (Japan); Hayashi, K. [Tohoku Univ., Sendai (Japan). Inst. of Fluid Science; Kato, O.; Doi, N.; Miyazaki, S. [Japan Metals and Chemicals Co. Ltd., Tokyo (Japan); Uchida, T. [New Energy and Industrial Technology Development Organization, Tokyo, (Japan)

1997-05-27

This paper describes estimation of a stress field in the earth`s crust in the Kakkonda geothermal field. Formation micro imager (FMI) logging known as a crack detecting logging was performed in the well WD-1. This FMI logging has made observation possible on cracks along well axis thought to indicate size and direction of the crust stress, and drilling-induced tensile fractures (DTF). It was verified that these DTFs are generated initially in an azimuth determined by in-situ stress (an angle up to the DTF as measured counterclockwise with due north as a starting point, expressed in {theta}) in the well`s circumferential direction. It was also confirmed that a large number of cracks incline at a certain angle to the well axis (an angle made by the well axis and the DTF, expressed in {gamma}). The DTF is a crack initially generated on well walls as a result of such tensile stresses as mud pressure and thermal stress acting on the well walls during well excavation, caused by the in-situ stress field. Measurement was made on the {theta} and {gamma} from the FMI logging result, and estimation was given on a three-dimensional stress field. Elucidating the three-dimensional crust stress field in a geothermal reservoir is important in making clear the formation mechanism thereof and the growth of water-permeable cracks. This method can be regarded as an effective method. 9 refs., 8 figs., 1 tab.

Fluorescent lamp with static magnetic field generating means

Science.gov (United States)

Moskowitz, P.E.; Maya, J.

1987-09-08

A fluorescent lamp wherein magnetic field generating means (e.g., permanent magnets) are utilized to generate a static magnetic field across the respective electrode structures of the lamp such that maximum field strength is located at the electrode's filament. An increase in efficacy during operation has been observed. 2 figs.

Stress generation in a developmental context: the role of youth depressive symptoms, maternal depression, the parent-child relationship, and family stress.

Science.gov (United States)

Chan, Priscilla T; Doan, Stacey N; Tompson, Martha C

2014-02-01

The present study examined stress generation in a developmental and family context among 171 mothers and their preadolescent children, ages 8-12 years, at baseline (Time 1) and 1-year follow-up (Time 2). In the current study, we examined the bidirectional relationship between children's depressive symptoms and dependent family stress. Results suggest that children's baseline level of depressive symptoms predicted the generation of dependent family stress 1 year later. However, baseline dependent family stress did not predict an increase in children's depressive symptoms 1 year later. In addition, we examined whether a larger context of both child chronic strain (indicated by academic, behavioral, and peer stress) and family factors, including socioeconomic status and parent-child relationship quality, would influence the stress generation process. Although both chronic strain and socioeconomic status were not associated with dependent family stress at Time 2, poorer parent-child relationship quality significantly predicted greater dependent family stress at Time 2. Child chronic strain, but neither socioeconomic status nor parent-child relationship quality, predicted children's depression symptoms at Time 2. Finally, gender, maternal depression history, and current maternal depressive symptoms did not moderate the relationship between level of dependent family stress and depressive symptoms. Overall, findings provide partial support for a developmental stress generation model operating in the preadolescent period.

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.

Laser-generated magnetic fields in quasi-hohlraum geometries

Science.gov (United States)

Pollock, Bradley; Turnbull, David; Ross, Steven; Hazi, Andrew; Ralph, Joseph; Lepape, Sebastian; Froula, Dustin; Haberberger, Dan; Moody, John

2014-10-01

Laser-generated magnetic fields of 10--40 T have been produced with 100--4000 J laser drives at Omega EP and Titan. The fields are generated using the technique described by Daido et al. [Phys. Rev. Lett. 56, 846 (1986)], which works by directing a laser through a hole in one plate to strike a second plate. Hot electrons generated in the laser-produced plasma on the second plate collect on the first plate. A strap connects the two plates allowing a current of 10 s of kA to flow and generate a solenoidal magnetic field. The magnetic field is characterized using Faraday rotation, b-dot probes, and proton radiography. Further experiments to study the effect of the magnetic field on hohlraum performance are currently scheduled for Omega. This work was performed under the auspices of the United States Department of Energy by the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA-27344.

Ancestral Exposure to Stress Generates New Behavioral Traits and a Functional Hemispheric Dominance Shift.

Science.gov (United States)

Ambeskovic, Mirela; Soltanpour, Nasrin; Falkenberg, Erin A; Zucchi, Fabiola C R; Kolb, Bryan; Metz, Gerlinde A S

2017-03-01

In a continuously stressful environment, the effects of recurrent prenatal stress (PS) accumulate across generations and generate new behavioral traits in the absence of genetic variation. Here, we investigated if PS or multigenerational PS across 4 generations differentially affect behavioral traits, laterality, and hemispheric dominance in male and female rats. Using skilled reaching and skilled walking tasks, 3 findings support the formation of new behavioral traits and shifted laterality by multigenerational stress. First, while PS in the F1 generation did not alter paw preference, multigenerational stress in the F4 generation shifted paw preference to favor left-handedness only in males. Second, multigenerational stress impaired skilled reaching and skilled walking movement abilities in males, while improving these abilities in females beyond the levels of controls. Third, the shift toward left-handedness in multigenerationally stressed males was accompanied by increased dendritic complexity and greater spine density in the right parietal cortex. Thus, cumulative multigenerational stress generates sexually dimorphic left-handedness and dominance shift toward the right hemisphere in males. These findings explain the origins of apparently heritable behavioral traits and handedness in the absence of DNA sequence variations while proposing epigenetic mechanisms. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Minimal generating sets of groups, rings, and fields | Halbeisen ...

African Journals Online (AJOL)

A subset X of a group (or a ring, or a field) is called generating, if the smallest subgroup (or subring, or subfield) containing X is the group (ring, field) itself. A generating set X is called minimal generating, if X does not properly contain any generating set. The existence and cardinalities of minimal generating sets of various ...

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

Dynamical mass generation in QED with weak magnetic fields

International Nuclear Information System (INIS)

Ayala, A.; Rojas, E.; Bashir, A.; Raya, A.

2006-01-01

We study the dynamical generation of masses for fundamental fermions in quenched quantum electrodynamics in the presence of magnetic fields using Schwinger-Dyson equations. We show that, contrary to the case where the magnetic field is strong, in the weak field limit eB << m(0)2, where m(0) is the value of the dynamically generated mass in the absence of the magnetic field, masses are generated above a critical value of the coupling and that this value is the same as in the case with no magnetic field. We carry out a numerical analysis to study the magnetic field dependence of the mass function above critical coupling and show that in this regime the dynamically generated mass and the chiral condensate for the lowest Landau level increase proportionally to (eB)2

Trans-generational effects of mild heat stress on the life history traits of an aphid parasitoid.

Science.gov (United States)

Ismaeil, Ibrahim; Doury, Géraldine; Desouhant, Emmanuel; Dubois, Françoise; Prevost, Geneviève; Couty, Aude

2013-01-01

Temperature changes are common in nature and insects are particularly exposed and sensitive to such variations which can be potential stresses, ultimately affecting life history traits and overall fitness. Braconids have been widely used to study the effects of temperature on host-parasitoid interactions and the present work focused on the solitary endoparasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae Aphidiidae), an efficient biological control agent commercially used against aphids such as the potato aphid Macrosiphum euphorbiae Thomas (Sternorrhyncha: Aphididae). Contrary to previous studies using heat shocks at extreme temperatures, we evaluated the effects of mild heat stresses by transferring young parasitoid adults from the constant temperature of 20°C to either a warm (25°C) or hot (28°C) temperature, for either 1 h or 48 h. Such treatments are consistent with situations commonly experienced by parasitoids when moved from their rearing conditions to greenhouses or field conditions. The effects were evaluated both on the heat stressed A. ervi adults (G0) (immediate effects) and on their first generation (G1) progeny (trans-generational effects). G0 wasps' mortality was significantly affected by the temperature in interaction with the duration of the stress. Longevity of G0 wasps surviving the heat stress was negatively affected by the temperature and females lived longer than males. Heat stress applied to A. ervi parents also had consequences on their G1 progeny whose developmental time, rates of mummification and percentage of parasitoid completing total development were negatively affected. Surprisingly, the egg load at emergence of the G1 female progeny was increased when their mothers had been submitted to a mild heat stress of 25°C or 28°C. These results clearly demonstrate trans-generational phenotypic plasticity, showing that adaptation to thermal stresses may be achieved via maternal effects. This study also sheds light on the complexity

Trans-generational effects of mild heat stress on the life history traits of an aphid parasitoid.

Directory of Open Access Journals (Sweden)

Ibrahim Ismaeil

Full Text Available Temperature changes are common in nature and insects are particularly exposed and sensitive to such variations which can be potential stresses, ultimately affecting life history traits and overall fitness. Braconids have been widely used to study the effects of temperature on host-parasitoid interactions and the present work focused on the solitary endoparasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae Aphidiidae, an efficient biological control agent commercially used against aphids such as the potato aphid Macrosiphum euphorbiae Thomas (Sternorrhyncha: Aphididae. Contrary to previous studies using heat shocks at extreme temperatures, we evaluated the effects of mild heat stresses by transferring young parasitoid adults from the constant temperature of 20°C to either a warm (25°C or hot (28°C temperature, for either 1 h or 48 h. Such treatments are consistent with situations commonly experienced by parasitoids when moved from their rearing conditions to greenhouses or field conditions. The effects were evaluated both on the heat stressed A. ervi adults (G0 (immediate effects and on their first generation (G1 progeny (trans-generational effects. G0 wasps' mortality was significantly affected by the temperature in interaction with the duration of the stress. Longevity of G0 wasps surviving the heat stress was negatively affected by the temperature and females lived longer than males. Heat stress applied to A. ervi parents also had consequences on their G1 progeny whose developmental time, rates of mummification and percentage of parasitoid completing total development were negatively affected. Surprisingly, the egg load at emergence of the G1 female progeny was increased when their mothers had been submitted to a mild heat stress of 25°C or 28°C. These results clearly demonstrate trans-generational phenotypic plasticity, showing that adaptation to thermal stresses may be achieved via maternal effects. This study also sheds light on

Field Effect Microparticle Generation for Cell Microencapsulation.

Science.gov (United States)

Hsu, Brend Ray-Sea; Fu, Shin-Huei

2017-01-01

The diameter and sphericity of alginate-poly-L-lysine-alginate microcapsules, determined by the size and the shape of calcium alginate microspheres, affect their in vivo durability and biocompatibility and the results of transplantation. The commonly used air-jet spray method generates microspheres with a wider variation in diameter, larger sphere morphology, and evenly distributed encapsulated cells. In order to overcome these drawbacks, we designed a field effect microparticle generator to create a stable electric field to prepare microparticles with a smaller diameter and more uniform morphology. Using this electric field microparticle generator the encapsulated cells will be located at the periphery of the microspheres, and thus the supply of oxygen and nutrients for the encapsulated cells will be improved compared with the centrally located encapsulated cells in the air-jet spray method.

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.

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

Self-generated magnetic fields in direct-drive implosion experiments

Energy Technology Data Exchange (ETDEWEB)

Igumenshchev, I. V.; Nilson, P. M.; Goncharov, V. N. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Zylstra, A. B.; Li, C. K.; Petrasso, R. D. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2014-06-15

Electric and self-generated magnetic fields in direct-drive implosion experiments on the OMEGA Laser Facility were investigated employing radiography with ∼10- to 60-MeV protons. The experiment used plastic-shell targets with imposed surface defects (glue spots, wires, and mount stalks), which enhance self-generated fields. The fields were measured during the 1-ns laser drive with an on-target intensity ∼10{sup 15} W/cm{sup 2}. Proton radiographs show multiple ring-like structures produced by electric fields ∼10{sup 7} V/cm and fine structures from surface defects, indicating self-generated fields up to ∼3 MG. These electric and magnetic fields show good agreement with two-dimensional magnetohydrodynamic simulations when the latter include the ∇T{sub e} × ∇n{sub e} source, Nernst convection, and anisotropic resistivity. The simulations predict that self-generated fields affect heat fluxes in the conduction zone and, through this, affect the growth of local perturbations.

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.

Generating functionals for quantum field theories with random potentials

International Nuclear Information System (INIS)

Jain, Mudit; Vanchurin, Vitaly

2016-01-01

We consider generating functionals for computing correlators in quantum field theories with random potentials. Examples of such theories include cosmological systems in context of the string theory landscape (e.g. cosmic inflation) or condensed matter systems with quenched disorder (e.g. spin glass). We use the so-called replica trick to define two different generating functionals for calculating correlators of the quantum fields averaged over a given distribution of random potentials. The first generating functional is appropriate for calculating averaged (in-out) amplitudes and involves a single replica of fields, but the replica limit is taken to an (unphysical) negative one number of fields outside of the path integral. When the number of replicas is doubled the generating functional can also be used for calculating averaged probabilities (squared amplitudes) using the in-in construction. The second generating functional involves an infinite number of replicas, but can be used for calculating both in-out and in-in correlators and the replica limits are taken to only a zero number of fields. We discuss the formalism in details for a single real scalar field, but the generalization to more fields or to different types of fields is straightforward. We work out three examples: one where the mass of scalar field is treated as a random variable and two where the functional form of interactions is random, one described by a Gaussian random field and the other by a Euclidean action in the field configuration space.

Generation of intense transient magnetic fields

International Nuclear Information System (INIS)

Benjamin, R.F.

1983-01-01

In a laser system, the return current of a laser generated plasma is conducted near a target to subject that target to a magnetic field. The target may be either a small non-fusion object for testing under the magnetic field or a laser-fusion pellet. In the laser-fusion embodiment, the laser-fusion pellet is irradiated during the return current flow and the intense transient magnetic field is used to control the hot electrons thereof to hinder them from striking and heating the core of the irradiated laser-fusion pellet. An emitter, e.g. a microballoon of glass, metal or plastics, is subjected to a laser pulse to generate the plasma from which the return current flows into a wire cage or a coil and then to earth. (author)

Generation as the origin of Higgs fields

International Nuclear Information System (INIS)

Izawa, K.I.

1991-01-01

This paper provides a simple reformulation of the standard electroweak theory of leptons with two generations as a generalized gauge theory. It is based on a discrete analogue of Kaluza-Klein theories, with the extra dimension being the generations of the matter. Higgs fields appear as part of a generalized gauge field. Hypercharge quantization results from the use of a simple Lie superalgebra su(1/2) as the generalized gauge algebra

The medial tibial stress syndrome score: Item generation for a new ...

African Journals Online (AJOL)

The medial tibial stress syndrome score: Item generation for a new patient reported outcome measure. ... instrument that evaluates injury severity and treatment effects for medial tibial stress syndrome (MTSS) patients. ... from 32 Countries:.

International Geomagnetic Reference Field: the 12th generation

DEFF Research Database (Denmark)

Thébault, Erwan; Finlay, Chris; Beggan, Ciarán D.

2015-01-01

The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch ...

Study of residual stresses generated in machining of AISI 4340 steel

International Nuclear Information System (INIS)

Reis, W.P. dos; Fonseca, M.P. Cindra; Serrao, L.F.; Chuvas, T.C.; Oliveira, L.C.

2010-01-01

Among the mechanical construction steels, AISI 4340 has good harden ability, while combining high strength with toughness and good fatigue strength, making it excellent for application in the metalworking industry, where it can work at different levels and types of requests. Residual stresses are generated in almost all processes of mechanical manufacturing. In this study, the residual stresses generated in different machining processes and heat treatment hardening of AISI 4340 were analyzed by X-ray diffraction, by the sen 2 ψ method, using Crκβ radiation and compared. All samples, except for turned and cut by EDM, presented compressive residual stresses in the surface with various magnitudes. (author)

Stress field control during large caldera-forming eruptions

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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.

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.

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

Relativistic Scott correction in self-generated magnetic fields

DEFF Research Database (Denmark)

Erdos, Laszlo; Fournais, Søren; Solovej, Jan Philip

2012-01-01

/3}$ and it is unchanged by including the self-generated magnetic field. We prove the first correction term to this energy, the so-called Scott correction of the form $S(\\alpha Z) Z^2$. The current paper extends the result of \\cite{SSS} on the Scott correction for relativistic molecules to include a self......-generated magnetic field. Furthermore, we show that the corresponding Scott correction function $S$, first identified in \\cite{SSS}, is unchanged by including a magnetic field. We also prove new Lieb-Thirring inequalities for the relativistic kinetic energy with magnetic fields....

Morphology of magnetic fields generated in laser-produced plasmas

International Nuclear Information System (INIS)

Boyd, T.J.M.; Cooke, D.

1988-01-01

Magnetic fields in the megagauss range have been measured in experiments on plasmas generated by irradiating targets with high power lasers. A study of the morphology of these self-generated fields is important not only for its intrinsic interest but for possible implications in laser--target physics. In this paper work on the numerical modeling of large magnetic fields generated in target experiments is reported. The results show generally satisfactory agreement with the fields measured experimentally both in terms of the magnitude of the peak fields and their morphology. In the numerical model the contribution from the Hall term in describing the evolution of the magnetic field is shown to be important especially in short pulse (≅100 psec) experiments

Attosecond pulse trains generated using two color laser fields

International Nuclear Information System (INIS)

Mauritsson, J.; Louisiana State University, Baton Rouge, LA; Johnsson, P.; Gustafsson, E.; L'Hullier, A.; Schafer, K.J.; Gaarde, M.B.

2006-01-01

Complete test of publication follows. We present the generation of attosecond pulse trains from a superposition of an infrared (IR) laser field and its second harmonic. Our attosecond pulses are synthesized by selecting a number of synchronized harmonics generated in argon. By adding the second harmonic to the driving field the inversion symmetry of generation process is broken and both odd and even harmonics are generated. Consecutive half cycles in the two color field differ beyond the simple sign change that occurs in a one color field and have very different shapes and amplitudes. This sub-cycle structure of the field, which governs the generation of the attosecond pulses, depends strongly on the relative phase and intensity of the two fields, thereby providing additional control over the generation process. The generation of attosecond pulses is frequently described using the semi-classical three step model where an electron is: (1) ionized through tunneling ionization during one half cycle; (2) reaccelerated back towards the ion core by the next half cycle; where it (3) recombines with the ground-state releasing the access energy in a short burst of light. In the two color field the symmetry between the ionizing and reaccelerating field is broken, which leads to two possible scenarios: the electron can either be ionized during a strong half cycle and reaccelerated by a weaker field or vice versa. The periodicity is a full IR cycle in both cases and hence two trains of attosecond pulses are generated which are offset from each other. The generation efficiency, however, is very different for the two cases since it is determined mainly by the electric field strength at the time of tunneling and one of the trains will therefore dominate the other. We investigate experimentally both the spectral and temporal structure of the generated attosecond pulse trains as a function of the relative phase between the two driving fields. We find that for a wide range of

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.

The Synchronous Generators Rated Speed’s Influence on Electromagnetic Stresses and on Costs

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Elisabeta Spunei

2013-09-01

Full Text Available During the design of synchronous generators is very important to establish the values of their electromagnetic stresses. The specific literature recommends that these stress values are to be chosen from the curves obtained during experimental design, where the independent values are the polar pitch and the number of pole pairs. The authors of this work propose a method of finding the dependency between the electromagnetic stress and the synchronous generator rated speed to rapidly estimate the stresses in a given interval of rated speed values.

The Effect of Creep on the Residual Stresses Generated During Silicon Sheet Growth

Science.gov (United States)

Hutchinson, J. W.; Lambropoulos, J. C.

1984-01-01

The modeling of stresses generated during the growth of thin silicon sheets at high speeds is an important part of the EFG technique since the experimental measurement of the stresses is difficult and prohibitive. The residual stresses which arise in such a growth process lead to serious problems which make thin Si ribbons unsuitable for fabrication. The constitutive behavior is unrealistic because at high temperature (close to the melting point) Si exhibits considerable creep which significantly relaxes the residual stresses. The effect of creep on the residual stresses generated during the growth of Si sheets at high speeds was addressed and the basic qualitative effect of creep are reported.

Acculturation-Related Stress and Mental Health Outcomes among Three Generations of Hispanic Adolescents

Science.gov (United States)

Cervantes, Richard C.; Padilla, Amado M.; Napper, Lucy E.; Goldbach, Jeremy T.

2013-01-01

Stress associated with acculturation and minority status among Hispanic youth is understudied. Using survey data from the Hispanic Stress Inventory-Adolescent Version (HSI-A), we examined psychosocial stress across eight domains including family economic stress and acculturation-gap stress in a national sample of three generations (first, second,…

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.

Generation Of Unipolar Field For The Control Of Charges

Directory of Open Access Journals (Sweden)

Barnabas Oluwaseyi Alabi

2017-10-01

Full Text Available Electric charge is the property of a matter that allow for electric and magnetic forces interaction. These charges can be controlled by unipolar electromagnetic field. In this study such unipolar field that can propagate was generated. This unipolar electromagnetic field was simulated and tested for propagation. To produce a propagating unipolar magnetic field a time-varying unipolar electric current generator was considered. The model considered was simulated in the National Instruments Multisim windows application environment. The generated electric voltage waveform was viewed via the output grapher of the application. Various loads were connected to ensure consistency in the unipolar waveform for different load value on the generator. The result obtained showed that a unipolar field which could propagate can be achievable only when the signal involved was properly rectified. After rectification however the desired waveform and signal was produced. The test for propagation was done using a core of iron and a small solenoid connected to the rectified output and the field produced was magnetic this attracted a metal clip 1.0 cm away and a larger core attracted a hammer from around 10.0 cm away. The study concluded that a propagating magnetic field useful for the control of charges can be generated if the signal involved is made to be unipolar in nature.

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.

International Geomagnetic Reference Field: the 12th generation

OpenAIRE

Thébault , Erwan; Finlay , Christopher ,; Beggan , Ciarán ,; Alken , Patrick; Aubert , Julien ,; Barrois , Olivier; Bertrand , François; Bondar , Tatiana; Boness , Axel; Brocco , Laura; Canet , Elisabeth ,; Chambodut , Aude; Chulliat , Arnaud ,; Coïsson , Pierdavide ,; Civet , François

2015-01-01

International audience; The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, p...

Stress analysis and fatigue life prediction for a U-bend steam generator tube

International Nuclear Information System (INIS)

Cheng Weili; Finnie, I.

1996-01-01

An analysis is carried out to determine the stresses in a steam generator tube that failed by fatigue. Using data available for the failed tube and for failures in two similar steam generators, the magnitudes of the alternating and mean stresses produced during operation are estimated. The cause for the early fatigue failure is shown to be the high mean stress caused by denting of the tube in the location where it passed through the tube sheet. (orig.)

Obesity and Age-Related Changes in Markers of Oxidative Stress and Inflammation Across Four Generations

NARCIS (Netherlands)

Hulsegge, Gerben; Herber-Gast, Gerrie-Cor M; Spijkerman, Annemieke M W; Picavet, H. Susan J; van der Schouw, Yvonne T; Bakker, Stephan J L; Gansevoort, Ron T; Dollé, Martijn E T; Smit, Henriette A; Monique Verschuren, W M

OBJECTIVE: The prevalence of obesity increases with age and is higher in each younger generation (unfavorable generation shift). This may influence patterns of oxidative stress and inflammation. Age-related changes and generation shifts in markers of oxidative stress and inflammation were

Obesity and Age-Related Changes in Markers of Oxidative Stress and Inflammation Across Four Generations

NARCIS (Netherlands)

Hulsegge, Gerben; Herber-Gast, Gerrie-Cor M; Spijkerman, Annemieke M W; Susan, H; Picavet, J; van der Schouw, Yvonne T; Bakker, Stephan J L; Gansevoort, Ron T; Dollé, Martijn E T; Smit, Henriette A; Monique Verschuren, W M

ObjectiveThe prevalence of obesity increases with age and is higher in each younger generation (unfavorable generation shift). This may influence patterns of oxidative stress and inflammation. Age-related changes and generation shifts in markers of oxidative stress and inflammation were

Stress generation and hierarchical fracturing in reactive systems

Science.gov (United States)

Jamtveit, B.; Iyer, K.; Royne, A.; Malthe-Sorenssen, A.; Mathiesen, J.; Feder, J.

2007-12-01

Hierarchical fracture patterns are the result of a slowly driven fracturing process that successively divides the rocks into smaller domains. In quasi-2D systems, such fracture patterns are characterized by four sided domains, and T-junctions where new fractures stop at right angles to pre-existing fractures. We describe fracturing of mm to dm thick enstatite layers in a dunite matrix from the Leka ophiolite complex in Norway. The fracturing process is driven by expansion of the dunite matrix during serpentinization. The cumulative distributions of fracture lengths show a scaling behavior that lies between a log - normal and power law (fractal) distribution. This is consistent with a simple fragmentation model in which domains are divided according to a 'top hat' distribution of new fracture positions within unfractured domains. Reaction-assisted hierarchical fracturing is also likely to be responsible for other (3-D) structures commonly observed in serpentinized ultramafic rocks, including the mesh-textures observed in individual olivine grains, and the high abundance of rectangular domains at a wide range of scales. Spectacular examples of 3-D hierarchical fracture patterns also form during the weathering of basaltic intrusions (dolerites). Incipient chemical weathering of dolerites in the Karoo Basin in South Africa occurs around water- filled fractures, originally produced by thermal contraction or by externally imposed stresses. This chemical weathering causes local expansion of the rock matrix and generates elastic stresses. On a mm to cm scale, these stresses lead to mechanical layer-by-layer spalling, producing the characteristic spheroidal weathering patterns. However, our field observations and computer simulations demonstrate that in confined environments, the spalling process alone is unable to relieve the elastic stresses. In such cases, chemical weathering drives a much larger scale hierarchical fracturing process in which fresh dolerite undergoes a

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

Magnetic field generations in planetary interiors

International Nuclear Information System (INIS)

Singh, R.N.

1981-01-01

One of the most fundamental properties of some better known planets is their internally generated magnetic field. A successful explanation of such magnetic fields in 'large hot planetary interiors' remains elusive. Starting from Sir Joseph Larmor's discussions of 'How could a rotating body such as Sun become a magnet' (1979) to present day general consensus that 'the existence of the geomagnetic field is a manifestation of a finite amplitude instability of the Earth's core', significant theoretical developments have taken place in this field. The essential ingredients of the successful theories are the presence of a rotating fluid core of large size having sufficiently high electrical conductivity and energy source to drive the convection. These theories use equations of Newton and Maxwell to generate the requisite kind of the magnetic and velocity fields in response to the preferred distribution of the energy sources. Studies before early seventies, were devoted, mainly, to resolve the kinematics of the problem, and have convincingly demonstrated the plausibility of regeneration action of the organised motion. However, the main problem of the dynamo-processes is yet in the early stages of development despite important contributions made by Soward and Busse. A review of some of these developments is presented. (author)

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

Experimental residual stress evaluation of hydraulic expansion transitions in Alloy 690 steam generator tubing

International Nuclear Information System (INIS)

McGregor, R.; Doherty, P.; Hornbach, D.; Abdelsalam, U.

1995-01-01

Nuclear Steam Generator (SG) service reliability and longevity have been seriously affected worldwide by corrosion at the tube-to-tubesheet joint expansion. Current SG designs for new facilities and replacement projects enhance corrosion resistance through the use of advanced tubing materials and improved joint design and fabrication techniques. Here, transition zones of hydraulic expansions have undergone detailed experimental evaluation to define residual stress and cold-work distribution on and below the secondary-side surface. Using X-ray diffraction techniques, with supporting finite element analysis, variations are compared in tubing metallurgical condition, tube/pitch geometry, expansion pressure, and tube-to-hole clearance. Initial measurements to characterize the unexpanded tube reveal compressive stresses associated with a thin work-hardened layer on the outer surface of the tube. The gradient of cold-work was measured as 3% to 0% within .001 inch of the surface. The levels and character of residual stresses following hydraulic expansion are primarily dependent on this work-hardened surface layer and initial stress state that is unique to each tube fabrication process. Tensile stresses following expansion are less than 25% of the local yield stress and are found on the transition in a narrow circumferential band at the immediate tube surface (< .0002 inch/0.005 mm depth). The measurements otherwise indicate a predominance of compressive stresses on and below the secondary-side surface of the transition zone. Excellent resistance to SWSCC initiation is offered by the low levels of tensile stress and cold-work. Propagation of any possible cracking would be deterred by the compressive stress field that surrounds this small volume of tensile material

Pulsed magnetic field generation suited for low-field unilateral nuclear magnetic resonance systems

Science.gov (United States)

Gaunkar, Neelam Prabhu; Selvaraj, Jayaprakash; Theh, Wei-Shen; Weber, Robert; Mina, Mani

2018-05-01

Pulsed magnetic fields can be used to provide instantaneous localized magnetic field variations. In presence of static fields, pulsed field variations are often used to apply torques and in-effect to measure behavior of magnetic moments in different states. In this work, the design and experimental performance of a pulsed magnetic field generator suited for low static field nuclear magnetic resonance (NMR) applications is presented. One of the challenges of low bias field NMR measurements is low signal to noise ratio due to the comparable nature of the bias field and the pulsed field. Therefore, a circuit is designed to apply pulsed currents through an inductive load, leading to generation of pulsed magnetic fields which can temporarily overpower the effect of the bias field on magnetic moments. The designed circuit will be tuned to operate at the precession frequency of 1H (protons) placed in a bias field produced by permanent magnets. The designed circuit parameters may be tuned to operate under different bias conditions. Therefore, low field NMR measurements can be performed for different bias fields. Circuit simulations were used to determine design parameters, corresponding experimental measurements will be presented in this work.

Quantitative Imaging of the Stress/Strain Fields and Generation of Macroscopic Cracks from Indents in Silicon

Directory of Open Access Journals (Sweden)

Brian K. Tanner

2017-11-01

Full Text Available The crack geometry and associated strain field around Berkovich and Vickers indents on silicon have been studied by X-ray diffraction imaging and micro-Raman spectroscopy scanning. The techniques are complementary; the Raman data come from within a few micrometres of the indentation, whereas the X-ray image probes the strain field at a distance of typically tens of micrometres. For example, Raman data provide an explanation for the central contrast feature in the X-ray images of an indent. Strain relaxation from breakout and high temperature annealing are examined and it is demonstrated that millimetre length cracks, similar to those produced by mechanical damage from misaligned handling tools, can be generated in a controlled fashion by indentation within 75 micrometres of the bevel edge of 200 mm diameter wafers.

SATURATION OF MAGNETOROTATIONAL INSTABILITY THROUGH MAGNETIC FIELD GENERATION

International Nuclear Information System (INIS)

Ebrahimi, F.; Prager, S. C.; Schnack, D. D.

2009-01-01

The saturation mechanism of magnetorotational instability (MRI) is examined through analytical quasi-linear theory and through nonlinear computation of a single mode in a rotating disk. We find that large-scale magnetic field is generated through the α-effect (the correlated product of velocity and magnetic field fluctuations) and causes the MRI mode to saturate. If the large-scale plasma flow is allowed to evolve, the mode can also saturate through its flow relaxation. In astrophysical plasmas, for which the flow cannot relax because of gravitational constraints, the mode saturates through field generation only.

Heat priming induces trans-generational tolerance to high temperature stress in wheat

Directory of Open Access Journals (Sweden)

Xiao eWang

2016-04-01

Full Text Available Wheat plants are very sensitive to high temperature stress during grain filling. Effects of heat priming applied to the first generation on tolerance of the successive generation to post-anthesis high temperature stress were investigated. Compared with the progeny of non-heat primed plants (NH, the progeny of heat-primed plants (PH possessed higher grain yield, leaf photosynthesis and activities of antioxidant enzymes and lower cell membrane damage under high temperature stress. In the transcriptome profile, 1430 probes showed obvious difference in expression between PH and NH. These genes were related to signal transduction, transcription, energy, defense, and protein destination and storage, respectively. The gene encoding the lysine-specific histone demethylase 1 (LSD1 which was involved in histone demethylation related to epigenetic modification was up-regulated in the PH compared with NH. The proteome analysis indicated that the proteins involved in photosynthesis, energy production and protein destination and storage were up-regulated in the PH compared with NH. In short, thermos-tolerance was induced through heritable epigenetic alternation and signaling transduction, both processes further triggered prompt modifications of defense related responses in anti-oxidation, transcription, energy production, and protein destination and storage in the progeny of the primed plants under high temperature stress. It was concluded that trans-generation thermo-tolerance was induced by heat priming in the first generation, and this might be an effective measure to cope with severe high-temperature stresses during key growth stages in wheat production.

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.

Generation of sheared poloidal flows via Reynolds stress and transport barrier physics

International Nuclear Information System (INIS)

Hidalgo, C.; Pedrosa, M.A.; Sanchez, E.; Balbin, R.; Lopez-Fraguas, A.; Milligen, B. van; Silva, C.; Fernandes, H.; Varandas, C.A.F.; Riccardi, C.; Carrozza, R.; Fontanesi, M.; Carreras, B.A.; Garcia, L.

2000-01-01

A view of the latest experimental results and progress in the understanding of the role of poloidal flows driven by fluctuations via Reynolds stress is given. Reynolds stress shows a radial gradient close to the velocity shear layer location in tokamaks and stellarators, indicating that this mechanism may drive significant poloidal flows in the plasma boundary. Observation of the generation of ExB sheared flows via Reynolds stress at the ion Bernstein resonance layer has been noticed in toroidal magnetized plasmas. The experimental evidence of sheared ExB flows linked to the location of rational surfaces in stellarator plasmas might be interpreted in terms of Reynolds stress sheared driven flows. These results show that ExB sheared flows driven by fluctuations can play an important role in the generation of transport barriers. (author)

Drought-induced trans-generational tradeoff between stress tolerance and defence: consequences for range limits?

OpenAIRE

Alsdurf, Jacob D.; Ripley, Tayler J.; Matzner, Steven L.; Siemens, David H.

2013-01-01

Areas just across species range boundaries are often stressful, but even with ample genetic variation within and among range-margin populations, adaptation towards stress tolerance across range boundaries often does not occur. Adaptive trans-generational plasticity should allow organisms to circumvent these problems for temporary range expansion; however, range boundaries often persist. To investigate this dilemma, we drought stressed a parent generation of Boechera stricta (A.Gray) A. L?ve &...

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.)

Error field generation of solenoid magnets

International Nuclear Information System (INIS)

Saunders, J.L.

1982-01-01

Many applications for large solenoids and solenoidal arrays depend on the high precision of the axial field profile. In cases where requirements of ΔB/B for nonaxial fields are on the order of 10 -4 , the actual winding techniques of the solenoid need to be considered. Whereas an ideal solenoid consisting of current loops would generate no radial fields along the axis, in reality, the actual current-carrying conductors must follow spiral or helical paths. A straightforward method for determining the radial error fields generated by coils wound with actual techniques employed in magnet fabrication has been developed. The method devised uses a computer code which models a magnet by sending a single, current-carrying filament along the same path taken by the conductor during coil winding. Helical and spiral paths are simulated using small, straight-line current segments. This technique, whose results are presented in this paper, was used to predict radial field errors for the Elmo Bumpy Torus-Proof of Principle magnet. These results include effects due to various winding methods, not only spiral/helical and layer-to-layer transitions, but also the effects caused by worst-case tolerance conditions both from the conductor and the winding form (bobbin). Contributions made by extraneous circuitry (e.g., overhead buswork and incoming leads) are also mentioned

A discrete stress-strength interference model based on universal generating function

International Nuclear Information System (INIS)

An Zongwen; Huang Hongzhong; Liu Yu

2008-01-01

Continuous stress-strength interference (SSI) model regards stress and strength as continuous random variables with known probability density function. This, to some extent, results in a limitation of its application. In this paper, stress and strength are treated as discrete random variables, and a discrete SSI model is presented by using the universal generating function (UGF) method. Finally, case studies demonstrate the validity of the discrete model in a variety of circumstances, in which stress and strength can be represented by continuous random variables, discrete random variables, or two groups of experimental data

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

transtensional reactivation of shear zones in the Kaoko Belt. Principle compressive stress switched from NW–SE to NNW–SSE shortening in both Kaoko and Damara Belts at this time. This marks the start of Congo-Kalahari stress field overwhelming the waning Rio De La Plata-Congo stress field, and from this time forward contraction across the Damara Belt generated the stress field governing subsequent low-strain events in the Kaoko Belt. (2 A sudden switch to E–W directed shortening at ∼508 Ma is interpreted as a far-field effect imposed on the Damara Orogenic System, most plausibly from arc obduction along the orogenic margin of Gondwana (Ross-Delamerian Orogen. (3 This imposed stress field established a N–S extension direction exploited by decompression melts, switch to vertical shortening, and triggered gravitational collapse and extension of the thermally weakened hot orogen core at ∼505 Ma, producing an extensional metamorphic core complex across the Central Zone.

Generation mechanisms for magnetic-field-aligned electric fields in the magnetosphere

International Nuclear Information System (INIS)

Faelthammar, C.-G.

1977-09-01

Magnetic-field-aligned electric fields in the magnetosphere can be generated in several different ways, and in this review some possible mechanisms are presented. Observational data now available indicates that more than one of the mechanisms mentioned are operative in the magnetosphere but it is not yet possible to evaluate their relative importance. (author)

Finite element simulations of internal stresses generated during the ferroelastic deformation of NiTi bodies

International Nuclear Information System (INIS)

Manach, P.Y.; Favier, D.; Rio, G.

1996-01-01

The aim of this paper is to analyse the generation of internal stresses during the predeformation of NiTi shape memory alloys in the martensitic state. This allows to determine the initial stress state in which the material will transform during the shape memory effect due to heating consecutively to this prestrain. In that way a three-dimensional finite element model of the deformation of shape memory alloys has been developed, the constitutive law being defined using an elastohysteresis tensor model. The influence of behavioural and geometrical factors are illustrated considering the numerical simulation of different cases of practical importance for industrial applications : the study of the bending behaviour of a NiTi cantilever beam as well as the study of the swelling of a pipe connection under both uniform and non uniform internal displacement fields. (orig.)

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.

Phenotypic effects of salt and heat stress over three generations in Arabidopsis thaliana.

Directory of Open Access Journals (Sweden)

Léonie Suter

Full Text Available Current and predicted environmental change will force many organisms to adapt to novel conditions, especially sessile organisms such as plants. It is therefore important to better understand how plants react to environmental stress and to what extent genotypes differ in such responses. It has been proposed that adaptation to novel conditions could be facilitated by heritable epigenetic changes induced by environmental stress, independent of genetic variation. Here we assessed phenotypic effects of heat and salt stress within and across three generations using four highly inbred Arabidopsis thaliana genotypes (Col, Cvi, Ler and Sha. Salt stress generally decreased fitness, but genotypes were differently affected, suggesting that susceptibility of A. thaliana to salt stress varies among genotypes. Heat stress at an early rosette stage had less detrimental effects but accelerated flowering in three out of four accessions. Additionally, we found three different modes of transgenerational effects on phenotypes, all harboring the potential of being adaptive: heat stress in previous generations induced faster rosette growth in Sha, both under heat and control conditions, resembling a tracking response, while in Cvi, the phenotypic variance of several traits increased, resembling diversified bet-hedging. Salt stress experienced in earlier generations altered plant architecture of Sha under salt but not control conditions, similar to transgenerational phenotypic plasticity. However, transgenerational phenotypic effects depended on the type of stress as well as on genotype, suggesting that such effects may not be a general response leading to adaptation to novel environmental conditions in A. thaliana.

Laser light absorption and harmonic generation due to self-generated magnetic fields

International Nuclear Information System (INIS)

Kruer, W.L.; Estabrook, K.G.

1977-01-01

It is shown that self-generated magnetic fields can play a significant role in laser light absorption. Even normally incident light will then be resonantly absorbed. Computer simulations and theoretical estimates for this absorption and the concomitant harmonic generation are given for parameters characteristic of some recent experiments

Generation of strong pulsed magnetic fields using a compact, short pulse generator

Science.gov (United States)

Yanuka, D.; Efimov, S.; Nitishinskiy, M.; Rososhek, A.; Krasik, Ya. E.

2016-04-01

The generation of strong magnetic fields (˜50 T) using single- or multi-turn coils immersed in water was studied. A pulse generator with stored energy of ˜3.6 kJ, discharge current amplitude of ˜220 kA, and rise time of ˜1.5 μs was used in these experiments. Using the advantage of water that it has a large Verdet constant, the magnetic field was measured using the non-disturbing method of Faraday rotation of a polarized collimated laser beam. This approach does not require the use of magnetic probes, which are sensitive to electromagnetic noise and damaged in each shot. It also avoids the possible formation of plasma by either a flashover along the conductor or gas breakdown inside the coil caused by an induced electric field. In addition, it was shown that this approach can be used successfully to investigate the interesting phenomenon of magnetic field enhanced diffusion into a conductor.

Class I review of LOFT steam generator stress and fatigue life analysis report

International Nuclear Information System (INIS)

Fors, R.M.; Silverman, S.

1977-01-01

Review of the LOFT steam generator stress and fatigue life analysis report is presented. Deficiencies were found which will require evaluation and in some areas reanalysis. The effects of these deficiencies upon the steam generator will include: to further reduce the allowable ΔP across the tubesheet for the abnormal design case of pressure on primary; and to reduce the allowable number of LOCE transients at some locations of the steam generator from the numbers listed in the stress report and to increase them at other locations

Megagauss field generation for high-energy-density plasma science experiments

International Nuclear Information System (INIS)

Rovang, Dean Curtis; Struve, Kenneth William; Porter, John Larry Jr.

2008-01-01

There is a need to generate magnetic fields both above and below 1 megagauss (100 T) with compact generators for laser-plasma experiments in the Beamlet and Petawatt test chambers for focused research on fundamental properties of high energy density magnetic plasmas. Some of the important topics that could be addressed with such a capability are magnetic field diffusion, particle confinement, plasma instabilities, spectroscopic diagnostic development, material properties, flux compression, and alternate confinement schemes, all of which could directly support experiments on Z. This report summarizes a two-month study to develop preliminary designs of magnetic field generators for three design regimes. These are, (1) a design for a relatively low-field (10 to 50 T), compact generator for modest volumes (1 to 10 cm3), (2) a high-field (50 to 200 T) design for smaller volumes (10 to 100 mm3), and (3) an extreme field (greater than 600 T) design that uses flux compression. These designs rely on existing Sandia pulsed-power expertise and equipment, and address issues of magnetic field scaling with capacitor bank design and field inductance, vacuum interface, and trade-offs between inductance and coil designs

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

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.

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)

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.

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.

Modulated Field Synchronous Generator for Wind Turbines

Directory of Open Access Journals (Sweden)

Petru Chioncel

2013-01-01

Full Text Available This paper presents a modern electromechanical conversion systemsolution as the modulated field synchronous generator, offering on theone hand, an output voltage with constant frequency in terms of speedvariation of the wind turbine and on the other hand an advantagepower / weight ratio due to the high frequency for which the magneticcircuit of the electric machine is sized. The mathematical model of the modulated field synchronous generator is implemented in MatLABmodeling language, highlighting the command structure on thetransistors bases of the inverter transistors, through which thefunctioning of the electric machine can be studied, especially in terms of the frequency of the delivered voltage.

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.

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)

Stress relief to prevent stress corrosion in the transition region of expanded Alloy 600 steam-generator tubing. Final report

International Nuclear Information System (INIS)

Woodward, J.; van Rooyen, D.

1983-05-01

The feasibility of preventing primary side roll transition cracking has been investigated, using induction heating to attain stress relief of expanded Ni-Cr-Fe Alloy 600 steam generator tubing. Work on rolled tubing and U-bends has shown that temperatures with which stress relief can be obtained range from 700 to 850 0 C, with lower temperatures in this range requiring longer times at temperature to provide the requisite reduction in residual stresses. No work has yet been done outside this range. Preliminary tests, using induction heating, have been carried out on a mock tube sheet assembly, designed to the dimensions of a typical steam generator, and have identified the type of heating/cooling cycle that would occur in the tube sheet during a stress relief operation. Preliminary results show that the times to reach the higher temperatures in the range observed to give stress relief, of the order of 850 0 C, can be as short as 8 seconds, and less with optimum coil design and power control

Transient porosity pulses and microfracturing during a stress-generating retrograde metamorphic reaction

Science.gov (United States)

Renard, F.; Zheng, X.; Cordonnier, B.; Zhu, W.; Jamtveit, B.

2017-12-01

Several geological processes involve mineral transformations where nominally dry rocks transform into hydrated ones when left in contact with water (i.e. eclogitization, serpentinization). In these systems, the transformation induces stress if the rock is confined, and the new minerals create a so-called force of crystallization. Here, we study a model retrograde metamorphic reaction, the hydration of periclase, MgO, into brucite, Mg(OH)2, to quantify the coupling between reaction, stress generation, porosity evolution and fracturing. This hydration reaction generates a volume increase of 110%, and a density decrease of 33.8% of the solid. Samples of a microporous MgO ceramics were reacted at 170-211°C, 5-80 MPa confining pressure, 6-95 MPa differential stress and 5 MPa pore fluid pressure. They were installed into an X-ray transparent triaxial deformation rig, called Hades, and mounted on a synchrotron microtomography stage. Each experiment lasted between 2 and 5 hours, during which between 35 and 130 three-dimensional images were acquired, allowing to follow the chemical transformation and the deformation of the sample. Below 30 MPa mean pressure, the hydration reaction was coupled to fracturing of the MgO ceramics, and the transformation rate followed a sigmoidal kinetics curve with a slow initiation, a fast reaction coupled to fracturing and the generation of a transient porosity pulse, and a slow-down until an almost complete transformation of periclase into brucite.. Conversely, above 30 MPa, the reaction kinetics was very slow, without fracturing over the time scale of the experiment. When considering the driving force of the hydration reaction, stress generation should be several hundreds MPa, whereas the present experiments show that fracturing occurred only below 30 MPa. This indicates that the potential energy due to phase transformation generates much lower stress than what is estimated from non-equilibrium thermodynamics. A possible interpretation of

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.

Tunneling ionization and harmonic generation in two-color fields

International Nuclear Information System (INIS)

Kondo, K.; Kobayashi, Y.; Sagisaka, A.; Nabekawa, Y.; Watanabe, S.

1996-01-01

Tunneling ionization and harmonic generation in two-color fields were studied with a fundamental beam (ω) and its harmonics (2ω,3ω), which were generated by a 100-fs Ti:sapphire laser. Ion yields of atoms and molecules were successfully controlled by means of a change in the relative phase between ω and 3ω pulses. Two-color interference was clearly observed in photoelectron spectra and harmonic spectra. In the ω endash 2ω field even-order harmonics were observed in which the intensity was almost equal to that of the odd harmonics because of an asymmetric optical field. These results were compared with the quasi-static model for ionization and with the quantum theory for harmonic generation. copyright 1996 Optical Society of America

Below-threshold harmonic generation from strong non-uniform fields

Science.gov (United States)

Yavuz, I.

2017-10-01

Strong-field photoemission below the ionization threshold is a rich/complex region where atomic emission and harmonic generation may coexist. We studied the mechanism of below-threshold harmonics (BTH) from spatially non-uniform local fields near the metallic nanostructures. Discrete harmonics are generated due to the broken inversion symmetry, suggesting enriched coherent emission in the vuv frequency range. Through the numerical solution of the time-dependent Schrödinger equation, we investigate wavelength and intensity dependence of BTH. Wavelength dependence identifies counter-regular resonances; individual contributions from the multi-photon emission and channel-closing effects due to quantum path interferences. In order to understand the underlying mechanism of BTH, we devised a generalized semi-classical model, including the influence of Coulomb and non-uniform field interactions. As in uniform fields, Coulomb potential in non-uniform fields is the determinant of BTH; we observed that the generation of BTH are due to returning trajectories with negative energies. Due to large distance effectiveness of the non-uniformity, only long trajectories are noticeably affected.

Statistical analysis of the turbulent Reynolds stress and its link to the shear flow generation in a cylindrical laboratory plasma device

International Nuclear Information System (INIS)

Yan, Z.; Yu, J. H.; Holland, C.; Xu, M.; Mueller, S. H.; Tynan, G. R.

2008-01-01

The statistical properties of the turbulent Reynolds stress arising from collisional drift turbulence in a magnetized plasma column are studied and a physical picture of turbulent driven shear flow generation is discussed. The Reynolds stress peaks near the maximal density gradient region, and is governed by the turbulence amplitude and cross-phase between the turbulent radial and azimuthal velocity fields. The amplitude probability distribution function (PDF) of the turbulent Reynolds stress is non-Gaussian and positively skewed at the density gradient maximum. The turbulent ion-saturation (Isat) current PDF shows that the region where the bursty Isat events are born coincides with the positively skewed non-Gaussian Reynolds stress PDF, which suggests that the bursts of particle transport appear to be associated with bursts of momentum transport as well. At the shear layer the density fluctuation radial correlation length has a strong minimum (∼4-6 mm∼0.5C s /Ω ci , where C s is the ion acoustic speed and Ω ci is the ion gyrofrequency), while the azimuthal turbulence correlation length is nearly constant across the shear layer. The results link the behavior of the Reynolds stress, its statistical properties, generation of bursty radially going azimuthal momentum transport events, and the formation of the large-scale shear layer.

Drought-induced trans-generational tradeoff between stress tolerance and defence: consequences for range limits?

Science.gov (United States)

Alsdurf, Jacob D; Ripley, Tayler J; Matzner, Steven L; Siemens, David H

2013-01-01

Areas just across species range boundaries are often stressful, but even with ample genetic variation within and among range-margin populations, adaptation towards stress tolerance across range boundaries often does not occur. Adaptive trans-generational plasticity should allow organisms to circumvent these problems for temporary range expansion; however, range boundaries often persist. To investigate this dilemma, we drought stressed a parent generation of Boechera stricta (A.Gray) A. Löve & D. Löve, a perennial wild relative of Arabidopsis, representing genetic variation within and among several low-elevation range margin populations. Boechera stricta is restricted to higher, moister elevations in temperate regions where generalist herbivores are often less common. Previous reports indicate a negative genetic correlation (genetic tradeoff) between chemical defence allocation and abiotic stress tolerance that may prevent the simultaneous evolution of defence and drought tolerance that would be needed for range expansion. In growth chamber experiments, the genetic tradeoff became undetectable among offspring sib-families whose parents had been drought treated, suggesting that the stress-induced trans-generational plasticity may circumvent the genetic tradeoff and thus enable range expansion. However, the trans-generational effects also included a conflict between plastic responses (environmental tradeoff); offspring whose parents were drought treated were more drought tolerant, but had lower levels of glucosinolate toxins that function in defence against generalist herbivores. We suggest that either the genetic or environmental tradeoff between defence allocation and stress tolerance has the potential to contribute to range limit development in upland mustards.

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

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

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

The influence of lead on stress corrosion cracking of steam generator tubing

International Nuclear Information System (INIS)

Ryan Curtis Wolfe

2015-01-01

Lead (Pb) is present at low concentrations on the secondary side of steam generators, but is known to accumulate in steam generator sludge and become concentrated in crevices and cracks. Pb is known to have played a role in the degradation of Alloy 600MA tubing, necessitating the replacement of those steam generators. There is new evidence which indicates that Pb has also played a role in the stress corrosion cracking (SCC) of Alloy 600TT. Furthermore. laboratory testing indicates that advanced tubing alloys such as Alloy 690TT and Alloy 800NG area also susceptible to this attack. In response to these vulnerabilities, utilities are attempting to manufacture tubing using processes which will impart optimal corrosion resistance, fabricate and operate SG's to minimize stress in the tubing, undertake efforts to identify and remove the sources of Pb, reduce the existing inventory of Pb using chemical or mechanical cleaning processes, and maintain rigorous chemistry controls. Research is warranted to qualify chemical methods to mitigate PbSCC that may be observed in service. This presentation will review work performed through the Electric Power Research Institute (EPRI) to address the issue of Pb-assisted stress corrosion cracking of steam generator tubing. (author)

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.

Recent progress in nanostructured next-generation field emission devices

International Nuclear Information System (INIS)

Mittal, Gaurav; Lahiri, Indranil

2014-01-01

Field emission has been known to mankind for more than a century, and extensive research in this field for the last 40–50 years has led to development of exciting applications such as electron sources, miniature x-ray devices, display materials, etc. In the last decade, large-area field emitters were projected as an important material to revolutionize healthcare and medical devices, and space research. With the advent of nanotechnology and advancements related to carbon nanotubes, field emitters are demonstrating highly enhanced performance and novel applications. Next-generation emitters need ultra-high emission current density, high brightness, excellent stability and reproducible performance. Novel design considerations and application of new materials can lead to achievement of these capabilities. This article presents an overview of recent developments in this field and their effects on improved performance of field emitters. These advancements are demonstrated to hold great potential for application in next-generation field emission devices. (topical review)

Recent progress in nanostructured next-generation field emission devices

Science.gov (United States)

Mittal, Gaurav; Lahiri, Indranil

2014-08-01

Field emission has been known to mankind for more than a century, and extensive research in this field for the last 40-50 years has led to development of exciting applications such as electron sources, miniature x-ray devices, display materials, etc. In the last decade, large-area field emitters were projected as an important material to revolutionize healthcare and medical devices, and space research. With the advent of nanotechnology and advancements related to carbon nanotubes, field emitters are demonstrating highly enhanced performance and novel applications. Next-generation emitters need ultra-high emission current density, high brightness, excellent stability and reproducible performance. Novel design considerations and application of new materials can lead to achievement of these capabilities. This article presents an overview of recent developments in this field and their effects on improved performance of field emitters. These advancements are demonstrated to hold great potential for application in next-generation field emission devices.

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

Two Prospective Studies of Changes in Stress Generation across Depressive Episodes in Adolescents and Emerging Adults

Science.gov (United States)

Morris, Matthew C.; Kouros, Chrystyna D.; Hellman, Natalie; Rao, Uma; Garber, Judy

2014-01-01

The stress generation hypothesis was tested in two different longitudinal studies examining relations between weekly depression symptom ratings and stress levels in adolescents and emerging adults at varied risk for depression. Participants in Study 1 included 240 adolescents who differed with regard to their mother’s history of depressive disorders. Youth were assessed annually across 6 years (Grades 6 through 12). Consistent with the depression autonomy model, higher numbers of prior major depressive episodes (MDEs) were associated with weaker stress generation effects, such that higher levels of depressive symptoms predicted increases in levels of dependent stressors for adolescents with ≤ 2 prior MDEs, but depressive symptoms were not significantly related to dependent stress levels for youth with ≥ 3 prior MDEs. In Study 2, participants were 32 remitted-depressed and 36 never-depressed young adults who completed a psychosocial stress task to determine cortisol reactivity and were re-assessed for depression and stress approximately eight months later. Stress generation effects were moderated by cortisol responses to a laboratory psychosocial stressor, such that individuals with higher cortisol responses exhibited a pattern consistent with the depression autonomy model, whereas individuals with lower cortisol responses showed a pattern more consistent with the depression sensitization model. Finally, comparing across the two samples, stress generation effects were weaker for older participants and for those with more prior MDEs. The complex, multi-factorial relation between stress and depression is discussed. PMID:25422968

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)

Stability and semiclassics in self-generated fields

DEFF Research Database (Denmark)

Erdös, Laszlo; Fournais, Søren; Solovej, Jan Philip

2013-01-01

We consider non-interacting particles subject to a fixed external potential V and a self-generated magnetic field B. The total energy includes the field energy β∫B^2 and we minimize over all particle states and magnetic fields. In the case of spin-1/2 particles this minimization leads...... measuring the field strength in the semiclassical limit is κ=βh. We are not able to give the exact leading order semiclassical asymptotics uniformly in κ or even for fixed κ. We do however give upper and lower bounds on E with almost matching dependence on κ. In the simultaneous limit h→0 and κ→∞ we show...

Wiggler magnetic field assisted third harmonic generation in expanding clusters

Science.gov (United States)

Vij, Shivani

2018-04-01

A simple theoretical model is constructed to study the wiggler magnetic field assisted third harmonic generation of intense short pulse laser in a cluster in its expanding phase. The ponderomotive force of laser causes density perturbations in cluster electron density which couples with wiggler magnetic field to produce a nonlinear current that generates transverse third harmonic. An intense short pulse laser propagating through a gas embedded with atomic clusters, converts it into hot plasma balls via tunnel ionization. Initially, the electron plasma frequency inside the clusters ω pe > \\sqrt{3}{ω }1 (with ω 1 being the frequency of the laser). As the cluster expands under Coulomb force and hydrodynamic pressure, ω pe decreases to \\sqrt{3}{ω }1. At this time, there is resonant enhancement in the efficiency of the third harmonic generation. The efficiency of third harmonic generation is enhanced due to cluster plasmon resonance and by phase matching due to wiggler magnetic field. The effect of cluster size on the expansion rate is studied to observe that the clusters of different radii would expand differently. The impact of laser intensity and wiggler magnetic field on the efficiency of third harmonic generation is also explored.

Thermodynamic method for generating random stress distributions on an earthquake fault

Science.gov (United States)

Barall, Michael; Harris, Ruth A.

2012-01-01

This report presents a new method for generating random stress distributions on an earthquake fault, suitable for use as initial conditions in a dynamic rupture simulation. The method employs concepts from thermodynamics and statistical mechanics. A pattern of fault slip is considered to be analogous to a micro-state of a thermodynamic system. The energy of the micro-state is taken to be the elastic energy stored in the surrounding medium. Then, the Boltzmann distribution gives the probability of a given pattern of fault slip and stress. We show how to decompose the system into independent degrees of freedom, which makes it computationally feasible to select a random state. However, due to the equipartition theorem, straightforward application of the Boltzmann distribution leads to a divergence which predicts infinite stress. To avoid equipartition, we show that the finite strength of the fault acts to restrict the possible states of the system. By analyzing a set of earthquake scaling relations, we derive a new formula for the expected power spectral density of the stress distribution, which allows us to construct a computer algorithm free of infinities. We then present a new technique for controlling the extent of the rupture by generating a random stress distribution thousands of times larger than the fault surface, and selecting a portion which, by chance, has a positive stress perturbation of the desired size. Finally, we present a new two-stage nucleation method that combines a small zone of forced rupture with a larger zone of reduced fracture energy.

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.

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.

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...

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.

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.

Generating functional of the mean field in quantum electrodynamics with non-stable vacuum

International Nuclear Information System (INIS)

Gitman, D.M.; Kuchin, V.A.

1981-01-01

Generating functional for calculating a mean field, in the case of unstable vacuum, in quantum field theory has been suggested. Continual representation for the generating functional of the mean field has been found in the case of quantum electrodynamics with an external field. Generating electron-positron pairs from vacuum [ru

Dispersed solar thermal generation employing parabolic dish-electric transport with field modulated generator systems

Science.gov (United States)

Ramakumar, R.; Bahrami, K.

1981-01-01

This paper discusses the application of field modulated generator systems (FMGS) to dispersed solar-thermal-electric generation from a parabolic dish field with electric transport. Each solar generation unit is rated at 15 kWe and the power generated by an array of such units is electrically collected for insertion into an existing utility grid. Such an approach appears to be most suitable when the heat engine rotational speeds are high (greater than 6000 r/min) and, in particular, if they are operated in the variable speed mode and if utility-grade a.c. is required for direct insertion into the grid without an intermediate electric energy storage and reconversion system. Predictions of overall efficiencies based on conservative efficiency figures for the FMGS are in the range of 25 per cent and should be encouraging to those involved in the development of cost-effective dispersed solar thermal power systems.

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.

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

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.

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

The intermittency of vector fields and random-number generators

Science.gov (United States)

Kalinin, A. O.; Sokoloff, D. D.; Tutubalin, V. N.

2017-09-01

We examine how well natural random-number generators can reproduce the intermittency phenomena that arise in the transfer of vector fields in random media. A generator based on the analysis of financial indices is suggested as the most promising random-number generator. Is it shown that even this generator, however, fails to reproduce the phenomenon long enough to confidently detect intermittency, while the C++ generator successfully solves this problem. We discuss the prospects of using shell models of turbulence as the desired generator.

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.

Stress corrosion cracking susceptibility of steam generator tubing on secondary side in restricted flow areas

International Nuclear Information System (INIS)

Fulger, M.; Lucan, D.; Radulescu, M.; Velciu, L.

2003-01-01

Nuclear steam generator tubes operate in high temperature water and on the secondary side in restricted flow areas many nonvolatile impurities accidentally introduced into circuit tend to concentrate. The concentration process leads to the formation of highly aggressive alkaline or acid solutions in crevices, and these solutions can cause stress corrosion cracking (SCC) on stressed tube materials. Even though alloy 800 has shown to be highly resistant to general corrosion in high temperature water, it has been found that the steam generator tubes may crack during service from the primary and/or secondary side. Stress corrosion cracking is still a serious problem occurring on outside tubes in operating steam generators. The purpose of this study was to evaluate the environmental factors affecting the stress corrosion cracking of steam generators tubing. The main test method was the exposure for 1000 hours into static autoclaves of plastically stressed C-rings of Incoloy 800 in caustic solutions (10% NaOH) and acidic chloride solutions because such environments may sometimes form accidentally in crevices on secondary side of tubes. Because the kinetics of corrosion of metals is indicated by anodic polarization curves, in this study, some stressed specimens were anodically polarized in caustic solutions in electrochemical cell, and other in chloride acidic solutions. The results presented as micrographs, potentiokinetic curves, and electrochemical parameters have been compared to establish the SCC behavior of Incoloy 800 in such concentrated environments. (authors)

Quality of Life and Stressful Life Events in First and Second Generation Immigrant Adolescents

Directory of Open Access Journals (Sweden)

Ida Lemos

2013-09-01

Full Text Available The aim of this study was to examine differences in quality of life and stressful life events, in first and second generation immigrant adolescents living in Algarve. A total of 172 immigrant adolescents participated in the study, completing the kidscreen-52, the stressful and negative life events inventory and a socio-demographic questionnaire. Results suggest that younger immigrant adolescents report more physical well-being and a higher mood level. Concerning gender differences, girls scored higher than boys in physical well-being, mood and self-perception, but no differences were found on the other kidscreen subscales. First generation immigrants scored significantly higher than second generation ones on the general quality of life index, psychological well-being, autonomy, financial resources and school environment. However, the second-generation immigrants did not seem to be more exposed to stressful life events than the first-generation group. When selecting relevant variables for well-being promotion and for intervention, we must consider that immigrants are more exposed to economic vulnerability, may experience difficulties in adapting to a different school context, and are at higher risk of social exclusion.

Stress corrosion cracking experience in steam generators at Bruce NGS

International Nuclear Information System (INIS)

King, P.J.; Gonzalez, F.; Brown, J.

1993-01-01

In late 1990 and through 1991, units 1 and 2 at the Bruce A Nuclear Generating Station (BNGS-A) experienced a number of steam generator tube leaks. Tube failures were identified by eddy current to be circumferential cracks at U-bend supports on the hot-leg side of the boilers. In late 1991, tubes were removed from these units for failure characterization. Two active failure modes were found: corrosion fatigue in both units 1 and 2 and stress corrosion cracking (SCC) in unit 2. In unit 2, lead was found in deposits, on tubes, and in cracks, and the cracking was mixed-mode: transgranular and intergranular. This convincingly indicated the involvement of lead in the stress corrosion cracking failures. A program of inspection and tube removals was carried out to investigate more fully the extent of the problem. This program found significant cracking only in lead-affected boilers in unit 2, and also revealed a limited extent of non-lead-related intergranular stress corrosion cracking in other boilers and units. Various aspects of the failures and tube examinations are presented in this paper. Included is discussion of the cracking morphology, measured crack size distributions, and chemical analysis of tube surfaces, crack faces, and deposits -- with particular emphasis on lead

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.

On the theory of magnetic field generation by relativistically strong laser radiation

International Nuclear Information System (INIS)

Berezhiani, V.I.; Shatashvili, N.L.; Mahajan, S.M.

1996-07-01

The authors consider the interaction of subpicosecond relativistically strong short laser pulses with an underdense cold unmagnetized electron plasma. It is shown that the strong plasma inhomogeneity caused by laser pulses results in the generation of a low frequency (quasistatic) magnetic field. Since the electron density distribution is determined completely by the pump wave intensity, the generated magnetic field is negligibly small for nonrelativistic laser pulses but increases rapidly in the ultrarelativistic case. Due to the possibility of electron cavitation (complete expulsion of electrons from the central region) for narrow and intense beams, the increase in the generated magnetic field slows down as the beam intensity is increased. The structure of the magnetic field closely resembles that of the field produced by a solenoid; the field is maximum and uniform in the cavitation region, then it falls, changes polarity and vanishes. In extremely dense plasmas, highly intense laser pulses in the self-channeling regime can generate magnetic fields ∼ 100 Mg and greater

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.

Modelling of stresses generated in steels by phase transformations

International Nuclear Information System (INIS)

Dudek, K.; Glowacki, M.; Pietrzyk, M.

1999-01-01

Numerical model describing stresses arising during phase transformations in steels products is presented. The full model consists of three components. The first component uses finite element solution of Fourier equation for an evaluation of the temperature field inside the sample. The second component predicts kinetics of phase transformation occurring during cooling of steel products. Coupling of these two components allows prediction of structure and properties of final products at room temperature. The third component uses elastic-plastic finite element model for prediction of stresses caused by non-uniform temperatures and by changes of volume during transformations. Typical results of simulations performed for cooling of rails after hot rolling are presented. (author)

Changes in Earth's core-generated magnetic field, as observed by Swarm

DEFF Research Database (Denmark)

Finlay, Chris; Olsen, Nils; Gillet, Nicolas

By far the largest part of the Earth's magnetic field is generated by motions taking place within our planet's liquid metal outer core. Variations of this core-generated field thus provide us with a unique means of probing the dynamics taking place in the deepest reaches of the Earth....... In this contribution, we will present the core-generated magnetic field, and its recent time changes, as seen by ESA's Earth explorer mission Swarm. We will present a new time-dependent geomagnetic field model, called CHAOS-6, derived from satellite data collected by the Swarm constellation, as well as data from...... the previous missions CHAMP and Oersted together with ground observatory data. Advantage is taken of the constellation aspect of the Swarm mission by ingesting field differences along track and across track between the lower pair of Swarm satellites. Evaluating the global field model at the outer boundary...

The spatial distribution and time evolution of impact-generated magnetic fields

Science.gov (United States)

Crawford, D. A.; Schultz, P. H.

1991-01-01

The production of magnetic fields was revealed by laboratory hypervelocity impacts in easily vaporized targets. As quantified by pressure measurements, high frame-rate photography, and electrostatic probes, these impacts tend to produce large quantities of slightly ionized vapor, which is referred to as impact-generated plasma. Nonaligned electron density and temperature gradients within this plasma may lead to production of the observed magnetic fields. Past experiments were limited to measuring a single component of the impact-generated magnetic fields at only a few locations about the developing impact crater and consequently gave little information about the field production mechanism. To understand this mechanism, the techniques were extended to map the three components of the magnetic field both in space and time. By conducting many otherwise identical experiments with arrayed magnetic detectors, a preliminary 3-D picture was produced of impact-generated magnetic fields as they develop through time.

On the electric and magnetic field generation in expanding plasmas

International Nuclear Information System (INIS)

Gielen, H.J.G.

1989-01-01

This thesis deals with the generation of electric and magnetic fields in expanding plasmas. The theoretical model used to calculate the different field quantities in such plasmas is discussed in part 1 and is in fact an analysis of Ohm's law. A general method is given that decomposes each of the forces terms in Ohm's law in a component that induces a charge separation in the plasma and in a component that can drive current. This decomposition is unambiguous and depends upon the boundary conditions for the electric potential. It is shown that in calculating the electromagnetic field quantities in a plasma that is located in the vicinity of a boundary that imposes constraints on the electric potential, Ohm's law should be analyzed instead of the so-called induction equation. Three applications of the model are presented. A description is given of the unipolar arc discharge where both plasma and sheath effects have been taken into account. Secondly a description is presented of the plasma effects of a cathode spot. The third application of the model deals with the generation of magnetic fields in laser-produced plasmas. The second part of this thesis describes the experiments on a magnetized argon plasma expanding from a cascaded arc. With the use of spectroscopic techniques the electron density, ion temperature and the rotation velocity profiles of the ion gas have been determined. The magnetic field generated by the plasma has been measured with the use of the Zeeman effect. Depending on the channel diameter of the nozzle of the cascaded arc, self-generated magnetic fields with axial components of the order of 1% of the externally applied mangetic field have been observed. From the measured ion rotation it has been concluded that this magnetic field is mainly generated by azimuthal electron currents. The corresponding azimuthal current density is of the order of 15% of the axial current density. The observed ion rotation is caused by electron-ion friction. (author

Numerical simulation of the leaky dielectric microdroplet generation in electric fields

Science.gov (United States)

Kamali, Reza; Manshadi, Mohammad Karim Dehghan

2016-07-01

Microdroplet generation has a vast range of applications in the chemical, biomedical, and biological sciences. Several devices are applied to produce microdroplets, such as Co-flow, T-junction and Flow-focusing. The important point in the producing process is controlling the separated fluid volume in these devices. On the other hand, a large number of liquids, especially aqueous one, are influenced by electric or magnetic fields. As a consequence, an electric field could be used in order to affect the separated fluid volume. In this study, effects of an electric field on the microdroplet generation in a Co-flow device are investigated numerically. Furthermore, effects of some electrical properties such as permittivity on the separating process of microdroplets are studied. Leaky dielectric and perfect dielectric models are used in this investigation. According to the results, in the microdroplet generating process, leaky dielectric fluids show different behaviors, when an electric field is applied to the device. In other words, in a constant electric field strength, the volume of generated microdroplets can increase or decrease, in comparison with the condition without the electric field. However, for perfect dielectric fluids, droplet volume always decreases with increasing the electric field strength. In order to validate the numerical method of this study, deformation of a leaky dielectric droplet in an electric field is investigated. Results are compared with Taylor theoretical model.

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.

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

DEFF Research Database (Denmark)

Liu, Dong; Polinder, Henk; Magnusson, Niklas

2016-01-01

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

Shear flow generation by Reynolds stress and suppression of resistive g-modes

International Nuclear Information System (INIS)

Sugama, H.; Horton, W.

1993-08-01

Suppression of resistive g-mode turbulence by background shear flow generated from a small external flow source and amplified by the fluctuation-induced Reynolds stress is demonstrated and analyzed. The model leads to a paradigm for the low-to-high (L-H) confinement mode transition. To demonstrate the L-H transition model, single-helicity nonlinear fluid simulations using the vorticity equation for the electrostatic potential, the pressure fluctuation equation and the background poloidal flow equation are used in the sheared slab configuration. The relative efficiency of the external flow and the Reynolds stress for producing shear flow depends on the poloidal flow damping parameter ν which is given by neoclassical theory. For large ν, the external flow is a dominant contribution to the total background poloidal shear flow and its strength predicted by the neoclassical theory is not enough to suppress the turbulence significantly. In contrast, for small ν, we show that the fluctuations drive a Reynolds stress that becomes large and suddenly, at some critical point in time, shear flow much larger than the external flow is generated and leads to an abrupt, order unity reduction of the turbulent transport just like that of the L-H transition in tokamak experiments. It is also found that, even in the case of no external flow, the shear flow generation due to the Reynolds stress occurs through the nonlinear interaction of the resistive g-modes and reduces the transport. To supplement the numerical solutions we derive the Landau equation for the mode amplitude of the resistive g-mode taking into account the fluctuation-induced shear flow and analyze the opposite action of the Reynolds stress in the resistive g turbulence compared with the classical shear flow Kelvin-Helmholtz (K-H) driven turbulence

Residual stresses associated with the hydraulic expansion of steam generator tubing into tubesheets

International Nuclear Information System (INIS)

Middlebrooks, W.B.; Harrod, D.L.; Gold, R.E.

1993-01-01

Various methods are being used to expand heat transfer tubes into the thick tubesheets of nuclear steam generators. The residual stresses in the as-expanded tubes and methods for reducing these stresses are important because of the role which residual stresses play in stress corrosion cracking and stress assisted corrosion of the tubing. Of the various expansion processes, the hydraulic expansion process is most amenable to analytical study. This paper presents results on the residual stresses and strains in hydraulically expanded tubes and the tubesheet as computed by two different finite element codes with three different finite element models and by a theoretical incremental analysis method. The calculations include a sensitivity analysis to assess the effects of the expansion variables and the effect of stress relief heat treatments. (orig.)

Generation of hydrogen free radicals from water for fuels by electric field induction

International Nuclear Information System (INIS)

Nong, Guangzai; Chen, Yiyi; Li, Ming; Zhou, Zongwen

2015-01-01

Highlights: • Hydrogen free radicals are generated from water splitting. • Hydrogen fuel is generated from water by electric field induction. • Hydrocarbon fuel is generated from CO_2 and water by electric field induction. - Abstract: Water is the most abundant resource for generating hydrogen fuel. In addition to dissociating H"+ and "−OH ions, certain water molecules dissociate to radicals under an electric field are considered. Therefore, an electric field inducing reactor is constructed and operated to generate hydrogen free radicals in this paper. Hydrogen free radicals begin to be generated under a 1.0 V electric field, and increasing the voltage and temperature increases the number of hydrogen free radicals. The production rate of hydrogen free radicals is 0.245 mmol/(L h) at 5.0 V and room temperature. The generated hydrogen free radicals are converted to polymer fuel and hydrogen fuel at production rates of 0.0093 mmol/(L h) and 0.0038 mmol/(L h) respectively, under 5.0 V and 0.25 mA. The results provide a way to generate hydrogen free radicals, which might be used to generate hydrocarbon fuel in industrial manufacture.

Highly stable and finely tuned magnetic fields generated by permanent magnet assemblies.

Science.gov (United States)

Danieli, E; Perlo, J; Blümich, B; Casanova, F

2013-05-03

Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays.

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

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.

Prenatal stress programs neuroendocrine stress responses and affective behaviors in second generation rats in a sex-dependent manner.

Science.gov (United States)

Grundwald, Natalia J; Brunton, Paula J

2015-12-01

An adverse environment in early life is often associated with dysregulation of the hypothalamo-pituitary-adrenal (HPA) axis and higher rates of mood disorders in adulthood. In rats, exposure to social stress during pregnancy results in hyperactive HPA axis responses to stress in the adult offspring and heightened anxiety behavior in the males, but not the females. Here we tested whether, without further intervention, the effects of prenatal stress (PNS) in the first filial generation (F1) are transmitted to the F2 generation via the maternal line. F1 control and PNS female rats were mated with control males and housed under non-stress conditions throughout pregnancy. HPA axis responses to acute stress, anxiety- and depressive-like behavior were assessed in the adult F2 offspring. ACTH and corticosterone responses to an acute stressor were markedly enhanced in F2 PNS females compared with controls. This was associated with greater corticotropin releasing hormone (Crh) mRNA expression in the paraventricular nucleus and reduced hippocampal glucocorticoid (Gr) and mineralocorticoid receptor (Mr) mRNA expression. Conversely, in the F2 PNS males, HPA axis responses to acute stress were attenuated and hippocampal Gr mRNA expression was greater compared with controls. F2 PNS males exhibited heightened anxiety-like behavior (light-dark box and elevated plus maze) compared with F2 control males. Anxiety-like behavior did not differ between F2 control and PNS females during metestrus/diestrus, however at proestrus/estrus, F2 control females displayed a reduction in anxiety-like behavior, but this effect was not observed in the F2 PNS females. Heightened anxiety in the F2 PNS males was associated with greater Crh mRNA expression in the central nucleus of the amygdala compared with controls. Moreover, Crh receptor-1 (Crhr1) mRNA expression was significantly increased, whereas Crhr2 mRNA was significantly decreased in discrete regions of the amygdala in F2 PNS males compared

Understanding the impact of prior depression on stress generation: examining the roles of current depressive symptoms and interpersonal behaviours.

Science.gov (United States)

Shih, Josephine H; Eberhart, Nicole K

2008-08-01

Stress generation is a process in which individuals contribute to stressful life events. While research has supported an association between current depression and stress generation, it has been noted that individuals with prior depression tend to contribute to stressors even when they are no longer experiencing a depressive episode. The aim of the study is to elucidate the pathways through which prior major depression predicts interpersonal stress generation in women. Specifically, we examined current subsyndromal depressive symptoms and problematic interpersonal behaviours as potential mediators. Fifty-one college women were followed prospectively for 6 weeks. Participants were interviewed to assess current and past depression as well as stressful life events they experienced over the 6-week period. The findings suggest that prior major depression continues to have an impact even after the episode has ended, as the disorder continues to contribute to stress generation through residual depressive symptoms.

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.

A review of self generated B-field in ICF corona

International Nuclear Information System (INIS)

Jha, L.N.

1989-07-01

Self generated high order magnetic field in the corona of Inertial Confinement Fusion Plasma plays a very important role in the design of fusion target because of its strong influence on the transport of thermal flux from the critical density region to the ablation layer. A review of the generation of megagauss magnetic field both experimental, theoretical and simulation studies has been presented. (author). 28 refs, 5 figs, 1 tab

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.

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

A computational study of the near-field generation and decay of wingtip vortices

International Nuclear Information System (INIS)

Craft, T.J.; Gerasimov, A.V.; Launder, B.E.; Robinson, C.M.E.

2006-01-01

The numerical prediction of the downstream trailing vortex shed from an aircraft wingtip is a particularly challenging CFD task because, besides predicting the development of the strong vortex itself, one needs to compute accurately the flow over the wing to resolve the boundary layer roll-up and shedding which provide the initial conditions for the free vortex. Computations are here reported of the flow over a NACA 0012 half-wing with rounded wing tip and the near-field wake as measured by [Chow, J.S., Zilliac, G., Bradshaw, P., 1997. Turbulence measurements in the near-field of a wingtip vortex. NASA Tech Mem 110418, NASA.]. The aim is to assess the performance of two turbulence models which, in principle, might be seen as capable of resolving both the three dimensional boundary layer on the wing and the generation and near-field decay of the strongly accelerated vortex that develops from the wingtip. Results using linear and non-linear eddy-viscosity models are presented, but these both exhibit a far too rapid decay of the vortex core. Only a stress-transport (or second-moment) model that satisfies the 'two-component limit', [Lumley, J.L., 1978. Computational modelling of turbulent flows. Adv. Appl. Mech. 18, 123-176.], reproduces the principal features found in the experimental measurements

Neutron-diffraction measurements of stress

International Nuclear Information System (INIS)

Holden, T.M.

1995-01-01

Experiments on bent steam-generator tubing have shown that different diffraction peaks, (1 1 1) or (0 0 2), give different results for the sign and magnitude of the stress and strain. From an engineering standpoint, the macroscopic stress field cannot be both positive and negative in the same volume, so this difference must be due to intergranular effects superposed on the macroscopic stress field. Uniaxial tensile test experiments with applied stresses beyond the 0.2% offset yield stress, help to understand this anomaly, by demonstrating the different strain response to applied stress along different crystallographic axes.When Zr-alloys are cooled from elevated temperatures, thermal stresses always develop, so that it is difficult to obtain a stress-free lattice spacing from which residual strains may be derived. From measurements of the temperature dependence of lattice spacing, the temperature at which the thermal stresses vanish may be found. From the lattice spacing at this temperature the stress-free lattice spacings at room temperature can be obtained readily.To interpret the measured strains in terms of macroscopic stress fields it is necessary to know the diffraction elastic constants. Neutron diffraction measurements of the diffraction elastic constants in a ferritic steel for the [1 1 0], [0 0 2] and [2 2 2] crystallographic axes, in directions parallel and perpendicular to the applied stress are compared with theoretical diffraction elastic constants. (orig.)

Microrelief-Controlled Overland Flow Generation: Laboratory and Field Experiments

Directory of Open Access Journals (Sweden)

Xuefeng Chu

2015-01-01

Full Text Available Surface microrelief affects overland flow generation and the related hydrologic processes. However, such influences vary depending on other factors such as rainfall characteristics, soil properties, and initial soil moisture conditions. Thus, in-depth research is needed to better understand and evaluate the combined effects of these factors on overland flow dynamics. The objective of this experimental study was to examine how surface microrelief, in conjunction with the factors of rainfall, soil, and initial moisture conditions, impacts overland flow generation and runoff processes in both laboratory and field settings. A series of overland flow experiments were conducted for rough and smooth surfaces that represented distinct microtopographic characteristics and the experimental data were analyzed and compared. Across different soil types and initial moisture conditions, both laboratory and field experiments demonstrated that a rough soil surface experienced a delayed initiation of runoff and featured a stepwise threshold flow pattern due to the microrelief-controlled puddle filling-spilling-merging dynamics. It was found from the field experiments that a smooth plot surface was more responsive to rainfall variations especially during an initial rainfall event. However, enhanced capability of overland flow generation and faster puddle connectivity of a rough field plot occurred during the subsequent rain events.

Real-time Image Generation for Compressive Light Field Displays

International Nuclear Information System (INIS)

Wetzstein, G; Lanman, D; Hirsch, M; Raskar, R

2013-01-01

With the invention of integral imaging and parallax barriers in the beginning of the 20th century, glasses-free 3D displays have become feasible. Only today—more than a century later—glasses-free 3D displays are finally emerging in the consumer market. The technologies being employed in current-generation devices, however, are fundamentally the same as what was invented 100 years ago. With rapid advances in optical fabrication, digital processing power, and computational perception, a new generation of display technology is emerging: compressive displays exploring the co-design of optical elements and computational processing while taking particular characteristics of the human visual system into account. In this paper, we discuss real-time implementation strategies for emerging compressive light field displays. We consider displays composed of multiple stacked layers of light-attenuating or polarization-rotating layers, such as LCDs. The involved image generation requires iterative tomographic image synthesis. We demonstrate that, for the case of light field display, computed tomographic light field synthesis maps well to operations included in the standard graphics pipeline, facilitating efficient GPU-based implementations with real-time framerates.

Poloidal spin up and electric-field generation related to displacement current and neoclassical transport

International Nuclear Information System (INIS)

Gervasini, G.; Lazzaro, E.; Minardi, E.

1996-01-01

In accordance with the conventional ordering of neoclassical theory, poloidal and toroidal accelerations with constant parallel flow can be driven by heat transport in the absence of external momentum input and with vanishing parallel viscous stress. In a transient phase in which the heat transport is the primary source of the time dependence, the torque generating the rotation is provided at third order in the adiabatic expansion by the surface-averaged (non ambipolar) displacement current, which in also responsible for charge build-up and for the radial electric field. The heat transport equation has been solved in a narrow layer interfaced with the intensely heated plasma core through heat flux continuity, assuming neoclassical multi collisional coefficients with self-consistent suppression mechanism of anomalous transport. Starting from low temperature in the edge layer, a strong temperature gradient, a mass poloidal rotation in the ion direction and a strongly negative sheared radial electric field can be generated, in agreement with the observations, and reach a stationary state after a displacement current-dominated triggering phase (intrinsically non-ambipolar) lasting few milliseconds. Momentum input becomes important on longer time scale and is responsible for the toroidal rotation, decoupled from temperature gradient and for a further development of the radial electric field. The results show the ability of edge transport processes to adapt flexibly to a high temperature imposed on the inner side of the edge layer and support the view that the edge processes are a integral part of a more fundamental global process involving possibly an internal bifurcation of state

Generation of macroscopic magnetic-field-aligned electric fields by the convection surge ion acceleratiom mechanism

International Nuclear Information System (INIS)

Mauk, B.H.

1989-01-01

The ''convection surge'' computer model presented previously (concerning the dramatic, nonadiabatic, magnetic-field-aligned energization of ions near the Earth's geosynchronous orbit in the presence of strong, transient, magnetic-field-perpendicular inductive electric fields) has been extended to include the self-consistent generation of magnetic-field-aligned electric fields. The field-aligned electric potential is obtained by imposing the quasi-neutrality condition using approximated electron distribution forms. The ions are forced to respond self-consistently to this potential. It is found that field-aligned potential drops up to 1 to 10 kV can be generated depending on electron temperatures and on the mass species of the ions. During transient periods of the process, these large potential drops can be confined to a few degrees of magnetic latitude at positions close to the magnetic equator. Anomalous, sometimes dramatic, additional magnetic-field-aligned ion acceleration also occurs in part as a result of a quasi-resonance between the parallel velocities of some ions and the propagating electric potential fronts. It is speculated that the convection surge mechanism could be a key player in the transient, field-aligned electromagnetic processes observed to operate within the middle (e.g., geosynchronous) magnetosphere. copyright American Geophysical Union 1989

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

Low pressure arc discharge lamp apparatus with magnetic field generating means

Science.gov (United States)

Grossman, Mark W.; George, William A.; Maya, Jakob

1987-01-01

A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25.degree. C.

Low pressure arc discharge lamp apparatus with magnetic field generating means

Science.gov (United States)

Grossman, M.W.; George, W.A.; Maya, J.

1987-10-06

A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25 C. 3 figs.

Measurements of magnetic fields generated in underdense plasmas by intense lasers

International Nuclear Information System (INIS)

Najmudin, Z.; Walton, B. R.; Mangles, S. P. D.; Dangor, A. E.; Krushelnick, K.; Fritzler, S.; Malka, V.; Faure, J.; Tatarakis, M.

2006-01-01

Measurements have been made of the magnetic field generated by the passage of high intensity short laser pulses through underdense plasmas. For a 30 fs, 1 J, 800 nm linearly-polarised laser pulse, an azimuthal magnetic field is observed at a radial extent of approximately 200 μm. The field is found to exceed 2.8 MG. For a 1 ps, 40 J, 1054 nm circularly-polarised laser pulse, a solenoidal field is observed that can exceed 7 MG. This solenoidal field is absent with linear polarised light, and hence can be considered as an Inverse Faraday effect. Both types of field are found to decay on the picosecond timescale. For both the azimuthal and solenoidal fields produced by such intense lasers, the production of energetic electrons by the interaction is thought to be vital for magnetic field generation

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.

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...

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...

Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets and Supernova Remnants

Science.gov (United States)

Nishikawa, K.-I.; Hartmann, D. H.; Hardee, P.; Hededal, C.; Mizunno, Y.; Fishman, G. J.

2006-01-01

We performed numerical simulations of particle acceleration, magnetic field generation, and emission from shocks in order to understand the observed emission from relativistic jets and supernova remnants. The investigation involves the study of collisionless shocks, where the Weibel instability is responsible for particle acceleration as well as magnetic field generation. A 3-D relativistic particle-in-cell (RPIC) code has been used to investigate the shock processes in electron-positron plasmas. The evolution of theWeibe1 instability and its associated magnetic field generation and particle acceleration are studied with two different jet velocities (0 = 2,5 - slow, fast) corresponding to either outflows in supernova remnants or relativistic jets, such as those found in AGNs and microquasars. Slow jets have intrinsically different structures in both the generated magnetic fields and the accelerated particle spectrum. In particular, the jet head has a very weak magnetic field and the ambient electrons are strongly accelerated and dragged by the jet particles. The simulation results exhibit jitter radiation from inhomogeneous magnetic fields, generated by the Weibel instability, which has different spectral properties than standard synchrotron emission in a homogeneous magnetic field.

Review on structured optical field generated from array beams

Science.gov (United States)

Hou, Tianyue; Zhou, Pu; Ma, Yanxing; Zhi, Dong

2018-03-01

Structured optical field (SOF), which includes vortex beams, non-diffraction beams, cylindrical vector beams and so on, has been under intensive investigation theoretically and experimentally in recent years. Generally, current research focus on the extraordinary properties (non-diffraction propagation, helical wavefront, rotation of electrical field, et al), which can be widely applied in micro-particle manipulation, super-resolution imaging, free-space communication and so on. There are mainly two technical routes, that is, inner-cavity and outer-cavity (spatial light modulators, diffractive phase holograms, q-plates). To date, most of the SOFs generated from both technical routes involves with single monolithic beam. As a novel technical route, SOF based on array beams has the advantage in more flexible freedom degree and power scaling potential. In this paper, research achievements in SOF generation based on array beams are arranged and discussed in detail. Moreover, experiment of generating exotic beam by array beams is introduced, which illustrates that SOF generated from array beams is theoretically valid and experimentally feasible. SOF generated from array beams is also beneficial for capacity increasing and data receiving for free-space optical communication systems at long distance.

A kinetic model for stress generation in thin films grown from energetic vapor fluxes

Energy Technology Data Exchange (ETDEWEB)

Chason, E.; Karlson, M. [School of Engineering, Brown University, Providence, Rhode Island 02912 (United States); Colin, J. J.; Abadias, G. [Institut P' , Département Physique et Mécanique des Matériaux, Université de Poitiers-CNRS-ENSMA, SP2MI, Téléport 2, Bd M. et P. Curie, F-86962 Chasseneuil-Futuroscope (France); Magnfält, D.; Sarakinos, K. [Nanoscale Engineering Division, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden)

2016-04-14

We have developed a kinetic model for residual stress generation in thin films grown from energetic vapor fluxes, encountered, e.g., during sputter deposition. The new analytical model considers sub-surface point defects created by atomic peening, along with processes treated in already existing stress models for non-energetic deposition, i.e., thermally activated diffusion processes at the surface and the grain boundary. According to the new model, ballistically induced sub-surface defects can get incorporated as excess atoms at the grain boundary, remain trapped in the bulk, or annihilate at the free surface, resulting in a complex dependence of the steady-state stress on the grain size, the growth rate, as well as the energetics of the incoming particle flux. We compare calculations from the model with in situ stress measurements performed on a series of Mo films sputter-deposited at different conditions and having different grain sizes. The model is able to reproduce the observed increase of compressive stress with increasing growth rate, behavior that is the opposite of what is typically seen under non-energetic growth conditions. On a grander scale, this study is a step towards obtaining a comprehensive understanding of stress generation and evolution in vapor deposited polycrystalline thin films.

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.

Influence of early stress on social abilities and serotonergic functions across generations in mice.

Directory of Open Access Journals (Sweden)

Tamara B Franklin

Full Text Available Exposure to adverse environments during early development is a known risk factor for several psychiatric conditions including antisocial behavior and personality disorders. Here, we induced social anxiety and altered social recognition memory in adult mice using unpredictable maternal separation and maternal stress during early postnatal life. We show that these social defects are not only pronounced in the animals directly subjected to stress, but are also transmitted to their offspring across two generations. The defects are associated with impaired serotonergic signaling, in particular, reduced 5HT1A receptor expression in the dorsal raphe nucleus, and increased serotonin level in a dorsal raphe projection area. These findings underscore the susceptibility of social behaviors and serotonergic pathways to early stress, and the persistence of their perturbation across generations.

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.

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.

Field-enhanced route to generating anti-Frenkel pairs in HfO2

Science.gov (United States)

Schie, Marcel; Menzel, Stephan; Robertson, John; Waser, Rainer; De Souza, Roger A.

2018-03-01

The generation of anti-Frenkel pairs (oxygen vacancies and oxygen interstitials) in monoclinic and cubic HfO2 under an applied electric field is examined. A thermodynamic model is used to derive an expression for the critical field strength required to generate an anti-Frenkel pair. The critical field strength of EaFcr˜101GVm-1 obtained for HfO2 exceeds substantially the field strengths routinely employed in the forming and switching operations of resistive switching HfO2 devices, suggesting that field-enhanced defect generation is negligible. Atomistic simulations with molecular static (MS) and molecular dynamic (MD) approaches support this finding. The MS calculations indicated a high formation energy of Δ EaF≈8 eV for the infinitely separated anti-Frenkel pair, and only a decrease to Δ EaF≈6 eV for the adjacent anti-Frenkel pair. The MD simulations showed no defect generation in either phase for E <3 GVm-1 , and only sporadic defect generation in the monoclinic phase (at E =3 GVm-1 ) with fast (trec<4 ps ) recombination. At even higher E but below EaFcr both monoclinic and cubic structures became unstable as a result of field-induced deformation of the ionic potential wells. Further MD investigations starting with preexisting anti-Frenkel pairs revealed recombination of all pairs within trec<1 ps , even for the case of neutral vacancies and charged interstitials, for which formally there is no electrostatic attraction between the defects. In conclusion, we find no physically reasonable route to generating point-defects in HfO2 by an applied field.

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

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.

Ambient fields generated by a laser spark

Czech Academy of Sciences Publication Activity Database

Rohlena, Karel; Mašek, Martin

2016-01-01

Roč. 61, č. 2 (2016), s. 119-124 ISSN 0029-5922 R&D Projects: GA MŠk(CZ) LD14089; GA MŠk(CZ) LG13031 Institutional support: RVO:68378271 Keywords : laser spark * radiation chemistry * field generation Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.760, year: 2016

[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.

Effects of external magnetic field on harmonics generated in laser interaction with underdense plasma

International Nuclear Information System (INIS)

Faghihi-Nik, M.; Ghorbanalilu, M.; Shokri, B.

2010-01-01

Complete text of publication follows. Generation of harmonic radiation is an important subject of laser plasma interaction and attracts great attention due to a wide range of applications. It has been seen that intense electromagnetic and quasi-static transverse magnetic fields are generated in laser plasma interaction. An extremely intense magnetic field (up to hundreds of MG) has been observed by experimental measurements in interaction of short laser pulses with plasma. These self-generated or applied magnetic fields affect the propagation of the laser pulses. In most laser interactions with homogeneous plasma, odd harmonics of laser frequency are generated. In this paper, we point out the possibility of even harmonics generation when a linearly polarized laser beam propagates in homogeneous plasma in the presence of a transverse magnetic field. It is shown that applying external field induces a transverse current density oscillating twice of the laser field which leds to generation of second harmonic radiation. This current density is derived using the perturbation method, and the steady state amplitude of the second harmonic obtained by solution of the wave equation. By the same procedure the current density and then the steady state amplitude of higher order harmonics are calculated. The efficiency of harmonic generation (the ratio of harmonic power to incident power) is a drastically function of the strength of external magnetic field. It is found that the efficiency of even harmonics is zero in the absence of magnetic field and increases as the magnetic field is increased. For odd harmonics, applying the external magnetic field enhances the generated harmonics as well. The conversion efficiency also increases with increase in plasma density and intensity of the laser beam.

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.

Stress analysis of HTR-10 steam generator heat exchanging tubes

International Nuclear Information System (INIS)

Dong Jianling; Zhang Xiaohang; Yin Dejian; Fu Jiyang

2001-01-01

Steam Generator (SG) heat exchanging tubes of 10 MW High Temperature Gas Cooled Reactor (HTR-10) are protective screens between the primary loop of helium with radioactivity and the secondary loop of feeding water and steam without radioactivity. Water and steam will enter into the primary loop when rupture of the heat exchanging tubes occurs, which lead to increase of the primary loop pressure and discharge of radioactive materials. Therefore it is important to guarantee the integrity of the tubes. The tube structure is spiral tube with small bending radius, which make it impossible to test with volumetric in-service detection. For such kind of spiral tube, using LBB concept to guarantee the integrity of the tubes is an important option. The author conducts stress analysis and calculation of HTR-10 SG heat exchanging tubes using the FEM code of piping stress analysis, PIPESTRESS. The maximum stress and the dangerous positions are obtained

Oxidative stress generated damage to DNA by gastrointestinal exposure to insoluble particles

DEFF Research Database (Denmark)

Møller, Peter; Folkmann, J K; Danielsen, P H

2012-01-01

that gastrointestinal exposure to single-walled carbon nanotubes (SWCNT), fullerenes C60, carbon black, titanium dioxide and diesel exhaust particles generates oxidized DNA base lesions in organs such as the bone marrow, liver and lung. Oral exposure to nanosized carbon black has also been associated with increased...... level of lipid peroxidation derived exocyclic DNA adducts in the liver, suggesting multiple pathways of oxidative stress for particle-generated damage to DNA. At equal dose, diesel exhaust particles (SRM2975) generated larger levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine in rat liver than carbon black...

Calculation of a steam generating tube stressed state under temperature oscillations in burnout zone

International Nuclear Information System (INIS)

Vorob'ev, V.A.; Loshchinin, V.M.; Remizov, O.V.

1982-01-01

The technique for evaluating the steam generating tube stressed state under the wall temperature oscillations in the burnout zone is described. The technique is based on analytical solutions for transfer functions connecting the amplitude of surface temperature oscillation with the amplitude and frequency of heat transfer coefficient oscillation and amplitude of thermoelastic stress oscillation with that of temperature oscillation. The results of calculations according to considered technique are compared with that of the problem numerical solution. The conclusion is made that the technique under consideration may be applied for evaluation of steam generator evaporating tube lifetime [ru

Methods for FEM stress initialization based on stress functions, and application to a reservoir cross-section

OpenAIRE

Aliguer Piferrer, Ignasi; Rafels Ybern, Carles; Jaqués Adell, Irene; Carol, Ignacio; Prat Catalán, Pere; Lakashmikhanta, Ramasesha; Segura Segarra, José María

2013-01-01

An accurate description of the in-situ stress field in a rock mass is crucial in different areas of geo-engineering such as: underground excavations, hydrocarbon extraction, CO2 storage, hydraulic fracture etc. In this paper, a novel methodology to numerically generate the in-situ stress state within the Finite Elements framework is presented. It involves two steps: 1) an estimate of the stress components is given for integration point of the discretization, and 2) global equilibrium is verif...

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.

Influence of treatment by vibration in residual stress generated in the laser welding of HSLA and IF steels

International Nuclear Information System (INIS)

Chuvas, T.C.; Fonseca, M.P. Cindra; Castello, D.A.

2010-01-01

The stress relieving treatment by vibration is a new technology under development, which has many advantages over thermal methods. In this work was analyzed the surface residual stress generated in the laser welding of biphasic HSLA and IF steels, both used in the automotive industry. Residual stresses were measured by X-ray diffraction, by the sen 2 Ψ method. Residual stresses generated in the welding of the samples were tensile at all points measured. After welding, the samples were submitted to the mechanical vibration treatment. Some samples presented a significant reduction in the stress values. The welded joints were also characterized by optical microscopy. (author)

Study of neutron fields around an intense neutron generator.

Science.gov (United States)

Kicka, L; Machrafi, R; Miller, A

2017-12-01

Neutron fields in the vicinity of the newly built neutron facility, at the University of Ontario Institute of Technology (UOIT), have been investigated in a series of Monte Carlo simulations and measurements. The facility hosts a P-385 neutron generator based on a deuterium-deuterium fusion reaction. The neutron fluence at different locations around the neutron generator facility has been simulated using MCNPX 2.7E Monte Carlo particle transport program. To characterize neutron fields, three neutron sources were modeled with distributions corresponding to different incident deuteron energies of 90kV, 110kV, and 130kV. Measurements have been carried out to determine the dose rate at locations adjacent to the generator using bubble detectors (BDs). The neutron intensity was evaluated and the total dose rates corresponding to different applied acceleration potentials were estimated at various locations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characterization of residual stresses generated during inhomogeneous plastic deformation

DEFF Research Database (Denmark)

Lorentzen, T.; Faurholdt, T.; Clausen, B.

1998-01-01

Residual stresses generated by macroscopic inhomogeneous plastic deformation are predicted by an explicit finite element (FE) technique. The numerical predictions are evaluated by characterizing the residual elastic strains by neutron diffraction using two different (hkl) reflections. Intergranular...... compare well and verify the capability of the numerical technique as well as the possibilities of experimental validation using neutron diffraction. The presented experimental and numerical approach will subsequently be utilized for the evaluation of more complicated plastic deformation processes...

Examining coping style and the relationship between stress and subjective well-being in Australia's 'sandwich generation'.

Science.gov (United States)

Gillett, Jade E; Crisp, Dimity A

2017-09-01

The sandwich generation represents adults, often in midlife, who care for both children and ageing parents/relatives. While the stress they experience has received some attention, little research has investigated the subjective well-being (SWB) of this population. This study examined the relationship between perceived stress and SWB and the moderating effect of coping style. Ninety-three participants (80 women), aged 23-63 years, completed an online survey measuring perceived stress, coping strategies, life satisfaction and positive and negative affect. Stress was negatively associated with SWB. While emotion- and problem-focused coping were directly associated with SWB outcomes, the only moderating effect found was for avoidance-focused coping (AFC). Specifically, AFC was associated with higher positive affect for those reporting lower stress. This study highlights the need to recognise the distinct circumstances that exist for the sandwich generation. Limitations and suggestions for future research are discussed. © 2017 AJA Inc.

Stress corrosion cracking susceptibility of steam generator tube materials in AVT (all volatile treatment) chemistry contaminated with lead

International Nuclear Information System (INIS)

Gomez Briceno, D.; Castano, M.L.; Garcia, M.S.

1996-01-01

Alloy 600 steam generator tubing has shown a high susceptibility to stress corrosion degradation at the operation conditions of pressurized water reactors. Several contaminants, such as lead, have been postulated as being responsible for producing the secondary side stress corrosion cracking that has occurred mainly at the location where these contaminants can concentrate. An extensive experimental work has been carried out in order to better understand the effects of lead on the stress corrosion cracking susceptibility of steam generator tube materials, namely Alloys 600, 690 and 800. This paper presents the experimental work conducted with a view to determining the influence of lead oxide concentration in AVT (all volatile treatment) conditions on the stress corrosion resistance of nickel alloys used in the fabrication of steam generator tubing. (orig.)

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.

Entropy Generation in Natural Convection Under an Evanescent Magnetic Field

International Nuclear Information System (INIS)

Magherbi, Mourad; El Jery, Atef; Ben Brahim, Ammar

2009-01-01

We numerically study the effect of an externally-evanescent magnetic field on total entropy generation in conducting and non-reactive fluid enclosed in a square cavity. The horizontal walls of the enclosure are assumed to be insulated while the vertical walls are kept isothermal. A control volume finite element method is used to solve the conservation equations at Prandtl number of 0.71. The values of relaxation time of the magnetic field are chosen, so that the Lorentz force acts only in the transient state of entropy generation in natural convection. The total entropy generation was calculated for fixed value of irreversibility distribution ratio, different relaxation time varying from 0 to 1/5 and Grashof number equal to 10 5

Internal stress distribution for generating closure domains in laser-irradiated Fe–3%Si(110) steels

International Nuclear Information System (INIS)

Iwata, Keiji; Imafuku, Muneyuki; Orihara, Hideto; Sakai, Yusuke; Ohya, Shin-Ichi; Suzuki, Tamaki; Shobu, Takahisa; Akita, Koichi; Ishiyama, Kazushi

2015-01-01

Internal stress distribution for generating closure domains occurring in laser-irradiated Fe–3%Si(110) steels was investigated using high-energy X-ray analysis and domain theory based on the variational principle. The measured triaxial stresses inside the specimen were compressive and the stress in the rolling direction became more dominant than stresses in the other directions. The calculations based on the variational principle of magnetic energy for closure domains showed that the measured triaxial stresses made the closure domains more stable than the basic domain without closure domains. The experimental and calculation results reveal that the laser-introduced internal stresses result in the occurrence of the closure domains

Electric-field effects in optically generated spin transport

International Nuclear Information System (INIS)

Miah, M. Idrish

2009-01-01

Transport of spin-polarized electrons in semiconductors is studied experimentally. Spins are generated by optical excitation because of the selection rules governing optical transitions from heavy-hole and light-hole states to conduction-band states. Experiments designed for the control of spins in semiconductors investigate the bias-dependent spin transport process and detect the spin-polarized electrons during transport. A strong bias dependence is observed. The electric-field effects on the spin-polarized electron transport are also found to be depended on the excitation photon energy and temperature. Based on a field-dependent spin relaxation mechanism, the electric-field effects in the transport process are discussed.

Electric-field effects in optically generated spin transport

Energy Technology Data Exchange (ETDEWEB)

Miah, M. Idrish [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)], E-mail: m.miah@griffith.edu.au

2009-05-25

Transport of spin-polarized electrons in semiconductors is studied experimentally. Spins are generated by optical excitation because of the selection rules governing optical transitions from heavy-hole and light-hole states to conduction-band states. Experiments designed for the control of spins in semiconductors investigate the bias-dependent spin transport process and detect the spin-polarized electrons during transport. A strong bias dependence is observed. The electric-field effects on the spin-polarized electron transport are also found to be depended on the excitation photon energy and temperature. Based on a field-dependent spin relaxation mechanism, the electric-field effects in the transport process are discussed.

Generation of an isolated sub-30 attosecond pulse in a two-color laser field and a static electric field

International Nuclear Information System (INIS)

Zhang Gang-Tai; Zhang Mei-Guang; Bai Ting-Ting

2012-01-01

We theoretically investigate high-order harmonic generation (HHG) from a helium ion model in a two-color laser field, which is synthesized by a fundamental pulse and its second harmonic pulse. It is shown that a supercontinuum spectrum can be generated in the two-color field. However, the spectral intensity is very low, limiting the application of the generated attosecond (as) pulse. By adding a static electric field to the synthesized two-color field, not only is the ionization yield of electrons contributing to the harmonic emission remarkably increased, but also the quantum paths of the HHG can be significantly modulated. As a result, the extension and enhancement of the supercontinuum spectrum are achieved, producing an intense isolated 26-as pulse with a bandwidth of about 170.5 eV. In particular, we also analyse the influence of the laser parameters on the ultrabroad supercontinuum spectrum and isolated sub-30-as pulse generation. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

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)

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

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

Field generated within the SSC magnets due to persistant currents in the superconductor

International Nuclear Information System (INIS)

Green, M.A.

1984-01-01

This report presents the results of a number of computer studies of the magnetic fields generated by persistent circulating currents in the superconductor of superconducting dipoles. These magnetic fields are referred to as residual fields throughout this report. Since the field generated by persistent currents have a hysteric behavior, they are analagous to the residual filed found in iron bound conventional solenoids. The residual field calculations presented in this report were done using the LBL SCMAG4 computer code. This code has not been well tested against measured data, but a comparison with measured CBA data given in this report suggests that good agreement is possible. The residual fields generated by persistent superconducting currents are rich in higher multipoles. This is of concern to the accelerator designer for SSC. This report shows the effect of various superconductor parameters and coil parameters on the magnitude and structure of the residual fields. The effect of the magnet charging history on residual fields is aldo discussed. 14 references

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.

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.

Heat generation in agglomerated ferrite nanoparticles in an alternating magnetic field

International Nuclear Information System (INIS)

Lima, E Jr; De Biasi, E; Mansilla, M Vasquez; Saleta, M E; Granada, M; Troiani, H E; Zysler, R D; Effenberger, F B; Rossi, L M; Rechenberg, H R

2013-01-01

The role of agglomeration and magnetic interparticle interactions in heat generation of magnetic ferrofluids in an ac magnetic field is still unclear, with apparent discrepancy between the results presented in the literature. In this work, we measured the heat generating capability of agglomerated ferrite nanoparticles in a non-invasive ac magnetic field with f = 100 kHz and H 0 = 13 kA m -1 . The nanoparticles were morphologically and magnetically characterized, and the specific absorption rate (SAR) for our ac magnetic field presents a clear dependence on the diameter of the nanoparticles, with a maximum SAR = 48 W g -1 for 15 nm. Our agglomerated nanoparticles have large hydrodynamic diameters, thus the mechanical relaxation can be neglected as a heat generation mechanism. Therefore, we present a model that simulates the SAR dependence of the agglomerated samples on the diameter of the nanoparticles based on the hysteresis losses that is valid for the non-linear region (with H 0 comparable to the anisotropy field). Our model takes into account the magnetic interactions among the nanoparticles in the agglomerate. For comparison, we also measured the SAR of non-agglomerated nanoparticles in a similar diameter range, in which Néel and Brown relaxations dominate the heat generation.

Stochastic generation of explicit pore structures by thresholding Gaussian random fields

Energy Technology Data Exchange (ETDEWEB)

Hyman, Jeffrey D., E-mail: jhyman@lanl.gov [Program in Applied Mathematics, University of Arizona, Tucson, AZ 85721-0089 (United States); Computational Earth Science, Earth and Environmental Sciences (EES-16), and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Winter, C. Larrabee, E-mail: winter@email.arizona.edu [Program in Applied Mathematics, University of Arizona, Tucson, AZ 85721-0089 (United States); Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721-0011 (United States)

2014-11-15

We provide a description and computational investigation of an efficient method to stochastically generate realistic pore structures. Smolarkiewicz and Winter introduced this specific method in pores resolving simulation of Darcy flows (Smolarkiewicz and Winter, 2010 [1]) without giving a complete formal description or analysis of the method, or indicating how to control the parameterization of the ensemble. We address both issues in this paper. The method consists of two steps. First, a realization of a correlated Gaussian field, or topography, is produced by convolving a prescribed kernel with an initial field of independent, identically distributed random variables. The intrinsic length scales of the kernel determine the correlation structure of the topography. Next, a sample pore space is generated by applying a level threshold to the Gaussian field realization: points are assigned to the void phase or the solid phase depending on whether the topography over them is above or below the threshold. Hence, the topology and geometry of the pore space depend on the form of the kernel and the level threshold. Manipulating these two user prescribed quantities allows good control of pore space observables, in particular the Minkowski functionals. Extensions of the method to generate media with multiple pore structures and preferential flow directions are also discussed. To demonstrate its usefulness, the method is used to generate a pore space with physical and hydrological properties similar to a sample of Berea sandstone. -- Graphical abstract: -- Highlights: •An efficient method to stochastically generate realistic pore structures is provided. •Samples are generated by applying a level threshold to a Gaussian field realization. •Two user prescribed quantities determine the topology and geometry of the pore space. •Multiple pore structures and preferential flow directions can be produced. •A pore space based on Berea sandstone is generated.

Residual stress control and design of next-generation ultra-hard gear steels

Science.gov (United States)

Qian, Yana

In high power density transmission systems, Ni-Co secondary hardening steels have shown great potential for next-generation gear applications due to their excellent strength, toughness and superior fatigue performance. Study of residual stress generation and evolution in Ferrium C61 and C67 gear steels revealed that shot peening and laser peening processes effectively produce desired beneficial residual stress in the steels for enhanced fatigue performance. Surface residual stress levels of -1.4GPa and -1.5GPa were achieved in shot peened C61 and laser peened C67, respectively, without introducing large surface roughness or defects. Higher compressive residual stress is expected in C67 according to a demonstrated correlation between attainable residual stress and material hardness. Due to the lack of appropriate shot media, dual laser peening is proposed for future peening optimization in C67. A novel non-destructive synchrotron radiation technique was implemented and applied for the first time for residual stress distribution analysis in gear steels with large composition and property gradients. Observed substantial residual stress redistribution and material microstructure change during the rolling contact fatigue screening test with extremely high 5.4GPa load indicates the unsuitability of the test as a fatigue life predictor. To exploit benefits of higher case hardness and associated residual stress, a new material and process (CryoForm70) aiming at 70Rc surface hardness was designed utilizing the systems approach based on thermodynamics and secondary hardening mechanisms. The composition design was first validated by the excellent agreement between experimental and theoretical core martensite start temperature in the prototype. A novel cryogenic deformation process was concurrently designed to increase the case martensite volume fraction from 76% to 92% for enhanced strengthening efficiency and surface hardness. High temperature vacuum carburizing was

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.

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

Numerical simulations on the temperature gradient and thermal stress of a thermoelectric power generator

International Nuclear Information System (INIS)

Wu, Yongjia; Ming, Tingzhen; Li, Xiaohua; Pan, Tao; Peng, Keyuan; Luo, Xiaobing

2014-01-01

Highlights: • An appropriate ceramic plate thickness is effective in alleviating the thermal stress. • A smaller distance between thermo-pins can help prolong lifecycle of the TE module. • Either a thicker or a thinner copper conducting strip effectively reduces thermal stress. • A suitable tin soldering thickness will alleviate thermal stress intensity and increase thermal efficiency. - Abstract: Thermoelectric generator is a device taking advantage of the temperature difference in thermoelectric material to generate electric power, where the higher the temperature difference of the hot-cold ends, the higher the efficiency will be. However, higher temperature or higher heat flux upon the hot end will cause strong thermal stress which will negatively influence the lifecycle of the thermoelectric module. This phenomenon is very common in industrial applications but seldom has research work been reported. In this paper, numerical analysis on the thermodynamics and thermal stress performance of the thermoelectric module has been performed, considering the variation on the thickness of materials; the influence of high heat flux on thermal efficiency, power output, and thermal stress has been examined. It is found that under high heat flux imposing upon the hot end, the thermal stress is so strong that it has a decisive effect on the life expectation of the device. To improve the module’s working condition, different geometrical configurations are tested and the optimum sizes are achieved. Besides, the side effects on the efficiency, power output, and open circuit voltage output of the thermoelectric module are taken into consideration

Strong terahertz field generation, detection, and application

Energy Technology Data Exchange (ETDEWEB)

Kim, Ki-Yong [Univ. of Maryland, College Park, MD (United States)

2016-05-22

This report describes the generation and detection of high-power, broadband terahertz (THz) radiation with using femtosecond terawatt (TW) laser systems. In particular, this focuses on two-color laser mixing in gases as a scalable THz source, addressing both microscopic and macroscopic effects governing its output THz yield and radiation profile. This also includes the characterization of extremely broad THz spectra extending from microwaves to infrared frequencies. Experimentally, my group has generated high-energy (tens of microjoule), intense (>8 MV/cm), and broadband (0.01~60 THz) THz radiation in two-color laser mixing in air. Such an intense THz field can be utilized to study THz-driven extremely nonlinear phenomena in a university laboratory.

Strong terahertz field generation, detection, and application

Energy Technology Data Exchange (ETDEWEB)

Kim, Ki-Yong [Univ. of Maryland, College Park, MD (United States)

2016-05-15

This report describes the generation and detection of high-power, broadband terahertz (THz) radiation with using femtosecond terawatt (TW) laser systems. In particular, this focuses on two-color laser mixing in gases as a scalable THz source, addressing both microscopic and macroscopic effects governing its output THz yield and radiation profile. This also includes the characterization of extremely broad THz spectra extending from microwaves to infrared frequencies. Experimentally, my group has generated high-energy (tens of microjoule), intense (>8 MV/cm), and broadband (0.01~60 THz) THz radiation in two-color laser mixing in air. Such an intense THz field can be utilized to study THz-driven extremely nonlinear phenomena in a university laboratory.

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

Near-field second-harmonic generation from gold nanoellipsoids

Energy Technology Data Exchange (ETDEWEB)

Celebrano, M; Zavelani-Rossi, M; Polli, D; Cerullo, G [Istituto di Fotonica e Nanotecnologie, CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Biagioni, P; Finazzi, M; Duo, L [LNESS - Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Labardi, M; Allegrini, M [CNR-INFM, polyLab, Dipartimento di Fisica ' Enrico Fermi' , Universita di Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy); Grand, J; Adam, P M; Royer, P [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de Technologie de Troyes, 12 rue Marie Curie, BP 2060 10010 Troyes cedex (France)

2008-07-01

Second-harmonic generation from single gold nanofabricated particles is experimentally investigated by a nonlinear scanning near-field optical microscope (SNOM). High peak power femtosecond polarized light pulses at the output of a hollow pyramid aperture allow for efficient second-harmonic imaging, with sub-100-nm spatial resolution and high contrast. The near-field nonlinear response is found to be directly related to both local surface plasmon resonances and particle morphology. The combined analysis of linear and second-harmonic SNOM images allows one to discriminate among near-field scattering, absorption and re-emission processes, which would not be possible with linear techniques alone. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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

Transient thermal stresses in an orthotropic finite rectangular plate due to arbitrary surface heat-generations

International Nuclear Information System (INIS)

Sugano, Y.

1980-01-01

The transient thermal stresses in an orthotropic finite rectangular plate due to arbitrary surface heat-generations on two edges are studied by means of the Airy stress function. The purposes of this paper are to present a method of determing the transient thermal stresses in an orthographic rectangular plate with four edges of distinct thermal boundary condition of the third kind which exactly satisfy the traction-free conditions of shear stress over all boundaries including four corners of the plate, and to consider the effects of the anisotropies of material properties and the convective heat transfer on the upper and lower surfaces on the thermal stress distribution. (orig.)

Self-Generated Magnetic Fields in Stagnation-Phase ICF Implosions

Science.gov (United States)

Walsh, Christopher; Chittenden, Jeremy; McGlinchey, Kristopher; Niasse, Nicolas

2016-10-01

3-D extended-MHD simulations of the stagnation phase of an ICF implosion are presented, showing significant self-generated magnetic fields (1000-5000T) due to the Biermann Battery effect. Perturbed hot-spots generate magnetic fields at their edges, as the extremities of hot bubbles are rapidly cooled by the surrounding low temperature fuel, giving non-parallel electron pressure and density gradients. Larger amplitude and higher mode-number perturbations lead to an increased hot-spot surface area and more heat flow, developing greater non-parallel gradients and therefore larger magnetic fields. Due to this, largely perturbed hot-spots can be affected more by magnetic fields, although the accelerated cooling associated with greater deviations from symmetry lowers magnetisation. The Nernst effect advects magnetic field down temperature gradients towards the outer region of the hot-spot, which can also lower the magnetisation of the plasma. In some regions, however, the Nernst velocity is convergent, magnetising the tips of cold fuel spikes, resulting in anisotropic heat-flow and an improvement in energy containment. Low-mode and multi-high-mode simulations are shown, with magnetisations reaching sufficiently high levels in some regions of the hot-spot to suppress thermal conduction to lower than 50% of the unmagnetised case. A quantitative analysis of how this affects the hot-spot energy balance is included.

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)

Ion Transport and Precipitation Kinetics as Key Aspects of Stress Generation on Pore Walls Induced by Salt Crystallization

Science.gov (United States)

Naillon, A.; Joseph, P.; Prat, M.

2018-01-01

The stress generation on pore walls due to the growth of a sodium chloride crystal in a confined aqueous solution is studied from evaporation experiments in microfluidic channels in conjunction with numerical computations of crystal growth. The study indicates that the stress buildup on the pore walls is a highly transient process taking place over a very short period of time (in less than 1 s in our experiments). The analysis makes clear that what matters for the stress generation is not the maximum supersaturation at the onset of the crystal growth but the supersaturation at the interface between the solution and the crystal when the latter is about to be confined between the pore walls. The stress generation is summarized in a simple stress diagram involving the pore aspect ratio and the Damkhöler number characterizing the competition between the precipitation reaction kinetics and the ion transport towards the growing crystal. This opens up the route for a better understanding of the damage of porous materials induced by salt crystallization, an important issue in Earth sciences, reservoir engineering, and civil engineering.

h-Adaptive Mesh Generation using Electric Field Intensity Value as a Criterion (in Japanese)

OpenAIRE

Toyonaga, Kiyomi; Cingoski, Vlatko; Kaneda, Kazufumi; Yamashita, Hideo

1994-01-01

Finite mesh divisions are essential to obtain accurate solution of two dimensional electric field analysis. It requires the technical knowledge to generate a suitable fine mesh divisions. In electric field problem, analysts are usually interested in the electric field intensity and its distribution. In order to obtain electric field intensity with high-accuracy, we have developed and adaptive mesh generator using electric field intensity value as a criterion.

Calculations of self-generated magnetic fields in parylene disc experiments

International Nuclear Information System (INIS)

Dahlbacka, G.H.; Mead, W.C.; Max, C.E.; Thomson, J.J.

1975-01-01

Experiments have been planned at Livermore to measure self-generated magnetic fields using the Faraday Rotation of frequency quadrupled 1.1 μm laser light. The LASNEX code was used during the planning of these experiments and has provided valuable information in establishing the conditions under which the thermoelectric fields expected can be measured. Suspected thermoelectric fields have been inferred from experiments that have been carried out at NRL

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.)

Piezoelectric components wirelessly driven by dipole antenna-like electric field generator

Energy Technology Data Exchange (ETDEWEB)

Bhuyan, S., E-mail: elesatya@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Kumar, R.; Panda, S.K. [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Hu, J. [Lab of Precision Drive, Nanjing University of Aeronautics and Astronautics, Nanjing 210026 (China)

2011-08-25

Highlights: > Wireless energy transmission technique. > Dipole antenna-like electric field generator. > Piezoelecctric resonance. > Finite element analyses. > Simulations and experimental verifications. - Abstract: A new technique of transmitting electric energy wirelessly to piezoelectric components by using a dipole antenna-like electric field generator is explored. Two square size brass plate-shaped live and ground electrodes are used to form a dipole antenna-like electric field generator. When the dipole antenna-like electric field generator in electric resonance with an inductor, a maximum output power of 2.72 mW and an energy conversion efficiency of 0.0174% have been achieved wirelessly by the piezoelectric plate area of 40 mm{sup 2} operating in the thickness vibration mode, placed at the center 4 mm away from the antenna plane with an optimum electrical load of 1365 {Omega}, resonant frequency of 782 kHz, 1 cm electrodes separation, 2500 cm{sup 2} electrode area of dipole antenna-like structure, and input ac source power of 15.58 W applied to the series of dipole antenna-like structure and inductor. The theoretically calculated results have been validated by the experimental studies. It is seen that at the resonance frequency and optimum electrical load, the output power of the wirelessly driven piezoelectric component decreases with the size of piezoelectric component, distance of piezoelectric component from the electrode of antenna plane, but increases with the antenna electrode area.

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.

Effects of stress conditions on the generation of negative bias temperature instability-associated interface traps

International Nuclear Information System (INIS)

Zhang Yue; Pu Shi; Lei Xiao-Yi; Chen Qing; Ma Xiao-Hua; Hao Yue

2013-01-01

The exponent n of the generation of an interface trap (N it ), which contributes to the power-law negative bias temperature instability (NBTI) degradation, and the exponent's time evolution are investigated by simulations with varying the stress voltage V g and temperature T. It is found that the exponent n in the diffusion-limited phase of the degradation process is irrelevant to both V g and T. The time evolution of the exponent n is affected by the stress conditions, which is reflected in the shift of the onset of the diffusion-limited phase. According to the diffusion profiles, the generation of the atomic hydrogen species, which is equal to the buildup of N it , is strongly correlated with the stress conditions, whereas the diffusion of the hydrogen species shows V g -unaffected but T-affected relations through the normalized results

Fracture mechanics analysis of the steam generator tube after shot peening

International Nuclear Information System (INIS)

Shin, Kyu In; Jhung, Myung Jo; Choi, Young Hwan; Park, Jai Hak

2003-01-01

One of the main degradation of steam generator tubes is stress corrosion cracking induced by residual stress. The resulting damages can cause tube bursting or leakage of the primary water which contained radioactivity. Primary water stress corrosion crack occurs at the location of tube/tubesheet hard rolled transition zone. In order to investigate the effect of shot peening on stress corrosion cracking, stress intensity factors are calculated for the crack which is located in the induced residual stress field

Mitigation of caustic stress corrosion cracking of steam generator tube materials by blowdown -a case study

International Nuclear Information System (INIS)

Dutta, Anu; Patwegar, I.A.; Chaki, S.K.; Venkat Raj, V.

2000-01-01

The vertical U-tube steam generators are among the most important equipment in nuclear power plants as they form the vital link between the reactor and the turbogenerator. Over ∼ 35 years of operating experience of water cooled reactor has demonstrated that steam generator tubes are susceptible to various forms of degradation. This degradation leads to failure and outages of the power plant. A majority of these failures have been attributed to concentrated alkali attacks in the low flow areas such as crevices in the tube to tube sheet joints, baffle plate location and the areas of sludge deposits. Free hydroxides can be produced by improper maintenance of phosphate chemical control in the secondary side of the steam generators and also by the thermal decomposition of impurities present in the condenser cooling water which may leak into the feed water through the condenser tubes. The free hydroxides concentrate in the low flow areas. This buildup of free hydroxide in combination with residual stress leads to caustic stress corrosion cracking. In order to mitigate caustic stress corrosion cracking of Inconel 600 tubes, the trend is to avoid phosphate dosing. Instead All Volatile Treatment (AVT) for secondary water is used backed by full flow condensate polishing. Sodium hydroxide concentration is now being considered as the basis for steam generator blowdown. A methodology has been established for determining the blowdown requirement in order to mitigate caustic stress corrosion cracking in the secondary side of the vertical U-tube natural circulation steam generator. A case study has been carried out for zero solid treatment (AVT coupled with full flow condensate polishing plant) water chemistry. Only continuous blowdown schemes have been studied based on maximum caustic concentration permissible in the secondary side of the steam generator. The methodology established can also be used for deciding concentration of any other impurities

A nonlinear magnetoelectric model for magnetoelectric layered composite with coupling stress

International Nuclear Information System (INIS)

Shi, Yang; Gao, Yuanwen

2014-01-01

Based on a linear piezoelectric relation and a nonlinear magnetostrictive constitutive relation, A nonlinear magnetoelectric (ME) effect model for flexural layered ME composites is established in in-plane magnetic field. In the proposed model, the true coupling stress and the equivalent piezomagnetic coefficient are taken into account and obtained through an iterative approach. Some calculations on nonlinear ME coefficient are conducted and discussed. Our results show that for both the flexural bilayer and trilayer composites, the true coupling stress in the composites first increase and then approach to a constant value with the increase of applied magnetic fields, affecting the nonlinear ME effect significantly. With consideration of the true coupling stress, the ME effect is smaller than that without consideration of the true coupling stress. Moreover, the proposed theoretical model predicts that the ME coefficient of the trilayer composite (does not generate the bending deflection) is much larger than that of bilayer composite (generates the bending deflection), which is in well agreement with the previous works. The influences of the applied magnetic field on the true coupling stress and fraction ratio corresponding to the extreme ME coefficients of layered structures are also investigated. - Highlights: • This paper develops a nonlinear model for layered ME composite. • The true coupling stress is obtained through an iterative approach. • The influences of coupling stress and flexural deformation are discussed. • The dependence of ME coefficient on magnetic field is studied

Methods of high current magnetic field generator for transcranial magnetic stimulation application

Science.gov (United States)

Bouda, N. R.; Pritchard, J.; Weber, R. J.; Mina, M.

2015-05-01

This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/-20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG1) and MOSFET circuits (HCMFG2) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

Mixed convection flow of couple stress nanofluid over oscillatory stretching sheet with heat absorption/generation effects

Directory of Open Access Journals (Sweden)

Sami Ullah Khan

2018-03-01

Full Text Available The aim of this article is to highlight the unsteady mixed convective couple stress nanoliquid flow passed through stretching surface. The flow is generated due to periodic oscillations of sheet. An appropriate set of dimensionless variables are used to reduce the independent variables in governing equations arising from mathematical modeling. An analytical solution has been computed by employing the technique of homotopy method. The outcomes of various sundry parameters like couple stress parameter, the ratio of angular velocity to stretching rate, thermophoresis parameter, Hartmann number, Prandtl number, heat source/sink parameter, Schmidt number described graphically and in tabular form. It is observed that the velocity profile increases by increasing mixed convection parameter and concentration buoyancy parameter. The temperature enhances for larger values of Hartmann number and Brownian. The concentration profile increases by increasing thermophoresis parameter. Results show that wall shear stress increases by increasing couple stress parameter and ratio of oscillating frequency to stretching rate. Keywords: Oscillatory surface, Couple stress fluid, Nanoparticles, Heat absorption/generation

Motionally-induced electromagnetic fields generated by idealized ocean currents

Science.gov (United States)

Tyler, R. H.; Mysak, L. A.

Using the induction equation, we investigate the generation of electromagnetic fields by the motional electromagnetic induction due to ocean currents. In this paper, solutions are presented for a linear induction equation for the magnetic flux density vector which contains prescribed time-independent ocean current and conductivity fields. Once the magnetic flux density is known, the electric field and electric current density are easily obtained by differentiation. Solutions are given for several examples of idealized flow which include: 1) Vertically and horizontally sheared plane-parallel flow with depth-dependent conductivity; 2) A simple Stommel circulation gyre; and 3) Symmetric gyres. The results indicate that typical ocean current features induce magnetic fields with magnitudes reaching 100's of nT within the water and about 1-10 outside of the water. For the case of a field of gyres, the ocean-induced magnetic fields decay away from the ocean on spatial scales set by the horizontal scale of the ocean feature. At the altitudes of magnetic field satellite surveys, ocean-induced magnetic fields may retain values of a few nT, which are strong enough to be detected. Thus it is concluded that satellite observations of the earth's main magnetic field and, in particular, the observed temporal variations, could be affected by the ocean circulation. Summary and discussion In Section 3, we found exact solutions to the induction equation for idealized flows. The results gave magnitudes of about tens to hundreds of nT for the magnetic fields bH, about 10-5 V/m for the electric fields E, and about 10-5 A/m2 for the electric current density J induced by the ocean currents. These figures are in general agreement with the calculations of Lilley et al. (1993). In Section 4.2 we obtained solutions for the magnetic field above the ocean surface for the case of a Stommel gyre and a field of symmetric gyres. It was found in the last case that ocean gyres with a total transport

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

Applications of field portable computers to NDE of nuclear power plant steam turbine/generator rotors, discs, and retaining rings

International Nuclear Information System (INIS)

Reinhart, E.R.; Leon-Salamanca, T.

2004-01-01

The new generation of compact, powerful portable computers have been incorporated into a number of nondestructive evaluation (NDE) systems used to inspect critical areas of the steam turbine and generator units of nuclear power plants. Due to the complex geometry of turbine rotors, generator rotors, retaining rings, and shrunk-on turbine discs, the computers are needed to rapidly calculate the optimum position of an ultrasonic transducer or eddy current probe in order to detect defects at several critical areas. Examples where computers have been used to overcome problems in nondestructive evaluation include; analysis of large numbers of closely spaced near-bore ultrasonic reflectors to determine their potential for link-up in turbine and generator rotor bores, distinguishing ultrasonic crack signals from other reflectors such as the shrink-fit form reflector detected during ultrasonic scanning of shrunk-on generator retaining rings, and detection and recording of eddy current and ultrasonic signals from defects that could be missed by data acquisition systems with inadequate response. The computers are also used to control scanners to insure total inspection coverage. To facilitate the use of data from detected discontinuities in conjunction with stress and fracture mechanics analysis programs, the computers provide presentations of flaws in color and in three dimensions. The field computers have been instrumental in allowing the inspectors to develop on-site reports that enable the owner/operator to rapidly make run/repair/replace decisions. Examples of recent experiences using field portable computers in NDE systems will be presented along with anticipated future developments. (author)

The effect of restraints type on the generated stresses in gantry crane beam

Directory of Open Access Journals (Sweden)

Sowa Leszek

2018-01-01

Full Text Available This paper includes an analysis of the mechanical phenomena in the gantry crane beam, because the cranes are currently one of the most common devices for the transporting loads. Designing modern mechanical structures is a complex task that requires the use of appropriate tools. Such a modern tool is the numerical simulation, which uses different numerical methods. One of the best known methods is the finite element method, also used here. Simulations are limited to analysis of the strength of the gantry crane beam that was the loaded of the force load movement along its length. The numerical analysis was made to the gantry crane beam which cross-section was an I-beam and ends were fixed in different ways. As the result of numerical calculations, the stresses and displacements of the structure of gantry were obtained. The influence of the restraints type and changing the loading force position on generate the Huber-Misses stress in the gantry crane beam was estimated. The aim was to ensure that the maximum equivalent stress generated in the gantry crane beam was less than the strength of material, because then the construction is safe.

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

Ecotoxicity of bisphenol A to Caenorhabditis elegans by multigenerational exposure and variations of stress response in vivo across generations

International Nuclear Information System (INIS)

Zhou, Dong; Yang, Jie; Li, Hui; Lu, Qiang; Liu, Yong-di; Lin, Kuang-fei

2016-01-01

In order to understand how bisphenol A (BPA) exposure acts on the evolutionary dynamics of populations and changes of stress response across generations, the model animal Caenorhabditis elegans was used to conduct the multigenerational testing. Multiple endpoints at the physiological (growth, reproduction, and locomotion behaviors) and molecular (stress-related gene expressions) levels were examined by multigenerational exposure to low-concentration BPA (0.001–10 μM) across four generations. The results showed that changes of physiological-level effects across four generations varied in magnitude and direction, depending on the exposure concentrations. C. elegans individuals in the first generation grew smaller, moved slower, and produced less offsprings than the controls by BPA exposure. As for each trait tested, the first generation response could be commonly mirrored in the subsequent generations at the highest concentration of 10 μM. However, at lower concentrations, response of parental generation was a relatively poor predictor of the effects on progeny, as acclimation or cumulative damage could occur in the subsequent generations. The integrated gene expression profiles visually illustrated that the tested gene expressions at low concentrations (0.001–0.01 μM) were more obviously changed in both G_1 and G_4 generations, and the G_1 generation showed a much greater degree of increase in stress-related gene expressions than the G_4 generation. The multigenerational toxicity data emphasize the need of considering biological effects over multiple generations to conduct accurate assessment of environmental risks of toxicants on population dynamics. - Highlights: • Multigenerational exposure was conducted to evaluate effects of BPA on C. elegans. • Changes of biological effects varied in magnitude and direction across generations. • A more significant induction in stress-related gene expressions was found in G_1. • Multigenerational tests have

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.

X-ray evaluation of residual stress distributions within surface machined layer generated by surface machining and sequential welding

International Nuclear Information System (INIS)

Taniguchi, Yuu; Okano, Shigetaka; Mochizuki, Masahito

2017-01-01

The excessive tensile residual stress generated by welding after surface machining may be an important factor to cause stress corrosion cracking (SCC) in nuclear power plants. Therefore we need to understand and control the residual stress distribution appropriately. In this study, residual stress distributions within surface machined layer generated by surface machining and sequential welding were evaluated by X-ray diffraction method. Depth directional distributions were also investigated by electrolytic polishing. In addition, to consider the effect of work hardened layer on the residual stress distributions, we also measured full width at half maximum (FWHM) obtained from X-ray diffraction. Testing material was a low-carbon austenitic stainless steel type SUS316L. Test specimens were prepared by surface machining with different cutting conditions. Then, bead-on-plate welding under the same welding condition was carried out on the test specimens with different surface machined layer. As a result, the tensile residual stress generated by surface machining increased with increasing cutting speed and showed nearly uniform distributions on the surface. Furthermore, the tensile residual stress drastically decreased with increasing measurement depth within surface machined layer. Then, the residual stress approached 0 MPa after the compressive value showed. FWHM also decreased drastically with increasing measurement depth and almost constant value from a certain depth, which was almost equal regardless of the machining condition, within surface machined layer in all specimens. After welding, the transverse distribution of the longitudinal residual stress varied in the area apart from the weld center according to machining conditions and had a maximum value in heat affected zone. The magnitude of the maximum residual stress was almost equal regardless of the machining condition and decreased with increasing measurement depth within surface machined layer. Finally, the

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.

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.)

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.

Methods of high current magnetic field generator for transcranial magnetic stimulation application

International Nuclear Information System (INIS)

Bouda, N. R.; Pritchard, J.; Weber, R. J.; Mina, M.

2015-01-01

This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG 1 ) and MOSFET circuits (HCMFG 2 ) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed

Methods of high current magnetic field generator for transcranial magnetic stimulation application

Energy Technology Data Exchange (ETDEWEB)

Bouda, N. R., E-mail: nybouda@iastate.edu; Pritchard, J.; Weber, R. J.; Mina, M. [Department of Electrical and Computer engineering, Iowa State University, Ames, Iowa 50011 (United States)

2015-05-07

This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG{sub 1}) and MOSFET circuits (HCMFG{sub 2}) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

N-particle effective generators of the Poincare group derived from a field theory

International Nuclear Information System (INIS)

Krueger, A.; Gloeckle, W.

1999-01-01

In quantum mechanics the principle of relativity is guaranteed by unitary operators being associated with inhomogeneous Lorentz transformations ensuring that quantum mechanical expectation values remain unchanged. In field theory the ten generators of inhomogeneous Lorentz transformations can be derived from a scalar Lagrangian density describing the physical system of interest. They obey the well known Poincare Lie algebra. For interacting systems some of the generators become operators allowing for particle production or annihilation so that the generators act on the full Fock space. However, given a field theory on the whole Fock space we prove that it is possible to construct generators acting on a subspace with a finite number of particles by one and the same unitary transformation of all generators leaving the Poincare algebra valid. In this manner it is in principle possible to derive a relativistically invariant theory of interacting particles on a Hilbert space with a finite number of particles from a field theoretical Lagrangian. Refs. 3 (author)

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

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

Artifacts Generated During Azoalkane Peroxy Radical Oxidative Stress Testing of Pharmaceuticals Containing Primary and Secondary Amines.

Science.gov (United States)

Nefliu, Marcela; Zelesky, Todd; Jansen, Patrick; Sluggett, Gregory W; Foti, Christopher; Baertschi, Steven W; Harmon, Paul A

2015-12-01

We report artifactual degradation of pharmaceutical compounds containing primary and secondary amines during peroxy radical-mediated oxidative stress carried out using azoalkane initiators. Two degradation products were detected when model drug compounds dissolved in methanol/water were heated to 40°C with radical initiators such as 2,2'-azobis(2-methylpropionitrile) (AIBN). The primary artifact was identified as an α-aminonitrile generated from the reaction of the amine group of the model drug with formaldehyde and hydrogen cyanide, generated as byproducts of the stress reaction. A minor artifact was generated from the reaction between the amine group and isocyanic acid, also a byproduct of the stress reaction. We report the effects of pH, initiator/drug molar ratio, and type of azoalkane initiator on the formation of these artifacts. Mass spectrometry and nuclear magnetic resonance were used for structure elucidation, whereas mechanistic studies, including stable isotope labeling experiments, cyanide analysis, and experiments exploring the effects of butylated hydroxyanisole addition, were employed to support the degradation pathways. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Quantum field theory near surfaces of discontinuity

International Nuclear Information System (INIS)

Onishi, H.T.

1981-01-01

This work deals with the problem of a quantized scalar field propagating near a surface of discontinuity. The proper time formalism is employed to express the Green's function and stress tensor as proper time integrals of a transformation function. The transformation function is calculated by a WKB approximation which exhibits the essential singularities generated by the high frequency behavior of waves propagating near the surface. Two singularities are present, the usual direct singularity and an additional reflected singularity generated by the high frequency behavior of waves reflected by the discontinuity. The stress tensor is calculated by dimensional continuation. The results are employed to analyze energy generated by the surface

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.

Scalable cavity-QED-based scheme of generating entanglement of atoms and of cavity fields

OpenAIRE

Lee, Jaehak; Park, Jiyong; Lee, Sang Min; Lee, Hai-Woong; Khosa, Ashfaq H.

2008-01-01

We propose a cavity-QED-based scheme of generating entanglement between atoms. The scheme is scalable to an arbitrary number of atoms, and can be used to generate a variety of multipartite entangled states such as the Greenberger-Horne-Zeilinger, W, and cluster states. Furthermore, with a role switching of atoms with photons, the scheme can be used to generate entanglement between cavity fields. We also introduce a scheme that can generate an arbitrary multipartite field graph state.

A Discrete Fracture Network Model with Stress-Driven Nucleation and Growth

Science.gov (United States)

Lavoine, E.; Darcel, C.; Munier, R.; Davy, P.

2017-12-01

The realism of Discrete Fracture Network (DFN) models, beyond the bulk statistical properties, relies on the spatial organization of fractures, which is not issued by purely stochastic DFN models. The realism can be improved by injecting prior information in DFN from a better knowledge of the geological fracturing processes. We first develop a model using simple kinematic rules for mimicking the growth of fractures from nucleation to arrest, in order to evaluate the consequences of the DFN structure on the network connectivity and flow properties. The model generates fracture networks with power-law scaling distributions and a percentage of T-intersections that are consistent with field observations. Nevertheless, a larger complexity relying on the spatial variability of natural fractures positions cannot be explained by the random nucleation process. We propose to introduce a stress-driven nucleation in the timewise process of this kinematic model to study the correlations between nucleation, growth and existing fracture patterns. The method uses the stress field generated by existing fractures and remote stress as an input for a Monte-Carlo sampling of nuclei centers at each time step. Networks so generated are found to have correlations over a large range of scales, with a correlation dimension that varies with time and with the function that relates the nucleation probability to stress. A sensibility analysis of input parameters has been performed in 3D to quantify the influence of fractures and remote stress field orientations.

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.

Single attosecond pulse generation in an orthogonally polarized two-color laser field combined with a static electric field

International Nuclear Information System (INIS)

Xia Changlong; Zhang Gangtai; Wu Jie; Liu Xueshen

2010-01-01

We investigate theoretic high-order harmonic generation and single attosecond pulse generation in an orthogonally polarized two-color laser field, which is synthesized by a mid-infrared (IR) pulse (12.5 fs, 2000 nm) in the y component and a much weaker (12 fs, 800 nm) pulse in the x component. We find that the width of the harmonic plateau can be extended when a static electric field is added in the y component. We also investigate emission time of harmonics in terms of a time-frequency analysis to illustrate the physical mechanism of high-order harmonic generation. We calculate the ionization rate using the Ammosov-Delone-Krainov model and interpret the variation of harmonic intensity for different static electric field strengths. When the ratio of strengths of the static and the y-component laser fields is 0.1, a continuous harmonic spectrum is formed from 220 to 420 eV. By superposing a properly selected range of the harmonic spectrum from 300 to 350 eV, an isolated attosecond pulse with a duration of about 75 as is obtained, which is near linearly polarized.

Electromagnetic Fields Associated with Commercial Solar Photovoltaic Electric Power Generating Facilities.

Science.gov (United States)

Tell, R A; Hooper, H C; Sias, G G; Mezei, G; Hung, P; Kavet, R

2015-01-01

The southwest region of the United States is expected to experience an expansion of commercial solar photovoltaic generation facilities over the next 25 years. A solar facility converts direct current generated by the solar panels to three-phase 60-Hz power that is fed to the grid. This conversion involves sequential processing of the direct current through an inverter that produces low-voltage three-phase power, which is stepped up to distribution voltage (∼12 kV) through a transformer. This study characterized magnetic and electric fields between the frequencies of 0 Hz and 3 GHz at two facilities operated by the Southern California Edison Company in Porterville, CA and San Bernardino, CA. Static magnetic fields were very small compared to exposure limits established by IEEE and ICNIRP. The highest 60-Hz magnetic fields were measured adjacent to transformers and inverters, and radiofrequency fields from 5-100 kHz were associated with the inverters. The fields measured complied in every case with IEEE controlled and ICNIRP occupational exposure limits. In all cases, electric fields were negligible compared to IEEE and ICNIRP limits across the spectrum measured and when compared to the FCC limits (≥0.3 MHz).

Automatically generating Feynman rules for improved lattice field theories

International Nuclear Information System (INIS)

Hart, A.; Hippel, G.M. von; Horgan, R.R.; Storoni, L.C.

2005-01-01

Deriving the Feynman rules for lattice perturbation theory from actions and operators is complicated, especially when improvement terms are present. This physically important task is, however, suitable for automation. We describe a flexible algorithm for generating Feynman rules for a wide range of lattice field theories including gluons, relativistic fermions and heavy quarks. We also present an efficient implementation of this in a freely available, multi-platform programming language (PYTHON), optimised to deal with a wide class of lattice field theories

Generation of magnetic fields for accelerators with permanent magnets

International Nuclear Information System (INIS)

Meinander, T.

1994-01-01

Commercially available permanent magnet materials and their properties are reviewed. Advantages and disadvantages of using permanent magnets as compared to electromagnets for the generation of specific magnetic fields are discussed. Basic permanent magnet configurations in multipole magnets and insertion devices are presented. (orig.)

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)

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....

SSWL and BWL: finite element models of compressed magnetic field current generators

Energy Technology Data Exchange (ETDEWEB)

Tucker, T.J.; Leeman, J.E.

1976-01-01

Documentation is presented for two new computer codes modeling the behavior of compressed magnetic field current generators. Code output results for the typical generator configurations are presented and compared to experimental results. (auth)

Investigating the degradation behavior under hot carrier stress for InGaZnO TFTs with symmetric and asymmetric structures

International Nuclear Information System (INIS)

Tsai, Ming-Yen; Chang, Ting-Chang; Chu, Ann-Kuo; Chen, Te-Chih; Hsieh, Tien-Yu; Chen, Yu-Te; Tsai, Wu-Wei; Chiang, Wen-Jen; Yan, Jing-Yi

2013-01-01

This letter studies the hot-carrier effect in indium–gallium–zinc oxide (IGZO) thin film transistors with symmetric and asymmetric source/drain structures. The different degradation behaviors after hot-carrier stress in symmetric and asymmetric source/drain devices indicate that different mechanisms dominate the degradation. Since the C–V measurement is highly sensitive to trap states compared to the I–V characterization, C–V curves are utilized to analyze the hot-carrier stress-induced trap state generation. Furthermore, the asymmetric C–V measurements C GD (gate-to-drain capacitance) and C GS (gate-to-source capacitance) are used to analyze the trap state in channel location. The asymmetric source/drain structure under hot-carrier stress induces an asymmetric electrical field and causes different degradation behaviors. In this work, the on-current and subthreshold swing (S.S.) degrade under low electrical field, whereas an apparent V t shift occurs under large electrical field. The different degradation behaviors indicate that trap states are generated under a low electrical field and the channel-hot-electron (CHE) effect occurs under a large electrical field. - Highlights: ► Asymmetric structure thin film transistors improve kick-back effect. ► Asymmetric structures under hot-carrier stress induce different degradation. ► Hot-carrier stress leads to capacitance–voltage curve distortion. ► Extra trap states are generated during hot-carrier stress

Inverse method for stress monitoring in pressure components of steam generators

International Nuclear Information System (INIS)

Duda, P.

2003-01-01

The purpose of this work is to formulate a space marching method, which can be used to solve inverse multidimensional heat conduction problems. The method is designed to reconstruct the transient temperature distribution in a whole construction element based on measured temperatures taken at selected points inside or on the outer surface of the construction element. Next, the Finite Element Method is used to calculate thermal stresses and stresses caused by other loads such as, for instance, internal pressure. The developed method for solving temperature and total stress distribution will be tested using the measured temperatures generated from a direct solution. Transient temperature and total stress distribution obtained from method presented below will be compared with the values obtained from the direct solution. Finally, the presented method will be applied in order to monitor temperature and stress distribution in an outlet header using the real measured temperature values at seven points on the header's outer surface during the power boiler's shut down operation. The presented method allows to optimize the power block's start-up and shut-down operations, contributes to the reduction of heat loss during these operations and to the extension of power block's life. The fatigue and creep usage factor can be computed in an on-line mode. The presented method herein can be applied to monitoring systems that work in conventional as well as in nuclear power plants. (author)

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...

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.

Ensuring Structural Integrity through Reliable Residual Stress Measurement: From Crystals to Crankshafts

International Nuclear Information System (INIS)

Edwards, Lyndon

2005-01-01

Full text: The determination of accurate, reliable stresses is critical to many fields of engineering and, in particular, the structural integrity and hence, safety, of many systems. Neutron stress measurement is a non-destructive technique that uniquely provides insights into stress fields deep within components and structures. As such, it has become an increasingly important tool within the engineering community leading to improved manufacturing processes to reduce stress and distortion as well as to the definition of more precise structural integrity lifting procedures. This talk describes the current state of the art and identifies the key opportunities for improved structural integrity provided by the 2nd generation dedicated engineering stress diffractometers currently being designed and commissioned world-wide. Examples are provided covering a range of industrially relevant problems from the fields. (author)

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

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.

Residual stresses associated with the hydraulic expansion of steam generator tubing into tubesheets

International Nuclear Information System (INIS)

Middlebrooks, W.B.; Harrod, D.L.; Gold, R.E.

1991-01-01

Westinghouse has used three different processes for the full depth expansion of tubes into the tube sheets of recirculating nuclear steam generators: mechanical rolling, explosive expansion and hydraulic expansion. Each process aims at expanding tubes tightly to tube sheets, leaving the smallest possible secondary side crevice depth, and minimizing the residual stress in the expanded tubes, all for the purpose of mitigating the effect of corrosion phenomena. The hydraulic expansion process was qualified and has been implemented since 1978, and more than 1.1 million tube ends have been hydraulically expanded into production units. In this paper, the results of the recent analytical studies related to the residual stress in the expanded tubes are summarized. The method of hydraulic expansion is explained, and some important parameters are given. Finite element method, theoretical incremental analysis, tube sheet yielding and residual stress, contact pressure, sensitivity analysis and temperature effect in the central region of tube sheets, and the residual stress in the transition zone are described. (K.I.)

Generation of a strong attosecond pulse train with an orthogonally polarized two-color laser field

International Nuclear Information System (INIS)

Kim, Chul Min; Kim, I Jong; Nam, Chang Hee

2005-01-01

We theoretically investigate the high-order harmonic generation from a neon atom irradiated by an intense two-color femtosecond laser pulse, in which the fundamental field and its second harmonic are linearly polarized and orthogonal to each other. In contrast to usual high-harmonic generation with linearly polarized fundamental field alone, a very strong and clean high-harmonic spectrum, consisting of both odd and even orders of harmonics, can be generated in the orthogonally polarized two-color laser field with proper selection of the relative phase between the fundamental and second-harmonic fields. In time domain, this results in a strong and regular attosecond pulse train. The origin of these behaviors is elucidated by analyzing semiclassical electron paths and by simulating high-harmonic generation quantum mechanically

The role and effect of residual stress on pore generation during anodization of aluminium thin films

International Nuclear Information System (INIS)

Liao, M.W.; Chung, C.K.

2013-01-01

Highlights: •Al films of varying residual stress were prepared by sputtering. •Variation of the residual stress in the Al films influences pore growth during anodization. •The change in average pore size with residual stress is fairly small. •Interaction of residual stress with oxide growth stress leads to change in structure. •Residual tensile stress increases the pore density of porous alumina. -- Abstract: The role and effect of residual stress on pore generation of anodized aluminium oxide (AAO) have been investigated into anodizing the various-residual-stresses aluminium films. The plane stresses were characterised by X-ray diffraction with sin 2 ψ method. The pore density roughly linearly increased with residual stress from 64.6 (−132.5 MPa) to 90.5 pores/μm 2 (135.9 MPa). However, the average pore size around 40 nm was not changed significantly except for the rougher film. The tensile residual stress lessened the compressive oxide growth stress to reduce AAO plastic deformation for higher pore density. The findings provide new foundations for realizing AAO films on silicon

Dynamics of self-generated magnetic fields in stagnation phase and their effects on hot spark formation

International Nuclear Information System (INIS)

Hata, Akiro; Mima, Kunioki; Nagatomo, Hideo; Sunahara, Atsushi; Nishiguchi, Akio

2006-01-01

The generalized temporal evolution equation of a magnetic field is derived for high density laser-fusion plasmas. Magnetic field generation and convection are simulated by using the 2D hydrodynamic code together with the magnetic field equation. It is found that magnetic fields are generated and compressed in association with the Rayleigh-Taylor instability of an imploding shell. In particular, the magnetic field convection by the Nernst effect is found to play an important role in the amplification of magnetic fields. The maximum magnetic field reaches 30 MG at maximum compression. This magnetic field may reduce the electron heat conduction around the hot spark. Therefore, it is concluded that the ignition condition for non-uniform implosion is influenced by self-generated magnetic fields. (author)

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

Magnetic Field Generation and Electron Acceleration in Relativistic Laser Channel

International Nuclear Information System (INIS)

Kostyukov, I.Yu.; Shvets, G.; Fisch, N.J.; Rax, J.M.

2001-01-01

The interaction between energetic electrons and a circularly polarized laser pulse inside an ion channel is studied. Laser radiation can be resonantly absorbed by electrons executing betatron oscillations in the ion channel and absorbing angular momentum from the laser. The absorbed angular momentum manifests itself as a strong axial magnetic field (inverse Faraday effect). The magnitude of this magnetic field is calculated and related to the amount of the absorbed energy. Absorbed energy and generated magnetic field are estimated for the small and large energy gain regimes. Qualitative comparisons with recent experiments are also made

Estimation of the supplementary axial wall stress generated at peak flow by an arterial stenosis

International Nuclear Information System (INIS)

Doriot, Pierre-Andre

2003-01-01

Mechanical stresses in arterial walls are known to be implicated in the development of atherosclerosis. While shear stress and circumferential stress have received a lot of attention, axial stress has not. Yet, stenoses can be intuitively expected to produce a supplementary axial stress during flow systole in the region immediately proximal to the constriction cone. In this paper, a model for the estimation of this effect is presented, and ten numerical examples are computed. These examples show that the cyclic increase in axial stress can be quite considerable in severe stenoses (typically 120% or more of the normal stress value). This result is in best agreement with the known mechanical or morphological risk factors of stenosis progression and restenosis (hypertension, elevated pulse pressure, degree of stenosis, stenosis geometry, residual stenosis, etc). The supplementary axial stress generated by a stenosis might create the damages in the endothelium and in the elastic membranes which potentiate the action of the other risk factors (hyperlipidaemia, diabetes, etc). It could thus be an important cause of stenosis progression and of restenosis

Estimation of the supplementary axial wall stress generated at peak flow by an arterial stenosis

Science.gov (United States)

Doriot, Pierre-André

2003-01-01

Mechanical stresses in arterial walls are known to be implicated in the development of atherosclerosis. While shear stress and circumferential stress have received a lot of attention, axial stress has not. Yet, stenoses can be intuitively expected to produce a supplementary axial stress during flow systole in the region immediately proximal to the constriction cone. In this paper, a model for the estimation of this effect is presented, and ten numerical examples are computed. These examples show that the cyclic increase in axial stress can be quite considerable in severe stenoses (typically 120% or more of the normal stress value). This result is in best agreement with the known mechanical or morphological risk factors of stenosis progression and restenosis (hypertension, elevated pulse pressure, degree of stenosis, stenosis geometry, residual stenosis, etc). The supplementary axial stress generated by a stenosis might create the damages in the endothelium and in the elastic membranes which potentiate the action of the other risk factors (hyperlipidaemia, diabetes, etc). It could thus be an important cause of stenosis progression and of restenosis.

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)

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.

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

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

Stress relief treatment of Alloy 600 steam generator tubing

International Nuclear Information System (INIS)

Rooyen, D. van; Cragnolino, C.

1994-01-01

The intergranular stress corrosion cracking (IGSCC) of Alloy 600 tubing in the primary side of operating steam generators is the subject of this investigation. The objective of the program was to examine the feasibility of heat treatment to alleviate the IGSCC problem. In addition to this, tests were also performed to examine the IGSCC susceptibility of nuclear grade Alloy 600 tubing obtained from various sources. Examination of temperature-time combinations that may hold potential for improved IGSCC resistance of the transition regions of tubes expanded into tube sheet holes was done. The combinations fall in two categories. One is of short duration and relatively high temperature, where induction is the best method of heating because the treatment only lasts from some tens of seconds to a few minutes. The other is carried out in a lower temperature range and lasts for several hours. This latter combination of temperatures and times is considered for the so-called global heat treatment of entire tube sheet. To assess the effect of these treatments, reverse U-bend testing in high purity deaerated water containing an overpressure of hydrogen was employed and several heats of Alloy 600 were compared in tests at 365 degrees C, which is well above actual operating temperatures of steam generators, but provides an accelerated test procedure. Results of furnace heating in the range of 550-610 degrees C indicated improvement in IGSCC resistance, with best performance after a heat treatment at 610 degrees C for nine hours. In addition to stress relief, carbide precipitation can also occur, and their relative contributions to the improvement is discussed

Infrared signal generation from AC induction field heating of graphite foam

Science.gov (United States)

Klett, James W.; Rios, Orlando

2018-02-27

A magneto-energy apparatus includes an electromagnetic field source for generating a time-varying electromagnetic field. A graphite foam conductor is disposed within the electromagnetic field. The graphite foam when exposed to the time-varying electromagnetic field conducts an induced electric current, the electric current heating the graphite foam to produce light. An energy conversion device utilizes light energy from the heated graphite foam to perform a light energy consuming function. A device for producing light and a method of converting energy are also disclosed.

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…

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

Valley-polarized quantum transport generated by gauge fields in graphene

DEFF Research Database (Denmark)

Settnes, Mikkel; Garcia, Jose H; Roche, Stephan

2017-01-01

We report on the possibility to simultaneously generate in graphene a bulk valley-polarized dissipative transport and a quantum valley Hall effect by combining strain-induced gauge fields and real magnetic fields. Such unique phenomenon results from a ‘resonance/anti-resonance’ effect driven by t...... Kubo transport methods combined with a valley projection scheme to access valley-dependent conductivities and show that the results are robust against disorder....

Finite Element Residual Stress Analysis of Planetary Gear Tooth

Directory of Open Access Journals (Sweden)

Jungang Wang

2013-01-01

Full Text Available A method to simulate residual stress field of planetary gear is proposed. In this method, the finite element model of planetary gear is established and divided to tooth zone and profile zone, whose different temperature field is set. The gear's residual stress simulation is realized by the thermal compression stress generated by the temperature difference. Based on the simulation, the finite element model of planetary gear train is established, the dynamic meshing process is simulated, and influence of residual stress on equivalent stress of addendum, pitch circle, and dedendum of internal and external meshing planetary gear tooth profile is analyzed, according to non-linear contact theory, thermodynamic theory, and finite element theory. The results show that the equivalent stresses of planetary gear at both meshing and nonmeshing surface are significantly and differently reduced by residual stress. The study benefits fatigue cracking analysis and dynamic optimization design of planetary gear train.

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

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.

Stress corrosion cracking of the tubing materials for nuclear steam generators in an environment containing lead

International Nuclear Information System (INIS)

Kim, Kyung Mo; Kim, Uh Chul; Lee, Eun Hee; Hwang, Seong Sik

2004-01-01

Steam generator tube materials show a high susceptibility to stress corrosion cracking (SCC) in an environment containing lead species and some nuclear power plants currently have degradation problems associated with lead-induced stress corrosion cracking in a caustic solution. Effects of an applied potential on SCC is tested for middle-annealed Alloy 600 specimens since their corrosion potential can be changed when lead oxide coexists with other oxidizing species like copper oxide in the sludge. In addition, all the steam generator tubing materials used for nuclear power plants being operated and currently under construction in Korea are tested in a caustic solution with lead oxide. (author)

Electric field measurements in a near atmospheric pressure nanosecond pulse discharge with picosecond electric field induced second harmonic generation

Science.gov (United States)

Goldberg, Benjamin M.; Chng, Tat Loon; Dogariu, Arthur; Miles, Richard B.

2018-02-01

We present an optical electric field measurement method for use in high pressure plasma discharges. The method is based upon the field induced second harmonic generation technique and can be used for localized electric field measurements with sub-nanosecond resolution in any gaseous species. When an external electric field is present, a dipole is induced in the typically centrosymmetric medium, allowing for second harmonic generation with signal intensities which scale by the square of the electric field. Calibrations have been carried out in 100 Torr room air, and a minimum sensitivity of 450 V/cm is demonstrated. Measurements were performed with nanosecond or faster temporal resolution in a 100 Torr room air environment both with and without a plasma present. It was shown that with no plasma present, the field follows the applied voltage to gap ratio, as measured using the back current shunt method. When the electric field is strong enough to exceed the breakdown threshold, the measured field was shown to exceed the anticipated voltage to gap ratio which is taken as an indication of the ionization wave front as it sweeps through the plasma volume.

Role of particle masses in the magnetic field generation driven by the parity violating interaction

Energy Technology Data Exchange (ETDEWEB)

Dvornikov, Maxim, E-mail: maxdvo@izmiran.ru [Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation (IZMIRAN), 142190 Troitsk, Moscow (Russian Federation); Physics Faculty, National Research Tomsk State University, 36 Lenin Avenue, 634050 Tomsk (Russian Federation); II. Institute for Theoretical Physics, University of Hamburg, 149 Luruper Chaussee, D-22761 Hamburg (Germany)

2016-09-10

Recently the new model for the generation of strong large scale magnetic fields in neutron stars, driven by the parity violating interaction, was proposed. In this model, the magnetic field instability results from the modification of the chiral magnetic effect in presence of the electroweak interaction between ultrarelativistic electrons and nucleons. In the present work we study how a nonzero mass of charged particles, which are degenerate relativistic electrons and nonrelativistic protons, influences the generation of the magnetic field in frames of this approach. For this purpose we calculate the induced electric current of these charged particles, electroweakly interacting with background neutrons and an external magnetic field, exactly accounting for the particle mass. This current is calculated by two methods: using the exact solution of the Dirac equation for a charged particle in external fields and computing the polarization operator of a photon in matter composed of background neutrons. We show that the induced current is vanishing in both approaches leading to the zero contribution of massive particles to the generated magnetic field. We discuss the implication of our results for the problem of the magnetic field generation in compact stars.

Nonlinear massive spin-2 field generated by higher derivative gravity

International Nuclear Information System (INIS)

Magnano, Guido; Sokolowski, Leszek M.

2003-01-01

We present a systematic exposition of the Lagrangian field theory for the massive spin-2 field generated in higher-derivative gravity upon reduction to a second-order theory by means of the appropriate Legendre transformation. It has been noticed by various authors that this nonlinear field overcomes the well-known inconsistency of the theory for a linear massive spin-2 field interacting with Einstein's gravity. Starting from a Lagrangian quadratically depending on the Ricci tensor of the metric, we explore the two possible second-order pictures usually called '(Helmholtz-)Jordan frame' and 'Einstein frame'. In spite of their mathematical equivalence, the two frames have different structural properties: in Einstein frame, the spin-2 field is minimally coupled to gravity, while in the other frame it is necessarily coupled to the curvature, without a separate kinetic term. We prove that the theory admits a unique and linearly stable ground state solution, and that the equations of motion are consistent, showing that these results can be obtained independently in either frame (each frame therefore provides a self-contained theory). The full equations of motion and the (variational) energy-momentum tensor for the spin-2 field in Einstein frame are given, and a simple but non-trivial exact solution to these equations is found. The comparison of the energy-momentum tensors for the spin-2 field in the two frames suggests that the Einstein frame is physically more acceptable. We point out that the energy-momentum tensor generated by the Lagrangian of the linearized theory is unrelated to the corresponding tensor of the full theory. It is then argued that the ghost-like nature of the nonlinear spin-2 field, found long ago in the linear approximation, may not be so harmful to classical stability issues, as has been expected

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

Study by X-ray diffraction and mechanical analysis of the residual stress generation during thermal spraying

International Nuclear Information System (INIS)

Pina, J.; Dias, A.; Lebrun, J.L.

2003-01-01

Thermally sprayed coatings are formed by the deposition of molten or partially molten particles, propelled onto a substrate where they impact, spread and solidify rapidly. Residual stresses are expected within the sprayed deposit as a consequence of the release of thermal and kinetic energies. A wide range of materials and two spraying techniques are considered in this study, namely atmospheric plasma spraying (APS) and high-velocity oxygen fuel. Stresses were determined by the X-ray diffraction (XRD) method. The results were compared with those calculated by mechanical analysis of stress relief in coatings detached from the substrate. Comparison of the results for adherent and free-standing coatings shows that the residual stress state can be resolved in terms of the components suggested by models that propose two stages of stress generation: quenching stresses and secondary-cooling stresses. The in-depth distribution of residual stresses, through the coating thickness, is discussed in terms of the nature of the coating system

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.

Mechanisms of stress generation and relaxation during pulsed laser deposition of epitaxial Fe-Pd magnetic shape memory alloy films on MgO

International Nuclear Information System (INIS)

Edler, Tobias; Mayr, S G; Buschbeck, Joerg; Mickel, Christine; Faehler, Sebastian

2008-01-01

Mechanical stress generation during epitaxial growth of Fe-Pd thin films on MgO from pulsed laser deposition is a key parameter for the suitability in shape memory applications. By employing in situ substrate curvature measurements, we determine the stress states as a function of film thickness and composition. Depending on composition, different stress states are observed during initial film growth, which can be attributed to different misfits. Compressive stress generation by atomic peening is observed in the later stages of growth. Comparison with ex situ x-ray based strain measurements allows integral and local stress to be distinguished and yields heterogeneities of the stress state between coherent and incoherent regions. In combination with cross-sectional TEM measurements the relevant stress relaxation mechanism is identified to be stress-induced martensite formation with (111) twinning

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

Instrumentation for electromagnetic field generation in biological measurements

International Nuclear Information System (INIS)

Malaric, K.; Malaric, R.; Tkalec, M.; Lenicek, I.; Sala, A.

2005-01-01

Electromagnetic fields (EMFs) are part of everyday life in modern world. Extremely low-frequency EMFs (50 Hz) are produced by most electric home appliance, electric power transmission and distribution lines. For the last ten years mobile phones have been widely used all around the world. They operate on the EMF frequencies from 400 MHz to 1900 MHz. The effects of EMFs on living organisms have been the subject of debate and research for the last thirty years. The instrumentation for generation of EMFs have been designed at the Faculty of Electrical Engineering and Computing, Zagreb, and can be used for controlled exposure to different EMFs. To study the effect of extremely low-frequency EMF, duckweed (Lemna minor) - the model plant in biological measurement, test setup was made for magnetic field in Helmholtz coil and for electric field between two parallel circle electrodes. For the effect of mobile phones frequencies, test setup with exposition to the electromagnetic field was done with Gigahertz Transversal Electromagnetic Mode (GTEM) cell. The research confirmed that instrumentation used in these experiments is suitable for evaluation of biological effects of EMFs. The effect of different field strengths, exposure times and modulation can be tested with these instrumentation.(author)

Enabling full field physics based OPC via dynamic model generation

Science.gov (United States)

Lam, Michael; Clifford, Chris; Raghunathan, Ananthan; Fenger, Germain; Adam, Kostas

2017-03-01

As EUV lithography marches closer to reality for high volume production, its peculiar modeling challenges related to both inter- and intra- field effects has necessitated building OPC infrastructure that operates with field position dependency. Previous state of the art approaches to modeling field dependency used piecewise constant models where static input models are assigned to specific x/y-positions within the field. OPC and simulation could assign the proper static model based on simulation-level placement. However, in the realm of 7nm and 5nm feature sizes, small discontinuities in OPC from piecewise constant model changes can cause unacceptable levels of EPE errors. The introduction of Dynamic Model Generation (DMG) can be shown to effectively avoid these dislocations by providing unique mask and optical models per simulation region, allowing a near continuum of models through field. DMG allows unique models for EMF, apodization, aberrations, etc to vary through the entire field and provides a capability to precisely and accurately model systematic field signatures.

Synchronous Generator with HTS-2G field coils for Windmills with output power 1 MW

Science.gov (United States)

Kovalev, K.; Kovalev, L.; Poltavets, V.; Samsonovich, S.; Ilyasov, R.; Levin, A.; Surin, M.

2014-05-01

Nowadays synchronous generators for wind-mills are developed worldwide. The cost of the generator is determined by its size and weight. In this deal the implementation of HTS-2G generators is very perspective. The application of HTS 2G field coils in the rotor allows to reduce the size of the generator is 1.75 times. In this work the design 1 MW HTS-2G generator is considered. The designed 1 MW HTS-2G generator has the following parameters: rotor diameter 800 mm, active length 400 mm, phase voltage 690V, rotor speed 600 min-1 rotor field coils with HTS-2G tapes. HTS-2G field coils located in the rotating cryostat and cooled by liquid nitrogen. The simulation and optimization of HTS-2G field coils geometry allowed to increase feed DC current up to 50A. Copper stator windings are water cooled. Magnetic and electrical losses in 1 MW HTS-2G generator do not exceed 1.6% of the nominal output power. In the construction of HTS-2G generator the wave multiplier with ratio 1:40 is used. The latter allows to reduce the total mass of HTS-2G generator down to 1.5 tons. The small-scale model of HTS-2G generator with output power 50 kW was designed, manufactured and tested. The test results showed good agreement with calculation results. The manufacturing of 1 MW HTS-2G generator is planned in 2014. This work is done under support of Rosatom within the frames of Russian Project "Superconducting Industry".

Potential of Partially Superconducting Generators for Large Direct-Drive Wind Turbines

DEFF Research Database (Denmark)

Liu, Dong; Polinder, Henk; Abrahamsen, Asger Bech

2017-01-01

This paper aims at assessing the potential of partially superconducting generators for 10 MW direct-drive wind turbines by investigating their performance for a very wide range of excitation currents. Performance indicators such as shear stress and efficiency and other generator characteristics...... are compared for 12 different generator topologies. To be sufficiently attractive, superconducting generators must have significant advantages over permanent magnet direct-drive generators, which typically have shear stresses of the order of 53 kPa and efficiencies of 96%. Therefore, we investigate what...... they achieve this performance. By examining the maximum magnetic flux density at the location of the superconducting field winding, feasible superconductors can be chosen according to their engineering current density capabilities. It is found that high- and low-temperature superconductors can meet...

To stress or not to stress: a question of models.

Science.gov (United States)

Gray, J Megan; Chaouloff, Francis; Hill, Matthew N

2015-01-05

Stress research is a rapidly evolving field that encompasses numerous disciplines ranging from neuroscience to metabolism. With many new researchers migrating into the field, navigating the hows and whys of specific research questions can sometimes be enigmatic given the availability of so many models in the stress field. Additionally, as with every field, there are many seemingly minor experimental details that can have dramatic influences on data interpretation, although many of these are unknown to those not familiar with the field. The aim of this overview is to provide some suggestions and points to guide researchers moving into the stress field and highlight relevant methodological points that they should consider when choosing a model for stress and deciding how to structure a study. We briefly provide a primer on the basics of endpoint measurements in the stress field, factors to consider when choosing a model for acute stress, the difference between repeated and chronic stress, and importantly, influencing variables that modulate endpoints of analysis in stress work. Copyright © 2015 John Wiley & Sons, Inc.

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.

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.

Improved structural integrity through advances in reliable residual stress measurement: the impact of ENGIN-X

Science.gov (United States)

Edwards, L.; Santisteban, J. R.

The determination of accurate reliable residual stresses is critical to many fields of structural integrity. Neutron stress measurement is a non-destructive technique that uniquely provides insights into stress fields deep within engineering components and structures. As such, it has become an increasingly important tool within engineering, leading to improved manufacturing processes to reduce stress and distortion as well as to the definition of more precise lifing procedures. This paper describes the likely impact of the next generation of dedicated engineering stress diffractometers currently being constructed and the utility of the technique using examples of residual stresses both beneficial and detrimental to structural integrity.

Electricity Generation in Microbial Fuel Cell (MFC) by Bacterium Isolated from Rice Paddy Field Soil

Science.gov (United States)

Fakhirruddin, Fakhriah; Amid, Azura; Salim, Wan Wardatul Amani Wan; Suhaida Azmi, Azlin

2018-03-01

Microbial fuel cell (MFC) is an alternative approach in generating renewable energy by utilising bacteria that will oxidize organic or inorganic substrates, producing electrons yielded as electrical energy. Different species of exoelectrogenic bacteria capable of generating significant amount of electricity in MFC has been identified, using various organic compounds for fuel. Soil sample taken from rice paddy field is proven to contain exoelectrogenic bacteria, thus electricity generation using mixed culture originally found in the soil, and pure culture isolated from the soil is studied. This research will isolate the exoelectrogenic bacterial species in the rice paddy field soil responsible for energy generation. Growth of bacteria isolated from the MFC is observed by measuring the optical density (OD), cell density weight (CDW) and viable cell count. Mixed bacterial species found in paddy field soil generates maximum power of 77.62 μW and 0.70 mA of current. In addition, the research also shows that the pure bacterium in rice paddy field soil can produce maximum power and current at 51.32 μW and 0.28 mA respectively.

Shallow magma diversions during explosive maar-diatreme eruptions in mafic volcanic fields

Science.gov (United States)

Le Corvec, N.; Muirhead, J.; White, J. D. L.

2017-12-01

Maar-diatremes are inverted conical structures formed by subterranean excavation and remobilization of country rocks during explosive volcanism and common in mafic volcanic fields. We focus on impacts of excavation and filling of maar-diatremes on the local state of stress, and its subsequent influence on underlying feeder dikes, which are critical for understanding the development of intrusive networks that feed surface eruptions. We address this issue using finite element models in COMSOL Multiphysics®. Inverted conical structures of varying sizes are excavated in a gravitationally loaded elastic half-space, and then progressively filled with volcaniclastic material, resulting in changes in the orientations and magnitudes of stresses generated within surrounding rocks and within the filling portion of the maar-diatreme. Our results show that rapid unloading during maar-diatreme excavation generates a horizontal compressive stress state beneath diatremes. These stresses allow magma to divert laterally as saucer-shaped sills and circumferential dikes at varying depths in the shallow feeder system, and produce intrusion geometries consistent with both field observations from exhumed volcanic fields and conceptual models of diatreme growth. Stresses generated in these models also provide an explanation for the evolving locations of fragmentation zones over the course of diatreme's filling. In particular, results from this study suggest that: (1) extensional stresses at the base of the diatreme fill favor magma ascent in the lower half of the structure, and possibly promote volatile exsolution and magma fragmentation; and (2) increased filling of diatremes creates a shallow compressive stress state that can inhibit magma ascent to the surface, promoting widespread intra-diatreme explosions, efficient mixing of host rock, and upward widening of the diatreme structure.

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.

Random source generating far field with elliptical flat-topped beam profile

International Nuclear Information System (INIS)

Zhang, Yongtao; Cai, Yangjian

2014-01-01

Circular and rectangular multi-Gaussian Schell-model (MGSM) sources which generate far fields with circular and rectangular flat-topped beam profiles were introduced just recently (Sahin and Korotkova 2012 Opt. Lett. 37 2970; Korotkova 2014 Opt. Lett. 39 64). In this paper, a random source named an elliptical MGSM source is introduced. An analytical expression for the propagation factor of an elliptical MGSM beam is derived. Furthermore, an analytical propagation formula for an elliptical MGSM beam passing through a stigmatic ABCD optical system is derived, and its propagation properties in free space are studied. It is interesting to find that an elliptical MGSM source generates a far field with an elliptical flat-topped beam profile, being qualitatively different from that of circular and rectangular MGSM sources. The ellipticity and the flatness of the elliptical flat-topped beam profile in the far field are determined by the initial coherence widths and the beam index, respectively. (paper)

Dynamic wave field synthesis: enabling the generation of field distributions with a large space-bandwidth product

OpenAIRE

Kamau, Edwin Ngugi

2016-01-01

The generation and manipulation of electromagnetic field distributions plays an essential role in physics in general, and particularly in the vast field of physical optics. In the current state of the art, one of the most convenient methods of performing this task is provided by either static or dynamic diffractive as well as holographic optical elements. Currently available dynamic optical elements, such as spatial light modulators, do offer on the one hand high temporal flexibility. They ho...

Measurement of full-field deformation induced by a dc electrical field in organic insulator films

Directory of Open Access Journals (Sweden)

Boudou L.

2010-06-01

Full Text Available Digital image correlation method (DIC using the correlation coefficient curve-fitting for full-field surface deformation measurements of organic insulator films is investigated in this work. First the validation of the technique was undertaken. The computer-generated speckle images and the measurement of coefficient of thermal expansion (CTE of aluminium are used to evaluate the measurement accuracy of the technique. In a second part the technique is applied to measure the mechanical deformation induced by electrical field application to organic insulators. For that Poly(ethylene naphthalene 2,6-dicarboxylate (PEN thin films were subjected to DC voltage stress and DIC provides the full-field induced deformations of the test films. The obtained results show that the DIC is a practical and robust tool for better comprehension of mechanical behaviour of the organic insulator films under electrical stress.

Thinking Across Generations: Unique Contributions of Maternal Early Life and Prenatal Stress to Infant Physiology.

Science.gov (United States)

Gray, Sarah A O; Jones, Christopher W; Theall, Katherine P; Glackin, Erin; Drury, Stacy S

2017-11-01

Respiratory sinus arrhythmia (RSA) is a parasympathetic-mediated biomarker of self-regulation linked to lifespan mental and physical health outcomes. Intergenerational impacts of mothers' exposure to prenatal stress have been demonstrated, but evidence for biological embedding of maternal preconception stress, including adverse childhood experiences (ACEs), on infant RSA is lacking. We examine the independent effects of maternal ACEs and prenatal stress on infant RSA, seeking to broaden the understanding of the earliest origins of mental and physical health risk. Mothers reported on ACEs and prenatal stress. RSA was recorded in a sample of 167 4-month-old infants (49% female and 51% male) during a dyadic stressor, the Still Face Paradigm. Independent contributions of maternal ACEs and prenatal stress to infant RSA were observed. High maternal ACEs were associated with lower RSA, whereas prenatal stress was associated with failure to recover following the stressor. Sex but not race differences were observed. Prenatal stress was associated with higher RSA among boys but lower RSA among girls. Infants' RSA is affected by mothers' life course experiences of stress, with ACEs predicting a lower set point and prenatal stress dampening recovery from stress. For prenatal stress but not ACEs, patterns vary across sex. Findings underscore that stress-reducing interventions for pregnant women or those considering pregnancy may lead to decreased physical and mental health risk across generations. Copyright © 2017 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.

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

Theory and experimental show up of axial magnetic fields self-generated in dense laser-produced plasmas

International Nuclear Information System (INIS)

El Tamer, M.

1986-09-01

The work presented in this thesis concerns the magnetic fields generated in laser produced plasma. A summary of the theoretical and experimental studies concerning the toroidal magnetic fields and realised by different groups of research is presented. Then, we present our original contribution on the generation of axial magnetic fields by the dynamo effect. The experimental work for the detection of magnetic field is based on the Faraday rotation and Zeeman effects. The experimental diagrams are detailed and discussed. The experimental results are presented and compared to the theory. Finaly, we present some consequences of the generation of the axial magnetic fields in laser produced plasma as a discussion of the thermal conductivity [fr

Generation of the reciprocal-binomial state for optical fields

International Nuclear Information System (INIS)

Valverde, C.; Avelar, A.T.; Baseia, B.; Malbouisson, J.M.C.

2003-01-01

We compare the efficiencies of two interesting schemes to generate truncated states of the light field in running modes, namely the 'quantum scissors' and the 'beam-splitter array' schemes. The latter is applied to create the reciprocal-binomial state as a travelling wave, required to implement recent experimental proposals of phase-distribution determination and of quantum lithography

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

Control of free-edge interlaminar stresses in composite laminates using piezoelectric actuators

International Nuclear Information System (INIS)

Huang, Bin; Soo Kim, Heung

2014-01-01

The control of free-edge interlaminar stresses in laminated composite structures using a stress function-based approach is proposed. The assumed stress fields satisfy pointwise traction and free boundary conditions at surfaces. Governing equations are derived using the principle of complementary virtual work. A general eigenvalue solution procedure was adopted to obtain accurate stress states of the laminated composite structure. The results obtained from the proposed method were compared with those obtained by three-dimensional finite element analyses. It was found that interlaminar stresses generated by mechanical loadings could be significantly reduced by applying proper electric fields to piezoelectric actuators, which were surface bonded or embedded in composite laminates. Locations of piezoelectric actuators also influenced the distributions of interlaminar stresses. The results provided that piezoelectric actuators have potential in the application to actively control interlaminar stresses in composite laminates. (paper)

Molecular force sensors to measure stress in cells

International Nuclear Information System (INIS)

Prabhune, Meenakshi; Rehfeldt, Florian; Schmidt, Christoph F

2017-01-01

Molecularly generated forces are essential for most activities of biological cells, but also for the maintenance of steady state or homeostasis. To quantitatively understand cellular dynamics in migration, division, or mechanically guided differentiation, it will be important to exactly measure stress fields within the cell and the extracellular matrix. Traction force microscopy and related techniques have been established to determine the stress transmitted from adherent cells to their substrates. However, different approaches are needed to directly assess the stress generated inside the cell. This has recently led to the development of novel molecular force sensors. In this topical review, we briefly mention methods used to measure cell-external forces, and then summarize and explain different designs for the measurement of cell-internal forces with their respective advantages and disadvantages. (topical review)

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

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

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

Stress studies in EFG

Science.gov (United States)

1983-01-01

Stress distributions were calculated for a creep law to predict a rate of plastic deformation. The expected reduction in stresses is obtained. Improved schemes for calculating growth system temperature distributions were evaluated. Temperature field modeling examined the possibility of using horizontal temperature gradients to influence stress distribution in ribbon. The defect structure of 10 cm wide ribbon grown in the cartridge system was examined. A new feature is identified from an examination of cross sectional micrographs. It consists of high density dislocation bands extending through the ribbon thickness. A four point bending apparatus was constructed for high temperature study of the creep response of silicon, to be used to generate defects for comparison with as grown defects in ribbon. The feasibility of laser interferometric techniques for sheet residual stress distribution measurement is examined. The mathematical formalism for calculating residual stress from changes in surface topology caused by an applied stress in a rectangular specimen was developed, and the system for laser interferometric measurement to obtain surface topology data was tested on CZ silicon.

The International Geomagnetic Reference Field: the twelfth generation

Science.gov (United States)

Thebault, Erwan; Finlay, Christopher; The IGRF Working Group

2015-04-01

The IGRF is an internationally-agreed reference model of the Earth's magnetic field produced under the auspices of the International Association of Geomagnetism and Aeronomy. The IGRF-12 is the latest update of this well-known model which is used each year by many thousands of users for both industrial and scientific purposes. In October 2014, ten institutions worldwide have made contributions to the IGRF. These models were evaluated and the twelfth generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014. In this presentation, we will report on the IGRF activities, briefly describe the candidate models, summarize the evaluation of models performed by different independent teams, show how the IGRF-12 models were calculated and finally discuss some of the main magnetic features of this new model.

Generating the optimal magnetic field for magnetic refrigeration

DEFF Research Database (Denmark)

Bjørk, Rasmus; Insinga, Andrea Roberto; Smith, Anders

2016-01-01

In a magnetic refrigeration device the magnet is the single most expensive component, and therefore it is crucially important to ensure that an effective magnetic field as possible is generated using the least amount of permanent magnets. Here we present a method for calculating the optimal...... remanence distribution for any desired magnetic field. The method is based on the reciprocity theorem, which through the use of virtual magnets can be used to calculate the optimal remanence distribution. Furthermore, we present a method for segmenting a given magnet design that always results...... in the optimal segmentation, for any number of segments specified. These two methods are used to determine the optimal magnet design of a 12-piece, two-pole concentric cylindrical magnet for use in a continuously rotating magnetic refrigeration device....

Reactive Oxygen Species Generation-Scavenging and Signaling during Plant-Arbuscular Mycorrhizal and Piriformospora indica Interaction under Stress Condition.

Science.gov (United States)

Nath, Manoj; Bhatt, Deepesh; Prasad, Ram; Gill, Sarvajeet S; Anjum, Naser A; Tuteja, Narendra

2016-01-01

A defined balance between the generation and scavenging of reactive oxygen species (ROS) is essential to utilize ROS as an adaptive defense response of plants under biotic and abiotic stress conditions. Moreover, ROS are not only a major determinant of stress response but also act as signaling molecule that regulates various cellular processes including plant-microbe interaction. In particular, rhizosphere constitutes the biologically dynamic zone for plant-microbe interactions which forms a mutual link leading to reciprocal signaling in both the partners. Among plant-microbe interactions, symbiotic associations of arbuscular mycorrhizal fungi (AMF) and arbuscular mycorrhizal-like fungus especially Piriformospora indica with plants are well known to improve plant growth by alleviating the stress-impacts and consequently enhance the plant fitness. AMF and P. indica colonization mainly enhances ROS-metabolism, maintains ROS-homeostasis, and thereby averts higher ROS-level accrued inhibition in plant cellular processes and plant growth and survival under stressful environments. This article summarizes the major outcomes of the recent reports on the ROS-generation, scavenging and signaling in biotic-abiotic stressed plants with AMF and P. indica colonization. Overall, a detailed exploration of ROS-signature kinetics during plant-AMF/ P. indica interaction can help in designing innovative strategies for improving plant health and productivity under stress conditions.